检索结果-南通市图书馆

Boundary Shift of Potential Suitable Agricultural Area in Farming-grazing Transitional Zone in Northeastern China under Background of Climate Change During 20th Century

在线全文

学校读者我要写书评

暂无评论

Chinese Geographical Science 2013年第6期23卷 655-665页

作者： YE yu fang Xiuqi School of Geography Beijing Normal University Key Laboratory of Environment Change and Natural Disaster Ministry of EducationBeijing Normal University

Climate change affected the agricultural expansion and the formation of farming-grazing transitional patterns during historical periods. This study analyzed the possible range of the boundary shift of the potential suitable agriculture area in the farming-grazing transitional zone in the northeastern China during the 20th century. Based on modem weather data, 1 km-resolution land cover data, historical climatic time series, and estimation by using similar historical climatic scenes, the following was concluded： 1） The climate conditions of suitable agriculture areas in the farming-grazing transitional zone in the northeastern China between 1971 and 2000 required an average annual temperature above 1℃ or ≥ 0℃ accumulated temperature above 2500℃-2700℃, and annual precipitation above 350 mm. 2） The northern boundary of the potential suitable agriculture area during the relatively warmer period of 1890-1910 was approximately located at the position of the 1961-2000 area. The northern boundary shifted back to the south by 75 km on average during the colder period of the earlier 20th century, whereas during the modem warm period of the 1990s, the area shifted north by 100 km on average. 3） The western and eastern boundaries of the suitable agricul^re area during the heaviest drought periods between 1920s and 1930s had shifted northeast by 250 km and 125 km, respectively, contrasting to the boundaries of 1951-2008. For the wettest period, that is, the 1890s to the 1910s, the shift of western and eastern boundaries was to the southwest by 125 km and 200 km, respectively, compared with that in the 1951-2008 period. This study serves as a reference for identifying a climatically sensitive area and planning future land use and agricultural production in the study area.

关键词： land cover changes farming-grazing transitional zone climate change agricultural production

An explanation for the peculiar periphery of supernova remnant G309.2–0.6

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2018年第9期18卷 133-140页

作者： Huan yu Jun fang Department of Physical Science and Technology Kunming University Department of Astronomy Key Laboratory of Astroparticle Physics of Yunnan Province Yunnan University

Supernova remnant（SNR） G309.2–0.6 has a peculiar radio morphology with two bright ears to the southwest and northeast, although the main shell outside the ears is roughly circular. Based on an earlier proposal that the supernova ejecta has a jet component with extra energy, the dynamical evolution of the remnant is solved using 3 D hydrodynamical（HD） simulation to investigate the formation of the periphery of the remnant. Assuming the ejecta with a kinetic energy of 10^51 erg and a mass of 3 M⊙evolved in a uniform ambient medium for a time of-4000 yr and the jet component has cylindrical symmetry with a half open angle of 10°, the result indicates that the energy contained in the jet is about10%–15% of the kinetic energy of the entire ejecta to reproduce the detected profile. This study supports that the remnant originated from a jet-driven core-collapse supernova.

关键词： hydrodynamics(HD) - methods numerical - ISM supernova remnants

Effects of C60 on the Glass Transition Temperature of Carbazole-based Photorefractive Polyphosphazenes

在线全文

学校读者我要写书评

暂无评论

Journal of Wuhan University of Technology(Materials Science) 2018年第4期33卷 974-979页

作者：陈百利 CHEN Shufan LUO xuan fang yu ZHANG Qingjun HUANG Chuanqun DENG Qinghua 吴卫东 Research Center of Laser Fusion China Academy of Engineering PhysicsMianyang 621900China

The bi-functional carbazole-based photorefractive polyphosphazenes with different content of C_（60）-doped were fabricated. The glass transition temperature（T_g） of these polymer composite materials was determined using a differential scanning calorimetric（DSC） method. According to the DSC measurement results with different heating rates, the variation of T_g and the active energy of glass transition（E_g） were analyzed in detail. The analysis results indicate that the transition region shifts to higher temperatures with increasing heating rate, and C_（60） content（below 1.0 wt%） can influence the T_g of photorefractive polyphosphazenes. The T_g first increases and then decreases with the C_（60） content（below 1.0 wt%）. The probable causes of the influence of C_（60） on T_g was proposed.

关键词： differential scanning calorimetric (DSC) fullerene C60 carbazole-based photorefractivepolyphosphazenes glass transition temperature (Tg) active energy of glass transition (Eg)

Optical properties of conductive silver-nanowire films with different nanowire lengths

在线全文

学校读者我要写书评

暂无评论

Nano Research 2017年第11期10卷 3706-3714页

作者： Xiaoming yu xuan yu Jianjun Zhang Liqiao Chen yunqian Long Dekun Zhang Innovation Application Institute Zhejiang Ocean University Zhoushan 316004 China College of Electronic Information and Optical Engineering Nankai University Tianjin 300071 China

Transparent electrodes made of silver nanowires （Ag NWs） exhibit a higher flexibility than conventional indium tin oxide *** this reason,Ag NWs may find applications in future flexible electronic and optoelectronic ***,different optoelectronic devices have different specific requirements for Ag *** example,the optical transmittance haze is an important but rarely studied aspect of Ag NW *** this study,the optical transmittance and optical scattering of long （5-50 μm,L-NWs） and short （1-20 μm,S-NWs） Ag NW films were *** L-NWs exhibited better optical transmission than the S-NWs,whereas the S-NWs exhibited better light-scattering properties than the *** results indicate that the L-NWs are suitable for touch-screen displays,whereas the S-NWs are better suited as transparent conductive films for solar *** analyzed the scattering ratio of forward-scattered light to backscattered light for both the L-NWs and S-NWs and discovered that the mesh size affected the scattering *** longer wavelengths,a larger mesh yielded a higher backscattering ratio,whereas a smaller mesh yielded a lower backscattering *** formulated an equation for calculating the reflection haze using the total reflection （Ag NWs/glass）,R and the reflection of glass,*** reflection haze of the S-NWs and L-NWs exhibited different trends in the visible-near-infrared *** omnidirectional scattering model for the Ag NWs was used to evaluate the Ag NW scattering *** results of this study have great significance for the evaluation of the performance of Ag NWs in optoelectronic devices.

关键词： transparent electrode silver nanowires transmittance haze factor forward scattering and backscattering reflection-haze factor

Stabilization of Cu/ZnO Based Catalysts by Nickel Additive in Methanol Decomposition

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chemical Research in Chinese Universities 2001年第4期17卷 420-425页

作者： XI Jing-yu WANG Zhi-fei LU Gong-xuan State Key Laboratory for Oxo Synthesis and Selective Oxidation Lanzhou Institute of Chemical PhysicsThe Chinese Academy of SciencesLanzhou 730000P.R.China

A series of Cu/Zn based catalysts with and without Ni, prepared by the co-precipitation method, has been studied for methanol decomposition. CO and H2 are the major products. The Cu/Zn catalysts show a low initial activity and a poor stability. The formation of the CuZn alloys was observed in the deactivated Cu/Zn catalysts which were used for methanol decomposition at 250 . When small amounts of Ni were added in the catalyst, the Cu/Zn/Ni(molar ratio 5/4/ x) catalysts showed a high activity at a low temperature. The activity and the stability of the catalyst depend on the nickel content. The activity of the Cu/Zn/Ni catalysts was maintained at a. relatively stable value of 78% conversion of methanol with 95% selectivity of H2, 93% selectivity of CO, and a more than 70% yield of hydrogen was obtained at 250 C when x >1. The stability of the Cu/Zn/Ni (molar ratio 5/4/x) catalysts showed the maximum (ca 88%) when x=1. The stabilization effect of nickel on the Cu/Zn based catalysts may lead to the increasing of the dispersion of active Cu species and the prevention of CuZn alloys formation.

关键词： Nickel Cu/Zn catalysts Stabilization Methanol Decomposition

Exosomes:Promising biomarkers and targets for cancer

在线全文

学校读者我要写书评

暂无评论

World Journal of Gastrointestinal Oncology 2022年第8期14卷 1594-1596页

作者： Zhen fang Yi-xuan Ding Fei Li Department of General Surgery Xuanwu Hospital of Capital Medical UniversityBeijing 100053China

The review article entitled"Exosomes as potential diagnosis and treatment for liver cancer"recently published in World Journal of Gastrointestinal Oncology 2022;14:334-347 concluded that exosomes can be used as effective biomarkers or therapeutic biotargets in liver *** are a hot spot in the field of tumor diagnosis and treatment *** had also previously published a review on exosomes and *** this letter to the editor,we summarize the clinical application prospects and current challenges of exosomes.

关键词： Exosomes Cancer Biomarkers Diagnosis Therapy

Enantioselective Synthesis of Benzimidazole Atropisomers Featuring a N-N Axis

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Chemistry 2024年第7期42卷 711-718页

作者： fang-Bei Ge Qi-Kun Yin Chuan-Jun Lu xuan xuan Jia Feng Ren-Rong Liu College of Chemistry and Chemical Engineering Qingdao UniversityQingdaoShandong 266071China School of Pharmacy Key Laboratory of Molecular Pharmacology and Drug EvaluationMinistry of EducationYantai UniversityYantaiShandong 264005China

Atroposelective synthesis of N-N atropisomers is an emerging area but remains underexplored;in particular,the synthesis of N-N benzimidazole atropisomers is still ***,the first enantioselective synthesis of N-N benzimidazole atropisomers via the palladium-catalyzed de novo construction of benzimidazole skeleton is *** readily available palladium catalyst and biphosphine ligand,a broad range of nonbiaryl benzimidazole and indole-benzimidazole atropisomers were conveniently ac-cessed in high yields and with excellent ***,these N-N benzimidazole atropisomers showed great anti-tumor activity and selectivity to breast cancer MCF-7 *** simple catalytic system,broad substrate scope,high enantioselectivi-ty,and good bioactivity make this approach highly attractive.

关键词： Asymmetric synthesis Atropisomerism Palladium Benzimidazole Antitumor

Advances in solid Mg-ion electrolytes for solid-state Mg batteries

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2023年第30期161卷 136-149页

作者： yuepeng Pang yu Zhu fang fang Dalin Sun Shiyou Zheng School of Materials and Chemistry University of Shanghai for Science and TechnologyShanghai 200093China Department of Materials Science Fudan UniversityShanghai 200433China

Rechargeable Mg batteries have attracted much attention in the past decade due to their high theoretical energy density and low production cost,in which the electrolyte is the key component that determines the overall *** solid Mg-ion electrolytes brings many benefits to rechargeable Mg bat-teries,which can improve safety under aggressive conditions and open opportunities for new electrode *** extensive investigations,researchers make major breakthroughs in the solid Mg-ion electrolyte field,especially in terms of Mg-ion ***,the development of solid-state Mg batteries is still at the early stage since their stable cycling has not been achieved *** this review,we introduce the Mg-ion conducting properties of current solid Mg-ion electrolytes,and then summarize the performances of corresponding solid-state Mg *** addition,we provide a discussion on the application potentials and future directions of each type of solid Mg-ion electrolytes that are applied in solid-state Mg batteries.

关键词： Solid Mg-ion electrolytes Solid-state Mg batteries Phosphates Borohydrides Chalcogenides Metal-organic frameworks Polymers

Discrete element modeling of sand behavior in a biaxial shear test

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第9期9卷 1176-1183页

作者： Zhi-yi HUANG Zhong-xuan YANG Zhen-yu WANG Department of Civil Engineering Zhejiang University Hangzhou 310027 China MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering Zhejiang University Hangzhou 310027 China Department of Civil Engineering The University of Hong Kong Hong Kong China

The mechanical behavior of sand is very complex, and depends on factors including confining pressure, density, and drainage condition. A soil mass can be contractive or dilative when subjected to shear loading, and eventually reaches an ultimate state, referred to as the critical state in soil mechanics. Conventional approach to explore the mechanical behavior of sand mainly relies on the experimental tests in laboratory. This paper gives an alternative view to this subject using discrete element method (DEM), which has attracted much attention in recent years. The implementation of the DEM is carried out by a series of numerical tests on granular assemblies with varying initial densities and confining pressures, under different test configurations. The results demonstrate that such numerical simulations can produce correct responses of the sand behavior in general, including the critical state response, as compared to experimental observations. In addition, the DEM can further provide details of the microstructure evolutions during shearing processes, and the resulting induced anisotropy can be fully captured and quantified in the particle scale.

关键词： Granular soil behavior Critical state Microstructure Discrete element method (DEM)