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Weakly nonlinear stability analysis of salt-finger convection in a longitudinally infinite cavity
This paper is a two-dimensional linear and weakly nonlinear stability analyses of the three-dimensional problem of Chang et al. ["Three-dimensional stability analysis for a salt-finger convecting layer,"J. Fluid Mech. 841, 636-653 (2018)] concerning salt-finger convection, which is seen when there is sideways heating and salting along the vertical walls along with a linear variation of temperature and concentration on the horizontal walls. A two-dimensional linear stability analysis is first carried out in the problem with the knowledge that the result could be different from those of a three-dimensional study. A two-dimensional weakly nonlinear stability analysis, that is, then performed points to the possibility of the occurrence of sub-critical motions. Stability curves are drawn to depict various instability regions. With the help of a detailed stability analysis, the stationary mode is shown to be the preferred one compared to oscillatory. Local nonlinear stability analysis of the system is done in a neighborhood of the critical Rayleigh number to predict a sub-critical instability region. The existence of a stable solution at the onset of a weakly nonlinear convective regime is indicated, allowing one to perform a bifurcation study in the problem. Heat and mass transports are discussed by analyzing the Nusselt number, Nu, and Sherwood number, Sh, respectively. A simple relationship is obtained between the Nusselt number and the Sherwood number exclusively in terms of the Lewis number, Le. 2022 Author(s). -
Weakly Non-linear Stability Analysis of Triple-Diffusive Convection in a Bi-viscous Bingham Fluid Layer with Cross-Diffusion Effects
The paper investigates the impact of cross-diffusion on triple-diffusive convection in a bi-viscous Bingham fluid layer. Non-linear stability analysis is performed, and the expression of the critical-Rayleigh-number is obtained, resulting in an analytical solution of the Ginzburg-Landau model (GLM). The coefficients in the GLM involve the scaled Rayleigh-number, the solutal Rayleigh-numbers, the solutal diffusivity rates, the bi-viscous Bingham fluid parameter, and the cross-diffusion parameters. The solutal Rayleigh-numbers, the solutal diffusivity rates, and the bi-viscous Bingham fluid parameter alone determine the critical-Rayleigh-number, which provides the condition for the stationary onset. The neutral curves for the stationary mode are examined. It is found that the solutal diffusivities and bi-viscous Bingham fluid parameter advance the onset of convection, whereas the solutal Rayleigh-numbers delay it. The Nusselt number, Nu, and the Sherwood numbers, Sh1 and Sh2, determine the heat- and mass-transfer rates obtained for the convection system. We see that Nu, Sh1 and Sh2 increase with an increase in the values of the bi-viscous Bingham fluid parameter. Also, we observe that increase in the Prandtl number effect increases them, and the same is true of the solutal Rayleigh-numbers, whereas the opposite impact on Nu, Sh1 and Sh2 is seen for solutal diffusivities, Soret and cross-diffusion parameters. In general, we observe that mass-transfer is more than the heat-transfer (Sh1>Sh2>Nu) depending on the value of diffusivities. The Author(s), under exclusive licence to Springer Nature India Private Limited 2024. -
We wear multiple hats: Exploratory study of role of special education teachers of public schools in India
The role of special education teachers (SETs) is multifaceted. A gap was recognised in the literature in the lack of studies on the roles and responsibilities of SETs in India and the field realities of carrying out the role. The aim was to explore to what extent the special education teachers fulfil their roles and responsibilities. The following is an exploratory study, using open-ended questions that interviewed 12 SETs from five public schools in Delhi, India. The policy documents shared that the SETs were responsible for direct instruction to special needs students, parentteacher collaboration and documentation, including IEPs for students with special needs. But in practice, there were not any clear-cut boundaries, the SETs played multiple rolesSubject teacher, taking substitution periods, para teachers, these were keeping the SETs away from their core responsibilities. The results of the study demonstrated an undervaluation of the work of SETs and lack of support from the principal and regular teachers. The results concluded with recommendations for policy proposal with regards to defining the role of all stakeholders in an inclusive education school and improvements for the teacher education program. 2024 National Association for Special Educational Needs. -
We wear multiple hats: Exploratory study of role of special education teachers of public schools in India
The role of special education teachers (SETs) is multifaceted. A gap was recognised in the literature in the lack of studies on the roles and responsibilities of SETs in India and the field realities of carrying out the role. The aim was to explore to what extent the special education teachers fulfil their roles and responsibilities. The following is an exploratory study, using open-ended questions that interviewed 12 SETs from five public schools in Delhi, India. The policy documents shared that the SETs were responsible for direct instruction to special needs students, parentteacher collaboration and documentation, including IEPs for students with special needs. But in practice, there were not any clear-cut boundaries, the SETs played multiple rolesSubject teacher, taking substitution periods, para teachers, these were keeping the SETs away from their core responsibilities. The results of the study demonstrated an undervaluation of the work of SETs and lack of support from the principal and regular teachers. The results concluded with recommendations for policy proposal with regards to defining the role of all stakeholders in an inclusive education school and improvements for the teacher education program. 2024 National Association for Special Educational Needs. -
We just keep pushing through: a mixed-method study on musculoskeletal discomfort and mental well-being among nurses in resource-limited settings
Background: Nurses in under-resourced settings frequently report high levels of musculoskeletal (MSK) discomfort, which significantly affects their mental well-being. While workplace strain is well documented, the combined impact of physical burden and institutional neglect remains underexplored in these environments. Aim: The study aims to examine the prevalence of MSK discomfort and its association with psychological well-being among nurses in under-resourced healthcare environments in Northeast India, and to explore the experiential and structural factors contributing to these occupational health risks. Methods: A sequential mixed-methods study design was employed, following an explanatory approach. The study commenced with a survey to gather quantitative data. Quantitative data were collected from 216 nurses using the Extended Nordic Musculoskeletal Questionnaire (Extended-NMQ) and the WHO-5 Well-Being Index, the results of which informed the development of subsequent interview questions. Semi-structured interviews were then conducted with 11 nurses to capture experiential and structural factors. This structure enabled deeper contextual understanding and facilitated triangulation across data types. Results: Among the participants, 47.2% reported experiencing lower back pain, followed by discomfort in the knees (27.3%) and upper back (25%). Higher levels of MSK discomfort were significantly associated with employment in the public sector and more than ten years of work experience. A strong negative correlation was observed between MSK discomfort and mental well-being. Thematic analysis revealed key stressors: physical depletion, emotional exhaustion, organizational apathy, and limited healthcare access. In response to these challenges, nurses often relied on self-management due to insufficient institutional support. Triangulated findings underscored how structural deficiencies intensified both physical and psychological strain among nurses. Conclusions: There is an urgent need for evidence-based occupational health interventions to address ergonomic, psychosocial, and institutional challenges, particularly in low-resource healthcare settings, to safeguard the well-being of frontline nursing staff. This study offers novel understanding from a high-need yet under-researched geographic context, namely the northeastern states of India, bridging empirical gaps in MSK health literature through the integration of experiential and structural factors. Clinical trial number: Not applicable. The Author(s) 2025. -
We are Treated as Outsiders in Our Own City: Lived Experiences of Intersectional Stigma Against Sex Workers in Kolkata, India
Introduction: Sex workers in India experience intersectional stigma related to their gender identity, sexuality, and profession. The objective of the present study is to analyze the lived experiences of intersectional stigma against sex workers in Kolkata. Methods: We interviewed 30 cisgender female sex workers in March 2023 in Kolkata, India. Interviews were digitally audio recorded, translated from Bengali into English, and transcribed and coded using thematic analysis. Results: We identified five main themes regarding intersectional stigma: (1) internalized stigma regarding the shame associated with being a female sex worker, (2) perceived stigma of sex work as a dirty profession, associated with lower caste status, (3) enacted stigma against sex workers who are mothers, (4) enacted stigma against the children of sex workers, and (5) reduction of stigma through unionization/labor organizing. Conclusions: Intersectional stigma against sex workersis impacted by negative attitudes regarding gender, caste status, single motherhood, and occupation. We identified internalized stigma as a source of shame for sex workers. Sex workers also were perceived to beengaged in afilthy profession, associated with lower caste status. Those sex workers who were mothers experienced discrimination, as did their children. Respondents reported how collectivization has helped to address these experiences of stigma anddiscrimination. Policy Implications: Addressing the intersectional stigma against sex workers in Kolkata necessitates a shift in social attitudes.Findings underscore the urgent need for stigma reduction interventions and socialpolicies, including (1) labor protections for sex workers, (2) individual/community-level interventions for sex workers, and (3) media campaigns to address stigma reduction. By understanding the lived experiences of sex workers, we may develop better interventions to reduce stigma in the lives of sex workers in Kolkata and throughout India. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2024. -
We are Treated as Outsiders in Our Own City: Lived Experiences of Intersectional Stigma Against Sex Workers in Kolkata, India
Introduction: Sex workers in India experience intersectional stigma related to their gender identity, sexuality, and profession. The objective of the present study is to analyze the lived experiences of intersectional stigma against sex workers in Kolkata. Methods: We interviewed 30 cisgender female sex workers in March 2023 in Kolkata, India. Interviews were digitally audio recorded, translated from Bengali into English, and transcribed and coded using thematic analysis. Results: We identified five main themes regarding intersectional stigma: (1) internalized stigma regarding the shame associated with being a female sex worker, (2) perceived stigma of sex work as a dirty profession, associated with lower caste status, (3) enacted stigma against sex workers who are mothers, (4) enacted stigma against the children of sex workers, and (5) reduction of stigma through unionization/labor organizing. Conclusions: Intersectional stigma against sex workersis impacted by negative attitudes regarding gender, caste status, single motherhood, and occupation. We identified internalized stigma as a source of shame for sex workers. Sex workers also were perceived to beengaged in afilthy profession, associated with lower caste status. Those sex workers who were mothers experienced discrimination, as did their children. Respondents reported how collectivization has helped to address these experiences of stigma anddiscrimination. Policy Implications: Addressing the intersectional stigma against sex workers in Kolkata necessitates a shift in social attitudes.Findings underscore the urgent need for stigma reduction interventions and socialpolicies, including (1) labor protections for sex workers, (2) individual/community-level interventions for sex workers, and (3) media campaigns to address stigma reduction. By understanding the lived experiences of sex workers, we may develop better interventions to reduce stigma in the lives of sex workers in Kolkata and throughout India. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2024. -
Waves, Velocity Addition and Doppler Effect in Light of EPRs Completeness Condition
It is a standard practice to derive velocity addition rules for point particles from Galilean and Lorentz transformations in point (classical) mechanics, and to apply such rules to wave velocities for explaining Doppler effect. However, in such standard practice, it is never shown whether the equation for wave propagation actually transforms in a way such that the velocity addition rules get manifested through the equation itself. We address this gap in the literature as follows. We claim that the velocity addition for waves, being the one and only mean to explain the empirically verified Doppler effect, should be considered as an element of physical reality in accord with EPRs completeness condition of a physical theory. Therefore, the equation for wave propagation should manifest such velocity addition so as to be considered as a part of the respective physical theory of waves. We show that such manifestation is possible if and only if wave propagation is modeled with first order partial differential equations. From a historical point of view, this work settles the Doppler-Petzval debate which originated from Petzvals demand for an explanation of Doppler effect in terms of differential equations. From the foundational perspective, this work sets the stage for a renewed focus on the mathematical modeling of wave phenomena, especially in the context of various Doppler effects. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2025. -
Wavelet packet transform based fusion of misaligned images
This paper proposes an image fusion method based on wavelet packet transform (WPT) for images with misaligned region of interest, which finds wide application in target recognition and feature extraction. The region of interest of the images are first aligned and then fused in the transform domain. The various no-reference parameters such as standard deviation (SD), spatial frequency (SF) are measured for the fused image. The result obtained from this method is compared with the other methods such as image fusion using discrete wavelet transform (DWT), stationary wavelet transform and guided filtering. It is evident from the simulation results that the two parameters are high for the fused image using wavelet packet transform. 2016 IEEE. -
Waveform Analysis and Feature Extraction from Speech Data of Dysarthric Persons
Speech recognition systems provide a natural way of interacting with computers and serve as an alternative to the more popular but less intuitive peripherals (input / output devices). Tools employing the techniques of Automatic Speech Recognition (ASR) can be extended to serve people with speech disabilities so that they can overcome the difficulties faced in their interaction with general public. An attempt is made here to achieve this goal by mapping the distorted speech signals of people with severe levels of dysarthria to that of a normal speech and/or less severe dysarthric speech. The analysis is carried out by comparing the speech waveforms of the people with and without communication disorders and then extracting the features from the audio files. The differences in time, duration, frequency and PSD are used to facilitate the mapping of unintelligible speech data to intelligible ones. When reasonable accuracy levels are achieved in this mapping, the normal voice can be used as the substitute / surrogate of the original distorted voice. 2019 IEEE. -
Wavefield analysis of nano-scale surface/interface effects on dynamic stress response in biphasic laminated media with circular defects
The dynamic stress concentration around a nanoscale circular hole located at the centre of a two-phase circular laminated medium subjected to localized anti-plane SH-wave loading is examined in this paper. The model (used in this paper) is developed using the complex variable function method combined with wavefield superposition and multipolar expansion. In this framework, GurtinMurdoch (GM) surface and interface elasticity is incorporated at both the material interface and the free surface of the nanohole, resulting in a coupled two-surface formulation that has not been previously reported for biphasic geometries. This leads to non-classical traction-jump conditions and modified stress-free boundary conditions. The resulting infinite system of linear equations is then solved through series truncation. Numerical results reveal that nanoscale surface and interface effects significantly reduce the dynamic stress concentration factor (DSCF) around the hole, with the most substantial attenuation occurring at low wavenumber ratios and low shear modulus ratios. Conversely, the stress reaches its maximum amplification under long-wavelength excitation or when the outer layer is relatively soft. Overall, these findings offer new insights into nanoscale toughening mechanisms in realistic multilayered systems, providing a solid foundation for defect detection, lifetime prediction, and the damage-tolerant design of laminated nanocomposites and coreshell nanostructures. The Author(s), under exclusive licence to Springer Nature B.V. 2026. -
Wave scattering and dynamic stress concentration in piezoelectric half-planes with semi-elliptical notches under SH-wave excitation
This study presents a comprehensive analytical framework for investigating the scattering and dynamic stress response of semi-elliptical notches in piezoelectric half-planes subjected to anti-plane shear (SH) waves. The primary objective is to unify the treatment of notches, cracks, and circular holes within a rigorous wavedefect interaction model while explicitly incorporating piezoelectric coupling and nanoscale surface/interface effects. The methodology employs the complex function method in conjunction with the Helmholtz equation and wavefield superposition theory, leading to an infinite system of equations that rigorously satisfies continuity and boundary conditions; a systematic truncation strategy is then applied to achieve convergent solutions. Results demonstrate that surface/interface effects significantly suppress the dynamic stress concentration factor, particularly under vertical SH-wave disturbance, while resonance peaks become sharper at low modulus ratios and higher piezoelectric constants such as PZT-5H and BaTiO3. Importantly, the formulation naturally recovers classical elasticity results in the absence of piezoelectric effects, providing strong theoretical consistency. Validation is achieved through analytical recovery of benchmark cases (semicircular notch and edge crack), graphical comparisons with established results, and rapid convergence of the truncated system, confirming both accuracy and robustness. The practical implications of these findings extend to structural health monitoring, non-destructive evaluation, and the optimal design of advanced piezoelectric composites, where accurate prediction of defect evolution and stress amplification is critical. While the present work is restricted to semi-elliptical notches under SH-wave excitation in half-plane geometries, the approach is readily extensible to more general defect shapes and mixed-mode disturbances. The novelty of this study lies in its ability to capture piezoelectric surface/interface effects within an exact analytical framework, providing predictive capability for defect-induced stress concentrations and offering a reliable basis for the design and reliability assessment of high-performance piezoelectric materials. The Author(s), under exclusive licence to SocietItaliana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature 2025. -
Wave Height Forecasting over Ocean of Things Based on Machine Learning Techniques: An Application for Ocean Renewable Energy Generation
With the evolution and integration of information and communication technologies, the marine environment is being converted into a smart ocean of things. The only way to monitor the marine environment is to access marine information through satellites, radar, etc. Recently, many researchers have focused their interest on generating power from renewable energy. Among all the available renewable resources, ocean waves are attracting the interest of researchers for power generation. Therefore, this article focuses on designing a data-driven forecasting model for marine renewable energy generation applications. This article applies a novel Gini-impurity-index-based bidirectional long short-term memory model for selecting the best ocean/marine environmental factors to forecast wave height and ultimately predict power generation using the numerical model. This article presents short- and long-term forecasting results. In the experiment, four stations each are taken for both short- and long-term forecasting. The average root-mean-square error was approximately 0.17 for long-term forecasting and approximately 0.05 for short-term forecasting. 1976-2012 IEEE. -
Water Sustainability and Smart Monitoring: IOT and AI for Water Use
This chapter discusses the contributions of Artificial Intelligence (AI) and the Internet of Things (IoT) to sustainable water management. It considers how traditional water management, including reservoirs, qanats, and aqueducts, has provided important lessons in climate adaptation and sustainability, while contemporary technologies effectively address challenges of scarcity, leakage, and inefficient management. AI-supported predictive analytics, IoT-enabled smart sensors, together with precision irrigation, can support leak detection and water demand forecasting, detecting soil moisture through sensors, and water quality monitoring. The chapter also touches on trends such as blockchain capabilities, circular water systems, and the use of citizen science. It offers new opportunities to innovate, focus on global partnerships, and small-scale capabilities, to help combine ancient wisdom with innovation to promote equitable, efficient, and durable approaches to water sustainability. The Author(s), under exclusive license to Springer Nature Switzerland AG 2026. -
Water Purification Using Subnanostructured Photocatalysts
Visible light is an abundant resource, and photocatalysts absorb this light and use it to energize chemical reactions. Of the many types of reactions that are catalyzed by photocatalysts, wastewater purification is an important area. Photocatalysis is an economical, eco-friendly, and sustainable method of purifying water, a precious resource for which need is increasing while availability is shrinking. Of the several types of photocatalytic materials available, atomically dispersed metals and metal oxides appear to be the most promising. In conventional materials, the efficiency of utilization of active photocatalytic material is rather poor because only a small fraction of those present on the surface can serve as active materials. As the particle size decreases, this efficiency increases. In this respect, subnanometric catalysts such as single-site heterogeneous catalysts, atomically dispersed catalysts, and single-atom catalysts have distinct advantages when compared with their bulk and nanometric counterparts. The challenges in preparing stable single-atom catalysts have largely been overcome, and several methods are now available for their preparation. Many atomically dispersed photocatalytic materials have been synthesized, and many new insights have been gained, unlocking the tremendous potential in purifying wastewater by utilizing solar radiation. The aspects of higher activity, improved selectivity, economical use of materials, and a better understanding of the structure-activity relationship offered by subnanometric photocatalysts have been explored in this chapter. 2020 American Chemical Society. -
Water purification membranes: state of the art, fundamentals, challenges, and opportunities
The rising global demand for clean and safe water has intensified the necessity for effective and sustainable purification technologies. This chapter thoroughly overviews membrane-based water purification systems, highlighting their basic principles, material types, operational mechanisms, and evolving roles in addressing water scarcity. It begins with the historical progression of membrane technology, discussing the various membrane types alongside essential separation processes including ultrafiltration, nanofiltration, reverse osmosis, and membrane distillation. The text also covers recent innovations in nanocomposite membranes, cutting-edge material design, and membrane module configurations, focusing on enhancing performance and energy efficiency. Special focus is placed on membrane fouling, its causes, effects, and strategies for mitigation, backed by computational modeling and machine learning insights. The chapter begins by exploring emerging trends, such as the development of fit-for-purpose membranes, their integration into zero liquid discharge systems, and scalable fabrication methods. Together, this information highlights the transformative capacity of membrane technology in tackling global water issues. 2026 Elsevier Inc. All rights reserved.. -
Water is life and death: Symbolic representation in all customs and rituals in India
For the Koch, Koch Rajbongshi, and Rajbanshi people of India, water is central to their culture. They share river music and ancestry. They lost their language in 1931 and split into three or more clans due to flood relocation. They also introduced food, the river, the sun, the moon, the bamboo tree, and cactus plant worship to the highlands. The parent group was identified as tribal in the 1931 census. Still, the Indian government could not grant Koch, Koch Rajbongshi, and Rajbanshi scheduled tribe status for Assam and conserve their culture, traditions, and language. Indian scientists are trying to solve Assam's centuries-old flood issues, which are worsening. The new Indian water framework must treat water access and value of water resources as essentially good and human rights issues. India must review its Assam flood failures and compensate locals. Assam needs political, social, economic, and administrative procedures to develop and manage water resources and offer services at different societal levels. 2023 Policy Studies Organization. -
Water dispute in Central Asia: Conflict potential
The Central Asian republics (CARs), which emerged as independent states in the post-Soviet phase, faced several challenges. During the Soviet era, the CARs were agriculturally oriented towards the Soviet economy and, accordingly, river water management was also centralized under the command economic model. However, with the collapse of the Soviet Union, the CARs had to review the existing water management arrangements. This is where the absence of a Moscow-centric central authority has proven detrimental to the region endowed with two major rivers and their several subsidiaries. In this context, the paper suggests an emphasis on multilateralism, rather than bilateralism, as a more feasible approach to river water management. Clearly, multilateralism would promote a more equitable solution compared to bilateralism, which does not adopt a holistic approach to the region. Considering the fact that the region is characterized by a water crisis in addition to the fragility of the environment makes a multilateral arrangement significantly more appropriate for the region in the long term. 2019, CA and C Press AB. All rights reserved. -
Water Diplomacy in the Cauvery River and Mullaperiyar Dam: A Case Study of Tamil Nadu's Experience With Karnataka and Kerala
Water sharing by multiple nations internationally often leads to issues concerning access, utilization, and sustainability. In South India, Tamil Nadu's incident with water diplomacy, mainly in managing the Cauvery River Basin shared with Karnataka, presents important implications for reserve management and conflict resolution. The state relies heavily on its river systems for irrigation, drinking water, and industrial use, but the scarcity and irregular allocation of water resources pose a significant challenge. Efficient water diplomacy can help achieve sustainable water administration by fostering common thought and cooperation among riparian states. This paper critically evaluates the challenges and opportunities in Tamil Nadu's water peacekeeping, focusing on its commitment to neighboring states over collective water resources. It explores key themes such as the historical context of interstate water-sharing disagreements, the efficiency of existing lawful and institutional frameworks, and the role of political and social arrangements in shaping water-sharing negotiations. The paper also underscores the need for a more practical and mutual approach to water distribution, moving away from legal arbitration and political negotiation to embrace the values of sustainable and evenhanded water management. 2025 Policy Studies Organization. -
Water Demand Prediction Using Support Vector Machine Regression
Water is a critical resource for sustainable economic and social development of a country. To maintain health hygiene, energy agricultural products, and the environment management water plays a key role. Water demand prediction is essential to analyze the requirement that indicate emergency state for water management decisions. This paper explores the water usage data for dairy plants to understand the spatial and temporal patterns for future water requirements, to optimize the water demand estimation. It uses concept of Machine learning algorithms to compare and achieve an effective and reliable system for water prediction. 2019 IEEE.