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Multi-objective optimization of the cathode catalyst layer micro-composition of polymer electrolyte membrane fuel cells using a multi-scale,two-phase fuel cell model and data-driven surrogates

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Journal of Energy Chemistry 2023年第6期81卷 28-41,I0003页

作者： Neil Vaz Jaeyoo Choi Yohan cha Jihoon Kong Yooseong Park Hyunchul Ju Department of Mechanical Engineering Inha University100 Inha-ro Michuhol-GuIncheon 22212Republic of Korea

Polymer electrolyte membrane fuel cells(PEMFCs)are considered a promising alternative to internal combustion engines in the automotive *** commercialization is mainly hindered due to the cost and effectiveness of using platinum(Pt)in *** cathode catalyst layer(CL)is considered a core component in PEMFCs,and its composition often considerably affects the cell performance(V_(cell))also PEMFC fabrication and production(C_(stack))*** this study,a data-driven multi-objective optimization analysis is conducted to effectively evaluate the effects of various cathode CL compositions on Vcelland *** essential cathode CL parameters,i.e.,platinum loading(L_(Pt)),weight ratio of ionomer to carbon(wt_(I/C)),weight ratio of Pt to carbon(wt_(Pt/c)),and porosity of cathode CL(ε_(cCL)),are considered as the design *** simulation results of a three-dimensional,multi-scale,two-phase comprehensive PEMFC model are used to train and test two famous surrogates:multi-layer perceptron(MLP)and response surface analysis(RSA).Their accuracies are verified using root mean square error and adjusted R^(2).MLP which outperforms RSA in terms of prediction capability is then linked to a multi-objective non-dominated sorting genetic algorithmⅡ.Compared to a typical PEMFC stack,the results of the optimal study show that the single-cell voltage,Vcellis improved by 28 m V for the same stack price and the stack cost evaluated through the U.S department of energy cost model is reduced by$5.86/k W for the same stack performance.

关键词： Polymer electrolyte membrane fuel cell Surrogate modeling Multi-layer perceptron(MLP) Response surface analysis(RSA) Non-dominated sorting genetic algorithmⅡ(NSGAⅡ)

Gastrointestinal and hepatic manifestations of COVID-19:A comprehensive review

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World Journal of Gastroenterology 2020年第19期26卷 2323-2332页

作者： Ming Han cha Miguel Regueiro Dalbir S Sandhu Department of Internal Medicine Cleveland ClinicAkron GeneralAkronOH 44307United States Department of Gastroenterology Hepatology and NutritionDigestive Disease and Surgery InstituteCleveland ClinicClevelandOH 44307United States

The severe acute respiratory syndrome-coronavirus-2(SARS-CoV-2)that causes coronavirus disease-2019(COVID-19)is a global pandemic,manifested by an infectious *** patients primarily present with fever,cough and dyspnea,some patients also develop gastrointestinal(GI)and hepatic *** most common GI symptoms reported are diarrhea,nausea,vomiting,and abdominal *** chemistry abnormalities are common and include elevation of aspartate transferase,alanine transferase,and total *** have shown that SARS-CoV-2 infects the GI tract via its viral receptor angiotensin converting enzyme Ⅱ,which is expressed on enterocytes of the ileum and *** RNA has also been isolated from stool specimens of COVID-19 patients,which raised the concern for fecal-oral transmission in addition to droplet *** indirect evidence has suggested possible fecal-oral transmission of SARS-CoV-2,more effort is needed to establish the role of the fecal-oral transmission *** research will help elucidate the association between patients with underlying GI diseases,such as chronic liver disease and inflammatory bowel disease,and severity of *** this review,we summarize the data on GI involvement to date,as well as the impact of COVID-19 on underlying GI diseases.

关键词： COVID-19 SARS-CoV-2 Gastrointestinal Liver Diarrhea Inflammatory bowel disease

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弯曲方管内爆燃向爆震转变特性

航空动力学报 2014年第8期29卷 1796-1801页

作者：王玮邱华范玮熊姹西北工业大学动力与能源学院西安710072

为缩短爆震管轴向尺寸,采用曲管爆震管替代直管爆震管.基于弯曲方管实验器,进行了二维数值仿真计算,研究了点火位置、点火能量及弯曲段曲率半径对爆震波形成及传播的影响规律.数值模拟结果表明:爆燃向爆震转变(DDT)时间随弯曲段曲率半... 详细信息

为缩短爆震管轴向尺寸,采用曲管爆震管替代直管爆震管.基于弯曲方管实验器,进行了二维数值仿真计算,研究了点火位置、点火能量及弯曲段曲率半径对爆震波形成及传播的影响规律.数值模拟结果表明:爆燃向爆震转变(DDT)时间随弯曲段曲率半径增大而减小,DDT距离在弯曲段曲率半径最大时达到最小值;点火能量越大,爆震管内激波强度越大,DDT时间越小;在距离爆震管进口300mm处点火时,爆震管内爆震波压力峰值最大,DDT时间最短.

关键词：爆震爆燃爆燃向爆震转变弯曲方管脉冲爆震发动机

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U型方管中爆燃向爆震转变特性实验研究

航空学报 2015年第6期36卷 1788-1794页

作者：邱华王玮范玮熊姹西北工业大学动力与能源学院西安710072

以脉冲爆震发动机(PDE)用曲管爆震燃烧室为应用背景,对气相(乙烯/空气)燃烧波在U型方管实验器中的传播过程进行了实验研究。通过改变实验器中弯曲段进口气流入射激波强度,基于弯曲段内压力、波速的测量及高速摄影实验得到了U型方管实验... 详细信息

以脉冲爆震发动机(PDE)用曲管爆震燃烧室为应用背景,对气相(乙烯/空气)燃烧波在U型方管实验器中的传播过程进行了实验研究。通过改变实验器中弯曲段进口气流入射激波强度,基于弯曲段内压力、波速的测量及高速摄影实验得到了U型方管实验器中半圆型弯段内的爆燃向爆震转变(DDT)特性。结果表明,弯曲段中DDT特性受到入射激波速度的影响:当入射激波速度小于794m/s(43.6%VCJ,VCJ为理论chapman-Jouguet爆震波速),在弯曲段内不能形成爆震;当入射激波速度介于870~908m/s(47.8%VCJ^50.0%VCJ)之间,弯曲段内首先会产生局部爆炸,并最终形成爆震;当入射激波速度大于934m/s(51.3%VCJ),爆燃波可以直接在弯曲段入口转化为爆震波。

关键词：爆震爆燃向爆震转变 U型方管脉冲爆震发动机曲管爆震燃烧室

Verification of SPE probability forecasts at the Space Environment Prediction Center(SEPC)

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Science China Earth Sciences 2016年第6期59卷 1292-1298页

作者： CUI YanMei LIU SiQing A Er cha ZHONG QiuZhen LUO BingXian AO XianZhi National Space Science Center Chinese Academy of Sciences

In space weather forecasting, forecast verification is necessary so that the forecast quality can be assessed. This paper provides an example of how to choose and devise verification methods and techniques according to different space weather forecast products. Solar proton events(SPEs) are hazardous space weather events, and forecasting them is one of the major tasks of the Space Environment Prediction Center(SEPC) at the National Space Science Center of the Chinese Academy of Sciences. Through analyzing SPE occurrence characteristics, SPE forecast properties, and verification requirements at SEPC, verification methods for SPE probability forecasts are identified, and verification results obtained. Overall, SPE probability forecasts at SEPC exhibit good accuracy, reliability, and discrimination. Compared with climatology and persistence forecasts, the SPE forecasts are more accurate. However, the forecasts for SPE onset days are substantially underestimated and need to be considerably improved.

关键词： Forecast verification SPE forecast SPE onset days Space weather forecasting

Sea level anomalies in the northwestern Pacific during 2011 associated with La Nina and negative Indian Ocean Dipole

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Acta Oceanologica Sinica 2019年第11期38卷 62-69页

作者： Fuwen Qiu Yun Qiu Aijun Pan Jing cha Shanwu Zhang Third Institute of Oceanography Ministry of Natural ResourcesXiamen 361005China Laboratory for Regional Oceanography and Numerical Modeling Pilot National Laboratory for Marine Science and Technology(Qingdao)Qingdao 266237China

The sea level anomalies(SLAs)pattern in the northwestern Pacific delineated significant differences between La Ni?a events occurring with and without negative Indian Ocean Dipole(IOD)*** the pure La Ni?a events,positive the sea surface level anomalies(SLAs)appear in the northwestern Pacific,but SLAs are weakened and negative SLAs appear in the northwestern Pacific under the contribution of the negative IOD events in 2010/*** negative IOD events can trigger significant westerly wind anomalies in the western tropical Pacific,which lead to the breakdown of the pronounced positive SLAs in the northwestern ***,negative SLAs excited by the positive wind stress curl near the dateline propagated westward in the form of Rossby waves until it approached the western Pacific boundary in mid-2011,which maintained and enhanced the negative phase of SLAs in the northwestern Pacific and eventually,it could significantly influence the bifurcation and transport of the North Equatorial Current(NEC).

关键词： sea level anomalies La Nina negative IOD northwestern Pacific

Effects of homogenization temperature on microstructure and mechanical properties of high-speed-extruded Mg–5Bi–3Al alloy

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Journal of Magnesium and Alloys 2022年第10期10卷 2833-2846页

作者： Jae Won cha Sang-Cheol Jin Jae-Gil Jung Sung Hyuk Park School of Materials Science and Engineering Kyungpook National University80 DaehakroDaegu 41566Republic of Korea Advanced Metals Division Korea Institute of Materials ScienceChangwon 51508Republic of Korea

This study investigates the effects of billet homogenization temperature on the dynamic recrystallization behavior during high-speed extrusion and resultant microstructure and tensile properties of the Mg–5Bi–3Al(BA53,wt%)*** billets homogenized at 350 and450℃(350H and 450H billets)are extruded at a high speed of 69 m/*** 350H billet has a relatively smaller grain size and a higher abundance of fine Mg3Bi2particles compared to the 450H *** extrusion of the 350H billet,enhanced dynamic recrystallization occurs as a result of its finer grains and abundance of particles,while the growth of recrystallized grains is suppressed by the grain-boundary pinning effect of ***,the extruded 350H material is characterized by smaller grains,relatively greater number of Mg3Bi2particles,and a higher internal strain energy than the extruded 450H *** tensile strength of the extruded 350H material is higher than that of the extruded 450H material owing to stronger grain-boundary hardening,particle hardening,and strain hardening *** extruded 350H material also exhibits a higher tensile elongation as its smaller grains inhibit the formation of crack-inducing undesirable twins during *** results from this study demonstrate that a decrease in the homogenization temperature from 450 to 350℃leads to improved strength and ductility in the high-speed-extruded BA53 material.

关键词： Mg–Bi–Al alloy High-speed extrusion Homogenization Dynamic recrystallization Tensile properties

A Regional Economy's Resistance to the COVID-19 Shock: Sales Revenues of Micro-, Small-, and Medium-Sized Enterprises in South Korea

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International Journal of Disaster Risk Science 2022年第2期13卷 190-198页

作者： Seong-Jin Lee Joong-Hoo Park Seung-Min cha Donghyun Kim Department of Public Policy and Management.Pusan National University Busan 46241South Korea Department of Urban Planning and Engineering Pusan National UniversityBusan 46241South Korea

The coronavirus disease 2019(COVID-19) is a global pandemic that has heavily impacted not only the health sector, but also the economic sector in *** countries have projected a negative economic impact, and the effect on micro-, small-, and medium-sized enterprises(MSMEs) is predicted to be significantly *** study estimated the regional resistance of MSME sales revenues and identified the regional economic factors that affect resistance by analyzing South Korea, a country with one of the lowest economic impact projections from COVID-19. Resistance was estimated by comparing sales revenues and changes in resistance observed during the early COVID-19 period to those recorded in the same weeks(weeks 6 to 9) of 2019. The factors that affect regional resistance were determined by conducting robust regression and spatial regression analyses. The results show that the number of confirmed COVID-19 cases, a direct risk factor, is negatively related to regional resilience, while diversity is positively related to regional resistance. To improve the regional resistance against uncertain events, this study recommends increased diversity among regional industrial structures to reduce the duration of the early shock of an unexpected adverse event.

关键词： COVID-19 Economic resistance MSMEs South Korea

Highly flexible conductive fabrics with hierarchically nanostructured amorphous nickel tungsten tetraoxide for enhanced electrochemical energy storage

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Nano Research 2015年第12期8卷 3749-3763页

作者： Goli Nagaraju Ramesh Kakarla Sung Min cha Jae Su Yu Department of Electronics and Radio Engineering Institute for Wearable Convergence Electronics Kyung Hee University 1 Seocheon-dong Giheung-gu Yongin-si Gyeonggi-do 446-701 Republic of Korea Department of Environmental Science and Engineering Kyung Hee University 1Seocheon-dong Giheung-gu Yongin-si Gyeonggido 446-701 Republic of Korea

Amorphous nickel tungsten tetraoxide （NiWO4） nanostructures （NSs） were successfully synthesized on a flexible conductive fabric （CF） using a facile one- step electrochemical deposition （ED） method. With an applied external cathodic voltage （-1.8 V for 15 min）, the amorphous NiWO4 NSs with burl-like morphologies adhered well on the seed-coated CF substrate. The burMike amorphous NiWO4 NSs on CF （NiWO4 NSs/CF） are employed as a flexible and binder-free electrode for pseudocapacitors, which exhibit remarkable electrochemical properties with high specific capacitance （1,190.2 F/g at 2 A/g）, excellent cyclic stability （92% at 10 A/g）, and good rate capability （765.7 F/g at 20 A/g） in 1 M KOH electrolyte solution. The superior electrochemical properties can be ascribed to the hierarchical structure and large specific surface area of the burl-like amorphous NiWO4 NSs/CF. This cost-effective facile method for the synthesis of metal tungsten tetraoxide nanomaterials on a flexible CF could be promising for advanced electronic and energy storage device applications.

关键词： amorphous NiWO4 nanostructures conductive fabrics electrochemical deposition electrochemical energystorage properties