The axial dispersion performance of an oscillatory flow meso-reactor with relevance to continuous flow operation

A laboratory scale continuous oscillatory flow meso-reactor was developed and residence time distribution (RTD) studies were carried out in order to establish certain process characteristics of the system. In particular, the dispersion coefficient as a function of the primary variables was established. Using optical probes the axial dispersion was investigated by monitoring the response of a pulse dye tracer at different locations within the meso-reactor. Three cases, net flow without oscillation, oscillation without net flow, and oscillation plus net flow were studied over a range of oscillation frequencies, amplitudes, and net flow rates. Both the imperfect and the perfect pulse injection methods were used to determine the axial dispersion coefficient for the system with and without net flow. The axial dispersion coefficient and the dimensionless dispersion number were analysed in the context of different flow conditions. A correlation was established and demonstrated that the axial dispersion within the meso-reactor could be quantified as a function of flow conditions. The results showed that the laboratory continuous flow meso-reactor was able to produce plug flow with modest axial dispersion over a wide range of parameter space, thereby indicating efficient mixing and effective RTD performance.     

Modeling Steel Frame Buildings in Three Dimensions. II: Elastofiber Beam Element and Examples

This is the second of two papers describing a procedure for the three-dimensional nonlinear time-history analysis of steel-framed buildings. An overview of the procedure and the theory for the panel zone element and the plastic hinge beam element are presented in part I. In this paper, the theory for an efficient new element for modeling beams and columns in steel frames called the elastofiber element is presented, along with four illustrative examples. The elastofiber beam element is divided into three segments—two end nonlinear segments and an interior elastic segment. The cross sections of the end segments are subdivided into fibers. Associated with each fiber is a nonlinear hysteretic stress-strain law for axial stress and strain. This accounts for coupling of nonlinear material behavior between bending about the major and minor axes of the cross section and axial deformation. Examples presented include large deflection of an elastic cantilever beam, cyclic loading of a cantilever beam, pushover analysis of a 20-story steel moment-frame building to collapse, and strong ground motion analysis of a two-story unsymmetric steel moment-frame building.     

Modelling steel frame behaviour under fire conditions

A formulation for the noblinear analysis of two-dimensional steel frames under fire conditions using the finite element method is presented. Deterioration in material strength with increasing temperature is represented by a set of nonlinear stress-strain-temperature relationships using a Ramberg-Osgood equation in which creep effects are implicitly included. Structures subject to increasing loads or temperatures are analysed using an incremental Newton - Raphson iterative procedure. The analysis permits deformation history and either collapse load or critical temperature to be calculated at a specified temperature or load level respectively. It includes the effects of geometric nonlinearity, temperature dependent nonlinear material behaviour and variations in temperature distributions both along and across each member. The effects of thermal strains, residual stresses and thermal bowing are also considered and different material models may be used. Comparisons are made with fire test results on frames and columns that represent a wide range of problem parameters such as slenderness, end conditions, load levels and temperature distributions. In all cases, the agreement is very satisfactory. An example two-bay frame is analysed to illustrate the potential of the analysis and to show the influence of various forms of partial protection on the collapse temperature of sway frames.     

镍铬眼镜框架材料的研究及应用

本文介绍了一种眼镜架用新型Ｎｉ－Ｃｒ合金，并对它的制造方法、成分配制、机械性能、抗腐蚀性能和抗高温软化性能进行了系列研究和实验。结果表明：该合金的主要性能指标均优于国内常用的眼镜框架材料。经镜架工厂试用后认为该材料适合于制作各类高档眼镜架。     

Optimal design of a welded I-section frame using four conceptually different optimization algorithms

The purpose of this study is to investigate the suitability of four conceptually different optimization algorithms for specifically the optimal design of welded I-section frames. The cost function to be minimized is the volume of the frame. Constraints on lateral-torsional buckling as well as local buckling of the beam and column webs and flanges are taken into consideration. The algorithms evaluated include a genetic algorithm, a novel leap-frog gradient method without line searches, as well as an orthogonal search method requiring no gradients and the differential evolution technique. Received September 26, 2001 RID="*" ID="*"Part of this paper was presented at the World Congress on Structural and Multidisciplinary Optimization, June 4–8 2001, Dalian, China     

A comparison of simulated annealing and genetic algorithm for optimum design of nonlinear steel space frames

In this article, two algorithms are presented for the optimum design of geometrically nonlinear steel space frames that are based on simulated annealing and genetic algorithm. The design algorithms obtain minimum weight frames by selecting suitable sections from a standard set of steel sections such as the American Institute of Steel Construction (AISC) wide-flange shapes. Stress constraints of AISC Load and Resistance Factor Design (LRFD) and AISC Allowable Stress Design (ASD) specifications, maximum (lateral displacement) and interstorey drift constraints, and also size constraints for columns were imposed on frames. The algorithms were applied to the optimum design of three space frame structures, which have a very small amount of nonlinearity. The unconstrained form of objective function was applied in both optimum design algorithms, and constant penalty factors were used instead of gradually increasing ones. Although genetic algorithm took much less time to converge, the comparisons showed that the simulated annealing algorithm yielded better designs together with AISC-LRFD code specification.     

计算机动画关键帧插补技术综述

对计算机辅助动画制作过程中关键帧的插补技术进行了研究。线性插值法通过给定的起始帧和结束帧对应点之间的直线距离算出中间插值帧。移动点约束条件插补法利用随时间空间变化的曲线与彩体上的点相关联，来控制关键帧上对应控制点的轨迹以厦动态特征。骨架插补法是将图形抽象成骨架，然后进行插补。     

Lessons learned from the testing of RC frames with masonry infills and proposals for new solutions / Untersuchungen an mit Mauerwerk ausgefachten Stahlbetonrahmen und neue Lösungsvorschläge

Past experience has shown that inadequate design of unreinforced masonry walls (URM) or inadequate selection of materials can lead to significant economic losses and fatalities in the case of a strong earthquake. In this context, this paper presents the experimental research that has been carried out with the aim of gaining a better insight into the traditional masonry infill walls commonly built in Portugal. The experimental research includes: (1) shaking table tests on reduced‐scale reinforced concrete (RC) buildings with masonry infills with distinct typologies, from traditional solutions to those with enhanced properties and solutions to improve the seismic behaviour; (2) in‐plane static cyclic tests on a representative one‐storey, one‐bay RC frame with masonry infills with distinct typologies but similar to the ones tested in the RC building models. It was concluded that the typology of masonry walls influences the global behaviour of RC buildings, particularly when there is no connection between masonry infill and RC frame. An appropriate design is necessary to prevent an unforeseen failure mechanism due to shear stresses in the RC columns induced by the infill. The in‐plane cyclic tests showed that render plays a central role in the lateral strength and stiffness. Additionally, it was observed that bed joint reinforcement and reinforced render are important measures for controlling damage but do not significantly influence the in‐plane lateral strength and stiffness.     

Optimizing a bi-objective multi-product EPQ model with defective items,rework and limited orders: NSGA-II and MOPSO algorithms

In this paper, a bi-objective multi-products economic production quantity (EPQ) model is developed, in which the number of orders is limited and imperfect items that are re-workable are produced. The objectives of the problem are minimization of the total inventory costs as well as minimizing the required warehouse space. The model is shown to be of a bi-objective nonlinear programming type, and in order to solve it two meta-heuristic algorithms namely, the non-dominated sorting genetic algorithm (NSGA-II) and multi-objective particle swarm optimization (MOPSO) algorithm, are proposed. To verify the solution obtained and to evaluate the performance of proposed algorithms, two-sample t-tests are employed to compare the means of the first objective value, the means of the second objective values, and the mean required CPU time of solving the problem using two algorithms. The results show while both algorithms are efficient to solve the model and the solution qualities of the two algorithms do not differ significantly, the computational CPU time of MOPSO is considerably lower than that of NSGA-II.