包兰铁路沙坡头段不同编制结构的枝条阻沙栅栏防护效应风洞模拟

对包兰铁路沙坡头段枝条阻沙栅栏流场结构进行风洞模拟试验。结果表明:气流在经过横向、竖向阻沙栅栏时均出现了明显的流速分区。气流在经过阻沙栅栏时速度会减弱,但是竖向枝条阻沙栅栏的综合阻风防沙效果明显优于横向阻沙栅栏,同时竖向枝条阻沙栅栏制作上具有工序简单、原材料广泛及不受枝条长度限制的特性,因此,在防沙治沙应用中,竖向枝条阻沙栅栏更适合推广。虽然孔隙度是阻沙栅栏设计的重要技术参数,但栅栏结构对风沙流场产生直接影响,是决定着其对风沙活动防护效应高低的关键因子。     

National and transnational borderlanders’ attitudes towards the security fence between Israel and the Palestinian Authority

The subject of the security fence between Israel and the Palestinians in the West Bank has become a major issue in Israel and in the world in the last several years. The main aim of this research is to reveal the attitudes and thoughts about the fence held by local residents living in settlements (borderlanders) in the proximity of a part of the security fence that has already been completed. The research concentrates on the western-Israeli side of the fence, as it aspires to delve into and understand the meaning and implications of the security fence on matters such as personal security, safety of property and freedom of movement, the possibility of maintaining social and economic ties between the two sides and feelings about living in the area in the future. Underlying this research is the transformation occurring in the border area as a result of its closure by construction of the security fence, after many years in which it was open partially. This process has many diverse consequences, some of them contradictory, on the two populations residing near the border in Israel: the majority Jewish population (the national borderlanders), and the minority Arab population (the transnational borderlanders).     

测量船的摇动对AIRSEA SystemⅡ的干扰分析

根据海洋重力测量的实际情况,结合AIRSEA SystemⅡ的结构特点,对仪器在测量中受到测量船摇动的影响进行分析,认为影响仪器观测精度的干扰因素有三类:垂直加速度、横摇与纵摇、交叉耦合效应。并对这三种干扰因素进行分析,给出了减弱干扰影响的措施,这些措施能使海洋重力测量外业获取更高的观测精度。     

Evaluating post-wildfire logging-slash cover treatment to reduce hillslope erosion after salvage logging using ground measurements and remote sensing

Continuing long and extensive wildfire seasons in the Western US emphasize the need for better understanding of wildfire impacts including post-fire management scenarios. Advancements in our understanding of post-fire hillslope erosion and watershed response such as flooding, sediment yield, and debris flows have recently received considerable attention. The potential impacts of removing dead trees, called salvage logging, has been studied, however the use of remotely sensed imagery after salvage logging to evaluate spatial patterns and recovery is novel. The 2015 North Star Fire provided an opportunity to evaluate hillslope erosion reduction using two field experiments and coincidental remotely sensed imagery over 3 years. Simulated rill experiments with four flow rates were used to quantify hillslope erosion on skidder trails with and without added logging slash compared with a burned-only control. Seven replicated hillslope silt fence plots with the same treatments were also evaluated for natural rainfall events. WorldView-2 satellite imagery was used to relate ground cover and erodible bare soil between the two experiments using multi-temporal Normalized Differenced Vegetation Index (NDVI) values. Results indicate that the skid trails produced significantly more sediment (0.70 g s⁻¹) than either the slash treated skid trail (0.34 g s⁻¹) or controls (0.04 g s⁻¹) with the simulated rill experiment. Similarly, under natural rainfall conditions sediment yield from hillslope silt fence plots was significantly greater for the skid trail (3.42 Mg ha⁻¹) than either the slash treated skid trail (0.18 Mg ha⁻¹) or controls (0 Mg ha⁻¹). An NDVI value of 0.32 on all plots over all years corresponded to a ground cover of about 60% which is an established threshold for erosion reduction. Significant relationships between NDVI, ground cover, and sediment values suggest that NDVI may help managers evaluate ground cover and erosion potential remotely after disturbances such as a wildfire or salvage logging.     

艾肯达坂风雪流形成机制及其治理

根据天山艾肯达坂地区的野外观测和风洞模拟实验,导出山区风雪流输送量与风速随高度分布方程,指出贴地气层分离是形成道路雪阻的主要原因。首次提出利用透风式下导风清除道路积雪的理论与方法,在风雪流灾害防治工程的实施中取得了巨大的经济和社会效益。     

Effect of protection against wind according to the variation porosity of wind fence

This study examines shelter effect against the wind by using wind fence with various porosities and distance. The shelter effect of wind fence was investigated by a wind tunnel test. Flow characteristics of velocities and turbulences behind wind fence were measured using a hot-wire anemometer. This was done by varying the porosity by 0, 20, and 40% of the wind fence. The wind fence distance ranged from 1H to 9H. In addition, the overall characterization of the wind fence was investigated by measuring a total of 28 points on the wind fence, which forms a lattice structure on it with 7 points in the lateral direction and 4 points in the vertical direction. The results indicate that the degree of the turbulence is lowered and the velocity of the wind is decreased when porosity of 40% is used at a distance of 4H–7H. The effectiveness of the wind fence depends on the porosity and distance. Porosity of 20% proved to be effective for the protection area of 1H–3H, while that of 40% was effective for the protection area of 4H–6H.     

栅栏防护体系空气动力学效应研究进展

栅栏防护体系的空气动力学效应研究是揭示其防护机理的重要基础,也是风沙工程学和风沙物理学应用研究的主要组成部分。根据已有的研究成果,全面综述了近半个多世纪以来有关栅栏防护体系空气动力学机制方面的研究进展,对各个时期的主要成果作以介绍,并对几种代表性防护栅栏最佳疏透度的确定方法及范围分别加以对比分析。分析认为,对栅栏空气动力学效应已取得了相对较深的认识,并且积累了大量的研究经验,对于认识栅栏防护机理具有重要的指导和启发作用。但影响栅栏防护效益的因素是复杂的,众多研究都运用了过多的简化与假设,而且研究者们对于栅栏防护效应的理解不同以及所强调的保护侧重点不同导致评判的标准也各不相同,最终得到的最佳疏透度也有所差异,不能直接运用于实践中。鉴于此,在将来的研究中运用现代测量技术获取可靠的数据资料仍然很重要。     

四川省青川县碾子村清岭沟泥石流特征及防灾对策

清岭沟位于四川省青川县碾子村五社,该区工程地质条件复杂。＂5.12＂地震后沟内出现大量崩塌落石和松散堆积物,为泥石流的爆发提供了充足的物源,2008年8月清岭沟地区发生连续强降雨,8月25日清岭沟爆发了泥石流。目前沟源及沟道两侧发育一处规模较大的潜在不稳定斜坡、三处规模较大的危岩体、一处形成于＂5.12＂地震期间的崩塌堆积物,一旦遭遇暴雨等不良地质作用这些潜在物源极易失稳,成为清岭沟泥石流的物源,使清岭沟再次发生泥石流灾害,威胁清岭沟下游村落及公路。通过野外对清岭沟进行地质调查、室内试验和动力学特征分析提出了UX—150型泥石流栅栏、拦砂坝、排导槽和桥涵改造的综合治理措施。     

复膜沙袋阻沙体与芦苇高立式方格沙障防沙机理风洞模拟实验

模型按1:10比例尺设计,在u_∞=7.0 m·s^-1、u_∞=10.0 m·s^-1和u_∞=15.0 m·s^-1实验风速下,先在纯气流作用下测定流场结构,然后在风沙流作用下测定蚀积状况。实验结果表明:紧密型、疏透型和通风型3种不同结构的复膜沙袋阻沙体前近处分布有拐角阻滞绕流区、阻沙体顶下方抬升加速区、阻沙体后回流区、阻沙体后贴地层低速回流区等流场特征结构,紧密型、疏透型两种类型复膜沙袋阻沙体防风阻沙效果显著;2.5 m×2.5 m、5 m×5 m和10 m×10 m的高立式芦苇方格前沿流速逐渐增大,最大值出现于迎风第一格上空,而后逐渐阻滞减速,至15~20 m处趋于稳定,区内积沙均匀。复膜沙袋阻沙体与原状芦苇高立式方格沙障适宜于流动性沙漠地区各种设施的沙害防治工程。