7940 research outputs found
Sort by
Nanostructured Si-C hybrids for Anode Application in Lithium Ion Batteries
No full textRechargeable lithium-ion batteries (LIB) have achieved tremendous attention as one of the most efficient energy storage options. However, significant advancement in electronic devices demands for higher energy and power density, requiring that alternative electrode materials to be explored. Silicon is well recognized as a highly promising anode material due to its remarkable lithium storage capacity of 3590 mAh g-1. However, during the process of alloying or de-alloying with lithium, Si undergoes a significant expansion in volume, surpassing 300%. The repeated expansion and contraction during cycling of the cells leads to the disintegration of particles, accelerated formation of a solid electrolyte interphase (SEI), damage in the electrode calendars, all of which result in capacity fade and failure of the electrode. To mitigate the limitations linked to Si, nanostructuring was found to be an effective method. The purpose of nanostructuring is to reduce the strain on the electrode, mostly caused by the volume dilation of Si. However, the implementation of nanostructured Si individually as anode material causes rapid capacity fading and failure of the electrode. A promising strategy involves dispersing active silicon materials on a carbon-based matrix, which significantly enhances the electrical connectivity between the active material and the current collector and acts as a buffer to accommodate the volume dilation that occurs during continuous charge and discharge cycles. In a similar vein, in this thesis we have adopted an innovative approach using a carbon matrix synthesized from a precursor polymer-derived silicon oxycarbide (SiCO). Silicon oxycarbide, prepared from the inert pyrolysis of Si-containing preceramic polymers, is a versatile material with excellent thermodynamic stability and flexible stoichiometry. Interestingly, it serves as an excellent material for the integration of nanoparticles (in-situ and ex-situ) into a matrix. The microstructure of SiCO ceramic may be suitably designed by the meticulous selection of initial polymer precursors and by exercising control over the synthesis and processing conditions. One of the standout characteristics of these non- crystalline ceramics is their distinctive nanostructure, consisting of nanodomains composed of SiO2, carbon layers resembling graphene, and an intermediate region with a blend of tetrahedral bonds made up of Si, O, and C. In order to obtain carbon derived from SiCO ceramics, its microstructure can be altered by selectively removing the SiO2 nanodomains. This process results in the development of a highly porous, graphene-like carbon material. The resulting oxycarbide derived carbon (ODC) material, which is both conductive and flexible, can be used in combination with Si nanoparticulates for anode applications. The ODC serves as a conduit for interfacial adhesion and mechanical support and prevents capacity degradation by ensuring continuous and effective electrical contact between the silicon nanoparticles. The current work investigates a process to fabricate Si-C hybrid material with tailorable microstructure. The fabrication process involves integration of nanostructured Si into a carbon rich preceramic polymer precursor matrix to accommodate the volume change of Si during lithium alloying process. The initial step in this process involves preparing nanostructured silicon through high-energy mechanical milling, which form the source of nanoparticulate Si in every fabrication process described for the Si-C hybrids. The first kind of Si-C composites is prepared from high energy mechanical milling of nanocrystalline Si and oxycarbide derived carbon. Carbon-rich polysilsesquioxane polymer precursor was pyrolyzed at 1000 and 1200 °C to synthesize a silicon oxycarbide, which were further etched with HF to prepare the ODC. The Si-ODC composite produced from the mixing of Si and the ODC from 1200 ºC pyrolysis exhibited improved performance compared to the ODC obtained from 1000°C pyrolysis. The material showed reversible specific capacity of 1000 mAh g-1 after 200 cycles at a current density of 0.1 A g-1, and 420 mAh g-1 at a high current density of 2 A g-1. In the second synthesis route of Si-C hybrids, additional pore forming agent in the form of amorphous SiO2 fillers were added into the hybrid nanostructure which were subsequently removed by HF etching. The hybrid anode structures were fabricated from materials pyrolyzed at two different temperatures of 1000 and 1200 ºC to study the effect of pyrolysis temperature on the structure and the electrochemical behavior of the anodes. The final composites prepared at 1000 ºC delivered better electrochemical properties and displayed stable cycle life of 622 mAh g-1 for the 400th cycle at 0.1 A g-1 current density. The composite also exhibited better power capability of 229 mAh g-1 at 2 A g-1 rate. In an effort to further enhance the electrochemical performance, another method for fabricating Si-C hybrids was pursued. This approach places emphasis on improving the adhesion between nanostructured Si and the surrounding carbon matrix by using a non-ionic surfactant, Triton-X-100, which plays a crucial role in achieving a homogeneous dispersion of crystalline Si particles within amorphous SiCO matrix. In this Si-C systems in addition to variation of pyrolysis temperature, composition ratios (Si: C) were also varied to analyze how their phase and microstructure varies according to change in processing parameters. Additionally, their effect on the resulting electrochemical properties was also studied. The composite fabricated with 1:2 ratio of silicon nanoparticles and preceramic polymer pyrolyzed at 1200 ºC followed by etching exhibited the maximum stable capacity of 1048 mAh g-1 after 200th cycle at a current density of 0.1 A g-1. The sample also demonstrated excellent rate capabilities with a capacity of 840 mAh g-1 at a high current density of 2 A g-1. All Si-C hybrids discussed in this thesis demonstrated exceptional electrochemical behavior. The significant performance of the electrodes is attributed to the synergistic combination of high-capacity Si with structurally stable SiCO-derived carbon which provides a harmony between capacity and mechanical stability. The present study provides a significant advancement from prior research by introducing etching induced porosity into the polymer derived carbon phase. This porosity provides additional space to accommodate the volume expansion of Si particles. Further, the combination of porous microstructure and interconnected network of the preceramic polymer-derived carbon absorb the mechanical strain resulting from lithiation induced volume dilation of Si as well as enhances the conductivity of the anode structure
Children’s Education, Migration, and Co-residence: Paving the Path to Health and Well-being of the Indian Older Adults
No full textInadequate social security provision, the growing cost of health care services, and deterioration in health and economic status force older adults to depend on their younger kin or caregivers. In India, the relationships between parents and children have always been central to old-age support and have become increasingly important as the old-age dependency ratio is increasing significantly. However, the blend of urbanisation, Western culture and the overseas location of children due to rapid globalisation have been affecting the traditional family system, patterns of living arrangements, and support for older adults. While studies exist on the downward mobility of socioeconomic position from parents to children, very little is known about how the upward mobility from children to older parents is associated with older adults’ health and well-being. The dependent variables are multi-morbidity conditions, functional health, nutritional outcomes, major depression, life satisfaction, and multidimensional well-being of the Indian Older adults. The predictors of interest are adult children’s education, migration and co-residence with the parents. The data was extracted for 30,265 older adults aged 60+ from wave-1 of the Longitudinal Ageing Study in India, 2017-18. The findings indicate that one-fourth of older adults were multi-morbid and had at least one limitation in the activities of daily living (ADL); meanwhile, one in every two older adults had at least one instrumental activities of daily living (IADL) limitation. The result also indicates that an increase in children’s average years of schooling is associated with a significantly lower rate (Incidence Rate Ratios [IRR] = 0.984, p < 0.05) of multiple limitations in the ADL and lower rate (IRR = 0.975, p < 0.001) of multiple limitations in the IADL, and lower odds of underweight (AOR=0.939, p < 0.05). Additionally, an increase in children’s average years of schooling is associated with a significantly higher rate (IRR = 1.035, p < 0.05) of multiple chronic diseases and overweight (AOR=1.068, p < 0.05). The association between children’s migration and major depression among older adults is also statistically significant. Specifically, older adults living in an empty nest (OR=1.83; 95% CI: 1.38–2.42) or were left behind (OR=1.5; 95% CI: 1.15–1.97) had higher odds of experiencing MDD compared to those living with all their children. Compared to older adults living alone, those who were co-residing ‘with both spouse and son’ were significantly more likely to report a higher level of Life satisfaction (RRR=3.17, p-value<0.001), followed by those who are living ‘with their spouse only’ (RRR = 2.68, p-value<0.001) and ‘with their spouse only’ (RRR= 2.65, p-value<0.001). In terms of multidimensional poverty (MDP), older adults whose children never went to school and whose none of the male children were co-residing were the most vulnerable. For instance, older adults whose children’s average years of schooling was 0-4 years were 28% less likely to experience MDP than older adults whose children never went to school. This pattern holds for the average years of schooling of both son(s) and daughter(s). While the migration status of son(s) seems to have an impact on the MDP, no significant association was established for daughter(s)’ migration status. Based on the son(s) characteristics, it was found that the empty nester was 1.209 times (AOR=1.209, p-value<0.001) more likely to experience MDP
Parental Engagement and Accountability: Educating Children from Slums in a ‘Smart City’
No full textEducation as a ‘social sub-system’ includes teachers, parents, students, and administrators to provide vital knowledge to children. The COVID-19 pandemic has transformed education by emphasising accessibility, digitisation, and heightened stakeholder responsibilities. Schools have adopted flexible and innovative teaching methods, but excluding parents complicates their role in children’s education. Interactive platforms have transformed urban education, yet the lack of focus on parents has hampered the effective use of educational resources and forced children from impoverished backgrounds to drop out of school. Parental engagement (PE) is vital in bridging the parent-school gap for student success, especially among low-income families. The semi-systematic review (SSR) approach addressed the topic’s broad scope, revealing research gaps such as studies neglecting the dynamic nature of PE influenced by evolving patterns, non-Western countries relying on strategies from developed nations and omitting broader sociological perspectives. Educational surveys also overlooked parents, disrupting the accountability balance between schools and stakeholders. In response to observed issues in ‘Smart City’ Rourkela in the Sundargarh district of Odisha (India), this research investigates patterns of parental engagement, analyses associated accountability practices, explores technological mediations, and identifies enablers. Current research has used multi-stage sampling and concurrent triangulation. It employed descriptive statistics, the Location Quotient Method (LQM), surveys, case studies, content analysis, and Focused Group Discussions (FGD). The study applied Anthony Giddens’s Structuration Theory (1984) and Van Dijk’s Digital Divide (2020) based on crucial components chosen for their relevance within the current context. Results of the first objective revealed that PE is procedural but shaped by structural factors and school policies, often resulting in parents surrendering their agency to teachers. The second objective on accountability practices highlighted accountable events, networks, metrics, and resources as vital. Schools can promote inclusivity and cultivate a culture of agency through community liaising, personalised support, and resource sharing. The results from the third and fourth objectives uncovered a shortage of technological resources, and only a few schools had functional websites. Schools with websites reflected a hierarchical orientation that disregarded broader audiences. While technology emerged as an enabler, concerns remain on substitution and inadequate representation of parental roles. Recommendations include voice notes through push notifications in local languages, a language-inclusive feedforward approach, home-school agreements, community outreach programmes, centralised school websites, and others. The novelty is in supporting schools in underprivileged areas and aid policymakers in aligning engagement programs with SDG 2030 goals. Lastly, the research urged continued investment in PE to promote an encouraging environment where parents can engage in their children’s education
Effect of Different Heat Treatment Procedures on Mechanical Properties and Wear Behavior of Ductile Cast Iron
No full textThe Ductile Cast Iron (also known as Nodular or Spheroidal Graphite Iron) was first manufactured in 1948. It came into being as a results of scientist’s effort to develop a particular type of cast iron which can be preferred to malleable cast iron. While malleable cast iron can be formed by a lengthy annealing process (known as malleabilization) of white cast iron, the ductile cast iron can be manufactured simply by adding some nodularizing agents like Mg or Ce (or both) into the liquid melt of gray cast iron. Due to the absence of any heat-treatment schedule of long duration, the production cost of ductile or spheroidal graphite (S.G) iron is much less than that of malleable iron. So the former is preferred to the latter even if the both are equal to each other as far as industrial use is concerned. The use of ductile (or nodular or S.G.) iron has been increasing day by day after its discovery in 1948. It is widely used as the material for windmill. Now it has completely replaced galvanized iron as the material for the water-supply pipes. Now research works are being conducted to examine whether this material can be used for the container for nuclear fuel waste. It has been found that S.G. Iron can be used as the material for the casks used for the transportation of the nuclear fuel wastes. As a result of all these developments extensive works are now being performed for the property development in the ductile cast iron. This can be done mainly by addition of alloying elements or by various heat treatment techniques. In this work the effect of different heat-treatment techniques on the microstructure and mechanical properties of ductile iron has been studied. A special importance has been given on the use of ductile cast iron as a material for the container of nuclear fuel wastes. In the current work, DCI or spheroidal graphite (SG) cast iron samples of four different grades (namely, SG1, SG2, SG3, and SG4) having carbon equivalent varies from 4.12% - 4.36%, were subjected to different types of heat treatment processes such as annealing, normalizing, quenching & tempering (Q&T), austempering and inter-critical austenitization (ICA) to develop dual matrix structure (DMS). The first objective is to study the microstructural features of as-cast and heat-treated samples. This was done by using an optical microscope (OM), transmission electron microscope, and X-ray diffraction (XRD) technique. From the results, it has been identified that each grade of DCI has graphite spheroids embedded in ferritic matrix in its as-received state. The nodules count in the graphite spheroids varies from 20-34 nodules/unit area, and they are Type-I (completely spheroids) nodules with a nodularity greater than 93%. Si addition increases the ferrite volume percentage, while the concentration of Mg, Cu, Si, and Ce are found to raise nodules' quantity and nodularity. With a graphite nodule incorporated in each matrix, normalizing, Q&T, and austempering heat treatments obtained pearlitic, ferritic, tempered martensitic, and coarse upper bainitic matrix, respectively. On the other hand, the as-cast ferrite matrix is transformed into a ferrite + martensite matrix after undergoing ICA heat treatment followed by quenching. Except for annealing, the greater cooling rate during the consequent quenching stages for all heat treatments increases the number of nodules in the matrix by restricting the transfer of carbon from the austenite to nearby graphite nodules. The second objective is to study different mechanical properties like hardness, uniaxial tension, compressive, and impact properties of differently heat treated specimens. The results show that greater hardness readings are obtained for Q&T, followed by austempering and normalizing for all grades of DCI specimens due to hard phases like martensite, bainite, and pearlite in their microstructures. The lower hardness values are obtained for annealed samples due to the existence of soft phases like ferrite for all grades of DCI samples. On the other hand, the optimum hardness values were obtained for all grades of ICA samples due to the existence of dual phases (i.e., soft ferrite and hard martensite) in its microstructures. The uniaxial tension tests were carried out at different strain rates. From the tensile data, it has been identified that strength decrease and ductility increase with the increase in the strain rate and vice-versa. The higher strength and lower elongation are obtained for Q&T and austempered specimens, the lower strength and higher elongation are obtained for the annealed sample, and optimum strength and elongation were obtained for the ICA sample. The tensile testing exhibits a substantial increase in texture intensity for both annealing and ICA specimens due to significant plastic deformation. On the other hand, the increase in texture intensity is less in the austempered and Q&T samples since it resists the tensile deformation by hard phases. The compression properties followed a similar trend like tensile properties. The bulk texture of deformed compressed samples shows that the high intensity ζ--fiber is formed due to increased plastic deformation of the annealed specimen. However, because of the less plastic deformation, less intensity of ζ-fiber combined with the formation of ϒ -fiber has been observed in the austempered and ICA samples. From the impact test results, it has been found that though, the annealed specimens possess the highest impact energy value at higher temperatures, their impact strength falls rapidly below 0oC. Moreover, even at higher x temperatures, the impact strength of the ICA sample is near that of annealed specimens and good at sub-zero temperatures. The last objective is the study of wear behavior. The heat-treated DCI samples were tested under a ball-on-plate type tribometer to study the wear behavior. The Taguchi optimization technique (L16) was initially applied to evaluate the influence of different process variables (load, time, heat treatment, and grade) during the ball-on-plate wear test. Meanwhile, the analysis of variance (ANOVA) method was adopted to know the significance of aforesaid process variables. ANOVA results confirms that the heat-treatment process has the highest significance (54.76%) within all process variables. Among heat-treated specimens, austempered samples have outstanding wear resistance, while the ICA samples have lower wear resistance. In addition, overall utility values have been evaluated using individual utility values of weight loss and hardness. The obtained overall utility value gives the optimum combination for achieving higher wear resistance and hardness. Additionally, the morphology of wear surfaces was examined in a scanning electron microscope, and the micrographs confirm the existence of inferior surfaces in terms of abrasive wear, adhesive wear, particle pullout, and delaminated sheets on the wear track. Enrichment of oxygen element has been observed on the worn path through energy-dispersive spectroscopy. XRD analysis confirms the existence of different compounds like iron and silicon oxides on the wear track surface which may improve its hardness
Design and Real-time Implementation of Robust Control Schemes for Twin Rotor Multivariable System
No full textIn the real world, many physical systems are not only nonlinear but also highly uncertain. Hence, it is necessary to design robust controllers for these systems to achieve efficient set-point tracking and disturbance rejection. A lot of research works have been directed in the past to develop controllers for Multi-Input Multi-Output (MIMO) systems. MIMO systems are more complex than a Single-Input Single-Output (SISO) systems, because in the former, loop interactions exist among different control loops. Thus, opportunities lie in developing control strategies for uncertain non-linear MIMO systems like magnetic levitation system, helicopter system, under water vehicle, and twin rotor system etc. Among the non-linear MIMO systems, helicopter system is considered as a one of the most popular complex MIMO system. As the model of the helicopter system is so expensive, various researchers have chosen the Twin Rotor MIMO System (TRMS) as it is a laboratory prototype model of helicopter system. Basically, aerodynamic control of helicopter and TRMS are little bit different. Aerodynamic control of helicopter varies the angle of the rotor blades whereas TRMS varies the speed of the motors. However, because of the external disturbances, model uncertainties and inherent cross-coupling effects, designing a suitable controller for TRMS becomes a challenging task. As the dynamics of the TRMS is complex due to its nonlinearities, cross coupling; System Identification (SI) method is adopted for modelling of the system. SI toolbox constructs mathematical models of dynamic systems from measured input-output data. SI toolbox of MATLAB is a good way of obtaining models for systems that are difficult to model. Autoregressive Moving Average Model with Exogenous inputs (ARMAX) model is very often used in performing system identification. After obtaining suitable model of the TRMS by employing SI, the thesis explores design of efficient robust control schemes. Several robust control approaches are exploited to realise these controllers as described below. The control of TRMS is difficult to operate because of external disturbances and uncertainties. Moreover, there is a coupling between the pitch and yaw channels, making it more difficult for the two channels to be controlled independently. For the control of pitch and yaw channels for TRMS, an Internal Model Control (IMC) based Proportional Integral Derivative (PID) controller is proposed in this thesis. In order to analyze the performance, robust PID controller based on Linear Quadratic Regulator-Linear Matrix Inequality (LQR-LMI) approach is compared with the proposed controller. From the Obtained results, it is confirme that IMC based PID controller exhibits superior performance than the L QR LMI based PID controller, in terms of improved attitude angle tracking and disturbance rejection ability. Considering the difficulties encountered in TRMS, a H¥ controller with two Degree of Freedom (TDOF) is designed to handle the mode lun certain ties and externaldi sturbances. For handling both of these, TRM Suses mixed sensitivity approach. For performance analysis, the proposed H¥ controller is compared with L QR-LMI based robust PID controller and IMC based PID controller in MATLAB/Simulink and then in real platform. Based on the results, the proposed controller can be concluded to be more robust, faster in tracking performance, and more accurate in disturbance attenuation than LQR-LMI-based robust PID controller sand IMC based PID controller. A TDOF-IMC based Generalized Active Disturbance Rejection Controller (GADRC) for TRMS is proposed in this thesis. Similar to ADRC, GADR Cuses the Extended State Observer (ESO) to estimate in ternalun certainties and lumped disturbances as external disturbances. GADRC is an extremely advantageous controller synthesis approach that can utilize any available data concerning the system. Further more, GADRC can also beutilized for non-minimum phase a swellasun stable processes that are extremely challenging to control using the ADRC. The GDRC structure is converted in to the renowned TDOF-IMC structure for ease of analysis and tuning. Further more, it is shown that the tuning b and widths for the set point filter and the disturbance rejection filter in TDOF-IM Care the inverse of the two time constants, thus tuning be comes easieror those practitioners familiar with the IMC method. Among all the robust controller proposed in the thesis, GADRC controller is found to be the most effective one
A Study on Cannabis Sativa L. Hemp Reinforced Polymer Composites for Marine Applications
No full textTraditional engineering materials pose a great challenge for marine environment due to their corrosive nature leading to ocean acidification. This further poses a great threat to marine creatures destroying their environment. Since decades, polymer composites started replacing traditional materials like metals for making marine structures due to their high strength to weight ratio, low elongation, and low life cycle cost because of fewer problems associated with wear and corrosion. Over the time, the use of fiber reinforced polymer (FRP) composites have grown from manufacturing pleasure boats, boat hulls etc. to large scale applications like submarines, military vessels, propellers and propulsion shafts. Apart from traditional marine ship and boat structures, FRP composites have gained popularity in the field of offshore industries like lifeboats, buoys, floats etc., and renewable marine energy such as tidal and floating wind turbines. The utilization of natural fiber over synthetic fiber as reinforcement in polymer composites have been growing recently, as the world becomes more environmentally conscious. So, this work is undertaken to study the potential of a natural fiber for marine applications. Natural plant fibers are primarily composed of cellulose, hemicellulose, lignin, pectin, and wax, with small amounts of other constituents. These constituents have an impact on the fiber’s physical, mechanical, thermal, and other characteristics. Therefore, the careful selection of suitable natural fiber for the desired application is required. The researchers’ estimations or limited evaluation perspectives still govern the selection of natural fibers for composite fabrication. By applying multi-criteria decision making (MCDM) methods to the properties of natural fibers, one can make a statistically sound decision about which fiber to use. However, this can be a disadvantage in terms of the complexity of testing for determining fiber properties when introducing a new fiber. Determination of chemical constituents is an easy and straightforward procedure. A novel technique is designed in MATLAB for natural plant fiber selection based on the chemical constituents of the fibers as well as the correlation between the properties of the fibers and their chemical constituents using MCDM techniques. The correlation matrix is used to convert the weights given to properties into the weights of chemical constituents by weighted scoring model. Hemp is one of the strongest and most durable commercially available natural fiber. Its biodegradability, low density, high fiber length, availability, low weight-to-strength ratio and more yield per acre makes it an ideal fiber for marine applications. Before reinforcing any fiber/fabric into the matrix to form composites, its characteristics should be investigated. The strength of fiber has significant effect on the performance of a composite because it bears majority of the load. The present work describes the modern and systematic methods for examining the physical and mechanical properties of Cannabis sativa L. hemp fiber and its fabric. The hemp fiber is characterized in this study based on its constituents. Additionally, thermal stability, crystallinity, elemental analysis, and Fourier transform infrared spectroscopy has also been determined. The physical, mechanical and dynamic mechanical properties, thermal stability, water absorption of hemp fiber reinforced polymer composites have been studied. A numerical simulation was performed to determine the loads on a surfboard in a marine environment. MCDM techniques are utilized to select the best suitable hemp composite among the alternatives for fabrication of surfboard. The findings of this study provide valuable insight into the potential use of hemp fiber for surfboard fabrication
Matching Theory based Efficient Task Offloading Strategies in IoT-Fog Networks
No full textTask offloading enables Internet of Things (IoT) devices with constrained resources to transfer tasks to remote Cloud/Fog Nodes (FNs), facilitating the execution of time-sensitive services. The delegation of tasks for real-time services, including industrial automation, online gaming, video streaming, virtual reality, augmented reality, and smart healthcare, to a distant cloud server results in undesirable delays. The factors contributing to these delays are intermittent communication channels, considerable physical distances between IoT devices and the Cloud, and the limited availability of spectrum resources. Thus, transferring tasks to nearby FNs proves more advantageous as it brings about numerous benefits, including improved latency, improved energy efficiency, higher scalability, and reduced costs. Nevertheless, the act of offloading tasks to FNs presents several notable research challenges: (i.) the allocation of limited FN resources, (ii.) adherence to maximum tolerable delay constraints for heterogeneous services, and (iii.) the necessity for computationally inexpensive and scalable strategies. Additionally, the task offloading problem has been established as NP-Hard problem. In this regard, the initial contribution introduces three protocols based on matching theory. These models utilize different variations of the Deferred Acceptance Algorithm (DAA) with maximum and minimum quotas at FN. The objectives of these protocols are to minimize the average offloading delay and outages caused by non-cluster assignments. Note that outages mean offloading delay of the task overshooting its prescribed tolerable delay. The initial protocol, called Artificial cap Deferred Acceptance based Fair Task Offloading A-DAFTO, incorporates an additional quota at FN, i.e., artificial quota, to provide a non-cluster allocation with a relatively balanced distribution. Imposition of artificial quotas at FNs can result in inefficient utilization of computationally efficient FNs, deleteriously impacting the objectives. To address this limitation, another matching-based protocol is devised, referred to as Multistage Deferred Acceptance Fair Task Offloading M-DAFTO. In this approach, the FN operates only with maximum and minimum quotas. Furthermore, enforcing the strict processing order of tasks in M-DAFTO is achieved by utilizing a Precedence List (PL) as input. It appears that M-DAFTO yields superior outcomes compared to A-DAFTO, but this configuration needs to be revised as it fails to fully exploit the potential of all the computationally efficient FNs inside the network with a restrictive environment. Hence, an alternative protocol, Extended Deferred Acceptance Fair Task Offloading E-DAFTO, is developed that does not impose strict task processing orders. This suggests that the tasks can propose the FNs in any processing order, demonstrating flexibility without compromising the objectives. All the protocols mentioned above have the following pitfalls: (i.) outcome of each protocol is partially stable, (ii.) the energy consumption at IoTs and FNs is discarded while taking offloading decision. The subsequent contribution introduces a framework Deferred Acceptance based Strongly Stable Task Offloading DASTO to rectify the limitations identified in the preceding contribution. The proposed approach in this study involves adopting a many-to-one matching-based offloading technique. This strategy considers the maximum quota of the FN and aims to provide a strongly stable matching that addresses the first issue. The second problem is addressed by considering energy usage in the context of the IoT and FN while making offloading decisions. Despite generating a strongly stable assignment, DASTO exhibits certain deficiencies. (i.) User cost should be considered in the decision-making process of offloading, potentially leading to a better Quality of Services (QoS) experienced by end users. (ii.) In a multiple Service Providers (SPs) scenario where they deploy the FNs, DASTO may not perform efficiently. To address the challenges associated with DASTO, the third contribution introduces a framework known as a Student Project Allocation based Strongly stable Task Offloading (SPASTO) model. This framework utilizes a Student Project Allocation Algorithm (SPAA). SPASTO provides a strongly stable matching plan and minimizes not only the average offloading delay, outages, and average offloading energy but also the total user cost
Factors Affecting the Earnings Management Practices in India
No full textThere is hardly a day on which we do not get any news of account manipulation, banking fraud, bankruptcy, insolvency and leading/large firms misleading investors by using discretion in reporting. The definition of a ‘true and fair view’ of the financial position disclosed by the firms is continuously under debate. The provisions of Generally Accepted Accounting Principles (GAAP) are being used at managerial discretion. These discretionary practices are called ‘Earnings Management (EM)’. This practice is followed by managers to reduce agency conflict among managers and shareholders or between controlling shareholders and minority shareholders. This affects the earnings quality of the firms in India. As a solution, researchers have developed some measures to detect earnings management. The main aim of this study is to find the inter-relationship among the measures of earnings management and to examine the impact of financiers, the board of directors and the exposure to the stock market. The role of financiers is measured by two variables: total debt amount and bank debt amount. Board size and board independence represent the impact of the board, while the listing status and International Financial Reporting Standards (IFRS) adoption measure the exposure a firm gets. The sample for the study is selected from Indian nonfinancial firms, which include the Food and Agriculture-Based industry and Mining industries. These industries represent the primary sector of the economy and contribute to the economy to a great extent. The data has been collected from the Prowess database of the Centre for Monitoring Indian Economy (CMIE), financial reports of the firms, various reports published by the Securities and Exchange Board of India (SEBI), Reserve Bank of India (RBI) and the Ministry of Corporate Affairs (MCA). The data has been processed for 1818 firms for the period of 2002-2022, after excluding the firms that do not have complete balance sheet data for at least five years. The numbers which do not support the basic accounting equation and the outliers are removed. Hence, 18672 firm-years are included in the final sample. However, some observations were removed while doing regression analysis with list-wise exclusion of missing data. First, discretionary accruals are estimated crosssectionally for each industry sub-sector, using ten different models of earnings management. Then all the measures are compared through different statistical tools and found to be consistent with each other. The absolute value of discretionary accrual estimated by the modified Jones (1991) model is used for further analysis. The impact of the variables is examined by using the Least Square Dummy Variable Regression model. The results depict a significant impact of bank loans on reducing earnings management while the level of earnings management increases with increased borrowings from outsiders. The board has an insignificant impact on earnings management. It is seen that earnings management is practised more in un-listed firms than in listed firms. But, implementing IFRS has no significant effect on EM behaviour in India. The major contributions of the study are - a) attempting three new measures of earnings management inspired by previous researcher criticism on EM measures, b) studying the perspective of of both banking and non-banking lenders, c) exploring the effect of exposure a firm gets by adopting IFRS and from stock exchange regulations. The study has various theoretical and practical implications for fraud detection, improving board quality, supervision on adopting accounting standards, and efficient implementation of strict policies
Processing-Microstructure-Mechanical Properties of Freeze-cast Porous Alumina Scaffolds with 3-Levels of Structural Hierarchy
No full textUnidirectional freeze casting (ice-templating) evolved as a promising processing route in the past decade to fabricate unique porous materials where pores are oriented in a single preferential direction. This simple and straightforward technique offer better tailorability of the pore structures, and hence the material processed by this route has potential applications in various fields like filtration, catalysis, biological scaffolds, energy generation and storage, electrodes for SOFC, impact protection etc. However, this wide diversity in applications demand large-scale ordered porosity with controlled pore morphology. In the quest of developing such materials, control of several processing/freezing conditions which are directly associated with the underlying principles of the technique, is utmost necessary. To this end, a holistic study on the processing microstructure-property is imperative to produce novel directional porous materials with desired pore structures and porosity fractions. The primary work of the dissertation involves directional freezing of anisotropic alumina platelets and unfold the effect of shape anisotropy on the growing freezing front, vis-à-vis, the final microstructure. Unidirectional freeze casting was carried out under large vertical temperature gradient in a custom-built setup, that resulted in large-scale ordered lamellar structure; mainly due to the fast and straightforward self-assembly of platelets during directional solidification. A microstructural montage was presented to delve into the effect of both smaller (4 μm) and bigger (8 μm) size platelets on the freezing induced microstructural evolution along the ice-growth direction of the scaffold. This observation was explained on the basis of ice physics and the interaction of ceramic platelets with the advancing freezing front. An array of microstructures was produced by freeze casting over a wide range of freezing velocities (1.4 – 2600 μm s-1), platelet sizes (4 and 8 μm) and solid loading (10 to 40 vol%) to study their influence on various structural parameters, viz. wavelength (λ), lamella thickness (δ), and bridge density ρb). The ensemble of micrographs presented indicate the influence of processing variables on the transition between platelet rejection and engulfment by the ice lamellae. This corresponds to the microstructural transition of either (a) lamellar to dendritic to isotropic (more accurately dendritic overlayer structure) or (b) directly from lamellar to isotropic (precisely lamellar overlayer structure). The microstructures were further quantified with a specific dimensionless parameter m. For smaller platelet (4 μm) scaffolds, the microstructure to be lamellar with low bridge density and m > 4. The wavelengths and bridge spacing were comparable for 2 2 and isotropic for m 85%). The microstructural evidences along with the Gibson-Ashby model prediction for out-of-plane deformation of honeycomb structure clearly suggest that buckling induced elastic instability of the lamella walls sets the limit for maximum compressive strength of the scaffolds (level-1 structure). The highly porous alumina platelet scaffolds (level-1) resulted in lower compressive strength mainly due to the presence of large amount of macropores as well as micropores present within the lamella walls. To overcome this and to strengthen and stiffen the freeze-cast scaffolds, a unique strategy was adopted by introducing a silica-calcia liquid phase sintering aid (LP), and creating another level of structural hierarchy (i.e. level-2). The idea of using SiO2-CaO liquid phase with molar ratio of 75:25 is due to its better wettability that facilitates the platelet rearrangement during liquid phase sintering, and thereby reducing the inter-platelet gap (i.e. micropores) which results in the enhanced densification of the ceramic walls. The response of the scaffolds (with level-2 hierarchy) under uniaxial compressive stress was strongly influenced by both pore morphologies and LP concentration. At fixed LP content, the compressive load bearing capability gradually increased from lamellar to dendritic to isotropic structures. Again, the higher amount of liquid phase (20 vol%) caused remarkable increase in the compressive strength of the freeze-cast scaffolds with level-2 architecture. More importantly, the failure mode of the scaffolds was changed from damageable, cellular- like (localized damage) to brittle-like failure (global fracture) at higher LP content. The transition of failure behaviour from cellular to brittle was observed to occur at ‘porosity fraction at transition’ of ~70%, and the corresponding critical buckling load (Pcrit) for the transition was calculated to be about 2.3. The robust walls produced by the addition of liquid phase sintering aid resulted in extraordinarily improvement of both strength and stiffness of level-2 hierarchy structure, i.e. almost two orders of magnitude higher than level-1. Further, 3rd level of structural hierarchy was created by adding submicron size equiaxed alumina particles in the level-2 structure containing alumina platelets and liquid phase precursors. The notion for this inclusion is to modify the lamella wall architecture by creating inter-platelets bridges, thus promoting extrinsic toughening of the lamella walls by large-scale crack deflection by these bridges. The particle induced interlocking of the platelets also offers additional resistance to the lateral bending (buckling) of the lamella walls by restricting the platelets movement during uniaxial compression. As a result, the compressive properties of level-3 architecture was remarkably increased (than level-2) due to the synergistic effect of alumina platelets, liquid phase sintering aid and alumina particles. The increase in the mechanical properties due to the reduction in porosity from level-1 to 3 was quantitatively assessed to be insignificant as compared to the combined effect of all 3 structural components. Overall, the present thesis elucidated an in-depth investigation on the processing-microstructure-property (mechanical) correlations for a multi-level hierarchical freeze-cast porous alumina scaffolds which would offer valuable insights to produce novel porous ceramics. The approach of improving the strength and stiffness of the directional porous ceramics as delineated in the present work can be utilized for the design and development of several bioinspired materials
Rationally Designed Peptides as Inhibitors of Hen Egg-White Lysozyme Amyloid Formation
No full textMisfolded and natively disordered globular proteins have a tendency to aggregate together to form fibrous, proteinaceous deposits referred to as amyloid fibrils. Formation and deposition of such insoluble fibrils are the hallmarks of a broad group of diseases known as amyloidosis, such as Amyloid-Beta (Aβ) in Alzheimer’s disease (AD), human Islet Amyloid Polypeptide (hIAPP, amylin) in type 2 diabetes, α-synuclein (α-syn) in Parkinson’s disease (PD) and so on. The fact that these proteins do not share any significant sequence or structural homology in their native states makes therapy quite challenging. Hotspot regions, known as aggregation-prone regions (APR), within the sequence of the amyloidogenic protein/peptides, are the nucleation point upon which fibril progression takes place. In the research presented in this thesis, we have meticulously designed synthetic hexapeptides based on the APR sequence of hen egg-white lysozyme (HEWL, a model amyloidogenic protein) and explored their anti-amyloidogenic potency on in-vitro amyloid formation of HEWL at acidic pH and physiological pH, and the peptide inhibitors are referred to as SqPs (Sequence-based Peptides). Notably, SqP1, amongst the others, exhibited a remarkable lysozyme amyloid inhibition rate of over 70% and ~50% at pH 2.2 and pH 7.5. Further, SqP1 was modified by incorporating either acidic (Aspartate or Glutamate) or basic (Lysine or Arginine) amino acid residues to impart net charge to the peptide. Out of these, Asp- modified SqP1 (SqP4) and Arg-modified SqP1 (SqP7) were further chosen based on computational docking, and the anti-amyloidogenic propensity of these modified peptides was further investigated. Interestingly, as the conditions chosen for conducting this study are different (acidic and neutral), SqP4 displayed a protonation-state-dependent anti-amyloidogenic propensity against HEWL amyloid formation. This study enabled us to shed light on the factors kept in mind while designing a sequence-based anti-amyloidogenic peptide inhibitor; the incorporation of amino acid residues should not only be done to achieve favorable interactions but also to carefully avoid any unfavorable interactions leading to non-specific binding. Furthermore, the Arg modified SqP1 (SqP7) showed excellent amyloid inhibition capability at both pH conditions and was further chosen as a coating agent on gold nanoparticles. The anti-amyloidogenic capability of the synthesized peptide-coated gold nanoparticles (SqP7-AuNP) was further evaluated, and it was observed that upon coating, the efficacy of SqP7 was increased around 10 times molarity-wise. The findings of this work were achieved using molecular docking techniques alongside an array of biophysical methodologies, including fluorescence spectroscopy, UV-vis spectroscopy, FTIR spectroscopy, CD spectral analysis, confocal laser microscopy, and transmission electron microscopy. The insights gained from this study can be further utilized to increase the efficacy of anti-amyloidogenic synthetic peptide inhibitors and aid in the development of synthetic peptides as therapeutics against other amyloid-related diseases such as Parkinson’s disease, Alzheimer’s disease, type II diabetes, etc. Moreover, the findings from this work can overall increase the quality of fundamental research and ventures taken in the future in the field of amyloid-related diseases