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Balancing D2D Communication Relayed Traffic Offloading in Multi-Tier HetNets

International Journal of Communications, Network and System Sciences 2019年第6期12卷 75-97页

作者： allafi omran Michel Kadoch Department of Electrical Engineering ETS Montreal Canada

In Heterogeneous Networks (HetNets), Integrating Device-to-Device communication (D2D) techniques presents as a promising solution for improving system performance by offloading traffic from heavily loaded macro cell (MC) to small cells (SCs). For instance, D2D can be used to offload traffic from heavily-loaded cells to light-loaded small cells. However, offloading new users may result in an unfair load distribution among small cells and consequently may affect the quality of service of some users. To achieve better performance and reduce blocking probability load balancing among small cells should be considered when we offload traffic from macro to small cells. In this paper, we consider a centralized offloaded relay selection scheme, in which a cellular provider can decide whether users can assist each other to relay their traffic to small cells. We propose a joint user-relay selection with dynamic load balancing scheme based on D2D communications using the Kuhn-Munkres (K-M) method. The offloading process considers the load from MC to SCs and among SCs. Compared to previous works, our simulation results show that the proposed scheme increases the number of admitted users in the system, and achieves a higher load balancing fairness index among small cells. Also, our scheme achieves a higher rate fairness index among users by adjusting the signal to interference plus noise ratio (SINR) threshold.

关键词： Device-to-Device Communications Heterogeneous Networks Kuhn-Munkres (K-M) Method Load Balancing Small Cell

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Influence of Mold Preheating and Silicon Content on Microstructure and Casting Properties of Ductile Iron in Permanent Mold

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Journal of Iron and Steel Research International 2011年第3期18卷 34-39页

作者： Jafar Khalil-allafi Behnam Amin-Ahmadi Faculty of Materials Engineering Sahand University of Technology Department of Materials Science and Engineering Sharif University of Technology

The effects of the mold preheating and the silicon content of ductile iron on the percentage of carbides,graphite nodule counts and shrinkage volume were *** results showed that the percentage of carbides and the shrinkage volume decreased when the mold preheating *** ductile iron with the carbon equivalent of 4.45 % and the silicon content of 2.5% without any porosity defects was achieved when the mold preheating was 450 ℃.Increasing the silicon content in the range of 2.1%-3.3% led to the increase in graphite nodule count and graphite size and the decrease in percentage of *** is due to the increase in induced expansion pressure during the graphite formation with the increasing of silicon *** suitable condition for casting a sound product of ductile iron without the riser at the mold preheating temperature of 300 ℃ is the silicon content of 3.3% and carbon equivalent of 4.7%.

关键词： ductile iron permanent mold preheating temperature carbide shrinkage volume silicon content

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Effect of Mold Hardness on Microstructure and Contraction Porosity in Ductile Cast Iron

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Journal of Iron and Steel Research International 2011年第4期18卷 44-47,67页

作者： Jafar Khalil-allafi Behnam Amin-Ahmadi Faculty of Materials Engineering Sahand University of Technology Department ofMaterials Science and Engineering Sharif University of Technology

The effect of mold hardness on the microstructure of ductile iron and the contraction porosity was *** with different hardnesses（0.41,0.48,0.55,0.62 MPa）and a sand mold prepared by Co2 method were *** influence of silicon content on the induced expansion pressure owing to the formation of graphite was also *** contraction during solidification can be compensated by an induced expansion owing to the graphite relief when the hardness of mold increases;therefore,the possibility of achieving a sound product without using any riser increases.

关键词： ductile iron graphite preheating temperature carbide shrinkage porosity

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