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Qincheng, China

Yang H.,Tianshui Normal University
International Journal of Control and Automation

This paper presents the mechanical joints normal contact stiffness model based on fractal geometry and contact mechanics theory. The joint normal dimensionless contact load and dimensionless contact stiffness relationship are analyzed in different fractal dimensions and materials. The result shows that relationship between joint normal contact load and contact stiffness plastic is the strongly nonlinear. At last, normal contact stiffness are compared and analyzed with the experimental values, as well as JZZ model used the present model. The comparison result indicates that the present model is consistent with experiment result. © 2014 SERSC. Source

Wang W.-Z.,Tianshui Normal University | Wei X.-P.,Lanzhou University
Computational Materials Science

Based on the first-principle calculations within density functional theory of electronic structure, we propose that the CuHg2Ti-type intermetallic ternary compound Mn2ZnCa is strong candidate for half-metallic (HM) antiferromagnet (AFM), the HM-AFM nature in Mn 2ZnCa originates from d-d orbital hybridization. We also find that the Fermi level just locates in the gap of spin-down states, and the HM properties of Mn2ZnCa is kept within the wide range of 5.91 and 6.60 where exhibit perfect 100% spin polarization of the conduction electrons. Our investigations also indicate the atom coordination surroundings have a great influence on the electron structure. © 2011 Elsevier B.V. All rights reserved. Source

Shen Y.,Beijing Institute of Technology | Shen Y.,Tianshui Normal University
Information Sciences

In this paper, some useful properties associated with the probabilistic Hausdorff distance are further derived. Especially, we provide a direct proof for an existing important result. Afterwards, the t-norm-based probabilistic decomposable measure is presented, in which the value of measure is characterized by a probability distribution function. Meantime, several examples are constructed to illustrate different notions, and then further properties are examined. Moreover, for a given Menger PM-space, a probabilistic decomposable measure can be induced by means of the resulting probabilistic Hausdorff distance. We prove that this type of measure is (σ)- probabilistic subdecomposable measure for the strongest t-norm. Furthermore, we also prove that the class of all measurable sets forms an algebra. Finally, an outer probabilistic measure is induced by a class of probabilistic decomposable measures and the t-norm. Based on this kind of measure, a Menger probabilistic pseudometric space can be obtained for a non-strict continuous Archimedean t-norm. © 2014 Published by Elsevier Inc. Source

Shen Y.,Tianshui Normal University | Shen Y.,Beijing Institute of Technology
Fuzzy Sets and Systems

In this paper we investigate, under some suitable conditions and generalized differentiability, the Ulam stability problems of three variants of first order linear fuzzy differential equations, respectively. © 2015 Elsevier B.V. Source

Shen Y.,Tianshui Normal University | Wang F.,Nanjing University of Posts and Telecommunications
International Journal of Approximate Reasoning

The combination of the rough set theory, vague set theory and fuzzy set theory is a novel research direction in dealing with incomplete and imprecise information. This paper mainly concerns the problem of how to construct rough approximations of a vague set in fuzzy approximation space. Firstly, the β-operator and its complement operator are introduced, and some new properties are examined. Secondly, the approximation operators are constructed based on β-(complement) operator. Meantime, λ-lower (upper) approximation is firstly proposed, and then some properties of two types of approximation operators are studied. Afterwards, for two different kinds of approximation operators, we introduce two roughness measure methods of the same vague set and discuss a property. Finally, an example is given to illustrate how to calculate the rough approximations and roughness measure of a vague set using the β-(complement) product between two fuzzy matrixes. The results show that the proposed rough approximations and roughness measure of a vague set in fuzzy environment are reasonable. © 2010 Published by Elsevier Inc. All rights reserved. Source

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