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- 저자 : Mohajer, Amin (검색결과 6 건)
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QoSCM: QoS-aware Coded Multicast Approach for Wireless Networks
Mohajer, Amin,Barari, Morteza,Zarrabi, Houman Korean Society for Internet Information 2016 KSII Transactions on Internet and Information Syst Vol.10 No.12
It is essential to satisfy class-specific QoS constraints to provide broadband services for new generation networks. The present study proposes a QoS-driven multicast scheme for wireless networks in which the transmission rate and end-to-end delay are assumed to be bounded during a multiple multicast session. A distributed algorithm was used to identify a cost-efficient sub-graph between the source and destination which can satisfy QoS constraints of a multicast session. The model was then modified as to be applied for wireless networks in which satisfying interference constraints is the main challenge. A discrete power control scheme was also applied for the QoS-aware multicast model to accommodate the effect of transmission power level based on link capacity requirements. We also proposed random power allocation (RPA) and gradient power allocation (GPA) algorithms to efficient resource distribution each of which has different time complexity and optimality levels. Experimental results confirm that the proposed power allocation techniques decrease the number of unavailable links between intermediate nodes in the sub-graph and considerably increase the chance of finding an optimal solution.
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Mohajer, Keivan,Yassemi, Siamak Korean Mathematical Society 1999 대한수학회보 Vol.36 No.4
It is a well-known result that a commutative ring R is von Neumann regular if and only if for any maximal ideal m of R the R-module R/m is flat. In this note we bring a generalization of this result for modules.
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QoSCM: QoS-aware Coded Multicast Approach for Wireless Networks
( Amin Mohajer ),( Morteza Barari ),( Houman Zarrabi ) 한국인터넷정보학회 2016 KSII Transactions on Internet and Information Syst Vol.10 No.12
It is essential to satisfy class-specific QoS constraints to provide broadband services for new generation networks. The present study proposes a QoS-driven multicast scheme for wireless networks in which the transmission rate and end-to-end delay are assumed to be bounded during a multiple multicast session. A distributed algorithm was used to identify a cost-efficient sub-graph between the source and destination which can satisfy QoS constraints of a multicast session. The model was then modified as to be applied for wireless networks in which satisfying interference constraints is the main challenge. A discrete power control scheme was also applied for the QoS-aware multicast model to accommodate the effect of transmission power level based on link capacity requirements. We also proposed random power allocation (RPA) and gradient power allocation (GPA) algorithms to efficient resource distribution each of which has different time complexity and optimality levels. Experimental results confirm that the proposed power allocation techniques decrease the number of unavailable links between intermediate nodes in the sub-graph and considerably increase the chance of finding an optimal solution.
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Amirhosein Mohajer,Vahidreza Kalatjari,Mohammadhosein Talebpour 한국강구조학회 2022 International Journal of Steel Structures Vol.22 No.1
This study aims to optimize the weight of steel frames (as the objective function) to satisfy the legal constraints (inter-story drift and strength). The ultimate goal was to select an optimal arrangement and coordinate the two types of convergent bracing (multi-story X-bracing and X-bracing) in low, mid, and high-rise steel frames with specifi c dimensions and spans. In the end, an optimal weight design will be presented for the frames under the design constraints (by LRFD method), frequency, drift, and position of braces in frame height, and the amount of the tensile force of braces. Since the frequency constraints in design variables are highly nonlinear and non-convex, it is cumbersome to use them in optimization problems. In this research, the frames have been optimized using the connection between two software OPENSEES and MATLAB based on a multi meta-heuristic optimization algorithm with discrete variables (a new, mixed-method based on parallel island model with four islands). The fi ndings of this research include the optimal position of braces, sections, and convergence history for the frames under a multi meta-heuristic optimization algorithm. The diagrams of convergence history were also provided for the particle swarm algorithm in mid-rise frames. The results show the superiority of the multi meta-heuristic search algorithm in the convergence speed and the quality of the optimal response compared to the particle swarm optimization algorithm. Optimizing with the multi meta-heuristic algorithm reduces the impact of parameters and the relations governing the operation. Finally, the optimal design is obtained. According to the results, the multi-story X-bracing frames (the combination of inverted V-Bracing and V-Bracing) have more optimized weight and, thus, better structural response than the X-bracing frames. Placing braces in the middle spans of frames and adjacent to each other was the optimal design and position for all frames.
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A New Hybrid Optimization Algorithm for Recognition of Hysteretic Non-linear Systems
S. Talatahari,N. Mohajer Rahbari,A. Kaveh 대한토목학회 2013 KSCE JOURNAL OF CIVIL ENGINEERING Vol.17 No.5
In this article, a new two-stage hybrid optimization method based on the Particle Swarm Optimization and the Big Bang-Big Crunch algorithm (BB-BC) is introduced for identification of highly non-linear systems. In this hybrid algorithm, the term of the center of mass from the BB-BC algorithm is incorporated into the standard particle swarm optimizer to markedly improve its searching abilities. In order to investigate the effectiveness of the newly formed optimization algorithm in identification of non-linear and hysteretic systems,it is utilized to optimally find the Bouc-Wen model’s parameters for a sample MR damper in which the damper’s force is related to its piston’s motion through a non-linear differential equation. The obtained results indicate that the proposed optimization method is highly robust and accurate and can be utilized successfully in such intricate non-linear identification problems.
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