增强型AlGaN/GaN高电子迁移率晶体管高温退火研究

深入研究了两种增强型AlGaN/GaN高电子迁移率晶体管(HEMT)高温退火前后的直流特性变化.槽栅增强型AlGaN/GaN HEMT在500 ℃ N₂中退火5 min后,阈值电压由0.12 V正向移动到0.57 V,器件Schottky反向栅漏电流减小一个数量级.F注入增强型AlGaN/GaN HEMT在 400 ℃ N₂中退火2 min后,器件阈值电压由0.23 V负向移动到-0.69 V,栅泄漏电流明显增大.槽栅增强型器件退火过程中Schottky有效势垒     

Identifying effects of local and nonlocal factors of soil water storage using cyclical correlation analysis

There are various factors governing the spatial and temporal variability of soil water storage including soil properties, topography and vegetation. Some factors act locally, whereas others act nonlocally, which means that a factor measured at one location has effect on soil water storage at another location. The objective of this study was to examine the effects of local and nonlocal controls of soil water storage in a hummocky landscape using cyclical correlation analysis. Soil water storage, soil properties and terrain indices were measured along a 128‐point transect of 576 m long from the semiarid, hummocky, prairie pothole region of North America. There are large coefficients of determination (r²) between soil water storage and sand content (r² = 0.32–0.53), organic carbon content (r² = 0.22–0.56), depth to carbonate layer (r² = 0.13–0.63), wetness index (r² = 0.25–0.45) and other variables at the measurement scale at different times, indicating strong local effects from these variables. The correlation coefficients were also calculated by physically shifting the spatial series of soil water storage with respect to that of controlling factors. The shifting improves the correlation between the spatial series, and the length of shifting indicated the difference in the response of soil water to its controlling factors. For example, the value of r² increased more than eightfold (r² = 0.47–0.64) after shifting the spatial series of soil water storage by 54 m, almost equal to the average length of existing slope, compared with the very weak correlation (r² = 0.02–0.08) at the measurement scale. This indicated the nonlocal effect from the relative elevation. The identification of nonlocal effects from factors improves the prediction of soil water storage. Copyright © 2011 John Wiley & Sons, Ltd.     

Characterising deep vadose zone water movement and solute transport under typical irrigated cropland in the North China Plain

Understanding the dynamics and mechanisms of soil water movement and solute transport is essential for accurately estimating recharge rates and evaluating the impacts of agricultural activities on groundwater resources. In a thick vadose zone (0–15 m) under irrigated cropland in the piedmont region of the North China Plain, soil water content, matric potential, and solute concentrations were measured. Based on these data, the dynamics of soil water and solutes were analysed to investigate the mechanisms of soil water and solute transport. The study showed that the 0–15‐m vadose zone can be divided into three layers: an infiltration and evaporation layer (0–2 m), an unsteady infiltration layer (2–6 m), and a quasi‐steady infiltration layer (6–15 m). The chloride, nitrate, and sulphate concentrations all showed greater variations in the upper soil layer (0–1 m) compared to values in the deep vadose zone (below 2 m). The average concentrations of these three anions in the deep vadose zone varied insignificantly with depth and approached values of 125, 242, and 116 mg/L. The accumulated chloride, sulphate, and nitrate were 2,179 ± 113, 1,760 ± 383, and 4,074 ± 421 kg/ha, respectively. The soil water potential and solute concentrations indicated that uniform flow and preferential flow both occurred in the deep vadose zone, and uniform flow was the dominant mechanism of soil water movement in this study. The piston‐like flow velocity of solute transport was 1.14 m per year, and the average value of calculated leached nitrate nitrogen was 107 kg/ha?year below the root zone. The results can be used to better understand recharge processes and improve groundwater resources management.     

从景观生态学构建城市旅游开发与规划的操作模式

本文尝试建立一个关于旅游开发与规划的应用理论模式,以兼顾理论的抽象性和操作性。模式的构建依据地理空间分析方法,同时借用景观生态学斑、廊、基的概念。文中详细论述了该斑廊基网络结构操作模式的基本特点、变换空间分析方法等运行机制,并以不同城市旅游规划、设计实例说明三大操作块的功能和操作意义。     

东亚梅雨锋暴雨研究进展

对梅雨锋的大尺度环流、梅雨锋的次天气尺度和中尺度特征、梅雨锋低空急流和暴雨发展等问题的研究进展作了概述，对低空急流和暴雨发展的各种观点进行了评述，并提出了新的见解和研究结果。     

日本GMS低云风的若干统计特征及应用于北太平洋西部风场分析的初步试验

气象卫星对气象科学的发展起着重大的作用。静止气象卫星对广大热带海洋区域提供的气象资料,对热带的天气分析和预报起着特别重要的作用。美国、欧洲空间厅和日本已开展了静止卫星云图云风测定业务。许多研究已证明,卫星云风与同高度无线电测风相当一致。而且在天气分析和预报以及大气环流的研究中是很有价值的气象资料。Hub—     

一次梅雨锋低空急流形成的分析

对1979年6月24—25日的一次梅雨锋低空急流的形成进行了分析,它的形成是由于在300mb高空急流中心附近产生的地转不平衡,使急流入口区的右侧造成高空辐散的作用。当高空急流中心东移,急流入口区右侧的高空辐散区移到江淮流域上空,由此高空辐散引起对流层下部的质量调整,致使低空造成降压区与辐合。这降压区造成的变压风迭加到低空的西南气流上,沿通过该负变压区(或负变高区)中心的西南气流作为一条轴线,轴线的右侧变压风使西南风偏向低压一侧,从而使西南风的动能增加;轴线的左侧变压风使西南风偏向高压一侧,从而使西南风的动     

Neotectonics of the Pontides: implications for ‘incompatible’ structures along the North Anatolian fault

Data for the post-Serravallian, ‘neotectonic’ evolution of the Pontides in northern Turkey indicate predominant ENE-WSW shortening with complementary NNW-SSE extension. We present a new fault plane solution for the Bartin earthquake (3 September 1968) and compare its mechanism with the movement picture of other neotectonic faults in the Pontides and northern Greece together with that of the Thessaloniki earthquake (20 May 1978). The general strain pattern exhibited by these structures agrees remarkably well with that inferred from early Tortonian-early Pleistocene structures reported from within the North Anatolian fault zone, which have been interpreted as indicating a possible reversal of the sense of movement along the North Anatolian transform fault. Here, we argue that such ‘incompatible’ structures may be related to the overall E-W shortening of Anatolia and the southern parts of the Black Sea resulting from the sideways continental escape from around the African and the Arabian promontories, rather than to hypothetical reversal of motion along the North Anatolian fault, for which there is no evidence other than the above-mentioned ‘incompatible’ structures. This new model also has important implications for seismicity and earthquake risk in regions contained within the southern part of the Black Sea plate.     

基于网络环境的MapMIS数字化生产管理系统

Map MIS是一个应用于数字化测绘生产的管理信息系统。它集成了网络、数据库、分布式数据仓库技术 ,它可以在生产过程中帮助生产管理人员、质量检查人员、作业人员管理与数字化测绘生产相关的事务流、信息流和海量的数据流。提出了数字化测绘生产管理的新模式     

我国西部开发中生态环境保护及其对策

西部地区生态环境脆弱 ,在实施西部开发战略中如何保护和优化生态环境显得尤为重要。在分析西部地区存在的生态环境问题的基础上 ,提出了适度调整资源开发导向战略 ;科技先行 ,强化生态环境建设 ;调整产业结构 ,加快城市化进程 ;制定合理的政策 ,加强环境立法、执法等对策和建议 ,保护和优化生态环境