Bedload Transport in Alluvial Channels

Hydraulic, sediment, land-use, and rock-erosivity data of 22 alluvial streams were used to evaluate conditions of bedload transport and the performance of selected bedload-transport equations. Transport categories of transport-limited (TL), partially transport-limited (PTL), and supply-limited (SL) were identified by a semiquantitative approach that considers hydraulic constraints on sediment movement and the processes that control sediment availability at the basin scale. Equations by Parker et al. in 1982, Schoklitsch in 1962, and Meyer-Peter and Muller in 1948 adequately predicted sediment transport in channels with TL condition, whereas the equations of Bagnold in 1980, and Schoklitsch, in 1962, performed well for PTL and SL conditions. Overall, the equation of Schoklitsch predicted well the measured bedload data for eight of 22 streams, and the Bagnold equation predicted the measured data in seven streams.     

玻璃钢管道的特点,设计原理及选用时的注意事项

本文旨在通过对玻璃钢管道及其标准的发展历史、产品特点、基本设计原理、质量影响因素及选用时应注意的事项等方面的介绍，使用户与工程设计人员对该产品有一个比较全面的了解，以便更好地选用并受益于这种管材。     

圆锥形零件冲压变形与成形载荷的分析

由于悬空侧壁部分的变形状态是圆锥形零件成形的关键，而径向拉应力是实现悬空部分成形的必要条件，同时也是该部分冲压成形成败的关键为此，经力学分析得出了侧壁部分径向拉应力的解析式和造成圆锥形零件破裂的最大径向拉应力的计算式。同时分析了圆锥形零件的成形载荷。     

采用荷载平衡的概念表达预应力度及在初步设计中的应用

利用荷载平衡法的概念，将预应力度用等效荷载与外荷载的比值表达，设计可利用其比值确定预应力度，便其更简捷，明确，同时，提出了预应力度的真实值问题。     

浅谈多层建筑的斜屋面结构设计

多层建筑的斜屋面结构，应建立合理的结构模型，选用合理的结构方案，在采用结构软件设计时，一定要正确采用倾斜构件沿水平或垂直方向的荷载。     

VERIFICATION AND COMPARISON OF FORMULAS FOR BED LOAD TRANSPORT

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｂｅｄｌｏａｄｔｒａｎｓｐｏｒｔｈａｓｂｅｅｎｅｘｔｅｎｓｉｖｅｌｙｓｔｕｄｉｅｄｉｎｔｈｅｐａｓｔｆｅｗｄｅｃａｄｅｓａｎｄｍａｎｙｆｏｒｍｕｌａｓｆｏｒｐｒｅｄｉｃｔｉｎｇｂｅｄｌｏａｄｔｒａｎｓｐｏｒｔｒａｔｅｈａｖｅｂｅｅｎｐｒｅｓｅｎｔｅｄ(Ｅｉｎｓｔｅｉｎ 1950 ;Ｍｅｙｅｒ Ｐｅｔｅｒ 194 8;Ｂａｇｎｏｌｄ 1973;Ｅｎｇｅｌｕｎｄ 1976;Ｙａｌｉｎ 1972 ;Ｓａｍａｇａ 1986;ａｎｄＫａｒｉｍ 1998) .Ｗｈｅｎａｐｐｌｉｅｄｔｏｓｔｒｅａｍｓｗｉｔｈｐａｒｔｉａｌ…     

Combined shape and sizing optimization of truss structures

 In this paper, an evolutionary optimization method is presented for weight minimum problem of a 3-dimensional truss structure in terms of nodal coordinates and element cross-sectional areas. The structure is subject to stress, local buckling and displacement constraints. Two types of design variables with different natures are optimized separately: (1) a fully stressed design (FSD) and scaling techniques are applied to sizing variables and (2) the evolutionary node shift method is applied to shape variables. Alternating procedure is utilized to couple the two types of variables and to combine the results. The optimum solution is achieved gradually from the initial configuration design. Two typical truss structures are examined to illustrate the validity of the method. Received: 22 October 2001 / Accepted: 04 June 2002 This research work is supported by the National Natural Science Foundation of China under the guarantees no. 10072050 and 10172072, respectively.     

注硼中子寿命测井注硼工艺优化设计

注硼中子寿命测井是一项水淹层测井新技术 ,对老油田的产层分析评价、剩余油含量估算等方面发挥了重要的作用。但测井施工时 ,往往由于注硼工艺不当导致硼酸的渗吸量难以准确反映地层可动水的含量 ,从而产生解释上的困难和误区。在渗流与扩散理论相结合的基础上 ,结合华北油田的施工实践 ,介绍了确定注硼管柱、硼酸用量、注硼压力以及硼酸扩散时间的基本原则和实际经验 ,为工艺的优化设计提供了一些方法与思路