Threshold velocity for wind erosion: the effects of porous fences

Porous fence is a kind of artificial windbreak that has many practical applications. The threshold wind velocities at different distances downwind from porous fences were measured and the corresponding characteristics of particle movement observed to assess their shelter effect. It is found that the fence’s porosity is the key factor that determines the resulting shelter effect. The area near a fence can be typically classified into five regions, each with a different mode of particle movement. Dense fences, and especially solid fences, favor the accumulation of sand upwind of the fences. Fences with porosities of 0.3–0.4 produce the maximum threshold wind velocity; those with porosities of 0.3–0.6 (depending on the fence height) provide the maximum effective shelter distance. It is confirmed that the fence porosities of 0.3–0.4 that have been proposed for practical application in previous research are the most effective for abating wind erosion.     

加固含水平软弱层高陡边坡预应力锚索倾角的取值范围

用直线和曲线滑面两种模型，模拟预应力锚索加固含有水平软弱层的高陡边坡的潜在滑动面，通过对锚索加固的力学机理分析来阐述预应力在滑动面主滑方向上产生分力的原因。从锚索受力角度上对锚索倾角的取值范围进行探讨，结合实际造孔过程有不同程度的孔斜或弯曲以及获取较好的锚固灌浆效果，就仰角锚固和俯角锚固两种锚固条件分别得出锚索倾角的取值范围，并以此来判定锚索的预应力是否会在滑动面走向方向上产生不利于坡体稳定的下滑力。     

松溪县域城镇体系发展研究

城镇体系建设是当今加快城市化进程的重要组成部分。本文通过对松溪县域城镇现状的调查,从城镇体系的等级规模结构、空间布局结构、职能结构3个方面剖析其发展中存在的一些问题。从建设社会主义新农村、改善人居环境的角度出发,提出相应的发展思路和建议,为松溪县“十一五”期间制定城镇发展战略提供一定的参考。     

论琅岐岛经济发展定位与开发建设

随着福州东扩南移的城市发展策略的推行,琅岐岛凭借独特的资源优势,经济地理位置日显重要,对其开发建设已成为大势所趋。本文在分析了琅岐岛区域经济发展的资源条件基础上,指出琅岐经济发展的合理定位,提出区域经济发展的若干对策,为琅岐经济持续、健康、稳定地发展提供意见。     

Estimating the minimum in-stream flow requirements via wetted perimeter method based on curvature and slope techniques

Under the assumptions of triangular cross section channel and uniform stable flow, an analytical solution of the minimum ecological in-stream flow requirement (MEIFR) is deduced. Based on the analytical solution, the uncertainty of the wetted perimeter method is analyzed by comparing the two techniques for the determination of the critical point on the relationship curve between wetted perimeter, P and discharge, Q. It is clearly shown that the results of MEIFR based on curvature technique (corresponding to the maximum curvature) and slope technique (slope being 1) are significantly different. On the P-Q curve, the slope of the critical point with the maximum curvature is 0.39 and the MEIFR varied prominently with the change of the slope threshold. This indicates that if a certain value of the slope threshold is not available for slope technique, curvature technique may be a better choice. By applying the analytical solution of MEIFR in the losing rivers of the Western Route South-to-North Water Transfer Project in China, the MEIFR value via curvature technique is 2.5%-23.7% of the multi-year average annual discharge, while that for slope technique is 11%-105.7%. General conclusions would rely on the more detailed research for all kinds of cross-sections.     

福建平潭虎潮山滑坡成因机理分析与评价

虎潮山滑坡位于平宏公路12k 704~12k 884段北侧山坡体上,是平潭海岛通往陆地的唯一公路通道。论文通过定性的工程地质分析和定量计算评价了虎潮山坡体稳定性的变化趋势,提出改建公路超挖深切坡脚和持续长时间强降雨导致的孔隙水压力作用是边坡发生滑动破坏的主要因素。     

惯性／双星组合导航系统的滤波与仿真

介绍了惯性导航系统和双星导航系统各自的运行方式和优缺点；详细推导了组合导航系统的误差方程和量测方程；介绍了Kalman滤波的整个过程并最后进行了仿真计算。仿真结果显示，惯性导航系统和双星导航系统的组合弥补了各自的不足，具有较好的精度和可靠性。     

藏北安多地区侏罗纪菊石动物群及其古地理意义

藏北安多地区新发现2套以黑色页岩、深灰色钙质泥岩和泥灰岩为主的舍菊石化石的侏罗纪地层，它们与羌塘地区广泛分布的雁石坪群无论在化石组合或沉积特征方面都明显不同．岗尼乡剖面地层中产太阳菊石科的菊石，主要有Sonninia，Dorsetensia，Witchellia等。、这套地层是双湖地区色哇组的东延部分，时代确定为中侏罗世早中巴柔期114道班剖面中羌姆勒曲组的菊石化石大多归属于Virgatosphinctinae科，计有Aulacosphinctes、Virgatosphinctes等，均为上侏罗统菊石化石的典型分子，产出层位应归于提塘阶中、上部。藏北安多-改则以北一线的侏罗系深水黑色岩系虽不十分连续，但从有化石证据的土阿辛阶到巴柔阶再到提塘阶都有零星出露，它们同属一个沉积相区。侏罗纪时羌塘南部可能存在一套大陆边缘型沉积地层，因此有必要对该区的构造属性和演化历史重新进行解释。     

塔里木河下游河道疏浚段水文地质和工程地质特征研究

塔里木河下游河道长期断流,生态环境恶化,必须实施河道疏浚工程,从根本上改善塔里木河下游的生态环境.掌握塔里木河下游河道的水文地质和工程地质特征是实施河道疏浚工程的关键,是沿线生态闸堰设置及两岸提防工程修建的基础.通过区域地质特性、水文地质条件、工程地质特征几个方面的研究,得出河道疏浚段的地层岩性、地下水类型、地下水化学类型等特征,为河道疏浚工程奠定了基础.     

气象资料三维化技术中的插值问题

通过对不同源气象资料及数字地理信息资料的插值，实现了不同气象资料与地理信息资料分辨率的协调；从而将多种信息叠加到一起，实现了多源资料的二维、三维仿真显示。这对于模拟真实的大气空间结构、理解地形及植被对大气运动的影响、辨识各种天气系统及多种信息的融合等有积极意义。