- EI核心期刊
Some problems are found in currently-available theoretical description of epitaxial crystal-growth mods, including that ①Frank-van der Merve mode is described as it only exists for positive dominance-level of the substrate surface energy and this is not in agreement with the experimental fact that a pair of materials with small enough lattice mismatch between them can grow alternately both in the Frank-van der Merve mode; ②the transition between Frank-van der Merve mode and Stranski-Krastanow (S-K) mode is regarded as it happens at a fixed lattice mismatch for different dominance-levels of the substrate surface energy and this description seems obviously unreasonable; ③the direct transitions from Frank-van der Merve mode to Volmer-Weber mode and vice versa are supposed possible and the truthfulness of this understanding might be seriously suspected. Taking these problems into consideration, a modified and more comprehensive theoretical description is proposed and the concept of quasi-Frank-van der Merve mode is introduced in it. Based upon the new theoretical understanding, the concept of "post S-K compatible-heterogeneous-growth mode" is proposed and the possibility to realize high quality compatible heterogeneous bulk crystal growth based on this new growth mode is investigated.
Analyzing the primitive of lossy trapdoor function, we know that all existing lossy trapdoor functions might not be provably secure when the adversary previously gets the related information on the trapdoor. This article presented a new lossy trapdoor function based on the d-linear assumption, and proved it to be auxiliary-input secure by using an extended version of the Goldreich-Levin theorem. It is verified that the slight variance of Peikert's learning with errors based lossy trapdoor function is auxiliary-input secure. Both lossy trapdoor functions in efficiency and security was analyzed.
This paper proposed a session initiation protocol(SIP) message inspection model combining the forward and backward rules inspection. With the capability of updating rules dynamically, this model can detect unknown type of malformed attack efficiently. Based on Map-Reduce model, the inspection procedure is divided into two phases: routine inspection and special inspection. In routine inspection, the basic format of SIP message is detected. In special inspection, the consistency with the grammar rules is verified in parallel after the segmentation of the SIP message. Experimental results show that the proposed inspection model can detect malformed features in the SIP message efficiently and accurately.
A new optical remote sensing image registration method signal gridding-scale invariant feature transform (SG-SIFT) based on signal theory and gridding is proposed. According to relationships among the image layers in the difference of Gaussians scale space, the feature points' number of each image is set in proportion to make the their distribution uniform in the scale space. In addition, a regular gridding method is introduced to achieve the well distribution of feature points in the image space. Then, error matching pairs are eliminated by a correspondence error checking. Statistical and visual results show that SG-SIFT is superior to standard scale invariant feature transform (SIFT) according to the feature points distribution, while the number of correct matching pairs from SG-SIFT is 17.47% more than that of uniform robust-scale invariant feature transform (UR-SIFT) in average and the evaluation indicator of root-mean square error confirms its superior performance to SIFT and UR-SIFT.
An interference cancellation method based on space-time code is proposed for 3-user multi-input multi-output interference channel. Each user employs rare-2 space-time block code. The multi-user interference at the third receiver is eliminated through the introduction of zero matrix at each user' transmit signals. The multi-user interference at the other two receivers is eliminated through pre-coding for codewords and unidirectional cooperative link. Compared with the existing scheme for the same scene, the proposed scheme reduces feedback amount and offers full diversity gain, while keeping the same transmission efficiency. Simulation results demonstrate that the proposed scheme outperforms the existing scheme for the same scene.
Proxy mobile IPv6 is a centralized network-based mobility management protocol. Its local mobility anchor has become the bottleneck of network size growth. To solve this problem, a partially distributed scheme of proxy mobile IPv6 is proposed, where the prefix allocation and routing function of local mobility anchor is distributed to the access network. The access router reaches a nearest database by an anycast address to manage location. Besides, when the mobile node is far from the initial access network and the handover latency is too long, the proposed scheme will restart flows connection. The comprehensive analysis shows the proposed scheme is feasible.
A method of T immune fuzzy control was proposed. The T immune cell regulatory factor was introduced in the mathematical model of feedback control by applying the principle of immune T cell concentration regulation. And the nonlinear function of the fuzzy controller was used to approximate T cell regulatory factor. Compared with traditional PI control and immune feedback control, it can effectively suppress the effect of load disturbance on speed, electromagnetic torque output and current output. So it has excellent capability of resistance to systematic errors and speed following. Application on permanent magnet synchronous motor (PMSM) speed system shows the practicability of the proposed method.
Analysis of transition feature of frequency hopping (FH) sequence was given for traditional frequency hopping (TFH) and correlated hopping enhances spread spectrum (CHESS) or differential frequency hopping (DFH) systems. It demonstrates that the transition probability distribution (TPD) of FH is very important for performance of both TFH and CHESS system, and that though CHESS can provide non-fixed frequency hopping pattern (FHP) for better anti-interceptions, its anti-jamming performance might be lower than that of TFH systems if its fan-out is not big enough. The proposed method TPD based FHP analysis and interference method does not require exact FHP, therefore it is much easier to implement; furthermore jamming strategy thus jamming efficiency can be dynamically adjusted according to some constraints or obtained TPD on-site.
Under the outdated channel state information, a scheme of the N-th best relay selection was proposed for the N-th best relay adoption in opportunistic two-way relay cooperative networks. The outage performance was discussed. The closed-form lower bound of the outage probability and its asymptotic expression for the high signal-to-noise ratio (SNR) regime were given based on the probability density function (PDF) of the SNR for the data transmission instant, which is obtained from the PDF of the SNR for the relay selection instant and the conditional PDF of the SNR for the data transmission instant. Simulations show that the analyses are close to the simulated ones, and the asymptotic results very well match the simulated ones in the high SNR regime.
A time context based collaborative filtering recommendation (TCCF-LI) algorithm this paper was proposed, and students' learning interest mining from university library borrow record was implemented. The time context information was imported into the traditional collaborative filtering recommendation algorithm, in which, both interest homoplasy of large scale user groups and short-term correlation of small scale user groups was considered. Good recommendation performance was gained. According to the experiments on real dataset, TCCF-LI algorithm presents higher precision and recall rate compared with traditional recommendation algorithm.
Focusing on the active multipath selection of concurrent multipath transfer protocol, the influence of path metric disparity on the throughput performance of concurrent multipath transferring system was studied based on exalt Padhye model. With qualitative analysis, the influence caused by the path differences under equal and unequal path parameters was simulated and validated on the system throughput. Some basic conclusions on how to determine the path measurements were then presented; they can provide help to the selection of active multipath in theory.
In order to improve the joint distance-velocity-resolution of the composed linear frequency modulation (CLFM) signal, a rotated linear frequency modulation (RLFM) signal based on fractional Fourier transform is proposed. The design method of RLFM signal is given, and the simulations of the signal about the ambiguity function, -3dB ambiguity graph, distance ambiguity graph and velocity ambiguity graph have been presented. Finally to put RLFM signal and CLFM signal are compared. The differences of them show that the RLFM signal has a better performance on velocity resolution and joint distance-velocity- resolution than the CLFM signal.
Due to the increasing traffic demand per user, the wireless networks are in a major transition from a carefully planned set of large tower-mounted base-stations (BSs) to an irregular deployment of distributed BSs. The location of distributed BSs is random essentially, unlike prior studies which assumed the base station to be deployed at fixed location. The studies were used to assume the base station was deployed at a random location in Poisson field, and system performance analysis of interference alignment (IA) with limited feedback in multiple input multiple output interference network is studied. Firstly, the base stations were distributed as a spatial homogeneous Poisson point process in Poisson field. The statistical characteristics of channel state information quantization were obtained, and the approximate analytical expressions of outage probability and network throughput were derived. The optimal base station deploying intensity was calculated by maximizing the lower bound of network throughput. Numerical results show that the expressions can provide sufficient precision for evaluating the systems performance of IA with limited feedback.
Recommender systems suggest a few items to the users by understanding their past behaviors. However, the existing collaborative filtering (CF) based recommender systems do not employ the information about latent item preference. In this article, a new CF personalized recommendation approaches was proposed. This approach aims to find user clusters using K-means clustering, and utilizes user clusters and utility matrix to construct item preference matrix,then, combines the item rating similarity, the item attribute and its preference features similarity in the item based CF process to produce recommendations. Experiments show the approach achieves the better result, but also to some extent alleviate the sparsity issue in the recommender systems.
Considering the current directory anonymous attestation (DAA) scheme complicated and time-consuming, which makes it limited in resource-constrained devices such as embedded, an improved DAA scheme is proposed. This scheme is based on bilinear pairing under the assumption of q strong Diffie-Hellman and decisional Diffie-Hellman. The analysis shows that this scheme is not only correct, security and anonymous, but also efficiently relieves the computation cost. This scheme further solves the computation bottleneck and accelerate application for DAA in mobile field.
In order to effectively improve the spectrum sharing performance in cognitive radio network, considering the transmission quality and channel utilization with centralized control mode, the spectrum aggregation strategy for primary users is investigated. For an aggregated spectrum consists of multiple channels, considering that primary users have higher priority to secondary users, a discrete time queueing model with multiple servers and synchronous transmission interruption is built. Using the method of matrix geometric solution, the steady state distribution of the system is given. Accordingly, performance measures in terms of blocking ratio of primary users, average delay of secondary users and channel utilization are derived. Experimental results show that when setting the spectrum aggregation capacity, there is a trade-off between different performance measures. By establishing a system cost function, the scheme for setting spectrum aggregation capacity is carried out, and the spectrum aggregation strategy in cognitive radio networks is optimized.
When a server authenticates users based on fingerprint over open network, the process of fingerprint matching is usually handled in the encrypted domain with purpose of protecting the privacy and security of both parties. However, an accurate alignment of the template and the query sample is rather difficult in this situation. An alignment-free fingerprint-matching scheme was presented, which extracts two kinds of local features around the minutiae, ridge orientation and minutiae local structure. Both features have the properties of invariant to rotation and translation. Garbled circuits were designed to implement the corresponding matching algorithm, which allow the server to verify the user without leaking the respective data. Experiment shows that the scheme achieves a relatively higher accuracy on FVC2002-DB2 public database.
Assume that anonymous participants have the same level of security is inconsistent and often questionable with the actual scenario in location k-anonymity techniques. The article drew from the theory of secure multiparty computation and presented a non-cooperative location privacy-preserving method in the distributed structure. Based on the spatial-temporal cloaking, the method introduced oblivious transferring for design privacy-aware query protocols. Security analysis and simulation show that this method can meet the conditions of the location k-anonymity and location obfuscation, and can achieve greater privacy.
A distributed Robust relay beamforming design in cognitive two-way relay networks by considering imperfect channel state information was proposed to improve the minimum worst-case signal-to- interference-plus-noise ratio (SINR) of two cognitive users, satisfying a total relay power constrains and keeping the interference at primary user receiver below an acceptable threshold. Based on S-Procedure, the non-convex problem is transformed into a convex feasibility problem by relaxing the rank constrains, which can be solved efficiently. Simulations show that the proposed design can satisfy both total relay power constrains and interference temperature constrains, and verify the effectiveness of the proposed method as well in comparison to the non-Robust relay beamforming technique.
Internet of vehicles (IoV) is an open converged network system supporting human-vehicles-environment cooperation. Based on in-depth analysis of the development trend of integration of people and vehicles, as well as the demand of human-vehicles-environment cooperation, an object cooperative model was proposed. This model established a new mechanism and an interactive mode of individual objects and group, meanwhile a group collaboration system was put forward. Furthermore, a general architectural reference model of IoV was presented. Utilizing the collaborative computing control layer, the multi-dimensional cooperation of objects-services-communications was performed. Also the key technical requirements for IoV were described.
Collaboration for a ubiquitous service is an inevitable demand of users in the future. This paper put forward the multi-terminal synergy (MTS) mechanism for ubiquitous service. With a hierarchical model and a service quality model adopted, MTS is composed of three modules. Pathfinding mechanism based on time stamp and time control window are added to the core algorithm. The result shows that MTS can quickly choose high quality executive nodes, ensure the service continuity and smoothness. Compared with others, it improves the performance in readjustment and delay.
It is critical problem how to meet all requested ubiquitous services simultaneously in ubiquitous stub environment with resource-limited devices and bandwidth-limited network. To achieve this goal, we first formulate multi-devices cooperation problem with ubiquitous service model and network model. And then a devices aggregative mechanism is proposed to support two key modules of multi-devices cooperation set construction and decision-making. At last, the simulation is implemented with OPNET and Matlab. The result shows this mechanism has better performance than others.
An enhanced gossip time synchronization algorithm for wireless sensor networks was proposed to improve the performance of synchronization by integrating the broadcasting characteristics of wireless channel. The communication mode of traditional gossip algorithm is peer to peer, while the mode of the proposed algorithm is peer-to-multi. Both analysis and simulation confirm the effectiveness of the proposed algorithm in expediting the convergence rate and reducing the energy consumption.
Exponentially embedded families (EEF) criterion based wideband spectrum sensing schemes were proposed for cognitive radios. Based on the EEF criterion, the signal and noise subspaces were considered in spectrum observation data and the EEF wideband sensing was improved by employing Gerschgorin unitary transformation in data processing. Correspondingly, the developed wideband sensing algorithm was operated under Gerschgorin EEF (GEEF) criterion. The proposed two algorithms estimate the cardinality of the primary user signal occupied subband set via EEF or GEEF criterion to identify idle subbands for secondary users dynamically accessing the licensed frequency band. Analysis and simulation verify that the proposed algorithms do not need any a prior knowledge of the noise power and the primary user signal. They are robust against the noise power uncertainty problem.
Part-of-speech tagging for Chinese English learner language is the base of automated essay scoring system. Much of fruitful part-of-speech tagging researches researchers was done, however, most of them are focused on the English essays written by native speaker, there is no research about essays of Chinese English learner. A corpus of Chinese English learner essay are annotated, and a part-of-speech tagging algorithm for Chinese English learner language is presented. This algorithm uses rich features, such as unsupervised word clusters, unsupervised tag dictionary and phonetic normalization. Based on these rich features, the system outperforms the state-of-art tagging on the corpus, and the tagging accuracy is raised from 94.49% to 97.07%.
Based on the analysis of the common routing algorithms in mobile ad hoc networks (MANETs), e. g., single-copy and flooding, a routing algorithm, which uses single copy and the similarities of the trace, is proposed. To address the problems of single-copy and flooding routing, such as the high transmission delay in single-copy routing, the large amount of the network overhead and packet loss in the flooding, we K-copies routing algorithm based on the similarities of nodes trace records. Finally, the algorithms are evaluated in terms of several performance parameters, i. e., the packet delivery ratio, the average transmission delay and forwarding hops. The results of the simulations show that our algorithms have the better performance than other existing routing algorithms in MANETs.