检索结果-南通市图书馆

Mechanism and mitigation of spontaneous Ga whisker growth on Cr2GaC

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2020年第3期63卷 440-445页

作者： ZHANG PeiGen DING JianXiang LIU YuShuang YANG Li TIAN WuBian OUYANG Jian ZHANG YaMei SUN ZhengMing Jiangsu Key Laboratory of Advanced Metallic Materials School of Materials Science and EngineeringSoutheast UniversityNanjing 211189China Jiangsu Key Laboratory of Construction Materials School of Materials Science and EngineeringSoutheast UniversityNanjing 211189China

Spontaneous growth of A-element whiskers on Mn+1AXn(MAX for short) phase materials poses a barrier to their practical applications, since it casts doubts on their stability. In this study, Ga whisker growth on sintered Cr2GaC samples was investigated. The elemental source for spontaneous growth of Ga whiskers is identified as the free Ga contained in the Cr2GaC material, not the lattice atoms from Cr2GaC grains, which removes the doubts on the stability of Cr2GaC material. The growth behavior and morphologies of the Ga whiskers follow a new catalysis-based model, with cleavage planes of Cr2GaC grains involved as nucleation sites. This model explains and predicts well the growth behavior of the whiskers. The mitigation strategy based on this model is in principle simple: to prevent free Ga in Cr2GaC material or limit it to a certain level;to avoid cleavage plane of Cr2GaC grains;to achieve high density of the Cr2GaC material.

关键词： MAX phase whisker growth nucleation model mitigation strategy

mitigation of greenhouse gases released from mining activities:A review

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2021年第4期28卷 513-521页

作者： Li-yuan Liu Hong-guang Ji Xiang-feng Lü Tao Wang Sheng Zhi Feng Pei Dao-lu Quan Beijing Key Laboratory of Urban Underground Space Engineering University of Science and Technology BeijingBeijing 100083China School of Civil and Resource Engineering University of Science and Technology BeijingBeijing 100083China Department of Energy and Mineral Engineering EMS Energy Institute and G3 CenterPennsylvania State UniversityUniversity ParkPA 16802USA

Climate changes that occur as a result of global warming caused by increasing amounts of greenhouse gases(GHGs)released into the atmosphere are an alarming *** greenhouse gas emissions is critically important for the current and future status of mining *** mining industry is one of the significant contributors of greenhouse *** essence,anthropogenic greenhouse gases are emitted directly during the actual mining and indirectly released by the energy-intensive activities associated with mining equipment,ore transport,and the processing ***,we reviewed both direct and indirect GHG emissions to analyze how mining contributes to climate *** addition,we showed how climate change impacts mineral *** assessment was performed using a GHG inventory model for the gases released from mines undergoing different product life *** also elucidate the key issues and various research outcomes to demonstrate how the mining industry and policymakers can mitigate GHG emission from the mining *** review concludes with an overview of GHG release reduction and mitigation strategies.

关键词： greenhouse gas emission greenhouse gas reduction mining climate change life cycle assessment mitigation strategy

Mechanisms of Accelerated Degradation in the Front Cells of PEMFC Stacks and Some mitigation Strategies

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2013年第6期26卷 1250-1258页

作者： LI Pengcheng PEI Pucheng HE Yongling YUAN Xing CHAO Pengxiang WANG Xizhong School of Transportation Science and Engineering Beihang University State Key Laboratory of Automotive Safety and Energy Tsinghua University

The accelerated degradation in the front ceils of a polymer electrolyte membrane fuel cell（PEMFC） stack seriously reduces the reliability and durability of the whole stack. Most researches only focus on the size and configuration of the gas intake manifold, which may lead to the maldistribution of flow and pressure. In order to find out the mechanisms of the accelerated degradation in the front cells, an extensive program of experimental and simulation work is initiated and the results are reported. It is found that after long-term lifetime tests the accelerated degradation in the front cells occurs in all three fuel cell stacks with different flow-fields under the U-type feed configuration. Compared with the rear cells of the stack, the voltage of the front cells is much lower at the same current densities and the membrane electrode assembly（MEA） has smaller active area, more catalyst particle agglomeration and higher ohmic impedance. For further investigation, a series of three dimensional isothermal numerical models are built to investigate the degradation mechanisms based on the experimental data. The simulation results reveal that the dry working condition of the membrane and the effect of high-speed gas scouting the MEA are the main causes of the accelerated degradation in the front cells of a PEM fuel cell stack under the U-type feed configuration. Several mitigation strategies that would mitigate these phenomena are presented： removing cells that have failed and replacing them with those of the same aging condition as the average of the stack; choosing a Z-type feed pattern instead of a U-type one; putting several air flow-field plates without MEA in the front of the stack; or exchanging the gas inlet and outlet alternately at a certain interval. This paper specifies the causes of the accelerated degradation in the front cells and provides the mitigation strategies.

关键词： Proton exchange membrane fuel cell Degradation mechanism mitigation strategy

Early performance of two tropical dry forest species after assisted migration to pine-oak forests at different altitudes:strategic response to climate change

在线全文

学校读者我要写书评

暂无评论

Journal of Forestry Research 2020年第4期31卷 1215-1223页

作者： Pilar Angélica Gómez-Ruiz Cuauhtémoc Sáenz-Romero Roberto Lindig-Cisneros Catedrática CONACYT Centro de Investigaciónde Ciencias Ambientales CICAFacultad de Ciencias NaturalesUniversidad Autónoma del CarmenCiudad del CarmenCampecheMexico Instituto de Investigaciones Agropecuarias y Forestales Universidad Michoacana de San Nicolás de Hidalgo(IIAFUMSNH)MoreliaMexico Instituto de Investigaciones en Ecosistemas y Sustentabilidad(IIES) Universidad Nacional Autónoma de MéxicoCampus MoreliaMoreliaMexico

Assisted migration has been proposed as a strategy for adaptive management of forest species in response to expected effects of climate change,but it is controversial for several *** dry forests are among the most threatened ecosystems in the *** Mexico,historically,land-use change and deforestation have been decreasing forest cover,and climate change is shifting the potential distribution of different forest types,exacerbating the risk of local *** altitudinal migration could be a feasible strategy for reducing local extinctions in response to climate change and lack of landscape *** objective was to evaluate survival and growth of Albizia plurijuga and Ceiba aesculifolia,two tropical deciduous forests species in *** transplanted 4-month-old seedlings to experimental raised beds at three altitudes(2100,2400 and 2700 m a.s.l.),exceeding their upper regional limit of distribution(2000 m a.s.l.).We also tested seed germination at each *** monitored the experiment for 10 *** both species,as altitude increased and cold weather was more prevalent,plant performance *** species,differences in individual growth were significant among *** survival was 18.5%for *** and 24.5%for *** species had higher survival and better growth at lower altitude,and no seedling emergence at any *** conclude that assisted migration can be implemented for each species by an upward attitudinal shift within,and not exceeding,400 m beyond their present upper altitudinal limit of *** results indicate that for many species that show altitudinal gradients at regional scales,unless current climate conditions change,the potential to establish outside their range is minimal.

关键词： Albizia plurijuga Ceiba aesculifolia Climate change Fabaceae Forest management mitigation strategy Range expansion

Stability of PGM-free fuel cell catalysts: Degradation mechanisms and mitigation strategies

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2020年第6期30卷 721-731页

作者： Xin Wan Xiaofang Liu Jianglan Shui School of Materials Science and Engineering Beihang University

While Platinum group metals(PGM) free catalysts are promising alternatives to expensive Pt as the cathode catalyst in proton exchange membrane fuel cells, their rapid degradation must be addressed for the commercial feasibility. This review provides a historical survey of the possible degradation mechanisms of PGM-free catalysts. Decades of extensive studies confirm that carbon oxidation and demetalation are primarily responsible for the instability, whereas the mechanisms of protonation and micropore flooding are strongly criticized. Based on the mechanism understanding, the mitigation strategies for improving stability are discussed in detail. Finally,some directions to achieve high-performance and durable PGM-free catalysts are proposed.

关键词： Fuel cell Oxygen reduction PGM-Free catalysts Stability mitigation strategy

Ochratoxin A:Carryover from animal feed into livestock and the mitigation strategies

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Animal Nutrition 2021年第1期7卷 56-63页

作者： Abirami Ramu Ganesan Balamuralikrishnan Balasubramanian Sungkwon Park Rajesh Jha Ines Andretta Archibold G.Bakare In Ho Kim Department of Food Science and Home Economics School of Applied SciencesCollege of EngineeringScience and TechnologyFiji National UniversitySuvaFiji Islands Department of Food Science and Biotechnology College of Life ScienceSejong UniversitySeoulSouth Korea Department of Human Nutrition Food and Animal SciencesCollege of Tropical Agriculture and Human ResourcesUniversity of Hawaii at ManoaHonoluluHIUSA Universidade Federal do Rio Grande do Sul Faculdade de AgronomiaDepartment of Animal SciencePorto AlegreRio Grande do SulBrazil Department of Animal Science College of AgricultureFisheries&ForestryFiji National UniversityFiji Islands Department of Animal Resource and Science Dankook UniversityCheonanSouth Korea

This review aims to highlight the effects of ochratoxin A(OTA)in the feed of meat-producing *** accumulation of OTA in feed and its distribution in various farm animals were compared and ***,the oral administration of OTA-contaminated feed and the predisposition in an animal's vital organ were critically examined in this *** collated reports show that OTA directly associated with endemic nephropathy and its high concentration leads to degeneration of liver cells,and necrosis of intestinal and lymphoid *** present,limited reports are available in the recent liter-ature on the problems and consequences of OTA in ***,this review focused on the OTA carryover from feed to farm animals and the interaction of its secondary metabolites on their biochemical ***,this report provides greater insights into animal health related to OTA residues in meat and meat *** article also explores mitigation strategies that can be used to prevent the carryover effects of OTA in livestock feeds and the effects in the food chain.

关键词： Ochratoxin A Feed Livestock Meat mitigation strategy

中美COVID-19疫情时空扩散差异及其应对策略分析

在线全文

学校读者我要写书评

暂无评论

Journal of Geographical Sciences 2020年第12期30卷 1963-1984页

作者：封志明肖池伟李鹏游珍尹旭郑方钰 Institute of Geographic Sciences and Natural Resources Research CASBeijing 100101China College of Resources and Environment University of Chinese Academy of SciencesBeijing 100049China

Investigating the spatio-temporal transmission features and process of novel coronavirus disease 2019(COVID-19)mitigation strategies are of great practical significance to understand the development of COVID-19 and establish international cooperation for prevention and *** this paper,the cumulative number of confirmed cases,number of confirmed cases per day and cumulative number of deaths,were used to compare transmission paths,outbreaks timelines,and coping strategies of COVID-19 in China and the *** results revealed that:first,the COVID-19 outbreaks in both China and the US exhibited a 6-week initiation *** China,the COVID-19 erupted in late *** lasted only a short period of time and was almost completely contained within 6-8 *** the COVID-19 erupted in early March in the US and was still in the peak or post-peak ***,in China,the COVID-19 emerged in Wuhan and spread to other regions of Hubei Province and then nationwide,exhibiting a cross('+')-shaped of spread with Wuhan city as the ***,the COVID-19 in China had a large concentration and there were no national *** contrast,the COVID-19 in the US first spread through New York and the western and eastern coasts but has since emerged throughout the entire ***,the lack of emergency response planning in both countries in the early stage(about 6-week)hampered COVID-19 ***,actively high-pressure prevention and control measures were used to basically control COVID-19 in early March in *** then China has gradually resumed business and production ***,the US government missed the best opportunity to contain the *** with the choice between economic recovery and coronavirus containment,the US removed the quarantine and restriction measures too *** COVID-19 is continuing to spread in the country and blossom everywhere,still showing no signs of receding.

关键词： COVID-19 spatio-temporal transmission timelines mitigation strategy China the US