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Uniqueness to Some Inverse Source Problems for the Wave Equation in Unbounded Domains
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作者 Guang-hui HU Yavar KIAN Yue ZHAO 《应用数学学报:英文版》 SCIE CSCD 2020年第1期134-150,共17页
This paper is concerned with inverse acoustic source problems in an unbounded domain with dynamical boundary surface data of Dirichlet kind.The measurement data are taken at a surface far away from the source support.... This paper is concerned with inverse acoustic source problems in an unbounded domain with dynamical boundary surface data of Dirichlet kind.The measurement data are taken at a surface far away from the source support.We prove uniqueness in recovering source terms of the form f(x)g(t)and f(x1,x2,t)h(x3),where g(t)and h(x3)are given and x=(x1,x2,x3)is the spatial variable in three dimensions.Without these a priori information,we prove that the boundary data of a family of solutions can be used to recover general source terms depending on both time and spatial variables.For moving point sources radiating periodic signals,the data recorded at four receivers are prove sufficient to uniquely recover the orbit function.Simultaneous determination of embedded obstacles and source terms was verified in an inhomogeneous background medium using the observation data of infinite time period.Our approach depends heavily on the Laplace transform. 展开更多
关键词 Inverse source problems Laplace transform moving point source UNIQUENESS
Assessment of Toxicity Potential of Sedimentary PAHS from Refome Lake, South-East Nigeria over the Last Century 预览
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作者 Inyang O Oyo-Ita Emmanuella E Oyo-Ita +2 位作者 Ekpo O Ikip Bassey B Asuquo Orok E Oyo-Ita 《地球科学和环境保护期刊(英文)》 2020年第1期1-15,共15页
In this study, toxic equivalent factors and sediment quality guidelines were employed for the assessment of toxicity potential of PAHs in 2 sediment cores collected from the center (RC) and shoreline (RS) of Reforme l... In this study, toxic equivalent factors and sediment quality guidelines were employed for the assessment of toxicity potential of PAHs in 2 sediment cores collected from the center (RC) and shoreline (RS) of Reforme lake, SE Nigeria over the last ~1 century. Boundary cross plots of isomeric ratios such as Ant/Ant + Phe (>0.1) vs. Fl/Fl + Pyr (>0.4) and BaA/BaA + Chry (>0.35) vs. Icdp/Icdp + Bper (>0.2) indicated biomass combustion/domestic coal utilization as the main sources of PAHs input. The result revealed toxicity unit indices (TU1, 1.22 - 1.57) for the two cores were above the thresholds of no effect. The highest TU1 value found in the near-bottom layer (RS5, 20 - 25 cm) of the RS corresponding to geological time-frame ~1930-1947 coincided with the period of inhabitation by the European settlers along the lake’s catchments when coal or coal products utilization for domestic and recreational purposes was at its peak. On the other hand, TU2 values were <1 at all depth intervals, revealing unlikely PAH effects to resident organisms. Total toxicity equivalency factors (TEqFs) for the surface sediment of RS and RC were 9.29 ng/g TEqFs and 9.16 ng/g TEqFs, respectively, and indicated that more attention should be paid to BaPyr accumulation in the lake’s sediment. 展开更多
关键词 TOXICITY PAHS Refome LAKE Sediment CORES ASSESSMENT Source
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Source Evolution and Its Relationship to Climate Change Since the Middle–Late Pleistocene in Laizhou Bay, China 预览
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作者 GONG Chuanzhang LI Guangxue +5 位作者 LIU Yong DING Dong XU Jishang MA Yanyan QIAO Lulu and WANG Haoyin 《中国海洋大学学报:英文版》 SCIE CAS CSCD 2020年第1期113-123,共11页
Through the geochemical analysis of two hundred-meters cores KD4 and ZK3 from Laizhou Bay,in this study,we determined the distribution law and controlling factors of the geochemical elements.We analyzed 24 elements wi... Through the geochemical analysis of two hundred-meters cores KD4 and ZK3 from Laizhou Bay,in this study,we determined the distribution law and controlling factors of the geochemical elements.We analyzed 24 elements with respect to their R factors and major principal components,which were combined with the source discrimination functions DFCr/Th and DFCa/Al to obtain the sediment source index and its variation with depth for this area.A comparison of the changes in climate indicators suggests a clear correlation between the source and climate changes.The results show that the Yellow River and surrounding short-term rivers are the main sediment sources in this area.The PC3 of the KD4 core and PC2 of the ZK3 core(e.g.,CaO,MnO,SiO2)exhibit significant variations and reflect the relative contributions of Yellow River sources.The deposition process can be divided into six stages:in Phase I(MIS 5c–MIS 5a),the Yellow River formed,and the composition of the Yellow River had a greater influence on the sedimentary composition of the study area.In Phase II(MIS 5a–MIS 3),the sediment sources of the Yellow River and the short-term streams in this area were wavering,with the sediments derived from short-term rivers playing a more important role.In Phase III(MIS 3),with a sharp drop in temperature,the study area was in the process of retreat,and the sediment source changed from the Yellow River to short-term rivers,after which the Yellow River source material remained the main sediment source for the region.A similar process occurred three more times in Phase IV(MIS 3–MIS 2),Phase V(MIS 2–MIS 1),and Phase VI(MIS 1).With changes in climate,especially during alternating sea-land phases,the sediment source varied in marine-terrestrial-marine phases,and the changes are observed as Yellow River source-surrounding provenance-Yellow River source.However,this process of change is not synchronized with the sea-land strata alternation. 展开更多
关键词 Laizhou Bay SOURCE geochemistry Yellow River climate change
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Stable Isotope Signatures and Moisture Transport of a Typical Heavy Precipitation Case in the Southern Tianshan Mountains 预览
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作者 WANG Liwei ZHANG Mingjun +5 位作者 WANG Shengjie Athanassios AARGIRIOU WANG Gaofei Vasileios SALAMALIKIS SHI Mengyu JIAO Rong 《中国地理科学:英文版》 SCIE CSCD 2020年第1期180-188,共9页
Stable oxygen isotopes in precipitation contain meaningful environmental information on a synoptic scale and can be applied to diagnose hydrometeorological processes.A series of rainstorms occurred at the southern Tia... Stable oxygen isotopes in precipitation contain meaningful environmental information on a synoptic scale and can be applied to diagnose hydrometeorological processes.A series of rainstorms occurred at the southern Tianshan Mountains during the period from May to June 2013,and the event-based precipitation was sampled along the mountain range from west to east.Based on δ18 O values in precipitation samples as well as the corresponding meteorological parameters,the moisture transport paths during the sampling period were identified.In late-May(stage 1),isotopes in precipitation collected generally showed a depleting trend.In mid-June(stage 2),there was no coherent trend of isotopes in precipitation for these stations,and only isotope values in Aksu showed a continually depleting trend.Checking other meteorological proxies during the sampling period,the event-based precipitation isotopes sensitively reflected the moisture process.In central Asia,both the westerly and monsoon moisture can be delivered to cause extreme precipitation events,and the isotopic information provides an alternative tool to investigate the atmospheric processes. 展开更多
关键词 precipitation stable isotope moisture source Tianshan Mountains
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A study on particle breakage behavior during pile penetration process using acoustic emission source location 预览
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作者 Wuwei Mao Shogo Aoyama Ikuo Towhata 《地学前缘:英文版》 CAS CSCD 2020年第2期413-427,共15页
Particle breakage is a common occurrence in granular systems when the external stress exceeds the individual particle strength.A large number of experimental evidences suggested that particle breakage may significantl... Particle breakage is a common occurrence in granular systems when the external stress exceeds the individual particle strength.A large number of experimental evidences suggested that particle breakage may significantly influence the soil behavior.In the case of pile foundations,the subsoil below the pile tip experiences considerable high stress and consequently prone to break.Due to the lack of sufficient understanding on particle breakage mechanism,there is currently no consentaneous theoretical background for particle breakage analysis during the pile penetration process.This study aims to clarify the location of particle breakage and its evolving characteristics with the aid of acoustic emission(AE)source location method.The spatial distribution of AE hypocenters is interpreted to be associated with the mechanism of particle breakage.Results showed that the AE sources were not uniformly distributed,but concentrated within certain zones below the pile tip.This AE concentration zone was pushed downward with the advancing pile tip,and its distance from the real time pile tip position decreased after certain depth of pile penetration.The location of particle breakage interpreted from AE source location was verified with posttest excavations and the insights on the particle breakage evolution zone were further discussed. 展开更多
关键词 Acoustic emission Source location SAND Particle breakage PILE
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安阳市大气PM2.5中水溶性离子季节特征及来源解析
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作者 孙有昌 姜楠 +2 位作者 王申博 段时光 张瑞芹 《环境科学》 EI CAS CSCD 北大核心 2020年第1期75-81,共7页
为探究安阳市大气PM2.5中水溶性离子的污染特征及其来源,于2018~2019年的典型月份在安阳市采集PM2.5样品,使用离子色谱测试了9种水溶性离子(Na+、NH4+、K+、Mg2+、Ca2+、F-、Cl-、NO3-和SO42-).开展了PM2.5和水溶性离子浓度水平的分析... 为探究安阳市大气PM2.5中水溶性离子的污染特征及其来源,于2018~2019年的典型月份在安阳市采集PM2.5样品,使用离子色谱测试了9种水溶性离子(Na+、NH4+、K+、Mg2+、Ca2+、F-、Cl-、NO3-和SO42-).开展了PM2.5和水溶性离子浓度水平的分析、阴阳离子平衡和氮氧化率(NOR)、硫氧化率(SOR)的计算、离子相关性和主成分分析等.结果表明,安阳市PM2.5和水溶性离子年均浓度分别为(85.81±45.43)μg·m-3和(48.21±30.04)μg·m-3,各离子浓度高低顺序为NO3->SO42->NH4+> Cl->K+> Ca2+> Na+>Mg2+>F-;阴阳离子电荷当量数值为0.75~0.94,大气气溶胶显碱性;NH4+和SO42-、NO3-以及K+和Cl-等具有显著的相关性;氮氧化率(NOR)和硫氧化率(SOR)的年均值分别为0.25和0.37;SO42-、NO3-和NH4+(SNA)的年均浓度为(42.72±27.87)μg·m-3,占水溶性离子总量的87.14%;春季、夏季和秋季的NH4+主要以(NH4)2SO4和NH4NO3的形式存在,冬季的NH4+主要以(NH4)2SO4、NH4NO3和NH4 Cl的形式存在;水溶性离子主要来自于二次生成、燃煤、生物质燃烧和扬尘. 展开更多
关键词 安阳 PM2.5 水溶性离子 存在形式 来源
Analysis of air quality characteristics of Beijing–Tianjin–Hebei and its surrounding air pollution transport channel cities in China
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作者 Cuicui Xiao Miao Chang +2 位作者 Peikun Guo Meifeng Gu Yang Li 《环境科学学报:英文版》 SCIE EI CAS CSCD 2020年第1期213-227,共15页
Beijing–Tianjin–Hebei(BTH)and its surrounding areas are very important to air pollution control in China.To analyze the characteristics of BTH and its surrounding areas of China,we collected 5,641,440 air quality da... Beijing–Tianjin–Hebei(BTH)and its surrounding areas are very important to air pollution control in China.To analyze the characteristics of BTH and its surrounding areas of China,we collected 5,641,440 air quality data from 161 air monitoring stations and 37,123,000 continuous monitoring data from air polluting enterprises in BTH and surrounding cities to establish an indicator system for urban air quality portraits.The results showed that particulate matter with aerodynamic diameters of<2.5μm(PM2.5),particulate matter with aerodynamic diameters of<10μm(PM10)and SO2 improved significantly in 31 cities from2015 to 2018,but ozone deteriorated.Air quality in BTH and the surrounding areas showed obvious seasonal characteristics,among which PM2.5,PM10,SO2,and NO2 showed a"U"type distribution from January to December,while O3 had an"inverted U"distribution.The hourly changes in air quality revealed that peaks of PM2.5,PM10 and NO2 appeared from 8:00 to 10:00,while those for O3 appeared at 15:00–16:00.The exposure characteristics of the 31 cities showed that six districts in Beijing had the highest air quality population exposure,and that exposure levels in Zhengzhou,Puyang,Anyang,Jincheng were higher than the average of the 31 investigated cities.Additionally,multiple linear regression revealed a negative correlation between meteorological factors(especially wind and precipitation)and air quality,while a positive correlation existed between industrial pollution emissions and air quality in most of BTH and its surrounding cities. 展开更多
关键词 Beijing–Tianjin–Hebei Air quality population exposure Seasonal index Hourly change Industrial pollution source emission Meteorology factors
Study on dynamic characteristics of fission products in 2 MW molten salt reactor 预览
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作者 Bo Zhou Xiao-Han Yu +6 位作者 Yang Zou Pu Yang Shi-He Yu Ya-Fen Liu Xu-Zhong Kang Gui-Feng Zhu Rui Yan 《核技术:英文版》 SCIE CAS CSCD 2020年第2期42-54,共13页
In this study,a numerical flow model of the fission products(FPs)in the primary loop system of a molten salt reactor(MSR)was established and solved using Mathematica 7.0.The simulation results were compared with those... In this study,a numerical flow model of the fission products(FPs)in the primary loop system of a molten salt reactor(MSR)was established and solved using Mathematica 7.0.The simulation results were compared with those of the ORIGEN-S program in the static burnup mode,and the deviation was found to be less than 10%,which indicates that the results are in good agreement.Furthermore,the FPs distribution in the primary loop system under normal operating conditions of the 2 MW MSR was quantitatively analyzed.In addition,the distribution phenomenon of the FPs under different flow rate conditions was studied.At the end of life,the FPs activity in the core region(including active region,and upper and lower plenum regions)accounted for 77.3%,and that in the hot leg #1,main pump,hot leg #2,heat exchanger,and cold leg region accounted for 1.2%,16.15%,0.99%,2.5%,and 1.9%,respectively,of the total FPs in the primary loop under normal operating conditions.The proportion of FPs in the core decreased with the increase in flow rate in the range of 2.24-22,400 cm^3 s^-1.The established analytical method and conclusions of this study can provide an important basis for radiation safety design of the primary loop,radioactive source management design,thermal-hydraulic safety analysis,and radiochemical analysis of FPs of 2 MW MSRs. 展开更多
关键词 Molten salt reactor Fission products Radioactive source term Primary loop system Flow model
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D-T孔隙度测井数据校正及实验研究
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作者 杨宁宁 《核技术》 CAS CSCD 北大核心 2020年第4期90-94,共5页
采用氘-氚(D-T)可控源进行中子孔隙度测井时,其响应结果与化学源中子孔隙度测井的响应结果存在差异,使得传统化学源中子孔隙度测井的实验数据和解释模型难以适用。为了验证已有的密度校正方法是否能够用于中子孔隙度测井的结果校正,使D-... 采用氘-氚(D-T)可控源进行中子孔隙度测井时,其响应结果与化学源中子孔隙度测井的响应结果存在差异,使得传统化学源中子孔隙度测井的实验数据和解释模型难以适用。为了验证已有的密度校正方法是否能够用于中子孔隙度测井的结果校正,使D-T源与化学源的响应结果相接近,本文通过模拟获取不同孔隙灰岩含水地层和泥岩中的响应结果,将模拟结果与研制的实验装置测量结果进行基准检测,然后分析D-T源中子孔隙度测井校正前后与化学源中子孔隙度测井对比的响应差异,并利用实际测井数据验证可控源孔隙度测井方法的有效性。结果表明:经过密度校正后,可控源与化学源中子孔隙度的测量结果有较好的相似性,在实际测井曲线上两者也存在较好的对应关系。因此,本研究对于验证可控源中子孔隙度测井方法的有效性和今后测井仪器中放射源的可兼容替代有一定的应用意义。 展开更多
关键词 中子孔隙度测井 氘-氚源 密度校正 蒙特卡罗模拟 测井曲线
铁路信号的激光器驱动电源集中监控
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作者 顾卫杰 楼竞 《激光杂志》 北大核心 2020年第2期155-159,共5页
为了提高铁路激光器驱动电源监控信号自动识别能力,实现铁路信号的激光器驱动电源集中监控,提出一种基于铁路信号激光器驱动电源集中监控方法。采用传感器进行铁路信号电源集中监控信息采集,对采集的信号模型采用空间阵列分布式设计方... 为了提高铁路激光器驱动电源监控信号自动识别能力,实现铁路信号的激光器驱动电源集中监控,提出一种基于铁路信号激光器驱动电源集中监控方法。采用传感器进行铁路信号电源集中监控信息采集,对采集的信号模型采用空间阵列分布式设计方法进行空间信源模型构建,对采集的铁路信号采用相干检测法进行滤波检测,提取铁路信号功率谱密度特征,采用小波分析方法进行铁路激光器驱动电源监控信号的多元尺度分解,实现铁路激光器驱动电源信号的自动检测和集中监控。仿真结果表明,采用该方法进行的铁路信号激光器驱动电源集中监控能力较强,误码率低于10-1,下降幅度较大且迅速,信号传输延迟缩短了30%,提高了信号的自动检测和识别能力。 展开更多
关键词 铁路信号 激光器驱动电源 集中监控 信源 相干检测
沙颍河流域水环境中多环芳烃污染及风险评价 预览
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作者 杜士林 丁婷婷 +4 位作者 董淮晋 刘晓雪 张亚辉 曾鸿鹄 何连生 《农业环境科学学报》 CAS CSCD 北大核心 2020年第3期601-611,共11页
为了研究沙颍河流域上覆水与表层沉积物中多环芳烃(PAHs)的空间分布、来源与生态风险,2018年7月对沙颍河流域30个采样点的上覆水与表层沉积物中16种PAHs使用气相色谱/质谱技术(GC/MS)进行调查研究。结果表明,在上覆水与表层沉积物中ΣP... 为了研究沙颍河流域上覆水与表层沉积物中多环芳烃(PAHs)的空间分布、来源与生态风险,2018年7月对沙颍河流域30个采样点的上覆水与表层沉积物中16种PAHs使用气相色谱/质谱技术(GC/MS)进行调查研究。结果表明,在上覆水与表层沉积物中ΣPAHs的浓度范围分别为:356.60~2275.04 ng·L^-1、64.27~11433.63 ng·g^-1,平均浓度分别为1051.23 ng·L^-1、965.77 ng·g^-1;各支流上覆水中PAHs含量呈现贾鲁河>颍河>沙河>澧河趋势,表层沉积物中PAHs含量呈现沙河>澧河>颍河>贾鲁河趋势,上覆水与表层沉积物中均以4~6环高环多环芳烃为主,与国内外其他河流相比沙颍河流域上覆水中PAHs处于较高污染水平,表层沉积物中PAHs污染水平相对较低;来源分析表明沙颍河流域上覆水与沉积物中多环芳烃主要来自高温燃烧源;生态风险评估表明上覆水中荧蒽(Fla)、芘(Pyr)、苯并[a]蒽(BaA)、苯并[b]荧蒽(BbF)、苯并[a]芘(BaP)、茚并[1,2,3-cd]芘(IcdP)和苯并[g,h,i]苝(BghiP)等PAHs单体为高风险多环芳烃单体,高分子量多环芳烃(4~6环)对生态风险贡献最大,沙颍河流域上覆水中PAHs属于高风险水平;沉积物中各PAHs单体的浓度除点位S27外均未超过效应区间中值(ERM)与频繁效应浓度值(FEL),表明沙颍河流域沉积物中PAHs潜在生态风险发生概率并不高。 展开更多
关键词 沙颍河流域 多环芳烃 来源 生态风险
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从“儿缀”的发展演变看杭州话后缀“儿”的来源
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作者 张海媚 《汉语学报》 CSSCI 北大核心 2020年第1期87-96,共10页
关于杭州话"儿缀"的来源异见歧出。文章通过考察"儿缀"的发展演变、历时与共时分布,考证出"儿缀"在历史文献中乃通语词,以此判断杭州话的"儿缀"应该是其固有,但其不同于周边地区的带强烈卷舌... 关于杭州话"儿缀"的来源异见歧出。文章通过考察"儿缀"的发展演变、历时与共时分布,考证出"儿缀"在历史文献中乃通语词,以此判断杭州话的"儿缀"应该是其固有,但其不同于周边地区的带强烈卷舌性质的发音是南宋以后受北方话影响所致,这从"儿缀"转化到"儿化"恰好发生在宋金时期也可证明。 展开更多
关键词 杭州话“儿缀” 发展演变 历时与共时分布 来源
DFM:“Design for Manufacturing”or“Design Friendly Manufacturing” 预览
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作者 Wenzhan Zhoul Hung-Wen Chao +5 位作者 Yu Zhang Chan-Yuan Hu Wei Yuan Yifei Lu Hongmei Hu Xiang Peng 《微电子制造学报》 2020年第1期1-8,共8页
As the IC manufacturing enter sub 20nm tech nodes,DFM become more and more important to make sure more stable yield and lower cost.However,by introducing newly designed hardware(1980i etc.)process chemical(NTD)and Con... As the IC manufacturing enter sub 20nm tech nodes,DFM become more and more important to make sure more stable yield and lower cost.However,by introducing newly designed hardware(1980i etc.)process chemical(NTD)and Control Algorithm(Focus APC)into the mature tech nodes such as 14nm/12nm,more process window and less process variations are expected for latecomer wafer fabs(Tier-2/3 companies)who just started the competition with Tier-1 companies.With improved weapons,latecomer companies are able to review their DFM strategy one more time to see whether the benefit from hardware/process/control algorithm improvement can be shared with designers.In this paper,we use OPC simulation tools from different EDA suppliers to see the feasibility of transferring the benefits of hardware/process/control algorithm improvement to more relaxed design limitation through source mask optimization(SMO):1)Better hardware:scanner(better focus/exposure variation),CMP(intrafield topo),Mask CD variation(relaxed MEEF spec),etc.2)New process:from positive tone development to negative tone development.3)Better control schemes:holistic focus feedback,feedback/forward overlay control,high order CD uniformity improvement.Simulations show all those gains in hardware and process can be transferred into more relaxed design such as sub design rule structure process window include forbidden pitches(1D)and smaller E2E gaps(2D weak points). 展开更多
关键词 Design for Manufacturing(DFM) Design Friendly Manufacturing EUV Lithography Source Mask Optimization(SMO) Design Technology Co-optimization(DTCO) Process Window Process Variation
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潮白河中游沉积物中重金属分布、来源及生态风险评估 预览
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作者 温泉 赵艳民 +4 位作者 曹伟 杨晨晨 张雷 张国宇 冯军坡 《环境科学研究》 EI CAS CSCD 北大核心 2020年第3期599-607,共9页
潮白河是海河五大支流之一,其中游位于河北省,地处北京市下游和天津市上游,非汛期来水主要为北京市工业废水和生活污水.为了解潮白河中游沉积物重金属污染分布特征、来源、生态风险及可能受北京市来水的影响,于2018年6月采集9个表层沉... 潮白河是海河五大支流之一,其中游位于河北省,地处北京市下游和天津市上游,非汛期来水主要为北京市工业废水和生活污水.为了解潮白河中游沉积物重金属污染分布特征、来源、生态风险及可能受北京市来水的影响,于2018年6月采集9个表层沉积物样品和2个柱状沉积物样品,使用电感耦合等离子质谱仪(ICP-MS)测定Cr、Ni、Cu、Zn、As、Cd和Pb等7种重金属的质量分数.结果表明:①潮白河中游表层沉积物中w(Cr)、w(Ni)、w(Cu)、w(Zn)、w(As)、w(Cd)、w(Pb)的平均值分别为31.47、14.74、14.73、44.80、4.91、0.23、17.98 mg/kg,7种重金属质量分数除在5号采样点突然增加外,均沿河流方向呈先降后升的趋势.在垂直方向上,7种重金属在5号采样点出现富集,在9号采样点其质量分数则呈减轻趋势.②通过相关性分析和主成分分析可知,潮白河中游沉积物中Cr、Ni、Cu、As、Pb主要来源于工业和交通污染;Zn和Cd则主要来源于农业面源和生活污染.③地累积指数评价和潜在生态风险指数显示,潮白河中游表层沉积物重金属污染主要以Cd、Pb、Cu和As为主,其中Cd的潜在危害最高,各采样点综合潜在生态风险指数大小依次为5号>2号>3号>9号>1号>8号>4号>7号>6号.研究显示,潮白河中游沉积物重金属污染在5号采样点最严重,其中Cd污染程度最高,其来源主要为区域农业生产和居民生活等人类活动,应加强区域内农业和生活污染防治. 展开更多
关键词 重金属 沉积物 空间分布 来源 生态风险评价
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Study of the Relationship between Precipitation and a Transverse Shear Line over the Qinghai-Tibet Plateau in Summer 预览
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作者 Qin GUAN Qingping LI +3 位作者 Xiuping YAO Liang XU Yuanchang MAA Delan QI 《气象与环境研究:英文版》 CAS 2020年第2期1-9,14,共10页
Based on the 4 times daily 0.75°×0.75°ERA-Interim data,the relationship between precipitation and a transverse shear line(TSL)over Qinghai-Tibet Plateau during August 15-19,2015 is analyzed.The results ... Based on the 4 times daily 0.75°×0.75°ERA-Interim data,the relationship between precipitation and a transverse shear line(TSL)over Qinghai-Tibet Plateau during August 15-19,2015 is analyzed.The results show that precipitation and TSL had obvious diurnal variation.That is,the intensity of the TSL and the precipitation tended to increase from afternoon to night and reduce from 00:00 to 06:00 UTC(the same below).The shape of the rain area was basically consistent with the direction of the TSL,and when the zonal characteristics of the rain area were obvious,the precipitation distribution was relatively uniform,otherwise the local short-term heavy precipitation was easy to occur.The precipitation center was basically consistent with the positive vorticity center near the TSL,and precipitation was directly proportional to the value of positive vorticity.The equation for the budget of vorticity shows that the horizontal advection term determined the moving direction of the TSL.The vertical transportation term determined the structural characteristics of the TSL on the vertical section,and positive vertical transport item of lower level was conducive to the formation of the plateau vortex.The horizontal convergence or divergence term determined the position of the TSL,and was conducive to the maintenance of the TSL.The evolution of apparent heat source and apparent water vapor sink near the TSL had a distinct diurnal feature.Meanwhile,atmospheric heating in the precipitation process was closely related to atmospheric upward movement,and the latent heat of condensation release caused by precipitation was beneficial to the maintenance of the plateau shear line and the formation and strengthening of plateau vortex.The precipitation of the TSL was mainly dominated by weak convective precipitation. 展开更多
关键词 Plateau shear line PRECIPITATION Vorticity budget Apparent heat source Apparent moisture sink
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Determination of an Unknown Time-dependent Heat Source from A Nonlocal Measurement by Finite Difference Method
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作者 Ze-wen WANG Zhou-sheng RUAN +1 位作者 He-lu HUANG Shu-fang QIU 《应用数学学报:英文版》 SCIE CSCD 2020年第1期151-165,共15页
In this paper,we consider an inverse time-dependent source problem of heat conduction equation.Firstly,the ill-posedness and conditional stability of this inverse source problem is analyzed.Then,a finite difference in... In this paper,we consider an inverse time-dependent source problem of heat conduction equation.Firstly,the ill-posedness and conditional stability of this inverse source problem is analyzed.Then,a finite difference inversion method is proposed for reconstructing the time-dependent source from a nonlocal measurement.The existence and uniqueness of the finite difference inverse solutions are rigorously analyzed,and the convergence is proved.Combined with the mollification method,the proposed finite difference inversion method can obtain more stable reconstructions from the nonlocal data with noise.Finally,numerical examples are given to illustrate the efficiency and convergence of the proposed finite difference inversion method. 展开更多
关键词 inverse source problem ill-posed problem finite difference heat equation mollification
The Mineral Composition and Sources of the Fine-Grained Sediments from the 49.6°E Hydrothermal Field at the SWIR 预览
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作者 ZHANG Wenqiang SUN Xiaoxia +3 位作者 FAN Dejiang LIU Ming JIA Qi YANG Zuosheng 《中国海洋大学学报:英文版》 SCIE CAS CSCD 2020年第1期60-68,共9页
We used the X-ray diffraction method to determine systematically the mineral phases in bulk sediment samples and acid undissolved residuals of the fine-grained fraction of the surface sediments from the 49.6°E hy... We used the X-ray diffraction method to determine systematically the mineral phases in bulk sediment samples and acid undissolved residuals of the fine-grained fraction of the surface sediments from the 49.6°E hydrothermal field at the Southwest Indian Ridge(SWIR)and discussed the mineral sources of the surface sediments.The results showed that the surface sediments in this region were composed of calcareous ooze,and calcite was the dominant mineral.The sediments also contained quartz,feldspar,clay minerals,pyroxene,sphalerite,barite,serpentine,and magnetite.The quartz,feldspar,and clay minerals were exogenous minerals that mainly originated from the Namib and Kalahari deserts in southern Africa.The pyroxene,serpentine,magnetite,sphalerite,calcite,and barite were endogenous minerals from weathering of seafloor basement rocks and seafloor hydrothermal activities.The sulfide particles in the sediments were mainly deposited from upwelling plumes. 展开更多
关键词 Southwest Indian Ridge surface sediment MINERAL SOURCE HYDROTHERMAL
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Research Progress on the Monitoring of Precursor of Atmospheric Ozone——Volatile Organic Compounds 预览
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作者 Shuchi CHEN Yiyao HUANG +3 位作者 Miao CHEN Juan LI Lianghong XIAO Yan GUO 《气象与环境研究:英文版》 CAS 2020年第2期29-36,共8页
Volatile organic compounds(VOCs)are important precursors of ozone and PM_(2.5).At present,VOCs have gradually become the focus of air pollution control after fine particles in China,and a series of documents,standards... Volatile organic compounds(VOCs)are important precursors of ozone and PM_(2.5).At present,VOCs have gradually become the focus of air pollution control after fine particles in China,and a series of documents,standards and planning on VOCs were issued from the state to each area.The analysis on source apportionment and control of VOCs have also become a hot spot in atmospheric environmental protection research of China at present stage.The research work on VOCs in ambient air is the basis and premise of scientific and effective prevention and control of VOCs pollution.In this paper,research progress on the monitoring of VOCs is introduced systemically,and main monitoring and evaluation methods of atmospheric VOCs are explored from monitoring analysis method,chemical reaction activity and health risk assessment.Moreover,concentration characteristics and source apportionment of VOCs in the regions at home and abroad that have carried out VOCs research work are compared and summarized.The research could provide reference for source apportionment of VOCs in other cities of China. 展开更多
关键词 Volatile organic compounds(VOCs) OZONE Chemical composition Source analysis
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The partial side information problem with additional reconstructions 预览
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作者 Viswanathan Ramachandran 《数字通信与网络:英文版》 2020年第1期123-128,共6页
We consider a quadratic Gaussian distributed lossy source coding setup with an additional constraint of identical reconstructions between the encoder and the decoder.The setup consists of two correlated Gaussian sourc... We consider a quadratic Gaussian distributed lossy source coding setup with an additional constraint of identical reconstructions between the encoder and the decoder.The setup consists of two correlated Gaussian sources,wherein one of them has to be reconstructed to be within some distortion constraint and match with a corresponding reconstruction at the encoder,while the other source acts as coded side information.We study the tradeoff between the rates of two encoders for a given distortion constraint on the reconstruction.An explicit characterization of this trade-off is the main result of the paper.We also give close inner and outer bounds for the discrete memoryless version of the problem. 展开更多
关键词 Rate-distortion theory Source coding Network information theory Wyner Ziv compression MMSE estimation Correlated Gaussian sources
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刘宓庆译学思想的哲学之“源”探析
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作者 张思永 《中国翻译》 CSSCI 北大核心 2020年第1期111-121,189,共12页
翻译学具有天生的跨学科性,来自他学科的理论之"源"有层次之分,而最高层次的"源"就是哲学之"源",即现代翻译学的发展离不开哲学之"源"的观照。分清"源"和"流",这是中国当... 翻译学具有天生的跨学科性,来自他学科的理论之"源"有层次之分,而最高层次的"源"就是哲学之"源",即现代翻译学的发展离不开哲学之"源"的观照。分清"源"和"流",这是中国当代翻译理论家刘宓庆在译学研究中坚持和践行的一个基本原则。文章分析了刘宓庆译学思想的中西哲学之"源",旨在探究其译学思想形成的哲学心路历程,并望对中国当前的译学研究有所启示。 展开更多
关键词 刘宓庆 译学思想 哲学之“源”
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