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Sample records for rapidly convergent iterative

  1. New concurrent iterative methods with monotonic convergence

    Energy Technology Data Exchange (ETDEWEB)

    Yao, Qingchuan [Michigan State Univ., East Lansing, MI (United States)

    1996-12-31

    This paper proposes the new concurrent iterative methods without using any derivatives for finding all zeros of polynomials simultaneously. The new methods are of monotonic convergence for both simple and multiple real-zeros of polynomials and are quadratically convergent. The corresponding accelerated concurrent iterative methods are obtained too. The new methods are good candidates for the application in solving symmetric eigenproblems.

  2. A Quadratically Convergent O(square root of nL-Iteration Algorithm for Linear Programming

    National Research Council Canada - National Science Library

    Ye, Y; Gueler, O; Tapia, Richard A; Zhang, Y

    1991-01-01

    ...)-iteration complexity while exhibiting superlinear convergence of the duality gap to zero under the assumption that the iteration sequence converges, and quadratic convergence of the duality gap...

  3. On the Convergence of Iterative Receiver Algorithms Utilizing Hard Decisions

    Directory of Open Access Journals (Sweden)

    Jürgen F. Rößler

    2009-01-01

    Full Text Available The convergence of receivers performing iterative hard decision interference cancellation (IHDIC is analyzed in a general framework for ASK, PSK, and QAM constellations. We first give an overview of IHDIC algorithms known from the literature applied to linear modulation and DS-CDMA-based transmission systems and show the relation to Hopfield neural network theory. It is proven analytically that IHDIC with serial update scheme always converges to a stable state in the estimated values in course of iterations and that IHDIC with parallel update scheme converges to cycles of length 2. Additionally, we visualize the convergence behavior with the aid of convergence charts. Doing so, we give insight into possible errors occurring in IHDIC which turn out to be caused by locked error situations. The derived results can directly be applied to those iterative soft decision interference cancellation (ISDIC receivers whose soft decision functions approach hard decision functions in course of the iterations.

  4. Strong convergence of modified Ishikawa iterations for nonlinear ...

    Indian Academy of Sciences (India)

    (1.3) where PK denotes the metric projection from H onto a closed convex subset K of H and proved that sequence {xn} converges strongly to PF (T )x0. Recently, Kim and Xu [13] has adapted the iteration (1.1) in a Hilbert space. More precisely, they introduced the following iteration process for asymptotically nonexpansive.

  5. Generic convergence of iterates for a class of nonlinear mappings

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    Alexander J. Zaslavski

    2004-08-01

    Full Text Available Let K be a nonempty, bounded, closed, and convex subset of a Banach space. We show that the iterates of a typical element (in the sense of Baire's categories of a class of continuous self-mappings of K converge uniformly on K to the unique fixed point of this typical element.

  6. Convergence of iterative image reconstruction algorithms for Digital Breast Tomosynthesis

    DEFF Research Database (Denmark)

    Sidky, Emil; Jørgensen, Jakob Heide; Pan, Xiaochuan

    2012-01-01

    solutions can aid in iterative image reconstruction algorithm design. This issue is particularly acute for iterative image reconstruction in Digital Breast Tomosynthesis (DBT), where the corresponding data model IS particularly poorly conditioned. The impact of this poor conditioning is that iterative......Most iterative image reconstruction algorithms are based on some form of optimization, such as minimization of a data-fidelity term plus an image regularizing penalty term. While achieving the solution of these optimization problems may not directly be clinically relevant, accurate optimization...... algorithms applied to this system can be slow to converge. Recent developments in first-order algorithms are now beginning to allow for accurate solutions to optimization problems of interest to tomographic imaging in general. In particular, we investigate an algorithm developed by Chambolle and Pock (2011 J...

  7. Improving Convergence of Iterative Feedback Tuning using Optimal External Perturbations

    DEFF Research Database (Denmark)

    Huusom, Jakob Kjøbsted; Hjalmarsson, Håkon; Poulsen, Niels Kjølstad

    2008-01-01

    Iterative feedback tuning constitutes an attractive control loop tuning method for processes in the absence of sufficient process insight. It is a purely data driven approach to optimization of the loop performance. The standard formulation ensures an unbiased estimate of the loop performance cost...... function gradient, which is used in a search algorithm. A slow rate of convergence of the tuning method is often experienced when tuning for disturbance rejection. This is due to a poor signal to noise ratio in the process data. A method is proposed for increasing the information content in data...... by introducing an optimal perturbation signal in the tuning algorithm. For minimum variance control design the optimal design of an external perturbation signal is derived in terms of the asymptotic accuracy of the iterative feedback tuning method....

  8. Comparison of the Rate of Convergence among Picard, Mann, Ishikawa, and Noor Iterations Applied to Quasicontractive Maps

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    Xue Zhiqun

    2010-01-01

    Full Text Available We provide sufficient conditions for Picard iteration to converge faster than Krasnoselskij, Mann, Ishikawa, or Noor iteration for quasicontractive operators. We also compare the rates of convergence between Krasnoselskij and Mann iterations for Zamfirescu operators.

  9. A Superlinearly Convergent O(square root of nL)-Iteration Algorithm for Linear Programming

    National Research Council Canada - National Science Library

    Ye, Y; Tapia, Richard A; Zhang, Y

    1991-01-01

    .... We demonstrate that the modified algorithm maintains its O(square root of nL)-iteration complexity, while exhibiting superlinear convergence for general problems and quadratic convergence for nondegenerate problems...

  10. Convergence of SART + OS + TV iterative reconstruction algorithm for optical CT imaging of gel dosimeters

    Science.gov (United States)

    Du, Yi; Yu, Gongyi; Xiang, Xincheng; Wang, Xiangang; De Deene, Yves

    2017-05-01

    Computational simulations are used to investigate the convergence of a hybrid iterative algorithm for optical CT reconstruction, i.e. the simultaneous algebraic reconstruction technique (SART) integrated with ordered subsets (OS) iteration and total variation (TV) minimization regularization, or SART+OS+TV for short. The influence of parameter selection to reach convergence, spatial dose gradient integrity, MTF and convergent speed are discussed. It’s shown that the results of SART+OS+TV algorithm converge to the true values without significant bias, and MTF and convergent speed are affected by different parameter sets used for iterative calculation. In conclusion, the performance of the SART+OS+TV depends on parameter selection, which also implies that careful parameter tuning work is required and necessary for proper spatial performance and fast convergence.

  11. On the Convergence of Implicit Iterative Processes for Asymptotically Pseudocontractive Mappings in the Intermediate Sense

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    Xiaolong Qin

    2011-01-01

    Full Text Available An implicit iterative process is considered. Strong and weak convergence theorems of common fixed points of a finite family of asymptotically pseudocontractive mappings in the intermediate sense are established in a real Hilbert space.

  12. on the convergence of a new iterative algorithm of three infinite ...

    Indian Academy of Sciences (India)

    20

    Manuscript Number: PMSC-D-16-00276R1. Full Title: On the convergence of a new iterative algorithm of three infinite families of generalized nonexpansive multi-valued mappings. Article Type: Reseach Article. Keywords: Common fixed point; generalized nonexpansive map; three step iterative scheme; weak and strong ...

  13. On the Convergence for an Iterative Method for Quasivariational Inclusions

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    Wu Changqun

    2010-01-01

    Full Text Available We introduce an iterative algorithm for finding a common element of the set of solutions of quasivariational inclusion problems and of the set of fixed points of strict pseudocontractions in the framework Hilbert spaces. The results presented in this paper improve and extend the corresponding results announced by many others.

  14. Convergence of GAOR Iterative Method with Strictly Diagonally Dominant Matrices

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    Guangbin Wang

    2011-01-01

    Full Text Available We discuss the convergence of GAOR method for linear systems with strictly diagonally dominant matrices. Moreover, we show that our results are better than ones of Darvishi and Hessari (2006, Tian et al. (2008 by using three numerical examples.

  15. SU-F-BRCD-09: Total Variation (TV) Based Fast Convergent Iterative CBCT Reconstruction with GPU Acceleration.

    Science.gov (United States)

    Xu, Q; Yang, D; Tan, J; Anastasio, M

    2012-06-01

    To improve image quality and reduce imaging dose in CBCT for radiation therapy applications and to realize near real-time image reconstruction based on use of a fast convergence iterative algorithm and acceleration by multi-GPUs. An iterative image reconstruction that sought to minimize a weighted least squares cost function that employed total variation (TV) regularization was employed to mitigate projection data incompleteness and noise. To achieve rapid 3D image reconstruction (spatial resolution and higher SNRs than those obtained from by use of a clinical FDK reconstruction algorithm. We have developed a fast convergence iterative algorithm for CBCT image reconstruction. The developed algorithm yielded images with better spatial resolution and higher SNR than those produced by a commercial FDK tool. In addition, from the few-view study, the iterative algorithm has shown great potential for significantly reducing imaging dose. We expect that the developed reconstruction approach will facilitate applications including IGART and patient daily CBCT-based treatment localization. © 2012 American Association of Physicists in Medicine.

  16. Reconsiderations on the Equivalence of Convergence between Mann and Ishikawa Iterations for Asymptotically Pseudocontractive Mappings

    Directory of Open Access Journals (Sweden)

    Haizhen Sun

    2013-01-01

    Full Text Available Our aim in this paper is to illustrate that the proof of main theorem of Rhoades and Şoltuz (2003 concerning the equivalence between the convergences of Ishikawa and Mann iterations for uniformly L-Lipschitzian asymptotically pseudocontractive maps is incorrect and to provide its correct version.

  17. A Rapid Convergent Low Complexity Interference Alignment Algorithm for Wireless Sensor Networks.

    Science.gov (United States)

    Jiang, Lihui; Wu, Zhilu; Ren, Guanghui; Wang, Gangyi; Zhao, Nan

    2015-07-29

    Interference alignment (IA) is a novel technique that can effectively eliminate the interference and approach the sum capacity of wireless sensor networks (WSNs) when the signal-to-noise ratio (SNR) is high, by casting the desired signal and interference into different signal subspaces. The traditional alternating minimization interference leakage (AMIL) algorithm for IA shows good performance in high SNR regimes, however, the complexity of the AMIL algorithm increases dramatically as the number of users and antennas increases, posing limits to its applications in the practical systems. In this paper, a novel IA algorithm, called directional quartic optimal (DQO) algorithm, is proposed to minimize the interference leakage with rapid convergence and low complexity. The properties of the AMIL algorithm are investigated, and it is discovered that the difference between the two consecutive iteration results of the AMIL algorithm will approximately point to the convergence solution when the precoding and decoding matrices obtained from the intermediate iterations are sufficiently close to their convergence values. Based on this important property, the proposed DQO algorithm employs the line search procedure so that it can converge to the destination directly. In addition, the optimal step size can be determined analytically by optimizing a quartic function. Numerical results show that the proposed DQO algorithm can suppress the interference leakage more rapidly than the traditional AMIL algorithm, and can achieve the same level of sum rate as that of AMIL algorithm with far less iterations and execution time.

  18. The convergence analysis of P-type iterative learning control with initial state error for some fractional system.

    Science.gov (United States)

    Liu, Xianghu; Li, Yanfang

    2017-01-01

    In this paper, the convergence of iterative learning control with initial state error for some fractional equation is studied. According to the Laplace transform and the M-L function, the concept of mild solutions is showed. The sufficient conditions of convergence for the open and closed P-type iterative learning control are obtained. Some examples are given to illustrate our main results.

  19. Some Convergence and Stability Results for the Kirk Multistep and Kirk-SP Fixed Point Iterative Algorithms

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    Faik Gürsoy

    2014-01-01

    Full Text Available The purpose of this paper is to introduce a new Kirk type iterative algorithm called Kirk multistep iteration and to study its convergence. We also prove some theorems related to the stability results for the Kirk multistep and Kirk-SP iterative processes by employing certain contractive-like operators. Our results generalize and unify some other results in the literature.

  20. Three-step iterative methods with eighth-order convergence for solving nonlinear equations

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    Mashallah Matinfar

    2013-01-01

    Full Text Available A family of eighth-order iterative methods for solution of nonlinear equations is presented. We propose an optimal three-step method with eight-order convergence for finding the simple roots of nonlinear equations by Hermite interpolation method. Per iteration of this method requires two evaluations of the function and two evaluations of its first derivative, which implies that the efficiency index of the developed methods is 1.682. Some numerical examples illustrate that the algorithms are more efficient and performs better than the other methods.

  1. Strong Convergence Iterative Algorithms for Equilibrium Problems and Fixed Point Problems in Banach Spaces

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    Shenghua Wang

    2013-01-01

    Full Text Available We first introduce the concept of Bregman asymptotically quasinonexpansive mappings and prove that the fixed point set of this kind of mappings is closed and convex. Then we construct an iterative scheme to find a common element of the set of solutions of an equilibrium problem and the set of common fixed points of a countable family of Bregman asymptotically quasinonexpansive mappings in reflexive Banach spaces and prove strong convergence theorems. Our results extend the recent ones of some others.

  2. Convergence of Variational Iteration Method for Solving Singular Partial Differential Equations of Fractional Order

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    Asma Ali Elbeleze

    2014-01-01

    Full Text Available We are concerned here with singular partial differential equations of fractional order (FSPDEs. The variational iteration method (VIM is applied to obtain approximate solutions of this type of equations. Convergence analysis of the VIM is discussed. This analysis is used to estimate the maximum absolute truncated error of the series solution. A comparison between the results of VIM solutions and exact solution is given. The fractional derivatives are described in Caputo sense.

  3. A globally convergent Lagrange and barrier function iterative algorithm for the traveling salesman problem.

    Science.gov (United States)

    Dang, C; Xu, L

    2001-03-01

    In this paper a globally convergent Lagrange and barrier function iterative algorithm is proposed for approximating a solution of the traveling salesman problem. The algorithm employs an entropy-type barrier function to deal with nonnegativity constraints and Lagrange multipliers to handle linear equality constraints, and attempts to produce a solution of high quality by generating a minimum point of a barrier problem for a sequence of descending values of the barrier parameter. For any given value of the barrier parameter, the algorithm searches for a minimum point of the barrier problem in a feasible descent direction, which has a desired property that the nonnegativity constraints are always satisfied automatically if the step length is a number between zero and one. At each iteration the feasible descent direction is found by updating Lagrange multipliers with a globally convergent iterative procedure. For any given value of the barrier parameter, the algorithm converges to a stationary point of the barrier problem without any condition on the objective function. Theoretical and numerical results show that the algorithm seems more effective and efficient than the softassign algorithm.

  4. The convergence analysis of P-type iterative learning control with initial state error for some fractional system

    Directory of Open Access Journals (Sweden)

    Xianghu Liu

    2017-01-01

    Full Text Available Abstract In this paper, the convergence of iterative learning control with initial state error for some fractional equation is studied. According to the Laplace transform and the M-L function, the concept of mild solutions is showed. The sufficient conditions of convergence for the open and closed P-type iterative learning control are obtained. Some examples are given to illustrate our main results.

  5. RRT*-SMART: A Rapid Convergence Implementation of RRT*

    OpenAIRE

    Nasir, Jauwairia; Islam, Fahad; Malik, Usman; Ayaz, Yasar; Hasan, Osman; Khan, Mushtaq; Muhammad, Mannan Saeed

    2013-01-01

    Many sampling based algorithms have been introduced recently. Among them Rapidly Exploring Random Tree (RRT) is one of the quickest and the most efficient obstacle free path finding algorithm. Although it ensures probabilistic completeness, it cannot guarantee finding the most optimal path. Rapidly Exploring Random Tree Star (RRT*), a recently proposed extension of RRT, claims to achieve convergence towards the optimal solution thus ensuring asymptotic optimality along with probabilistic comp...

  6. A rapid and convergent synthesis of the integrastatin core

    KAUST Repository

    Tadross, Pamela M.

    2011-01-01

    The tetracyclic core of the integrastatin natural products has been prepared in a convergent and rapid manner. Our strategy relies upon a palladium(ii)-catalyzed oxidative cyclization to form the central [3.3.1]-dioxabicycle of the natural product core. Overall, the core has been completed in only 4 linear steps from known compounds. © 2011 The Royal Society of Chemistry.

  7. Toward faster OPC convergence: advanced analysis for OPC iterations and simulation environment

    Science.gov (United States)

    Bahnas, Mohamed; Al-Imam, Mohamed; Tawfik, Tamer

    2008-10-01

    Achieving faster Turn-Around-Time (TAT) is one of the most attractive objectives for the silicon wafer manufacturers despite the technology node they are processing. This is valid for all the active technology nodes from 130nm till the cutting edge technologies. There have been several approaches adopted to cut down the OPC simulation runtime without sacrificing the OPC output quality, among them is using stronger CPU power and Hardware acceleration which is a good usage for the advancing powerful processing technology. Another favorable approach for cutting down the runtime is to look deeper inside the used OPC algorithm and the implemented OPC recipe. The OPC algorithm includes the convergence iterations and simulation sites distribution, and the OPC recipe is in definition how to smartly tune the OPC knobs to efficiently use the implemented algorithm. Many previous works were exposed to monitoring the OPC convergence through iterations and analyze the size of the shift per iteration, similarly several works tried to calculate the amount of simulation capacity needed for all these iterations and how to optimize it for less amount. The scope of the work presented here is an attempt to decrease the number of optical simulations by reducing the number of control points per site and without affecting OPC accuracy. The concept is proved by many simulation results and analysis. Implementing this flow illustrated the achievable simulation runtime reduction which is reflected in faster TAT. For its application, it is not just runtime optimization, additionally it puts some more intelligence in the sparse OPC engine by eliminating the headache of specifying the optimum simulation site length.

  8. Application of a repetitive process setting to design of monotonically convergent iterative learning control

    Science.gov (United States)

    Boski, Marcin; Paszke, Wojciech

    2015-11-01

    This paper deals with the problem of designing an iterative learning control algorithm for discrete linear systems using repetitive process stability theory. The resulting design produces a stabilizing output feedback controller in the time domain and a feedforward controller that guarantees monotonic convergence in the trial-to-trial domain. The results are also extended to limited frequency range design specification. New design procedure is introduced in terms of linear matrix inequality (LMI) representations, which guarantee the prescribed performances of ILC scheme. A simulation example is given to illustrate the theoretical developments.

  9. An analysis of the convergence of Newton iterations for solving elliptic Kepler's equation

    Science.gov (United States)

    Elipe, A.; Montijano, J. I.; Rández, L.; Calvo, M.

    2017-12-01

    In this note a study of the convergence properties of some starters E_0 = E_0(e,M) in the eccentricity-mean anomaly variables for solving the elliptic Kepler's equation (KE) by Newton's method is presented. By using a Wang Xinghua's theorem (Xinghua in Math Comput 68(225):169-186, 1999) on best possible error bounds in the solution of nonlinear equations by Newton's method, we obtain for each starter E_0(e,M) a set of values (e,M) \\in [0, 1) × [0, π ] that lead to the q-convergence in the sense that Newton's sequence (E_n)_{n ≥ 0} generated from E_0 = E_0(e,M) is well defined, converges to the exact solution E^* = E^*(e,M) of KE and further \\vert E_n - E^* \\vert ≤ q^{2^n -1} \\vert E_0 - E^* \\vert holds for all n ≥ 0. This study completes in some sense the results derived by Avendaño et al. (Celest Mech Dyn Astron 119:27-44, 2014) by using Smale's α -test with q=1/2. Also since in KE the convergence rate of Newton's method tends to zero as e → 0, we show that the error estimates given in the Wang Xinghua's theorem for KE can also be used to determine sets of q-convergence with q = e^k \\widetilde{q} for all e \\in [0,1) and a fixed \\widetilde{q} ≤ 1. Some remarks on the use of this theorem to derive a priori estimates of the error \\vert E_n - E^* \\vert after n Kepler's iterations are given. Finally, a posteriori bounds of this error that can be used to a dynamical estimation of the error are also obtained.

  10. RRT*-SMART: A Rapid Convergence Implementation of RRT*

    Directory of Open Access Journals (Sweden)

    Jauwairia Nasir

    2013-07-01

    Full Text Available Many sampling based algorithms have been introduced recently. Among them Rapidly Exploring Random Tree (RRT is one of the quickest and the most efficient obstacle free path finding algorithm. Although it ensures probabilistic completeness, it cannot guarantee finding the most optimal path. Rapidly Exploring Random Tree Star (RRT*, a recently proposed extension of RRT, claims to achieve convergence towards the optimal solution thus ensuring asymptotic optimality along with probabilistic completeness. However, it has been proven to take an infinite time to do so and with a slow convergence rate. In this paper an extension of RRT*, called as RRT*-Smart, has been prposed to overcome the limitaions of RRT*. The goal of the proposecd method is to accelerate the rate of convergence, in order to reach an optimum or near optimum solution at a much faster rate, thus reducing the execution time. The novel approach of the proposed algorithm makes use of two new techniques in RRT*–Path Optimization and Intelligent Sampling. Simulation results presented in various obstacle cluttered environments along with statistical and mathematical analysis confirm the efficiency of the proposed RRT*-Smart algorithm.

  11. Convergence of an Iterative Algorithm for Common Solutions for Zeros of Maximal Accretive Operator with Applications

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    Uamporn Witthayarat

    2012-01-01

    Full Text Available The aim of this paper is to introduce an iterative algorithm for finding a common solution of the sets (A+M2−1(0 and (B+M1−1(0, where M is a maximal accretive operator in a Banach space and, by using the proposed algorithm, to establish some strong convergence theorems for common solutions of the two sets above in a uniformly convex and 2-uniformly smooth Banach space. The results obtained in this paper extend and improve the corresponding results of Qin et al. 2011 from Hilbert spaces to Banach spaces and Petrot et al. 2011. Moreover, we also apply our results to some applications for solving convex feasibility problems.

  12. Strong convergence with a modified iterative projection method for hierarchical fixed point problems and variational inequalities

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    Ibrahim Karahan

    2016-04-01

    Full Text Available Let C be a nonempty closed convex subset of a real Hilbert space H. Let {T_{n}}:C›H be a sequence of nearly nonexpansive mappings such that F:=?_{i=1}^{?}F(T_{i}?Ø. Let V:C›H be a ?-Lipschitzian mapping and F:C›H be a L-Lipschitzian and ?-strongly monotone operator. This paper deals with a modified iterative projection method for approximating a solution of the hierarchical fixed point problem. It is shown that under certain approximate assumptions on the operators and parameters, the modified iterative sequence {x_{n}} converges strongly to x^{*}?F which is also the unique solution of the following variational inequality: ?0, ?x?F. As a special case, this projection method can be used to find the minimum norm solution of above variational inequality; namely, the unique solution x^{*} to the quadratic minimization problem: x^{*}=argmin_{x?F}?x?². The results here improve and extend some recent corresponding results of other authors.

  13. Convergent Polishing: A Simple, Rapid, Full Aperture Polishing Process of High Quality Optical Flats & Spheres

    OpenAIRE

    Suratwala, Tayyab; Steele, Rusty; Feit, Michael; Dylla-Spears, Rebecca; Desjardin, Richard; Mason, Dan; Wong, Lana; GERAGHTY Paul"; Miller, Phil; Shen, Nan

    2014-01-01

    Convergent Polishing is a novel polishing system and method for finishing flat and spherical glass optics in which a workpiece, independent of its initial shape (i.e., surface figure), will converge to final surface figure with excellent surface quality under a fixed, unchanging set of polishing parameters in a single polishing iteration. In contrast, conventional full aperture polishing methods require multiple, often long, iterative cycles involving polishing, metrology and process changes ...

  14. Weak and Strong Convergence of an Implicit Iteration Process for an Asymptotically Quasi- -Nonexpansive Mapping in Banach Space

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    Mukhamedov Farrukh

    2010-01-01

    Full Text Available We prove the weak and strong convergence of the implicit iterative process to a common fixed point of an asymptotically quasi- -nonexpansive mapping and an asymptotically quasi-nonexpansive mapping , defined on a nonempty closed convex subset of a Banach space.

  15. Weak and Strong Convergence of an Implicit Iteration Process for an Asymptotically Quasi-I-Nonexpansive Mapping in Banach Space

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    Farrukh Mukhamedov

    2010-01-01

    Full Text Available We prove the weak and strong convergence of the implicit iterative process to a common fixed point of an asymptotically quasi-I-nonexpansive mapping T and an asymptotically quasi-nonexpansive mapping I, defined on a nonempty closed convex subset of a Banach space.

  16. Convergence of an implicit iteration process for a finite family of asymptotically quasi-nonexpansive mappings in convex metric spaces

    Directory of Open Access Journals (Sweden)

    Gurucharan Singh Saluja

    2010-01-01

    Full Text Available In this paper, we give some necessary and sufficient conditions for an implicit iteration process with errors for a finite family of asymptotically quasi-nonexpansive mappings converging to a common fixed of the mappings in convex metric spaces. Our results extend and improve some recent results of Sun, Wittmann, Xu and Ori, and Zhou and Chang.

  17. On the convergence rate of the Dirichlet-Neumann iteration for unsteady thermal fluid-structure interaction

    Science.gov (United States)

    Monge, Azahar; Birken, Philipp

    2017-11-01

    We consider the Dirichlet-Neumann iteration for partitioned simulation of thermal fluid-structure interaction, also called conjugate heat transfer. We analyze its convergence rate for two coupled fully discretized 1D linear heat equations with jumps in the material coefficients across the interface. The heat equations are discretized using an implicit Euler scheme in time, whereas a finite element method on one domain and a finite volume method with variable aspect ratio on the other one are used in space. We provide an exact formula for the spectral radius of the iteration matrix. The formula indicates that for large time steps, the convergence rate is the aspect ratio times the quotient of heat conductivities and that decreasing the time step will improve the convergence rate. Numerical results confirm the analysis and show that the 1D formula is a very good estimator in 2D and even for nonlinear thermal FSI applications.

  18. Convergence analysis of the nonlinear iterative method for two-phase flow in porous media associated with nanoparticle injection

    KAUST Repository

    El-Amin, Mohamed

    2017-08-29

    Purpose In this paper, we introduce modeling, numerical simulation, and convergence analysis of the problem nanoparticles transport carried by a two-phase flow in a porous medium. The model consists of equations of pressure, saturation, nanoparticles concentration, deposited nanoparticles concentration on the pore-walls, and entrapped nanoparticles concentration in pore-throats. Design/methodology/approach Nonlinear iterative IMPES-IMC (IMplicit Pressure Explicit Saturation–IMplicit Concentration) scheme is used to solve the problem under consideration. The governing equations are discretized using the cell-centered finite difference (CCFD) method. The pressure and saturation equations are coupled to calculate the pressure, then the saturation is updated explicitly. Therefore, the equations of nanoparticles concentration, the deposited nanoparticles concentration on the pore walls and the entrapped nanoparticles concentration in pore throats are computed implicitly. Then, the porosity and the permeability variations are updated. Findings We stated and proved three lemmas and one theorem for the convergence of the iterative method under the natural conditions and some continuity and boundedness assumptions. The theorem is proved by induction states that after a number of iterations the sequences of the dependent variables such as saturation and concentrations approach solutions on the next time step. Moreover, two numerical examples are introduced with convergence test in terms of Courant–Friedrichs–Lewy (CFL) condition and a relaxation factor. Dependent variables such as pressure, saturation, concentration, deposited concentrations, porosity and permeability are plotted as contours in graphs, while the error estimations are presented in table for different values of number of time steps, number of iterations and mesh size. Research limitations/implications The domain of the computations is relatively small however, it is straightforward to extend this method

  19. Iter

    Science.gov (United States)

    Iotti, Robert

    2015-04-01

    ITER is an international experimental facility being built by seven Parties to demonstrate the long term potential of fusion energy. The ITER Joint Implementation Agreement (JIA) defines the structure and governance model of such cooperation. There are a number of necessary conditions for such international projects to be successful: a complete design, strong systems engineering working with an agreed set of requirements, an experienced organization with systems and plans in place to manage the project, a cost estimate backed by industry, and someone in charge. Unfortunately for ITER many of these conditions were not present. The paper discusses the priorities in the JIA which led to setting up the project with a Central Integrating Organization (IO) in Cadarache, France as the ITER HQ, and seven Domestic Agencies (DAs) located in the countries of the Parties, responsible for delivering 90%+ of the project hardware as Contributions-in-Kind and also financial contributions to the IO, as ``Contributions-in-Cash.'' Theoretically the Director General (DG) is responsible for everything. In practice the DG does not have the power to control the work of the DAs, and there is not an effective management structure enabling the IO and the DAs to arbitrate disputes, so the project is not really managed, but is a loose collaboration of competing interests. Any DA can effectively block a decision reached by the DG. Inefficiencies in completing design while setting up a competent organization from scratch contributed to the delays and cost increases during the initial few years. So did the fact that the original estimate was not developed from industry input. Unforeseen inflation and market demand on certain commodities/materials further exacerbated the cost increases. Since then, improvements are debatable. Does this mean that the governance model of ITER is a wrong model for international scientific cooperation? I do not believe so. Had the necessary conditions for success

  20. Convergence Analysis of a Fully Discrete Family of Iterated Deconvolution Methods for Turbulence Modeling with Time Relaxation

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    R. Ingram

    2012-01-01

    Full Text Available We present a general theory for regularization models of the Navier-Stokes equations based on the Leray deconvolution model with a general deconvolution operator designed to fit a few important key properties. We provide examples of this type of operator, such as the (modified Tikhonov-Lavrentiev and (modified Iterated Tikhonov-Lavrentiev operators, and study their mathematical properties. An existence theory is derived for the family of models and a rigorous convergence theory is derived for the resulting algorithms. Our theoretical results are supported by numerical testing with the Taylor-Green vortex problem, presented for the special operator cases mentioned above.

  1. Moving mesh finite element simulation for phase-field modeling of brittle fracture and convergence of Newton's iteration

    Science.gov (United States)

    Zhang, Fei; Huang, Weizhang; Li, Xianping; Zhang, Shicheng

    2018-03-01

    A moving mesh finite element method is studied for the numerical solution of a phase-field model for brittle fracture. The moving mesh partial differential equation approach is employed to dynamically track crack propagation. Meanwhile, the decomposition of the strain tensor into tensile and compressive components is essential for the success of the phase-field modeling of brittle fracture but results in a non-smooth elastic energy and stronger nonlinearity in the governing equation. This makes the governing equation much more difficult to solve and, in particular, Newton's iteration often fails to converge. Three regularization methods are proposed to smooth out the decomposition of the strain tensor. Numerical examples of fracture propagation under quasi-static load demonstrate that all of the methods can effectively improve the convergence of Newton's iteration for relatively small values of the regularization parameter but without compromising the accuracy of the numerical solution. They also show that the moving mesh finite element method is able to adaptively concentrate the mesh elements around propagating cracks and handle multiple and complex crack systems.

  2. A Design Algorithm using External Perturbation to Improve Iterative Feedback Tuning Convergence

    DEFF Research Database (Denmark)

    Huusom, Jakob Kjøbsted; Hjalmarsson, Håkan; Poulsen, Niels Kjølstad

    2011-01-01

    gradient, which is used in a search algorithm for minimizing the performance cost. A slow rate of convergence of the tuning method is often experienced when tuning for disturbance rejection. This is due to a poor signal to noise ratio in the process data. A method is proposed for increasing the data...... information content by introducing an optimal perturbation signal in the tuning algorithm. The theoretical analysis is supported by a simulation example where the proposed method is compared to an existing method for acceleration of the convergence by use of optimal prefilters....

  3. Convergence

    DEFF Research Database (Denmark)

    Madsen, Ole Brun; Nielsen, Jens Frederik Dalsgaard; Schiøler, Henrik

    2002-01-01

    Convergence trends between the WAN Internet area, characterized by best effort service provision, and the real time LAN domain, with requirements for guaranteed services, are identified and discussed. A bilateral evolution is identified, where typical bulk service applications from WAN...

  4. Convergence

    Science.gov (United States)

    Darcie, Thomas E.; Doverspike, Robert; Zirngibl, Martin; Korotky, Steven K.

    2005-09-01

    Call for Papers: Convergence The Journal of Optical Networking (JON) invites submissions to a special issue on Convergence. Convergence has become a popular theme in telecommunications, one that has broad implications across all segments of the industry. Continual evolution of technology and applications continues to erase lines between traditionally separate lines of business, with dramatic consequences for vendors, service providers, and consumers. Spectacular advances in all layers of optical networking-leading to abundant, dynamic, cost-effective, and reliable wide-area and local-area connections-have been essential drivers of this evolution. As services and networks continue to evolve towards some notion of convergence, the continued role of optical networks must be explored. One vision of convergence renders all information in a common packet (especially IP) format. This vision is driven by the proliferation of data services. For example, time-division multiplexed (TDM) voice becomes VoIP. Analog cable-television signals become MPEG bits streamed to digital set-top boxes. T1 or OC-N private lines migrate to Ethernet virtual private networks (VPNs). All these packets coexist peacefully within a single packet-routing methodology built on an optical transport layer that combines the flexibility and cost of data networks with telecom-grade reliability. While this vision is appealing in its simplicity and shared widely, specifics of implementation raise many challenges and differences of opinion. For example, many seek to expand the role of Ethernet in these transport networks, while massive efforts are underway to make traditional TDM networks more data friendly within an evolved but backward-compatible SDH/SONET (synchronous digital hierarchy and synchronous optical network) multiplexing hierarchy. From this common underlying theme follow many specific instantiations. Examples include the convergence at the physical, logical, and operational levels of voice and

  5. Convergence

    Science.gov (United States)

    Darcie, Thomas E.; Doverspike, Robert; Zirngibl, Martin; Korotky, Steven K.

    2005-01-01

    .p {padding-bottom:6px} Call for Papers: Convergence Guest Editors: Thomas E. Darcie, University of Victoria Robert Doverspike, AT&T Martin Zirngibl, Lucent Technologies Coordinating Associate Editor: Steven K. Korotky, Lucent Technologies The Journal of Optical Networking (JON) invites submissions to a special issue on Convergence. Convergence has become a popular theme in telecommunications, one that has broad implications across all segments of the industry. Continual evolution of technology and applications continues to erase lines between traditionally separate lines of business, with dramatic consequences for vendors, service providers, and consumers. Spectacular advances in all layers of optical networking-leading to abundant, dynamic, cost-effective, and reliable wide-area and local-area connections-have been essential drivers of this evolution. As services and networks continue to evolve towards some notion of convergence, the continued role of optical networks must be explored. One vision of convergence renders all information in a common packet (especially IP) format. This vision is driven by the proliferation of data services. For example, time-division multiplexed (TDM) voice becomes VoIP. Analog cable-television signals become MPEG bits streamed to digital set-top boxes. T1 or OC-N private lines migrate to Ethernet virtual private networks (VPNs). All these packets coexist peacefully within a single packet-routing methodology built on an optical transport layer that combines the flexibility and cost of data networks with telecom-grade reliability. While this vision is appealing in its simplicity and shared widely, specifics of implementation raise many challenges and differences of opinion. For example, many seek to expand the role of Ethernet in these transport networks, while massive efforts are underway to make traditional TDM networks more data friendly within an evolved but backward-compatible SDH/SONET (synchronous digital hierarchy and

  6. Strong Convergence of Parallel Iterative Algorithm with Mean Errors for Two Finite Families of Ćirić Quasi-Contractive Operators

    Directory of Open Access Journals (Sweden)

    Feng Gu

    2012-01-01

    Full Text Available The purpose of this paper is to establish a strong convergence of a new parallel iterative algorithm with mean errors to a common fixed point for two finite families of Ćirić quasi-contractive operators in normed spaces. The results presented in this paper generalize and improve the corresponding results of Berinde, Gu, Rafiq, Rhoades, and Zamfirescu.

  7. Rapidly convergent algorithms for 3-D tandem and stellarator equilibria in the paraxial approximation

    Energy Technology Data Exchange (ETDEWEB)

    McNamara, B.

    1984-04-01

    Tandem and stellarator equilibria at high ..beta.. have proved hard to compute and the relaxation methods of Bauer et al., Chodura and Schluter, Hirshman, Strauss, and Pearlstein et al. have been slow to converge. This paper reports an extension of the low-..beta.. analytic method of Pearlstein, Kaiser, and Newcomb to arbitrary ..beta.. for tandem mirrors which converges in 10 to 20 iterations. Extensions of the method to stellarator equilibria are proposed and are very close to the analytic method of Johnson and Greene - the stellarator expansion. Most of the results of all these calculations can be adequately described by low-..beta.. approximations since the MHD stability limits occur at low ..beta... The tandem mirror, having weak curvature and a long central cell, allows finite Larmor radius effects to eliminate most ballooning modes and offers the possibility of really high average ..beta... This is the interest in developing such three-dimensional numerical algorithms.

  8. Face and Convergent Validity of Persian Version of Rapid Office Strain Assessment (ROSA Checklist

    Directory of Open Access Journals (Sweden)

    Afrouz Armal

    2016-01-01

    Full Text Available Objective: The aim of this work was the translation, cultural adaptation and validation of the Persian version of the Rapid Office Stress Assessment (ROSA checklist. Material & Methods: This methodological study was conducted according of IQOLA method. 100 office worker were selected in order to carry out a psychometric evaluation of the ROSA checklist by performing validity (face and convergent analyses. The convergent validity was evaluated using RULA checklist. Results: Upon major changes made to the ROSA checklist during the translation/cultural adaptation process, face validity of the Persian version was obtained. Spearman correlation coefficient between total score of ROSA check list and RULA checklist was significant (r=0.76, p<0.0001. Conclusion: The results indicated that the translated version of the ROSA checklist is acceptable in terms of face validity, convergent validity in target society, and hence provides a useful instrument for assessing Iranian office workers

  9. Convergence and Stability of a Class of Iteratively Re-weighted Least Squares Algorithms for Sparse Signal Recovery in the Presence of Noise.

    Science.gov (United States)

    Babadi, Behtash; Ba, Demba; Purdon, Patrick L; Brown, Emery N

    2013-10-30

    In this paper, we study the theoretical properties of a class of iteratively re-weighted least squares (IRLS) algorithms for sparse signal recovery in the presence of noise. We demonstrate a one-to-one correspondence between this class of algorithms and a class of Expectation-Maximization (EM) algorithms for constrained maximum likelihood estimation under a Gaussian scale mixture (GSM) distribution. The IRLS algorithms we consider are parametrized by 0 0. The EM formalism, as well as the connection to GSMs, allow us to establish that the IRLS(ν, ε) algorithms minimize ε-smooth versions of the ℓ ν 'norms'. We leverage EM theory to show that, for each 0 < ν ≤ 1, the limit points of the sequence of IRLS(ν, ε) iterates are stationary point of the ε-smooth ℓ ν 'norm' minimization problem on the constraint set. Finally, we employ techniques from Compressive sampling (CS) theory to show that the class of IRLS(ν, ε) algorithms is stable for each 0 < ν ≤ 1, if the limit point of the iterates coincides the global minimizer. For the case ν = 1, we show that the algorithm converges exponentially fast to a neighborhood of the stationary point, and outline its generalization to super-exponential convergence for ν < 1. We demonstrate our claims via simulation experiments. The simplicity of IRLS, along with the theoretical guarantees provided in this contribution, make a compelling case for its adoption as a standard tool for sparse signal recovery.

  10. Rapid prototyping of the Central Safety System for Nuclear Risk in ITER

    Energy Technology Data Exchange (ETDEWEB)

    Scibile, L. [ITER Organization, CS 90 046, St. Paul-lez-Durance, Cedex (France); Ambrosino, G. [Consorzio CREATE, Universita degli Studi di Napoli Federico II, via Claudio 21, 80125, Napoli (Italy); De Tommasi, G., E-mail: detommas@unina.i [Consorzio CREATE, Universita degli Studi di Napoli Federico II, via Claudio 21, 80125, Napoli (Italy); Pironti, A. [Consorzio CREATE, Universita degli Studi di Napoli Federico II, via Claudio 21, 80125, Napoli (Italy)

    2010-07-15

    The Central Safety System for Nuclear Risk (CSS-N) coordinates the safety control systems to ensure nuclear safety for the ITER complex. Since the CSS-N is a safety critical system, its validation and commissioning play a very important role; in particular the required level of reliability must be demonstrated. In such a scenario, it is strongly recommended to use modeling and simulation tools since the early design phase. Indeed, the modeling tools will help in the definition of the control system requirements. Furthermore the models can than be used for the rapid prototyping of the safety system. Hardware-in-the-loop simulations can also be performed in order to assess the performance of the control hardware against a plant simulator. The proposed approach relies on the availability of a plant simulator to develop the prototype of the control system. This paper introduces the methodology used to design and develop both the CSS-N Oriented Plant Simulator and the CSS-N Prototype.

  11. Rapid Prototyping of the Central Safety System for Nuclear Risk in ITER

    Energy Technology Data Exchange (ETDEWEB)

    Scibile, L. [ITER Organization, 13 - St. Paul lez Durance (France); Ambrosino, G.; De Tommasi, G.; Pironti, A. [Euratom-ENEA-CREATE, Universita di Napoli Federico II, Napoli (Italy)

    2009-07-01

    Full text of publication follows: In the current ITER Baseline design, the Central Safety System for Nuclear Risk (CSS-N) is the safety control system in charge to assure nuclear safety for the plant, personnel and environment. In particular it is envisaged that the CSS shall interface to the plant safety systems for nuclear risk and shall coordinate the individual protection provided by the intervention of these systems by the activation, where required, of additional protections. The design of such a system, together with its implementation, strongly depends on the requirements, particularly in terms of reliability. The CSS-N is a safety critical system, thus its validation and commissioning play a very important role, since the required level of reliability must be demonstrated. In such a scenario, where a new and non-conventional system has to be deployed, it is strongly recommended to use modeling and simulation tools since the early design phase. Indeed, the modeling tools will help in the definition of the system requirements, and they will be used to test and validate the control logic. Furthermore these tools can be used to rapid design the safety system and to carry out hardware-in-the-loop (HIL) simulations, which permit to assess the performance of the control hardware against a plant simulator. Both a control system prototype and a safety system oriented plant simulator have been developed to assess first the requirements and then the performance of the CSS-N. In particular the presented SW/HW framework permits to design and verify the CSS protection logics and to test and validate these logics by means of HIL simulations. This work introduces both the prototype and plant simulator architectures, together with the methodology adopted to design and implement these validation tools. (authors)

  12. Strong convergence theorems for equilibrium problems and fixed point problems: A new iterative method, some comments and applications

    Directory of Open Access Journals (Sweden)

    Du Wei-Shih

    2011-01-01

    Full Text Available Abstract In this paper, we introduce a new approach method to find a common element in the intersection of the set of the solutions of a finite family of equilibrium problems and the set of fixed points of a nonexpansive mapping in a real Hilbert space. Under appropriate conditions, some strong convergence theorems are established. The results obtained in this paper are new, and a few examples illustrating these results are given. Finally, we point out that some 'so-called' mixed equilibrium problems and generalized equilibrium problems in the literature are still usual equilibrium problems. 2010 Mathematics Subject Classification: 47H09; 47H10, 47J25.

  13. Does Rapid and Sustained Economic Growth Lead to Convergence in Health Resources: The Case of China From 1980 to 2010.

    Science.gov (United States)

    Liang, Di; Zhang, Donglan; Huang, Jiayan; Schweitzer, Stuart

    2016-01-01

    China's rapid and sustained economic growth offers an opportunity to ask whether the advantages of growth diffuse throughout an economy, or remain localized in areas where the growth has been the greatest. A critical policy area in China has been the health system, and health inequality has become an issue that has led the government to broaden national health insurance programs. This study investigates whether health system resources and performance have converged over the past 30 years across China's 31 provinces. To examine geographic variation of health system resources and performance at the provincial level, we measure the degree of sigma convergence and beta convergence in indicators of health system resources (structure), health services utilization (process), and outcome. All data are from officially published sources: the China Health Statistics Year Book and the China Statistics Year Book. Sigma convergence is found for resource indicators, whereas it is not observed for either process or outcome indicators, indicating that disparities only narrowed in health system resources. Beta convergence is found in most indicators, except for 2 procedure indicators, reflecting that provinces with poorer resources were catching up. Convergence found in this study probably reflects the mixed outcome of government input, and market forces. Thus, left alone, the equitable distribution of health care resources may not occur naturally during a period of economic growth. Governmental and societal efforts are needed to reduce geographic health variation and promote health equity. © The Author(s) 2016.

  14. Approximating the trace of iterative solutions at the interfaces with Nonuniform Fourier transform and singular value decomposition for cost-effectively accelerating the convergence of Schwarz domain decomposition

    Directory of Open Access Journals (Sweden)

    Tromeur-Dervout Damien

    2013-12-01

    Full Text Available This paper deals with the representation of the trace of iterative Schwarz solutions at the interfaces of domain decomposition to approximate adaptively the interface error operator. This allows to build a cost-effectively accelerating of the convergence of the iterative method by extending to the vectorial case the Aitken’s accelerating convergence technique. The first representation is based on the building of a nonuniform discrete Fourier transform defined on a non-regular grid. We show how to construct a Fourier basis of dimension N+1 on this grid by building numerically a sesquilinear form, its exact accuracy to represent trigonometric polynomials of degree N / 2, and its spectral approximation property that depends on the continuity of the function to approximate. The decay of Fourier-like modes of the approximation of the trace of the iterative solution at the interfaces provides an estimate to adaptively select the modes involved in the acceleration. The drawback of this approach is to be dependent on the continuity of the trace of the iterated solution at the interfaces. The second representation, purely algebraic, uses a singular value decomposition of the trace of the iterative solution at the interfaces to provide a set of orthogonal singular vectors of which the associated singular values provide an estimate to adapt the acceleration. The resulting Aitken-Schwarz methodology is then applied to large scale computing on 3D linear Darcy flow where the permeability follows a log normal random distribution. Cet acte traite de la représentation des solutions itérées aux interfaces de la méthode de décomposition de domaine de type Schwarz afin d’approximer de manière adaptative son opérateur d’erreur aux interfaces des sous domaines. Ceci permet de construire de manière économique l’accélération de la convergence de la méthode itérative en étendant la technique d’accélération de la convergence de Aitken au cas

  15. A rapidly converging filtered-error algorithm for multichannel active noise control

    NARCIS (Netherlands)

    Berkhoff, Arthur P.; Nijsse, G.

    2006-01-01

    In this paper, a multichannel adaptive control algorithm is described which has good convergence properties while having relatively small computational complexity. This complexity is similar to that of the filtered-error algorithm. In order to obtain these properties, the algorithm is based on a

  16. Convergent losses of decay mechanisms and rapid turnover of symbiosis genes in mycorrhizal mutualists.

    Science.gov (United States)

    Kohler, Annegret; Kuo, Alan; Nagy, Laszlo G; Morin, Emmanuelle; Barry, Kerrie W; Buscot, Francois; Canbäck, Björn; Choi, Cindy; Cichocki, Nicolas; Clum, Alicia; Colpaert, Jan; Copeland, Alex; Costa, Mauricio D; Doré, Jeanne; Floudas, Dimitrios; Gay, Gilles; Girlanda, Mariangela; Henrissat, Bernard; Herrmann, Sylvie; Hess, Jaqueline; Högberg, Nils; Johansson, Tomas; Khouja, Hassine-Radhouane; LaButti, Kurt; Lahrmann, Urs; Levasseur, Anthony; Lindquist, Erika A; Lipzen, Anna; Marmeisse, Roland; Martino, Elena; Murat, Claude; Ngan, Chew Y; Nehls, Uwe; Plett, Jonathan M; Pringle, Anne; Ohm, Robin A; Perotto, Silvia; Peter, Martina; Riley, Robert; Rineau, Francois; Ruytinx, Joske; Salamov, Asaf; Shah, Firoz; Sun, Hui; Tarkka, Mika; Tritt, Andrew; Veneault-Fourrey, Claire; Zuccaro, Alga; Tunlid, Anders; Grigoriev, Igor V; Hibbett, David S; Martin, Francis

    2015-04-01

    To elucidate the genetic bases of mycorrhizal lifestyle evolution, we sequenced new fungal genomes, including 13 ectomycorrhizal (ECM), orchid (ORM) and ericoid (ERM) species, and five saprotrophs, which we analyzed along with other fungal genomes. Ectomycorrhizal fungi have a reduced complement of genes encoding plant cell wall-degrading enzymes (PCWDEs), as compared to their ancestral wood decayers. Nevertheless, they have retained a unique array of PCWDEs, thus suggesting that they possess diverse abilities to decompose lignocellulose. Similar functional categories of nonorthologous genes are induced in symbiosis. Of induced genes, 7-38% are orphan genes, including genes that encode secreted effector-like proteins. Convergent evolution of the mycorrhizal habit in fungi occurred via the repeated evolution of a 'symbiosis toolkit', with reduced numbers of PCWDEs and lineage-specific suites of mycorrhiza-induced genes.

  17. Natural Preconditioning and Iterative Methods for Saddle Point Systems

    KAUST Repository

    Pestana, Jennifer

    2015-01-01

    © 2015 Society for Industrial and Applied Mathematics. The solution of quadratic or locally quadratic extremum problems subject to linear(ized) constraints gives rise to linear systems in saddle point form. This is true whether in the continuous or the discrete setting, so saddle point systems arising from the discretization of partial differential equation problems, such as those describing electromagnetic problems or incompressible flow, lead to equations with this structure, as do, for example, interior point methods and the sequential quadratic programming approach to nonlinear optimization. This survey concerns iterative solution methods for these problems and, in particular, shows how the problem formulation leads to natural preconditioners which guarantee a fast rate of convergence of the relevant iterative methods. These preconditioners are related to the original extremum problem and their effectiveness - in terms of rapidity of convergence - is established here via a proof of general bounds on the eigenvalues of the preconditioned saddle point matrix on which iteration convergence depends.

  18. Rapid convergence of optimal control in NMR using numerically-constructed toggling frames

    Science.gov (United States)

    Coote, Paul; Anklin, Clemens; Massefski, Walter; Wagner, Gerhard; Arthanari, Haribabu

    2017-08-01

    We present a numerical method for rapidly solving the Bloch equation for an arbitrary time-varying spin-1/2 Hamiltonian. The method relies on fast, vectorized computations such as summation and quaternion multiplication, rather than slow computations such as matrix exponentiation. A toggling frame is constructed in which the Hamiltonian is time-invariant, and therefore has a simple analytical solution. The key insight is that constructing this frame is faster than solving the system dynamics in the original frame. Rapidly solving the Bloch equations for an arbitrary Hamiltonian is particularly useful in the context of NMR optimal control. Optimal control theory can be used to design pulse shapes for a range of tasks in NMR spectroscopy. However, it requires multiple simulations of the Bloch equations at each stage of the algorithm, and for each relevant set of parameters (e.g. chemical shift frequencies). This is typically time consuming. We demonstrate that by working in an appropriate toggling frame, optimal control pulses can be generated much faster. We present a new alternative to the well-known GRAPE algorithm to continuously update the toggling-frame as the optimal pulse is generated, and demonstrate that this approach is extremely fast. The use and benefit of rapid optimal pulse generation is demonstrated for 19F fragment screening experiments.

  19. Complex-plane generalization of scalar Levin transforms: A robust, rapidly convergent method to compute potentials and fields in multi-layered media

    Energy Technology Data Exchange (ETDEWEB)

    Sainath, Kamalesh, E-mail: sainath.1@osu.edu [The Ohio State University, Electroscience Laboratory, 1330 Kinnear Road, Columbus, OH 43212 (United States); Teixeira, Fernando L., E-mail: teixeira@ece.osu.edu [The Ohio State University, Electroscience Laboratory, 1330 Kinnear Road, Columbus, OH 43212 (United States); Donderici, Burkay, E-mail: Burkay.Donderici@Halliburton.com [Halliburton, Sensor Physics and Technology, 3000 N. Sam Houston Pkwy E, Houston, TX 77032 (United States)

    2014-07-15

    We propose the complex-plane generalization of a powerful algebraic sequence acceleration algorithm, the method of weighted averages (MWA), to guarantee exponential-cum-algebraic convergence of Fourier and Fourier–Hankel (F–H) integral transforms. This “complex-plane” MWA, effected via a linear-path detour in the complex plane, results in rapid, absolute convergence of field and potential solutions in multi-layered environments regardless of the source-observer geometry and anisotropy/loss of the media present. In this work, we first introduce a new integration path used to evaluate the field contribution arising from the radiation spectra. Subsequently, we (1) exhibit the foundational relations behind the complex-plane extension to a general Levin-type sequence convergence accelerator, (2) specialize this analysis to one member of the Levin transform family (the MWA), (3) address and circumvent restrictions, arising for two-dimensional integrals associated with wave dynamics problems, through minimal complex-plane detour restrictions and a novel partition of the integration domain, (4) develop and compare two formulations based on standard/real-axis MWA variants, and (5) present validation results and convergence characteristics for one of these two formulations.

  20. A Comparative Approach to the Solution of the Zabolotskaya-Khokhlov Equation by Iteration Methods

    Directory of Open Access Journals (Sweden)

    Saeed Ahmed

    2016-01-01

    Full Text Available We employed different iteration methods like Homotopy Analysis Method (HAM, Adomian Decomposition Method (ADM, and Variational Iteration Method (VIM to find the approximate solution to the Zabolotskaya-Khokhlov (ZK equation. Iteration methods are used to solve linear and nonlinear PDEs whose classical methods are either very complex or too limited to apply. A comparison study has been made to see which of these methods converges to the approximate solution rapidly. The result revealed that, amongst these methods, ADM is more effective and simpler tool in its nature which does not require any transformation or linearization.

  1. System Convergence in Transport Modelling

    DEFF Research Database (Denmark)

    Rich, Jeppe; Nielsen, Otto Anker; Cantarella, Guilio E.

    2010-01-01

    -of-successive-averages (MSA) have been proposed. Convergence of the MSA under fairly weak regularity conditions was shown in Robbins and Monro (1951). The iteration between demand and assignment ? the external equilibrium ? are in many models either decoupled or follow a very simple iteration pattern. However, as demand...

  2. Local Convergence and Radius of Convergence for Modified Newton Method

    Directory of Open Access Journals (Sweden)

    Măruşter Ştefan

    2017-12-01

    Full Text Available We investigate the local convergence of modified Newton method, i.e., the classical Newton method in which the derivative is periodically re-evaluated. Based on the convergence properties of Picard iteration for demicontractive mappings, we give an algorithm to estimate the local radius of convergence for considered method. Numerical experiments show that the proposed algorithm gives estimated radii which are very close to or even equal with the best ones.

  3. Rapid pulses of uplift, subsidence, and subduction erosion offshore Central America: Implications for building the rock record of convergent margins

    Digital Repository Service at National Institute of Oceanography (India)

    Vannucchi, P.; Sak, P.B.; Morgan, J.P.; Ohkushi, K.; Ujiie, K.; IODP Expedition 334 Shipboard Scientists; Yatheesh, V.

    at convergent margins. It currently occurs at roughly one-half of Earth’s subduction zones (von Huene and Scholl, 1991; Clift and Vannucchi, 2004), accounting for one-third of the ~5.25 km3 of continental crust consumed annually (Stern, 2011). It also plays...., Leandro, G., Schulze, A., and Dañobeitia, J.J., 1998, Seismic wideangle investigations in Costa Rica—A crustal velocity model from the Pacifi c to the Caribbean: Zentralblatt für Geologie und Paläontologie, v. 1, p. 393–408. Stern, C.R., 2011...

  4. Larger Convergence Zones for Newton's Method

    Science.gov (United States)

    Campbell, C. W.

    1986-01-01

    Iterative technique applies over wider range of initial guesses. New theorem describes convergence zone of Newton's iterative method for finding zeros of real function. Involves two points, Xp and Xp*, called primary conjugate points. If exact solution lies between these points (Xp is less than Xz is less than Xp*) and no other conjugate points in interval, then according to theorem, subsequent iterations will converge upon exact solution if initial guess lies in interval.

  5. Enhancing the Usability of an Optical Reader System to Support Point-of-Care Rapid Diagnostic Testing: An Iterative Design Approach.

    Science.gov (United States)

    Hohenstein, Jess; O'Dell, Dakota; Murnane, Elizabeth L; Lu, Zhengda; Erickson, David; Gay, Geri

    2017-11-21

    In today's health care environment, increasing costs and inadequate medical resources have created a worldwide need for more affordable diagnostic tools that are also portable, fast, and easy to use. To address this issue, numerous research and commercial efforts have focused on developing rapid diagnostic technologies; however, the efficacy of existing systems has been hindered by usability problems or high production costs, making them infeasible for deployment in at-home, point-of-care (POC), or resource-limited settings. The aim of this study was to create a low-cost optical reader system that integrates with any smart device and accepts any type of rapid diagnostic test strip to provide fast and accurate data collection, sample analysis, and diagnostic result reporting. An iterative design methodology was employed by a multidisciplinary research team to engineer three versions of a portable diagnostic testing device that were evaluated for usability and overall user receptivity. Repeated design critiques and usability studies identified a number of system requirements and considerations (eg, software compatibility, biomatter contamination, and physical footprint) that we worked to incrementally incorporate into successive system variants. Our final design phase culminated in the development of Tidbit, a reader that is compatible with any Wi-Fi-enabled device and test strip format. The Tidbit includes various features that support intuitive operation, including a straightforward test strip insertion point, external indicator lights, concealed electronic components, and an asymmetric shape, which inherently signals correct device orientation. Usability testing of the Tidbit indicates high usability for potential user communities. This study presents the design process, specification, and user reception of the Tidbit, an inexpensive, easy-to-use, portable optical reader for fast, accurate quantification of rapid diagnostic test results. Usability testing suggests

  6. Various Newton-type iterative methods for solving nonlinear equations

    Directory of Open Access Journals (Sweden)

    Manoj Kumar

    2013-10-01

    Full Text Available The aim of the present paper is to introduce and investigate new ninth and seventh order convergent Newton-type iterative methods for solving nonlinear equations. The ninth order convergent Newton-type iterative method is made derivative free to obtain seventh-order convergent Newton-type iterative method. These new with and without derivative methods have efficiency indices 1.5518 and 1.6266, respectively. The error equations are used to establish the order of convergence of these proposed iterative methods. Finally, various numerical comparisons are implemented by MATLAB to demonstrate the performance of the developed methods.

  7. Transcriptome sequence-based phylogeny of chalcidoid wasps (Hymenoptera: Chalcidoidea) reveals a history of rapid radiations, convergence, and evolutionary success.

    Science.gov (United States)

    Peters, Ralph S; Niehuis, Oliver; Gunkel, Simon; Bläser, Marcel; Mayer, Christoph; Podsiadlowski, Lars; Kozlov, Alexey; Donath, Alexander; van Noort, Simon; Liu, Shanlin; Zhou, Xin; Misof, Bernhard; Heraty, John; Krogmann, Lars

    2017-12-13

    Chalcidoidea are a megadiverse group of mostly parasitoid wasps of major ecological and economical importance that are omnipresent in almost all extant terrestrial habitats. The timing and pattern of chalcidoid diversification is so far poorly understood and has left many important questions on the evolutionary history of Chalcidoidea unanswered. In this study, we infer the early divergence events within Chalcidoidea and address the question of whether or not ancestral chalcidoids were small egg parasitoids. We also trace the evolution of some key traits: jumping ability, development of enlarged hind femora, and associations with figs. Our phylogenetic inference is based on the analysis of 3,239 single-copy genes across 48 chalcidoid wasps and outgroups representatives. We applied an innovative a posteriori evaluation approach to molecular clock-dating based on nine carefully validated fossils, resulting in the first molecular clock-based estimation of deep Chalcidoidea divergence times. Our results suggest a late Jurassic origin of Chalcidoidea, with a first divergence of morphologically and biologically distinct groups in the early to mid Cretaceous, between 129 and 81 million years ago (mya). Diversification of most extant lineages happened rapidly after the Cretaceous in the early Paleogene, between 75 and 53 mya. The inferred Chalcidoidea tree suggests a transition from ancestral minute egg parasitoids to larger-bodied parasitoids of other host stages during the early history of chalcidoid evolution. The ability to jump evolved independently at least three times, namely in Eupelmidae, Encyrtidae, and Tanaostigmatidae. Furthermore, the large-bodied strongly sclerotized species with enlarged hind femora in Chalcididae and Leucospidae are not closely related. Finally, the close association of some chalcidoid wasps with figs, either as pollinators, or as inquilines/gallers or as parasitoids, likely evolved at least twice independently: in the Eocene, giving rise

  8. Iterant Algebra

    Directory of Open Access Journals (Sweden)

    Louis H. Kauffman

    2017-07-01

    Full Text Available We give an exposition of iterant algebra, a generalization of matrix algebra that is motivated by the structure of measurement for discrete processes. We show how Clifford algebras and matrix algebras arise naturally from iterants, and we then use this point of view to discuss the Schrödinger and Dirac equations, Majorana Fermions, representations of the braid group and the framed braids in relation to the structure of the Standard Model for physics.

  9. A rapid, strong, and convergent genetic response to urban habitat fragmentation in four divergent and widespread vertebrates.

    Science.gov (United States)

    Delaney, Kathleen Semple; Riley, Seth P D; Fisher, Robert N

    2010-09-16

    Urbanization is a major cause of habitat fragmentation worldwide. Ecological and conservation theory predicts many potential impacts of habitat fragmentation on natural populations, including genetic impacts. Habitat fragmentation by urbanization causes populations of animals and plants to be isolated in patches of suitable habitat that are surrounded by non-native vegetation or severely altered vegetation, asphalt, concrete, and human structures. This can lead to genetic divergence between patches and in turn to decreased genetic diversity within patches through genetic drift and inbreeding. We examined population genetic patterns using microsatellites in four common vertebrate species, three lizards and one bird, in highly fragmented urban southern California. Despite significant phylogenetic, ecological, and mobility differences between these species, all four showed similar and significant reductions in gene flow over relatively short geographic and temporal scales. For all four species, the greatest genetic divergence was found where development was oldest and most intensive. All four animals also showed significant reduction in gene flow associated with intervening roads and freeways, the degree of patch isolation, and the time since isolation. Despite wide acceptance of the idea in principle, evidence of significant population genetic changes associated with fragmentation at small spatial and temporal scales has been rare, even in smaller terrestrial vertebrates, and especially for birds. Given the striking pattern of similar and rapid effects across four common and widespread species, including a volant bird, intense urbanization may represent the most severe form of fragmentation, with minimal effective movement through the urban matrix.

  10. ITER Status and Plans

    Science.gov (United States)

    Greenfield, Charles M.

    2017-10-01

    The US Burning Plasma Organization is pleased to welcome Dr. Bernard Bigot, who will give an update on progress in the ITER Project. Dr. Bigot took over as Director General of the ITER Organization in early 2015 following a distinguished career that included serving as Chairman and CEO of the French Alternative Energies and Atomic Energy Commission and as High Commissioner for ITER in France. During his tenure at ITER the project has moved into high gear, with rapid progress evident on the construction site and preparation of a staged schedule and a research plan leading from where we are today through all the way to full DT operation. In an unprecedented international effort, seven partners ``China, the European Union, India, Japan, Korea, Russia and the United States'' have pooled their financial and scientific resources to build the biggest fusion reactor in history. ITER will open the way to the next step: a demonstration fusion power plant. All DPP attendees are welcome to attend this ITER town meeting.

  11. Iterative methods for weighted least-squares

    Energy Technology Data Exchange (ETDEWEB)

    Bobrovnikova, E.Y.; Vavasis, S.A. [Cornell Univ., Ithaca, NY (United States)

    1996-12-31

    A weighted least-squares problem with a very ill-conditioned weight matrix arises in many applications. Because of round-off errors, the standard conjugate gradient method for solving this system does not give the correct answer even after n iterations. In this paper we propose an iterative algorithm based on a new type of reorthogonalization that converges to the solution.

  12. Convergent origins and rapid evolution of spliced leader trans-splicing in metazoa: insights from the ctenophora and hydrozoa.

    Science.gov (United States)

    Derelle, Romain; Momose, Tsuyoshi; Manuel, Michael; Da Silva, Corinne; Wincker, Patrick; Houliston, Evelyn

    2010-04-01

    Replacement of mRNA 5' UTR sequences by short sequences trans-spliced from specialized, noncoding, spliced leader (SL) RNAs is an enigmatic phenomenon, occurring in a set of distantly related animal groups including urochordates, nematodes, flatworms, and hydra, as well as in Euglenozoa and dinoflagellates. Whether SL trans-splicing has a common evolutionary origin and biological function among different organisms remains unclear. We have undertaken a systematic identification of SL exons in cDNA sequence data sets from non-bilaterian metazoan species and their closest unicellular relatives. SL exons were identified in ctenophores and in hydrozoan cnidarians, but not in other cnidarians, placozoans, or sponges, or in animal unicellular relatives. Mapping of SL absence/presence obtained from this and previous studies onto current phylogenetic trees favors an evolutionary scenario involving multiple origins for SLs during eumetazoan evolution rather than loss from a common ancestor. In both ctenophore and hydrozoan species, multiple SL sequences were identified, showing high sequence diversity. Detailed analysis of a large data set generated for the hydrozoan Clytia hemisphaerica revealed trans-splicing of given mRNAs by multiple alternative SLs. No evidence was found for a common identity of trans-spliced mRNAs between different hydrozoans. One feature found specifically to characterize SL-spliced mRNAs in hydrozoans, however, was a marked adenosine enrichment immediately 3' of the SL acceptor splice site. Our findings of high sequence divergence and apparently indiscriminate use of SLs in hydrozoans, along with recent findings in other taxa, indicate that SL genes have evolved rapidly in parallel in diverse animal groups, with constraint on SL exon sequence evolution being apparently rare.

  13. Solution of one-dimensional moving boundary problem with periodic boundary conditions by variational iteration method

    Directory of Open Access Journals (Sweden)

    Rai Nath Kabindra Rajeev

    2009-01-01

    Full Text Available In this paper, the solution of the one dimensional moving boundary problem with periodic boundary conditions is obtained with the help of variational iterational method. By using initial and boundary values, the explicit solutions of the equations have been derived, which accelerate the rapid convergence of the series solution. The method performs extremely well in terms of efficiency and simplicity. The temperature distribution and the position of moving boundary are evaluated and numerical results are presented graphically.

  14. A hyperpower iterative method for computing the generalized Drazin ...

    Indian Academy of Sciences (India)

    Shwetabh Srivastava

    Abstract. A quadratically convergent Newton-type iterative scheme is proposed for approximating the gen- eralized Drazin inverse bd of the Banach algebra element b. Further, its extension into the form of the hyper- power iterative method of arbitrary order p ! 2 is presented. Convergence criteria along with the estimation of.

  15. An efficient iterative method for solving Zakharov-Kuznetsov Equation

    Science.gov (United States)

    Saravi, Masoud; Nikkar, Ali

    2013-11-01

    In this paper, we apply new modified of Variational Iteration Method (VIM-II) which is a kind of analytical approximate method then, use it to solve Zakharov-Kuznetsov (ZK) equation that governs the behavior of the weakly nonlinear ion-acoustic waves in plasma. Two cases of this equation are considered and the results are compared with those that obtained by Adomian Decomposition Method (ADM) and Variational Homotopy Perturbation Method (VHPM). The results illustrate that proposed technique yields a very rapid convergence of the solution as well as low computational effort.

  16. A new iterative speech enhancement scheme based on Kalman filtering

    DEFF Research Database (Denmark)

    Li, Chunjian; Andersen, Søren Vang

    2005-01-01

    A new iterative speech enhancement scheme that can be seen as an approximation to the Expectation-Maximization (EM) algorithm is proposed. The algorithm employs a Kalman filter that models the excitation source as a spectrally white process with a rapidly time-varying variance, which calls...... for a high temporal resolution estimation of this variance. A Local Variance Estimator based on a Prediction Error Kalman Filter is designed for this high temporal resolution variance estimation. To achieve fast convergence and avoid local maxima of the likelihood function, a Weighted Power Spectral...

  17. Preasymptotic convergence of randomized Kaczmarz method

    Science.gov (United States)

    Jiao, Yuling; Jin, Bangti; Lu, Xiliang

    2017-12-01

    Kaczmarz method is one popular iterative method for solving inverse problems, especially in computed tomography. Recently, it was established that a randomized version of the method enjoys an exponential convergence for well-posed problems, and the convergence rate is determined by a variant of the condition number. In this work, we analyze the preasymptotic convergence behavior of the randomized Kaczmarz method, and show that the low-frequency error (with respect to the right singular vectors) decays faster during first iterations than the high-frequency error. Under the assumption that the initial error is smooth (e.g. sourcewise representation), the result explains the fast empirical convergence behavior, thereby shedding new insights into the excellent performance of the randomized Kaczmarz method in practice. Further, we propose a simple strategy to stabilize the asymptotic convergence of the iteration by means of variance reduction. We provide extensive numerical experiments to confirm the analysis and to elucidate the behavior of the algorithms.

  18. Stochastic convergence

    CERN Document Server

    Lukacs, Eugene; Lukacs, E

    1975-01-01

    Stochastic Convergence, Second Edition covers the theoretical aspects of random power series dealing with convergence problems. This edition contains eight chapters and starts with an introduction to the basic concepts of stochastic convergence. The succeeding chapters deal with infinite sequences of random variables and their convergences, as well as the consideration of certain sets of random variables as a space. These topics are followed by discussions of the infinite series of random variables, specifically the lemmas of Borel-Cantelli and the zero-one laws. Other chapters evaluate the po

  19. Convergence of Newton's method for a single real equation

    Science.gov (United States)

    Campbell, C. W.

    1985-01-01

    Newton's method for finding the zeroes of a single real function is investigated in some detail. Convergence is generally checked using the Contraction Mapping Theorem which yields sufficient but not necessary conditions for convergence of the general single point iteration method. The resulting convergence intervals are frequently considerably smaller than actual convergence zones. For a specific single point iteration method, such as Newton's method, better estimates of regions of convergence should be possible. A technique is described which, under certain conditions (frequently satisfied by well behaved functions) gives much larger zones where convergence is guaranteed.

  20. Iterative robust adaptive beamforming

    Science.gov (United States)

    Li, Yang; Ma, Hong; Cheng, Li

    2017-12-01

    The minimum power distortionless response beamformer has a good interference rejection capability, but the desired signal will be suppressed if signal steering vector or data covariance matrix is not precise. The worst-case performance optimization-based robust adaptive beamformer (WCB) has been developed to solve this problem. However, the solution of WCB cannot be expressed in a closed form, and its performance is affected by a prior parameter, which is the steering vector error norm bound of the desired signal. In this paper, we derive an approximate diagonal loading expression of WCB. This expression reveals a feedback loop relationship between steering vector and weight vector. Then, a novel robust adaptive beamformer is developed based on the iterative implementation of this feedback loop. Theoretical analysis indicates that as the iterative step increases, the performance of the proposed beamformer gets better and the iteration converges. Furthermore, the proposed beamformer does not subject to the steering vector error norm bound constraint. Simulation examples show that the proposed beamformer has better performance than some classical and similar beamformers.

  1. A New Iterative Scheme of Modified Mann Iteration in Banach Space

    Directory of Open Access Journals (Sweden)

    Jinzuo Chen

    2014-01-01

    Full Text Available We introduce the modified iterations of Mann's type for nonexpansive mappings and asymptotically nonexpansive mappings to have the strong convergence in a uniformly convex Banach space. We study approximation of common fixed point of asymptotically nonexpansive mappings in Banach space by using a new iterative scheme. Applications to the accretive operators are also included.

  2. Rapid determination of 9 aromatic amines in mainstream cigarette smoke by modified dispersive liquid liquid microextraction and ultraperformance convergence chromatography tandem mass spectrometry.

    Science.gov (United States)

    Deng, Huimin; Yang, Fei; Li, Zhonghao; Bian, Zhaoyang; Fan, Ziyan; Wang, Ying; Liu, Shanshan; Tang, Gangling

    2017-07-21

    Aromatic amines in mainstream cigarette smoke have long been monitored due to their carcinogenic toxicity. In this work, a reliable and rapid method was developed for the simultaneous determination of 9 aromatic amines in mainstream cigarette smoke by modified dispersive liquid liquid microextraction (DLLME) and ultraperformance convergence chromatography tandem mass spectrometry (UPC2-MS/MS). Briefly, the particulate phase of the cigarette smoke was captured by a Cambridge filter pad, and diluted hydrogen chloride aqueous solution is employed to extract the aromatic amines under mechanical shaking. After alkalization with sodium hydroxide solution, small amount of toluene was introduced to further extract and enrich aromatic amines by modified DLLME under vortexing. After centrifugation, toluene phase was purified by a universal QuEChERS cleanup kit and was finally analyzed by UPC2-MS/MS. Attributing to the superior performance of UPC2-MS/MS, this novel approach allowed the separation and determination of 9 aromatic amines within 5.0min with satisfactory resolution and sensitivity. The proposed method was finally validated using Kentucky reference cigarette 3R4F, and emission levels of targeted aromatic amines determined were comparable to previously reported methods At three different spiked levels, the recoveries of most analytes were ranged from 74.01% to 120.50% with relative standard deviation (RSD) less than 12%, except that the recovery of p-toluidine at low spiked level and 3-aminobiphenyl at medium spiked level was 62.77% and 69.37% respectively. Thus, this work provides a novel alternative method for the simultaneous analysis of 9 aromatic amines in mainstream cigarette smoke. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. Convergence theorems for inertial KM-type algorithms

    Science.gov (United States)

    Maingé, Paul-Emile

    2008-09-01

    This paper deals with the convergence analysis of a general fixed point method which unifies KM-type (Krasnoselskii-Mann) iteration and inertial type extrapolation. This strategy is intended to speed up the convergence of algorithms in signal processing and image reconstruction that can be formulated as KM iterations. The convergence theorems established in this new setting improve known ones and some applications are given regarding convex feasibility problems, subgradient methods, fixed point problems and monotone inclusions.

  4. Advances in iterative methods for nonlinear equations

    CERN Document Server

    Busquier, Sonia

    2016-01-01

    This book focuses on the approximation of nonlinear equations using iterative methods. Nine contributions are presented on the construction and analysis of these methods, the coverage encompassing convergence, efficiency, robustness, dynamics, and applications. Many problems are stated in the form of nonlinear equations, using mathematical modeling. In particular, a wide range of problems in Applied Mathematics and in Engineering can be solved by finding the solutions to these equations. The book reveals the importance of studying convergence aspects in iterative methods and shows that selection of the most efficient and robust iterative method for a given problem is crucial to guaranteeing a good approximation. A number of sample criteria for selecting the optimal method are presented, including those regarding the order of convergence, the computational cost, and the stability, including the dynamics. This book will appeal to researchers whose field of interest is related to nonlinear problems and equations...

  5. Improved fixed point iterative method for blade element momentum computations

    DEFF Research Database (Denmark)

    Sun, Zhenye; Shen, Wen Zhong; Chen, Jin

    2017-01-01

    , the convergence ability of the iterative method will be greatly enhanced. Numerical tests have been performed under different combinations of local tip speed ratio, local solidity, local twist and airfoil aerodynamic data. Results show that the simple iterative methods have a good convergence ability which...... to the physical solution, especially for the locations near the blade tip and root where the failure rate of the iterative method is high. The stability and accuracy of aerodynamic calculations and optimizations are greatly reduced due to this problem. The intrinsic mechanisms leading to convergence problems...

  6. Iterating skeletons

    DEFF Research Database (Denmark)

    Dieterle, Mischa; Horstmeyer, Thomas; Berthold, Jost

    2012-01-01

    to successively improving data, the repeated instantiation of a skeleton incurs a certain overhead that could be saved by reusing existing processes, threads and communication structures. This is especially important when running parallel applications in a distributed environment. However, customising......Skeleton-based programming is an area of increasing relevance with upcoming highly parallel hardware, since it substantially facilitates parallel programming and separates concerns. When parallel algorithms expressed by skeletons involve iterations – applying the same algorithm repeatedly...... a particular skeleton ad-hoc for repeated execution turns out to be considerably complicated, and raises general questions about introducing state into a stateless parallel computation. In addition, one would strongly prefer an approach which leaves the original skeleton intact, and only uses it as a building...

  7. Convergence from divergence

    Science.gov (United States)

    Costin, Ovidiu; Dunne, Gerald V.

    2018-01-01

    We show how to convert divergent series, which typically occur in many applications in physics, into rapidly convergent inverse factorial series. This can be interpreted physically as a novel resummation of perturbative series. Being convergent, these new series allow rigorous extrapolation from an asymptotic region with a large parameter, to the opposite region where the parameter is small. We illustrate the method with various physical examples, and discuss how these convergent series relate to standard methods such as Borel summation, and also how they incorporate the physical Stokes phenomenon. We comment on the relation of these results to Dyson’s physical argument for the divergence of perturbation theory. This approach also leads naturally to a wide class of relations between bosonic and fermionic partition functions, and Klein–Gordon and Dirac determinants.

  8. Semi-convergence properties of Kaczmarz’s method

    DEFF Research Database (Denmark)

    Elfving, Tommy; Hansen, Per Christian; Nikazad, Touraj

    2014-01-01

    Kaczmarz’s method—sometimes referred to as the algebraic reconstruction technique—is an iterative method that is widely used in tomographic imaging due to its favorable semi-convergence properties. Specifically, when applied to a problem with noisy data, during the early iterations it converges......-convergence of Kaczmarz’s method as well as its projected counterpart (and their block versions). To do this we study how the data errors propagate into the iteration vectors and we derive upper bounds for this noise propagation. Our bounds are compared with numerical results obtained from tomographic imaging....

  9. Convergent chaos

    Science.gov (United States)

    Pradas, Marc; Pumir, Alain; Huber, Greg; Wilkinson, Michael

    2017-07-01

    Chaos is widely understood as being a consequence of sensitive dependence upon initial conditions. This is the result of an instability in phase space, which separates trajectories exponentially. Here, we demonstrate that this criterion should be refined. Despite their overall intrinsic instability, trajectories may be very strongly convergent in phase space over extremely long periods, as revealed by our investigation of a simple chaotic system (a realistic model for small bodies in a turbulent flow). We establish that this strong convergence is a multi-facetted phenomenon, in which the clustering is intense, widespread and balanced by lacunarity of other regions. Power laws, indicative of scale-free features, characterize the distribution of particles in the system. We use large-deviation and extreme-value statistics to explain the effect. Our results show that the interpretation of the ‘butterfly effect’ needs to be carefully qualified. We argue that the combination of mixing and clustering processes makes our specific model relevant to understanding the evolution of simple organisms. Lastly, this notion of convergent chaos, which implies the existence of conditions for which uncertainties are unexpectedly small, may also be relevant to the valuation of insurance and futures contracts.

  10. Robust Monotone Iterates for Nonlinear Singularly Perturbed Boundary Value Problems

    Directory of Open Access Journals (Sweden)

    Boglaev Igor

    2009-01-01

    Full Text Available This paper is concerned with solving nonlinear singularly perturbed boundary value problems. Robust monotone iterates for solving nonlinear difference scheme are constructed. Uniform convergence of the monotone methods is investigated, and convergence rates are estimated. Numerical experiments complement the theoretical results.

  11. Runaway electrons and ITER

    Science.gov (United States)

    Boozer, Allen H.

    2017-05-01

    The potential for damage, the magnitude of the extrapolation, and the importance of the atypical—incidents that occur once in a thousand shots—make theory and simulation essential for ensuring that relativistic runaway electrons will not prevent ITER from achieving its mission. Most of the theoretical literature on electron runaway assumes magnetic surfaces exist. ITER planning for the avoidance of halo and runaway currents is focused on massive-gas or shattered-pellet injection of impurities. In simulations of experiments, such injections lead to a rapid large-scale magnetic-surface breakup. Surface breakup, which is a magnetic reconnection, can occur on a quasi-ideal Alfvénic time scale when the resistance is sufficiently small. Nevertheless, the removal of the bulk of the poloidal flux, as in halo-current mitigation, is on a resistive time scale. The acceleration of electrons to relativistic energies requires the confinement of some tubes of magnetic flux within the plasma and a resistive time scale. The interpretation of experiments on existing tokamaks and their extrapolation to ITER should carefully distinguish confined versus unconfined magnetic field lines and quasi-ideal versus resistive evolution. The separation of quasi-ideal from resistive evolution is extremely challenging numerically, but is greatly simplified by constraints of Maxwell’s equations, and in particular those associated with magnetic helicity. The physics of electron runaway along confined magnetic field lines is clarified by relations among the poloidal flux change required for an e-fold in the number of electrons, the energy distribution of the relativistic electrons, and the number of relativistic electron strikes that can be expected in a single disruption event.

  12. Fractional Variational Iteration Method for Solving Fractional Partial Differential Equations with Proportional Delay

    Directory of Open Access Journals (Sweden)

    Brajesh Kumar Singh

    2017-01-01

    Full Text Available This paper deals with an alternative approximate analytic solution to time fractional partial differential equations (TFPDEs with proportional delay, obtained by using fractional variational iteration method, where the fractional derivative is taken in Caputo sense. The proposed series solutions are found to converge to exact solution rapidly. To confirm the efficiency and validity of FRDTM, the computation of three test problems of TFPDEs with proportional delay was presented. The scheme seems to be very reliable, effective, and efficient powerful technique for solving various types of physical models arising in science and engineering.

  13. A Study on Iterative Algorithm for Stochastic Distribution Free Inventory Models

    Directory of Open Access Journals (Sweden)

    Jennifer Lin

    2013-01-01

    Full Text Available We studied the iterative algorithm in Tung et al. (2010 to find out that their assertion is questionable. We derived two new relations between safe factor and order quantity so that we can execute the iterative algorithm proposed by Wu and Ouyang (2001. We have proved that three generated sequences indeed converge to provide a theoretical validation for their iterative procedure.

  14. The optimal modified variational iteration method for the Lane-Emden equations with Neumann and Robin boundary conditions

    Science.gov (United States)

    Singh, Randhir; Das, Nilima; Kumar, Jitendra

    2017-06-01

    An effective analytical technique is proposed for the solution of the Lane-Emden equations. The proposed technique is based on the variational iteration method (VIM) and the convergence control parameter h . In order to avoid solving a sequence of nonlinear algebraic or complicated integrals for the derivation of unknown constant, the boundary conditions are used before designing the recursive scheme for solution. The series solutions are found which converges rapidly to the exact solution. Convergence analysis and error bounds are discussed. Accuracy, applicability of the method is examined by solving three singular problems: i) nonlinear Poisson-Boltzmann equation, ii) distribution of heat sources in the human head, iii) second-kind Lane-Emden equation.

  15. On the convergence of the extended conjugate gradient method for ...

    African Journals Online (AJOL)

    One striking factor that attracts problem solvers to use particular algorithm is its convergence behavior. In this paper, the convergence of the iterates generated by the ECGM for DOCP as proposed by [14] is examined. Journal of the Nigerian Association of Mathematical Physics Vol. 9 2005: pp. 493-500 ...

  16. Predictive Variable Gain Iterative Learning Control for PMSM

    Directory of Open Access Journals (Sweden)

    Huimin Xu

    2015-01-01

    Full Text Available A predictive variable gain strategy in iterative learning control (ILC is introduced. Predictive variable gain iterative learning control is constructed to improve the performance of trajectory tracking. A scheme based on predictive variable gain iterative learning control for eliminating undesirable vibrations of PMSM system is proposed. The basic idea is that undesirable vibrations of PMSM system are eliminated from two aspects of iterative domain and time domain. The predictive method is utilized to determine the learning gain in the ILC algorithm. Compression mapping principle is used to prove the convergence of the algorithm. Simulation results demonstrate that the predictive variable gain is superior to constant gain and other variable gains.

  17. Strong Convergence of Hybrid Algorithm for Asymptotically Nonexpansive Mappings in Hilbert Spaces

    Directory of Open Access Journals (Sweden)

    Juguo Su

    2012-01-01

    Full Text Available The hybrid algorithms for constructing fixed points of nonlinear mappings have been studied extensively in recent years. The advantage of this methods is that one can prove strong convergence theorems while the traditional iteration methods just have weak convergence. In this paper, we propose two types of hybrid algorithm to find a common fixed point of a finite family of asymptotically nonexpansive mappings in Hilbert spaces. One is cyclic Mann's iteration scheme, and the other is cyclic Halpern's iteration scheme. We prove the strong convergence theorems for both iteration schemes.

  18. Cosmic Divergence, Weak Cosmic Convergence, and Fixed Points at Infinity

    OpenAIRE

    Ryu, Ernest K.

    2017-01-01

    To characterize the asymptotic behavior of fixed-point iterations of non-expansive operators with no fixed points, Bauschke et al. [Fixed Point Theory Appl. (2016)] recently studied cosmic convergence and conjectured that cosmic convergence always holds. This paper presents a cosmically divergent counter example, which disproves this conjecture. This paper also demonstrates, with a counter example, that cosmic convergence can be weak in infinite dimensions. Finally, this paper shows positive ...

  19. On the Convergence of an Implicitly Restarted Arnoldi Method

    Energy Technology Data Exchange (ETDEWEB)

    Lehoucq, Richard B.

    1999-07-12

    We show that Sorensen's [35] implicitly restarted Arnoldi method (including its block extension) is simultaneous iteration with an implicit projection step to accelerate convergence to the invariant subspace of interest. By using the geometric convergence theory for simultaneous iteration due to Watkins and Elsner [43], we prove that an implicitly restarted Arnoldi method can achieve a super-linear rate of convergence to the dominant invariant subspace of a matrix. Moreover, we show how an IRAM computes a nested sequence of approximations for the partial Schur decomposition associated with the dominant invariant subspace of a matrix.

  20. A Family of Newton Type Iterative Methods for Solving Nonlinear Equations

    Directory of Open Access Journals (Sweden)

    Xiaofeng Wang

    2015-09-01

    Full Text Available In this paper, a general family of n-point Newton type iterative methods for solving nonlinear equations is constructed by using direct Hermite interpolation. The order of convergence of the new n-point iterative methods without memory is 2n requiring the evaluations of n functions and one first-order derivative in per full iteration, which implies that this family is optimal according to Kung and Traub’s conjecture (1974. Its error equations and asymptotic convergence constants are obtained. The n-point iterative methods with memory are obtained by using a self-accelerating parameter, which achieve much faster convergence than the corresponding n-point methods without memory. The increase of convergence order is attained without any additional calculations so that the n-point Newton type iterative methods with memory possess a very high computational efficiency. Numerical examples are demonstrated to confirm theoretical results.

  1. Dictionary Learning for Sparse Coding: Algorithms and Convergence Analysis.

    Science.gov (United States)

    Bao, Chenglong; Ji, Hui; Quan, Yuhui; Shen, Zuowei

    2016-07-01

    In recent years, sparse coding has been widely used in many applications ranging from image processing to pattern recognition. Most existing sparse coding based applications require solving a class of challenging non-smooth and non-convex optimization problems. Despite the fact that many numerical methods have been developed for solving these problems, it remains an open problem to find a numerical method which is not only empirically fast, but also has mathematically guaranteed strong convergence. In this paper, we propose an alternating iteration scheme for solving such problems. A rigorous convergence analysis shows that the proposed method satisfies the global convergence property: the whole sequence of iterates is convergent and converges to a critical point. Besides the theoretical soundness, the practical benefit of the proposed method is validated in applications including image restoration and recognition. Experiments show that the proposed method achieves similar results with less computation when compared to widely used methods such as K-SVD.

  2. Further remarks on convergence of decomposition method.

    Science.gov (United States)

    Cherruault, Y; Adomian, G; Abbaoui, K; Rach, R

    1995-01-01

    The decomposition method solves a wide class of nonlinear functional equations. This method uses a series solution with rapid convergence. This paper is intended as a useful review and clarification of related issues.

  3. Applied iterative methods

    CERN Document Server

    Hageman, Louis A

    1981-01-01

    This graduate-level text examines the practical use of iterative methods in solving large, sparse systems of linear algebraic equations and in resolving multidimensional boundary-value problems. Assuming minimal mathematical background, it profiles the relative merits of several general iterative procedures. Topics include polynomial acceleration of basic iterative methods, Chebyshev and conjugate gradient acceleration procedures applicable to partitioning the linear system into a "red/black" block form, adaptive computational algorithms for the successive overrelaxation (SOR) method, and comp

  4. AIR Tools - A MATLAB package of algebraic iterative reconstruction methods

    DEFF Research Database (Denmark)

    Hansen, Per Christian; Saxild-Hansen, Maria

    2012-01-01

    We present a MATLAB package with implementations of several algebraic iterative reconstruction methods for discretizations of inverse problems. These so-called row action methods rely on semi-convergence for achieving the necessary regularization of the problem. Two classes of methods are impleme......We present a MATLAB package with implementations of several algebraic iterative reconstruction methods for discretizations of inverse problems. These so-called row action methods rely on semi-convergence for achieving the necessary regularization of the problem. Two classes of methods...... are implemented: Algebraic Reconstruction Techniques (ART) and Simultaneous Iterative Reconstruction Techniques (SIRT). In addition we provide a few simplified test problems from medical and seismic tomography. For each iterative method, a number of strategies are available for choosing the relaxation parameter...

  5. Iterative quantum-classical path integral with dynamically consistent state hopping

    Energy Technology Data Exchange (ETDEWEB)

    Walters, Peter L.; Makri, Nancy [Department of Chemistry, University of Illinois, Urbana, Illinois 61801 (United States)

    2016-01-28

    We investigate the convergence of iterative quantum-classical path integral calculations in sluggish environments strongly coupled to a quantum system. The number of classical trajectories, thus the computational cost, grows rapidly (exponentially, unless filtering techniques are employed) with the memory length included in the calculation. We argue that the choice of the (single) trajectory branch during the time preceding the memory interval can significantly affect the memory length required for convergence. At short times, the trajectory branch associated with the reactant state improves convergence by eliminating spurious memory. We also introduce an instantaneous population-based probabilistic scheme which introduces state-to-state hops in the retained pre-memory trajectory branch, and which is designed to choose primarily the trajectory branch associated with the reactant at early times, but to favor the product state more as the reaction progresses to completion. Test calculations show that the dynamically consistent state hopping scheme leads to accelerated convergence and a dramatic reduction of computational effort.

  6. Picard Trajectory Approximation Iteration for Efficient Orbit Propagation

    Science.gov (United States)

    2015-07-21

    AFRL-OSR-VA-TR-2015-0203 Picard Trajectory Approximation Iteration for Efficient Orbit Propagation John Junkins TEXAS ENGINEERING EXPERIMENT STATION...Junkins, J., “Terminal Convergence Approximation Modified Chebyshev Picard Iteration for Efficient Numerical Integration of Orbital Trajectories ...problem, separated by an orbital period (these differ only in sign and along a particular Keplerian u trajectory , these sign switches occur when the

  7. Fractal aspects and convergence of Newton`s method

    Energy Technology Data Exchange (ETDEWEB)

    Drexler, M. [Oxford Univ. Computing Lab. (United Kingdom)

    1996-12-31

    Newton`s Method is a widely established iterative algorithm for solving non-linear systems. Its appeal lies in its great simplicity, easy generalization to multiple dimensions and a quadratic local convergence rate. Despite these features, little is known about its global behavior. In this paper, we will explain a seemingly random global convergence pattern using fractal concepts and show that the behavior of the residual is entirely explicable. We will also establish quantitative results for the convergence rates. Knowing the mechanism of fractal generation, we present a stabilization to the orthodox Newton method that remedies the fractal behavior and improves convergence.

  8. ITER at Cadarache; ITER a Cadarache

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2005-06-15

    This public information document presents the ITER project (International Thermonuclear Experimental Reactor), the definition of the fusion, the international cooperation and the advantages of the project. It presents also the site of Cadarache, an appropriate scientifical and economical environment. The last part of the documentation recalls the historical aspect of the project and the today mobilization of all partners. (A.L.B.)

  9. An iterative approach to a constrained least squares problem

    Directory of Open Access Journals (Sweden)

    Simeon Reich

    2003-01-01

    In the case where the set of the constraints is the nonempty intersection of a finite collection of closed convex subsets of H, an iterative algorithm is designed. The resulting sequence is shown to converge strongly to the unique solution of the regularized problem. The net of the solutions to the regularized problems strongly converges to the minimum norm solution of the least squares problem if its solution set is nonempty.

  10. A New Inexact Inverse Subspace Iteration for Generalized Eigenvalue Problems

    Directory of Open Access Journals (Sweden)

    Fatemeh Mohammad

    2014-05-01

    Full Text Available In this paper‎, ‎we represent an inexact inverse‎ ‎subspace iteration method for computing a few eigenpairs of the‎ ‎generalized eigenvalue problem $Ax = \\lambda Bx$[Q.~Ye and P.~Zhang‎, ‎Inexact inverse subspace iteration for generalized eigenvalue‎ ‎problems‎, ‎Linear Algebra and its Application‎, ‎434 (2011 1697-1715‎‎]‎. ‎In particular‎, ‎the linear convergence property of the inverse‎ ‎subspace iteration is preserved‎.

  11. An iterative solver for the 3D Helmholtz equation

    Science.gov (United States)

    Belonosov, Mikhail; Dmitriev, Maxim; Kostin, Victor; Neklyudov, Dmitry; Tcheverda, Vladimir

    2017-09-01

    We develop a frequency-domain iterative solver for numerical simulation of acoustic waves in 3D heterogeneous media. It is based on the application of a unique preconditioner to the Helmholtz equation that ensures convergence for Krylov subspace iteration methods. Effective inversion of the preconditioner involves the Fast Fourier Transform (FFT) and numerical solution of a series of boundary value problems for ordinary differential equations. Matrix-by-vector multiplication for iterative inversion of the preconditioned matrix involves inversion of the preconditioner and pointwise multiplication of grid functions. Our solver has been verified by benchmarking against exact solutions and a time-domain solver.

  12. A modified iterative ensemble Kalman filter data assimilation method

    Science.gov (United States)

    Xu, Baoxiong; Bai, Yulong; Wang, Yizhao; Li, Zhe; Ma, Boyang

    2017-08-01

    High nonlinearity is a typical characteristic associated with data assimilation systems. Additionally, iterative ensemble based methods have attracted a large amount of research attention, which has been focused on dealing with nonlinearity problems. To solve the local convergence problem of the iterative ensemble Kalman filter, a modified iterative ensemble Kalman filter algorithm was put forward, which was based on a global convergence strategy from the perspective of a Gauss-Newton iteration. Through self-adaption, the step factor was adjusted to enable every iteration to approach expected values during the process of the data assimilation. A sensitivity experiment was carried out in a low dimensional Lorenz-63 chaotic system, as well as a Lorenz-96 model. The new method was tested via ensemble size, observation variance, and inflation factor changes, along with other aspects. Meanwhile, comparative research was conducted with both a traditional ensemble Kalman filter and an iterative ensemble Kalman filter. The results showed that the modified iterative ensemble Kalman filter algorithm was a data assimilation method that was able to effectively estimate a strongly nonlinear system state.

  13. ERROR CONVERGENCE ANALYSIS FOR LOCAL HYPERTHERMIA APPLICATIONS

    Directory of Open Access Journals (Sweden)

    NEERU MALHOTRA

    2016-01-01

    Full Text Available The accuracy of numerical solution for electromagnetic problem is greatly influenced by the convergence of the solution obtained. In order to quantify the correctness of the numerical solution the errors produced on solving the partial differential equations are required to be analyzed. Mesh quality is another parameter that affects convergence. The various quality metrics are dependent on the type of solver used for numerical simulation. The paper focuses on comparing the performance of iterative solvers used in COMSOL Multiphysics software. The modeling of coaxial coupled waveguide applicator operating at 485MHz has been done for local hyperthermia applications using adaptive finite element method. 3D heat distribution within the muscle phantom depicting spherical leison and localized heating pattern confirms the proper selection of the solver. The convergence plots are obtained during simulation of the problem using GMRES (generalized minimal residual and geometric multigrid linear iterative solvers. The best error convergence is achieved by using nonlinearity multigrid solver and further introducing adaptivity in nonlinear solver.

  14. Fixing convergence of Gaussian belief propagation

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Jason K [Los Alamos National Laboratory; Bickson, Danny [IBM RESEARCH LAB; Dolev, Danny [HEBREW UNIV

    2009-01-01

    Gaussian belief propagation (GaBP) is an iterative message-passing algorithm for inference in Gaussian graphical models. It is known that when GaBP converges it converges to the correct MAP estimate of the Gaussian random vector and simple sufficient conditions for its convergence have been established. In this paper we develop a double-loop algorithm for forcing convergence of GaBP. Our method computes the correct MAP estimate even in cases where standard GaBP would not have converged. We further extend this construction to compute least-squares solutions of over-constrained linear systems. We believe that our construction has numerous applications, since the GaBP algorithm is linked to solution of linear systems of equations, which is a fundamental problem in computer science and engineering. As a case study, we discuss the linear detection problem. We show that using our new construction, we are able to force convergence of Montanari's linear detection algorithm, in cases where it would originally fail. As a consequence, we are able to increase significantly the number of users that can transmit concurrently.

  15. The EU's Convergence Dilemma

    Directory of Open Access Journals (Sweden)

    Notermans Ton

    2015-02-01

    Full Text Available As economic stagnation continues to mark the EU in the fifth year of the euro zone crisis, political support for integration is waning. The European Parliament elections of 2014 returned a hitherto unparalleled number of Eurosceptic MEPs, with EU-critical parties becoming the largest ones in several Member States. Much of this Euroscepticism is driven by economic polarisation between core and peripheral countries. While an increasing number of voters in the northwestern creditor countries resent having to foot the bill for what they consider economic mismanagement in the periphery, voters in peripheral countries increasingly rebel against what they deem to be an economically catastrophic Diktat from Germany and its allies. Continued political support for European integration will hinge on successful income convergence in the EU but the current dilemma is that such policies might not be politically feasible. Periods of rapid convergence would seem to suggest that success depends on two main policy strategies. First, a monetary policy that promotes credit for productive purposes, leaves inflation control to other instruments, and employs selective credit rationing to prevent asset booms. Second, a vertical industrial policy prioritising selected industrial sectors. The first policy conflicts with the present framework of euro zone monetary policy, but that framework was only installed in the first place because many peripheral countries were desperately in search of an external constraint on domestic distributional conflict. Industrial policies, in turn, require a sufficient degree of state autonomy from business elites in order to be effective, but it is highly questionable whether most states in the EU possess such autonomy. Though there are, as yet hesitant, signs of a reorientation of both monetary and cohesion policy in the EU, the question of the institutional and political preconditions for their successful implementation has been largely

  16. Accelerating nuclear configuration interaction calculations through a preconditioned block iterative eigensolver

    Science.gov (United States)

    Shao, Meiyue; Aktulga, H. Metin; Yang, Chao; Ng, Esmond G.; Maris, Pieter; Vary, James P.

    2018-01-01

    We describe a number of recently developed techniques for improving the performance of large-scale nuclear configuration interaction calculations on high performance parallel computers. We show the benefit of using a preconditioned block iterative method to replace the Lanczos algorithm that has traditionally been used to perform this type of computation. The rapid convergence of the block iterative method is achieved by a proper choice of starting guesses of the eigenvectors and the construction of an effective preconditioner. These acceleration techniques take advantage of special structure of the nuclear configuration interaction problem which we discuss in detail. The use of a block method also allows us to improve the concurrency of the computation, and take advantage of the memory hierarchy of modern microprocessors to increase the arithmetic intensity of the computation relative to data movement. We also discuss the implementation details that are critical to achieving high performance on massively parallel multi-core supercomputers, and demonstrate that the new block iterative solver is two to three times faster than the Lanczos based algorithm for problems of moderate sizes on a Cray XC30 system.

  17. An iterative method for determination of a minimal eigenvalue

    DEFF Research Database (Denmark)

    Kristiansen, G.K.

    1968-01-01

    Kristiansen (1963) has discussed the convergence of a group of iterative methods (denoted the Equipoise methods) for the solution of reactor criticality problems. The main result was that even though the methods are said to work satisfactorily in all practical cases, examples of divergence can be...

  18. A new iterative scheme for solving the discrete Smoluchowski equation

    Science.gov (United States)

    Smith, Alastair J.; Wells, Clive G.; Kraft, Markus

    2018-01-01

    This paper introduces a new iterative scheme for solving the discrete Smoluchowski equation and explores the numerical convergence properties of the method for a range of kernels admitting analytical solutions, in addition to some more physically realistic kernels typically used in kinetics applications. The solver is extended to spatially dependent problems with non-uniform velocities and its performance investigated in detail.

  19. A cyclic iterative method for solving multiple sets split feasibility ...

    African Journals Online (AJOL)

    (An iterative regularization method for the solution of the split feasibility problem in Banach spaces, Inverse Problems 24 (2008), 055008) and many important recent results in this direction. Mathematics Subject Classification (2010): 49J53, 65K10, 49M37, 90C25. Keywords: Bregman projection, strong convergence, metric ...

  20. GPU-Accelerated Asynchronous Error Correction for Mixed Precision Iterative Refinement

    Energy Technology Data Exchange (ETDEWEB)

    Antz, Hartwig [Karlsruhe Inst. of Technology (KIT) (Germany); Luszczek, Piotr [Univ. of Tennessee, Knoxville, TN (United States); Dongarra, Jack [Univ. of Tennessee, Knoxville, TN (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Manchester (United Kingdom); Heuveline, Vinent [Karlsruhe Inst. of Technology (KIT) (Germany)

    2011-12-14

    In hardware-aware high performance computing, block- asynchronous iteration and mixed precision iterative refinement are two techniques that are applied to leverage the computing power of SIMD accelerators like GPUs. Although they use a very different approach for this purpose, they share the basic idea of compensating the convergence behaviour of an inferior numerical algorithm by a more efficient usage of the provided computing power. In this paper, we want to analyze the potential of combining both techniques. Therefore, we implement a mixed precision iterative refinement algorithm using a block-asynchronous iteration as an error correction solver, and compare its performance with a pure implementation of a block-asynchronous iteration and an iterative refinement method using double precision for the error correction solver. For matrices from theUniversity of FloridaMatrix collection,we report the convergence behaviour and provide the total solver runtime using different GPU architectures.

  1. The General Iterative Methods for Asymptotically Nonexpansive Semigroups in Banach Spaces

    Directory of Open Access Journals (Sweden)

    Rabian Wangkeeree

    2012-01-01

    Full Text Available We introduce the general iterative methods for finding a common fixed point of asymptotically nonexpansive semigroups which is a unique solution of some variational inequalities. We prove the strong convergence theorems of such iterative scheme in a reflexive Banach space which admits a weakly continuous duality mapping. The main result extends various results existing in the current literature.

  2. A New General Iterative Method for a Finite Family of Nonexpansive Mappings in Hilbert Spaces

    Directory of Open Access Journals (Sweden)

    Singthong Urailuk

    2010-01-01

    Full Text Available We introduce a new general iterative method by using the -mapping for finding a common fixed point of a finite family of nonexpansive mappings in the framework of Hilbert spaces. A strong convergence theorem of the purposed iterative method is established under some certain control conditions. Our results improve and extend the results announced by many others.

  3. A New Newton-Like Iterative Method for Roots of Analytic Functions

    Science.gov (United States)

    Otolorin, Olayiwola

    2005-01-01

    A new Newton-like iterative formula for the solution of non-linear equations is proposed. To derive the formula, the convergence criteria of the one-parameter iteration formula, and also the quasilinearization in the derivation of Newton's formula are reviewed. The result is a new formula which eliminates the limitations of other methods. There is…

  4. Iterative solution of the Helmholtz equation

    Energy Technology Data Exchange (ETDEWEB)

    Larsson, E.; Otto, K. [Uppsala Univ. (Sweden)

    1996-12-31

    We have shown that the numerical solution of the two-dimensional Helmholtz equation can be obtained in a very efficient way by using a preconditioned iterative method. We discretize the equation with second-order accurate finite difference operators and take special care to obtain non-reflecting boundary conditions. We solve the large, sparse system of equations that arises with the preconditioned restarted GMRES iteration. The preconditioner is of {open_quotes}fast Poisson type{close_quotes}, and is derived as a direct solver for a modified PDE problem.The arithmetic complexity for the preconditioner is O(n log{sub 2} n), where n is the number of grid points. As a test problem we use the propagation of sound waves in water in a duct with curved bottom. Numerical experiments show that the preconditioned iterative method is very efficient for this type of problem. The convergence rate does not decrease dramatically when the frequency increases. Compared to banded Gaussian elimination, which is a standard solution method for this type of problems, the iterative method shows significant gain in both storage requirement and arithmetic complexity. Furthermore, the relative gain increases when the frequency increases.

  5. A linearly convergent first-order algorithm for total variation minimisation in image processing.

    Science.gov (United States)

    Dang, Cong D; Dai, Kaiyu; Lan, Guanghui

    2014-01-01

    We introduce a new formulation for total variation minimisation in image denoising. We also present a linearly convergent first-order method for solving this reformulated problem and show that it possesses a nearly dimension-independent iteration complexity bound.

  6. Iterative learning control an optimization paradigm

    CERN Document Server

    Owens, David H

    2016-01-01

    This book develops a coherent theoretical approach to algorithm design for iterative learning control based on the use of optimization concepts. Concentrating initially on linear, discrete-time systems, the author gives the reader access to theories based on either signal or parameter optimization. Although the two approaches are shown to be related in a formal mathematical sense, the text presents them separately because their relevant algorithm design issues are distinct and give rise to different performance capabilities. Together with algorithm design, the text demonstrates that there are new algorithms that are capable of incorporating input and output constraints, enable the algorithm to reconfigure systematically in order to meet the requirements of different reference signals and also to support new algorithms for local convergence of nonlinear iterative control. Simulation and application studies are used to illustrate algorithm properties and performance in systems like gantry robots and other elect...

  7. Robust iterative methods

    Energy Technology Data Exchange (ETDEWEB)

    Saadd, Y.

    1994-12-31

    In spite of the tremendous progress achieved in recent years in the general area of iterative solution techniques, there are still a few obstacles to the acceptance of iterative methods in a number of applications. These applications give rise to very indefinite or highly ill-conditioned non Hermitian matrices. Trying to solve these systems with the simple-minded standard preconditioned Krylov subspace methods can be a frustrating experience. With the mathematical and physical models becoming more sophisticated, the typical linear systems which we encounter today are far more difficult to solve than those of just a few years ago. This trend is likely to accentuate. This workshop will discuss (1) these applications and the types of problems that they give rise to; and (2) recent progress in solving these problems with iterative methods. The workshop will end with a hopefully stimulating panel discussion with the speakers.

  8. Accelerated iterative beam angle selection in IMRT

    Energy Technology Data Exchange (ETDEWEB)

    Bangert, Mark, E-mail: m.bangert@dkfz.de [Department of Medical Physics in Radiation Oncology, German Cancer Research Center—DKFZ, Im Neuenheimer Feld 280, Heidelberg D-69120 (Germany); Unkelbach, Jan [Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114 (United States)

    2016-03-15

    Purpose: Iterative methods for beam angle selection (BAS) for intensity-modulated radiation therapy (IMRT) planning sequentially construct a beneficial ensemble of beam directions. In a naïve implementation, the nth beam is selected by adding beam orientations one-by-one from a discrete set of candidates to an existing ensemble of (n − 1) beams. The best beam orientation is identified in a time consuming process by solving the fluence map optimization (FMO) problem for every candidate beam and selecting the beam that yields the largest improvement to the objective function value. This paper evaluates two alternative methods to accelerate iterative BAS based on surrogates for the FMO objective function value. Methods: We suggest to select candidate beams not based on the FMO objective function value after convergence but (1) based on the objective function value after five FMO iterations of a gradient based algorithm and (2) based on a projected gradient of the FMO problem in the first iteration. The performance of the objective function surrogates is evaluated based on the resulting objective function values and dose statistics in a treatment planning study comprising three intracranial, three pancreas, and three prostate cases. Furthermore, iterative BAS is evaluated for an application in which a small number of noncoplanar beams complement a set of coplanar beam orientations. This scenario is of practical interest as noncoplanar setups may require additional attention of the treatment personnel for every couch rotation. Results: Iterative BAS relying on objective function surrogates yields similar results compared to naïve BAS with regard to the objective function values and dose statistics. At the same time, early stopping of the FMO and using the projected gradient during the first iteration enable reductions in computation time by approximately one to two orders of magnitude. With regard to the clinical delivery of noncoplanar IMRT treatments, we could

  9. Iterative Learning Control with Forgetting Factor for Linear Distributed Parameter Systems with Uncertainty

    Directory of Open Access Journals (Sweden)

    Xisheng Dai

    2014-01-01

    Full Text Available Iterative learning control is an intelligent control algorithm which imitates human learning process. Based on this concept, this paper discussed iterative learning control problem for a class parabolic linear distributed parameter systems with uncertainty coefficients. Iterative learning control algorithm with forgetting factor is proposed and the conditions for convergence of algorithm are established. Combining the matrix theory with the basic theory of distributed parameter systems gives rigorous convergence proof of the algorithm. Finally, by using the forward difference scheme of partial differential equation to solve the problems, the simulation results are presented to illustrate the feasibility of the algorithm.

  10. Converged Registries Solution (CRS)

    Data.gov (United States)

    Department of Veterans Affairs — The Converged Registries platform is a hardware and software architecture designed to host individual patient registries and eliminate duplicative development effort...

  11. Strong convergence to common fixed points of a finite family of Z ...

    African Journals Online (AJOL)

    In this paper, we consider an implicit iteration process for approximating common fixed points of a finite family of Zoperators and we prove strong convergence theorem for such mappings in normed spaces. Also, we give a few corollaries and conclusions for same mappings. Our process contains implicit iteration processes ...

  12. Acceleration of Convergence of a Vector Sequence by Reduced Rank Extrapolation.

    Science.gov (United States)

    1981-11-01

    iteration, x n vi ABSTRACT A new family of methods, called reduced rank extrap - olation, is developed for accelerating convergence of the sequence of...flow of air around aircraft and missiles, and the flux of neutrons in a nuclear reactor . Standard methods of setting up the iteration matrix A in

  13. Convergence analysis for column-action methods in image reconstruction

    DEFF Research Database (Denmark)

    Elfving, Tommy; Hansen, Per Christian; Nikazad, Touraj

    2016-01-01

    Column-oriented versions of algebraic iterative methods are interesting alternatives to their row-version counterparts: they converge to a least squares solution, and they provide a basis for saving computational work by skipping small updates. In this paper we consider the case of noise-free data...

  14. Investigating Convergence Patterns for Numerical Methods Using Data Analysis

    Science.gov (United States)

    Gordon, Sheldon P.

    2013-01-01

    The article investigates the patterns that arise in the convergence of numerical methods, particularly those in the errors involved in successive iterations, using data analysis and curve fitting methods. In particular, the results obtained are used to convey a deeper level of understanding of the concepts of linear, quadratic, and cubic…

  15. AIR Tools - A MATLAB Package of Algebraic Iterative Reconstruction Techniques

    DEFF Research Database (Denmark)

    Hansen, Per Christian; Saxild-Hansen, Maria

    This collection of MATLAB software contains implementations of several Algebraic Iterative Reconstruction methods for discretizations of inverse problems. These so-called row action methods rely on semi-convergence for achieving the necessary regularization of the problem. Two classes of methods...... are implemented: Algebraic Reconstruction Techniques (ART) and Simultaneous Iterative Reconstruction Techniques (SIRT). In addition we provide a few simplified test problems from medical and seismic tomography. For each iterative method, a number of strategies are available for choosing the relaxation parameter...... criterion; for the first two methods “training” can be used to find the optimal discrepancy parameter. The corresponding manuscript is: • P. C. Hansen and M. Saxild-Hansen, AIR Tools – A MATLAB Package of Algebraic Iterative Reconstruction Techniques, submitted to Journal of Computational and Applied...

  16. Milestones in the Development of Iterative Solution Methods

    Directory of Open Access Journals (Sweden)

    Owe Axelsson

    2010-01-01

    Full Text Available Iterative solution methods to solve linear systems of equations were originally formulated as basic iteration methods of defect-correction type, commonly referred to as Richardson's iteration method. These methods developed further into various versions of splitting methods, including the successive overrelaxation (SOR method. Later, immensely important developments included convergence acceleration methods, such as the Chebyshev and conjugate gradient iteration methods and preconditioning methods of various forms. A major strive has been to find methods with a total computational complexity of optimal order, that is, proportional to the degrees of freedom involved in the equation. Methods that have turned out to have been particularly important for the further developments of linear equation solvers are surveyed. Some of them are presented in greater detail.

  17. An Iteration Scheme for Contraction Mappings with an Application to Synchronization of Discrete Logistic Maps

    Directory of Open Access Journals (Sweden)

    Ke Ding

    2017-01-01

    Full Text Available This paper deals with designing a new iteration scheme associated with a given scheme for contraction mappings. This new scheme has a similar structure to that of the given scheme, in which those two iterative schemes converge to the same fixed point of the given contraction mapping. The positive influence of feedback parameters on the convergence rate of this new scheme is investigated. Moreover, the derived convergence and comparison results can be extended to nonexpansive mappings. As an application, the derived results are utilized to study the synchronization of logistic maps. Two illustrated examples are used to reveal the effectiveness of our results.

  18. The application of contraction theory to an iterative formulation of electromagnetic scattering

    Science.gov (United States)

    Brand, J. C.; Kauffman, J. F.

    1985-01-01

    Contraction theory is applied to an iterative formulation of electromagnetic scattering from periodic structures and a computational method for insuring convergence is developed. A short history of spectral (or k-space) formulation is presented with an emphasis on application to periodic surfaces. To insure a convergent solution of the iterative equation, a process called the contraction corrector method is developed. Convergence properties of previously presented iterative solutions to one-dimensional problems are examined utilizing contraction theory and the general conditions for achieving a convergent solution are explored. The contraction corrector method is then applied to several scattering problems including an infinite grating of thin wires with the solution data compared to previous works.

  19. The Dirichlet problem successive upper relaxation numerical method convergence relaxation parameters influence investigations

    Directory of Open Access Journals (Sweden)

    Oliynyk A.P.

    2012-12-01

    Full Text Available The relaxation parameters values to definite sequential upper relaxation block method convergence optimal velocity have been determined for the Dirichlet's problem in two-dimensional rectangle spatial region, the iteration procedure convergence and positive definiteness of the corresponding linear algebraic equations system matrix have been proved.

  20. Threshold-Based Bit Error Rate for Stopping Iterative Turbo Decoding in a Varying SNR Environment

    Science.gov (United States)

    Mohamad, Roslina; Harun, Harlisya; Mokhtar, Makhfudzah; Adnan, Wan Azizun Wan; Dimyati, Kaharudin

    2017-01-01

    Online bit error rate (BER) estimation (OBE) has been used as a stopping iterative turbo decoding criterion. However, the stopping criteria only work at high signal-to-noise ratios (SNRs), and fail to have early termination at low SNRs, which contributes to an additional iteration number and an increase in computational complexity. The failure of the stopping criteria is caused by the unsuitable BER threshold, which is obtained by estimating the expected BER performance at high SNRs, and this threshold does not indicate the correct termination according to convergence and non-convergence outputs (CNCO). Hence, in this paper, the threshold computation based on the BER of CNCO is proposed for an OBE stopping criterion (OBEsc). From the results, OBEsc is capable of terminating early in a varying SNR environment. The optimum number of iterations achieved by the OBEsc allows huge savings in decoding iteration number and decreasing the delay of turbo iterative decoding.

  1. Numerical analysis for 2D waveguide by applying Raleigh Quotient Iteration Method

    Science.gov (United States)

    Adnan, Farasatul; Kabir, Ariful; Khan, A. F. M. Khodadad

    2015-05-01

    Rayleigh Quotient Iteration is an optimal shifted inverse iteration method that converges in less iteration than the other standard methods. Finite Element Method (FEM) is used to solve for the eigenvalues of a 2D rectangular waveguide using first order triangular elements. The FEM requires a large matrix equation to be solved and thus various techniques are sought to reduce the computation time. By using the Raleigh Quotient Iteration Method, we reduce computation time which saves memory. Our calculation gives good results compared to other standard techniques such as QR method, QZ method etc.

  2. Revised Variational Iteration Method for Solving Systems of Nonlinear Fractional-Order Differential Equations

    Directory of Open Access Journals (Sweden)

    C. Ünlü

    2013-01-01

    Full Text Available A modification of the variational iteration method (VIM for solving systems of nonlinear fractional-order differential equations is proposed. The fractional derivatives are described in the Caputo sense. The solutions of fractional differential equations (FDE obtained using the traditional variational iteration method give good approximations in the neighborhood of the initial position. The main advantage of the present method is that it can accelerate the convergence of the iterative approximate solutions relative to the approximate solutions obtained using the traditional variational iteration method. Illustrative examples are presented to show the validity of this modification.

  3. A Numerical, Literal, and Converged Perturbation Algorithm

    Science.gov (United States)

    Wiesel, William E.

    2017-09-01

    The KAM theorem and von Ziepel's method are applied to a perturbed harmonic oscillator, and it is noted that the KAM methodology does not allow for necessary frequency or angle corrections, while von Ziepel does. The KAM methodology can be carried out with purely numerical methods, since its generating function does not contain momentum dependence. The KAM iteration is extended to allow for frequency and angle changes, and in the process apparently can be successfully applied to degenerate systems normally ruled out by the classical KAM theorem. Convergence is observed to be geometric, not exponential, but it does proceed smoothly to machine precision. The algorithm produces a converged perturbation solution by numerical methods, while still retaining literal variable dependence, at least in the vicinity of a given trajectory.

  4. The dynamics of iterated transportation simulations

    Energy Technology Data Exchange (ETDEWEB)

    Nagel, K.; Rickert, M.; Simon, P.M.

    1998-12-01

    Transportation-related decisions of people often depend on what everybody else is doing. For example, decisions about mode choice, route choice, activity scheduling, etc., can depend on congestion, caused by the aggregated behavior of others. From a conceptual viewpoint, this consistency problem causes a deadlock, since nobody can start planning because they do not know what everybody else is doing. It is the process of iterations that is examined in this paper as a method for solving the problem. In this paper, the authors concentrate on the aspect of the iterative process that is probably the most important one from a practical viewpoint, and that is the ``uniqueness`` or ``robustness`` of the results. Also, they define robustness more in terms of common sense than in terms of a mathematical formalism. For this, they do not only want a single iterative process to converge, but they want the result to be independent of any particular implementation. The authors run many computational experiments, sometimes with variations of the same code, sometimes with totally different code, in order to see if any of the results are robust against these changes.

  5. Iterative Decoding of Concatenated Codes: A Tutorial

    Directory of Open Access Journals (Sweden)

    Phillip A. Regalia

    2005-05-01

    Full Text Available The turbo decoding algorithm of a decade ago constituted a milestone in error-correction coding for digital communications, and has inspired extensions to generalized receiver topologies, including turbo equalization, turbo synchronization, and turbo CDMA, among others. Despite an accrued understanding of iterative decoding over the years, the “turbo principle” remains elusive to master analytically, thereby inciting interest from researchers outside the communications domain. In this spirit, we develop a tutorial presentation of iterative decoding for parallel and serial concatenated codes, in terms hopefully accessible to a broader audience. We motivate iterative decoding as a computationally tractable attempt to approach maximum-likelihood decoding, and characterize fixed points in terms of a “consensus” property between constituent decoders. We review how the decoding algorithm for both parallel and serial concatenated codes coincides with an alternating projection algorithm, which allows one to identify conditions under which the algorithm indeed converges to a maximum-likelihood solution, in terms of particular likelihood functions factoring into the product of their marginals. The presentation emphasizes a common framework applicable to both parallel and serial concatenated codes.

  6. An iterative homogenization technique that preserves assembly core exchanges

    Energy Technology Data Exchange (ETDEWEB)

    Mondot, Ph. [Electricite de France, Recherche et Developement, SINETICS, 92 - Clamart (France); Sanchez, R. [CEA Saclay, Direction des Etudes Nucleaires, Service Etude des Reacteurs et de Modelisations Avancees, 91 - Gilf sur Yvette (France)

    2003-07-01

    A new interactive homogenization procedure for reactor core calculations is proposed that requires iterative transport assembly and diffusion core calculations. At each iteration the transport solution of every assembly type is used to produce homogenized cross sections for the core calculation. The converged solution gives assembly fine multigroup transport fluxes that preserve macro-group assembly exchanges in the core. This homogenization avoids the periodic lattice-leakage model approximation and gives detailed assembly transport fluxes without need of an approximated flux reconstruction. Preliminary results are given for a one-dimensional core model. (authors)

  7. Novel Computational Iterative Methods with Optimal Order for Nonlinear Equations

    Directory of Open Access Journals (Sweden)

    F. Soleymani

    2011-01-01

    Full Text Available This paper contributes a very general class of two-point iterative methods without memory for solving nonlinear equations. The class of methods is developed using weight function approach. Per iteration, each method of the class includes two evaluations of the function and one of its first-order derivative. The analytical study of the main theorem is presented in detail to show the fourth order of convergence. Furthermore, it is discussed that many of the existing fourth-order methods without memory are members from this developed class. Finally, numerical examples are taken into account to manifest the accuracy of the derived methods.

  8. Iterative supervirtual refraction interferometry

    KAUST Repository

    Al-Hagan, Ola

    2014-05-02

    In refraction tomography, the low signal-to-noise ratio (S/N) can be a major obstacle in picking the first-break arrivals at the far-offset receivers. To increase the S/N, we evaluated iterative supervirtual refraction interferometry (ISVI), which is an extension of the supervirtual refraction interferometry method. In this method, supervirtual traces are computed and then iteratively reused to generate supervirtual traces with a higher S/N. Our empirical results with both synthetic and field data revealed that ISVI can significantly boost up the S/N of far-offset traces. The drawback is that using refraction events from more than one refractor can introduce unacceptable artifacts into the final traveltime versus offset curve. This problem can be avoided by careful windowing of refraction events.

  9. Iterative initial condition reconstruction

    Science.gov (United States)

    Schmittfull, Marcel; Baldauf, Tobias; Zaldarriaga, Matias

    2017-07-01

    Motivated by recent developments in perturbative calculations of the nonlinear evolution of large-scale structure, we present an iterative algorithm to reconstruct the initial conditions in a given volume starting from the dark matter distribution in real space. In our algorithm, objects are first moved back iteratively along estimated potential gradients, with a progressively reduced smoothing scale, until a nearly uniform catalog is obtained. The linear initial density is then estimated as the divergence of the cumulative displacement, with an optional second-order correction. This algorithm should undo nonlinear effects up to one-loop order, including the higher-order infrared resummation piece. We test the method using dark matter simulations in real space. At redshift z =0 , we find that after eight iterations the reconstructed density is more than 95% correlated with the initial density at k ≤0.35 h Mpc-1 . The reconstruction also reduces the power in the difference between reconstructed and initial fields by more than 2 orders of magnitude at k ≤0.2 h Mpc-1 , and it extends the range of scales where the full broadband shape of the power spectrum matches linear theory by a factor of 2-3. As a specific application, we consider measurements of the baryonic acoustic oscillation (BAO) scale that can be improved by reducing the degradation effects of large-scale flows. In our idealized dark matter simulations, the method improves the BAO signal-to-noise ratio by a factor of 2.7 at z =0 and by a factor of 2.5 at z =0.6 , improving standard BAO reconstruction by 70% at z =0 and 30% at z =0.6 , and matching the optimal BAO signal and signal-to-noise ratio of the linear density in the same volume. For BAO, the iterative nature of the reconstruction is the most important aspect.

  10. Conformable variational iteration method

    Directory of Open Access Journals (Sweden)

    Omer Acan

    2017-02-01

    Full Text Available In this study, we introduce the conformable variational iteration method based on new defined fractional derivative called conformable fractional derivative. This new method is applied two fractional order ordinary differential equations. To see how the solutions of this method, linear homogeneous and non-linear non-homogeneous fractional ordinary differential equations are selected. Obtained results are compared the exact solutions and their graphics are plotted to demonstrate efficiency and accuracy of the method.

  11. Neutron cameras for ITER

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, L.C.; Barnes, C.W.; Batistoni, P. [ITER San Diego Joint Work Site, La Jolla, CA (United States)] [and others

    1998-12-31

    Neutron cameras with horizontal and vertical views have been designed for ITER, based on systems used on JET and TFTR. The cameras consist of fan-shaped arrays of collimated flight tubes, with suitably chosen detectors situated outside the biological shield. The sight lines view the ITER plasma through slots in the shield blanket and penetrate the vacuum vessel, cryostat, and biological shield through stainless steel windows. This paper analyzes the expected performance of several neutron camera arrangements for ITER. In addition to the reference designs, the authors examine proposed compact cameras, in which neutron fluxes are inferred from {sup 16}N decay gammas in dedicated flowing water loops, and conventional cameras with fewer sight lines and more limited fields of view than in the reference designs. It is shown that the spatial sampling provided by the reference designs is sufficient to satisfy target measurement requirements and that some reduction in field of view may be permissible. The accuracy of measurements with {sup 16}N-based compact cameras is not yet established, and they fail to satisfy requirements for parameter range and time resolution by large margins.

  12. Kaczmarz Iterative Projection and Nonuniform Sampling with Complexity Estimates

    Directory of Open Access Journals (Sweden)

    Tim Wallace

    2014-01-01

    Full Text Available Kaczmarz’s alternating projection method has been widely used for solving mostly over-determined linear system of equations Ax=b in various fields of engineering, medical imaging, and computational science. Because of its simple iterative nature with light computation, this method was successfully applied in computerized tomography. Since tomography generates a matrix A with highly coherent rows, randomized Kaczmarz algorithm is expected to provide faster convergence as it picks a row for each iteration at random, based on a certain probability distribution. Since Kaczmarz’s method is a subspace projection method, the convergence rate for simple Kaczmarz algorithm was developed in terms of subspace angles. This paper provides analyses of simple and randomized Kaczmarz algorithms and explains the link between them. New versions of randomization are proposed that may speed up convergence in the presence of nonuniform sampling, which is common in tomography applications. It is anticipated that proper understanding of sampling and coherence with respect to convergence and noise can improve future systems to reduce the cumulative radiation exposures to the patient. Quantitative simulations of convergence rates and relative algorithm benchmarks have been produced to illustrate the effects of measurement coherency and algorithm performance, respectively, under various conditions in a real-time kernel.

  13. Convergent Aeronautics Solutions Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The Convergent Aeronautics Solutions (CAS) Project uses short-duration activities to establish early-stage concept and technology feasibility for high-potential...

  14. Fixed mobile convergence handbook

    CERN Document Server

    Ahson, Syed A

    2010-01-01

    From basic concepts to future directions, this handbook provides technical information on all aspects of fixed-mobile convergence (FMC). The book examines such topics as integrated management architecture, business trends and strategic implications for service providers, personal area networks, mobile controlled handover methods, SIP-based session mobility, and supervisory and notification aggregator service. Case studies are used to illustrate technical and systematic implementation of unified and rationalized internet access by fixed-mobile network convergence. The text examines the technolo

  15. IT-BT convergence technology

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2012-12-15

    This book explains IT-BT convergence technology as the future technology, which includes a prolog, easy IT-BT convergence technology that has infinite potentials for new value, policy of IT-BT convergence technology showing the potential of smart Korea, IT-BT convergence opening happy future, for the new future of IT powerful nation Korea with IT-BT convergence technology and an epilogue. This book reveals the conception, policy, performance and future of IT-BT convergence technology.

  16. Convergence of estuarine channels

    Science.gov (United States)

    Dronkers, Job

    2017-07-01

    Tide-dominated coastal plain estuaries have typically up-estuary convergent tidal channels. Analysis of estuarine characteristics indicates a dependence of the convergence length on relative tidal amplitude, relative intertidal area and river flow velocity. In order to explain these relationships we investigate a condition for continuity of net sediment transport throughout the estuary, corresponding to morphodynamic equilibrium. We show, by using an analytical solution of the tidal equations, that this condition is equivalent to a condition on the convergence length. This condition is evaluated for 21 estuaries in different regions of the world. It appears that the convergence length determined in this way can explain observed convergence lengths for the considered set of estuaries. The dependence of the convergence length on different estuarine characteristics is analysed by solving the fully coupled hydro-morphodynamic equations. We show that this dependence limits the range of variation of the tidal velocity amplitude. The analysis provides insight in the morphological response of estuaries to human interventions. The condition can easily be evaluated to yield an estimate of this response.

  17. On the relation between traditional iterative methods and modern multilevel/domain decomposition methods

    Energy Technology Data Exchange (ETDEWEB)

    Griebel, M. [Technische Universitaet Muenchen (Germany)

    1994-12-31

    In recent years, it has turned out that many modern iterative algorithms (multigrid schemes, multilevel preconditioners, domain decomposition methods etc.) for solving problems resulting from the discretization of PDEs can be interpreted as additive (Jacobi-like) or multiplicative (Gauss-Seidel-like) subspace correction methods. The key to their analysis is the study of certain metric properties of the underlying splitting of the discretization space V into a sum of subspaces V{sub j}, j = 1{hor_ellipsis}, J resp. of the variational problem on V into auxiliary problems on these subspaces. Here, the author proposes a modified approach to the abstract convergence theory of these additive and multiplicative Schwarz iterative methods, that makes the relation to traditional iteration methods more explicit. To this end he introduces the enlarged Hilbert space V = V{sub 0} x {hor_ellipsis} x V{sub j} which is nothing else but the usual construction of the Cartesian product of the Hilbert spaces V{sub j} and use it now in the discretization process. This results in an enlarged, semidefinite linear system to be solved instead of the usual definite system. Then, modern multilevel methods as well as domain decomposition methods simplify to just traditional (block-) iteration methods. Now, the convergence analysis can be carried out directly for these traditional iterations on the enlarged system, making convergence proofs of multilevel and domain decomposition methods more clear, or, at least, more classical. The terms that enter the convergence proofs are exactly the ones of the classical iterative methods. It remains to estimate them properly. The convergence proof itself follow basically line by line the old proofs of the respective traditional iterative methods. Additionally, new multilevel/domain decomposition methods are constructed straightforwardly by now applying just other old and well known traditional iterative methods to the enlarged system.

  18. Spirit and prospects of ITER

    Energy Technology Data Exchange (ETDEWEB)

    Velikhov, E.P. [Kurchatov Institute of Atomic Energy, Moscow (Russian Federation)

    2002-10-01

    ITER is the unique and the most straightforward way to study the burning plasma science in the nearest future. ITER has a firm physics ground based on the results from the world tokamaks in terms of confinement, stability, heating, current drive, divertor, energetic particle confinement to an extend required in ITER. The flexibility of ITER will allow the exploration of broad operation space of fusion power, beta, pulse length and Q values in various operational scenarios. Success of the engineering R and D programs has demonstrated that all party has an enough capability to produce all the necessary equipment in agreement with the specifications of ITER. The acquired knowledge and technologies in ITER project allow us to demonstrate the scientific and technical feasibility of a fusion reactor. It can be concluded that ITER must be constructed in the nearest future. (author)

  19. On domains of convergence in optimization problems

    Science.gov (United States)

    Diaz, Alejandro R.; Shaw, Steven S.; Pan, Jian

    1990-01-01

    Numerical optimization algorithms require the knowledge of an initial set of design variables. Starting from an initial design x(sup 0), improved solutions are obtained by updating the design iteratively in a way prescribed by the particular algorithm used. If the algorithm is successful, convergence is achieved to a local optimal solution. Let A denote the iterative procedure that characterizes a typical optimization algorithm, applied to the problem: Find x belonging to R(sup n) that maximizes f(x) subject to x belonging to Omega contained in R(sup n). We are interested in problems with several local maxima (x(sub j))(sup *), j=1, ..., m, in the feasible design space Omega. In general, convergence of the algorithm A to a specific solution (x(sub j))(sup *) is determined by the choice of initial design x(sup 0). The domain of convergence D(sub j) of A associated with a local maximum (x(sub j))(sup *) is a subset of initial designs x(sup 0) in Omega such that the sequence (x(sup k)), k=0,1,2,... defined by x(sup k+1) = A(x(sup k)), k=0,1,... converges to (x(sub j))(sup *). The set D(sub j) is also called the basin of attraction of (x(sub j))(sup *). Cayley first proposed the problem of finding the basin of attraction for Newton's method in 1897. It has been shown that the basin of attraction for Newton's method exhibits chaotic behavior in problems with polynomial objective. This implies that there may be regions in the feasible design space where arbitrarily close starting points will converge to different local optimal solutions. Furthermore, the boundaries of the domains of convergence may have a very complex, even fractal structure. In this paper we show that even simple structural optimization problems solved using standard gradient based (first order) algorithms exhibit similar features.

  20. Robust Multiscale Iterative Solvers for Nonlinear Flows in Highly Heterogeneous Media

    KAUST Repository

    Efendiev, Y.

    2012-08-01

    In this paper, we study robust iterative solvers for finite element systems resulting in approximation of steady-state Richards\\' equation in porous media with highly heterogeneous conductivity fields. It is known that in such cases the contrast, ratio between the highest and lowest values of the conductivity, can adversely affect the performance of the preconditioners and, consequently, a design of robust preconditioners is important for many practical applications. The proposed iterative solvers consist of two kinds of iterations, outer and inner iterations. Outer iterations are designed to handle nonlinearities by linearizing the equation around the previous solution state. As a result of the linearization, a large-scale linear system needs to be solved. This linear system is solved iteratively (called inner iterations), and since it can have large variations in the coefficients, a robust preconditioner is needed. First, we show that under some assumptions the number of outer iterations is independent of the contrast. Second, based on the recently developed iterative methods, we construct a class of preconditioners that yields convergence rate that is independent of the contrast. Thus, the proposed iterative solvers are optimal with respect to the large variation in the physical parameters. Since the same preconditioner can be reused in every outer iteration, this provides an additional computational savings in the overall solution process. Numerical tests are presented to confirm the theoretical results. © 2012 Global-Science Press.

  1. On Two Iterative Methods for Mixed Monotone Variational Inequalities

    Directory of Open Access Journals (Sweden)

    Xiwen Lu

    2010-01-01

    Full Text Available A mixed monotone variational inequality (MMVI problem in a Hilbert space H is formulated to find a point u∗∈H such that 〈Tu∗,v−u∗〉+φ(v−φ(u∗≥0 for all v∈H, where T is a monotone operator and φ is a proper, convex, and lower semicontinuous function on H. Iterative algorithms are usually applied to find a solution of an MMVI problem. We show that the iterative algorithm introduced in the work of Wang et al., (2001 has in general weak convergence in an infinite-dimensional space, and the algorithm introduced in the paper of Noor (2001 fails in general to converge to a solution.

  2. Flocking in the depths of strategic iterated reasoning

    CERN Document Server

    Frey, Seth

    2015-01-01

    Must it be the case that increasingly deep levels of strategic iterated reasoning by humans give increasingly close approximations of normative economic rationality? And if not, what might they do instead? We argue that human higher-level reasoning processes may support non-equilibrium, non-convergent "flocking" behavior. Flocking in the physical world is the sustained convergence of both the positions and velocities of the members of a group. We make the metaphor to flocking in our experiments by introducing decision environments in which participants' choices and reasoning processes function as their positions and velocities, respectively. With this definition, we demonstrate flocking in multiple group experiments over three unrelated economic games. The first game is the classic Beauty Pageant, the second is called the Mod Game, and we introduce the Runway Game. Though they three bear no formal resemblance to each other, subjects play them the same: as eliciting iterated reasoning in a way that causes indi...

  3. Iterative procedures for wave propagation in the frequency domain

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Seongjai [Rice Univ., Houston, TX (United States); Symes, W.W.

    1996-12-31

    A parallelizable two-grid iterative algorithm incorporating a domain decomposition (DD) method is considered for solving the Helmholtz problem. Since a numerical method requires choosing at least 6 to 8 grid points per wavelength, the coarse-grid problem itself is not an easy task for high frequency applications. We solve the coarse-grid problem using a nonoverlapping DD method. To accelerate the convergence of the iteration, an artificial damping technique and relaxation parameters are introduced. Automatic strategies for finding efficient parameters are discussed. Numerical results are presented to show the effectiveness of the method. It is numerically verified that the rate of convergence of the algorithm depends on the wave number sub-linearly and does not deteriorate as the mesh size decreases.

  4. A VLSI design concept for parallel iterative algorithms

    Directory of Open Access Journals (Sweden)

    C. C. Sun

    2009-05-01

    Full Text Available Modern VLSI manufacturing technology has kept shrinking down to the nanoscale level with a very fast trend. Integration with the advanced nano-technology now makes it possible to realize advanced parallel iterative algorithms directly which was almost impossible 10 years ago. In this paper, we want to discuss the influences of evolving VLSI technologies for iterative algorithms and present design strategies from an algorithmic and architectural point of view. Implementing an iterative algorithm on a multiprocessor array, there is a trade-off between the performance/complexity of processors and the load/throughput of interconnects. This is due to the behavior of iterative algorithms. For example, we could simplify the parallel implementation of the iterative algorithm (i.e., processor elements of the multiprocessor array in any way as long as the convergence is guaranteed. However, the modification of the algorithm (processors usually increases the number of required iterations which also means that the switch activity of interconnects is increasing. As an example we show that a 25×25 full Jacobi EVD array could be realized into one single FPGA device with the simplified μ-rotation CORDIC architecture.

  5. Implicit and Explicit Iterations with Meir-Keeler-Type Contraction for a Finite Family of Nonexpansive Semigroups in Banach Spaces

    Directory of Open Access Journals (Sweden)

    Jiancai Huang

    2012-01-01

    Full Text Available We introduce an implicit and explicit iterative schemes for a finite family of nonexpansive semigroups with the Meir-Keeler-type contraction in a Banach space. Then we prove the strong convergence for the implicit and explicit iterative schemes. Our results extend and improve some recent ones in literatures.

  6. Iterative participatory design

    DEFF Research Database (Denmark)

    Simonsen, Jesper; Hertzum, Morten

    2010-01-01

    iterative process of mutual learning by designers and domain experts (users), who aim to change the users’ work practices through the introduction of information systems. We provide an illustrative case example with an ethnographic study of clinicians experimenting with a new electronic patient record......The theoretical background in this chapter is information systems development in an organizational context. This includes theories from participatory design, human-computer interaction, and ethnographically inspired studies of work practices. The concept of design is defined as an experimental...

  7. Searching with iterated maps

    Science.gov (United States)

    Elser, V.; Rankenburg, I.; Thibault, P.

    2007-01-01

    In many problems that require extensive searching, the solution can be described as satisfying two competing constraints, where satisfying each independently does not pose a challenge. As an alternative to tree-based and stochastic searching, for these problems we propose using an iterated map built from the projections to the two constraint sets. Algorithms of this kind have been the method of choice in a large variety of signal-processing applications; we show here that the scope of these algorithms is surprisingly broad, with applications as diverse as protein folding and Sudoku. PMID:17202267

  8. Comment on ``Iterative Bogoliubov transformations and anharmonic oscillators''

    Science.gov (United States)

    Fernández, Francisco M.; Castro, Eduardo A.

    1993-10-01

    We discuss a recently proposed method [R. Jáuregui and J. Récamier, Phys. Rev. A 46, 2240 (1992)] based on the application of iterative Bogoliubov transformations to anharmonic oscillators and show that, if the algorithm converges, one easily obtains the final result directly in one step. We prove that the Bogoliubov transformation can be written in terms of scaling and translation parameters and present exact results for the coefficients of the Bogoliubov transformation for some selected examples.

  9. Convergent beam neutron crystallography

    Science.gov (United States)

    Gibson, Walter M.; Schultz, Arthur J.; Richardson, James W.; Carpenter, John M.; Mildner, David F. R.; Chen-Mayer, Heather H.; Miller, M. E.; Maxey, E.; Prask, Henry J.; Gnaeupel-Herold, Thomas H.; Youngman, Russell

    2004-01-01

    Applications of neutron diffraction for small samples (small fiducial areas are limited by the available neutron flux density. Recent demonstrations of convergent beam electron and x-ray diffraction and focusing of cold (λ>1 Å) neutrons suggest the possibility to use convergent beam neutron diffraction for small sample crystallography. We have carried out a systematic study of diffraction of both monoenergetic and broad bandwidth neutrons at the NIST Research Reactor and at the Intense Pulsed Neutron Source (IPNS) at Argonne National Laboratory. Combining convergent beams with time-of-flight Laue diffraction is particularly attractive for high efficiency small sample diffraction studies. We have studied single crystal and powder diffraction of neutrons with convergence angles as large as 15° and have observed diffracted peak intensity gains greater than 20. The convergent beam method (CBM) shows promise for crystallography on small samples of small to medium size molecules (potentially even for proteins), ultra-high pressure samples, and for mapping of strain and texture distributions in larger samples.

  10. Convergence Theorem for Finite Family of Total Asymptotically Nonexpansive Mappings

    Directory of Open Access Journals (Sweden)

    E.U. Ofoedu

    2015-11-01

    Full Text Available In this paper we introduce an explicit iteration process and prove strong convergence of the scheme in a real Hilbert space $H$ to the common fixed point of finite family of total asymptotically nonexpansive mappings which is nearest to the point $u \\in H$.  Our results improve previously known ones obtained for the class of asymptotically nonexpansive mappings. As application, iterative method for: approximation of solution of variational Inequality problem, finite family of continuous pseudocontractive mappings, approximation of solutions of classical equilibrium problems and approximation of solutions of convex minimization problems are proposed. Our theorems unify and complement many recently announced results.

  11. Iterative Learning Control with Forgetting Factor for Urban Road Network

    Directory of Open Access Journals (Sweden)

    Tianyi Lan

    2017-01-01

    Full Text Available In order to improve the traffic condition, a novel iterative learning control (ILC algorithm with forgetting factor for urban road network is proposed by using the repeat characteristics of traffic flow in this paper. Rigorous analysis shows that the proposed ILC algorithm can guarantee the asymptotic convergence. Through iterative learning control of the traffic signals, the number of vehicles on each road in the network can gradually approach the desired level, thereby preventing oversaturation and traffic congestion. The introduced forgetting factor can effectively adjust the control input according to the states of the system and filter along the direction of the iteration. The results show that the forgetting factor has an important effect on the robustness of the system. The theoretical analysis and experimental simulations are given to verify the validity of the proposed method.

  12. Iterative Learning Impedance for Lower Limb Rehabilitation Robot.

    Science.gov (United States)

    Guo, Chenhui; Guo, Shuai; Ji, Jiancheng; Xi, Fengfeng

    2017-01-01

    This paper discusses the problem of squatting training of stroke patients. The main idea is to correct the patient's training trajectory through an iterative learning control (ILC) method. To obtain better rehabilitation effect, a patient will typically be required to practice a reference posture for many times, while most of active training methods can hardly keep the patients training with correct posture. Instead of the conventional ILC strategy, an impedance-based iterative learning method is proposed to regulate the impedance value dynamically and smartly which will help patients correct their posture gradually and perform better. To facilitate impedance-based ILC, we propose two objectives. The first objective is to find the suitable values of impedance based on the ILC scheme. The second objective is to search the moderate learning convergence speed and robustness in the iterative domain. The simulation and experimental results demonstrate that the performance of trajectory tracking will be improved greatly via the proposed algorithm.

  13. Field convergence between technical writers and technical translators

    DEFF Research Database (Denmark)

    Gnecchi, M.; Maylath, B.; Mousten, Birthe

    2011-01-01

    As translation of technical documents continues to grow rapidly and translation becomes more automated, the roles of professional communicators and translators appear to be converging. This paper updates preliminary findings first presented at the 2008 International Professional Communication...

  14. A semi-analytical iterative technique for solving chemistry problems

    Directory of Open Access Journals (Sweden)

    Majeed Ahmed AL-Jawary

    2017-07-01

    Full Text Available The main aim and contribution of the current paper is to implement a semi-analytical iterative method suggested by Temimi and Ansari in 2011 namely (TAM to solve two chemical problems. An approximate solution obtained by the TAM provides fast convergence. The current chemical problems are the absorption of carbon dioxide into phenyl glycidyl ether and the other system is a chemical kinetics problem. These problems are represented by systems of nonlinear ordinary differential equations that contain boundary conditions and initial conditions. Error analysis of the approximate solutions is studied using the error remainder and the maximal error remainder. Exponential rate for the convergence is observed. For both problems the results of the TAM are compared with other results obtained by previous methods available in the literature. The results demonstrate that the method has many merits such as being derivative-free, and overcoming the difficulty arising in calculating Adomian polynomials to handle the non-linear terms in Adomian Decomposition Method (ADM. It does not require to calculate Lagrange multiplier in Variational Iteration Method (VIM in which the terms of the sequence become complex after several iterations, thus, analytical evaluation of terms becomes very difficult or impossible in VIM. No need to construct a homotopy in Homotopy Perturbation Method (HPM and solve the corresponding algebraic equations. The MATHEMATICA® 9 software was used to evaluate terms in the iterative process.

  15. Iterative integral parameter identification of a respiratory mechanics model

    Directory of Open Access Journals (Sweden)

    Schranz Christoph

    2012-07-01

    Full Text Available Abstract Background Patient-specific respiratory mechanics models can support the evaluation of optimal lung protective ventilator settings during ventilation therapy. Clinical application requires that the individual’s model parameter values must be identified with information available at the bedside. Multiple linear regression or gradient-based parameter identification methods are highly sensitive to noise and initial parameter estimates. Thus, they are difficult to apply at the bedside to support therapeutic decisions. Methods An iterative integral parameter identification method is applied to a second order respiratory mechanics model. The method is compared to the commonly used regression methods and error-mapping approaches using simulated and clinical data. The clinical potential of the method was evaluated on data from 13 Acute Respiratory Distress Syndrome (ARDS patients. Results The iterative integral method converged to error minima 350 times faster than the Simplex Search Method using simulation data sets and 50 times faster using clinical data sets. Established regression methods reported erroneous results due to sensitivity to noise. In contrast, the iterative integral method was effective independent of initial parameter estimations, and converged successfully in each case tested. Conclusion These investigations reveal that the iterative integral method is beneficial with respect to computing time, operator independence and robustness, and thus applicable at the bedside for this clinical application.

  16. Randomized Block Frank–Wolfe for Convergent Large-Scale Learning

    Science.gov (United States)

    Zhang, Liang; Wang, Gang; Romero, Daniel; Giannakis, Georgios B.

    2017-12-01

    Owing to their low-complexity iterations, Frank-Wolfe (FW) solvers are well suited for various large-scale learning tasks. When block-separable constraints are present, randomized block FW (RB-FW) has been shown to further reduce complexity by updating only a fraction of coordinate blocks per iteration. To circumvent the limitations of existing methods, the present work develops step sizes for RB-FW that enable a flexible selection of the number of blocks to update per iteration while ensuring convergence and feasibility of the iterates. To this end, convergence rates of RB-FW are established through computational bounds on a primal sub-optimality measure and on the duality gap. The novel bounds extend the existing convergence analysis, which only applies to a step-size sequence that does not generally lead to feasible iterates. Furthermore, two classes of step-size sequences that guarantee feasibility of the iterates are also proposed to enhance flexibility in choosing decay rates. The novel convergence results are markedly broadened to encompass also nonconvex objectives, and further assert that RB-FW with exact line-search reaches a stationary point at rate $\\mathcal{O}(1/\\sqrt{t})$. Performance of RB-FW with different step sizes and number of blocks is demonstrated in two applications, namely charging of electrical vehicles and structural support vector machines. Extensive simulated tests demonstrate the performance improvement of RB-FW relative to existing randomized single-block FW methods.

  17. Iterative Diffusion-Based Distributed Cubature Gaussian Mixture Filter for Multisensor Estimation.

    Science.gov (United States)

    Jia, Bin; Sun, Tao; Xin, Ming

    2016-10-20

    In this paper, a distributed cubature Gaussian mixture filter (DCGMF) based on an iterative diffusion strategy (DCGMF-ID) is proposed for multisensor estimation and information fusion. The uncertainties are represented as Gaussian mixtures at each sensor node. A high-degree cubature Kalman filter provides accurate estimation of each Gaussian mixture component. An iterative diffusion scheme is utilized to fuse the mean and covariance of each Gaussian component obtained from each sensor node. The DCGMF-ID extends the conventional diffusion-based fusion strategy by using multiple iterative information exchanges among neighboring sensor nodes. The convergence property of the iterative diffusion is analyzed. In addition, it is shown that the convergence of the iterative diffusion can be interpreted from the information-theoretic perspective as minimization of the Kullback-Leibler divergence. The performance of the DCGMF-ID is compared with the DCGMF based on the average consensus (DCGMF-AC) and the DCGMF based on the iterative covariance intersection (DCGMF-ICI) via a maneuvering target-tracking problem using multiple sensors. The simulation results show that the DCGMF-ID has better performance than the DCGMF based on noniterative diffusion, which validates the benefit of iterative information exchanges. In addition, the DCGMF-ID outperforms the DCGMF-ICI and DCGMF-AC when the number of iterations is limited.

  18. Iterative Diffusion-Based Distributed Cubature Gaussian Mixture Filter for Multisensor Estimation

    Directory of Open Access Journals (Sweden)

    Bin Jia

    2016-10-01

    Full Text Available In this paper, a distributed cubature Gaussian mixture filter (DCGMF based on an iterative diffusion strategy (DCGMF-ID is proposed for multisensor estimation and information fusion. The uncertainties are represented as Gaussian mixtures at each sensor node. A high-degree cubature Kalman filter provides accurate estimation of each Gaussian mixture component. An iterative diffusion scheme is utilized to fuse the mean and covariance of each Gaussian component obtained from each sensor node. The DCGMF-ID extends the conventional diffusion-based fusion strategy by using multiple iterative information exchanges among neighboring sensor nodes. The convergence property of the iterative diffusion is analyzed. In addition, it is shown that the convergence of the iterative diffusion can be interpreted from the information-theoretic perspective as minimization of the Kullback–Leibler divergence. The performance of the DCGMF-ID is compared with the DCGMF based on the average consensus (DCGMF-AC and the DCGMF based on the iterative covariance intersection (DCGMF-ICI via a maneuvering target-tracking problem using multiple sensors. The simulation results show that the DCGMF-ID has better performance than the DCGMF based on noniterative diffusion, which validates the benefit of iterative information exchanges. In addition, the DCGMF-ID outperforms the DCGMF-ICI and DCGMF-AC when the number of iterations is limited.

  19. Convergence theorems for fixed points of demicontinuous pseudocontractive mappings

    Directory of Open Access Journals (Sweden)

    Chidume CE

    2005-01-01

    Full Text Available Let be an open subset of a real uniformly smooth Banach space . Suppose is a demicontinuous pseudocontractive mapping satisfying an appropriate condition, where denotes the closure of . Then, it is proved that (i for every ; (ii for a given , there exists a unique path , , satisfying . Moreover, if or there exists such that the set is bounded, then it is proved that, as , the path converges strongly to a fixed point of . Furthermore, explicit iteration procedures with bounded error terms are proved to converge strongly to a fixed point of .

  20. A novel method of Newton iteration-based interval analysis for multidisciplinary systems

    Science.gov (United States)

    Wang, Lei; Xiong, Chuang; Wang, RuiXing; Wang, XiaoJun; Wu, Di

    2017-09-01

    A Newton iteration-based interval uncertainty analysis method (NI-IUAM) is proposed to analyze the propagating effect of interval uncertainty in multidisciplinary systems. NI-IUAM decomposes one multidisciplinary system into single disciplines and utilizes a Newton iteration equation to obtain the upper and lower bounds of coupled state variables at each iterative step. NI-IUAM only needs to determine the bounds of uncertain parameters and does not require specific distribution formats. In this way, NI-IUAM may greatly reduce the necessity for raw data. In addition, NI-IUAM can accelerate the convergence process as a result of the super-linear convergence of Newton iteration. The applicability of the proposed method is discussed, in particular that solutions obtained in each discipline must be compatible in multidisciplinary systems. The validity and efficiency of NI-IUAM is demonstrated by both numerical and engineering examples.

  1. Convergent Filter Bases

    Directory of Open Access Journals (Sweden)

    Coghetto Roland

    2015-09-01

    Full Text Available We are inspired by the work of Henri Cartan [16], Bourbaki [10] (TG. I Filtres and Claude Wagschal [34]. We define the base of filter, image filter, convergent filter bases, limit filter and the filter base of tails (fr: filtre des sections.

  2. Convergence of Networks

    DEFF Research Database (Denmark)

    Prasad, Ramjee; Ruggieri, Marina

    2008-01-01

    The paper focuses on the revolutionary changes that could characterise the future of networks. Those changes involve many aspects in the conceivement and exploitation of networks: architecture, services, technologies and modeling. The convergence of wired and wireless technologies along with the ...

  3. The Convergence Years

    Science.gov (United States)

    Kolodzy, Janet; Grant, August E.; DeMars, Tony R.; Wilkinson, Jeffrey S.

    2014-01-01

    The emergence of the Internet, social media, and digital technologies in the twenty-first century accelerated an evolution in journalism and communication that fit under the broad term of convergence. That evolution changed the relationship between news producers and consumers. It broke down the geographical boundaries in defining our communities,…

  4. The asymptotic convergence factor for a polygon under a perturbation

    Energy Technology Data Exchange (ETDEWEB)

    Li, X. [Georgia Southern Univ., Statesboro, GA (United States)

    1994-12-31

    Let Ax = b be a large system of linear equations, where A {element_of} C{sup NxN}, nonsingular and b {element_of} C{sup N}. A few iterative methods for solving have recently been presented in the case where A is nonsymmetric. Many of their algorithms consist of two phases: Phase I: estimate the extreme eigenvalues of A; Phase II: construct and apply an iterative method based on the estimates. For convenience, it is rewritten as an equivalent fixed-point form, x = Tx + c. Let {Omega} be a compact set excluding 1 in the complex plane, and let its complement in the extended complex plane be simply connected. The asymptotic convergence factor (ACF) for {Omega}, denoted by {kappa}({Omega}), measures the rate of convergence for the asymptotically optimal semiiterative methods for solving, where {sigma}(T) {contained_in} {Omega}.

  5. Hybrid Second-Order Iterative Algorithm for Orthogonal Projection onto a Parametric Surface

    Directory of Open Access Journals (Sweden)

    Xiaowu Li

    2017-08-01

    Full Text Available To compute the minimum distance between a point and a parametric surface, three well-known first-order algorithms have been proposed by Hartmann (1999, Hoschek, et al. (1993 and Hu, et al. (2000 (hereafter, the First-Order method. In this paper, we prove the method’s first-order convergence and its independence of the initial value. We also give some numerical examples to illustrate its faster convergence than the existing methods. For some special cases where the First-Order method does not converge, we combine it with Newton’s second-order iterative method to present the hybrid second-order algorithm. Our method essentially exploits hybrid iteration, thus it performs very well with a second-order convergence, it is faster than the existing methods and it is independent of the initial value. Some numerical examples confirm our conclusion.

  6. A Globally Convergent Parallel SSLE Algorithm for Inequality Constrained Optimization

    Directory of Open Access Journals (Sweden)

    Zhijun Luo

    2014-01-01

    Full Text Available A new parallel variable distribution algorithm based on interior point SSLE algorithm is proposed for solving inequality constrained optimization problems under the condition that the constraints are block-separable by the technology of sequential system of linear equation. Each iteration of this algorithm only needs to solve three systems of linear equations with the same coefficient matrix to obtain the descent direction. Furthermore, under certain conditions, the global convergence is achieved.

  7. Improved coupled perturbed Hartree Fock and Kohn Sham convergence acceleration

    Science.gov (United States)

    Weber, Valéry; Daul, Claude

    2003-03-01

    A derivative version of the well-known direct inversion in the iterative subspace (DIIS) algorithm is presented. The method is used to solve the coupled perturbed Hartree-Fock (CPHF) equation to obtain the first and second derivatives of the density matrix with respect to an external electric field which, in this case, leads to the electric molecular polarizability and hyperpolarizability. Some comparisons are presented and the method shows good convergences in almost all cases.

  8. Fused analytical and iterative reconstruction (AIR) via modified proximal forward-backward splitting: a FDK-based iterative image reconstruction example for CBCT.

    Science.gov (United States)

    Gao, Hao

    2016-10-07

    This work is to develop a general framework, namely analytical iterative reconstruction (AIR) method, to incorporate analytical reconstruction (AR) method into iterative reconstruction (IR) method, for enhanced CT image quality and reconstruction efficiency. Specifically, AIR is established based on the modified proximal forward-backward splitting (PFBS) algorithm, and its connection to the filtered data fidelity with sparsity regularization is discussed. As a result, AIR decouples data fidelity and image regularization with a two-step iterative scheme, during which an AR-projection step updates the filtered data fidelity term, while a denoising solver updates the sparsity regularization term. During the AR-projection step, the image is projected to the data domain to form the data residual, and then reconstructed by certain AR to a residual image which is then weighted together with previous image iterate to form next image iterate. Intuitively since the eigenvalues of AR-projection operator are close to the unity, PFBS based AIR has a fast convergence. Such an advantage is rigorously established through convergence analysis and numerical computation of convergence rate. The proposed AIR method is validated in the setting of circular cone-beam CT with AR being FDK and total-variation sparsity regularization, and has improved image quality from both AR and IR. For example, AIR has improved visual assessment and quantitative measurement in terms of both contrast and resolution, and reduced axial and half-fan artifacts.

  9. Fused analytical and iterative reconstruction (AIR) via modified proximal forward-backward splitting: a FDK-based iterative image reconstruction example for CBCT

    Science.gov (United States)

    Gao, Hao

    2016-10-01

    This work is to develop a general framework, namely analytical iterative reconstruction (AIR) method, to incorporate analytical reconstruction (AR) method into iterative reconstruction (IR) method, for enhanced CT image quality and reconstruction efficiency. Specifically, AIR is established based on the modified proximal forward-backward splitting (PFBS) algorithm, and its connection to the filtered data fidelity with sparsity regularization is discussed. As a result, AIR decouples data fidelity and image regularization with a two-step iterative scheme, during which an AR-projection step updates the filtered data fidelity term, while a denoising solver updates the sparsity regularization term. During the AR-projection step, the image is projected to the data domain to form the data residual, and then reconstructed by certain AR to a residual image which is then weighted together with previous image iterate to form next image iterate. Intuitively since the eigenvalues of AR-projection operator are close to the unity, PFBS based AIR has a fast convergence. Such an advantage is rigorously established through convergence analysis and numerical computation of convergence rate. The proposed AIR method is validated in the setting of circular cone-beam CT with AR being FDK and total-variation sparsity regularization, and has improved image quality from both AR and IR. For example, AIR has improved visual assessment and quantitative measurement in terms of both contrast and resolution, and reduced axial and half-fan artifacts.

  10. The probability of iterated conditionals

    NARCIS (Netherlands)

    van Wijnbergen-Huitink, Janneke; Elqayam, Shira; Over, David E.

    Iterated conditionals of the form If p, then if q, r are an important topic in philosophical logic. In recent years, psychologists have gained much knowledge about how people understand simple conditionals, but there are virtually no published psychological studies of iterated conditionals. This

  11. Summable series and convergence factors

    CERN Document Server

    Moore, Charles N

    1938-01-01

    Fairly early in the development of the theory of summability of divergent series, the concept of convergence factors was recognized as of fundamental importance in the subject. One of the pioneers in this field was C. N. Moore, the author of the book under review.... Moore classifies convergence factors into two types. In type I he places the factors which have only the property that they preserve convergence for a convergent series or produce convergence for a summable series. In type II he places the factors which not only maintain or produce convergence but have the additional property that

  12. Improvement of the image quality of random phase--free holography using an iterative method

    CERN Document Server

    Shimobaba, Tomoyoshi; Endo, Yutaka; Hirayama, Ryuji; Hiyama, Daisuke; Hasegawa, Satoki; Nagahama, Yuki; Sano, Marie; Oikawa, Minoru; Sugie, Takashige; Ito, Tomoyoshi

    2015-01-01

    Our proposed method of random phase-free holography using virtual convergence light can obtain large reconstructed images exceeding the size of the hologram, without the assistance of random phase. The reconstructed images have low-speckle noise in the amplitude and phase-only holograms (kinoforms); however, in low-resolution holograms, we obtain a degraded image quality compared to the original image. We propose an iterative random phase-free method with virtual convergence light to address this problem.

  13. Enclosing roots of polynomial equations and their applications to iterative processes

    Directory of Open Access Journals (Sweden)

    Saïd Hilout

    2009-11-01

    Full Text Available We introduce a special class of real recurrentpolynomials fn (n ≥ 1 of degree n,with unique positive roots sn, which are decreasingas n increases. The first root s1, as well asthe last one denoted by s∞ are expressed in closedform, and enclose all sn (n > 1. This technique is also used to find weaker than before[Kantorovich and Akilov, 1982] sufficient convergence conditions for some popular iterative processes converging to solutions of equations.

  14. Sparse magnetic resonance imaging reconstruction using the bregman iteration

    Science.gov (United States)

    Lee, Dong-Hoon; Hong, Cheol-Pyo; Lee, Man-Woo

    2013-01-01

    Magnetic resonance imaging (MRI) reconstruction needs many samples that are sequentially sampled by using phase encoding gradients in a MRI system. It is directly connected to the scan time for the MRI system and takes a long time. Therefore, many researchers have studied ways to reduce the scan time, especially, compressed sensing (CS), which is used for sparse images and reconstruction for fewer sampling datasets when the k-space is not fully sampled. Recently, an iterative technique based on the bregman method was developed for denoising. The bregman iteration method improves on total variation (TV) regularization by gradually recovering the fine-scale structures that are usually lost in TV regularization. In this study, we studied sparse sampling image reconstruction using the bregman iteration for a low-field MRI system to improve its temporal resolution and to validate its usefulness. The image was obtained with a 0.32 T MRI scanner (Magfinder II, SCIMEDIX, Korea) with a phantom and an in-vivo human brain in a head coil. We applied random k-space sampling, and we determined the sampling ratios by using half the fully sampled k-space. The bregman iteration was used to generate the final images based on the reduced data. We also calculated the root-mean-square-error (RMSE) values from error images that were obtained using various numbers of bregman iterations. Our reconstructed images using the bregman iteration for sparse sampling images showed good results compared with the original images. Moreover, the RMSE values showed that the sparse reconstructed phantom and the human images converged to the original images. We confirmed the feasibility of sparse sampling image reconstruction methods using the bregman iteration with a low-field MRI system and obtained good results. Although our results used half the sampling ratio, this method will be helpful in increasing the temporal resolution at low-field MRI systems.

  15. Rapid assembly of the doubly-branched pentasaccharide domain of the immunoadjuvant jujuboside A via convergent B(C6F5)3-catalyzed glycosylation of sterically-hindered precursors.

    Science.gov (United States)

    Karimov, Rashad R; Tan, Derek S; Gin, David Y

    2017-05-30

    A convergent synthesis of the complex, doubly-branched pentasaccharide domain of the natural-product immunoadjuvant jujuboside A is described. The key step is a sterically-hindered glycosylation reaction between a branched trisaccharide trichloroacetimidate glycosyl donor and a disaccharide glycosyl acceptor. Conventional Lewis acids (TMSOTf, BF3·Et2O) were ineffective in this glycosylation, but B(C6F5)3 catalyzed the reaction successfully. Inherent complete diastereoselectivity for the undesired α-anomer was overcome by rational optimization with a nitrile solvent system (1 : 5 t-BuCN/CF3Ph) to provide flexible, effective access to the β-linked pentasaccharide.

  16. REAL CONVERGENCE AND INTEGRATION

    Directory of Open Access Journals (Sweden)

    Aurel Iancu

    2007-12-01

    Full Text Available The study is based on the critical observations that competitive market forces alone are not able to assure convergence with the developed countries. These observations are grounded on the results of the computation of the marginal rate of return to capital (which contradict the neoclassical model hypotheses, as well as on the real process of polarisation of the economic activities, taking place worldwide and in accordance with the law of competition. Unlike those who trust the perfect competitive market virtues, the EU’s economic policy is realistic as it is based on the harmonisation of the market forces with an economic policy based on the principle of cohesion, which supports, by means of economic levers, the less developed regions and member countries. This paper deals with the evolution of the EU cohesion funds, as well as with the results of convergence.

  17. The Convergent Learning Space:

    DEFF Research Database (Denmark)

    Kjærgaard, Hanne Wacher; Kjeldsen, Lars Peter; Asmussen, Jørgen Bering

    This paper describes the concept of “The Convergent Learning Space” as it is being explored in an ongoing action research project carried out at undergraduate level in select bachelor programs at a Danish University College. The background nature, design, and beginning of this work in progress......, trajectories of participation etc. calls for new action and new pedagogies by teachers in order to secure alignment between students’ worlds and expectations and aims and plans of the teacher. Action research methods are being used to define and test the constituents and variables of the convergent learning...... is described as well as the theoretical construct and hypotheses surrounding the emergence of the concept in technology-rich classrooms, where students bring their own devices and involve their personal learning spaces and networks. The need for new ways of approaching concepts like choice, learning resources...

  18. The Convergent Learning Space

    DEFF Research Database (Denmark)

    Kjeldsen, Lars Peter; Kjærgaard, Hanne Wacher

    The concept of the Convergent Learning Space has been hypothesized and explored in an ongoing action research project carried out at undergraduate level in select bachelor programs at a Danish University College, where classrooms are technology rich and students bring their own devices. The changes...... networks are still more prominently expected by students. Against this backdrop, an action research project has worked with the definition and testing of the hypothesized constituents of the Convergent Learning Space and how it challenges our traditional conceptions of learning spaces. The article...... describes this pilot study involving teachers in conscious, documented reflection on methods, approaches, and procedures conducive to learning processes in this new learning space. As a perspective, the article briefly outlines an intervention study aimed at investigating how students benefit from...

  19. Multiplier convergent series and uniform convergence of mapping ...

    Indian Academy of Sciences (India)

    j=1 Aj (xj ) converges uniformly with respect to (xj ) in any M ∈ M. Moreover, in the last section we give some applications for mapping series. 2. The space of multiplier convergent series. First, we define the frame property of complex sequence set λ, which is important in studying multiplier convergent series. DEFINITION 2.1.

  20. Iterative CT reconstruction using coordinate descent with ordered subsets of data

    Science.gov (United States)

    Noo, F.; Hahn, K.; Schöndube, H.; Stierstorfer, K.

    2016-04-01

    Image reconstruction based on iterative minimization of a penalized weighted least-square criteria has become an important topic of research in X-ray computed tomography. This topic is motivated by increasing evidence that such a formalism may enable a significant reduction in dose imparted to the patient while maintaining or improving image quality. One important issue associated with this iterative image reconstruction concept is slow convergence and the associated computational effort. For this reason, there is interest in finding methods that produce approximate versions of the targeted image with a small number of iterations and an acceptable level of discrepancy. We introduce here a novel method to produce such approximations: ordered subsets in combination with iterative coordinate descent. Preliminary results demonstrate that this method can produce, within 10 iterations and using only a constant image as initial condition, satisfactory reconstructions that retain the noise properties of the targeted image.

  1. IT Convergence and Security 2012

    CERN Document Server

    Chung, Kyung-Yong

    2013-01-01

    The proceedings approaches the subject matter with problems in technical convergence and convergences of security technology. This approach is new because we look at new issues that arise from techniques converging. The general scope of the proceedings content is convergence security and the latest information technology. The intended readership are societies, enterprises, and research institutes, and intended content level is mid- to highly educated personals. The most important features and benefits of the proceedings are the introduction of the most recent information technology and its related ideas, applications and problems related to technology convergence, and its case studies and finally an introduction of converging existing security techniques through convergence security. Overall, through the proceedings, authors will be able to understand the most state of the art information strategies and technologies of convergence security.

  2. Mission of ITER and Challenges for the Young

    Science.gov (United States)

    Ikeda, Kaname

    2009-02-01

    It is recognized that the ongoing effort to provide sufficient energy for the wellbeing of the globe's population and to power the world economy is of the greatest importance. ITER is a joint international research and development project that aims to demonstrate the scientific and technical feasibility of fusion power. It represents the responsible actions of governments whose countries comprise over half the world's population, to create fusion power as a source of clean, economic, carbon dioxide-free energy. This is the most important science initiative of our time. The partners in the Project—the ITER Parties—are the European Union, Japan, the People's Republic of China, India, the Republic of Korea, the Russian Federation and the USA. ITER will be constructed in Europe, at Cadarache in the South of France. The talk will illustrate the genesis of the ITER Organization, the ongoing work at the Cadarache site and the planned schedule for construction. There will also be an explanation of the unique aspects of international collaboration that have been developed for ITER. Although the present focus of the project is construction activities, ITER is also a major scientific and technological research program, for which the best of the world's intellectual resources is needed. Challenges for the young, imperative for fulfillment of the objective of ITER will be identified. It is important that young students and researchers worldwide recognize the rapid development of the project, and the fundamental issues that must be overcome in ITER. The talk will also cover the exciting career and fellowship opportunities for young people at the ITER Organization.

  3. Ensuring convergence in total-variation-based reconstruction for accurate microcalcification imaging in breast X-ray CT

    CERN Document Server

    Jørgensen, Jakob H; Pan, Xiaochuan

    2011-01-01

    Breast X-ray CT imaging is being considered in screening as an extension to mammography. As a large fraction of the population will be exposed to radiation, low-dose imaging is essential. Iterative image reconstruction based on solving an optimization problem, such as Total-Variation minimization, shows potential for reconstruction from sparse-view data. For iterative methods it is important to ensure convergence to an accurate solution, since important image features, such as presence of microcalcifications indicating breast cancer, may not be visible in a non-converged reconstruction, and this can have clinical significance. To prevent excessively long computational times, which is a practical concern for the large image arrays in CT, it is desirable to keep the number of iterations low, while still ensuring a sufficiently accurate reconstruction for the specific imaging task. This motivates the study of accurate convergence criteria for iterative image reconstruction. In simulation studies with a realistic...

  4. Digital Convergence – Smart Devices

    Indian Academy of Sciences (India)

    First page Back Continue Last page Overview Graphics. Digital Convergence – Smart Devices. More and more devices become cheap one-chip components. Different devices are joined to form new multi-purpose devices. Devices and applications converge to form digital personal tools. Behind digital convergence is the ...

  5. Two-level method with coarse space size independent convergence

    Energy Technology Data Exchange (ETDEWEB)

    Vanek, P.; Brezina, M. [Univ. of Colorado, Denver, CO (United States); Tezaur, R.; Krizkova, J. [UWB, Plzen (Czech Republic)

    1996-12-31

    The basic disadvantage of the standard two-level method is the strong dependence of its convergence rate on the size of the coarse-level problem. In order to obtain the optimal convergence result, one is limited to using a coarse space which is only a few times smaller than the size of the fine-level one. Consequently, the asymptotic cost of the resulting method is the same as in the case of using a coarse-level solver for the original problem. Today`s two-level domain decomposition methods typically offer an improvement by yielding a rate of convergence which depends on the ratio of fine and coarse level only polylogarithmically. However, these methods require the use of local subdomain solvers for which straightforward application of iterative methods is problematic, while the usual application of direct solvers is expensive. We suggest a method diminishing significantly these difficulties.

  6. Iterative optimization in inverse problems

    CERN Document Server

    Byrne, Charles L

    2014-01-01

    Iterative Optimization in Inverse Problems brings together a number of important iterative algorithms for medical imaging, optimization, and statistical estimation. It incorporates recent work that has not appeared in other books and draws on the author's considerable research in the field, including his recently developed class of SUMMA algorithms. Related to sequential unconstrained minimization methods, the SUMMA class includes a wide range of iterative algorithms well known to researchers in various areas, such as statistics and image processing. Organizing the topics from general to more

  7. Ensuring convergence in total-variation-based reconstruction for accurate microcalcification imaging in breast X-ray CT

    DEFF Research Database (Denmark)

    Jørgensen, Jakob Heide; Sidky, Emil Y.; Pan, Xiaochuan

    2011-01-01

    , shows potential for reconstruction from sparse-view data. For iterative methods it is important to ensure convergence to an accurate solution, since important diagnostic image features, such as presence of microcalcifications indicating breast cancer, may not be visible in a non-converged reconstruction....... This motivates the study of accurate convergence criteria for iterative image reconstruction. In simulation studies with a realistic breast phantom with microcalcifications we investigate the issue of ensuring sufficiently converged solution for reliable reconstruction. Our results show that it can......Breast X-ray CT imaging is being considered in screening as an extension to mammography. As a large fraction of the population will be exposed to radiation, low·dose imaging is essential. Iterative image reconstruction based on solving an optimization problem, such as Total-Variation minimization...

  8. Convergence of Simar's Algorithm for Finding the Maximum Likelihood Estimate of a Compound Poisson Process

    OpenAIRE

    Bohning, Dankmar

    1982-01-01

    Simar (1976) suggested an iteration procedure for finding the maximum likelihood estimate of a compound Poisson process, but he could not show convergence. Here the more general case of maximizing a concave functional on the set of all probability measures is treated. As a generalization of Simar's procedure, an algorithm is given for solving this problem, including assumptions to ensure convergence to an optimum. Finally, it is shown that Simar's functional fulfills these assumptions.

  9. Rollout sampling approximate policy iteration

    NARCIS (Netherlands)

    Dimitrakakis, C.; Lagoudakis, M.G.

    2008-01-01

    Several researchers have recently investigated the connection between reinforcement learning and classification. We are motivated by proposals of approximate policy iteration schemes without value functions, which focus on policy representation using classifiers and address policy learning as a

  10. Cooperation between CERN and ITER

    CERN Multimedia

    2008-01-01

    CERN and the International Fusion Organisation ITER have just signed a first cooperation agreeement. Kaname Ikeda, the Director-General of the International Fusion Energy Organisation (ITER) (on the right) and Robert Aymar, Director-General of CERN, signing the agreement.The Director-General of the International Fusion Energy Organization, Mr Kaname Ikeda, and CERN Director-General, Robert Aymar, signed a cooperation agreement at a meeting on the Meyrin site on Thursday 6 March. One of the main purposes of this agreement is for CERN to give ITER the benefit of its experience in the field of technology as well as in administrative domains such as finance, procurement, human resources and informatics through the provision of consultancy services. Currently in its start-up phase at its Cadarache site, 70 km from Marseilles (France), ITER will focus its research on the scientific and technical feasibility of using fusion energy as a fu...

  11. Semi-convergence and relaxation parameters for a class of SIRT algorithms

    DEFF Research Database (Denmark)

    Elfving, Tommy; Nikazad, Touraj; Hansen, Per Christian

    2010-01-01

    adaptively during the iterations, so as to control the propagated noise component of the error. The advantage of using this strategy for the choice of relaxation parameters on noisy and ill-conditioned problems is demonstrated with an example from tomography (image reconstruction from projections).......This paper is concerned with the Simultaneous Iterative Reconstruction Technique (SIRT) class of iterative methods for solving inverse problems. Based on a careful analysis of the semi-convergence behavior of these methods, we propose two new techniques to specify the relaxation parameters...

  12. ITER leader to head CERN

    CERN Multimedia

    Feder, Toni

    2003-01-01

    After successfully chairing an external review committee for CERN last year, Robert Aymar will leave ITER to become director general of the European particle physics laboratory rom 2004. Before ITER he also successfully managed the startup or Tore Supra. He will attempt to ensure that the LHC begins operating in 2007 - two years late - and is paid for by 2010 and will also start the planning for life after the LHC (1 page)

  13. New Hybrid Iterative Schemes for an Infinite Family of Nonexpansive Mappings in Hilbert Spaces

    Directory of Open Access Journals (Sweden)

    Guo Baohua

    2010-01-01

    Full Text Available We propose some new iterative schemes for finding common fixed point of an infinite family of nonexpansive mappings in a Hilbert space and prove the strong convergence of the proposed schemes. Our results extend and improve ones of Nakajo and Takahashi (2003.

  14. Applications of normal S-iterative method to a nonlinear integral equation.

    Science.gov (United States)

    Gürsoy, Faik

    2014-01-01

    It has been shown that a normal S-iterative method converges to the solution of a mixed type Volterra-Fredholm functional nonlinear integral equation. Furthermore, a data dependence result for the solution of this integral equation has been proven.

  15. An Iterative Method for the Matrix Principal n-th Root

    OpenAIRE

    Lakić, Slobodan

    1995-01-01

    In this paper we give an iterative method to compute the principal n-th root and the principal inverse n-th root of a given matrix. As we shall show this method is locally convergent. This method is analyzed and its numerical stability is investigated.

  16. Comment on an application of the asymptotic iteration method to a perturbed Coulomb model

    Energy Technology Data Exchange (ETDEWEB)

    Amore, Paolo [Facultad de Ciencias, Universidad de Colima, Bernal DIaz del Castillo 340, Colima (Mexico); Fernandez, Francisco M [INIFTA (Conicet, UNLP), Blvd. 113 y 64 S/N, Sucursal 4, Casilla de Correo 16, 1900 La Plata (Argentina)

    2006-08-18

    We discuss a recent application of the asymptotic iteration method (AIM) to a perturbed Coulomb model. Contrary to what was argued before we show that the AIM converges and yields accurate energies for that model. We also consider alternative perturbation approaches and show that one of them is equivalent to that recently proposed by another author.

  17. A two-step iterative method and its acceleration for outer inverses

    Indian Academy of Sciences (India)

    A two-step iterative method and its accelerated version for approximating outer inverse A2 T,S of an arbitrary matrix A are proposed. A convergence theorem for its existence is established. The rigorous error bounds are derived. Numerical experiments involving singular square, rectangular, random matrices and a sparse ...

  18. Formulations to overcome the divergence of iterative method of fixed-point in nonlinear equations solution

    Directory of Open Access Journals (Sweden)

    Wilson Rodríguez Calderón

    2015-04-01

    Full Text Available When we need to determine the solution of a nonlinear equation there are two options: closed-methods which use intervals that contain the root and during the iterative process reduce the size of natural way, and, open-methods that represent an attractive option as they do not require an initial interval enclosure. In general, we know open-methods are more efficient computationally though they do not always converge. In this paper we are presenting a divergence case analysis when we use the method of fixed point iteration to find the normal height in a rectangular channel using the Manning equation. To solve this problem, we propose applying two strategies (developed by authors that allow to modifying the iteration function making additional formulations of the traditional method and its convergence theorem. Although Manning equation is solved with other methods like Newton when we use the iteration method of fixed-point an interesting divergence situation is presented which can be solved with a convergence higher than quadratic over the initial iterations. The proposed strategies have been tested in two cases; a study of divergence of square root of real numbers was made previously by authors for testing. Results in both cases have been successful. We present comparisons because are important for seeing the advantage of proposed strategies versus the most representative open-methods.

  19. Solving large mixed linear models using preconditioned conjugate gradient iteration.

    Science.gov (United States)

    Strandén, I; Lidauer, M

    1999-12-01

    Continuous evaluation of dairy cattle with a random regression test-day model requires a fast solving method and algorithm. A new computing technique feasible in Jacobi and conjugate gradient based iterative methods using iteration on data is presented. In the new computing technique, the calculations in multiplication of a vector by a matrix were recorded to three steps instead of the commonly used two steps. The three-step method was implemented in a general mixed linear model program that used preconditioned conjugate gradient iteration. Performance of this program in comparison to other general solving programs was assessed via estimation of breeding values using univariate, multivariate, and random regression test-day models. Central processing unit time per iteration with the new three-step technique was, at best, one-third that needed with the old technique. Performance was best with the test-day model, which was the largest and most complex model used. The new program did well in comparison to other general software. Programs keeping the mixed model equations in random access memory required at least 20 and 435% more time to solve the univariate and multivariate animal models, respectively. Computations of the second best iteration on data took approximately three and five times longer for the animal and test-day models, respectively, than did the new program. Good performance was due to fast computing time per iteration and quick convergence to the final solutions. Use of preconditioned conjugate gradient based methods in solving large breeding value problems is supported by our findings.

  20. Improved Savitzky-Golay-method-based fluorescence subtraction algorithm for rapid recovery of Raman spectra.

    Science.gov (United States)

    Chen, Kun; Zhang, Hongyuan; Wei, Haoyun; Li, Yan

    2014-08-20

    In this paper, we propose an improved subtraction algorithm for rapid recovery of Raman spectra that can substantially reduce the computation time. This algorithm is based on an improved Savitzky-Golay (SG) iterative smoothing method, which involves two key novel approaches: (a) the use of the Gauss-Seidel method and (b) the introduction of a relaxation factor into the iterative procedure. By applying a novel successive relaxation (SG-SR) iterative method to the relaxation factor, additional improvement in the convergence speed over the standard Savitzky-Golay procedure is realized. The proposed improved algorithm (the RIA-SG-SR algorithm), which uses SG-SR-based iteration instead of Savitzky-Golay iteration, has been optimized and validated with a mathematically simulated Raman spectrum, as well as experimentally measured Raman spectra from non-biological and biological samples. The method results in a significant reduction in computing cost while yielding consistent rejection of fluorescence and noise for spectra with low signal-to-fluorescence ratios and varied baselines. In the simulation, RIA-SG-SR achieved 1 order of magnitude improvement in iteration number and 2 orders of magnitude improvement in computation time compared with the range-independent background-subtraction algorithm (RIA). Furthermore the computation time of the experimentally measured raw Raman spectrum processing from skin tissue decreased from 6.72 to 0.094 s. In general, the processing of the SG-SR method can be conducted within dozens of milliseconds, which can provide a real-time procedure in practical situations.

  1. NUFFT-Based Iterative Image Reconstruction via Alternating Direction Total Variation Minimization for Sparse-View CT

    Directory of Open Access Journals (Sweden)

    Bin Yan

    2015-01-01

    Full Text Available Sparse-view imaging is a promising scanning method which can reduce the radiation dose in X-ray computed tomography (CT. Reconstruction algorithm for sparse-view imaging system is of significant importance. The adoption of the spatial iterative algorithm for CT image reconstruction has a low operation efficiency and high computation requirement. A novel Fourier-based iterative reconstruction technique that utilizes nonuniform fast Fourier transform is presented in this study along with the advanced total variation (TV regularization for sparse-view CT. Combined with the alternating direction method, the proposed approach shows excellent efficiency and rapid convergence property. Numerical simulations and real data experiments are performed on a parallel beam CT. Experimental results validate that the proposed method has higher computational efficiency and better reconstruction quality than the conventional algorithms, such as simultaneous algebraic reconstruction technique using TV method and the alternating direction total variation minimization approach, with the same time duration. The proposed method appears to have extensive applications in X-ray CT imaging.

  2. ITER Central Solenoid Module Fabrication

    Energy Technology Data Exchange (ETDEWEB)

    Smith, John [General Atomics, San Diego, CA (United States)

    2016-09-23

    The fabrication of the modules for the ITER Central Solenoid (CS) has started in a dedicated production facility located in Poway, California, USA. The necessary tools have been designed, built, installed, and tested in the facility to enable the start of production. The current schedule has first module fabrication completed in 2017, followed by testing and subsequent shipment to ITER. The Central Solenoid is a key component of the ITER tokamak providing the inductive voltage to initiate and sustain the plasma current and to position and shape the plasma. The design of the CS has been a collaborative effort between the US ITER Project Office (US ITER), the international ITER Organization (IO) and General Atomics (GA). GA’s responsibility includes: completing the fabrication design, developing and qualifying the fabrication processes and tools, and then completing the fabrication of the seven 110 tonne CS modules. The modules will be shipped separately to the ITER site, and then stacked and aligned in the Assembly Hall prior to insertion in the core of the ITER tokamak. A dedicated facility in Poway, California, USA has been established by GA to complete the fabrication of the seven modules. Infrastructure improvements included thick reinforced concrete floors, a diesel generator for backup power, along with, cranes for moving the tooling within the facility. The fabrication process for a single module requires approximately 22 months followed by five months of testing, which includes preliminary electrical testing followed by high current (48.5 kA) tests at 4.7K. The production of the seven modules is completed in a parallel fashion through ten process stations. The process stations have been designed and built with most stations having completed testing and qualification for carrying out the required fabrication processes. The final qualification step for each process station is achieved by the successful production of a prototype coil. Fabrication of the first

  3. Constructing Frozen Jacobian Iterative Methods for Solving Systems of Nonlinear Equations, Associated with ODEs and PDEs Using the Homotopy Method

    Directory of Open Access Journals (Sweden)

    Uswah Qasim

    2016-03-01

    Full Text Available A homotopy method is presented for the construction of frozen Jacobian iterative methods. The frozen Jacobian iterative methods are attractive because the inversion of the Jacobian is performed in terms of LUfactorization only once, for a single instance of the iterative method. We embedded parameters in the iterative methods with the help of the homotopy method: the values of the parameters are determined in such a way that a better convergence rate is achieved. The proposed homotopy technique is general and has the ability to construct different families of iterative methods, for solving weakly nonlinear systems of equations. Further iterative methods are also proposed for solving general systems of nonlinear equations.

  4. The irace package: Iterated racing for automatic algorithm configuration

    Directory of Open Access Journals (Sweden)

    Manuel López-Ibáñez

    2016-01-01

    Full Text Available Modern optimization algorithms typically require the setting of a large number of parameters to optimize their performance. The immediate goal of automatic algorithm configuration is to find, automatically, the best parameter settings of an optimizer. Ultimately, automatic algorithm configuration has the potential to lead to new design paradigms for optimization software. The irace package is a software package that implements a number of automatic configuration procedures. In particular, it offers iterated racing procedures, which have been used successfully to automatically configure various state-of-the-art algorithms. The iterated racing procedures implemented in irace include the iterated F-race algorithm and several extensions and improvements over it. In this paper, we describe the rationale underlying the iterated racing procedures and introduce a number of recent extensions. Among these, we introduce a restart mechanism to avoid premature convergence, the use of truncated sampling distributions to handle correctly parameter bounds, and an elitist racing procedure for ensuring that the best configurations returned are also those evaluated in the highest number of training instances. We experimentally evaluate the most recent version of irace and demonstrate with a number of example applications the use and potential of irace, in particular, and automatic algorithm configuration, in general.

  5. An efficient iterative algorithm for computation of scattering from dielectric objects.

    Energy Technology Data Exchange (ETDEWEB)

    Liao, L.; Gopalsami, N.; Venugopal, A.; Heifetz, A.; Raptis, A. C. (Nuclear Engineering Division)

    2011-02-14

    We have developed an efficient iterative algorithm for electromagnetic scattering of arbitrary but relatively smooth dielectric objects. The algorithm iteratively adapts the equivalent surface currents until the electromagnetic fields inside and outside the dielectric objects match the boundary conditions. Theoretical convergence is analyzed for two examples that solve scattering of plane waves incident upon air/dielectric slabs of semi-infinite and finite thicknesses. We applied the iterative algorithm for simulation of sinusoidally-perturbed dielectric slab on one side and the method converged for such unsmooth surfaces. We next simulated the shift in radiation pattern of a 6-inch dielectric lens for different offsets of the feed antenna on the focal plane. The result is compared to that of the Geometrical Optics (GO).

  6. An Efficient Iterative Scheme Using Family of Chebyshev’s Operations

    Directory of Open Access Journals (Sweden)

    Seyed Hossein Mahdavi

    2015-01-01

    Full Text Available This paper presents an efficient iterative method originated from the family of Chebyshev’s operations for the solution of nonlinear problems. For this aim, the product operation matrix of integration is presented, and therefore the operation of derivative is developed by using Chebyshev wavelet functions of the first and second kind, initially. Later, Chebyshev’s iterative method is improved by approximation of the first and second derivatives. The analysis of convergence demonstrates that the method is at least fourth-order convergent. The effectiveness of the proposed scheme is numerically and practically evaluated. It is concluded that it requires the less number of iterations and lies on the best performance of the proposed method, especially for highly varying nonlinear problems.

  7. Iterative methods for photoacoustic tomography in attenuating acoustic media

    Science.gov (United States)

    Haltmeier, Markus; Kowar, Richard; Nguyen, Linh V.

    2017-11-01

    The development of efficient and accurate reconstruction methods is an important aspect of tomographic imaging. In this article, we address this issue for photoacoustic tomography. To this aim, we use models for acoustic wave propagation accounting for frequency dependent attenuation according to a wide class of attenuation laws that may include memory. We formulate the inverse problem of photoacoustic tomography in attenuating medium as an ill-posed operator equation in a Hilbert space framework that is tackled by iterative regularization methods. Our approach comes with a clear convergence analysis. For that purpose we derive explicit expressions for the adjoint problem that can efficiently be implemented. In contrast to time reversal, the employed adjoint wave equation is again damping and, thus has a stable solution. This stability property can be clearly seen in our numerical results. Moreover, the presented numerical results clearly demonstrate the efficiency and accuracy of the derived iterative reconstruction algorithms in various situations including the limited view case.

  8. Information technology convergence security, robotics, automations and communication

    CERN Document Server

    Barolli, Leonard; Xhafa, Fatos; Jeong, Hwa-Young

    2013-01-01

    Information technology and its convergence issue is emerging rapidly as an exciting new paradigm with user-centric environment to provide computing and communication services. This area will be the most comprehensive topics with various aspects of advances in information technology and its convergence services. This book covers all topics as computational science and applications, electronics engineering, manufacturing technology, services, technical skill to control the robot, automatic operation and application, simulation and testing communication and many more.

  9. Homology, convergence and parallelism.

    Science.gov (United States)

    Ghiselin, Michael T

    2016-01-05

    Homology is a relation of correspondence between parts of parts of larger wholes. It is used when tracking objects of interest through space and time and in the context of explanatory historical narratives. Homologues can be traced through a genealogical nexus back to a common ancestral precursor. Homology being a transitive relation, homologues remain homologous however much they may come to differ. Analogy is a relationship of correspondence between parts of members of classes having no relationship of common ancestry. Although homology is often treated as an alternative to convergence, the latter is not a kind of correspondence: rather, it is one of a class of processes that also includes divergence and parallelism. These often give rise to misleading appearances (homoplasies). Parallelism can be particularly hard to detect, especially when not accompanied by divergences in some parts of the body. © 2015 The Author(s).

  10. Medialogy - convergence and transdisciplinarity

    DEFF Research Database (Denmark)

    Nordahl, Rolf

    2007-01-01

    Art and design have many qualities which intuitively by society are appreciated. But on daily basis they are also assessed and evaluated. Some communities also share common understandings that norms, standards, conventions evolve, both from artistic desire as well as from more physical needs...... for changes in society, developments in taste etc.  However, it certainly seems fair to say, that available technology makes a great difference to the development of any art form or practice. With the up rise of new educations such as Medialogy, new aspects of convergence and different forms...... of interdisciplinarity and transdisciplinarity is a pre-requisite for both researchers and students. In this talk we will demonstrate our approach through concrete examples of student productions and projects. We will also display the pedagogical method (problem based learning), that enables students to bridge gaps...

  11. Iterative Solutions of Nonlinear Integral Equations of Hammerstein Type

    Directory of Open Access Journals (Sweden)

    Abebe R. Tufa

    2015-11-01

    Full Text Available Let H be a real Hilbert space. Let F,K : H → H be Lipschitz monotone mappings with Lipschtiz constants L1and L2, respectively. Suppose that the Hammerstein type equation u + KFu = 0 has a solution in H. It is our purpose in this paper to construct a new explicit iterative sequence and prove strong convergence of the sequence to a solution of the generalized Hammerstein type equation. The results obtained in this paper improve and extend known results in the literature.

  12. Dhage Iteration Method for Generalized Quadratic Functional Integral Equations

    Directory of Open Access Journals (Sweden)

    Bapurao C. Dhage

    2015-01-01

    Full Text Available In this paper we prove the existence as well as approximations of the solutions for a certain nonlinear generalized quadratic functional integral equation. An algorithm for the solutions is developed and it is shown that the sequence of successive approximations starting at a lower or upper solution converges monotonically to the solutions of related quadratic functional integral equation under some suitable mixed hybrid conditions. We rely our main result on Dhage iteration method embodied in a recent hybrid fixed point theorem of Dhage (2014 in partially ordered normed linear spaces. An example is also provided to illustrate the abstract theory developed in the paper.

  13. Iterative Schemes for Time Parallelization with Application to Reservoir Simulation

    Energy Technology Data Exchange (ETDEWEB)

    Garrido, I; Fladmark, G E; Espedal, M S; Lee, B

    2005-04-18

    Parallel methods are usually not applied to the time domain because of the inherit sequentialness of time evolution. But for many evolutionary problems, computer simulation can benefit substantially from time parallelization methods. In this paper, they present several such algorithms that actually exploit the sequential nature of time evolution through a predictor-corrector procedure. This sequentialness ensures convergence of a parallel predictor-corrector scheme within a fixed number of iterations. The performance of these novel algorithms, which are derived from the classical alternating Schwarz method, are illustrated through several numerical examples using the reservoir simulator Athena.

  14. Optimizing convergence rates of alternating minimization reconstruction algorithms for real-time explosive detection applications

    Science.gov (United States)

    Bosch, Carl; Degirmenci, Soysal; Barlow, Jason; Mesika, Assaf; Politte, David G.; O'Sullivan, Joseph A.

    2016-05-01

    X-ray computed tomography reconstruction for medical, security and industrial applications has evolved through 40 years of experience with rotating gantry scanners using analytic reconstruction techniques such as filtered back projection (FBP). In parallel, research into statistical iterative reconstruction algorithms has evolved to apply to sparse view scanners in nuclear medicine, low data rate scanners in Positron Emission Tomography (PET) [5, 7, 10] and more recently to reduce exposure to ionizing radiation in conventional X-ray CT scanners. Multiple approaches to statistical iterative reconstruction have been developed based primarily on variations of expectation maximization (EM) algorithms. The primary benefit of EM algorithms is the guarantee of convergence that is maintained when iterative corrections are made within the limits of convergent algorithms. The primary disadvantage, however is that strict adherence to correction limits of convergent algorithms extends the number of iterations and ultimate timeline to complete a 3D volumetric reconstruction. Researchers have studied methods to accelerate convergence through more aggressive corrections [1], ordered subsets [1, 3, 4, 9] and spatially variant image updates. In this paper we describe the development of an AM reconstruction algorithm with accelerated convergence for use in a real-time explosive detection application for aviation security. By judiciously applying multiple acceleration techniques and advanced GPU processing architectures, we are able to perform 3D reconstruction of scanned passenger baggage at a rate of 75 slices per second. Analysis of the results on stream of commerce passenger bags demonstrates accelerated convergence by factors of 8 to 15, when comparing images from accelerated and strictly convergent algorithms.

  15. A Two-Point Newton Method Suitable for Nonconvergent Cases and with Super-Quadratic Convergence

    Directory of Open Access Journals (Sweden)

    Ababu Teklemariam Tiruneh

    2013-01-01

    Full Text Available An iterative formula based on Newton’s method alone is presented for the iterative solutions of equations that ensures convergence in cases where the traditional Newton Method may fail to converge to the desired root. In addition, the method has super-quadratic convergence of order 2.414 (i.e., . Newton method is said to fail in certain cases leading to oscillation, divergence to increasingly large number, or offshooting away to another root further from the desired domain or offshooting to an invalid domain where the function may not be defined. In addition when the derivative at the iteration point is zero, Newton method stalls. In most of these cases, hybrids of several methods such as Newton, bisection, and secant methods are suggested as substitute methods and Newton method is essentially blended with other methods or altogether abandoned. This paper argues that a solution is still possible in most of these cases by the application of Newton method alone without resorting to other methods and with the same computational effort (two functional evaluations per iteration like the traditional Newton method. In addition, the proposed modified formula based on Newton method has better convergence characteristics than the traditional Newton method.

  16. The Pugh Controlled Convergence method : Model-based evaluation and implications for design theory

    NARCIS (Netherlands)

    Frey, D.D.; Herder, P.M.; Wijnia, Y.; Saubrahmanian, E.; Katsikopoulos, K.; Clausing, D.P.

    2008-01-01

    This paper evaluates the Pugh Controlled Convergence method and its relationship to recent developments in design theory. Computer executable models are proposed simulating a team of people involved in iterated cycles of evaluation, ideation, and investigation. The models suggest that: (1)

  17. How to co-add images? I. A new iterative method for image reconstruction of dithered observations

    Science.gov (United States)

    Wang, Lei; Li, Guo-Liang

    2017-09-01

    By employing the previous Voronoi approach and replacing its nearest neighbor approximation with Drizzle in iterative signal extraction, we develop a fast iterative Drizzle algorithm, named fiDrizzle, to reconstruct the underlying band-limited image from undersampled dithered frames. Compared with the existing iDrizzle, the new algorithm improves rate of convergence and accelerates the computational speed. Moreover, under the same conditions (e.g. the same number of dithers and iterations), fiDrizzle can make a better quality reconstruction than iDrizzle, due to the newly discovered High Sampling caused Decelerating Convergence (HSDC) effect in the iterative signal extraction process. fiDrizzle demonstrates its powerful ability to perform image deconvolution from undersampled dithers.

  18. Elliptic Preconditioner for Accelerating the Self-Consistent Field Iteration in Kohn--Sham Density Functional Theory

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Lin [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Computational Research Division; Yang, Chao [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Computational Research Division

    2013-10-28

    We discuss techniques for accelerating the self consistent field (SCF) iteration for solving the Kohn-Sham equations. These techniques are all based on constructing approximations to the inverse of the Jacobian associated with a fixed point map satisfied by the total potential. They can be viewed as preconditioners for a fixed point iteration. We point out different requirements for constructing preconditioners for insulating and metallic systems respectively, and discuss how to construct preconditioners to keep the convergence rate of the fixed point iteration independent of the size of the atomistic system. We propose a new preconditioner that can treat insulating and metallic system in a unified way. The new preconditioner, which we call an elliptic preconditioner, is constructed by solving an elliptic partial differential equation. The elliptic preconditioner is shown to be more effective in accelerating the convergence of a fixed point iteration than the existing approaches for large inhomogeneous systems at low temperature.

  19. The ITER project technological challenges

    CERN Document Server

    CERN. Geneva; Lister, Joseph; Marquina, Miguel A; Todesco, Ezio

    2005-01-01

    The first lecture reminds us of the ITER challenges, presents hard engineering problems, typically due to mechanical forces and thermal loads and identifies where the physics uncertainties play a significant role in the engineering requirements. The second lecture presents soft engineering problems of measuring the plasma parameters, feedback control of the plasma and handling the physics data flow and slow controls data flow from a large experiment like ITER. The last three lectures focus on superconductors for fusion. The third lecture reviews the design criteria and manufacturing methods for 6 milestone-conductors of large fusion devices (T-7, T-15, Tore Supra, LHD, W-7X, ITER). The evolution of the designer approach and the available technologies are critically discussed. The fourth lecture is devoted to the issue of performance prediction, from a superconducting wire to a large size conductor. The role of scaling laws, self-field, current distribution, voltage-current characteristic and transposition are...

  20. ITER Disruption Mitigation System Design

    Science.gov (United States)

    Rasmussen, David; Lyttle, M. S.; Baylor, L. R.; Carmichael, J. R.; Caughman, J. B. O.; Combs, S. K.; Ericson, N. M.; Bull-Ezell, N. D.; Fehling, D. T.; Fisher, P. W.; Foust, C. R.; Ha, T.; Meitner, S. J.; Nycz, A.; Shoulders, J. M.; Smith, S. F.; Warmack, R. J.; Coburn, J. D.; Gebhart, T. E.; Fisher, J. T.; Reed, J. R.; Younkin, T. R.

    2015-11-01

    The disruption mitigation system for ITER is under design and will require injection of up to 10 kPa-m3 of deuterium, helium, neon, or argon material for thermal mitigation and up to 100 kPa-m3 of material for suppression of runaway electrons. A hybrid unit compatible with the ITER nuclear, thermal and magnetic field environment is being developed. The unit incorporates a fast gas valve for massive gas injection (MGI) and a shattered pellet injector (SPI) to inject a massive spray of small particles, and can be operated as an SPI with a frozen pellet or an MGI without a pellet. Three ITER upper port locations will have three SPI/MGI units with a common delivery tube. One equatorial port location has space for sixteen similar SPI/MGI units. Supported by US DOE under DE-AC05-00OR22725.

  1. Proceedings of the International Conference on IT Convergence and Security 2011

    CERN Document Server

    Ahn, Seong

    2012-01-01

    As we entered the 21st century, the rapid growth of information technology has changed our lives more conveniently than we have ever speculated. Recently in all fields of the industry, heterogeneous technologies have converged with information technology resulting in a new paradigm, information technology convergence. In the process of information technology convergence, the latest issues in the structure of data, system, network, and infrastructure have become the most challenging task. Proceedings of the International Conference on IT Convergence and Security 2011 approaches the subject matter with problems in technical convergence and convergences of security technology by looking at new issues that arise from techniques converging. The general scope is convergence security and the latest information technology with the following most important features and benefits: 1.      Introduction of the most recent information technology and its related ideas 2.      Applications and problems related to t...

  2. Status of research toward the ITER disruption mitigation system

    Energy Technology Data Exchange (ETDEWEB)

    Hollmann, E. M.; Izzo, V. A. [Center for Energy Research, University of California, San Diego, La Jolla, California 92093-0417 (United States); Aleynikov, P. B.; Lehnen, M.; Snipes, J. A. [ITER Organization, Route de Vinon sur Verdon, CS 90 046 - 13067 Saint Paul lez Durance (France); Fülöp, T. [Department of Applied Physics, Chalmers University of Technology, Göteborg (Sweden); Humphreys, D. A. [General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States); Lukash, V. E. [Institute of Nuclear Fusion, RRC Kurchatov Institute, Moscow (Russian Federation); Papp, G.; Pautasso, G. [Max-Planck Institute for Plasma Physics, EURATOM Association, Garching (Germany); Saint-Laurent, F. [CEA, IRFM, Saint Paul lez Durance (France)

    2015-02-15

    An overview of the present status of research toward the final design of the ITER disruption mitigation system (DMS) is given. The ITER DMS is based on massive injection of impurities, in order to radiate the plasma stored energy and mitigate the potentially damaging effects of disruptions. The design of this system will be extremely challenging due to many physics and engineering constraints such as limitations on port access and the amount and species of injected impurities. Additionally, many physics questions relevant to the design of the ITER disruption mitigation system remain unsolved such as the mechanisms for mixing and assimilation of injected impurities during the rapid shutdown and the mechanisms for the subsequent formation and dissipation of runaway electron current.

  3. Impact of element-level static condensation on iterative solver performance

    KAUST Repository

    Pardo, D.

    2015-10-02

    This paper provides theoretical estimates that quantify and clarify the savings associated to the use of element-level static condensation as a first step of an iterative solver. These estimates are verified numerically. The numerical evidence shows that static condensation at the element level is beneficial for higher-order methods. For lower-order methods or when the number of iterations required for convergence is low, the setup cost of the elimination as well as its implementation may offset the benefits obtained during the iteration process. However, as the iteration count (e.g., above 50) or the polynomial order (e.g., above cubics) grows, the benefits of element-level static condensation are significant.

  4. Another Simple Way of Deriving Several Iterative Functions to Solve Nonlinear Equations

    Directory of Open Access Journals (Sweden)

    Ramandeep Behl

    2012-01-01

    Full Text Available We present another simple way of deriving several iterative methods for solving nonlinear equations numerically. The presented approach of deriving these methods is based on exponentially fitted osculating straight line. These methods are the modifications of Newton's method. Also, we obtain well-known methods as special cases, for example, Halley's method, super-Halley method, Ostrowski's square-root method, Chebyshev's method, and so forth. Further, new classes of third-order multipoint iterative methods free from a second-order derivative are derived by semidiscrete modifications of cubically convergent iterative methods. Furthermore, a simple linear combination of two third-order multipoint iterative methods is used for designing new optimal methods of order four.

  5. Iterative Schemes for Zero Points of Maximal Monotone Operators and Fixed Points of Nonexpansive Mappings and Their Applications

    Directory of Open Access Journals (Sweden)

    Yeol Je Cho

    2008-03-01

    Full Text Available Two iterative schemes for finding a common element of the set of zero points of maximal monotone operators and the set of fixed points of nonexpansive mappings in the sense of Lyapunov functional in a real uniformly smooth and uniformly convex Banach space are obtained. Two strong convergence theorems are obtained which extend some previous work. Moreover, the applications of the iterative schemes are demonstrated.

  6. Exact solutions for some of the fractional differential equations by using modification of He's variational iteration method

    Directory of Open Access Journals (Sweden)

    S. Irandoust-pakchin

    2011-03-01

    Full Text Available In this paper, the modification of He's variational iteration method(MVIM is developed to solve fractional ordinary differentialequations and fractional partial differential equations. It is usedthe free choice of initial approximation to propose the reliablemodification of He's variational iteration method. Some of thefractional differential equations are examined to illustrate theeffectiveness and convenience of the method. The results show thatthe proposed method has accelerated convergence.

  7. Convergence of generalized eigenfunction expansions

    Directory of Open Access Journals (Sweden)

    Mayumi Sakata

    2007-05-01

    Full Text Available We present a simplified theory of generalized eigenfunction expansions for a commuting family of bounded operators and with finitely many unbounded operators. We also study the convergence of these expansions, giving an abstract type of uniform convergence result, and illustrate the theory by giving two examples: The Fourier transform on Hecke operators, and the Laplacian operators in hyperbolic spaces.

  8. Giant lobelias exemplify convergent evolution

    Directory of Open Access Journals (Sweden)

    Givnish Thomas J

    2010-01-01

    Full Text Available Abstract Giant lobeliads on tropical mountains in East Africa and Hawaii have highly unusual, giant-rosette growth forms that appear to be convergent on each other and on those of several independently evolved groups of Asteraceae and other families. A recent phylogenetic analysis by Antonelli, based on sequencing the widest selection of lobeliads to date, raises doubts about this paradigmatic example of convergent evolution. Here I address the kinds of evidence needed to test for convergent evolution and argue that the analysis by Antonelli fails on four points. Antonelli's analysis makes several important contributions to our understanding of lobeliad evolution and geographic spread, but his claim regarding convergence appears to be invalid. Giant lobeliads in Hawaii and Africa represent paradigmatic examples of convergent evolution.

  9. Gas/electricity convergence: role of marketers

    Energy Technology Data Exchange (ETDEWEB)

    Peterson, K.G. [Powerex Corp., Inc., Youngwood, PA (United States)

    1997-04-01

    The role of marketers in the convergence of the gas and electricity industry was presented. Topics of discussion included types of convergence, such as wholesale price convergence, BTU convergence, energy information systems service convergence, and corporate convergence. Also discussed was a review of technical, economic, political and regulatory barriers to convergence. Implications for customers, regulators and vertically integrated utilities and trade associations were also assessed.

  10. Modified Spectral Projected Subgradient Method: Convergence Analysis and Momentum Parameter Heuristics

    Directory of Open Access Journals (Sweden)

    Milagros Loreto

    2016-09-01

    Full Text Available The Modified Spectral Projected Subgradient (MSPS was proposed to solve Langrangen Dual Problems, and its convergence was shown when the momentum term was zero. The MSPS uses a momentum term in order to speed up its convergence. The momentum term is built on the multiplication of a momentum parameter and the direction of the previous iterate. In this work, we show convergence when the momentum parameter is a non-zero constant. We also propose heuristics to choose the momentum parameter intended to avoid the Zigzagging Phenomenon of Kind I. This phenomenon is present in the MSPS when at an iterate the subgradient forms an obtuse angle with the previous direction. We identify and diminish the Zigzagging Phenomenon of Kind I on Setcovering problems, and compare our numerical results to those of the original MSPS algorithm.

  11. Iterative Addition of Kinetic Effects to Cold Plasma RF Wave Solvers

    Science.gov (United States)

    Green, David; Berry, Lee; RF-SciDAC Collaboration

    2017-10-01

    The hot nature of fusion plasmas requires a wave vector dependent conductivity tensor for accurate calculation of wave heating and current drive. Traditional methods for calculating the linear, kinetic full-wave plasma response rely on a spectral method such that the wave vector dependent conductivity fits naturally within the numerical method. These methods have seen much success for application to the well-confined core plasma of tokamaks. However, quantitative prediction of high power RF antenna designs for fusion applications has meant a requirement of resolving the geometric details of the antenna and other plasma facing surfaces for which the Fourier spectral method is ill-suited. An approach to enabling the addition of kinetic effects to the more versatile finite-difference and finite-element cold-plasma full-wave solvers was presented by where an operator-split iterative method was outlined. Here we expand on this approach, examine convergence and present a simplified kinetic current estimator for rapidly updating the right-hand side of the wave equation with kinetic corrections. This research used resources of the Oak Ridge Leadership Computing Facility at the Oak Ridge National Laboratory, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC05-00OR22725.

  12. International Workshop on Diagnostics for ITER

    CERN Document Server

    Gorini, Giuseppe; Sindoni, Elio

    1996-01-01

    This book of proceedings collects the papers presented at the Workshop on Diagnostics for ITER, held at Villa Monastero, Varenna (Italy), from August 28 to September 1, 1995. The Workshop was organised by the International School of Plasma Physics "Piero Caldirola. " Established in 1971, the ISPP has organised over fifty advanced courses and workshops on topics mainly related to plasma physics. In particular, courses and workshops on plasma diagnostics (previously held in 1975, 1978, 1982, 1986, and 1991) can be considered milestones in the history of this institution. Looking back at the proceedings of the previous meetings in Varenna, one can appreciate the rapid progress in the field of plasma diagnostics over the past 20 years. The 1995 workshop was co-organised by the Istituto di Fisica del Plasma of the National Research Council (CNR). In contrast to previous Varenna meetings on diagnostics, which have covered diagnostics in present-day tokamaks and which have had a substantial tutorial component, the 1...

  13. CONVERGENCE OF TECHNOLOGIES

    Directory of Open Access Journals (Sweden)

    R. Siriram

    2012-01-01

    Full Text Available

    ENGLISH ABSTRACT: Technology is a catalyst for competitive advantage. However, it is how technology is used that leads to a firm’s improved performance. In this article, an investigative framework is constructed to understand better what strategically drives new technology adoption. The strategic drivers include technology and business strategy alignment, better technology planning and selection of new technologies, the effects on a firm’s culture and climate, links to a firm’s organisational and environmental evolution, and benefits through convergence and collaboration. Using an investigative framework, it is shown how the strategic drivers link to improve a firm’s performance, producing competitive advantage. The investigative framework is tested using structural equation modelling. Various hypotheses are formed, and recommendations for further research are made.

    AFRIKAANSE OPSOMMING: Tegnologie is ‘n katalisator vir mededingende voordeel. Dit is egter hoe tegnologie aangewend word wat aanleiding gee tot ‘n onderneming se verbeterde prestasie. In hierdie artikel word ‘n ondersoekende raamwerk gekonstrueer om insig te kry in dit wat die aanvaarding van nuwe tegnologie strategies dryf. Die strategiese dryfvere sluit in die belyning van tegnologie en ondernemingstrategie, beter tegnologiebeplanning en seleksie van nuwe tegnologieë, die effek op ‘n onderneming se kultuur en klimaat, koppeling na ‘n onderneming se organisatoriese en omgewingsevolusie, en voordele verkry deur konvergensie en samewerking. Deur ‘n ondersoekende raamwerk te gebruik, word daar getoon dat die strategiese dryfvere koppel om ‘n onderneming se prestasie te verbeter en sodoende ‘n mededingende voordeel te skep. Die raamwerk word getoets en hipoteses geformuleer waarna aanbevelings oor verdere navorsing aan die hand gedoen word.

  14. Further notes on convergence of the Weiszfeld algorithm

    Directory of Open Access Journals (Sweden)

    Brimberg Jack

    2003-01-01

    Full Text Available The Fermat-Weber problem is one of the most widely studied problems in classical location theory. In his previous work, Brimberg (1995 attempts to resolve a conjecture posed by Chandrasekaran and Tamir (1989 on a convergence property of the Weiszfeld algorithm, a well-known iterative procedure used to solve this problem. More recently, Canovas, Marin and Canavate (2002 provide counterexamples that appear to reopen the question. However, they do not attempt to reconcile their counterexamples with the previous work. We now show that in the light of these counterexamples, the proof is readily modified and the conjecture of Chandrasekaran and Tamir reclosed. .

  15. Renormalization Group in the uniqueness region weak Gibbsianity and convergence.

    CERN Document Server

    Bertini, L; Olivieri, E

    2004-01-01

    We analyze the block averaging transformation applied to lattice gas models with short range interaction in the uniqueness region below the critical temperature. %We discuss the %Gibbs property of the renormalized measure and the convergence of %renormalized potential under iteration of the map. We prove weak Gibbsianity of the renormalized measure and convergence of the renormalized potential in a weak sense. Since we are arbitrarily close to the coexistence region we have a diverging characteristic length of the system: the correlation length or the critical length for metastability, or both. Thus, to perturbatively treat the problem we have to use a scale--adapted expansion. Moreover, such a model below the critical temperature resembles a disordered system in presence of Griffiths' singularity. Then the cluster expansion that we use must be graded with its minimal scale length diverging when the coexistence line is approached.

  16. A Block Preconditioned Conjugate Gradient-type Iterative Solver for Linear Systems in Thermal Reservoir Simulation

    Science.gov (United States)

    Betté, Srinivas; Diaz, Julio C.; Jines, William R.; Steihaug, Trond

    1986-11-01

    A preconditioned residual-norm-reducing iterative solver is described. Based on a truncated form of the generalized-conjugate-gradient method for nonsymmetric systems of linear equations, the iterative scheme is very effective for linear systems generated in reservoir simulation of thermal oil recovery processes. As a consequence of employing an adaptive implicit finite-difference scheme to solve the model equations, the number of variables per cell-block varies dynamically over the grid. The data structure allows for 5- and 9-point operators in the areal model, 5-point in the cross-sectional model, and 7- and 11-point operators in the three-dimensional model. Block-diagonal-scaling of the linear system, done prior to iteration, is found to have a significant effect on the rate of convergence. Block-incomplete-LU-decomposition (BILU) and block-symmetric-Gauss-Seidel (BSGS) methods, which result in no fill-in, are used as preconditioning procedures. A full factorization is done on the well terms, and the cells are ordered in a manner which minimizes the fill-in in the well-column due to this factorization. The convergence criterion for the linear (inner) iteration is linked to that of the nonlinear (Newton) iteration, thereby enhancing the efficiency of the computation. The algorithm, with both BILU and BSGS preconditioners, is evaluated in the context of a variety of thermal simulation problems. The solver is robust and can be used with little or no user intervention.

  17. Robust design of feedback feed-forward iterative learning control based on 2D system theory for linear uncertain systems

    Science.gov (United States)

    Li, Zhifu; Hu, Yueming; Li, Di

    2016-08-01

    For a class of linear discrete-time uncertain systems, a feedback feed-forward iterative learning control (ILC) scheme is proposed, which is comprised of an iterative learning controller and two current iteration feedback controllers. The iterative learning controller is used to improve the performance along the iteration direction and the feedback controllers are used to improve the performance along the time direction. First of all, the uncertain feedback feed-forward ILC system is presented by an uncertain two-dimensional Roesser model system. Then, two robust control schemes are proposed. One can ensure that the feedback feed-forward ILC system is bounded-input bounded-output stable along time direction, and the other can ensure that the feedback feed-forward ILC system is asymptotically stable along time direction. Both schemes can guarantee the system is robust monotonically convergent along the iteration direction. Third, the robust convergent sufficient conditions are given, which contains a linear matrix inequality (LMI). Moreover, the LMI can be used to determine the gain matrix of the feedback feed-forward iterative learning controller. Finally, the simulation results are presented to demonstrate the effectiveness of the proposed schemes.

  18. Iterative interferometry-based method for picking microseismic events

    Science.gov (United States)

    Iqbal, Naveed; Al-Shuhail, Abdullatif A.; Kaka, SanLinn I.; Liu, Entao; Raj, Anupama Govinda; McClellan, James H.

    2017-05-01

    Continuous microseismic monitoring of hydraulic fracturing is commonly used in many engineering, environmental, mining, and petroleum applications. Microseismic signals recorded at the surface, suffer from excessive noise that complicates first-break picking and subsequent data processing and analysis. This study presents a new first-break picking algorithm that employs concepts from seismic interferometry and time-frequency (TF) analysis. The algorithm first uses a TF plot to manually pick a reference first-break and then iterates the steps of cross-correlation, alignment, and stacking to enhance the signal-to-noise ratio of the relative first breaks. The reference first-break is subsequently used to calculate final first breaks from the relative ones. Testing on synthetic and real data sets at high levels of additive noise shows that the algorithm enhances the first-break picking considerably. Furthermore, results show that only two iterations are needed to converge to the true first breaks. Indeed, iterating more can have detrimental effects on the algorithm due to increasing correlation of random noise.

  19. Fast Multi-Symbol Based Iterative Detectors for UWB Communications

    Directory of Open Access Journals (Sweden)

    Lottici Vincenzo

    2010-01-01

    Full Text Available Ultra-wideband (UWB impulse radios have shown great potential in wireless local area networks for localization, coexistence with other services, and low probability of interception and detection. However, low transmission power and high multipath effect make the detection of UWB signals challenging. Recently, multi-symbol based detection has caught attention for UWB communications because it provides good performance and does not require explicit channel estimation. Most of the existing multi-symbol based methods incur a higher computational cost than can be afforded in the envisioned UWB systems. In this paper, we propose an iterative multi-symbol based method that has low complexity and provides near optimal performance. Our method uses only one initial symbol to start and applies a decision directed approach to iteratively update a filter template and information symbols. Simulations show that our method converges in only a few iterations (less than 5, and that when the number of symbols increases, the performance of our method approaches that of the ideal Rake receiver.

  20. Iterative Perceptual Learning for Social Behavior Synthesis

    NARCIS (Netherlands)

    de Kok, I.A.; Poppe, Ronald Walter; Heylen, Dirk K.J.

    We introduce Iterative Perceptual Learning (IPL), a novel approach for learning computational models for social behavior synthesis from corpora of human-human interactions. The IPL approach combines perceptual evaluation with iterative model refinement. Human observers rate the appropriateness of

  1. Existence test for asynchronous interval iterations

    DEFF Research Database (Denmark)

    Madsen, Kaj; Caprani, O.; Stauning, Ole

    1997-01-01

    In the search for regions that contain fixed points ofa real function of several variables, tests based on interval calculationscan be used to establish existence ornon-existence of fixed points in regions that are examined in the course ofthe search. The search can e.g. be performed...... as a synchronous (sequential) interval iteration:In each iteration step all components of the iterate are calculatedbased on the previous iterate. In this case it is straight forward to base simple interval existence and non-existencetests on the calculations done in each step of the iteration. The search can also...... be performed as an asynchronous (parallel) iteration: Only a few components are changed in each stepand this calculation is in general based on components from differentprevious iterates. For the asynchronous iteration it turns out thatsimple tests of existence and non-existence can be based...

  2. Iterative perceptual learning for social behavior synthesis

    NARCIS (Netherlands)

    de Kok, I.A.; Poppe, Ronald Walter; Heylen, Dirk K.J.

    We introduce Iterative Perceptual Learning (IPL), a novel approach to learn computational models for social behavior synthesis from corpora of human–human interactions. IPL combines perceptual evaluation with iterative model refinement. Human observers rate the appropriateness of synthesized

  3. Iterative Method for Solving the Second Boundary Value Problem for Biharmonic-Type Equation

    Directory of Open Access Journals (Sweden)

    Dang Quang A.

    2012-01-01

    Full Text Available Solving boundary value problems (BVPs for the fourth-order differential equations by the reduction of them to BVPs for the second-order equations with the aim to use the achievements for the latter ones attracts attention from many researchers. In this paper, using the technique developed by ourselves in recent works, we construct iterative method for the second BVP for biharmonic-type equation, which describes the deflection of a plate resting on a biparametric elastic foundation. The convergence rate of the method is established. The optimal value of the iterative parameter is found. Several numerical examples confirm the efficiency of the proposed method.

  4. Numerical Solutions of Fractional Fokker-Planck Equations Using Iterative Laplace Transform Method

    Directory of Open Access Journals (Sweden)

    Limei Yan

    2013-01-01

    Full Text Available A relatively new iterative Laplace transform method, which combines two methods; the iterative method and the Laplace transform method, is applied to obtain the numerical solutions of fractional Fokker-Planck equations. The method gives numerical solutions in the form of convergent series with easily computable components, requiring no linearization or small perturbation. The numerical results show that the approach is easy to implement and straightforward when applied to space-time fractional Fokker-Planck equations. The method provides a promising tool for solving space-time fractional partial differential equations.

  5. Distributed Video Coding: Iterative Improvements

    DEFF Research Database (Denmark)

    Luong, Huynh Van

    at the decoder side offering such benefits for these applications. Although there have been some advanced improvement techniques, improving the DVC coding efficiency is still challenging. The thesis addresses this challenge by proposing several iterative algorithms at different working levels, e.g. bitplane......, band, and frame levels. In order to show the information theoretic basis, theoretical foundations of DVC are introduced. The first proposed algorithm applies parallel iterative decoding using multiple LDPC decoders to utilize cross bitplane correlation. To improve Side Information (SI) generation...... and noise modeling and also learn from the previous decoded Wyner-Ziv (WZ) frames, side information and noise learning (SING) is proposed. The SING scheme introduces an optical flow technique to compensate the weaknesses of the block based SI generation and also utilizes clustering of DCT blocks to capture...

  6. European Integration through Economic Convergence

    Directory of Open Access Journals (Sweden)

    Savoiu Gheorghe

    2016-05-01

    Full Text Available The thematic topicality of the main issues of European integration through convergence, in the context subsequent to financial-inspired global recession, is relevant through both the ever more extended international impact of the inertiality of a number of integration processes, and the specific developments of convergence in the Eurozone or the European Monetary Union (EMU. The regionally structured system of the European economy, approached aggregatively from the micro-economic to the macro-economic level, like the physical system or molecularly investigated system, from economic transactions, as a major milestone, to the complexity of the transactions tissue or flows, or activities, similar to biological systems, is permanently faced with various specific disturbing factors. The European Union (EU has historically evolved in an alternative manner, sometimes divergently or towards differentiation through separation, and sometimes convergently or coherently towards unity, fusion, integrity, evincing divergence or convergence trends, with the latter eventually becoming prevalent in the contemporary world.

  7. On convergence completeness in symmetric spaces | Moshokoa ...

    African Journals Online (AJOL)

    convergence complete symmetric space. As applications of convergence completeness, we present some fixed point results for self-maps defined on a symmetric space. Keywords: completeness; convergence completeness; fixed points; metric ...

  8. Periodic Convergences: Dance and Computers

    OpenAIRE

    deLahunta, Scott

    2002-01-01

    Published in German and English, this chapter is one of deLahunta's major outputs to emerge from a group of related research outputs, concerning "dance and technology". In it he explores the history of the convergence between dance and computers from the 1960s to the 1990s, arguing that this convergence has been periodic, involving particular artists at particular times, rather than producing a genre of work (as others have speculated). As the mainstream of contemporary dance evolved alongsid...

  9. Hausdorff convergence of Julia sets

    NARCIS (Netherlands)

    Krauskopf, B; Kriete, H

    1999-01-01

    Consider a sequence {g(d)}(d is an element of N) converging uniformly on compact sets to g, where g and g(d) are meromorphic functions on C. We show that the Julia sets J(g(d)) converge to the Julia set J(g) in the Hausdorff metric, if the Fatou set F(g) is the union of basins of attracting periodic

  10. Convergence palsy secondary to amoxicillin.

    Science.gov (United States)

    Pérez-Roca, F; Alfaro Juárez, A; Sánchez Merino, C; Navarro Mingorance, A

    2016-12-01

    We present the case of an 11-year-old boy with acute diplopia in near vision secondary to transient convergence palsy, possibly in relation to amoxicillin. Convergence palsy is an uncommon eye disorder. The causes are reviewed, and amoxicilin is identified as presumptive etiologic agent. This is the first case reported. Copyright © 2016 Sociedad Española de Oftalmología. Publicado por Elsevier España, S.L.U. All rights reserved.

  11. Searching for convergence and its causes – an industry perspective

    NARCIS (Netherlands)

    Inklaar, Robert; Jorgenson, Dale W.; Fukao, Kyoji; Timmer, Marcel P.

    2016-01-01

    The past 20 years has been a period of rapid growth in emerging economies, leading to convergence in income and productivity levels. Less is known about the industry origins of this development, a gap this chapter aims to fill. For 30 industries in 40 economies, I estimate industry relative

  12. Globalization and Contemporary Fertility Convergence.

    Science.gov (United States)

    Hendi, Arun S

    2017-09-01

    The rise of the global network of nation-states has precipitated social transformations throughout the world. This article examines the role of political and economic globalization in driving fertility convergence across countries between 1965 and 2009. While past research has typically conceptualized fertility change as a country-level process, this study instead employs a theoretical and methodological framework that examines differences in fertility between pairs of countries over time. Convergence in fertility between pairs of countries is hypothesized to result from increased cross-country connectedness and cross-national transmission of fertility-related schemas. I investigate the impact of various cross-country ties, including ties through bilateral trade, intergovernmental organizations, and regional trade blocs, on fertility convergence. I find that globalization acts as a form of social interaction to produce fertility convergence. There is significant heterogeneity in the effects of different cross-country ties. In particular, trade with rich model countries, joint participation in the UN and UNESCO, and joining a free trade agreement all contribute to fertility convergence between countries. Whereas the prevailing focus in fertility research has been on factors producing fertility declines, this analysis highlights specific mechanisms-trade and connectedness through organizations-leading to greater similarity in fertility across countries. Globalization is a process that propels the spread of culturally laden goods and schemas impinging on fertility, which in turn produces fertility convergence.

  13. Variational Iteration Method for Nonlinear Singular Two-Point Boundary Value Problems Arising in Human Physiology

    Directory of Open Access Journals (Sweden)

    Marwan Abukhaled

    2013-01-01

    Full Text Available The variational iteration method is applied to solve a class of nonlinear singular boundary value problems that arise in physiology. The process of the method, which produces solutions in terms of convergent series, is explained. The Lagrange multipliers needed to construct the correctional functional are found in terms of the exponential integral and Whittaker functions. The method easily overcomes the obstacle of singularities. Examples will be presented to test the method and compare it to other existing methods in order to confirm fast convergence and significant accuracy.

  14. From Fourier Series to Rapidly Convergent Series for Zeta(3)

    DEFF Research Database (Denmark)

    Scheufens, Ernst E

    2011-01-01

    The article presents a mathematical study which investigates the exact values of the Riemann zeta (ζ) function. It states that exact values can be determined from Fourier series for periodic versions of even power functions. It notes that using power series for logarithmic functions on this such ......The article presents a mathematical study which investigates the exact values of the Riemann zeta (ζ) function. It states that exact values can be determined from Fourier series for periodic versions of even power functions. It notes that using power series for logarithmic functions...

  15. Irreversible Local Markov Chains with Rapid Convergence towards Equilibrium

    Science.gov (United States)

    Kapfer, Sebastian C.; Krauth, Werner

    2017-12-01

    We study the continuous one-dimensional hard-sphere model and present irreversible local Markov chains that mix on faster time scales than the reversible heat bath or Metropolis algorithms. The mixing time scales appear to fall into two distinct universality classes, both faster than for reversible local Markov chains. The event-chain algorithm, the infinitesimal limit of one of these Markov chains, belongs to the class presenting the fastest decay. For the lattice-gas limit of the hard-sphere model, reversible local Markov chains correspond to the symmetric simple exclusion process (SEP) with periodic boundary conditions. The two universality classes for irreversible Markov chains are realized by the totally asymmetric SEP (TASEP), and by a faster variant (lifted TASEP) that we propose here. We discuss how our irreversible hard-sphere Markov chains generalize to arbitrary repulsive pair interactions and carry over to higher dimensions through the concept of lifted Markov chains and the recently introduced factorized Metropolis acceptance rule.

  16. An Iterative Method for Problems with Multiscale Conductivity

    Directory of Open Access Journals (Sweden)

    Hyea Hyun Kim

    2012-01-01

    Full Text Available A model with its conductivity varying highly across a very thin layer will be considered. It is related to a stable phantom model, which is invented to generate a certain apparent conductivity inside a region surrounded by a thin cylinder with holes. The thin cylinder is an insulator and both inside and outside the thin cylinderare filled with the same saline. The injected current can enter only through the holes adopted to the thin cylinder. The model has a high contrast of conductivity discontinuity across the thin cylinder and the thickness of the layer and the size of holes are very small compared to the domain of the model problem. Numerical methods for such a model require a very fine mesh near the thin layer to resolve the conductivity discontinuity. In this work, an efficient numerical method for such a model problem is proposed by employing a uniform mesh, which need not resolve the conductivity discontinuity. The discrete problem is then solved by an iterative method, where the solution is improved by solving a simple discrete problem with a uniform conductivity. At each iteration, the right-hand side is updated by integrating the previous iterate over the thin cylinder. This process results in a certain smoothing effect on microscopic structures and our discrete model can provide a more practical tool for simulating the apparent conductivity. The convergence of the iterative method is analyzed regarding the contrast in the conductivity and the relative thickness of the layer. In numerical experiments, solutions of our method are compared to reference solutions obtained from COMSOL, where very fine meshes are used to resolve the conductivity discontinuity in the model. Errors of the voltage in L2 norm follow O(h asymptotically and the current density matches quitewell those from the reference solution for a sufficiently small mesh size h. The experimental results present a promising feature of our approach for simulating the apparent

  17. Iterated elliptic and hypergeometric integrals for Feynman diagrams

    Energy Technology Data Exchange (ETDEWEB)

    Ablinger, J.; Radu, C.S.; Schneider, C. [Johannes Kepler Univ., Linz (Austria). Research Inst. for Symbolic Computation (RISC); Bluemlein, J.; Freitas, A. de [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Van Hoeij, M.; Imamoglu, E. [Florida State Univ., Tallahassee, FL (United States). Dept. of Mathematics; Raab, C.G. [Linz Univ. (Austria). Inst. for Algebra

    2017-05-15

    We calculate 3-loop master integrals for heavy quark correlators and the 3-loop QCD corrections to the ρ-parameter. They obey non-factorizing differential equations of second order with more than three singularities, which cannot be factorized in Mellin-N space either. The solution of the homogeneous equations is possible in terms of convergent close integer power series as {sub 2}F{sub 1} Gauss hypergeometric functions at rational argument. In some cases, integrals of this type can be mapped to complete elliptic integrals at rational argument. This class of functions appears to be the next one arising in the calculation of more complicated Feynman integrals following the harmonic polylogarithms, generalized polylogarithms, cyclotomic harmonic polylogarithms, square-root valued iterated integrals, and combinations thereof, which appear in simpler cases. The inhomogeneous solution of the corresponding differential equations can be given in terms of iterative integrals, where the new innermost letter itself is not an iterative integral. A new class of iterative integrals is introduced containing letters in which (multiple) definite integrals appear as factors. For the elliptic case, we also derive the solution in terms of integrals over modular functions and also modular forms, using q-product and series representations implied by Jacobi's θ{sub i} functions and Dedekind's η-function. The corresponding representations can be traced back to polynomials out of Lambert-Eisenstein series, having representations also as elliptic polylogarithms, a q-factorial 1/η{sup κ}(τ), logarithms and polylogarithms of q and their q-integrals. Due to the specific form of the physical variable x(q) for different processes, different representations do usually appear. Numerical results are also presented.

  18. Dynamics of iterative schemes for quadratic polynomial

    Science.gov (United States)

    Goyal, Komal; Prasad, Bhagwati

    2017-10-01

    Most of the fractals are generated by applying a map recursively to an initial point or a set of the space such as complex plane. An orbit of a point is a sequence of iteratively obtained points from it and the orbit is said to be diverging when its points grow unbounded. A set of all the points whose orbits are not diverging may be termed as a fractal. The fractal dynamics of the orbits depends on the rule of iteration also. In this paper, we study the dynamics of iterations for a number of iterative schemes. The results regarding the escape criteria for quadratic complex polynomials under various iteration procedures are established.

  19. Generalized Monotone Iterative Technique for Caputo Fractional Differential Equation with Periodic Boundary Condition via Initial Value Problem

    Directory of Open Access Journals (Sweden)

    J. D. Ramírez

    2012-01-01

    boundary conditions of order , where . We develop results which provide natural monotone sequences or intertwined monotone sequences which converge uniformly and monotonically to coupled minimal and maximal periodic solutions. However, these monotone iterates are solutions of linear initial value problems which are easier to compute.

  20. Maximum Likelihood-Based Iterated Divided Difference Filter for Nonlinear Systems from Discrete Noisy Measurements

    Directory of Open Access Journals (Sweden)

    Changyuan Wang

    2012-06-01

    Full Text Available A new filter named the maximum likelihood-based iterated divided difference filter (MLIDDF is developed to improve the low state estimation accuracy of nonlinear state estimation due to large initial estimation errors and nonlinearity of measurement equations. The MLIDDF algorithm is derivative-free and implemented only by calculating the functional evaluations. The MLIDDF algorithm involves the use of the iteration measurement update and the current measurement, and the iteration termination criterion based on maximum likelihood is introduced in the measurement update step, so the MLIDDF is guaranteed to produce a sequence estimate that moves up the maximum likelihood surface. In a simulation, its performance is compared against that of the unscented Kalman filter (UKF, divided difference filter (DDF, iterated unscented Kalman filter (IUKF and iterated divided difference filter (IDDF both using a traditional iteration strategy. Simulation results demonstrate that the accumulated mean-square root error for the MLIDDF algorithm in position is reduced by 63% compared to that of UKF and DDF algorithms, and by 7% compared to that of IUKF and IDDF algorithms. The new algorithm thus has better state estimation accuracy and a fast convergence rate.

  1. Convergence theorems of fixed points for Lipschitz pseudo-contractions in Hilbert spaces

    Science.gov (United States)

    Zhou, Haiyun

    2008-07-01

    Let C be a closed convex subset of a real Hilbert space H and assume that T is a [kappa]-strict pseudo-contraction on C. Consider Mann's iteration algorithm given by It is proved that if the control sequence {[alpha]n} is chosen so that [kappa]Rhoades [B.E. Rhoades, Fixed point iterations using infinite matrices, Trans. Amer. Math. Soc. 196 (1974) 162-176] and of Marino and Xu [G. Marino, H.-K. Xu, Weak and strong convergence theorems for strict pseudo-contractions in Hilbert spaces, J. Math. Anal. Appl. 329 (1) (2007) 336-346].

  2. Cryogenic instrumentation for ITER magnets

    Science.gov (United States)

    Poncet, J.-M.; Manzagol, J.; Attard, A.; André, J.; Bizel-Bizellot, L.; Bonnay, P.; Ercolani, E.; Luchier, N.; Girard, A.; Clayton, N.; Devred, A.; Huygen, S.; Journeaux, J.-Y.

    2017-02-01

    Accurate measurements of the helium flowrate and of the temperature of the ITER magnets is of fundamental importance to make sure that the magnets operate under well controlled and reliable conditions, and to allow suitable helium flow distribution in the magnets through the helium piping. Therefore, the temperature and flow rate measurements shall be reliable and accurate. In this paper, we present the thermometric chains as well as the venturi flow meters installed in the ITER magnets and their helium piping. The presented thermometric block design is based on the design developed by CERN for the LHC, which has been further optimized via thermal simulations carried out by CEA. The electronic part of the thermometric chain was entirely developed by the CEA and will be presented in detail: it is based on a lock-in measurement and small signal amplification, and also provides a web interface and software to an industrial PLC. This measuring device provides a reliable, accurate, electromagnetically immune, and fast (up to 100 Hz bandwidth) system for resistive temperature sensors between a few ohms to 100 kΩ. The flowmeters (venturi type) which make up part of the helium mass flow measurement chain have been completely designed, and manufacturing is on-going. The behaviour of the helium gas has been studied in detailed thanks to ANSYS CFX software in order to obtain the same differential pressure for all types of flowmeters. Measurement uncertainties have been estimated and the influence of input parameters has been studied. Mechanical calculations have been performed to guarantee the mechanical strength of the venturis required for pressure equipment operating in nuclear environment. In order to complete the helium mass flow measurement chain, different technologies of absolute and differential pressure sensors have been tested in an applied magnetic field to identify equipment compatible with the ITER environment.

  3. Nuclear analysis of ITER ports

    Energy Technology Data Exchange (ETDEWEB)

    Santoro, R.T.; Khripunov, V.; Lida, H.; Plenteda, D. [ITER Joint Central Team Garching, Muenchen (Germany); Sato, S. [Japan Atomic Energy Research Inst., Tokai-Mura (Japan); Inoue, T. [ITER Joint Central Team, naka (Japan)

    1998-07-01

    The steel/water blanket and vacuum vessel for the ITER Basic Performance Phase were designed reliable radiation shield for protecting the superconducting magnets, cryogenic systems and the cryostat from excessive heating from plasma neutrons and secondary gamma-rays. Proposed experiments, tests, diagnostics, and operation / maintenance equipment require numerous penetrations that weaken the effectiveness of the shield. However, comprehensive three-dimensional neutronic analyses and corresponding design developments, reported below, indicated that the key shielding requirements (nuclear heat deposition in the superconducting magnets {<=} 17 kW and residual equivalent dose rates {approx}100 {mu}Sv/h suitable for a personnel access) can be satisfied. (authors)

  4. Approximate solution of time-fractional advection-dispersion equation via fractional variational iteration method.

    Science.gov (United States)

    Ibiş, Birol; Bayram, Mustafa

    2014-01-01

    This paper aims to obtain the approximate solution of time-fractional advection-dispersion equation (FADE) involving Jumarie's modification of Riemann-Liouville derivative by the fractional variational iteration method (FVIM). FVIM provides an analytical approximate solution in the form of a convergent series. Some examples are given and the results indicate that the FVIM is of high accuracy, more efficient, and more convenient for solving time FADEs.

  5. Iterative computation of the optimal H(infinity) norm by using two-Riccati-equation method

    Science.gov (United States)

    Chang, B. C.; Li, X. P.; Yeh, H. H.; Banda, S. S.

    1990-01-01

    The two-Riccati-equation method solution to a standard H(infinity) control problem can be used to characterize all possible stabilizing optimal or suboptimal H(infinity) controllers if the optimal or suboptimal H(infinity) norm is available in the literature. An iterative algorithm for computing the optimal H(infinity) norm is proposed. The algorithm employs fixed-point, double secant and bisection to guarantee a super linear convergence.

  6. A fast poly-energetic iterative FBP algorithm

    Science.gov (United States)

    Lin, Yuan; Samei, Ehsan

    2014-04-01

    The beam hardening (BH) effect can influence medical interpretations in two notable ways. First, high attenuation materials, such as bones, can induce strong artifacts, which severely deteriorate the image quality. Second, voxel values can significantly deviate from the real values, which can lead to unreliable quantitative evaluation results. Some iterative methods have been proposed to eliminate the BH effect, but they cannot be widely applied for clinical practice because of the slow computational speed. The purpose of this study was to develop a new fast and practical poly-energetic iterative filtered backward projection algorithm (piFBP). The piFBP is composed of a novel poly-energetic forward projection process and a robust FBP-type backward updating process. In the forward projection process, an adaptive base material decomposition method is presented, based on which diverse body tissues (e.g., lung, fat, breast, soft tissue, and bone) and metal implants can be incorporated to accurately evaluate poly-energetic forward projections. In the backward updating process, one robust and fast FBP-type backward updating equation with a smoothing kernel is introduced to avoid the noise accumulation in the iteration process and to improve the convergence properties. Two phantoms were designed to quantitatively validate our piFBP algorithm in terms of the beam hardening index (BIdx) and the noise index (NIdx). The simulation results showed that piFBP possessed fast convergence speed, as the images could be reconstructed within four iterations. The variation range of the BIdx's of various tissues across phantom size and spectrum were reduced from [-7.5, 17.5] for FBP to [-0.1, 0.1] for piFBP while the NIdx's were maintained in the same low level (about [0.3, 1.7]). When a metal implant presented in a complex phantom, piFBP still had excellent reconstruction performance, as the variation range of the BIdx's of body tissues were reduced from [-2.9, 15.9] for FBP to [-0

  7. Digital Convergence and Content Regulation

    Directory of Open Access Journals (Sweden)

    Michael John Starks

    2014-12-01

    Full Text Available Broadcasting, Press and Internet journalism systems of distribution are converging: the same infrastructure can deliver all three historically separate services. Reception devices mirror this: the Connected TV, the tablet and the smart phone overlap in their functionality. Service overlaps are evident too, with broadcasters providing online and on-demand services and newspapers developing electronic versions. Does this mean that media regulation policies must converge too?My argument is that they should, though only where historically different communications are now fulfilling a similar function, e.g. broadcaster online services and electronic versions of newspapers. Convergence requires a degree of harmonisation and, to this end, I advocate a review of UK broadcasting's 'due impartiality' requirement and of the UK's application of the public service concept. I also argue for independent self-regulation (rather than state-based regulation of non-public-service broadcasting journalism.

  8. IHadoop: Asynchronous iterations for MapReduce

    KAUST Repository

    Elnikety, Eslam Mohamed Ibrahim

    2011-11-01

    MapReduce is a distributed programming frame-work designed to ease the development of scalable data-intensive applications for large clusters of commodity machines. Most machine learning and data mining applications involve iterative computations over large datasets, such as the Web hyperlink structures and social network graphs. Yet, the MapReduce model does not efficiently support this important class of applications. The architecture of MapReduce, most critically its dataflow techniques and task scheduling, is completely unaware of the nature of iterative applications; tasks are scheduled according to a policy that optimizes the execution for a single iteration which wastes bandwidth, I/O, and CPU cycles when compared with an optimal execution for a consecutive set of iterations. This work presents iHadoop, a modified MapReduce model, and an associated implementation, optimized for iterative computations. The iHadoop model schedules iterations asynchronously. It connects the output of one iteration to the next, allowing both to process their data concurrently. iHadoop\\'s task scheduler exploits inter-iteration data locality by scheduling tasks that exhibit a producer/consumer relation on the same physical machine allowing a fast local data transfer. For those iterative applications that require satisfying certain criteria before termination, iHadoop runs the check concurrently during the execution of the subsequent iteration to further reduce the application\\'s latency. This paper also describes our implementation of the iHadoop model, and evaluates its performance against Hadoop, the widely used open source implementation of MapReduce. Experiments using different data analysis applications over real-world and synthetic datasets show that iHadoop performs better than Hadoop for iterative algorithms, reducing execution time of iterative applications by 25% on average. Furthermore, integrating iHadoop with HaLoop, a variant Hadoop implementation that caches

  9. Residual replacement strategies for Krylov subspace iterative methods for the convergence of true residuals

    NARCIS (Netherlands)

    Vorst, H.A. van der; Ye, Q.

    1999-01-01

    In this paper, a strategy is proposed for alternative computations of the residual vectors in Krylov subspace methods, which improves the agreement of the computed residuals and the true residuals to the level of O(u)kAkkxk. Building on earlier ideas on residual replacement and on insights in

  10. Lattice-valued convergence ring and its uniform convergence structure

    African Journals Online (AJOL)

    Considering L a frame, we introduce the notion of stratified L-neighborhood topological ring, produce some characterization theorems including its Luniformizability. With the help of the notions of stratified convergence structures attributed to Gunther J¨ager [10], we introduce and study various subcategories of stratified ...

  11. Fourier mode analysis of slab-geometry transport iterations in spatially periodic media

    Energy Technology Data Exchange (ETDEWEB)

    Larsen, E W; Zika, M R

    1999-05-07

    We describe a Fourier analysis of the diffusion-synthetic acceleration (DSA) and transport-synthetic acceleration (TSA) iteration schemes for a spatially periodic, but otherwise arbitrarily heterogeneous, medium. Both DSA and TSA converge more slowly in a heterogeneous medium than in a homogeneous medium composed of the volume-averaged scattering ratio. In the limit of a homogeneous medium, our heterogeneous analysis contains eigenvalues of multiplicity two at ''resonant'' wave numbers. In the presence of material heterogeneities, error modes corresponding to these resonant wave numbers are ''excited'' more than other error modes. For DSA and TSA, the iteration spectral radius may occur at these resonant wave numbers, in which case the material heterogeneities most strongly affect iterative performance.

  12. Fourier mode analysis of slab-geometry transport iterations in spatially periodic media

    Energy Technology Data Exchange (ETDEWEB)

    Larsen, E; Zika, M

    1999-04-01

    We describe a Fourier analysis of the diffusion-synthetic acceleration (DSA) and transport-synthetic acceleration (TSA) iteration schemes for a spatially periodic, but otherwise arbitrarily heterogeneous, medium. Both DSA and TSA converge more slowly in a heterogeneous medium than in a homogeneous medium composed of the volume-averaged scattering ratio. In the limit of a homogeneous medium, our heterogeneous analysis contains eigenvalues of multiplicity two at ''resonant'' wave numbers. In the presence of material heterogeneities, error modes corresponding to these resonant wave numbers are ''excited'' more than other error modes. For DSA and TSA, the iteration spectral radius may occur at these resonant wave numbers, in which case the material heterogeneities most strongly affect iterative performance.

  13. Research on Open-Closed-Loop Iterative Learning Control with Variable Forgetting Factor of Mobile Robots

    Directory of Open Access Journals (Sweden)

    Hongbin Wang

    2016-01-01

    Full Text Available We propose an iterative learning control algorithm (ILC that is developed using a variable forgetting factor to control a mobile robot. The proposed algorithm can be categorized as an open-closed-loop iterative learning control, which produces control instructions by using both previous and current data. However, introducing a variable forgetting factor can weaken the former control output and its variance in the control law while strengthening the robustness of the iterative learning control. If it is applied to the mobile robot, this will reduce position errors in robot trajectory tracking control effectively. In this work, we show that the proposed algorithm guarantees tracking error bound convergence to a small neighborhood of the origin under the condition of state disturbances, output measurement noises, and fluctuation of system dynamics. By using simulation, we demonstrate that the controller is effective in realizing the prefect tracking.

  14. Iterative learning control with sampled-data feedback for robot manipulators

    Directory of Open Access Journals (Sweden)

    Delchev Kamen

    2014-09-01

    Full Text Available This paper deals with the improvement of the stability of sampled-data (SD feedback control for nonlinear multiple-input multiple-output time varying systems, such as robotic manipulators, by incorporating an off-line model based nonlinear iterative learning controller. The proposed scheme of nonlinear iterative learning control (NILC with SD feedback is applicable to a large class of robots because the sampled-data feedback is required for model based feedback controllers, especially for robotic manipulators with complicated dynamics (6 or 7 DOF, or more, while the feedforward control from the off-line iterative learning controller should be assumed as a continuous one. The robustness and convergence of the proposed NILC law with SD feedback is proven, and the derived sufficient condition for convergence is the same as the condition for a NILC with a continuous feedback control input. With respect to the presented NILC algorithm applied to a virtual PUMA 560 robot, simulation results are presented in order to verify convergence and applicability of the proposed learning controller with SD feedback controller attached

  15. Cultura da Convergência

    Directory of Open Access Journals (Sweden)

    Rogério Christofoletti

    2008-12-01

    Full Text Available Três idéias já seriam suficientes para que a leitura de “Cultura da Convergência”, de Henry Jenkins, interessasse a jornalistas e pesquisadores da área: a convergência midiática como um processo cultural; o fortalecimento de uma economia afetiva que orienta consumidores de bens simbólicos e criadores midiáticos; a expansão de formas narrativas transmidiáticas.

  16. Weak convergence theorem for a class of split variational inequality problems and applications in a Hilbert space.

    Science.gov (United States)

    Tian, Ming; Jiang, Bing-Nan

    2017-01-01

    In this paper, we consider the algorithm proposed in recent years by Censor, Gibali and Reich, which solves split variational inequality problem, and Korpelevich's extragradient method, which solves variational inequality problems. As our main result, we propose an iterative method for finding an element to solve a class of split variational inequality problems under weaker conditions and get a weak convergence theorem. As applications, we obtain some new weak convergence theorems by using our weak convergence result to solve related problems in nonlinear analysis and optimization.

  17. ETR/ITER systems code

    Energy Technology Data Exchange (ETDEWEB)

    Barr, W.L.; Bathke, C.G.; Brooks, J.N.; Bulmer, R.H.; Busigin, A.; DuBois, P.F.; Fenstermacher, M.E.; Fink, J.; Finn, P.A.; Galambos, J.D.; Gohar, Y.; Gorker, G.E.; Haines, J.R.; Hassanein, A.M.; Hicks, D.R.; Ho, S.K.; Kalsi, S.S.; Kalyanam, K.M.; Kerns, J.A.; Lee, J.D.; Miller, J.R.; Miller, R.L.; Myall, J.O.; Peng, Y-K.M.; Perkins, L.J.; Spampinato, P.T.; Strickler, D.J.; Thomson, S.L.; Wagner, C.E.; Willms, R.S.; Reid, R.L. (ed.)

    1988-04-01

    A tokamak systems code capable of modeling experimental test reactors has been developed and is described in this document. The code, named TETRA (for Tokamak Engineering Test Reactor Analysis), consists of a series of modules, each describing a tokamak system or component, controlled by an optimizer/driver. This code development was a national effort in that the modules were contributed by members of the fusion community and integrated into a code by the Fusion Engineering Design Center. The code has been checked out on the Cray computers at the National Magnetic Fusion Energy Computing Center and has satisfactorily simulated the Tokamak Ignition/Burn Experimental Reactor II (TIBER) design. A feature of this code is the ability to perform optimization studies through the use of a numerical software package, which iterates prescribed variables to satisfy a set of prescribed equations or constraints. This code will be used to perform sensitivity studies for the proposed International Thermonuclear Experimental Reactor (ITER). 22 figs., 29 tabs.

  18. A unified treatment of some perturbed fixed point iterative methods with an infinite pool of operators

    Science.gov (United States)

    Nikazad, Touraj; Abbasi, Mokhtar

    2017-04-01

    In this paper, we introduce a subclass of strictly quasi-nonexpansive operators which consists of well-known operators as paracontracting operators (e.g., strictly nonexpansive operators, metric projections, Newton and gradient operators), subgradient projections, a useful part of cutter operators, strictly relaxed cutter operators and locally strongly Féjer operators. The members of this subclass, which can be discontinuous, may be employed by fixed point iteration methods; in particular, iterative methods used in convex feasibility problems. The closedness of this subclass, with respect to composition and convex combination of operators, makes it useful and remarkable. Another advantage with members of this subclass is the possibility to adapt them to handle convex constraints. We give convergence result, under mild conditions, for a perturbation resilient iterative method which is based on an infinite pool of operators in this subclass. The perturbation resilient iterative methods are relevant and important for their possible use in the framework of the recently developed superiorization methodology for constrained minimization problems. To assess the convergence result, the class of operators and the assumed conditions, we illustrate some extensions of existence research works and some new results.

  19. Accuracy and convergence of a finite element algorithm for turbulent boundary layer flow

    Science.gov (United States)

    Soliman, M. O.; Baker, A. J.

    1981-08-01

    The Galerkin-Weighted Residuals formulation is employed to derive an implicit finite element solution algorithm for the nonlinear parabolic partial differential equation system governing turbulent boundary layer flow. Solution accuracy and convergence with discretization refinement are quantized in several error norms using linear and quadratic basis functions. Richardson extrapolation is used to isolate integration truncation error in all norms, and Newton iteration is employed for all equation solutions performed in double-precision. The mathematical theory supporting accuracy and convergence concepts for linear elliptic equations appears extensible to the nonlinear equations characteristic of turbulent boundary layer flow.

  20. Collisional-radiative switching - A powerful technique for converging non-LTE calculations

    Science.gov (United States)

    Hummer, D. G.; Voels, S. A.

    1988-01-01

    A very simple technique has been developed to converge statistical equilibrium and model atmospheric calculations in extreme non-LTE conditions when the usual iterative methods fail to converge from an LTE starting model. The proposed technique is based on a smooth transition from a collision-dominated LTE situation to the desired non-LTE conditions in which radiation dominates, at least in the most important transitions. The proposed approach was used to successfully compute stellar models with He abundances of 0.20, 0.30, and 0.50; Teff = 30,000 K, and log g = 2.9.

  1. Coarse Spaces by Algebraic Multigrid: Multigrid Convergence and Upscaled Error Estimates

    Energy Technology Data Exchange (ETDEWEB)

    Vassilevski, P S

    2010-04-30

    We give an overview of a number of algebraic multigrid methods targeting finite element discretization problems. The focus is on the properties of the constructed hierarchy of coarse spaces that guarantee (two-grid) convergence. In particular, a necessary condition known as 'weak approximation property', and a sufficient one, referred to as 'strong approximation property' are discussed. Their role in proving convergence of the TG method (as iterative method) and also on the approximation properties of the AMG coarse spaces if used as discretization tool is pointed out. Some preliminary numerical results illustrating the latter aspect are also reported.

  2. A convergence analysis for a sweeping preconditioner for block tridiagonal systems of linear equations

    KAUST Repository

    Bagci, Hakan

    2014-11-11

    We study sweeping preconditioners for symmetric and positive definite block tridiagonal systems of linear equations. The algorithm provides an approximate inverse that can be used directly or in a preconditioned iterative scheme. These algorithms are based on replacing the Schur complements appearing in a block Gaussian elimination direct solve by hierarchical matrix approximations with reduced off-diagonal ranks. This involves developing low rank hierarchical approximations to inverses. We first provide a convergence analysis for the algorithm for reduced rank hierarchical inverse approximation. These results are then used to prove convergence and preconditioning estimates for the resulting sweeping preconditioner.

  3. CT radiation dose and iterative reconstruction techniques.

    Science.gov (United States)

    Padole, Atul; Ali Khawaja, Ranish Deedar; Kalra, Mannudeep K; Singh, Sarabjeet

    2015-04-01

    1. CT radiation dose optimization is one of the major concerns for the scientific community. 2. CT image quality is dependent on the selected image reconstruction algorithm. 3. Iterative reconstruction algorithms have reemerged with the potential of radiation dose optimization by lowering image noise. 4. Tube current is the most common parameter used to reduce radiation dose along with iterative reconstruction. 5. Tube potential (kV) is also used for dose optimization with iterative reconstruction in CT angiography protocols and small patients.

  4. Digital Convergence and Content Regulation

    NARCIS (Netherlands)

    Starks, Michael John

    2014-01-01

    abstractBroadcasting, Press and Internet journalism systems of distribution are converging: the same infrastructure can deliver all three historically separate services. Reception devices mirror this: the Connected TV, the tablet and the smart phone overlap in their functionality. Service overlaps

  5. Converge, Version 3.0

    Directory of Open Access Journals (Sweden)

    Lotfi Tadj

    1993-01-01

    Full Text Available Although intended for college teachers/students, Converge presents a feature that may interest all scientists: it allows an easy export of graphic files to most known word processors, specifically to the ℙ, Version 2.1, a powerful WYSIWYG mathematical word processor.

  6. At the Eve of Convergence?

    DEFF Research Database (Denmark)

    Henriksen, Lars Skov; Zimmer, Annette; Smith, Steven Rathgeb

    . Specifically, we will investigate whether and to what extent social services and health care in these three countries are affected by current changes. With a special focus on nonprofit organizations, we will particularly address the question whether a trend towards convergence of the very different welfare...

  7. Converging Information and Communication Systems

    DEFF Research Database (Denmark)

    Øst, Alexander

    2003-01-01

    in the future to have - significant importance to the process and consequences of the convergence. The project focuses on the appliances, i.e. the TV sets, the computers and their peripheral equipment. It also takes into account the infrastructure and signals, which contain and deliver the information...

  8. Industrial Evolution Through Complementary Convergence

    DEFF Research Database (Denmark)

    Frøslev Christensen, Jens

    2011-01-01

    The article addresses the dynamics through which product markets become derailed from early product life cycle (PLC)-tracks and engaged in complementary convergence with other product markets or industries. We compare and contrast the theories that can explain, respectively, the PLC...

  9. Privatization, convergence, and institutional autonomy

    NARCIS (Netherlands)

    Rooijen, van M.

    2011-01-01

    Some of the trends incoming for 2011 – greater institutional autonomy, public/private convergence, entrepreneurial management, civic engagement – suggest innovation for hard times, with socio-economic and political rationales increasingly driving borderless developments. Others – open learning and

  10. Iterative autofocusing strategy for axial distance error correction in ptychography

    Science.gov (United States)

    Dou, Jiantai; Gao, Zhishan; Ma, Jun; Yuan, Caojin; Yang, Zhongming; Wang, Lei

    2017-11-01

    The axial distance error can degrade the quality and resolution of the image reconstructed by ptychography. An iterative autofocusing method is proposed to correct the axial distance error. Based on the Fresnel integral theory, an axial distance error model is established to present the effect of the axial distance error on the recovered image. The information of the retrieved image is chosen to calculate the axial distance by autofocusing algorithm. The calculated distance is used to replace the axial distance and applied for the image reconstruction. When the calculated axial distance reaches the convergence, the distance can be accurately obtained that can be used to enhance the quality and resolution of the reconstructed image. Simulations and experiments have been conducted to verify the performance of the proposed method.

  11. An iterative algorithm for calculating stylus radius unambiguously

    Energy Technology Data Exchange (ETDEWEB)

    Vorburger, T V; Zheng, A; Renegar, T B; Song, J-F; Ma, L, E-mail: tvtv@nist.gov [National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD 20899 (United States)

    2011-08-19

    The stylus radius is an important specification for stylus instruments and is commonly provided by instrument manufacturers. However, it is difficult to measure the stylus radius unambiguously. Accurate profiles of the stylus tip may be obtained by profiling over an object sharper than itself, such as a razor blade. However, the stylus profile thus obtained is a partial arc, and unless the shape of the stylus tip is a perfect sphere or circle, the effective value of the radius depends on the length of the tip profile over which the radius is determined. We have developed an iterative, least squares algorithm aimed to determine the effective least squares stylus radius unambiguously. So far, the algorithm converges to reasonable results for the least squares stylus radius. We suggest that the algorithm be considered for adoption in documentary standards describing the properties of stylus instruments.

  12. Distributed weighted least-squares estimation with fast convergence for large-scale systems.

    Science.gov (United States)

    Marelli, Damián Edgardo; Fu, Minyue

    2015-01-01

    In this paper we study a distributed weighted least-squares estimation problem for a large-scale system consisting of a network of interconnected sub-systems. Each sub-system is concerned with a subset of the unknown parameters and has a measurement linear in the unknown parameters with additive noise. The distributed estimation task is for each sub-system to compute the globally optimal estimate of its own parameters using its own measurement and information shared with the network through neighborhood communication. We first provide a fully distributed iterative algorithm to asymptotically compute the global optimal estimate. The convergence rate of the algorithm will be maximized using a scaling parameter and a preconditioning method. This algorithm works for a general network. For a network without loops, we also provide a different iterative algorithm to compute the global optimal estimate which converges in a finite number of steps. We include numerical experiments to illustrate the performances of the proposed methods.

  13. Is the Standard Monte Carlo Power Iteration Approach the Wrong Approach?

    Energy Technology Data Exchange (ETDEWEB)

    Booth, Thomas E [Los Alamos National Laboratory

    2012-06-05

    The power iteration method is the standard Monte Carlo approach for obtaining the eigenfunctions of a nuclear system, but the power method sometimes converges very slowly. Most discussions give a mathematical reason for the slow convergence of the Monte Carlo power method using the same concepts and terminology as when the power method is applied to a deterministic problem. This note first looks at why the convergence is slow from an intuitive Monte Carlo neutron perspective. Second, this note proposes building an eigenfunction intuitively in a cumulative (and noniterative) neutron by neutron manner that tends to better direct neutrons to where the neutrons need to be. Third, a very similar method for building the second eigenfunction is speculatively proposed.

  14. Convergence of Batch Split-Complex Backpropagation Algorithm for Complex-Valued Neural Networks

    Directory of Open Access Journals (Sweden)

    Huisheng Zhang

    2009-01-01

    Full Text Available The batch split-complex backpropagation (BSCBP algorithm for training complex-valued neural networks is considered. For constant learning rate, it is proved that the error function of BSCBP algorithm is monotone during the training iteration process, and the gradient of the error function tends to zero. By adding a moderate condition, the weights sequence itself is also proved to be convergent. A numerical example is given to support the theoretical analysis.

  15. Weak and Strong Convergence Theorems for Nonexpansive Mappings in Banach Spaces

    Directory of Open Access Journals (Sweden)

    Su Yongfu

    2008-01-01

    Full Text Available Abstract The purpose of this paper is to introduce two implicit iteration schemes for approximating fixed points of nonexpansive mapping and a finite family of nonexpansive mappings , respectively, in Banach spaces and to prove weak and strong convergence theorems. The results presented in this paper improve and extend the corresponding ones of H.-K. Xu and R. Ori, 2001, Z. Opial, 1967, and others.

  16. Blind Source Separation Based on Fast-Convergence Algorithm Using ICA and Beamforming

    OpenAIRE

    Hiroshi Saruwatari; Toshiya Kawamura; Kiyohiro Shikano

    2001-01-01

    We propose a new algorithm for blind source separation (BSS), in which independent component analysis (ICA) and beamforming are combined to resolve the low-convergence problem through optimization in ICA. The proposed method consists of the following three parts: (1) frequency-domain ICA with direction-of-arrival (DOA) estimation, (2) null beamforming based on the estimated DOA, and (3) integration of (1) and (2) based on the algorithm diversity in both iteration and frequency domain. The inv...

  17. Blind Source Separation for Speech Based on Fast-convergence Algorithm with ICA and Beamforming

    OpenAIRE

    Hiroshi Saruwatari; Toshiya Kawamura; Kiyohiro Shikano

    2001-01-01

    We propose a new algorithm for blind source separation (BSS), in which independent component analysis (ICA) and beamforming are combined to resolve the low-convergence problem through optimization in ICA. The proposed method consists of the following three parts: (1) frequency-domain ICA with direction-of-arrival (DOA) estimation, (2) null beamforming based on the estimated DOA, and (3) integration of (1) and (2) based on the algorithm diversity in both iteration and frequency domain. The inv...

  18. Rapid Prototyping of Mobile Learning Games

    Science.gov (United States)

    Federley, Maija; Sorsa, Timo; Paavilainen, Janne; Boissonnier, Kimo; Seisto, Anu

    2014-01-01

    This position paper presents the first results of an on-going project, in which we explore rapid prototyping method to efficiently produce digital learning solutions that are commercially viable. In this first phase, rapid game prototyping and an iterative approach was tested as a quick and efficient way to create learning games and to evaluate…

  19. Independent Molecular Basis of Convergent Highland Adaptation in Maize

    Science.gov (United States)

    Takuno, Shohei; Ralph, Peter; Swarts, Kelly; Elshire, Rob J.; Glaubitz, Jeffrey C.; Buckler, Edward S.; Hufford, Matthew B.; Ross-Ibarra, Jeffrey

    2015-01-01

    Convergent evolution is the independent evolution of similar traits in different species or lineages of the same species; this often is a result of adaptation to similar environments, a process referred to as convergent adaptation. We investigate here the molecular basis of convergent adaptation in maize to highland climates in Mesoamerica and South America, using genome-wide SNP data. Taking advantage of archaeological data on the arrival of maize to the highlands, we infer demographic models for both populations, identifying evidence of a strong bottleneck and rapid expansion in South America. We use these models to then identify loci showing an excess of differentiation as a means of identifying putative targets of natural selection and compare our results to expectations from recently developed theory on convergent adaptation. Consistent with predictions across a wide parameter space, we see limited evidence for convergent evolution at the nucleotide level in spite of strong similarities in overall phenotypes. Instead, we show that selection appears to have predominantly acted on standing genetic variation and that introgression from wild teosinte populations appears to have played a role in highland adaptation in Mexican maize. PMID:26078279

  20. An Iterative Decoding Algorithm for Fusion of Multimodal Information

    Science.gov (United States)

    Shivappa, Shankar T.; Rao, Bhaskar D.; Trivedi, Mohan M.

    2007-12-01

    Human activity analysis in an intelligent space is typically based on multimodal informational cues. Use of multiple modalities gives us a lot of advantages. But information fusion from different sources is a problem that has to be addressed. In this paper, we propose an iterative algorithm to fuse information from multimodal sources. We draw inspiration from the theory of turbo codes. We draw an analogy between the redundant parity bits of the constituent codes of a turbo code and the information from different sensors in a multimodal system. A hidden Markov model is used to model the sequence of observations of individual modalities. The decoded state likelihoods from one modality are used as additional information in decoding the states of the other modalities. This procedure is repeated until a certain convergence criterion is met. The resulting iterative algorithm is shown to have lower error rates than the individual models alone. The algorithm is then applied to a real-world problem of speech segmentation using audio and visual cues.

  1. A new iterative algorithm to reconstruct the refractive index.

    Science.gov (United States)

    Liu, Y J; Zhu, P P; Chen, B; Wang, J Y; Yuan, Q X; Huang, W X; Shu, H; Li, E R; Liu, X S; Zhang, K; Ming, H; Wu, Z Y

    2007-06-21

    The latest developments in x-ray imaging are associated with techniques based on the phase contrast. However, the image reconstruction procedures demand significant improvements of the traditional methods, and/or new algorithms have to be introduced to take advantage of the high contrast and sensitivity of the new experimental techniques. In this letter, an improved iterative reconstruction algorithm based on the maximum likelihood expectation maximization technique is presented and discussed in order to reconstruct the distribution of the refractive index from data collected by an analyzer-based imaging setup. The technique considered probes the partial derivative of the refractive index with respect to an axis lying in the meridional plane and perpendicular to the propagation direction. Computer simulations confirm the reliability of the proposed algorithm. In addition, the comparison between an analytical reconstruction algorithm and the iterative method has been also discussed together with the convergent characteristic of this latter algorithm. Finally, we will show how the proposed algorithm may be applied to reconstruct the distribution of the refractive index of an epoxy cylinder containing small air bubbles of about 300 micro of diameter.

  2. Quantifying convergence in the sciences

    Directory of Open Access Journals (Sweden)

    Sara Lumbreras

    2016-02-01

    Full Text Available Traditional epistemological models classify knowledge into separate disciplines with different objects of study and specific techniques, with some frameworks even proposing hierarchies (such as Comte’s. According to thinkers such as John Holland or Teilhard de Chardin, the advancement of science involves the convergence of disciplines. This proposed convergence can be studied in a number of ways, such as how works impact research outside a specific area (citation networks or how authors collaborate with other researchers in different fields (collaboration networks. While these studies are delivering significant new insights, they cannot easily show the convergence of different topics within a body of knowledge. This paper attempts to address this question in a quantitative manner, searching for evidence that supports the idea of convergence in the content of the sciences themselves (that is, whether the sciences are dealing with increasingly the same topics. We use Latent Dirichlet Analysis (LDA, a technique that is able to analyze texts and estimate the relative contributions of the topics that were used to generate them. We apply this tool to the corpus of the Santa Fe Institute (SFI working papers, which spans research on Complexity Science from 1989 to 2015. We then analyze the relatedness of the different research areas, the rise and demise of these sub-disciplines over time and, more broadly, the convergence of the research body as a whole. Combining the topic structure obtained from the collected publication history of the SFI community with techniques to infer hierarchy and clustering, we reconstruct a picture of a dynamic community which experiences trends, periodically recurring topics, and shifts in the closeness of scholarship over time. We find that there is support for convergence, and that the application of quantitative methods such as LDA to the study of knowledge can provide valuable insights that can help

  3. Installation of the ITER committee industry. Participants guide; Installation du Comite industrie ITER. Dossier des participants

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2006-07-01

    ITER is an international project to design and build an experimental fusion reactor based on the tokamak concept. This guide presents the ITER project and objectives and the associated organizations in France, the recommendations and actions for ITER, the industrial mobilization, the industrial committee and its members, technological sheets for the enterprises and the statistical document of the SESSI. (A.L.B.)

  4. An efficient iterative method for solving the Fokker-Planck equation

    Science.gov (United States)

    AL-Jawary, M. A.

    In the present paper, the new iterative method proposed by Daftardar-Gejji and Jafari (NIM or DJM) (2006) is used to solve the linear and nonlinear Fokker-Planck equations and some similar equations. In this iterative method the solution is obtained in the series form that converge to the exact solution with easily computed components. The results demonstrate that the method has many merits such as being derivative-free, overcome the difficulty arising in calculating Adomian polynomials to handle the nonlinear terms in Adomian decomposition method (ADM). It does not require to calculate Lagrange multiplier as in variational iteration method (VIM) and for solving a nonlinear case, the terms of the sequence become complex after several iterations. Thus, analytical evaluation of terms becomes very difficult or impossible in VIM. No needs to construct a homotopy and solve the corresponding algebraic equations as in homotopy perturbation method (HPM). In this work, the applications of the DJM for 1D, 2D, 3D linear and nonlinear Fokker-Planck equations are given and the results demonstrate that the presented method is very effective and reliable and does not require any restrictive assumptions for nonlinear terms and provide the analytic solutions. A symbolic manipulator Mathematica® 10.0 was used to evaluate terms in the iterative process.

  5. Iterative Neighbour-Information Gathering for Ranking Nodes in Complex Networks

    Science.gov (United States)

    Xu, Shuang; Wang, Pei; Lü, Jinhu

    2017-01-01

    Designing node influence ranking algorithms can provide insights into network dynamics, functions and structures. Increasingly evidences reveal that node’s spreading ability largely depends on its neighbours. We introduce an iterative neighbourinformation gathering (Ing) process with three parameters, including a transformation matrix, a priori information and an iteration time. The Ing process iteratively combines priori information from neighbours via the transformation matrix, and iteratively assigns an Ing score to each node to evaluate its influence. The algorithm appropriates for any types of networks, and includes some traditional centralities as special cases, such as degree, semi-local, LeaderRank. The Ing process converges in strongly connected networks with speed relying on the first two largest eigenvalues of the transformation matrix. Interestingly, the eigenvector centrality corresponds to a limit case of the algorithm. By comparing with eight renowned centralities, simulations of susceptible-infected-removed (SIR) model on real-world networks reveal that the Ing can offer more exact rankings, even without a priori information. We also observe that an optimal iteration time is always in existence to realize best characterizing of node influence. The proposed algorithms bridge the gaps among some existing measures, and may have potential applications in infectious disease control, designing of optimal information spreading strategies.

  6. Boosting iterative stochastic ensemble method for nonlinear calibration of subsurface flow models

    KAUST Repository

    Elsheikh, Ahmed H.

    2013-06-01

    A novel parameter estimation algorithm is proposed. The inverse problem is formulated as a sequential data integration problem in which Gaussian process regression (GPR) is used to integrate the prior knowledge (static data). The search space is further parameterized using Karhunen-Loève expansion to build a set of basis functions that spans the search space. Optimal weights of the reduced basis functions are estimated by an iterative stochastic ensemble method (ISEM). ISEM employs directional derivatives within a Gauss-Newton iteration for efficient gradient estimation. The resulting update equation relies on the inverse of the output covariance matrix which is rank deficient.In the proposed algorithm we use an iterative regularization based on the ℓ2 Boosting algorithm. ℓ2 Boosting iteratively fits the residual and the amount of regularization is controlled by the number of iterations. A termination criteria based on Akaike information criterion (AIC) is utilized. This regularization method is very attractive in terms of performance and simplicity of implementation. The proposed algorithm combining ISEM and ℓ2 Boosting is evaluated on several nonlinear subsurface flow parameter estimation problems. The efficiency of the proposed algorithm is demonstrated by the small size of utilized ensembles and in terms of error convergence rates. © 2013 Elsevier B.V.

  7. On equivalence classes in iterative learning control

    NARCIS (Netherlands)

    Verwoerd, M.H.A.; Meinsma, Gjerrit; de Vries, Theodorus J.A.

    2003-01-01

    This paper advocates a new approach to study the relation between causal iterative learning control (ILC) and conventional feedback control. Central to this approach is the introduction of the set of admissible pairs (of operators) defined with respect to a family of iterations. Considered are two

  8. Iterative Brinkman penalization for remeshed vortex methods

    DEFF Research Database (Denmark)

    Hejlesen, Mads Mølholm; Koumoutsakos, Petros; Leonard, Anthony

    2015-01-01

    We introduce an iterative Brinkman penalization method for the enforcement of the no-slip boundary condition in remeshed vortex methods. In the proposed method, the Brinkman penalization is applied iteratively only in the neighborhood of the body. This allows for using significantly larger time...

  9. The ITER Thomson scattering core LIDAR diagnostic

    NARCIS (Netherlands)

    Naylor, G.A.; Scannell, R.; Beurskens, M.; Walsh, M.J.; Pastor, I.; Donné, A.J.H.; Snijders, B.; Biel, W.; Meszaros, B.; Giudicotti, L.; Pasqualotto, R.; Marot, L.

    2012-01-01

    The central electron temperature and density of the ITER plasma may be determined by Thomson scattering. A LIDAR topology is proposed in order to minimize the port access required of the ITER vacuum vessel. By using a LIDAR technique, a profile of the electron temperature and density can be

  10. Controlled Iteration Grammars and Hyper-AFL's

    NARCIS (Netherlands)

    Asveld, P.R.J.

    1975-01-01

    We study $K$-iteration grammars equiped with a control on the application sequence of the substitutions, called $(\\Gamma,K)$-iteration grammars. In fact, the control is a language over the indices of the substitutions, prescribing the specific order in which one has to apply the different

  11. ITER Fast Ion Collective Thomson Scattering

    DEFF Research Database (Denmark)

    Bindslev, Henrik; Meo, Fernando; Korsholm, Søren Bang

    for measurements of the confined fusion alpha particles in ITER set by the ITER team. Then we outline the considerations, which enter into the selection and evaluation of CTS systems. System definition includes choice of probe frequency, geometry of probe and receiver beam patterns and probe power, but ultimately...

  12. The Convergence of Alexithymia Measures

    Directory of Open Access Journals (Sweden)

    Reitske Meganck

    2011-11-01

    Full Text Available The construct of alexithymia is most frequently measured by means of the 20-item Toronto Alexithymia Scale (TAS-20. However a number of other instruments have been developed to compensate for problems with measuring alexithymia through self-report measures. Convergence between the different alexithymia measures is rarely studied. This study investigates the convergence among the TAS-20, the Observer Alexithymia Scale (OAS, the Toronto Structured Interview for Alexithymia (TSIA, the modified Beth Israel Hospital Psychosomatic Questionnaire (M-BIQ, and the alexithymia dimensions as judged by the treating psychologist in an inpatient sample ('N' = 80. Correlations between the total scores were all significant. However exploratory factor analyses of these measures and their subscales indicate that they do not tap into one underlying factor. It is concluded that the TSIA and the M-BIQ are the best indicators of alexithymia, yet a multi-method approach and care in interpreting results are warranted.

  13. Proliferating Connections and Communicating Convergence

    Directory of Open Access Journals (Sweden)

    Aylish Wood

    2008-01-01

    Full Text Available In this paper I use the work of Niklas Luhmann to explore what pressure the concept of convergence exerts over how we communicate about the changing expressive practices of digital games following the emergence of digital technologies. My claim will be that in its current form, convergence privileges either the human users of technological platforms, or the combination of aesthetic conventions from different media what connects is either the user or the aesthetic code. While neither of these two positions would be likely to deny a reliance on the interplay between humans and technologies, such an interplay is taken for granted rather than explored. By using Luhmann’s version of systems theory, I argue that we can more effectively grasp the interplay of human and technological participants by understanding their combined roles in changing expressive practices.

  14. Clusters, Convergence, and Economic Performance

    OpenAIRE

    Mercedes Delgado; Porter, Michael E.; Scott Stern

    2010-01-01

    This paper evaluates the role of regional cluster composition in the economic performance of industries, clusters and regions. On the one hand, diminishing returns to specialization in a location can result in a convergence effect: the growth rate of an industry within a region may be declining in the level of activity of that industry. At the same time, positive spillovers across complementary economic activities provide an impetus for agglomeration: the growth rate of an industry within a r...

  15. Analytic practice: convergences and divergences.

    Science.gov (United States)

    Laks Eizirik, Cláudio

    2010-04-01

    The author discusses current convergences and divergences concerning analytic practice. After presenting a clinical vignette that can be understood differently according to different theoretical approaches, he discusses Wallerstein's proposal of a common ground in psychoanalysis and suggests that the present state of the art indicates that psychoanalysis is a pluralistic discipline, with different ways of training and practising it, and that the main challenge is to improve our ability to listen to and to learn from different approaches.

  16. Convergence Patterns in Latin America

    DEFF Research Database (Denmark)

    Quiroga, Paola Andrea Barrientos

    characteristics, and external shocks in the region. I study three important phases, following Thorp (1998): from 1900 to 1930, the exporting phase, from 1931 to 1974, the industrialization phase, and from 1975 to 2007, the globalization phase. During the last two phases, I find strong evidence of convergence...... among those countries that succeeded in industrializing and/or building good institutions. The reason is that technology dissusion and capital accumulation is easier when these 2 phenomena occur....

  17. Convergence of multiple ergodic averages

    OpenAIRE

    Host, Bernard

    2006-01-01

    These notes are based on a course for a general audience given at the Centro de Modeliamento Matem\\'atico of the University of Chile, in December 2004. We study the mean convergence of multiple ergodic averages, that is, averages of a product of functions taken at different times. We also describe the relations between this area of ergodic theory and some classical and some recent results in additive number theory.

  18. Techniques in Iterative Proton CT Image Reconstruction

    CERN Document Server

    Penfold, Scott

    2015-01-01

    This is a review paper on some of the physics, modeling, and iterative algorithms in proton computed tomography (pCT) image reconstruction. The primary challenge in pCT image reconstruction lies in the degraded spatial resolution resulting from multiple Coulomb scattering within the imaged object. Analytical models such as the most likely path (MLP) have been proposed to predict the scattered trajectory from measurements of individual proton location and direction before and after the object. Iterative algorithms provide a flexible tool with which to incorporate these models into image reconstruction. The modeling leads to a large and sparse linear system of equations that can efficiently be solved by projection methods-based iterative algorithms. Such algorithms perform projections of the iterates onto the hyperlanes that are represented by the linear equations of the system. They perform these projections in possibly various algorithmic structures, such as block-iterative projections (BIP), string-averaging...

  19. Surface meshing with curvature convergence

    KAUST Repository

    Li, Huibin

    2014-06-01

    Surface meshing plays a fundamental role in graphics and visualization. Many geometric processing tasks involve solving geometric PDEs on meshes. The numerical stability, convergence rates and approximation errors are largely determined by the mesh qualities. In practice, Delaunay refinement algorithms offer satisfactory solutions to high quality mesh generations. The theoretical proofs for volume based and surface based Delaunay refinement algorithms have been established, but those for conformal parameterization based ones remain wide open. This work focuses on the curvature measure convergence for the conformal parameterization based Delaunay refinement algorithms. Given a metric surface, the proposed approach triangulates its conformal uniformization domain by the planar Delaunay refinement algorithms, and produces a high quality mesh. We give explicit estimates for the Hausdorff distance, the normal deviation, and the differences in curvature measures between the surface and the mesh. In contrast to the conventional results based on volumetric Delaunay refinement, our stronger estimates are independent of the mesh structure and directly guarantee the convergence of curvature measures. Meanwhile, our result on Gaussian curvature measure is intrinsic to the Riemannian metric and independent of the embedding. In practice, our meshing algorithm is much easier to implement and much more efficient. The experimental results verified our theoretical results and demonstrated the efficiency of the meshing algorithm. © 2014 IEEE.

  20. User Configurations and Convergence in Consumer Electronics

    DEFF Research Database (Denmark)

    Jørgensen, Ulrik

    2000-01-01

    Convergence has been a technical fix motivated by the digital developments in media technologies.......Convergence has been a technical fix motivated by the digital developments in media technologies....

  1. Origin and convergent evolution of exendin genes.

    Science.gov (United States)

    Irwin, David M

    2012-01-01

    Exendins are secretin hormone-like peptides that are components of the toxins from two venomous lizards, Heloderma suspectum (Gila monster) and Heloderma horridium (Mexican bearded lizard). Exendins-1 and -2 are vasoactive intestinal peptide (VIP)-like, both in sequence and function, while exendins-3 and -4 are glucagon-like peptide-1 (GLP-1)-like. The evolutionary origin of these peptides, and the genes that encode them, has been unclear. Recently, genes orthologous to exendin have been identified in reptiles, birds and amphibians. Analysis of the orthologous sequences demonstrates that the Heloderma exendins diversified by gene duplication from a common exendin ancestor on the Heloderma lineage after divergence from other reptiles, including the anole lizard and Burmese python. In addition, the exendin toxin peptide sequences, but not their pro or signal peptides, have evolved very rapidly on the Heloderma lineage, likely as they adapted to their new function as toxins. Exendins-1 and -2 not only evolved rapidly but their sequences have evolved convergently upon that of VIP, resulting in a doubling of its identity with VIP, while exendins-3 and -4 have retained an ancestral property of being more GLP-1-like sequences. These results suggest that the ancestral role of exendin, which is potentially still retained in some species, had greater similarity with proglucagon-derived peptides or GIP. Copyright © 2011 Elsevier Inc. All rights reserved.

  2. Converging shocks for DSD modelling

    Science.gov (United States)

    Matignon, Christophe

    2013-06-01

    Modelling of pyrotechnic systems requires both, a good understanding and precise prediction capabilities of the dynamics of detonation. When using insensitive high explosives IHE (such as TATB-based explosives) the interaction of the detonation front with the confinement can lead to very different detonation velocities. One of the most popular engineering tools used to model this behaviour is the Detonation Shock Dynamics (DSD). In the DSD assumption, the detonation front propagates at a normal shock velocity (Dn) which depends only on its local curvature (κ). For divergent detonations, the DSD limit is very well established both experimentally and theoretically and one can easily propose a model (which obeys the 1D quasi-steady weakly curved detonation theory) to reproduce this behavior. We propose to extend the DSD theory to slightly convergent detonation fronts and to validate it against experimental data. Two series of experiments were carried out. The first series was designed to collect precise information regarding converging detonation. Usually, in such configurations, the detonation is non steady, making precise and simultaneous measurements of velocity and curvature difficult to achieve. The originality of the proposed setup is to drive a self similar convergent detonation at constant speed in an IHE rod by an external explosive tube of greater detonation velocity (allowing an accurate recording of both velocity and curvature). A wide range EOS/reaction rate model (inspired from previous works of Wescott et al.) was then calibrated to reproduce both the strong shock initiation and the newly extended (Dn- κ) law. This model can be used to perform either direct numerical simulation (DNS) on fine resolved mesh grid, or its reduced PZR model (DSD based) on a much coarser grid. This model was then successfully validated against the second series of experiments involving a detonation propagating around an obstacle and exhibiting a non steady converging front

  3. Fiscal Convergence in an Enlarged European Union

    Directory of Open Access Journals (Sweden)

    Georgeta VINTILĂ

    2014-02-01

    Full Text Available Taxation convergence in the European Union has always been a heatedly debated issue, and it has constantly resurfaced to the limelight as more and more fiscal directive proposals are being discussed. The current study is an analysis of the evolution of taxation convergence tendencies within the European Union in recent years, using sigma-convergence and cluster analysis. Our goal is to analyze the fiscal convergence trends in the context of European Union enlargement over the last two decades.

  4. Convergence of barycentric coordinates to barycentric kernels

    KAUST Repository

    Kosinka, Jiří

    2016-02-12

    We investigate the close correspondence between barycentric coordinates and barycentric kernels from the point of view of the limit process when finer and finer polygons converge to a smooth convex domain. We show that any barycentric kernel is the limit of a set of barycentric coordinates and prove that the convergence rate is quadratic. Our convergence analysis extends naturally to barycentric interpolants and mappings induced by barycentric coordinates and kernels. We verify our theoretical convergence results numerically on several examples.

  5. Iterative bandgap engineering at selected areas of quantum semiconductor wafers.

    Science.gov (United States)

    Stanowski, Radoslaw; Martin, Matthieu; Ares, Richard; Dubowski, Jan J

    2009-10-26

    We report on the application of a laser rapid thermal annealing technique for iterative bandgap engineering at selected areas of quantum semiconductor wafers. The approach takes advantage of the quantum well intermixing (QWI) effect for achieving targeted values of the bandgap in a series of small annealing steps. Each QWI step is monitored by collecting a photoluminescence map and, consequently, choosing the annealing strategy of the next step. An array of eight sites, 280 mum in diameter, each emitting at 1480 nm, has been fabricated with a spectral accuracy of better than 2 nm in a standard InGaAs/InGaAsP QW heterostructure that originally emitted at 1550 nm.

  6. Iterative Reconstruction of Memory Kernels.

    Science.gov (United States)

    Jung, Gerhard; Hanke, Martin; Schmid, Friederike

    2017-06-13

    In recent years, it has become increasingly popular to construct coarse-grained models with non-Markovian dynamics to account for an incomplete separation of time scales. One challenge of a systematic coarse-graining procedure is the extraction of the dynamical properties, namely, the memory kernel, from equilibrium all-atom simulations. In this article, we propose an iterative method for memory reconstruction from dynamical correlation functions. Compared to previously proposed noniterative techniques, it ensures by construction that the target correlation functions of the original fine-grained systems are reproduced accurately by the coarse-grained system, regardless of time step and discretization effects. Furthermore, we also propose a new numerical integrator for generalized Langevin equations that is significantly more accurate than the more commonly used generalization of the velocity Verlet integrator. We demonstrate the performance of the above-described methods using the example of backflow-induced memory in the Brownian diffusion of a single colloid. For this system, we are able to reconstruct realistic coarse-grained dynamics with time steps about 200 times larger than those used in the original molecular dynamics simulations.

  7. Iterants, Fermions and Majorana Operators

    Science.gov (United States)

    Kauffman, Louis H.

    Beginning with an elementary, oscillatory discrete dynamical system associated with the square root of minus one, we study both the foundations of mathematics and physics. Position and momentum do not commute in our discrete physics. Their commutator is related to the diffusion constant for a Brownian process and to the Heisenberg commutator in quantum mechanics. We take John Wheeler's idea of It from Bit as an essential clue and we rework the structure of that bit to a logical particle that is its own anti-particle, a logical Marjorana particle. This is our key example of the amphibian nature of mathematics and the external world. We show how the dynamical system for the square root of minus one is essentially the dynamics of a distinction whose self-reference leads to both the fusion algebra and the operator algebra for the Majorana Fermion. In the course of this, we develop an iterant algebra that supports all of matrix algebra and we end the essay with a discussion of the Dirac equation based on these principles.

  8. Convergence analysis of combinations of different methods

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Y. [Clarkson Univ., Potsdam, NY (United States)

    1994-12-31

    This paper provides a convergence analysis for combinations of different numerical methods for solving systems of differential equations. The author proves that combinations of two convergent linear multistep methods or Runge-Kutta methods produce a new convergent method of which the order is equal to the smaller order of the two original methods.

  9. A very fast iterative algorithm for TV-regularized image reconstruction with applications to low-dose and few-view CT

    CERN Document Server

    Kudo, Hiroyuki; Nemoto, Takuya; Takaki, Keita

    2016-01-01

    This paper concerns iterative reconstruction for low-dose and few-view CT by minimizing a data-fidelity term regularized with the Total Variation (TV) penalty. We propose a very fast iterative algorithm to solve this problem. The algorithm derivation is outlined as follows. First, the original minimization problem is reformulated into the saddle point (primal-dual) problem by using the Lagrangian duality, to which we apply the first-order primal-dual iterative methods. Second, we precondition the iteration formula using the ramp flter of Filtered Backprojection (FBP) reconstruction algorithm in such a way that the problem solution is not altered. The resulting algorithm resembles the structure of so-called iterative FBP algorithm, and it converges to the exact minimizer of cost function very fast.

  10. A very fast iterative algorithm for TV-regularized image reconstruction with applications to low-dose and few-view CT

    Science.gov (United States)

    Kudo, Hiroyuki; Yamazaki, Fukashi; Nemoto, Takuya; Takaki, Keita

    2016-10-01

    This paper concerns iterative reconstruction for low-dose and few-view CT by minimizing a data-fidelity term regularized with the Total Variation (TV) penalty. We propose a very fast iterative algorithm to solve this problem. The algorithm derivation is outlined as follows. First, the original minimization problem is reformulated into the saddle point (primal-dual) problem by using the Lagrangian duality, to which we apply the first-order primal-dual iterative methods. Second, we precondition the iteration formula using the ramp filter of Filtered Backprojection (FBP) reconstruction algorithm in such a way that the problem solution is not altered. The resulting algorithm resembles the structure of so-called iterative FBP algorithm, and it converges to the exact minimizer of cost function very fast.

  11. Comparisons of NIF convergent ablation simulations with radiograph data.

    Science.gov (United States)

    Olson, R E; Hicks, D G; Meezan, N B; Koch, J A; Landen, O L

    2012-10-01

    A technique for comparing simulation results directly with radiograph data from backlit capsule implosion experiments will be discussed. Forward Abel transforms are applied to the kappa*rho profiles of the simulation. These provide the transmission ratio (optical depth) profiles of the simulation. Gaussian and top hat blurs are applied to the simulated transmission ratio profiles in order to account for the motion blurring and imaging slit resolution of the experimental measurement. Comparisons between the simulated transmission ratios and the radiograph data lineouts are iterated until a reasonable backlighter profile is obtained. This backlighter profile is combined with the blurred, simulated transmission ratios to obtain simulated intensity profiles that can be directly compared with the radiograph data. Examples will be shown from recent convergent ablation (backlit implosion) experiments at the NIF.

  12. Strong Convergence Theorems for a Pair of Strictly Pseudononspreading Mappings

    Directory of Open Access Journals (Sweden)

    Bin-Chao Deng

    2013-01-01

    Full Text Available Let H be a real Hilbert space. Let T1,T2:H→H be k1-, k2-strictly pseudononspreading mappings; let αn and βn be two real sequences in (0,1. For given x0∈H, the sequence xn is generated iteratively by xn+1=βnxn+1-βnTw1αnγfxn+I-μαnBTw2xn, ∀n∈N, where Twi=1−wiI+wiTi with i=1,2 and B:H→H is strongly monotone and Lipschitzian. Under some mild conditions on parameters αn and βn, we prove that the sequence xn converges strongly to the set FixT1∩FixT2 of fixed points of a pair of strictly pseudononspreading mappings T1 and T2.

  13. Adaptive learning rate of SpikeProp based on weight convergence analysis.

    Science.gov (United States)

    Shrestha, Sumit Bam; Song, Qing

    2015-03-01

    A Spiking Neural Network (SNN) training using SpikeProp and its variants is usually affected by sudden rise in learning cost called surges. These surges cause diversion in the learning process and often cause it to fail as well. Researches have shown that proper learning rate is crucial to avoid these surges. In this paper, we perform weight convergence analysis to determine the proper step size in each iteration of weight update and derive an adaptive learning rate extension to SpikeProp that assures convergence of the learning process. We have analyzed the performance of this learning rate adaptation with existing methods via simulations on different benchmarks. The results show that using adaptive learning rate significantly improves the weight convergence and speeds up learning as well. Copyright © 2014 Elsevier Ltd. All rights reserved.

  14. A 2D systems approach to iterative learning control for discrete linear processes with zero Markov parameters

    Science.gov (United States)

    Hladowski, Lukasz; Galkowski, Krzysztof; Cai, Zhonglun; Rogers, Eric; Freeman, Chris T.; Lewin, Paul L.

    2011-07-01

    In this article a new approach to iterative learning control for the practically relevant case of deterministic discrete linear plants with uniform rank greater than unity is developed. The analysis is undertaken in a 2D systems setting that, by using a strong form of stability for linear repetitive processes, allows simultaneous consideration of both trial-to-trial error convergence and along the trial performance, resulting in design algorithms that can be computed using linear matrix inequalities (LMIs). Finally, the control laws are experimentally verified on a gantry robot that replicates a pick and place operation commonly found in a number of applications to which iterative learning control is applicable.

  15. Strong Convergence Theorems for Variational Inequalities and Split Equality Problem

    Directory of Open Access Journals (Sweden)

    Yu Jing Wu

    2013-01-01

    Full Text Available Let H1, H2, and H3 be real Hilbert spaces, let C⊆H1, Q⊆H2 be two nonempty closed convex sets, and let A:H1→H3, B:H2→H3 be two bounded linear operators. The split equality problem (SEP is to find x∈C, y∈Q such that Ax=By. Let H=H1×H2; consider f:H→H a contraction with coefficient 00, and M:H→H is a β-inverse strongly monotone mapping. Let 0<γ<γ̅/α, S=C×Q and G:H→H3 be defined by restricting to H1 is A and restricting to H2 is -B, that is, G has the matrix form G=[A,-B]. It is proved that the sequence {wn}={(xn,yn}⊆H generated by the iterative method wn+1=PS[αnγf(wn+(I-αnTPS(I-γnG*GPS(wn-λnMwn] converges strongly to w̃ which solves the SEP and the following variational inequality: 〈(T-λfw̃,w-w̃〉≥0 and 〈Mw̃,w-w̃〉≥0 for all w∈S. Moreover, if we take M=G*G:H→H,  γn=0, then M is a β-inverse strongly monotone mapping, and the sequence {wn} generated by the iterative method wn+1=αnγf(wn+(I-αnTPS(wn-λnG*Gwn converges strongly to w̃ which solves the SEP and the following variational inequality: 〈(T-λfw̃,w-w̃〉≥0 for all w∈S.

  16. ITER Fast Ion Collective Thomson Scattering

    DEFF Research Database (Denmark)

    Bindslev, Henrik; Larsen, Axel Wright; Meo, Fernando

    2005-01-01

    The EFDA Contract 04-1213 with Risø National Laboratory concerning a detailed integrated design of a Fast Ion Collective Thomson Scattering (CTS) diagnostic for ITER was signed on 31 December 2004. In 2003 the Risø CTS group finished a feasibility study and a conceptual design of an ITER Fast Ion...... Collective Thomson Scattering System (Contract 01.654) [1, 2]. The purpose of the CTS diagnostic is to measure the distribution function of fast ions in the plasma. The feasibility study demonstrated that the only system that can fully meet the ITER measurement requirements for confined fusion alphas is a 60...

  17. Ecomorphological convergence in planktivorous surgeonfishes

    KAUST Repository

    Friedman, S. T.

    2016-01-26

    © 2016 European Society For Evolutionary Biology. Morphological convergence plays a central role in the study of evolution. Often induced by shared ecological specialization, homoplasy hints at underlying selective pressures and adaptive constraints that deterministically shape the diversification of life. Although midwater zooplanktivory has arisen in adult surgeonfishes (family Acanthuridae) at least four independent times, it represents a clearly specialized state, requiring the capacity to swiftly swim in midwater locating and sucking small prey items. Whereas this diet has commonly been associated with specific functional adaptations in fishes, acanthurids present an interesting case study as all nonplanktivorous species feed by grazing on benthic algae and detritus, requiring a vastly different functional morphology that emphasizes biting behaviours. We examined the feeding morphology in 30 acanthurid species and, combined with a pre-existing phylogenetic tree, compared the fit of evolutionary models across two diet regimes: zooplanktivores and nonzooplanktivorous grazers. Accounting for phylogenetic relationships, the best-fitting model indicates that zooplanktivorous species are converging on a separate adaptive peak from their grazing relatives. Driving this bimodal landscape, zooplanktivorous acanthurids tend to develop a slender body, reduced facial features, smaller teeth and weakened jaw adductor muscles. However, despite these phenotypic changes, model fitting suggests that lineages have not yet reached the adaptive peak associated with plankton feeding even though some transitions appear to be over 10 million years old. These findings demonstrate that the selective demands of pelagic feeding promote repeated - albeit very gradual - ecomorphological convergence within surgeonfishes, while allowing local divergences between closely related species, contributing to the overall diversity of the clade. Journal of Evolutionary Biology

  18. Progress of ITER vacuum vessel

    Energy Technology Data Exchange (ETDEWEB)

    Ioki, K., E-mail: Kimihiro.Ioki@iter.org [ITER Organization, Route de Vinon sur Verdon, 13115 St Paul-lez-Durance (France); Bayon, A. [F4E, c/ Josep Pla, No. 2, Torres Diagonal Litoral, Edificio B3, E-08019 Barcelona (Spain); Choi, C.H.; Daly, E.; Dani, S.; Davis, J.; Giraud, B.; Gribov, Y.; Hamlyn-Harris, C.; Jun, C.; Levesy, B. [ITER Organization, Route de Vinon sur Verdon, 13115 St Paul-lez-Durance (France); Kim, B.C. [NFRI, 52 Yeoeundong Yuseonggu, Daejeon 305-333 (Korea, Republic of); Kuzmin, E. [NTC “Sintez”, Efremov Inst., 189631 Metallostroy, St. Petersburg (Russian Federation); Le Barbier, R.; Martinez, J.-M. [ITER Organization, Route de Vinon sur Verdon, 13115 St Paul-lez-Durance (France); Pathak, H. [ITER-India, A-29, GIDC Electronic Estate, Sector 25, Gandhinagar 382025 (India); Preble, J. [ITER Organization, Route de Vinon sur Verdon, 13115 St Paul-lez-Durance (France); Sa, J.W. [NFRI, 52 Yeoeundong Yuseonggu, Daejeon 305-333 (Korea, Republic of); Terasawa, A.; Utin, Yu. [ITER Organization, Route de Vinon sur Verdon, 13115 St Paul-lez-Durance (France); and others

    2013-10-15

    Highlights: ► This covers the overall status and progress of the ITER vacuum vessel activities. ► It includes design, R and D, manufacturing and approval process of the regulators. ► The baseline design was completed and now manufacturing designs are on-going. ► R and D includes ISI, dynamic test of keys and lip-seal welding/cutting technology. ► The VV suppliers produced full-scale mock-ups and started VV manufacturing. -- Abstract: Design modifications were implemented in the vacuum vessel (VV) baseline design in 2011–2012 for finalization. The modifications are mostly due to interface components, such as support rails and feedthroughs for the in-vessel coils (IVC). Manufacturing designs are being developed at the domestic agencies (DAs) based on the baseline design. The VV support design was also finalized and tests on scale mock-ups are under preparation. Design of the in-wall shielding (IWS) has progressed, considering the assembly methods and the required tolerances. Further modifications are required to be consistent with the DAs’ manufacturing designs. Dynamic tests on the inter-modular and stub keys to support the blanket modules are being performed to measure the dynamic amplification factor (DAF). An in-service inspection (ISI) plan has been developed and R and D was launched for ISI. Conceptual design of the VV instrumentation has been developed. The VV baseline design was approved by the agreed notified body (ANB) in accordance with the French Nuclear Pressure Equipment Order procedure.

  19. SCORE DIGITAL TECHNOLOGY: THE CONVERGENCE

    Directory of Open Access Journals (Sweden)

    Chernyshov Alexander V.

    2013-12-01

    Full Text Available Explores the role of digital scorewriters in today's culture, education, and music industry and media environment. The main principle of the development of software is not only publishing innovation (relating to the sheet music, and integration into the area of composition, arrangement, education, creative process for works based on digital technology (films, television and radio broadcasting, Internet, audio and video art. Therefore the own convergence of musically-computer technology is a total phenomenon: notation program combined with means MIDI-sequencer, audio and video editor. The article contains the unique interview with the creator of music notation processors.

  20. Technology Convergence and National Security

    Science.gov (United States)

    2010-08-25

    best minds from science, medicine, philosophy and the arts  at the  Medici  Court in 15th Century Florence catalyzed the Renaissance. It was the...transdisciplinary nature of that convergence that was critical. Sandro Botticelli Michelangelo Buonarroti Lorenzo  the Magnificent Andrea del Verrocchio Leonardo

  1. Accelerated fast iterative shrinkage thresholding algorithms for sparsity-regularized cone-beam CT image reconstruction

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Qiaofeng; Sawatzky, Alex; Anastasio, Mark A., E-mail: anastasio@wustl.edu [Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri 63130 (United States); Yang, Deshan [Department of Radiation Oncology, School of Medicine, Washington University in St. Louis, St. Louis, Missouri 63110 (United States); Tan, Jun [Department of Radiation Oncology, The University of Texas Southwestern Medical Center, Dallas, Texas 75390 (United States)

    2016-04-15

    Purpose: The development of iterative image reconstruction algorithms for cone-beam computed tomography (CBCT) remains an active and important research area. Even with hardware acceleration, the overwhelming majority of the available 3D iterative algorithms that implement nonsmooth regularizers remain computationally burdensome and have not been translated for routine use in time-sensitive applications such as image-guided radiation therapy (IGRT). In this work, two variants of the fast iterative shrinkage thresholding algorithm (FISTA) are proposed and investigated for accelerated iterative image reconstruction in CBCT. Methods: Algorithm acceleration was achieved by replacing the original gradient-descent step in the FISTAs by a subproblem that is solved by use of the ordered subset simultaneous algebraic reconstruction technique (OS-SART). Due to the preconditioning matrix adopted in the OS-SART method, two new weighted proximal problems were introduced and corresponding fast gradient projection-type algorithms were developed for solving them. We also provided efficient numerical implementations of the proposed algorithms that exploit the massive data parallelism of multiple graphics processing units. Results: The improved rates of convergence of the proposed algorithms were quantified in computer-simulation studies and by use of clinical projection data corresponding to an IGRT study. The accelerated FISTAs were shown to possess dramatically improved convergence properties as compared to the standard FISTAs. For example, the number of iterations to achieve a specified reconstruction error could be reduced by an order of magnitude. Volumetric images reconstructed from clinical data were produced in under 4 min. Conclusions: The FISTA achieves a quadratic convergence rate and can therefore potentially reduce the number of iterations required to produce an image of a specified image quality as compared to first-order methods. We have proposed and investigated

  2. Structural analysis of the ITER Vacuum Vessel regarding 2012 ITER Project-Level Loads

    Energy Technology Data Exchange (ETDEWEB)

    Martinez, J.-M., E-mail: jean-marc.martinez@live.fr [ITER Organization, Route de Vinon sur Verdon, 13115 St Paul lez Durance (France); Jun, C.H.; Portafaix, C.; Choi, C.-H.; Ioki, K.; Sannazzaro, G.; Sborchia, C. [ITER Organization, Route de Vinon sur Verdon, 13115 St Paul lez Durance (France); Cambazar, M.; Corti, Ph.; Pinori, K.; Sfarni, S.; Tailhardat, O. [Assystem EOS, 117 rue Jacquard, L' Atrium, 84120 Pertuis (France); Borrelly, S. [Sogeti High Tech, RE2, 180 rue René Descartes, Le Millenium – Bat C, 13857 Aix en Provence (France); Albin, V.; Pelletier, N. [SOM Calcul – Groupe ORTEC, 121 ancien Chemin de Cassis – Immeuble Grand Pré, 13009 Marseille (France)

    2014-10-15

    Highlights: • ITER Vacuum Vessel is a part of the first barrier to confine the plasma. • ITER Vacuum Vessel as Nuclear Pressure Equipment (NPE) necessitates a third party organization authorized by the French nuclear regulator to assure design, fabrication, conformance testing and quality assurance, i.e. Agreed Notified Body (ANB). • A revision of the ITER Project-Level Load Specification was implemented in April 2012. • ITER Vacuum Vessel Loads (seismic, pressure, thermal and electromagnetic loads) were summarized. • ITER Vacuum Vessel Structural Margins with regards to RCC-MR code were summarized. - Abstract: A revision of the ITER Project-Level Load Specification (to be used for all systems of the ITER machine) was implemented in April 2012. This revision supports ITER's licensing by accommodating requests from the French regulator to maintain consistency with the plasma physics database and our present understanding of plasma transients and electro-magnetic (EM) loads, to investigate the possibility of removing unnecessary conservatism in the load requirements and to review the list and definition of incidental cases. The purpose of this paper is to present the impact of this 2012 revision of the ITER Project-Level Load Specification (LS) on the ITER Vacuum Vessel (VV) loads and the main structural margins required by the applicable French code, RCC-MR.

  3. Solving large test-day models by iteration on data and preconditioned conjugate gradient.

    Science.gov (United States)

    Lidauer, M; Strandén, I; Mäntysaari, E A; Pösö, J; Kettunen, A

    1999-12-01

    A preconditioned conjugate gradient method was implemented into an iteration on a program for data estimation of breeding values, and its convergence characteristics were studied. An algorithm was used as a reference in which one fixed effect was solved by Gauss-Seidel method, and other effects were solved by a second-order Jacobi method. Implementation of the preconditioned conjugate gradient required storing four vectors (size equal to number of unknowns in the mixed model equations) in random access memory and reading the data at each round of iteration. The preconditioner comprised diagonal blocks of the coefficient matrix. Comparison of algorithms was based on solutions of mixed model equations obtained by a single-trait animal model and a single-trait, random regression test-day model. Data sets for both models used milk yield records of primiparous Finnish dairy cows. Animal model data comprised 665,629 lactation milk yields and random regression test-day model data of 6,732,765 test-day milk yields. Both models included pedigree information of 1,099,622 animals. The animal model ¿random regression test-day model¿ required 122 ¿305¿ rounds of iteration to converge with the reference algorithm, but only 88 ¿149¿ were required with the preconditioned conjugate gradient. To solve the random regression test-day model with the preconditioned conjugate gradient required 237 megabytes of random access memory and took 14% of the computation time needed by the reference algorithm.

  4. Morphological convergence in 'river dolphin' skulls.

    Science.gov (United States)

    Page, Charlotte E; Cooper, Natalie

    2017-01-01

    Convergent evolution can provide insights into the predictability of, and constraints on, the evolution of biodiversity. One striking example of convergence is seen in the 'river dolphins'. The four dolphin genera that make up the 'river dolphins' ( Inia geoffrensis, Pontoporia blainvillei, Platanista gangetica and Lipotes vexillifer ) do not represent a single monophyletic group, despite being very similar in morphology. This has led many to using the 'river dolphins' as an example of convergent evolution. We investigate whether the skulls of the four 'river dolphin' genera are convergent when compared to other toothed dolphin taxa in addition to identifying convergent cranial and mandibular features. We use geometric morphometrics to uncover shape variation in the skulls of the 'river dolphins' and then apply a number of phylogenetic techniques to test for convergence. We find significant convergence in the skull morphology of the 'river dolphins'. The four genera seem to have evolved similar skull shapes, leading to a convergent morphotype characterised by elongation of skull features. The cause of this morphological convergence remains unclear. However, the features we uncover as convergent, in particular elongation of the rostrum, support hypotheses of shared feeding mode or diet and thus provide the foundation for future work into convergence within the Odontoceti.

  5. Dynamics of a new family of iterative processes for quadratic polynomials

    Science.gov (United States)

    Gutiérrez, J. M.; Hernández, M. A.; Romero, N.

    2010-03-01

    In this work we show the presence of the well-known Catalan numbers in the study of the convergence and the dynamical behavior of a family of iterative methods for solving nonlinear equations. In fact, we introduce a family of methods, depending on a parameter . These methods reach the order of convergence m+2 when they are applied to quadratic polynomials with different roots. Newton's and Chebyshev's methods appear as particular choices of the family appear for m=0 and m=1, respectively. We make both analytical and graphical studies of these methods, which give rise to rational functions defined in the extended complex plane. Firstly, we prove that the coefficients of the aforementioned family of iterative processes can be written in terms of the Catalan numbers. Secondly, we make an incursion into its dynamical behavior. In fact, we show that the rational maps related to these methods can be written in terms of the entries of the Catalan triangle. Next we analyze its general convergence, by including some computer plots showing the intricate structure of the Universal Julia sets associated with the methods.

  6. Accelerated perturbation-resilient block-iterative projection methods with application to image reconstruction

    Science.gov (United States)

    Nikazad, T.; Davidi, R.; Herman, G. T.

    2012-03-01

    We study the convergence of a class of accelerated perturbation-resilient block-iterative projection methods for solving systems of linear equations. We prove convergence to a fixed point of an operator even in the presence of summable perturbations of the iterates, irrespective of the consistency of the linear system. For a consistent system, the limit point is a solution of the system. In the inconsistent case, the symmetric version of our method converges to a weighted least-squares solution. Perturbation resilience is utilized to approximate the minimum of a convex functional subject to the equations. A main contribution, as compared to previously published approaches to achieving similar aims, is a more than an order of magnitude speed-up, as demonstrated by applying the methods to problems of image reconstruction from projections. In addition, the accelerated algorithms are illustrated to be better, in a strict sense provided by the method of statistical hypothesis testing, than their unaccelerated versions for the task of detecting small tumors in the brain from x-ray CT projection data.

  7. Ocular convergence deficits in schizophrenia

    Directory of Open Access Journals (Sweden)

    Mark S Bolding

    2012-10-01

    Full Text Available Individuals with schizophrenia have been reported to exhibit a higher prevalence of convergence insufficiency (CI than the normal adult population. The purpose of this study was to determine if individuals with schizophrenia exhibit clinical signs of CI and to determine if the Convergence Insufficiency Symptom Survey (CISS is an effective instrument for identifying CI in this population.Twenty participants with schizophrenia (SZ and 20 healthy controls (HC completed the study. The prevalence of CI (15% in the SZ group was slightly higher than reported norms, but the difference was not significant. The SZ group had significantly higher scores on the CISS than the HC group, but the CISS scores did not correlate with clinical measures of CI in individuals with SZ. The only exception was that SZ patients had a significantly reduced fusional reserve as determined by Sheard’s criteria. Further study is needed to determine why individuals with schizophrenia reported symptoms associated with CI even though clinical measures did not support this diagnosis.

  8. Iterative Contracts as Proactive Law Instruments

    DEFF Research Database (Denmark)

    Henschel, René Franz

    2012-01-01

    The purpose of this article is to analyse the use of proactive law in contracts illustrated by the use of a particular type of contract within the IT industry, the so-called iterative contract. This type of contract has its root in a special software development process called iterative...... and incremental software development. In contrast to traditional IT project methodologies, where the product development takes place in a sequential design process, the iterative process is characterized by the so_ ware being developed through a series of repeated cycles in smaller portions at a time....... This software development process has driven the need for a new contract design that supports the product life cycle better than the traditional contracts. As will be shown in the analysis, the iterative contracts represent important legal innovation and can be categorized as a proactive law instrument that has...

  9. On the safety of ITER accelerators.

    Science.gov (United States)

    Li, Ge

    2013-01-01

    Three 1 MV/40A accelerators in heating neutral beams (HNB) are on track to be implemented in the International Thermonuclear Experimental Reactor (ITER). ITER may produce 500 MWt of power by 2026 and may serve as a green energy roadmap for the world. They will generate -1 MV 1 h long-pulse ion beams to be neutralised for plasma heating. Due to frequently occurring vacuum sparking in the accelerators, the snubbers are used to limit the fault arc current to improve ITER safety. However, recent analyses of its reference design have raised concerns. General nonlinear transformer theory is developed for the snubber to unify the former snubbers' different design models with a clear mechanism. Satisfactory agreement between theory and tests indicates that scaling up to a 1 MV voltage may be possible. These results confirm the nonlinear process behind transformer theory and map out a reliable snubber design for a safer ITER.

  10. CT radiation dose and iterative reconstruction techniques

    National Research Council Canada - National Science Library

    Padole, Atul; Ali Khawaja, Ranish Deedar; Kalra, Mannudeep K; Singh, Sarabjeet

    2015-01-01

    .... CT image quality is dependent on the selected image reconstruction algorithm. 3. Iterative reconstruction algorithms have reemerged with the potential of radiation dose optimization by lowering image noise. 4...

  11. Anderson Acceleration for Fixed-Point Iterations

    Energy Technology Data Exchange (ETDEWEB)

    Walker, Homer F. [Worcester Polytechnic Institute, MA (United States)

    2015-08-31

    The purpose of this grant was to support research on acceleration methods for fixed-point iterations, with applications to computational frameworks and simulation problems that are of interest to DOE.

  12. Archimedes' Pi--An Introduction to Iteration.

    Science.gov (United States)

    Lotspeich, Richard

    1988-01-01

    One method (attributed to Archimedes) of approximating pi offers a simple yet interesting introduction to one of the basic ideas of numerical analysis, an iteration sequence. The method is described and elaborated. (PK)

  13. Emerging interdisciplinary fields in the coming intelligence/convergence era

    Science.gov (United States)

    Noor, Ahmed

    2012-09-01

    Dramatic advances are in the horizon resulting from rapid pace of development of several technologies, including, computing, communication, mobile, robotic, and interactive technologies. These advances, along with the trend towards convergence of traditional engineering disciplines with physical, life and other science disciplines will result in the development of new interdisciplinary fields, as well as in new paradigms for engineering practice in the coming intelligence/convergence era (post-information age). The interdisciplinary fields include Cyber Engineering, Living Systems Engineering, Biomechatronics/Robotics Engineering, Knowledge Engineering, Emergent/Complexity Engineering, and Multiscale Systems engineering. The paper identifies some of the characteristics of the intelligence/convergence era, gives broad definition of convergence, describes some of the emerging interdisciplinary fields, and lists some of the academic and other organizations working in these disciplines. The need is described for establishing a Hierarchical Cyber-Physical Ecosystem for facilitating interdisciplinary collaborations, and accelerating development of skilled workforce in the new fields. The major components of the ecosystem are listed. The new interdisciplinary fields will yield critical advances in engineering practice, and help in addressing future challenges in broad array of sectors, from manufacturing to energy, transportation, climate, and healthcare. They will also enable building large future complex adaptive systems-of-systems, such as intelligent multimodal transportation systems, optimized multi-energy systems, intelligent disaster prevention systems, and smart cities.

  14. Overview and status of ITER Cryostat manufacturing

    Energy Technology Data Exchange (ETDEWEB)

    Bhardwaj, Anil K., E-mail: anil.bhardwaj@iter-india.org [ITER-India, Institute For Plasma Research, A-29, GIDC Electronics Estate, Sector-25, Gandhinagar 382016 (India); Gupta, Girish; Prajapati, Rajnikant; Joshi, Vaibhav; Patel, Mitul; Bhavsar, Jagrut; More, Vipul; Jindal, Mukesh; Bhattacharya, Avik; Jogi, Gourav; Palaliya, Amit; Jha, Saroj; Pandey, Manish; Shukla, Dileep [ITER-India, Institute For Plasma Research, A-29, GIDC Electronics Estate, Sector-25, Gandhinagar 382016 (India); Iyer, Ganesh; Jadhav, Pandurang; Goyal, Dipesh; Desai, Anish [Larsen & Toubro Limited, Heavy Engineering, Hazira Manufacturing Complex, Gujarat (India); Sekachev, I.; Vitupier, Guillaume [ITER Organization, Route de Vinon sur Verdon – CS 90046, 13067 Saint Paul Lez Durance Cedex (France); and others

    2016-11-01

    Highlights: • Manufacturing status of one of the largest and the heaviest fully welded stainless steel vacuum chambers in the world (ITER Cryostat). • Overview of manufacturing stages and its segmentation. • Overview of manufacturing procedures and assembly and installation. - Abstract: One of ITER-India's commitments to the ITER Organization is procurement of the ITER Cryostat. It is a large vacuum vessel (∼29 m dia. and ∼29 m height), which is made up of 304/304 L dual marked stainless steel and has a total mass over 3500 t. The thickness of the vessel wall varies from 50 mm to 190 mm. It is one of the largest and the heaviest fully welded stainless steel vacuum chambers in the world which provides vacuum thermal insulation for the superconducting magnets operating at 4.5 K and for the thermal shield operating at 80 K. It also mechanically supports the magnet system along with the vacuum vessel (VV). The cryostat is designed and constructed according to ASME Section-VIII Division-2 with additional ITER Vacuum Handbook requirements and it is classified as protection important component (PIC-2). Manufacturing of cryostat segments is ongoing in India; sub-assembly of four major sections of the cryostat from the segments will be done at the ITER site in a temporary workshop building and the final assembly will be done in the pit of the tokamak building, the final location. The cryostat manufacturing contract has been awarded to Larsen and Toubro Limited in August 2012 after completion of design [4] and signing of Procurement Arrangement [1] with ITER Organization. Manufacturing of the cryostat was started in January 2014 after approval of the manufacturing drawings and procedures. The temporary workshop of 44 m × 110 m × 26 m in height has been completed in November 2014 at the ITER site with a 200 t crane installed. This paper gives an overview and the status of the cryostat manufacturing.

  15. ITER driver blanket, European Community design

    Energy Technology Data Exchange (ETDEWEB)

    Simbolotti, G. (EURATOM-ENEA Association on Fusion Research, C.R.E., Frascati (Italy)); Zampaglione, V. (EURATOM-ENEA Association on Fusion Research, C.R.E., Frascati (Italy)); Ferrari, M. (EURATOM-ENEA Association on Fusion Research, C.R.E., Frascati (Italy)); Gallina, M. (EURATOM-ENEA Association on Fusion Research, C.R.E., Frascati (Italy)); Mazzone, G. (EURATOM-ENEA Association on Fusion Research, C.R.E., Frascati (Italy)); Nardi, C. (EURATOM-ENEA Association on Fusion Research, C.R.E., Frascati (Italy)); Petrizzi, L. (EURATOM-ENEA Association on Fusion Research, C.R.E., Frascati (Italy)); Rado, V. (EURATOM-ENEA Association on Fusion Research, C.R.E., Frascati (Italy)); Violante, V. (EURATOM-ENEA Association on Fusion Research, C.R.E., Frascati (Italy)); Daenner, W. (NET Team, Max-Planck-Inst. fuer Plasmaphysik, Garching (Germany)); Lorenzetto, P. (NET Team, Max-Planck-Inst. fuer Plasmaphysik, Garching (Germany)); Gierszewski, P. (CFFTP, Mississauga, ON (Canada)); Gratt

    1993-07-01

    Depending on the final decision on the operation time of ITER (International Thermonuclear Experimental Reactor), the Driver Blanket might become a basic component of the machine with the main function of producing a significant fraction (close to 0.8) of the tritium required for the ITER operation, the remaining fraction being available from external supplies. The Driver Blanket is not required to provide reactor relevant performance in terms of tritium self-sufficiency. However, reactor relevant reliability and safety are mandatory requirements for this component in order not to significantly afftect the overall plant availability and to allow the ITER experimental program to be safely and successfully carried out. With the framework of the ITER Conceptual Design Activities (CDA, 1988-1990), a conceptual design of the ITER Driver Blanket has been carried out by ENEA Fusion Dept., in collaboration with ANSALDO S.p.A. and SRS S.r.l., and in close consultation with the NET Team and CFFTP (Canadian Fusion Fuels Technology Project). Such a design has been selected as EC (European Community) reference design for the ITER Driver Blanket. The status of the design at the end of CDA is reported in the present paper. (orig.)

  16. Mechanical Analogy-based Iterative Method for Solving a System of Linear Equations

    Directory of Open Access Journals (Sweden)

    Yu. V. Berchun

    2015-01-01

    Full Text Available The paper reviews prerequisites to creating a variety of the iterative methods to solve a system of linear equations (SLE. It considers the splitting methods, variation-type methods, projection-type methods, and the methods of relaxation.A new iterative method based on mechanical analogy (the movement without resistance of a material point, that is connected by ideal elastically-linear constraints with unending guides defined by equations of solved SLE. The mechanical system has the unique position of stable equilibrium, the coordinates of which correspond to the solution of linear algebraic equation. The model of the mechanical system is a system of ordinary differential equations of the second order, integration of which allows you to define the point trajectory. In contrast to the classical methods of relaxation the proposed method does not ensure a trajectory passage through the equilibrium position. Thus the convergence of the method is achieved through the iterative stop of a material point at the moment it passes through the next (from the beginning of the given iteration minimum of potential energy. After that the next iteration (with changed initial coordinates starts.A resource-intensive process of numerical integration of differential equations in order to obtain a precise law of motion (at each iteration is replaced by defining its approximation. The coefficients of the approximating polynomial of the fourth order are calculated from the initial conditions, including higher-order derivatives. The resulting approximation enables you to evaluate the kinetic energy of a material point to calculate approximately the moment of time to reach the maximum kinetic energy (and minimum of the potential one, i.e. the end of the iteration.The software implementation is done. The problems with symmetric positive definite matrix, generated as a result of using finite element method, allowed us to examine a convergence rate of the proposed method

  17. Picard Iteration, Chebyshev Polynomials and Chebyshev-Picard Methods: Application in Astrodynamics

    Science.gov (United States)

    Junkins, John L.; Bani Younes, Ahmad; Woollands, Robyn M.; Bai, Xiaoli

    2013-12-01

    This paper extends previous work on parallel-structured Modified Chebyshev Picard Iteration (MCPI) Methods. The MCPI approach iteratively refines path approximation of the state trajectory for smooth nonlinear dynamical systems and this paper shows that the approach is especially suitable for initial value problems of astrodynamics. Using Chebyshev polynomials, as the orthogonal approximation basis, it is straightforward to distribute the computation of force functions needed in MCPI to generate the polynomial coefficients (approximating the path iterations) to different processors. Combining Chebyshev polynomials with Picard iteration, MCPI methods iteratively refines path estimates over large time intervals chosen to be within the domain of convergence of Picard iteration. The developed vector-matrix form makes MCPI methods computationally efficient and a more systematic approach is given, leading to a modest correction to results in the published dissertation by Bai. The power of MCPI methods for solving IVPs is clearly illustrated using a simple nonlinear differential equation with a known analytical solution. Compared with the most common integration scheme, the standard Runge-Kutta 4-5 method as implemented in MATLAB, MCPI methods generate solutions with better accuracy as well as orders of magnitude speedups, on a serial machine. MCPI performance is also compared to state of the art integrators such as the Runge-Kutta Nystrom 12(10) methods applied to the relevant orbit mechanics problems. The MCPI method is shown to be well-suited to solving these problems in serial processors with over an order of magnitude speedup relative to known methods. Furthermore, the approach is parallel-structured so that it is suited for parallel implementation and further speedups. When used in conjunction with the recently developed local gravity approximations in conjunction with parallel computation, we anticipate MCPI will enable revolutionary speedups while ensuring

  18. Block quasi-minimal residual iterations for non-Hermitian linear systems

    Energy Technology Data Exchange (ETDEWEB)

    Freund, R.W. [AT& T Bell Labs., Murray Hill, NJ (United States)

    1994-12-31

    Many applications require the solution of multiple linear systems that have the same coefficient matrix, but differ only in their right-hand sides. Instead of applying an iterative method to each of these systems individually, it is usually more efficient to employ a block version of the method that generates blocks of iterates for all the systems simultaneously. An example of such an iteration is the block conjugate gradient algorithm, which was first studied by Underwood and O`Leary. On parallel architectures, block versions of conjugate gradient-type methods are attractive even for the solution of single linear systems, since they have fewer synchronization points than the standard versions of these algorithms. In this talk, the author presents a block version of Freund and Nachtigal`s quasi-minimal residual (QMR) method for the iterative solution of non-Hermitian linear systems. He describes two different implementations of the block-QMR method, one based on a block version of the three-term Lanczos algorithm and one based on coupled two-term block recurrences. In both cases, the underlying block-Lanczos process still allows arbitrary normalizations of the vectors within each block, and the author discusses different normalization strategies. To maintain linear independence within each block, it is usually necessary to reduce the block size in the course of the iteration, and the author describes a deflation technique for performing this reduction. He also present some convergence results, and reports results of numerical experiments with the block-QMR method. Finally, the author discusses possible block versions of transpose-free Lanczos-based iterations such as the TFQMR method.

  19. Convergent Validity of the PUTS

    Directory of Open Access Journals (Sweden)

    Valerie Cathérine Brandt

    2016-04-01

    Full Text Available Premonitory urges are a cardinal feature in Gilles de la Tourette syndrome. Severity of premonitory urges can be assessed with the Premonitory Urge for Tic Disorders Scale (PUTS. However, convergent validity of the measure has been difficult to assess due to the lack of other urge measures.We investigated the relationship between average real-time urge intensity assessed by an in-house developed real-time urge monitor, measuring urge intensity continuously for 5mins on a visual analogue scale, and general urge intensity assessed by the PUTS in 22 adult Tourette patients (mean age 29.8+/- 10.3; 19 male. Additionally, underlying factors of premonitory urges assessed by the PUTS were investigated in the adult sample using factor analysis and were replicated in 40 children and adolescents diagnosed with Tourette syndrome (mean age 12.05 +/- 2.83 SD, 31 male.Cronbach’s alpha for the PUTS10 was acceptable (α = .79 in the adult sample. Convergent validity between average real-time urge intensity scores (as assessed with the real-time urge monitor and the 10-item version of the PUTS (r = .64 and the 9-item version of the PUTS (r = .66 was good. A factor analysis including the 10 items of the PUTS and average real-time urge intensity scores revealed three factors. One factor included the average real-time urge intensity score and appeared to measure urge intensity, while the other two factors can be assumed to reflect the (sensory quality of urges and subjective control, respectively. The factor structure of the 10 PUTS items alone was replicated in a sample of children and adolescents.The results indicate that convergent validity between the PUTS and the real-time urge assessment monitor is good. Furthermore, the results suggest that the PUTS might assess more than one dimension of urges and it may be worthwhile developing different sub-scales of the PUTS assessing premonitory urges in terms of intensity and quality, as well as subjectively

  20. Obtaining the Preinverse of a Power Amplifier Using Iterative Learning Control

    Science.gov (United States)

    Schoukens, Maarten; Hammenecker, Jules; Cooman, Adam

    2017-11-01

    Telecommunication networks make extensive use of power amplifiers to broaden the coverage from transmitter to receiver. Achieving high power efficiency is challenging and comes at a price: the wanted linear performance is degraded due to nonlinear effects. To compensate for these nonlinear disturbances, existing techniques compute the pre-inverse of the power amplifier by estimation of a nonlinear model. However, the extraction of this nonlinear model is involved and requires advanced system identification techniques. We used the plant inversion iterative learning control algorithm to investigate whether the nonlinear modeling step can be simplified. This paper introduces the iterative learning control framework for the pre-inverse estimation and predistortion of power amplifiers. The iterative learning control algorithm is used to obtain a high quality predistorted input for the power amplifier under study without requiring a nonlinear model of the power amplifier. In a second step a nonlinear pre-inverse model of the amplifier is obtained. Both the nonlinear and memory effects of a power amplifier can be compensated by this approach. The convergence of the iterative approach, and the predistortion results are illustrated on a simulation of a Motorola LDMOS transistor based power amplifier and a measurement example using the Chalmers RF WebLab measurement setup.

  1. Performance and Complexity Evaluation of Iterative Receiver for Coded MIMO-OFDM Systems

    Directory of Open Access Journals (Sweden)

    Rida El Chall

    2016-01-01

    Full Text Available Multiple-input multiple-output (MIMO technology in combination with channel coding technique is a promising solution for reliable high data rate transmission in future wireless communication systems. However, these technologies pose significant challenges for the design of an iterative receiver. In this paper, an efficient receiver combining soft-input soft-output (SISO detection based on low-complexity K-Best (LC-K-Best decoder with various forward error correction codes, namely, LTE turbo decoder and LDPC decoder, is investigated. We first investigate the convergence behaviors of the iterative MIMO receivers to determine the required inner and outer iterations. Consequently, the performance of LC-K-Best based receiver is evaluated in various LTE channel environments and compared with other MIMO detection schemes. Moreover, the computational complexity of the iterative receiver with different channel coding techniques is evaluated and compared with different modulation orders and coding rates. Simulation results show that LC-K-Best based receiver achieves satisfactory performance-complexity trade-offs.

  2. Enhancement of vibration desensitising capability of iterative algorithms for phase-shifting interferometers

    Science.gov (United States)

    Liu, Qian; Yuan, Daocheng; He, Huabin

    2017-11-01

    The sensitivity of phase-shifting interferometers (PSIs) to vibration impairs their application in unsteady environment. Iterative algorithms were developed to desensitise the effect of vibration on PSIs, but their desensitising capability is restricted by the estimated initial value. In this paper, a spatial carrier-assisted method is proposed, in which a wavefront phase retrieved from an additional spatial-carrier interferogram is used as the initial value. Because of the benefits of spatial carrier, vibration immunity and sign determination, iteration could converge to accurate value even when interferometers are under severe vibration. To reduce the possibility of transverse movement of the measured surface, subsampling strategy is further proposed to decrease the required tilt angle, with the additional benefit of decreasing the calculation time of iteration. Computer simulations and experiments are performed to verify the effectiveness of the proposed method. Results indicate that the vibration desensitising capability of an iterative algorithm is significantly enhanced by the proposed method. The proposed method improves the vibration desensitising capability with low cost and is thus highly compatible.

  3. Effect of block-iterative acceleration on Ga-67 tumor detection in thoracic SPECT

    Science.gov (United States)

    Gifford, H. C.; King, M. A.; Narayanan, M. V.; Pretorius, P. H.; Smyczynski, M. S.; Wells, R. G.

    2002-02-01

    A combination of human localization receiver operating characteristic (LROC) and channelized Hotelling observer (CHO) ROC psychophysical studies were used to investigate how accelerated ordered-subset expectation maximization (OSEM) and rescaled block-iterative (RBI) EM reconstruction affect tumor detection in simulated Ga-67 SPECT images, The tumors were 1-cm-diameter spheres within the chest region of the three-dimensional mathematical cardiac-torso phantom. Previous work with iterative detector resolution compensation showed that eight iterations of the OSEM algorithm with a subset size of eight (16 subsets) offered optimal observer performance. For the LROC study in this paper, the OSEM and RBI algorithms were implemented using subset sizes P and iterations K that satisfied the relation P=K for P=1, 2, 4, and 8. The CHO was applied to reconstruction strategies that deviated from this relation. Results show that using P/spl les/2 penalized observer performance compared to strategies with larger subset sizes. Other researchers have reported on the more stable convergence and noise properties of the RBI algorithm [(Byrne, 1996) and (Lalush and Tsui, 2000)]. In a similar vein, we found that an RBI strategy with a subset size of P produced the same performance as an OSEM strategy with subset size 2P. As neither algorithm displayed a decisive advantage in speed over the other, we conclude that the RBI algorithm is the better choice for accelerating the Ga-67 reconstructions.

  4. Frozen Jacobian Multistep Iterative Method for Solving Nonlinear IVPs and BVPs

    Directory of Open Access Journals (Sweden)

    Fayyaz Ahmad

    2017-01-01

    Full Text Available In this paper, we present and illustrate a frozen Jacobian multistep iterative method to solve systems of nonlinear equations associated with initial value problems (IVPs and boundary value problems (BVPs. We have used Jacobi-Gauss-Lobatto collocation (J-GL-C methods to discretize the IVPs and BVPs. Frozen Jacobian multistep iterative methods are computationally very efficient. They require only one inversion of the Jacobian in the form of LU-factorization. The LU factors can then be used repeatedly in the multistep part to solve other linear systems. The convergence order of the proposed iterative method is 5m-11, where m is the number of steps. The validity, accuracy, and efficiency of our proposed frozen Jacobian multistep iterative method is illustrated by solving fifteen IVPs and BVPs. It has been observed that, in all the test problems, with one exception in this paper, a single application of the proposed method is enough to obtain highly accurate numerical solutions. In addition, we present a comprehensive comparison of J-GL-C methods on a collection of test problems.

  5. Analytical approximate solution of time-fractional Fornberg–Whitham equation by the fractional variational iteration method

    Directory of Open Access Journals (Sweden)

    Birol İbiş

    2014-12-01

    Full Text Available The purpose of this paper was to obtain the analytical approximate solution of time-fractional Fornberg–Whitham, equation involving Jumarie’s modified Riemann–Liouville derivative by the fractional variational iteration method (FVIM. FVIM provides the solution in the form of a convergent series with easily calculable terms. The obtained approximate solutions are compared with the exact or existing numerical results in the literature to verify the applicability, efficiency and accuracy of the method.

  6. The Use of Iterative Methods to Solve Two-Dimensional Nonlinear Volterra-Fredholm Integro-Differential Equations

    Directory of Open Access Journals (Sweden)

    shadan sadigh behzadi

    2012-03-01

    Full Text Available In this present paper, we solve a two-dimensional nonlinear Volterra-Fredholm integro-differential equation by using the following powerful, efficient but simple methods: (i Modified Adomian decomposition method (MADM, (ii Variational iteration method (VIM, (iii Homotopy analysis method (HAM and (iv Modified homotopy perturbation method (MHPM. The uniqueness of the solution and the convergence of the proposed methods are proved in detail. Numerical examples are studied to demonstrate the accuracy of the presented methods.

  7. Iterative Method to Solve a Data Completion Problem for Biharmonic Equation for Rectangular Domain

    Directory of Open Access Journals (Sweden)

    Tajani Chakir

    2017-07-01

    Full Text Available In this work, we are interested in a class of problems of great importance in many areas of industry and engineering. It is the invese problem for the biharmonic equation. It consists to complete the missing data on the inaccessible part from the measured data on the accessible part of the boundary. To solve this ill-posed problem, we opted for the alternative iterative method developed by Kozlov, Mazya and Fomin which is a convergent method for the elliptical Cauchy problems in general. The numerical implementation of the iterative algorithm is based on the application of the boundary element method (BEM for a sequence of mixed well-posed direct problems. Numerical results are performed for a square domain showing the effectiveness of the algorithm by BEM to produce accurate and stable numerical results.

  8. Hybrid Extragradient Iterative Algorithms for Variational Inequalities, Variational Inclusions, and Fixed-Point Problems

    Directory of Open Access Journals (Sweden)

    Lu-Chuan Ceng

    2012-01-01

    Full Text Available We investigate the problem of finding a common solution of a general system of variational inequalities, a variational inclusion, and a fixed-point problem of a strictly pseudocontractive mapping in a real Hilbert space. Motivated by Nadezhkina and Takahashi's hybrid-extragradient method, we propose and analyze new hybrid-extragradient iterative algorithm for finding a common solution. It is proven that three sequences generated by this algorithm converge strongly to the same common solution under very mild conditions. Based on this result, we also construct an iterative algorithm for finding a common fixed point of three mappings, such that one of these mappings is nonexpansive, and the other two mappings are strictly pseudocontractive mappings.

  9. Shrinkage-thresholding enhanced born iterative method for solving 2D inverse electromagnetic scattering problem

    KAUST Repository

    Desmal, Abdulla

    2014-07-01

    A numerical framework that incorporates recently developed iterative shrinkage thresholding (IST) algorithms within the Born iterative method (BIM) is proposed for solving the two-dimensional inverse electromagnetic scattering problem. IST algorithms minimize a cost function weighted between measurement-data misfit and a zeroth/first-norm penalty term and therefore promote "sharpness" in the solution. Consequently, when applied to domains with sharp variations, discontinuities, or sparse content, the proposed framework is more efficient and accurate than the "classical" BIM that minimizes a cost function with a second-norm penalty term. Indeed, numerical results demonstrate the superiority of the IST-BIM over the classical BIM when they are applied to sparse domains: Permittivity and conductivity profiles recovered using the IST-BIM are sharper and more accurate and converge faster. © 1963-2012 IEEE.

  10. On iterative algorithms for quantitative photoacoustic tomography in the radiative transport regime

    Science.gov (United States)

    Wang, Chao; Zhou, Tie

    2017-11-01

    In this paper, we present a numerical reconstruction method for quantitative photoacoustic tomography (QPAT), based on the radiative transfer equation (RTE), which models light propagation more accurately than diffusion approximation (DA). We investigate the reconstruction of absorption coefficient and scattering coefficient of biological tissues. An improved fixed-point iterative method to retrieve the absorption coefficient, given the scattering coefficient, is proposed for its cheap computational cost; the convergence of this method is also proved. The Barzilai-Borwein (BB) method is applied to retrieve two coefficients simultaneously. Since the reconstruction of optical coefficients involves the solutions of original and adjoint RTEs in the framework of optimization, an efficient solver with high accuracy is developed from Gao and Zhao (2009 Transp. Theory Stat. Phys. 38 149-92). Simulation experiments illustrate that the improved fixed-point iterative method and the BB method are competitive methods for QPAT in the relevant cases.

  11. Video compressed sensing using iterative self-similarity modeling and residual reconstruction

    Science.gov (United States)

    Kim, Yookyung; Oh, Han; Bilgin, Ali

    2013-04-01

    Compressed sensing (CS) has great potential for use in video data acquisition and storage because it makes it unnecessary to collect an enormous amount of data and to perform the computationally demanding compression process. We propose an effective CS algorithm for video that consists of two iterative stages. In the first stage, frames containing the dominant structure are estimated. These frames are obtained by thresholding the coefficients of similar blocks. In the second stage, refined residual frames are reconstructed from the original measurements and the measurements corresponding to the frames estimated in the first stage. These two stages are iterated until convergence. The proposed algorithm exhibits superior subjective image quality and significantly improves the peak-signal-to-noise ratio and the structural similarity index measure compared to other state-of-the-art CS algorithms.

  12. Stellar surface as low-rank modification in iterative methods for binary neutron stars

    Science.gov (United States)

    Lau, Stephen R.

    2017-11-01

    We present a new multidomain spectral method for the treatment of non-spherical stellar surfaces in iterative methods for binary neutron stars. A stellar surface changes throughout the course of an iterative solution, potentially stalling the convergence. Our method affords low-complexity updates of the relevant subdomain preconditioners, thereby avoiding such stalling. Unlike current collocation (or nodal) approaches for treating surfaces (which rely on coordinate transformations to ensure that stellar surfaces arise at subdomain boundaries), our approach requires no regridding or nontrivial Jacobians. For polytropes with an equation of state specified by an integer polytropic index, our method delivers exponential accuracy with increased truncation, although for "stiff" equations of state (e.g. fractional) it suffers from the same accuracy loss as current methods. We have presented an outline of our approach before, but here present details with numerical tests.

  13. On iterative path integral calculations for a system interacting with a shifted dissipative bath.

    Science.gov (United States)

    Walters, Peter L; Banerjee, Tuseeta; Makri, Nancy

    2015-08-21

    Real-time path integral calculations for the propagation of a system in contact with a harmonic dissipative environment often employ the iterative quasi-adiabatic propagator path integral (i-QuAPI) methodology. We compare two simple ways of applying this methodology to a bath initially in equilibrium with the localized state of the system (e.g., the donor in the case of charge transfer). The first way involves modifying the phase of the system via a time-local phase given in terms of integrals of the spectral density or in terms of the coefficients entering the QuAPI-discretized influence functional. In the iterative decomposition of the path integral, this approach requires consistent memory truncation to avoid extremely slow convergence. The second, alternative approach involves shifting the coordinate of the system, to bring the donor state in equilibrium with the bath, and requires no further modification of the i-QuAPI algorithm.

  14. A New Three-step Iterative Method for Solving Nonlinear Equations

    Directory of Open Access Journals (Sweden)

    M. Matin Far

    2012-03-01

    Full Text Available In this paper, a new three-step iterative method for finding a simple root of the nonlinear equation of f(x = 0 will be introduced. This method is based on the two-step method of [C. Chun, Y. Ham, Some fourth-order modifications of Newton’s method, Appl. Math. Comput. 197 (2008 654-658]. The new method requires three evaluations of the function and two of its first-derivative. We will prove that the order of convergence of the new method and its efficiency index will respectively be 8, and 1.5157. Some numerical experiments are given to illustrate the performance of the three-step iterative method.

  15. Diagonalization of complex symmetric matrices: Generalized Householder reflections, iterative deflation and implicit shifts

    Science.gov (United States)

    Noble, J. H.; Lubasch, M.; Stevens, J.; Jentschura, U. D.

    2017-12-01

    We describe a matrix diagonalization algorithm for complex symmetric (not Hermitian) matrices, A ̲ =A̲T, which is based on a two-step algorithm involving generalized Householder reflections based on the indefinite inner product 〈 u ̲ , v ̲ 〉 ∗ =∑iuivi. This inner product is linear in both arguments and avoids complex conjugation. The complex symmetric input matrix is transformed to tridiagonal form using generalized Householder transformations (first step). An iterative, generalized QL decomposition of the tridiagonal matrix employing an implicit shift converges toward diagonal form (second step). The QL algorithm employs iterative deflation techniques when a machine-precision zero is encountered ;prematurely; on the super-/sub-diagonal. The algorithm allows for a reliable and computationally efficient computation of resonance and antiresonance energies which emerge from complex-scaled Hamiltonians, and for the numerical determination of the real energy eigenvalues of pseudo-Hermitian and PT-symmetric Hamilton matrices. Numerical reference values are provided.

  16. Mosaic convergence of rodent dentitions.

    Directory of Open Access Journals (Sweden)

    Vincent Lazzari

    Full Text Available BACKGROUND: Understanding mechanisms responsible for changes in tooth morphology in the course of evolution is an area of investigation common to both paleontology and developmental biology. Detailed analyses of molar tooth crown shape have shown frequent homoplasia in mammalian evolution, which requires accurate investigation of the evolutionary pathways provided by the fossil record. The necessity of preservation of an effective occlusion has been hypothesized to functionally constrain crown morphological changes and to also facilitate convergent evolution. The Muroidea superfamily constitutes a relevant model for the study of molar crown diversification because it encompasses one third of the extant mammalian biodiversity. METHODOLOGY/PRINCIPAL FINDINGS: Combined microwear and 3D-topographic analyses performed on fossil and extant muroid molars allow for a first quantification of the relationships between changes in crown morphology and functionality of occlusion. Based on an abundant fossil record and on a well resolved phylogeny, our results show that the most derived functional condition associates longitudinal chewing and non interlocking of cusps. This condition has been reached at least 7 times within muroids via two main types of evolutionary pathways each respecting functional continuity. In the first type, the flattening of tooth crown which induces the removal of cusp interlocking occurs before the rotation of the chewing movement. In the second type however, flattening is subsequent to rotation of the chewing movement which can be associated with certain changes in cusp morphology. CONCLUSION/SIGNIFICANCE: The reverse orders of the changes involved in these different pathways reveal a mosaic evolution of mammalian dentition in which direction of chewing and crown shape seem to be partly decoupled. Either can change in respect to strong functional constraints affecting occlusion which thereby limit the number of the possible

  17. Cosmic Convergence: Art and Science

    Science.gov (United States)

    Mayo, Elizabeth A.; Zisholtz, E.; Hilton, H.

    2010-01-01

    The I.P. Stanback Museum and Planetarium is a major educational and teaching resource for South Carolina State University, K-12 schools, other universities and the community of Orangeburg and well beyond. The concept of creating a museum with a planetarium on the campus of SC State was ahead of its time. Today scholars are writing about the unity of creative disciplines. Through its integration of the arts, humanities and sciences, the Stanback, the only art museum with a planetarium at any of the Historically Black Colleges and Universities and one of the few in the nation, stands in the forefront of modern thinking. Cosmic Convergence: Art and Science, opening at the I.P. Stanback Museum and Planetarium in February 2010, will feature the works of Mildred Thompson (1936-2003), a prominent African American artist who worked in the media of painting, drawing, print making, sculpture, and photography. Thompson’s artwork shows the strong influences of her interest in physics, astronomy, and metaphysics as well as music and spiritualism. “My work in the visual arts is, and has always been, a continuous search for understanding. It is an expression of purpose and reflects a personal interpretation of the Universe.” Cosmic Convergence will explore the meeting of Art and Science through Mildred Thompson's work and the scientific basis of that work. The paintings and sculptures of the exhibit will be combined with astronomical images showing both the reality and interpretation of the surrounding Universe. Support for this work was provided by the NSF PAARE program to South Carolina State University under award AST-0750814.

  18. Regional Convergence and Sustainable Development in China

    Directory of Open Access Journals (Sweden)

    Fang Yang

    2016-01-01

    Full Text Available Based on the convergence theory of economic growth, this paper extends this concept to the human development index and carries out an empirical analysis of regional development in China between 1997 and 2006. Our research shows that the conditional convergence has been identified. Investment in fixed assets, government expenditure on education, health and infrastructure construction have positive effects on regional convergence of social development. Population weighted analysis of human development index provides support for weak convergence amongst provinces. Analysis of dynamics of regional distribution reveals the club convergence, which indicate two different convergence states. Central China is in the shade and lags behind, giving rise to the so-called “central downfall”. To solve this problem, the “Rise of Central China” Plan is necessary to promote the connection between coastal and inland regions of China and reduce the regional development gap.

  19. Vadose zone flow convergence test suite

    Energy Technology Data Exchange (ETDEWEB)

    Butcher, B. T. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2017-06-05

    Performance Assessment (PA) simulations for engineered disposal systems at the Savannah River Site involve highly contrasting materials and moisture conditions at and near saturation. These conditions cause severe convergence difficulties that typically result in unacceptable convergence or long simulation times or excessive analyst effort. Adequate convergence is usually achieved in a trial-anderror manner by applying under-relaxation to the Saturation or Pressure variable, in a series of everdecreasing RELAxation values. SRNL would like a more efficient scheme implemented inside PORFLOW to achieve flow convergence in a more reliable and efficient manner. To this end, a suite of test problems that illustrate these convergence problems is provided to facilitate diagnosis and development of an improved convergence strategy. The attached files are being transmitted to you describing the test problem and proposed resolution.

  20. Phase retrieval using iterative Fourier transform and convex optimization algorithm

    Science.gov (United States)

    Zhang, Fen; Cheng, Hong; Zhang, Quanbing; Wei, Sui

    2015-05-01

    Phase is an inherent characteristic of any wave field. Statistics show that greater than 25% of the information is encoded in the amplitude term and 75% of the information is in the phase term. The technique of phase retrieval means acquire phase by computation using magnitude measurements and provides data information for holography display, 3D field reconstruction, X-ray crystallography, diffraction imaging, astronomical imaging and many other applications. Mathematically, solving phase retrieval problem is an inverse problem taking the physical and computation constraints. Some recent algorithms use the principle of compressive sensing, such as PhaseLift, PhaseCut and compressive phase retrieval etc. they formulate phase retrieval problems as one of finding the rank-one solution to a system of linear matrix equations and make the overall algorithm a convex program over n × n matrices. However, by "lifting" a vector problem to a matrix one, these methods lead to a much higher computational cost as a result. Furthermore, they only use intensity measurements but few physical constraints. In the paper, a new algorithm is proposed that combines above convex optimization methods with a well known iterative Fourier transform algorithm (IFTA). The IFTA iterates between the object domain and spectral domain to reinforce the physical information and reaches convergence quickly which has been proved in many applications such as compute-generated-hologram (CGH). Herein the output phase of the IFTA is treated as the initial guess of convex optimization methods, and then the reconstructed phase is numerically computed by using modified TFOCS. Simulation results show that the combined algorithm increases the likelihood of successful recovery as well as improves the precision of solution.

  1. An iterative approach of protein function prediction.

    Science.gov (United States)

    Chi, Xiaoxiao; Hou, Jingyu

    2011-11-10

    Current approaches of predicting protein functions from a protein-protein interaction (PPI) dataset are based on an assumption that the available functions of the proteins (a.k.a. annotated proteins) will determine the functions of the proteins whose functions are unknown yet at the moment (a.k.a. un-annotated proteins). Therefore, the protein function prediction is a mono-directed and one-off procedure, i.e. from annotated proteins to un-annotated proteins. However, the interactions between proteins are mutual rather than static and mono-directed, although functions of some proteins are unknown for some reasons at present. That means when we use the similarity-based approach to predict functions of un-annotated proteins, the un-annotated proteins, once their functions are predicted, will affect the similarities between proteins, which in turn will affect the prediction results. In other words, the function prediction is a dynamic and mutual procedure. This dynamic feature of protein interactions, however, was not considered in the existing prediction algorithms. In this paper, we propose a new prediction approach that predicts protein functions iteratively. This iterative approach incorporates the dynamic and mutual features of PPI interactions, as well as the local and global semantic influence of protein functions, into the prediction. To guarantee predicting functions iteratively, we propose a new protein similarity from protein functions. We adapt new evaluation metrics to evaluate the prediction quality of our algorithm and other similar algorithms. Experiments on real PPI datasets were conducted to evaluate the effectiveness of the proposed approach in predicting unknown protein functions. The iterative approach is more likely to reflect the real biological nature between proteins when predicting functions. A proper definition of protein similarity from protein functions is the key to predicting functions iteratively. The evaluation results demonstrated that

  2. Convergence on local labour markets in Poland

    OpenAIRE

    Kusideł, Ewa

    2011-01-01

    The purpose of presented study was to verify a hypothesis of convergence on local labor markets in Poland. Convergence phenomenon, understood as economic development levels balancing (falling differentiation) has been known since the mid- 1950s. In Poland the convergence problems have been a specific subject of research since the accession to the European Union and the implementation of cohesion policy whose financing is largely related to co...

  3. Modeling Risk Convergence for European Financial Markets

    Directory of Open Access Journals (Sweden)

    Radu LUPU

    2014-09-01

    Full Text Available This article studies the convergence of risk on a sample of 13 European indexes. We use a set of 31 model specifications of a significant number of models belonging to the GARCH class and on their estimates we build an aggregate index in a Value-at-Risk approach. We use this index as a base for our convergence analysis. The results indicate a positive and significant tendency of convergence growth for the European financial market

  4. PREFACE: Progress in the ITER Physics Basis

    Science.gov (United States)

    Ikeda, K.

    2007-06-01

    I would firstly like to congratulate all who have contributed to the preparation of the `Progress in the ITER Physics Basis' (PIPB) on its publication and express my deep appreciation of the hard work and commitment of the many scientists involved. With the signing of the ITER Joint Implementing Agreement in November 2006, the ITER Members have now established the framework for construction of the project, and the ITER Organization has begun work at Cadarache. The review of recent progress in the physics basis for burning plasma experiments encompassed by the PIPB will be a valuable resource for the project and, in particular, for the current Design Review. The ITER design has been derived from a physics basis developed through experimental, modelling and theoretical work on the properties of tokamak plasmas and, in particular, on studies of burning plasma physics. The `ITER Physics Basis' (IPB), published in 1999, has been the reference for the projection methodologies for the design of ITER, but the IPB also highlighted several key issues which needed to be resolved to provide a robust basis for ITER operation. In the intervening period scientists of the ITER Participant Teams have addressed these issues intensively. The International Tokamak Physics Activity (ITPA) has provided an excellent forum for scientists involved in these studies, focusing their work on the high priority physics issues for ITER. Significant progress has been made in many of the issues identified in the IPB and this progress is discussed in depth in the PIPB. In this respect, the publication of the PIPB symbolizes the strong interest and enthusiasm of the plasma physics community for the success of the ITER project, which we all recognize as one of the great scientific challenges of the 21st century. I wish to emphasize my appreciation of the work of the ITPA Coordinating Committee members, who are listed below. Their support and encouragement for the preparation of the PIPB were

  5. A block variational procedure for the iterative diagonalization of non-Hermitian random-phase approximation matrices.

    Science.gov (United States)

    Rocca, Dario; Bai, Zhaojun; Li, Ren-Cang; Galli, Giulia

    2012-01-21

    We present a technique for the iterative diagonalization of random-phase approximation (RPA) matrices, which are encountered in the framework of time-dependent density-functional theory (TDDFT) and the Bethe-Salpeter equation. The non-Hermitian character of these matrices does not permit a straightforward application of standard iterative techniques used, i.e., for the diagonalization of ground state Hamiltonians. We first introduce a new block variational principle for RPA matrices. We then develop an algorithm for the simultaneous calculation of multiple eigenvalues and eigenvectors, with convergence and stability properties similar to techniques used to iteratively diagonalize Hermitian matrices. The algorithm is validated for simple systems (Na(2) and Na(4)) and then used to compute multiple low-lying TDDFT excitation energies of the benzene molecule. © 2012 American Institute of Physics

  6. Newton iterative methods for large scale nonlinear systems

    Energy Technology Data Exchange (ETDEWEB)

    Walker, H.F.; Turner, K.

    1993-01-01

    Objective is to develop robust, efficient Newton iterative methods for general large scale problems well suited for discretizations of partial differential equations, integral equations, and other continuous problems. A concomitant objective is to develop improved iterative linear algebra methods. We first outline research on Newton iterative methods and then review work on iterative linear algebra methods. (DLC)

  7. On Controlled Iterated GSM Mappings and Related Operations

    NARCIS (Netherlands)

    Asveld, P.R.J.

    1979-01-01

    In [17] G. Paun studied families of languages generated by iterated gsm mappings, iterated finite substitutions, and iterated homomorphisms. In this note we generalize some results in [17], and we discuss the relation between iterated finite substitutions (homomorphisms) and (deterministic) tabled

  8. On Controlled Iterated GSM Mappings and Related Operations

    NARCIS (Netherlands)

    Asveld, P.R.J.

    1980-01-01

    In [17] G. Paun studied families of languages generated by iterated gsm mappings, iterated finite substitutions, and iterated homomorphisms. In this note we generalize some results in [17], and we discuss the relation between iterated finite substitutions (homomorphisms) and (deterministic) tabled

  9. Convergence analysis of two-phase methods for approximating the Edgeworth-Pareto hull in nonlinear multicriteria optimization problems

    Science.gov (United States)

    Berezkin, V. E.; Kamenev, G. K.

    2012-06-01

    The convergence of two-phase methods for approximating the Edgeworth-Pareto hull (EPH) in nonlinear multicriteria optimization problems is analyzed. The methods are based on the iterative supplement of the finite set of feasible criteria vectors (approximation basis) whose EPH approximates the desired set. A feature of two-phase methods is that the criteria images of randomly generated points of the decision space approach the Pareto frontier via local optimization of adaptively chosen convolutions of criteria. The convergence of two-phase methods is proved for both an abstract form of the algorithm and for a two-phase method based on the Germeier convolution.

  10. Increasing dominance of IT in ICT convergence

    DEFF Research Database (Denmark)

    Henten, Anders; Tadayoni, Reza

    The aim of the paper is to examine the increasing dominance of IT companies in the converging ICT industry and, on the basis of this development, to contribute to extending the theoretical understanding of market and industry convergence in the ICT area.......The aim of the paper is to examine the increasing dominance of IT companies in the converging ICT industry and, on the basis of this development, to contribute to extending the theoretical understanding of market and industry convergence in the ICT area....

  11. Generalized Mann Iterations for Approximating Fixed Points of a Family of Hemicontractions

    Directory of Open Access Journals (Sweden)

    Jin Liang

    2008-06-01

    Full Text Available This paper concerns common fixed points for a finite family of hemicontractions or a finite family of strict pseudocontractions on uniformly convex Banach spaces. By introducing a new iteration process with error term, we obtain sufficient and necessary conditions, as well as sufficient conditions, for the existence of a fixed point. As one will see, we derive these strong convergence theorems in uniformly convex Banach spaces and without any requirement of the compactness on the domain of the mapping. The results given in this paper extend some previous theorems.

  12. Multipoint Iterative Methods for Finding All the Simple Zeros in an Interval

    Directory of Open Access Journals (Sweden)

    T. Lotfi

    2014-01-01

    Full Text Available Two new families of multipoint without memory iterative methods with eighth- and sixteenth-orders are constructed using the symbolic software Mathematica. The key idea in constructing such methods is based on producing some generic suitable functions to reduce the functional evaluations and increase the order of convergence along the computational efficiency. Again by applying Mathematica, we design a hybrid algorithm to capture all the simple real solutions of nonlinear equations in an interval. The application of the new schemes in producing fractal pictures is also furnished.

  13. Dhage Iteration Method for Approximating Positive Solutions of PBVPs of Nonlinear Quadratic Differential Equations with Maxima

    Directory of Open Access Journals (Sweden)

    Shyam B. Dhage

    2016-03-01

    Full Text Available In this paper authors prove the existence as well as approximation of the positive solutions for a periodic boundary value problem of first order ordinary nonlinear quadratic differential equations with maxima. An algorithm for the solutions is developed and it is shown that certain sequence of successive approximations converges monotonically to the positive solution of considered quadratic differential equations under some suitable mixed hybrid conditions. Our results rely on the Dhage iteration principle embodied in a recent hybrid fixed point theorem of Dhage (2014. A numerical example is also provided to illustrate the hypotheses and abstract theory developed in this paper.

  14. Solving the Fractional Rosenau-Hyman Equation via Variational Iteration Method and Homotopy Perturbation Method

    Directory of Open Access Journals (Sweden)

    R. Yulita Molliq

    2012-01-01

    Full Text Available In this study, fractional Rosenau-Hynam equations is considered. We implement relatively new analytical techniques, the variational iteration method and the homotopy perturbation method, for solving this equation. The fractional derivatives are described in the Caputo sense. The two methods in applied mathematics can be used as alternative methods for obtaining analytic and approximate solutions for fractional Rosenau-Hynam equations. In these schemes, the solution takes the form of a convergent series with easily computable components. The present methods perform extremely well in terms of efficiency and simplicity.

  15. Variational Iteration Method for Volterra Functional Integrodifferential Equations with Vanishing Linear Delays

    Directory of Open Access Journals (Sweden)

    Ali Konuralp

    2014-01-01

    Full Text Available Application process of variational iteration method is presented in order to solve the Volterra functional integrodifferential equations which have multi terms and vanishing delays where the delay function θ(t vanishes inside the integral limits such that θ(t=qt for 0converging to the exact solutions or the exact solutions of three test problems are obtained by using this presented process. The numerical solutions and the absolute errors are shown in figures and tables.

  16. Iterative Reproducing Kernel Method for Solving Second-Order Integrodifferential Equations of Fredholm Type

    Directory of Open Access Journals (Sweden)

    Iryna Komashynska

    2014-01-01

    Full Text Available We present an efficient iterative method for solving a class of nonlinear second-order Fredholm integrodifferential equations associated with different boundary conditions. A simple algorithm is given to obtain the approximate solutions for this type of equations based on the reproducing kernel space method. The solution obtained by the method takes form of a convergent series with easily computable components. Furthermore, the error of the approximate solution is monotone decreasing with the increasing of nodal points. The reliability and efficiency of the proposed algorithm are demonstrated by some numerical experiments.

  17. Two Efficient Derivative-Free Iterative Methods for Solving Nonlinear Systems

    Directory of Open Access Journals (Sweden)

    Xiaofeng Wang

    2016-02-01

    Full Text Available In this work, two multi-step derivative-free iterative methods are presented for solving system of nonlinear equations. The new methods have high computational efficiency and low computational cost. The order of convergence of the new methods is proved by a development of an inverse first-order divided difference operator. The computational efficiency is compared with the existing methods. Numerical experiments support the theoretical results. Experimental results show that the new methods remarkably reduce the computing time in the process of high-precision computing.

  18. Iterative Algorithm for Solving a Class of Quaternion Matrix Equation over the Generalized (P,Q-Reflexive Matrices

    Directory of Open Access Journals (Sweden)

    Ning Li

    2013-01-01

    Full Text Available The matrix equation ∑l=1uAlXBl+∑s=1vCsXTDs=F, which includes some frequently investigated matrix equations as its special cases, plays important roles in the system theory. In this paper, we propose an iterative algorithm for solving the quaternion matrix equation ∑l=1uAlXBl+∑s=1vCsXTDs=F over generalized (P,Q-reflexive matrices. The proposed iterative algorithm automatically determines the solvability of the quaternion matrix equation over generalized (P,Q-reflexive matrices. When the matrix equation is consistent over generalized (P,Q-reflexive matrices, the sequence {X(k} generated by the introduced algorithm converges to a generalized (P,Q-reflexive solution of the quaternion matrix equation. And the sequence {X(k} converges to the least Frobenius norm generalized (P,Q-reflexive solution of the quaternion matrix equation when an appropriate initial iterative matrix is chosen. Furthermore, the optimal approximate generalized (P,Q-reflexive solution for a given generalized (P,Q-reflexive matrix X0 can be derived. The numerical results indicate that the iterative algorithm is quite efficient.

  19. Adaptive fractional-order total variation image restoration with split Bregman iteration.

    Science.gov (United States)

    Li, Dazi; Tian, Xiangyi; Jin, Qibing; Hirasawa, Kotaro

    2017-09-08

    Alleviating the staircase artifacts for variation method and adjusting the regularization parameters adaptively with the characteristics of different regions are two main issues in image restoration regularization process. An adaptive fractional-order total variation l1 regularization (AFOTV-l1) model is proposed, which is resolved by using split Bregman iteration algorithm (SBI) for image estimation. An improved fractional-order differential kernel mask (IFODKM) with an extended degree of freedom (DOF) is proposed, which can preserve more image details and effectively avoid the staircase artifact. With the SBI algorithm adopted in this paper, fast convergence and small errors are achieved. Moreover, a novel regularization parameters adaptive strategy is given. Experimental results, by using the standard image library (SIL), the lung imaging database consortium and image database resource initiative (LIDC-IDRI), demonstrate that the proposed methods have better approximation, robustness and fast convergence performances for image restoration. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

  20. Study of neutron spectrometers for ITER

    Energy Technology Data Exchange (ETDEWEB)

    Kaellne, Jan

    2005-11-15

    A review is presented of the developments in the field of neutron emission spectrometry (NES) which is of relevance for identifying the role of NES diagnostics on ITER and selecting suitable instrumentation. Neutron spectrometers will be part of the ITER neutron diagnostic complement and this study makes a special effort to examine which performance characteristics the spectrometers should possess to provide the best burning plasma diagnostic information together with neutron cameras and neutron yield monitors. The performance of NES diagnostics is coupled to how much interface space can be provided which has lead to an interest to find compact instruments and their NES capabilities. This study assesses all known spectrometer types of potential interest for ITER and makes a ranking of their performance (as demonstrated or projected), which, in turn, are compared with ITER measurement requirements as a reference; the ratio of diagnostic performance to interface cost for different spectrometers is also discussed for different spectrometer types. The overall result of the study is an assessment of which diagnostic functions neutron measurements can provide in burning plasma fusion experiments on ITER and the role that NES can play depending on the category of instrument installed. Of special note is the result that much higher quality diagnostic information can be obtained from neutron measurements with total yield monitors, profile flux cameras and spectrometers when the synergy in the data is considered in the analysis and interpretation.

  1. Societal response to nanotechnology: converging technologies–converging societal response research?

    NARCIS (Netherlands)

    Ronteltap, A.; Fischer, A.R.H.; Tobi, H.

    2011-01-01

    Nanotechnology is an emerging technology particularly vulnerable to societal unrest, which may hinder its further development. With the increasing convergence of several technological domains in the field of nanotechnology, so too could convergence of social science methods help to anticipate

  2. Re-starting an Arnoldi iteration

    Energy Technology Data Exchange (ETDEWEB)

    Lehoucq, R.B. [Argonne National Lab., IL (United States)

    1996-12-31

    The Arnoldi iteration is an efficient procedure for approximating a subset of the eigensystem of a large sparse n x n matrix A. The iteration produces a partial orthogonal reduction of A into an upper Hessenberg matrix H{sub m} of order m. The eigenvalues of this small matrix H{sub m} are used to approximate a subset of the eigenvalues of the large matrix A. The eigenvalues of H{sub m} improve as estimates to those of A as m increases. Unfortunately, so does the cost and storage of the reduction. The idea of re-starting the Arnoldi iteration is motivated by the prohibitive cost associated with building a large factorization.

  3. SPARSE ELECTROMAGNETIC IMAGING USING NONLINEAR LANDWEBER ITERATIONS

    KAUST Repository

    Desmal, Abdulla

    2015-07-29

    A scheme for efficiently solving the nonlinear electromagnetic inverse scattering problem on sparse investigation domains is described. The proposed scheme reconstructs the (complex) dielectric permittivity of an investigation domain from fields measured away from the domain itself. Least-squares data misfit between the computed scattered fields, which are expressed as a nonlinear function of the permittivity, and the measured fields is constrained by the L0/L1-norm of the solution. The resulting minimization problem is solved using nonlinear Landweber iterations, where at each iteration a thresholding function is applied to enforce the sparseness-promoting L0/L1-norm constraint. The thresholded nonlinear Landweber iterations are applied to several two-dimensional problems, where the ``measured\\'\\' fields are synthetically generated or obtained from actual experiments. These numerical experiments demonstrate the accuracy, efficiency, and applicability of the proposed scheme in reconstructing sparse profiles with high permittivity values.

  4. Burning plasmas in ITER for energy source

    Energy Technology Data Exchange (ETDEWEB)

    Inoue, Nobuyuki [Atomic Energy Commission, Tokyo (Japan)

    2002-10-01

    Fusion research and development has two aspects. One is an academic research on science and technology, i.e., discovery and understanding of unexpected phenomena and, development of innovative technology, respectively. The other is energy source development to realize fusion as a viable energy future. Fusion research has been made remarkable progress in the past several decades, and ITER will soon realize burning plasma that is essential for both academic research and energy development. With ITER, scientific research on unknown phenomena such as self-organization of the plasma in burning state will become possible and it contributes to create a variety of academic outcome. Fusion researchers will have a responsibility to generate actual energy, and electricity generation immediately after the success of burning plasma control experiment in ITER is the next important step that has to be discussed seriously. (author)

  5. Ecomorphological convergence of cave communities.

    Science.gov (United States)

    Trontelj, Peter; Blejec, Andrej; Fišer, Cene

    2012-12-01

    Extreme selective environments are commonly believed to funnel evolution toward a few predictable outcomes. Caves are well-known extreme environments with characteristically adapted faunas that are similar in appearance, physiology, and behavior all over the world, even if not closely related. Morphological diversity between closely related cave species has been explained by difference in time since colonization and different ecological influence from the surface. Here, we tested a more classical hypothesis: morphological diversity is niche-based, and different morphologies reflect properties of microhabitats within caves. We analyzed seven communities with altogether 30 species of the subterranean amphipod (crustacean) genus Niphargus using multivariate morphometrics, multinomial logit models cross-validation, and phylogenetic reconstruction. Species clustered into four distinct ecomorph classes-small pore, cave stream, cave lake, and lake giants-associated with specific cave microhabitats and of multiple independent phylogenetic origins. Traits commonly regarded as adaptations to caves, such as antenna length, were shown to be related to microhabitat parameters, such as flow velocity. These results demonstrate that under the selection pressure of extreme environment, the ecomorphological structure of communities can converge. Thus, morphological diversity does not result from adaptive response to temporal and ecological gradients, but from fine-level niche partitioning. © 2012 The Author(s). Evolution© 2012 The Society for the Study of Evolution.

  6. Temporal Convergence for Knowledge Management

    Directory of Open Access Journals (Sweden)

    Christopher Phillip Martin

    2008-05-01

    Full Text Available Time and knowledge have tended to be conceptualised in conventional knowledge management systems as either ‘timeless’ recordings of procedures, or time-stamped records of past events and states. The concept of temporal convergence was previously developed to help apply knowledge-management theory to complex military processes such as commander’s intent, shared situation awareness, and self-synchronisation. This paper clarifies the concept and introduces several others in forming a framework to assist discussion and exploration of the types of knowledge required for complex endeavours, such as warfighting, characterised by opposition and uncertainty. The approach is grounded in a pragmatist philosophy and constructivist epistemology. Argument proceeds along mathematical lines from a basis that the types of knowledge most valuable to goal-directed agents in uncertain environments can be modelled as directed graph topologies. The framework is shown to be useful in describing and reasoning about the knowledge requirements and prerequisites for distributed decision-making through the sharing of situational knowledge and common intentions, with practical application to the planning and execution of operations. To the designers of knowledge management systems seeking to address this space, it presents a challenge that cannot be addressed merely by construction, storage, search and retrieval of documents and records pertaining to the past.

  7. Statistical Convergence of Double Sequences of Order

    Directory of Open Access Journals (Sweden)

    R. Çolak

    2013-01-01

    Full Text Available We intend to make a new approach and introduce the concepts of statistical convergence of order and strongly -Cesàro summability of order for double sequences of complex or real numbers. Also, some relations between the statistical convergence of order and strong -Cesàro summability of order are given.

  8. Beyond Brainstorming: Exploring Convergence in Teams

    DEFF Research Database (Denmark)

    Seeber, Isabella; de Vreede, Gert-Jan; Maier, Ronald

    2017-01-01

    Collaborative brainstorming is often followed by a convergence activity where teams extract the most promising ideas on a useful level of detail from the brainstorming results. Contrary to the wealth of research on electronic brainstorming, there is a dearth of research on convergence. We used...

  9. Explaining convergence of oecd welfare states

    DEFF Research Database (Denmark)

    Schmitt, C.; Starke, Peter

    2011-01-01

    of conditional convergence helps to both better describe and explain the phenomenon. By applying error correction models, we examine conditional convergence of various types of social expenditure in 21 OECD countries between 1980 and 2005. Our empirical findings go beyond the existing literature in two respects...

  10. Challenges and status of ITER conductor production

    Science.gov (United States)

    Devred, A.; Backbier, I.; Bessette, D.; Bevillard, G.; Gardner, M.; Jong, C.; Lillaz, F.; Mitchell, N.; Romano, G.; Vostner, A.

    2014-04-01

    Taking the relay of the large Hadron collider (LHC) at CERN, ITER has become the largest project in applied superconductivity. In addition to its technical complexity, ITER is also a management challenge as it relies on an unprecedented collaboration of seven partners, representing more than half of the world population, who provide 90% of the components as in-kind contributions. The ITER magnet system is one of the most sophisticated superconducting magnet systems ever designed, with an enormous stored energy of 51 GJ. It involves six of the ITER partners. The coils are wound from cable-in-conduit conductors (CICCs) made up of superconducting and copper strands assembled into a multistage cable, inserted into a conduit of butt-welded austenitic steel tubes. The conductors for the toroidal field (TF) and central solenoid (CS) coils require about 600 t of Nb3Sn strands while the poloidal field (PF) and correction coil (CC) and busbar conductors need around 275 t of Nb-Ti strands. The required amount of Nb3Sn strands far exceeds pre-existing industrial capacity and has called for a significant worldwide production scale up. The TF conductors are the first ITER components to be mass produced and are more than 50% complete. During its life time, the CS coil will have to sustain several tens of thousands of electromagnetic (EM) cycles to high current and field conditions, way beyond anything a large Nb3Sn coil has ever experienced. Following a comprehensive R&D program, a technical solution has been found for the CS conductor, which ensures stable performance versus EM and thermal cycling. Productions of PF, CC and busbar conductors are also underway. After an introduction to the ITER project and magnet system, we describe the ITER conductor procurements and the quality assurance/quality control programs that have been implemented to ensure production uniformity across numerous suppliers. Then, we provide examples of technical challenges that have been encountered and

  11. Rational Verification in Iterated Electric Boolean Games

    Directory of Open Access Journals (Sweden)

    Youssouf Oualhadj

    2016-07-01

    Full Text Available Electric boolean games are compact representations of games where the players have qualitative objectives described by LTL formulae and have limited resources. We study the complexity of several decision problems related to the analysis of rationality in electric boolean games with LTL objectives. In particular, we report that the problem of deciding whether a profile is a Nash equilibrium in an iterated electric boolean game is no harder than in iterated boolean games without resource bounds. We show that it is a PSPACE-complete problem. As a corollary, we obtain that both rational elimination and rational construction of Nash equilibria by a supervising authority are PSPACE-complete problems.

  12. PENENTUAN ANGGOTA ASRAMA DENGAN ITERATIVE DICHOMOTISER THREE

    Directory of Open Access Journals (Sweden)

    Muhammad Hasan

    2016-04-01

    Full Text Available Determination of the members of the boarding will done through assessment the criteria for determining the status of the members of the Sorority. This determination is usually consultation between members according to their respective conscience. Therefore, determination of the members of the boarding will done using Iterative Dichomotiser Three by displaying the root criteria so that it becomes a reference node in the assessment of the Member. Determination of the Member of a dormitory with Iterative Dichomotiser Three produce entropy values i.e. (Kitchen 0.121596288; Hall 0.091945213; Bathroom 0.114734253; Living room 0.159141033; Terrace 0.271219296; Manners 0.228396102; Religious 0.217768967; sensitivity 0.339842104; and the money base of 0. The results of calculation of the information gain is generating decision tree with nodes of the criteria each branch. Based on the results that sensitivity of root and the money Base into base of decision tree with reference to the value of the information gain. The result also shows determination of the predictive reports members of the dormitory with Iterative Dichomotiser Three Keywords: Members of the boarding, Iterative Dichomotiser Three, Entropy, lnformation Gain, Decision Tree Penentuan anggota asrama dilakukan melalui penilaian kriteria-kriteria untuk menentukan status anggota asrama. Penentuan ini biasanya melalui musyawarah antar anggota sesuai hati nurani masing-masing. Oleh karena itu, penentuan anggota asrama dilakukan menggunakan Iterative Dichomotiser Three dengan menampilkan root kriteria sehingga menjadi acuan node dalam penilaian anggota asrama. Penentuan anggota asrama dengan Iterative Dichomotiser Three menghasilkan nilai entropy yaitu 0,89357112 dan nilai information gain dari 9 kriteria penilaian anggota asrama yaitu (Dapur 0,121596288; Aula 0,091945213; Kamar Mandi 0,114734253; Ruang Tamu 0,159141033; Teras 0,271219296; Tata Krama 0,228396102; Keagamaan 0,217768967; Kepekaan 0

  13. Iterated learning and the evolution of language.

    Science.gov (United States)

    Kirby, Simon; Griffiths, Tom; Smith, Kenny

    2014-10-01

    Iterated learning describes the process whereby an individual learns their behaviour by exposure to another individual's behaviour, who themselves learnt it in the same way. It can be seen as a key mechanism of cultural evolution. We review various methods for understanding how behaviour is shaped by the iterated learning process: computational agent-based simulations; mathematical modelling; and laboratory experiments in humans and non-human animals. We show how this framework has been used to explain the origins of structure in language, and argue that cultural evolution must be considered alongside biological evolution in explanations of language origins. Copyright © 2014 Elsevier Ltd. All rights reserved.

  14. Geometric Aspects of Iterated Matrix Multiplication

    DEFF Research Database (Denmark)

    Gesmundo, Fulvio

    2016-01-01

    This paper studies geometric properties of the Iterated Matrix Multiplication polynomial and the hypersurface that it defines. We focus on geometric aspects that may be relevant for complexity theory such as the symmetry group of the polynomial, the dual variety and the Jacobian loci of the hyper......This paper studies geometric properties of the Iterated Matrix Multiplication polynomial and the hypersurface that it defines. We focus on geometric aspects that may be relevant for complexity theory such as the symmetry group of the polynomial, the dual variety and the Jacobian loci...

  15. Blind Source Separation Based on Fast-Convergence Algorithm Using ICA and Beamforming for Real Convolutive Mixture

    OpenAIRE

    Hiroshi Saruwatari; Toshiya Kawamura; Katsuyuki Sawai; Atsunobu Kamimura; Masao Sakata

    2002-01-01

    We propose a new algorithm for blind source separation (BSS), in which independent component analysis (ICA) and beamforming are combined to resolve the low-convergence problem through optimization in ICA. The proposed method consists of the following three parts: (1) frequency-domain ICA with direction-of-arrival (DOA) estimation, (2) null beamforming based on the estimated DOA, and (3) integration of (1) and (2) based on the algorithm diversity in both iteration and frequency domain. The inv...

  16. Diffusion Patterns in Convergence among High-Technology Industries: A Co-Occurrence-Based Analysis of Newspaper Article Data

    Directory of Open Access Journals (Sweden)

    Hyeokseong Lee

    2016-10-01

    Full Text Available Firms in high-technology industries have faced great technological and market uncertainty and volatility in the past few decades. In order to be competitive and sustainable in this environment, firms have been pursuing technological innovation, product differentiation, vertical integration, and alliances, which eventually drive industry convergence, defined as the process of blurring boundaries between previously distinct industries. Although industry convergence has greatly affected industrial structure and the economy, little research has investigated this phenomenon, especially its diffusion patterns; thus, it is still unclear which industries are converging more rapidly or have a higher potential for convergence. This paper explores these issues by investigating industry convergence in U.S. high-technology industries, using a large set of newspaper articles from 1987 to 2012. We perform a co-occurrence-based analysis to obtain information on industry convergence and estimate its diffusion patterns using an internal-influence logistic model. We find heterogeneous diffusion patterns, depending on convergent-industry pairs and their wide dispersion. In addition, we find that the potential degree of industry convergence is significantly negatively associated with its growth rate, which indicates that a great deal of time will be required for industry convergence between high-technology industries with this high potential to achieve a high degree of convergence.

  17. Robust Adaptive LCMV Beamformer Based On An Iterative Suboptimal Solution

    Directory of Open Access Journals (Sweden)

    Xiansheng Guo

    2015-06-01

    Full Text Available The main drawback of closed-form solution of linearly constrained minimum variance (CF-LCMV beamformer is the dilemma of acquiring long observation time for stable covariance matrix estimates and short observation time to track dynamic behavior of targets, leading to poor performance including low signal-noise-ratio (SNR, low jammer-to-noise ratios (JNRs and small number of snapshots. Additionally, CF-LCMV suffers from heavy computational burden which mainly comes from two matrix inverse operations for computing the optimal weight vector. In this paper, we derive a low-complexity Robust Adaptive LCMV beamformer based on an Iterative Suboptimal solution (RAIS-LCMV using conjugate gradient (CG optimization method. The merit of our proposed method is threefold. Firstly, RAIS-LCMV beamformer can reduce the complexity of CF-LCMV remarkably. Secondly, RAIS-LCMV beamformer can adjust output adaptively based on measurement and its convergence speed is comparable. Finally, RAIS-LCMV algorithm has robust performance against low SNR, JNRs, and small number of snapshots. Simulation results demonstrate the superiority of our proposed algorithms.

  18. Convergence Guaranteed Nonlinear Constraint Model Predictive Control via I/O Linearization

    Directory of Open Access Journals (Sweden)

    Xiaobing Kong

    2013-01-01

    Full Text Available Constituting reliable optimal solution is a key issue for the nonlinear constrained model predictive control. Input-output feedback linearization is a popular method in nonlinear control. By using an input-output feedback linearizing controller, the original linear input constraints will change to nonlinear constraints and sometimes the constraints are state dependent. This paper presents an iterative quadratic program (IQP routine on the continuous-time system. To guarantee its convergence, another iterative approach is incorporated. The proposed algorithm can reach a feasible solution over the entire prediction horizon. Simulation results on both a numerical example and the continuous stirred tank reactors (CSTR demonstrate the effectiveness of the proposed method.

  19. Correlation Analysis between Nominal and Real Convergence. The Romanian Case

    Directory of Open Access Journals (Sweden)

    Marius-Corneliu Marinas

    2006-05-01

    Full Text Available This study aims to analyze the sources of the correlation between the nominal and real convergence, as well as the impact of the macroeconomic politics on it. The perspective of Euro adoption will impose stricter management of monetary and budgetary politics, which will affect negatively the catching up process of the economic delays given the lack of higher economic flexibility. This enables a more rapid adjustment of the economy to some persistent shocks as a result of applying growth aggregate supply politics.

  20. Correlation Analysis between Nominal and Real Convergence. The Romanian Case

    Directory of Open Access Journals (Sweden)

    Marius-Corneliu Marinas

    2006-03-01

    Full Text Available This study aims to analyze the sources of the correlation between the nominal and real convergence, as well as the impact of the macroeconomic politics on it. The perspective of Euro adoption will impose stricter management of monetary and budgetary politics, which will affect negatively the catching up process of the economic delays given the lack of higher economic flexibility. This enables a more rapid adjustment of the economy to some persistent shocks as a result of applying growth aggregate supply politics.

  1. An iteratively adaptive multi-scale finite element method for elliptic PDEs with rough coefficients

    Science.gov (United States)

    Hou, Thomas Y.; Hwang, Feng-Nan; Liu, Pengfei; Yao, Chien-Chou

    2017-05-01

    We propose an iteratively adaptive Multi-scale Finite Element Method (MsFEM) for elliptic PDEs with rough coefficients. The choice of the local boundary conditions for the multi-sale basis functions determines the accuracy of the MsFEM numerical solution, and one needs to incorporate the global information of the elliptic equation into the local boundary conditions of the multi-scale basis functions to recover the underlying fine-mesh solution of the equation. In our proposed iteratively adaptive method, we achieve this global-to-local information transfer through the combination of coarse-mesh solving using adaptive multi-scale basis functions and fine-mesh smoothing operations. In each iteration step, we first update the multi-scale basis functions based on the approximate numerical solutions of the previous iteration steps, and obtain the coarse-mesh approximate solution using a Galerkin projection. Then we apply several steps of smoothing operations to the coarse-mesh approximate solution on the underlying fine mesh to get the updated approximate numerical solution. The proposed algorithm can be viewed as a nonlinear two-level multi-grid method with the restriction and prolongation operators adapted to the approximate numerical solutions of the previous iteration steps. Convergence analysis of the proposed algorithm is carried out under the framework of two-level multi-grid method, and the harmonic coordinates are employed to establish the approximation property of the adaptive multi-scale basis functions. We demonstrate the efficiency of our proposed multi-scale methods through several numerical examples including a multi-scale coefficient problem, a high-contrast interface problem, and a convection-dominated diffusion problem.

  2. A sequential partly iterative approach for multicomponent reactive transport with CORE2D

    Energy Technology Data Exchange (ETDEWEB)

    Samper, J.; Xu, T.; Yang, C.

    2008-11-01

    . Numerical analyses performed with synthetic examples confirm that these modifications improve the efficiency and convergence of the iterative algorithm.

  3. On Unification of the Strong Convergence Theorems for a Finite Family of Total Asymptotically Nonexpansive Mappings in Banach Spaces

    Directory of Open Access Journals (Sweden)

    Farrukh Mukhamedov

    2012-01-01

    Full Text Available We unify all known iterative methods by introducing a new explicit iterative scheme for approximation of common fixed points of finite families of total asymptotically I-nonexpansive mappings. Note that such a scheme contains a particular case of the method introduced by (C. E. Chidume and E. U. Ofoedu, 2009. We construct examples of total asymptotically nonexpansive mappings which are not asymptotically nonexpansive. Note that no such kind of examples were known in the literature. We prove the strong convergence theorems for such iterative process to a common fixed point of the finite family of total asymptotically I-nonexpansive and total asymptotically nonexpansive mappings, defined on a nonempty closed-convex subset of uniformly convex Banach spaces. Moreover, our results extend and unify all known results.

  4. On the convergence of finite state mean-field games through Γ-convergence

    KAUST Repository

    Ferreira, Rita C.

    2014-10-01

    In this study, we consider the long-term convergence (trend toward an equilibrium) of finite state mean-field games using Γ-convergence. Our techniques are based on the observation that an important class of mean-field games can be viewed as the Euler-Lagrange equation of a suitable functional. Therefore, using a scaling argument, one can convert a long-term convergence problem into a Γ-convergence problem. Our results generalize previous results related to long-term convergence for finite state problems. © 2014 Elsevier Inc.

  5. Data Convergence - An Australian Perspective

    Science.gov (United States)

    Allen, S. S.; Howell, B.

    2012-12-01

    Coupled numerical physical, biogeochemical and sediment models are increasingly being used as integrators to help understand the cumulative or far field effects of change in the coastal environment. This reliance on modeling has forced observations to be delivered as data streams ingestible by modeling frameworks. This has made it easier to create near real-time or forecasting models than to try to recreate the past, and has lead in turn to the conversion of historical data into data streams to allow them to be ingested by the same frameworks. The model and observation frameworks under development within Australia's Commonwealth and Industrial Research Organisation (CSIRO) are now feeding into the Australian Ocean Data Network's (AODN's) MARine Virtual Laboratory (MARVL) . The sensor, or data stream, brokering solution is centred around the "message" and all data flowing through the gateway is wrapped as a message. Messages consist of a topic and a data object and their routing through the gateway to pre-processors and listeners is determined by the topic. The Sensor Message Gateway (SMG) method is allowing data from different sensors measuring the same thing but with different temporal resolutions, units or spatial coverage to be ingested or visualized seamlessly. At the same time the model output as a virtual sensor is being explored, this again being enabled by the SMG. It is only for two way communications with sensor that rigorous adherence to standards is needed, by accepting existing data in less than ideal formats, but exposing them though the SMG we can move a step closer to the Internet Of Things by creating an Internet of Industries where each vested interest can continue with business as usual, contribute to data convergence and adopt more open standards when investment seems appropriate to that sector or business.Architecture Overview

  6. An incremental-iterative method for modeling damage evolution in voxel-based microstructure models

    Science.gov (United States)

    Zhu, Qi-Zhi; Yvonnet, Julien

    2015-02-01

    Numerical methods motivated by rapid advances in image processing techniques have been intensively developed during recent years and increasingly applied to simulate heterogeneous materials with complex microstructure. The present work aims at elaborating an incremental-iterative numerical method for voxel-based modeling of damage evolution in quasi-brittle microstructures. The iterative scheme based on the Lippmann-Schwinger equation in the real space domain (Yvonnet, in Int J Numer Methods Eng 92:178-205, 2012) is first cast into an incremental form so as to implement nonlinear material models efficiently. In the proposed scheme, local strain increments at material grid points are computed iteratively by a mapping operation through a transformation array, while local stresses are determined using a constitutive model that accounts for material degradation by damage. For validation, benchmark studies and numerical simulations using microtomographic data of concrete are performed. For each test, numerical predictions by the incremental-iterative scheme and the finite element method, respectively, are presented and compared for both global responses and local damage distributions. It is emphasized that the proposed incremental-iterative formulation can be straightforwardly applied in the framework of other Lippmann-Schwinger equation-based schemes, like the fast Fourier transform method.

  7. Genome-Wide Convergence during Evolution of Mangroves from Woody Plants.

    Science.gov (United States)

    Xu, Shaohua; He, Ziwen; Guo, Zixiao; Zhang, Zhang; Wyckoff, Gerald J; Greenberg, Anthony; Wu, Chung-I; Shi, Suhua

    2017-04-01

    When living organisms independently invade a new environment, the evolution of similar phenotypic traits is often observed. An interesting but contentious issue is whether the underlying molecular biology also converges in the new habitat. Independent invasions of tropical intertidal zones by woody plants, collectively referred to as mangrove trees, represent some dramatic examples. The high salinity, hypoxia, and other stressors in the new habitat might have affected both genomic features and protein structures. Here, we developed a new method for detecting convergence at conservative Sites (CCS) and applied it to the genomic sequences of mangroves. In simulations, the CCS method drastically reduces random convergence at rapidly evolving sites as well as falsely inferred convergence caused by the misinferences of the ancestral character. In mangrove genomes, we estimated ∼400 genes that have experienced convergence over the background level of convergence in the nonmangrove relatives. The convergent genes are enriched in pathways related to stress response and embryo development, which could be important for mangroves' adaptation to the new habitat. © The Author 2017. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  8. Interpolation and Iteration for Nonlinear Filters

    Energy Technology Data Exchange (ETDEWEB)

    Chorin, Alexandre J. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States); Tu, Xuemin [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States)

    2009-10-16

    We present a general form of the iteration and interpolation process used in implicit particle filters. Implicit filters are based on a pseudo-Gaussian representation of posterior densities, and are designed to focus the particle paths so as to reduce the number of particles needed in nonlinear data assimilation. Examples are given.

  9. On iterative procedures of asymptotic inference

    NARCIS (Netherlands)

    K.O. Dzhaparidze (Kacha)

    1983-01-01

    textabstractAbstract  An informal discussion is given on performing an unconstrained maximization or solving non‐linear equations of statistics by iterative methods with the quadratic termination property. It is shown that if a miximized function, e.g. likelihood, is asymptotically quadratic, then

  10. Iterative Reconstruction for Differential Phase Contrast Imaging

    NARCIS (Netherlands)

    Koehler, T.; Brendel, B.; Roessl, E.

    2011-01-01

    Purpose: The purpose of this work is to combine two areas of active research in tomographic x-ray imaging. The first one is the use of iterative reconstruction techniques. The second one is differential phase contrast imaging (DPCI). Method: We derive an SPS type maximum likelihood (ML)

  11. A Fibonacci-like Iterated Nonlinear Map

    NARCIS (Netherlands)

    Asveld, P.R.J.

    1989-01-01

    We study a second-order Fibonacci-like iterated nonlinear map that contains two parameters of which one is kept fixed, whereas the other one varies from 0 to 1. This gives rise to some complicated behavior which is displayed in a few interesting pictures.

  12. Evaluating ITER remote handling middleware concepts

    NARCIS (Netherlands)

    Koning, J. F.; Heemskerk, C. J. M.; Schoen, P.; Smedinga, D.; Boode, A. H.; Hamilton, D. T.

    2013-01-01

    Remote maintenance activities in ITER will be performed by a unique set of hardware systems, supported by an extensive software kit. A layer of middleware will manage and control a complex set of interconnections between teams of operators, hardware devices in various operating theatres, and

  13. Codimension 2 Bifurcations of Iterated Maps

    NARCIS (Netherlands)

    Meijer, H.G.E.

    2006-01-01

    This thesis investigates some properties of discrete-time dynamical systems, generated by iterated maps. In particular we study local bifurcations where two parameters are essential to describe the dynamical properties of the system near a fixed point or a cycle. There are 11 such cases. Knowledge

  14. ITER PF6 double pancakes winding line

    Energy Technology Data Exchange (ETDEWEB)

    Du, Shuangsong [Institute of Plasma Physics, Chinese Academy of Science, Hefei (China); University of Science and Technology of China, Hefei (China); Wen, Wei, E-mail: wenwei@ipp.ac.cn [Institute of Plasma Physics, Chinese Academy of Science, Hefei (China); Chen, Jin; Wu, Weiyue; Song, Yuntao; Shen, Guang [Institute of Plasma Physics, Chinese Academy of Science, Hefei (China)

    2017-03-15

    Highlights: • ITER PF6 double pancakes “two-in-hand” winding line layout and main parameters were introduced, main winding sequences were also included. • Main features of each winding unit include de-spooling unit, straightening unit, sandblasting and cleaning unit, bending unit, turn insulation wrapping head, rotary table and automatic control system were depicted. • PF6 double pancake winding line was commissioned with PF5 empty jacket conductor after the installation and testing of each unit, ±0.5 mm turn positioning and ±2 turn to turn deviations were achieved. - Abstract: The Poloidal Field (PF) coils are one of the main sub-systems of the ITER magnets. The PF6 coil is being manufactured by the Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP) as per the Poloidal Field coils cooperation agreement signed between ASIPP and Fusion for Energy (F4E).The ITER PF6 winding pack is composed by stacking of 9 double pancakes. Each double pancake is wound with a “two-in-hand” configuration. This paper describes the ITER PF6 double pancakes winding line, including layout and main parameters of the winding line, features of main units and the commissioning trial with PF5 empty jacket conductor.

  15. Solving Differential Equations Using Modified Picard Iteration

    Science.gov (United States)

    Robin, W. A.

    2010-01-01

    Many classes of differential equations are shown to be open to solution through a method involving a combination of a direct integration approach with suitably modified Picard iterative procedures. The classes of differential equations considered include typical initial value, boundary value and eigenvalue problems arising in physics and…

  16. Academic Training: The ITER project: technological challenges

    CERN Document Server

    Françoise Benz

    2005-01-01

    2004-2005 ACADEMIC TRAINING PROGRAMME LECTURE SERIES 31 May, 1, 2, 3, June from 11:00 to 12:00 on 31 May and 2, 3, June. From 10:00 to 12:00 on 1 June - Main Auditorium, bldg. 500 The ITER project: technological challenges J. LISTER / CRPP-EPFL, Lausanne, CH and P. BRUZZONE / CRPP-EPFL, Zürich, CH The first lecture reminds us of the ITER challenges, presents hard engineering problems, typically due to mechanical forces and thermal loads and identifies where the physics uncertainties play a significant role in the engineering requirements. The second lecture presents soft engineering problems of measuring the plasma parameters, feedback control of the plasma and handling the physics data flow and slow controls data flow from a large experiment like ITER. The last three lectures focus on superconductors for fusion. The third lecture reviews the design criteria and manufacturing methods for 6 milestone-conductors of large fusion devices (T-7, T-15, Tore Supra, LHD, W-7X, ITER). The evolution of the...

  17. Academic Training: The ITER project: technological challenges

    CERN Document Server

    Françoise Benz

    2005-01-01

    2004-2005 ACADEMIC TRAINING PROGRAMME LECTURE SERIES 31 May, 1, 2, 3, June from 11:00 to 12:00 on 31 May and 2, 3, June. From 10:00 to 12:00 on 1 June - Main Auditorium, bldg. 500 The ITER project: technological challenges J. LISTER / CRPP-EPFL, Lausanne and P. BRUZZONE / CRPP-EPFL, Zürich The first lecture reminds us of the ITER challenges, presents hard engineering problems, typically due to mechanical forces and thermal loads and identifies where the physics uncertainties play a significant role in the engineering requirements. The second lecture presents soft engineering problems of measuring the plasma parameters, feedback control of the plasma and handling the physics data flow and slow controls data flow from a large experiment like ITER. The last three lectures focus on superconductors for fusion. The third lecture reviews the design criteria and manufacturing methods for 6 milestone-conductors of large fusion devices (T-7, T-15, Tore Supra, LHD, W-7X, ITER). The evolution of the de...

  18. Activation analysis of ITER blanket first wall

    Energy Technology Data Exchange (ETDEWEB)

    Lopatkin, A.; Muratov, V. [RDIPE (NIKIET), Moscow (Russian Federation)

    1998-09-01

    To analyze the activation of ITER blanket structural components, the authors have prepared the AUCDAS code that calculates changes in nuclide concentrations and radioactivity characteristics during neutron irradiation and during cooling. UCDAS takes into account all neutron reactions and decay types, the prepared library of constants contains nuclear data of nuclides from hydrogen to californium. A comparative analysis of the results as obtained using UCDAS code and the widely known FISPACT code is given. The analysis of decay heat, gas generation and activity of ITER blanket first wall`s structural components was carried out. The beryllium coating, copper alloy and stainless steel were analysed. Calculations were performed for the first plasma burning pulse, 6 months and 1 year of operation in accordance with the ITER scenario. The materials recommended by ITER central team and their Russian analogs were considered: TGR and B1 (beryllium coating), GlidCop AL-25 Ds and Br-MKX (copper alloy), 316LN-IG and 12Cr18Ni10Ti (stainless steel). It has been demonstrated that there is a difference in all of the considered characteristics between the above materials. It is caused by impurities which are present in the materials. The report also considers the accumulation of gases (H, D, T, He{sup 3}, He{sup 4}) in the above materials. Besides, the change in the activity of irradiated materials during the cooling of up to 10{sup 7} years was calculated. (orig.) 7 refs.

  19. Nonconforming finite elements and the Cascade iteration

    NARCIS (Netherlands)

    Stevenson, R.

    1999-01-01

    We derive sucient conditions under which the Cascade iteration applied to nonconforming nite element discretizations yields an optimal solver. Key ingredients are optimal error estimates of such discretizations, which we therefore study in detail. We derive a new, ecient modied Morley nite element

  20. Transmission line studies for ITER compatible reflectometers

    NARCIS (Netherlands)

    Wagner, D.; Kasparek, W.; Gantenbein, G.; Manso, M. E.; Sanchez, J.; Donne, A. J. H.

    1997-01-01

    Corrugated circular transmission lines are considered as high performance, low loss, broadband lines for reflectometry on ITER. These lines are proposed as a possible solution for the equatorial low-field-side system and as a part (receiver-vacuum vessel) of the transmission lines for the high-field

  1. Iterated Differential Forms III: Integral Calculus

    OpenAIRE

    Vinogradov, A.M.; Vitagliano, L.

    2006-01-01

    Basic elements of integral calculus over algebras of iterated differential forms, are presented. In particular, defining complexes for modules of integral forms are described and the corresponding berezinians and complexes of integral forms are computed. Various applications and the integral calculus over the algebra $\\Lambda_{\\infty}$ will be discussed in subsequent notes.

  2. Monotone iterative method for fractional differential equations

    Directory of Open Access Journals (Sweden)

    Zhanbing Bai

    2016-01-01

    Full Text Available In this article, by using the lower and upper solution method, we prove the existence of iterative solutions for a class of fractional initial value problem with non-monotone term $$\\displaylines{ D_{0+}^\\alpha u(t=f(t, u(t, \\quad t \\in (0, h, \\cr t^{1-\\alpha}u(t\\big|_{t=0} = u_0 \

  3. Design and analysis of ITER shield blanket

    Energy Technology Data Exchange (ETDEWEB)

    Ohmori, Junji; Hatano, Toshihisa; Ezato, Kouichiro [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment] [and others

    1998-12-01

    This report includes electromagnetic analyses for ITER shielding blanket modules, fabrication methods for the blanket modules and the back plate, the design and the fabrication methods for port limiter have been investigated. Studies on the runaway electron impact for Be armor have been also performed. (J.P.N.)

  4. Iterated Hardy-type inequalities involving suprema

    Czech Academy of Sciences Publication Activity Database

    Gogatishvili, Amiran; Mustafayev, R.Ch.

    2017-01-01

    Roč. 20, č. 4 (2017), s. 901-927 ISSN 1331-4343 R&D Projects: GA ČR GA13-14743S Institutional support: RVO:67985840 Keywords : quasilinear operators * iterated Hardy inequalities * weights Subject RIV: BA - General Mathematics Impact factor: 0.603, year: 2016 http://files.ele-math.com/preprints/mia-20-57.pdf

  5. Weighted iterated Hardy-type inequalities

    Czech Academy of Sciences Publication Activity Database

    Gogatishvili, Amiran; Mustafayev, R.Ch.

    2017-01-01

    Roč. 20, č. 3 (2017), s. 683-728 ISSN 1331-4343 R&D Projects: GA ČR GA13-14743S Institutional support: RVO:67985840 Keywords : quasilinear operators * iterated Hardy inequalities * weights Subject RIV: BA - General Mathematics Impact factor: 0.603, year: 2016 http://files.ele-math.com/preprints/mia-20-45.pdf

  6. Neutronic analysis for bolometers in ITER

    Energy Technology Data Exchange (ETDEWEB)

    Suarez, A., E-mail: alejandro.suarez@iter.org [CIEMAT, Avda. Complutense 40, 28040 Madrid (Spain); Reichle, R.; Loughlin, M.; Polunovskiy, E.; Walsh, M. [ITER Organization, Route de Vinon sur Verdon, 13115, St. Paul lez Durance (France)

    2013-10-15

    Highlights: ► Radiation damage calculations for the bolometers in ITER. ► Redesign of the bolometric diagnostic in EPP01. ► New bolometer radiation damage values in EPP01 in the safe zone. -- Abstract: Neutronic considerations in ITER have such importance that they drive the design of many diagnostics and components of the machine, and bolometers are not an exception. Bolometer cameras will be installed on the vacuum vessel, viewing the plasma through the gaps between blanket modules, divertor, equatorial and upper port plugs. The ITER reference bolometer sensors are of a resistive type. For this study it is assumed that they are composed of a thin silicon nitride carrier film and platinum resistors disposed in a Wheatstone bridge configuration. Their assumed radiation hardness is 0.1 dpa. Neutronic calculations were performed with the Monte Carlo program MCNP5, the FENDL 2.1 nuclear data library and the latest B-lite ITER neutronic model with the appropriate modifications using the CAD to MCNP converter MCAM. A complete characterization of the neutron fluxes in all the bolometer locations and the calculation of neutron damage were performed. Values above the failure threshold damage were obtained for some of the bolometers, leading to a complete redesign of some parts of the bolometric system in order to extend its lifetime.

  7. Iteration of Complex Functions and Newton's Method

    Science.gov (United States)

    Dwyer, Jerry; Barnard, Roger; Cook, David; Corte, Jennifer

    2009-01-01

    This paper discusses some common iterations of complex functions. The presentation is such that similar processes can easily be implemented and understood by undergraduate students. The aim is to illustrate some of the beauty of complex dynamics in an informal setting, while providing a couple of results that are not otherwise readily available in…

  8. Precise fixpoint computation through strategy iteration

    DEFF Research Database (Denmark)

    Gawlitza, Thomas; Seidl, Helmut

    2007-01-01

    We present a practical algorithm for computing least solutions of systems of equations over the integers with addition, multiplication with positive constants, maximum and minimum. The algorithm is based on strategy iteration. Its run-time (w.r.t. the uniform cost measure) is independent...

  9. On the convergence of a linesearch based proximal-gradient method for nonconvex optimization

    Science.gov (United States)

    Bonettini, S.; Loris, I.; Porta, F.; Prato, M.; Rebegoldi, S.

    2017-05-01

    We consider a variable metric linesearch based proximal gradient method for the minimization of the sum of a smooth, possibly nonconvex function plus a convex, possibly nonsmooth term. We prove convergence of this iterative algorithm to a critical point if the objective function satisfies the Kurdyka-Łojasiewicz property at each point of its domain, under the assumption that a limit point exists. The proposed method is applied to a wide collection of image processing problems and our numerical tests show that our algorithm results to be flexible, robust and competitive when compared to recently proposed approaches able to address the optimization problems arising in the considered applications.

  10. Local convergence of exact and inexact newton’s methods for subanalytic variational inclusions

    Directory of Open Access Journals (Sweden)

    Catherine Cabuzel

    2015-01-01

    Full Text Available This paper deals with the study of an iterative method for solving a variational inclusion of the form 0 ∈ f (x+F (x where f is a locally Lipschitz subanalytic function and F is a set-valued map from Rn to the closed subsets of Rn. To this inclusion, we firstly associate a Newton then secondly an Inexact Newton type sequence and with some semistability and hemistability properties of the solution x∗ of the previous inclusion, we prove the existence of a sequence which is locally superlinearly convergent.

  11. Optimal sixteenth order convergent method based on quasi-Hermite interpolation for computing roots.

    Science.gov (United States)

    Zafar, Fiza; Hussain, Nawab; Fatimah, Zirwah; Kharal, Athar

    2014-01-01

    We have given a four-step, multipoint iterative method without memory for solving nonlinear equations. The method is constructed by using quasi-Hermite interpolation and has order of convergence sixteen. As this method requires four function evaluations and one derivative evaluation at each step, it is optimal in the sense of the Kung and Traub conjecture. The comparisons are given with some other newly developed sixteenth-order methods. Interval Newton's method is also used for finding the enough accurate initial approximations. Some figures show the enclosure of finitely many zeroes of nonlinear equations in an interval. Basins of attractions show the effectiveness of the method.

  12. Optimal Sixteenth Order Convergent Method Based on Quasi-Hermite Interpolation for Computing Roots

    Science.gov (United States)

    Hussain, Nawab; Fatimah, Zirwah

    2014-01-01

    We have given a four-step, multipoint iterative method without memory for solving nonlinear equations. The method is constructed by using quasi-Hermite interpolation and has order of convergence sixteen. As this method requires four function evaluations and one derivative evaluation at each step, it is optimal in the sense of the Kung and Traub conjecture. The comparisons are given with some other newly developed sixteenth-order methods. Interval Newton's method is also used for finding the enough accurate initial approximations. Some figures show the enclosure of finitely many zeroes of nonlinear equations in an interval. Basins of attractions show the effectiveness of the method. PMID:25197701

  13. Low-Complexity Iterative Approximated Water-Filling Based Power Allocation in an Ultra-Dense Network

    Directory of Open Access Journals (Sweden)

    Xin Su

    2016-05-01

    Full Text Available It is highly possible that future wireless communication systems will adopt ultra-dense deployment to cope with the increasing demand on spectrum efficiency and energy efficiency. The pivotal issue to achieve the potential benefits of the ultra-dense network is to deal with the complex inter-site interference. In this paper, in order to maximize the spectrum efficiency of the system, we first make a reasonable approximation on the inter-site interference to convert the problem into a convex optimization problem. Then, the Lagrangian Multiplier method is adopted to obtain the expression of the optimum power allocation, and the water filling algorithm, as one of the most classical algorithms in the information theory, can be applied to maximize the sum rate or spectrum efficiency of the system. Since the classical iteratively searching water filling algorithm needs many iterations to converge to the optimal solution, we develop a low-complexity iterative approximate water filling algorithm. Simulation results show that the developed algorithm can achieve very close performance to the classical iteratively searching water filling based power allocation with only a few iterations under different scenarios, which leads to a significant complexity reduction.

  14. The fixed-point iteration method for IMRT optimization with truncated dose deposition coefficient matrix

    CERN Document Server

    Tian, Zhen; Jia, Xun; Jiang, Steve B

    2013-01-01

    In the treatment plan optimization for intensity modulated radiation therapy (IMRT), dose-deposition coefficient (DDC) matrix is often pre-computed to parameterize the dose contribution to each voxel in the volume of interest from each beamlet of unit intensity. However, due to the limitation of computer memory and the requirement on computational efficiency, in practice matrix elements of small values are usually truncated, which inevitably compromises the quality of the resulting plan. A fixed-point iteration scheme has been applied in IMRT optimization to solve this problem, which has been reported to be effective and efficient based on the observations of the numerical experiments. In this paper, we aim to point out the mathematics behind this scheme and to answer the following three questions: 1) whether the fixed-point iteration algorithm converges or not? 2) when it converges, whether the fixed point solution is same as the original solution obtained with the complete DDC matrix? 3) if not the same, wh...

  15. Construction and Iterative Decoding of LDPC Codes Over Rings for Phase-Noisy Channels

    Directory of Open Access Journals (Sweden)

    William G. Cowley

    2008-04-01

    Full Text Available This paper presents the construction and iterative decoding of low-density parity-check (LDPC codes for channels affected by phase noise. The LDPC code is based on integer rings and designed to converge under phase-noisy channels. We assume that phase variations are small over short blocks of adjacent symbols. A part of the constructed code is inherently built with this knowledge and hence able to withstand a phase rotation of 2π/M radians, where “M” is the number of phase symmetries in the signal set, that occur at different observation intervals. Another part of the code estimates the phase ambiguity present in every observation interval. The code makes use of simple blind or turbo phase estimators to provide phase estimates over every observation interval. We propose an iterative decoding schedule to apply the sum-product algorithm (SPA on the factor graph of the code for its convergence. To illustrate the new method, we present the performance results of an LDPC code constructed over ℤ4 with quadrature phase shift keying (QPSK modulated signals transmitted over a static channel, but affected by phase noise, which is modeled by the Wiener (random-walk process. The results show that the code can withstand phase noise of 2∘ standard deviation per symbol with small loss.

  16. Velocity Tracking Control of Wheeled Mobile Robots by Iterative Learning Control

    Directory of Open Access Journals (Sweden)

    Xiaochun Lu

    2016-05-01

    Full Text Available This paper presents an iterative learning control (ILC strategy to resolve the trajectory tracking problem of wheeled mobile robots (WMRs based on dynamic model. In the previous study of WMRs’ trajectory tracking, ILC was usually applied to the kinematical model of WMRs with the assumption that desired velocity can be tracked immediately. However, this assumption cannot be realized in the real world at all. The kinematic and dynamic models of WMRs are deduced in this chapter, and a novel combination of D-type ILC algorithm and dynamic model of WMR with random bounded disturbances are presented. To analyze the convergence of the algorithm, the method of contracting mapping, which shows that the designed controller can make the velocity tracking errors converge to zero completely when the iteration times tend to infinite, is adopted. Simulation results show the effectiveness of D-type ILC in the trajectory tracking problem of WMRs, demonstrating the effectiveness and robustness of the algorithm in the condition of random bounded disturbance. A comparative study conducted between D-type ILC and compound cosine function neural network (NN controller also demonstrates the effectiveness of the ILC strategy.

  17. Strategic business transformation through technology convergence

    DEFF Research Database (Denmark)

    Agarwal, Nivedita; Brem, Alexander

    2015-01-01

    -time intelligence. This paper presents the case of General Electric (GE) and studies the various transitional phases and transformation dimensions that GE is experiencing, to manage this technology convergence. The evaluation of GE's experience indicates that convergence-related business transformation is nonlinear......Technology adoption is crucial for an organisation to remain competitive in the marketplace. Traditionally, two technologies - operational technology (OT) and information technology (IT) - have operated independently from one another; however, technological advancements that businesses......, and that some dimensions and stages of transformation previously thought to be relevant may not be pertinent for successful business transformations through technology convergence....

  18. Convergent, discriminant, and criterion validity of DSM-5 traits.

    Science.gov (United States)

    Yalch, Matthew M; Hopwood, Christopher J

    2016-10-01

    Section III of the Diagnostic and Statistical Manual of Mental Disorders (5th edi.; DSM-5; American Psychiatric Association, 2013) contains a system for diagnosing personality disorder based in part on assessing 25 maladaptive traits. Initial research suggests that this aspect of the system improves the validity and clinical utility of the Section II Model. The Computer Adaptive Test of Personality Disorder (CAT-PD; Simms et al., 2011) contains many similar traits as the DSM-5, as well as several additional traits seemingly not covered in the DSM-5. In this study we evaluate the convergent and discriminant validity between the DSM-5 traits, as assessed by the Personality Inventory for DSM-5 (PID-5; Krueger et al., 2012), and CAT-PD in an undergraduate sample, and test whether traits included in the CAT-PD but not the DSM-5 provide incremental validity in association with clinically relevant criterion variables. Results supported the convergent and discriminant validity of the PID-5 and CAT-PD scales in their assessment of 23 out of 25 DSM-5 traits. DSM-5 traits were consistently associated with 11 criterion variables, despite our having intentionally selected clinically relevant criterion constructs not directly assessed by DSM-5 traits. However, the additional CAT-PD traits provided incremental information above and beyond the DSM-5 traits for all criterion variables examined. These findings support the validity of pathological trait models in general and the DSM-5 and CAT-PD models in particular, while also suggesting that the CAT-PD may include additional traits for consideration in future iterations of the DSM-5 system. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

  19. Improving ozone profile retrieval from spaceborne UV backscatter spectrometers using convergence behaviour diagnostics

    Directory of Open Access Journals (Sweden)

    B. Mijling

    2010-11-01

    Full Text Available The Ozone Profile Algorithm (OPERA, developed at KNMI, retrieves the vertical ozone distribution from nadir spectral satellite measurements of back scattered sunlight in the ultraviolet and visible wavelength range. To produce consistent global datasets the algorithm needs to have good global performance, while short computation time facilitates the use of the algorithm in near real time applications.

    To test the global performance of the algorithm we look at the convergence behaviour as diagnostic tool of the ozone profile retrievals from the GOME instrument (on board ERS-2 for February and October 1998. In this way, we uncover different classes of retrieval problems, related to the South Atlantic Anomaly, low cloud fractions over deserts, desert dust outflow over the ocean, and the intertropical convergence zone. The influence of the first guess and the external input data including the ozone cross-sections and the ozone climatologies on the retrieval performance is also investigated. By using a priori ozone profiles which are selected on the expected total ozone column, retrieval problems due to anomalous ozone distributions (such as in the ozone hole can be avoided.

    By applying the algorithm adaptations the convergence statistics improve considerably, not only increasing the number of successful retrievals, but also reducing the average computation time, due to less iteration steps per retrieval. For February 1998, non-convergence was brought down from 10.7% to 2.1%, while the mean number of iteration steps (which dominates the computational time dropped 26% from 5.11 to 3.79.

  20. Testing Short Samples of ITER Conductors and Projection of Their Performance in ITER Magnets

    Energy Technology Data Exchange (ETDEWEB)

    Martovetsky, N N

    2007-08-20

    Qualification of the ITER conductor is absolutely necessary. Testing large scale conductors is expensive and time consuming. To test straight 3-4m long samples in a bore of a split solenoid is a relatively economical way in comparison with fabrication of a coil to be tested in a bore of a background field solenoid. However, testing short sample may give ambiguous results due to different constraints in current redistribution in the cable or other end effects which are not present in the large magnet. This paper discusses processes taking place in the ITER conductor, conditions when conductor performance could be distorted and possible signal processing to deduce behavior of ITER conductors in ITER magnets from the test data.

  1. Structural hybrid reliability index and its convergent solving method based on random–fuzzy–interval reliability model

    Directory of Open Access Journals (Sweden)

    Hai An

    2016-08-01

    Full Text Available Aiming to resolve the problems of a variety of uncertainty variables that coexist in the engineering structure reliability analysis, a new hybrid reliability index to evaluate structural hybrid reliability, based on the random–fuzzy–interval model, is proposed in this article. The convergent solving method is also presented. First, the truncated probability reliability model, the fuzzy random reliability model, and the non-probabilistic interval reliability model are introduced. Then, the new hybrid reliability index definition is presented based on the random–fuzzy–interval model. Furthermore, the calculation flowchart of the hybrid reliability index is presented and it is solved using the modified limit-step length iterative algorithm, which ensures convergence. And the validity of convergent algorithm for the hybrid reliability model is verified through the calculation examples in literature. In the end, a numerical example is demonstrated to show that the hybrid reliability index is applicable for the wear reliability assessment of mechanisms, where truncated random variables, fuzzy random variables, and interval variables coexist. The demonstration also shows the good convergence of the iterative algorithm proposed in this article.

  2. Non-LTE radiative transfer with lambda-acceleration - Convergence properties using exact full and diagonal lambda-operators

    Science.gov (United States)

    Macfarlane, J. J.

    1992-01-01

    We investigate the convergence properties of Lambda-acceleration methods for non-LTE radiative transfer problems in planar and spherical geometry. Matrix elements of the 'exact' A-operator are used to accelerate convergence to a solution in which both the radiative transfer and atomic rate equations are simultaneously satisfied. Convergence properties of two-level and multilevel atomic systems are investigated for methods using: (1) the complete Lambda-operator, and (2) the diagonal of the Lambda-operator. We find that the convergence properties for the method utilizing the complete Lambda-operator are significantly better than those of the diagonal Lambda-operator method, often reducing the number of iterations needed for convergence by a factor of between two and seven. However, the overall computational time required for large scale calculations - that is, those with many atomic levels and spatial zones - is typically a factor of a few larger for the complete Lambda-operator method, suggesting that the approach should be best applied to problems in which convergence is especially difficult.

  3. Studies on effects of feedback delay on the convergence performance of adaptive time-domain equalizers for fiber dispersive channels

    Science.gov (United States)

    Guo, Qun; Xu, Bo; Qiu, Kun

    2016-04-01

    Adaptive time-domain equalizer (TDE) is an important module for digital optical coherent receivers. From an implementation perspective, we analyze and compare in detail the effects of error signal feedback delay on the convergence performance of TDE using either least-mean square (LMS) or constant modulus algorithm (CMA). For this purpose, a simplified theoretical model is proposed based on which iterative equations on the mean value and the variance of the tap coefficient are derived with or without error signal feedback delay for both LMS- and CMA-based methods for the first time. The analytical results show that decreased step size has to be used for TDE to converge and a slower convergence speed cannot be avoided as the feedback delay increases. Compared with the data-aided LMS-based method, the CMA-based method has a slower convergence speed and larger variation after convergence. Similar results are confirmed using numerical simulations for fiber dispersive channels. As the step size increases, a feedback delay of 20 clock cycles might cause the TDE to diverge. Compared with the CMA-based method, the LMS-based method has a higher tolerance on the feedback delay and allows a larger step size for a faster convergence speed.

  4. Cultivate technology convergence for product innovation.

    Science.gov (United States)

    Wilkinson, J Malcolm

    2006-04-01

    Technologies from diverse scientific disciplines are being combined to drive innovation in medical devices. How technology convergence and innovation could be further stimulated is explored here using developments in imaging and point-of-care devices as examples.

  5. International Convergence of Accounting Standards: Issues and ...

    African Journals Online (AJOL)

    Unarguably, globalization has become a key driver of the increasing integration and synergy among countries, systems and standards. Consequently, the clamor for ... the Nigerian environment. Keywords: Accounting, international financial reporting standards (IFRS), market liquidity, convergence, institutional setting.

  6. (Crime Victims’ Compensation: The Emergence of Convergence

    Directory of Open Access Journals (Sweden)

    Renée S.B. Kool

    2014-07-01

    Full Text Available Crime victims’ compensation has become a major issue within Dutch criminal policy. Legal procedures have been subject to change, leading towards the convergence of tort law and criminal law. Such a convergence calls for a reflection (on the application of the core concepts of responsibility, accountability and liability. Moreover, the current pursuit of victims’ compensation affects procedural issues, specifically with regard to the issue of enforcement. Leaving aside the issue of the legitimacy of victims’ compensation, this convergence raises the question of how to preserve the delicate balance that flows from the use of the law as an instrument to preserve social order. The topical question is not whether convergence is occurring, but how we must deal with it in order to find a (new equilibrium between the public interest and the interest of the individual who has experienced a harmful wrong.

  7. Impact of fixed-mobile convergence

    DEFF Research Database (Denmark)

    Pachnicke, Stephan; Andrus, Bogdan-Mihai; Autenrieth, Achim

    2016-01-01

    Fixed-Mobile Convergence (FMC) is a very trendy concept as it promises integration of the previously separated fixed access network and the mobile network. From this novel approach telecommunication operators expect significant cost savings and performance improvements. FMC can be separated...... into structural convergence (regarding the infrastructure) and functional convergence (regarding the necessary functionalities required in fixed and mobile networks). The latter one goes hand-in-hand with Network Function Virtualization (NFV), where important network functions are provided by a server inside...... of the next generation point-of-presence (NG-POP). In this article implications on the system architecture as well as structural and functional convergence topics will be discussed....

  8. Divergence and convergence in nutrition science

    NARCIS (Netherlands)

    Penders, Bart; Spruit, Shannon L.; Sikkema, Jan; Maat, Jan; Schuurbiers, Daan

    2015-01-01

    Nutrigenomics diverged from mainstream nutrition science, ideologically, instrumentally and culturally, due to the establishment of a protective niche. That protection is fading. This article chronicles a case in which convergence between nutrigenomics and nutrition science is pursued. Here we

  9. Modes of convergence for term graph rewriting

    DEFF Research Database (Denmark)

    Bahr, Patrick

    2012-01-01

    Term graph rewriting provides a simple mechanism to finitely represent restricted forms of infinitary term rewriting. The correspondence between infinitary term rewriting and term graph rewriting has been studied to some extent. However, this endeavour is impaired by the lack of an appropriate...... counterpart of infinitary rewriting on the side of term graphs. We aim to fill this gap by devising two modes of convergence based on a partial order respectively a metric on term graphs. The thus obtained structures generalise corresponding modes of convergence that are usually studied in infinitary term...... rewriting. We argue that this yields a common framework in which both term rewriting and term graph rewriting can be studied. In order to substantiate our claim, we compare convergence on term graphs and on terms. In particular, we show that the modes of convergence on term graphs are conservative...

  10. Convergence of Attitudes among College Students

    Science.gov (United States)

    Whatley, Alice E.; Appel, Victor H.

    1973-01-01

    Attempts to determine whether the intersex convergence phenomenon could be applicable to the measured attitudes of collegiate samples. Both sexes seemed to be moving toward a more liberal view on issues related to marriage and the family. (Author)

  11. On Paranorm Zweier -Convergent Sequence Spaces

    Directory of Open Access Journals (Sweden)

    Vakeel A. Khan

    2013-01-01

    Full Text Available In this paper, we introduce the paranorm Zweier -convergent sequence spaces , , and , a sequence of positive real numbers. We study some topological properties, prove the decomposition theorem, and study some inclusion relations on these spaces.

  12. Statistical convergence, selection principles and asymptotic analysis

    Energy Technology Data Exchange (ETDEWEB)

    Di Maio, G. [Dipartimento di Matematica, Seconda Universita di Napoli, Via Vivaldi 43, 81100 Caserta (Italy)], E-mail: giuseppe.dimaio@unina2.it; Djurcic, D. [Technical Faculty, University of Kragujevac, Svetog Save 65, 32000 Cacak (Serbia)], E-mail: dragandj@tfc.kg.ac.yu; Kocinac, Lj.D.R. [Faculty of Sciences and Mathematics, University of Nis, Visegradska 33, 18000 Nis (Serbia)], E-mail: lkocinac@ptt.rs; Zizovic, M.R. [Technical Faculty, University of Kragujevac, Svetog Save 65, 32000 Cacak (Serbia)], E-mail: zizo@tfc.kg.ac.yu

    2009-12-15

    We consider the set S of sequences of positive real numbers in the context of statistical convergence/divergence and show that some subclasses of S have certain nice selection and game-theoretic properties.

  13. Iterative Solutions to the Inverse Geometric Problem for Manipulators with no Closed Form Solution

    Directory of Open Access Journals (Sweden)

    Pål Johan From

    2008-07-01

    Full Text Available A set of new iterative solutions to the inverse geometric problem is presented. The approach is general and does not depend on intersecting axes or calculation of the Jacobian. The solution can be applied to any manipulator and is well suited for manipulators for which convergence is poor for conventional Jacobian-based iterative algorithms. For kinematically redundant manipulators, weights can be applied to each joint to introduce stiffness and for collision avoidance. The algorithm uses the unit quaternion to represent the position of each joint and calculates analytically the optimal position of the joint when only the respective joint is considered. This sub-problem is computationally very efficient due to the analytical solution. Several algorithms based on the solution of this sub-problem are presented. For difficult problems, for which the initial condition is far from a solution or the geometry of the manipulator makes the solution hard to reach, it is shown that the algorithm finds a solution fairly close to the solution in only a few iterations.

  14. A POCS method for iterative deblending constrained by a blending mask

    Science.gov (United States)

    Zhou, Yatong

    2017-03-01

    A recently emerging seismic acquisition technology called simultaneous source shooting has attracted much attention from both academia and industry. The key topic in the newly developed technique is the removal of intense blending interferences caused by the simultaneous ignition of multiple airgun sources. In this paper, I propose a novel inversion strategy with multiple convex constraints to improve the deblending performance based on the projection onto convex sets (POCS) iterative framework. In the POCS iterative framework, as long as the multiple constraints are convex, the iterations are guaranteed to converge. In addition to the sparse constraint, I seek another important constraint from the untainted data. I create a blending mask in order to fully utilize the useful information hidden behind the noisy blended data. The blending mask is constructed by numerically blending a matrix with all its entries set to be one and then setting the non-one entries of the blended matrix zero. I use both synthetic and field data examples to demonstrate the successful performance of the proposed method.

  15. An iterative fast sweeping based eikonal solver for tilted orthorhombic media

    KAUST Repository

    Waheed, Umair bin

    2014-08-01

    Computing first-arrival traveltimes of quasi-P waves in the presence of anisotropy is important for high-end near-surface modeling, microseismic-source localization, and fractured-reservoir characterization, and requires solving an anisotropic eikonal equation. Anisotropy deviating from elliptical anisotropy introduces higher-order nonlinearity into the eikonal equation, which makes solving the eikonal equation a challenge. We address this challenge by iteratively solving a sequence of simpler tilted elliptically anisotropic eikonal equations. At each iteration, the source function is updated to capture the effects of the higher order nonlinear terms. We use Aitken extrapolation to speed up the convergence rate of the iterative algorithm. The result is an algorithm for first-arrival traveltime computations in tilted anisotropic media. We demonstrate our method on tilted transversely isotropic media and tilted orthorhombic media. Our numerical tests demonstrate that the proposed method can match the first arrivals obtained by wavefield extrapolation, even for strong anisotropy and complex structures. Therefore, for the cases where oneor two-point ray tracing fails, our method may be a potential substitute for computing traveltimes. Our approach can be extended to anisotropic media with lower symmetries, such as monoclinic or even triclinic media.

  16. A General Iterative Shrinkage and Thresholding Algorithm for Non-convex Regularized Optimization Problems.

    Science.gov (United States)

    Gong, Pinghua; Zhang, Changshui; Lu, Zhaosong; Huang, Jianhua Z; Ye, Jieping

    2013-01-01

    Non-convex sparsity-inducing penalties have recently received considerable attentions in sparse learning. Recent theoretical investigations have demonstrated their superiority over the convex counterparts in several sparse learning settings. However, solving the non-convex optimization problems associated with non-convex penalties remains a big challenge. A commonly used approach is the Multi-Stage (MS) convex relaxation (or DC programming), which relaxes the original non-convex problem to a sequence of convex problems. This approach is usually not very practical for large-scale problems because its computational cost is a multiple of solving a single convex problem. In this paper, we propose a General Iterative Shrinkage and Thresholding (GIST) algorithm to solve the nonconvex optimization problem for a large class of non-convex penalties. The GIST algorithm iteratively solves a proximal operator problem, which in turn has a closed-form solution for many commonly used penalties. At each outer iteration of the algorithm, we use a line search initialized by the Barzilai-Borwein (BB) rule that allows finding an appropriate step size quickly. The paper also presents a detailed convergence analysis of the GIST algorithm. The efficiency of the proposed algorithm is demonstrated by extensive experiments on large-scale data sets.

  17. Single-channel color image encryption based on iterative fractional Fourier transform and chaos

    Science.gov (United States)

    Sui, Liansheng; Gao, Bo

    2013-06-01

    A single-channel color image encryption is proposed based on iterative fractional Fourier transform and two-coupled logistic map. Firstly, a gray scale image is constituted with three channels of the color image, and permuted by a sequence of chaotic pairs which is generated by two-coupled logistic map. Firstly, the permutation image is decomposed into three components again. Secondly, the first two components are encrypted into a single one based on iterative fractional Fourier transform. Similarly, the interim image and third component are encrypted into the final gray scale ciphertext with stationary white noise distribution, which has camouflage property to some extent. In the process of encryption and description, chaotic permutation makes the resulting image nonlinear and disorder both in spatial domain and frequency domain, and the proposed iterative fractional Fourier transform algorithm has faster convergent speed. Additionally, the encryption scheme enlarges the key space of the cryptosystem. Simulation results and security analysis verify the feasibility and effectiveness of this method.

  18. An efficient iterative penalization method using recycled Krylov subspaces and its application to impulsively started flows

    Science.gov (United States)

    Gillis, T.; Winckelmans, G.; Chatelain, P.

    2017-10-01

    We formulate the penalization problem inside a vortex particle-mesh method as a linear system. This system has to be solved at every wall boundary condition enforcement within a time step. Furthermore, because the underlying problem is a Poisson problem, the solution of this linear system is computationally expensive. For its solution, we here use a recycling iterative solver, rBiCGStab, in order to reduce the number of iterations and therefore decrease the computational cost of the penalization step. For the recycled subspace, we use the orthonormalized previous solutions as only the right hand side changes from the solution at one time to the next. This method is validated against benchmark results: the impulsively started cylinder, with validation at low Reynolds number (Re = 550) and computational savings assessments at moderate Reynolds number (Re = 9500); then on a flat plate benchmark (Re = 1000). By improving the convergence behavior, the approach greatly reduces the computational cost of iterative penalization, at a moderate cost in memory overhead.

  19. An iterative, fast-sweeping-based eikonal solver for 3D tilted anisotropic media

    KAUST Repository

    Waheed, Umair bin

    2015-03-30

    Computation of first-arrival traveltimes for quasi-P waves in the presence of anisotropy is important for high-end near-surface modeling, microseismic-source localization, and fractured-reservoir characterization - and it requires solving an anisotropic eikonal equation. Anisotropy deviating from elliptical anisotropy introduces higher order nonlinearity into the eikonal equation, which makes solving the eikonal equation a challenge. We addressed this challenge by iteratively solving a sequence of simpler tilted elliptically anisotropic eikonal equations. At each iteration, the source function was updated to capture the effects of the higher order nonlinear terms. We used Aitken\\'s extrapolation to speed up convergence rate of the iterative algorithm. The result is an algorithm for computing first-arrival traveltimes in tilted anisotropic media. We evaluated the applicability and usefulness of our method on tilted transversely isotropic media and tilted orthorhombic media. Our numerical tests determined that the proposed method matches the first arrivals obtained by wavefield extrapolation, even for strongly anisotropic and highly complex subsurface structures. Thus, for the cases where two-point ray tracing fails, our method can be a potential substitute for computing traveltimes. The approach presented here can be easily extended to compute first-arrival traveltimes for anisotropic media with lower symmetries, such as monoclinic or even the triclinic media.

  20. A superlinear iteration method for calculation of finite length journal bearing's static equilibrium position.

    Science.gov (United States)

    Zhou, Wenjie; Wei, Xuesong; Wang, Leqin; Wu, Guangkuan

    2017-05-01

    Solving the static equilibrium position is one of the most important parts of dynamic coefficients calculation and further coupled calculation of rotor system. The main contribution of this study is testing the superlinear iteration convergence method-twofold secant method, for the determination of the static equilibrium position of journal bearing with finite length. Essentially, the Reynolds equation for stable motion is solved by the finite difference method and the inner pressure is obtained by the successive over-relaxation iterative method reinforced by the compound Simpson quadrature formula. The accuracy and efficiency of the twofold secant method are higher in comparison with the secant method and dichotomy. The total number of iterative steps required for the twofold secant method are about one-third of the secant method and less than one-eighth of dichotomy for the same equilibrium position. The calculations for equilibrium position and pressure distribution for different bearing length, clearance and rotating speed were done. In the results, the eccentricity presents linear inverse proportional relationship to the attitude angle. The influence of the bearing length, clearance and bearing radius on the load-carrying capacity was also investigated. The results illustrate that larger bearing length, larger radius and smaller clearance are good for the load-carrying capacity of journal bearing. The application of the twofold secant method can greatly reduce the computational time for calculation of the dynamic coefficients and dynamic characteristics of rotor-bearing system with a journal bearing of finite length.