检索结果-南通市图书馆

在线全文

学校读者我要写书评

暂无评论

遗传算法反演地球等离子体层离子密度分布

地球物理学报 2012年第1期55卷 29-35页

作者：何飞张效信陈波 fok mei-ching 中国科学院长春光学精密机械与物理研究所长春130033 中国气象局国家空间天气监测与预警中心北京100081 NASA Goddard Space Flight Center GreenbeltMD 20771USA

本文介绍了采用一维遗传算法从地球等离子体层极紫外图像反演地球等离子体层He+密度的原理.首先采用通量管近似和磁偶极近似将三维问题转化为一维问题.通过引入权矩阵,将极紫外光强积分离散为求和函数,再采用一维实数编码遗传算法反演... 详细信息

本文介绍了采用一维遗传算法从地球等离子体层极紫外图像反演地球等离子体层He+密度的原理.首先采用通量管近似和磁偶极近似将三维问题转化为一维问题.通过引入权矩阵,将极紫外光强积分离散为求和函数,再采用一维实数编码遗传算法反演得到磁赤道面等离子体层He+密度,最后通过磁力线追迹得到三维密度分布.算法采用动态全球核心等离子体模式模拟的密度和光强分布作为初始输入参数,并通过遗传算法得到相应密度分布.反演结果表明,等离子体层密度相对误差在8%以内,光强相对误差趋于0,算法有效可行.本文研究为中国探月二期工程中月基极紫外图像反演奠定了基础.

关键词：地球等离子体层密度分布遗传算法反演

在线全文

学校读者我要写书评

暂无评论

地球等离子层极紫外波段辐射特性计算

中国科学（E辑） 2010年第1期40卷 71-76页

作者：何飞张效信陈波 fok mei-ching 中国科学院长春光学精密机械与物理研究所长春130033 中国气象局国家空间天气监测与预警中心北京100081 NASA Goddard Space Flight Center GreenbeltMD20771USA 中国科学院研究生院北京100039

介绍了计算地球等离子体层He+密度分布的动态全球核心等离子体层模式(DGCPM),模拟了等离子体层结构特性和30.4nm辐射特性,与IMAGE卫星观测结果的对比分析表明:(1)等离子体层顶主要位于5.5RE以内,10min收缩或扩张的特征尺度约0.1RE;(2)... 详细信息

介绍了计算地球等离子体层He+密度分布的动态全球核心等离子体层模式(DGCPM),模拟了等离子体层结构特性和30.4nm辐射特性,与IMAGE卫星观测结果的对比分析表明:(1)等离子体层顶主要位于5.5RE以内,10min收缩或扩张的特征尺度约0.1RE;(2)等离子体层肩产生于行星际磁场南向偏转并从晨侧向正午方向旋转;(3)等离子体层尾在行星际磁场南向偏转时会向昏侧旋转并变窄.模拟得到从月球上观测时等离子体层位于5.5RE以内,对应月基极紫外相机视场角10.7°×10.7°;等离子体层30.4nm辐射强度为0.1～11.4Rayleigh;首次从侧面模拟出了等离子体层肩和尾结构,其空间变化尺度量级为0.1RE.以上计算结果为月基极紫外相机参数设计提供了重要理论依据.

关键词：地球等离子体层动态对流模式极紫外辐射月基探测

Reassessing the contributions of terrestrial waters to sea level variations in the South China Sea and its response to alternating ENSO events

在线全文

学校读者我要写书评

暂无评论

Science China Earth Sciences 2024年第7期67卷 2253-2267页

作者： Pengfei YANG Hok Sum fok Zhongtian MA MOE Key Laboratory of Geospace Environment and Geodesy&MNR Key Laboratory of Geophysical Geodesy School of Geodesy and GeomaticsWuhan UniversityWuhan 430079China Hubei Luojia Laboratory Wuhan 730079China Department of Land Surveying and Geo-Informatics The Hong Kong Polytechnic UniversityHong Kong 999077China

Regional sea level variability is linked to regional terrestrial water and the El Ni?o-Southern Oscillation(ENSO).This study assessed the relationships between the sea level variations in the South China Sea(SCS)and ENSO,the impact of terrestrial water storage(TWS)on non-steric sea level(NSSL),and the contributions of steric sea level(SSL)and NSSL to sea level anomaly(SLA),*** 2003 to 2015,the SLAs exhibited a long-term trend of 6.65±0.78 mm/yr,which was primarily attributed to the ***,during 2003-2015,ENSO events alternating with varying intensities might also be responsible for the unusually high SLA *** to the SSLs,the NSSLs contributed the seasonal signals to the SLAs,while the NSSLs changes were largely explained by the TWS in the Mekong River Basin at the seasonal scale and in the Pearl River Basin and Red River Basin at other time *** contrast to the TWS,the contributions of precipitation and evapotranspiration were relatively minor.A negative correlation between the sea level variations and ENSO was also found,with cross-correlation coefficients between the oceanic Ni?o index and SLAs/SSLs/NSSLs of -0.36/-0.37/-0.62 with lags of 2/3/2 months,*** findings systematically reassessed the contributions of different components to the sea level *** study provided a benchmark for in-depth analysis of the impacts of terrestrial water and other potential causes on sea level rise in the SCS.

关键词： South China Sea Sea level variations Terrestrial water storage ENSO

Correlating the interplanetary factors to distinguish extreme and major geomagnetic storms

在线全文

学校读者我要写书评

暂无评论

Earth and Planetary Physics 2021年第2期5卷 180-186页

作者： Ragini Balachandran Li-Jen Chen Shan Wang mei-ching fok Cornell University IthacaNY 14853USA NASA Goddard Space Flight Center GreenbeltMD 20770USA Department of Astronomy University of MarylandCollege ParkMD 20742USA

We investigate the correlation between Disturbance Storm Time(Dst)characteristics and solar wind conditions for the main phase of geomagnetic storms,seeking possible factors that distinguish extreme storms(minimum Dst<−250 nT)and major storms(minimum Dst<−100 nT).In our analysis of 170 storms,there is a marked correlation between the average rate of change of Dst during a storm’s main phase(ΔDst/Δt)and the storm’s minimum Dst,indicating a fasterΔDst/Δt as storm intensity *** events add a new regime toΔDst/Δt,the hourly time derivative of Dst(dDst/dt),and sustained periods of large amplitudes for southward interplanetary magnetic field Bz and solar wind convection electric field *** find that Ey is a less efficient driver of dDst/dt for extreme storms compared to major storms,even after incorporating the effects of solar wind pressure and ring current *** minimum Dst is correlated with minimum Bz,we observe a similar divergence,with extreme storms tending to have more negative Dst than the trend predicted on the basis of major *** results enable further improvements in existing models for storm predictions,including extreme events,based on interplanetary measurements.

关键词： extreme geomagnetic storm Dst prediction solar wind driving major storms

D53 represses rice blast resistance by directly targeting phenylalanine ammonia lyases

在线全文

学校读者我要写书评

暂无评论

Journal of Integrative Plant Biology 2024年第9期66卷 1827-1830页

作者： Haitao Ye Qingqing Hou Haitao Lv Hui Shi Duo Wang Yujie Chen Tangshuai Xu mei Wang Min He Junjie Yin Xiang Lu Yongyan Tang Xiaobo Zhu Lijuan Zou Xuewei Chen Jiayang Li Bing Wang Jing Wang State Key Laboratory of Crop Gene Exploration and Utilization in Southwest China Sichuan Agricultural UniversityChengdu 611130China Key Laboratory of Seed Innovation Institute of Genetics and Developmental BiologyChinese Academy of SciencesBeijing 100101China Yazhouwan National Laboratory Sanya 572024China

Phytohormones play important roles in orchestrating plantimmune responses to pathogen ***(SLs),a group of carotenoid-derived phytohormones,modulate diverse biological processes in plants,including shoot branching,plant height,root architecture,leaf senescence,seed germination of parasitic plants,and symbiosis of arbuscular mycorrhizal fungi(Burger and Chory,2020).Recently,increasing evidence has indicated potential roles for SLs in regulating responses against biotic stresses,including defense responses against certain pathogenic fungi and bacteria in roots and leaves(Yi et al.,2023).

关键词： ammonia resistance branching

Plasmaspheric trough evolution under different conditions of subauroral ion drift

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2012年第5期55卷 1287-1294页

作者： HE Fei ZHANG XiaoXin CHEN Bo fok meiching Changchun Institute of Optics Fine Mechanics and PhysicsChinese Academy of SciencesChangchun 130033China National Center for Space Weather China Meteorological AdministrationBeijing 100081China NASA Goddard Space Flight Center GreenbeltMD 20771USA

The statistical characteristics of the subauroral ion drift (SAID) in the ionosphere and the plasmaspheric trough evolution under different conditions of SAID were investigated in this paper, based on 566 SAID events observed by Akebono, Astrid-2, DE-2, and Freja satellites. The relationships between the latitudinal location of SAID and the Kp, AL, and Dst indices for these events were also discussed. It was found that the SAID events happened mainly at invariant latitude (ILAT) of 60.4° and magnetic local time (MLT) of 21.6 MLT and that 92.4% of the events happened when the Kp index was below 5.0, indicating a medium geomagnetic activity. The latitudinal half-width of SAID varied from 0.5° to 3.0° with a typical half-width of 1.0°. The SAID would happen at low latitudes if the geomagnetic activity was high. The effects of SAID on equatorial outer plas- masphere trough evolutions were studied with the dynamic global core plasma model (DGCPM) driven by the statistical results of SAID signatures. It was noted that locations, shapes and density of troughs vary with ILAT, MLT, latitudinal width, cross polar cap potential and lifetime of SAID events. The evolution of a trough is determined by the extent of SAID electric field penetrating into plasmasphere and not all SAID events can result in trough formations.

关键词： subauroral ion drift plasmaspheric trough dynamic global core plasma model simulation

Application of digital image correlation to full-field measurement of shrinkage strain of dental composites

在线全文

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2013年第1期14卷 1-10页

作者： Jian-ying LI Andrew LAU Alex S. L. fok Minnesota Dental Research Centre for Biomaterials and Biomechanics School of Dentistry University of Minnesota Minneapolis MN 55455 USA

Objectives： Polymerization shrinkage of dental composites remains a major concern in restorative dentistry because it can lead to micro-cracking of the tooth and debonding at the tooth-restoration interface. The aim of this study was to measure the full-field polymerization shrinkage of dental composites using the optical digital image correlation （DIC） method and to evaluate how the measurement is influenced by the factors in experiment setup and image analysis. Methods： Four commercial dental composites, Premise Dentine, Z 100, Z250 and Tetric EvoCeram, were tested. Composite was first placed into a slot mould to form a bar specimen with rectangular-section of 4 mmx2 mm, followed by the surface painting to create irregular speckles. Curing was then applied at one end of the specimen while the other part were covered against curing light for simulating the clinical curing condition of composite in dental cavity. The painted surface was recorded by a charge-coupled device （CCD） camera before and after curing. Subsequently, the volumetric shrinkage of the specimen was calculated with specialist DIC software based on image cross correlation. In addition, a few factors that may influence the measuring accuracy, including the subset window size, speckle size, illumination light and specimen length, were also evaluated. Results： The volumetric shrinkage of the specimen generally decreases with increasing distance from the irradiated surface with a conspicuous exception being the composite Premise Dentine as its maximum shrinkage occurred at a subsurface distance of about 1 mm instead of the irradiated surface. Z100 had the greatest maximum shrinkage strain, followed by Z250, Tetric EvoCeram and then Premise Dentine. Larger subset window size made the shrinkage strain contour smoother. But the cost was that some details in the heterogeneity of the material were lost. Very small subset window size resulted in a lot of noise in the data, making it difficult to discern the g

关键词： Image correlation Dental composite Polymerization shrinkage Depth of cure

Bt cotton seed purity in Burkina Faso:status and lessons learnt

在线全文

学校读者我要写书评

暂无评论

Journal of Cotton Research 2020年第4期3卷 260-267页

作者： BOURGOU Larbouga KARGOUGOU Ester SAWADOGO Mahamadou fok Michel INERA Programme CotonBP 208Bobo-DioulassoBurkina Faso SOFITEX Laboratoire Contrôle QualitéSemences01 BP 147Bobo-Dioulasso 01Burkina Faso UniversitéOuaga1 Joseph Ki-Zerbo 09 BP 848Ouagadougou 09Burkina Faso CIRAD F-34398 MontpellierFrance UPR AIDA Univ MontpellierMontpellierFrance.

Background:Since the commercial release of Bt cotton in Burkina Faso in 2009,the issue of seed purity in producers’fields has rarely been addressed in an unbiased and objective *** potential for contamination of conventional seed varieties with Bt traits and the consequent threat to the continuation of organic cotton production has been ***,studies are rare on the varietal purity of Bt cotton seeds,despite the implications for the effectiveness and sustainability of their *** paper compensates for the lack of research on the varietal purity of cotton seeds in Burkina Faso by reporting the results of Enzyme linked immunosorbent assay tests collected in 2015 on samples of both conventional and Bt varieties from 646 ***:According to the conservative criteria used to declare the presence of a Bt gene in a given variety(more than 10%of seeds of conventional variety exhibit Bt traits,and at least 90%of seeds of Bt variety exhibit Bt traits),seed purity was very questionable for both types of *** the supposedly conventional variety,the Cry1Ac gene was observed in 63.6%of samples,the Cry2Ab gene was observed in 59.3%of samples,and both genes were detected in 52.2%of the seed *** 29.3%of the seeds that were supposed to be of conventional type contained no Bt ***,for the labeled Bt variety,the Cry1Ac gene was found in only 59.6%of samples,the Cry2Ab gene was found in 53.6%of the samples,and both genes were found in 40.4%of the ***,for the seeds that were supposed to contain both genes(Bollguard 2),both Cry1Ac and Cry2Ab genes were found in only 40.4%of the samples,only one of the genes was found in 32.4%of the samples,and 27.2%of the seeds in the samples contained *** factors are responsible for the severe lack of seed ***,conventional varieties are being contaminated with Bt traits because of a failure to revise the seed production scheme in Burkina Faso to prevent cross-pollinat

关键词： Conventional cotton Organic cotton GM cotton Seed production scheme Seed control Burkina Faso

The Application of GGE Biplot Analysis for Evaluating Test Locations and Mega-Environment Investigation of Cotton Regional Trials

在线全文

学校读者我要写书评

暂无评论

Journal of Integrative Agriculture 2014年第9期13卷 1921-1933页

作者： XU Nai-yin fok Michel ZHANG Guo-wei LI Jian ZHOU Zhi-guo Key Laboratory of Corp Growth Regulation Ministry of Agriculture/Nanjing Agricultural University Key Laboratory of Cotton and Rapeseed Ministry of Agriculture/Institute of Industrial Crops Jiangsu Academy of Agriculture Sciences Center of International Cooperation on Agronomic Research for Development (CIRAD) TA B102/0234398 Montpellier Cedex 5France

In the process to the marketing of cultivars, identification of superior test locations within multi-environment variety trial schemes is of critical relevance. It is relevant to breeding organizations as well as to governmental organizations in charge of cultivar registration. Where competition among breeding companies exists, effective and fair multi-environment variety trials are of utmost importance to motivate investment in breeding. The objective of this study was to use genotype main effect plus genotype by environment interaction（GGE） biplot analysis to evaluate test locations in terms of discrimination ability, representativeness and desirability, and to investigate the presence of multiple mega-environments in cotton production in the Yangtze River Valley（YaRV）, China. Four traits（cotton lint yield, fiber length, lint breaking tenacity, micronaire） and two composite selection indices were considered. It was found that the assumption of a single mega-environment in the YaRV for cotton production does not hold. The YaRV consists of three cotton mega-environments： a main one represented by 11 locations and two minor ones represented by two test locations each. This demands that the strategy of cotton variety registration or recommendation must be adjusted. GGE biplot analysis has also led to the identification of test location superior for cotton variety evaluation. Although test location desirable for selecting different traits varied greatly, Jinzhou, Hubei Province, China, was found to be desirable for selecting for all traits considered while Jianyang, Sichuan Province, China, was found to be desirable for none.

关键词： cotton multi-environmental trial GGE biplot test location mega-environment