- EI核心期刊
A survey was summarized on the current researches and development about network dynamics from the whole network. The potential applications and guiding ideas in developing network technologies were discussed. The importance of the research of network dynamics was emphasized in detail when considered with the research results.
A new method based on finite difference time domain (FDTD) method was presented for numeric analyze of the transmission and reflection characteristic of the composite materials with negative effective permittivity. The simulation was compared with the existed theoretic model and other experiment data. The result shows that the feasibility of using FDTD method to analyze the composite materials is validated, and also shows that it is a sample work for the design and application composite materials.
How to improve the strings segmentation process was investigated. The components connected were detected based on isolated components analysis, and the length estimation of the components using the feature of lower contours was discussed, the problem of segmenting overlapping or touching characters settled by the improved “drop-falling” algorithm was also studied in details. This method has been incorporated into a complete bank check character recognition system. It shows promising results.
There are a great deal and various types of resource in a distributed grid environment. A grid resource search algorithm: small-world-clustering-based routing algorithm was described to improve the search and location of diverse properties. According to the small world theory, the clustering center was used to the grade diffuse and the request for performing a well-ordered search from a global view. In order to improve scalability，a few shortcuts with distant peers were inserted into the routing tables with some probabilities，and then the average path length was reduced. The preliminary simulation results show that the key clustering algorithm with shortcuts is efficient and scalable.
A new sign-cryption scheme with the feature of forward secrecy was presented in order to realize the authentication during the procedure of mobile communication. The analysis result of scheme shows that superiority in efficiency and secrecy of elliptic curve system has been maintained exactly, the new scheme is sufficient to the forward secrecy unlike those sign-cryption schemes in existence. If two parties in the communication crash with each other, the third one will solve the problem, it means the arbiter.
A genetic algorithm for virtual topology design was proposed. Path length and load balancing of links and nodes were taken into account. The natural number coding, the random population selection, the simple crossover strategy of “two-parents-and-one-kid” and the fixed mutation probability were totally adopted. The algorithm was proved in virtual topology design of NSF（National Science Foundation）network. The effect of parameters of the object functions was discussed. The relation between generation and fitness was analyzed. And the effect of the selection range was referred to as well.
An optical receiver model based on narrowband Guassion process was proposed. Moreover, the receiver model based on Karhunen-Loève transform was improved to include the main transmission impairments in wavelength division multiplexing system. The statistics of the decision current in two models were obtained and turned out to be consistent in some degree. The two analytical results show exact agreement with that of Monte-Carlo simulations, so they are reliable for accurate estimation of bit error ratio (BER). By comparison with the analytical results, Gaussion approximation method tends to overestimate the BER whose application is restricted within narrow limits. The improved Karhunen-Loève transform approach is of great scalability, with which more factors can be taken into account through proper modification, so it can serve as a general method for performance evaluation of IM-DD optical transmission systems.
To import the response time factor into the routing mechanism of wireless sensor networks, the network architecture was refined, the response time model was analyzed and two feasible solutions based on two-tiered architecture were provided. Based on the energy efficient routing algorithm, in the new routing mechanisms, the routing paths were modified, and the routing table, according to response time restriction was decorated. The analyzing result can show that both the solutions, between which there exists a balance of computing complexity and communicating power consuming, are efficient. The emulating experiment verifies the necessity of importing the response time.
By the tools of group rings and character sums, it was shown that there didn't exist any type of Generalized perfect binary arrays of order 2×2×pn for any n and any odd prime p≠1(mod 8). Meanwhile, the existence problem of Generalized perfect binary arrays of order 2×2×2n was solved. The methods could also be used to study other perfect signals.
A new definition of linear spectrum of multi-valued logical functions over finite field was proposed. And then the formulae of the two spectra were simplified. Furthermore the linear structures of multi-valued logical function were classified, and the study of the degeneration of multi-valued logical function over finite field and its zero class linear structure were proved to be equivalent.
A bit loading and power allocation algorithm with low complexity in adaptive modulation for vertical-Bell laboratory layered space-time systems was proposed to implement the rate maximization, satisfying peak power constraint on each antenna as well as the average total power limit. The proposed algorithm is of the same optimal allocation as the incremental algorithm while the computation complexity declines significantly. The simulation results show that the limitation of per-antenna peak power will decrease the bit rate under the target bit error rate.
After analyzing the hardware and software architectures of service control point (SCP) in mobile intelligent network, a model for computing the minimizing cost hardware configuration of distributed SCP was presented. Experiential formulae were used to verify the validity of this model. According to the service requirements, the processing features of computers in which the SCP software resides, and the capabilities of inter-connect network, the method to get the minimizing cost hardware configuration was given.
Introduction of Ad hoc access mode into cellular communication certainly will enhance the agility of end systems accessing into backbone network. Taken into account of the advantages and drawbacks of the traditional single-hop access method used in 3G cellular network as well as the dynamic multi-hop routing method used in mobile Ad hoc networks, an adaptive multi-hop access routing protocol is presented. Its principle is described in detail. Also a system simulation is provided to demonstrate its effectiveness in hybrid communication systems. The results show that this method can guarantee the quality of service of the communication traffics and decrease the overload of base station greatly.
A new three-phase flyback rectifier with loss recovery snubber is presented. A discontinuous current mode (DCM) operation with constant duty ratio allows achieving unity power factor. The principal characteristics are the very simple topology with only one switch, simple control scheme without input current feedback, and galvanic isolation between the input and output. By using a resonant energy recovery snubber, the switch can achieve zero voltage state (ZVS) at the turn off, and can also be protected against over-voltage caused by the leakage of transformers. Meanwhile, the switching loss is evidently reduced and the efficiency is greatly improved. There is not additional control circuit in the snubber. Simulation and experiment results confirm the validity of circuit, showing sinusoidal input currents and a ripple-less output voltage. The topology can be used as wireless base station power supply.
The uplink capacity and load of the smart antenna based time division-synchronous code division multiple access (TD-SCDMA) system were analyzed. The uplink admission control algorithm, considering the impacts of smart antenna technique, was proposed. The relations of admission control threshold between the new users and the handover users were investigated, and their theoretical analysis model was presented simultaneously. The dynamical system level simulation results showed the proposed admission control algorithms' performances and the relations between the admission control threshold and the number of new/handover users.
The contamination on contact surfaces was found to be one of the main reasons to cause electric contact failure by analyzing lots of gold plated contacts in failed mobile phones. The contaminants are with complex morphology, and mainly concentrated on the contacts on printed circuit boards. The element compositions of contaminants include C, O, Si, Al, S, Cl, Na, Ni etc. They come from the dusts in environment and wear debris by fretting. Image process technology was adopted to compute the coverage areas percentage of contaminants; it concluded that the contamination degree on contacts was classified into 5 levels. As the contamination levels increased, the average thickness of the contaminants raised and the wear zones also expanded. 60% of the contact resistance tested on contaminated zones was higher than the design limitation. The maximum contact resistance attained to 4?Ω. The unreliable electric contact made the reliability of mobile phones degraded.
To resolve the problem of just in time distribution for multi-restrictions in virtual logistics center, a model of combinatorial optimization was established. And the morbidity then generated from the model was analyzed. A new method combined by Floyd algorithm and genetic algorithm was also proposed. Its purpose is to resolve the three interrelated sub-problems: the shortest distance among customs, the scheme of vehicle allotment and the running route of a single car. The actual usage shows that this model is very efficient.
When several popular Internet charging schemes were analyzed. A service level agreement (SLA) based and usage-based charging mechanism, with the help of usage-based charging strategy for Internet service-oriented quality of service (QoS) management, was proposed. Using this mechanism, a statistics and calculation were done on the reserved and engrossed resource of service. When considering the real resource consumption of the service at the same time the billing will become a combination affected by both the two resources. So the service bill can reflect the results of different QoS assurance.
According to the demand on the admission control of softswitch-based clustered media server, a new dynamic quota-based admission control algorithm was proposed. A sub-negotiation process was presented with the algorithm. Meanwhile, not only the advantages of quota-based algorithm was inherited but new ideas was adopted in the new algorithm. Simulations have been conducted on the Petri net model. The result shows that this algorithm can be of excellent performance. In order to find the optimal size of each resource section in real time, two approximation analysis methods were proposed. It can be seen from experiments that these methods can be used to get sub-optimal quota values quickly and effectively. These two approximation analysis methods will play important roles in implementation of system algorithms.
An adaptive fair queue management algorithm-adaptive flow random early detection (AFRED) is proposed to protect transfor control protocal(TCP) flows in the presence of user data protocal (UDP) flows and to provide flow fairness. By dynamically varying the threshold of each flow, that could be allowed into the buffer and the drop probability, the algorithm can protect TCP flows effectively and improve the fairness of the system and the efficiency of the bandwidth utilization. The analysis and simulations indicate that the implementation complexity of AFRED is comparable to flow random early detection (FRED), but its performance is better than FRED.
Based on study of requirement for service QoS (quality of service) monitoring, a SLS-based (service level specification based) QoS monitoring mechanism was proposed. The QoS monitoring of specific services and the assessment of QoS according to their SLSs were performed with the mechanism. With higher efficience, flexibility and scalablity, there exist SLS layer, network layer and node layer in the so called layered-based mechanism architecture. In addition, when considering both subjective and objective facts of QoS, the violation of QoS consistency was presented according to continuous degradation of performance indexes. The quantitative representation of service satisfaction level was also defined.
Based on different multi-hop cooperative network configurations, five single-relaying cooperative transmitted protocols were investigated. Their non-regenerative performances were analyzed and compared from a capacity and a diversity point-of-view over Rayleigh fading environments. And some impacts of the mobility of the relaying nodes on the performances were considered. The simulated results and theoretic analysis show that the cooperative systems can offer the two-order full diversity at some given manners, e.g. virtual multiple input single output(VMISO) system achieves two-order diversity if the relaying node is close to the source node. However, it will degrade to one-order diversity if the relaying node is close to the destination node. Since these cooperative systems need two times time-slot resources corresponding to the single-hop systems, the capacity of the former is smaller than that of the latter.
With the analysis on mobile data services, an overload hybrid control mechanism, a combination of window method and leaky bucket method, is presented. Some features of mobile data services, such as service differences and strong burst are adopted in the mechanism. By computer simulations, it is proved that both the throughput of critical services and the fairness of general services can be guaranteed.
Combined timing synchronization function (TSF) and token polling model, a new Ad hoc networks timing synchronization algorithm was proposed. The proposed algorithm can be switched smoothly between TSF and token polling model according to the number of nodes in Ad hoc networks. The problem of scalability in IEEE 802.11 TSF can be effectively resolved by this algorithm. Simulation results show that the proposed algorithm can achieve the predominant performance of timing synchronization in variable scale Ad hoc networks when the threshold is set appropriately.
To meet the policy-based network management requirements on policy language, a language continuum, based on TMF's(teleManagement forum's) policy continuum, was proposed. Considering that the development of high-level languages have lagged behind what the policy-based network management demands, the requests for high-level policy languages were presented, including grouping structures, expressive power for the process and a finite state machine model. Furthermore, in order to implement consistency and continuity of a policy in the language continuum, two basic principles when describing policy semantics were also provided. And a policy-based billing prototype for the next generation IP-based network was designed and implemented for validation of the proposed viewpoints.
The calculations of the rate coefficients for dielectronic recombination (DR) along the CuI isoelectronic sequence in the ground state Au50+ are performed using the model of spin-orbit-split arrays(SOSA). The trend of the DR rate coefficients is founded with the changing of the electronic temperature in the range of 0.02～5?keV. The main factors which put effects on the DR coefficients are the principal quantum numbers of the relative spectator electrons, the relative auto-ionization coefficients and auto-ionized energy. All the mentioned above will provide some important parameters for diagnosing the palasmas.
We mainly discuss the constructions and properties of orthomorphisms, and concern whether the power of one orthomorphism is still one orthomorphism. For linear orthomorphism, using the properties of canonical form of matrix, if integer i can't be divided exactly by the orders of roots of the minimum polynomial of the matrix corresponding to this orthomorphism, then the i-th power of this linear orthomorphism is still one linear orthomorphism. For nonlinear orthomophisms, we provide some useful results.
Some new features are introduced in H.264, such as variable-size block motion compensation, prediction in Intra-coded frame etc. A novel error concealment method based on Intra-coded frame was proposed it uses the prediction mode of the surrounding sub-blocks to infer the prediction mode of the missing block. The missing block was reconstructed with the inferred prediction mode. Experiments show that the prediction mode of the missing block can be well recovered with the proposed method and good results can be achieved in images of various content types.
For effect evaluation on the network attack (NA), the essentiality of the application of analytic hierarchy process (AHP) and Fuzzy synthetic evaluation method (Fuzzy-AHP method) were introduced. With the help of AHP method, an index system was established, and then a judgment matrix was constructed, and the weight of each index was calculated as well. Meanwhile the normalization model of the evaluation index was presented. The Fuzzy synthetical evaluation model was analyzed, also the method to calculate the membership matrix was presented, and the application of the Fuzzy-AHP method in the effect evaluation of network attack was illustrated.
In order to improve the key generation rate of the quantum key distribution protocols, a perfect complete orthogonal basis of the bipartite three-level system was constructed. By using this basis and swapping the entanglement between the particles, a quantum key distribution protocol was presented. Therefore, a three-level can be generalized to multi-level. Using entanglement swapping between the particles and multi-level key distribution, it can significantly improve the efficiency of the detection of eavesdropping and the key generation rate and the information flux.