普遍的平面断裂配点法和超奇异性问题的讨论

本文对平面断裂中的应力分析问题建立了普遍的配点计算法,并用巴波柯维奇—纽勃通解代替威廉斯应力函数,文中所得公式适于计算机的编程和计算。文中使用的试函数既可用于应力边界条件问题,又可用于位移边界条件问题。本方法中全部边界上的边界条件都是近似满足的。由于在计算中使用了较多的试函数,所以能分析复杂的边界条件问题,文中算例说明了这一方法的计算精度和广泛用途。 本文还讨论了平面断裂的超奇异性问题。     

Imposition of boundary conditions by modifying the weighting coefficient matrices in the differential quadrature method

One of the important issues in the implementation of the differential quadrature method is the imposition of the given boundary conditions. There may be multiple boundary conditions involving higher‐order derivatives at the boundary points. The boundary conditions can be imposed by modifying the weighting coefficient matrices directly. However, the existing method is not robust and is known to have many limitations. In this paper, a systematic procedure is proposed to construct the modified weighting coefficient matrices to overcome these limitations. The given boundary conditions are imposed exactly. Furthermore, it is found that the numerical results depend only on those sampling grid points where the differential quadrature analogous equations of the governing differential equations are established. The other sampling grid points with no associated boundary conditions are not essential. Copyright © 2002 John Wiley & Sons, Ltd.     

Digital simulation of industrial steam reformers for natural gas using heterogeneous models

A model is developed for industrial natural gas steam reformers with top-fired and side-fired furnance design. The one-dimensional heterogeneous model for catalyst tubes takes into account the intra-particle diffusion resistances. Two approximations are used for the computation of the effective diffusivities via the Stefan-Maxwell equations. The two-point boundary value differential equations for the catalyst pellets are solved by a novel efficient and modified orthogonal collocation technique. The performance of the model has been checked in the case of two industrial reformers used in the ammonia and methanol industries in Egypt and Saudi Arabia.     

住宅厨、卫给水排水系统设计探讨

本文阐述了住宅建设方案设计阶段,设备专业配合设计的必要性,住宅设计优化、给排水设计方案和推广应用新材料新设备的重要性。     

新疆下坂地工程大坝防渗体形式的选择

根据下坂地工程地处海拔高、年温度变化大、冬季气候寒冷地区的特点,本文主要从沥青混凝土心墙的墙体布置形式和施工方式两方面来论述下坂地工程大坝心墙形式的选择。     

Single edge-crack stress intensity factor solutions

Weight function arguments and a boundary collocation technique are used to re-examine the stress intensity factor solutions to several classic two-dimensional linear elastic single edge-crack configurations. Limits to applicability and the solutions to the three and four-point bend, pure bending, eccentrically loaded tension, and other boundary condition problems are extracted from the solution to the uniformly loaded single edge-cracked configuration. A simple representation of the asymptotic behavior is proposed and a common expression that captures the full range of crack length to specimen width ratio is presented.     

级配碎石基层施工与检测

本文对级配碎石基层规划流程进行了细化分析,将内部材料搭配机理以及施工流程规划完全,保证了后期检测细务的畅快进行。整个研究活动涉及细化因素众多,包括创新技术节点和注意事项等,需要技术人员谨慎应对。     

Global space–time multiquadric method for inverse heat conduction problem

In this paper, a radial basis collocation method (RBCM) based on the global space–time multiquadric (MQ) is proposed to solve the inverse heat conduction problem (IHCP). The global MQ is simply constructed by incorporating time dimension into the MQ function as a new variable in radial coordinate. The method approximates the IHCP as an over‐determined linear system with the use of two sets of collocation points: one is satisfied with the governing equation and another is for the given conditions. The least‐square technique is introduced to find the solution of the over‐determined linear system. The present work investigates two types of the ill‐posed heat conduction problems: the IHCP to recover the surface temperature and heat flux history on a source point from the measurement data at interior locations, and the backward heat conduction problem (BHCP) to retrieve the initial temperature distribution from the known temperature distribution at a given time. Numerical results of four benchmark examples show that the proposed method can provide accurate and stable numerical solutions for one‐dimensional and two‐dimensional IHCP problems. The sensitivity of the method with respect to the measured data, location of measurement, time step, shape parameter and scaling factor is also investigated. Copyright © 2010 John Wiley & Sons, Ltd.     

精馏过程动态机理模型建立

为了实现精馏过程的动态优化和先进控制,必须解决精确的动态数学模型的建立问题.本文介绍了精馏过程动态机理建模的方法,该模型的特点是考虑每块塔板温度、压力、汽相流量、液相流量、汽相浓度、液相浓度和持液量的动态特性,并且,利用正交配置方法离散模型方程,利用牛顿一拉夫逊方法解模型方程,研究结果表明该模型精度高,误差小于3%,适合于精馏过程的动态优化和先进控制策略研究.     

清涧河流域不同水土保持措施配置下蓄水拦沙效益分析

从分析清涧河流域不同年代水土保持措施配置人手,以蓄水拦沙效益为研究目标,探讨了水土保持措施优化配置问题。分析认为：水土保持措施配置与蓄水拦沙效益是密切相关的,淤地坝在水土保持措施配置中应占有合理比重,坡面治理措施配置中需进一步加大封禁治理比例。