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101.
In this paper we study the profitability of car manufacturers in relation to industry-wide profitability targets such as industry averages. Specifically we are interested in whether firms adjust their profitability in the direction of these targets, whether it is possible to detect any such change, and, if so, what the precise nature is of these changes. 相似文献
102.
Manoj Chacko P. Yageen Thomas 《Annals of the Institute of Statistical Mathematics》2008,60(2):301-318
Ranked set sampling is applicable whenever ranking of a set of sampling units can be done easily by a judgement method or
based on the measurement of an auxiliary variable on the units selected. In this work, we consider ranked set sampling, in
which ranking of units are done based on measurements made on an easily and exactly measurable auxiliary variable X which is correlated with the study variable Y. We then estimate the mean of the study variate Y by the BLUE based on the measurements made on the units of the ranked set sampling regarding the study variable Y, when (X ,Y) follows a Morgenstern type bivariate exponential distribution. We then consider unbalanced multistage ranked set sampling
and estimate the mean of the study variate Y by the BLUE based on the observations made on the units of multistage ranked set sample regarding the study variable Y. Efficiency comparison is also made on all estimators considered in this work. 相似文献
103.
R. Kreißig U. Benedix U.-J. Görke 《Archive of Applied Mechanics (Ingenieur Archiv)》2001,71(2-3):123-134
Summary The presented method to identify material parameters for inelastic deformation laws is based on the numerical analysis of
inhomogeneous stress and strain fields received from suitable experiments. Tensile and bending tests were carried out to obtain
elastic and hardening parameters. The deformation law for small elasto-plastic strains is presented as a system of nonlinear
differential and algebraic equations (DAE) consisting of the stress–strain relation, evolution equations for the internal
variables and the yield condition. Different rules for the evolution equations of isotropic, kinematic and distorsional hardening
are proposed. The DAE are discretized using an implicit Euler method, and the resulting system of nonlinear algebraic equations
is solved using the Newton method. Deterministic optimization procedures are preferred to identify material parameters from
a least-squares functional of numerical and measured comparative quantities. The gradient of the objective function was calculated
using a semianalytical sensitivity analysis. Due to measurement errors, the optimal sets of material parameters are non unique.
The approximate estimation of confidence regions and the calculation of correlation coefficients is presented.
The results of several optimization processes for material parameters of elasto-plastic deformation laws show a good agreement
between measured and calculated values, but they show also problems which may occur if systematic errors will not be recognized
and deleted.
Received 30 September 1999; accepted for publication 8 March 2000 相似文献
104.
J. Török S. Krishnamurthy J. Kertész S. Roux 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(4):697-701
We introduce a model for the slow relaxation of an energy landscape caused by its local interaction with a random walker whose
motion is dictated by the landscape itself. By choosing relevant measures of time and potential this self-quenched dynamics can be mapped on to the “True” Self-Avoiding Walk model. This correspondence reveals that the average distance of
the walker at time t from its starting point is , where for one dimension and 1/2 for all higher dimensions. Furthermore, the evolution of the landscape is similar to that in growth
models with extremal dynamics.
Received 8 August 2000 相似文献
105.
Recently Heyde, Kou and Peng [C.C. Heyde, S.G. Kou, X.H. Peng, What is a good external risk measure: Bridging the gaps between robustness, subadditivity, and insurance risk measures, 2007, preprint.] proposed the notion of a natural risk statistic associated with a finite sample that relaxes the subadditivity assumption in the classical coherent risk statistics. In this note we use convex analysis to provide alternate proofs of the representation results regarding natural risk statistics. 相似文献
106.
Yi-Ching Yao 《Annals of the Institute of Statistical Mathematics》1987,39(1):377-383
Summary The problem of testing for constant hazard against a change-point alternative is considered. It is shown that this problem
is related to another one in quality control. Based on this relationship, a test is proposed. The main advantages of this
test are its computational simplicity and the ready availability of small and large sample distribution theory. 相似文献
107.
We propose a perturbation method for determining the (largest) group of invariance of a toric ideal defined in [S. Aoki, A. Takemura, The largest group of invariance for Markov bases and toric ideals, J. Symbolic Comput. 43 (5) (2008) 342–358]. In the perturbation method, we investigate how a generic element in the row space of the configuration defining a toric ideal is mapped by a permutation of the indeterminates. Compared to the proof by Aoki and Takemura which was based on stabilizers of a subset of indeterminates, the perturbation method gives a much simpler proof of the group of invariance. In particular, we determine the group of invariance for a general hierarchical model of contingency tables in statistics, under the assumption that the numbers of the levels of the factors are generic. We prove that it is a wreath product indexed by a poset related to the intersection poset of the maximal interaction effects of the model. 相似文献
108.
Jigao Yan 《Journal of Mathematical Analysis and Applications》2008,343(2):644-653
Let X(i,n,m,k), i=1,…,n, be generalized order statistics based on F. For fixed r∈N, and a suitable counting process N(t), t>0, we mainly discuss the precise asymptotic of the generalized stochastic order statistics X(N(n)−r+1,N(n),m,k). It not only makes the results of Yan, Wang and Cheng [J.G. Yan, Y.B. Wang, F.Y. Cheng, Precise asymptotics for order statistics of a non-random sample and a random sample, J. Systems Sci. Math. Sci. 26 (2) (2006) 237-244] as the special case of our result, and presents many groups of weighted functions and boundary functions, but also permits a unified approach to several models of ordered random variables. 相似文献
109.
从大学生学习成绩出发,应用广义线性回归模型研究了学生学年间成绩的相关性,揭示了大学一年级,尤其是一年级的二学期是影响学生后期学习的关键阶段.进一步应用聚类分析,得到学生成绩在大学一年级就已经埋下了两极分化的隐患,应用判别分析得出了两极分化的关键课程.该结论为教育教学和学生管理提供决策依据. 相似文献
110.
负二项分布类的条件概率封闭性 总被引:1,自引:0,他引:1
在研究只允许部分服务台进入休假状态的多服务台M/M/c排队系统时,我们发现了条件Erlang分布的一些有趣的性质,进一步研究我们发现相对应离散随机状态的负二项分布也具有很好的性质(概率封闭性.本文证明了一类负二项分布的概率封闭性.它们对导出复杂排队系统中离散状态下顾客等待时问分布及保险公司中破产概率上界的计算起着重要作用. 相似文献