ISSN 
2008 Vol. 37, No. 5
2008, 37(5): 641-644.
Abstract:
Based on the existing intercarrier interference (ICI) self-cancellation scheme, we propose an improved scheme using symbol transform for canceling the ICI effectively. This scheme builds a symbol transform matrix as platform to extend the existing scheme and increase flexibility of design. Through the optimal design of transform matrix, compared with the existing scheme, the improved scheme can reduce ICI more effectively and broaden the applicable frequency offset scope. Simulations show the validity of the scheme.
Based on the existing intercarrier interference (ICI) self-cancellation scheme, we propose an improved scheme using symbol transform for canceling the ICI effectively. This scheme builds a symbol transform matrix as platform to extend the existing scheme and increase flexibility of design. Through the optimal design of transform matrix, compared with the existing scheme, the improved scheme can reduce ICI more effectively and broaden the applicable frequency offset scope. Simulations show the validity of the scheme.
2008, 37(5): 645-648.
Abstract:
For the different communication cases of specific network on chip (NOC) applications, a customized arbitral priority NOC router is proposed. This router uses the arbitral mechanism based on lottery algorithm instead of the round robin (RR) algorithm, which is widely used in the arbiter of current NOC routers. The arbitral priority of lottery router can be customized by users according to the communication cases among IPs in NOC. This router also includes a time unit multiplex (TUM) transmission mechanism to alleviate the problem of internal block, which may be induced by the case of several input ports competing for one output port. The TUM mechanism guarantees the number of input data is equal to the number of output data and improves the router processing performance.
For the different communication cases of specific network on chip (NOC) applications, a customized arbitral priority NOC router is proposed. This router uses the arbitral mechanism based on lottery algorithm instead of the round robin (RR) algorithm, which is widely used in the arbiter of current NOC routers. The arbitral priority of lottery router can be customized by users according to the communication cases among IPs in NOC. This router also includes a time unit multiplex (TUM) transmission mechanism to alleviate the problem of internal block, which may be induced by the case of several input ports competing for one output port. The TUM mechanism guarantees the number of input data is equal to the number of output data and improves the router processing performance.
2008, 37(5): 649-652.
Abstract:
A traffic-rate-based joint power control strategy for co-channel operation in cognitive radio system is proposed. The strategy allocates transmitting power according to both terminals' locations and traffic data rate requirements, so heterogeneous terminals can be provided with desired transmitting power. System simulation shows that the proposed strategy can achieve higher system throughput and spectrum utilization than two existing uniform power allocation schemes.
A traffic-rate-based joint power control strategy for co-channel operation in cognitive radio system is proposed. The strategy allocates transmitting power according to both terminals' locations and traffic data rate requirements, so heterogeneous terminals can be provided with desired transmitting power. System simulation shows that the proposed strategy can achieve higher system throughput and spectrum utilization than two existing uniform power allocation schemes.
2008, 37(5): 653-656.
Abstract:
By analyzing the degree distribution of low density parity check (LDPC) codes in definite quantity with gaussian approximation (GA) and optimal method, the performance of degree distribution for LDPC codes is investigated. Research results show that when the initial channel state and degree distribution of the LDPC codes are known, the optimal retransmission fractions can be determined. Maximum retransmission efficiency would be achieved if bits can be retransmitted according to these fractions. Calculation results reveal that the retransmission fractions in degree distribution based hybrid automatic repeat quest (DDB-HARQ) scheme are optimal.
By analyzing the degree distribution of low density parity check (LDPC) codes in definite quantity with gaussian approximation (GA) and optimal method, the performance of degree distribution for LDPC codes is investigated. Research results show that when the initial channel state and degree distribution of the LDPC codes are known, the optimal retransmission fractions can be determined. Maximum retransmission efficiency would be achieved if bits can be retransmitted according to these fractions. Calculation results reveal that the retransmission fractions in degree distribution based hybrid automatic repeat quest (DDB-HARQ) scheme are optimal.
2008, 37(5): 657-659,663.
Abstract:
For the uplink in CDMA distributed wireless communication system (DWCS) employing the multi-user detection receiver, an antenna dynamic selection algorithm is proposed. As the bit signal-to-interference-plus-noise ratio from a virtual cell arrives at the threshold, antennas are selected dynamically as many as possible to minimize the average power of mobile terminal by getting the trade-off between the increment in the bit signal-to-interference-plus-noise ratio and the increment in the receiver complexity. The simulation shows that the proposed algorithm can achieve almost similar outage capacity as the antenna static selection (ASS) method while the ratio of average power decrement of mobile terminal to average receiver complexity of the proposed algorithm is greater than that of ASS.
For the uplink in CDMA distributed wireless communication system (DWCS) employing the multi-user detection receiver, an antenna dynamic selection algorithm is proposed. As the bit signal-to-interference-plus-noise ratio from a virtual cell arrives at the threshold, antennas are selected dynamically as many as possible to minimize the average power of mobile terminal by getting the trade-off between the increment in the bit signal-to-interference-plus-noise ratio and the increment in the receiver complexity. The simulation shows that the proposed algorithm can achieve almost similar outage capacity as the antenna static selection (ASS) method while the ratio of average power decrement of mobile terminal to average receiver complexity of the proposed algorithm is greater than that of ASS.
2008, 37(5): 660-663.
Abstract:
A novel ultra-wideband (UWB) pulse design algorithm combining the methods of spectrum analysis and orthogonal basis synthesis in time domain is presented to improve the spectrum utilization efficiency and conform the federal communications commission (FCC) emission mask constraint. UWB pulse can be obtained by orthogonal synthesis of finite number of prolate spheroidal wave function (PSWF) pulse basis, which matching FCC emission mask. The simulation results show that the pulse designed by this algorithm can perfectly meet the requirement of FCC emission mask and has higher spectrum utilization efficiency.
A novel ultra-wideband (UWB) pulse design algorithm combining the methods of spectrum analysis and orthogonal basis synthesis in time domain is presented to improve the spectrum utilization efficiency and conform the federal communications commission (FCC) emission mask constraint. UWB pulse can be obtained by orthogonal synthesis of finite number of prolate spheroidal wave function (PSWF) pulse basis, which matching FCC emission mask. The simulation results show that the pulse designed by this algorithm can perfectly meet the requirement of FCC emission mask and has higher spectrum utilization efficiency.
2008, 37(5): 664-667.
Abstract:
The construction of the check matrix and the coding and decoding algorithms of low density parity check (LDPC) are introduced. The adaptive loading technique of orthogonal frequency division multiplexing (OFDM) and multiple-input multiple-output (MIMO) are discussed. The model of the LDPC coded MIMO-OFDM system with adaptive-loading is given. The performance of the system under multiple-path rayleigh fading channels is simulated and analyzed. It is obtained that the performance of irregular LDPC coded system based on GF(2)is better than that based on GF(q,q<>2), The presented MIMO-OFDM system can greatly enhance the transfer rate and has an excellent anti-fading feature under multiple-path fading channels.
The construction of the check matrix and the coding and decoding algorithms of low density parity check (LDPC) are introduced. The adaptive loading technique of orthogonal frequency division multiplexing (OFDM) and multiple-input multiple-output (MIMO) are discussed. The model of the LDPC coded MIMO-OFDM system with adaptive-loading is given. The performance of the system under multiple-path rayleigh fading channels is simulated and analyzed. It is obtained that the performance of irregular LDPC coded system based on GF(2)is better than that based on GF(q,q<>2), The presented MIMO-OFDM system can greatly enhance the transfer rate and has an excellent anti-fading feature under multiple-path fading channels.
2008, 37(5): 668-672.
Abstract:
By employing the symmetric property of the uplink and downlink channel, a transmit signal processing technique is proposed, which can lead to spatial division multiple access (SDMA) for time divisionsynchronous code division multiple access (TD-SCDMA). With space and time two dimensional signal, a matrix is constructed, and the null space of the matrix is utilized to realize SDMA. The complexity of this technigue is analyzed. Without any changes in the user equipment, this technique can increase the capacity several times with moderate complexity.
By employing the symmetric property of the uplink and downlink channel, a transmit signal processing technique is proposed, which can lead to spatial division multiple access (SDMA) for time divisionsynchronous code division multiple access (TD-SCDMA). With space and time two dimensional signal, a matrix is constructed, and the null space of the matrix is utilized to realize SDMA. The complexity of this technigue is analyzed. Without any changes in the user equipment, this technique can increase the capacity several times with moderate complexity.
2008, 37(5): 673-676,692.
Abstract:
Ultra-wideband (UWB) which is very suitable for short range and high data-rate wireless application has received much attention from the researchers all over the world, and the UWB modulation scheme is one of the research emphases. In this paper, a new time-hopping UWB modulation method called multi-pulse position modulation (MPPM) constructed by constant weight code (CWC) is proposed. The MPPM is based on the existing single pulse position modulation (SPPM) and employs more than one pulse in a symbol. The channel capacity and error probability of MPPM are derived over an AWGN channel respectively. Theory analysis and simulation results show that MPPM can get better communication performance than single pulse position modulation and pulse amplitude modulation (PAM) with lower receiver complexity under some given condition.
Ultra-wideband (UWB) which is very suitable for short range and high data-rate wireless application has received much attention from the researchers all over the world, and the UWB modulation scheme is one of the research emphases. In this paper, a new time-hopping UWB modulation method called multi-pulse position modulation (MPPM) constructed by constant weight code (CWC) is proposed. The MPPM is based on the existing single pulse position modulation (SPPM) and employs more than one pulse in a symbol. The channel capacity and error probability of MPPM are derived over an AWGN channel respectively. Theory analysis and simulation results show that MPPM can get better communication performance than single pulse position modulation and pulse amplitude modulation (PAM) with lower receiver complexity under some given condition.
2008, 37(5): 677-680,729.
Abstract:
A three-dimensional Kalman filter based digital frequency-locked loop design approach is proposed for the carrier tracking of high dynamic global positioning system signals. The equivalence between Kalman filer and digital frequency-locked loop is derived. The transient-state and steady-state loop performance are analyzed. The simulation results show that the Kalman filter based digital frequency locked loop (DFLL) has much wider bandwidth in the transient-state than the fixed-gain DFLL while both have the same steady-state bandwidth, and the convergence time decreases a lot.
A three-dimensional Kalman filter based digital frequency-locked loop design approach is proposed for the carrier tracking of high dynamic global positioning system signals. The equivalence between Kalman filer and digital frequency-locked loop is derived. The transient-state and steady-state loop performance are analyzed. The simulation results show that the Kalman filter based digital frequency locked loop (DFLL) has much wider bandwidth in the transient-state than the fixed-gain DFLL while both have the same steady-state bandwidth, and the convergence time decreases a lot.
2008, 37(5): 681-684.
Abstract:
A passive tracking system consisting of multi-radar reconnaissance stations usually uses the time difference of arrival (TDOA) tracking measurement method, which can achieve high tracking precision. However, when the communication among these stations is interfered, the measurement error of the TDOA method will increase and thus the tracking precision of the system will deteriorate. In this paper, a new fault-tolerant tracking algorithm is proposed, in which both the TDOA method and the directions of arrival (DOA) method are used. In each period, the state variables of targets will be detected with χ2 to determine whether the switchover from the TDOA method to the DOA method should be made. The analysis shows that the proposed algorithm is characterized by high anti-interference while its tracking precision does not deteriorate. Some simulation experiments are used to verify the validity of the new algorithm.
A passive tracking system consisting of multi-radar reconnaissance stations usually uses the time difference of arrival (TDOA) tracking measurement method, which can achieve high tracking precision. However, when the communication among these stations is interfered, the measurement error of the TDOA method will increase and thus the tracking precision of the system will deteriorate. In this paper, a new fault-tolerant tracking algorithm is proposed, in which both the TDOA method and the directions of arrival (DOA) method are used. In each period, the state variables of targets will be detected with χ2 to determine whether the switchover from the TDOA method to the DOA method should be made. The analysis shows that the proposed algorithm is characterized by high anti-interference while its tracking precision does not deteriorate. Some simulation experiments are used to verify the validity of the new algorithm.
2008, 37(5): 685-688.
Abstract:
As one of high-resolution radars, millimeter wave stepped frequency waveforms radar is successfully and widely used in many military applications. Main factors affecting the performance of radar are analyzed. Apart from target velocity, the dispersion of frequency synthesizer providing signals to radar also deteriorates the performance of radar. Specifically speaking, the dispersion in microwave band will be transferred to millimeter-wave band, this will result in the fact that the initial phase difference between transmitter and local oscillator is not constant, and brings bad impact on the resolution of radar. In order to ameliorate such effect, one possible way is to compensate dispersion. In this paper, an effective way to compensate dispersion is successfully applied in the design of a W-band stepped frequency waveforms radar. The final experiment shows that it can meet the requirement of 0.45 m range resolution.
As one of high-resolution radars, millimeter wave stepped frequency waveforms radar is successfully and widely used in many military applications. Main factors affecting the performance of radar are analyzed. Apart from target velocity, the dispersion of frequency synthesizer providing signals to radar also deteriorates the performance of radar. Specifically speaking, the dispersion in microwave band will be transferred to millimeter-wave band, this will result in the fact that the initial phase difference between transmitter and local oscillator is not constant, and brings bad impact on the resolution of radar. In order to ameliorate such effect, one possible way is to compensate dispersion. In this paper, an effective way to compensate dispersion is successfully applied in the design of a W-band stepped frequency waveforms radar. The final experiment shows that it can meet the requirement of 0.45 m range resolution.
2008, 37(5): 689-692.
Abstract:
Incorporating array of metallic wires into the host media, such as ferrimagnet YIG under an external magnetic bias field, is a novel method to synthesize negative refractive index (NRI) material. A modified effective medium theory of composite medium permittivity tensor is deduced. In our theory, the composite medium in the mass are transformed into an equivalent media that both permeability and permittivity are anisotropic. The effective permeability and permittivity tensors are calculated, the dispersive curves are presented, and the negative refractive condition is obtained by analysis.
Incorporating array of metallic wires into the host media, such as ferrimagnet YIG under an external magnetic bias field, is a novel method to synthesize negative refractive index (NRI) material. A modified effective medium theory of composite medium permittivity tensor is deduced. In our theory, the composite medium in the mass are transformed into an equivalent media that both permeability and permittivity are anisotropic. The effective permeability and permittivity tensors are calculated, the dispersive curves are presented, and the negative refractive condition is obtained by analysis.
2008, 37(5): 693-697.
Abstract:
An effictive seperated independent component analysis (ICA) algorithm is obtained by introducing a skewness-adjusting parameter to the Pearson mixture density model in extended Infomax algorithm. This model with skewness-adjusting parameter can cover a wider range of sub-Gaussian distribution including asymmetrical and multi-modal ones, resulting in more precisely approximating source's density. When dealing with non-skewed mixed sources, the new algorithm can achieve less steady-state error while maintaining fast convergence speed.
An effictive seperated independent component analysis (ICA) algorithm is obtained by introducing a skewness-adjusting parameter to the Pearson mixture density model in extended Infomax algorithm. This model with skewness-adjusting parameter can cover a wider range of sub-Gaussian distribution including asymmetrical and multi-modal ones, resulting in more precisely approximating source's density. When dealing with non-skewed mixed sources, the new algorithm can achieve less steady-state error while maintaining fast convergence speed.
2008, 37(5): 698-700,708.
Abstract:
Based on the discussion of the structure of digital down-conversion (DDC) in software radio receiver, this paper suggests the classification of decimation filtering to reduce the taps of the anti-aliasing filters, and the suggestion to use different resources at separate step of decimation filtering during the multiple steps, so as to make the resources of FPGA high-efficient utilization. Besides, a new algorithm——clock-selective-computing algorithm fitting for FIR decimation filter is proposed and tested by Altera's EP2S60F484C4. Results validate that the new algorithm spends less resources.
Based on the discussion of the structure of digital down-conversion (DDC) in software radio receiver, this paper suggests the classification of decimation filtering to reduce the taps of the anti-aliasing filters, and the suggestion to use different resources at separate step of decimation filtering during the multiple steps, so as to make the resources of FPGA high-efficient utilization. Besides, a new algorithm——clock-selective-computing algorithm fitting for FIR decimation filter is proposed and tested by Altera's EP2S60F484C4. Results validate that the new algorithm spends less resources.
2008, 37(5): 701-704.
Abstract:
D-S combination rule and other modified methods are defective in resolving evidence combination problem of highly conflict evidences. So we propose a new modified method. The new method still uses the D-S combination rule. All evidences must have the same important degree when they are combined with D-S combination rule. In practice, evidences may have different important degree so we maybe get paradoxical result if we directly combine these evidences. Therefore we introduce a concept of evidence weight and give the concrete algorithm for the evidence weight. Then new evidences with the same evidence weight can be got by modifying the basic belief assignment function of primary evidences through the algorithm to the evidence weight. Finally, an example indicates that the new method can give the more reasonable combination results compared with D-S combination rule and the other modified methods.
D-S combination rule and other modified methods are defective in resolving evidence combination problem of highly conflict evidences. So we propose a new modified method. The new method still uses the D-S combination rule. All evidences must have the same important degree when they are combined with D-S combination rule. In practice, evidences may have different important degree so we maybe get paradoxical result if we directly combine these evidences. Therefore we introduce a concept of evidence weight and give the concrete algorithm for the evidence weight. Then new evidences with the same evidence weight can be got by modifying the basic belief assignment function of primary evidences through the algorithm to the evidence weight. Finally, an example indicates that the new method can give the more reasonable combination results compared with D-S combination rule and the other modified methods.
2008, 37(5): 705-708.
Abstract:
The reinitialization process is quite time-consuming in level set method. A new variational formulation which is the difference between the level set function and the signed distance function is introduced to C-V model. In this way, the level set function is forced close to a signed distance function, and therefore completely eliminates the need of the constly re-initialization procedure. Also, when detecting more than one object, a group of curves are choosed to be the initial curve. In the numerical implementation, AOS scheme is adopted to eliminates limit of time step. So the large time step can be selected to accelerate the evolution velocity. The result shows that the evolution velocity is greatly improved and the precision doesn't reduce.
The reinitialization process is quite time-consuming in level set method. A new variational formulation which is the difference between the level set function and the signed distance function is introduced to C-V model. In this way, the level set function is forced close to a signed distance function, and therefore completely eliminates the need of the constly re-initialization procedure. Also, when detecting more than one object, a group of curves are choosed to be the initial curve. In the numerical implementation, AOS scheme is adopted to eliminates limit of time step. So the large time step can be selected to accelerate the evolution velocity. The result shows that the evolution velocity is greatly improved and the precision doesn't reduce.
2008, 37(5): 709-711,741.
Abstract:
In order to increase the calculation speed of the n sharing's generation and the m partners to recover the secret in Shamir(m,n) threshold scheme, the discrete Fourier transform (DFT) over finite field is adopted other than the classical Lagrange interpolation. Because the DFT over finite field has some similar properties of the DFT over complex, such as the cycling convolution and the FFT algorithm, this method can improve the efficient of Shamir(m,n) threshold scheme. If m >[n/2], it can increase the calculation speed of the trust center to divide the key to n sharing components. Moreover, if m=n and it is the power of 2, this scheme can increase the calculation speed of the partners to recover the secret key.
In order to increase the calculation speed of the n sharing's generation and the m partners to recover the secret in Shamir(m,n) threshold scheme, the discrete Fourier transform (DFT) over finite field is adopted other than the classical Lagrange interpolation. Because the DFT over finite field has some similar properties of the DFT over complex, such as the cycling convolution and the FFT algorithm, this method can improve the efficient of Shamir(m,n) threshold scheme. If m >[n/2], it can increase the calculation speed of the trust center to divide the key to n sharing components. Moreover, if m=n and it is the power of 2, this scheme can increase the calculation speed of the partners to recover the secret key.
2008, 37(5): 712-715.
Abstract:
Up to now all the known proxy digital signature schemes are based on discrete logarithmic problems or big number factorization problems. Based on the elliptic curve, a new multi-proxy multi-signature scheme is proposed. Furthermore, we also analyze the new scheme's security problem. In this scheme, an original group of signers can authorize a group of proxy signers under the agreement of all singers, and only all singers in proxy group can generate multi-proxy multi-signatures instead of the original group of signers. The scheme takes full advantage of elliptic curve cryptosystem, such as shorter private key, higher signature efficiency and so on, so it is more secure and efficient than the existing schemes.
Up to now all the known proxy digital signature schemes are based on discrete logarithmic problems or big number factorization problems. Based on the elliptic curve, a new multi-proxy multi-signature scheme is proposed. Furthermore, we also analyze the new scheme's security problem. In this scheme, an original group of signers can authorize a group of proxy signers under the agreement of all singers, and only all singers in proxy group can generate multi-proxy multi-signatures instead of the original group of signers. The scheme takes full advantage of elliptic curve cryptosystem, such as shorter private key, higher signature efficiency and so on, so it is more secure and efficient than the existing schemes.
2008, 37(5): 716-719.
Abstract:
By analyzing the period of the bit computation of AND, OR, and XOR, it is proved that the frequency characters of the bit computation of XOR is better than the original frequency characters. The study of the linear complexity of the combined bits demonstrates that:the linear complexity of the bit computation of AND and OR is equal to the product of the linear complexity of the originals; and the linear complexity of the bit computation of XOR equal to the addition of the linear complexity of the originals. Computer simulation demonstrates that the combined pseudorandom sequence generator has simple architecture and high speed information processing characters, and can efficiently increase the period and linear complexity efficiently of pseudorandom sequence.
By analyzing the period of the bit computation of AND, OR, and XOR, it is proved that the frequency characters of the bit computation of XOR is better than the original frequency characters. The study of the linear complexity of the combined bits demonstrates that:the linear complexity of the bit computation of AND and OR is equal to the product of the linear complexity of the originals; and the linear complexity of the bit computation of XOR equal to the addition of the linear complexity of the originals. Computer simulation demonstrates that the combined pseudorandom sequence generator has simple architecture and high speed information processing characters, and can efficiently increase the period and linear complexity efficiently of pseudorandom sequence.
2008, 37(5): 720-723,781.
Abstract:
A new scheme to suppress carrier frequency deviation for PCM/FM telemetry digital receiver is presented. Theoretical deduction proves that under the condition of all digital receiver, the ideal FM demodulated signal is equivalent to a signal with amplitude modulated by the frequency deviation. From this theoretical result, we propose a new scheme to suppress the carrier frequency deviation. Design examples and computer simulation show the new scheme is effective and applicable for more higher frequency variable rate.
A new scheme to suppress carrier frequency deviation for PCM/FM telemetry digital receiver is presented. Theoretical deduction proves that under the condition of all digital receiver, the ideal FM demodulated signal is equivalent to a signal with amplitude modulated by the frequency deviation. From this theoretical result, we propose a new scheme to suppress the carrier frequency deviation. Design examples and computer simulation show the new scheme is effective and applicable for more higher frequency variable rate.
2008, 37(5): 724-726,776.
Abstract:
The phenomenon of coherence resonance of a nonlinear integral-and-fire model subject to a voltage-gated channel noise and a synaptic noise is investigated. Based on the adiabatic approximation theory, we obtain the approximate expressions of the firing rate (FR), the probability distribution of the first fire (FPD), and the coefficient of variation (CV) of interspike interval of firing. It is shown that the FPD and the FR are non-monotonic functions of the strength of the voltage-gated channel noise and the synaptic noise. Furthermore, by choosing appropriate noise parameter, spontaneous fire of neuron can occur, i.e., the phenomenon of coherence resonance can take place.
The phenomenon of coherence resonance of a nonlinear integral-and-fire model subject to a voltage-gated channel noise and a synaptic noise is investigated. Based on the adiabatic approximation theory, we obtain the approximate expressions of the firing rate (FR), the probability distribution of the first fire (FPD), and the coefficient of variation (CV) of interspike interval of firing. It is shown that the FPD and the FR are non-monotonic functions of the strength of the voltage-gated channel noise and the synaptic noise. Furthermore, by choosing appropriate noise parameter, spontaneous fire of neuron can occur, i.e., the phenomenon of coherence resonance can take place.
2008, 37(5): 727-729.
Abstract:
The simplified perturbation formulas of the superhyperfine parameters for a 3d9 ion in tetragonally elongated octahedra are established from the crystal-field model and the cluster approach. In these expressions, the relationships are obtained for the orbital mixing coefficients, unpaired spin densities, and average covalence factor. The simplified formulas are applied to the Cu2+ centers in K2PdX4(X=Cl, Br). The calculated results show the agreement with the experimental data and the theoretical values based on the complicated molecular orbital calculations in the previous work.
The simplified perturbation formulas of the superhyperfine parameters for a 3d9 ion in tetragonally elongated octahedra are established from the crystal-field model and the cluster approach. In these expressions, the relationships are obtained for the orbital mixing coefficients, unpaired spin densities, and average covalence factor. The simplified formulas are applied to the Cu2+ centers in K2PdX4(X=Cl, Br). The calculated results show the agreement with the experimental data and the theoretical values based on the complicated molecular orbital calculations in the previous work.
2008, 37(5): 730-732,796.
Abstract:
According to the analysis of periodic dielectric Cerenkov maser, by using of equivalence theory, periodic dielectric cerenkov maser is considered as uniform anisotropic dielectric. the dispersion equation of periodic dielectric cerenkov maser are derived. Through the way of particle-in-cell (PIC) simulation, we can see that the output power and output frequency will be changed corresponding to the εz and εr (same as to adjust the percentage of dielectric area). So it is possible to achieve high frequency microwave output by adjusting the width of dielectric film.
According to the analysis of periodic dielectric Cerenkov maser, by using of equivalence theory, periodic dielectric cerenkov maser is considered as uniform anisotropic dielectric. the dispersion equation of periodic dielectric cerenkov maser are derived. Through the way of particle-in-cell (PIC) simulation, we can see that the output power and output frequency will be changed corresponding to the εz and εr (same as to adjust the percentage of dielectric area). So it is possible to achieve high frequency microwave output by adjusting the width of dielectric film.
2008, 37(5): 733-736.
Abstract:
The remote user authentication schemes with smart cards using bilinear pairings are discussed. As the scheme proposed by Giri et al is vulnerable to masquerade attack in the case that the information stored in the smart card is stolen, a new remote user authentication scheme with smart cards using bilinear pairings is proposed. The proposed scheme is performed lower computation cost since in login phase only the addition in the group is needed. The scheme provides better security because it can withstand replay attack, off-line attack and masquerade attack.
The remote user authentication schemes with smart cards using bilinear pairings are discussed. As the scheme proposed by Giri et al is vulnerable to masquerade attack in the case that the information stored in the smart card is stolen, a new remote user authentication scheme with smart cards using bilinear pairings is proposed. The proposed scheme is performed lower computation cost since in login phase only the addition in the group is needed. The scheme provides better security because it can withstand replay attack, off-line attack and masquerade attack.
2008, 37(5): 737-741.
Abstract:
To assure the safety in bulk carrier transportation and improve the quality, efficiency and reliability of the ship stowage, a design plan of formalizing knowledge base is presented. Introduced by knowledge base and using genetic algorithm, the system controls the vessel's strength in loading by optimizing the loading scheme. At last, the vessel's shear force and bending moment in loading process are optimized to the lowest extent, and the knowledge is form into a unified data structure. The loading result of program on bulk carrier shows that automatic stowage planner based on knowledge base could optimize the process of loading.
To assure the safety in bulk carrier transportation and improve the quality, efficiency and reliability of the ship stowage, a design plan of formalizing knowledge base is presented. Introduced by knowledge base and using genetic algorithm, the system controls the vessel's strength in loading by optimizing the loading scheme. At last, the vessel's shear force and bending moment in loading process are optimized to the lowest extent, and the knowledge is form into a unified data structure. The loading result of program on bulk carrier shows that automatic stowage planner based on knowledge base could optimize the process of loading.
2008, 37(5): 742-745,781.
Abstract:
Based on Markov Random Fields (MRF) and Gaussian Mixture (GM) models, a new method to label surface features using hyperspectral imaging is presented. The dimension of the hyperspectral image is reduced by PCA, and the stochastic model is built based on prior of the dimension-reduced images and its difference images. Then the maximum posteriori is designed as the optimal criterion and the final labels are obtained by the simulated annealing algorithm. Experimental results show that this method is accurate, efficient and robust for surface features labeling.
Based on Markov Random Fields (MRF) and Gaussian Mixture (GM) models, a new method to label surface features using hyperspectral imaging is presented. The dimension of the hyperspectral image is reduced by PCA, and the stochastic model is built based on prior of the dimension-reduced images and its difference images. Then the maximum posteriori is designed as the optimal criterion and the final labels are obtained by the simulated annealing algorithm. Experimental results show that this method is accurate, efficient and robust for surface features labeling.
2008, 37(5): 746-749.
Abstract:
Domain ontology plays an important role in the system of information extraction. In this paper, after a discuss of the relation of domain ontology and information extraction, the design principles and steps of domain ontology in the system of information extraction are proposed. The domain ontology about monitor is implemeneted in a prototype system of information extraction, and the domain ontology is applied to some tasks of information extraction, including named entity recognition, extraction pattern acquisition, and thematic concept extraction. The application results show that the principles and steps are feasible.
Domain ontology plays an important role in the system of information extraction. In this paper, after a discuss of the relation of domain ontology and information extraction, the design principles and steps of domain ontology in the system of information extraction are proposed. The domain ontology about monitor is implemeneted in a prototype system of information extraction, and the domain ontology is applied to some tasks of information extraction, including named entity recognition, extraction pattern acquisition, and thematic concept extraction. The application results show that the principles and steps are feasible.
2008, 37(5): 750-752.
Abstract:
Locality Preserving Projections (LPP) is based on a nearest neighbor graph which models the local geometrical structure of the image manifold. However, this graph can not always accurately estimate the intrinsic manifold structure. A novel algorithm called Iterative locality preserving projections (ILPP) is preposed. ILPP iteratively updates the nearest neighbor graph, so that it can better model the intrinsic manifold structure. Experimental results comparison show that our algorithm outperforms PCA and LPP for image retrieval.
Locality Preserving Projections (LPP) is based on a nearest neighbor graph which models the local geometrical structure of the image manifold. However, this graph can not always accurately estimate the intrinsic manifold structure. A novel algorithm called Iterative locality preserving projections (ILPP) is preposed. ILPP iteratively updates the nearest neighbor graph, so that it can better model the intrinsic manifold structure. Experimental results comparison show that our algorithm outperforms PCA and LPP for image retrieval.
2008, 37(5): 753-756.
Abstract:
An interactive multimedia presentation system is usually composed of present flow and present content. Generalized transition network (GTN) is used to describe control flow as formal description in the system. Based on the presentation context and presentable object, the method to describe present content is proposed. This method can be used to design an authoring tool for interactive multimedia presentation system. The system produced by the tool can present the multimedia content concurrently, and its component can be reused in other presentation system.
An interactive multimedia presentation system is usually composed of present flow and present content. Generalized transition network (GTN) is used to describe control flow as formal description in the system. Based on the presentation context and presentable object, the method to describe present content is proposed. This method can be used to design an authoring tool for interactive multimedia presentation system. The system produced by the tool can present the multimedia content concurrently, and its component can be reused in other presentation system.
2008, 37(5): 757-760.
Abstract:
In hybrid Peer-to-Peer (P2P) networks, the decision of whether to use flooding or DHT depends mainly on the popularity of desired data. Previous work either used only local information, or do not consider the dynamic factors of P2P systems. In this paper, an improved algorithm called dynamic adaptive hybrid based on Gossip (DAHG) is presented. In DAHG, a P2P ultrapeer tosses a coin when an end node joins or leaves the P2P networks, and uses a gossip-style algorithm to collect global statistics about document popularity. Therefore the dynamics of the resources is taken into consideration by DAHG, which it can be used to get the exact popularity of resources in a dynamic P2P network. Simulation shows that DAHG outperforms existing approaches and also scales well.
In hybrid Peer-to-Peer (P2P) networks, the decision of whether to use flooding or DHT depends mainly on the popularity of desired data. Previous work either used only local information, or do not consider the dynamic factors of P2P systems. In this paper, an improved algorithm called dynamic adaptive hybrid based on Gossip (DAHG) is presented. In DAHG, a P2P ultrapeer tosses a coin when an end node joins or leaves the P2P networks, and uses a gossip-style algorithm to collect global statistics about document popularity. Therefore the dynamics of the resources is taken into consideration by DAHG, which it can be used to get the exact popularity of resources in a dynamic P2P network. Simulation shows that DAHG outperforms existing approaches and also scales well.
2008, 37(5): 761-764.
Abstract:
In wireless multi-hop Ad hoc networks, nodes need to contend for the shared wireless channel, this could result in partial congestion in the network and degrade the network performance. And first in first out (FIFO) queue within a node could easily cause the head-of-line blocking problem. A novel congestion-based opportunistic scheduling (CBOS) algorithm is proposed. In CBOS, the sender sends multicast request to send (RTS) frame targeted to several receivers, and the receivers would reply priority-based clear to send (CTS) by the probability according to its queue congestion status. The simulation results show that CBOS can remarkably increase the network end-to-end saturation throughput and the utilization ratio of wireless channel, and can increase the fairness among traffic flows.
In wireless multi-hop Ad hoc networks, nodes need to contend for the shared wireless channel, this could result in partial congestion in the network and degrade the network performance. And first in first out (FIFO) queue within a node could easily cause the head-of-line blocking problem. A novel congestion-based opportunistic scheduling (CBOS) algorithm is proposed. In CBOS, the sender sends multicast request to send (RTS) frame targeted to several receivers, and the receivers would reply priority-based clear to send (CTS) by the probability according to its queue congestion status. The simulation results show that CBOS can remarkably increase the network end-to-end saturation throughput and the utilization ratio of wireless channel, and can increase the fairness among traffic flows.
2008, 37(5): 765-768.
Abstract:
To solve the problem of lack adequate protection mechanism for high priority data flows, in 802.11 media access process, a multiple reserving media access control (MAC) protocol with congestion control is proposed. In access process, the protocol uses multiple reserving mechanism to protect successful access probability of high priority flows. And the forwarding nodes rejects low priority flows' access request with probability through admission control, in order to avoid congestion in them. The simulation result shows that the protocol proposed in the paper can effectively protects end-to-end throughput, delay and reduce drop ration of high priority flows.
To solve the problem of lack adequate protection mechanism for high priority data flows, in 802.11 media access process, a multiple reserving media access control (MAC) protocol with congestion control is proposed. In access process, the protocol uses multiple reserving mechanism to protect successful access probability of high priority flows. And the forwarding nodes rejects low priority flows' access request with probability through admission control, in order to avoid congestion in them. The simulation result shows that the protocol proposed in the paper can effectively protects end-to-end throughput, delay and reduce drop ration of high priority flows.
2008, 37(5): 769-772.
Abstract:
Based on the computer and cognitive science theory, the representation of knowledge work process is a key point to increase the efficiency of knowledge work. Compared the representation of AI with that of KI, the shortage of these methods is analyzed. With the case analysis, a new method which describes the programming process using the mental operation (MO) is given. The confirmatory factor analysis demonstrates that knowledge work process can be represented using MO. The sample data support that concept collection entire model formed with nine essential factors of the MO can represent knowledge work processes. It provides a basic concept and an idea to increase the efficiency of knowledge work.
Based on the computer and cognitive science theory, the representation of knowledge work process is a key point to increase the efficiency of knowledge work. Compared the representation of AI with that of KI, the shortage of these methods is analyzed. With the case analysis, a new method which describes the programming process using the mental operation (MO) is given. The confirmatory factor analysis demonstrates that knowledge work process can be represented using MO. The sample data support that concept collection entire model formed with nine essential factors of the MO can represent knowledge work processes. It provides a basic concept and an idea to increase the efficiency of knowledge work.
2008, 37(5): 773-776.
Abstract:
With planar interdigitated electrodes, polyaniline-titanium dioxide (PANI/TiO2) composite thin film gas sensor doped by hydrochloric acid and para toluene sulfonic acid (PTSA) respectively were prepared by combining in situ chemical oxidation polymerization and electrostatic self-assembly technique at the room temperature. The film characterized by scanning electron microscope (SEM). The sensitive properties of sensors to NH3 at room temperature were studied. The results show that the sensitivity, response and recovery characteristic, and the stability of PANI/TiO2 composite thin film doped by hydrochloric acid are superior to that of PANI/TiO2 composite thin film doped by PTSA. This study is helpful for the development of are NH3 sensitive device with low cost and high sensitivity.
With planar interdigitated electrodes, polyaniline-titanium dioxide (PANI/TiO2) composite thin film gas sensor doped by hydrochloric acid and para toluene sulfonic acid (PTSA) respectively were prepared by combining in situ chemical oxidation polymerization and electrostatic self-assembly technique at the room temperature. The film characterized by scanning electron microscope (SEM). The sensitive properties of sensors to NH3 at room temperature were studied. The results show that the sensitivity, response and recovery characteristic, and the stability of PANI/TiO2 composite thin film doped by hydrochloric acid are superior to that of PANI/TiO2 composite thin film doped by PTSA. This study is helpful for the development of are NH3 sensitive device with low cost and high sensitivity.
2008, 37(5): 777-781.
Abstract:
The surface of metal magnetic powders was modified by polystyrene, which was formed by chemical bond quomodo grafting styrene to the surface of metal magnetic powders by silane coupling agent A-151.We research the temperature, dosage of silane coupling agent A-151, dosage of BPO, and length to the graft efficiency. The appearance, phase constitution were characterized by SEM, RA-IR. And the powders were randomly dispersed in paraffin for microwave electromagnetic parameters test and comparison. The results show that a high resistivity film was formed on the powders surface by chemical bonding, and the real and imaginary parts of complex permittivity of the sample decrease largely but corresponding complex permeability decrease slightly.
The surface of metal magnetic powders was modified by polystyrene, which was formed by chemical bond quomodo grafting styrene to the surface of metal magnetic powders by silane coupling agent A-151.We research the temperature, dosage of silane coupling agent A-151, dosage of BPO, and length to the graft efficiency. The appearance, phase constitution were characterized by SEM, RA-IR. And the powders were randomly dispersed in paraffin for microwave electromagnetic parameters test and comparison. The results show that a high resistivity film was formed on the powders surface by chemical bonding, and the real and imaginary parts of complex permittivity of the sample decrease largely but corresponding complex permeability decrease slightly.
2008, 37(5): 782-784.
Abstract:
High efficiency red organic light-emitting diodes (OLEDs) using tris-(8-hydroxyquinoline) aluminum (AlQ) as host material fabricated via a thermal vacuum deposition process were investigated. Red organic EL devices with the structure of ITO/NPB/AlQ:Rubence(3%):DCM(3%)/AlQ/Mg:Ag/Al with a CIE coordinates of (0.45, 0.50), a maximum luminance of 4 330 cd/m2, and a maximum luminance efficiency of 6.77 lm/W have been achieved.
High efficiency red organic light-emitting diodes (OLEDs) using tris-(8-hydroxyquinoline) aluminum (AlQ) as host material fabricated via a thermal vacuum deposition process were investigated. Red organic EL devices with the structure of ITO/NPB/AlQ:Rubence(3%):DCM(3%)/AlQ/Mg:Ag/Al with a CIE coordinates of (0.45, 0.50), a maximum luminance of 4 330 cd/m2, and a maximum luminance efficiency of 6.77 lm/W have been achieved.
2008, 37(5): 785-788.
Abstract:
An embedded motion system which can run independently is constructed by applying the ARM embedded microprocessor and combining the MCX34 motion control chip. A conjunctive spot S-curve velocity look-ahead control method is applied in this system. The maximal linkup speed at the conjunctive spot is determined according to the actual conditions of the conjunctive spot on the process route. The linkup of the high process speed between each route section is realized by using the S-curve velocity control.
An embedded motion system which can run independently is constructed by applying the ARM embedded microprocessor and combining the MCX34 motion control chip. A conjunctive spot S-curve velocity look-ahead control method is applied in this system. The maximal linkup speed at the conjunctive spot is determined according to the actual conditions of the conjunctive spot on the process route. The linkup of the high process speed between each route section is realized by using the S-curve velocity control.
2008, 37(5): 789-792,800.
Abstract:
The truck assembly line is one of the most important phases of a vehicle manufacturing. One of the most key factors to make the enterprise more efficient and competitive is how to find and eliminate the bottleneck of the line in time. Based on the current production status of a truck manufacturing enterprise, a whole assembly line is modeled by the computer simulation software named ProModel. The parameters of the line, such as utilization of workstation, cycle time, work-in-process (WIP) etc., are obtained, and therefore, the bottlenecks of the line can be identified. Simulation results can help the factory managers to make better capacity plan and inventory control and improve the production efficiency.
The truck assembly line is one of the most important phases of a vehicle manufacturing. One of the most key factors to make the enterprise more efficient and competitive is how to find and eliminate the bottleneck of the line in time. Based on the current production status of a truck manufacturing enterprise, a whole assembly line is modeled by the computer simulation software named ProModel. The parameters of the line, such as utilization of workstation, cycle time, work-in-process (WIP) etc., are obtained, and therefore, the bottlenecks of the line can be identified. Simulation results can help the factory managers to make better capacity plan and inventory control and improve the production efficiency.
2008, 37(5): 793-796.
Abstract:
A variable structure dynamic model of gear driving system is established based on backlash hysteresis model and friction aggregation model. The influence of backlash and friction is compensated based on a compound controller formed by radial basis function (RBF) neural network and sliding mode. The switching plus of sliding mode controller can be adjusted by RBF neural network, which can reduce the buffeting of sliding mode control. The feasibility of this method is validated by simulation results.
A variable structure dynamic model of gear driving system is established based on backlash hysteresis model and friction aggregation model. The influence of backlash and friction is compensated based on a compound controller formed by radial basis function (RBF) neural network and sliding mode. The switching plus of sliding mode controller can be adjusted by RBF neural network, which can reduce the buffeting of sliding mode control. The feasibility of this method is validated by simulation results.
2008, 37(5): 797-800.
Abstract:
The magnetic flux leakage (MFL) method is widely used in-line inspection technique for the evaluation of gas and oil pipelines. The actual status of the defects in the pipeline is very complex. It is very difficult to research the changing rule of magnetic flux leakage field by using physics experiment method. In this paper, the MFL signals obtained during the inspection of steel pipelines has been simulated using 3D finite element analysis. The interaction of the adjacent defects has been studied. The numerical simulations imply that the adjacent defects have significant effects on the character of the MFL signals. The results show that the effect is minimal with the parallel alignment defect, and the effect is maximal with the group defect.
The magnetic flux leakage (MFL) method is widely used in-line inspection technique for the evaluation of gas and oil pipelines. The actual status of the defects in the pipeline is very complex. It is very difficult to research the changing rule of magnetic flux leakage field by using physics experiment method. In this paper, the MFL signals obtained during the inspection of steel pipelines has been simulated using 3D finite element analysis. The interaction of the adjacent defects has been studied. The numerical simulations imply that the adjacent defects have significant effects on the character of the MFL signals. The results show that the effect is minimal with the parallel alignment defect, and the effect is maximal with the group defect.
