Applied Mechanics and Materials Vols. 519-520

Abstract: An acceleration strategy for TV-ADM reconstruction algorithm in Compton scattering tomography (CST) is proposed. By analyzing the sparse characteristic of CST projection matrixes, firstly, the sparse matrix vector CSR format and ELL format are used to store them, which greatly reduce the memory consumption. Then, a Sparse Matrix Vector multiplication (SpMV) method is utilized to accelerate the projector and back projector process. Finally, based on the parallel features, the TV-ADM is computed with Graphics Processing Unit (GPU). Numerical experiments show that the TV-ADM with the presented acceleration strategy could achieve a 96 times speedup ratio and 224 times memory compression ratio without precision loss.

Abstract: This paper studies resource reservation mechanisms in the strict parallel computing grid,and proposed to support the parallel strict resource reservation request scheduling model and algorithms, FCFS and EASY backfill analysis of two important parallel scheduling algorithm, given four parallel scheduling algorithms supporting resource reservation. Simulation results of four algorithms of resource utilization, job bounded slowdown factor and the success rate of Advanced Reservation (AR) jobs were studied. The results show that the EASY backfill + firstfit algorithm can ensure QoS of AR jobs while taking into account the performance of good non-AR jobs.

Abstract: Much work has been done to solve the unfairness problems caused by hidden terminals and exposed terminals in Ad Hoc networks. The back-off mechanism is one of the widely used methods to ensure the fair allocation of channel resources associated with other mechanisms. In this paper, a modified back-off algorithm DEIED (Dynamic Exponential Increase and Exponential Decrease) is proposed based on the previous back-off scheme EIED (Exponential Increase and Exponential Decrease), and a comparison of BEB (Binary Exponential Back-off), EIED, DEIED, is presented. Both qualitative analysis and simulation results show that the proposed back-off algorithm scheme outperforms EIED and BEB algorithms in term of the opportunities given to each node to transmit.

Abstract: WIA-PA networks have been widely used in industrial monitoring systems, but its real-time performance limits its usage in industrial control systems. And no existing works on real-time scheduling have taken into account all features of WIA-PA. So, in this paper, we propose an algorithm to schedule transmissions under real-time constraints for WIA-PA star-mesh networks. The algorithm is based on hybrid centralized and distributed network management, so it can quickly determine how to schedule transmissions. Experimental results show that our algorithm is fast and efficient.

Abstract: Network security issues came from traditional network, wireless network and cloud computing environment. Large-scale cloud computing, versatility and virtualization features of network security had become a hidden threat source. This paper analyzed the sources of network security threats, and established a network security model which encompasses all types of currently known network security factors; it could provide countermeasures to ensure network security. The security model had capabilities of real-time detection, rapid response, immediate recovery, and interaction between various independent modules. The security model used such security technologies as firewall, intrusion detection, intrusion deception, security scanning and PKI.

Abstract: The author analyzes the traditional foreign language teaching website system structure and function, and points out the weakness of its client/server network computing model. By using the Peer to Peer (P2P) system, we can make full use of every online node computing power and communication bandwidth; we can provide better online communication resource sharing among students, teachers, students and teachers. This paper proposes a foreign language teaching system based on P2P, which can effectively make up for the inadequacy of traditional teaching website. We can also explore the application of P2P technology in multimedia network teaching.

Abstract: Digital library has been a part of our modern life. It is clear of the importance of cultural resources and its pushing on history. In a certain area, digital library can solve the problem of dynamic catalogue, permutation and combination, which helps to serve the public in time. We propose the cloud computing digital library in the background of the development of cloud computing during these years.Cloud computing digital library can settle in a local area and can sort cultural resources barcode rapidly. It can organize small virtual Cultural Center for special purpose,also can provide real-time audio and video transmission service. It can also arrange the redundancy cultural resources from all the library in the area to online service process. This paper propose: a multi-redundancy structure model of cloud computing digital library and analyze the reasonability and the feasibility of the model. This model can be used in big libraries of university and social.

Abstract: Delay and packet loss caused by the basic mobile IPv6 handover protocol can not guarantee the service quality of real-time communication. In order to improve the performance of fast handover of the mobile IPv6, we proposed a fast handover scheme based on hierarchical mobility which combines micro mobility and the link layer trigger. By shielding local mobility of the mobile node, the scheme can greatly reduce the signaling information traffic from mobile node to HA and CN. Through the link layer trigger mechanism, the scheme builds a tunnel in advance to avoid packet loss. In order to verify the performance of the proposed scheme, we did some simulation experiments in the NS-2 environment. The simulation results show that the scheme reduces handover delay and packet loss effectively.

Abstract: Data replication techniques are used in cloud computing to reduce access latency, network bandwidth and enhance data availability, system reliability. Replica selection involves selecting the best replica location to access the data for job execution in cloud computing. In order to select the best replica, a novel response time-driven replica selection approach based on Dirichlet probability distribution (DPRS) is proposed in this paper. Dirichlet PDF is the conjugate prior of categorical distribution to predict the posteriori value. The response time is calculated based on the network parameters such as network bandwidth, file size and access latency. The best replica can be predicted in corresponding with the historical log file by using Dirichlet PDF. Simulation results show that DPRS method conducts high performance in lower mean response time, while compared with No replica, LRU and LFU strategies.

Abstract: Owing to the limitations of mobile terminals and network bandwidth, the current Secure Electronic Transaction (SET) protocol can not be introduced into mobile payment directly. Present mobile payment system often uses symmetric encryption algorithm that may bring in some security risks. A new secure mobile payment protocol based on ECC was presented ,which ensures information flows from merchant to customer and enhances the security of customer’s information. Theoretical analysis shows that, ECC can not only meet the requirements of short key generation time, but also ensure that at the same time of cracking code the ratio of RSA and ECC key length is greater than 5:1. The number of signing the certificate verification, asymmetric and symmetric encryption of the new protocol is also lesser than SET protocol, so the current mobile terminal and network capabilities can support this protocol to ensure safe and effective mobile payment process.