检索结果-南通市图书馆

Estimation of the quantity of aeolian saltation sediments blown into the Yellow River from the Ulanbuh Desert,China

Journal of Arid Land 2014年第2期6卷 205-218页

作者： HeQiang DU xian xue Tao WANG Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences

The Ulanbuh Desert borders the upper reach of the Yellow River. Every year, a mass of aeolian sand is blown into the Yellow River by the prevailing wind and the coarse aeolian sand results in serious silting in the Yellow River. To estimate the quantity of aeolian sediments from the Ulanbuh Desert blown into the Yellow River, we simulated the saltation processes of aeolian sediments in the Ulanbuh Desert. Then we used a saltation submodel of the IWEMS （integrated Wind-Erosion Modeling System） and its accompanying RS （Remote Sensing） and GIS （Geographic Information System） modules to estimate the quantity of saltation sediments blown into the Yellow River from the Ulanbuh Desert. We calibrated the saltation submodel by the synchronous observation to wind ve- locity and saltation sediments on several points with different vegetation cover. The vegetation cover, frontal area of vegetation, roughness length, and threshold friction velocity in various regions of the Ulanbuh Desert were obtained using NDVI （Normalized Difference Vegetation Index） data, measured sand-particle sizes, and empirical relation- ships among vegetation cover, sand-particle diameters, and wind velocity. Using these variables along with the observed wind velocities and saltation sediments for the observed points, the saltation model was validated. The model results were shown to be satisfactory （RMSE less than 0.05 and IRel less than 17%）. In this study, a subdaily wind-velocity program, WlNDGEN, was developed using this model to simulate hourly wind velocities around the Ulanbuh Desert. By incorporating simulated hourly wind-velocity and wind-direction data, the quantity of saltation sediments blown into the Yellow River was calculated with the saltation submodel. The annual quantity of aeolian sediments blown into the Yellow River from the Ulanbuh Desert was 5.56x106 t from 2001 to 2010, most of which occurred in spring （from March to May）; for example, 6.54x10~ tons of aeolian sand were blown in

关键词： aeolian sand sediments integrated wind-erosion modeling system NDVI WlNDGEN Ulanbuh Desert

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Neurons-system-like structured SnS_(2)/CNTs composite for high-performance sodium-ion battery anode

引用

Rare Metals 2021年第6期40卷 1383-1390页

作者： Ling Zhu xue-xian Yang Yan-Hong xiang Peng Kong xian-Wen Wu School of Physics and Electromechanical Engineering Jishou UniversityJishou 416000China School of Chemistry and Chemical Engineering Jishou UniversityJishou 416000China

Sodium-ion batteries(SIBs)have attracted significant attention with respect to renewable energy power generation systems because of the abundant reserves of sodium on ***,anode materials are presently limited by low energy density,poor rate performance and inferior cycling *** recent years,tin disulfide(SnS_(2))with a particular layered structure has been considered as a promising anode material for SIBs due to its high theoretical capacity and low ***,a nervoussystem-like structured SnS_(2)/CNTs composite was successfully synthesized via a hydrothermal *** SnS_(2)sheets were strung with carbon nanotubes(CNTs)to form a hierarchical porous structure,which is effective for electrolyte diffusion and electronic *** large distance of the(001)plane(0.5899 nm)of SnS_(2)favors Na+insertion-extraction *** from these structural characteristics,SnS_(2)/CNTs electrodes exhibit high specific capacity,excellent rate performance and superior cycling stability.A high charge capacity of 642 mAh·g^(-1)was released at 0.2 A·g^(-1),and then,a high reversible capacity of 427 mAh·g^(-1)was retained after 100 *** charged at 2 A·g^(-1),the SnS_(2)/CNTS electrode maintained a capacity of 282 mAh·g^(-1).The nervous-system-like structure of the SnS_(2)/CNTs composite provides a novel strategy for the development of SIBs with high electrochemical performance.

关键词： SnS_(2)/CNTs Sodium-ion batteries Anode Composite Rate capability

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

盐胁迫对干旱区植物能量代谢过程的影响综述

引用

中国沙漠 2024年第1期44卷 111-118页

作者：潘晶王磊黄翠华尤全刚郭平林郭琪薛娴中国科学院西北生态环境资源研究院、沙漠与沙漠化重点实验室干旱区盐渍化研究站甘肃兰州730000 甘肃省水利厅石羊河流域水资源利用中心甘肃武威733000 中国科学院大学北京100049 甘肃省科学院生物研究所、甘肃省微生物资源开发利用重点实验室“特色微生物与植物资源创新”甘肃省国际科技合作基地甘肃兰州730000

盐胁迫是影响干旱区植物生长的重要非生物胁迫,会干扰植物能量代谢过程,进而对植物的生长发育产生不良影响。盐胁迫条件下植物是否具有稳定的能量供应与其耐盐性能密切相关。本文从植物种子萌发、营养生长和生殖生长等3个阶段入手,浅析... 详细信息

盐胁迫是影响干旱区植物生长的重要非生物胁迫,会干扰植物能量代谢过程,进而对植物的生长发育产生不良影响。盐胁迫条件下植物是否具有稳定的能量供应与其耐盐性能密切相关。本文从植物种子萌发、营养生长和生殖生长等3个阶段入手,浅析土壤盐分增加造成的渗透胁迫、离子胁迫、营养亏缺、氧化胁迫和光合损伤等对植物能量产生与消耗的影响,以期为提高干旱区植物的耐盐性能和合理利用盐碱地提供理论依据和参考。

关键词：盐胁迫能量代谢种子萌发营养生长生殖生长

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Colorimetric enantiodiscrimination of mandelic acid by indicator displacement assay

引用

Chinese Chemical Letters 2015年第8期26卷 1019-1021页

作者： xue-xian Chen Li-Ming Yuan School of Energy and Environment Yunnan Normal University

The colorimetric enantiodiscrimination between mandelic acid and L-proline-Cu（II） is exploited to develop enantioselective indicator displacement assays. The sensitivity of the assay could be tuned by using a colorimetric indicator. The chromophoric ligand, pyrocatechol violet, effectively competes with the mandelic acid guest for open coordination sites on L-proline-Cu（II）. The △A could be increased to 0.12 by changing the ratio of（＋）- and（-）-mandelic acid concentrations that were found to be optimal from the displacement experiments. The resultant enantiomer excess versus △A relationship is linear. From the calibration curves, the absorbance values of the unknowns may be calculated for the enantiomeric excess value and the colorimetric enantiodiscrimination of mandelic acid can thus be obtained.

关键词： proline indicator reserved resultant calibration excess violet guest isotherm tuned

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Mapping the Risk of Water Erosion in the Watershed of the Ningxia-Inner Mongolia Reach of the Yellow River, China

引用

Journal of Mountain Science 2015年第1期12卷 70-84页

作者： DU He-qiang xue xian WANG Tao Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences

Mapping and assessing soil-erosion risk can address the likelihood of occurrence of erosion as well as its consequences. This in turn provides precautionary and relevant suggestions to assist in disaster reduction. Because soil erosion by water in the watershed of the Ningxia-Inner Mongolia reach of the Yellow River is closely related to silting of the upper reaches of the Yellow River, it is necessary to assess erosion risk in this watershed. This study aims to identify the soil-erosion risk caused by water in the watershed of the Ningxia-Inner Mongolia reach of the Yellow River from 2ool to aOlO. Empirical models called Chinese Soil Loss Equation （CSLE） and Modified Universal Soil Loss Equation （MUSLE） were used to predict the erosion modulus in slope surfaces and gullies. Then the soil erosion risk in this watershed was assessed according to the classification criteria of soil erosion intensities （SL19o-2oo7）. The study results showed that the range of values of the erosion modulus in this watershed was o-44,733 t/km2/a. More than 20% of the total watershed area was found to present an erosion risk, with the regions at risk mainly located in channels and their upper reaches, and in mountainous areas. To determine the regression coefficients of the erosion factors with respect to erosion modulus, a GWR （geographically weighted regression） was carried out using the ArcGIS software. It was found that the topographic factor has the highest contribution rate to the soil erosion modulus, while the highest contribution rate of the erosion factors to the erosion modulus and the largest values of the factors were not located in the same places. Based on this result, the authors propose that slope management is the most important task in preventing soil loss in this watershed, and the soil- conservation projects should be built according to the eontribution rate of the erosion factors.

关键词： Chinese Soil Loss Equation (CSLE) Erosion risk Geographically weighted regression(GWR) Yellow River

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

建筑结构工程中吊环、拉环设计原理与应用分析

引用

建筑技术开发 2024年第2期51卷 82-85页

作者：邹容洪薛线妮遵义市水利水电勘测设计研究院有限责任公司贵州遵义563000 遵义众惠工程检测有限责任公司贵州遵义563000

吊环与拉环广泛应用在建筑结构中,如民用建筑中电梯轿厢吊环,厂房建筑中水泵、闸阀、卷扬机的起重吊环,预制构件的吊装吊环等。从设计原理、材料选择、锚固长度、规范要求入手分析吊环和拉环受力性能、延性要求,对垂直起吊最大荷载标准... 详细信息

吊环与拉环广泛应用在建筑结构中,如民用建筑中电梯轿厢吊环,厂房建筑中水泵、闸阀、卷扬机的起重吊环,预制构件的吊装吊环等。从设计原理、材料选择、锚固长度、规范要求入手分析吊环和拉环受力性能、延性要求,对垂直起吊最大荷载标准值进行计算,并从构造措施、设计参考图、现场施工和后期运维等方面作论述,用以解决工程参与者对吊环、拉环的认识,可作为相关工程建设的参考。

关键词：建筑结构吊环拉环锚固长度

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Warming effects on plant biomass allocation and correlations with the soil environment in an alpine meadow,China

引用

Journal of Arid Land 2016年第5期8卷 773-786页

作者： XU Manhou LIU Min xue xian ZHAI Datong Taiyuan Normal University Jinzhong 030619 China Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou 730000 China

Alpine meadow ecosystem is fragile and highly sensitive to climate *** understanding of the allocation of above-and below-ground plant biomass and correlations with environmental factors in alpine meadow ecosystem can result in better protection and effective utilization of alpine meadow *** chose an alpine meadow in the Qinghai-Tibetan Plateau of China as the study area and designed experimental warming plots using a randomized block experimental *** used single-tube infrared radiators as warming devices,established the warming treatments,and measured plant above- （AGB） and below-ground biomass （BGB） during the growing seasons （May to September） in 2012 and *** determined the allocation of biomass and the relationship between biomass and soil environment under the warming *** indices including above-ground biomass,below-ground biomass and the ratio of root to shoot （R/S） ,and soil factors including soil moisture and soil temperature at different depths were *** results showed that （1） BGB of the alpine meadow had the most significant allometric correlation with its AGB （y=298.7x~ （0.44） ,P〈0.001） ,but the relationship decreased under warming treatment and the determination coefficient of the functional equation was 0.102 which was less than that of 0.188 of the unwarming treatment （control） ; （2） BGB increased,especially in the deeper soil layers under warming treatment （P〉0.05） .At 0–10 cm soil depth,the percentages of BGB under warming treatment were smaller than those of the control treatment with the decreases being 8.52% and 8.23% in 2012 and 2013,***,the BGB increased 2.13% and 2.06% in 2012 and 2013,respectively,at 10–50 cm soil depths; （3） BGB had significant positive correlations with soil moisture at 100 cm depth and with soil temperature at 20–100 cm depths （P〈0.05） ,but the mean correlation coefficient of soil temperature was 0.354,greater than the 0.245 of soil moisture.R/S ratio had a s

关键词： alpine meadow above-ground biomass below-ground biomass soil environment warming

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Modulation of Soil Particle Size and Nutrient Availability in the Maize Rhizosheath

引用

Pedosphere 2011年第4期21卷 483-490页

作者： MA Wei LI xue-xian LI Chun-Jian Department of Plant Nutrition China Agricultural University Beijing 100193 (China)

Root exudates,microorganism colonization and soil aggregates together form the rhizosheath,a special cylinder of micro-ecosystem adhering to the root *** study how the rhizosheath affects soil structure and nutrient distribution,we analyzed the impact of maize rhizosheath on soil particle size and nutrient availability in pot and field *** results showed that there was a significant size decrease of soil particles in the ***,the soil mineral nitrogen in the rhizosheath was significantly higher than that in the rhizosphere or bulk soil at tasseling and maturity stages of *** contents of Fe and Mn were also differentially altered in the *** development,indicated by a dry weight ratio of rhizosheath soil to the root,was relatively independent of root development during the whole experimental *** formation of maize rhizosheath contributed to the modulation of soil particle size and nutrient *** subtle local changes of soil physical and chemical properties may have profound influence on soil formation,rhizospheric ecosystem initiation,and mineral nutrient mobilization over the long history of plant evolution and domestication.

关键词： micronutrient mineral nitrogen mucilage rhizosphere root exudates

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

基于YOLOv5的轻量化无人机航拍小目标检测算法

引用

广东工业大学学报 2024年第3期41卷 71-80页

作者：李雪森谭北海余荣薛先斌广东工业大学自动化学院广东广州510006 广东工业大学集成电路学院广东广州510006

针对无人机航拍视角下图像目标特征尺寸小且存在背景复杂、分布密集的问题,提出了一种基于YOLOv5的轻量化无人机航拍小目标检测改进算法GA-YOLO。该算法改进了Mosaic数据增强方法和网络整体结构,并增加了微小物体检测头,同时设计了轻量... 详细信息

针对无人机航拍视角下图像目标特征尺寸小且存在背景复杂、分布密集的问题,提出了一种基于YOLOv5的轻量化无人机航拍小目标检测改进算法GA-YOLO。该算法改进了Mosaic数据增强方法和网络整体结构,并增加了微小物体检测头,同时设计了轻量化的全局注意力模块和并行结构的空间通道注意力机制模块,提高了网络的全局特征提取能力和训练过程中卷积通道之间的竞争和合作关系。以4.0版本的YOLOv5s为基准,在公开无人机航拍数据集Vis Drone2019-DET上实验,结果表明,改进后的模型相较于原模型,参数量下降了48%,计算量下降了26%,而m AP@0.5提高了4.9个百分点,m AP@0.5:0.95提高了3.3个百分点,有效地提高了无人机空中视角下对密集型小目标的检测能力。

关键词：无人机航拍 YOLOv5s 小目标检测数据增强注意力机制

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Synthesis and Crystal Structure of (L)_2W(CO)_4·CH_3COCH_3 (L=1-Phenacylimidazole)

引用

Chinese Journal of Structural Chemistry 2006年第6期25卷 663-666页

作者： GAN xian-xue ZHAO xue-Mei SONG Hai-Bin WANG Ji-Tao TANG Liang-Fu Department of Chemistry and Chemical Engineering Yibin University Yibin 644007 China Department of Chemistry State Key Laboratory of Elemento-Organic Chemistry Nankai University Tianjin 300071 China

The reaction of 1-phenacylimidazole with W（CO）6 in a 1：1 molar ratio under irradiation with a high-pressure Hg lamp mainly yielded the title compound （C29H26N4O7W, Mr = 726.39）, which is of orthorhombic, space group Pbca with a = 27.665（4）, b = 7.7807（12）, c = 27.803（4） A, V = 5984.8（16）A^3, Z = 8, Dc = 1.612 g/cm^3, λ（MoKa） = 0.71073 A ,μ= 3.911 mm^-1, F（000） = 2864, R = 0.0583 and wR = 0.1502 for 3356 observed reflections （I 〉 2σ（I））. The crystal structural analysis indicates that in the coordination geometry of tungsten, 1-phenacylimidazole acts as a monodentate ligand and two imidazole ligands locate in a cis-position.

关键词： imidazole tungsten carbonyl X-ray structure

来源：

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

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：