佛山市中心组团桥梁群对河道影响的数值分析

在不同频率流量和阻水程度条件下,采用一维明渠非恒定流网河数学模型,分析规划中的佛山市桥梁群对区间河道洪季行洪、枯季水环境的影响,计算洪季不同频率洪峰流量下规划桥梁群对区间河道行洪洪水位、分流比的影响,枯季时规划桥梁群对区间河道过流量、分流比的影响,结果表明,利用一维网河数学模型计算佛山市中心组团规划桥梁群对区间河道断面平均水位、流量和流速的影响,结果有足够的数值精度,是可信的。     

明渠断面水流流速与边界剪切应力横向分布模型

天然河流的横断面多为由主槽和漫滩组成的复式断面,水流在这种断面中比在单一断面中受到更多因素影响,流态也更加复杂。通过将明渠横断面上微元体在水流方向的N-S控制方程沿水深积分,得出描述垂线平均流速和边界剪切应力横向分布的模型,并通过对实验数据的验证,确定了模型的实用性。     

A procedure to prepare cross-sectional samples for TEM

Cross-sectional transmission electron microscopy (XTEM) is an imaging technique particularly suited to the study of layered structures. For integrated electronic devices it has become a common practice to use XTEM to assess the shape and crystallinity of component layers as well as defect structures introduced by processing. A procedure for preparing samples to be viewed by XTEM is described.     

螺栓角钢钢节点的三维非线性有限元分析

对螺栓角钢钢节点半刚性连接采用非线性有限元分析方法 ,对连接中的主要构件的顶部、底部、腹板角钢、高强螺栓、梁翼缘、柱翼缘和柱翼缘加劲肋进行三维非线性有限元精细模拟 ,针对有无柱加劲肋、有无腹板角钢等几种连接的情况进行比较分析 ,探讨了螺栓角钢半刚性连接的受力性能。     

Managing logical channel configurations in complex satellite architectures

As a result of the increased switching complexity of many communications satellites, often transponders are available with a variety of configuration options offering flexibility in power, bandwidth, and coverage. Many of these configurations share resources that prevent them from being simultaneously active, making it a challenge to understand and manage the satellite capacity inventory. In this paper we define the logical channel configuration (LCC) as an unambiguous unit of the inventory and present a novel method of modelling the interdependencies between these LCCs using linear algebra. In particular, a projector matrix is defined which can be used to update the activation state of all LCCs when the state of one or more of these is changed. As a result, a number of valid LCC scenarios can be easily generated and evaluated for optimal use of the satellite resources. Copyright © 2005 John Wiley & Sons, Ltd.     

黄河下游河道萎缩致灾机理探讨

本文基于水力学原理，结合实体模型试验及原型实测资料分析，探讨了黄河下游河道萎缩的概念、致灾效应和致灾机理。分析表明，河道萎缩是造床过程中河道排洪输沙功能衰退的一种演变现象，其致灾效应是使洪水涨率增大，同流量下洪水水位不断抬升。致灾的现象主要表现在畸型河势增加、工程险情增多、直接造成工程损失及滩区经济损失等。试验研究揭示，主河槽宽度缩窄造成洪水水位涨幅增大，河底平均高程抬升和过水断面面积减小造成洪水水位起涨的基准面抬升是河道萎缩致灾的主要原因。河道萎缩致灾效应的大小与萎缩模式有关，其中以“集中淤槽”模式所形成的致灾效应尤为明显。     

Potential use of phenolic antioxidants on peanut to control growth and aflatoxin B1 accumulation by Aspergillus flavus and Aspergillus parasiticus

Food‐grade antioxidants: butylated hydroxyanisole (BHA), propyl paraben (PP) and butylated hydroxytoluene (BHT) (10 and 20 mmol g^?1) and all the mixtures of these chemicals were tested for inhibitory activity on the growth of and aflatoxin B₁ (AFB₁) accumulation by Aspergillus parasiticus and A. flavus on irradiated (7 kGy) peanut grains. Also, the influence of these treatments was evaluated in different water conditions (0.982, 0.955, 0.937a_w) at 11 and 35 days of incubation at 28 °C. Water activity (a_w) affected the fungal growth, no fungal development was observed at the highest stress water condition (0.937a_w). Butylated hydroxyanisole at 10 mmol g^?1 level and all the mixtures with PP and/or BHT were significantly effective (P = 0.05) in increasing lag phase and reducing growth rate and colony forming units per gram of peanut of both Aspergillus section Flavi strains and AFB₁ accumulation. The application of BHA at concentrations of 20 mmol g^?1 alone or with PP and/or BHT totally inhibited fungal growth at 11 and 35 days of incubation. The results suggest that the addition of these chemical mixtures on peanut grains at low levels has potential to impact synergically on the control of Aspergillus section Flavi. Copyright © 2007 Society of Chemical Industry     

板栅模具设计中的几个问题

通过对板栅模具设计中遇到的几个实际问题的分析提出处理意见 ,从而达到科学合理地设计板栅模具。     

A new stereological principle for test lines in three-dimensional space

A new principle is presented to generate isotropic uniform random (IUR) test lines hitting a geometric structure in three-dimensional space (3D). The principle therefore concerns the estimation of surface area, volume, membrane thickness, etc., of arbitrary structures with piecewise smooth boundary. The principle states that a point-sampled test line on an isotropic plane through a fixed point in 3D is effectively an invariant test line in 3D. Particular attention is devoted to the stereology of particles, where an alternative to the surfactor method is obtained to estimate surface area. An interesting case arises when the particle is convex. The methods are illustrated with synthetic examples.     

多码CDMA系统中联合并行干扰抵消与迭代信道估计方法

本文针对多码CDMA系统提出了一种联合并行干扰抵消与迭代信道估计方法。该方法首先通过导频符号对信道进行估计，然后使用RAKE接收机后的软信息对信道参数进行修正，最后通过并行干扰抵消(PIC)去除多码干扰(MCI)。仿真结果表明，经过多次迭代后，该方法可显著地降低多码CDMA系统的误比特率平台。本文同时还给出了信道估计质量、码道数和PIC次数对多码CDMA系统性能的影响。