OALib Journal期刊

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匹配条件: “ Xin-Huan Yang” ,找到相关结果约74342条。
Phase Behavior of Sphere-Forming Triblock Copolymers in Films  [PDF]
Hong-Ge Tan, Qing-Gong Song, Xin-Huan Yang, Ya-Jing Deng
Open Journal of Applied Sciences (OJAppS) , 2012, DOI: 10.4236/ojapps.2012.23023
Abstract: The self-assembly of sphere-forming triblock copolymers confined between two thin homogeneous surfaces is investigated based on mean-field dynamic density functional theory. The morphologies deviating from the bulk sphere-forming phase are revealed, including cylinders oriented perpendicular to the surface, cylinders oriented parallel to the surface, perforated lamellae and lamellae by varying film thickness and surface field strength. The phase diagram of surface reconstruction is also constructed. By comparing the present phase diagram with the other relevant phase diagram for the cylinder-forming triblock copolymer film, the difference between the sphere-forming and the cylinder-forming triblock copolymer thin film is discussed.
A Study on Spatial Evolution and Development Strategy for Urumqi Metropolitan Area

ZHANG Xin-huan,XU Jian-gang,YANG De-gang,

自然资源学报 , 2007,
Abstract: In this paper Urumqi metropolitan area is taken as an example for the study.The Urumqi metropolitan area is an oasis urban agglomeration in arid region and plays an important role in Xinjiang.Recently,the government has paid more attention to the Urumqi metropolitan area and the economic co-development.The process of economic co-development will bring out some spatial problems in arid region and possibly a fragile ecosystem.Therefore,it is necessary to study land use change and development modes to guide the regional sustainable development. The data were dealt with and analyzed in ArcGIS Desktop 9.0 software.Based on the TM (1989)/ETM+(2002) which have a spatial resolution of 28.5m,the macro spatial evolution in the study area is analyzed in detail.Based on the data from urban planning maps of 1998,2002 and 2006 and multi-phase land use information,the micro spatial change is also analyzed clearly.As a result,the following conclusions are drawn:(1) From 1989 to 2002,the areas increased in main land uses for agricultural,urban,rural residential and road construction purposes are 457.45km2,115.27km2,26.50km2 and 10.33km2 respectively.These increased parts mainly come from bare land,primary agriculture land and natural vegetation.Agriculture land and built-up land in the north of the study area expands obviously.And the rapid expansion of the built-up land makes the oasis landscape more fragmented to some extent.(2) From 1998 to 2006 the urban land in the Urumqi metropolitan area does not expand apparently.While to each city,in some localities the built-up land expands apparently,even expands toward central city.The main land uses of the center city such as common establishment land,residential land and industrial land are distributed regularly.The common establishment land centralizes within a scope of 2km,the residential land is distributed in a range 2 to 6km and the industrial land is in the range of 7-13km and 10-15km.The middle and small cities do not have such characteristics because of their small land scale.However,the industrial clusters exist through planning in the peripheries of Changji and Miquan,so some industrial land use area appeared.(3) Some problems appearing from the spatial development process of the metropolitan area are discussed.One is that the landscape becomes more fractional,especially the agricultural land and the rural residential land.The other is that administrative boundary restricts the urban expansion process and the central city,Urumqi,can not exert its radiative function in a limited space.Still the other is the cities developed disorderly in space.According to the above problems,we put forward some modes of this area in spatial development to help oasis urban sustainable development.Centralization and separation in space is a better spatial pattern for the Urumqi metropolitan area.Co-development is the foundation for the metropolitan to develop orderly.Re-adjustment of the functional space in the Urumqi metropo
Simulation of Urban Land Expansion Using CA Model in Urumqi Metropolitan Area

ZHANG Xin-huan,QI Yi,YANG De-gang,XU Jian-gang,

中国沙漠 , 2009,
Abstract: 借助CA模型技术,基于乌鲁木齐都市圈城市用地发展的特点,构建了模拟多个城市群体扩展的CA模型,重点对模型的转换规则进行了扩展,把用地适宜性约束、城市内部社会经济驱动、城市之间相互作用力、区域生态格局限制、城市发展规模有限这几个方面的作用机制融入到模型的规则制定中,通过宏观约束、中观调节、微观驱动3个层次逐步实现;为了使社会经济数据与CA模型中的空间数据相匹配,对社会经济数据进行了空间化表达;在历史数据的参照下,所构建的模型经过反复调试与修正,模拟结果达到了较为满意的效果;应用此模型模拟了经济优先、生态优先与规划优先3种不同情景下的城市用地扩展,对都市圈城市用地今后的发展起到重要的启示作用。
Relationship between intensive utilization and environmental pressure of cultivatedland: a case study on 780 cropland parcels in Tarim River Basin
基于地块尺度的耕地集约利用与环境压力关系—— 以塔里木河流域780 个地块为例

ZHANG Xin-Huan,YANG De-Gang,WANG Chang-Yan,HOU Yan-Jun,

中国生态农业学报 , 2012,
Abstract: Intensive degree (ID) is a common index used to judge the effectiveness of land utilization. With increasing ID, cultivated lands generate certain environmental pressures from extensive use of agro-chemicals like fertilizers and pesticides, and mulching, etc. This paper analyzed the intensity of utilization and environmental pressure of 780 cropland parcels in the Tarim River Basin (TRB) using data acquired from household questionnaire survey. The aim of the study was to explore environmental pressures generated by highly intensive utilization of cultivated lands. The results showed that intensive utilization of cultivated lands caused some degrees of environmental pressure in TRB study area. Environmental load ratio (ELR) of investigated cultivated lands revealed changing trends with increasing IDs of cropland parcels. In 75.90% of the cropland parcels with ID < 1.0 Yuan·m?2, ELR increased with increasing ID. ELR change in 18.60% of cropland parcels with ID in the range of 1~1.5 Yuan·m?2 showed a stable trend relative to increasing ID. Only in 5.50% of cropland parcels with ID > 1.5 Yuan·m?2 did LER decrease with increasing ID. Differences in input structures in cultivated lands were the main driver of the variations in ELR. Rise in the proportion of non-renewable emergy input resulted in increasing ELR. However, with the increasing non-renewable emergy input, ELR rise was restrained by enhanced renewable emergy input. To a certain degree, differences in the trends of cropland parcel ELR suggested that in the study area, the utilization of most cropland parcels was primarily intensive. However, some cropland parcels had been transformed into advanced use intensity. Environmental pressure of cultivated lands was related to crop type and cropland parcel size. For cropland parcels under wheat and fruits, ELR at any scale parcel increased with increasing ID. For cotton fields, small-scale parcel ELR increased with increasing ID. It, however, showed no obvious ELR change for large-scale cotton fields (>0.33 hm2). For cucurbits fields, LER was stable due to low and stable ID driven by the predominantly small-scale cropland parcels. However, LER increased with increasing ID once parcel size exceeded 0.33 hm2. It suggested that alleviation measures of environmental pressure of cultivated lands should be on the basis for crop type and cropland area.
Regional differences and reasons for farmers'' irrigation as households perspective: A case study of Sangong River Basin

XIAO Yan-Qiu,ZHANG Xin-Huan,YANG De-Gang,

中国生态农业学报 , 2011,
Abstract: Uneven spatial and temporal distribution of water shortage coupled with low water use efficiency is a critical constraint to socio-economic development in semi-(arid) regions. Using questionnaires, quantitative statistics and OLS estimation, this study analyzed the regional differences in irrigation as affected by farmer household characteristics in the Sangong River Basin. The study showed gradual increases in water-saving facilities and water price from the upper reaches down to the lower reaches of the basin. Water-saving irrigation ratios were 3%, 10% and 28% in the upper, middle and lower reaches, respectively. The corresponding water price in the upper, middle and lower reaches was <0.075 Yuan·m-3, 0.069~0.075 Yuan·m-3 and 0.13~0.35 Yuan·m-3, respectively. There was a gradual decline in irrigation amount and water burden from the upper down to the lower reaches. Irrigation amount in the upper, middle and lower reaches was 18 510 m3·hm-2, 12 810 m3·hm-2 and 9 075 m3·hm-2; water burden were 18%, 14% and 12% respectively. In the basin, planting structure had evolved from traditional to cash driven crops with increasingly rational cultivation structures. Natural factors were the most fundamental reasons for differences in irrigation among different regions. The amount of water resources, soil retention capacity, field size and fragmentation influenced not only farmers' awareness of water conservation, but also choices of water-saving facilities. This had led to differences in farmers' irrigation modes, which in turn significantly influenced local governments' decision-makings. While local governments passed irrigation burdens to farmers by increasing water price, they also enhanced water use efficiency and crop-irrigation demand curve by improving canal quality and subsidizing the costs of water-saving facilities. Empirical analysis showed that when water price rose by 0.01 Yuan·m-3, irrigation amount dropped by 484 m3·hm-2. By using drip irrigation, irrigation amount dropped by 1 617 m3·hm-2. Also by improving water canal quality from earth to cement pavement, irrigation amount dropped by 736 m3·hm-2.
Land Use/Cover Change of Urumqi Metropolitan Area based on Different Spatial Scales

ZHANG Xin-huan,QI Yi,YANG De-gang,DU Hong-ru,

资源科学 , 2008,
Abstract: The Urumqi metropolitan area is located at the northern foot of the Tianshan Mountains in Xinjiang, China. It is an urban oasis in an arid environment. Economic growth in Urumqi is causing changes in spatial patterns, therefore it is necessary to study these changes based on land use/cover change in order to guide the sustainable development of the metropolitan area.We studied the land use/cover change patterns in Urumqi at multiple scales of analysis, based on remote sensing images and land use maps. The macro-scale analysis provides information on the arid regional context of Urumqi, the meso-scale explains the characteristics of land use change and spatial urban expansion trends, and the micro-scale analysis depicts the rules of urban land change and urban spatial patterns. From the macro-scale analysis of land use/cover change in Urumqi, we reached some conclusions on land cover characteristics and patterns of change. The land cover in mountainous areas, oasis and desert is very different. The actual land use change was indistinct, and the spatial patterns of land cover tend to be stable, but land use changed markedly in oasis areas, and land cover was strongly affected by changes in human activity. From the analysis of land use/cover change in oasis areas from 1989 to 2002, we see that agricultural land and built-up land expanded greatly and the spatial structure of the metropolitan area was formed. Bare land and natural vegetation decreased largely because of human activity, while agricultural land and land with buildings increased rapidly, and expanded in the northern part of the study area. For urban land change from 1998 to 2006, the area of the central city is much more than the others, so the city of Urumqi is dominant in the metropolitan area. The compact ratio of urban land generally increased but the central city is more dispersed than others, and the built-up land of each city expands in different amounts in different directions. The main land of the central city such as public areas, residential land and industrial land are regularly distributed. The medium and small cities do not have these characteristic because of their small size. Some industry clusters were planned in Changji and Miquan, so in these places there was an increase in industrial land area.
Exploration for the Algorithm of Snow Cover Mapping Based on NDVI Background Field

LIANG Ji,ZHANG Xin-huan,WANG Jian,

遥感学报 , 2007,
Abstract: In the process of obtaining the snow cover area from MSS image with NDSI algorithm,there is a shortcoming that MSS does not have short wave infrared band which can help to distinguish high reflectance of cumulus.To improve the accuracy of obtaining the snow cover area from MSS,this paper explores a method of snow cover mapping based on NDVI background field.Firstly,the land surface reflectance image is derived through 6S model while making radiometric calibration.Then,according to the difference of spectral characteristic and the difference of NDVI characteristic of land objects,we build a Lookup Table on threshold of snow spectrum in the SPECTRAL extension of ENVI software.Through the three demonstrations of ETM+ and TM,the process of algorithm and the way to build LUT are illuminated in detail.And the accuracy of snow cover mapping of this method is tested by NDSI.The results show that the new algorithm has higher Overall accuracy and Kappa Coefficient compared with generally classified method(such as Maximum Likelihood Method).
Fast semi-fragile watermarking algorithm for H.264/AVC

LIU Xin-huan,KANG Zhi-wei,WANG Ke-ji,

计算机应用研究 , 2010,
Abstract: 提出了一种基于H.264/AVC低比特率视频流的快速半脆弱水印算法。该算法一方面将I帧DCT量化残差矩阵能量值E的大小作为嵌入鲁棒水印的判决条件,以增强水印的鲁棒性和透明性,降低对编码比特率的影响;另一方面通过限制P帧运动矢量的搜索范围和估计精度嵌入脆弱水印,以提高水印嵌入的实时性。鲁棒水印与脆弱水印相结合有效地实现视频版权保护和内容完整性认证。实验结果表明,该算法实时性高、复杂度低,具有较好的率失真特性。
Land Use and Land Cover Change and the Evaluation of Land Suitability for Construction Use in the Area with Lakes and Rivers: A Case in Luxu Town of Wujiang

ZHANG Xin-huan,XU Jian-gang,YU Lan-jun,

资源科学 , 2006,
Abstract: Based on the land use and land cover information derived from SPOT images,this paper analyzes the dynamic change of land use/cover and evaluates the land suitability for construction use in Luxu town of Wujiang city.The study area is typically featured with rapid economic development and frail water-environment.Therefore,it's necessary to study the land use/cover change in such area in order to provide guidelines for the region's sustainable development.Firstly,the process of image interpretation and land use/cover classification is introduced briefly,and two maps of classification on land use/cover are collected. Secondly,the dynamic land use and land cover change is analyzed according to the information from SPOT image.In the area,town-building land,road and industrial land are increasing obviously,while land occupation by ponds,lakes and river,agriculture land and rural residential land are reduced.For the change speed,the fastest are pond land and town-building land;the second are road industrial land.Besides of the quantitative change on land use/cover,the characteristic of the landscape is more fragmental,especially the agriculture land.Thirdly,some prominent problems are put forward and narrated in detail.The spatial pattern and eco-environment are destroyed in virtue of such two aspects as some waterway in the town are filled blindly for construction use and the buffer zones for flooding prevention are also occupied unreasonably.The town expansion shows rapidness and in-order characteristic in the process of industrial land growth.The building land spatial pattern is dispersed visibly,especially the rural residential land.Finally,the evaluation on building land suitability is illustrated from quantitative and spatial scale.The area of most suitable land for construction is 2167ha,the area of superior suitable land for construction reaches 1406 ha,the area of land less suitable for construction is 1384ha,and the area of land unsuitable for construction is 3403ha.It is concluded that the potential of land supply is lover than the demand for construction use.
Experimental Investigation of High Power Erbium--Ytterbium Co-doped Double Clad Fibre Laser
Experimental Investigation of High Power Erbium-Ytterbium Co-doped Double Clad Fibre Laser

LI Li-Jun,FENG Xin-Huan,LIU Yan-Ge,LI Yao,YUAN Shu-Zhong,DONG Xiao-Yi,

中国物理快报 , 2004,
Abstract: All-fibre high power erbium--ytterbium co-doped double clad fibre lasers are proposed and demonstrated. By using different back-cavity mirrors, the different double clad fibre lasers are constructed. It is experimentally found that the output behaviour of laser can be controlled by a back-cavity mirror. The lower the reflectivity of the back-cavity mirror, the higher the output power and the high the slop efficiency. The maximum output power is about 1.6\,W and the slop efficiency is 27.6%.

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