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Non-Probabilistic Uncertainty Analysis for Radon Transport Mechanisms
No full textRadon is a well-known radioactive inert gas that usually emanates from rock, soil, concrete and enclosed places like house, building, and underground mine, etc. It is usually undetectable to the human senses. Radon may enter into various enclosures such as buildings and it can be able to accumulate due to improper ventilation. A worldwide average of 60.4 percent of total indoor radon originates from under-ground and surrounding enclosures (Cothern et al., (2013)). High concentrations of it may cause lung cancer. Radon is the second leading reason for the cause of lung cancer after alcohol and tobacco. It causes more deaths per year than drunken driving, earthquakes, flood, and drought (Clavensjo and Akerblom, (1992)). In general, the radon problem is a major concern in cold climate regions compared to other regions. Further, it has also been used as a trace gas in terrestrial, hydrogeological and atmospheric studies because of its ability to travel long distances from host rocks as well as its efficient detection at very low levels. Radon transport in soil pore is mainly governed by two physical processes namely, diffusion and advection. Different transport models are developed by various researchers to study the anomalous behavior of soil gas radon in geothermal fields. These models have been employed to estimate process-driven parameters (such as diffusion coefficient, carrier gas velocity, etc.) from the measured data of soil gas radon. Estimation of these parameters may deviate significantly from the true values if the uncertainty associated with the various input parameters of the models are not taken into consideration. The primary aim of this investigation has been to solve uncertain (interval/fuzzy) radon transport equations. As such, new methods have been proposed to handle steady and unsteady-state uncertain radon transport equations in various mediums. In this regard, Galerkin and collocation methods are extended to solve the steady-state uncertain radon transport equations. On the other hand, the uncertain unsteady-state radon transport problem has been solved by introducing interval midpoint and parametric concepts in the explicit finite difference method. vii Further, Geo Station Continuous Monitoring System Lab has been set up for a soil chamber experiment. Corresponding experiments are conducted for estimating the uncertain (fuzzy) band of radon concentration in order to predict the anomaly behavior of the radon transport in the earth's crust. The experimental results are also used to validate few of the proposed methods. In this research, another challenge has been to study the related forward and inverse problems with respect to fractional order in an uncertain environment. Accordingly, the fractional uncertain diffusion problem has been studied. To the best of our knowledge, the inverse problems with respect to the diffusion problem of an integer as well as fractional order in the uncertain environment have been investigated for the first time. Finally, the experimental results are used to validate few of the proposed method
A Study on Arithmetic Functions and Diophantine Equations Associated with Balancing and Related Sequences
No full textA Lucas sequence is a binary recurrence sequences that includes as special cases, the Pell, the associatedPell, the balancing, the Lucasbalancing, the balancinglike and the associated balancinglike sequences. Arithmetic functions of some of these sequences result in interesting inequalities. In particular, σk(Bn) ≤ Bσk(n), where σk denotes the sum of the kth power of divisors function and Bn is the nth balancing number. Repdigits are positive integers with one distinct digit, that is, a single digit appears in the unit place, decimal place and so on. The Euler functions of Pell numbers has no repdigit with at least two digits. However, it is not known whether the Euler function of any associated Pell number is a repdigit with more than one digit. Moreover, if the Euler function of an associated Pell number is a repdigit, then its index must be odd, and the repdigit consists of the digits 4 or 8; in case it contains the digit 4, then its index is an odd prime or its square. The third term of every balancinglike sequence is one less than a square, while, by choice, the second term may or may not be one less than a square and no other term of any balancinglike sequence has this property. Furthermore, except the first and second terms, no other term of any balancinglike sequence is one more than a square. There are just 2 perfect powers in sums and differences of two balancing numbers and in any balancinglike sequence, the number of perfect squares in the sums and differences of two balancinglike numbers is always finite. BrocardRamanujan identity consists of finding positive integer solutions of the equation n! + 1 = m2 and the only known solutions are (n,m) = (4, 5), (5, 11), (7, 71). This problem can be generalized by replacing the positive integers in n! and m by balancinglike or associated balancinglike numbers. The revised problem has sometimes no solution and sometimes finitely many solutions
Formation Control of Autonomous Underwater Vehicles under Communication Delay and Actuator Saturation
No full textAutonomous Underwater Vehicles (AUVs) are robots which autonomously carry out desired underwater operations. With the advancements in efficient sensors, actuators and processors, AUVs can be deployed for various applications such as underwater mineral detection, studying life patterns of aquatic plants and animals so that measures can be taken to protect endangered species, scanning deep sea beds for installing underwater pipelines, overhauling and repair of installed pipelines and defence applications which includes carrying as well as detecting warheads. In order to accomplish the aforementioned applications, various sensors are necessary to be installed with the AUV. Thus, deploying a group of AUVs with a distributed sensor configuration, helps in reducing the payloads on a single AUV. Moreover, when AUVs are deployed in a group, larger areas can be scanned in less time and it also makes the mission redundant in case a single AUV fails. There are various approaches of formation control such as behaviour based, synchronization based, virtual structure based and leader-follower based approach. The leader-follower approach is one of the most widely used formation control approaches owing to its simple structure. In this approach, the leader AUV states are sent to the follower AUVs for maintaining the formation. These states are transferred in underwater via acoustic modem. However, the low data rate of acoustic medium introduces communication delay into the AUV motion control system. This delay varies as the distance between the leader and follower AUVs varies with the ocean currents. In the literature [1, 2], most often, this delay is minimized by either transferring least number of AUV states or accurately estimating these states. However, the communication delay can still increase as well as vary significantly due to change in distance between the AUVs with the ocean current. Hence, in this thesis, a leader-follower approach is considered for studying the effects of this variable communication delay on the performance of follower AUVs. Optimal control facilitates path following by optimizing the error between the desired and actual AUV positions [3, 4]. Moreover, when this control is employed for formation control while considering the communication delay among multiple AUVs, it also provides an optimal control law which can handle the effects of delay along with ensuring smooth path following during formation control. Thus, in the thesis, an optimal kinematic control is developed to deal with the communication delay during formation control. In this approach, a linear augmented system comprising the kinematics of both leader as well as the follower AUVs is constructed. This co-operative AUV system also takes into consideration the leader AUV states received by the follower AUVs. Further, an optimal control law is derived for both the leader and follower AUVs. By using these optimal gains, the leader AUV converge to the desired path and also the follower AUVs maintain the formation under the effects of communication delay without yielding oscillations. The performance of the optimal control scheme is compared with a Linear Quadratic Regulator (LQR) based formation controller. The results clearly show that the follower AUVs in case of proposed controller follows the path without oscillations, whereas, in case of LQR, for a chosen set of Qlqr and Rlqr matrices, the response is oscillatory. The simulation results also show that though the steady state error occurs in case of the proposed controller, it is significantly less than LQR. To minimize the aforesaid steady-state error, a convex optimization based modified constrained adaptive control is then proposed in the thesis considering non-linear kinematics and dynamics of AUV. In this approach, the cost function comprising communication delay information based position and velocity error equations is minimized in every iteration. Thus, the effect of communication delay is considered in every sampling time and adaptive control is developed to deal with these effects. This proposed controller also resolves the issue of actuator saturation. However, the results in this case are compared to a backstepping control based formation controller. The backstepping controller is one of the most widely adopted control paradigms for non-linear systems as it considers all the system non-linearities while calculating the control input. Moreover, as backstepping is a Lyapunov function based approach, it also guarantees asymptotic stability of the system. Nevertheless, from the results, it is clearly evident that, under the effects of communication delay, in case of the constrained adaptive control, the AUVs follow the desired path within an accuracy of 5cm, thereby reducing the steady-state error. But in case of backtepping control, with stamping based technique is used in this approach to determine the communication delay. In this technique, the packet of leader AUV states also contains time information at which it is sent. When this packet is received by the follower AUV, the time at which it is received is also noted. The time-difference between these two time-stamps gives the actual delay which is used for controller design. This technique not only increases the packet-size, which subsequently increases the communication delay, it also necessitates that all the clocks pertaining to every AUV to be synchronized. To address increased communication delay and clock synchronization issues, next, a gradient descent method based delay estimator is designed to handle the effects of the time stamping of every sent packet of the leader AUV states. It also does not necessitate time synchronization of AUV system clocks. This estimator is employed along with the developed constrained adaptive controller to reduce the delay and achieve the desired formation control performance. The results show that the gradient-descent method based estimator accurately estimates the communication delay. Moreover, employing the proposed estimator also helps in significantly reducing the communication delay occurring in each sampling-time. The formation control of AUVs considering small or negligible communication delay has been widely studied in the available literature. However, in this thesis, a leader-follower approach based formation control of AUVs under the effects of significantly large variable communication delay has been investigated. Simulations were conducted by implementing a group of a leader AUV and two follower AUVs using MATLAB/Simulink. In case of all the aforementioned proposed algorithms, it is observed that, the AUVs follow the desired formation with accuracy and without oscillations. To verify the efficiency of all the developed control schemes for formation of AUVs, in real-time, an experimental setup is developed. A torpedo-shaped prototype AUV is designed for implementation of proposed control algorithms. Moreover, the hydrodynamic parameters of the developed prototype AUV are also determined. Since, in the proposed constrained adaptive technique which is employed to handle varying communication delay between the AUVs, the determination of the hydrodynamic parameters a priori helps in minimizing the computational burden. Moreover, the determined parameters can also be used for controller design in the future applications. Furthermore, a virtual AUV is considered as the leader AUV and the prototype AUV with Robot Operating System which supports python based programming is employed as the follower AUV. The experimental results also support the observations from the simulation studies. In case of all the aforesaid proposed algorithms such as optimal and constrained adaptive control, the follower AUV follows the desired orientation, under communication delay without oscillations. Moreover, the designed estimator helps in estimating the communication delay accurately and also helps in reducing the delay which occurs due to time-stamping. Thus, from the results it is evident that for small linearization errors or slowly changing paths (as the linearization errors depend on angular velocity of the desired path), the proposed optimal kinematic control law can be employed to deal with communication delay during formation control. Since, the optimal control gains in this case are calculated off-line, it helps in reducing the computation burden, while achieving smooth formation between the AUVs. As the linearization error increases, the constrained adaptive control can be employed for the aforementioned objective. This control adapts on-line to the variable communication delay occurring during formation control and also helps in avoiding actuator saturation. This proposed control being adaptive in nature, still computes the control law within the considered sampling time, thereby adhering to the limit of computation time. Moreover, this adaptive control law when employed along with the gradient descent method based estimator helps in accurately estimating and reducing the communication delay by avoiding time-stamping. However, based on these aforesaid advantages, it is evident that, with the advancements in the processor speed, the adaptive control algorithm offers better performance and the delay estimator can appropriately replace time-stamping technique
Laser Sensor Assisted Industrial Arc Welding Robot System for Producing Quality Welded Joints
No full textThe task of automating the welding operation requires motion control, sensor integration and coordination with the welding power source. It is essential to set the robotic welding parameter specifications before starting of any welding cycle as these parameters affect the weld quality differently. The weld quality parameters are highly affected by the GMAW process parameters such as welding current, welding voltage, gas flow rate, robot travel speed and robot orientation etc. In the present research work, the effect of these process parameters on the weld quality has been studied combinely. The weld quality has been measured in a combined form of welding joint properties like bead penetration, width, height, ultimate strength, yield strength, micro-hardness, width of heat affected zone and surface defects.The prediction and optimization of this type of problem can’t be achieved by a single objective optimization technique as the input welding parameters affect the output parameters differently. Therefore, it is essential to introduce artificial intelligence technique in to the robotic welding process so that the best weld quality can be predicted from the manipulation of weld parameter setting without performing a number of experiments. A new approach based on combined Fuzzy and ANN (Artificial Neural Network) logic is presented for predicting best weld quality measures with respect to variations in weld process parameters. First, Fuzzy logic has been used to solve the complex interrelationships among the multiple weld quality measures like weld bead features, mechanical and microstructural properties by converting them in to a single Weld Quality Characteristic Index (WQCI). FIS can effectively acknowledge these conditions into internal hierarchy of it, by which it can overcome different drawbacks of other optimization techniques. Then ANN has been utilized to predict the WQCI from input of different settings robotic welding process parameters. From the results and analysis, it has been depicted that the developed neural network structure with four hidden layers can predict multiple weld quality measures from various welding process variables efficiently with a very strong correlation between the experimental and predicted outcomes by which cost involving for quality inspection in experimental trials can be removed. Afterthat, multi objective hybrid approaches like Fuzzy with meta-heuristic algorithms have been applied to achieve the optimal robotic welding conditions. Fuzzy-regression based approach has been utilized to establish mathematical model for the combined weld quality measures. Finally, an Enhanced TLBO algorithm has been applied to get optimal setting of the all the significant welding parameters. The proposed methodology has been found to be more efficient in achieving best weld quality in terms of maximized yield strength, ultimate strength, micro-hardness of welded joint, weld bead fautures with minimized heat affected zones, welding defects in comparison to other existing optimization techniques In this research work, robot assisted gas metal arc welding (GMAW) is introduced by controlling two subsystems; welding equipment and the laser sensor integrated industrial welding robot. An intelligent control strategy is adopted here to identify the feasible process related parameters and these are controlled in a way to obtain the desired weld quality. At first vision sensor has been used to obtain the seam positions, so that there is no need to teach the robot manually. For repeatable environment or for similar designed weld path, the weld seam can then be found by laser sensor and if there is any error any positioning, it is then notified to robot controller to move the robot end effector to the actual position. By this, if there is any change in weld gap in the weld seam, the robot tool centre point can be positioned accordingly. The output data of the sensor in terms of variation of weld gap has been used for control of welding parameters with Fuzzy controller to achieve maximum weld quality. This algorithm performs the seam finding in terms of weld geometry using laser sensing technology and alters the welding process parameters according to the geometric variations. Moreover, this paradigm maintains the torch orientation which is equipped to the end effector mounting plate in order to produce smoother and quality weld joints during the real time arc welding applications. The proposed Fuzzy controller based approach with laser and vision sensor intregration has been fond to be a cost effective, flexible method adding more value to the process of automatic robotic welding welding process. Use of robots in arc welding operations needs planning of trajectory path positions along which the robot end effector will be moved. For this, an optimal minimum time-jerk-acceleration-torque rate weld seam trajectory planning for MOTOMAN MA-1440 welding robot has been developed. This trajectory problem has been solved by newly developed hybrid Evolutionary Algorithm like NSGA-II with Achievement Scalaraizing Function local search algorithm to obtain a Pareto front which can give trade-offs between the objectives. From the simulation and experimental results, it can be concluded that by the implementation of the proposed optimal trajectory planning a smooth robot joint trajectory with reduced vibration of robot end effector travel, velocity stability and uniform weld bead along the weld seam can be achived. The influence of robot parameters like robot orientation, robot travel speed, focal length of sensor on the positional error, associated joint jerk-torque rate and the weld quality has also been investigated. NSGA-II with Nelder mead local search hybrid multi-objective algorithm has been proposed to obtain optimal values of robot and sensor parameters for getting minimum positional error with minimum jerk-torque rate and maximum weld quality. From the experimental investigation of the proposed approach, it has been observed that the measured weld quality features, positional errors of tool centre point along weld seam and joint kinematic parameter and dynmic parameter values have been optimized with the output setting of evolutionary algorithm over repeated cycle
Determinants of M&A Success & Failure: Evidence from Indian Corporate Sector
No full textThe business scenario has become dynamic and competitive by providing challenges to the companies for their survival in today's economic era. For avoiding such type of competitive pressure, companies adopt several strategic development approaches, and Merger & Acquisition (M&A) is one of them. M&A strategy helps companies to generate revenue for their growth and development by integrating with other companies. It also helps in achieving the market power, acquiring new customers, gaining new technology along with maximising the profit. Because of these benefits of M&A, companies of many countries want to go for such transactions. India as an emerging economy is also hugely going for M&A deals. But it is noticed that, during such transactions, companies are facing numerous problems. Some determinants and factors affect the performance of the company throughout the pre and post-M&A period. As a result, maximum numbers of M&As are considered as unsuccessful. In this context, the study proposed to find out the crucial factors that have their positive and negative impact on the deals and posses a vital role in the success and failure of M&A. Further, this research studied the psychological inferences of people towards a merger and found out the crucial factors related to a deal. Design/Methodology/Approach This research is primarily based on both qualitative as well as quantitative approach. Further, data were collected from both primary and secondary sources to resolve the proposed research questions and to find the results. The secondary data were collected from various M&A databases viz Bloomberg, CMIE (Centre for Monitoring Indian Economy) Prowess database and CMIE Economic Outlook. Additionally, secondary information related to deal were collected from the involved company websites, print and electronic media sources, BSE (Bombay Stock Exchange) and NSE (National Stock Exchange) websites, published reports and other government reports and websites. Further, data from social media like Twitter was collected to study the practical scenario of M&A deals along with measuring the psychological presumptions of the customers and the general public towards a deal. Primary data was collected through interview and questionnaire method from M&A experts, deal makers and leading management of companies to determine the M&A motives of Indian companies and to identify the critical factors of a deal. Besides these, three case studies were developed to analyse the practical scenario of an M&A deal firmly and to discover the success and failure determinants associated with those deals. Methodologies like Paired t-test, Analytical Hierarchy Process (AHP), Relative to an Identified Distribution (RIDIT) and Sentiment Analysis using R programming language techniques were used to derive results. Findings This study critically analysed the merger situations and found out some factors associated with the M&A deal. Further, the past and present situation of M&A, along with the motives of M&A in India is determined in this research. From this study, we observed that the number of acquisitions in India is higher than the number of merger deals from 2000 to 2017. During this period, maximum numbers of M&A were registered in the chemical and chemical product industry of the manufacturing sector, and the same scenario was also observed in the miscellaneous and information technology industry of the service sector. Further, by analysing the motives behind M&A in India, this study found out that, Indian companies go for M&A transactions with other companies to achieve the operating synergies. Besides, this research also derived some success and failure factors of M&A. By critically analysing the factors of M&A, we found out that, inefficiency in handling the human resource issues, late integration procedure, fail to combine the culture of the organisations and improper pre-merger planning lead the deal towards failure. In the same time, it is also observed that proper deal-related communication with the employees and shareholders of the organisation, a quick and efficient technological integration, and efficient management of the post-merger related issues help to execute the deal successfully. Further, this research suggests measuring the sentiment and feelings of the stakeholders of the companies correctly both in the pre and post-deal duration to understand their sufferings because of the M&A deal and help them to come across from the problem. Academic/Practical/Social Implications This research is an endeavour to enrich the existing academic literature by collecting a large number of factors from previous studies and analysing their level of importance while finalising an M&A deal. Besides, judging the impact of a transaction on different components of the society is another novelty of this study. The findings of this study would be beneficial for managers, investors, policymakers, and the stakeholders of the companies to judge a deal from its financial, operational, managerial, legal, and social prospects. Finding out critical factors may be helpful for the companies to increase their financial performance by reducing unnecessary expenditures, to enhance operating performance by applying innovative strategies, and to improve managerial performance by adding skilled workforce. Originality/Value Earlier studies in India have focused only on a single specific industry to determine the critical factors and compare the financial performance of companies in the pre and post-M&A period. This study is not limited to any particular industry or sector. Perhaps this is the first study in the case of M&A in India to evaluate the importance of critical factors of M&A by collecting data from M&A experts in India. Further, as per the researcher’s knowledge, evaluating the psychological impact of M&A on the stakeholders of the involved company with the help of the social media data is a unique study and perhaps the first to be conducted in India
Polyvinyl Alcohol - Polyvinyl Pyrrolidone and Polycaprolactone Based Matrices for Cardiac Tissue Engineering Applications
No full textCardiovascular diseases (CVDs) are leading cause of death in the developed and industrialised world and are responsible for approximately ~30% of all global death. In recent years, stem cell-based cardiac tissue engineering (CTE) has emerged as promising technology for the treatment of CVDs in severely damaged heart. The present study deals with the development of polymeric construct for CTE applications. In the first set of experiments, polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP) blended film and nanofiber were fabricated and effects of cross-linker and plasticizers on their physico-chemical and biological properties were analyzed. In the second set of experiments, random and aligned polycaprolactone (PCL) nanofibers were spun by electrospinning and were characterized for their application in CTE. Results showed that, PVA-PVP blends could be successfully developed as biodegradable, haemocompatible and cytocompatible cardiac patches with desirable mechanical properties. Optimized molar ratio of PVA, PVP and plasticizers resulted in films, which were dry at room temperature and had desirable folding endurance value (FEV) of at least 300, tensile strength of 5-30 MPa and, percentage elongation at break of more than 250%. Upon contact with PBS, these PVA-PVP films formed hydrogel patches having the tensile strength of 1.3 to 3.0 MPa and supported the attachment, viability and proliferation of H9C2 cardiac cells and primary neonatal cardiomyocytes (CMs). In vivo transplantation of the PVA-PVP patches into subcutaneous pouch and on the heart revealed them to be biodegradable, biocompatible and safe for use. The PVA-PVP blends could also be electrospun to develop nanofibrous matrices (av. dia. 100-200 nm). The study further showed that both random and aligned nanofibrous matrices (av. dia: 350-850 nm) could also be successfully spun from PCL by electrospinning on copper and stainless steel collectors, respectively. Collagen-coated aligned PCL nanofibers showed significantly higher cell adhesion, proliferation and, enhanced cell growth of H9C2 cardiac cells when compared to random PCL nanofibers. Moreover, aligned PCL nanofibers showed an ability to control the orientation of the cells in parallel direction of fibers, thus providing an effective way to control anisotropic nature under in vitro condition. The umbilical cord matrix (UCM)-derived mesenchymal stem cell (MSCs) and adult foreskin-derived induced pluripotent stem cells (iPSCs) were also differentiated into CMs for subsequent construction of cardiac tissue construct. UCM-derived MSCs were isolated successfully by routine enzymatic digestion and a non-enzymatic explant culture method and characterized based on their microscopic observation, differentiation into different lineages such as chondrocytes, osteocytes and adipocytes and surface marker expression of CD34, CD45, CD73, CD14, CD19, HLA-DR, CD90, CD105 by flow cytometry analysis. Treatment of UCM-derived MSCs, with 5-Azacytidine (5 μM) induced their differentiation into putative cardiac cells, as revealed by the expression of Cardiac-specific Troponin T (cTnT), smooth muscles actin (SMA), Myogenin (MYOG), Smoothelin (SMTN), and Cardiac α-actin (ACTC) genes and cTnT and α-actinin proteins by RT-PCR and immunocytochemistry, respectively. However, no beating cells were observed in differentiated MSCs. On the other hand, adult human foreskin-derived iPSCs could be successfully expanded and proliferated on MatrigelTM - coated aligned PCL nanofibrous matrices and was superior to SynthemaxTM - coated PCL nanofiber or tissue culture coated polystyrene (TCP) surfaces. The iPSCs cultured on MatrigelTM - coated aligned PCL nanofibrous matrices showed anisotropic behaviour along the PCL nanofibers and, upon differentiation, expressed cardiac-specific cTnT proteins and showed spontaneous beating. The beating CMs differentiated on MatrigelTM - coated PCL nanofibrous matrices showed significantly higher percentage of cTnT-positive CMs (23.34 vs. 32.55%) and showed more synchronized beating than those differentiated on MatrigelTM - coated TCP. Thus, electrospun aligned PCL nanofibers may be more suitable for proliferation and differentiation of stem cells into beating CMs than random PCL nanofibers or TCP. Results also suggest that the topology of PCL nanofibers, 5-Azacytidine treatment and collagen coating together contributes to the generation of cTnT and α-actinin positive aligned CMs from UCM-MSCs on aligned PCL nanofibers, which was not possible on TCPs. On the other hand, MatrigelTM supported for proliferation of iPSCs whereas PCL topology together with temporal modulation of Wnt signalling has contributed to their differentiation into beating CMs. Furthermore, the aligned PCL fibers not only increased the differentiation of iPSCs into CMs but also resulted in the alignment of the cells to resemble the anisotropic nature of CMs in native heart. In conclusion, the results of the present study suggest that plasticized PVA-PVP may be suitable for developing cardiac patches for CTE. On the other hand, electrospun, aligned PCL nanofibrous matrices, coated with MatrigelTM, may be useful for the development of cardiac tissue construct for culture and differentiation of stem cells into CMs for CT
Investigations of Blast Furnace Cooling Staves and Intelligent Prediction Using Artificial Neural Network
No full textSteel making through Blast Furnace route is the cheapest source among the available industrial practices developed till now. That is why almost all large integrated steel plants opted Blast Furnace as a process for of iron making. In the succeeding years due to intense competition and globalization the iron making technology has transformed in myriad way. The campaign life of a furnace has shifted from 10 years to 25 years in modern furnaces with useful capacity as large as more than 5000m3. This is only possible by relentless development in lining and its cooling technology. The campaign life of a furnace is basically depend upon the life of its refractory lining which in turn depend on the cooling system used to keep these lining in stable condition without disintegration or wear out. These wear out may be for different reason like abrasion, spalling, stress cracking etc. In total we can say that campaign life as a whole can be dependent on three factors. First stable furnace operation, second design of cooling system with suitable refractory combination and third most important is its proper application in furnace during lining.
The objective of the present research work is to understand indepth the application of computational method in design of cooling system of blast furnace. Considering the process application, Blast furnace can be sub divided in to hearth, bosh, belly, lower stack and upper stack zones from bottom to the top of the furnace. In the present work, stave coolers of different region, more particularly tap hole region, lower stack and upper stack regions are taken for investigation. The performance is also compared taking different cooling stave materials, cooling channels and refractory materials used for lining with varying thickness. An attempt has been made to develop simulation models for stave coolers replicating actually fitted ones in these zones in blast furnace #4 of Rourkela Steel Plant, Odisha, India. The experiments conducted on these stave coolers at Rourkela Steel Plant is used to validate the numerical model developed through ANSYS® Work bench.
The numerical model thus developed is used to investigate the behaviour of stave using different stave and lining materials, cooling channels, etc., as described earlier. The structural analysis is conducted to investigate the stress concentration in the stave when subjected such high heat load. Also the experimental data obtained through this modelling is being used to develop a predictive model to predict stave hot surface temperature by artificial neural network using MATLAB® R2012b software
Laser Weld-Brazing of Aluminum Alloy (AA6082/AA5083) and Galvanized Interstitial Free Steel with an Emphasis on Fatigue and Corrosion Study
No full textTo decrease fuel consumption and environmental impact, the use of more aluminum-based alloys in automobiles is the current trend which necessitates reliable aluminum - steel dissimilar joint. For this, traditional fusion joining techniques due to their high heat input which promotes the excessive formation of thick intermetallics at the interface of the joint that leads to low strength and premature failure. Brazing is a probable solution which utilizes a filler material and eliminates the melting of the steel and can potentially avoid/decrease intermetallics formation but requires careful selection of the filler metal and process parameters. In the present study laser brazing technique was employed to weld-braze 2 mm thick galvanized interstitial free (IF) steel (mentioned as GI) with 2 mm thick aluminum alloys (i.e., AA6082 (AlMg-Si) and AA5082 (Al-Mg)) in flange joint configuration, using 2 mm diameter solid AlSi12 (4047) filler wire. Experiments were performed with a constant spot size (1.7 mm) and varying other laser parameters, i.e., laser power (2.0-4.0 kW), wire feed rates (2.0 – 3.6 m/min) and at a scan speed of (2-2.5 m/min). Subsequently, the joints were subjected to phase evaluation study (microstructure, XRD), mechanical characterization (hardness, tensile and low cycle fatigue) and corrosion studies (immersion, salt-spray, potentiodynamic polarization, EIS). From macrographs, it was noticed that the size and shape of the weld-braze joint appearance vary with respect to the laser parameters. Microstructural observation of the etched specimens under SEM demonstrated columnar dendritic structure at the brazed zone, while eutectic structure at the inter-dendritic region. At the aluminum side, epitaxial growth was noticed, and a two-layered (planar and needle structured) interface towards the galvanized steel in both the compositions (i.e., AA6082/GI and AA5083/GI). EDS point analysis and X-ray diffraction technique were used to study the interface, and the results confirmed that the planar and needle structures are comprised of ternary Alx-Fey-Siz and binary Alx-Fey intermetallic phases respectively in both the combinations (i.e., AA6082/GI and AA5083/GI). The asymmetrical hardness profile throughout the braze joint with the lowest value in the brazed region was noted. In the case of nanoindentation testing, intermetallics have shown higher hardness values compared to base materials. From the tensile testing, it was pointed out that joints produced with AA6082/GI has exhibited higher strength and failed at the base material (aluminum-side). AA503/GI joints demonstrated marginally lower strength and recorded interfacial failure. The fatigue life of the laser brazed joints (AA6082/GI and AA5083/GI) at lower stain amplitude recorded higher fatigue life, and it was close to aluminum base material value. Fatigue tested specimens recorded brazed zone failure and revealed flow lines, intergranular cracking, and typical fatigue striations. From the salt spray test, it was revealed that galvanized steel was highly susceptible to corrosion compared to the Al-rich phase in both the joint combinations (i.e., AA6082/GI and AA5083/GI). Polarization results showed a substantial change in corrosion resistance from the steel interface to the brazed region due to variation in the microstructure. AA5083/GI brazed joints have shown marginally higher corrosion resistance as compared to the joints made with AA6082/GI. Post corrosion microstructure revealed pit formation at the brazed regio
Feminist Revisionist Mythmaking: Analysing Kavita Kané’s Retelling
Get PDFThe discourse of mythology can be considered as male-centered, which means that mythological stories generally glorify and idolize masculine prowess. Women on the other hand have been portrayed as docile puppets with their roles being confined in as much as playing victims or mute observers, with no representation of feminine prowess or even female nature as such. Thus, mythology as a form of canonical literature is androcentric and since most myths are constructed and read by men (Guerin 206), women’s representation in myths is usually stereotyped, repressed, and generally ignored. Feminist writers have been concerned with this absence or rather negative portrayal of women in literature. Therefore, they seek to re-read patriarchal myths and in the process, they not only represent women from women’s point of view but tend to rewrite the literary canon. This study discusses myths as one of the foremost sites of the construction of ideological subjects and it analyses the rewritings of Hindu myths by the postmodern writer, Kavita Kané. The writer by employing the strategy of revisionist mythmaking has subverted the patriarchal ideology by bringing ‘other’ characters like Urmila, Surpanakha, Menaka, and Satyavati from the periphery to the centre. This study therefore intends to explore the gynocentric myth created by Kavita Kané in her books, Lanka’s Princess (2017), Menaka’s Choice (2015), The Fisher Queen’s Dynasty (2017), and Sita’s Sister (2014), which serves as an alternative definition of female identity. This thesis argues that the modern retellings have broken the ideological frontiers set by the phallocentric male canon and have created an alternative feminine discourse by presenting women within an imagined female community and history
Adsorption of Cr(VI) using Natural Iron Oxyhydroxides
No full textHexavalent chromium [Cr(VI)] is one of the common toxic ions caused due to both natural and anthropogenic processes. It is easily soluble in water and highly mobile in an aquatic environment. A long exposure to Cr(VI) may cause many disorders on human health such as sickness, increase the risk of lung cancer, nausea and may also damage the small capillaries in the kidneys and intestine. Thus, according to the World Health Organization and US Environmental Protection Agency, its maximum permissible limit for potable water and inland surface water are 0.05 mg/L and 0.1 mg/L, respectively.
Therefore, in this thesis, an attempt is made to evaluate the removal of Cr(VI) from aqueous solution by using natural Fe-oxyhydroxides, namely, goethite, calcined goethite, schwertmannite, 2-line ferrihydrite and 6-line ferrihydrite as adsorbents. Natural Fe-oxyhydroxides are identified using X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, N2 adsorption/desorption isotherm and high resolution transmission electron microscope (HRTEM). Then adsorption batch experiments are conducted under different concentration of Cr(VI), time of contact, pH of the solution, temperature and dose of adsorbents. It is found that Langmuir isotherm fits the adsorption data of Cr(VI) for all the adsorbents. The Langmuir adsorption capacity is found to be maximum for 6-line ferrihydrite followed by 2-line ferrihydrite, schwertmannite, calcined goethite at 300 °C and goethite. The variation in the adsorption capacity is mostly attributed to the differences in the surface area. The surface area of 2-line ferrihydrite, schwertmannite, calcined goethite at 300 °C and goethite is 259, 164, 78, 126 and 7 m2/g respectively. The N2 adsorption/desorption isotherms used for determination of BET surface area indicate that adsorbents belong to a type-IV category which is an indicative of the presence of mesoporosity. The hysteresis loop can be classified into H3-type which indicates that the adsorbents consist of slit-shaped pores and the pores are interconnected. Though schwertmannite has less surface area than that of calcined goethite at 300 °C but the former has higher removal capacity. It might be due to its tunnel shaped structure. This indicates that the natural Fe-oxyhydroxides can act as an effective and promising adsorbent for removal of Cr(VI) ions from aqueous solution. Except schwertmannite, removal of Cr(VI) decreases with increase in pH whereas for schwertmannite, removal increases up to pH 9 and then decreases. Removal increases with increase in contact time and decreases with increase in initial concentration of Cr(VI).
Based on thermodynamic study, the negative change in Gibbs free energy indicates that adsorption process is spontaneous and feasible and endothermic in nature. The values of ΔH˚ are positive for all adsorbents which indicate adsorption is endothermic in nature. Positive value of ΔS˚ for all adsorbents also reflect increase in randomness at the solid–solution interface during the fixation of Cr(VI) on their active sites. The pseudo-second order model is more feasible than pseudo-first order model for all adsorbents which indicate that chemisorption is the dominant process. The intraparticle diffusion model indicates more than one mechanism controls the adsorption process. The boundary layer thickness is found to be very less