三种有限元软件在砌体结构中的对比分析

砌体结构由于其独特的材料特性,采用有限元分析存在一定难度.本文结合一个足尺的砌体结构模型的试验研究结果,对比分析了国外研究者利用有限元原理,采用三种不同有限元软件模拟该模型.模拟所得的结果可为我国科研工作者利用有限元原理分析砌体结构提供参考,弥补国内关于砌体结构有限元分析的不足.     

自动化挖掘机动臂结构有限元分析策略研究

针对当前挖掘机动臂结构有限元分析方法中人工操作强度大、建模效率低等问题,研究基于Pro/TOOLKIT、APDL命令流和ANSYS的Batch工作模式的自动化动臂结构有限元分析运行机制,建立自动化动臂结构有限元分析系统体系结构,提出相应的有限元分析工作流程。结合具有双动臂液压缸的鹅颈式动臂结构,开发人机界面友好的自动化动臂结构有限元分析软件,验证自动化有限元分析方法的可行性及其在提高批量动臂结构有限元分析效率方面的有效性。     

Revealed Preference and Location Choice

The assumption that population and structural densities are defined over parcels of land with zero area is problematic when interpreting the standard residential land use model as approximating a large finite economy. This paper extends revealed preference theory to depict a spatial economy with land parcels of finite area. The model generalizes the standard utility function approach, allowing for many consumer types with different tastes and incomes and labor-leisure choice, to show that the most important predictions of the standard theory hold in the general finite framework studied here.     

The core of the inductive limit of a direct system of economies with a communication structure

This paper studies direct systems of finite, that is with finitely many agents, communication structures, finite (balanced and superadditive) NTU games and finite economies. The inductive limit of such a system is again a communication structure, an NTU game or an economy, this time possibly with infinitely many agents. As a matter of fact, each infinite communication structure, each infinite NTU game and each infinite economy, is the inductive limit of a direct system of finite communication structures, finite NTU games and finite economies. A communication game is an NTU game with a communication structure on the set of players. To each economy, there corresponds a balanced and superadditive NTU game. To each economy with a communication structure on the set of agents, there corresponds a communication game. In the paper it is proved that the core of the inductive limit of a direct system of communication games is not empty and in fact the intersection of the cores of the finite communication games of the direct system. It follows that each infinite economy (with or without a communication structure on the set of agents) has a nonempty core. A direct system of economies is a generalisation of the Debreu and Scarf [Debreu, G., Scarf, H. A limit theorem on the core of an economy, International Economic Review 4, pp. 235–246.] example of `replica economies'. The proof of the nonemptiness of the core of the inductive limit of a direct system of economies is along the lines of the proof by Debreu and Scarf. As by-product it is shown that an NTU game is totally balanced if and only if all its finite subgames are balanced.     

Pure strategy equilibria in games with countable actions

In this paper, we extend the Radner–Rosenthal theorem with finite action spaces on the existence of a pure strategy equilibrium for a finite game to the case that the action space is countable and complete. We also prove the existence of a pure strategy equilibrium for a game with a continuum of players of finite types and with a countable and complete action space. To work with the countably infinite action spaces, we prove some regularity properties on the set of distributions induced by the measurable selections of a correspondence with a countable range by using the Bollobás–Varopoulos extension of the marriage lemma.     

三维有限元方法在大坝安全监测中的应用研究

近年来,混凝土非线性有限元理论获得了重大的发展,与线弹性分析方法以及常规计算模型相比,非线性有限元方法具有适应性强、力学概念明确、分析精确等优点。本文针对某混凝土重力坝,利用ANSYS建立有限元模型。通过计算得出了混凝土重力坝裂缝发生的因素,可能产生的危害,预防和控制措施,并提出建议。     

Finite sample inference for quantile regression models

Under minimal assumptions, finite sample confidence bands for quantile regression models can be constructed. These confidence bands are based on the “conditional pivotal property” of estimating equations that quantile regression methods solve and provide valid finite sample inference for linear and nonlinear quantile models with endogenous or exogenous covariates. The confidence regions can be computed using Markov Chain Monte Carlo (MCMC) methods. We illustrate the finite sample procedure through two empirical examples: estimating a heterogeneous demand elasticity and estimating heterogeneous returns to schooling. We find pronounced differences between asymptotic and finite sample confidence regions in cases where the usual asymptotics are suspect.     

Pareto-undominated and socially-maximal equilibria in non-atomic games

This paper makes the observation that a finite Bayesian game with diffused and disparate private information can be conceived of as a large game with a non-atomic continuum of players. By using this observation as its methodological point of departure, it shows that (i) a Bayes–Nash equilibrium (BNE) exists in a finite Bayesian game with private information if and only if a Nash equilibrium exists in the induced large game, and (ii) both Pareto-undominated and socially-maximal BNE exist in finite Bayesian games with private information. In particular, it shows these results to be a direct consequence of results for a version of a large game re-modeled for situations where different players may have different action sets.     

Computability of simple games: A characterization and application to the core

The class of algorithmically computable simple games (i) includes the class of games that have finite carriers and (ii) is included in the class of games that have finite winning coalitions. This paper characterizes computable games, strengthens the earlier result that computable games violate anonymity, and gives examples showing that the above inclusions are strict. It also extends Nakamura’s theorem about the nonemptyness of the core and shows that computable games have a finite Nakamura number, implying that the number of alternatives that the players can deal with rationally is restricted.     

Threshold estimation of Markov models with jumps and interest rate modeling

We reconstruct the level-dependent diffusion coefficient of a univariate semimartingale with jumps which is observed discretely. The consistency and asymptotic normality of our estimator are provided in the presence of both finite and infinite activity (finite variation) jumps. Our results rely on kernel estimation, using the properties of the local time of the data generating process, and the fact that it is possible to disentangle the discontinuous part of the state variable through those squared increments between observations not exceeding a suitable threshold function. We also reconstruct the drift and the jump intensity coefficients when they are level-dependent and jumps have finite activity, through consistent and asymptotically normal estimators. Simulated experiments show that the newly proposed estimators perform better in finite samples than alternative estimators, and this allows us to reexamine the estimation of a univariate model for the short term interest rate, for which we find fewer jumps and more variance due to the diffusion part than previous studies.     

A characterization and an impossibility of finite length anonymity for infinite generations

In the context of ranking infinite utility streams, the impartiality axiom of finite length anonymity requires the equal ranking of any two utility streams that are equal up to a finite length permutation ( Fleurbaey and Michel, 2003). We first characterize any finite length permutation as a composition of a fixed step permutation and an “almost” fixed step permutation. We then show that if a binary relation satisfies finite length anonymity, then it violates all the distributional axioms that are based on a segment-wise comparison. Examples of those axioms include the weak Pareto principle and the weak Pigou-Dalton principle.     

On Models with an Uncongestible Public Good and a Continuum of Consumers

This short note shows that models with an uncongestible or mildly congestible public good and a (non-atomic) continuum of consumers have an interesting but unfortunate property. Only an infinite level of public good provision in the continuum economy can be approximated by feasible public good levels in a sequence of economies with finite populations. We discuss the theoretical and practical problems this creates for familiar models that employ a continuum of consumers and a finite level of an uncongestible public good.     

Finite order implications of common priors in infinite models

Lipman [Lipman, B., 2003. Finite order implications of common priors, Econometrica, 71 (July), 1255–1267] shows that in a finite model, the common prior assumption has weak implications for finite orders of beliefs about beliefs. In particular, the only such implications are those stemming from the weaker assumption of a common support. To explore the role of the finite model assumption in generating this conclusion, this paper considers the finite order implications of common priors in the simplest possible infinite model, namely, a countable model. I show that in countable models, the common prior assumption also implies a tail consistency condition regarding beliefs. More specifically, I show that in a countable model, the finite order implications of the common prior assumption are the same as those stemming from the assumption that priors have a common support and have tail probabilities converging to zero at the same rate.     

双瓣抓斗铰链卡死有限元模型的计算机仿真

首先介绍系统CAE仿真特点和流程,利用系统CAE仿真技术建立抓斗铰链卡死工况的基本有限元模型,指出系统CAE技术常见的零部件装配的有限元处理方法,分析该工况下的边界条件,施加合理的约束与载荷。最后通过计算机仿真结果来验证有限元模型的正确性。     

Rationally inattentive macroeconomic wedges

This paper argues that the solution to a dynamic optimization problem of consumption and labor under finite information-processing capacity can simultaneously explain the intertemporal and intratemporal labor wedges. It presents a partial equilibrium model where a representative risk adverse consumer chooses information about wealth with limited attention. The paper compares ex-post realizations of models with finite and infinite capacity. The model produces macroeconomic wedges and measures of elasticity consistent with the literature. These findings suggest that aconsumption-labor model with information-processing constraints can explain the difference between predicted and observed consumption and employment behavior.     

An application of approximate finite sample results to parameter estimation in a linear errors-in-variables model

In the simple errors-in-variables model the least squares estimator of the slope coefficient is known to be biased towards zero for finite sample size as well as asymptotically. In this paper we suggest a new corrected least squares estimator, where the bias correction is based on approximating the finite sample bias by a lower bound. This estimator is computationally very simple. It is compared with previously proposed corrected least squares estimators, where the correction aims at removing the asymptotic bias or the exact finite sample bias. For each type of corrected least squares estimators we consider the theoretical form, which depends on an unknown parameter, as well as various feasible forms. An analytical comparison of the theoretical estimators is complemented by a Monte Carlo study evaluating the performance of the feasible estimators. The new estimator proposed in this paper proves to be superior with respect to the mean squared error.     

Ratchet consumption over finite and infinite planning horizons

Ratchet consumers want their spending to always increase and never decrease. We find an optimal consumption rule for ratchet consumers by maximizing an expected utility that eschews spending declines, yet permits a range of choices for felicity and time preference functions. This solution can be tailored to fit both retirees with finite planning horizons and endowments with infinite planning horizons. We assume complete markets modeled by a pricing kernel generated by a Lévy process. When the kernel is log-normal, we obtain closed-form solutions for both finite and infinite horizons.     

Another look at the Tail Area Influence Function

A new way of computing the Tail Area Influence Function (TAIF) exactly is proposed and a new finite sample robustness measure, based on the TAIF, is introduced. The main properties of this robustness measure are also studied, for both finite and asymptotic sample sizes. Next, a very accurate approximation to the finite sample power function of a test is obtained; this is based on the TAIF plus an iterative procedure. The results are valid when there are no nuisance parameters.     

泵站底板应力弹性地基梁法与三维静力计算对比分析

底板在泵站结构计算中占重要地位。在对长洲水利枢纽库区防护下六河泵站底板应力进行计算,分别采用弹性地基梁法、三维静力（通用软件KNSYS）计算,对应力结果进行综合分析表明,三维应力分析对边墙与底板结合处、弹性地基梁法对底板中部,与实际受力状态较为一致,为下一步结构设计优化提供依据。     

Nonlinear supporting prices : The superadditive case

Assumptions on allocations and preferences sufficient to allow superadditive price support are considered for an exchange economy with a finite number of traders when the commodity space is an ordered topological vector space. The main requirements are a uniformmonotonicity assumption on preferences and that no permutation of the allocation among agents yields a Pareto improvement. No convexity assumption on preferences is used, the positive orthant need not have interior, while the proof is constructive. Applications to finite and infinite dimensional commodity spaces are discussed.