青龙山特大桥空间异形刚架桥设计及优化

空间刚架结构采用墩梁固结的构造，在竖向荷载作用下，能够利用固结端的负弯矩降低梁的跨中弯矩，从而达到减小梁高的目的。在桥下净空受限的情况下，根据刚架结构的力学特点，进行形状优化可极大地改善线路条件，更好适应地形。结合青龙山特大桥的设计，介绍了空间刚架结构的特点及不同桥式方案的选择。采用有限元方法对选取1号节段刚架进行验算，结果表明刚架各控制点参数均满足标准要求。空间异型刚架桥方案可为线路夹角小、净空受限的桥梁工程施工设计提供有益参考。     

复合桩基优化设计方法与工程验证

提出用基于 Geddes应力解的分层总和法计算桩群分担荷载所引起的地基沉降 ,用基于 Boussinesq解的分层总和法计算承台下土分担的荷载所引起的地基沉降 ,将两者之和作为桩基沉降量。结合一个具体的工程将该方法计算的沉降量和其它方法计算的沉降量及实测值进行对比 ,通过研究沉降量与各种因素的关系 ,对复合桩基的优化设计进行了探讨。     

刚架剪力、弯矩图浅析

根据弯曲内力图可以确定危险截面的位置，并能进行强度、刚度校核方面的工作，因此，全面掌握弯曲内力图是材料力学中的一个重点。而由于种种原因，目前对刚架中弯曲内力图的绘制存在较大的困难。就如何绘制刚架中的内力的剪力／弯矩图进行了详细分析。     

大跨度门式刚架中柱连接形式对玻纤厂房造价的影响分析

大跨度门式刚架节点连接形式对结构承载力及用钢量影响较大,所以合理选择连接形式,从而提出较为合理的刚架优化设计;针对大跨度无吊车门式刚架中柱与梁及基础的连接形式,运用PKPM中STS对不同连接形式的门式刚架进行计算分析;对中柱与梁、柱与基础连接的3种组合模型进行用钢量分析,结果表明门刚结构在跨度相同的情况下,中柱与梁的连接采用刚接,柱脚均采用铰接可以有效节省钢材。     

集体形变原理在连续梁、刚架及排架计算中的应用

根据集体分配法的基本原理,考虑结构的集体形变,从理论上建立直接求解超静定结构的新概念;并相应的建立了关于连续梁、刚架、以及排架的实用计算方法。     

静置分层法净化精苯再生酸

介绍了净化再生酸的静置分层法,将处理剂ANPA加入再生酸中,搅拌后静置,使再生酸分层分离而得到净化。该法具有操作简单、无二次污染和经济效益好等优点。     

平台对门式刚架结构稳定性的影响分析

带工作平台门式刚架钢结构体系现已广泛应用于工业与民用建筑,当刚架柱参与承担平台竖向荷载时,平台与刚架成为协同工作体系。由于平台梁约束与竖向荷载的存在,将对刚架的稳定性产生影响。本文建立了平台-刚架协同工作体系的力学计算模型,对刚架柱的稳定系数计算公式进行了推导,对其刚架柱进行非线性屈曲分析,考察了高跨比、平台梁刚度等因素对平台协同工作刚架稳定性的影响。     

减少门式刚架用钢量措施分析

门式刚架是目前单层工业厂房中一种常见的结构形式,如何降低门式刚架用钢量很值得探讨。为此,从柱距、跨度、次构件、钢材类型以及结构形式等几方面分析了它们对用钢量的影响,并根据分析结果提出了相关合理化建议。     

图表2-43 铸铁齿轮的轮辐宽度

齿轮的轮辐承受使轮缘转动的力,而依靠弯矩的作用把此力传递到轮毂上,作用在一根轮辐上的弯矩的大小,大致等于节圆上所传递的截荷 P(公斤)乘以节圆半径[D/2=R(厘米)]再除以轮辐数而得的值,即     

门式刚架抗地表变形的研究现状分析

门式刚架结构抗地表变形的研究现状主要表现在门式刚架平面分析、空间分析及蒙皮效应的研究成果上。由于模拟技术上的限制，门式刚架结构的传统研究主要以平面内分析为主，对于结构简单，纵向刚度小的建筑可以获得较为合理的结果；空间作用分析研究表明，通过考虑纵向传力构件可使计算结果更贴合实际情况，使整体结构附加内力的形成原因及传递路径更加明确，得到直观的附加变形影响范围；蒙皮效应对结构受力性能提升显著，在空间分析的基础上把控围护结构对附加应力、变形的影响规律，以求安全、经济最大化。     

An alternative solution for the edge moment factors of the unbalanced adhesive single-lap joint in tension

An evaluation of the existing theoretical solutions and a proposal of an improved one for edge moment factors of the unbalanced adhesive single-lap joint are performed. Firstly, the existing classical solutions are reviewed and studied in detail. The scope of applications and limitations related to the classical solutions are identified. Meanwhile, the determination for the long and short unbalanced single-lap joint (SLJ) is performed. Then, through removing disadvantages of the existing theoretical solutions, an improved theoretical solution considering the effect of large deflection for overlap is proposed. Meanwhile, the adherends of the overlap regions are treated as individual beams in the improved theoretical solution. The fully-coupled nonlinear formulations for determining adherend displacements (includes axial deformation and transverse deformation) in the overlap and edge moment factors are constructed using the improved theoretical solution. Finally, the results of the existing solutions and the improved theoretical solution are compared with the results of the finite element analysis.     

Calculation of a Cross Flow Past a Rotating Cylinder in the Vicinity of the Stagnation Point

The stationary laminar boundary layer on a rotating infinite cylinder in a cross flow of an incompressible liquid (gas) is considered at relatively low rotation frequencies. An immobile coordinate system fixed to a cross section of the cylinder is used. In the vicinity of the stagnation point, solving this problem is reduced to integrating a set of two ordinary differential equations, one of which is an analogue of the Faukner–Skan equation. The equation obtained is compared to the solution found by the finite-difference method.     

Theoretical Study on Sulfur Dioxide Absorption with Citrate Solution

The citrate absorption of SO2 is currently one of the most successful and economic methods to harness sulfur dioxide pollution. In order to theoretically elucidate the mechanism of SO2 absorption by citrate solution and provide theoretical instruction for experiments and industrial process, the theory of multi-buffer solution, combined with computer numerical calculation methods, was applied to study the distribution parameters of the components of the citrate solution in the process of SO2 absorption and the following results were obtained: (1) HCi2- and H2Ci- in the citrate solution played the dominant role in the absorption and desorption processes; (2) Through the calculation for the buffer capacity of citrate solution, it was found that the pH of the absorption and desorption solution should be in the range of 2~8, while at pH=4.5 the buffer capacity reached its maximum. Some valuable parameters were obtained, which are instructive to the ensuing experiments and industrial design.     

Transient solutions of potential steps at the rotating disc electrode with steady state initial concentration profiles for one electron transfer reactions

In this paper the transient solution of a potential step at a rotating disc electrode (RDE) for irreversible and quasireversible one electron transfer reactions is derived by Nernst diffusion layer approximation and separation of variables. This is then compared to finite element simulation results. For the initial conditions steady state concentrations are chosen, such that with this theory it is possible to fit and simulate quasi steady-state linear sweep RDE measurements or other quasi steady-state sequences of potential steps.It was found that it is possible to derive accurate closed form solutions for the initial parts of the transient response. However, the Nernst diffusion layer approximation leads to inaccuracies in the intermediate times with relative errors of up to 10%.By fitting the initial transient to the closed form solution it is possible to extract steady state background currents. Additionally, we use the potential step theory to derive an expression for kinetically controlled transition times and show that these can exceed the mass transport controlled transition time.     

Analytical Solution of Mass Transfer Equation with Interfacial Resistance in Food Drying

A simplification of boundary conditions of the mass transfer equation in food drying was obtained. An average distribution constant between food and air humidity was introduced. With this simplification and analytical solution for the mass transter equation with interfacial resistance was; found. and a medihcd Bi number is proposed: Thc analytical solution for infinite flat slab was comparcd to the numcrical solution without the simplification. The analytical solution showed a good approximation to thc numerical solution. The equation oblained from thc analytical solution predicted ha1 for modified Bi numbers greater han 30. the drying curve bccamcs indcpcndcnt o f thc boundary conditions, which means that drying is diffusion controlled. Experimental drying curves of carrots were obtained at modified Bi numbers between 10 and 60. The crperimenwl drying cumes did not show statistical diffcrencc for modified Bi numbcrs grcater than 40, which approaches to the same limit predicted by the analytical solution.     

Change in particle size distribution of aerosol undergoing condensational growth: alternative analytical solution for the low Knudsen number regime

Condensational growth of a polydisperse aerosol was studied employing the moment method of log-normal size distribution function. The previous analytical solution for the size distribution of a condensationally growing aerosol (Park et al., J. Aerosol. Sci. 32 (2001) 187) was extended to cover the low Knudsen number transition regime. In order to cover the transition regime, the harmonic mean method was used for obtaining the transition correction factors for mass and heat fluxes. Comparisons were made with the existing solution and good agreement was obtained.     

Novel Nanocomposite PEM Membranes with Continuous Proton Transportation Channel and Reinforcing Network Formed by Electrospinning Solution Casting Method

In this work, a kind of novel nanocomposite proton exchange membranes (PEMs) with excellent properties for fuel cell application is obtained through the combination of electrospinning and solution casting. PEMs are obtained via the electrospinning of solution of sulfonated poly(arylene ether ketone)s (SPAEK)s with carboxylic acid group (SPAEK‐COOH) inserted with nanocrystal cellulose (NCC) first, and then, the SPAEK‐COOH solution is cast on the obtained electrospinning membrane to fill the voids. According to the scanning electron microscopy image of the membrane surface and freeze‐fractured cross section, the nonporous membrane was successfully obtained. The water uptake and the swelling rate of the nanocomposite membrane with 2% NCC (NF‐NCC2) decrease to 62% and 61.5%, respectively, and the membrane shows much higher proton conductivity (0.29 S cm^?1) than the pristine SPAEK‐COOH membrane (NF‐NCC0) (0.196 S cm^?1) at 100 °C. Furthermore, NF‐NCC2 shows a tensile strength of 38 MPa, which is an increase of 36% compared to NF‐NCC0 (28 MPa). The orderly and uniform distribution of NCC in the electrospinning nanofiber and further in the membranes.     

A simple equation for ohmic solution resistance in cells with mercury drop electrodes

A simple analytical expression for the ohmic solution resistance in cells with mercury drop electrodes is presented. This expression is derived using a geometric model in which the bottom of the glass capillary is treated as an infinite insulating plane and equipotentials in solution are considered to be spheres centered about the drop electrode and truncated by the insulating plane. A simple modification of the expression makes it possible to treat the hanging merecury drop electrode as well as the dropping mercury electrode. It is shown that the resistance predicted by the equation derived in the present work closely approximates that obtained from a rigorous solution of the primary potential and current distribution.     

Analytical Solution of Mass Transfer Equation with Interfacial Resistance in Food Drying

ABSTRACT

A simplification of boundary conditions of the mass transfer equation in food drying was obtained. An average distribution constant between food and air humidity was introduced. With this simplification and analytical solution for the mass transter equation with interfacial resistance was; found. and a medihcd Bi number is proposed: Thc analytical solution for infinite flat slab was comparcd to the numcrical solution without the simplification. The analytical solution showed a good approximation to thc numerical solution. The equation oblained from thc analytical solution predicted ha1 for modified Bi numbers greater han 30. the drying curve bccamcs indcpcndcnt o f thc boundary conditions, which means that drying is diffusion controlled. Experimental drying curves of carrots were obtained at modified Bi numbers between 10 and 60. The crperimenwl drying cumes did not show statistical diffcrencc for modified Bi numbcrs grcater than 40, which approaches to the same limit predicted by the analytical solution.     

A Moment Method for Evaporation Using a Logarithmic Size Distribution with the Smallest Size

A moment method of the log-normal distribution with the smallest size is applied to evaporation by newly introducing correction factors obtained from the error function. In this article, the improved moment method is tested for the evaporation, and is compared with the exact solutions calculated by the CIP semi-Lagrangian (CIP-SL) method. In small particle regime, the size distributions and the time histories of the total number and volume per unit volume are reproduced by the moment method for the evaporation near the smallest size. In large particle regime, however, the differences between the moment and exact solutions are larger with time, after the exact distribution spreads to the smallest size. This new moment solver can reproduce the evaporation near the smallest size even when large time step size is given, and thus is expected to be used for the parameterization of the evaporation of small particles in aerosol-transport model.