Inverse identification of wheel–rail contact forces based on observation of wheel disc strains: an evaluation of three numerical algorithms

In this paper, three numerical algorithms for the identification of wheel–rail contact forces based on measured wheel disc strains on an instrumented railway wheelset are discussed and compared. The three algorithms include one approach resting on static calibration, one that is applying a Kalman filter and the third is exploiting an inverse identification scheme. To demonstrate and evaluate the alternative methods, two load cases including periodic excitation by sinusoidal wheel–rail irregularities and transient excitation by an insulated rail joint are considered. Based on a previously presented vehicle–track interaction model in the time domain, load scenarios are defined by taking the calculated vertical wheel–rail contact forces as the reference force to be re-identified by the proposed algorithms. The reference contact forces are applied on a finite element model of the wheel to generate synthetic observation data, that is, radial strains at the positions of the strain gauges, serving as input to the identification procedures. It is concluded that the inverse identification scheme leads to superior accuracy at higher computational cost. If on-line implementation and evaluation is required, the Kalman filter generates better accuracy than the static calibration approach.     

On the scattering of test data and the significance of the standard coefficients ‘dynamic stiffness’ and ‘loss angle’ for hydraulic engine mounts

Based on the test results, a study on the scattering of the standard coefficients c _dyn and δ within the test cycles on a standard testing machine as well as within the samples of a batch of hydraulic engine mounts is performed; furthermore, an estimate for the systematic error caused by the testing machine is given. By a simulated example, the pronounced sensitivity of the response of the engine to the scattering of c _dyn and δ as well as to even small deviations of the hysteresis curves for otherwise identical values of the standard coefficients is demonstrated. As a main result, it is found that the most important source of uncertainty is scattering within the batch, which, in conjunction with the observed sensitivity of the response of the engine, raises the question for the meaningful level of sophistication of a model for predictive purposes.     

Design of robust-stable and quadratic finite-horizon optimal controllers with low trajectory sensitivity for uncertain active suspension systems

This paper presents a design method for designing the robust-stable and quadratic-finite-horizon-optimal controllers of uncertain active suspension systems. The method integrates a robust stabilisability condition, the orthogonal functions approach (OFA) and the hybrid Taguchi-genetic algorithm (HTGA). Using the integrative computational method, a robust-stable and quadratic-finite-horizon-optimal controller with low-trajectory sensitivity can be obtained such that (i) the active suspension system with elemental parametric uncertainties is stabilised and (ii) a quadratic-finite-horizon-integral performance index including a quadratic trajectory sensitivity term for the nominal active suspension system is minimised. The robust stabilisability condition is proposed in terms of linear matrix inequalities (LMIs). Based on the OFA, an algebraic algorithm only involving the algebraic computation is derived for solving the nominal active suspension feedback dynamic equations. By using the OFA and the LMI-based robust stabilisability condition, the dynamic optimisation problem for the robust-stable and quadratic-finite-horizon-optimal controller design of the linear uncertain active suspension system is transformed into a static-constrained-optimisation problem represented by the algebraic equations with constraint of LMI-based robust stabilisability condition; thus greatly simplifies the design problem. Then, for the static-constrained-optimisation problem, the HTGA is employed to find the robust-stable and quadratic-finite-horizon-optimal controllers of the linear uncertain active suspension systems. A design example is given to demonstrate the applicability of the proposed integrative computational approach.     

生态工法在国内外公路工程中的应用和启示

介绍生态工法的内涵、发展历史、工法实例及在国内外公路建设中的应用，提出一些工作建议，并指出：在观念上要从人定胜天向善待自然、尊重自然转变；在建设工法上应从“传统工法”向“生态工法”转变。     

加强高校海洋生态环境道德教育的思考

21世纪是海洋世纪,海洋是人类未来的希望,是全球生命支持系统的一个基本组成部分,也是一种有助于实现可持续发展的宝贵财富.在海洋生态环境日益恶化的今天,高校应积极开展海洋生态环境道德教育,提高大学生的海洋生态环境道德意识.阐释了海洋生态环境道德教育的定义,分析了加强高校海洋生态环境道德教育必要性,提出了加强海洋生态环境道德教育的有效途径.     

生态袋护岸的设计要点探讨

通过算例探讨了生态袋在边坡稳定分析中的作用和水位波动区下满足局部稳定的生态袋最小尺寸，给出了生态袋安全分析方法。结果表明:生态袋能提高边坡的稳定，避免表层的浅层滑动，边坡稳定安全系数随着生态袋防护范围厚度的增加而增加； 生态袋的尺寸基本随河道流速的增长呈幂指数增长，对河道流速较为敏感；生态袋护岸抗滑移分析、抗倾覆分析和抗剪切分析计算公式简单直观，但技术参数和安全系数的取值是关键。     

Comparing Fisher Interviews,Logbooks, and Catch Landings Estimates of Extraction Rates in a Small-Scale Fishery

Researchers are turning to alternative data sources (e.g., resource user knowledge) to provide information required for wildlife management. Little is known about the reliability of data elicited from resource users relative to data obtained from user-independent approaches (e.g., observations of fish catches). We test for consensus among three methods that quantify past (1996 to 2007) seahorse catch-per-unit-effort (CPUE) for a small-scale, data-poor fishery in the Philippines: interviews with fishers about good, bad, and typical catch; fisher logbooks; and observations of catch landings. Interviews and logbooks indicated no trends in CPUE through time, consistent with results from the fisher-independent metric, catch landings. Although interview estimates of “typical” CPUE greatly exceeded “typical” observed catches and logbook estimates, interview estimates of “bad” CPUE were comparable. Catch landings estimates for a fisher in a particular year were uncorrelated to what he reported during retrospective interviews. Interviews should be used cautiously to inform specific catch targets (e.g., total allowable catches), although including interview questions about a range of catch experiences (e.g., good, bad and typical), may improve interview-derived data. Logbooks are particularly useful for capturing information about fishing expeditions that produce no fish, which are largely missed by other methods.     

Sensitivity of the wheel–rail contact interactions and Dang Van Fatigue Index in the rail with respect to irregularities of the track geometry

This paper investigates the effects of the track geometry irregularities on the wheel–rail dynamic interactions and the rail fatigue initiation through the application of the Dang Van criterion, that supposes an elastic shakedown of the structure. The irregularities are modelled, using experimental data, as a stochastic field which is representative of the considered railway network. The tracks thus generated are introduced as the input of a railway dynamics software to characterise the stochastic contact patch and the parameters on which it depends: contact forces and wheelset–rail relative position. A variance-based global sensitivity analysis is performed on quantities of interest representative of the dynamic behaviour of the system, with respect to the stochastic geometry irregularities and for different curve radius classes and operating conditions. The estimation of the internal stresses and the fatigue index being more time-consuming than the dynamical simulations, the sensitivity analysis is performed through a metamodel, whose input parameters are the wheel–rail relative position and velocity. The coefficient of variation of the number of fatigue cycles, when the simulations are performed with random geometry irregularities, varies between 0.13 and 0.28. In a large radius curve, the most influent irregularity is the horizontal curvature, while, in a tight curve, the gauge becomes more important.     

DOE技术在起重臂优化设计中的应用

为提高某船用起重机起重臂结构刚度,减小其最大应力以及结构质量,首先对各变量进行灵敏度计算,去除对目标函数不灵敏的设计变量,以提高后续计算效率。基于DOE试验设计理论及有限元法构建优化问题的近似模型,借助拉丁采样对该近似模型拟合精度进行检验。基于遗传优化算法(GA)对该近似模型进行优化。优化结果表明:刚度提高9.4%,最大应力值减小21.4%,结构质量减轻9.3%。     

鄱阳湖生态经济区区域物流竞争力研究

区域物流竞争力成为区域竞争力的核心组成部分之一,对于区域物流竞争力的客观评价研究已成为现实的必然要求。以鄱阳湖生态经济区的9个城市为研究对象,对区域物流竞争力的发展现状进行分析,通过指标变量的选取,构建鄱阳湖生态经济区区域物流竞争力的评价体系,采用SPSS统计软件中的聚类分析和因子分析法对各城市的物流竞争力进行了得分排名以及提出对策建议。