**1. Introduction**

Sustainable stormwater management has been and still is a long-time issue in urban drainage systems. In addition to potentially causing adverse impacts on wastewater treatment operations in traditional combined systems [1], flooding during storm events has always been a common problem in urban areas: in fact, almost every city, regardless of the type of sewer network, is potentially vulnerable to this phenomenon, whose frequency has exacerbated due to the increased intensity and recurrence of extreme hydro-meteorological events linked to long term climate variability. Increases in impervious urban surfaces, poor resiliency of urban drainage system design and increased frequency of downpours in urban areas can increase peak storm runoff with corresponding impact on human life and health, property and water security. The Intergovernmental Panel on Climate Change (IPCC) reported that the number of heavy precipitation events has significantly increased in inland areas worldwide [2]. Climate indicators for the last decades show generalized statistical increase of event-specific maximum precipitation in many cities [3,4]. In addition, extreme hydro-meteorological events impact on the physical, chemical and biological parameters of water in urban water bodies, both through direct runoff, and separate or combined sewer overflows (CSOs) [5]. Pollutants conveyed by storm flows in addition to organic matter include pathogens (Fecal Indicator Bacteria, FIB), nutrients, metals and emerging contaminants [6,7], the latter often at low level concentrations, which are difficult to monitor by traditional means [8].

Safe urban stormwater management is becoming a major concern: the conventional approach based on piped drainage is currently criticized as poorly efficient as, only partly effective during meteorological extremes, it does not eliminate environmental problems [9]. In the 1980s, structurally intensive approaches were proposed such as the "deep tunnel" concept: large, underground collectors designed to relieve urban sewer systems from excess stormwater flow and curtail overflow frequency. These systems were built in large cities in the U.S. (e.g., Milwaukee, Chicago, Boston, Atlanta) and around the world (e.g., Hong Kong, Guangzhou, Singapore) [10,11]. In addition to the high cost involved (the deep tunnel project in Milwaukee, one of the first of this kind, required 14 years, at a cost in excess of US\$2.3 billion, to complete [12]), the features of these systems may raise unexpected management challenges [13]. Furthermore, their operation requires high energy inputs for pumping and subsequent treatment of dilute sewage, increasing the already high greenhouse gases (GHG) emission footprint of water systems [14].

While these may have proven use in large urban areas, this approach may not be fully resolutive for the targeted impacts. Low-tech, more sustainable methods in accordance with the EU Water Framework Directive (WFD) [15] may be effective in many cases, especially in smaller urbanizations [16]. Sustainable storm water management should promote source control methods at, or nearby, the source. The most effective approach, which could successfully complement technologically-intensive approaches, consists of trapping stormwater and storing it into temporary impoundments for evaporation or ground infiltration. Rain and roof gardens, grassy swales or ditches (bioswales and bioretention basins) and permeable pavements could be highly beneficial [17]. Many mitigation measures are also being proposed to increase urban systems' resilience against floods [5,18]. These include discharge separation at source [19], local water reuse [20] and implementation of decentralized water management [21]. Modern stormwater management requires separation of rainwater from sewage, providing a higher level of service and benefits such as: elimination of CSOs, pollution prevention and possible use of stormwater as an alternative resource.

Sustainable storm water management is connected with so-called blue-green infrastructure (BGI). BGI foresees the implementation of either natural or man-provided solutions to enhance management of water resources and water infrastructure and services risk resilience. Innovative fiscal and non-fiscal tools, which may include payment for ecosystem services schemes [22], may be introduced to encourage their implementation on public and private property [23]. These practices are described in the literature under various labels, such as Low Impact Development (LID) [24], nature-based solutions (NBS) [25] or Sustainable Urban Drainage Systems (SUDS) [26]. All reduce the impact of constructed impervious surface areas (ISA) and of their hydrological and ecological disturbances. A generally accepted scale to assess ISA impact on urban watersheds indicates stress conditions, with ISA between 1% and 10%, impacted if between 10–25% and degraded if greater than 25% [27]. The global ISA average is estimated at 93 m2 per person. As a comparison, ISA in Poland is about 110 m2 /person, similar to other European countries (Germany, Italy, the United Kingdom, the Czech Republic, Hungary, Austria, Switzerland, Bulgaria, Slovakia, and Denmark) with ISAs around 100-150 m2 /person. In France, Portugal, Belgium, Ireland, Sweden and Spain, ISA is between 150–220 m2 /person, in the USA, close to 300 m2 /person, and in China around 68 m2 /person [28].

This article presents two case studies of sustainable stormwater management practices in small urban developments in Polish catchments, respectively concerning: (1) on-site retention and reuse, and (2) rainwater infiltration gardens. The aim of the analysis of the two approaches is to highlight

their application's sustainability, considering also related legal and economic aspects. With this objective, a simple cost-benefit analysis and a general discussion on urban stormwater management are also presented. *Sustainability* **2020**, *12*, x FOR PEER REVIEW 3 of 19


**2. Study Area**

The study area is the Corso del Popolo district, located in the historical city centre of Terni, Central Italy (Figure 1). Terni (city centre coordinates 42.56◦ N, 12.64◦ E) has about 112,000 inhabitants, covers an overall area of 212 km2, and its average altitude is 130 m above mean sea level. The city is quite far from the sea, and is located in a flat valley surrounded by mountainous areas; it has a temperate climate typical of mid-latitude regions, with hot, humid and poorly ventilated summers. The selected zone of Corso del Popolo (Figure 2) covers a surface of 300 × 300 m: The Universal Transverse Mercator (UTM) WGS84 coordinates (33T zone) are: longitude range (m E): 306,690–306,990 and latitude range (m N): 4,714,300–4,714,600.

Terni is an average Italian city characterized by an industrial texture at the top of the national table in the manufacturing of iron and steel and the production of electricity. From the second half of the 19th century, Terni underwent a transformation from a historic town, still structured along the lines of the urban layout of the ancient Roman town, into a dynamic industrial city.

The analysed district is an example of urban texture change planned in the framework of the regeneration of the ancient part of Terni following urban sustainable criteria (projected by Mario Ridolfi and Wolfgang Frankl architects) [27]. The construction interventions, between the Nera riverside and Corso del Popolo Street, started in 2006 and were completed in June 2014. Before 2006, a paved car park (with light-coloured asphalt) with perimetral trees was present. The new zone consists of a private area (seven buildings for residential, commercial and managerial end use) and a public area (a three-level underground car park with 1036 parking spaces, a building of 7000 m2 with parking used as municipal offices, subway, green areas, underground roadway and a pedestrian bridge).

**Figure 1.** (**a**) Terni location (city centre coordinates 42.56◦ N, 12.64◦ E); (**b**): the new built-up area of Corso del Popolo, picture from [27].

**Figure 2.** (**a**) Regione Umbria (RU) image of Corso del Popolo district on 2005 [28] selected area of 300 × 300 m; (**b**) Google Earth (GE) image on 2015. Universal Transverse Mercator (UTM) WGS84 coordinates (33T zone): longitude range (m E): 306,690–306,990, latitude range (m N): 4,714,300–4,714,600.

The main idea of this operation, embracing an area approximately 4 acres large, is the regeneration of the historical centre of the town integrating it with the neighbour river zone (named "Città Giardino") through both the partial covering of the local roadway and the construction of a pedestrian bridge. The Municipality of Terni chose the project financing system as the most appropriate way to realize

the interventions, applied for the first time to an urban area (with both private and public buildings) instead of a single public work. Some environmentally friendly materials were used in the building construction [27]. Figure 3 reports the main external materials employed in the new area.

**Figure 3.** Main external materials used in the new study area.

The brown zones in Figure 3 (lawn finish) correspond to the green spots of Figure 2b.


**2.2. Nanoparticle formation for organic molecules in water**

Laser ablation of organic molecules was performed with dispersed mixture of organic molecules in the distilled water in quartz cuvette of 1 × 1 × 5 cm3 at a concentration in the range from 2 × 10−2 to 5 × 10−5 mol/l. The microcrystals in suspension were irradiated by laser pulses for a few minutes. The wavelengths of the irradiated laser pulse were selected corresponding to absorption band of molecules. Here, results for two materials are presented; a yellow pigment quinacridone quinone (QQ, Aldrich) was irradiated at the wavelength 430 nm, and rubrene (Rb, Aldrich, sublimated grade) was irradiated at 520 nm. More details of preparation procedure were described in Refs. [34, 35].

Post-irradiated solution was investigated by UV-VIS absorption measurement with a conventional system (JASCO, V-560) and a dynamic light scattering (DLS) measurement (HORIBA Scientific, nanopartica, or Otsuka Electronics, Photal). The mode diameter, which indicates the most frequent diameter of nanoparticles in the ensemble, was employed to estimate the size of particles. Dried nanoparticles in deposited films were visualized by an atomic force microscopy (AFM) (SII, SPA400) and the transmission electron microscopy (TEM) (JEOL, 2000EX). Surface electric potential on the nanoparticles was obtained by a ζ-potential measurement (HORIBA Scientific, nanopartica, or Otsuka Electronics, Photal). A film of the QQ nanoparticles was prepared on a glass substrate covered by an indium-tin-oxide (ITO) transparent electrode by the electrophoretic deposition (EPD) method, and its UV-VIS absorption spectrum was compared with that of a vapor-deposited film of QQ with a thickness of 46.5 nm and that of solutions.

Time-resolved EPR measurement was carried out in QQ 2-methyltetrahydrofuran solution at 90 K and C60 toluene solutions at 100 K by the excitation at 430 and 532 nm, respectively, with an instrument (Bruker, ELEXSYS E580).

### **2.3. Gas generation via laser ablation of carbon materials in aqueous solution**

In the laser ablation of carbon in aqueous solution, binchotan charcoal powder of a mean diameter 5 μm (A, Latest Coop., Wakayama, Japan), high-grade carbon powder of a mean diameter 5 μm (B, SEC, SCN-5, 99.5%), and graphite powder of a mean diameter less than 45 μm (C, Wako, 072-03845) were used. Surface area of powder was measured by the BET method developed by Brunauer, Emmett, and Teller. The mixture of the powder and distilled water was irradiated by an unfocused beam (6.2 mm in diameter) of laser pulses for 30 or 60 min. The wavelengths of the laser pulses were selected in the VIS-near-infrared (NIR) region. The generated gas was collected by the water displacement method. The collected gas volume was measured with a scale on a tube at a resolution of 0.05 mL.

Gas components were analyzed by quadrupole mass spectrometry (Nuclear Engineering Co., Ltd., Ibaraki, Japan) for gases generated under argon atmosphere. The gas components were compared with two gas samples generated from binchotan powder in 100% distilled water and in 50% ethanol aqueous solution. The portion of molecules N2, CO, and C2H4 of the same molecular mass at 28 was determined by filtered partial presser measurements and mass fragments at N and C in quadrupole mass spectrometer. More details of preparation procedure were described in Refs. [20, 21].

During the hydrogen generation, optical radiation from the irradiated site was observed for a commercial binchotan charcoal block and a carbon electrode block (99.9%) in distilled water (H2O) or in 50% ethanol aqueous solution (EtOH/H2O). The block was irradiated by loosely focused nanosecond laser pulses (5 ns, 10 Hz, 532 nm) with a laser beam size of 0.50 × 0.25 cm2 . The emission spectrum was detected using an intensified charge-coupled device (ICCD) (Roper Scientific, PI-MAX) attached to a monochromator (Acton, 300i) with 4 nm spectral resolution. Strong light scattering was blocked by a super notch filter designed for 532 nm incident light. More details of preparation procedure were described in Ref. [36].

Post-irradiated solutions and ablation products were investigated by UV-VIS, DLS, and TEM methods, similar to the organic nanoparticles as mentioned in Section 2.2. In addition, FT-IR spectrum of dried carbon-based nanoparticles deposited on a pure silicon substrate was observed.


**2. Atmospheric pressure ionization**

Ionization in atmospheric ionization sources occur at atmospheric pressure and ions then gets transferred into the vacuum. As the liquid completely converts in to gas phase in the ionization source, those ionization techniques that use atmospheric pressure ionization are more convenient to hyphenate with liquid chromatography. These ionization techniques include electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), and atmospheric pressure photoionization (APPI) and are most widely used. Additionally, MALDI that also uses atmospheric pressure ionization is getting popular with its unique feature in performing mass spectrometry imaging (MSI) and analysis of large molecules [18]. Also, other ionization techniques such as desorption electrospray (DESI) or direct analysis in real time (DART) are becoming popular for the analysis of surface or solid samples [19, 20]. However, their applications in the field of drug metabolism and pharmacokinetics are very limited.

**41**

**Figure 1.**

*Mechanism of electrospray ionization process.*

molecules.

**2.2 Atmospheric pressure chemical ionization (APCI)**

In atmospheric pressure chemical ionization, unlike ESI, sample evaporation occurs first, followed by ionization in gas phase through corona discharge needle (**Figure 2**) [25]. The ionization principle is mostly similar to chemical ionization; however, it occurs at atmospheric pressure. APCI-MS can also be called as masssensitive detector, as the higher flow that goes in to ionization source, the higher will

*Mass Spectrometry as a Workhorse for Preclinical Drug Discovery: Special Emphasis on Drug…*

In ESI, analytes initially get charged with the assistance of electrical energy and charged ions transfer from solution to gaseous phase, before subjecting to mass spectrometric analysis. Ionic species in solution can be analyzed as such, whereas neutral compounds can be converted to ionic species and studied by ESI-MS. Electrospray ionization occurs in four stages: 1) charging of analytes in the capillary tube 2) formation of fine spray of charged droplets 3) solvent evaporation 4) columbic explosion/Rayleigh scattering of ions from the droplet (**Figure 1**). The liquid effluent moves from liquid chromatography to the mass spectrometer through a fused silica capillary maintained at voltage of 2.5–6.0 KV. In negative mode, to avoid discharge the range is lower (3–4 KV) than positive mode. ESI is a condensed phase ionization process and the ions have to be already present in solution. To generate ions, the pH has to be adjusted in such a way that ionizable groups are either protonated or deprotonated. In some cases, neutral molecules can be analyzed by the formation of adducts with ions such as ammonium, sodium, potassium, acetate or silver. Charged droplets undergo nebulization in the presence of nebulizer gas. After nebulization, charged droplets further reduce in size with the assistance of heat and breakdown in to minute droplets. Finally, as the droplets grow smaller and smaller, ions get released in to gaseous phase by a mechanism called rayleigh scattering/columbic explosion. The emitted ions are sampled by a sampling skimmer cone and are then accelerated into the mass analyzer for subsequent measurement of molecular mass and ion intensity [21–24]. An important characteristic of ESI-MS is it works as a concentration-dependent detector, which means MS response is directly proportional to concentration of analyte. Hence, irrespective of flow rate of mobile phase post column to the ionization source, response remains the same as long as the source-gas conditions are optimal for the flow rate. ESI technique is suitable for the analysis of polar to moderately polar

*DOI: http://dx.doi.org/10.5772/intechopen.88385*

**2.1 Electrospray ionization (ESI)**

*Mass Spectrometry as a Workhorse for Preclinical Drug Discovery: Special Emphasis on Drug… DOI: http://dx.doi.org/10.5772/intechopen.88385*


**9. Conclusion**

Depression and anxiety are commonly reported among university students globally, and it is rife with suicide rates escalating daily, especially in developing countries. Students' environment is a stressful one that often bears mental health issues. Students' quality of life and psychosocial well-being upon adjusting and adapting well to the lifestyle, academic challenges, and stressors lead to depression and anxiety. Therefore, programs targeting families, friends, community members, and students are essential. Given the gap in knowledge about what depression and anxiety are among rural communities, it is recommended that programs focus on educating people and equipping them to understand, which will allow them to identify and sufficiently support those suffering from mental health illnesses. In addition, existing wellness programs in higher education institutions that target students must be continuous, and social media platforms must also be maximized for their capacity to reach students at ease. The potential for students to achieve their goals will increase when their mental health is at its optimal functioning, consequently reducing the health burden caused by depression and anxiety.


Preface

Chapter 8 **A Unified Approach to Analysing the Anisoplanatism of**

**Adaptive Optical Systems 191** Jingyuan Chen and Xiang Chang

**VI** Contents

For over four decades there has been continuous progress in adaptive optics technology, theory, and systems development. Recently there also has been an explosion of applications of adaptive optics throughout the fields of communications and medicine in addition to its original uses in astronomy and beam propagation. This volume is a compilation of research and tutorials from a variety of international authors with expertise in theory, engineering, and technology.

The first section, Integrated Adaptive Optics Systems, contains a chapter by Zoran Popovic, Jörgen Thaung, Per Knutsson and Mette Owner-Peterson from Sweden that describes in great detail the challenges, system development, and success of high resolution retinal imag‐ ing. The second chapter in this section, Deqing Ren and Yongtian Zhu from China present a design and detailed performance analysis of a solar adaptive optics system.

The second section, Devices and Techniques, goes into more detail in various areas. Bonora, Zawadzki, Naletto, Bortolozzo, Residori describe a number of algorithms to assist an adap‐ tive optics system that does not directly use wavefront sensors. The Italian team show the principle applied to a number of applications such as conventional imaging, optical coher‐ ence tomography, and laser processing.

A broad tutorial chapter by Chinese reseachers Xuan, Cao, Mu, Hu, and Peng presents an overview of liquid crystal technology with the applications to wavefront correction. The chapter describes many of the benefits as well as the limitations of liquid crystals with sup‐ porting theory and analysis.

Over the past 20 years, micromachined deformable membrane mirrors have been advancing rapidly, and because of their low cost, they have become commonplace. Europeans Thomas Ruppel et al. present a chapter to bring us up to date on the technology, manufacture, and applications of the devices.

The final chapter of this section by Aubailly and Vorontsov discusses the limitations of con‐ ventional adaptive optics in terms of field-of-view and anisoplanatism. Then the American collaborators present a novel approach the does not use a wavefront measurement alone, but rather a measure of the entire received complex electromagnatic field to synthesize the images.

The third and last section to the volume, Optical and Atmospheric Effects, explores the ap‐ plication of adaptive optics to complex wave phonomena. Russian researchers Garanin, Starikov, and Malakhov present a discussion of optical vortices, showing how they appear in actual atmospheric propagation. Through analysis and simulation, the authors devote the better part of the chapter to describe sensing the vortices and applying a phase correction.

The final chapter, by Jingyuan Chen and Xiang Chang of Yunnan Observatory in China, ad‐ dresses the problem of combined and coupled effects of various types of anisoplanatism. Rigorous analysis is used in a number of special cases to provide guidelines for analyzing system performance and designing telescope concepts.

> **Robert K. Tyson, Ph.D.** University of North Carolina at Charlotte, North Carolina, USA

**Section 1**

**Integrated Adaptive Optics Systems**

**Integrated Adaptive Optics Systems**

in actual atmospheric propagation. Through analysis and simulation, the authors devote the better part of the chapter to describe sensing the vortices and applying a phase correction. The final chapter, by Jingyuan Chen and Xiang Chang of Yunnan Observatory in China, ad‐ dresses the problem of combined and coupled effects of various types of anisoplanatism. Rigorous analysis is used in a number of special cases to provide guidelines for analyzing

**Robert K. Tyson, Ph.D.**

North Carolina, USA

University of North Carolina at Charlotte,

system performance and designing telescope concepts.

VIII Preface

**Chapter 1**

**Dual Conjugate Adaptive Optics Prototype for Wide**

Retinal imaging is limited due to optical aberrations caused by imperfections in the optical media of the eye. Consequently, diffraction limited retinal imaging can be achieved if optical aberrations in the eye are measured and corrected. Information about retinal pathology and structure on a cellular level is thus not available in a clinical setting but only from histologi‐ cal studies of excised retinal tissue. In addition to limitations such as tissue shrinkage and distortion, the main limitation of histological preparations is that longitudinal studies of dis‐

Adaptive optics (AO) is the science, technology and art of capturing diffraction-limited im‐ ages in adverse circumstances that would normally lead to strongly degraded image quality and loss of resolution. In non-military applications, it was first proposed and implemented in astronomy [1]. AO technology has since been applied in many disciplines, including vi‐ sion science, where retinal features down to a few microns can be resolved by correcting the aberrations of ocular optics. As the focus of this chapter is on AO retinal imaging, we will

The general principle of AO is to measure the aberrations introduced by the media between an object of interest and its image with a wavefront sensor, analyze the measurements, and calculate a correction with a control computer. The corrections are applied to a deformable mirror (DM) positioned in the optical path between the object and its image, thereby ena‐

Modern telescopes with integrated AO systems employ the laser guide star technique [2] to create an artificial reference object above the earth's atmosphere. Analogously, the vast ma‐

> © 2013 Popovic et al.; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2013 Popovic et al.; licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

ease progression and/or results of medical treatment are not possible.

focus our description to this particular field.

bling high-resolution imaging of the object.

**Field High Resolution Retinal Imaging**

Zoran Popovic, Jörgen Thaung, Per Knutsson and

Additional information is available at the end of the chapter

Mette Owner-Petersen

http://dx.doi.org/10.5772/53640

**1. Introduction**


**5. Conclusions**

This study sheds light on the utilization of telehealth and access to healthcare services. The result of the present study confirms the outcome of the previous studies [14,22,23]. There will be an increasing demand for initiatives to improve telehealth benefits or use among patients as more information about the benefits and consequences of using telehealth becomes available. Policymakers appeared to be reacting to the impending pandemic's uncertainty as COVID-19 spread. Considering our findings, policymakers should think about making these temporary telehealth policies permanent in the event of another epidemic. To better prepare patients for future and unanticipated hurdles to in-person healthcare, authorities should consider adopting rules that favor the growth of telehealth services, such as specialized care. Owing to the potential benefits of telehealth services, policymakers should conduct additional analyses before devising strategies for managing future and unexpected obstacles that prevent patients from receiving in-person treatment.

**Author Contributions:** Study design: H.Y.H., N.M.A.Z. and J.X.; funding acquisition N.M.A.Z.; data collection and analysis: D.I.A., M.S.O. and M.G.A.; manuscript writing: H.Y.H., N.M.A.Z., J.X., D.I.A., M.S.O. and M.G.A.; agrees to be accountable for all aspects of work: H.Y.H., N.M.A.Z., J.X., D.I.A., M.S.O. and M.G.A. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by AlMaarefa University, grant number TUMA-2021-25.

**Institutional Review Board Statement:** Institutional Review Board Statement: The study was conducted according to the guidelines of the Declaration of Helsinki and approved by the Institutional Review Board (or Ethics Committee) of AlMaarefa University (protocol code 2021-25).

**Informed Consent Statement:** Informed consent was obtained from all subjects involved in the study.

**Data Availability Statement:** The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.

**Acknowledgments:** The authors would like to express their gratitude to AlMaarefa University, Riyadh, Saudi Arabia, for providing funding to this work under TUMA project grant number (TUMA-2021-25).

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

## **References**


**7.3. Ablation efficiency in different environments**

**7.2. Ablation rate in different environments**

environment.

(0.51 and 0.43%, respectively) [67].

implies that less sample is vaporized' [23].

and (b) as a function of water level at a fixed laser fluence (0.22 J/cm2

The rate at which materials are ablated is also different in different environments. This may be due to different ablation mechanisms and ablation thresholds. Ben-Yakar and Byer [67] showed that in the case of single-shot laser ablation, the ablation threshold in air is lower than that in a vacuum. The reason for this may be due to the modified absorption process because air may accelerate the ablation chemistry; due to air resistance, the hot plasma expands at a slower speed in comparison with that in a vacuum. On the other hand, in the case of multiple laser pulses overlapping, the resulting incubation effect reduces dependence on the processing

188 Applications of Laser Ablation - Thin Film Deposition, Nanomaterial Synthesis and Surface Modification

In air, ablation rate decreases with ablating deep holes because of the non-linear effect. The non-linear effect of laser ablation in air is due to localising the laser beam. This means that ablation products cannot escape the holes, which causes self-focusing of the laser pulses even at a power less than the critical power for self-focusing in ambient air. Based on these effects, it has been shown that the ablation efficiency in air is slightly higher than that in a vacuum

The effects of using a buffer gas on the ablation rate of Ti, W, Fe, Cu and Mo target materials at different fluencies have been studied. In general, the effect of He gas at 1000 mbar and air at 1 mbar is quite similar, so in both cases, the averaged ablation rate slightly increased; this effect is more acute with increasing laser fluence. In the case of Ar gas, the average ablation rate decreased because the absorption of the laser beam by the plasma is more considerable in comparison with this in He or in ambient air. This effect was found to be independent of the laser fluence. As a result, 'more absorption of the laser energy reaching the sample necessarily

**Figure 7.** (a) The ablation rate of Ag and Ti target materials as a function of laser fluence at a fixed water level (2 mm),

**Figure 7a** shows the ablation rate of Ag and Ti target materials as a function of laser fluence in deionised water at a fixed water level above the targets. A picosecond laser at *λ* = 1064 nm, *f* = 200 kHz, *v* = 30 mm/s, *t* = 1/2 h and a laser spot size = 125 μm was used to ablate the materials in deionised water. At lower laser fluencies, the ablation rates of both samples increased

).

It was expected that the ablation efficiency would be lower in a vacuum than that in air because in a vacuum less work is required for the hydrodynamic expansion of plasma in a non-resistant environment. However, a larger groove diameter can be obtained in air because the single-shot ablation threshold is lower in air. In addition, the ablation volume is slightly higher in air than in a vacuum because the ablation depth is determined by the optical penetration depth, which is independent of the processing environment [67]. The non-linear dependence of the ablation rate or productivity on the laser fluence in a vacuum with femtosecond-laser ablation of nickel was also observed [70].

It has been reported that the laser-ablation efficiency of nanosecond-laser pulses is similar in both a liquid environment and ambient air, but in the case of laser ablation by femtosecondlaser pulses, the ablation efficiency was higher in air in comparison with that in water [32]. The mass rate of nanoparticle generation in air (aerosol) was observed to be 100 times higher than in water (colloid) [71]. The laser-ablation efficiency was also influenced by the laser-spot size and the irradiation time [72]. It was also reported that the laser-ablation efficiency in the vacuum decreased with increasing laser fluence, caused by increasing the duration of the atomisation stage [73, 74]. Although laser ablation of materials depends upon their thermal properties, laser ablation is more effective in a liquid environment that in air. In addition, in air, the microparticles were notably distinct both near and far from the crater on the brass target. However, in water, the narrow distribution of nanoparticles away from the crater was also sound. It was concluded that water is a more suitable environment in which to produce uniform and large quantities of nanoparticles by laser ablation [11]. Hermann et al. [74] determined that the ablation depth of copper and gold in a vacuum chamber increased gradually at low laser fluence up to 0.5 J/cm2 , but that this figure increased considerably at high laser fluence.

The laser-ablation process is also used to clean the surfaces of materials. The effectiveness of laser-ablation cleaning methods on silver artefacts in different media (air, water and a vacuum) was characterised. Before cleaning the samples, they were treated with HCl (37%) solutions for several hours to simulate the formation of a chloride patina (AgCl) on marine archeological silver artefacts. It was shown that the patina was removed from a few to 300 μm in air and in water and removed completely under vacuum conditions. However, the formation of a white patina in air and water and an increasing amount of oxygen on the surface of the samples were observed during cleaning process. This situation shows that 'in ambient reach in oxygen laser ablation favourite the oxygen absorbance on surface and the formation of a thin layer of AgO which dulls the surface' [75]. This hypothesis is proven by unobserving surface tarnishing in a vacuum during laser ablation. It can be concluded that the optimal conditions in which to clean silver artefacts is under vacuum conditions [75].


**3.5. Natural frequencies**

Determination of the natural frequencies is similar to the determination of critical buckling load and the natural frequencies are found by solving the eigenvalue problem.

Natural frequencies of thin-walled structures were determined by solving a dynamic problem, which uses the approach proposed by Koiter in his asymptotic stability theory of conservative systems in the first-order approximation [52].

To determine the natural frequencies [55] of the structure the adopted equilibrium equations (26) contain cross-sectional inertia forces acting in the direction normal to the middle surface

of the plate (column wall) and in the middle plane of plate (i.e. .. *h u* 0 and .. *h v* 0).


**4. Conclusion**

Heavy metal pollution in water and soil has increased in the last few decades due to anthropogenic activities. For this reason, the issue of dealing with heavy metal pollution in environmental matrices still maintains its importance. Legal regulations are enforced by governments, and monitoring studies, assessment of environmental impacts, use of soluble and non-toxic compounds in environmental compartments (air, water, soil and plants) in industrial processes, heavy metalfree pesticides, appropriate wastewater treatment plants and renewable energy sources instead of fossil fuels are priority measures to reduce the concentrations of heavy metals in the environment. In addition, heavy metals, which cause serious health problems even at very low concentrations due to their long-term persistence, must be removed from receiving environments in order to protect the integrity of the ecosystem and human health. As a bioremediation approach, removing toxic wastes from the environment by using bioaccumulatory organisms such as plants or mussels maintains its importance among studies aimed at recovery. Studies have shown that integrated methods - especially the combination of suitable plants and microorganisms - are very effective in mitigating the effects of heavy metals in the environment.

*Environmental Impacts of Heavy Metals and Their Bioremediation DOI: http://dx.doi.org/10.5772/intechopen.95103*


*Edited by Adel Zaki El-Sonbati*

Thermoplastics can be used for various applications, which range from household articles to the aeronautic sector. This book, "Thermoplastic Elastomers", is comprised of nineteen chapters, written by specialized scientists dealing with physical and/or chemical modifications of thermoplastics and thermoplastic starch. Such studies will provide a great benefit to specialists in food, electric, telecommunication devices, and plastic industries. Each chapter provides a comprehensive introduction to a specific topic, with a survey of developments to date.

ISBN 978-953-51-0346-2

Thermoplastic Elastomers

Photo by ISMODE / iStock


*2.1. Assistive Navigation Systems for the VCP*

A review on relevant systems proposed until 2008 was presented in [18], where three categories of navigation systems were identified. The first category is based on positioning systems, including the Global Positioning System (GPS) for outdoor positioning, and preinstalled pilots and beacons emitting signals to determine the absolute position of the user in a local structured environment; the second is based on radio frequency identification (RFID) tags with contextual information, such as surrounding landmarks and turning points; and the third concerns vision-based systems that exploit information acquired from digital cameras to perceive the surrounding environment. Moreover, in a survey conducted in 2010 [19], wearable obstacle avoidance electronic travel aids for blind were reviewed and ranked based on their features. A more recent study [20] reviewed the state-of-the-art sensor-based assistive technologies, where it was concluded that most of the current solutions are still at a research stage, only partially solving the problem of either indoor or outdoor navigation. In addition, some guidelines for the development of relevant systems were suggested, including real-time performance (i.e., fast processing of the exchanged information between user and sensors and detection of suddenly appearing objects within a range of 0.5–5 m), wireless connectivity, reliability, simplicity, wearability, and low cost.

In more recent vision-based systems, the main and most critical functionalities include the detection of obstacles, provision of navigational assistance, as well as recognition of objects or scenes in general. A wearable mobility aid solution based on embedded 3D vision was proposed in [21], which enables the user to perceive, be guided by audio messages and tactile feedback, receive information about the surrounding environment, and avoid obstacles along a path. Another relevant system was proposed in [4], where a stereo camera was used to perceive the environment, providing information to the user about obstacles and other objects in the form of intuitive acoustic feedback. A system for joint detection, tracking, and recognition of objects encountered during navigation in outdoor environments was proposed in [3]. In that system, the key principle was the alternation between tracking using motion information and prediction of the position of an object in time based on visual similarity. Another project [2] investigated the development of a smart-glass system consisting of a camera and ultrasonic sensors able to recognize obstacles ahead, and assess their distance in real-time. In [22], a wearable camera system was proposed, capable of identifying walkable spaces, planning a safe motion trajectory in space, recognizing and localizing certain types of objects, as well as providing haptic-feedback to the user through vibrations. A system named Sound of Vision was presented in [5], aiming to provide the users with a 3D representation of the surrounding environment, conveyed by means of hearing and tactile senses. The system comprised an RGB-depth (RGB-D) sensor and an inertial measurement unit (IMU) to track the head/camera orientation. A simple smart-phone-based guiding system was proposed in [23], which incorporated a fast feature recognition module running on a smart-phone for fast processing of visual data. In addition, it included two remotely accessible modules, one for more demanding feature recognition tasks and another for direction and distance estimation. In the context of assisted navigation, an indoor positioning framework was proposed by the authors of [24]. Their positioning framework is based on a panoramic visual odometry for the visually challenged people.

An augmented reality system using predefined markers to identify specific facilities, such as hallways, restrooms, staircases, and offices within indoor environments, was proposed in [25]. In [26], a scene perception system based on a multi-modal fusion-based framework for object detection and classification was proposed. The authors of [27] aimed to the development of a method integrated in a wearable device for the efficient place recognition using multimodal data. In [28], a unifying terrain awareness framework was proposed, extending the basic vision system based on an IR RGB-D sensor proposed in [10] and aiming at achieving efficient semantic understanding of the environment. The above approach, combined with a depth segmentation method, was integrated into a wearable navigation system. Another vision-based navigational aid using an RGB-D sensor was presented in [29], which solely focused on a specific component for road barrier recognition. Even more recently, a live object recognition blind aid system based on convolutional neural network was proposed in [30], which comprised a camera and a computer system. In [9], a system based on a Google Glass device was developed to navigate the user in unfamiliar healthcare environments, such as clinics, hospitals, and urgent cares. A wearable vision assistance system for visually challenged users based on big data and binocular vision sensors was proposed in [13]. Another assistive navigation system

proposed in [12] combined two devices, a smart glass and a smart pair of shoes, where various sensors were integrated with Raspberry Pi, and the data from both devices are processed to provide more efficient navigation solutions. In [11], a low-power MMW radar and an RGB-D camera were used to unify obstacle detection, recognition, and fusion methods. The proposed system is not wearable but hangs from the neck of the user at the height of the chest. A navigation and object recognition system presented in [31] consisted of an RGB-D sensor and an IMU attached on a pair of glasses and a smartphone. A simple obstacle detection glass model, incorporating ultrasonic sensors, was proposed in [15]. Another wearable image recognition system, comprising a micro camera, an ultrasonic sensor, an infrared sensor, and a Raspberry Pi as the local processor, was presented in [14]. On the one side of the wearable device were the sensors and the controller and on the other the battery. In [32], a wearable system with three ultrasonic sensors and a camera was developed to recognize texts and detect obstacles and then relay the information to the user via an audio outlet device. A similar but less sophisticated system was presented in [16].

A relevant pre-commercial system, called EyeSynth (Audio-Visual System for the Blind Allowing Visually Impaired to See Through Hearing), promises both obstacle detection and audio-based user communication, and it is developed in the context of a H2020 funding scheme for small medium enterprises (SMEs). It consists of a stereoscopic imaging system mounted on a pair of eyeglasses, and non-verbal and abstract audio signals are communicated to the user. Relevant commercially available solutions include ORCAM MyEye, a device attachable to eyeglasses that discreetly reads printed and digital text aloud from various surfaces and recognizes faces, products, and money notes; eSight Eyewear, which uses a high-speed and high-definition camera that captures whatever the user sees and then displays it on two near-to-eye displays enhancing the vision of partially blind individuals; and the AIRA system, which connects blind or low-vision people with trained, remotely-located human agents who, at the touch of a button, can have access to what the user sees through a wearable camera. The above commercially available solutions do not yet incorporate any intelligent components for automated assistance.

In the proposed system, barebone computer unit (BCU), namely a Raspberry Pi Zero, is employed, since it is easily accessible to everyone and easy to use, contrary to other devices such as Raspberry Pi processors. In contrast to haptic feedback or audio feedback in the form of short sound signals, the proposed method uses linguistic expressions incurring from fuzzy modeling to inform the user about obstacles, their position in space, and scene description. The human eye-fixation saliency used for obstacle detection provides the system with human-like eye-sight characteristics. The proposed method relies on visual cues provided only by a stereo camera system, instead of the various different sensors used in previous systems, thus reducing the computational demands, design complexity, and energy requirements, while enhancing user comfort. Furthermore, the system can be personalized according to the user's height, and the wearable frame is 3D printed, therefore, adjusting to the preferences of each individual user, e.g., head anatomy, and avoiding restrictions imposed by using commercially available glass frames.

#### *2.2. Obstacle Detection*

Image-based obstacle detection is a component of major importance for assistive navigation systems for the VCP. A user requirement analysis [17], revealed that the users need a system that aims to real-time performance and mainly detects vertical objects, e.g., trees, humans, stairs, and ground anomalies.

Obstacle detection methodologies consists of two steps: (a) an object detection step and (b) an estimation step of the threat that an object poses to the agent/VCP. The image-based object detection problem has been previously tackled with the deployment of deep learning models. The authors of [33] proposed a Convolutional Neural Network (CNN) model, namely Faster Region-Based CNN, that was used for real-time object detection and tracking [26]. In [3], the authors proposed a joint object detection, tracking and recognition in the context of the DEEP-SEE framework.  The system uses three CNN models, namely, the Faster Region-Based CNN [33], You Only Look Once (YOLO) CNN model [34], and Single Shot multi-box Detectors (SSDs) [35]. Nevertheless, the goal of the aforementioned methods was solely to detect objects and not to classify them as obstacles.

In another work, a module of a wearable mobility aid was proposed based on the LeNet model for obstacle detection [21]. However, this machine learning method treats obstacle detection as a 2D problem. A multi-task deep learning model, which estimates the depth of a scene and extracts the obstacles without the need to compute a global map with an application in micro air vehicle flights, has been proposed in [35]. Other, mainly preliminary, studies have approached the obstacle detection problem for the safe navigation of VCP as a 3D problem by using images along with depth information and enhancing the performance by exploiting the capabilities of CNN models [36–38].

Aiming to robust obstacle detection, in this paper we propose a novel, uncertainty-aware personalized method, implemented by our VPS, based on a GAN and fuzzy sets. The GAN is used to detect salient regions within an image, where the detected salient regions are then combined with the 3D spatial information acquired by an RGB-D sensor using fuzzy sets theory. This way, unlike previous approaches, the proposed methodology is able to determine the level of threat posed by the obstacle to the user and its position in the environment with linguistic expressions. In addition, the proposed method takes into consideration the height of the user in order to describe the threat of an obstacle more efficiently. Finally, when compared to other deep learning assisted approaches, our methodology does not require any training regarding the obstacle detection part.

#### *2.3. Object Recognition*

Although object detection has a critical role in the safety assurance of VCP, the VPS aims to provide an effective object and scene recognition module, which enables the user to make decisions based on the visual context of the environment. More specifically, object recognition provides the capability to the user to identify what type of object has been detected by the object detection module. Object recognition can be considered as a more complex module compared to object detection, since it requires an intelligent system that can incorporate the additional free parameters required to distinguish between the different detected objects.

In the last decade, object recognition techniques have been drastically improved, mainly due to the appearance of CNN architectures, such as [39]. CNNs are a type of ANNs that consist of multiple convolutional layers with neuron arrangement mimicking the biological visual cortex. This enables CNNs to automatically extract features from the entire image, instead of relying on hand-crafted features, such as color and texture. Multiple CNN architectures have been proposed over the last years, each one contributing some unique characteristics [17]. Although conventional CNN architectures, such as the Visual Geometry Group Network (VGGNet) [40], offer great classification performance, they usually require large, high-end workstations equipped with Graphical Processing Units (GPUs) to execute them. This is mainly due to their large number of free-parameters [40] that increase their computational complexity and inference time, which in some applications, such as the assistance of VCP, is a problem of major importance. Recently, architectures, such as MobileNets [41] and ShuffleNets [42], have been specifically proposed to enable their execution on mobile and embedded devices. More specifically, MobileNets [41] are a series of architectures, which by using depth-wise separable convolutions [43] instead of conventional convolutions, vastly reduce the number of free-parameters of the network, enabling their execution on mobile devices. The authors in [42] proposed the use of the ShuffleNets architecture by using point-wise group convolution and channel shuffling to achieve a low number of free-parameters with high classification accuracy. Both architectures try to balance the trade-off between classification accuracy and computational complexity.

CNNs have also been used for object and scene recognition tasks in the context of assisting VCP. In the work of [21], a mobility aid solution was proposed that uses a LeNet architecture for object

categorization in 8 classes. An architecture named "KrNet" was proposed in [29], which relies on a CNN architecture to provide real-time road barrier recognition in the context of navigational assistance of VCP. A terrain awareness framework was proposed in [28] that uses CNN architectures, such as SegNet [44], to provide semantic image segmentation.

In VPS, we make use of a state-of-the-art CNN architecture named Look Behind Fully Convolutional Network light or LB-FCN light [45], which offers high object recognition accuracy, while maintaining low computational complexity. Its architecture is based on the original LB-FCN architecture [46], which offers multi-scale feature extraction and shortcut connections that enhance the overall object recognition capabilities. LB-FCN light replaces the original convolutional layers with depth-wise separable convolutions and improves the overall architecture by extracting features under three different sizes (3 × 3, 5 × 5, and 7 × 7), lowering the number of free parameters of the original architecture. This enables the computationally efficient performance of the trained network while maintaining the recognition robustness, which is important for systems that require fast recognition responses, such as the one proposed in this paper. In addition to the low computational complexity provided by the LB-FCN light architecture, the system is cost-effective, since the obstacle recognition task does not require high-end expensive GPUs. Consequently, multiple conventional low-cost CPUs can be used instead, which enable relatively easy horizontal scaling of the system architecture.

#### **3. System Architecture**

The architecture of the cultural navigation module of the proposed VPS, consists of four components; a stereoscopic depth-aware RGB camera, a BCU, a wearable Bluetooth speaker device, and cloud infrastructure. The first three components are mounted on a single smart wearable system, with the shape of sunglasses, capable of performing lightweight tasks, such as risk assessment, while the computationally intense tasks, such as object detection and recognition, are performed on a cloud computing infrastructure. These components are further analyzed in the following Sections 3.1 and 3.2.


**Author details**

Muniyandi Balasubramanian

Centre for Ecological Economics and Natural Resources, Institute for Social and Economic Change, Bangalore, Karnataka, India

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© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


**6. Halides**

A halide has a binary form in which one region is a halogen and the other region is a component or radical that is less electronegative/electropositive than the halogen [65]. For preparing NLO halides, the physical, chemical, and crystallographic aspects are important. In halides, hyperpolarizabilities were used to find out the NLO susceptibilities. Moreover, these crystals have high LDT and good mechanical properties. HgBr2 crystal was grown using a lowering temperature technique with a size of about 15 × 15 × 1.5 mm3 [66]. Tl3PbBr5, Tl4PbI6, Tl4HgI6, and Tl3PbI5 were grown by the vertical Bridgman method [5]. The 3:1:5 ratio showed orthorhombic symmetry and the 4:1:6 ratio indicated tetragonal symmetry. In this method, they maintained the temperature gradients in the range from 20 K/cm to 30 K/cm and cooling rates were in the range from 5 to 10 K/h, which showed a growth of 1 cm/day and 3–5 cm/day. Tl3PbCl5 [67] and Tl3PbBr5 [68] single crystals were grown by Bridgman-Stockbarger technique. Tl3PbI5 is colorless and Tl3PbBr5 (**Figure 6**) crystal is a yellow color and transparent. Tl4HgI6 crystal is grown using Bridgman-Stockbarger method [69, 70] and they melt consistently at 396°C. The crystal was red and when the iodine concentration increases in the stoichiometric ratio, the crystal becomes changed to black. It belongs to the point symmetry group C4v. BaMgF4 crystal was grown using the Czochralski technique [71]. It belongs to the pyroelectric fluoride group BaMF4 (M = Mg, Co, Ni, Zn) and it has space group Cmc21. SrAlF5 crystal belongs to the class of uniaxial ferroelectric [72] and is grown using Czochralski technique [71]. Tl3PbCl5 and Tl3PbBr5 are nonhygroscopic. In Tl3PbBr5, the phase transition is observed at ~237°C, and for Tl3PbCl5, phase transition is noted at 171°C. Tl2HgI4 compound has a melting point temperature of 318°C.

HgBr2 crystal showed good phase matchable SHG efficiency, which is 10 times greater than that of KDP and has transparency between 2.5 and 25 mm. It covers the whole mid-IR range. Tl3PbCl5 and Tl3PbBr5 have transparency of 0.5–20 mm and 0.65–24 mm, respectively. The Tl4HgI6 crystal is optically positive and transparent vfrom 1.2 to 40 mm. BaMgF4 is a ferroelectric fluoride due to its wide transparency between 125 nm and 13 mm, and it can be used for UV and mid-IR optical applications [71, 72]. In the UV region, the shortest band is noted at 368 nm, which represents the potential behavior of BaMgF4 as a nonlinear material. It can be used for the production of all solid-state lasers and mid-IR wavelength areas. BaMgF4 and SrAlF5 crystals are promising crystals for solid-state lasers. The LDT value of the HgBr2 crystal is 0.3 GW/cm2 .

**Figure 6.** *Crystal of Tl3PbBr5.*


**3.1 Triphase interfaces**

In the liquid phase, air pockets are stuck with the rough topological surface of the superhydrophobic substrate, forming a triphasic solid–liquid-air interface. For photocatalytic reactions, this triphasic contact line usually serves as an active area for interfacial reactions and provides a vital clue to surface behavior. The oxygen supply from the air reacts with photogenerated electrons from the surface of the photocatalyst, producing oxidative reactive oxygen species (ROS) such as superoxide radicals (O2 •−) and hydroxide radicals (OH• ) and resulting in the degradation of organic pollutants (**Figure 4**). Especially, during organic pollutant degradation, the carbon bonds breaks the on the superhydrophobic surface and can show long-term stability. Practically, a superhydrophobic with long-term stability catalyst is required.