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Fracture Behavior of Pure Epoxy Resin and Effect of Inclusions: A Size Effect Study
No full textThe fracture behavior of pure epoxy resin is studied under varying loading rates. The study continued by toughening the epoxy resin with multi-walled carbon nanotubes (MWCNTs) and alumina nanoparticles (ANPs). The size effect testing methodology is adopted to prepare geometrically similar specimens with geometrically similar notches. The Single Edge Notched Tensile (SENT) specimens are scaled geometrically in the ratio of 1:2:3:4 while maintaining a constant notch depth-to-width ratio (a/D) of 0.25 and a constant gauge length-to-width ratio (L/D) of 4. The tensile testing of an unnotched specimen determines Young’s modulus. The experimental investigation tested 414 specimens, including unnotched and SENT specimens, under mode-I tensile loading conditions. The fracture behavior of pure epoxy resin is studied under displacement loading rates of 0.01, 0.05, 0.5, 5, 50, and 500 mm/min. The nominal strength of the SENT specimens followed type II energetic strength scaling laws. With the increase in loading rate, the mechanism of failure transitioned from brittle mode i.e. Linear elastic fracture mechanics (LEFM) criteria characterized by negligible fracture process zone (FPZ) to quasi-brittle mode characterized by large FPZ and back to brittle mode. The toughening effect of MWCNTs and ANPs on the fracture behavior of epoxy resin is studied individually for weight fractions of epoxy as 0%, 0.1%, 0.2%, 0.3%, 0.4%, and 0.5%. The addition of nanofillers resulted in a non negligible FPZ. The mode-I fracture toughness, fracture energy, and FPZ size increased with the amount of MWCNTs, peaked at the optimum weight fraction, and then decreased at a higher weight fraction. On the other hand, the fracture parameters increased monotonically as the quantity of ANPs increased. As ANP content increases, the brittleness number shifts from the energy region, explained by LEFM, to the transition region between the energy and strength regions. Whereas in the case of MWCNT toughening, further addition after optimum content resulted in the shifting back of the brittleness number towards the energy region. The decrease in notch width adopted from the varying loading rates study to the toughening effect study resulted in reduced fracture parameters
Investigations of Biomass-based Adsorbents for Carbon Capture in Compression Ignition Engines
No full textIn this research work, the possibility of using a biomass-based adsorbent for capturing carbon dioxide (CO2) in a compression ignition (CI) engine is explored. For this purpose, coconut shell, rice husk, and eucalyptus wood are selected as feedstocks to prepare activated carbon using carbonization and activation. Coconut shell, rice husk, and eucalyptus wood-activated carbons are termed coconut shell, rice husk, and eucalyptus wood-adsorbents, respectively. As a first step, activated carbon samples are characterized using different sophisticated instruments. Then, a simulation study is performed using three biomass-based adsorbents to examine CO2 adsorption performance. Aspen Adsorption is used to carry out the adsorption and desorption of CO2 in a fixed bed adsorption chamber. The recovery rate, product purity, adsorption duration, breakthrough curve, isosteric heat of adsorption, and energy consumption for regeneration are determined. As investigation on the use of biomass-based adsorbent for CO2 capture by post-combustion method in CI engines is in early stage, few experimentations are performed in a single-cylinder diesel engine which is available in the heat and power laboratory at NIT Rourkela. Therefore, the characterized adsorbent is loaded in an in-house fabricated adsorption chamber and attached to the exhaust of a test engine. A stationary single-cylinder, four-stroke, air-cooled, naturally-aspirated, direct-injection (DI) CI engine developing 4.4 kW at 1500 rpm is used for experimental investigation. The test engine runs on petro-diesel (D100). The maximum adsorption capacity of the adsorbent samples is assessed by adjusting the adsorption gas pressure from 0.5 bar to 2.5 bar at a regular interval of 0.5 bar pressure, and the adsorption temperature is maintained from 25 °C to 75 °C at a regular interval of 25 °C temperature. Experimental investigations are further conducted by varying the adsorbent quantities, viz., 1.25 kg, 2.50 kg, 3.75 kg, 5.00 kg, and 6.25 kg. Hydrocarbon (HC), carbon monoxide (CO), nitric oxide (NO), and CO2 are measured at every load during diesel fuel operation. Then, the parameters related to CO2 capture in the exhaust are evaluated. Nowadays, diesel generators are used in many applications. Therefore, investigations are carried out on CO2 capture using biomass adsorbents in a turbocharged, in-line multi-cylinder, four-stroke, direct-injection (DI) diesel engine generator which is used as a standby power unit to supply electricity to a guest house of an educational institution. The engine develops 62.5 kW and runs at 1500 rpm. Initially, this investigation is carried out on the generator to study emissions and CO2 capture using an adsorbent-filled single adsorption chamber attached to the exhaust of the generator set. Experiments are conducted at different loads using 8 kg, 16 kg, 24 kg, 32 kg, and 40 kg of adsorbents in the adsorption chamber. Exhaust gas temperature and pressure are maintained at 25 oC and 2.5 bar. The adsorption efficiency of adsorbent samples is studied for different adsorption parameters. Adsorbed gas emissions are further captured and stored in a gas bag during regeneration. The captured gas emissions are subjected to Gas Chromatography-Mass Spectroscopy (GS-MC) characterization to evaluate their peak spectra of gas adsorption for adsorbent samples. The adsorption isotherm of adsorbent samples is examined with standard adsorption isotherm models. The kinetics data of the adsorption mechanism is evaluated with adsorption kinetic models. Results reveal that CO2 is reduced by 48% when an adsorption chamber captures CO2 in the exhaust gas than in conventional diesel operation. Further, an attempt is made to reduce CO2 by attaching another adsorption chamber filled with the same adsorbents. Similar experiments are performed on the generator connected to two adsorption chambers. It is observed that CO2 is further reduced by 16%. Complete results are presented in the thesis
The Debate of Cash and In-kind Transfers in India: Decoding Universal Basic Income
No full textThe debate regarding the applicability of Universal Basic Income (UBI) in developing countries like that of India has been doing rounds worldwide. The proposal of UBI in India was associated with the replacement of existing poverty alleviation schemes which majorly are in-kind by nature, i.e., food transfers, provision of cooked meals, or supplementary nutrition to the children and pregnant and lactating mothers. This study tries to narrow down the debate to that of the forms of transfers made by the government to economically backward sections of the society by the mode of cash and in-kind through various welfare schemes. The present study aims to focus on the preferences of the demand-side stakeholder, i.e., the beneficiaries, for cash or in-kind transfers. The key objectives of the study are to measure the strength of the contextual conditions and other allied scheme-specific facets in shaping their preferences for either form of transfer. For this purpose, households availing benefits from Targeted Public Distribution System (TPDS), Mid-Day Meal Scheme (MDMS), and Integrated Child Development Services (ICDS) of the study area have been taken into consideration. The study is confined to the selected blocks of chosen districts of Odisha, i.e., Khordha, and Mayurbhanj and has used quantitative approach for collection and analysis of data. The collection of data has been done primarily through open and close-ended schedules. Further, logit regressions have been carried out for the analysis of data at hand, to measure the influence of contextual conditions, including the respondents’ educational status, caste category, primary occupation, monthly income, access to banks, and transition costs, on the preference of the beneficiaries for cash or in-kind transfers. The findings suggest that the beneficiaries of all three schemes under consideration are in favour of continuation of the same and stated their preferences for in-kind transfers. The preferences in case of ICDS was observed to achieve an enormous majority in favour of food and services transfers as against cash transfers. TPDS came with a 14.4 percent preference for cash transfers whereas, 31.4 percent of MDMS beneficiaries preferred cash in Khordha. In Mayurbhanj however, more than 90 percent respondents equivocally cite their preference for all the schemes in their in-kind form, i.e., as food or cooked meals or take-home rations. Furthermore, of the factors under consideration representing the contextual conditions of the respective districts, it has been found that education has a prominent impact on the choices made in case of TPDS and MDM in Khordha. Primary occupation, monthly income and transaction costs are also noted to be leading reasons for shaping preferences of the beneficiaries for all the schemes. Moreover, the scheme specific benefits and disadvantages, alongside Covid-19 effects also show significant effects in moulding preferences in favour of in-kind or food transfers. Furthermore, the reasons regarding the benefits and concerns of either form of transfers as stated by the beneficiaries are also discussed. Regulation of expenditure and lower transaction costs involved are cited as primary reasons for preferring in-kind transfers. Additionally, unfamiliarity with the cashless transaction systems, inconvenience, inflationary pressures and inadequate cash transfers are noted to be major concerns regarding cash transfers. The findings of the study will help to critically analyse the effectiveness of welfare schemes under implementation, the contribution of the contextual conditions in the decision-making of the beneficiaries for either form of transfer, and the applicability and acceptance of UBI, if implemented in India
Effect of Carbon Nanotube Functionalization and Alignment on the Out-of-plane Mechanical Performance and Environmental Durability of GFRP Composites
No full textGlobally Glass fiber reinforced polymer (GFRP) composites are one of the most widely used material for critical applications like structural, renewable energy, marine, automotive, and aerospace applications as a substitute for traditional metallic materials. They have an added advantage over traditional metals in terms of high corrosion resistance, greater in-plane strength and modulus. However, this laminated composites are comparatively weak when subjected to out-of-plane (perpendicular to the plane of glass fiber fabric) and in-plane shear (parallel to the plane of glass fiber fabric) loading. This weakness makes them particularly susceptible to delamination and interfacial debonding, due to the absence of reinforcement in the thickness direction (also known as the "z" direction). The improvement in the out-of-plane properties can be carried out by introducing a third phase into the composites i.e., nanofillers. Research on the use of carbon nanotubes (CNTs) to improve the out-of-plane properties and environmental durability study of GFRP composites has been ongoing for roughly one to two decades, with more intensive research and development in recent years. In our past studies, it was observed that adding CNTs to glass fiber reinforced epoxy (GE) composites improves its water resistance, with the extent of improvement dependent on the water bath temperature[1]. Moreover, functionalizing the CNTs resulted in even higher enhancements in the mechanical and creep performance of GE composites, compared to using pristine CNTs[2]. Building on this work, the present investigation begins with assessing the hydrothermal conditioning behavior of GE composites with varying wt. % (0.1, 0.3, and 0.5) of pristine and functionalized multi walled carbon nanotubes (CNTs and FCNTs) at two different water bath temperatures: (i) 15℃ (Low-Temperature Hydrothermal Conditioning (LTHC)) and (ii) 50℃ (Elevated-Temperature Hydrothermal Conditioning (ETHC)). The gravimetric analysis revealed that, FCNTs greatly hinders the water absorption through the interfaces at LTHC. At LTHC, the water saturated 0.1FCNT-GE composites exhibited superior flexural strength than GE and 0.1CNT-GE composites. At ETHC, generation of unfavorable hygroscopic and thermal stresses at the weak CNT/polymer interface adversely affected the water resistance of 0.1CNT-GE composites compared to 0.1FCNT-GE composites with stronger FCNT/polymer interface. The elevated in-service environmental temperature had posed a significant decrement in the flexural strength of all the composites compare to room temperature (RT) testing. The extent of recovery in the flexural strength was evaluated by complete desorption of water-saturated specimens. FTIR and DSC were conducted to study the changes in chemical bonding characteristics and glass transition temperature of GE composite due to above mentioned factors. Since actual environmental temperatures may not be static, it is important to investigate the effect of fluctuating temperatures on the durability of GE composites embedded with CNTs and FCNTs. To address this, the impact of repeated hydrothermal cycling on the out-of-plane durability of GE composites modified with CNTs and FCNTs, compared to control GE composites was assessed. Each HC consists of 24 hours of conditioning in a water bath maintained at 15 °C, followed by 24 hours of conditioning in a water bath maintained at 50 °C. Control GE, 0.1CNT-GE, and 0.1FCNT-GE were exposed to 20, 40, and 60 HC cycles to assess their durability. Initially, for a lower number of HC cycles, the 0.1FCNT-GE composite showed the best water resistance, followed by 0.1CNT-GE and GE composites. However, after 40 and 60 HC cycles, the trend changed. Flexural testing was conducted to assess the mechanical strength of these composites upon 20, 40, and 60 HC cycles. Additionally, the extent to which the flexural properties of the composites recovered after 60 HC cycles was evaluated by conducting a desorption process. The cyclic changes in water bath temperature caused expedited interfacial debonding at the weak CNT/matrix interface, resulting in accelerated water absorption and reduced flexural performance in 0.1CNT-GE composite compared to 0.1FCNT-GE composite. The water absorption by the composites had a detrimental effect on their Tg and the matrices' chemical bonding. Changes in the failure modes of these composites before cycling and after 60 HC cycles were compared using scanning electron microscopy (SEM) analysis. Conventional mechanical mixing techniques typically result in a random orientation of CNTs within GE composites. However, in order to effectively enhance the out-of-plane mechanical performance of these materials, it is beneficial to achieve through thickness CNTs alignment in composites to create a 3D reinforcement structure. To achieve this objective, an electric field alignment technique was utilized with CNTs and FCNTs in GE composites. The optimization process involved evaluating flexural properties at varying electric voltage and CNTs/FCNTs content. The use of aligned FCNTs in the GE composite showed the best performance, asconfirmed by a series of mechanical and thermo-mechanical tests, including flexural properties, interlaminar shear strength (ILSS), mode-I and II interlaminar fracture toughness (ILFT), and dynamic mechanical analyser (DMA). The key finding of this work includes an enhancement in the critical energy release rate under crack opening mode (i.e., GIC) as high as ~82% in the case of A-0.1FCNT-GE (0.1 wt.% FCNT aligned at 600V in GE composite) over the control GE composite. Fractographic studies reveal the evidence of CNT alignment along with various strengthening and toughening mechanisms responsible for the improved mechanical properties of the composites due to alignment and functionalization of CNTs. In continuation, the impact of in-situ environmental temperature on the out-of-plane durability of random and aligned CNT/FCNT modified GE composites was studied. For this reason, flexural and short beam shear (SBS) tests on neat and modified GE composites with random and aligned (at 600V) 0.1 wt.% of CNT/FCNT at both in-situ cryogenic and elevated (70℃) environmental temperatures (CT and ET). It was revealed that the well-being of the matrix and its interfaces with the reinforcement, i.e., fibers and nanotubes, was significantly influenced by the in-situ environmental temperature. The A-0.1FCNT-GE composite exhibited remarkable improvement, with an increase of approximately 41% and 47% in flexural strength, 29% and 35% in flexural modulus, and 30% and 24% in ILSS over the neat GE composite at CT and ET, respectively. The synergistic effect of functionalization and alignment of CNTs provided a much enhanced load-carrying capacity along the through-thickness direction which effectively prevented delamination at both CT and ET. To better understand the mode of failure, SEM was employed to observe the tested samples
Efficient Computational Approaches and Their Convergence Analysis for Integro-differential Equations with Small Parameters and Fractional Derivatives
No full textIntegro-differential equations (IDEs) combining both differential and integral terms emerge in diverse fields of science and engineering, for conceptualizing systems that depend on past values of the function. For instance in physics, IDEs depict the conduct of materials possessing memory, like viscoelastic substances. In the field of ecology, these equations find utility in depicting population dynamics, wherein the integral component captures the impact of previous populations on the present state. In the domain of finance, they find application in modeling option valuation and risk management, accounting for the historical trajectory of underlying assets. So, IDEs can be used to model economic systems where past decisions or events can influence the current behavior and this feature of IDEs attracted many researchers to attain insights into a broad array of complex phenomena spanning diverse scientific domains. It is really intricate to find the analytical solutions of the IDEs. So, several ideas are proposed in literature basically consisting of the numerical as well as semi-analytical approaches which are used for finding the solutions to the IDEs. Some of the techniques involves the Adomian decomposition method, homotopy perturbation method, variational iteration method, reproducing kernel method, which are meshfree in nature. Also, there are many numerical techniques such as the finite difference method, finite element method, spectral/collocation method, that are employed to approximate the solution of IDEs. As already mentioned, finding the solutions to IDEs are complicated, but it is even more difficult to obtain the solutions of singular IDEs, where the solution has singularities at some point of the domain. These type of situations often cannot be dealt with the conventional numerical methods, so specially tailored methods are used to deal with such model problems. Researchers have gained insights in solving the regular IDEs but very less contributions are made for analyzing the IDEs with singularities. This thesis intends to develop the higher order numerical methods and semi-analytical methods for finding the solutions of IDEs involving small parameters and fractional derivatives. Also, the convergence analysis/error estimates of all the proposed schemes for various kinds of model problems are broadly discussed. Some numerical simulations are carried out so as to give a pictorial description of how the solution behaves and thereby drawing a validation to the theoretical prospects. Since, we have dealt with two types of IDEs, this thesis is partitioned in two categories, wherein the first five chapters are devoted to find the numerical solutions of singularly perturbed IDEs where the solution undergoes vital changes as the parameter approaches zero. The next three chapters are dedicated to find the approximate/numerical solutions of fractional order IDEs. This dissertation is comprised of a total of ten chapters, of which Chapter 1 deals with the basic ideas of the singularly perturbed differential equations and fractional calculus, inclusive of the important definitions, properties, and the motive of working out various model equations of IDEs. Chapter 2 describes the numerical schemes and their convergence analysis for studying a singularly perturbed Volterra integro differential equation (SPVIDE) using the conventional upwind scheme with the trapezoidal rule for the integral term. The accuracy is further improved by using a post-processing scheme which is validated with a few examples and comparison results. The idea used for the first order SPVIDE is further extended to a second order SPVIDE wherein the kernel is taken to be of the nonlinear type and a hybrid scheme is used for obtaining direct second order convergence. The numerical approach used in Chapter 1 is extended to solve IVP and BVP cases of the singularly perturbed Fredholm integro differential equation (SPFIDE) and singularly perturbed Volterra-Fredholm integro differential equation (SPV-FIDE) in Chapter 3 and Chapter 4 respectively. The system of SPVIDEs is considered in Chapter 5, where the problem is solved using a first order convergent scheme. The numerical approximation is done using the backward Euler method for the differential operator and rectangular rule for the integral operator and with a proper error analysis of the concerned scheme. Further, the scheme is subjected to post-processing technique, thereby giving better accuracy. In Chapter 6, the numerical solution of the singularly perturbed partial differential equation with a Volterra integral is proposed. Firstly, the problem is solved by forming a difference scheme that consists of the implicit-Euler method for the time derivative, an upwind scheme for the spatial derivative, and a left rectangular rule for the integral part that gives a first ordere-uniform convergence. The order of accuracy is then enhanced by successfully applying the Richardson extrapolation technique. Secondly, a direct second order convergent difference scheme is employed, comprising of the Crank-Nicolson scheme in the temporal direction, a hybrid scheme in the spatial direction, and a composite trapezoidal rule in the integral part. Finally, the performance of the numerical schemes is tested by a few examples. The next three chapters of the thesis study the model problems related to fractional IDEs. Chapter 7 focuses on different semi-analytical methods to solve a time fractional partial IDEs (PIDEs). The Adomian decomposition method, the homotopy perturbation method, and the modified homotopy perturbation method are applied to solve the model equation. A brief convergence analysis is carried out for all the proposed techniques and numerical experiments are done to show the efficiency of the suggested methods. In the next chapter, Chapter 8, investigates the fractional order Fredholm-Volterra IDE using both semi-analytical and numerical methods. The semi-analytical approximations are done using the Chebyshev and Bernstein polynomials in the ADM and the numerical scheme is developed using the L1 scheme for the fractional order derivative in combination with appropriate quadrature rules for the integral parts. Some comparisons with the existing results show that the proposed methods are highly productive and reliable. Chapter 9 aims to develop an efficient scheme for a fractional IDE involving a weakly singular kernel. The weakly singular Volterra integral is approached with the production integration rule, and the Caputo order derivative is approximated using the L1 scheme. First order accuracy of this method has been demonstrated. Additionally, the Richardson extrapolation strategy is effectively used to boost the accuracy. Finally, the model problem is also investigated using another scheme wherein, the integral part is discretized using the product trapezoidal rule and fractional derivative is discretized using the L1 scheme which gives better convergence rate in comparison to scheme I. Numerical tests are done to demonstrate the efficacy of the proposed methodologies. Finally, Chapter 10 presents the concluding statements derived from the diverse outcomes discussed in this thesis, along with a handful of potential future avenues for further exploration based on the current research
An Investigation of Solar Photovoltaic Power Fed Induction Motor Drive
No full textIn general, the growth of a county is measured in terms of one of the parameters, electrical power consumption. So, in the progressive world, the amount of electrical energy consumption is increasing exponentially. However, traditional power generation mainly depends on fossil fuels. The major concerns associated with fossil fuels are limited in nature, low efficiency, and high cost. In addition, power generation using fossil fuels not only causes a greater part of the pollution but also unbalances the ecosystem. Hence, the world requires clean energy sources for sustainable growth. Renewable energy sources such as solar, wind, tidal, etc. are available for clean power generation. Among the available renewable energy sources (RESs), wind and solar electrical power generation are dominating the current electrical market. Wind turbines have high energy conversion efficiency as compared to solar. But, due to easy installation, less maintenance, and noise solar energy is highly preferred than other RESs. Solar photovoltaic (SPV) panels convert solar energy into direct electric current. Hence, SPV power is used for domestic, agricultural, and industrial appliances as solar energy is freely available and the cost of SPV panels is less. The utilization of SPV-fed motor drives is increasing day by day. Especially, for solar water pumping applications induction motor (IM) drives are used due to their rugged and reliable operation as compared to other commercial electrical drives. Therefore, a part of research is focused on SPV-fed AC drives especially IM appliances, and the evolution of various configurations of SPV-fed IM drives and control so that they can be effectively employed in required applications. Moreover, the concern associated with the SPV system is the variable output power. Hence, overcoming this problem without any storage system can be achieved using a variable-speed IM drive operation. The control of the IM drive had been carried out using inverter pulse width modulation (PWM) control. These PWM methods are likely sinusoidal PWM (SPWM), third harmonic injection method (THIPWM), etc. In the THIPWM method, enhancement of the DC bus utilization by 15.5 % more than SPWM with increased linear modulation index range by 0.907. For implementing both the attributes of THIPWM at a time, the conventional space vector duty ratio control (CSVDRC) is used to further improve the switching losses than the SPWM and THIPWM. Moreover, the CSVDRC improves the current ripple slightly with a significant increase in computation. Another method of PWM also known as hybrid duty ratio control gives reduced current THD for modulation index (MI) in between the range of 0.5 to 0.907 as compared to CSVDRC at a given average switching frequency. So, in this thesis, the hybrid duty ratio control is used to further improve the overall ripple performance of the SPV-fed IM drive. Moreover, to further reduce the overall cost of SPV-fed IM drives, reduced switch count-based inverter topology is also implemented for both two-stage and single-stage operations. With the help of solar simulator and DSPACE-DS 1104, the proposed concepts are implemented experimentally and compared the results with conventional control techniques. However, the real-time controlled pulses for the converter circuits are generated using DSPACE DS-1104
Detecting Human Alertness on System onChip (SoC) using Dual Cues
No full textDiminishing alertness in human subjects impacts safety-critical operations severely. Although the perception of a low level of alertness is inherently subjective, we very often lose the required self-awareness during demanding jobs such as automobile driving, operation control of nuclear power plants, etc. In such contexts, we need a continuous and real-time measurement of alertness levels in human operators to avoid any adverse consequences. Literature suggests that alertness level can be influenced by several factors and essentially need a multidimensional approach for measurement. The current state of the art in this regard is expensive and very specific to vehicular technology. Therefore, some of the cues may not be usable for other safety-critical operations. On the other hand, the low-cost solutions of alertness detection systems lack effectiveness due to the usage of a single cue. Therefore, in this work, we aim to design a portable and robust alertness-level detection system using two cascaded cues, which utilize variations in sensory-motor neuron coordinated response and ocular parameters like PERcentage CLOSure (PERCLOS) of eyelids over time. To attain this, as well as to keep provision for future augmentation of other ocular parameters like saccadic ratio, we have chosen System-on-Chip (SoC) —essentially a heterogeneous digital system— to mitigate the multi-processing requirement using hardware accelerator and soft processing units. Out of the two cues used, the sensory-motor neuron coordination is measured using the response of human subjects from the Choice Reaction Test (CRT). Generally, such a test is carried out with a predefined time-bound, which may introduce possibilities of manipulation of response during time-pressing jobs. We have designed trial-bound in a short time span CRT and proposed a new reaction time metric, Peak-to-Spread Ratio (PSd), to measure the alertness level of the subject. Experimental results on the database generated from 65 subjects —for audio and visual response to the CRT— confirm that PSd has better resolution and sensitivity than state-of-the-art metrics. A combined hardware-software co-designed architecture with Viola-Jones face detector as a pre processor is adopted for PERCLOS detection. Integral image computation and cascaded classifier sub-modules are implemented on Programmable Logic (PL-FPGA), while the image scaling, non-maximum suppression, sub-modules of face detection along with PERCLOS measurement module are implemented on Processing System (PS-ARM). To validate the system, we have generated a database with various levels of challenges associated with eyelid motion and high-speed saccadic eye movement measurement at different levels of alertness. Performance with eyelid motion at various alertness levels —measured with PERCLOS— is tested with the proposed digital architecture. A preliminary experiment is carried out on the algorithmic level for saccadic eye movement analysis and the hardware implementation of it is kept for future augmentation to improve the efficacy of the overall system
Investigating Structure, Morphology and Photophysical Properties of Rare-earth Activated Fluorides
No full textThe scientific community has shown a growing interest in relating to the rare-earth based luminescent materials owing to their versatility and potentiality to improve the lives of mankind. Photo-physics of luminescent materials plays an important role for their diversified practical applications viz. solid state lighting (pcLED), spectral converters in solar cells, optical thermometry, fluorescent based lamps, liquid crystal display, field emission display etc. In this endeavor, this thesis work focuses on the fluoride based down- and up-conversion phosphors as they possess low phonon energy, wide band gap and high chemical stability as compared to other host matrices. The primary goal is to design the fluoride based phosphors by the various sensitizer-activator approach as well as the incorporation of impurity ions and to establish their structural, morphological, spectroscopic and photo-physical properties which can evince their practical utility in variety of applications. The material science description of the synthesis techniques used to prepare different series of inorganic fluoride based phosphors and characterization of the phosphors along with the results based on the structural, morphological, vibrational and spectroscopic techniques are discussed in a systematic manner. The luminescence properties of synthesized phosphors and the underlying mechanisms are extensively studied in this work and are systematically documented. An effort has been made to prepare a series of Eu3+ (x) activated YF3 nanophosphors with a minimal concentration (0.05) of Gd3+ as sensitizer. The energy transfer mechanism from Gd3+ to Eu3+ in YF3 host matrix is explored by using the photoluminescence spectra at the indirect excitation of 272 nm. The intensity of the dominant emission peak at 591 nm corresponds to 5D0→7F1 transition increases with rising concentration of Eu3+ ion and quenching occurs above x = 0.05. Further, 94.78% of efficient energy transfer process between Gd3+ and Eu3+ is governed by dominant dipole-dipole transitions. Quantum efficiency, colorimetric parameters are also calculated and the results indicate the suitability of this red nanophosphor for solid state lighting application. In an attempt to obtain an intense green emission, a series of YF3:xTb3+ nanophosphors are sensitized with minimal Gd3+ doping. The structures, morphologies, and optical properties of the synthesized nanophosphors are analyzed in detail. The characteristic emissions of both the Gd3+ ( 6P7/2 → 8S7/2) and Tb3+ ( 5D4 → 7FJ) ions can be observed in the photoluminescence spectra at the 272 nm excitation of Gd3+ ions and the Gd3+ → Tb3+ energy transfer leading to 15-fold enhancement in the green emission of the trivalent terbium ion. The possible energy transfer mechanism from Gd3+ to Tb3+ is presented schematically and 88.92% energy transfer ix efficiency is achieved, which is dominated by electric dipole–dipole interactions. The calculated branching ratio (for 5D4 → 7F5), quantum efficiency of 89% and obtained colorimetric parameters suggest the applicability of the synthesized nanophosphors in ultraviolet excitable phosphors for white light-emitting diodes and solid-state green lasers. In a similar approach, a series of -Na(Y0.95-x,Gd0.05)F4:xEu3+ phosphors with minimal concentration of Gd3+ is developed using hydrothermal techniques. Characteristics photoluminescence emissions of Gd3+ ( 6P7/2 8S7/2) and Eu3+ ( 5D0 7Fj) are observed in the doped and co-doped phosphors by an indirect excitation at 272 nm (of Gd3+). Local environment of Eu3+ ions is analyzed using Judd-Ofelt model and the observed 2 > 4 values suggests a local asymmetricity around Eu3+ ions in NaYF4 host matrix. The emission peak intensity at 615 nm varies with Eu3+ concentrations and quenching occurs at higher doping level (x > 0.10). Moreover, the emission spectra and luminescence lifetime based on Inokuti-Hirayama model reveals an efficient energy transfer from Gd3+ to Eu3+ which is mainly mediated through dipole-dipole interaction. A detail schematic representation of the energy transfer process between activator ions is also documented. Comparatively a better emission color tunability and color purity (90.08%) of red emission is achieved in Gd3+ -Eu3+ doped phosphors for indirect excitation of Eu3+ ions at 272 nm. The effective tunability of the photo-physical properties of these UV excitable phosphors suggest its applicability in fabricating w-LED using UVchips and spectral converters for solar cell. Double impurities doping approach has been adopted to enhance the up-conversion luminescence in β-NaYF4:0.2Yb3+/0.02Ho3+ phosphors via simultaneous co-doping of xMg2+/ySc3+ ions. The correlation among structure, morphology and up-conversion properties of prepared phosphors has been well established. The effect of Mg2+/Sc3+ co-doping on the UC green emission ( 5F4, 5S2→5 I8) is studied and about 31-fold enhancement is observed for the 0.08Mg2+/0.12Sc3+ co-doped phosphor. The down-conversion properties of the phosphors is also discussed to showcase the dual mode luminescence. The temperature sensing performance is investigated using luminescence intensity ratio (LIR) technique for non thermally coupled levels (5F5/ 5F4, 5S2) of Ho3+ ions and maximum relative sensitivity of 0.258% K-1 at 374 K is obtained for the optimized phosphor. The phosphor is found to be sustainable at high temperature as the UC emission intensity retains about 65% and 36% at 423 K and 574 K. From chromaticity diagram, the maximum color purity of 91.37% is obtained for 0.08Mg2+/0.12Sc3+ doping concentration. The significant enhancement in UC emission, estimated thermal parameters and color purity of Mg2+/Sc3+ co-doped β NaYF4:0.2Yb3+/0.02Ho3+ UC phosphors suggest their applicability in fabricating temperature sensors and LEDs
Molecular Dynamics Simulation of Deformation Behavior of Al90Sm10 Metallic Glass and Al-Al90Sm10 Crystalline-amorphou Nanolaminate.
No full textMetallic Glasses (MGs) have gained significant attention from scientific and technological community due to their unique properties such as corrosion resistance, high specific strength, ultrahigh fracture toughness and superior biocompatibility. However, lack of ductility in MGs have hindered its structural applications immensely despite possessing combination of attractive properties. According to literature suitable patterning of amorphous MGs with its crystalline counterpart has proven to overcome the ductility barrier. However, an understanding of the structural evolution at the crystalline-amorphous (C/A) interface at the nano-scale level under the subjugation of different modes of loading is still an open question. In this thesis, the glass forming process of Al90Sm10 MG and deformation behaviour of Al-Al90Sm10 MG C/A nanolaminate under different loading conditions by employing molecular dynamics (MD) at nano-scale is investigated. MD has proven to be an invaluable tool in overcoming the difficulties that has been countered in experimental investigations at atomic- scale, owing to its ability to provide detailed atomic trajectories and dynamic characterization under different conditions. One of the contributory attributes associated with this work is to provide an insight of the structural evolution and underlying physics associated with the glass formation process Al90Sm10 MG and deformation behaviour of Al-Al90Sm10 MG C/A nanolaminate under different modes of loading. Firstly, this thesis constitutes of a detailed study of the role of hydrostatic pressure on the glass transition behavior of Al90Sm10 MG. The glass transition temperature rises with increasing values of applied hydrostatic pressure by virtue of increasing population of distorted ICO-like structures. Secondly, the shock compression behavior of Al-Al90Sm10 MG C/A nanolaminate has been investigated with variation of shock intensities, shock direction and architectural variation in the crystalline counterpart. The shock profile behavior is found to be dependent of shock intensities with transition from elastic to plastic behavior with increasing values of shock intensities. The shock profile behavior is also influenced by the architecture of the crystalline counterpart in C/A nanolaminate, elastic behaviour is apparent for single crystal and columnar grained nanolaminate whereas plastic behaviour dominates in nanocrystalline nanolaminate. Shock induced martensitic phase transformation is apparent in single crystal and nanocrystalline nanolaminate. Rarefaction waves are generated at the crystalline-amorphous interface under the subjugation of shock compression. Third, shock response and spall behavior of different configurations of C/A Al Al90Sm10 MG nanoporous nanolaminate has been thoroughly analyzed. The martensitic transformation in the crystalline counterpart follows KS relationship. The void collapse behavior is hardly affected by the configurations of the NP nanolaminate specimen. Fourth, the torsion behavior of Al90Sm10 MG and C/A Al-Al90Sm10 MG have been studied with intricate details. Shear transformation zones (STZs) nucleate homogenously near the vicinity of the clamped regions, grow and coalesce into the wide shear bands (SB) that grow along the interior of the NW specimen with increasing degree of rotation in case of Al90Sm10 MG. The amelioration of ICO-like Voronoi polyhedral (VPs) with increasing torsional angle possessing liquid like character encourages collective shear transformation and thereby enhancing plastic deformation under torsion load. The localization of dislocation density rings induces the formation of dislocation substructure in Al/Al90Sm10 nanolaminate under torsional loading leading to torsional buckling. The C/A interface serves as a nucleation site for the generation STZs in Al90Sm10/Al nanolaminate and serves free surface and encourages the formation of such dislocation substructure Al/Al90Sm10 nanolaminate. Finally, nano-indentation behaviour of Al2O3 coated Al and Al-Al90Sm10 nanolaminate with variation in test temperature and indentation speed has been investigated with intricate details. With the increasing nano-indentation test temperature, load bearing capacity as well as calculated hardness of Al2O3film deposited Al becomes less for a particular depth of indentation. The nano-indentation behaviour as a consequence of dislocation activity and VP population exhibits a strong dependency on the orientation of the C/A nanolaminate. To sum up, the work done in this thesis can serve as a platform for understanding the fundamentals associated with the role of C/A interface C/A nanolaminate and deformation mechanism of MG under different modes of loading
Understanding The Role Of Sirtuin1- Activating Compounds In Autophagy And Associated Signalling To Induce Cell Death In Oral Cancer
No full textThe role SIRT1 in cancer during tumorigenesis is debatable since it could exhibit both tumor suppressor and oncogenic nature by transcriptional activation of various physiological processes, including apoptosis and autophagy. This study aimed to identify small molecule activators of SIRT1 as chemotherapeutic drugs via modulation of autophagic cell death pathways. Our study demonstrated that Terminalia bellirica fruit extract containing gallic acid (GA), a bioactive SIRT1 activator, induced apoptosis and autophagy by regulating the mitochondrial ROS in oral cancer cells. Further, gamma-irradiation-induced electrochemical changes in GA enhanced its anticancer activity via the induction of apoptosis. Downregulation of NFE2L2-antioxidant signalling paired with autophagic flux inhibition generated lipophagosome accumulation and aided apoptosis induction in oral cancer cells. Moreover, in synergism with anticancer drugs, gamma-irradiated GA chemosensitizes the cancer cells to apoptosis. In another study, we demonstrated that cisplatin-induced apoptosis inhibition caused SIRT1 downregulation, subsequently leading to mitochondrial hyperfusion associated mito-bulb formation as a resistance mechanism to apoptosis. Overexpression of SIRT1 or priming the cancer cells with GA inhibited the cisplatin-induced mitochondrial hyperfusion and resensitized the cells to apoptosis. Intriguingly, we established the role of SIRT1-regulated NFE2L2-antioxidant signalling in the induction of apoptosis after inhibiting mitochondrial hyperfusion in oral cancer and oral cancer-derived polyploid giant cancer cells (PGCCs). Moreover, our study established the critical involvement of GA-induced SIRT1 activation for mitochondrial asymmetric fission with mitophagic flux inhibition to generate mitochondrial superoxide. The mitochondrial superoxide elicits BAX-dependent lysosomal membrane permeabilization followed by TFEB-mediated lysosomal biogenesis inhibition and non-recruitment of ESCRT to orchestrate LMP-driven apoptosis via downregulation of NFE2L2-antioxidant signalling. In apoptosis-deficient and resistant PGCCs, GA-induced LMP provokes NLRP3-mediated pyroptotic cell death. In this setting, we have synthesized a small molecule activator of SIRT1, S36, facilitating nuclear translocation of SIRT1 to commence bulk autophagy. S36-induced bulk autophagy depleted the cellular lysosomal pool and inhibited TFEB-mediated lysosomal biogenesis, which havocked cellular homeostasis. In addition, S36 impaired the recruitment of clathrin, stonin 2 and PI(4)P to the autolysosomal perturbation site as a precursor of autophagic lysosome reformation, eventually leading to autophagy dependent cell death. In conclusion, our work established a novel therapeutic aspect of targeting autophagy via small molecule activators of SIRT1 to commence autophagy-mediated and autophagy-dependent cell death for oral cancer therapeutics