Based on the log-linear virtual age process, an imperfect preventive maintenance policy for numerical control(NC)machine tools with random maintenance quality is proposed. The proposed model is a combination of the Ki...Based on the log-linear virtual age process, an imperfect preventive maintenance policy for numerical control(NC)machine tools with random maintenance quality is proposed. The proposed model is a combination of the Kijima type virtual age model and the failure intensity adjustment model. Maintenance intervals of the proposed hybrid model are derived when the failure intensity increase factor and the restoration factor are both random variables with uniform distribution. The optimal maintenance policy in infinite time horizon is presented. A numerical example is given when the failures of NC machine tools are described by the log-linear process. Finally, a discussion is presented to show how the optimal results depend on the different cost parameters.展开更多
Numerical simulation of enhanced fluid flow characteristics in a three-stage double-stirring extraction tank was conducted with the coupling of an Eulerian multiphase flow model and a Morsi-Alexander interphase drag f...Numerical simulation of enhanced fluid flow characteristics in a three-stage double-stirring extraction tank was conducted with the coupling of an Eulerian multiphase flow model and a Morsi-Alexander interphase drag force model. Results show that the addition of a stirring device into the settler can efficiently reduce the volume fraction of out-of-phase impurity in the outlet, and accelerate the settling separation of oil-water mixture. Such addition can also effectively break down the oil-water-wrapped liquid droplets coming from the mixer, inhibit reflux from the outlet, and improve the oil-water separation. The addition of a stirring device induces ignorable power consumption compared with that by the mixer, and can thus facilitate the commercialized promotion of this novel equipment.展开更多
External confinement by fiber reinforced polymer (FRP) is an efficient technique to increase the bearing capacity and ductility of concrete. To better study the mechanical behavior of bidirectional FRP confined concre...External confinement by fiber reinforced polymer (FRP) is an efficient technique to increase the bearing capacity and ductility of concrete. To better study the mechanical behavior of bidirectional FRP confined concrete, the yield criterion of bidirectional FRP is presented based on the static equilibrium condition in this paper, and a model for calculating the bearing capacity of bidirectional FRP confined concrete is established. The model can capture the character of bidirectional FRP confined concrete. Effects of the confinement effect coefficient, the unconfined concrete strength and the material properties of FRP on bearing capacity are analyzed. Results show that each parameter has different effects on the bearing capacity of bidirectional FRP confined concrete.展开更多
This paper establishes the theoretical hypothesis of carbon intensity convergence, and through statistics to analyze and describe the whole country and the eastern and western regions with the use of mixed regression ...This paper establishes the theoretical hypothesis of carbon intensity convergence, and through statistics to analyze and describe the whole country and the eastern and western regions with the use of mixed regression model and fixed effects regression method, and test σ -convergence, absolute convergence and conditional convergence in order to have an empirical study on carbon convergence hypothesis.展开更多
This paper considers experimental situations where the interested effects have to be or- thogonal to a set of nonnegligible effects. It is shown that various types of orthogonal arrays with mixed strength are A-optima...This paper considers experimental situations where the interested effects have to be or- thogonal to a set of nonnegligible effects. It is shown that various types of orthogonal arrays with mixed strength are A-optimal for estimating the parameters in ANOVA high dimension model representation. Both cases including interactions or not are considered in the model. In particularly, the estimations of all main effects are A-optimal in a mixed strength （2, 2）3 orthogonal array and the estimations of all main effects and two-factor interactions in G~ x G~ are A-optimal in a mixed strength （2, 2）4 orthogonal array. The properties are also illustrated through a simulation study.展开更多
The strong consistency of M estimators of the regression parameters in linear models for ρ-mixing random errors under some mild conditions is established, which is an essential improvement over the relevant results i...The strong consistency of M estimators of the regression parameters in linear models for ρ-mixing random errors under some mild conditions is established, which is an essential improvement over the relevant results in the literature on the moment conditions and mixing errors. Especially, Theorem of Wu （2005） is improved essentially on the moment conditions.展开更多
基金Project(51465034)supported by the National Natural Science Foundation of China
文摘Based on the log-linear virtual age process, an imperfect preventive maintenance policy for numerical control(NC)machine tools with random maintenance quality is proposed. The proposed model is a combination of the Kijima type virtual age model and the failure intensity adjustment model. Maintenance intervals of the proposed hybrid model are derived when the failure intensity increase factor and the restoration factor are both random variables with uniform distribution. The optimal maintenance policy in infinite time horizon is presented. A numerical example is given when the failures of NC machine tools are described by the log-linear process. Finally, a discussion is presented to show how the optimal results depend on the different cost parameters.
基金financially supported by the National 863 Plan(2010AA03A405and 2012AA062303)+4 种基金the National 973 Plan(2012CBA01205)the National Natural Science Foundation of China(U120227451204040)the National Science and Technology Support Program(2012BAE01B02)the Fundamental Research Funds for the Central Universities(N130702001 and N130607001)
文摘Numerical simulation of enhanced fluid flow characteristics in a three-stage double-stirring extraction tank was conducted with the coupling of an Eulerian multiphase flow model and a Morsi-Alexander interphase drag force model. Results show that the addition of a stirring device into the settler can efficiently reduce the volume fraction of out-of-phase impurity in the outlet, and accelerate the settling separation of oil-water mixture. Such addition can also effectively break down the oil-water-wrapped liquid droplets coming from the mixer, inhibit reflux from the outlet, and improve the oil-water separation. The addition of a stirring device induces ignorable power consumption compared with that by the mixer, and can thus facilitate the commercialized promotion of this novel equipment.
基金Sponsored by the National Natural Science Foundation of China(Grant No.50538060)the Excellent Young College Teacher Foundation of Anhui Province(Grant No.2009SQRZ081)
文摘External confinement by fiber reinforced polymer (FRP) is an efficient technique to increase the bearing capacity and ductility of concrete. To better study the mechanical behavior of bidirectional FRP confined concrete, the yield criterion of bidirectional FRP is presented based on the static equilibrium condition in this paper, and a model for calculating the bearing capacity of bidirectional FRP confined concrete is established. The model can capture the character of bidirectional FRP confined concrete. Effects of the confinement effect coefficient, the unconfined concrete strength and the material properties of FRP on bearing capacity are analyzed. Results show that each parameter has different effects on the bearing capacity of bidirectional FRP confined concrete.
文摘This paper establishes the theoretical hypothesis of carbon intensity convergence, and through statistics to analyze and describe the whole country and the eastern and western regions with the use of mixed regression model and fixed effects regression method, and test σ -convergence, absolute convergence and conditional convergence in order to have an empirical study on carbon convergence hypothesis.
基金the National Natural Science Foundation of China under Grant Nos.11171065,11301073the Natural Science Foundation of Jiangsu under Grant No.BK20141326+1 种基金the Research Fund for the Doctoral Program of Higher Education of China under Grant No.20120092110021Scientific Research Foundation of Graduate School of Southeast University under Grant No.YBJJ1444
文摘This paper considers experimental situations where the interested effects have to be or- thogonal to a set of nonnegligible effects. It is shown that various types of orthogonal arrays with mixed strength are A-optimal for estimating the parameters in ANOVA high dimension model representation. Both cases including interactions or not are considered in the model. In particularly, the estimations of all main effects are A-optimal in a mixed strength （2, 2）3 orthogonal array and the estimations of all main effects and two-factor interactions in G~ x G~ are A-optimal in a mixed strength （2, 2）4 orthogonal array. The properties are also illustrated through a simulation study.
基金This research is supported by the National Natural Science Foundation of China under Grant No. 11061012, the Support Program of the New Century Guangxi China Ten-hundred-thousand Talents Project under Grant No. 2005214, and the Guangxi, China Science Foundation under Grant No. 0991081.
文摘The strong consistency of M estimators of the regression parameters in linear models for ρ-mixing random errors under some mild conditions is established, which is an essential improvement over the relevant results in the literature on the moment conditions and mixing errors. Especially, Theorem of Wu （2005） is improved essentially on the moment conditions.
