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RISS 인기검색어
- 검색키워드
- 저자 : Guangqiang Shi (검색결과 4 건)
- 무료
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Cooperative Spectrum Sharing in Cognitive Radio Networks : A Centralized Contracted-Based Approach
Guangqiang Shi,Ying Liu,Xiaomin Mu 보안공학연구지원센터 2016 International Journal of Multimedia and Ubiquitous Vol.11 No.3
In this paper, we study the relay-based communication schemes for cooperative spectrum sharing among multiple primary users (PUs) and multiple secondary users (SUs) with incomplete information. Inspired by contract theory, we model the network as a labor market. In this market, PUs and SUs are regarded as employer and employee respectively. Each PU proposes certain contracts to attract the SUs, the contract include relay power and spectrum access time, each SU maximize its utility by selecting the most suitable contract. But PUs and SUs have conflicting objectives in contract content. To tackle this problem, we put forward to a centralized maximizing expectation utility scheme, which convert the optimal contract design into an optimization problem. After that, a approximate method for solving the optimization problem is proposed. Simulation results show that the losses of PUs’ total utilities caused by incomplete information and approximate algorithm are relatively small, especially when the number of SUs is very large.
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Guangqiang Fang,Peng Qu,Zhengli Cao,Feizhou Shi 한국섬유공학회 2022 Fibers and polymers Vol.23 No.5
In this paper, the mechanical properties of a single-ply woven composites are investigated through a combinationof multiscale numerical simulation and experimental test. The tensile experiments of three woven structures with differentthread counts, 4.5+4.0, 5.5+7.0 and 5.5+5.0, are conducted. A multiscale numerical method is proposed in order tounderstand the influence mechanism of thread count on the mechanical properties. The numerical predictions have a goodagreement with the experimental results. Many unique characteristics of the single-ply woven composites have beenobserved, such as the clearly nonlinear mechanical behavior of samples with large thread count, the positive transversalnormal strain during the initial phase of longitudinal uniaxial tension and the breakage morphology in relation to threadcount. The M/L ratio is proposed in this paper to investigate the effect of the difference in the thread count between warp andfill direction on the mechanical behavior. The M/L ratio of thread count of 5.5+7.0 specimen is larger than 4.5+4.0 and5.5+5.0 by 38 % and 41 %, respectively, the corresponding M/T ratio of modulus is larger by 34 % and 29 %, and for strengthit is 23 % and 24 %. It is found that the increase of thread count in one direction improves the mechanical properties in thisdirection but reduces the equivalent elastic modulus and strength in the vertical direction. The simulated stress and straindistribution inside the RUC helps to better understand the influence mechanism of thread count on the mechanical propertiesof single-ply woven composites.
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Dynamic Spectrum Access with Spatial Reuse
Ying Liu,Guangqiang Shi,Xiaomin Mu 보안공학연구지원센터 2016 International Journal of Multimedia and Ubiquitous Vol.11 No.1
We investigate the problem of achieving utility function optimization for distributed channel selection using game theoretic solutions in opportunistic spectrum access system, where secondary users are spatially located and mutual interference only emerges between neighboring users. In addition, interference graph of spatial position is introduced to measure interference and evaluate the possible opportunities of spectrum access. Based on this we propose an optimization problem of minimizing loss throughput, which is solved by a game theory and an optimal channel selection set is derived. The main work of this paper is to prove that this game is an exact potential game, which has at least one pure strategy Nash equilibrium. Finally simulation results is given to verify the correctness of the theoretical analysis. Especially meanwhile after considering spatial reuse by users’ position, the system throughput is significantly increased, thus the spectrum utilization rate is effectively improved.
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Xiaodong Yu,Weicheng Gao,Yanan Feng,Guangqiang Shi,Shihao Li,Minmin Chen,Ruiming Zhang,Junfeng Wang,Wentao Jia,Jianhua Jiao,Ruichun Dai 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.24 No.6
Hydrostatic bearing has the advantages of wide speed range, large bearing capacity, high precision and stability. Hydrostatic-hydrodynamic hybrid bearing can make up for the lack of stiffness of hydrostatic bearing and prevent tribological failure under the condition of high speed and heavy load. Therefore, hydrostatic bearing and hydrostatic-hydrodynamic hybrid bearing have become important bearing parts of high-end computer numerical control (CNC) machine equipment. The research on hydrostatic and hydrostatic-hydrodynamic open a new way for precision improvement of high-end CNC machine equipment. This paper reviews research progress of hydrostatic linear guideway, hydrostatic rest and ram, hydrostatic thrust bearing, hydrostatic-hydrodynamic thrust bearing and hydrostatic-hydrodynamic spindle of high-end CNC machine equipment, and discusses the influence of structure and working parameters on lubrication performance, accuracy and stability of bearing parts. Finally, the future research direction in hydrostatic bearing and hydrostatic-hydrodynamic hybrid bearing are suggested. This review provides a theoretical basis for design and development of high-end CNC machine equipment in the future.
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