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Comparative efficiency analysis of RF power amplifiers with fixed bias and envelope tracking bias
RF power amplifier (RF PA) finds its application in almost all the areas of electronics, mobile communication being identified as a major area. The paper performs a comparative efficiency analysis of RF power amplifiers operating with a fixed bias and an envelope tracking bias. Simulations are performed using Keysight advanced design system (ADS) tool. A class a RF PA operating at a 12 dB gain is fixed for the work. 16 QAM LTE signal operating at 5 MHz input frequency, with a peak to average power ratio (PAPR) of 6.0 dB is used as input signal. An envelope simulation at 2.5 GHz is performed on the RF power amplifier. Simulation result shows an improvement of 12% in power added efficiency (PAE) at 6 dB back-off and 6.422% in mean PAE while using envelope tracking power amplifiers, compared to RF PA with fixed supply. Envelope tracking power amplifiers reduced AM/AM distortions also by a factor of 0.248. The results obtained are much better than that obtained using a conventional RF PA with fixed bias. RF PA being the most power dissipative block in a mobile handset, improving its efficiency contributes directly to a great improvement in the battery lifetime of mobile phones. The major challenges faced by envelope tracking PA (ETPA) designers in achieving this efficiency improvement is also delineated in the paper. 2024 Institute of Advanced Engineering and Science. All rights reserved. -
Delay Minimization Technique to improve the efficiency of Parameter Optimized Hysteretic Current Controlled Parallel Hybrid ETPA in Mobile Communication
This paper proposes a delay minimization technique to improve the efficiency of a parameter-optimized hysteretic current-controlled parallel hybrid envelope tracking power amplifier (etpa). In a hysteretic current-controlled hybrid topology, a linear amplifier operates parallel with a hysteretic current-controlled switching converter. Block level simulation of etpa is performed using the simulink tool. The traditional parameter optimization technique is first implemented, and its limitation is analysed. The proposed delay minimization technique helps to overcome the limitation of the traditional approach and has been proven to be valid for any input frequency. The proposed technique offers an efficiency improvement of 14.9% compared to the traditional technique for an input frequency of 20mhz and provides an average efficiency improvement of 6.26% for an input frequency range of 2mhz to 60mhz. 2024 IEEE. -
Fluorescent detection of Pb2+ pollutant in water samples with the help of Delonix regia leaf-derived CQDs
Heavy metals released from different sources into water bodies are a major concern in the view of environmental protection. Their non-biodegradability and the numerous health hazards add to the issue. Scientists worldwide have emphasized the issue and are trying to resolve it by different means. Among all the methods, the fluorescent method stands out for its simplicity and rapid results. Here, the study focuses on the development of an efficient and sustainable method for the detection of lead in waste-water effluents. Carbon quantum dots (GCDs), a highly non-toxic substance developed from Delonix regia leaves for the purpose via a simple hydrothermal method. The prepared GCDs exhibited good photostability and water solubility; they also displayed a bright red emission when irradiated with ultraviolet (UV) light. Here, the authors propose the synthesized GCDs as an effective fluorescent probe for sensitive detection of lead ions in aqueous samples. Photoluminescence quenching of GCDs by the addition of lead was studied and a good detection limit of 3.3 nM with a linear range of 10180 M was achieved. Further, real sample analysis was also conducted to prove the applicability of the synthesized GCDs. 2022 Elsevier B.V. -
Boosting Surface Coverage of CO Intermediates through Multimetallic Interface Interactions for Efficient CO2 Electrochemical Reduction
Given the inherent challenges of the CO2 electroreduction (CO2ER) reaction, solely from CO2 and H2O, it is desirable to develop selective product formation pathways. This can be achieved by designing multimetallic nanocomposites that provide optimal CO coverage, allowing for tunability in the product formation. In this work, Ag and Zn codoped-SrTiO3 (ZAST) composite immobilized carbon black (CB)-modified GCE working electrode (ZAST@CB/GCE) was developed for the electrochemical conversion of CO2 to multicarbon products. The complete reaction was carried out in a CO2-saturated aqueous system of 0.5 M KHCO3 electrolyte. A potential-dependent product selectivity was suggested based on the NMR results, wherein raising the potential value enhanced the formation of liquid products such as acetone and alcohols while suppressing competitive HER. The total Faradaic efficiency for liquid products reached an impressive 97% at a potential of ?0.6 V vs. RHE. This represents a significant advancement in acetone production pathways and valorization of CO2ER technology. 2025 American Chemical Society. -
Surface modulation and structural engineering of graphitic carbon nitride for electrochemical sensing applications
The rediscovery of the old-age material graphitic carbon nitride (g-C3N4), a 2D conducting polymer, has given rise to a tide of articles exploring its diverse applications. Recently, owing to its excellent physicochemical stability and tunable electronic structure, the material has proven to be an eminent candidate for improving the sensing quality of electrodes. Excellent properties of g-C3N4 such as exposed surface area, metal-free characteristics, and low-cost synthesis have attracted facile and economical designing of sensors for a variety of analyte molecules. Herein, the readers are introduced to the historical development of g-C3N4 and escorted to the present findings of its electrochemical sensing applications. Along with its sensing utilities, the review shares some exciting insights into the synthesis, structural, and surface chemistry modulations of g-C3N4. A great many approaches for overcoming the inherent limitations have also been critically discussed, starting with the precursor in use. This review article aims to provide a concise perspective and direction to future researchers for enabling them to fabricate smart and eco-friendly sensors using g-C3N4. Graphical abstract: [Figure not available: see fulltext.] 2021, The Author(s), under exclusive licence to Islamic Azad University. -
Temperature-induced variations in the structural, morphological and optical features of cobalt oxide nanoparticles synthesized via hydrothermal method
Cobalt oxide is a promising material that attracts the researchers to find its application in various fields like catalysts, dielectric applications, gas sensors and electronics devices, etc. In this work, we investigated the effect of temperature in the structural, elemental, morphological and optical properties of Co3O4 nanoparticles synthesized by hydrothermal method. The as-prepared and annealed samples were observed for their structural and optical properties. The structural analysis and micro-strain effects of Co3O4 nanoparticles with cubic spinel structure were carried out through X-ray diffraction (XRD) studies. The crystallite size of as-prepared and annealed samples were around 27 nm and 29 nm, respectively. Raman spectrum showed the lattice vibrations of both oxidation states of cobalt oxide nanoparticles. Elemental analysis were observed through X-ray photoelectron spectroscopy (XPS). The morphology and chemical composition of the samples were determined from the field emission scanning electron microscope (FESEM) image and energy dispersive X-ray spectroscopy (EDAX). Moreover, the internal structure of both samples were compared through transmission electron microscopic (TEM) studies. The optical studies were done using the absorption spectrum and photoluminescence spectroscopy. Two direct band gaps (1.8 and 3.2 eV) were observed in the as-prepared, which got red-shifted on annealing (1.7 and 2.5 eV) due to size effects. The charge transfer process in two oxidation states of cobalt oxide could be identified from these bandgaps. Emission peaks in the photoluminescence spectrum of samples are due to the recombination of free-excitons and point defects in the crystal lattice. 2024 -
Electrochemical characteristics of Co3O4 nanoparticles synthesized via the hydrothermal approach for supercapacitor applications
Cobalt oxide (Co3O4), a transition metal oxide known for its favourable capacitive properties and surface characteristics, is a promising candidate for electrode materials in supercapacitive energy storage applications. This study presents a comprehensive analysis of cobalt oxide nanoparticles synthesized through the hydrothermal method at varying synthesis temperatures, focusing on their structural, optical, electrochemical, and surface properties. X-ray diffraction analysis confirmed the cubic spinel structure of Co3O4, while Raman spectroscopy verified the phase composition of the nanoparticles. X-ray photoelectron spectroscopy offered insights into the near-surface chemistry of the synthesized material. The study determined two direct bandgaps of Co3O4 through absorption spectra and Tauc plots. To assess surface morphology and particle size distribution, field-emitting scanning electron microscopy and transmission electron microscopy were employed. Electrochemical investigations involved cyclic voltammetry and Nyquist plots, while galvanostatic chargedischarge tests demonstrated a specific capacitance (Csp) of 450 Fg?1 at 1 Ag?1. Impedance analysis indicated favourable capacitive behaviour with low charge transfer resistance. Furthermore, the study observed cyclic stability with a capacitive retention rate exceeding 88% at a current density of 20 Ag?1 over 10,000 cycles. The paper also discusses the capacitive and diffusion-controlled charge storage mechanisms at lower scan rates, emphasizing the potential of Co3O4 nanoparticles as the electrode material in the development of supercapacitor devices. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2023. -
Symmetric supercapacitor based on Co3O4 nanoparticles with an improved specific capacitance and energy density
Metal oxides have garnered significant research interest as highly effective electrode materials for supercapacitors. In this study, we synthesized Co3O4, an electrode material for supercapacitors, utilizing an in-situ hydrothermal method with varying pH levels in the precursor solution. The obtained samples underwent through structural, optical, surface morphological, electrical, and electrochemical analyses, affirming their exceptional suitability for supercapacitor applications. The influence of pH fluctuations in the synthesis process, on the specific capacitance values were analyzed. The X-ray diffraction pattern and Raman spectrum confirmed the normal cubic spinel structure of Co3O4 nanoparticles. The X-ray photoelectron spectrum revealed the chemical bond states of Co3O4. The optical bandgap have been investigated from the Tauc plot. The surface area and morphology were determined through Brunauer Emmett and Teller method and field emission scanning electron microscope images. A high specific capacitance of 1195.05 Fg?1 at a current density of 1.5 Ag?1 was obtained in the three-electrode study for the sample synthesized at a pH of 10. A symmetric supercapacitor (SSC) device was fabricated to facilitate practical analysis. The symmetric supercapacitor device demonstrated a notably elevated specific capacitance of 870.6 Fg?1 at an operational current density of 5 Ag?1, concurrently achieving an enhanced energy density of 77.3 W h/kg and superior power density of 1997.7 W/kg. These performance metrics surpassed those of prior studies in the field. Furthermore, the SSC device exhibited an excellent cyclic stability of 88 % after undergoing 970 charge/discharge cycles. As a result, Co3O4 emerges as a promising and efficient electrode material for applications in supercapacitors. 2024 Elsevier Ltd -
A model for analyzing the sustainability performance in educational institutions
During the past two decades innumerable international initiatives have emphasized that education is an imperative for societies to become more sustainable. Sustainable development is the current context in which higher education must begin to focus its action plans. But the present system heavily relies on archaic models which reduce learning and action to reductionist thinking and mechanistic interpretation. Campus sustainability is receiving growing attention and has become a well-established study field, even though campus sustainability itself has not become a reality yet in most universities. The paper then validates a pre-existing model using multiple regression models. The results validated the proposed model. A sustainability index could be developed for the education sector in future using this conceptual framework. The educational institutions can use the sustainability index to analyze their sustainability performance and take the necessary steps for achieving the same. This paper is an initial step in this direction which could be researched further to measure the sustainability performance in the education system. Grenze Scientific Society, 2020. -
Reconceptualizing Empowerment And Autonomy: Ethnographic Narratives From A Self Help Group In South India
The paper revisits academics' conceptualizations of women empowerment as stopping short of autonomy. It departs from the general observation that women empowerment movements by and large have failed to translate the new agency of women outside the domains of socio economy; that women empowerment movements' capacity to re-engage with patriarchal structures and ideologies is seriously contained. Through an ethnography of Kudumbashree, an SHG in the South Indian state of Keralam, we question the neat distinctions between empowerment and autonomy that prevail in the academic common sense. The transition of agency from the economic to the political domain is a subtle enterprise and is mediated by a number of factors including the economic independence, decision making capability and political participation. Socio -economic - political implications of women empowerment could be the first step in challenging and overcoming the relations of oppression in any society. The stereotypical assumptions can be negotiated by solely apportioning responsibilities and re-engaging with the system through everyday practices. The nuances of empowered women's re-engagement with local gender/power regimes lead to changes at the conceptual level that cuts beyond the individual and group level material transformations. The Electrochemical Society -
Model and Algorithm of Multimodal Transportation in Logistics Transportation Based on Particle Swarm Optimization
With the rapid improvement of market economy and modern logistics technique, the logistics distribution link is receiving more and more attention, and the logistics distribution path question in distribution has become the core question in logistics distribution. Study the optimization of logistics distribution path. Logistics distribution path optimization needs to find an optimal distribution route with less distribution vehicles and the shortest total length of the path, and has the rapidity of distribution. The traditional algorithm takes a long time to search the optimal route, which makes it difficult to find the optimal distribution route, resulting in high logistics distribution costs. In order to quickly find the optimal distribution route and improve the quality of logistics service, a logistics model based on particle swarm optimization algorithm is proposed. The group is composed of several non-intelligent individuals or groups of individuals. Each individual's behavior follows certain simple rules and has no intelligence; Individuals or groups of individuals can cooperate to solve questions through certain principles of message exchange, thus showing the behavioral characteristics of collective intelligence. After research, the algorithm in this paper is effective and suitable for wide application in practice. 2023 IEEE. -
Employees Job Satisfaction, Work-Life Balance, and Health During the Pandemic
The impact of the COVID-19 pandemic on private enterprises has been particularly noticeable in the IT and non-ITES sectors. Work came to a complete halt due to the ensuing lockdown, severely affecting businesses and further harming industries like aviation and hospitality. Widespread job losses, shortened workweeks, minimum wage reductions, short-term leave policies, and even company closures have been the results. To understand the extent of these impacts, a descriptive study was conducted online in AprilMay 2021, involving 2439 white-collar workers from various private companies. Convenient sampling methods were used to gather data on the experiences of employees in these sectors during the pandemic. The survey's findings demonstrate a positive but weak association between Work-Life Balance and Health Stress (r?=?0.24, p?<?0.01) and a positive low correlation between Work-Life Balance and Job Satisfaction (r?=?0.23, p?<?0.01). Therefore, work-life balance and job satisfaction among employees were significantly correlated throughout the epidemic. Additionally, there was a negative moderate correlation between Health Stress and Job Satisfaction (r?= ?0.48, p?<?0.01), indicating that as Health Stress decreases, Job Satisfaction increases at moderate levels. The implications of the study were discussed further. The Author(s), under exclusive license to Springer Nature Switzerland AG 2024. -
The mathematical and machine learning models to forecast the COVID-19 outbreaks in Bangladesh
The COVID-19 virus mutates in many different variants after its outbreak. Although several vaccines have been developed by many countries and implemented worldwide, it is difficult to prevent the outbreaks due to the pops out of different variants from its regular mutations. This study is an attempt to develop models which could precisely forecast the COVID-19 outbreaks in Bangladesh. In this study, we have developed a SEIRD based machine learning model to forecast the next possible one year outbreaks scenario in this country. We have tested the accuracy of this model by fitting the results with the considered historical data from March 08, 2020 to October 14, 2021. Also, we have validated this model by predicting the future inside the existing dataset, which is almost similar to the real dataset. It is observed that the final future forecasting results are very realistic compared to the current outbreak situation. Additionally, we have shown that the classical SEIRD model cannot predict the COVID-19 future outbreaks even it does not fit with the real datasets of outbreaks. Moreover, another machine learning time series forecasting model, FBProphet, has been implemented to forecast the future outbreaks of Bangladesh. Finally, we have analyzed and compared the forecasting results and hence identify the limitations of the proposed models which can improve future research in this field. 2022 Taru Publications. -
Hepatoprotective activity of Peltophorum pterocarpum leaf and bark in the isoniazid and rifampicin-induced hepatotoxic rats
Background: In recent years, various phytomedicines have been used in the treatment of hepatic disorders. The aim of this study is to find out whether Peltophorum pterocarpum bark and leaves can help rats that have been exposed to isoniazid and rifampicin-induced hepatotoxicity. Materials and Methods: The rats were divided into 10 groups each with 6 rats. The liver damage is induced by isoniazid and rifampicin. The leaf and bark of P. pterocarpum extracted with ethanol are freshly mixed in sterile water (100, 200 and 400 mg/kg body weight), and given to rats orally in the early morning as a single dosage per day until the study period. The animals were sacrificed and the tissue and serum samples were collected for further investigations. Results: The liver damage induced by isoniazid and rifampicin altered the various biochemical parameters levels, but after the treatment of P. pterocarpum barks and leaves the levels were significantly altered when compared to the negative control rats. The drug silymarin was used as a standard. Conclusion: The extracts have the protective effect of liver markers and membrane-bound enzymes against the toxin-treated rats. This result highlights the hepatoprotective properties of the leaves and barks of the plant in a similar manner and the formulation (Group 10) have high beneficial effects than other groups. 2024 -
Photosensitizer Anchored Nanoparticles: A Potential Material for Photodynamic Therapy
Detection and treatment of cancer have been demanding areas with the increase in cancer and malignant diseases across the globe. Photodynamic therapy is a multi-step treatment procedure using photosensitizers as a drug in the presence of light. Photosensitizers anchored on different nanomaterials through covalent and non-covalent interactions contribute significantly to photodynamic therapy. Nanoparticles have been employed as promising carriers to transport photosensitizers to the target cells. Photosensitizer functionalized nanoparticles are more effective in terms of stability and water solubility than bare ones. This review is a brief account of different types of nanoparticles functionalized on photosensitizers currently used for photodynamic therapy. We have focused on photosensitizer anchored organic, inorganic, and carbon-based nanomaterials, which can be effectively used in photodynamic therapy. 2022 Wiley-VCH GmbH. -
Drill hole surface characterisation of hybrid FRP laminates through statistical analysis
As it is known that the hybrid Fibre Reinforced Polymer (FRP) composite laminate is a recently evolved class of structural material. Hence, the present work deals with secondary processing ability like hole drilling on hard to machine FRP laminate. The influence of drilling attributes on the delamination factor and surface roughness contours are studied for a high thickness hybrid (carbon/glass FRP) laminates. Here, the experimentation was performed utilising Taguchis L27 design of experiments array. Later, on post-drilling, the predominant and optimum variables were studied through taguchi and variance analysis to highlight their contribution on the response functions. Taguchi results indicate that the combination of the 90?tungsten carbide tool, speed of 800 rpm, and rate of feed 50 mm/min gives the best performance concerning the delamination. Also, it was observed that the combination of the 118?tungsten carbide tool, cutting speed of 900 rpm and the rate of feed 60 mm/min give the best performance concerning surface roughness. Whereas, as per ANOVA, the highest percentage contribution factor was concerned to a tool material followed by other factors and analysed data lie with the confidence level of 95%. The work also indicates that tungsten carbide tool yield better results compared to high-speed steel tool. Further, fibre morphology has been studied, which indicates optimal structure with minimal damage. 2020 Engineers Australia. -
A Systematic Review of Various Advancements Implementation in the Field of Crop (Plant) Production
An essential component of agricultural output is pest management, especially in fertigation-based farming. Although fertigation systems in Malaysia are beneficial for irrigation and fertilization, they frequently don't have effective pest control techniques. Because pests usually live beneath crop leaves, hand spraying is difficult and labor-intensive. Insect pests have the power to seriously harm, weaken, or even kill agricultural plants, which can lead to lower yields, worse-quality goods, and unsalable outcomes. Furthermore, insects may still cause harm to processed or stored items after harvest. Therefore, creating an autonomous pesticide sprayer specifically designed for chilli fertigation systems is the main goal of this research. The main goal is to create a sprayer arm that is flexible enough to reach under crop leaves. The goal of this project is to build an autonomous, unmanned pesticide sprayer. The goal of autonomous operation is to reduce the amount of dangerous pesticides that people are exposed to, especially in enclosed spaces like greenhouses. In addition, the sprayer arm's adaptability to different agricultural circumstances makes it a valuable tool in both greenhouse and outdoor settings. It is expected that the successful adoption of the autonomous pesticide sprayer would completely transform fertigation-based farming's approach to pest management. 2024 IEEE. -
CONVECTIVE INSTABILITY IN POROUS MEDIA: IMPACT OF CHEMICAL REACTION ON MAXWELL-CATTANEO COUPLE-STRESS FERROMAGNETIC FLUIDS; [??????????? ??????????? ? ???????? ???????????: ????? ???????? ??????? ?? ?????????? ??? ?????????-???????? ? ????????????? ???????]
The current study analyzes the initiation of convection in a Maxwell-Cattaneo couple-stress ferrofluid within a porous layer, considering the effects of a chemical reaction. Small perturbations are applied to the fluid under the assumption of a zero-order energy release chemical reaction. The system is cooled from the upper layer while maintaining a steady temperature at the lower boundary. We employed linear stability analysis and determined Rayleigh number using the Galerkin Method (GM). This study emphasizes the influence of magnetic, chemical, Maxwell-Cattaneo, and couple-stress parameters on the initiation of ferro-convection. The findings indicate that both magnetic and chemical reaction parameters hasten the initiation of ferro-convection, while the porous medium and couple-stress parameters have a stabilizing effect. Notably, it is demonstrated that the destabilizing effects of chemical reactions and magnetic stresses can be effectively regulated in the presence of couple-stresses. The solutions provide insights into the potential application of ferromagnetic fluids for controlling efficient heat transfer mechanisms. 2024 Oles Honchar Dnipro National University. -
COUPLE STRESS EFFECT ON FERRO-CONVECTION TRIGGERED BY CHEMICAL REACTION IN A POROUS LAYER WITH SPARSE DISTRIBUTION; [????? ??????? ?????????? ?? ?????????????, ??????????? ???????? ???????? ? ????????? ???? ? ??????????? ??????????]
The study delves into the impact of couple stress on the commencement of convection in a porous material oriented horizontally. This layer contains a chemically reactive ferromagnetic fluid and experiences bottom heating. The investigation utilizes small perturbation methodology to explore and understand the impact of couple stress on the initiation of convection in this specific system. With the assumption of a non-autocatalytic exothermic reaction, eigenvalues are determined utilizing the Galerkin method. The analysis explores the effects of magnetic and couple stress parameters, as well as the Frank-Kamenetskii number. The observation indicates that the acceleration of the onset of ferroconvection is influenced by both magnetic forces and chemical reactions. Simultaneously, the presence of the couple stress component serves to stabilize the system. Moreover, when the nonlinearity of magnetization is sufficiently pronounced, the destabilization of the fluid layer is observed to be marginal. 2024 Oles Honchar Dnipro National University; -
Post listing IPO returns and performance in India: An empirical investigation
Objectives: (a) To analyse the performance of Indian IPOs in the short term. (b) To determine the significance of abnormal return of the IPOs. (c) To study the impact of over-subscription, profit after tax, promoters' holdings, issue price and market returns on IPO performance. Design/ Methodology/Approach: This research paper is based on empirical analysis. All the 52 IPO's listed in the NSE (National Stock Exchange, India) during the year 2018 to 2020 were considered for the study. The study is based on secondary data. The daily share price and Nifty-50 index value were taken from NSE website (www.nseindia.com) and other relevant data from red-herring prospectus of the respective company. The research / statistical tools used are: Market adjusted short run performance model, Wealth relative model, 't' test and regression analysis. Scope of the study: The scope of the study is limited to the IPO's listed only in the National Stock Exchange (NSE), India. Period of study: The study covers a period from January 2018 to December, 2020. Limitation of the study: The study considers only the influence of the external factors on the performance of IPOs. Findings: The average IPO return on the first trading day is 13.52%, ranging from -23.15% to 82.16% with standard deviation of 26.72%. The average IPO return on the third trading day was the highest and is found to be14.52%, ranging from -19.22% to 117.55% with standard deviation of 18.57%. The analysis reveals that the over subscription impacts the IPO performance and the other factors namely, issue price, Profit after Tax, market returns and promoters holdings do not influence IPO returns. Originality / Value: This is an original work that analyses the listing gain or loss and the post listing performance of IPO's in India and other factors that might influence the listing gain or loss. Copyright 2021. T. Ramesh Chandra Babu and Aaron Ethan Charles Dsouza. Distributed under Creative Commons Attribution 4.0 International CC-BY 4.0