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Molecular Dynamics Simulation of Deformation Behavior During Nanoscale Rolling
No full textCost-effective processing of textured nanoscale metallic systems is extremely sought after, as tuning the crystallographic orientations can significantly impact their mechanical properties. In this regard, the metal rolling process is known to have considerable influence on the structural properties of nanomaterials. Previous literature studies have shown that manipulating the processing parameters during the rolling of bulk metallic systems can alter the morphology, internal stresses, texture, and defect density of the system. However, comprehension of the deformation mechanism at the nanoscale level during the rolling process is still unclear due to constraints in instrument setup and the high cost involved. The present thesis is a thorough investigation of the nanoscale rolling process of various metallic systems using molecular dynamics (MD) simulations. MD simulations have effectively analyzed the underlying physics behind the nanoscale deformation mechanisms, phase transformation, defect evolution, and texture. The original contribution of this work is to provide insights into the atomistic mechanisms during the nano-rolling process of crystalline, amorphous, and nanolaminate metallic systems and apprehend the deformation behavior and structural evolution during the rolling process. First, this thesis includes investigating the effect of initial crystallographic orientation, stacking fault energy (SFE), and processing parameters on the rolling behavior of single-crystal (SC) metallic systems. Nano-rolling of SC Al and Cu have shown variation in the defect generation and strain distribution due to their difference in the SFE. Whereas the evolution of new grains with enhancement in ultimate tensile strength with respect to higher roller speed is observed in SC Mg. Moreover, the lattice distortion and the grain rotation phenomenon are analyzed through the virtual characterization method for SC Fe. Second, the nano-rolling process has been implemented to investigate the deformation behavior, stress distribution, and orientation evolution in nanocrystalline (NC) metallic systems. Nanoscale rolling of NC Ni has revealed that the compressive stresses accumulate at the grain boundaries, whereas the triple junctions accrete the tensile stresses. The effect of rolling temperature is also analyzed, which demonstrated that cryo- and cold-rolling processes facilitated the formation of sub-grain boundaries and grain refinement in NC Ni and W specimens. Moreover, the grain refinement along with the twinning phenomenon aided in the texture weakening in NC Mg specimen during the nano-rolling process. After investigation of the crystalline systems, this work is then extended to explore the structural transformation in metallic glass (MG) during the nano rolling process. The low-temperature rolling process has shown dense and concentrated primary shear bands (SBs) in Cu-Zr MG. Whereas comparatively dispersed and thicker SBs are formed in the MG during the hot-rolling process. Finally, the influence of processing parameters such as the rolling speed and temperature on the atomic-level deformation mechanism and structural evolution is studied during the accumulative roll bonding process of Cu and Zr crystalline nanolaminates. Also, the effect of residual stress and defect density after the nano-rolling process on the shock deformation behavior is examined for the crystalline Cu /amorphous Cu-Zr nanolaminates. In summary, the work done in this thesis provides a fundamental comprehension of the deformation mechanism during the nano-rolling process. Moreover, this novel simulation technique aids in understanding the influence of initial crystallographic orientation and operating parameters on structural evolution, mechanical properties, and texture
Polymeric Nanocomposite Materials for the Removal of Hexavalent Chromium
No full textWater pollution due to heavy metals is a global concern in degrading nature’s resources and is causing serious threat to living organisms. Hexavalent chromium (Cr(VI)) is a highly toxic heavy metal contaminant to which millions of people are exposed all over the world. Even short-term exposures to Cr(VI) can lead to DNA mutation and damages genetic information causing cancerous tumours. Therefore, Cr(VI) remediation is one among the major concerns for researcher. In this thesis, the synthesis and application of polymeric nanocomposite based novel materials has been described for sequestration of hexavalent chromium by adsorptive route. Initially, the polymeric nanocomposite of thorium oxide polyaniline and lanthanum phosphate polyaniline are synthesised by taking aniline as organic component and thorium oxide and lanthanum phosphate nanoparticles as inorganic constituents. Later, the polymeric nanocomposite of polypyrrole layered double hydroxide and cerium phosphate polypyrrole nanocomposite are developed by pyrrole as organic component and layered double hydroxide and cerium phosphate nanoparticles as inorganic components. The structural, functional, morphological, textural and thermal stability of the as-prepared materials are evaluated by XRD, FESEM, EDX, TEM, TGA- DTA, FTIR, Raman, XPS, Zeta potential, N2 sorption isotherm and other instrumental analysis. The core shell thorium oxide polyaniline nanocomposite is synthesized using aniline as a favourable conducting polymer by situ polymerization method and used for the removal of Cr(VI) from water. The thorium oxide polyaniline nanocomposite effectively adsorb Cr(VI) ions through electrostatic attractions, which are partially reduced to Cr(III) during the adsorption experiment. The synthesized nanocomposite material exhibits high uptake capacity towards Cr(VI) as compared to other reported materials. The Langmuir isotherm model follows the adsorption process better than the Freundlich isotherm with maximum adsorption capacity of 141 mg g-1. Thermodynamic parameters are also computed which indicated the spontaneous and the endothermic nature of the adsorption process. A novel lanthanum phosphate polyaniline nanocomposite is synthesised by the simple sol-gel technique and used for selective adsorption of Cr(VI). The selectivity is estimated by evaluating the distribution coefficient, electrical double layer theory as well as valency and Pauling’s ionic radii of interfering ions (phosphate, iodide, sulfate, chloride, sulfide). The high tolerance capability of lanthanum phosphate polyaniline against the interfering ions make it appropriate for efficient removal of Cr(VI) ions. The nanocomposite shows the highest removal percentage of 98.6% towards Cr(VI) at room temperature. The XPS analysis reveals the adsorption mechanism due to the combined effect of both adsorption and reduction. Cr(VI) is adsorbed through electrostatic interactions while the =N-/-NH- group facilitated the in situ chemical reduction. Polypyrrole modified Mg-Al layer double hydroxides material is synthesized via in-situ oxidative polymerization method followed by microwave irradiation. The material is then used as an adsorbent for Cr(VI) removal at varying temperatures. The maximum Langmuir adsorption capacity of PPY-LDHs is calculated as 76.21 mg g-1. The high distribution coefficient value (> 104 mL g−1) reveals the great affinity for Cr(VI). The adsorption mechanism is proposed which asserts that the removal of Cr(VI) onto the adsorbent is a combine effect of reduction of Cr(VI) to Cr(III) and chemical sorption which takes place through ion-exchange in the interlayer regions and over the surface through electrostatic attractions and hydrogen bonding. Flower like cerium phosphate polypyrrole nanocomposite material is synthesized by in situ oxidative polymerization method and used for sequestration for Cr(VI). Field emission scanning electron microscopy and transmission electron microscopy images reveal the flower-like morphology of the synthesized nanocomposite. Meanwhile, the fabrication of polypyrrole on cerium phosphate nanoparticles provides a plentiful of active adsorption sites to interact with hexavalent chromium ions. The Cr(VI) adsorption follows Langmuir isotherm model showing a high adsorption capacity of 117.78 mg g-1 at room temperature at low pH. The adsorption dynamic study demonstrates that the rate- determining step of adsorption is controlled by surface diffusion, pore diffusion and film diffusion. XPS spectra confirmed the simultaneous adsorption of Cr(VI) and in situ chemical reduction to Cr(III). Regeneration studies illustrate the efficiency of more than 80%, even after five cycles. All the above synthesized materials are effectively adsorbed Cr(VI) ions from water. Therefore, these materials could be a unique alternative to act as an ideal adsorbent for the effective treatment of Cr(VI) containing wastewater
Children in Conflict with Law: A Study on the Biopsychosocial Correlates of Juvenile Delinquency
No full textJuvenile delinquency is an unfathomable social problem afflicting the globe at present, India being no exception. Its ubiquitous corrosive tentacles are unmistakably discernible in the social structure leading to erosion of values and generation gap. The very matrix of our society is rudely shaken by the wanton and willful attitude of adolescents who resort to criminal activities like fish taking to water. Therefore, lots of debates, discussions and studies are carried out in India based on the juvenile justice system i.e. on juvenile crime rate, Juvenile Justice (care and protection) Acts (2000, 2006 and 2015) and on the amendments made in them or on amendments to be made. Not many focus on the actual risk factors that play an influential role in motivating the juveniles to commit crime. Therefore, there exists a huge disparity between Western countries and India in terms of understanding this complex phenomenon i.e. juvenile delinquency. To appraise the lack of understanding of the individual and social level stressors present in India and the gap found in the existing literature, the following objectives are proposed: a) to examine the rate of change in proportion of crime among children in conflict with law, b) to determine the factors responsible for increased commission of violent and property crime by the children in conflict with law, c) to examine whether children living with parents commit more crime than homeless children d) to explore the causal correlates of juvenile delinquency, e) to develop a biopsychosocial causal model of criminal behavior in the children in conflict with law. The study population comprises male children in conflict with law (n=100) and female children in conflict with law (n=16) apprehended for various crimes (IPC and SLL crime) residing in the four Government-run Observation and Special Homes (O&SHs), Odisha situated in Angul, Berhampur and Rourkela. Data have been collected through semistructured interview schedules and revised Kuppuswamy Socio-economic scale (2016) has been used to calculate the socio-economic status of the family. Qualitative and quantitative data sets are analyzed independently and collectively for an in-depth understanding of the phenomenon i.e., juvenile delinquency. Mixed method approach is used for the purpose of data analysis in the study. Chi-square test of independence is conducted to find the relationship between the variables. Verbatim collected from the children are thoroughly analyzed using QDA (Qualitative Data Analysis) Miner Lite software (Version 2.0) to find out the factors that have played a crucial role in the commission of crime. The finding of the study: I. Juvenile Crime Trend Analysis over The Period of Twenty-Five Years (1990-2015) of India and Odisha Incidences of juvenile delinquency (IPC and SLL) cases have increased from 15021 in 1995 to 33433 in 2015 and from 341 in 1990 to 934 in 2015 in India and Odisha respectively. Over the period of twenty-five years, increase in incidences of IPC and decline in SLL crimes have occurred in both India and Odisha. Incidences of murder, rape and kidnapping & abduction, theft and burglary have multiplied in these years in India and Odisha too.
II. Factors Responsible for Commission of Crime by Children in Conflict with Law Boys are more likely to commit both violent and property crime compared to girls. Children mostly commit crime in later adolescence phase (i.e. 15-19 years). A significant association is found between violent criminal propensities in adolescents and the marital status of the parents, relationship between parents, lack of proper guidance and supervision, criminal parents and sibling, maltreatment experienced, working status of father, income of mother and child, annual income of the family and socio-economic status of family, good relationship with peer, the amount of time spent with peer , place of association with peer, irregularity in attending school, relationship shared with classmates, no interaction in class, living in semi urban areas characterised by poor, disorganized neighbourhood. Similarly, in case of property crime a significant link exists between the delinquents and their criminal siblings, maltreatment experienced, working of the child and annual income of the family, association with anti-social peer, no interest in education, no interaction in class and truancy, living in semi urban areas characterised by poor disorganised violent neighbourhood. Children Living with Parents Commit More Crime Than Homeless Children share a strong feeling of cohesion and belongingness to the family and, therefore, don’t hesitate to resort to crime when family honor is at stake. Despite coming from poor and dysfunctional family and staying in violent, disorganized neighborhood, living with parents provides a sense of security to children. Most often working parents do not impose necessary control on their children as they spend most of the time outside home. Hence, children labor under the belief that their parents will cover up their mistakes and wrong doings. But it is not the same for homeless children and children living with guardians. In the absence of this feeling of cohesion and solidarity, these homeless children and children living with guardians feel relutant to resort to crime as they do not have the security of somebody’s hand over their head. Biopsychosocial Explanation of Juvenile Delinquency Victimization and lack of parental trust and faith cause trauma, anger and aggressive behavioral problems in girls. The sense of insecurity and neglect are primarily associated with deviancy and criminality in girls. Biopsychosocial factors are found to be the most influential in commission of crime by girls followed by psychosocial factors. The influence of peers, poverty, sexual urges, criminal parents and siblings, lack of parental care and trust (i.e. feeling neglected and unloved) are some of the factors that have had a negative effect on the psychological wellbeing of boys. These factors promote stress, resentment, anger and aggressive behavior towards others. In case of boys, psychosocial factors are found to play an influential role in their commission of crime than biopsychosocial factors. Finally, based on the complete analysis of the verbatim, psychosocial factors i.e. social stressors (poverty, trauma, lack of parental care, neglect etc.) engendering psychological distress (anger, aggressive behavior, stress, trauma etc.) and vice versa are found to be the most influential factors in comparison to the biopsychosocial ones. A Biopsychosocial causal model is proposed. Besides filling some gaps in literature, the findings sometimes affirm and sometimes contradict with the findings of previous studies. The current study makes a significant contribution towards providing a biopsychosocial causal model of juvenile delinquency
Mathematical Modelling of Microalgal Cultivation in Open Ponds and Bioprocess Optimization for Biodiesel Production
No full textAlgal biofuels are regarded as a greener alternative since microalgae could remediate nutrients from waste sources and sequester carbon dioxide (CO2) from the atmosphere assimilating them into biomass. Though sustained benefits of algal technology are very well known, the economic and technical hindrances exist during scale-up. Also, the ongoing researches have nevertheless provided a direction forward but the specificity associated with the robustness of strain selection and acclimatization with the site-specific and other culture conditions often makes the process unsuitable during extrapolation at a particular location. Thus, the present study comprehensively evaluates the feasibility of National Institute of Technology (NIT) Rourkela for microalgal cultivation and also analyzes alternative strategies to reduce the costs associated with the upstream process of cultivation and downstream process for harvesting and transesterification. The first part of the study aims to estimate the microalgal productivity at NIT Rourkela using a comprehensive mathematical model. Site-specific climatological variables were utilized as the baseline information to predict the biomass, lipid productivity, and CO2 sequestration potential of microalgae using biophysical model formulated in MATLAB ODE 45s solver. Algal productivity was found to be influenced by light intensity (including the effects of photoinhibition), water temperature, and design criteria like pond depth, microalgal concentration. Maximum biomass and lipid productivity of 170.28 kg (dry mass) ha-1 d-1 and 39.42 L ha-1 d-1 respectively were predicted in September with a CO2 capture potential of 224.77 kg ha-1 d-1. A threshold limit of pond depth and algal concentration exists that influences light attenuation, thereby the performance of microalgae in open ponds. Also, it was observed based on the metabolism of microalgae, photoinhibition had a profound effect as it declined the areal productivity by 19%. Later, the study was further extrapolated using the climatologic data sets of a nearby coal-based power plant situated at Jharsuguda, to analyze the technical and economic feasibility at the industrial location. CO2 capture of 147.03 kg ha-1 d-1 with biomass productivity of 111.39 kg ha-1 d-1 was predicted in February, which was thereby used as the baseline information for techno-economic assessment. Process feasibility assessment using SuperPro Designer revealed the technical and economic viability with yearly carbon credits of 52 M$ and, a reasonable rate of returns with an acceptable short payback time of 2.81 years. Sensitivity analysis showed the process to be raw materials and facility dependent. The next part of the study mainly dealt with the use of waste resources during algal cultivation, harvesting, and transesterification process to make the algal technology sustainable. Optimization with response surface methodology resulted in 211.63 mg L-1 d-1 biomass productivity, 26.27% lipids with 6.50% v/v of urine, pH of 7.69 and at a light intensity of 205.40 μ ℎ −2−1. Subsequently, to wave-off the negative impacts associated with the chemicals during algal flocculation, the harvesting potential of natural plant-based flocculants was explored. It was observed that M. oleifera showed 75.55% biomass removal efficiency at 8 mg mL-1 after 100 min. Further, it was observed that the biomass removal efficiency increased to 95.76% when 4 mg mL-1 M. oleifera extracts were combined with 0.75 mg mL-1 chitosan. The last section dealt with the use of biochar as a solid heterogeneous catalyst for the transesterification of algal oil. Peanut shell pyrolyzed at 400 ℃ with sulfonic acid density of 0.837 mmol g-1 having 6.616 m2 g-1 surface area was selected for efficient catalysis. Biodiesel yield of 94.91% was obtained with 5% wt. catalyst loading, MeOH: oil ratio of 20:1 at 65 ºC after 4 h. GC-MS analysis of algal biodiesel showed the presence of a significant amount of palmitic and oleic acids. Thus, the results obtained in the overall study could act as a benchmark for the policymakers to translate microalgal technology to field scale
Performance Assessment of Rapid Tool Electrodes During Electrical Discharge Machining of Titanium and Its Alloy
No full textElectrical discharge machining (EDM) is a non-conventional machining process, which is widely used these days, for machining of difficult-to-machine materials or where other conventional machining processes are unable to machine the materials. In this dissertation work, possibility of potential application of tool electrodes made of copper, tungsten and boron carbide manufactured by conventional powder metallurgy (PM), microwave sintering (MWS) and spark plasma sintering (SPS) route has been explored during electrical discharge machining of titanium alloy (Ti6Al4V) work piece. In addition to usual performance measures like material removal rate and tool wear rate, surface integrity of the machined surface in terms of surface roughness, surface crack density, white layer thickness and micro-hardness on white layer has been emphasized. Effect of change of weight percentage of tungsten and boron carbide in the tool on the listed performance measures is evaluated with respect to a traditionally used solid copper tool. The experimental plan is made based on Taguchi’s orthogonal array for different tool electrode and work piece combinations so that maximum process related information can be gathered with limited number of experiments. Analysis of data gathered through extensive experimentation reveals that the tools can be made as good as normally used copper tool electrode provided that proper ratio of weight percentage of different powders is maintained in case of preparing the tool electrodes by conventional powder metallurgy route. However, compaction of the powders and sintering of the green sample during preparation of the tool are still major concerns of the tool makers. Densification of the tool plays a major role in delivering adequate performance in machining otherwise material deposition on the work piece occurs rather than machining. In case of microwave sintering, it is observed that increase in weight percentage of tungsten and boron carbide makes the tool less dense because bonding of powder elements such as tungsten and boron carbide with copper becomes difficult. Therefore, increase in weight percentage of tungsten and boron carbide in the microwave sintered tools exhibit excessive tool wear and increased surface roughness, white layer thickness and micro-hardness on the machined surface with reduced material removal rate. The microwave sintered tool is no way superior to conventional solid copper tool insofar as the performance measures considered in this dissertation work. The tool electrodes produced by spark plasma sintering process exhibit low tool wear as compared to conventional PM tool electrodes and microwave sintered tool electrodes at higher percentage of tungsten and boron carbide in tool electrodes (weight percentage of fifteen each). As far as cracks on the machined surface are concerned, more surface cracks are found with the use of solid copper electrode in comparison to composite tool electrodes produced by spark plasma sintering process with any weight percentage of tungsten and boron carbide. Therefore, it can be concluded that spark plasma sintered tool electrodes perform in a superior manner when integrity of the machined surface is emphasized. The possibility of tool electrodes composed of aluminium, silicon and manganese powders (AlSi10Mg) produced through additive manufacturing route (selective laser sintering) has been explored for potential application in electrical discharge machining of titanium and titanium alloy (Ti6Al4V). The performance of the tool produced by selective laser sintering (SLS) process is compared with conventional copper and graphite tool electrodes. It is found that higher material removal rate can be achieved with the use of graphite electrode followed by copper and AlSi10Mg SLS electrodes. Similarly, lower tool wear can be achieved by the usage of graphite electrode followed by copper and AlSi10Mg SLS electrodes. It is concluded that AlSi10Mg SLS electrode can be conveniently used if superior surface integrity (low value of surface roughness, surface crack density, white layer thickness, and micro-hardness) is desired. In this regard, AlSi10Mg SLS electrode performs well followed by copper and graphite electrode. EDX analysis of machined work surface reveals that transfer of electrode material onto the machined work piece surface occurs during machining. Presence of silicon and magnesium on the machined work surface with increased percentage of aluminium, oxygen and carbon is found in case of usage of AlSi10Mg SLS electrode. EDX analysis of machined electrode surface reveals the transfer of work piece materials like titanium, vanadium and aluminium onto the electrode surface during the machining of titanium alloy. Optimization of the process parameters is made with the use of well tested multi-objective optimization techniques such as grey relational analysis (GRA), technique for order preference through similarity to ideal solution (TOPSIS), Grey-TOPSIS, grey-TOPSIS combined with quantum behaved particle swarm optimization (QPSO), desirability based grey relational analysis combined with firefly algorithm (FA). This is to be noted that tool fabrication cost and time can be substantially reduced if the tools with complex shape is made by powder metallurgy or additive manufacturing route rather than making the tool by conventional machining processes
Robust Non-Parametric Diffusion Strategies Over Distributed Adaptive Networks And Their Applications
No full textDistributed adaptive networks consist of a collection of sensor nodes distributed across a geographical area of interest. Each node is equipped with processing unit, sensing unit, memory unit, power supply unit and transceiver unit. The nodes collectively solve global estimation problems through local interaction among the neighbor nodes. The local communication among the nodes results in diffusion of information throughout the network. In this dissertation, the problem of robust distributed estimation is investigated, where the nodes communicate local measurements and local estimated parameters with neighbor nodes. The presence of outliers in the collected data can be treated as the impulsive noise. The presence of impulsive noise at any node in a distributed network will affect the entire network due to the local interactions and information exchange among the nodes in the network. Most of the classical distributed estimation techniques have considered the presence of only Gaussian noise, but in practical scenarios the presence of outliers is unavoidable. Such methods fail to attain the optimum solution in impulsive noise scenarios, since the underlying noise violates the theoretical assumptions considered for the algorithm development. This doctoral dissertation focuses on the development of robust non-parametric distributed estimation algorithms and their variants, which can handle impulsive contamination. Rank based estimators from the robust statistics are found to be robust against impulsive contamination involving systems. The Wilcoxon and Generalized rank (GR) norms are some of the rank based robust estimators. The Wilcoxon norm (WN) can handle impulsive noise in the desired/filter output data. In most of the practical scenarios, both the input and desired data contain impulsive noise along with Gaussian noise. The GR norm based estimators are robust against impulsive noise in both the input and desired data. The distributed robust algorithm named diffusion minimum generalized rank norm (DGR) is developed by minimizing the GR norm of the residual error in the optimization problem. The influence function of the GR norm is bounded in both desired and input data space, hence the GR norm based estimation techniques are robust against impulsive noise in both desired and input data. The performance analysis of the algorithm is analyzed using the asymptotic linearity relation between the null and alternate hypotheses of the GR norm gradient. Simulation based experiments are carried out to validate the robustness of the proposed algorithm compared to the state-of-the art algorithms. The proposed DGR algorithm exhibits slow convergence speed. To improve its convergence speed, the GR norm based optimization problem can be solved using the QR decomposition. The recursive least squares (RLS) based methods converge faster compared to the least mean squares (LMS) based methods and QR decomposition based RLS algorithms are numerically more stable than their counter parts. A fast diffusion minimum generalized rank norm algorithm based on QR decomposition (FDGR-QR) is proposed, which is robust against outliers in both desired and input data and has faster convergence rate than the DGR. The main intuition behind the proposed work is to enhance the performance of the DGR by solving the GR norm of the residual error cost using QR decomposition. Simulation based experiments are carried out to validate the robustness and enhanced convergence speed of the proposed algorithm. The parameter of interest or the parameter to be estimated could be sparse, i.e. only a few elements have large values and the rest being negligible. If some prior information about the sparsity of the parameter of interest is known, then it can be incorporated in the cost function using regularization technique. This type of optimization problems have extensive applications in practical scenarios like cognitive radio, direction of arrival estimation, distributed sparse demodulation and sparse signal detection. The robust diffusion algorithms based on WN and GR norm are extended for adaptive distributed systems with sparse parameters in impulsive noise environments. The techniques from compressive sensing endow the network with adaptive learning of the sparse structure form the incoming data in real time and it also enables tracking of the sparsity variations of the system model. The mean and mean square convergence of the proposed algorithms are analyzed and the conditions under which the proposed algorithm outperforms the unregularized diffusion GR norm and diffusion Wilcoxon norm algorithms are also investigated. The proposed robust sparse diffusion algorithms are validated for sparse parameter estimation in different simulation based experiments
Impact of Employee Relations on Decent Workplace and Employee Engagement: A Study on Indian Power Sector Undertakings
No full textIndian power sector has significant contribution towards the economic growth and welfare of the nation. Power is the core industry and the enabler of financial development in various sectors of India. In such a challenging business scenario, it becomes imperative for power sector undertakings to drive their human resources by stimulating employee satisfaction, engagement and proactive participation in organizational doings. This reciprocal exchange of obligations and rights between the employers and employees is the prime promoter of employee relations. Ultimately, a harmonious climate of employee relations is established as the most indispensable and integrated approach that synthesizes human capitals and diverse resources to reinvigorate organizational growth and prosperity. Social Exchange Theory (SET) is the prevailing approach adopted for explaining the relationship between employers and employees by developing a conceptual framework in the Indian perspective. The need for effective employee relations is therefore obligatory which would support the organizations to build up a decent workplace and increase the employees’ level of engagement.
Employee relations (ER) is one of the most widely researched phenomena that attracts considerable attention of both academicians and practitioners in the national as well as international perspectives. Seminal works on employee relations are researched in the Western literature considering organizational justice, employee empowerment, and conflict management as the antecedents and employee engagement as the outcome. However, empirical investigation on employee relations in the Indian power sector is sparse. Although power utilities are equipped with good employer-employee relations, proactive strategies, policies, and practices are required to be implemented effectively. The importance of decent workplace and its influence in uplifting the level of employee engagement in power sector is scant. Therefore, this study was undertaken to explore the impact of employee relations towards developing decent workplace and encouraging employee engagement in the Indian power sector. The study primarily focuses on evaluating the perception of the power sector employees on drivers of ER, employee relations, role of actors, decent workplace, and employee engagement to establish logical relationship among these variables.
In order to validate this research model, a questionnaire survey was administered among the executives and non-executives of four public power sector undertakings to accumulate both primary and secondary data. Nationinal Thermal Power Corporation Ltd., Talcher; Odisha Power Transmission Corporation Ltd., Bhubaneswar; Odisha Power Generation Corporation Ltd., Bhubaneswar; and Odisha Hydro Power Corporation Ltd., Bhubaneswar are the four power units selected for this study. A structured questionnaire consisting of 115 items was distributed to a total of 940 respondents using a simple random sampling method to collect the primary data. Based on the perception of the respondents, 652 useful responses were retrieved corresponding to a response rate of 69.36 percent. The responses congregated were further analyzed using SPSS 20 and Amos 20 software. The preliminary analysis of the data was conducted using descriptive statistics, correlation, and regression analysis. The statistical tools such as exploratory factor analysis and structural equation modeling were adopted to validate the hypothesized research model.
The findings of the study demonstrated that drivers of ER (interpersonal relationship, healthy work environment, employee compensation, organizational justice, employee empowerment, and conflict management) have a positive and significant relationship with employee relations. Furthermore, employee relations was found to be positively and significantly related to decent workplace and employee engagement. Subsequently, the study established that decent workplace positively and significantly influenced the encouragement of employee engagement. The role of actors including role of employee, role of employer, and role of government were the significant moderators strengthening the relationship between employee relations and decent workplace, except role of trade union. Additionally, the results divulged that decent workplace played the role of a partial mediator in the relationship between employee relations and employee engagement.
Hence, this research furnishes a holistic framework which could support the power sector undertakings to assess and develop cordial employee relations, decent workplace, and employee engagement. Further, this study provides necessary suggestions and implications to the theorists and practitioners to implement effective strategies for flourishing better employee relations climate. An organization with healthy employee relations could develop a decent workplace and enhance the degree of employee engagement. Finally, this research work advocates the significance of decent workplace as a critical constituent of the power sector undertakings
Production of Innovative Angular Fly Ash Aggregate and Its Performance in Light Weight Concrete
No full textThe present study describes the manufacturing process of a new product, the angular fly ash aggregates (AFAA), that does not involve pelletization process. In previous studies, round fly ash aggregates are produced by using pelletization procedure. Although pelletized fly ash aggregates are commercially used, it has some drawbacks like less interlocking effect due to the round shape, requires more equipment that consumes more energy, need high supervision and lacks reproducibility. To overcome these limitations, an innovative idea for producing angular fly ash aggregates is suggested. AFAA was manufactured by crushing sintered briquettes (obtained from the mixture of fly ash, binder, and water) into angular aggregates. This newly manufactured aggregate possesses a rough surface and greater surface area as compared to round pellets thus result in the better interlocking of aggregates with paste. Different types of AFAA were manufactured in the laboratory by using two different types of fly ash and four different types of binders. Cement, bentonite, glass powder, and lime powder were used as the binder that provides compaction to briquettes and reduces the water absorption of AFAA. The proportions of binders, fly ash and the quantity of water to be used for manufacturing of aggregates were decided after various trials. The aggregates manufactured varying the proportions of binder and fly ash were then tested and concluded that the optimum quantity of cement and lime is 20%, whereas for bentonite and glass powder, it is 15% and the selected water to fly ash ratio is 0.25 for preparation of angular fly ash aggregates. Also, the influence of characteristics of fly ash and binder on the behavior of manufactured aggregates was observed. Performance of AFAA showed that chemical composition and specific surface area of fly ash influence the sintering behavior of ash and as a result, internal microstructure of aggregates also gets affected. It is observed that the performance of bentonite is superior as a binder because of its cohesive nature and swelling property. This study also explains the strength characteristics of structural lightweight concrete produced using manufactured AFAA. Mix design of lightweight concrete was done as per guidelines provided in ACI 211.2-98. Concrete produced using AFAA was found to be lighter in weight compared to the concrete of natural aggregate. It was concluded that the strength of concrete depends on the properties of manufactured AFAA and the nature of the bond between cement and aggregates at the interfacial transition zone (ITZ). 28 day’s compressive strength varies from 22.23 to 35.12 MPa. Split tensile strength varies 2.42 to 3.93 MPa and flexural strength varies from 3.51 to 4.5 MPa. Concrete produced using lightweight AFAA meets the strength requirements of LWC for structural applications as per ASTM C330. The microstructural analysis has been carried out through scanning electron microscopy (SEM) to observe the distribution of pores within aggregates and to understand the interfacial bond between cement and aggregate in produced concrete. It can be concluded from X-ray diffractometer (XRD) analysis that even after the sintering process, there is no change in the chemical composition of AFAA. Regression analysis was done to study the relationship between compressive and split tensile strength and also between compressive and flexural strength of produced fly ash aggregate concrete and equations were suggested. Also, the result obtained was compared with equations proposed by other researchers. Some of the durability tests have been conducted on concrete produced using these aggregates to check its suitability for structural applications. The obtained water absorption of all AFAA are within range of those of good one i.e. below 10%. Sorptivity coefficients are in the range of 0.0138 to 0.0213 mm/√s that shows acceptable performance of concrete. Loss in weight and strength was observed on acid attack that increases with increasing period of acid immersion. Due to penetration of binder within porous aggregate, bond strength is better in lightweight fly ash aggregate concrete and hence surface area is more susceptible than aggregate on acid attack. It was observed that concrete produced using bentonite as binder, showed maximum pulse velocities of 4.896 km/sand 4.983 km/s after 28 and 56 days of curing respectively. Overall, obtained UPV Values of all fly ash aggregate concrete shows good and excellent quality. The present study reveals that fly ash aggregate is adequate to use for structural purpose due to its lightweight nature and acceptable strength. The utilization of fly as in production of lightweight AFAA not only saves our depleting natural resources but also reduce environmental pollution and hence promote sustainable construction practices
Modelling and Analysis of Various Issues in Viscoelastic Composite Rotors
No full textRotordynamics is a specific wing of science that deals with various issues related to rotating structures. The shaft or rotor is a rotating module that acts as the significant vibration source in most machines. Vibration brings in severe effects, and minimizing it is essential for the smooth and efficient operation of machines. Apart from balancing, replacing heavy metals with viscoelastic substances exhibiting lesser density and proficient material damping mechanism can stand as an alternative to reduce the excessive vibration. However, the main disadvantage of viscoelastic material is its low elastic modulus, which can be overcome by reinforcements. Composite materials have been extensively used for rotor design due to their lightweight, environment-friendly, low cost, quality, and better performance. Unlike a nonrotating system, material damping in the rotor shaft plays a significant role in deciding its dynamics. It produces a speed-dependent force acting tangentially and destabilizes the system after a certain spin speed. Hence, along with proper modelling of rotor systems with asymmetries due to internal damping, it also becomes essential to model the shaft considering the laminated nature of the composite that would satisfy both symmetric and non-symmetric stacking sequences. Further, under dynamic conditions, one of the main reasons for rotating systems' failure is the development of fatigue cracks. Considering the fact that breathing nature is indeed observed in the crack while the system is in operation, it is crucial to appropriately model the breathing behaviour of the crack and further study its effect on the rotating shaft dynamics. Along with the issues mentioned above, a common concern is observed in the large computational effort by the bulky and non-self-adjoint system, especially for more realistic models like submarine shafts, which considerably have a large continuum, lead to large and complex finite element models. The study based on the first issue proposes a novel mathematical technique named Equivalent Modulus Theory (EMT) to model viscoelastic laminated composite shafts and compare it with another method known as Direct Procedure Technique (DPT). The operator-based constitutive relationship is endorsed to each lamina to integrate the material damping, leading to a higher-order finite element (FE) model. Timoshenko beam theory is used in the finite element formulation to incorporate the shear deformation effect. Numerical results are acquired through eigenanalysis and unbalance response. On comparison, the results obtained out of the two procedures authenticate the suitability of EMT for complex heterogeneously laminated structures like rotor-shaft systems. The vital contribution of the study lies in the application of the novel mathematical formulation which uses the material properties of just the single lamina, eliminating the need for fabricating the whole composite irrespective of the stacking sequence. Further, the study has been continued to carry out the dynamic analysis of the composite rotor systems subjected to an important issue, i.e., cracks. Geometry based novel mathematical formulation for breathing mechanism is proposed. This introduces a time-varying stiffness matrix for simulating the breathing behaviour of the crack in a rotating composite shaft. The stiffness matrix is incorporated into the previously obtained higher-order FE model to study the effect of crack on stacking sequence and mode shapes of the heterogeneous laminated shaft. The issue of bulky and complex finite element models leading to higher computational time is dealt with using the reduction process, i.e., Modified SEREP (System Equivalent Reduction Expansion Process). The reduction process is applied over a realistic multilayer propeller shaft system exhibiting viscoelastic nature to check the efficiency of the process through computational time comparison. The carried out research work presents mathematical models that can be applied to any viscoelastic unidirectional composite shaft systems subjected to breathing cracks and exhibit complex and bulky natur
Processing Ferroalloys from Lean Ore and Fines using Thermal Plasma
No full textThe depletion of high grade ore minerals and scarcity of fossil fuel reserves are challenging factors for metallurgical industries in the future. In addition, extensive mining for increased steel demand results in the generation of fines, often found unsuitable for use as direct feedstock for the production of metals and alloys. Apart from mines waste, the other major sources of fine minerals are leftover in charge burdens, sludges, and dust generated in the high-temperature process. Sludge and fines generated during beneficiation of ore add to this woe, as the outcomes of beneficiation plants for lean ores show better yield for fine particles. These are becoming an environmental hazard, and need utilization for economic and environmental aspects. The production of ferroalloys is dominated by the Submerged Arc smelting route and also is limited to lumpy ores or agglomerates. With the evolution of DC/plasma arc smelting, direct charging of fines for ferroalloys production, particularly ferrochrome, has been made feasible in recent years. However, continuous improvements in the process economy are essential. The utilization of lean ore and wastes in ferroalloys production requires wide research and adoption of new advanced technologies for quality production with time-saving operations. Thermal plasma has several advantages over conventional pyro-metallurgical processes viz. no constraint in size and composition of the feedstock, comparatively higher recovery rates, purity in alloy grade, and so on. Thus, the present research is focused on the use of thermal arc plasma for production of ferroalloys, i.e., ferrochrome, ferromanganese, and ferrotitanium from ore mineral fines and mines waste. Friable chrome ore of Indian origin is subjected to carbothermic reduction at 1450 ℃, where the chromium and iron oxides are partially reduced and metallized with the formation of slag phases. The addition of flux and the type of reductant affects the reduction rate as confirmed from characterization studies. The subsequent milling and magnetic separation result in the elimination of gangue up to 70% by weight. The fine magnetic materials are found suitable for plasma smelting with a lime-rich melilite composition, which is advantageous over the current industrial (cordierite slag) practice. The comparative study of smelting ore with/without slag chemistry and magnetic parts of partially reduced chromite evidences that the latter route i.e. smelting after magnetic separation, is more advantageous for minimizing processing cost and improving alloy quality as well as recovery rates. The chromium and silicon content in ferrochrome alloy is about 68% and less than 0.5% by weight, with overall metallic recovery rates exceeding 95%.The generated melilite slag can also be used in cement production after granulation. Phase, composition, and thermal analyses of different manganese ore fines are investigated. The minerals associated with ores exhibit various thermal transformations and inversions, and are quantified. The ores are of medium grade, ferruginous, alumina-rich ferruginous, and siliceous types. Reducibility, phase, and microstructure evolution of stiff extruded briquettes under vacuum made from above ores are studied in the temperature range of 1000 ℃-1400 ℃. Physico-mechanical properties are evaluated for cold and reduced briquettes and observed that beyond 1300 ℃ briquettes partially melted and deformed. XRD and SEM-EDS analyses evidence the presence, formation, and distribution of liquid silicate and or aluminate complex phases, might be responsible for retarding reduction rates. Further, smelting tests/works are carried out for studying different slag chemistry. The comparative study shows that high alumina in the final slag has less impact when basicity increases beyond 1.0. Alumina rich ferruginous ores are adjusted to the MgO-Al2O3-CaO-SiO2 and CaO-SiO2-Al2O3 slag systems, and it is observed that the increase in basicity ratios improves recovery rates. Siliceous ore upon smelting results in high silicon pick-up in the alloy, and the phase and composition satisfies ferro-silicomanganese alloy grade. Ilmenite on carbothermic smelting in thermal plasma resulted in pig iron and titania-rich slag as end products. Further, to produce ferrotitanium, combined carbothermic and aluminothermic reduction approaches are made in stages and varying compositions. It is seen that lime addition into charge mixture lowered the recovery rate of titanium, by forming calcium titanate (in varying CaO/Al2O3 ratios). However, the addition of carbon and aluminium in stages has the benefit of utilization of heat lost in between steps if carried out in separate processes. Phase analysis and the microstructural investigation reveals the presence of iron-rich FeTi and Ti phases in the produced alloy. The next approach made to use carbon, aluminium, and silicon as reductants in stages. This combined stage-wise reductant injections in an uninterrupted single process form ferrotitanium silicide of varying composition, which is of high value particularly while making RH degassing of steel. The direct use of ore fines and wastes avoiding agglomeration is cost-effective over lumpy high-grade ore minerals. The beneficiation of lean ores with subsequent change in slag chemistry fit into the requirement of thermal plasma