半立方抛物线形渠道正常水深算法

为了给半立方抛物线形渠道断面正常水深的计算提供一种简捷、通用、精度较高的显函数计算公式,根据迭代理论并采用优化计算确定初值函数的方法进行分析研究.通过引入断面特征水深的概念,对半立方抛物线形渠道正常水深的基本方程进行变换处理,推导出收敛速度较快的迭代公式,并证明了公式的收敛性;在断面特征水深范围即无量纲正常水深H∈[0.025,40]范围内,对迭代公式进行优化计算,取得合理的迭代初值函数;合理初值与迭代公式的配合使用,得到半立方抛物线形渠道断面正常水深的显函数直接计算公式,并对公式进行了误差分析以及用工程实例进行了验证.结果表明：在工程常用的断面特征水深范围内,正常水深的最大相对误差小于0.3%,计算公式具有形式简单、精度高、适用范围广的优点,该研究为排灌渠道的断面设计以及渠道流量控制时求解均匀流水深提供了简捷方法.     

谷子根、茎、叶的显微结构

制作谷子根、茎、叶的连续石蜡切片,观察它们的显微结构.结果表明:谷子的根、茎和叶的显微结构具有单子叶植物所具有的特征,也具有长期适应生存环境而特化的特征.谷子根的表皮脱落得比较早,根的后生木质部形成大的空腔;谷子茎的维管束分散排列在基本组织中,皮层占的空间比较大;幼嫩谷子叶的发育和多数单子叶植物叶的结构一致.     

转子泵容积利用系数的通用计算模型

为构建适用于各类外啮合转子泵容积利用系数的通用计算模型,首先,针对能减少径向泄漏的一类宽顶转子,给出通用轮廓构造和关于瞬心半径的轮廓方程;其次,基于一对结构与尺寸完全相同的转子副,通过分析其处于最小余隙位置的几何关系,逐步推导出共轭截面积、容积利用系数关于瞬心半径的精确计算公式;最后,以摆线转子进行实例验证.结果表明:...     

河岸植被缓冲带完整性及恢复措施——以北京市密云水库上游潮白河流域为例

通过对潮白河流域22个断面的调查分析,根据潮白河河道断面形态、河岸土地利用类型及岸坡坡度等条件,将潮白河河道断面划分为:U形+缓坡、U形+陡坡、U形+陡坎、V形+陡坡和漫滩型,并对潮白河河岸植被缓冲带完整性进行了评价。结果显示,潮河河段内植被缓冲带完整性较差,以次不完整状况为主;白河河段内河岸植被缓冲带状况相对较好,大部分调查断面内植被缓冲带为基本完整及完整状态。针对潮白河河岸植被缓冲带存在的问题,提出了潮白河流域不同河岸带断面类型植被缓冲带的恢复对策。     

干旱区公路浅碟型边沟设计——以宁夏省道盐池至红井段为例(英文)

笔者结合宁夏省道304线盐池至红井段公路,设计浅碟型断面形式边沟,对浅碟型边沟进行水力计算,得出适合本地采用的1.5、2 m宽边沟在不同的沟底纵坡条件下对应的出水口间距,介绍边沟施工技术要点,并推荐适合的草种。     

利用兰州放射性束流线R I B L L测量反应总截面的方法

介绍了一种利用兰州放射性束流线(RIBLL)测量反应总截面的方法.该方法将束流线的前半段作为所需放射性核的传输和选择,将反应靶置于束流线的中间焦点处,使我们在反应靶前和靶后都可以清晰地分辨出粒子.将该方法得到的截面值与传统ΔE-E方法得到的截面值进行了比较,并指出了该方法的优、缺点.     

One-loop Electroweak Radiative Corrections to Electron-positron Pair Production Via Two Photon Collisions

The authors calculate the cross-section with one-loop electroweak corrections to electron-positron pair production via two photon collisions in the standard model (SM), including virtual corrections and soft photon radiative correction. The relations between the cross-sections are discussed in tree level (and one-loop corrected cross sections) and center-mass energy in the luminosity measuring ranges of GLC. At last, the authors acquire the relation curves between differential cross section and the outgoing electron angle.     

Effects of land use and landscape on spatial distribution and morphological features of gullies in an agropastoral area in Sardinia (Italy)

According to the United Nations Convention to Combat Desertification (UNCCD), soil erosion is one of the main causes of desertification in the Northern Mediterranean. Recently, the role of channelled erosion in sediment delivery has been underlined by several studies. The aim of this paper is to describe a simplified experimental methodology settled up for studying the relationships between gully erosion and land use.The experimental site, which is wide about 720 ha, is located in a hilly area threatened by desertification in Central Eastern Sardinia (Italy). This area is characterised by irregular morphology with steep slopes, where agropastoral activities, particularly tillage with heavy machinery and overgrazing, are causing severe soil erosion and compromising agricultural productivity. Previous studies carried out in the same area highlighted the need to quantify and monitor soil erosion in order to outline management guidelines for farmers. In this study, an integrated methodology that uses aerial photographs and field surveys was applied to inventory the gullies of the area. The degree of activity and morphological characteristics of gullies were assessed in the field by measuring the position and shape of gully heads, and their width and depth. Total gully volume was also estimated. Relationships among distribution, density and morphological characteristics of gullies, and geomorphological features, land use and land use historical dynamics of the area have been studied. The results show the very significant impact of agricultural activities on gully activity and density.     

U形渠道横向流速分布规律及测流

借助U形渠道试验，利用指数公式对实测流速值进行分析。结果表明，指数公式可以很好的表示U形渠道横向流速分布规律。结合推导出的流速指数公式及流速-面积法，探索出了U形渠道流量计算公式，经实例验证，该公式误差较小。     

几种防渗渠道断面的比较分析

通过对防渗渠道的U形、梯形、矩形、半圆形、复合式、暗渠等断面组成及其水力学特性的对比分析,认为在防渗渠道的建设中,干、支渠应选用宽浅式梯形断面,而农渠中应选用U形断面.