WorldWideScience

Sample records for approximate reasoning methods

  1. Approximate spatial reasoning

    Science.gov (United States)

    Dutta, Soumitra

    1988-01-01

    Much of human reasoning is approximate in nature. Formal models of reasoning traditionally try to be precise and reject the fuzziness of concepts in natural use and replace them with non-fuzzy scientific explicata by a process of precisiation. As an alternate to this approach, it has been suggested that rather than regard human reasoning processes as themselves approximating to some more refined and exact logical process that can be carried out with mathematical precision, the essence and power of human reasoning is in its capability to grasp and use inexact concepts directly. This view is supported by the widespread fuzziness of simple everyday terms (e.g., near tall) and the complexity of ordinary tasks (e.g., cleaning a room). Spatial reasoning is an area where humans consistently reason approximately with demonstrably good results. Consider the case of crossing a traffic intersection. We have only an approximate idea of the locations and speeds of various obstacles (e.g., persons and vehicles), but we nevertheless manage to cross such traffic intersections without any harm. The details of our mental processes which enable us to carry out such intricate tasks in such apparently simple manner are not well understood. However, it is that we try to incorporate such approximate reasoning techniques in our computer systems. Approximate spatial reasoning is very important for intelligent mobile agents (e.g., robots), specially for those operating in uncertain or unknown or dynamic domains.

  2. Approximate Assertional Reasoning Over Expressive Ontologies

    OpenAIRE

    Tserendorj, Tuvshintur

    2010-01-01

    In this thesis, approximate reasoning methods for scalable assertional reasoning are provided whose computational properties can be established in a well-understood way, namely in terms of soundness and completeness, and whose quality can be analyzed in terms of statistical measurements, namely recall and precision. The basic idea of these approximate reasoning methods is to speed up reasoning by trading off the quality of reasoning results against increased speed.

  3. An approximate reasoning-based method for screening high-level-waste tanks for flammable gas

    International Nuclear Information System (INIS)

    The in situ retention of flammable gas produced by radiolysis and thermal decomposition in high-level waste can pose a safety problem if the gases are released episodically into the dome space of a storage tank. Screening efforts at the Hanford site have been directed at identifying tanks in which this situation could exist. Problems encountered in screening motivated an effort to develop and improved screening methodology. Approximate reasoning (AR) is a formalism designed to emulate the kinds of complex judgments made by subject matter experts. It uses inductive logic structures to build a sequence of forward-chaining inferences about a subject. Approximate-reasoning models incorporate natural language expressions known as linguistic variables to represent evidence. The use of fuzzy sets to represent these variables mathematically makes it practical to evaluate quantitative and qualitative information consistently. In a pilot study to investigate the utility of AR for flammable gas screening, the effort to implement such a model was found to be acceptable, and computational requirements were found to be reasonable. The preliminary results showed that important judgments about the validity of observational data and the predictive power of models could be made. These results give new insights into the problems observed in previous screening efforts

  4. An Approximate Reasoning-Based Method for Screening High-Level-Waste Tanks for Flammable Gas

    International Nuclear Information System (INIS)

    The in situ retention of flammable gas produced by radiolysis and thermal decomposition in high-level waste can pose a safety problem if the gases are released episodically into the dome space of a storage tank. Screening efforts at the Hanford site have been directed at identifying tanks in which this situation could exist. Problems encountered in screening motivated an effort to develop an improved screening methodology. Approximate reasoning (AR) is a formalism designed to emulate the kinds of complex judgments made by subject matter experts. It uses inductive logic structures to build a sequence of forward-chaining inferences about a subject. Approximate-reasoning models incorporate natural language expressions known as linguistic variables to represent evidence. The use of fuzzy sets to represent these variables mathematically makes it practical to evaluate quantitative and qualitative information consistently. In a pilot study to investigate the utility of AR for flammable gas screening, the effort to implement such a model was found to be acceptable, and computational requirements were found to be reasonable. The preliminary results showed that important judgments about the validity of observational data and the predictive power of models could be made. These results give new insights into the problems observed in previous screening efforts

  5. Assessment of effective parameters on dilution using approximate reasoning methods in longwall mining method, Iran coal mines

    CERN Document Server

    Owladeghaffari, H; Saeedi, G H R

    2008-01-01

    Approximately more than 90% of all coal production in Iranian underground mines is derived directly longwall mining method. Out of seam dilution is one of the essential problems in these mines. Therefore the dilution can impose the additional cost of mining and milling. As a result, recognition of the effective parameters on the dilution has a remarkable role in industry. In this way, this paper has analyzed the influence of 13 parameters (attributed variables) versus the decision attribute (dilution value), so that using two approximate reasoning methods, namely Rough Set Theory (RST) and Self Organizing Neuro- Fuzzy Inference System (SONFIS) the best rules on our collected data sets has been extracted. The other benefit of later methods is to predict new unknown cases. So, the reduced sets (reducts) by RST have been obtained. Therefore the emerged results by utilizing mentioned methods shows that the high sensitive variables are thickness of layer, length of stope, rate of advance, number of miners, type of...

  6. Approximate Reasoning with Fuzzy Booleans

    NARCIS (Netherlands)

    Broek, van den P.M.; Noppen, J.A.R.

    2004-01-01

    This paper introduces, in analogy to the concept of fuzzy numbers, the concept of fuzzy booleans, and examines approximate reasoning with the compositional rule of inference using fuzzy booleans. It is shown that each set of fuzzy rules is equivalent to a set of fuzzy rules with singleton crisp ante

  7. An approximate-reasoning-based method for screening high-level waste tanks for flammable gas

    International Nuclear Information System (INIS)

    The in situ retention of flammable gas produced by radiolysis and thermal decomposition in high-level waste can pose a safety problem if the gases are released episodically into the dome space of a storage tank. Screening efforts at Hanford have been directed at identifying tanks in which this situation could exist. Problems encountered in screening motivated an effort to develop an improved screening methodology. Approximate reasoning (AR) is a formalism designed to emulate the kinds of complex judgments made by subject matter experts. It uses inductive logic structures to build a sequence of forward-chaining inferences about a subject. AR models incorporate natural language expressions known as linguistic variables to represent evidence. The use of fuzzy sets to represent these variables mathematically makes it practical to evaluate quantitative and qualitative information consistently. The authors performed a pilot study to investigate the utility of AR for flammable gas screening. They found that the effort to implement such a model was acceptable and that computational requirements were reasonable. The preliminary results showed that important judgments about the validity of observational data and the predictive power of models could be made. These results give new insights into the problems observed in previous screening efforts

  8. An approximate-reasoning-based method for screening flammable gas tanks

    Energy Technology Data Exchange (ETDEWEB)

    Eisenhawer, S.W.; Bott, T.F.; Smith, R.E.

    1998-03-01

    High-level waste (HLW) produces flammable gases as a result of radiolysis and thermal decomposition of organics. Under certain conditions, these gases can accumulate within the waste for extended periods and then be released quickly into the dome space of the storage tank. As part of the effort to reduce the safety concerns associated with flammable gas in HLW tanks at Hanford, a flammable gas watch list (FGWL) has been established. Inclusion on the FGWL is based on criteria intended to measure the risk associated with the presence of flammable gas. It is important that all high-risk tanks be identified with high confidence so that they may be controlled. Conversely, to minimize operational complexity, the number of tanks on the watchlist should be reduced as near to the true number of flammable risk tanks as the current state of knowledge will support. This report presents an alternative to existing approaches for FGWL screening based on the theory of approximate reasoning (AR) (Zadeh 1976). The AR-based model emulates the inference process used by an expert when asked to make an evaluation. The FGWL model described here was exercised by performing two evaluations. (1) A complete tank evaluation where the entire algorithm is used. This was done for two tanks, U-106 and AW-104. U-106 is a single shell tank with large sludge and saltcake layers. AW-104 is a double shell tank with over one million gallons of supernate. Both of these tanks had failed the screening performed by Hodgson et al. (2) Partial evaluations using a submodule for the predictor likelihood for all of the tanks on the FGWL that had been flagged previously by Whitney (1995).

  9. An approximate-reasoning-based method for screening flammable gas tanks

    International Nuclear Information System (INIS)

    High-level waste (HLW) produces flammable gases as a result of radiolysis and thermal decomposition of organics. Under certain conditions, these gases can accumulate within the waste for extended periods and then be released quickly into the dome space of the storage tank. As part of the effort to reduce the safety concerns associated with flammable gas in HLW tanks at Hanford, a flammable gas watch list (FGWL) has been established. Inclusion on the FGWL is based on criteria intended to measure the risk associated with the presence of flammable gas. It is important that all high-risk tanks be identified with high confidence so that they may be controlled. Conversely, to minimize operational complexity, the number of tanks on the watchlist should be reduced as near to the true number of flammable risk tanks as the current state of knowledge will support. This report presents an alternative to existing approaches for FGWL screening based on the theory of approximate reasoning (AR) (Zadeh 1976). The AR-based model emulates the inference process used by an expert when asked to make an evaluation. The FGWL model described here was exercised by performing two evaluations. (1) A complete tank evaluation where the entire algorithm is used. This was done for two tanks, U-106 and AW-104. U-106 is a single shell tank with large sludge and saltcake layers. AW-104 is a double shell tank with over one million gallons of supernate. Both of these tanks had failed the screening performed by Hodgson et al. (2) Partial evaluations using a submodule for the predictor likelihood for all of the tanks on the FGWL that had been flagged previously by Whitney (1995)

  10. Approximate level method

    OpenAIRE

    Richtárik, Peter

    2008-01-01

    In this paper we propose and analyze a variant of the level method [4], which is an algorithm for minimizing nonsmooth convex functions. The main work per iteration is spent on 1) minimizing a piecewise-linear model of the objective function and on 2) projecting onto the intersection of the feasible region and a polyhedron arising as a level set of the model. We show that by replacing exact computations in both cases by approximate computations, in relative scale, the theoretical ...

  11. A comparison of approximate reasoning results using information uncertainty

    Energy Technology Data Exchange (ETDEWEB)

    Chavez, Gregory [Los Alamos National Laboratory; Key, Brian [Los Alamos National Laboratory; Zerkle, David [Los Alamos National Laboratory; Shevitz, Daniel [Los Alamos National Laboratory

    2009-01-01

    An Approximate Reasoning (AR) model is a useful alternative to a probabilistic model when there is a need to draw conclusions from information that is qualitative. For certain systems, much of the information available is elicited from subject matter experts (SME). One such example is the risk of attack on a particular facility by a pernicious adversary. In this example there are several avenues of attack, i.e. scenarios, and AR can be used to model the risk of attack associated with each scenario. The qualitative information available and provided by the SME is comprised of linguistic values which are well suited for an AR model but meager for other modeling approaches. AR models can produce many competing results. Associated with each competing AR result is a vector of linguistic values and a respective degree of membership in each value. A suitable means to compare and segregate AR results would be an invaluable tool to analysts and decisions makers. A viable method would be to quantify the information uncertainty present in each AR result then use the measured quantity comparatively. One issue of concern for measuring the infornlation uncertainty involved with fuzzy uncertainty is that previously proposed approaches focus on the information uncertainty involved within the entire fuzzy set. This paper proposes extending measures of information uncertainty to AR results, which involve only one degree of membership for each fuzzy set included in the AR result. An approach to quantify the information uncertainty in the AR result is presented.

  12. Approximation methods in probability theory

    CERN Document Server

    Čekanavičius, Vydas

    2016-01-01

    This book presents a wide range of well-known and less common methods used for estimating the accuracy of probabilistic approximations, including the Esseen type inversion formulas, the Stein method as well as the methods of convolutions and triangle function. Emphasising the correct usage of the methods presented, each step required for the proofs is examined in detail. As a result, this textbook provides valuable tools for proving approximation theorems. While Approximation Methods in Probability Theory will appeal to everyone interested in limit theorems of probability theory, the book is particularly aimed at graduate students who have completed a standard intermediate course in probability theory. Furthermore, experienced researchers wanting to enlarge their toolkit will also find this book useful.

  13. Uncertainty and approximate reasoning in waste pretreatment planning

    International Nuclear Information System (INIS)

    Waste pretreatment process planning within the DOE complex must consider many different outcomes in order to perform the tradeoffs necessary to accomplish this important national mission. One of the difficulties encountered by many who assess these tradeoffs is that the complexity of this problem taxes the abilities of any single person or small group of individuals. For example, uncertainties in waste composition as well as process efficiency are well known yet incompletely considered in the search for optimum solutions. This paper describes a tool, the pre-treatment Process Analysis Tool (PAT), for evaluating tank waste pretreatment options at Hanford, Oak Ridge, Idaho National Environmental and Engineering Laboratory, and Savannah River Sites. The PAT propagates uncertainty in both tank waste composition and process partitioning into a set of ten outcomes. These outcomes are, for example, total cost, Cs-137 in iLAW, iHLW MT, and so on. Tradeoffs among outcomes are evaluated or scored by means of an approximate reasoning module that uses linguistic bases to evaluate tradeoffs for each process based on user valuations of outcomes

  14. System reliability assessment with an approximate reasoning model

    Energy Technology Data Exchange (ETDEWEB)

    Eisenhawer, S.W.; Bott, T.F.; Helm, T.M.; Boerigter, S.T.

    1998-12-31

    The projected service life of weapons in the US nuclear stockpile will exceed the original design life of their critical components. Interim metrics are needed to describe weapon states for use in simulation models of the nuclear weapons complex. The authors present an approach to this problem based upon the theory of approximate reasoning (AR) that allows meaningful assessments to be made in an environment where reliability models are incomplete. AR models are designed to emulate the inference process used by subject matter experts. The emulation is based upon a formal logic structure that relates evidence about components. This evidence is translated using natural language expressions into linguistic variables that describe membership in fuzzy sets. The authors introduce a metric that measures the acceptability of a weapon to nuclear deterrence planners. Implication rule bases are used to draw a series of forward chaining inferences about the acceptability of components, subsystems and individual weapons. They describe each component in the AR model in some detail and illustrate its behavior with a small example. The integration of the acceptability metric into a prototype model to simulate the weapons complex is also described.

  15. Artificial neural networks and approximate reasoning for intelligent control in space

    Science.gov (United States)

    Berenji, Hamid R.

    1991-01-01

    A method is introduced for learning to refine the control rules of approximate reasoning-based controllers. A reinforcement-learning technique is used in conjunction with a multi-layer neural network model of an approximate reasoning-based controller. The model learns by updating its prediction of the physical system's behavior. The model can use the control knowledge of an experienced operator and fine-tune it through the process of learning. Some of the space domains suitable for applications of the model such as rendezvous and docking, camera tracking, and tethered systems control are discussed.

  16. Information processing systems, reasoning modules, and reasoning system design methods

    Energy Technology Data Exchange (ETDEWEB)

    Hohimer, Ryan E.; Greitzer, Frank L.; Hampton, Shawn D.

    2016-08-23

    Information processing systems, reasoning modules, and reasoning system design methods are described. According to one aspect, an information processing system includes working memory comprising a semantic graph which comprises a plurality of abstractions, wherein the abstractions individually include an individual which is defined according to an ontology and a reasoning system comprising a plurality of reasoning modules which are configured to process different abstractions of the semantic graph, wherein a first of the reasoning modules is configured to process a plurality of abstractions which include individuals of a first classification type of the ontology and a second of the reasoning modules is configured to process a plurality of abstractions which include individuals of a second classification type of the ontology, wherein the first and second classification types are different.

  17. Information processing systems, reasoning modules, and reasoning system design methods

    Energy Technology Data Exchange (ETDEWEB)

    Hohimer, Ryan E.; Greitzer, Frank L.; Hampton, Shawn D.

    2015-08-18

    Information processing systems, reasoning modules, and reasoning system design methods are described. According to one aspect, an information processing system includes working memory comprising a semantic graph which comprises a plurality of abstractions, wherein the abstractions individually include an individual which is defined according to an ontology and a reasoning system comprising a plurality of reasoning modules which are configured to process different abstractions of the semantic graph, wherein a first of the reasoning modules is configured to process a plurality of abstractions which include individuals of a first classification type of the ontology and a second of the reasoning modules is configured to process a plurality of abstractions which include individuals of a second classification type of the ontology, wherein the first and second classification types are different.

  18. Information processing systems, reasoning modules, and reasoning system design methods

    Energy Technology Data Exchange (ETDEWEB)

    Hohimer, Ryan E; Greitzer, Frank L; Hampton, Shawn D

    2014-03-04

    Information processing systems, reasoning modules, and reasoning system design methods are described. According to one aspect, an information processing system includes working memory comprising a semantic graph which comprises a plurality of abstractions, wherein the abstractions individually include an individual which is defined according to an ontology and a reasoning system comprising a plurality of reasoning modules which are configured to process different abstractions of the semantic graph, wherein a first of the reasoning modules is configured to process a plurality of abstractions which include individuals of a first classification type of the ontology and a second of the reasoning modules is configured to process a plurality of abstractions which include individuals of a second classification type of the ontology, wherein the first and second classification types are different.

  19. Approximation methods for stochastic petri nets

    Science.gov (United States)

    Jungnitz, Hauke Joerg

    1992-01-01

    Stochastic Marked Graphs are a concurrent decision free formalism provided with a powerful synchronization mechanism generalizing conventional Fork Join Queueing Networks. In some particular cases the analysis of the throughput can be done analytically. Otherwise the analysis suffers from the classical state explosion problem. Embedded in the divide and conquer paradigm, approximation techniques are introduced for the analysis of stochastic marked graphs and Macroplace/Macrotransition-nets (MPMT-nets), a new subclass introduced herein. MPMT-nets are a subclass of Petri nets that allow limited choice, concurrency and sharing of resources. The modeling power of MPMT is much larger than that of marked graphs, e.g., MPMT-nets can model manufacturing flow lines with unreliable machines and dataflow graphs where choice and synchronization occur. The basic idea leads to the notion of a cut to split the original net system into two subnets. The cuts lead to two aggregated net systems where one of the subnets is reduced to a single transition. A further reduction leads to a basic skeleton. The generalization of the idea leads to multiple cuts, where single cuts can be applied recursively leading to a hierarchical decomposition. Based on the decomposition, a response time approximation technique for the performance analysis is introduced. Also, delay equivalence, which has previously been introduced in the context of marked graphs by Woodside et al., Marie's method and flow equivalent aggregation are applied to the aggregated net systems. The experimental results show that response time approximation converges quickly and shows reasonable accuracy in most cases. The convergence of Marie's method and flow equivalent aggregation are applied to the aggregated net systems. The experimental results show that response time approximation converges quickly and shows reasonable accuracy in most cases. The convergence of Marie's is slower, but the accuracy is generally better. Delay

  20. Dynamical equations and approximation methods

    International Nuclear Information System (INIS)

    The integral equations approach to the three-body problem, decisively stimulated by Faddeev's formulation, provides the most powerful tool for studying the internal structure of this system. An essential step towards a detailed understanding of composite particle dynamics has been done in this way. The search for adequate extensions to the general N-body situation therefore represented, and still represents a natural challenge. For various reasons this transition is non-trivial and non-unique. Emphasizing different aspects of the three-body theory, different generalizations have been found. In particular, it was the concept of connectedness of the (iterated) integral kernel which allows for an arbitrary number of formulations, many of them being presumably only mathematically correct, but physically rather unsatisfactory. Therefore, the present status of the N-body theory is reviewed in a less technical way. Starting from the basic, physically convincing definitions of scattering states, the defining equations are replaced by more appropriate matrix relations. This is done in a reversible way, thus preserving in every step the original structure and information. In order to be as close as possible to the basic definitions, all relations are first derived for scattering states or half-on-shell transition amplitudes. The ambiguity in going over to corresponding operator identities (fully off-shell equations) is demonstrated. (Auth.)

  1. Evaluation of high-level waste pretreatment processes with an approximate reasoning model

    International Nuclear Information System (INIS)

    The development of an approximate-reasoning (AR)-based model to analyze pretreatment options for high-level waste is presented. AR methods are used to emulate the processes used by experts in arriving at a judgment. In this paper, the authors first consider two specific issues in applying AR to the analysis of pretreatment options. They examine how to combine quantitative and qualitative evidence to infer the acceptability of a process result using the example of cesium content in low-level waste. They then demonstrate the use of simple physical models to structure expert elicitation and to produce inferences consistent with a problem involving waste particle size effects

  2. A Linear Approximation Method for Probabilistic Inference

    OpenAIRE

    Shachter, Ross D.

    2013-01-01

    An approximation method is presented for probabilistic inference with continuous random variables. These problems can arise in many practical problems, in particular where there are "second order" probabilities. The approximation, based on the Gaussian influence diagram, iterates over linear approximations to the inference problem.

  3. A New Method for Reasoning about Action

    Institute of Scientific and Technical Information of China (English)

    杨杰

    1996-01-01

    Reasoning about action is an important aspect of common sense reasoning and planning.It gives rise to three classical problems:the frame problem,the qualification problem and the ramification problem.Existing approaches cannot deal with these problems efficiently.This paper presents a new method which uses the stratified ATMS for reasoning about action to overcome the limitations of these approaches.

  4. Scientific Facts and Methods in Public Reason

    DEFF Research Database (Denmark)

    Jønch-Clausen, Karin; Kappel, Klemens

    2016-01-01

    Should scientific facts and methods have an epistemically privileged status in public reason? In Rawls’s public reason account he asserts what we will label the Scientific Standard Stricture: citizens engaged in public reason must be guided by non-controversial scientific methods, and public reason......’s Scientific Standards Stricture. We then use Rawls’s general theoretical framework to examine various potential justifications for privileging these ‘non-controversial’ scientific methods and conclusions. We conclude that no viable justification is available to Rawls....... must be in line with non-controversial scientific conclusions. The Scientific Standard Stricture is meant to fulfill important tasks such as enabling the determinateness and publicity of the public reason framework. However, Rawls leaves us without elucidation with regard to when science is and is not...

  5. Approximate error conjugation gradient minimization methods

    Science.gov (United States)

    Kallman, Jeffrey S

    2013-05-21

    In one embodiment, a method includes selecting a subset of rays from a set of all rays to use in an error calculation for a constrained conjugate gradient minimization problem, calculating an approximate error using the subset of rays, and calculating a minimum in a conjugate gradient direction based on the approximate error. In another embodiment, a system includes a processor for executing logic, logic for selecting a subset of rays from a set of all rays to use in an error calculation for a constrained conjugate gradient minimization problem, logic for calculating an approximate error using the subset of rays, and logic for calculating a minimum in a conjugate gradient direction based on the approximate error. In other embodiments, computer program products, methods, and systems are described capable of using approximate error in constrained conjugate gradient minimization problems.

  6. Approximate path integral methods for partition functions

    International Nuclear Information System (INIS)

    We review several approximate methods for evaluating quantum mechanical partition functions with the goal of obtaining a method that is easy to implement for multidimensional systems but accurately incorporates quantum mechanical corrections to classical partition functions. A particularly promising method is one based upon an approximation to the path integral expression of the partition function. In this method, the partition-function expression has the ease of evaluation of a classical partition function, and quantum mechanical effects are included by a weight function. Anharmonicity is included exactly in the classical Boltzmann average and local quadratic expansions around the centroid of the quantum paths yield a simple analytic form for the quantum weight function. We discuss the relationship between this expression and previous approximate methods and present numerical comparisons for model one-dimensional potentials and for accurate three-dimensional vibrational force fields for H2O and SO2

  7. Generalized If ... Then...Else Inference Rules with Linguistic Modifiers for Approximate Reasoning

    OpenAIRE

    Le Anh Phuong; Tran Dinh Khang

    2012-01-01

    In this paper, based on the our previous researchs about generalized modus ponens with linguistic modifiers for If...Then rules, we propose generalized If...Then...Else inference rules with linguistic modifiers in linguistic many-valued logic framework with using hedge moving rules for approximate reasoning.

  8. Research of Approximate Reasoning in Semantic Web%语义Web近似推理研究

    Institute of Scientific and Technical Information of China (English)

    廖先旭; 黄佳进

    2011-01-01

    随着语义Web本体技术的快速发展和近似推理技术的应用,语义Web近似推理满足了快速有效地搜索有用的信息和知识的需求。本文主要从语义Web近似推理的难点介绍了近年来关于语义web近似推理的研究,并在最后对语义web近似推理研究的发展趋势做了总结。%With the fast development of ontology technology for Semantic Web and the application of approximate reasoning, approximate reasoning on the Semantic Web can satisfy the demand of finding useful information and knowledge fast and efficiently. This paper introduces approximate reasoning on the Semantic Web research in recent years from its key problems and the research trends of approximate reasoning on Semantic Web.

  9. Iterative Methods for the Force-based Quasicontinuum Approximation

    OpenAIRE

    Dobson, Matthew; Luskin, Mitchell; Ortner, Christoph

    2009-01-01

    Force-based atomistic-continuum hybrid methods are the only known pointwise consistent methods for coupling a general atomistic model to a finite element continuum model. For this reason, and due to their algorithmic simplicity, force-based coupling methods have become a popular class of atomistic-continuum hybrid models as well as other types of multiphysics models. However, the recently discovered unusual stability properties of the linearized force-based quasicontinuum (QCF) approximation,...

  10. LinguisticBelief: a java application for linguistic evaluation using belief, fuzzy sets, and approximate reasoning.

    Energy Technology Data Exchange (ETDEWEB)

    Darby, John L.

    2007-03-01

    LinguisticBelief is a Java computer code that evaluates combinations of linguistic variables using an approximate reasoning rule base. Each variable is comprised of fuzzy sets, and a rule base describes the reasoning on combinations of variables fuzzy sets. Uncertainty is considered and propagated through the rule base using the belief/plausibility measure. The mathematics of fuzzy sets, approximate reasoning, and belief/ plausibility are complex. Without an automated tool, this complexity precludes their application to all but the simplest of problems. LinguisticBelief automates the use of these techniques, allowing complex problems to be evaluated easily. LinguisticBelief can be used free of charge on any Windows XP machine. This report documents the use and structure of the LinguisticBelief code, and the deployment package for installation client machines.

  11. Reverse triple I method of fuzzy reasoning

    Institute of Scientific and Technical Information of China (English)

    宋士吉; 吴澄

    2002-01-01

    A theory of reverse triple I method with sustention degree is presented by using the implication operator R0 in every step of the fuzzy reasoning. Its computation formulas of supremum for fuzzy modus ponens and infimum for fuzzy modus tollens are given respectively. Moreover, through the generalization of this problem, the corresponding formulas of ?-reverse triple I method with sustention degree are also obtained. In addition, the theory of reverse triple I method with restriction degree is proposed as well by using the operator R0, and the computation formulas of infimum for fuzzy modus ponens and supremum for fuzzy modus tollens are shown.

  12. Approximate syllogistic reasoning: a contribution to inference patterns and use cases

    OpenAIRE

    Pereira-Fariña, Martín

    2014-01-01

    In this thesis two models of syllogistic reasoning for dealing with arguments that involve fuzzy quantified statements and approximate chaining are proposed. The modeling of quantified statements is based on the Theory of Generalized Quantifiers, which allows us to manage different kind of quantifiers simultaneously, and the inference process is interpreted in terms of a mathematical optimization problem, which allows us to deal with more arguments that standard deductive ones. For the case o...

  13. Impulse approximation versus elementary particle method

    International Nuclear Information System (INIS)

    Calculations are made for radiative muon capture in 3He, both in impulse approximation and with the elementary particle method, and results are compared. It is argued that a diagrammatic method which takes a selected set of Feynman diagrams into account only provides insufficient warrant that effects not included are small. Therefore low-energy theorems are employed, as first given by Adler and Dothan, to determine the amplitude up to and including all terms linear in photon momentum and momentum transfer at the weak vertex. This amplitude is applied to radiative muon capture with the elementary particle method (EPM). The various form factors needed are discussed. It is shown that the results are particularly sensitive to the π-3He-3H coupling constant of which many contradictory determinations have been described in the literature. The classification of the nuclear wave function employed in the impulse approximation (IA) is summarized. The ν-decay of 3H and (radiative muon capture in 3He is treated and numerical results are given. Next, pion photoproduction and radiative pion capture are considered. IA and EPM for radiative muon capture are compared more closely. It is concluded that two-step processes are inherently difficult; the elementary particle method has convergence problems, and unknown parameters are present. In the impulse approximation, which is perhaps conceptually more difficult, the two-step interaction for the nucleon is considered as effectively point-like with small non-local corrections. (Auth.)

  14. An approximate method for classical scattering problems

    International Nuclear Information System (INIS)

    An approximate method of calculating scattering cross sections is presented. Newton's second law and the conservation of energy are used to relate the scattering angle to the impulse delivered to the projectile by the scatterer. In order to calculate the impulse, it is necessary to know the time dependence of the trajectory. We assume that the projectile travels the two asymptotes to the actual trajectory with constant velocity

  15. Study of quarkonium spectroscopy through the approximated variational method

    International Nuclear Information System (INIS)

    The spectroscopy of the qq sup(-) bound states in a non-relativistic approximation using a approximate variational method is studied. Because of its similarity to positronium, a wave function of the hidrogen atom, is used. The 'coulomb-logaritmic-linear' was the potential used to described it. The fitting is done, and relevant coupling constant due to a logaritmic piece is found. All states described in this way furnishes v2 3P are reasonably explained and it no occurs with the mass diference between psi and eta sub(c). (Author)

  16. Approximations in the PE-method

    DEFF Research Database (Denmark)

    Arranz, Marta Galindo

    Two differenct sources of errors may occur in the implementation of the PE methods; a phase error introduced in the approximation of a pseudo-differential operator and an amplitude error generated from the starting field. First, the inherent phase errors introduced in the solution are analyzed for...... a case where the normal mode solution to the wave equation is valid, when the sound is propagated in a downward refracting atmosphere. The angular limitations for the different parabolic approximations are deduced, and calculations showing shifts in the starter as the second source of error is...... investigated. Numerical and analytical starters are compared for source locations close to the ground. The spectral properties of several starters are presented....

  17. Combining qualitative and quantitative spatial and temporal information in a hierarchical structure: Approximate reasoning for plan execution monitoring

    Science.gov (United States)

    Hoebel, Louis J.

    1993-01-01

    The problem of plan generation (PG) and the problem of plan execution monitoring (PEM), including updating, queries, and resource-bounded replanning, have different reasoning and representation requirements. PEM requires the integration of qualitative and quantitative information. PEM is the receiving of data about the world in which a plan or agent is executing. The problem is to quickly determine the relevance of the data, the consistency of the data with respect to the expected effects, and if execution should continue. Only spatial and temporal aspects of the plan are addressed for relevance in this work. Current temporal reasoning systems are deficient in computational aspects or expressiveness. This work presents a hybrid qualitative and quantitative system that is fully expressive in its assertion language while offering certain computational efficiencies. In order to proceed, methods incorporating approximate reasoning using hierarchies, notions of locality, constraint expansion, and absolute parameters need be used and are shown to be useful for the anytime nature of PEM.

  18. A Method for Approximate Reasoning in Exploratory Data Analysis

    Czech Academy of Sciences Publication Activity Database

    Holeňa, Martin

    Wien : Austrian Society for Cybernetic Studies, 1996, s. 329-334. ISBN 3-85206-133-4. [European Meeting on Cybernetics and Systems Research /13./. Vienna (AT), 09.04.1996-12.04.1996] Grant ostatní: COPERNICUS(XE) MUM-10053

  19. Sparse Approximation via Penalty Decomposition Methods

    CERN Document Server

    Lu, Zhaosong

    2012-01-01

    In this paper we consider sparse approximation problems, that is, general $l_0$ minimization problems with the $l_0$-"norm" of a vector being a part of constraints or objective function. In particular, we first study the first-order optimality conditions for these problems. We then propose penalty decomposition (PD) methods for solving them in which a sequence of penalty subproblems are solved by a block coordinate descent (BCD) method. Under some suitable assumptions, we establish that any accumulation point of the sequence generated by the PD methods satisfies the first-order optimality conditions of the problems. Furthermore, for the problems in which the $l_0$ part is the only nonconvex part, we show that such an accumulation point is a local minimizer of the problems. In addition, we show that any accumulation point of the sequence generated by the BCD method is a saddle point of the penalty subproblem. Moreover, for the problems in which the $l_0$ part is the only nonconvex part, we establish that such ...

  20. On approximate reasoning and minimal models for the development of robust outdoor vehicle navigation schemes

    International Nuclear Information System (INIS)

    Outdoor sensor-based operation of autonomous robots has revealed to be an extremely challenging problem, mainly because of the difficulties encountered when attempting to represent the many uncertainties which are always present in the real world. These uncertainties are primarily due to sensor imprecisions and unpredictability of the environment, i.e., lack of full knowledge of the environment characteristics and dynamics. Two basic principles, or philosophies, and their associated methodologies are proposed in an attempt to remedy some of these difficulties. The first principle is based on the concept of ''minimal model'' for accomplishing given tasks and proposes to utilize only the minimum level of information and precision necessary to accomplish elemental functions of complex tasks. This approach diverges completely from the direction taken by most artificial vision studies which conventionally call for crisp and detailed analysis of every available component in the perception data. The paper will first review the basic concepts of this approach and will discuss its pragmatic feasibility when embodied in a behaviorist framework. The second principle which is proposed deals with implicit representation of uncertainties using Fuzzy Set Theory-based approximations and approximate reasoning, rather than explicit (crisp) representation through calculation and conventional propagation techniques. A framework which merges these principles and approaches is presented, and its application to the problem of sensor-based outdoor navigation of a mobile robot is discussed. Results of navigation experiments with a real car in actual outdoor environments are also discussed to illustrate the feasibility of the overall concept

  1. On approximate reasoning and minimal models for the development of robust outdoor vehicle navigation schemes

    Energy Technology Data Exchange (ETDEWEB)

    Pin, F.G.

    1993-11-01

    Outdoor sensor-based operation of autonomous robots has revealed to be an extremely challenging problem, mainly because of the difficulties encountered when attempting to represent the many uncertainties which are always present in the real world. These uncertainties are primarily due to sensor imprecisions and unpredictability of the environment, i.e., lack of full knowledge of the environment characteristics and dynamics. Two basic principles, or philosophies, and their associated methodologies are proposed in an attempt to remedy some of these difficulties. The first principle is based on the concept of ``minimal model`` for accomplishing given tasks and proposes to utilize only the minimum level of information and precision necessary to accomplish elemental functions of complex tasks. This approach diverges completely from the direction taken by most artificial vision studies which conventionally call for crisp and detailed analysis of every available component in the perception data. The paper will first review the basic concepts of this approach and will discuss its pragmatic feasibility when embodied in a behaviorist framework. The second principle which is proposed deals with implicit representation of uncertainties using Fuzzy Set Theory-based approximations and approximate reasoning, rather than explicit (crisp) representation through calculation and conventional propagation techniques. A framework which merges these principles and approaches is presented, and its application to the problem of sensor-based outdoor navigation of a mobile robot is discussed. Results of navigation experiments with a real car in actual outdoor environments are also discussed to illustrate the feasibility of the overall concept.

  2. Methods of Fourier analysis and approximation theory

    CERN Document Server

    Tikhonov, Sergey

    2016-01-01

    Different facets of interplay between harmonic analysis and approximation theory are covered in this volume. The topics included are Fourier analysis, function spaces, optimization theory, partial differential equations, and their links to modern developments in the approximation theory. The articles of this collection were originated from two events. The first event took place during the 9th ISAAC Congress in Krakow, Poland, 5th-9th August 2013, at the section “Approximation Theory and Fourier Analysis”. The second event was the conference on Fourier Analysis and Approximation Theory in the Centre de Recerca Matemàtica (CRM), Barcelona, during 4th-8th November 2013, organized by the editors of this volume. All articles selected to be part of this collection were carefully reviewed.

  3. Reasons and Methods to Learn the Management

    Science.gov (United States)

    Li, Hongxin; Ding, Mengchun

    2010-01-01

    Reasons for learning the management include (1) perfecting the knowledge structure, (2) the management is the base of all organizations, (3) one person may be the manager or the managed person, (4) the management is absolutely not simple knowledge, and (5) the learning of the theoretical knowledge of the management can not be replaced by the…

  4. An Analysis of General Fuzzy Logic and Fuzzy Reasoning Method

    OpenAIRE

    Il, Kwak Son

    2016-01-01

    In this article, we describe the fuzzy logic, fuzzy language and algorithms as the basis of fuzzy reasoning, one of the intelligent information processing method, and then describe the general fuzzy reasoning method.

  5. Evaluating methods for approximating stochastic differential equations

    OpenAIRE

    Brown, Scott D; RATCLIFF, ROGER; Smith, Philip L.

    2006-01-01

    Models of decision making and response time (RT) are often formulated using stochastic differential equations (SDEs). Researchers often investigate these models using a simple Monte Carlo method based on Euler’s method for solving ordinary differential equations. The accuracy of Euler’s method is investigated and compared to the performance of more complex simulation methods. The more complex methods for solving SDEs yielded no improvement in accuracy over the Euler method. However, the matri...

  6. PERSONNEL DEMOTIVATING: THE REASONS, FACTORS, ELIMINATION METHODS

    OpenAIRE

    Kuznetsova Ekaterina Andreevna

    2012-01-01

    The motivation of the personnel in any economic conditions remains a leading link in an enterprise control system. At creation of system of motivation tracking of extent of its impact on productivity of work of the personnel is important. The boomerang effect which is shown in a demotivating of separate groups of the personnel is often observed. In article features of manifestation of demotivating factors at various stages of work of the personnel are analyzed, the circle of the reasons bring...

  7. Shape theory categorical methods of approximation

    CERN Document Server

    Cordier, J M

    2008-01-01

    This in-depth treatment uses shape theory as a ""case study"" to illustrate situations common to many areas of mathematics, including the use of archetypal models as a basis for systems of approximations. It offers students a unified and consolidated presentation of extensive research from category theory, shape theory, and the study of topological algebras.A short introduction to geometric shape explains specifics of the construction of the shape category and relates it to an abstract definition of shape theory. Upon returning to the geometric base, the text considers simplical complexes and

  8. Augmenting Ordinal Methods of Attribute Weight Approximation

    DEFF Research Database (Denmark)

    Daneilson, Mats; Ekenberg, Love; He, Ying

    2014-01-01

    Multicriteria decision aid (MCDA) methods have been around for quite some time. However, the elicitation of preference information in MCDA processes and the lack of supporting practical means are problematic in real-life applications. Various proposals have been made for how to eliminate some...... of the obstacles and methods for introducing so-called surrogate weights have proliferated in the form of ordinal ranking methods for criteria weights. Considering the decision quality, one main problem is that the input information allowed in ordinal methods is sometimes too restricted. At the same time, decision...... makers often possess more background information, for example, regarding the relative strengths of the criteria, and might want to use that. We propose combined methods for facilitating the elicitation process and show how this provides a way to use partial information from the strength of preference...

  9. A unified approximate reasoning theory suitable for both propositional calculus system L* and predicate calculus system K*

    Institute of Scientific and Technical Information of China (English)

    WANG Guojun; CHIN K. S.; DANG C.Y.

    2005-01-01

    The concepts of metric R0-algebra and Hilbert cube of type R0 are introduced.A unified approximate reasoning theory in propositional caculus system L* and predicate calculus system K* is established semantically as well as syntactically, and a unified complete theorem is obtained.

  10. Approximating Mathematical Semantic Web Services Using Approximation Formulas and Numerical Methods

    CERN Document Server

    Mogos, Andrei-Horia

    2009-01-01

    Mathematical semantic web services are very useful in practice, but only a small number of research results are reported in this area. In this paper we present a method of obtaining an approximation of a mathematical semantic web service, from its semantic description, using existing mathematical semantic web services, approximation formulas, and numerical methods techniques. We also give a method for automatic comparison of two complexity functions. In addition, we present a method for classifying the numerical methods mathematical semantic web services from a library.

  11. High order source approximation for the EFEN method

    International Nuclear Information System (INIS)

    The flat source approximation in one dimensional Exponential Function Expansion Nodal (EFEN) method is extended to a high order polynomial approximation while maintaining the simplicity of the nodal response matrix. By applying the new method to a one dimensional PWR pin-by-pin problem, it has been observed that quadratic source approximation is good enough for PWR pin-by-pin calculation, while the flat source approximation causes about 5% of relative error to the thermal flux. By applying the new method to a one dimensional assembly homogenized problem, it has been found that the EFEN method with cubic source approximation can be employed to handle PWR core diffusion problems. Numerical results suggest the optimization of source approximation order for different energy groups and different spacial locations to achieve more accurate results with less computing effort. (author)

  12. Approximations of continuous Newton's method: An extension of Cayley's problem

    Directory of Open Access Journals (Sweden)

    Jon Jacobsen

    2007-02-01

    Full Text Available Continuous Newton's Method refers to a certain dynamical system whose associated flow generically tends to the roots of a given polynomial. An Euler approximation of this system, with step size $h=1$, yields the discrete Newton's method algorithm for finding roots. In this note we contrast Euler approximations with several different approximations of the continuous ODE system and, using computer experiments, consider their impact on the associated fractal basin boundaries of the roots.

  13. A Semantic Retrieval Method Based on the Fuzzy Reasoning

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    This paper gives a semantic fuzzy retrieval method of multimedia object,discusses the principle of fuzzy semantic retrieval technique,presents a fuzzy reasoning mechanism based on the knowledge base,and designs the relevant reasoning algorithms.Researchful results have innovative significance.

  14. Nonlinear ordinary differential equations analytical approximation and numerical methods

    CERN Document Server

    Hermann, Martin

    2016-01-01

    The book discusses the solutions to nonlinear ordinary differential equations (ODEs) using analytical and numerical approximation methods. Recently, analytical approximation methods have been largely used in solving linear and nonlinear lower-order ODEs. It also discusses using these methods to solve some strong nonlinear ODEs. There are two chapters devoted to solving nonlinear ODEs using numerical methods, as in practice high-dimensional systems of nonlinear ODEs that cannot be solved by analytical approximate methods are common. Moreover, it studies analytical and numerical techniques for the treatment of parameter-depending ODEs. The book explains various methods for solving nonlinear-oscillator and structural-system problems, including the energy balance method, harmonic balance method, amplitude frequency formulation, variational iteration method, homotopy perturbation method, iteration perturbation method, homotopy analysis method, simple and multiple shooting method, and the nonlinear stabilized march...

  15. Approximate inverse preconditioning of iterative methods for nonsymmetric linear systems

    Energy Technology Data Exchange (ETDEWEB)

    Benzi, M. [Universita di Bologna (Italy); Tuma, M. [Inst. of Computer Sciences, Prague (Czech Republic)

    1996-12-31

    A method for computing an incomplete factorization of the inverse of a nonsymmetric matrix A is presented. The resulting factorized sparse approximate inverse is used as a preconditioner in the iterative solution of Ax = b by Krylov subspace methods.

  16. Approximate Method for Solving the Linear Fuzzy Delay Differential Equations

    Directory of Open Access Journals (Sweden)

    S. Narayanamoorthy

    2015-01-01

    Full Text Available We propose an algorithm of the approximate method to solve linear fuzzy delay differential equations using Adomian decomposition method. The detailed algorithm of the approach is provided. The approximate solution is compared with the exact solution to confirm the validity and efficiency of the method to handle linear fuzzy delay differential equation. To show this proper features of this proposed method, numerical example is illustrated.

  17. An approximate methods approach to probabilistic structural analysis

    Science.gov (United States)

    Mcclung, R. C.; Millwater, H. R.; Wu, Y.-T.; Thacker, B. H.; Burnside, O. H.

    1989-01-01

    A major research and technology program in Probabilistic Structural Analysis Methods (PSAM) is currently being sponsored by the NASA Lewis Research Center with Southwest Research Institute as the prime contractor. This program is motivated by the need to accurately predict structural response in an environment where the loadings, the material properties, and even the structure may be considered random. The heart of PSAM is a software package which combines advanced structural analysis codes with a fast probability integration (FPI) algorithm for the efficient calculation of stochastic structural response. The basic idea of PAAM is simple: make an approximate calculation of system response, including calculation of the associated probabilities, with minimal computation time and cost, based on a simplified representation of the geometry, loads, and material. The deterministic solution resulting should give a reasonable and realistic description of performance-limiting system responses, although some error will be inevitable. If the simple model has correctly captured the basic mechanics of the system, however, including the proper functional dependence of stress, frequency, etc. on design parameters, then the response sensitivities calculated may be of significantly higher accuracy.

  18. Energy of Bardeen Model Using Approximate Symmetry Method

    OpenAIRE

    Sharif, M.; Waheed, Saira

    2010-01-01

    In this paper, we investigate the energy problem in general relativity using approximate Lie symmetry methods for differential equations. This procedure is applied to Bardeen model (the regular black hole solution). Here we are forced to evaluate the third-order approximate symmetries of the orbital and geodesic equations. It is shown that energy must be re-scaled by some factor in the third-order approximation. We discuss the insights of this re-scaling factor.

  19. Approximate analytical methods for solving ordinary differential equations

    CERN Document Server

    Radhika, TSL; Rani, T Raja

    2015-01-01

    Approximate Analytical Methods for Solving Ordinary Differential Equations (ODEs) is the first book to present all of the available approximate methods for solving ODEs, eliminating the need to wade through multiple books and articles. It covers both well-established techniques and recently developed procedures, including the classical series solution method, diverse perturbation methods, pioneering asymptotic methods, and the latest homotopy methods.The book is suitable not only for mathematicians and engineers but also for biologists, physicists, and economists. It gives a complete descripti

  20. Numerical Stability and Convergence of Approximate Methods for Conservation Laws

    Science.gov (United States)

    Galkin, V. A.

    We present the new approach to background of approximate methods convergence based on functional solutions theory for conservation laws. The applications to physical kinetics, gas and fluid dynamics are considered.

  1. A double power series method for approximating cosmological perturbations

    CERN Document Server

    Wren, Andrew J

    2016-01-01

    We introduce a double power series method for finding approximate analytical solutions for systems of differential equations commonly found in cosmological perturbation theory. The method was set out, in a non-cosmological context, by Feshchenko, Shkil' and Nikolenko (FSN) in 1966, and is applicable to cases where perturbations are on sub-horizon scales. The FSN method is essentially an extension of the well known Wentzel-Kramers-Brillouin (WKB) method for finding approximate analytical solutions for ordinary differential equations. The FSN method is well suited for solving systems of linear second order ordinary differential equations, that also depend on a small parameter, which here we take to be the inverse wave-number. We use the FSN method to find new approximate oscillating solutions in linear order cosmological perturbation theory for a flat radiation-matter universe. Together with this model's well known growing and decaying M\\'esz\\'aros solutions, these oscillating modes provide a complete set of su...

  2. Children's Expression of Negative Affect: Reasons and Methods.

    Science.gov (United States)

    Zeman, Janice; Shipman, Kimberly

    1996-01-01

    Examines the influence of socialization figures (parents, friends), emotion type (anger, sadness, physical pain), age, and gender on 66 second-grade and 71 fifth-grade children's reasons for and methods of affect expression. Found that girls reported using verbal means to communicate emotion, whereas boys cited mildly aggressive methods. (MDM)

  3. An approximate method to acoustic radiation problems: element radiation superposition method

    Institute of Scientific and Technical Information of China (English)

    wANG Bin; TANG weilin; FAN Jun

    2008-01-01

    An approximate method is brought forward to predict the acoustic pressure based on the surface velocity.It is named Element Radiation Superposition Method(ERSM).The study finds that each element in Acoustic Transfer Vector(ATV)equals the acoustic pressure radiated by the corresponding surface element vibrating in unit velocity and other surface elements keep still.that is the acoustic pressure radiated by the corresponding baffled pistonvibrating in unit velocity.So,it utilizes the acoustic pressure radiated by a baffled piston to establish the transfer relationship between the surfaEe velocity and the acoustic pressure.The total acoustic pressure is obtained through summing up the products of the surface velocity and the transfer quantity.It adopts the regular baffle to fit the actual baffle in order to calculate the acoustic pressure radiated by the baffled piston.This approximate method has larger advantage in calculating speed and memory space than Boundary Element Method.Numerical simulations show that this approximate method is reasonable and feasible.

  4. Dual methods and approximation concepts in structural synthesis

    Science.gov (United States)

    Fleury, C.; Schmit, L. A., Jr.

    1980-01-01

    Approximation concepts and dual method algorithms are combined to create a method for minimum weight design of structural systems. Approximation concepts convert the basic mathematical programming statement of the structural synthesis problem into a sequence of explicit primal problems of separable form. These problems are solved by constructing explicit dual functions, which are maximized subject to nonnegativity constraints on the dual variables. It is shown that the joining together of approximation concepts and dual methods can be viewed as a generalized optimality criteria approach. The dual method is successfully extended to deal with pure discrete and mixed continuous-discrete design variable problems. The power of the method presented is illustrated with numerical results for example problems, including a metallic swept wing and a thin delta wing with fiber composite skins.

  5. Approximating methods for intractable probabilistic models: Applications in neuroscience

    OpenAIRE

    Højen-Sørensen, Pedro; Hansen, Lars Kai; Rasmussen, Carl Edward; Larsen, Jan

    2002-01-01

    This thesis investigates various methods for carrying out approximate inference in intractable probabilistic models. By capturing the relationships between random variables, the framework of graphical models hints at which sets of random variables pose a problem to the inferential step. The approximating techniques used in this thesis originate from the field of statistical physics which for decades has been facing the same type of intractable computations when analyzing large systems of inte...

  6. A further development of the flux polynomial approximations method

    International Nuclear Information System (INIS)

    In this paper two of the transport problems were treated: the energy independent particle transport in spherical geometry and the energy dependent neutron transport in plane hydrogen media. Using the asymptotic behaviours in space and lethargy of the known analytical solutions of these problems (given by the singular eigenfunction method and by the 'Marshak approximation') some significant improvements in the synthesis of an elementary function method and the bi-orthogonal polynomial flux approximations method were done. The computed values were compared to the referent data and agreement was achieved. (author)

  7. Intermediate boundary conditions for LOD, ADI and approximate factorization methods

    Science.gov (United States)

    Leveque, R. J.

    1985-01-01

    A general approach to determining the correct intermediate boundary conditions for dimensional splitting methods is presented. The intermediate solution U is viewed as a second order accurate approximation to a modified equation. Deriving the modified equation and using the relationship between this equation and the original equation allows us to determine the correct boundary conditions for U*. This technique is illustrated by applying it to locally one dimensional (LOD) and alternating direction implicit (ADI) methods for the heat equation in two and three space dimensions. The approximate factorization method is considered in slightly more generality.

  8. Approximate methods in gamma-ray skyshine calculations

    International Nuclear Information System (INIS)

    An approximate computational method for gamma-ray skyshine calculations is described. The method is suitable for a source collimated uniformly about the vertical and accounts for uniform overhead concrete shielding above the source. Results of calculations are compared to measurements as well as results of other calculations

  9. Analytical Evaluation of Beam Deformation Problem Using Approximate Methods

    DEFF Research Database (Denmark)

    Barari, Amin; Kimiaeifar, A.; Domairry, G.

    2010-01-01

    , and this process produces noise in the obtained answers. This paper deals with the solution of second order of differential equation governing beam deformation using four analytical approximate methods, namely the Perturbation, Homotopy Perturbation Method (HPM), Homotopy Analysis Method (HAM) and......The beam deformation equation has very wide applications in structural engineering. As a differential equation, it has its own problem concerning existence, uniqueness and methods of solutions. Often, original forms of governing differential equations used in engineering problems are simplified...... Variational Iteration Method (VIM). The comparisons of the results reveal that these methods are very effective, convenient and quite accurate for systems of non-linear differential equation....

  10. A working-set framework for sequential convex approximation methods

    DEFF Research Database (Denmark)

    Stolpe, Mathias

    2008-01-01

    to guarantee global convergence of the method. The algorithm works directly on the nonlinear constraints in the convex sub-problems and solves a sequence of relaxations of the current sub-problem. The algorithm terminates with the optimal solution to the sub-problem after solving a finite number of relaxations.......We present an active-set algorithmic framework intended as an extension to existing implementations of sequential convex approximation methods for solving nonlinear inequality constrained programs. The framework is independent of the choice of approximations and the stabilization technique used...

  11. Higher-order Chebyshev rational approximation method (CRAM)

    International Nuclear Information System (INIS)

    The burnup equations can in principle be solved by computing the exponential of the burnup matrix. However, due to the difficult numerical characteristics of burnup matrices, the problem is extremely stiff, and the matrix exponential solution was long considered infeasible for an entire burnup system containing over a thousand nuclides. After discovering that the eigenvalues of burnup matrices are generally confined to a region near the negative real axis, the Chebyshev rational approximation method (CRAM) was introduced as a novel method to solve the burnup equations. It can be characterized as the best rational function on the negative real axis and it has been shown to be capable of simultaneously solving an entire burnup system both accurately and efficiently. The main difficulty in using CRAM for computing the matrix exponential is determining the coefficients of the rational function for a given approximation order. Some polynomial CRAM coefficients have been published in 1984, and based on these literature values, CRAM approximations up to the order 16 have been thus far applied in burnup calculations. The topic of this paper is the computation of CRAM approximations and their application to burnup equations. A Remez-type method utilizing the equioscillation property of best approximations is used to construct the CRAM approximants for approximation orders 1,. . . , 50. Numerical results are presented for a large burnup system and for a decay system. It is demonstrated that higher-order CRAM can be used to accurately solve the burnup equations even with time steps of the order of millions of years. (author)

  12. Metamorphic computer virus detection by Case- Based Reasoning (CBR) methods

    OpenAIRE

    Abdellatif Berkat

    2011-01-01

    Metamorphic virus employs code obfuscation techniques to mutate itself. It absconds from signaturebaseddetection system by modifying internal structure without compromising original functionality.In this paper, we propose a new method, for detecting metamorphic computer viruses, that is based on thetechnique of Case-Based Reasoning (CBR). In this method:-Can detect similar viruses with high probability.- The updating of the virus database is done automatically without connecting to the Intern...

  13. Approximating methods for intractable probabilistic models: Applications in neuroscience

    DEFF Research Database (Denmark)

    Højen-Sørensen, Pedro

    2002-01-01

    This thesis investigates various methods for carrying out approximate inference in intractable probabilistic models. By capturing the relationships between random variables, the framework of graphical models hints at which sets of random variables pose a problem to the inferential step. The appro...

  14. Approximate iterative operator method for potential-field downward continuation

    Science.gov (United States)

    Tai, Zhenhua; Zhang, Fengxu; Zhang, Fengqin; Hao, Mengcheng

    2016-05-01

    An approximate iterative operator method in wavenumber domain was proposed to improve the stability and accuracy of downward continuation of potential fields measured from the ground surface, marine or airborne. Firstly, the generalized iterative formula of downward continuation is derived in wavenumber domain; then, the transformational relationship between horizontal second-order partial derivatives and continuation is derived based on the Taylor series and Laplace equation, to obtain an approximate operator. By introducing this operator to the generalized iterative formula, a rapid algorithm is developed for downward continuation. The filtering and convergence characteristics of this method are analyzed for the purpose of estimating the optimal interval of number of iterations. We demonstrate the proposed method on synthetic data, and the results validate the flexibility of the proposed method. At last, we apply the proposed method to real data, and the results show the proposed method can enhance gravity anomalies generated by concealed orebodies. And in the contour obtained by making our proposed method results continue upward to measured level, the numerical results have approximate distribution and amplitude with original anomalies.

  15. Complex method for approximated solutions to Born-Infeld equation

    CERN Document Server

    Ferraro, Rafael

    2015-01-01

    We display the method to solve the Born-Infeld equation in the complex plane. As the exact solution is obtained in an implicit form, we turn it into an explicit form by means of a perturbative procedure which takes care of secular behaviors common to this kind of approximations. We apply the method to build solutions to Born-Infeld electrodynamics. In particular, we study BI electromagnetic waves at interfaces, with the aim of searching for effects susceptible of experimental detection.

  16. Error Estimates for Approximate Optimization by the Extended Ritz Method

    Czech Academy of Sciences Publication Activity Database

    Kůrková, Věra; Sanguineti, M.

    2005-01-01

    Roč. 15, č. 2 (2005), s. 461-487. ISSN 1052-6234 R&D Projects: GA ČR GA201/02/0428 Institutional research plan: CEZ:AV0Z10300504 Keywords : functional optimization * rates of convergence of suboptimal solutions * (extended) Ritz method * curse of dimensionality * convex best approximation problems * learning from data by kernel methods Subject RIV: BA - General Mathematics Impact factor: 1.238, year: 2005

  17. An approximation concepts method for space frame synthesis

    Science.gov (United States)

    Mills-Curran, W. C.; Lust, R. V.; Schmit, L. A.

    1982-01-01

    A method is presented for the minimum mass design of three dimensional space frames constructed of thin walled rectangular cross-section members. Constraints on nodal displacements and rotations, material stress, local buckling, and cross sectional dimensions are included. A high quality separable approximate problem is formed in terms of the reciprocals of the four section properties of the frame element cross section, replacing all implicit functions with simplified explicit relations. The cross sectional dimensions are efficiently calculated without using multilevel techniques. Several test problems are solved, demonstrating that a series of approximate problem solutions converge rapidly to an optimal design.

  18. Multiuser detection and channel estimation: Exact and approximate methods

    DEFF Research Database (Denmark)

    Fabricius, Thomas

    2003-01-01

    This dissertation deals with optimal and close to optimal multiuser detection in Code Division Multiple Access. We derive optimal detection strategies in the sense of minimum expected probability of bit error, sequence error, and mean square error. These are implemented efficiently by the use of...... the Junction Tree Algorithm, which is a generalisation of Pearl's Belief Propagation, the BCJR, sum product, min/max sum, and Viterbi's algorithm. Although efficient algoithms, they have an inherent exponential complexity in the number of users when applied to CDMA multiuser detection. For this reason...... subtractive interference cancellation with hyperbolic tangent tentative decision device, in statistical mechanics and machine learning called the naive mean field approach. The differences between the proposed algorithms lie in how the bias is estimated/approximated. We propose approaches based on a second...

  19. Space-angle approximations in the variational nodal method

    International Nuclear Information System (INIS)

    The variational nodal method is formulated such that the angular and spatial approximations maybe examined separately. Spherical harmonic, simplified spherical harmonic, and discrete ordinate approximations are coupled to the primal hybrid finite element treatment of the spatial variables. Within this framework, two classes of spatial trial functions are presented: (1) orthogonal polynomials for the treatment of homogeneous nodes and (2) bilinear finite subelement trial functions for the treatment of fuel assembly sized nodes in which fuel-pin cell cross sections are represented explicitly. Polynomial and subelement trial functions are applied to benchmark water-reactor problems containing MOX fuel using spherical harmonic and simplified spherical harmonic approximations. The resulting accuracy and computing costs are compared

  20. Approximation methods for the partition functions of anharmonic systems

    International Nuclear Information System (INIS)

    The analytical approximations for the classical, quantum mechanical and reduced partition functions of the diatomic molecule oscillating internally under the influence of the Morse potential have been derived and their convergences have been tested numerically. This successful analytical method is used in the treatment of anharmonic systems. Using Schwinger perturbation method in the framework of second quantization formulism, the reduced partition function of polyatomic systems can be put into an expression which consists separately of contributions from the harmonic terms, Morse potential correction terms and interaction terms due to the off-diagonal potential coefficients. The calculated results of the reduced partition function from the approximation method on the 2-D and 3-D model systems agree well with the numerical exact calculations

  1. Interfacing Relativistic and Nonrelativistic Methods: A Systematic Sequence of Approximations

    Science.gov (United States)

    Dyall, Ken; Langhoff, Stephen R. (Technical Monitor)

    1997-01-01

    A systematic sequence of approximations for the introduction of relativistic effects into nonrelativistic molecular finite-basis set calculations is described. The theoretical basis for the approximations is the normalized elimination of the small component (ESC) within the matrix representation of the modified Dirac equation. The key features of the normalized method are the retention of the relativistic metric and the ability to define a single matrix U relating the pseudo-large and large component coefficient matrices. This matrix is used to define a modified set of one- and two-electron integrals which have the same appearance as the integrals of the Breit-Pauli Hamiltonian. The first approximation fixes the ratios of the large and pseudo-large components to their atomic values, producing an expansion in atomic 4-spinors. The second approximation defines a local fine-structure constant on each atomic centre, which has the physical value for centres considered to be relativistic and zero for nonrelativistic centres. In the latter case, the 4-spinors are the positive-energy kinetic al ly-balanced solutions of the Levy-Leblond equation, and the integrals involving pseudo-large component basis functions on these centres, are set to zero. Some results are presented for test systems to illustrate the various approximations.

  2. Approximation methods for efficient learning of Bayesian networks

    CERN Document Server

    Riggelsen, C

    2008-01-01

    This publication offers and investigates efficient Monte Carlo simulation methods in order to realize a Bayesian approach to approximate learning of Bayesian networks from both complete and incomplete data. For large amounts of incomplete data when Monte Carlo methods are inefficient, approximations are implemented, such that learning remains feasible, albeit non-Bayesian. The topics discussed are: basic concepts about probabilities, graph theory and conditional independence; Bayesian network learning from data; Monte Carlo simulation techniques; and, the concept of incomplete data. In order to provide a coherent treatment of matters, thereby helping the reader to gain a thorough understanding of the whole concept of learning Bayesian networks from (in)complete data, this publication combines in a clarifying way all the issues presented in the papers with previously unpublished work.

  3. Parallel iterative solvers and preconditioners using approximate hierarchical methods

    Energy Technology Data Exchange (ETDEWEB)

    Grama, A.; Kumar, V.; Sameh, A. [Univ. of Minnesota, Minneapolis, MN (United States)

    1996-12-31

    In this paper, we report results of the performance, convergence, and accuracy of a parallel GMRES solver for Boundary Element Methods. The solver uses a hierarchical approximate matrix-vector product based on a hybrid Barnes-Hut / Fast Multipole Method. We study the impact of various accuracy parameters on the convergence and show that with minimal loss in accuracy, our solver yields significant speedups. We demonstrate the excellent parallel efficiency and scalability of our solver. The combined speedups from approximation and parallelism represent an improvement of several orders in solution time. We also develop fast and paralellizable preconditioners for this problem. We report on the performance of an inner-outer scheme and a preconditioner based on truncated Green`s function. Experimental results on a 256 processor Cray T3D are presented.

  4. How the great scientists reasoned the scientific method in action

    CERN Document Server

    Tibbetts, Gary G

    2012-01-01

    The scientific method is one of the most basic and essential concepts across the sciences, ensuring that investigations are carried out with precision and thoroughness. The scientific method is typically taught as a step-by-step approach, but real examples from history are not always given. This book teaches the basic modes of scientific thought, not by philosophical generalizations, but by illustrating in detail how great scientists from across the sciences solved problems using scientific reason. Examples include Christopher Columbus, Joseph Priestly, Antoine Lavoisier, Michael Faraday, W

  5. A multiscale two-point flux-approximation method

    International Nuclear Information System (INIS)

    A large number of multiscale finite-volume methods have been developed over the past decade to compute conservative approximations to multiphase flow problems in heterogeneous porous media. In particular, several iterative and algebraic multiscale frameworks that seek to reduce the fine-scale residual towards machine precision have been presented. Common for all such methods is that they rely on a compatible primal–dual coarse partition, which makes it challenging to extend them to stratigraphic and unstructured grids. Herein, we propose a general idea for how one can formulate multiscale finite-volume methods using only a primal coarse partition. To this end, we use two key ingredients that are computed numerically: (i) elementary functions that correspond to flow solutions used in transmissibility upscaling, and (ii) partition-of-unity functions used to combine elementary functions into basis functions. We exemplify the idea by deriving a multiscale two-point flux-approximation (MsTPFA) method, which is robust with regards to strong heterogeneities in the permeability field and can easily handle general grids with unstructured fine- and coarse-scale connections. The method can easily be adapted to arbitrary levels of coarsening, and can be used both as a standalone solver and as a preconditioner. Several numerical experiments are presented to demonstrate that the MsTPFA method can be used to solve elliptic pressure problems on a wide variety of geological models in a robust and efficient manner

  6. Optimization in engineering sciences approximate and metaheuristic methods

    CERN Document Server

    Stefanoiu, Dan; Popescu, Dumitru; Filip, Florin Gheorghe; El Kamel, Abdelkader

    2014-01-01

    The purpose of this book is to present the main metaheuristics and approximate and stochastic methods for optimization of complex systems in Engineering Sciences. It has been written within the framework of the European Union project ERRIC (Empowering Romanian Research on Intelligent Information Technologies), which is funded by the EU's FP7 Research Potential program and has been developed in co-operation between French and Romanian teaching researchers. Through the principles of various proposed algorithms (with additional references) this book allows the reader to explore various methods o

  7. Generation method of educational materials using qualitative reasoning

    International Nuclear Information System (INIS)

    Central Research Institute of Electric Power Industry has developed a nuclear power plant educational system in which educational materials for several events are included. The system effectively teaches operators by tailoring the event explanations to their knowledge levels of understanding. The preparation of the educational materials, however, is laborious and this becomes one of the problems in the practical use of the system. Discussed in the present paper is a basic explanation generation method using qualitative reasoning. This has been developed to solve the problem. Qualitative equations describing a recirculation pumps trip were transformed into production rules. These were stored in the knowledge base of an event explanation generation system together with explanation sentences. When an operator selects a certain variable's time-interval in which he wants to know the reasons for a variable change, the inference engine searches for the rule which satisfies both the qualitative value and qualitative differential value concerned with this time-interval. Then the event explanation generation section provides explanations by combining the explanation sentences attached to the rules. This paper demonstrates that it is possible to apply qualitative reasoning to such complex reactor systems, and also that explanations can be generated using the simulation results from a transient analysis code. (author)

  8. Simple Methods to Approximate CPC Shape to Preserve Collection Efficiency

    Directory of Open Access Journals (Sweden)

    David Jafrancesco

    2012-01-01

    Full Text Available The compound parabolic concentrator (CPC is the most efficient reflective geometry to collect light to an exit port. Anyway, to allow its actual use in solar plants or photovoltaic concentration systems, a tradeoff between system efficiency and cost reduction, the two key issues for sunlight exploitation, must be found. In this work, we analyze various methods to model an approximated CPC aimed to be simpler and more cost-effective than the ideal one, as well as to preserve the system efficiency. The manufacturing easiness arises from the use of truncated conic surfaces only, which can be realized by cheap machining techniques. We compare different configurations on the basis of their collection efficiency, evaluated by means of nonsequential ray-tracing software. Moreover, due to the fact that some configurations are beam dependent and for a closer approximation of a real case, the input beam is simulated as nonsymmetric, with a nonconstant irradiance on the CPC internal surface.

  9. A Surface Approximation Method for Image and Video Correspondences.

    Science.gov (United States)

    Huang, Jingwei; Wang, Bin; Wang, Wenping; Sen, Pradeep

    2015-12-01

    Although finding correspondences between similar images is an important problem in image processing, the existing algorithms cannot find accurate and dense correspondences in images with significant changes in lighting/transformation or with the non-rigid objects. This paper proposes a novel method for finding accurate and dense correspondences between images even in these difficult situations. Starting with the non-rigid dense correspondence algorithm [1] to generate an initial correspondence map, we propose a new geometric filter that uses cubic B-Spline surfaces to approximate the correspondence mapping functions for shared objects in both images, thereby eliminating outliers and noise. We then propose an iterative algorithm which enlarges the region containing valid correspondences. Compared with the existing methods, our method is more robust to significant changes in lighting, color, or viewpoint. Furthermore, we demonstrate how to extend our surface approximation method to video editing by first generating a reliable correspondence map between a given source frame and each frame of a video. The user can then edit the source frame, and the changes are automatically propagated through the entire video using the correspondence map. To evaluate our approach, we examine applications of unsupervised image recognition and video texture editing, and show that our algorithm produces better results than those from state-of-the-art approaches. PMID:26241974

  10. An Approximate Analytical Method of the Nonlinear Vibroacoustic Coupling System

    Directory of Open Access Journals (Sweden)

    Qizheng Zhou

    2014-01-01

    Full Text Available An approximate analytical method of the nonlinear vibroacoustic coupling system is proposed for the first time. Taking the Duffing oscillator-plate-medium system as an example, the nonlinear vibroacoustic coupling equations are developed using variational principle. The two major difficulties which lie in solving the coupling equations are the uncertain motion of the oscillator and the surface acoustic pressure on the plate, a system for which the fluid-structure coupling cannot be neglected. Based on the incremental harmonic balance (IHB method, the motion of the oscillator is expressed in the form of the Fourier series, and then the modal expression method and the incoherent assumption are employed to discretize the displacement and the surface pressure of the plate. Then the approximate analytical solution is given by the IHB method. The characteristics of acoustic radiation and surface quadratic velocity of the plate, the nonlinear characteristics of oscillator, and the influence of the excitation frequency and the nonlinear stiffness on the results are investigated by the numerical simulation. The results show that the excitation at the frequency close to the natural frequency of the oscillator can produce a significant response of the third-harmonic generation which determines the vibroacoustic characteristics of the plate.

  11. Approximate method for controlling solid elastic waves by transformation media

    Science.gov (United States)

    Hu, Jin; Chang, Zheng; Hu, Gengkai

    2011-11-01

    By idealizing a general mapping as a series of local affine ones, we derive approximately transformed material parameters necessary to control solid elastic waves within classical elasticity theory. The transformed elastic moduli are symmetric, and can be used with Navier's equation to manipulate elastic waves. It is shown numerically that the method can provide a powerful tool to control elastic waves in solids in case of high frequency or small material gradient. Potential applications can be anticipated in nondestructive testing, structure impact protection, petroleum exploration, and seismology.

  12. Approximate design calculation methods for radiation streaming in shield irregularities

    International Nuclear Information System (INIS)

    Investigation and assessment are made for approximate design calculation methods of radiation streaming in shield irregularities. Investigation is made for (1) source, (2) definition of streaming radiation components, (3) calculation methods of streaming radiation, (4) streaming formulas for each irregularity, (5) difficulties in application of streaming formulas, etc. Furthermore, investigation is made for simple calculation codes and albedo data. As a result, it is clarified that streaming calculation formulas are not enough to cover various irregularities and their accuracy or application limit is not sufficiently clear. Accurate treatment is not made in the formulas with respect to the radiation behavior for slant incidence, bend part, offset etc., that results in too much safety factors in the design calculation and distrust of the streaming calculation. To overcome the state and improve the accuracy of the design calculation for shield irregularities, it is emphasized to assess existing formulas and develop better formulas based on systematic experimental studies. (author)

  13. Parabolic approximation method for the mode conversion-tunneling equation

    International Nuclear Information System (INIS)

    The derivation of the wave equation which governs ICRF wave propagation, absorption, and mode conversion within the kinetic layer in tokamaks has been extended to include diffraction and focussing effects associated with the finite transverse dimensions of the incident wavefronts. The kinetic layer considered consists of a uniform density, uniform temperature slab model in which the equilibrium magnetic field is oriented in the z-direction and varies linearly in the x-direction. An equivalent dielectric tensor as well as a two-dimensional energy conservation equation are derived from the linearized Vlasov-Maxwell system of equations. The generalized form of the mode conversion-tunneling equation is then extracted from the Maxwell equations, using the parabolic approximation method in which transverse variations of the wave fields are assumed to be weak in comparison to the variations in the primary direction of propagation. Methods of solving the generalized wave equation are discussed. 16 refs

  14. Discrete Dipole Approximation Aided Design Method for Nanostructure Arrays

    Institute of Scientific and Technical Information of China (English)

    ZHU Shao-Li; LUO Xian-Gang; DU Chun-Lei

    2007-01-01

    A discrete dipole approximation (DDA) aided design method is proposed to determine the parameters of nanostructure arrays. The relationship between the thickness, period and extinction efficiency of nanostructure arrays for the given shape can be calculated using the DDA. Based on the calculated curves, the main parameters of the nanostructure arrays such as thickness and period can be determined. Using this aided method, a rhombic sliver nanostructure array is designed with the determinant parameters of thickness (40 nm) and period (440 nm).We further fabricate the rhombic sliver nanostructure arrays and testify the character of the extinction spectra.The obtained extinction spectra is within the visible range and the full width at half maximum is 99nm, as is expected.

  15. The method of approximate inverse theory and applications

    CERN Document Server

    Schuster, Thomas

    2007-01-01

    Inverse problems arise whenever one tries to calculate a required quantity from given measurements of a second quantity that is associated to the first one. Besides medical imaging and non-destructive testing, inverse problems also play an increasing role in other disciplines such as industrial and financial mathematics. Hence, there is a need for stable and efficient solvers. The book is concerned with the method of approximate inverse which is a regularization technique for stably solving inverse problems in various settings such as L2-spaces, Hilbert spaces or spaces of distributions. The performance and functionality of the method is demonstrated on several examples from medical imaging and non-destructive testing such as computerized tomography, Doppler tomography, SONAR, X-ray diffractometry and thermoacoustic computerized tomography. The book addresses graduate students and researchers interested in the numerical analysis of inverse problems and regularization techniques or in efficient solvers for the...

  16. Back-transformation of treatment differences - an approximate method

    DEFF Research Database (Denmark)

    Laursen, Rikke Pilmann; Dalskov, Stine-Mathilde; Damsgaard, Camilla Trab; Ritz, Christian

    2014-01-01

    -transformed estimated differences, and corresponding standard errors and 95% confidence intervals.Subjects/Methods:Based on data from two randomized controlled studies and an exemplary data set that had all previously been published, we evaluated our approximate procedure by comparing results for different approaches......Background/Objectives:Transformation of outcomes is frequently used in the analysis of studies in clinical nutrition. However, back-transformation of estimated treatment means and differences is complicated by the nonlinear nature of the transformations. It is not straightforward to obtain an...... estimated treatment difference that can be interpreted without any reference to the additional predictors included in the statistical model; and moreover, standard errors are not easily available. The aim of this work was to provide a generally applicable, yet operational procedure for obtaining back...

  17. On rational approximation methods for inverse source problems

    KAUST Repository

    Rundell, William

    2011-02-01

    The basis of most imaging methods is to detect hidden obstacles or inclusions within a body when one can only make measurements on an exterior surface. Such is the ubiquity of these problems, the underlying model can lead to a partial differential equation of any of the major types, but here we focus on the case of steady-state electrostatic or thermal imaging and consider boundary value problems for Laplace\\'s equation. Our inclusions are interior forces with compact support and our data consists of a single measurement of (say) voltage/current or temperature/heat flux on the external boundary. We propose an algorithm that under certain assumptions allows for the determination of the support set of these forces by solving a simpler "equivalent point source" problem, and which uses a Newton scheme to improve the corresponding initial approximation. © 2011 American Institute of Mathematical Sciences.

  18. Methods of Approximation Theory in Complex Analysis and Mathematical Physics

    CERN Document Server

    Saff, Edward

    1993-01-01

    The book incorporates research papers and surveys written by participants ofan International Scientific Programme on Approximation Theory jointly supervised by Institute for Constructive Mathematics of University of South Florida at Tampa, USA and the Euler International Mathematical Instituteat St. Petersburg, Russia. The aim of the Programme was to present new developments in Constructive Approximation Theory. The topics of the papers are: asymptotic behaviour of orthogonal polynomials, rational approximation of classical functions, quadrature formulas, theory of n-widths, nonlinear approximation in Hardy algebras,numerical results on best polynomial approximations, wavelet analysis. FROM THE CONTENTS: E.A. Rakhmanov: Strong asymptotics for orthogonal polynomials associated with exponential weights on R.- A.L. Levin, E.B. Saff: Exact Convergence Rates for Best Lp Rational Approximation to the Signum Function and for Optimal Quadrature in Hp.- H. Stahl: Uniform Rational Approximation of x .- M. Rahman, S.K. ...

  19. Portable Rule Extraction Method for Neural Network Decisions Reasoning

    Directory of Open Access Journals (Sweden)

    Darius PLIKYNAS

    2005-08-01

    Full Text Available Neural network (NN methods are sometimes useless in practical applications, because they are not properly tailored to the particular market's needs. We focus thereinafter specifically on financial market applications. NNs have not gained full acceptance here yet. One of the main reasons is the "Black Box" problem (lack of the NN decisions explanatory power. There are though some NN decisions rule extraction methods like decompositional, pedagogical or eclectic, but they suffer from low portability of the rule extraction technique across various neural net architectures, high level of granularity, algorithmic sophistication of the rule extraction technique etc. The authors propose to eliminate some known drawbacks using an innovative extension of the pedagogical approach. The idea is exposed by the use of a widespread MLP neural net (as a common tool in the financial problems' domain and SOM (input data space clusterization. The feedback of both nets' performance is related and targeted through the iteration cycle by achievement of the best matching between the decision space fragments and input data space clusters. Three sets of rules are generated algorithmically or by fuzzy membership functions. Empirical validation of the common financial benchmark problems is conducted with an appropriately prepared software solution.

  20. Approximate solutions of theWei Hua oscillator using the Pekeris approximation and Nikiforov–Uvarov method

    Indian Academy of Sciences (India)

    P K Bera

    2012-01-01

    The approximate analytical bound-state solutions of the Schrödinger equation for the Wei Hua oscillator are carried out in N-dimensional space by taking Pekeris approximation scheme to the orbital centrifugal term. Solutions of the corresponding hyper-radial equation are obtained using the conventional Nikiforov–Uvarov (NU) method.

  1. Approximation by randomly weighting method in censored regression model

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Censored regression ("Tobit") models have been in common use, and their linear hypothesis testings have been widely studied. However, the critical values of these tests are usually related to quantities of an unknown error distribution and estimators of nuisance parameters. In this paper, we propose a randomly weighting test statistic and take its conditional distribution as an approximation to null distribution of the test statistic. It is shown that, under both the null and local alternative hypotheses, conditionally asymptotic distribution of the randomly weighting test statistic is the same as the null distribution of the test statistic. Therefore, the critical values of the test statistic can be obtained by randomly weighting method without estimating the nuisance parameters. At the same time, we also achieve the weak consistency and asymptotic normality of the randomly weighting least absolute deviation estimate in censored regression model. Simulation studies illustrate that the per-formance of our proposed resampling test method is better than that of central chi-square distribution under the null hypothesis.

  2. Approximation by randomly weighting method in censored regression model

    Institute of Scientific and Technical Information of China (English)

    WANG ZhanFeng; WU YaoHua; ZHAO LinCheng

    2009-01-01

    Censored regression ("Tobit") models have been in common use,and their linear hypothesis testings have been widely studied.However,the critical values of these tests are usually related to quantities of an unknown error distribution and estimators of nuisance parameters.In this paper,we propose a randomly weighting test statistic and take its conditional distribution as an approximation to null distribution of the test statistic.It is shown that,under both the null and local alternative hypotheses,conditionally asymptotic distribution of the randomly weighting test statistic is the same as the null distribution of the test statistic.Therefore,the critical values of the test statistic can be obtained by randomly weighting method without estimating the nuisance parameters.At the same time,we also achieve the weak consistency and asymptotic normality of the randomly weighting least absolute deviation estimate in censored regression model.Simulation studies illustrate that the performance of our proposed resampling test method is better than that of central chi-square distribution under the null hypothesis.

  3. Conditioning Methods for Exact and Approximate Inference in Causal Networks

    OpenAIRE

    Darwiche, Adnan

    2013-01-01

    We present two algorithms for exact and approximate inference in causal networks. The first algorithm, dynamic conditioning, is a refinement of cutset conditioning that has linear complexity on some networks for which cutset conditioning is exponential. The second algorithm, B-conditioning, is an algorithm for approximate inference that allows one to trade-off the quality of approximations with the computation time. We also present some experimental results illustrating the properties of the ...

  4. OWL-based reasoning methods for validating archetypes.

    Science.gov (United States)

    Menárguez-Tortosa, Marcos; Fernández-Breis, Jesualdo Tomás

    2013-04-01

    Some modern Electronic Healthcare Record (EHR) architectures and standards are based on the dual model-based architecture, which defines two conceptual levels: reference model and archetype model. Such architectures represent EHR domain knowledge by means of archetypes, which are considered by many researchers to play a fundamental role for the achievement of semantic interoperability in healthcare. Consequently, formal methods for validating archetypes are necessary. In recent years, there has been an increasing interest in exploring how semantic web technologies in general, and ontologies in particular, can facilitate the representation and management of archetypes, including binding to terminologies, but no solution based on such technologies has been provided to date to validate archetypes. Our approach represents archetypes by means of OWL ontologies. This permits to combine the two levels of the dual model-based architecture in one modeling framework which can also integrate terminologies available in OWL format. The validation method consists of reasoning on those ontologies to find modeling errors in archetypes: incorrect restrictions over the reference model, non-conformant archetype specializations and inconsistent terminological bindings. The archetypes available in the repositories supported by the openEHR Foundation and the NHS Connecting for Health Program, which are the two largest publicly available ones, have been analyzed with our validation method. For such purpose, we have implemented a software tool called Archeck. Our results show that around 1/5 of archetype specializations contain modeling errors, the most common mistakes being related to coded terms and terminological bindings. The analysis of each repository reveals that different patterns of errors are found in both repositories. This result reinforces the need for making serious efforts in improving archetype design processes. PMID:23246613

  5. The generalized Mayer theorem in the approximating hamiltonian method

    International Nuclear Information System (INIS)

    With the help of the generalized Mayer theorem we obtain the improved inequality for free energies of model and approximating systems, where only ''connected parts'' over the approximating hamiltonian are taken into account. For the concrete system we discuss the problem of convergency of appropriate series of ''connected parts''. (author)

  6. Maximum likelihood phylogenetic estimation from DNA sequences with variable rates over sites: approximate methods.

    Science.gov (United States)

    Yang, Z

    1994-09-01

    Two approximate methods are proposed for maximum likelihood phylogenetic estimation, which allow variable rates of substitution across nucleotide sites. Three data sets with quite different characteristics were analyzed to examine empirically the performance of these methods. The first, called the "discrete gamma model," uses several categories of rates to approximate the gamma distribution, with equal probability for each category. The mean of each category is used to represent all the rates falling in the category. The performance of this method is found to be quite good, and four such categories appear to be sufficient to produce both an optimum, or near-optimum fit by the model to the data, and also an acceptable approximation to the continuous distribution. The second method, called "fixed-rates model", classifies sites into several classes according to their rates predicted assuming the star tree. Sites in different classes are then assumed to be evolving at these fixed rates when other tree topologies are evaluated. Analyses of the data sets suggest that this method can produce reasonable results, but it seems to share some properties of a least-squares pairwise comparison; for example, interior branch lengths in nonbest trees are often found to be zero. The computational requirements of the two methods are comparable to that of Felsenstein's (1981, J Mol Evol 17:368-376) model, which assumes a single rate for all the sites. PMID:7932792

  7. Communication: Improved pair approximations in local coupled-cluster methods

    International Nuclear Information System (INIS)

    In local coupled cluster treatments the electron pairs can be classified according to the magnitude of their energy contributions or distances into strong, close, weak, and distant pairs. Different approximations are introduced for the latter three classes. In this communication, an improved simplified treatment of close and weak pairs is proposed, which is based on long-range cancellations of individually slowly decaying contributions in the amplitude equations. Benchmark calculations for correlation, reaction, and activation energies demonstrate that these approximations work extremely well, while pair approximations based on local second-order Møller-Plesset theory can lead to errors that are 1-2 orders of magnitude larger

  8. Mobile Monitoring and Reasoning Methods to Prevent Cardiovascular Diseases

    Directory of Open Access Journals (Sweden)

    Diego López-de-Ipiña

    2013-05-01

    Full Text Available With the recent technological advances, it is possible to monitor vital signs using Bluetooth-enabled biometric mobile devices such as smartphones, tablets or electric wristbands. In this manuscript, we present a system to estimate the risk of cardiovascular diseases in Ambient Assisted Living environments. Cardiovascular disease risk is obtained from the monitoring of the blood pressure by means of mobile devices in combination with other clinical factors, and applying reasoning techniques based on the Systematic Coronary Risk Evaluation Project charts. We have developed an end-to-end software application for patients and physicians and a rule-based reasoning engine. We have also proposed a conceptual module to integrate recommendations to patients in their daily activities based on information proactively inferred through reasoning techniques and context-awareness. To evaluate the platform, we carried out usability experiments and performance benchmarks.

  9. Production-passage-time approximation: a new approximation method to accelerate the simulation process of enzymatic reactions.

    Science.gov (United States)

    Kuwahara, Hiroyuki; Myers, Chris J

    2008-09-01

    Given the substantial computational requirements of stochastic simulation, approximation is essential for efficient analysis of any realistic biochemical system. This paper introduces a new approximation method to reduce the computational cost of stochastic simulations of an enzymatic reaction scheme which in biochemical systems often includes rapidly changing fast reactions with enzyme and enzyme-substrate complex molecules present in very small counts. Our new method removes the substrate dissociation reaction by approximating the passage time of the formation of each enzyme-substrate complex molecule which is destined to a production reaction. This approach skips the firings of unimportant yet expensive reaction events, resulting in a substantial acceleration in the stochastic simulations of enzymatic reactions. Additionally, since all the parameters used in our new approach can be derived by the Michaelis-Menten parameters which can actually be measured from experimental data, applications of this approximation can be practical even without having full knowledge of the underlying enzymatic reaction. Here, we apply this new method to various enzymatic reaction systems, resulting in a speedup of orders of magnitude in temporal behavior analysis without any significant loss in accuracy. Furthermore, we show that our new method can perform better than some of the best existing approximation methods for enzymatic reactions in terms of accuracy and efficiency. PMID:18662102

  10. An approximation method for diffusion based leaching models

    International Nuclear Information System (INIS)

    In connection with the fixation of nuclear waste in a glassy matrix equations have been derived for leaching models based on a uniform concentration gradient approximation, and hence a uniform flux, therefore requiring the use of only Fick's first law. In this paper we improve on the uniform flux approximation, developing and justifying the approach. The resulting set of equations are solved to a satisfactory approximation for a matrix dissolving at a constant rate in a finite volume of leachant to give analytical expressions for the time dependence of the thickness of the leached layer, the diffusional and dissolutional contribution to the flux, and the leachant composition. Families of curves are presented which cover the full range of all the physical parameters for this system. The same procedure can be readily extended to more complex systems. (author)

  11. Sherlock Holmes's Methods of Deductive Reasoning Applied to Medical Diagnostics

    OpenAIRE

    Miller, Larry

    1985-01-01

    Having patterned the character of Sherlock Holmes after one of his professors, Sir Arthur Conan Doyle, himself a physician, incorporated many of the didactic qualities of the 19th century medical diagnostician into the character of Holmes. In this paper I explore Holmes's techniques of deductive reasoning and their basis in 19th and 20th century medical diagnostics.

  12. Sherlock Holmes's Methods of Deductive Reasoning Applied to Medical Diagnostics

    Science.gov (United States)

    Miller, Larry

    1985-01-01

    Having patterned the character of Sherlock Holmes after one of his professors, Sir Arthur Conan Doyle, himself a physician, incorporated many of the didactic qualities of the 19th century medical diagnostician into the character of Holmes. In this paper I explore Holmes's techniques of deductive reasoning and their basis in 19th and 20th century medical diagnostics. PMID:3887762

  13. Sherlock Holmes' methods of deductive reasoning applied to medical diagnostics.

    Science.gov (United States)

    Miller, L

    1985-03-01

    Having patterned the character of Sherlock Holmes after one of his professors, Sir Arthur Conan Doyle, himself a physician, incorporated many of the didactic qualities of the 19th century medical diagnostician into the character of Holmes. In this paper I explore Holmes's techniques of deductive reasoning and their basis in 19th and 20th century medical diagnostics. PMID:3887762

  14. α-Automated Reasoning Method Based on Lattice-Valued Propositional Logic LP(X)

    Institute of Scientific and Technical Information of China (English)

    王伟; 徐扬; 王学芳

    2002-01-01

    This paper is focused on automated reasoning based on classical propositional logic and lattice-valued propositional logic LP(X). A new method of automated reasoning is given, and the soundness and completeness theorems of this method are proved.

  15. Stochastic Approximation Methods for Latent Regression Item Response Models

    Science.gov (United States)

    von Davier, Matthias; Sinharay, Sandip

    2010-01-01

    This article presents an application of a stochastic approximation expectation maximization (EM) algorithm using a Metropolis-Hastings (MH) sampler to estimate the parameters of an item response latent regression model. Latent regression item response models are extensions of item response theory (IRT) to a latent variable model with covariates…

  16. Importance sampling approach for the nonstationary approximation error method

    International Nuclear Information System (INIS)

    The approximation error approach has previously been proposed to handle modelling, numerical and computational errors. This approach has been developed both for stationary and nonstationary inverse problems (Kalman filtering). The key idea of the approach is to compute the approximate statistics of the errors over the distribution of all unknowns and uncertainties and carry out approximative marginalization with respect to these errors. In nonstationary problems, however, information is accumulated over time, and the initial uncertainties may turn out to have been exaggerated. In this paper, we propose an algorithm with which the approximation error statistics can be updated during the accumulation of measurement information. The proposed algorithm is based on importance sampling. The recursions that are proposed here are, however, based on the (extended) Kalman filter and therefore do not employ the often exceedingly heavy computational load of particle filtering. As a computational example, we study an estimation problem that is related to a convection–diffusion problem in which the velocity field is not accurately specified

  17. A method of approximating range size of small mammals

    Science.gov (United States)

    Stickel, L.F.

    1965-01-01

    In summary, trap success trends appear to provide a useful approximation to range size of easily trapped small mammals such as Peromyscus. The scale of measurement can be adjusted as desired. Further explorations of the usefulness of the plan should be made and modifications possibly developed before adoption.

  18. 26 CFR 1.412(c)(3)-1 - Reasonable funding methods.

    Science.gov (United States)

    2010-04-01

    ... 26 Internal Revenue 5 2010-04-01 2010-04-01 false Reasonable funding methods. 1.412(c)(3)-1... Reasonable funding methods. (a) Introduction—(1) In general. This section prescribes rules for determining whether or not, in the case of an ongoing plan, a funding method is reasonable for purposes of section...

  19. Fuzzy Reasoning Methods by Choosing Different Fuzzy Counters and Analysis of Effect

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Different fuzzy reasoning methods were gave by choosing different fuzzy counters. This article generally introduced the basic structure of fuzzy controller,and compared and analysised the reasoning effect of fuzzy reasoning methods and the effect of computer simulating control basicly on different fuzzy counters.

  20. Study of hybrid methods for approximating the Edgeworth-Pareto hull in nonlinear multicriteria optimization problems

    Science.gov (United States)

    Berezkin, V. E.; Lotov, A. V.; Lotova, E. A.

    2014-06-01

    Methods for approximating the Edgeworth-Pareto hull (EPH) of the set of feasible criteria vectors in nonlinear multicriteria optimization problems are examined. The relative efficiency of two EPH approximation methods based on classical methods of searching for local extrema of convolutions of criteria is experimentally studied for a large-scale applied problem (with several hundred variables). A hybrid EPH approximation method combining classical and genetic approximation methods is considered.

  1. Topological approximation methods for evolutionary problem of nonlinear hydrodynamics

    CERN Document Server

    Zvyagin, Victor

    2008-01-01

    The authors present functional analytical methods for solving a class of partial differential equations. The results have important applications to the numerical treatment of rheology (specific examples are the behaviour of blood or print colours) and to other applications in fluid mechanics. A class of methods for solving problems in hydrodynamics is presented.

  2. Automated Reasoning and Equation Solving with the Characteristic Set Method

    Institute of Scientific and Technical Information of China (English)

    Wen-Tsun Wu; Xiao-Shan Gao

    2006-01-01

    A brief introduction to the characteristic set method is given for solving algebraic equation systems and then the method is extended to algebraic difference systems. The method can be used to decompose the zero set for a difference polynomial set in general form to the union of difference polynomial sets in triangular form. Based on the characteristic set method, a decision procedure for the first order theory over an algebraically closed field and a procedure to prove certain difference identities are proposed.

  3. Approximated methods for the generation of dark matter halo catalogs in the age of precision cosmology

    CERN Document Server

    Monaco, Pierluigi

    2016-01-01

    Precision cosmology has recently triggered new attention on the topic of approximate methods for the clustering of matter on large scales, whose foundations date back to the period from late '60s to early '90s. Indeed, although the prospect of reaching sub-percent accuracy in the measurement of clustering poses a challenge even to full N-body simulations, an accurate estimation of the covariance matrix of clustering statistics requires usage of a large number (hundreds in the most favourable cases) of simulated (mock) galaxy catalogs. Combination of few N-body simulations with a large number of realizations performed with approximate methods, combined with the shrinkage technique or a similar tool, gives the most promising approach to solve this problem with a reasonable amount of resources. In this paper I review this topic, starting from the foundations of the methods, then going through the pioneering efforts of the '90s, and finally presenting the latest extensions and a few codes that are now being used ...

  4. Reverse triple I method of restriction for fuzzy reasoning

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A theory of reverse triple I method of restriction for implication operator R0 is proposed.And the general computation formulas of infimum for fuzzy modus ponens and supremum for fuzzy modus tollens of a-reverse triple I method of restriction are obtained respectively.

  5. Elastic wave scattering calculations and the matrix variational Pade approximant method

    International Nuclear Information System (INIS)

    The matrix variational Pade approximant and its generalization to elastic wave scattering are discussed. Predictions of the method for the scattering of a longitudinal plane wave are compared with the exact scattering from spherical voids and inclusions. Its predictions are also compared to those of the first and second Born approximations and to the standard matrix Pade approximant based on these Born approximations

  6. A method to reduce ambiguities of qualitative reasoning for conceptual design applications

    OpenAIRE

    D' Amelio, V.; Chmarra, M.K.; Tomiyama, T

    2013-01-01

    Qualitative reasoning can generate ambiguous behaviors due to the lack of quantitative information. Despite many different research results focusing on ambiguities reduction, fundamentally it is impossible to totally remove ambiguities with only qualitative methods and to guarantee the consistency of results. This prevents the wide use of qualitative reasoning techniques in practical situations, particularly in conceptual design, where qualitative reasoning is considered intrinsically useful....

  7. SET: A Pupil Detection Method Using Sinusoidal Approximation

    Directory of Open Access Journals (Sweden)

    Amir-Homayoun eJavadi

    2015-04-01

    Full Text Available Mobile eye-tracking in external environments remains challenging, despite recent advances in eye-tracking software and hardware engineering. Many current methods fail to deal with the vast range of outdoor lighting conditions and the speed at which these can change. This confines experiments to artificial environments where conditions must be tightly controlled. Additionally, the emergence of low-cost eye tracking devices calls for the development of analysis tools that enable non-technical researchers to process the output of their images. We have developed a fast and accurate method (known as ‘SET’ that is suitable even for natural environments with uncontrolled, dynamic and even extreme lighting conditions. We compared the performance of SET with that of two open-source alternatives by processing two collections of eye images: images of natural outdoor scenes with extreme lighting variations (‘Natural’; and images of less challenging indoor scenes (‘CASIA-Iris-Thousand’. We show that SET excelled in outdoor conditions and was faster, without significant loss of accuracy, indoors. SET offers a low cost eye-tracking solution, delivering high performance even in challenging outdoor environments. It is offered through an open-source MATLAB toolkit as well as a dynamic-link library (‘DLL’, which can be imported into many programming languages including C# and Visual Basic in Windows OS (www.eyegoeyetracker.co.uk.

  8. SET: a pupil detection method using sinusoidal approximation.

    Science.gov (United States)

    Javadi, Amir-Homayoun; Hakimi, Zahra; Barati, Morteza; Walsh, Vincent; Tcheang, Lili

    2015-01-01

    Mobile eye-tracking in external environments remains challenging, despite recent advances in eye-tracking software and hardware engineering. Many current methods fail to deal with the vast range of outdoor lighting conditions and the speed at which these can change. This confines experiments to artificial environments where conditions must be tightly controlled. Additionally, the emergence of low-cost eye tracking devices calls for the development of analysis tools that enable non-technical researchers to process the output of their images. We have developed a fast and accurate method (known as "SET") that is suitable even for natural environments with uncontrolled, dynamic and even extreme lighting conditions. We compared the performance of SET with that of two open-source alternatives by processing two collections of eye images: images of natural outdoor scenes with extreme lighting variations ("Natural"); and images of less challenging indoor scenes ("CASIA-Iris-Thousand"). We show that SET excelled in outdoor conditions and was faster, without significant loss of accuracy, indoors. SET offers a low cost eye-tracking solution, delivering high performance even in challenging outdoor environments. It is offered through an open-source MATLAB toolkit as well as a dynamic-link library ("DLL"), which can be imported into many programming languages including C# and Visual Basic in Windows OS (www.eyegoeyetracker.co.uk). PMID:25914641

  9. Efficient Path Query and Reasoning Method Based on Rare Axis

    Institute of Scientific and Technical Information of China (English)

    姜洋; 冯志勇; 王鑫马晓宁

    2015-01-01

    A new concept of rare axis based on statistical facts is proposed, and an evaluation algorithm is designed thereafter. For the nested regular expressions containing rare axes, the proposed algorithm can reduce its evaluation complexity from polynomial time to nearly linear time. The distributed technique is also employed to construct the navigation axis indexes for resource description framework (RDF) graph data. Experiment results in DrugBank and BioGRID show that this method can improve the query efficiency significantly while ensuring the accuracy and meet the query requirements on Web-scale RDF graph data.

  10. A new method to obtain approximate symmetry of nonlinear evolution equation from perturbations

    Institute of Scientific and Technical Information of China (English)

    Zhang Zhi-Yong; Yong Xue-Lin; Chen Yu-Fu

    2009-01-01

    A novel method for obtaining the approximate symmetry of a partial differential equation with a small parameter is introduced. By expanding the independent variable and the dependent variable in the small parameter series, we obtain more affluent approximate symmetries. The method is applied to two perturbed nonlinear partial differential equations and new approximate solutions are derived.

  11. Reason and Condition for Mode Kissing in MASW Method

    Science.gov (United States)

    Gao, Lingli; Xia, Jianghai; Pan, Yudi; Xu, Yixian

    2016-05-01

    Identifying correct modes of surface waves and picking accurate phase velocities are critical for obtaining an accurate S-wave velocity in MASW method. In most cases, inversion is easily conducted by picking the dispersion curves corresponding to different surface-wave modes individually. Neighboring surface-wave modes, however, will nearly meet (kiss) at some frequencies for some models. Around the frequencies, they have very close roots and energy peak shifts from one mode to another. At current dispersion image resolution, it is difficult to distinguish different modes when mode-kissing occurs, which is commonly seen in near-surface earth models. It will cause mode misidentification, and as a result, lead to a larger overestimation of S-wave velocity and error on depth. We newly defined two mode types based on the characteristics of the vertical eigendisplacements calculated by generalized reflection and transmission coefficient method. Rayleigh-wave mode near the kissing points (osculation points) change its type, that is to say, one Rayleigh-wave mode will contain different mode types. This mode type conversion will cause the mode-kissing phenomenon in dispersion images. Numerical tests indicate that the mode-kissing phenomenon is model dependent and that the existence of strong S-wave velocity contrasts increases the possibility of mode-kissing. The real-world data shows mode misidentification caused by mode-kissing phenomenon will result in higher S-wave velocity of bedrock. It reminds us to pay attention to this phenomenon when some of the underground information is known.

  12. Convergence of hausdorff approximation methods for the Edgeworth-Pareto hull of a compact set

    Science.gov (United States)

    Efremov, R. V.

    2015-11-01

    The Hausdorff methods comprise an important class of polyhedral approximation methods for convex compact bodies, since they have an optimal convergence rate and possess other useful properties. The concept of Hausdorff methods is extended to a problem arising in multicriteria optimization, namely, to the polyhedral approximation of the Edgeworth-Pareto hull (EPH) of a convex compact set. It is shown that the sequences of polyhedral sets generated by Hausdorff methods converge to the EPH to be approximated. It is shown that the Estimate Refinement method, which is most frequently used to approximate the EPH of convex compact sets, is a Hausdorff method and, hence, generates sequences of sets converging to the EPH.

  13. Aptitude Treatment Effects of Laboratory Grouping Method for Students of Differing Reasoning Ability.

    Science.gov (United States)

    Lawrenz, Frances

    1985-01-01

    Determined: (1) if elementary education majors (N=91) from different levels of reasoning ability learned more science concepts under different grouping methods in an inquiry/learning cycle-based physical science class; and (2) if these students became able to reason more effectively under the different grouping methods. (JN)

  14. Method for constructing approximate analytic solutions of differential equations with a polynomial right-hand side

    Science.gov (United States)

    Afanas'ev, A. P.; Dzyuba, S. M.

    2015-10-01

    A method for constructing approximate analytic solutions of systems of ordinary differential equations with a polynomial right-hand side is proposed. The implementation of the method is based on the Picard method of successive approximations and a procedure of continuation of local solutions. As an application, the problem of constructing the minimal sets of the Lorenz system is considered.

  15. Method for disclosing the reasoning behind computer-aided diagnosis of pulmonary nodules

    International Nuclear Information System (INIS)

    This paper proposes a method for disclosing the reasoning behind computer-aided diagnosis (CADx) based on a Bayesian network. The purpose of this method is to promote the acceptance of CADx by physicians by providing the reasoning behind the inferences. The proposed method first calculates the influence ratio to the inference result for each subset of input information. It then selects some subsets that have large influence ratios and shows them as the reasoning or grounds for the inference. In experiments using artificial data with known classification rules, the proposed method detected correct rules for about 90% of the data. With regard to clinical data, the average value for the effectiveness of reasoning as judged by two physicians was 3.4. This value is greater than '3', which is considered a reasonable grade. (author)

  16. Beam propagation method using a [(p- 1)/ p] Padé approximant of the propagator.

    Science.gov (United States)

    Lu, Ya Yan; Ho, Pui Lin

    2002-05-01

    A new beam propagation method (BPM) is developed based on a direct approximation to the propagator by its [(p-1)/p] Padé approximant. The approximant is simple to construct and has the desired damping effect for the evanescent modes. The method is applied to a tapered waveguide for TM-polarized waves, based on the energy-conserving improvement of the one-way Helmholtz equation. Numerical results are compared with those obtained with other variants of the BPM. PMID:18007898

  17. A Conflict Context Reasoning Method Based on Dempster-Shafer Theory in Ubiquitous Computing

    Directory of Open Access Journals (Sweden)

    Xinkai Yang

    2013-08-01

    Full Text Available In this paper, one conflict context reasoning method based on Dempster-Shafer theory is proposed. Firstly the context conflict problems are illustrated and partitioned based on theory of evidence. Then the context model combined with Dempster-Shafer theory is presented and applied to the reasoning method based on Dempster rule of combination. The effectiveness of this method is verified with a RFID application example.

  18. A Conflict Context Reasoning Method Based on Dempster-Shafer Theory in Ubiquitous Computing

    OpenAIRE

    Xinkai Yang

    2013-01-01

    In this paper, one conflict context reasoning method based on Dempster-Shafer theory is proposed. Firstly the context conflict problems are illustrated and partitioned based on theory of evidence. Then the context model combined with Dempster-Shafer theory is presented and applied to the reasoning method based on Dempster rule of combination. The effectiveness of this method is verified with a RFID application example.

  19. Formalizing Default Reasoning

    Institute of Scientific and Technical Information of China (English)

    1990-01-01

    Fuzzy set systems can be used to solve the problem with uncertain knowledge,and default logic can be used to solve the problem with incomplete knowledge,in some sense.In this paper,based on interval-valued fuzzy sets we introduce a method of inference which combines approximate reasoning an default ogic,and give the procedure of transforming monotonic reasoning into default reasoning.

  20. Approximate method in estimation sensitivity responses to variations in delayed neutron energy spectra

    Energy Technology Data Exchange (ETDEWEB)

    Yoo, J.; Shin, H. S.; Song, T. Y.; Park, W. S. [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    1997-12-31

    Previous our numerical results in computing point kinetics equations show a possibility in developing approximations to estimate sensitivity responses of nuclear reactor. We recalculate sensitivity responses by maintaining the corrections with first order of sensitivity parameter. We present a method for computing sensitivity responses of nuclear reactor based on an approximation derived from point kinetics equations. Exploiting this approximation, we found that the first order approximation works to estimate variations in the time to reach peak power because of their linear dependence on a sensitivity parameter, and that there are errors in estimating the peak power in the first order approximation for larger sensitivity parameters. To confirm legitimacy of out approximation, these approximate results are compared with exact results obtained from out previous numerical study. 4 refs., 2 figs., 3 tabs. (Author)

  1. First and second order approximate reliability analysis methods using evidence theory

    International Nuclear Information System (INIS)

    The first order approximate reliability method (FARM) and second order approximate reliability method (SARM) are formulated based on evidence theory in this paper. The proposed methods can significantly improve the computational efficiency for evidence-theory-based reliability analysis, while generally provide sufficient precision. First, the most probable focal element (MPFE), an important concept as the most probable point (MPP) in probability-theory-based reliability analysis, is searched using a uniformity approach. Subsequently, FARM approximates the limit-state function around the MPFE using the linear Taylor series, while SARM approximates it using the quadratic Taylor series. With the first and second order approximations, the reliability interval composed of the belief measure and the plausibility measure is efficiently obtained for FARM and SARM, respectively. Two simple problems with explicit expressions and one engineering application of vehicle frontal impact are presented to demonstrate the effectiveness of the proposed methods. - Highlights: • The first order approximate reliability method using evidence theory is proposed. • The second order approximate reliability method using evidence theory is proposed. • The proposed methods can significantly improve the computational efficiency. • The proposed methods can provide sufficient accuracy for general engineering problems

  2. An explicit approximate solution to the Duffing-harmonic oscillator by a cubication method

    Energy Technology Data Exchange (ETDEWEB)

    Belendez, A., E-mail: a.belendez@ua.e [Departamento de Fisica, Ingenieria de Sistemas y Teoria de la Senal, Universidad de Alicante, Apartado 99, E-03080 Alicante (Spain); Mendez, D.I. [Departamento de Fisica, Ingenieria de Sistemas y Teoria de la Senal, Universidad de Alicante, Apartado 99, E-03080 Alicante (Spain); Fernandez, E. [Departamento de Optica, Farmacologia y Anatomia, Universidad de Alicante, Apartado 99, E-03080 Alicante (Spain); Marini, S. [Departamento de Fisica, Ingenieria de Sistemas y Teoria de la Senal, Universidad de Alicante, Apartado 99, E-03080 Alicante (Spain); Pascual, I. [Departamento de Optica, Farmacologia y Anatomia, Universidad de Alicante, Apartado 99, E-03080 Alicante (Spain)

    2009-08-03

    The nonlinear oscillations of a Duffing-harmonic oscillator are investigated by an approximated method based on the 'cubication' of the initial nonlinear differential equation. In this cubication method the restoring force is expanded in Chebyshev polynomials and the original nonlinear differential equation is approximated by a Duffing equation in which the coefficients for the linear and cubic terms depend on the initial amplitude, A. The replacement of the original nonlinear equation by an approximate Duffing equation allows us to obtain explicit approximate formulas for the frequency and the solution as a function of the complete elliptic integral of the first kind and the Jacobi elliptic function, respectively. These explicit formulas are valid for all values of the initial amplitude and we conclude this cubication method works very well for the whole range of initial amplitudes. Excellent agreement of the approximate frequencies and periodic solutions with the exact ones is demonstrated and discussed and the relative error for the approximate frequency is as low as 0.071%. Unlike other approximate methods applied to this oscillator, which are not capable to reproduce exactly the behaviour of the approximate frequency when A tends to zero, the cubication method used in this Letter predicts exactly the behaviour of the approximate frequency not only when A tends to infinity, but also when A tends to zero. Finally, a closed-form expression for the approximate frequency is obtained in terms of elementary functions. To do this, the relationship between the complete elliptic integral of the first kind and the arithmetic-geometric mean as well as Legendre's formula to approximately obtain this mean are used.

  3. An explicit approximate solution to the Duffing-harmonic oscillator by a cubication method

    International Nuclear Information System (INIS)

    The nonlinear oscillations of a Duffing-harmonic oscillator are investigated by an approximated method based on the 'cubication' of the initial nonlinear differential equation. In this cubication method the restoring force is expanded in Chebyshev polynomials and the original nonlinear differential equation is approximated by a Duffing equation in which the coefficients for the linear and cubic terms depend on the initial amplitude, A. The replacement of the original nonlinear equation by an approximate Duffing equation allows us to obtain explicit approximate formulas for the frequency and the solution as a function of the complete elliptic integral of the first kind and the Jacobi elliptic function, respectively. These explicit formulas are valid for all values of the initial amplitude and we conclude this cubication method works very well for the whole range of initial amplitudes. Excellent agreement of the approximate frequencies and periodic solutions with the exact ones is demonstrated and discussed and the relative error for the approximate frequency is as low as 0.071%. Unlike other approximate methods applied to this oscillator, which are not capable to reproduce exactly the behaviour of the approximate frequency when A tends to zero, the cubication method used in this Letter predicts exactly the behaviour of the approximate frequency not only when A tends to infinity, but also when A tends to zero. Finally, a closed-form expression for the approximate frequency is obtained in terms of elementary functions. To do this, the relationship between the complete elliptic integral of the first kind and the arithmetic-geometric mean as well as Legendre's formula to approximately obtain this mean are used.

  4. Approximate Analytic Solutions for the Two-Phase Stefan Problem Using the Adomian Decomposition Method

    Directory of Open Access Journals (Sweden)

    Xiao-Ying Qin

    2014-01-01

    Full Text Available An Adomian decomposition method (ADM is applied to solve a two-phase Stefan problem that describes the pure metal solidification process. In contrast to traditional analytical methods, ADM avoids complex mathematical derivations and does not require coordinate transformation for elimination of the unknown moving boundary. Based on polynomial approximations for some known and unknown boundary functions, approximate analytic solutions for the model with undetermined coefficients are obtained using ADM. Substitution of these expressions into other equations and boundary conditions of the model generates some function identities with the undetermined coefficients. By determining these coefficients, approximate analytic solutions for the model are obtained. A concrete example of the solution shows that this method can easily be implemented in MATLAB and has a fast convergence rate. This is an efficient method for finding approximate analytic solutions for the Stefan and the inverse Stefan problems.

  5. An Approximate Proximal Bundle Method to Minimize a Class of Maximum Eigenvalue Functions

    Directory of Open Access Journals (Sweden)

    Wei Wang

    2014-01-01

    Full Text Available We present an approximate nonsmooth algorithm to solve a minimization problem, in which the objective function is the sum of a maximum eigenvalue function of matrices and a convex function. The essential idea to solve the optimization problem in this paper is similar to the thought of proximal bundle method, but the difference is that we choose approximate subgradient and function value to construct approximate cutting-plane model to solve the above mentioned problem. An important advantage of the approximate cutting-plane model for objective function is that it is more stable than cutting-plane model. In addition, the approximate proximal bundle method algorithm can be given. Furthermore, the sequences generated by the algorithm converge to the optimal solution of the original problem.

  6. On the Influence of New Media and Methods to Achieve Reasonable Spread

    Institute of Scientific and Technical Information of China (English)

    胡海燕

    2016-01-01

    The emergence of new media not only accelerates the spread of information and brings convenience to people, but also subtly changes every aspect of people's life.This paper aims to discuss the influences that the new media bring for people and the methods that can achieve reasonable spread. All of us have the responsibility and obligation to achieve reasonable spread and make the new media serve better for the human progress.

  7. An Iterative Method for the Approximation of Fibers in Slow-Fast Systems

    DEFF Research Database (Denmark)

    Kristiansen, Kristian Uldall; Brøns, Morten; Starke, Jens

    2014-01-01

    In this paper we extend a method for iteratively improving slow manifolds so that it also can be used to approximate the fiber directions. The extended method is applied to general finite-dimensional real analytic systems where we obtain exponential estimates of the tangent spaces to the fibers....... The method is demonstrated on the Michaelis--Menten--Henri model and the Lindemann mechanism. The latter example also serves to demonstrate the method on a slow-fast system in nonstandard slow-fast form. Finally, we extend the method further so that it also approximates the curvature of the fibers....

  8. An efficient method of computing higher-order bond price perturbation approximations

    OpenAIRE

    Andreasen, Martin; Zabczyk, Pawel

    2011-01-01

    This paper develops a fast method of computing arbitrary order perturbation approximations to bond prices in DSGE models. The procedure is implemented to third order where it can shorten the approximation process by more than 100 times. In a consumption-based endowment model with habits, it is further shown that a third-order perturbation solution is more accurate than the log-normal method and a procedure using consol bonds.

  9. OPTIMAL ERROR ESTIMATES OF THE PARTITION OF UNITY METHOD WITH LOCAL POLYNOMIAL APPROXIMATION SPACES

    Institute of Scientific and Technical Information of China (English)

    Yun-qing Huang; Wei Li; Fang Su

    2006-01-01

    In this paper, we provide a theoretical analysis of the partition of unity finite element method(PUFEM), which belongs to the family of meshfree methods. The usual error analysis only shows the order of error estimate to the same as the local approximations[12].Using standard linear finite element base functions as partition of unity and polynomials as local approximation space, in 1-d case, we derive optimal order error estimates for PUFEM interpolants. Our analysis show that the error estimate is of one order higher than the local approximations. The interpolation error estimates yield optimal error estimates for PUFEM solutions of elliptic boundary value problems.

  10. Aptitude treatment effects of laboratory grouping method for students of differing reasoning ability

    Science.gov (United States)

    Lawrenz, Frances; Munch, Theodore W.

    This study examines aptitude treatment effects in an inquiry/learning cycle based physical science class for elementary education majors. The aptitude was formal reasoning ability and the students were arranged into three groups: high, middle, and low ability reasoners. The treatment was method of forming groups to work in the laboratory. Students in each of three classes were grouped according to reasoning ability. In one class the laboratory groups were homogeneous, i.e., students of similar reasoning ability were grouped together. In the second class the students were grouped heterogeneously, i.e., students of different reasoning ability were grouped together. In the third class, the student choice pattern, the students chose their own partners. The findings were that there were no aptitude treatment interaction for achievement or for gain in formal reasoning ability, that grouping students of similar cognitive ability together for laboratory work in the class was more effective in terms of science achievement than grouping students of differing cognitive ability together or than allowing students to choose their own partners, and that students at different levels of reasoning ability experienced differential gains in that ability over the semester.

  11. A New Inexactness Criterion for Approximate Logarithmic-Quadratic Proximal Methods

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Recently, a class of logarithmic-quadratic proximal (LQP) methods was introduced by Auslender, Teboulle and Ben-Tiba. The inexact versions of these methods solve the sub-problems in each iteration approximately. In this paper, we present a practical inexactness criterion for the inexact version of these methods.

  12. 12 CFR 41.25 - Reasonable and simple methods of opting out.

    Science.gov (United States)

    2010-01-01

    ... CREDIT REPORTING Affiliate Marketing § 41.25 Reasonable and simple methods of opting out. (a) In general... means to opt out, such as a form that can be electronically mailed or processed at an Internet Web site... affiliate marketing opt-out under the Act, by a single method, such as by calling a single...

  13. 12 CFR 334.25 - Reasonable and simple methods of opting out.

    Science.gov (United States)

    2010-01-01

    ... STATEMENTS OF GENERAL POLICY FAIR CREDIT REPORTING Affiliate Marketing § 334.25 Reasonable and simple methods... or processed at an Internet Web site, if the consumer agrees to the electronic delivery of... opt-out under the Act, and the affiliate marketing opt-out under the Act, by a single method, such...

  14. 12 CFR 717.25 - Reasonable and simple methods of opting out.

    Science.gov (United States)

    2010-01-01

    ... CREDIT UNIONS FAIR CREDIT REPORTING Affiliate Marketing § 717.25 Reasonable and simple methods of opting... an Internet Web site, if the consumer agrees to the electronic delivery of information; (iv... the Act, and the affiliate marketing opt-out under the Act, by a single method, such as by calling...

  15. GENERALIZATION OF THE INTERACTION BETWEEN HAAR APPROXIMATION AND POLYNOMIAL OPERATORS TO HIGHER ORDER METHODS

    Institute of Scientific and Technical Information of China (English)

    Fran(c)ois Chaplais

    2006-01-01

    In applications it is useful to compute the local average of a function f(u) of an input u from empirical statistics on u. A very simple relation exists when the local averages are given by a Haar approximation. The question is to know if it holds for higher order approximation methods. To do so,it is necessary to use approximate product operators defined over linear approximation spaces. These products are characterized by a Strang and Fix like condition. An explicit construction of these product operators is exhibited for piecewise polynomial functions, using Hermite interpolation. The averaging relation which holds for the Haar approximation is then recovered when the product is defined by a two point Hermite interpolation.

  16. An approximate method for design and analysis of an ALOHA system

    Science.gov (United States)

    Kobayashi, H.; Onozato, Y.; Huynh, D.

    1977-01-01

    An approximate method for the design and performance prediction of a multiaccess communication system which employs the ALOHA packet-switching technique is developed, based on the use of a diffusion process approximation of an ALOHA-like system (with or without time-slotting). A simple closed-form solution for the variable Q(t), a variant of the number of backlog messages at time t, is given in terms of a few system and user parameters. Final results are expressed in terms of ordinary performance measures such as throughput and average delay. Several numerical examples are given to demonstrate the usefulness of the approximation technique developed.

  17. Development of approximate shielding calculation method for high energy cosmic radiation on LEO satellites

    International Nuclear Information System (INIS)

    To calculate total dose effect on semi-conductor devices in satellite for a period of space mission effectively, two approximate calculation models for a comic radiation shielding were proposed. They are a sectoring method and a chord-length distribution method. When an approximate method was applied in this study, complex structure of satellite was described into multiple 1-dimensional slabs, structural materials were converted to reference material(aluminum), and the pre-calculated dose-depth conversion function was introduced to simplify the calculation process. Verification calculation was performed for orbit location and structure geometry of KITSAT-1 and compared with detailed 3-dimensional calculation results and experimental values. The calculation results from approximate method were estimated conservatively with acceptable error. However, results for satellite mission simulation were underestimated in total dose rate compared with experimental values

  18. Approximate analytical solution of diffusion equation with fractional time derivative using optimal homotopy analysis method

    Directory of Open Access Journals (Sweden)

    S. Das

    2013-12-01

    Full Text Available In this article, optimal homotopy-analysis method is used to obtain approximate analytic solution of the time-fractional diffusion equation with a given initial condition. The fractional derivatives are considered in the Caputo sense. Unlike usual Homotopy analysis method, this method contains at the most three convergence control parameters which describe the faster convergence of the solution. Effects of parameters on the convergence of the approximate series solution by minimizing the averaged residual error with the proper choices of parameters are calculated numerically and presented through graphs and tables for different particular cases.

  19. Analytical Approximation Methods for the Stabilizing Solution of the Hamilton–Jacobi Equation

    NARCIS (Netherlands)

    Sakamoto, Noboru; Schaft, Arjan J. van der

    2008-01-01

    In this paper, two methods for approximating the stabilizing solution of the Hamilton–Jacobi equation are proposed using symplectic geometry and a Hamiltonian perturbation technique as well as stable manifold theory. The first method uses the fact that the Hamiltonian lifted system of an integrable

  20. Analytical Approximation Methods for the Stabilizing Solution of the Hamilton-Jacobi Equation

    NARCIS (Netherlands)

    Sakamoto, Noboru; van der Schaft, Arjan J.

    2008-01-01

    In this paper, two methods for approximating the stabilizing solution of the Hamilton-Jacobi equation are proposed using symplectic geometry and a Hamiltonian perturbation technique as well as stable manifold theory. The first method uses the fact that the Hamiltonian lifted system of an integrable

  1. Approximate Analytic and Numerical Solutions to Lane-Emden Equation via Fuzzy Modeling Method

    Directory of Open Access Journals (Sweden)

    De-Gang Wang

    2012-01-01

    Full Text Available A novel algorithm, called variable weight fuzzy marginal linearization (VWFML method, is proposed. This method can supply approximate analytic and numerical solutions to Lane-Emden equations. And it is easy to be implemented and extended for solving other nonlinear differential equations. Numerical examples are included to demonstrate the validity and applicability of the developed technique.

  2. Rotational correction on the Morse potential through the Pekeris approximation and Nikiforov-Uvarov method

    International Nuclear Information System (INIS)

    The Nikiforov-Uvarov method is employed to calculate the Schroedinger equation with a rotation Morse potential. The bound state energy eigenvalues and the corresponding eigenfunction are obtained. All of these calculations present an effective and clear method under a Pekeris approximation to solve a rotation Morse model. Meanwhile the results obtained here are in good agreement with the previous ones. (author)

  3. Numerical solution of 2D-vector tomography problem using the method of approximate inverse

    Science.gov (United States)

    Svetov, Ivan; Maltseva, Svetlana; Polyakova, Anna

    2016-08-01

    We propose a numerical solution of reconstruction problem of a two-dimensional vector field in a unit disk from the known values of the longitudinal and transverse ray transforms. The algorithm is based on the method of approximate inverse. Numerical simulations confirm that the proposed method yields good results of reconstruction of vector fields.

  4. 12 CFR 222.25 - Reasonable and simple methods of opting out.

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    2010-01-01

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  5. 12 CFR 571.25 - Reasonable and simple methods of opting out.

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    2010-01-01

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  6. 16 CFR 680.25 - Reasonable and simple methods of opting out.

    Science.gov (United States)

    2010-01-01

    ... AFFILIATE MARKETING § 680.25 Reasonable and simple methods of opting out. (a) In general. You must not use... a form that can be electronically mailed or processed at an Internet Web site, if the consumer..., 15 U.S.C. 6801 et seq., the affiliate sharing opt-out under the Act, and the affiliate marketing...

  7. Approximate homotopy symmetry method:Homotopy series solutions to the sixth-order Boussinesq equation

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    An approximate homotopy symmetry method for nonlinear problems is proposed and applied to the sixth-order Boussinesq equation,which arises from fluid dynamics.We summarize the general formulas for similarity reduction solutions and similarity reduction equations of different orders,educing the related homotopy series solutions.Zero-order similarity reduction equations are equivalent to the Painlevé IV type equation or Weierstrass elliptic equation.Higher order similarity solutions can be obtained by solving linear variable coefficients ordinary differential equations.The auxiliary parameter has an effect on the convergence of homotopy series solutions.Series solutions and similarity reduction equations from the approximate symmetry method can be retrieved from the approximate homotopy symmetry method.

  8. Quantum Approximate Methods for the Atomistic Modeling of Multicomponent Alloys. Chapter 7

    Science.gov (United States)

    Bozzolo, Guillermo; Garces, Jorge; Mosca, Hugo; Gargano, pablo; Noebe, Ronald D.; Abel, Phillip

    2007-01-01

    This chapter describes the role of quantum approximate methods in the understanding of complex multicomponent alloys at the atomic level. The need to accelerate materials design programs based on economical and efficient modeling techniques provides the framework for the introduction of approximations and simplifications in otherwise rigorous theoretical schemes. As a promising example of the role that such approximate methods might have in the development of complex systems, the BFS method for alloys is presented and applied to Ru-rich Ni-base superalloys and also to the NiAI(Ti,Cu) system, highlighting the benefits that can be obtained from introducing simple modeling techniques to the investigation of such complex systems.

  9. GPGCD, an Iterative Method for Calculating Approximate GCD, for Multiple Univariate Polynomials

    CERN Document Server

    Terui, Akira

    2010-01-01

    We present an extension of our GPGCD method, an iterative method for calculating approximate greatest common divisor (GCD) of univariate polynomials, to multiple polynomial inputs. For a given pair of polynomials and a degree, our algorithm finds a pair of polynomials which has a GCD of the given degree and whose coefficients are perturbed from those in the original inputs, making the perturbations as small as possible, along with the GCD. In our GPGCD method, the problem of approximate GCD is transferred to a constrained minimization problem, then solved with the so-called modified Newton method, which is a generalization of the gradient-projection method, by searching the solution iteratively. In this paper, we extend our method to accept more than two polynomials with the real coefficients as an input.

  10. Analytical numerical methods applied to linear discontinuous angular approximations of the transport equation in slab geometry

    International Nuclear Information System (INIS)

    In this paper we describe two analytical numerical methods applied to one-speed slab-geometry deep penetration transport problems. The linear discontinuous (LDN) equations are used to approximate the monoenergetic Boltzmann equation in slab geometry; they are obtained by considering a linear expansion of the angular flux inside each of the N elements of a uniform angular grid. The two analytical numerical methods are referred to as the spectral Green's function (SGF) nodal method and the Laplace transform (LTLDN) method. The SGF nodal method and the LTLDN method generate numerical solutions to the LDN equations that are completely free of spatial approximations, apart from finite arithmetic considerations. Numerical results to typical model problems and suggestions for future work are also presented. (orig.)

  11. Approximate two layer (inviscid/viscous) methods to model aerothermodynamic environments

    Science.gov (United States)

    Dejarnette, Fred R.

    1992-01-01

    Approximate inviscid and boundary layer techniques for aerodynamic heating calculations are discussed. An inviscid flowfield solution is needed to provide surface pressures and boundary-layer edge properties. Modified Newtonian pressures coupled with an approximate shock shape will suffice for relatively simple shapes like sphere-cones with cone half-angles between 15 and 45 deg. More accurate approximate methods have been developed which make use of modified Maslen techniques. Slender and large angle sphere-cones and more complex shapes generally require an Euler code, like HALIS, to provide that information. The boundary-layer solution is reduced significantly by using the axisymmetric analog and approximate heating relations developed by Zoby, et al. (1981). Analysis is presented for the calculation of inviscid surface streamlines and metrics. Entropy-layer swallowing effects require coupling the inviscid and boundary-layer solutions.

  12. A New Homotopy Analysis Method for Approximating the Analytic Solution of KdV Equation

    Directory of Open Access Journals (Sweden)

    Vahid Barati

    2014-01-01

    Full Text Available In this study a new technique of the Homotopy Analysis Method (nHAM is applied to obtain an approximate analytic solution of the well-known Korteweg-de Vries (KdV equation. This method removes the extra terms and decreases the time taken in the original HAM by converting the KdV equation to a system of first order differential equations. The resulted nHAM solution at third order approximation is then compared with that of the exact soliton solution of the KdV equation and found to be in excellent agreement.

  13. Model reference adaptive control in fractional order systems using discrete-time approximation methods

    Science.gov (United States)

    Abedini, Mohammad; Nojoumian, Mohammad Ali; Salarieh, Hassan; Meghdari, Ali

    2015-08-01

    In this paper, model reference control of a fractional order system has been discussed. In order to control the fractional order plant, discrete-time approximation methods have been applied. Plant and reference model are discretized by Grünwald-Letnikov definition of the fractional order derivative using "Short Memory Principle". Unknown parameters of the fractional order system are appeared in the discrete time approximate model as combinations of parameters of the main system. The discrete time MRAC via RLS identification is modified to estimate the parameters and control the fractional order plant. Numerical results show the effectiveness of the proposed method of model reference adaptive control.

  14. AN ANISOTROPIC NONCONFORMING FINITE ELEMENT METHOD FOR APPROXIMATING A CLASS OF NONLINEAR SOBOLEV EQUATIONS

    Institute of Scientific and Technical Information of China (English)

    Dongyang Shi; Haihong Wang; Yuepeng Du

    2009-01-01

    An anisotropic nonconforming finite element method is presented for a class of nonlinear Sobolev equations. The optimal error estimates and supercloseness are obtained for both semi-discrete and fully-discrete approximate schemes, which are the same as the traditional finite element methods. In addition, the global superconvergence is derived through the postprocessing technique. Numerical experiments are included to illustrate the feasibility of the proposed method.

  15. A numeric-analytic method for approximating quadratic Riccati differential equation

    Directory of Open Access Journals (Sweden)

    Belal Batiha

    2012-03-01

    Full Text Available In this paper, the multistage variational iteration method (MVIM isapplied to the solution of quadratic Riccati differential equations. The solution of quadratic Riccati differential equation obtained using the classical variational iteration method (VIM give good approximationsonly in the neighborhood of the initial position. The solution obtained by MVIM give good approximations for a larger interval. Comparison MVIM solution with classical VIM and exact solution show that the MVIM is a powerful method for the solution of nonlinear equations.

  16. A New Trigonometric Method of Summation and its Application to the Degree of Approximation

    Indian Academy of Sciences (India)

    G Das; Anasuya Nath; B K Ray

    2002-05-01

    The object of the present investigation is to introduce a new trigonometric method of summation which is both regular and Fourier effective and determine its status with reference to other methods of summation (see $\\mathcal{x}$2–$\\mathcal{x}$4) and also give an application of this method to determine the degree of approximation in a new Banach space of functions conceived as a generalized Hölder metric (see $\\mathcal{x}$5).

  17. An Approximate Method for the Surge Response of the Tension Leg Platform

    Institute of Scientific and Technical Information of China (English)

    Rahim Shoghi; Mohammad Reza Tabeshpour

    2014-01-01

    The solution for the Duffing equation in a nonlinear vibration problem is studied in this paper. Clearly, in the case of the perturb parameter being a larger value, the traditional perturbation method is no longer valid but the Homotopy Perturbation Method (HPM) is applicable usually. HPM is used to solve the weak and strong nonlinear differential equations for finding the perturbed frequency of the response. The obtained frequencies via HPM and the approximate method have good accordance for weak and strong nonlinear differential equations. Additionally, the calculated responses by use of the approximate method are compared with the responses obtained from the Numerical method in the time history of the response and phase plane. The results represent good accordance between them.

  18. Global collocation methods for approximation and the solution of partial differential equations

    Science.gov (United States)

    Solomonoff, A.; Turkel, E.

    1986-01-01

    Polynomial interpolation methods are applied both to the approximation of functions and to the numerical solutions of hyperbolic and elliptic partial differential equations. The derivative matrix for a general sequence of the collocation points is constructed. The approximate derivative is then found by a matrix times vector multiply. The effects of several factors on the performance of these methods including the effect of different collocation points are then explored. The resolution of the schemes for both smooth functions and functions with steep gradients or discontinuities in some derivative are also studied. The accuracy when the gradients occur both near the center of the region and in the vicinity of the boundary is investigated. The importance of the aliasing limit on the resolution of the approximation is investigated in detail. Also examined is the effect of boundary treatment on the stability and accuracy of the scheme.

  19. An approximate method to study the one-velocity neutron integral transport equation

    International Nuclear Information System (INIS)

    An approximate method to study the monokinetic linear transport equation is outlined, starting from its integral form, rather than the integro-differential one. The approximate solution may be deduced either analytically, in simple cases, or numerically by means of typical space discretization techniques, through a system of second-order differential equations, associated with proper boundary conditions. Both the system and the boundary conditions may be matched with the standard neutron diffusion multigroup ones, by means of a proper correspondence of the coefficients and of the unknowns. The slab and the radially-symmetric sphere are then analysed in detail. It is shown how, in the plane case, the present approximation is perfectly equivalent to the well-known discrete ordinate one. For curved geometries no such equivalence exists, and it is in these cases that the application of the method at hand looks promising, in order to avoid complications and numerical problems in practical applications. (author)

  20. The information-based complexity of approximation problem by adaptive Monte Carlo methods

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    In this paper, we study the complexity of information of approximation problem on the multivariate Sobolev space with bounded mixed derivative MWpr,α(Td), 1 < p < ∞, in the norm of Lq(Td), 1 < q < ∞, by adaptive Monte Carlo methods. Applying the discretization technique and some properties of pseudo-s-scale, we determine the exact asymptotic orders of this problem.

  1. Viscosity Approximation Method for Infinitely Many Asymptotically Nonexpansive Maps in Banach Spaces

    Institute of Scientific and Technical Information of China (English)

    Ruo Feng RAO

    2011-01-01

    In the framework of reflexive Banach spaces satisfying a weakly continuous duality map,the author uses the viscosity approximation method to obtain the strong convergence theorem for iterations with infinitely many asymptotically nonexpansive mappings.The main results obtained in this paper improve and extend some recent results.

  2. Efficiency fitting for TDCR measurement data using polynomial approximation and the Newton–Raphson method

    International Nuclear Information System (INIS)

    A tritium radioactivity source was measured by triple-to-double coincidence ratio (TDCR) equipment of the National Metrology Institute of Japan (NMIJ), and measured data were fitted using polynomial approximation and the Newton–Raphson method, a technique whereby equations are solved numerically by successive approximations. The method used to obtain the activity minimizes the difference between statistically calculated data and experimental data. In the fitting, since calculated statistical efficiency and TDCR values are discrete, the calculated efficiencies are approximated by quadratic functions around experimental values and the Newton–Raphson method is used for convergence at the minimal difference between experimental data and calculated data. In this way, the activity of tritium was successfully obtained. - Highlights: ► The TDCR data were fitted using polynomial approximation and the Newton–Raphson method. ► Activity was then successfully obtained by this fitting. ► The fitting procedure developed in this paper enables kB to be extracted for the scintilltor being used.

  3. Analytical Approximation Method for the Center Manifold in the Nonlinear Output Regulation Problem

    Czech Academy of Sciences Publication Activity Database

    Suzuki, H.; Sakamoto, N.; Čelikovský, Sergej

    Cancum: IEEE, 2008, s. 1163-1168. ISBN 978-1-4244-3124-3. [47th IEEE Conference on Decision and Control. Cancum (MX), 09.12.2008-11.12.2008] Institutional research plan: CEZ:AV0Z10750506 Keywords : approximate methods * nonlinear systems * output regulation Subject RIV: BC - Control Systems Theory

  4. A Restarted Induced Dimension Reduction method to approximate eigenpairs of large unsymmetric matrices

    NARCIS (Netherlands)

    Astudillo, R.; Van Gijzen, M.B.

    2014-01-01

    A new algorithm to compute eigenpairs of large unsymmetric matrices is presented. Using the Induced Dimension Reduction method (IDR), which was originally proposed for solving linear systems, we obtain a Hessenberg decomposition from which we approximate the eigen-values and eigenvectors of a matrix

  5. Approximation to the Mean and Variance of Moments Method Estimate Due to Gamma Distribution

    International Nuclear Information System (INIS)

    In this paper, we shall consider the approximation to the mean and variance of moments method estimators due to gamma distribution by using Taylor series expansion approach.This approach showed that the estimators are asymptotically unbiased with mean square error approach zero as the sample size approach infinity.The theoretical approach assessed practically by using Monte-Carlo simulation

  6. Study of the scientific reasoning methods: Identifying the salient reasoning characteristics exhibited by engineers and scientists in an R&D environment

    Science.gov (United States)

    Kuhn, William F.

    At the core of what it means to be a scientist or engineer is the ability to think rationally using scientific reasoning methods. Yet, typically if asked, scientist and engineers are hard press for a reply what that means. Some may argue that the meaning of scientific reasoning methods is a topic for the philosophers and psychologist, but this study believes and will prove that the answers lie with the scientists and engineers, for who really know the workings of the scientific reasoning thought process than they. This study will provide evidence to the aims: (a) determine the fundamental characteristics of cognitive reasoning methods exhibited by engineer/scientists working in R&D projects, (b) sample the engineer/scientist community to determine their views as to the importance, frequency, and ranking of each of characteristics towards benefiting their R&D projects, (c) make concluding remarks regarding any identified competency gaps in the exhibited or expected cognitive reasoning methods of engineer/scientists working on R&D projects. To drive these aims are the following three research questions. The first, what are the salient characteristics of cognitive reasoning methods exhibited by engineer/scientists in an R&D environment? The second, what do engineer/scientists consider to be the frequency and importance of the salient cognitive reasoning methods characteristics? And the third, to what extent, if at all, do patent holders and technical fellows differ with regard to their perceptions of the importance and frequency of the salient cognitive reasoning characteristics of engineer/scientists? The methodology and empirical approach utilized and described: (a) literature search, (b) Delphi technique composed of seven highly distinguish engineer/scientists, (c) survey instrument directed to distinguish Technical Fellowship, (d) data collection analysis. The results provide by Delphi Team answered the first research question. The collaborative effort validated

  7. Approximation and inference methods for stochastic biochemical kinetics - a tutorial review

    CERN Document Server

    Schnoerr, David; Grima, Ramon

    2016-01-01

    Stochastic fluctuations of molecule numbers are ubiquitous in biological systems. Important examples include gene expression and enzymatic processes in living cells. Such systems are typically modelled as chemical reaction networks whose dynamics are governed by the Chemical Master Equation. Despite its simple structure, no analytic solutions to the Chemical Master Equation are known for most systems. Moreover, stochastic simulations are computationally expensive, making systematic analysis and statistical inference a challenging task. Consequently, significant effort has been spent in recent decades on the development of efficient approximation and inference methods. This article gives an introduction to basic modelling concepts as well as an overview of state of the art methods. First, we motivate and introduce deterministic and stochastic models for chemical networks, and give an overview of simulation and exact solution methods. Next, we discuss several approximation methods, including the chemical Langev...

  8. New finite volume methods for approximating partial differential equations on arbitrary meshes

    International Nuclear Information System (INIS)

    This dissertation presents some new methods of finite volume type for approximating partial differential equations on arbitrary meshes. The main idea lies in solving twice the problem to be dealt with. One addresses the elliptic equations with variable (anisotropic, antisymmetric, discontinuous) coefficients, the parabolic linear or non linear equations (heat equation, radiative diffusion, magnetic diffusion with Hall effect), the wave type equations (Maxwell, acoustics), the elasticity and Stokes'equations. Numerous numerical experiments show the good behaviour of this type of method. (author)

  9. Classification of Stochastic Runge-Kutta Methods for the Weak Approximation of Stochastic Differential Equations

    OpenAIRE

    Debrabant, Kristian; Rößler, Andreas

    2013-01-01

    In the present paper, a class of stochastic Runge-Kutta methods containing the second order stochastic Runge-Kutta scheme due to E. Platen for the weak approximation of It\\^o stochastic differential equation systems with a multi-dimensional Wiener process is considered. Order one and order two conditions for the coefficients of explicit stochastic Runge-Kutta methods are solved and the solution space of the possible coefficients is analyzed. A full classification of the coefficients for such ...

  10. An efficient computer based wavelets approximation method to solve Fuzzy boundary value differential equations

    Science.gov (United States)

    Alam Khan, Najeeb; Razzaq, Oyoon Abdul

    2016-03-01

    In the present work a wavelets approximation method is employed to solve fuzzy boundary value differential equations (FBVDEs). Essentially, a truncated Legendre wavelets series together with the Legendre wavelets operational matrix of derivative are utilized to convert FB- VDE into a simple computational problem by reducing it into a system of fuzzy algebraic linear equations. The capability of scheme is investigated on second order FB- VDE considered under generalized H-differentiability. Solutions are represented graphically showing competency and accuracy of this method.

  11. On-site approximation for spin-orbit coupling in LCAO density functional methods

    OpenAIRE

    Fernandez-Seivane, Lucas; Oliveira, Miguel A; Sanvito, Stefano; Ferrer, Jaime

    2006-01-01

    We propose a computational method that simplifies drastically the inclusion of spin-orbit interaction in density functional theory implemented on localised atomic orbital basis sets. Our method is based on a well-known procedure for obtaining pseudopotentials from atomic relativistic 'ab initio' calculations and on an on-site approximation for the spin-orbit matrix elements. We have implemented the technique in the SIESTA code, and we show that it provides accurate results for the overall ban...

  12. Modelling CH$_3$OH masers: Sobolev approximation and accelerated lambda iteration method

    CERN Document Server

    Nesterenok, Aleksandr

    2015-01-01

    A simple one-dimensional model of CH$_3$OH maser is considered. Two techniques are used for the calculation of molecule level populations: the accelerated lambda iteration (ALI) method and the large velocity gradient (LVG), or Sobolev, approximation. The LVG approximation gives accurate results provided that the characteristic dimensions of the medium are larger than 5-10 lengths of the resonance region. We presume that this condition can be satisfied only for the largest observed maser spot distributions. Factors controlling the pumping of class I and class II methanol masers are considered.

  13. Adomian Decomposition Method and Padé Approximants for Nonlinear Differential-Difference Equations

    Institute of Scientific and Technical Information of China (English)

    LIU Yan-Ming; CHEN Yong

    2009-01-01

    Combining Adomian decomposition method (ADM) with Padd approximants, we solve two differential-difference equations (DDEs): the relativistic Toda lattice equation and the modified Volterra lattice equation.With the help of symbolic computation Maple, the results obtained by ADM-Padé technique are compared with those obtained by using ADM alone.The numerical results demonstrate that ADM-Padé technique give the approximate solution with faster convergence rate and higher accuracy and relative in larger domain of convergence than using ADM.

  14. Discrete dipole approximation of gold nanospheres on substrates: Considerations and comparison with other discretization methods

    Directory of Open Access Journals (Sweden)

    M. P. Menguc

    2011-09-01

    Full Text Available We embark on this preliminary study of the suitability of the discrete dipole approximation with surface interaction (DDA-SI method to model electric field scattering from noble metal nano-structures on dielectric substrates. The refractive index of noble metals, particularly due to their high imaginary components, require smaller lattice spacings and are especially sensitive to the shape integrity and the volume of the dipole model. The results of DDA-SI method are validated against those of the well-established finite element method (FEM and the finite difference time domain (FDTD method.

  15. Transportation problem by Monalisha\\'s approximation method for optimal solution (mamos

    Directory of Open Access Journals (Sweden)

    Monalisha Pattnaik

    2015-09-01

    Full Text Available Background: This paper finds initial basic feasible solution and optimal solution to the transportation problem by using MAM's (Monalisha's Approximation Method. Methods: Using the concept of comparison of the transportation problem by other methods of solution, the paper introduces a very effective method in terms of cost and time for solving these problems. This paper extends transportation problem by using different method of obtaining both initial basic feasible solution and optimal solution simultaneously other than existing methods. Results and conclusions:  It is presented a cost saving and less time consuming and accurate method for obtaining the best optimal solution of the transportation problem . With the problem assumptions, the optimal solution can still be theoretically solved using the existing methods. Finally, numerical examples and sensitivity analysis are presented to illustrate the effectiveness of the theoretical results, and to gain additional managerial insights.  

  16. A Scalable Method for Solving High-Dimensional Continuous POMDPs Using Local Approximation

    CERN Document Server

    Erez, Tom

    2012-01-01

    Partially-Observable Markov Decision Processes (POMDPs) are typically solved by finding an approximate global solution to a corresponding belief-MDP. In this paper, we offer a new planning algorithm for POMDPs with continuous state, action and observation spaces. Since such domains have an inherent notion of locality, we can find an approximate solution using local optimization methods. We parameterize the belief distribution as a Gaussian mixture, and use the Extended Kalman Filter (EKF) to approximate the belief update. Since the EKF is a first-order filter, we can marginalize over the observations analytically. By using feedback control and state estimation during policy execution, we recover a behavior that is effectively conditioned on incoming observations despite the unconditioned planning. Local optimization provides no guarantees of global optimality, but it allows us to tackle domains that are at least an order of magnitude larger than the current state-of-the-art. We demonstrate the scalability of ...

  17. Parallel Preconditioned Conjugate Gradient Square Method Based on Normalized Approximate Inverses

    Directory of Open Access Journals (Sweden)

    George A. Gravvanis

    2005-01-01

    Full Text Available A new class of normalized explicit approximate inverse matrix techniques, based on normalized approximate factorization procedures, for solving sparse linear systems resulting from the finite difference discretization of partial differential equations in three space variables are introduced. A new parallel normalized explicit preconditioned conjugate gradient square method in conjunction with normalized approximate inverse matrix techniques for solving efficiently sparse linear systems on distributed memory systems, using Message Passing Interface (MPI communication library, is also presented along with theoretical estimates on speedups and efficiency. The implementation and performance on a distributed memory MIMD machine, using Message Passing Interface (MPI is also investigated. Applications on characteristic initial/boundary value problems in three dimensions are discussed and numerical results are given.

  18. The Financial Impact of Risk Factors Affecting Project Cost Contingency: Evidential Reasoning Method

    OpenAIRE

    Emmanuel Abeere-Inga; Joseph Ignatius Teye Buertey; Theophilus Adjei Kumi

    2013-01-01

    The process of cost modeling using risk analysis for construction projects is very crucial for the achievement of project success. The purpose of this paper is to present an analysis of the financial impact of risk factors affecting key construction work sections; using a systematic risk methodology based on empirical judgment. The failure mode effect analysis (FMEA) and the evidential reasoning methods are presented as qualitative and quantitative risk tools respectively. Data analysis from ...

  19. Coupled-cluster method: A lattice-path-based subsystem approximation scheme for quantum lattice models

    Science.gov (United States)

    Bishop, R. F.; Li, P. H. Y.

    2011-04-01

    An approximation hierarchy, called the lattice-path-based subsystem (LPSUBm) approximation scheme, is described for the coupled-cluster method (CCM). It is applicable to systems defined on a regular spatial lattice. We then apply it to two well-studied prototypical (spin-(1)/(2) Heisenberg antiferromagnetic) spin-lattice models, namely, the XXZ and the XY models on the square lattice in two dimensions. Results are obtained in each case for the ground-state energy, the ground-state sublattice magnetization, and the quantum critical point. They are all in good agreement with those from such alternative methods as spin-wave theory, series expansions, quantum Monte Carlo methods, and the CCM using the alternative lattice-animal-based subsystem (LSUBm) and the distance-based subsystem (DSUBm) schemes. Each of the three CCM schemes (LSUBm, DSUBm, and LPSUBm) for use with systems defined on a regular spatial lattice is shown to have its own advantages in particular applications.

  20. Coupled-cluster method: A lattice-path-based subsystem approximation scheme for quantum lattice models

    International Nuclear Information System (INIS)

    An approximation hierarchy, called the lattice-path-based subsystem (LPSUBm) approximation scheme, is described for the coupled-cluster method (CCM). It is applicable to systems defined on a regular spatial lattice. We then apply it to two well-studied prototypical (spin-(1/2) Heisenberg antiferromagnetic) spin-lattice models, namely, the XXZ and the XY models on the square lattice in two dimensions. Results are obtained in each case for the ground-state energy, the ground-state sublattice magnetization, and the quantum critical point. They are all in good agreement with those from such alternative methods as spin-wave theory, series expansions, quantum Monte Carlo methods, and the CCM using the alternative lattice-animal-based subsystem (LSUBm) and the distance-based subsystem (DSUBm) schemes. Each of the three CCM schemes (LSUBm, DSUBm, and LPSUBm) for use with systems defined on a regular spatial lattice is shown to have its own advantages in particular applications.

  1. Saddlepoint approximation based line sampling method for uncertainty propagation in fuzzy and random reliability analysis

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    For structural system with random basic variables as well as fuzzy basic variables,uncertain propagation from two kinds of basic variables to the response of the structure is investigated.A novel algorithm for obtaining membership function of fuzzy reliability is presented with saddlepoint approximation(SA)based line sampling method.In the presented method,the value domain of the fuzzy basic variables under the given membership level is firstly obtained according to their membership functions.In the value domain of the fuzzy basic variables corresponding to the given membership level,bounds of reliability of the structure response satisfying safety requirement are obtained by employing the SA based line sampling method in the reduced space of the random variables.In this way the uncertainty of the basic variables is propagated to the safety measurement of the structure,and the fuzzy membership function of the reliability is obtained.Compared to the direct Monte Carlo method for propagating the uncertainties of the fuzzy and random basic variables,the presented method can considerably improve computational efficiency with acceptable precision.The presented method has wider applicability compared to the transformation method,because it doesn’t limit the distribution of the variable and the explicit expression of performance function, and no approximation is made for the performance function during the computing process.Additionally,the presented method can easily treat the performance function with cross items of the fuzzy variable and the random variable,which isn’t suitably approximated by the existing transformation methods.Several examples are provided to illustrate the advantages of the presented method.

  2. Evaluation of approximate methods for the prediction of noise shielding by airframe components

    Science.gov (United States)

    Ahtye, W. F.; Mcculley, G.

    1980-01-01

    An evaluation of some approximate methods for the prediction of shielding of monochromatic sound and broadband noise by aircraft components is reported. Anechoic-chamber measurements of the shielding of a point source by various simple geometric shapes were made and the measured values compared with those calculated by the superposition of asymptotic closed-form solutions for the shielding by a semi-infinite plane barrier. The shields used in the measurements consisted of rectangular plates, a circular cylinder, and a rectangular plate attached to the cylinder to simulate a wing-body combination. The normalized frequency, defined as a product of the acoustic wave number and either the plate width or cylinder diameter, ranged from 4.6 to 114. Microphone traverses in front of the rectangular plates and cylinders generally showed a series of diffraction bands that matched those predicted by the approximate methods, except for differences in the magnitudes of the attenuation minima which can be attributed to experimental inaccuracies. The shielding of wing-body combinations was predicted by modifications of the approximations used for rectangular and cylindrical shielding. Although the approximations failed to predict diffraction patterns in certain regions, they did predict the average level of wing-body shielding with an average deviation of less than 3 dB.

  3. The DSUBm approximation scheme for the coupled cluster method and applications to quantum magnets

    Directory of Open Access Journals (Sweden)

    R.F. Bishop

    2009-01-01

    Full Text Available A new approximate scheme, DSUBm, is described for the coupled cluster method. We apply it to two well-studied (spin-1/2 Heisenberg antiferromagnet spin-lattice models, namely: the XXZ and the XY models on the square lattice in two dimensions. Results are obtained in each case for the ground-state energy, the sublattice magnetization and the quantum critical point. They are in good agreement with those from such alternative methods as spin-wave theory, series expansions, exact diagonalization techniques, quantum Monte Carlo methods and those from the CCM using the LSUBm scheme.

  4. Born approximation to a perturbative numerical method for the solution of the Schroedinger equation

    International Nuclear Information System (INIS)

    A step function perturbative numerical method (SF-PN method) is developed for the solution of the Cauchy problem for the second order liniar differential equation in normal form. An important point stressed in the present paper, which seems to have been previously ignored in the literature devoted to the PN methods, is the close connection between the first order perturbation theory of the PN approach and the wellknown Born approximation, and, in general, the connection between the varjous orders of the PN corrections and the Neumann series. (author)

  5. Approximate Explicit Solution of Falkner-Skan Equation by Homotopy Perturbation Method

    Directory of Open Access Journals (Sweden)

    N. Moallemi

    2012-08-01

    Full Text Available In this study, by mean`s of He`s Homotopy Perturbation Method (HPM an approximate solution of Falkner-Skan equation obtained. In boundary layer theory, we have seen how similarity methods combine two independent variables into one, and therefore our problems our simplified to ODE Equations. If we use HPM we can deforms a difficult ordinary differential equation into a simple problem which can be easily solved. Comparison is made between the solution of Falkner Skan equation for 4 cases and those in open literature to verify accuracy of this work. Results show that the method is very effective and simple.

  6. Accumulated approximation: A new method for structural optimization by iterative improvement

    Science.gov (United States)

    Rasmussen, John

    1990-01-01

    A new method for the solution of non-linear mathematical programming problems in the field of structural optimization is presented. It is an iterative scheme which for each iteration refines the approximation of objective and constraint functions by accumulating the function values of previously visited design points. The method has proven to be competitive for a number of well-known examples of which one is presented here. Furthermore because of the accumulation strategy, the method produces convergence even when the sensitivity analysis is inaccurate.

  7. A STUDY ON THE WEIGHT FUNCTION OF THE MOVING LEAST SQUARE APPROXIMATION IN THE LOCAL BOUNDARY INTEGRAL EQUATION METHOD

    Institute of Scientific and Technical Information of China (English)

    LongShuyao; HuDe'an

    2003-01-01

    The meshless method is a new numerical technique presented in recent years .It uses the moving least square (MLS) approximation as a shape function . The smoothness of the MLS approximation is determined by that of the basic function and of the weight function, and is mainly determined by that of the weight function. Therefore, the weight function greatly affects the accuracy of results obtained. Different kinds of weight functions, such as the spline function, the Gauss function and so on, are proposed recently by many researchers. In the present work, the features of various weight functions are illustrated through solving elasto-static problems using the local boundary integral equation method. The effect of various weight functions on the accuracy, convergence and stability of results obtained is also discussed. Examples show that the weight function proposed by Zhou Weiyuan and Gauss and the quartic spline weight function are better than the others if parameters c and a in Gauss and exponential weight functions are in the range of reasonable values, respectively, and the higher the smoothness of the weight function, the better the features of the solutions.

  8. A New Newton's Method with Diagonal Jacobian Approximation for Systems of Nonlinear Equations

    Directory of Open Access Journals (Sweden)

    M. Y. Waziri

    2010-01-01

    Full Text Available Problem statement: The major weaknesses of Newton method for nonlinear equations entail computation of Jacobian matrix and solving systems of n linear equations in each of the iterations. Approach: In some extent function derivatives are quit costly and Jacobian is computationally expensive which requires evaluation (storage of n×n matrix in every iteration. Results: This storage requirement became unrealistic when n becomes large. We proposed a new method that approximates Jacobian into diagonal matrix which aims at reducing the storage requirement, computational cost and CPU time, as well as avoiding solving n linear equations in each iterations. Conclusion/Recommendations: The proposed method is significantly cheaper than Newton’s method and very much faster than fixed Newton’s method also suitable for small, medium and large scale nonlinear systems with dense or sparse Jacobian. Numerical experiments were carried out which shows that, the proposed method is very encouraging.

  9. An atmospheric backscatter model on wind measurements using far-field approximation method

    Institute of Scientific and Technical Information of China (English)

    SHU Weiping; ZHAO Zhengyu

    2007-01-01

    A backscatter model was developed for measuring wind field with the far-field approximation method.The theoretical computation and computer simulations with one spatial dimension show that this model can realistically describe the physical meaning and process of the three methods in wind measurements including the spaced antenna (SA) method,Doppler beam swing (DBS) method,and spaced interferometry (SI).The computational difficulties of the traditional theoretical model cannot only be smoothed away,but common characteristics and differences of the three methods can be compared deeply.The comparison of the numerical results between the Wuhan medium frequency (MF) radar (30° N,114° E) observation and the computer simulation of the full correlation analysis (FCA) of the SA method indicates that the two results agree very well and this model has practical application.

  10. A Resampling-Based Stochastic Approximation Method for Analysis of Large Geostatistical Data

    KAUST Repository

    Liang, Faming

    2013-03-01

    The Gaussian geostatistical model has been widely used in modeling of spatial data. However, it is challenging to computationally implement this method because it requires the inversion of a large covariance matrix, particularly when there is a large number of observations. This article proposes a resampling-based stochastic approximation method to address this challenge. At each iteration of the proposed method, a small subsample is drawn from the full dataset, and then the current estimate of the parameters is updated accordingly under the framework of stochastic approximation. Since the proposed method makes use of only a small proportion of the data at each iteration, it avoids inverting large covariance matrices and thus is scalable to large datasets. The proposed method also leads to a general parameter estimation approach, maximum mean log-likelihood estimation, which includes the popular maximum (log)-likelihood estimation (MLE) approach as a special case and is expected to play an important role in analyzing large datasets. Under mild conditions, it is shown that the estimator resulting from the proposed method converges in probability to a set of parameter values of equivalent Gaussian probability measures, and that the estimator is asymptotically normally distributed. To the best of the authors\\' knowledge, the present study is the first one on asymptotic normality under infill asymptotics for general covariance functions. The proposed method is illustrated with large datasets, both simulated and real. Supplementary materials for this article are available online. © 2013 American Statistical Association.

  11. Effective cluster interactions using the generalized perturbation method in the atomic-sphere approximation

    International Nuclear Information System (INIS)

    We describe the generalized perturbation method in the atomic-sphere approximation (ASA) for calculating the effective cluster interactions. Based on our development of Korringa-Kohn-Rostoker coherent-potential approximation in the ASA [Singh et al., Phys. Rev. B 44, 8578 (1991)], the present approach is the next step towards developing a first-principles method that can be easily applied to describe substitutionally disordered alloys based on simple lattice structures as well as complex lattice structures with low symmetry. To test the accuracy of the ASA results, we have calculated the effective pair interactions (EPI) up to fourth-nearest neighbors for the substitutionally disordered Pd0.5V0.5 and Pd0.75Rh0.25 alloys. Our calculated EPI's are in good agreement with the respective muffin-tin results

  12. About the Generalized Reasoning Methods and their Use in Semiotic Systems

    Directory of Open Access Journals (Sweden)

    Mihaela I. MUNTEAN

    2006-01-01

    Full Text Available In computational semiotics the problem is to emulate a semiosis cycle within a digital computer. This needs the construction of intelligent systems, able to perform intelligent behavior, such as sensorial perception, world modeling, value judgement and behavior generation. These intelligent systems could be generally implemented through object networks and the basic functions mentioned above could be obtained by generalization of some elementary knowledge operators. Based on the three main reasoning methods, deduction, induction and abduction, well known in the philosophy of science and used in AI systems, there were three knew knowledge operators defined: knowledge extraction, knowledge generation and knowledge generation, operators that could be viewed as generalized interpretations of the standard reasoning procedures. This paper presents these new concepts and their connection, the current understanding of generalized deduction, induction and abduction and also how these operators could serve as the building blocks of universal intelligent systems.

  13. An Improved Approximate-Bayesian Model-choice Method for Estimating Shared Evolutionary History

    OpenAIRE

    Oaks, Jamie R.

    2014-01-01

    Background To understand biological diversification, it is important to account for large-scale processes that affect the evolutionary history of groups of co-distributed populations of organisms. Such events predict temporally clustered divergences times, a pattern that can be estimated using genetic data from co-distributed species. I introduce a new approximate-Bayesian method for comparative phylogeographical model-choice that estimates the temporal distribution of divergences across taxa...

  14. Approximations to the Probability of Failure in Random Vibration by Integral Equation Methods

    DEFF Research Database (Denmark)

    Nielsen, Søren R.K.; Sørensen, John Dalsgaard

    Close approximations to the first passage probability of failure in random vibration can be obtained by integral equation methods. A simple relation exists between the first passage probability density function and the distribution function for the time interval spent below a barrier before outcr...... passage probability density. The results of the theory agree well with simulation results for narrow banded processes dominated by a single frequency, as well as for bimodal processes with 2 dominating frequencies in the structural response....

  15. Error Analysis in Measured Conductivity under Low Induction Number Approximation for Electromagnetic Methods

    OpenAIRE

    George Caminha-Maciel; Irineu Figueiredo

    2013-01-01

    We present an analysis of the error involved in the so-called low induction number approximation in the electromagnetic methods. In particular, we focus on the EM34 equipment settings and field configurations, widely used for geophysical prospecting of laterally electrical conductivity anomalies and shallow targets. We show the theoretical error for the conductivity in both vertical and horizontal dipole coil configurations within the low induction number regime and up to the maximum measurin...

  16. An approximate method for solving a melting problem with periodic boundary conditions

    OpenAIRE

    Qu Liang-Hui; Xing Lin; Yu Zhi-Yun; Ling Feng; Xu Jian-Guo

    2014-01-01

    An effective thermal diffusivity method is used to solve one-dimensional melting problem with periodic boundary conditions in a semi-infinite domain. An approximate analytic solution showing the functional relation between the location of the moving boundary and time is obtained by using Laplace transform. The evolution of the moving boundary and the temperature field in the phase change domain are simulated numerically, and the numerical results are compar...

  17. A nodal method for solving the time-depending diffusion equation in the IQS approximation

    International Nuclear Information System (INIS)

    The fast and slow variation of the neutron flux shape needed for the dynamical description of nuclear reactor cores can be described advantageously in the Improved Quasistatic (IQS) model where the flux is factorized by a fast changing space-independent amplitude and a slow changing shape function. The basic equations of a time-dependent nodal approximation using the IQS method is presented.The calculational procedure of the response matrices is also described. (R.P.) 2 refs

  18. An approximate method for solving a melting problem with periodic boundary conditions

    Directory of Open Access Journals (Sweden)

    Qu Liang-Hui

    2014-01-01

    Full Text Available An effective thermal diffusivity method is used to solve one-dimensional melting problem with periodic boundary conditions in a semi-infinite domain. An approximate analytic solution showing the functional relation between the location of the moving boundary and time is obtained by using Laplace transform. The evolution of the moving boundary and the temperature field in the phase change domain are simulated numerically, and the numerical results are compared with previous results in open literature.

  19. 3-D numerical investigation of subsurface flow in anisotropic porous media using multipoint flux approximation method

    KAUST Repository

    Negara, Ardiansyah

    2013-01-01

    Anisotropy of hydraulic properties of subsurface geologic formations is an essential feature that has been established as a consequence of the different geologic processes that they undergo during the longer geologic time scale. With respect to petroleum reservoirs, in many cases, anisotropy plays significant role in dictating the direction of flow that becomes no longer dependent only on the pressure gradient direction but also on the principal directions of anisotropy. Furthermore, in complex systems involving the flow of multiphase fluids in which the gravity and the capillarity play an important role, anisotropy can also have important influences. Therefore, there has been great deal of motivation to consider anisotropy when solving the governing conservation laws numerically. Unfortunately, the two-point flux approximation of finite difference approach is not capable of handling full tensor permeability fields. Lately, however, it has been possible to adapt the multipoint flux approximation that can handle anisotropy to the framework of finite difference schemes. In multipoint flux approximation method, the stencil of approximation is more involved, i.e., it requires the involvement of 9-point stencil for the 2-D model and 27-point stencil for the 3-D model. This is apparently challenging and cumbersome when making the global system of equations. In this work, we apply the equation-type approach, which is the experimenting pressure field approach that enables the solution of the global problem breaks into the solution of multitude of local problems that significantly reduce the complexity without affecting the accuracy of numerical solution. This approach also leads in reducing the computational cost during the simulation. We have applied this technique to a variety of anisotropy scenarios of 3-D subsurface flow problems and the numerical results demonstrate that the experimenting pressure field technique fits very well with the multipoint flux approximation

  20. A method for the accurate and smooth approximation of standard thermodynamic functions

    Science.gov (United States)

    Coufal, O.

    2013-01-01

    A method is proposed for the calculation of approximations of standard thermodynamic functions. The method is consistent with the physical properties of standard thermodynamic functions. This means that the approximation functions are, in contrast to the hitherto used approximations, continuous and smooth in every temperature interval in which no phase transformations take place. The calculation algorithm was implemented by the SmoothSTF program in the C++ language which is part of this paper. Program summaryProgram title:SmoothSTF Catalogue identifier: AENH_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AENH_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 3807 No. of bytes in distributed program, including test data, etc.: 131965 Distribution format: tar.gz Programming language: C++. Computer: Any computer with gcc version 4.3.2 compiler. Operating system: Debian GNU Linux 6.0. The program can be run in operating systems in which the gcc compiler can be installed, see http://gcc.gnu.org/install/specific.html. RAM: 256 MB are sufficient for the table of standard thermodynamic functions with 500 lines Classification: 4.9. Nature of problem: Standard thermodynamic functions (STF) of individual substances are given by thermal capacity at constant pressure, entropy and enthalpy. STF are continuous and smooth in every temperature interval in which no phase transformations take place. The temperature dependence of STF as expressed by the table of its values is for further application approximated by temperature functions. In the paper, a method is proposed for calculating approximation functions which, in contrast to the hitherto used approximations, are continuous and smooth in every temperature interval. Solution method: The approximation functions are

  1. The reliability of approximate radiation transport methods for irradiated disk studies

    CERN Document Server

    Kuiper, Rolf

    2013-01-01

    Context: Dynamical studies of irradiated circumstellar disks require an accurate treatment of radiation transport to, for example, properly determine cooling and fragmentation properties. The radiation transport algorithm should be as fast as the (magneto-) hydrodynamics to allow for an efficient usage of computing resources. Methods: We use a setup of a central star and a slightly flared circumstellar disk. We perform simulations for a wide range of optical depths of the disk's midplane from tau(550nm) = 0.1 up to tau(810nm) = 1 million. We check the accuracy of the gray flux-limited diffusion (FLD) approximation and a gray and frequency-dependent ray-tracing plus FLD approximation. Results: 1. For moderate optical depths, a gray approximation of the stellar irradiation yields a slightly hotter inner rim and a slightly cooler midplane of the disk at larger radii, but is otherwise in agreement with the frequency-dependent treatment. 2. The gray FLD approximation fails to compute an appropriate temperature pro...

  2. A recursive model-reduction method for approximate inference in Gaussian Markov random fields.

    Science.gov (United States)

    Johnson, Jason K; Willsky, Alan S

    2008-01-01

    This paper presents recursive cavity modeling--a principled, tractable approach to approximate, near-optimal inference for large Gauss-Markov random fields. The main idea is to subdivide the random field into smaller subfields, constructing cavity models which approximate these subfields. Each cavity model is a concise, yet faithful, model for the surface of one subfield sufficient for near-optimal inference in adjacent subfields. This basic idea leads to a tree-structured algorithm which recursively builds a hierarchy of cavity models during an "upward pass" and then builds a complementary set of blanket models during a reverse "downward pass." The marginal statistics of individual variables can then be approximated using their blanket models. Model thinning plays an important role, allowing us to develop thinned cavity and blanket models thereby providing tractable approximate inference. We develop a maximum-entropy approach that exploits certain tractable representations of Fisher information on thin chordal graphs. Given the resulting set of thinned cavity models, we also develop a fast preconditioner, which provides a simple iterative method to compute optimal estimates. Thus, our overall approach combines recursive inference, variational learning and iterative estimation. We demonstrate the accuracy and scalability of this approach in several challenging, large-scale remote sensing problems. PMID:18229805

  3. One Fairing Method of Cubic B-spline Curves Based on Weighted Progressive Iterative Approximation

    Institute of Scientific and Technical Information of China (English)

    ZHANG Li; YANG Yan; LI Yuan-yuan; TAN Jie-qing

    2014-01-01

    A new method to the problem of fairing planar cubic B-spline curves is introduced in this paper. The method is based on weighted progressive iterative approximation (WPIA for short) and consists of following steps:finding the bad point which needs to fair, deleting the bad point, re-inserting a new data point to keep the structure of the curve and applying WPIA method with the new set of the data points to obtain the faired curve. The new set of the data points is formed by the rest of the original data points and the new inserted point. The method can be used for shape design and data processing. Numerical examples are provided to demonstrate the effectiveness of the method.

  4. The effect of method and format on the responses of subjects to a Piagetian reasoning problem

    Science.gov (United States)

    Staver, John R.; Pascarella, Ernest T.

    Researchers interested in studying the effects of subjects' reasoning levels, as defined by Piaget (Inhelder & Piaget, 1958), on science achievement or other dependent variables face two measurement problems. First, the traditional clinical method is time-consuming and impractical for large numbers of subjects. Second, alternative methods of assessment, although reliable and valid, may over- or underestimate subjects' reasoning levels. The objective of this investigation was to determine the effects of various methods and formats of administering a Piagetian task on subjects' performance. The task chosen for this investigation was the Mr. Short-Mr. Tall problem (Karplus & Lavatelli, 1969; Karplus et al., 1977). The task was presented using four methods: (1) individual clinical interview, (2) group presentation of task followed by paper-and-pencil problem with illustration, (3) group administration of paper-and-pencil instrument with illustration, and (4) group administration of paper-and-pencil instrument without illustration. Each method included four formats: (1) completion answer with essay justification, (2) completion answer with multiple-choice justification, (3) multiple-choice answer with essay justification, and (4) multiple-choice answer with multiple-choice justification. Three hundred seventy-six students who were enrolled in a freshman level biological science class participated in the study. The research design was a 4 × 4 factorial design with method and format of assessment as the main effects. The participants were in 16 distinct laboratory or discussion sections, and each section was randomly assigned to a cell in the research design. Regression analysis with the individual as the unit of analysis showed that neither method nor format of assessment accounted for a significant amount of variance in student performance. The overall interaction remained nonsignificant. Regression analysis with sections as the unit of analysis revealed similar

  5. MATHEMATICAL SOLUTIONS OF VEHIULAR DELAY COMPONENTS AT SIGNALIZED INTERSECTIONS BASED ON APPROXIMATE CALCULATION METHOD

    Directory of Open Access Journals (Sweden)

    Halim CEYLAN

    2007-02-01

    Full Text Available This study develops approximate mathematical expressions for delay components at signalized intersections. Delay components are solved with the coordinate transformation method. The performance indicators for the signalized intersection are determined as an oversaturated and under saturated cases. During the analysis, the steady-state and the deterministic queuing theory are investigated first, and then time-dependent transformation is made. Developed model, called YHM, is applied to an example signalized intersection. Results are compared with the current situation and the Webster method. YHM is improved the intersection performance by about 500 % for this example. Moreover, signal parameters are significantly differs from the current and Webster signal control.

  6. Exact and approximate interior corner problem in neutron diffusion by integral transform methods

    Energy Technology Data Exchange (ETDEWEB)

    Bareiss, E.H.; Chang, K.S.J.; Constatinescu, D.A.

    1976-09-01

    The mathematical solution of the neutron diffusion equation exhibits singularities in its derivatives at material corners. A mathematical treatment of the nature of these singularities and its impact on coarse network approximation methods in computational work is presented. The mathematical behavior is deduced from Green's functions, based on a generalized theory for two space dimensions, and the resulting systems of integral equations, as well as from the Kontorovich--Lebedev Transform. The effect on numerical calculations is demonstrated for finite difference and finite element methods for a two-region corner problem.

  7. Approximation of magnetic data surface with ANN (artificial neural network) method

    International Nuclear Information System (INIS)

    Complete text of publication follows. Aero magnetic digital gridded data acquired and processed by US geological survey with Mexican collaborators have been downloaded from internet. The field dataset is a part of the Online Magnetic Dataset for North America, with more than 200,000 data points. Using ANN method a surface has been fitted to the magnetic data. ANN is programmed under Matlab software environment by using Multi Layer Perception (MLP) structure.The ANN model had multilayer perception structure most programmed on there Matlab. The accuracy of surface approximation was tested by 1) comparison with result of other methods contained in Surfer program; 2) Interpolated known data on the surface.

  8. Comparison of approximative Markov and Monte Carlo simulation methods for reliability assessment of crack containing components

    International Nuclear Information System (INIS)

    Reliability assessments based on probabilistic fracture mechanics can give insight into the effects of changes in design parameters, operational conditions and maintenance schemes. Although they are often not capable of providing absolute reliability values, these methods at least allow the ranking of different solutions among alternatives. Due to the variety of possible solutions for design, operation and maintenance problems numerous probabilistic reliability assessments have to be carried out. This is a laborous task especially for crack containing welds of nuclear pipes subjected to fatigue. The objective of this paper is to compare the Monte Carlo simulation method and a newly developed approximative approach using the Markov process ansatz for this task

  9. A new method for extraction of approximately vertical lines from natural images

    Institute of Scientific and Technical Information of China (English)

    赵建坤; 吴江华; 张田文

    2002-01-01

    For natural images with complex background and noise, this new approach appears is more effective than other techniques for three key reasons: 1)edge elements treated interdependently to overcome the weakness of standard Hough transform (HT); 2)gradient orientation information taken into account in the process of HT; 3) an effective method used to "merge" the HT result, i.e. many "clustered short lines" into single straight line to represent the edge of object to be recognized. This method consists of three steps are: 1) edge detection; 2)modified Hough transform to extract "clustered short lines"; 3) merging "clustered short lines" into a single line after few modifications. The method presented in this paper could also be used for extraction of non-vertical straight lines.

  10. The approximate inversion as a reconstruction method in X-ray computerized tomography

    CERN Document Server

    Dietz, R L

    1999-01-01

    The mathematical model of the X-ray computerized tomography will be developed in the first chapter, the approximate inversion will be introduced, and the Radon Transform will be used as an example to demonstrate calculation of a reconstruction cone. In the second chapter, a reconstruction method for the parallel geometry is discussed, leading to derivation of the method for a fan-beam geometry. The approximate inversion calculated for the limited-angle case is presented as an example of incomplete data problems. As with complete data problems, numerical examples are given and the method is compared with existing other methods. 3D reconstruction is the topic of the third chapter. Although of no relevance in practice, a parallel geometry will be examined. No problems are encountered in transferring the reconstruction cone to the cone beam geometry, but only for a scanning curve which also is of no relevance in practice. A further reconstruction method is presented for curves fulfilling the so-called Tuy conditi...

  11. New identification method for Hammerstein models based on approximate least absolute deviation

    Science.gov (United States)

    Xu, Bao-Chang; Zhang, Ying-Dan

    2016-07-01

    Disorder and peak noises or large disturbances can deteriorate the identification effects of Hammerstein non-linear models when using the least-square (LS) method. The least absolute deviation technique can be used to resolve this problem; however, its absolute value cannot meet the need of differentiability required by most algorithms. To improve robustness and resolve the non-differentiable problem, an approximate least absolute deviation (ALAD) objective function is established by introducing a deterministic function that exhibits the characteristics of absolute value under certain situations. A new identification method for Hammerstein models based on ALAD is thus developed in this paper. The basic idea of this method is to apply the stochastic approximation theory in the process of deriving the recursive equations. After identifying the parameter matrix of the Hammerstein model via the new algorithm, the product terms in the matrix are separated by calculating the average values. Finally, algorithm convergence is proven by applying the ordinary differential equation method. The proposed algorithm has a better robustness as compared to other LS methods, particularly when abnormal points exist in the measured data. Furthermore, the proposed algorithm is easier to apply and converges faster. The simulation results demonstrate the efficacy of the proposed algorithm.

  12. Approximation by random weighting method for M-test in linear models

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The M-test has been in common use and widely studied in testing the linear hypotheses in linear models. However, the critical value for the test is usually related to the quantities of the unknown error distribution and the estimate of the nuisance parameters may be rather involved, not only for the M-test method but also for the existing bootstrap methods. In this paper we suggest a random weighting resampling method for approximating the null distribution of the M-test statistic. It is shown that, under both the null and the local alternatives, the random weighting statistic has the same asymptotic distribution as the null distribution of the M-test. The critical values of the M-test can therefore be obtained by the random weighting method without estimating the nuisance parameters. A distinguished feature of the proposed method is that the approximation is valid even the null hypothesis is not true and the power evaluation is possible under the local alternatives.

  13. S-curve networks and an approximate method for estimating degree distributions of complex networks

    International Nuclear Information System (INIS)

    In the study of complex networks almost all theoretical models have the property of infinite growth, but the size of actual networks is finite. According to statistics from the China Internet IPv4 (Internet Protocol version 4) addresses, this paper proposes a forecasting model by using S curve (logistic curve). The growing trend of IPv4 addresses in China is forecasted. There are some reference values for optimizing the distribution of IPv4 address resource and the development of IPv6. Based on the laws of IPv4 growth, that is, the bulk growth and the finitely growing limit, it proposes a finite network model with a bulk growth. The model is said to be an S-curve network. Analysis demonstrates that the analytic method based on uniform distributions (i.e., Barabási-Albert method) is not suitable for the network. It develops an approximate method to predict the growth dynamics of the individual nodes, and uses this to calculate analytically the degree distribution and the scaling exponents. The analytical result agrees with the simulation well, obeying an approximately power-law form. This method can overcome a shortcoming of Barabási-Albert method commonly used in current network research. (general)

  14. Approximation by random weighting method for M-test in linear models

    Institute of Scientific and Technical Information of China (English)

    Xiao-yan WU; Ya-ning YANG; Lin-cheng ZHAO

    2007-01-01

    The M-test has been in common use and widely studied in testing the linear hypotheses in linear models. However, the critical value for the test is usually related to the quantities of the unknown error distribution and the estimate of the nuisance parameters may be rather involved, not only for the M-test method but also for the existing bootstrap methods. In this paper we suggest a random weighting resampling method for approximating the null distribution of the M-test statistic.It is shown that, under both the null and the local alternatives, the random weighting statistic has the same asymptotic distribution as the null distribution of the M-test. The critical values of the M-test can therefore be obtained by the random weighting method without estimating the nuisance parameters. A distinguished feature of the proposed method is that the approximation is valid even the null hypothesis is not true and the power evaluation is possible under the local alternatives.

  15. A general approximate method for the groundwater response problem caused by water level variation

    Science.gov (United States)

    Jiang, Qinghui; Tang, Yuehao

    2015-10-01

    The Boussinesq equation (BEQ) can be used to describe groundwater flow through an unconfined aquifer. Based on 1D BEQ, we present a general approximate method to predict the water table response in a semi-infinite aquifer system with a vertical or sloping boundary. A decomposition method is adopted by separating the original problem into a linear diffusion equation (DE) and two correction functions. The linear DE satisfies all the initial and boundary conditions, reflecting the basic characteristics of groundwater movement. The correction functions quantitatively measure the errors due to the degeneration from the original BEQ to a linear DE. As the correction functions must be linearized to obtain analytical solution forms, the proposed method is an approximate approach. In the case studies, we apply this method to four different situations of water level variation (i.e., constant, sudden, linear and periodic change) resting on vertical or sloping boundaries. The results are compared against numerical results, field data and other analytical solutions, which demonstrate that the proposed method has a good accuracy and versatility over a wide range of applications.

  16. a Comparison of Methods for the Approximation and Analysis of Rainfall Fields in Environmental Applications

    Science.gov (United States)

    Patané, G.; Cerri, A.; Skytt, V.; Pittaluga, S.; Biasotti, S.; Sobrero, D.; Dokken, T.; Spagnuolo, M.

    2015-08-01

    Digital environmental data are becoming commonplace and the amount of information they provide is huge, yet complex to process, due to the size, variety, and dynamic nature of the data captured by the available sensing devices. Making use of the data largely relies on the availability of efficient methods to extract meaningful information, and requires to process the environmental events at the speed data are acquired. This paper focuses on the evaluation of methods to approximate observed rain data, in real conditions of sparsity of the observations. The novelty stands in the selection of a particularly complex area, Liguria region, located in the north-west of Italy, where the orography and the closeness to the sea causes complex hydro-meteorological events. Approximation results are compared on a fine granularity in terms of cumulated rain interval used, gathered from two different rain gauge networks, with different characteristics and spatial distribution. Moreover, beside traditional cross-validation comparison, we provide a qualitative comparison based on the analysis of the number and location of maxima of the approximation. Rain maxima are indeed crucial features of rain fields needed for storm tracking, to support effective monitoring of meteorological events.

  17. Complex-valued derivative propagation method with approximate Bohmian trajectories for quantum barrier scattering

    Energy Technology Data Exchange (ETDEWEB)

    Chou, Chia-Chun, E-mail: ccchou@mx.nthu.edu.tw

    2015-08-18

    Highlights: • The complex quantum Hamilton–Jacobi equation is approximately solved in real space. • Equations of motion are derived through use of the derivative propagation method. • Numerically unstable reflected trajectories may pass through the potential barrier. • Transmitted wave packet is obtained by propagating individual Bohmian trajectories. • Excellent transmission probabilities are obtained for both thick and thin barriers. - Abstract: The complex quantum Hamilton–Jacobi equation for the complex action is approximately solved by propagating individual Bohmian trajectories in real space. Equations of motion for the complex action and its spatial derivatives are derived through use of the derivative propagation method. We transform these equations into the arbitrary Lagrangian–Eulerian version with the grid velocity matching the flow velocity of the probability fluid. Setting higher-order derivatives equal to zero, we obtain a truncated system of equations of motion describing the rate of change in the complex action and its spatial derivatives transported along approximate Bohmian trajectories. A set of test trajectories is propagated to determine appropriate initial positions for transmitted trajectories. Computational results for transmitted wave packets and transmission probabilities are presented and analyzed for a one-dimensional Eckart barrier and a two-dimensional system involving either a thick or thin Eckart barrier along the reaction coordinate coupled to a harmonic oscillator.

  18. Complex-valued derivative propagation method with approximate Bohmian trajectories for quantum barrier scattering

    International Nuclear Information System (INIS)

    Highlights: • The complex quantum Hamilton–Jacobi equation is approximately solved in real space. • Equations of motion are derived through use of the derivative propagation method. • Numerically unstable reflected trajectories may pass through the potential barrier. • Transmitted wave packet is obtained by propagating individual Bohmian trajectories. • Excellent transmission probabilities are obtained for both thick and thin barriers. - Abstract: The complex quantum Hamilton–Jacobi equation for the complex action is approximately solved by propagating individual Bohmian trajectories in real space. Equations of motion for the complex action and its spatial derivatives are derived through use of the derivative propagation method. We transform these equations into the arbitrary Lagrangian–Eulerian version with the grid velocity matching the flow velocity of the probability fluid. Setting higher-order derivatives equal to zero, we obtain a truncated system of equations of motion describing the rate of change in the complex action and its spatial derivatives transported along approximate Bohmian trajectories. A set of test trajectories is propagated to determine appropriate initial positions for transmitted trajectories. Computational results for transmitted wave packets and transmission probabilities are presented and analyzed for a one-dimensional Eckart barrier and a two-dimensional system involving either a thick or thin Eckart barrier along the reaction coordinate coupled to a harmonic oscillator

  19. Studying approximating method and numerical computation of heat transfer of a fuel rod in PWR

    International Nuclear Information System (INIS)

    Based on the differential form of the general heat conduction equation, the approximating expression for a nu clear fuel rod was derived through integral. The fuel rod has asymmetrical heat resource distribution. Bessel function distribution is in radial direction and Cosine function distribution is in axis direction. Also, using the model of the advanced pressure water reactor 600, and taking an iterative calculation between tangential and normal diffusion terms in every control cell, temperature distribution of the fuel rod was computed by the finite volume method (FVM) in the unstructured grids. Comparing the approximate solutions with the numerical results, there was a good agreement between them. On this condition, we derived the location and size of maximum temperature by analysis the temperature distribution and variation. All of these can provide a useful reference for the pressure water reactor thermal design and thermal protection of nuclear engineering. (authors)

  20. Optimal motion planning of an underactuated spacecraft using wavelet approximate method

    Institute of Scientific and Technical Information of China (English)

    GE Xinsheng; CHEN Liqun; LIU Yanzhu

    2006-01-01

    An optimal motion planning scheme using wavelet approximation is proposed for an underactuated spacecraft. The motion planning of an underactuated spacecraft can be formulated as an optimal control of a drift-free system. A cost functional is used to incorporate the control energy and the final state errors. The motion planning is to determine control inputs to minimize the cost functional.Using the method of wavelet, one can transform an infinite-dimensional optimal control problem to a finite-dimensional one and use GaussNewton algorithm to solve it for a feasible trajectory which satisfies nonholonomic constraints. The proposed scheme has been applied to a rigid spacecraft with two momentum wheels. The numerical simulation results indicate that optimal control with wavelet approximation is an effective approach to steering an underactuated spacecraft system from the initial configuration to the final configuration.

  1. Potential function methods for approximately solving linear programming problems theory and practice

    CERN Document Server

    Bienstock, Daniel

    2002-01-01

    Potential Function Methods For Approximately Solving Linear Programming Problems breaks new ground in linear programming theory. The book draws on the research developments in three broad areas: linear and integer programming, numerical analysis, and the computational architectures which enable speedy, high-level algorithm design. During the last ten years, a new body of research within the field of optimization research has emerged, which seeks to develop good approximation algorithms for classes of linear programming problems. This work both has roots in fundamental areas of mathematical programming and is also framed in the context of the modern theory of algorithms. The result of this work, in which Daniel Bienstock has been very much involved, has been a family of algorithms with solid theoretical foundations and with growing experimental success. This book will examine these algorithms, starting with some of the very earliest examples, and through the latest theoretical and computational developments.

  2. Elastic wave scattering calculations, the Born series, and the matrix-variational Pade approximant method

    International Nuclear Information System (INIS)

    The matrix variational Pade approximant and its generalization to elastic wave scattering are discussed. Predictions of the method for the scattering of a longitudinal plane wave are compared with the exact scattering from spherical voids and inclusions. Its predictions are also compared to those of the first four partial sums of the Born Series for the scattered amplitude. Generally, the fourth partial sum and the variational results compare poorly with the exact results for ka less than or equal to 2 if the scatterer is strong, but compare well for ka less than or equal to 10 if the scatterer strength is at best modest. The breakdown of the favorable comparison is traced to the divergence of the Born Series for strong scatterers. It is also demonstrated that by use of the N-point Pade approximant a good comparison with exact results can be obtained for all scatterer strengths

  3. The Wentzel-Kramers-Brillouin approximation method applied to the Wigner function

    Science.gov (United States)

    Tosiek, J.; Cordero, R.; Turrubiates, F. J.

    2016-06-01

    An adaptation of the Wentzel-Kramers-Brilluoin method in the deformation quantization formalism is presented with the aim to obtain an approximate technique of solving the eigenvalue problem for energy in the phase space quantum approach. A relationship between the phase σ ( r →) of a wave function exp (" separators=" /i ħ σ ( r →)) and its respective Wigner function is derived. Formulas to calculate the Wigner function of a product and of a superposition of wave functions are proposed. Properties of a Wigner function of interfering states are also investigated. Examples of this quasi-classical approximation in deformation quantization are analysed. A strict form of the Wigner function for states represented by tempered generalised functions has been derived. Wigner functions of unbound states in the Poeschl-Teller potential have been found.

  4. On the Consistency of Approximate Quantum Dynamics Simulation Methods for Vibrational Spectra in the Condensed Phase

    CERN Document Server

    Rossi, Mariana; Paesani, Francesco; Bowman, Joel; Ceriotti, Michele

    2014-01-01

    Including quantum mechanical effects on the dynamics of nuclei in the condensed phase is challenging, because the complexity of exact methods grows exponentially with the number of quantum degrees of freedom. Efforts to circumvent these limitations can be traced down to two approaches: methods that treat a small subset of the degrees of freedom with rigorous quantum mechanics, considering the rest of the system as a static or classical environment, and methods that treat the whole system quantum mechanically, but using approximate dynamics. Here we perform a systematic comparison between these two philosophies for the description of quantum effects in vibrational spectroscopy, taking the Embedded Local Monomer (LMon) model and a mixed quantum-classical (MQC) model as representatives of the first family of methods, and centroid molecular dynamics (CMD) and thermostatted ring polymer molecular dynamics (TRPMD) as examples of the latter. We use as benchmarks D$_2$O doped with HOD and pure H$_2$O at three distinc...

  5. A novel approximation method of CTF amplitude correction for 3D single particle reconstruction

    International Nuclear Information System (INIS)

    The typical resolution of three-dimensional reconstruction by cryo-EM single particle analysis is now being pushed up to and beyond the nanometer scale. Correction of the contrast transfer function (CTF) of electron microscopic images is essential for achieving such a high resolution. Various correction methods exist and are employed in popular reconstruction software packages. Here, we present a novel approximation method that corrects the amplitude modulation introduced by the contrast transfer function by convoluting the images with a piecewise continuous function. Our new approach can easily be implemented and incorporated into other packages. The implemented method yielded higher resolution reconstructions with data sets from both highly symmetric and asymmetric structures. It is an efficient alternative correction method that allows quick convergence of the 3D reconstruction and has a high tolerance for noisy images, thus easing a bottleneck in practical reconstruction of macromolecules.

  6. Domain decomposition methods for systems of conservation laws: Spectral collocation approximations

    Science.gov (United States)

    Quarteroni, Alfio

    1989-01-01

    Hyperbolic systems of conversation laws are considered which are discretized in space by spectral collocation methods and advanced in time by finite difference schemes. At any time-level a domain deposition method based on an iteration by subdomain procedure was introduced yielding at each step a sequence of independent subproblems (one for each subdomain) that can be solved simultaneously. The method is set for a general nonlinear problem in several space variables. The convergence analysis, however, is carried out only for a linear one-dimensional system with continuous solutions. A precise form of the error reduction factor at each iteration is derived. Although the method is applied here to the case of spectral collocation approximation only, the idea is fairly general and can be used in a different context as well. For instance, its application to space discretization by finite differences is straight forward.

  7. Approximate method for stochastic chemical kinetics with two-time scales by chemical Langevin equations.

    Science.gov (United States)

    Wu, Fuke; Tian, Tianhai; Rawlings, James B; Yin, George

    2016-05-01

    The frequently used reduction technique is based on the chemical master equation for stochastic chemical kinetics with two-time scales, which yields the modified stochastic simulation algorithm (SSA). For the chemical reaction processes involving a large number of molecular species and reactions, the collection of slow reactions may still include a large number of molecular species and reactions. Consequently, the SSA is still computationally expensive. Because the chemical Langevin equations (CLEs) can effectively work for a large number of molecular species and reactions, this paper develops a reduction method based on the CLE by the stochastic averaging principle developed in the work of Khasminskii and Yin [SIAM J. Appl. Math. 56, 1766-1793 (1996); ibid. 56, 1794-1819 (1996)] to average out the fast-reacting variables. This reduction method leads to a limit averaging system, which is an approximation of the slow reactions. Because in the stochastic chemical kinetics, the CLE is seen as the approximation of the SSA, the limit averaging system can be treated as the approximation of the slow reactions. As an application, we examine the reduction of computation complexity for the gene regulatory networks with two-time scales driven by intrinsic noise. For linear and nonlinear protein production functions, the simulations show that the sample average (expectation) of the limit averaging system is close to that of the slow-reaction process based on the SSA. It demonstrates that the limit averaging system is an efficient approximation of the slow-reaction process in the sense of the weak convergence. PMID:27155630

  8. A Comparison between Effective Cross Section Calculations using the Intermediate Resonance Approximation and More Exact Methods

    International Nuclear Information System (INIS)

    In order to investigate some aspects of the 'Intermediate Resonance Approximation' developed by Goldstein and Cohen, comparative calculations have been made using this method together with more accurate methods. The latter are as follows: a) For homogeneous materials the slowing down equation is solved in the fundamental mode approximation with the computer programme SPENG. All cross sections are given point by point. Because the spectrum can be calculated for at most 2000 energy points, the energy regions where the resonances are accurately described are limited. Isolated resonances in the region 100 to 240 eV are studied for 238U/Fe and 238U/Fe/Na mixtures. In the regions 161 to 251 eV and 701 to 1000 eV, mixtures of 238U and Na are investigated. 239Pu/Na and 239Pu/238U/Na mixtures are studied in the region 161 to 251 eV. b) For heterogeneous compositions in slab geometry the integral transport equation is solved using the FLIS programme in 22 energy groups. Thus, only one resonance can be considered in each calculation. Two resonances are considered, namely those belonging to 238U at 190 and 937 eV. The compositions are lattices of 238U and Fe plates. The computer programme DORIX is used for the calculations using the Intermediate Resonance Approximation. Calculations of reaction rates and effective cross sections are made at 0, 300 and 1100 deg K for homogeneous media and at 300 deg K for heterogeneous media. The results are compared to those obtained by using the programmes SPENG and FLIS and using the narrow resonance approximation

  9. Approximate-model Based Estimation Method for Dynamic Response of Forging Processes

    Institute of Scientific and Technical Information of China (English)

    LEI Jie; LU Xinjiang; LI Yibo; HUANG Minghui; ZOU Wei

    2015-01-01

    Many high-quality forging productions require the large-sized hydraulic press machine (HPM) to have a desirable dynamic response. Since the forging process is complex under the low velocity, its response is difficult to estimate. And this often causes the desirable low-velocity forging condition difficult to obtaln. So far little work has been found to estimate the dynamic response of the forging process under low velocity. In this paper, an approximate-model based estimation method is proposed to estimate the dynamic response of the forging process under low velocity. First, an approximate model is developed to represent the forging process of this complex HPM around the low-velocity working point. Under guaranteeing the modeling performance, the model may greatly ease the complexity of the subsequent estimation of the dynamic response because it has a good linear structure. On this basis, the dynamic response is estimated and the conditions for stability, vibration, and creep are derived according to the solution of the velocity. All these analytical results are further verified by both simulations and experiment. In the simulation verification for modeling, the original movement model and the derived approximate model always have the same dynamic responses with very small approximate error. The simulations and experiment finally demonstrate and test the effectiveness of the derived conditions for stability, vibration, and creep, and these conditions will benefit both the prediction of the dynamic response of the forging process and the design of the controller for the high-quality forging. The proposed method is an effective solution to achieve the desirable low-velocity forging condition.

  10. Influence of Three Different Methods of Teaching Physics on the Gain in Students' Development of Reasoning

    Science.gov (United States)

    Marušić, Mirko; Sliško, Josip

    2012-01-01

    The Lawson Classroom Test of Scientific Reasoning (LCTSR) was used to gauge the relative effectiveness of three different methods of pedagogy, Reading, Presenting, and Questioning (RPQ), Experimenting and Discussion (ED), and Traditional Methods (TM), on increasing students' level of scientific thinking. The data of a one-semester-long senior high-school project indicate that, for the LCTSR: (a) the RPQ group (n = 91) achieved effect-sizes d = 0.30 and (b) the ED group (n  =  85) attained effect-sizes d = 0.64. These methods have shown that the Piagetian and Vygotskian visions on learning and teaching can go hand in hand and as such achieve respectable results. To do so, it is important to challenge the students and thus encourage the shift towards higher levels of reasoning. This aim is facilitated through class management which recognizes the importance of collaborative learning. Carrying out Vygotsky's original intention to use teaching to promote cognitive development as well as subject concepts, this research has shown that it is better to have students experience cognitive conflict from directly observed experiments than by reflecting on reported experience from popularization papers or writings found on the internet.

  11. Reasons of bleeding complications and prevention methods in endovascular stenting for intracranial artery stenosis

    International Nuclear Information System (INIS)

    Objective: To summarize the reasons of bleeding complications and the prevention methods in stenting for intracranial arterial stenosis. Methods: The clinical data of 366 patients underwent stent-assistant angioplasty of intracranial artery stenosis from July 2006 to December 2011 were analyzed retrospectively. Among them, 14 patients with bleeding complications were found. The initial 100 patients were categorized as early stage group and the rest as mature stage group. The reasons of bleeding and the methods for preventing this complication were summarized. Results: The overall incidence of bleeding complication was 3.8% (14/366). In the early stage group and mature stage group,the rates was 10%(10/100) and 1.5% (4/266). Six cases were related to the operational manipulation and 8 cases secondary to hyperperfusion injury. Death was found in 6 patients,severe disability in 3, mild paralysis in 2, and no neurological deficits in 3. Conclusions: The bleeding complications in stent-assisted angioplasty of intracranial artery stenosis have a high disability and mortality. The improvement of operative techniques and the more strict indications decrease the bleeding complications rate effectively. (authors)

  12. Linguistic hesitant fuzzy multi-criteria decision-making method based on evidential reasoning

    Science.gov (United States)

    Zhou, Huan; Wang, Jian-qiang; Zhang, Hong-yu; Chen, Xiao-hong

    2016-01-01

    Linguistic hesitant fuzzy sets (LHFSs), which can be used to represent decision-makers' qualitative preferences as well as reflect their hesitancy and inconsistency, have attracted a great deal of attention due to their flexibility and efficiency. This paper focuses on a multi-criteria decision-making approach that combines LHFSs with the evidential reasoning (ER) method. After reviewing existing studies of LHFSs, a new order relationship and Hamming distance between LHFSs are introduced and some linguistic scale functions are applied. Then, the ER algorithm is used to aggregate the distributed assessment of each alternative. Subsequently, the set of aggregated alternatives on criteria are further aggregated to get the overall value of each alternative. Furthermore, a nonlinear programming model is developed and genetic algorithms are used to obtain the optimal weights of the criteria. Finally, two illustrative examples are provided to show the feasibility and usability of the method, and comparison analysis with the existing method is made.

  13. Accurate gradient approximation for complex interface problems in 3D by an improved coupling interface method

    International Nuclear Information System (INIS)

    Most elliptic interface solvers become complicated for complex interface problems at those “exceptional points” where there are not enough neighboring interior points for high order interpolation. Such complication increases especially in three dimensions. Usually, the solvers are thus reduced to low order accuracy. In this paper, we classify these exceptional points and propose two recipes to maintain order of accuracy there, aiming at improving the previous coupling interface method [26]. Yet the idea is also applicable to other interface solvers. The main idea is to have at least first order approximations for second order derivatives at those exceptional points. Recipe 1 is to use the finite difference approximation for the second order derivatives at a nearby interior grid point, whenever this is possible. Recipe 2 is to flip domain signatures and introduce a ghost state so that a second-order method can be applied. This ghost state is a smooth extension of the solution at the exceptional point from the other side of the interface. The original state is recovered by a post-processing using nearby states and jump conditions. The choice of recipes is determined by a classification scheme of the exceptional points. The method renders the solution and its gradient uniformly second-order accurate in the entire computed domain. Numerical examples are provided to illustrate the second order accuracy of the presently proposed method in approximating the gradients of the original states for some complex interfaces which we had tested previous in two and three dimensions, and a real molecule ( (1D63)) which is double-helix shape and composed of hundreds of atoms

  14. Semantic Ontology Method of Learning Resource based on the Approximate Subgraph Isomorphism

    Directory of Open Access Journals (Sweden)

    Lili Zhang

    2014-02-01

    Full Text Available Digital learning resource ontology is often based on different specification building. It is hard to find resources by linguistic ontology matching method. The existing structural matching method fails to solve the problem of calculation of structural similarity well. For the heterogeneity problem among learning resource ontology, an algorithm is presented based on subgraph approximate isomorphism. First of all, we can preprocess the resource of clustering algorithm through the semantic analysis, then describe the ontology by the directed graph and calculate the similarity, and finally judge the semantic relations through calculating and analyzing different resource between the ontology of different learning resource to achieve semantic compatibility or mapping of ontology. This method is an extension of existing methods in ontology matching. Under the comprehensive application of features such as edit distance and hierarchical relations, the similarity of graph structures between two ontologies is calculated. And, the ontology matching is determined on the condition of subgraph approximate isomorphism based on the alternately mapping of nodes and arcs in the describing graphs of ontologies. An example is used to demonstrate this ontology matching process and the time complexity is analyzed to explain its effectiveness

  15. 26 CFR 1.412(c)(2)-1 - Valuation of plan assets; reasonable actuarial valuation methods.

    Science.gov (United States)

    2010-04-01

    ... 26 Internal Revenue 5 2010-04-01 2010-04-01 false Valuation of plan assets; reasonable actuarial valuation methods. 1.412(c)(2)-1 Section 1.412(c)(2)-1 Internal Revenue INTERNAL REVENUE SERVICE, DEPARTMENT... Plans, Etc. § 1.412(c)(2)-1 Valuation of plan assets; reasonable actuarial valuation methods....

  16. Bayesian network modeling method based on case reasoning for emergency decision-making

    Directory of Open Access Journals (Sweden)

    XU Lei

    2013-06-01

    Full Text Available Bayesian network has the abilities of probability expression, uncertainty management and multi-information fusion.It can support emergency decision-making, which can improve the efficiency of decision-making.Emergency decision-making is highly time sensitive, which requires shortening the Bayesian Network modeling time as far as possible.Traditional Bayesian network modeling methods are clearly unable to meet that requirement.Thus, a Bayesian network modeling method based on case reasoning for emergency decision-making is proposed.The method can obtain optional cases through case matching by the functions of similarity degree and deviation degree.Then,new Bayesian network can be built through case adjustment by case merging and pruning.An example is presented to illustrate and test the proposed method.The result shows that the method does not have a huge search space or need sample data.The only requirement is the collection of expert knowledge and historical case models.Compared with traditional methods, the proposed method can reuse historical case models, which can reduce the modeling time and improve the efficiency.

  17. Approximate restoration of translational and rotational symmetries within the Lipkin method

    CERN Document Server

    Gao, Y; Toivanen, P

    2015-01-01

    Background: Nuclear self-consistent mean-field approaches are rooted in the density functional theory and, through the spontaneous symmetry breaking mechanism, allow for including important correlations, while keeping the simplicity of the approach. Because real ground states should have all symmetries of the nuclear Hamiltonian, these methods require subsequent symmetry restoration. Purpose: We implement and study Lipkin method of approximate variation after projection applied to the restoration of the translational or rotational symmetries. Methods: We use Lipkin operators up to quadratic terms in momenta or angular momenta with self-consistently determined values of the Peierls-Yoccoz translational masses or moments of inertia, respectively. Calculations based on Skyrme energy-density functional are performed for heavy, deformed, and paired nuclei. Results: In deformed nuclei, the Peierls-Yoccoz translational masses along three different principal-axes directions of the intrinsic system can be different, w...

  18. The Second-Order Polarization Propagator Approximation (SOPPA) method coupled to the polarizable continuum model

    DEFF Research Database (Denmark)

    Eriksen, Janus Juul; Solanko, Lukasz Michal; Nåbo, Lina J.;

    2014-01-01

    We present an implementation of the Polarizable Continuum Model (PCM) in combination with the Second–Order Polarization Propagator Approximation (SOPPA) electronic structure method. In analogy with the most common way of designing ground state calculations based on a Second–Order Møller-Plesset (MP...... functional theory employing a range-separated exchange-correlation functional, we find the PCM-SOPPA/RPA approach to be slightly superior with respect to systematicity. On the other hand, the absolute values of the predicted excitation energies are largely underestimated. This – however – is a well...

  19. Markovian Approximation for the Nos\\'e--Hoover method and H-theorem

    OpenAIRE

    Watanabe, Hiroshi

    2008-01-01

    A Langevin equation with state-dependent random force is considered. When the Helmholtz free energy is a nonincreasing function of time (the H-theorem), a generalized Einstein relation is obtained. A stochastic process of the Nos\\'e--Hoover method is discussed on the basis of the Markovian approximation. It is found that the generalized Einstein relation holds for the Fokker--Planck equation associated with the stochastic Nos\\'e--Hoover equation. The present result indicates that the Nos\\'e--...

  20. A Modified Fast Approximated Power Iteration Subspace Tracking Method for Space-Time Adaptive Processing

    Directory of Open Access Journals (Sweden)

    Yang Zhiwei

    2010-01-01

    Full Text Available We propose a subspace-tracking-based space-time adaptive processing technique for airborne radar applications. By applying a modified approximated power iteration subspace tracing algorithm, the principal subspace in which the clutter-plus-interference reside is estimated. Therefore, the moving targets are detected by projecting the data on the minor subspace which is orthogonal to the principal subspace. The proposed approach overcomes the shortcomings of the existing methods and has satisfactory performance. Simulation results confirm that the performance improvement is achieved at very small secondary sample support, a feature that is particularly attractive for applications in heterogeneous environments.

  1. Quasi-Isotropic Approximation of Geometrical Optics Method as Adequate Electrodynamical Basis for Tokamak Plasma Polarimetry

    Science.gov (United States)

    Bieg, Bohdan; Chrzanowski, Janusz; Kravtsov, Yury A.; Orsitto, Francesco

    Basic principles and recent findings of quasi-isotropic approximation (QIA) of a geometrical optics method are presented in a compact manner. QIA was developed in 1969 to describe electromagnetic waves in weakly anisotropic media. QIA represents the wave field as a power series in two small parameters, one of which is a traditional geometrical optics parameter, equal to wavelength ratio to plasma characteristic scale, and the other one is the largest component of anisotropy tensor. As a result, "" QIA ideally suits to tokamak polarimetry/interferometry systems in submillimeter range, where plasma manifests properties of weakly anisotropic medium.

  2. A Method for Generating Approximate Similarity Solutions of Nonlinear Partial Differential Equations

    Directory of Open Access Journals (Sweden)

    Mazhar Iqbal

    2014-01-01

    Full Text Available Standard application of similarity method to find solutions of PDEs mostly results in reduction to ODEs which are not easily integrable in terms of elementary or tabulated functions. Such situations usually demand solving reduced ODEs numerically. However, there are no systematic procedures available to utilize these numerical solutions of reduced ODE to obtain the solution of original PDE. A practical and tractable approach is proposed to deal with such situations and is applied to obtain approximate similarity solutions to different cases of an initial-boundary value problem of unsteady gas flow through a semi-infinite porous medium.

  3. Non-approximate method for designing annular field of two-mirror concentric system

    Institute of Scientific and Technical Information of China (English)

    Yuanshen Huang; Dongyue Zhu; Baicheng Li; Dawei Zhang; Zhengji Ni; Songlin Zhuang

    2012-01-01

    Annular field aberrations of a three-reflection concentric system, which are composed of two spherical mirrors, are analyzed. An annular field with a high level of aberration correction exists near the position where the principal ray is perpendicular to the object-image plane. Aberrations are determined by the object height and aperture angle. In this letter, the general expression of the system aberration is derived using the geometric method, and the non-approximate design method is proposed to calculate the radii of the annular fields that have minimum aberrations under different aperture angles. The closer to 0.5 (the ratio of the radius of convex mirror to the radius of concave mirror) is, the smaller the system aberration is. The examples analyzed by LABVIEW indicate that the annular field designed by the proposed method has the smallest aberration in a given system.%Annular field aberrations of a three-reflection concentric system,which are composed of two spherical mirrors,are analyzed.An annular field with a high level of aberration correction exists near the position where the principal ray is perpendicular to the object-image plane.Aberrations are determined by the object height and aperture angle.In this letter,the general expression of the system aberration is derived using the geometric method,and the non-approximate design method is proposed to calculate the radii of the annular fields that have minimum aberrations under different aperture angles.The closer to 0.5 (the ratio of the radius of convex mirror to the radius of concave mirror) is,the smaller the system aberration is.The examples analyzed by LABVIEW indicate that the annular field designed by the proposed method has the smallest aberration in a given system.

  4. Fine Mapping Causal Variants with an Approximate Bayesian Method Using Marginal Test Statistics.

    Science.gov (United States)

    Chen, Wenan; Larrabee, Beth R; Ovsyannikova, Inna G; Kennedy, Richard B; Haralambieva, Iana H; Poland, Gregory A; Schaid, Daniel J

    2015-07-01

    Two recently developed fine-mapping methods, CAVIAR and PAINTOR, demonstrate better performance over other fine-mapping methods. They also have the advantage of using only the marginal test statistics and the correlation among SNPs. Both methods leverage the fact that the marginal test statistics asymptotically follow a multivariate normal distribution and are likelihood based. However, their relationship with Bayesian fine mapping, such as BIMBAM, is not clear. In this study, we first show that CAVIAR and BIMBAM are actually approximately equivalent to each other. This leads to a fine-mapping method using marginal test statistics in the Bayesian framework, which we call CAVIAR Bayes factor (CAVIARBF). Another advantage of the Bayesian framework is that it can answer both association and fine-mapping questions. We also used simulations to compare CAVIARBF with other methods under different numbers of causal variants. The results showed that both CAVIARBF and BIMBAM have better performance than PAINTOR and other methods. Compared to BIMBAM, CAVIARBF has the advantage of using only marginal test statistics and takes about one-quarter to one-fifth of the running time. We applied different methods on two independent cohorts of the same phenotype. Results showed that CAVIARBF, BIMBAM, and PAINTOR selected the same top 3 SNPs; however, CAVIARBF and BIMBAM had better consistency in selecting the top 10 ranked SNPs between the two cohorts. Software is available at https://bitbucket.org/Wenan/caviarbf. PMID:25948564

  5. An analytical approximation method for the stabilizing solution of the Hamilton-Jacobi equation based on stable manifold theory

    NARCIS (Netherlands)

    Sakamoto, Noboru; Schaft, Arjan J. van der

    2007-01-01

    In this paper, an analytical approximation approach for the stabilizing solution of the Hamilton-Jacobi equation using stable manifold theory is proposed. The proposed method gives approximated flows on the stable manifold of the associated Hamiltonian system and provides approximations of the stabl

  6. Approximate method for solving the velocity dependent transport equation in a slab lattice

    International Nuclear Information System (INIS)

    A method is described that is intended to provide an approximate solution of the transport equation in a medium simulating a water-moderated plate filled reactor core. This medium is constituted by a periodic array of water channels and absorbing plates. The velocity dependent transport equation in slab geometry is included. The computation is performed in a water channel: the absorbing plates are accounted for by the boundary conditions. The scattering of neutrons in water is assumed isotropic, which allows the use of a double Pn approximation to deal with the angular dependence. This method is able to represent the discontinuity of the angular distribution at the channel boundary. The set of equations thus obtained is dependent only on x and v and the coefficients are independent on x. This solution suggests to try solutions involving Legendre polynomials. This scheme leads to a set of equations v dependent only. To obtain an explicit solution, a thermalization model must now be chosen. Using the secondary model of Cadilhac a solution of this set is easy to get. The numerical computations were performed with a particular secondary model, the well-known model of Wigner and Wilkins. (author)

  7. On the optimal polynomial approximation of stochastic PDEs by galerkin and collocation methods

    KAUST Repository

    Beck, Joakim

    2012-09-01

    In this work we focus on the numerical approximation of the solution u of a linear elliptic PDE with stochastic coefficients. The problem is rewritten as a parametric PDE and the functional dependence of the solution on the parameters is approximated by multivariate polynomials. We first consider the stochastic Galerkin method, and rely on sharp estimates for the decay of the Fourier coefficients of the spectral expansion of u on an orthogonal polynomial basis to build a sequence of polynomial subspaces that features better convergence properties, in terms of error versus number of degrees of freedom, than standard choices such as Total Degree or Tensor Product subspaces. We consider then the Stochastic Collocation method, and use the previous estimates to introduce a new class of Sparse Grids, based on the idea of selecting a priori the most profitable hierarchical surpluses, that, again, features better convergence properties compared to standard Smolyak or tensor product grids. Numerical results show the effectiveness of the newly introduced polynomial spaces and sparse grids. © 2012 World Scientific Publishing Company.

  8. LORENTZ TIME-SPACE TRANSFORMATION IS A APPROXIMATE CALCULATION METHOD IN AERODYNAMICS FOR COMPRESSIBILITY

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Between the transformations, witch can transform the compressible wave equation to the incompressible flow, a kind of relativity character can be found, which have the almost equal character as Lorenz time and space relation. This result leads to a new inference: incompressible wave equation with time and space structure of sonic special relativity is only different description of approximate compressible flow. This conclusion can be extended to Euler equation, and arise the interest of "compressible expression" of Maxwell equation. To study the rule of compressibility and thermodynamic character of metastructure field, a try is made by the using KamanTsian virtual gas method, this would give the relation,similar as mass and energy of special relativity theory.At first searching a transformation, witch can transform the compressible wave equation to the incompressible flow, but it is almost equal Lorenz time and space relation, So arrive to the conclusion: incompressible wave equation with approximate Lorentz transformation is only different description of compressible flow. This conclusion is expected be used to Maxwell equation, because its wave equation is also perfectly equal form. To search the rule of electromagnet and gravity field, by the using of Kaman-Tsian virtual gas method, the relation of mass and energy of relativity theory is given.``

  9. Approximation-Exact Penalty Function Method for Solving a Class of Stochastic Programming

    Institute of Scientific and Technical Information of China (English)

    WangGuang-min; WanZhong-ping

    2003-01-01

    We present an approximation-exact penalty function method for solving the single stage stochastic programming problem with continuous random variable. The original problem is transformed into a determinate nonlinear programming problem with a discrete random variable sequence, which is obtained by some discrete method. We construct an exact penalty function and obtain an unconstrained optimization. It avoids the difficulty in solution by the rapid growing of the number of constraints for discrete precision.Under lenient conditions, we prove the equivalence of the minimum solution of penalty function and the solution of the determinate programming, and prove that the solution sequences of the discrete problem converge to a solution to the original problem.

  10. Approximate Reasoning Based onΓ-deduction Truth Degree in L* Logic System%逻辑系统L*中基于Г-演绎真度的近似推理

    Institute of Scientific and Technical Information of China (English)

    郝国平; 惠小静; 赵玛瑙

    2015-01-01

    This paper introduces theΓ-deduction truth degree of formulas in L* logic system at first. Based onΓ-deduction truth degree, this paper definesΓ-deduction similarity degree and pseudo distance, and discusses some basic properties. Then this paper defines three different types of approximate reasoning models in L* logical system, and conducts a detailed analysis on the relationship between three different types of approximate reasoning models ofΓ-deduction truth degree. Finally, three types of approximate reasoning models are equivalent. The research in this paper lays a good foundation for further research on the divergence and compatibility ofΓ-deduction truth degree and approximate reasoning.%在逻辑系统L*中引入了公式Γ-演绎真度的概念,在Γ-演绎真度的基础上,定义了Γ-演绎相似度与伪距离,并讨论了它的一些基本性质。接着在逻辑系统L*中定义了3种不同类型的近似推理模式,对Γ-演绎真度的3种不同类型的近似推理模式之间的关系进行了详细的研究,结果表明这3种不同类型近似推理模式是等价的。通过对这些理论的研究,为进一步研究基于Γ-演绎真度的发散度、相容度和近似推理奠定了良好的基础。

  11. The spectral element method for static neutron transport in AN approximation. Part I

    International Nuclear Information System (INIS)

    Highlights: ► Spectral elements methods (SEMs) are extended for the neutronics of nuclear reactor cores. ► The second-order, AN formulation of neutron trasport is adopted. ► Results for classical benchmark cases in 2D are presented and compared to finite elements. ► The advantages of SEM in terms of precision and convergence rate are illustrated. ► SEM consitutes a promising approach for the solution of neutron transport problems. - Abstract: Spectral elements methods provide very accurate solutions of elliptic problems. In this paper we apply the method to the AN (i.e. SP2N−1) approximation of neutron transport. Numerical results for classical benchmark cases highlight its performance in comparison with finite element computations, in terms of accuracy per degree of freedom and convergence rate. All calculations presented in this paper refer to two-dimensional problems. The method can easily be extended to three-dimensional cases. The results illustrate promising features of the method for more complex transport problems

  12. Approximate Methods for Analyzing and Controlling Axisymmetric Instabilities of Elongated Tokamak Plasmas.

    Science.gov (United States)

    Frantz, Eric Randall

    Elongation and shaping of the tokamak plasma cross -section can allow increased beta and other favorable improvements. As the cross-section is made non-circular, however, the plasma can become unstable against axisymmetric motions, the most predominant one being a nearly uniform displacement in the direction of elongation. Without additional stabilizing mechanisms, this instability has growth rates typically (TURN)10('6)sec('-1). With passive and active feedback from external conductors, the plasma can be significantly slowed down and controlled. In this work, a mathematical formulism for analyzing the vertical instability is developed in which the external conductors are treated (or broken -up) as discrete coils. The circuit equations for the plasma induced currents can be included within the same mathematical framework. The plasma equation of motion and the circuit equations are combined and manipulated into a diagonalized form that can be graphically analyzed to determine the growth rate. An effective mode approximation (EMA) to the dispersion relation in introduced to simplify and approximate the growth rate of the more exact case. Controller voltage equations for active feedback are generalized to include position and velocity feedback and time delay. A position cut-off displacement is added to model finite spatial resolution of the position detectors or a dead-band voltage level. Stability criteria are studied for EMA and the more exact case. The time dependent responses for plasma position controller voltages, and currents are determined from the Laplace transformations. Slow responses are separated from the fast ones (dependent on plasma inertia) using a typical tokamak ordering approximation. The methods developed are applied in numerous examples for the machine geometry and plasma of TNS, an inside-D configuration plasma resembling JET, INTOR, or FED.

  13. Are Better Feature Selection Methods Actually Better? Discussion, Reasoning and Examples

    Czech Academy of Sciences Publication Activity Database

    Somol, Petr; Novovičová, Jana; Pudil, Pavel

    Madeira: INSTICC Press, 2008, s. 246-253. ISBN 978-989-8111-16-6. [ International Conference on Health Informatics. Funchal Madeira (PT), 28.01.2008-31.01.2008] R&D Projects: GA ČR GA102/07/1594; GA MŠk 1M0572; GA AV ČR IAA2075302 EU Projects: European Commission(XE) 507752 - MUSCLE Grant ostatní: GA MŠk(CZ) 2C06019 Institutional research plan: CEZ:AV0Z10750506 Keywords : feature selection * subset search * performance estimation * classification accuracy Subject RIV: IN - Informatics, Computer Science http://library.utia.cas.cz/separaty/2008/RO/somol-are better feature selection methods actually better discussion, reasoning and examples.pdf

  14. Mixed multiscale finite element methods using approximate global information based on partial upscaling

    KAUST Repository

    Jiang, Lijian

    2009-10-02

    The use of limited global information in multiscale simulations is needed when there is no scale separation. Previous approaches entail fine-scale simulations in the computation of the global information. The computation of the global information is expensive. In this paper, we propose the use of approximate global information based on partial upscaling. A requirement for partial homogenization is to capture long-range (non-local) effects present in the fine-scale solution, while homogenizing some of the smallest scales. The local information at these smallest scales is captured in the computation of basis functions. Thus, the proposed approach allows us to avoid the computations at the scales that can be homogenized. This results in coarser problems for the computation of global fields. We analyze the convergence of the proposed method. Mathematical formalism is introduced, which allows estimating the errors due to small scales that are homogenized. The proposed method is applied to simulate two-phase flows in heterogeneous porous media. Numerical results are presented for various permeability fields, including those generated using two-point correlation functions and channelized permeability fields from the SPE Comparative Project (Christie and Blunt, SPE Reserv Evalu Eng 4:308-317, 2001). We consider simple cases where one can identify the scales that can be homogenized. For more general cases, we suggest the use of upscaling on the coarse grid with the size smaller than the target coarse grid where multiscale basis functions are constructed. This intermediate coarse grid renders a partially upscaled solution that contains essential non-local information. Numerical examples demonstrate that the use of approximate global information provides better accuracy than purely local multiscale methods. © 2009 Springer Science+Business Media B.V.

  15. Research on conflict resolution of collaborative design with fuzzy case-based reasoning method

    Institute of Scientific and Technical Information of China (English)

    HOU Jun-ming; SU Chong; LIANG Shuang; WANG Wan-shan

    2009-01-01

    Collaborative design is a new style for modern mechanical design to meet the requirement of increasing competition. Designers of different places complete the same work, but the conflict appears in the process of design which may interface the design. Case-based reasoning (CBR) method is applied to the problem of conflict resolution, which is in the artificial intelligence field. However, due to the uncertainties in knowledge representation, attribute description, and similarity measures of CBR, it is very difficult to find the similar cases from case database. A fuzzy CBR method was proposed to solve the problem of conflict resolution in collaborative design. The process of fuzzy CBR was introduced. Based on the feature attributes and their relative weights determined by a fuzzy technique, a fuzzy CBR retrieving mechanism was developed to retrieve conflict resolution cases that tend to enhance the functions of the database. By indexing, calculating the weight and defuzzicating of the cases, the case similarity can be obtained. Then the case consistency was measured to keep the right result. Finally, the fuzzy CBR method for conflict resolution was demonstrated by means of a case study. The prototype system based on web is developed to illustrate the methodology.

  16. An approximate method for analyzing transient condensation on spray in HYLIFE-II

    Energy Technology Data Exchange (ETDEWEB)

    Bai, R.Y.; Schrock, V.E. (California Univ., Berkeley, CA (USA). Dept. of Nuclear Engineering)

    1990-01-01

    The HYLIFE-II conceptual design calls for analysis of highly transient condensation on droplets to achieve a rapidly decaying pressure field. Drops exposed to the required transient vapor pressure field are first heated by condensation but later begin to reevaporate after the vapor temperature falls below the drop surface temperature. An approximate method of analysis has been developed based on the assumption that the thermal resistance is concentrated in the liquid. The time dependent boundary condition is treated via the Duhamel integral for the pure conduction model. The resulting Nusselt number is enhanced to account for convection within the drop and then used to predict the drop mean temperature history. Many histories are considered to determine the spray rate necessary to achieve the required complete condensation.

  17. Coherent-potential approximation in the tight-binding linear muffin-tin orbital method

    Energy Technology Data Exchange (ETDEWEB)

    Singh, P.P.; Gonis, A. (Chemistry and Materials Science Department, L-268, Lawrence Livermore National Laboratory, Livermore, California 94550 (United States))

    1993-07-15

    We describe a consistent approach for applying the coherent-potential approximation (CPA) to the various representations of the linear muffin-tin orbital method. Unlike the previous works of Kudrnovsky [ital et] [ital al]. [Phys. Rev. B 35, 2487 (1987); 41, 7515 (1990)], our results for the ensemble-averaged Green functions in the tight-binding representation yield [ital E]- and [bold r]-dependent quantities that are consistent with the traditional applications of the single-site CPA. To illustrate the reliability and the usefulness of our approach we compare the nonspherically averaged charge densities, calculated in real space, of ordered NiPt in [ital L]1[sub 0] structure and the substitutionally disordered Ni[sub 0.5]Pt[sub 0.5] on a face-centered-cubic lattice.

  18. Calculation method of radiation shielding in the nuclear medicine facility. Evaluation based on the reasonable calculation method

    International Nuclear Information System (INIS)

    According to the acceptance of ICRP Publication 60 (1990), the dose equivalent limit for the boarder of controlled area will be defined as 1.3 mSv/3 months in the Regulation for the Enforcement of the Medical Service Law which is scheduled to be revised. The calculating methods of radiation shielding to be considered are as follows: The first method is calculating the dose equivalent for each nuclide using 3-month maximum estimated use dose. The second method is calculating the dose equivalent using 3-month maximum estimated use dose after the conversion of all nuclide dose into that of 131I. The third method is calculating the dose equivalent using 1 day maximum estimated use dose after the conversion of all nuclide dose into that of 131I. We've investigated which of methods can meet the new regulation value (1.3 mSv/3 months). In modeled facility, we've tried to calculate the dose by the first method to confirm if we can perform the reasonable control in safe. Total dose equivalent for the boarder of controlled area (B) was 883 μSv/3 months by the first method, and its value turned out to be about 1/4 of that of the third method. Only the result by the first method was found to be within the confines of new dose equivalent limit of 1.3 mSv/3 months. The results of both method the second and the third were found to be within the confines of existing dose equivalent limit. The method as to calculate the shielding for each nuclide by using 3-month maximum estimated use dose has been accepted in the Law Concerning Prevention from Radiation Hazards due to Radioisotopes, etc. As the method is practically in accordance with the current use of radioisotope in nuclear medicine facility, the possibility of it coping with the new dose equivalent limit was indicated. (author)

  19. Diffusion approximation-based simulation of stochastic ion channels: which method to use?

    Science.gov (United States)

    Pezo, Danilo; Soudry, Daniel; Orio, Patricio

    2014-01-01

    To study the effects of stochastic ion channel fluctuations on neural dynamics, several numerical implementation methods have been proposed. Gillespie's method for Markov Chains (MC) simulation is highly accurate, yet it becomes computationally intensive in the regime of a high number of channels. Many recent works aim to speed simulation time using the Langevin-based Diffusion Approximation (DA). Under this common theoretical approach, each implementation differs in how it handles various numerical difficulties—such as bounding of state variables to [0,1]. Here we review and test a set of the most recently published DA implementations (Goldwyn et al., 2011; Linaro et al., 2011; Dangerfield et al., 2012; Orio and Soudry, 2012; Schmandt and Galán, 2012; Güler, 2013; Huang et al., 2013a), comparing all of them in a set of numerical simulations that assess numerical accuracy and computational efficiency on three different models: (1) the original Hodgkin and Huxley model, (2) a model with faster sodium channels, and (3) a multi-compartmental model inspired in granular cells. We conclude that for a low number of channels (usually below 1000 per simulated compartment) one should use MC—which is the fastest and most accurate method. For a high number of channels, we recommend using the method by Orio and Soudry (2012), possibly combined with the method by Schmandt and Galán (2012) for increased speed and slightly reduced accuracy. Consequently, MC modeling may be the best method for detailed multicompartment neuron models—in which a model neuron with many thousands of channels is segmented into many compartments with a few hundred channels. PMID:25404914

  20. Diffusion approximation-based simulation of stochastic ion channels: which method to use?

    Directory of Open Access Journals (Sweden)

    Danilo ePezo

    2014-11-01

    Full Text Available To study the effects of stochastic ion channel fluctuations on neural dynamics, several numerical implementation methods have been proposed. Gillespie’s method for Markov Chains (MC simulation is highly accurate, yet it becomes computationally intensive in the regime of high channel numbers. Many recent works aim to speed simulation time using the Langevin-based Diffusion Approximation (DA. Under this common theoretical approach, each implementation differs in how it handles various numerical difficulties – such as bounding of state variables to [0,1]. Here we review and test a set of the most recently published DA implementations (Dangerfield et al., 2012; Linaro et al., 2011; Huang et al., 2013a; Orio and Soudry, 2012; Schmandt and Galán, 2012; Goldwyn et al., 2011; Güler, 2013, comparing all of them in a set of numerical simulations that asses numerical accuracy and computational efficiency on three different models: the original Hodgkin and Huxley model, a model with faster sodium channels, and a multi-compartmental model inspired in granular cells. We conclude that for low channel numbers (usually below 1000 per simulated compartment one should use MC – which is both the most accurate and fastest method. For higher channel numbers, we recommend using the method by Orio and Soudry (2012, possibly combined with the method by Schmandt and Galán (2012 for increased speed and slightly reduced accuracy. Consequently, MC modelling may be the best method for detailed multicompartment neuron models – in which a model neuron with many thousands of channels is segmented into many compartments with a few hundred channels.

  1. Mixed-hybrid finite element method for the transport equation and diffusion approximation of transport problems

    International Nuclear Information System (INIS)

    This thesis focuses on mathematical analysis, numerical resolution and modelling of the transport equations. First of all, we deal with numerical approximation of the solution of the transport equations by using a mixed-hybrid scheme. We derive and study a mixed formulation of the transport equation, then we analyse the related variational problem and present the discretization and the main properties of the scheme. We particularly pay attention to the behavior of the scheme and we show its efficiency in the diffusion limit (when the mean free path is small in comparison with the characteristic length of the physical domain). We present academical benchmarks in order to compare our scheme with other methods in many physical configurations and validate our method on analytical test cases. Unstructured and very distorted meshes are used to validate our scheme. The second part of this thesis deals with two transport problems. The first one is devoted to the study of diffusion due to boundary conditions in a transport problem between two plane plates. The second one consists in modelling and simulating radiative transfer phenomenon in case of the industrial context of inertial confinement fusion. (author)

  2. Improved locality-sensitive hashing method for the approximate nearest neighbor problem

    International Nuclear Information System (INIS)

    In recent years, the nearest neighbor search (NNS) problem has been widely used in various interesting applications. Locality-sensitive hashing (LSH), a popular algorithm for the approximate nearest neighbor problem, is proved to be an efficient method to solve the NNS problem in the high-dimensional and large-scale databases. Based on the scheme of p-stable LSH, this paper introduces a novel improvement algorithm called randomness-based locality-sensitive hashing (RLSH) based on p-stable LSH. Our proposed algorithm modifies the query strategy that it randomly selects a certain hash table to project the query point instead of mapping the query point into all hash tables in the period of the nearest neighbor query and reconstructs the candidate points for finding the nearest neighbors. This improvement strategy ensures that RLSH spends less time searching for the nearest neighbors than the p-stable LSH algorithm to keep a high recall. Besides, this strategy is proved to promote the diversity of the candidate points even with fewer hash tables. Experiments are executed on the synthetic dataset and open dataset. The results show that our method can cost less time consumption and less space requirements than the p-stable LSH while balancing the same recall. (general)

  3. Application of a computationally efficient method to approximate gap model results with a probabilistic approach

    Directory of Open Access Journals (Sweden)

    M. Scherstjanoi

    2014-02-01

    Full Text Available To be able to simulate climate change effects on forest dynamics over the whole of Switzerland, we adapted the second generation DGVM LPJ-GUESS to the Alpine environment. We modified model functions, tuned model parameters, and implemented new tree species to represent the potential natural vegetation of Alpine landscapes. Furthermore, we increased the computational efficiency of the model to enable area-covering simulations in a fine resolution (1 km sufficient for the complex topography of the Alps, which resulted in more than 32 000 simulation grid cells. To this aim, we applied the recently developed method GAPPARD (Scherstjanoi et al., 2013 to LPJ-GUESS. GAPPARD derives mean output values from a combination of simulation runs without disturbances and a patch age distribution defined by the disturbance frequency. With this computationally efficient method, that increased the model's speed by approximately the factor 8, we were able to faster detect shortcomings of LPJ-GUESS functions and parameters. We used the adapted LPJ-GUESS together with GAPPARD to assess the influence of one climate change scenario on dynamics of tree species composition and biomass throughout the 21st century in Switzerland. To allow for comparison with the original model, we additionally simulated forest dynamics along a north-south-transect through Switzerland. The results from this transect confirmed the high value of the GAPPARD method despite some limitations towards extreme climatic events. It allowed for the first time to obtain area-wide, detailed high resolution LPJ-GUESS simulation results for a large part of the Alpine region.

  4. Rooted Tree Analysis for Order Conditions of Stochastic Runge-Kutta Methods for the Weak Approximation of Stochastic Differential Equations

    OpenAIRE

    Rößler, Andreas

    2013-01-01

    A general class of stochastic Runge-Kutta methods for the weak approximation of It\\^o and Stratonovich stochastic differential equations with a multi-dimensional Wiener process is introduced. Colored rooted trees are used to derive an expansion of the solution process and of the approximation process calculated with the stochastic Runge-Kutta method. A theorem on general order conditions for the coefficients and the random variables of the stochastic Runge-Kutta method is proved by rooted tre...

  5. Intelligent design of investment casting mold based on a hybrid reasoning method

    Institute of Scientific and Technical Information of China (English)

    Jiang Ruisong; Zhang Dinghua; Wang Wenhu; Bu Kun

    2009-01-01

    A hybrid reasoning model was proposed in which CBR (case-based reasoning) was applied to the conceptual design and RBR (rule-based reasoning) was applied to the detailed design after research of the design process and domain knowledge of the acre-engine turbine blade investment casting mold design field. In the conceptual design stage, the representation and retrieval technologies were researched which improve the retrieval efficiency. Meanwhile, RBR was used to modify the retrieval result. The experimentation shows that the approach in this study can be used to obtain a more satisfactory design result.

  6. Scalable learning method for feedforward neural networks using minimal-enclosing-ball approximation.

    Science.gov (United States)

    Wang, Jun; Deng, Zhaohong; Luo, Xiaoqing; Jiang, Yizhang; Wang, Shitong

    2016-06-01

    Training feedforward neural networks (FNNs) is one of the most critical issues in FNNs studies. However, most FNNs training methods cannot be directly applied for very large datasets because they have high computational and space complexity. In order to tackle this problem, the CCMEB (Center-Constrained Minimum Enclosing Ball) problem in hidden feature space of FNN is discussed and a novel learning algorithm called HFSR-GCVM (hidden-feature-space regression using generalized core vector machine) is developed accordingly. In HFSR-GCVM, a novel learning criterion using L2-norm penalty-based ε-insensitive function is formulated and the parameters in the hidden nodes are generated randomly independent of the training sets. Moreover, the learning of parameters in its output layer is proved equivalent to a special CCMEB problem in FNN hidden feature space. As most CCMEB approximation based machine learning algorithms, the proposed HFSR-GCVM training algorithm has the following merits: The maximal training time of the HFSR-GCVM training is linear with the size of training datasets and the maximal space consumption is independent of the size of training datasets. The experiments on regression tasks confirm the above conclusions. PMID:27049545

  7. Simple finite element methods for approximating predator-prey dynamics in two dimensions using MATLAB.

    Science.gov (United States)

    Garvie, Marcus R; Burkardt, John; Morgan, Jeff

    2015-03-01

    We describe simple finite element schemes for approximating spatially extended predator-prey dynamics with the Holling type II functional response and logistic growth of the prey. The finite element schemes generalize 'Scheme 1' in the paper by Garvie (Bull Math Biol 69(3):931-956, 2007). We present user-friendly, open-source MATLAB code for implementing the finite element methods on arbitrary-shaped two-dimensional domains with Dirichlet, Neumann, Robin, mixed Robin-Neumann, mixed Dirichlet-Neumann, and Periodic boundary conditions. Users can download, edit, and run the codes from http://www.uoguelph.ca/~mgarvie/ . In addition to discussing the well posedness of the model equations, the results of numerical experiments are presented and demonstrate the crucial role that habitat shape, initial data, and the boundary conditions play in determining the spatiotemporal dynamics of predator-prey interactions. As most previous works on this problem have focussed on square domains with standard boundary conditions, our paper makes a significant contribution to the area. PMID:25616741

  8. The Approximate Bayesian Computation methods in the localization of the atmospheric contamination source

    Science.gov (United States)

    Kopka, P.; Wawrzynczak, A.; Borysiewicz, M.

    2015-09-01

    In many areas of application, a central problem is a solution to the inverse problem, especially estimation of the unknown model parameters to model the underlying dynamics of a physical system precisely. In this situation, the Bayesian inference is a powerful tool to combine observed data with prior knowledge to gain the probability distribution of searched parameters. We have applied the modern methodology named Sequential Approximate Bayesian Computation (S-ABC) to the problem of tracing the atmospheric contaminant source. The ABC is technique commonly used in the Bayesian analysis of complex models and dynamic system. Sequential methods can significantly increase the efficiency of the ABC. In the presented algorithm, the input data are the on-line arriving concentrations of released substance registered by distributed sensor network from OVER-LAND ATMOSPHERIC DISPERSION (OLAD) experiment. The algorithm output are the probability distributions of a contamination source parameters i.e. its particular location, release rate, speed and direction of the movement, start time and duration. The stochastic approach presented in this paper is completely general and can be used in other fields where the parameters of the model bet fitted to the observable data should be found.

  9. Indirect estimation of unsteady temperature profiles by means of a numerical method based on finite approximations

    International Nuclear Information System (INIS)

    In this paper we present the results of a short phenomenological investigation on indirect heat transfer. The aim of this investigation is to gain a better understanding towards the service life of a solid structure subject to thermal stresses (e.g., a pipeline). A numerical scheme, based on finite approximations, is used to estimate temperature profiles at an inaccessible wall. Such a situation occurs in a nuclear power plant, for example, when monitoring pipelines subject to thermal stresses. Due to the operating conditions (e.g., high pressure and/or high temperatures) it is not always feasible to measure the temperature at each location of the pipeline. Therefore, the temperature is measured at a certain location (for instance, at an outer surface) and the temperature at the inner surface, must be estimated. The word estimate is used to indicate that an exact solution at the given conditions is not known, or is not suitable for use in practice. Thus, the estimation of the temperature can be seen as an indirect method for the prediction of temperature profiles. Accurate estimation of the temperature profiles relies on the quality of the measurements. This serves as a basis for monitoring and predicting the expected service life in systems such as pipelines. (author)

  10. Approximate rational Jacobi elliptic function solutions of the fractional differential equations via the enhanced Adomian decomposition method

    International Nuclear Information System (INIS)

    In this Letter, an enhanced Adomian decomposition method which introduces the h-curve of the homotopy analysis method into the standard Adomian decomposition method is proposed. Some examples prove that this method can derive successfully approximate rational Jacobi elliptic function solutions of the fractional differential equations.

  11. Approximation methods for the calculation of eigenvalues in ODE with periodic or anti periodic boundary conditions: Application to nanotubes

    CERN Document Server

    Gadella, M; Negro, J

    2016-01-01

    We compare three different methods to obtain solutions of Sturm-Liouville problems: a successive approximation method and two other iterative methods. We look for solutions with periodic or anti periodic boundary conditions. With some numerical test over the Mathieu equation, we compare the efficiency of these three methods. As an application, we make a numerical analysis on a model for carbon nanotubes.

  12. The approximate planimetric method. A simple, rapid and reliable method for estimation of lesion size in acute ischemic stroke

    International Nuclear Information System (INIS)

    Magnetic resonance imaging is increasingly used in stroke trials for early diagnosis and follow-up of lesion size. Since volumetric measurement remains a laborious and time-consuming task, a rapid and reliable method for the assessment of lesion size has been developed and validated in diffusion weighted imaging (DWI) and fluid attenuated inversion recovery (FLAIR) sequences. These were serially obtained in 40 patients less than 8 h after the onset of symptoms of a middle cerebral artery territory stroke (day 1), as well as on days 3 and 18. For each of 16 (DWI) or 20 (FLAIR) transverse sections obtained on each occasion, lesion size was estimated as a percentage of the total hemisphere. Percentage values from all sections were summed up and expressed as arbitrary units. Results obtained using this approximate planimetric method (APM) were compared with those from a standard volumetric approach. Lesion volumes as determined by both methods were highly correlated (DWI: r = 0.966, FLAIR: r = 0.979, p < 0.001). To conclude, the APM is simple, rapid and reliable for the estimation of lesion size in acute ischemic stroke. It can be recommended for broader application in clinical trials. (orig.)

  13. A penalty method for approximations of the stationary power-law Stokes problem

    Directory of Open Access Journals (Sweden)

    Lew Lefton

    2001-01-01

    Full Text Available We study approximations of the steady state Stokes problem governed by the power-law model for viscous incompressible non-Newtonian flow using the penalty formulation. We establish convergence and find error estimates.

  14. On the Behavior of Combination High-Order Compact Approximations with Preconditioned Methods in the Diffusion-Convection Equation

    Directory of Open Access Journals (Sweden)

    Ahmad Golbabai

    2011-12-01

    Full Text Available In this paper, a family of high-order compact finite difference methods in combination preconditioned methods are used for solution of the Diffusion-Convection equation. We developed numerical methods by replacing the time and space derivatives by compact finite-difference approximations. The system of resulting nonlinear finite difference equations are solved by preconditioned Krylov subspace methods. Numerical results are given to verify the behavior of high-order compact approximations in combination preconditioned methods for stability, convergence. Also, the accuracy and efficiency of the proposed scheme are considered.

  15. A novel window based method for approximating the Hausdorff in 3D range imagery.

    Energy Technology Data Exchange (ETDEWEB)

    Koch, Mark William

    2004-10-01

    Matching a set of 3D points to another set of 3D points is an important part of any 3D object recognition system. The Hausdorff distance is known for it robustness in the face of obscuration, clutter, and noise. We show how to approximate the 3D Hausdorff fraction with linear time complexity and quadratic space complexity. We empirically demonstrate that the approximation is very good when compared to actual Hausdorff distances.

  16. Application of the probabilistic approximate analysis method to a turbopump blade analysis. [for Space Shuttle Main Engine

    Science.gov (United States)

    Thacker, B. H.; Mcclung, R. C.; Millwater, H. R.

    1990-01-01

    An eigenvalue analysis of a typical space propulsion system turbopump blade is presented using an approximate probabilistic analysis methodology. The methodology was developed originally to investigate the feasibility of computing probabilistic structural response using closed-form approximate models. This paper extends the methodology to structures for which simple closed-form solutions do not exist. The finite element method will be used for this demonstration, but the concepts apply to any numerical method. The results agree with detailed analysis results and indicate the usefulness of using a probabilistic approximate analysis in determining efficient solution strategies.

  17. Accuracy of Approximate Eigenstates

    CERN Document Server

    Lucha, Wolfgang; Lucha, Wolfgang

    2000-01-01

    Besides perturbation theory, which requires, of course, the knowledge of the exact unperturbed solution, variational techniques represent the main tool for any investigation of the eigenvalue problem of some semibounded operator H in quantum theory. For a reasonable choice of the employed trial subspace of the domain of H, the lowest eigenvalues of H usually can be located with acceptable precision whereas the trial-subspace vectors corresponding to these eigenvalues approximate, in general, the exact eigenstates of H with much less accuracy. Accordingly, various measures for the accuracy of the approximate eigenstates derived by variational techniques are scrutinized. In particular, the matrix elements of the commutator of the operator H and (suitably chosen) different operators, with respect to degenerate approximate eigenstates of H obtained by some variational method, are proposed here as new criteria for the accuracy of variational eigenstates. These considerations are applied to that Hamiltonian the eig...

  18. Lectures on constructive approximation Fourier, spline, and wavelet methods on the real line, the sphere, and the ball

    CERN Document Server

    Michel, Volker

    2013-01-01

    Lectures on Constructive Approximation: Fourier, Spline, and Wavelet Methods on the Real Line, the Sphere, and the Ball focuses on spherical problems as they occur in the geosciences and medical imaging. It comprises the author’s lectures on classical approximation methods based on orthogonal polynomials and selected modern tools such as splines and wavelets. Methods for approximating functions on the real line are treated first, as they provide the foundations for the methods on the sphere and the ball and are useful for the analysis of time-dependent (spherical) problems. The author then examines the transfer of these spherical methods to problems on the ball, such as the modeling of the Earth’s or the brain’s interior. Specific topics covered include: * the advantages and disadvantages of Fourier, spline, and wavelet methods * theory and numerics of orthogonal polynomials on intervals, spheres, and balls * cubic splines and splines based on reproducing kernels * multiresolution analysis using wavelet...

  19. Study of internal rotation in molecules using molecular orbital method in the CNDO/BW approximation

    International Nuclear Information System (INIS)

    It is presented a LCAO-MO-SCF study of Internal Rotation for the molecules C2H6, CH3NH2, H2O2, and N2H4 by ysing the CNDO/BW approximation and an M-center energy partition. Our results are compared with those obtained with the CNDO/2 approximation. It is shown that there are differences in the analysis of the process involved in the internal rotation barriers mechanism. Thus the interpretation of the results is strongly dependent on the parametrization used. (author)

  20. Elementary School Children's Reasoning about Social Class: A Mixed-Methods Study

    Science.gov (United States)

    Mistry, Rashmita S.; Brown, Christia S.; White, Elizabeth S.; Chow, Kirby A.; Gillen-O'Neel, Cari

    2015-01-01

    The current study examined children's identification and reasoning about their subjective social status (SSS), their beliefs about social class groups (i.e., the poor, middle class, and rich), and the associations between the two. Study participants were 117 10- to 12-year-old children of diverse racial, ethnic, and socioeconomic backgrounds…

  1. Stochastic Approximation Methods for Latent Regression Item Response Models. Research Report. ETS RR-09-09

    Science.gov (United States)

    von Davier, Matthias; Sinharay, Sandip

    2009-01-01

    This paper presents an application of a stochastic approximation EM-algorithm using a Metropolis-Hastings sampler to estimate the parameters of an item response latent regression model. Latent regression models are extensions of item response theory (IRT) to a 2-level latent variable model in which covariates serve as predictors of the…

  2. General Viscosity Approximation Methods for Common Fixed Points of Nonexpansive Semigroups in Hilbert Spaces

    Directory of Open Access Journals (Sweden)

    Kim JongKyu

    2011-01-01

    Full Text Available Abstract This paper is devoted to the strong convergence of two kinds of general viscosity iteration processes for approximating common fixed points of a nonexpansive semigroup in Hilbert spaces. The results presented in this paper improve and generalize some corresponding results in (X. Li et al., 2009, S. Li et al., 2009, and Marino and Xu, 2006.

  3. Approximate solutions of dirac equation with a ring-shaped woods-saxon potential by Nikiforov-Uvarov method

    International Nuclear Information System (INIS)

    An approximate analytical solution of the Dirac equation is obtained for the ring-shaped Woods-Saxon potential within the framework of an exponential approximation to the centrifugal term. The radial and angular parts of the equation are solved by the Nikiforov-Uvarov method. The general results obtained in this work can be reduced to the standard forms already present in the literature. (authors)

  4. Method for the approximate calculation of the composition of the detonation products of hydrogen-oxygen gas mixtures

    International Nuclear Information System (INIS)

    A method for the approximate calculation of the composition of the detonation products of gas mixtures is reported in the paper. The method is based on the assumption of partial equilibrium in the subsystem of biomolecular reactions. The description of the equilibrium composition in the subsystem of biomolecular reactions is reduced to the solution of the system of linear equations

  5. A Diffusion Approximation and Numerical Methods for Adaptive Neuron Models with Stochastic Inputs

    Science.gov (United States)

    Rosenbaum, Robert

    2016-01-01

    Characterizing the spiking statistics of neurons receiving noisy synaptic input is a central problem in computational neuroscience. Monte Carlo approaches to this problem are computationally expensive and often fail to provide mechanistic insight. Thus, the field has seen the development of mathematical and numerical approaches, often relying on a Fokker-Planck formalism. These approaches force a compromise between biological realism, accuracy and computational efficiency. In this article we develop an extension of existing diffusion approximations to more accurately approximate the response of neurons with adaptation currents and noisy synaptic currents. The implementation refines existing numerical schemes for solving the associated Fokker-Planck equations to improve computationally efficiency and accuracy. Computer code implementing the developed algorithms is made available to the public.

  6. A Diffusion Approximation and Numerical Methods for Adaptive Neuron Models with Stochastic Inputs.

    Science.gov (United States)

    Rosenbaum, Robert

    2016-01-01

    Characterizing the spiking statistics of neurons receiving noisy synaptic input is a central problem in computational neuroscience. Monte Carlo approaches to this problem are computationally expensive and often fail to provide mechanistic insight. Thus, the field has seen the development of mathematical and numerical approaches, often relying on a Fokker-Planck formalism. These approaches force a compromise between biological realism, accuracy and computational efficiency. In this article we develop an extension of existing diffusion approximations to more accurately approximate the response of neurons with adaptation currents and noisy synaptic currents. The implementation refines existing numerical schemes for solving the associated Fokker-Planck equations to improve computationally efficiency and accuracy. Computer code implementing the developed algorithms is made available to the public. PMID:27148036

  7. A COMPARATIVE STUDY OF TWO GENERAL METHODS FOR THE APPROXIMATE CONSTRUCTION OF REGULAR POLYGONS BY USING MATHEMATICA 3.0

    OpenAIRE

    Аледо, Хуан; Кортес, Хуан; Пелайо, Фернандо

    1999-01-01

    In this paper we study two classic methods for the approximate construction of regular polygons by using Mathematica 3.0: the method of Archimedes and the method of Bardin. In the same way, we make a comparative study of the errors of both methods, concluding that the exactness of Bardin's method is higher than the Archimedes' one. Moreover, we improve both methods, by giving the respective algorithms. We also include the coded algorithm in Mathematica 3.0 for the animation of both methods.

  8. A new weak approximation scheme of stochastic differential equations and the Runge-Kutta method

    OpenAIRE

    Ninomiya, Mariko; Ninomiya, Syoiti

    2007-01-01

    In this paper, authors successfully construct a new algorithm for the new higher order scheme of weak approximation of SDEs. The algorithm presented here is based on [1][2]. Although this algorithm shares some features with the algorithm presented by [3], algorithms themselves are completely different and the diversity is not trivial. They apply this new algorithm to the problem of pricing Asian options under the Heston stochastic volatility model and obtain encouraging results. [1] Shigeo Ku...

  9. Vibration suppression with approximate finite dimensional compensators for distributed systems: Computational methods and experimental results

    Science.gov (United States)

    Banks, H. T.; Smith, Ralph C.; Wang, Yun

    1994-01-01

    Based on a distributed parameter model for vibrations, an approximate finite dimensional dynamic compensator is designed to suppress vibrations (multiple modes with a broad band of frequencies) of a circular plate with Kelvin-Voigt damping and clamped boundary conditions. The control is realized via piezoceramic patches bonded to the plate and is calculated from information available from several pointwise observed state variables. Examples from computational studies as well as use in laboratory experiments are presented to demonstrate the effectiveness of this design.

  10. The LOCV method versus the fermion (hypernetted) chain approximations using the Bethe homework problem

    Energy Technology Data Exchange (ETDEWEB)

    Modarres, M., E-mail: mmodares@ut.ac.ir [Physics Department, University of Tehran, North-Kargar Ave., 1439955961 Tehran (Iran, Islamic Republic of); Tafrihi, A.; Hatami, A. [Physics Department, University of Tehran, North-Kargar Ave., 1439955961 Tehran (Iran, Islamic Republic of)

    2012-04-01

    The neutron matter equation of states of the so-called Bethe homework problem (NMESB) is obtained using the (extended) lowest order constrained variational ((E) LOCV), the lowest order factorized Iwamoto-Yamada (LOF) and the Fermi (hypernetted) chain (FC (FHNC)) formalisms. The FC and the FHNC approximations are performed, using the LOCV or the ELOCV correlation function. It is shown that, if the normalization constraint is satisfied, then the NMESB results by using the LOCV, the ELOCV, the FC and the FHNC formalisms, will become close together and agree well with the corresponding FHNC calculations performed by Zabolitzky (Z) with the parameterized Krotscheck and Takahashi (KT) correlation function. It is also demonstrated that the LOF and the FC calculations, evaluated by employing a parameterized correlation function, are far from the above results, particularly at high densities. Finally, in order to test the convergence of LOF approximation, the two- and the three-body normalization factors are calculated and it is shown that in the LOF approximation, the truncation of cluster expansion after the first few leading terms is not reliable (which is well known as the Emery difficulty).

  11. The LOCV method versus the fermion (hypernetted) chain approximations using the Bethe homework problem

    International Nuclear Information System (INIS)

    The neutron matter equation of states of the so-called Bethe homework problem (NMESB) is obtained using the (extended) lowest order constrained variational ((E) LOCV), the lowest order factorized Iwamoto–Yamada (LOF) and the Fermi (hypernetted) chain (FC (FHNC)) formalisms. The FC and the FHNC approximations are performed, using the LOCV or the ELOCV correlation function. It is shown that, if the normalization constraint is satisfied, then the NMESB results by using the LOCV, the ELOCV, the FC and the FHNC formalisms, will become close together and agree well with the corresponding FHNC calculations performed by Zabolitzky (Z) with the parameterized Krotscheck and Takahashi (KT) correlation function. It is also demonstrated that the LOF and the FC calculations, evaluated by employing a parameterized correlation function, are far from the above results, particularly at high densities. Finally, in order to test the convergence of LOF approximation, the two- and the three-body normalization factors are calculated and it is shown that in the LOF approximation, the truncation of cluster expansion after the first few leading terms is not reliable (which is well known as the Emery difficulty).

  12. Understanding Set Cover: Sub-exponential Time Approximations and Lift-and-Project Methods

    CERN Document Server

    Chlamtac, Eden; Georgiou, Konstantinos

    2012-01-01

    We study sub-exponential time approximation algorithms for the Set-Cover problem. Our main algorithmic result is a combinatorial ln(n/d)+O(1) approximation in poly(n,m)*m^O(d) time, where n is the number of items to be covered and m is the number of sets. Setting d = n^eps for any constant 0 < eps < 1 results in a (1-eps)*ln n approximation running in sub-exponential time. By recent work of Moshkovitz, assuming the Projection Games Conjecture, the running time of our algorithm is optimal up to a constant factor in the exponent of n, unless SAT has sub-exponential time algorithms. At a high level, our algorithm is similar to a well-known PTAS for Knapsack. Recently, Karlin, Mathieu, and Nguyen examined this PTAS and its connection to hierarchies of linear programming (LP) and semidefinite programing (SDP) relaxations for Knapsack. Inspired by their work, we also consider the integrality gap of Set-Cover relaxations arising from such hierarchies. We show that, using the trick of "lifting the objective fun...

  13. Six Forms of Variety in Students' Moral Reasoning: An Age-Old Distinction Enabling New Methods and Findings

    Science.gov (United States)

    Backman, Ylva; Gardelli, Viktor

    2015-01-01

    In this study, the age-old distinction between decision method and criterion of rightness, commonly employed in normative ethics, was used to attain a detailed understanding of inter- and intrapersonal variety in students' moral reasoning. A total of 24 Swedish students, 12-15 years of age, were interviewed. Inter- and intrapersonal varieties in…

  14. Curse of dimensionality reduction in max-plus based approximation methods: theoretical estimates and improved pruning algorithms

    CERN Document Server

    Gaubert, Stephane; Qu, Zheng

    2011-01-01

    Max-plus based methods have been recently developed to approximate the value function of possibly high dimensional optimal control problems. A critical step of these methods consists in approximating a function by a supremum of a small number of functions (max-plus "basis functions") taken from a prescribed dictionary. We study several variants of this approximation problem, which we show to be continuous versions of the facility location and $k$-center combinatorial optimization problems, in which the connection costs arise from a Bregman distance. We give theoretical error estimates, quantifying the number of basis functions needed to reach a prescribed accuracy. We derive from our approach a refinement of the curse of dimensionality free method introduced previously by McEneaney, with a higher accuracy for a comparable computational cost.

  15. Comparative assessment of density functional methods for evaluating essential parameters to simulate SERS spectra within the excited state energy gradient approximation.

    Science.gov (United States)

    Mohammadpour, Mozhdeh; Jamshidi, Zahra

    2016-05-21

    The prospect of challenges in reproducing and interpretation of resonance Raman properties of molecules interacting with metal clusters has prompted the present research initiative. Resonance Raman spectra based on the time-dependent gradient approximation are examined in the framework of density functional theory using different methods for representing the exchange-correlation functional. In this work the performance of different XC functionals in the prediction of ground state properties, excitation state energies, and gradients are compared and discussed. Resonance Raman properties based on time-dependent gradient approximation for the strongly low-lying charge transfer states are calculated and compared for different methods. We draw the following conclusions: (1) for calculating the binding energy and ground state geometry, dispersion-corrected functionals give the best performance in comparison to ab initio calculations, (2) GGA and meta GGA functionals give good accuracy in calculating vibrational frequencies, (3) excited state energies determined by hybrid and range-separated hybrid functionals are in good agreement with EOM-CCSD calculations, and (4) in calculating resonance Raman properties GGA functionals give good and reasonable performance in comparison to the experiment; however, calculating the excited state gradient by using the hybrid functional on the hessian of GGA improves the results of the hybrid functional significantly. Finally, we conclude that the agreement of charge-transfer surface enhanced resonance Raman spectra with experiment is improved significantly by using the excited state gradient approximation. PMID:27208944

  16. Nuclear transmission coefficients for calculation of the absorption cross section in the adiabatic coupled-channel approximation method

    International Nuclear Information System (INIS)

    Formulas which are needed to calculate transmission coefficients for the adiabatic coupled-channel approximation method are described. In terms of these coefficients, nuclear absorption cross sections may be obtained. First, derivations are given of various cross sections for a system of coupled inelastic channels in terms of the S matrix. The adiabatic approximation method is discussed for a rotational band, and the dynamical nuclear S matrix is obtained from the S matrix for scattering from a static rotor. The formulas are valid for a spheroidal rotor, with or without an extra-core particle, which does not interact with the projectile but does provide angular momentum to the target

  17. Non-Equilibrium Liouville and Wigner Equations: Moment Methods and Long-Time Approximations

    Directory of Open Access Journals (Sweden)

    Ramon F. Álvarez-Estrada

    2014-03-01

    Full Text Available We treat the non-equilibrium evolution of an open one-particle statistical system, subject to a potential and to an external “heat bath” (hb with negligible dissipation. For the classical equilibrium Boltzmann distribution, Wc,eq, a non-equilibrium three-term hierarchy for moments fulfills Hermiticity, which allows one to justify an approximate long-time thermalization. That gives partial dynamical support to Boltzmann’s Wc,eq, out of the set of classical stationary distributions, Wc;st, also investigated here, for which neither Hermiticity nor that thermalization hold, in general. For closed classical many-particle systems without hb (by using Wc,eq, the long-time approximate thermalization for three-term hierarchies is justified and yields an approximate Lyapunov function and an arrow of time. The largest part of the work treats an open quantum one-particle system through the non-equilibrium Wigner function, W. Weq for a repulsive finite square well is reported. W’s (< 0 in various cases are assumed to be quasi-definite functionals regarding their dependences on momentum (q. That yields orthogonal polynomials, HQ,n(q, for Weq (and for stationary Wst, non-equilibrium moments, Wn, of W and hierarchies. For the first excited state of the harmonic oscillator, its stationary Wst is a quasi-definite functional, and the orthogonal polynomials and three-term hierarchy are studied. In general, the non-equilibrium quantum hierarchies (associated with Weq for the Wn’s are not three-term ones. As an illustration, we outline a non-equilibrium four-term hierarchy and its solution in terms of generalized operator continued fractions. Such structures also allow one to formulate long-time approximations, but make it more difficult to justify thermalization. For large thermal and de Broglie wavelengths, the dominant Weq and a non-equilibrium equation for W are reported: the non-equilibrium hierarchy could plausibly be a three-term one and possibly not

  18. Accuracy of approximations of solutions to Fredholm equations by kernel methods

    Czech Academy of Sciences Publication Activity Database

    Gnecco, G.; Kůrková, Věra; Sanguineti, M.

    2012-01-01

    Roč. 218, č. 14 (2012), s. 7481-7497. ISSN 0096-3003 R&D Projects: GA ČR GAP202/11/1368; GA MŠk OC10047 Grant ostatní: CNR-AV ČR(CZ-IT) Project 2010–2012 “Complexity of Neural-Network and Kernel Computational Models Institutional research plan: CEZ:AV0Z10300504 Keywords : approximate solutions to integral equations * radial and kernel-based networks * Gaussian kernels * model complexity * analysis of algorithms Subject RIV: IN - Informatics, Computer Science Impact factor: 1.349, year: 2012

  19. AN APPROXIMATION METHOD TO ESTIMATE THE HAUSDORFF MEASURE OF THE SIERPINSKI GASKET

    Institute of Scientific and Technical Information of China (English)

    Ruan Huojun; Su Weiyi

    2004-01-01

    In this paper, we firstly define a decreasing sequence {Pn(S)} by the generation of the Sierpinski gasket where each pn(S) can be obtained in finite steps. Then we prove that the Hausdorff measure Hs(S)of the Sierpinski gasket S can be approximated by {Pn(S)} with Pn(S)/(1 + 1/2n-3)s ≤ Hs(S) ≤ pn(S).An algorithm is presented to get Pn(S) for n ≤ 5. As an application, we obtain the best lower bound of Hs(S) till now: Hs(S) ≥ 0.5631.

  20. Bandwidth Selection for Recursive Kernel Density Estimators Defined by Stochastic Approximation Method

    Directory of Open Access Journals (Sweden)

    Yousri Slaoui

    2014-01-01

    Full Text Available We propose an automatic selection of the bandwidth of the recursive kernel estimators of a probability density function defined by the stochastic approximation algorithm introduced by Mokkadem et al. (2009a. We showed that, using the selected bandwidth and the stepsize which minimize the MISE (mean integrated squared error of the class of the recursive estimators defined in Mokkadem et al. (2009a, the recursive estimator will be better than the nonrecursive one for small sample setting in terms of estimation error and computational costs. We corroborated these theoretical results through simulation study.

  1. Approximate method for calculating the lifetime of positrons trapped by lattice defects

    International Nuclear Information System (INIS)

    A method which takes account of core as well as valence electrons is presented for theoretically estimating the life-time of positrons trapped in lattice defects. The method is illustrated by calculations for vacancies and divacancies in aluminum

  2. Laguerre-like methods for the simultaneous approximation of polynomial multiple zeros

    Directory of Open Access Journals (Sweden)

    Petković Miodrag

    2006-01-01

    Full Text Available Two new methods of the fourth order for the simultaneous determination of multiple zeros of a polynomial are proposed. The presented methods are based on the fixed point relation of Laguerre's type and realized in ordinary complex arithmetic as well as circular complex interval arithmetic. The derived iterative formulas are suitable for the construction of modified methods with improved convergence rate with negligible additional operations. Very fast convergence of the considered methods is illustrated by two numerical examples.

  3. A multistage differential transformation method for approximate solution of Hantavirus infection model

    Science.gov (United States)

    Gökdoğan, Ahmet; Merdan, Mehmet; Yildirim, Ahmet

    2012-01-01

    The goal of this study is presented a reliable algorithm based on the standard differential transformation method (DTM), which is called the multi-stage differential transformation method (MsDTM) for solving Hantavirus infection model. The results obtanied by using MsDTM are compared to those obtained by using the Runge-Kutta method (R-K-method). The proposed technique is a hopeful tool to solving for a long time intervals in this kind of systems.

  4. Multi-Scaling Sampling: An Adaptive Sampling Method for Discovering Approximate Association Rules

    Institute of Scientific and Technical Information of China (English)

    Cai-Yan Jia; Xie-Ping Gao

    2005-01-01

    One of the obstacles of the efficient association rule mining is the explosive expansion of data sets since it is costly or impossible to scan large databases, esp., for multiple times. A popular solution to improve the speed and scalability of the association rule mining is to do the algorithm on a random sample instead of the entire database. But how to effectively define and efficiently estimate the degree of error with respect to the outcome of the algorithm, and how to determine the sample size needed are entangling researches until now. In this paper, an effective and efficient algorithm is given based on the PAC (Probably Approximate Correct) learning theory to measure and estimate sample error. Then, a new adaptive, on-line, fast sampling strategy - multi-scaling sampling - is presented inspired by MRA (Multi-Resolution Analysis) and Shannon sampling theorem, for quickly obtaining acceptably approximate association rules at appropriate sample size. Both theoretical analysis and empirical study have showed that the sampling strategy can achieve a very good speed-accuracy trade-off.

  5. Integration of large chemical kinetic mechanisms via exponential methods with Krylov approximations to Jacobian matrix functions

    KAUST Repository

    Bisetti, Fabrizio

    2012-06-01

    Recent trends in hydrocarbon fuel research indicate that the number of species and reactions in chemical kinetic mechanisms is rapidly increasing in an effort to provide predictive capabilities for fuels of practical interest. In order to cope with the computational cost associated with the time integration of stiff, large chemical systems, a novel approach is proposed. The approach combines an exponential integrator and Krylov subspace approximations to the exponential function of the Jacobian matrix. The components of the approach are described in detail and applied to the ignition of stoichiometric methane-air and iso-octane-air mixtures, here described by two widely adopted chemical kinetic mechanisms. The approach is found to be robust even at relatively large time steps and the global error displays a nominal third-order convergence. The performance of the approach is improved by utilising an adaptive algorithm for the selection of the Krylov subspace size, which guarantees an approximation to the matrix exponential within user-defined error tolerance. The Krylov projection of the Jacobian matrix onto a low-dimensional space is interpreted as a local model reduction with a well-defined error control strategy. Finally, the performance of the approach is discussed with regard to the optimal selection of the parameters governing the accuracy of its individual components. © 2012 Copyright Taylor and Francis Group, LLC.

  6. A New Method in the Location Problem using Fuzzy Evidential Reasoning

    Directory of Open Access Journals (Sweden)

    Sh. Rahgan

    2012-11-01

    Full Text Available One of the most important factors leading to the success of a company is its location. Branches have a strategic importance on an organization’s performance and its competitiveness. The purpose of this study is to present a decision-making model for selecting the most appropriate location for a bank branch. This research is the first study in the bank branch location researches considering various types of uncertainties. This model involves both quantitative and qualitative attributes as well as various types of uncertainty. So, we propose a methodology by integrating the fuzzy AHP and Evidential Reasoning approach. The fuzzy extent analysis is used to determine the weights of attributes and sub-attributes and the interval ER algorithm is used to rank the alternatives. This methodology can be used to help the decision makers, because it is capable of handling incomplete and imprecise judgments. We have demonstrated the applicability of the methodology through a case study.

  7. Parallel iterative procedures for approximate solutions of wave propagation by finite element and finite difference methods

    Energy Technology Data Exchange (ETDEWEB)

    Kim, S. [Purdue Univ., West Lafayette, IN (United States)

    1994-12-31

    Parallel iterative procedures based on domain decomposition techniques are defined and analyzed for the numerical solution of wave propagation by finite element and finite difference methods. For finite element methods, in a Lagrangian framework, an efficient way for choosing the algorithm parameter as well as the algorithm convergence are indicated. Some heuristic arguments for finding the algorithm parameter for finite difference schemes are addressed. Numerical results are presented to indicate the effectiveness of the methods.

  8. A summary of methods for approximating salt creep and disposal room closure in numerical models of multiphase flow

    Energy Technology Data Exchange (ETDEWEB)

    Freeze, G.A.; Larson, K.W. [INTERA, Inc., Albuquerque, NM (United States); Davies, P.B. [Sandia National Labs., Albuquerque, NM (United States)

    1995-10-01

    Eight alternative methods for approximating salt creep and disposal room closure in a multiphase flow model of the Waste Isolation Pilot Plant (WIPP) were implemented and evaluated: Three fixed-room geometries three porosity functions and two fluid-phase-salt methods. The pressure-time-porosity line interpolation method is the method used in current WIPP Performance Assessment calculations. The room closure approximation methods were calibrated against a series of room closure simulations performed using a creep closure code, SANCHO. The fixed-room geometries did not incorporate a direct coupling between room void volume and room pressure. The two porosity function methods that utilized moles of gas as an independent parameter for closure coupling. The capillary backstress method was unable to accurately simulate conditions of re-closure of the room. Two methods were found to be accurate enough to approximate the effects of room closure; the boundary backstress method and pressure-time-porosity line interpolation. The boundary backstress method is a more reliable indicator of system behavior due to a theoretical basis for modeling salt deformation as a viscous process. It is a complex method and a detailed calibration process is required. The pressure lines method is thought to be less reliable because the results were skewed towards SANCHO results in simulations where the sequence of gas generation was significantly different from the SANCHO gas-generation rate histories used for closure calibration. This limitation in the pressure lines method is most pronounced at higher gas-generation rates and is relatively insignificant at lower gas-generation rates. Due to its relative simplicity, the pressure lines method is easier to implement in multiphase flow codes and simulations have a shorter execution time.

  9. A summary of methods for approximating salt creep and disposal room closure in numerical models of multiphase flow

    International Nuclear Information System (INIS)

    Eight alternative methods for approximating salt creep and disposal room closure in a multiphase flow model of the Waste Isolation Pilot Plant (WIPP) were implemented and evaluated: Three fixed-room geometries three porosity functions and two fluid-phase-salt methods. The pressure-time-porosity line interpolation method is the method used in current WIPP Performance Assessment calculations. The room closure approximation methods were calibrated against a series of room closure simulations performed using a creep closure code, SANCHO. The fixed-room geometries did not incorporate a direct coupling between room void volume and room pressure. The two porosity function methods that utilized moles of gas as an independent parameter for closure coupling. The capillary backstress method was unable to accurately simulate conditions of re-closure of the room. Two methods were found to be accurate enough to approximate the effects of room closure; the boundary backstress method and pressure-time-porosity line interpolation. The boundary backstress method is a more reliable indicator of system behavior due to a theoretical basis for modeling salt deformation as a viscous process. It is a complex method and a detailed calibration process is required. The pressure lines method is thought to be less reliable because the results were skewed towards SANCHO results in simulations where the sequence of gas generation was significantly different from the SANCHO gas-generation rate histories used for closure calibration. This limitation in the pressure lines method is most pronounced at higher gas-generation rates and is relatively insignificant at lower gas-generation rates. Due to its relative simplicity, the pressure lines method is easier to implement in multiphase flow codes and simulations have a shorter execution time

  10. Method of adiabatic modes in research of smoothly irregular integrated optical waveguides: zero approximation

    International Nuclear Information System (INIS)

    We consider the application of the method of adiabatic waveguide modes for calculating the propagation of electromagnetic radiation in three-dimensional (3D) irregular integrated optical waveguides. The method of adiabatic modes takes into account a three-dimensional distribution of quasi-waveguide modes and explicit ('inclined') tangential boundary conditions. The possibilities of the method are demonstrated on the example of numerical research of two major elements of integrated optics: a waveguide of 'horn' type and a thin-film generalised waveguide Luneburg lens by the methods of adiabatic modes and comparative waveguides. (integral optical waveguides)

  11. Application of the coupled cluster method to the Jaynes-Cummings model without the rotating-wave approximation

    OpenAIRE

    Bishop, RF; Davidson, NJ; Quick, RM and van der Walt, DM

    1996-01-01

    We investigate the Rabi Hamiltonian (or the Jaynes-Cummings model without the rotating-wave approximation), describing the coupling of a single mode of electromagnetic radiation to a two-level system, by means of the coupled cluster method. We find strong evidence for a second-order quantum phase transition.

  12. An approximation method for the stabilizing solution of the Hamilton-Jacobi equation for integrable systems using Hamiltonian perturbation theory

    NARCIS (Netherlands)

    Sakamoto, Noboru; Schaft, Arjan J. van der

    2006-01-01

    In this report, a method for approximating the stabilizing solution of the Hamilton-Jacobi equation for integrable systems is proposed using symplectic geometry and a Hamiltonian perturbation technique. Using the fact that the Hamiltonian lifted system of an integrable system is also integrable, the

  13. An approximating method for the stabilizing solution of the Hamilton-Jacobi equation for integrable systems using Hamiltonian perturbation theory

    NARCIS (Netherlands)

    Sakamoto, N.; Schaft, van der A.J.

    2006-01-01

    In this report, a method for approximating the stabilizing solution of the Hamilton-Jacobi equation for integrable systems is proposed using symplectic geometry and a Hamiltonian perturbation technique. Using the fact that the Hamiltonian lifted system of an integrable system is also integrable, the

  14. Variational approximation of flux in conforming finite element methods for elliptic partial differential equations: a model problem

    OpenAIRE

    Brezzi, Franco; Hughes, T.J.R.; Suli, Endre

    2001-01-01

    We consider the approximation of elliptic boundary value problems by conforming finite element methods. A model problem, the Poisson equation with Dirichlet boundary conditions, is used to examine the convergence behavior of flux defined on an internal boundary which splits the domain in two. A variational definition of flux, designed to satisfy local conservation laws, is shown to lead to improved rates of convergence.

  15. Viscosity Approximation Methods for Generalized Mixed Equilibrium Problems and Fixed Points of a Sequence of Nonexpansive Mappings

    Directory of Open Access Journals (Sweden)

    Zhao Chang-Wen

    2008-01-01

    Full Text Available We introduce an iterative scheme by the viscosity approximation method for finding a common element of the set of common solutions for generalized mixed equilibrium problems and the set of common fixed points of a sequence of nonexpansive mappings in Hilbert spaces. We show a strong convergence theorem under some suitable conditions.

  16. Viscosity Approximation Methods for Generalized Mixed Equilibrium Problems and Fixed Points of a Sequence of Nonexpansive Mappings

    Directory of Open Access Journals (Sweden)

    Chang-Wen Zhao

    2008-12-01

    Full Text Available We introduce an iterative scheme by the viscosity approximation method for finding a common element of the set of common solutions for generalized mixed equilibrium problems and the set of common fixed points of a sequence of nonexpansive mappings in Hilbert spaces. We show a strong convergence theorem under some suitable conditions.

  17. Method for approximate determination of the roots of a cubic equation with positive coefficients and complex conjugate roots

    International Nuclear Information System (INIS)

    A method for approximate determination of roots of a cubic equation that has one real and two complex-conjugate roots and satisfies the conditions of stability has been proposed. The formulas obtained are quite accurate, simple, and convenient for analysis and optimization of systems and objects

  18. Relations between Inductive Reasoning and Deductive Reasoning

    Science.gov (United States)

    Heit, Evan; Rotello, Caren M.

    2010-01-01

    One of the most important open questions in reasoning research is how inductive reasoning and deductive reasoning are related. In an effort to address this question, we applied methods and concepts from memory research. We used 2 experiments to examine the effects of logical validity and premise-conclusion similarity on evaluation of arguments.…

  19. Biases in approximate solution to the criticality problem and alternative Monte Carlo method

    International Nuclear Information System (INIS)

    The solution to the problem of criticality for the neutron transport equation using the source iteration method is addressed. In particular, the question of convergence of the iterations is examined. It is concluded that slow convergence problems will occur in cases where the optical thickness of the space region in question is large. Furthermore it is shown that in general, the final result of the iterative process is strongly affected by an insufficient accuracy of the individual iterations. To avoid these problems, a modified method of the solution is suggested. This modification is based on the results of the theory of positive operators. The criticality problem is solved by means of the Monte Carlo method by constructing special random variables so that the differences between the observed and exact results are arbitrarily small. The efficiency of the method is discussed and some numerical results are presented

  20. High order filtering methods for approximating hyberbolic systems of conservation laws

    Science.gov (United States)

    Lafon, F.; Osher, S.

    1990-01-01

    In the computation of discontinuous solutions of hyperbolic systems of conservation laws, the recently developed essentially non-oscillatory (ENO) schemes appear to be very useful. However, they are computationally costly compared to simple central difference methods. A filtering method which is developed uses simple central differencing of arbitrarily high order accuracy, except when a novel local test indicates the development of spurious oscillations. At these points, the full ENO apparatus is used, maintaining the high order of accuracy, but removing spurious oscillations. Numerical results indicate the success of the method. High order of accuracy was obtained in regions of smooth flow without spurious oscillations for a wide range of problems and a significant speed up of generally a factor of almost three over the full ENO method.

  1. Finite Difference Approximation for Linear Stochastic Partial Differential Equations with Method of Lines

    OpenAIRE

    McDonald, Stuart

    2006-01-01

    A stochastic partial differential equation, or SPDE, describes the dynamics of a stochastic process defined on a space-time continuum. This paper provides a new method for solving SPDEs based on the method of lines (MOL). MOL is a technique that has largely been used for numerically solving deterministic partial differential equations (PDEs). MOL works by transforming the PDE into a system of ordinary differential equations (ODEs) by discretizing the spatial dimension of the PDE. The resultin...

  2. EMPIRICAL COMPARISON OF VARIOUS APPROXIMATE ESTIMATORS OF THE VARIANCE OF HORVITZ THOMPSON ESTIMATOR UNDER SPLIT METHOD OF SAMPLING

    Directory of Open Access Journals (Sweden)

    Neeraj Tiwari

    2014-06-01

    Full Text Available Under inclusion probability proportional to size (IPPS sampling, the exact secondorder inclusion probabilities are often very difficult to obtain, and hence variance of the Horvitz- Thompson estimator and Sen-Yates-Grundy estimate of the variance of Horvitz-Thompson estimator are difficult to compute. Hence the researchers developed some alternative variance estimators based on approximations of the second-order inclusion probabilities in terms of the first order inclusion probabilities. We have numerically compared the performance of the various alternative approximate variance estimators using the split method of sample selection

  3. Novel diagrammatic method for computing transport coefficients - beyond the Boltzmann approximation

    International Nuclear Information System (INIS)

    We propose a novel diagrammatic method for computing transport coefficients in relativistic quantum field theory. Our method is based on a reformulation and extension of the diagrammatic method by Eliashberg given in the imaginary-time formalism to the relativistic quantum field theory in the real-time formalism, in which the cumbersome analytical continuation problem can be avoided. The transport coefficients are obtained from a two-point function via Kubo formula. It is know that naive perturbation theory breaks down owing to a so called pinch singularity, and hence a resummation is required for getting a finite and sensible result. As a novel resummation method, we first decompose the two point function into the singular part and the regular part, and then reconstruct the diagrams. We find that a self-consistent equation for the two-point function has the same structure as the linearized Boltzmann equation. It is known that the two-point function at the leading order is equivalent to the linearized Boltzmann equation. We find the higher order corrections are nicely summarized as a renormalization of the vertex function, spectral function, and collision term. We also discuss the critical behavior of the transport coefficients near a phase transition, applying our method. (author)

  4. Iterative and direct methods employing distributed approximating functionals for the reconstruction of a potential energy surface from its sampled values

    Science.gov (United States)

    Szalay, Viktor

    1999-11-01

    The reconstruction of a function from knowing only its values on a finite set of grid points, that is the construction of an analytical approximation reproducing the function with good accuracy everywhere within the sampled volume, is an important problem in all branches of sciences. One such problem in chemical physics is the determination of an analytical representation of Born-Oppenheimer potential energy surfaces by ab initio calculations which give the value of the potential at a finite set of grid points in configuration space. This article describes the rudiments of iterative and direct methods of potential surface reconstruction. The major new results are the derivation, numerical demonstration, and interpretation of a reconstruction formula. The reconstruction formula derived approximates the unknown function, say V, by linear combination of functions obtained by discretizing the continuous distributed approximating functional (DAF) approximation of V over the grid of sampling. The simplest of contracted and ordinary Hermite-DAFs are shown to be sufficient for reconstruction. The linear combination coefficients can be obtained either iteratively or directly by finding the minimal norm least-squares solution of a linear system of equations. Several numerical examples of reconstructing functions of one and two variables, and very different shape are given. The examples demonstrate the robustness, high accuracy, as well as the caveats of the proposed method. As to the mathematical foundation of the method, it is shown that the reconstruction formula can be interpreted as, and in fact is, frame expansion. By recognizing the relevance of frames in determining analytical approximation to potential energy surfaces, an extremely rich and beautiful toolbox of mathematics has come to our disposal. Thus, the simple reconstruction method derived in this paper can be refined, extended, and improved in numerous ways.

  5. Informing Tobacco Cessation Benefit Use Interventions for Unionized Blue-Collar Workers: A Mixed-Methods Reasoned Action Approach.

    Science.gov (United States)

    Yzer, Marco; Weisman, Susan; Mejia, Nicole; Hennrikus, Deborah; Choi, Kelvin; DeSimone, Susan

    2015-08-01

    Blue-collar workers typically have high rates of tobacco use but low rates of using tobacco cessation resources available through their health benefits. Interventions to motivate blue-collar tobacco users to use effective cessation support are needed. Reasoned action theory is useful in this regard as it can identify the beliefs that shape tobacco cessation benefit use intentions. However, conventional reasoned action research cannot speak to how those beliefs can best be translated into intervention messages. In the present work, we expand the reasoned action approach by adding additional qualitative inquiry to better understand blue-collar smokers' beliefs about cessation benefit use. Across three samples of unionized blue-collar tobacco users, we identified (1) the 35 attitudinal, normative, and control beliefs that represented tobacco users' belief structure about cessation benefit use; (2) instrumental attitude as most important in explaining cessation intention; (3) attitudinal beliefs about treatment options' efficacy, health effects, and monetary implications of using benefits as candidates for message design; (4) multiple interpretations of cessation beliefs (e.g., short and long-term health effects); and (5) clear implications of these interpretations for creative message design. Taken together, the findings demonstrate how a mixed-method reasoned action approach can inform interventions that promote the use of tobacco cessation health benefits. PMID:25975798

  6. On Approximate Analytical Solutions of Nonlinear Vibrations of Inextensible Beams using Parameter-Expansion Method

    DEFF Research Database (Denmark)

    Kimiaeifar, Amin; Lund, Erik; Thomsen, Ole Thybo; Barari, Amin

    2010-01-01

    In this work, an analytical method, which is referred to as Parameter-expansion Method is used to obtain the exact solution for the problem of nonlinear vibrations of an inextensible beam. It is shown that one term in the series expansion is sufficient to obtain a highly accurate solution, which is...... valid for the whole domain of the problem. A comparison of the obtained the numerical solution demonstrates that PEM is effective and convenient for solving such problems. After validation of the obtained results, the system response and stability are also discussed....

  7. An approximation method for solution of the coupled channels inverse scattering problem at fixed energy

    International Nuclear Information System (INIS)

    We present a method for the quantum mechanical inverse scattering problem at fixed energy for coupled channels in reactions with particles having internal degrees of freedom. The scattered particles can be excited by a local interaction between the relative motion and the internal dynamics which can be expanded in multipoles. The inverse scattering problem is solved by an extension of the modified Newton-Sabatier method, assuming a special ansatz for the integral kernel in the radial wave function. Application has been made for a hypothetical scattering of two nuclei interacting by a dipole-type interaction. Good agreement between the obtained potentials and the input data is found

  8. High order filtering methods for approximating hyperbolic systems of conservation laws

    Science.gov (United States)

    Lafon, F.; Osher, S.

    1991-01-01

    The essentially nonoscillatory (ENO) schemes, while potentially useful in the computation of discontinuous solutions of hyperbolic conservation-law systems, are computationally costly relative to simple central-difference methods. A filtering technique is presented which employs central differencing of arbitrarily high-order accuracy except where a local test detects the presence of spurious oscillations and calls upon the full ENO apparatus to remove them. A factor-of-three speedup is thus obtained over the full-ENO method for a wide range of problems, with high-order accuracy in regions of smooth flow.

  9. Approximate solutions for the two-dimensional integral transport equation. The critically mixed methods of resolution

    International Nuclear Information System (INIS)

    This work is divided into two part the first part (note CEA-N-2165) deals with the solution of complex two-dimensional transport problems, the second one treats the critically mixed methods of resolution. These methods are applied for one-dimensional geometries with highly anisotropic scattering. In order to simplify the set of integral equation provided by the integral transport equation, the integro-differential equation is used to obtain relations that allow to lower the number of integral equation to solve; a general mathematical and numerical study is presented

  10. An Approximate Method for Calculation of Fluid Force and Response of A Circular Cylinder at Lock-in

    Institute of Scientific and Technical Information of China (English)

    WANG Yi

    2008-01-01

    In this paper, equations calculating lift force of a rigid circular cylinder at lock-in in uniform flow are deduced in detail. Besides, equations calculating the lift force on a long flexible circular cylinder at lock-in are deduced based on mode analysis of a multi-degree freedom system. The simplified forms of these equations are also given. Furthermore, an approximate method to predict the forces and response of rigid circular cylinders and long flexible circular cylinders at lock-in is introduced in the case of low mass-damping ratio. A method to eliminate one deficiency of these equations is introduced. Comparison with experimental results shows the effectiveness of this approximate method.

  11. Methods for determination and approximation of the domain of attraction in the case of autonomous discrete dynamical systems

    Directory of Open Access Journals (Sweden)

    Grigis A

    2006-01-01

    Full Text Available A method for determination and two methods for approximation of the domain of attraction Da(0 of the asymptotically stable zero steady state of an autonomous, ℝ-analytical, discrete dynamical system are presented. The method of determination is based on the construction of a Lyapunov function V, whose domain of analyticity is Da(0. The first method of approximation uses a sequence of Lyapunov functions Vp, which converge to the Lyapunov function V on Da(0. Each Vp defines an estimate Np of Da(0. For any x ∈ Da(0, there exists an estimate which contains x. The second method of approximation uses a ball B(R ⊂ Da(0 which generates the sequence of estimates Mp = f-p(B(R. For any x ∈ Da(0, there exists an estimate which contains x. The cases ||∂0f||<1 and ρ(∂0f < 1 ≤||∂0f|| are treated separately because significant differences occur.

  12. A conjugate direction method for approximating the analytic center of a polytope

    OpenAIRE

    Megiddo Nimrod; Mizuno Shinji; Kojima Masakazu

    1998-01-01

    The analytic center of an -dimensional polytope with a nonempty interior is defined as the unique minimizer of the logarithmic potential function over . It is shown that one cycle of a conjugate direction method, applied to the potential function at any such that , generates a point such that .

  13. On the approximation of a nonlinear aeroelastic problem by finite elment method

    Czech Academy of Sciences Publication Activity Database

    Sváček, P.; Horáček, Jaromír

    Cambridge, USA : Massachusetts Institute of Technology, 2007. s. 39-39. [Fourth M.I.T. Conference on Computational Fluid and Solid Mechanics. 13.06.2007-15.06.2007, Cambridge] R&D Projects: GA AV ČR IAA200760613 Institutional research plan: CEZ:AV0Z20760514 Keywords : numerical simulations * aeroelastic instability * ALE method Subject RIV: BI - Acoustics

  14. Comparison of the FORT approximation of the coupling ray theory with the Fourier pseudospectral method

    Czech Academy of Sciences Publication Activity Database

    Pšenčík, Ivan; Farra, V.; Tessmer, E.

    Prague : Charles University, 2011, s. 129-165 R&D Projects: GA ČR(CZ) GAP210/11/0117; GA ČR GA205/08/0332 Institutional research plan: CEZ:AV0Z30120515 Keywords : coupling ray theory * Fourier pseudospectral method * first-order ray tracing Subject RIV: DC - Siesmology, Volcanology, Earth Structure

  15. Comparison of the FORT approximation of the coupling ray theory with the Fourier pseudospectral method

    Czech Academy of Sciences Publication Activity Database

    Pšenčík, Ivan; Farra, V.; Tessmer, E.

    2012-01-01

    Roč. 56, č. 1 (2012), s. 35-64. ISSN 0039-3169 R&D Projects: GA ČR(CZ) GAP210/11/0117 Institutional research plan: CEZ:AV0Z30120515 Keywords : coupling ray theory * Fourier pseudospectral method * first-order ray tracing Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 0.975, year: 2012

  16. Approximation for Transient of Nonlinear Circuits Using RHPM and BPES Methods

    Directory of Open Access Journals (Sweden)

    H. Vazquez-Leal

    2013-01-01

    Full Text Available The microelectronics area constantly demands better and improved circuit simulation tools. Therefore, in this paper, rational homotopy perturbation method and Boubaker Polynomials Expansion Scheme are applied to a differential equation from a nonlinear circuit. Comparing the results obtained by both techniques revealed that they are effective and convenient.

  17. A computational intensive method- Lubrication approximation theory for blade coating process

    Directory of Open Access Journals (Sweden)

    Saira Bhatti

    2016-09-01

    Full Text Available This paper presents the analysis of the process of blade coating through a computational intensive method for an incompressible Newtonian fluid along with Magnetohydrodynamics (MHD. The slip between the substrate and the fluid is also taken into account. The nature of the existing steady solutions has been investigated with the help of exact and numerical methods. Those obtained exact solutions include the solutions for the velocity profiles, volumetric flow rate and pressure gradient. The important engineering quantities like maximum pressure, pressure distribution and load are also computed. It is assumed that the relative velocity between the plate and the fluid is proportional to the shear rate at the plate. An external magnetic field is applied normal to the plates. It is observed and concluded that both slip parameter and the magnetic field parameter serve as the controlling parameters in the industrial blade coating process.

  18. A Discontinuous Galerkin Method for Parabolic Problems with Modified hp-Finite Element Approximation Technique

    Science.gov (United States)

    Kaneko, Hideaki; Bey, Kim S.; Hou, Gene J. W.

    2004-01-01

    A recent paper is generalized to a case where the spatial region is taken in R(sup 3). The region is assumed to be a thin body, such as a panel on the wing or fuselage of an aerospace vehicle. The traditional h- as well as hp-finite element methods are applied to the surface defined in the x - y variables, while, through the thickness, the technique of the p-element is employed. Time and spatial discretization scheme based upon an assumption of certain weak singularity of double vertical line u(sub t) double vertical line 2, is used to derive an optimal a priori error estimate for the current method.

  19. Window-based method for approximating the Hausdorff in three-dimensional range imagery

    Science.gov (United States)

    Koch, Mark W.

    2009-06-02

    One approach to pattern recognition is to use a template from a database of objects and match it to a probe image containing the unknown. Accordingly, the Hausdorff distance can be used to measure the similarity of two sets of points. In particular, the Hausdorff can measure the goodness of a match in the presence of occlusion, clutter, and noise. However, existing 3D algorithms for calculating the Hausdorff are computationally intensive, making them impractical for pattern recognition that requires scanning of large databases. The present invention is directed to a new method that can efficiently, in time and memory, compute the Hausdorff for 3D range imagery. The method uses a window-based approach.

  20. Entropy Viscosity Method for High-Order Approximations of Conservation Laws

    KAUST Repository

    Guermond, J. L.

    2010-09-17

    A stabilization technique for conservation laws is presented. It introduces in the governing equations a nonlinear dissipation function of the residual of the associated entropy equation and bounded from above by a first order viscous term. Different two-dimensional test cases are simulated - a 2D Burgers problem, the "KPP rotating wave" and the Euler system - using high order methods: spectral elements or Fourier expansions. Details on the tuning of the parameters controlling the entropy viscosity are given. © 2011 Springer.

  1. On application of finite element method for approximation of 3D flow problems

    Czech Academy of Sciences Publication Activity Database

    Sváček, P.; Horáček, Jaromír

    Prague : Institute of Thermomechanics ASCR v. v. i., 2015 - (Šimurda, D.; Bodnár, T.), s. 175-182 ISBN 978-80-87012-55-0. ISSN 2336-5781. [Topical Problems of Fluid Mechanics 2015. Praha (CZ), 11.02.2015-13.02.2015] R&D Projects: GA ČR(CZ) GAP101/11/0207 Institutional support: RVO:61388998 Keywords : aeroelasticity * finite element method * NACA 0015 airfoil Subject RIV: BI - Acoustics

  2. Numerical Methods for Chemically Reacting Fluid Flow Computation under Low-Mach Number Approximation

    OpenAIRE

    Arima, Toshiyuki

    2006-01-01

    A mathematical model of environmental fluid is presented to describe fluid flow motions with large density variations. Moreover the associated numerical methods are discussed. The model of environmental fluid is formulated as an unsteady low-Mach number flow based on the compressible Navier-Stokes equations. For low-Mach number flows, the acoustic effects are assumed to be weak relative to the advection effects. Under this assumption, detailed acoustic effects can be removed fr...

  3. Comparison of three approximations to the linear-linear nodal transport method in weighted diamond-difference form

    International Nuclear Information System (INIS)

    Two previously derived approximations to the linear-linear nodal transport method, the linear-nodal (LN) and the linear-linear (LL) methods, are reexamined, together with a new approximation, the bilinear (BL) method, that takes into account the bilinear nodal flux moment. The three methods differ in the degree of analyticity retained in the final discrete variable equations; however, they all possess the very high accuracy characteristic of nodal methods. Unlike previous work, the final equations are manipulated and cast in the form of the classical weighted diamond-difference (WDD) equations (not just a WDD algorithm). This makes them simple to implement in a computer code, especially for those users who have experience with WDD algorithms. Other algorithms, such as the nodal algorithm, also can be used to solve the WDD-form equations. A computer program that solves two-dimensional transport problems using the LN, LL, or the BL method is used to solve three test problems. The results are used to confirm our algebraic manipulations of the nodal equations and also to compare the performance of the three methods from the computational, as well as the theoretical, point of view. The three methods are found to have comparable accuracies for the problems studies, especially on meshes that are sufficiently fine

  4. Drug utilization according to reason for prescribing: a pharmacoepidemiologic method based on an indication hierarchy

    DEFF Research Database (Denmark)

    Kildemoes, Helle Wallach; Hendriksen, Carsten; Morten, Andersen

    2011-01-01

    ABSTRACT Purpose To develop a pharmacoepidemiologic method for drug utilization analysis according to indication, gender, and age by means of register-based information. Statin utilization in 2005 was applied as an example. Methods Following the recommendations for statin therapy, we constructed an...... indication hierarchy with eight mutually exclusive levels of register markers of cardiovascular disease and diabetes. Danish residents, as of January 1, 1996, were followed at the individual level in nationwide registers with respect to dispensed prescriptions of cardiovascular drugs and antidiabetics (1996...... prescription patterns of statins. The method can be implemented for other drug categories and could be useful for studying trends in drug utilization, differential drug adherence, and cross-national comparisons...

  5. A fast method for approximate registration of whole-slide images of serial sections using local curvature

    Science.gov (United States)

    Trahearn, Nicholas; Epstein, David; Snead, David; Cree, Ian; Rajpoot, Nasir

    2014-03-01

    We present a method for fast, approximate registration of whole-slide images (WSIs) of histopathology serial sections. Popular histopathology slide registration methods in the existing literature tend towards intensity-based approaches.1, 2 Further input, in the form of an approximate initial transformation to be applied to one of the two WSIs, is then usually required, and this transformation needs to be optimised. Such a transformation is not readily available in this context and thus there is a need for fast approximation of these parameters. Fast registration is achieved by comparison of the external boundaries of adjacent tissue sections, using local curvature on multiple scales to assess similarity. Our representation of curvature is a modified version of the Curvature Scale Space (CSS)3 image. We substitute zero crossings with signed local absolute maxima of curvature to improve the registration's robustness to the subtle morphological differences of adjacent sections. A pairwise matching is made between curvature maxima at scales increasing exponentially, the matching minimizes the distance between maxima pairs at each scale. The boundary points corresponding to the matched maxima pairs are used to estimate the desired transformation. Our method is highly robust to translation, rotation, and linear scaling, and shows good performance in cases of moderate non-linear scaling. On our set of test images the algorithm shows improved reliability and processing speed in comparison to existing CSS based registration methods.

  6. A Perceptually Reweighted Mixed-Norm Method for Sparse Approximation of Audio Signals

    DEFF Research Database (Denmark)

    Christensen, Mads Græsbøll; Sturm, Bob L.

    In this paper, we consider the problem of finding sparse representations of audio signals for coding purposes. In doing so, it is of utmost importance that when only a subset of the present components of an audio signal are extracted, it is the perceptually most important ones. To this end, we...... using standard software. A prominent feature of the new method is that it solves a problem that is closely related to the objective of coding, namely rate-distortion optimization. In computer simulations, we demonstrate the properties of the algorithm and its application to real audio signals....

  7. Linewidth of Cyclotron Absorption in Band-Gap Graphene: Relaxation Time Approximation vs. Monte Carlo Method

    Directory of Open Access Journals (Sweden)

    S.V. Kryuchkov

    2015-03-01

    Full Text Available The power of the elliptically polarized electromagnetic radiation absorbed by band-gap graphene in presence of constant magnetic field is calculated. The linewidth of cyclotron absorption is shown to be non-zero even if the scattering is absent. The calculations are performed analytically with the Boltzmann kinetic equation and confirmed numerically with the Monte Carlo method. The dependence of the linewidth of the cyclotron absorption on temperature applicable for a band-gap graphene in the absence of collisions is determined analytically.

  8. Foundation of the semiclassical approximation by means of path integral methods

    International Nuclear Information System (INIS)

    The aim of our study is to find a technically unique semiclassical treatment to describe the collision processes between heavy ions. Thereby it shall be started from a complete quantum mechanical formulation of the collision process. This aim requires: 1. A completely quantum mechanical initial formulation for the whole system, 2. a unique and conceptually clear transition to semiclassics. In order to fulfil the requirements a method is offered which is in closest connection with the Feynman propagator respectively influence functional. (orig./HSI)

  9. Approximate natural vibration analysis of rectangular plates with openings using assumed mode method

    Science.gov (United States)

    Cho, Dae Seung; Vladimir, Nikola; Choi, Tae MuK

    2013-09-01

    Natural vibration analysis of plates with openings of different shape represents an important issue in naval architecture and ocean engineering applications. In this paper, a procedure for vibration analysis of plates with openings and arbitrary edge constraints is presented. It is based on the assumed mode method, where natural frequencies and modes are determined by solving an eigenvalue problem of a multi-degree-of-freedom system matrix equation derived by using Lagrange's equations of motion. The presented solution represents an extension of a procedure for natural vibration analysis of rectangular plates without openings, which has been recently presented in the literature. The effect of an opening is taken into account in an intuitive way, i.e. by subtracting its energy from the total plate energy without opening. Illustrative numerical examples include dynamic analysis of rectangular plates with rectangular, elliptic, circular as well as oval openings with various plate thicknesses and different combinations of boundary conditions. The results are compared with those obtained by the finite element method (FEM) as well as those available in the relevant literature, and very good agreement is achieved.

  10. An approximate method for lateral stability analysis of wall-frame buildings including shear deformations of walls

    Indian Academy of Sciences (India)

    Kanat Burak Bozdogan; Duygu Ozturk

    2010-06-01

    This study presents an approximate method based on the continuum approach and transfer matrix method for lateral stability analysis of buildings. In this method, the whole structure is idealized as an equivalent sandwich beam which includes all deformations. The effect of shear deformations of walls has been taken into consideration and incorporated in the formulation of the governing equations. Initially the stability differential equation of this equivalent sandwich beam is presented, and then shape functions for each storey is obtained by the solution of the differential equations. By using boundary conditions and stability storey transfer matrices obtained by shape functions, system buckling load can be calculated. To verify the presented method, four numerical examples have been solved. The results of the samples demonstrate the agreement between the presented method and the other methods given in the literature.

  11. Linear interpolation method in ensemble Kohn-Sham and range-separated density-functional approximations for excited states

    CERN Document Server

    Senjean, Bruno; Jensen, Hans Jørgen Aa; Fromager, Emmanuel

    2015-01-01

    The computation of excitation energies in range-separated ensemble density-functional theory (DFT) is discussed. The latter approach is appealing as it enables the rigorous formulation of a multi-determinant state-averaged DFT method. In the exact theory, the short-range density functional, that complements the long-range wavefunction-based ensemble energy contribution, should vary with the ensemble weights even when the density is held fixed. This weight dependence ensures that the range-separated ensemble energy varies linearly with the ensemble weights. When the (weight-independent) ground-state short-range exchange-correlation functional is used in this context, curvature appears thus leading to an approximate weight-dependent excitation energy. In order to obtain unambiguous approximate excitation energies, we simply propose to interpolate linearly the ensemble energy between equiensembles. It is shown that such a linear interpolation method (LIM) effectively introduces weight dependence effects. LIM has...

  12. Domain decomposition method for nonconforming finite element approximations of anisotropic elliptic problems on nonmatching grids

    Energy Technology Data Exchange (ETDEWEB)

    Maliassov, S.Y. [Texas A& M Univ., College Station, TX (United States)

    1996-12-31

    An approach to the construction of an iterative method for solving systems of linear algebraic equations arising from nonconforming finite element discretizations with nonmatching grids for second order elliptic boundary value problems with anisotropic coefficients is considered. The technique suggested is based on decomposition of the original domain into nonoverlapping subdomains. The elliptic problem is presented in the macro-hybrid form with Lagrange multipliers at the interfaces between subdomains. A block diagonal preconditioner is proposed which is spectrally equivalent to the original saddle point matrix and has the optimal order of arithmetical complexity. The preconditioner includes blocks for preconditioning subdomain and interface problems. It is shown that constants of spectral equivalence axe independent of values of coefficients and mesh step size.

  13. The investigation of the 2 decay by Pyatov method within quasiparticle random phase approximation formalism

    Indian Academy of Sciences (India)

    S Unlu; T Babacan; N Cakmak; C Selam

    2008-09-01

    The violated commutation condition between the total shell model Hamiltonian and Gamow–Teller operator (GT) has been restored by Pyatov method (PM). The considered nuclear model Hamiltonian in PM includes the separable GT residual interaction in ph and pp channels and is differentiated from the traditional schematic model by ℎ0 (restoration term). The influence of the h0 effective interaction on the 2 decay of 48Ca, 76Ge, 82Se, 96Zr, 100Mo, 116Cd, 128,130Te and 136Xe is investigated. All the calculations have been done within the framework of standard QRPA. The results obtained by PM are compared with those of other approaches and experimental data. The influence of the restoration term on the stability of the 2 decay nuclear matrix elements is analysed.

  14. Mystery shoppers test the reference service in a public library. Reasons, methods and results

    OpenAIRE

    Simon, Ingeborg; Bertele, Maria; Müller, Solveig; Obermeier, Ilona; Zelch, Ute

    2010-01-01

    The reference service is becoming a marketing tool for libraries which should be used, verified and improved. One way to evaluate this service is the method of “mystery shopping”, which allows to test the quality of the reference service and in particular the quality of interaction at the service desk. The results show the need for quality improvements. Quality can be improved for example by providing training to enhance communication skills, by rearranging the service desks and by developing...

  15. A formalism and method for representing and reasoning with process models authored by subject matter experts

    OpenAIRE

    Gómez-Pérez, José Manuel; Erdmann, M; Greaves, M; Corcho, Oscar

    2013-01-01

    Enabling Subject Matter Experts (SMEs) to formulate knowledge without the intervention of Knowledge Engineers (KEs) requires providing SMEs with methods and tools that abstract the underlying knowledge representation and allow them to focus on modeling activities. Bridging the gap between SME-authored models and their representation is challenging, especially in the case of complex knowledge types like processes, where aspects like frame management, data, and control flow need to be addressed...

  16. Application and evaluation of inductive reasoning methods for the semantic web and software analysis

    OpenAIRE

    Kiefer, Christoph; Bernstein, Abraham

    2011-01-01

    Exploiting the complex structure of relational data enables to build better models by taking into account the additional information provided by the links between objects. We extend this idea to the Semantic Web by introducing our novel SPARQL-ML approach to perform data mining for Semantic Web data. Our approach is based on traditional SPARQL and statistical relational learning methods, such as Relational Probability Trees and Relational Bayesian Classifiers. We analyze our approach thorough...

  17. An Approximate Bayesian Method Applied to Estimating the Trajectories of Four British Grey Seal (Halichoerus grypus) Populations from Pup Counts

    OpenAIRE

    Mike Lonergan; Dave Thompson; Len Thomas; Callan Duck

    2011-01-01

    1. For British grey seals, as with many pinniped species, population monitoring is implemented by aerial surveys of pups at breeding colonies. Scaling pup counts up to population estimates requires assumptions about population structure; this is straightforward when populations are growing exponentially, but not when growth slows, since it is unclear whether density dependence affects pup survival or fecundity. 2. We present an approximate Bayesian method for fitting pup trajectories, estimat...

  18. Comparison of the analytical approximation formula and Newton's method for solving a class of nonlinear Black-Scholes parabolic equations

    OpenAIRE

    Duris, Karol; Tan, Shih-Hau; Lai, Choi-Hong; Sevcovic, Daniel

    2015-01-01

    Market illiquidity, feedback effects, presence of transaction costs, risk from unprotected portfolio and other nonlinear effects in PDE based option pricing models can be described by solutions to the generalized Black-Scholes parabolic equation with a diffusion term nonlinearly depending on the option price itself. Different linearization techniques such as Newton's method and analytic asymptotic approximation formula are adopted and compared for a wide class of nonlinear Black-Scholes equat...

  19. An efficient wavelet based approximation method for a few second order differential equations arising in science and engineering

    OpenAIRE

    Padma, S; G. Hariharan; Kannan, K.

    2013-01-01

    A new wavelet based approximation method for solving the second order differential equations arising science and engineering is presented in this paper. Such differential equation is often applied to model phenomena in various fields of science and engineering. In this study, shifted second kind Chebyshev wavelet (CW) operational matrices of derivatives is introduced and applied for solvingthe second order differential equations with various initial conditions. The key idea for getting the nu...

  20. Heuristic reasoning

    CERN Document Server

    2015-01-01

    How can we advance knowledge? Which methods do we need in order to make new discoveries? How can we rationally evaluate, reconstruct and offer discoveries as a means of improving the ‘method’ of discovery itself? And how can we use findings about scientific discovery to boost funding policies, thus fostering a deeper impact of scientific discovery itself? The respective chapters in this book provide readers with answers to these questions. They focus on a set of issues that are essential to the development of types of reasoning for advancing knowledge, such as models for both revolutionary findings and paradigm shifts; ways of rationally addressing scientific disagreement, e.g. when a revolutionary discovery sparks considerable disagreement inside the scientific community; frameworks for both discovery and inference methods; and heuristics for economics and the social sciences.

  1. Metacognition and reasoning

    OpenAIRE

    Fletcher, Logan; Carruthers, Peter

    2012-01-01

    This article considers the cognitive architecture of human meta-reasoning: that is, metacognition concerning one's own reasoning and decision-making. The view we defend is that meta-reasoning is a cobbled-together skill comprising diverse self-management strategies acquired through individual and cultural learning. These approximate the monitoring-and-control functions of a postulated adaptive system for metacognition by recruiting mechanisms that were designed for quite other purposes.

  2. A Viscosity of Cesàro Mean Approximation Methods for a Mixed Equilibrium, Variational Inequalities, and Fixed Point Problems

    Directory of Open Access Journals (Sweden)

    Jitpeera Thanyarat

    2011-01-01

    Full Text Available We introduce a new iterative method for finding a common element of the set of solutions for mixed equilibrium problem, the set of solutions of the variational inequality for a -inverse-strongly monotone mapping, and the set of fixed points of a family of finitely nonexpansive mappings in a real Hilbert space by using the viscosity and Cesàro mean approximation method. We prove that the sequence converges strongly to a common element of the above three sets under some mind conditions. Our results improve and extend the corresponding results of Kumam and Katchang (2009, Peng and Yao (2009, Shimizu and Takahashi (1997, and some authors.

  3. Uncertainties and biases arising from methods approximations: the calculation of reaction rates in the PCA 8/7 configuration

    International Nuclear Information System (INIS)

    In the determination of the energy spectrum of the neutron fluxes at the surveillance and 1/4 T positions of LWRs by analyzing measured reaction rates, a calculation of these fluxes is both useful and informative in guiding the unfolding, regardless of the particular unfolding procedure used. It should thus be an important part of any unfolding procedure to be able to calculate not only the fluxes but also to estimate both the corrections to this calculation arising from various methods approximations and the uncertainties in these corrections. In at least one unfolding procedure, that utilizing a generalized least squares technique, knowledge of all uncertainties including those arising from calculational methods approximations is an essential part of the input. The particular problem addressed in this paper is the estimation of some correction factors (i.e., biases or bias factors) and their uncertainties arising from various approximations used in calculating the fluxes and reaction rates in the Pool Critical Assembly (PCA) at Oak Ridge for the 8/7 configuration. In addition, the uncertainties in the calculated fluxes and reaction rates arising as the result of uncertainties in the non-nuclear data input was investigated

  4. An efficient wavelet based approximation method for a few second order differential equations arising in science and engineering

    Directory of Open Access Journals (Sweden)

    S.Padma

    2013-06-01

    Full Text Available A new wavelet based approximation method for solving the second order differential equations arising science and engineering is presented in this paper. Such differential equation is often applied to model phenomena in various fields of science and engineering. In this study, shifted second kind Chebyshev wavelet (CW operational matrices of derivatives is introduced and applied for solvingthe second order differential equations with various initial conditions. The key idea for getting the numerical solutions for these equations is to convert the differential equations (linear or nonlinear to a system of linear or nonlinear algebraic equations in the unknown expansion coefficients. Some illustrative examples are given to demonstrate the validity and applicability of the proposed method. The power of the manageable method is confirmed. Moreover the use of the shifted second kind Chebyshev wavelet method (CWM is found to be simple, flexible, efficient, small computation costs and computationally attractive.

  5. Approximate solution for nonlinear model of the second and half order reactions in porous catalyst by decomposition method

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The problem of the process of coupled diffusion and reaction in catalyst pellets is considered for the case of second and half order reactions. The Adomian decomposition method is used to solve the non-linear model. For the second, half and first order reactions, analytical approximate solutions are obtained. The variation of reactant concentration in the catalyst pellet and the effectiveness factors at φ<10 are determined and compared with those by the BAND's finite difference numerical method developed by Newman. At lower values of φ, the decomposition solution with 3 terms gives satisfactory agreement with the numerical solution; at higher values of φ, as the term number in the decomposition method is increased, an acceptable agreement between the two methods is achieved. In general, the solution with 6 terms gives a satisfactory agreement.

  6. A holistic method to assess building energy efficiency combining D-S theory and the evidential reasoning approach

    International Nuclear Information System (INIS)

    The assessment of building energy efficiency is one of the most effective measures for reducing building energy consumption. This paper proposes a holistic method (HMEEB) for assessing and certifying energy efficiency of buildings based on the D-S (Dempster-Shafer) theory of evidence and the Evidential Reasoning (ER) approach. HMEEB has three main features: (i) it provides both a method to assess and certify building energy efficiency, and exists as an analytical tool to identify improvement opportunities; (ii) it combines a wealth of information on building energy efficiency assessment, including identification of indicators and a weighting mechanism; and (iii) it provides a method to identify and deal with inherent uncertainties within the assessment procedure. This paper demonstrates the robustness, flexibility and effectiveness of the proposed method, using two examples to assess the energy efficiency of two residential buildings, both located in the ‘Hot Summer and Cold Winter’ zone in China. The proposed certification method provides detailed recommendations for policymakers in the context of carbon emission reduction targets and promoting energy efficiency in the built environment. The method is transferable to other countries and regions, using an indicator weighting system to modify local climatic, economic and social factors. - Highlights: ► Assessing energy efficiency of buildings holistically; ► Applying the D-S (Dempster-Shafer) theory of evidence and the Evidential Reasoning (ER) approach; ► Involving large information and uncertainties in the energy efficiency decision-making process. ► rigorous measures for policymakers to meet carbon emission reduction targets.

  7. Developpement of a numerical method for Navier-Stokes equations in anelastic approximation: application to Rayleigh-Taylor instabilities

    International Nuclear Information System (INIS)

    The 'anelastic' approximation allows us to filter the acoustic waves thanks to an asymptotic development of the Navier-Stokes equations, so increasing the averaged time step, during the numerical simulation of hydrodynamic instabilities development. So, the anelastic equations for a two fluid mixture in case of Rayleigh-Taylor instability are established.The linear stability of Rayleigh-Taylor flow is studied, for the first time, for perfect fluids in the anelastic approximation. We define the Stokes problem resulting from Navier-Stokes equations without the non linear terms (a part of the buoyancy is considered); the ellipticity is demonstrated, the Eigenmodes and the invariance related to the pressure are detailed. The Uzawa's method is extended to the anelastic approximation and shows the decoupling speeds in 3D, the particular case k = 0 and the spurious modes of pressure. Passing to multi-domain allowed to establish the transmission conditions.The algorithms and the implementation in the existing program are validated by comparing the Uzawa's operator in Fortran and Mathematica languages, to an experiment with incompressible fluids and results from anelastic and compressible numerical simulations. The study of the influence of the initial stratification of both fluids on the development of the Rayleigh-Taylor instability is initiated. (author)

  8. An Approximate Bayesian Method Applied to Estimating the Trajectories of Four British Grey Seal (Halichoerus grypus Populations from Pup Counts

    Directory of Open Access Journals (Sweden)

    Mike Lonergan

    2011-01-01

    Full Text Available For British grey seals, as with many pinniped species, population monitoring is implemented by aerial surveys of pups at breeding colonies. Scaling pup counts up to population estimates requires assumptions about population structure; this is straightforward when populations are growing exponentially but not when growth slows, since it is unclear whether density dependence affects pup survival or fecundity. We present an approximate Bayesian method for fitting pup trajectories, estimating adult population size and investigating alternative biological models. The method is equivalent to fitting a density-dependent Leslie matrix model, within a Bayesian framework, but with the forms of the density-dependent effects as outputs rather than assumptions. It requires fewer assumptions than the state space models currently used and produces similar estimates. We discuss the potential and limitations of the method and suggest that this approach provides a useful tool for at least the preliminary analysis of similar datasets.

  9. A Neurodynamic Optimization Method for Recovery of Compressive Sensed Signals With Globally Converged Solution Approximating to l0 Minimization.

    Science.gov (United States)

    Guo, Chengan; Yang, Qingshan

    2015-07-01

    Finding the optimal solution to the constrained l0 -norm minimization problems in the recovery of compressive sensed signals is an NP-hard problem and it usually requires intractable combinatorial searching operations for getting the global optimal solution, unless using other objective functions (e.g., the l1 norm or lp norm) for approximate solutions or using greedy search methods for locally optimal solutions (e.g., the orthogonal matching pursuit type algorithms). In this paper, a neurodynamic optimization method is proposed to solve the l0 -norm minimization problems for obtaining the global optimum using a recurrent neural network (RNN) model. For the RNN model, a group of modified Gaussian functions are constructed and their sum is taken as the objective function for approximating the l0 norm and for optimization. The constructed objective function sets up a convexity condition under which the neurodynamic system is guaranteed to obtain the globally convergent optimal solution. An adaptive adjustment scheme is developed for improving the performance of the optimization algorithm further. Extensive experiments are conducted to test the proposed approach in this paper and the output results validate the effectiveness of the new method. PMID:25122603

  10. Constructing mathematical models for simulating the technological processes in thermal power equipment on the basis of statistical approximation methods

    Science.gov (United States)

    Kolchev, K. K.; Mezin, S. V.

    2015-07-01

    A technique for constructing mathematical models simulating the technological processes in thermal power equipment developed on the basis of the statistical approximation method is described. The considered method was used in the developed software module (plug-in) intended for calculating nonlinear mathematical models of gas turbine units and for diagnosing them. The mathematical models constructed using this module are used for describing the current state of a system. Deviations of the system's actual state from the estimate obtained using the mathematical model point to malfunctions in operation of this system. The multidimensional interpolation and approximation method and the theory of random functions serve as a theoretical basis of the developed technique. By using the developed technique it is possible to construct complex static models of plants that are subject to control and diagnostics. The module developed using the proposed technique makes it possible to carry out periodic diagnostics of the operating equipment for revealing deviations from the normal mode of its operation. The specific features relating to construction of mathematical models are considered, and examples of applying them with the use of observations obtained on the equipment of gas turbine units are given.

  11. Discretizing of linear systems with time-delay Using method of Euler’s and Tustin’s approximations

    Directory of Open Access Journals (Sweden)

    Bemri H’mida

    2015-03-01

    Full Text Available Delays deteriorate the control performance and could destabilize the overall system in the theory of discretetime signals and dynamic systems. Whenever a computer is used in measurement, signal processing or control applications, the data as seen from the computer and systems involved are naturally discrete-time because a computer executes program code at discrete points of time. Theory of discrete-time dynamic signals and systems is useful in design and analysis of control systems, signal filters, state estimators and model estimation from time-series of process data system identification. In this paper, a new approximated discretization method and digital design for control systems with delays is proposed. System is transformed to a discrete-time model with time delays. To implement the digital modeling, we used the z-transfer functions matrix which is a useful model type of discrete-time systems, being analogous to the Laplace-transform for continuous-time systems. The most important use of the z-transform is for defining z-transfer functions matrix is employed to obtain an extended discrete-time. The proposed method can closely approximate the step response of the original continuous timedelayed control system by choosing various of energy loss level. Illustrative example is simulated to demonstrate the effectiveness of the developed method.

  12. Approximate solutions of a time-fractional diffusion equation with a source term using the variational iteration method

    OpenAIRE

    Ali, Iftikhar; Chanane, Bilal; Malik, Nadeem A.

    2014-01-01

    We consider a time fractional differential equation of order $\\alpha$, $0 0, \\quad c(x,0)=f(x). $$ where ${}^C_0\\mathcal{D}_t^{\\alpha}$ is the Caputo fractional derivative of order $\\alpha$, $A$ is a linear differential operator, $q(x,t)$ is a source term, and $f(x)$ is the inital condition. Approximate (truncated) series solutions are obtained by means of the Variational Iteration Method (VIM). We find the series solutions for different cases of the source term, in a form that is readily imp...

  13. FELIX-1.0: A finite element solver for the time dependent generator coordinate method with the Gaussian overlap approximation

    Science.gov (United States)

    Regnier, D.; Verrière, M.; Dubray, N.; Schunck, N.

    2016-03-01

    We describe the software package FELIX that solves the equations of the time-dependent generator coordinate method (TDGCM) in N-dimensions (N ≥ 1) under the Gaussian overlap approximation. The numerical resolution is based on the Galerkin finite element discretization of the collective space and the Crank-Nicolson scheme for time integration. The TDGCM solver is implemented entirely in C++. Several additional tools written in C++, Python or bash scripting language are also included for convenience. In this paper, the solver is tested with a series of benchmarks calculations. We also demonstrate the ability of our code to handle a realistic calculation of fission dynamics.

  14. FELIX-1.0: A finite element solver for the time dependent generator coordinate method with the Gaussian overlap approximation

    CERN Document Server

    Regnier, D; Dubray, N; Schunck, N

    2015-01-01

    We describe the software package FELIX that solves the equations of the time-dependent generator coordinate method (TDGCM) in N-dimensions (N $\\geq$ 1) under the Gaussian overlap approximation. The numerical resolution is based on the Galerkin finite element discretization of the collective space and the Crank-Nicolson scheme for time integration. The TDGCM solver is implemented entirely in C++. Several additional tools written in C++, Python or bash scripting language are also included for convenience. In this paper, the solver is tested with a series of benchmarks calculations. We also demonstrate the ability of our code to handle a realistic calculation of fission dynamics.

  15. Communication: On the consistency of approximate quantum dynamics simulation methods for vibrational spectra in the condensed phase

    International Nuclear Information System (INIS)

    Including quantum mechanical effects on the dynamics of nuclei in the condensed phase is challenging, because the complexity of exact methods grows exponentially with the number of quantum degrees of freedom. Efforts to circumvent these limitations can be traced down to two approaches: methods that treat a small subset of the degrees of freedom with rigorous quantum mechanics, considering the rest of the system as a static or classical environment, and methods that treat the whole system quantum mechanically, but using approximate dynamics. Here, we perform a systematic comparison between these two philosophies for the description of quantum effects in vibrational spectroscopy, taking the Embedded Local Monomer model and a mixed quantum-classical model as representatives of the first family of methods, and centroid molecular dynamics and thermostatted ring polymer molecular dynamics as examples of the latter. We use as benchmarks D2O doped with HOD and pure H2O at three distinct thermodynamic state points (ice Ih at 150 K, and the liquid at 300 K and 600 K), modeled with the simple q-TIP4P/F potential energy and dipole moment surfaces. With few exceptions the different techniques yield IR absorption frequencies that are consistent with one another within a few tens of cm−1. Comparison with classical molecular dynamics demonstrates the importance of nuclear quantum effects up to the highest temperature, and a detailed discussion of the discrepancies between the various methods let us draw some (circumstantial) conclusions about the impact of the very different approximations that underlie them. Such cross validation between radically different approaches could indicate a way forward to further improve the state of the art in simulations of condensed-phase quantum dynamics

  16. Approximating model for multilayer gamma-ray buildup factors by transmission matrix method: Application to point isotropic source geometry

    International Nuclear Information System (INIS)

    An approximating formula recently proposed by the authors for gamma-ray buildup factors of multilayered shields is applied to point isotropic source problems. The formula, which is formulated in vector form with a four-group approximation, handles the gamma-ray energy spectrum directly and uses the transmission and albedo matrices to take gamma-ray transmission and backscattering effects into consideration. The gamma-ray transmission and back-scattering probabilities through a 1-mean-free-path- (mfp-) thick shell depend on the shell curvature. This phenomenon plays an important role in simulating the gamma-ray buildup factor in point isotropic source geometry. In this model, the dependence is described by simplified expressions. The feasibility of the formula for systematically describing the point isotropic buildup factors was tested by using buildup factors calculated by the Monte Carlo method as reference data. The materials used in the tests were water, iron, and lead, and the source energies assumed were 0.5, 1, and 10 MeV. Through the tests, the method was found to reproduce the reference data of double-layered shields of these materials very well. With the same parameters, the buildup factors of three-layered shields are also reproducible. Buildup factors computed with two different group structures were examined to test the adequacy of the energy group structure adopted. The group structure previously adopted was found to be adequate in the energy range of 0.5 to 10 MeV

  17. ROAM: a Radial-basis-function Optimization Approximation Method for diagnosing the three-dimensional coronal magnetic field

    CERN Document Server

    Dalmasse, K; Gibson, S E; Fan, Y; Flyer, N

    2016-01-01

    The Coronal Multichannel Polarimeter (CoMP) routinely performs coronal polarimetric measurements using the Fe XIII 10747 $\\AA$ and 10798 $\\AA$ lines, which are sensitive to the coronal magnetic field. However, inverting such polarimetric measurements into magnetic field data is a difficult task because the corona is optically thin at these wavelengths and the observed signal is therefore the integrated emission of all the plasma along the line of sight. To overcome this difficulty, we take on a new approach that combines a parameterized 3D magnetic field model with forward modeling of the polarization signal. For that purpose, we develop a new, fast and efficient, optimization method for model-data fitting: the Radial-basis-functions Optimization Approximation Method (ROAM). Model-data fitting is achieved by optimizing a user-specified log-likelihood function that quantifies the differences between the observed polarization signal and its synthetic/predicted analogue. Speed and efficiency are obtained by comb...

  18. Proportional reasoning

    DEFF Research Database (Denmark)

    Dole, Shelley; Hilton, Annette; Hilton, Geoff;

    2015-01-01

    Proportional reasoning is widely acknowledged as a key to success in school mathematics, yet students’ continual difficulties with proportion-related tasks are well documented. This paper draws on a large research study that aimed to support 4th to 9th grade teachers to design and implement tasks...... to foster students’ proportional reasoning. Classroom data revealed limited initial teacher knowledge and awareness of the pervasive nature of proportional reasoning required in the mathematics curriculum. Teacher capacity to seize teachable moments for building students’ proportional reasoning...... skills increased throughout the project. From this background, this paper presents an analysis of the proportional reasoning demands and opportunities of topics within the school mathematics curriculum in Australia. Implications for the study of whole number arithmetic (WNA) and other topics to promote...

  19. A POSTERIORI ENERGY-NORM ERROR ESTIMATES FOR ADVECTION-DIFFUSION EQUATIONS APPROXIMATED BY WEIGHTED INTERIOR PENALTY METHODS

    Institute of Scientific and Technical Information of China (English)

    Alexandre Ern; Annette F.Stephansen

    2008-01-01

    We propose and analyze a posteriori energy-norm error estimates for weighted interior penalty discontinuous Galerkin approximations of advection-diffusion-reaction equations with heterogeneous and anisotropic diffusion.The weights,which play a key role in the analysis.depend on the diffusion tensor and are used to formulate the consistency terms in the discontinuous Galerkin method.The error upper bounds,in which all the constants are specified.consist of three terms:a residual estimator which depends only on the elementwise fluctuation of the discrete solution residual,a diffusive flux estimator where the weights used in the method enter explicitly,and a non-conforming estimator which is nonzero because of the use of discontinuous finite element spaces.The three estimators can be bounded locally by the approximation error.A particular attention is given to the dependency on problem parameters of the constants in the local lower error bounds,For moderate advection.it.is shown that full robustness with respect to diffusion heterogeneities is achieved owing to the specific design of the weights in the discontinuous Galerkin method,while diffusion anisotropies remain purely local and impact the constants through the square root of the condition number of the diffusion tensor.For dominant advection,the local lower error bounds can be written with constants involving a cut-off for the ratio of local mesh size to the reciprocal of the square root of the lowest local eignevalue of the diffusion tensor.

  20. An approximate semi-analytical method for prediction of interlaminar shear stresses in an arbitrarily laminated thick plate

    Science.gov (United States)

    Chaudhuri, Reaz A.; Seide, Paul

    1987-01-01

    An approximate semianalytical method for determination of interlaminar shear stress distribution through the thickness of an arbitrarily laminated thick plate has been presented. The method is based on the assumptions of transverse inextensibility and layerwise constant shear angle theory (LCST) and utilizes an assumed quadratic displacement potential energy based finite element method (FEM). Centroid of the triangular surface has been proved from a rigorous mathematical point of view (Aubin-Nitsche theory), to be the point of exceptional accuracy for the interlaminar shear stresses. Numerical results indicate close agreement with the available three-dimensional elasticity theory solutions. A comparison between the present theory and that due to an assumed stress hybrid FEM suggest that the (normal) traction-free-edge condition is not satisfied in the latter approach. Furthermore, the present paper is the first to present the results for interlaminar shear stresses in a two-layer thick square plate of balanced unsymmetric angle-ply construction. A comparison with the recently proposed Equilibrium Method (EM) indicates the superiority of the present method, because the latter assures faster convergence as well as simultaneous vanishing of the transverse shear stresses on both of the exposed surfaces of the laminate. Superiority of the present method over the EM, in the case of a symmetric laminate, is limited to faster convergence alone. It has also been demonstrated that the combination of the present method and the reduced (quadratic order) numerical integration scheme yields convergence of the interlaminar shear stresses almost as rapidly as that of the nodal displacements, in the case of a thin plate.

  1. Estimation of geological formation thermal conductivity by using stochastic approximation method based on well-log temperature data

    International Nuclear Information System (INIS)

    Thermal conductivity is a key parameter for evaluating wellbore heat losses which plays an important role in determining the efficiency of steam injection processes. In this study, an unsteady formation heat-transfer model was established and a cost-effective in situ method by using stochastic approximation method based on well-log temperature data was presented. The proposed method was able to estimate the thermal conductivity and the volumetric heat capacity of geological formation simultaneously under the in situ conditions. The feasibility of the present method was assessed by a sample test, the results of which shown that the thermal conductivity and the volumetric heat capacity could be obtained with the relative errors of −0.21% and −0.32%, respectively. In addition, three field tests were conducted based on the easily obtainable well-log temperature data from the steam injection wells. It was found that the relative errors of thermal conductivity for the three field tests were within ±0.6%, demonstrating the excellent performance of the proposed method for calculating thermal conductivity. The relative errors of volumetric heat capacity ranged from −6.1% to −14.2% for the three field tests. Sensitivity analysis indicated that this was due to the low correlation between the volumetric heat capacity and the wellbore temperature, which was used to generate the judgment criterion. -- Highlights: ► A cost-effective in situ method for estimating thermal properties of formation was presented. ► Thermal conductivity and volumetric heat capacity can be estimated simultaneously by the proposed method. ► The relative error of thermal conductivity estimated was within ±0.6%. ► Sensitivity analysis was conducted to study the estimated results of thermal properties.

  2. Energy of a slowly-rotating black hole in Horava-Lifshitz gravity by using approximate Lie symmetry methods

    International Nuclear Information System (INIS)

    The energy content of the Lee-Kim-Myung slowly-rotating black hole (Lee et al., Eur. Phys. J. C 70, 361 (2010)), in the Horava-Lifshitz (HL) theory of gravity is investigated by using approximate Lie symmetry methods for differential equations. The energy of this slowly-rotating black hole in the HL gravity is found to be is rescaled by a r-dependent factor. From the rescaling of energy, the rotation is observed to be added to the mass of the black hole, and this effect decreases with increasing coordinate r. This expression of energy rescaling reduces to the Schwarzschild mass for the limits in which the Lee-Kim-Myung slowly rotating black hole solution in the HL gravity reduces to the Schwarzschild solution in general relativity.

  3. Calculating the Optimum Angle of Filament-Wound Pipes in Natural Gas Transmission Pipelines Using Approximation Methods.

    Science.gov (United States)

    Reza Khoshravan Azar, Mohammad; Emami Satellou, Ali Akbar; Shishesaz, Mohammad; Salavati, Bahram

    2013-04-01

    Given the increasing use of composite materials in various industries, oil and gas industry also requires that more attention should be paid to these materials. Furthermore, due to variation in choice of materials, the materials needed for the mechanical strength, resistance in critical situations such as fire, costs and other priorities of the analysis carried out on them and the most optimal for achieving certain goals, are introduced. In this study, we will try to introduce appropriate choice for use in the natural gas transmission composite pipelines. Following a 4-layered filament-wound (FW) composite pipe will consider an offer our analyses under internal pressure. The analyses' results will be calculated for different combinations of angles 15 deg, 30 deg, 45 deg, 55 deg, 60 deg, 75 deg, and 80 deg. Finally, we will compare the calculated values and the optimal angle will be gained by using the Approximation methods. It is explained that this layering is as the symmetrical. PMID:24891748

  4. Pritchard's Reasons

    OpenAIRE

    Littlejohn, Clayton Mitchell

    2016-01-01

    Pritchard’s epistemological disjunctivist thinks that when we come to know things through vision our perceptual beliefs are based on reasons that provide factive support. The reasons that constitute the rational basis for your belief that the page before you is white and covered in black marks entails that it is and includes things that could not have provided rational support for your beliefs if you had been hallucinating. There are some issues that I would like to raise. First, what motivat...

  5. Approximate iterative algorithms

    CERN Document Server

    Almudevar, Anthony Louis

    2014-01-01

    Iterative algorithms often rely on approximate evaluation techniques, which may include statistical estimation, computer simulation or functional approximation. This volume presents methods for the study of approximate iterative algorithms, providing tools for the derivation of error bounds and convergence rates, and for the optimal design of such algorithms. Techniques of functional analysis are used to derive analytical relationships between approximation methods and convergence properties for general classes of algorithms. This work provides the necessary background in functional analysis a

  6. The surface morphology analysis based on progressive approximation method using confocal three-dimensional micro X-ray fluorescence

    Science.gov (United States)

    Yi, Longtao; Sun, Tianxi; Wang, Kai; Qin, Min; Yang, Kui; Wang, Jinbang; Liu, Zhiguo

    2016-08-01

    Confocal three-dimensional micro X-ray fluorescence (3D MXRF) is an excellent surface analysis technology. For a confocal structure, only the X-rays from the confocal volume can be detected. Confocal 3D MXRF has been widely used for analysing elements, the distribution of elements and 3D image of some special samples. However, it has rarely been applied to analysing surface topography by surface scanning. In this paper, a confocal 3D MXRF technology based on polycapillary X-ray optics was proposed for determining surface topography. A corresponding surface adaptive algorithm based on a progressive approximation method was designed to obtain surface topography. The surface topography of the letter "R" on a coin of the People's Republic of China and a small pit on painted pottery were obtained. The surface topography of the "R" and the pit are clearly shown in the two figures. Compared with the method in our previous study, it exhibits a higher scanning efficiency. This approach could be used for two-dimensional (2D) elemental mapping or 3D elemental voxel mapping measurements as an auxiliary method. It also could be used for analysing elemental mapping while obtaining the surface topography of a sample in 2D elemental mapping measurement.

  7. Reflections on clinical reasoning in mental health occupational therapy: the case of the occupational therapy dynamic method

    OpenAIRE

    Taís Quevedo Marcolino

    2014-01-01

    The Clinical Reasoning Study supported by the American Occupational Therapy Association/AOTA and the American Occupational Therapy Foundation/AOTF in the United States in the late 1980s, had inaugurated the scientific production in the field and offered an initial framework on clinical reasoning for understanding and conducting clinical cases in Occupational Therapy. Most of the researches in this field have focused on reasoning processes, and point out the need to understand the contents of ...

  8. Comparison of iterative methods and preconditioners for two-phase flow in porous media using exact and approximate Jacobians

    Science.gov (United States)

    Büsing, Henrik

    2013-04-01

    Two-phase flow in porous media occurs in various settings, such as the sequestration of CO2 in the subsurface, radioactive waste management, the flow of oil or gas in hydrocarbon reservoirs, or groundwater remediation. To model the sequestration of CO2, we consider a fully coupled formulation of the system of nonlinear, partial differential equations. For the solution of this system, we employ the Box method after Huber & Helmig (2000) for the space discretization and the fully implicit Euler method for the time discretization. After linearization with Newton's method, it remains to solve a linear system in every Newton step. We compare different iterative methods (BiCGStab, GMRES, AGMG, c.f., [Notay (2012)]) combined with different preconditioners (ILU0, ASM, Jacobi, and AMG as preconditioner) for the solution of these systems. The required Jacobians can be obtained elegantly with automatic differentiation (AD) [Griewank & Walther (2008)], a source code transformation providing exact derivatives. We compare the performance of the different iterative methods with their respective preconditioners for these linear systems. Furthermore, we analyze linear systems obtained by approximating the Jacobian with finite differences in terms of Newton steps per time step, steps of the iterative solvers and the overall solution time. Finally, we study the influence of heterogeneities in permeability and porosity on the performance of the iterative solvers and their robustness in this respect. References [Griewank & Walther(2008)] Griewank, A. & Walther, A., 2008. Evaluating Derivatives: Principles and Techniques of Algorithmic Differentiation, SIAM, Philadelphia, PA, 2nd edn. [Huber & Helmig(2000)] Huber, R. & Helmig, R., 2000. Node-centered finite volume discretizations for the numerical simulation of multiphase flow in heterogeneous porous media, Computational Geosciences, 4, 141-164. [Notay(2012)] Notay, Y., 2012. Aggregation-based algebraic multigrid for convection

  9. A novel arc jointing robot scheduling method in electric power plants using adaptive neural network and fuzzy reasoning

    Energy Technology Data Exchange (ETDEWEB)

    Chen, X. [Jiangxi Univ., Nanchang, Jiangxi Province (China). School of Software]|[UFIDA Software Co. Ltd., Beijing (China); Xu, H. [Tsinghua Univ., Beijing (China). Tsinghua National Lab. for Information Science and Technology

    2007-07-01

    An experiment was conducted at an electric power plant in which a multi robot scheduling approach was tested on 2 arc jointing robot systems. Such scheduling is an important but difficult task in the construction and maintenance of turbines at electric power plants. The purpose of this experiment was to assign a new task to one of the robots to assure maximum use of resources and to guarantee high productivity from the multi arc jointing robots. An innovative multi robot scheduling approach based on Adaptive Artificial Neural Networks (NN) was used to schedule the proper arc jointing robot when jointing turbines. Feed forward, multi-layered neural network meta-models were trained through the back-error-propagation (BEP) learning algorithm to provide a versatile trajectory prediction of every robot. A fuzzy reasoning based intelligent selection mechanism was also used simultaneously to schedule the proper arc jointing robot. The method was shown to offer optimized solutions for practical robot scheduling problems. It was concluded that the proposed method has the potential to be used in hardware with much better speed and quality, thereby improving scheduling efficiency. As such, it has value during the construction and maintenance of turbines in electric power plants. 10 refs., 1 fig.

  10. Approximate method for measurement of phase-distribution in multiphase materials with small neutrondashattenuation using a neutron beam as a probe

    Science.gov (United States)

    Hibiki, Takashi; Mishima, Kaichiro

    1996-02-01

    An approximate method for the quantification of a neutron radiography image was proposed for measuring the phase-distribution of multiphase materials with small neutrondashattenuation. Since it is not necessary for this method to put a standard calibration sample in a field of a view, this method has an advantage of measuring the phase-distribution of multiphase materials with unknown internal-structure and neutrondashattenuation in the object in an enlarged field of view. Although its application is limited to an object with small neutrondashattenuation, it was revealed from a numerical analysis that the approximate method can be applicable to heavy water, liquid sodium andliquid potassium, which are important materials in relation to research on the thermalhydraulics of the nuclear reactor. The validity of the approximate method was also confirmed experimentally by comparing the void fraction of air-water flows in round tubes measured by the approximate method with those by the other more-accurate method.

  11. Efficient and accurate local approximations to coupled-electron pair approaches: An attempt to revive the pair natural orbital method

    Science.gov (United States)

    Neese, Frank; Wennmohs, Frank; Hansen, Andreas

    2009-03-01

    Coupled-electron pair approximations (CEPAs) and coupled-pair functionals (CPFs) have been popular in the 1970s and 1980s and have yielded excellent results for small molecules. Recently, interest in CEPA and CPF methods has been renewed. It has been shown that these methods lead to competitive thermochemical, kinetic, and structural predictions. They greatly surpass second order Møller-Plesset and popular density functional theory based approaches in accuracy and are intermediate in quality between CCSD and CCSD(T) in extended benchmark studies. In this work an efficient production level implementation of the closed shell CEPA and CPF methods is reported that can be applied to medium sized molecules in the range of 50-100 atoms and up to about 2000 basis functions. The internal space is spanned by localized internal orbitals. The external space is greatly compressed through the method of pair natural orbitals (PNOs) that was also introduced by the pioneers of the CEPA approaches. Our implementation also makes extended use of density fitting (or resolution of the identity) techniques in order to speed up the laborious integral transformations. The method is called local pair natural orbital CEPA (LPNO-CEPA) (LPNO-CPF). The implementation is centered around the concepts of electron pairs and matrix operations. Altogether three cutoff parameters are introduced that control the size of the significant pair list, the average number of PNOs per electron pair, and the number of contributing basis functions per PNO. With the conservatively chosen default values of these thresholds, the method recovers about 99.8% of the canonical correlation energy. This translates to absolute deviations from the canonical result of only a few kcal mol-1. Extended numerical test calculations demonstrate that LPNO-CEPA (LPNO-CPF) has essentially the same accuracy as parent CEPA (CPF) methods for thermochemistry, kinetics, weak interactions, and potential energy surfaces but is up to 500

  12. Reasons for non-participation in a parental program concerning underage drinking: a mixed-method study

    Directory of Open Access Journals (Sweden)

    Eriksson Charli

    2009-12-01

    Full Text Available Abstract Background Alcohol consumption among adolescents is a serious public health concern. Research has shown that prevention programs targeting parents can help prevent underage drinking. The problem is that parental participation in these kinds of interventions is generally low. Therefore, the aim of the present study is to examine non-participation in a parental support program aiming to prevent underage alcohol drinking. The Health Belief Model has been used as a tool for the analysis. Methods To understand non-participation in a parental program a quasi-experimental mixed-method design was used. The participants in the study were invited to participate in a parental program targeting parents with children in school years 7-9. A questionnaire was sent home to the parents before the program started. Two follow-up surveys were also carried out. The inclusion criteria for the study were that the parents had answered the questionnaire in school year 7 and either of the questionnaires in the two subsequent school years (n = 455. Multinomial logistic regression analysis was used to examine reasons for non-participation. The final follow-up questionnaire included an opened-ended question about reasons for non-participation. A qualitative content analysis was carried out and the two largest categories were included in the third model of the multinomial logistic regression analysis. Results Educational level was the most important socio-demographic factor for predicting non-participation. Parents with a lower level of education were less likely to participate than those who were more educated. Factors associated with adolescents and alcohol did not seem to be of significant importance. Instead, program-related factors predicted non-participation, e.g. parents who did not perceive any need for the intervention and who did not attend the information meeting were more likely to be non-participants. Practical issues, like time demands, also seemed to

  13. Short-range correlations and the A-representability problem within the low-order approximation to the Jastrow method

    International Nuclear Information System (INIS)

    Analytical expressions for the one-body density matrix and the related characteristics of closed s-d shell nuclei are obtained within the low-order approximation (LOA) to the Jastrow correlation method (JCM). The resulting local densities and elastic form factors are in agreement with the experimental data and associated nucleon momentum distributions are consistent with the calculated ones, using the much more complicated exp(S)-method. The correlation effects on the nucleon momentum and density distributions as well as the occupation numbers and the depletion of the Fermi sea are discussed. The short-range correlation accounted for in LOA of the JCM cause a depletion of the nuclear Fermi sea of about 4-8% for closed s-d shell nuclei. The resulting occupation of the states above the Fermi level forms the proper significant high-momentum tail of n(k). A violation of the A-representability condition for the one-body density matrix appears and the JCM in LOA fails to reproduce the first single particle states above the Fermi level whose angular momentum l is among the angular momenta of the states occupied in the uncorrelated ground state of nuclei. The closed analytical expression obtained for the one-body nuclear characteristics can be used to analyze the short-range correlation effects observed in the measured experimental data. 1 fig., 1 tab., 17 refs. (orig.)

  14. Diagrammatic Reasoning

    DEFF Research Database (Denmark)

    Tylén, Kristian; Fusaroli, Riccardo; Stege Bjørndahl, Johanne;

    2015-01-01

    Many types of everyday and specialized reasoning depend on diagrams: we use maps to find our way, we draw graphs and sketches to communicate concepts and prove geometrical theorems, and we manipulate diagrams to explore new creative solutions to problems. The active involvement and manipulation of...... representational artifacts for purposes of thinking and communicating is discussed in relation to C.S. Peirce’s notion of diagrammatical reasoning. We propose to extend Peirce’s original ideas and sketch a conceptual framework that delineates different kinds of diagram manipulation: Sometimes diagrams are...

  15. Rational offset approximation of rational Bézier curves

    Institute of Scientific and Technical Information of China (English)

    CHENG Min; WANG Guo-jin

    2006-01-01

    The problem of parametric speed approximation of a rational curve is raised in this paper. Offset curves are widely used in various applications. As for the reason that in most cases the offset curves do not preserve the same polynomial or rational polynomial representations, it arouses difficulty in applications. Thus approximation methods have been introduced to solve this problem. In this paper, it has been pointed out that the crux of offset curve approximation lies in the approximation of parametric speed. Based on the Jacobi polynomial approximation theory with endpoints interpolation, an algebraic rational approximation algorithm of offset curve, which preserves the direction of normal, is presented.

  16. Diophantine approximations

    CERN Document Server

    Niven, Ivan

    2008-01-01

    This self-contained treatment originated as a series of lectures delivered to the Mathematical Association of America. It covers basic results on homogeneous approximation of real numbers; the analogue for complex numbers; basic results for nonhomogeneous approximation in the real case; the analogue for complex numbers; and fundamental properties of the multiples of an irrational number, for both the fractional and integral parts.The author refrains from the use of continuous fractions and includes basic results in the complex case, a feature often neglected in favor of the real number discuss

  17. Reasonable Forecasts

    Science.gov (United States)

    Taylor, Kelley R.

    2010-01-01

    This article presents a sample legal battle that illustrates school officials' "reasonable forecasts" of substantial disruption in the school environment. In 2006, two students from a Texas high school came to school carrying purses decorated with images of the Confederate flag. The school district has a zero-tolerance policy for clothing or…

  18. Multi-sheet surface rebinning methods for reconstruction from asymmetrically truncated cone beam projections: I. Approximation and optimality

    International Nuclear Information System (INIS)

    The mechanical motion of the gantry in conventional cone beam CT scanners restricts the speed of data acquisition in applications with near real time requirements. A possible resolution of this problem is to replace the moving source detector assembly with static parts that are electronically activated. An example of such a system is the Rapiscan Systems RTT80 real time tomography scanner, with a static ring of sources and axially offset static cylinder of detectors. A consequence of such a design is asymmetrical axial truncation of the cone beam projections resulting, in the sense of integral geometry, in severely incomplete data. In particular we collect data only in a fraction of the Tam–Danielsson window, hence the standard cone beam reconstruction techniques do not apply. In this work we propose a family of multi-sheet surface rebinning methods for reconstruction from such truncated projections. The proposed methods combine analytical and numerical ideas utilizing linearity of the ray transform to reconstruct data on multi-sheet surfaces, from which the volumetric image is obtained through deconvolution. In this first paper in the series, we discuss the rebinning to multi-sheet surfaces. In particular we concentrate on the underlying transforms on multi-sheet surfaces and their approximation with data collected by offset multi-source scanning geometries like the RTT. The optimal multi-sheet surface and the corresponding rebinning function are found as a solution of a variational problem. In the case of the quadratic objective, the variational problem for the optimal rebinning pair can be solved by a globally convergent iteration. Examples of optimal rebinning pairs are computed for different trajectories. We formulate the axial deconvolution problem for the recovery of the volumetric image from the reconstructions on multi-sheet surfaces. Efficient and stable solution of the deconvolution problem is the subject of the second paper in this series (Betcke and

  19. Subsurface Flow Modeling in Single and Dual Continuum Anisotropic Porous Media using the Multipoint Flux Approximation Method

    KAUST Repository

    Negara, Ardiansyah

    2015-05-01

    Anisotropy of hydraulic properties of the subsurface geologic formations is an essential feature that has been established as a consequence of the different geologic processes that undergo during the longer geologic time scale. With respect to subsurface reservoirs, in many cases, anisotropy plays significant role in dictating the direction of flow that becomes no longer dependent only on driving forces like the pressure gradient and gravity but also on the principal directions of anisotropy. Therefore, there has been a great deal of motivation to consider anisotropy into the subsurface flow and transport models. In this dissertation, we present subsurface flow modeling in single and dual continuum anisotropic porous media, which include the single-phase groundwater flow coupled with the solute transport in anisotropic porous media, the two-phase flow with gravity effect in anisotropic porous media, and the natural gas flow in anisotropic shale reservoirs. We have employed the multipoint flux approximation (MPFA) method to handle anisotropy in the flow model. The MPFA method is designed to provide correct discretization of the flow equations for general orientation of the principal directions of the permeability tensor. The implementation of MPFA method is combined with the experimenting pressure field approach, a newly developed technique that enables the solution of the global problem breaks down into the solution of multitude of local problems. The numerical results of the study demonstrate the significant effects of anisotropy of the subsurface formations. For the single-phase groundwater flow coupled with the solute transport modeling in anisotropic porous media, the results shows the strong impact of anisotropy on the pressure field and the migration of the solute concentration. For the two-phase flow modeling with gravity effect in anisotropic porous media, it is observed that the buoyancy-driven flow, which emerges due to the density differences between the

  20. Approximate Representations and Approximate Homomorphisms

    OpenAIRE

    Moore, Cristopher; Russell, Alexander

    2010-01-01

    Approximate algebraic structures play a defining role in arithmetic combinatorics and have found remarkable applications to basic questions in number theory and pseudorandomness. Here we study approximate representations of finite groups: functions f:G -> U_d such that Pr[f(xy) = f(x) f(y)] is large, or more generally Exp_{x,y} ||f(xy) - f(x)f(y)||^2$ is small, where x and y are uniformly random elements of the group G and U_d denotes the unitary group of degree d. We bound these quantities i...

  1. Tilnærmede metoder for beregning av maksimale søylemoment / Approximate methods for calculation of maximum moment in columns

    OpenAIRE

    2005-01-01

    In frame structures, consisting of columns and beams, gravity loading on beams (floors) leads to moments as well as axial forces in the columns. In cases with slender columns, maximum moments may develop between columns ends due to second order effects. Approximate methods for calculating maximum moments between column ends are given in Norwegian and international standards. These ``conventional'' methods are formulated in terms of approximate effective lengths and a moment gradient factor (o...

  2. Polynomial Lie algebra methods in solving the second-harmonic generation model: some exact and approximate calculations

    OpenAIRE

    Karassiov, V. P.; A. A. Gusev; Vinitsky, S. I.

    2001-01-01

    We compare exact and SU(2)-cluster approximate calculation schemes to determine dynamics of the second-harmonic generation model using its reformulation in terms of a polynomial Lie algebra $su_{pd}(2)$ and related spectral representations of the model evolution operator realized in algorithmic forms. It enabled us to implement computer experiments exhibiting a satisfactory accuracy of the cluster approximations in a large range of characteristic model parameters.

  3. Waveless Approximation Theories of Gravity

    CERN Document Server

    Isenberg, J A

    2007-01-01

    The analysis of a general multibody physical system governed by Einstein's equations in quite difficult, even if numerical methods (on a computer) are used. Some of the difficulties -- many coupled degrees of freedom, dynamic instability -- are associated with the presence of gravitational waves. We have developed a number of ``waveless approximation theories'' (WAT) which repress the gravitational radiation and thereby simplify the analysis. The matter, according to these theories, evolves dynamically. The gravitational field, however, is determined at each time step by a set of elliptic equations with matter sources. There is reason to believe that for many physical systems, the WAT-generated system evolution is a very accurate approximation to that generated by the full Einstein theory.

  4. Two Major Types of Reasons in Common Law Method%普通法中的两类主要推理依据

    Institute of Scientific and Technical Information of China (English)

    贾海龙

    2011-01-01

    普通法方法中为了回答法律问题,要使用到多种推理依据,其中最重要的两种依据是形式性依据和实质性依据。形式性依据是具有权威形式的推理依据,典型代表为制定法和案例,还包括学者的论述、评论、法律汇编、重述等内容。其中有法律拘束力的制定法和案例是最有力的形式性依据。实质性依据不具有权威形式,而是凭借其内容的内在逻辑而获得说服力的推理依据,主要包括道德依据和政策目标依据两大类。普通法法官推理中,形式性依据的重要性是首位的,实质性依据起到辅助的作用,只有存在法律不周全的情况下,实质性依据才能成为首要推理依据。%In order to answer legal questions,the common law method employs a number of different types of reasons,among which formal reasons and substantive reasons are the two major types.Formal reasons are reasons with authoritative forms,including statutes and precedents and other authorities which are not sources of law.Substantive reasons are reasons without authoritative forms,including moral reasons and policy reasons.In common law reasoning,formal reasons are most important,while substantive reasons are of assistance.Only when there is deficiency in positive law can substantive reasons take a more important responsibility.

  5. Methods and Algorithms for Approximating the Gamma Function and Related Functions. A survey. Part I: Asymptotic Series

    Directory of Open Access Journals (Sweden)

    Cristinel Mortici

    2015-01-01

    Full Text Available In this survey we present our recent results on analysis of gamma function and related functions. The results obtained are in the theory of asymptotic analysis, approximation of gamma and polygamma functions, or in the theory of completely monotonic functions. The motivation of this first part is the work of C. Mortici [Product Approximations via Asymptotic Integration Amer. Math. Monthly 117 (2010 434-441] where a simple strategy for constructing asymptotic series is presented. The classical asymptotic series associated to Stirling, Wallis, Glaisher-Kinkelin are rediscovered. In the second section we discuss some new inequalities related to Landau constants and we establish some asymptotic formulas.

  6. Approximate Likelihood

    CERN Document Server

    CERN. Geneva

    2015-01-01

    Most physics results at the LHC end in a likelihood ratio test. This includes discovery and exclusion for searches as well as mass, cross-section, and coupling measurements. The use of Machine Learning (multivariate) algorithms in HEP is mainly restricted to searches, which can be reduced to classification between two fixed distributions: signal vs. background. I will show how we can extend the use of ML classifiers to distributions parameterized by physical quantities like masses and couplings as well as nuisance parameters associated to systematic uncertainties. This allows for one to approximate the likelihood ratio while still using a high dimensional feature vector for the data. Both the MEM and ABC approaches mentioned above aim to provide inference on model parameters (like cross-sections, masses, couplings, etc.). ABC is fundamentally tied Bayesian inference and focuses on the “likelihood free” setting where only a simulator is available and one cannot directly compute the likelihood for the dat...

  7. Diophantine approximation

    CERN Document Server

    Schmidt, Wolfgang M

    1980-01-01

    "In 1970, at the U. of Colorado, the author delivered a course of lectures on his famous generalization, then just established, relating to Roth's theorem on rational approxi- mations to algebraic numbers. The present volume is an ex- panded and up-dated version of the original mimeographed notes on the course. As an introduction to the author's own remarkable achievements relating to the Thue-Siegel-Roth theory, the text can hardly be bettered and the tract can already be regarded as a classic in its field."(Bull.LMS) "Schmidt's work on approximations by algebraic numbers belongs to the deepest and most satisfactory parts of number theory. These notes give the best accessible way to learn the subject. ... this book is highly recommended." (Mededelingen van het Wiskundig Genootschap)

  8. Sparse approximation with bases

    CERN Document Server

    2015-01-01

    This book systematically presents recent fundamental results on greedy approximation with respect to bases. Motivated by numerous applications, the last decade has seen great successes in studying nonlinear sparse approximation. Recent findings have established that greedy-type algorithms are suitable methods of nonlinear approximation in both sparse approximation with respect to bases and sparse approximation with respect to redundant systems. These insights, combined with some previous fundamental results, form the basis for constructing the theory of greedy approximation. Taking into account the theoretical and practical demand for this kind of theory, the book systematically elaborates a theoretical framework for greedy approximation and its applications.  The book addresses the needs of researchers working in numerical mathematics, harmonic analysis, and functional analysis. It quickly takes the reader from classical results to the latest frontier, but is written at the level of a graduate course and do...

  9. Methods for increasing the accuracy of approximate formulas for the roots of a cubic equation with complex conjugate roots

    International Nuclear Information System (INIS)

    Approximate formulas for determining the frequency and Q-factor of the complex conjugate roots, as well as the frequency of the real root, of the cubic equation for the case where the frequency of the complex-conjugate roots is close to the frequency of the real root have been presented in this work

  10. Stochastic approximation methods-Powerful tools for simulation and optimization: A survey of some recent work on multi-agent systems and cyber-physical systems

    International Nuclear Information System (INIS)

    Stochastic approximation methods have found extensive and diversified applications. Recent emergence of networked systems and cyber-physical systems has generated renewed interest in advancing stochastic approximation into a general framework to support algorithm development for information processing and decisions in such systems. This paper presents a survey on some recent developments in stochastic approximation methods and their applications. Using connected vehicles in platoon formation and coordination as a platform, we highlight some traditional and new methodologies of stochastic approximation algorithms and explain how they can be used to capture essential features in networked systems. Distinct features of networked systems with randomly switching topologies, dynamically evolving parameters, and unknown delays are presented, and control strategies are provided

  11. Approximation of irrationals

    OpenAIRE

    Malvina Baica

    1985-01-01

    The author uses a new modification of Jacobi-Perron Algorithm which holds for complex fields of any degree (abbr. ACF), and defines it as Generalized Euclidean Algorithm (abbr. GEA) to approximate irrationals.This paper deals with approximation of irrationals of degree n=2,3,5. Though approximations of these irrationals in a variety of patterns are known, the results are new and practical, since there is used an algorithmic method.

  12. Approximate solution of two-term fractional-order diffusion, wave-diffusion, and telegraph models arising in mathematical physics using optimal homotopy asymptotic method

    Science.gov (United States)

    Sarwar, S.; Rashidi, M. M.

    2016-07-01

    This paper deals with the investigation of the analytical approximate solutions for two-term fractional-order diffusion, wave-diffusion, and telegraph equations. The fractional derivatives are defined in the Caputo sense, whose orders belong to the intervals [0,1], (1,2), and [1,2], respectively. In this paper, we extended optimal homotopy asymptotic method (OHAM) for two-term fractional-order wave-diffusion equations. Highly approximate solution is obtained in series form using this extended method. Approximate solution obtained by OHAM is compared with the exact solution. It is observed that OHAM is a prevailing and convergent method for the solutions of nonlinear-fractional-order time-dependent partial differential problems. The numerical results rendering that the applied method is explicit, effective, and easy to use, for handling more general fractional-order wave diffusion, diffusion, and telegraph problems.

  13. Summary of Time Period-Based and Other Approximation Methods for Determining the Capacity Value of Wind and Solar in the United States: September 2010 - February 2012

    Energy Technology Data Exchange (ETDEWEB)

    Rogers, J.; Porter, K.

    2012-03-01

    This paper updates previous work that describes time period-based and other approximation methods for estimating the capacity value of wind power and extends it to include solar power. The paper summarizes various methods presented in utility integrated resource plans, regional transmission organization methodologies, regional stakeholder initiatives, regulatory proceedings, and academic and industry studies. Time period-based approximation methods typically measure the contribution of a wind or solar plant at the time of system peak - sometimes over a period of months or the average of multiple years.

  14. IS GRATUITOUSNESS A REASON FOR JOINING AN EDUCATIONAL MASTER PROGRAMME IN AUDIT? SURVEY EVIDENCE USING STATISTICAL METHODS

    Directory of Open Access Journals (Sweden)

    Span Georgeta Ancuta

    2012-07-01

    Full Text Available The study shows the reasons taken into account by the students in choosing an academic preparation. Free courses and employment opportunities during or after graduation are the most important advantages students expect to receive from an educational program that aims to follow. The empirical section results emphasize the efficiency and performance of the master program financed by the European Social Fund. \\\\\\\\r\\\\\\\

  15. Approximation of The Neutron Diffusion Equation on Hexagonal Geometries Using a h-p finite element method

    OpenAIRE

    FAYEZ MOUSTAFA MOAWAD, RAGAB

    2016-01-01

    [EN] The neutron diffusion equation is an approximation of the neutron transport equation that describes the neutron population in a nuclear reactor core. In particular, we will consider here VVER-type reactors which use the neutron diffusion equation discretized on hexagonal meshes. Most of the simulation codes of a nuclear power reactor use the multigroup neutron diffusion equation to describe the neutron distribution inside the reactor core.To study the stationary state of a reactor, the r...

  16. An effective method to suppress numerical dispersion in 2D acoustic and elastic modelling using a high-order Padé approximation

    International Nuclear Information System (INIS)

    In this paper, we propose a method that can effectively reduce the numerical dispersion for solving the acoustic and elastic-wave equations. The method is a fourth-order Padé approximation scheme, in which the time difference operator is a rational function and a block tridiagonal system needs to be solved at each step. On the one hand, to efficiently solve a large linear system of equations we propose an explicit method for this implicit algrithom. On the other hand, to approximate the high-order spatial derivatives we use an eighth-order stereo-modelling method using wavefield displacements and their gradients simultaneously. For this new method, we investigate some mathematical properties including the stability, errors and the numerical dispersion relationship for 1D and 2D cases. We also present numerical results computed by the Padé approximation and compare them with the eighth-order Lax–Wendroff correction method and the eighth-order staggered-grid method. Numerical results show that the high-order Padé approximation scheme can effectively suppress the numerical dispersion caused by discretizing the wave equations when coarse spatial grids are used or models have strong velocity contrasts between adjacent grids. In contrast to other high-order finite-difference methods, the new method takes substantially less computational time and requires less memory because large spatial and time increments can be used. Thus the high-order Padé approximation method can potentially be used to solve large-scale wave propagation problems and seismic tomography based on the wave equations. (paper)

  17. Dual Control for Approximate Bayesian Reinforcement Learning

    OpenAIRE

    Klenske, Edgar D.; Hennig, Philipp

    2015-01-01

    Control of non-episodic, finite-horizon dynamical systems with uncertain dynamics poses a tough and elementary case of the exploration-exploitation trade-off. Bayesian reinforcement learning, reasoning about the effect of actions and future observations, offers a principled solution, but is intractable. We review, then extend an old approximate approach from control theory---where the problem is known as dual control---in the context of modern regression methods, specifically generalized line...

  18. Accurate and Efficient Solution of the Electronic Schr\\"odinger Equation with the Coulomb Singularity by the Distributed Approximating Functional Method

    CERN Document Server

    Sun, Zhigang

    2016-01-01

    We proposed a distributed approximating functional method for efficiently describing the electronic dynamics in atoms and molecules in the presence of the Coulomb singularities, using the kernel of a grid representation derived by using the solutions of the Coulomb differential equation based upon the Schwartz's interpolation formula, and a grid representation using the Lobatto/Radau shape functions. The elements of the resulted Hamiltonian matrix are confined in a narrow diagonal band, which is similar to that using the (higher order) finite difference methods. However, the spectral convergence properties of the original grid representations are retained in the proposed distributed approximating functional method for solving the Schr\\"odinger equation involving the Coulomb singularity. Thus the method is effective for solving the electronic Schr\\"odinger equation using iterative methods where the action of the Hamiltonian matrix on the wave function need to evaluate many times. The method is investigated by ...

  19. Lagrange-distributed approximating-functional approach to wave-packet propagation: Application to the time-independent wave-packet reactant-product decoupling method

    International Nuclear Information System (INIS)

    A connection is made between a recently introduced Lagrange-distributed approximating-functional and the Paley-Wiener sampling theorem. The Lagrange-distributed approximating-functional sampling is found to provide much superior results to that of Paley-Wiener sampling. The relations between discrete variable representation and Lagrange-distributed approximating functionals are discussed. The latter is used to provide an even spaced, interpolative grid representation of the Hamiltonian, in which the kinetic energy matrix has a banded, Toeplitz structure. In this paper we demonstrate that the Lagrange-distributed approximating-functional representation is an accurate and reliable representation for use in fast-Fourier-transform wave-packet propagation methods and apply it to the time-independent wave-packet reactant-product decoupling method, calculating state-to-state reaction probabilities for the two-dimensional (collinear) and three-dimensional (J=0) H+H2 reactions. The results are in very close agreement with those of previous calculations. We also discuss the connection between the distributed approximating-functional method and the existing mathematical formalism of moving least-squares theory. copyright 1998 The American Physical Society

  20. Approximating the Exponential, the Lanczos Method and an \\tilde{O}(m)-Time Spectral Algorithm for Balanced Separator

    CERN Document Server

    Orecchia, Lorenzo; Vishnoi, Nisheeth K

    2011-01-01

    We give a novel spectral approximation algorithm for the balanced separator problem that, given a graph G, a constant balance b \\in (0,1/2], and a parameter \\gamma, either finds an \\Omega(b)-balanced cut of conductance O(\\sqrt(\\gamma)) in G, or outputs a certificate that all b-balanced cuts in G have conductance at least \\gamma, and runs in time \\tilde{O}(m). This settles the question of designing asymptotically optimal spectral algorithms for balanced separator. Our algorithm relies on a variant of the heat kernel random walk and requires, as a subroutine, an algorithm to compute \\exp(-L)v where L is the Laplacian of a graph related to G and v is a vector. Algorithms for computing the matrix-exponential-vector product efficiently comprise our next set of results. Our main result here is a new algorithm which computes a good approximation to \\exp(-A)v for a class of PSD matrices A and a given vector u, in time roughly \\tilde{O}(m_A), where m_A is the number of non-zero entries of A. This uses, in a non-trivia...

  1. 一种集成式不确定推理方法研究%Research on an Ensemble Method of Uncertainty Reasoning

    Institute of Scientific and Technical Information of China (English)

    贺怀清; 李建伏

    2011-01-01

    Ensemble learning is a machine learning paradigm where multiple models are strategically generated and combined to obtain better predictive performance than a single learning method.It was proven that ensemble learning is feasible and tends to yield better results.Uncertainty reasoning is one of the important directions in artificial intelligence.Various uncertainty reasoning methods have been developed and all have their own advantages and disadvantages.Motivated by ensemble learning, an ensemble method of uncertainty reasoning was proposed.The main idea of the new method is in accordance with the basic framework of ensemble learning,where multiple uncertainty reasoning methods is used in time and the result of various reasoning methods is integrated by some rules as the final result.Finally, theoretical analysis and experimental tests show that the ensemble uncertainty reasoning method is effective and feasible.%集成学习是采用某种规则把一系列学习器的结果进行整合以获得比单个学习器更好的学习效果的一种机器学习方法.研究表明集成学习是可行的,能取得比传统学习方法更好的性能.不确定推理是人工智能的重要研究方向之一,目前已经开发出了多种不确定推理方法,这些方法在实际应用中各有优缺点.借鉴集成学习,提出一种集成式不确定推理方法,其基本思想是按照一定的策略集成多种不确定推理方法,以提高推理的准确性.理论分析和实验结果验证了方法的合理性和可行性.

  2. Time-dependent density-functional and reduced density-matrix methods for few electrons: Exact versus adiabatic approximations

    International Nuclear Information System (INIS)

    Graphical abstract: We solve a 1D N-electron system, with N small, by mapping it onto an N-dimensional one-electron problem. We compare the exact solutions to the results from adiabatic density and density matrix functionals for different physical situations. Highlights: ► Static and dynamical correlations. ► Memory dependence of exchange-correlation functionals in TDDFT. ► Linear and non-linear response. ► Laser-induced population control. - Abstract: To address the impact of electron correlations in the linear and non-linear response regimes of interacting many-electron systems exposed to time-dependent external fields, we study one-dimensional (1D) systems where the interacting problem is solved exactly by exploiting the mapping of the 1D N-electron problem onto an N-dimensional single electron problem. We analyze the performance of the recently derived 1D local density approximation as well as the exact-exchange orbital functional for those systems. We show that the interaction with an external resonant laser field shows Rabi oscillations which are detuned due to the lack of memory in adiabatic approximations. To investigate situations where static correlations play a role, we consider the time-evolution of the natural occupation numbers associated to the reduced one-body density matrix. Those studies shed light on the non-locality and time-dependence of the exchange and correlation functionals in time-dependent density and density-matrix functional theories.

  3. A B-Spline-Based Colocation Method to Approximate the Solutions to the Equations of Fluid Dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Richard Wayne; Landon, Mark Dee

    1999-07-01

    The potential of a B-spline collocation method for numerically solving the equations of fluid dynamics is discussed. It is known that B-splines can resolve curves with drastically fewer data than can their standard shape function counterparts. This feature promises to allow much faster numerical simulations of fluid flow than standard finite volume/finite element methods without sacrificing accuracy. An example channel flow problem is solved using the method.

  4. A B-Spline-Based Colocation Method to Approximate the Solutions to the Equations of Fluid Dynamics

    Energy Technology Data Exchange (ETDEWEB)

    M. D. Landon; R. W. Johnson

    1999-07-01

    The potential of a B-spline collocation method for numerically solving the equations of fluid dynamics is discussed. It is known that B-splines can resolve complex curves with drastically fewer data than can their standard shape function counterparts. This feature promises to allow much faster numerical simulations of fluid flow than standard finite volume/finite element methods without sacrificing accuracy. An example channel flow problem is solved using the method.

  5. Software Architecture Design Reasoning

    Science.gov (United States)

    Tang, Antony; van Vliet, Hans

    Despite recent advancements in software architecture knowledge management and design rationale modeling, industrial practice is behind in adopting these methods. The lack of empirical proofs and the lack of a practical process that can be easily incorporated by practitioners are some of the hindrance for adoptions. In particular, the process to support systematic design reasoning is not available. To rectify this issue, we propose a design reasoning process to help architects cope with an architectural design environment where design concerns are cross-cutting and diversified.We use an industrial case study to validate that the design reasoning process can help improve the quality of software architecture design. The results have indicated that associating design concerns and identifying design options are important steps in design reasoning.

  6. Analysis of field-angle dependent specific heat in unconventional superconductors: A comparison between Doppler-shift method and Kramer-Pesch approximation

    International Nuclear Information System (INIS)

    We theoretically discuss the magnetic-field-angle dependence of the zero-energy density of states (ZEDOS) in superconductors. Point-node and line-node superconducting gaps on spherical and cylindrical Fermi surfaces are considered. The Doppler-shift (DS) method and the Kramer-Pesch approximation (KPA) are used to calculate the ZEDOS. Numerical results show that consequences of the DS method are corrected by the KPA.

  7. Ordered cones and approximation

    CERN Document Server

    Keimel, Klaus

    1992-01-01

    This book presents a unified approach to Korovkin-type approximation theorems. It includes classical material on the approximation of real-valuedfunctions as well as recent and new results on set-valued functions and stochastic processes, and on weighted approximation. The results are notonly of qualitative nature, but include quantitative bounds on the order of approximation. The book is addressed to researchers in functional analysis and approximation theory as well as to those that want to applythese methods in other fields. It is largely self- contained, but the readershould have a solid background in abstract functional analysis. The unified approach is based on a new notion of locally convex ordered cones that are not embeddable in vector spaces but allow Hahn-Banach type separation and extension theorems. This concept seems to be of independent interest.

  8. Approximate Modified Policy Iteration

    CERN Document Server

    Scherrer, Bruno; Ghavamzadeh, Mohammad; Geist, Matthieu

    2012-01-01

    Modified policy iteration (MPI) is a dynamic programming (DP) algorithm that contains the two celebrated policy and value iteration methods. Despite its generality, MPI has not been thoroughly studied, especially its approximation form which is used when the state and/or action spaces are large or infinite. In this paper, we propose three approximate MPI (AMPI) algorithms that are extensions of the well-known approximate DP algorithms: fitted-value iteration, fitted-Q iteration, and classification-based policy iteration. We provide an error propagation analysis for AMPI that unifies those for approximate policy and value iteration. We also provide a finite-sample analysis for the classification-based implementation of AMPI (CBMPI), which is more general (and somehow contains) than the analysis of the other presented AMPI algorithms. An interesting observation is that the MPI's parameter allows us to control the balance of errors (in value function approximation and in estimating the greedy policy) in the fina...

  9. Approximately Quintic and Sextic Mappings Form r-Divisible Groups into Ŝerstnev Probabilistic Banach Spaces: Fixed Point Method

    OpenAIRE

    M. B. Ghaemi; H. Majani; Cho, Y J; Eshaghi Gordji, M.

    2011-01-01

    Using the fixed point method, we investigate the stability of the systems of quadratic-cubic and additive-quadratic-cubic functional equations with constant coefficients form r-divisible groups into Ŝerstnev probabilistic Banach spaces.

  10. Technical Note: Weight approximation of coccoliths using a circular polarizer and interference colour derived retardation estimates - (The CPR Method)

    Science.gov (United States)

    Bollmann, J.

    2014-04-01

    A circular polarizer is used for the first time to image coccoliths without the extinction pattern of crossed polarized light at maximum interference colour. The combination of a circular polarizer with retardation measurements based on grey values derived from theoretical calculations allows for the first time accurate calculations of the weight of single coccoliths thinner than 1.37 μm. The weight estimates of 364 Holocene coccoliths using this new method are in good agreement with published volumetric estimates. A robust calibration method based on the measurement of a calibration target of known retardation enables the comparison of data between different imaging systems. Therefore, the new method overcomes the shortcomings of the error prone empirical calibration procedure of a previously reported method based on birefringence of calcite. Furthermore, it greatly simplifies the identification of coccolithophore species on the light microscope as well as the calculation of the area and thus weight of a coccolith.

  11. Study on optical radiation of a relativistic electron beam for giving reasons for the impulse-dosimetry absolute method

    International Nuclear Information System (INIS)

    Spectral and amplitude-time characteristics of optical emission of a relativistic electron beam in air is stidied by the photoelectron method. Application of the optical method for absolute measurements of characteristics of the dose field of an impulse relativistic electron beam is considered. The distribution of the energy absorbed along the 1 MeV electron beam axis is experimentally investigated. The absolute method of impulse dosimetry of heightened accuracy is substantiated on the basis of the results obtained

  12. Pricing American Options under Stochastic Volatility: A New Method Using Chebyshev Polynomials to Approximate the Early Exercise Boundary

    OpenAIRE

    Tzavalis, Elias; Wang, Shijun

    2003-01-01

    This paper presents a new numerical method for pricing American call options when the volatility of the price of the underlying stock is stochastic. By exploiting a log-linear relationship of the optimal exercise boundary with respect to volatility changes, we derive an integral representation of an American call price and the early exercise premium which holds under stochastic volatility. This representation is used to develop a numerical method for pricing the American options based on an a...

  13. CranSLIK v1.0: stochastic prediction of oil spill transport and fate using approximation methods

    Directory of Open Access Journals (Sweden)

    B. J. Snow

    2014-07-01

    Full Text Available This paper investigates the development of a model, called CranSLIK, to predict the transport and transformations of a point mass oil spill via a stochastic approach. Initially the various effects on destination are considered and key parameters are chosen which are expected to dominate the displacement. The variables considered are: wind velocity, surface water velocity, spill size, and spill age. For a point mass oil spill, it is found that the centre of mass can be determined by the wind and current data only, and the spill size and age can then be used to reconstruct the surface of the spill. These variables are sampled and simulations are performed using an open-source Lagrangian approach-based code, MEDSLIK II. Regression modelling is applied to create two sets of polynomials: one for the centre of mass, and one for the spill size. Simulations performed for a real oil spill case show that a minimum of approximately 80% of the oil is captured by CranSLIK. Finally, Monte Carlo simulation is implemented to allow for consideration of the most likely destination for the oil spill, when the distributions for the oceanographic conditions are known.

  14. A semi-alternating direction method for a 2-D fractional FitzHugh-Nagumo monodomain model on an approximate irregular domain

    Science.gov (United States)

    Liu, F.; Zhuang, P.; Turner, I.; Anh, V.; Burrage, K.

    2015-07-01

    A FitzHugh-Nagumo monodomain model has been used to describe the propagation of the electrical potential in heterogeneous cardiac tissue. In this paper, we consider a two-dimensional fractional FitzHugh-Nagumo monodomain model on an irregular domain. The model consists of a coupled Riesz space fractional nonlinear reaction-diffusion model and an ordinary differential equation, describing the ionic fluxes as a function of the membrane potential. Second, we use a decoupling technique and focus on solving the Riesz space fractional nonlinear reaction-diffusion model. A novel spatially second-order accurate semi-implicit alternating direction method (SIADM) for this model on an approximate irregular domain is proposed. Third, stability and convergence of the SIADM are proved. Finally, some numerical examples are given to support our theoretical analysis and these numerical techniques are employed to simulate a two-dimensional fractional FitzHugh-Nagumo model on both an approximate circular and an approximate irregular domain.

  15. Approximate Solution of Schrodinger Equation in D-Dimensions for Scarf Hyperbolic plus Non-Central Poschl- Teller Potential Using Nikiforov-Uvarov Method

    International Nuclear Information System (INIS)

    The approximate analytical solution of Schrodinger equation in D-Dimensions for Scarf hyperbolic plus non-central Pocshl-Teller potential were investigated using Nikiforov- Uvarov method. The approximate bound state energy are given in the close form and the corresponding approximate wave function for arbitary l-state in D-dimensions are formulated in the form of generalized Jacobi Polynomials. Special case is given for the ground state in 3 dimensions. The existence of arbitrary dimensions increase bound state energy system. In the other hand, the existence of arbitrary dimensions decreases the amplitude of wave function. The effect of Scarf Hyperbolic potential increases the bound state energy of system. The effect of non central Poschl-Teller potential decreases the bound state energy of system

  16. Practical Methods for Including Torsional Anharmonicity in Thermochemical Calculations on Complex Molecules: The Internal-Coordinate Multi-Structural Approximation

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, J.; Yu, T.; Papajak, E.; Alecu, I. M.; Mielke, S. L.; Truhlar, D. G.

    2011-01-01

    Many methods for correcting harmonic partition functions for the presence of torsional motions employ some form of one-dimensional torsional treatment to replace the harmonic contribution of a specific normal mode. However, torsions are often strongly coupled to other degrees of freedom, especially other torsions and low-frequency bending motions, and this coupling can make assigning torsions to specific normal modes problematic. Here, we present a new class of methods, called multi-structural (MS) methods, that circumvents the need for such assignments by instead adjusting the harmonic results by torsional correction factors that are determined using internal coordinates. We present three versions of the MS method: (i) MS-AS based on including all structures (AS), i.e., all conformers generated by internal rotations; (ii) MS-ASCB based on all structures augmented with explicit conformational barrier (CB) information, i.e., including explicit calculations of all barrier heights for internal-rotation barriers between the conformers; and (iii) MS-RS based on including all conformers generated from a reference structure (RS) by independent torsions. In the MS-AS scheme, one has two options for obtaining the local periodicity parameters, one based on consideration of the nearly separable limit and one based on strongly coupled torsions. The latter involves assigning the local periodicities on the basis of Voronoi volumes. The methods are illustrated with calculations for ethanol, 1-butanol, and 1-pentyl radical as well as two one-dimensional torsional potentials. The MS-AS method is particularly interesting because it does not require any information about conformational barriers or about the paths that connect the various structures.

  17. Use Residual Correction Method and Monotone Iterative Technique to Calculate the Upper and Lower Approximate Solutions of Singularly Perturbed Non-linear Boundary Value Problems

    Directory of Open Access Journals (Sweden)

    Chi-Chang Wang

    2013-09-01

    Full Text Available This paper seeks to use the proposed residual correction method in coordination with the monotone iterative technique to obtain upper and lower approximate solutions of singularly perturbed non-linear boundary value problems. First, the monotonicity of a non-linear differential equation is reinforced using the monotone iterative technique, then the cubic-spline method is applied to discretize and convert the differential equation into the mathematical programming problems of an inequation, and finally based on the residual correction concept, complex constraint solution problems are transformed into simpler questions of equational iteration. As verified by the four examples given in this paper, the method proposed hereof can be utilized to fast obtain the upper and lower solutions of questions of this kind, and to easily identify the error range between mean approximate solutions and exact solutions.

  18. Approximations to toroidal harmonics

    International Nuclear Information System (INIS)

    Toroidal harmonics P/sub n-1/2/1(cosh μ) and Q/sub n-1/2/1(cosh μ) are useful in solutions to Maxwell's equations in toroidal coordinates. In order to speed their computation, a set of approximations has been developed that is valid over the range 0 -10. The simple method used to determine the approximations is described. Relative error curves are also presented, obtained by comparing approximations to the more accurate values computed by direct summation of the hypergeometric series

  19. Linear interpolation method in ensemble Kohn-Sham and range-separated density-functional approximations for excited states

    DEFF Research Database (Denmark)

    Senjean, Bruno; Knecht, Stefan; Jensen, Hans Jørgen Aa;

    2015-01-01

    equiensembles. It is shown that such a linear interpolation method (LIM) can be rationalized and that it effectively introduces weight dependence effects. As proof of principle, the LIM has been applied to He, Be, and H2 in both equilibrium and stretched geometries as well as the stretched HeH+ molecule. Very...

  20. Covariant approximation averaging

    CERN Document Server

    Shintani, Eigo; Blum, Thomas; Izubuchi, Taku; Jung, Chulwoo; Lehner, Christoph

    2014-01-01

    We present a new class of statistical error reduction techniques for Monte-Carlo simulations. Using covariant symmetries, we show that correlation functions can be constructed from inexpensive approximations without introducing any systematic bias in the final result. We introduce a new class of covariant approximation averaging techniques, known as all-mode averaging (AMA), in which the approximation takes account of contributions of all eigenmodes through the inverse of the Dirac operator computed from the conjugate gradient method with a relaxed stopping condition. In this paper we compare the performance and computational cost of our new method with traditional methods using correlation functions and masses of the pion, nucleon, and vector meson in $N_f=2+1$ lattice QCD using domain-wall fermions. This comparison indicates that AMA significantly reduces statistical errors in Monte-Carlo calculations over conventional methods for the same cost.

  1. An experimental and analytical method for approximate determination of the tilt rotor research aircraft rotor/wing download

    Science.gov (United States)

    Jordon, D. E.; Patterson, W.; Sandlin, D. R.

    1985-01-01

    The XV-15 Tilt Rotor Research Aircraft download phenomenon was analyzed. This phenomenon is a direct result of the two rotor wakes impinging on the wing upper surface when the aircraft is in the hover configuration. For this study the analysis proceeded along tow lines. First was a method whereby results from actual hover tests of the XV-15 aircraft were combined with drag coefficient results from wind tunnel tests of a wing that was representative of the aircraft wing. Second, an analytical method was used that modeled that airflow caused gy the two rotors. Formulas were developed in such a way that acomputer program could be used to calculate the axial velocities were then used in conjunction with the aforementioned wind tunnel drag coefficinet results to produce download values. An attempt was made to validate the analytical results by modeling a model rotor system for which direct download values were determinrd..

  2. Hermite-distributed approximating functional-based formulation of multiconfiguration time-dependent Hartree method: A case study of quantum tunnelling in a coupled double-well system

    Indian Academy of Sciences (India)

    KAUSHIK MAJI

    2016-08-01

    We propose a variant of the multiconfiguration time-dependent Hartree (MCTDH) method within the framework of Hermite-distributed approximating functional (HDAF) method. The discretized Hamiltonian is a highly banded Toeplitz matrix which significantly reduces computational cost in terms of both storage and number of operations. The method proposed is employed to carry out the study of tunnelling dynamics of two coupled double well oscillators. We have calculated the orthogonality time \\tau , which is a measure of the time interval for an initial state to evolve into its orthogonal state. It is observed that the coupling has a significant effect on \\tau .

  3. On computing upper and lower bounds on the outputs of linear elasticity problems approximated by the smoothed finite element method

    OpenAIRE

    Xuan, Z C; Lassila, T. (Toni); Rozza, G; Quarteroni, A

    2010-01-01

    Verification of the computation of local quantities of interest, e.g. the displacements at a point, the stresses in a local area and the stress intensity factors at crack tips, plays an important role in improving the structural design for safety. In this paper, the smoothed finite element method (SFEM) is used for finding upper and lower bounds on the local quantities of interest that are outputs of the displacement field for linear elasticity problems, based on bounds on strain energy in bo...

  4. The effect of the application of the exact and approximate methods on values of selected ecological indices

    OpenAIRE

    Maria Ługowska; Zofia Rzymowska

    2014-01-01

    The work presents the results of a study on the biodiversity of agrocenoses using ecological indices. In order to calculate the measures, phytosociological relevés were made and exact methods were applied in winter cereals, spring cereals, tuber crops and stubble fields. The objective of the work was to compare ecological indices (Simpson’s index of dominance C, Simpson’s index of species richness D, and Shannon-Wiener index of biodiversity H’) calculated using the number of plants and their ...

  5. On negative binomial approximation to k-runs

    OpenAIRE

    Wang, Xiaoxin; Xia, Aihua

    2008-01-01

    The distributions of the run occurrences for a sequence of independent and identically distributed (i.i.d.) experiments are usually obtained by combinatorial methods (see Balakrishnan and Koutras (2002, Chapter 5)) and the resulting formulae are often very tedious, while the distributions for non i.i.d. experiments are generally intractable. It is therefore of practical interest to find a suitable approximate model with reasonable approximation accuracy. In this paper we ...

  6. The Reasons behind the (Non)Use of Feedback Reports for Quality Improvement in Physical Therapy: A Mixed-Method Study

    Science.gov (United States)

    Scholte, Marijn; Neeleman-van der Steen, Catherina W. M.; van der Wees, Philip J.; Nijhuis-van der Sanden, Maria W. G.; Braspenning, Jozé

    2016-01-01

    Objectives To explain the use of feedback reports for quality improvements by the reasons to participate in quality measuring projects and to identify barriers and facilitators. Design Mixed methods design. Methods In 2009–2011 a national audit and feedback system for physical therapy (Qualiphy) was initiated in the Netherlands. After each data collection round, an evaluation survey was held amongst its participants. The evaluation survey data was used to explain the use of feedback reports by studying the reasons to participate with Qualiphy with correlation measures and logistic regression. Semi-structured interviews with PTs served to seek confirmation and disentangle barriers and facilitators. Results Analysis of 257 surveys (response rate: 42.8%) showed that therapists with only financial reasons were less likely to use feedback reports (OR = 0.24;95%CI = 0.11–0.52) compared to therapists with a mixture of reasons. PTs in 2009 and 2010 were more likely to use the feedback reports for quality improvement than PTs in 2011 (OR = 2.41;95%CI = 1.25–4.64 respectively OR = 3.28;95%CI = 1.51–7.10). Changing circumstances in 2011, i.e. using EHRs and financial incentives, had a negative effect on the use of feedback reports (OR = 0.40, 95%CI = 0.20–0.78). Interviews with 12 physical therapists showed that feedback reports could serve as a tool to support and structure quality improvement plans. Barriers were distrust and perceived self-reporting bias on indicator scores. Conclusions Implementing financial incentives that are not well-specified and well-targeted can have an adverse effect on using feedback reports to improve quality of care. Distrust is a major barrier to implementing quality systems. PMID:27518113

  7. Approximate method for estimating plasma ionization characteristics based on numerical simulation of the dynamics of a plasma bunch with a high specific energy in the upper ionosphere

    Science.gov (United States)

    Motorin, A. A.; Stupitsky, E. L.; Kholodov, A. S.

    2016-07-01

    The spatiotemporal pattern for the development of a plasma cloud formed in the ionosphere and the main cloud gas-dynamic characteristics have been obtained from 3D calculations of the explosion-type plasmodynamic flows previously performed by us. An approximate method for estimating the plasma temperature and ionization degree with the introduction of the effective adiabatic index has been proposed based on these results.

  8. ADAPE program for calculation of the cross sections of neutron inelastic scattering on deformed nuclei in the adiabatic approximation by the coupled channel method

    International Nuclear Information System (INIS)

    The program for calculation of the cross sections of neutron interaction with deformed nuclei by the strongly coupled channel method in the adiabatic approximation is described. The results of test calculations of cross sections of elastic and inelastic neutron scattering with initial energy of 0.1; 0.6; 2.0; 2.5 MeV on the sup(238)U nucleus are presented

  9. Approximation by planar elastic curves

    DEFF Research Database (Denmark)

    Brander, David; Gravesen, Jens; Nørbjerg, Toke Bjerge

    2015-01-01

    We give an algorithm for approximating a given plane curve segment by a planar elastic curve. The method depends on an analytic representation of the space of elastic curve segments, together with a geometric method for obtaining a good initial guess for the approximating curve. A gradient......-driven optimization is then used to find the approximating elastic curve....

  10. CranSLIK v2.0: improving the stochastic prediction of oil spill transport and fate using approximation methods

    Science.gov (United States)

    Rutherford, R.; Moulitsas, I.; Snow, B. J.; Kolios, A. J.; De Dominicis, M.

    2015-10-01

    Oil spill models are used to forecast the transport and fate of oil after it has been released. CranSLIK is a model that predicts the movement and spread of a surface oil spill at sea via a stochastic approach. The aim of this work is to identify parameters that can further improve the forecasting algorithms and expand the functionality of CranSLIK, while maintaining the run-time efficiency of the method. The results from multiple simulations performed using the operational, validated oil spill model, MEDSLIK-II, were analysed using multiple regression in order to identify improvements which could be incorporated into CranSLIK. This has led to a revised model, namely CranSLIK v2.0, which was validated against MEDSLIK-II forecasts for real oil spill cases. The new version of CranSLIK demonstrated significant forecasting improvements by capturing the oil spill accurately in real validation cases and also proved capable of simulating a broader range of oil spill scenarios.

  11. Convergence of the standard RLS method and UDUT factorisation of covariance matrix for solving the algebraic Riccati equation of the DLQR via heuristic approximate dynamic programming

    Science.gov (United States)

    Moraes Rêgo, Patrícia Helena; Viana da Fonseca Neto, João; Ferreira, Ernesto M.

    2015-08-01

    The main focus of this article is to present a proposal to solve, via UDUT factorisation, the convergence and numerical stability problems that are related to the covariance matrix ill-conditioning of the recursive least squares (RLS) approach for online approximations of the algebraic Riccati equation (ARE) solution associated with the discrete linear quadratic regulator (DLQR) problem formulated in the actor-critic reinforcement learning and approximate dynamic programming context. The parameterisations of the Bellman equation, utility function and dynamic system as well as the algebra of Kronecker product assemble a framework for the solution of the DLQR problem. The condition number and the positivity parameter of the covariance matrix are associated with statistical metrics for evaluating the approximation performance of the ARE solution via RLS-based estimators. The performance of RLS approximators is also evaluated in terms of consistence and polarisation when associated with reinforcement learning methods. The used methodology contemplates realisations of online designs for DLQR controllers that is evaluated in a multivariable dynamic system model.

  12. A minimalistic approach to static and dynamic electron correlations: Amending generalized valence bond method with extended random phase approximation correlation correction

    Science.gov (United States)

    Chatterjee, Koushik; Pastorczak, Ewa; Jawulski, Konrad; Pernal, Katarzyna

    2016-06-01

    A perfect-pairing generalized valence bond (GVB) approximation is known to be one of the simplest approximations, which allows one to capture the essence of static correlation in molecular systems. In spite of its attractive feature of being relatively computationally efficient, this approximation misses a large portion of dynamic correlation and does not offer sufficient accuracy to be generally useful for studying electronic structure of molecules. We propose to correct the GVB model and alleviate some of its deficiencies by amending it with the correlation energy correction derived from the recently formulated extended random phase approximation (ERPA). On the examples of systems of diverse electronic structures, we show that the resulting ERPA-GVB method greatly improves upon the GVB model. ERPA-GVB recovers most of the electron correlation and it yields energy barrier heights of excellent accuracy. Thanks to a balanced treatment of static and dynamic correlation, ERPA-GVB stays reliable when one moves from systems dominated by dynamic electron correlation to those for which the static correlation comes into play.

  13. Development of node-decoupled extended Kalman filter (NDEKF) training method to design neural network diagnostic/prognostic reasoners

    Science.gov (United States)

    Kaneshige, Kenichi; Wang, Xudong; Saewong, Mark; Syrmos, Vassilis

    2004-07-01

    In this paper, we have proposed diagnostic techniques using a multilayered neural network where the weights in the network are updated using node-decoupled extended Kalman filter (NDEKF) training method. Sensor signals in both time domain and frequency domain are analyzed to show the effectiveness of the NDEKF algorithm in each domain. Comparisons of the NDEKF algorithm with other popular neural network training algorithms such as extended Kalman filter (EKF) and backpropagation (BP) will be discussed in the paper through a system identification problem. First, the simulation results reveal the comparison of outputs from actual system and trained neural network. Secondly, the ability of diagnosing a system with one normal condition and three known fault conditions is demonstrated. Thirdly, the robustness of the machine condition monitoring when the inputs to the system vary is shown. The proposed technique works even when there is noise in sensor signals as well.

  14. An Approximate Treatment of Reflection Coefficient in the Phased Beam Tracing Method for the Simulation of Enclosed Sound Fields at Medium Frequencies

    DEFF Research Database (Denmark)

    Jeong, Cheol-Ho; Ih, Jeong-Guon; Rindel, Jens Holger

    2008-01-01

    surface and the complex wave number for describing the propagation characteristics. In this study, two types of approximate real reflection coefficients derived from the measured absorption coefficient were tested for a practical applicability. As a test example, pressure impulse responses and energy......The phased beam tracing method (PBTM) was suggested as a medium-frequency simulation technique for the calculation of impulse response, although main assumptions of geometric acoustics still hold. The phased method needs the reflection coefficient for characterizing the acoustic property of a...

  15. Synthesis of approximation errors

    Energy Technology Data Exchange (ETDEWEB)

    Bareiss, E.H.; Michel, P.

    1977-07-01

    A method is developed for the synthesis of the error in approximations in the large of regular and irregular functions. The synthesis uses a small class of dimensionless elementary error functions which are weighted by the coefficients of the expansion of the regular part of the function. The question is answered whether a computer can determine the analytical nature of a solution by numerical methods. It is shown that continuous least-squares approximations of irregular functions can be replaced by discrete least-squares approximation and how to select the discrete points. The elementary error functions are used to show how the classical convergence criterions can be markedly improved. There are eight numerical examples included, 30 figures and 74 tables.

  16. Approximate nonlinear self-adjointness and approximate conservation laws

    International Nuclear Information System (INIS)

    In this paper, approximate nonlinear self-adjointness for perturbed PDEs is introduced and its properties are studied. Consequently, approximate conservation laws which cannot be obtained by the approximate Noether theorem are constructed by means of the method. As an application, a class of perturbed nonlinear wave equations is considered to illustrate the effectiveness. (paper)

  17. Approximation by Cylinder Surfaces

    DEFF Research Database (Denmark)

    Randrup, Thomas

    1997-01-01

    We present a new method for approximation of a given surface by a cylinder surface. It is a constructive geometric method, leading to a monorail representation of the cylinder surface. By use of a weighted Gaussian image of the given surface, we determine a projection plane. In the orthogonal...... projection of the surface onto this plane, a reference curve is determined by use of methods for thinning of binary images. Finally, the cylinder surface is constructed as follows: the directrix of the cylinder surface is determined by a least squares method minimizing the distance to the points in the...

  18. Derivation and evaluation of an approximate analysis for three-dimensional viscous subsonic flow with large secondary velocities. [finite difference method

    Science.gov (United States)

    Anderson, O. L.; Briley, W. R.; Mcdonald, H.

    1978-01-01

    An approximate analysis is presented for calculating three-dimensional, low Mach number, laminar viscous flows in curved passages with large secondary flows and corner boundary layers. The analysis is based on the decomposition of the overall velocity field into inviscid and viscous components with the overall velocity being determined from superposition. An incompressible vorticity transport equation is used to estimate inviscid secondary flow velocities to be used as corrections to the potential flow velocity field. A parabolized streamwise momentum equation coupled to an adiabatic energy equation and global continuity equation is used to obtain an approximate viscous correction to the pressure and longitudinal velocity fields. A collateral flow assumption is invoked to estimate the viscous correction to the transverse velocity fields. The approximate analysis is solved numerically using an implicit ADI solution for the viscous pressure and velocity fields. An iterative ADI procedure is used to solve for the inviscid secondary vorticity and velocity fields. This method was applied to computing the flow within a turbine vane passage with inlet flow conditions of M = 0.1 and M = 0.25, Re = 1000 and adiabatic walls, and for a constant radius curved rectangular duct with R/D = 12 and 14 and with inlet flow conditions of M = 0.1, Re = 1000, and adiabatic walls.

  19. The metabolic network of Clostridium acetobutylicum: Comparison of the approximate Bayesian computation via sequential Monte Carlo (ABC-SMC) and profile likelihood estimation (PLE) methods for determinability analysis.

    Science.gov (United States)

    Thorn, Graeme J; King, John R

    2016-01-01

    The Gram-positive bacterium Clostridium acetobutylicum is an anaerobic endospore-forming species which produces acetone, butanol and ethanol via the acetone-butanol (AB) fermentation process, leading to biofuels including butanol. In previous work we looked to estimate the parameters in an ordinary differential equation model of the glucose metabolism network using data from pH-controlled continuous culture experiments. Here we combine two approaches, namely the approximate Bayesian computation via an existing sequential Monte Carlo (ABC-SMC) method (to compute credible intervals for the parameters), and the profile likelihood estimation (PLE) (to improve the calculation of confidence intervals for the same parameters), the parameters in both cases being derived from experimental data from forward shift experiments. We also apply the ABC-SMC method to investigate which of the models introduced previously (one non-sporulation and four sporulation models) have the greatest strength of evidence. We find that the joint approximate posterior distribution of the parameters determines the same parameters as previously, including all of the basal and increased enzyme production rates and enzyme reaction activity parameters, as well as the Michaelis-Menten kinetic parameters for glucose ingestion, while other parameters are not as well-determined, particularly those connected with the internal metabolites acetyl-CoA, acetoacetyl-CoA and butyryl-CoA. We also find that the approximate posterior is strongly non-Gaussian, indicating that our previous assumption of elliptical contours of the distribution is not valid, which has the effect of reducing the numbers of pairs of parameters that are (linearly) correlated with each other. Calculations of confidence intervals using the PLE method back this up. Finally, we find that all five of our models are equally likely, given the data available at present. PMID:26561777

  20. A variational multi-scale method with spectral approximation of the sub-scales: Application to the 1D advection-diffusion equations

    KAUST Repository

    Chacón Rebollo, Tomás

    2015-03-01

    This paper introduces a variational multi-scale method where the sub-grid scales are computed by spectral approximations. It is based upon an extension of the spectral theorem to non necessarily self-adjoint elliptic operators that have an associated base of eigenfunctions which are orthonormal in weighted L2 spaces. This allows to element-wise calculate the sub-grid scales by means of the associated spectral expansion. We propose a feasible VMS-spectral method by truncation of this spectral expansion to a finite number of modes. We apply this general framework to the convection-diffusion equation, by analytically computing the family of eigenfunctions. We perform a convergence and error analysis. We also present some numerical tests that show the stability of the method for an odd number of spectral modes, and an improvement of accuracy in the large resolved scales, due to the adding of the sub-grid spectral scales.

  1. Numerically oriented static response approach based on state-specific multi-reference coupled electron-pair approximation (SS-MRCEPA) like methods

    International Nuclear Information System (INIS)

    In this paper, we have exploited the recently developed state-specific multi-reference coupled electron-pair approximation (SS-MRCEPA) like methods for computing the electrostatic response properties. The SS-MRCEPA methods are formulated on complete active space reference functions and the required energies are computed via the diagonalization of an effective operator within this space. The SS-MRCEPA theories are size-consistent and size-extensive. They are very efficient for treating quasidegeneracy of varying extent and for bypassing the intruder problem. The efficacy of the methods is illustrated via the computation of the static dipole moment and polarizability of the ground state and the corresponding first excited state of the trapezoidal H4 model (H4) as well as the lowest two singlet states of the CH2 system using perturbed orbitals generated via the finite-field strategy, a numerically oriented static response approach

  2. An approximate theoretical method for modeling the static thrust performance of non-axisymmetric two-dimensional convergent-divergent nozzles. M.S. Thesis - George Washington Univ.

    Science.gov (United States)

    Hunter, Craig A.

    1995-01-01

    An analytical/numerical method has been developed to predict the static thrust performance of non-axisymmetric, two-dimensional convergent-divergent exhaust nozzles. Thermodynamic nozzle performance effects due to over- and underexpansion are modeled using one-dimensional compressible flow theory. Boundary layer development and skin friction losses are calculated using an approximate integral momentum method based on the classic karman-Polhausen solution. Angularity effects are included with these two models in a computational Nozzle Performance Analysis Code, NPAC. In four different case studies, results from NPAC are compared to experimental data obtained from subscale nozzle testing to demonstrate the capabilities and limitations of the NPAC method. In several cases, the NPAC prediction matched experimental gross thrust efficiency data to within 0.1 percent at a design NPR, and to within 0.5 percent at off-design conditions.

  3. An approximate method for solving the problem of the establishment of chemical equilibrium in the products of explosion of gas mixture

    Science.gov (United States)

    Shargatov, V. A.; Gubin, S. A.; Okunev, D. Yu

    2015-11-01

    Based on the assumption of the existence of the partial chemical equilibrium in the detonation products, an approximate method for calculating composition of the detonation products is developed. The method uses the assumption of the existence of extremum of Helmholtz free energy for a given density, temperature, and molecular weight of the detonation products mixture. Without significant loss of accuracy to the solution of stiff differential equations, detailed kinetic mechanism can be replaced by one differential equation and a system of algebraic equations. This method is always consistent with the detailed mechanism and can be used separately or in conjunction with the decision of a stiff system, replacing it when bimolecular reactions are near equilibrium.

  4. An approximate inversion method of geoelectrical sounding data using linear and bayesian statistical approaches. Examples of Tritrivakely volcanic lake and Mahitsy area (central part of Madagascar)

    International Nuclear Information System (INIS)

    This paper is concerned with resistivity sounding measurements performed from single site (vertical sounding) or from several sites (profiles) within a bounded area. The objective is to present an accurate information about the study area and to estimate the likelihood of the produced quantitative models. The achievement of this objective obviously requires quite relevant data and processing methods. It also requires interpretation methods which should take into account the probable effect of an heterogeneous structure. In front of such difficulties, the interpretation of resistivity sounding data inevitably involves the use of inversion methods. We suggest starting the interpretation in simple situation (1-D approximation), and using the rough but correct model obtained as an a-priori model for any more refined interpretation. Related to this point of view, special attention should be paid for the inverse problem applied to the resistivity sounding data. This inverse problem is nonlinear, while linearity inherent in the functional response used to describe the physical experiment. Two different approaches are used to build an approximate but higher dimensional inversion of geoelectrical data: the linear approach and the bayesian statistical approach. Some illustrations of their application in resistivity sounding data acquired at Tritrivakely volcanic lake (single site) and at Mahitsy area (several sites) will be given. (author). 28 refs, 7 figs

  5. Approximative methods for the stability analysis of anchored liquid storage tanks under earthquake excitation; Naeherungsmethoden zur Stabilitaetsuntersuchung von erdbebenerregten verankerten Fluessigkeitsbehaeltern

    Energy Technology Data Exchange (ETDEWEB)

    Seiler, C.

    2001-07-01

    This doctoral thesis presents approximative methods for the stability analysis of anchored liquid storage tanks under earthquake excitation. By first introducing a quasistatic model well known phenomena of collapse are analysed with little numerical effort and the underlying mechanisms of collapse are explained. Subsequently, a more detailed analysis of the structural behavior in the time domain is obtained by a complete interactive model and by employing a suitable time integration method. In this context, the dynamic stability behavior is calculated by defining a problem oriented criterion. Performing an extensive parameter study the approximative methods are discussed and the results lead to a new empirical design concept which may be implemented in the current draft of Eurocode 8, part 4 for stability verifications. (orig.) [German] In der vorliegenden Arbeit wird das Stabilitaetsverhalten von verankerten Fluessigkeitsbehaeltern unter seismischer Einwirkung mit Hilfe unterschiedlicher Naeherungsmethoden behandelt. Die Einfuehrung eines quasistatischen Ersatzmodells bietet zunaechst die Moeglichkeit, bekannte Versagensphaenomene mit geringem numerischen Aufwand zu berechnen und die zugrundeliegenden Versagensmechanismen zu erklaeren. Zu einer genaueren Analyse des Tragverhaltens im Zeitbereich wird anschliessend ein vollstaendiges Interaktionsmodell in Verbindung mit einem geeigneten Zeitintegrationsverfahren herangezogen. Das dynamische Stabilitaetsverhalten wird dabei mit einem Kriterium beurteilt, das problemorientiert definiert wird. Eine umfangreiche Parameterstudie stellt die vorgestellten Naeherungsverfahren gegenueber und dient als Datenbasis fuer ein neu entwickeltes empirisches Bemessungskonzept, das in die aktuelle Normengebung des EC 8, Teil 4 in bezug auf die erforderlichen Stabilitaetsnachweise aufgenommen werden koennte. (orig.)

  6. Diophantine approximations on fractals

    CERN Document Server

    Einsiedler, Manfred; Shapira, Uri

    2009-01-01

    We exploit dynamical properties of diagonal actions to derive results in Diophantine approximations. In particular, we prove that the continued fraction expansion of almost any point on the middle third Cantor set (with respect to the natural measure) contains all finite patterns (hence is well approximable). Similarly, we show that for a variety of fractals in [0,1]^2, possessing some symmetry, almost any point is not Dirichlet improvable (hence is well approximable) and has property C (after Cassels). We then settle by similar methods a conjecture of M. Boshernitzan saying that there are no irrational numbers x in the unit interval such that the continued fraction expansions of {nx mod1 : n is a natural number} are uniformly eventually bounded.

  7. A posteriori error estimator based on gradient recovery by averaging for convection-diffusion-reaction problems approximated by discontinuous Galerkin methods

    CERN Document Server

    Creusé, Emmanuel

    2010-01-01

    We consider some (anisotropic and piecewise constant) convection-diffusion-reaction problems in domains of R2, approximated by a discontinuous Galerkin method with polynomials of any degree. We propose two a posteriori error estimators based on gradient recovery by averaging. It is shown that these estimators give rise to an upper bound where the constant is explicitly known up to some additional terms that guarantees reliability. The lower bound is also established, one being robust when the convection term (or the reaction term) becomes dominant. Moreover, the estimator is asymptotically exact when the recovered gradient is superconvergent. The reliability and efficiency of the proposed estimators are confirmed by some numerical tests.

  8. The Integration of Compiled and Explicit Causal Knowledge for Diagnostic Reasoning

    OpenAIRE

    Senyk, Oksana

    1988-01-01

    Causal reasoning gained prominence in the “second generation” of artificial intelligence in medicine (AIM) programs in the late 1970s. Today we face the challenge of developing methods of compiled causal reasoning which approximates the clinical reasoning employed by expert diagnosticians for the efficient solution of most cases. To this end, we have developed the compiled causal link technique, by means of which a diagnostic system can solve routine cases quickly and can deal efficiently wit...

  9. An Approximate Model of Microchannel Cooling

    Institute of Scientific and Technical Information of China (English)

    ShipingYu; MingdaoXin

    1994-01-01

    Forced convective heat transfer in micro-rectangular channels can be described by a group of two-dimensional differential equations.These equations take the conduction in microchannel wall along the direction of flow of coolants into account,which are more generalized than those which neglect the conduction.For the same reason,they are suitable particularly for gases-cooled microchannels.With only numerical solution to the equations till today,an approximate analytic solution is derived here,From this solution,a rather simple formula can be introduced further,by which the differences between considering the conduction and neglecting it are easily found.In addition,the reasonableness of the classical fin method is also discussed.An experimental example of air-cooled microchannels is illustrated.

  10. On the WKBJ approximation

    International Nuclear Information System (INIS)

    A simple approach employing properties of solutions of differential equations is adopted to derive an appropriate extension of the WKBJ method. Some of the earlier techniques that are commonly in use are unified, whereby the general approximate solution to a second-order homogeneous linear differential equation is presented in a standard form that is valid for all orders. In comparison to other methods, the present one is shown to be leading in the order of iteration, and thus possibly has the ability of accelerating the convergence of the solution. The method is also extended for the solution of inhomogeneous equations. (author)

  11. Finite elements and approximation

    CERN Document Server

    Zienkiewicz, O C

    2006-01-01

    A powerful tool for the approximate solution of differential equations, the finite element is extensively used in industry and research. This book offers students of engineering and physics a comprehensive view of the principles involved, with numerous illustrative examples and exercises.Starting with continuum boundary value problems and the need for numerical discretization, the text examines finite difference methods, weighted residual methods in the context of continuous trial functions, and piecewise defined trial functions and the finite element method. Additional topics include higher o

  12. AN APPROXIMATE SOLUTION FOR THE EFFECTIVE ELASTIC MODULI OF DIFFERENTIAL METHOD%有效弹性模量微分法的一种近似解法

    Institute of Scientific and Technical Information of China (English)

    吴云章; 兑关锁; 朱玉萍

    2011-01-01

    鉴于Eshelby张量在整个微分法的"取出-添入"过程中的变化对等效模量变化影响较小,论文推出了微分法的近似显式解.该近似解形式简捷,计算方便,不仅适用于球形颗粒夹杂,对随机短纤维夹杂等情况也同样适应,所得结果与实验数据非常接近.%Considering that the effect of Eshelby's tensor in view of the entire differential method of ‘extraction-accession' during the process of change in modulus variation is less,an approximate explicit expression of the differential method is established in the paper. The simple form of approximate solution is facilitating to calculation. The expression can be fit very well for spherical inclusions and stochastic short fiber inclusions. It shows that the theoretical prediction results are in good agreement with the existed experimental data.

  13. Improved S2 approximations

    International Nuclear Information System (INIS)

    Highlights: • Development of optimization rules for S2 quadrature sets. • Studying the dependency of optimized S2 quadratures on composition and geometry. • Demonstrating S2 procedures preserving the features of higher approximations. - Abstract: Discrete ordinates method relies on approximating the integral term of the transport equation with the aid of quadrature summation rules. These quadratures are usually based on certain assumptions which assure specific symmetry rules and transport/diffusion limits. Generally, these assumptions are not problem-dependent which results in inaccuracies in some instances. Here, various methods have been developed for more accurate estimation of the independent angle in S2 approximation, as it is tightly related to valid estimation of the diffusion coefficient/length. We proposed and examined a method to reduce a complicated problem that usually is consisting many energy groups and discrete directions (SN) to an equivalent one-group S2 problem while it mostly preserves general features of the original model. Some numerical results are demonstrated to show the accuracy of proposed method

  14. A comparison between the discrete point approximation and NOMOGRAM methods for estimation of dose resulting from gamma rays emitted by radionuclide in finite cloud

    International Nuclear Information System (INIS)

    Both the nomogram method and discrete point approximation can be used for estimation of doses resulting from gamma rays emitted by radionuclides in finite cloud. The former can only be applied for evaluation of dose from nine noble gas finite clouds in case of constant weather conditions, but the later can be used for estimation of doses from some radionuclides finite clouds is case of changing weather condition during the transport times. Some calculations using the two methods have been made under the described situation. The comparison computations for absorbed dose rate in air show a very good agreement. Mostly, above 86% of the computed data are within a factor of 2, up to 96% of data are within a factor of 3. Naturally, it should be noticed that the remaining percentage have an error up to a factor of 6 at stable atmospheric condition. (2 tabs.)

  15. Defeasibility in Legal Reasoning

    OpenAIRE

    Sartor, Giovanni

    2009-01-01

    I shall first introduce the idea of reasoning, and of defeasible reasoning in particular. I shall then argue that cognitive agents need to engage in defeasible reasoning for coping with a complex and changing environment. Consequently, defeasibility is needed in practical reasoning, and in particular in legal reasoning

  16. Diophantine approximation and badly approximable sets

    DEFF Research Database (Denmark)

    Kristensen, S.; Thorn, R.; Velani, S.

    2006-01-01

    Let (X,d) be a metric space and (Omega, d) a compact subspace of X which supports a non-atomic finite measure m.  We consider `natural' classes of badly approximable  subsets of Omega. Loosely speaking, these consist of points in Omega which `stay clear' of some given set of points in X....... The classical set Bad of `badly approximable' numbers in the theory of Diophantine approximation falls within our framework as do the sets Bad(i,j) of simultaneously badly approximable numbers. Under various natural conditions we prove that the badly approximable subsets of Omega have full Hausdorff dimension...

  17. The accuracy of the DDA (Discrete Dipole Approximation) method in determining the optical properties of black carbon fractal-like aggregates

    Science.gov (United States)

    Skorupski, Krzysztof

    2015-05-01

    Black carbon (BC) particles are a product of incomplete combustion of carbon-based fuels. One of the possibilities of studying the optical properties of BC structures is to use the DDA (Discrete Dipole Approximation) method. The main goal of this work was to investigate its accuracy and to approximate the most reliable simulation parameters. For the light scattering simulations the ADDA code was used and for the reference program the superposition T-Matrix code by Mackowski was selected. The study was divided into three parts. First, DDA simulations for a single particle (sphere) were performed. The results proved that the meshing algorithm can significantly affect the particle shape, and therefore, the extinction diagrams. The volume correction procedure is recommended for sparse or asymmetrical meshes. In the next step large fractal-like aggregates were investigated. When sparse meshes are used, the impact of the volume correction procedure cannot be easily predicted. In some cases it can even lead to more erroneous results. Finally, the optical properties of fractal-like aggregates composed of spheres in point contact were compared to much more realistic structures made up of connected, non-spherical primary particles.

  18. An Efficient Method for Calculating the Characteristics of the Integrated Lens Antennas on the Basis of the Geometrical and Physical Optics Approximations

    Science.gov (United States)

    Mozharovskiy, A. V.; Artemenko, A. A.; Mal'tsev, A. A.; Maslennikov, R. O.; Sevast'yanov, A. G.; Ssorin, V. N.

    2015-11-01

    We develop a combined method for calculating the characteristics of the integrated lens antennas for millimeter-wave wireless local radio-communication systems on the basis of the geometrical and physical optics approximations. The method is based on the concepts of geometrical optics for calculating the electromagnetic-field distribution on the lens surface (with allowance for multiple internal re-reflections) and physical optics for determining the antenna-radiated fields in the Fraunhofer zone. Using the developed combined method, we study various integrated lens antennas on the basis of the data on the used-lens shape and material and the primary-feed radiation model, which is specified analytically or by computer simulation. Optimal values of the cylindrical-extension length, which ensure the maximum antenna directivity equal to 19.1 and 23.8 dBi for the greater and smaller lenses, respectively, are obtained for the hemispherical quartz-glass lenses having the cylindrical extensions with radii of 7.5 and 12.5 mm. In this case, the scanning-angle range of the considered antennas is greater than ±20° for an admissible 2-dB decrease in the directivity of the deflected beam. The calculation results obtained using the developed method are confirmed by the experimental studies performed for the prototypes of the integrated quartz-glass lens antennas within the framework of this research.

  19. A New Approach of Asymmetric Homoclinic and Heteroclinic Orbits Construction in Several Typical Systems Based on the Undetermined Padé Approximation Method

    Directory of Open Access Journals (Sweden)

    Jingjing Feng

    2016-01-01

    Full Text Available In dynamic systems, some nonlinearities generate special connection problems of non-Z2 symmetric homoclinic and heteroclinic orbits. Such orbits are important for analyzing problems of global bifurcation and chaos. In this paper, a general analytical method, based on the undetermined Padé approximation method, is proposed to construct non-Z2 symmetric homoclinic and heteroclinic orbits which are affected by nonlinearity factors. Geometric and symmetrical characteristics of non-Z2 heteroclinic orbits are analyzed in detail. An undetermined frequency coefficient and a corresponding new analytic expression are introduced to improve the accuracy of the orbit trajectory. The proposed method shows high precision results for the Nagumo system (one single orbit; general types of non-Z2 symmetric nonlinear quintic systems (orbit with one cusp; and Z2 symmetric system with high-order nonlinear terms (orbit with two cusps. Finally, numerical simulations are used to verify the techniques and demonstrate the enhanced efficiency and precision of the proposed method.

  20. 一种基于本体推理的业务特征获取方法%Service Feature Acquisition Method Based on Ontology Reasoning

    Institute of Scientific and Technical Information of China (English)

    盖炳帅; 王劲林; 刘学

    2013-01-01

    In the field of service data sampling, this paper provides a service feature acquisition method based on ontology reasoning to solve the problem of lacking automatic methods for data sampling item acquisition. Firstly, this method eliminates OWL conflicts in the service ontology using Racer and eliminates SWRL conflicts in the service ontology using JESS. Secondly, this method acquests explicit service features by ontology parsing and implicit service features in the service ontology using rules designed based on the ontology-based service model. Lastly, this method generates service data sampling items with the features in the service ontology. The analysis result of the example shows that this method can make data sampling item acquisition process automaticly.%在业务数据采集领域中,针对采集数据项不能自动获取的问题,提出一种利用本体推理的业务特征获取方法.在方法中,首先用Racer推理机消除业务本体中存在的OWL语义冲突,采用JESS推理机消除业务本体中存在的SWRL语义冲突,然后通过本体解析获取明显业务特征,并基于本体业务模型设计隐含业务特征获取规则,获取隐含业务特征,最后结合业务本体生成业务采集数据项集合.实例仿真结果表明,改进方法能够实现自动化的业务采集数据项获取过程.