ISSN 
2017 Vol. 46, No. 6
2017, 46(6): 801-805, 818.
doi: 10.3969/j.issn.1001-0548.2017.06.001
Abstract:
In cellular system, to reduce the interference of the cell-edge users and ensure communication among the cell-edge users of a single cell, a user selection scheme based on cuckoo search algorithm and interference alignment algorithm is proposed.First, the cell-edge users are selected by the cuckoo search algorithm. Then interference alignment scheme is adopted to eliminate interference.Finally, an encoding and decoding based on MMSE criterion are applied to eliminate interference among users.Compared with the quick sort search algorithm, the proposed scheme based on cuckoo search algorithm has less time complexity.And numerical results show that, compared to zero-forcing decoding, the proposed algorithm will increase the system capacity by 2 b·s-1·Hz-2, and the bit error rate improvement is about 4 dB.
In cellular system, to reduce the interference of the cell-edge users and ensure communication among the cell-edge users of a single cell, a user selection scheme based on cuckoo search algorithm and interference alignment algorithm is proposed.First, the cell-edge users are selected by the cuckoo search algorithm. Then interference alignment scheme is adopted to eliminate interference.Finally, an encoding and decoding based on MMSE criterion are applied to eliminate interference among users.Compared with the quick sort search algorithm, the proposed scheme based on cuckoo search algorithm has less time complexity.And numerical results show that, compared to zero-forcing decoding, the proposed algorithm will increase the system capacity by 2 b·s-1·Hz-2, and the bit error rate improvement is about 4 dB.
2017, 46(6): 806-811.
doi: 10.3969/j.issn.1001-0548.2017.06.002
Abstract:
Current mode circuit is a circuit which is used to process the current signal. Compared with the voltage mode, it has excellent performance in speed, bandwidth and dynamic range, so it has been developed rapidly in recent years. Translinear loop (TLL) theory is a rapid and effective means for analyzing current mode circuits. This paper first introduces the basic principle of translinear circuits. Then the bipolar transistor translinear loop principle is extended to MOS transistors. At last, the typical applications of translinear loop in current mode circuits are given.
Current mode circuit is a circuit which is used to process the current signal. Compared with the voltage mode, it has excellent performance in speed, bandwidth and dynamic range, so it has been developed rapidly in recent years. Translinear loop (TLL) theory is a rapid and effective means for analyzing current mode circuits. This paper first introduces the basic principle of translinear circuits. Then the bipolar transistor translinear loop principle is extended to MOS transistors. At last, the typical applications of translinear loop in current mode circuits are given.
2017, 46(6): 812-818.
doi: 10.3969/j.issn.1001-0548.2017.06.003
Abstract:
Based on the existing control strategy and experimental result of the digital current following controlling Buck DC-DC converter, the reasons why load chances the dynamic response time is long and the output voltage can not recover expected value are analyzed, and an improved control strategy is proposed. Based on the existing control strategy, the improved control strategy adds the detection of the load changes process. If the load changes occur, the new control strategy is switched automatically. According to the shock loading and unloading, the mathematical models of the changes are established respectively, the corresponding control strategies are designed, and the hardware test results are given. The experimental results show that the proposed control strategy is correct and feasible in steady state control and dynamic process control. On the basis of ensuring the output voltage accuracy in steady state, the dynamic performance of the converter is improved.
Based on the existing control strategy and experimental result of the digital current following controlling Buck DC-DC converter, the reasons why load chances the dynamic response time is long and the output voltage can not recover expected value are analyzed, and an improved control strategy is proposed. Based on the existing control strategy, the improved control strategy adds the detection of the load changes process. If the load changes occur, the new control strategy is switched automatically. According to the shock loading and unloading, the mathematical models of the changes are established respectively, the corresponding control strategies are designed, and the hardware test results are given. The experimental results show that the proposed control strategy is correct and feasible in steady state control and dynamic process control. On the basis of ensuring the output voltage accuracy in steady state, the dynamic performance of the converter is improved.
2017, 46(6): 819-824.
doi: 10.3969/j.issn.1001-0548.2017.06.004
Abstract:
The formation method of connected-dominating set (CDS) in ad hoc wireless network is studied and improved. There are two improvements in this paper, the first one is numbering the nodes by introducing the eigenvector center value of the network topology information, which avoids the randomness during node reduction and makes the node reduction be related to the actual network topology closely. The second one is that CDS algorithm ignores the removal of the largest numbered nodes, the improved one proposes a new rule to achieve the reduction of the maximum number nodes. Thus, the improved method solves the NP-complete problem of the CDS algorithm in formation method of connected-dominating set and achieves the conditional optimal connected-dominating set. The simulation results show the excellent characteristics of the improved method.
The formation method of connected-dominating set (CDS) in ad hoc wireless network is studied and improved. There are two improvements in this paper, the first one is numbering the nodes by introducing the eigenvector center value of the network topology information, which avoids the randomness during node reduction and makes the node reduction be related to the actual network topology closely. The second one is that CDS algorithm ignores the removal of the largest numbered nodes, the improved one proposes a new rule to achieve the reduction of the maximum number nodes. Thus, the improved method solves the NP-complete problem of the CDS algorithm in formation method of connected-dominating set and achieves the conditional optimal connected-dominating set. The simulation results show the excellent characteristics of the improved method.
2017, 46(6): 825-829, 840.
doi: 10.3969/j.issn.1001-0548.2017.06.005
Abstract:
In monitoring for uranium tailing, wireless sensor network (WSN) is superior to traditional line layout. Due to energy constraint, it is necessary to use energy efficiently in routing. After analyzing low energy adaptive clustering hierarchy (LEACH) and geographical adaptive fidelity (GAF) algorithms, an improved routing algorithm based on intersecting circle amd GAF is proposed. It uses location information of nodes and intersecting circle model to separate monitoring areas into a grid of circle. Cluster heads selection is carried out with surplus energy and distance to the virtual circle center. And, cluster heads choose the most optimal next hop to transmit information. The simulation results show that the algorithm can balance energy consumption effectively and extend network lifetime.
In monitoring for uranium tailing, wireless sensor network (WSN) is superior to traditional line layout. Due to energy constraint, it is necessary to use energy efficiently in routing. After analyzing low energy adaptive clustering hierarchy (LEACH) and geographical adaptive fidelity (GAF) algorithms, an improved routing algorithm based on intersecting circle amd GAF is proposed. It uses location information of nodes and intersecting circle model to separate monitoring areas into a grid of circle. Cluster heads selection is carried out with surplus energy and distance to the virtual circle center. And, cluster heads choose the most optimal next hop to transmit information. The simulation results show that the algorithm can balance energy consumption effectively and extend network lifetime.
2017, 46(6): 830-835.
doi: 10.3969/j.issn.1001-0548.2017.06.006
Abstract:
Integrated radar and communication system can make full use of radar equipment and play an important role in achievement of multi-functional integration of electronic equipment. A kind of integrated radar and communication signal is proposed based on the relationship between chirp-rate of chirp signal and the order of fractional Fourier transform. Its main carrier adopts the unique chirp signal to implement radar function, while communication information is modulated by the subcarrier with communication code keying chirp-rate chirp signal. The superposition of the main carrier and the subcarrier enables the signal to transmit multi-binary information by single signal without degrading radar's performance. Finally, simulations demonstrate that the proposed signal has an advantage of high robustness.
Integrated radar and communication system can make full use of radar equipment and play an important role in achievement of multi-functional integration of electronic equipment. A kind of integrated radar and communication signal is proposed based on the relationship between chirp-rate of chirp signal and the order of fractional Fourier transform. Its main carrier adopts the unique chirp signal to implement radar function, while communication information is modulated by the subcarrier with communication code keying chirp-rate chirp signal. The superposition of the main carrier and the subcarrier enables the signal to transmit multi-binary information by single signal without degrading radar's performance. Finally, simulations demonstrate that the proposed signal has an advantage of high robustness.
2017, 46(6): 836-840.
doi: 10.3969/j.issn.1001-0548.2017.06.007
Abstract:
The modern satellite communication uses non-constant envelope digital modulation techniques and thus demands for the high efficiency, wideband linear high-power amplifiers. The travelling wave tube (TWT) amplifier is widely used in digital wireless communication systems because of its high power efficiency and broadband, but its strong nonlinear characteristic generates intermodulation distortion, which degrades the data quality of transmitted signal and causes interference in adjacent channels. The current techniques such as baseband prediction and feedforward technique cannot achieve wideband greater than 1 GHz, and they are too complex to be used on satellite. This paper presents a broadband predistortion TWT linearizer. A frequency bandwidth of 1.2 GHz has been demonstrated with a K-band TWTA between 19.8 GHz and 21.0 GHz. The measurement result shows that the linearizer delivers about 2 dB to 5 dB of gain expansion and 20-50 degrees phase shift expansion. And the cascaded LTWTA shows good nonlinearity improvement of 17.8 dB at 6 dB input power back off point.
The modern satellite communication uses non-constant envelope digital modulation techniques and thus demands for the high efficiency, wideband linear high-power amplifiers. The travelling wave tube (TWT) amplifier is widely used in digital wireless communication systems because of its high power efficiency and broadband, but its strong nonlinear characteristic generates intermodulation distortion, which degrades the data quality of transmitted signal and causes interference in adjacent channels. The current techniques such as baseband prediction and feedforward technique cannot achieve wideband greater than 1 GHz, and they are too complex to be used on satellite. This paper presents a broadband predistortion TWT linearizer. A frequency bandwidth of 1.2 GHz has been demonstrated with a K-band TWTA between 19.8 GHz and 21.0 GHz. The measurement result shows that the linearizer delivers about 2 dB to 5 dB of gain expansion and 20-50 degrees phase shift expansion. And the cascaded LTWTA shows good nonlinearity improvement of 17.8 dB at 6 dB input power back off point.
2017, 46(6): 841-844.
doi: 10.3969/j.issn.1001-0548.2017.06.008
Abstract:
For expanding communication network available bandwidth and optimizing the distribution of the intelligent network resources, a cognitive radio network routing method for smart grid-oriented ad hoc communication protocol is proposed. Based on the principle of minimum energy consumption and the smallest time delay, the spectrum allocation scheme and transmission rate are studied according to the requirement of the number of nodes and transmission rate. The aim is to provide a new design idea for building a highly efficient and stable ad hoc smart grid communication network. The numerical simulation shows that the performance achieved is superior to the traditional algorithms, and the method is suitable for smart grid applications.
For expanding communication network available bandwidth and optimizing the distribution of the intelligent network resources, a cognitive radio network routing method for smart grid-oriented ad hoc communication protocol is proposed. Based on the principle of minimum energy consumption and the smallest time delay, the spectrum allocation scheme and transmission rate are studied according to the requirement of the number of nodes and transmission rate. The aim is to provide a new design idea for building a highly efficient and stable ad hoc smart grid communication network. The numerical simulation shows that the performance achieved is superior to the traditional algorithms, and the method is suitable for smart grid applications.
2017, 46(6): 845-849.
doi: 10.3969/j.issn.1001-0548.2017.06.009
Abstract:
Based on generalized theory of transmission line, a set of partial differential equations of first orderare obtained to study characteristic parameters of cavity and beam-wave interaction of gyrotron. A calculationcode including "cold cavity" and "hot cavity" is developed. Taking the advantages of the code and commercial software, characteristic parameters of the same line-joint cavity are simulated. Correctness of the code is proved by simulation results. Purity of operating mode and efficiency of beam-wave interaction in two kinds of cavities, namely line-joint structure and arc-joint structure, are studied by the code when TE22, 6mode is regarded as the operating mode of a110 GHz gyrotron. As a result, compared with the line-joint cavity, purity of the operating mode and efficiency are raised about 4.7 dB and 4%, respectively. In the gyrotron with an arc-joint cavity, an output power of 1.9 MW, corresponding to 50% efficiency and an oscillation frequency of 110.1 GHz, has been achieved with a 96 kV, 40 A helical electron beam at a guiding magnetic field of 4.41 T.
Based on generalized theory of transmission line, a set of partial differential equations of first orderare obtained to study characteristic parameters of cavity and beam-wave interaction of gyrotron. A calculationcode including "cold cavity" and "hot cavity" is developed. Taking the advantages of the code and commercial software, characteristic parameters of the same line-joint cavity are simulated. Correctness of the code is proved by simulation results. Purity of operating mode and efficiency of beam-wave interaction in two kinds of cavities, namely line-joint structure and arc-joint structure, are studied by the code when TE22, 6mode is regarded as the operating mode of a110 GHz gyrotron. As a result, compared with the line-joint cavity, purity of the operating mode and efficiency are raised about 4.7 dB and 4%, respectively. In the gyrotron with an arc-joint cavity, an output power of 1.9 MW, corresponding to 50% efficiency and an oscillation frequency of 110.1 GHz, has been achieved with a 96 kV, 40 A helical electron beam at a guiding magnetic field of 4.41 T.
2017, 46(6): 850-855, 860.
doi: 10.3969/j.issn.1001-0548.2017.06.010
Abstract:
Based on the auxiliary differential equation (ADE) finite-difference time-domain (FDTD) method, distributions of electromagnetic fields and Lorentz force densities in a dispersive chiral column are simulated. Firstly, relationships between electromagnetic polarization densities and induced electromagnetic polarization densities, as well as coupled electromagnetic polarization densities of chiral media, are presented based on the constitutive relations. Wave equations and recurrence formula of electric are given. Secondly, the Lorentz force density in chiral media containing bound electric charge and electric current densities, as well as bound magnetic charge and magnetic current densities, is derived. Then, we verify the correctness of the ADE-FDTD method and the Lorentz force density method by comparing with literature's results. Finally, distributions of fields and optical forces for an active chiral cylinder are simulated. The contribution of electromagnetic current and electromagnetic charge densities to the Lorentz force density is discussed. The work in this paper provides some theoretical guidance for chiral media's potential engineering applications in optical tweezers and measurement of chiral parameter.
Based on the auxiliary differential equation (ADE) finite-difference time-domain (FDTD) method, distributions of electromagnetic fields and Lorentz force densities in a dispersive chiral column are simulated. Firstly, relationships between electromagnetic polarization densities and induced electromagnetic polarization densities, as well as coupled electromagnetic polarization densities of chiral media, are presented based on the constitutive relations. Wave equations and recurrence formula of electric are given. Secondly, the Lorentz force density in chiral media containing bound electric charge and electric current densities, as well as bound magnetic charge and magnetic current densities, is derived. Then, we verify the correctness of the ADE-FDTD method and the Lorentz force density method by comparing with literature's results. Finally, distributions of fields and optical forces for an active chiral cylinder are simulated. The contribution of electromagnetic current and electromagnetic charge densities to the Lorentz force density is discussed. The work in this paper provides some theoretical guidance for chiral media's potential engineering applications in optical tweezers and measurement of chiral parameter.
2017, 46(6): 856-860.
doi: 10.3969/j.issn.1001-0548.2017.06.011
Abstract:
The structural and thermodynamic properties of Nb2AsC have been investigated with the first-principles density functional theory computations. The calculated equilibrium structural parameters agree well with the available experimental and theoretical values of Medkour et al. The calculated elastic constants are in excellent agreement with the theoretical values at ambient pressure. The elastic constant indicates that hexagonal structure Nb2AsC is mechanically stable at ambient pressure. Also, the elastic anisotropy is examined through the computation of the Young's modulus. Based on quasi-harmonic Debye model, the thermodynamic properties including the adiabatic bulk modulus, thermal expansion coefficient, Debye temperature and heat capacity at constant volume under high temperature and pressure are predicted.
The structural and thermodynamic properties of Nb2AsC have been investigated with the first-principles density functional theory computations. The calculated equilibrium structural parameters agree well with the available experimental and theoretical values of Medkour et al. The calculated elastic constants are in excellent agreement with the theoretical values at ambient pressure. The elastic constant indicates that hexagonal structure Nb2AsC is mechanically stable at ambient pressure. Also, the elastic anisotropy is examined through the computation of the Young's modulus. Based on quasi-harmonic Debye model, the thermodynamic properties including the adiabatic bulk modulus, thermal expansion coefficient, Debye temperature and heat capacity at constant volume under high temperature and pressure are predicted.
2017, 46(6): 861-865, 889.
doi: 10.3969/j.issn.1001-0548.2017.06.012
Abstract:
In smart grid, distributed energy resources are flexible and able to support the fast-changing wireless charging demand from electric vehicles. An iterative double auction algorithm is employed to match power supply and demand for the wireless charging market, in which distributed energy resources act as power sellers, and aggregators that aggregate charging demands of electric vehicles act as power buyers. Buyers and sellers offer prices based on the principle of self-utility maximization. An agent, as an auctioneer, determines power allocation and payment according to the offered prices, and it can maximize the total utility while the private information of buyers and sellers is unknown. Simulation results show that the algorithm can maximize the total benefit of supply and demand at a fast convergence speed, ensuring the efficiency of power allocation between electric vehicles and distributed energy resources.
In smart grid, distributed energy resources are flexible and able to support the fast-changing wireless charging demand from electric vehicles. An iterative double auction algorithm is employed to match power supply and demand for the wireless charging market, in which distributed energy resources act as power sellers, and aggregators that aggregate charging demands of electric vehicles act as power buyers. Buyers and sellers offer prices based on the principle of self-utility maximization. An agent, as an auctioneer, determines power allocation and payment according to the offered prices, and it can maximize the total utility while the private information of buyers and sellers is unknown. Simulation results show that the algorithm can maximize the total benefit of supply and demand at a fast convergence speed, ensuring the efficiency of power allocation between electric vehicles and distributed energy resources.
2017, 46(6): 866-870.
doi: 10.3969/j.issn.1001-0548.2017.06.013
Abstract:
Direct current (DC) ionized field generator plays an important role in the test and calibration of electric field sensors under the condition of ionized field. Traditional DC ionized field generator is difficult to meet the development needs of novel electric field sensors and inconvenient to apply in outdoor fields for its large volume. This paper presents a reduced-scale DC ionized field generator. Based on theoretical calculations and finite element simulation, the critical parameters of device size and structure are analyzed and optimized. The structure is optimized and the fringing field effect is eliminated by equaling potential at the edge of the parallel plate. So the uniform electric field region between the parallel plates is increased and the uniformity error of electric field is reduced. The experimental results show that the relative average deviation of the ion current intensity at different places of the ionized field is only 1.66% when the voltage of corona wires is 7 kV. The reduced-scale DC ionized field generator presented in this paper can generate the uniform ionized field.
Direct current (DC) ionized field generator plays an important role in the test and calibration of electric field sensors under the condition of ionized field. Traditional DC ionized field generator is difficult to meet the development needs of novel electric field sensors and inconvenient to apply in outdoor fields for its large volume. This paper presents a reduced-scale DC ionized field generator. Based on theoretical calculations and finite element simulation, the critical parameters of device size and structure are analyzed and optimized. The structure is optimized and the fringing field effect is eliminated by equaling potential at the edge of the parallel plate. So the uniform electric field region between the parallel plates is increased and the uniformity error of electric field is reduced. The experimental results show that the relative average deviation of the ion current intensity at different places of the ionized field is only 1.66% when the voltage of corona wires is 7 kV. The reduced-scale DC ionized field generator presented in this paper can generate the uniform ionized field.
Fast Identification of Inside and Outside Faults of HVDC Based on Frequency Spectrum Characteristics
2017, 46(6): 871-876.
doi: 10.3969/j.issn.1001-0548.2017.06.014
Abstract:
Fast identification of internal and external faults of high voltage direct current (HVDC) is the basis of protection. Due to the influence of direct current (DC) filter, smoothing reactor and line distribution capacitance, there exists a big difference of physical boundary which the DC current transmits through to the relay location when internal and external faults occur. Therefore, the energy distribution of DC current frequency band is obviously different. In this paper, the DC current signals are decomposed by the ensemble empirical mode decomposition (EEMD) method, and the signals are decomposed into the sum of several intrinsic mode components (IMF). Then, the energy of each modal component is calculated. By comparing and analyzing, the distinguishing features are identified, and then the energy ratio index is defined to distinguish the normal, internal fault, external fault on both sides. This method only uses the DC current signal, which is easy to implement, and can meet the requirements of rapidity and selectivity. Finally, the simulation and analysis of a large number of faults in HVDC under various operating conditions verify the effectiveness and robustness of the proposed method.
Fast identification of internal and external faults of high voltage direct current (HVDC) is the basis of protection. Due to the influence of direct current (DC) filter, smoothing reactor and line distribution capacitance, there exists a big difference of physical boundary which the DC current transmits through to the relay location when internal and external faults occur. Therefore, the energy distribution of DC current frequency band is obviously different. In this paper, the DC current signals are decomposed by the ensemble empirical mode decomposition (EEMD) method, and the signals are decomposed into the sum of several intrinsic mode components (IMF). Then, the energy of each modal component is calculated. By comparing and analyzing, the distinguishing features are identified, and then the energy ratio index is defined to distinguish the normal, internal fault, external fault on both sides. This method only uses the DC current signal, which is easy to implement, and can meet the requirements of rapidity and selectivity. Finally, the simulation and analysis of a large number of faults in HVDC under various operating conditions verify the effectiveness and robustness of the proposed method.
2017, 46(6): 877-882.
doi: 10.3969/j.issn.1001-0548.2017.06.015
Abstract:
An image stitching method for two images with parallax taking at different viewpoints is proposed based on the planar similarity among matching pairs of feature points. This method makes use of the property that feature points belonging to the same plane often share the same transformation matrix. By defining the planar similarity measure between feature point pairs, the missed matching rate is effectively decreased, and the image registration accuracy is improved. Subsequently, we adopt a graph cut-based algorithm to obtain the optimal stitching line. Experimental results on several datasets have demonstrated that our method outperforms the current state-of-art methods with a better anti-parallax robustness.
An image stitching method for two images with parallax taking at different viewpoints is proposed based on the planar similarity among matching pairs of feature points. This method makes use of the property that feature points belonging to the same plane often share the same transformation matrix. By defining the planar similarity measure between feature point pairs, the missed matching rate is effectively decreased, and the image registration accuracy is improved. Subsequently, we adopt a graph cut-based algorithm to obtain the optimal stitching line. Experimental results on several datasets have demonstrated that our method outperforms the current state-of-art methods with a better anti-parallax robustness.
2017, 46(6): 883-889.
doi: 10.3969/j.issn.1001-0548.2017.06.016
Abstract:
As the mobile phone plays a more important role in our life, the problem about security and privacy of smart phone become more prominent. To solve this problem, this paper presents an approach to implement more virtual phone (VP), which is based on Linux container technology, running two or more Android systems in a single smart phone device. In order to allow each VP uses devices concurrently, we present a virtualization technology based on device proxy, and realize it on radio device. A prototype system is implemented on Nubia Z7max smartphone and the functionality of virtualization, data isolation etc. are tested. The experiment results show that our approach is useful and feasible. Each VP can simultaneously shares devices, user's data about devices and applications are isolated between isolated Android systems, and the system cost is kept in allowable range. Due to the VPs are isolated each other, there are three benefits:this approach can protect the user's privacy effectively, even one VP is corrupted the whole system can still work, and it also can satisfy user's personalized demand because the VP's functions can be customized by application scenarios and user's requirements.
As the mobile phone plays a more important role in our life, the problem about security and privacy of smart phone become more prominent. To solve this problem, this paper presents an approach to implement more virtual phone (VP), which is based on Linux container technology, running two or more Android systems in a single smart phone device. In order to allow each VP uses devices concurrently, we present a virtualization technology based on device proxy, and realize it on radio device. A prototype system is implemented on Nubia Z7max smartphone and the functionality of virtualization, data isolation etc. are tested. The experiment results show that our approach is useful and feasible. Each VP can simultaneously shares devices, user's data about devices and applications are isolated between isolated Android systems, and the system cost is kept in allowable range. Due to the VPs are isolated each other, there are three benefits:this approach can protect the user's privacy effectively, even one VP is corrupted the whole system can still work, and it also can satisfy user's personalized demand because the VP's functions can be customized by application scenarios and user's requirements.
2017, 46(6): 890-895.
doi: 10.3969/j.issn.1001-0548.2017.06.017
Abstract:
The performance of task scheduling algorithm on heterogeneous MPSoC is affected by heterogeneous cores, run-time load and tasks dependencies. A novel load-aware task scheduling algorithm is proposed on heterogeneous MPSoC, which divides task-set into task-subsets based on tasks dependencies, computation overhead and communication overhead. In considering the core's load state, task-subsets are dispatched to appropriate cores by maximum weight matching of weighted bipartite graph, which improves the overall efficiency of task-set. Simulation results show that the proposed algorithm can reduce the length of task-set scheduling and improve the utilization of cores.
The performance of task scheduling algorithm on heterogeneous MPSoC is affected by heterogeneous cores, run-time load and tasks dependencies. A novel load-aware task scheduling algorithm is proposed on heterogeneous MPSoC, which divides task-set into task-subsets based on tasks dependencies, computation overhead and communication overhead. In considering the core's load state, task-subsets are dispatched to appropriate cores by maximum weight matching of weighted bipartite graph, which improves the overall efficiency of task-set. Simulation results show that the proposed algorithm can reduce the length of task-set scheduling and improve the utilization of cores.
2017, 46(6): 896-901.
doi: 10.3969/j.issn.1001-0548.2017.06.018
Abstract:
Aiming at the major issues for data over-generalization and no unique attributes of K-anonymity model, a modified K-anonymity algorithm based on multiple attributes generalization is proposed in this paper. The conception of attribute approximation degree is introduced which describes the discrete degree of quasi-identifiers, and determines the candidate quasi-identifier attribute to be generalized. In the meantime, breadth-first generalization is exploited to avoid over-generalization and meets the K-anonymity requirements ultimately. The experimental results show that the new K-anonymity algorithm based on multiple attribute generalization can improve data precision and its efficiency is equal to Datafly algorithm. The proposed algorithm can effectively solve the issue of generalization attribute selecting when quasi-identifiers are not unique, the over-generalization of quasi-identifiers attributes can be avoided, and the usability of data can be improved.
Aiming at the major issues for data over-generalization and no unique attributes of K-anonymity model, a modified K-anonymity algorithm based on multiple attributes generalization is proposed in this paper. The conception of attribute approximation degree is introduced which describes the discrete degree of quasi-identifiers, and determines the candidate quasi-identifier attribute to be generalized. In the meantime, breadth-first generalization is exploited to avoid over-generalization and meets the K-anonymity requirements ultimately. The experimental results show that the new K-anonymity algorithm based on multiple attribute generalization can improve data precision and its efficiency is equal to Datafly algorithm. The proposed algorithm can effectively solve the issue of generalization attribute selecting when quasi-identifiers are not unique, the over-generalization of quasi-identifiers attributes can be avoided, and the usability of data can be improved.
2017, 46(6): 902-906, 948.
doi: 10.3969/j.issn.1001-0548.2017.06.019
Abstract:
The botnet has been one of the most common threats to the network security since it exploits multiple malicious codes like worm, Trojans, Rootkit, etc. toperform thedenial-of-service attack, send phishing links, and provide malicious services. Peer-to-peer (P2P) botnet is more difficult to be detected compared with IRC, HTTP and other types of botnets because it has typical features of the centralization and distribution. To solve these problems, we propose an effective two-stage traffic classification method to detect P2P botnet traffic based on both non-P2P traffic filtering mechanism and machine learning techniques on conversation features. At the first stage, the non-P2P packages are filtered to reduce the amount of network traffic, according to well-known ports, DNS query, and flow counting. At the second stage, the conversation features based on data flow features and flow similarity are extracted. Finally, the P2P botnet is detected by using Random Forest based on the decision tree model. Experimental evaluations on UNB ISCX botnet dataset shows that our two-stage detection method has a higher accuracy than traditional P2P botnet detection methods.
The botnet has been one of the most common threats to the network security since it exploits multiple malicious codes like worm, Trojans, Rootkit, etc. toperform thedenial-of-service attack, send phishing links, and provide malicious services. Peer-to-peer (P2P) botnet is more difficult to be detected compared with IRC, HTTP and other types of botnets because it has typical features of the centralization and distribution. To solve these problems, we propose an effective two-stage traffic classification method to detect P2P botnet traffic based on both non-P2P traffic filtering mechanism and machine learning techniques on conversation features. At the first stage, the non-P2P packages are filtered to reduce the amount of network traffic, according to well-known ports, DNS query, and flow counting. At the second stage, the conversation features based on data flow features and flow similarity are extracted. Finally, the P2P botnet is detected by using Random Forest based on the decision tree model. Experimental evaluations on UNB ISCX botnet dataset shows that our two-stage detection method has a higher accuracy than traditional P2P botnet detection methods.
2017, 46(6): 907-912.
doi: 10.3969/j.issn.1001-0548.2017.06.020
Abstract:
Recommendation algorithms have been commonly adopted in many fields. However, traditional recommendation algorithms fail to achieve the expected recommendation results if they are applied to predict browsing behaviors of the mobile users and further to recommend personalized content to the mobile users. By analyzing the Internet browsing data of the mobile users, this paper proposes a recommendation model based on browsing data of mobile users, denoted as RMBDMU, to predict the future browsing activities of the mobile users and take them as the bases to recommend contents to the mobile users. An experiment on the Internet browsing behavior data of the real mobile users is conducted to verify the effectiveness of the model. The experiment result shows that the recommendation model based on browsing data of mobile users is more effective than the traditional recommendation algorithms.
Recommendation algorithms have been commonly adopted in many fields. However, traditional recommendation algorithms fail to achieve the expected recommendation results if they are applied to predict browsing behaviors of the mobile users and further to recommend personalized content to the mobile users. By analyzing the Internet browsing data of the mobile users, this paper proposes a recommendation model based on browsing data of mobile users, denoted as RMBDMU, to predict the future browsing activities of the mobile users and take them as the bases to recommend contents to the mobile users. An experiment on the Internet browsing behavior data of the real mobile users is conducted to verify the effectiveness of the model. The experiment result shows that the recommendation model based on browsing data of mobile users is more effective than the traditional recommendation algorithms.
2017, 46(6): 913-919.
doi: 10.3969/j.issn.1001-0548.2017.06.021
Abstract:
With the rise of deep learning waves, the full force of deep learning methods has hit the Natural Language Process (NLP) and ushered in amazing technological advances in many different application areas of NLP. In this article, we firstly present the development history, main advantages and research situation of deep learning. Secondly, in terms of both feature representation and model theory, we introduces the neural language model and word embedding as the entry point, and present an overview of modeling and implementations of Deep Neural Network (DNN). Then we focus on the newest deep learning models with their wonderful and competitive performances related to different NLP tasks. At last, we discuss and summarize the existing problems of deep learning in NLP with the possible future directions.
With the rise of deep learning waves, the full force of deep learning methods has hit the Natural Language Process (NLP) and ushered in amazing technological advances in many different application areas of NLP. In this article, we firstly present the development history, main advantages and research situation of deep learning. Secondly, in terms of both feature representation and model theory, we introduces the neural language model and word embedding as the entry point, and present an overview of modeling and implementations of Deep Neural Network (DNN). Then we focus on the newest deep learning models with their wonderful and competitive performances related to different NLP tasks. At last, we discuss and summarize the existing problems of deep learning in NLP with the possible future directions.
2017, 46(6): 920-925.
doi: 10.3969/j.issn.1001-0548.2017.06.022
Abstract:
Completion time and accuracy are the most important attributes of processing products' business, however, single attribute optimization algorithm only can optimize one attribute, let alone balancing these two attributes dynamically. In order to fix this problem, a serial reduction algorithm based on directed acyclic graph is proposed. The algorithm constraints each tasks' activity section by using backwards iterative eduction to choose appropriate service for achieving the optimization of these two attributes. Statistical data shows that serial reduction algorithm does get an optimized path with time and accuracy balance, but its optimization efficiency is limited by the completion deadline and the number of tasks. The research conclusion provides a certain theoretical reference for the optimization of production scheduling.
Completion time and accuracy are the most important attributes of processing products' business, however, single attribute optimization algorithm only can optimize one attribute, let alone balancing these two attributes dynamically. In order to fix this problem, a serial reduction algorithm based on directed acyclic graph is proposed. The algorithm constraints each tasks' activity section by using backwards iterative eduction to choose appropriate service for achieving the optimization of these two attributes. Statistical data shows that serial reduction algorithm does get an optimized path with time and accuracy balance, but its optimization efficiency is limited by the completion deadline and the number of tasks. The research conclusion provides a certain theoretical reference for the optimization of production scheduling.
2017, 46(6): 926-933.
doi: 10.3969/j.issn.1001-0548.2017.06.023
Abstract:
The output results of clone code detection tool cannot be directly refactored because of the two reasons:one is the false positives of clone inconsistency related bugs detection and the other is that all the detected clones cannot be suitable for refactoring. Therefore, the output results of clone code detection tool need to be pre-processed for reducing the error checking of cloning inconsistencies defect. A pre-processing approach combing adaptive K-nearest neighbor clustering with program dependence graph is proposed in this paper to solve these problems. First, adaptive K-nearest neighbor clustering and program dependence graph are used to reduce the false positives of clones inconsistency related bugs detection. And then the refactorable clone code is identified to reduce the cost of clone maintenance. The results of the study show that our approach not only effectively prunes the false positives of clone inconsistency related bugs but also eliminates the gap between clone code detection and clone refactoring. Therefore, our method contributes to improving the quality of the software and decreasing the cost of software maintenance.
The output results of clone code detection tool cannot be directly refactored because of the two reasons:one is the false positives of clone inconsistency related bugs detection and the other is that all the detected clones cannot be suitable for refactoring. Therefore, the output results of clone code detection tool need to be pre-processed for reducing the error checking of cloning inconsistencies defect. A pre-processing approach combing adaptive K-nearest neighbor clustering with program dependence graph is proposed in this paper to solve these problems. First, adaptive K-nearest neighbor clustering and program dependence graph are used to reduce the false positives of clones inconsistency related bugs detection. And then the refactorable clone code is identified to reduce the cost of clone maintenance. The results of the study show that our approach not only effectively prunes the false positives of clone inconsistency related bugs but also eliminates the gap between clone code detection and clone refactoring. Therefore, our method contributes to improving the quality of the software and decreasing the cost of software maintenance.
2017, 46(6): 934-941.
doi: 10.3969/j.issn.1001-0548.2017.06.024
Abstract:
In order to eliminate noise and preserve details in image, an algorithm of image denoising based on visual receptive fields properties is proposed. Based on neuron electrophysiology research result, an image denoising processing has been realized by simulating adaptive mechanism in primary visual cortex and response characteristics of visual receptive fields. First, noise is detected by a small scale template. Then, according to the size and the location of the noise, an ON/OFF receptive field model is applied to adaptively deal with the noise. Finally, the brightness of the image is adjusted. Compared with some current denoising methods, experimental results show that textures and edges information in images processed by this proposed algorithm are better preserved. It is superior to other methods in objective image quality indexes, such as peak signal to noise ratio (PSNR) and mean squared error (MSE). It can not only remove noise in image process, but has ability to strengthen image edge details as well.
In order to eliminate noise and preserve details in image, an algorithm of image denoising based on visual receptive fields properties is proposed. Based on neuron electrophysiology research result, an image denoising processing has been realized by simulating adaptive mechanism in primary visual cortex and response characteristics of visual receptive fields. First, noise is detected by a small scale template. Then, according to the size and the location of the noise, an ON/OFF receptive field model is applied to adaptively deal with the noise. Finally, the brightness of the image is adjusted. Compared with some current denoising methods, experimental results show that textures and edges information in images processed by this proposed algorithm are better preserved. It is superior to other methods in objective image quality indexes, such as peak signal to noise ratio (PSNR) and mean squared error (MSE). It can not only remove noise in image process, but has ability to strengthen image edge details as well.
2017, 46(6): 942-948.
doi: 10.3969/j.issn.1001-0548.2017.06.025
Abstract:
Liver fibrosis is the intermediate stage from chronic liver disease to cirrhosis, the quantification of stiffness of different liver fibrosis stages has important significance to clinic application. To overcome the shortcomings that elasticity detection is not yet accurate to quantitatively measure the stiffness of liver fibrosis, a new method based on acoustic radiation force impulse (ARFI) for the elastic coefficient quantification of liver tissue is proposed. In this paper, ultrasound echo signals are collected before and after the elastic tissue pushed by acoustic radiation forces to implement the strain detection by the cumulative phase autocorrelation, and the results shows that the proposed method is feasible to assess the degree of liver fibrosis. The relationship between the elasticity coefficient and the strain of the stimulated tissue is established by the Voigt viscoelastic model to obtain the absolute elastic modulus of different stages of liver fibrosis. Experiments on different fibrosis stages of rabbit liver show that the longitudinal displacement obtained using single radiation force is not stable, so the average longitudinal displacement under a variety of intensity and pulse length radiation forces is used. The elastic coefficients of the different stages of liver fibrosis are:F0:(11.95±1.91) kPa, F1:(13.28±1.89) kPa, F2:(15.40±1.98) kPa, F3:(16.83±2.01) kPa, F4:(18.52±2.28) kPa. Results illustrate that the rabbit liver with different levels of liver fibrosis is distinguished and the elastic parameters are obtained. This result provides a new means for the accurate examination and diagnosis of liver fibrosis in clinic.
Liver fibrosis is the intermediate stage from chronic liver disease to cirrhosis, the quantification of stiffness of different liver fibrosis stages has important significance to clinic application. To overcome the shortcomings that elasticity detection is not yet accurate to quantitatively measure the stiffness of liver fibrosis, a new method based on acoustic radiation force impulse (ARFI) for the elastic coefficient quantification of liver tissue is proposed. In this paper, ultrasound echo signals are collected before and after the elastic tissue pushed by acoustic radiation forces to implement the strain detection by the cumulative phase autocorrelation, and the results shows that the proposed method is feasible to assess the degree of liver fibrosis. The relationship between the elasticity coefficient and the strain of the stimulated tissue is established by the Voigt viscoelastic model to obtain the absolute elastic modulus of different stages of liver fibrosis. Experiments on different fibrosis stages of rabbit liver show that the longitudinal displacement obtained using single radiation force is not stable, so the average longitudinal displacement under a variety of intensity and pulse length radiation forces is used. The elastic coefficients of the different stages of liver fibrosis are:F0:(11.95±1.91) kPa, F1:(13.28±1.89) kPa, F2:(15.40±1.98) kPa, F3:(16.83±2.01) kPa, F4:(18.52±2.28) kPa. Results illustrate that the rabbit liver with different levels of liver fibrosis is distinguished and the elastic parameters are obtained. This result provides a new means for the accurate examination and diagnosis of liver fibrosis in clinic.
2017, 46(6): 949-954.
doi: 10.3969/j.issn.1001-0548.2017.06.026
Abstract:
Impedance control is an effective method to deal with contact task of robot, but this method can only guarantee the stability of system for assumed range of environments. Aiming at this problem, this paper proposes a new adaptive energy boundary method (EBM), which improves system performance by on-line estimation of control parameters, and guarantees the stability of system. Under the control method, the system can keep expected contact force stably, and have strong robustness when contact with uncertain environment. To verify the effectiveness of the proposed method, theoretical and simulation researches are conducted to pneumatic hydraulic combination compliant control system, which prove the effectiveness of the method.
Impedance control is an effective method to deal with contact task of robot, but this method can only guarantee the stability of system for assumed range of environments. Aiming at this problem, this paper proposes a new adaptive energy boundary method (EBM), which improves system performance by on-line estimation of control parameters, and guarantees the stability of system. Under the control method, the system can keep expected contact force stably, and have strong robustness when contact with uncertain environment. To verify the effectiveness of the proposed method, theoretical and simulation researches are conducted to pneumatic hydraulic combination compliant control system, which prove the effectiveness of the method.
2017, 46(6): 955-960.
doi: 10.3969/j.issn.1001-0548.2017.06.027
Abstract:
A transmission error analytical mothed of dual-eccentric gears is proposed. The relation among instantaneous node, transmission ratio error, and transmission error is deduced. In order to demonstrate the validity of the analytical method, the solid model is constructed in the dynamics simulation software RecurDyn and the simulation transmission error is obtained. By comparison, the simulation transmission error curve agrees well with the analytical one. On this basis, dynamic transmission error under meshing frequency varying load is explored and the relation between dynamic transmission error, the theoretical transmission error and backlash is studied simultaneously. Finally, the optimum initial phase has been given to decrease the transmission error under the circumstance of fixed eccentricity
A transmission error analytical mothed of dual-eccentric gears is proposed. The relation among instantaneous node, transmission ratio error, and transmission error is deduced. In order to demonstrate the validity of the analytical method, the solid model is constructed in the dynamics simulation software RecurDyn and the simulation transmission error is obtained. By comparison, the simulation transmission error curve agrees well with the analytical one. On this basis, dynamic transmission error under meshing frequency varying load is explored and the relation between dynamic transmission error, the theoretical transmission error and backlash is studied simultaneously. Finally, the optimum initial phase has been given to decrease the transmission error under the circumstance of fixed eccentricity
