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Extraction of locked-up coal by strengthening of rib pillars with FRP--A comparative study through numerical modelling

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International Journal of Mining Science and Technology 2017年第2期27卷 261-267页

作者： das arka Jyoti Mandal Prabhat Kumar Ghosh Chandra Nath Sinha Amalendu CSIR-Central Institute of Mining and Fuel Research Dhanbad 826001India

In some of the coalfields in India, coal seams are only developed but no extraction of pillars is possible due to the presence of surface or sub-surface structures and also non-availability of stowing materials which leads to huge amounts of coal being locked-up underground. Spontaneous heating and fire, accumulation of poisonous gases, severe stability issues leading to unsafe workings and environmental hazards are the major problems associated with the developed coal pillars. So, there is a pressing need for a technology for the mining industry to extract the huge amount of coal locked-up under different constraints. In this study, the locked-up coal is proposed to be extracted by artificially strengthening the rib pillars. The detailed comparative study is carried out to know the increase of extraction percentage of locked-up coal by strengthening the rib pillars with FRP. Extraction methodology is designed and studied through numerical modelling for its stability analysis to evaluate its suitability of application in underground.

关键词： Locked-up coal Confined core Yield criterion Strengthened rib pillar Strain softening

Real-Time Thermomechanical Modeling of PV Cell Fabrication via a POD-Trained RBF Interpolation Network

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Computer Modeling in Engineering & Sciences 2020年第3期122卷 757-777页

作者： arka das Anthony Khoury Eduardo Divo Victor Huayamave AndresCeballos Ron Eaglin Alain Kassab Adam Payne Vijay Yelundur Hubert Seigneur Embry-Riddle Aeronautical University Department of Mechanical Engineering1 Aerospace Blvd.Daytona BeachFL 32114USA. Central Technological Corporation LongwoodFL 32779USA. University of Central Florida Department of Mechanical and Aerospace Engineering4000 Central Florida Blvd.OrlandoFL 32816USA. Suniva Inc. 5765 Peachtree Industrial Blvd.NorcrossGA 30092USA. Florida Solar Energy Center University of Central FloridaCocoa BeachFL 32922USA.

This paper presents a numerical reduced order model framework to simulate the physics of the thermomechanical processes that occur during c-Si photovoltaic(PV)cell fabrication.A response surface based on a radial basis function(RBF)interpolation network trained by a Proper Orthogonal Decomposition(POD)of the solution fields is developed for fast and accurate approximations of thermal loading conditions on PV cells during the fabrication *** outcome is a stand-alone computational tool that provides,in real time,the quantitative and qualitative thermomechanical response as a function of user-controlled input parameters for fabrication processes with the precision of 3D finite element analysis(FEA).This tool provides an efficient and effective avenue for design and optimization as well as for failure prediction of PV cells.

关键词： Silicon wafers photovoltaic cell contact firing proper orthogonal decomposition radial basis functions.

Scalable orthogonal delay-division multiplexed OEO artificial neural network trained for TI-ADC equalization

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Photonics Research 2024年第1期12卷 85-105页

作者： ANDREA ZAZZI arka DIPTA das LUKAS HüSSEN RENATO NEGRA JEREMY WITZENS Institute of Integrated Photonics RWTH Aachen University52074 AachenGermany Chair of High-Frequency Electronics RWTH Aachen University52074 AachenGermany

We propose a new signaling scheme for on-chip optical-electrical-optical artificial neural networks that utilizes orthogonal delay-division multiplexing and pilot-tone-based self-homodyne *** scheme offers a more efficient scaling of the optical power budget with increasing network *** simulations,based on220 nm silicon-on-insulator silicon photonics technology,suggest that the network can support 31×31 neurons,with 961 links and freely programmable weights,using a single 500 m W optical comb and a signal-to-noise ratio of 21.3 d B per ***,it features a low sensitivity to temperature fluctuations,ensuring that it can be operated outside of a laboratory *** demonstrate the network’s effectiveness in nonlinear equalization tasks by training it to equalize a time-interleaved analog-to-digital converter(ADC)architecture,achieving an effective number of bits over 4 over the entire 75 GHz ADC *** anticipate that this network architecture will enable broadband and low latency nonlinear signal processing in practical settings such as ultra-broadband data converters and real-time control systems.

关键词： network delay artificial

Polarization-controlled optical holography using flat optics

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Light(Science & Applications) 2020年第1期9卷 724-725页

作者： arka Majumdar Shane Colburn Electrical and Computer Engineering University of WashingtonSeattleWA 98195USA

Due to the large number of degrees of freedom offered by nanoscale scatterers,a single flat optic can project different images at different distances depending on the polarization of the light,opening up opportunities... 详细信息

关键词： Polarization optics flat

Synthesis of Nanocrystalline FeS_2 with Increased Band Gap for Solar Energy Harvesting

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Journal of Materials Science & Technology 2014年第8期30卷 770-775页

作者： Somnath Middya Animesh Layek arka Dey Partha Pratim Ray Department of Physics Jadavpur University

In this paper,we have reported the synthesis of FeS2 of higher band gap energy（2.75 eV） by using capping reagent and its successive application in organic-inorganic based hybrid solar *** route was adopted for preparing iron pyrite（FeS2） nanoparticles with capping reagent *** quality of synthesized FeS2 material was confirmed by X-ray diffraction,field emission scanning electron microscopy,transmission electron microscopy,Fourier transform infrared,thermogravimetric analyzer,and Raman *** optical band gap energy and electro-chemical band gap energy of the synthesized FeS2 were investigated by UV-vis spectrophotometry and cyclic *** band gap engineered FeS2 has been successfully used in conjunction with conjugated polymer MEHPPV for harvesting solar *** energy conversion efficiency was obtained as 0.064%with a fill-factor of 0.52.

关键词： Hydrothermal synthesis FeS2 nanoparticles Optical characterization Energy band gap

MEMS-actuated metasurface Alvarez lens

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Microsystems & Nanoengineering 2020年第1期6卷 334-344页

作者： Zheyi Han Shane Colburn arka Majumdar Karl F.Bohringer Department of Electrical and Computer Engineering University of WashingtonSeattleWashington 98195USA Institute for Nano-Engineered Systems University of WashingtonSeattleWashington 98195USA Department of Physics University of WashingtonSeattleWashington 98195USA Department of Bioengineering University of WashingtonSeattleWashington 98195USA

Miniature lenses with a tunable focus are essential components for many modern applications involving compact optical *** several tunable lenses have been reported with various tuning mechanisms,they often face challenges with respect to power consumption,tuning speed,fabrication cost,or production *** this work,we have adapted the mechanism of an Alvarez lens–a varifocal composite lens in which lateral shifts of two optical elements with cubic phase surfaces give rise to a change in the optical power–to construct a miniature,microelectromechanical system(MEMS)-actuated metasurface Alvarez *** based on an electrostatic MEMS generates fast and controllable actuation with low power *** utilization of metasurfaces–ultrathin and subwavelength-patterned diffractive optics–as optical elements greatly reduces the device volume compared to systems using conventional freeform *** entire MEMS Alvarez metalens is fully compatible with modern semiconductor fabrication technologies,granting it the potential to be mass-produced at a low unit *** the reported prototype operating at 1550 nm wavelength,a total uniaxial displacement of 6.3µm was achieved in the Alvarez metalens with a direct-current(DC)voltage application up to 20V,which modulated the focal position within a total tuning range of 68µm,producing more than an order of magnitude change in the focal length and a 1460-diopter change in the optical *** MEMS Alvarez metalens has a robust design that can potentially generate a much larger tuning range without substantially increasing the device volume or energy consumption,making it desirable for a wide range of imaging and display applications.

关键词： electrostatic optics adapted

Transcatheter pulmonic valve implantation: Techniques, current roles, and future implications

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World Journal of Cardiology 2021年第5期13卷 117-129页

作者： Mark Aaron Law arka Chatterjee Department of Pediatric Cardiology Division of CardiologyUniversity of Alabama at BirminghamBirminghamAL 35233United States Division of Cardiology University of Arizona College of MedicineTusconAZ 85724United States

Right ventricular outflow tract(RVOT)obstruction is present in a variety of congenital heart disease states including tetralogy of Fallot,pulmonary atresia/stenosis and other conotruncal abnormalities *** surgical repair,these patients develop RVOT residual abnormalities of pulmonic stenosis and/or insufficiency of their native outflow tract or right ventricle to pulmonary artery *** are also sequelae of other surgeries like the Ross operation for aortic valve disease that lead to right ventricle to pulmonary artery conduit *** pulmonic valve replacement(SPVR)has been the mainstay for these patients and is considered standard of *** pulmonic valve implantation(TPVI)was first reported in 2000 and has made strides as a comparable alternative to SPVR,being approved in the United States in *** provide a comprehensive review in this space–indications for TPVI,detailed procedural facets and up-to-date review of the literature regarding outcomes of *** has been shown to have favorable medium-term outcomes free of reinterventions especially after the adoption of the practice of pre-stenting the *** mortality and complications are *** more experience,recognition of risk of dreaded outcomes like coronary compression has ***,conduit rupture is increasingly being managed with transcatheter *** over endocarditis risk still prevail in the TPVI ***-to-head comparisons to SPVR are still limited but available data suggests *** also discuss newer valve technologies that have limited data currently and may have more applicability for treatment of native dysfunctional RVOT substrates.

关键词： Pulmonary valve Congenital heart defects Heart valve prosthesis implant Pulmonary valve insufficiency Pulmonary atresia Pulmonary valve stenosis

Charge transport properties and variable photo-switching of three-terminal Cs_(2)AgBiBr_(6) device

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Journal of Semiconductors 2024年第11期45卷 89-98页

作者： Iman Biswas arka Dey Jean Michel Nunzi Nilanjan Halder Aniruddha Mondal Department of Physics National Institute of Technology DurgapurDurgapur 713209India Department of Chemistry Queen’s UniversityKingstonOntario K7L3N6Canada Department of Physics Manipal University JaipurJaipurRajasthan 303007India

In this study,we present an in-depth exploration of charge transport phenomena and variable photo-switching characteristics in a novel double-perovskite-based three-terminal *** Cs_(2)AgBiBr_(6) thin film(TF)was synthesized through a three-step thermal evaporation process followed by precise open-air annealing,ensuring superior film quality as confirmed by structural and morphological *** spectroscopy revealed distinct emissions at 2.28 and 2.07 eV,indicative of both direct and indirect electronic *** device exhibited space-charge limited current(SCLC)behaviour beyond 0.35 V,aligning with the relationship Current(I)∝Voltage(V)^(m),where the exponent m transitioned from≤1 to>*** analysis of Schottky parameters within the trap-filled limit(TFL)regime was conducted,accounting for variations in temperature and optical ***,the self-powered photodetector demonstrated outstanding performance under *** sensitivity of the device was finely tunable via the applied bias voltages at the third ***,an optimal bias voltage of±100μV yielded maximum responsivity(R)of 0.48 A/W and an impressive detectivity(D*)of 1.07×10^(9) Jones,highlighting the potential of this double-perovskite-based device for advanced optoelectronic applications.

关键词： double-perovskite charge-transport mechanism space-charge limited current(SCLC) three-terminal device voltage-dependent photo-switching

Organic geochemical and petrographic characteristics of the Cambrian-Ordovician organic-rich marine shales in Scandinavia

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Petroleum Science 2023年第5期20卷 2637-2647页

作者： Xiao-Wei Zheng Niels-HSchovsbo Lei-Bo Bian arka Rudra Hamed Sanei Lithospheric Organic Carbon(LOC)Group Department of GeoscienceAarhus University8000Denmark Department of Reservoir Geology Geological Survey of Denmark and Greenland(GEUS)Oster Voldgade 10Dk-1350Copenhagen KDenmark Research Institute of Petroleum Exploration and Development PetroChinaBeijing 100083China

This work used organic geochemistry and organic petrology to study the depositional environment,organic matter characteristics,and thermal maturity of the Cambrian-Ordovician organic-rich marine shales in the Baltic *** main macerals in Cambrian samples include alginite,bituminite and solid bitumen,while zooclastic macerals become the major proportion of organic matter in the Ordovician *** the maturity increase,solid bitumen becomes abundant and ***-like maceral was observed only in Furongian of well DBH15/73,which probably indicates the local intrusion of Permo-Carboniferous dolerite *** programmed pyrolysis results show that immature,early mature,and over-mature samples are ***,the data of high-uranium Furongian samples were greatly altered by igneous intrusives from local *** calculation model is simulated based on pyrolysis data and fitted according to the least-square fitting *** simulated fitting HIo:400mg HC/g TOC(369.5 mg HC/g TOC,430.5 mg HC/g TOC as 95%confidence bounds)is within the worldwide marine shale HI_(o)and indicates a marine anoxia and transgressive sea with shallow water column(organofacies B).

关键词： Lower paleozoic Organic petrology Initial hydrogen index Original geochemical properties