ISSN 
2008 Vol. 37, No. 4
2008, 37(4): 481-484.
Abstract:
The systematic generalized repeat-accumulate (GRA) code is constituted by a repeater, an interleaver, a combiner and a generalized accumulator. Under the belief propagation (BP) decoding of low density parity check (LDPC) codes, the performance of the GRA codes be affected by small cycles of the sparse parity check matrix which depends on encoding method. In this paper we present an optimized method for a class of GRA codes design. The parity check matrix is constructed based on the joint design between interleaver and combiner under the demand of no 4-cycles. With the simple encoding, simulation results show that the class of GRA codes outperforms conventional RA codes.
The systematic generalized repeat-accumulate (GRA) code is constituted by a repeater, an interleaver, a combiner and a generalized accumulator. Under the belief propagation (BP) decoding of low density parity check (LDPC) codes, the performance of the GRA codes be affected by small cycles of the sparse parity check matrix which depends on encoding method. In this paper we present an optimized method for a class of GRA codes design. The parity check matrix is constructed based on the joint design between interleaver and combiner under the demand of no 4-cycles. With the simple encoding, simulation results show that the class of GRA codes outperforms conventional RA codes.
2008, 37(4): 485-488.
Abstract:
A genetic-algorithm (GA) based on multiuser detection (MUD) is proposed for the antennadiversity-assisted multicarrier code-division multiple-access (MC-CDMA) systems in the frequency-selective fading channel. Two kinds of GA-based individual-selection strategies are investigated with three different cost functions, which are log-likelihood function (LLF), squared error and squared phase error, respectively. Simulation analysis shows that:with the same cost function, the individual-selection strategy based on Pareto optimality criterion has better performance than the linear combing criterion; with the same individual-selection strategy, the cost function based on squared phase error has the better bit error rate (BER) performance and the better near-far resistance performance than those of two other cost functions.
A genetic-algorithm (GA) based on multiuser detection (MUD) is proposed for the antennadiversity-assisted multicarrier code-division multiple-access (MC-CDMA) systems in the frequency-selective fading channel. Two kinds of GA-based individual-selection strategies are investigated with three different cost functions, which are log-likelihood function (LLF), squared error and squared phase error, respectively. Simulation analysis shows that:with the same cost function, the individual-selection strategy based on Pareto optimality criterion has better performance than the linear combing criterion; with the same individual-selection strategy, the cost function based on squared phase error has the better bit error rate (BER) performance and the better near-far resistance performance than those of two other cost functions.
2008, 37(4): 489-492.
Abstract:
An efficient method that can blindly estimate and synchronize to PN sequence of direct sequence spread spectrum (DS-SS) signal quickly is presented in a non-cooperative context. The method is based on the character of the DS-SS signal, firstly the period of PN sequence is estimated with a second-order cyclic-cumulant, and then the method of segmented cross-correlation is used to identify the synchronous start bit of the PN codes. The intercepted signal is divided into windows, from which the cross-correlation average is computed, and then the multiple correlations are utilized to estimate the PN sequence. Both theoretical analysis and simulations show that this method can get a good estimation without prior knowledge even if the intercepted signal is far below the noise, and it also has no hypothesis on the nature of the PN code sequence.
An efficient method that can blindly estimate and synchronize to PN sequence of direct sequence spread spectrum (DS-SS) signal quickly is presented in a non-cooperative context. The method is based on the character of the DS-SS signal, firstly the period of PN sequence is estimated with a second-order cyclic-cumulant, and then the method of segmented cross-correlation is used to identify the synchronous start bit of the PN codes. The intercepted signal is divided into windows, from which the cross-correlation average is computed, and then the multiple correlations are utilized to estimate the PN sequence. Both theoretical analysis and simulations show that this method can get a good estimation without prior knowledge even if the intercepted signal is far below the noise, and it also has no hypothesis on the nature of the PN code sequence.
2008, 37(4): 493-496.
Abstract:
Because the estimation of instantaneous frequency (IF) can be easily affected by noise, a method of noise reduction for Chirp signal based on K-L orthogonal division is presented. The signal is concentrated to a principal component, but the noise is equally distributed to several components. Thus, the SNR is improved. Both analysis and simulation indicate that this method works well and makes the estimation of IF more accurate. And the SNR can be improved over 6 dB. Moreover, associated with the characteristic of Chirp's auto-correlation function, the simplification of this method is considered for some applications.
Because the estimation of instantaneous frequency (IF) can be easily affected by noise, a method of noise reduction for Chirp signal based on K-L orthogonal division is presented. The signal is concentrated to a principal component, but the noise is equally distributed to several components. Thus, the SNR is improved. Both analysis and simulation indicate that this method works well and makes the estimation of IF more accurate. And the SNR can be improved over 6 dB. Moreover, associated with the characteristic of Chirp's auto-correlation function, the simplification of this method is considered for some applications.
2008, 37(4): 497-499,507.
Abstract:
In this paper we present a four dimensional (4D) multilevel trellis coded continuous phase modulation (CPM) scheme. In order to use a coherent linear receiver the transmitted signal is pre-coded so that the information is in the received phase and not in the phase difference between the two consecutive phase samples. The receiver is composed of a simple quadrature demodulator, followed by a symbol-rate sampler and a Viterbi decoder matched to the code trellis. BER performance shows 1 dB improvement at the BER of 10-5.
In this paper we present a four dimensional (4D) multilevel trellis coded continuous phase modulation (CPM) scheme. In order to use a coherent linear receiver the transmitted signal is pre-coded so that the information is in the received phase and not in the phase difference between the two consecutive phase samples. The receiver is composed of a simple quadrature demodulator, followed by a symbol-rate sampler and a Viterbi decoder matched to the code trellis. BER performance shows 1 dB improvement at the BER of 10-5.
2008, 37(4): 500-503.
Abstract:
Based on the introduction of the space-time time-frequency-shift keying (ST-TFSK) systems, the paper deduces the noncoherent ML decision metric at the receiver with the knowledge of relative delay. The performance of the ST-TFSK systems in the presence of distinct normalized relative delay is discussed for the different SNRs, and the relative delay sensitivity between ST-TFSK systems and quaternary ST-FSK systems is compored. Both theoretical analysis and simulation results show that, (1) lower SNR lessens the normalized relative delay sensitivity of ST-TFSK systems; (2) the sensitivity of ST-TFSK systems is less than that of quaternary ST-FSK systems.
Based on the introduction of the space-time time-frequency-shift keying (ST-TFSK) systems, the paper deduces the noncoherent ML decision metric at the receiver with the knowledge of relative delay. The performance of the ST-TFSK systems in the presence of distinct normalized relative delay is discussed for the different SNRs, and the relative delay sensitivity between ST-TFSK systems and quaternary ST-FSK systems is compored. Both theoretical analysis and simulation results show that, (1) lower SNR lessens the normalized relative delay sensitivity of ST-TFSK systems; (2) the sensitivity of ST-TFSK systems is less than that of quaternary ST-FSK systems.
2008, 37(4): 504-507.
Abstract:
The data transmission rate will be update to 100 Mb/s in future mobile communication system, which require to supply multimedia traffic. So, high spectrum effective and great capacity techniques need to be researched. In this paper, we put forward a random access information bearing method, in which a constant amplitude zero auto-correlation (CAZAC) sequences is added by a cyclic code shift keying (CCSK) sequences, and the CCSK sequences are constructed by circle shifting of m sequences. With the method, the mutual interference of two sequences will be reduced. To cancel the interference, one power ratio adjustment technique is proposed, which is able to improve detection performance dramatically by simulation.
The data transmission rate will be update to 100 Mb/s in future mobile communication system, which require to supply multimedia traffic. So, high spectrum effective and great capacity techniques need to be researched. In this paper, we put forward a random access information bearing method, in which a constant amplitude zero auto-correlation (CAZAC) sequences is added by a cyclic code shift keying (CCSK) sequences, and the CCSK sequences are constructed by circle shifting of m sequences. With the method, the mutual interference of two sequences will be reduced. To cancel the interference, one power ratio adjustment technique is proposed, which is able to improve detection performance dramatically by simulation.
2008, 37(4): 508-510,514.
Abstract:
An equivalent circuit for receiving antennas, which is composed of open-circuit voltage source and radiation impedance, is derived rigorously from electromagnetic boundary conditions based both on reciprocity theorem and the concept of reaction. The parameters of the equivalent circuit are related to the selected current distribution reacted with the electric field. Illuminated by the numerical example of a dipole, it shows that the equivalent circuit with open-circuit voltage source has a clear physical meaning and it is more suitable in the analysis of receiving systems.
An equivalent circuit for receiving antennas, which is composed of open-circuit voltage source and radiation impedance, is derived rigorously from electromagnetic boundary conditions based both on reciprocity theorem and the concept of reaction. The parameters of the equivalent circuit are related to the selected current distribution reacted with the electric field. Illuminated by the numerical example of a dipole, it shows that the equivalent circuit with open-circuit voltage source has a clear physical meaning and it is more suitable in the analysis of receiving systems.
2008, 37(4): 511-514.
Abstract:
This paper presents and analyzes a constant modulus algorithm (CMA) adaptive beamforming algorithm which is based on conjugate gradient method. This algorithm focuses on a new technique for data block modificatory method with conjugate gradient, and overcomes the shortcoming of traditional CMA algorithms, such as slow convergence speed or vast complexity. An analysis is given to find the misadjustments performance in MCG-CMA algorithm with different sampling length. Computer simulations show that the algorithm has better convergence performance and better signal to interference plus noise ratio (SINR) capability than LS-CMA and SCG-CMA algorithm.
This paper presents and analyzes a constant modulus algorithm (CMA) adaptive beamforming algorithm which is based on conjugate gradient method. This algorithm focuses on a new technique for data block modificatory method with conjugate gradient, and overcomes the shortcoming of traditional CMA algorithms, such as slow convergence speed or vast complexity. An analysis is given to find the misadjustments performance in MCG-CMA algorithm with different sampling length. Computer simulations show that the algorithm has better convergence performance and better signal to interference plus noise ratio (SINR) capability than LS-CMA and SCG-CMA algorithm.
2008, 37(4): 515-518.
Abstract:
Reducing location management signaling overhead is an important aspect in personal communication service (PCS) networks design. In implicit deregistration algorithms, the visitor location register (VLR) user previously visited does not perform deregistration. The traditional implicit deregistration algorithms have following disadvantages:(1) the system needs a large database since a record in VLR may be invalid; (2) the maintenance of VLR is difficult; (3) when a large number of users enter a full VLR, the system will create a mass of extra registration cost. Aiming at solving these problems in traditional implicit algorithms, we present a new implicit scheme in which a database periodically deletes invalid records. The proposed scheme can effectively limit the storage volume for invalid records. Simulation results and running experiences show that the proposed scheme is very feasible.
Reducing location management signaling overhead is an important aspect in personal communication service (PCS) networks design. In implicit deregistration algorithms, the visitor location register (VLR) user previously visited does not perform deregistration. The traditional implicit deregistration algorithms have following disadvantages:(1) the system needs a large database since a record in VLR may be invalid; (2) the maintenance of VLR is difficult; (3) when a large number of users enter a full VLR, the system will create a mass of extra registration cost. Aiming at solving these problems in traditional implicit algorithms, we present a new implicit scheme in which a database periodically deletes invalid records. The proposed scheme can effectively limit the storage volume for invalid records. Simulation results and running experiences show that the proposed scheme is very feasible.
2008, 37(4): 519-522.
Abstract:
In the paper, considering the problem of robust resource provisioning in WDM mesh networks under the uncertain traffic matrix (hose model), we design the resilient WDM mesh networks. The strategy of dedicated-path protection is used. We propose two heuristic algorithms whose optimization objective is to minimize total network cost. Some comparisons for these algorithms by simulations, show that the maximal resource utilization (MRU) algorithm has fewer total network cost.
In the paper, considering the problem of robust resource provisioning in WDM mesh networks under the uncertain traffic matrix (hose model), we design the resilient WDM mesh networks. The strategy of dedicated-path protection is used. We propose two heuristic algorithms whose optimization objective is to minimize total network cost. Some comparisons for these algorithms by simulations, show that the maximal resource utilization (MRU) algorithm has fewer total network cost.
2008, 37(4): 523-526.
Abstract:
In order to select optimal multicast service node (MSN) of layered overlay network, a hybrid real-coded genetic algorithm (HRCGA) is proposed. The fitness function with penalty operator is created to prevent bad chromosomes participating evolution. Also, an evolving control strategy is proposed to enhance the local search ability. Results of computer simulation show that HRCGA not only avoids converging to local minimum value, but also is robust to initialization. And the global search ability is enhanced compared with SGA.
In order to select optimal multicast service node (MSN) of layered overlay network, a hybrid real-coded genetic algorithm (HRCGA) is proposed. The fitness function with penalty operator is created to prevent bad chromosomes participating evolution. Also, an evolving control strategy is proposed to enhance the local search ability. Results of computer simulation show that HRCGA not only avoids converging to local minimum value, but also is robust to initialization. And the global search ability is enhanced compared with SGA.
2008, 37(4): 527-529.
Abstract:
Synchronization algorithm for orthogonal frequency division multiplex (OFDM) systems is discussed. A joint algorithm is proposed based on cyclic prefix and virtual carriers. This algorithm does not need assistant data hence decreases system redundancy. In the algorithm, the symbol synchronization and the fractional frequency offset are obtained by using ML algorithm based on the cyclic prefix property, and the integral frequency offset is obtained by the position offset of virtual carriers. The results show the proposed algorithm not only achieves symbol synchronization and large range of frequency offset estimation, without increased calculation complexity and system redundancy, but also can be used for fast synchronization.
Synchronization algorithm for orthogonal frequency division multiplex (OFDM) systems is discussed. A joint algorithm is proposed based on cyclic prefix and virtual carriers. This algorithm does not need assistant data hence decreases system redundancy. In the algorithm, the symbol synchronization and the fractional frequency offset are obtained by using ML algorithm based on the cyclic prefix property, and the integral frequency offset is obtained by the position offset of virtual carriers. The results show the proposed algorithm not only achieves symbol synchronization and large range of frequency offset estimation, without increased calculation complexity and system redundancy, but also can be used for fast synchronization.
2008, 37(4): 530-533.
Abstract:
In this paper, we present a novel admission control scheme for multi-priority self-organized networks. Based on bandwidth allocation scheme, we calculate the bandwidth prediction function and two upper bounds that guarantee the quality of service (QoS) of admitted real-time flows. The proposed scheme protects the throughput of active flows and prevents QoS degradation due to flow's number increases. Simulation results show the proposed admission control is feasible.
In this paper, we present a novel admission control scheme for multi-priority self-organized networks. Based on bandwidth allocation scheme, we calculate the bandwidth prediction function and two upper bounds that guarantee the quality of service (QoS) of admitted real-time flows. The proposed scheme protects the throughput of active flows and prevents QoS degradation due to flow's number increases. Simulation results show the proposed admission control is feasible.
2008, 37(4): 534-537.
Abstract:
In order to avoid broadcast storm, the energy adaptive flooding broadcast (EAB) strategy is proposed. The algorithm is based on probability rebroadcast to reduce the number of rebroadcast. According the remain energy of the nodes, EAB decides which nodes need to rebroadcast to reduce the chance of contention and collision among neighboring nodes in the networks and restrain the flooding effectively. Analyses and simulations show that adaptive flooding broadcast strategy outperforms the ordinary flooding broadcast method.
In order to avoid broadcast storm, the energy adaptive flooding broadcast (EAB) strategy is proposed. The algorithm is based on probability rebroadcast to reduce the number of rebroadcast. According the remain energy of the nodes, EAB decides which nodes need to rebroadcast to reduce the chance of contention and collision among neighboring nodes in the networks and restrain the flooding effectively. Analyses and simulations show that adaptive flooding broadcast strategy outperforms the ordinary flooding broadcast method.
2008, 37(4): 538-540,555.
Abstract:
In order to determine the position of equivalent phase centers of pyramidal horn antenna, which keep the phase of the antenna's field relative invariable in some range of the antenna's main lobe, an approach to analyze the equivalent phase centers of pyramidal horn antenna is presented in this paper. Through analyzing the far field of the pyramidal horn using its simplified model, the E and H plane phase centers and their equiphase surface width of the pyramidal horn are analyzed and calculated by using the method of moving reference point, and the relationship of deviation of equiphase surface between the phase center and equiphase surface width is achieved.
In order to determine the position of equivalent phase centers of pyramidal horn antenna, which keep the phase of the antenna's field relative invariable in some range of the antenna's main lobe, an approach to analyze the equivalent phase centers of pyramidal horn antenna is presented in this paper. Through analyzing the far field of the pyramidal horn using its simplified model, the E and H plane phase centers and their equiphase surface width of the pyramidal horn are analyzed and calculated by using the method of moving reference point, and the relationship of deviation of equiphase surface between the phase center and equiphase surface width is achieved.
2008, 37(4): 541-544.
Abstract:
Inverse synthetic aperture radar (ISAR) imaging of the non-cooperative maneuvering multi-target is a challenging task due to its time-varying orientation and the relative motion among targets. Conventional motion compensation methods assume that targets' positions are almost fixed during the imaging time. In this paper, the model of relative motion targets is established and the effect of relative motion for ISAR image is analyzed. A new algorithm for relative motion compensation based on Keystone transformation and Autoclean algorithm is proposed. The imaging results using simulation and real data validate the new relative motion compensation method.
Inverse synthetic aperture radar (ISAR) imaging of the non-cooperative maneuvering multi-target is a challenging task due to its time-varying orientation and the relative motion among targets. Conventional motion compensation methods assume that targets' positions are almost fixed during the imaging time. In this paper, the model of relative motion targets is established and the effect of relative motion for ISAR image is analyzed. A new algorithm for relative motion compensation based on Keystone transformation and Autoclean algorithm is proposed. The imaging results using simulation and real data validate the new relative motion compensation method.
2008, 37(4): 545-548.
Abstract:
By applying generalized likelihood ratio test (GLRT), This paper gives the detector of polynomial phase signal (PPS) with unknown parameters. The detector is optimal in Neyman-Pearson sense. When the power of phase polynomial is one or two respectively, periodogram and chirp Fourier transform method are the corresponding optimal detection methods. The probability density function, detection probability, and false detection probability are derived. Consequently the relationship between detection probability and false detection probability, signal energy to noise ratio, and the number of searching points in the parameter space are achieved. The simulation demonstrates the validness of the analysis.
By applying generalized likelihood ratio test (GLRT), This paper gives the detector of polynomial phase signal (PPS) with unknown parameters. The detector is optimal in Neyman-Pearson sense. When the power of phase polynomial is one or two respectively, periodogram and chirp Fourier transform method are the corresponding optimal detection methods. The probability density function, detection probability, and false detection probability are derived. Consequently the relationship between detection probability and false detection probability, signal energy to noise ratio, and the number of searching points in the parameter space are achieved. The simulation demonstrates the validness of the analysis.
2008, 37(4): 549-551.
Abstract:
Generally, range and velocity ambiguity existin pulse Doppler (PD) radars Multiple pulse recurrence frequency (PRF) is needed for resolving ambiguity in the conventional PD radars. This paper provides a technique to resolve the ambiguities with high performance, which is a computationally efficient algorithm and easy to process in a real-time mode. It is able to achieve range and velocity estimates with high precision besides resolving ambiguity by the use of the presented technique. An example and corresponding experimental results show the correctness and validity of the introduced approach. This technique can be also used in sub-Nyquist sampling and interferometer-like with multiple baselines, or others homologous systems to increase their scopes of unambiguous measurements and resolve ambiguities.
Generally, range and velocity ambiguity existin pulse Doppler (PD) radars Multiple pulse recurrence frequency (PRF) is needed for resolving ambiguity in the conventional PD radars. This paper provides a technique to resolve the ambiguities with high performance, which is a computationally efficient algorithm and easy to process in a real-time mode. It is able to achieve range and velocity estimates with high precision besides resolving ambiguity by the use of the presented technique. An example and corresponding experimental results show the correctness and validity of the introduced approach. This technique can be also used in sub-Nyquist sampling and interferometer-like with multiple baselines, or others homologous systems to increase their scopes of unambiguous measurements and resolve ambiguities.
2008, 37(4): 552-555.
Abstract:
In the system of traffic alert and collision avoidance system (TCAS), the time of closest point of approach of the aircraft, horizontal miss distance (HMD), and vertical miss distance (VMD) are the primary parameters to describe the concept of collision avoidance. Firstly, the time of Tau is explained physically which approximates the time to closest point of approach (CPA), and then the formal expression of HMD is induced via the transforming of coordinate which is expressed by relative distance, relative distance rate, and relative acceleration between aircrafts. Finally, the modified model for engineering application is considered.
In the system of traffic alert and collision avoidance system (TCAS), the time of closest point of approach of the aircraft, horizontal miss distance (HMD), and vertical miss distance (VMD) are the primary parameters to describe the concept of collision avoidance. Firstly, the time of Tau is explained physically which approximates the time to closest point of approach (CPA), and then the formal expression of HMD is induced via the transforming of coordinate which is expressed by relative distance, relative distance rate, and relative acceleration between aircrafts. Finally, the modified model for engineering application is considered.
2008, 37(4): 556-557,605.
Abstract:
The perturbation formulas of the electron paramagnetic resonance (EPR) parameters g factors g//, g⊥ and the hyperfine structure constants A//, A⊥ are established for a 3d1 ion in tetragonally distorted octahedra, by including the contributions from the p-and s-orbitals as well as the spin-orbit coupling of the ligands based on the cluster approach. The related energy separations can be obtained from the superposition model (SPM) and local structure of impurity center. These formulas are applied to the studies of the EPR parameters for the interstitial V4+ in anatase (TiO2). The calculated results of present work show better agreement than those of the previous studies with the observed values. It can be found that the contributions to the EPR parameters from the ligand orbitals and spin-orbit coupling interactions cannot be neglected for the systems with significant covalency.
The perturbation formulas of the electron paramagnetic resonance (EPR) parameters g factors g//, g⊥ and the hyperfine structure constants A//, A⊥ are established for a 3d1 ion in tetragonally distorted octahedra, by including the contributions from the p-and s-orbitals as well as the spin-orbit coupling of the ligands based on the cluster approach. The related energy separations can be obtained from the superposition model (SPM) and local structure of impurity center. These formulas are applied to the studies of the EPR parameters for the interstitial V4+ in anatase (TiO2). The calculated results of present work show better agreement than those of the previous studies with the observed values. It can be found that the contributions to the EPR parameters from the ligand orbitals and spin-orbit coupling interactions cannot be neglected for the systems with significant covalency.
2008, 37(4): 558-560.
Abstract:
The relative stability of single He defect in bcc and fcc metals is investigated using ab initio calculations based on density functional theory (DFT). The calculations reveal that for all metals involved, except for V and Nb, the substitutional position is the most stable. Furthermore, the tetrahedral site is energetically more favorable for the He interstitial than the octahedral site in the bcc metals, but the relative stability of He defects in the fcc metals is not definitive. The He formation energies in bcc Fe and fcc Ni at the tetrahedral and octahedral sites with or without spin polarization are investigated. It is interesting to find that the magnetism of host atoms does not directly affect the relative stabilities of He interstitial sites.
The relative stability of single He defect in bcc and fcc metals is investigated using ab initio calculations based on density functional theory (DFT). The calculations reveal that for all metals involved, except for V and Nb, the substitutional position is the most stable. Furthermore, the tetrahedral site is energetically more favorable for the He interstitial than the octahedral site in the bcc metals, but the relative stability of He defects in the fcc metals is not definitive. The He formation energies in bcc Fe and fcc Ni at the tetrahedral and octahedral sites with or without spin polarization are investigated. It is interesting to find that the magnetism of host atoms does not directly affect the relative stabilities of He interstitial sites.
2008, 37(4): 561-564.
Abstract:
Based on the coupled equations and dispersion equation of spiral waveguide, the numerical calculation is carried out to get the dispersion line and the coupling mechanism of the two modes is analyzed. Based on the characteristics of the linear polarization TE11 mode, line polarization TE11 pulse is applied as a probe to simulate the dispersion characteristics of the cold cavity with a three-dimensional particle in cell code. The results of computer simulations agree well with the numerical calculations. Moreover, by computer simulation a mixed mode of the electric field is obtained. Combined the computer simulations with the numerical calculations, the law of influence of the dispersion characteristics by adjusting the parameters of the slotted screw geometry is obtained.
Based on the coupled equations and dispersion equation of spiral waveguide, the numerical calculation is carried out to get the dispersion line and the coupling mechanism of the two modes is analyzed. Based on the characteristics of the linear polarization TE11 mode, line polarization TE11 pulse is applied as a probe to simulate the dispersion characteristics of the cold cavity with a three-dimensional particle in cell code. The results of computer simulations agree well with the numerical calculations. Moreover, by computer simulation a mixed mode of the electric field is obtained. Combined the computer simulations with the numerical calculations, the law of influence of the dispersion characteristics by adjusting the parameters of the slotted screw geometry is obtained.
2008, 37(4): 565-568.
Abstract:
In the paper, a novel fault diagnosis method integrating rough sets and neural network in wireless sensor network (WSN) is presented. Firstly, the decision-making table of fault diagnosis can be gained by application environment and fault characteristic in WSN. Secondly, the attribute reduction of the table of decision-making is implemented by inductive attribute reduction algorithm in rough sets theory. Finally, a set of method for fault classification is founded by hamming network. The result of simulation shows that this method has the feathers such as high veracity of diagnosis, a little expenditure of communication, low energy consumption, and strong robustness.
In the paper, a novel fault diagnosis method integrating rough sets and neural network in wireless sensor network (WSN) is presented. Firstly, the decision-making table of fault diagnosis can be gained by application environment and fault characteristic in WSN. Secondly, the attribute reduction of the table of decision-making is implemented by inductive attribute reduction algorithm in rough sets theory. Finally, a set of method for fault classification is founded by hamming network. The result of simulation shows that this method has the feathers such as high veracity of diagnosis, a little expenditure of communication, low energy consumption, and strong robustness.
2008, 37(4): 569-573.
Abstract:
A parameters learning approach for generalized takagi-sugeno (T-S) fuzzy model is proposed in this paper on the base of analysis of generalized T-S Fuzzy model. The structural parameters of the approach are denoted by the position of discrete binary particles and the parameters of membership function in the approach are denoted by the position of ordinary particles. The combination of positions of the two kind of particles composes complete premise parameters set of a model. A learning cycle consists of two phases:first, all reasoning parameters are adjusted by evolutionary iteration of particle swarm; second, all consequent parameters are estimated through orthogonal least square error algorithm. The method requests scarcely any previous information about objects, take less calculating time, and is able to obtain compact fuzzy model. The simulation result shows the validity of the approach.
A parameters learning approach for generalized takagi-sugeno (T-S) fuzzy model is proposed in this paper on the base of analysis of generalized T-S Fuzzy model. The structural parameters of the approach are denoted by the position of discrete binary particles and the parameters of membership function in the approach are denoted by the position of ordinary particles. The combination of positions of the two kind of particles composes complete premise parameters set of a model. A learning cycle consists of two phases:first, all reasoning parameters are adjusted by evolutionary iteration of particle swarm; second, all consequent parameters are estimated through orthogonal least square error algorithm. The method requests scarcely any previous information about objects, take less calculating time, and is able to obtain compact fuzzy model. The simulation result shows the validity of the approach.
2008, 37(4): 574-577.
Abstract:
The parameters of transient testing stimulus for nonlinear analog circuits greatly influence the fault diagnosis efficiency. In the course of finding the optimum stimulus, we have to develop the nonlinear analog circuits' models. Elman network which is a dynamic recurrent neural network can approximate any dynamic nonlinear system. In this paper, Elman network is used to develop the models of the fault circuits and fault free circuit, the optimum stimulus is searched with genetic algorithm. Experiment results demonstrate that the optimum stimulus achieved has high fault identification.
The parameters of transient testing stimulus for nonlinear analog circuits greatly influence the fault diagnosis efficiency. In the course of finding the optimum stimulus, we have to develop the nonlinear analog circuits' models. Elman network which is a dynamic recurrent neural network can approximate any dynamic nonlinear system. In this paper, Elman network is used to develop the models of the fault circuits and fault free circuit, the optimum stimulus is searched with genetic algorithm. Experiment results demonstrate that the optimum stimulus achieved has high fault identification.
2008, 37(4): 578-581.
Abstract:
This paper focuses on the theory, setup, and experiment of a visualization system for surface acoustic wave (SAW) distribution based on knife-edge laser probe. The surface micro-bend caused by the SAW leads to variations of incident light to an optical detector. The converted electrical signal is down-converted to intermediate frequency for detection, and the output signals including both the amplitude and phase are fed to the high-speed data-logger. Data acquisition of 2 620(x)×410(y) points in 20 min is realized, then image can be formed from the data.
This paper focuses on the theory, setup, and experiment of a visualization system for surface acoustic wave (SAW) distribution based on knife-edge laser probe. The surface micro-bend caused by the SAW leads to variations of incident light to an optical detector. The converted electrical signal is down-converted to intermediate frequency for detection, and the output signals including both the amplitude and phase are fed to the high-speed data-logger. Data acquisition of 2 620(x)×410(y) points in 20 min is realized, then image can be formed from the data.
2008, 37(4): 582-585.
Abstract:
Routing algorithm problem is one of the major issues to be resolved in wireless sensor network research. This article analyses the best hop routing algorithms hop routing, energy, and load of wireless sensor network's to achieve a balance in all the optimum network routing. The simulation shows that the results achieved in this article can successfully improve the reliability and stability of the wireless senor network routing.
Routing algorithm problem is one of the major issues to be resolved in wireless sensor network research. This article analyses the best hop routing algorithms hop routing, energy, and load of wireless sensor network's to achieve a balance in all the optimum network routing. The simulation shows that the results achieved in this article can successfully improve the reliability and stability of the wireless senor network routing.
2008, 37(4): 586-589.
Abstract:
According to the characteristics of DoS/DDoS attack, a defense model adopting data-mining technology is proposed. Based on real-time sample traffic, this model extracts trusted IP list by association analysis to filter, and evaluates packets' danger degree by adopting bayes algorithm. This model makes up disadvantages of traditional filtering based on trusted source IP, and effectively differentiates normal traffic and abnormal traffic. Experimental datum proves this model can launch real-time and effective defense against DoS/DDoS attack.
According to the characteristics of DoS/DDoS attack, a defense model adopting data-mining technology is proposed. Based on real-time sample traffic, this model extracts trusted IP list by association analysis to filter, and evaluates packets' danger degree by adopting bayes algorithm. This model makes up disadvantages of traditional filtering based on trusted source IP, and effectively differentiates normal traffic and abnormal traffic. Experimental datum proves this model can launch real-time and effective defense against DoS/DDoS attack.
2008, 37(4): 590-593.
Abstract:
RMIPv6, proposed by IETF, is an improved mobility management scheme to Mobile IP, which features employing the dynamic regional anchor points to carry out the micro mobility management inside domains. This paper analyzes the advantages and disadvantages of RMIPv6, and improves the scheme by using a method based on region discovery. Benefited from the anchor points' region advertisement and the given cost constraints, the mobile nodes can start the proper handover routine in advance, so reducing the cost effectively when mobile nodes moving from one region to another. The amended scheme can be implemented by extending the OSPF's packet header. The simulation result shows the advantage of the improved scheme in the cost of location update compared with the original RMIPv6.
RMIPv6, proposed by IETF, is an improved mobility management scheme to Mobile IP, which features employing the dynamic regional anchor points to carry out the micro mobility management inside domains. This paper analyzes the advantages and disadvantages of RMIPv6, and improves the scheme by using a method based on region discovery. Benefited from the anchor points' region advertisement and the given cost constraints, the mobile nodes can start the proper handover routine in advance, so reducing the cost effectively when mobile nodes moving from one region to another. The amended scheme can be implemented by extending the OSPF's packet header. The simulation result shows the advantage of the improved scheme in the cost of location update compared with the original RMIPv6.
2008, 37(4): 594-597.
Abstract:
Fast synchronization for remote file is widely used in many scenarios such as file system backup and restore, web mirroring, etc. A new method for remote file fast synchronization is proposed. The file state difference set is calculated at client end. The difference synchronization and rename optimization are achieved by replaying the file state difference set at server end. The generation, replay and optimization methods for the file state difference set are given. The experimental results indicate that this method offers signficant improvement over rsync. The network traffic of file content synchornization decreases remarkablely. And the network traffic of rename optimization is KB-level and independent of file length.
Fast synchronization for remote file is widely used in many scenarios such as file system backup and restore, web mirroring, etc. A new method for remote file fast synchronization is proposed. The file state difference set is calculated at client end. The difference synchronization and rename optimization are achieved by replaying the file state difference set at server end. The generation, replay and optimization methods for the file state difference set are given. The experimental results indicate that this method offers signficant improvement over rsync. The network traffic of file content synchornization decreases remarkablely. And the network traffic of rename optimization is KB-level and independent of file length.
2008, 37(4): 598-601.
Abstract:
The energy of many modern embedded systems is power-supplied by the batteries. Based on real-time operating system, this paper presents an elastic task model on energy-constrained with universalization, then designs a corresponding real-time scheduling algorithm for guaranteeing the system stabilization and avoiding failtures caused by running out the energy of the non-recharge power-supply according to the rest energy of the battery. The result shows that this model could change the periods of taks according to the rest energy of the battery effectively and timely, so the computation could be completed in their mission times.
The energy of many modern embedded systems is power-supplied by the batteries. Based on real-time operating system, this paper presents an elastic task model on energy-constrained with universalization, then designs a corresponding real-time scheduling algorithm for guaranteeing the system stabilization and avoiding failtures caused by running out the energy of the non-recharge power-supply according to the rest energy of the battery. The result shows that this model could change the periods of taks according to the rest energy of the battery effectively and timely, so the computation could be completed in their mission times.
2008, 37(4): 602-605.
Abstract:
In order to increase the access ability of high-level node in wireless ad hoc network, a novel binary negative exponential backoff (BNEB) algorithm is proposed. In this algorithm, the high-level node sets its contention window (CW) to the minimum CW of normal nodes after successful transmission, and reduces its CW as times of retransmission increased. The simulation results show that the BNEB algorithm can remarkably increase the access ability of high-level node and reduce the end-to-end delay.
In order to increase the access ability of high-level node in wireless ad hoc network, a novel binary negative exponential backoff (BNEB) algorithm is proposed. In this algorithm, the high-level node sets its contention window (CW) to the minimum CW of normal nodes after successful transmission, and reduces its CW as times of retransmission increased. The simulation results show that the BNEB algorithm can remarkably increase the access ability of high-level node and reduce the end-to-end delay.
2008, 37(4): 606-609,629.
Abstract:
The research goal of data association in the past has primarily focused on establishing a computational approach for association processing algorithms. In this paper, a performance evaluation model is proposed for data association based on temporal finit automata. An algorithm for checking the consistency and reachability of the model is developed. A simulation experiment illustrates the effectiveness of this method in the analysis and verification of the performance of data association algorithms.
The research goal of data association in the past has primarily focused on establishing a computational approach for association processing algorithms. In this paper, a performance evaluation model is proposed for data association based on temporal finit automata. An algorithm for checking the consistency and reachability of the model is developed. A simulation experiment illustrates the effectiveness of this method in the analysis and verification of the performance of data association algorithms.
2008, 37(4): 610-613.
Abstract:
The paper use mainly ray casting algorithm to convert the 2D image to 3D image. We use tri-linear interpolation algorithm to calculate the color and opacity of the sampling in order to improve the accuracy of 3 D reconstruction. The algorithm caculates the accurate projective region of 3D regular data field based on the OpenGL library and its 3D view matrices. Consequently it reduces the amount of rays in ray casting algorithm. This method also computes shading tables for the data field in advance according to the light of phone illumination model. In addition, the regular implementation codes of the algorithm are optimized. These stategies work together to speed up the ray casting volume rendering algorithm effectively. The algorithm improve not only the accuracy of 3D reconstruction but also the effective of 3D reconstruction.
The paper use mainly ray casting algorithm to convert the 2D image to 3D image. We use tri-linear interpolation algorithm to calculate the color and opacity of the sampling in order to improve the accuracy of 3 D reconstruction. The algorithm caculates the accurate projective region of 3D regular data field based on the OpenGL library and its 3D view matrices. Consequently it reduces the amount of rays in ray casting algorithm. This method also computes shading tables for the data field in advance according to the light of phone illumination model. In addition, the regular implementation codes of the algorithm are optimized. These stategies work together to speed up the ray casting volume rendering algorithm effectively. The algorithm improve not only the accuracy of 3D reconstruction but also the effective of 3D reconstruction.
2008, 37(4): 614-617.
Abstract:
A storage centered transaction and authentication model (SCTAM) is proposed with all information stored in transaction center (TC) where operations are carried out automatically and information security and consistency are ensured. The user does not interact with the owner in transaction; the judge can make decision without the aids from the owner and the user, which is fairer. Different watermark techniques are used to embed and extract watermarks for the owner and for the user to ensure the security of the watermarks. SCTAM can settle all problems discovered so far and make watermarking protocol easy to implement.
A storage centered transaction and authentication model (SCTAM) is proposed with all information stored in transaction center (TC) where operations are carried out automatically and information security and consistency are ensured. The user does not interact with the owner in transaction; the judge can make decision without the aids from the owner and the user, which is fairer. Different watermark techniques are used to embed and extract watermarks for the owner and for the user to ensure the security of the watermarks. SCTAM can settle all problems discovered so far and make watermarking protocol easy to implement.
2008, 37(4): 618-620.
Abstract:
Using a novel chelate 2,2,3,3-tetraphenyl-4,4-bisthienylsilole (TPBTSi) as emissive material and Alq3 as eletron transporting material, a triple layer organic light-emitting device was fabricated using convetional vaccum deposition method. The device structure is:ITO/N,N'-Diphenyl-N, N'-bis(1-naphthyl)(1,1'-biphenyl)-4,4'-diamine (NPB)/TPBTSi/tri-(8-hydroxyquinoline)-aluminum (Alq3)/Mg:Ag. The peak of electroluminescence (EL) spectrum locates at 516 nm, which is the spectrum of TPBTSi. The commissions internationale l'eclairage (CIE) coordinates are (0.275,0.448 8), which are independent on the variation of bias voltage. Under the bias voltage of 15 V, the maximum luminance and luminance efficiency are 7 032 cd/m2 and 0.79 lm/W, respectively.
Using a novel chelate 2,2,3,3-tetraphenyl-4,4-bisthienylsilole (TPBTSi) as emissive material and Alq3 as eletron transporting material, a triple layer organic light-emitting device was fabricated using convetional vaccum deposition method. The device structure is:ITO/N,N'-Diphenyl-N, N'-bis(1-naphthyl)(1,1'-biphenyl)-4,4'-diamine (NPB)/TPBTSi/tri-(8-hydroxyquinoline)-aluminum (Alq3)/Mg:Ag. The peak of electroluminescence (EL) spectrum locates at 516 nm, which is the spectrum of TPBTSi. The commissions internationale l'eclairage (CIE) coordinates are (0.275,0.448 8), which are independent on the variation of bias voltage. Under the bias voltage of 15 V, the maximum luminance and luminance efficiency are 7 032 cd/m2 and 0.79 lm/W, respectively.
2008, 37(4): 621-623.
Abstract:
A total dose radiation hardened power VDMOS device is fabricated by growing the thin gate SiO2 after the P-body diffusion and using a double passivation layer (Si3N4-SiO2). The experimental results are presented and fit 2D simulation. For the specified power VDMOS device, the threshold voltage shifts is only -1 V at a x-ray total dose of 972×103 rad (Si). It is demonstrated that the total dose radiation tolerance of the power VDMOS device are improved significantly.
A total dose radiation hardened power VDMOS device is fabricated by growing the thin gate SiO2 after the P-body diffusion and using a double passivation layer (Si3N4-SiO2). The experimental results are presented and fit 2D simulation. For the specified power VDMOS device, the threshold voltage shifts is only -1 V at a x-ray total dose of 972×103 rad (Si). It is demonstrated that the total dose radiation tolerance of the power VDMOS device are improved significantly.
2008, 37(4): 624-626.
Abstract:
Nanocomposites consisting of particles of Nd2Fe14B and α-Fe have been prepared from a compound NdxFe94-xB6 (x=9.5, 10.5, 11.5) by melt-spinning techniques. The effect of Nd content on microwave permeability and the nature resonance frequency was studied. Phase structure, microstructure, static magnetic property, and microwave electromagnetism property were analyzed by the ways of XRD, VSM, and a vector network analyzer. The result shows that the nature resonance frequency of the nanocomposites increase from 6.53 GHz to 15.91 GHz, and the imaginary permeability (μ"r) of the nanocomposites gradually reduces from 1.59 to 0.56 with the increase of Nd content from 9.5% to 11.5%.
Nanocomposites consisting of particles of Nd2Fe14B and α-Fe have been prepared from a compound NdxFe94-xB6 (x=9.5, 10.5, 11.5) by melt-spinning techniques. The effect of Nd content on microwave permeability and the nature resonance frequency was studied. Phase structure, microstructure, static magnetic property, and microwave electromagnetism property were analyzed by the ways of XRD, VSM, and a vector network analyzer. The result shows that the nature resonance frequency of the nanocomposites increase from 6.53 GHz to 15.91 GHz, and the imaginary permeability (μ"r) of the nanocomposites gradually reduces from 1.59 to 0.56 with the increase of Nd content from 9.5% to 11.5%.
2008, 37(4): 627-629.
Abstract:
Based on the class fuzzy C-means clustering algorithm (FCMA) is a well-known clustering method to partition an image into homogeneous region.We know FCMA is dependent on the choice of the initial distribution of cluster center, and consequently the algorithm ends up in a local optimum. Because of the genetic algorithm which can achieve the global optimum, we directly unified them in the magnetic resonance images (MRI) segmentation. By applying genetic algorithm, we can achieve the global optimum in MRI segmentation application.
Based on the class fuzzy C-means clustering algorithm (FCMA) is a well-known clustering method to partition an image into homogeneous region.We know FCMA is dependent on the choice of the initial distribution of cluster center, and consequently the algorithm ends up in a local optimum. Because of the genetic algorithm which can achieve the global optimum, we directly unified them in the magnetic resonance images (MRI) segmentation. By applying genetic algorithm, we can achieve the global optimum in MRI segmentation application.
2008, 37(4): 630-633.
Abstract:
Region of interest (ROI) plays an important role in biomedical image analysis. The calcium ions laser scanning confocal microscope (LSCM) real-time optical sections of fluo-4 labeled rat ventricular myocyte show point distribution and are interfered by random noise. The fluorescent images have no continuous grayscale distribution and obvious edge. It is difficult to apply the methods which process static fluorescent images to our experiment. A self-adaptive segmentation is proposed based on spatial point pattern cluster features comparability in Markov field. The advantage of this method is that the ROI of calcium within all the disturbed optical sections can be properly segmented under a coincident standard. This method will benefit to other dynamic analysis researches using LSCM.
Region of interest (ROI) plays an important role in biomedical image analysis. The calcium ions laser scanning confocal microscope (LSCM) real-time optical sections of fluo-4 labeled rat ventricular myocyte show point distribution and are interfered by random noise. The fluorescent images have no continuous grayscale distribution and obvious edge. It is difficult to apply the methods which process static fluorescent images to our experiment. A self-adaptive segmentation is proposed based on spatial point pattern cluster features comparability in Markov field. The advantage of this method is that the ROI of calcium within all the disturbed optical sections can be properly segmented under a coincident standard. This method will benefit to other dynamic analysis researches using LSCM.
2008, 37(4): 634-636,640.
Abstract:
Mixed Weibull distribution is usually used to model reliability of products with more than one failure modes. Due to the difficulty of estimation of distribution parameters, it has not been widely used. In this paper, a mixed model involving two Weibull distributions is considered; and its parameters estimation model is established using nonlinear least square theory. Levenberg-Marquardt algorithm is used to solve the optimization problem. To reduce iterative time, the estimator from graphical method is used as initial value. A numerical example is employed to illustrate the feasibility and accuracy of the proposed method.
Mixed Weibull distribution is usually used to model reliability of products with more than one failure modes. Due to the difficulty of estimation of distribution parameters, it has not been widely used. In this paper, a mixed model involving two Weibull distributions is considered; and its parameters estimation model is established using nonlinear least square theory. Levenberg-Marquardt algorithm is used to solve the optimization problem. To reduce iterative time, the estimator from graphical method is used as initial value. A numerical example is employed to illustrate the feasibility and accuracy of the proposed method.
2008, 37(4): 637-640.
Abstract:
Thermal analysis of LiTaO3 film infrared detector based on ANSYS has been studied in this paper. The influences on the thermal analysis results are obtained, through changing the substrate material and its thickness and the thickness and thermal conductivity of thermal-insulation layer of the LiTaO3 film infrare sensing element. The thermal response of the infrared detector increases with the thickness of thermal-insulation layer but is in inverse proportion to its thermal conductivity. Among the substrate materials of silicon, nickel, and sapphire, the LiTaO3 thin film infrared detector with sapphire substrate has the best thermal response. The influence of the thickness of substrate can be ignored when the infrared detector with 2 μm thick thermal-insulation layer. An optimized model is presented and the comparing simulation results of the optimized and the original are given out. The experiment result verifies the validity of the optimized model.
Thermal analysis of LiTaO3 film infrared detector based on ANSYS has been studied in this paper. The influences on the thermal analysis results are obtained, through changing the substrate material and its thickness and the thickness and thermal conductivity of thermal-insulation layer of the LiTaO3 film infrare sensing element. The thermal response of the infrared detector increases with the thickness of thermal-insulation layer but is in inverse proportion to its thermal conductivity. Among the substrate materials of silicon, nickel, and sapphire, the LiTaO3 thin film infrared detector with sapphire substrate has the best thermal response. The influence of the thickness of substrate can be ignored when the infrared detector with 2 μm thick thermal-insulation layer. An optimized model is presented and the comparing simulation results of the optimized and the original are given out. The experiment result verifies the validity of the optimized model.
