Investigation of the Influence of Pseudoinverse Matrix Calculations on Multibody Dynamics Simulations by Means of the Udwadia-Kalaba Formulation

The formulation of the dynamic equations of motion proposed by Udwadia-Kalaba is discussed from the point of view of numerical efficiency. Since this formulation requires the computation of a pseudoinverse matrix, it has investigated the influence of the method of pseudoinverse computation on the dynamic simulation of an overconstrained linkage. Finally, it has been proposed that a new dynamic equation which explicitly computes accelerations also in the case of mathematical models with rank deficient Jacobian and mass matrices.     

A typology of different development and testing options for symbolic regression modelling of measured and calculated datasets

Data-driven modelling is used to develop two alternative types of predictive environmental model: a simulator, a model of a real-world process developed from either a conceptual understanding of physical relations and/or using measured records, and an emulator, an imitator of some other model developed on predicted outputs calculated by that source model. A simple four-way typology called Emulation Simulation Typology (EST) is proposed that distinguishes between (i) model type and (ii) different uses of model development period and model test period datasets. To address the question of to what extent simulator and emulator solutions might be considered interchangeable i.e. provide similar levels of output accuracy when tested on data different from that used in their development, a pair of counterpart pan evaporation models was created using symbolic regression. Each model type delivered similar levels of predictive skill to that other of published solutions. Input–output sensitivity analysis of the two different model types likewise confirmed two very similar underlying response functions. This study demonstrates that the type and quality of data on which a model is tested, has a greater influence on model accuracy assessment, than the type and quality of data on which a model is developed, providing that the development record is sufficiently representative of the conceptual underpinnings of the system being examined. Thus, previously reported substantial disparities occurring in goodness-of-fit statistics for pan evaporation models are most likely explained by the use of either measured or calculated data to test particular models, where lower scores do not necessarily represent major deficiencies in the solution itself.     

Isogeometric computation reuse method for complex objects with topology-consistent volumetric parameterization

Volumetric spline parameterization and computational efficiency are two main challenges in isogeometric analysis (IGA). To tackle this problem, we propose a framework of computation reuse in IGA on a set of three-dimensional models with similar semantic features. Given a template domain, B-spline based consistent volumetric parameterization is first constructed for a set of models with similar semantic features. An efficient quadrature-free method is investigated in our framework to compute the entries of stiffness matrix by Bézier extraction and polynomial approximation. In our approach, evaluation on the stiffness matrix and imposition of the boundary conditions can be pre-computed and reused during IGA on a set of CAD models. Examples with complex geometry are presented to show the effectiveness of our methods, and efficiency similar to the computation in linear finite element analysis can be achieved for IGA taken on a set of models.     

The Application of Nearly Embarrassingly Parallel Computation in the Optimization of Fluid-Film Lubrication©

The combination of powerful, yet inexpensive PCs and readily available open sources for parallel computation marks a new era of easy access to massive computation for the tribology community. The study demonstrates the applicability of embarrassingly parallel computation in the optimization of air-lubricated porous bearings with four design variables. To achieve high speedup without increasing the coding complexity, the master computer implements the lattice method to allocate the near-the-same computational load in the master-slave cluster. The effect of master capability on the cluster performance is also presented. The results are compared with that of an unparallelized simplex method and indicate a significant reduction in execution time due to parallelism. In a simulated analysis, a high speedup can also be obtained in dealing with a problem with many design variables. This study provides the framework for optimization of applications with complex tribological models to be solved with minimum execution time.     

Bioinspired Computational Framework for Enhancing Creativity, Optimality, and Robustness in Design

This paper presents results of transdisciplinary research on the development of a bioinspired computational framework for engineering design. This framework is intended to support design by addressing three critical design objectives, including novelty, optimality, and robustness. It provides several computational models and methods, which are inspired by fundamental processes occurring in nature, and discusses their potential for enhancing design. They include models and methods for evolutionary, developmental, and coevolutionary design. Their use is illustrated with examples from the area of steel structural design ranging from a simple cantilever beam design problem to a much more complex problem of designing wind bracings in tall buildings. The paper also shows how several methods and models can be integrated and form a coherent bioinspired computational framework for engineering design.     

Measurement and Stochastic Computational Modeling of the Elastic Properties of Parallel Strand Lumber

This paper describes a model for the spatial variation of the elastic modulus of parallel strand lumber (PSL) that is based on bending experiments and also describes a validated stochastic computational model that incorporates orthotropic elasticity and uncertainty in strand geometry and material properties. The PSL exhibits significant variability both within members and between members, but this variability is less than that of equivalent sawn-wood members, and decreases with increasing member size. The correlation length of the elastic modulus is found to be several meters and is independent of the cross-sectional size. The variance of PSL elastic modulus is found to scale inversely with the number of strands in the cross section. The validated computational model is flexible enough to allow preliminary exploration of the properties of new mixes of species and strand sizes in PSL material design.     

Object-Oriented Approach to the Enhancement of Energy Management Systems Software Engineering

This paper presents the idea of an operational model of a power system as the background for Energy Management Systems (EMS) software. Due to the Object Oriented Approach, with use of the proposed model, all kinds of standard power system analyses can be provided. The objects and their hierarchy is organized in such a way that all inconveniences well known in practical applications (multiwinding transformers, mutually coupled lines, busbar couplers, tapped lines, dummy nodes, control systems, FACTS devices, etc.) are taken into account and included in consistent data structures. Possibilities for a clear connection between operational models and numerical models of power systems are indicated.     

装载机工作装置的力分析及电算程序设计

本文运用计算机程序设计,将装载机的工作机构解体分成五个构件,分别建立力和力偶平衡方程,用矩阵方程表示,然后用主元素消去法解得各未知力的大小及其方向。     

电磁场计算边界元方法中的奇异积分求解

边界元方法是电磁场数值计算中的有效方法之一。然而，边界元方法中的奇异积分求解在三维场计算中显得非常困难。目前，一般采用数值计算近似处理的方法，它难以得到精确计算结果。本文给出了采用场强矢量计算三维电磁场边界元方程中奇异积分的分析解，是在线性三角形单元的基础上得出的。分析解的获得使相应的奇异积分值可以精确地得到，从而大大提高了边界元方法的计算精度。     

稀相气固两相流动的数值求解

本文对SIMPLE方法作了推广,提出了一种求解二维湍流稀相气固两相流动的数值方法。流动的六个控制方程都是非线性的,而且是互相耦合的偏微分方程。本文给出了求解固相容积率方程的一个稳定的差分格式,讨论了松驰因子,源项的处理方法及迭代方法的改进等因素对整个数值解的收敛性的影响,绘出了变量的残留误差随迭代次数的变化曲线。并就水平直管内的高载荷比气固两相流动进行了数值计算,其计算结果和收敛速度都是令人满意的。