ISSN 
2013 Vol. 42, No. 1
2013, 42(1): 10-22.
doi: 10.3969/j.issn.1001-0548.2013.01.005
Abstract:
This paper summarize recent researches about the networked coevolutionary games. Firstly, a systematical introduction is presented to social dilemma games, including the Prisoner's dilemma game and the public goods games, associated with a variety of structural properties, e. g., degree heterogeneity, assortative mixing and clustering. The essential relationship between network structure and cooperative dynamics is revealed. Subsequently, we review the achievements with respect to coevolution of cooperation with learning and selection rules in the static networks, such as, time scale, individual selection, teaching activity, rationality and aspiration, and restrained interaction. Furthermore, we summarize recent works about coevolution of cooperative dynamics and interaction patterns, especially involving vanish of interactions, birth and death process and migration. Finally, we provide some remarks and outlook for the development of evolutionary games on networks in the future.
This paper summarize recent researches about the networked coevolutionary games. Firstly, a systematical introduction is presented to social dilemma games, including the Prisoner's dilemma game and the public goods games, associated with a variety of structural properties, e. g., degree heterogeneity, assortative mixing and clustering. The essential relationship between network structure and cooperative dynamics is revealed. Subsequently, we review the achievements with respect to coevolution of cooperation with learning and selection rules in the static networks, such as, time scale, individual selection, teaching activity, rationality and aspiration, and restrained interaction. Furthermore, we summarize recent works about coevolution of cooperative dynamics and interaction patterns, especially involving vanish of interactions, birth and death process and migration. Finally, we provide some remarks and outlook for the development of evolutionary games on networks in the future.
2013, 42(1): 23-28.
doi: 10.3969/j.issn.1001-0548.2013.01.006
Abstract:
A briefly review about the interdependent networks is given in this article. The concept and models of interdependent networks are introduced. The failure of nodes in one network may trigger cascading failures and catastrophic consequences. According to the topology of the system, the existing empirical research on the robustness of interdependent networks is reviewed from four aspects: the systems with one-to-one connection relationship, the systems with multiple dependencies, the systems of networks, and the scale-free networks. The existing methods for enhancing network robustness are given. At last, the research on interdependent networks is briefly summarized.
A briefly review about the interdependent networks is given in this article. The concept and models of interdependent networks are introduced. The failure of nodes in one network may trigger cascading failures and catastrophic consequences. According to the topology of the system, the existing empirical research on the robustness of interdependent networks is reviewed from four aspects: the systems with one-to-one connection relationship, the systems with multiple dependencies, the systems of networks, and the scale-free networks. The existing methods for enhancing network robustness are given. At last, the research on interdependent networks is briefly summarized.
2013, 42(1): 29-32.
doi: 10.3969/j.issn.1001-0548.2013.01.007
Abstract:
The present paper describes the studies on an intra-pulses linear frequency modulation (LFM) and inter-pulses binary phase shift keying (BPSK) compression radar altimeter. The design technology on subsystems is given. Performance verification test including the maximum detection height, IF echo signal, pulse compression test results, and final processed output of signal processor in different geomorphies have been presented. Flight test shows that high altitude pulse compression radar altimeter has superior performance in measuring altitude. All specifications are well in accordance with technical requirements.
The present paper describes the studies on an intra-pulses linear frequency modulation (LFM) and inter-pulses binary phase shift keying (BPSK) compression radar altimeter. The design technology on subsystems is given. Performance verification test including the maximum detection height, IF echo signal, pulse compression test results, and final processed output of signal processor in different geomorphies have been presented. Flight test shows that high altitude pulse compression radar altimeter has superior performance in measuring altitude. All specifications are well in accordance with technical requirements.
2013, 42(1): 33-35.
doi: 10.3969/j.issn.1001-0548.2013.01.008
Abstract:
The narrow-band band-stop filters are often used in microwave systems to suppress the nonlinear harmonic output of high-power transmitters and the parasitic passband of band-pass filters. The difficulty of the design is to eliminate the parasitic stopband at three times the center frequency f0. This paper effectively solved the problem of parasitic stopband at 3f0 and largely extended the upper passband by means of loading a lumped capacity at the open end of the parallel-coupled line. According to this method, a narrow band-stop filter with a center frequency at 5. 3 GHz has been presented. The test result shows that this filter has a good performance at upper passband.
The narrow-band band-stop filters are often used in microwave systems to suppress the nonlinear harmonic output of high-power transmitters and the parasitic passband of band-pass filters. The difficulty of the design is to eliminate the parasitic stopband at three times the center frequency f0. This paper effectively solved the problem of parasitic stopband at 3f0 and largely extended the upper passband by means of loading a lumped capacity at the open end of the parallel-coupled line. According to this method, a narrow band-stop filter with a center frequency at 5. 3 GHz has been presented. The test result shows that this filter has a good performance at upper passband.
2013, 42(1): 36-40.
doi: 10.3969/j.issn.1001-0548.2013.01.009
Abstract:
The optimization of downlink power allocation of cognitive OFDM wireless network is converted into an optimization problem with constraints. An immune clonal algorithm is proposed to solve this problem. The power allocation model, key techniques, and implementation processes are described. The coding, clonal, and maturation operators are designed. The experiments results show that, with the constraints of total power, the bit error rate (BER) and the acceptable interferences of primary user, the algorithm can maximizes the total transmit rate and converges rapidly. It can get the better power allocation scheme and improve the reuse of spectrum.
The optimization of downlink power allocation of cognitive OFDM wireless network is converted into an optimization problem with constraints. An immune clonal algorithm is proposed to solve this problem. The power allocation model, key techniques, and implementation processes are described. The coding, clonal, and maturation operators are designed. The experiments results show that, with the constraints of total power, the bit error rate (BER) and the acceptable interferences of primary user, the algorithm can maximizes the total transmit rate and converges rapidly. It can get the better power allocation scheme and improve the reuse of spectrum.
2013, 42(1): 41-43,86.
doi: 10.3969/j.issn.1001-0548.2013.01.010
Abstract:
The unitary problem between numerical solutions and the analytic solutions is an important issue to value whether or not the physical nature and structure of a numerical method are reasonable in computational electromagnetics. This paper presents the structure functions of T-matrix method based on H-wave incident, boundary conditions of 2D dielectric scattering, and 2D Green's function and extinction theorem. The full analysis of T-matrix's limitation problem shows that when the boundary of a dielectric is limited to the cylindrical one, the limitation transition from the T-matrix solutions to classical ones is obtained.
The unitary problem between numerical solutions and the analytic solutions is an important issue to value whether or not the physical nature and structure of a numerical method are reasonable in computational electromagnetics. This paper presents the structure functions of T-matrix method based on H-wave incident, boundary conditions of 2D dielectric scattering, and 2D Green's function and extinction theorem. The full analysis of T-matrix's limitation problem shows that when the boundary of a dielectric is limited to the cylindrical one, the limitation transition from the T-matrix solutions to classical ones is obtained.
Spreading Sequence Estimation of Direct Sequence Spread Spectrum Signals with Unknown Carrier Offset
2013, 42(1): 44-47,80.
doi: 10.3969/j.issn.1001-0548.2013.01.011
Abstract:
In this paper, by absorbing the carrier frequency into the spreading waveform, an efficient algorithm to estimate the spreading sequence of direct sequence spread spectrum (DSSS) signals with unknown carrier offset is proposed. The proposed algorithm is based on the subspace decomposition of covariance matrix. The signal to noise ratio (SNR) of the spreading waveform estimation with unknown carrier offset is improved by signal subspace decomposition, which reduces the difficulty in carrier frequency estimation. Under the stochastic signal model assumption, we also derive the Cramer-Rao lower bound (CRB) of spreading waveform estimators. Simulation results demonstrate the effectiveness of proposed algorithm in lower SNR situations.
In this paper, by absorbing the carrier frequency into the spreading waveform, an efficient algorithm to estimate the spreading sequence of direct sequence spread spectrum (DSSS) signals with unknown carrier offset is proposed. The proposed algorithm is based on the subspace decomposition of covariance matrix. The signal to noise ratio (SNR) of the spreading waveform estimation with unknown carrier offset is improved by signal subspace decomposition, which reduces the difficulty in carrier frequency estimation. Under the stochastic signal model assumption, we also derive the Cramer-Rao lower bound (CRB) of spreading waveform estimators. Simulation results demonstrate the effectiveness of proposed algorithm in lower SNR situations.
2013, 42(1): 48-52.
doi: 10.3969/j.issn.1001-0548.2013.01.012
Abstract:
A common subexpression elimination (CSE) method based on identical weight criteria is presented to reduce silicon area and power of finite impulse response (FIR) filters. The novelty of the method is twofold. Firstly, it only requires a few small size adders by selecting subexpressions composed of identical weight coefficient bits and then eliminating common subexpressions of different weight. Secondly, it utilizes the folded direct-form structure instead of the widely used transposed structure, thus approximately 50% registers can be reduced when compared with conventional methods. In order to find the optimum common subexpressions, a matrix search process with low complexity is introduced. Implementation examples show that our method offers an average reduction of 46% cell area and 69% power consumption over the existing H-CSE method, and an average reduction of 45% cell area and 68% power consumption over the V-CSE method.
A common subexpression elimination (CSE) method based on identical weight criteria is presented to reduce silicon area and power of finite impulse response (FIR) filters. The novelty of the method is twofold. Firstly, it only requires a few small size adders by selecting subexpressions composed of identical weight coefficient bits and then eliminating common subexpressions of different weight. Secondly, it utilizes the folded direct-form structure instead of the widely used transposed structure, thus approximately 50% registers can be reduced when compared with conventional methods. In order to find the optimum common subexpressions, a matrix search process with low complexity is introduced. Implementation examples show that our method offers an average reduction of 46% cell area and 69% power consumption over the existing H-CSE method, and an average reduction of 45% cell area and 68% power consumption over the V-CSE method.
2013, 42(1): 53-57.
doi: 10.3969/j.issn.1001-0548.2013.01.013
Abstract:
A computationally efficient direction-of-arrival (DOA) estimation algorithm for noncircular signals based on multistage wiener filter theory and polynomial rooting technique is proposed. Firstly, the array extension matrix is constructed by utilizing the noncircularity of the signals. Secondly, the signal subspace is achieved with multistage Wiener filter (MSWF), which does not require the formation of the covariance matrix and its eigendecomposition. Thirdly, the polynomial rooting method of the signal subspace is derived based on uniform linear arrays, by which the estimate of DOA are obtained. The proposed algorithm is more computationally efficient, especially for the case of large number of sensors, in comparison with NC-root-MUSIC, NC-ESPRIT and extended propagator method (EPM), although their performances are near the same.
A computationally efficient direction-of-arrival (DOA) estimation algorithm for noncircular signals based on multistage wiener filter theory and polynomial rooting technique is proposed. Firstly, the array extension matrix is constructed by utilizing the noncircularity of the signals. Secondly, the signal subspace is achieved with multistage Wiener filter (MSWF), which does not require the formation of the covariance matrix and its eigendecomposition. Thirdly, the polynomial rooting method of the signal subspace is derived based on uniform linear arrays, by which the estimate of DOA are obtained. The proposed algorithm is more computationally efficient, especially for the case of large number of sensors, in comparison with NC-root-MUSIC, NC-ESPRIT and extended propagator method (EPM), although their performances are near the same.
2013, 42(1): 58-62.
doi: 10.3969/j.issn.1001-0548.2013.01.014
Abstract:
Channel equalization and coherent detection require accurate channel state information (CSI) at the receiver for multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems. The conventional linear recovery methods, such as least squares (LS) and minimum mean square error (MMSE), are widely adapted in channel estimation under the assumption of rich multipath. However, numerous physical measurements have verified that the practical multipath channels tend to exhibit sparse structures. In this paper, exploiting the channel sparsity, we propose a compressive sensing-based CoSaMP recovery algorithm for MIMO-OFDM sparse channel estimation. Simulations show that the compressive sensing estimation method can obtain the accurate CSI with fewer pilots than conventional linear estimation for MIMO-OFDM systems at the cost of less computational complexity. The proposed method can greatly improve the spectrum efficiency for MIMO-OFDM systems.
Channel equalization and coherent detection require accurate channel state information (CSI) at the receiver for multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems. The conventional linear recovery methods, such as least squares (LS) and minimum mean square error (MMSE), are widely adapted in channel estimation under the assumption of rich multipath. However, numerous physical measurements have verified that the practical multipath channels tend to exhibit sparse structures. In this paper, exploiting the channel sparsity, we propose a compressive sensing-based CoSaMP recovery algorithm for MIMO-OFDM sparse channel estimation. Simulations show that the compressive sensing estimation method can obtain the accurate CSI with fewer pilots than conventional linear estimation for MIMO-OFDM systems at the cost of less computational complexity. The proposed method can greatly improve the spectrum efficiency for MIMO-OFDM systems.
2013, 42(1): 63-68.
doi: 10.3969/j.issn.1001-0548.2013.01.015
Abstract:
In this paper, a cross-layer approach is used to maximize the overall video quality or minimize the end-to-end video distortion under the constraints of resource and delay through cross-layer adaptation of parameters in physical, link, and application (video encoder) layers. The rate-distortion behavior of video encoders under energy constraints is modeled and controlled. The video packet queuing behavior at the link layer is analyzed and the impact of packet loss due to delay bound violation on the end-to-end video distortion is studied. Analysis and experiment demonstrate that the proposed scheme allows us to find optimum energy tradeoff between video encoding and wireless transmission under delay constraints, exploit the link-layer delay as a system resource, and achieve significant performance gain.
In this paper, a cross-layer approach is used to maximize the overall video quality or minimize the end-to-end video distortion under the constraints of resource and delay through cross-layer adaptation of parameters in physical, link, and application (video encoder) layers. The rate-distortion behavior of video encoders under energy constraints is modeled and controlled. The video packet queuing behavior at the link layer is analyzed and the impact of packet loss due to delay bound violation on the end-to-end video distortion is studied. Analysis and experiment demonstrate that the proposed scheme allows us to find optimum energy tradeoff between video encoding and wireless transmission under delay constraints, exploit the link-layer delay as a system resource, and achieve significant performance gain.
2013, 42(1): 69-74.
doi: 10.3969/j.issn.1001-0548.2013.01.016
Abstract:
The research on the bridge structural monitoring focuses mainly on the identification of the structure damage position and degree. However, these researches are based on the data of the structural health monitoring system. In the actual environment, the abnormal data caused by the failure monitoring system can often make the false prognosis, increasing the false alarm rate. Meanwhile, the bridge may have serious structural damage from the unexpected events caused by some external loads. They are not conducive to the bridge safety maintenance and management. In order to ensure the bridge safety and improve the effectiveness of the bridge structure monitoring, it is necessary to diagnose these special events. In the paper, kernel principal component analysis (KPCA) and hyperspherical support vector machine method are employed to separate the general monitoring data from the event data. The acceleration sensor data in Jiangyin Bridge is used to validate the effectiveness of the method under the ship collision, typhoons, sensor installed noise, and sensor step signals.
The research on the bridge structural monitoring focuses mainly on the identification of the structure damage position and degree. However, these researches are based on the data of the structural health monitoring system. In the actual environment, the abnormal data caused by the failure monitoring system can often make the false prognosis, increasing the false alarm rate. Meanwhile, the bridge may have serious structural damage from the unexpected events caused by some external loads. They are not conducive to the bridge safety maintenance and management. In order to ensure the bridge safety and improve the effectiveness of the bridge structure monitoring, it is necessary to diagnose these special events. In the paper, kernel principal component analysis (KPCA) and hyperspherical support vector machine method are employed to separate the general monitoring data from the event data. The acceleration sensor data in Jiangyin Bridge is used to validate the effectiveness of the method under the ship collision, typhoons, sensor installed noise, and sensor step signals.
2013, 42(1): 75-80.
doi: 10.3969/j.issn.1001-0548.2013.01.017
Abstract:
The bandwidth of the conventional hysteresis controller for the Bang-Bang control is constant in the direct torque control (DTC) systems of induction motors, thus the ripple of the tuned flux and torque is stronger in low speed. In order to improve the torque and flux response, a hysteresis bandwidth adaptive control algorithm is proposed on the basis of conventional hysteresis comparator. By the comprehensive comparison of the current sample value, historical sample value of the torque error or flux linkage error as well as the historical output values of the hysteresis comparator, the current hysteresis control signal is achieved, and the zero voltage vector and the backward voltage vector are used fully to achieve satisfactory control effect. The simulation result shows that the new hysteresis control algorithm can not only effectively reduce the stator flux and torque ripple, but also can effectively reduce the switching frequency, and improve the efficiency of the inverter.
The bandwidth of the conventional hysteresis controller for the Bang-Bang control is constant in the direct torque control (DTC) systems of induction motors, thus the ripple of the tuned flux and torque is stronger in low speed. In order to improve the torque and flux response, a hysteresis bandwidth adaptive control algorithm is proposed on the basis of conventional hysteresis comparator. By the comprehensive comparison of the current sample value, historical sample value of the torque error or flux linkage error as well as the historical output values of the hysteresis comparator, the current hysteresis control signal is achieved, and the zero voltage vector and the backward voltage vector are used fully to achieve satisfactory control effect. The simulation result shows that the new hysteresis control algorithm can not only effectively reduce the stator flux and torque ripple, but also can effectively reduce the switching frequency, and improve the efficiency of the inverter.
2013, 42(1): 81-86.
doi: 10.3969/j.issn.1001-0548.2013.01.018
Abstract:
Aimed at the charging control of contactless power transfer (CPT) systems, the paper proposes a primary side control method based on H∞ control. With the conversion of differential dynamic model in frequency domain, the generalized state space averaging model is set up. The control system structure and performance weighted function are proposed. The Ricatti equations for controller and observer are put forward and solved with Hermitian matrix as well. Furthermore, an iterative computing method is designed to acquire optimal H∞ controller. The control method can regulate the energy injection according to different load condition and improves the system efficiency especially for light load condition. The experimental results verify this method.
Aimed at the charging control of contactless power transfer (CPT) systems, the paper proposes a primary side control method based on H∞ control. With the conversion of differential dynamic model in frequency domain, the generalized state space averaging model is set up. The control system structure and performance weighted function are proposed. The Ricatti equations for controller and observer are put forward and solved with Hermitian matrix as well. Furthermore, an iterative computing method is designed to acquire optimal H∞ controller. The control method can regulate the energy injection according to different load condition and improves the system efficiency especially for light load condition. The experimental results verify this method.
2013, 42(1): 87-91.
Abstract:
In this paper, information filtering fusion theory is introducted into the field of low-speed maglev train speed and position detection. Beside the cross induction coil, radar speed sensors and balise are also adopted. The relative positioning is realized by the radar and cross induction coil, and the absolute positioning is realized by the balise. The information fusion comes true by this way. The accuracy and reliability of speed and position detection can be significantly improved. The final conclusion is verified by MATLAB simulation.
In this paper, information filtering fusion theory is introducted into the field of low-speed maglev train speed and position detection. Beside the cross induction coil, radar speed sensors and balise are also adopted. The relative positioning is realized by the radar and cross induction coil, and the absolute positioning is realized by the balise. The information fusion comes true by this way. The accuracy and reliability of speed and position detection can be significantly improved. The final conclusion is verified by MATLAB simulation.
2013, 42(1): 92-97,104.
doi: 10.3969/j.issn.1001-0548.2013.01.020
Abstract:
In order to achieve a secure network transactions, the main problem we are facing to is the trust, risk and other issues. In this paper, taking the network transactions of complex network environment as the researching background, we proposed the trust evaluation model based on cloud model. This trust evaluation model can implement the conversion between qualitative and quantitative of trusts, and it can objectively reflect the randomness, fuzziness, and unpredictability of the trusts. In order to effectively evaluate transaction risk in complex networks, the risk evaluation approach based on cloud model is researched and proposed. The simulation results confirm that this trust evaluation model can make a reasonable evaluation of the entities' trust in the complex network environment, and that the risk evaluation approach researched in this paper can reasonably predict the risk of network transactions. Finally, we design and realize a risk evaluation system based on cloud model, further also confirm the feasibility and rationality of the proposed risk evaluation approach.
In order to achieve a secure network transactions, the main problem we are facing to is the trust, risk and other issues. In this paper, taking the network transactions of complex network environment as the researching background, we proposed the trust evaluation model based on cloud model. This trust evaluation model can implement the conversion between qualitative and quantitative of trusts, and it can objectively reflect the randomness, fuzziness, and unpredictability of the trusts. In order to effectively evaluate transaction risk in complex networks, the risk evaluation approach based on cloud model is researched and proposed. The simulation results confirm that this trust evaluation model can make a reasonable evaluation of the entities' trust in the complex network environment, and that the risk evaluation approach researched in this paper can reasonably predict the risk of network transactions. Finally, we design and realize a risk evaluation system based on cloud model, further also confirm the feasibility and rationality of the proposed risk evaluation approach.
2013, 42(1): 98-104.
doi: 10.3969/j.issn.1001-0548.2013.01.021
Abstract:
A parallel trust structure is proposed to contain application software into its credence coverage. The structure passes trust from the TPM to the applications in virtual domains. Based on this structure, we design and implement a trusted software protection agent (TSPA), a module in hypervisor, which simplifies the trust complexity and makes trust transfer more controllable and more secure. This paper also contributes a model for protecting software integrity.
A parallel trust structure is proposed to contain application software into its credence coverage. The structure passes trust from the TPM to the applications in virtual domains. Based on this structure, we design and implement a trusted software protection agent (TSPA), a module in hypervisor, which simplifies the trust complexity and makes trust transfer more controllable and more secure. This paper also contributes a model for protecting software integrity.
2013, 42(1): 105-108.
Abstract:
Community dipartition is used in biochemistry, sociology, eco-systems, etc. The reliability of the results and the efficiency of the algorithm are the focus of the study. The Louvain algorithm is an algorithm with relatively reliable result and better efficiency. In this paper, the Louvain algorithm is improved in dealing with the leaf nodes. By studying the characteristics of the leaf nodes and the inadequacies of Louvain algorithm, the improved algorithm prunes the leaf nodes to avoid redundant computation. 18 sets of artificial data and the email data of our school are respectively processed using improved algorithm and Louvain algorithm. The comparison of results shows that the improved algorithm improves the processing speed while maintaining the result reliable.
Community dipartition is used in biochemistry, sociology, eco-systems, etc. The reliability of the results and the efficiency of the algorithm are the focus of the study. The Louvain algorithm is an algorithm with relatively reliable result and better efficiency. In this paper, the Louvain algorithm is improved in dealing with the leaf nodes. By studying the characteristics of the leaf nodes and the inadequacies of Louvain algorithm, the improved algorithm prunes the leaf nodes to avoid redundant computation. 18 sets of artificial data and the email data of our school are respectively processed using improved algorithm and Louvain algorithm. The comparison of results shows that the improved algorithm improves the processing speed while maintaining the result reliable.
2013, 42(1): 109-114.
doi: 10.3969/j.issn.1001-0548.2013.01.023
Abstract:
Quality of service (QoS) as the manifestation of system viability is analyzed in this paper. A hierarchical evaluation model for the distributed system survivability based on the attributes association analysis of QoS is proposed. The calculation method for the correlations of QoS and the quantifiable evolution method for key attributes and distributed system survivability are given. The evaluating situation of survivability of three kinds of key services during one week is observed and studied by experiments. The comparative analysis with other algorithms is also presented.
Quality of service (QoS) as the manifestation of system viability is analyzed in this paper. A hierarchical evaluation model for the distributed system survivability based on the attributes association analysis of QoS is proposed. The calculation method for the correlations of QoS and the quantifiable evolution method for key attributes and distributed system survivability are given. The evaluating situation of survivability of three kinds of key services during one week is observed and studied by experiments. The comparative analysis with other algorithms is also presented.
2013, 42(1): 115-120.
doi: 10.3969/j.issn.1001-0548.2013.01.024
Abstract:
The generation of Ajax web pages and the Ajax page navigation must execute the client JavaScript, thus it is impossible to extract the complete content of an Ajax page through the traditional crawling algorithms. In this paper, the working mode of Ajax is analyzed, the problem of crawling Ajax web pages is elaborated, and an effective algorithm for crawling Ajax pages is proposed. The algorithm can realize the dynamic generation of Ajax web contents in client browser and the navigation of Ajax web pages, and also it can assign identification number for the crawled pages whose static pages can be generated. Experimental result shows that the number of Ajax pages crawled by the proposed algorithm is obvious bigger than the traditional ones', and the presented replicas-detecting policies can effectively reduce the time consumption of the algorithm.
The generation of Ajax web pages and the Ajax page navigation must execute the client JavaScript, thus it is impossible to extract the complete content of an Ajax page through the traditional crawling algorithms. In this paper, the working mode of Ajax is analyzed, the problem of crawling Ajax web pages is elaborated, and an effective algorithm for crawling Ajax pages is proposed. The algorithm can realize the dynamic generation of Ajax web contents in client browser and the navigation of Ajax web pages, and also it can assign identification number for the crawled pages whose static pages can be generated. Experimental result shows that the number of Ajax pages crawled by the proposed algorithm is obvious bigger than the traditional ones', and the presented replicas-detecting policies can effectively reduce the time consumption of the algorithm.
2013, 42(1): 121-124.
doi: 10.3969/j.issn.1001-0548.2013.01.025
Abstract:
Classic R-D optimized algorithms, which use the objective image quality as distortion assessment standard, do not consider the effect produced by human visual system (HVS). This paper proposes an H.264 encode mode decision algorithm based on just-noticeable distortion (JND) model. The R-D values in coding process are calculated by using modified DCT-based JND model, incorporating the spatio-temporal contrast sensitivity function, luminance adaptation, and intra- and inter-band contrast masking. The redundant coefficients which can't be noticeable are removed to optimize the subjective quality. The simulation results show that under same subjective quality, the proposed algorithm can obviously reduce the production of bit-rate and hence improve the coding efficiency.
Classic R-D optimized algorithms, which use the objective image quality as distortion assessment standard, do not consider the effect produced by human visual system (HVS). This paper proposes an H.264 encode mode decision algorithm based on just-noticeable distortion (JND) model. The R-D values in coding process are calculated by using modified DCT-based JND model, incorporating the spatio-temporal contrast sensitivity function, luminance adaptation, and intra- and inter-band contrast masking. The redundant coefficients which can't be noticeable are removed to optimize the subjective quality. The simulation results show that under same subjective quality, the proposed algorithm can obviously reduce the production of bit-rate and hence improve the coding efficiency.
2013, 42(1): 125-129.
doi: 10.3969/j.issn.1001-0548.2013.01.026
Abstract:
This paper presents an algorithm of image mosaic based on local features to improve the effect and speed of aerial image mosaic. The method registers images according to multi-resolution analysis and local features. The problem of image mosaic is turned into the problem of the coordinate transformation between the pixels by using affine transformation. The weighted average algorithm is used to achieve smooth stitching results and eliminate intensity seam globally. Experimental results show that the proposed method is effective for the mosaic of real aerial sequences and video images.
This paper presents an algorithm of image mosaic based on local features to improve the effect and speed of aerial image mosaic. The method registers images according to multi-resolution analysis and local features. The problem of image mosaic is turned into the problem of the coordinate transformation between the pixels by using affine transformation. The weighted average algorithm is used to achieve smooth stitching results and eliminate intensity seam globally. Experimental results show that the proposed method is effective for the mosaic of real aerial sequences and video images.
2013, 42(1): 130-136.
doi: 10.3969/j.issn.1001-0548.2013.01.027
Abstract:
A general equivalent model is introduced based on the convex relaxation model of a class of vector-valued minimization problems. The presented model can be solved by split-Bregman algorithm. The computational efficiency is greatly improved. The method is applied to the Vese-Chan multi-phase segmentation model and Mumford-Shah model. Numerical experiments show our method has fast computing speed and good segmentation results, and is robust to the initial condition.
A general equivalent model is introduced based on the convex relaxation model of a class of vector-valued minimization problems. The presented model can be solved by split-Bregman algorithm. The computational efficiency is greatly improved. The method is applied to the Vese-Chan multi-phase segmentation model and Mumford-Shah model. Numerical experiments show our method has fast computing speed and good segmentation results, and is robust to the initial condition.
2013, 42(1): 137-143.
doi: 10.3969/j.issn.1001-0548.2013.01.028
Abstract:
Refinement of software architecture deals with mapping and transformation between architectural models at different abstraction levels. This paper reviews current researches on software architecture refinement, analyzes their inadequacies, and then proposes a new concept of interactive action refinement of software architecture based on πADL architecture description language, defines the formal specification method and principles of interactive action refinement, develops a refinement reasoning algorithm, which can preserve the higher-level architectural behavior properties across refinement hierarchies and generates lower-level architectures automatically. Interactive action refinement can effectively eliminate the mismatches of abstraction levels between components and their interactive actions that occur in the architectural refinement process. A case study shows the validity of the proposed method.
Refinement of software architecture deals with mapping and transformation between architectural models at different abstraction levels. This paper reviews current researches on software architecture refinement, analyzes their inadequacies, and then proposes a new concept of interactive action refinement of software architecture based on πADL architecture description language, defines the formal specification method and principles of interactive action refinement, develops a refinement reasoning algorithm, which can preserve the higher-level architectural behavior properties across refinement hierarchies and generates lower-level architectures automatically. Interactive action refinement can effectively eliminate the mismatches of abstraction levels between components and their interactive actions that occur in the architectural refinement process. A case study shows the validity of the proposed method.
2013, 42(1): 144-148.
doi: 10.3969/j.issn.1001-0548.2013.01.029
Abstract:
Management of cryptography keys for data encapsulation in classified network has been troubling people. The aim of this article is to present a new mechanism for protecting classified data by using trusted cryptography module. The solution contains both runtime data protection and static file data protection. The key technique is using the feature of cryptography keys hidden technology of trusted cryptography module. The result of a simple performance test of the trusted cryptography module is provided while the solution for its insufficiency is also presented. By using the trusted cryptography module, an implementation with experiment result of a network control is presented.
Management of cryptography keys for data encapsulation in classified network has been troubling people. The aim of this article is to present a new mechanism for protecting classified data by using trusted cryptography module. The solution contains both runtime data protection and static file data protection. The key technique is using the feature of cryptography keys hidden technology of trusted cryptography module. The result of a simple performance test of the trusted cryptography module is provided while the solution for its insufficiency is also presented. By using the trusted cryptography module, an implementation with experiment result of a network control is presented.
2013, 42(1): 149-153.
doi: 10.3969/j.issn.1001-0548.2013.01.030
Abstract:
This paper proposes an improved key management scheme based on random key-seeds predistribution for wireless sensor networks (WSNs). According to the key generation method which needs the key-seed and generation factor, we formulate the proper key generation and update methods with different key types. The analysis and simulation of connectivity rates and security show that our scheme can enhance the capability against nodes capture and provide high flexibility. Finally the scheme is implemented on the Lab platform. The analysis indicates the feature of low overhead in communication, computation and storage.
This paper proposes an improved key management scheme based on random key-seeds predistribution for wireless sensor networks (WSNs). According to the key generation method which needs the key-seed and generation factor, we formulate the proper key generation and update methods with different key types. The analysis and simulation of connectivity rates and security show that our scheme can enhance the capability against nodes capture and provide high flexibility. Finally the scheme is implemented on the Lab platform. The analysis indicates the feature of low overhead in communication, computation and storage.
2013, 42(1): 154-160.
doi: 10.3969/j.issn.1001-0548.2013.01.031
Abstract:
Personalized recommendation has now been widely used in E-commerce, but there are still some problems to be solved such as cold-start problem, data sparsity, diversity-accuracy dilemma and so on. Existing literatures have focused on single data set, lacking a systematic understanding about the accessing behavior involving multiple web sites. Thanks to the real data, provided by Baifendian Information Technology recommendation engine, we analyze users' behavior on multi-B2Cs (business-to-customers) and propose a crossing recommendation algorithm which is able to recommend items of a B2C site to users according to the records of users in other B2C web sites. This algorithm largely improves accuracy compared with purely random recommendation under completely cold-start environment and can still keep high diversity and novelty.
Personalized recommendation has now been widely used in E-commerce, but there are still some problems to be solved such as cold-start problem, data sparsity, diversity-accuracy dilemma and so on. Existing literatures have focused on single data set, lacking a systematic understanding about the accessing behavior involving multiple web sites. Thanks to the real data, provided by Baifendian Information Technology recommendation engine, we analyze users' behavior on multi-B2Cs (business-to-customers) and propose a crossing recommendation algorithm which is able to recommend items of a B2C site to users according to the records of users in other B2C web sites. This algorithm largely improves accuracy compared with purely random recommendation under completely cold-start environment and can still keep high diversity and novelty.
