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Efficient Solution (efficient + solution)
Selected AbstractsDirect Comparison of Highly Efficient Solution- and Vacuum-Processed Organic Solar Cells Based on Merocyanine DyesADVANCED MATERIALS, Issue 37 2010Nils M. Kronenberg Identically configured bulk heterojunction organic solar cells based on merocyanine dye donor and fullerene acceptor compounds (see figure) are manufactured either from solution or by vacuum deposition, to enable a direct comparison. Whereas the former approach is more suitable for screening purposes, the latter approach affords higher short-circuit current density and power conversion efficiency. [source] Recurrent Neural Networks for Uncertain Time-Dependent Structural BehaviorCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 5 2010W. Graf The approach is based on recurrent neural networks trained by time-dependent measurement results. Thereby, the uncertainty of the measurement results is modeled as fuzzy processes which are considered within the recurrent neural network approach. An efficient solution for network training and prediction is developed utilizing ,-cuts and interval arithmetic. The capability of the approach is demonstrated by means of the prediction of the long-term structural behavior of a reinforced concrete plate strengthened by a textile reinforced concrete layer. [source] Welding Automation in Space-Frame Bridge ConstructionCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 3 2001Alistair Greig The SPACES system has been proposed as an alternative for long-span bridge construction. Tubular space frames offer a structurally more efficient solution for bridges, but they have been considered too expensive because the joints at the nodal intersections of the tubular members are difficult and expensive to weld. The benefits of the SPACES system can only be realized by using a computer-integrated construction system to drive down the fabrication costs. A key component of the computer-integrated construction is the robotic welding system. This article describes the development of a lightweight automated welding system for the joining of tubular members. It addresses the geometry of intersecting cylinders and the kinematics and design of a 5-degree-of-freedom manipulator. Summary solutions are given for both. The control software is described briefly, and mention of the welding tests and overall business process is also made. A consortium of U.K. industry and universities is conducting the work. [source] Usability levels for sparse linear algebra components,CONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 12 2008M. Sosonkina Abstract Sparse matrix computations are ubiquitous in high-performance computing applications and often are their most computationally intensive part. In particular, efficient solution of large-scale linear systems may drastically improve the overall application performance. Thus, the choice and implementation of the linear system solver are of paramount importance. It is difficult, however, to navigate through a multitude of available solver packages and to tune their performance to the problem at hand, mainly because of the plethora of interfaces, each requiring application adaptations to match the specifics of solver packages. For example, different ways of setting parameters and a variety of sparse matrix formats hinder smooth interactions of sparse matrix computations with user applications. In this paper, interfaces designed for components that encapsulate sparse matrix computations are discussed in the light of their matching with application usability requirements. Consequently, we distinguish three levels of interfaces, high, medium, and low, corresponding to the degree of user involvement in the linear system solution process and in sparse matrix manipulations. We demonstrate when each interface design choice is applicable and how it may be used to further users' scientific goals. Component computational overheads caused by various design choices are also examined, ranging from low level, for matrix manipulation components, to high level, in which a single component contains the entire linear system solver. Published in 2007 by John Wiley & Sons, Ltd. [source] Comprehensive proteome analysis by chromatographic protein prefractionationELECTROPHORESIS, Issue 7-8 2004Pierre Lescuyer Abstract Protein copy number is distributed from 7 to 8 orders of magnitude in cells and probably up to 12 orders of magnitude in plasma. Classical silver-stained two-dimensional electrophoresis (2-DE) can only display up to four orders of magnitude. This is a major drawback since it is assumed that most of the regulatory proteins are low-abundance gene products. It is thus clear that the separation of low copy number proteins in amounts sufficient for postseparation analysis is an important issue in proteome studies to complete the comprehensive description of the proteome of any given cell type. The visualization of a polypeptide on a 2-DE gel will depend on the copy number, on the quantity loaded onto the gel and on the method of detection. As the amount of protein that can be loaded onto a gel is limited, one efficient solution is to fractionate the sample prior to 2-DE analysis. Several approaches exist including subcellular fractionation, affinity purification and chromatographic and electrophoretic protein prefractionation. The chromatographic step adds a new dimension in the protein separation using specific protein properties. It allows proteins to be adsorbed to a surface and eluted differentially under certain conditions. This review article presents studies combining chromatography-based methods to 2-DE analysis and draws general conclusions on this strategy. [source] Functionalized Self-Assembled InAs/GaAs Quantum-Dot Structures Hybridized with Organic MoleculesADVANCED FUNCTIONAL MATERIALS, Issue 3 2010Miaoxiang Chen Abstract Low-dimensional III,V semiconductors have many advantages over other semiconductors; however, they are not particularly stable under physiological conditions. Hybridizing biocompatible organic molecules with advanced optical and electronic semiconductor devices based on quantum dots (QDs) and quantum wires could provide an efficient solution to realize stress-free and nontoxic interfaces to attach larger functional biomolecules. Monitoring the modifications of the optical properties of the hybrid molecule,QD systems by grafting various types of air-stable diazonium salts onto the QD structures surfaces provides a direct approach to prove the above concepts. The InAs/GaAs QD structures used in this work consist of a layer of surface InAs QDs and a layer of buried InAs QDs embedded in a wider-bandgap GaAs matrix. An enhancement in photoluminescence intensity by a factor of 3.3 from the buried QDs is achieved owing to the efficient elimination of the dangling bonds on the surface of the structures and to the decrease in non-radiative recombination caused by their surface states. Furthermore, a narrow photoluminescence band peaking at 1620,nm with a linewidth of 49 meV corresponding to the eigenstates interband transition of the surface InAs QDs is for the first time clearly observed at room temperature, which is something that has rarely been achieved without the use of such engineered surfaces. The experimental results demonstrate that the hybrid molecule,QD systems possess a high stability, and both the surface and buried QDs are very sensitive to changes in their surficial conditions, indicating that they are excellent candidates as basic sensing elements for novel biosensor applications. [source] Monopoly and Oligopoly Provision of Addictive GoodsINTERNATIONAL ECONOMIC REVIEW, Issue 1 2001Robert Driskill This article investigates monopoly and oligopoly provision of an addictive good. Consumer preferences are modeled as in Becker and Murphy (1988). Addictive goods have characteristics that create interesting strategic issues when suppliers are noncompetitive. We characterize the perfect Markov equilibrium of a market with noncompetitive supply of an addictive good and compare it with the efficient solution. Depending on particular parameter values, we find a wide variety of possible steady-state outcomes, including ones with output above the efficient level and price below marginal cost. We also find that market power can be disadvantageous. [source] Performance of parallel preconditioners for adaptive hp FEM discretization of incompressible flowsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 5 2002Andrew C. Bauer Abstract Adaptive hp finite element (FEM) approximations of incompressible flow make special demands on parallel solution algorithms. We report here on the performance of standard algebraic preconditioning techniques for the efficient solution of such problems. We employ a Schur complement scheme to eliminate the ,bubble' degrees of freedom associated with the velocity field, thus removing the zeros from the diagonals and enabling the use of standard algebraic techniques. Using new data management strategies and the PETSc library of iterative solvers for linear systems, numerical results for Jacobi, Block Jacobi and Additive Schwartz preconditioners are presented. Copyright © 2002 John Wiley & Sons, Ltd. [source] A discontinuous enrichment method for the efficient solution of plate vibration problems in the medium-frequency regimeINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 2 2010Paolo Massimi Abstract A discontinuous enrichment method (DEM) is presented for the efficient discretization of plate vibration problems in the medium-frequency regime. This method enriches the polynomial shape functions of the classical finite element discretization with free-space solutions of the biharmonic operator governing the elastic vibrations of an infinite Kirchhoff plate. These free-space solutions, which represent flexural waves and decaying modes, are discontinuous across the element interfaces. For this reason, two different and carefully constructed Lagrange multiplier approximations are introduced along the element edges to enforce a weak continuity of the transversal displacement and its normal derivative, and discrete Lagrange multipliers are introduced at the element corners to enforce there a weak continuity of the transversal displacement. The proposed DEM is illustrated with the solution of sample plate vibration problems with different types of harmonic loading in the medium-frequency regime, away from and close to resonance. In all cases, its performance is found to be significantly superior to that of the classical higher-order finite element method. Copyright © 2010 John Wiley & Sons, Ltd. [source] An efficient out-of-core multifrontal solver for large-scale unsymmetric element problemsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 7 2009J. K. Reid Abstract In many applications where the efficient solution of large sparse linear systems of equations is required, a direct method is frequently the method of choice. Unfortunately, direct methods have a potentially severe limitation: as the problem size grows, the memory needed generally increases rapidly. However, the in-core memory requirements can be limited by storing the matrix and its factors externally, allowing the solver to be used for very large problems. We have designed a new out-of-core package for the large sparse unsymmetric systems that arise from finite-element problems. The code, which is called HSL_MA78, implements a multifrontal algorithm and achieves efficiency through the use of specially designed code for handling the input/output operations and efficient dense linear algebra kernels. These kernels, which are available as a separate package called HSL_MA74, use high-level BLAS to perform the partial factorization of the frontal matrices and offer both threshold partial and rook pivoting. In this paper, we describe the design of HSL_MA78 and explain its user interface and the options it offers. We also describe the algorithms used by HSL_MA74 and illustrate the performance of our new codes using problems from a range of practical applications. Copyright © 2008 John Wiley & Sons, Ltd. [source] Three-dimensional discontinuous Galerkin elements with plane waves and Lagrange multipliers for the solution of mid-frequency Helmholtz problemsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 5 2006Radek Tezaur Abstract Recently, a discontinuous Galerkin finite element method with plane wave basis functions and Lagrange multiplier degrees of freedom was proposed for the efficient solution in two dimensions of Helmholtz problems in the mid-frequency regime. In this paper, this method is extended to three dimensions and several new elements are proposed. Computational results obtained for several wave guide and acoustic scattering model problems demonstrate one to two orders of magnitude solution time improvement over the higher-order Galerkin method. Copyright © 2005 John Wiley & Sons, Ltd. [source] A dual mesh multigrid preconditioner for the efficient solution of hydraulically driven fracture problemsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 13 2005A. P. Peirce Abstract We present a novel multigrid (MG) procedure for the efficient solution of the large non-symmetric system of algebraic equations used to model the evolution of a hydraulically driven fracture in a multi-layered elastic medium. The governing equations involve a highly non-linear coupled system of integro-partial differential equations along with the fracture front free boundary problem. The conditioning of the algebraic equations typically degrades as O(N3). A number of characteristics of this problem present significant new challenges for designing an effective MG strategy. Large changes in the coefficients of the PDE are dealt with by taking the appropriate harmonic averages of the discrete coefficients. Coarse level Green's functions for multiple elastic layers are constructed using a single dual mesh and superposition. Coarse grids that are sub-sets of the finest grid are used to treat mixed variable problems associated with ,pinch points.' Localized approximations to the Jacobian at each MG level are used to devise efficient Gauss,Seidel smoothers and preferential line iterations are used to eliminate grid anisotropy caused by large aspect ratio elements. The performance of the MG preconditioner is demonstrated in a number of numerical experiments. Copyright © 2005 John Wiley & Sons, Ltd. [source] Language conflicts in the European UnionINTERNATIONAL JOURNAL OF APPLIED LINGUISTICS, Issue 3 2006On finding a politically acceptable, practicable solution for EU institutions that satisfies diverging interests Europäische Union; institutionelle Arbeitssprachen; Sprachinteressen; Sprachkonflikte For EU institutions, having a single internal working language , for which English is the only candidate , would be the most efficient solution and, to all appearances, in the best interests of each member state and language community whose language is excluded as a working language. However, for member states from the large non-anglophone language communities, such a solution seems barely acceptable and, in addition, would not correspond to the EU's official language policy on the preservation of language diversity. This is because "English only" is expected to inevitably transcend the borders of internal institutions and further limit the function of the remaining widely-spoken languages, especially as a lingua franca and in foreign language teaching. This contribution presents the conflict of interests between the smaller and the larger language communities in having only one or several institutional working languages for the EU and sketches out a possible solution which would serve both political and communicative demands. Für die EU-Institutionen w,re eine einzige interne Arbeitssprache, für die nur Englisch in Frage k,me, am effizientesten, und sie läge allem Anschein nach auch im Interesse derjenigen Mitgliedstaaten und Sprachgemeinschaften, deren Sprachen von den Arbeitssprachen ohnehin ausgeschlossen sind. Für die Mitgliedstaaten der großen Sprachgemeinschaften (außer Englisch) erscheint eine solche Lösung aber kaum akzeptabel, und sie entspräche auch nicht der offiziellen EU-Sprachenpolitik des Erhalts der Sprachenvielfalt. Es ist nämlich damit zu rechnen, dass "English only" unvermeidlich über die internen Institutionen hinaus wirken und die übrigen großen Sprachen funktional weiter einschränken würde, vor allem als Lingua franca und im Fremdsprachenunterricht. Der Beitrag stellt die Interessenskonflikte zwischen den kleineren und den größeren Sprachgemeinschaften der EU bezüglich nur einer oder aber mehrerer institutioneller Arbeitssprachen dar und skizziert eine mögliche Lösung, die sowohl politischen als auch kommunikativen Erfordernissen gerecht wird. [source] A wavelet-based piecewise approach for steady-state analysis of power electronics circuitsINTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 5 2006K. C. Tam Abstract Simulation of steady-state waveforms is important to the design of power electronics circuits, as it reveals the maximum voltage and current stresses being imposed upon specific devices and components. This paper proposes an improved approach to finding steady-state waveforms of power electronics circuits based on wavelet approximation. The proposed method exploits the time-domain piecewise property of power electronics circuits in order to improve the accuracy and computational efficiency. Instead of applying one wavelet approximation to the whole period, several wavelet approximations are applied in a piecewise manner to fit the entire waveform. This wavelet-based piecewise approximation approach can provide very accurate and efficient solution, with much less number of wavelet terms, for approximating steady-state waveforms of power electronics circuits. Copyright © 2006 John Wiley & Sons, Ltd. [source] GPSPA: a new adaptive algorithm for maintaining shortest path routing trees in stochastic networksINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 10 2004Sudip Misra Abstract This paper presents a new efficient solution to the Dynamic Shortest Path Routing Problem, using the principles of Generalized Pursuit Learning. It proposes an efficient algorithm for maintaining shortest path routing trees in networks that undergo stochastic updates in their structure. It involves finding the shortest path in a stochastic network, where there are continuous probabilistically based updates in link-costs. In vast, rapidly changing telecommunications (wired or wireless) networks, where links go up and down continuously and rapidly, and where there are simultaneous random updates in link costs, the existing algorithms are inefficient. In such cases, shortest paths need to be computed within a very short time (often in the order of microseconds) by scanning and processing the minimal number of nodes and links. The proposed algorithm, referred to as the Generalized Pursuit Shortest Path Algorithm (GPSPA), will be very useful in this regard, because after convergence, it seems to be the best algorithm to-date for this purpose. Indeed, it has the advantage that it can be used to find the shortest path within the ,statistical' average network, which converges irrespective of whether there are new changes in link-costs or not. Existing algorithms are not characterized by such a behaviour inasmuch as they would recalculate the affected shortest paths after each link-cost update. The algorithm has been rigorously evaluated experimentally, and it has been found to be a few orders of magnitude superior to the algorithms available in the literature. Copyright © 2004 John Wiley & Sons, Ltd. [source] Blind equalization of quadrature partial response-trellis coded modulated signals in Rician fading,INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 2 2001Hakan A. Cirpan Abstract In this paper, a blind maximum-likelihood channel estimation algorithm is developed for quadrature partial response-trellis coded modulated (QPR-TCM) signals propagating through a Rician fading environment. A hidden Markov model (HMM) formulation of the problem is introduced and the Baum,Welch parameter estimation algorithm is modified to provide a computationally efficient solution to the resulting optimization problem. Performance analysis of the proposed method is carried out through the evaluation of bit-error probability upper bound for Rician fading channels. Also, some illustrative simulations are presented. Copyright © 2001 John Wiley & Sons, Ltd. [source] An Interactive Reference Direction Algorithm For Solving Multi-Objective Convex Nonlinear Integer Programming ProblemsINTERNATIONAL TRANSACTIONS IN OPERATIONAL RESEARCH, Issue 4 2001Vassil S. Vassilev We present a learning-oriented interactive reference direction algorithm for solving multi-objective convex nonlinear integer programming problems. At each iteration the decision-maker (DM) sets his/her preferences as aspiration levels of the objective functions. The modified aspiration point and the solution found at the previous iteration define the reference direction. Based on the reference direction, we formulate a mixed-integer scalarizing problem with specific properties. By solving this problem approximately, we find one or more integer solutions located close to the efficient surface. At some iteration (usually at the last iteration), the DM may want to solve the scalarizing problem to obtain an exact (weak) efficient solution. Based on the proposed algorithm, we have developed a research-decision support system that includes one exact and one heuristic algorithm. Using this system, we illustrate the proposed algorithm with an example, and report some computational results. [source] It Ain't Broke: The Past, Present, and Future of Venture CapitalJOURNAL OF APPLIED CORPORATE FINANCE, Issue 2 2010Steven N. Kaplan This article presents a selective history of the U.S. venture capital (VC) industry, a discussion of the current state of the market, and some predictions about where the market is going. There is no doubt that the U.S. venture capital industry has been very successful. The VC model has provided an efficient solution to a difficult problem,that of enabling people with promising ideas but often limited track records to raise capital from outside investors. A large fraction of IPOs, including many of the most successful, have been funded by venture capitalists, and the U.S. VC model has been copied around the world. Armed with this historical perspective, the authors view with skepticism the recent claims that the VC model is broken. In the past, VC investments in companies have represented a remarkably constant 0.15% of the total value of the stock market; and commitments to VC funds, while more variable, have been consistently in the 0.10% to 0.20% range. Both of these percentages have continued to hold in recent years. And despite the relatively low number of IPOs, the returns to VC funds this decade have largely maintained their historical relationship to the overall stock market. To be sure, VC investment and returns continue to be subject to boom-and-bust cycles. But if the recent period has most of the features of a bust, the authors view today's historically low level of commitments to U.S. VC funds as a fairly reliable indicator of relatively high expected returns for the 2009 and (probably) 2010 vintage years. Perhaps the most promising future role for venture capital, as the authors suggest in closing, is to increase the productivity of the corporate research and development function through various kinds of partnerships and outsourcing arrangements. [source] Mapping of unstressed lattice parameters using pulsed neutron transmission diffractionJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 4 2002Javier Roberto Santisteban Stress measurement by neutron diffraction depends critically on knowledge of the unstressed lattice parameter (a0) of the specimen under study. As a result, measurement of stress profiles in components where a0 is not homogeneous throughout the sample, such as welds or carburized surfaces, can be particularly difficult. An efficient solution to this problem is proposed based on the pulsed neutron transmission diffraction technique. This technique exploits the sharp steps in intensity, the so-called Bragg edges, appearing in the transmitted neutron spectra of polycrystalline materials, such steps being produced by coherent scattering from lattice planes. The position of these Bragg edges as defined by the time-of-flight technique is used to determine precisely local interplanar distances. In this work it is shown that the unstressed lattice parameter of thin specimens subjected to plane stress fields can be defined by recording transmission spectra at different sample inclinations, in complete analogy with the sin2, technique used in X-ray diffraction. Moreover, by using an array of detectors it is possible to produce a radiographic `image' of a0 for plane specimens or thin sections out of three-dimensional ones. The capability of the technique is exemplified by mapping the changes in a0 for a ferritic weld that was used as a round robin sample in an international program for standardization of stress measurements by neutron diffraction. [source] A direct Schur,Fourier decomposition for the efficient solution of high-order Poisson equations on loosely coupled parallel computersNUMERICAL LINEAR ALGEBRA WITH APPLICATIONS, Issue 4 2006F. X. Trias Abstract In this paper a parallel direct Schur,Fourier decomposition (DSFD) algorithm for the direct solution of arbitrary order discrete Poisson equations on parallel computers is proposed. It is based on a combination of a Direct Schur method and a Fourier decomposition and allows to solve each Poisson equation almost to machine accuracy using only one communication episode. Thus, it is well suited for loosely coupled parallel computers, that have a high network latency compared with the CPU performance. Several three-dimensional direct numerical simulations (DNS) of wall-bounded turbulent incompressible flows have been carried out using the DSFD algorithm. Numerical examples illustrating the robustness and scalability of the method on a PC cluster with a conventional 100 Mbits/s network are also presented. Copyright © 2005 John Wiley & Sons, Ltd. [source] An algebraic multigrid method for finite element discretizations with edge elementsNUMERICAL LINEAR ALGEBRA WITH APPLICATIONS, Issue 3 2002S. Reitzinger Abstract This paper presents an algebraic multigrid method for the efficient solution of the linear system arising from a finite element discretization of variational problems in H0(curl,,). The finite element spaces are generated by Nédélec's edge elements. A coarsening technique is presented, which allows the construction of suitable coarse finite element spaces, corresponding transfer operators and appropriate smoothers. The prolongation operator is designed such that coarse grid kernel functions of the curl-operator are mapped to fine grid kernel functions. Furthermore, coarse grid kernel functions are ,discrete' gradients. The smoothers proposed by Hiptmair and Arnold, Falk and Winther are directly used in the algebraic framework. Numerical studies are presented for 3D problems to show the high efficiency of the proposed technique. Copyright © 2002 John Wiley & Sons, Ltd. [source] On the efficiency of cell-like and tissue-like recognizing membrane systemsINTERNATIONAL JOURNAL OF INTELLIGENT SYSTEMS, Issue 7 2009Miguel A. Gutiérrez-Naranjo Cell-like recognizing membrane systems are computational devices in the framework of membrane computing inspired from the structure of living cells, where biological membranes are arranged hierarchically. In this paper tissue-like recognizing membrane systems are presented. The idea is to consider that membranes are placed in the nodes of a graph, mimicking the cell intercommunication in tissues. In this context, polynomial complexity classes associated with recognizing membrane systems can be defined. We recall the definition for cell-like systems, and we introduce the corresponding complexity classes for the tissue-like case. Moreover, in this paper two efficient solutions to the satisfiability problem are analyzed and compared from a complexity point of view. © 2009 Wiley Periodicals, Inc. [source] Optimal design and planning of sustainable chemical supply chains under uncertaintyAICHE JOURNAL, Issue 1 2009Gonzalo Guillén-Gosálbez Abstract This article addresses the design of sustainable chemical supply chains in the presence of uncertainty in the life cycle inventory associated with the network operation. The design task is mathematically formulated as a bi-criterion stochastic mixed-integer nonlinear program (MINLP) that simultaneously accounts for the maximization of the net present value and the minimization of the environmental impact for a given probability level. The environmental performance is measured through the Eco-indicator 99, which incorporates the recent advances made in Life Cycle Assessment. The stochastic model is converted into its deterministic equivalent by reformulating the probabilistic constraint required to calculate the environmental impact in the space of uncertain parameters. The resulting deterministic bi-criterion MINLP problem is further reformulated as a parametric MINLP, which is solved by decomposing it into two sub-problems and iterating between them. The capabilities of the proposed model and solution procedure are illustrated through two case studies for which the set of Pareto optimal, or efficient solutions that trade-off environmental impact and profit, are calculated. These solutions provide valuable insights into the design problem and are intended to guide the decision maker towards the adoption of more sustainable design alternatives. © 2008 American Institute of Chemical Engineers AIChE J, 2009 [source] | ||||||||||||||||||||||