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Performance and Steady State Heat Transfer Analysis of Functionally Graded Thermal Barrier Coatings Systems
Thermal barrier coatings (TBCfs), typically 8 wt.% Yttria Stabilized Zirconia (8YSZ), in single layered configuration have been traditionally used in aerospace components to protect them from degradation at high temperatures and to improve the thermal efficiency of the system. This paper compares the performance of two types of TBC configurations: Single layered and multilayered functionally graded materials (FGM). Aerospace alloy, Inconel 718 substrates, NiCrAlY bond coat (BC) and 8YPSZ top coat (TC) were the materials used. FGM configuration was used to improve the durability and life of the conventional TBC system by reducing the coefficient of thermal expansion (CTE) mismatch. The TBCs were subjected to thermal fatigue (thermal shock and thermal barrier test) in laboratory scale burner rig test and oxidation stability test in high temperature furnace upto 1000. The as-sprayed and thermal fatigue tested specimen were characterized by X-ray diffraction (XRD) analysis and Scanning Electron Microscope (micro-structure). Results are discussed in the light of suitability of coating configuration, thermal fatigue and spalling characteristics with reference to aerospace applications at temperatures in the 9000C to 15000C range. Computational work was carried out comprising a simulation model involving the developed TBCs. 2018 Elsevier Ltd. -
Influence of atmospheric plasma spray process parameters on crystal and micro structures of pyrochlore phase in rare earth zirconate thermal barrier coatings
Yttria-stabilized zirconia (YSZ) thermal barrier coatings is most widely used in gas turbine engines applications and its primary role is to protect the underlying base metal from degradation at its high temperature (>1000 C) service environment. While YSZ serves well in this role, materials with higher thermal stability and lower thermal conductivities are required to be developed for attaining higher operating temperatures and thereby higher energy conversion efficiencies. A number of rare-earth zirconates which form the cubic fluorite-derived pyrochlore structures (A2B2O7) where A: La, Gd, Sm, Ce and B: Zr are being developed, some compositions are more attractive due to their good amalgamation of thermal and mechanical properties. However, when these materials are plasma spray coated on metal substrates, the favorable properties are not immediately realized due to various contributing factors such as poor adhesion/cohesion, microstructure (porosity, defects) or even incomplete stabilization or destabilization of the desired phase (crystal structure) after passing through the plasma. In this paper, plasma sprayable powders of zirconate pyrochlores (or with disordered fluorite structures) synthesized from using La and Ce as the trivalent ''A cation, were plasma sprayed onto Inconel 718 substrates, by using different plasma spray parameters. The considerable influence of these spray parameters on the structural phases (analyzed via XRD) and microstructures (studied via SEM on polished cross section metallographs) are presented in detail. 2019 Elsevier Ltd. All rights reserved. -
Zirconia based pyrochlore thermal barrier coatings
Improvements in thermal barrier coatings (TBCs) technology, further than what is already in service to enable adequate protection to metallic components from higher (>1100C) operating temperatures requires newer developments in materials. Many research activities have been undertaken by scientists to seek alternatives after discovering the threshold of Yttria-stabilized zirconia (YSZ) TBCs on standard aero-space materials at elevated temperatures. To increase the thermal performance of gas turbine engines, alternate TBC materials with better sintering resistance and lower thermal conductivity are required. One of the promising candidates for the TBCs is Pyrochlore-type rare earth zirconium oxides (Re2Zr2O7, Re = rare earth). Re2Zr2O7 TBCs have higher phase stability, lower thermal conductivity, lower sintering rate, no phase transformation, and lower coefficient of thermal expansion at elevated temperatures when compared with YSZ. In this work, plasma spray powders of Lanthanum Zirconate (La2Zr2O7) and Lanthanum Ceria Zirconate (La2 (Zr0.7Ce0.3)2O7) were synthesized by the solid-state reaction method with the goal to develop pyrochlore oxide-based coatings with desired properties at high temperatures (>1200C), better than the YSZ TBCs: Currently the most popular choice for TBCs. These TBCs are expected to increase gas turbine efficiencies while protecting the underlying metallic substrate at high operation temperatures. The evaluation of the synthesised TBCs has been carrying out by studying their performances at 1200C. Results of evaluation for phase composition by employing X-Ray Diffractometry (XRD), microstructure via Scanning electron Microscope (SEM) and chemical composition via Energy Dispersive spectroscopy (EDS) also have been included. Published under licence by IOP Publishing Ltd. -
Adhesion strength studies on zirconia based pyrochlore and functionally gradient thermal barrier coatings
Thermal Barrier Coating (TBC) plays a major role in the improvement of gas turbine and engine components in terms of their service life and performance. Generally, all coatings must possess certain primary properties to perform in the intended applications. However, regardless of applications, suitable adhesion strength is one major characteristic they must have to adequately protect the basic components on which they are applied upon. In TBCs, adhesion (or Bond) strength is a parameter that helps to illustrate the resistance of the ceramic top coat against spallation either from the bond coat (and component) or within the TBC layers itself. The performance of TBCs are reliant upon the adhesion between the coating and the metal substrate and also adhesion (or cohesion) between the bond coat and the overlying ceramic top coat layer. The de-bonding of the top coat layer or the inter-metallic bond coat layers are the main reasons of the failure of the overall TBC system. Some of the prominent problems associated with coatings applications are residual stresses, micro-cracks and pores etc. These and many other factors influence the adhesion of the coatings in addition to service environment conditions and pre coating substrate preparations such as substrate cleaning, grit blasting and very importantly plasma spray parameters. In the present work, results obtained from adhesion strength measurements carried out by following the ASTM C 633 standard test method, on various types of TBCs are being shared. Thermal barrier coatings (TBCs) were synthesized with NiCrAlY bond coat deposited on SS 304L substrate by using air plasma spray and different ceramic top coats (a) commercial 8%Yttria Stabilized Zirconia (8YSZ) (b) lab synthesized plasma spray powders of (i) Lanthanum Zirconate (La2Zr2O7) (ii) Lanthanum Ceria Zirconate (La2 (Zr0.7Ce0.3)2O7) and (iii) Lanthanum cerate (La2Ce2O7). The coating depositions were carried out in different configurations i.e. two layers, three layers and gradient layers (Functionally gradient materials). The evaluation of properties includes the studies of morphology of the strength (adhesive/cohesive failure mode) tested specimen as well. General conclusions drawn from the studies on several specimen in various configurations are that cohesive failures (between the ceramic top coat layers) is the predominant mechanisms followed by few adhesive failures in bond coat coat/ceramic interface. 2019 Elsevier Ltd. All rights reserved. -
Thermal fatigue characteristics of 8Y2O3-ZrO2, La2Zr2O7, La2(Zr0.7Ce0.3)2O7 and La2Ce2O7 thermal barrier coatings in duplex, multilayer functionally graded and multilayer configurations
La2Zr2O7, La2(Zr0.7Ce0.3)2O7 and La2Ce2O7 pyrochlore plasma sprayable powders were synthesized and plasma spray coated on steel plates with NiCrAlY bond coat. Three different configurations were used: duplex, multilayer functionally graded and multilayer, with different combinations of commercial 8% yttria stabilized zirconia (8YSZ) and NiCrAlY (bond coat) layers. The prepared coatings were compared with the standard duplex 8YSZ thermal barrier coatings (TBCs) with a goal to study their suitability to serve as TBCs. TBCs layer thicknesses and interfaces were studied via SEM on polished cross section metallographic samples removed from the spray coated TBCs. Thermal fatigue resistance was evaluated by directing a gas flame on the ceramic surface at 1200 and 1400 C, followed by its rapid withdrawal and forced cooling by pedestal fan. The maximum number of thermal shock cycles the coatings could withstand before failure was determined. The multilayered TBCs with lanthanum cerate composition stacked with 8YSZ exhibited the superior thermal fatigue resistance characteristics compared to all other studied TBCs. The findings were correlated with the crystalline phases of the ceramic coatings, obtained via XRD, and discussed in the light of existing literature. 2023 University of Novi Sad, Faculty of Technology. All rights reserved. -
Executive functions and psychological flourishing in public sector employees
The present study examined the relationship between executive functions and psychological flourishing. Executive functions are based on three broad brain capacities namely: inhibitory control, working memory and cognitive flexibility. The participants for the study comprised 99 executives working in public sector organizations in India. Correlational analysis was computed to examine the relationship between executive functions and psychological flourishing. Multiple regression was used to find out if executive functions predicted psychological flourishing. The significant positive association of psychological flourishing with self-restraint, working memory, emotional control, focus, task initiation, planning/prioritization, organization, time management, defining and achieving goals, flexibility and observation was observed. The results of the multiple regression indicated that working memory, focus and observation predicted psychological flourishing. 2021 Ecological Society of India. All rights reserved. -
Advancements in optical steganography for secure medical data transmission in telehealth systems
Secure medical data transfer technologies have advanced as a result of the brisk growth of telehealth services. This study provides a thorough review of the most up-to-date research on using optical steganography to conceal medical records from prying eyes. Data concealing capacity has been increased without sacrificing picture quality using new techniques that make it difficult for unauthorised parties to access hidden information. Using adaptive steganography methods, medical data may be encoded in images in a way that makes it impossible to detect or extract by prying eyes. By concealing information over many picture layers, multi-layer steganography adds an extra degree of protection from prying eyes. The development of steganographic techniques has been spurred on by the use of machine learning and artificial intelligence to enhance steganalysis and the use of quantum characteristics to offer an extra layer of security in quantum steganography. Combining this with cryptographic safeguards like encryption provides an additional layer of security. In order to successfully safeguard sensitive medical data during transmission, standardisation and compliance in optical steganography are becoming more important as telehealth systems become more widespread. 2023, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature. -
Application of neuroscience methods in HRDM for brain-based human capital optimization
For years, human resource development and management (HRDM) has used behavioral assessments to gauge employee potential. However, advancements in cognitive behavioral neuroscience (CBN) have opened up new possibilities for understanding how the human mind works. This chapter explores the practical applications of neuroscience methods like EEG, ERP, MRI, and fMRI, as well as neurofeedback and biofeedback, in talent identification, leadership development, and employee well-being. Importantly, these insights can be directly applied in HRDM practices, leading to more effective talent management, leadership development, and improved employee well-being. While recognizing the ethical considerations involved with these technologies, the chapter presents a compelling vision for a future where HRDM practices are informed by a deeper understanding of the brain, enabling the workforce to reach its full potential. 2024 by IGI Global. All rights reserved. -
Work-Cognition and Subjective Well-being Among Female Professional Educators During the COVID-19 Pandemic: Moderating Role of Resilience
Teaching demands educators to be both caretakers and educators, leading to significant cognitive and emotional strain. The pandemic has worsened these challenges, requiring teachers to seek psychological and professional support. Online teaching has added to these difficulties, with educators having to adapt to new technologies while managing virtual classrooms and addressing the unique needs of students in remote learning environments. This present study sought to understand the relationship between work cognition (WCog) and subjective well-being (SWB) among female professional educators during the COVID-19 pandemic. The study also examines the moderating effect of Resilience (RSL) on the association between WCog and SWB. Using a purposive sampling technique, data was collected through an online survey from 181 female professional educators in India. Female professional educators reported moderate levels of WCog, high levels of RSL, and high levels of SWB, which indicates that the female professional educators faced cognitive and emotional strain during online teaching but demonstrated resilience and maintained positive well-being. RSL moderated the relationship between WCog and SWB, highlighting its influence on educators cognitive management and well-being during online teaching. These insights have implications for support system to enhance the well-being of educators and promoting their professional development. The Author(s) 2023. -
Development of the House of Collaborative Partnership to overcome supply chain disruptions: evidence from the textile industry in India
Collaboration in a supply chain becomes a significant competitive weapon for member firms in an uncertain business environment. The present study develops a model of supply chain collaboration named as House of Collaborative Partnership (HCP) and includes the enablers and impeders of a successful Collaborative Partnership (CP). Model development follows a three-phase process. The first phase consists of the identification of enablers and impeders of CP based on the literature review and experts opinions. The second phase applies Total Interpretive Structural Modelling (TISM) as a tool to construct hierarchical structures of the enablers and impeders of CP. The third phase deals with the development of HCP based on the hierarchical structures of enablers and impeders. The HCP is then validated with two case studies in the Indian textile industry. Eight enablers and seven impeders were identified in the first phase. After analyzing these factors with TISM, the HCP was developed consisting of four parts: Foundation, Columns, Beam, and Roof. The existence of trust, commitment to long-term collaboration, top management support, adequate financial support, ability to deal with technological changes, and providing regular training to employees constitute the HCP Foundation to achieve supply chain collaboration. The study concludes with the managerial implications of HCP to help supply chain partners in becoming resilient during an uncertain business environment. 2022 Informa UK Limited, trading as Taylor & Francis Group. -
Does energy transition reduce carbon inequality? A global analysis
Energy transition from fossil fuels to renewables is instrumental in mitigating climate change. Low-income countries have a higher share of renewable energy in their total energy consumption than rich countries (WDI, 2023). Thus, it is imperative to examine the role of energy transition in affecting relative CO2 emissions between rich and poor sections of the societies across income groups of the countries. In this context, our study contributes by constructing the carbon inequality models with renewable and non-renewable energy consumption as prime explanatory variables separately for 114 countries over a data period 19902019. The models are estimated individually for high-middle-low-income countries by controlling for foreign direct investment (FDI), economic growth, and innovations. Starting with preliminary econometric operations, we employ the dynamic simulated panel autoregressive distributed lag approach and Driscoll-Kraay standard error regression for empirical investigation. We find that energy transition reduces carbon inequality globally. Innovation has a negative impact, economic growth has a positive impact on carbon inequality, and FDI has an asymmetric impact based on the income level of the countries. The crucial global policy implications are discussed. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2024. -
Human behavior analysis on political retweets using machine learning algorithms
The exponential rise in the use of social media has resulted in a massive increase in the volume of unstructured text created. This content is presented through messages, conversations, postings, and blogs. Microblogging has become a popular way for people to share what they are thinking. Many people express their thoughts on various issues relating to their hobbies. As a result, microblogging websites have become a valuable resource for opinion mining and sentiment research. Twitter is a well-known microblogging network, with over 500 million new tweets posted daily. The goal of this study was to mine tweets for political sentiments. The extraction of tweets relating to India's well-known political leaders of different states & parties in India and applying the polarity detection analysis of human behavior on the retweeted messages As a result, the sentiment classification algorithm is designed to determine whether tweets are more likely to predict the popularity of certain politicians among the general public. The subjectivity and polarity present in the tweets of political leaders are compared. The engagements of these leaders are then taken into account to determine their popularity. All these comparisons are then portrayed using data visualizations. 2023 The Authors -
Comparative analysis of Histogram Equalization techniques
Histogram Equalization (HE) is one of the techniques which is used for Image enhancement. This paper shows the comparative studies of Global Histogram Equalization, Local Histogram Equalization and Fast Quadratic Dynamic Histogram Equalization based on the execution time, mean squared error and Peak Signal to Noise Ratio (PSNR). This paper shows the experimental results for these three methods with graphical representation. 2014 IEEE. -
Sustainable materials for urban streets: trends, challenges, and case studies
Urban planners face a growing need for efficient, smart, and sustainable projects. One of the dynamic urban elements of cities is its streets, which accommodate the majority of the public realm. This study aims to identify sustainable materials that are employed in the construction of urban streets and analyze the potential for other sustainable materials in future street design. We conduct a thorough literature review through case studies and identify sustainable materials currently in use in the construction of urban streets across the world. This study focuses on existing and potential sustainable materials for urban streets suitable for Qatar. Hence, the objectives of this study are: (1) to identify sustainable materials in the construction of urban streets; (2) to analyze challenges to using sustainable materials in making urban streets more sustainable; (3) comparative analysis of the case studies. The study concludes with sustainable urban street design guidelines derived from Qatar. 2025 Elsevier Ltd. All rights are reserved, including those for text and data mining, AI training, and similar technologies. -
Forecasting Stock Market Indexes Through Machine Learning Using Technical Analysis Indicators and DWT
In recent years, the stock market prices have become more volatile due to refinement in technology and a rise in trading volume. As these seemingly unpredictable price trends continue, the stock market investors and consumers refer to the security indices to assess these financial markets. To maximise their return on investment, the investors could employ appropriate methods to forecast the stock market trends, taking into account the nonlinearity and nonstationarity of the stock market data. This research aims to assess the predictive capability of supervised machine learning models for the stock market regression analysis. The dataset utilised in this research includes the daily prices and additional technical indicator data of S&P 500 Index of US stock exchange and Nifty50 Index of Indian stock exchange from January 2008 to June 2016; both the indexes are weighted measurements of the top companies listed on respective stock exchanges. The model proposed in this research combines the discrete wavelet transform and support vector regression (SVR) with various kernels such as Linear, Poly and Radial basis function kernel (RBF) of the support vector machine. The results show that using the RBF kernel on Nifty 50 index data, the proposed model achieves the lowest MSE and RMSE error during testing are 0.0019 and 0.0431, respectively, and on S&P 500 index data, it achieves 0.0027 and 0.0523, respectively. 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. -
Mobile-Based Indian Currency Detection Model for the Visually Impaired
According to surveys held in 2019, India holds the largest population standing just after China, but when it comes to visually impaired people, India ranks number one. There are approximately 37 million people across India who are suffering from visual impairment. Special care and measures are taken to help these people live a peaceful life as any other citizen of India, but with the demonetization that happened in the recent years, the Indian economy was replaced with newer currency notes as an attempt to stop black money and fight corruption. Even though the objectives were clear and attainable, with the newer currency notes, the visually impaired people are facing various problems, as there is no provision for them to actually check the currency as the notes are not equipped with Braille system and the sizes of each and every currency is also the same in many cases. To counteract this problem, a mobile-based Indian currency detection model would be a better solution as it enables a visually impaired person to identify the value of specific currency he is holding. The mobile-based Indian currency detection model is the proposed model which will be using image processing for feature extraction and a basic CNN (convolutional neural network) for identification of currency with the given feature inputs. This model is being made into a mobile-based application so as to enable a visually impaired person to check for any possible frauds as fast as possible. 2020, Springer Nature Switzerland AG. -
Porous carbon nanoparticles dispersed nematic liquid crystal: influence of the particle size on electro-optical and dielectric parameters
Porous carbon nanoparticles (PCNPs) of four different sizes (~180nm, ~51nm, ~41 and ~25nm) were dispersed into a nematic liquid crystal (NLC) in 0.25wt% concentration. PCNPs were derived from biowaste materials and pyrolysed at elevated temperatures to get the porous structure. Polarising optical microscopic observations were carried out in dark and bright states on both the pure NLC as well as NLC-PCNPs composites. Homogeneous alignment was well maintained in all the composites except the one with the highest sized (~180nm) PCNPs. Birefringence, relative permittivity and dielectric anisotropy, increases as the size of the PCNPs is decreased in the composites. The threshold voltage was also found to decrease with the decrease in the size of the PCNPs. Such investigations may be useful for the fabrication of display devices such as flat panel displays (FPDs) and phase shifters. 2021 Informa UK Limited, trading as Taylor & Francis Group. -
Impact of porous nanoparticles on the electro-optical and dielectric parameters of nematic liquid crystals for display applications: Cost effective approach
In this study, several vital electro-optical and dielectric properties of nematic liquid crystal (NLC) dispersed with porous carbon nanoparticles (PCNP) with three different concentrations were measured. NLCs are birefringent materials. Increased birefringence was observed for NLC-PCNP composites. Dielectric study was also performed for NLC dispersed with PCNPs. Dielectric anisotropy was found to be increased for PCNP dispersed NLC system. Contrast ratio was also measured for NLC dispersed with PCNP, and it is found to be enhanced. Decreased threshold voltage was observed after dispersing PCNP into NLC. High birefringence reduces the cell gap so this work may be applicable in the making of flat panel displays (FPDs). 2024 Taylor & Francis Group, LLC. -
Influence of composite mixtures between nematic liquid crystal and porous carbon nanoparticles towards photoluminescence and UV absorbance
The optical parameters of the liquid crystalline materials can be tuned by the dispersion of nanoparticles. Concentration of dopant in the host LC material affects its optical properties significantly, which makes the dispersed system suitable for LC-based devices. In the present investigation, we have studied the effect of different concentrations of nanoparticles on the optical properties of LC, as a guesthost system, where PCNP is guest material and NLC is host material. Porous carbon nanoparticles (PCNPs) were dispersed into the nematic liquid crystal (NLC) in three different concentrations. Optical parameters were measured for pure NLC and NLC-PCNP composites. Photoluminescence (PL) study was performed and it was found that the PL intensity increased for the PCNP dispersed system. High photoluminescence has much importance in the luminescent displays. Full width half maxima (FWHM) were also determined by the Gaussian fitting of PL intensity data. UV absorbance was also measured which gets increased for the PCNP dispersed NLC system when compared to pure NLC. Optical bandgap was found to be reduced after the dispersion of PCNP into NLC. Several other parameters such as absorption coefficient and optical density were also determined. The proposed work may be significant for the liquid crystal displays (LCDs) and other devices which require less bandgap materials. This work may also put some light on the effect of dopants on the LC material in the research based on guesthost system. Increasing the photoluminescence and creating less bandgap materials using carbon nanoparticles is a real challenge, and porous nanoparticles used here overcome this challenge. 2023, The Author(s), under exclusive licence to Springer-Verlag GmbH, DE part of Springer Nature. -
Cost effective porous areca nut carbon nanospheres for adsorptive removal of dyes and their binary mixtures
Novel porous nanospheres from areca nuts (ACNPs) were synthesized via one-step pyrolysis without the use of any chemical treatment and the materials were used as adsorbents for the removal of cationic methylene blue (MB) and anionic methyl orange (MO) as well as their binary mixtures. Around, 67 tonnes of areca nut biowaste is generated every year which are then burnt due to their slow rate of decomposition resulting in higher carbon footprints. Biosorbents are generally a preferable alternative for dye adsorption but involve chemical modification for surface enhancement and complex sample treatment. In this work, ACNPs, were investigated for their efficiency in the raw form and were characterized by SEM, EDS, FTIR, XRD, and BET techniques before and after subjecting to the dye adsorption studies. The BET analysis of the adsorbents showed a high specific surface area of 693.8 m2/g when prepared at 1000 C, while the N2 adsorption-desorption plot showed type-IV isotherm, suggesting the microporous nature of the carbon matrix. Batch equilibrium studies showed the removal efficiency of >95% for both the dyes and their binary mixtures under the optimum conditions of 0.15 g/L dosage, 10 ?M concentration and contact time of 70 min. Due to the synergistic effects of the binary dyes, higher removal efficiency of MB compared to MO was observed in the binary mixture. Adsorption results were tested using Langmuir, Freundlich, Temkin, Redlich-Peterson, and Elovich isotherms to assess the best fit of the models. The qm value of MB was found to be 97.37 mg/g, while that of MO was 71.22 mg/g which is higher compared to individual dye components having lower values of 86.12 mg/g and 50.35 mg/g, respectively. Extended Langmuir and Jain and Snoeyink isotherms were used for binary data interpretation. The kinetic results showed good agreement with the Pseudo-second order equation, indicating internal diffusion. The possible mechanism involved electrostatic and ?-? interactions between the dye molecules and ACNPs. This approach is comprehensible and cost effective and can be utilized for dye removal in textile industries. 2023 Elsevier Inc.