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Study of damage behavior and repair effectiveness of patch repaired carbon fiber laminate under quasi-static indentation loading

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Defence Technology（防务技术） 2024年第4期34卷 29-41页

作者： alok kumar Chinmaya kumar Sahoo A.Arockiarajan Department of Applied Mechanics Indian Institute of Technology MadrasChennai 600036India

Damage caused due to low-velocity impacts in composites leads to substantial deterioration in their residual strength and eventually provokes structural *** work presents an experimental investigation on the effects of different patch and parent laminate stacking sequences on the enhancement of impact strength of Carbon Fiber Reinforced Polymers(CFRP)composites by utilising the adhesively bonded external patch repair *** evolution study is also performed with the aid of Acoustic Emission(AE).Two different quasi-isotropic configurations were selected for the parent laminate,viz.,[45°/45°/0°/0°]s and[45°/0°/45°/0°]*** Static Indentation(QSI)test was performed on both the pristine laminates,and damage areas were detected by using the C-scan inspection *** laminates were repaired by using a single-sided patch of two different configurations,viz.,[45°/45°/45°/45°]and[45°/0°/0°/45°],and employing a circular plug to fill the damaged *** different combinations of repaired laminates with two configurations of each parent and patch laminate were produced,which were further subjected to the QSI *** results reveal the effectiveness of the repair method,as all the repaired laminates show higher impact resistance compared to the respective pristine *** of[45°/0°/0°/45°]configuration when repaired by taking[45°/45°/0°/0°]s and[45°/0°/45°/0°]s as parents exhibited 68%and 73%higher peak loads,respectively,than the respective pristine ***,parent and patch of configuration[45°/0°/45°/0°]s and[45°/0°/0°/45°],respectively,attain the highest peak load,whereas[45°/45°/0°/0°]s and[45°/45°/45°/45°]combinations possess the most gradual decrease in the load.

关键词： Carbon fiber reinforced polymers(CFRP) Quasi-isotropic laminate Quasi static indentation(QSI) Acoustic emission(AE) Composite repair

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An improved reverse time migration for subsurface imaging over complex geological structures:A numerical study

Energy Geoscience

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Energy Geoscience 2024年第2期5卷 290-297页

作者： alok kumar Routa Priya Ranjan Monahty Department of Applied Geophysics IIT(ISM)DhanbadJharkhandIndia

In seismic exploration,it is a critical task to image and interpret different seismic signatures over complex geology due to strong lateral velocity contrast,steep reflectors,overburden strata and dipping *** understand the behavior of these seismic signatures,nowadays Reverse Time Migration(RTM)technique is used extensively by the oil&gas *** the extrapolation phase of RTM,the source wavefield needs to be saved,which needs high storage memory and large computing *** two are the main obstacles of RTM for production *** order to overcome these disadvantages,in this study,a second-generation improved RTM technique is *** this improved form,a shift operator is introduced at the time of imaging condition of RTM algorithm which is performed automatically both in space and time *** effort is made to produce a better-quality image by minimizing the computational time as well as numerical *** proposed method is applied over various benchmark models and validated by implementing over one field data set from the Jaisalmer Basin,*** the analysis,it is observed that the method consumes a minimum of 45%less storage space and reduce the execution time by 20%,as compared to conventional *** proposed RTM is found to work efficiently in comparison to the conventional RTM both in terms of imaging quality and minimization of numerical artefacts for all the benchmark models as well as field data.

关键词： Imaging condition Reverse time migration(RTM) Seismic imaging Velocity-depth model Wave propagation

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Powder mixed electrochemical discharge process for micro machining of C103 niobium alloy

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Defence Technology（防务技术） 2023年第8期26卷 84-101页

作者： Niladri Mandal Nitesh kumar alok kumar Das Defence Research&Development Laboratory(DRDL)-DRDO HyderabadIndia Department of Mechanical Engineering Indian Institute of Technology(ISM)DhanbadIndia

This work demonstrates the viability of the powder-mixed micro-electrochemical discharge machining(PMECDM) process to fabricate micro-holes on C103 niobium-based alloy for high temperature *** processes are involved simultaneously *** erosion,chemical etching,and abrasive grinding for removal of material while the classical electrochemical discharge machining process involves double actions *** erosion,and chemical *** powder-mixed electrolyte process resulted in rapid material removal along with a better surface finish as compared to the classical microelectrochemical discharge machining(MECDM).Further,the results are optimized through a multiobjective optimization approach and study of the surface topography of the hole wall surface obtained at optimized *** the selected range of experimental parameters,PMECDM shows a higher material removal rate(MRR) and lower surface roughness(R_(a))(MRR:2.8 mg/min and R_(a) of 0.61 μm) as compared to the MECDM process(MRR:2.01 mg/min and corresponding Raof 1.11 μm).A detailed analysis of the results is presented in this paper.

关键词： Micro-electrochemical discharge machining C103 niobium alloy Surface integrity Material removal rate Hybrid powder mixed ECDM

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Modeling the effect of time delay in implementation of mitigation policies on the control of atmospheric greenhouse gases

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生物数学学报:英文版 2023年第8期16卷 75-108页

作者： alok kumar Verma Maitri Verma Department of Mathematics School of Physical and Decision Science Babasaheb Bhimrao Ambedkar University Lucknow India

Mitigation of the enhanced greenhouse gas(GHG)concentrations in the Earth's atmosphere is imperative to meet the climate change mitigation *** of many countries are developing and implementing various mitigation strategies to reduce their GHG ***,a time delay between the formulation and implementation of these mitigation policies can affect their effectiveness in controlling greenhouse gas levels in the *** work presents a nonlinear mathematical model to investigate the effect of application of mitigation strategies and the delay involved in their implementation over the reduction of atmospheric greenhouse *** model formulation,it is assumed that the mitigation strategies work two-fold;first they reduce the GHG emission rate from the anthropogenic source and second they increase the removal rate of greenhouse gas from the atmosphere.A comprehensive stability analysis of the proposed model system is made to examine its long-term *** model analysis shows that an increase in the implementation rate of mitigation strategies and their efficiencies to cut down the GHG emission rate from point sources and increase the GHG uptake rate lead to reduction in equilibrium GHG *** is found that a long delay in the execution of mitigation policies can destabilize the system dynamics and leads to the generation of periodic *** expression for the threshold value of the delay parameter at which periodic oscillations arise via Hopf-bifurcation is *** stability and direction of bifurcating periodic solutions are discussed.A sensitivity analysis is performed to investigate the effect of changes in key parameters over system dynamics.

关键词： Mathematical model greenhouse gases global warming mitigation strategies time delay Hopf-bifurcation

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Spatial variability of soil hydraulic and physical properties in erosive sloping agricultural fields

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Water Science and Engineering 2023年第1期16卷 57-66页

作者： Deepak Singh alok kumar Mishra Sridhar Patra Sankar Mariappan Nisha Singh Saswat kumar Kar ICAR-Indian Institute of Soil and Water Conservation Dehradun 248195India Sam Higginbottom University of Agriculture Technology and SciencesPrayagraj 211007India Hemvati Nandan Bahuguna Garhwal University Srinagar(Garhwal)246174India

It is essential to minimize soil quality degradation in sloping agricultural fields through stabilization and improvement of soil hydraulic properties using sustainable soil *** study aimed to analyze the impact of different tillage practices,including conventional tillage(CT),minimum tillage(MT),and zero tillage(ZT),on soil hydraulic conductivity in a sloping agricultural field under maizeewheat *** results showed that the highest runoff volume(257.40 m3),runoff coefficient(42.84%),and soil loss(11.3 t)were observed when the CT treatment was *** contrast,the lowest runoff volume(67.95 m3),runoff coefficient(11.35%),and soil loss(1.05 t)were observed when the ZT treatment was *** soil organic carbon and aggregate mean weight diameter were found to be significantly greater(with mean values of 0.79%and 1.19 mm,respectively)with the ZT treatment than with the CT *** the tilled treatments(CT and MT),substantial changes in the saturated soil hydraulic conductivity(ks),near-saturated soil hydraulic conductivity(k),and water-conducting porosity(ε)were observed between two crop *** three soil parameters were significantly higher in the period after maize harvesting than in the wheat growing *** contrast,no significant difference in these soil parameters was found when the untilled treatment(ZT)was carried *** regard to the slope positions,ks,k,andεshowed different behaviors under different *** toe slope position showed significantly lower ks andεvalues than the summit and middle slope *** the evaluated tillage practices,ZT was found to be the most promising means to improve the soil hydro-physical properties and effectively reduce surface runoff and soil erosion.

关键词： Hydraulic conductivity Macropore Conservation tillage Spatiotemporal variability Soil erosion

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Conservation aquaculture of Ompok bimaculatus (Butter catfish), a near threatened catfish in India

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Aquaculture and Fisheries 2023年第1期8卷 1-17页

作者： Pradyut Biswas alok kumar Jena Soibam Khogen Singh Department of Aquaculture College of FisheriesCentral Agricultural University(Imphal)LembucherraTripura(W)792210India Aquaculture Division ICAR-Central Institute of Fisheries EducationMumbai400061India

The butter catfish,Ompok bimaculatus,belonging to the silurid family,is widely regarded as an important food fish for aquaculture diversification in ***,the species poses a threat due to habitat degradation and other anthropogenic factors,and has been categorised as“near threatened”,therefore,its culture promotion is *** establish a successful breeding programme,a precise understanding of the life history,and biology(reproductive/feeding)of the fish will assist hatchery managers and *** in these areas have been undertaken by several groups over the years,but without much coherence,the data are still *** attempts on the culture attributes of this catfish have been performed under both mono-and polyculture systems to bring about parallel promotion through aquaculture in a larger part of the *** this,we have tried to analyse and present a consolidated account of the morphological characteristics,feeding habits,reproductive biology,early developmental ontogeny,and culture potentials of *** in *** review was also prompted by the paucity of information on the cultural aspects of the ***,based on the reported studies,future directions and perspectives of the culture promotion of the species are proffered to ensure future research initiatives.

关键词： Ompok bimaculatus Ontogeny Polyculture Reproductive biology Threatened

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Magnitude and Determinants of Mortalities Related to COVID-19:Evidence from 94 Countries Using Regression Techniques

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Fudan Journal of the Humanities and Social Sciences 2022年第4期15卷 475-499页

作者： Ashis kumar Pradhan Ronny Thomas Sandhyarani Rout alok kumar Pradhan Department of Humanities and Social Sciences Maulana Azad National Institute of TechnologyBhopalMadhya PradeshIndia Rajagiri Business School(RBS)and Rajagiri College of Social Sciences(RCSS) Rajagiri Valley CampusKakkanadKochiKeralaIndia Department of Social Science Fakir Mohan UniversityBalasoreOdishaIndia Indian Institute of Management Nagpur DahegaonIndia

This study attempts to investigate the factors determining COVID-19 deaths during the pandemic across countries by employing a rich dataset sourced from 94 countries updated till 6 February,*** empirical analysis,the study makes use of cross-sectional linear regression technique in the first part and after required diagnostic tests use 2SLS regression technique for correcting possible endogeneity bias in the second *** from the study indicate that factors like total reported cases,population size,population over 70 years of age,extreme poverty,and human development index play significant role in determining COVID-19-related ***,to check the robustness of the findings the present study employed LASSO *** from the study highlight the possibility of government intervention to devise appropriate policies to control COVID-related incidence and death.

关键词： COVID-19 deaths Mortality risks Infectious diseases LASSO regression Pandemic

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激光包覆工艺的实验研究及人工神经网络对工艺参数的预测

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Journal of Central South University 2022年第10期29卷 3489-3502页

作者： Rashi TYAGI Shakti kumar Mohammad Shahid RAZA Ashutosh TRIPATHI alok kumar DAS University Centre for Research and Development Chandigarh UniversityMohali-140413India Department of Mechanical Engineering Chandigarh UniversityMohali-140413India Department of Mechanical Engineering IIT(ISM)Dhanbad-826004India Department of Mechanical Engineering IIT KharagpurIndia

根据正交实验(L^(16))设计方案,将氮化钛与SS304的粉末混合物在光纤激光器上对SS304衬底进行激光包覆。利用Taguchi信噪比方法对得到的包覆层微观硬度和包厚度进行分析,得到了最优的参数组合。并利用人工神经网络(ANN)对比分析得到与Tag... 详细信息

根据正交实验(L^(16))设计方案,将氮化钛与SS304的粉末混合物在光纤激光器上对SS304衬底进行激光包覆。利用Taguchi信噪比方法对得到的包覆层微观硬度和包厚度进行分析,得到了最优的参数组合。并利用人工神经网络(ANN)对比分析得到与Taguchi方法不同的最优组合,但二种方法得到的包覆层厚度和微观硬度几乎是相同的,包覆层微观硬度(HV_(0.5)121)是SS304衬底硬度(HV_(0.5)752)的6倍多。氮化物陶瓷的存在导致了更高的微观硬度,包覆层表面无裂缝和孔隙,平均包覆层厚度达0.6 mm。

关键词：激光包覆 Taguchi正交设计人工神经网络微观硬度显微结构

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Dual-Core Photonic Crystal Fiber Plasmonic Refractive Index Sensor: A Numerical Analysis

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Photonic Sensors 2019年第2期9卷 151-161页

作者： alok kumar PAUL Ajay Krishno SARKAR Department of Electrical & Electronic Engineering Rajshahi University of Engineering & Technology Rajshahi-6204 Bangladesh

A numerical analysis on dual core photonic crystal fiber (DC-PCF) based surface plasmon resonance (SPR) refractive index sensor is presented. The guiding parameters and required sensing performances are examined with finite element method (FEM) based software under MATLAB environment. According to simulation, it is warranted that the proposed refractive index sensor offers the maximum amplitude sensitivity of 554.9 refractive index unit (RIU-1) and 636.5 RIU 1 with the maximum wavelength sensitivity of 5800nm/RIU and 11 500nm/RIU, and the sensor resolutions of 1.72 ×10^-5RIU and 8.7× 10^-6 RIU, at analyte refractive index (RI) of 1.40 for x- and y-polarized modes, respectively. As the sensing performance in different wavelength ranges is quite high, the proposed sensor can be used in simultaneous detection for different wavelength ranges. Therefore, the proposed device is of a suitable platform for detecting biological, chemical, biochemical, and organic chemical analytes.

关键词： Photonic crystal fiber biosensor refractive index sensor finite element method plasmonic material

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Ferroelectric composite-based piezoelectric energy harvester for selfpowered detection of obstructive sleep

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Journal of Materiomics 2023年第4期9卷 609-617页

作者： Swati Panda Hyoju Shin Sugato Hajra Yumi Oh Wonjeong Oh Jeonghyeon Lee P.M.Rajaitha Basanta kumar Panigrahi Jyoti Shukla alok kumar Sahu Perumal Alagarsamy Hoe Joon Kim Department of Robotics and Mechatronics Engineering Daegu Gyeongbuk Institute of Science and Technology(DGIST)Daegu42988South Korea Department of Electrical Engineering Siksha‘O’Anusandhan UniversityBhubaneswar751030India Department of Electrical Engineering Poornima College of EngineeringJaipur303903India Department of Physics Indian Institute of Technology-GuwahatiAssam781039India Robotics and Mechatronics Research Center Daegu Gyeongbuk Institute of Science and Technology(DGIST)Daegu42988South Korea

Lead-free piezoelectric ceramic is a promising material for energy harvesters,as they have superior electromechanical,ferroelectric,and piezoelectric *** addition,piezoelectric ceramics can be blended with polymer to achieve high-flexibility polymer-ceramic composites,providing mechanical robustness and *** this context,a new lead-free ferroelectric material,having the chemical formula SrTi_(2)O_(5)(STO),was synthesized using a high-temperature solid-state *** analyses of the structural,morphological,and electrical properties of the synthesized material were *** crystallizes with orthorhombic symmetry and space group of *** frequency and temperature-dependent dielectric parameters were evaluated,and impedance spectroscopy shed light on the charge *** PDMS-STO composites at different mass fraction of the STO were prepared using a solvent casting route,and a corresponding piezoelectric nanogenerator(PENG)was *** electrical output of the different PENG by varying massfractions of STO in PDMS and varying force were *** 15%(in mass)PENG device delivered the highest peak-to-peak voltage,current,and power density of 25 V,92 nA,and 0.64 mW@500 MU,*** biomechanical energy harvesting using the PENG device by daily human motions,bending of the device,and attaching the device to laboratory equipment was *** the PENG device was attached to the human throat region,and snoring signals were recorded.A classification model was designed employing the convolutional neural network(CNN)*** have been laid to differentiate between normal and abnormal snores,which could help the patient with screening and early disease detection,contributing to self-powered healthcare applications.

关键词： Lead-free Ferroelectric Nanogenerator Sleepdisorder

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