The three-dimensional numerical simulation of two-phase plume flow of solid propellant micro-thrusters was developed.Then it was used to investigate the plume interference effect by combining the direct simulation Mon...The three-dimensional numerical simulation of two-phase plume flow of solid propellant micro-thrusters was developed.Then it was used to investigate the plume interference effect by combining the direct simulation Monte Carlo(DSMC) method for multi-component gas flow with the two-way coupling model for two-phase rarefied flow.At different space between the two micro-thrusters and different wall temperature,the plume interference effect was analyzed specifically.The results show that under the plume interference effect the gas is compressed and the flow direction is changed,which resulted in the increasing of gas pressure and temperature;solid phase made no significant effect on the flow parameters of gas phase;with the rising of the space between the two micro-thrusters,the maximum pressure decreased and the maximum temperature increased in the domain under the plume interference effect;the wall temperature could influence the temperature of the gas which is extremely close to the wall,but not the gas pressure.展开更多
Considering the mutual interference between species, a stochastic predator-prey model with impulses and Holling-II functional response is proposed in this paper. Firstly, by constructing an equivalent system without i...Considering the mutual interference between species, a stochastic predator-prey model with impulses and Holling-II functional response is proposed in this paper. Firstly, by constructing an equivalent system without impulses, the existence of a globally unique positive solution is proved. Secondly, in cases of the mutual coefficient m = 1 and 0 m < 1, by constructing suitable Lyapunov functional, the existence of T-periodic solution is investigated under some certain conditions. Finally, numerical simulation is introduced to verify our main results.展开更多
This paper treats the digital design of a probabilistic energy equalizer for impulse radio (IR) UWB receiver in high data rate (100Mbps). The aim of this study is to bypass certain complex mathematical function as a c...This paper treats the digital design of a probabilistic energy equalizer for impulse radio (IR) UWB receiver in high data rate (100Mbps). The aim of this study is to bypass certain complex mathematical function as a chi-squared distribution and reduce the computational complexity of the equalizer for a low cost hardware implementation. As in Sub-MAP algorithm, the max* operation is investigated for complexity reduction and tested by computer simulation with fixed point data types under 802.15.3a channel models. The obtained re-sults prove that the complexity reduction involves a very slight algorithm deterioration and still meet the low-cost constraint of the implementation.展开更多
In this letter,we propose a hybrid analog/digital detection algorithm,the Correlated In-terference Cancellation(CIC) algorithm,for Impulse Radio Ultra-WideBand(IR-UWB) system.The CIC algorithm correlates received sign...In this letter,we propose a hybrid analog/digital detection algorithm,the Correlated In-terference Cancellation(CIC) algorithm,for Impulse Radio Ultra-WideBand(IR-UWB) system.The CIC algorithm correlates received signal with its delayed versions in the analog domain and samples the correlation output at the symbol rate.The symbol rate samples are processed in the digital domain to perform interference cancellation.Therefore,CIC works for high data rate systems with heavy In-terSymbol Interference(ISI).Simulation results show that CIC achieves good performance in typical UWB channels.展开更多
By using the modernly developed techniques of possibility and set-valued statistics, this paper determined the thresholds of various categories of noise annoyance and defined the dose-response relation between the lev...By using the modernly developed techniques of possibility and set-valued statistics, this paper determined the thresholds of various categories of noise annoyance and defined the dose-response relation between the levels of noise and their annoyance. Three factors controlled in the experiment were types of noise: impulse and traffic; level of noise: 5Leq from 45 - 85 dB (A); and performance task: with and without speech recognition. Noise interference with speech recognition was measured with the SDT method. Our ex-perimental results showed that Leq of impulse noise should be higher than that of traffic noise to get equal annoyance; the speech recognition task might lighten the experience of annoyance; the higher the level of noise, the more its interference with the speech recognition, that is. the less the value of d '.展开更多
针对舰船辐射噪声低频线谱动态频率精细特征提取存在的频率分辨率低、瞬时频率跟踪性差、频率分析不够精细等问题,提出了一种基于移频频率细化瞬时自相关函数滤波的改进维格纳威利分布(Wigner Ville distribution,WVD)算法Z-FIR-WVD(zoo...针对舰船辐射噪声低频线谱动态频率精细特征提取存在的频率分辨率低、瞬时频率跟踪性差、频率分析不够精细等问题,提出了一种基于移频频率细化瞬时自相关函数滤波的改进维格纳威利分布(Wigner Ville distribution,WVD)算法Z-FIR-WVD(zoom-finite impulse response filter-WVD)。通过对移频降采样瞬时自相关函数在时域进行FIR(finite impulse response)滤波后的信号进行细化分析,可有效提高对WVD中多线谱交叉项干扰的抑制能力和频率分辨能力,实现对低频线谱动态精细特征的有效提取。仿真实验和实测信号验证结果表明,该算法在保持WVD频率聚集性的前提下,可有效抑制交叉项干扰,并实现对低频线谱的高频率分辨率动态分析,为舰船辐射噪声低频线谱动态频率精细特征提取问题提供了一种新的解决方法。展开更多
In this paper, a periodic Volterra model with mutual interference and impulsive effect is proposed and analyzed. By applying the Floquet theory of impulsive differential equa- tion, some conditions are obtained for th...In this paper, a periodic Volterra model with mutual interference and impulsive effect is proposed and analyzed. By applying the Floquet theory of impulsive differential equa- tion, some conditions are obtained for the linear stability of semi-trivial periodic solution. Some sufficient conditions are also given for the permanence of the system. Further, stan- dard bifurcation theory is used to show the existence of coexistence state which arises near the semi-trivial periodic solution. Finally, theoretical results are confirmed by some special cases of the system.展开更多
在电力变压器有源降噪系统实际运行时,声传感器采集的参考信号和误差信号可能存在冲击干扰,当采用传统的滤波最小均方(filtered-x least mean square,Fx LMS)算法对控制器的参数自适应更新时,控制器易受冲击性干扰的影响而出现振荡甚至...在电力变压器有源降噪系统实际运行时,声传感器采集的参考信号和误差信号可能存在冲击干扰,当采用传统的滤波最小均方(filtered-x least mean square,Fx LMS)算法对控制器的参数自适应更新时,控制器易受冲击性干扰的影响而出现振荡甚至是发散。为了抑制冲击性干扰对控制器的影响,提出了归一化滤波语音压缩?律变换的最小均方(normalized filtered-x?law mean square,NFx?LMS)算法。该算法采用经语音压缩?律函数变换后的误差信号的均方作为代价函数,并对参考信号做归一化处理以提高算法鲁棒性。算法可以根据不同声场环境的初级噪声特点选取不同的压缩系数以提高算法的实用性。仿真显示,在冲击性干扰的环境下,论文提出的算法表现出很好的鲁棒性和收敛效果。展开更多
文摘The three-dimensional numerical simulation of two-phase plume flow of solid propellant micro-thrusters was developed.Then it was used to investigate the plume interference effect by combining the direct simulation Monte Carlo(DSMC) method for multi-component gas flow with the two-way coupling model for two-phase rarefied flow.At different space between the two micro-thrusters and different wall temperature,the plume interference effect was analyzed specifically.The results show that under the plume interference effect the gas is compressed and the flow direction is changed,which resulted in the increasing of gas pressure and temperature;solid phase made no significant effect on the flow parameters of gas phase;with the rising of the space between the two micro-thrusters,the maximum pressure decreased and the maximum temperature increased in the domain under the plume interference effect;the wall temperature could influence the temperature of the gas which is extremely close to the wall,but not the gas pressure.
文摘Considering the mutual interference between species, a stochastic predator-prey model with impulses and Holling-II functional response is proposed in this paper. Firstly, by constructing an equivalent system without impulses, the existence of a globally unique positive solution is proved. Secondly, in cases of the mutual coefficient m = 1 and 0 m < 1, by constructing suitable Lyapunov functional, the existence of T-periodic solution is investigated under some certain conditions. Finally, numerical simulation is introduced to verify our main results.
文摘This paper treats the digital design of a probabilistic energy equalizer for impulse radio (IR) UWB receiver in high data rate (100Mbps). The aim of this study is to bypass certain complex mathematical function as a chi-squared distribution and reduce the computational complexity of the equalizer for a low cost hardware implementation. As in Sub-MAP algorithm, the max* operation is investigated for complexity reduction and tested by computer simulation with fixed point data types under 802.15.3a channel models. The obtained re-sults prove that the complexity reduction involves a very slight algorithm deterioration and still meet the low-cost constraint of the implementation.
基金863 project (No.2007AA01Z2B1)Natural Science Foundation of Jiangsu Province (No.BK2005409)Jiangsu "Six-Top" Project (No.07-E-018)
文摘In this letter,we propose a hybrid analog/digital detection algorithm,the Correlated In-terference Cancellation(CIC) algorithm,for Impulse Radio Ultra-WideBand(IR-UWB) system.The CIC algorithm correlates received signal with its delayed versions in the analog domain and samples the correlation output at the symbol rate.The symbol rate samples are processed in the digital domain to perform interference cancellation.Therefore,CIC works for high data rate systems with heavy In-terSymbol Interference(ISI).Simulation results show that CIC achieves good performance in typical UWB channels.
文摘By using the modernly developed techniques of possibility and set-valued statistics, this paper determined the thresholds of various categories of noise annoyance and defined the dose-response relation between the levels of noise and their annoyance. Three factors controlled in the experiment were types of noise: impulse and traffic; level of noise: 5Leq from 45 - 85 dB (A); and performance task: with and without speech recognition. Noise interference with speech recognition was measured with the SDT method. Our ex-perimental results showed that Leq of impulse noise should be higher than that of traffic noise to get equal annoyance; the speech recognition task might lighten the experience of annoyance; the higher the level of noise, the more its interference with the speech recognition, that is. the less the value of d '.
文摘In this paper, a periodic Volterra model with mutual interference and impulsive effect is proposed and analyzed. By applying the Floquet theory of impulsive differential equa- tion, some conditions are obtained for the linear stability of semi-trivial periodic solution. Some sufficient conditions are also given for the permanence of the system. Further, stan- dard bifurcation theory is used to show the existence of coexistence state which arises near the semi-trivial periodic solution. Finally, theoretical results are confirmed by some special cases of the system.
文摘在电力变压器有源降噪系统实际运行时,声传感器采集的参考信号和误差信号可能存在冲击干扰,当采用传统的滤波最小均方(filtered-x least mean square,Fx LMS)算法对控制器的参数自适应更新时,控制器易受冲击性干扰的影响而出现振荡甚至是发散。为了抑制冲击性干扰对控制器的影响,提出了归一化滤波语音压缩?律变换的最小均方(normalized filtered-x?law mean square,NFx?LMS)算法。该算法采用经语音压缩?律函数变换后的误差信号的均方作为代价函数,并对参考信号做归一化处理以提高算法鲁棒性。算法可以根据不同声场环境的初级噪声特点选取不同的压缩系数以提高算法的实用性。仿真显示,在冲击性干扰的环境下,论文提出的算法表现出很好的鲁棒性和收敛效果。
