Species evolution is essentially a random process of interaction between biological populations and their environ- ments. As a result, some physical parameters in evolution models are subject to statistical fluctuatio...Species evolution is essentially a random process of interaction between biological populations and their environ- ments. As a result, some physical parameters in evolution models are subject to statistical fluctuations. In this work, two important parameters in the Eigen model, the fitness and mutation rate, are treated as Gaassian dis- tributed random variables simultaneously to examine the property of the error threshold. Numerical simulation results show that the error threshold in the fully random model appears as a crossover region instead of a phase transition point, and ＆s the fluctuation strength increases the crossover region becomes smoother and smoother. Furthermore, it is shown that the randomization of the mutation rate plays a dominant role in changing the error threshold in the fully random model, which is consistent with the existing experimental data. The implication of the threshold change due to the randomization for antiviral strategies is discussed.展开更多
We have studied sharp peak landscapes of the Eigen model from a new perspective about how the quasispecies are distributed in the sequence space. To analyse the distribution more carefully, we bring in two tools. One ...We have studied sharp peak landscapes of the Eigen model from a new perspective about how the quasispecies are distributed in the sequence space. To analyse the distribution more carefully, we bring in two tools. One tool is the variance of Hamming distance of the sequences at a given generation. It not only offers us a different avenue for accurately locating the error threshold and illustrates how the configuration of the distribution varies with copying fidelity q in the sequence space, but also divides the copying fidelity into three distinct regimes. The other tool is the similarity network of a certain Hamming distance do, by which we can gain a visual and in-depth result about how the sequences axe distributed. We find that there are several local similarity optima around the centre （global similarity optimum） in the distribution of the sequences reproduced near the threshold. Furthermore, it is interesting that the distribution of clustering coefficient C（k） follows lognormal distribution and the curve of clustering coefficient C of the network versus do appears to be linear near the threshold.展开更多
High-accuracy geoid determination is an essential goal that many groups of scientists and countries are striving to achieve. Techniques for determining geoid models have evolved over time. Unfortunately, this all-impo...High-accuracy geoid determination is an essential goal that many groups of scientists and countries are striving to achieve. Techniques for determining geoid models have evolved over time. Unfortunately, this all-important determination requires relatively substantial technical and financial resources, depending on the type of geoid to be determined. This situation justifies the inadequacy, and sometimes absence, of accurate geoid models in many countries, despite the new challenges of altimetric positioning using space or satellite positioning techniques. This study focuses on the establishment of a geometric geoid model using simplistic techniques that are accessible and applicable in restricted or wide areas, with or without gravimetric data. The study was applied to the Dakar-Thiès-Mbour triangle, the two regions in the extreme west of Senegal that are home to the most infrastructure projects with the highest socio-economic stakes, as well as mines currently being exploited, and therefore the highest stakes in terms of positioning. This study also enabled us to assess the accuracy of a number of global field models in Senegal, which are used by some professionals for altimetric positioning using Global Positioning Satellite Systems (GNSS) in the absence of a local geoid model. The estimated geoid model is based on the determination of undulation at various sample points in the study area. To this end, a campaign of GNSS observations and direct levelling was carried out on the various points spread across the study area. These measurements were then used to determine the undulation at each point. Bilinear interpolation was used to deduce the undulations throughout the study area, based on the altimeter conversion grid. This grid was evaluated using GPS/level control points.展开更多
To reduce high computational cost of existing Direction-Of-Arrival(DOA) estimation techniques within a sparse representation framework,a novel method with low computational com-plexity is proposed.Firstly,a sparse lin...To reduce high computational cost of existing Direction-Of-Arrival(DOA) estimation techniques within a sparse representation framework,a novel method with low computational com-plexity is proposed.Firstly,a sparse linear model constructed from the eigenvectors of covariance matrix of array received signals is built.Then based on the FOCal Underdetermined System Solver(FOCUSS) algorithm,a sparse solution finding algorithm to solve the model is developed.Compared with other state-of-the-art methods using a sparse representation,our approach also can resolve closely and highly correlated sources without a priori knowledge of the number of sources.However,our method has lower computational complexity and performs better in low Signal-to-Noise Ratio(SNR).Lastly,the performance of the proposed method is illustrated by computer simulations.展开更多
A novel approach to design Internal Model Controller(IMC)is proposed in this paper directly from measuredinput and output plant data,which are assumed to becontaminated by measurement noise.In order to avoidthe compli...A novel approach to design Internal Model Controller(IMC)is proposed in this paper directly from measuredinput and output plant data,which are assumed to becontaminated by measurement noise.In order to avoidthe complicated structure-identification problem inmost cases,two Finite Impulse Response(FIR)modelsare taken to represent the plant model and the internalmodel controller respectively.Taking account of mea-surement noise both in the plant input and its output,anESD based Total Least Squares(TLS)solution is appliedfor the unbiased identification of the plant model and itsinverse model,the latter constitutes the internal modelcontroller according to the principle that the internalmodel controller approximates the inverse dynamics ofthe plant model.Simulations are given for a testifica-tion.展开更多
Based on the construction of supersymmetric generators, we use the Lewis-Riesenfeld invariant method to deduce the exact and explicit eigen-energy spectrum with the time-dependent thermo Jaynes-Cummings model. One of ...Based on the construction of supersymmetric generators, we use the Lewis-Riesenfeld invariant method to deduce the exact and explicit eigen-energy spectrum with the time-dependent thermo Jaynes-Cummings model. One of the advantages of this approach is that it can transform the hidden form, related to the chronological product, of the time evolution operator into an explicit expression. Moreover, the dynamical and statistics properties of physical quantities are obtained for the given initial states in the thermo Jaynes Cummings system.展开更多
基金Supported by the Natural Science Foundation of Hebei Province under Grant No C2013202192
文摘Species evolution is essentially a random process of interaction between biological populations and their environ- ments. As a result, some physical parameters in evolution models are subject to statistical fluctuations. In this work, two important parameters in the Eigen model, the fitness and mutation rate, are treated as Gaassian dis- tributed random variables simultaneously to examine the property of the error threshold. Numerical simulation results show that the error threshold in the fully random model appears as a crossover region instead of a phase transition point, and ＆s the fluctuation strength increases the crossover region becomes smoother and smoother. Furthermore, it is shown that the randomization of the mutation rate plays a dominant role in changing the error threshold in the fully random model, which is consistent with the existing experimental data. The implication of the threshold change due to the randomization for antiviral strategies is discussed.
基金Project supported by the National Natural Science Foundation of China （Grant Nos 10105007 and 10334020）.
文摘We have studied sharp peak landscapes of the Eigen model from a new perspective about how the quasispecies are distributed in the sequence space. To analyse the distribution more carefully, we bring in two tools. One tool is the variance of Hamming distance of the sequences at a given generation. It not only offers us a different avenue for accurately locating the error threshold and illustrates how the configuration of the distribution varies with copying fidelity q in the sequence space, but also divides the copying fidelity into three distinct regimes. The other tool is the similarity network of a certain Hamming distance do, by which we can gain a visual and in-depth result about how the sequences axe distributed. We find that there are several local similarity optima around the centre （global similarity optimum） in the distribution of the sequences reproduced near the threshold. Furthermore, it is interesting that the distribution of clustering coefficient C（k） follows lognormal distribution and the curve of clustering coefficient C of the network versus do appears to be linear near the threshold.
文摘High-accuracy geoid determination is an essential goal that many groups of scientists and countries are striving to achieve. Techniques for determining geoid models have evolved over time. Unfortunately, this all-important determination requires relatively substantial technical and financial resources, depending on the type of geoid to be determined. This situation justifies the inadequacy, and sometimes absence, of accurate geoid models in many countries, despite the new challenges of altimetric positioning using space or satellite positioning techniques. This study focuses on the establishment of a geometric geoid model using simplistic techniques that are accessible and applicable in restricted or wide areas, with or without gravimetric data. The study was applied to the Dakar-Thiès-Mbour triangle, the two regions in the extreme west of Senegal that are home to the most infrastructure projects with the highest socio-economic stakes, as well as mines currently being exploited, and therefore the highest stakes in terms of positioning. This study also enabled us to assess the accuracy of a number of global field models in Senegal, which are used by some professionals for altimetric positioning using Global Positioning Satellite Systems (GNSS) in the absence of a local geoid model. The estimated geoid model is based on the determination of undulation at various sample points in the study area. To this end, a campaign of GNSS observations and direct levelling was carried out on the various points spread across the study area. These measurements were then used to determine the undulation at each point. Bilinear interpolation was used to deduce the undulations throughout the study area, based on the altimeter conversion grid. This grid was evaluated using GPS/level control points.
基金Supported by the National Natural Science Foundation of China (No. 60502040)the Innovation Foundation for Outstanding Postgraduates in the Electronic Engineering Institute of PLA (No. 2009YB005)
文摘To reduce high computational cost of existing Direction-Of-Arrival(DOA) estimation techniques within a sparse representation framework,a novel method with low computational com-plexity is proposed.Firstly,a sparse linear model constructed from the eigenvectors of covariance matrix of array received signals is built.Then based on the FOCal Underdetermined System Solver(FOCUSS) algorithm,a sparse solution finding algorithm to solve the model is developed.Compared with other state-of-the-art methods using a sparse representation,our approach also can resolve closely and highly correlated sources without a priori knowledge of the number of sources.However,our method has lower computational complexity and performs better in low Signal-to-Noise Ratio(SNR).Lastly,the performance of the proposed method is illustrated by computer simulations.
文摘A novel approach to design Internal Model Controller(IMC)is proposed in this paper directly from measuredinput and output plant data,which are assumed to becontaminated by measurement noise.In order to avoidthe complicated structure-identification problem inmost cases,two Finite Impulse Response(FIR)modelsare taken to represent the plant model and the internalmodel controller respectively.Taking account of mea-surement noise both in the plant input and its output,anESD based Total Least Squares(TLS)solution is appliedfor the unbiased identification of the plant model and itsinverse model,the latter constitutes the internal modelcontroller according to the principle that the internalmodel controller approximates the inverse dynamics ofthe plant model.Simulations are given for a testifica-tion.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 10775097 and 10874174)
文摘Based on the construction of supersymmetric generators, we use the Lewis-Riesenfeld invariant method to deduce the exact and explicit eigen-energy spectrum with the time-dependent thermo Jaynes-Cummings model. One of the advantages of this approach is that it can transform the hidden form, related to the chronological product, of the time evolution operator into an explicit expression. Moreover, the dynamical and statistics properties of physical quantities are obtained for the given initial states in the thermo Jaynes Cummings system.
