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Search Results: 1 - 10 of 81069 matches for " XU Zhen-Feng "
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trans-Bis[4-amino-N-(pyrimidin-2-yl)benzenesulfonamidato]dipyridinecobalt(II) hemihydrate
Yan-Fei Wang,Hong-Li Zou,Xu-Jian Luo,Zhen-Feng Chen
Acta Crystallographica Section E , 2010, DOI: 10.1107/s1600536810013802
Abstract: The asymmeric unit of the title compound, [Co(C10H9N4O2S)2(C5H5N)2]·0.5H2O, contains the distorted octahedral trans-[Co(sdz)2(py)2] (sdz is the sulfadiazine anion and py is pyridine) complex molecule and a half-molecule of water, which lies on a twofold rotation axis. A three-dimensional network is generated by N—H...O and O—H...O hydrogen bonds between the complex and the water molecules.
Constructing Optimistic ID-Based Fair Exchange Protocols via Proxy Signature

XU Jing,ZHANG Zhen-Feng,FENG Deng-Guo,

软件学报 , 2007,
Abstract: This paper introduces a natural paradigm for fair exchange protocols,called ID-based partial proxy signature scheme. A security model with precise and formal definitions is presented,and an efficient and provably secure partial proxy signature scheme is proposed. This is a full ID-based optimistic fair exchange protocol. Unlike the vast majority of previously proposed protocols,this approach does not use any zero knowledge proofs,and thus avoids most of the costly computations.
Study on VSP with different constraints based on genetic algorithm

WANG Zhen-feng,WANG Xu,GE Xian-longa,

计算机应用研究 , 2010,
Abstract: This paper studied the shortest run distances of vehicle scheduling problem (VSP) with different constraints.Established the vehicle scheduling models with different constraints include driving distance, time window, full loads and non-full loads. And then designed genetic algorithm of natural number coding for vehicle scheduling models and improved the cross algorithm of it.Retained the optimal gene transmissibility as much as possible and accelerated the convergence of the algorithm.Finally,verified the model and algorithm through numerical example.
Characteristics and Mechanism for Three-dimensional UV-fluorescence Spectroscopy of Plasma

GAO Shu-mei,GE Li-xin,XU Zhen-feng,
,葛立新 徐振峰

光子学报 , 2008,
Abstract: The plasma three-dimensional UV fluorescence excitation and emission spectra,the wavelength of 220~320 nm,are obtained by FLS920 Combined Fluorescence Lifetime & Steady State Spectrometer.There is a wide peak with 100 nm in the fluorescence emission spectra near 334 nm,from 300 nm to 400 nm.It is presented that the peak derivers from many fluorophores interaction,which is mostly Tryptophan and tyrosine in plasma protein.In addition,the other proteins and small molecules in the plasma made the fluorescence peak widen by emitting fluorescence and indirect energy transfer or interaction,which may modulate the spectral characteristic.
Fog-and-Haze Risk Mapping of Sichuan Basin Area

QING Qing-tao
,XU Jin-xia,MA Zhen-feng,SUN Yu

- , 2017, DOI: 10.13718/j.cnki.xdzk.2017.09.022
Abstract: 利用四川盆地区1981-2014年逐日地面气象观测资料和社会经济数据,选取不同等级雾、霾频率作为致灾因子危险性评估指标,以人口密度、公路密度和地均三产业值作为孕灾环境脆弱性影响因子,考虑地形因子、河网密度和地均GDP作为承灾体易损性评估指标,从这3个角度出发,基于GIS技术,运用层次分析法建立影响四川盆地区雾霾灾害的风险评估模型,得到四川省盆地地区的雾霾灾害风险区划结果.分析表明:四川盆地区雾霾灾害风险等级呈现出从盆周山区到盆底区域不断升高的基本特征.高、次高风险区主要集中在盆地底部的大部分区域,与高原接壤的高海拔区域和盆周山区处于雾霾灾害低风险区和次低风险区,与盆周山区相邻的盆底边缘地区大部分为中等风险区,研究结果与实际情况基本相符.
In a study based on the daily ground meteorological observation data and the socio-economic data of Sichuan basin area (1981-2014), multi-level fog and haze frequency was selected as the disaster risk evaluation indicator, population density, traffic density and tertiary industry GDP as the hazard-inducing environment vulnerability indicators, and terrain indices, watercourse density and local GDP as the vulnerability evaluation indices. Starting from the three elements listed above and exploiting the GIS technology, the authors constructed a risk evaluation model by AHP and verified the fog and haze risk mapping of Sichuan basin area. The results demonstrated that the risk level of fog and haze steadily rose from the mountainous regions surrounding the basin to its bottom. High or sub-high risk was mostly at the bottom of the Sichuan basin. The high-altitude areas adjacent to west Sichuan plateau and the mountainous areas surrounding the basin were the low-risk or sub-low-risk areas. The areas located between the margin mountainous areas and the basin bottom were the medium risk area. The above results were proved to be consistent with the reality of Sichuan basin
Probe into the Automatic Score of Subjective Items Based Upon Computer-Assisted Assessment
JIANG Zhen-feng,LIU Li
Journal of Chongqing Normal University , 2013,
Abstract: In allusion to the hot and difficult problem of computer-assisted assessment, in order to improve the function of computer-assisted assessment system, in this study, a new assessment method is presented to realize the automatic score of subjective items. To perform the assessment, it is necessary to establish a repository of reference answers written by course instructors or related experts. Then focused on how to use the BLEU algorithm to assessment, and through the n-gram processing, this paper improved the algorithm in the synonyms and spelling errors, etc. Applied the modified version of the BLEU to identify the most similar reference answer to the student answer and then the student answer is scored on its similarity with the selected reference answer. At last, through one empirical research we proved the availability of the new evaluation method. The results showed that,combined with the existing relatively mature evaluation method, this method can be used to for subjective answers assessment, and play a more active role in CAA.
Seasonal dynamics in soil microbial biomass carbon and nitrogen and microbial quantity in a forest-alpine tundra ecotone,Eastern Qinghai-Tibetan Plateau,China

LIU Yang,ZHANG Jian,YAN Bang-Guo,HUANG Xu,XU Zhen-Feng,WU Fu-Zhong,

植物生态学报 , 2012,
Abstract: Aims The forest-alpine tundra ecotone is one of the most conspicuous climate-driven ecological boundaries.However,dynamics of soil microbial biomass and quantity during different stages of the growing season in the ecotone remain unclear.Our objective was to understand the temporal and spatial variations of microbial biomass and quantity to explore the main drivers in the ecotone.Methods We collected soil samples in a forest-alpine tundra ecotone(dark-conifer forest,timberline,treeline,dense shrub,sparse shrub and alpine meadow) during early,mid and late growing season(EGS,MGS and LGS).The number and species composition of soil microorganisms were determined by means of the plate count method.Soil microbial biomass carbon(MBC) and nitrogen(MBN) were measured by the chloroform fumigation leaching method.Important findings Vegetation and seasonality significantly influence MBC,MBN and microbial community structure.Microbial biomass distribution among vegetation types was different in the three stages of the growing season.MBC above treeline was higher than below during EGS and MGS.The MBC of dark-conifer forest,timberline and treeline during LGS was significantly increased,and MBC differences among different vegetation types decreased.There were significant differences in measured soil microbial quantity between above-and below-treeline vegetation types;bacteria of dense shrub were highest among vegetation types.The amount of cultivated microorganisms was LGS>EGS>MGS.The ratio of MBC to MBN was the highest and the quantity of fungi increased largely late in the growing season.Statistical analysis showed that there were significant correlations between MBN and bacteria,fungi and actinomyces quantity,while only MBC and fungi quantity weresignificantly correlated(p < 0.05).Litter input and snow cover late in the growing season were external factors of microbial seasonal variation.Soil microbes and alpine plants competing for nitrogen may be internal factors.Plant nitrogen absorption early in the growing season and microorganisms’ nitrogen fixation late in the growing season enhanced the alpine ecosystem’s nitrogen fixation and utilization.Climate warming may extend the growing season of alpine plants,increasing the alpine soil microbial biomass,and accelerate the decomposition of soil organic matter,which may change soil carbon sequestration rates in the alpine ecosystem.
Effects of simulated warming on the growth, leaf phenology, and leaf traits of Salix eriostachya in sub-alpine timberline ecotone of Western Sichuan, China.

XU Zhen-feng,HU Ting-xing,ZHANG Li,ZHANG Yuan-bin,XIAN Jun-ren,WANG Kai-yun,

应用生态学报 , 2009,
Abstract: 采用开顶式生长室(open-top chamber, OTC)模拟增温的方法,研究了模拟增温对川西亚高 山林线交错带绵穗柳生长和叶性状的影响.结果表明:与对照样地相比,OTC内日平均气温(地上12 m)在植物生长季中增加2.9 ℃,而5 cm土壤温度仅增加0.4 ℃;温度升高使绵穗柳芽开放时间明显提前、落叶时间明显推迟,叶寿命延长;OTC内绵穗柳叶面积和侧枝生长速率明显加快,比叶面积明显增加,而叶氮浓度却显著下降;OTC内绵穗柳的气孔导度、净光合速率、光呼吸速率和暗呼吸速率总体上呈增加趋势.综上所述,绵穗柳适应增温效应的能力较强,在未来气候变化背景下,其分布的海拔高度有可能上升.

XU Zhen-Feng,HU Ting-Xing,ZHANG Yuan-Bin,XIAN Jun-Ren,WANG Kai-Yun,

植物生态学报 , 2008,
Abstract: 采用开顶式生长室(Open-top chamber,OTC)模拟增温对植被影响的研究方法,研究了川西亚高山林线交错带糙皮桦(Betula utilis)和岷江冷杉(Abies faxoniana)幼苗物候及生长特性对模拟增温的响应.结果表明,温度升高使岷江冷杉幼苗芽开放时间显著提前(15.2 d);糙皮桦春季芽物候期变化不显著,而落叶时间明显推迟(19.7 d),叶寿命延长(22.8 d).与对照(CK)相比,OTC内糙皮桦叶面积和岷江冷杉叶片长度及两者侧枝生长速率都显著加快.模拟增温对两物种基径相对生长速率都表现为正效应,增温对两物种枝叶特性及分布格局表现为不同程度的正效应、负效应或无影响.不同功能型两物种对模拟增温响应方式存在一定程度差异.
Comprehensive geological and geophysical study in middle southern region of China

JIANG Wei-Wei,HAO Tian-Yao,XU Yi,LIU Zhen-Feng,ZHU Dong-Ying,TU Guang-Hong,

地球物理学报 , 2007,
Abstract: We use gravity,magnetic,and earthquake data to carry out a comprehensive geological and geophysical study in the middle southern region of China.According to the distribution of gravity and magnetic anomalies,four gravity anomalous zones and three magnetic anomalous zones are identified.According to calculations of gravity data,the crustal thickness ranges between 29.5 and 41 km with a general trend of being thick in the west and thin in the east.There is a mirror image relationship between crust thickness and terrain relief.According to magnetic data,the depth of Curie interface ranges between 12 and 40 km in the study area.The crust of study region is divided into four layers by velocity interfaces at 3,13,23km and 36km,and below the crust two velocity interfaces at 71km and 120km are adopted in seismic tomographic study.Tomographic imaging result indicates that velocity distribution generally reflects the characteristics of crossed fault blocks.Longitudinally,the upper crust structure in Jianghan-Dongting basins and their marginal orogenic belts does not change much,the middle and lower crust were generally transformed by modern tectonic activities,leading to certain changes in lithospheric structure.Their main presentation is the enlargement of low velocity areas,it is particularly so in the lower part of the crust.This is closely related to the tension of depressive basins and lithospheric intrusion in orogenic belt.Analysis and calculations of geophysical fields reveal 34 principal fault zones in the study area.According to geotectonic theory of lithospheric plate,as well as the variations of deep-seated structures of lithosphere,crustal structure and crystalline basement,the different tectonic units-massives in the study area can be taken as primary tectonic units.The deep grand fault zones between them can be taken as boundary contact zones.In light of this principle,two primary tectonic units and five secondary tectonic units are identified.
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