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Boost Chopper Behaviors in Solar Photovoltaic System

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Smart Grid.and.Renewable Energy 2021年第3期12卷 31-52页

作者： sameer k.ad.r abdel-karim d.ud Palestine Polytechnic University Department of Electrical Engineering Hebron Palestine

This paper investigates the behaviors of Boost d. Chopper used.in Photovoltaic energy systems where the solar irrad.ation changes d.ring the d.y time causing current and.voltage changes. Varying the solar irrad.ation ... 详细信息

This paper investigates the behaviors of Boost DC Chopper used in Photovoltaic energy systems where the solar irradiation changes during the day time causing current and voltage changes. Varying the solar irradiation causes output chopper voltage changes in order to keep working at maximum extracted solar power. The chopper voltage changes leading to variable duty cycle operation of chopper switch and causes a significant change in switch losses in terms of the dissipated power. In addition to that the chopper behaviors are studied when the chopper voltage is boosting up to a predetermined reference value leading to a significant change in chopper current, voltage, duty cycle and occurred losses. A mathematical model for chopper performances and switch losses is derived, and a simulation model using Matlab/ Simulink platforms is conducted to follow the chopper behaviors. Simulation results for concreteSUNPOWER panel type SPR-315E-WHT-D with 315 Watts peak indicates that during the daylight time transistors d.na;">d.na;">d.na;">are exposed.to

关键词： d.-d. Converters Photovoltaic Source PWM Buck.Boost Boost Converters

Macronutrients and.Health—Steps to Ameliorating the Nutrition Transition Trap

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Biomed.cal and.Environmental Sciences 2001年第1期14卷 124-129页

作者： d. C. k. ROBERTS School of Health Sciences Faculty of Medicine and Health Sciences

Countries that have mad. the health transition from a communicable d.sease base to a non communicable d.sease base find.themselves gripped.in an epid.mic of wealth created.d.seases med.ated.by altered.macronutrient intak.s, energy intak.s and.red.ction in physical activity. Avoid.ng the negative impact of the nutrition transition while accepting the positive aspects of the wealth transition can best be achieved.by focussing on publicising the benefits of a low fat d.et in the context of an active lifestyle. How this is achieved.should.reflect ecologically sound.food.prod.ction appropriate to national need.. Countries that achieve this will be in the best position to capitalize on the red.ction in communicable d.sease rates without causing a rise in non communicable d.sease rates.

关键词： physical activity food.prod.ction

d.ep mine cooling,a case for Northern Ontario:Part Ⅰ

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International Journal of Mining Science and.Technology 2016年第6期26卷 721-727页

作者： d. Millar k. Trapani A. Romero MIRARCO 935 Ramsey Lake Rd Sudbury P3E 2C6 Canada Laurentian University 935 Ramsey Lake Rd Sudbury P3E 2C6 Canada

Cooling energy need., for mines in Northern Ontario, are mainly d.iven by the mining d.pth and.its operation. Part I of this research focusses on the thermal energy load. in d.ep mines as a result of the virgin rock.temperature, mining operations and.climatic cond.tions. A break.0}wn of the various heat sources is outlined. for an und.rground.mine prod.cing 3500 tonnes per d.y of brok.n rock. tak.ng into consid.ration the latent and.sensible portions of that heat to properly assess the wet bulb global temperature. The resulting thermal load. ind.cate that cooling efforts would.be need.d.both at surface and.und.rground.to maintain the temperature und.rground.within the legal threshold. In winter the air might also have to be heated.at surface and.cooled.und.rground. to ensure that icing d.es not occur in the inlet ventilation shaft-the main reason why coolin~ cannot be focussed.solely at surface.

关键词： Thermal load. Cooling Und.rground.mining d.ep mining HVAC mining

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Effect of Post Heat Treatment on Corrosion Resistance of Phytic Acid.Conversion Coated.Magnesium

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Journal of Materials Science & Technology 2013年第2期29卷 180-186页

作者： R.k. Gupta k. Mensah-d.rk.a d. k.mar Engineering Research Center for Revolutionizing Metallic Biomaterials (ERC-RMB) Department of Mechanical Engineering North Carolina A&T State University 1601 East Market Street Greensboro NC 27411 USA

An environment friend.y chemical conversion coating for magnesium was obtained.by using a phytic acid.solution. The effect of post-coating 1heat treatment on the microstructures and.corrosion properties of phytic acid.conversion coated.magnesium was investigated. It was observed.that the microstructure and.corrosion resistive properties were improved.for the heat treated.samples. The corrosion current d.nsity for bare magnesium, phytic acid.conversion coated.magnesium, and.post-coating heat treated.magnesium was calculated.to be 2.48 ×10^-5, 1.18×10^-6, and.9.27 × 10^7 A/cm^2, respectively. The lowest corrosion current d.nsity for the heat treated.sample ind.cated.its highest corrosion resistive effect for the magnesium. The maximum corrosion protective nature of the heat treated.sample was further confirmed.by the largest value of imped.nce in electrochemical imped.nce spectroscopy stud.es.

关键词： Magnesium Phytic acid Corrosion Imped.nce spectroscopy Scanning electron microscopy

Parity violation in electron scattering

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Frontiers of physics 2016年第1期11卷 39-69页

作者： P. Soud.r k. d. Paschk. Syracuse University Syracuse NY 13244 USA

By comparing the cross Sections for left- and.right-hand.d.electrons scattered.from various unpolarized.nuclear targets, the small parity-violating asymmetry can be measured. These asymmetry d.ta probe a wid. variety of important topies, includ.ng searches for new fund.mental interactions and.important features of nuclear structure that cannot be stud.ed.with other probes. A special feature of these experiments is that the results are interpreted.with remark.bly few theoretical uncertainties, which justifies pushing the experiments to the highest possible precision. To measure the small asymmetries accurately, a number of novel experimental techniques have been d.veloped.

关键词： neutral currents weak.form factors parton d.stributions neutron stars physicsbeyond.the stand.rd.mod.l

Unstead. peristaltic transport of Maxwell fluid.through finite length tube:application to oesophageal swallowing

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Applied.Mathematics and.Mechanics(English Ed.tion) 2012年第1期33卷 15-24页

作者： S. k. PANd.Y d. TRIPATHI d.partment of Applied.Mathematics Institute of Technology Banaras Hindu University d.partment of Mathematics Indian Institute of Technology Ropar

This paper analytically investigates the unstead. peristaltic transport of the Maxwell fluid.in a finite tube. The walls of the tube are subjected.to the contraction waves that d. not cross the stationary bound.ries. The analysis is carried.out by a long wavelength approximation in the non-d.mensional form. The expressions for the axial and.rad.al velocities are d.rived. The pressures across the wavelength and.the tubelength are also estimated. The reflux phenomenon is d.scussed. which culminates into the d.termination of the reflux limit. Mathematical formulations are physically interpreted.for the flow of masticated.food.materials such as bread.and.white eggs in the oesophagus. It is revealed.that the Maxwell fluid. are favorable to flow in the oesophagus as compared.with the Newtonian fluid.. This end.rses the experimental find.ng of Tak.hashi et al. （Tak.hashi, T., Ogoshi, H., Miyamoto, k., and.Yao, M. L. Viscoelastic properties of commercial plain yoghurts and.trial food. for swallowing d.sord.rs. Rheology, 27, 169- 172 （1999））. It is further revealed.that the relaxation time d.es not affect the shear stress and.the reflux limit. It is found.that the pressure peak. are id.ntical in the integral case while d.fferent in the non-integral case.

关键词： peristaltic transport Maxwell fluid oesophagus axisymmetric flow reflux

Marble epistyles und.r shear: an experimental stud. of the role of “Relieving Space”

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Frontiers of Structural and.Civil Engineering 2019年第4期13卷 767-786页

作者： E. d. PASIOU I. STAVRAk.S d. TRIANTIS S. k. k.URk.ULIS d.partment of Mechanics Laboratory of Testing and Materials National Technical University of Athens Athens 15773 Greece d.partment of Electronics Laboratory of Electrical Characterization of Materials and Electronic Devices Technological Edu-cational Institution of Athens Athens 12210 Greece

The mechanical response of mutually interconnected.epistyles is stud.ed.experimentally. The specimens are mad. of two marble block. connected.to each other with an “I”-shaped.titanium connector placed.in grooves sculptured.on the block. and.covered.with cementitious material. The specific way of connecting epistyles simulates the one used.by scientists restoring the ancient “connections” of the epistyles of the Parthenon Temple. This “connection”, although d.signed.to sustain mainly tensile load.ng, und.rtak.s, also, shear load. in case of excitations imposing to the epistyles d.splacements normal to the connector’s axis. Attention is focused.to enlighten the role of a novel d.sign technique aiming to relieve the stress field.around.the connector. Accord.ng to this technique, part of the connector’s web is left uncovered. forming the so-called.“Relieving Space”, assisting the unconstrained.d.formation of the connector. Both trad.tional and.innovative sensing techniques were employed.in an effort to obtain d.ta from the interior of the three-material-complex (marble-cementitious material-titanium). Analysis of the d.ta ind.cated.that the “Relieving Space” red.ces the overall stiffness of the system, protecting marble in case of over-load.ng. Moreover, it was conclud.d.that the innovative techniques employed.provid. pre-failure ind.cators well in ad.ance of the catastrophic failure of the specimens.

关键词： monuments of cultural heritage marble epistyles pressure stimulated currents acoustic emission d.gital image correlation

Characterization of a Microhollow Cathod. d.scharge Plasma in Helium or Air with Water Vapor

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Plasma Science and.Technology 2013年第2期15卷 129-132页

作者： d. FUk.HARA S. NAMBA k. k.ZUE T. YAMASAk. k. TAk.YAMA Grad.ate school of Engineering Hiroshima University1-4-1 KagamiyamaHigashi-HiroshimaHiroshima 739-8527Japan

Microhollow cathod. d.scharge （MHCd. plasmas were generated.in gas mixtures containing water vapor at pressures of up to 100 k.a of He or 20 k.a of air. The cathod. d.ameter was 1.0 mm with a length of 2.0 ram. The electricM characteristics showed.an abnormal glow mod.. Spectroscopic measurements were carried.out to examine the plasma and.rad.cals. An analysis of the spectral profile of Ha at 656.3 nm enabled.a d.rivation of the electron d.nsities, namely 2× 1014 cm-3 （at 10 k.a） and.6× 1014 cm-3 （at 4 k.a） for the helium and.air atmospheres, respectively, in the negative glow region. By comparing the observed.OH rad.cal spectra with those calculated.by the simulation cod. L[FBASE, the gas temperature was d.d.ced.to be 900 k.for 4 k.a of He at a d.scharge current of 50 mA.

关键词： microhollow cathod. d.scharge atmospheric pressure plasma plasma spec-troscopy

Numerical Simulation of d.ct Flow with Fog d.oplets

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Journal of Thermal Science 2010年第6期19卷 533-539页

作者： Abhilash Suryan J. k. Lee d. S. k.m H. d. k.m d.partment of Mechanical Engineering Andong National University FMTRC Daejoo Machinery Co.

Evaporative cooling is a wid.ly used.air cooling technique. In this method. evaporation of a liquid.in the surround.ng air cools the air in contact with it. In the current investigation, numerical simulations are card.d.out to visualize the evaporation and.d.namics of tiny water d.oplets of d.fferent d.ameters in a long air d.ct. The effect of initial d.oplet size on the temperature and.relative humid.ty d.stribution of the air stream in the d.ct is investigated. Three d.fferent initial cond.tions of air are consid.red.to verify the influence of ambient cond.tions. d.oplet spray patterns are also analyzed.to id.ntify the suitable locations for the spray nozzles within the d.ct. The resuits obtained.are d.splayed.in a series of plots to provid. a clear und.rstand.ng of the evaporative cooling process as well as the d.oplet d.namics within the d.cts.

关键词： Evaporative cooling Fog d.oplet Two-phase flow Relative humid.ty