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Shen Y.,Tianshui Normal University | Wang F.,Nanjing University of Posts and Telecommunications
Soft Computing | Year: 2011

The extension of rough set model is an important research direction in the rough set theory. In this paper, based on the rough set model over two universes, we firstly propose the variable precision rough set model (VPRS-model) over two universes using the inclsion degree. Meantime, the concepts of the reverse lower and upper approximation operators are presented. Afterwards, the properties of the approximation operators are studied. Finally, the approximation operators with two parameters are introduced as a generalization of the VPRS-model over two universes, and the related conclusions are discussed. © 2010 Springer-Verlag.


Shen Y.,Tianshui Normal University | Wang F.,Nanjing University of Posts and Telecommunications
International Journal of Approximate Reasoning | Year: 2011

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.


Wang W.-Z.,Tianshui Normal University | Wei X.-P.,Lanzhou University
Computational Materials Science | Year: 2011

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.


Yang H.,Tianshui Normal University
International Journal of Control and Automation | Year: 2014

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.


Zhang F.-D.,Tianshui Normal University
Advanced Materials Research | Year: 2013

In this paper, the synchronization of fractional-order Lü chaotic system is studied. Based on the fractional stability theory, suitable controller is designed to realize the synchronization between fractional-order Lü system and a integer-order system. Numerical simulations show that the effectiveness and feasibility of the controllers. © (2013) Trans Tech Publications, Switzerland.


Yang L.-X.,Tianshui Normal University
2010 2nd International Conference on Computational Intelligence and Natural Computing, CINC 2010 | Year: 2010

Based on RBF neural network, making chaotic time series that was generated by Lorenz dynamical system as an object of study. The network prediction model was established Input variables of network model have been optimized to improve. And compared to the BP, REF neural network models, based on improved REF neural network for chaotic time series forecasting model with higher predictive precision, smaller error and superior peiformance than the convectional BP or REF neural network model, so the improved method is feasible and effective. ©2010 IEEE.


Shen Y.,Beijing Institute of Technology | Shen Y.,Tianshui Normal University
Information Sciences | Year: 2014

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.


Shen Y.,Tianshui Normal University | Shen Y.,Beijing Institute of Technology
Fuzzy Sets and Systems | Year: 2015

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.


Ding H.-F.,Tianshui Normal University | Zhang Y.-X.,Tianshui Normal University
Computers and Mathematics with Applications | Year: 2012

In this paper, we consider the numerical solution of the Riesz space fractional diffusion equation and advectiondispersion equation. First, a system of ordinary differential equations is obtained from the above equations with respect to the space variable by using the improved matrix transform method. Furthermore, we use the (2,2) Pade approximation to compute the exponential matrix in the analytic solution of the ordinary differential equation, and get two difference schemes. Second, using the matrix analysis method, we prove that the two difference schemes are unconditionally stable. Finally, some numerical results are given, which demonstrate the effectiveness of the two difference schemes. © 2011 Elsevier Ltd. All rights reserved.


Yang F.,Zhejiang University | Yang F.,Tianshui Normal University | Zhang B.,Zhejiang University | Ma Q.,Chinese Academy of Cultural Heritage
Accounts of Chemical Research | Year: 2010

Replacing or repairing masonry mortar is usually necessary in the restoration of historical constructions, but the selection of a proper mortar is often problematic. An inappropriate choice can lead to failure of the restoration work, and perhaps even further damage. Thus, a thorough understanding of the original mortar technology and the fabrication of appropriate replacement materials are important research goals. Many kinds of materials have been used over the years in masonry mortars, and the technology has gradually evolved from the single-component mortar of ancient times to hybrid versions containing several ingredients. Beginning in 2450 BCE, lime was used as masonry mortar in Europe. In the Roman era, ground volcanic ash, brick powder, and ceramic chip were added to lime mortar, greatly improving performance. Because of its superior properties, the use of this hydraulic (that is, capable of setting underwater) mortar spread, and it was adopted throughout Europe and western Asia. Perhaps because of the absence of natural materials such as volcanic ash, hydraulic mortar technology was not developed in ancient China. However, a special inorganic-organic composite building material, sticky rice-lime mortar, was developed. This technology was extensively used in important buildings, such as tombs, in urban constructions, and even in water conservancy facilities. It may be the first widespread inorganic-organic composite mortar technology in China, or even in the world. In this Account, we discuss the origins, analysis, performance, and utility in historic preservation of sticky rice-lime mortar. Mortar samples from ancient constructions were analyzed by both chemical methods (including the iodine starch test and the acid attack experiment) and instrumental methods (including thermogravimetric differential scanning calorimetry, X-ray diffraction, Fourier transform infrared, and scanning electron microscopy). These analytical results show that the ancient masonry mortar is a special organic-inorganic composite material. The inorganic component is calcium carbonate, and the organic component is amylopectin, which is presumably derived from the sticky rice soup added to the mortar. A systematic study of sticky rice-lime mortar technology was conducted to help determine the proper courses of action in restoring ancient buildings. Lime mortars with varying sticky rice content were prepared and tested. The physical properties, mechanical strength, and compatibility of lime mortar were found to be significantly improved by the introduction of sticky rice, suggesting that sticky rice-lime mortar is a suitable material for repairing mortar in ancient masonry. Moreover, the amylopectin in the lime mortar was found to act as an inhibitor; the growth of the calcium carbonate crystals is controlled by its presence, and a compact structure results, which may explain the enhanced performance of this organic-inorganic composite compared to single-component lime mortar. © 2010 American Chemical Society.

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