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Unravelling the Role of Heme in Bacterioferritin and Regulating Ferritin Self-Assembly: Implication Towards Health and Diseases
No full textIron behaves as a double-edged sword, i.e., beneficial as well as harmful, for both host and pathogens. During the host-pathogen battle for iron, host secretes H2O2 to kill pathogens but pathogens employ counter mechanisms/ antioxidative proteins to detoxify it. Mycobacterium tuberculosis (Mtb), the causative pathogen of tuberculosis, expresses two maxi-ferritins: a heme binding bacterioferritin (BfrA) and a non-heme ferritin (BfrB) but not the mini-ferritin, i.e. Dps protein (which protects DNA from H2O2 induced oxidative stress). In the absence of Dps, Mtb must have evolved with other defensive strategies. Moreover, the expression of BfrA along with BfrB possibly suggests the existence of some additional functions for BfrA/heme. The current study on Mtb BfrA revealed its two new functions (catalase and Dps-like DNA protection activity) along with rapid ferroxidase activity. The presence of heme in Mtb BfrA contributes to its enhanced cage stability and reductive iron mobilization. Ferritin proteins are hollow, spherical, nanocaged structures, which are self-assembled from 24-polypeptide subunits and are capable of storing ~4500 iron atoms as ferrihydrite mineral. Although the factors that drive self-assembly process and control its kinetics are little investigated, the inherent reversibility of this phenomena has been recently exploited in cellular imaging and targeted drug delivery. The laser light scattering studies on ferritin self-assembly identified subunit monomers/dimers as starting materials and revealed the factors that altered the kinetics whereas electrostatics predicted the critical amino acid residues. In addition, the ferritin environment was modified by a biopolymer (guar gum) to repress iron mobilization by inhibiting the cage disintegration under acidic conditions, possibly suggesting its implication in oral iron formulations. Therefore, the current dissertation not only strengthens the understanding of the new functions of Mtb BfrA along with the role of heme, to possibly serve as a future platform to curb tuberculosis, but also provides insights on ferritin self-assembly to optimize the loading/unloading of drugs and nanomaterials for biomedical applications
Wavelets Based Numerical Techniques for Solving Integral and Integro-Differential Equations
No full textIntegral equations have emerged as one of the most effective tools in applied mathematics. We adopted different approximation techniques to solve both linear and nonlinear integral and integro-differential equations of both integer and fractional order. The main objective of this study is to classify the approached techniques and estimate their accuracy and efficiency. Also, the concept of fractional calculus has been discussed in our work. Fractional calculus has many applications in the field of science and engineering such as electromagnetics, viscoelasticity, fluid mechanics, electrochemistry, signal processing etc. It plays an important role in the integration and differentiation of functions with non-integer orders. The present dissertation deals with the development of operational matrix method and collocation method based on different types of one-dimensional and two-dimensional wavelets for solving linear and nonlinear integral and integro-differential equations. The purpose is to analyse the accuracy and efficiency of the wavelet methods of solving the proposed equations. The preliminary concept of integral equations and integro-differential equations along with different kinds of kernels and the introductory concept of fractional calculus have been described in Chapter 1. In Chapter 2, basic definitions and properties of different types of wavelets such as Legendre wavelet, Bernoulli wavelet, Jacobi wavelet, Gegenabuer wavelet, CAS wavelet, Mu¨ntz-Legendre wavelet, Euler wavelet, Taylor wavelet and Laguerre wavelet have been discussed. In Chapter 3, a novel technique based on Bernoulli wavelets has been proposed to solve two-dimensional Fredholm integral equation of second kind. Bernoulli wavelets have been created by dilation and translation of Bernoulli polynomials. Also, a collocation scheme based on Laguerre wavelets has been introduced for solving the linear and nonlinear Fredholm integral equations as well as the linear system of Fredholm integral equations with weakly singular logarithmic kernel. The approached techniques have been used to transform the respective proposed equations into an algebraic system of equations. Moreover, the obtained simulation results of the several experiments are also presented in both tabular and graphical form to describe the efficiency and applicability of the approached scheme. In Chapter 4, two numerical methods, known as Gegenbauer wavelet method and CAS wavelet method have been introduced for the numerical simulation of two-dimensional Volterra integral equation. In addition, a collocation-based method based on the Jacobi wavelets method has been studied for the solution of system of two-dimensional Volterra integral equations. Finally, a brief discussion including numerical problems are presented in order to show the accuracy and effectiveness of the proposed schemes. In Chapter 5, an effective approach has been proposed to obtain the approximate solutions of linear and nonlinear two-dimensional Volterra integro-differential equations. The operational matrices of integration, differentiation, and product based on two-dimensional Bernoulli wavelets have been constructed. By utilizing the properties and matrices of wavelets along with the collocation point, the two-dimensional linear and nonlinear Volterra integro-differential equations are reduced into the system of linear and nonlinear algebraic equations respectively. The convergence analysis and error analysis have been extensively studied by the help of two-dimensional wavelets approximation. Comparison of error values and some figures obtained by the proposed wavelets have been presented in order to justify the error analysis of the proposed method. In Chapter 6, an operational matrix scheme based on two-dimensional wavelets has been introduced for the solution of weakly singular linear partial integro-differential equations and nonlinear partial integro- differential equations. By implementing two-dimensional wavelets approximations and its operational matrices of integration and differentiation along with collocation points, the linear and nonlinear weakly singular PIDEs are reduced into the system of linear and nonlinear algebraic equations respectively. Some numerical examples are included to establish the accuracy of the proposed scheme via Bernoulli wavelet approximation and Legendre wavelet approximation respectively. In Chapter 7, an effective numerical framework has been developed to obtain the solution of the Pantograph Volterra delay-integro differential equation. By utilizing the Mu¨ntz-Legendre wavelet based operational matrices along with the collocation points, the one-dimensional Pantograph Volterra delay-integro-differential equation has been reduced into an explicit system of algebraic equations. Also, a numerical operational matrix approach based on Euler wavelet is proposed to solve the nonlinear Pantograph Volterra delay-integro-differential equation of fractional order. Additionally, some numerical problems are solved to justify the applicability and validity of the presented techniques. In Chapter 8, the main objective is to establish a fractional-order operational matrix method based on Euler wavelet for solving linear Volterra-Fredholm integro differential equations with weakly singular kernels. Again, an approximation technique based on Taylor wavelet has been employed for the solution of linear and nonlinear fractional order Volterra integro-differential equation with weakly singular kernels. The results of numerical experiments have also been reported in both graphical and tabular form to illustrate the efficiency and validity of the presented methodologies. In Chapter 9, a numerical operational matrix approach based on Taylor wavelet method is proposed for solving the linear and nonlinear Volterra-Fredholm integro-differential equations. Several theorems are presented to establish the convergence and error analysis of the proposed method. Additionally, several numerical problems are included to justify the efficiency and validity of the presented technique
Essays on the Perspective of Foreign Direct Investment in South and South-East Asian Economies: Beyond its Growth Effects
No full textForeign Direct Investment (FDI) is the process that enables the residents of one country to acquire ownership of assets in another country thereby controlling the production, distribution, and other activities in a firm of that country. The period of globalization in the 1990s marked the flow of private investment from developed countries to developing countries, mostly in the form of FDI. The developing countries are left behind in the process of economic growth due to lack of capital accumulation, poor infrastructural facilities, technological backwardness, low investment and paucity of research and development. FDI from the developed countries helps in boosting their economy by increasing investment and efficiency, leading to economic growth. It provides capital for financing new industries and enhancing the existing ones, boosts the infrastructure, creates new employment opportunities and increases productivity. It has been considered as a source of employment generation and modernization through transferring technical know-how and enhancement of technology. It helps in increasing the efficiency of resource use as well as total factor productivity in the host economy. As a result, it aids in increasing the production capacity and capital accumulation. Thus, it acts as a catalyst to economic growth. Prior to the 1990s, South Asia and Southeast Asia were only partially open to FDI; however, after realizing the importance of FDI in determining investment, economic growth, and employment, the governments of these regions began to act as 'facilitators' to draw FDI. South Asia and Southeast Asia have recently been favored recipients of FDI inflows due to their strong economic growth in services and exports, their sizable domestic market, and the favorable opinions of international investors. The World Bank anticipates that these regions will be crucial to the global development narrative in the Asian century. Although South Asia and Southeast Asia were only partially open to FDI before the 1990s, their governments came to understand that FDI is a key factor in determining investment, economic growth, and employment during this time and began acting as "facilitators" to draw FDI. Due to this, FDI inflows rose, making South Asia and Southeast Asia a more desirable location for foreign investors, albeit not as desirable as China or Brazil. This is due to the unfavorable business environment, which includes subpar infrastructure, stringent labour laws, a lack of coordination between government departments on policy, a policy for special economic zones (SEZs) that is dormant, a lack of institutional reforms, corruption, and cost and time overruns in infrastructure projects as a result of contractual and institutional failures, which are frequently brought on by a lack of coordination between central and state government departments on land acquisition and environmental clearance. The present study broadly examines the determinants and impact of FDI inflows in South Asian and Southeast Asian countries. The first objective of the study is to investigate the determinants of FDI inflows in South Asian and Southeast Asian countries. We have used data from WDI over the period 1980-2019 for this study. Six explanatory variables (market size, trade openness, infrastructure, inflation, exchange rate and human capital) were considered for the study. We used the Hausman test to determine which of the two models (fixed effect model and random effect model) fits our data the best. We found the fixed effect model to be the best fit and the results indicate that market size and human capital yield significant coefficients in relation to FDI inflow for the panel of 18 countries under consideration. The findings also reveal that the influence of inflation on FDI was negative and significant. This implies that with a decrease in the rate of inflation, FDI inflows increase in the South Asian and Southeast Asian countries. The second objective is to examine the role of foreign aid on FDI inflows and economic growth in South Asian and Southeast Asian countries. We examine the interrelationship among foreign aid, FDI and economic growth during 1980–2019. For unit root tests, we have applied LLC, IPS and PP-Fisher tests. After testing the stationarity of the variables, we run the Johansen-Fisher Co-integration test to establish the long run relationship among the variables during the concerned time period. Further we proceed with OLS, quantile regression and system GMM. Our empirical results from alternate empirical estimations suggest that FDI flows positively impact economic growth in the region. Whereas GDP growth attracts FDI only when entire in South Asian and Southeast Asian region as a whole is considered; underlying the importance of trade integration to benefit from foreign capital. In this regard, our findings also suggest that being a member of WTO have shown mixed impact on FDI and economic growth in the region. This clearly indicates that mere compliance of WTO norms might not work well for most of these economies due to their macroeconomic constraints and structural bottlenecks. We find that foreign aid flows have contemporaneous negative relation with FDI flows. The results indicate that foreign aid crowds out FDI. The third objective examines the effect of institutional quality on FDI inflows in South Asian and Southeast Asian countries by controlling the effects of macroeconomic instabilities during the period 2002-2019. We have used six governance indicators as a measure of institutional quality by the use of Principal Component Analysis. The governance indicators have been extracted from the WGI database. In this study, we have applied Iterated-GLS (IGLS) model for estimation of the results. We find that institutional quality affects FDI inflows in this region positively. Furthermore, we have investigated the impact of each of the six variables separately on FDI inflows and found that except for the 2 variables, that is, rule of law and voice and accountability, all the other institutional variables have a positive impact on FDI inflows. The fourth objective investigates the impact of FDI inflows on domestic investment in South Asian and Southeast Asian countries over the period 1990-2019. We have used various panel methods such as Westerlund co-integration, pooled OLS, fixed effect, GMM system, and FMOLS. We found the existence of long run stable relationship among the variables from the cointegration test. Further, the results showed that, in the South Asian and Southeast countries, a one unit increase in FDI led to increase in domestic investment by more than one unit in the long run. This implies that an increase in FDI will lead to improvement in the domestic investment in the South Asian and Southeast Asian countries. In other words, FDI crowds in domestic investment in these regions. Lastly, the fifth objective examines the effect of ICT and FDI on environmental pollution in South Asia and Southeast Asia during the year 1990–2019. We use Pooled Mean Group (PMG) and Dumitrescu-Hurlin Panel Causality for the estimation of the results. Our results suggest that ICT and FDI affect the carbon emissions or environmental pollution negatively. This implies that with the rise in ICT infrastructure and FDI inflows, environmental pollution decreases significantly in the long run. The Dumitrescu-Hurlin causality results suggest the existence of bidirectional causality among ICT and FDI which implies that increase in foreign investment leads to increase in ICT infrastructure and also, with increasing ICT infrastructure, the foreign investment increases in the South Asian and Southeast Asian countries
Strategies for Load Balancing in Multi-tenant 5G C-RAN Architecture
No full textThe availability of resources to meet the ever-growing demand of traffic limits the efficiency of existing cellular networks. The next-generation cellular platforms need to be scalable, flexible and support multiple radio access technology (M-RAT) to overcome the resource availability problem. Moreover, to minimize capital expenditure (CAPEX) and operational expenditure (OPEX) there is also a need to modify the network architecture and control strategy. The 5G C-RAN architecture is in this direction to meet the above objectives. Centralized processing and controlling in C-RAN reduce associated cost and make the base station energy efficient. However, centralization of all baseband processing increases computational complexity and associated delay. An unbalanced condition at remote radio head (RRH) and centralized base band unit (C-BBU) arises when utilization of physical resources goes beyond a certain threshold limit due to an increase in traffic or processing load. Due to unbalanced conditions, the system performance at RRH and C-BBU worsens and increases corresponding power consumption. This thesis has attempted to enhance resource utilization by distributing the load across the available processor at C-BBU. A co-operative load balancing (CLB) technique is proposed to maximize resource utilization and system throughput by sharing traffic and processing load between RRHs and C-BBUs. Efficiency of the proposed co-operative approach is evaluated using different parameters like waiting time, blocking probability, and processing time at RRH and C-BBU. It is observed that the CLB has the lowest waiting and processing time as well as the blocking probability compared to the existing contemporary algorithm. For load balancing across the BBU-pool, an inter-BBU migration is proposed; here, VBs from an unbalanced C-BBU is migrated to another C-BBU within the same BBU-pool. Performance results show that migration based load balancing reduces migration time and downtime by a significant amount. To reduce load of fronthaul and C-BBU, a multi-tier delay aware load balancing (MDALB) algorithm is proposed. A load distribution factor is used to estimate available capacity for packets allocation inorder to minimize system delay and packet loss. A power consumption analysis for traditional D-RAN and C-RAN was carried out. The analysis shows that C-RAN provides 40% to 50% energy efficiency compared to D-RAN architecture
Studies on Dry and Wet Torrefaction of Sugarcane Bagasse to Maximize the Recovery of Sugars and Bioethanol Yield
No full textBiomass size disruption is a key operation in the process of ethanol production from lignocellulosic materials since enzymatic saccharification of carbohydrate polymers occurs at the molecular level. Various pretreatments of biomass have been extensively studied for the production of sugars and ethanol. However, torrefaction was less explored in the production of sugars. Dry and wet torrefaction techniques have been employed for the production of solid biofuels for many years. Torrefaction technique has been used widely in increasing energy density, hydrophobicity, grindability, enhancing pore structure, and reducing the cost of transportation. In this work, the effect of dry torrefaction of sugarcane bagasse on the production of sugars and ethanol was studied. Moreover, the optimizations of acid (HCl, H2SO4, H3PO4, and HNO3) and alkali (NaOH, KOH, and NH3OH) impregnated sugarcane bagasse (SB) torrefaction were conducted using response surface methodology. Statistically significant models that can predict yields of total reducing sugars were generated. The dry and wet torrefaction experiments of SB were performed at temperatures of 160 °C, 180 °C, 200 °C and 220 °C and residence times of 20 min, 40 min, and 60 min. The sugarcane bagasse pretreated via dry torrefaction at 200 °C for 20 min was observed to produce the highest glucose yields of 199.62 mg g-1 of biomass (dry basis) after saccharification. Furthermore, the pretreated SB under anaerobic fermentation with supplementation of cysteine hydrochloride was noticed to produce ethanol yield up to 81.85 mg g-1 of biomass (dry basis). Moreover, the ethanol yield represents a 19.34% increase for SB when compared with ethanol yields of untreated biomass fermented under anaerobic conditions with cysteine hydrochloride supplement. Moreover, cysteine hydrochloride supplementation enhances ethanol yields through anaerobic fermentation. The crystallinity and chemical nature of biomass materials were analyzed by SEM, XRD, and FTIR. The sulfuric acid impregnated biomass torrefaction using model generated optimized conditions viz temperature (220 °C), sulphuric acid concentration (0.63%w/w) and residence time (10 min) has produced the highest amount of sugars up to 705 mg g-1 of biomass (dry basis) and ethanol up to 320 mg g-1 of biomass (dry basis)
Thermo-mechanical Investigation of Dissimilar Welding of AISI 304 Stainless Steel with Commercially Pure Copper
No full textLaser welding represents a delicate balance between heating and cooling within a spatially localized volume overlapping two or more solids such that a liquid pool is formed and remains stable until solidification. The main objective of this research work is to analyses thermal, metallurgical and physical stages of AISI 304 Stainless Steel – Copper dissimilar couple during laser welding in keyhole mode by numerically and then validate it experimentally. 10.6 μm wavelength CO2 laser and 1.064 μm wavelength Nd: YAG welder machine is used for conducting this experimental analysis and ANSYS FLUENT® software is used for simulation. The difference in metallurgical, chemical, thermal and physical properties of AISI 304 Stainless Steel and Copper makes their laser welding a challenging task. When compared to steel, the thermal conductivity and diffusivity of copper is very high. This result in 90-98% reflection of total laser power impinged on the copper surface, i.e., the property of absorptivity decreases with increase in diffusivity of metal. The transport phenomena (heat transfer, fluid flow and species distribution) are numerically modelled for the case of laser welding of dissimilar metals. The model involves convection in the weld pool along with melting and mixing. The associated metallurgical phenomenon is an extremely complex one, and the present work is a preliminary attempt to model the process after making suitable assumptions. The numerical study is performed using a pressure based finite volume technique after making appropriate modifications to the algorithm to include the associated phase change processes and dissimilarity in the metal properties. The phase change process is modelled using an enthalpy-porosity technique, while the dissimilar metal properties are handled using appropriate mixture theories. As a case study, we have used dissimilar couples of copper- 304 SS. It is observed that the weld pool shape becomes asymmetric when the heat source is symmetrically applied on the two metals forming the couple. As the weld pool develops, the side melting earlier is found to experience more convection and better mixing. Corresponding experiments are performed using the same parameters as in the computations, showing a good qualitative agreement between the two results. After a calibration phase between simulation and experimental results for the same working environment, the FLUENT® model has been very good agreement with the experimental tests
Investigation on Robotic Grasping and Manipulation: An Analytical and Experimental Approach
No full textRobots are employed in the manufacturing plants for the manufacturing of high-quality products and for having a high production rate. Robot grasping and manipulation is an active research area for several decades. Although significant research works are done, stable robotic grasping and manipulation is still a challenging problem. Automatic robotic grasping is a broad area with complicated and challenging tasks to fulfil that includes grasp planning, analysis, grasp synthesis, optimal grasp planning, grasp stability analysis, development of grasp control algorithm, obstacle avoidance, and design of robotic hand, among others. In this research work, an investigation is carried out to study robotic grasping and manipulation using both analytical and experimental approaches. The analytical approach that used the grasp planning and synthesis methods to find the appropriate strategy for grasping the objects. Grasp planning and synthesis are used in grasping and manipulation to find the stable grasp configuration by locating the position of the fingertip of the robotic hand to be placed on the objects. The stability of the robotic grasp is measured in terms of grasp quality measures, which is a mathematical quantification to measure the grasp quality. An evolutionary approach is proposed to enhance the grasp quality measures, so that the obtained robotic grasp achieves stability without any failure. The proposed evolutionary algorithm evaluates the automated robotic grasp planning and manipulation problem as a maximizing problem to enhance the grasp quality. The grasp planning problem is addressed by incorporating the uncertainty in the coefficient of friction while modelling the contact model between fingertips and objects. The proposed model that includes the uncertainty associated with the friction coefficient is handled by an interval arithmetic approach. The experimental approach of robotic grasping and manipulation is carried out for handling objects with different shapes, weights, and sizes, and that can be achieved by the development of a multi-finger robotic hand with adaptive nature to hold a variety of objects. A systematic approach is introduced by using the V-design approach to find a suitable design that fulfils the required design solution by evaluating all the possible scenarios to meet the functional requirements like speed as well as flexibility while grasping the objects. The bio-inspired design approach is adopted to fulfil the design goals (human-robot interaction, robot-environment interaction) and design requirements (efficiency, safety, robustness, adaptivity, control simplicity, and natural motion) through the integration of rigid and soft materials similar to bone and skin of the human hand. The joints of the robotic hands are developed from the inspiration taken from hydraulic joints of spider legs. The mechanics of the proposed robotic hand is fabricated using soft and rigid materials and are investigated with the help of lie algebra, screw theory, and cosserat based approach. The optimal design of the robotic hand is investigated using a proposed evolutionary meta-heuristics method. A case study of the optimal design study is conducted considering three standard parallel gripper configuration to validate the efficiency of the proposed evolutionary algorithm. Then the optimal design study of the proposed robotic hand is carried out considering a single robotic finger as all the robotic fingers are equivalent. The uncertainties associated with kinematic parameters, material properties, and joint inputs of the proposed design are investigated using the affine arithmetic approach. An elaborated study is conducted to characterize the material properties for both rigid (ABS, PLA), flexible (TPU) and soft materials (Ecoflex 00-10, 00-30, 00-50, and Dragonskin 30) used to develop the prototype of the hybrid robotic hand. A tendon driven mechanism is used to actuate the proposed robotic hand, and the soft joints of each finger are operated with pneumatic pressure to perform the in-hand manipulation operations. It is essential to find out the different performance metrics of the developed robotic finger such as finger strength, grasp strength, grasp cycle time, grasp efficiency, slip resistance, and in-hand manipulations. All the above performance metrics are evaluated to find the efficiency of the proposed robot hand. Finally, experimentation is conducted on a variety of objects used in daily life
Fabrication of liquid-repellent Coatings on Cellulosic and Glass Surfaces for Various Industrial Applications
No full textOne of the foremost fascinating properties of materials in nature is the superhydrophobic and self-cleaning abilities of various insect wings and plant leaves. Superhydrophobic/Ultrahydrophobic surfaces exhibit high water repellence, and oleophobic surfaces resist the wetting of liquids which have low surface tension than water. The present research work focuses on surface modification of numerous types of substrates like cellulose-based materials (e.g., filter paper, cotton fabric) and glass substrates by creating superhydrophobic/superoleophobic and superliquiphobic coatings for the different types of applications such as self-cleaning, oil-water separation, biodegradation, stain-resistance, anti-bio adhesion, and transparency. Silica nanoparticles, polymers, and silanes are starting materials are used to produce superhydrophobic coatings by different synthesis techniques such as solution-casting, dip coating, immersion, etc. To optimize the synthesis process, the material variables such as the concentration of polymer, silanes, and nanoparticles are being varied. The process parameters, like immersion time and ambient temperature, are also being needed to vary.
In this thesis, the superhydrophobic coating was developed on the filter paper surface by using polymethyl methacrylate-co-ethyl acrylate polymer (PMMA) /silica nanoparticles (SiO2) by employing the solution-casting technique. The superhydrophobic filter paper was developed by the solution-casting method using hexadecyltrimethoxysilane (HDTMS)/ SiO2 nanoparticles. The superhydrophobic and superliquiphobic cotton fabric was fabricated with Carnauba wax (C.wax)/HDTMS/SiO2 nanoparticles composite. Superhydrophobic/superoleophobic coating on filter paper surface and superhydrophobic coating on glass surface were fabricated using sol-gel of PMMA, 1H, 1H, 2H, 2H, perfluorooctyltrichlorosilane (PFOTS), and SiO2 nanoparticles by employing the dip-coating technique. The prepared superoleophobic/superliquiphobic surfaces were able to repel liquids with surface energy as low as 27 mN/m.
Different structural characterizations viz., the wettability, surface morphology, surface roughness measurement, functionalization of the materials were evaluated. For industrial and practical applications, superhydrophobic surfaces should last under extreme surroundings. So, the stability and durability of these surfaces were widely and systematically inspected under a sequence of extremely harsh conditions. The coatings were assessed at harsh conditions like annealing at high temperatures (40 - 400 °C), irradiation by UV light, and pH resistance at different alkali and acidic conditions (pH 2 - 13), and mechanical durability by performing water-jet, abrasion, sand abrasion, adhesion, and washing (ultra-sonication) tests.
The contact angles were measured, and it has shown more than 170 ° ± 1.5° on all substrates of filter paper, cotton fabric, and glass surfaces. Additionally, the coated samples exhibit excellent self-cleaning, > 96% separation efficiency was studied of oil-water mixtures and emulsion separations in all prepared filter paper samples and cotton fabric. All the filter papers, viz., uncoated, coated, and tested for the separation process, were shown biodegradation. The coated fabrics were shown stain-resistance, anti-bio adhesion (microbial activity) properties. 93% of the transparency was achieved on the coated glass surface. All the results indicate that such types of coatings could also be used for self-cleaning, oil-water separations, stain-resistance, anti-bio adhesion, and transparent coatings at the industrial level applications
Evaluation and Development of Digital Image Correlation Approach to Predict Coal Pillar Failure
No full textUnderground Coal mining is showing an increasing trend to address the technical, societal and environmental challenges faced by surface mining operations. Conventionally coal structure behavior is predicted from laboratory investigation using contactbased approaches. Scientific pillar design has potential to reduce the blocked pillar dimensions. There have been many attempts to study the pillar behavior under loading. Though there exists many investigations to correlate stress and strain under loading, yet pillar failures continue to occur. It is observed that preexisting cracks in the coal specimen dilate substantially before failure occurs under loading. Digital image correlation (DIC), a noncontact based approach is being used successfully to predict material weakness in many industrial applications. The technique is being used to predict crack propagation in geomaterials with limited success. The undertaken investigation is an attempt to establish correlation of crack development and propagation with the weakening of coal pillar through DIC approach. Conventional measurement systems as strain gauges and Linear variable Differential Transducer (LVDT) and DIC based analyses were evaluated for heterogeneous specimen as coal. The experiments were conducted for more than 270 carefully prepared coal specimen sourced from varying depths of 30 m, 75 m and 100 m. DIC based analysis involved more than 20,000 images taken through an image acquisition system. A detailed characterization i.e. physicomechanical and microstructural analysis of those coal specimen were carried out at beginning. Development of experimental setup for DIC is a challenge. DIC approach involves taking images of the surface under loading and comparing those at different stages with that of the undeformed surfaces. The investigation involved more than Speckle pattern is an important step prior to performing DIC analysis with improved accuracy. In this work, two types of speckle patterns were evaluated. A novel method of applying speckle pattern used in this research work was by generating it numerically and applying onto the specimen by silk printing method. The DIC processing parameters as subset size and step sizes were chosen after careful consideration. A comparative study between two types of speckle patterns were evaluated using FEM analysis and a subset size of 99 x 99 and step size of 8 pixels were determined. The DIC approach was found to be very sensitive to small strains than that by conventional approaches irrespective of depths of occurrence. The knowledge of crack threshold stresses are required to realize the failure process of any material. In this investigation, the failure process of coal has been analysed by crack initiation stress, crack damage stress, and peak stress. The crack initiation and
crack damage stresses were determined using three popular methods using volumetric strain, crack volumetric strain and lateral strain. The rate of change in the effective stored strain energy was used to analyze and develop a precursor failure indicator for coal specimens under uniaxial loading. An algorithm has also been developed to find the precursor failure indicator for coal specimens. A comparative study between codes using DaVis and open source code NCorr has been carried out. NCorr was observed to be comparable favourably with that by DaVis with an error of about 4.25 %. The applicability of DIC under cyclic loading in coal specimens exhibited threshold values for fatigue failure strength at 77.10 %,
79.95 % and 66.79 % of uniaxial strength of respective coal specimens at 30 m, 75 m and 100 m depths respectively. DIC analysis was more reliable and exhibited sensitive behavior of coal under axial loading. DIC is a better method of deformation measurement approach
Structural, Vibrational, Dielectric, Ferroelectric and Electrical Properties of (1-x) Na0.5Bi0.5TiO3–x BaTiO3 Solid Solutions and The Effect of Ion Irradiations on Functional Properties of Ferroelectric Ceramic-Polymer Composites
No full textDielectric oxides are an important class of materials, which are widely used in modern electronic and optoelectronic device applications. Ferroelectrics are the non-linear dielectrics, which possess piezoelectric, pyroelectric, and ferroelectric properties. Ferroelectric ceramic oxides are extensively utilized in various devices such as piezoelectric sensors, actuators, IR detectors, capacitors, energy storage, energy harvesting, and memory devices due to their outstanding physical properties. Among the different structural families, ferroelectric oxides belonging to the perovskite structure are widely used due to the possibility of tuning the physical properties as per the requirement of device applications. In order to further enhance the electromechanical, dielectric and ferroelectric properties, the fabrication of solid solutions with different types of perovskites are one of the suitable approaches. Around the morphotropic phase boundary (MPB) compositions of the ferroelectric solid solutions, anomalous enhancement of dielectric permittivity, polarization, electromechanical and piezoelectric properties are observed. In view of the processing and environmental issues pertaining to leadbased ferroelectric materials, investigations on lead-free ferroelectrics are carried out intensively in recent years. The 1st part of this work is mainly focused on the synthesis and characterization of high quality lead free ferroelectric ceramic oxides having general formula: (1-x) Na0.5Bi0.5TiO3–x BaTiO3 (NBT-BT) solid solutions (x = 0.00, 0.02, 0.04, 0.05, 0.06, 0.07, 0.08 and 0.10). Among the available lead free ferroelectric ceramics, the A-site distorted perovskite (Na0.5Bi0.5)TiO3 (NBT) system has drawn immense attention due to their excellent dielectric, and ferroelectric properties. However, it has some limitations such as (i) high coercive field, (ii) high conductivity, (iii) high dielectric loss and (iv) high leakage current, which is against the use of this system in various device applications. In order to overcome these limitations, fabrication of solid solutions of NBT with BaTiO3 (BT) system has been studied. The NBT-BT ceramics are prepared by sol–gel auto combustion method followed by the sintering using microwave sintering technique. Structural, vibrational, dielectric, ferroelectric, and electrical properties of NBT-BT solid-solution are investigated using a wide variety of experimental techniques. The formation of single phase material with perovskite structure is confirmed from the X ray diffraction (XRD) patterns. A compositional driven structural phase transition from R3c (x = 0.0 to 0.05) to P4mm (x = 0.08 to 0.10) through an intermediate co-existence of R3c + P4mm (x = 0.06 and 0.07) is observed from X-ray Rietveld refinement and Raman spectroscopic studies. Existence of MPB composition has been observed in (1-x) Na0.5Bi0.5TiO3–x BaTiO3 solid solutions at x = 0.06. The same observation is also clearly seen in Raman spectroscopic studies. The scanning electron micrographs confirmed the presence of grains and grain boundaries with dense microstructure. It has been found that the grain size decreases with increasing of BaTiO3 (BT) concentration. The ferroelectric property has been studied by measuring P-E hysteresis loop after electrical poling and observed enhanced and welldeveloped ferroelectric loops after poling the ceramic samples. The highest polarization (2Pr O is observed for x = 0.06 sample. This enhancement of the ferroelectric properties could be resulted due to the presence of the MPB, i.e. the presence of both the rhombohedral and tetragonal phases. The temperature variation of dielectric properties shows two types of phase transitions such as (i) Relaxor ferroelectric to ferroelectric (TFR) and (ii) ferroelectric to paraelectric (FE-PE) phase transition (Tm or TC), for all compositions. It has been observed that the value of Tm is decreased with the increasing x, whereas there is a decrease in value of TFR with increase in composition up to x = 0.06 and thereafter it increases again. On the other hand, the value of dielectric permittivity at Tm (εrmax) increases with an increase in the composition up to x = 0.06 but with further increasing x, it decreases. The observed maximum value of dielectric permittivity at Tm and a minimum value of TFR for x = 0.06 may be due to the existence of MPB. Complex impedance, complex electrical modulus formalism, and frequency dependent ac conductivity analysis have also been carried out to study the relaxation and conduction mechanism. The presence of grain- and grain boundary contribution to impedance spectra in NBT–BT ceramics are analyzed using complex impedance plot (Nyquist plot) in association with complex modulus plot. The experimental data of these materials are fitted using suitable equivalent circuit to explain the electrical response of the materials. The frequency dependent of ac conductivity of these materials fits well with the double power law. The demand for miniaturized, flexible and light weight devices, leads to the development of flexible dielectric materials. There are two types of dielectric materials namely ceramics and polymers are widely used for storing the capacitive energy in capacitor. In view of this, ferroelectric polymer ceramic composites are one of the important R & D activities in the field of materials science. The polymer matrix in the polymer composites has the functionalities such as flexibility, easy processing, low cost and exhibit high breakdown strength. However, polymers are the materials having low dielectric permittivity. On the other hand, ferroelectric ceramic oxides have high dielectric permittivity but low breakdown strength. Therefore, the fabrication of ceramic-polymer composites can be a suitable solution for the problems associated with the ceramics and polymers, when considered separately for the energy storage. Solution-casting technique is used to prepare the free standing and flexible ferroelectric ceramic- polymer composite having general formula PVDF (Polyvinylidene fluoride) + ϕ wt.% of 0.94(Na0.5Bi0.5TiO3)-0.06BaTiO3 (BNBT) (ϕ = 0, 5, 10, 15, 20, 25, 30, 35, 40 and 50) with 0-3 connectivity. This MPB composition BNBT has been chosen as filler as it possesses high dielectric permittivity and maximum polarization in the entire BNBT series. The semicrystalline nature and formation of composite due to the addition of BNBT filler to PVDF is confirmed from XRD analysis. The surface morphology of the prepared samples is studied using Field Emission Scanning Electron Microscope (FE-SEM), which shows the presence of spherulite and homogeneous distribution of ceramic filler particles in PVDF confirming the semicrystalline nature of the samples. In the polymeric chain of PVDF, systematic packing of parallel dipoles of fluorine atoms on one side yields higher electronegativity and hydrogen atoms on the other side (less electronegativity as compared to fluorine) with carbon as a backbone results in polar β-phase. FTIR and XRD results suggest that the fraction of the electro active β-phase increases with increase in filler concentrations and peaked for 35 wt.% of the ceramic filler. The increase in the fraction of β-phase has been explained based on ion (negatively charged surface ion of the ferroelectric ceramic filler)-dipole (-CH2 dipole of the polymer matrix) interactions, as evidenced from FTIR spectra. It has been observed that dielectric permittivity keep on increasing with addition of ceramic filler up to 35 wt.%. However, above 35 wt.% a decrease in the dielectric permittivity value has been observed for all the frequencies. Swift Heavy Ion (SHI) irradiation is one of the most effective, powerful and emerging techniques for tailoring the physico-chemical properties of the material suitable for a particular application. The effect of Swift Heavy Li3+ ion beam (50 MeV) irradiation with different fluence (ranging from 1×1011 to 3.3×1013 ions/cm2) on the structural, morphological, vibrational, dielectric and ferroelectric properties of PVDF and PVDF + 35 wt.% BNBT (PVDF-BNBT) composite are studied. XRD patterns show an increase of β-phase and degree of crystallinity upon irradiation for the respective films. The scanning electron microscopic study showed a systematic increase in the spherulites size with irradiation. Dielectric permittivity and ferroelectric polarization of PVDF and PVDF-BNBT composite is increased with increase of fluence and the highest value is observed for the highest fluence. So the interaction of Li3+ ions with polymer composite leading to the enhancement β-phase, which plays the decisive role for the enhancement of the functional properties such as dielectric and ferroelectric propertie