In the seismic safety evaluation (SSE) for key projects, the probability-consistent spectrum (PCS), usually obtained from probabilistic seismic hazard analysis (PSHA), is not consistent with the design response spectr...In the seismic safety evaluation (SSE) for key projects, the probability-consistent spectrum (PCS), usually obtained from probabilistic seismic hazard analysis (PSHA), is not consistent with the design response spectrum given by Code for Seismic Design of Buildings (GB50011-2001). Sometimes, there may be a remarkable difference be-tween them. If the PCS is lower than the corresponding code design response spectrum (CDS), the seismic fortifi-cation criterion for the key projects would be lower than that for the general industry and civil buildings. In the paper, the relation between PCS and CDS is discussed by using the ideal simple potential seismic source. The re-sults show that in the most areas influenced mainly by the potential sources of the epicentral earthquakes and the regional earthquakes, PCS is generally lower than CDS in the long periods. We point out that the long-period re-sponse spectra of the code should be further studied and combined with the probability method of seismic zoning as much as possible. Because of the uncertainties in SSE, it should be prudent to use the long-period response spectra given by SSE for key projects when they are lower than CDS.展开更多
In the seismic safety evaluation (SSE) for key projects, the probability-consistent spectrum (PCS), usually obtained from probabilistic seismic hazard analysis (PSHA), is not consistent with the design response spectr...In the seismic safety evaluation (SSE) for key projects, the probability-consistent spectrum (PCS), usually obtained from probabilistic seismic hazard analysis (PSHA), is not consistent with the design response spectrum given by Code for Seismic Design of Buildings (GB50011-2001). Sometimes, there may be a remarkable difference be-tween them. If the PCS is lower than the corresponding code design response spectrum (CDS), the seismic fortifi-cation criterion for the key projects would be lower than that for the general industry and civil buildings. In the paper, the relation between PCS and CDS is discussed by using the ideal simple potential seismic source. The re-sults show that in the most areas influenced mainly by the potential sources of the epicentral earthquakes and the regional earthquakes, PCS is generally lower than CDS in the long periods. We point out that the long-period re-sponse spectra of the code should be further studied and combined with the probability method of seismic zoning as much as possible. Because of the uncertainties in SSE, it should be prudent to use the long-period response spectra given by SSE for key projects when they are lower than CDS.展开更多
The quality of spectrum sensing plays a significant role in determining the outage probability during the data transmission phase in an interweave cognitive radio network.If the secondary user(SU)fails to detect the p...The quality of spectrum sensing plays a significant role in determining the outage probability during the data transmission phase in an interweave cognitive radio network.If the secondary user(SU)fails to detect the primary user(PU)activity,it can re-sult in interference that limits the system performance.Additionally,since the wireless medium is broadcast in nature,there is a risk of eavesdroppers intercepting the cognitive users’data.Therefore,it is crucial to consider secrecy in the system analysis.In this paper,we analyze the secrecy outage probability(SOP)at the secondary receiver and derive the secret diversity gain for an interweave cognitive multiple-input multiple-output(MIMO)fading channel in the presence of an eavesdropper.Our study takes into account the ef-fects of the fading channel,the PU interference,and the eavesdropper on both spectrum sensing and data transmission phases.We demonstrate that utilizing all the antennas for sensing eliminates the limiting effects of missed detection probability and PU interference on the secret diversity gain.As a result,the cognitive user can achieve the same level of secret diversity gain as a conventional non-cognitive system(CNCS).Our an-alytical results are further validated through simula-tions.展开更多
针对时频谱模型估计语音不准确的问题,文中提出采用模型变换的方式来获得噪声和语音的对数概率密度函数,同时借助带噪语音、干净语音和噪声之间的对数关系并结合最小均方误差(Minimum Mean Square Error,MMSE)估计理论推导出估计语音对...针对时频谱模型估计语音不准确的问题,文中提出采用模型变换的方式来获得噪声和语音的对数概率密度函数,同时借助带噪语音、干净语音和噪声之间的对数关系并结合最小均方误差(Minimum Mean Square Error,MMSE)估计理论推导出估计语音对数谱的时频掩模。基于语音和噪声的对数概率分布推导出了一种软掩模,该软掩模可对带噪语音的对数子带进行加权以降低噪声,提高语音估计的准确性。仿真结果表明,与未处理的含噪语音相比,所提方法在噪声抑制方面具有3 dB以上的提升,基于最小均方误差的时频掩模和软掩模在听觉感知方面的平均提升量分别为27.7%和29.4%,在可懂度方面的平均提升量分别为12.7%和14.3%。展开更多
Weighted one bit hard combination for cooperative spectrum sensing is proposed in this paper. Two thresholds are adopted to divide the possible energy value into three weighted regions. If the energy value falls into ...Weighted one bit hard combination for cooperative spectrum sensing is proposed in this paper. Two thresholds are adopted to divide the possible energy value into three weighted regions. If the energy value falls into the corresponding region,it will be judged as "1",no information or "0". When the probability of false alarm is constrained to be constant,the objective is to maximize the probability of detection. The optimization problem is simplified by separating the weight of the middle region into several intervals. Simulation results show that the sensing performance of the proposed scheme is much better than that of the traditional one bit hard combination scheme and almost the same as that of the equal gain combination(EGC) scheme. Moreover,compared with the traditional one bit hard combination,fewer average sensing bits are required to transmit to the data fusion center with the proposed method.展开更多
Stochastic geometry is widely employed to model cellular network. But in most existing works, base stations(BSs) are modelled following a homogeneous Poisson point process(PPP) for one-tier network, or several indepen...Stochastic geometry is widely employed to model cellular network. But in most existing works, base stations(BSs) are modelled following a homogeneous Poisson point process(PPP) for one-tier network, or several independent homogeneous PPP for multi-tier network, which ignore the dependence among BSs. In this paper, a three-tier UDN(Ultra dense network) with Macrocell BSs(MBS) for basic coverage, Picocell BSs(PBSs) deployed outside the coverage area of MBSs for compensating coverage holes, and Femtocell BSs(FBSs) surrounding MBSs for capacity improvement modelled by point process with inter-tier dependence is proposed. The tier association probability, the coverage probability and area spectrum efficiency(ASE) are derived. Simulation results validate our derivation, and results show that the proposed network model has 25%-45% performance gain in ASE.展开更多
In order to reduce interference to primary users and provide better performance of detection probability and channel capacity in multi-user cooperative spectrum sensing networks, a high capacity spectrum sensing frame...In order to reduce interference to primary users and provide better performance of detection probability and channel capacity in multi-user cooperative spectrum sensing networks, a high capacity spectrum sensing framework is proposed based on the analysis of amplification factors on the performance of detection probability and channel capacity. Thanks to the energy concentration property of chirp signals in the Fractional Fourier Transform(Fr FT) domain, sinusoidal signal and different chirp signals are utilized for primary user and cognitive users, respectively. Hence, spectrum sensing and signal transmission can be performed simultaneously in our proposed framework. Simulation results show that compared with the previous relay-based framework, the modified cooperative spectrum sensing framework can improve the detection probability significantly, and the channel capacity can also be improved. Moreover, the amplification factor can be used to realize the tradeoff between detection probability and channel capacity in our proposed framework.展开更多
The majority of existing papers about spectrum sensing have the assumption that secondary users(SUs) are stationary. However,mobility is an essential feature of mobile communications networks. In this paper,the detect...The majority of existing papers about spectrum sensing have the assumption that secondary users(SUs) are stationary. However,mobility is an essential feature of mobile communications networks. In this paper,the detection performance of spectrum sensing by mobile SUs was analyzed. Three performance metrics,i.e.,detection probability,miss detection probability and false alarm probability,were thoroughly investigated. In our analysis,a critical variable was the real-time received primary user signal power by a mobile SU. Its probability distribution and mathematical expectation were analytically derived. Moreover,the three performance metrics in single-node spectrum sensing and multi-node collaborative spectrum sensing systems were also derived. Extensive simulations were performed. The results are consistent with the theoretical analysis. And it is concluded that SU mobility has a significant impact on the detection probability and the miss detection probability,but not on the false alarm probability.展开更多
As to the sonic fatigue problem of an aero-engine combustor liner structure under the random acoustic loadings,an effective method for predicting the fatigue life of a structure under random loadings was studied.First...As to the sonic fatigue problem of an aero-engine combustor liner structure under the random acoustic loadings,an effective method for predicting the fatigue life of a structure under random loadings was studied.Firstly,the probability distribution of Von Mises stress of thin-walled structure under random loadings was studied,analysis suggested that probability density function of Von Mises stress process accord approximately with two-parameter Weibull distribution.The formula for calculating Weibull parameters were given.Based on the Miner linear theory,the method for predicting the random sonic fatigue life based on the stress probability density was developed,and the model for fatigue life prediction was constructed.As an example,an aero-engine combustor liner structure was considered.The power spectrum density(PSD) of the vibrational stress response was calculated by using the coupled FEM/BEM(finite element method/boundary element method) model,the fatigue life was estimated by using the constructed model.And considering the influence of the wide frequency band,the calculated results were modified.Comparetive analysis shows that the estimated results of sonic fatigue of the combustor liner structure by using Weibull distribution of Von Mises stress are more conservative than using Dirlik distribution to some extend.The results show that the methods presented in this paper are practical for the random fatigue life analysis of the aeronautical thin-walled structures.展开更多
Aiming at improving acquisition performance for direct sequence spread spectrum （DSSS） signals, a new acquisition algorithm based on fast Fourier transform （FFT） is proposed. The code phases are parallel searched ...Aiming at improving acquisition performance for direct sequence spread spectrum （DSSS） signals, a new acquisition algorithm based on fast Fourier transform （FFT） is proposed. The code phases are parallel searched throughout the Doppler frequency domain. Since the influence of Doppler frequency errors on peak-to- average ratios of correlation power shows a pattern similar to the sinc function, it is our belief that by judging on peak-to-average ratios for different Doppler frequency errors false alarm probabilities should be lowered. Analyses have supported the underlying principle of this new algorithm. Simulation results have also indicated that the new algorithm can effectively improve the acquisition performance for DSSS signals.展开更多
In this paper, a new method for seismic hazard analysis, the probability-consistent method based on practical ground surface motion is proposed. Time histories on ground surface in the method correspond to earthquakes...In this paper, a new method for seismic hazard analysis, the probability-consistent method based on practical ground surface motion is proposed. Time histories on ground surface in the method correspond to earthquakes occurring at potential sources around sites. So of the envelope parameter, response spectrum, peak ground acceleration are of physical sense. Neglecting the response of site soil layers, the method is the same as routine probability-consistent method. The natural seismic acceleration time histories can be used for input wave directly. Generating ground motion is an approximation under lack of data of strong motion. Along with accumulating of the strong motion data around sites, we can describe the seismic environment more objectively.展开更多
By the flexible redefinition of frequency-occupation and frequency-collision event, the frequency-(collision) probability of hybrid(DS/FH) spread spectrum network is analyzed. This probability is based on the simultan...By the flexible redefinition of frequency-occupation and frequency-collision event, the frequency-(collision) probability of hybrid(DS/FH) spread spectrum network is analyzed. This probability is based on the simultaneous transmission number threshold and is discussed in synchronous and asynchronous circumstances respectively. And then, the network throughput based on the packet correct reception probability is analyzed. Two models which have finite and infinite population respectively is discussed. At last, the numerical results are given.展开更多
When every element of a random vector X =(X1,X2,...,Xn)?assumes the cumulative distribution function F0?and F1?with probability p?and 1 - p, respectively, we have shown that the probability S0?that the first order sta...When every element of a random vector X =(X1,X2,...,Xn)?assumes the cumulative distribution function F0?and F1?with probability p?and 1 - p, respectively, we have shown that the probability S0?that the first order statistic of X?is originally under F0?can be expressed as . We have also shown that , where ?and ??with ?the support of F?i?(x)?. Applications and implications of the results are discussed in the performance of wideband spectrum sensing schemes.展开更多
Random Matrix Theory (RMT) is a valuable tool for describing the asymptotic behavior of multiple systems,especially for large matrices. In this paper,using asymptotic random matrix theory,a new cooperative Multiple-In...Random Matrix Theory (RMT) is a valuable tool for describing the asymptotic behavior of multiple systems,especially for large matrices. In this paper,using asymptotic random matrix theory,a new cooperative Multiple-Input Multiple-Output (MIMO) scheme for spectrum sensing is proposed,which shows how asymptotic free property of random matrices and the property of Wishart distribution can be used to assist spectrum sensing for Cognitive Radios (CRs). Simulations over Rayleigh fading and AWGN channels demonstrate the proposed scheme has better detection performance compared with the energy detection techniques even in the case of a small sample of observations.展开更多
基金Shanghai Science & Technology Development Foundation (022512065) and Shanghai Construction Technology Development Foundation (A0206101).
文摘In the seismic safety evaluation (SSE) for key projects, the probability-consistent spectrum (PCS), usually obtained from probabilistic seismic hazard analysis (PSHA), is not consistent with the design response spectrum given by Code for Seismic Design of Buildings (GB50011-2001). Sometimes, there may be a remarkable difference be-tween them. If the PCS is lower than the corresponding code design response spectrum (CDS), the seismic fortifi-cation criterion for the key projects would be lower than that for the general industry and civil buildings. In the paper, the relation between PCS and CDS is discussed by using the ideal simple potential seismic source. The re-sults show that in the most areas influenced mainly by the potential sources of the epicentral earthquakes and the regional earthquakes, PCS is generally lower than CDS in the long periods. We point out that the long-period re-sponse spectra of the code should be further studied and combined with the probability method of seismic zoning as much as possible. Because of the uncertainties in SSE, it should be prudent to use the long-period response spectra given by SSE for key projects when they are lower than CDS.
文摘In the seismic safety evaluation (SSE) for key projects, the probability-consistent spectrum (PCS), usually obtained from probabilistic seismic hazard analysis (PSHA), is not consistent with the design response spectrum given by Code for Seismic Design of Buildings (GB50011-2001). Sometimes, there may be a remarkable difference be-tween them. If the PCS is lower than the corresponding code design response spectrum (CDS), the seismic fortifi-cation criterion for the key projects would be lower than that for the general industry and civil buildings. In the paper, the relation between PCS and CDS is discussed by using the ideal simple potential seismic source. The re-sults show that in the most areas influenced mainly by the potential sources of the epicentral earthquakes and the regional earthquakes, PCS is generally lower than CDS in the long periods. We point out that the long-period re-sponse spectra of the code should be further studied and combined with the probability method of seismic zoning as much as possible. Because of the uncertainties in SSE, it should be prudent to use the long-period response spectra given by SSE for key projects when they are lower than CDS.
文摘The quality of spectrum sensing plays a significant role in determining the outage probability during the data transmission phase in an interweave cognitive radio network.If the secondary user(SU)fails to detect the primary user(PU)activity,it can re-sult in interference that limits the system performance.Additionally,since the wireless medium is broadcast in nature,there is a risk of eavesdroppers intercepting the cognitive users’data.Therefore,it is crucial to consider secrecy in the system analysis.In this paper,we analyze the secrecy outage probability(SOP)at the secondary receiver and derive the secret diversity gain for an interweave cognitive multiple-input multiple-output(MIMO)fading channel in the presence of an eavesdropper.Our study takes into account the ef-fects of the fading channel,the PU interference,and the eavesdropper on both spectrum sensing and data transmission phases.We demonstrate that utilizing all the antennas for sensing eliminates the limiting effects of missed detection probability and PU interference on the secret diversity gain.As a result,the cognitive user can achieve the same level of secret diversity gain as a conventional non-cognitive system(CNCS).Our an-alytical results are further validated through simula-tions.
文摘针对时频谱模型估计语音不准确的问题,文中提出采用模型变换的方式来获得噪声和语音的对数概率密度函数,同时借助带噪语音、干净语音和噪声之间的对数关系并结合最小均方误差(Minimum Mean Square Error,MMSE)估计理论推导出估计语音对数谱的时频掩模。基于语音和噪声的对数概率分布推导出了一种软掩模,该软掩模可对带噪语音的对数子带进行加权以降低噪声,提高语音估计的准确性。仿真结果表明,与未处理的含噪语音相比,所提方法在噪声抑制方面具有3 dB以上的提升,基于最小均方误差的时频掩模和软掩模在听觉感知方面的平均提升量分别为27.7%和29.4%,在可懂度方面的平均提升量分别为12.7%和14.3%。
基金supported in part by the Hi-tech research and development program of China (2009AA011805)National Natural Science Foundation of China (61032002)+1 种基金the Important National Science and Technology Specifi c Projects of China (2009ZX03003-007)the Joint State Key Program of the National Natural Science Foundation of China and the National Railway Ministry of China (60830001)
文摘Weighted one bit hard combination for cooperative spectrum sensing is proposed in this paper. Two thresholds are adopted to divide the possible energy value into three weighted regions. If the energy value falls into the corresponding region,it will be judged as "1",no information or "0". When the probability of false alarm is constrained to be constant,the objective is to maximize the probability of detection. The optimization problem is simplified by separating the weight of the middle region into several intervals. Simulation results show that the sensing performance of the proposed scheme is much better than that of the traditional one bit hard combination scheme and almost the same as that of the equal gain combination(EGC) scheme. Moreover,compared with the traditional one bit hard combination,fewer average sensing bits are required to transmit to the data fusion center with the proposed method.
基金partially supported by National 863 Program (2014AA01A702)national major project (2016ZX03001011-005)national natural science foundation project (61521061)
文摘Stochastic geometry is widely employed to model cellular network. But in most existing works, base stations(BSs) are modelled following a homogeneous Poisson point process(PPP) for one-tier network, or several independent homogeneous PPP for multi-tier network, which ignore the dependence among BSs. In this paper, a three-tier UDN(Ultra dense network) with Macrocell BSs(MBS) for basic coverage, Picocell BSs(PBSs) deployed outside the coverage area of MBSs for compensating coverage holes, and Femtocell BSs(FBSs) surrounding MBSs for capacity improvement modelled by point process with inter-tier dependence is proposed. The tier association probability, the coverage probability and area spectrum efficiency(ASE) are derived. Simulation results validate our derivation, and results show that the proposed network model has 25%-45% performance gain in ASE.
基金supported in part by the National Basic Research Program of China(973 Program),under grant No.2013CB329003National Nature Science Foundation of China under grant No.61301100Hydro-Quebec,the Natural Sciences and Engineering Research Council of Canada,and Mc Gill University in the framework of the NSERC/Hydro-Quebec Industrial Research Chair in Interactive Information Infrastructure for the Power Grid under grant No.IRCPJ406021-14
文摘In order to reduce interference to primary users and provide better performance of detection probability and channel capacity in multi-user cooperative spectrum sensing networks, a high capacity spectrum sensing framework is proposed based on the analysis of amplification factors on the performance of detection probability and channel capacity. Thanks to the energy concentration property of chirp signals in the Fractional Fourier Transform(Fr FT) domain, sinusoidal signal and different chirp signals are utilized for primary user and cognitive users, respectively. Hence, spectrum sensing and signal transmission can be performed simultaneously in our proposed framework. Simulation results show that compared with the previous relay-based framework, the modified cooperative spectrum sensing framework can improve the detection probability significantly, and the channel capacity can also be improved. Moreover, the amplification factor can be used to realize the tradeoff between detection probability and channel capacity in our proposed framework.
基金supported by National Natural Science Foundation of China under Grand No.61671183
文摘The majority of existing papers about spectrum sensing have the assumption that secondary users(SUs) are stationary. However,mobility is an essential feature of mobile communications networks. In this paper,the detection performance of spectrum sensing by mobile SUs was analyzed. Three performance metrics,i.e.,detection probability,miss detection probability and false alarm probability,were thoroughly investigated. In our analysis,a critical variable was the real-time received primary user signal power by a mobile SU. Its probability distribution and mathematical expectation were analytically derived. Moreover,the three performance metrics in single-node spectrum sensing and multi-node collaborative spectrum sensing systems were also derived. Extensive simulations were performed. The results are consistent with the theoretical analysis. And it is concluded that SU mobility has a significant impact on the detection probability and the miss detection probability,but not on the false alarm probability.
基金Supported by the National Aviation Fundamental Science Foundation of China(No.02C54007)
文摘As to the sonic fatigue problem of an aero-engine combustor liner structure under the random acoustic loadings,an effective method for predicting the fatigue life of a structure under random loadings was studied.Firstly,the probability distribution of Von Mises stress of thin-walled structure under random loadings was studied,analysis suggested that probability density function of Von Mises stress process accord approximately with two-parameter Weibull distribution.The formula for calculating Weibull parameters were given.Based on the Miner linear theory,the method for predicting the random sonic fatigue life based on the stress probability density was developed,and the model for fatigue life prediction was constructed.As an example,an aero-engine combustor liner structure was considered.The power spectrum density(PSD) of the vibrational stress response was calculated by using the coupled FEM/BEM(finite element method/boundary element method) model,the fatigue life was estimated by using the constructed model.And considering the influence of the wide frequency band,the calculated results were modified.Comparetive analysis shows that the estimated results of sonic fatigue of the combustor liner structure by using Weibull distribution of Von Mises stress are more conservative than using Dirlik distribution to some extend.The results show that the methods presented in this paper are practical for the random fatigue life analysis of the aeronautical thin-walled structures.
基金Sponsored by the National "863" Program Project (1010021310XXX)
文摘Aiming at improving acquisition performance for direct sequence spread spectrum （DSSS） signals, a new acquisition algorithm based on fast Fourier transform （FFT） is proposed. The code phases are parallel searched throughout the Doppler frequency domain. Since the influence of Doppler frequency errors on peak-to- average ratios of correlation power shows a pattern similar to the sinc function, it is our belief that by judging on peak-to-average ratios for different Doppler frequency errors false alarm probabilities should be lowered. Analyses have supported the underlying principle of this new algorithm. Simulation results have also indicated that the new algorithm can effectively improve the acquisition performance for DSSS signals.
文摘In this paper, a new method for seismic hazard analysis, the probability-consistent method based on practical ground surface motion is proposed. Time histories on ground surface in the method correspond to earthquakes occurring at potential sources around sites. So of the envelope parameter, response spectrum, peak ground acceleration are of physical sense. Neglecting the response of site soil layers, the method is the same as routine probability-consistent method. The natural seismic acceleration time histories can be used for input wave directly. Generating ground motion is an approximation under lack of data of strong motion. Along with accumulating of the strong motion data around sites, we can describe the seismic environment more objectively.
文摘By the flexible redefinition of frequency-occupation and frequency-collision event, the frequency-(collision) probability of hybrid(DS/FH) spread spectrum network is analyzed. This probability is based on the simultaneous transmission number threshold and is discussed in synchronous and asynchronous circumstances respectively. And then, the network throughput based on the packet correct reception probability is analyzed. Two models which have finite and infinite population respectively is discussed. At last, the numerical results are given.
文摘When every element of a random vector X =(X1,X2,...,Xn)?assumes the cumulative distribution function F0?and F1?with probability p?and 1 - p, respectively, we have shown that the probability S0?that the first order statistic of X?is originally under F0?can be expressed as . We have also shown that , where ?and ??with ?the support of F?i?(x)?. Applications and implications of the results are discussed in the performance of wideband spectrum sensing schemes.
基金Supported by the National Natural Science Foundation of China (No.60972039)Natural Science Foundation of Jiangsu Province (No.BK2007729)Natural Science Funding of Jiangsu Province (No.06KJA51001)
文摘Random Matrix Theory (RMT) is a valuable tool for describing the asymptotic behavior of multiple systems,especially for large matrices. In this paper,using asymptotic random matrix theory,a new cooperative Multiple-Input Multiple-Output (MIMO) scheme for spectrum sensing is proposed,which shows how asymptotic free property of random matrices and the property of Wishart distribution can be used to assist spectrum sensing for Cognitive Radios (CRs). Simulations over Rayleigh fading and AWGN channels demonstrate the proposed scheme has better detection performance compared with the energy detection techniques even in the case of a small sample of observations.
