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Sample records for global exponential stability

  1. Global exponential stability for nonautonomous cellular neural networks with delays

    International Nuclear Information System (INIS)

    Zhang Qiang; Wei Xiaopeng; Xu Jin

    2006-01-01

    In this Letter, by utilizing Lyapunov functional method and Halanay inequalities, we analyze global exponential stability of nonautonomous cellular neural networks with delay. Several new sufficient conditions ensuring global exponential stability of the network are obtained. The results given here extend and improve the earlier publications. An example is given to demonstrate the effectiveness of the obtained results

  2. New Results of Global Exponential Stabilization for BLDCMs System

    OpenAIRE

    Fengxia Tian; Fangchao Zhen; Guopeng Zhou; Xiaoxin Liao

    2015-01-01

    The global exponential stabilization for brushless direct current motor (BLDCM) system is studied. Four linear and simple feedback controllers are proposed to realize the global stabilization of BLDCM with exponential convergence rate; the control law used in each theorem is less conservative and more concise. Finally, an example is given to demonstrate the correctness of the proposed results.

  3. Global robust exponential stability for interval neural networks with delay

    International Nuclear Information System (INIS)

    Cui Shihua; Zhao Tao; Guo Jie

    2009-01-01

    In this paper, new sufficient conditions for globally robust exponential stability of neural networks with either constant delays or time-varying delays are given. We show the sufficient conditions for the existence, uniqueness and global robust exponential stability of the equilibrium point by employing Lyapunov stability theory and linear matrix inequality (LMI) technique. Numerical examples are given to show the approval of our results.

  4. Global robust exponential stability analysis for interval recurrent neural networks

    International Nuclear Information System (INIS)

    Xu Shengyuan; Lam, James; Ho, Daniel W.C.; Zou Yun

    2004-01-01

    This Letter investigates the problem of robust global exponential stability analysis for interval recurrent neural networks (RNNs) via the linear matrix inequality (LMI) approach. The values of the time-invariant uncertain parameters are assumed to be bounded within given compact sets. An improved condition for the existence of a unique equilibrium point and its global exponential stability of RNNs with known parameters is proposed. Based on this, a sufficient condition for the global robust exponential stability for interval RNNs is obtained. Both of the conditions are expressed in terms of LMIs, which can be checked easily by various recently developed convex optimization algorithms. Examples are provided to demonstrate the reduced conservatism of the proposed exponential stability condition

  5. Globally exponential stability of neural network with constant and variable delays

    International Nuclear Information System (INIS)

    Zhao Weirui; Zhang Huanshui

    2006-01-01

    This Letter presents new sufficient conditions of globally exponential stability of neural networks with delays. We show that these results generalize recently published globally exponential stability results. In particular, several different globally exponential stability conditions in the literatures which were proved using different Lyapunov functionals are generalized and unified by using the same Lyapunov functional and the technique of inequality of integral. A comparison between our results and the previous results admits that our results establish a new set of stability criteria for delayed neural networks. Those conditions are less restrictive than those given in the earlier references

  6. Globally exponential stability condition of a class of neural networks with time-varying delays

    International Nuclear Information System (INIS)

    Liao, T.-L.; Yan, J.-J.; Cheng, C.-J.; Hwang, C.-C.

    2005-01-01

    In this Letter, the globally exponential stability for a class of neural networks including Hopfield neural networks and cellular neural networks with time-varying delays is investigated. Based on the Lyapunov stability method, a novel and less conservative exponential stability condition is derived. The condition is delay-dependent and easily applied only by checking the Hamiltonian matrix with no eigenvalues on the imaginary axis instead of directly solving an algebraic Riccati equation. Furthermore, the exponential stability degree is more easily assigned than those reported in the literature. Some examples are given to demonstrate validity and excellence of the presented stability condition herein

  7. Global exponential stability of fuzzy cellular neural networks with delays and reaction-diffusion terms

    International Nuclear Information System (INIS)

    Wang Jian; Lu Junguo

    2008-01-01

    In this paper, we study the global exponential stability of fuzzy cellular neural networks with delays and reaction-diffusion terms. By constructing a suitable Lyapunov functional and utilizing some inequality techniques, we obtain a sufficient condition for the uniqueness and global exponential stability of the equilibrium solution for a class of fuzzy cellular neural networks with delays and reaction-diffusion terms. The result imposes constraint conditions on the network parameters independently of the delay parameter. The result is also easy to check and plays an important role in the design and application of globally exponentially stable fuzzy neural circuits

  8. Global exponential stability of reaction-diffusion recurrent neural networks with time-varying delays

    International Nuclear Information System (INIS)

    Liang Jinling; Cao Jinde

    2003-01-01

    Employing general Halanay inequality, we analyze the global exponential stability of a class of reaction-diffusion recurrent neural networks with time-varying delays. Several new sufficient conditions are obtained to ensure existence, uniqueness and global exponential stability of the equilibrium point of delayed reaction-diffusion recurrent neural networks. The results extend and improve the earlier publications. In addition, an example is given to show the effectiveness of the obtained result

  9. Global exponential stability of mixed discrete and distributively delayed cellular neural network

    International Nuclear Information System (INIS)

    Yao Hong-Xing; Zhou Jia-Yan

    2011-01-01

    This paper concernes analysis for the global exponential stability of a class of recurrent neural networks with mixed discrete and distributed delays. It first proves the existence and uniqueness of the balance point, then by employing the Lyapunov—Krasovskii functional and Young inequality, it gives the sufficient condition of global exponential stability of cellular neural network with mixed discrete and distributed delays, in addition, the example is provided to illustrate the applicability of the result. (general)

  10. Globally exponential stability and periodic solutions of CNNS with variable coefficients and variable delays

    International Nuclear Information System (INIS)

    Liu Haifei; Wang Li

    2006-01-01

    In this Letter, by using the inequality method and the Lyapunov functional method, we analyze the globally exponential stability and the existence of periodic solutions of a class of cellular neutral networks with delays and variable coefficients. Some simple and new sufficient conditions ensuring the existence and uniqueness of globally exponential stability of periodic solutions for cellular neutral networks with variable coefficients and delays are obtained. In addition, one example is also worked out to illustrate our theory

  11. Global exponential stability for reaction-diffusion recurrent neural networks with multiple time varying delays

    International Nuclear Information System (INIS)

    Lou, X.; Cui, B.

    2008-01-01

    In this paper we consider the problem of exponential stability for recurrent neural networks with multiple time varying delays and reaction-diffusion terms. The activation functions are supposed to be bounded and globally Lipschitz continuous. By means of Lyapunov functional, sufficient conditions are derived, which guarantee global exponential stability of the delayed neural network. Finally, a numerical example is given to show the correctness of our analysis. (author)

  12. Globally exponential stability and periodic solutions of CNNS with variable coefficients and variable delays

    Energy Technology Data Exchange (ETDEWEB)

    Liu Haifei [School of Management and Engineering, Nanjing University, Nanjing 210093 (China)]. E-mail: hfliu80@126.com; Wang Li [School of Management and Engineering, Nanjing University, Nanjing 210093 (China)

    2006-09-15

    In this Letter, by using the inequality method and the Lyapunov functional method, we analyze the globally exponential stability and the existence of periodic solutions of a class of cellular neutral networks with delays and variable coefficients. Some simple and new sufficient conditions ensuring the existence and uniqueness of globally exponential stability of periodic solutions for cellular neutral networks with variable coefficients and delays are obtained. In addition, one example is also worked out to illustrate our theory.

  13. Global exponential stability of BAM neural networks with time-varying delays and diffusion terms

    International Nuclear Information System (INIS)

    Wan Li; Zhou Qinghua

    2007-01-01

    The stability property of bidirectional associate memory (BAM) neural networks with time-varying delays and diffusion terms are considered. By using the method of variation parameter and inequality technique, the delay-independent sufficient conditions to guarantee the uniqueness and global exponential stability of the equilibrium solution of such networks are established

  14. Global exponential stability of BAM neural networks with time-varying delays and diffusion terms

    Science.gov (United States)

    Wan, Li; Zhou, Qinghua

    2007-11-01

    The stability property of bidirectional associate memory (BAM) neural networks with time-varying delays and diffusion terms are considered. By using the method of variation parameter and inequality technique, the delay-independent sufficient conditions to guarantee the uniqueness and global exponential stability of the equilibrium solution of such networks are established.

  15. On global exponential stability of high-order neural networks with time-varying delays

    International Nuclear Information System (INIS)

    Zhang Baoyong; Xu Shengyuan; Li Yongmin; Chu Yuming

    2007-01-01

    This Letter investigates the problem of stability analysis for a class of high-order neural networks with time-varying delays. The delays are bounded but not necessarily differentiable. Based on the Lyapunov stability theory together with the linear matrix inequality (LMI) approach and the use of Halanay inequality, sufficient conditions guaranteeing the global exponential stability of the equilibrium point of the considered neural networks are presented. Two numerical examples are provided to demonstrate the effectiveness of the proposed stability criteria

  16. On global exponential stability of high-order neural networks with time-varying delays

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Baoyong [School of Automation, Nanjing University of Science and Technology, Nanjing 210094, Jiangsu (China)]. E-mail: baoyongzhang@yahoo.com.cn; Xu Shengyuan [School of Automation, Nanjing University of Science and Technology, Nanjing 210094, Jiangsu (China)]. E-mail: syxu02@yahoo.com.cn; Li Yongmin [School of Automation, Nanjing University of Science and Technology, Nanjing 210094, Jiangsu (China) and Department of Mathematics, Huzhou Teacher' s College, Huzhou 313000, Zhejiang (China)]. E-mail: ymlwww@163.com; Chu Yuming [Department of Mathematics, Huzhou Teacher' s College, Huzhou 313000, Zhejiang (China)

    2007-06-18

    This Letter investigates the problem of stability analysis for a class of high-order neural networks with time-varying delays. The delays are bounded but not necessarily differentiable. Based on the Lyapunov stability theory together with the linear matrix inequality (LMI) approach and the use of Halanay inequality, sufficient conditions guaranteeing the global exponential stability of the equilibrium point of the considered neural networks are presented. Two numerical examples are provided to demonstrate the effectiveness of the proposed stability criteria.

  17. Global exponential stability of cellular neural networks with mixed delays and impulses

    International Nuclear Information System (INIS)

    Xiong Wanmin; Zhou Qiyuan; Xiao Bing; Yu Yuehua

    2007-01-01

    In this paper cellular neural networks with mixed delays and impulses are considered. Sufficient conditions for the existence and global exponential stability of a unique equilibrium point are established by using the fixed point theorem and differential inequality technique. The results of this paper are new and they complement previously known results

  18. Global exponential stability of cellular neural networks with continuously distributed delays and impulses

    International Nuclear Information System (INIS)

    Wang Yixuan; Xiong Wanmin; Zhou Qiyuan; Xiao Bing; Yu Yuehua

    2006-01-01

    In this Letter cellular neural networks with continuously distributed delays and impulses are considered. Sufficient conditions for the existence and global exponential stability of a unique equilibrium point are established by using the fixed point theorem and differential inequality techniques. The results of this Letter are new and they complement previously known results

  19. Existence and global exponential stability of periodic solution of CNNs with impulses

    Energy Technology Data Exchange (ETDEWEB)

    Li Yongkun [Department of Mathematics, Yunnan University, Kunming, Yunnan 650091 (China); Xing Zhiwei [Department of Mathematics, Yunnan University, Kunming, Yunnan 650091 (China)

    2007-08-15

    Sufficient conditions are obtained for the existence and global exponential stability of a unique periodic solution of cellular neural networks with variable time delays and impulses by using Mawhin's continuation theorem of coincidence degree and by means of a method based on delay differential inequality.

  20. Existence and global exponential stability of periodic solution of CNNs with impulses

    International Nuclear Information System (INIS)

    Li Yongkun; Xing Zhiwei

    2007-01-01

    Sufficient conditions are obtained for the existence and global exponential stability of a unique periodic solution of cellular neural networks with variable time delays and impulses by using Mawhin's continuation theorem of coincidence degree and by means of a method based on delay differential inequality

  1. New results on global exponential stability of recurrent neural networks with time-varying delays

    International Nuclear Information System (INIS)

    Xu Shengyuan; Chu Yuming; Lu Junwei

    2006-01-01

    This Letter provides new sufficient conditions for the existence, uniqueness and global exponential stability of the equilibrium point of recurrent neural networks with time-varying delays by employing Lyapunov functions and using the Halanay inequality. The time-varying delays are not necessarily differentiable. Both Lipschitz continuous activation functions and monotone nondecreasing activation functions are considered. The derived stability criteria are expressed in terms of linear matrix inequalities (LMIs), which can be checked easily by resorting to recently developed algorithms solving LMIs. Furthermore, the proposed stability results are less conservative than some previous ones in the literature, which is demonstrated via some numerical examples

  2. New results on global exponential stability of recurrent neural networks with time-varying delays

    Energy Technology Data Exchange (ETDEWEB)

    Xu Shengyuan [Department of Automation, Nanjing University of Science and Technology, Nanjing 210094 (China)]. E-mail: syxu02@yahoo.com.cn; Chu Yuming [Department of Mathematics, Huzhou Teacher' s College, Huzhou, Zhejiang 313000 (China); Lu Junwei [School of Electrical and Automation Engineering, Nanjing Normal University, 78 Bancang Street, Nanjing, 210042 (China)

    2006-04-03

    This Letter provides new sufficient conditions for the existence, uniqueness and global exponential stability of the equilibrium point of recurrent neural networks with time-varying delays by employing Lyapunov functions and using the Halanay inequality. The time-varying delays are not necessarily differentiable. Both Lipschitz continuous activation functions and monotone nondecreasing activation functions are considered. The derived stability criteria are expressed in terms of linear matrix inequalities (LMIs), which can be checked easily by resorting to recently developed algorithms solving LMIs. Furthermore, the proposed stability results are less conservative than some previous ones in the literature, which is demonstrated via some numerical examples.

  3. Global exponential stability of fuzzy BAM neural networks with time-varying delays

    International Nuclear Information System (INIS)

    Zhang Qianhong; Luo Wei

    2009-01-01

    In this paper, a class of fuzzy bidirectional associated memory (BAM) neural networks with time-varying delays are studied. Employing fixed point theorem, matrix theory and inequality analysis, some sufficient conditions are established for the existence, uniqueness and global exponential stability of equilibrium point. The sufficient conditions are easy to verify at pattern recognition and automatic control. Finally, an example is given to show feasibility and effectiveness of our results.

  4. Global exponential stability of BAM neural networks with delays and impulses

    International Nuclear Information System (INIS)

    Li Yongkun

    2005-01-01

    Sufficient conditions are obtained for the existence and global exponential stability of a unique equilibrium of a class of two-layer heteroassociative networks called bidirectional associative memory (BAM) networks with Lipschitzian activation functions without assuming their boundedness, monotonicity or differentiability and subjected to impulsive state displacements at fixed instants of time. An illustrative example is given to demonstrate the effectiveness of the obtained results

  5. Global exponential stability analysis on impulsive BAM neural networks with distributed delays

    Science.gov (United States)

    Li, Yao-Tang; Yang, Chang-Bo

    2006-12-01

    Using M-matrix and topological degree tool, sufficient conditions are obtained for the existence, uniqueness and global exponential stability of the equilibrium point of bidirectional associative memory (BAM) neural networks with distributed delays and subjected to impulsive state displacements at fixed instants of time by constructing a suitable Lyapunov functional. The results remove the usual assumptions that the boundedness, monotonicity, and differentiability of the activation functions. It is shown that in some cases, the stability criteria can be easily checked. Finally, an illustrative example is given to show the effectiveness of the presented criteria.

  6. Global exponential stability of bidirectional associative memory neural networks with distributed delays

    Science.gov (United States)

    Song, Qiankun; Cao, Jinde

    2007-05-01

    A bidirectional associative memory neural network model with distributed delays is considered. By constructing a new Lyapunov functional, employing the homeomorphism theory, M-matrix theory and the inequality (a[greater-or-equal, slanted]0,bk[greater-or-equal, slanted]0,qk>0 with , and r>1), a sufficient condition is obtained to ensure the existence, uniqueness and global exponential stability of the equilibrium point for the model. Moreover, the exponential converging velocity index is estimated, which depends on the delay kernel functions and the system parameters. The results generalize and improve the earlier publications, and remove the usual assumption that the activation functions are bounded . Two numerical examples are given to show the effectiveness of the obtained results.

  7. Global exponential stability of BAM neural networks with transmission delays and nonlinear impulses

    International Nuclear Information System (INIS)

    Huang Zhenkun; Xia Yonghui

    2008-01-01

    In this paper, a class of bidirectional associative memory (BAM) networks with transmission delays and nonlinear impulses are studied. Some new sufficient conditions are established for the existence and global exponential stability of a unique equilibrium, which generalize and improve the previously known results. The sufficient conditions are easy to verify and when the impulsive jumps are linear or absent the results reduce to those of common impulsive or non-impulsive systems. Finally, an example is given to show the feasibility and effectiveness of our results

  8. Global Exponential Stability of Delayed Cohen-Grossberg BAM Neural Networks with Impulses on Time Scales

    Directory of Open Access Journals (Sweden)

    Yongkun Li

    2009-01-01

    Full Text Available Based on the theory of calculus on time scales, the homeomorphism theory, Lyapunov functional method, and some analysis techniques, sufficient conditions are obtained for the existence, uniqueness, and global exponential stability of the equilibrium point of Cohen-Grossberg bidirectional associative memory (BAM neural networks with distributed delays and impulses on time scales. This is the first time applying the time-scale calculus theory to unify the discrete-time and continuous-time Cohen-Grossberg BAM neural network with impulses under the same framework.

  9. Existence and globally exponential stability of equilibrium for BAM neural networks with impulses

    International Nuclear Information System (INIS)

    Xia Yonghui; Huang Zhenkun; Han Maoan

    2008-01-01

    In this paper, a class of two-layer heteroassociative networks called bidirectional associative memory (BAM) networks with impulses is studied. Some new sufficient conditions are established for the existence and globally exponential stability of a unique equilibrium, which generalize and improve the previously known results. The sufficient conditions are easy to verify and when the impulsive jumps are absent the results reduce to those of the non-impulsive systems. The approaches are based on employing Banach's fixed point theorem, matrix theory and its spectral theory. Our results generalize and significantly improve the previous known results due to this method. Examples are given to show the feasibility and effectiveness of our results

  10. Global exponential stability and existence of periodic solutions of CNNs with delays

    Science.gov (United States)

    Dong, Meifang

    2002-07-01

    In this Letter, we establish general sufficient conditions for global exponential stability and existence of periodic solutions of a class of cellular neural networks (CNNs) with delays. The key to proving the sufficient conditions is the construction of a new Lyapunov functional. An elementary inequality, which may be of independent interest, has been employed in the proof. Checking the sufficient conditions is often reduced to checking some algebraic relations among certain set of parameter. Our sufficient conditions recover the known results in literature as special cases. Finally, we give two examples to illustrate the usage of our main results.

  11. Global exponential stability and periodicity of reaction-diffusion recurrent neural networks with distributed delays and Dirichlet boundary conditions

    International Nuclear Information System (INIS)

    Lu Junguo; Lu Linji

    2009-01-01

    In this paper, global exponential stability and periodicity of a class of reaction-diffusion recurrent neural networks with distributed delays and Dirichlet boundary conditions are studied by constructing suitable Lyapunov functionals and utilizing some inequality techniques. We first prove global exponential convergence to 0 of the difference between any two solutions of the original neural networks, the existence and uniqueness of equilibrium is the direct results of this procedure. This approach is different from the usually used one where the existence, uniqueness of equilibrium and stability are proved in two separate steps. Secondly, we prove periodicity. Sufficient conditions ensuring the existence, uniqueness, and global exponential stability of the equilibrium and periodic solution are given. These conditions are easy to verify and our results play an important role in the design and application of globally exponentially stable neural circuits and periodic oscillatory neural circuits.

  12. Global exponential stability for discrete-time neural networks with variable delays

    International Nuclear Information System (INIS)

    Chen Wuhua; Lu Xiaomei; Liang Dongying

    2006-01-01

    This Letter provides new exponential stability criteria for discrete-time neural networks with variable delays. The main technique is to reduce exponential convergence estimation of the neural network solution to that of one component of the corresponding solution by constructing Lyapunov function based on M-matrix. By introducing the tuning parameter diagonal matrix, the delay-independent and delay-dependent exponential stability conditions have been unified in the same mathematical formula. The effectiveness of the new results are illustrated by three examples

  13. Global exponential stability of a class of retarded impulsive differential equations with applications

    International Nuclear Information System (INIS)

    Xia Yonghui; Wong, Patricia J.Y.

    2009-01-01

    This paper studies the dynamics of a class of retarded impulsive differential equations (IDE), which generalizes the delayed cellular neural networks (DCNN), delayed bidirectional associative memory (BAM) neural networks and some population growth models. Some sufficient criteria are obtained for the existence and global exponential stability of a unique equilibrium. When the impulsive jumps are absent, our results reduce to its corresponding results for the non-impulsive systems. The approaches are based on Banach's fixed point theorem, matrix theory and its spectral theory. Due to this method, our results generalize and improve many previous known results such as . Some examples are also included to illustrate the feasibility and effectiveness of the results obtained

  14. A new criterion on the global exponential stability for cellular neural networks with multiple time-varying delays

    International Nuclear Information System (INIS)

    Jiang Haijun; Teng Zhidong

    2005-01-01

    In this Letter, based on the Lyapunov stability theorem as well as some facts about the positive definiteness and inequality of matrices, a new sufficient condition to ensure the global exponential stability of equilibrium point for autonomous delayed CNNs is obtained. This condition is less restrictive than given in the earlier references

  15. Global exponential stability of uncertain fuzzy BAM neural networks with time-varying delays

    International Nuclear Information System (INIS)

    Syed Ali, M.; Balasubramaniam, P.

    2009-01-01

    In this paper, the Takagi-Sugeno (TS) fuzzy model representation is extended to the stability analysis for uncertain Bidirectional Associative Memory (BAM) neural networks with time-varying delays using linear matrix inequality (LMI) theory. A novel LMI-based stability criterion is obtained by LMI optimization algorithms to guarantee the exponential stability of uncertain BAM neural networks with time-varying delays which are represented by TS fuzzy models. Finally, the proposed stability conditions are demonstrated with numerical examples.

  16. Global exponential stability of impulsive fuzzy cellular neural networks with mixed delays and reaction-diffusion terms

    International Nuclear Information System (INIS)

    Wang Xiaohu; Xu Daoyi

    2009-01-01

    In this paper, the global exponential stability of impulsive fuzzy cellular neural networks with mixed delays and reaction-diffusion terms is considered. By establishing an integro-differential inequality with impulsive initial condition and using the properties of M-cone and eigenspace of the spectral radius of nonnegative matrices, several new sufficient conditions are obtained to ensure the global exponential stability of the equilibrium point for fuzzy cellular neural networks with delays and reaction-diffusion terms. These results extend and improve the earlier publications. Two examples are given to illustrate the efficiency of the obtained results.

  17. Novel criteria for global exponential periodicity and stability of recurrent neural networks with time-varying delays

    International Nuclear Information System (INIS)

    Song Qiankun

    2008-01-01

    In this paper, the global exponential periodicity and stability of recurrent neural networks with time-varying delays are investigated by applying the idea of vector Lyapunov function, M-matrix theory and inequality technique. We assume neither the global Lipschitz conditions on these activation functions nor the differentiability on these time-varying delays, which were needed in other papers. Several novel criteria are found to ascertain the existence, uniqueness and global exponential stability of periodic solution for recurrent neural network with time-varying delays. Moreover, the exponential convergence rate index is estimated, which depends on the system parameters. Some previous results are improved and generalized, and an example is given to show the effectiveness of our method

  18. Global Exponential Stability of Positive Almost Periodic Solutions for a Fishing Model with a Time-Varying Delay

    Directory of Open Access Journals (Sweden)

    Hong Zhang

    2014-01-01

    Full Text Available This paper is concerned with a nonautonomous fishing model with a time-varying delay. Under proper conditions, we employ a novel argument to establish a criterion on the global exponential stability of positive almost periodic solutions of the model with almost periodic coefficients and delays. Moreover, an example and its numerical simulation are given to illustrate the main results.

  19. Global exponential stability of BAM neural networks with time-varying delays: The discrete-time case

    Science.gov (United States)

    Raja, R.; Marshal Anthoni, S.

    2011-02-01

    This paper deals with the problem of stability analysis for a class of discrete-time bidirectional associative memory (BAM) neural networks with time-varying delays. By employing the Lyapunov functional and linear matrix inequality (LMI) approach, a new sufficient conditions is proposed for the global exponential stability of discrete-time BAM neural networks. The proposed LMI based results can be easily checked by LMI control toolbox. Moreover, an example is also provided to demonstrate the effectiveness of the proposed method.

  20. Global exponential stability of inertial memristor-based neural networks with time-varying delays and impulses.

    Science.gov (United States)

    Zhang, Wei; Huang, Tingwen; He, Xing; Li, Chuandong

    2017-11-01

    In this study, we investigate the global exponential stability of inertial memristor-based neural networks with impulses and time-varying delays. We construct inertial memristor-based neural networks based on the characteristics of the inertial neural networks and memristor. Impulses with and without delays are considered when modeling the inertial neural networks simultaneously, which are of great practical significance in the current study. Some sufficient conditions are derived under the framework of the Lyapunov stability method, as well as an extended Halanay differential inequality and a new delay impulsive differential inequality, which depend on impulses with and without delays, in order to guarantee the global exponential stability of the inertial memristor-based neural networks. Finally, two numerical examples are provided to illustrate the efficiency of the proposed methods. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Existence and global exponential stability of periodic solutions for n-dimensional neutral dynamic equations on time scales.

    Science.gov (United States)

    Li, Bing; Li, Yongkun; Zhang, Xuemei

    2016-01-01

    In this paper, by using the existence of the exponential dichotomy of linear dynamic equations on time scales and the theory of calculus on time scales, we study the existence and global exponential stability of periodic solutions for a class of n-dimensional neutral dynamic equations on time scales. We also present an example to illustrate the feasibility of our results. The results of this paper are completely new and complementary to the previously known results even in both the case of differential equations (time scale [Formula: see text]) and the case of difference equations (time scale [Formula: see text]).

  2. Impulsive effect on global exponential stability of BAM fuzzy cellular neural networks with time-varying delays

    Science.gov (United States)

    Li, Kelin

    2010-02-01

    In this article, a class of impulsive bidirectional associative memory (BAM) fuzzy cellular neural networks (FCNNs) with time-varying delays is formulated and investigated. By employing delay differential inequality and M-matrix theory, some sufficient conditions ensuring the existence, uniqueness and global exponential stability of equilibrium point for impulsive BAM FCNNs with time-varying delays are obtained. In particular, a precise estimate of the exponential convergence rate is also provided, which depends on system parameters and impulsive perturbation intention. It is believed that these results are significant and useful for the design and applications of BAM FCNNs. An example is given to show the effectiveness of the results obtained here.

  3. Global exponential stability and lag synchronization for delayed memristive fuzzy Cohen-Grossberg BAM neural networks with impulses.

    Science.gov (United States)

    Yang, Wengui; Yu, Wenwu; Cao, Jinde; Alsaadi, Fuad E; Hayat, Tasawar

    2018-02-01

    This paper investigates the stability and lag synchronization for memristor-based fuzzy Cohen-Grossberg bidirectional associative memory (BAM) neural networks with mixed delays (asynchronous time delays and continuously distributed delays) and impulses. By applying the inequality analysis technique, homeomorphism theory and some suitable Lyapunov-Krasovskii functionals, some new sufficient conditions for the uniqueness and global exponential stability of equilibrium point are established. Furthermore, we obtain several sufficient criteria concerning globally exponential lag synchronization for the proposed system based on the framework of Filippov solution, differential inclusion theory and control theory. In addition, some examples with numerical simulations are given to illustrate the feasibility and validity of obtained results. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. Global exponential stability and periodicity of reaction-diffusion delayed recurrent neural networks with Dirichlet boundary conditions

    International Nuclear Information System (INIS)

    Lu Junguo

    2008-01-01

    In this paper, the global exponential stability and periodicity for a class of reaction-diffusion delayed recurrent neural networks with Dirichlet boundary conditions are addressed by constructing suitable Lyapunov functionals and utilizing some inequality techniques. We first prove global exponential converge to 0 of the difference between any two solutions of the original reaction-diffusion delayed recurrent neural networks with Dirichlet boundary conditions, the existence and uniqueness of equilibrium is the direct results of this procedure. This approach is different from the usually used one where the existence, uniqueness of equilibrium and stability are proved in two separate steps. Furthermore, we prove periodicity of the reaction-diffusion delayed recurrent neural networks with Dirichlet boundary conditions. Sufficient conditions ensuring the global exponential stability and the existence of periodic oscillatory solutions for the reaction-diffusion delayed recurrent neural networks with Dirichlet boundary conditions are given. These conditions are easy to check and have important leading significance in the design and application of reaction-diffusion recurrent neural networks with delays. Finally, two numerical examples are given to show the effectiveness of the obtained results

  5. The existence and global exponential stability of a periodic solution of a class of delay differential equations

    International Nuclear Information System (INIS)

    Tang, X H; Zou, Xingfu

    2009-01-01

    By employing Schauder's fixed point theorem and a non-Liapunov method (matrix theory, inequality analysis), we obtain some new criteria that ensure existence and global exponential stability of a periodic solution to a class of functional differential equations. Applying these criteria to a cellular neural network with time delays (delayed cellular neural network, DCNN) under a periodic environment leads to some new results that improve and generalize many existing ones we know on this topic. These results are of great significance in designs and applications of globally stable periodic DCNNs

  6. Global exponential stability of octonion-valued neural networks with leakage delay and mixed delays.

    Science.gov (United States)

    Popa, Călin-Adrian

    2018-06-08

    This paper discusses octonion-valued neural networks (OVNNs) with leakage delay, time-varying delays, and distributed delays, for which the states, weights, and activation functions belong to the normed division algebra of octonions. The octonion algebra is a nonassociative and noncommutative generalization of the complex and quaternion algebras, but does not belong to the category of Clifford algebras, which are associative. In order to avoid the nonassociativity of the octonion algebra and also the noncommutativity of the quaternion algebra, the Cayley-Dickson construction is used to decompose the OVNNs into 4 complex-valued systems. By using appropriate Lyapunov-Krasovskii functionals, with double and triple integral terms, the free weighting matrix method, and simple and double integral Jensen inequalities, delay-dependent criteria are established for the exponential stability of the considered OVNNs. The criteria are given in terms of complex-valued linear matrix inequalities, for two types of Lipschitz conditions which are assumed to be satisfied by the octonion-valued activation functions. Finally, two numerical examples illustrate the feasibility, effectiveness, and correctness of the theoretical results. Copyright © 2018 Elsevier Ltd. All rights reserved.

  7. Existence and global exponential stability of periodic solution to BAM neural networks with periodic coefficients and continuously distributed delays

    International Nuclear Information System (INIS)

    Zhou Tiejun; Chen Anping; Zhou Yuyuan

    2005-01-01

    By using the continuation theorem of coincidence degree theory and Liapunov function, we obtain some sufficient criteria to ensure the existence and global exponential stability of periodic solution to the bidirectional associative memory (BAM) neural networks with periodic coefficients and continuously distributed delays. These results improve and generalize the works of papers [J. Cao, L. Wang, Phys. Rev. E 61 (2000) 1825] and [Z. Liu, A. Chen, J. Cao, L. Huang, IEEE Trans. Circuits Systems I 50 (2003) 1162]. An example is given to illustrate that the criteria are feasible

  8. Existence and global exponential stability of periodic solution to BAM neural networks with periodic coefficients and continuously distributed delays

    Science.gov (United States)

    Zhou, distributed delays [rapid communication] T.; Chen, A.; Zhou, Y.

    2005-08-01

    By using the continuation theorem of coincidence degree theory and Liapunov function, we obtain some sufficient criteria to ensure the existence and global exponential stability of periodic solution to the bidirectional associative memory (BAM) neural networks with periodic coefficients and continuously distributed delays. These results improve and generalize the works of papers [J. Cao, L. Wang, Phys. Rev. E 61 (2000) 1825] and [Z. Liu, A. Chen, J. Cao, L. Huang, IEEE Trans. Circuits Systems I 50 (2003) 1162]. An example is given to illustrate that the criteria are feasible.

  9. Global Exponential Stability of Periodic Oscillation for Nonautonomous BAM Neural Networks with Distributed Delay

    Directory of Open Access Journals (Sweden)

    Hongli Liu

    2009-01-01

    Full Text Available We derive a new criterion for checking the global stability of periodic oscillation of bidirectional associative memory (BAM neural networks with periodic coefficients and distributed delay, and find that the criterion relies on the Lipschitz constants of the signal transmission functions, weights of the neural network, and delay kernels. The proposed model transforms the original interacting network into matrix analysis problem which is easy to check, thereby significantly reducing the computational complexity and making analysis of periodic oscillation for even large-scale networks.

  10. Global exponential stability of neutral high-order stochastic Hopfield neural networks with Markovian jump parameters and mixed time delays.

    Science.gov (United States)

    Huang, Haiying; Du, Qiaosheng; Kang, Xibing

    2013-11-01

    In this paper, a class of neutral high-order stochastic Hopfield neural networks with Markovian jump parameters and mixed time delays is investigated. The jumping parameters are modeled as a continuous-time finite-state Markov chain. At first, the existence of equilibrium point for the addressed neural networks is studied. By utilizing the Lyapunov stability theory, stochastic analysis theory and linear matrix inequality (LMI) technique, new delay-dependent stability criteria are presented in terms of linear matrix inequalities to guarantee the neural networks to be globally exponentially stable in the mean square. Numerical simulations are carried out to illustrate the main results. © 2013 ISA. Published by ISA. All rights reserved.

  11. Existence and global exponential stability of periodic solution of memristor-based BAM neural networks with time-varying delays.

    Science.gov (United States)

    Li, Hongfei; Jiang, Haijun; Hu, Cheng

    2016-03-01

    In this paper, we investigate a class of memristor-based BAM neural networks with time-varying delays. Under the framework of Filippov solutions, boundedness and ultimate boundedness of solutions of memristor-based BAM neural networks are guaranteed by Chain rule and inequalities technique. Moreover, a new method involving Yoshizawa-like theorem is favorably employed to acquire the existence of periodic solution. By applying the theory of set-valued maps and functional differential inclusions, an available Lyapunov functional and some new testable algebraic criteria are derived for ensuring the uniqueness and global exponential stability of periodic solution of memristor-based BAM neural networks. The obtained results expand and complement some previous work on memristor-based BAM neural networks. Finally, a numerical example is provided to show the applicability and effectiveness of our theoretical results. Copyright © 2015 Elsevier Ltd. All rights reserved.

  12. Global exponential stability of periodic solution for shunting inhibitory CNNs with delays [rapid communication

    Science.gov (United States)

    Li, Yongkun; Liu, Chunchao; Zhu, Lifei

    2005-03-01

    By using the continuation theorem of coincidence degree theory and constructing suitable Lyapunov functions, we study the existence and stability of periodic solution for shunting inhibitory cellular neural networks (SICNNs) with delays x˙ij(t)=-aij(t)xij(t)-∑Bkl∈Nr(i,j)Bijkl(t)fij(xkl(t))xij(t)-∑Ckl∈Nr(i,j)Cijkl(t)gij(xkl(t-τkl))xij(t)+Lij(t).

  13. Global finite-time attitude stabilization for rigid spacecraft in the exponential coordinates

    Science.gov (United States)

    Shi, Xiao-Ning; Zhou, Zhi-Gang; Zhou, Di

    2018-06-01

    This paper addresses the global finite-time attitude stabilisation problem on the special orthogonal group (SO(3)) for a rigid spacecraft via homogeneous feedback approach. Considering the topological and geometric properties of SO(3), the logarithm map is utilised to transform the stabilisation problem on SO(3) into the one on its associated Lie algebra (?). A model-independent discontinuous state feedback plus dynamics compensation scheme is constructed to achieve the global finite-time attitude stabilisation in a coordinate-invariant way. In addition, to address the absence of angular velocity measurements, a sliding mode observer is proposed to reconstruct the unknown angular velocity information within finite time. Then, an observer-based finite-time output feedback control strategy is obtained. Numerical simulations are finally performed to demonstrate the effectiveness of the proposed finite-time controllers.

  14. Global exponential stability of periodic solution for shunting inhibitory CNNs with delays

    International Nuclear Information System (INIS)

    Li Yongkun; Liu Chunchao; Zhu Lifei

    2005-01-01

    By using the continuation theorem of coincidence degree theory and constructing suitable Lyapunov functions, we study the existence and stability of periodic solution for shunting inhibitory cellular neural networks (SICNNs) with delays x-bar ij (t)=-a ij (t)x ij (t)--bar B kl -bar Nr(i,j)B ij kl (t)f ij (x kl (t))x ij (t)--bar C kl -bar Nr(i,j)C ij kl (t)g ij (x kl (t-τ kl ))x ij (t)+L ij (t)

  15. Global exponential stability of periodic solution for shunting inhibitory CNNs with delays

    Energy Technology Data Exchange (ETDEWEB)

    Li Yongkun [Department of Mathematics, Yunnan University, Kunming, Yunnan 650091 (China)]. E-mail: yklie@ynu.edu.cn; Liu Chunchao [Department of Mathematics, Yunnan University, Kunming, Yunnan 650091 (China); Zhu Lifei [Department of Mathematics, Yunnan University, Kunming, Yunnan 650091 (China)

    2005-03-28

    By using the continuation theorem of coincidence degree theory and constructing suitable Lyapunov functions, we study the existence and stability of periodic solution for shunting inhibitory cellular neural networks (SICNNs) with delays x-bar {sub ij}(t)=-a{sub ij}(t)x{sub ij}(t)--bar B{sup kl}-bar Nr(i,j)B{sub ij}{sup kl}(t)f{sub ij}(x{sub kl}(t))x{sub ij}(t)--bar C{sup kl}-bar Nr(i,j)C{sub ij}{sup kl}(t)g{sub ij}(x{sub kl}(t-{tau}{sub kl}))x{sub ij}(t)+L{sub ij}(t)

  16. Exponential Stabilization of Underactuated Vehicles

    Energy Technology Data Exchange (ETDEWEB)

    Pettersen, K.Y.

    1996-12-31

    Underactuated vehicles are vehicles with fewer independent control actuators than degrees of freedom to be controlled. Such vehicles may be used in inspection of sub-sea cables, inspection and maintenance of offshore oil drilling platforms, and similar. This doctoral thesis discusses feedback stabilization of underactuated vehicles. The main objective has been to further develop methods from stabilization of nonholonomic systems to arrive at methods that are applicable to underactuated vehicles. A nonlinear model including both dynamics and kinematics is used to describe the vehicles, which may be surface vessels, spacecraft or autonomous underwater vehicles (AUVs). It is shown that for a certain class of underactuated vehicles the stabilization problem is not solvable by linear control theory. A new stability result for a class of homogeneous time-varying systems is derived and shown to be an important tool for developing continuous periodic time-varying feedback laws that stabilize underactuated vehicles without involving cancellation of dynamics. For position and orientation control of a surface vessel without side thruster a new continuous periodic feedback law is proposed that does not cancel any dynamics, and that exponentially stabilizes the origin of the underactuated surface vessel. A further issue considered is the stabilization of the attitude of an AUV. Finally, the thesis discusses stabilization of both position and attitude of an underactuated AUV. 55 refs., 28 figs.

  17. Periodicity and global exponential stability of generalized Cohen-Grossberg neural networks with discontinuous activations and mixed delays.

    Science.gov (United States)

    Wang, Dongshu; Huang, Lihong

    2014-03-01

    In this paper, we investigate the periodic dynamical behaviors for a class of general Cohen-Grossberg neural networks with discontinuous right-hand sides, time-varying and distributed delays. By means of retarded differential inclusions theory and the fixed point theorem of multi-valued maps, the existence of periodic solutions for the neural networks is obtained. After that, we derive some sufficient conditions for the global exponential stability and convergence of the neural networks, in terms of nonsmooth analysis theory with generalized Lyapunov approach. Without assuming the boundedness (or the growth condition) and monotonicity of the discontinuous neuron activation functions, our results will also be valid. Moreover, our results extend previous works not only on discrete time-varying and distributed delayed neural networks with continuous or even Lipschitz continuous activations, but also on discrete time-varying and distributed delayed neural networks with discontinuous activations. We give some numerical examples to show the applicability and effectiveness of our main results. Copyright © 2013 Elsevier Ltd. All rights reserved.

  18. Transverse exponential stability and applications

    NARCIS (Netherlands)

    Andrieu, Vincent; Jayawardhana, Bayu; Praly, Laurent

    2016-01-01

    We investigate how the following properties are related to each other: i) A manifold is “transversally” exponentially stable; ii) The “transverse” linearization along any solution in the manifold is exponentially stable; iii) There exists a field of positive definite quadratic forms whose

  19. Periodic oscillation and exponential stability of delayed CNNs

    Science.gov (United States)

    Cao, Jinde

    2000-05-01

    Both the global exponential stability and the periodic oscillation of a class of delayed cellular neural networks (DCNNs) is further studied in this Letter. By applying some new analysis techniques and constructing suitable Lyapunov functionals, some simple and new sufficient conditions are given ensuring global exponential stability and the existence of periodic oscillatory solution of DCNNs. These conditions can be applied to design globally exponentially stable DCNNs and periodic oscillatory DCNNs and easily checked in practice by simple algebraic methods. These play an important role in the design and applications of DCNNs.

  20. Exponential stability in a scalar functional differential equation

    Directory of Open Access Journals (Sweden)

    Pituk Mihály

    2006-01-01

    Full Text Available We establish a criterion for the global exponential stability of the zero solution of the scalar retarded functional differential equation whose linear part generates a monotone semiflow on the phase space with respect to the exponential ordering, and the nonlinearity has at most linear growth.

  1. Exponential Stability of Switched Positive Homogeneous Systems

    Directory of Open Access Journals (Sweden)

    Dadong Tian

    2017-01-01

    Full Text Available This paper studies the exponential stability of switched positive nonlinear systems defined by cooperative and homogeneous vector fields. In order to capture the decay rate of such systems, we first consider the subsystems. A sufficient condition for exponential stability of subsystems with time-varying delays is derived. In particular, for the corresponding delay-free systems, we prove that this sufficient condition is also necessary. Then, we present a sufficient condition of exponential stability under minimum dwell time switching for the switched positive nonlinear systems. Some results in the previous literature are extended. Finally, a numerical example is given to demonstrate the effectiveness of the obtained results.

  2. On exponential stability and periodic solutions of CNNs with delays

    Science.gov (United States)

    Cao, Jinde

    2000-03-01

    In this Letter, the author analyses further problems of global exponential stability and the existence of periodic solutions of cellular neural networks with delays (DCNNs). Some simple and new sufficient conditions are given ensuring global exponential stability and the existence of periodic solutions of DCNNs by applying some new analysis techniques and constructing suitable Lyapunov functionals. These conditions have important leading significance in the design and applications of globally stable DCNNs and periodic oscillatory DCNNs and are weaker than those in the earlier works [Phys. Rev. E 60 (1999) 3244], [J. Comput. Syst. Sci. 59 (1999)].

  3. Exponential Stabilization of an Underactuated Surface Vessel

    Directory of Open Access Journals (Sweden)

    Kristin Y. Pettersen

    1997-07-01

    Full Text Available The paper shows that a large class of underactuated vehicles cannot be asymptotically stabilized by either continuous or discontinuous state feedback. Furthermore, stabilization of an underactuated surface vessel is considered. Controllability properties of the surface vessels is presented, and a continuous periodic time-varying feedback law is proposed. It is shown that this feedback law exponentially stabilizes the surface vessel to the origin, and this is illustrated by simulations.

  4. Delay-dependent exponential stability of cellular neural networks with time-varying delays

    International Nuclear Information System (INIS)

    Zhang Qiang; Wei Xiaopeng; Xu Jin

    2005-01-01

    The global exponential stability of cellular neural networks (CNNs) with time-varying delays is analyzed. Two new sufficient conditions ensuring global exponential stability for delayed CNNs are obtained. The conditions presented here are related to the size of delay. The stability results improve the earlier publications. Two examples are given to demonstrate the effectiveness of the obtained results

  5. On the stability of some systems of exponential difference equations

    Directory of Open Access Journals (Sweden)

    N. Psarros

    2018-01-01

    Full Text Available In this paper we prove the stability of the zero equilibria of two systems of difference equations of exponential type, which are some extensions of an one-dimensional biological model. The stability of these systems is investigated in the special case when one of the eigenvalues is equal to -1 and the other eigenvalue has absolute value less than 1, using centre manifold theory. In addition, we study the existence and uniqueness of positive equilibria, the attractivity and the global asymptotic stability of these equilibria of some related systems of difference equations.

  6. Estimation of exponential convergence rate and exponential stability for neural networks with time-varying delay

    International Nuclear Information System (INIS)

    Tu Fenghua; Liao Xiaofeng

    2005-01-01

    We study the problem of estimating the exponential convergence rate and exponential stability for neural networks with time-varying delay. Some criteria for exponential stability are derived by using the linear matrix inequality (LMI) approach. They are less conservative than the existing ones. Some analytical methods are employed to investigate the bounds on the interconnection matrix and activation functions so that the systems are exponentially stable

  7. Exponential stability of fuzzy cellular neural networks with constant and time-varying delays

    International Nuclear Information System (INIS)

    Liu Yanqing; Tang Wansheng

    2004-01-01

    In this Letter, the global stability of delayed fuzzy cellular neural networks (FCNN) with either constant delays or time varying delays is proposed. Firstly, we give the existence and uniqueness of the equilibrium point by using the theory of topological degree and the properties of nonsingular M-matrix and the sufficient conditions for ascertaining the global exponential stability by constructing a suitable Lyapunov functional. Secondly, the criteria for guaranteeing the global exponential stability of FCNN with time varying delays are given and the estimation of exponential convergence rate with regard to speed of vary of delays is presented by constructing a suitable Lyapunov functional

  8. Exponential stability of delayed fuzzy cellular neural networks with diffusion

    International Nuclear Information System (INIS)

    Huang Tingwen

    2007-01-01

    The exponential stability of delayed fuzzy cellular neural networks (FCNN) with diffusion is investigated. Exponential stability, significant for applications of neural networks, is obtained under conditions that are easily verified by a new approach. Earlier results on the exponential stability of FCNN with time-dependent delay, a special case of the model studied in this paper, are improved without using the time-varying term condition: dτ(t)/dt < μ

  9. Existence and exponential stability of almost periodic solution for stochastic cellular neural networks with delay

    International Nuclear Information System (INIS)

    Huang Zaitang; Yang Qigui

    2009-01-01

    The paper considers the problems of existence of quadratic mean almost periodic and global exponential stability for stochastic cellular neural networks with delays. By employing the Holder's inequality and fixed points principle, we present some new criteria ensuring existence and uniqueness of a quadratic mean almost periodic and global exponential stability. These criteria are important in signal processing and the design of networks. Moreover, these criteria are also applied in others stochastic biological neural systems.

  10. Asymptotic estimates and exponential stability for higher-order monotone difference equations

    Directory of Open Access Journals (Sweden)

    Pituk Mihály

    2005-01-01

    Full Text Available Asymptotic estimates are established for higher-order scalar difference equations and inequalities the right-hand sides of which generate a monotone system with respect to the discrete exponential ordering. It is shown that in some cases the exponential estimates can be replaced with a more precise limit relation. As corollaries, a generalization of discrete Halanay-type inequalities and explicit sufficient conditions for the global exponential stability of the zero solution are given.

  11. Asymptotic estimates and exponential stability for higher-order monotone difference equations

    Directory of Open Access Journals (Sweden)

    Mihály Pituk

    2005-03-01

    Full Text Available Asymptotic estimates are established for higher-order scalar difference equations and inequalities the right-hand sides of which generate a monotone system with respect to the discrete exponential ordering. It is shown that in some cases the exponential estimates can be replaced with a more precise limit relation. As corollaries, a generalization of discrete Halanay-type inequalities and explicit sufficient conditions for the global exponential stability of the zero solution are given.

  12. Criteria for exponential asymptotic stability in the large of ...

    African Journals Online (AJOL)

    The purpose of this study is to provide necessary and sufficient conditions for exponential asymptotic stability in the large and uniform asymptotic stability of perturbations of linear systems with unbounded delays. A strong relationship is established between the two types of asymptotic stability. It is found that if the ...

  13. Mean square exponential stability of stochastic delayed Hopfield neural networks

    International Nuclear Information System (INIS)

    Wan Li; Sun Jianhua

    2005-01-01

    Stochastic effects to the stability property of Hopfield neural networks (HNN) with discrete and continuously distributed delay are considered. By using the method of variation parameter, inequality technique and stochastic analysis, the sufficient conditions to guarantee the mean square exponential stability of an equilibrium solution are given. Two examples are also given to demonstrate our results

  14. Stability of the Exponential Functional Equation in Riesz Algebras

    Directory of Open Access Journals (Sweden)

    Bogdan Batko

    2014-01-01

    Full Text Available We deal with the stability of the exponential Cauchy functional equation F(x+y=F(xF(y in the class of functions F:G→L mapping a group (G, + into a Riesz algebra L. The main aim of this paper is to prove that the exponential Cauchy functional equation is stable in the sense of Hyers-Ulam and is not superstable in the sense of Baker. To prove the stability we use the Yosida Spectral Representation Theorem.

  15. Exponential stability of neural networks with asymmetric connection weights

    International Nuclear Information System (INIS)

    Yang Jinxiang; Zhong Shouming

    2007-01-01

    This paper investigates the exponential stability of a class of neural networks with asymmetric connection weights. By dividing the network state variables into various parts according to the characters of the neural networks, some new sufficient conditions of exponential stability are derived via constructing a Lyapunov function and using the method of the variation of constant. The new conditions are associated with the initial values and are described by some blocks of the interconnection matrix, and do not depend on other blocks. Examples are given to further illustrate the theory

  16. A Lie algebraic condition for exponential stability of discrete hybrid systems and application to hybrid synchronization.

    Science.gov (United States)

    Zhao, Shouwei

    2011-06-01

    A Lie algebraic condition for global exponential stability of linear discrete switched impulsive systems is presented in this paper. By considering a Lie algebra generated by all subsystem matrices and impulsive matrices, when not all of these matrices are Schur stable, we derive new criteria for global exponential stability of linear discrete switched impulsive systems. Moreover, simple sufficient conditions in terms of Lie algebra are established for the synchronization of nonlinear discrete systems using a hybrid switching and impulsive control. As an application, discrete chaotic system's synchronization is investigated by the proposed method.

  17. Stochastic exponential stability of the delayed reaction-diffusion recurrent neural networks with Markovian jumping parameters

    International Nuclear Information System (INIS)

    Wang Linshan; Zhang Zhe; Wang Yangfan

    2008-01-01

    Some criteria for the global stochastic exponential stability of the delayed reaction-diffusion recurrent neural networks with Markovian jumping parameters are presented. The jumping parameters considered here are generated from a continuous-time discrete-state homogeneous Markov process, which are governed by a Markov process with discrete and finite state space. By employing a new Lyapunov-Krasovskii functional, a linear matrix inequality (LMI) approach is developed to establish some easy-to-test criteria of global exponential stability in the mean square for the stochastic neural networks. The criteria are computationally efficient, since they are in the forms of some linear matrix inequalities

  18. Delay-dependent exponential stability for neural networks with discrete and distributed time-varying delays

    International Nuclear Information System (INIS)

    Zhu Xunlin; Wang Youyi

    2009-01-01

    This Letter studies the exponential stability for a class of neural networks (NNs) with both discrete and distributed time-varying delays. Under weaker assumptions on the activation functions, by defining a more general type of Lyapunov functionals and developing a new convex combination technique, new less conservative and less complex stability criteria are established to guarantee the global exponential stability of the discussed NNs. The obtained conditions are dependent on both discrete and distributed delays, are expressed in terms of linear matrix inequalities (LMIs), and contain fewer decision variables. Numerical examples are given to illustrate the effectiveness and the less conservatism of the proposed conditions.

  19. Global impulsive exponential synchronization of stochastic perturbed chaotic delayed neural networks

    International Nuclear Information System (INIS)

    Hua-Guang, Zhang; Tie-Dong, Ma; Jie, Fu; Shao-Cheng, Tong

    2009-01-01

    In this paper, the global impulsive exponential synchronization problem of a class of chaotic delayed neural networks (DNNs) with stochastic perturbation is studied. Based on the Lyapunov stability theory, stochastic analysis approach and an efficient impulsive delay differential inequality, some new exponential synchronization criteria expressed in the form of the linear matrix inequality (LMI) are derived. The designed impulsive controller not only can globally exponentially stabilize the error dynamics in mean square, but also can control the exponential synchronization rate. Furthermore, to estimate the stable region of the synchronization error dynamics, a novel optimization control algorithm is proposed, which can deal with the minimum problem with two nonlinear terms coexisting in LMIs effectively. Simulation results finally demonstrate the effectiveness of the proposed method

  20. Discrete-time recurrent neural networks with time-varying delays: Exponential stability analysis

    International Nuclear Information System (INIS)

    Liu, Yurong; Wang, Zidong; Serrano, Alan; Liu, Xiaohui

    2007-01-01

    This Letter is concerned with the analysis problem of exponential stability for a class of discrete-time recurrent neural networks (DRNNs) with time delays. The delay is of the time-varying nature, and the activation functions are assumed to be neither differentiable nor strict monotonic. Furthermore, the description of the activation functions is more general than the recently commonly used Lipschitz conditions. Under such mild conditions, we first prove the existence of the equilibrium point. Then, by employing a Lyapunov-Krasovskii functional, a unified linear matrix inequality (LMI) approach is developed to establish sufficient conditions for the DRNNs to be globally exponentially stable. It is shown that the delayed DRNNs are globally exponentially stable if a certain LMI is solvable, where the feasibility of such an LMI can be easily checked by using the numerically efficient Matlab LMI Toolbox. A simulation example is presented to show the usefulness of the derived LMI-based stability condition

  1. Exponential stability of uncertain stochastic neural networks with mixed time-delays

    International Nuclear Information System (INIS)

    Wang Zidong; Lauria, Stanislao; Fang Jian'an; Liu Xiaohui

    2007-01-01

    This paper is concerned with the global exponential stability analysis problem for a class of stochastic neural networks with mixed time-delays and parameter uncertainties. The mixed delays comprise discrete and distributed time-delays, the parameter uncertainties are norm-bounded, and the neural networks are subjected to stochastic disturbances described in terms of a Brownian motion. The purpose of the stability analysis problem is to derive easy-to-test criteria under which the delayed stochastic neural network is globally, robustly, exponentially stable in the mean square for all admissible parameter uncertainties. By resorting to the Lyapunov-Krasovskii stability theory and the stochastic analysis tools, sufficient stability conditions are established by using an efficient linear matrix inequality (LMI) approach. The proposed criteria can be checked readily by using recently developed numerical packages, where no tuning of parameters is required. An example is provided to demonstrate the usefulness of the proposed criteria

  2. Exponential stability of Cohen-Grossberg neural networks with a general class of activation functions

    International Nuclear Information System (INIS)

    Wan Anhua; Wang Miansen; Peng Jigen; Qiao Hong

    2006-01-01

    In this Letter, the dynamics of Cohen-Grossberg neural networks model are investigated. The activation functions are only assumed to be Lipschitz continuous, which provide a much wider application domain for neural networks than the previous results. By means of the extended nonlinear measure approach, new and relaxed sufficient conditions for the existence, uniqueness and global exponential stability of equilibrium of the neural networks are obtained. Moreover, an estimate for the exponential convergence rate of the neural networks is precisely characterized. Our results improve those existing ones

  3. New exponential stability criteria for stochastic BAM neural networks with impulses

    International Nuclear Information System (INIS)

    Sakthivel, R; Samidurai, R; Anthoni, S M

    2010-01-01

    In this paper, we study the global exponential stability of time-delayed stochastic bidirectional associative memory neural networks with impulses and Markovian jumping parameters. A generalized activation function is considered, and traditional assumptions on the boundedness, monotony and differentiability of activation functions are removed. We obtain a new set of sufficient conditions in terms of linear matrix inequalities, which ensures the global exponential stability of the unique equilibrium point for stochastic BAM neural networks with impulses. The Lyapunov function method with the Ito differential rule is employed for achieving the required result. Moreover, a numerical example is provided to show that the proposed result improves the allowable upper bound of delays over some existing results in the literature.

  4. New exponential stability criteria for stochastic BAM neural networks with impulses

    Science.gov (United States)

    Sakthivel, R.; Samidurai, R.; Anthoni, S. M.

    2010-10-01

    In this paper, we study the global exponential stability of time-delayed stochastic bidirectional associative memory neural networks with impulses and Markovian jumping parameters. A generalized activation function is considered, and traditional assumptions on the boundedness, monotony and differentiability of activation functions are removed. We obtain a new set of sufficient conditions in terms of linear matrix inequalities, which ensures the global exponential stability of the unique equilibrium point for stochastic BAM neural networks with impulses. The Lyapunov function method with the Itô differential rule is employed for achieving the required result. Moreover, a numerical example is provided to show that the proposed result improves the allowable upper bound of delays over some existing results in the literature.

  5. Exponential stability of delayed recurrent neural networks with Markovian jumping parameters

    International Nuclear Information System (INIS)

    Wang Zidong; Liu Yurong; Yu Li; Liu Xiaohui

    2006-01-01

    In this Letter, the global exponential stability analysis problem is considered for a class of recurrent neural networks (RNNs) with time delays and Markovian jumping parameters. The jumping parameters considered here are generated from a continuous-time discrete-state homogeneous Markov process, which are governed by a Markov process with discrete and finite state space. The purpose of the problem addressed is to derive some easy-to-test conditions such that the dynamics of the neural network is stochastically exponentially stable in the mean square, independent of the time delay. By employing a new Lyapunov-Krasovskii functional, a linear matrix inequality (LMI) approach is developed to establish the desired sufficient conditions, and therefore the global exponential stability in the mean square for the delayed RNNs can be easily checked by utilizing the numerically efficient Matlab LMI toolbox, and no tuning of parameters is required. A numerical example is exploited to show the usefulness of the derived LMI-based stability conditions

  6. On transverse exponential stability and its use in incremental stability, observer and synchronization

    NARCIS (Netherlands)

    Andrieu, Vincent; Jayawardhana, Bayu; Praly, Laurent

    2013-01-01

    We study the relation between the exponential stability of an invariant manifold and the existence of a Riemannian metric for which the flow is “transversally” contracting. More precisely, we investigate how the following properties are related to each other: i). A manifold is “transversally”

  7. Lagrange α-exponential stability and α-exponential convergence for fractional-order complex-valued neural networks.

    Science.gov (United States)

    Jian, Jigui; Wan, Peng

    2017-07-01

    This paper deals with the problem on Lagrange α-exponential stability and α-exponential convergence for a class of fractional-order complex-valued neural networks. To this end, some new fractional-order differential inequalities are established, which improve and generalize previously known criteria. By using the new inequalities and coupling with the Lyapunov method, some effective criteria are derived to guarantee Lagrange α-exponential stability and α-exponential convergence of the addressed network. Moreover, the framework of the α-exponential convergence ball is also given, where the convergence rate is related to the parameters and the order of differential of the system. These results here, which the existence and uniqueness of the equilibrium points need not to be considered, generalize and improve the earlier publications and can be applied to monostable and multistable fractional-order complex-valued neural networks. Finally, one example with numerical simulations is given to show the effectiveness of the obtained results. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Exponential p-stability of delayed Cohen-Grossberg-type BAM neural networks with impulses

    International Nuclear Information System (INIS)

    Xia Yonghui; Huang Zhenkun; Han Maoan

    2008-01-01

    An impulsive Cohen-Grossberg-type bidirectional associative memory (BAM) neural networks with distributed delays is studied. Some new sufficient conditions are established for the existence and global exponential stability of a unique equilibrium without strict conditions imposed on self regulation functions. The approaches are based on Laypunov-Kravsovskii functional and homeomorphism theory. When our results are applied to the BAM neural networks, our results generalize some previously known results. It is believed that these results are significant and useful for the design and applications of Cohen-Grossberg-type bidirectional associative memory networks

  9. Convergence and stability of the exponential Euler method for semi-linear stochastic delay differential equations.

    Science.gov (United States)

    Zhang, Ling

    2017-01-01

    The main purpose of this paper is to investigate the strong convergence and exponential stability in mean square of the exponential Euler method to semi-linear stochastic delay differential equations (SLSDDEs). It is proved that the exponential Euler approximation solution converges to the analytic solution with the strong order [Formula: see text] to SLSDDEs. On the one hand, the classical stability theorem to SLSDDEs is given by the Lyapunov functions. However, in this paper we study the exponential stability in mean square of the exact solution to SLSDDEs by using the definition of logarithmic norm. On the other hand, the implicit Euler scheme to SLSDDEs is known to be exponentially stable in mean square for any step size. However, in this article we propose an explicit method to show that the exponential Euler method to SLSDDEs is proved to share the same stability for any step size by the property of logarithmic norm.

  10. Convergence and stability of the exponential Euler method for semi-linear stochastic delay differential equations

    Directory of Open Access Journals (Sweden)

    Ling Zhang

    2017-10-01

    Full Text Available Abstract The main purpose of this paper is to investigate the strong convergence and exponential stability in mean square of the exponential Euler method to semi-linear stochastic delay differential equations (SLSDDEs. It is proved that the exponential Euler approximation solution converges to the analytic solution with the strong order 1 2 $\\frac{1}{2}$ to SLSDDEs. On the one hand, the classical stability theorem to SLSDDEs is given by the Lyapunov functions. However, in this paper we study the exponential stability in mean square of the exact solution to SLSDDEs by using the definition of logarithmic norm. On the other hand, the implicit Euler scheme to SLSDDEs is known to be exponentially stable in mean square for any step size. However, in this article we propose an explicit method to show that the exponential Euler method to SLSDDEs is proved to share the same stability for any step size by the property of logarithmic norm.

  11. Almost sure exponential stability of stochastic fuzzy cellular neural networks with delays

    International Nuclear Information System (INIS)

    Zhao Hongyong; Ding Nan; Chen Ling

    2009-01-01

    This paper is concerned with the problem of exponential stability analysis for fuzzy cellular neural network with delays. By constructing suitable Lyapunov functional and using stochastic analysis we present some sufficient conditions ensuring almost sure exponential stability for the network. Moreover, an example is given to demonstrate the advantages of our method.

  12. Exponential stability of switched linear systems with time-varying delay

    Directory of Open Access Journals (Sweden)

    Satiracoo Pairote

    2007-11-01

    Full Text Available We use a Lyapunov-Krasovskii functional approach to establish the exponential stability of linear systems with time-varying delay. Our delay-dependent condition allows to compute simultaneously the two bounds that characterize the exponential stability rate of the solution. A simple procedure for constructing switching rule is also presented.

  13. Global exponential synchronization of inertial memristive neural networks with time-varying delay via nonlinear controller.

    Science.gov (United States)

    Gong, Shuqing; Yang, Shaofu; Guo, Zhenyuan; Huang, Tingwen

    2018-06-01

    The paper is concerned with the synchronization problem of inertial memristive neural networks with time-varying delay. First, by choosing a proper variable substitution, inertial memristive neural networks described by second-order differential equations can be transformed into first-order differential equations. Then, a novel controller with a linear diffusive term and discontinuous sign term is designed. By using the controller, the sufficient conditions for assuring the global exponential synchronization of the derive and response neural networks are derived based on Lyapunov stability theory and some inequality techniques. Finally, several numerical simulations are provided to substantiate the effectiveness of the theoretical results. Copyright © 2018 Elsevier Ltd. All rights reserved.

  14. Mean Square Exponential Stability of Stochastic Switched System with Interval Time-Varying Delays

    Directory of Open Access Journals (Sweden)

    Manlika Rajchakit

    2012-01-01

    Full Text Available This paper is concerned with mean square exponential stability of switched stochastic system with interval time-varying delays. The time delay is any continuous function belonging to a given interval, but not necessary to be differentiable. By constructing a suitable augmented Lyapunov-Krasovskii functional combined with Leibniz-Newton’s formula, a switching rule for the mean square exponential stability of switched stochastic system with interval time-varying delays and new delay-dependent sufficient conditions for the mean square exponential stability of the switched stochastic system are first established in terms of LMIs. Numerical example is given to show the effectiveness of the obtained result.

  15. W-transform for exponential stability of second order delay differential equations without damping terms.

    Science.gov (United States)

    Domoshnitsky, Alexander; Maghakyan, Abraham; Berezansky, Leonid

    2017-01-01

    In this paper a method for studying stability of the equation [Formula: see text] not including explicitly the first derivative is proposed. We demonstrate that although the corresponding ordinary differential equation [Formula: see text] is not exponentially stable, the delay equation can be exponentially stable.

  16. Exponential Stability for Impulsive BAM Neural Networks with Time-Varying Delays and Reaction-Diffusion Terms

    Directory of Open Access Journals (Sweden)

    Qiankun Song

    2007-06-01

    Full Text Available Impulsive bidirectional associative memory neural network model with time-varying delays and reaction-diffusion terms is considered. Several sufficient conditions ensuring the existence, uniqueness, and global exponential stability of equilibrium point for the addressed neural network are derived by M-matrix theory, analytic methods, and inequality techniques. Moreover, the exponential convergence rate index is estimated, which depends on the system parameters. The obtained results in this paper are less restrictive than previously known criteria. Two examples are given to show the effectiveness of the obtained results.

  17. Exponential Stability for Impulsive BAM Neural Networks with Time-Varying Delays and Reaction-Diffusion Terms

    Directory of Open Access Journals (Sweden)

    Cao Jinde

    2007-01-01

    Full Text Available Impulsive bidirectional associative memory neural network model with time-varying delays and reaction-diffusion terms is considered. Several sufficient conditions ensuring the existence, uniqueness, and global exponential stability of equilibrium point for the addressed neural network are derived by M-matrix theory, analytic methods, and inequality techniques. Moreover, the exponential convergence rate index is estimated, which depends on the system parameters. The obtained results in this paper are less restrictive than previously known criteria. Two examples are given to show the effectiveness of the obtained results.

  18. Well-posedness and exponential stability for a wave equation with nonlocal time-delay condition

    Directory of Open Access Journals (Sweden)

    Carlos Alberto Raposo

    2017-11-01

    Full Text Available Well-posedness and exponential stability of nonlocal time-delayed of a wave equation with a integral conditions of the 1st kind forms the center of this work. Through semigroup theory we prove the well-posedness by the Hille-Yosida theorem and the exponential stability exploring the dissipative properties of the linear operator associated to damped model using the Gearhart-Huang-Pruss theorem.

  19. The motion planning problem and exponential stabilization of a heavy chain. Part II

    OpenAIRE

    Piotr Grabowski

    2008-01-01

    This is the second part of paper [P. Grabowski, The motion planning problem and exponential stabilization of a heavy chain. Part I, to appear in International Journal of Control], where a model of a heavy chain system with a punctual load (tip mass) in the form of a system of partial differential equations was interpreted as an abstract semigroup system and then analysed on a Hilbert state space. In particular, in [P. Grabowski, The motion planning problem and exponential stabilization of a h...

  20. Exponential p-stability of impulsive stochastic differential equations with delays

    International Nuclear Information System (INIS)

    Yang Zhiguo; Xu Daoyi; Xiang Li

    2006-01-01

    In this Letter, we establish a method to study the exponential p-stability of the zero solution of impulsive stochastic differential equations with delays. By establishing an L-operator inequality and using the properties of M-cone and stochastic analysis technique, we obtain some new conditions ensuring the exponential p-stability of the zero solution of impulsive stochastic differential equations with delays. Two illustrative examples have been provided to show the effectiveness of our results

  1. Robust exponential stabilization of nonholonomic wheeled mobile robots with unknown visual parameters

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    The visual servoing stabilization of nonholonomic mobile robot with unknown camera parameters is investigated.A new kind of uncertain chained model of nonholonomic kinemetic system is obtained based on the visual feedback and the standard chained form of type (1,2) mobile robot.Then,a novel time-varying feedback controller is proposed for exponentially stabilizing the position and orientation of the robot using visual feedback and switching strategy when the camera parameters are not known.The exponential s...

  2. On exponential stability of bidirectional associative memory neural networks with time-varying delays

    International Nuclear Information System (INIS)

    Park, Ju H.; Lee, S.M.; Kwon, O.M.

    2009-01-01

    For bidirectional associate memory neural networks with time-varying delays, the problems of determining the exponential stability and estimating the exponential convergence rate are investigated by employing the Lyapunov functional method and linear matrix inequality (LMI) technique. A novel criterion for the stability, which give information on the delay-dependent property, is derived. A numerical example is given to demonstrate the effectiveness of the obtained results.

  3. Exponential Stability of Time-Switched Two-Subsystem Nonlinear Systems with Application to Intermittent Control

    Directory of Open Access Journals (Sweden)

    Huang Tingwen

    2009-01-01

    Full Text Available This paper studies the exponential stability of a class of periodically time-switched nonlinear systems. Three cases of such systems which are composed, respectively, of a pair of unstable subsystems, of both stable and unstable subsystems, and of a pair of stable systems, are considered. For the first case, the proposed result shows that there exists periodically switching rule guaranteeing the exponential stability of the whole system with (sufficient small switching period if there is a Hurwitz linear convex combination of two uncertain linear systems derived from two subsystems by certain linearization. For the second case, we present two general switching criteria by means of multiple and single Lyapunov function, respectively. We also investigate the stability issue of the third case, and the switching criteria of exponential stability are proposed. The present results for the second case are further applied to the periodically intermittent control. Several numerical examples are also given to show the effectiveness of theoretical results.

  4. Global Stability of Complex-Valued Genetic Regulatory Networks with Delays on Time Scales

    Directory of Open Access Journals (Sweden)

    Wang Yajing

    2016-01-01

    Full Text Available In this paper, the global exponential stability of complex-valued genetic regulatory networks with delays is investigated. Besides presenting conditions guaranteeing the existence of a unique equilibrium pattern, its global exponential stability is discussed. Some numerical examples for different time scales.

  5. Robust exponential stability and domains of attraction in a class of interval neural networks

    International Nuclear Information System (INIS)

    Yang Xiaofan; Liao Xiaofeng; Bai Sen; Evans, David J

    2005-01-01

    This paper addresses robust exponential stability as well as domains of attraction in a class of interval neural networks. A sufficient condition for an equilibrium point to be exponentially stable is established. And an estimate on the domains of attraction of exponentially stable equilibrium points is presented. Both the condition and the estimate are formulated in terms of the parameter intervals, the neurons' activation functions and the equilibrium point. Hence, they are easily checkable. In addition, our results neither depend on monotonicity of the activation functions nor on coupling conditions between the neurons. Consequently, these results are of practical importance in evaluating the performance of interval associative memory networks

  6. Exponential stability result for discrete-time stochastic fuzzy uncertain neural networks

    International Nuclear Information System (INIS)

    Mathiyalagan, K.; Sakthivel, R.; Marshal Anthoni, S.

    2012-01-01

    This Letter addresses the stability analysis problem for a class of uncertain discrete-time stochastic fuzzy neural networks (DSFNNs) with time-varying delays. By constructing a new Lyapunov–Krasovskii functional combined with the free weighting matrix technique, a new set of delay-dependent sufficient conditions for the robust exponential stability of the considered DSFNNs is established in terms of Linear Matrix Inequalities (LMIs). Finally, numerical examples with simulation results are provided to illustrate the applicability and usefulness of the obtained theory. -- Highlights: ► Applications of neural networks require the knowledge of dynamic behaviors. ► Exponential stability of discrete-time stochastic fuzzy neural networks is studied. ► Linear matrix inequality optimization approach is used to obtain the result. ► Delay-dependent stability criterion is established in terms of LMIs. ► Examples with simulation are provided to show the effectiveness of the result.

  7. Contractivity and Exponential Stability of Solutions to Nonlinear Neutral Functional Differential Equations in Banach Spaces

    Institute of Scientific and Technical Information of China (English)

    Wan-sheng WANG; Shou-fu LI; Run-sheng YANG

    2012-01-01

    A series of contractivity and exponential stability results for the solutions to nonlinear neutral functional differential equations (NFDEs) in Banach spaces are obtained,which provide unified theoretical foundation for the contractivity analysis of solutions to nonlinear problems in functional differential equations (FDEs),neutral delay differential equations (NDDEs) and NFDEs of other types which appear in practice.

  8. Existence and exponential stability of almost periodic solution for Hopfield-type neural networks with impulse

    International Nuclear Information System (INIS)

    Zhang Huiying; Xia Yonghui

    2008-01-01

    In this paper, some sufficient conditions are obtained for checking the existence and exponential stability of almost periodic solution for bidirectional associative memory Hopfield-type neural networks with impulse. The approaches are based on contraction principle and Gronwall-Bellman's inequality. This paper is considering the almost periodic solution for impulsive Hopfield-type neural networks

  9. Existence and exponential stability of traveling waves for delayed reaction-diffusion systems

    Science.gov (United States)

    Hsu, Cheng-Hsiung; Yang, Tzi-Sheng; Yu, Zhixian

    2018-03-01

    The purpose of this work is to investigate the existence and exponential stability of traveling wave solutions for general delayed multi-component reaction-diffusion systems. Following the monotone iteration scheme via an explicit construction of a pair of upper and lower solutions, we first obtain the existence of monostable traveling wave solutions connecting two different equilibria. Then, applying the techniques of weighted energy method and comparison principle, we show that all solutions of the Cauchy problem for the considered systems converge exponentially to traveling wave solutions provided that the initial perturbations around the traveling wave fronts belong to a suitable weighted Sobolev space.

  10. Decentralized Feedback Controllers for Exponential Stabilization of Hybrid Periodic Orbits: Application to Robotic Walking*

    Science.gov (United States)

    Hamed, Kaveh Akbari; Gregg, Robert D.

    2016-01-01

    This paper presents a systematic algorithm to design time-invariant decentralized feedback controllers to exponentially stabilize periodic orbits for a class of hybrid dynamical systems arising from bipedal walking. The algorithm assumes a class of parameterized and nonlinear decentralized feedback controllers which coordinate lower-dimensional hybrid subsystems based on a common phasing variable. The exponential stabilization problem is translated into an iterative sequence of optimization problems involving bilinear and linear matrix inequalities, which can be easily solved with available software packages. A set of sufficient conditions for the convergence of the iterative algorithm to a stabilizing decentralized feedback control solution is presented. The power of the algorithm is demonstrated by designing a set of local nonlinear controllers that cooperatively produce stable walking for a 3D autonomous biped with 9 degrees of freedom, 3 degrees of underactuation, and a decentralization scheme motivated by amputee locomotion with a transpelvic prosthetic leg. PMID:27990059

  11. Exponential Stability of the Monotubular Heat Exchanger Equation with Time Delay in Boundary Observation

    Directory of Open Access Journals (Sweden)

    Xue-Lian Jin

    2017-01-01

    Full Text Available The exponential stability of the monotubular heat exchanger equation with boundary observation possessing a time delay and inner control was investigated. Firstly, the close-loop system was translated into an abstract Cauchy problem in the suitable state space. A uniformly bounded C0-semigroup generated by the close-loop system, which implies that the unique solution of the system exists, was shown. Secondly, the spectrum configuration of the closed-loop system was analyzed and the eventual differentiability and the eventual compactness of the semigroup were shown by the resolvent estimates on some resolvent sets. This implies that the spectrum-determined growth assumption holds. Finally, a sufficient condition, which is related to the physical parameters in the system and is independent of the time delay, of the exponential stability of the closed-loop system was given.

  12. Exponential stabilization and synchronization for fuzzy model of memristive neural networks by periodically intermittent control.

    Science.gov (United States)

    Yang, Shiju; Li, Chuandong; Huang, Tingwen

    2016-03-01

    The problem of exponential stabilization and synchronization for fuzzy model of memristive neural networks (MNNs) is investigated by using periodically intermittent control in this paper. Based on the knowledge of memristor and recurrent neural network, the model of MNNs is formulated. Some novel and useful stabilization criteria and synchronization conditions are then derived by using the Lyapunov functional and differential inequality techniques. It is worth noting that the methods used in this paper are also applied to fuzzy model for complex networks and general neural networks. Numerical simulations are also provided to verify the effectiveness of theoretical results. Copyright © 2015 Elsevier Ltd. All rights reserved.

  13. Delay-dependent exponential stability analysis of bi-directional associative memory neural networks with time delay: an LMI approach

    International Nuclear Information System (INIS)

    Li Chuandong; Liao Xiaofeng; Zhang Rong

    2005-01-01

    For bi-directional associative memory (BAM) neural networks (NNs) with different constant or time-varying delays, the problems of determining the exponential stability and estimating the exponential convergence rate are investigated in this paper. An approach combining the Lyapunov-Krasovskii functional with the linear matrix inequality (LMI) is taken to study the problems, which provide bounds on the interconnection matrix and the activation functions, so as to guarantee the system's exponential stability. Some criteria for the exponential stability, which give information on the delay-dependent property, are derived. The results obtained in this paper provide one more set of easily verified guidelines for determining the exponential stability of delayed BAM (DBAM) neural networks, which are less conservative and less restrictive than the ones reported so far in the literature. Some typical examples are presented to show the application of the criteria obtained in this paper

  14. Mean square stabilization and mean square exponential stabilization of stochastic BAM neural networks with Markovian jumping parameters

    International Nuclear Information System (INIS)

    Ye, Zhiyong; Zhang, He; Zhang, Hongyu; Zhang, Hua; Lu, Guichen

    2015-01-01

    Highlights: •This paper introduces a non-conservative Lyapunov functional. •The achieved results impose non-conservative and can be widely used. •The conditions are easily checked by the Matlab LMI Tool Box. The desired state feedback controller can be well represented by the conditions. -- Abstract: This paper addresses the mean square exponential stabilization problem of stochastic bidirectional associative memory (BAM) neural networks with Markovian jumping parameters and time-varying delays. By establishing a proper Lyapunov–Krasovskii functional and combining with LMIs technique, several sufficient conditions are derived for ensuring exponential stabilization in the mean square sense of such stochastic BAM neural networks. In addition, the achieved results are not difficult to verify for determining the mean square exponential stabilization of delayed BAM neural networks with Markovian jumping parameters and impose less restrictive and less conservative than the ones in previous papers. Finally, numerical results are given to show the effectiveness and applicability of the achieved results

  15. On the absolute stability regions corresponding to partial sums of the exponential function

    KAUST Repository

    Ketcheson, David I.

    2013-12-03

    Certain numerical methods for initial value problems have as stability function the nth partial sum of the exponential function. We study the stability region, i.e., the set in the complex plane over which the nth partial sum has at most unit modulus. It is known that the asymptotic shape of the part of the stability region in the left half-plane is a semi-disk. We quantify this by providing disks that enclose or are enclosed by the stability region or its left half-plane part. The radius of the smallest disk centered at the origin that contains the stability region (or its portion in the left half-plane) is determined for 1 n 20. Bounds on such radii are proved for n 2; these bounds are shown to be optimal in the limit n ! +1. We prove that the stability region and its complement, restricted to the imaginary axis, consist of alternating intervals of length tending to , as n ! 1. Finally, we prove that a semi-disk in the left half-plane with vertical boundary being the imaginary axis and centered at the origin is included in the stability region if and only if n 0 mod 4 or n 3 mod 4. The maximal radii of such semi-disks are exactly determined for 1 n 20.

  16. New exponential stability conditions for linear delayed systems of differential equations

    Directory of Open Access Journals (Sweden)

    Leonid Berezansky

    2016-08-01

    where $t\\ge 0$, $m$ and $r_{ij}$, $i,j=1,\\dots,m$ are natural numbers, $a_{ij}^{k}\\colon [0,\\infty\\to\\mathbb{R}$ are measurable coefficients, and $h_{ij}^{k}\\colon [0,\\infty\\to\\mathbb{R}$ are measurable delays. The progress was achieved by using a new technique making it possible to replace the constant $1$ by the constant $1+{1}/{\\mathrm{e}}$ on the right-hand sides of crucial inequalities ensuring exponential stability.

  17. Delay-Dependent Exponential Stability for Discrete-Time BAM Neural Networks with Time-Varying Delays

    Directory of Open Access Journals (Sweden)

    Yonggang Chen

    2008-01-01

    Full Text Available This paper considers the delay-dependent exponential stability for discrete-time BAM neural networks with time-varying delays. By constructing the new Lyapunov functional, the improved delay-dependent exponential stability criterion is derived in terms of linear matrix inequality (LMI. Moreover, in order to reduce the conservativeness, some slack matrices are introduced in this paper. Two numerical examples are presented to show the effectiveness and less conservativeness of the proposed method.

  18. Exponential mean-square stability of two classes of theta Milstein methods for stochastic delay differential equations

    Science.gov (United States)

    Rouz, Omid Farkhondeh; Ahmadian, Davood; Milev, Mariyan

    2017-12-01

    This paper establishes exponential mean square stability of two classes of theta Milstein methods, namely split-step theta Milstein (SSTM) method and stochastic theta Milstein (STM) method, for stochastic differential delay equations (SDDEs). We consider the SDDEs problem under a coupled monotone condition on drift and diffusion coefficients, as well as a necessary linear growth condition on the last term of theta Milstein method. It is proved that the SSTM method with θ ∈ [0, ½] can recover the exponential mean square stability of the exact solution with some restrictive conditions on stepsize, but for θ ∈ (½, 1], we proved that the stability results hold for any stepsize. Then, based on the stability results of SSTM method, we examine the exponential mean square stability of the STM method and obtain the similar stability results to that of the SSTM method. In the numerical section the figures show thevalidity of our claims.

  19. On the conditions of exponential stability in active disturbance rejection control based on singular perturbation analysis

    Science.gov (United States)

    Shao, S.; Gao, Z.

    2017-10-01

    Stability of active disturbance rejection control (ADRC) is analysed in the presence of unknown, nonlinear, and time-varying dynamics. In the framework of singular perturbations, the closed-loop error dynamics are semi-decoupled into a relatively slow subsystem (the feedback loop) and a relatively fast subsystem (the extended state observer), respectively. It is shown, analytically and geometrically, that there exists a unique exponential stable solution if the size of the initial observer error is sufficiently small, i.e. in the same order of the inverse of the observer bandwidth. The process of developing the uniformly asymptotic solution of the system reveals the condition on the stability of the ADRC and the relationship between the rate of change in the total disturbance and the size of the estimation error. The differentiability of the total disturbance is the only assumption made.

  20. New results on global exponential dissipativity analysis of memristive inertial neural networks with distributed time-varying delays.

    Science.gov (United States)

    Zhang, Guodong; Zeng, Zhigang; Hu, Junhao

    2018-01-01

    This paper is concerned with the global exponential dissipativity of memristive inertial neural networks with discrete and distributed time-varying delays. By constructing appropriate Lyapunov-Krasovskii functionals, some new sufficient conditions ensuring global exponential dissipativity of memristive inertial neural networks are derived. Moreover, the globally exponential attractive sets and positive invariant sets are also presented here. In addition, the new proposed results here complement and extend the earlier publications on conventional or memristive neural network dynamical systems. Finally, numerical simulations are given to illustrate the effectiveness of obtained results. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Global existence and exponential growth for a viscoelastic wave equation with dynamic boundary conditions

    KAUST Repository

    Gerbi, Sté phane; Said-Houari, Belkacem

    2013-01-01

    The goal of this work is to study a model of the wave equation with dynamic boundary conditions and a viscoelastic term. First, applying the Faedo-Galerkin method combined with the fixed point theorem, we show the existence and uniqueness of a local in time solution. Second, we show that under some restrictions on the initial data, the solution continues to exist globally in time. On the other hand, if the interior source dominates the boundary damping, then the solution is unbounded and grows as an exponential function. In addition, in the absence of the strong damping, then the solution ceases to exist and blows up in finite time.

  2. Globally exponential synchronization in an array of asymmetric coupled neural networks

    International Nuclear Information System (INIS)

    Lu Jianquan; Ho, Daniel W.C.; Liu Ming

    2007-01-01

    In this Letter, we study the globally exponential synchronization in an array of linearly coupled neural networks with delayed coupling. The coupling configuration matrix is assumed to be asymmetric, which is more coincident with the real-world network. The difficulty arising from the asymmetry of the coupling matrix has been overcame in this work. Some synchronization criteria are given in terms of strict linear matrix inequalities (LMIs), which can be efficiently solved by using interior point algorithm. Some previous synchronization results are generalized. Numerical simulation is also given to verify our theoretical analysis

  3. Global existence and exponential growth for a viscoelastic wave equation with dynamic boundary conditions

    KAUST Repository

    Gerbi, Stéphane

    2013-01-15

    The goal of this work is to study a model of the wave equation with dynamic boundary conditions and a viscoelastic term. First, applying the Faedo-Galerkin method combined with the fixed point theorem, we show the existence and uniqueness of a local in time solution. Second, we show that under some restrictions on the initial data, the solution continues to exist globally in time. On the other hand, if the interior source dominates the boundary damping, then the solution is unbounded and grows as an exponential function. In addition, in the absence of the strong damping, then the solution ceases to exist and blows up in finite time.

  4. A new criterion to global exponential periodicity for discrete-time BAM neural network with infinite delays

    International Nuclear Information System (INIS)

    Zhou Tiejun; Liu Yuehua; Li Xiaoping; Liu Yirong

    2009-01-01

    The discrete-time bidirectional associative memory neural network with periodic coefficients and infinite delays is studied. And not by employing the continuation theorem of coincidence degree theory as other literatures, but by constructing suitable Liapunov function, using fixed point theorem and some analysis techniques, a sufficient criterion is obtained which ensures the existence and global exponential stability of periodic solution for the type of discrete-time BAM neural network. The obtained result is less restrictive to the BAM neural networks than previously known criteria. Furthermore, it can be applied to the BAM neural network which signal transfer functions are neither bounded nor differentiable. In addition, an example and its numerical simulation are given to illustrate the effectiveness of the obtained result

  5. THE EXPONENTIAL STABILIZATION FOR A SEMILINEAR WAVE EQUATION WITH LOCALLY DISTRIBUTED FEEDBACK

    Institute of Scientific and Technical Information of China (English)

    JIA CHAOHUA; FENG DEXING

    2005-01-01

    This paper considers the exponential decay of the solution to a damped semilinear wave equation with variable coefficients in the principal part by Riemannian multiplier method. A differential geometric condition that ensures the exponential decay is obtained.

  6. TRANSMUTED EXPONENTIATED EXPONENTIAL DISTRIBUTION

    OpenAIRE

    MEROVCI, FATON

    2013-01-01

    In this article, we generalize the exponentiated exponential distribution using the quadratic rank transmutation map studied by Shaw etal. [6] to develop a transmuted exponentiated exponential distribution. Theproperties of this distribution are derived and the estimation of the model parameters is discussed. An application to real data set are finally presented forillustration

  7. Stability of Global Geodetic Results

    Science.gov (United States)

    Herring, T.

    The precision of global geodetic techniques has reached unprecedented levels. Sys- tems capable of millimeter level horizontal and several millimeter vertical precisions are now deployed. The Global Positioning System (GPS) has the most deployed continuously-operating receivers with several hundred providing data through the in- ternet for analysis. However, the satellite system used with GPS evolves with time as new generations of GPS satellites are launched. During the 1990's, the constellation evolved from Block I to Block II and IIA with the most recent generation being Block IIR. There are considerable differences in the size and antenna configurations in the different generations of satellites. The antenna configuration specifically could cause systematic changes in the terrestrial reference system. Results from the ITRF2000 combinations suggest that there are significant time variations in the scale of GPS system possibly due to phase center variations in GPS transmission antennas. These variations could result in height changes of up to 3 mm/yr. We will investigate the stability of the GPS system through combination of GPS results with results from VLBI and SLR. All components of the transformation between the systems, rotation, translation and scale will be investigated.

  8. Positivity of Fundamental Matrix and Exponential Stability of Delay Differential System

    Directory of Open Access Journals (Sweden)

    Alexander Domoshnitsky

    2014-01-01

    Full Text Available The classical Wazewski theorem established that nonpositivity of all nondiagonal elements pij  (i≠j,  i,j=1,…,n is necessary and sufficient for nonnegativity of the fundamental (Cauchy matrix and consequently for applicability of the Chaplygin approach of approximate integration for system of linear ordinary differential equations xi′t+∑j=1n‍pijtxjt=fit,   i=1,…,n. Results on nonnegativity of the Cauchy matrix for system of delay differential equations xi′t+∑j=1n‍pijtxjhijt=fit,   i=1,…,n, which were based on nonpositivity of all diagonal elements, were presented in the previous works. Then examples, which demonstrated that nonpositivity of nondiagonal coefficients pij is not necessary for systems of delay equations, were found. In this paper first sufficient results about nonnegativity of the Cauchy matrix of the delay system without this assumption are proven. A necessary condition of nonnegativity of the Cauchy matrix is proposed. On the basis of these results on nonnegativity of the Cauchy matrix, necessary and sufficient conditions of the exponential stability of the delay system are obtained.

  9. pth moment exponential stability of stochastic memristor-based bidirectional associative memory (BAM) neural networks with time delays.

    Science.gov (United States)

    Wang, Fen; Chen, Yuanlong; Liu, Meichun

    2018-02-01

    Stochastic memristor-based bidirectional associative memory (BAM) neural networks with time delays play an increasingly important role in the design and implementation of neural network systems. Under the framework of Filippov solutions, the issues of the pth moment exponential stability of stochastic memristor-based BAM neural networks are investigated. By using the stochastic stability theory, Itô's differential formula and Young inequality, the criteria are derived. Meanwhile, with Lyapunov approach and Cauchy-Schwarz inequality, we derive some sufficient conditions for the mean square exponential stability of the above systems. The obtained results improve and extend previous works on memristor-based or usual neural networks dynamical systems. Four numerical examples are provided to illustrate the effectiveness of the proposed results. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. Global Asymptotic Stability of Impulsive CNNs with Proportional Delays and Partially Lipschitz Activation Functions

    Directory of Open Access Journals (Sweden)

    Xueli Song

    2014-01-01

    Full Text Available This paper researches global asymptotic stability of impulsive cellular neural networks with proportional delays and partially Lipschitz activation functions. Firstly, by means of the transformation vi(t=ui(et, the impulsive cellular neural networks with proportional delays are transformed into impulsive cellular neural networks with the variable coefficients and constant delays. Secondly, we provide novel criteria for the uniqueness and exponential stability of the equilibrium point of the latter by relative nonlinear measure and prove that the exponential stability of equilibrium point of the latter implies the asymptotic stability of one of the former. We furthermore obtain a sufficient condition to the uniqueness and global asymptotic stability of the equilibrium point of the former. Our method does not require conventional assumptions on global Lipschitz continuity, boundedness, and monotonicity of activation functions. Our results are generalizations and improvements of some existing ones. Finally, an example and its simulations are provided to illustrate the correctness of our analysis.

  11. Global stability of almost periodic solution of shunting inhibitory cellular neural networks with variable coefficients

    International Nuclear Information System (INIS)

    Chen Ling; Zhao Hongyong

    2008-01-01

    The paper investigates the almost periodicity of shunting inhibitory cellular neural networks with delays and variable coefficients. Several sufficient conditions are established for the existence and globally exponential stability of almost periodic solutions by employing fixed point theorem and differential inequality technique. The results of this paper are new and they complement previously known results

  12. Global Practical Stabilization and Tracking for an Underactuated Ship - A Combined Averaging and Backstepping Approach

    Directory of Open Access Journals (Sweden)

    Kristin Y. Pettersen

    1999-10-01

    Full Text Available We solve both the global practical stabilization and tracking problem for an underactuated ship, using a combined integrator backstepping and averaging approach. Exponential convergence to an arbitrarily small neighbourhood of the origin and of the reference trajectory, respectively, is proved. Simulation results are included.

  13. Global and exponential attractors of the three dimensional viscous primitive equations of large-scale moist atmosphere

    OpenAIRE

    You, Bo; Li, Fang

    2016-01-01

    This paper is concerned with the long-time behavior of solutions for the three dimensional viscous primitive equations of large-scale moist atmosphere. We prove the existence of a global attractor for the three dimensional viscous primitive equations of large-scale moist atmosphere by asymptotic a priori estimate and construct an exponential attractor by using the smoothing property of the semigroup generated by the three dimensional viscous primitive equations of large-scale moist atmosphere...

  14. Exponential stability of continuous-time and discrete-time bidirectional associative memory networks with delays

    International Nuclear Information System (INIS)

    Liang Jinling; Cao Jinde

    2004-01-01

    First, convergence of continuous-time Bidirectional Associative Memory (BAM) neural networks are studied. By using Lyapunov functionals and some analysis technique, the delay-independent sufficient conditions are obtained for the networks to converge exponentially toward the equilibrium associated with the constant input sources. Second, discrete-time analogues of the continuous-time BAM networks are formulated and studied. It is shown that the convergence characteristics of the continuous-time systems are preserved by the discrete-time analogues without any restriction imposed on the uniform discretionary step size. An illustrative example is given to demonstrate the effectiveness of the obtained results

  15. Exponential Growth and the Shifting Global Center of Gravity of Science Production, 1900-2011

    Science.gov (United States)

    Zhang, Liang; Powell, Justin J. W.; Baker, David P.

    2015-01-01

    Long historical trends in scientific discovery led mid-20th century scientometricians to mark the advent of "big science"--extensive science production--and predicted that over the next few decades, the exponential growth would slow, resulting in lower rates of increase in production at the upper limit of a logistic curve. They were…

  16. The Western Africa ebola virus disease epidemic exhibits both global exponential and local polynomial growth rates.

    Science.gov (United States)

    Chowell, Gerardo; Viboud, Cécile; Hyman, James M; Simonsen, Lone

    2015-01-21

    While many infectious disease epidemics are initially characterized by an exponential growth in time, we show that district-level Ebola virus disease (EVD) outbreaks in West Africa follow slower polynomial-based growth kinetics over several generations of the disease. We analyzed epidemic growth patterns at three different spatial scales (regional, national, and subnational) of the Ebola virus disease epidemic in Guinea, Sierra Leone and Liberia by compiling publicly available weekly time series of reported EVD case numbers from the patient database available from the World Health Organization website for the period 05-Jan to 17-Dec 2014. We found significant differences in the growth patterns of EVD cases at the scale of the country, district, and other subnational administrative divisions. The national cumulative curves of EVD cases in Guinea, Sierra Leone, and Liberia show periods of approximate exponential growth. In contrast, local epidemics are asynchronous and exhibit slow growth patterns during 3 or more EVD generations, which can be better approximated by a polynomial than an exponential function. The slower than expected growth pattern of local EVD outbreaks could result from a variety of factors, including behavior changes, success of control interventions, or intrinsic features of the disease such as a high level of clustering. Quantifying the contribution of each of these factors could help refine estimates of final epidemic size and the relative impact of different mitigation efforts in current and future EVD outbreaks.

  17. Exponential stability for formation control systems with generalized controllers: A unified approach

    NARCIS (Netherlands)

    Sun, Zhiyong; Mou, Shaoshuai; Anderson, Brian D.O.; Cao, Ming

    2016-01-01

    This paper discusses generalized controllers for distance-based rigid formation shape stabilization and aims to provide a unified approach for the convergence analysis. We consider two types of formation control systems according to different characterizations of target formations: minimally rigid

  18. New results for global exponential synchronization in neural networks via functional differential inclusions.

    Science.gov (United States)

    Wang, Dongshu; Huang, Lihong; Tang, Longkun

    2015-08-01

    This paper is concerned with the synchronization dynamical behaviors for a class of delayed neural networks with discontinuous neuron activations. Continuous and discontinuous state feedback controller are designed such that the neural networks model can realize exponential complete synchronization in view of functional differential inclusions theory, Lyapunov functional method and inequality technique. The new proposed results here are very easy to verify and also applicable to neural networks with continuous activations. Finally, some numerical examples show the applicability and effectiveness of our main results.

  19. An Exponential Stability Result of a Timoshenko System with Thermoelasticity with Second Sound and in the Presence of Delay

    Energy Technology Data Exchange (ETDEWEB)

    Apalara, Tijani A., E-mail: tijani@kfupm.edu.sa [King Fahd University of Petroleum and Minerals, Affiliated Colleges at Hafr Al-Batin, General Science and Studies Unit-Mathematics (Saudi Arabia); Messaoudi, Salim A., E-mail: messaoud@kfupm.edu.sa [King Fahd University of Petroleum and Minerals, Department of Mathematics and Statistics (Saudi Arabia)

    2015-06-15

    In this paper, we consider a one-dimensional linear thermoelastic system of Timoshenko type with a delay, where the heat flux is given by Cattaneo’s law. We prove an exponential decay result under a smallness condition on the delay and a stability number introduced first in Santos et al. (J Diff Eqs 253:2715–2733, 2012), using a method different from that of Santos et al. (J Diff Eqs 253:2715–2733, 2012). We also reproduce the polynomial decay of Santos et al. (J Diff Eqs 253:2715–2733, 2012) using the multiplier method in the case of absence of delay. The polynomial decay issue in the presence of a small delay is an open question.

  20. On stability of exponential cosmological solutions with non-static volume factor in the Einstein-Gauss-Bonnet model

    Energy Technology Data Exchange (ETDEWEB)

    Ivashchuk, V.D. [VNIIMS, Center for Gravitation and Fundamental Metrology, Moscow (Russian Federation); Peoples' Friendship University of Russia (RUDN University), Institute of Gravitation and Cosmology, Moscow (Russian Federation)

    2016-08-15

    A (n + 1)-dimensional gravitational model with Gauss-Bonnet term and a cosmological constant term is considered. When ansatz with diagonal cosmological metrics is adopted, the solutions with an exponential dependence of the scale factors, a{sub i} ∝ exp(v{sup i}t), i = 1,.., n, are analyzed for n > 3. We study the stability of the solutions with non-static volume factor, i.e. K(v) = sum {sub k=1}{sup n} v{sup k} ≠ 0. We prove that under a certain restriction R imposed solutions with K(v) > 0 are stable, while solutions with K(v) < 0 are unstable. Certain examples of stable solutions are presented. We show that the solutions with v{sup 1} = v{sup 2} = v{sup 3} = H > 0 and zero variation of the effective gravitational constant are stable if the restriction R is obeyed. (orig.)

  1. Stabilizing greenhouse gases. Global and regional consequences

    International Nuclear Information System (INIS)

    Alcamo, J.; Krol, M.; Leemans, R.

    1995-01-01

    This paper assesses the environmental consequences of two targets for CO 2 stabilization: 350 ppm by the year 2150 (367 ppm by 2100), and 450 ppm by 2100. As a tool for this investigation we use the IMAGE 2 integrated model of climate change. It was found that these targets lead to much lower regional impacts on crop productivity, natural vegetation, and sea level rise as compared to the baseline case. Nevertheless some negative impacts do occur, and to further reduce these impacts would require more stringent stabilization targets. It was also found that to achieve these stabilization targets in the atmosphere, global emissions should not substantially increase at any time in the future, and eventually they must be significantly reduced. 8 figs., 1 tab., 7 refs., 1 appendix

  2. New Delay-Dependent Robust Exponential Stability Criteria of LPD Neutral Systems with Mixed Time-Varying Delays and Nonlinear Perturbations

    Directory of Open Access Journals (Sweden)

    Sirada Pinjai

    2013-01-01

    Full Text Available This paper is concerned with the problem of robust exponential stability for linear parameter-dependent (LPD neutral systems with mixed time-varying delays and nonlinear perturbations. Based on a new parameter-dependent Lyapunov-Krasovskii functional, Leibniz-Newton formula, decomposition technique of coefficient matrix, free-weighting matrices, Cauchy’s inequality, modified version of Jensen’s inequality, model transformation, and linear matrix inequality technique, new delay-dependent robust exponential stability criteria are established in terms of linear matrix inequalities (LMIs. Numerical examples are given to show the effectiveness and less conservativeness of the proposed methods.

  3. Exponential stability for stochastic delayed recurrent neural networks with mixed time-varying delays and impulses: the continuous-time case

    International Nuclear Information System (INIS)

    Karthik Raja, U; Leelamani, A; Raja, R; Samidurai, R

    2013-01-01

    In this paper, the exponential stability for a class of stochastic neural networks with time-varying delays and impulsive effects is considered. By constructing suitable Lyapunov functionals and by using the linear matrix inequality optimization approach, we obtain sufficient delay-dependent criteria to ensure the exponential stability of stochastic neural networks with time-varying delays and impulses. Two numerical examples with simulation results are provided to illustrate the effectiveness of the obtained results over those already existing in the literature. (paper)

  4. Global robust stability for shunting inhibitory CNNs with delays.

    Science.gov (United States)

    Wang, Lingna; Lin, Yiping

    2004-08-01

    In this paper, the problem of global robust stability for shunting inhibitory cellular neural networks (SICNNs) is studied. A sufficient condition guaranteeing the network's global robust stability is established. The result can easily be used to verify globally robust stable networks. An example is given to illustrate that the conditions of our results are feasible.

  5. Stability of fundamental couplings: A global analysis

    Science.gov (United States)

    Martins, C. J. A. P.; Pinho, A. M. M.

    2017-01-01

    Astrophysical tests of the stability of fundamental couplings are becoming an increasingly important probe of new physics. Motivated by the recent availability of new and stronger constraints we update previous works testing the consistency of measurements of the fine-structure constant α and the proton-to-electron mass ratio μ =mp/me (mostly obtained in the optical/ultraviolet) with combined measurements of α , μ and the proton gyromagnetic ratio gp (mostly in the radio band). We carry out a global analysis of all available data, including the 293 archival measurements of Webb et al. and 66 more recent dedicated measurements, and constraining both time and spatial variations. While nominally the full data sets show a slight statistical preference for variations of α and μ (at up to two standard deviations), we also find several inconsistencies between different subsets, likely due to hidden systematics and implying that these statistical preferences need to be taken with caution. The statistical evidence for a spatial dipole in the values of α is found at the 2.3 sigma level. Forthcoming studies with facilities such as ALMA and ESPRESSO should clarify these issues.

  6. Hydrogen energy strategies and global stability and unrest

    International Nuclear Information System (INIS)

    Midilli, A.; Dincer, I.; Rosen, M.A.

    2004-01-01

    This paper focuses on hydrogen energy strategies and global stability and unrest. In order to investigate the strategic relationship between these concepts, two empirical relations that describe the effects of fossil fuels on global stability and global unrest are developed. These relations incorporate predicted utilization ratios for hydrogen energy from non-fossil fuels, and are used to investigate whether hydrogen utilization can reduce the negative global effects related to fossil fuel use, eliminate or reduce the possibilities of global energy conflicts, and contribute to achieving world stability. It is determined that, if utilization of hydrogen from non-fossil fuels increases, for a fixed usage of petroleum, coal and natural gas, the level of global unrest decreases. However, if the utilization ratio of hydrogen energy from non-fossil fuels is lower than 100%, the level of global stability decreases as the symptoms of global unrest increase. It is suggested that, to reduce the causes of global unrest and increase the likelihood of global stability in the future, hydrogen energy should be widely and efficiently used, as one component of plans for sustainable development. (author)

  7. An exponential observer for the generalized Rossler chaotic system

    International Nuclear Information System (INIS)

    Sun, Y.-J.

    2009-01-01

    In this paper, the generalized Rossler chaotic system is considered and the state observation problem of such a system is investigated. Based on the time-domain approach, a state observer for the generalized Rossler chaotic system is developed to guarantee the global exponential stability of the resulting error system. Moreover, the guaranteed exponential convergence rate can be arbitrarily pre-specified. Finally, a numerical example is provided to illustrate the feasibility and effectiveness of the obtained result.

  8. Non Lyapunov stability of the constant spatially developing 1-D gas flow in presence of solutions having strictly positive exponential growth rate

    Science.gov (United States)

    Balint, Stefan; Balint, Agneta M.

    2017-01-01

    Different types of stabilities (global, local) and instabilities (global absolute, local convective) of the constant spatially developing 1-D gas flow are analyzed in the phase space of continuously differentiable functions, endowed with the usual algebraic operations and the topology generated by the uniform convergence on the real axis. For this purpose the Euler equations linearized at the constant flow are used. The Lyapunov stability analysis was presented in [1] and this paper is a continuation of [1].

  9. Novel global robust stability criterion for neural networks with delay

    International Nuclear Information System (INIS)

    Singh, Vimal

    2009-01-01

    A novel criterion for the global robust stability of Hopfield-type interval neural networks with delay is presented. An example illustrating the improvement of the present criterion over several recently reported criteria is given.

  10. On the stability of evolution equations | Egwurube | Global Journal of ...

    African Journals Online (AJOL)

    accretive operator is considered and conditions which guarantee asymptotic stability of its solution in a dense subset of the space are given. Global Jouranl of Mathematical Sciences Vol. 6 (1) 2007: pp. 27-30 ...

  11. Novel results for global robust stability of delayed neural networks

    International Nuclear Information System (INIS)

    Yucel, Eylem; Arik, Sabri

    2009-01-01

    This paper investigates the global robust convergence properties of continuous-time neural networks with discrete time delays. By employing suitable Lyapunov functionals, some sufficient conditions for the existence, uniqueness and global robust asymptotic stability of the equilibrium point are derived. The conditions can be easily verified as they can be expressed in terms of the network parameters only. Some numerical examples are also given to compare our results with previous robust stability results derived in the literature.

  12. Global exponential convergence of neutral-type Hopfield neural networks with multi-proportional delays and leakage delays

    International Nuclear Information System (INIS)

    Xu, Changjin; Li, Peiluan

    2017-01-01

    This paper is concerned with a class of neutral-type Hopfield neural networks with multi-proportional delays and leakage delays. Using the differential inequality theory, a set of sufficient conditions which guarantee that all solutions of neutral-type Hopfield neural networks with multi-proportional delays and leakage delays converge exponentially to zero vector are derived. Computer simulations are carried out to verify our theoretical findings. The obtained results of this paper are new and complement some previous studies.

  13. Global stability of phase lock near a chaotic crisis in the rf-biased Josephson junction

    International Nuclear Information System (INIS)

    Kautz, R.L.

    1987-01-01

    The global stability of phase lock in the rf-biased Josephson junction is studied through digital simulations. Global stability is determined by calculating the lifetime of the phase-locked state in the presence of thermal noise. This lifetime, the mean time required for thermal noise to induce a 2π phase slip, increases exponentially with inverse temperature in the limit of low temperatures, and the low-temperature asymptote can be parametrized in terms of an activation energy E-script and an attempt time tau 0 . The activation energy is a useful measure of global stability for both periodic and chaotic phase-locked states. The behavior of E-script and tau 0 is studied over a range of critical-current densities which take the system from a region of harmonic motion through a period-doubling cascade and into a region of phase-locked chaotic behavior which is ended by a chaotic crisis. At the crisis point, the activation energy goes to zero and the attempt time goes to infinity. The results are used to determine the optimum critical-current density for series-array voltage standards

  14. Policy options for stabilizing global climate

    International Nuclear Information System (INIS)

    Lashof, D.A.; Tirpak, D.A.

    1990-12-01

    This report to congress by the US EPA explains the greenhouse effect and its influence on global climate. It outlines the trends in the greenhouse gases - their concentration history, distribution, sources and sinks and chemical and radiative properties. Climate change processes are discussed including climate feedbacks. Human activities affecting trace gases and climate are explained, followed by a chapter on the technical options for reducing greenhouse gas emissions which looks at energy services, energy supply, industry, forestry and agriculture. The future is considered, and the final chapters are concerned with policy options and international cooperation to reduce greenhouse gas emissions. 934 refs., 102 figs., 84 tabs

  15. Global temperature stability by rule induction: An interdisciplinary bridge

    International Nuclear Information System (INIS)

    Gunn, J.D.; Grzymala-Busse, J.W.

    1994-01-01

    Rules incorporating influences on global temperature, an estimate of radiation balance, were induced from astronomical, geophysical, and anthropogenic variables. During periods of intermediate global temperatures (generally like the present century), the influences assume canceling roles; influences cancel the effects of extreme states potentially imposed by other influences because they are, in aggregate, most likely to be assuming opposite values. This imparts an overall stability to the global temperature. To achieve cold or hot global temperature, influences assume reinforcing roles. CO 2 is an active influence on global temperature. By virtue of its constancy in the atmosphere, it can be expected to sponsor frequent hot years in combination with the other influences as they cycle through their periods. If measures were implemented to maintain warm or cool global temperatures, it could retain the status quo of present global agricultural regions. They are probably more productive than hot world regions would be because of narrow storm tracks

  16. GLOBALIZATION, CONSUMPTION PATTERNS AND POLITICAL STABILITY

    Directory of Open Access Journals (Sweden)

    Grzegorz Malinowski

    2017-06-01

    Full Text Available Rapid changes in technology and economy that we observe nowadays are accompanied by rapid changes in traditional values and attitudes. In the contemporary world, a permanent proximity of internet, computer, television or smartphone makes us all citizens of the globalised, virtual world rather than a physical, geographical, real one. But even if people consider themselves to be citizens of the “global village”, a political architecture of the real world has remained based on the nation-state. One of the main characteristics of a nation-state is its territory defined by its borders. Recognition and respect of nation-state borders is considered to be a principle of national sovereignty, national interest and territorial independence, which shape international relations. Historically, rulers always usurped the right to control what happens on their territory, but there were some areas that had escaped their supervision. The first one is the sphere of science and more broadly – ideas. Whether it was religion, superstition or steam engine, ideas were unstoppable even for isolated countries. Second area is a realm of trade. Rulers were usually rather kind for merchants, therefore borders were always wide open for business people. It is worth mentioning that both ideas and trade are significant driving forces in the history of world. Their influence is sometimes stronger and sometimes weaker but it is always meaningful. Yet the very hypothesis of this article states that in contemporary, globalised world a third important factor has arrived. It was always present but until the economy hasn’t become globalized, its impact wasn’t noticeable. This third factor can be described as universalisation of western consumption patterns and it plays an important role particularly in developing countries.

  17. Global robust stability of delayed recurrent neural networks

    International Nuclear Information System (INIS)

    Cao Jinde; Huang Deshuang; Qu Yuzhong

    2005-01-01

    This paper is concerned with the global robust stability of a class of delayed interval recurrent neural networks which contain time-invariant uncertain parameters whose values are unknown but bounded in given compact sets. A new sufficient condition is presented for the existence, uniqueness, and global robust stability of equilibria for interval neural networks with time delays by constructing Lyapunov functional and using matrix-norm inequality. An error is corrected in an earlier publication, and an example is given to show the effectiveness of the obtained results

  18. Global Asymptotic Stability of Switched Neural Networks with Delays

    Directory of Open Access Journals (Sweden)

    Zhenyu Lu

    2015-01-01

    Full Text Available This paper investigates the global asymptotic stability of a class of switched neural networks with delays. Several new criteria ensuring global asymptotic stability in terms of linear matrix inequalities (LMIs are obtained via Lyapunov-Krasovskii functional. And here, we adopt the quadratic convex approach, which is different from the linear and reciprocal convex combinations that are extensively used in recent literature. In addition, the proposed results here are very easy to be verified and complemented. Finally, a numerical example is provided to illustrate the effectiveness of the results.

  19. Sensitivity of ITER MHD global stability to edge pressure gradients

    International Nuclear Information System (INIS)

    Hogan, J.T.; Martynov, A.

    1994-01-01

    In view of the preliminary nature of boundary models for reactor tokamaks, the sensitivity to edge gradients of the global mode MHD stability of the ITER EDA configuration has been examined. The POLAR-2D equilibrium and TORUS stability codes developed by the Keldysh Institute have been used. Transport-related profiles from the PRETOR transport code (developed by the ITER Joint Central Team) and axisymmetric equilibria for these profiles from the TEQ code (L.D. Pearlstein, LLNL) were taken as a starting point for the study. These baseline profiles are found to have quite high global stability limits, in the range g(Troyon) = 4-5. The major focus of this study is to examine global mode stability assuming small variations about the baseline profiles, changing the pressure gradients near the boundary. Such changes can be expected with an improved boundary model. Reduced stability limits are found in such cases, and unstable cases with g = 2-3 are found. Thus, the assumption of ITER stability limits higher than g = 2 must be treated with caution

  20. Global asymptotic stability of delayed Cohen-Grossberg neural networks

    International Nuclear Information System (INIS)

    Wu Wei; Cui Baotong; Huang Min

    2007-01-01

    In this letter, the global asymptotic stability of a class of Cohen-Grossberg neural networks with time-varying delays is discussed. A new set of sufficient conditions for the neural networks are proposed to guarantee the global asymptotic convergence. Our criteria represent an extension of the existing results in literatures. An example is also presented to compare our results with the previous results

  1. Exponential Synchronization of Uncertain Complex Dynamical Networks with Delay Coupling

    International Nuclear Information System (INIS)

    Wang Lifu; Kong Zhi; Jing Yuanwei

    2010-01-01

    This paper studies the global exponential synchronization of uncertain complex delayed dynamical networks. The network model considered is general dynamical delay networks with unknown network structure and unknown coupling functions but bounded. Novel delay-dependent linear controllers are designed via the Lyapunov stability theory. Especially, it is shown that the controlled networks are globally exponentially synchronized with a given convergence rate. An example of typical dynamical network of this class, having the Lorenz system at each node, has been used to demonstrate and verify the novel design proposed. And, the numerical simulation results show the effectiveness of proposed synchronization approaches. (general)

  2. Unconditional nonlinear exponential stability in the Benard problem; Stabilita' nonlineare esponenziale incondizionata nel problema di Be'nard per ina miscela: condizioni necessarie e sufficienti.

    Energy Technology Data Exchange (ETDEWEB)

    Mulione, G. [Catania, Univ. (Italy). Dip. di Matematica; Rionero, S. [Napoli, Univ. (Italy). Dip. di Matematica e applicazioni

    1998-07-01

    The Lyapunov direct method is applied to study nonlinear stability of a basic motionless state to imposed linear temperature and concentration fields of a binary fluid mixture heated and salted from below, in the Oberbeck-Boussinesq scheme. Stress-free and rigid surfaces are considered and absence of Hopf bifurcation is assumed. We prove the coincidence of the linear and (unconditional) nonlinear critical stability limits, when the ratio between the Schmidt and the Prandtl numbers is less or equal to 1. Precisely, we obtain necessary and sufficient conditions of unconditional nonlinear exponential stability of the basic motionless state. [Italian] Si applica il metodo diretto di Lyapunov allo studio della stabilita' non lineare esponenziale della soluzione di conduzione-diffusione di una miscela fluida binaria riscaldata e salata da sotto, nello schema di Oberbeck-Boussinesq. Si considerano superfici rigide e 'stress-free'; si supponeche non ci sia biforcazione di Hpf. Supposto che il rapporto fra i numeri di Schmidt e di Prandtl e' minore o uguale a 1, si prova la coincidenza tra i paramentri critici della stabilita' lineare e non lineare. Si ottengono condizioni necessarie e sufficienti di stabilita' non lineare esponenziale del moto base.

  3. Exponential convergence rate estimation for uncertain delayed neural networks of neutral type

    International Nuclear Information System (INIS)

    Lien, C.-H.; Yu, K.-W.; Lin, Y.-F.; Chung, Y.-J.; Chung, L.-Y.

    2009-01-01

    The global exponential stability for a class of uncertain delayed neural networks (DNNs) of neutral type is investigated in this paper. Delay-dependent and delay-independent criteria are proposed to guarantee the robust stability of DNNs via LMI and Razumikhin-like approaches. For a given delay, the maximal allowable exponential convergence rate will be estimated. Some numerical examples are given to illustrate the effectiveness of our results. The simulation results reveal significant improvement over the recent results.

  4. Global asymptotic stability of density dependent integral population projection models.

    Science.gov (United States)

    Rebarber, Richard; Tenhumberg, Brigitte; Townley, Stuart

    2012-02-01

    Many stage-structured density dependent populations with a continuum of stages can be naturally modeled using nonlinear integral projection models. In this paper, we study a trichotomy of global stability result for a class of density dependent systems which include a Platte thistle model. Specifically, we identify those systems parameters for which zero is globally asymptotically stable, parameters for which there is a positive asymptotically stable equilibrium, and parameters for which there is no asymptotically stable equilibrium. Copyright © 2011 Elsevier Inc. All rights reserved.

  5. Global stability of an SEIR epidemic model with constant immigration

    Energy Technology Data Exchange (ETDEWEB)

    Li Guihua [Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), Faculty of Life Science, Southwest China Normal University, Chongqing 400715 (China) and Department of Mathematics, Southwest China Normal University, Chongqing 400715 (China) and Department of Mathematics, North University of China, Taiyuan Shanxi 030051 (China)]. E-mail: liguihua@nuc.edu.cn; Wang Wendi [Department of Mathematics, Southwest China Normal University, Chongqing 400715 (China); Jin Zhen [Department of Mathematics, North University of China, Taiyuan Shanxi 030051 (China)

    2006-11-15

    An SEIR epidemic model with the infectious force in the latent (exposed), infected and recovered period is studied. It is assumed that susceptible and exposed individuals have constant immigration rates. The model exhibits a unique endemic state if the fraction p of infectious immigrants is positive. If the basic reproduction number R is greater than 1, sufficient conditions for the global stability of the endemic equilibrium are obtained by the compound matrix theory.

  6. Global stability of an SEIR epidemic model with constant immigration

    International Nuclear Information System (INIS)

    Li Guihua; Wang Wendi; Jin Zhen

    2006-01-01

    An SEIR epidemic model with the infectious force in the latent (exposed), infected and recovered period is studied. It is assumed that susceptible and exposed individuals have constant immigration rates. The model exhibits a unique endemic state if the fraction p of infectious immigrants is positive. If the basic reproduction number R is greater than 1, sufficient conditions for the global stability of the endemic equilibrium are obtained by the compound matrix theory

  7. Global stability of two models with incomplete treatment for tuberculosis

    International Nuclear Information System (INIS)

    Yang Yali; Li Jianquan; Ma Zhien; Liu Luju

    2010-01-01

    Research highlights: → Two tuberculosis models with incomplete treatment. → Intuitive epidemiological interpretations for the basic reproduction numbers. → Global dynamics of the two models. → Strategies to control the spread of tuberculosis. - Abstract: Two tuberculosis (TB) models with incomplete treatment are investigated. It is assumed that the treated individuals may enter either the latent compartment due to the remainder of Mycobacterium tuberculosis or the infectious compartment due to the treatment failure. The first model is a simple one with treatment failure reflecting the current TB treatment fact in most countries with high tuberculosis incidence. The second model refines the simple one by dividing the latent compartment into slow and fast two kinds of progresses. This improvement can be used to describe the case that the latent TB individuals have been infected with some other chronic diseases (such as HIV and diabetes) which may weaken the immunity of infected individuals and shorten the latent period of TB. Both of the two models assume mass action incidence and exponential distributions of transfers between different compartments. The basic reproduction numbers of the two models are derived and their intuitive epidemiological interpretations are given. The global dynamics of two models are all proved by using Liapunov functions. At last, some strategies to control the spread of tuberculosis are discussed.

  8. Exploring the temporal stability of global road safety statistics.

    Science.gov (United States)

    Dimitriou, Loukas; Nikolaou, Paraskevas; Antoniou, Constantinos

    2018-02-08

    Given the importance of rigorous quantitative reasoning in supporting national, regional or global road safety policies, data quality, reliability, and stability are of the upmost importance. This study focuses on macroscopic properties of road safety statistics and the temporal stability of these statistics at a global level. A thorough investigation of two years of measurements was conducted to identify any unexpected gaps that could highlight the existence of inconsistent measurements. The database used in this research includes 121 member countries of the United Nation (UN-121) with a population of at least one million (smaller country data shows higher instability) and includes road safety and socioeconomic variables collected from a number of international databases (e.g. WHO and World Bank) for the years 2010 and 2013. For the fulfillment of the earlier stated goal, a number of data visualization and exploratory analyses (Hierarchical Clustering and Principal Component Analysis) were conducted. Furthermore, in order to provide a richer analysis of the data, we developed and compared the specification of a number of Structural Equation Models for the years 2010 and 2013. Different scenarios have been developed, with different endogenous variables (indicators of mortality rate and fatality risk) and structural forms. The findings of the current research indicate inconsistency phenomena in global statistics of different instances/years. Finally, the results of this research provide evidence on the importance of careful and systematic data collection for developing advanced statistical and econometric techniques and furthermore for developing road safety policies. Copyright © 2017 Elsevier Ltd. All rights reserved.

  9. GLOBAL STABILITY AND PERIODIC SOLUTION OF A VIRAL DYNAMIC MODEL

    Directory of Open Access Journals (Sweden)

    Erhan COŞKUN

    2009-02-01

    Full Text Available Abstract:In this paper, we consider the classical viral dynamic mathematical model. Global dynamics of the model is rigorously established. We prove that, if the basic reproduction number, the HIV infection is cleared from the T-cell population; if , the HIV infection persists. For an open set of parameter values, the chronic-infection equilibrium can be unstable and periodic solutions may exist. We establish parameter regions for which is globally stable. Keywords: Global stability, HIV infection; CD4+ T cells; Periodic solution Mathematics Subject Classifications (2000: 65L10, 34B05 BİR VİRAL DİNAMİK MODELİN GLOBAL KARARLILIĞI VE PERİYODİK ÇÖZÜMÜ Özet: Bu makalede klasik viral dinamik modeli ele aldık. Modelin global dinamikleri oluşturuldu. Eğer temel üretim sayısı olur ise HIV enfeksiyonu T hücre nüfusundan çıkartılır, eğer olursa HIV enfeksiyonu çıkartılamaz. Parametre değerlerinin açık bir kümesi için kronik enfeksiyon dengesi kararsızdır ve periyodik çözüm oluşabilir. ın global kararlı olduğu parametre bölgeleri oluşturuldu. Anahtar Kelimeler: Global Kararlılık, HIV enfeksiyon, CD4+ T hücreler, Periyodik çözüm

  10. An exponential distribution

    International Nuclear Information System (INIS)

    Anon

    2009-01-01

    In this presentation author deals with the probabilistic evaluation of product life on the example of the exponential distribution. The exponential distribution is special one-parametric case of the weibull distribution.

  11. Stability analysis of impulsive parabolic complex networks

    Energy Technology Data Exchange (ETDEWEB)

    Wang Jinliang, E-mail: wangjinliang1984@yahoo.com.cn [Science and Technology on Aircraft Control Laboratory, School of Automation Science and Electrical Engineering, Beihang University, XueYuan Road, No. 37, HaiDian District, Beijing 100191 (China); Wu Huaining [Science and Technology on Aircraft Control Laboratory, School of Automation Science and Electrical Engineering, Beihang University, XueYuan Road, No. 37, HaiDian District, Beijing 100191 (China)

    2011-11-15

    Highlights: > Two impulsive parabolic complex network models are proposed. > The global exponential stability of impulsive parabolic complex networks are considered. > The robust global exponential stability of impulsive parabolic complex networks are considered. - Abstract: In the present paper, two kinds of impulsive parabolic complex networks (IPCNs) are considered. In the first one, all nodes have the same time-varying delay. In the second one, different nodes have different time-varying delays. Using the Lyapunov functional method combined with the inequality techniques, some global exponential stability criteria are derived for the IPCNs. Furthermore, several robust global exponential stability conditions are proposed to take uncertainties in the parameters of the IPCNs into account. Finally, numerical simulations are presented to illustrate the effectiveness of the results obtained here.

  12. Stability analysis of impulsive parabolic complex networks

    International Nuclear Information System (INIS)

    Wang Jinliang; Wu Huaining

    2011-01-01

    Highlights: → Two impulsive parabolic complex network models are proposed. → The global exponential stability of impulsive parabolic complex networks are considered. → The robust global exponential stability of impulsive parabolic complex networks are considered. - Abstract: In the present paper, two kinds of impulsive parabolic complex networks (IPCNs) are considered. In the first one, all nodes have the same time-varying delay. In the second one, different nodes have different time-varying delays. Using the Lyapunov functional method combined with the inequality techniques, some global exponential stability criteria are derived for the IPCNs. Furthermore, several robust global exponential stability conditions are proposed to take uncertainties in the parameters of the IPCNs into account. Finally, numerical simulations are presented to illustrate the effectiveness of the results obtained here.

  13. Exponential synchronization of complex networks with nonidentical time-delayed dynamical nodes

    International Nuclear Information System (INIS)

    Cai Shuiming; He Qinbin; Hao Junjun; Liu Zengrong

    2010-01-01

    In this Letter, exponential synchronization of a complex network with nonidentical time-delayed dynamical nodes is considered. Two effective control schemes are proposed to drive the network to synchronize globally exponentially onto any smooth goal dynamics. By applying open-loop control to all nodes and adding some intermittent controllers to partial nodes, some simple criteria for exponential synchronization of such network are established. Meanwhile, a pinning scheme deciding which nodes need to be pinned and a simply approximate formula for estimating the least number of pinned nodes are also provided. By introducing impulsive effects to the open-loop controlled network, another synchronization scheme is developed for the network with nonidentical time-delayed dynamical nodes, and an estimate of the upper bound of impulsive intervals ensuring global exponential stability of the synchronization process is also given. Numerical simulations are presented finally to demonstrate the effectiveness of the theoretical results.

  14. Impacts of GNSS position offsets on global frame stability

    Science.gov (United States)

    Griffiths, Jake; Ray, Jim

    2014-05-01

    Positional offsets appear in Global Navigation Satellite System (GNSS) time series for a variety of reasons. Antenna or radome changes are the most common cause for these discontinuities. Many others are from earthquakes, receiver changes, and different anthropogenic modifications at or near the stations. Some jumps appear for unknown or undocumented reasons. The accurate determination of station velocities, and therefore geophysical parameters and terrestrial reference frames, requires that positional offsets be correctly found and compensated. Williams (2003) found that undetected offsets introduce a random walk error component in individual station time series. The topic of detecting positional offsets has received considerable attention in recent years (e.g., Detection of Offsets in GPS Experiment; DOGEx), and most research groups using GNSS have adopted a combination of manual and automated methods for finding them. The removal of a positional offset is usually handled by estimating the average station position on both sides of the discontinuity, assuming a constant, continuous velocity. This is sufficient in the absence of time-correlated errors. However, GNSS time series contain systematic and power-law errors (white to random walk noise). In this paper, we aim to evaluate the impact to both individual station results and the overall stability of the global reference frame from adding increasing numbers of positional discontinuities. We use the International GNSS Service (IGS) weekly SINEX files, and iteratively insert positional offset parameters at the midpoint of each data segment. Each iteration includes a restacking of the modified SINEX files using the CATREF software from Institut National de l'Information Géographique et Forestière (IGN) to estimate: regularized station positions, secular velocities, Earth orientation parameters, Helmert frame alignment parameters, and the empirical shifts across all positional discontinuities. A comparison of the

  15. Stability analysis of stochastic delayed cellular neural networks by LMI approach

    International Nuclear Information System (INIS)

    Zhu Wenli; Hu Jin

    2006-01-01

    Some sufficient mean square exponential stability conditions for a class of stochastic DCNN model are obtained via the LMI approach. These conditions improve and generalize some existing global asymptotic stability conditions for DCNN model

  16. Extended Poisson Exponential Distribution

    Directory of Open Access Journals (Sweden)

    Anum Fatima

    2015-09-01

    Full Text Available A new mixture of Modified Exponential (ME and Poisson distribution has been introduced in this paper. Taking the Maximum of Modified Exponential random variable when the sample size follows a zero truncated Poisson distribution we have derived the new distribution, named as Extended Poisson Exponential distribution. This distribution possesses increasing and decreasing failure rates. The Poisson-Exponential, Modified Exponential and Exponential distributions are special cases of this distribution. We have also investigated some mathematical properties of the distribution along with Information entropies and Order statistics of the distribution. The estimation of parameters has been obtained using the Maximum Likelihood Estimation procedure. Finally we have illustrated a real data application of our distribution.

  17. Dynamics of exponential maps

    OpenAIRE

    Rempe, Lasse

    2003-01-01

    This thesis contains several new results about the dynamics of exponential maps $z\\mapsto \\exp(z)+\\kappa$. In particular, we prove that periodic external rays of exponential maps with nonescaping singular value always land. This is an analog of a theorem of Douady and Hubbard for polynomials. We also answer a question of Herman, Baker and Rippon by showing that the boundary of an unbounded exponential Siegel disk always contains the singular value. In addition to the presentation of new resul...

  18. A new criterion for global robust stability of interval neural networks with discrete time delays

    International Nuclear Information System (INIS)

    Li Chuandong; Chen Jinyu; Huang Tingwen

    2007-01-01

    This paper further studies global robust stability of a class of interval neural networks with discrete time delays. By introducing an equivalent transformation of interval matrices, a new criterion on global robust stability is established. In comparison with the results reported in the literature, the proposed approach leads to results with less restrictive conditions. Numerical examples are also worked through to illustrate our results

  19. Bayesian Exponential Smoothing.

    OpenAIRE

    Forbes, C.S.; Snyder, R.D.; Shami, R.S.

    2000-01-01

    In this paper, a Bayesian version of the exponential smoothing method of forecasting is proposed. The approach is based on a state space model containing only a single source of error for each time interval. This model allows us to improve current practices surrounding exponential smoothing by providing both point predictions and measures of the uncertainty surrounding them.

  20. Accelerating cosmologies from exponential potentials

    International Nuclear Information System (INIS)

    Neupane, Ishwaree P.

    2003-11-01

    It is learnt that exponential potentials of the form V ∼ exp(-2cφ/M p ) arising from the hyperbolic or flux compactification of higher-dimensional theories are of interest for getting short periods of accelerated cosmological expansions. Using a similar potential but derived for the combined case of hyperbolic-flux compactification, we study a four-dimensional flat (or open) FRW cosmologies and give analytic (and numerical) solutions with exponential behavior of scale factors. We show that, for the M-theory motivated potentials, the cosmic acceleration of the universe can be eternal if the spatial curvature of the 4d spacetime is negative, while the acceleration is only transient for a spatially flat universe. We also briefly discuss about the mass of massive Kaluza-Klein modes and the dynamical stabilization of the compact hyperbolic extra dimensions. (author)

  1. Topics in stability and transport in tokamaks: Dynamic transition to second stability with auxiliary heating; stability of global Alfven waves in an ignited plasma

    International Nuclear Information System (INIS)

    Fu, G.

    1988-01-01

    The problem of access to the high-beta ballooning second-stability regime by means of auxiliary heating and the problem of the stability of global-shear Alfven waves in an ignited tokamak plasma are theoretically investigated. These two problems are related to the confinement of both the bulk plasma as well as the fusion-product alpha particles an dare fundamentally important to the operation of ignited tokamak plasma. First, a model that incorporates both transport and ballooning mode stability was developed in order to estimate the auxiliary heating power required for tokamak plasma to evolve in time self-consistently into a high-beta, globally self-stabilized equilibrium. The critical heating power needed for access to second stability is found to be proportional to the square root of the anomalous diffusivity induced by the ballooning instability. Next, the full effects of toroidicity are retained in a theoretical description of global-type-shear Alfven modes whose stability can be modified by the fusion-product alpha particles that will present in an ignited tokamak plasma. Toroidicity is found to induce mode coupling and to stabilize the so-called Global Alfven Eigenmodes (GAE)

  2. Exponential Cardassian universe

    International Nuclear Information System (INIS)

    Liu Daojun; Sun Changbo; Li Xinzhou

    2006-01-01

    The expectation of explaining cosmological observations without requiring new energy sources is forsooth worthy of investigation. In this Letter, a new kind of Cardassian models, called exponential Cardassian models, for the late-time universe are investigated in the context of the spatially flat FRW universe scenario. We fit the exponential Cardassian models to current type Ia supernovae data and find they are consistent with the observations. Furthermore, we point out that the equation-of-state parameter for the effective dark fluid component in exponential Cardassian models can naturally cross the cosmological constant divide w=-1 that observations favor mildly without introducing exotic material that destroy the weak energy condition

  3. THE ROLE OF THE INTERNATIONAL MONETARY FUND IN PROMOTING GLOBAL ECONOMIC STABILITY

    Directory of Open Access Journals (Sweden)

    Alina HAGIU

    2017-12-01

    Full Text Available This paper presents the role that the International Monetary Fund performs in promoting global economic stability. Global economic and financial stability plays a key role in the financial system and the economy as a whole. The increase in the importance of the concept of financial stability by supervisors at both European and global level was concretized by defining a framework for the operationalization of macroprudential policy, together with the establishment of coordination bodies in this field, thus recognizing its role in the mix of established economic policies such as monetary, fiscal or competitive policy.

  4. Local and global stability for Lotka-Volterra systems with distributed delays and instantaneous negative feedbacks

    Science.gov (United States)

    Faria, Teresa; Oliveira, José J.

    This paper addresses the local and global stability of n-dimensional Lotka-Volterra systems with distributed delays and instantaneous negative feedbacks. Necessary and sufficient conditions for local stability independent of the choice of the delay functions are given, by imposing a weak nondelayed diagonal dominance which cancels the delayed competition effect. The global asymptotic stability of positive equilibria is established under conditions slightly stronger than the ones required for the linear stability. For the case of monotone interactions, however, sharper conditions are presented. This paper generalizes known results for discrete delays to systems with distributed delays. Several applications illustrate the results.

  5. An Unusual Exponential Graph

    Science.gov (United States)

    Syed, M. Qasim; Lovatt, Ian

    2014-01-01

    This paper is an addition to the series of papers on the exponential function begun by Albert Bartlett. In particular, we ask how the graph of the exponential function y = e[superscript -t/t] would appear if y were plotted versus ln t rather than the normal practice of plotting ln y versus t. In answering this question, we find a new way to…

  6. Exponential and Logarithmic Functions

    OpenAIRE

    Todorova, Tamara

    2010-01-01

    Exponential functions find applications in economics in relation to growth and economic dynamics. In these fields, quite often the choice variable is time and economists are trying to determine the best timing for certain economic activities to take place. An exponential function is one in which the independent variable appears in the exponent. Very often that exponent is time. In highly mathematical courses, it is a truism that students learn by doing, not by reading. Tamara Todorova’s Pr...

  7. Global Stability for a Binge Drinking Model with Two Stages

    Directory of Open Access Journals (Sweden)

    Hai-Feng Huo

    2012-01-01

    are determined by the basic reproduction number, R0. The alcohol-free equilibrium is globally asymptotically stable, and the alcohol problems are eliminated from the population if R01. Numerical simulations are also conducted in the analytic results.

  8. Globally Asymptotic Stability of Stochastic Nonlinear Systems by the Output Feedback

    Directory of Open Access Journals (Sweden)

    Wenwen Cheng

    2015-01-01

    the traditional mathematical induction method. Indeed, we develop a new method to study the globally asymptotic stability by introducing a series of specific inequalities. Moreover, an example and its simulations are given to illustrate the theoretical result.

  9. Global stability analysis of epidemiological models based on Volterra–Lyapunov stable matrices

    International Nuclear Information System (INIS)

    Liao Shu; Wang Jin

    2012-01-01

    Highlights: ► Global dynamics of high dimensional dynamical systems. ► A systematic approach for global stability analysis. ► Epidemiological models of environment-dependent diseases. - Abstract: In this paper, we study the global dynamics of a class of mathematical epidemiological models formulated by systems of differential equations. These models involve both human population and environmental component(s) and constitute high-dimensional nonlinear autonomous systems, for which the global asymptotic stability of the endemic equilibria has been a major challenge in analyzing the dynamics. By incorporating the theory of Volterra–Lyapunov stable matrices into the classical method of Lyapunov functions, we present an approach for global stability analysis and obtain new results on some three- and four-dimensional model systems. In addition, we conduct numerical simulation to verify the analytical results.

  10. An analysis of global robust stability of uncertain cellular neural networks with discrete and distributed delays

    International Nuclear Information System (INIS)

    Park, Ju H.

    2007-01-01

    This paper considers the robust stability analysis of cellular neural networks with discrete and distributed delays. Based on the Lyapunov stability theory and linear matrix inequality (LMI) technique, a novel stability criterion guaranteeing the global robust convergence of the equilibrium point is derived. The criterion can be solved easily by various convex optimization algorithms. An example is given to illustrate the usefulness of our results

  11. Bifurcation analysis of the simplified models of boiling water reactor and identification of global stability boundary

    Energy Technology Data Exchange (ETDEWEB)

    Pandey, Vikas; Singh, Suneet, E-mail: suneet.singh@iitb.ac.in

    2017-04-15

    Highlights: • Non-linear stability analysis of nuclear reactor is carried out. • Global and local stability boundaries are drawn in the parameter space. • Globally stable, bi-stable, and unstable regions have been demarcated. • The identification of the regions is verified by numerical simulations. - Abstract: Nonlinear stability study of the neutron coupled thermal hydraulics instability has been carried out by several researchers for boiling water reactors (BWRs). The focus of these studies has been to identify subcritical and supercritical Hopf bifurcations. Supercritical Hopf bifurcation are soft or safe due to the fact that stable limit cycles arise in linearly unstable region; linear and global stability boundaries are same for this bifurcation. It is well known that the subcritical bifurcations can be considered as hard or dangerous due to the fact that unstable limit cycles (nonlinear phenomena) exist in the (linearly) stable region. The linear stability leads to a stable equilibrium in such regions, only for infinitesimally small perturbations. However, finite perturbations lead to instability due to the presence of unstable limit cycles. Therefore, it is evident that the linear stability analysis is not sufficient to understand the exact stability characteristics of BWRs. However, the effect of these bifurcations on the stability boundaries has been rarely discussed. In the present work, the identification of global stability boundary is demonstrated using simplified models. Here, five different models with different thermal hydraulics feedback have been investigated. In comparison to the earlier works, current models also include the impact of adding the rate of change in temperature on void reactivity as well as effect of void reactivity on rate of change of temperature. Using the bifurcation analysis of these models the globally stable region in the parameter space has been identified. The globally stable region has only stable solutions and

  12. Bifurcation analysis of the simplified models of boiling water reactor and identification of global stability boundary

    International Nuclear Information System (INIS)

    Pandey, Vikas; Singh, Suneet

    2017-01-01

    Highlights: • Non-linear stability analysis of nuclear reactor is carried out. • Global and local stability boundaries are drawn in the parameter space. • Globally stable, bi-stable, and unstable regions have been demarcated. • The identification of the regions is verified by numerical simulations. - Abstract: Nonlinear stability study of the neutron coupled thermal hydraulics instability has been carried out by several researchers for boiling water reactors (BWRs). The focus of these studies has been to identify subcritical and supercritical Hopf bifurcations. Supercritical Hopf bifurcation are soft or safe due to the fact that stable limit cycles arise in linearly unstable region; linear and global stability boundaries are same for this bifurcation. It is well known that the subcritical bifurcations can be considered as hard or dangerous due to the fact that unstable limit cycles (nonlinear phenomena) exist in the (linearly) stable region. The linear stability leads to a stable equilibrium in such regions, only for infinitesimally small perturbations. However, finite perturbations lead to instability due to the presence of unstable limit cycles. Therefore, it is evident that the linear stability analysis is not sufficient to understand the exact stability characteristics of BWRs. However, the effect of these bifurcations on the stability boundaries has been rarely discussed. In the present work, the identification of global stability boundary is demonstrated using simplified models. Here, five different models with different thermal hydraulics feedback have been investigated. In comparison to the earlier works, current models also include the impact of adding the rate of change in temperature on void reactivity as well as effect of void reactivity on rate of change of temperature. Using the bifurcation analysis of these models the globally stable region in the parameter space has been identified. The globally stable region has only stable solutions and

  13. Lyapunov functions and global stability for SIR and SEIR models with age-dependent susceptibility

    KAUST Repository

    Korobeinikov, Andrei; Melnik, Andrey V.

    2013-01-01

    We consider global asymptotic properties for the SIR and SEIR age structured models for infectious diseases where the susceptibility depends on the age. Using the direct Lyapunov method with Volterra type Lyapunov functions, we establish conditions for the global stability of a unique endemic steady state and the infection-free steady state.

  14. Global Stability in Dynamical Systems with Multiple Feedback Mechanisms

    DEFF Research Database (Denmark)

    Andersen, Morten; Vinther, Frank; Ottesen, Johnny T.

    2016-01-01

    A class of n-dimensional ODEs with up to n feedbacks from the n’th variable is analysed. The feedbacks are represented by non-specific, bounded, non-negative C1 functions. The main result is the formulation and proof of an easily applicable criterion for existence of a globally stable fixed point...

  15. Consideration on the price stability – financial stability relationship in the context of financial globalization

    Directory of Open Access Journals (Sweden)

    Marius Apostoaie

    2010-12-01

    Full Text Available This study is focused upon the involvement of the central banks regarding the fulfillment of the two main objectives: price  stability and financial stability. These two key concepts are part of an old and ongoing debate that the current turmoil has revived, and that is whether monetary policy should aim, or not, at ensuring financial stability in parallel to its main objective of price stability. On both sides there are solid and well known arguments. In the beginning of the study I have  considered a literature review with regard to price and financial stability issues. After that I have tried to shed some light (from a theoretical point of view on the nature and dynamics of the fundamental interlinkages between the two aspects and there implications on the central banks and the economy. Finally I outline some general conclusions that have emerged in the present study.

  16. Towards a rational theory for CFD global stability

    International Nuclear Information System (INIS)

    Baker, A.J.; Iannelli, G.S.

    1989-01-01

    The fundamental notion of the consistent stability of semidiscrete analogues of evolution PDEs is explored. Lyapunov's direct method is used to develop CFD semidiscrete algorithms which yield the TVD constraint as a special case. A general formula for supplying dissipation parameters for arbitrary multidimensional conservation law systems is proposed. The reliability of the method is demonstrated by the results of two numerical tests for representative Euler shocked flows. 18 refs

  17. Fast quantum modular exponentiation

    International Nuclear Information System (INIS)

    Meter, Rodney van; Itoh, Kohei M.

    2005-01-01

    We present a detailed analysis of the impact on quantum modular exponentiation of architectural features and possible concurrent gate execution. Various arithmetic algorithms are evaluated for execution time, potential concurrency, and space trade-offs. We find that to exponentiate an n-bit number, for storage space 100n (20 times the minimum 5n), we can execute modular exponentiation 200-700 times faster than optimized versions of the basic algorithms, depending on architecture, for n=128. Addition on a neighbor-only architecture is limited to O(n) time, whereas non-neighbor architectures can reach O(log n), demonstrating that physical characteristics of a computing device have an important impact on both real-world running time and asymptotic behavior. Our results will help guide experimental implementations of quantum algorithms and devices

  18. Global marginal stability of TAEs in the presence of fast ions

    International Nuclear Information System (INIS)

    Villard, L.; Brunner, S.; Vaclavik, J.

    1994-09-01

    The global stability of toroidicity-induced Alfven eigenmodes (TAEs) in the presence of fast ions in realistic tokamak fusion-grade plasmas is analyzed with a global, perturbative approach. Volume averaged fast particle betas for marginal stability are obtained and analyzed for a wide range of plasma parameters such as the fast ion radial density profile width, the ratio of birth velocity to the Alfven velocity on axis and the bulk plasma beta. The different stability behaviour of two types of TAEs ('internal' or 'external') is evidenced. (author) 19 figs., 22 refs

  19. Continuous multivariate exponential extension

    International Nuclear Information System (INIS)

    Block, H.W.

    1975-01-01

    The Freund-Weinman multivariate exponential extension is generalized to the case of nonidentically distributed marginal distributions. A fatal shock model is given for the resulting distribution. Results in the bivariate case and the concept of constant multivariate hazard rate lead to a continuous distribution related to the multivariate exponential distribution (MVE) of Marshall and Olkin. This distribution is shown to be a special case of the extended Freund-Weinman distribution. A generalization of the bivariate model of Proschan and Sullo leads to a distribution which contains both the extended Freund-Weinman distribution and the MVE

  20. L2-stability of the Vlasov-Maxwell-Boltzmann system near global Maxwellians

    International Nuclear Information System (INIS)

    Ha, Seung-Yeal; Xiao, Qinghua; Xiong, Linjie; Zhao, Huijiang

    2013-01-01

    We present a L 2 -stability theory of the Vlasov-Maxwell-Boltzmann system for the two-species collisional plasma. We show that in a perturbative regime of a global Maxwellian, the L 2 -distance between two strong solutions can be controlled by that between initial data in a Lipschitz manner. Our stability result extends earlier results [Ha, S.-Y. and Xiao, Q.-H., “A revisiting to the L 2 -stability theory of the Boltzmann equation near global Maxwellians,” (submitted) and Ha, S.-Y., Yang, X.-F., and Yun, S.-B., “L 2 stability theory of the Boltzmann equation near a global Maxwellian,” Arch. Ration. Mech. Anal. 197, 657–688 (2010)] on the L 2 -stability of the Boltzmann equation to the Boltzmann equation coupled with self-consistent external forces. As a direct application of our stability result, we show that classical solutions in Duan et al. [“Optimal large-time behavior of the Vlasov-Maxwell-Boltzmann system in the whole space,” Commun. Pure Appl. Math. 24, 1497–1546 (2011)] and Guo [“The Vlasov-Maxwell-Boltzmann system near Maxwellians,” Invent. Math. 153(3), 593–630 (2003)] satisfy a uniform L 2 -stability estimate. This is the first result on the L 2 -stability of the Boltzmann equation coupled with self-consistent field equations in three dimensions

  1. Study of global stability of tall buildings with prestressed slabs

    Directory of Open Access Journals (Sweden)

    L. A. Feitosa

    Full Text Available The use of prestressed concrete flat slabs in buildings has been increasing in recent years in the Brazilian market. Since the implementation of tall and slender buildings a trend in civil engineering and architecture fields, arises from the use of prestressed slabs a difficulty in ensuring the overall stability of a building without beams. In order to evaluate the efficiency of the main bracing systems used in this type of building, namely pillars in formed "U" in elevator shafts and stairs, and pillars in which the lengths are significantly larger than their widths, was elaborated a computational models of fictional buildings, which were processed and analyzed using the software CAD/TQS. From the variation of parameters such as: geometry of the pillars, thick slabs, characteristic strength of the concrete, reduceofthe coefficient of inertia for consideration of non-linearities of the physical elements, stiffness of the connections between slabs and pillars, among others, to analyze the influence of these variables on the overall stability of the building from the facing of instability parameter Gama Z, under Brazilian standard NBR 6118, in addition to performing the processing of building using the P-Delta iterative calculation method for the same purpose.

  2. Global Stability of an Epidemic Model of Computer Virus

    Directory of Open Access Journals (Sweden)

    Xiaofan Yang

    2014-01-01

    Full Text Available With the rapid popularization of the Internet, computers can enter or leave the Internet increasingly frequently. In fact, no antivirus software can detect and remove all sorts of computer viruses. This implies that viruses would persist on the Internet. To better understand the spread of computer viruses in these situations, a new propagation model is established and analyzed. The unique equilibrium of the model is globally asymptotically stable, in accordance with the reality. A parameter analysis of the equilibrium is also conducted.

  3. Global stability of a vaccination model with immigration

    Directory of Open Access Journals (Sweden)

    Sarah Henshaw

    2015-04-01

    Full Text Available We study an SVIR model of disease transmission with immigration into all four classes. Vaccinated individuals may only receive partial immunity to the disease, giving a leaky vaccine. The incidence function permits a nonlinear response to the number of infectives, so that mass action and saturating incidence are included as special cases. Because of the immigration of infected individuals, there is no disease-free equilibrium and hence no basic reproduction number. We use the Brouwer Fixed Point Theorem to show that an endemic equilibrium exists and the Poincare-Hopf Theorem to show that it is unique. We show the equilibrium is globally asymptotically stable by using a Lyapunov function.

  4. Global physical and numerical stability of a nuclear reactor core

    International Nuclear Information System (INIS)

    Morales-Sandoval, Jaime; Hernandez-Solis, Augusto

    2005-01-01

    Low order models are used to investigate the influence of integration methods on observed power oscillations of some nuclear reactor simulators. The zero-power point reactor kinetics with six-delayed neutron precursor groups are time discretized using explicit, implicit and Crank-Nicholson methods, and the stability limit of the time mesh spacing is exactly obtained by locating their characteristic poles in the z-transform plane. These poles are the s to z mappings of the inhour equation roots and, except for one of them, they show little or no dependence on the integration method. Conditions for stable power oscillations can be also obtained by tracking when steady state output signals resulting from reactivity oscillations in the s-Laplace plane cross the imaginary axis. The dynamics of a BWR core operating at power conditions is represented by a reduced order model obtained by adding three ordinary differential equations, which can model void and Doppler reactivity feedback effects on power, and collapsing all delayed neutron precursors in one group. Void dynamics are modeled as a second order system and fuel heat transfer as a first order system. This model shows rich characteristics in terms of indicating the relative importance of different core parameters and conditions on both numerical and physical oscillations observed by large computer code simulations. A brief discussion of the influence of actual core and coolant conditions on the reduced order model is presented

  5. Global stability of a susceptible-infected-susceptible epidemic model on networks with individual awareness

    International Nuclear Information System (INIS)

    Li Ke-Zan; Xu Zhong-Pu; Zhu Guang-Hu; Ding Yong

    2014-01-01

    Recent research results indicate that individual awareness can play an important influence on epidemic spreading in networks. By local stability analysis, a significant conclusion is that the embedded awareness in an epidemic network can increase its epidemic threshold. In this paper, by using limit theory and dynamical system theory, we further give global stability analysis of a susceptible-infected-susceptible (SIS) epidemic model on networks with awareness. Results show that the obtained epidemic threshold is also a global stability condition for its endemic equilibrium, which implies the embedded awareness can enhance the epidemic threshold globally. Some numerical examples are presented to verify the theoretical results. (interdisciplinary physics and related areas of science and technology)

  6. Global robust stability of neural networks with multiple discrete delays and distributed delays

    International Nuclear Information System (INIS)

    Gao Ming; Cui Baotong

    2009-01-01

    The problem of global robust stability is investigated for a class of uncertain neural networks with both multiple discrete time-varying delays and distributed time-varying delays. The uncertainties are assumed to be of norm-bounded form and the activation functions are supposed to be bounded and globally Lipschitz continuous. Based on the Lyapunov stability theory and linear matrix inequality technique, some robust stability conditions guaranteeing the global robust convergence of the equilibrium point are derived. The proposed LMI-based criteria are computationally efficient as they can be easily checked by using recently developed algorithms in solving LMIs. Two examples are given to show the effectiveness of the proposed results.

  7. Stability of global entanglement in thermal states of spin chains

    International Nuclear Information System (INIS)

    Brennen, Gavin K.; Bullock, Stephen S.

    2004-01-01

    We investigate the entanglement properties of a one-dimensional chain of qubits coupled via nearest-neighbor spin-spin interactions. The entanglement measure used is the n-concurrence, which is distinct from other measures on spin chains such as bipartite entanglement in that it can quantify 'global' entanglement across the spin chain. Specifically, it computes the overlap of a quantum state with its time-reversed state. As such, this measure is well suited to study ground states of spin-chain Hamiltonians that are intrinsically time-reversal-symmetric. We study the robustness of n-concurrence of ground states when the interaction is subject to a time-reversal antisymmetric magnetic field perturbation. The n-concurrence in the ground state of the isotropic XX model is computed and it is shown that there is a critical magnetic field strength at which the entanglement experiences a jump discontinuity from the maximum value to zero. The n-concurrence for thermal mixed states is derived and a threshold temperature is computed below which the system has nonzero entanglement

  8. Improved Offshore Wind Resource Assessment in Global Climate Stabilization Scenarios

    Energy Technology Data Exchange (ETDEWEB)

    Arent, D.; Sullivan, P.; Heimiller, D.; Lopez, A.; Eurek, K.; Badger, J.; Jorgensen, H. E.; Kelly, M.; Clarke, L.; Luckow, P.

    2012-10-01

    This paper introduces a technique for digesting geospatial wind-speed data into areally defined -- country-level, in this case -- wind resource supply curves. We combined gridded wind-vector data for ocean areas with bathymetry maps, country exclusive economic zones, wind turbine power curves, and other datasets and relevant parameters to build supply curves that estimate a country's offshore wind resource defined by resource quality, depth, and distance-from-shore. We include a single set of supply curves -- for a particular assumption set -- and study some implications of including it in a global energy model. We also discuss the importance of downscaling gridded wind vector data to capturing the full resource potential, especially over land areas with complex terrain. This paper includes motivation and background for a statistical downscaling methodology to account for terrain effects with a low computational burden. Finally, we use this forum to sketch a framework for building synthetic electric networks to estimate transmission accessibility of renewable resource sites in remote areas.

  9. Robust Stability Clearance of Flight Control Law Based on Global Sensitivity Analysis

    OpenAIRE

    Ou, Liuli; Liu, Lei; Dong, Shuai; Wang, Yongji

    2014-01-01

    To validate the robust stability of the flight control system of hypersonic flight vehicle, which suffers from a large number of parametrical uncertainties, a new clearance framework based on structural singular value ( $\\mu $ ) theory and global uncertainty sensitivity analysis (SA) is proposed. In this framework, SA serves as the preprocess of uncertain model to be analysed to help engineers to determine which uncertainties affect the stability of the closed loop system more slightly. By ig...

  10. On global stability criterion for neural networks with discrete and distributed delays

    International Nuclear Information System (INIS)

    Park, Ju H.

    2006-01-01

    Based on the Lyapunov functional stability analysis for differential equations and the linear matrix inequality (LMI) optimization approach, a new delay-dependent criterion for neural networks with discrete and distributed delays is derived to guarantee global asymptotic stability. The criterion is expressed in terms of LMIs, which can be solved easily by various convex optimization algorithms. Some numerical examples are given to show the effectiveness of proposed method

  11. Global robust asymptotical stability of multi-delayed interval neural networks: an LMI approach

    International Nuclear Information System (INIS)

    Li Chuandong; Liao Xiaofeng; Zhang Rong

    2004-01-01

    Based on the Lyapunov-Krasovskii stability theory for functional differential equations and the linear matrix inequality (LMI) technique, some delay-dependent criteria for interval neural networks (IDNN) with multiple time-varying delays are derived to guarantee global robust asymptotic stability. The main results are generalizations of some recent results reported in the literature. Numerical example is also given to show the effectiveness of our results

  12. Global robust stability of bidirectional associative memory neural networks with multiple time delays.

    Science.gov (United States)

    Senan, Sibel; Arik, Sabri

    2007-10-01

    This correspondence presents a sufficient condition for the existence, uniqueness, and global robust asymptotic stability of the equilibrium point for bidirectional associative memory neural networks with discrete time delays. The results impose constraint conditions on the network parameters of the neural system independently of the delay parameter, and they are applicable to all bounded continuous nonmonotonic neuron activation functions. Some numerical examples are given to compare our results with the previous robust stability results derived in the literature.

  13. Global asymptotic stability of Cohen-Grossberg neural networks with constant and variable delays

    International Nuclear Information System (INIS)

    Wu Wei; Cui Baotong; Huang Min

    2007-01-01

    Global asymptotic stability of Cohen-Grossberg neural networks with constant and variable delays is studied. Some sufficient conditions for the neural networks are proposed to guarantee the global asymptotic convergence by using different Lyapunov functionals. Our criteria represent an extension of the existing results in literatures. A comparison between our results and the previous results admits that our results establish a new set of stability criteria for delayed Cohen-Grossberg neural networks. Those conditions are less restrictive than those given in the earlier reference

  14. Global stabilization of linear continuous time-varying systems with bounded controls

    International Nuclear Information System (INIS)

    Phat, V.N.

    2004-08-01

    This paper deals with the problem of global stabilization of a class of linear continuous time-varying systems with bounded controls. Based on the controllability of the nominal system, a sufficient condition for the global stabilizability is proposed without solving any Riccati differential equation. Moreover, we give sufficient conditions for the robust stabilizability of perturbation/uncertain linear time-varying systems with bounded controls. (author)

  15. Global kink and ballooning modes in high-beta systems and stability of toroidal drift modes

    International Nuclear Information System (INIS)

    Galvao, R.M.O.; Goedbloed, J.P.; Rem, J.; Sakanaka, P.H.; Schep, T.J.; Venema, M.

    1983-01-01

    A numerical code (HBT) has been developed which solves for the equilibrium, global stability and high-n stability of plasmas with arbitrary cross-section. Various plasmas are analysed for their stability to these modes in the high-beta limit. Screw-pinch equilibria are stable to high-n ballooning modes up to betas of 18%. The eigenmode equation for drift waves is analysed numerically. The toroidal branch is shown to be destabilized by the non-adiabatic response of trapped and circulating particles. (author)

  16. An input-to-state stability approach to verify almost global stability of a synchronous-machine-infinite-bus system.

    Science.gov (United States)

    Schiffer, Johannes; Efimov, Denis; Ortega, Romeo; Barabanov, Nikita

    2017-08-13

    Conditions for almost global stability of an operating point of a realistic model of a synchronous generator with constant field current connected to an infinite bus are derived. The analysis is conducted by employing the recently proposed concept of input-to-state stability (ISS)-Leonov functions, which is an extension of the powerful cell structure principle developed by Leonov and Noldus to the ISS framework. Compared with the original ideas of Leonov and Noldus, the ISS-Leonov approach has the advantage of providing additional robustness guarantees. The efficiency of the derived sufficient conditions is illustrated via numerical experiments.This article is part of the themed issue 'Energy management: flexibility, risk and optimization'. © 2017 The Author(s).

  17. Global asymptotic stability of Cohen-Grossberg neural network with continuously distributed delays

    International Nuclear Information System (INIS)

    Wan Li; Sun Jianhua

    2005-01-01

    The convergence dynamical behaviors of Cohen-Grossberg neural network with continuously distributed delays are discussed. By using Brouwer's fixed point theorem, matrix theory and analysis techniques such as Gronwall inequality, some new sufficient conditions guaranteeing the existence, uniqueness of an equilibrium point and its global asymptotic stability are obtained. An example is given to illustrate the theoretical results

  18. Global stability of the coexistence equilibrium for a general class of models of facultative mutualism

    Czech Academy of Sciences Publication Activity Database

    Maxin, D.; Georgescu, P.; Sega, L.; Berec, Luděk

    2017-01-01

    Roč. 11, č. 1 (2017), s. 339-364 ISSN 1751-3758 Institutional support: RVO:60077344 Keywords : mutualistic interaction * global stability * Lyapunov functional Subject RIV: EH - Ecology, Behaviour OBOR OECD: Ecology Impact factor: 1.279, year: 2016

  19. Impulsive effects on global asymptotic stability of delay BAM neural networks

    International Nuclear Information System (INIS)

    Chen Jun; Cui Baotong

    2008-01-01

    Based on the proper Lyapunov functions and the Jacobsthal liner inequality, some sufficient conditions are presented in this paper for global asymptotic stability of delay bidirectional associative memory neural networks with impulses. The obtained results are independently of the delay parameters and can be easily verified. Also, some remarks and an illustrative example are given to demonstrate the effectiveness of the obtained results

  20. Regional Climate Impacts of Stabilizing Global Warming at 1.5 K Using Solar Geoengineering

    Science.gov (United States)

    Jones, Anthony C.; Hawcroft, Matthew K.; Haywood, James M.; Jones, Andy; Guo, Xiaoran; Moore, John C.

    2018-02-01

    The 2015 Paris Agreement aims to limit global warming to well below 2 K above preindustrial levels, and to pursue efforts to limit global warming to 1.5 K, in order to avert dangerous climate change. However, current greenhouse gas emissions targets are more compatible with scenarios exhibiting end-of-century global warming of 2.6-3.1 K, in clear contradiction to the 1.5 K target. In this study, we use a global climate model to investigate the climatic impacts of using solar geoengineering by stratospheric aerosol injection to stabilize global-mean temperature at 1.5 K for the duration of the 21st century against three scenarios spanning the range of plausible greenhouse gas mitigation pathways (RCP2.6, RCP4.5, and RCP8.5). In addition to stabilizing global mean temperature and offsetting both Arctic sea-ice loss and thermosteric sea-level rise, we find that solar geoengineering could effectively counteract enhancements to the frequency of extreme storms in the North Atlantic and heatwaves in Europe, but would be less effective at counteracting hydrological changes in the Amazon basin and North Atlantic storm track displacement. In summary, solar geoengineering may reduce global mean impacts but is an imperfect solution at the regional level, where the effects of climate change are experienced. Our results should galvanize research into the regionality of climate responses to solar geoengineering.

  1. Continuous exponential martingales and BMO

    CERN Document Server

    Kazamaki, Norihiko

    1994-01-01

    In three chapters on Exponential Martingales, BMO-martingales, and Exponential of BMO, this book explains in detail the beautiful properties of continuous exponential martingales that play an essential role in various questions concerning the absolute continuity of probability laws of stochastic processes. The second and principal aim is to provide a full report on the exciting results on BMO in the theory of exponential martingales. The reader is assumed to be familiar with the general theory of continuous martingales.

  2. Stability and change in political conservatism following the global financial crisis.

    Science.gov (United States)

    Milojev, Petar; Greaves, Lara; Osborne, Danny; Sibley, Chris G

    2015-01-01

    The current study analyzes data from a national probability panel sample of New Zealanders (N = 5,091) to examine stability and change in political orientation over four consecutive yearly assessments (2009-2012) following the 2007/2008 global financial crisis. Bayesian Latent Growth Modeling identified systematic variation in the growth trajectory of conservatism that was predicted by age and socio-economic status. Younger people (ages 25-45) did not change in their political orientation. Older people, however, became more conservative over time. Likewise, people with lower socio-economic status showed a marked increase in political conservatism. In addition, tests of rank-order stability showed that age had a cubic relationship with the stability of political orientation over our four annual assessments. Our findings provide strong support for System Justification Theory by showing that increases in conservatism in the wake of the recent global financial crisis occurred primarily among the poorest and most disadvantaged.

  3. Exponential smoothing weighted correlations

    Science.gov (United States)

    Pozzi, F.; Di Matteo, T.; Aste, T.

    2012-06-01

    In many practical applications, correlation matrices might be affected by the "curse of dimensionality" and by an excessive sensitiveness to outliers and remote observations. These shortcomings can cause problems of statistical robustness especially accentuated when a system of dynamic correlations over a running window is concerned. These drawbacks can be partially mitigated by assigning a structure of weights to observational events. In this paper, we discuss Pearson's ρ and Kendall's τ correlation matrices, weighted with an exponential smoothing, computed on moving windows using a data-set of daily returns for 300 NYSE highly capitalized companies in the period between 2001 and 2003. Criteria for jointly determining optimal weights together with the optimal length of the running window are proposed. We find that the exponential smoothing can provide more robust and reliable dynamic measures and we discuss that a careful choice of the parameters can reduce the autocorrelation of dynamic correlations whilst keeping significance and robustness of the measure. Weighted correlations are found to be smoother and recovering faster from market turbulence than their unweighted counterparts, helping also to discriminate more effectively genuine from spurious correlations.

  4. NL(q) Theory: A Neural Control Framework with Global Asymptotic Stability Criteria.

    Science.gov (United States)

    Vandewalle, Joos; De Moor, Bart L.R.; Suykens, Johan A.K.

    1997-06-01

    In this paper a framework for model-based neural control design is presented, consisting of nonlinear state space models and controllers, parametrized by multilayer feedforward neural networks. The models and closed-loop systems are transformed into so-called NL(q) system form. NL(q) systems represent a large class of nonlinear dynamical systems consisting of q layers with alternating linear and static nonlinear operators that satisfy a sector condition. For such NL(q)s sufficient conditions for global asymptotic stability, input/output stability (dissipativity with finite L(2)-gain) and robust stability and performance are presented. The stability criteria are expressed as linear matrix inequalities. In the analysis problem it is shown how stability of a given controller can be checked. In the synthesis problem two methods for neural control design are discussed. In the first method Narendra's dynamic backpropagation for tracking on a set of specific reference inputs is modified with an NL(q) stability constraint in order to ensure, e.g., closed-loop stability. In a second method control design is done without tracking on specific reference inputs, but based on the input/output stability criteria itself, within a standard plant framework as this is done, for example, in H( infinity ) control theory and &mgr; theory. Copyright 1997 Elsevier Science Ltd.

  5. Robustness and flexibility in compact quasiaxial stellarators: Global ideal MHD stability and energetic particle transport

    International Nuclear Information System (INIS)

    Redi, M.H.; Diallo, A.; Cooper, W.A.; Fu, G.Y.

    2000-01-01

    Concerns about the flexibility and robustness of a compact quasiaxial stellarator design are addressed by studying the effects of varied pressure and rotational transform profiles on expected performance. For thirty, related, fully three-dimensional configurations the global, ideal magnetohydrodynamic stability is evaluated as well as energetic particle transport. It is found that tokamak intuition is relevant to understanding the magnetohydrodynamic stability, with pressure gradient driving terms and shear stabilization controlling both the periodicity preserving, N=0, and the non-periodicity preserving, N=1, unstable kink modes. Global kink modes are generated by steeply peaked pressure profiles near the half radius and edge localized kink modes are found for plasmas with steep pressure profiles at the edge as well as with edge rotational transform above 0.5. Energetic particle transport is not strongly dependent on these changes of pressure and current (or rotational transform) profiles, although a weak inverse dependence on pressure peaking through the corresponding Shafranov shift is found. While good transport and MHD stability are not anticorrelated in these equilibria, stability only results from a delicate balance of the pressure and shear stabilization forces. A range of interesting MHD behaviors is found for this large set of equilibria, exhibiting similar particle transport properties

  6. Tracking performance and global stability guaranteed neural control of uncertain hypersonic flight vehicle

    Directory of Open Access Journals (Sweden)

    Tao Teng

    2016-02-01

    Full Text Available In this article, a global adaptive neural dynamic surface control with predefined tracking performance is developed for a class of hypersonic flight vehicles, whose accurate dynamics is hard to obtain. The control scheme developed in this paper overcomes the limitations of neural approximation region by employing a switching mechanism which incorporates an additional robust controller outside the neural approximation region to pull the transient state variables back when they overstep the neural approximation region, such that globally uniformly ultimately bounded stability can be guaranteed. Especially, the developed global adaptive neural control also improves the tracking performance by introducing an error transformation mechanism, such that both transient and steady-state performance can be shaped according to the predefined bounds. Simulation studies on the hypersonic flight vehicle validate that the designed controller has good velocity modulation and velocity stability performance.

  7. Estimating exponential scheduling preferences

    DEFF Research Database (Denmark)

    Hjorth, Katrine; Börjesson, Maria; Engelson, Leonid

    2015-01-01

    of car drivers' route and mode choice under uncertain travel times. Our analysis exposes some important methodological issues related to complex non-linear scheduling models: One issue is identifying the point in time where the marginal utility of being at the destination becomes larger than the marginal......Different assumptions about travelers' scheduling preferences yield different measures of the cost of travel time variability. Only few forms of scheduling preferences provide non-trivial measures which are additive over links in transport networks where link travel times are arbitrarily...... utility of being at the origin. Another issue is that models with the exponential marginal utility formulation suffer from empirical identification problems. Though our results are not decisive, they partly support the constant-affine specification, in which the value of travel time variability...

  8. Blowing-up semilinear wave equation with exponential nonlinearity ...

    Indian Academy of Sciences (India)

    H1-norm. Hence, it is legitimate to consider an exponential nonlinearity. Moreover, the choice of an exponential nonlinearity emerges from a possible control of solutions via a. Moser–Trudinger type inequality [1, 16, 19]. In fact, Nakamura and Ozawa [17] proved global well-posedness and scattering for small Cauchy data in ...

  9. Global stability of stochastic high-order neural networks with discrete and distributed delays

    International Nuclear Information System (INIS)

    Wang Zidong; Fang Jianan; Liu Xiaohui

    2008-01-01

    High-order neural networks can be considered as an expansion of Hopfield neural networks, and have stronger approximation property, faster convergence rate, greater storage capacity, and higher fault tolerance than lower-order neural networks. In this paper, the global asymptotic stability analysis problem is considered for a class of stochastic high-order neural networks with discrete and distributed time-delays. Based on an Lyapunov-Krasovskii functional and the stochastic stability analysis theory, several sufficient conditions are derived, which guarantee the global asymptotic convergence of the equilibrium point in the mean square. It is shown that the stochastic high-order delayed neural networks under consideration are globally asymptotically stable in the mean square if two linear matrix inequalities (LMIs) are feasible, where the feasibility of LMIs can be readily checked by the Matlab LMI toolbox. It is also shown that the main results in this paper cover some recently published works. A numerical example is given to demonstrate the usefulness of the proposed global stability criteria

  10. Exponentially asymptotical synchronization in uncertain complex dynamical networks with time delay

    Energy Technology Data Exchange (ETDEWEB)

    Luo Qun; Yang Han; Li Lixiang; Yang Yixian [Information Security Center, State Key Laboratory of Networking and Switching Technology, Beijing University of Posts and Telecommunications, Beijing 100876 (China); Han Jiangxue, E-mail: luoqun@bupt.edu.c [National Engineering Laboratory for Disaster Backup and Recovery, Beijing University of Posts and Telecommunications, Beijing 100876 (China)

    2010-12-10

    Over the past decade, complex dynamical network synchronization has attracted more and more attention and important developments have been made. In this paper, we explore the scheme of globally exponentially asymptotical synchronization in complex dynamical networks with time delay. Based on Lyapunov stability theory and through defining the error function between adjacent nodes, four novel adaptive controllers are designed under four situations where the Lipschitz constants of the state function in nodes are known or unknown and the network structure is certain or uncertain, respectively. These controllers could not only globally asymptotically synchronize all nodes in networks, but also ensure that the error functions do not exceed the pre-scheduled exponential function. Finally, simulations of the synchronization among the chaotic system in the small-world and scale-free network structures are presented, which prove the effectiveness and feasibility of our controllers.

  11. Semi-Global Practical Stabilization and Disturbance Adaptation for an Underactuated Ship

    Directory of Open Access Journals (Sweden)

    Kristin Y. Pettersen

    2001-04-01

    Full Text Available We consider the problem of stabilizing the position and orientation of a ship to constant desired values, when the ship has only two independent controls and also the ship is subject to an environmental force of unknown magnitude. We propose a time-varying feedback control law and a disturbance adaptation law, and show that this provides semi-global practical asymptotic stability. The control and adaptation laws are derived using a combined integrator backstepping and averaging approach. Simulation results are presented.

  12. Global Stability of an Eco-Epidemiological Model with Time Delay and Saturation Incidence

    Directory of Open Access Journals (Sweden)

    Shuxue Mao

    2011-01-01

    Full Text Available We investigate a delayed eco-epidemiological model with disease in predator and saturation incidence. First, by comparison arguments, the permanence of the model is discussed. Then, we study the local stability of each equilibrium of the model by analyzing the corresponding characteristic equations and find that Hopf bifurcation occurs when the delay τ passes through a sequence of critical values. Next, by means of an iteration technique, sufficient conditions are derived for the global stability of the disease-free planar equilibrium and the positive equilibrium. Numerical examples are carried out to illustrate the analytical results.

  13. Global asymptotic stability analysis of bidirectional associative memory neural networks with time delays.

    Science.gov (United States)

    Arik, Sabri

    2005-05-01

    This paper presents a sufficient condition for the existence, uniqueness and global asymptotic stability of the equilibrium point for bidirectional associative memory (BAM) neural networks with distributed time delays. The results impose constraint conditions on the network parameters of neural system independently of the delay parameter, and they are applicable to all continuous nonmonotonic neuron activation functions. It is shown that in some special cases of the results, the stability criteria can be easily checked. Some examples are also given to compare the results with the previous results derived in the literature.

  14. New results for global robust stability of bidirectional associative memory neural networks with multiple time delays

    International Nuclear Information System (INIS)

    Senan, Sibel; Arik, Sabri

    2009-01-01

    This paper presents some new sufficient conditions for the global robust asymptotic stability of the equilibrium point for bidirectional associative memory (BAM) neural networks with multiple time delays. The results we obtain impose constraint conditions on the network parameters of neural system independently of the delay parameter, and they are applicable to all bounded continuous non-monotonic neuron activation functions. We also give some numerical examples to demonstrate the applicability and effectiveness of our results, and compare the results with the previous robust stability results derived in the literature.

  15. Test Exponential Pile

    Science.gov (United States)

    Fermi, Enrico

    The Patent contains an extremely detailed description of an atomic pile employing natural uranium as fissile material and graphite as moderator. It starts with the discussion of the theory of the intervening phenomena, in particular the evaluation of the reproduction or multiplication factor, K, that is the ratio of the number of fast neutrons produced in one generation by the fissions to the original number of fast neutrons, in a system of infinite size. The possibility of having a self-maintaining chain reaction in a system of finite size depends both on the facts that K is greater than unity and the overall size of the system is sufficiently large to minimize the percentage of neutrons escaping from the system. After the description of a possible realization of such a pile (with many detailed drawings), the various kinds of neutron losses in a pile are depicted. Particularly relevant is the reported "invention" of the exponential experiment: since theoretical calculations can determine whether or not a chain reaction will occur in a give system, but can be invalidated by uncertainties in the parameters of the problem, an experimental test of the pile is proposed, aimed at ascertaining if the pile under construction would be divergent (i.e. with a neutron multiplication factor K greater than 1) by making measurements on a smaller pile. The idea is to measure, by a detector containing an indium foil, the exponential decrease of the neutron density along the length of a column of uranium-graphite lattice, where a neutron source is placed near its base. Such an exponential decrease is greater or less than that expected due to leakage, according to whether the K factor is less or greater than 1, so that this experiment is able to test the criticality of the pile, its accuracy increasing with the size of the column. In order to perform this measure a mathematical description of the effect of neutron production, diffusion, and absorption on the neutron density in the

  16. Globally Asymptotic Stability of Stochastic Nonlinear Systems with Time-Varying Delays via Output Feedback Control

    Directory of Open Access Journals (Sweden)

    Mingzhu Song

    2016-01-01

    Full Text Available We address the problem of globally asymptotic stability for a class of stochastic nonlinear systems with time-varying delays. By the backstepping method and Lyapunov theory, we design a linear output feedback controller recursively based on the observable linearization for a class of stochastic nonlinear systems with time-varying delays to guarantee that the closed-loop system is globally asymptotically stable in probability. In particular, we extend the deterministic nonlinear system to stochastic nonlinear systems with time-varying delays. Finally, an example and its simulations are given to illustrate the theoretical results.

  17. Global asymptotic stability to a generalized Cohen-Grossberg BAM neural networks of neutral type delays.

    Science.gov (United States)

    Zhang, Zhengqiu; Liu, Wenbin; Zhou, Dongming

    2012-01-01

    In this paper, we first discuss the existence of a unique equilibrium point of a generalized Cohen-Grossberg BAM neural networks of neutral type delays by means of the Homeomorphism theory and inequality technique. Then, by applying the existence result of an equilibrium point and constructing a Lyapunov functional, we study the global asymptotic stability of the equilibrium solution to the above Cohen-Grossberg BAM neural networks of neutral type. In our results, the hypothesis for boundedness in the existing paper, which discussed Cohen-Grossberg neural networks of neutral type on the activation functions, are removed. Finally, we give an example to demonstrate the validity of our global asymptotic stability result for the above neural networks. Copyright © 2011 Elsevier Ltd. All rights reserved.

  18. A general framework for global asymptotic stability analysis of delayed neural networks based on LMI approach

    International Nuclear Information System (INIS)

    Cao Jinde; Ho, Daniel W.C.

    2005-01-01

    In this paper, global asymptotic stability is discussed for neural networks with time-varying delay. Several new criteria in matrix inequality form are given to ascertain the uniqueness and global asymptotic stability of equilibrium point for neural networks with time-varying delay based on Lyapunov method and Linear Matrix Inequality (LMI) technique. The proposed LMI approach has the advantage of considering the difference of neuronal excitatory and inhibitory efforts, which is also computationally efficient as it can be solved numerically using recently developed interior-point algorithm. In addition, the proposed results generalize and improve previous works. The obtained criteria also combine two existing conditions into one generalized condition in matrix form. An illustrative example is also given to demonstrate the effectiveness of the proposed results

  19. Novel global robust stability criteria for interval neural networks with multiple time-varying delays

    International Nuclear Information System (INIS)

    Xu Shengyuan; Lam, James; Ho, Daniel W.C.

    2005-01-01

    This Letter is concerned with the problem of robust stability analysis for interval neural networks with multiple time-varying delays and parameter uncertainties. The parameter uncertainties are assumed to be bounded in given compact sets and the activation functions are supposed to be bounded and globally Lipschitz continuous. A sufficient condition is obtained by means of Lyapunov functionals, which guarantees the existence, uniqueness and global asymptotic stability of the delayed neural network for all admissible uncertainties. This condition is in terms of a linear matrix inequality (LMI), which can be easily checked by using recently developed algorithms in solving LMIs. Finally, a numerical example is provided to demonstrate the effectiveness of the proposed method

  20. Cosmology with exponential potentials

    International Nuclear Information System (INIS)

    Kehagias, Alex; Kofinas, Georgios

    2004-01-01

    We examine in the context of general relativity the dynamics of a spatially flat Robertson-Walker universe filled with a classical minimally coupled scalar field φ of exponential potential V(φ) ∼ exp(-μφ) plus pressureless baryonic matter. This system is reduced to a first-order ordinary differential equation for Ω φ (w φ ) or q(w φ ), providing direct evidence on the acceleration/deceleration properties of the system. As a consequence, for positive potentials, passage into acceleration not at late times is generically a feature of the system for any value of μ, even when the late-times attractors are decelerating. Furthermore, the structure formation bound, together with the constraints Ω m0 ∼ 0.25 - 0.3, -1 ≤ w φ0 ≤ -0.6, provides, independently of initial conditions and other parameters, the necessary condition 0 N , while the less conservative constraint -1 ≤ w φ ≤ -0.93 gives 0 N . Special solutions are found to possess intervals of acceleration. For the almost cosmological constant case w φ ∼ -1, the general relation Ω φ (w φ ) is obtained. The generic (nonlinearized) late-times solution of the system in the plane (w φ , Ω φ ) or (w φ , q) is also derived

  1. OPINION: Safe exponential manufacturing

    Science.gov (United States)

    Phoenix, Chris; Drexler, Eric

    2004-08-01

    In 1959, Richard Feynman pointed out that nanometre-scale machines could be built and operated, and that the precision inherent in molecular construction would make it easy to build multiple identical copies. This raised the possibility of exponential manufacturing, in which production systems could rapidly and cheaply increase their productive capacity, which in turn suggested the possibility of destructive runaway self-replication. Early proposals for artificial nanomachinery focused on small self-replicating machines, discussing their potential productivity and their potential destructiveness if abused. In the light of controversy regarding scenarios based on runaway replication (so-called 'grey goo'), a review of current thinking regarding nanotechnology-based manufacturing is in order. Nanotechnology-based fabrication can be thoroughly non-biological and inherently safe: such systems need have no ability to move about, use natural resources, or undergo incremental mutation. Moreover, self-replication is unnecessary: the development and use of highly productive systems of nanomachinery (nanofactories) need not involve the construction of autonomous self-replicating nanomachines. Accordingly, the construction of anything resembling a dangerous self-replicating nanomachine can and should be prohibited. Although advanced nanotechnologies could (with great difficulty and little incentive) be used to build such devices, other concerns present greater problems. Since weapon systems will be both easier to build and more likely to draw investment, the potential for dangerous systems is best considered in the context of military competition and arms control.

  2. Global stability and quadratic Hamiltonian structure in Lotka-Volterra and quasi-polynomial systems

    Energy Technology Data Exchange (ETDEWEB)

    Szederkenyi, Gabor; Hangos, Katalin M

    2004-04-26

    We show that the global stability of quasi-polynomial (QP) and Lotka-Volterra (LV) systems with the well-known logarithmic Lyapunov function is equivalent to the existence of a local generalized dissipative Hamiltonian description of the LV system with a diagonal quadratic form as a Hamiltonian function. The Hamiltonian function can be calculated and the quadratic dissipativity neighborhood of the origin can be estimated by solving linear matrix inequalities.

  3. Global stability and quadratic Hamiltonian structure in Lotka-Volterra and quasi-polynomial systems

    Science.gov (United States)

    Szederkényi, Gábor; Hangos, Katalin M.

    2004-04-01

    We show that the global stability of quasi-polynomial (QP) and Lotka-Volterra (LV) systems with the well-known logarithmic Lyapunov function is equivalent to the existence of a local generalized dissipative Hamiltonian description of the LV system with a diagonal quadratic form as a Hamiltonian function. The Hamiltonian function can be calculated and the quadratic dissipativity neighborhood of the origin can be estimated by solving linear matrix inequalities.

  4. Global stability and quadratic Hamiltonian structure in Lotka-Volterra and quasi-polynomial systems

    International Nuclear Information System (INIS)

    Szederkenyi, Gabor; Hangos, Katalin M.

    2004-01-01

    We show that the global stability of quasi-polynomial (QP) and Lotka-Volterra (LV) systems with the well-known logarithmic Lyapunov function is equivalent to the existence of a local generalized dissipative Hamiltonian description of the LV system with a diagonal quadratic form as a Hamiltonian function. The Hamiltonian function can be calculated and the quadratic dissipativity neighborhood of the origin can be estimated by solving linear matrix inequalities

  5. Global asymptotic stability of hybrid bidirectional associative memory neural networks with time delays

    International Nuclear Information System (INIS)

    Arik, Sabri

    2006-01-01

    This Letter presents a sufficient condition for the existence, uniqueness and global asymptotic stability of the equilibrium point for bidirectional associative memory (BAM) neural networks with distributed time delays. The results impose constraint conditions on the network parameters of neural system independently of the delay parameter, and they are applicable to all bounded continuous non-monotonic neuron activation functions. The results are also compared with the previous results derived in the literature

  6. Global asymptotic stability of hybrid bidirectional associative memory neural networks with time delays

    Science.gov (United States)

    Arik, Sabri

    2006-02-01

    This Letter presents a sufficient condition for the existence, uniqueness and global asymptotic stability of the equilibrium point for bidirectional associative memory (BAM) neural networks with distributed time delays. The results impose constraint conditions on the network parameters of neural system independently of the delay parameter, and they are applicable to all bounded continuous non-monotonic neuron activation functions. The results are also compared with the previous results derived in the literature.

  7. A new delay-independent condition for global robust stability of neural networks with time delays.

    Science.gov (United States)

    Samli, Ruya

    2015-06-01

    This paper studies the problem of robust stability of dynamical neural networks with discrete time delays under the assumptions that the network parameters of the neural system are uncertain and norm-bounded, and the activation functions are slope-bounded. By employing the results of Lyapunov stability theory and matrix theory, new sufficient conditions for the existence, uniqueness and global asymptotic stability of the equilibrium point for delayed neural networks are presented. The results reported in this paper can be easily tested by checking some special properties of symmetric matrices associated with the parameter uncertainties of neural networks. We also present a numerical example to show the effectiveness of the proposed theoretical results. Copyright © 2015 Elsevier Ltd. All rights reserved.

  8. Robust Stability Clearance of Flight Control Law Based on Global Sensitivity Analysis

    Directory of Open Access Journals (Sweden)

    Liuli Ou

    2014-01-01

    Full Text Available To validate the robust stability of the flight control system of hypersonic flight vehicle, which suffers from a large number of parametrical uncertainties, a new clearance framework based on structural singular value (μ theory and global uncertainty sensitivity analysis (SA is proposed. In this framework, SA serves as the preprocess of uncertain model to be analysed to help engineers to determine which uncertainties affect the stability of the closed loop system more slightly. By ignoring these unimportant uncertainties, the calculation of μ can be simplified. Instead of analysing the effect of uncertainties on μ which involves solving optimal problems repeatedly, a simpler stability analysis function which represents the effect of uncertainties on closed loop poles is proposed. Based on this stability analysis function, Sobol’s method, the most widely used global SA method, is extended and applied to the new clearance framework due to its suitability for system with strong nonlinearity and input factors varying in large interval, as well as input factors subjecting to random distributions. In this method, the sensitive indices can be estimated via Monte Carlo simulation conveniently. An example is given to illustrate the efficiency of the proposed method.

  9. Low frequency azimuthal stability of the ionization region of the Hall thruster discharge. II. Global analysis

    International Nuclear Information System (INIS)

    Escobar, D.; Ahedo, E.

    2015-01-01

    The linear stability of the Hall thruster discharge is analysed against axial-azimuthal perturbations in the low frequency range using a time-dependent 2D code of the discharge. This azimuthal stability analysis is spatially global, as opposed to the more common local stability analyses, already afforded previously (D. Escobar and E. Ahedo, Phys. Plasmas 21(4), 043505 (2014)). The study covers both axial and axial-azimuthal oscillations, known as breathing mode and spoke, respectively. The influence on the spoke instability of different operation parameters such as discharge voltage, mass flow, and thruster size is assessed by means of different parametric variations and compared against experimental results. Additionally, simplified models are used to unveil and characterize the mechanisms driving the spoke. The results indicate that the spoke is linked to azimuthal oscillations of the ionization process and to the Bohm condition in the transition to the anode sheath. Finally, results obtained from local and global stability analyses are compared in order to explain the discrepancies between both methods

  10. Multivariate Matrix-Exponential Distributions

    DEFF Research Database (Denmark)

    Bladt, Mogens; Nielsen, Bo Friis

    2010-01-01

    be written as linear combinations of the elements in the exponential of a matrix. For this reason we shall refer to multivariate distributions with rational Laplace transform as multivariate matrix-exponential distributions (MVME). The marginal distributions of an MVME are univariate matrix......-exponential distributions. We prove a characterization that states that a distribution is an MVME distribution if and only if all non-negative, non-null linear combinations of the coordinates have a univariate matrix-exponential distribution. This theorem is analog to a well-known characterization theorem...

  11. Sharp conditions for global stability of Lotka-Volterra systems with distributed delays

    Science.gov (United States)

    Faria, Teresa

    We give a criterion for the global attractivity of a positive equilibrium of n-dimensional non-autonomous Lotka-Volterra systems with distributed delays. For a class of autonomous Lotka-Volterra systems, we show that such a criterion is sharp, in the sense that it provides necessary and sufficient conditions for the global asymptotic stability independently of the choice of the delay functions. The global attractivity of positive equilibria is established by imposing a diagonal dominance of the instantaneous negative feedback terms, and relies on auxiliary results showing the boundedness of all positive solutions. The paper improves and generalizes known results in the literature, namely by considering systems with distributed delays rather than discrete delays.

  12. Credit Rating As a Factor of Stability in the Global Capital Market

    Directory of Open Access Journals (Sweden)

    Ismail Musabegović

    2014-12-01

    Full Text Available Credit rating has an outstanding importance on the capital market. Opinions and assessments of rating agencies help us to improve growth, stability and efficiency of international and domestic markets, which now include over 80 trillion dollars of rated bonds and other securities with the fixed income. The contribution of the credit agencies to the market stability and efficiency is reflected in their ability to provide accurate, clear and reliable assessments of the solvency of participants on the financial markets. An adequate and proper risk assessment of securities contributes to stability. In order to achieve a given goal and to satisfy its purpose, the assessments should be based on a fundamental understanding of the key components of the credit risk. Also, in order to ensure a reliable framework for making investment decisions, the rating agencies are obliged to offer and to provide a wide range of securities, which are based on a global comparability of rating symbols and onthe support given by the credit rating assignment committee and by the other relevant decision making bodies. Markets for structured products could not have developed without the quality assurance provided by CRAs. When analyzing a securitization program CRAs examine legal and structural protections provided to investors. Since the globalization is an inevitable phenomenon in today’s world the importance of the credit rating becomes more noticeable. On the other hand, the rating agencies have an obligation to reanalyze their decision making models in order to contribute tothe reliability of the evaluation.

  13. Global Uniform Asymptotic Stability of a Class of Switched Linear Systems with an Infinite Number of Subsystems

    Directory of Open Access Journals (Sweden)

    L. F. Araghi

    2014-01-01

    Full Text Available Stability of switching systems with an infinite number of subsystems is important in some structure of systems, like fuzzy systems, neural networks, and so forth. Because of the relationship between stability of a set of matrices and switching systems, this paper first studies the stability of a set of matrices, then and the results are applied for stability of switching systems. Some new conditions for globally uniformly asymptotically stability (GUAS of discrete-time switched linear systems with an infinite number of subsystems are proposed. The paper considers some examples and simulation results.

  14. The global stability of a delayed predator-prey system with two stage-structure

    International Nuclear Information System (INIS)

    Wang Fengyan; Pang Guoping

    2009-01-01

    Based on the classical delayed stage-structured model and Lotka-Volterra predator-prey model, we introduce and study a delayed predator-prey system, where prey and predator have two stages, an immature stage and a mature stage. The time delays are the time lengths between the immature's birth and maturity of prey and predator species. Results on global asymptotic stability of nonnegative equilibria of the delay system are given, which generalize and suggest that good continuity exists between the predator-prey system and its corresponding stage-structured system.

  15. Global stability, periodic solutions, and optimal control in a nonlinear differential delay model

    Directory of Open Access Journals (Sweden)

    Anatoli F. Ivanov

    2010-09-01

    Full Text Available A nonlinear differential equation with delay serving as a mathematical model of several applied problems is considered. Sufficient conditions for the global asymptotic stability and for the existence of periodic solutions are given. Two particular applications are treated in detail. The first one is a blood cell production model by Mackey, for which new periodicity criteria are derived. The second application is a modified economic model with delay due to Ramsey. An optimization problem for a maximal consumption is stated and solved for the latter.

  16. Epidemic spreading and global stability of an SIS model with an infective vector on complex networks

    Science.gov (United States)

    Kang, Huiyan; Fu, Xinchu

    2015-10-01

    In this paper, we present a new SIS model with delay on scale-free networks. The model is suitable to describe some epidemics which are not only transmitted by a vector but also spread between individuals by direct contacts. In view of the biological relevance and real spreading process, we introduce a delay to denote average incubation period of disease in a vector. By mathematical analysis, we obtain the epidemic threshold and prove the global stability of equilibria. The simulation shows the delay will effect the epidemic spreading. Finally, we investigate and compare two major immunization strategies, uniform immunization and targeted immunization.

  17. Global asymptotic stability analysis of bidirectional associative memory neural networks with distributed delays and impulse

    International Nuclear Information System (INIS)

    Huang Zaitang; Luo Xiaoshu; Yang Qigui

    2007-01-01

    Many systems existing in physics, chemistry, biology, engineering and information science can be characterized by impulsive dynamics caused by abrupt jumps at certain instants during the process. These complex dynamical behaviors can be model by impulsive differential system or impulsive neural networks. This paper formulates and studies a new model of impulsive bidirectional associative memory (BAM) networks with finite distributed delays. Several fundamental issues, such as global asymptotic stability and existence and uniqueness of such BAM neural networks with impulse and distributed delays, are established

  18. Global stability and tumor clearance conditions for a cancer chemotherapy system

    Science.gov (United States)

    Valle, Paul A.; Starkov, Konstantin E.; Coria, Luis N.

    2016-11-01

    In this paper we study the global dynamics of a cancer chemotherapy system presented by de Pillis et al. (2007). This mathematical model describes the interaction between tumor cells, effector-immune cells, circulating lymphocytes and chemotherapy treatment. By applying the localization method of compact invariant sets, we find lower and upper bounds for these three cells populations. Further, we define a bounded domain in R+,04 where all compact invariant sets of the system are located and provide conditions under which this domain is positively invariant. We apply LaSalle's invariance principle and one result concerning two-dimensional competitive systems in order to derive sufficient conditions for tumor clearance and global asymptotic stability of the tumor-free equilibrium point. These conditions are computed by using bounds of the localization domain and they are given in terms of the chemotherapy treatment. Finally, we perform numerical simulations in order to illustrate our results.

  19. Polyhedral Lyapunov functions structurally ensure global asymptotic stability of dynamical networks iff the Jacobian is non-singular

    NARCIS (Netherlands)

    Blanchini, Franco; Giordano, G.

    2017-01-01

    For a vast class of dynamical networks, including chemical reaction networks (CRNs) with monotonic reaction rates, the existence of a polyhedral Lyapunov function (PLF) implies structural (i.e., parameter-free) local stability. Global structural stability is ensured under the additional

  20. Existence and stability of periodic solution in impulsive Hopfield neural networks with finite distributed delays

    International Nuclear Information System (INIS)

    Yang Xiaofan; Liao Xiaofeng; Evans, David J.; Tang Yuanyan

    2005-01-01

    In this Letter, we introduce a class of Hopfield neural networks with periodic impulses and finite distributed delays. We then derive a sufficient condition for the existence and global exponential stability of a unique periodic solution of the networks, which assumes neither the differentiability nor the monotonicity of the activation functions. Our condition extends and generalizes a known condition for the global exponential periodicity of continuous Hopfield neural networks with finite distributed delays

  1. Climate change impacts on US agriculture and forestry: benefits of global climate stabilization

    Energy Technology Data Exchange (ETDEWEB)

    Beach, Robert H.; Cai, Yongxia; Thomson, Allison; Zhang, Xuesong; Jones, Russell; McCarl, Bruce A.; Crimmins, Allison; Martinich, Jeremy; Cole, Jefferson; Ohrel, Sara; DeAngelo, Benjamin; McFarland, James; Strzepek, Kenneth; Boehlert, Brent

    2015-09-01

    Increasing atmospheric carbon dioxide levels, higher temperatures, altered precipitation patterns, and other climate change impacts have already begun to affect US agriculture and forestry, with impacts expected to become more substantial in the future. There have been numerous studies of climate change impacts on agriculture or forestry, but relatively little research examining the long-term net impacts of a stabilization scenario relative to a case with unabated climate change. We provide an analysis of the potential benefits of global climate change mitigation for US agriculture and forestry through 2100, accounting for landowner decisions regarding land use, crop mix, and management practices. The analytic approach involves a combination of climate models, a crop process model (EPIC), a dynamic vegetation model used for forests (MC1), and an economic model of the US forestry and agricultural sector (FASOM-GHG). We find substantial impacts on productivity, commodity markets, and consumer and producer welfare for the stabilization scenario relative to unabated climate change, though the magnitude and direction of impacts vary across regions and commodities. Although there is variability in welfare impacts across climate simulations, we find positive net benefits from stabilization in all cases, with cumulative impacts ranging from $32.7 billion to $54.5 billion over the period 2015-2100. Our estimates contribute to the literature on potential benefits of GHG mitigation and can help inform policy decisions weighing alternative mitigation and adaptation actions.

  2. Climate change impacts on US agriculture and forestry: benefits of global climate stabilization

    Science.gov (United States)

    Beach, Robert H.; Cai, Yongxia; Thomson, Allison; Zhang, Xuesong; Jones, Russell; McCarl, Bruce A.; Crimmins, Allison; Martinich, Jeremy; Cole, Jefferson; Ohrel, Sara; DeAngelo, Benjamin; McFarland, James; Strzepek, Kenneth; Boehlert, Brent

    2015-09-01

    Increasing atmospheric carbon dioxide levels, higher temperatures, altered precipitation patterns, and other climate change impacts have already begun to affect US agriculture and forestry, with impacts expected to become more substantial in the future. There have been numerous studies of climate change impacts on agriculture or forestry, but relatively little research examining the long-term net impacts of a stabilization scenario relative to a case with unabated climate change. We provide an analysis of the potential benefits of global climate change mitigation for US agriculture and forestry through 2100, accounting for landowner decisions regarding land use, crop mix, and management practices. The analytic approach involves a combination of climate models, a crop process model (EPIC), a dynamic vegetation model used for forests (MC1), and an economic model of the US forestry and agricultural sector (FASOM-GHG). We find substantial impacts on productivity, commodity markets, and consumer and producer welfare for the stabilization scenario relative to unabated climate change, though the magnitude and direction of impacts vary across regions and commodities. Although there is variability in welfare impacts across climate simulations, we find positive net benefits from stabilization in all cases, with cumulative impacts ranging from 32.7 billion to 54.5 billion over the period 2015-2100. Our estimates contribute to the literature on potential benefits of GHG mitigation and can help inform policy decisions weighing alternative mitigation and adaptation actions.

  3. Global stability analysis of axisymmetric boundary layer over a circular cylinder

    Science.gov (United States)

    Bhoraniya, Ramesh; Vinod, Narayanan

    2018-05-01

    This paper presents a linear global stability analysis of the incompressible axisymmetric boundary layer on a circular cylinder. The base flow is parallel to the axis of the cylinder at inflow boundary. The pressure gradient is zero in the streamwise direction. The base flow velocity profile is fully non-parallel and non-similar in nature. The boundary layer grows continuously in the spatial directions. Linearized Navier-Stokes (LNS) equations are derived for the disturbance flow quantities in the cylindrical polar coordinates. The LNS equations along with homogeneous boundary conditions forms a generalized eigenvalues problem. Since the base flow is axisymmetric, the disturbances are periodic in azimuthal direction. Chebyshev spectral collocation method and Arnoldi's iterative algorithm is used for the solution of the general eigenvalues problem. The global temporal modes are computed for the range of Reynolds numbers and different azimuthal wave numbers. The largest imaginary part of the computed eigenmodes is negative, and hence, the flow is temporally stable. The spatial structure of the eigenmodes shows that the disturbance amplitudes grow in size and magnitude while they are moving towards downstream. The global modes of axisymmetric boundary layer are more stable than that of 2D flat-plate boundary layer at low Reynolds number. However, at higher Reynolds number they approach 2D flat-plate boundary layer. Thus, the damping effect of transverse curvature is significant at low Reynolds number. The wave-like nature of the disturbance amplitudes is found in the streamwise direction for the least stable eigenmodes.

  4. Assessing the Benefits of Global Climate Stabilization Within an Integrated Modeling Framework

    Science.gov (United States)

    Beach, R. H.

    2015-12-01

    Increasing atmospheric carbon dioxide levels, higher temperatures, altered precipitation patterns, and other climate change impacts have already begun to affect US agriculture and forestry, with impacts expected to become more substantial in the future. There have been a number of studies of climate change impacts on agriculture or forestry. However, relatively few studies explore climate change impacts on both agriculture and forests simultaneously, including the interactions between alternative land uses and implications for market outcomes. Additionally, there is a lack of detailed analyses of the effects of stabilization scenarios relative to unabated emissions scenarios. Such analyses are important for developing estimates of the benefits of those stabilization scenarios, which can play a vital role in assessing tradeoffs associated with allocating resources across alternative mitigation and adaptation activities. We provide an analysis of the potential benefits of global climate change mitigation for US agriculture and forestry through 2100, accounting for landowner decisions regarding land use, crop mix, and management practices. The analytic approach involves a combination of climate models, a crop process model (EPIC), a dynamic vegetation model used for forests (MC1), and an economic model of the US forestry and agricultural sector (FASOM-GHG). We find substantial impacts on productivity, commodity markets, and consumer and producer welfare for the stabilization scenario relative to unabated climate change, though the magnitude and direction of impacts vary across regions and commodities. Although there is variability in welfare impacts across climate simulations, we find positive net benefits from stabilization in all cases, with cumulative impacts ranging from 32.7 billion to 54.5 billion over the period 2015-2100. Our estimates contribute to the literature on potential benefits of GHG mitigation and can help inform policy decisions weighing alternative

  5. Generalized approach to non-exponential relaxation

    Indian Academy of Sciences (India)

    Non-exponential relaxation is a universal feature of systems as diverse as glasses, spin ... which changes from a simple exponential to a stretched exponential and a power law by increasing the constraints in the system. ... Current Issue

  6. Universality in stochastic exponential growth.

    Science.gov (United States)

    Iyer-Biswas, Srividya; Crooks, Gavin E; Scherer, Norbert F; Dinner, Aaron R

    2014-07-11

    Recent imaging data for single bacterial cells reveal that their mean sizes grow exponentially in time and that their size distributions collapse to a single curve when rescaled by their means. An analogous result holds for the division-time distributions. A model is needed to delineate the minimal requirements for these scaling behaviors. We formulate a microscopic theory of stochastic exponential growth as a Master Equation that accounts for these observations, in contrast to existing quantitative models of stochastic exponential growth (e.g., the Black-Scholes equation or geometric Brownian motion). Our model, the stochastic Hinshelwood cycle (SHC), is an autocatalytic reaction cycle in which each molecular species catalyzes the production of the next. By finding exact analytical solutions to the SHC and the corresponding first passage time problem, we uncover universal signatures of fluctuations in exponential growth and division. The model makes minimal assumptions, and we describe how more complex reaction networks can reduce to such a cycle. We thus expect similar scalings to be discovered in stochastic processes resulting in exponential growth that appear in diverse contexts such as cosmology, finance, technology, and population growth.

  7. Necessary and Sufficient Condition for Local Exponential Synchronization of Nonlinear Systems

    NARCIS (Netherlands)

    Andrieu, Vincent; Jayawardhana, Bayu; Tarbouriech, Sophie

    2015-01-01

    Based on recent works on transverse exponential stability, some necessary and sufficient conditions for the existence of a (locally) exponential synchronizer are established. We show that the existence of a structured synchronizer is equivalent to the existence of a stabilizer for the individual

  8. Real-Time Exponential Curve Fits Using Discrete Calculus

    Science.gov (United States)

    Rowe, Geoffrey

    2010-01-01

    An improved solution for curve fitting data to an exponential equation (y = Ae(exp Bt) + C) has been developed. This improvement is in four areas -- speed, stability, determinant processing time, and the removal of limits. The solution presented avoids iterative techniques and their stability errors by using three mathematical ideas: discrete calculus, a special relationship (be tween exponential curves and the Mean Value Theorem for Derivatives), and a simple linear curve fit algorithm. This method can also be applied to fitting data to the general power law equation y = Ax(exp B) + C and the general geometric growth equation y = Ak(exp Bt) + C.

  9. Exponential Expansion in Evolutionary Economics

    DEFF Research Database (Denmark)

    Frederiksen, Peter; Jagtfelt, Tue

    2013-01-01

    This article attempts to solve current problems of conceptual fragmentation within the field of evolutionary economics. One of the problems, as noted by a number of observers, is that the field suffers from an assemblage of fragmented and scattered concepts (Boschma and Martin 2010). A solution...... to this problem is proposed in the form of a model of exponential expansion. The model outlines the overall structure and function of the economy as exponential expansion. The pictographic model describes four axiomatic concepts and their exponential nature. The interactive, directional, emerging and expanding...... concepts are described in detail. Taken together it provides the rudimentary aspects of an economic system within an analytical perspective. It is argued that the main dynamic processes of the evolutionary perspective can be reduced to these four concepts. The model and concepts are evaluated in the light...

  10. Exponential x-ray transform

    International Nuclear Information System (INIS)

    Hazou, I.A.

    1986-01-01

    In emission computed tomography one wants to determine the location and intensity of radiation emitted by sources in the presence of an attenuating medium. If the attenuation is known everywhere and equals a constant α in a convex neighborhood of the support of f, then the problem reduces to that of inverting the exponential x-ray transform P/sub α/. The exponential x-ray transform P/sub μ/ with the attenuation μ variable, is of interest mathematically. For the exponential x-ray transform in two dimensions, it is shown that for a large class of approximate δ functions E, convolution kernels K exist for use in the convolution backprojection algorithm. For the case where the attenuation is constant, exact formulas are derived for calculating the convolution kernels from radial point spread functions. From these an exact inversion formula for the constantly attenuated transform is obtained

  11. Global stability of a two-mediums rumor spreading model with media coverage

    Science.gov (United States)

    Huo, Liang'an; Wang, Li; Song, Guoxiang

    2017-09-01

    Rumor spreading is a typical form of social communication and plays a significant role in social life, and media coverage has a great influence on the spread of rumor. In this paper, we present a new model with two media coverage to investigate the impact of the different mediums on rumor spreading. Then, we calculate the equilibria of the model and construct the reproduction number ℜ0. And we prove the global asymptotic stability of equilibria by using Lyapunov functions. Finally, we can conclude that the transition rate of the ignorants between two mediums has a direct effect on the scale of spreaders, and different media coverage has significant effects on the dynamics behaviors of rumor spreading.

  12. Global stability and pattern formation in a nonlocal diffusive Lotka-Volterra competition model

    Science.gov (United States)

    Ni, Wenjie; Shi, Junping; Wang, Mingxin

    2018-06-01

    A diffusive Lotka-Volterra competition model with nonlocal intraspecific and interspecific competition between species is formulated and analyzed. The nonlocal competition strength is assumed to be determined by a diffusion kernel function to model the movement pattern of the biological species. It is shown that when there is no nonlocal intraspecific competition, the dynamics properties of nonlocal diffusive competition problem are similar to those of classical diffusive Lotka-Volterra competition model regardless of the strength of nonlocal interspecific competition. Global stability of nonnegative constant equilibria are proved using Lyapunov or upper-lower solution methods. On the other hand, strong nonlocal intraspecific competition increases the system spatiotemporal dynamic complexity. For the weak competition case, the nonlocal diffusive competition model may possess nonconstant positive equilibria for some suitably large nonlocal intraspecific competition coefficients.

  13. Measured improvement of global magnetohydrodynamic mode stability at high-beta, and in reduced collisionality spherical torus plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Berkery, J. W.; Sabbagh, S. A.; Balbaky, A. [Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States); Bell, R. E.; Diallo, A.; Gerhardt, S. P.; LeBlanc, B. P.; Manickam, J.; Menard, J. E.; Podestà, M. [Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States); Betti, R. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623 (United States)

    2014-05-15

    Global mode stability is studied in high-β National Spherical Torus Experiment (NSTX) plasmas to avoid disruptions. Dedicated experiments in NSTX using low frequency active magnetohydrodynamic spectroscopy of applied rotating n = 1 magnetic fields revealed key dependencies of stability on plasma parameters. Observations from previous NSTX resistive wall mode (RWM) active control experiments and the wider NSTX disruption database indicated that the highest β{sub N} plasmas were not the least stable. Significantly, here, stability was measured to increase at β{sub N}∕l{sub i} higher than the point where disruptions were found. This favorable behavior is shown to correlate with kinetic stability rotational resonances, and an experimentally determined range of measured E × B frequency with improved stability is identified. Stable plasmas appear to benefit further from reduced collisionality, in agreement with expectation from kinetic RWM stabilization theory, but low collisionality plasmas are also susceptible to sudden instability when kinetic profiles change.

  14. Stability and Global Hopf Bifurcation Analysis on a Ratio-Dependent Predator-Prey Model with Two Time Delays

    Directory of Open Access Journals (Sweden)

    Huitao Zhao

    2013-01-01

    Full Text Available A ratio-dependent predator-prey model with two time delays is studied. By means of an iteration technique, sufficient conditions are obtained for the global attractiveness of the positive equilibrium. By comparison arguments, the global stability of the semitrivial equilibrium is addressed. By using the theory of functional equation and Hopf bifurcation, the conditions on which positive equilibrium exists and the quality of Hopf bifurcation are given. Using a global Hopf bifurcation result of Wu (1998 for functional differential equations, the global existence of the periodic solutions is obtained. Finally, an example for numerical simulations is also included.

  15. Do forests have a say in global carbon markets for climate stabilization policy?

    Energy Technology Data Exchange (ETDEWEB)

    Tavoni, M.; Bosetti, V. [Fondazione Eni Enrico Mattei, FEEM (Italy); Sohngen, B. [Ohio State Univ., Dept. of Agr., Env., and Dev. Economics (United States)

    2007-05-15

    While carbon sequestration was included in the Kyoto Protocol, its potential scope as a mitigation activity has been highly debated in subsequent negotiations. Notwithstanding the widespread research suggesting that biological sequestration of carbon can play an important role for reducing greenhouse gas emissions, the nations in the Kyoto Protocol have so far only haltingly incorporated forestry measures, for a variety of reasons. One concern revolved around the validity of measuring and monitoring land-based activities to prove that they provided additional carbon storage, as for example error bounds for measuring and monitoring carbon in forests are fairly large. A second reason for the setbacks to forest sequestration regarded whether carbon sequestration would reduce carbon prices and consequently the quantity of abatement provided by the energy sector. Only the energy sector, after all, can ensure permanent reductions in CO{sub 2} emissions. This concern implies that forest carbon sequestration could be large enough to influence carbon prices in a global carbon market. Clearly, if prices are lower the deployment of low carbon measures and technologies could be delayed, for example by reducing incentives for technological evolution. Yet, enriching the mitigation portfolio with forestry could bring a significant contribution. Global policies meant to stabilize greenhouse gas concentrations in the future will arguably require a vast bundle of measures to meet ambitious targets. The first set of concerns has been widely addressed in a range of publications, including those of the Intergovernmental Panel on Climate Change. Remarkably less attention has been devoted to the second set of concerns. In this article we try to fill the gap by analyzing the impact biological carbon sequestration has on a policy to stabilize carbon emissions. In doing so we are able to evaluate a potentially attractive mitigation option like carbon sinks accounting for the influence the

  16. Exponential Potential versus Dark Matter

    Science.gov (United States)

    1993-10-15

    scale of the solar system. Galaxy, Dark matter , Galaxy cluster, Gravitation, Quantum gravity...A two parameter exponential potential explains the anomalous kinematics of galaxies and galaxy clusters without need for the myriad ad hoc dark ... matter models currently in vogue. It also explains much about the scales and structures of galaxies and galaxy clusters while being quite negligible on the

  17. Phenomenology of stochastic exponential growth

    Science.gov (United States)

    Pirjol, Dan; Jafarpour, Farshid; Iyer-Biswas, Srividya

    2017-06-01

    Stochastic exponential growth is observed in a variety of contexts, including molecular autocatalysis, nuclear fission, population growth, inflation of the universe, viral social media posts, and financial markets. Yet literature on modeling the phenomenology of these stochastic dynamics has predominantly focused on one model, geometric Brownian motion (GBM), which can be described as the solution of a Langevin equation with linear drift and linear multiplicative noise. Using recent experimental results on stochastic exponential growth of individual bacterial cell sizes, we motivate the need for a more general class of phenomenological models of stochastic exponential growth, which are consistent with the observation that the mean-rescaled distributions are approximately stationary at long times. We show that this behavior is not consistent with GBM, instead it is consistent with power-law multiplicative noise with positive fractional powers. Therefore, we consider this general class of phenomenological models for stochastic exponential growth, provide analytical solutions, and identify the important dimensionless combination of model parameters, which determines the shape of the mean-rescaled distribution. We also provide a prescription for robustly inferring model parameters from experimentally observed stochastic growth trajectories.

  18. Global Asymptotic Stability of a Predator-Prey Model with Modified Leslie-Gower and Holling-Type II Schemes

    Directory of Open Access Journals (Sweden)

    Shengbin Yu

    2012-01-01

    Full Text Available We study the predator-prey model proposed by Aziz-Alaoui and Okiye (Appl. Math. Lett. 16 (2003 1069–1075 First, the structure of equilibria and their linearized stability is investigated. Then, we provide two sufficient conditions on the global asymptotic stability of a positive equilibrium by employing the Fluctuation Lemma and Lyapunov direct method, respectively. The obtained results not only improve but also supplement existing ones.

  19. Global robust stability of delayed neural networks: Estimating upper limit of norm of delayed connection weight matrix

    International Nuclear Information System (INIS)

    Singh, Vimal

    2007-01-01

    The question of estimating the upper limit of -parallel B -parallel 2 , which is a key step in some recently reported global robust stability criteria for delayed neural networks, is revisited ( B denotes the delayed connection weight matrix). Recently, Cao, Huang, and Qu have given an estimate of the upper limit of -parallel B -parallel 2 . In the present paper, an alternative estimate of the upper limit of -parallel B -parallel 2 is highlighted. It is shown that the alternative estimate may yield some new global robust stability results

  20. The exponentiated generalized Pareto distribution | Adeyemi | Ife ...

    African Journals Online (AJOL)

    Recently Gupta et al. (1998) introduced the exponentiated exponential distribution as a generalization of the standard exponential distribution. In this paper, we introduce a three-parameter generalized Pareto distribution, the exponentiated generalized Pareto distribution (EGP). We present a comprehensive treatment of the ...

  1. Boundedness and global robust stability analysis of delayed complex-valued neural networks with interval parameter uncertainties.

    Science.gov (United States)

    Song, Qiankun; Yu, Qinqin; Zhao, Zhenjiang; Liu, Yurong; Alsaadi, Fuad E

    2018-07-01

    In this paper, the boundedness and robust stability for a class of delayed complex-valued neural networks with interval parameter uncertainties are investigated. By using Homomorphic mapping theorem, Lyapunov method and inequality techniques, sufficient condition to guarantee the boundedness of networks and the existence, uniqueness and global robust stability of equilibrium point is derived for the considered uncertain neural networks. The obtained robust stability criterion is expressed in complex-valued LMI, which can be calculated numerically using YALMIP with solver of SDPT3 in MATLAB. An example with simulations is supplied to show the applicability and advantages of the acquired result. Copyright © 2018 Elsevier Ltd. All rights reserved.

  2. Global stability of plasmas with helical boundary deformation and net toroidal current against n=1,2 external modes

    International Nuclear Information System (INIS)

    Ardela, A.; Cooper, W.A.

    1996-01-01

    In this paper we resume a numerical study of the global stability of plasma with helical boundary deformation and non null net toroidal current. The aim was to see whether external modes with n=1,2 (n toroidal mode number) can be stabilized at values of β inaccessible to the tokamak. L=2,3 configurations with several aspect ratios and different numbers of equilibrium field periods are considered. A large variety of toroidal current densities and different pressure profiles are taken into account. Mercier stability is also investigated. (author) 4 figs., 6 refs

  3. Construction of extended exponential general linear methods 524 ...

    African Journals Online (AJOL)

    This paper introduces a new approach for constructing higher order of EEGLM which have become very popular and novel due to its enviable stability properties. This paper also shows that methods 524 is stable with its characteristics root lies in a unit circle. Numerical experiments indicate that Extended Exponential ...

  4. Stability Results, Almost Global Generalized Beltrami Fields and Applications to Vortex Structures in the Euler Equations

    Science.gov (United States)

    Enciso, Alberto; Poyato, David; Soler, Juan

    2018-05-01

    Strong Beltrami fields, that is, vector fields in three dimensions whose curl is the product of the field itself by a constant factor, have long played a key role in fluid mechanics and magnetohydrodynamics. In particular, they are the kind of stationary solutions of the Euler equations where one has been able to show the existence of vortex structures (vortex tubes and vortex lines) of arbitrarily complicated topology. On the contrary, there are very few results about the existence of generalized Beltrami fields, that is, divergence-free fields whose curl is the field times a non-constant function. In fact, generalized Beltrami fields (which are also stationary solutions to the Euler equations) have been recently shown to be rare, in the sense that for "most" proportionality factors there are no nontrivial Beltrami fields of high enough regularity (e.g., of class {C^{6,α}}), not even locally. Our objective in this work is to show that, nevertheless, there are "many" Beltrami fields with non-constant factor, even realizing arbitrarily complicated vortex structures. This fact is relevant in the study of turbulent configurations. The core results are an "almost global" stability theorem for strong Beltrami fields, which ensures that a global strong Beltrami field with suitable decay at infinity can be perturbed to get "many" Beltrami fields with non-constant factor of arbitrarily high regularity and defined in the exterior of an arbitrarily small ball, and a "local" stability theorem for generalized Beltrami fields, which is an analogous perturbative result which is valid for any kind of Beltrami field (not just with a constant factor) but only applies to small enough domains. The proof relies on an iterative scheme of Grad-Rubin type. For this purpose, we study the Neumann problem for the inhomogeneous Beltrami equation in exterior domains via a boundary integral equation method and we obtain Hölder estimates, a sharp decay at infinity and some compactness

  5. Science in an Exponential World

    Science.gov (United States)

    Szalay, Alexander

    The amount of scientific information is doubling every year. This exponential growth is fundamentally changing every aspect of the scientific process - the collection, analysis and dissemination of scientific information. Our traditional paradigm for scientific publishing assumes a linear world, where the number of journals and articles remains approximately constant. The talk presents the challenges of this new paradigm and shows examples of how some disciplines are trying to cope with the data avalanche. In astronomy, the Virtual Observatory is emerging as a way to do astronomy in the 21st century. Other disciplines are also in the process of creating their own Virtual Observatories, on every imaginable scale of the physical world. We will discuss how long this exponential growth can continue.

  6. Exponential asymptotics of homoclinic snaking

    International Nuclear Information System (INIS)

    Dean, A D; Matthews, P C; Cox, S M; King, J R

    2011-01-01

    We study homoclinic snaking in the cubic-quintic Swift–Hohenberg equation (SHE) close to the onset of a subcritical pattern-forming instability. Application of the usual multiple-scales method produces a leading-order stationary front solution, connecting the trivial solution to the patterned state. A localized pattern may therefore be constructed by matching between two distant fronts placed back-to-back. However, the asymptotic expansion of the front is divergent, and hence should be truncated. By truncating optimally, such that the resultant remainder is exponentially small, an exponentially small parameter range is derived within which stationary fronts exist. This is shown to be a direct result of the 'locking' between the phase of the underlying pattern and its slowly varying envelope. The locking mechanism remains unobservable at any algebraic order, and can only be derived by explicitly considering beyond-all-orders effects in the tail of the asymptotic expansion, following the method of Kozyreff and Chapman as applied to the quadratic-cubic SHE (Chapman and Kozyreff 2009 Physica D 238 319–54, Kozyreff and Chapman 2006 Phys. Rev. Lett. 97 44502). Exponentially small, but exponentially growing, contributions appear in the tail of the expansion, which must be included when constructing localized patterns in order to reproduce the full snaking diagram. Implicit within the bifurcation equations is an analytical formula for the width of the snaking region. Due to the linear nature of the beyond-all-orders calculation, the bifurcation equations contain an analytically indeterminable constant, estimated in the previous work by Chapman and Kozyreff using a best fit approximation. A more accurate estimate of the equivalent constant in the cubic-quintic case is calculated from the iteration of a recurrence relation, and the subsequent analytical bifurcation diagram compared with numerical simulations, with good agreement

  7. Limit laws for exponential families

    OpenAIRE

    Balkema, August A.; Klüppelberg, Claudia; Resnick, Sidney I.

    1999-01-01

    For a real random variable [math] with distribution function [math] , define ¶ [math] ¶ The distribution [math] generates a natural exponential family of distribution functions [math] , where ¶ [math] ¶ We study the asymptotic behaviour of the distribution functions [math] as [math] increases to [math] . If [math] then [math] pointwise on [math] . It may still be possible to obtain a non-degenerate weak limit law [math] by choosing suitable scaling and centring constants [math] an...

  8. Stability analysis of switched linear systems defined by graphs

    NARCIS (Netherlands)

    Athanasopoulos, N.; Lazar, M.

    2014-01-01

    We present necessary and sufficient conditions for global exponential stability for switched discrete-time linear systems, under arbitrary switching, which is constrained within a set of admissible transitions. The class of systems studied includes the family of systems under arbitrary switching,

  9. Global stability of discrete-time recurrent neural networks with impulse effects

    International Nuclear Information System (INIS)

    Zhou, L; Li, C; Wan, J

    2008-01-01

    This paper formulates and studies a class of discrete-time recurrent neural networks with impulse effects. A stability criterion, which characterizes the effects of impulse and stability property of the corresponding impulse-free networks on the stability of the impulsive networks in an aggregate form, is established. Two simplified and numerically tractable criteria are also provided

  10. Is Radioactive Decay Really Exponential?

    OpenAIRE

    Aston, Philip J.

    2012-01-01

    Radioactive decay of an unstable isotope is widely believed to be exponential. This view is supported by experiments on rapidly decaying isotopes but is more difficult to verify for slowly decaying isotopes. The decay of 14C can be calibrated over a period of 12,550 years by comparing radiocarbon dates with dates obtained from dendrochronology. It is well known that this approach shows that radiocarbon dates of over 3,000 years are in error, which is generally attributed to past variation in ...

  11. A note on exponential convergence of neural networks with unbounded distributed delays

    Energy Technology Data Exchange (ETDEWEB)

    Chu Tianguang [Intelligent Control Laboratory, Center for Systems and Control, Department of Mechanics and Engineering Science, Peking University, Beijing 100871 (China)]. E-mail: chutg@pku.edu.cn; Yang Haifeng [Intelligent Control Laboratory, Center for Systems and Control, Department of Mechanics and Engineering Science, Peking University, Beijing 100871 (China)

    2007-12-15

    This note examines issues concerning global exponential convergence of neural networks with unbounded distributed delays. Sufficient conditions are derived by exploiting exponentially fading memory property of delay kernel functions. The method is based on comparison principle of delay differential equations and does not need the construction of any Lyapunov functionals. It is simple yet effective in deriving less conservative exponential convergence conditions and more detailed componentwise decay estimates. The results of this note and [Chu T. An exponential convergence estimate for analog neural networks with delay. Phys Lett A 2001;283:113-8] suggest a class of neural networks whose globally exponentially convergent dynamics is completely insensitive to a wide range of time delays from arbitrary bounded discrete type to certain unbounded distributed type. This is of practical interest in designing fast and reliable neural circuits. Finally, an open question is raised on the nature of delay kernels for attaining exponential convergence in an unbounded distributed delayed neural network.

  12. A note on exponential convergence of neural networks with unbounded distributed delays

    International Nuclear Information System (INIS)

    Chu Tianguang; Yang Haifeng

    2007-01-01

    This note examines issues concerning global exponential convergence of neural networks with unbounded distributed delays. Sufficient conditions are derived by exploiting exponentially fading memory property of delay kernel functions. The method is based on comparison principle of delay differential equations and does not need the construction of any Lyapunov functionals. It is simple yet effective in deriving less conservative exponential convergence conditions and more detailed componentwise decay estimates. The results of this note and [Chu T. An exponential convergence estimate for analog neural networks with delay. Phys Lett A 2001;283:113-8] suggest a class of neural networks whose globally exponentially convergent dynamics is completely insensitive to a wide range of time delays from arbitrary bounded discrete type to certain unbounded distributed type. This is of practical interest in designing fast and reliable neural circuits. Finally, an open question is raised on the nature of delay kernels for attaining exponential convergence in an unbounded distributed delayed neural network

  13. A qualitative content analysis of global health engagements in Peacekeeping and Stability Operations Institute's stability operations lessons learned and information management system.

    Science.gov (United States)

    Nang, Roberto N; Monahan, Felicia; Diehl, Glendon B; French, Daniel

    2015-04-01

    Many institutions collect reports in databases to make important lessons-learned available to their members. The Uniformed Services University of the Health Sciences collaborated with the Peacekeeping and Stability Operations Institute to conduct a descriptive and qualitative analysis of global health engagements (GHEs) contained in the Stability Operations Lessons Learned and Information Management System (SOLLIMS). This study used a summative qualitative content analysis approach involving six steps: (1) a comprehensive search; (2) two-stage reading and screening process to identify first-hand, health-related records; (3) qualitative and quantitative data analysis using MAXQDA, a software program; (4) a word cloud to illustrate word frequencies and interrelationships; (5) coding of individual themes and validation of the coding scheme; and (6) identification of relationships in the data and overarching lessons-learned. The individual codes with the most number of text segments coded included: planning, personnel, interorganizational coordination, communication/information sharing, and resources/supplies. When compared to the Department of Defense's (DoD's) evolving GHE principles and capabilities, the SOLLIMS coding scheme appeared to align well with the list of GHE capabilities developed by the Department of Defense Global Health Working Group. The results of this study will inform practitioners of global health and encourage additional qualitative analysis of other lessons-learned databases. Reprint & Copyright © 2015 Association of Military Surgeons of the U.S.

  14. Potential and flux field landscape theory. I. Global stability and dynamics of spatially dependent non-equilibrium systems.

    Science.gov (United States)

    Wu, Wei; Wang, Jin

    2013-09-28

    We established a potential and flux field landscape theory to quantify the global stability and dynamics of general spatially dependent non-equilibrium deterministic and stochastic systems. We extended our potential and flux landscape theory for spatially independent non-equilibrium stochastic systems described by Fokker-Planck equations to spatially dependent stochastic systems governed by general functional Fokker-Planck equations as well as functional Kramers-Moyal equations derived from master equations. Our general theory is applied to reaction-diffusion systems. For equilibrium spatially dependent systems with detailed balance, the potential field landscape alone, defined in terms of the steady state probability distribution functional, determines the global stability and dynamics of the system. The global stability of the system is closely related to the topography of the potential field landscape in terms of the basins of attraction and barrier heights in the field configuration state space. The effective driving force of the system is generated by the functional gradient of the potential field alone. For non-equilibrium spatially dependent systems, the curl probability flux field is indispensable in breaking detailed balance and creating non-equilibrium condition for the system. A complete characterization of the non-equilibrium dynamics of the spatially dependent system requires both the potential field and the curl probability flux field. While the non-equilibrium potential field landscape attracts the system down along the functional gradient similar to an electron moving in an electric field, the non-equilibrium flux field drives the system in a curly way similar to an electron moving in a magnetic field. In the small fluctuation limit, the intrinsic potential field as the small fluctuation limit of the potential field for spatially dependent non-equilibrium systems, which is closely related to the steady state probability distribution functional, is

  15. Global Mittag-Leffler stability analysis of fractional-order impulsive neural networks with one-side Lipschitz condition.

    Science.gov (United States)

    Zhang, Xinxin; Niu, Peifeng; Ma, Yunpeng; Wei, Yanqiao; Li, Guoqiang

    2017-10-01

    This paper is concerned with the stability analysis issue of fractional-order impulsive neural networks. Under the one-side Lipschitz condition or the linear growth condition of activation function, the existence of solution is analyzed respectively. In addition, the existence, uniqueness and global Mittag-Leffler stability of equilibrium point of the fractional-order impulsive neural networks with one-side Lipschitz condition are investigated by the means of contraction mapping principle and Lyapunov direct method. Finally, an example with numerical simulation is given to illustrate the validity and feasibility of the proposed results. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. Stability analysis for cellular neural networks with variable delays

    International Nuclear Information System (INIS)

    Zhang Qiang; Wei Xiaopeng; Xu Jin

    2006-01-01

    Some sufficient conditions for the global exponential stability of cellular neural networks with variable delay are obtained by means of a method based on delay differential inequality. The method, which does not make use of Lyapunov functionals, is simple and effective for the stability analysis of neural networks with delay. Some previously established results in the literature are shown to be special cases of the presented result

  17. Global asymptotic stability of bistable traveling fronts in reaction-diffusion systems and their applications to biological models

    International Nuclear Information System (INIS)

    Wu Shiliang; Li Wantong

    2009-01-01

    This paper deals with the global asymptotic stability and uniqueness (up to translation) of bistable traveling fronts in a class of reaction-diffusion systems. The known results do not apply in solving these problems because the reaction terms do not satisfy the required monotone condition. To overcome the difficulty, a weak monotone condition is proposed for the reaction terms, which is called interval monotone condition. Under such a weak monotone condition, the existence and comparison theorem of solutions is first established for reaction-diffusion systems on R by appealing to the theory of abstract differential equations. The global asymptotic stability and uniqueness (up to translation) of bistable traveling fronts are then proved by the elementary super- and sub-solution comparison and squeezing methods for nonlinear evolution equations. Finally, these abstract results are applied to a two species competition-diffusion model and a system modeling man-environment-man epidemics.

  18. Fully exponentially correlated wavefunctions for small atoms

    Energy Technology Data Exchange (ETDEWEB)

    Harris, Frank E. [Department of Physics, University of Utah, Salt Lake City, UT 84112 and Quantum Theory Project, University of Florida, P.O. Box 118435, Gainesville, FL 32611 (United States)

    2015-01-22

    Fully exponentially correlated atomic wavefunctions are constructed from exponentials in all the interparticle coordinates, in contrast to correlated wavefunctions of the Hylleraas form, in which only the electron-nuclear distances occur exponentially, with electron-electron distances entering only as integer powers. The full exponential correlation causes many-configuration wavefunctions to converge with expansion length more rapidly than either orbital formulations or correlated wavefunctions of the Hylleraas type. The present contribution surveys the effectiveness of fully exponentially correlated functions for the three-body system (the He isoelectronic series) and reports their application to a four-body system (the Li atom)

  19. Direction-dependent exponential biassing

    International Nuclear Information System (INIS)

    Bending, R.C.

    1974-01-01

    When Monte Carlo methods are applied to penetration problems, the use of variance reduction techniques is essential if realistic computing times are to be achieved. A technique known as direction-dependent exponential biassing is described which is simple to apply and therefore suitable for problems with difficult geometry. The material cross section in any region is multiplied by a factor which depends on the particle direction, so that particles travelling in a preferred direction ''see'' a smaller cross section than those travelling in the opposite direction. A theoretical study shows that substantial gains may be obtained, and that the choice of biassing parameter is not critical. The method has been implemented alongside other importance sampling techniques in the general Monte Carlo code SPARTAN, and results obtained for simple problems using this code are included. 4 references. (U.S.)

  20. Deformed exponentials and portfolio selection

    Science.gov (United States)

    Rodrigues, Ana Flávia P.; Guerreiro, Igor M.; Cavalcante, Charles Casimiro

    In this paper, we present a method for portfolio selection based on the consideration on deformed exponentials in order to generalize the methods based on the gaussianity of the returns in portfolio, such as the Markowitz model. The proposed method generalizes the idea of optimizing mean-variance and mean-divergence models and allows a more accurate behavior for situations where heavy-tails distributions are necessary to describe the returns in a given time instant, such as those observed in economic crises. Numerical results show the proposed method outperforms the Markowitz portfolio for the cumulated returns with a good convergence rate of the weights for the assets which are searched by means of a natural gradient algorithm.

  1. Coarse Grained Exponential Variational Autoencoders

    KAUST Repository

    Sun, Ke

    2017-02-25

    Variational autoencoders (VAE) often use Gaussian or category distribution to model the inference process. This puts a limit on variational learning because this simplified assumption does not match the true posterior distribution, which is usually much more sophisticated. To break this limitation and apply arbitrary parametric distribution during inference, this paper derives a \\\\emph{semi-continuous} latent representation, which approximates a continuous density up to a prescribed precision, and is much easier to analyze than its continuous counterpart because it is fundamentally discrete. We showcase the proposition by applying polynomial exponential family distributions as the posterior, which are universal probability density function generators. Our experimental results show consistent improvements over commonly used VAE models.

  2. Role of individual histidines in the pH-dependent global stability of human chloride intracellular channel 1.

    Science.gov (United States)

    Achilonu, Ikechukwu; Fanucchi, Sylvia; Cross, Megan; Fernandes, Manuel; Dirr, Heini W

    2012-02-07

    Chloride intracellular channel proteins exist in both a soluble cytosolic form and a membrane-bound form. The mechanism of conversion between the two forms is not properly understood, although one of the contributing factors is believed to be the variation in pH between the cytosol (~7.4) and the membrane (~5.5). We systematically mutated each of the three histidine residues in CLIC1 to an alanine at position 74 and a phenylalanine at positions 185 and 207. We examined the effect of the histidine-mediated pH dependence on the structure and global stability of CLIC1. None of the mutations were found to alter the global structure of the protein. However, the stability of H74A-CLIC1 and H185F-CLIC1, as calculated from the equilibrium unfolding data, is no longer dependent on pH because similar trends are observed at pH 7.0 and 5.5. The crystal structures show that the mutations result in changes in the local hydrogen bond coordination. Because the mutant total free energy change upon unfolding is not different from that of the wild type at pH 7.0, despite the presence of intermediates that are not seen in the wild type, we propose that it may be the stability of the intermediate state rather than the native state that is dependent on pH. On the basis of the lower stability of the intermediate in the H74A and H185F mutants compared to that of the wild type, we conclude that both His74 and His185 are involved in triggering the pH changes to the conformational stability of wild-type CLIC1 via their protonation, which stabilizes the intermediate state.

  3. Numerical simulation and global linear stability analysis of low-Re flow past a heated circular cylinder

    KAUST Repository

    Zhang, Wei

    2016-03-31

    We perform two-dimensional unsteady Navier-Stokes simulation and global linear stability analysis of flow past a heated circular cylinder to investigate the effect of aided buoyancy on the stabilization of the flow. The Reynolds number of the incoming flow is fixed at 100, and the Richardson number characterizing the buoyancy is varied from 0.00 (buoyancy-free case) to 0.10 at which the flow is still unsteady. We investigate the effect of aided buoyancy in stabilizing the wake flow, identify the temporal and spatial characteristics of the growth of the perturbation, and quantify the contributions from various terms comprising the perturbed kinetic energy budget. Numerical results reveal that the increasing Ri decreases the fluctuation magnitude of the characteristic quantities monotonically, and the momentum deficit in the wake flow decays rapidly so that the flow velocity recovers to that of the free-stream; the strain on the wake flow is reduced in the region where the perturbation is the most greatly amplified. Global stability analysis shows that the temporal growth rate of the perturbation decreases monotonically with Ri, reflecting the stabilization of the flow due to aided buoyancy. The perturbation grows most significantly in the free shear layer separated from the cylinder. As Ri increases, the location of maximum perturbation growth moves closer to the cylinder and the perturbation decays more rapidly in the far wake. The introduction of the aided buoyancy alters the base flow, and destabilizes the near wake shear layer mainly through the strain-induced transfer term and the pressure term of the perturbed kinetic energy, whereas the flow is stabilized in the far wake as the strain is alleviated. © 2016 Elsevier Ltd. All rights reserved.

  4. Numerical simulation and global linear stability analysis of low-Re flow past a heated circular cylinder

    KAUST Repository

    Zhang, Wei; Samtaney, Ravi

    2016-01-01

    We perform two-dimensional unsteady Navier-Stokes simulation and global linear stability analysis of flow past a heated circular cylinder to investigate the effect of aided buoyancy on the stabilization of the flow. The Reynolds number of the incoming flow is fixed at 100, and the Richardson number characterizing the buoyancy is varied from 0.00 (buoyancy-free case) to 0.10 at which the flow is still unsteady. We investigate the effect of aided buoyancy in stabilizing the wake flow, identify the temporal and spatial characteristics of the growth of the perturbation, and quantify the contributions from various terms comprising the perturbed kinetic energy budget. Numerical results reveal that the increasing Ri decreases the fluctuation magnitude of the characteristic quantities monotonically, and the momentum deficit in the wake flow decays rapidly so that the flow velocity recovers to that of the free-stream; the strain on the wake flow is reduced in the region where the perturbation is the most greatly amplified. Global stability analysis shows that the temporal growth rate of the perturbation decreases monotonically with Ri, reflecting the stabilization of the flow due to aided buoyancy. The perturbation grows most significantly in the free shear layer separated from the cylinder. As Ri increases, the location of maximum perturbation growth moves closer to the cylinder and the perturbation decays more rapidly in the far wake. The introduction of the aided buoyancy alters the base flow, and destabilizes the near wake shear layer mainly through the strain-induced transfer term and the pressure term of the perturbed kinetic energy, whereas the flow is stabilized in the far wake as the strain is alleviated. © 2016 Elsevier Ltd. All rights reserved.

  5. Stabilization

    Directory of Open Access Journals (Sweden)

    Muhammad H. Al-Malack

    2016-07-01

    Full Text Available Fuel oil flyash (FFA produced in power and water desalination plants firing crude oils in the Kingdom of Saudi Arabia is being disposed in landfills, which increases the burden on the environment, therefore, FFA utilization must be encouraged. In the current research, the effect of adding FFA on the engineering properties of two indigenous soils, namely sand and marl, was investigated. FFA was added at concentrations of 5%, 10% and 15% to both soils with and without the addition of Portland cement. Mixtures of the stabilized soils were thoroughly evaluated using compaction, California Bearing Ratio (CBR, unconfined compressive strength (USC and durability tests. Results of these tests indicated that stabilized sand mixtures could not attain the ACI strength requirements. However, marl was found to satisfy the ACI strength requirement when only 5% of FFA was added together with 5% of cement. When the FFA was increased to 10% and 15%, the mixture’s strength was found to decrease to values below the ACI requirements. Results of the Toxicity Characteristics Leaching Procedure (TCLP, which was performed on samples that passed the ACI requirements, indicated that FFA must be cautiously used in soil stabilization.

  6. Lupus nephritis: prolonged immunoadsorption (IAS) reduces proteinuria and stabilizes global disease activity.

    Science.gov (United States)

    Stummvoll, Georg H; Schmaldienst, Sabine; Smolen, Josef S; Derfler, Kurt; Biesenbach, Peter

    2012-02-01

    Systemic lupus erythematosus (SLE) is characterized by pathogenic autoantibodies, which can be removed by extracorporeal procedures. While previous studies have shown short-term efficacy of immunoadsorption (IAS) in SLE, no information on long-term benefit and safety is available. IAS was offered to patients with highly active renal disease when conventional therapy had failed. Eleven patients entered the prolonged IAS programme and were followed for up to 10 years (mean 6.4 ± 3.5). Efficacy of IAS was determined by reduction in proteinuria (primary outcome), global disease activity [SLE Disease Activity Index (SLEDAI)] and anti-double-stranded DNA (anti-dsDNA) levels (secondary outcomes). Full/partial remission was defined as ≤ 0.5/≤ 1.0 g/day for proteinuria, ≤ 5/≤ 8 for SLEDAI and ≤ 25/≤ 50 IU/mL for anti-dsDNA levels. We further assessed flares, infections, malignancies and procedure-related adverse events. Short-term IAS (≤ 1 year) resulted in a significant reduction of proteinuria (9.2 ± 3.7 to 2.3 ± 2.4, P = 0.0001), disease activity (SLEDAI 19 ± 8 to 4 ± 2, P = 0.0004) and dsDNA levels (168 ± 205 to 45 ± 34, P = 0.001). In patients without remission after 1 year (n = 5), prolonged IAS decreased proteinuria from 4.3 ± 2.4 to 0.5 ± 0.4 g/day, P = 0.02. At the end of observation, complete remission in proteinuria was achieved in seven patients (64%) and partial remission in two (18%) additional patients. One patient flared and was discontinued; in all other patients, disease activity and anti-dsDNA stabilized at remission levels. Flares (0.28 ± 0.30) and infections (0.66 ± 0.70 per patient/year) were relatively uncommon; no malignancies, anaphylactic or orthostatic adverse events were observed. IAS is effective in short-term use but prolonged IAS can provide additional therapeutic benefit while showing an acceptable safety profile. The vast majority of initially therapy-refractory patients met the remission criteria at the end of

  7. Stability of the stratifield cylindrical annulus flow. [toward a model of global atmospheric circulation

    Science.gov (United States)

    Antar, B. N.

    1980-01-01

    The linear stability analysis for the stratified flow between two rotating circular cylinders is formulated. Two approaches for the stability analysis are presented. The first approach results in an algebraic eigenvalue problem, while the second results in an initial value problem for the perturbation function. The advantages and disadvantages of both approaches are discussed and a preferable numerical solution technique is outlined.

  8. Robust and global delay-dependent stability for genetic regulatory networks with parameter uncertainties.

    Science.gov (United States)

    Tian, Li-Ping; Wang, Jianxin; Wu, Fang-Xiang

    2012-09-01

    The study of stability is essential for designing or controlling genetic regulatory networks, which can be described by nonlinear differential equations with time delays. Much attention has been paid to the study of delay-independent stability of genetic regulatory networks and as a result, many sufficient conditions have been derived for delay-independent stability. Although it might be more interesting in practice, delay-dependent stability of genetic regulatory networks has been studied insufficiently. Based on the linear matrix inequality (LMI) approach, in this study we will present some delay-dependent stability conditions for genetic regulatory networks. Then we extend these results to genetic regulatory networks with parameter uncertainties. To illustrate the effectiveness of our theoretical results, gene repressilatory networks are analyzed .

  9. Stability of Almost Periodic Solution for a General Class of Discontinuous Neural Networks with Mixed Time-Varying Delays

    Directory of Open Access Journals (Sweden)

    Yingwei Li

    2013-01-01

    Full Text Available The global exponential stability issues are considered for almost periodic solution of the neural networks with mixed time-varying delays and discontinuous neuron activations. Some sufficient conditions for the existence, uniqueness, and global exponential stability of almost periodic solution are achieved in terms of certain linear matrix inequalities (LMIs, by applying differential inclusions theory, matrix inequality analysis technique, and generalized Lyapunov functional approach. In addition, the existence and asymptotically almost periodic behavior of the solution of the neural networks are also investigated under the framework of the solution in the sense of Filippov. Two simulation examples are given to illustrate the validity of the theoretical results.

  10. Time-resolved infrared stimulated luminescence signals in feldspars: Analysis based on exponential and stretched exponential functions

    International Nuclear Information System (INIS)

    Pagonis, V.; Morthekai, P.; Singhvi, A.K.; Thomas, J.; Balaram, V.; Kitis, G.; Chen, R.

    2012-01-01

    Time-resolved infrared-stimulated luminescence (TR-IRSL) signals from feldspar samples have been the subject of several recent experimental studies. These signals are of importance in the field of luminescence dating, since they exhibit smaller fading effects than the commonly employed continuous-wave infrared signals (CW-IRSL). This paper presents a semi-empirical analysis of TR-IRSL data from feldspar samples, by using a linear combination of exponential and stretched exponential (SE) functions. The best possible estimates of the five parameters in this semi-empirical approach are obtained using five popular commercially available software packages, and by employing a variety of global optimization techniques. The results from all types of software and from the different fitting algorithms were found to be in close agreement with each other, indicating that a global optimum solution has likely been reached during the fitting process. Four complete sets of TR-IRSL data on well-characterized natural feldspars were fitted by using such a linear combination of exponential and SE functions. The dependence of the extracted fitting parameters on the stimulation temperature is discussed within the context of a recently proposed model of luminescence processes in feldspar. Three of the four feldspar samples studied in this paper are K-rich, and these exhibited different behavior at higher stimulation temperatures, than the fourth sample which was a Na-rich feldspar. The new method of analysis proposed in this paper can help isolate mathematically the more thermally stable components, and hence could lead to better dating applications in these materials. - Highlights: ► TR-IRSL from four feldspars were analyzed using exponential and stretched exponential functions. ► A variety of global optimization techniques give good agreement. ► Na-rich sample behavior is different from the three K-rich samples. ► Experimental data are fitted for stimulation temperatures

  11. Greenhouse gas emission reduction scenarios for BC : meeting the twin objectives of temperature stabilization and global equity

    International Nuclear Information System (INIS)

    Campbell, C.R.

    2008-08-01

    Greenhouse gas (GHG) emissions reduction strategies are needed in order to prevent rises in global temperatures. This report presented 6 GHG emission scenarios conducted to understand the kind of contribution that the province of British Columbia (BC) might make towards reducing global warming in the future. Short, medium, and longer term GHG reduction targets were benchmarked. The University of Victoria earth system climate model was used to calculate emission pathways where global average temperature did not exceed 2 degrees C above pre-industrial values, and where atmospheric GHGs were stabilized at 400 ppm of carbon dioxide equivalent (CO 2 e). Global carbon emission budgets of the total amount of GHG emissions permissible between now and 2100 were identified. A carbon emission budget for 2008 to 2100 was then developed based on the population of BC. Average annual emission reduction rates for the world and for BC were also identified. It was concluded that dramatically reduced emissions will be insufficient to achieve an equilibrium temperature less than 2 degrees C above pre-industrial levels. Global reductions of greater than 80 per cent are needed to prevent unacceptable levels of ocean acidification. Results suggested that carbon sequestration technologies may need to be used to remove CO 2 from the atmosphere by artificial means. 38 refs., 5 tabs., 4 figs

  12. Convective and global stability analysis of a Mach 5.8 boundary layer grazing a compliant surface

    Science.gov (United States)

    Dettenrieder, Fabian; Bodony, Daniel

    2016-11-01

    Boundary layer transition on high-speed vehicles is expected to be affected by unsteady surface compliance. The stability properties of a Mach 5.8 zero-pressure-gradient laminar boundary layer grazing a nominally-flat thermo-mechanically compliant panel is considered. The linearized compressible Navier-Stokes equations describe small amplitude disturbances in the fluid while the panel deformations are described by the Kirchhoff-Love plate equation and its thermal state by the transient heat equation. Compatibility conditions that couple disturbances in the fluid to those in the solid yield simple algebraic and robin boundary conditions for the velocity and thermal states, respectively. A local convective stability analysis shows that the panel can modify both the first and second Mack modes when, for metallic-like panels, the panel thickness exceeds the lengthscale δ99 Rex- 0 . 5 . A global stability analysis, which permits finite panel lengths with clamped-clamped boundary conditions, shows a rich eigenvalue spectrum with several branches. Unstable modes are found with streamwise-growing panel deformations leading to Mach wave-type radiation. Stable global modes are also found and have distinctly different panel modes but similar radiation patterns. Air Force Office of Scientific Research.

  13. Stability of the Global Alfven Eigenmode in the presence of fusion alpha particles in an ignited tokamak plasma

    International Nuclear Information System (INIS)

    Fu, G.Y.; Van Dam, J.W.

    1989-05-01

    The stability of the Global Alfven Eigenmodes is investigated in the presence of super-Alfvenic energetic particles, such as the fusion-product alpha particles in an ignited deuterium-tritium tokamak plasma. Alpha particles tend to destabilize these modes when ω *α > ω A , where ω A is the shear-Alfven modal frequency and ω *α is the alpha particle diamagnetic drift frequency. This destabilization due to alpha particles is found to be significantly enhanced when the alpha particles are modeled with a slowing-down distribution function rather than with a Maxwellian. However, previously neglected electron damping due to the magnetic curvature drift is found to be comparable in magnitude to the destabilizing alpha particle term. Furthermore, the effects of toroidicity are also found to be stabilizing, since the intrinsic toroidicity induces poloidal mode coupling, which enhances the parallel electron damping from the sideband shear-Alfven Landau resonance. In particular, for the parameters of the proposed Compact Ignition Tokamak, the Global Alfven Eigenmodes are found to be completely stabilized by either the electron damping that enters through the magnetic curvature drift or the damping introduced by finite toroidicity. 29 refs., 8 figs., 1 tab

  14. Exponential Hilbert series of equivariant embeddings

    OpenAIRE

    Johnson, Wayne A.

    2018-01-01

    In this article, we study properties of the exponential Hilbert series of a $G$-equivariant projective variety, where $G$ is a semisimple, simply-connected complex linear algebraic group. We prove a relationship between the exponential Hilbert series and the degree and dimension of the variety. We then prove a combinatorial identity for the coefficients of the polynomial representing the exponential Hilbert series. This formula is used in examples to prove further combinatorial identities inv...

  15. The carbon-budget approach to climate stabilization: Cost-effective subglobal versus global action

    OpenAIRE

    Eichner, Thomas; Pethig, Rüdiger

    2010-01-01

    Scientific expertise suggests that mitigating extreme world-wide climate change damages requires avoiding increases in the world mean temperature exceeding 2 degrees Celsius. To achieve the two degree target, the cumulated global emissions must not exceed some limit, the so-called global carbon budget. In a two-period two country general equilibrium model with a finite stock of fossil fuels we compare the cooperative cost-effective policy with the unilateral cost-effective policy of restricti...

  16. The carbon-budget approach to climate stabilization: Costeffective subglobal versus global action

    OpenAIRE

    Eichner, Thomas; Pethig, Rüdiger

    2010-01-01

    Scientific expertise suggests that mitigating extreme world-wide climate change damages requires avoiding increases in the world mean temperature exceeding 2ê Celsius. To achieve the two degree target, the cumulated global emissions must not exceed some limit, the so-called global carbon budget. In a two-period twocountry general equilibrium model with a finite stock of fossil fuels we compare the cooperative cost-effective policy with the unilateral cost-effective policy of restricting emiss...

  17. Global insights into acetic acid resistance mechanisms and genetic stability of Acetobacter pasteurianus strains by comparative genomics

    Science.gov (United States)

    Wang, Bin; Shao, Yanchun; Chen, Tao; Chen, Wanping; Chen, Fusheng

    2015-12-01

    Acetobacter pasteurianus (Ap) CICC 20001 and CGMCC 1.41 are two acetic acid bacteria strains that, because of their strong abilities to produce and tolerate high concentrations of acetic acid, have been widely used to brew vinegar in China. To globally understand the fermentation characteristics, acid-tolerant mechanisms and genetic stabilities, their genomes were sequenced. Genomic comparisons with 9 other sequenced Ap strains revealed that their chromosomes were evolutionarily conserved, whereas the plasmids were unique compared with other Ap strains. Analysis of the acid-tolerant metabolic pathway at the genomic level indicated that the metabolism of some amino acids and the known mechanisms of acetic acid tolerance, might collaboratively contribute to acetic acid resistance in Ap strains. The balance of instability factors and stability factors in the genomes of Ap CICC 20001 and CGMCC 1.41 strains might be the basis for their genetic stability, consistent with their stable industrial performances. These observations provide important insights into the acid resistance mechanism and the genetic stability of Ap strains and lay a foundation for future genetic manipulation and engineering of these two strains.

  18. Global rotational motion and displacement estimation of digital image stabilization based on the oblique vectors matching algorithm

    Science.gov (United States)

    Yu, Fei; Hui, Mei; Zhao, Yue-jin

    2009-08-01

    The image block matching algorithm based on motion vectors of correlative pixels in oblique direction is presented for digital image stabilization. The digital image stabilization is a new generation of image stabilization technique which can obtains the information of relative motion among frames of dynamic image sequences by the method of digital image processing. In this method the matching parameters are calculated from the vectors projected in the oblique direction. The matching parameters based on the vectors contain the information of vectors in transverse and vertical direction in the image blocks at the same time. So the better matching information can be obtained after making correlative operation in the oblique direction. And an iterative weighted least square method is used to eliminate the error of block matching. The weights are related with the pixels' rotational angle. The center of rotation and the global emotion estimation of the shaking image can be obtained by the weighted least square from the estimation of each block chosen evenly from the image. Then, the shaking image can be stabilized with the center of rotation and the global emotion estimation. Also, the algorithm can run at real time by the method of simulated annealing in searching method of block matching. An image processing system based on DSP was used to exam this algorithm. The core processor in the DSP system is TMS320C6416 of TI, and the CCD camera with definition of 720×576 pixels was chosen as the input video signal. Experimental results show that the algorithm can be performed at the real time processing system and have an accurate matching precision.

  19. 4th Global CRO Council for Bioanalysis: coadministered drugs stability, EMA/US FDA guidelines, 483s and carryover.

    Science.gov (United States)

    Lowes, Steve; Jersey, Jim; Shoup, Ronald; Garofolo, Fabio; Needham, Shane; Couerbe, Philippe; Lansing, Tim; Bhatti, Masood; Sheldon, Curtis; Hayes, Roger; Islam, Rafiq; Lin, Zhongping; Garofolo, Wei; Moussallie, Marc; Teixeira, Leonardo de Souza; Rocha, Thais; Jardieu, Paula; Truog, James; Lin, Jenny; Lundberg, Richard; Breau, Alan; Dilger, Carmen; Bouhajib, Mohammed; Levesque, Ann; Gagnon-Carignan, Sofi; Jenkins, Rand; Nicholson, Robert; Lin, Ming Hung; Karnik, Shane; DeMaio, William; Smith, Kirk; Cojocaru, Laura; Allen, Mike; Fatmi, Saadya; Sayyarpour, Farhad; Malone, Michele; Fang, Xinping

    2012-04-01

    The Global CRO Council for Bioanalysis (GCC) was formed in September 2010. Since then, the representatives of the member companies come together periodically to openly discuss bioanalysis and the regulatory challenges unique to the outsourcing industry. The 4th GCC Closed Forum brought together experts from bioanalytical CROs to share and discuss recent issues in regulated bioanalysis, such as the impact of coadministered drugs on stability, some differences between European Medicines Agency and US FDA bioanalytical guidance documents and lessons learned following recent Untitled Letters. Recent 483s and agency findings, as well as issues on method carryover, were also part of the topics discussed.

  20. Stability of Delayed Hopfield Neural Networks with Variable-Time Impulses

    Directory of Open Access Journals (Sweden)

    Yangjun Pei

    2014-01-01

    Full Text Available In this paper the globally exponential stability criteria of delayed Hopfield neural networks with variable-time impulses are established. The proposed criteria can also be applied in Hopfield neural networks with fixed-time impulses. A numerical example is presented to illustrate the effectiveness of our theoretical results.

  1. Global stability for infectious disease models that include immigration of infected individuals and delay in the incidence

    Directory of Open Access Journals (Sweden)

    Chelsea Uggenti

    2018-03-01

    Full Text Available We begin with a detailed study of a delayed SI model of disease transmission with immigration into both classes. The incidence function allows for a nonlinear dependence on the infected population, including mass action and saturating incidence as special cases. Due to the immigration of infectives, there is no disease-free equilibrium and hence no basic reproduction number. We show there is a unique endemic equilibrium and that this equilibrium is globally asymptotically stable for all parameter values. The results include vector-style delay and latency-style delay. Next, we show that previous global stability results for an SEI model and an SVI model that include immigration of infectives and non-linear incidence but not delay can be extended to systems with vector-style delay and latency-style delay.

  2. Stability and special metrics for complex vector bundles with global sections

    International Nuclear Information System (INIS)

    Xi Zhang

    2004-07-01

    In this paper, we study one kind of vortex equations on complex vector bundles over almost Hermitian manifolds and prove a Hitchin-Kobayashi type correspondence relating the existence of solutions of these vortex equations to a certain stability condition. (author)

  3. Globalization

    Directory of Open Access Journals (Sweden)

    Tulio Rosembuj

    2006-12-01

    Full Text Available There is no singular globalization, nor is the result of an individual agent. We could start by saying that global action has different angles and subjects who perform it are different, as well as its objectives. The global is an invisible invasion of materials and immediate effects.

  4. Globalization

    OpenAIRE

    Tulio Rosembuj

    2006-01-01

    There is no singular globalization, nor is the result of an individual agent. We could start by saying that global action has different angles and subjects who perform it are different, as well as its objectives. The global is an invisible invasion of materials and immediate effects.

  5. Method for nonlinear exponential regression analysis

    Science.gov (United States)

    Junkin, B. G.

    1972-01-01

    Two computer programs developed according to two general types of exponential models for conducting nonlinear exponential regression analysis are described. Least squares procedure is used in which the nonlinear problem is linearized by expanding in a Taylor series. Program is written in FORTRAN 5 for the Univac 1108 computer.

  6. Multivariate Marshall and Olkin Exponential Minification Process ...

    African Journals Online (AJOL)

    A stationary bivariate minification process with bivariate Marshall-Olkin exponential distribution that was earlier studied by Miroslav et al [15]is in this paper extended to multivariate minification process with multivariate Marshall and Olkin exponential distribution as its stationary marginal distribution. The innovation and the ...

  7. On Uniform Exponential Trichotomy in Banach Spaces

    Directory of Open Access Journals (Sweden)

    Kovacs Monteola Ilona

    2014-06-01

    Full Text Available In this paper we consider three concepts of uniform exponential trichotomy on the half-line in the general framework of evolution operators in Banach spaces. We obtain a systematic classification of uniform exponential trichotomy concepts and the connections between them.

  8. Dual exponential polynomials and linear differential equations

    Science.gov (United States)

    Wen, Zhi-Tao; Gundersen, Gary G.; Heittokangas, Janne

    2018-01-01

    We study linear differential equations with exponential polynomial coefficients, where exactly one coefficient is of order greater than all the others. The main result shows that a nontrivial exponential polynomial solution of such an equation has a certain dual relationship with the maximum order coefficient. Several examples illustrate our results and exhibit possibilities that can occur.

  9. Does proton decay follow the exponential law

    International Nuclear Information System (INIS)

    Sanchez-Gomez, J.L.; Alvarez-Estrada, R.F.; Fernandez, L.A.

    1984-01-01

    In this paper, we discuss the exponential law for proton decay. By using a simple model based upon SU(5)GUT and the current theories of hadron structure, we explicitely show that the corrections to the Wigner-Weisskopf approximation are quite negligible for present day protons, so that their eventual decay should follow the exponential law. Previous works are critically analyzed. (orig.)

  10. Global stability of an SIR model with differential infectivity on complex networks

    Science.gov (United States)

    Yuan, Xinpeng; Wang, Fang; Xue, Yakui; Liu, Maoxing

    2018-06-01

    In this paper, an SIR model with birth and death on complex networks is analyzed, where infected individuals are divided into m groups according to their infection and contact between human is treated as a scale-free social network. We obtain the basic reproduction number R0 as well as the effects of various immunization schemes. The results indicate that the disease-free equilibrium is locally and globally asymptotically stable in some conditions, otherwise disease-free equilibrium is unstable and exists an unique endemic equilibrium that is globally asymptotically stable. Our theoretical results are confirmed by numerical simulations and a promising way for infectious diseases control is suggested.

  11. Global asymptotic stability of a delayed SEIRS epidemic model with saturation incidence

    International Nuclear Information System (INIS)

    Zhang Tailei; Teng Zhidong

    2008-01-01

    In this paper, the asymptotic behavior of solutions of an autonomous SEIRS epidemic model with the saturation incidence is studied. Using the method of Liapunov-LaSalle invariance principle, we obtain the disease-free equilibrium is globally stable if the basic reproduction number is not greater than one. Moreover, we show that the disease is permanent if the basic reproduction number is greater than one. Furthermore, the sufficient conditions of locally and globally asymptotically stable convergence to an endemic equilibrium are obtained base on the permanence

  12. Stability of Global Alfven Waves (Tae, Eae) in Jet Tritium Discharges

    NARCIS (Netherlands)

    Kerner, W.; Borba, D.; Huysmans, G. T. A.; Porcelli, F.; Poedts, S.; Goedbloed, J. P.; Betti, R.

    1994-01-01

    The interaction of alpha-particles in JET tritium discharges with global Alfven waves via inverse Landau damping is analysed. It is found that alpha-particle driven eigenmodes were stable in the PTE1 and should also be stable in a future 50:50 deuterium-tritium mix discharge aiming at Q(DT) = 1,

  13. Dependency of global primary bioenergy crop potentials in 2050 on food systems, yields, biodiversity conservation and political stability

    International Nuclear Information System (INIS)

    Erb, Karl-Heinz; Haberl, Helmut; Plutzar, Christoph

    2012-01-01

    The future bioenergy crop potential depends on (1) changes in the food system (food demand, agricultural technology), (2) political stability and investment security, (3) biodiversity conservation, (4) avoidance of long carbon payback times from deforestation, and (5) energy crop yields. Using a biophysical biomass-balance model, we analyze how these factors affect global primary bioenergy potentials in 2050. The model calculates biomass supply and demand balances for eleven world regions, eleven food categories, seven food crop types and two livestock categories, integrating agricultural forecasts and scenarios with a consistent global land use and NPP database. The TREND scenario results in a global primary bioenergy potential of 77 EJ/yr, alternative assumptions on food-system changes result in a range of 26–141 EJ/yr. Exclusion of areas for biodiversity conservation and inaccessible land in failed states reduces the bioenergy potential by up to 45%. Optimistic assumptions on future energy crop yields increase the potential by up to 48%, while pessimistic assumptions lower the potential by 26%. We conclude that the design of sustainable bioenergy crop production policies needs to resolve difficult trade-offs such as food vs. energy supply, renewable energy vs. biodiversity conservation or yield growth vs. reduction of environmental problems of intensive agriculture. - Highlights: ► Global energy crop potentials in 2050 are calculated with a biophysical biomass-balance model. ► The study is focused on dedicated energy crops, forestry and residues are excluded. ► Depending on food-system change, global energy crop potentials range from 26–141 EJ/yr. ► Exclusion of protected areas and failed states may reduce the potential up to 45%. ► The bioenergy potential may be 26% lower or 45% higher, depending on energy crop yields.

  14. Globalization

    OpenAIRE

    Andru?cã Maria Carmen

    2013-01-01

    The field of globalization has highlighted an interdependence implied by a more harmonious understanding determined by the daily interaction between nations through the inducement of peace and the management of streamlining and the effectiveness of the global economy. For the functioning of the globalization, the developing countries that can be helped by the developed ones must be involved. The international community can contribute to the institution of the development environment of the gl...

  15. Global asymptotic stabilization of large-scale hydraulic networks using positive proportional controls

    DEFF Research Database (Denmark)

    Jensen, Tom Nørgaard; Wisniewski, Rafal

    2014-01-01

    An industrial case study involving a large-scale hydraulic network underlying a district heating system subject to structural changes is considered. The problem of controlling the pressure drop across the so-called end-user valves in the network to a designated vector of reference values under...... directional actuator constraints is addressed. The proposed solution consists of a set of decentralized positively constrained proportional control actions. The results show that the closed-loop system always has a globally asymptotically stable equilibrium point independently on the number of end......-users. Furthermore, by a proper design of controller gains the closed-loop equilibrium point can be designed to belong to an arbitrarily small neighborhood of the desired equilibrium point. Since there exists a globally asymptotically stable equilibrium point independently on the number of end-users in the system...

  16. Effect of compressibility on the global stability of axisymmetric wake flows

    OpenAIRE

    Meliga , Philippe; Sipp , D.; Chomaz , Jean-Marc

    2010-01-01

    International audience; We study the linear dynamics of global eigenmodes in compressible axisymmetric wake flows, up to the high subsonic regime. We consider both an afterbody flow at zero angle of attack and a sphere, and find that the sequence of bifurcations destabilizing the axisymmetric steady flow is independent of the Mach number and reminiscent of that documented in the incompressible wake past a sphere and a disk (Natarajan & Acrivos, J. Fluid Mech., vol. 254, 1993, p. 323), hence s...

  17. Global instability of currencies: reasons and perspectives according to the state-corporation hegemonic stability theory

    Directory of Open Access Journals (Sweden)

    DARIUSZ ELIGIUSZ STASZCZAK

    2015-03-01

    Full Text Available This paper analyses reasons of the instability of the world monetary system. The author considers this problem from historical and contemporary perspectives. According to presented point of view banknotes and electronic money which replaced gold and silver coins in popular circulation are the most important reason of the instability. There are also proven positive and negative consequences of money instability. Reforms of the world monetary system need agreement within the global collective hegemony of state-powers and transnational corporations.

  18. Global stability and existence of periodic solutions of discrete delayed cellular neural networks

    International Nuclear Information System (INIS)

    Li Yongkun

    2004-01-01

    We use the continuation theorem of coincidence degree theory and Lyapunov functions to study the existence and stability of periodic solutions for the discrete cellular neural networks (CNNs) with delays xi(n+1)=xi(n)e-bi(n)h+θi(h)-bar j=1maij(n)fj(xj(n))+θi(h)-bar j=1mbij(n)fj(xj(n- τij(n)))+θi(h)Ii(n),i=1,2,...,m. We obtain some sufficient conditions to ensure that for the networks there exists a unique periodic solution, and all its solutions converge to such a periodic solution

  19. Exponential Frequency Spectrum in Magnetized Plasmas

    International Nuclear Information System (INIS)

    Pace, D. C.; Shi, M.; Maggs, J. E.; Morales, G. J.; Carter, T. A.

    2008-01-01

    Measurements of a magnetized plasma with a controlled electron temperature gradient show the development of a broadband spectrum of density and temperature fluctuations having an exponential frequency dependence at frequencies below the ion cyclotron frequency. The origin of the exponential frequency behavior is traced to temporal pulses of Lorentzian shape. Similar exponential frequency spectra are also found in limiter-edge plasma turbulence associated with blob transport. This finding suggests a universal feature of magnetized plasma turbulence leading to nondiffusive, cross-field transport, namely, the presence of Lorentzian shaped pulses

  20. Matrix-exponential description of radiative transfer

    International Nuclear Information System (INIS)

    Waterman, P.C.

    1981-01-01

    By appling the matrix-exponential operator technique to the radiative-transfer equation in discrete form, new analytical solutions are obtained for the transmission and reflection matrices in the limiting cases x >1, where x is the optical depth of the layer. Orthongonality of the eigenvectors of the matrix exponential apparently yields new conditions for determining. Chandrasekhar's characteristic roots. The exact law of reflection for the discrete eigenfunctions is also obtained. Finally, when used in conjuction with the doubling method, the matrix exponential should result in reduction in both computation time and loss of precision

  1. Stability of strong species interactions resist the synergistic effects of local and global pollution in kelp forests.

    Directory of Open Access Journals (Sweden)

    Laura J Falkenberg

    Full Text Available Foundation species, such as kelp, exert disproportionately strong community effects and persist, in part, by dominating taxa that inhibit their regeneration. Human activities which benefit their competitors, however, may reduce stability of communities, increasing the probability of phase-shifts. We tested whether a foundation species (kelp would continue to inhibit a key competitor (turf-forming algae under moderately increased local (nutrient and near-future forecasted global pollution (CO(2. Our results reveal that in the absence of kelp, local and global pollutants combined to cause the greatest cover and mass of turfs, a synergistic response whereby turfs increased more than would be predicted by adding the independent effects of treatments (kelp absence, elevated nutrients, forecasted CO(2. The positive effects of nutrient and CO(2 enrichment on turfs were, however, inhibited by the presence of kelp, indicating the competitive effect of kelp was stronger than synergistic effects of moderate enrichment of local and global pollutants. Quantification of physicochemical parameters within experimental mesocosms suggests turf inhibition was likely due to an effect of kelp on physical (i.e. shading rather than chemical conditions. Such results indicate that while forecasted climates may increase the probability of phase-shifts, maintenance of intact populations of foundation species could enable the continued strength of interactions and persistence of communities.

  2. Dependency of global primary bioenergy crop potentials in 2050 on food systems, yields, biodiversity conservation and political stability.

    Science.gov (United States)

    Erb, Karl-Heinz; Haberl, Helmut; Plutzar, Christoph

    2012-08-01

    The future bioenergy crop potential depends on (1) changes in the food system (food demand, agricultural technology), (2) political stability and investment security, (3) biodiversity conservation, (4) avoidance of long carbon payback times from deforestation, and (5) energy crop yields. Using a biophysical biomass-balance model, we analyze how these factors affect global primary bioenergy potentials in 2050. The model calculates biomass supply and demand balances for eleven world regions, eleven food categories, seven food crop types and two livestock categories, integrating agricultural forecasts and scenarios with a consistent global land use and NPP database. The TREND scenario results in a global primary bioenergy potential of 77 EJ/yr, alternative assumptions on food-system changes result in a range of 26-141 EJ/yr. Exclusion of areas for biodiversity conservation and inaccessible land in failed states reduces the bioenergy potential by up to 45%. Optimistic assumptions on future energy crop yields increase the potential by up to 48%, while pessimistic assumptions lower the potential by 26%. We conclude that the design of sustainable bioenergy crop production policies needs to resolve difficult trade-offs such as food vs. energy supply, renewable energy vs. biodiversity conservation or yield growth vs. reduction of environmental problems of intensive agriculture.

  3. Stability and Scalability of the CMS Global Pool: Pushing HTCondor and GlideinWMS to New Limits

    Energy Technology Data Exchange (ETDEWEB)

    Balcas, J. [Caltech; Bockelman, B. [Nebraska U.; Hufnagel, D. [Fermilab; Hurtado Anampa, K. [Notre Dame U.; Aftab Khan, F. [NCP, Islamabad; Larson, K. [Fermilab; Letts, J. [UC, San Diego; Marra da Silva, J. [Sao Paulo, IFT; Mascheroni, M. [Fermilab; Mason, D. [Fermilab; Perez-Calero Yzquierdo, A. [Madrid, CIEMAT; Tiradani, A. [Fermilab

    2017-11-22

    The CMS Global Pool, based on HTCondor and glideinWMS, is the main computing resource provisioning system for all CMS workflows, including analysis, Monte Carlo production, and detector data reprocessing activities. The total resources at Tier-1 and Tier-2 grid sites pledged to CMS exceed 100,000 CPU cores, while another 50,000 to 100,000 CPU cores are available opportunistically, pushing the needs of the Global Pool to higher scales each year. These resources are becoming more diverse in their accessibility and configuration over time. Furthermore, the challenge of stably running at higher and higher scales while introducing new modes of operation such as multi-core pilots, as well as the chaotic nature of physics analysis workflows, places huge strains on the submission infrastructure. This paper details some of the most important challenges to scalability and stability that the CMS Global Pool has faced since the beginning of the LHC Run II and how they were overcome.

  4. Linear analysis of sheared flow stabilization of global magnetohydrodynamic instabilities based on the Hall fluid model

    International Nuclear Information System (INIS)

    Sotnikov, V.I.; Paraschiv, I.; Makhin, V.; Bauer, B.S.; Leboeuf, J.N.; Dawson, J.M.

    2002-01-01

    A systematic study of the linear stage of sheared flow stabilization of Z-pinch plasmas based on the Hall fluid model with equilibrium that contains sheared flow and an axial magnetic field is presented. In the study we begin with the derivation of a general set of equations that permits the evaluation of the combined effect of sheared flow and axial magnetic field on the development of the azimuthal mode number m=0 sausage and m=1 kink magnetohydrodynamic (MHD) instabilities, with the Hall term included in the model. The incorporation of sheared flow, axial magnetic field, and the Hall term allows the Z-pinch system to be taken away from the region in parameter space where ideal MHD is applicable to a regime where nonideal effects tend to govern stability. The problem is then treated numerically by following the linear development in time of an initial perturbation. The numerical results for linear growth rates as a function of axial sheared flow, an axial magnetic field, and the Hall term are reported

  5. Impact of credit information on the banks stability: Global experience and lessons for Ukraine

    Directory of Open Access Journals (Sweden)

    Inna Bielova

    2016-05-01

    Full Text Available A quality of the credit portfolio is one of the most important factors of banking system reliability. It is obviously, that there is a direct relationship between this indicator and financial stability of the bank. In turn, the quality of the loan portfolio depends on many factors that are investigated in scientific and educational literature. In this paper, we propose to focus on a group of factors of credit risk that are connected with the availability of information about the borrower. The low efficiency of the national system of collecting information about borrowers in Ukraine in comparison with foreign models was confirmed by the quantitative analysis. This tendency cases the high level of credit risks and low financial stability level of domestic banks. It is necessary to make active efforts on improving the effectiveness of credit bureaus in Ukraine by establishing public credit registry and also to focus on solving other problems associated with the collection and use of information about borrowers

  6. Analysis of global warming stabilization scenarios. The Asian-Pacific Integrated Model

    International Nuclear Information System (INIS)

    Kainuma, Mikiko; Morita, Tsuneyuki; Masui, Toshihiko; Takahashi, Kiyoshi; Matsuoka, Yuzuru

    2004-01-01

    This paper analyzes the economic and climatic impacts of the EMF 19 emission scenarios. A reference scenario, three emission scenarios targeting 550 ppmv atmospheric concentration, and three tax scenarios are analyzed. The profiles of energy consumption and economic losses of each policy scenario are compared to the reference scenario. The model also estimates that global mean temperature will increase 1.7-2.9 C in 2100, and the sea level will rise 40-51 cm, compared to the 1990 levels under the EMF scenarios. Impacts on food productivity and malaria infection are estimated to be very severe in some countries in the Asian region

  7. When the feasibility of an ecosystem is sufficient for global stability?

    Science.gov (United States)

    Porati, A; Granero, M I

    2000-01-01

    We show via a Liapunov function that in every model ecosystem governed by generalized Lotka-Volterra equations, a feasible steady state is globally asymptotically stable if the number of interaction branches equals n-1, where n is the number of species. This means that the representative graph for which the theorem holds is a 'tree' and not only an alimentary chain. Our result is valid also in the case of non-homogeneous systems, which model situations in which input fluxes are present.

  8. A Novel Organic Rankine Cycle System with Improved Thermal Stability and Low Global Warming Fluids

    Directory of Open Access Journals (Sweden)

    Panesar Angad S

    2014-07-01

    Full Text Available This paper proposes a novel Organic Rankine Cycle (ORC system for long haul truck application. Rather than typical tail pipe heat recovery configurations, the proposed setup exploits the gaseous streams that are already a load on the engine cooling module. The system uses dual loops connected only by the Exhaust Gas Recirculation (EGR stream. A water blend study is conducted to identify suitable mixtures for the High Temperature (HT loop, while the Low Temperature (LT loop utilises a Low Global Warming (GWP Hydrofluoroether.

  9. Stabilization of model-based networked control systems

    Energy Technology Data Exchange (ETDEWEB)

    Miranda, Francisco [CIDMA, Universidade de Aveiro, Aveiro (Portugal); Instituto Politécnico de Viana do Castelo, Viana do Castelo (Portugal); Abreu, Carlos [Instituto Politécnico de Viana do Castelo, Viana do Castelo (Portugal); CMEMS-UMINHO, Universidade do Minho, Braga (Portugal); Mendes, Paulo M. [CMEMS-UMINHO, Universidade do Minho, Braga (Portugal)

    2016-06-08

    A class of networked control systems called Model-Based Networked Control Systems (MB-NCSs) is considered. Stabilization of MB-NCSs is studied using feedback controls and simulation of stabilization for different feedbacks is made with the purpose to reduce the network trafic. The feedback control input is applied in a compensated model of the plant that approximates the plant dynamics and stabilizes the plant even under slow network conditions. Conditions for global exponential stabilizability and for the choosing of a feedback control input for a given constant time between the information moments of the network are derived. An optimal control problem to obtain an optimal feedback control is also presented.

  10. On the formation of exponential discs

    International Nuclear Information System (INIS)

    Yoshii, Yuzuru; Sommer-Larsen, Jesper

    1989-01-01

    Spiral galaxy discs are characterized by approximately exponential surface luminosity profiles. In this paper the evolutionary equations for a star-forming, viscous disc are solved analytically or semi-analytically. It is shown that approximately exponential stellar surface density profiles result if the viscous time-scale t ν is comparable to the star-formation time scale t * everywhere in the disc. The analytical solutions are used to illuminate further on the issue of why the above mechanism leads to resulting exponential stellar profiles under certain conditions. The sensitivity of the solution to variations of various parameters are investigated and show that the initial gas surface density distribution has to be fairly regular in order that final exponential stellar surface density profiles result. (author)

  11. Exponential attractors for a nonclassical diffusion equation

    Directory of Open Access Journals (Sweden)

    Qiaozhen Ma

    2009-01-01

    Full Text Available In this article, we prove the existence of exponential attractors for a nonclassical diffusion equation in ${H^{2}(Omega}cap{H}^{1}_{0}(Omega$ when the space dimension is less than 4.

  12. Global stability and exact solution of an arbitrary-solute nonlinear cellular mass transport system.

    Science.gov (United States)

    Benson, James D

    2014-12-01

    The prediction of the cellular state as a function of extracellular concentrations and temperatures has been of interest to physiologists for nearly a century. One of the most widely used models in the field is one where mass flux is linearly proportional to the concentration difference across the membrane. These fluxes define a nonlinear differential equation system for the intracellular state, which when coupled with appropriate initial conditions, define the intracellular state as a function of the extracellular concentrations of both permeating and nonpermeating solutes. Here we take advantage of a reparametrization scheme to extend existing stability results to a more general setting and to a develop analytical solutions to this model for an arbitrary number of extracellular solutes. Copyright © 2014 Elsevier Inc. All rights reserved.

  13. Global Dental Research Productivity and Its Association With Human Development, Gross National Income, and Political Stability.

    Science.gov (United States)

    Allareddy, Veerasathpurush; Allareddy, Veeratrishul; Rampa, Sankeerth; Nalliah, Romesh P; Elangovan, Satheesh

    2015-09-01

    The objective of this study is to examine the associations between country level factors (such as human development, economic productivity, and political stability) and their dental research productivity. This study is a cross-sectional analysis of bibliometric data from Scopus search engine. Human Development Index (HDI), Gross National Income per capita (GNI), and Failed State Index measures were the independent variables. Outcomes were "Total number of publications (articles or articles in press) in the field of dentistry" and "Total number of publications in the field of dentistry per million population." Non-parametric tests were used to examine the association between the independent and outcome variables. During the year 2013, a total of 11,952 dental research articles were published across the world. The top 5 publishing countries were United States, Brazil, India, Japan, and United Kingdom. "Very High" HDI countries had significantly higher number of total dental research articles and dental research articles per million population when compared to the "High HDI," "Medium HDI," and "Low HDI" countries (p < 0.0001). There was a significant linear relationship between the GNI quartile income levels and outcome metrics (p ≤ 0.007). Countries which were highly politically stable were associated with significantly higher dental research productivity (p < 0.0001). There appears to be a regional concentration of articles with just five countries contributing to over 50% of all articles. The human development and economic development of a country are linearly correlated with dental research productivity. Dental research productivity also increases with increasing political stability of a country. Copyright © 2015 Elsevier Inc. All rights reserved.

  14. Central limit theorem and deformed exponentials

    International Nuclear Information System (INIS)

    Vignat, C; Plastino, A

    2007-01-01

    The central limit theorem (CLT) can be ranked among the most important ones in probability theory and statistics and plays an essential role in several basic and applied disciplines, notably in statistical thermodynamics. We show that there exists a natural extension of the CLT from exponentials to so-called deformed exponentials (also denoted as q-Gaussians). Our proposal applies exactly in the usual conditions in which the classical CLT is used. (fast track communication)

  15. Sampling from the normal and exponential distributions

    International Nuclear Information System (INIS)

    Chaplin, K.R.; Wills, C.A.

    1982-01-01

    Methods for generating random numbers from the normal and exponential distributions are described. These involve dividing each function into subregions, and for each of these developing a method of sampling usually based on an acceptance rejection technique. When sampling from the normal or exponential distribution, each subregion provides the required random value with probability equal to the ratio of its area to the total area. Procedures written in FORTRAN for the CYBER 175/CDC 6600 system are provided to implement the two algorithms

  16. Stabilization of global temperature at 1.5°C and 2.0°C: implications for coastal areas.

    Science.gov (United States)

    Nicholls, Robert J; Brown, Sally; Goodwin, Philip; Wahl, Thomas; Lowe, Jason; Solan, Martin; Godbold, Jasmin A; Haigh, Ivan D; Lincke, Daniel; Hinkel, Jochen; Wolff, Claudia; Merkens, Jan-Ludolf

    2018-05-13

    The effectiveness of stringent climate stabilization scenarios for coastal areas in terms of reduction of impacts/adaptation needs and wider policy implications has received little attention. Here we use the Warming Acidification and Sea Level Projector Earth systems model to calculate large ensembles of global sea-level rise (SLR) and ocean pH projections to 2300 for 1.5°C and 2.0°C stabilization scenarios, and a reference unmitigated RCP8.5 scenario. The potential consequences of these projections are then considered for global coastal flooding, small islands, deltas, coastal cities and coastal ecology. Under both stabilization scenarios, global mean ocean pH (and temperature) stabilize within a century. This implies significant ecosystem impacts are avoided, but detailed quantification is lacking, reflecting scientific uncertainty. By contrast, SLR is only slowed and continues to 2300 (and beyond). Hence, while coastal impacts due to SLR are reduced significantly by climate stabilization, especially after 2100, potential impacts continue to grow for centuries. SLR in 2300 under both stabilization scenarios exceeds unmitigated SLR in 2100. Therefore, adaptation remains essential in densely populated and economically important coastal areas under climate stabilization. Given the multiple adaptation steps that this will require, an adaptation pathways approach has merits for coastal areas.This article is part of the theme issue 'The Paris Agreement: understanding the physical and social challenges for a warming world of 1.5°C above pre-industrial levels'. © 2018 The Authors.

  17. Stabilization of global temperature at 1.5°C and 2.0°C: implications for coastal areas

    Science.gov (United States)

    Nicholls, Robert J.; Brown, Sally; Goodwin, Philip; Wahl, Thomas; Lowe, Jason; Solan, Martin; Godbold, Jasmin A.; Haigh, Ivan D.; Lincke, Daniel; Hinkel, Jochen; Wolff, Claudia; Merkens, Jan-Ludolf

    2018-05-01

    The effectiveness of stringent climate stabilization scenarios for coastal areas in terms of reduction of impacts/adaptation needs and wider policy implications has received little attention. Here we use the Warming Acidification and Sea Level Projector Earth systems model to calculate large ensembles of global sea-level rise (SLR) and ocean pH projections to 2300 for 1.5°C and 2.0°C stabilization scenarios, and a reference unmitigated RCP8.5 scenario. The potential consequences of these projections are then considered for global coastal flooding, small islands, deltas, coastal cities and coastal ecology. Under both stabilization scenarios, global mean ocean pH (and temperature) stabilize within a century. This implies significant ecosystem impacts are avoided, but detailed quantification is lacking, reflecting scientific uncertainty. By contrast, SLR is only slowed and continues to 2300 (and beyond). Hence, while coastal impacts due to SLR are reduced significantly by climate stabilization, especially after 2100, potential impacts continue to grow for centuries. SLR in 2300 under both stabilization scenarios exceeds unmitigated SLR in 2100. Therefore, adaptation remains essential in densely populated and economically important coastal areas under climate stabilization. Given the multiple adaptation steps that this will require, an adaptation pathways approach has merits for coastal areas. This article is part of the theme issue `The Paris Agreement: understanding the physical and social challenges for a warming world of 1.5°C above pre-industrial levels'.

  18. Geochemical constraints on sustainable development: Can an advanced global economy achieve long-term stability?

    Science.gov (United States)

    Pickard, William F.

    2008-04-01

    The eighty-one stable chemical elements are examined individually with respect to (i) recent annual demand and (ii) worst case long-term availability in a distant future in which they must be extracted from the background sources of air, seawater, and ordinary rock. It is shown that, if a conventional use scenario is envisioned, the supplies of ruthenium, rhodium, palladium, tellurium, rhenium, osmium, iridium, platinum, gold, and especially phosphorus will be questionable while the supplies of copper, zinc, molybdenum, silver, cadmium, tin, antimony, tungsten, mercury, lead, and bismuth will be inadequate. It is therefore concluded that, in the long run, only the promotion of massive recycling and substitution technologies will suffice to maintain the global industrial society now developing.

  19. New results for exponential synchronization of linearly coupled ordinary differential systems

    International Nuclear Information System (INIS)

    Tong Ping; Chen Shi-Hua

    2017-01-01

    This paper investigates the exponential synchronization of linearly coupled ordinary differential systems. The intrinsic nonlinear dynamics may not satisfy the QUAD condition or weak-QUAD condition. First, it gives a new method to analyze the exponential synchronization of the systems. Second, two theorems and their corollaries are proposed for the local or global exponential synchronization of the coupled systems. Finally, an application to the linearly coupled Hopfield neural networks and several simulations are provided for verifying the effectiveness of the theoretical results. (paper)

  20. Analysis of Nonlinear Duopoly Games with Product Differentiation: Stability, Global Dynamics, and Control

    Directory of Open Access Journals (Sweden)

    S. S. Askar

    2017-01-01

    Full Text Available Many researchers have used quadratic utility function to study its influences on economic games with product differentiation. Such games include Cournot, Bertrand, and a mixed-type game called Cournot-Bertrand. Within this paper, a cubic utility function that is derived from a constant elasticity of substitution production function (CES is introduced. This cubic function is more desirable than the quadratic one besides its amenability to efficiency analysis. Based on that utility a two-dimensional Cournot duopoly game with horizontal product differentiation is modeled using a discrete time scale. Two different types of games are studied in this paper. In the first game, firms are updating their output production using the traditional bounded rationality approach. In the second game, firms adopt Puu’s mechanism to update their productions. Puu’s mechanism does not require any information about the profit function; instead it needs both firms to know their production and their profits in the past time periods. In both scenarios, an explicit form for the Nash equilibrium point is obtained under certain conditions. The stability analysis of Nash point is considered. Furthermore, some numerical simulations are carried out to confirm the chaotic behavior of Nash equilibrium point. This analysis includes bifurcation, attractor, maximum Lyapunov exponent, and sensitivity to initial conditions.

  1. Stability analysis of switched linear systems defined by graphs

    OpenAIRE

    Athanasopoulos, Nikolaos; Lazar, Mircea

    2015-01-01

    We present necessary and sufficient conditions for global exponential stability for switched discrete-time linear systems, under arbitrary switching, which is constrained within a set of admissible transitions. The class of systems studied includes the family of systems under arbitrary switching, periodic systems, and systems with minimum and maximum dwell time specifications. To reach the result, we describe the set of rules that define the admissible transitions with a weighted directed gra...

  2. Ebola Viral Disease in West Africa: A Threat to Global Health, Economy and Political Stability

    Science.gov (United States)

    Mohammed, Ibrahim; Saidu, Yauba

    2016-01-01

    The West African sub-continent is currently experiencing its first, and ironically, the largest and longest Ebola viral diseases (EVD) outbreak ever documented in modern medical history. The current outbreak is significant in several ways, including longevity, magnitude of morbidity and mortality, occurrence outside the traditional niches, rapid spread and potential of becoming a global health tragedy. The authors provided explicit insights into the current and historical background, drivers of the epidemic, societal impacts, status of vaccines and drugs development and proffered recommendations to halt and prevent future occurrences. The authors reviewed mainly five databases and a hand search of key relevant literature. We reviewed 51 articles that were relevant up until the 18th of August 2014. The authors supplemented the search with reference list of relevant articles and grey literature as well as relevant Internet websites. Article searches were limited to those published either in English or French. There are strong indications that the EVD may have been triggered by increased human activities and encroachment into the forest ecosystem spurred by increasing population and poverty-driven forest-dependent local economy. Containment efforts are being hampered by weak and fragile health systems, including public health surveillance and weak governance, certain socio-anthropological factors, fast travels (improved transport systems) and globalization. The societal impacts of the EBV outbreak are grave, including economic shutdown, weakening of socio-political systems, psychological distress, and unprecedented consumption of scarce health resources. The research and development (R&D) pipeline for product against EBV seems grossly insufficient. The outbreak of Ebola and the seeming difficulty to contain the epidemic is simply a reflection of the weak health system, poor surveillance and emergency preparedness/response, poverty and disconnect between the government

  3. Ebola viral disease in West Africa: a threat to global health, economy and political stability

    Directory of Open Access Journals (Sweden)

    Semeeh Akinwale Omoleke

    2016-08-01

    Full Text Available The West African sub-continent is currently experiencing its first, and ironically, the largest and longest Ebola viral diseases (EVD outbreak ever documented in modern medical history. The current outbreak is significant in several ways, including longevity, magnitude of morbidity and mortality, occurrence outside the traditional niches, rapid spread and potential of becoming a global health tragedy. The authors provided explicit insights into the current and historical background, drivers of the epidemic, societal impacts, status of vaccines and drugs development and proffered recommendations to halt and prevent future occurrences. The authors reviewed mainly five databases and a hand search of key relevant literature. We reviewed 51 articles that were relevant up until the 18th of August 2014. The authors supplemented the search with reference list of relevant articles and grey literature as well as relevant Internet websites. Article searches were limited to those published either in English or French. There are strong indications that the EVD may have been triggered by increased human activities and encroachment into the forest ecosystem spurred by increasing population and povertydriven forest-dependent local economy. Containment efforts are being hampered by weak and fragile health systems, including public health surveillance and weak governance, certain socio-anthropological factors, fast travels (improved transport systems and globalization. The societal impacts of the EBV outbreak are grave, including economic shutdown, weakening of socio-political systems, psychological distress, and unprecedented consumption of scarce health resources. The research and development (R&D pipeline for product against EBV seems grossly insufficient. The outbreak of Ebola and the seeming difficulty to contain the epidemic is simply a reflection of the weak health system, poor surveillance and emergency preparedness/ response, poverty and disconnect

  4. Ebola Viral Disease in West Africa: A Threat to Global Health, Economy and Political Stability.

    Science.gov (United States)

    Omoleke, Semeeh Akinwale; Mohammed, Ibrahim; Saidu, Yauba

    2016-08-17

    The West African sub-continent is currently experiencing its first, and ironically, the largest and longest Ebola viral diseases (EVD) outbreak ever documented in modern medical history. The current outbreak is significant in several ways, including longevity, magnitude of morbidity and mortality, occurrence outside the traditional niches, rapid spread and potential of becoming a global health tragedy. The authors provided explicit insights into the current and historical background, drivers of the epidemic, societal impacts, status of vaccines and drugs development and proffered recommendations to halt and prevent future occurrences. The authors reviewed mainly five databases and a hand search of key relevant literature. We reviewed 51 articles that were relevant up until the 18 th of August 2014. The authors supplemented the search with reference list of relevant articles and grey literature as well as relevant Internet websites. Article searches were limited to those published either in English or French. There are strong indications that the EVD may have been triggered by increased human activities and encroachment into the forest ecosystem spurred by increasing population and poverty-driven forest-dependent local economy. Containment efforts are being hampered by weak and fragile health systems, including public health surveillance and weak governance, certain socio-anthropological factors, fast travels (improved transport systems) and globalization. The societal impacts of the EBV outbreak are grave, including economic shutdown, weakening of socio-political systems, psychological distress, and unprecedented consumption of scarce health resources. The research and development (R&D) pipeline for product against EBV seems grossly insufficient. The outbreak of Ebola and the seeming difficulty to contain the epidemic is simply a reflection of the weak health system, poor surveillance and emergency preparedness/response, poverty and disconnect between the

  5. Banks' Stability: The effect of Monetary Policies in the light of Global Financial Crisis

    Directory of Open Access Journals (Sweden)

    Wael Bakhit

    2014-04-01

    Full Text Available This paper employs a quarterly time series to determine the timing of structural breaks for interest rates in USA over the last 60 years. The Chow test is used for investigating the non-stationary, where the date of the potential break is assumed to be known. Moreover, an empirically examination of the financial sector to check if it is positively related to deviations from an assumed interest rate as given in a standard Taylor rule. The empirical analysis is strengthened by analysing the rule from a historical perspective and look at the effect of setting the interest rate by the central bank on financial imbalances. The empirical evidence indicates that deviation in monetary policy has a potential causal factor in the build up of financial imbalances and the subsequent crisis where macro prudential intervention could have beneficial effect. Thus, my findings tend to support the view which states that the probable existence of central banks has been one source of global financial crisis since the past decade.

  6. Active Flow Control and Global Stability Analysis of Separated Flow Over a NACA 0012 Airfoil

    Science.gov (United States)

    Munday, Phillip M.

    definition of the coefficient of momentum, which successfully characterizes suppression of separation and lift enhancement. The effect of angular momentum is incorporated into the modified coefficient of momentum by introducing a characteristic swirling jet velocity based on the non-dimensional swirl number. With the modified coefficient of momentum, this single value is able to categorize controlled flows into separated, transitional, and attached flows. With inadequate control input (separated flow regime), lift decreased compared to the baseline flow. Increasing the modified coefficient of momentum, flow transitions from separated to attached and accordingly results in improved aerodynamic forces. Modifying the spanwise spacing, it is shown that the minimum modified coefficient of momentum input required to begin transitioning the flow is dependent on actuator spacing. The growth (or decay) of perturbations can facilitate or inhibit the influence of flow control inputs. Biglobal stability analysis is considered to further analyze the behavior of control inputs on separated flow over a symmetric airfoil. Assuming a spanwise periodic waveform for the perturbations, the eigenvalues and eigenvectors about a base flow are solved to understand the influence of spanwise variation on the development of the flow. Two algorithms are developed and validated to solve for the eigenvalues of the flow: an algebraic eigenvalue solver (matrix based) and a time-stepping algorithm. The matrix based approach is formulated without ever storing the matrices, creating a computationally memory efficient algorithm. Increasing the Reynolds number to Re = 23,000 over a NACA 0012 airfoil, the time-stepper method is implemented due to rising computational cost of the matrix-based method. Stability analysis about the time-averaged flow is performed for spanwise wavenumbers of beta = 1/c, 10pi/ c and 20pi/c, which the latter two wavenumbers are representative of the spanwise spacing between the

  7. Implicit and fully implicit exponential finite difference methods

    Indian Academy of Sciences (India)

    Burgers' equation; exponential finite difference method; implicit exponential finite difference method; ... This paper describes two new techniques which give improved exponential finite difference solutions of Burgers' equation. ... Current Issue

  8. Global stability results for a generalized Lotka-Volterra system with distributed delays. Applications to predator-prey and to epidemic systems.

    Science.gov (United States)

    Beretta, E; Capasso, V; Rinaldi, F

    1988-01-01

    The paper contains an extension of the general ODE system proposed in previous papers by the same authors, to include distributed time delays in the interaction terms. The new system describes a large class of Lotka-Volterra like population models and epidemic models with continuous time delays. Sufficient conditions for the boundedness of solutions and for the global asymptotic stability of nontrivial equilibrium solutions are given. A detailed analysis of the epidemic system is given with respect to the conditions for global stability. For a relevant subclass of these systems an existence criterion for steady states is also given.

  9. Globalization

    DEFF Research Database (Denmark)

    Plum, Maja

    Globalization is often referred to as external to education - a state of affair facing the modern curriculum with numerous challenges. In this paper it is examined as internal to curriculum; analysed as a problematization in a Foucaultian sense. That is, as a complex of attentions, worries, ways...... of reasoning, producing curricular variables. The analysis is made through an example of early childhood curriculum in Danish Pre-school, and the way the curricular variable of the pre-school child comes into being through globalization as a problematization, carried forth by the comparative practices of PISA...

  10. Globalization

    OpenAIRE

    F. Gerard Adams

    2008-01-01

    The rapid globalization of the world economy is causing fundamental changes in patterns of trade and finance. Some economists have argued that globalization has arrived and that the world is “flat†. While the geographic scope of markets has increased, the author argues that new patterns of trade and finance are a result of the discrepancies between “old†countries and “new†. As the differences are gradually wiped out, particularly if knowledge and technology spread worldwide, the t...

  11. STABILITY AND GROWTH PACT, COMMUNITY DOCUMENT „REVIVED” IN THE CURRENT GLOBAL ECONOMIC CRISIS”

    Directory of Open Access Journals (Sweden)

    ROXANA-DANIELA PAUN

    2011-04-01

    Full Text Available The article proposes to make a reasoned radiography Stability and Growth Pact, EU document revived therefore need to strengthen financial discipline and budget 6 to 7 September 2010 meeting of the Economic and Financial Affairs Council (ECOFIN. He talked about the introduction of the Stability and Growth in a 'European quarter' which will be monitored in structural and fiscal policies of the Member States. He also held a first exchange of views about the possible introduction of a levy on banks and a tax on financial transactions. Thus, the European Union has moved to create the world's first supranational system of control over the financial markets, particularly in order to reduce the risk of global financial crisis. The system will act in early 2011. For the first time in history, European financial control agencies will have more seats than national governments. In addition, the European Central Bank will see a branch that will track the emergence of crisis risk.The financial crisis has diminished the EU's growth potential, and made it clear just how interdependent its members' economies are, particularly inside the eurozone. The most important priority now is to restore growth and create effective mechanisms for regulating financial markets - in Europe and internationally. In strengthening its system of economic governance, Europe must learn from previous shortcomings which have put the financial stability of the whole eurozone at risk:- poor observance of the EU's sound rules and procedures for economic policy coordination- insufficient reduction in public debt during the good times – with peer pressure proving an adequate incentive- failure to deal effectively with the build-up of macroeconomic imbalances - despite the Commission's warnings – resulting in high current account deficits, large external indebtedness and high public debt levels in a number of countries (above the official 60% limit for eurozone countries. Greater economic

  12. Dynamic Transcriptional Regulation of Fis in Salmonella During the Exponential Phase.

    Science.gov (United States)

    Wang, Hui; Wang, Lei; Li, Ping; Hu, Yilang; Zhang, Wei; Tang, Bo

    2015-12-01

    Fis is one of the most important global regulators and has attracted extensive research attention. Many studies have focused on comparing the Fis global regulatory networks for exploring Fis function during different growth stages, such as the exponential and stationary stages. Although the Fis protein in bacteria is mainly expressed in the exponential phase, the dynamic transcriptional regulation of Fis during the exponential phase remains poorly understood. To address this question, we used RNA-seq technology to identify the Fis-regulated genes in the S. enterica serovar Typhimurium during the early exponential phase, and qRT-PCR was performed to validate the transcriptional data. A total of 1495 Fis-regulated genes were successfully identified, including 987 Fis-repressed genes and 508 Fis-activated genes. Comparing the results of this study with those of our previous study, we found that the transcriptional regulation of Fis was diverse during the early- and mid-exponential phases. The results also showed that the strong positive regulation of Fis on Salmonella pathogenicity island genes in the mid-exponential phase transitioned into insignificant effect in the early exponential phase. To validate these results, we performed a cell infection assay and found that Δfis only exhibited a 1.49-fold decreased capacity compared with the LT2 wild-type strain, indicating a large difference from the 6.31-fold decrease observed in the mid-exponential phase. Our results provide strong evidence for a need to thoroughly understand the dynamic transcriptional regulation of Fis in Salmonella during the exponential phase.

  13. Exponential synchronization of the Genesio-Tesi chaotic system via a novel feedback control

    International Nuclear Information System (INIS)

    Park, Ju H

    2007-01-01

    A novel feedback control scheme is proposed for exponential synchronization of the Genesio-Tesi chaotic system. The feedback controller consists of two parts: a linear dynamic control law and a nonlinear control one. For exponential synchronization between the drive and response Genesio-Tesi systems, the Lyapunov stability analysis is used. Then an existence criterion for the stabilizing controller is presented in terms of linear matrix inequalities (LMIs). The LMIs can be solved easily by various convex optimization algorithms. Finally, a numerical simulation is illustrated to show the effectiveness of the proposed chaos synchronization scheme

  14. The technological singularity and exponential medicine

    Directory of Open Access Journals (Sweden)

    Iraj Nabipour

    2016-01-01

    Full Text Available The "technological singularity" is forecasted to occur in 2045. It is a point when non-biological intelligence becomes more intelligent than humans and each generation of intelligent machines re-designs itself smarter. Beyond this point, there is a symbiosis between machines and humans. This co-existence will produce incredible impacts on medicine that its sparkles could be seen in healthcare industry and the future medicine since 2025. Ray Kurzweil, the great futurist, suggested that three revolutions in science and technology consisting genetic and molecular science, nanotechnology, and robotic (artificial intelligence provided an exponential growth rate for medicine. The "exponential medicine" is going to create more disruptive technologies in healthcare industry. The exponential medicine shifts the paradigm of medical philosophy and produces significant impacts on the healthcare system and patient-physician relationship.   

  15. ESTIMATION ACCURACY OF EXPONENTIAL DISTRIBUTION PARAMETERS

    Directory of Open Access Journals (Sweden)

    muhammad zahid rashid

    2011-04-01

    Full Text Available The exponential distribution is commonly used to model the behavior of units that have a constant failure rate. The two-parameter exponential distribution provides a simple but nevertheless useful model for the analysis of lifetimes, especially when investigating reliability of technical equipment.This paper is concerned with estimation of parameters of the two parameter (location and scale exponential distribution. We used the least squares method (LSM, relative least squares method (RELS, ridge regression method (RR,  moment estimators (ME, modified moment estimators (MME, maximum likelihood estimators (MLE and modified maximum likelihood estimators (MMLE. We used the mean square error MSE, and total deviation TD, as measurement for the comparison between these methods. We determined the best method for estimation using different values for the parameters and different sample sizes

  16. Liver fibrosis: stretched exponential model outperforms mono-exponential and bi-exponential models of diffusion-weighted MRI.

    Science.gov (United States)

    Seo, Nieun; Chung, Yong Eun; Park, Yung Nyun; Kim, Eunju; Hwang, Jinwoo; Kim, Myeong-Jin

    2018-07-01

    To compare the ability of diffusion-weighted imaging (DWI) parameters acquired from three different models for the diagnosis of hepatic fibrosis (HF). Ninety-five patients underwent DWI using nine b values at 3 T magnetic resonance. The hepatic apparent diffusion coefficient (ADC) from a mono-exponential model, the true diffusion coefficient (D t ), pseudo-diffusion coefficient (D p ) and perfusion fraction (f) from a biexponential model, and the distributed diffusion coefficient (DDC) and intravoxel heterogeneity index (α) from a stretched exponential model were compared with the pathological HF stage. For the stretched exponential model, parameters were also obtained using a dataset of six b values (DDC # , α # ). The diagnostic performances of the parameters for HF staging were evaluated with Obuchowski measures and receiver operating characteristics (ROC) analysis. The measurement variability of DWI parameters was evaluated using the coefficient of variation (CoV). Diagnostic accuracy for HF staging was highest for DDC # (Obuchowski measures, 0.770 ± 0.03), and it was significantly higher than that of ADC (0.597 ± 0.05, p bi-exponential DWI model • Acquisition of six b values is sufficient to obtain accurate DDC and α.

  17. A method for nonlinear exponential regression analysis

    Science.gov (United States)

    Junkin, B. G.

    1971-01-01

    A computer-oriented technique is presented for performing a nonlinear exponential regression analysis on decay-type experimental data. The technique involves the least squares procedure wherein the nonlinear problem is linearized by expansion in a Taylor series. A linear curve fitting procedure for determining the initial nominal estimates for the unknown exponential model parameters is included as an integral part of the technique. A correction matrix was derived and then applied to the nominal estimate to produce an improved set of model parameters. The solution cycle is repeated until some predetermined criterion is satisfied.

  18. Quantum Zeno effect for exponentially decaying systems

    International Nuclear Information System (INIS)

    Koshino, Kazuki; Shimizu, Akira

    2004-01-01

    The quantum Zeno effect - suppression of decay by frequent measurements - was believed to occur only when the response of the detector is so quick that the initial tiny deviation from the exponential decay law is detectable. However, we show that it can occur even for exactly exponentially decaying systems, for which this condition is never satisfied, by considering a realistic case where the detector has a finite energy band of detection. The conventional theories correspond to the limit of an infinite bandwidth. This implies that the Zeno effect occurs more widely than expected thus far

  19. Calorimeter prediction based on multiple exponentials

    International Nuclear Information System (INIS)

    Smith, M.K.; Bracken, D.S.

    2002-01-01

    Calorimetry allows very precise measurements of nuclear material to be carried out, but it also requires relatively long measurement times to do so. The ability to accurately predict the equilibrium response of a calorimeter would significantly reduce the amount of time required for calorimetric assays. An algorithm has been developed that is effective at predicting the equilibrium response. This multi-exponential prediction algorithm is based on an iterative technique using commercial fitting routines that fit a constant plus a variable number of exponential terms to calorimeter data. Details of the implementation and the results of trials on a large number of calorimeter data sets will be presented

  20. Exponential Growth of Nonlinear Ballooning Instability

    International Nuclear Information System (INIS)

    Zhu, P.; Hegna, C. C.; Sovinec, C. R.

    2009-01-01

    Recent ideal magnetohydrodynamic (MHD) theory predicts that a perturbation evolving from a linear ballooning instability will continue to grow exponentially in the intermediate nonlinear phase at the same linear growth rate. This prediction is confirmed in ideal MHD simulations. When the Lagrangian compression, a measure of the ballooning nonlinearity, becomes of the order of unity, the intermediate nonlinear phase is entered, during which the maximum plasma displacement amplitude as well as the total kinetic energy continues to grow exponentially at the rate of the corresponding linear phase.

  1. The Matrix exponential, Dynamic Systems and Control

    DEFF Research Database (Denmark)

    Poulsen, Niels Kjølstad

    The matrix exponential can be found in various connections in analysis and control of dynamic systems. In this short note we are going to list a few examples. The matrix exponential usably pops up in connection to the sampling process, whatever it is in a deterministic or a stochastic setting...... or it is a tool for determining a Gramian matrix. This note is intended to be used in connection to the teaching post the course in Stochastic Adaptive Control (02421) given at Informatics and Mathematical Modelling (IMM), The Technical University of Denmark. This work is a result of a study of the litterature....

  2. Exponential Operators, Dobinski Relations and Summability

    International Nuclear Information System (INIS)

    Blasiak, P; Gawron, A; Horzela, A; Penson, K A; Solomon, A I

    2006-01-01

    We investigate properties of exponential operators preserving the particle number using combinatorial methods developed in order to solve the boson normal ordering problem. In particular, we apply generalized Dobinski relations and methods of multivariate Bell polynomials which enable us to understand the meaning of perturbation-like expansions of exponential operators. Such expansions, obtained as formal power series, are everywhere divergent but the Pade summation method is shown to give results which very well agree with exact solutions got for simplified quantum models of the one mode bosonic systems

  3. Exponentially tapered Josephson flux-flow oscillator

    DEFF Research Database (Denmark)

    Benabdallah, A.; Caputo, J. G.; Scott, Alwyn C.

    1996-01-01

    We introduce an exponentially tapered Josephson flux-flow oscillator that is tuned by applying a bias current to the larger end of the junction. Numerical and analytical studies show that above a threshold level of bias current the static solution becomes unstable and gives rise to a train...... of fluxons moving toward the unbiased smaller end, as in the standard flux-flow oscillator. An exponentially shaped junction provides several advantages over a rectangular junction including: (i) smaller linewidth, (ii) increased output power, (iii) no trapped flux because of the type of current injection...

  4. Exponential Data Fitting and its Applications

    CERN Document Server

    Pereyra, Victor

    2010-01-01

    Real and complex exponential data fitting is an important activity in many different areas of science and engineering, ranging from Nuclear Magnetic Resonance Spectroscopy and Lattice Quantum Chromodynamics to Electrical and Chemical Engineering, Vision and Robotics. The most commonly used norm in the approximation by linear combinations of exponentials is the l2 norm (sum of squares of residuals), in which case one obtains a nonlinear separable least squares problem. A number of different methods have been proposed through the years to solve these types of problems and new applications appear

  5. An Exponential Growth Learning Trajectory: Students' Emerging Understanding of Exponential Growth through Covariation

    Science.gov (United States)

    Ellis, Amy B.; Ozgur, Zekiye; Kulow, Torrey; Dogan, Muhammed F.; Amidon, Joel

    2016-01-01

    This article presents an Exponential Growth Learning Trajectory (EGLT), a trajectory identifying and characterizing middle grade students' initial and developing understanding of exponential growth as a result of an instructional emphasis on covariation. The EGLT explicates students' thinking and learning over time in relation to a set of tasks…

  6. BiGlobal linear stability analysis on low-Re flow past an airfoil at high angle of attack

    KAUST Repository

    Zhang, Wei

    2016-04-04

    We perform BiGlobal linear stability analysis on flow past a NACA0012 airfoil at 16° angle of attack and Reynolds number ranging from 400 to 1000. The steady-state two-dimensional base flows are computed using a well-tested finite difference code in combination with the selective frequency damping method. The base flow is characterized by two asymmetric recirculation bubbles downstream of the airfoil whose streamwise extent and the maximum reverse flow velocity increase with the Reynolds number. The stability analysis of the flow past the airfoil is carried out under very small spanwise wavenumber β = 10−4 to approximate the two-dimensional perturbation, and medium and large spanwise wavenumbers (β = 1–8) to account for the three-dimensional perturbation. Numerical results reveal that under small spanwise wavenumber, there are at most two oscillatory unstable modes corresponding to the near wake and far wake instabilities; the growth rate and frequency of the perturbation agree well with the two-dimensional direct numerical simulation results under all Reynolds numbers. For a larger spanwise wavenumber β = 1, there is only one oscillatory unstable mode associated with the wake instability at Re = 400 and 600, while at Re = 800 and 1000 there are two oscillatory unstable modes for the near wake and far wake instabilities, and one stationary unstable mode for the monotonically growing perturbation within the recirculation bubble via the centrifugal instability mechanism. All the unstable modes are weakened or even suppressed as the spanwise wavenumber further increases, among which the stationary mode persists until β = 4.

  7. BiGlobal linear stability analysis on low-Re flow past an airfoil at high angle of attack

    KAUST Repository

    Zhang, Wei; Samtaney, Ravi

    2016-01-01

    We perform BiGlobal linear stability analysis on flow past a NACA0012 airfoil at 16° angle of attack and Reynolds number ranging from 400 to 1000. The steady-state two-dimensional base flows are computed using a well-tested finite difference code in combination with the selective frequency damping method. The base flow is characterized by two asymmetric recirculation bubbles downstream of the airfoil whose streamwise extent and the maximum reverse flow velocity increase with the Reynolds number. The stability analysis of the flow past the airfoil is carried out under very small spanwise wavenumber β = 10−4 to approximate the two-dimensional perturbation, and medium and large spanwise wavenumbers (β = 1–8) to account for the three-dimensional perturbation. Numerical results reveal that under small spanwise wavenumber, there are at most two oscillatory unstable modes corresponding to the near wake and far wake instabilities; the growth rate and frequency of the perturbation agree well with the two-dimensional direct numerical simulation results under all Reynolds numbers. For a larger spanwise wavenumber β = 1, there is only one oscillatory unstable mode associated with the wake instability at Re = 400 and 600, while at Re = 800 and 1000 there are two oscillatory unstable modes for the near wake and far wake instabilities, and one stationary unstable mode for the monotonically growing perturbation within the recirculation bubble via the centrifugal instability mechanism. All the unstable modes are weakened or even suppressed as the spanwise wavenumber further increases, among which the stationary mode persists until β = 4.

  8. Stability in Cohen Grossberg-type bidirectional associative memory neural networks with time-varying delays

    Science.gov (United States)

    Cao, Jinde; Song, Qiankun

    2006-07-01

    In this paper, the exponential stability problem is investigated for a class of Cohen-Grossberg-type bidirectional associative memory neural networks with time-varying delays. By using the analysis method, inequality technique and the properties of an M-matrix, several novel sufficient conditions ensuring the existence, uniqueness and global exponential stability of the equilibrium point are derived. Moreover, the exponential convergence rate is estimated. The obtained results are less restrictive than those given in the earlier literature, and the boundedness and differentiability of the activation functions and differentiability of the time-varying delays are removed. Two examples with their simulations are given to show the effectiveness of the obtained results.

  9. Exponential operations and aggregation operators of interval neutrosophic sets and their decision making methods.

    Science.gov (United States)

    Ye, Jun

    2016-01-01

    An interval neutrosophic set (INS) is a subclass of a neutrosophic set and a generalization of an interval-valued intuitionistic fuzzy set, and then the characteristics of INS are independently described by the interval numbers of its truth-membership, indeterminacy-membership, and falsity-membership degrees. However, the exponential parameters (weights) of all the existing exponential operational laws of INSs and the corresponding exponential aggregation operators are crisp values in interval neutrosophic decision making problems. As a supplement, this paper firstly introduces new exponential operational laws of INSs, where the bases are crisp values or interval numbers and the exponents are interval neutrosophic numbers (INNs), which are basic elements in INSs. Then, we propose an interval neutrosophic weighted exponential aggregation (INWEA) operator and a dual interval neutrosophic weighted exponential aggregation (DINWEA) operator based on these exponential operational laws and introduce comparative methods based on cosine measure functions for INNs and dual INNs. Further, we develop decision-making methods based on the INWEA and DINWEA operators. Finally, a practical example on the selecting problem of global suppliers is provided to illustrate the applicability and rationality of the proposed methods.

  10. When economic growth is less than exponential

    DEFF Research Database (Denmark)

    Groth, Christian; Koch, Karl-Josef; Steger, Thomas

    2010-01-01

    This paper argues that growth theory needs a more general notion of "regularity" than that of exponential growth. We suggest that paths along which the rate of decline of the growth rate is proportional to the growth rate itself deserve attention. This opens up for considering a richer set...

  11. When Economic Growth is Less than Exponential

    DEFF Research Database (Denmark)

    Groth, Christian; Koch, Karl-Josef; Steger, Thomas M.

    This paper argues that growth theory needs a more general notion of "regularity" than that of exponential growth. We suggest that paths along which the rate of decline of the growth rate is proportional to the growth rate itself deserve attention. This opens up for considering a richer set...

  12. Academic Sacred Cows and Exponential Growth.

    Science.gov (United States)

    Heterick, Robert C., Jr.

    1991-01-01

    The speech notes the linear growth of resources versus the exponential growth of costs in higher education. It identifies opportunities arising from information technology to transform teaching and learning through creation of a new scholarly information delivery system. An integrated triad of communications, computing, and library organizations…

  13. Students' Understanding of Exponential and Logarithmic Functions.

    Science.gov (United States)

    Weber, Keith

    Exponential, and logarithmic functions are pivotal mathematical concepts that play central roles in advanced mathematics. Unfortunately, these are also concepts that give students serious difficulty. This report describe a theory of how students acquire an understanding of these functions by prescribing a set of mental constructions that a student…

  14. Intersection of the Exponential and Logarithmic Curves

    Science.gov (United States)

    Boukas, Andreas; Valahas, Theodoros

    2009-01-01

    The study of the number of intersection points of y = a[superscript x] and y = log[subscript a]x can be an interesting topic to present in a single-variable calculus class. In this article, the authors present a classroom presentation outline involving the basic algebra and the elementary calculus of the exponential and logarithmic functions. The…

  15. The evolution of stellar exponential discs

    NARCIS (Netherlands)

    Ferguson, AMN; Clarke, CJ

    2001-01-01

    Models of disc galaxies which invoke viscosity-driven radial flows have long been known to provide a natural explanation for the origin of stellar exponential discs, under the assumption that the star formation and viscous time-scales are comparable. We present models which invoke simultaneous star

  16. Chapter 3: The analysis of exponential experiments

    International Nuclear Information System (INIS)

    Brown, G.; Moore, P.F.G.; Richmond, R.

    1963-01-01

    A description is given of the methods used by the BICEP group for the analysis of exponential experiments on graphite-moderated natural uranium lattices. These differ in some respects from the methods formerly employed at A.E.R.E. and have resulted in a reduction by a factor of four in the time taken to carry out and analyse an experiment. (author)

  17. Exponential Lower Bounds For Policy Iteration

    OpenAIRE

    Fearnley, John

    2010-01-01

    We study policy iteration for infinite-horizon Markov decision processes. It has recently been shown policy iteration style algorithms have exponential lower bounds in a two player game setting. We extend these lower bounds to Markov decision processes with the total reward and average-reward optimality criteria.

  18. Exponential rate of convergence in current reservoirs

    OpenAIRE

    De Masi, Anna; Presutti, Errico; Tsagkarogiannis, Dimitrios; Vares, Maria Eulalia

    2015-01-01

    In this paper, we consider a family of interacting particle systems on $[-N,N]$ that arises as a natural model for current reservoirs and Fick's law. We study the exponential rate of convergence to the stationary measure, which we prove to be of the order $N^{-2}$.

  19. On the Role of Situational Stressors in the Disruption of Global Neural Network Stability during Problem Solving.

    Science.gov (United States)

    Liu, Mengting; Amey, Rachel C; Forbes, Chad E

    2017-12-01

    When individuals are placed in stressful situations, they are likely to exhibit deficits in cognitive capacity over and above situational demands. Despite this, individuals may still persevere and ultimately succeed in these situations. Little is known, however, about neural network properties that instantiate success or failure in both neutral and stressful situations, particularly with respect to regions integral for problem-solving processes that are necessary for optimal performance on more complex tasks. In this study, we outline how hidden Markov modeling based on multivoxel pattern analysis can be used to quantify unique brain states underlying complex network interactions that yield either successful or unsuccessful problem solving in more neutral or stressful situations. We provide evidence that brain network stability and states underlying synchronous interactions in regions integral for problem-solving processes are key predictors of whether individuals succeed or fail in stressful situations. Findings also suggested that individuals utilize discriminate neural patterns in successfully solving problems in stressful or neutral situations. Findings overall highlight how hidden Markov modeling can provide myriad possibilities for quantifying and better understanding the role of global network interactions in the problem-solving process and how the said interactions predict success or failure in different contexts.

  20. Optimal Exponential Synchronization of Chaotic Systems with Multiple Time Delays via Fuzzy Control

    Directory of Open Access Journals (Sweden)

    Feng-Hsiag Hsiao

    2013-01-01

    Full Text Available This study presents an effective approach to realize the optimal exponential synchronization of multiple time-delay chaotic (MTDC systems. First, a neural network (NN model is employed to approximate the MTDC system. Then, a linear differential inclusion (LDI state-space representation is established for the dynamics of the NN model. Based on this LDI state-space representation, this study proposes a delay-dependent exponential stability criterion of the error system derived in terms of Lyapunov’s direct method to ensure that the trajectories of the slave system can approach those of the master system. Subsequently, the stability condition of this criterion is reformulated into a linear matrix inequality (LMI. Based on the LMI, a fuzzy controller is synthesized not only to realize the exponential synchronization but also to achieve the optimal performance by minimizing the disturbance attenuation level. Finally, a numerical example with simulations is provided to illustrate the concepts discussed throughout this work.

  1. Stability analysis of impulsive fuzzy cellular neural networks with distributed delays and reaction-diffusion terms

    International Nuclear Information System (INIS)

    Li Zuoan; Li Kelin

    2009-01-01

    In this paper, we investigate a class of impulsive fuzzy cellular neural networks with distributed delays and reaction-diffusion terms. By employing the delay differential inequality with impulsive initial conditions and M-matrix theory, we find some sufficient conditions ensuring the existence, uniqueness and global exponential stability of equilibrium point for impulsive fuzzy cellular neural networks with distributed delays and reaction-diffusion terms. In particular, the estimate of the exponential converging index is also provided, which depends on the system parameters. An example is given to show the effectiveness of the results obtained here.

  2. Statistical estimation for truncated exponential families

    CERN Document Server

    Akahira, Masafumi

    2017-01-01

    This book presents new findings on nonregular statistical estimation. Unlike other books on this topic, its major emphasis is on helping readers understand the meaning and implications of both regularity and irregularity through a certain family of distributions. In particular, it focuses on a truncated exponential family of distributions with a natural parameter and truncation parameter as a typical nonregular family. This focus includes the (truncated) Pareto distribution, which is widely used in various fields such as finance, physics, hydrology, geology, astronomy, and other disciplines. The family is essential in that it links both regular and nonregular distributions, as it becomes a regular exponential family if the truncation parameter is known. The emphasis is on presenting new results on the maximum likelihood estimation of a natural parameter or truncation parameter if one of them is a nuisance parameter. In order to obtain more information on the truncation, the Bayesian approach is also considere...

  3. Exponentiated Lomax Geometric Distribution: Properties and Applications

    Directory of Open Access Journals (Sweden)

    Amal Soliman Hassan

    2017-09-01

    Full Text Available In this paper, a new four-parameter lifetime distribution, called the exponentiated Lomax geometric (ELG is introduced. The new lifetime distribution contains the Lomax geometric and exponentiated Pareto geometric as new sub-models. Explicit algebraic formulas of probability density function, survival and hazard functions are derived. Various structural properties of the new model are derived including; quantile function, Re'nyi entropy, moments, probability weighted moments, order statistic, Lorenz and Bonferroni curves. The estimation of the model parameters is performed by maximum likelihood method and inference for a large sample is discussed. The flexibility and potentiality of the new model in comparison with some other distributions are shown via an application to a real data set. We hope that the new model will be an adequate model for applications in various studies.

  4. Matrix-exponential distributions in applied probability

    CERN Document Server

    Bladt, Mogens

    2017-01-01

    This book contains an in-depth treatment of matrix-exponential (ME) distributions and their sub-class of phase-type (PH) distributions. Loosely speaking, an ME distribution is obtained through replacing the intensity parameter in an exponential distribution by a matrix. The ME distributions can also be identified as the class of non-negative distributions with rational Laplace transforms. If the matrix has the structure of a sub-intensity matrix for a Markov jump process we obtain a PH distribution which allows for nice probabilistic interpretations facilitating the derivation of exact solutions and closed form formulas. The full potential of ME and PH unfolds in their use in stochastic modelling. Several chapters on generic applications, like renewal theory, random walks and regenerative processes, are included together with some specific examples from queueing theory and insurance risk. We emphasize our intention towards applications by including an extensive treatment on statistical methods for PH distribu...

  5. Harmonic analysis on exponential solvable Lie groups

    CERN Document Server

    Fujiwara, Hidenori

    2015-01-01

    This book is the first one that brings together recent results on the harmonic analysis of exponential solvable Lie groups. There still are many interesting open problems, and the book contributes to the future progress of this research field. As well, various related topics are presented to motivate young researchers. The orbit method invented by Kirillov is applied to study basic problems in the analysis on exponential solvable Lie groups. This method tells us that the unitary dual of these groups is realized as the space of their coadjoint orbits. This fact is established using the Mackey theory for induced representations, and that mechanism is explained first. One of the fundamental problems in the representation theory is the irreducible decomposition of induced or restricted representations. Therefore, these decompositions are studied in detail before proceeding to various related problems: the multiplicity formula, Plancherel formulas, intertwining operators, Frobenius reciprocity, and associated alge...

  6. Financing exponential growth at H3

    OpenAIRE

    Silva, João Ricardo Ferreira Hipolito da

    2012-01-01

    H3 is a fast-food chain that introduced the concept of gourmet hamburgers in the Portuguese market. This case-study illustrates its financing strategy that supported an exponential growth represented by opening 33 restaurants within approximately 3 years of its inception. H3 is now faced with the challenge of structuring its foreign ventures and change its financial approach. The main covered topics are the options an entrepreneur has for financing a new venture and how it evolves along th...

  7. Exponentially Light Dark Matter from Coannihilation

    OpenAIRE

    D'Agnolo, Raffaele Tito; Mondino, Cristina; Ruderman, Joshua T.; Wang, Po-Jen

    2018-01-01

    Dark matter may be a thermal relic whose abundance is set by mutual annihilations among multiple species. Traditionally, this coannihilation scenario has been applied to weak scale dark matter that is highly degenerate with other states. We show that coannihilation among states with split masses points to dark matter that is exponentially lighter than the weak scale, down to the keV scale. We highlight the regime where dark matter does not participate in the annihilations that dilute its numb...

  8. Heterogeneous dipolar theory of the exponential pile

    International Nuclear Information System (INIS)

    Mastrangelo, P.V.

    1981-01-01

    We present a heterogeneous theory of the exponential pile, closely related to NORDHEIM-SCALETTAR's. It is well adapted to lattice whose pitch is relatively large (D-2O, grahpite) and the dimensions of whose channels are not negligible. The anisotropy of neutron diffusion is taken into account by the introduction of dipolar parameters. We express the contribution of each channel to the total flux in the moderator by means of multipolar coefficients. In order to be able to apply conditions of continuity between the flux and their derivatives, on the side of the moderator, we develop in a Fourier series the fluxes found at the periphery of each channel. Using Wronski's relations of Bessel's functions, we express the multipolar coefficients of the surfaces of each channel, on the side of the moderator, by means of the harmonics of each flux and their derivatives. We retain only monopolar (A 0 sub(g)) and dipolar (A 1 sub(g)) coefficients; those of a higher order are ignored. We deduce from these coefficients the systems of homogeneous equations of the exponential pile with monopoles on their own and monopoles plus dipoles. It should be noted that the systems of homogeneous equations of the critical pile are contained in those of the exponential pile. In another article, we develop the calculation of monopolar and dipolar heterogeneous parameters. (orig.)

  9. Unwrapped phase inversion with an exponential damping

    KAUST Repository

    Choi, Yun Seok

    2015-07-28

    Full-waveform inversion (FWI) suffers from the phase wrapping (cycle skipping) problem when the frequency of data is not low enough. Unless we obtain a good initial velocity model, the phase wrapping problem in FWI causes a result corresponding to a local minimum, usually far away from the true solution, especially at depth. Thus, we have developed an inversion algorithm based on a space-domain unwrapped phase, and we also used exponential damping to mitigate the nonlinearity associated with the reflections. We construct the 2D phase residual map, which usually contains the wrapping discontinuities, especially if the model is complex and the frequency is high. We then unwrap the phase map and remove these cycle-based jumps. However, if the phase map has several residues, the unwrapping process becomes very complicated. We apply a strong exponential damping to the wavefield to eliminate much of the residues in the phase map, thus making the unwrapping process simple. We finally invert the unwrapped phases using the back-propagation algorithm to calculate the gradient. We progressively reduce the damping factor to obtain a high-resolution image. Numerical examples determined that the unwrapped phase inversion with a strong exponential damping generated convergent long-wavelength updates without low-frequency information. This model can be used as a good starting model for a subsequent inversion with a reduced damping, eventually leading to conventional waveform inversion.

  10. An Exponentially Weighted Moving Average Control Chart for Bernoulli Data

    DEFF Research Database (Denmark)

    Spliid, Henrik

    2010-01-01

    of the transformation is given and its limit for small values of p is derived. Control of high yield processes is discussed and the chart is shown to perform very well in comparison with both the most common alternative EWMA chart and the CUSUM chart. The construction and the use of the proposed EWMA chart......We consider a production process in which units are produced in a sequential manner. The units can, for example, be manufactured items or services, provided to clients. Each unit produced can be a failure with probability p or a success (non-failure) with probability (1-p). A novel exponentially...... weighted moving average (EWMA) control chart intended for surveillance of the probability of failure, p, is described. The chart is based on counting the number of non-failures produced between failures in combination with a variance-stabilizing transformation. The distribution function...

  11. On Using Exponential Parameter Estimators with an Adaptive Controller

    Science.gov (United States)

    Patre, Parag; Joshi, Suresh M.

    2011-01-01

    Typical adaptive controllers are restricted to using a specific update law to generate parameter estimates. This paper investigates the possibility of using any exponential parameter estimator with an adaptive controller such that the system tracks a desired trajectory. The goal is to provide flexibility in choosing any update law suitable for a given application. The development relies on a previously developed concept of controller/update law modularity in the adaptive control literature, and the use of a converse Lyapunov-like theorem. Stability analysis is presented to derive gain conditions under which this is possible, and inferences are made about the tracking error performance. The development is based on a class of Euler-Lagrange systems that are used to model various engineering systems including space robots and manipulators.

  12. Transport of super-thermal particles and their effect on the stability of global modes in fusion plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Schneller, Mirjam Simone

    2013-08-02

    In thermonuclear plasmas, a population of super-thermal particles generated by external heating methods or fusion reactions can lead to the excitation of global instabilities. The transport processes due to nonlinear wave-particle interactions and the consequential particle losses reduce the plasma heating and the efficiency of the fusion reaction rate. Furthermore, these energetic or fast particles may cause severe damages to the wall of the device. This thesis addresses the resonance mechanisms between these energetic particles and global MHD and kinetic MHD waves, employing the hybrid code HAGIS. A systematic investigation of energetic particles resonant with multiple modes (double-resonance) is presented for the first time. The double-resonant mode coupling is modeled for waves with different frequencies in various overlapping scenarios. It is found that, depending on the radial mode distance, double-resonance is able to significantly enhance, both the growth rates and the saturation amplitudes. Small radial mode distances, however can lead to strong nonlinear mode stabilization of a linear dominant mode. For the first time, simulations of experimental conditions in the ASDEX Upgrade fusion device are performed for different plasma equilibria (particularly for different q profiles). An understanding of fast particle behavior for non-monotonic q profiles is important for the development of advanced fusion scenarios. The numerical tool is the extended version of the HAGIS code, which computes the particle motion in the vacuum region between vessel wall in addition to the internal plasma volume. For this thesis, a consistent fast particle distribution function was implemented, to represent the fast particle population generated by the particular heating method (ICRH). Furthermore, HAGIS was extended to use more realistic eigenfunctions, calculated by the gyrokinetic eigenvalue solver LIGKA. One important aim of these simulations is to allow fast ion loss

  13. Transport of super-thermal particles and their effect on the stability of global modes in fusion plasmas

    International Nuclear Information System (INIS)

    Schneller, Mirjam Simone

    2013-01-01

    In thermonuclear plasmas, a population of super-thermal particles generated by external heating methods or fusion reactions can lead to the excitation of global instabilities. The transport processes due to nonlinear wave-particle interactions and the consequential particle losses reduce the plasma heating and the efficiency of the fusion reaction rate. Furthermore, these energetic or fast particles may cause severe damages to the wall of the device. This thesis addresses the resonance mechanisms between these energetic particles and global MHD and kinetic MHD waves, employing the hybrid code HAGIS. A systematic investigation of energetic particles resonant with multiple modes (double-resonance) is presented for the first time. The double-resonant mode coupling is modeled for waves with different frequencies in various overlapping scenarios. It is found that, depending on the radial mode distance, double-resonance is able to significantly enhance, both the growth rates and the saturation amplitudes. Small radial mode distances, however can lead to strong nonlinear mode stabilization of a linear dominant mode. For the first time, simulations of experimental conditions in the ASDEX Upgrade fusion device are performed for different plasma equilibria (particularly for different q profiles). An understanding of fast particle behavior for non-monotonic q profiles is important for the development of advanced fusion scenarios. The numerical tool is the extended version of the HAGIS code, which computes the particle motion in the vacuum region between vessel wall in addition to the internal plasma volume. For this thesis, a consistent fast particle distribution function was implemented, to represent the fast particle population generated by the particular heating method (ICRH). Furthermore, HAGIS was extended to use more realistic eigenfunctions, calculated by the gyrokinetic eigenvalue solver LIGKA. One important aim of these simulations is to allow fast ion loss

  14. Existence and Globally Asymptotic Stability of Equilibrium Solution for Fractional-Order Hybrid BAM Neural Networks with Distributed Delays and Impulses

    Directory of Open Access Journals (Sweden)

    Hai Zhang

    2017-01-01

    Full Text Available This paper investigates the existence and globally asymptotic stability of equilibrium solution for Riemann-Liouville fractional-order hybrid BAM neural networks with distributed delays and impulses. The factors of such network systems including the distributed delays, impulsive effects, and two different fractional-order derivatives between the U-layer and V-layer are taken into account synchronously. Based on the contraction mapping principle, the sufficient conditions are derived to ensure the existence and uniqueness of the equilibrium solution for such network systems. By constructing a novel Lyapunov functional composed of fractional integral and definite integral terms, the globally asymptotic stability criteria of the equilibrium solution are obtained, which are dependent on the order of fractional derivative and network parameters. The advantage of our constructed method is that one may directly calculate integer-order derivative of the Lyapunov functional. A numerical example is also presented to show the validity and feasibility of the theoretical results.

  15. Exponential synchronization of two nonlinearly non-delayed and delayed coupled complex dynamical networks

    International Nuclear Information System (INIS)

    Zheng Song

    2012-01-01

    In this paper, the exponential synchronization between two nonlinearly coupled complex networks with non-delayed and delayed coupling is investigated with Lyapunov-Krasovskii-type functionals. Based on the stability analysis of the impulsive differential equation and the linear matrix inequality, sufficient delay-dependent conditions for exponential synchronization are derived, and a linear impulsive controller and simple updated laws are also designed. Furthermore, the coupling matrices need not be symmetric or irreducible. Numerical examples are presented to verify the effectiveness and correctness of the synchronization criteria obtained.

  16. Adaptive exponential synchronization of delayed neural networks with reaction-diffusion terms

    International Nuclear Information System (INIS)

    Sheng Li; Yang Huizhong; Lou Xuyang

    2009-01-01

    This paper presents an exponential synchronization scheme for a class of neural networks with time-varying and distributed delays and reaction-diffusion terms. An adaptive synchronization controller is derived to achieve the exponential synchronization of the drive-response structure of neural networks by using the Lyapunov stability theory. At the same time, the update laws of parameters are proposed to guarantee the synchronization of delayed neural networks with all parameters unknown. It is shown that the approaches developed here extend and improve the ideas presented in recent literatures.

  17. Exponential temperature dependence of the critical transport current in Y-Ba-Cu-O thin films

    International Nuclear Information System (INIS)

    Yom, S.S.; Hahn, T.S.; Kim, Y.H.; Chu, H.; Choi, S.S.

    1989-01-01

    We have measured the critical currents in rf-sputtered YBa 2 Cu 3 O/sub 7-x/ thin films deposited on polycrystalline yttria-stabilized zirconia substrates as a function of temperature down to 10 K. The dependence of the granular films at low temperature indicated exponential behavior which is similar to the superconductor-normal metal-superconductor (S-N-S) type tunneling junctions. For the films with a grain size of approximately 1 μm, we observed two exponential decay constants, which suggest that Josephson junctions limiting the transport critical current are possible both at the grain boundaries and at twin boundaries

  18. Stability analysis for discrete-time stochastic memristive neural networks with both leakage and probabilistic delays.

    Science.gov (United States)

    Liu, Hongjian; Wang, Zidong; Shen, Bo; Huang, Tingwen; Alsaadi, Fuad E

    2018-06-01

    This paper is concerned with the globally exponential stability problem for a class of discrete-time stochastic memristive neural networks (DSMNNs) with both leakage delays as well as probabilistic time-varying delays. For the probabilistic delays, a sequence of Bernoulli distributed random variables is utilized to determine within which intervals the time-varying delays fall at certain time instant. The sector-bounded activation function is considered in the addressed DSMNN. By taking into account the state-dependent characteristics of the network parameters and choosing an appropriate Lyapunov-Krasovskii functional, some sufficient conditions are established under which the underlying DSMNN is globally exponentially stable in the mean square. The derived conditions are made dependent on both the leakage and the probabilistic delays, and are therefore less conservative than the traditional delay-independent criteria. A simulation example is given to show the effectiveness of the proposed stability criterion. Copyright © 2018 Elsevier Ltd. All rights reserved.

  19. Finite difference computing with exponential decay models

    CERN Document Server

    Langtangen, Hans Petter

    2016-01-01

    This text provides a very simple, initial introduction to the complete scientific computing pipeline: models, discretization, algorithms, programming, verification, and visualization. The pedagogical strategy is to use one case study – an ordinary differential equation describing exponential decay processes – to illustrate fundamental concepts in mathematics and computer science. The book is easy to read and only requires a command of one-variable calculus and some very basic knowledge about computer programming. Contrary to similar texts on numerical methods and programming, this text has a much stronger focus on implementation and teaches testing and software engineering in particular. .

  20. Exponential expansion: galactic destiny or technological hubris?

    Science.gov (United States)

    Finney, B. R.

    Is it our destiny to expand exponentially to populate the galaxy, or is such a vision but an extreme example of technological hubris? The overall record of human evolution and dispersion over the Earth can be cited to support the view that we are a uniquely expansionary and technological animal bound for the stars, yet an examination of the fate of individual migrations and exploratory initiatives raises doubts. Although it may be in keeping with our hubristic nature to predict ultimate galactic expansion, there is no way to specify how far expansionary urges may drive our spacefaring descendants.

  1. Progressive Exponential Clustering-Based Steganography

    Directory of Open Access Journals (Sweden)

    Li Yue

    2010-01-01

    Full Text Available Cluster indexing-based steganography is an important branch of data-hiding techniques. Such schemes normally achieve good balance between high embedding capacity and low embedding distortion. However, most cluster indexing-based steganographic schemes utilise less efficient clustering algorithms for embedding data, which causes redundancy and leaves room for increasing the embedding capacity further. In this paper, a new clustering algorithm, called progressive exponential clustering (PEC, is applied to increase the embedding capacity by avoiding redundancy. Meanwhile, a cluster expansion algorithm is also developed in order to further increase the capacity without sacrificing imperceptibility.

  2. Exponentially Convergent Algorithms for Abstract Differential Equations

    CERN Document Server

    Gavrilyuk, Ivan; Vasylyk, Vitalii

    2011-01-01

    This book presents new accurate and efficient exponentially convergent methods for abstract differential equations with unbounded operator coefficients in Banach space. These methods are highly relevant for the practical scientific computing since the equations under consideration can be seen as the meta-models of systems of ordinary differential equations (ODE) as well as the partial differential equations (PDEs) describing various applied problems. The framework of functional analysis allows one to obtain very general but at the same time transparent algorithms and mathematical results which

  3. Blowing-up Semilinear Wave Equation with Exponential ...

    Indian Academy of Sciences (India)

    Blowing-up Semilinear Wave Equation with Exponential Nonlinearity in Two Space ... We investigate the initial value problem for some semi-linear wave equation in two space dimensions with exponential nonlinearity growth. ... Current Issue

  4. Hyperbolic Cosine–Exponentiated Exponential Lifetime Distribution and its Application in Reliability

    Directory of Open Access Journals (Sweden)

    Omid Kharazmi

    2017-02-01

    Full Text Available Recently, Kharazmi and Saadatinik (2016 introduced a new family of lifetime distributions called hyperbolic cosine – F (HCF distribution. In the present paper, it is focused on a special case of HCF family with exponentiated exponential distribution as a baseline distribution (HCEE. Various properties of the proposed distribution including explicit expressions for the moments, quantiles, mode, moment generating function, failure rate function, mean residual lifetime, order statistics and expression of the entropy are derived. Estimating parameters of HCEE distribution are obtained by eight estimation methods: maximum likelihood, Bayesian, maximum product of spacings, parametric bootstrap, non-parametric bootstrap, percentile, least-squares and weighted least-squares. A simulation study is conducted to examine the bias, mean square error of the maximum likelihood estimators. Finally, one real data set has been analyzed for illustrative purposes and it is observed that the proposed model fits better than Weibull, gamma and generalized exponential distributions.

  5. Stability analysis of delayed Cohen-Grossberg BAM neural networks with impulses via nonsmooth analysis

    International Nuclear Information System (INIS)

    Wen Zhen; Sun Jitao

    2009-01-01

    In this paper, we investigate the existence and uniqueness of equilibrium point for delayed Cohen-Grossberg bidirectional associative memory (BAM) neural networks with impulses, based on nonsmooth analysis method. And we give the criteria of global exponential stability of the unique equilibrium point for the delayed BAM neural networks with impulses using Lyapunov method. The new sufficient condition generalizes and improves the previously known results. Finally, we present examples to illustrate that our results are effective.

  6. Exponential cluster synchronization in directed community networks via adaptive nonperiodically intermittent pinning control

    Science.gov (United States)

    Zhou, Peipei; Cai, Shuiming; Jiang, Shengqin; Liu, Zengrong

    2018-02-01

    In this paper, the problem of exponential cluster synchronization for a class of directed community networks is investigated via adaptive nonperiodically intermittent pinning control. By constructing a novel piecewise continuous Lyapunov function, some sufficient conditions to guarantee globally exponential cluster synchronization are derived. It is noted that the derived cluster synchronization criteria rely on the control rates, but not the control widths or the control periods, which facilitates the choice of the control periods in practical applications. A numerical example is finally presented to show the effectiveness of the obtained theoretical results.

  7. Exponential potentials, scaling solutions and inflation

    International Nuclear Information System (INIS)

    Wands, D.; Copeland, E.J.; Liddle, A.R.

    1993-01-01

    The goal of driving a period of rapid inflation in the early universe in a model motivated by grand unified theories has been given new life in recent years in the context of extended gravity theories. Extended inflation is one model based on a Brans-Dicke type gravity which can allow a very general first-order phase transition to complete by changing the expansion of the false vacuum dominated universe from an exponential to a power law expansion. This inflation is conformally equivalent to general relativity where the vacuum energy density is exponentially dependent upon a dilaton field. With this in mind, the authors consider in this paper the evolution of a scalar field σ with a potential V(σ) = V 0 exp(-λκ 1/2 σ) in a spatially flat (κ = 0) Friedmann-Robertson-Walker metric in the presence of a barotropic (P = (γ - 1)ρ) fluid. Here κ = 8πG, and λ is a dimensionless constant describing the steepness of the potential. It is well known that if the potential is sufficiently flat (λ small), the energy density of the scalar field dominated and the universe undergoes power law inflation. The behavior of fields with a steep potential seems to be less well known, although the results the authors present here are not new. 11 refs., 2 figs

  8. Exponential inflation with F (R ) gravity

    Science.gov (United States)

    Oikonomou, V. K.

    2018-03-01

    In this paper, we shall consider an exponential inflationary model in the context of vacuum F (R ) gravity. By using well-known reconstruction techniques, we shall investigate which F (R ) gravity can realize the exponential inflation scenario at leading order in terms of the scalar curvature, and we shall calculate the slow-roll indices and the corresponding observational indices, in the context of slow-roll inflation. We also provide some general formulas of the slow-roll and the corresponding observational indices in terms of the e -foldings number. In addition, for the calculation of the slow-roll and of the observational indices, we shall consider quite general formulas, for which it is not necessary for the assumption that all the slow-roll indices are much smaller than unity to hold true. Finally, we investigate the phenomenological viability of the model by comparing it with the latest Planck and BICEP2/Keck-Array observational data. As we demonstrate, the model is compatible with the current observational data for a wide range of the free parameters of the model.

  9. Exponential decay and exponential recovery of modal gains in high count rate channel electron multipliers

    International Nuclear Information System (INIS)

    Hahn, S.F.; Burch, J.L.

    1980-01-01

    A series of data on high count rate channel electron multipliers revealed an initial drop and subsequent recovery of gains in exponential fashion. The FWHM of the pulse height distribution at the initial stage of testing can be used as a good criterion for the selection of operating bias voltage of the channel electron multiplier

  10. An exponentiation method for XML element retrieval.

    Science.gov (United States)

    Wichaiwong, Tanakorn

    2014-01-01

    XML document is now widely used for modelling and storing structured documents. The structure is very rich and carries important information about contents and their relationships, for example, e-Commerce. XML data-centric collections require query terms allowing users to specify constraints on the document structure; mapping structure queries and assigning the weight are significant for the set of possibly relevant documents with respect to structural conditions. In this paper, we present an extension to the MEXIR search system that supports the combination of structural and content queries in the form of content-and-structure queries, which we call the Exponentiation function. It has been shown the structural information improve the effectiveness of the search system up to 52.60% over the baseline BM25 at MAP.

  11. Statistics on exponential averaging of periodograms

    Energy Technology Data Exchange (ETDEWEB)

    Peeters, T.T.J.M. [Netherlands Energy Research Foundation (ECN), Petten (Netherlands); Ciftcioglu, Oe. [Istanbul Technical Univ. (Turkey). Dept. of Electrical Engineering

    1994-11-01

    The algorithm of exponential averaging applied to subsequent periodograms of a stochastic process is used to estimate the power spectral density (PSD). For an independent process, assuming the periodogram estimates to be distributed according to a {chi}{sup 2} distribution with 2 degrees of freedom, the probability density function (PDF) of the PSD estimate is derived. A closed expression is obtained for the moments of the distribution. Surprisingly, the proof of this expression features some new insights into the partitions and Eulers infinite product. For large values of the time constant of the averaging process, examination of the cumulant generating function shows that the PDF approximates the Gaussian distribution. Although restrictions for the statistics are seemingly tight, simulation of a real process indicates a wider applicability of the theory. (orig.).

  12. Statistics on exponential averaging of periodograms

    International Nuclear Information System (INIS)

    Peeters, T.T.J.M.; Ciftcioglu, Oe.

    1994-11-01

    The algorithm of exponential averaging applied to subsequent periodograms of a stochastic process is used to estimate the power spectral density (PSD). For an independent process, assuming the periodogram estimates to be distributed according to a χ 2 distribution with 2 degrees of freedom, the probability density function (PDF) of the PSD estimate is derived. A closed expression is obtained for the moments of the distribution. Surprisingly, the proof of this expression features some new insights into the partitions and Eulers infinite product. For large values of the time constant of the averaging process, examination of the cumulant generating function shows that the PDF approximates the Gaussian distribution. Although restrictions for the statistics are seemingly tight, simulation of a real process indicates a wider applicability of the theory. (orig.)

  13. Poissonian renormalizations, exponentials, and power laws

    Science.gov (United States)

    Eliazar, Iddo

    2013-05-01

    This paper presents a comprehensive “renormalization study” of Poisson processes governed by exponential and power-law intensities. These Poisson processes are of fundamental importance, as they constitute the very bedrock of the universal extreme-value laws of Gumbel, Fréchet, and Weibull. Applying the method of Poissonian renormalization we analyze the emergence of these Poisson processes, unveil their intrinsic dynamical structures, determine their domains of attraction, and characterize their structural phase transitions. These structural phase transitions are shown to be governed by uniform and harmonic intensities, to have universal domains of attraction, to uniquely display intrinsic invariance, and to be intimately connected to “white noise” and to “1/f noise.” Thus, we establish a Poissonian explanation to the omnipresence of white and 1/f noises.

  14. Poissonian renormalizations, exponentials, and power laws.

    Science.gov (United States)

    Eliazar, Iddo

    2013-05-01

    This paper presents a comprehensive "renormalization study" of Poisson processes governed by exponential and power-law intensities. These Poisson processes are of fundamental importance, as they constitute the very bedrock of the universal extreme-value laws of Gumbel, Fréchet, and Weibull. Applying the method of Poissonian renormalization we analyze the emergence of these Poisson processes, unveil their intrinsic dynamical structures, determine their domains of attraction, and characterize their structural phase transitions. These structural phase transitions are shown to be governed by uniform and harmonic intensities, to have universal domains of attraction, to uniquely display intrinsic invariance, and to be intimately connected to "white noise" and to "1/f noise." Thus, we establish a Poissonian explanation to the omnipresence of white and 1/f noises.

  15. An exponential multireference wave-function Ansatz

    International Nuclear Information System (INIS)

    Hanrath, Michael

    2005-01-01

    An exponential multireference wave-function Ansatz is formulated. In accordance with the state universal coupled-cluster Ansatz of Jeziorski and Monkhorst [Phys. Rev. A 24, 1668 (1981)] the approach uses a reference specific cluster operator. In order to achieve state selectiveness the excitation- and reference-related amplitude indexing of the state universal Ansatz is replaced by an indexing which is based on excited determinants. There is no reference determinant playing a particular role. The approach is size consistent, coincides with traditional single-reference coupled cluster if applied to a single-reference, and converges to full configuration interaction with an increasing cluster operator excitation level. Initial applications on BeH 2 , CH 2 , Li 2 , and nH 2 are reported

  16. Transient accelerating scalar models with exponential potentials

    International Nuclear Information System (INIS)

    Cui Wen-Ping; Zhang Yang; Fu Zheng-Wen

    2013-01-01

    We study a known class of scalar dark energy models in which the potential has an exponential term and the current accelerating era is transient. We find that, although a decelerating era will return in the future, when extrapolating the model back to earlier stages (z ≳ 4), scalar dark energy becomes dominant over matter. So these models do not have the desired tracking behavior, and the predicted transient period of acceleration cannot be adopted into the standard scenario of the Big Bang cosmology. When couplings between the scalar field and matter are introduced, the models still have the same problem; only the time when deceleration returns will be varied. To achieve re-deceleration, one has to turn to alternative models that are consistent with the standard Big Bang scenario.

  17. An Exponentiation Method for XML Element Retrieval

    Science.gov (United States)

    2014-01-01

    XML document is now widely used for modelling and storing structured documents. The structure is very rich and carries important information about contents and their relationships, for example, e-Commerce. XML data-centric collections require query terms allowing users to specify constraints on the document structure; mapping structure queries and assigning the weight are significant for the set of possibly relevant documents with respect to structural conditions. In this paper, we present an extension to the MEXIR search system that supports the combination of structural and content queries in the form of content-and-structure queries, which we call the Exponentiation function. It has been shown the structural information improve the effectiveness of the search system up to 52.60% over the baseline BM25 at MAP. PMID:24696643

  18. Cascade DNA nanomachine and exponential amplification biosensing.

    Science.gov (United States)

    Xu, Jianguo; Wu, Zai-Sheng; Shen, Weiyu; Xu, Huo; Li, Hongling; Jia, Lee

    2015-11-15

    DNA is a versatile scaffold for the assembly of multifunctional nanostructures, and potential applications of various DNA nanodevices have been recently demonstrated for disease diagnosis and treatment. In the current study, a powerful cascade DNA nanomachine was developed that can execute the exponential amplification of p53 tumor suppressor gene. During the operation of the newly-proposed DNA nanomachine, dual-cyclical nucleic acid strand-displacement polymerization (dual-CNDP) was ingeniously introduced, where the target trigger is repeatedly used as the fuel molecule and the nicked fragments are dramatically accumulated. Moreover, each displaced nicked fragment is able to activate the another type of cyclical strand-displacement amplification, increasing exponentially the value of fluorescence intensity. Essentially, one target binding event can induce considerable number of subsequent reactions, and the nanodevice was called cascade DNA nanomachine. It can implement several functions, including recognition element, signaling probe, polymerization primer and template. Using the developed autonomous operation of DNA nanomachine, the p53 gene can be quantified in the wide concentration range from 0.05 to 150 nM with the detection limit of 50 pM. If taking into account the final volume of mixture, the detection limit is calculated as lower as 6.2 pM, achieving an desirable assay ability. More strikingly, the mutant gene can be easily distinguished from the wild-type one. The proof-of-concept demonstrations reported herein is expected to promote the development and application of DNA nanomachine, showing great potential value in basic biology and medical diagnosis. Copyright © 2015 Elsevier B.V. All rights reserved.

  19. Rank-shaping regularization of exponential spectral analysis for application to functional parametric mapping

    International Nuclear Information System (INIS)

    Turkheimer, Federico E; Hinz, Rainer; Gunn, Roger N; Aston, John A D; Gunn, Steve R; Cunningham, Vincent J

    2003-01-01

    Compartmental models are widely used for the mathematical modelling of dynamic studies acquired with positron emission tomography (PET). The numerical problem involves the estimation of a sum of decaying real exponentials convolved with an input function. In exponential spectral analysis (SA), the nonlinear estimation of the exponential functions is replaced by the linear estimation of the coefficients of a predefined set of exponential basis functions. This set-up guarantees fast estimation and attainment of the global optimum. SA, however, is hampered by high sensitivity to noise and, because of the positivity constraints implemented in the algorithm, cannot be extended to reference region modelling. In this paper, SA limitations are addressed by a new rank-shaping (RS) estimator that defines an appropriate regularization over an unconstrained least-squares solution obtained through singular value decomposition of the exponential base. Shrinkage parameters are conditioned on the expected signal-to-noise ratio. Through application to simulated and real datasets, it is shown that RS ameliorates and extends SA properties in the case of the production of functional parametric maps from PET studies

  20. Recommendations on: internal standard criteria, stability, incurred sample reanalysis and recent 483s by the Global CRO Council for Bioanalysis.

    Science.gov (United States)

    Lowes, Steve; Jersey, Jim; Shoup, Ronald; Garofolo, Fabio; Savoie, Natasha; Mortz, Ejvind; Needham, Shane; Caturla, Maria Cruz; Steffen, Ray; Sheldon, Curtis; Hayes, Roger; Samuels, Tim; Di Donato, Lorella; Kamerud, John; Michael, Steve; Lin, Zhongping John; Hillier, Jim; Moussallie, Marc; de Souza Teixeira, Leonardo; Rocci, Mario; Buonarati, Mike; Truog, James; Hussain, Saleh; Lundberg, Richard; Breau, Alan; Zhang, Tianyi; Jonker, Jianine; Berger, Neil; Gagnon-Carignan, Sofi; Nehls, Corey; Nicholson, Robert; Hilhorst, Martijn; Karnik, Shane; de Boer, Theo; Houghton, Richard; Smith, Kirk; Cojocaru, Laura; Allen, Mike; Harter, Tammy; Fatmi, Saadya; Sayyarpour, Farhad; Vija, Jenifer; Malone, Michele; Heller, Dennis

    2011-06-01

    "The Global CRO Council (GCC) for Bioanalysis was formed in an effort to bring together many CRO leaders to openly discuss bioanalysis and the regulatory challenges unique to the outsourcing industry"

  1. Global existence and uniform stabilization of a generalized dissipative Klein-Gordon equation type with boundary damping

    International Nuclear Information System (INIS)

    Zhang Zaiyun; Miao Xiujin; Chen Yuezhong; Liu Zhenhai

    2011-01-01

    In this paper, we prove the existence, uniqueness, and uniform stability of strong and weak solutions of the nonlinear generalized Klein-Gordon equation (1.1) 1 (see Sec. I) in bounded domains with nonlinear damped boundary conditions given by (1.1) 3 (see Sec. I) with some restrictions on function f(u), h(∇u), g(u t ), and b(x), we prove the existence and uniqueness by means of nonlinear semigroup method and obtain the uniform stabilization by using the multiplier technique.

  2. Adjusting Mitigation Pathways to Stabilize Climate at 1.5°C and 2.0°C Rise in Global Temperatures to Year 2300

    Science.gov (United States)

    Goodwin, Philip; Brown, Sally; Haigh, Ivan David; Nicholls, Robert James; Matter, Juerg M.

    2018-03-01

    To avoid the most dangerous consequences of anthropogenic climate change, the Paris Agreement provides a clear and agreed climate mitigation target of stabilizing global surface warming to under 2.0°C above preindustrial, and preferably closer to 1.5°C. However, policy makers do not currently know exactly what carbon emissions pathways to follow to stabilize warming below these agreed targets, because there is large uncertainty in future temperature rise for any given pathway. This large uncertainty makes it difficult for a cautious policy maker to avoid either: (1) allowing warming to exceed the agreed target or (2) cutting global emissions more than is required to satisfy the agreed target, and their associated societal costs. This study presents a novel Adjusting Mitigation Pathway (AMP) approach to restrict future warming to policy-driven targets, in which future emissions reductions are not fully determined now but respond to future surface warming each decade in a self-adjusting manner. A large ensemble of Earth system model simulations, constrained by geological and historical observations of past climate change, demonstrates our self-adjusting mitigation approach for a range of climate stabilization targets ranging from 1.5°C to 4.5°C, and generates AMP scenarios up to year 2300 for surface warming, carbon emissions, atmospheric CO2, global mean sea level, and surface ocean acidification. We find that lower 21st century warming targets will significantly reduce ocean acidification this century, and will avoid up to 4 m of sea-level rise by year 2300 relative to a high-end scenario.

  3. Global dynamics of a dengue epidemic mathematical model

    Energy Technology Data Exchange (ETDEWEB)

    Cai Liming [Department of Mathematics, Xinyang Normal University, Xinyang 464000 (China); Academy of Mathematics and Systems Science, Academia Sinica, Beijing 100080 (China)], E-mail: lmcai06@yahoo.com.cn; Guo Shumin [Beijing Institute of Information Control, Beijing 100037 (China); Li, XueZhi [Department of Mathematics, Xinyang Normal University, Xinyang 464000 (China); Ghosh, Mini [School of Mathematics and Computer Application, Thapar University, Patiala 147004 (India)

    2009-11-30

    The paper investigates the global stability of a dengue epidemic model with saturation and bilinear incidence. The constant human recruitment rate and exponential natural death, as well as vector population with asymptotically constant population, are incorporated into the model. The model exhibits two equilibria, namely, the disease-free equilibrium and the endemic equilibrium. The stability of these two equilibria is controlled by the threshold number R{sub 0}. It is shown that if R{sub 0} is less than one, the disease-free equilibrium is globally asymptotically stable and in such a case the endemic equilibrium does not exist; if R{sub 0} is greater than one, then the disease persists and the unique endemic equilibrium is globally asymptotically stable.

  4. Global dynamics of a dengue epidemic mathematical model

    International Nuclear Information System (INIS)

    Cai Liming; Guo Shumin; Li, XueZhi; Ghosh, Mini

    2009-01-01

    The paper investigates the global stability of a dengue epidemic model with saturation and bilinear incidence. The constant human recruitment rate and exponential natural death, as well as vector population with asymptotically constant population, are incorporated into the model. The model exhibits two equilibria, namely, the disease-free equilibrium and the endemic equilibrium. The stability of these two equilibria is controlled by the threshold number R 0 . It is shown that if R 0 is less than one, the disease-free equilibrium is globally asymptotically stable and in such a case the endemic equilibrium does not exist; if R 0 is greater than one, then the disease persists and the unique endemic equilibrium is globally asymptotically stable.

  5. A Semilinear Wave Equation with a Boundary Condition of Many-Point Type: Global Existence and Stability of Weak Solutions

    Directory of Open Access Journals (Sweden)

    Giai Giang Vo

    2015-01-01

    Full Text Available This paper is devoted to the study of a wave equation with a boundary condition of many-point type. The existence of weak solutions is proved by using the Galerkin method. Also, the uniqueness and the stability of solutions are established.

  6. An exponential decay model for mediation.

    Science.gov (United States)

    Fritz, Matthew S

    2014-10-01

    Mediation analysis is often used to investigate mechanisms of change in prevention research. Results finding mediation are strengthened when longitudinal data are used because of the need for temporal precedence. Current longitudinal mediation models have focused mainly on linear change, but many variables in prevention change nonlinearly across time. The most common solution to nonlinearity is to add a quadratic term to the linear model, but this can lead to the use of the quadratic function to explain all nonlinearity, regardless of theory and the characteristics of the variables in the model. The current study describes the problems that arise when quadratic functions are used to describe all nonlinearity and how the use of nonlinear functions, such as exponential decay, address many of these problems. In addition, nonlinear models provide several advantages over polynomial models including usefulness of parameters, parsimony, and generalizability. The effects of using nonlinear functions for mediation analysis are then discussed and a nonlinear growth curve model for mediation is presented. An empirical example using data from a randomized intervention study is then provided to illustrate the estimation and interpretation of the model. Implications, limitations, and future directions are also discussed.

  7. Stretched Exponential relaxation in pure Se glass

    Science.gov (United States)

    Dash, S.; Ravindren, S.; Boolchand, P.

    A universal feature of glasses is the stretched exponential relaxation, f (t) = exp[ - t / τ ] β . The model of diffusion of excitations to randomly distributed traps in a glass by Phillips1 yields the stretched exponent β = d[d +2] where d, the effective dimensionality. We have measured the enthalpy of relaxation ΔHnr (tw) at Tg of Se glass in modulated DSC experiments as glasses age at 300K and find β = 0.43(2) for tw in the 0

  8. Exponential growth and atmospheric carbon dioxide

    International Nuclear Information System (INIS)

    Laurmann, J.A.; Rotty, R.M.

    1983-01-01

    The adequacy of assumptions required to project atmospheric CO 2 concentrations in time frames of practical importance is reviewed. Relevant issues concern the form assumed for future fossil fuel release, carbon cycle approximations, and the implications of revisions in fossil fuel patterns required to maintain atmospheric CO 2 levels below a chosen threshold. In general, we find that with a judiciously selected exponential fossil fuel release rate, and with a constant airborn fraction, we can estimate atmospheric CO 2 growth over the next 50 years based on essentially surprise free scenarios. Resource depletion effects must be included for projections beyond about 50 years, and on this time frame the constant airborne fraction approximation has to be questioned as well (especially in later years when the fossil fuel use begins to taper off). For projections for over 100 years, both energy demand scenarios and currently available carbon cycle models have sufficient uncertainties that atmospheric CO 2 levels derived from them are not much better than guesses

  9. Simulation and characterization of the RF system and global stability analysis at the REGAE linear electron accelerator

    International Nuclear Information System (INIS)

    Mayet, Frank

    2012-12-01

    LAOLA (LAboratory for Laser- and beam-driven plasma Acceleration), is a collaboration between groups from DESY and the University of Hamburg. Its mission is to complement basic research in the relatively new field of plasma wakefield acceleration (PWA) by an explicit combination with DESY's conventional, modern accelerators. The linear electron accelerator REGAE is designed to produce sub 10 fs low charge electron bunches with ultra-low emittance at a repetition rate of 50 Hz. The planned experiments include femtosecond electron diffraction (R.J. Dwayne Miller), as well as the probing of laser induced plasma wakefields with well characterized bunches (LAOLA). They all require high bunch time of flight stability down to 10 fs. The REGAE machine consists of two RF cavities, both fed by a single klystron. While the first one - the gun cavity - is used for acceleration of the electrons, the second one - the buncher cavity - can be used to reduce the electron bunch length. This scheme only works for a specific RF phase relation between the two cavities. This thesis is split into two parts. In the first one the implications of the unique two cavity design on day-to-day machine operation are analyzed. To this end an analytical model of the RF system is developed, which is necessary for understanding how to individually adjust the cavity phases. In the second part the influence of the setup on time of flight stability is discussed with an emphasis on phase jitter compensation. RF phase stability measurements reveal that the current machine setup allows for a time of flight stability down to 50 fs right after the gun.

  10. Improved delay-dependent globally asymptotic stability of delayed uncertain recurrent neural networks with Markovian jumping parameters

    International Nuclear Information System (INIS)

    Yan, Ji; Bao-Tong, Cui

    2010-01-01

    In this paper, we have improved delay-dependent stability criteria for recurrent neural networks with a delay varying over a range and Markovian jumping parameters. The criteria improve over some previous ones in that they have fewer matrix variables yet less conservatism. In addition, a numerical example is provided to illustrate the applicability of the result using the linear matrix inequality toolbox in MATLAB. (general)

  11. Simulation and characterization of the RF system and global stability analysis at the REGAE linear electron accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Mayet, Frank

    2012-12-15

    LAOLA (LAboratory for Laser- and beam-driven plasma Acceleration), is a collaboration between groups from DESY and the University of Hamburg. Its mission is to complement basic research in the relatively new field of plasma wakefield acceleration (PWA) by an explicit combination with DESY's conventional, modern accelerators. The linear electron accelerator REGAE is designed to produce sub 10 fs low charge electron bunches with ultra-low emittance at a repetition rate of 50 Hz. The planned experiments include femtosecond electron diffraction (R.J. Dwayne Miller), as well as the probing of laser induced plasma wakefields with well characterized bunches (LAOLA). They all require high bunch time of flight stability down to 10 fs. The REGAE machine consists of two RF cavities, both fed by a single klystron. While the first one - the gun cavity - is used for acceleration of the electrons, the second one - the buncher cavity - can be used to reduce the electron bunch length. This scheme only works for a specific RF phase relation between the two cavities. This thesis is split into two parts. In the first one the implications of the unique two cavity design on day-to-day machine operation are analyzed. To this end an analytical model of the RF system is developed, which is necessary for understanding how to individually adjust the cavity phases. In the second part the influence of the setup on time of flight stability is discussed with an emphasis on phase jitter compensation. RF phase stability measurements reveal that the current machine setup allows for a time of flight stability down to 50 fs right after the gun.

  12. Novel criteria for exponential synchronization of inner time-varying complex networks with coupling delay

    International Nuclear Information System (INIS)

    Zhang Qun-Jiao; Zhao Jun-Chan

    2012-01-01

    This paper mainly investigates the exponential synchronization of an inner time-varying complex network with coupling delay. Firstly, the synchronization of complex networks is decoupled into the stability of the corresponding dynamical systems. Based on the Lyapunov function theory, some sufficient conditions to guarantee its stability with any given convergence rate are derived, thus the synchronization of the networks is achieved. Finally, the results are illustrated by a simple time-varying network model with a coupling delay. All involved numerical simulations verify the correctness of the theoretical analysis. (general)

  13. Characterizing quantum correlations. Entanglement, uncertainty relations and exponential families

    Energy Technology Data Exchange (ETDEWEB)

    Niekamp, Soenke

    2012-04-20

    This thesis is concerned with different characterizations of multi-particle quantum correlations and with entropic uncertainty relations. The effect of statistical errors on the detection of entanglement is investigated. First, general results on the statistical significance of entanglement witnesses are obtained. Then, using an error model for experiments with polarization-entangled photons, it is demonstrated that Bell inequalities with lower violation can have higher significance. The question for the best observables to discriminate between a state and the equivalence class of another state is addressed. Two measures for the discrimination strength of an observable are defined, and optimal families of observables are constructed for several examples. A property of stabilizer bases is shown which is a natural generalization of mutual unbiasedness. For sets of several dichotomic, pairwise anticommuting observables, uncertainty relations using different entropies are constructed in a systematic way. Exponential families provide a classification of states according to their correlations. In this classification scheme, a state is considered as k-correlated if it can be written as thermal state of a k-body Hamiltonian. Witness operators for the detection of higher-order interactions are constructed, and an algorithm for the computation of the nearest k-correlated state is developed.

  14. Characterizing quantum correlations. Entanglement, uncertainty relations and exponential families

    International Nuclear Information System (INIS)

    Niekamp, Soenke

    2012-01-01

    This thesis is concerned with different characterizations of multi-particle quantum correlations and with entropic uncertainty relations. The effect of statistical errors on the detection of entanglement is investigated. First, general results on the statistical significance of entanglement witnesses are obtained. Then, using an error model for experiments with polarization-entangled photons, it is demonstrated that Bell inequalities with lower violation can have higher significance. The question for the best observables to discriminate between a state and the equivalence class of another state is addressed. Two measures for the discrimination strength of an observable are defined, and optimal families of observables are constructed for several examples. A property of stabilizer bases is shown which is a natural generalization of mutual unbiasedness. For sets of several dichotomic, pairwise anticommuting observables, uncertainty relations using different entropies are constructed in a systematic way. Exponential families provide a classification of states according to their correlations. In this classification scheme, a state is considered as k-correlated if it can be written as thermal state of a k-body Hamiltonian. Witness operators for the detection of higher-order interactions are constructed, and an algorithm for the computation of the nearest k-correlated state is developed.

  15. Stability of Nonlinear Neutral Stochastic Functional Differential Equations

    Directory of Open Access Journals (Sweden)

    Minggao Xue

    2010-01-01

    Full Text Available Neutral stochastic functional differential equations (NSFDEs have recently been studied intensively. The well-known conditions imposed for the existence and uniqueness and exponential stability of the global solution are the local Lipschitz condition and the linear growth condition. Therefore, the existing results cannot be applied to many important nonlinear NSFDEs. The main aim of this paper is to remove the linear growth condition and establish a Khasminskii-type test for nonlinear NSFDEs. New criteria not only cover a wide class of highly nonlinear NSFDEs but they can also be verified much more easily than the classical criteria. Finally, several examples are given to illustrate main results.

  16. Stability of Polymer Solar Cells

    DEFF Research Database (Denmark)

    Jørgensen, Mikkel; Norrman, Kion; Gevorgyan, Suren

    2012-01-01

    Organic photovoltaics (OPVs) evolve in an exponential manner in the two key areas of efficiency and stability. The power conversion efficiency (PCE) has in the last decade been increased by almost a factor of ten approaching 10%. A main concern has been the stability that was previously measured ...

  17. Finite Difference Solution of Elastic-Plastic Thin Rotating Annular Disk with Exponentially Variable Thickness and Exponentially Variable Density

    Directory of Open Access Journals (Sweden)

    Sanjeev Sharma

    2013-01-01

    Full Text Available Elastic-plastic stresses, strains, and displacements have been obtained for a thin rotating annular disk with exponentially variable thickness and exponentially variable density with nonlinear strain hardening material by finite difference method using Von-Mises' yield criterion. Results have been computed numerically and depicted graphically. From the numerical results, it can be concluded that disk whose thickness decreases radially and density increases radially is on the safer side of design as compared to the disk with exponentially varying thickness and exponentially varying density as well as to flat disk.

  18. Exponential local discriminant embedding and its application to face recognition.

    Science.gov (United States)

    Dornaika, Fadi; Bosaghzadeh, Alireza

    2013-06-01

    Local discriminant embedding (LDE) has been recently proposed to overcome some limitations of the global linear discriminant analysis method. In the case of a small training data set, however, LDE cannot directly be applied to high-dimensional data. This case is the so-called small-sample-size (SSS) problem. The classical solution to this problem was applying dimensionality reduction on the raw data (e.g., using principal component analysis). In this paper, we introduce a novel discriminant technique called "exponential LDE" (ELDE). The proposed ELDE can be seen as an extension of LDE framework in two directions. First, the proposed framework overcomes the SSS problem without discarding the discriminant information that was contained in the null space of the locality preserving scatter matrices associated with LDE. Second, the proposed ELDE is equivalent to transforming original data into a new space by distance diffusion mapping (similar to kernel-based nonlinear mapping), and then, LDE is applied in such a new space. As a result of diffusion mapping, the margin between samples belonging to different classes is enlarged, which is helpful in improving classification accuracy. The experiments are conducted on five public face databases: Yale, Extended Yale, PF01, Pose, Illumination, and Expression (PIE), and Facial Recognition Technology (FERET). The results show that the performances of the proposed ELDE are better than those of LDE and many state-of-the-art discriminant analysis techniques.

  19. Exponential Correlation of IQ and the Wealth of Nations

    Science.gov (United States)

    Dickerson, Richard E.

    2006-01-01

    Plots of mean IQ and per capita real Gross Domestic Product for groups of 81 and 185 nations, as collected by Lynn and Vanhanen, are best fitted by an exponential function of the form: GDP = "a" * 10["b"*(IQ)], where "a" and "b" are empirical constants. Exponential fitting yields markedly higher correlation coefficients than either linear or…

  20. Is the basic law of radioactive decay exponential?

    International Nuclear Information System (INIS)

    Gopych, P.M.; Zalyubovskii, I.I.

    1988-01-01

    Basic theoretical approaches to the explanation of the observed exponential nature of the decay law are discussed together with the hypothesis that it is not exponential. The significance of this question and its connection with fundamental problems of modern physics are considered. The results of experiments relating to investigation of the form of the decay law are given

  1. Review of "Going Exponential: Growing the Charter School Sector's Best"

    Science.gov (United States)

    Garcia, David

    2011-01-01

    This Progressive Policy Institute report argues that charter schools should be expanded rapidly and exponentially. Citing exponential growth organizations, such as Starbucks and Apple, as well as the rapid growth of molds, viruses and cancers, the report advocates for similar growth models for charter schools. However, there is no explanation of…

  2. Exponential convergence on a continuous Monte Carlo transport problem

    International Nuclear Information System (INIS)

    Booth, T.E.

    1997-01-01

    For more than a decade, it has been known that exponential convergence on discrete transport problems was possible using adaptive Monte Carlo techniques. An adaptive Monte Carlo method that empirically produces exponential convergence on a simple continuous transport problem is described

  3. Stochastic B-series and order conditions for exponential integrators

    DEFF Research Database (Denmark)

    Arara, Alemayehu Adugna; Debrabant, Kristian; Kværnø, Anne

    2018-01-01

    We discuss stochastic differential equations with a stiff linear part and their approximation by stochastic exponential integrators. Representing the exact and approximate solutions using B-series and rooted trees, we derive the order conditions for stochastic exponential integrators. The resulting...

  4. Residual, restarting and Richardson iteration for the matrix exponential

    NARCIS (Netherlands)

    Bochev, Mikhail A.; Grimm, Volker; Hochbruck, Marlis

    2013-01-01

    A well-known problem in computing some matrix functions iteratively is the lack of a clear, commonly accepted residual notion. An important matrix function for which this is the case is the matrix exponential. Suppose the matrix exponential of a given matrix times a given vector has to be computed.

  5. Residual, restarting and Richardson iteration for the matrix exponential

    NARCIS (Netherlands)

    Bochev, Mikhail A.

    2010-01-01

    A well-known problem in computing some matrix functions iteratively is a lack of a clear, commonly accepted residual notion. An important matrix function for which this is the case is the matrix exponential. Assume, the matrix exponential of a given matrix times a given vector has to be computed. We

  6. Ranking Exponential Trapezoidal Fuzzy Numbers by Median Value

    Directory of Open Access Journals (Sweden)

    S. Rezvani

    2013-12-01

    Full Text Available In this paper, we want represented a method for ranking of two exponential trapezoidal fuzzy numbers. A median value is proposed for the ranking of exponential trapezoidal fuzzy numbers. For the validation the results of the proposed approach are compared with different existing approaches.

  7. Possible stretched exponential parametrization for humidity absorption in polymers.

    Science.gov (United States)

    Hacinliyan, A; Skarlatos, Y; Sahin, G; Atak, K; Aybar, O O

    2009-04-01

    Polymer thin films have irregular transient current characteristics under constant voltage. In hydrophilic and hydrophobic polymers, the irregularity is also known to depend on the humidity absorbed by the polymer sample. Different stretched exponential models are studied and it is shown that the absorption of humidity as a function of time can be adequately modelled by a class of these stretched exponential absorption models.

  8. Exponential B-splines and the partition of unity property

    DEFF Research Database (Denmark)

    Christensen, Ole; Massopust, Peter

    2012-01-01

    We provide an explicit formula for a large class of exponential B-splines. Also, we characterize the cases where the integer-translates of an exponential B-spline form a partition of unity up to a multiplicative constant. As an application of this result we construct explicitly given pairs of dual...

  9. Global classical solvability and stabilization in a two-dimensional chemotaxis-Navier-Stokes system modeling coral fertilization

    Science.gov (United States)

    Espejo, Elio; Winkler, Michael

    2018-04-01

    The interplay of chemotaxis, convection and reaction terms is studied in the particular framework of a refined model for coral broadcast spawning, consisting of three equations describing the population densities of unfertilized sperms and eggs and the concentration of a chemical released by the latter, coupled to the incompressible Navier-Stokes equations. Under mild assumptions on the initial data, global existence of classical solutions to an associated initial-boundary value problem in bounded planar domains is established. Moreover, all these solutions are shown to approach a spatially homogeneous equilibrium in the large time limit.

  10. Exponential attractors for a Cahn-Hilliard model in bounded domains with permeable walls

    Directory of Open Access Journals (Sweden)

    Ciprian G. Gal

    2006-11-01

    Full Text Available In a previous article [7], we proposed a model of phase separation in a binary mixture confined to a bounded region which may be contained within porous walls. The boundary conditions were derived from a mass conservation law and variational methods. In the present paper, we study the problem further. Using a Faedo-Galerkin method, we obtain the existence and uniqueness of a global solution to our problem, under more general assumptions than those in [7]. We then study its asymptotic behavior and prove the existence of an exponential attractor (and thus of a global attractor with finite dimension.

  11. Cosmic baldness and stability

    Energy Technology Data Exchange (ETDEWEB)

    Panchapakesan, N.; Lohiya, D.

    1985-04-01

    The stability of the de Sitter metric and the relevance of the initial state of a domain which approaches a de Sitter universe asymptotically are investigated analytically, adapting the one-dimensional wave equation with effective potential derived by Khanal and Panchapakesan (1981), for the perturbations of the de Sitter-Schwarzschild metric, to the de Sitter case. It is demonstrated that initial nonspherical perturbations do not increase exponentially with time but rather decay, the frozen modes exponentially and the backscattered perturbations of finite angular momentum l as t to the -(2l - l). It is concluded that the cosmic horizon is stable and has no hair. 14 references.

  12. Delay-Dependent Exponential Optimal Synchronization for Nonidentical Chaotic Systems via Neural-Network-Based Approach

    Directory of Open Access Journals (Sweden)

    Feng-Hsiag Hsiao

    2013-01-01

    Full Text Available A novel approach is presented to realize the optimal exponential synchronization of nonidentical multiple time-delay chaotic (MTDC systems via fuzzy control scheme. A neural-network (NN model is first constructed for the MTDC system. Then, a linear differential inclusion (LDI state-space representation is established for the dynamics of the NN model. Based on this LDI state-space representation, a delay-dependent exponential stability criterion of the error system derived in terms of Lyapunov's direct method is proposed to guarantee that the trajectories of the slave system can approach those of the master system. Subsequently, the stability condition of this criterion is reformulated into a linear matrix inequality (LMI. According to the LMI, a fuzzy controller is synthesized not only to realize the exponential synchronization but also to achieve the optimal performance by minimizing the disturbance attenuation level at the same time. Finally, a numerical example with simulations is given to demonstrate the effectiveness of our approach.

  13. Impact of short-lived non-CO2 mitigation on carbon budgets for stabilizing global warming

    International Nuclear Information System (INIS)

    Rogelj, Joeri; Riahi, Keywan; Meinshausen, Malte; Schaeffer, Michiel; Knutti, Reto

    2015-01-01

    Limiting global warming to any level requires limiting the total amount of CO 2 emissions, or staying within a CO 2 budget. Here we assess how emissions from short-lived non-CO 2 species like methane, hydrofluorocarbons (HFCs), black-carbon, and sulphates influence these CO 2 budgets. Our default case, which assumes mitigation in all sectors and of all gases, results in a CO 2 budget between 2011–2100 of 340 PgC for a >66% chance of staying below 2°C, consistent with the assessment of the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Extreme variations of air-pollutant emissions from black-carbon and sulphates influence this budget by about ±5%. In the hypothetical case of no methane or HFCs mitigation—which is unlikely when CO 2 is stringently reduced—the budgets would be much smaller (40% or up to 60%, respectively). However, assuming very stringent CH 4 mitigation as a sensitivity case, CO 2 budgets could be 25% higher. A limit on cumulative CO 2 emissions remains critical for temperature targets. Even a 25% higher CO 2 budget still means peaking global emissions in the next two decades, and achieving net zero CO 2 emissions during the third quarter of the 21st century. The leverage we have to affect the CO 2 budget by targeting non-CO 2 diminishes strongly along with CO 2 mitigation, because these are partly linked through economic and technological factors. (letter)

  14. ESTIMATION OF PARAMETERS AND RELIABILITY FUNCTION OF EXPONENTIATED EXPONENTIAL DISTRIBUTION: BAYESIAN APPROACH UNDER GENERAL ENTROPY LOSS FUNCTION

    Directory of Open Access Journals (Sweden)

    Sanjay Kumar Singh

    2011-06-01

    Full Text Available In this Paper we propose Bayes estimators of the parameters of Exponentiated Exponential distribution and Reliability functions under General Entropy loss function for Type II censored sample. The proposed estimators have been compared with the corresponding Bayes estimators obtained under Squared Error loss function and maximum likelihood estimators for their simulated risks (average loss over sample space.

  15. Global Robust Stability of Switched Interval Neural Networks with Discrete and Distributed Time-Varying Delays of Neural Type

    Directory of Open Access Journals (Sweden)

    Huaiqin Wu

    2012-01-01

    Full Text Available By combing the theories of the switched systems and the interval neural networks, the mathematics model of the switched interval neural networks with discrete and distributed time-varying delays of neural type is presented. A set of the interval parameter uncertainty neural networks with discrete and distributed time-varying delays of neural type are used as the individual subsystem, and an arbitrary switching rule is assumed to coordinate the switching between these networks. By applying the augmented Lyapunov-Krasovskii functional approach and linear matrix inequality (LMI techniques, a delay-dependent criterion is achieved to ensure to such switched interval neural networks to be globally asymptotically robustly stable in terms of LMIs. The unknown gain matrix is determined by solving this delay-dependent LMIs. Finally, an illustrative example is given to demonstrate the validity of the theoretical results.

  16. Exponentially Stable Stationary Solutions for Stochastic Evolution Equations and Their Perturbation

    International Nuclear Information System (INIS)

    Caraballo, Tomas; Kloeden, Peter E.; Schmalfuss, Bjoern

    2004-01-01

    We consider the exponential stability of stochastic evolution equations with Lipschitz continuous non-linearities when zero is not a solution for these equations. We prove the existence of anon-trivial stationary solution which is exponentially stable, where the stationary solution is generated by the composition of a random variable and the Wiener shift. We also construct stationary solutions with the stronger property of attracting bounded sets uniformly. The existence of these stationary solutions follows from the theory of random dynamical systems and their attractors. In addition, we prove some perturbation results and formulate conditions for the existence of stationary solutions for semilinear stochastic partial differential equations with Lipschitz continuous non-linearities

  17. Exponential Synchronization of Networked Chaotic Delayed Neural Network by a Hybrid Event Trigger Scheme.

    Science.gov (United States)

    Fei, Zhongyang; Guan, Chaoxu; Gao, Huijun; Zhongyang Fei; Chaoxu Guan; Huijun Gao; Fei, Zhongyang; Guan, Chaoxu; Gao, Huijun

    2018-06-01

    This paper is concerned with the exponential synchronization for master-slave chaotic delayed neural network with event trigger control scheme. The model is established on a network control framework, where both external disturbance and network-induced delay are taken into consideration. The desired aim is to synchronize the master and slave systems with limited communication capacity and network bandwidth. In order to save the network resource, we adopt a hybrid event trigger approach, which not only reduces the data package sending out, but also gets rid of the Zeno phenomenon. By using an appropriate Lyapunov functional, a sufficient criterion for the stability is proposed for the error system with extended ( , , )-dissipativity performance index. Moreover, hybrid event trigger scheme and controller are codesigned for network-based delayed neural network to guarantee the exponential synchronization between the master and slave systems. The effectiveness and potential of the proposed results are demonstrated through a numerical example.

  18. Global Stability of Polytopic Linear Time-Varying Dynamic Systems under Time-Varying Point Delays and Impulsive Controls

    Directory of Open Access Journals (Sweden)

    M. de la Sen

    2010-01-01

    Full Text Available This paper investigates the stability properties of a class of dynamic linear systems possessing several linear time-invariant parameterizations (or configurations which conform a linear time-varying polytopic dynamic system with a finite number of time-varying time-differentiable point delays. The parameterizations may be timevarying and with bounded discontinuities and they can be subject to mixed regular plus impulsive controls within a sequence of time instants of zero measure. The polytopic parameterization for the dynamics associated with each delay is specific, so that (q+1 polytopic parameterizations are considered for a system with q delays being also subject to delay-free dynamics. The considered general dynamic system includes, as particular cases, a wide class of switched linear systems whose individual parameterizations are timeinvariant which are governed by a switching rule. However, the dynamic system under consideration is viewed as much more general since it is time-varying with timevarying delays and the bounded discontinuous changes of active parameterizations are generated by impulsive controls in the dynamics and, at the same time, there is not a prescribed set of candidate potential parameterizations.

  19. Sub-exponential mixing of random billiards driven by thermostats

    International Nuclear Information System (INIS)

    Yarmola, Tatiana

    2013-01-01

    We study the class of open continuous-time mechanical particle systems introduced in the paper by Khanin and Yarmola (2013 Commun. Math. Phys. 320 121–47). Using the discrete-time results from Khanin and Yarmola (2013 Commun. Math. Phys. 320 121–47) we demonstrate rigorously that, in continuous time, a unique steady state exists and is sub-exponentially mixing. Moreover, all initial distributions converge to the steady state and, for a large class of initial distributions, convergence to the steady state is sub-exponential. The main obstacle to exponential convergence is the existence of slow particles in the system. (paper)

  20. Analytic results for asymmetric random walk with exponential transition probabilities

    International Nuclear Information System (INIS)

    Gutkowicz-Krusin, D.; Procaccia, I.; Ross, J.

    1978-01-01

    We present here exact analytic results for a random walk on a one-dimensional lattice with asymmetric, exponentially distributed jump probabilities. We derive the generating functions of such a walk for a perfect lattice and for a lattice with absorbing boundaries. We obtain solutions for some interesting moment properties, such as mean first passage time, drift velocity, dispersion, and branching ratio for absorption. The symmetric exponential walk is solved as a special case. The scaling of the mean first passage time with the size of the system for the exponentially distributed walk is determined by the symmetry and is independent of the range

  1. Exponential Shear Flow of Linear, Entangled Polymeric Liquids

    DEFF Research Database (Denmark)

    Neergaard, Jesper; Park, Kyungho; Venerus, David C.

    2000-01-01

    A previously proposed reptation model is used to interpret exponential shear flow data taken on an entangled polystyrenesolution. Both shear and normal stress measurements are made during exponential shear using mechanical means. The model iscapable of explaining all trends seen in the data......, and suggests a novel analysis of the data. This analysis demonstrates thatexponential shearing flow is no more capable of stretching polymer chains than is inception of steady shear at comparableinstantaneous shear rates. In fact, all exponential shear flow stresses measured are bounded quantitatively...

  2. (Anti)symmetric multivariate exponential functions and corresponding Fourier transforms

    International Nuclear Information System (INIS)

    Klimyk, A U; Patera, J

    2007-01-01

    We define and study symmetrized and antisymmetrized multivariate exponential functions. They are defined as determinants and antideterminants of matrices whose entries are exponential functions of one variable. These functions are eigenfunctions of the Laplace operator on the corresponding fundamental domains satisfying certain boundary conditions. To symmetric and antisymmetric multivariate exponential functions there correspond Fourier transforms. There are three types of such Fourier transforms: expansions into the corresponding Fourier series, integral Fourier transforms and multivariate finite Fourier transforms. Eigenfunctions of the integral Fourier transforms are found

  3. Exponential integrators in time-dependent density-functional calculations

    Science.gov (United States)

    Kidd, Daniel; Covington, Cody; Varga, Kálmán

    2017-12-01

    The integrating factor and exponential time differencing methods are implemented and tested for solving the time-dependent Kohn-Sham equations. Popular time propagation methods used in physics, as well as other robust numerical approaches, are compared to these exponential integrator methods in order to judge the relative merit of the computational schemes. We determine an improvement in accuracy of multiple orders of magnitude when describing dynamics driven primarily by a nonlinear potential. For cases of dynamics driven by a time-dependent external potential, the accuracy of the exponential integrator methods are less enhanced but still match or outperform the best of the conventional methods tested.

  4. Laminar phase flow for an exponentially tapered Josephson oscillator

    DEFF Research Database (Denmark)

    Benabdallah, A.; Caputo, J. G.; Scott, Alwyn C.

    2000-01-01

    Exponential tapering and inhomogeneous current feed were recently proposed as means to improve the performance of a Josephson flux flow oscillator. Extensive numerical results backed up by analysis are presented here that support this claim and demonstrate that exponential tapering reduces...... the small current instability region and leads to a laminar flow regime where the voltage wave form is periodic giving the oscillator minimal spectral width. Tapering also leads to an increased output power. Since exponential tapering is not expected to increase the difficulty of fabricating a flux flow...

  5. Stability of XIST repression in relation to genomic imprinting following global genome demethylation in a human cell line

    International Nuclear Information System (INIS)

    Araújo, E.S.S. de; Vasques, L.R.; Stabellini, R.; Krepischi, A.C.V.; Pereira, L.V.

    2014-01-01

    DNA methylation is essential in X chromosome inactivation and genomic imprinting, maintaining repression of XIST in the active X chromosome and monoallelic repression of imprinted genes. Disruption of the DNA methyltransferase genes DNMT1 and DNMT3B in the HCT116 cell line (DKO cells) leads to global DNA hypomethylation and biallelic expression of the imprinted gene IGF2 but does not lead to reactivation of XIST expression, suggesting that XIST repression is due to a more stable epigenetic mark than imprinting. To test this hypothesis, we induced acute hypomethylation in HCT116 cells by 5-aza-2′-deoxycytidine (5-aza-CdR) treatment (HCT116-5-aza-CdR) and compared that to DKO cells, evaluating DNA methylation by microarray and monitoring the expression of XIST and imprinted genes IGF2, H19, and PEG10. Whereas imprinted genes showed biallelic expression in HCT116-5-aza-CdR and DKO cells, the XIST locus was hypomethylated and weakly expressed only under acute hypomethylation conditions, indicating the importance of XIST repression in the active X to cell survival. Given that DNMT3A is the only active DNMT in DKO cells, it may be responsible for ensuring the repression of XIST in those cells. Taken together, our data suggest that XIST repression is more tightly controlled than genomic imprinting and, at least in part, is due to DNMT3A

  6. Stability of XIST repression in relation to genomic imprinting following global genome demethylation in a human cell line

    Energy Technology Data Exchange (ETDEWEB)

    Araújo, E.S.S. de [Departamento de Genética e Biologia Evolutiva, Instituto de Biociências, Universidade de São Paulo, São Paulo, SP (Brazil); Centro Internacional de Pesquisa, A.C. Camargo Cancer Center, São Paulo, SP (Brazil); Vasques, L.R. [Departamento de Genética e Biologia Evolutiva, Instituto de Biociências, Universidade de São Paulo, São Paulo, SP (Brazil); Stabellini, R.; Krepischi, A.C.V. [Departamento de Genética e Biologia Evolutiva, Instituto de Biociências, Universidade de São Paulo, São Paulo, SP (Brazil); Centro Internacional de Pesquisa, A.C. Camargo Cancer Center, São Paulo, SP (Brazil); Pereira, L.V. [Departamento de Genética e Biologia Evolutiva, Instituto de Biociências, Universidade de São Paulo, São Paulo, SP (Brazil)

    2014-10-17

    DNA methylation is essential in X chromosome inactivation and genomic imprinting, maintaining repression of XIST in the active X chromosome and monoallelic repression of imprinted genes. Disruption of the DNA methyltransferase genes DNMT1 and DNMT3B in the HCT116 cell line (DKO cells) leads to global DNA hypomethylation and biallelic expression of the imprinted gene IGF2 but does not lead to reactivation of XIST expression, suggesting that XIST repression is due to a more stable epigenetic mark than imprinting. To test this hypothesis, we induced acute hypomethylation in HCT116 cells by 5-aza-2′-deoxycytidine (5-aza-CdR) treatment (HCT116-5-aza-CdR) and compared that to DKO cells, evaluating DNA methylation by microarray and monitoring the expression of XIST and imprinted genes IGF2, H19, and PEG10. Whereas imprinted genes showed biallelic expression in HCT116-5-aza-CdR and DKO cells, the XIST locus was hypomethylated and weakly expressed only under acute hypomethylation conditions, indicating the importance of XIST repression in the active X to cell survival. Given that DNMT3A is the only active DNMT in DKO cells, it may be responsible for ensuring the repression of XIST in those cells. Taken together, our data suggest that XIST repression is more tightly controlled than genomic imprinting and, at least in part, is due to DNMT3A.

  7. Exponentially-convergent Monte Carlo via finite-element trial spaces

    International Nuclear Information System (INIS)

    Morel, Jim E.; Tooley, Jared P.; Blamer, Brandon J.

    2011-01-01

    Exponentially-Convergent Monte Carlo (ECMC) methods, also known as adaptive Monte Carlo and residual Monte Carlo methods, were the subject of intense research over a decade ago, but they never became practical for solving the realistic problems. We believe that the failure of previous efforts may be related to the choice of trial spaces that were global and thus highly oscillatory. As an alternative, we consider finite-element trial spaces, which have the ability to treat fully realistic problems. As a first step towards more general methods, we apply piecewise-linear trial spaces to the spatially-continuous two-stream transport equation. Using this approach, we achieve exponential convergence and computationally demonstrate several fundamental properties of finite-element based ECMC methods. Finally, our results indicate that the finite-element approach clearly deserves further investigation. (author)

  8. Global existence of periodic solutions of BAM neural networks with variable coefficients

    International Nuclear Information System (INIS)

    Guo Shangjiang; Huang Lihong; Dai Binxiang; Zhang Zhongzhi

    2003-01-01

    In this Letter, we study BAM (bidirectional associative memory) networks with variable coefficients. By some spectral theorems and a continuation theorem based on coincidence degree, we not only obtain some new sufficient conditions ensuring the existence, uniqueness, and global exponential stability of the periodic solution but also estimate the exponentially convergent rate. Our results are less restrictive than previously known criteria and can be applied to neural networks with a broad range of activation functions assuming neither differentiability nor strict monotonicity. Moreover, these conclusions are presented in terms of system parameters and can be easily verified for the globally Lipschitz and the spectral radius being less than 1. Therefore, our results should be useful in the design and applications of periodic oscillatory neural circuits for neural networks with delays

  9. Unsteady MHD flow in porous media past over exponentially ...

    African Journals Online (AJOL)

    International Journal of Engineering, Science and Technology ... rotation and magnetic field on the flow past an exponentially accelerated vertical plate with ... Let (u, v, w) be the components of the velocity vector V. Then using the equation.

  10. Effects of Exponential Trends on Correlations of Stock Markets

    Directory of Open Access Journals (Sweden)

    Ai-Jing Lin

    2014-01-01

    Full Text Available Detrended fluctuation analysis (DFA is a scaling analysis method used to estimate long-range power-law correlation exponents in time series. In this paper, DFA is employed to discuss the long-range correlations of stock market. The effects of exponential trends on correlations of Hang Seng Index (HSI are investigated with emphasis. We find that the long-range correlations and the positions of the crossovers of lower order DFA appear to have no immunity to the additive exponential trends. Further, our analysis suggests that an increase in the DFA order increases the efficiency of eliminating on exponential trends. In addition, the empirical study shows that the correlations and crossovers are associated with DFA order and magnitude of exponential trends.

  11. Re-analysis of exponential rigid-rotor astron equilibria

    International Nuclear Information System (INIS)

    Lovelace, R.V.; Larrabee, D.A.; Fleischmann, H.H.

    1978-01-01

    Previous studies of exponential rigid-rotor astron equilibria include particles which are not trapped in the self-field of the configuration. The modification of these studies required to exclude untrapped particles is derived

  12. Studying the method of linearization of exponential calibration curves

    International Nuclear Information System (INIS)

    Bunzh, Z.A.

    1989-01-01

    The results of study of the method for linearization of exponential calibration curves are given. The calibration technique and comparison of the proposed method with piecewise-linear approximation and power series expansion, are given

  13. Sustaining the Exponential Growth of Embedded Digital Signal Processing Capability

    National Research Council Canada - National Science Library

    Shaw, Gary A; Richards, Mark A

    2004-01-01

    .... We conjecture that as IC shrinkage and attendant performance improvements begin to slow, the exponential rate of improvement we have become accustomed to for embedded applications will be sustainable...

  14. Demonstration of the exponential decay law using beer froth

    International Nuclear Information System (INIS)

    Leike, A.

    2002-01-01

    The volume of beer froth decays exponentially with time. This property is used to demonstrate the exponential decay law in the classroom. The decay constant depends on the type of beer and can be used to differentiate between different beers. The analysis shows in a transparent way the techniques of data analysis commonly used in science - consistency checks of theoretical models with the data, parameter estimation and determination of confidence intervals. (author)

  15. Meet and Join Matrices in the Poset of Exponential Divisors

    Indian Academy of Sciences (India)

    ... exponential divisor ( G C E D ) and the least common exponential multiple ( L C E M ) do not always exist. In this paper we embed this poset in a lattice. As an application we study the G C E D and L C E M matrices, analogues of G C D and L C M matrices, which are both special cases of meet and join matrices on lattices.

  16. Bivariate copulas on the exponentially weighted moving average control chart

    Directory of Open Access Journals (Sweden)

    Sasigarn Kuvattana

    2016-10-01

    Full Text Available This paper proposes four types of copulas on the Exponentially Weighted Moving Average (EWMA control chart when observations are from an exponential distribution using a Monte Carlo simulation approach. The performance of the control chart is based on the Average Run Length (ARL which is compared for each copula. Copula functions for specifying dependence between random variables are used and measured by Kendall’s tau. The results show that the Normal copula can be used for almost all shifts.

  17. Testable Implications of Quasi-Hyperbolic and Exponential Time Discounting

    OpenAIRE

    Echenique, Federico; Imai, Taisuke; Saito, Kota

    2014-01-01

    We present the first revealed-preference characterizations of the models of exponential time discounting, quasi-hyperbolic time discounting, and other time-separable models of consumers’ intertemporal decisions. The characterizations provide non-parametric revealed-preference tests, which we take to data using the results of a recent experiment conducted by Andreoni and Sprenger (2012). For such data, we find that less than half the subjects are consistent with exponential discounting, and on...

  18. Fast Modular Exponentiation and Elliptic Curve Group Operation in Maple

    Science.gov (United States)

    Yan, S. Y.; James, G.

    2006-01-01

    The modular exponentiation, y[equivalent to]x[superscript k](mod n) with x,y,k,n integers and n [greater than] 1; is the most fundamental operation in RSA and ElGamal public-key cryptographic systems. Thus the efficiency of RSA and ElGamal depends entirely on the efficiency of the modular exponentiation. The same situation arises also in elliptic…

  19. Confronting quasi-exponential inflation with WMAP seven

    International Nuclear Information System (INIS)

    Pal, Barun Kumar; Pal, Supratik; Basu, B.

    2012-01-01

    We confront quasi-exponential models of inflation with WMAP seven years dataset using Hamilton Jacobi formalism. With a phenomenological Hubble parameter, representing quasi exponential inflation, we develop the formalism and subject the analysis to confrontation with WMAP seven using the publicly available code CAMB. The observable parameters are found to fair extremely well with WMAP seven. We also obtain a ratio of tensor to scalar amplitudes which may be detectable in PLANCK

  20. THE ATKINSON INDEX, THE MORAN STATISTIC, AND TESTING EXPONENTIALITY

    OpenAIRE

    Nao, Mimoto; Ricardas, Zitikis; Department of Statistics and Probability, Michigan State University; Department of Statistical and Actuarial Sciences, University of Western Ontario

    2008-01-01

    Constructing tests for exponentiality has been an active and fruitful research area, with numerous applications in engineering, biology and other sciences concerned with life-time data. In the present paper, we construct and investigate powerful tests for exponentiality based on two well known quantities: the Atkinson index and the Moran statistic. We provide an extensive study of the performance of the tests and compare them with those already available in the literature.