Preface

The growth and development of infants during the first two years of life are greatly influenced by nutrition. Meeting basic nutritional requirements is vital for proper and optimal growth and development, both physically and mentally. Infant feeding practice has greatly changed since the beginning of the last century. Many factors have influenced the rate of breastfeeding and the proper timing of complementary feed introduction. Poverty, world wars, the influx of women in the workforce, and the development of commercial infant formula are among these factors. Feeding during the first 1000 days of life is crucial for the growth and development of an individual and their long-term health outcomes. On many occasions, major nutritional problems such as obesity and undernutrition have been linked to nutrition during infancy. These problems not only affect the individual but also impact the future of developing countries. In four sections containing five chapters, this book discusses selected topics on infant feeding.

Chapter 1 by Jain et al. discusses the need for universal health care for all infants. The authors state that exclusively breastfeeding for the first six months, then for two or more years with proper weaning, is desirable. As such, the authors propose the 'ABC mothers' plan.

In Chapter 2, Masereka et al. discuss infant and young child feeding in developing countries. Infant feeding challenges continue to manifest in developed and developing countries. Worldwide, more than 80% of babies are breastfed in the first few weeks of birth. However, about 37%, 25%, and less than 1% are exclusively breastfed at 6 months of age in Africa, the United States, and the United Kingdom, respectively. These statistics are far below the World Health Organization targets of 50% by 2025 and 70% by 2030. Complementary feeding practices are varied as well due to non-adherence to infant and young child feeding guidelines among parents.

Chapter 3 by Manosalvas discusses the causes of policy failure to reduce chronic childhood undernutrition in Ecuador during a period of economic growth. The overall reduction of undernutrition from 1999 to the time of writing this chapter is 0.83 percent per year. Surprisingly, the period of highest GDP between 2006 and 2014, in which Ecuador exhibited economic growth of more than 4% of GDP per year on average, showed a lesser reduction in childhood malnutrition of only 0.2 percent per year. The author uses a mixed research strategy to explain this paradox.

Chapter 4 by Ka-Huen et al. discusses the issue of breastfeeding during the COVID-19 pandemic in Hong Kong. As new mothers are understandably concerned about COVID-19 and its high rate of infection, they are often unsure if they should breastfeed their infants. In general, hospitals do not allow direct breastfeeding by mothers with an active infection of SARS-CoV-2. Some neonatal units in Hong Kong maintain safe practices by isolating infants and mothers for at least 7 to 14 days,

even if the infant remains SARS-CoV-2 negative. During isolation, mothers encourage the expression of milk to maintain milk duct patency and to prepare for lactation when they and their infants are discharged.

Finally, Chapter 5 by Volf et al. presents the authors' original research on fat component safety and pre-clinical evaluation of the physiological effect of infant-adapted dry milk mixtures. The fat component is one of the key components of an infant's diet. Its important aspects are biological effectiveness and safety changes during processing, storage, transportation, and subsequent storage after opening the package. Consumption of oxidized fats leads to pathological changes in the organism.

We would like to thank all the contributing authors for their excellent chapters and for their patience and cooperation. Furthermore, I would like to express my gratitude and sincere appreciation to the staff at IntechOpen, especially Author Service Manager Iva Ribic for her assistance throughout the publication process.

#### **Isam Jaber AL-Zwaini**

Professor, Department of Pediatrics, AL-Kindy College of Medicine, University of Baghdad, Baghdad, Iraq

#### **Haider Hadi AL-Musawi**

Assistant Professor, Department of Pediatrics, AL-Kindy College of Medicine, University of Baghdad, Baghdad, Iraq

## Section 1


*Article* **Bidirectional Recurrent Neural Network Approach for Arabic Named Entity Recognition**

**Mohammed N. A. Ali 1, Guanzheng Tan 1,\* and Aamir Hussain 2**

Received: 28 October 2018; Accepted: 10 December 2018; Published: 13 December 2018

**Abstract:** Recurrent neural network (RNN) has achieved remarkable success in sequence labeling tasks with memory requirement. RNN can remember previous information of a sequence and can thus be used to solve natural language processing (NLP) tasks. Named entity recognition (NER) is a common task of NLP and can be considered a classification problem. We propose a bidirectional long short-term memory (LSTM) model for this entity recognition task of the Arabic text. The LSTM network can process sequences and relate to each part of it, which makes it useful for the NER task. Moreover, we use pre-trained word embedding to train the inputs that are fed into the LSTM network. The proposed model is evaluated on a popular dataset called "ANERcorp." Experimental results show that the model with word embedding achieves a high F-score measure of approximately 88.01%.

**Keywords:** Arabic named entity recognition; bidirectional recurrent neural network; GRU; LSTM; natural language processing; word embedding


*2.1.3. CD44*

[28]. Through *in vivo* lineage tracing experiments, these authors found that LGR5-positive cells were self-renewing and multipotent and were responsible for the renewal of the gastric epithelium. Interestingly, they observed that the transformation of this population of stem cells could drive gastric tumorigenesis *in vivo* [28], fact that has been strongly demonstrated more recently by Li and collaborators [29]. Consistently with the observation in mice, in human gastric tissue, LGR5 expression has also been found in the bottom of gastric glands [30]. Supporting the putative role of LGR5 as a gastric CSC regulator in humans, independent studies have reported LGR5 overexpression in human gastric cancer samples respect to normal gastric mucosa in a progressively increasing manner from well-differentiated to poorly differentiated gastric carcinomas [20, 31]. Furthermore, LGR5 expression has been strongly linked to a high degree of tumor infiltration, high TNM stage, recurrence and dismal prognosis of gastric cancer patients [18–20, 31]. More recently, Wang and collaborators have shown that sphere cells derived from a gastric cancer cell line presented increased expression of some canonical stem regulators, being LGR5 particularly elevated [32]. They also showed that ectopic LGR5 overexpression potentiated the sphere cell growth and cell migration capabilities of gastric cancer cells and also their tolerance to oxaliplatin, associating LGR5 expression with the characteristic features of CSCs [32]. These findings are in concordance with previous observations showing the impairment of the invasiveness and the reduction in the expression of metalloproteinase 2 (MMP2) and β-catenin in gastric cancer cells in response to LGR5 silencing *in vitro*; and revealing a positive correlation between the expression of LGR5 and MMP2 in gastric cancer tissue samples [20]. Regarding the implications of the carcinogenic agent *H. pylori* in the LGR5 positive cells in the stomach, it has been found that this population of cells is expanded in gastric cancer tissues affected by the bacteria, indicating that LGR5 likely represents a marker

of stem cells susceptible of oncogenic transformation driven by *H. pylori* [13, 33].

CD133 (also Prominin 1) is a pentaspan transmembrane glycoprotein present in embryonic epithelial structures, thought to function as an organizer of plasma membrane topology, and regulating the maintenance of the appropriate lipid composition within the plasma membrane [34]. CD133 has been presented as a marker of cancer stem cells in colon, pancreas, brain or lung cancer [35], yet its role in gastric CSCs is controversial. Several findings related to different aspects of gastric CSCs have been published in support of its role as a gastric CSC marker and regulator. In gastric cancer cell lines, CD133 silencing abrogates sphere formation capacity [36] and, consistently, CD133 has been found overexpressed in gastric sphere cultures [37, 38]. Noteworthy, a large number of publications show increased CD133 expression in human gastric cancer tissue respect to non-neoplastic gastric mucosa and highlight the prognostic significance of CD133, associating its overexpression with a big plethora of adverse clinic-pathological features, such as elevated cellular proliferation rates, high T stage, venous invasion, lymph node and distant metastasis, chemoresistance, recurrence, poor 5-year disease-free and overall survival and so on [37, 39–42]. According to this, studies performed in gastric cancer cell lines demonstrate that CD133-positive gastric cancer cells present a CSC phenotype, since they are more tumorigenic, more chemoresistant and exhibit higher migration or invasion capacities than CD133-negative cells [37, 38, 43]. However, some controversial findings have been published indicating that CD133 expression is not a *sine qua non* condition for gastric cancer cells

*2.1.2. CD133*

46 Gastric Cancer

CD44 is a transmembrane glycoprotein expressed on leukocytes, endothelial cells, hepatocytes or gastric epithelial cells, which acts as a receptor for hyaluronic acid (HA) [47] and can also interact with other ligands, such as osteopontin, collagens and MMPs. CD44 is a fetal and adult hematopoietic stem cell regulator that is involved in cell-cell interactions, cell adhesion and migration and participates in a wide variety of cellular functions, including hematopoiesis and lymphocyte activation, recirculation and homing [48]. CD44 gene contains 20 exons. Ten of these exons (exons l–5 and 16–20) are expressed together on many cell types and the product is referred to as the "standard" form of CD44. Additionally, complex alternative splicing of the transcripts affecting exons from 6 to 15 (variant exons) results in many functionally distinct isoforms or variants (CD44v) [49]. The role of CD44 as a CSC marker has been broadly studied in myeloid leukemia and also in several solid tumors such as lung, brain, liver, head and neck or gastric cancer [50]. In gastric cancer, the first temptative characterization of CSCs in terms of markers was performed by Takaishi and collaborators, who found that CD44+ cells isolated from different gastric cancer cell lines presented sphere formation ability *in vitro* and tumorigenic potential when inoculated into stomach and skin of immunodeficient mice, abilities that were abrogated by CD44 silencing. Moreover, these CD44+ gastric cancer cells showed the stem cell characteristics of self-renewal and the ability to give rise to differentiated progeny [44]. In concordance, other authors have documented CD44 enrichment in spheres derived from gastric cancer cell lines [51] or have identified that CD44-positive cells derived from gastric cancer cell lines are resistant to 5-fluorouracil and cisplatin chemotherapy and also exhibit significantly more migration, invasion and anchorage-independent growth capabilities [52]. Regarding gastric cancer clinical samples, CD44 is expressed in 80% of gastric tumor resected specimens [40] and its high expression has been associated with tumor size, lymphatic vessel and intravenous invasion, moderate grade of differentiation and low response to chemotherapy [52–54]. Furthermore, the presence of CD44+ cancer cells at the invasive front of gastric tumors entails poor survival and constitutes a prognostic factor for this malignancy [55]. In relation to this aspect, Watanabe and collaborators have found that in gastric cancer patients, the frequency of circulating CD44-positive tumor cells correlates with disease stage, depth of tumors and venous invasion [56]. Moreover, it has been suggested that the emergence of gastric CSCs induced by *H. pylori* infection of gastric mucosa may rely on CD44 upregulation [57]. Nevertheless, in contraposition to these evidences, some works have not found CSC characteristics in the subpopulations of CD44-positive cells isolated from gastric tumors [45, 58]. Besides, it is being sustained the notion that some CD44 variants are more relevant for gastric CSCs than standard CD44. An example of it is the work of Lau and collaborators, who show that CD44v8-10 is the predominant CD44 variant expressed in gastric cancer cells, whose expression levels, unlike those of standard CD44, are increased in gastric tumors respect to adjacent normal tissue. The authors also showed that ectopic expression of CD44v8-10, but not standard CD44, in gastric cancer cells potentiates their ability to initiate tumors in mice at limiting cell concentrations and that total CD44 silencing impairs tumor-initiating potential of cells, which could be rescued by restoration of CD44v8-10, but not standard CD44, expression [46].


*Article* **Molecular Simulation of Improved Mechanical Properties and Thermal Stability of Insulation Paper Cellulose by Modification with Silane-Coupling-Agent-Grafted Nano-SiO2**

**Zhengxiang Zhang 1 , Haibin Zhou 1 , Wentao Li 1 and Chao Tang 2,\***

**Abstract:** Cellulose is an important part of transformer insulation paper. Thermal aging of cellulose occurs in long-term operation of transformers, which deteriorates the mechanical properties and thermal stability of cellulose, resulting in a decrease in the transformer life. Therefore, improvement of the mechanical properties and thermal stability of cellulose has become a research hotspot. In this study, the effects of different silane coupling agents on the mechanical properties and thermal stability of modified cellulose were studied. The simulation results showed that the mechanical parameters of cellulose are only slightly improved by KH560 (*γ*-glycidyl ether oxypropyl trimethoxysilane) and KH570 (*γ*-methylacrylloxy propyl trimethoxy silane) modified nano-SiO2 , while the mechanical parameters of cellulose are greatly improved by KH550 (*γ*-aminopropyl triethoxy silane) and KH792 (*N*-(2-aminoethyl)-3-amino propyl trimethoxy silane) modified nano-SiO2 . The glass-transition temperature of the composite model is 24 K higher than that of the unmodified model. The mechanism of the change of the glass-transition temperature was analyzed from the point of view of free-volume theory. The main reason for the change of the glass-transition temperature is that the free volume abruptly changes, which increases the space for movement of the cellulose chain and accelerates the whole movement of the molecular chain. Therefore, modifying cellulose with KH792-modified nano-SiO2 can significantly enhance the thermal stability of cellulose.

**Keywords:** nano-SiO2 ; silane coupling agent; thermal stability; mechanical parameter; molecular simulation

#### **1. Introduction**

Oil–paper insulation systems guarantee safe operation of oil-immersed transformers, but they are affected by various factors in long-term transformer operation [1–5]. Improvement of the mechanical properties and thermal stability of cellulose has become a research hotspot. In recent years, the rise of nanotechnology has prompted research on nanoparticle-modified cellulose insulating paper. Many researchers have made progress in this field [6–10]. Liu used nano-Al2O3 to modify insulating paper and studied the depth and degree of the traps [11]. The results showed that with increasing trap depth and density, the breakdown field strength of the modified insulating paper increases, and the conductivity decreases. The trap characteristics are the main reasons for the change of the dielectric properties of the modified insulating paper. Liao used nanoparticles to modify cellulose insulating paper, added SiO2 hollow microspheres and soaked the modified insulating paper, and tested and analyzed its dielectric constant and breakdown voltage [12]. When the content of SiO2 hollow microspheres was 5%, the dielectric constant of the modified insulating paper was 34% lower than that of the unmodified insulating paper, and the breakdown voltage of the oil–paper composite insulation system increased by 15.5%. However, nanoparticles agglomerate in the process of modification. At present, the main method to avoid agglomeration of nanoparticles is to modify the nanoparticles

**Citation:** Zhang, Z.; Zhou, H.; Li, W.; Tang, C. Molecular Simulation of Improved Mechanical Properties and Thermal Stability of Insulation Paper Cellulose by Modification with Silane-Coupling-Agent-Grafted Nano-SiO2. *Processes* **2021**, *9*, 766. https://doi.org/10.3390/pr9050766

Academic Editor: Eduardo Vivaldo-Lima

Received: 17 March 2021 Accepted: 24 April 2021 Published: 27 April 2021

**Publisher's Note:** MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

with silane coupling agents. Wang investigated the influences of different types of silane coupling agents and grafting rate on the interface between nano-SiO2 and cellulose [13]. They found that the interface effect was different for silane coupling agents with different chain lengths and groups. Therefore, it is necessary to study the mechanical properties and thermal stability of cellulose modified by different types of silane coupling agents.

In this study, the nano-SiO2 content in all of the models was 5% [9,12,14]. The mechanical properties (tensile modulus, shear modulus, volume model, and Poisson's ratio) and thermal stability (glass-transition temperature and free-volume fraction) of cellulose modified by nano-SiO2 modified by different silane coupling agents were investigated and compared through a molecular dynamics simulation based on the same grafting rate of the silane coupling agent. The mechanism of the change of the properties and thermal stability was also investigated.

#### **2. Molecular Dynamics Simulation**

Because of the high surface activity of nano-SiO2, it is easily oxidized and produces hydroxyl groups on the nano-SiO2 surface. First, the surface of the nano-SiO2 model needs to be hydroxylated (the unsaturated O atoms on the surface must be treated with H and the unsaturated Si atoms with -OH). Second, the hydroxyl groups at one end of the silane coupling agent combine with the hydroxyl groups on the surface of nano-SiO2 to form Si–O–Si so that the silane coupling agent can randomly connect to the O atoms on the surface of nano-SiO2. There are three hydroxyl groups in a general silane coupling agent. One of the hydroxyl groups of the silane coupling agent bonds to a hydroxyl group on the surface of nano-SiO2, and the remaining two hydroxyl groups form condensation with other grafted silane coupling agent molecules or exist in a free state. To simplify the model, we considered that the other two hydroxyl groups in the model do not participate in the condensation reaction.

Wang et al. [13] found that the grafting ratio is relatively good when the grafting quantity is 4, and the influence of the size of the model on the simulation time has also been investigated [15–17]. Therefore, different types of silane coupling agents with grafting quantity of 4 were grafted on the surface of nano-SiO2, and the particle size of nano-SiO2 was 5 Å. First, nano-SiO2 was placed in a cell with dimensions of 40 × 40 × 40 Å, and its centroid was set to coincide with the centroid of the cell. The cellulose chain (degree of polymerization = 10) was filled in [18] using the packing function in the AC module, and the initial density was set to 0.6 g/cm3 . By applying pressure to different models, the density can reach 1.45 g/cm3 . Subsequently, the relevant parameters were calculated and analyzed. The composite models constructed in this study are shown in Figure 1.

**Figure 1.** Composite models: (**a**) unmodified model, (**b**) KH550 model, (**c**) KH560 model, (**d**) KH570 model, and (**e**) KH792 model.

In this study, we used Molecular Simulation (MS) software. First, 5000 steps of geometric optimization were performed for the established amorphous model of nano-SiO2 and cellulose. Second, annealing of the model was performed with annealing cycle of 5, initial temperature of 300 K, and heating ramps per cycle of 13. Finally, 100 steps of the annealed

convergence model were performed in the NVT ensemble. The dynamic simulation of 200 ps was performed in the NPT ensemble, and then the rationality criterion of the model after the dynamic simulation was obtained. After the system reached a stable configuration, the relevant parameters were analyzed. The pressure was set to 0.0001 GPa (standard atmospheric pressure), the Ewald method was used for the electrostatic interactions, the atom-based method was used for the van der Waals interactions, and the COMPASS force field was used. A Nose–Hoover thermostat was used to collect the dynamic information every 0.5 ps [19,20].

#### **3. Results and Discussion**

#### *3.1. Mechanical Properties*

The mechanical properties of materials are important indicators for characterizing the mechanical strength. In this study, the relevant mechanical parameters of cellulose were obtained by static elastic constant analysis (Table 1). The tensile modulus (*E*) is the ratio of the stress to the strain. The material has higher rigidity and greater ability to resist deformation due to the larger *E*. The shear modulus (*G*) is the ratio of the shear stress to the strain. The bulk modulus (*K*) is the incompressibility of the material. Poisson's ratio (*V*) is the plasticity of the material, with a high value indicating high plasticity [21,22]. The mechanical parameters of the models are shown in Figure 2. With increasing temperature, the modulus values (*E*, *G*, and *K*) of each model gradually decrease, while Poisson's ratio (*V*) is relatively stable. This indicates that the temperature has a relatively large effect on the deformation resistance, shear deformation resistance, and incompressibility of cellulose, while the effect of temperature on the plasticity of cellulose is relatively small. Comparing the mechanical properties of the models with four commonly used silane coupling agents, the mechanical parameters (*E*, *K*, and *V*) of cellulose are only slightly improved by KH560 and KH570-modified nano-SiO2, but the mechanical parameters (*E* and *K*) of cellulose are greatly improved by KH550- and KH792-modified nano-SiO2, although Poisson's ratio (*V*) is not significantly improved. Therefore, compared with KH560 and KH570, nano-SiO2 modified with silane coupling agents containing amino groups (KH550 and KH792) can significantly improve the deformation resistance, shear deformation resistance, and incompressibility of cellulose, with little effect on the plasticity.

**Table 1.** Free volume of the unmodified nano-SiO2 and cellulose composite model.

#### *3.2. Cross Energy*

The energy is the most important property for the stability of the system. The energy of the system can be expressed as

$$E\_{\text{total}} = (E\_{\text{internal}} + E\_{\text{cross}}) + E\_{\text{nonbound}} \tag{1}$$

where *E*internal + *E*cross is the bond interaction term and *Enonbond* is the non-bonding interaction term. The changes of the overall potential energy and non-bonding interaction energy of the models with temperature are shown in Figure 3.

**Figure 2.** Mechanical parameters of the models.

**Figure 3.** Energies of the models: (**a**) ungrafted model, (**b**) KH550 model, (**c**) KH560 model, (**d**) KH570 model, and (**e**) KH792 model.

From Figure 3, the total potential energy and non-bonding interaction energy of all of the models essentially linearly increase, but the growth rate of the non-bonding interaction energy is significantly lower than that of the total potential energy. In the ungrafted model and KH550, KH560, KH570, and KH792 composite models, the starting temperatures of the total potential energies are 386, 395, 411, 432, and 455 K, respectively. From Equation (1), when the total potential energy of the system becomes greater than the non-bonding interaction energy, the bond energy interaction term in the system changes from the previously negative value to a positive value, while the repulsion force between the atoms is greater than the attraction force between the atoms in the molecule, and the chemical bonds become unstable. When the temperature gradually increases, some active bonds and glycoside bonds are easy to break, which is the phenomenon of cellulose thermal degradation. Once cellulose thermal degradation occurs, the degree of polymerization of cellulose decreases, which leads to deterioration of the mechanical properties of cellulose. Therefore, the main reason for the decrease of the mechanical properties of cellulose is that the internal atomic force changes from attractive to repulsive, which makes the chemical bonds unstable. The order of the temperatures corresponding to the cross-energy points of the different models is KH792 > KH550 > KH560 > KH570 > pure.

#### *3.3. Glass-Transition Temperature*

The glass-transition temperature is the temperature of the transition from the glass state to the high-elastic state. As a glassy substance, cellulose has a glassy state, a highelastic state, and a viscous-flow state, which are the three states of the polymer related to temperature. The transition points between these states are called the glass-transition temperature and melting point. The thermodynamic properties of the material obviously change before and after the glass-transition temperature. Therefore, it is of great importance to study the glass-transition characteristics of cellulose at high temperature to improve its thermal stability. When studying the glass-transition temperatures of polymers, the most commonly used and reliable method is the specific volume–temperature curve method [23–26]. The specific volume is the reciprocal of the density, and it is the most commonly used physical quantity in determination of the glass-transition temperature. During the glass transition, the specific volume and other properties of the material significantly change along with molecular segment movement, and the curve of the specific volume against the temperature abruptly changes. In this method, the specific volume obtained by the NPT molecular dynamics simulation is plotted against the temperature. The inflection point of the specific volume change with temperature is determined, and linear fitting is performed before and after the inflection point. The intersection of the two fitted curves is the turning point of vitrification, and the corresponding temperature is the vitrification temperature. The obtained fitted curves of the vitrification temperature for the unmodified and KH792-modified models are shown in Figure 4.

**Figure 4.** Specific volume–temperature curves of the models: (**a**) unmodified model and (**b**) KH792 model.

From Figure 4, the glass-transition temperature of the cellulose and unmodified nano-SiO2 composite model is 414 K, while that of the KH792-modified nano-SiO2 and

cellulose composite model is 438 K. Thus, the glass-transition temperature of the KH792 modified nano-SiO2 and cellulose composite model increases by 24 K. The glass-transition temperature range of cellulose in the polymer manual is 250 to 580 K, so the value of the glass-transition temperature obtained from simulation analysis in this study is reasonable. However, it is only for reference, and it does not affect comparison between the glasstransition temperatures of the modified model and unmodified model. The glass-transition temperature of the KH792-modified nano-SiO2 and cellulose composite model is higher than that of the unmodified nano-SiO2 and cellulose composite model, which shows that the glass state to high-elastic state transition of the cellulose chain modified by KH792 is slower than that of the unmodified model, which effectively delays the cellulose chain transition from the glass state to the high-elastic state. Therefore, compared with the unmodified composite model, for the cellulose chain modified by KH792, the modified nano-SiO2 and cellulose composite model can maintain better performance, the thermodynamic performance is less affected by temperature, and the thermal stability is significantly enhanced.

#### *3.4. Free-Volume Fraction*

In the molecular dynamics simulation, the free volume can be determined by the interstices between the chains in the model system. The free volume and occupied volume of the system can be measured by the Atom Volumes and Surface Tool in MS, and the free-volume fraction (FFV) of the system can be obtained by the ratio of the free volume to the total volume of the system (the sum of the free volume and occupied volume). Because of the different expansion coefficient, the occupied volume of the polymer linearly increases with temperature, and the free volume abruptly increases near the glass-transition temperature. Therefore, the mechanism of the glass-transition temperature was analyzed using free-volume theory. When calculating the free volume, the hard ball probe method was used, and the probe radius was set to 1 Å [26–28]. The free-volume distributions of the unmodified composite model and KH792-modified composite model are shown in Figure 5. The blue parts of the figures are the free-volume distribution areas. The free volumes of the unmodified composite model and KH792-modified composite model are given in Tables 1 and 2, respectively.

**Table 2.** Free volume of the KH792-modified nano-SiO2 and cellulose composite model.

From Table 1, for the unmodified nano-SiO2 composite model, when the temperature is 303–403 K, the change of the free volume is relatively small, However, above 423 K, the free volume starts to increase, and a clear increasing trend appears. From Table 2, for the KH792-modified nano-SiO2 composite model, when the temperature is 303–423 K, the change of the free volume is small. However, above 443 K, the free volume starts to increase, and the free volume also shows a significant increasing trend. The sudden increase of the free volume increases the space for movement of the cellulose chain, leading to increased movement. The cellulose changes from the glassy state to the high-elastic state, and the thermal stability of the cellulose chain sharply decreases after it changes to the

high-elastic state. The free volume increase of the unmodified nano-SiO2 composite model occurs at 403–423 K, which is essentially the same as the glass-transition temperature of the unmodified nano-SiO2 composite model obtained by the specific-volume method in Section 3.3 (413 K). The free volume increase of the KH792-modified nano-SiO2 composite model occurs at 423–443 K. This is consistent with the glass-transition temperature of the modified composite model obtained by the specific-volume method in Section 3.3 (438 K). Therefore, this section explains the microscale mechanism of improvement of the thermal stability of cellulose modified by KH792-modified nano-SiO2 from the perspective of the free volume.

**Figure 5.** Free volume of the models: (**a**) unmodified model and (**b**) KH792 model.

Above all, hydroxyl groups are produced after hydrolysis of silane coupling agent. Therefore, the silane coupling agent can react with the silicon hydroxyl groups on the surface of nano-SiO2, so that one end of the silane coupling agent can be connected with the surface of nano-SiO2. The organic functional group of KH550 is amino, the organic functional group of KH560 is epoxy, the organic functional group of KH570 is acyloxy, and the organic functional group of kh792 is aminopropyl. Organic functional groups determine the binding ability between nano-SiO2 modified by silane coupling agent and cellulose. The addition of silane coupling agent enhances the compatibility between organic phase and inorganic phase to a certain extent. At the same time, the addition of silane coupling agent creates more hydrogen bonds between nano-SiO2 and cellulose, which makes the structure of cellulose more compact.

#### **4. Conclusions**

In this study, the effects of silane coupling agents (KH550, KH560, KH570, and KH792) on the mechanical properties and thermal stability of cellulose were investigated with molecular dynamics simulation. It was found that the mechanical properties and thermal stability of cellulose can be improved by silane coupling agents.

The temperature has a great effect on the deformation resistance, shear deformation resistance, and incompressibility of cellulose, but it has little effect on its plasticity. The mechanical parameters (*E*, *K*, and *V*) of cellulose are only slightly improved by KH560- and KH570-modified nano-SiO2. However, the mechanical parameters (*E* and *K*) of cellulose are significantly improved by KH550- and KH792-modified nano-SiO2, while Poisson's ratio (*V*) is only slightly improved. Therefore, this shows that silane-coupling-agent-modified nano-SiO2 mainly affects the deformation resistance, shear deformation resistance, and incompressibility of cellulose, but it has little effect on its plasticity. Silane coupling agents containing amino groups significantly improve the deformation resistance, shear deformation resistance, and incompressibility of cellulose. The mechanism of the change of the mechanical properties was analyzed from the point of view of the energy. The reason for the decrease of the mechanical properties of cellulose is that the internal atomic force changes from attractive to repulsive, which makes the chemical bonds unstable. The overall potential energy obtained from energy analysis is higher than the starting temperature of the non-bonding energy, and the analysis results of the mechanical properties are essentially the same. Therefore, nano-SiO2 modified by silane coupling agents can enhance the mechanical properties of cellulose, and nano-SiO2 modified by KH792 most significantly improves the mechanical properties of cellulose.

The glass-transition temperature of the nano-SiO2-modified cellulose composite model without surface modification is 414 K, and that of the KH792-modified nano-SiO2 composite model is 438 K. Thus, the glass-transition temperature of the composite model increases by 24% after surface modification of nano-SiO2 by KH792. The mechanism of the change of the glass-transition temperature was analyzed from the point of view of free-volume theory. The main reason for the change of the glass-transition temperature is that the free volume abruptly changes, which increases the space for cellulose chain movement and intensifies the overall movement of the molecular chain. The range of the glass-transition temperature obtained by free-volume theory is essentially the same as that obtained by the specific-volume method. Therefore, the thermal stability of cellulose is significantly enhanced by modifying cellulose by KH792-modified nano-SiO2.

**Author Contributions:** Conceptualization, Z.Z. and C.T.; formal analysis, W.L. and C.T.; software, H.Z.; validation, Z.Z., H.Z. and C.T.; data curation, Z.Z., H.Z. and C.T. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the science and technology project of EHV Power Transmission Company, China Southern Power Grid.

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

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data that support the findings of this study are available from the corresponding author, C.T., upon reasonable request.

**Conflicts 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.

#### **References**


*2.1. Ice Thickness*

Glacial isostasy is calculated based on the palaeo ice extent (from dated marginal moraines) and models of the ice thicknesses. Observational data increasingly constrain the extent of the Quaternary ice sheets. The thickness and volume of these ice sheets are much harder to reconstruct and generally need to be inferred from indirect evidence and modeling.

Several models of ice thickness of LGM and the late-glacial deglaciation are published; the loading scenarios are produced using different methods and sets of constraints. Some of them consider thermomechanical coupling (e.g., [37]). A number of models of the LGM ice thickness are presented in [38]. We follow the work of [36]; their LGM extent model is shown in Figure 1.

**Figure 1.** Extent (based on [36]) and maximum thickness model for the Last Glacial Maximum (LGM), from [3]. The production licenses (from www.npd.no) in the Norwegian continental shelf are shown by grey polygons.

### *2.2. Glacial Isostasy and Tilting of Reservoirs*

The Earth's response to deglaciation shows that the lithosphere acts as an elastic shell overlying a viscous mantle. If a load is applied to the elastic lithosphere, part of the applied load will be supported by the elastic lithosphere, and part by buoyant forces of the mantle underneath, acting through the lithosphere.

In the literature, there is disagreement on the elastic thickness of the lithosphere; the elastic thickness of the lithosphere of Fennoscandia in GIA (Glacial Isostatic Adjustment) modeling varies from 30 to 160 km [39]. Our modeling of the post-glacial isostatic response, calibrated with the observations onshore Norway, gave best fit with an elastic thickness of 30 km; see [34]. Calibration with the Barents Sea gave similar results; see [40]. The method used in the isostatic calculations is described in [41] and in the Appendix A. The spatial resolution is 10 km.

There will be significant subsidence of potential sedimentary basins formerly covered by ice sheets. Sedimentary basins that are located in the periphery of the former ice sheet will be notably affected by tilting of the Earth's surface as the subsidence (or uplift after the melting) is gradually decreasing towards the periphery of the former ice sheet. Therefore, the largest tilts of the Earth's surface are found in the more peripheral areas of former ice sheets. This is clearly seen along the entire Norwegian coast and in the Barents Sea (Figure 2). Sedimentary basins located in the peripheral areas in the SW Barents Sea could be tilted by up to 2.7 m/km due to the LGM ice sheet (Figure 2), and even more in the previous greater glaciations [3]. The ice sheets will act as seesaw during the total glaciation period (Quaternary); the Earth will subside under the ice sheets and rise again in interglacial periods.

**Figure 2.** *Cont.*

**Figure 2.** Calculated tilts (m/km) due to glacial isostasy for the LGM ice sheet (based on [3]). The white box in **a**) marks the Norwegian part of the Barents Sea that is open for petroleum exploration (production licenses are marked in grey). The tilts of this area are shown in **b**).

This process is, of course, important for migration modelling. Figure 3 shows how a simple structure behaves during one glacial cycle. It is assumed, for illustration purposes, that the structure is filled with hydrocarbons to the spill point at the onset of glaciation. When the lithosphere and the structure subside due to the glacial load, the reservoir is tilted hydrocarbons start to spill out of the structure. This goes on until the maximum tilting is reached (Figure 3, upper right). The closure volume will be reduced.

When the lithosphere and structure are uplifted due to deglaciation, a new hydrocarbon-water contact (HCWC) will be established (Figure 3, bottom). Paleo-HCWCs can theoretically be found at the spill point level for the positions before and after deglaciation. Residual oil can be found in the water zone down to the original spill point level. In a gas-filled reservoir with an oil leg originally, residual oil can also be found in the gas-filled part, limited by the uppermost HCWC.

The effect of the glacially induced hydrocarbon migration is determined by several factors:

The isostatic response on the Pleistocene sediment redistribution and ice loading has been evaluated for the Bjørnøyrenna Fault Complex in the Barents Sea [11]. The isostatic impact on hydrocarbon trap capacity changes and hydrocarbon maximum spillage was assessed in that study and the conclusion was that tilting together with gas volume expansion might have been responsible for some part of the hydrocarbon loss during the Cenozoic.

**Figure 3.** Illustration of tilting during one glacial cycle (redrawn from [5]). **Upper left** shows the situation prior to tilting; **upper right** during tilting. **Lower panel** shows the situation after deglaciation. "Spill point" is the structurally lowest point in a hydrocarbon trap that can retain hydrocarbons. Once a trap has been filled to its spill point, further storage or retention of hydrocarbons will not occur. The illustration assumes the trap filled to the spill point. HCWC is the hydrocarbon-water contact.


**4. Data analysis and results**

This section deals with the surveys that were conducted with road users, road specialists and experts, and the results obtained from processing this data in the SPSS program.

#### **4.1 The drivers' questionnaire**

A questionnaire was distributed to road users and drivers of various types of vehicles to gauge their feelings about the current state of the road and their willingness to accept the implementation of the toll road system. The sample consisted of 94 users, whose responses are shown in **Table 1**. The table shows that 77% refuse to pay the fees for using the road in its current condition, while 87% agree to pay the fees if maintenance is done for the road and the provision of services and safety factors.

Also, 63% of the respondents indicated that they would increase the fare for passengers if the fees were collected from them to use the road. Finally, 94% of them expressed their desire to limit the speed on the expressway and impose fines on violators.

**Figure 2** depicts the order of services sought by road users in order to optimize efficiency.

#### **4.2 Questionnaire for specialized academics**

The questionnaire items included a group of carefully designed questions that aim at determining and describing the quality and operational performance of the road based on a set of main criteria from which a set of sub criteria were derived **Table 2**. From the table the highest importance was given to safety by 9 degrees, and the least importance in determining the efficiency of the road was given to the

#### **Table 1.**

*Percentage weights of questionnaire questions.*

**Figure 2.** *Services according to the drivers' required priority.*

#### **Table 2.**

*Academics evaluation of the importance of primary and secondary standards.*

#### **Table 3.**

*Evaluation scores for the road condition using the main criteria.*

environment by 6 degrees, while road conditions and geometric design were of great importance by 8 degrees, followed by services and cost by 7 degrees. In the same way, the importance and importance of the secondary criteria can be read, as the evaluation was done on a scale from 1 to the least important and 9 to the highest importance.


**3. Decentralized energy-water-food systems**

Decentralized energy-water-food systems are the proposed solution for rural farmers in SSA to provide the necessary amount of electricity that fosters a higher level of human development. It addresses the low purchase power of the local community, gives renewable-based power access as pillar for human development, and increases the income of local community through agricultural productivity. It is based on the water-energy-food nexus, a conceptual framework for integrated resource management, which took particular prominence in 2011 as a wake-up call reacting to the forecast of a worldwide increasing resource demand, climate change, and the awareness of the unsustainable stress on scarce resources (energy, water, and food) [18]. As a result, it supports the coordination and management of the three sectors and the decision-making process under the consideration of synergies and trade-offs between the three resources when dealing with human development challenges [19]. This system thinking has from henceforth had an impact on the new policy frameworks, business assessment methods, and modeling tools, specially addressing challenges in the urban context and the multi-sectoral use of energy [20]. However, the application of this approach in the context of rural development of farming communities is limited. Due to the transformational effect of the nexus thinking [21], it deserves the formalization of a concept framework that is suited for rural farming communities and for sustainable economic development.

The model scheme for a decentralized energy-water-food system with their major inputs and outputs is depicted in **Figure 2**. Key system characteristics are: into biogas and later converted into electricity (4). As a by-product, the biogas digestion process produces fertilizer that is used for agricultural purposes.

*boundaries, technological components, and commodity flows are depicted. Modified from [6, 7].*

**3.1 Least-cost design of decentralized energy-water-food systems**

Decentralized EWFS have potential to deliver social, environmental, and economic returns. The sector coupling causes an unavoidable complexity in designing EWFS, specially when the lowest cost and technical feasibility are to be guaranteed. Optimization models facilitate the engineering effort to provide basic dimensions for the system implementation. These models are the state of the art for rural electrification as they enable stakeholders to understand, evaluate, and ultimately make decisions about the system setup [25, 26]. To date, there are only a limited number of models accessible to researchers that address all three resources of an EWF system together, and most tools cannot be customized to the specific environmental and economic characteristics of the respective project location [27]. The

energies.

**103**

**Figure 2.**

As a result, the rural community not only has gained access to electricity and domestic water supply but also secures the year-round supply of water for productive uses and food. In the medium to long term, the improved agriculture has the potential to create fair-paid jobs, increase the community's purchasing power, lead to a higher standard of living, and provide economic opportunities [12]. This concept also suggests that the high, so far unaffordable, investment costs for infrastructure development can be repaid by the local population through their revenues in agriculture as crops yield increase by up to 300% with regular irrigation [24]. After paying the system investment and operational costs, profits are distributed to the local community. Besides this socioeconomic benefits, preliminary studies of this concept in [6, 7] showed that due to the high resource potential of solar and biomass, the cheapest power generation is based to over 90% on renewable

*Business model scheme of decentralized energy-water-food systems. Major inputs and outputs as well as system*

*Economic Development of Rural Communities in Sub-Saharan Africa through Decentralized…*

*DOI: http://dx.doi.org/10.5772/intechopen.90424*

1.Hybrid power system

The combination of the photovoltaic battery and biogas system provides electricity to meet the private demands of a community. Because the deployment of diesel generators in off-grid villages is widespread [22], it is considered in this concept as well (1). Private power is provided free of charge in a first step and priced to cover potential system losses if needed. The hybrid power system generates enough power to operate electric groundwater pumps (2), powered mainly with cheap solar energy enabled by the strong global irradiation in SSA and by the flexible load management of water pumps. These pumps supply the community with domestic water demand. In this concept, up to 50 liters per day and capita are provided free of charge to meet the drinking and sanitation water right standards [23]. The pumps supply also all-year irrigation under the consideration of arable land and groundwater use constraints. Community farmers are able to grow crops independent of the rainfall pattern. This allows multiple harvests per year for selling to the domestic or external market participants (3). The resulting higher agricultural productivity leads also to an increase in biomass waste, which is fermented

### *Economic Development of Rural Communities in Sub-Saharan Africa through Decentralized… DOI: http://dx.doi.org/10.5772/intechopen.90424*

#### **Figure 2.**

development goals and opportunities to use energy access to stimulate economic activity" [9]. In the absence thereof, rural electrification may not bring the

Decentralized energy-water-food systems are the proposed solution for rural farmers in SSA to provide the necessary amount of electricity that fosters a higher level of human development. It addresses the low purchase power of the local community, gives renewable-based power access as pillar for human development, and increases the income of local community through agricultural productivity. It is based on the water-energy-food nexus, a conceptual framework for integrated resource management, which took particular prominence in 2011 as a wake-up call reacting to the forecast of a worldwide increasing resource demand, climate change, and the awareness of the unsustainable stress on scarce resources (energy, water, and food) [18]. As a result, it supports the coordination and management of the three sectors and the decision-making process under the consideration of synergies and trade-offs between the three resources when dealing with human development challenges [19]. This system thinking has from henceforth had an impact on the new policy frameworks, business assessment methods, and modeling tools, specially addressing challenges in the urban context and the multi-sectoral use of energy [20]. However, the application of this approach in the context of rural development of farming communities is limited. Due to the transformational effect of the nexus thinking [21], it deserves the formalization of a concept framework that is suited for rural farming communities and for sustainable economic

The model scheme for a decentralized energy-water-food system with their major inputs and outputs is depicted in **Figure 2**. Key system characteristics are:

The combination of the photovoltaic battery and biogas system provides electricity to meet the private demands of a community. Because the deployment of diesel generators in off-grid villages is widespread [22], it is considered in this concept as well (1). Private power is provided free of charge in a first step and priced to cover potential system losses if needed. The hybrid power system generates enough power to operate electric groundwater pumps (2), powered mainly with cheap solar energy enabled by the strong global irradiation in SSA and by the flexible load management of water pumps. These pumps supply the community with domestic water demand. In this concept, up to 50 liters per day and capita are provided free of charge to meet the drinking and sanitation water right standards [23]. The pumps supply also all-year irrigation under the consideration of arable land and groundwater use constraints. Community farmers are able to grow crops independent of the rainfall pattern. This allows multiple harvests per year for selling to the domestic or external market participants (3). The resulting higher agricultural productivity leads also to an increase in biomass waste, which is fermented

economic development it promises.

*Regional Development in Africa*

development.

**102**

1.Hybrid power system

2.Electric water pumps

3.Yield optimizing and sustainable agriculture

4.Biogas generation through agricultural waste

**3. Decentralized energy-water-food systems**

*Business model scheme of decentralized energy-water-food systems. Major inputs and outputs as well as system boundaries, technological components, and commodity flows are depicted. Modified from [6, 7].*

into biogas and later converted into electricity (4). As a by-product, the biogas digestion process produces fertilizer that is used for agricultural purposes.

As a result, the rural community not only has gained access to electricity and domestic water supply but also secures the year-round supply of water for productive uses and food. In the medium to long term, the improved agriculture has the potential to create fair-paid jobs, increase the community's purchasing power, lead to a higher standard of living, and provide economic opportunities [12]. This concept also suggests that the high, so far unaffordable, investment costs for infrastructure development can be repaid by the local population through their revenues in agriculture as crops yield increase by up to 300% with regular irrigation [24]. After paying the system investment and operational costs, profits are distributed to the local community. Besides this socioeconomic benefits, preliminary studies of this concept in [6, 7] showed that due to the high resource potential of solar and biomass, the cheapest power generation is based to over 90% on renewable energies.

#### **3.1 Least-cost design of decentralized energy-water-food systems**

Decentralized EWFS have potential to deliver social, environmental, and economic returns. The sector coupling causes an unavoidable complexity in designing EWFS, specially when the lowest cost and technical feasibility are to be guaranteed. Optimization models facilitate the engineering effort to provide basic dimensions for the system implementation. These models are the state of the art for rural electrification as they enable stakeholders to understand, evaluate, and ultimately make decisions about the system setup [25, 26]. To date, there are only a limited number of models accessible to researchers that address all three resources of an EWF system together, and most tools cannot be customized to the specific environmental and economic characteristics of the respective project location [27]. The

water infrastructure, or telecommunications network. Although agriculture is their main economic activity and livelihood, farming in Kpori is 100% rainfall dependent. At the same time, domestic water supply relies on rainwater harvesting and hand pumps. As a result of a significant drop in rainfall and an increase in temperature over the last century, the already climatically stressed region is dependent on drought-resistant plants such as maize and sorghum. According to on-ground questionnaire, Kpori's inhabitants have an annual income per capita below the lower

*Economic Development of Rural Communities in Sub-Saharan Africa through Decentralized…*

As depicted in **Figure 3**, *urbs* already includes the EWFS model and optimization

• Technical parameters: Efficiency, capacity, and lifetime of machinery and

• Economic parameters: Weighted average cost of capital (WACC), investment cost, fixed cost, variable cost, purchase cost, and fuel cost of machinery and

The community demand for residential electricity and domestic water is determined by the approx. 300 Kpori inhabitants distributed over 70 households with an average household size of 4.4 [32]. The hourly private power demand is obtained by a Monte Carlo simulation based on the hourly utilization probability of residential appliances and their rated power. This data was obtained from an on-site survey on the nearest electrified farming community. The results of **Figure 4** show a typical load profile of a farming community with a total annual consumption of 42.5 MWh

Domestic water demand is set to 50 liters per day and person based on the drinking and sanitation water right standards [23]. Daily food demand is modeled as 658 g of maize grain per inhabitant, which covers the minimum dietary calorie intake of 2400 kcal [33]. In Kpori, up to 263 tons of maize grain can be produced annually on the domestic farmland due to the maximum capacity of arable land of

*Time series electricity demand for a Kpori house obtained with Monte Carlo simulation.*

script. The input data needed about Kpori are the following:

• Supply time series: Solar irradiation, rainfall

• Demand time series: Residential electricity, domestic water, food

poverty line of 208 USD/year [31].

*DOI: http://dx.doi.org/10.5772/intechopen.90424*

**4.1 Model input**

storage units

storage units

or 138 kWh per inhabitant.

**Figure 4.**

**105**

#### **Figure 3.**

*Work flow to obtain least-cost design of decentralized energy-water-food systems with programming tool urbs. A business analysis is derived from the output results.*

contribution [6, 7] addressed the adaption of *urbs*, an economic model, which was originally designed by the Chair of Renewable and Sustainable Energy Systems of the Technical University of Munich (ENS) for distributed energy systems. *Urbs* has a well-documented mathematical description; it is open-source and can be used for cross-sectoral models in any spatial and temporal resolution [28]. Hence, it is used to conduct the economic feasibility analysis aimed in this work.

*urbs* is a linear optimization tool programmed in Python and identifies the optimal system configuration based on the minimization of the total system costs resulting from the techno-economic modeling of each process and storage technologies in the system. **Figure 3** gives an overview of the *urbs* model for decentralized EWFS.

It requires three kinds of input data. Site data is defined by the demand, solar and rainfall time series, techno-economic parameters of the processes and storages as depicted in the EWFS model schema (**Figure 2**), and lastly the market prices of the commodities that can be bought or sold between the system boundaries. This data is read by *urbs*, which already has an implemented script adapted to model EWFS with a linear approach [7], and the total system costs are optimized. The output data includes the installed capacities related to the three sectors, the commodity flows, total revenues, and costs. A pre-feasibility analysis can be conducted on the basis of these results to evaluate the business attractiveness and ensure a sustainable project operation.