Browse Items (14421 total)
Sort by:
-
Long-term Optical and ?-Ray Variability of the Blazar PKS 1222+216
The ?-ray emission from flat-spectrum radio quasars (FSRQs) is thought to be dominated by the inverse Compton scattering of the external sources of photon fields, e.g., accretion disk, broad-line region (BLR), and torus. FSRQs show strong optical emission lines and hence can be a useful probe of the variability in BLR output, which is the reprocessed disk emission. We study the connection between the optical continuum, H? line, and ?-ray emissions from the FSRQ PKS 1222+216, using long-term (?2011-2018) optical spectroscopic data from Steward Observatory and ?-ray observations from Fermi Large Area Telescope (LAT). We measured the continuum (F C,opt) and H? (F H? ) fluxes by performing a systematic analysis of the 6029-6452 optical spectra. We observed stronger variability in F C,opt than F H? , an inverse correlation between the H? equivalent width and F C,opt, and a redder-when-brighter trend. Using discrete cross-correlation analysis, we found a positive correlation (DCF ? 0.5) between the F ??ray>100 MeV and F C,opt (6024-6092 light curves with a time lag consistent with zero at the 2? level. We found no correlation between the F ??ray>100 MeV and F H? light curves, probably dismissing the disk contribution to the optical and ?-ray variability. The observed strong variability in the Fermi-LAT flux and F ??ray>100 MeV ? F C,opt correlation could be due to the changes in the particle acceleration at various epochs. We derived the optical-to-?-ray spectral energy distributions during the ?-ray flaring and quiescent epochs that show a dominant disk component with no variability. Our study suggests that the ?-ray emission zone is likely located at the edge of the BLR or in the radiation field of the torus. 2022. The Author(s). Published by the American Astronomical Society. -
Soft excess in AGN with relativistic X-ray reflection
The soft X-ray excess, emission below (Formula presented.) 2keV over the X-ray power-law, is a marked spectral component in the X-ray spectra of many Seyfert1 galaxies. We investigate if the observed soft X-ray excess in a sample of Seyfert1s is in accordance with the prediction of the relativistic reflection model by analyzing the XMM-Newton and NuSTAR spectra. The fractional difference in the soft excess (SE) obtained from the blurred reflection emission predicted (from NuSTAR) and the observed (from XMM-Newton) luminosities show that the reflection model underestimates the SE emission in our sample. The results point to alternative models (for example, warm Comptonization) to explain the soft X-ray excess in AGN. 2023 Wiley-VCH GmbH. -
Serendipitous detection of an intense X-ray flare in the weak-line T Tauri star KM Ori with SRG/eROSITA
Weak-line T Tauri stars (WTTS) exhibit X-ray flares, likely resulting from magnetic reconnection that heats the stellar plasma to very high temperatures. These flares are difficult to identify through targeted observations. Here, we report the serendipitous detection of the brightest X-ray flaring state of the WTTS KM Ori in the eROSITA DR1 survey. Observations from SRG/eROSITA, Chandra X-ray Observatory, and XMM-Newton are analysed to assess the X-ray properties of KM Ori, thereby establishing its flaring state at the eROSITA epoch. The long-term (1999-2020) X-ray light curve generated for the Chandra observations confirmed that eROSITA captured the source at its highest X-ray flaring state recorded to date. Multi-instrument observations support the X-ray flaring state of the source, with time-averaged X-ray luminosity reaching at the eROSITA epoch, marking it the brightest and possibly the longest flare observed so far. Such intense X-ray flares have been detected only in a few WTTS. The X-ray spectral analysis unveils the presence of multiple thermal plasma components at all epochs. The notably high luminosity , energy (erg), and the elevated emission measures of the thermal components in the eROSITA epoch indicate a superflare/megaflare state of KM Ori. Additionally, the H line equivalent width of from our optical spectral analysis, combined with the lack of infrared excess in the spectral energy distribution, were used to re-confirm the WTTS (thin disc/disc-less) classification of the source. The long-duration flare of KM Ori observed by eROSITA indicates the possibility of a slow-rise top-flat flare. The detection demonstrates the potential of eROSITA to uncover such rare, transient events, thereby providing new insights into the X-ray activity of WTTS. The Author(s), 2025. Published by Cambridge University Press on behalf of Astronomical Society of Australia. -
Analysis of the Performance of a 5-Level Modular Multilevel Inverter for a Solar Grid-Connected System
The main purpose of a multilevel inverter is to combine numerous levels of DC voltage to create a nearly sinusoidal voltage. The synthesized output waveform has more stages as the number of levels rises, creating a staircase ripple which resembles the preferred waveform. As the number of voltage levels rises, the output waves harmonic distortion diminishes and eventually approaches zero. In particular, the performance analysis of a five-level inverter with variable loads is highlighted in this paper. This topology has fewer devices than traditional multilevel inverters for the same five output levels, which makes it more affordable due to lesser driver circuits. The proposed modular five level topology is simulated using both high frequencies switching pulse width modulation and basic frequency switching modulation techniques. The output voltage, current waveform, and total harmonic distortion are examined and compared using simulink to confirm the viability of the modular multilevel inverter topology. 2024, TUBITAK. All rights reserved. -
Development of effective charging station for EVs using multiport converter and photovoltaic cell integration
The adoption of electric vehicles (EVs) is increasing rapidly as a response to the urgent need to reduce greenhouse gas emissions and dependence on fossil fuels. However, the deployment of a reliable and cost-effective EV charging infrastructure remains a challenge. To address this challenge, this paper proposes the development of an effective charging station using multiport converter and photovoltaic cell integration. A promising approach in the transportation sector is an efficient charging station with multiport converter and photovoltaic cell integration. A multiport converter, photovoltaic cells, a battery energy storage system, and an electric vehicle charging port constitute the proposed charging station. The power flow between the photovoltaic cells, the battery energy storage system, and the electric vehicle charging port is controlled by the multiport converter. The excess energy generated by the photovoltaic cells is stored in the battery energy storage system. The proposed charging station is designed and analysed using MATLAB/Simulink. The simulation results show that the proposed charging station is capable of providing an electric vehicle a reliable and consistent power supply. In contrast to conventional charging stations, the proposed charging station is also capable of offering a faster charging rate. 2024 Nova Science Publishers, Inc. All rights reserved. -
Analysis of the Effectiveness of a Two-Stage Three-Phase Grid-Connected Inverter for Photovoltaic Applications
This paper proposes a two-stage three-phase grid-connected inverter for photovoltaic applications. The proposed inverter topology consists of a DC-DC boost converter and a three-phase grid-connected inverter. The DC-DC boost converter is used to boost the low voltage DC output of the PV array to a high voltage DC level that is suitable for feeding into the grid-connected inverter. The three-phase grid-connected inverter is used to convert the high voltage DC output of the boost converter into a three-phase AC output that is synchronized with the grid voltage. The proposed inverter topology offers several advantages over traditional single-stage inverters. Firstly, the DC-DC boost converter allows for the use of a smaller, more efficient inverter in the second stage, reducing the overall cost of the system. Secondly, the use of a boost converter allows for the maximum power point tracking of the PV array, which can increase the overall efficiency of the system. The proposed inverter topology offers improved control of the grid current, reducing the impact of the PV system on the grid. The proposed topology has been simulated using MATLAB/Simulink and the results show that the system is capable of delivering a high-quality three-phase AC output with low harmonic distortion. The Author(s). Publisher: University of Tehran Press. -
Enhancing power conversion efficiency in five-level multilevel inverters using reduced switch topology
This paper presents extensive research on improving the power conversion efficiency of five-level multilevel inverters (MLIs) by utilizing a reduced switch topology. MLIs have received an abundance of focus because of their ability to generate high-quality output waveforms and have better harmonic outcomes than traditional two-level inverters. The high number of switches in MLIs, on the other hand, can result in increased power losses and lower overall efficiency. In this paper, a novel reduced switch topology for five-level MLIs, which is having five switches is proposed with the aim of minimizing power losses while preserving superior performance due to lesser number of switches. To achieve efficient power conversion, the proposed topology employs advanced pulse width modulation control strategies and optimized switching patterns. The simulation results show that the minimized switch topology improves the power conversion efficiency of the five-level MLI, resulting in lower losses and better overall system performance. The total harmonic distortion (THD) value of the output current has been reduced to 7.12% and the efficiency has been achieved to 96.92%. The findings of this investigation help to advance MLI technology, allowing for more efficient and reliable power conversion in a variety of applications such as renewable energy systems, electric vehicles, and industrial drives. 2024, Institute of Advanced Engineering and Science. All rights reserved. -
Digital Competencies in the Structure of Training of Advertising and Public Relations Specialists
The article examines the problem of the formation of digital competencies in the training of specialists in the field of media communications. An extensive review of the literature on the issue under study is given. The article examines the trends in the transformation of the profession of a communicator in the context of the intensive development of the latest technologies in the field of big data, gamification, artificial intelligence, etc. The article presents the research results on the basis of which an innovative educational program for training specialists in the field of advertising and public relations has been developed. The program includes modules related to general digital literacy, artificial intelligence resources, management in the digital environment, Internet marketing, technologies for working on various media platforms, as well as project activities using digital technologies. The Author(s), under exclusive license to Springer Nature Switzerland AG 2025. -
Investigation on window opening behavior in naturally ventilated hostels of warm and humid climate
A window is an inevitable element of a naturally ventilated building, and its usage improves indoor environmental conditions. Various research has presented window opening behavior models, stating that it may vary with region, climate, season, building type and many more environmental and non-environmental factors. Major studies in India relied on survey data and were not focused on continuous monitoring. Limited occupants behavior studies have been reported in warm and humid climatic zones, specifically in hostel buildings. Also, a realistic description of occupants window opening behavior is require for more accurate evaluation of building performance using energy simulation. Therefore, there is a need to study the window opening behavior to predict the indoor environment more accurately by using energy simulation tools. In this context, a one-year field research involving questionnaire survey, physical observation, and monitoring was conducted in different hostel buildings in Tiruchirappalli, India. Logistic models were developed to predict the window state in hostel buildings in warm and humid region based on physical observational and long-term monitoring data. It is found that window use is influenced by season, time of the day, weekdays, floor level, buildings orientation, user type, and gender. Results also showed that insects and animal menace (snakes, squirrels, lizards, mosquitoes etc.) impede window opening behavior. The study also presented a logistic model for window opening behavior based on outdoor environment conditions for simulation modeling. 2022 Elsevier B.V. -
Revolutionizing Road Transportation: The Role of Artificial Intelligence in Smart and Efficient Systems
This chapter is about how AI is transforming road transportation by improving efficiency, safety, and comfort. By emphasising the importance of AI integration and moving on to main AI technologies such as machine learning (ML) for applications like traffic prediction and autonomous driving. Deep learning techniques, such as convolutional neural networks (CNNs) and recurrent neural networks (RNNs), are essential for vehicle detection and traffic analysis. Also, natural language processing (NLP) enhances traffic planning and customer support by providing real-time information and virtual assistants. We can also know from the chapter that AI applications like self-driving cars that use AI for vision and control, intelligent traffic management systems that optimise signal timings, and predictive maintenance to avoid vehicle problems. It also discusses data privacy, technology, and ethics questions, as well as demonstrates effective real-world AI deployments and future trends. Overall, the chapter emphasises AIs disruptive impact on road transport and its potential for ongoing innovation and improvement in the pursuit of a smarter, more efficient transportation network. The Author(s), under exclusive license to Springer Nature Switzerland AG 2025. -
Bimetallic Cobalt-Vanadium Boride as a Bifunctional Electrocatalyst for Overall Water Splitting
The transition to a hydrogen-based economy necessitates the development of sustainable and cost-effective electrocatalysts for green hydrogen production via water electrolysis. In this study, we report a novel cobalt-vanadium boride (CoVB) catalyst, which exhibits enhanced bifunctional activity for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline media. CoVB was synthesized using a facile one-step chemical reduction method with varying vanadium concentrations, optimizing performance at a 3% vanadium content. Electrochemical analyses demonstrated that CoVB significantly outperformed cobalt boride (CoB), achieving an HER and OER overpotential (?10) of 80mV and 320mV, respectively, comparable to noble metal benchmarks. Characterization results revealed that V plays a promoting role in inhibiting the growth of particles and agglomeration of particles, leading to an increase in surface area and producing unique mixed amorphous and crystalline structures in CoVB to enhance catalytic activity by increasing the number of active sites and conductivity across the interface. Furthermore, in two-electrode systems, the cell voltage of 1.66V was needed to achieve 10mA/cm2 of current density with superior stability and reusability. Overall, the CoVB catalyst, a new candidate from the metal boride family, presents a promising alternative to precious metals for efficient and sustainable water-splitting in alkaline electrolyzers. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2025. -
Fabrication of NiO nanoparticles modified with carboxymethyl cellulose and D-carvone for enhanced antimicrobial, antioxidant and anti-cancer activities
Colon cancer is a deadly disease while pathogens such as Klebsiella pneumoniae (K. pneumoniae), Shigella dysenteriae (S. dysenteriae), Bacillus subtilis (B. subtilis), Staphylococcus aureus (S. aureus), and Candida albicans (C. albicans) are serious threat to the human health due to their persistent nature and resistant to conventional drugs. This study aims to develop NiO nanoparticles via single one pot chemical approach and to modifying them with natural molecules carboxymethyl cellulose and D-carvone to enhance antioxidant, anticancer and antibacterial activity. The NiO and NiO-CMC-Dcar exhibit fcc structure confirmed by XRD. The band gap values were found be 4.15 eV for NiO and 4.23 eV for NiO-CMC-Dcar nanocomposite. DLS study confirmed that the mean particles diameter of NiO and NiO-CMC-Dcar were 154.1 nm and 130.3 nm respectively. The TEM and SEM analysis confirmed that both NiO and NiO-CMC-Dcar samples were roughly spherical. PL emission spectra of NiO-CMC- Dcar nanoparticles at 426 nm and 506 nm indicate the electronic structural modification due to incorporation of CMC and Dcar molecules in to NiO materials. The green emission observed at 506 nm is due to oxygen vacancy that can be correlated to production of more reactive oxygen species (ROS) to kill microorganism. The experimental results show that the NiO-CMC- Dcar nanoparticles exhibit enhanced antimicrobial, anticancer and antioxidant activity when compared to NiO alone. 2024 Elsevier B.V. -
Fabrication of NiO nanoparticles modified with carboxymethyl cellulose and D-carvone for enhanced antimicrobial, antioxidant and anti-cancer activities
Colon cancer is a deadly disease while pathogens such as Klebsiella pneumoniae (K. pneumoniae), Shigella dysenteriae (S. dysenteriae), Bacillus subtilis (B. subtilis), Staphylococcus aureus (S. aureus), and Candida albicans (C. albicans) are serious threat to the human health due to their persistent nature and resistant to conventional drugs. This study aims to develop NiO nanoparticles via single one pot chemical approach and to modifying them with natural molecules carboxymethyl cellulose and D-carvone to enhance antioxidant, anticancer and antibacterial activity. The NiO and NiO-CMC-Dcar exhibit fcc structure confirmed by XRD. The band gap values were found be 4.15 eV for NiO and 4.23 eV for NiO-CMC-Dcar nanocomposite. DLS study confirmed that the mean particles diameter of NiO and NiO-CMC-Dcar were 154.1 nm and 130.3 nm respectively. The TEM and SEM analysis confirmed that both NiO and NiO-CMC-Dcar samples were roughly spherical. PL emission spectra of NiO-CMC- Dcar nanoparticles at 426 nm and 506 nm indicate the electronic structural modification due to incorporation of CMC and Dcar molecules in to NiO materials. The green emission observed at 506 nm is due to oxygen vacancy that can be correlated to production of more reactive oxygen species (ROS) to kill microorganism. The experimental results show that the NiO-CMC- Dcar nanoparticles exhibit enhanced antimicrobial, anticancer and antioxidant activity when compared to NiO alone. 2024 Elsevier B.V. -
On the Anti-Adjacency Spectra of Regular Graphs
For a graph G with vertex set V (G) = {v1, , vn}, the anti-adjacency matrix, denoted by A?(G) is a square matrix of order n with rows and columns indexed by V (G), whose (i, j)? entry (i ? j) is 1, if the vertices vi and vj are not adjacent and 0, otherwise. The diagonal entries of A?(G) is 1. The eigenvalues obtained from A?(G) are called the anti-adjacency eigenvalues of the graph G and the corresponding spectra is called the anti-adjacency spectra, denoted by a-spec(G). In this paper, we discuss the anti-adjacency spectra of connected and disconnected regular graphs and their complement graphs. 2025, SINUS Association. All rights reserved. -
Self-Powered Dynamic Glazing Based on Nematic Liquid Crystals and Organic Photovoltaic Layers for Smart Window Applications
Dynamic windows allow monitoring of in-door solar radiation and thus improve user comfort and energy efficiency in buildings and vehicles. Existing technologies are, however, hampered by limitations in switching speed, energy efficiency, user control, or production costs. Here, we introduce a new concept for self-powered switchable glazing that combines a nematic liquid crystal, as an electro-optic active layer, with an organic photovoltaic material. The latter aligns the liquid crystal molecules and generates, under illumination, an electric field that changes the molecular orientation and thereby the device transmittance in the visible and near-infrared region. Small-area devices can be switched from clear to dark in hundreds of milliseconds without an external power supply. The drop in transmittance can be adjusted using a variable resistor and is shown to be reversible and stable for more than 5 h. First solution-processed large-area (15 cm2) devices are presented, and prospects for smart window applications are discussed. 2023 American Chemical Society. -
Hindu nationalism and media violence in news discourses in India
The mainstream media and communication discourses in India in the present times engender media violence embedded in the dominant productions of Hinduism together with aspirations for neoliberal development. The media violence engenders indigenous forms of racism and colonialism. This article attempts to examine the nature of these productions through critical theories of postcoloniality and decolonial approaches put into conversation with theories of journalism. Through the examination of the instances of selective silencing of journalistic voices, and erasures embedded within the journalistic practices, this article argues for critical theories of press freedom. The productions of racial superiority and internal colonialism in India only begin to make sense when read together with the interplays of religion, class, caste, and global reach of the privileged sections of Indian society, namely the civil society. Against the backdrop of the historical role of the press in India in freedom struggle against colonial rule, the history of press censorship after independence, the civil society voices that are amplified in the neoliberal restructuring of news media, and the Dalit movements that expose the Brahminical dominance in the imaginary of the Indian culture, the meanings of race and coloniality in India unfold. 2020 National Communication Association. -
Bt cotton and the voices of the widows in the face of farmer-suicides
This article deploys the culture-centered approach to foreground the everyday constructions of farmer-suicides amid the agrarian epidemic among the farmer-widows to attend to the everyday structures that constitute the meanings of the suicides. The depictions of the patriarchal structures of decision-making in agriculture are intertwined with the broader erasure of the interplays of inequality in farmers experiences from the discursive sites of neoliberal agriculture. Furthermore, the voices of the widows disrupt the monolithic construction of agricultural technologies as tools of modernization and progress dominant in the development communication scholarship, instead, depicting the ways in which new technologies (such as Bt cotton) are constituted within, and reproduce, the overarching inequalities. 2020 National Communication Association. -
Development and Exploratory Factor Analysis of a United States Version of the International Survey of School Counselors Activities
This manuscript details the development and exploratory factor analysis of a United States version of the International Survey of School Counselors Activities (ISSCA-US), a 42-item instrument that identifies activities of school counselors. Responses were collected from 390 US school counselors. Separate EFAs were conducted for two distinct sections of the survey involving appropriateness of role activities and their actually being undertaken, both resulting in reliable 6-factor models. 2018, Springer Science+Business Media, LLC, part of Springer Nature. -
A Qualitative Investigation of Adversities Experienced by Non-Alcoholic Adult Children of Alcoholics (ACOAs) in an Indigenous Community
This study explores the distinctive adversities encountered by non-alcoholic adult children of alcoholics (ACOAs) within the Mizo indigenous culture. Despite the abundance of literature on the adverse consequences of ACOAs, there is a dearth of global literature on the unique lived experiences of adversity among non-alcoholic ACOAs. Analysis of 13 in-depth interviews using the grounded theory approach identified that non-alcoholic ACOAs experienced a multitude of adversities across cognitive, affective, behavioral, and somatic domains. These adversities manifested as challenges in sustaining attention, lack of proficiency in problem-solving, distorted beliefs and negative emotions concerning relationships, skewed attachment styles, difficulty in managing oneself and adhering to rules, flawed relationship praxis, and somatic complaints such as fatigue, heightened psychomotor activity, and various aches and pains. These findings emphasize that parental alcohol misuse has lasting impacts on non-alcoholic ACOAs. Tailored early intervention and support programs are necessary to address these challenges. 2025, Institute for Human Rehabilitation. All rights reserved.