**Abstract**

There are various ways school leadership is understood and practised in education systems worldwide. Any act of leadership that gives rise to something new is a creative leadership. Drawing on complex dynamical systems critical social theory perspective of Pierre Bourdieu, the chapter analyses the views of selected teachers and school leaders in five basic schools in Ghana to explicate the ways leadership is conceptualized and enacted in practice in their schools. Doing so, the chapter argues that leadership evolves from human habitus in the interaction of capital within fields of practice. This view allows us to envision the non-linearity of leadership and to move away from reproductive or colonial leadership.

**Keywords:** Bourdieu, education, Ghana, habitus, leadership


**3. Discussion and Conclusion**

The FOST can be thought of as generalizations of two existing pricing methodologies. First, it generalizes the Forest of Trees method to a high-dimensional underlying. Second, it generalizes the Stochastic Tree pricing method for single-exercise right options to multiple exercise rights. We construct high and low FOST estimators analogous to those defined for the Stochastic Tree. We prove properties regarding FOST estimator bias, ordering, and convergence and present numerical results as illustrations.

In related work, we have replaced the binomial/trinomial trees in the Forest of Trees method with Stochastic Meshes Broadie and Glasserman (2004), creating the Forest of Stochastic Meshes Marshall and Reesor (2011). This avoids the exponential growth in computing time with the number of exercise opportunities experienced by the FOST. Another avenue of future work involves algorithmic enhancement. In Section 2.5 we discussed the use of parallel processing to reduce computing time. Two alternatives to this are variance reduction and bias reduction. There are some standard variance reduction methods (e.g., antithetic variates, control variates) that could be used to produce more efficient estimators. The bias reduction technique given in Whitehead et al. (2012) for Stochastic Tree estimators successfully reduces the branching factor required to obtain a desired accuracy for an American option value. This technique can be extended to correct the bias in FOST estimators and we have preliminary evidence of its effectiveness Marshall (2012). Combinations of variance reduction, bias reduction, and parallel processing can be investigated to further improve the algorithm's performance.

**Author Contributions:** R.M.R. and T.J.M. contributed equally to all aspects of this paper. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded in part by the Natural Sciences and Engineering Research Council of Canada grant number RGPIN-2017-05441.

**Acknowledgments:** The authors thank SHARCNet for computational resources and technical support, particular acknowledgement goes to both Tyson Whitehead and Baolai Ge. We also thank graduate students and faculty in the Financial Mathematics group at Western University, in particular, Matt Davison, Adam Metzler, Rogemar Mamon, and Lars Stentoft.

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results. The views represented herein are the authors' own views and do not necessarily represent the views of Bank of Montreal or its affiliates and are not a product of its research.


Comparing the three scenarios' costs as calculated over the entire project time horizon (Table 5), it is clear that Scenario C is the costliest to implement and maintain with total costs for installation as well as operation and maintenance. These high costs can be explained by the much higher area to be covered with additional UGI measures for Scenario C as compared to the other two scenarios, particularly with regard to facade greening, which generates the highest operation and maintenance costs of all UGI measures (Table 1).

**Table 5.** Present value of all costs and installation (I) and annual operation and maintenance (O&M) costs of the three scenarios [54].

Table 6 shows the NPVs and BCRs of the three scenarios, combining both discounted costs (Table 5) and discounted benefits (Table 4) linked to each scenario. Scenario B clearly performed the best given the higher BCR and NPV. Despite greatly different implementation of UGI and corresponding costs, the performances of Scenarios A and C are very similar in both the NPV and BCR calculations and make the cutoff for economic feasibility. The significantly better performance of Scenario B despite its comparatively low benefit contribution is largely due to the fact that implementation costs for this scenario are by far the lowest. Scenario B included a high share of additional trees with tree drains, which are the costliest UGI type in terms of installation However, tree drains are also the most inexpensive measure when it comes to operation and maintenance costs (Table 1), lowering the overall cost over the project life span. Scenario B also receives the lowest share of facade greening, which is the costliest measure in terms of operation and maintenance. In sum, these low costs compensate for the relatively low benefits to be gained from implementing Scenario B.

**Table 6.** Net present values (NPV) and benefit–cost ratios (BCR) of the three scenarios.

The similar performances of scenarios A and C, even with Scenario C receiving a significantly higher share of UGI, can be traced back to the more efficient UGI placement for Scenario A mentioned above. This results in almost the same level of UHI mitigation benefits for both scenarios, which combined with lower costs for Scenario A ultimately leads to the slightly better performance of this scenario. In other words, Scenario A achieves the same level of UHI mitigation benefits at a much lower cost, meaning that benefits are reached in a more cost-effective manner. Nevertheless, both Scenarios A and C have low BCRs, which becomes a relevant factor in the sensitivity analysis presented in 5.3. This leaves Scenario B as the most robust option; while the scenario generates lower benefits than the other two, the discounted costs are also substantially lower, resulting in a higher positive net outcome and thus confirming that this scenario generates substantial value for society.

#### *4.3. Sensitivity Analysis*

A Monte Carlo analysis was performed with 10,000 draws from the given distribution of parameters in Table 2 to test the sensitivity of the NPV to the parameters. The number of draws is assumed to be amply large to obtain a random sample from each distribution with all possible combinations. We obtained probabilities of achieving an economically feasible result (NPV > 0) of 64%, 100%, and 63% for Scenarios A, B, and C, respectively. Therefore, the results are robust given the uncertainty of the tested parameters. Given that Scenario B would remain positive even with a significantly lower VSL estimate, we achieve a much higher likelihood of economic feasibility.

We also tested the probabilities of achieving the baseline NPV, which resulted in probabilities of 34%, 39%, and 40% for Scenarios A, B, and C, respectively. The triangular distribution of the VSL became a significant factor for these probabilities because the maximum VSL was already the estimate used for the baseline calculation. Additionally, the uniform distribution for a ±20% change in total installation and operation and maintenance costs lead to higher risks in terms of the likelihood of achieving a positive outcome. However, we maintain that the cost estimates provided by Strehl et al. [53] are already general costs estimates from the literature and expert estimations, and a 20% variation from these would likely gravitate to more extreme outliers.

#### **5. Discussion**

Statistical climate data analysis and CBA were used as methods for determining the effectiveness of three stormwater management scenarios developed for a neighborhood in Pankow, Berlin, in combating UHI effects and thereby creating value for society. The findings indicate two things: first, the climate data analysis reveals mean temperature reductions in locations where UGI measures were added, confirming that UGI measures in stormwater management can be effective in mitigating UHI effects. Secondly, lower morbidity and mortality rates resulting from this decreased heat stress created monetized benefits which contributed significantly to the positive economic performance of the three scenarios, allowing the conclusion that UGI measures can be implemented in an economically feasible manner.

The climate data analysis showed that UGI can be effectively employed to mitigate urban heat stress, with varying results depending on UGI type as well as strategic placement of measures. The results for all three scenarios generally match the findings of previous studies. For tree drains, the climate data analysis showed the highest daytime heat stress reductions of up to 711 h per year (Table 3). This is in line with the findings of existing literature, where trees are found to have the strongest heat mitigation effect which can even extend to several meters distance from the trees themselves [8,21,78]. Facade greening, by contrast, achieved considerably lower cooling effects; a maximum of 381 h in annual heat stress reductions could be confirmed. This pattern is also found in existing studies which are in general agreement that green facades contribute less to heat stress mitigation for residents, as the effect seems to be limited to the immediate proximity of the

walls [21,33,79]. One finding that could not be confirmed by the climate data analysis is the indoor cooling effect of facade greening, as the climate data were measured and simulated for outdoor areas only in the KURAS project. Green roofs reached cooling effects very similar to those of green facades, with the same maximum daytime heat stress reduction of 381 h per year. Existing literature offers mixed findings for the climate effects of green roofs, with some studies not finding any effect at street level, and others acknowledging very slight effects [7,8,21,31,65]. The effects that are revealed by the climate data analysis are mostly due to low roofs such as underground parking lots, but overall the UHI mitigation contribution of green roofs is low during the day [44].

Given the high heat-related benefits of the study, it is important to consider plausibility as few studies have empirically investigated the green cover and improved health outcomes relationship, i.e., [80]. The UHI mitigation benefits that were calculated for the study site, that is, reductions in heat-related hospitalizations and deaths, were tested for plausibility by extrapolating the CBA results to national level and comparing them with actual heat-related hospitalization and mortality statistics for Germany. For heat-related hospitalizations in Germany, 1856 cases were recorded in 2013, while 2003, the year of the European heat wave, resulted in 2561 hospitalizations [81]. Taking the maximum number of hospitalization cases avoided for the Pankow, Berlin study site, hospitalizations were reduced by 2.66 cases for a total of 23,276 residents. Linearly extrapolating this to a population of roughly 80 million for all of Germany yields a reduction of 9142 cases per year. This figure evidently exceeds the number of regular countrywide hospitalization cases by a factor of 4. Possible reasons for this could be that due to the UHI effect, urban dwellers are at a higher risk of suffering heat-related illnesses, leading to a higher share of hospitalizations in the city compared to the national average. Conversely, building resilience against heat stress through UGI has a greater impact and reaches a greater number of citizens in a more efficient manner in densely populated urban areas, which could also lead to the comparatively high number of avoided hospitalization cases in the model site area. Nonetheless, assuming that the benefits could indeed have been overestimated, this would be counterbalanced to a degree by a conservative hospitalization cost estimate. Calculating total treatment costs for Germany for 9142 heat-related hospitalizations at EUR 3300 per case—the amount used in the CBA we arrive at just over EUR 30 million in annual costs, representing less than 40% of the EUR 82 million in national heat-related hospitalization costs [28]. Moreover, the economic effect of reduced hospital admissions on the CBA calculations remains in any event limited, as these savings account for only 1% of total UHI mitigation benefits.

Annual heat-related mortality cases for Germany have been estimated at 4500 deaths [65]. Taking the maximum number of deaths avoided for the model site area, we arrive at 0.78 cases for a population of 23,276, which would correspond to 2681 deaths avoided at national level. This equals only approximately 60% of the number of heat-related deaths in Germany estimated by Tröltzsch et al. [65]. Assuming that, as with hospitalizations, the occurrence of heat-related fatalities is not evenly distributed throughout the country, but that incidence is clustered in urban areas, the results appear to be even more conservative estimates. However, we tread lightly in this conclusion as there is evidence of urban-rural disparities in heat-related mortality, with higher rates being found in rural areas [82]. Despite this evidence, the outcome is consistent with observations made in the literature review of Berlin accounting for a disproportionate share of Germany's heat-related deaths. Looking at the economic valuation of heat-related deaths, Tröltzsch et al. [65] arrive at an inflation-adjusted annual cost to society of EUR 2.24 billion for 4500 deaths, assuming an average of 8 lost life years per death. Using the number of fatalities as calculated for the Pankow study site and extrapolating it to national level, total heat-related deaths in Germany amount to 2681 cases. Applying the same VOLY of 62,126 as calculated by Tröltzsch et al. [65] as well as a slightly higher average of 9.56 life years lost per case, total cost savings would amount to EUR 1.59 billion, or 70% of the total costs calculated by Tröltzsch et al. [65], suggesting conservative benefit estimates for this study.

Overall, the results show that by addressing stormwater management issues, specific UGI measures can be used as a cost-effective method for lowering urban heat stress, but at the same time the strategic selection and placement of measures is key to achieving economic feasibility. This becomes most evident when comparing the shares of green cover and temperature reduction effects for Scenarios A and C, with Scenario C receiving by far the highest share of UGI, but Scenario A still performs better in terms of heat mitigation due to more effective placement of the measures.

#### **6. Conclusions**

Urban areas are increasingly affected by stormwater management issues and the UHI effect due to a continuing urbanization trend leading to growing urban populations and further consolidation of already heavily built-up city centers. The implementation of UGI measures encompassed in sustainable stormwater management represents one solution to mitigating heat stress for the urban population while also providing numerous additional benefits. The purpose of this study was to quantify and value the UHI mitigation potential through heat-related mortality and morbidity reductions in three different UGI scenarios and assess the economic feasibility using a CBA approach. Two contributions were made to the literature on valuing UGI benefits in a UHI context. First, a climate data analysis with the aim of assessing the heat stress mitigation potential for different UGI scenarios in a typical neighborhood of Berlin, Germany was conducted. The second contribution was delivered in the form of CBAs with a focus on social benefits related to reduced morbidity and mortality rates as a result of UHI mitigation through UGI. While previous studies have addressed the UHI mitigation benefits of individual UGI measures, and stormwater management related UGI benefits on a neighborhood scale, this study proposes a method for analyzing complete UGI scenarios, including both ecosystem services and economic benefits related to reduced morbidity and mortality. The results of the climate data analysis indicate clear heat mitigation effects of UGI. The CBA results show that UHI mitigation through implementation of UGI measures at the neighborhood level is economically feasible. The methods for quantification of UGI project costs and benefits proposed in this study can be applied by urban planners in the objective evaluation of project proposals. Since UGI benefits create significant social value, the quantification thereof is essential for urban planning in providing a scientific foundation for the inclusion of UGI in UHI mitigation strategies. This is important as UGI installation and maintenance costs are high and delivering value to society can only be achieved through identification of the most suitable UGI measures and ensuring their effective placement.

**Author Contributions:** Conceptualization, D.J. and S.G.; methodology, J.E. and D.J.; formal analysis, J.E.; investigation, J.E.; data curation, D.J. and J.E.; writing—original draft preparation, J.E. and D.J.; writing—review and editing, S.G.; visualization, J.E.; supervision, S.G. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** 3rd party data. Restrictions apply to the availability of these data. Data was obtained from the Institute of Meteorology and Climatology at Leibniz University Hannover and from GEO-NET Umweltconsulting GmbH and are available from the authors upon request with permission.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **References**

MDPI St. Alban-Anlage 66 4052 Basel Switzerland Tel. +41 61 683 77 34 Fax +41 61 302 89 18 www.mdpi.com

*Sustainability* Editorial Office E-mail<EMAIL_ADDRESS>www.mdpi.com/journal/sustainability

MDPI St. Alban-Anlage 66 4052 Basel Switzerland

Tel: +41 61 683 77 34 Fax: +41 61 302 89 18

www.mdpi.com ISBN 978-3-0365-3711-5


*3.2. Charging Stations, EV Variability and Campus Profit*

The time of day, price of electricity and net profit for all involved in this V2G method are analysed and explained. If the campus buys at off-peak prices, not giving the EV owners an incentive, they make 43.56 p/day using a 3.63 kW/h charger (Table 1).

**Table 1.** Energy sale management based on time and price between EV owner and the university campus.

Figure 4 demonstrates how the profit can vary throughout the day; if the peak-time, and off-peak prices are paid for the electricity, there will be no profit. The '*x*' axis represents the hours of charge and the '*y*' axis represents net profit in pence. There are more discharge hours than charge hours for the EVs, meaning the building must purchase the electricity at 15 p/h and must sell it back to the EV at 12 p/h to break even. The main operating hours are 09:00–17:00, with 12 p showing the peak times and −15 p showing off-peak times for the building for an average day.

A 3.63 kW/h charger's values were calculated using the EVs' batteries at peak times and re-charging at off-peak prices. It also shows that if the University charges the EV batteries at off-peak rates instead of peak rates, the EV owner's and the campus can profit, as is shown in columns 4 and 5 in Table 1. If the university buys and sells at off-peak prices, it makes money throughout the day. While the campus pays both peak, and off-peak prices with a 1 kW/h charger, it breaks even, as the last payment of the day takes net profit to zero (Figure 4).

The tariff rate changes throughout the day. The low tariff rate is 12 p/h, and the high tariff rate is 15 p/h. When these prices are paid, the net profit ends at zero at 17:00. If the campus pays off-peak prices to the EV owner for any hour of the day, 12 p/day is earned as the last payment of the day takes net profit to 12 p. Figure 5 presents the outcome of net profit.

*Sustainability* **2021**, *13*, x FOR PEER REVIEW 9 of 25

**Figure 4.** Campus net profit while peak-time and off-peak prices are paid. **Figure 4.** Campus net profit while peak-time and off-peak prices are paid. net profit.

A 3.63 kW/h charger's values were calculated using the EVs' batteries at peak times

**Figure 5.** Campus net profit while exclusively pays off-peak prices. **Figure 5.** Campus net profit while exclusively pays off-peak prices.

Table 2 presents a 6.66 kW/h charger that brings in a net profit of 79.92 p/day when the campus pays off-peak prices at all times of the day.

**Figure 5.** Campus net profit while exclusively pays off-peak prices. The battery capacity needed to match 10 charging stations costs £27,432.90 depending on the supplier, whereas the 10 charging stations purchase and installation costs £8790, giving the same amount of energy storage at one time, assuming maximum capacity of EVs. This provides a saving of £18,642.90. Lithium-ion batteries have a lifespan of 2–3 years or 300–500 charge cycles meaning this cost will build up over time. The charging stations are designed to last at least 10 years with parts that are easily replaceable, and most of them have a warranty of 3 years. The charging and discharging rate of a 6.66 kW/h charger throughout the day has been presented in Figure 6. The outcome of charging and discharging the EV battery by 6.66 kW/h using a 6.66 kW charger if the car leaves with the same capacity as it was once plugged in, the EV owner could earn 79.92 p/day. If the EVs' owners return to their vehicle and it is out of charge, they are unlikely to use the V2G method. Taking this into account, for this simulation, the campus must have the car fully charged by 17:00 when most classes are finished.

*Sustainability* **2021**, *13*, x FOR PEER REVIEW 10 of 25

the campus pays off-peak prices at all times of the day.

**Time Price (Pence) Charge/Discharge EV Owner (Pence) Campus (Pence)**

**Table 2.** Net profit per day while the campus pays off-peak prices.

08:00–09:00 79.92 Charge −79.92 +79.92 +79.92 09:00–10:00 99.99 Discharge +99.9 −99.9 −79.92 10:00–11:00 99.99 Discharge +99.9 −99.9 −79.92 11:00–12:00 79.92 Charge −79.92 +79.92 +79.92 12:00–13:00 99.99 Discharge +99.9 −99.9 −79.92 13:00–14:00 99.99 Discharge +99.9 −99.9 −79.92 14:00–15:00 79.92 Charge −79.92 +79.92 +79.92 15:00–16:00 79.92 Charge −79.92 +79.92 +79.92

Table 2 presents a 6.66 kW/h charger that brings in a net profit of 79.92 p/day when

Net profit 0 0 79.92

**Campus at off-Peak Prices (Pence)**

**Figure 6.** The profit earned by the campus per day. **Figure 6.** The profit earned by the campus per day.

The EV owner could earn 79.92 p per day, but the campus would lose that too. The campus, however, would not have to pay for large battery installation for the energy storage. In the case of 10 charging stations, the approximate loss becomes £7.99 a day for the university. The loss may accumulate up to the total cost of the battery capacity of 10 charging stations after 6.4 years. The battery must be changed every 2–3 years depending on the frequency of use. Overall, if the university campus installed ten 6.66 kW/h EV charging stations instead of buying the lithium-ion battery capacity to cover the capacity of the charging stations, the university would save £79,856.29 every 10 years. It is assumed that the batteries had to be replaced every two years and the charging stations are every 10 years. The day was simulated and mapped out, assuming the car was plugged in at 08:00 at 80% and unplugged at 17:00 at 100%, as is shown in Figure 7.

This method charges the battery as much as possible, which is 6.66 kW/h for 5 h in the day and thus, discharges it, so it sums to 100% by 17:00. This was calculated through:

$$D\mathbf{c} = \mathbf{Oc} + \mathbf{C}r - \mathbf{Fc} = \mathbf{32}\,\text{kW} + \mathbf{33.3}\,\text{kW} - 40\,\text{kW} = \mathbf{25.3}\,\text{kW} \tag{11}$$

In Equation (11), the '*Dc*' is the discharge/day, the '*Oc*' is the charge before the EV is plugged in, the '*Cr*' is how much the EV is charged during a cycle, and the '*Fc*' is the EV's capacity at 100% charge. This allows the EV to leave with 100% charge, while still discharging as much as possible at peak times.

**Figure 7.** The times of peak and off-peak while the battery is being charged or discharged.


*2.4. Nephrolithiasis*

Prevalence and incidence of nephrolithiasis is increased in obese subjects. Association is facilitated by lower urinary pH, increased urinary oxalate, sodium and phosphate excretion, and uric acid. Other factors such as the effect of insulin resistance on tubular H-Na exchanger and ammoniagenesis promoting urine acidification have also been implicated in the pathogenesis [79]. It is worth commenting that the risk increases after certain weight loss therapies. In fact, after Roux-en-Y, gastric bypass absorption of oxalate in the intestine largely increases and the risk of nephrolithiasis needs to be prevented by reducing dietary oxalate consumption and oral calcium supplementation.


3.3.2. Immobilized Catalysts

In the HKR of terminal epoxides catalyzed by Co(III)salen complexes, the main recycling procedure for most homogenous catalysts is to distill off all the volatile fractions and collect the solid residue. However, distillation is not an ideal separation method for industrial purposes due to the large amount of energy needed and may be limited by the stability of the catalysts at elevated temperatures. In light of this, much research has been aimed at improving the separation of the catalyst and products.

One strategy is to use a fluorous biphasic catalytic system, where employing fluorinated catalysts allows the reaction to be worked up through an organic/fluorocarbon phase separation. The products dissolve into the organic phase and the F-containing catalyst dissolves into the fluorocarbon phase. This concept was explored by Pozzi and coworkers [135,136], who synthesized a number of fluorinated Co–salen complexes for the HKR of terminal epoxides. Some of the fluorinated complexes worked well, but some complexes suffered from a compromise between the solubility in organic solvent to induce the reaction and the solubility in fluorocarbon to achieve the biphasic extraction. Other approaches to achieving improved catalyst separation include the use of ionic liquids and solvent-resistant nanofiltration, both of which have been applied successfully [137,138].

Still, the most investigated approach is the immobilization of the catalyst on polymers and inorganic materials. Following this line, Jacobsen and coworkers [139] investigated Co–salen complexes immobilized on polystyrene resin. The hydroxymethylpolystyrene-supported heterogeneous catalyst **108** (Figure 41) was applied in the HKR of epichlorohydrin and 4-hydroxy-1-butene oxide, two substrates that were not suitable for distillation. The HKR of epichlorohydrin was conducted in CH2Cl2, and the HKR of 4-hydroxy-1-butene oxide was run in THF. Both the ring-opened products and the unreacted epoxides were obtained in good yields (36–52% and 38–41%, respectively) and with high enantioselectivities (up to >99% *ee* for the unreacted epoxides and up to 95% *ee* for the ring-opened products). Catalyst **108** was also used for the dynamic HKR of epibromohydrin, affording the ring-opened product in 94% yield and 96% *ee*. The catalyst could be recovered by simple filtration and recycled up to five times with no apparent loss of reactivity or enantioselectivity.

Kirschning and coworkers [140] reported on a related system, where the Co–salen complex was immobilized on a chloromethylpolystyrene resin (catalyst **109** in Figure 41). Catalyst **109** was investigated in the HKR of epichlorohydrin, styrene oxide, and phenyl glycidyl ether in THF, affording ring-opened products and unreacted epoxides in similar or slightly inferior yields and enantioselectivities compared those obtained with homogeneous Co–salen catalyst **64** (Figure 26). Catalyst **109** was also effective in catalyzing the dynamic HKR of epibromohydrin in THF, giving the corresponding diol with 94% yield and 95% *ee*. The same study also included the immobilization of Co–salen complexes on a porous glass/polymer composite material inside a "PASSflow" reactor [141] which was used to study the catalysis of the dynamic HKR of epibromohydrin in THF under continuous-flow conditions. With reactivation after each run, the modified microreactor could be used for four consecutive runs, affording the ring-opened product in 76–87% yield and 91–93% *ee* [140].

**Figure 41.** Resin-supported Co–salen catalysts **108** and **109**.

**109**

Weck and coworkers [142] synthesized polystyrene resin-supported dendronized Co–salen catalyst **110** (Figure 42) which was employed in the HKR of epichlorohydrin, 1,2-epoxyhexane, allyl glycidyl ether, and styrene oxide. Reactions performed with very low catalyst loading (0.04–0.06 mol% Co) and under solvent-free conditions afforded unreacted epoxides in high yields (40–47%) and with excellent enantioselectivities (>99% *ee*). The excellent catalytic properties were attributed to the flexible linkers and the dendronized framework which probably assisted to promote the cooperative interactions among Co–salen sites and facilitate the bimolecular pathway. Catalyst **110** could be used in five successive HKR reactions with maintained reactivity and enantioselectivity.

**110 Figure 42.** Resin-supported dendronized Co–salen catalyst **110**.

Weck and coworkers [143] grafted their macrocyclic oligomeric catalyst **76** (Figure 31) on a polystyrene resin. The resulting catalyst **111** (Figure 43) was used in the solvent-free HKR of epichlorohydrin and 1,2-epoxyhexane, achieving complete resolution (≥50% conversions and 99% *ee* of the unreacted epoxides) in 3 h or less with only 0.01 mol% Co loading. As such, catalyst **111** is the most efficient heterogeneous catalyst for the HKR of terminal epoxides to date. The catalyst could be recovered by filtration and reused up to five times with maintained enantioselectivity, although the reaction time required to reach full conversion increased after each run. A noteworthy observation was that the use of an excess of water (six equivalents instead of 0.6) led to a significant rate enhancement. The enhanced reactivity was attributed to the formation of a biphasic reaction system, in which the formed diol partitions into the aqueous phase, leaving a higher concentration of epoxide and catalyst in the organic phase.

**111 Figure 43.** Resin-supported macrocyclic oligosalen catalyst **111** based on oligomer **76** (Figure 31).

In addition to the immobilization on polystyrene resin, Co–salen catalysts have also been immobilized on different silica-based supports. Compared to polystyrene, silica is a more rigid support and thus potentially better suited for use as a stationary phase in continuous-flow apparatus. Jacobsen and coworkers covalently immobilized a Co–salen complex on silica (Figure 44) [139]. The resulting catalyst **112** was employed as stationary phase in a continuous-flow system for the HKR of 4-hydroxy-1-butene oxide. Employing THF/H2O as mobile phase, the reaction afforded the corresponding triol in a good yield (37%) and with high enantioselectivity (94% *ee*).


**6. Strategy of intervention**

In order to develop a meaningful relief program we first took stock of existing interventions in the region. Next we trained the NGO staffs in the management of traumatic stress symptoms. In the course of fieldwork we constantly modified what information was useful to adopt in the management of psycho trauma symptoms.

Activity follow up was made through telephone calls with the field teams who used to call as soon as a need arose or whenever problems cropped up.


**1. Introduction**

In 2017 1.63 billion tons of steel was produced in the world as given in **Table 1** and first share of that was China with 631 million ton first and even highest consumption with 736,8 million tons of pig iron and the other share countries were sequentially classified as Japan, USA, India and Russia. Iron ore production in the same years was also reached 2162 billion tons as given in **Table 2**. In the first ranks in iron ore production was first state Australia, Brazil, China, India and Russia was competed

#### **Table 1.**

*Crude steel production [world steel association, 2019].*

#### **Table 2.**

*Iron ore production [world steel association, 2019].*

by even scrap trade. In these years in the world 88,664 million tons of reduced iron (**Table 3**), about 101 million tons scrap and sponge iron was imported [1, 2].

Iron ore reserves in our country distrıbuted in Divriği, Bingöl, Kayseri regions. Besides these ores Kesikköprü, Balikesir and Adapazari different types of iron ore reserves are available. The low quality iron ore was extracted and mixed a certain weight rate amount with high quality ores evaluated in sinter making [3].

Iron ore is used in iron and steel plants. Turkish iron ore reserves can be absolute ore deposits 115 mill tons, apparant iron ore deposits 950 mill tons, potential iron ore deposits 432 millions determined in three groups as tons. Substantially expressing our country's iron ores as low quality, high titaniferrous iron ore is a serious mistake. Low grade iron ore deposits occurred in mainly Sivas, Malatya and Erzincan [4, 5].

In 2019, the recent years by Erdemir Plant of OYAK, in Turkey, produced pig iron in 4 iron blast furnaces used high grade (63% Fe total) imported iron ores mixed with at high rate over 5/1 local iron ores evaluated [4, 5]. Hence, this

**109**

*Concentration and Microwave Radiated Reduction of Southeastern Anatolian Hematite...*

**Thousand tons 2015 2016 2017 Europian Union (28)** 659 702 703 **CIS** 5436 5820 7200 **North America** 10,621 8644 9618 **South America** 2680 1691 1722 **Africa** 4025 4019 6152 **Middle East** 28,906 29,816 33,194 **Asia** 23,654 27,638 30,075 **Oceania** 5717 5837 5985 **World** 75,982 78,331 88,664

evaluation of low grade explored iron ore deposits prompted. The limonite ore deposites contained low grade Fe such as 25–42% Fe in South Eastern Anatolia needed enrichment for evaluation in blast furnaces after sizing suitable for use. Low grade hematite ore was concentrated to over 65% Fe grade by gravity and magnetic separation. The advanced methods were searched for low grade iron ore potential to evaluate. But some of the ore undesirable by integrated impurities and low iron content. It was partially operated in certain periods. An important part of these resources contains limonitic and sideritic iron ores and below 44% Fe as low grade hematite river sands. The limonite ore deposits range between 19 and 44% Fe. Low grade hematite ores 20% Fe grade could be evaluated in India and China. The

The pelleting plant projected in Divrigi contained a concentrator and pelleting facility established at a capacity of 1 million hematite ore. Regarding our iron ore qualities over undesirable contents such as Ti and Mn the resources was not projected in evaluation as long years since no study conducted on behalf of preparation

India ranked first reduced iron ore use in world steel production with integrated iron and steelmaking waste gases in established in the direct reduction facility [5]. In Turkey, imported scrap at 9 million used for 22 million tons EAF iron and steel making instead of concentration and pelleting our low grade ores. Reduced ıron ore pellet plants in India [6–9]. produced 36.9 million tons in 2019 and varied total ore production of 232 million tons. Vertical gas shaft furnaces were commonly used in evaluation of reduced low grade hematite sands followed pelleting and imported low grade ores in this country directed to horizontal grate for production reduced sinters on grate-reduction using coal gas or steel making flue gas. Although reduced pellets were high grade 85% Fe total ore produced, sponge iron production

The most effective and cost-effective technologies are needed for iron ore products in today's modern technologies. Turkish pig iron industry needs direct reduced iron ore products and related technologies and high quality at lower cost

Şırnak and Hakkari region asphaltite coal combusted and ash discarded in the boiler bottom contains 15% limonite at fine sand size below 2 mm from furnace [10]. The rivers and some local land soil contained below 22% Fe grade hematite at slime size of below 150 micron simply excavated as river sand and exported to Iran. In this study this low quality hematite and limonite ores were evaluated for steelmaking reduced iron ore [11–13]. The gravity concentration was affective in limonite

with various types of local iron resources should be investigated.

*DOI: http://dx.doi.org/10.5772/intechopen.95231*

limonite ores are enriched and pelletized [4, 5].

*Direct reduced iron ore production [world steel association, 2019].*

cost and mining cost of iron ore.

**Table 3.**

was not commonjust 3 million tons.

*Concentration and Microwave Radiated Reduction of Southeastern Anatolian Hematite... DOI: http://dx.doi.org/10.5772/intechopen.95231*

**Table 3.**

*Iron Ores*

**108**

Erzincan [4, 5].

**Table 2.**

**Table 1.**

*Iron ore production [world steel association, 2019].*

*Crude steel production [world steel association, 2019].*

by even scrap trade. In these years in the world 88,664 million tons of reduced iron (**Table 3**), about 101 million tons scrap and sponge iron was imported [1, 2].

**Million tons 2015 2016 2017 Europian Union (28)** 27,825 30,187 30,675 **Turkey** 9994 7520 6226 **Other Europian** 15,407 11,072 9526 **CIS** 195,298 189,064 177,906 **North America** 112,451 107,590 113,838 **South America** 448,122 465,811 465,590 **Africa** 93,760 90,559 85,657 **Middle East** 39,370 43,280 55,087 **Asia** 283,527 316,758 336,879 **Oceania** 814,403 861,521 887,365 **World** 2,030,164 2,115,842 2,162,524

**Thousand tons 2015 2016 2017 Europian Union (28)** 166,115 162,024 168,305 **Turkey** 31,517 33,163 37,524 **Other Europian** 35,778 37,601 42,203 **CIS** 101,552 102,108 100,933 **North America** 110,938 110,638 115,761 **South America** 43,899 40,220 43,693 **Africa** 13,701 13,099 15,053 **Middle East** 29,429 31,480 34,475 **Asia** 1,112,873 1,123,948 1,123,948 **Oceania** 5717 5837 5985 **World** 1,620,001 1,626,954 1,690,479

weight rate amount with high quality ores evaluated in sinter making [3].

Iron ore reserves in our country distrıbuted in Divriği, Bingöl, Kayseri regions. Besides these ores Kesikköprü, Balikesir and Adapazari different types of iron ore reserves are available. The low quality iron ore was extracted and mixed a certain

Iron ore is used in iron and steel plants. Turkish iron ore reserves can be absolute ore deposits 115 mill tons, apparant iron ore deposits 950 mill tons, potential iron ore deposits 432 millions determined in three groups as tons. Substantially expressing our country's iron ores as low quality, high titaniferrous iron ore is a serious mistake. Low grade iron ore deposits occurred in mainly Sivas, Malatya and

In 2019, the recent years by Erdemir Plant of OYAK, in Turkey, produced pig iron in 4 iron blast furnaces used high grade (63% Fe total) imported iron ores mixed with at high rate over 5/1 local iron ores evaluated [4, 5]. Hence, this *Direct reduced iron ore production [world steel association, 2019].*

evaluation of low grade explored iron ore deposits prompted. The limonite ore deposites contained low grade Fe such as 25–42% Fe in South Eastern Anatolia needed enrichment for evaluation in blast furnaces after sizing suitable for use. Low grade hematite ore was concentrated to over 65% Fe grade by gravity and magnetic separation. The advanced methods were searched for low grade iron ore potential to evaluate. But some of the ore undesirable by integrated impurities and low iron content. It was partially operated in certain periods. An important part of these resources contains limonitic and sideritic iron ores and below 44% Fe as low grade hematite river sands. The limonite ore deposits range between 19 and 44% Fe. Low grade hematite ores 20% Fe grade could be evaluated in India and China. The limonite ores are enriched and pelletized [4, 5].

The pelleting plant projected in Divrigi contained a concentrator and pelleting facility established at a capacity of 1 million hematite ore. Regarding our iron ore qualities over undesirable contents such as Ti and Mn the resources was not projected in evaluation as long years since no study conducted on behalf of preparation cost and mining cost of iron ore.

India ranked first reduced iron ore use in world steel production with integrated iron and steelmaking waste gases in established in the direct reduction facility [5].

In Turkey, imported scrap at 9 million used for 22 million tons EAF iron and steel making instead of concentration and pelleting our low grade ores. Reduced ıron ore pellet plants in India [6–9]. produced 36.9 million tons in 2019 and varied total ore production of 232 million tons. Vertical gas shaft furnaces were commonly used in evaluation of reduced low grade hematite sands followed pelleting and imported low grade ores in this country directed to horizontal grate for production reduced sinters on grate-reduction using coal gas or steel making flue gas. Although reduced pellets were high grade 85% Fe total ore produced, sponge iron production was not commonjust 3 million tons.

The most effective and cost-effective technologies are needed for iron ore products in today's modern technologies. Turkish pig iron industry needs direct reduced iron ore products and related technologies and high quality at lower cost with various types of local iron resources should be investigated.

Şırnak and Hakkari region asphaltite coal combusted and ash discarded in the boiler bottom contains 15% limonite at fine sand size below 2 mm from furnace [10]. The rivers and some local land soil contained below 22% Fe grade hematite at slime size of below 150 micron simply excavated as river sand and exported to Iran. In this study this low quality hematite and limonite ores were evaluated for steelmaking reduced iron ore [11–13]. The gravity concentration was affective in limonite and hematite sands. The Humphrey spirals were also used in the washing of Şırnak asphaltite coal bottom ash. The limonite sands gave high Fe yields in the low intensity magnetic separation and especially in the washing of the hematite sands in the coal ash widely [12]. In the high load density and high ash coals Humphrey spirals and magnetic separation was specific performances of concentration sellectively at 82% during the washing was observed to increase the amount of high grade iron ore concentrates.


Silver Nanoparticles - Preparation Methods and Anti-Bacterial/Viral Remedy Impacts against COVID 19

*Lyubomir Lazov, Risham Singh Ghalot and Edmunds Teirumnieks*

## **Abstract**

Silver has been an influential segment of pharmaceutical utilization for remedies & hygiene in the latest era. The first topic reviews the study on air sanitization ventilation & air sanitizer systems using laser ablated silver nanoparticles (inspired by 2020 Pandemic) directing to contamination of deadly biological particles. Intention of this investigation is to validate possible antiviral silver nanoparticles construction to be distributed by retention, to abate the aggravation of breathing organs flu. The underlying description of investigation consists of bibliometric reasoning of the review of the outcome of silver nanoparticles on the sterilization of viral ailments. The investigation will deliberate the approach of use of laser ablated silver nanoparticles for anti-actions. The chapter outcomes in the fascinating utilization of silver nanoparticles for pharmaceutical purposes for contagious diseases, viruses or bacteria and devotes to the upgradation of therapeutic education to safeguard health care workers from threatening viruses at therapeutic organizations. Morally, the investigation will obtain a hygienic scheme, which might be installed at every communal or individual places cost-effectively including silver nanoparticles (because of their therapeutic properties). The second section of investigation considers distinct techniques for manufacturing silver nanoparticles. The various schemes have been compared based on their pros & cons. The method of laser ablation for generating nanoparticles underwater is briefed. The intention of this part is to disclose the current & anticipation probabilities of the process - laser ablation, as a profitable and eco-favorable innovation for manufacturing silver nanoparticle in liquid solutions. The chapter is motivated by two of our reviewed papers i.e., "*Antibacterial and anti-viral effects of silver nanoparticles in medicine against covid 19"* and "*Methods for obtaining silver nanoparticles*".

**Keywords:** Air disinfectant, Air filters, Antibacterial, Antimicrobial, Antiviral, COVID-19, Laser Ablation, Pulsed Laser Ablation in Liquid, Silver nanoparticles

#### **1. Introduction**

The 2020 circumstances of COVID -19 pandemic, health & sanitization issues in communal buildings have increased recently. Infectious diseases resulted with the Corona Virus expansion were dominating challenge to humanity. That is why innovation into advance strain of practical sterilization strategies is the priority.

Disinfectants are reagents used to coat surfaces to reach out for microbes that either contaminate or eradicate them. Reagents are mostly used for the sanitization of diverse facades in communal premises and medical equipment. Disinfectants used in daily life can be handy to keep interacting surfaces clean by destroying biological microorganism on them and still pose no threat to human lives. Also, sterilizers must have a plentiful quantity for repeated utilization in short periods [1].

Presently, synthetic segments & oxidants like aldehydes, alcohols & sodium hypochlorite, hydrogen peroxides, iodine, and others, respectively, are favorably used for sanitization processes. In some events, these elements present numerous cons like metal corrosion, resistance to various bacteria, as well as other unfavorable environmental effects.

With the invention & promising features of nanomaterials, a wide range of options have been disclosed to overwhelming flaws. As interpreted by the International Organization for Standardization (ISO), "nanomaterials" are somewhat material particles of diameter varying between 1 nm & 100 nm. In present-day, distinct material nanoparticles are favorably utilized as efficient sanitizers. The preeminent attempts of scientists from nanotechnology, at the present day, are concentrated on enhancing their physiochemical features & increasing the results of their sanitizing ramification on emerging or modified viruses. Distinct nanoparticles of metals like copper (Cu), silver (Ag), and gold (Au), are now strongly preferred as antiseptics.

Products based on Ag ions and its other antimicrobial works are known since 1000 BC. They were commonly adopted by the archaic Indians in food & medicinal products as a remedy [2].

Antimicrobial effects of silver nitrate (AgNO3) are generally well-known, but with Ag NPs onset, its beneficial properties have raised undoubtedly. This is briefed by the advanced physicochemical features that Ag NPs consists of. With a higher

**109**

viruses [17].

**Figure 1.**

**2. Silver nanoparticles**

*Silver Nanoparticles - Preparation Methods and Anti-Bacterial/Viral Remedy Impacts…*

surface/volume, ratio they have a great synergy with microbe surfaces and leads to great antimicrobial safety. The size, shape of Ag NPs portrays a vital aspect in this mechanism. These physiochemical features of Ag NPs are necessary and compatible

These substantial physiochemical features of Ag NPs are also universally accepted in fields like ecology, industry, and many more. The table beneath briefs the investi-

According to **Table 1**, Ag NPs play a crucial function in air and water sanitization, as well as a medical assistant in a few therapeutic actions. They radiate highly significant behavior in interaction with various bacteria & viruses like *Staphylococcus aureus*, *Pseudomonas aeruginosa* coli and many others [16]. The extraordinary activities of Ag NPs are due to binding capability to sulfur (S) and phosphorus (P), as well as functionalized biomolecules, directing to a rise in their physicochemical features and the competence to destroy various

**Figure 1** represents simplified promising operations of Ag NPs. Because of the multi-sphere utilization of Ag NPs, the vast sphere of the biomedical line, as an ingenious organization connected to the 21st century COVID-19 pandemic, that occurred globally and bringing the world to a halt. This review chapter is notably directed to the performance of Ag NPs as a purifying agent for isolating the escalation of Coronavirus, to quarantine Internal airborne ailments in which humans are

Silver is the exceptionally integral anti-microbial/bacterial (**Figure 2**) agent accessible way before the initiation of antibiotics [19]. Ag NPs are nanoparticles (NPs) of Ag constructed via nano-techniques of distinct size & shape in any proportion [20]. Approximately, three hundred and twenty tons of tiny silver is produced in a year and used worldwide at present [21]. For the past few decades, Ag NPs is the prime investigation theme because of their size, shape, antimicrobial effects, chemical stability, catalytic activity high conductivity, and other extraordinary features. Processes & methods like laser ablation, microwave processing, gamma irradiation, electron irradiation, chemical reduction, photochemical

to the seek for new technics to tackle any future pandemics like COVID-19.

*Utilization of silver nanoparticles as a sanitizing agent at different communal places.*

gation of distinct research teams, demonstrating their fields of utilization.

likely to be contaminated with the viral atoms at communal places.

*DOI: http://dx.doi.org/10.5772/intechopen.99368*

#### **Table 1.**

*Prominent physicochemical features of silver nanoparticles & products as a preservative.*

*Silver Nanoparticles - Preparation Methods and Anti-Bacterial/Viral Remedy Impacts… DOI: http://dx.doi.org/10.5772/intechopen.99368*

**Figure 1.** *Utilization of silver nanoparticles as a sanitizing agent at different communal places.*

surface/volume, ratio they have a great synergy with microbe surfaces and leads to great antimicrobial safety. The size, shape of Ag NPs portrays a vital aspect in this mechanism. These physiochemical features of Ag NPs are necessary and compatible to the seek for new technics to tackle any future pandemics like COVID-19.

These substantial physiochemical features of Ag NPs are also universally accepted in fields like ecology, industry, and many more. The table beneath briefs the investigation of distinct research teams, demonstrating their fields of utilization.

According to **Table 1**, Ag NPs play a crucial function in air and water sanitization, as well as a medical assistant in a few therapeutic actions. They radiate highly significant behavior in interaction with various bacteria & viruses like *Staphylococcus aureus*, *Pseudomonas aeruginosa* coli and many others [16]. The extraordinary activities of Ag NPs are due to binding capability to sulfur (S) and phosphorus (P), as well as functionalized biomolecules, directing to a rise in their physicochemical features and the competence to destroy various viruses [17].

**Figure 1** represents simplified promising operations of Ag NPs. Because of the multi-sphere utilization of Ag NPs, the vast sphere of the biomedical line, as an ingenious organization connected to the 21st century COVID-19 pandemic, that occurred globally and bringing the world to a halt. This review chapter is notably directed to the performance of Ag NPs as a purifying agent for isolating the escalation of Coronavirus, to quarantine Internal airborne ailments in which humans are likely to be contaminated with the viral atoms at communal places.

#### **2. Silver nanoparticles**

Silver is the exceptionally integral anti-microbial/bacterial (**Figure 2**) agent accessible way before the initiation of antibiotics [19]. Ag NPs are nanoparticles (NPs) of Ag constructed via nano-techniques of distinct size & shape in any proportion [20]. Approximately, three hundred and twenty tons of tiny silver is produced in a year and used worldwide at present [21]. For the past few decades, Ag NPs is the prime investigation theme because of their size, shape, antimicrobial effects, chemical stability, catalytic activity high conductivity, and other extraordinary features. Processes & methods like laser ablation, microwave processing, gamma irradiation, electron irradiation, chemical reduction, photochemical

*Silver Micro-Nanoparticles - Properties, Synthesis, Characterization, and Applications*

environmental effects.

products as a remedy [2].

LA/ZnO:Cu/Ag Bio-nanocomposites

Disinfectants are reagents used to coat surfaces to reach out for microbes that either contaminate or eradicate them. Reagents are mostly used for the sanitization of diverse facades in communal premises and medical equipment. Disinfectants used in daily life can be handy to keep interacting surfaces clean by destroying biological microorganism on them and still pose no threat to human lives. Also, sterilizers must have a plentiful quantity for repeated utilization in short periods [1].

Presently, synthetic segments & oxidants like aldehydes, alcohols & sodium hypochlorite, hydrogen peroxides, iodine, and others, respectively, are favorably used for sanitization processes. In some events, these elements present numerous cons like metal corrosion, resistance to various bacteria, as well as other unfavorable

With the invention & promising features of nanomaterials, a wide range of options have been disclosed to overwhelming flaws. As interpreted by the

International Organization for Standardization (ISO), "nanomaterials" are somewhat material particles of diameter varying between 1 nm & 100 nm. In present-day, distinct material nanoparticles are favorably utilized as efficient sanitizers. The preeminent attempts of scientists from nanotechnology, at the present day, are concentrated on enhancing their physiochemical features & increasing the results of their sanitizing ramification on emerging or modified viruses. Distinct nanoparticles of metals like copper (Cu), silver (Ag), and gold (Au), are now strongly preferred as antiseptics. Products based on Ag ions and its other antimicrobial works are known since 1000 BC. They were commonly adopted by the archaic Indians in food & medicinal

Antimicrobial effects of silver nitrate (AgNO3) are generally well-known, but with Ag NPs onset, its beneficial properties have raised undoubtedly. This is briefed by the advanced physicochemical features that Ag NPs consists of. With a higher

Ag ZnO O2-, OH Photo-oxidative elimination of

Noticeable active antibacterial

Photocatalytic, self-sanitization bacterial deactivation [7–10] Eradication of aerosolized bacteriophage MS2 virus

antibacterial ramification [12].

Strengthening the lifespan of

antibacterial action of air sanitization [14]

Injury healing strength [15]

ion for

results [3, 4]

bacteria [5, 6]

particles [11]

food [11]

**Component Physicochemical features of Ag NPs Disinfectant results**

Ag polyamide 40–60 nm of size Viable discharge of Ag+

Mechanical/structural, antibacterial & railing characteristics to UV light

Ag Co-NPs Magnetic & antibacterial Water Cleaning [13] AgNP-SiO2 Spherical morphology Propelling & synergic

Ag/BC Porosity Injury healing strength [8]

blood-clotting proficiency

*Prominent physicochemical features of silver nanoparticles & products as a preservative.*

noticeable active material

Ag/TiO2 Contraction in bandgap points to the

Anti-viral

Ag NPs/Chitosan Porosity, moisture retention efficiency,

Ag NPs Surface functionalization

**108**

**Table 1.**

#### **Figure 2.**

*Biological process of antibacterial impacts of silver nanoparticles & silver ions [18].*

methods, and synthetic biological procedures are some prior researched techniques for constructed Ag NPs [22].

Nanotechnology is a fundamental research attention of present-day, managing design, synthesis, and molecule structures varying not more than 100 nm. NPs have several functions in medication, cosmetics, Eatables, optics, biomedical sciences, space industries, electronics, and in many other broad areas. Synthesized Ag NPs are valued for numerous medical functions such as [22, 23].

Relying on the reducing agents and procedure there are 3 heyday mechanisms to develop Ag NPs.

**111**

**Figure 3.**

*reference [27]).*

*Silver Nanoparticles - Preparation Methods and Anti-Bacterial/Viral Remedy Impacts…*

Currently, several human acts while the discrete modification practices direct a negative impact on air quality. Nowadays, the preeminent threat is to obtain a healthy air quality exempted from harmful particles like airborne bacteria/viruses, fine dust fragments, capricious biological elements & noxious gases. The eviction of threatening airborne microorganisms fascinate scientists because they are liable for chronic contagious disease and are genuine threats of airborne toxicity. Such microbes generate a need for air cleaning systems, which will lower the stability of several microorganisms in the air and will provide healthy air for inhalation. Mentioned microbes are the reason for several diseases like severe acute respiratory

Studies confirm that bioaerosols gather on air conditioner filters in massive amount & breed with high moisture [25]. Presently, several engineering solutions are available for bioaerosol removals like photocatalytic oxidation, UV irradiation

It is believed that a fruitful remedy for pandemics like COVID-19 also associates with the utilization of Ag NPs & Cu NPs (Copper nanoparticles) as a sanitizer agent. Enhanced air quality is obtained with Ag NPs sprayed on air filters [26]. Therefore, a belief is born, that nanomaterials & air filters coated with Ag NPs can

Ag NPs coated with silica, in symmetric distribution, perform symbiotic antibacterial actions with gram-positive/negative, microbe in the air refining arrangements. Moreover, Ag NPs & SiO2 infused together certifies a six-month steady solution & performs 99.99% antibacterial actions. Generating Ag aerosol NPs in a puffer as an antiviral assistant to Hay Bacillus & COVID-19 aerosols under expert medical guidance are favored applicable. Overall, we can claim that combined elements are beneficial for installing with air purifiers (**Figure 3**) in air refining devices [11, 14]. **Figure 3** represents a schematic of the anti-viral impacts of Ag NPs coated on an air refiner. In the research paper, Herzong et al. manifested the probability of manufacturing an airway barrier with aerosolized Ag NPs featuring basic cytotoxicity [27]. Our research in this line confronts the Ag NPs originated products have a greater impact in safety and avoidance of viral ailments for upper respiratory section. It happens because, transfer of viral flu is observed primarily through

*Anti-viral impact of silver nanoparticles on bioaerosols impregnated in the air filter. (Regenerated from*

*DOI: http://dx.doi.org/10.5772/intechopen.99368*

syndrome (SARS), anthrax, asthma etc.

be an engineering solution to pandemics.

inhalation, ingestion, and dermal routes.

with germicides, and aerial ozonolytic methods.

**3. Air decontamination**

*Silver Nanoparticles - Preparation Methods and Anti-Bacterial/Viral Remedy Impacts… DOI: http://dx.doi.org/10.5772/intechopen.99368*

#### **3. Air decontamination**

*Silver Micro-Nanoparticles - Properties, Synthesis, Characterization, and Applications*

methods, and synthetic biological procedures are some prior researched techniques

Nanotechnology is a fundamental research attention of present-day, managing design, synthesis, and molecule structures varying not more than 100 nm. NPs have several functions in medication, cosmetics, Eatables, optics, biomedical sciences, space industries, electronics, and in many other broad areas. Synthesized Ag NPs

• Lacquering of surgical mesh for pelvic repair & breathing mask patent, used in

Relying on the reducing agents and procedure there are 3 heyday mechanisms to

• Physical techniques generally strive with laser impulse energy to dwindle Ag

• Synthetic techniques utilize reducing chemical agents to reduce Ag ions from

• Biological techniques utilize reducing organic agents to reduce Ag ions from

are valued for numerous medical functions such as [22, 23].

*Biological process of antibacterial impacts of silver nanoparticles & silver ions [18].*

• Exposure of viral arrangements (SERS & Ag nanorods)

• Remedy to ulcerative colitis, acne & dermatitis

• Antimicrobial impacts for infectious organisms

• Inhibition of HIV-1 replication

COVID-19.

develop Ag NPs.

• Molecular imaging of cancer units

from volume to atoms and ions.

the bulk of metallic Ag.

the bulk of metallic Ag [24].

for constructed Ag NPs [22].

**Figure 2.**

**110**

Currently, several human acts while the discrete modification practices direct a negative impact on air quality. Nowadays, the preeminent threat is to obtain a healthy air quality exempted from harmful particles like airborne bacteria/viruses, fine dust fragments, capricious biological elements & noxious gases. The eviction of threatening airborne microorganisms fascinate scientists because they are liable for chronic contagious disease and are genuine threats of airborne toxicity. Such microbes generate a need for air cleaning systems, which will lower the stability of several microorganisms in the air and will provide healthy air for inhalation. Mentioned microbes are the reason for several diseases like severe acute respiratory syndrome (SARS), anthrax, asthma etc.

Studies confirm that bioaerosols gather on air conditioner filters in massive amount & breed with high moisture [25]. Presently, several engineering solutions are available for bioaerosol removals like photocatalytic oxidation, UV irradiation with germicides, and aerial ozonolytic methods.

It is believed that a fruitful remedy for pandemics like COVID-19 also associates with the utilization of Ag NPs & Cu NPs (Copper nanoparticles) as a sanitizer agent. Enhanced air quality is obtained with Ag NPs sprayed on air filters [26]. Therefore, a belief is born, that nanomaterials & air filters coated with Ag NPs can be an engineering solution to pandemics.

Ag NPs coated with silica, in symmetric distribution, perform symbiotic antibacterial actions with gram-positive/negative, microbe in the air refining arrangements. Moreover, Ag NPs & SiO2 infused together certifies a six-month steady solution & performs 99.99% antibacterial actions. Generating Ag aerosol NPs in a puffer as an antiviral assistant to Hay Bacillus & COVID-19 aerosols under expert medical guidance are favored applicable. Overall, we can claim that combined elements are beneficial for installing with air purifiers (**Figure 3**) in air refining devices [11, 14].

**Figure 3** represents a schematic of the anti-viral impacts of Ag NPs coated on an air refiner. In the research paper, Herzong et al. manifested the probability of manufacturing an airway barrier with aerosolized Ag NPs featuring basic cytotoxicity [27]. Our research in this line confronts the Ag NPs originated products have a greater impact in safety and avoidance of viral ailments for upper respiratory section. It happens because, transfer of viral flu is observed primarily through inhalation, ingestion, and dermal routes.

#### **Figure 3.**

*Anti-viral impact of silver nanoparticles on bioaerosols impregnated in the air filter. (Regenerated from reference [27]).*

So, sprayers originated from nanotechnology discharging airborne particles & Ag compounds have proven to boost good human health. Such ways substantiate a better air quality in communal places & provides enhanced protection against COVID-19 at its primary stage. Thus, mobile oxygen generating system & air coolers can easily be equipped with Ag NPs coated filters with improved efficiency & without being overpriced [28, 29].


**1. Introduction**

There are over 1 billion disabled people today around the world, comprising 15% of the world population, and this number is greatly increasing due to ageing, chronic diseases, and poor environments and health according to the World Health Organization (WHO) [1]. WHO defines disability as having three dimensions, "impairment in a person's body structure or function, or mental functioning; activity limitation; and participation restrictions in normal daily activities", and states that disability "results from the interaction between individuals with a health condition with personal and environmental factors" [2]. Cambridge Dictionary defines disability as "not having one or more of the physical or mental abilities that most people have" [3]. Wikipedia defines physical disability as "a limitation on a person's physical functioning, mobility, dexterity, or stamina" [4]. Disabilities can relate to various human functions, including hearing, mobility, communication, intellectual ability, learning, and vision [5]. In the UK, 14.6 million people are disabled [6], forming over 20% of the population. In the US, 13.2% of the population were disabled according to the 2019 statistics, comprising over 43 million people [7]. Similar statistics could be found in various countries around the world, some worse than others, which means that, on average, disabled people make up 15% of the population globally.

With 253 million people affected by visual impairment and blindness around the globe, it is the second most prevalent disability in the world population after hearing loss and deafness [8]. Four terminologies can be used to identify various rates of loss of vision and blindness, namely, partially sighted, low vision, legally blind, and totally blind [9]. People with partial vision in one or both eyes are considered partially sighted. Low vision relates to a serious visual impairment, where visual acuity in the good-seeing eye is 20/70 or lower and cannot be enhanced with glasses or contact lenses. If the best-seeing eye can be corrected to achieve 20/200, then the person is considered legally blind [9]. Finally, people who are totally blind are those with a total loss of vision [10]. Even though vision impairment can happen at any point in life, it is more common among older people. Visual impairment can be hereditary. In these kinds of circumstances, it occurs from birth or in childhood [11].

While visual impairment and blindness are among the most disabling disabilities, we know relatively little about the lives of visually impaired and blind individuals [12]. The WHO predicts that the number of people with visual impairments will increase owing to population growth and aging. Moreover, contemporary lifestyles have spawned a multitude of chronic disorders that degrade vision and other human functions [13]. Diabetes and hyperglycemia, for instance, can cause a range of health issues, including visual impairment. Several tissues of the ocular system can be affected by diabetes, and cataracts are one of the most prevalent causes of vision impairment [14].

Behavioral and neurological investigations relevant to human navigation have demonstrated that the way in which we perceive visual information is a critical part of our spatial representation [15]. It is typically hard for visually impaired individuals to orient themselves and move in an unknown location without help [16]. For example, landplane tracking is a natural mobility task for humans, but it is an issue for individuals with poor or no eyesight. This capacity is necessary for individuals to avoid the risk of falling and to alter their position, posture, and balance [16]. Moving up and down staircases, low and high static movable obstacles, damp flooring, potholes, a lack of information about recognized landmarks, obstacle detection, object identification, and dangers are among the major challenges that visually impaired people confront indoors and outdoors [17,18].

The disability and visual impairment statistics of Saudi Arabia are also alarming. Around 3% of people in Saudi Arabia reported the presence of a disability in 2016 [19]. According to the General Authority for Statistics in Saudi Arabia, 46% of all the disabled in Saudi Arabia who have one disability are visually impaired or blind, and 2.9% of the Saudi population have disabilities amounting to extreme difficulty [20]. The information provided above highlights the urgent need for research in the development of assistive technologies for general disabilities, including visual impairment.

A white cane is the most popular tool used by visually impaired individuals to navigate their environments; nevertheless, it has a number of drawbacks. It requires physical contact with the environment [12], cannot detect barriers above the ground, such as ladders, scaffolding, tree branches, and open windows [21], and generates neuromusculoskeletal overuse injuries and syndromes that may require rehabilitation [22]. Moreover, the user of a white cane is sometimes ostracized for social reasons [12]. In the absence of appropriate assistive technologies, visually impaired individuals must rely on family members or other people [23]. However, human guides can be dissatisfying at times, since they may be unavailable when assistance is required [24]. The use of assistive technologies can help visually impaired and blind people engage with sighted people and enrich their lives [12].

Smart societies and environments are driving extraordinary technical advancements with the promise of a high quality of life [25–28]. Smart wearable technologies are generating numerous new opportunities in order to enhance the quality of life of all people.  The same holds true for visually impaired people. Multiple devices have been developed and marketed to aid visually impaired individuals in navigating their environments [29]. An electronic travel aid (ETA) is a regularly used type of mobilityenhancing assistive equipment for the visually impaired and blind. It is anticipated that ETAs will increasingly facilitate "independent, efficient, effective, and safe movement in new environments" [30]. ETAs can provide information about the environment through the integration of multiple electronic sensors and have shown their effectiveness in improving the daily lives of visually impaired people [31]. ETAs are available in a variety of wearable and handheld devices and may be categorized according to their usage of cellphones, sensors, or computer vision [32]. The acceptance rate of ETAs is poor among the visually impaired and blind population [23]. Their use is not common among potential users because they have inadequate user interface designs, are restricted to navigation purposes, are functionally complex, weighty to carry, expensive, and lack functionality for object recognition, even in familiar indoor environments [23]. The low adoption rate does not necessarily indicate that disabled people oppose the use of ETAs; rather, it confirms that additional research is required to investigate the causes of the low adoption rate and to improve the functionality, usability, and adaptability of assistive technologies [33]. In addition, the introduction of unnecessarily complicated ETAs that may necessitate extensive and supplementary training to learn additional and difficult abilities is not a realistic alternative and is not a feasible solution [22]. Robots can assist the visually impaired in navigating from one location to another, but they are costly, along with their other challenges [34]. Augmented reality has been used as a solution for magnifying text and images through a finger wearable applied with a camera to project on a HoloLens [35], but this technology is not suitable for blind people.

We developed a comprehensive understanding of the state-of-the-art requirements of, and solutions for, visually impaired assistive technologies using a detailed literature review (see Section 2) and a survey [36] of this topic. Using this knowledge, we identified the design space for assistive technologies for the visually impaired and the research gaps. We found that the design considerations for assistive technologies for the visually impaired are complex and include reliability, usability, and functionality in indoor, outdoor, and dark environments; transparent object detection; hand-free operations; high-speed, real-time operations; low battery usage and energy consumption; low computation and memory requirements; low device weight; and cost effectiveness. Despite the fact that several devices and systems for the visually impaired have been proposed and developed in academic and commercial settings, the current devices and systems lack maturity and do not completely fulfill user requirements and satisfaction [18,37]. For instance, numerous camera-based and computer-based solutions have been produced. However, the computational cost and energy consumption of image processing algorithms pose a concern for low-power portable or wearable devices [38]. These solutions require large storage and computational resources, including large RAMs to process large volumes of data containing images. This

would require substantial processing, communication, and decision-making times, and would also consume energy and battery life. Significantly more research effort is required to bring innovation, intelligence, and user satisfaction to this crucial area.

In this paper, we propose a novel approach that uses a combination of a LiDAR with a servo motor and an ultrasonic sensor to collect data and predict objects using machine and deep learning for environment perception and navigation. We implemented this approach using a pair of smart glasses, called LidSonic V2.0, to identify obstacles for the visually impaired. The LidSonic system consists of an Arduino Uno edge computing device integrated into the smart glasses and a smartphone app that transmits data via Bluetooth. Arduino gathers data, operates the sensors on smart glasses, detects obstacles using simple data processing, and provides buzzer feedback to visually impaired users. The smartphone application collects data from Arduino, detects and classifies items in the spatial environment, and gives spoken feedback to the user on the detected objects. LidSonic uses far less processing time and energy than image-processing-based glasses by classifying obstacles using simple LiDAR data and using several integer measurements.

We comprehensively describe the proposed system's hardware and software design, having constructed their prototype implementations and tested them in real-world environments. Using the open platforms WEKA and TensorFlow, the entire LidSonic system was built with affordable off-the-shelf sensors and a microcontroller board costing less than USD 80. Essentially, we provide the design of inexpensive, miniature green devices that can be built into, or mounted on, any pair of glasses or even a wheelchair so as to help the visually impaired. Our approach affords faster inference and decision-making using relatively low energy with smaller data sizes. Smaller data sizes are also beneficial in communications, such as those between the sensor and processing device, or in the case of fog and cloud computing, because they require less bandwidth and energy and can be transferred in relatively shorter periods of time. Moreover, our approach does not require a white cane (although it can be adapted to be used with a white cane) and, therefore, it allows for handsfree operation.

The work presented in this paper is a substantial extension of our earlier system LidSonic (V1.0) [39]. LidSonic V2.0, the new version of the system, uses both machine learning and deep learning methods for classification, as opposed to V1.0, which uses machine learning alone. LidSonic V2.0 provides a higher accuracy of 96% compared to 92% for LidSonic V1.0, despite the fact that it uses a lower number of data features (14 compared to 45) and a wider vision angle of 60 degrees compared to 45 degrees for LidSonic V1.0. The benefits of a lower number of features are evident in LidSonic V2.0, requiring even lower computing resources and energy than LidSonic V1.0. We have extended the LidSonic system with additional obstacle classes, provided an improved and extended explanation of its various system components, and conducted extensive testing with two new datasets, six machine learning models, and two deep learning models. System V2.0 was implemented using the Weka and TensorFlow platforms (providing dual options for open-source development) compared to the previous system that was implemented using Weka alone. Moreover, this paper provides a much extended, completely new literature review and taxonomy of assistive technologies and solutions for the blind and visually impaired.

Earlier in this section, we noted that, despite the fact that several devices and systems for the visually impaired have been developed in academic and commercial settings, the current devices and systems lack maturity and do not completely fulfill user requirements and satisfaction. Increased research activity in this field will encourage the development, commercialization, and widespread acceptance of devices for the visually impaired. The technologies developed in this paper are of high potential and are expected to open new directions for the design of smart glasses and other solutions for the visually impaired using open software tools and off-the-shelf hardware.

The paper is structured as follows. Section 2 explores relevant works in the field of assistive technologies for the visually impaired and provides a taxonomy. Section 3 gives an overview of the LidSonic V2.0 system, highlighting its user, developer, and system features. Section 4 provides a detailed illustration of the software and hardware design and implementation. The system is evaluated in Section 5 Conclusions and thoughts regarding future work are provided in Section 6.

### **2. Related Work**

This section reviews the literature relating to this paper. Section 2.1 presents the sensor technologies and the types of sensor technologies used in the assistive tools for the visually impaired. Section 2.2 reviews the processing methods. Section 2.3 discusses the feedback techniques. A taxonomy of functions and applications is provided in Section 2.4. Section 2.5 identifies the research gap and justifies the need for this research. A taxonomy of the research on the visually impaired presented in this section is given in Figure 1. An extensive complimentary review of the assistive technologies for the visually impaired and blind can be found in our earlier work [39].

**Figure 1.** A Taxonomy of Research on Assistive Technologies for the Visually Impaired.

### *2.1. Sensor Technologies and Types Used in Assistive Tools*

Sensors are indistinguishable components of cyberphysical systems. They collect knowledge regarding environmental factors, as well as non-electrical system parameters, and provide the findings as electrical signals. With the development of microelectronics, sensors are available as compact devices at low costs and have a wide range of applications in different fields, especially in control systems [40]. There are two types of sensors, including passive and active sensors. The active sensor needs an incentive to activate. On the contrary, the passive sensor detects inputs and generates output signals directly without an external incentive. The classification may be dependent on the sensor's means of detection, e.g., electric, biological, chemical, radioactive, etc. [41].

A number of sensors have been employed in the field of technologies for visually impaired people. They have been used to solve a wide range of vision issues. The most frequent types of sensors used in assistive devices for the visually impaired are listed in Table 1. It also shows the sensors' functions (functionality), types of wearables, and types of feedback.

### 2.1.1. Ultrasonic Sensors

An ultrasonic sensor is an electronic device that uses ultrasonic sound waves to detect the distance between the user and a target item and transforms the reflected sound into an electric signal. Fauzul and Salleh [42] developed a visual assistive technology to assist visually impaired individuals in safely and conveniently navigating both indoor and outdoor situations. A smartphone app and an obstacle sensor are the two major components of the system. To deliver auditory cue instructions to the user, the mobile software makes use of the smartphone's microelectromechanical sensors, location services, and Google Maps. Ultrasonic sensors in the obstacle sensor are used to detect objects and offer tactile feedback. The obstacle avoidance gadget attaches to a standard cane and vibrates the handle with varying intensities according to the nature of the obstructions. The spatial distance and direction from the present position to the intended location are used to produce spatial sound cues. Gearhart et al. [43] proposed a technique for identifying the position of the detected object using triangulation by geometric relationships with scalar measurements. The authors placed two ultrasonic sensors one on each shoulder, which were angled towards each other at five degrees from parallel, with a space of 10 inches. However, this technique is too complex to be applied to several objects in front of the sensor. A significant number of research papers in the field of objects detection have depended on ultrasonic sensors. Tudor et al. [44] proposed a wearable belt with two ultrasonic sensors and two vibration motors to direct the visually impaired away from obstacles. The authors used an Arduino Nano Board with an ATmega328P microcontroller to connect and build their system. According to their findings, the authors in [45] found that ultrasonic sensors and vibrator devices are easily operated by Arduino UNO R3Impatto Zero boards. Noman et al. The authors of [46] proposed a robot equipped with several ultrasonic sensors and Arduino Mega (ATMega 2560 processor) to detect obstacles, holes, and stairs. The robots can be utilized in indoor environments; however, their use outdoors is not practical.

### 2.1.2. LiDAR Sensors

Light detection and ranging, or LiDAR, is a common remote sensing technique used for determining an object's distance. Chitra et al. [47] proposed a handsfree LVU (LiDARs and Vibrotactile Units) discrete wearable gadget that helps blind persons to identify impediments. Proper mobile assistance equipment is required. The proposed gadget consists of a wearable sensor strap. Liu et al. proposed HIDA. This is a lightweight assistance system used for comprehensive indoor detection and avoidance based on 3D point cloud instance segmentation and a solid-state LiDAR sensor. The authors created a point cloud segmentation model with dual lightweight decoders for semantic and offset predictions, ensuring the system's efficiency. The segmented point cloud was post-processed by eliminating outliers and projecting all points onto a top-view 2D map representation after the 3D instance segmentation.

### 2.1.3. Infrared (IR) Sensors

An infrared (IR) sensor is an electronic device that monitors and senses the infrared radiation in its surroundings [48]. Infrared signals are similar to RFID in that they rely on distant data transfer. As previously stated, the latter uses radio waves, whilst the former uses light signals. Air conditioner remotes and motion detectors, for example, all use infrared technology. Smartphones now come with infrared blasters, allowing users to control any compatible device with an infrared receiver. It is an eye-safe light, which emits pulses and measures the time taken to calculate the distance using the reflected light. Every metric of the IR consists of thousands of separate pulses of light that lead to reliable measurements of rain, snow, fog, or dust and can be obtained by an infrared sensor. These measurements are difficult to capture with cameras [22]. In addition, IR has a long range in both indoor and outdoor environments, high precision, small size, and low latency. An IR sensor can detect obstacles up to 14 m away, with a 0.5 resolution and 4 cm accuracy [12]. IR has medium width among the ultrasonic and laser sensors. The laser has a rather narrow scope, and it gathers a very limited amount of space information, which is not large enough for free paths. On the other hand, ultrasonic sensors have many reflections; thus, they are limited [49].

### 2.1.4. RFID Sensors

RFID is the abbreviation of radio frequency identification. Data may be transferred and received through radio waves using RFID. In RFID, the sender sends a radio receiver. In this method, the sender is commonly an RFID chip (or an RFID tag) inserted into the object being read or scanned. The receiver, on the other hand, is an electrical device that detects the RFID chip's data. The chip and receiver do not need to be in physical contact, because the data is broadcast and received by radio waves. RFID is appealing because of its remote capabilities, but it is also harmful. Because the chip's RFID signal may be read by anybody with an RFID reader, it may lead to an unethical and harmful situation, namely, data theft. The fact that the person using the scanner does not even have to be near the chip/tag increases the danger. Another disadvantage is that each tag has a certain range, which necessitates extensive individual testing, limiting the scope. In addition, the system may be quickly turned off if the tags are wrapped or covered, preventing them from receiving radio signals [50].

An intelligent walking stick for the blind was proposed by Chaitrali et al. [51]. The proposed navigation system for vision impairment uses infrared sensors, RFID technology, and Android handsets to provide speech output for the purpose of obstacle navigation. The gadget is equipped with proximity infrared sensors, and RFID tags are implanted in public buildings, as well as in the walking sticks of blind people. The gadget is Bluetoothconnected to an Android phone. An Android application that provides voice navigation based on the RFID tag reading and also updates the server with the user's position information is being developed. Another application allows family members to access the location of the blind person via the server at any time. The whereabouts of a blind person may be traced at any time, providing further security. This approach has the disadvantage of not being compact. When the intelligent stick is within the range of the PCB unit, the active RFID tags immediately send location information. It is not necessary for the RFID sensor to read it explicitly.

### 2.1.5. Electromagnetic Sensors (Microwave Radar)

Adopting a pulsed chirp scheme can reduce the power consumption and preserve a high resolution by managing the spatial resolution in terms of the frequency modulation bandwidth. A pulsed signal enables the transmitter to be turned off in the listening time of the echo, thereby significantly reducing the energy consumption [37]. Using a millimeterwave radar and a typical white cane, a method of electronic travel assistance for blind and visually impaired persons was proposed [52]. It is a sophisticated system that not only warns the user of possible difficulties but also distinguishes between human and nonhuman targets. Because real-world situations are likely to include moving targets, a novel range alignment approach was developed to detect minute chest movements caused by physiological activity as vital evidence of human presence. The proposed system recognizes humans in complicated situations, with many moving targets, giving the user a comprehensive set of information, including the presence, location, and type of the accessible targets. The authors used a 122 GHz radar board to carry out appropriate measurements, which were used to demonstrate the system's working principle and efficacy.

### 2.1.6. Liquid Detection Sensors

Research usually involves more than one type of sensor in order to cover most of the prevalent challenges facing the visually impaired. Ikbal et al. [53] proposed a stick that is equipped with various kinds of sensors to assist in detecting obstacles. One of the major obstacles that jeopardize the visually impaired is water on the floor [54]. Therefore, the

authors included a water sensor in their solution, in addition to two ultrasonic sensors to detect 180 cm obstacles, including one IR sensor to detect stairway gaps and holes on streets, and a temperature sensor for fire alert. The authors connected all the sensors with an Arduino microcontroller board. This sensor must come into contact with the surface of the water in order to provide the result; thus, this method must consider the appropriate wearable. One of the most important uses of a liquid detector for the blind is the use of a sensor that is placed on the cup to prevent it from spilling. To improve navigation safety, the authors present a polarized RGB-Depth (pRGB-D) framework to detect the traversable area and water hazards while using polarization-color-depth-attitude information [55].


*4.3. Pros and Cons of Using Eye-Gaze AT in Communicative Interaction*

This study demonstrated that EGAT could provide opportunities for children with complex needs to initiate a conversation with minimal movements and engage in a wider range of communication demands, for instance, providing explicit information to others or making comments where the natural modes of communication could not be achieved. Increasing communication intelligibility could also reduce the burden of guessing for communication partners and make the co-construction of conversation easier. This innovative

technology on the children's interactions with others could enhance a child's control in communication and potentially increase the long-term opportunities in social participation.

Despite the advantages, the severe motor impairments in children/youths with complex needs necessitate assistance from communication partners to set up an eye-gaze controlled computer and adapt AAC content to meet their changing needs in communication [16]. Moreover, these children might take a longer time to operate/navigate computers compared with using gestures or vocalizations, particularly when they are novice users. Insufficient eye control skills at early stages of learning and cognitive demands might cause the children to tire easily which could decrease the efficiency of EGAT use over time [48]. Recent research showed children with complex needs normally used EGAT for up to two hours per day [17], which means they might use other modes of communication in communicative interactions in daily contexts more often. It is important to develop strategies and means for increasing the frequency that children are exposed to EGAT every day, i.e., embed opportunity to use EGAT in everyday activities in natural contexts, according to a newly developed clinical guideline [49]. As of today, the time spent using EGAT is too low to allow children to use the whole communicative potential.

As AAC is certainly multimodal [13], children/youths utilize multiple communication methods, by which they think fast and efficiently to fulfill communication needs depending on the communication contexts and demands. This study supported previous research [5,14,15] by showing these children demonstrated preferences using gestures or vocalizations in communicating social routines such as greetings, responding yes–no answers, or expressing affection, probably because these natural modes might be faster and more accessible for them. Thus, the findings indicated the importance of supporting their functional use of the multimodal approach in everyday contexts [50] and echoed the statement by Light and McNaughton [23] that the central focus of AAC intervention is the communication needs of children/youths with complex needs, rather than the devices.


The Role of Friction on Metal Forming Processes

*Luis Fernando Folle, Bruno Caetano dos Santos Silva, Gilmar Ferreira Batalha and Rodrigo Santiago Coelho*

#### **Abstract**

The friction that occurs in forming processes plays a fundamental role in the industry as it can be responsible for both manufacturing failure and its success. Scientific research has been done to try to understand this phenomenon as well as simulation software has been implemented aiming to predict the tribological behavior of the metallic pair in contact. Thus, this chapter is dedicated to the analysis of the main parameters that can influence the coefficient of friction, especially for metal manufacturing processes. Some simulation models that try to predict the behavior of friction under certain conditions of process speed, contact pressure and operating temperature will also be presented.

**Keywords:** metal forming process, friction coefficient, shear friction factor, Tribological Modeling and simulation, friction test, Tribological parameters

#### **1. Introduction**

The plastic deformation manufacturing area can be divided into two large sets, massive forming (which includes the processes of rolling, forging, extrusion, and wire drawing) and sheet forming (which includes bending, cup drawing, shearing and miscellaneous processes). This can be seen schematically in **Figure 1**. The main difference between these two sets lies in the dimensions of the final part after it is processed. In terms of dimensions in the Cartesian plane, a sheet has two dimensions much larger than the third and in massive forming there is no definable difference between the dimensions in the Cartesian plane. For each of these large groups, friction has a characteristic behavior due to both applied force levels and strain levels. Generally, when talking about sheet processes, considering the same material, both the strains and the applied forces are smaller because there is not much material in the thickness to generate a great resistance against the load application.

For all these processes illustrated above, friction will occur, since there will always be contact between two or more surfaces and eventually a lubricant between them. Friction occurs when there is contact between a (forming) tool and the material being deformed.

In general, friction is associated with a negative aspect of forming processes (energy consumption, tool wear, increased forming force, increased tool temperature, etc.). However, this is not always the case. In some processes such as rolling, friction is fundamental for the material to be "holding" by the cylinders. Even in sheet forming, friction plays a fundamental role in preventing defects such as wrinkling.

#### **Figure 1.** *Classification of metal forming operations. Source: Groover [1].*

So that excessive friction is not the agent causing defects, a lubricating film is used between the contact surfaces. In industrial processes, it is normal to use excess lubricating oils to avoid problems such as die wear. However, with the demand for cleaner manufacturing processes so as not to harm the environment, the use of lubricating oils must be reduced or replaced with another one with non-harmful components or even eliminated. In this way, there are studies which focuses on the lubricant free forming using tools with structured or textured surfaces (**Figure 2**), as can be understood in more detail in the studies carried out by [2–4].

In the case of cold forming, liquid lubricants are generally used. In the past, the use of animal fats and natural oils was common, nowadays the use is concentrated in mineral oils. The exact physical principle that governs the behavior of these lubricants is not yet fully known, but their application always brings improvements to the process, such as:

Consequently, the control of friction levels plays an important role in the distribution of stresses and strains. A very low friction coefficient can generate fixing *The Role of Friction on Metal Forming Processes DOI: http://dx.doi.org/10.5772/intechopen.101387*

**Figure 2.** *Conceptual model of different structured test tool surfaces [2].*

problems, promoting the appearance of geometric defects such as shape distortions. In sheet forming, for example, the friction force between the sheet press and the die must be high enough to obtain the desired plastic deformations, avoiding the wrinkling of the sheet. On the other hand, a very high friction force will promote wear of the surfaces in contact, which can lead to the appearance of cracks in the final product. Therefore, it is very important to control the friction levels in forming operations.

In the forming processes, it is well known that the success to obtain a part depends on three main factors: the geometry of the tools, the material properties of the piece and the interaction between the contact surface of these two materials. It is also known that the costs associated with the third factor represent around 5% of the final production value of the part. As such, any friction-related improvement in sheet forming can generate immediate payback for manufacturers. Decreasing the friction on the forming process can contribute to a lesser wear on the tools, thus increasing their useful lives, as well as representing a reduction in the required presses forces and, consequently, an increase in the energy efficiency of the forming process.

With the emergence of stricter environmental laws and the tendency to manufacture parts with zero waste, it will be necessary to create more efficient manufacturing methods that operate with highly reduced wastes. In this aspect, numerical simulation can contribute considerably, offering fast solutions that are very close to reality, that is, they can predict failures in the manufacture of parts without these being physically created. Within this context, a critical area is the measurement of

friction in forming, where the methods created so far sometimes fail to adapt to what happens in practice.