Superior cubic channel section and analytical solution of best hydraulic properties

Channel cross section is an important element in water management. Numerous studies regarding parabolic and semi-cubic sections have been published. This paper introduces a new cubic channel section that has superior properties. Section characteristics are formulated and an explicit approximate formula for the wetted perimeter is derived using the Gauss-Legendre integration method. The theoretical solution of the best hydraulic cubic section is derived using the complex function method and the undetermined Lagrange multiplier optimization algorithm. A comparison with four best hydraulic sections (parabolic, semi-cubic, trapezoidal, and catenary) shows that the discharge of the cubic section is the largest, given the same cross-section flow area and/or wetted perimeter. The results also show that the cubic section is the most economic under the best hydraulic condition. Given its simple form and superior properties, the cubic section should be of interest to water resources engineers.     

机织物中纱线截面形态与集合形态模型研究

探讨机织物中纱线的截面形态及集合形态模型的应用。在分析前人研究工作的基础上,通过对实际织物中纱线截面形态进行分析,结果表明:把纱线在织物中的截面形态归结到一个统一的圆形、椭圆形、跑道圆形、凸透镜形等模型下是不科学的;并针对多组织点织物中纱线截面形态的复杂性提出了集合形态模型。指出:集合形态模型是描述纱线在织物中截面形态的一种新的思路,是某些复杂组织织物中纱线截面形态的一个广义解决办法。     

纯滚动式绕弯工艺分析与实验研究

为研究一种纯滚动式绕弯成形工艺,采用实验方法研究工艺系统中各个几何参数和工艺参数对于烧结式微热管弯曲中横截面畸变的影响机制。实验结果表明:靠模距弯曲起始线的尺寸越小、模具孔尺寸越小、弯曲角度越小、弯曲角速度越小、相对弯曲半径越大,则弯曲时横截面畸变越小;反之横截面畸变则越大。实验中优化出各个几何参数和工艺参数的最优值。同时该弯管工艺系统能成倍的提高弯管效率。     

Transport model based on three-dimensional cross-section generation for TRIGA core analysis

Three-dimensional (3-D) transport model for the Pennsylvania State University Breazeale Reactor (PSBR) core analysis has been developed based on the discrete ordinates (S_n) method. The effective fine- and broad-group structures for the TRIGA cross-section libraries were selected based on CPXSD (Contributon and Point-wise Cross-Section Driven) methodology. The study shows results of the following effective broad-group energy structures – a 12-group structure in 2-D geometry vs. a 26-group structure in 3-D geometry. Different 3-D pin/core configurations were used to verify and validate the selected effective group structures. The results agree with continuous energy cross-section Monte Carlo calculations for eigenvalues and normalized pin-power distributions, which are used as a reference in this research.     

人台的立体结构与礼服样板的关系研究

以人台为对象进行测量并绘制横截面图,研究了人台各部位的体型特征,并结合礼服研究平面样板的结构、比例分配、省道的大小及形状,建立了立体到平面转化的关系。     

Cross-Section preparation for tem of film-substrate combinations with a large difference in sputtering yields

The preparation of cross-section samples of thin films for TEM, may be difficult and tedious, especially if the difference in chemical or physical etching rates is large between the film and the substrate. In this paper, a method is presented whereby cross-sections can be prepared even if the film and the substrate have a large difference in sputtering yield. By utilizing the strong angular dependence of the sputtering yield and sputter at a low ion incidence angle with respect to the substrate surface of 7–12° and, furthermore, by avoiding sputtering parallel to the interface, samples with homogeneous thickness can be obtained. The technique is demonstrated on reactively sputtered titanium nitride coatings on high speed steel substrates. The difference in sputtering yields is about three for this film-substrate combination with the substrate being sputtered fastest.     

Finite element modelling of structural stainless steel cross-sections

Stainless steel's characteristic nonlinear, rounded stress–strain behaviour requires accurate recognition in numerical modelling. Its response to cold-working is far more pronounced than that of ordinary carbon steel and hence appropriate modelling of the cold-worked corner regions is very important. Despite the importance of geometrical imperfections, their measurement is not a very common practice and assumed models are generally adopted in numerical investigations—often without proper verification. This paper investigates all important aspects for modelling stainless steel cross-sections through carefully designed parametric studies. Different cross-section types have been considered and the numerically obtained load–deformation responses have been compared with selected experimental results; the findings form the basis for specific guidelines. These proposals have been verified by application to all available stainless steel stub column tests obtained from different sources. The predicted numerical results have shown excellent agreement with those obtained experimentally.     

城市轨道交通调线调坡测量中圆隧道横断面测量方法的探讨

介绍了城市轨道交通在调线调坡测量中圆隧道结构横断面测量的两种不同的方法,并以上海市轨道交通2号线东延伸段工程调线调坡测量为例,对这两种方法进行分析比较.     

On the shear deformation modes in the framework of Generalized Beam Theory

This paper extends previous work concerning the determination of cross-section deformation modes in thin-walled members with arbitrary polygonal cross-section, in the framework of Generalized Beam Theory (Gonçalves et al., 2010 [1]). In particular, the paper addresses the so-called “natural shear deformation modes” (i.e. the deformation modes that involve non-null membrane shear strains and are independent of the cross-section discretization employed), which are relevant for capturing the behaviour of thin-walled members with complex multi-cell cross-sections undergoing torsion and/or distortion. The contributions of the paper are (i) the derivation of fundamental properties of the shear modes, (ii) the proposal of an efficient mode extraction procedure and (iii) the development of analytical results for several particular cases. In order to illustrate the application of the proposed mode extraction procedure and demonstrate the validity of the derived properties, several cross-sections are analyzed, including complex multi-cell tubes.