The inverse maximum dynamic flow problem
BAGHERIAN; Mehri
2010-01-01
We consider the inverse maximum dynamic flow (IMDF) problem.IMDF problem can be described as: how to change the capacity vector of a dynamic network as little as possible so that a given feasible dynamic flow becomes a maximum dynamic flow.After discussing some characteristics of this problem,it is converted to a constrained minimum dynamic cut problem.Then an efficient algorithm which uses two maximum dynamic flow algorithms is proposed to solve the problem.
The inverse maximum flow problem with lower and upper bounds for the flow
Deaconu Adrian
2008-01-01
Full Text Available The general inverse maximum flow problem (denoted GIMF is considered, where lower and upper bounds for the flow are changed so that a given feasible flow becomes a maximum flow and the distance (considering l1 norm between the initial vector of bounds and the modified vector is minimum. Strongly and weakly polynomial algorithms for solving this problem are proposed. In the paper it is also proved that the inverse maximum flow problem where only the upper bound for the flow is changed (IMF is a particular case of the GIMF problem.
An Exact Solution Approach for the Maximum Multicommodity K-splittable Flow Problem
Gamst, Mette; Petersen, Bjørn
2009-01-01
This talk concerns the NP-hard Maximum Multicommodity k-splittable Flow Problem (MMCkFP) in which each commodity may use at most k paths between its origin and its destination. A new branch-and-cut-and-price algorithm is presented. The master problem is a two-index formulation of the MMCk......FP and the pricing problem is the shortest path problem with forbidden paths. A new branching strategy forcing and forbidding the use of certain paths is developed. The new branch-and-cut-and-price algorithm is computationally evaluated and compared to results from the literature. The new algorithm shows very...
A route-based decomposition for the Multi-Commodity k-splittable Maximum Flow Problem
Gamst, Mette
2012-01-01
The Multi-Commodity k-splittable Maximum Flow Problem routes flow through a capacitated graph such that each commodity uses at most k paths and such that the total amount of routedflow is maximized. This paper proposes a branch-and-price algorithm based on a route-based Dantzig-Wolfe decomposition......, where a route consists of up to k paths. Computational results show that the new algorithm has best performance on seven benchmark instances and is capable of solving two previously unsolved instances....
A local search heuristic for the Multi-Commodity k-splittable Maximum Flow Problem
Gamst, Mette
2014-01-01
The Multi-Commodity k-splittable Maximum Flow Problem consists of maximizing the amount of flow routed through a network such that each commodity uses at most k paths and such that edge capacities are satisfied. The problem is NP -hard and has application in a.o. telecommunications. In this paper......, a local search heuristic for solving the problem is proposed. The heuristic is an iterative shortest path procedure on a reduced graph combined with a local search procedure to modify certain path flows and prioritize the different commodities. The heuristic is tested on benchmark instances from...
A decomposition based on path sets for the Multi-Commodity k-splittable Maximum Flow Problem
Gamst, Mette
Switching. In the literature, the problem is solved to optimality using branch-and-price algorithms built on path-based Dantzig-Wolfe decompositions. This paper proposes a new branch-and-price algorithm built on a path set-based Dantzig-Wolfe decomposition. A path set consists of up to k paths, each...... carrying a certain amount of flow. The new branch-and-price algorithm is implemented and compared to the leading algorithms in the literature. Results for the proposed method are competitive and the method even has best performance on some instances. However, the results also indicate some scaling issues....
Comparing branch-and-price algorithms for the Multi-Commodity k-splittable Maximum Flow Problem
Gamst, Mette; Petersen, Bjørn
2012-01-01
-Protocol Label Switching. The problem has previously been solved to optimality through branch-and-price. In this paper we propose two exact solution methods both based on an alternative decomposition. The two methods differ in their branching strategy. The first method, which branches on forbidden edge sequences...
Hard graphs for the maximum clique problem
Hoede, Cornelis
1988-01-01
The maximum clique problem is one of the NP-complete problems. There are graphs for which a reduction technique exists that transforms the problem for these graphs into one for graphs with specific properties in polynomial time. The resulting graphs do not grow exponentially in order and number. Gra
The Wiener maximum quadratic assignment problem
Cela, Eranda; Woeginger, Gerhard J
2011-01-01
We investigate a special case of the maximum quadratic assignment problem where one matrix is a product matrix and the other matrix is the distance matrix of a one-dimensional point set. We show that this special case, which we call the Wiener maximum quadratic assignment problem, is NP-hard in the ordinary sense and solvable in pseudo-polynomial time. Our approach also yields a polynomial time solution for the following problem from chemical graph theory: Find a tree that maximizes the Wiener index among all trees with a prescribed degree sequence. This settles an open problem from the literature.
The Maximum Resource Bin Packing Problem
Boyar, J.; Epstein, L.; Favrholdt, L.M.
2006-01-01
Usually, for bin packing problems, we try to minimize the number of bins used or in the case of the dual bin packing problem, maximize the number or total size of accepted items. This paper presents results for the opposite problems, where we would like to maximize the number of bins used...... algorithms, First-Fit-Increasing and First-Fit-Decreasing for the maximum resource variant of classical bin packing. For the on-line variant, we define maximum resource variants of classical and dual bin packing. For dual bin packing, no on-line algorithm is competitive. For classical bin packing, we find...
The Maximum Resource Bin Packing Problem
Boyar, J.; Epstein, L.; Favrholdt, L.M.
2006-01-01
algorithms, First-Fit-Increasing and First-Fit-Decreasing for the maximum resource variant of classical bin packing. For the on-line variant, we define maximum resource variants of classical and dual bin packing. For dual bin packing, no on-line algorithm is competitive. For classical bin packing, we find......Usually, for bin packing problems, we try to minimize the number of bins used or in the case of the dual bin packing problem, maximize the number or total size of accepted items. This paper presents results for the opposite problems, where we would like to maximize the number of bins used...... the competitive ratio of various natural algorithms. We study the general versions of the problems as well as the parameterized versions where there is an upper bound of on the item sizes, for some integer k....
Inverse feasibility problems of the inverse maximum ﬂow problems
Adrian Deaconu; Eleonor Ciurea
2013-04-01
A linear time method to decide if any inverse maximum ﬂow (denoted General Inverse Maximum Flow problems (IMFG)) problem has solution is deduced. If IMFG does not have solution, methods to transform IMFG into a feasible problem are presented. The methods consist of modifying as little as possible the restrictions to the variation of the bounds of the ﬂow. New inverse combinatorial optimization problems are introduced and solved.
Maximum process problems in optimal control theory
Goran Peskir
2005-01-01
Full Text Available Given a standard Brownian motion (Btt≥0 and the equation of motion dXt=vtdt+2dBt, we set St=max0≤s≤tXs and consider the optimal control problem supvE(Sτ−Cτ, where c>0 and the supremum is taken over all admissible controls v satisfying vt∈[μ0,μ1] for all t up to τ=inf{t>0|Xt∉(ℓ0,ℓ1} with μ0g∗(St, where s↦g∗(s is a switching curve that is determined explicitly (as the unique solution to a nonlinear differential equation. The solution found demonstrates that the problem formulations based on a maximum functional can be successfully included in optimal control theory (calculus of variations in addition to the classic problem formulations due to Lagrange, Mayer, and Bolza.
A polynomial algorithm for abstract maximum flow
McCormick, S.T. [Univ. of British Columbia, Vancouver, British Columbia (Canada)
1996-12-31
Ford and Fulkerson`s original 1956 max flow/min cut paper formulated max flow in terms of flows on paths, rather than the more familiar flows on arcs. In 1974 Hoffman pointed out that Ford and Fulkerson`s original proof was quite abstract, and applied to a wide range of max flow-like problems. In this abstract model we have capacitated elements, and linearly ordered subsets of elements called paths. When two paths share an element ({open_quote}cross{close_quote}), then there must be a path that is a subset of the first path up to the cross, and a subset of the second path after the cross. (Hoffman`s generalization of) Ford and Fulkerson`s proof showed that the max flow/min cut theorem still holds under this weak assumption. However, this proof is non-constructive. To get an algorithm, we assume that we have an oracle whose input is an arbitrary subset of elements, and whose output is either a path contained in that subset, or the statement that no such path exists. We then use complementary slackness to show how to augment any feasible set of path flows to a set with a strictly larger total flow value using a polynomial number of calls to the oracle. Then standard scaling techniques yield an overall polynomial algorithm for finding both a max flow and a min cut. Hoffman`s paper actually considers a sort of supermodular objective on the path flows, which allows him to include transportation problems and thus rain-cost flow in his frame-work. We also discuss extending our algorithm to this more general case.
A Fast Parametric Maximum Flow Algorithm. Revision,
1987-07-01
26]. ". N. Perfect sharing arises in a network transmission problem studied by Itai and Rodeh [21] and 1 Gusfield [17] and in a network...the network transmission scheduling problem described below. Another application will arise in Section 4.2. Scheduling transmissions. Itai and Rodeh...constructed from the flow in 0(m) time as described in [21]. Itai and Rodeh proposed two 22 "-N., -- %’%’ % %""’ . ,’ ""€"" ",. . -",/a
Improved Minimum Cuts and Maximum Flows in Undirected Planar Graphs
Italiano, Giuseppe F
2010-01-01
In this paper we study minimum cut and maximum flow problems on planar graphs, both in static and in dynamic settings. First, we present an algorithm that given an undirected planar graph computes the minimum cut between any two given vertices in O(n log log n) time. Second, we show how to achieve the same O(n log log n) bound for the problem of computing maximum flows in undirected planar graphs. To the best of our knowledge, these are the first algorithms for those two problems that break the O(n log n) barrier, which has been standing for more than 25 years. Third, we present a fully dynamic algorithm that is able to maintain information about minimum cuts and maximum flows in a plane graph (i.e., a planar graph with a fixed embedding): our algorithm is able to insert edges, delete edges and answer min-cut and max-flow queries between any pair of vertices in O(n^(2/3) log^3 n) time per operation. This result is based on a new dynamic shortest path algorithm for planar graphs which may be of independent int...
Exploring the Constrained Maximum Edge-weight Connected Graph Problem
Zhen-ping Li; Shi-hua Zhang; Xiang-Sun Zhang; Luo-nan Chen
2009-01-01
Given an edge weighted graph,the maximum edge-weight connected graph (MECG) is a connected subgraph with a given number of edges and the maximal weight sum.Here we study a special case,i.e.the Constrained Maximum Edge-Weight Connected Graph problem (CMECG),which is an MECG whose candidate subgraphs must include a given set of k edges,then also called the k-CMECG.We formulate the k-CMECG into an integer linear programming model based on the network flow problem.The k-CMECG is proved to be NP-hard.For the special case 1-CMECG,we propose an exact algorithm and a heuristic algorithm respectively.We also propose a heuristic algorithm for the k-CMECG problem.Some simulations have been done to analyze the quality of these algorithms.Moreover,we show that the algorithm for 1-CMECG problem can lead to the solution of the general MECG problem.
An Interval Maximum Entropy Method for Quadratic Programming Problem
RUI Wen-juan; CAO De-xin; SONG Xie-wu
2005-01-01
With the idea of maximum entropy function and penalty function methods, we transform the quadratic programming problem into an unconstrained differentiable optimization problem, discuss the interval extension of the maximum entropy function, provide the region deletion test rules and design an interval maximum entropy algorithm for quadratic programming problem. The convergence of the method is proved and numerical results are presented. Both theoretical and numerical results show that the method is reliable and efficient.
Maximum Flow in Planar Networks with Exponentially Distributed Arc Capacities.
1984-12-01
avoid constructing the dual, are described in Itai and Shiloach P 97 91. In this paper, we consider the maximum flow problem in (st) planar networks...use arc e and lies completely below P. If no such path exists we say P(e) - *. An algorithm tc construct P(e) given P and e is described in Itai and...suggested in Ford and Fulkerson [1956], developed in Berge and Ghouila-Houri [1962] and its time complexity is reduced to 0( IVI log IVI ) by Itai and
The directed flow maximum near cs = 0
Brachmann, J.; Dumitru, A.; Stöcker, H.; Greiner, W.
2000-07-01
We investigate the excitation function of quark-gluon plasma formation and of directed in-plane flow of nucleons in the energy range of the BNL-AGS and for the E {Lab/kin} = 40 AGeV Pb + Pb collisions performed recently at the CERN-SPS. We employ the three-fluid model with dynamical unification of kinetically equilibrated fluid elements. Within our model with first-order phase transition at high density, droplets of QGP coexisting with hadronic matter are produced already at BNL-AGS energies, E {Lab/kin} ≃ 10 AGeV. A substantial decrease of the isentropic velocity of sound, however, requires higher energies, E {Lab/kin} ≃ 0 AGeV. We show the effect on the flow of nucleons in the reaction plane. According to our model calculations, kinematic requirements and EoS effects work hand-in-hand at E {Lab/kin} = 40 AGeV to allow the observation of the dropping velocity of sound via an increase of the directed flow around midrapidity as compared to top BNL-AGS energy.
A MAXIMUM ENTROPY METHOD FOR CONSTRAINED SEMI-INFINITEPROGRAMMING PROBLEMS
ZHOU Guanglu; WANG Changyu; SHI Zhenjun; SUN Qingying
1999-01-01
This paper presents a new method, called the maximum entropy method,for solving semi-infinite programming problems, in which thesemi-infinite programming problem is approximated by one with a singleconstraint. The convergence properties for this method are discussed.Numerical examples are given to show the high effciency of thealgorithm.
AN INVERSE MAXIMUM CAPACITY PATH PROBLEM WITH LOWER BOUND CONSTRAINTS
杨超; 陈学旗
2002-01-01
The computational complexity of inverse mimimum capacity path problem with lower bound on capacity of maximum capacity path is examined, and it is proved that solution of this problem is NP-complete. A strong polynomial algorithm for a local optimal solution is provided.
A Maximum Entropy Method for a Robust Portfolio Problem
Yingying Xu
2014-06-01
Full Text Available We propose a continuous maximum entropy method to investigate the robustoptimal portfolio selection problem for the market with transaction costs and dividends.This robust model aims to maximize the worst-case portfolio return in the case that allof asset returns lie within some prescribed intervals. A numerical optimal solution tothe problem is obtained by using a continuous maximum entropy method. Furthermore,some numerical experiments indicate that the robust model in this paper can result in betterportfolio performance than a classical mean-variance model.
Payoff-monotonic game dynamics and the maximum clique problem.
Pelillo, Marcello; Torsello, Andrea
2006-05-01
Evolutionary game-theoretic models and, in particular, the so-called replicator equations have recently proven to be remarkably effective at approximately solving the maximum clique and related problems. The approach is centered around a classic result from graph theory that formulates the maximum clique problem as a standard (continuous) quadratic program and exploits the dynamical properties of these models, which, under a certain symmetry assumption, possess a Lyapunov function. In this letter, we generalize previous work along these lines in several respects. We introduce a wide family of game-dynamic equations known as payoff-monotonic dynamics, of which replicator dynamics are a special instance, and show that they enjoy precisely the same dynamical properties as standard replicator equations. These properties make any member of this family a potential heuristic for solving standard quadratic programs and, in particular, the maximum clique problem. Extensive simulations, performed on random as well as DIMACS benchmark graphs, show that this class contains dynamics that are considerably faster than and at least as accurate as replicator equations. One problem associated with these models, however, relates to their inability to escape from poor local solutions. To overcome this drawback, we focus on a particular subclass of payoff-monotonic dynamics used to model the evolution of behavior via imitation processes and study the stability of their equilibria when a regularization parameter is allowed to take on negative values. A detailed analysis of these properties suggests a whole class of annealed imitation heuristics for the maximum clique problem, which are based on the idea of varying the parameter during the imitation optimization process in a principled way, so as to avoid unwanted inefficient solutions. Experiments show that the proposed annealing procedure does help to avoid poor local optima by initially driving the dynamics toward promising regions in
Maximum-entropy for the laser fusion problem
Madkour, M.A. [Nansoura Univ. (Egypt). Dept. of Phys.
1996-09-01
The problem of heat flux at the critical surfaces and the surfaces of a pellet of deuterium and tritium (conduction zone) heated by laser have been considered. Ion-electron collisions are only allowed for: i.e. the linear transport equation is used to describe the problem with boundary conditions. The maximum-entropy approach is used to calculate the electron density and temperature across the conduction zone as well as the heat flux. Numerical results are given and compared with those of Rouse and Williams and El-Wakil et al. (orig.).
On some problems of the maximum entropy ansatz
K Bandyopadhyay; K Bhattacharyya; A K Bhattacharyya
2000-03-01
Some problems associated with the use of the maximum entropy principle, namely, (i) possible divergence of the series that is exponentiated, (ii) input-dependent asymptotic behaviour of the density function resulting from the truncation of the said series, and (iii) non-vanishing of the density function at the boundaries of a ﬁnite domain are pointed out. Prescriptions for remedying the aforesaid problems are put forward. Pilot calculations involving the ground quantum eigenenergy states of the quartic oscillator, the particle-in-a-box model, and the classical Maxwellian speed and energy distributions lend credence to our approach.
Berry, Vincent; Nicolas, François
2006-01-01
Given a set of evolutionary trees on a same set of taxa, the maximum agreement subtree problem (MAST), respectively, maximum compatible tree problem (MCT), consists of finding a largest subset of taxa such that all input trees restricted to these taxa are isomorphic, respectively compatible. These problems have several applications in phylogenetics such as the computation of a consensus of phylogenies obtained from different data sets, the identification of species subjected to horizontal gene transfers and, more recently, the inference of supertrees, e.g., Trees Of Life. We provide two linear time algorithms to check the isomorphism, respectively, compatibility, of a set of trees or otherwise identify a conflict between the trees with respect to the relative location of a small subset of taxa. Then, we use these algorithms as subroutines to solve MAST and MCT on rooted or unrooted trees of unbounded degree. More precisely, we give exact fixed-parameter tractable algorithms, whose running time is uniformly polynomial when the number of taxa on which the trees disagree is bounded. The improves on a known result for MAST and proves fixed-parameter tractability for MCT.
MSClique: Multiple Structure Discovery through the Maximum Weighted Clique Problem.
Sanroma, Gerard; Penate-Sanchez, Adrian; Alquézar, René; Serratosa, Francesc; Moreno-Noguer, Francesc; Andrade-Cetto, Juan; González Ballester, Miguel Ángel
2016-01-01
We present a novel approach for feature correspondence and multiple structure discovery in computer vision. In contrast to existing methods, we exploit the fact that point-sets on the same structure usually lie close to each other, thus forming clusters in the image. Given a pair of input images, we initially extract points of interest and extract hierarchical representations by agglomerative clustering. We use the maximum weighted clique problem to find the set of corresponding clusters with maximum number of inliers representing the multiple structures at the correct scales. Our method is parameter-free and only needs two sets of points along with their tentative correspondences, thus being extremely easy to use. We demonstrate the effectiveness of our method in multiple-structure fitting experiments in both publicly available and in-house datasets. As shown in the experiments, our approach finds a higher number of structures containing fewer outliers compared to state-of-the-art methods.
A flexible annealing chaotic neural network to maximum clique problem.
Yang, Gang; Tang, Zheng; Zhang, Zhiqiang; Zhu, Yunyi
2007-06-01
Based on the analysis and comparison of several annealing strategies, we present a flexible annealing chaotic neural network which has flexible controlling ability and quick convergence rate to optimization problem. The proposed network has rich and adjustable chaotic dynamics at the beginning, and then can converge quickly to stable states. We test the network on the maximum clique problem by some graphs of the DIMACS clique instances, p-random and k random graphs. The simulations show that the flexible annealing chaotic neural network can get satisfactory solutions at very little time and few steps. The comparison between our proposed network and other chaotic neural networks denotes that the proposed network has superior executive efficiency and better ability to get optimal or near-optimal solution.
Fixed-parameter tractability of the maximum agreement supertree problem.
Guillemot, Sylvain; Berry, Vincent
2010-01-01
Given a set L of labels and a collection of rooted trees whose leaves are bijectively labeled by some elements of L, the Maximum Agreement Supertree (SMAST) problem is given as follows: find a tree T on a largest label set L(') is included in L that homeomorphically contains every input tree restricted to L('). The problem has phylogenetic applications to infer supertrees and perform tree congruence analyses. In this paper, we focus on the parameterized complexity of this NP-hard problem, considering different combinations of parameters as well as particular cases. We show that SMAST on k rooted binary trees on a label set of size n can be solved in O((8n)k) time, which is an improvement with respect to the previously known O(n3k2) time algorithm. In this case, we also give an O((2k)pkn2) time algorithm, where p is an upper bound on the number of leaves of L missing in a SMAST solution. This shows that SMAST can be solved efficiently when the input trees are mostly congruent. Then, for the particular case where any triple of leaves is contained in at least one input tree, we give O(4pn3) and O(3:12p + n4) time algorithms, obtaining the first fixed-parameter tractable algorithms on a single parameter for this problem. We also obtain intractability results for several combinations of parameters, thus indicating that it is unlikely that fixed-parameter tractable algorithms can be found in these particular cases.
Mapping the MPM maximum flow algorithm on GPUs
Solomon, Steven; Thulasiraman, Parimala
2010-11-01
The GPU offers a high degree of parallelism and computational power that developers can exploit for general purpose parallel applications. As a result, a significant level of interest has been directed towards GPUs in recent years. Regular applications, however, have traditionally been the focus of work on the GPU. Only very recently has there been a growing number of works exploring the potential of irregular applications on the GPU. We present a work that investigates the feasibility of Malhotra, Pramodh Kumar and Maheshwari's "MPM" maximum flow algorithm on the GPU that achieves an average speedup of 8 when compared to a sequential CPU implementation.
Invulnerability of power grids based on maximum flow theory
Fan, Wenli; Huang, Shaowei; Mei, Shengwei
2016-11-01
The invulnerability analysis against cascades is of great significance in evaluating the reliability of power systems. In this paper, we propose a novel cascading failure model based on the maximum flow theory to analyze the invulnerability of power grids. In the model, node initial loads are built on the feasible flows of nodes with a tunable parameter γ used to control the initial node load distribution. The simulation results show that both the invulnerability against cascades and the tolerance parameter threshold αT are affected by node load distribution greatly. As γ grows, the invulnerability shows the distinct change rules under different attack strategies and different tolerance parameters α respectively. These results are useful in power grid planning and cascading failure prevention.
Chemical Reaction Optimization for Max Flow Problem
Reham Barham
2016-08-01
Full Text Available This study presents an algorithm for MaxFlow problem using "Chemical Reaction Optimization algorithm (CRO". CRO is a recently established meta-heuristics algorithm for optimization, inspired by the nature of chemical reactions. The main concern is to find the best maximum flow value at which the flow can be shipped from the source node to the sink node in a flow network without violating any capacity constraints in which the flow of each edge remains within the upper bound value of the capacity. The proposed MaxFlow-CRO algorithm is presented, analyzed asymptotically and experimental test is conducted. Asymptotic runtime is derived theoretically. The algorithm is implemented using JAVA programming language. Results show a good performance with a complexity of O(I E2, for I iterations and E edges. The number of iterations I in the algorithm, is an important factor that will affect the results obtained. As number of iterations is increased, best possible max-Flow value is obtained.
Maximum speeds and alpha angles of flowing avalanches
McClung, David; Gauer, Peter
2016-04-01
A flowing avalanche is one which initiates as a slab and, if consisting of dry snow, will be enveloped in a turbulent snow dust cloud once the speed reaches about 10 m/s. A flowing avalanche has a dense core of flowing material which dominates the dynamics by serving as the driving force for downslope motion. The flow thickness typically on the order of 1 -10 m which is on the order of about 1% of the length of the flowing mass. We have collected estimates of maximum frontal speed um (m/s) from 118 avalanche events. The analysis is given here with the aim of using the maximum speed scaled with some measure of the terrain scale over which the avalanches ran. We have chosen two measures for scaling, from McClung (1990), McClung and Schaerer (2006) and Gauer (2012). The two measures are the √H0-;√S0-- (total vertical drop; total path length traversed). Our data consist of 118 avalanches with H0 (m)estimated and 106 with S0 (m)estimated. Of these, we have 29 values with H0 (m),S0 (m)and um (m/s)estimated accurately with the avalanche speeds measured all or nearly all along the path. The remainder of the data set includes approximate estimates of um (m/s)from timing the avalanche motion over a known section of the path where approximate maximum speed is expected and with either H0or S0or both estimated. Our analysis consists of fitting the values of um/√H0--; um/√S0- to probability density functions (pdf) to estimate the exceedance probability for the scaled ratios. In general, we found the best fits for the larger data sets to fit a beta pdf and for the subset of 29, we found a shifted log-logistic (s l-l) pdf was best. Our determinations were as a result of fitting the values to 60 different pdfs considering five goodness-of-fit criteria: three goodness-of-fit statistics :K-S (Kolmogorov-Smirnov); A-D (Anderson-Darling) and C-S (Chi-squared) plus probability plots (P-P) and quantile plots (Q-Q). For less than 10% probability of exceedance the results show that
Wu, Yating; Kuang, Bin; Wang, Tao; Zhang, Qianwu; Wang, Min
2015-12-01
This paper presents a minimum cost maximum flow (MCMF) based upstream bandwidth allocation algorithm, which supports differentiated QoS for orthogonal frequency division multiple access passive optical networks (OFDMA-PONs). We define a utility function as the metric to characterize the satisfaction degree of an ONU on the obtained bandwidth. The bandwidth allocation problem is then formulated as maximizing the sum of the weighted total utility functions of all ONUs. By constructing a flow network graph, we obtain the optimized bandwidth allocation using the MCMF algorithm. Simulation results show that the proposed scheme improves the performance in terms of mean packet delay, packet loss ratio and throughput.
Continuous maximum flow segmentation method for nanoparticle interaction analysis.
Marak, L; Tankyevych, O; Talbot, H
2011-10-01
In recent years, tomographic three-dimensional reconstruction approaches using electrons rather than X-rays have become popular. Such images produced with a transmission electron microscope make it possible to image nanometre-scale materials in three-dimensional. However, they are also noisy, limited in contrast and most often have a very poor resolution along the axis of the electron beam. The analysis of images stemming from such modalities, whether fully or semiautomated, is therefore more complicated. In particular, segmentation of objects is difficult. In this paper, we propose to use the continuous maximum flow segmentation method based on a globally optimal minimal surface model. The use of this fully automated segmentation and filtering procedure is illustrated on two different nanoparticle samples and provide comparisons with other classical segmentation methods. The main objectives are the measurement of the attraction rate of polystyrene beads to silica nanoparticle (for the first sample) and interaction of silica nanoparticles with large unilamellar liposomes (for the second sample). We also illustrate how precise measurements such as contact angles can be performed.
Maximum flow-based resilience analysis: From component to system
Jin, Chong; Li, Ruiying; Kang, Rui
2017-01-01
Resilience, the ability to withstand disruptions and recover quickly, must be considered during system design because any disruption of the system may cause considerable loss, including economic and societal. This work develops analytic maximum flow-based resilience models for series and parallel systems using Zobel’s resilience measure. The two analytic models can be used to evaluate quantitatively and compare the resilience of the systems with the corresponding performance structures. For systems with identical components, the resilience of the parallel system increases with increasing number of components, while the resilience remains constant in the series system. A Monte Carlo-based simulation method is also provided to verify the correctness of our analytic resilience models and to analyze the resilience of networked systems based on that of components. A road network example is used to illustrate the analysis process, and the resilience comparison among networks with different topologies but the same components indicates that a system with redundant performance is usually more resilient than one without redundant performance. However, not all redundant capacities of components can improve the system resilience, the effectiveness of the capacity redundancy depends on where the redundant capacity is located. PMID:28545135
Analyzing Quadratic Unconstrained Binary Optimization Problems Via Multicommodity Flows.
Wang, Di; Kleinberg, Robert D
2009-11-28
Quadratic Unconstrained Binary Optimization (QUBO) problems concern the minimization of quadratic polynomials in n {0, 1}-valued variables. These problems are NP-complete, but prior work has identified a sequence of polynomial-time computable lower bounds on the minimum value, denoted by C(2), C(3), C(4),…. It is known that C(2) can be computed by solving a maximum-flow problem, whereas the only previously known algorithms for computing C(k) (k > 2) require solving a linear program. In this paper we prove that C(3) can be computed by solving a maximum multicommodity flow problem in a graph constructed from the quadratic function. In addition to providing a lower bound on the minimum value of the quadratic function on {0, 1}(n), this multicommodity flow problem also provides some information about the coordinates of the point where this minimum is achieved. By looking at the edges that are never saturated in any maximum multicommodity flow, we can identify relational persistencies: pairs of variables that must have the same or different values in any minimizing assignment. We furthermore show that all of these persistencies can be detected by solving single-commodity flow problems in the same network.
Nezhel'skaya, L. A.
2016-09-01
A flow of physical events (photons, electrons, and other elementary particles) is studied. One of the mathematical models of such flows is the modulated MAP flow of events circulating under conditions of unextendable dead time period. It is assumed that the dead time period is an unknown fixed value. The problem of estimation of the dead time period from observations of arrival times of events is solved by the method of maximum likelihood.
Guillemot, Sylvain
2008-01-01
Given a set of leaf-labeled trees with identical leaf sets, the well-known "Maximum Agreement SubTree" problem (MAST) consists of finding a subtree homeomorphically included in all input trees and with the largest number of leaves. Its variant called "Maximum Compatible Tree" (MCT) is less stringent, as it allows the input trees to be refined. Both problems are of particular interest in computational biology, where trees encountered have often small degrees. In this paper, we study the parameterized complexity of MAST and MCT with respect to the maximum degree, denoted by D, of the input trees. It is known that MAST is polynomial for bounded D. As a counterpart, we show that the problem is W[1]-hard with respect to parameter D. Moreover, elying on recent advances in parameterized complexity we obtain a tight lower bound: while MAST can be solved in O(N^{O(D)}) time where N denotes the input length, we show that an O(N^{o(D)}) bound is not achievable, unless SNP is contained in SE. We also show that MCT is W[1...
Maximum Likelihood Blood Velocity Estimator Incorporating Properties of Flow Physics
Schlaikjer, Malene; Jensen, Jørgen Arendt
2004-01-01
The aspect of correlation among the blood velocities in time and space has not received much attention in previous blood velocity estimators. The theory of fluid mechanics predicts this property of the blood flow. Additionally, most estimators based on a cross-correlation analysis are limited...... of simulated and in vivo data from the carotid artery. The estimator is meant for two-dimensional (2-D) color flow imaging. The resulting mathematical relation for the estimator consists of two terms. The first term performs a cross-correlation analysis on the signal segment in the radio frequency (RF......)-data under investigation. The flow physic properties are exploited in the second term, as the range of velocity values investigated in the cross-correlation analysis are compared to the velocity estimates in the temporal and spatial neighborhood of the signal segment under investigation. The new estimator...
Maximum entropy analysis of flow and reaction networks
Niven, Robert K.; Abel, Markus; Schlegel, Michael; Waldrip, Steven H.
2015-01-01
We present a generalised MaxEnt method to infer the stationary state of a flow network, subject to "observable" constraints on expectations of various parameters, as well as "physical" constraints arising from frictional properties (resistance functions) and conservation laws (Kirchhoff laws). The method invokes an entropy defined over all uncertainties in the system, in this case the internal and external flow rates and potential differences. The proposed MaxEnt framework is readily extendable to the analysis of networks with uncertainty in the network structure itself.
Wavelength selection in injection-driven Hele-Shaw flows: A maximum amplitude criterion
Dias, Eduardo; Miranda, Jose
2013-11-01
As in most interfacial flow problems, the standard theoretical procedure to establish wavelength selection in the viscous fingering instability is to maximize the linear growth rate. However, there are important discrepancies between previous theoretical predictions and existing experimental data. In this work we perform a linear stability analysis of the radial Hele-Shaw flow system that takes into account the combined action of viscous normal stresses and wetting effects. Most importantly, we introduce an alternative selection criterion for which the selected wavelength is determined by the maximum of the interfacial perturbation amplitude. The effectiveness of such a criterion is substantiated by the significantly improved agreement between theory and experiments. We thank CNPq (Brazilian Sponsor) for financial support.
Maximum Likelihood Estimation of Monocular Optical Flow Field for Mobile Robot Ego-motion
Huajun Liu
2016-01-01
Full Text Available This paper presents an optimized scheme of monocular ego-motion estimation to provide location and pose information for mobile robots with one fixed camera. First, a multi-scale hyper-complex wavelet phase-derived optical flow is applied to estimate micro motion of image blocks. Optical flow computation overcomes the difficulties of unreliable feature selection and feature matching of outdoor scenes; at the same time, the multi-scale strategy overcomes the problem of road surface self-similarity and local occlusions. Secondly, a support probability of flow vector is defined to evaluate the validity of the candidate image motions, and a Maximum Likelihood Estimation (MLE optical flow model is constructed based not only on image motion residuals but also their distribution of inliers and outliers, together with their support probabilities, to evaluate a given transform. This yields an optimized estimation of inlier parts of optical flow. Thirdly, a sampling and consensus strategy is designed to estimate the ego-motion parameters. Our model and algorithms are tested on real datasets collected from an intelligent vehicle. The experimental results demonstrate the estimated ego-motion parameters closely follow the GPS/INS ground truth in complex outdoor road scenarios.
Maximum estimates for generalized Forchheimer flows in heterogeneous porous media
Celik, Emine; Hoang, Luan
2017-02-01
This article continues the study in [4] of generalized Forchheimer flows in heterogeneous porous media. Such flows are used to account for deviations from Darcy's law. In heterogeneous media, the derived nonlinear partial differential equation for the pressure can be singular and degenerate in the spatial variables, in addition to being degenerate for large pressure gradient. Here we obtain the estimates for the L∞-norms of the pressure and its time derivative in terms of the initial and the time-dependent boundary data. They are established by implementing De Giorgi-Moser's iteration in the context of weighted norms with the weights specifically defined by the Forchheimer equation's coefficient functions. With these weights, we prove suitable weighted parabolic Poincaré-Sobolev inequalities and use them to facilitate the iteration. Moreover, local in time L∞-bounds are combined with uniform Gronwall-type energy inequalities to obtain long-time L∞-estimates.
Topology optimization of flow problems
Gersborg, Allan Roulund
2007-01-01
of the velocity field or mixing properties. To reduce the computational complexity of the topology optimization problems the primary focus is put on the Stokes equation in 2D and in 3D. However, the thesis also contains examples with the 2D Navier-Stokes equation as well as an example with convection dominated....... Although the study of the FVM is carried out using a simple heat conduction problem, the work illuminates and discusses the technicalities of employing the FVM in connection with topology optimization. Finally, parallelized solution methods are investigated using the high performance computing facility...
Ke, Xinyou; Alexander, J. Iwan D.; Prahl, Joseph M.; Savinell, Robert F.
2014-12-01
Flow batteries show promise for very large-scale stationary energy storage such as needed for the grid and renewable energy implementation. In recent years, researchers and developers of redox flow batteries (RFBs) have found that electrode and flow field designs of PEM fuel cell (PEMFC) technology can increase the power density and consequently push down the cost of flow battery stacks. In this paper we present a macroscopic model of a typical PEMFC-like RFB electrode-flow field design. The model is a layered system comprised of a single passage of a serpentine flow channel and a parallel underlying porous electrode (or porous layer). The effects of the inlet volumetric flow rate, permeability of the porous layer, thickness of the porous layer and thickness of the flow channel on the flow penetration into the porous layer are investigated. The maximum current density corresponding to stoichiometry is estimated to be 377 mA cm-2 and 724 mA cm-2, which compares favorably with experiments of ∼400 mA cm-2 and ∼750 mA cm-2, for a single layer and three layers of the carbon fiber paper, respectively.
The directed flow maximum near $c_{s} = 0$
Brachmann, J; Stöcker, H; Greiner, W
2000-01-01
We investigate the excitation function of quark-gluon plasma formation and the rapidity dependence of directed in-plane flow of nucleons in the energy range of the BNL-AGS and for the $E^{kin}_{Lab}=40A$~GeV Pb+Pb collisions performed recently at the CERN-SPS. We employ the three-fluid model with dynamical unification of kinetically equilibrated fluid elements. Within our model with first-order phase transition at high density, droplets of QGP coexisting with hadronic matter are produced already at BNL-AGS energies, $E^{kin}_{Lab}\\simeq 10A$~GeV. A substantial decrease of the isentropic velocity of sound, however, requires higher energies, $E^{kin}_{Lab}\\simeq40A$~GeV. We calculate the response of the directed in-plane momentum per nucleon, $(y)$. According to our model calculations, kinematic requirements and EoS effects work hand-in-hand at $E^{kin}_{Lab}=40A$~GeV to allow the observation of the dropping velocity of sound and of the ``slowly burning'' mixed phase via an {\\em increase} of the directed flow a...
Cetin, Bilge Kartal; Prasad, Neeli R.; Prasad, Ramjee
2011-01-01
of the maximum lifetime routing problem that considers the operation modes of the node. Solution of the linear programming gives the upper analytical bound for the network lifetime. In order to illustrate teh application of the optimization model, we solved teh problem for different parameter settings...... protocols, and the energy model for transmission. In this paper, we tackle the routing challenge for maximum lifetime of the sensor network. We introduce a novel linear programming approach to the maximum lifetime routing problem. To the best of our knowledge, this is the first mathematical programming...
Computational complexity of some maximum average weight problems with precedence constraints
Faigle, Ulrich; Kern, Walter
1994-01-01
Maximum average weight ideal problems in ordered sets arise from modeling variants of the investment problem and, in particular, learning problems in the context of concepts with tree-structured attributes in artificial intelligence. Similarly, trying to construct tests with high reliability leads t
Comparison Between Bayesian and Maximum Entropy Analyses of Flow Networks†
Steven H. Waldrip
2017-02-01
Full Text Available We compare the application of Bayesian inference and the maximum entropy (MaxEnt method for the analysis of ﬂow networks, such as water, electrical and transport networks. The two methods have the advantage of allowing a probabilistic prediction of ﬂow rates and other variables, when there is insufﬁcient information to obtain a deterministic solution, and also allow the effects of uncertainty to be included. Both methods of inference update a prior to a posterior probability density function (pdf by the inclusion of new information, in the form of data or constraints. The MaxEnt method maximises an entropy function subject to constraints, using the method of Lagrange multipliers,to give the posterior, while the Bayesian method ﬁnds its posterior by multiplying the prior with likelihood functions incorporating the measured data. In this study, we examine MaxEnt using soft constraints, either included in the prior or as probabilistic constraints, in addition to standard moment constraints. We show that when the prior is Gaussian,both Bayesian inference and the MaxEnt method with soft prior constraints give the same posterior means, but their covariances are different. In the Bayesian method, the interactions between variables are applied through the likelihood function, using second or higher-order cross-terms within the posterior pdf. In contrast, the MaxEnt method incorporates interactions between variables using Lagrange multipliers, avoiding second-order correlation terms in the posterior covariance. The MaxEnt method with soft prior constraints, therefore, has a numerical advantage over Bayesian inference, in that the covariance terms are avoided in its integrations. The second MaxEnt method with soft probabilistic constraints is shown to give posterior means of similar, but not identical, structure to the other two methods, due to its different formulation.
Shape flows for spectral optimization problems
Bucur, Dorin; Stefanelli, Ulisse
2011-01-01
We consider a general formulation of gradient flow evolution for problems whose natural framework is the one of metric spaces. The applications we deal with are concerned with the evolution of {\\it capacitary measures} with respect to the $\\gamma$-convergence dissipation distance and with the evolution of domains in spectral optimization problems.
A Pseudo-Boolean Solution to the Maximum Quartet Consistency Problem
Morgado, Antonio
2008-01-01
Determining the evolutionary history of a given biological data is an important task in biological sciences. Given a set of quartet topologies over a set of taxa, the Maximum Quartet Consistency (MQC) problem consists of computing a global phylogeny that satisfies the maximum number of quartets. A number of solutions have been proposed for the MQC problem, including Dynamic Programming, Constraint Programming, and more recently Answer Set Programming (ASP). ASP is currently the most efficient approach for optimally solving the MQC problem. This paper proposes encoding the MQC problem with pseudo-Boolean (PB) constraints. The use of PB allows solving the MQC problem with efficient PB solvers, and also allows considering different modeling approaches for the MQC problem. Initial results are promising, and suggest that PB can be an effective alternative for solving the MQC problem.
Cetin, Bilge Kartal; Prasad, Neeli R.; Prasad, Ramjee
2011-01-01
of the maximum lifetime routing problem that considers the operation modes of the node. Solution of the linear programming gives the upper analytical bound for the network lifetime. In order to illustrate teh application of the optimization model, we solved teh problem for different parameter settings...
Jingtao Shi
2013-01-01
Full Text Available This paper is concerned with the relationship between maximum principle and dynamic programming for stochastic recursive optimal control problems. Under certain differentiability conditions, relations among the adjoint processes, the generalized Hamiltonian function, and the value function are given. A linear quadratic recursive utility portfolio optimization problem in the financial engineering is discussed as an explicitly illustrated example of the main result.
Lau Nguyen Dinh
2016-01-01
Full Text Available The problem of finding maximum flow in network graph is extremely interesting and practically applicable in many fields in our daily life, especially in transportation. Therefore, a lot of researchers have been studying this problem in various methods. Especially in 2013, we has developed a new algorithm namely, postflow-pull algorithm to find the maximum flow on traditional networks. In this paper, we revised postflow-push methods to solve this problem of finding maximum flow on extended mixed network. In addition, to take more advantage of multi-core architecture of the parallel computing system, we build this parallel algorithm. This is a completely new method not being announced in the world. The results of this paper are basically systematized and proven. The idea of this algorithm is using multi processors to work in parallel by postflow_push algorithm. Among these processors, there is one main processor managing data, sending data to the sub processors, receiving data from the sub-processors. The sub-processors simultaneously execute their work and send their data to the main processor until the job is finished, the main processor will show the results of the problem.
Study on the Hungarian algorithm for the maximum likelihood data association problem
Wang Jianguo; He Peikun; Cao Wei
2007-01-01
A specialized Hungarian algorithm was developed here for the maximum likelihood data association problem with two implementation versions due to presence of false alarms and missed detections. The maximum likelihood data association problem is formulated as a bipartite weighted matching problem. Its duality and the optimality conditions are given. The Hungarian algorithm with its computational steps, data structure and computational complexity is presented. The two implementation versions, Hungarian forest (HF) algorithm and Hungarian tree (HT) algorithm, and their combination with the na(i)ve auction initialization are discussed. The computational results show that HT algorithm is slightly faster than HF algorithm and they are both superior to the classic Munkres algorithm.
A maximum principle for smooth optimal impulsive control problems with multipoint state constraints
Dykhta, V. A.; Samsonyuk, O. N.
2009-06-01
A nonlinear optimal impulsive control problem with trajectories of bounded variation subject to intermediate state constraints at a finite number on nonfixed instants of time is considered. Features of this problem are discussed from the viewpoint of the extension of the classical optimal control problem with the corresponding state constraints. A necessary optimality condition is formulated in the form of a smooth maximum principle; thorough comments are given, a short proof is presented, and examples are discussed.
On Problems with Downscaling in Internal Flows
Rudolf DVO(R)(A)K
2005-01-01
Problems that may accompany downscaling in internal flows are discussed. Non-dimensional similarity parameters (like Re, M, etc.) depend on parameters that scale down fully (e.g., length), or that are specified by design (velocities, cascade geometry), or that are scale invariant (like thermophysical and transport properties of fluids).This fact has to be taken into acount in the similarity considerations. With decreasing Reynolds number the surface forces become of growing importance, however, if not going down directly to microflows the main problems are connected with the three-dimensional flow structure affecting the skin friction, and with the fact that some of the flow phenomena (e.g. vortical structures) cannot fully develop.
Domoshnitsky Alexander
2009-01-01
Full Text Available We obtain the maximum principles for the first-order neutral functional differential equation where , and are linear continuous operators, and are positive operators, is the space of continuous functions, and is the space of essentially bounded functions defined on . New tests on positivity of the Cauchy function and its derivative are proposed. Results on existence and uniqueness of solutions for various boundary value problems are obtained on the basis of the maximum principles.
The Distribution of Maximum Flow with Application to Multi-State Reliability Systems.
1985-11-01
in 0( lVI • JEJ )time, using the max-flow algorithm of Itai and Shiloach (1979). Frank and Frisch (1971) provide a comprehensive discussion of the...maximum flow; for example, taking 0( Ivi log IVI time per replication for a planar network ( Itai and Shiloach 1979). With regard to computing the cell...Edition 8, Houston, Texas. 11. Itai , A. and Y. Shiloach (1979). Maximum flow in planar networks, SIAM J. Comput., 8, 135-150. 12. Kulkarni, V.G. and V. G
Takahashi, Jun; Takabe, Satoshi; Hukushima, Koji
2017-07-01
A recently proposed exact algorithm for the maximum independent set problem is analyzed. The typical running time is improved exponentially in some parameter regions compared to simple binary search. Furthermore, the algorithm overcomes the core transition point, where the conventional leaf removal algorithm fails, and works up to the replica symmetry breaking (RSB) transition point. This suggests that a leaf removal core itself is not enough for typical hardness in the random maximum independent set problem, providing further evidence for RSB being the obstacle for algorithms in general.
Dynamic Flow Management Problems in Air Transportation
Patterson, Sarah Stock
1997-01-01
In 1995, over six hundred thousand licensed pilots flew nearly thirty-five million flights into over eighteen thousand U.S. airports, logging more than 519 billion passenger miles. Since demand for air travel has increased by more than 50% in the last decade while capacity has stagnated, congestion is a problem of undeniable practical significance. In this thesis, we will develop optimization techniques that reduce the impact of congestion on the national airspace. We start by determining the optimal release times for flights into the airspace and the optimal speed adjustment while airborne taking into account the capacitated airspace. This is called the Air Traffic Flow Management Problem (TFMP). We address the complexity, showing that it is NP-hard. We build an integer programming formulation that is quite strong as some of the proposed inequalities are facet defining for the convex hull of solutions. For practical problems, the solutions of the LP relaxation of the TFMP are very often integral. In essence, we reduce the problem to efficiently solving large scale linear programming problems. Thus, the computation times are reasonably small for large scale, practical problems involving thousands of flights. Next, we address the problem of determining how to reroute aircraft in the airspace system when faced with dynamically changing weather conditions. This is called the Air Traffic Flow Management Rerouting Problem (TFMRP) We present an integrated mathematical programming approach for the TFMRP, which utilizes several methodologies, in order to minimize delay costs. In order to address the high dimensionality, we present an aggregate model, in which we formulate the TFMRP as a multicommodity, integer, dynamic network flow problem with certain side constraints. Using Lagrangian relaxation, we generate aggregate flows that are decomposed into a collection of flight paths using a randomized rounding heuristic. This collection of paths is used in a packing integer
Solving the Maximum Weighted Clique Problem Based on Parallel Biological Computing Model
Zhaocai Wang
2015-01-01
Full Text Available The maximum weighted clique (MWC problem, as a typical NP-complete problem, is difficult to be solved by the electronic computer algorithm. The aim of the problem is to seek a vertex clique with maximal weight sum in a given undirected graph. It is an extremely important problem in the field of optimal engineering scheme and control with numerous practical applications. From the point of view of practice, we give a parallel biological algorithm to solve the MWC problem. For the maximum weighted clique problem with m edges and n vertices, we use fixed length DNA strands to represent different vertices and edges, fully conduct biochemical reaction, and find the solution to the MVC problem in certain length range with O(n2 time complexity, comparing to the exponential time level by previous computer algorithms. We expand the applied scope of parallel biological computation and reduce computational complexity of practical engineering problems. Meanwhile, we provide a meaningful reference for solving other complex problems.
Lattice Field Theory with the Sign Problem and the Maximum Entropy Method
Masahiro Imachi
2007-02-01
Full Text Available Although numerical simulation in lattice field theory is one of the most effective tools to study non-perturbative properties of field theories, it faces serious obstacles coming from the sign problem in some theories such as finite density QCD and lattice field theory with the θ term. We reconsider this problem from the point of view of the maximum entropy method.
Wood flow problems in the Swedish forestry
Carlsson, Dick [Forestry Research Inst. of Sweden, Uppsala (Sweden); Roennqvist, M. [Linkoeping Univ. (Sweden). Dept. of Mathematics
1998-12-31
In this paper we give an overview of the wood-flow in Sweden including a description of organization and planning. Based on that, we will describe a number of applications or problem areas in the wood-flow chain that are currently considered by the Swedish forest companies to be important and potential in order to improve overall operations. We have focused on applications which are short term planning or operative planning. We do not give any final results as much of the development is currently ongoing or is still in a planning phase. Instead we describe what kind of models and decision support systems that could be applied in order to improve co-operation within and integration of the wood-flow chain 13 refs, 20 figs, 1 tab
Finite element methods for incompressible flow problems
John, Volker
2016-01-01
This book explores finite element methods for incompressible flow problems: Stokes equations, stationary Navier-Stokes equations, and time-dependent Navier-Stokes equations. It focuses on numerical analysis, but also discusses the practical use of these methods and includes numerical illustrations. It also provides a comprehensive overview of analytical results for turbulence models. The proofs are presented step by step, allowing readers to more easily understand the analytical techniques.
On Bounding Problems of Quantitative Information Flow
Yasuoka, Hirotoshi
2011-01-01
Researchers have proposed formal definitions of quantitative information flow based on information theoretic notions such as the Shannon entropy, the min entropy, the guessing entropy, belief, and channel capacity. This paper investigates the hardness of precisely checking the quantitative information flow of a program according to such definitions. More precisely, we study the "bounding problem" of quantitative information flow, defined as follows: Given a program M and a positive real number q, decide if the quantitative information flow of M is less than or equal to q. We prove that the bounding problem is not a k-safety property for any k (even when q is fixed, for the Shannon-entropy-based definition with the uniform distribution), and therefore is not amenable to the self-composition technique that has been successfully applied to checking non-interference. We also prove complexity theoretic hardness results for the case when the program is restricted to loop-free boolean programs. Specifically, we show...
Flow shop rescheduling problem under rush orders
无
2005-01-01
In the environment of customization, disturbances such as rush orders and material shortages often occur in the manufacturing system, so rescheduling is necessary for the manufacturing system. The rescheduling methodology should be able to dispose of the disturbance efficiently so as to keep production going smoothly. This aims researching flow shop rescheduling problem (FSRP) necessitated by rush orders. Disjunctive graph is employed to demonstrate the FSRP. For a flow shop processing n jobs, after the original schedule has been made, and z out of n jobs have been processed in the flow shop, x rush orders come, so the original n jobs together with x rush orders should be rescheduled immediately so that the rush orders would be processed in the shortest time and the original jobs could be processed subject to some optimized criteria. The weighted mean flow time of both original jobs and rush orders is used as objective function. The weight for rush orders is much bigger than that of the original jobs,so the rush orders should be processed early in the new schedule. The ant colony optimization (ACO) algorithm used to solve the rescheduling problem has a weakness in that the search may fall into a local optimum. Mutation operation is employed to enhance the ACO performance. Numerical experiments demonstrated that the proposed algorithm has high computation repeatability and efficiency.
Mansoureh Haj Mohammad Hosseini
2011-04-01
Full Text Available In this paper, a bi-objective mathematical model for emergency services location-allocation problem on a tree network considering maximum distance constraint is presented. The first objective function called centdian is a weighted mean of a minisum and a minimax criterion and the second one is a maximal covering criterion. For the solution of the bi-objective optimization problem, the problem is split in two sub problems: the selection of the best set of locations, and a demand assignment problem to evaluate each selection of locations. We propose a heuristic algorithm to characterize the efficient location point set on the network. Finally, some numerical examples are presented to illustrate the effectiveness of the proposed algorithms.
Monotone Approximations of Minimum and Maximum Functions and Multi-objective Problems
Stipanovic, Dusan M., E-mail: dusan@illinois.edu [University of Illinois at Urbana-Champaign, Coordinated Science Laboratory, Department of Industrial and Enterprise Systems Engineering (United States); Tomlin, Claire J., E-mail: tomlin@eecs.berkeley.edu [University of California at Berkeley, Department of Electrical Engineering and Computer Science (United States); Leitmann, George, E-mail: gleit@berkeley.edu [University of California at Berkeley, College of Engineering (United States)
2012-12-15
In this paper the problem of accomplishing multiple objectives by a number of agents represented as dynamic systems is considered. Each agent is assumed to have a goal which is to accomplish one or more objectives where each objective is mathematically formulated using an appropriate objective function. Sufficient conditions for accomplishing objectives are derived using particular convergent approximations of minimum and maximum functions depending on the formulation of the goals and objectives. These approximations are differentiable functions and they monotonically converge to the corresponding minimum or maximum function. Finally, an illustrative pursuit-evasion game example with two evaders and two pursuers is provided.
Topology optimization of mass distribution problems in Stokes flow
Gersborg-Hansen, Allan; Berggren, Martin; Dammann, Bernd
We consider topology optimization of mass distribution problems in 2D and 3D Stokes flow with the aim of designing devices that meet target outflow rates. For the purpose of validation, the designs have been post processed using the image processing tools available in FEMLAB. In turn, this has...... enabled an evaluation of the design with a body fitted mesh in a standard analysis software relevant in engineering practice prior to design manufacturing. This work investigates the proper choice of a maximum penalization value during the optimization process that ensures that the target outflow rates...
Importance of maximum snow accumulation for summer low flows in humid catchments
Jenicek, M.; Seibert, J.; Zappa, M.; Staudinger, M.; Jonas, T.
2015-07-01
The expected increase of air temperature will increase the ratio of liquid to solid precipitation during winter and, thus decrease the amount of snow, especially in mid-elevation mountain ranges across Europe. The decrease of snow will affect groundwater recharge during spring and might cause low streamflow values in the subsequent summer period. To evaluate these potential climate change impacts, we investigated the effects of inter-annual variations in snow accumulation on summer low flow and addressed the following research questions: (1) how important is snow for summer low flows and how long is the "memory effect" in catchments with different elevations? (2) How sensitive are summer low flows to any change of winter snowpack? To find suitable predictors of summer low flow we used long time series from 14 alpine and pre-alpine catchments in Switzerland and computed different variables quantifying winter and spring snow conditions. We assessed the sensitivity of individual catchments to the change of maximum snow water equivalent (SWEmax) using the non-parametric Theil-Sen approach as well as an elasticity index. In general, the results indicated that maximum winter snow accumulation influenced summer low flow, but could only partly explain the observed inter-annual variations. One other important factor was the precipitation between maximum snow accumulation and summer low flow. When only the years with below average precipitation amounts during this period were considered, the importance of snow accumulation as a predictor of low flows increased. The slope of the regression between SWEmax and summer low flow and the elasticity index both increased with increasing mean catchment elevation. This indicated a higher sensitivity of summer low flow to snow accumulation in alpine catchments compared to lower elevation catchments.
Two- and three-index formulations of the minimum cost multicommodity k-splittable flow problem
Gamst, Mette; Jensen, Peter Neergaard; Pisinger, David
2010-01-01
of commodities has to be satisfied at the lowest possible cost. The problem has applications in transportation problems where a number of commodities must be routed, using a limited number of distinct transportation units for each commodity. Based on a three-index formulation by Truffot et al. [J. Truffot, C......The multicommodity flow problem (MCFP) considers the efficient routing of commodities from their origins to their destinations subject to capacity restrictions and edge costs. Baier et al. [G. Baier, E. Köhler, M. Skutella, On the k-splittable flow problem, in: 10th Annual European Symposium...... on Algorithms, 2002, 101–113] introduced the maximum flow multicommodity k-splittable flow problem (MCkFP) where each commodity may use at most k paths between its origin and its destination. This paper studies the -hard minimum cost multicommodity k-splittable flow problem (MCMCkFP) in which a given flow...
Maximum at ALS: A powerful tool to investigate open problems in micro and optoelectronics
Lorusso, G.F.; Solak, H.; Singh, S.; Cerrina, F. [Univ. of Wisconsin, Madison, WI (United States). Center of X-ray Lithography; Batson, P.J.; Underwood, J.H. [Lawrence Berkeley National Lab., CA (United States). Center of X-ray Optics
1998-12-31
The authors present recent results obtained by MAXIMUM at the Advanced Light Source (ALS), at the Lawrence Berkeley National Laboratory. MAXIMUM is a scanning photoemission microscope, based on a multilayer coated Schwarzschild objective. An electron energy analyzer collects the emitted photoelectrons to form an image as the sample itself is scanned. The microscope has been purposely designed to take advantage of the high brightness of the third generation synchrotron radiation sources, and its installation at ALS has been recently completed. The spatial resolution of 100 nm and the spectral resolution of 200 meV make the instrument an extremely interesting tool to investigate current problems in opto- and microelectronics. In order to illustrate the potential of MAXIMUM in these fields, the authors report new results obtained by studying the electromigration in Al-Cu lines and the Al segregation in AlGaN thin films.
Applying the maximum information principle to cell transmission model of tra-ffic flow
刘喜敏; 卢守峰
2013-01-01
This paper integrates the maximum information principle with the Cell Transmission Model (CTM) to formulate the velo-city distribution evolution of vehicle traffic flow. The proposed discrete traffic kinetic model uses the cell transmission model to cal-culate the macroscopic variables of the vehicle transmission, and the maximum information principle to examine the velocity distri-bution in each cell. The velocity distribution based on maximum information principle is solved by the Lagrange multiplier method. The advantage of the proposed model is that it can simultaneously calculate the hydrodynamic variables and velocity distribution at the cell level. An example shows how the proposed model works. The proposed model is a hybrid traffic simulation model, which can be used to understand the self-organization phenomena in traffic flows and predict the traffic evolution.
An O (n log n) algorithm for the Maximum Agreement Subtree problem for binary trees
Cole, R.; Hariharan, R.
1996-12-31
The Maximum Agreement Subtree problem is the following: given two trees whose leaves are drawn from the same set of items (e.g., species), find the largest subset of these items so that the portions of the two trees restricted to these items are isomorphic. We consider the case which occurs frequently in practice, i.e., the case when the trees are binary, and give an O(n log n) time algorithm for this problem. This improves the previous best bound of O(n log{sup 3} n) due to Farach, Przytycka, and Thorup.
Research on configuration of railway self-equipped tanker based on minimum cost maximum flow model
Yang, Yuefang; Gan, Chunhui; Shen, Tingting
2017-05-01
In the study of the configuration of the tanker of chemical logistics park, the minimum cost maximum flow model is adopted. Firstly, the transport capacity of the park loading and unloading area and the transportation demand of the dangerous goods are taken as the constraint condition of the model; then the transport arc capacity, the transport arc flow and the transport arc edge weight are determined in the transportation network diagram; finally, the software calculations. The calculation results show that the configuration issue of the tankers can be effectively solved by the minimum cost maximum flow model, which has theoretical and practical application value for tanker management of railway transportation of dangerous goods in the chemical logistics park.
Topology optimization of Channel flow problems
Gersborg-Hansen, Allan; Sigmund, Ole; Haber, R. B.
2005-01-01
]. Further, the inclusion of inertia effects significantly alters the physics, enabling solutions of new classes of optimization problems, such as velocity--driven switches, that are not addressed by the earlier method. Specifically, we determine optimal layouts of channel flows that extremize a cost...... sensitivities. Our target application is optimal layout design of channels in fluid network systems. Using concepts borrowed from topology optimization of compliant mechanisms in solid mechanics, we introduce a method for the synthesis of fluidic components, such as switches, diodes, etc....
Distributed Algorithms for Optimal Power Flow Problem
Lam, Albert Y S; Tse, David
2011-01-01
Optimal power flow (OPF) is an important problem for power generation and it is in general non-convex. With the employment of renewable energy, it will be desirable if OPF can be solved very efficiently so its solution can be used in real time. With some special network structure, e.g. trees, the problem has been shown to have a zero duality gap and the convex dual problem yields the optimal solution. In this paper, we propose a primal and a dual algorithm to coordinate the smaller subproblems decomposed from the convexified OPF. We can arrange the subproblems to be solved sequentially and cumulatively in a central node or solved in parallel in distributed nodes. We test the algorithms on IEEE radial distribution test feeders, some random tree-structured networks, and the IEEE transmission system benchmarks. Simulation results show that the computation time can be improved dramatically with our algorithms over the centralized approach of solving the problem without decomposition, especially in tree-structured...
Mlpnp - a Real-Time Maximum Likelihood Solution to the Perspective-N Problem
Urban, S.; Leitloff, J.; Hinz, S.
2016-06-01
In this paper, a statistically optimal solution to the Perspective-n-Point (PnP) problem is presented. Many solutions to the PnP problem are geometrically optimal, but do not consider the uncertainties of the observations. In addition, it would be desirable to have an internal estimation of the accuracy of the estimated rotation and translation parameters of the camera pose. Thus, we propose a novel maximum likelihood solution to the PnP problem, that incorporates image observation uncertainties and remains real-time capable at the same time. Further, the presented method is general, as is works with 3D direction vectors instead of 2D image points and is thus able to cope with arbitrary central camera models. This is achieved by projecting (and thus reducing) the covariance matrices of the observations to the corresponding vector tangent space.
Minimizing Flow Time in the Wireless Gathering Problem
Bonifaci, Vincenzo; Marchetti-Spaccamela, Alberto; Stougie, Leen
2008-01-01
We address the problem of efficient data gathering in a wireless network through multi-hop communication. We focus on the objective of minimizing the maximum flow time of a data packet. We prove that no polynomial time algorithm for this problem can have approximation ratio less than $\\Omega(m^{1/3)$ when $m$ packets have to be transmitted, unless $P = NP$. We then use resource augmentation to assess the performance of a FIFO-like strategy. We prove that this strategy is 5-speed optimal, i.e., its cost remains within the optimal cost if we allow the algorithm to transmit data at a speed 5 times higher than that of the optimal solution we compare to.
Towards faster solution of large power flow problems
Idema, R.; Papaefthymiou, G.; Lahaye, D.J.P.; Vuik, C.; Van der Sluis, L.
2012-01-01
Current and future developments in the power system industry demand fast power flow solvers for larger power flow problems. The established methods are no longer viable for such problems, as they are not scalable in the problem size. In this paper, the use of Newton-Krylov power flow methods is prop
A STATISTICAL AND HYDROLOGICAL ANALYSIS OF THE MAXIMUM FLOW IN THE TERPEZITA RIVER DRAINAGE BASIN
GABRIELA ADINA MOROŞANU
2015-03-01
Full Text Available A statistical and hydrological analysis of the maximum flow in the Terpezița river drainage basin. Starting from the idea that hydrological and hydrometeorological parameters have a statistical existence over time and a spatial distribution that can be represented by an interaction between the mathematical and geographical elements, the present paper aims to analyze the relationship between maximum flows, hourly rains, flow coefficients and concentration times of the Terpezita Basin. This is the second-largest sub-basin (182km2 in the basin of Desnatui, which is located in the SW of Romania and is a first degree tributary of the Danube. The assessment of the concentration time, which involves the sizes of the liquid flow and specific liquid flow, was attained according to the physical and geographical characteristics of the basin. Thus taking into account the homogenous character from this point of view and the existence of statistically established hydrological and pluviometric background, we could outline the behavior of Terpezița River Basin during the extreme hydro-meteorological events. The documentation was completed through an exemplification of previously calculated results, using observations and measurements of the river bed in the vicinity of Terpezita village and processing the values that resulted from the hydro-graph of the 2005 flash-flood.
Dynamic Programming and Error Estimates for Stochastic Control Problems with Maximum Cost
Bokanowski, Olivier, E-mail: boka@math.jussieu.fr [Laboratoire Jacques-Louis Lions, Université Paris-Diderot (Paris 7) UFR de Mathématiques - Bât. Sophie Germain (France); Picarelli, Athena, E-mail: athena.picarelli@inria.fr [Projet Commands, INRIA Saclay & ENSTA ParisTech (France); Zidani, Hasnaa, E-mail: hasnaa.zidani@ensta.fr [Unité de Mathématiques appliquées (UMA), ENSTA ParisTech (France)
2015-02-15
This work is concerned with stochastic optimal control for a running maximum cost. A direct approach based on dynamic programming techniques is studied leading to the characterization of the value function as the unique viscosity solution of a second order Hamilton–Jacobi–Bellman (HJB) equation with an oblique derivative boundary condition. A general numerical scheme is proposed and a convergence result is provided. Error estimates are obtained for the semi-Lagrangian scheme. These results can apply to the case of lookback options in finance. Moreover, optimal control problems with maximum cost arise in the characterization of the reachable sets for a system of controlled stochastic differential equations. Some numerical simulations on examples of reachable analysis are included to illustrate our approach.
Faggian, Silvia
2007-01-01
The paper concerns the study of the Pontryagin Maximum Principle for an infinite dimensional and infinite horizon boundary control problem for linear partial differential equations. The optimal control model has already been studied both in finite and infinite horizon with Dynamic Programming methods in a series of papers by the same author, or by Faggian and Gozzi. Necessary and sufficient optimality conditions for open loop controls are established. Moreover the co-state variable is shown to coincide with the spatial gradient of the value function evaluated along the trajectory of the system, creating a parallel between Maximum Principle and Dynamic Programming. The abstract model applies, as recalled in one of the first sections, to optimal investment with vintage capital.
Protein side-chain packing problem: a maximum edge-weight clique algorithmic approach.
Dukka Bahadur, K C; Tomita, Etsuji; Suzuki, Jun'ichi; Akutsu, Tatsuya
2005-02-01
"Protein Side-chain Packing" has an ever-increasing application in the field of bio-informatics, dating from the early methods of homology modeling to protein design and to the protein docking. However, this problem is computationally known to be NP-hard. In this regard, we have developed a novel approach to solve this problem using the notion of a maximum edge-weight clique. Our approach is based on efficient reduction of protein side-chain packing problem to a graph and then solving the reduced graph to find the maximum clique by applying an efficient clique finding algorithm developed by our co-authors. Since our approach is based on deterministic algorithms in contrast to the various existing algorithms based on heuristic approaches, our algorithm guarantees of finding an optimal solution. We have tested this approach to predict the side-chain conformations of a set of proteins and have compared the results with other existing methods. We have found that our results are favorably comparable or better than the results produced by the existing methods. As our test set contains a protein of 494 residues, we have obtained considerable improvement in terms of size of the proteins and in terms of the efficiency and the accuracy of prediction.
Svyatskiy, Daniil [Los Alamos National Laboratory; Shashkov, Mikhail [Los Alamos National Laboratory; Kuzmin, D [DORTMUND UNIV
2008-01-01
A new approach to the design of constrained finite element approximations to second-order elliptic problems is introduced. This approach guarantees that the finite element solution satisfies the discrete maximum principle (DMP). To enforce these monotonicity constrains the sufficient conditions for elements of the stiffness matrix are formulated. An algebraic splitting of the stiffness matrix is employed to separate the contributions of diffusive and antidiffusive numerical fluxes, respectively. In order to prevent the formation of spurious undershoots and overshoots, a symmetric slope limiter is designed for the antidiffusive part. The corresponding upper and lower bounds are defined using an estimate of the steepest gradient in terms of the maximum and minimum solution values at surrounding nodes. The recovery of nodal gradients is performed by means of a lumped-mass L{sub 2} projection. The proposed slope limiting strategy preserves the consistency of the underlying discrete problem and the structure of the stiffness matrix (symmetry, zero row and column sums). A positivity-preserving defect correction scheme is devised for the nonlinear algebraic system to be solved. Numerical results and a grid convergence study are presented for a number of anisotropic diffusion problems in two space dimensions.
McDonald, James G.; Groth, Clinton P. T.
2013-09-01
The ability to predict continuum and transition-regime flows by hyperbolic moment methods offers the promise of several advantages over traditional techniques. These methods offer an extended range of physical validity as compared with the Navier-Stokes equations and can be used for the prediction of many non-equilibrium flows with a lower expense than particle-based methods. Also, the hyperbolic first-order nature of the resulting partial differential equations leads to mathematical and numerical advantages. Moment equations generated through an entropy-maximization principle are particularly attractive due to their apparent robustness; however, their application to practical situations involving viscous, heat-conducting gases has been hampered by several issues. Firstly, the lack of closed-form expressions for closing fluxes leads to numerical expense as many integrals of distribution functions must be computed numerically during the course of a flow computation. Secondly, it has been shown that there exist physically realizable moment states for which the entropy-maximizing problem on which the method is based cannot be solved. Following a review of the theory surrounding maximum-entropy moment closures, this paper shows that both of these problems can be addressed in practice, at least for a simplified one-dimensional gas, and that the resulting flow predictions can be surprisingly good. The numerical results described provide significant motivations for the extension of these ideas to the fully three-dimensional case.
Structure of Turbulence in Katabatic Flows Below and Above the Wind-Speed Maximum
Grachev, Andrey A.; Leo, Laura S.; Sabatino, Silvana Di; Fernando, Harindra J. S.; Pardyjak, Eric R.; Fairall, Christopher W.
2016-06-01
Measurements of small-scale turbulence made in the atmospheric boundary layer over complex terrain during the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) Program are used to describe the structure of turbulence in katabatic flows. Turbulent and mean meteorological data were continuously measured on four towers deployed along the east lower slope (2-4°) of Granite Mountain near Salt Lake City in Utah, USA. The multi-level (up to seven) observations made during a 30-day long MATERHORN field campaign in September-October 2012 allowed the study of temporal and spatial structure of katabatic flows in detail, and herein we report turbulence statistics (e.g., fluxes, variances, spectra, and cospectra) and their variations in katabatic flow. Observed vertical profiles show steep gradients near the surface, but in the layer above the slope jet the vertical variability is smaller. It is found that the vertical (normal to the slope) momentum flux and horizontal (along-slope) heat flux in a slope-following coordinate system change their sign below and above the wind maximum of a katabatic flow. The momentum flux is directed downward (upward) whereas the along-slope heat flux is downslope (upslope) below (above) the wind maximum. This suggests that the position of the jet-speed maximum can be obtained by linear interpolation between positive and negative values of the momentum flux (or the along-slope heat flux) to derive the height where the flux becomes zero. It is shown that the standard deviations of all wind-speed components (and therefore of the turbulent kinetic energy) and the dissipation rate of turbulent kinetic energy have a local minimum, whereas the standard deviation of air temperature has an absolute maximum at the height of wind-speed maximum. We report several cases when the destructive effect of vertical heat flux is completely cancelled by the generation of turbulence due to the along-slope heat flux. Turbulence above the wind
Creep measurements confirm steady flow after stress maximum in extension of branched polymer melts
Javier Alvarez, Nicolas; Román Marín, José Manuel; Huang, Qian;
2013-01-01
We provide conclusive evidence of nonmonotonic mechanical behavior in the extension of long-chain branched polymer melts. While nonmonotonic behavior is known to occur for solids, for the case of polymeric melts, this phenomenon is in direct contrast with current theoretical models. We rule out...... the possibility of the overshoot being an experimental artifact by confirming the existence of steady flow after a maximum in the ratio of stress to strain rate versus strain under both constant stress and constant strain-rate kinematics. This observation indicates the omission of important physics from current...
An electromagnetism-like method for the maximum set splitting problem
Kratica Jozef
2013-01-01
Full Text Available In this paper, an electromagnetism-like approach (EM for solving the maximum set splitting problem (MSSP is applied. Hybrid approach consisting of the movement based on the attraction-repulsion mechanisms combined with the proposed scaling technique directs EM to promising search regions. Fast implementation of the local search procedure additionally improves the efficiency of overall EM system. The performance of the proposed EM approach is evaluated on two classes of instances from the literature: minimum hitting set and Steiner triple systems. The results show, except in one case, that EM reaches optimal solutions up to 500 elements and 50000 subsets on minimum hitting set instances. It also reaches all optimal/best-known solutions for Steiner triple systems.
Hybrid genetic algorithm in the Hopfield network for maximum 2-satisfiability problem
Kasihmuddin, Mohd Shareduwan Mohd; Sathasivam, Saratha; Mansor, Mohd. Asyraf
2017-08-01
Heuristic method was designed for finding optimal solution more quickly compared to classical methods which are too complex to comprehend. In this study, a hybrid approach that utilizes Hopfield network and genetic algorithm in doing maximum 2-Satisfiability problem (MAX-2SAT) was proposed. Hopfield neural network was used to minimize logical inconsistency in interpretations of logic clauses or program. Genetic algorithm (GA) has pioneered the implementation of methods that exploit the idea of combination and reproduce a better solution. The simulation incorporated with and without genetic algorithm will be examined by using Microsoft Visual 2013 C++ Express software. The performance of both searching techniques in doing MAX-2SAT was evaluate based on global minima ratio, ratio of satisfied clause and computation time. The result obtained form the computer simulation demonstrates the effectiveness and acceleration features of genetic algorithm in doing MAX-2SAT in Hopfield network.
Murphy, Patrick Charles
1985-01-01
An algorithm for maximum likelihood (ML) estimation is developed with an efficient method for approximating the sensitivities. The algorithm was developed for airplane parameter estimation problems but is well suited for most nonlinear, multivariable, dynamic systems. The ML algorithm relies on a new optimization method referred to as a modified Newton-Raphson with estimated sensitivities (MNRES). MNRES determines sensitivities by using slope information from local surface approximations of each output variable in parameter space. The fitted surface allows sensitivity information to be updated at each iteration with a significant reduction in computational effort. MNRES determines the sensitivities with less computational effort than using either a finite-difference method or integrating the analytically determined sensitivity equations. MNRES eliminates the need to derive sensitivity equations for each new model, thus eliminating algorithm reformulation with each new model and providing flexibility to use model equations in any format that is convenient. A random search technique for determining the confidence limits of ML parameter estimates is applied to nonlinear estimation problems for airplanes. The confidence intervals obtained by the search are compared with Cramer-Rao (CR) bounds at the same confidence level. It is observed that the degree of nonlinearity in the estimation problem is an important factor in the relationship between CR bounds and the error bounds determined by the search technique. The CR bounds were found to be close to the bounds determined by the search when the degree of nonlinearity was small. Beale's measure of nonlinearity is developed in this study for airplane identification problems; it is used to empirically correct confidence levels for the parameter confidence limits. The primary utility of the measure, however, was found to be in predicting the degree of agreement between Cramer-Rao bounds and search estimates.
Cristian Enache
2006-06-01
Full Text Available For a class of nonlinear elliptic boundary value problems in divergence form, we construct some general elliptic inequalities for appropriate combinations of u(x and |Ã¢ÂˆÂ‡u|2, where u(x are the solutions of our problems. From these inequalities, we derive, using Hopf's maximum principles, some maximum principles for the appropriate combinations of u(x and |Ã¢ÂˆÂ‡u|2, and we list a few examples of problems to which these maximum principles may be applied.
ADRIANA MIHAELA PORCUȚAN
2016-11-01
Full Text Available Suceava river basin gets its tributaries from the eastern slopes of the northern group of the Eastern Romanian Carpathians, situated under the influence of Baltic air masses, which bring rainfalls and cold weather, felt into the water flow regime of rivers in the region studied. This water flow regime varies from month to month, with the maximum flow having the most important role in the restoration of underground water reserves. This study examines the temporal (frequency, duration and intensity and quantitative (volume and flow parameters of periods with maximum flow, at monthly and seasonal level, revealing the differences in the water flow regime induced by the relief’s morphometric particularities (altitude, fragmentation degree, exhibition. For the evaluation of mentioned parameters was appealed to the TML 2.1 extension from the HydroOffice software package, which uses quantitative thresholds, depending on which it is set the appearance, and disappearance of periods with maximum flow.
Molecular Sticker Model Stimulation on Silicon for a Maximum Clique Problem.
Ning, Jianguo; Li, Yanmei; Yu, Wen
2015-06-12
Molecular computers (also called DNA computers), as an alternative to traditional electronic computers, are smaller in size but more energy efficient, and have massive parallel processing capacity. However, DNA computers may not outperform electronic computers owing to their higher error rates and some limitations of the biological laboratory. The stickers model, as a typical DNA-based computer, is computationally complete and universal, and can be viewed as a bit-vertically operating machine. This makes it attractive for silicon implementation. Inspired by the information processing method on the stickers computer, we propose a novel parallel computing model called DEM (DNA Electronic Computing Model) on System-on-a-Programmable-Chip (SOPC) architecture. Except for the significant difference in the computing medium--transistor chips rather than bio-molecules--the DEM works similarly to DNA computers in immense parallel information processing. Additionally, a plasma display panel (PDP) is used to show the change of solutions, and helps us directly see the distribution of assignments. The feasibility of the DEM is tested by applying it to compute a maximum clique problem (MCP) with eight vertices. Owing to the limited computing sources on SOPC architecture, the DEM could solve moderate-size problems in polynomial time.
Molecular Sticker Model Stimulation on Silicon for a Maximum Clique Problem
Jianguo Ning
2015-06-01
Full Text Available Molecular computers (also called DNA computers, as an alternative to traditional electronic computers, are smaller in size but more energy efficient, and have massive parallel processing capacity. However, DNA computers may not outperform electronic computers owing to their higher error rates and some limitations of the biological laboratory. The stickers model, as a typical DNA-based computer, is computationally complete and universal, and can be viewed as a bit-vertically operating machine. This makes it attractive for silicon implementation. Inspired by the information processing method on the stickers computer, we propose a novel parallel computing model called DEM (DNA Electronic Computing Model on System-on-a-Programmable-Chip (SOPC architecture. Except for the significant difference in the computing medium—transistor chips rather than bio-molecules—the DEM works similarly to DNA computers in immense parallel information processing. Additionally, a plasma display panel (PDP is used to show the change of solutions, and helps us directly see the distribution of assignments. The feasibility of the DEM is tested by applying it to compute a maximum clique problem (MCP with eight vertices. Owing to the limited computing sources on SOPC architecture, the DEM could solve moderate-size problems in polynomial time.
Structure of Turbulence in Katabatic Flows below and above the Wind-Speed Maximum
Grachev, Andrey A; Di Sabatino, Silvana; Fernando, Harindra J S; Pardyjak, Eric R; Fairall, Christopher W
2015-01-01
Measurements of small-scale turbulence made over the complex-terrain atmospheric boundary layer during the MATERHORN Program are used to describe the structure of turbulence in katabatic flows. Turbulent and mean meteorological data were continuously measured at multiple levels at four towers deployed along the East lower slope (2-4 deg) of Granite Mountain. The multi-level observations made during a 30-day long MATERHORN-Fall field campaign in September-October 2012 allowed studying of temporal and spatial structure of katabatic flows in detail, and herein we report turbulence and their variations in katabatic winds. Observed vertical profiles show steep gradients near the surface, but in the layer above the slope jet the vertical variability is smaller. It is found that the vertical (normal to the slope) momentum flux and horizontal (along the slope) heat flux in a slope-following coordinate system change their sign below and above the wind maximum of a katabatic flow. The vertical momentum flux is directed...
Thermodynamics, maximum power, and the dynamics of preferential river flow structures on continents
A. Kleidon
2012-06-01
Full Text Available The organization of drainage basins shows some reproducible phenomena, as exemplified by self-similar fractal river network structures and typical scaling laws, and these have been related to energetic optimization principles, such as minimization of stream power, minimum energy expenditure or maximum "access". Here we describe the organization and dynamics of drainage systems using thermodynamics, focusing on the generation, dissipation and transfer of free energy associated with river flow and sediment transport. We argue that the organization of drainage basins reflects the fundamental tendency of natural systems to deplete driving gradients as fast as possible through the maximization of free energy generation, thereby accelerating the dynamics of the system. This effectively results in the maximization of sediment export to deplete topographic gradients as fast as possible and potentially involves large-scale feedbacks to continental uplift. We illustrate this thermodynamic description with a set of three highly simplified models related to water and sediment flow and describe the mechanisms and feedbacks involved in the evolution and dynamics of the associated structures. We close by discussing how this thermodynamic perspective is consistent with previous approaches and the implications that such a thermodynamic description has for the understanding and prediction of sub-grid scale organization of drainage systems and preferential flow structures in general.
A. Kleidon
2013-01-01
Full Text Available The organization of drainage basins shows some reproducible phenomena, as exemplified by self-similar fractal river network structures and typical scaling laws, and these have been related to energetic optimization principles, such as minimization of stream power, minimum energy expenditure or maximum "access". Here we describe the organization and dynamics of drainage systems using thermodynamics, focusing on the generation, dissipation and transfer of free energy associated with river flow and sediment transport. We argue that the organization of drainage basins reflects the fundamental tendency of natural systems to deplete driving gradients as fast as possible through the maximization of free energy generation, thereby accelerating the dynamics of the system. This effectively results in the maximization of sediment export to deplete topographic gradients as fast as possible and potentially involves large-scale feedbacks to continental uplift. We illustrate this thermodynamic description with a set of three highly simplified models related to water and sediment flow and describe the mechanisms and feedbacks involved in the evolution and dynamics of the associated structures. We close by discussing how this thermodynamic perspective is consistent with previous approaches and the implications that such a thermodynamic description has for the understanding and prediction of sub-grid scale organization of drainage systems and preferential flow structures in general.
Multiple Objective Minimum Cost Flow Problems: A Review
Hamacher, H.W.; Pedersen, Christian Roed; Ruzika, S.
2005-01-01
In this paper, theory and algorithms for solving the multiple objective minimum cost flow problem are reviewed. For both the continuous and integer case exact and approximation algorithms are presented. In addition, a section on compromise solutions summarizes corresponding results. The reference...... list consists of all papers known to the authors which deal with the multiple objective minimum cost flow problem....
Minimum cost network flows: Problems, algorithms, and software
Sifaleras Angelo
2013-01-01
Full Text Available We present a wide range of problems concerning minimum cost network flows, and give an overview of the classic linear single-commodity Minimum Cost Network Flow Problem (MCNFP and some other closely related problems, either tractable or intractable. We also discuss state-of-the-art algorithmic approaches and recent advances in the solution methods for the MCNFP. Finally, optimization software packages for the MCNFP are presented.
Spreadsheet Implementations for Solving Power-Flow Problems
Mark A Lau
2008-08-01
Full Text Available The solution to the power-flow problem is of fundamental importance in power system analysis and design. Transient stability studies and fault analysis in power systems demand solutions to a power-flow problem as a first step in the analysis. Although commercial software such as PSS/E (Power System Simulator for Engineers or PowerWorld can be used for power flow calculations, such specialized programs may not be widely available in many universities or colleges. Spreadsheets, on the other hand, provide an economic alternative for the implementation of the numerical algorithms encountered in power flows.
FlowMax: A Computational Tool for Maximum Likelihood Deconvolution of CFSE Time Courses.
Maxim Nikolaievich Shokhirev
Full Text Available The immune response is a concerted dynamic multi-cellular process. Upon infection, the dynamics of lymphocyte populations are an aggregate of molecular processes that determine the activation, division, and longevity of individual cells. The timing of these single-cell processes is remarkably widely distributed with some cells undergoing their third division while others undergo their first. High cell-to-cell variability and technical noise pose challenges for interpreting popular dye-dilution experiments objectively. It remains an unresolved challenge to avoid under- or over-interpretation of such data when phenotyping gene-targeted mouse models or patient samples. Here we develop and characterize a computational methodology to parameterize a cell population model in the context of noisy dye-dilution data. To enable objective interpretation of model fits, our method estimates fit sensitivity and redundancy by stochastically sampling the solution landscape, calculating parameter sensitivities, and clustering to determine the maximum-likelihood solution ranges. Our methodology accounts for both technical and biological variability by using a cell fluorescence model as an adaptor during population model fitting, resulting in improved fit accuracy without the need for ad hoc objective functions. We have incorporated our methodology into an integrated phenotyping tool, FlowMax, and used it to analyze B cells from two NFκB knockout mice with distinct phenotypes; we not only confirm previously published findings at a fraction of the expended effort and cost, but reveal a novel phenotype of nfkb1/p105/50 in limiting the proliferative capacity of B cells following B-cell receptor stimulation. In addition to complementing experimental work, FlowMax is suitable for high throughput analysis of dye dilution studies within clinical and pharmacological screens with objective and quantitative conclusions.
The problem of the maximum volumes and particle horizon in the Friedmann universe model
Gong, S. M.
1989-08-01
The maximum volume of the closed Friedmann universe is further investigated and is shown to be 2 x pi squared x R cubed (t), instead of pi squared x R cubed (t) as found previously. This discrepancy comes from the incomplete use of the volume formula of 3-dimensional spherical space in the astronomical literature. Mathematically, the maximum volume exists at any cosmic time t in a 3-dimensional spherical case. However, the Friedmann closed universe in expansion reaches its maximum volume only at the time of the maximum scale factor. The particle horizon has no limitation for the farthest objects in the closed Friedmann universe if the proper distance of objects is compared with the particle horizon as is should be. This leads to absurdity if the luminosity distance of objects is compared with the proper distance of the particle horizon.
Topology Optimization of Large Scale Stokes Flow Problems
Aage, Niels; Poulsen, Thomas Harpsøe; Gersborg-Hansen, Allan
2008-01-01
This note considers topology optimization of large scale 2D and 3D Stokes flow problems using parallel computations. We solve problems with up to 1.125.000 elements in 2D and 128.000 elements in 3D on a shared memory computer consisting of Sun UltraSparc IV CPUs.......This note considers topology optimization of large scale 2D and 3D Stokes flow problems using parallel computations. We solve problems with up to 1.125.000 elements in 2D and 128.000 elements in 3D on a shared memory computer consisting of Sun UltraSparc IV CPUs....
FASB 95--a tool for identifying cash flow problems.
Edwards, D E; Hauser, R C
1989-06-01
Increasing expenditures and longer collection periods for receivables are symptoms of the cash flow problem that many not-for-profit healthcare organizations face. The FASB 95 provisions for a cash flow statement could help many of these organizations deal with their cash flow crises. The statement allows managers to evaluate their institution's financial performance, providing timely information that may make the difference in the struggle to maintain an adequate cash position.
García-Arnau, Marc; Manrique, Daniel; Rodríguez-Patón, Alfonso; Sosík, Petr
2007-01-01
We present a P system with replicated rewriting to solve the Maximum Clique Problem for a graph. Strings representing cliques are built gradually. This involves the use of inhibitors that control the space of all generated solutions to the problem. Calculating the maximum clique for a graph is a highly relevant issue not only on purely computational grounds, but also because of its relationship to fundamental problems in genomics. We propose to implement the designed P system by means of a DNA algorithm. This algorithm is then compared with two standard papers that addressed the same problem and its DNA implementation in the past. This comparison is carried out on the basis of a series of computational and physical parameters. Our solution features a significantly lower cost in terms of time, the number and size of strands, as well as the simplicity of the biological implementation.
Vegetative treatment systems (VTSs) are one type of control structure that has shown potential to control runoff from open feedlots. To achieve maximum performance, sheet-flow over the width of the vegetative treatment area (VTA) is required. Tools, such as maps of flow paths through the VTA, are ne...
Malone, Stephen M.; McGue, Matt; Iacono, William G.
2010-01-01
Background: The maximum number of alcoholic drinks consumed in a single 24-hr period is an alcoholism-related phenotype with both face and empirical validity. It has been associated with severity of withdrawal symptoms and sensitivity to alcohol, genes implicated in alcohol metabolism, and amplitude of a measure of brain activity associated with…
Multi-Objective Simulating Annealing for Permutation Flow Shop Problems
Mokotoff, E.; Pérez, J.
2007-09-01
Real life scheduling problems require more than one criterion. Nevertheless, the complex nature of the Permutation Flow Shop problem has prevented the development of models with multiple criteria. Considering only one regular criterion, this scheduling problem was shown to be NP-complete. The Multi-Objective Simulated Annealing (MOSA) methods are metaheuristics based on Simulated Annealing to solve Multi-Objective Combinatorial Optimization (MOCO) problems, like the problem at hand. Starting from the general MOSA method introduced by Loukil et al. [1], we developed MOSA models to provide the decision maker with efficient solutions for the Permutation Flow Shop problem (common in the production of ceramic tiles). In this paper we present three models: two bicriteria models and one based on satisfaction levels for the main criterion.
Uncertainties in transient projections of maximum and minimum flows over the United States
Giuntoli, Ignazio; Villarini, Gabriele; Prudhomme, Christel; Hannah, David M.
2016-04-01
Global multi-model ensemble experiments provide a valuable basis for the examination of potential future changes in runoff. However, these projections suffer from uncertainties that originate from different sources at different levels in the modelling chain. We present the partitioning of uncertainty into four distinct sources of projections of decadally-averaged annual maximum (AMax) and minimum (AMin) flows over the USA. More specifically, we quantify the relative contribution of the uncertainties arising from internal variability, global impact models (GIMs), global climate models (GCMs), and representative concentration pathways (RCPs). We use a set of nine state-of-the-art GIMs driven by five CMIP5 GCMs under four RCPs from the ISI-MIP multi-model ensemble. We examine the temporal changes in the relative contribution of each source of uncertainty over the course of the 21st century. Results show that GCMs and GIMs are responsible for the majority of uncertainty over most of the study area, followed by internal variability and RCPs. Proportions vary regionally and depend on the end of the runoff spectrum (AMax, AMin) considered. In particular, for AMax, large fractions of uncertainty are attributable to GCMs throughout the century with the GIMs increasing their share especially in mountainous and cold areas. For Amin, the contribution of GIMs to uncertainty increases with time, becoming the dominant source over most of the country by the end of the 21st century. Importantly, compared to the other sources, the RCPs contribution to uncertainty is negligible generally (for AMin especially). This finding indicates that the effects of different emission scenarios are barely noticeable in hydrological impact studies, while GIMs and GCMs make up most of the amplitude of the ensemble spread (uncertainty).
3D Topology optimization of Stokes flow problems
Gersborg-Hansen, Allan; Dammann, Bernd
of energy efficient devices for 2D Stokes flow. Creeping flow problems are described by the Stokes equations which model very viscous fluids at macro scales or ordinary fluids at very small scales. The latter gives the motivation for topology optimization problems based on the Stokes equations being a model...... the designs are 3D. Moreover, preliminary results show that a formulation of an optimization problem that maximizes mixing with a constraint on the pressure drop across the device gives promising results. To measure the mixing a step temperature profile is convected through the design and the resulting...
Topology optimization of 3D Stokes flow problems
Gersborg-Hansen, Allan
to different flow problems. However, this research has focused on 2D fluid modelling, which limits the practical impact of the computed designs. The explanation of the limitation is that the finite size domain used in topology optimization problems ensures that the velocity components couples, even for Stokes......Topology optimization has been applied to a multitude of physical systems and is now a mature technology used in industrial practice, see [1] for an overview. Borrvall and Petersson [2] introduced topology optimization of Stokes flow problems which initiated works on extending topology optimization...... flow [3]. Furthermore, it is questionable if such a coupling can be captured by a 2D model especially in non-trivial geometries as typically seen in topology design. This statement is widely accepted in the fluid mechanics community, i.e. that planar fluid models are useful for academic test problems...
Topology optimization of 3D Stokes flow problems
Gersborg-Hansen, Allan; Sigmund, Ole; Bendsøe, Martin P.
is caused by the finite size domain used in topology optimization problems which ensures that the velocity components couples, even for Stokes flow [3]. Physically Stokes flow is an exotic inertia free flow, which in practice complicates mixing by passive devices. Passive mixing devices are relevant......The design of MEMS devices have benefitted from the topology optimization tool and complicated layout problems have been solved, see [1] for an overview. This research is aimed at micro fluidic devices known as micro-Total-Analysis-Systems (muTAS) where the main physical phenomena originate from...... fluid mechanics. In future practice a muTAS could be used by doctors, engineers etc. as a hand held device with short reaction time that provides on-site analysis of a flowing substance such as blood, polluted water or similar. Borrvall and Petersson [2] paved the road for using the topology...
On Howard's Conjecture in Heterogeneous Shear Flow Problem
R G Shandil; Jagjit Singh
2003-11-01
Howard's conjecture, which states that in the linear instability problem of inviscid heterogeneous parallel shear flow growth rate of an arbitrary unstable wave must approach zero as the wave length decreases to zero, is established in a mathematically rigorous fashion for plane parallel heterogeneous shear flows with negligible buoyancy force $g \\ll 1$ (Miles J W, J. Fluid Mech. 10 (1961) 496–508), where is the basic heterogeneity distribution function).
Model problem of MHD flow in a lithium blanket
Cherepanov, V.Y.
1978-01-01
A model problem is considered for a feasibility study concerning controlled MHD flow in the blanket of a Tokamak nuclear reactor. The fundamental equations for the steady flow of an incompressible viscous fluid in a uniform transverse magnetic field are solved in rectangular coordinates, in the zero-induction approximation and with negligible induced currents. A numerical solution obtained for a set of appropriate boundary constraints establishes the conditions under which no stagnation zones will be formed.
ε-MAXIMUM PRINCIPLE IN LINEAR PROBLEM OF HYBRID SYSTEM OPTIMUM CONTROL
O. R. Gabasova
2009-01-01
Full Text Available The paper reveals necessary and sufficient conditions of optimality and sub-optimality of the programs for a hybrid system in the class of discrete control actions. The conditions are formulated in the support terms of the initial problem.
Ahmad Zeraatkar Moghaddam
2012-01-01
Full Text Available This paper presents a mathematical model for the problem of minimizing the maximum lateness on a single machine when the deteriorated jobs are delivered to each customer in various size batches. In reality, this issue may happen within a supply chain in which delivering goods to customers entails cost. Under such situation, keeping completed jobs to deliver in batches may result in reducing delivery costs. In literature review of batch scheduling, minimizing the maximum lateness is known as NP-Hard problem; therefore the present issue aiming at minimizing the costs of delivering, in addition to the aforementioned objective function, remains an NP-Hard problem. In order to solve the proposed model, a Simulation annealing meta-heuristic is used, where the parameters are calibrated by Taguchi approach and the results are compared to the global optimal values generated by Lingo 10 software. Furthermore, in order to check the efficiency of proposed method to solve larger scales of problem, a lower bound is generated. The results are also analyzed based on the effective factors of the problem. Computational study validates the efficiency and the accuracy of the presented model.
The Liner Shipping Fleet Repositioning Problem with Cargo Flows
Tierney, Kevin; Jensen, Rune Møller
2012-01-01
We solve an important problem for the liner shipping industry called the Liner Shipping Fleet Repositioning Problem (LSFRP). The LSFRP poses a large financial burden on liner shipping firms. During repositioning, vessels are moved between services in a liner shipping network. Shippers wish...... in the literature. We introduce a novel mathematical model of the LSFRP with cargo flows based on a carefully constructed graph and evaluate it on real world data from our industrial collaborator....
Optimal Results and Numerical Simulations for Flow Shop Scheduling Problems
Tao Ren
2012-01-01
Full Text Available This paper considers the m-machine flow shop problem with two objectives: makespan with release dates and total quadratic completion time, respectively. For Fm|rj|Cmax, we prove the asymptotic optimality for any dense scheduling when the problem scale is large enough. For Fm‖ΣCj2, improvement strategy with local search is presented to promote the performance of the classical SPT heuristic. At the end of the paper, simulations show the effectiveness of the improvement strategy.
Analytical methods for heat transfer and fluid flow problems
Weigand, Bernhard
2015-01-01
This book describes useful analytical methods by applying them to real-world problems rather than solving the usual over-simplified classroom problems. The book demonstrates the applicability of analytical methods even for complex problems and guides the reader to a more intuitive understanding of approaches and solutions. Although the solution of Partial Differential Equations by numerical methods is the standard practice in industries, analytical methods are still important for the critical assessment of results derived from advanced computer simulations and the improvement of the underlying numerical techniques. Literature devoted to analytical methods, however, often focuses on theoretical and mathematical aspects and is therefore useless to most engineers. Analytical Methods for Heat Transfer and Fluid Flow Problems addresses engineers and engineering students. The second edition has been updated, the chapters on non-linear problems and on axial heat conduction problems were extended. And worked out exam...
2008-01-01
In this paper,we explore some weakly consistent properties of quasi-maximum likelihood estimates(QMLE) concerning the quasi-likelihood equation in=1 Xi(yi-μ(Xiβ)) = 0 for univariate generalized linear model E(y |X) = μ(X’β).Given uncorrelated residuals {ei = Yi-μ(Xiβ0),1 i n} and other conditions,we prove that βn-β0 = Op(λn-1/2) holds,where βn is a root of the above equation,β0 is the true value of parameter β and λn denotes the smallest eigenvalue of the matrix Sn = ni=1 XiXi.We also show that the convergence rate above is sharp,provided independent non-asymptotically degenerate residual sequence and other conditions.Moreover,paralleling to the elegant result of Drygas(1976) for classical linear regression models,we point out that the necessary condition guaranteeing the weak consistency of QMLE is Sn-1→ 0,as the sample size n →∞.
ZHANG SanGuo; LIAO Yuan
2008-01-01
In this paper, we explore some weakly consistent properties of quasi-maximum likelihood estimates(QMLE)concerning the quasi-likelihood equation ∑ni=1 Xi(yi-μ(X1iβ)) =0 for univariate generalized linear model E(y|X) =μ(X1β). Given uncorrelated residuals{ei=Yi-μ(X1iβ0), 1≤i≤n}and other conditions, we prove that (β)n-β0=Op(λ--1/2n)holds, where (β)n is a root of the above equation,β0 is the true value of parameter β and λ-n denotes the smallest eigenvalue of the matrix Sn=Σni=1 XiX1i. We also show that the convergence rate above is sharp, provided independent nonasymptotically degenerate residual sequence and other conditions. Moreover, paralleling to the elegant result of Drygas(1976)for classical linear regression models,we point out that the necessary condition guaranteeing the weak consistency of QMLE is S-1n→0, as the sample size n→∞.
Eigenvalues of the time—dependent fluid flow problem I
El-Sayed M. Zayed
1990-01-01
Full Text Available The direct and inverse boundary value problems for the linear unsteady viscous fluid flow through a closed conduit of a circular annular cross-section Ω with arbitrary time-dependent pressure gradient under the third boundary conditions have been investigated.
Degree-Based Approach for the Maximum Clique Problem%度数法求解最大团问题
胡新; 王丽珍; 何瓦特; 姚华传
2013-01-01
由于最大团问题(maximum clique problem,MCP)的复杂性、挑战性,以及在数据挖掘等领域的广泛应用,使得求解MCP问题具有非常重要的意义.根据最大团顶点度数较大的特点,提出了从图中第一个度数最大的顶点出发递归求解最大团的算法(简称度数法).为了进一步提高算法的效率,根据图的特点和最大团的特点提出了三个改进的剪枝策略.从理论上证明了算法的正确性和完整性,其时间复杂度为 O(1.442n),空间为 O(n2).通过实验验证了度数法及其改进剪枝策略的效果和效率.%The maximum clique problem (MCP) is a significant problem in computer science field because of its complexity, challenging and the extensive applications in data mining and other fields. This paper puts forward a new degree-based approach to finding the maximum clique in a given graph G. According to the characteristic that the degree of the vertexes in a maximum clique is relatively larger, the new approach solves the maximum clique by starting from the first vertex which degree is the largest in the graph G. In order to further improve the efficiency of the algorithm, this paper presents three improvement and pruning strategies based on the characteristics of the graph and the maximum clique. This paper proves that the new approach is correct and complete, the time complexity is O(1.442n) , and the space cost is O(n2) . Finally, an empirical study verifies the effectiveness and efficiency of the new approach.
Topology optimization of 3D Stokes flow problems
Gersborg-Hansen, Allan
to different flow problems. However, this research has focused on 2D fluid modelling, which limits the practical impact of the computed designs. The explanation of the limitation is that the finite size domain used in topology optimization problems ensures that the velocity components couples, even for Stokes...... flow [3]. Furthermore, it is questionable if such a coupling can be captured by a 2D model especially in non-trivial geometries as typically seen in topology design. This statement is widely accepted in the fluid mechanics community, i.e. that planar fluid models are useful for academic test problems...... fundamental aspects of the topology optimization method applied to the Stokes equations as described below. This work consists of two parts. The main part elaborates on effects caused by 3D fluid modelling on the design. Numerical examples are shown where the design is planar - relevant to micro fluidic...
R. van Mastrigt (Ron)
1990-01-01
textabstractThe contractility of the urinary bladder can be adequately described in terms of the parameters P0 (isometric pressure) and Vmax (maximum contraction velocity). In about 12% of urodynamic evaluations of patients these clinically relevant parameters can be calculated from pressure and flo
Qing-ping Deng; Xue-jun Xu; Shu-min Shen
2000-01-01
This paper deals with Crouzeix-Raviart nonconforming finite element approxi mation of Navier-Stokes equation in a plane bounded domain, by using the so-called velocity-pressure mixed formulation. The quasi-optimal maximum norm error es timates of the velocity and its first derivatives and of the pressure are derived for nonconforming C-R scheme of stationary Navier-Stokes problem. The analysis is based on the weighted inf-sup condition and the technique of weighted Sobolev norm. By the way, the optimal L2-error estimate for nonconforming finite element approximation is obtained.
Solving the Liner Shipping Fleet Repositioning Problem with Cargo Flows
Tierney, Kevin; Askelsdottir, Björg; Jensen, Rune Møller
2015-01-01
We solve a central problem in the liner shipping industry called the liner shipping fleet repositioning problem (LSFRP). The LSFRP poses a large financial burden on liner shipping firms. During repositioning, vessels are moved between routes in a liner shipping network. Liner carriers wish...... introduce a novel mathematical model and a simulated annealing algorithm for the LSFRP with cargo flows that makes use of a carefully constructed graph; we evaluate these approaches using real-world data from our industrial collaborator. Additionally, we compare the performance of our approach against...
Reduced-Complexity Semidefinite Relaxations of Optimal Power Flow Problems
Andersen, Martin Skovgaard; Hansson, Anders; Vandenberghe, Lieven
2014-01-01
We propose a new method for generating semidefinite relaxations of optimal power flow problems. The method is based on chordal conversion techniques: by dropping some equality constraints in the conversion, we obtain semidefinite relaxations that are computationally cheaper, but potentially weaker......, than the standard semidefinite relaxation. Our numerical results show that the new relaxations often produce the same results as the standard semidefinite relaxation, but at a lower computational cost....
Nonclassical Symmetry Analysis of Heated Two-Dimensional Flow Problems
Naeem, Imran; Naz, Rehana; Khan, Muhammad Danish
2015-12-01
This article analyses the nonclassical symmetries and group invariant solution of boundary layer equations for two-dimensional heated flows. First, we derive the nonclassical symmetry determining equations with the aid of the computer package SADE. We solve these equations directly to obtain nonclassical symmetries. We follow standard procedure of computing nonclassical symmetries and consider two different scenarios, ξ1≠0 and ξ1=0, ξ2≠0. Several nonclassical symmetries are reported for both scenarios. Furthermore, numerous group invariant solutions for nonclassical symmetries are derived. The similarity variables associated with each nonclassical symmetry are computed. The similarity variables reduce the system of partial differential equations (PDEs) to a system of ordinary differential equations (ODEs) in terms of similarity variables. The reduced system of ODEs are solved to obtain group invariant solution for governing boundary layer equations for two-dimensional heated flow problems. We successfully formulate a physical problem of heat transfer analysis for fluid flow over a linearly stretching porous plat and, with suitable boundary conditions, we solve this problem.
Flow-shop scheduling problem under uncertainties: Review and trends
Eliana María González-Neira
2017-03-01
Full Text Available Among the different tasks in production logistics, job scheduling is one of the most important at the operational decision-making level to enable organizations to achieve competiveness. Scheduling consists in the allocation of limited resources to activities over time in order to achieve one or more optimization objectives. Flow-shop (FS scheduling problems encompass the sequencing processes in environments in which the activities or operations are performed in a serial flow. This type of configuration includes assembly lines and the chemical, electronic, food, and metallurgical industries, among others. Scheduling has been mostly investigated for the deterministic cases, in which all parameters are known in advance and do not vary over time. Nevertheless, in real-world situations, events are frequently subject to uncertainties that can affect the decision-making process. Thus, it is important to study scheduling and sequencing activities under uncertainties since they can cause infeasibilities and disturbances. The purpose of this paper is to provide a general overview of the FS scheduling problem under uncertainties and its role in production logistics and to draw up opportunities for further research. To this end, 100 papers about FS and flexible flow-shop scheduling problems published from 2001 to October 2016 were analyzed and classified. Trends in the reviewed literature are presented and finally some research opportunities in the field are proposed.
Lu Lin
2009-10-01
Full Text Available Estimation of Distribution Algorithm (EDA is a new kinds of colony evolution algorithm, through counting excellent information of individuals of the present colony EDA construct probability distribution model, then sample the model produces newt generation. To solve the NP-Hard question as EDA searching optimum network structure a new Maximum Entropy Distribution Algorithm (MEEDA is provided. The algorithm takes Jaynes principle as the basis, makes use of the maximum entropy of random variables to estimate the minimum bias probability distribution of random variables, and then regard it as the evolution model of the algorithm, which produces the optimal/near optimal solution. Then this paper presents a rough programming model for job shop scheduling under uncertain information problem. The method overcomes the defects of traditional methods which need pre-set authorized characteristics or amount described attributes, designs multi-objective optimization mechanism and expands the application space of a rough set in the issue of job shop scheduling under uncertain information environment. Due to the complexity of the proposed model, traditional algorithms have low capability in producing a feasible solution. We use MEEDA in order to enable a definition of a solution within a reasonable amount of time. We assume that machine flexibility in processing operations to decrease the complexity of the proposed model. Muth and Thompson’s benchmark problems tests are used to verify and validate the proposed rough programming model and its algorithm. The computational results obtained by MEEDA are compared with GA. The compared results prove the effectiveness of MEEDA in the job shop scheduling problem under uncertain information environment.
Break the Ties for NEH Heuristic in Solving the Permutation Flow Shop Problems
GAO Shou-wei; LEISTEN Rainer; DAI Yang; ZHANG Wei-dong
2008-01-01
This study deals with the Permutation Flow Shop Scheduling Problem (PFSP) based on the maximum completion time (makespan). NEH (the algorithm of Nawaz, Enscore and Ham) is the concluded most efficient constructive method in solving this NP-hard problem. The principal features of its strengths are the initial arrangement of jobs and the job insertion phase. In some instances, ties will occur in both the initial permutation and the partial sequences. The problem of ties breaking may have a significant impact on the NEH performance, but evaluate all the ties will be non-polynomial in the worst case. Several kinds of methods are presented in the paper to break the ties in a quick time. Together with the basic one, all 22 methods are tested on the famous Taillard's benchmarks and the most suitable ties breaking policy is recommended.
Solving microscopic flow problems using Stokes equations in SPH
Van Liedekerke, P.; Smeets, B.; Odenthal, T.; Tijskens, E.; Ramon, H.
2013-07-01
Starting from the Smoothed Particle Hydrodynamics method (SPH), we propose an alternative way to solve flow problems at a very low Reynolds number. The method is based on an explicit drop out of the inertial terms in the normal SPH equations, and solves the coupled system to find the velocities of the particles using the conjugate gradient method. The method will be called NSPH which refers to the non-inertial character of the equations. Whereas the time-step in standard SPH formulations for low Reynolds numbers is linearly restricted by the inverse of the viscosity and quadratically by the particle resolution, the stability of the NSPH solution benefits from a higher viscosity and is independent of the particle resolution. Since this method allows for a much higher time-step, it solves creeping flow problems with a high resolution and a long timescale up to three orders of magnitude faster than SPH. In this paper, we compare the accuracy and capabilities of the new NSPH method to canonical SPH solutions considering a number of standard problems in fluid dynamics. In addition, we show that NSPH is capable of modeling more complex physical phenomena such as the motion of a red blood cell in plasma.
Minimizing makespan in a two-stage hybrid flow shop scheduling problem with open shop in one stage
DONG Jian-ming; HU Jue-liang; CHEN Yong
2013-01-01
This paper considers a scheduling problem in two-stage hybrid flow shop, where the first stage consists of two machines formed an open shop and the other stage has only one machine. The objective is to minimize the makespan, i.e., the maximum completion time of all jobs. We first show the problem is NP-hard in the strong sense, then we present two heuristics to solve the problem. Computational experiments show that the combined algorithm of the two heuristics performs well on randomly generated problem instances.
George Cristian Gruia
2013-05-01
Full Text Available In the aviation industry, propeller motor engines have a lifecycle of several thousand hours of flight and the maintenance is an important part of their lifecycle. The present article considers a multi-resource, priority-based case scheduling problem, which is applied in a Romanian manufacturing company, that repairs and maintains helicopter and airplane engines at a certain quality level imposed by the aviation standards. Given a reduced budget constraint, the management’s goal is to maximize the utilization of their resources (financial, material, space, workers, by maintaining a prior known priority rule. An Off-Line Dual Maximum Resource Bin Packing model, based on a Mixed Integer Programming model is thus presented. The obtained results show an increase with approx. 25% of the Just in Time shipping of the engines to the customers and approx. 12,5% increase in the utilization of the working area.
Solving the Cooling Flow Problem through Mechanical AGN Feedback
Gaspari, M; Ruszkowski, M
2012-01-01
Unopposed radiative cooling of plasma would lead to the cooling catastrophe, a massive inflow of condensing gas, manifest in the core of galaxies, groups and clusters. The last generation X-ray telescopes, Chandra and XMM, have radically changed our view on baryons, indicating AGN heating as the balancing counterpart of cooling. This work reviews our extensive investigation on self-regulated heating. We argue that the mechanical feedback, based on massive subrelativistic outflows, is the key to solving the cooling flow problem, i.e. dramatically quenching the cooling rates for several Gyr without destroying the cool-core structure. Using a modified version of the 3D hydrocode FLASH, we show that bipolar AGN outflows can further reproduce fundamental observed features, such as buoyant bubbles, weak shocks, metals dredge- up, and turbulence. The latter is an essential ingredient to drive nonlinear thermal instabilities, which cause the formation of extended cold gas, a residual of the quenched cooling flow and,...
Robust quadratic assignment problem with budgeted uncertain flows
Mohammad Javad Feizollahi
2015-12-01
Full Text Available We consider a generalization of the classical quadratic assignment problem, where material flows between facilities are uncertain, and belong to a budgeted uncertainty set. The objective is to find a robust solution under all possible scenarios in the given uncertainty set. We present an exact quadratic formulation as a robust counterpart and develop an equivalent mixed integer programming model for it. To solve the proposed model for large-scale instances, we also develop two different heuristics based on 2-Opt local search and tabu search algorithms. We discuss performance of these methods and the quality of robust solutions through extensive computational experiments.
Karia Ritesh M
2012-04-01
Full Text Available Objective: Objectives of this study is to study effect of smoking on Peak Expiratory Flow Rate and Maximum Voluntary Ventilation in apparently healthy tobacco smokers and non-smokers and to compare the result of both the studies to assess the effects of smoking Method: The present study was carried out by computerized software of Pulmonary Function Test named ‘Spiro Excel’ on 50 non-smokers and 50 smokers. Smokers are divided in three gropus. Full series of test take 4 to 5 minutes. Tests were compared in the both smokers and non-smokers group by the ‘unpaired t test’. Statistical significance was indicated by ‘p’ value < 0.05. Results: From the result it is found that actual value of Peak Expiratory Flow Rate and Maximum Voluntary Ventilation are significantly lower in all smokers group than non-smokers. The difference of actual mean value is increases as the degree of smoking increases. [National J of Med Res 2012; 2(2.000: 191-193
Water flow algorithm decision support tool for travelling salesman problem
Kamarudin, Anis Aklima; Othman, Zulaiha Ali; Sarim, Hafiz Mohd
2016-08-01
This paper discuss about the role of Decision Support Tool in Travelling Salesman Problem (TSP) for helping the researchers who doing research in same area will get the better result from the proposed algorithm. A study has been conducted and Rapid Application Development (RAD) model has been use as a methodology which includes requirement planning, user design, construction and cutover. Water Flow Algorithm (WFA) with initialization technique improvement is used as the proposed algorithm in this study for evaluating effectiveness against TSP cases. For DST evaluation will go through usability testing conducted on system use, quality of information, quality of interface and overall satisfaction. Evaluation is needed for determine whether this tool can assists user in making a decision to solve TSP problems with the proposed algorithm or not. Some statistical result shown the ability of this tool in term of helping researchers to conduct the experiments on the WFA with improvements TSP initialization.
Natural Examples of Olivine Lattice Preferred Orientation Patterns With a Flow-Normal a-Axis Maximum
Mizukami, T.; Wallis, S.; Yamamoto, J.
2004-12-01
Olivine lattice preferred orientation (LPO) due to ductile deformation is one of the main causes of mechanical anisotropy in the upper mantle and the patterns are useful to infer the direction of mantle flow from the seismic anisotropy in various settings. In subduction zones the mantle anisotropy near subduction boundaries suggests that olivine a-axes are arranged roughly perpendicular to plate motion. This anisotropy has been attributed to localized subduction-normal flow, applying a common type of olivine LPO with a `flow-parallel' a-axis maximum to the mantle. However, a recent deformational experiment provides an alternative interpretation that the B-type LPO with a `flow-normal' a-axis maximum can be developed in water-rich mantle above subducting slab. We document the widespread occurrence of B-type LPO in the Higashi-akaishi peridotite body, SW Japan, and examine the physical conditions in which it was formed. Our structural studies define four deformational phases in the Higashi-akaishi body (D1-D4) that are related to the tectonic evolution in the Cretaceous subduction zone at the Eurasian margin. The main deformational stage, D2, is associated with dynamic recrystallization of olivine to form porphyroclastic microstructure consisting of clear olivine neoblasts and porphyroclasts with abundant micro-inclusions. Parallel alginment of olivine neoblasts defines a stretching lineation (L2) and tectonic foliation (S2) and the D2 olivine LPO is identified as the B-type fabric with a-axes normal to L2, b-axes normal to S2 and c-axes parallel to L2. Micro-Raman spectroscopic analyses reveal that the syn-D2 micro-inclusions include hydrous minerals such as serpentine, indicating water-rich conditions for the D2 deformation. Garnet-orthopyroxene geothermobarometry applied to the D2 garnet peridotite reveals that the D2 stage was associated with the almost isothermal burial (700-800C, 2-3GPa). These D2 physical conditions in which the B-type LPO was formed are
Pressure transient analysis of two-phase flow problems
Chu, W.C.; Reynolds, A.C.; Raghavan, R.
1981-01-01
This work investigates methods to determine reservoir parameters from pressure drawdown and buildup data in a reservoir in which oil and water flow simultaneously. The authors examine the pressure response at a well located at the center of a cylindrical reservoir and consider the pressure response at fully penetrating and partially penetrating wells. The primary concern of the study is to examine the applicability of classical methods for determining phase mobilities, skin factor, average reservoir pressure and reservoir pore volume. Incidental to this study, the authors discuss a method for treating the rate equation in a finite difference model. this method avoids the problem of correctly allocating a total specified rate among producing blocks in a numerical simulator. 18 refs.
Harry X.ZHANG; Shaw L.YU
2008-01-01
One of the key challenges in the total max-imum daily load (TMDL) development process is how to define the critical condition for a receiving water-body. The main concern in using a continuous simu-lation approach is the absence of any guarantee that the most critical condition will be captured during the selected representative hydrologic period, given the scar-city of long-term continuous data. The objectives of this paper are to clearly address the critical condition in the TMDL development process and to compare continu-ous and evEnt-based approaches in defining critical con-dition during TMDL development for a waterbody impacted by both point and nonpoint source pollution. A practical, event-based critical flow-storm (CFS) approach was developed to explicitly addresses the crit-ical condition as a combination of a low stream flow and a storm event of a selected magnitude, both having cer-tain frequencies of occurrence. This paper illustrated the CFS concept and provided its theoretical basis using a derived analytical conceptual model. The CFS approach clearly defined a critical condition, obtained reasonable results and could be considered as an alternative method in TMDL development.
Two Proposed Algorithms for Re-Entrant Flow Shop Problem
Abe, Kazumi; Ida, Kenichi
In a re-entrant flow shop scheduling problem we proposed some algorithms to get a better TAT (turn around time) with a genetic search method. One is an operation which searches for a solution that shifts the start timing in limited areas of each lot. Another is an operation which searches for a solution that shifts left and chooses the machine which starts fastest. Some algorithms are effective on the benchmark including those proposed by Taji et al. In the first step, it is easiest to choose the probabilistic problem by local search. The second step is to search for the solution that shifts the start timing in limited areas of each lot, makes the Gantt chart, chooses the machine and gets the results. The third step is to search for the solution that again shifts left, makes the Gantt chart, chooses the machine and gets the results. The proposed algorithms are more valid than local search methods by Taji et al, such as swap, move, swap-2 neighborhood and FIFO (first in first out). The first algorithm has produced the best result in an experimental test when interval time was short. The second algorithm produced the best result of all solutions. The results have shown that the proposed algorithms are effective for interval time cut and get better TAT than previous methods.
Research on network maximum flows algorithm of cascade level graph%级连层次图的网络最大流算法研究
潘荷新; 伊崇信; 李满
2011-01-01
给出一种通过构造网络级连层次图的方法,来间接求出最大网络流的算法.对于给定的有n个顶点,P条边的网络N=(G,s,t,C),该算法可在O(n2)时间内快速求出流经网络N的最大网络流及达最大流时的网络流.%This paper gives an algoritm that structures a network cascade level graph to find out maximum flow of the network indirectly.For the given network N=(G,s,t,C) that has n vetexes and e arcs,this algorithm finds out the maximum value of the network flow fast in O(n2) time that flows from the network N and the network flows when the value of the one reach maximum.
THE FLOW PROBLEM OF FLUIDS FLOW IN A FRACTAL RESERVOIR WITH DOUBLE POROSITY
同登科; 张鸿庆
2001-01-01
The effective radius of oil well is introduced in the inner boundary in the problem of fluids flow through fractal reservoir with double porosity, and thus a new model is established. Taking the wellbore storage and steady-state skin effect into consideration, the exact solutions of the pressure distribution of fluids flow in fractal reservoirs with double porosity are given for the cases of an infinite outer boundary, a finite closed outer boundary and a bounded domain with the constant pressure outer boundary conditions. The pressure behavior of fractal reservoir with double porosity is analyzed by using a numerical inversion of the Laplace transform solution. The pressure responses of changing various parameters are discussed.
Mitigating cold flow problems of biodiesel: Strategies with additives
Mohanan, Athira
The present thesis explores the cold flow properties of biodiesel and the effect of vegetable oil derived compounds on the crystallization path as well as the mechanisms at play at different stages and length scales. Model systems including triacylglycerol (TAG) oils and their derivatives, and a polymer were tested with biodiesel. The goal was to acquire the fundamental knowledge that would help design cold flow improver (CFI) additives that would address effectively and simultaneously the flow problems of biodiesel, particularly the cloud point (CP) and pour point (PP). The compounds were revealed to be fundamentally vegetable oil crystallization modifiers (VOCM) and the polymer was confirmed to be a pour point depressant (PPD). The results obtained with the VOCMs indicate that two cis-unsaturated moieties combined with a trans-/saturated fatty acid is a critical structural architecture for depressing the crystallization onset by a mechanism wherein while the straight chain promotes a first packing with the linear saturated FAMEs, the kinked moieties prevent further crystallization. The study of model binary systems made of a VOCM and a saturated FAME with DSC, XRD and PLM provided a complete phase diagram including the thermal transformation lines, crystal structure and microstructure that impact the phase composition along the different crystallization stages, and elicited the competing effects of molecular mass, chain length mismatch and isomerism. The liquid-solid boundary is discussed in light of a simple thermodynamic model based on the Hildebrand equation and pair interactions. In order to test for synergies, the PP and CP of a biodiesel (Soy1500) supplemented with several VOCM and PLMA binary cocktails were measured using a specially designed method inspired by ASTM standards. The results were impressive, the combination of additives depressed CP and PP better than any single additive. The PLM and DSC results suggest that the cocktail additives are most
The Graetz–Nusselt problem extended to continuum flows with finite slip
Haase, A. Sander; Chapman, S. Jonathan; Tsai, Peichun Amy; Lohse, Detlef; Lammertink, Rob G.H.
2015-01-01
Graetz and Nusselt studied heat transfer between a developed laminar fluid flow and a tube at constant wall temperature. Here, we extend the Graetz–Nusselt problem to dense fluid flows with partial wall slip. Its limits correspond to the classical problems for no-slip and no-shear flow. The amount o
Pressure transient analysis of two-phase flow problems
Chu, W.C.; Reynolds, A.C.; Raghavan, R.
1986-04-01
This paper considers the analysis of pressure drawdown and buildup data for two-phase flow problems. Of primary concern is the analysis of data influenced by saturation gradients that exist within the reservoir. Wellbore storage effects are assumed to be negligible. The pressure data considered are obtained from a two-dimensional (2D) numerical coning model for an oil/water system. The authors consider constant-rate production followed by a buildup period and assume that the top, bottom, and outer boundaries of the reservoir are sealed. First, they consider the case where the producing interval is equal to the total formation thickness. Second, they discuss the effect of partial penetration. In both cases, they show that average pressure can be estimated by the Matthews-Brons-Hazebroek method and consider the computation of the skin factor. They also show that a reservoir limit test can estimate reservoir PV only if the total mobility adjacent to the wellbore does not vary with time.
Luo, Hong; Ma, You-xin; Liu, Wen-jun; Li, Hong-mei
2010-05-01
By using maximum upstream flow path, a self-developed new method for calculating slope length value based on Arc Macro Language (AML), five groups of DEM data for different regions in Bijie Prefecture of Guizhou Province were extracted to compute the slope length and topographical factors in the Prefecture. The time cost for calculating the slope length and the values of the topographical factors were analyzed, and compared with those by iterative slope length method based on AML (ISLA) and on C++ (ISLC). The results showed that the new method was feasible to calculate the slope length and topographical factors in revised universal soil loss model, and had the same effect as iterative slope length method. Comparing with ISLA, the new method had a high computing efficiency and greatly decreased the time consumption, and could be applied to a large area to estimate the slope length and topographical factors based on AML. Comparing with ISLC, the new method had the similar computing efficiency, but its coding was easily to be written, modified, and debugged by using AML. Therefore, the new method could be more broadly used by GIS users.
张素君; 顾幸生
2015-01-01
An effective discrete artificial bee colony(DABC) algorithm is proposed for the flow shop scheduling problem with intermediate buffers (IBFSP) in order to minimize the maximum completion time (i.e makespan). The effective combination of the insertion and swap operator is applied to producing neighborhood individual at the employed bee phase. The tournament selection is adopted to avoid falling into local optima, while, the optimized insert operator embeds in onlooker bee phase for further searching the neighborhood solution to enhance the local search ability of algorithm. The tournament selection with size 2 is again applied and a better selected solution will be performed destruction and construction of iterated greedy (IG) algorithm, and then the result replaces the worse one. Simulation results show that our algorithm has a better performance compared with the HDDE and CHS which were proposed recently. It provides the better known solutions for the makespan criterion to flow shop scheduling problem with limited buffers for the Car benchmark by Carlier and Rec benchmark by Reeves. The convergence curves show that the algorithm not only has faster convergence speed but also has better convergence value.
Kinkhabwala, Ali
2013-01-01
The most fundamental problem in statistics is the inference of an unknown probability distribution from a finite number of samples. For a specific observed data set, answers to the following questions would be desirable: (1) Estimation: Which candidate distribution provides the best fit to the observed data?, (2) Goodness-of-fit: How concordant is this distribution with the observed data?, and (3) Uncertainty: How concordant are other candidate distributions with the observed data? A simple unified approach for univariate data that addresses these traditionally distinct statistical notions is presented called "maximum fidelity". Maximum fidelity is a strict frequentist approach that is fundamentally based on model concordance with the observed data. The fidelity statistic is a general information measure based on the coordinate-independent cumulative distribution and critical yet previously neglected symmetry considerations. An approximation for the null distribution of the fidelity allows its direct conversi...
Fast estimation from above of the maximum wave speed in the Riemann problem for the Euler equations
Guermond, Jean-Luc; Popov, Bojan
2016-09-01
This paper is concerned with the construction of a fast algorithm for computing the maximum speed of propagation in the Riemann solution for the Euler system of gas dynamics with the co-volume equation of state. The novelty in the algorithm is that it stops when a guaranteed upper bound for the maximum speed is reached with a prescribed accuracy. The convergence rate of the algorithm is cubic and the bound is guaranteed for gasses with the co-volume equation of state and the heat capacity ratio γ in the range (1 , 5 / 3 ].
Mazhar A. Memon
2016-04-01
Full Text Available ABSTRACT Objective: To evaluate correlation between visual prostate score (VPSS and maximum flow rate (Qmax in men with lower urinary tract symptoms. Material and Methods: This is a cross sectional study conducted at a university Hospital. Sixty-seven adult male patients>50 years of age were enrolled in the study after signing an informed consent. Qmax and voided volume recorded at uroflowmetry graph and at the same time VPSS were assessed. The education level was assessed in various defined groups. Pearson correlation coefficient was computed for VPSS and Qmax. Results: Mean age was 66.1±10.1 years (median 68. The mean voided volume on uroflowmetry was 268±160mL (median 208 and the mean Qmax was 9.6±4.96mLs/sec (median 9.0. The mean VPSS score was 11.4±2.72 (11.0. In the univariate linear regression analysis there was strong negative (Pearson's correlation between VPSS and Qmax (r=848, p<0.001. In the multiple linear regression analyses there was a significant correlation between VPSS and Qmax (β-http://www.blogapaixonadosporviagens.com.br/p/caribe.html after adjusting the effect of age, voided volume (V.V and level of education. Multiple linear regression analysis done for independent variables and results showed that there was no significant correlation between the VPSS and independent factors including age (p=0.27, LOE (p=0.941 and V.V (p=0.082. Conclusion: There is a significant negative correlation between VPSS and Qmax. The VPSS can be used in lieu of IPSS score. Men even with limited educational background can complete VPSS without assistance.
Solving the Liner Shipping Fleet Repositioning Problem with Cargo Flows
Tierney, Kevin; Askelsdottir, Björg; Jensen, Rune Møller;
2015-01-01
to reposition vessels as cheaply as possible without disrupting cargo flows. The LSFRP is characterized by chains of interacting activities with a multicommodity flow over paths defined by the activities chosen. Despite its industrial importance, the LSFRP has received little attention in the literature. We...... introduce a novel mathematical model and a simulated annealing algorithm for the LSFRP with cargo flows that makes use of a carefully constructed graph; we evaluate these approaches using real-world data from our industrial collaborator. Additionally, we compare the performance of our approach against...
最大团问题的改进蚁群算法求解%Improved Ant Colony Algorithm for Maximum Clique Problem
陈荣
2011-01-01
为了更好的解决最大团问题,提出一种改进的蚁群算法.通过提取图的顶点信息,将图用信息素模型来表示;根据最大团问题的约束条件利用蚁群构造极大团,并进行实时的全局信息素更新和局部信息素更新,直到找到最大团.实验结果表明,算法能较好的实现最大团问题,算法性能高于通用的蚁群算法.%In order to solve maximum clique problem better, an improved ant colony algorithm is proposed. By extracting vertex information of the graph, the graph is represented by pheromone trail.According to the constraints of maximum clique problem, larger clique is constructed by ant colony, and updating global pheromone information and local pheromone information real- time, until finding the maximum clique. Experimental results show that this method can achieve maximum clique problem and the performance is higher than the common ant colony algorithms.
The Liner Shipping Fleet Repositioning Problem with Cargo Flows
Tierney, Kevin; Jensen, Rune Møller
2012-01-01
We solve an important problem for the liner shipping industry called the Liner Shipping Fleet Repositioning Problem (LSFRP). The LSFRP poses a large financial burden on liner shipping firms. During repositioning, vessels are moved between services in a liner shipping network. Shippers wish...
Lorber, A.A.; Carey, G.F.; Bova, S.W.; Harle, C.H. [Univ. of Texas, Austin, TX (United States)
1996-12-31
The connection between the solution of linear systems of equations by iterative methods and explicit time stepping techniques is used to accelerate to steady state the solution of ODE systems arising from discretized PDEs which may involve either physical or artificial transient terms. Specifically, a class of Runge-Kutta (RK) time integration schemes with extended stability domains has been used to develop recursion formulas which lead to accelerated iterative performance. The coefficients for the RK schemes are chosen based on the theory of Chebyshev iteration polynomials in conjunction with a local linear stability analysis. We refer to these schemes as Chebyshev Parameterized Runge Kutta (CPRK) methods. CPRK methods of one to four stages are derived as functions of the parameters which describe an ellipse {Epsilon} which the stability domain of the methods is known to contain. Of particular interest are two-stage, first-order CPRK and four-stage, first-order methods. It is found that the former method can be identified with any two-stage RK method through the correct choice of parameters. The latter method is found to have a wide range of stability domains, with a maximum extension of 32 along the real axis. Recursion performance results are presented below for a model linear convection-diffusion problem as well as non-linear fluid flow problems discretized by both finite-difference and finite-element methods.
3D Topology optimization of Stokes flow problems
Gersborg-Hansen, Allan; Dammann, Bernd
for the fluid behavior in a micro fluidic device. Such a device has finite size and a large degree of freedom for the design of geometry. Physically Stokes flow is an exotic inertia free flow. This, however, complicates mixing by passive devices. Passive devices, that is, devices without moving parts, are often......, the optimizer suggests a design that stretches the hot-cold interface, which is encouraging since "stretching and folding" is known to be key ingredients in efficient mixing. The modelling is performed using a finite element based solver, with analytically derived sensitivities that drives a gradient based...... Program Interface, http://www.openmp.org/...
Computation of Load Flow Problems with Homotopy Methods
陈玉荣; 蔡大用
2001-01-01
Load flow computations are the basis for voltage security assessments in power systems. All of theflow equation solutions must be computed to explore the mechanisms of voltage instability and voltagecollapse. Conventional algorithms, such as Newton's methods and its variations, are not very desirablebecause they can not be easily used to find all of the solutions. This paper investigates homotopy methodswhich can be used for numerically computing the set of all isolated solutions of multivariate polynomial systemsresulting from load flow computations. The results significantly reduce the number of paths being followed.``
Existence and uniqueness of solutions in general multisolute renal flow problems.
Garner, J B; Kellogg, R B
1988-01-01
This paper considers systems of differential equations that describe flows in renal networks. The flow geometry is of the type that occurs in modelling the renal medulla. The unknowns in the system include the flow rate, the hydrostatic pressure, and the concentrations of the various solutes. Existence and uniqueness of solutions of the appropriate boundary value problems are established, in the case of small permeability coefficients and transport rates, or large diffusion coefficients and small resistance to flow constants.
Application of essentially nonoscillatory methods to aeroacoustic flow problems
Atkins, Harold L.
1995-01-01
A finite-difference essentially nonoscillatory (ENO) method has been applied to several of the problems prescribed for the workshop sponsored jointly by the Institute for Computer Applications in Science and Engineering and by NASA Langley Research Center entitled 'Benchmark Problems in Computational Aeroacoustics'. The workshop focused on computational challenges specific to aeroacoustics. Among these are long-distance propagation of a short-wavelength disturbance, propagation of small-amplitude disturbances, and nonreflective boundary conditions. The shock capturing-capability inherent to the ENO method effectively eliminates oscillations near shock waves without the need to add and tune dissipation or filter terms. The method-of-lines approach allows the temporal and spatial operators to be chosen separately in accordance with the demands of a particular problem. The ENO method was robust and accurate for all problems in which the propagating wave was resolved with 8 or more points per wavelength. The finite-wave-model boundary condition, a local nonlinear acoustic boundary condition, performed well for the one-dimensional problems. The buffer-domain approach performed well for the two-dimensional test problem. The amplitude of nonphysical reflections were less than 1 percent of the exiting wave's amplitude.
TOUGH Simulations of the Updegraff's Set of Fluid and Heat Flow Problems
Moridis, G.J.; Pruess (editor), K.
1992-11-01
The TOUGH code [Pruess, 1987] for two-phase flow of water, air, and heat in penneable media has been exercised on a suite of test problems originally selected and simulated by C. D. Updegraff [1989]. These include five 'verification' problems for which analytical or numerical solutions are available, and three 'validation' problems that model laboratory fluid and heat flow experiments. All problems could be run without any code modifications (*). Good and efficient numerical performance, as well as accurate results were obtained throughout. Additional code verification and validation problems from the literature are briefly summarized, and suggestions are given for proper applications of TOUGH and related codes.
Literature Review on the Hybrid Flow Shop Scheduling Problem with Unrelated Parallel Machines
Eliana Marcela Peña Tibaduiza
2017-01-01
Full Text Available Context: The flow shop hybrid problem with unrelated parallel machines has been less studied in the academia compared to the flow shop hybrid with identical processors. For this reason, there are few reports about the kind of application of this problem in industries. Method: A literature review of the state of the art on flow-shop scheduling problem was conducted by collecting and analyzing academic papers on several scientific databases. For this aim, a search query was constructed using keywords defining the problem and checking the inclusion of unrelated parallel machines in such definition; as a result, 50 papers were finally selected for this study. Results: A classification of the problem according to the characteristics of the production system was performed, also solution methods, constraints and objective functions commonly used are presented. Conclusions: An increasing trend is observed in studies of flow shop with multiple stages, but few are based on industry case-studies.
2009-01-01
The paper is concerned with a stochastic optimal control problem in which the controlled system is described by a fully coupled nonlinear forward-backward stochastic differential equation driven by a Brownian motion.It is required that all admissible control processes are adapted to a given subfiltration of the filtration generated by the underlying Brownian motion.For this type of partial information control,one sufficient(a verification theorem) and one necessary conditions of optimality are proved.The control domain need to be convex and the forward diffusion coefficient of the system can contain the control variable.
MENG QingXin
2009-01-01
The paper is concerned with a stochastic optimal control problem in which the controlled system is described by a fully coupled nonlinear forward-backward stochastic differential equation driven by a Brownian motion. It is required that all admissible control processes are adapted to a given subfiltration of the filtration generated by the underlying Brownian motion. For this type of partial information control, one sufficient (a verification theorem) and one necessary conditions of optimality are proved. The control domain need to be convex and the forward diffusion coefficient of the system can contain the control variable.
An integrated approach to combating flow assurance problems
Abney, Laurence; Browne, Alan [Halliburton, Houston, TX (United States)
2005-07-01
Any upset to the internal pipe surface of a pipeline can significantly impact both pipeline through-put and energy requirements for maintaining design flow rates. Inefficient flow through pipelines can have a significant negative impact on operating expense (Opex) and the energy requirements necessary to maintain pipeline through-put. Effective flow maintenance helps ensure that Opex remains within budget, processing equipment life is extended and that excessive use of energy is minimized. A number of events can result in debris generation and deposition in a pipeline. Corrosion, hydrate formation, paraffin deposition, asphaltene deposition, development of 'black powder' and scale formation are the most common sources of pipeline debris. Generally, a combination of pigging and chemical treatments is used to remove debris; these two techniques are commonly used in isolation. Incorporation of specialized fluids with enhanced solid-transport capabilities, specialized dispersants, or specialized surfactants can improve the success of routine pigging operations. An array of alternative and often complementary remediation technologies can be used to effect the removal of deposits or even full restrictions from pipelines. These include the application of acids, specialized chemical products, and intrusive interventions techniques. This paper presents a review of methods of integrating existing technologies. (author)
A General Approach to Time Periodic Incompressible Viscous Fluid Flow Problems
Geissert, Matthias; Hieber, Matthias; Nguyen, Thieu Huy
2016-06-01
This article develops a general approach to time periodic incompressible fluid flow problems and semilinear evolution equations. It yields, on the one hand, a unified approach to various classical problems in incompressible fluid flow and, on the other hand, gives new results for periodic solutions to the Navier-Stokes-Oseen flow, the Navier-Stokes flow past rotating obstacles, and, in the geophysical setting, for Ornstein-Uhlenbeck and various diffusion equations with rough coefficients. The method is based on a combination of interpolation and topological arguments, as well as on the smoothing properties of the linearized equation.
Cyclic flow shop scheduling problem with two-machine cells
Bożejko Wojciech
2017-06-01
Full Text Available In the paper a variant of cyclic production with setups and two-machine cell is considered. One of the stages of the problem solving consists of assigning each operation to the machine on which it will be carried out. The total number of such assignments is exponential. We propose a polynomial time algorithm finding the optimal operations to machines assignment.
Navier-Stokes Solvers and Generalizations for Reacting Flow Problems
Elman, Howard C
2013-01-27
This is an overview of our accomplishments during the final term of this grant (1 September 2008 -- 30 June 2012). These fall mainly into three categories: fast algorithms for linear eigenvalue problems; solution algorithms and modeling methods for partial differential equations with uncertain coefficients; and preconditioning methods and solvers for models of computational fluid dynamics (CFD).
Sander, Pia; Mouritsen, L; Andersen, J Thorup
2002-01-01
OBJECTIVE: The aim of this study was to evaluate the value of routine measurements of urinary flow rate and residual urine volume as a part of a "minimal care" assessment programme for women with urinary incontinence in detecting clinical significant bladder emptying problems. MATERIAL AND METHOD...... female urinary incontinence. Thus, primary health care providers can assess women based on simple guidelines without expensive equipment for assessment of urine flow rate and residual urine....
关于极大似然算法的辨识问题%identification problem about maximum likelihood algorithm
徐敏
2013-01-01
传统控制系统的被控对象多是考虑到线性时不变系统，由于工业的高速发展，控制系统面临着巨大的变化，被控对象呈现出非线性、时变、时延和外界干扰的系统，并且系统的模型不容易被确定，因此我们首先必须对系统进行辨识，确定系统的模型，才能进行有效地控制。本篇文章利用极大似然算法对非线性系统进行辨识，然后给出辨识的方法和步骤，最后辨识的仿真结果。%The controlled object of the traditional control systems more likely considered the linear time-invariant systems. Due to the rapid development of industy, control systems facing great change, the controlled object showed a nonlinear, time-varying ,delay and outside disturbance system and the system model is not easily determined, thus,we must firstly identify the system to determine the model of the system in order to effectively control. This article using the maximum likelihood algorithm for nonlinear system identification, and then gives identification methods and procedures, the final identification of the simulation results.
Chen, Miawjane; Yan, Shangyao; Wang, Sin-Siang; Liu, Chiu-Lan
2015-02-01
An effective project schedule is essential for enterprises to increase their efficiency of project execution, to maximize profit, and to minimize wastage of resources. Heuristic algorithms have been developed to efficiently solve the complicated multi-mode resource-constrained project scheduling problem with discounted cash flows (MRCPSPDCF) that characterize real problems. However, the solutions obtained in past studies have been approximate and are difficult to evaluate in terms of optimality. In this study, a generalized network flow model, embedded in a time-precedence network, is proposed to formulate the MRCPSPDCF with the payment at activity completion times. Mathematically, the model is formulated as an integer network flow problem with side constraints, which can be efficiently solved for optimality, using existing mathematical programming software. To evaluate the model performance, numerical tests are performed. The test results indicate that the model could be a useful planning tool for project scheduling in the real world.
Pre-test CFD Calculations for a Bypass Flow Standard Problem
Rich Johnson
2011-11-01
The bypass flow in a prismatic high temperature gas-cooled reactor (HTGR) is the flow that occurs between adjacent graphite blocks. Gaps exist between blocks due to variances in their manufacture and installation and because of the expansion and shrinkage of the blocks from heating and irradiation. Although the temperature of fuel compacts and graphite is sensitive to the presence of bypass flow, there is great uncertainty in the level and effects of the bypass flow. The Next Generation Nuclear Plant (NGNP) program at the Idaho National Laboratory has undertaken to produce experimental data of isothermal bypass flow between three adjacent graphite blocks. These data are intended to provide validation for computational fluid dynamic (CFD) analyses of the bypass flow. Such validation data sets are called Standard Problems in the nuclear safety analysis field. Details of the experimental apparatus as well as several pre-test calculations of the bypass flow are provided. Pre-test calculations are useful in examining the nature of the flow and to see if there are any problems associated with the flow and its measurement. The apparatus is designed to be able to provide three different gap widths in the vertical direction (the direction of the normal coolant flow) and two gap widths in the horizontal direction. It is expected that the vertical bypass flow will range from laminar to transitional to turbulent flow for the different gap widths that will be available.
ROBUST PARTIAL INVERSE NETWORK FLOW PROBLEMS%强部分逆网络流问题
杨晓光
2001-01-01
In this paper,a new model for inverse network flow problems,robust partial inverse problem is presented. For a given partial solution,the robust partial inverse problem is to modify the coefficients optimally such that all full solutions containing the partial solution become optimal under new coefficients. It has been shown that the robust partial inverse spanning tree problem can be formulated as a combinatorial linear program,while the robust partial inverse minimum cut problem and the robust partial inverse assignment problem can be solved by combinatorial strongly polynomial algorithms.
Topology optimization of 3D Stokes flow problems
Gersborg-Hansen, Allan; Sigmund, Ole; Bendsøe, Martin P.
examples relevant for optimal micro fluidic mixer design are shown where the design is planar - compliant with micro fabrication techniques - and where the designs are 3D. In addition issues related to the parallel solution of the linear algebra problems are discussed. The implementation uses...... the commercial COMSOL multiphysics programme which is sufficiently flexible to provide semi--automated analytical sensitivities. 1. M. P. Bendsoe and O. Sigmund, "Topology Optimization - Theory, Methods and Applications", Springer Verlag, Berlin Heidelberg, 2003. 2. T. Borrvall and J. Petersson, "Topology...
Element Free Lattice Boltzmann Method for Fluid-Flow Problems
Jo, Jong Chull; Roh, Kyung Wan; Yune, Young Gill; Kim, Hho Jhung [Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of); Kwon, Young Kwon [US Naval Postgraduate School, New York (United States)
2007-10-15
The Lattice Boltzmann Method (LBM) has been developed for application to thermal-fluid problems. Most of the those studies considered a regular shape of lattice or mesh like square and cubic grids. In order to apply the LBM to more practical cases, it is necessary to be able to solve complex or irregular shapes of problem domains. Some techniques were based on the finite element method. Generally, the finite element method is very powerful for solving two or three-dimensional complex or irregular shapes of domains using the iso-parametric element formulation which is based on a mathematical mapping from a regular shape of element in an imaginary domain to a more general and irregular shape of element in the physical domain. In addition, the element free technique is also quite useful to analyze a complex shape of domain because there is no need to divide a domain by a compatible finite element mesh. This paper presents a new finite element and element free formulations for the lattice Boltzmann equation using the general weighted residual technique. Then, a series of validation examples are presented.
Disperse two-phase flows, with applications to geophysical problems
Berselli, Luigi Carlo; Iliescu, Traian
2014-01-01
In this paper we study the motion of a fluid with several dispersed particles whose concentration is very small (smaller than $10^{-3}$), with possible applications to problems coming from geophysics, meteorology, and oceanography. We consider a very dilute suspension of heavy particles in a quasi-incompressible fluid (low Mach number). In our case the Stokes number is small and --as pointed out in the theory of multiphase turbulence-- we can use an Eulerian model instead of a Lagrangian one. The assumption of low concentration allows us to disregard particle--particle interactions, but we take into account the effect of particles on the fluid (two-way coupling). In this way we can study the physical effect of particle inertia (and not only passive tracers), with a model similar to the Boussinesq equations. The resulting model is used in both direct numerical simulations and large eddy simulations of a dam-break (lock-exchange) problem, which is a well-known academic test case. Keywords: Dilute suspensions, E...
Topology optimization of unsteady flow problems using the lattice Boltzmann method
Nørgaard, Sebastian Arlund; Sigmund, Ole; Lazarov, Boyan Stefanov
2016-01-01
This article demonstrates and discusses topology optimization for unsteady incompressible fluid flows. The fluid flows are simulated using the lattice Boltzmann method, and a partial bounceback model is implemented to model the transition between fluid and solid phases in the optimization problems...
Numerical methods in fluid flow problems. Citations from the NTIS data base
Habercom, G. E., Jr.
1980-09-01
Numerical techniques for analysis of fluid flow problems include finite difference theory, finite element analysis, and numerical integration of differential equations including the Navier Stokes equations discussed in approximately 164 citations. Areas studied include boundary layer, hypersonic, supersonic, transonic regimes, atmosphere entry, heat transfer, blunt and concave bodies, gas dynamics, nozzle gas flow, turbomachinery, and hydrodynamics.
On the Eikonal equation in the pedestrian flow problem
Felcman, J.; Kubera, P.
2017-07-01
We consider the Pedestrian Flow Equations (PFEs) as the coupled system formed by the Eikonal equation and the first order hyperbolic system with the source term. The hyperbolic system consists of the continuity equation and momentum equation of fluid dynamics. Specifying the social and pressure forces in the momentum equation we come to the assumption that each pedestrian is trying to move in a desired direction (e.g. to the exit in the panic situation) with a desired velocity, where his velocity and the direction of movement depend on the density of pedestrians in his neighborhood. In [1] we used the model, where the desired direction of movement is given by the solution of the Eikonal equation (more precisely by the gradient of the solution). Here we avoid the solution of the Eikonal equation, which is the novelty of the paper. Based on the fact that the solution of the Eikonal equation has the meaning of the shortest time to reach the exit, we define explicitly such a function in the framework of the Dijkstra's algorithm for the shortest path in the graph. This is done at the discrete level of the solution. As the graph we use the underlying triangulation, where the norm of each edge is density depending and has the dimension of the time. The numerical examples of the solution of the PFEs with and without the solution of the Eikonal equation are presented.
Game-Theoretic Approach for Solving Multiobjective Flow Problems on Networks
Maria A. Fonoberova
2005-10-01
Full Text Available The game-theoretic formulation of the multiobjective multicommodity flow problem is considered. The dynamic version of this problem is studied and an algorithm for its solving, based on the concept of multiobjective games, is proposed. Mathematics Subject Classification 2000: 90B10, 90C35, 90C27, 90C47.
An unstructured parallel least-squares spectral element solver for incompressible flow problems
Nool, M.; Proot, M.M.J.
2003-01-01
The parallelization of the least-squares spectral element formulation of the Stokes problem has recently been discussed for incompressible flow problems on structured grids. In the present work, the extension to unstructured grids is discussed. It will be shown that, to obtain an efficient and scala
Albuquerque, Fabio; Beier, Paul
2015-01-01
Here we report that prioritizing sites in order of rarity-weighted richness (RWR) is a simple, reliable way to identify sites that represent all species in the fewest number of sites (minimum set problem) or to identify sites that represent the largest number of species within a given number of sites (maximum coverage problem). We compared the number of species represented in sites prioritized by RWR to numbers of species represented in sites prioritized by the Zonation software package for 11 datasets in which the size of individual planning units (sites) ranged from algorithms remain superior for conservation prioritizations that consider compactness and multiple near-optimal solutions in addition to species representation. But because RWR can be implemented easily and quickly in R or a spreadsheet, it is an attractive alternative to integer programming or heuristic algorithms in some conservation prioritization contexts.
Application of Program Generation Technology in Solving Heat and Flow Problems
Shui Wan; Bangxian Wu; Ningning Chen
2007-01-01
Based on a new DIY concept for software development, an automatic program-generating technology attached on a software system called as Finite Element Program Generator (FEPG) provides a platform of developing programs, through which a scientific researcher can submit his special physico-mathematical problem to the system in a more direct and convenient way for solution. For solving flow and heat problems by using finite element method, the stabilization technologies and fraction-step methods are adopted to overcome the numerical difficulties caused mainly due to the dominated convection. A couple of benchmark problems are given in this paper as examples to illustrate the usage and the superiority of the automatic program generation technique, including the flow in a lid-driven cavity, the starting flow in a circular pipe, the natural convection in a square cavity, and the flow past a circular cylinder, etc. They are also shown as the verification of the algorithms.
Marriage in Honey Bees Optimization Algorithm for Flow-shop Problems
Pedro PALOMINOS
2012-01-01
Full Text Available The objective of this work is to make a comparative study of the Marriage in Honeybees Op-timization (MBO metaheuristic for flow-shop scheduling problems. This paper is focused on the design possibilities of the mating flight space shared by queens and drones. The proposed algorithm uses a 2-dimensional torus as an explicit mating space instead of the simulated an-nealing one in the original MBO. After testing different alternatives with benchmark datasets, the results show that the modeled and implemented metaheuristic is effective to solve flow-shop type problems, providing a new approach to solve other NP-Hard problems.
Heuristics methods for the flow shop scheduling problem with separated setup times
Marcelo Seido Nagano
2012-06-01
Full Text Available This paper deals with the permutation flow shop scheduling problem with separated machine setup times. As a result of an investigation on the problem characteristics, four heuristics methods are proposed with procedures of the construction sequencing solution by an analogy with the asymmetric traveling salesman problem with the objective of minimizing makespan. Experimental results show that one of the new heuristics methods proposed provide high quality solutions in comparisons with the evaluated methods considered in the literature.
The maximum agreement subtree problem
Martin, Daniel M
2012-01-01
Given two binary phylogenetic trees on $n$ leaves, we show that they have a common subtree on at least $O((\\log{n})^{1/2-\\epsilon})$ leaves, thus improving on the previously known bound of $O(\\log\\log n)$. To achieve this bound, we combine different special cases: when one of the trees is balanced or when one of the trees is a caterpillar, we show a lower bound of $O(\\log n)$. Another ingredient is the proof that every binary tree contains a large balanced subtree or a large caterpillar, a result that is intersting on its own. Finally, we also show that, there is an $\\alpha > 0$ such that when both the trees are balanced, they have a common subtree on at least $O(n^\\alpha)$ leaves.
Supersonic flow onto solid wedges, multidimensional shock waves and free boundary problems
Chen, Gui-Qiang
2017-08-01
When an upstream steady uniform supersonic flow impinges onto a symmetric straight-sided wedge, governed by the Euler equations, there are two possible steady oblique shock configurations if the wedge angle is less than the detachment angle -- the steady weak shock with supersonic or subsonic downstream flow (determined by the wedge angle that is less or larger than the sonic angle) and the steady strong shock with subsonic downstream flow, both of which satisfy the entropy condition. The fundamental issue -- whether one or both of the steady weak and strong shocks are physically admissible solutions -- has been vigorously debated over the past eight decades. In this paper, we survey some recent developments on the stability analysis of the steady shock solutions in both the steady and dynamic regimes. For the static stability, we first show how the stability problem can be formulated as an initial-boundary value type problem and then reformulate it into a free boundary problem when the perturbation of both the upstream steady supersonic flow and the wedge boundary are suitably regular and small, and we finally present some recent results on the static stability of the steady supersonic and transonic shocks. For the dynamic stability for potential flow, we first show how the stability problem can be formulated as an initial-boundary value problem and then use the self-similarity of the problem to reduce it into a boundary value problem and further reformulate it into a free boundary problem, and we finally survey some recent developments in solving this free boundary problem for the existence of the Prandtl-Meyer configurations that tend to the steady weak supersonic or transonic oblique shock solutions as time goes to infinity. Some further developments and mathematical challenges in this direction are also discussed.
Multitime maximum principle approach of minimal submanifolds and harmonic maps
Udriste, Constantin
2011-01-01
Some optimization problems coming from the Differential Geometry, as for example, the minimal submanifolds problem and the harmonic maps problem are solved here via interior solutions of appropriate multitime optimal control problems. Section 1 underlines some science domains where appear multitime optimal control problems. Section 2 (Section 3) recalls the multitime maximum principle for optimal control problems with multiple (curvilinear) integral cost functionals and $m$-flow type constraint evolution. Section 4 shows that there exists a multitime maximum principle approach of multitime variational calculus. Section 5 (Section 6) proves that the minimal submanifolds (harmonic maps) are optimal solutions of multitime evolution PDEs in an appropriate multitime optimal control problem. Section 7 uses the multitime maximum principle to show that of all solids having a given surface area, the sphere is the one having the greatest volume. Section 8 studies the minimal area of a multitime linear flow as optimal c...
Costa, Rui J.; Wilkinson-Herbots, Hilde
2017-01-01
The isolation-with-migration (IM) model is commonly used to make inferences about gene flow during speciation, using polymorphism data. However, it has been reported that the parameter estimates obtained by fitting the IM model are very sensitive to the model’s assumptions—including the assumption of constant gene flow until the present. This article is concerned with the isolation-with-initial-migration (IIM) model, which drops precisely this assumption. In the IIM model, one ancestral population divides into two descendant subpopulations, between which there is an initial period of gene flow and a subsequent period of isolation. We derive a very fast method of fitting an extended version of the IIM model, which also allows for asymmetric gene flow and unequal population sizes. This is a maximum-likelihood method, applicable to data on the number of segregating sites between pairs of DNA sequences from a large number of independent loci. In addition to obtaining parameter estimates, our method can also be used, by means of likelihood-ratio tests, to distinguish between alternative models representing the following divergence scenarios: (a) divergence with potentially asymmetric gene flow until the present, (b) divergence with potentially asymmetric gene flow until some point in the past and in isolation since then, and (c) divergence in complete isolation. We illustrate the procedure on pairs of Drosophila sequences from ∼30,000 loci. The computing time needed to fit the most complex version of the model to this data set is only a couple of minutes. The R code to fit the IIM model can be found in the supplementary files of this article. PMID:28193727
Lombardo, L.
2016-07-18
This study aims at evaluating the performance of the Maximum Entropy method in assessing landslide susceptibility, exploiting topographic and multispectral remote sensing predictors. We selected the catchment of the Giampilieri stream, which is located in the north-eastern sector of Sicily (southern Italy), as test site. On 1/10/2009, a storm rainfall triggered in this area hundreds of debris flow/avalanche phenomena causing extensive economical damage and loss of life. Within this area a presence-only-based statistical method was applied to obtain susceptibility models capable of distinguish future activation sites of debris flow and debris slide, which where the main source failure mechanisms for flow or avalanche type propagation. The set of predictors used in this experiment comprised primary and secondary topographic attributes, derived by processing a high resolution digital elevation model, CORINE land cover data and a set of vegetation and mineral indices obtained by processing multispectral ASTER images. All the selected data sources are dated before the disaster. A spatially random partition technique was adopted for validation, generating fifty replicates for each of the two considered movement typologies in order to assess accuracy, precision and reliability of the models. The debris slide and debris flow susceptibility models produced high performances with the first type being the best fitted. The evaluation of the probability estimates around the mean value for each mapped pixel shows an inverted relation, with the most robust models corresponding to the debris flows. With respect to the role of each predictor within the modelling phase, debris flows appeared to be primarily controlled by topographic attributes whilst the debris slides were better explained by remotely sensed derived indices, particularly by the occurrence of previous wildfires across the slope. The overall excellent performances of the two models suggest promising perspectives for
Max-Flow Problem in Undirected Planar Networks with Node Capacities Being in NC
Xian-Chao Zhang; Ying-Yu Wan; Guo-Liang Chen
2004-01-01
The max-flow problem in planar networks with only edge capacities has been proved to be in NC (Nickle's Class). This paper considers a more general version of the problem when the nodes as well as the edges have capacities. In a general network, the node-edge-capacity problem can be easily reduced to the edge-capacity problem. But in the case of planar network this reduction may destroy the planarity, and reduces the problem to the edge-capacity problem in a general network, which is P-complete. A recent contribution presents a new reduction for planar networks, that maintains the planarity. In this paper, it is proved that this reduction is in NC and thus the node-edge-capacity problem in undirected planar networks is in NC.
Flow Formulation-based Model for the Curriculum-based Course Timetabling Problem
Bagger, Niels-Christian Fink; Kristiansen, Simon; Sørensen, Matias;
2015-01-01
In this work we will present a new mixed integer programming formulation for the curriculum-based course timetabling problem. We show that the model contains an underlying network model by dividing the problem into two models and then connecting the two models back into one model using a maximum ow...... problem. This decreases the number of integer variables signicantly and improves the performance compared to the basic formulation. It also shows competitiveness with other approaches based on mixed integer programming from the literature and improves the currently best known lower bound on one data...
Jin–Xin relaxation method for solving a traffic flow problem in one dimension
Ambar Sulistiyawati, Bernadetta; Mungkasi, Sudi
2017-01-01
We test the performance of the Jin–Xin relaxation and Lax–Friedrichs finite volume numerical methods in solving a traffic flow problem. In particular, we focus on traffic flow at a traffic light turning from red to green. Numerical solutions are compared with the analytical solution to the mathematical model. We find that the Jin–Xin relaxation solution is more accurate than the Lax–Friedrichs finite volume solution.
GH. ŞERBAN
2016-03-01
Full Text Available The purpose of the paper is to identify and locate some species related to habitats from Pricop-Huta-Certeze and Upper Tisa Natura 2000 Protected Areas (PHCTS and to determine if they are vulnerable to risks induced by maximum flow phases. In the first chapter are mentioned few references about the morphometric parameters of the hydrographic networks within the study area, as well as some references related to the maximum flow phases frequency. After the second chapter, where methods and databases used in the study are described, we proceed to the identification of the areas that are covered by water during flood, as well as determining the risk level related to these areas. The GIS modeling reveals small extent of the flood high risk for natural environment related to protected areas and greater extent for the anthropic environment. The last chapter refers to several species of fish and batrachia, as well as to those amphibious mammals identified in the study area that are vulnerable to floods (high turbidity effect, reduction of dissolved oxygen quantity, habitats destruction etc..
Jilian Wu
2013-01-01
Full Text Available We discuss several stabilized finite element methods, which are penalty, regular, multiscale enrichment, and local Gauss integration method, for the steady incompressible flow problem with damping based on the lowest equal-order finite element space pair. Then we give the numerical comparisons between them in three numerical examples which show that the local Gauss integration method has good stability, efficiency, and accuracy properties and it is better than the others for the steady incompressible flow problem with damping on the whole. However, to our surprise, the regular method spends less CPU-time and has better accuracy properties by using Crout solver.
The Planar Sandwich and Other 1D Planar Heat Flow Test Problems in ExactPack
Singleton, Jr., Robert [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2017-01-24
This report documents the implementation of several related 1D heat flow problems in the verification package ExactPack [1]. In particular, the planar sandwich class defined in Ref. [2], as well as the classes PlanarSandwichHot, PlanarSandwichHalf, and other generalizations of the planar sandwich problem, are defined and documented here. A rather general treatment of 1D heat flow is presented, whose main results have been implemented in the class Rod1D. All planar sandwich classes are derived from the parent class Rod1D.
Vegh, Laszlo A.
2011-01-01
A well-studied nonlinear extension of the minimum-cost flow problem is to minimize the objective $\\sum_{ij\\in E} C_{ij}(f_{ij})$ over feasible flows $f$, where on every arc $ij$ of the network, $C_{ij}$ is a convex function. We give a strongly polynomial algorithm for the case when all $C_{ij}$'s are convex quadratic functions, settling an open problem raised e.g. by Hochbaum [1994]. We also give strongly polynomial algorithms for computing market equilibria in Fisher markets with linear util...
Hunt, J. C. R.
1981-05-01
The ways in which advances in fluid mechanics have led to improvements in engineering design are discussed, with attention to the stimulation of fluid mechanics research by industrial and environmental problems. The development of many practical uses of fluid flow without the benefit of scientific study is also emphasized. Among the topics discussed are vortices and coherent structures in turbulent flows, lubrication, jet and multiphase flows, the control and exploitation of waves, the effect of unsteady forces on structures, and dispersion phenomena. Among the practical achievements covered are the use of bluff shields to control separated flow over truck bodies and reduce aerodynamic drag, ink-jet printing, hovercraft stability, fluidized-bed combustion, the fluid/solid instabilities caused by air flow around a computer memory floppy disc, and various wind turbines.
Examining the Bernstein global optimization approach to optimal power flow problem
Patil, Bhagyesh V.; Sampath, L. P. M. I.; Krishnan, Ashok; Ling, K. V.; Gooi, H. B.
2016-10-01
This work addresses a nonconvex optimal power flow problem (OPF). We introduce a `new approach' in the context of OPF problem based on the Bernstein polynomials. The applicability of the approach is studied on a real-world 3-bus power system. The numerical results obtained with this new approach for a 3-bus system reveal a satisfactory improvement in terms of optimality. The results are found to be competent with generic global optimization solvers BARON and COUENNE.
Parallel patterns determination in solving cyclic flow shop problem with setups
Bożejko Wojciech
2017-06-01
Full Text Available The subject of this work is the new idea of blocks for the cyclic flow shop problem with setup times, using multiple patterns with different sizes determined for each machine constituting optimal schedule of cities for the traveling salesman problem (TSP. We propose to take advantage of the Intel Xeon Phi parallel computing environment during so-called ’blocks’ determination basing on patterns, in effect significantly improving the quality of obtained results.
A Special Class of Univalent Functions in Hele-Shaw Flow Problems
Paula Curt
2011-01-01
Full Text Available We study the time evolution of the free boundary of a viscous fluid for planar flows in Hele-Shaw cells under injection. Applying methods from the theory of univalent functions, we prove the invariance in time of Φ-likeness property (a geometric property which includes starlikeness and spiral-likeness for two basic cases: the inner problem and the outer problem. We study both zero and nonzero surface tension models. Certain particular cases are also presented.
Modeling granular material flows: The angle of repose, fluidization and the cliff collapse problem
Holsapple, Keith A.
2013-07-01
I discuss theories of granular material flows, with application to granular flows on the earth and planets. There are two goals. First, there is a lingering belief of some that the standard continuum plasticity Mohr-Coulomb and/or Drucker-Prager models are not adequate for many large-scale granular flow problems. The stated reason for those beliefs is the fact that the final slopes of the run-outs in collapse, landslide problems, and large-scale cratering are well below the angle of repose of the material. That observation, combined with the supposition that in those models flow cannot occur with slopes less than the angle of repose, has led to a number of researchers suggesting a need for lubrication or fluidization mechanisms and modeling. That issue is investigated in detail and shown to be false. A complete analysis of slope failures according to the Mohr-Coulomb model is presented, with special attention to the relations between the angle of repose and slope failures. It is shown that slope failure can occur for slope angles both larger than and smaller than the angle of repose. Second, to study the details of landslide run-outs, finite-difference continuum code simulations of the prototypical cliff collapse problem, using the classical plasticity models, are presented, analyzed and compared to experiments. Although devoid of any additional fluidization models, those simulations match experiments in the literature extremely well. The dynamics of this problem introduces additional important features relating to the run-out and final slope angles. The vertical free surface begins to fall at the initial 90° and flow continues to a final slope less than 10°. The detail in the calculation is examined to show why flow persists at slope angles that appear to be less than the angle of repose. The motions include regions of solid-like, fluid-like, and gas-like flows without invoking any additional models.
Bounds on the Phase Velocity in the Linear Instability of Viscous Shear Flow Problem in the -Plane
R G Shandil; Jagjit Singh
2003-05-01
Results obtained by Joseph (J. Fluid Mech. 33 (1968) 617) for the viscous parallel shear flow problem are extended to the problem of viscous parallel, shear flow problem in the beta plane and a sufficient condition for stability has also been derived.
High order methods for incompressible fluid flow: Application to moving boundary problems
Bjoentegaard, Tormod
2008-04-15
Fluid flows with moving boundaries are encountered in a large number of real life situations, with two such types being fluid-structure interaction and free-surface flows. Fluid-structure phenomena are for instance apparent in many hydrodynamic applications; wave effects on offshore structures, sloshing and fluid induced vibrations, and aeroelasticity; flutter and dynamic response. Free-surface flows can be considered as a special case of a fluid-fluid interaction where one of the fluids are practically inviscid, such as air. This type of flows arise in many disciplines such as marine hydrodynamics, chemical engineering, material processing, and geophysics. The driving forces for free-surface flows may be of large scale such as gravity or inertial forces, or forces due to surface tension which operate on a much smaller scale. Free-surface flows with surface tension as a driving mechanism include the flow of bubbles and droplets, and the evolution of capillary waves. In this work we consider incompressible fluid flow, which are governed by the incompressible Navier-Stokes equations. There are several challenges when simulating moving boundary problems numerically, and these include - Spatial discretization - Temporal discretization - Imposition of boundary conditions - Solution strategy for the linear equations. These are some of the issues which will be addressed in this introduction. We will first formulate the problem in the arbitrary Lagrangian-Eulerian framework, and introduce the weak formulation of the problem. Next, we discuss the spatial and temporal discretization before we move to the imposition of surface tension boundary conditions. In the final section we discuss the solution of the resulting linear system of equations. (Author). refs., figs., tabs
Ogawa, Akira; Anzou, Hideki; Yamamoto, So; Shimagaki, Mituru
2015-11-01
In order to control the maximum tangential velocity Vθm(m/s) of the turbulent rotational air flow and the collection efficiency ηc (%) using the fly ash of the mean diameter XR50=5.57 µm, two secondary jet nozzles were installed to the body of the axial flow cyclone dust collector with the body diameter D1=99mm. Then in order to estimate Vθm (m/s), the conservation theory of the angular momentum flux with Ogawa combined vortex model was applied. The comparisons of the estimated results of Vθm(m/s) with the measured results by the cylindrical Pitot-tube were shown in good agreement. And also the estimated collection efficiencies ηcth (%) basing upon the cut-size Xc (µm) which was calculated by using the estimated Vθ m(m/s) and also the particle size distribution R(Xp) were shown a little higher values than the experimental results due to the re-entrainment of the collected dust. The best method for adjustment of ηc (%) related to the contribution of the secondary jet flow is principally to apply the centrifugal effect Φc (1). Above stated results are described in detail.
Grigoriev, I. S.; Grigoriev, K. G.
2003-05-01
The necessary first-order conditions of strong local optimality (conditions of maximum principle) are considered for the problems of optimal control over a set of dynamic systems. To derive them a method is suggested based on the Lagrange principle of removing constraints in the problems on a conditional extremum in a functional space. An algorithm of conversion from the problem of optimal control of an aggregate of dynamic systems to a multipoint boundary value problem is suggested for a set of systems of ordinary differential equations with the complete set of conditions necessary for its solution. An example of application of the methods and algorithm proposed is considered: the solution of the problem of constructing the trajectories of a spacecraft flight at a constant altitude above a preset area (or above a preset point) of a planet's surface in a vacuum (for a planet with atmosphere beyond the atmosphere). The spacecraft is launched from a certain circular orbit of a planet's satellite. This orbit is to be determined (optimized). Then the satellite is injected to the desired trajectory segment (or desired point) of a flyby above the planet's surface at a specified altitude. After the flyby the satellite is returned to the initial circular orbit. A method is proposed of correct accounting for constraints imposed on overload (mixed restrictions of inequality type) and on the distance from the planet center: extended (nonpointlike) intermediate (phase) restrictions of the equality type.
A Flow-dependent Quadratic Steiner Tree Problem in the Euclidean Plane
Brazil, Marcus; Thomas, Doreen
2011-01-01
We introduce a flow-dependent version of the quadratic Steiner tree problem in the plane. An instance of the problem on a set of embedded sources and a sink asks for a directed tree $T$ spanning these nodes and a bounded number of Steiner points, such that $\\displaystyle\\sum_{e \\in E(T)}f(e)|e|^2$ is a minimum, where $f(e)$ is the flow on edge $e$. The edges are uncapacitated and the flows are determined additively, i.e., the flow on an edge leaving a node $u$ will be the sum of the flows on all edges entering $u$. Our motivation for studying this problem is its utility as a model for relay augmentation of wireless sensor networks. In these scenarios one seeks to optimise power consumption -- which is predominantly due to communication and, in free space, is proportional to the square of transmission distance -- in the network by introducing additional relays. We prove several geometric and combinatorial results on the structure of optimal and locally optimal solution-trees (under various strategies for bound...
The Non-selfsimilar Riemann Problem for 2-D Zero-Pressure Flow in Gas Dynamics
Wenhua SUN; Wancheng SHENG
2007-01-01
The non-selfsimilar Riemann problem for two-dimensional zero-pressure flow in gas dynamics with two constant states separated by a convex curve is considered. By means of the generalized Rankine-Hugoniot relation and the generalized characteristic analysis method, the global solution involving delta shock wave and vacuum is constructed. The explicit solution for a special case is also given.
Santoprete, Manuele
2002-01-01
Resorting to classical techniques of Riemannian geometry we develop a geometrical method suitable to investigate the nonintegrability of geodesic flows and of natural Hamiltonian systems. Then we apply such method to the Anisotropic Kepler Problem (AKP) and we prove that it is not analytically integrable.
A Chebyshev collocation method for solving two-phase flow stability problems
Boomkamp, P.A.M.; Boersma, B.J.; Miesen, R.H.M.; Beijnon, G.V.
1997-01-01
This paper describes a Chebyshev collocation method for solving the eigenvalue problem that governs the stability of parallel two-phase flow. The method is based on the expansion of the eigenfunctions in terms of Chebyshev polynomials, point collocation, and the subsequent solution of the resulting
A Minimum-Cost Network-Flow Solution to the Case v Thurstone Scaling Problem.
Lattin, James M.
1990-01-01
An approach is presented for determining unidimensional scale estimates that are relatively insensitive to limited inconsistencies in paired comparisons data. The solution procedure--a minimum-cost network-flow problem--is presented in conjunction with a sensitivity diagnostic that assesses the influence of a single pairwise comparison on…
Applications of Taylor-Galerkin finite element method to compressible internal flow problems
Sohn, Jeong L.; Kim, Yongmo; Chung, T. J.
1989-01-01
A two-step Taylor-Galerkin finite element method with Lapidus' artificial viscosity scheme is applied to several test cases for internal compressible inviscid flow problems. Investigations for the effect of supersonic/subsonic inlet and outlet boundary conditions on computational results are particularly emphasized.
Complexity Analysis of New Task Allocation Problem Using Network Flow Method on Multicore Clusters
Jixiang Yang
2014-01-01
Full Text Available The task allocation problem (TAP generally aims to minimize total execution cost and internode communication cost in traditional parallel computing systems. New TAP (NTAP considering additive intranode communication cost in emerging multicore cluster systems is investigated in this paper. We analyze the complexity of NTAP with network flow method and conclude that the intranode communication cost is a key to the complexity of NTAP, and prove that (1 the NTAP can be cast as a generalized linear network minimum cost flow problem and can be solved in O(m2n4 time if the intranode communication cost equals the internode communication cost, and (2 the NTAP can be cast as a generalized convex cost network minimum cost flow problem and can be solved in polynomial time if the intranode communication cost is more than the internode communication cost. More in particular, the uniform cost NTAP can be cast as a convex cost flow problem and can be solved in O(m2n2log(m+n time. Furthermore, solutions to the NTAP are also discussed. Our work extends currently known theoretical results and the theorems and conclusions presented in this paper can provide theoretical basis for task allocating strategies on multicore clusters.
The Cauchy problem for a model of immiscible gas flow with large data
Sande, Hilde
2008-12-15
The thesis consists of an introduction and two papers; 1. The solution of the Cauchy problem with large data for a model of a mixture of gases. 2. Front tracking for a model of immiscible gas flow with large data. (AG) refs, figs
A Water Flow-Like Algorithm for the Travelling Salesman Problem
Ayman Srour
2014-01-01
Full Text Available The water flow-like algorithm (WFA is a relatively new metaheuristic that performs well on the object grouping problem encountered in combinatorial optimization. This paper presents a WFA for solving the travelling salesman problem (TSP as a graph-based problem. The performance of the WFA on the TSP is evaluated using 23 TSP benchmark datasets and by comparing it with previous algorithms. The experimental results show that the proposed WFA found better solutions in terms of the average solution and the percentage deviation of the average solution from the best-known solution.
Ganji, S. S.; Barari, Amin; Ibsen, Lars Bo
2010-01-01
In this paper we aim to find an analytical solution for jamming transition in traffic flow. Generally the Jamming Transition Problem (JTP) can be modeled via Lorentz system. So, in this way, the governing differential equation achieved is modeled in the form of a nonlinear damped oscillator....... In current research the authors utilized the Differential Transformation Method (DTM) for solving the nonlinear problem and compared the analytical results with those ones obtained by the 4th order Runge-Kutta Method (RK4) as a numerical method. Further illustration embedded in this paper shows the ability...... of DTM in solving nonlinear problems when a so accurate solution is required....
MODIFIED BOTTLENECK-BASED PROCEDURE FOR LARGE-SCALE FLOW-SHOP SCHEDULING PROBLEMS WITH BOTTLENECK
ZUO Yan; GU Hanyu; XI Yugeng
2006-01-01
A new bottleneck-based heuristic for large-scale flow-shop scheduling problems with a bottleneck is proposed, which is simpler but more tailored than the shifting bottleneck (SB)procedure. In this algorithm, a schedule for the bottleneck machine is first constructed optimally and then the non-bottleneck machines are scheduled around the bottleneck schedule by some effective dispatching rules. Computational results show that the modified bottleneck-based procedure can achieve a tradeoff between solution quality and computational time comparing with SB procedure for medium-size problems. Furthermore it can obtain a good solution in quite short time for large-scale scheduling problems.
Dragomirescu, Florica Ioana
2012-11-01
The main motivation for a temporal stability investigation of initially localized perturbations in a swirling flow stability problem consists in pointing out the critical frequencies at which instability can sets in, an important key in predicting and understanding the flow particularities. The linearized disturbance equations define a second order ordinary differential equation with non-constant coefficients which we solve in order to determine the critical frequency in different physical parameters spaces. A non-classical polynomials based spectral method is proposed for the numerical treatment of the resulting generalized eigenvalue problem governing the stability of the flow. Numerical investigation are performed in the inviscid case for a moderate level of swirl and dominant temporal instability modes are retrieved for each Fourier component pair. The obtained values of the growth rate associated with the most amplified wavenumber are compared with existing inviscid temporal instability evaluations and good agreements are found.
A Riemann problem based method for solving compressible and incompressible flows
Lu, Haitian; Zhu, Jun; Wang, Chunwu; Wang, Donghong; Zhao, Ning
2017-02-01
A Riemann problem based method for solving two-medium flow including compressible and incompressible regions is presented. The material interface is advanced by front tracking method and the material interface boundary conditions are defined by modified ghost fluid method. A coupled compressible and incompressible Riemann problem constructed in the normal direction of the material interface is proposed to predict the interfacial states. With the ghost fluid states, the compressible and incompressible flows are solved by discontinuous Galerkin method. An incompressible discontinuous Galerkin method with nonuniform time step is also deduced. For shock wave formed in compressible flow, the numerical errors for the ghost fluid method in earlier works are analyzed and discussed in the numerical examples. It shows that the proposed method can provide reasonable results including shock wave location.
The Stochastic Galerkin Method for Darcy Flow Problem with Log-Normal Random Field Coefficients
Michal Beres
2017-01-01
Full Text Available This article presents a study of the Stochastic Galerkin Method (SGM applied to the Darcy flow problem with a log-normally distributed random material field given by a mean value and an autocovariance function. We divide the solution of the problem into two parts. The first one is the decomposition of a random field into a sum of products of a random vector and a function of spatial coordinates; this can be achieved using the Karhunen-Loeve expansion. The second part is the solution of the problem using SGM. SGM is a simple extension of the Galerkin method in which the random variables represent additional problem dimensions. For the discretization of the problem, we use a finite element basis for spatial variables and a polynomial chaos discretization for random variables. The results of SGM can be utilised for the analysis of the problem, such as the examination of the average flow, or as a tool for the Bayesian approach to inverse problems.
MULTICRITERIA HYBRID FLOW SHOP SCHEDULING PROBLEM: LITERATURE REVIEW, ANALYSIS, AND FUTURE RESEARCH
Marcia de Fatima Morais
2014-12-01
Full Text Available This research focuses on the Hybrid Flow Shop production scheduling problem, which is one of the most difficult problems to solve. The literature points to several studies that focus the Hybrid Flow Shop scheduling problem with monocriteria functions. Despite of the fact that, many real world problems involve several objective functions, they can often compete and conflict, leading researchers to concentrate direct their efforts on the development of methods that take consider this variant into consideration. The goal of the study is to review and analyze the methods in order to solve the Hybrid Flow Shop production scheduling problem with multicriteria functions in the literature. The analyses were performed using several papers that have been published over the years, also the parallel machines types, the approach used to develop solution methods, the type of method develop, the objective function, the performance criterion adopted, and the additional constraints considered. The results of the reviewing and analysis of 46 papers showed opportunities for future research on this topic, including the following: (i use uniform and dedicated parallel machines, (ii use exact and metaheuristics approaches, (iv develop lower and uppers bounds, relations of dominance and different search strategies to improve the computational time of the exact methods, (v develop other types of metaheuristic, (vi work with anticipatory setups, and (vii add constraints faced by the production systems itself.
New scheduling rules for a dynamic flexible flow line problem with sequence-dependent setup times
Kia, Hamidreza; Ghodsypour, Seyed Hassan; Davoudpour, Hamid
2017-01-01
In the literature, the application of multi-objective dynamic scheduling problem and simple priority rules are widely studied. Although these rules are not efficient enough due to simplicity and lack of general insight, composite dispatching rules have a very suitable performance because they result from experiments. In this paper, a dynamic flexible flow line problem with sequence-dependent setup times is studied. The objective of the problem is minimization of mean flow time and mean tardiness. A 0-1 mixed integer model of the problem is formulated. Since the problem is NP-hard, four new composite dispatching rules are proposed to solve it by applying genetic programming framework and choosing proper operators. Furthermore, a discrete-event simulation model is made to examine the performances of scheduling rules considering four new heuristic rules and the six adapted heuristic rules from the literature. It is clear from the experimental results that composite dispatching rules that are formed from genetic programming have a better performance in minimization of mean flow time and mean tardiness than others.
New scheduling rules for a dynamic flexible flow line problem with sequence-dependent setup times
Kia, Hamidreza; Ghodsypour, Seyed Hassan; Davoudpour, Hamid
2017-01-01
In the literature, the application of multi-objective dynamic scheduling problem and simple priority rules are widely studied. Although these rules are not efficient enough due to simplicity and lack of general insight, composite dispatching rules have a very suitable performance because they result from experiments. In this paper, a dynamic flexible flow line problem with sequence-dependent setup times is studied. The objective of the problem is minimization of mean flow time and mean tardiness. A 0-1 mixed integer model of the problem is formulated. Since the problem is NP-hard, four new composite dispatching rules are proposed to solve it by applying genetic programming framework and choosing proper operators. Furthermore, a discrete-event simulation model is made to examine the performances of scheduling rules considering four new heuristic rules and the six adapted heuristic rules from the literature. It is clear from the experimental results that composite dispatching rules that are formed from genetic programming have a better performance in minimization of mean flow time and mean tardiness than others.
MHD and heat transfer benchmark problems for liquid metal flow in rectangular ducts. Final paper
Sidorenkov, S.I. [D.V. Efremov Scientific Research Inst. of Electrophysical Apparatus, St. Petersburg (Russian Federation); Hua, T.Q. [Argonne National Lab., IL (United States); Araseki, Hideo [Central Research Inst. of Electric Power Industry, Tokyo (Japan)
1994-07-01
Liquid metal cooling systems of a self-cooled blanket in a tokamak reactor will likely include channels of rectangular cross section where liquid metal is circulated in the presence of strong magnetic fields. MHD pressure drop, velocity distribution and heat transfer characteristics are important issues in the engineering design considerations. Computer codes for the reliable solution of three-dimensional MHD flow problems are needed for fusion relevant conditions. This paper describes four benchmark problems to validate magnetohydrodynamic (MHD) and heat transfer computer codes. The problems include rectangular duct geometry with uniform and nonuniform magnetic fields, with and without surface heat flux, and various rectangular cross sections. Two of the problems are based on experiments. Participants in this benchmarking activity come from three countries: The Russian Federation, The United States, and Japan. The solution methods to the problems are described. Results from the different computer codes are presented and compared.
Parallel Simulation of Three-Dimensional Free Surface Fluid Flow Problems
BAER,THOMAS A.; SACKINGER,PHILIP A.; SUBIA,SAMUEL R.
1999-10-14
Simulation of viscous three-dimensional fluid flow typically involves a large number of unknowns. When free surfaces are included, the number of unknowns increases dramatically. Consequently, this class of problem is an obvious application of parallel high performance computing. We describe parallel computation of viscous, incompressible, free surface, Newtonian fluid flow problems that include dynamic contact fines. The Galerkin finite element method was used to discretize the fully-coupled governing conservation equations and a ''pseudo-solid'' mesh mapping approach was used to determine the shape of the free surface. In this approach, the finite element mesh is allowed to deform to satisfy quasi-static solid mechanics equations subject to geometric or kinematic constraints on the boundaries. As a result, nodal displacements must be included in the set of unknowns. Other issues discussed are the proper constraints appearing along the dynamic contact line in three dimensions. Issues affecting efficient parallel simulations include problem decomposition to equally distribute computational work among a SPMD computer and determination of robust, scalable preconditioners for the distributed matrix systems that must be solved. Solution continuation strategies important for serial simulations have an enhanced relevance in a parallel coquting environment due to the difficulty of solving large scale systems. Parallel computations will be demonstrated on an example taken from the coating flow industry: flow in the vicinity of a slot coater edge. This is a three dimensional free surface problem possessing a contact line that advances at the web speed in one region but transitions to static behavior in another region. As such, a significant fraction of the computational time is devoted to processing boundary data. Discussion focuses on parallel speed ups for fixed problem size, a class of problems of immediate practical importance.
Solvability identification and feasibility restoring of divergent optimal power flow problems
JIANG QuanYuan; HAN ZhenXiang
2009-01-01
Optimal power flow (OPF) has been considered as an important problem in power systems. Although several excellent algorithms, such as Newton method end interior point method, have been developed to solve the OPF problem, divergences still often occur. Till now, few works have focused on the solvability identification and feasibility restoring of divergent OPF problems. In this paper, we propose a systematic approach to identify the solvability of divergent OPF problems, and restore a feasible solution for unsolvable OPF cases. The proposed approach consists of two phases: solvability identification phase (SIP) and feasibility restoring phase (FRP). In SIP, a novel methodology based on problem transformation and active set is adopted to identify the solvability of divergent OPF problem. If a feasible solution can be obtained in SIP, then this divergent OPF problem is solvable, otherwise, FRP is used to restore a feasible or optimal solution by relaxing soft constraints and load shedding. In FRP, a feasibility restoring model is presented, and a priority-listing strategy of restoring actions is proposed to restore the unsolvable OPF problems. Numerical studies indicate that the proposed SIP and FRP are reliable to diagnose the solvability of the divergent OPF problems, give an index to measure the unsolvability, and restore an unsolvable OPF case.
Solvability identification and feasibility restoring of divergent optimal power flow problems
无
2009-01-01
Optimal power flow (OPF) has been considered as an important problem in power systems. Although several excellent algorithms, such as Newton method and interior point method, have been developed to solve the OPF problem, divergences still often occur. Till now, few works have focused on the solv- ability identification and feasibility restoring of divergent OPF problems. In this paper, we propose a systematic approach to identify the solvability of divergent OPF problems, and restore a feasible solu- tion for unsolvable OPF cases. The proposed approach consists of two phases: solvability identifica- tion phase (SIP) and feasibility restoring phase (FRP). In SIP, a novel methodology based on problem transformation and active set is adopted to identify the solvability of divergent OPF problem. If a fea- sible solution can be obtained in SIP, then this divergent OPF problem is solvable, otherwise, FRP is used to restore a feasible or optimal solution by relaxing soft constraints and load shedding. In FRP, a feasibility restoring model is presented, and a priority-listing strategy of restoring actions is proposed to restore the unsolvable OPF problems. Numerical studies indicate that the proposed SIP and FRP are reliable to diagnose the solvability of the divergent OPF problems, give an index to measure the un- solvability, and restore an unsolvable OPF case.
Modelling of stratified flows in the problem of the morphological behaviour of a sandpit
Parshakova, Ya N.; Lyubimova, T. P.; Ivantsov, A. O.
2016-02-01
The problem of the removal of brines from underwater sand pits is studied. The intensity of the removal of brines from the pits due to the changes in the hydrological regime of the river is calculated in three-dimensional approach. It is found that for the flow rates typical for the summer, the removal of brines collected in underwater pits does not occur. At flow rates typical for the spring, there is a fairly intensive removal of accumulated brines. Numerical experiments have shown that the underwater pits can serve as brines batteries, becoming an additional source of river pollution under certain hydrological conditions.
Cauchy problem for a class of nonlinear dispersive wave equations arising in elasto-plastic flow
Zhijian, Yang
2006-01-01
The paper studies the existence, both locally and globally in time, stability, decay estimates and blowup of solutions to the Cauchy problem for a class of nonlinear dispersive wave equations arising in elasto-plastic flow. Under the assumption that the nonlinear term of the equations is of polynomial growth order, say [alpha], it proves that when [alpha]>1, the Cauchy problem admits a unique local solution, which is stable and can be continued to a global solution under rather mild conditions; when [alpha][greater-or-equal, slanted]5 and the initial data is small enough, the Cauchy problem admits a unique global solution and its norm in L1,p(R) decays at the rate for 2
problem blow up in finite time.
VaMpy: A Python Package to Solve 1D Blood Flow Problems
Alexandra K. Diem
2017-06-01
Full Text Available Finite-differences methods such as the Lax-Wendroff method (LW are commonly used to solve 1D models of blood flow. These models solve for blood flow and lumen area and are useful in disease research, such as hypertension and atherosclerosis, where flow and pressure are good indicators for the presence of disease. Despite the popularity of the LW method to solve the blood flow equations, no implementation of a LW solver for these equations has been published and made publicly available. This leads to the reimplementation of the same methods within different research groups and makes verification of results more difficult. The Vascular Modelling in Python (VaMpy toolkit is a Python package that aims to fill this gap. It implements Richtmyer’s two-step Lax-Wendroff scheme to solve 1D model equations of blood flow in arterial trees and aims at facilitating the solution of blood flow problems for various medical applications. Funding statement: The development of this software was supported by an EPSRC Doctoral Training Centre grant (EP/G03690X/1.
Inverse Problem for Color Doppler Ultrasound-Assisted Intracardiac Blood Flow Imaging
Jaeseong Jang
2016-01-01
Full Text Available For the assessment of the left ventricle (LV, echocardiography has been widely used to visualize and quantify geometrical variations of LV. However, echocardiographic image itself is not sufficient to describe a swirling pattern which is a characteristic blood flow pattern inside LV without any treatment on the image. We propose a mathematical framework based on an inverse problem for three-dimensional (3D LV blood flow reconstruction. The reconstruction model combines the incompressible Navier-Stokes equations with one-direction velocity component of the synthetic flow data (or color Doppler data from the forward simulation (or measurement. Moreover, time-varying LV boundaries are extracted from the intensity data to determine boundary conditions of the reconstruction model. Forward simulations of intracardiac blood flow are performed using a fluid-structure interaction model in order to obtain synthetic flow data. The proposed model significantly reduces the local and global errors of the reconstructed flow fields. We demonstrate the feasibility and potential usefulness of the proposed reconstruction model in predicting dynamic swirling patterns inside the LV over a cardiac cycle.
A New Spectral Local Linearization Method for Nonlinear Boundary Layer Flow Problems
S. S. Motsa
2013-01-01
Full Text Available We propose a simple and efficient method for solving highly nonlinear systems of boundary layer flow problems with exponentially decaying profiles. The algorithm of the proposed method is based on an innovative idea of linearizing and decoupling the governing systems of equations and reducing them into a sequence of subsystems of differential equations which are solved using spectral collocation methods. The applicability of the proposed method, hereinafter referred to as the spectral local linearization method (SLLM, is tested on some well-known boundary layer flow equations. The numerical results presented in this investigation indicate that the proposed method, despite being easy to develop and numerically implement, is very robust in that it converges rapidly to yield accurate results and is more efficient in solving very large systems of nonlinear boundary value problems of the similarity variable boundary layer type. The accuracy and numerical stability of the SLLM can further be improved by using successive overrelaxation techniques.
ZhuDetong
2004-01-01
This paper proposes a nonmonotonic backtracking trust region algorithm via bilevel linear programming for solving the general multicommodity minimal cost flow problems. Using the duality theory of the linear programming and convex theory, the generalized directional derivative of the general multicommodity minimal cost flow problems is derived. The global convergence and superlinear convergence rate of the proposed algorithm are established under some mild conditions.
Flow-induced cylinder noise formulated as a diffraction problem for low Mach numbers
Gloerfelt, X.; Pérot, F.; Bailly, C.; Juvé, D.
2005-10-01
The role of surfaces in the mechanism of sound generation by low Mach number flows interacting with solid nonvibrating surfaces is well established by the classical aeroacoustic papers by Powell, Doak, Ffowcs Williams, Crighton, or Howe. It can be formulated as a problem of diffraction of the flow sources by the rigid body. The present study illustrates this statement in the case of flow-induced cylinder noise. Curle's formulation is analytically and numerically compared to a formulation based on an exact Green's function tailored to a cylindrical geometry. The surface integral of Curle's formulation represents exactly the diffraction effects by the rigid body. The direct and scattered parts of the sound field are studied. In this low Mach number configuration, the cylinder is compact, and the scattered (dipole) field dominates the direct (quadrupole) field. The classical properties of the scattering by a cylinder are retrieved by considering a point quadripole source near the cylinder surface.
Riemann problem for the zero-pressure flow in gas dynamics
李杰权; 荔炜
2001-01-01
The Riemann problem for zero-pressure flow in gas dynamics in one dimension and two dimensions is investigated. Through studying the generalized Rankine-Hugoniot conditions of delta-shock waves, the one-dimensional Riemann solution is proposed which exhibits four different structures when the initial density involves Dirac measure. For the two-dimensional case, the Riemann solution with two pieces of initial constant states separated at a smooth curve is obtained.
无
2006-01-01
An efficient analytical decomposition technique was presented for solving the singular nonlinear boundary value problem arising in viscous flow when the Crocco variable was introduced. The approximate analytical solution may be represented in terms of a rapid convergent power series with elegantly computable terms. The reliability and efficiency of the approximate solutions were verified by numerical ones in the literature. The approximate analytical solutions can be successfully applied to give the values of skin friction coefficient.
Linear stability of the Couette flow of a vibrationally excited gas. 2. viscous problem
Grigor'ev, Yu. N.; Ershov, I. V.
2016-03-01
Based on the linear theory, stability of viscous disturbances in a supersonic plane Couette flow of a vibrationally excited gas described by a system of linearized equations of two-temperature gas dynamics including shear and bulk viscosity is studied. It is demonstrated that two sets are identified in the spectrum of the problem of stability of plane waves, similar to the case of a perfect gas. One set consists of viscous acoustic modes, which asymptotically converge to even and odd inviscid acoustic modes at high Reynolds numbers. The eigenvalues from the other set have no asymptotic relationship with the inviscid problem and are characterized by large damping decrements. Two most unstable viscous acoustic modes (I and II) are identified; the limits of these modes were considered previously in the inviscid approximation. It is shown that there are domains in the space of parameters for both modes, where the presence of viscosity induces appreciable destabilization of the flow. Moreover, the growth rates of disturbances are appreciably greater than the corresponding values for the inviscid flow, while thermal excitation in the entire considered range of parameters increases the stability of the viscous flow. For a vibrationally excited gas, the critical Reynolds number as a function of the thermal nonequilibrium degree is found to be greater by 12% than for a perfect gas.
Managing the Budget: Stock-Flow Reasoning and the CO2 Accumulation Problem.
Newell, Ben R; Kary, Arthur; Moore, Chris; Gonzalez, Cleotilde
2016-01-01
The majority of people show persistent poor performance in reasoning about "stock-flow problems" in the laboratory. An important example is the failure to understand the relationship between the "stock" of CO2 in the atmosphere, the "inflow" via anthropogenic CO2 emissions, and the "outflow" via natural CO2 absorption. This study addresses potential causes of reasoning failures in the CO2 accumulation problem and reports two experiments involving a simple re-framing of the task as managing an analogous financial (rather than CO2 ) budget. In Experiment 1 a financial version of the task that required participants to think in terms of controlling debt demonstrated significant improvements compared to a standard CO2 accumulation problem. Experiment 2, in which participants were invited to think about managing savings, suggested that this improvement was fortuitous and coincidental rather than due to a fundamental change in understanding the stock-flow relationships. The role of graphical information in aiding or abetting stock-flow reasoning was also explored in both experiments, with the results suggesting that graphs do not always assist understanding. The potential for leveraging the kind of reasoning exhibited in such tasks in an effort to change people's willingness to reduce CO2 emissions is briefly discussed.
An enhanced FIVER method for multi-material flow problems with second-order convergence rate
Main, Alex; Zeng, Xianyi; Avery, Philip; Farhat, Charbel
2017-01-01
The finite volume (FV) method with exact two-material Riemann problems (FIVER) is an Eulerian computational method for the solution of multi-material flow problems. It is robust in the presence of large density jumps at the fluid-fluid interfaces, and the presence of large structural motions, deformations, and even topological changes at the fluid-structure interfaces. To achieve simplicity in implementation, it approximates each material interface by a surrogate surface which conforms to the control volume boundaries. Unfortunately, this approximation introduces a first-order error of the geometric type in the solution process. In this paper, it is first shown that this error causes the original version of FIVER to be inconsistent in the neighborhood of material interfaces and degrades its global order of spatial accuracy. Then, an enhanced version of FIVER is presented to rectify this issue, restore consistency, and achieve for smooth problems the desired global convergence rate. To this effect, the original definition of a surrogate material interface is retained because of its attractive simplicity. However, the solution at this interface of a two-material Riemann problem is enhanced with a simple reconstruction procedure based on interpolation and extrapolation. Next, the extrapolation component of this procedure is equipped with a limiter in order to achieve nonlinear stability for non-smooth problems. In the one-dimensional inviscid setting, the resulting FIVER method is also shown to be total variation bounded. Focusing on the context of a second-order FV semi-discretization, the nonlinear stability and second-order global convergence rate of this enhanced FIVER method are illustrated for several model multi-fluid and fluid-structure interaction problems. The potential of this computational method for complex multi-material flow problems is also demonstrated with the simulation of the collapse of an air bubble submerged in water and the comparison of the
Analysis of dispatching rules application on scheduling problem in flexible-flow shop production
Rakićević Zoran M.
2014-01-01
Full Text Available In this paper we analyzed a group of simple heuristic methods, which are used for solving the scheduling problem in manufacturing and services. The analysis was performed on the scheduling problem in a flexible-flow shop production, which is known by the English term - Flexible-Flow Shop (FFS. The task is to determine the schedule of processing multiple products on multiple machines, where all the products have the same sequence of processing and for each process there are multiple machines available. For this FFS problem we present the corresponding mathematical model of mixed integer programming. Among potential methods for solving the set task, we consider simple heuristics because the original scheduling problem is NP-hard and finding the exact optimal solution would require unacceptably long computing time. Heuristic methods are based on priority rules that are performed based on the relations of importance between products and their processing time on individual machines. Heuristic methods are widely used for solving practical problems, which was the motivation for the analysis performed in this paper. The aim of the analysis is to identify those priority rules, from a set of considered, which provide a good solution to a hypothetical scheduling problem example, where the evaluation of solution is performed using different criteria functions. The analysis that is presented in the paper was obtained by using the computer program LEKIN. The main results of the analysis indicated that priority rules give different solutions to the problem of FFS and that each of these solutions is a significantly good result in terms of some of the considered criteria functions.
Wei, Xiu; Zhang, Wenqiang; Weng, Wei; Fujimura, Shigeru
This paper proposed a multi-objective local search procedure (MOLS). It is combined with NSGA-II for solving bi-criteria PFSP with the objectives of minimizing makespan and maximum tardiness. Utilizing the properties of active blocks for flow shop scheduling problem, neighborhood structures MOINS (multi-objective insertion) and MOEXC (multi-objective exchange) are designed in order to improve efficiency of perturbation. Any perturbation based on MOINS and MOEXC takes effect on different criteria simultaneously. The original idea of MOLS is systematic change neighborhoods in the local search procedure. The search direction of MOLS on an individual is naturally guided by interaction of MOINS and MOEXC. Moreover, there is no need to set parameters in MOLS. The MOLS combined with popular multi-objective evolutionary algorithm NSGA-II (Non-dominated Sorting Genetic Algorithm-II) is called as “NSGA-II-MOLS”. To illustrate the efficacy of proposed approach, four different scaled problems are used to test performance of NSGA-II-MOLS. The numerous comparisons show efficacy of NSGA-II-MOLS is better than most of algorithms even with the same number of individual evaluations and parameters setting.
Tsuji, Takuya; Yokomine, Takehiko; Shimizu, Akihiko
2002-11-01
We have been engaged in the development of multi-scale adaptive simulation technique for incompressible turbulent flow. This is designed as that important scale components in the flow field are detected automatically by lifting wavelet and solved selectively. In conventional incompressible scheme, it is very common to solve Poisson equation of pressure to meet the divergence free constraints of incompressible flow. It may be not impossible to solve the Poisson eq. in the adaptive way, but this is very troublesome because it requires generation of control volume at each time step. We gave an eye on weakly compressible model proposed by Bao(2001). This model was derived from zero Mach limit asymptotic analysis of compressible Navier-Stokes eq. and does not need to solve the Poisson eq. at all. But it is relatively new and it requires demonstration study before the combination with the adaptation by wavelet. In present study, 2-D and 3-D Backstep flow were selected as test problems and applicability to turbulent flow is verified in detail. Besides, combination of adaptation by wavelet with weakly compressible model towards the adaptive turbulence simulation is discussed.
Paterson, Mike; Thorup, Mikkel; Winkler, Peter; Zwick, Uri
2007-01-01
How far can a stack of $n$ identical blocks be made to hang over the edge of a table? The question dates back to at least the middle of the 19th century and the answer to it was widely believed to be of order $\\log n$. Recently, Paterson and Zwick constructed $n$-block stacks with overhangs of order $n^{1/3}$, exponentially better than previously thought possible. We show here that order $n^{1/3}$ is indeed best possible, resolving the long-standing overhang problem up to a constant factor.
MHD and heat transfer benchmark problems for liquid metal flow in rectangular ducts
Sidorenkov, S.I. [D.V. Efremov Scientific Research Inst. of Electrophysical Apparatus, St. Petersburg (Russian Federation); Hua, T.Q. [Argonne National Lab., IL (United States); Araseki, H. [Central Research Inst. of Electric Power Industry, Tokoyo (Japan)
1994-12-31
Liquid metal cooling systems of a self-cooled blanket in a tokamak reactor will likely include channels of rectangular cross section where liquid metal is circulated in the presence of strong magnetic fields. MHD pressure drop, velocity distribution and heat transfer characteristics are important issues in the engineering design considerations. Computer codes for the reliable solution of three-dimensional MHD flow problems are needed for fusion relevant conditions. Argonne National Laboratory and The Efremov Institute have jointly defined several benchmark problems for code validation. The problems, described in this paper, are based on two series of rectangular duct experiments conducted at ANL; one of the series is a joint ANL/Efremov experiment. The geometries consist of variation of aspect ratio and wall thickness (thus wall conductance ratio). The transverse magnetic fields are uniform and nonuniform in the axial direction.
Aragon-Aguilar, Alfonso; Izquierdo-Montalvo, Georgina; Pal-Verma, Mahendra; Santoyo-Gutierrez, Socrates [Instituto de Investigaciones Electricas (Mexico); Moya-Acosta, Sara L [Centro Nacional de Investigacion y Desarrollo Tecnologico (Mexico)
2009-01-15
Inflow performance relationships developed for petroleum and geothermal reservoirs are presented. Four of them were selected to be used in this work. Such relationships were developed considering features of a typical geothermal system. The performance of the selected relationships was assessed using data from production tests in several wells of different fields. A methodology is presented to determine the value of the maximum flow (W{sub max}) from the inflow relationships; its application is demonstrated using the data of the 10 production tests. It was found that the calculated value of W{sub max} under stabilization conditions may be related to the reservoir response. In general, there is a good agreement between the calculated values of W{sub max} from the different methods. The differences in the W{sub max} values vary within 10%. It was found that the stability in the calculated values of W{sub max} as a response of the reservoir is a function of the flow magnitude. So, the wells with flow greater than 200 t/h reach the stability of W{sub max} at openings 50% less of their total capacity. [Spanish] Se presentan las relaciones del comportamiento de influjo desarrolladas para yacimientos petroleros y geotermicos. Se seleccionaron cuatro de ellas para usar en este trabajo. Tales relaciones fueron desarrolladas considerando condiciones de un sistema geotermico tipico. Se analizo el comportamiento de las relaciones escogidas utilizando datos de pruebas de produccion de varios pozos de diferentes campos. Se presenta una metodologia para determinar el valor del flujo maximo (W{sub max}) a partir de las relaciones de influjo; se demuestra su aplicabilidad usando los datos de diez pruebas de produccion. Se encontro que el valor de W{sub max} calculado bajo condiciones de estabilizacion se puede relacionar con la respuesta del yacimiento. En general se encuentra buena concordancia entre los valores calculados de W{sub max} usando los diferentes metodos. Las
Algorithm Preserving Mass Fraction Maximum Principle for Multi-component Flows%多组份流动质量分数保极值原理算法
唐维军; 蒋浪; 程军波
2014-01-01
We propose a new method for compressible multi⁃component flows with Mie⁃Gruneisen equation of state based on mass fraction. The model preserves conservation law of mass, momentum and total energy for mixture flows. It also preserves conservation of mass of all single components. Moreover, it prevents pressure and velocity from jumping across interface that separate regions of different fluid components. Wave propagation method is used to discretize this quasi⁃conservation system. Modification of numerical method is adopted for conservative equation of mass fraction. This preserves the maximum principle of mass fraction. The wave propagation method which is not modified for conservation equations of flow components mass, cannot preserve the mass fraction in the interval [0,1]. Numerical results confirm validity of the method.%对基于质量分数的Mie⁃Gruneisen状态方程多流体组份模型提出了新的数值方法。该模型保持混合流体的质量、动量、和能量守恒，保持各组份分质量守恒，在多流体组份界面处保持压力和速度一致。该模型是拟守恒型方程系统。对该模型系统的离散采用波传播算法。与直接对模型中所有守恒方程采用相同算法不同的是，在处理分介质质量守恒方程时，对波传播算法进行了修正，使之满足质量分数保极值原理。而不作修改的算法则不能保证质量分数在[0，1]范围。数值实验验证了该方法有效。
Shao, H.; Huang, Y.; Kolditz, O.
2015-12-01
Multiphase flow problems are numerically difficult to solve, as it often contains nonlinear Phase transition phenomena A conventional technique is to introduce the complementarity constraints where fluid properties such as liquid saturations are confined within a physically reasonable range. Based on such constraints, the mathematical model can be reformulated into a system of nonlinear partial differential equations coupled with variational inequalities. They can be then numerically handled by optimization algorithms. In this work, two different approaches utilizing the complementarity constraints based on persistent primary variables formulation[4] are implemented and investigated. The first approach proposed by Marchand et.al[1] is using "local complementary constraints", i.e. coupling the constraints with the local constitutive equations. The second approach[2],[3] , namely the "global complementary constrains", applies the constraints globally with the mass conservation equation. We will discuss how these two approaches are applied to solve non-isothermal componential multiphase flow problem with the phase change phenomenon. Several benchmarks will be presented for investigating the overall numerical performance of different approaches. The advantages and disadvantages of different models will also be concluded. References[1] E.Marchand, T.Mueller and P.Knabner. Fully coupled generalized hybrid-mixed finite element approximation of two-phase two-component flow in porous media. Part I: formulation and properties of the mathematical model, Computational Geosciences 17(2): 431-442, (2013). [2] A. Lauser, C. Hager, R. Helmig, B. Wohlmuth. A new approach for phase transitions in miscible multi-phase flow in porous media. Water Resour., 34,(2011), 957-966. [3] J. Jaffré, and A. Sboui. Henry's Law and Gas Phase Disappearance. Transp. Porous Media. 82, (2010), 521-526. [4] A. Bourgeat, M. Jurak and F. Smaï. Two-phase partially miscible flow and transport modeling in
A Data Flow Model to Solve the Data Distribution Changing Problem in Machine Learning
Shang Bo-Wen
2016-01-01
Full Text Available Continuous prediction is widely used in broad communities spreading from social to business and the machine learning method is an important method in this problem.When we use the machine learning method to predict a problem. We use the data in the training set to fit the model and estimate the distribution of data in the test set.But when we use machine learning to do the continuous prediction we get new data as time goes by and use the data to predict the future data, there may be a problem. As the size of the data set increasing over time, the distribution changes and there will be many garbage data in the training set.We should remove the garbage data as it reduces the accuracy of the prediction. The main contribution of this article is using the new data to detect the timeliness of historical data and remove the garbage data.We build a data flow model to describe how the data flow among the test set, training set, validation set and the garbage set and improve the accuracy of prediction. As the change of the data set, the best machine learning model will change.We design a hybrid voting algorithm to fit the data set better that uses seven machine learning models predicting the same problem and uses the validation set putting different weights on the learning models to give better model more weights. Experimental results show that, when the distribution of the data set changes over time, our time flow model can remove most of the garbage data and get a better result than the traditional method that adds all the data to the data set; our hybrid voting algorithm has a better prediction result than the average accuracy of other predict models
王晓冬; 朱光亚; 王磊
2015-01-01
By defining new dimensionless variables, nonlinear mathematical models for one-dimensional flow with unknown moving boundaries in semi-infinite porous media are modified to be solved analytically. The exact analytical solutions for both constant-rate and constant-pressure inner boundary constraint problems are obtained by applying the Green’s function. Two transcendental equations for moving boundary problems are obtained and solved using the Newton-Raphson iteration. The exact analytical solutions are then compared with the approximate solutions. The Pascal’s approximate formula in reference is fairly accurate for the moving boundary development under the constant-rate condition. But another Pascal’s approximate formula given in reference is not very robust for constant-pressure condition problems during the early production period, and could lead to false results at the maximum moving boundary distance. Our results also show that, in presence of larger TPG, more pressure drop is required to maintain a constant-rate production. Under the constant-pressure producing condition, the flow rate may decline dramatically due to a large TPG. What’s more, there exists a maximum distance for a given TPG, beyond which the porous media is not disturbed.
COUETTE FLOW PROBLEM FOR AN UNSTEADY MHD THIRD-GRADE FLUID WITH HALL CURRENTS
Muhammad Azram
2014-12-01
Full Text Available ABSTRACT: In this work, we analyze Coutte flow problem for an unsteady mangneto-hydrodynamic (MHD third-grade fluid in the presence of a pressure gradient and Hall currnts. Existing literature on the topic shows that the effecs of Hall current on Coutte flow of an unsteady MHD third-grade fluid with a prssure gradient has not yet been investigated. The arising non-linear problem is solved by the homotopy analysis method (HAM and the convergence of the obtained complex series solution is carefully analyzed. The effects of pressure number, Hartmann number and Hall parameter on unsteady velocity are discussed via analysis of plots. ABSTRAK: Kajian dijalan untuk menganalisa masalah aliran Coutte bagi bendalir MHD gred ketiga dan arus Hall. Bagi topik ini kesan arus Hall terhadap aliran Couette dalam bendalir MHD gred ketiga tak mantap dengan kecerunan tekanan, belum pernah dikaji selidik. Masalah tak linear berbangkit diselesaikan dengan kaedah analisis homotopi (HAM dan ketumpuan solusi rangkaian kompleks dianalisa dengan teliti. Kesan nilai tekanan, nombor Hartmann dan parameter Hall terhadap halaju tak mantap diperbincangkan melalui plot yang dianalisis.KEYWORDS: Cuette; flow; hall currents; unsteady; third-grade fluid; HAM
Efficiency Improvements in Meta-Heuristic Algorithms to Solve the Optimal Power Flow Problem
Reddy, S. Surender; Bijwe, P. R.
2016-12-01
This paper proposes the efficient approaches for solving the Optimal Power Flow (OPF) problem using the meta-heuristic algorithms. Mathematically, OPF is formulated as non-linear equality and inequality constrained optimization problem. The main drawback of meta-heuristic algorithm based OPF is the excessive execution time required due to the large number of power flows needed in the solution process. The proposed efficient approaches uses the lower and upper bounds of objective function values. By using this approach, the number of power flows to be performed are reduced substantially, resulting in the solution speed up. The efficiently generated objective function bounds can result in the faster solutions of meta-heuristic algorithms. The original advantages of meta-heuristic algorithms, such as ability to handle complex non-linearities, discontinuities in the objective function, discrete variables handling, and multi-objective optimization, etc., are still available in the proposed efficient approaches. The proposed OPF formulation includes the active and reactive power generation limits, Valve Point Loading (VPL) and Prohibited Operating Zones (POZs) effects of generating units. The effectiveness of proposed approach is examined on IEEE 30, 118 and 300 bus test systems, and the simulation results confirm the efficiency and superiority of the proposed approaches over the other meta-heuristic algorithms. The proposed efficient approach is generic enough to use with any type of meta-heuristic algorithm based OPF.
Bürger, Raimund; Kumar, Sarvesh; Ruiz-Baier, Ricardo
2015-10-01
The sedimentation-consolidation and flow processes of a mixture of small particles dispersed in a viscous fluid at low Reynolds numbers can be described by a nonlinear transport equation for the solids concentration coupled with the Stokes problem written in terms of the mixture flow velocity and the pressure field. Here both the viscosity and the forcing term depend on the local solids concentration. A semi-discrete discontinuous finite volume element (DFVE) scheme is proposed for this model. The numerical method is constructed on a baseline finite element family of linear discontinuous elements for the approximation of velocity components and concentration field, whereas the pressure is approximated by piecewise constant elements. The unique solvability of both the nonlinear continuous problem and the semi-discrete DFVE scheme is discussed, and optimal convergence estimates in several spatial norms are derived. Properties of the model and the predicted space accuracy of the proposed formulation are illustrated by detailed numerical examples, including flows under gravity with changing direction, a secondary settling tank in an axisymmetric setting, and batch sedimentation in a tilted cylindrical vessel.
Optimizing a multi-objectives flow shop scheduling problem by a novel genetic algorithm
R. Tavakkoli-Moghaddam
2013-06-01
Full Text Available Flow-shop problems, as a typical manufacturing challenge, have become an interesting area of research. The primary concern is that the solution space is huge and, therefore, the set of feasible solutions cannot be enumerated one by one. In this paper, we present an efficient solution strategy based on a genetic algorithm (GA to minimize the makespan, total waiting time and total tardiness in a flow shop consisting of n jobs and m machines. The primary objective is to minimize the job waiting time before performing the related operations. This is a major concern for some industries such as food and chemical for planning and production scheduling. In these industries, there is a probability of the decay and deterioration of the products prior to accomplishment of operations in workstation, due to the increase in the waiting time. We develop a model for a flowshop scheduling problem, which uses the planner-specified weights for handling a multi-objective optimization problem. These weights represent the priority of planning objectives given by managers. The results of the proposed GA and classic GA are analyzed by the analysis of variance (ANOVA method and the results are discussed.
ANN BASED CONTROL PATTERNS ESTIMATOR FOR UPFC USED IN POWER FLOW PROBLEM
K.Krishnaveni
2007-09-01
Full Text Available The continuous growth in the demand for electric power necessitates the flexibility of operation in power system. Of different power electronics-based Flexible AC Transmission System (FACTS devices, which enhance the power transmission capabilities, Unified Power Flow Controller (UPFC provides an emerging and promising solution for the power flow problems in the system, as it simultaneously and/or selectively controls the transmission parameters. In this context, the paper proposes the power flow control in a simple system by injecting the series compensating voltage, which is an important function of UPFC. For this purpose, ANN controller based UPFC is used. Control patterns are generated for obtaining the adjustable series voltage from the second converter that, in turn, controls the power flow in the system. With the proposed model, by varying control coefficient the series injected voltage can be adjusted. MATLAB Simulation is used to test the proposed model. The control horizon is identified and presented for various values of existing active and reactive powers.
Solving the angular momentum problem in the cold feedback mechanism of cooling flows
Pizzolato, Fabio
2010-01-01
We show that cold clumps in the intra--cluster medium (ICM) efficiently lose their angular momentum as they fall in, such that they can rapidly feed the central AGN and maintain a heating feedback process. Such cold clumps are predicted by the cold feedback model, a model for maintaining the ICM in cooling flows hot by a feedback process. The clumps very effectively lose their angular momentum in two channels: the drag force exerted by the ICM and the random collisions between clumps when they are close to the central black hole. We conclude that the angular momentum cannot prevent the accretion of the cold clumps, and the cold feedback mechanism is a viable model for a feedback mechanism in cooling flows. Cold feedback does not suffer from the severe problems of models that are based on the Bondi accretion.
Chan, B. C.
1986-05-01
A basic, limited scope, fast-running computer model is presented for the solution of two-dimensional, transient, thermally-coupled fluid flow problems. This model is to be the module in the SSC (an LMFBR thermal-hydraulic systems code) for predicting complex flow behavior, as occurs in the upper plenum of the loop-type design or in the sodium pool of the pool-type design. The nonlinear Navier-Stokes equations and the two-equation (two-variable) transport model of turbulence are reduced to a set of linear algebraic equations in an implicit finite difference scheme, based on the control volume approach. These equations are solved iteratively in a line-by-line procedure using the tri-diagonal matrix algorithm. The results of calculational examplers are shown in the computer-generated plots.
Badescu, V.; Murariu, V.; Rotariu, O; Rezlescu, N.
1996-01-01
The theory of magnetic particles′ capture on a HGMF-axial magnetic filter cell with bounded flow field is presented. The equations of particle motion for both potential and laminar flow are obtained. By analytical solving of these equations, the trajectories of particles are established. The flow velocity of the fluid suspension for the case of potential flow is set equal with the velocity averaged across the tube section for the laminar flow. Thus, it is possible to make a comparison between...
Rosewarne, P J; Wilson, J M; Svendsen, J C
2016-01-01
Metabolic rate is one of the most widely measured physiological traits in animals and may be influenced by both endogenous (e.g. body mass) and exogenous factors (e.g. oxygen availability and temperature). Standard metabolic rate (SMR) and maximum metabolic rate (MMR) are two fundamental physiological variables providing the floor and ceiling in aerobic energy metabolism. The total amount of energy available between these two variables constitutes the aerobic metabolic scope (AMS). A laboratory exercise aimed at an undergraduate level physiology class, which details the appropriate data acquisition methods and calculations to measure oxygen consumption rates in rainbow trout Oncorhynchus mykiss, is presented here. Specifically, the teaching exercise employs intermittent flow respirometry to measure SMR and MMR, derives AMS from the measurements and demonstrates how AMS is affected by environmental oxygen. Students' results typically reveal a decline in AMS in response to environmental hypoxia. The same techniques can be applied to investigate the influence of other key factors on metabolic rate (e.g. temperature and body mass). Discussion of the results develops students' understanding of the mechanisms underlying these fundamental physiological traits and the influence of exogenous factors. More generally, the teaching exercise outlines essential laboratory concepts in addition to metabolic rate calculations, data acquisition and unit conversions that enhance competency in quantitative analysis and reasoning. Finally, the described procedures are generally applicable to other fish species or aquatic breathers such as crustaceans (e.g. crayfish) and provide an alternative to using higher (or more derived) animals to investigate questions related to metabolic physiology.
Simulation of two-phase flow in elbow with problem solving
Ahmai, Somayeh; Al-Makky, Ahmed
2014-04-01
Multiphase flows occurring in circular curved pipes exhibit important physical phenomena.They are characterized by a large pressure drop and are composed of different phases. In the past, erosion-corrosion was measured through the use of experimental methods. Today numerical simulation models provide a more in depth look into the problem of erosion. Solid particle erosion is of major concern in the industrial engineering sector. In this study, erosion occurring in a (90)-degree elbow has been simulated. The generated two-dimensional data was done through the use of the Commercial software ANSYS Fluent. The primary idea comes from the petrochemicals industry. To overcome this problem, counter measures are proposed in this paper to the piping setup in order to protect pumps from unwanted excessive sand concentrations. Note that the physical properties of the simulated fluid mixture are taken the same as for the real-studied sample.
On a boundary layer problem related to the gas flow in shales
Barenblatt, G. I.
2013-01-16
The development of gas deposits in shales has become a significant energy resource. Despite the already active exploitation of such deposits, a mathematical model for gas flow in shales does not exist. Such a model is crucial for optimizing the technology of gas recovery. In the present article, a boundary layer problem is formulated and investigated with respect to gas recovery from porous low-permeability inclusions in shales, which are the basic source of gas. Milton Van Dyke was a great master in the field of boundary layer problems. Dedicating this work to his memory, we want to express our belief that Van Dyke\\'s profound ideas and fundamental book Perturbation Methods in Fluid Mechanics (Parabolic Press, 1975) will live on-also in fields very far from the subjects for which they were originally invented. © 2013 US Government.
MOHAMED KEZZAR
2015-08-01
Full Text Available In this research, an efficient technique of computation considered as a modified decomposition method was proposed and then successfully applied for solving the nonlinear problem of the two dimensional flow of an incompressible viscous fluid between nonparallel plane walls. In fact this method gives the nonlinear term Nu and the solution of the studied problem as a power series. The proposed iterative procedure gives on the one hand a computationally efficient formulation with an acceleration of convergence rate and on the other hand finds the solution without any discretization, linearization or restrictive assumptions. The comparison of our results with those of numerical treatment and other earlier works shows clearly the higher accuracy and efficiency of the used Modified Decomposition Method.
A velocity tracking approach for the data assimilation problem in blood flow simulations.
Tiago, J; Guerra, T; Sequeira, A
2016-11-24
Several advances have been made in data assimilation techniques applied to blood flow modeling. Typically, idealized boundary conditions, only verified in straight parts of the vessel, are assumed. We present a general approach, on the basis of a Dirichlet boundary control problem, that may potentially be used in different parts of the arterial system. The relevance of this method appears when computational reconstructions of the 3D domains, prone to be considered sufficiently extended, are either not possible, or desirable, because of computational costs. On the basis of taking a fully unknown velocity profile as the control, the approach uses a discretize then optimize methodology to solve the control problem numerically. The methodology is applied to a realistic 3D geometry representing a brain aneurysm. The results show that this data assimilation approach may be preferable to a pressure control strategy and that it can significantly improve the accuracy associated to typical solutions obtained using idealized velocity profiles.
Karsten, Christian Vad; Pisinger, David; Røpke, Stefan
2015-01-01
The multi-commodity network flow problem is an important sub-problem in several heuristics and exact methods for designing route networks for container ships. The sub-problem decides how cargoes should be transported through the network provided by shipping routes. This paper studies the multi......-commodity network flow problem with transit time constraints which puts limits on the duration of the transit of the commodities through the network. It is shown that for the particular application it does not increase the solution time to include the transit time constraints and that including the transit time...
Amir Abbas Najafi
2009-01-01
Full Text Available Resource investment problem with discounted cash flows (RIPDCFs is a class of project scheduling problem. In RIPDCF, the availability levels of the resources are considered decision variables, and the goal is to find a schedule such that the net present value of the project cash flows optimizes. In this paper, we consider a new RIPDCF in which tardiness of project is permitted with defined penalty. We mathematically formulated the problem and developed a heuristic method to solve it. The results of the performance analysis of the proposed method show an effective solution approach to the problem.
M. Saravanan
2014-03-01
Full Text Available A Hybrid flow shop scheduling is characterized ‘n’ jobs ‘m’ machines with ‘M’ stages by unidirectional flow of work with a variety of jobs being processed sequentially in a single-pass manner. The paper addresses the multi-stage hybrid flow shop scheduling problems with missing operations. It occurs in many practical situations such as stainless steel manufacturing company. The essential complexity of the problem necessitates the application of meta-heuristics to solve hybrid flow shop scheduling. The proposed Simulated Annealing algorithm (SA compared with Particle Swarm Optimization (PSO with the objective of minimization of makespan. It is show that the SA algorithm is efficient in finding out good quality solutions for the hybrid flow shop problems with missing operations.
Enrique Castillo
2015-01-01
Full Text Available A state-of-the-art review of flow observability, estimation, and prediction problems in traffic networks is performed. Since mathematical optimization provides a general framework for all of them, an integrated approach is used to perform the analysis of these problems and consider them as different optimization problems whose data, variables, constraints, and objective functions are the main elements that characterize the problems proposed by different authors. For example, counted, scanned or “a priori” data are the most common data sources; conservation laws, flow nonnegativity, link capacity, flow definition, observation, flow propagation, and specific model requirements form the most common constraints; and least squares, likelihood, possible relative error, mean absolute relative error, and so forth constitute the bases for the objective functions or metrics. The high number of possible combinations of these elements justifies the existence of a wide collection of methods for analyzing static and dynamic situations.
On a finite-difference method for solving transient viscous flow problems
Li, C. P.
1983-01-01
A method has been developed to solve the unsteady, compressible Navier-Stokes equation with the property of consistency and the ability of minimizing the equation stiffness. It relies on innovative extensions of the state-of-the-art finite-difference techniques and is composed of: (1) the upwind scheme for split-flux and the central scheme for conventional flux terms in the inviscid and viscous regions, respectively; (2) the characteristic treatment of both inviscid and viscous boundaries; (3) an ADI procedure compatible with interior and boundary points; and (4) a scalar matrix coefficient including viscous terms. The performance of this method is assessed with four sample problems; namely, a standing shock in the Laval duct, a shock reflected from the wall, the shock-induced boundary-layer separation, and a transient internal nozzle flow. The results from the present method, an existing hybrid block method, and a well-known two-step explicit method are compared and discussed. It is concluded that this method has an optimal trade-off between the solution accuracy and computational economy, and other desirable properties for analyzing transient viscous flow problems.
Pore-scale modeling of moving contact line problems in immiscible two-phase flow
Kucala, Alec; Noble, David; Martinez, Mario
2016-11-01
Accurate modeling of moving contact line (MCL) problems is imperative in predicting capillary pressure vs. saturation curves, permeability, and preferential flow paths for a variety of applications, including geological carbon storage (GCS) and enhanced oil recovery (EOR). Here, we present a model for the moving contact line using pore-scale computational fluid dynamics (CFD) which solves the full, time-dependent Navier-Stokes equations using the Galerkin finite-element method. The MCL is modeled as a surface traction force proportional to the surface tension, dependent on the static properties of the immiscible fluid/solid system. We present a variety of verification test cases for simple two- and three-dimensional geometries to validate the current model, including threshold pressure predictions in flows through pore-throats for a variety of wetting angles. Simulations involving more complex geometries are also presented to be used in future simulations for GCS and EOR problems. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.
MPSalsa a finite element computer program for reacting flow problems. Part 2 - user`s guide
Salinger, A.; Devine, K.; Hennigan, G.; Moffat, H. [and others
1996-09-01
This manual describes the use of MPSalsa, an unstructured finite element (FE) code for solving chemically reacting flow problems on massively parallel computers. MPSalsa has been written to enable the rigorous modeling of the complex geometry and physics found in engineering systems that exhibit coupled fluid flow, heat transfer, mass transfer, and detailed reactions. In addition, considerable effort has been made to ensure that the code makes efficient use of the computational resources of massively parallel (MP), distributed memory architectures in a way that is nearly transparent to the user. The result is the ability to simultaneously model both three-dimensional geometries and flow as well as detailed reaction chemistry in a timely manner on MT computers, an ability we believe to be unique. MPSalsa has been designed to allow the experienced researcher considerable flexibility in modeling a system. Any combination of the momentum equations, energy balance, and an arbitrary number of species mass balances can be solved. The physical and transport properties can be specified as constants, as functions, or taken from the Chemkin library and associated database. Any of the standard set of boundary conditions and source terms can be adapted by writing user functions, for which templates and examples exist.
GPU computing of compressible flow problems by a meshless method with space-filling curves
Ma, Z. H.; Wang, H.; Pu, S. H.
2014-04-01
A graphic processing unit (GPU) implementation of a meshless method for solving compressible flow problems is presented in this paper. Least-square fit is used to discretize the spatial derivatives of Euler equations and an upwind scheme is applied to estimate the flux terms. The compute unified device architecture (CUDA) C programming model is employed to efficiently and flexibly port the meshless solver from CPU to GPU. Considering the data locality of randomly distributed points, space-filling curves are adopted to re-number the points in order to improve the memory performance. Detailed evaluations are firstly carried out to assess the accuracy and conservation property of the underlying numerical method. Then the GPU accelerated flow solver is used to solve external steady flows over aerodynamic configurations. Representative results are validated through extensive comparisons with the experimental, finite volume or other available reference solutions. Performance analysis reveals that the running time cost of simulations is significantly reduced while impressive (more than an order of magnitude) speedups are achieved.
MPSalsa a finite element computer program for reacting flow problems. Part 2 - user`s guide
Salinger, A.; Devine, K.; Hennigan, G.; Moffat, H. [and others
1996-09-01
This manual describes the use of MPSalsa, an unstructured finite element (FE) code for solving chemically reacting flow problems on massively parallel computers. MPSalsa has been written to enable the rigorous modeling of the complex geometry and physics found in engineering systems that exhibit coupled fluid flow, heat transfer, mass transfer, and detailed reactions. In addition, considerable effort has been made to ensure that the code makes efficient use of the computational resources of massively parallel (MP), distributed memory architectures in a way that is nearly transparent to the user. The result is the ability to simultaneously model both three-dimensional geometries and flow as well as detailed reaction chemistry in a timely manner on MT computers, an ability we believe to be unique. MPSalsa has been designed to allow the experienced researcher considerable flexibility in modeling a system. Any combination of the momentum equations, energy balance, and an arbitrary number of species mass balances can be solved. The physical and transport properties can be specified as constants, as functions, or taken from the Chemkin library and associated database. Any of the standard set of boundary conditions and source terms can be adapted by writing user functions, for which templates and examples exist.
Wang W
2016-12-01
Full Text Available Wei Wang, Mengshuang Xie, Shuang Dou, Liwei Cui, Wei Xiao Department of Pulmonary Medicine, Qilu Hospital, Shandong University, Jinan, People’s Republic of China Background: In a previous study, we demonstrated that asthma patients with signs of emphysema on quantitative computed tomography (CT fulfill the diagnosis of asthma-COPD overlap syndrome (ACOS. However, quantitative CT measurements of emphysema are not routinely available for patients with chronic airway disease, which limits their application. Spirometry was a widely used examination tool in clinical settings and shows emphysema as a sharp angle in the maximum expiratory flow volume (MEFV curve, called the “angle of collapse (AC”. The aim of this study was to investigate the value of the AC in the diagnosis of emphysema and ACOS. Methods: This study included 716 participants: 151 asthma patients, 173 COPD patients, and 392 normal control subjects. All the participants underwent pulmonary function tests. COPD and asthma patients also underwent quantitative CT measurements of emphysema. The AC was measured using computer models based on Matlab software. The value of the AC in the diagnosis of emphysema and ACOS was evaluated using receiver-operating characteristic (ROC curve analysis. Results: The AC of COPD patients was significantly lower than that of asthma patients and control subjects. The AC was significantly negatively correlated with emphysema index (EI; r=-0.666, P<0.001, and patients with high EI had a lower AC than those with low EI. The ROC curve analysis showed that the AC had higher diagnostic efficiency for high EI (area under the curve =0.876 than did other spirometry parameters. In asthma patients, using the AC ≤137° as a surrogate criterion for the diagnosis of ACOS, the sensitivity and specificity were 62.5% and 89.1%, respectively. Conclusion: The AC on the MEFV curve quantified by computer models correlates with the extent of emphysema. The AC may become a
咸爱勇; 朱大铭
2015-01-01
合取范式可满足与最大可满足问题是理论计算机科学的核心问题．最大不全满足问题是最大可满足问题的一般化．限制每个子句均含有 k（2）个字母的最大不全满足问题又称为最大不全 k 满足问题．最大不全满足问题的算法进展，以解答该类问题的半定规划松弛法最具代表性．关于最大不全2满足、3满足和4满足问题，目前性能最好的近似算法分别由Goemans 与 Williamson、Zwick、Karloff 与 Zwick 给出，近似性能比分别为1．139（1／0．878）、1．10047（1／0．9087）和8／7．当 k5时，最大不全 k 满足问题的近似算法则未曾见到．文中给出了一个解答最大不全k 满足问题的局部搜索算法，近似性能比可达到2k －1／（2k －1－1），k 2；进一步将该方法推广到解答由不少于 k 个字母的子句构成的最大不全k 满足问题，近似性能比亦可达到2k －1／（2k －1－1）．利用解答最大不全 k 满足问题的近似算法，给出了解答最大 k 可满足问题的新近似算法，近似性能比可达到2k／（2k －1）．文中最后证明了若 P≠NP，则 k4的最大不全 k 满足问题不能近似到小于2k －1／（2k －1－1），从而说明文中解答最大不全 k 满足问题的算法近似性能比是最优的．%The satisfiability problem as well as the maximum satisfiability problem of conjunctive norm forms are the central problems in theoretical computer science.The maximum not-all-equal satisfiability problem is a generalization of the maximum satisfiability problem.The maximum not-all-equal satisfiability problem is named maximum not-all-equal k satisfiability problem,if each clause of its instance contains k (2)literals.Semi-definite programming relaxation is the frequently-used also the most typical method for solving the maximum not-all-equal satisfiability problems.To our knowledge at present,the best algorithms for
Min Dai
2013-01-01
Full Text Available A flexible flow-shop scheduling (FFS with nonidentical parallel machines for minimizing the maximum completion time or makespan is a well-known combinational problem. Since the problem is known to be strongly NP-hard, optimization can either be the subject of optimization approaches or be implemented for some approximated cases. In this paper, an improved genetic-simulated annealing algorithm (IGAA, which combines genetic algorithm (GA based on an encoding matrix with simulated annealing algorithm (SAA based on a hormone modulation mechanism, is proposed to achieve the optimal or near-optimal solution. The novel hybrid algorithm tries to overcome the local optimum and further to explore the solution space. To evaluate the performance of IGAA, computational experiments are conducted and compared with results generated by different algorithms. Experimental results clearly demonstrate that the improved metaheuristic algorithm performs considerably well in terms of solution quality, and it outperforms several other algorithms.
Kaiadi, Mehrzad; Tunestål, Per; Johansson, Bengt
2010-01-01
High EGR rates combined with turbocharging has been identified as a promising way to increase the maximum load and efficiency of heavy duty spark ignition Natural Gas engines. With stoichiometric conditions a three way catalyst can be used which means that regulated emissions can be kept at very low levels. Most of the heavy duty NG engines are diesel engines which are converted for SI operation. These engine's components are in common with the diesel-engine which put limits on higher exh...
A COMBINATORIAL PROPERTY OF PALLET-CONSTRAINED TWO MACHINE FLOW SHOP PROBLEM IN MINIMIZING MAKESPAN
HOU Sixiang; Han Hoogeveen; Petra Schuurman
2002-01-01
We consider the problem of scheduling n jobs in a pallet-constrained flowshop so as to minimize the makespan. In such a flow shop environment, each job needs apallet the entire time, from the start of its first operation until the completion of the lastoperation, and the number of pallets in the shop at any given time is limited by a positiveinteger K ≤ n. Generally speaking, the optimal schedules may be passing schedules. In thispaper, we present a combinatorial property which shows that for two machines, K(K ≥ 3)pallets, there exists a no-passing schedule which is an optimal schedule for n ≤ 2K - 1 and2K - 1 is tight.
Applications of Quantum Theory of Atomic and Molecular Scattering to Problems in Hypersonic Flow
Malik, F. Bary
1995-01-01
The general status of a grant to investigate the applications of quantum theory in atomic and molecular scattering problems in hypersonic flow is summarized. Abstracts of five articles and eleven full-length articles published or submitted for publication are included as attachments. The following topics are addressed in these articles: fragmentation of heavy ions (HZE particles); parameterization of absorption cross sections; light ion transport; emission of light fragments as an indicator of equilibrated populations; quantum mechanical, optical model methods for calculating cross sections for particle fragmentation by hydrogen; evaluation of NUCFRG2, the semi-empirical nuclear fragmentation database; investigation of the single- and double-ionization of He by proton and anti-proton collisions; Bose-Einstein condensation of nuclei; and a liquid drop model in HZE particle fragmentation by hydrogen.
Elsheikh, Ahmed H., E-mail: aelsheikh@ices.utexas.edu [Institute for Computational Engineering and Sciences (ICES), University of Texas at Austin, TX (United States); Institute of Petroleum Engineering, Heriot-Watt University, Edinburgh EH14 4AS (United Kingdom); Wheeler, Mary F. [Institute for Computational Engineering and Sciences (ICES), University of Texas at Austin, TX (United States); Hoteit, Ibrahim [Department of Earth Sciences and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal (Saudi Arabia)
2014-02-01
A Hybrid Nested Sampling (HNS) algorithm is proposed for efficient Bayesian model calibration and prior model selection. The proposed algorithm combines, Nested Sampling (NS) algorithm, Hybrid Monte Carlo (HMC) sampling and gradient estimation using Stochastic Ensemble Method (SEM). NS is an efficient sampling algorithm that can be used for Bayesian calibration and estimating the Bayesian evidence for prior model selection. Nested sampling has the advantage of computational feasibility. Within the nested sampling algorithm, a constrained sampling step is performed. For this step, we utilize HMC to reduce the correlation between successive sampled states. HMC relies on the gradient of the logarithm of the posterior distribution, which we estimate using a stochastic ensemble method based on an ensemble of directional derivatives. SEM only requires forward model runs and the simulator is then used as a black box and no adjoint code is needed. The developed HNS algorithm is successfully applied for Bayesian calibration and prior model selection of several nonlinear subsurface flow problems.
Scheduling of flow shop problems on 3 machines in fuzzy environment with double transport facility
Sathish, Shakeela; Ganesan, K.
2016-06-01
Flow shop scheduling is a decision making problem in production and manufacturing field which has a significant impact on the performance of an organization. When the machines on which jobs are to be processed are placed at different places, the transportation time plays a significant role in production. Further two different transport agents where 1st takes the job from 1st machine to 2nd machine and then returns back to the first machine and the 2nd takes the job from 2nd machine to 3rd machine and then returns back to the 2nd machine are also considered. We propose a method to minimize the total make span; without converting the fuzzy processing time to classical numbers by using a new type of fuzzy arithmetic and a fuzzy ranking method. A numerical example is provided to explain the proposed method.
F. M. T. Supriyanti
2015-04-01
Full Text Available The purpose of this research was to determine the implementation of the IDEAL (Identify, Define, Explore, Anticipat and Act, Looking Back and Learn problem solving model of Bransford (1998 on the lecture material flow of genetic information, its influence on the mastery of conceps. The method uses quasi-experimental research with pretest-posttest nonequivalent control design. The results of the research show that : (1 the lecture model of problem solving IDEAL on the material flow of genetic information can implemented very well in each stage; (2 had a significant influence on student mastery of concepts; (3 in each of the indicators developed, the experimental class, it is known that the lectures with a problem-solving model of the flow of information on the subject of genetically high yield category on several indicators; (4 gives effect to the problem solving ability of students.
Metin I Eren
Full Text Available BACKGROUND: Estimating assemblage species or class richness from samples remains a challenging, but essential, goal. Though a variety of statistical tools for estimating species or class richness have been developed, they are all singly-bounded: assuming only a lower bound of species or classes. Nevertheless there are numerous situations, particularly in the cultural realm, where the maximum number of classes is fixed. For this reason, a new method is needed to estimate richness when both upper and lower bounds are known. METHODOLOGY/PRINCIPAL FINDINGS: Here, we introduce a new method for estimating class richness: doubly-bounded confidence intervals (both lower and upper bounds are known. We specifically illustrate our new method using the Chao1 estimator, rarefaction, and extrapolation, although any estimator of asymptotic richness can be used in our method. Using a case study of Clovis stone tools from the North American Lower Great Lakes region, we demonstrate that singly-bounded richness estimators can yield confidence intervals with upper bound estimates larger than the possible maximum number of classes, while our new method provides estimates that make empirical sense. CONCLUSIONS/SIGNIFICANCE: Application of the new method for constructing doubly-bound richness estimates of Clovis stone tools permitted conclusions to be drawn that were not otherwise possible with singly-bounded richness estimates, namely, that Lower Great Lakes Clovis Paleoindians utilized a settlement pattern that was probably more logistical in nature than residential. However, our new method is not limited to archaeological applications. It can be applied to any set of data for which there is a fixed maximum number of classes, whether that be site occupancy models, commercial products (e.g. athletic shoes, or census information (e.g. nationality, religion, age, race.
He, Xinguang; Ren, Li
2009-07-01
SummaryIn this paper we present an adaptive multiscale finite element method for solving the unsaturated water flow problems in heterogeneous porous media spanning over many scales. The main purpose is to design a numerical method which is capable of adaptively capturing the large-scale behavior of the solution on a coarse-scale mesh without resolving all the small-scale details at each time step. This is accomplished by constructing the multiscale base functions that are adapted to the time change of the unsaturated hydraulic conductivity field. The key idea of our method is to use a criterion based on the temporal variation of the hydraulic conductivity field to determine when and where to update our multiscale base functions. As a consequence, these base functions are able to dynamically account for the spatio-temporal variability in the equation coefficients. We described the principle for constructing such a method in detail and gave an algorithm for implementing it. Numerical experiments were carried out for the unsaturated water flow equation with randomly generated lognormal hydraulic parameters to demonstrate the efficiency and accuracy of the proposed method. The results show that throughout the adaptive simulation, only a very small fraction of the multiscale base functions needs to be recomputed, and the level of accuracy of the adaptive method is higher than that of the multiscale finite element technique in which the base functions are not updated with the time change of the hydraulic conductivity.
Some free boundary problems in potential flow regime usinga based level set method
Garzon, M.; Bobillo-Ares, N.; Sethian, J.A.
2008-12-09
Recent advances in the field of fluid mechanics with moving fronts are linked to the use of Level Set Methods, a versatile mathematical technique to follow free boundaries which undergo topological changes. A challenging class of problems in this context are those related to the solution of a partial differential equation posed on a moving domain, in which the boundary condition for the PDE solver has to be obtained from a partial differential equation defined on the front. This is the case of potential flow models with moving boundaries. Moreover the fluid front will possibly be carrying some material substance which will diffuse in the front and be advected by the front velocity, as for example the use of surfactants to lower surface tension. We present a Level Set based methodology to embed this partial differential equations defined on the front in a complete Eulerian framework, fully avoiding the tracking of fluid particles and its known limitations. To show the advantages of this approach in the field of Fluid Mechanics we present in this work one particular application: the numerical approximation of a potential flow model to simulate the evolution and breaking of a solitary wave propagating over a slopping bottom and compare the level set based algorithm with previous front tracking models.
Hybrid water flow-like algorithm with Tabu search for traveling salesman problem
Bostamam, Jasmin M.; Othman, Zulaiha
2016-08-01
This paper presents a hybrid Water Flow-like Algorithm with Tabu Search for solving travelling salesman problem (WFA-TS-TSP).WFA has been proven its outstanding performances in solving TSP meanwhile TS is a conventional algorithm which has been used since decades to solve various combinatorial optimization problem including TSP. Hybridization between WFA with TS provides a better balance of exploration and exploitation criteria which are the key elements in determining the performance of one metaheuristic. TS use two different local search namely, 2opt and 3opt separately. The proposed WFA-TS-TSP is tested on 23 sets on the well-known benchmarked symmetric TSP instances. The result shows that the proposed WFA-TS-TSP has significant better quality solutions compared to WFA. The result also shows that the WFA-TS-TSP with 3-opt obtained the best quality solution. With the result obtained, it could be concluded that WFA has potential to be further improved by using hybrid technique or using better local search technique.
The use of wavelet transforms in the solution of two-phase flow problems
Moridis, G.J. [Lawrence Berkeley Lab., CA (United States); Nikolaou, M.; You, Yong [Texas A& M Univ., College Station, TX (United States). Dept. of Chemical Engineering
1994-10-01
In this paper we present the use of wavelets to solve the nonlinear Partial Differential.Equation (PDE) of two-phase flow in one dimension. The wavelet transforms allow a drastically different approach in the discretization of space. In contrast to the traditional trigonometric basis functions, wavelets approximate a function not by cancellation but by placement of wavelets at appropriate locations. When an abrupt chance, such as a shock wave or a spike, occurs in a function, only local coefficients in a wavelet approximation will be affected. The unique feature of wavelets is their Multi-Resolution Analysis (MRA) property, which allows seamless investigational any spatial resolution. The use of wavelets is tested in the solution of the one-dimensional Buckley-Leverett problem against analytical solutions and solutions obtained from standard numerical models. Two classes of wavelet bases (Daubechies and Chui-Wang) and two methods (Galerkin and collocation) are investigated. We determine that the Chui-Wang, wavelets and a collocation method provide the optimum wavelet solution for this type of problem. Increasing the resolution level improves the accuracy of the solution, but the order of the basis function seems to be far less important. Our results indicate that wavelet transforms are an effective and accurate method which does not suffer from oscillations or numerical smearing in the presence of steep fronts.
On the modelling of compressible inviscid flow problems using AUSM schemes
Hajžman M.
2007-11-01
Full Text Available During last decades, upwind schemes have become a popular method in the field of computational fluid dynamics. Although they are only first order accurate, AUSM (Advection Upstream Splitting Method schemes proved to be well suited for modelling of compressible flows due to their robustness and ability of capturing shock discontinuities. In this paper, we review the composition of the AUSM flux-vector splitting scheme and its improved version noted AUSM+, proposed by Liou, for the solution of the Euler equations. Mach number splitting functions operating with values from adjacent cells are used to determine numerical convective fluxes and pressure splitting is used for the evaluation of numerical pressure fluxes. Both versions of the AUSM scheme are applied for solving some test problems such as one-dimensional shock tube problem and three dimensional GAMM channel. Features of the schemes are discussed in comparison with some explicit central schemes of the first order accuracy (Lax-Friedrichs and of the second order accuracy (MacCormack.
Analytical solution to the circularity problem in the discounted cash flow valuation framework
Felipe Mejía-Peláez
2011-12-01
Full Text Available In this paper we propose an analytical solution to the circularity problem between value and cost of capital. Our solution is derived starting from a central principle of finance that relates value today to value, cash flow, and the discount rate for next period. We present a general formulation without circularity for the equity value (E, cost of levered equity (Ke, levered firm value (V, and the weighted average cost of capital (WACC. We furthermore compare the results obtained from these formulas with the results of the application of the Adjusted Present Value approach (no circularity and the iterative solution of circularity based upon the iteration feature of a spreadsheet, concluding that all methods yield exactly the same answer. The advantage of this solution is that it avoids problems such as using manual methods (i.e., the popular “Rolling WACC” ignoring the circularity issue, setting a target leverage (usually constant with the inconsistencies that result from it, the wrong use of book values, or attributing the discrepancies in values to rounding errors.
Analysis of the turbulent flow field in a spherically convergent implosion problem
Boureima, Ismael; Ramaprabhu, Praveen; Attal, Nitesh
2016-11-01
We describe results from 3D, numerical simulations of a spherically convergent, implosion problem. The problem definition follows, and involves a time-dependent pressure drive that sustains the implosion of an interface in a slow-fast configuration. The simulations are performed within a spherical wedge, where the interface is initialized with multimode perturbations leading to turbulent flow. The initial stages of the implosion are dominated by the Richtymer-Meshkov (RM) instability, while the late stages involve a stagnation phase interspersed with reshocks during which both RM and Rayleigh-Taylor (RT) instabilities are observed. The simulations were performed with the FLASH code, with a mesh resolution corresponding to 512x512 zones in the (θ, ϕ) directions, and proportional gridding in the r-direction. We report on several quantities that could provide insights in to the evaluation of turbulence models including the turbulent kinetic energy, anisotropy tensor, density self-correlation, and atomic mixing among others. This work was supported in part by the (U.S.) Department of Energy (DOE) under Contract No. DE-AC52-06NA2-5396.
Xu, Ye; Wang, Ling; Wang, Shengyao; Liu, Min
2014-09-01
In this article, an effective hybrid immune algorithm (HIA) is presented to solve the distributed permutation flow-shop scheduling problem (DPFSP). First, a decoding method is proposed to transfer a job permutation sequence to a feasible schedule considering both factory dispatching and job sequencing. Secondly, a local search with four search operators is presented based on the characteristics of the problem. Thirdly, a special crossover operator is designed for the DPFSP, and mutation and vaccination operators are also applied within the framework of the HIA to perform an immune search. The influence of parameter setting on the HIA is investigated based on the Taguchi method of design of experiment. Extensive numerical testing results based on 420 small-sized instances and 720 large-sized instances are provided. The effectiveness of the HIA is demonstrated by comparison with some existing heuristic algorithms and the variable neighbourhood descent methods. New best known solutions are obtained by the HIA for 17 out of 420 small-sized instances and 585 out of 720 large-sized instances.
A hybrid flow shop model for an ice cream production scheduling problem
Imma Ribas Vila
2009-07-01
Full Text Available Normal 0 21 false false false ES X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Taula normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman","serif";} In this paper we address the scheduling problem that comes from an ice cream manufacturing company. This production system can be modelled as a three stage nowait hybrid flow shop with batch dependent setup costs. To contribute reducing the gap between theory and practice we have considered the real constraints and the criteria used by planners. The problem considered has been formulated as a mixed integer programming. Further, two competitive heuristic procedures have been developed and one of them will be proposed to schedule in the ice cream factory.
Liling Sun
2015-01-01
Full Text Available An improved multiobjective ABC algorithm based on K-means clustering, called CMOABC, is proposed. To fasten the convergence rate of the canonical MOABC, the way of information communication in the employed bees’ phase is modified. For keeping the population diversity, the multiswarm technology based on K-means clustering is employed to decompose the population into many clusters. Due to each subcomponent evolving separately, after every specific iteration, the population will be reclustered to facilitate information exchange among different clusters. Application of the new CMOABC on several multiobjective benchmark functions shows a marked improvement in performance over the fast nondominated sorting genetic algorithm (NSGA-II, the multiobjective particle swarm optimizer (MOPSO, and the multiobjective ABC (MOABC. Finally, the CMOABC is applied to solve the real-world optimal power flow (OPF problem that considers the cost, loss, and emission impacts as the objective functions. The 30-bus IEEE test system is presented to illustrate the application of the proposed algorithm. The simulation results demonstrate that, compared to NSGA-II, MOPSO, and MOABC, the proposed CMOABC is superior for solving OPF problem, in terms of optimization accuracy.
Prosperetti, A.; Wijngaarden, van L.
1976-01-01
For the study of transients in gas-liquid flows, the equations of the so-called separated flow model are inadequate, because they possess, in the general case where gas and liquid move at different velocities, complex characteristics. This paper is concerned with the equations of motion for bubbly f
Denisov, S. L.; Korolkov, A. I.
2017-07-01
A study of the phenomenon of diffraction of acoustic waves in application to the task of noise shielding by the method of maximum length sequences has been carried out. Rectangular plates and an aircraft model of integrated layout are used as the screens. In the study of noise shielding by aircraft model, the theorem of reciprocity is used. A comparison of experimental results with calculations performed in the framework of the geometrical theory of diffraction (GTD) is performed. On the basis of calculations, the identification of the contributions from different areas of the shielding surface in the full acoustic field is carried out. For the aircraft model, the shielding factor is calculated depending on the frequency.
T. Karpagam
2012-01-01
Full Text Available Problem statement: Network topology design problems find application in several real life scenario. Approach: Most designs in the past either optimize for a single criterion like shortest or cost minimization or maximum flow. Results: This study discussed about solving a multi objective network topology design problem for a realistic traffic model specifically in the pipeline transportation. Here flow based algorithm focusing to transport liquid goods with maximum capacity with shortest distance, this algorithm developed with the sense of basic pert and critical path method. Conclusion/Recommendations: This flow based algorithm helps to give optimal result for transporting maximum capacity with minimum cost. It could be used in the juice factory, milk industry and its best alternate for the vehicle routing problem.
Lahimer, Asma; Haouari, Mohamed
2011-01-01
This paper considers multiprocessor task scheduling in a multistage hybrid flow-shop environment. The problem even in its simplest form is NP-hard in the strong sense. The great deal of interest for this problem, besides its theoretical complexity, is animated by needs of various manufacturing and computing systems. We propose a new approach based on limited discrepancy search to solve the problem. Our method is tested with reference to a proposed lower bound as well as the best-known solutions in literature. Computational results show that the developed approach is efficient in particular for large-size problems.
Petra, N.; Alexanderian, A.; Stadler, G.; Ghattas, O.
2015-12-01
We address the problem of optimal experimental design (OED) for Bayesian nonlinear inverse problems governed by partial differential equations (PDEs). The inverse problem seeks to infer a parameter field (e.g., the log permeability field in a porous medium flow model problem) from synthetic observations at a set of sensor locations and from the governing PDEs. The goal of the OED problem is to find an optimal placement of sensors so as to minimize the uncertainty in the inferred parameter field. We formulate the OED objective function by generalizing the classical A-optimal experimental design criterion using the expected value of the trace of the posterior covariance. This expected value is computed through sample averaging over the set of likely experimental data. Due to the infinite-dimensional character of the parameter field, we seek an optimization method that solves the OED problem at a cost (measured in the number of forward PDE solves) that is independent of both the parameter and the sensor dimension. To facilitate this goal, we construct a Gaussian approximation to the posterior at the maximum a posteriori probability (MAP) point, and use the resulting covariance operator to define the OED objective function. We use randomized trace estimation to compute the trace of this covariance operator. The resulting OED problem includes as constraints the system of PDEs characterizing the MAP point, and the PDEs describing the action of the covariance (of the Gaussian approximation to the posterior) to vectors. We control the sparsity of the sensor configurations using sparsifying penalty functions, and solve the resulting penalized bilevel optimization problem via an interior-point quasi-Newton method, where gradient information is computed via adjoints. We elaborate our OED method for the problem of determining the optimal sensor configuration to best infer the log permeability field in a porous medium flow problem. Numerical results show that the number of PDE
Karsten, Christian Vad; Pisinger, David; Røpke, Stefan
The liner shipping network design problem has proven to be hard to solve. However, well-designed route nets are paramount to liner shipping companies both in terms of competitiveness and environmental impact. Fast evaluations of the multicommodity flow subproblem is one of the bottlenecks when...... determining the optimal routing and fleet deployment in the network design problem. Additionally, most existing models do not consider the level of service. To accommodate that, we present an algorithm for solving the multicommodity flow subproblem with limits on commodity travel time....
Karsten, Christian Vad; Pisinger, David; Røpke, Stefan
The liner shipping network design problem has proven to be hard to solve. However, well-designed route nets are paramount to liner shipping companies both in terms of competitiveness and environmental impact. Fast evaluations of the multicommodity flow subproblem is one of the bottlenecks when...... determining the optimal routing and fleet deployment in the network design problem. Additionally, most existing models do not consider the level of service. To accommodate that, we present an algorithm for solving the multicommodity flow subproblem with limits on commodity travel time....
Bai Jing-Song; Zhang Zhan-Ji; Li Ping; Zhong Min
2006-01-01
Based on the classical Roe method, we develop an interface capture method according to the general equation of state, and extend the single-fluid Roe method to the two-dimensional (2D) multi-fluid flows, as well as construct the continuous Roe matrix for the whole flow field. The interface capture equations and fluid dynamic conservative equations are coupled together and solved by using any high-resolution schemes that usually suit for the single-fluid flows. Some numerical examples are given to illustrate the solution of 1D and 2D multi-fluid Riemann problems.
H Dattu; M Subbiah
2015-09-01
We consider the linear stability problem of inviscid, incompressible swirling flows with radius-dependent density with respect to two-dimensional disturbances. Some results of Miles on the parallel flow stability theory are extended to the swirling flow stability theory. In particular, series solutions for the stability equation for swirling flows are obtained and these solutions are used in the study of the variation of the Reynolds stress. For singular neutral modes it is shown that the Reynolds stress varies like the inverse square of the radial distance in agreement with the homogeneous flow result of Maslowe & Nigam. It is also proved that singular neutral modes do not exist whenever the value of the Richardson number at the critical layer exceeds one quarter.
Traffic Management as a Service: The Traffic Flow Pattern Classification Problem
Carlos T. Calafate
2015-01-01
Full Text Available Intelligent Transportation System (ITS technologies can be implemented to reduce both fuel consumption and the associated emission of greenhouse gases. However, such systems require intelligent and effective route planning solutions to reduce travel time and promote stable traveling speeds. To achieve such goal these systems should account for both estimated and real-time traffic congestion states, but obtaining reliable traffic congestion estimations for all the streets/avenues in a city for the different times of the day, for every day in a year, is a complex task. Modeling such a tremendous amount of data can be time-consuming and, additionally, centralized computation of optimal routes based on such time-dependencies has very high data processing requirements. In this paper we approach this problem through a heuristic to considerably reduce the modeling effort while maintaining the benefits of time-dependent traffic congestion modeling. In particular, we propose grouping streets by taking into account real traces describing the daily traffic pattern. The effectiveness of this heuristic is assessed for the city of Valencia, Spain, and the results obtained show that it is possible to reduce the required number of daily traffic flow patterns by a factor of 4210 while maintaining the essence of time-dependent modeling requirements.
Elsheikh, Ahmed H.
2014-02-01
A Hybrid Nested Sampling (HNS) algorithm is proposed for efficient Bayesian model calibration and prior model selection. The proposed algorithm combines, Nested Sampling (NS) algorithm, Hybrid Monte Carlo (HMC) sampling and gradient estimation using Stochastic Ensemble Method (SEM). NS is an efficient sampling algorithm that can be used for Bayesian calibration and estimating the Bayesian evidence for prior model selection. Nested sampling has the advantage of computational feasibility. Within the nested sampling algorithm, a constrained sampling step is performed. For this step, we utilize HMC to reduce the correlation between successive sampled states. HMC relies on the gradient of the logarithm of the posterior distribution, which we estimate using a stochastic ensemble method based on an ensemble of directional derivatives. SEM only requires forward model runs and the simulator is then used as a black box and no adjoint code is needed. The developed HNS algorithm is successfully applied for Bayesian calibration and prior model selection of several nonlinear subsurface flow problems. © 2013 Elsevier Inc.
Parallel genetic algorithms with migration for the hybrid flow shop scheduling problem
K. Belkadi
2006-01-01
Full Text Available This paper addresses scheduling problems in hybrid flow shop-like systems with a migration parallel genetic algorithm (PGA_MIG. This parallel genetic algorithm model allows genetic diversity by the application of selection and reproduction mechanisms nearer to nature. The space structure of the population is modified by dividing it into disjoined subpopulations. From time to time, individuals are exchanged between the different subpopulations (migration. Influence of parameters and dedicated strategies are studied. These parameters are the number of independent subpopulations, the interconnection topology between subpopulations, the choice/replacement strategy of the migrant individuals, and the migration frequency. A comparison between the sequential and parallel version of genetic algorithm (GA is provided. This comparison relates to the quality of the solution and the execution time of the two versions. The efficiency of the parallel model highly depends on the parameters and especially on the migration frequency. In the same way this parallel model gives a significant improvement of computational time if it is implemented on a parallel architecture which offers an acceptable number of processors (as many processors as subpopulations.
Heemstra de Groot, S.M.; Herrmann, O.E.
1990-01-01
An algorithm based on an alternative scheduling approach for iterative acyclic and cyclid DFGs (data-flow graphs) with limited resources that exploits inter- and intra-iteration parallelism is presented. The method is based on guiding the scheduling algorithm with the information supplied by a
Regularized maximum correntropy machine
Wang, Jim Jing-Yan
2015-02-12
In this paper we investigate the usage of regularized correntropy framework for learning of classifiers from noisy labels. The class label predictors learned by minimizing transitional loss functions are sensitive to the noisy and outlying labels of training samples, because the transitional loss functions are equally applied to all the samples. To solve this problem, we propose to learn the class label predictors by maximizing the correntropy between the predicted labels and the true labels of the training samples, under the regularized Maximum Correntropy Criteria (MCC) framework. Moreover, we regularize the predictor parameter to control the complexity of the predictor. The learning problem is formulated by an objective function considering the parameter regularization and MCC simultaneously. By optimizing the objective function alternately, we develop a novel predictor learning algorithm. The experiments on two challenging pattern classification tasks show that it significantly outperforms the machines with transitional loss functions.
Yousfi, Ammar; Mechergui, Mohammed
2016-04-01
al. (2001). In this work, a novel solution based on theoretical approach will be adapted to incorporate both the seepage face and the unsaturated zone flow contribution for solving ditch drained aquifers problems. This problem will be tackled on the basis of the approximate 2D solution given by Castro-Orgaz et al. (2012). This given solution yields the generalized water table profile function with a suitable boundary condition to be determined and provides a modified DF theory which permits as an outcome the analytical determination of the seepage face. To assess the ability of the developed equation for water-table estimations, the obtained results were compared with numerical solutions to the 2-D problem under different conditions. It is shown that results are in fair agreement and thus the resulting model can be used for designing ditch drainage systems. With respect to drainage design, the spacings calculated with the newly derived equation are compared with those computed from the DF theory. It is shown that the effect of the unsaturated zone flow contribution is limited to sandy soils and The calculated maximum increase in drain spacing is about 30%. Keywords: subsurface ditch drainage; unsaturated zone; seepage face; water-table, ditch spacing equation
Richard W. Johnson; Hugh M. McIlroy
2010-08-01
The U. S. Department of Energy (DOE) is supporting the development of a next generation nuclear plant (NGNP), which will be based on a very high temperature reactor (VHTR) design. The VHTR is a single-phase helium-cooled reactor wherein the helium will be heated initially to 750 °C and later to temperatures approaching 1000 °C. The high temperatures are desired to increase reactor efficiency and to provide a heat source for the manufacture of hydrogen and other applications. While computational fluid dynamics (CFD) has not been used in the past to design or license nuclear reactors in the U. S., it is expected that CFD will be used in the design and safety analysis of forthcoming designs. This is partly because of the maturity of CFD and partly because detailed information is desired of the flow and heat transfer inside the reactor to avoid hot spots and other conditions that might compromise reactor safety. Numerical computations of turbulent flow should be validated against experimental data for flow conditions that contain some or all of the physics expected in the thermal fluid machinery of interest. To this end, a scaled model of a narrow slice of the lower plenum of the prismatic VHTR was constructed and installed in the Idaho National Laboratory’s (INL) matched index of refraction (MIR) test facility and data were taken. The data were then studied and compared to CFD calculations to help determine their suitability for validation data. One of the main findings was that the inlet data, which were measured and controlled by calibrated mass flow rotameters and were also measured using detailed stereo particle image velocimetry (PIV) showed considerable discrepancies in mass flow rate between the two methods. The other finding was that a randomly unstable recirculation zone occurs in the flow. This instability has a very significant effect on the flow field in the vicinity of the inlet jets. Because its time scale is long and because it is apparently a
A parallel, state-of-the-art, least-squares spectral element solver for incompressible flow problems
Nool, M.; Proot, M.M.J.
2003-01-01
The paper deals with the efficient parallelization of least-squares spectral element methods for incompressible flows. The parallelization of this sort of problems requires two different strategies. On the one hand, the spectral element discretization benefits from an element-by-element paralleli
SAHADEB KUILA; T RAJA SEKHAR; G C SHIT
2016-09-01
In this paper, we consider the Riemann problem for a five-equation, two-pressure (5E2P) model proposed by Ransom and Hicks for an isentropic compressible gas–liquid two-phase flows. The model is given by a strictly hyperbolic, non-conservative system of five partial differential equations (PDEs). We investigate the structure of the Riemann problem and construct an approximate solution for it. We solve the Riemann problemfor this model approximately assuming that all waves corresponding to the genuinely nonlinear characteristic fields are rarefaction and discuss their properties. To verify the solver, a series of test problems selected from the literature are presented.
Tao Ren
2014-01-01
Full Text Available We address the scheduling problem for a no-wait flow shop to optimize total completion time with release dates. With the tool of asymptotic analysis, we prove that the objective values of two SPTA-based algorithms converge to the optimal value for sufficiently large-sized problems. To further enhance the performance of the SPTA-based algorithms, an improvement scheme based on local search is provided for moderate scale problems. New lower bound is presented for evaluating the asymptotic optimality of the algorithms. Numerical simulations demonstrate the effectiveness of the proposed algorithms.
Multilevel markov chain monte carlo method for high-contrast single-phase flow problems
Efendiev, Yalchin R.
2014-12-19
In this paper we propose a general framework for the uncertainty quantification of quantities of interest for high-contrast single-phase flow problems. It is based on the generalized multiscale finite element method (GMsFEM) and multilevel Monte Carlo (MLMC) methods. The former provides a hierarchy of approximations of different resolution, whereas the latter gives an efficient way to estimate quantities of interest using samples on different levels. The number of basis functions in the online GMsFEM stage can be varied to determine the solution resolution and the computational cost, and to efficiently generate samples at different levels. In particular, it is cheap to generate samples on coarse grids but with low resolution, and it is expensive to generate samples on fine grids with high accuracy. By suitably choosing the number of samples at different levels, one can leverage the expensive computation in larger fine-grid spaces toward smaller coarse-grid spaces, while retaining the accuracy of the final Monte Carlo estimate. Further, we describe a multilevel Markov chain Monte Carlo method, which sequentially screens the proposal with different levels of approximations and reduces the number of evaluations required on fine grids, while combining the samples at different levels to arrive at an accurate estimate. The framework seamlessly integrates the multiscale features of the GMsFEM with the multilevel feature of the MLMC methods following the work in [26], and our numerical experiments illustrate its efficiency and accuracy in comparison with standard Monte Carlo estimates. © Global Science Press Limited 2015.
Peres, A.M.M.; Serra, K.V. (PETROBRAS, Rio de Janeiro, RJ (Brazil)); Reynolds, A.C. (Tulsa Univ., OK (USA))
1990-06-01
This work presents an analytical solution for the pseudopressure function that represents the reservoir and wellbore responses resulting from production at a constant oil rate in a solution-gas-drive reservoir. The solution can also be reduced to obtain the analytical solution for the corresponding single-phase-flow problem. The general analytical solution suggests a new definition for the dimensionless flow rate. The analytical solutionis used to construct new type curves for analysis of interference tests conducted under multiphase-flow conditions. It is shown that if one ignores multiphase-flow effects and analyze interference data with the line-source-solution type curve, then the estimates of the permeability and porosity-compressibility product obtained may be in error by 20 to 40%.
Yekini Shehu
2010-01-01
real Banach space which is also uniformly smooth using the properties of generalized f-projection operator. Using this result, we discuss strong convergence theorem concerning general H-monotone mappings and system of generalized mixed equilibrium problems in Banach spaces. Our results extend many known recent results in the literature.
A Robust volume conservative divergence-free ISPH framework for free-surface flow problems
Pahar, Gourabananda; Dhar, Anirban
2016-10-01
This study presents a Volume Conservative approach for resolving volume conservation issue in divergence-free incompressible Smoothed Particle Hydrodynamics (ISPH). Irregular free surface deformation may introduce error in volume computation, which has a cascading effect over time. Proposed correction decreases this numerical compressibility to a minimal value. The correction is obtained directly by solving Navier-Stokes momentum equation. Consequently, the framework does not require any parametric study for mixed source/sink term or iterative solution of pressure Poisson equations. The correction is implemented on four different types of flow: (a) pressurized flow in a closed box, (b) dambreak flow, (c) flow through porous block, (d) lock-exchange flow of immiscible fluids (both free-surface and pressurized flow). All four scenarios are shown to have minimal error compared to pure divergence-free ISPH.
Reduced Gravity Gas and Liquid Flows: Simple Data for Complex Problems
McQuillen, John; Motil, Brian
2001-01-01
While there have been many studies for two-phase flow through straight cylindrical tubes, more recently, a new group of studies have emerged that examine two-phase flow through non-straight, non-cylindrical geometries, including expansions, contractions, tees, packed beds and cyclonic separation devices. Although these studies are still, relatively speaking, in their infancy, they have provided valuable information regarding the importance of the flow momentum, and the existence of liquid dryout due to sharp comers in microgravity.
Y. Y. Yan
2007-01-01
Over the last decade, computational methods have been intensively applied to a variety of scientific researches and engineering designs. Although the computational fluid dynamics (CFD) method has played a dominant role in studying and simulating transport phenomena involving fluid flow and heat and mass transfers, in recent years, other numerical methods for the simulations at meso- and micro-scales have also been actively applied to solve the physics of complex flow and fluid-interface interactions. This paper presents a review of recent advances in multi-scale computational simulation of biomimetics related fluid flow problems. The state-of-the-art numerical techniques, such as lattice Boltzmann method (LBM), molecular dynamics (MD), and conventional CFD, applied to different problems such as fish flow, electro-osmosis effect of earthworm motion, and self-cleaning hydrophobic surface, and the numerical approaches are introduced. The new challenging of modelling biomimetics problems in developing the physical conditions of self-clean hydrophobic surfaces is discussed.
Magnetohydrodynamics and heat transfer benchmark problems for liquid-metal flow in rectangular ducts
Sidorenkov, S.I. [D.V. Efremov Scientific Research Institute of Electrophysical Apparatus, St. Petersburg (Russian Federation); Hua, T.Q. [Fusion Power Program, Technology Development Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Araseki, Hideo [Central Research Institute of the Electric Power Industry, 1646 Abiko, Abiko-shi, 270-11 (Japan)
1995-03-01
This paper describes four benchmark problems to validate magnetohydrodynamic and heat transfer computer codes. The problems include rectangular duct geometry with uniform and non-uniform magnetic fields, with and without surface heat flux, and various rectangular cross-sections. Two of the problems are based on experiments. Participants in this benchmarking activity come from three countries: Russia, USA and Japan. The solution methods to the problems are described. Results from the different computer codes are presented and compared. (orig.).
Solving the Extended Tree Knapsack Problem with fixed cost flow expansion functions
DJ van der Merwe
2010-06-01
Full Text Available Parts of the Local Access Telecommunication Network planning problem may be modelled as an Extended Tree Knapsack Problem. The Local Access Telecommunication Network can contribute up to 60% of the total network costs. This paper presents partitioning algorithms that use standard off-the-shelf software coupled with enhanced modelling. Enhancements to the algorithms and empirical results for both the Tree Knapsack Problem and Extended Tree Knapsack Problem are presented.
Flowing toward Correct Contributions during Group Problem Solving: A Statistical Discourse Analysis
Chiu, Ming Ming
2008-01-01
Groups that created more correct ideas (correct contributions or CCs) might be more likely to solve a problem, and students' recent actions (micro-time context) might aid CC creation. 80 high school students worked in groups of 4 on an algebra problem. Groups with higher mathematics grades or more CCs were more likely to solve the problem. Dynamic…
Si, Haiqing; Shen, Wen Zhong; Zhu, Wei Jun
2013-01-01
Acoustic propagation in the presence of a non-uniform mean flow is studied numerically by using two different acoustic propagating models, which solve linearized Euler equations (LEE) and acoustic perturbation equations (APE). As noise induced by turbulent flows often propagates from near field t...
Bai, Danyu
2015-08-01
This paper discusses the flow shop scheduling problem to minimise the total quadratic completion time (TQCT) with release dates in offline and online environments. For this NP-hard problem, the investigation is focused on the performance of two online algorithms based on the Shortest Processing Time among Available jobs rule. Theoretical results indicate the asymptotic optimality of the algorithms as the problem scale is sufficiently large. To further enhance the quality of the original solutions, the improvement scheme is provided for these algorithms. A new lower bound with performance guarantee is provided, and computational experiments show the effectiveness of these heuristics. Moreover, several results of the single-machine TQCT problem with release dates are also obtained for the deduction of the main theorem.
Liou, Cheng-Dar; Hsieh, Yi-Chih; Chen, Yin-Yann
2013-01-01
This article investigates the two-machine flow-shop group scheduling problem (GSP) with sequence-dependent setup and removal times, and job transportation times between machines. The objective is to minimise the total completion time. As known, this problem is an NP-hard problem and generalises the typical two-machine GSPs. In this article, a new encoding scheme based on permutation representation is proposed to transform a random job permutation to a feasible permutation for GSPs. The proposed encoding scheme simultaneously determines both the sequence of jobs in each group and the sequence of groups. By reasonably combining particle swarm optimisation (PSO) and genetic algorithm (GA), we develop a fast and easily implemented hybrid algorithm (HA) for solving the considered problems. The effectiveness and efficiency of the proposed HA are demonstrated and compared with those of standard PSO and GA by numerical results of various tested instances with group numbers up to 20. In addition, three different lower bounds are developed to evaluate the solution quality of the HA. Limited numerical results indicate that the proposed HA is a viable and effective approach for the studied two-machine flow-shop group scheduling problem.
Bagchi, Prosenjit
2016-11-01
In this talk, two problems in multiphase biological flows will be discussed. The first is the direct numerical simulation of whole blood and drug particulates in microvascular networks. Blood in microcirculation behaves as a dense suspension of heterogeneous cells. The erythrocytes are extremely deformable, while inactivated platelets and leukocytes are nearly rigid. A significant progress has been made in recent years in modeling blood as a dense cellular suspension. However, many of these studies considered the blood flow in simple geometry, e.g., straight tubes of uniform cross-section. In contrast, the architecture of a microvascular network is very complex with bifurcating, merging and winding vessels, posing a further challenge to numerical modeling. We have developed an immersed-boundary-based method that can consider blood cell flow in physiologically realistic and complex microvascular network. In addition to addressing many physiological issues related to network hemodynamics, this tool can be used to optimize the transport properties of drug particulates for effective organ-specific delivery. Our second problem is pseudopod-driven motility as often observed in metastatic cancer cells and other amoeboid cells. We have developed a multiscale hydrodynamic model to simulate such motility. We study the effect of cell stiffness on motility as the former has been considered as a biomarker for metastatic potential. Funded by the National Science Foundation.
Cheng Xiaoliang; Ying Weiting
2005-01-01
In this paper, we discuss the existence of solution of a nonlinear two-point boundary value problem with a positive parameter Q arising in the study of surfacetension-induced flows of a liquid metal or semiconductor. By applying the Schauder's fixed-point theorem, we prove that the problem admits a solution for 0 ≤ Q ≤ 14.306.It improves the result of 0 ≤ Q ＜ 1 in [2] and 0 ≤ Q ≤ 13.213 in [3].
Simulation of heterogeneous flow and the problem of application of the Navier-Stokes equations
Tsymbal, V. P.; Sechenov, P. A.; Olennikov, A. A.; Padalko, A. G.
2016-09-01
The article describes a dissipative structure - gravity separator in the jet-emulsion reactor. The simulation model is based on “first principles” and the Monte Carlo method of statistical tests. Dispersed particles of the charge and reaction products, their possible transformations and variants of interactions are treated as the first level. The core of this model is the process flow of the condensed particles in the vertical gas flow. Taking into account the experience of simulation and the presented considerations the concept of turbulent viscosity for heterogeneous flow is defined, the task and the direction of further investigations are defined.
Hozejowski Leszek
2012-04-01
Full Text Available The paper is devoted to a computational problem of predicting a local heat transfer coefficient from experimental temperature data. The experimental part refers to boiling flow of a refrigerant in a minichannel. Heat is dissipated from heating alloy to the flowing liquid due to forced convection. The mathematical model of the problem consists of the governing Poisson equation and the proper boundary conditions. For accurate results it is required to smooth the measurements which was obtained by using Trefftz functions. The measurements were approximated with a linear combination of Trefftz functions. Due to the computational procedure in which the measurement errors are known, it was possible to smooth the data and also to reduce the residuals of approximation on the boundaries.
Shin, Y.W.; Wiedermann, A.H.
1984-02-01
A method was published, based on the integral method of characteristics, by which the junction and boundary conditions needed in computation of a flow in a piping network can be accurately formulated. The method for the junction and boundary conditions formulation together with the two-step Lax-Wendroff scheme are used in a computer program; the program in turn, is used here in calculating sample problems related to the blowdown transient of a two-phase flow in the piping network downstream of a PWR pressurizer. Independent, nearly exact analytical solutions also are obtained for the sample problems. Comparison of the results obtained by the hybrid numerical technique with the analytical solutions showed generally good agreement. The good numerical accuracy shown by the results of our scheme suggest that the hybrid numerical technique is suitable for both benchmark and design calculations of PWR pressurizer blowdown transients.
Riemann–Hilbert problem approach for two-dimensional flow inverse scattering
Agaltsov, A. D., E-mail: agalets@gmail.com [Faculty of Computational Mathematics and Cybernetics, Lomonosov Moscow State University, 119991 Moscow (Russian Federation); Novikov, R. G., E-mail: novikov@cmap.polytechnique.fr [CNRS (UMR 7641), Centre de Mathématiques Appliquées, Ecole Polytechnique, 91128 Palaiseau (France); IEPT RAS, 117997 Moscow (Russian Federation); Moscow Institute of Physics and Technology, Dolgoprudny (Russian Federation)
2014-10-15
We consider inverse scattering for the time-harmonic wave equation with first-order perturbation in two dimensions. This problem arises in particular in the acoustic tomography of moving fluid. We consider linearized and nonlinearized reconstruction algorithms for this problem of inverse scattering. Our nonlinearized reconstruction algorithm is based on the non-local Riemann–Hilbert problem approach. Comparisons with preceding results are given.
On the application of two-fluid flows solver to the casting problem
Kamran, Kazem; Rossi, Riccardo; Dadvand, Pooyan; Idelsohn Barg, Sergio Rodolfo
2014-01-01
This book presents and discusses mathematical models, numerical methods and computational techniques used for solving coupled problems in science and engineering. It takes a step forward in the formulation and solution of real-life problems with a multidisciplinary vision, accounting for all of the complex couplings involved in the physical description. Simulation of multifaceted physics problems is a common task in applied research and industry. Often a suitable solver is built by connecting...
无
2009-01-01
The Boltzmann simplified velocity distribution function equation describing the gas transfer phenomena from various flow regimes will be explored and solved numerically in this study. The discrete velocity ordinate method of the gas kinetic theory is studied and applied to simulate the complex multi-scale flows. Based on the uncoupling technique on molecular movement and colliding in the DSMC method, the gas-kinetic finite difference scheme is constructed to directly solve the discrete velocity distribution functions by extending and applying the unsteady time-splitting method from computational fluid dynamics. The Gauss-type discrete velocity numerical quadrature technique for different Mach number flows is developed to evaluate the macroscopic flow parameters in the physical space. As a result, the gas-kinetic numerical algorithm is established to study the three-dimensional complex flows from rarefied transition to continuum regimes. The parallel strategy adapted to the gas-kinetic numerical algorithm is investigated by analyzing the inner parallel degree of the algorithm, and then the HPF parallel processing program is developed. To test the reliability of the present gas-kinetic numerical method, the three-dimensional complex flows around sphere and spacecraft shape with various Knudsen numbers are simulated by HPF parallel computing. The computational results are found in high resolution of the flow fields and good agreement with the theoretical and experimental data. The computing practice has confirmed that the present gas-kinetic algorithm probably provides a promising approach to resolve the hypersonic aerothermodynamic problems with the complete spectrum of flow regimes from the gas-kinetic point of view of solving the Boltzmann model equation.
Johan Soewanda; Tanti Octavia; Iwan Halim Sahputra
2007-01-01
This paper discusses the application of Robust Hybrid Genetic Algorithm to solve a flow-shop scheduling problem. The proposed algorithm attempted to reach minimum makespan. PT. FSCM Manufacturing Indonesia Plant 4's case was used as a test case to evaluate the performance of the proposed algorithm. The proposed algorithm was compared to Ant Colony, Genetic-Tabu, Hybrid Genetic Algorithm, and the company's algorithm. We found that Robust Hybrid Genetic produces statistically better result than...
Punnen, Abraham P
2007-01-01
The bottleneck network flow problem (BNFP) is a generalization of several well-studied bottleneck problems such as the bottleneck transportation problem (BTP), bottleneck assignment problem (BAP), bottleneck path problem (BPP), and so on. In this paper we provide a review of important results on this topic and its various special cases. We observe that the BNFP can be solved as a sequence of $O(\\log n)$ maximum flow problems. However, special augmenting path based algorithms for the maximum flow problem can be modified to obtain algorithms for the BNFP with the property that these variations and the corresponding maximum flow algorithms have identical worst case time complexity. On unit capacity network we show that BNFP can be solved in $O(\\min \\{{m(n\\log n)}^{{2/3}}, m^{{3/2}}\\sqrt{\\log n}\\})$. This improves the best available algorithm by a factor of $\\sqrt{\\log n}$. On unit capacity simple graphs, we show that BNFP can be solved in $O(m \\sqrt {n \\log n})$ time. As a consequence we have an $O(m \\sqrt {n \\l...
Amit Kumar; Manjot Kaur
2014-02-01
Several authors have proposed different methods for solving fuzzy minimum cost flow (MCF) problems. In this paper, some single and multi-objective fuzzy MCF problems are chosen which cannot be solved by using any of the existing methods and a new method is proposed for solving such type of problems. The main advantage of the proposed method over existing methods is that the fuzzy MCF problems which can be solved by using the existing methods can also be solved by the proposed method. But, there exist several fuzzy MCF problems which can be solved only by using the proposed method i.e., it is not possible to solve these problems by using the existing methods. To illustrate the proposed method and also to show the advantages of the proposed method over existing methods some single and multiobjective fuzzy MCF problems which cannot be solved by using the existing methods are solved by using the proposed method and the obtained results are discussed.
Salama, Amgad
2014-09-01
In this work we apply the experimenting pressure field approach to the numerical solution of the single phase flow problem in anisotropic porous media using the multipoint flux approximation. We apply this method to the problem of flow in saturated anisotropic porous media. In anisotropic media the component flux representation requires, generally multiple pressure values in neighboring cells (e.g., six pressure values of the neighboring cells is required in two-dimensional rectangular meshes). This apparently results in the need for a nine points stencil for the discretized pressure equation (27 points stencil in three-dimensional rectangular mesh). The coefficients associated with the discretized pressure equation are complex and require longer expressions which make their implementation prone to errors. In the experimenting pressure field technique, the matrix of coefficients is generated automatically within the solver. A set of predefined pressure fields is operated on the domain through which the velocity field is obtained. Apparently such velocity fields do not satisfy the mass conservation equations entailed by the source/sink term and boundary conditions from which the residual is calculated. In this method the experimenting pressure fields are designed such that the residual reduces to the coefficients of the pressure equation matrix. © 2014 Elsevier B.V. All rights reserved.
Kleinstreuer, C.; Patterson, M.R.
1980-05-01
A two- or three-dimensional finite difference mesh generator capable of discretizing subrectangular flow regions (planar coordinates) with arbitrarily shaped bottom contours (vertical dimension) was developed. This economical, interactive computer code, written in FORTRAN IV and employing DISSPLA software together with graphics terminal, generates first a planar rectangular grid of variable element density according to the geometry and local kinematic flow patterns of a given fluid flow problem. Then subrectangular areas are deleted to produce canals, tributaries, bays, and the like. For three-dimensional problems, arbitrary bathymetric profiles (river beds, channel cross section, ocean shoreline profiles, etc.) are approximated with grid lines forming steps of variable spacing. Furthermore, the code works as a preprocessor numbering the discrete elements and the nodal points. Prescribed values for the principal variables can be automatically assigned to solid as well as kinematic boundaries. Cabinet drawings aid in visualizing the complete flow domain. Input data requirements are necessary only to specify the spacing between grid lines, determine land regions that have to be excluded, and to identify boundary nodes. 15 figures, 2 tables.
Xanming Wang
1996-01-01
Full Text Available A technique is developed for evaluation of eigenvalues in solution of the differential equation d2y/dr2+(1/rdy/dr+λ2(β−r2y=0 which occurs in the problem of heat convection in laminar flow through a circular tube with silp-flow (β>1. A series solution requires the expansions of coeffecients involving extremely large numbers. No work has been reported in the case of β>1, because of its computational complexity in the evaluation of the eigenvalues. In this paper, a matrix was constructed and a computational algorithm was obtained to calculate the first four eigenvalues. Also, an asymptotic formula was developed to generate the full spectrum of eigenvalues. The computational results for various values of β were obtained.
Seyyed Mohammad Hassan Hosseini
2016-05-01
Full Text Available Scheduling problem for the hybrid flow shop scheduling problem (HFSP followed by an assembly stage considering aging effects additional preventive and maintenance activities is studied in this paper. In this production system, a number of products of different kinds are produced. Each product is assembled with a set of several parts. The first stage is a hybrid flow shop to produce parts. All machines can process all kinds of parts in this stage but each machine can process only one part at the same time. The second stage is a single assembly machine or a single assembly team of workers. The aim is to schedule the parts on the machines and assembly sequence and also determine when the preventive maintenance activities get done in order to minimize the completion time of all products (makespan. A mathematical modeling is presented and its validation is shown by solving an example in small scale. Since this problem has been proved strongly NP-hard, in order to solve the problem in medium and large scale, four heuristic algorithms is proposed based on the Johnson’s algorithm. The numerical experiments are used to run the mathematical model and evaluate the performance of the proposed algorithms.
Canepa, Edward S.
2012-09-01
This article presents a new mixed integer programming formulation of the traffic density estimation problem in highways modeled by the Lighthill Whitham Richards equation. We first present an equivalent formulation of the problem using an Hamilton-Jacobi equation. Then, using a semi-analytic formula, we show that the model constraints resulting from the Hamilton-Jacobi equation result in linear constraints, albeit with unknown integers. We then pose the problem of estimating the density at the initial time given incomplete and inaccurate traffic data as a Mixed Integer Program. We then present a numerical implementation of the method using experimental flow and probe data obtained during Mobile Century experiment. © 2012 IEEE.
Aerodynamics of knuckle ball: Flow-structure interaction problem on a pitched baseball without spin
Higuchi, Hiroshi; Kiura, Toshiro
2012-07-01
In the game of baseball, the knuckleball—so-called because the baseball is gripped with the knuckles in a certain position—is pitched in a way that introduces nearly no rotation, resulting in erratic flight paths which confuse batters. The “knuckleball” effect is believed to be caused by asymmetric flow separation over the baseball, but little is known about its flow physics. In the experiment described in this paper, the flow near the seams of the baseball is visualized thoroughly and the velocity vector fields near the surface and in the wake are obtained with Digital Particle Image Velocimetry. Depending on its position, the seam is found to trigger the boundary layer transition thus delaying the separation, or to cause separation itself. Three-dimensional wake patterns associated with specific ball orientations are identified and related to the force variations on the ball.
Xing-cai Liu
2014-01-01
Full Text Available The railway freight center stations location and wagon flow organization in railway transport are interconnected, and each of them is complicated in a large-scale rail network. In this paper, a two-stage method is proposed to optimize railway freight center stations location and wagon flow organization together. The location model is present with the objective to minimize the operation cost and fixed construction cost. Then, the second model of wagon flow organization is proposed to decide the optimal train service between different freight center stations. The location of the stations is the output of the first model. A heuristic algorithm that combined tabu search (TS with adaptive clonal selection algorithm (ACSA is proposed to solve those two models. The numerical results show the proposed solution method is effective.
Application of partially-coupled hydro-mechanical schemes to multiphase flow problems
Tillner, Elena; Kempka, Thomas
2016-04-01
Utilization of subsurface reservoirs by fluid storage or production generally triggers pore pressure changes and volumetric strains in reservoirs and cap rocks. The assessment of hydro-mechanical effects can be undertaken using different process coupling strategies. The fully-coupled geomechanics and flow simulation, constituting a monolithic system of equations, is rarely applied for simulations involving multiphase fluid flow due to the high computational efforts required. Pseudo-coupled simulations are driven by static tabular data on porosity and permeability changes as function of pore pressure or mean stress, resulting in a rather limited flexibility when encountering complex subsurface utilization schedules and realistic geological settings. Partially-coupled hydro-mechanical simulations can be distinguished into one-way and iterative two-way coupled schemes, whereby the latter one is based on calculations of flow and geomechanics, taking into account the iterative exchange of coupling parameters between the two respective numerical simulators until convergence is achieved. In contrast, the one-way coupling scheme is determined by the provision of pore pressure changes calculated by the flow simulator to the geomechanical simulator neglecting any feedback. In the present study, partially-coupled two-way schemes are discussed in view of fully-coupled single-phase flow and geomechanics, and their applicability to multiphase flow simulations. For that purpose, we introduce a comparison study between the different coupling schemes, using selected benchmarks to identify the main requirements for the partially-coupled approach to converge with the numerical solution of the fully-coupled one.
Hypertension: a problem of organ blood flow supply–demand mismatch
Koeners, Maarten P; Lewis, Kirsty E; Ford, Anthony P; Paton, Julian FR
2016-01-01
This review introduces a new hypothesis that sympathetically mediated hypertensive diseases are caused, in the most part, by the activation of visceral afferent systems that are connected to neural circuits generating sympathetic activity. We consider how organ hypoperfusion and blood flow supply–demand mismatch might lead to both sensory hyper-reflexia and aberrant afferent tonicity. We discuss how this may drive sympatho-excitatory-positive feedback and extend across multiple organs initiating, or at least amplifying, sympathetic hyperactivity. The latter, in turn, compounds the challenge to sufficient organ blood flow through heightened vasoconstriction that both maintains and exacerbates hypertension. PMID:27091483
Hypertension: a problem of organ blood flow supply-demand mismatch.
Koeners, Maarten P; Lewis, Kirsty E; Ford, Anthony P; Paton, Julian Fr
2016-05-01
This review introduces a new hypothesis that sympathetically mediated hypertensive diseases are caused, in the most part, by the activation of visceral afferent systems that are connected to neural circuits generating sympathetic activity. We consider how organ hypoperfusion and blood flow supply-demand mismatch might lead to both sensory hyper-reflexia and aberrant afferent tonicity. We discuss how this may drive sympatho-excitatory-positive feedback and extend across multiple organs initiating, or at least amplifying, sympathetic hyperactivity. The latter, in turn, compounds the challenge to sufficient organ blood flow through heightened vasoconstriction that both maintains and exacerbates hypertension.
Numerical simulation for a two-phase porous medium flow problem with rate independent hysteresis
Brokate, M.
2012-05-01
The paper is devoted to the numerical simulation of a multiphase flow in porous medium with a hysteretic relation between the capillary pressures and the saturations of the phases. The flow model we use is based on Darcys law. The hysteretic relation between the capillary pressures and the saturations is described by a play-type hysteresis operator. We propose a numerical algorithm for treating the arising system of equations, discuss finite element schemes and present simulation results for the case of two phases. © 2011 Elsevier B.V. All rights reserved.
Malkus, David S.
1989-01-01
This project concerned the development of a new fast finite element algorithm to solve flow problems of non-Newtonian fluids such as solutions or melts of polymers. Many constitutive theories for such materials involve single integrals over the deformation history of the particle at the stress evaluation point; examples are the Doi-Edwards and Curtiss-Bird molecular theories and the BKZ family derived from continuum arguments. These theories are believed to be among the most accurate in describing non-Newtonian effects important to polymer process design, effects such as stress relaxation, shear thinning, and normal stress effects. This research developed an optimized version of the algorithm which would run a factor of two faster than the pilot algorithm on scalar machines and would be able to take full advantage of vectorization on machines. Significant progress was made in code vectorization; code enhancement and streamlining; adaptive memory quadrature; model problems for the High Weissenberg Number Problem; exactly incompressible projection; development of multimesh extrapolation procedures; and solution of problems of physical interest. A portable version of the code is in the final stages of benchmarking and testing. It interfaces with the widely used FIDAP fluid dynamics package.
Streng, Martin; Streng, M.; ten Cate, Eric; ten Cate, Eric (H.H.); Geurts, Bernardus J.; Kuerten, Johannes G.M.
1998-01-01
We consider several aspects of efficient numerical simulation of viscous compressible flow on both homogeneous and heterogeneous workstation-clusters. We consider dedicated systems, as well as clusters operating in a multi-user environment. For dedicated homogeneous clusters, we show that with
A service flow model for the liner shipping network design problem
Plum, Christian Edinger Munk; Pisinger, David; Sigurd, Mikkel M.
2014-01-01
. The model ensures strictly weekly frequencies of services, ensures that port-vessel draft capabilities are not violated, respects vessel capacities and the number of vessels available. The profit of the generated network is maximized, i.e. the revenue of flowed cargo subtracted operational costs...
Lavrent'ev problem for separated flows with an external perturbation
Dmitriy K. Potapov
2013-11-01
Full Text Available We study the Lavrent'ev mathematical model for separated flows with an external perturbation. This model consists of a differential equation with discontinuous nonlinearity and a boundary condition. Using a variational method, we show the existence of a semiregular solution. As a particular case, we study the one-dimensional model.
Maximum Autocorrelation Factorial Kriging
Nielsen, Allan Aasbjerg; Conradsen, Knut; Pedersen, John L.
2000-01-01
This paper describes maximum autocorrelation factor (MAF) analysis, maximum autocorrelation factorial kriging, and its application to irregularly sampled stream sediment geochemical data from South Greenland. Kriged MAF images are compared with kriged images of varimax rotated factors from...
Suprayogi Suprayogi
2016-12-01
Full Text Available This paper considers a location problem in a supply chain network. The problem addressed in this paper is motivated by an initiative to develop an efficient supply chain network for supporting the agricultural activities. The supply chain network consists of regions, warehouses, distribution centers, plants, and markets. The products include a set of inbound products and a set of outbound products. In this paper, definitions of the inbound and outbound products are seen from the region’s point of view. The inbound product is the product demanded by regions and produced by plants which flows on a sequence of the following entities: plants, distribution centers, warehouses, and regions. The outbound product is the product demanded by markets and produced by regions and it flows on a sequence of the following entities: regions, warehouses, and markets. The problem deals with determining locations of the warehouses and the distribution centers to be opened and shipment quantities associated with all links on the network that minimizes the total cost. The problem can be considered as a strategic supply chain network problem. A solution approach based on genetic algorithm (GA is proposed. The proposed GA is examined using hypothetical instances and its results are compared to the solution obtained by solving the mixed integer linear programming (MILP model. The comparison shows that there is a small gap (0.23%, on average between the proposed GA and MILP model in terms of the total cost. The proposed GA consistently provides solutions with least total cost. In terms of total cost, based on the experiment, it is demonstrated that coefficients of variation are closed to 0.
Mielke, Alexander
1991-01-01
The theory of center manifold reduction is studied in this monograph in the context of (infinite-dimensional) Hamil- tonian and Lagrangian systems. The aim is to establish a "natural reduction method" for Lagrangian systems to their center manifolds. Nonautonomous problems are considered as well assystems invariant under the action of a Lie group ( including the case of relative equilibria). The theory is applied to elliptic variational problemson cylindrical domains. As a result, all bounded solutions bifurcating from a trivial state can be described by a reduced finite-dimensional variational problem of Lagrangian type. This provides a rigorous justification of rod theory from fully nonlinear three-dimensional elasticity. The book will be of interest to researchers working in classical mechanics, dynamical systems, elliptic variational problems, and continuum mechanics. It begins with the elements of Hamiltonian theory and center manifold reduction in order to make the methods accessible to non-specialists,...
Hybrid partheno-genetic algorithm and its application in flow-shop problem
李树刚; 吴智铭; 庞小红
2004-01-01
In order to solve the constraint satisfied problem in the genetic algorithm, the partheno-genetic algorithm is designed. And then the schema theorem of the partheno-genetic algorithm is proposed to show that the high rank schemas at the subsequent generation decrease exponentially even though its fitness is more optimal than the average one in the population and the low rank schemas at the subsequent generation increase exponentially when its fitness is more optimal than the average one in the population. In order to overcome the shortcoming that the optimal high rank schema can be deserted arbitrarily, the HGA (hybrid partheno-genetic algorithm) is proposed, that is, the hill-climbing algorithm is integrated to search for a better individual. Finally, the results of the simulation for facility layout problem and no-wait schedule problem are given. It is shown that the hybrid partheno- genetic algorithm is of high efficiency.
Simultaneous PIV and pulsed shadow technique in slug flow: a solution for optical problems
Nogueira, S. [Karman Institute for Fluid Dynamics, Chaussee de Waterloo 72, B-1640, Rhode Saint Genese (Belgium); Centro de Estudos de Fenomenos de Transporte, Departamento de Eng. Quimica, Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias, 4200-465, Porto (Portugal); Sousa, R.G.; Pinto, A.M.F.R.; Campos, J.B.L.M. [Centro de Estudos de Fenomenos de Transporte, Departamento de Eng. Quimica, Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias, 4200-465, Porto (Portugal); Riethmuller, M.L. [Karman Institute for Fluid Dynamics, Chaussee de Waterloo 72, B-1640, Rhode Saint Genese (Belgium)
2003-12-01
A recent technique of simultaneous particle image velocimetry (PIV) and pulsed shadow technique (PST) measurements, using only one black and white CCD camera, is successfully applied to the study of slug flow. The experimental facility and the operating principle are described. The technique is applied to study the liquid flow pattern around individual Taylor bubbles rising in an aqueous solution of glycerol with a dynamic viscosity of 113 x 10{sup -3} Pa s. With this technique the optical perturbations found in PIV measurements at the bubble interface are completely solved in the nose and in annular liquid film regions as well as in the rear of the bubble for cases in which the bottom is flat. However, for Taylor bubbles with concave oblate bottoms, some optical distortions appear and are discussed. The measurements achieved a spatial resolution of 0.0022 tube diameters. The results reported show high precision and are in agreement with theoretical and experimental published data. (orig.)
Study on disruption management scheduling problem of flow shop under supply chain environment
Bo Hong Guang
2016-01-01
Full Text Available This paper presents a disruption scheduling model for an environment of proportional two-machine no-wait flow shop. To achieve the objects of minimization of weighted sum of makespan and minimization of weighted sum of tardiness, we introduce a revised PSO algorithm which is designed with a neighborhood search structure. According to the experiment, the effectivity of the method proposed is proven.
Upper bounds for the critical car densities in traffic flow problems
Chau, H F; Woo, Y F; Chau, H F; Hui, P M; Woo, Y F
1995-01-01
In most models of traffic flow, the car density p is the only free parameter in determining the average car velocity \\langle v \\rangle. The critical car density p_c, which is defined to be the car density separating the jamming phase (with \\langle v \\rangle = 0) and the moving phase (with \\langle v \\rangle > 0), is an important physical quantity to investigate. By means of simple statistical argument, we show that p_c 2) dimensions.
Brown-Dymkoski, Eric; Kasimov, Nurlybek; Vasilyev, Oleg V.
2014-04-01
In order to introduce solid obstacles into flows, several different methods are used, including volume penalization methods which prescribe appropriate boundary conditions by applying local forcing to the constitutive equations. One well known method is Brinkman penalization, which models solid obstacles as porous media. While it has been adapted for compressible, incompressible, viscous and inviscid flows, it is limited in the types of boundary conditions that it imposes, as are most volume penalization methods. Typically, approaches are limited to Dirichlet boundary conditions. In this paper, Brinkman penalization is extended for generalized Neumann and Robin boundary conditions by introducing hyperbolic penalization terms with characteristics pointing inward on solid obstacles. This Characteristic-Based Volume Penalization (CBVP) method is a comprehensive approach to conditions on immersed boundaries, providing for homogeneous and inhomogeneous Dirichlet, Neumann, and Robin boundary conditions on hyperbolic and parabolic equations. This CBVP method can be used to impose boundary conditions for both integrated and non-integrated variables in a systematic manner that parallels the prescription of exact boundary conditions. Furthermore, the method does not depend upon a physical model, as with porous media approach for Brinkman penalization, and is therefore flexible for various physical regimes and general evolutionary equations. Here, the method is applied to scalar diffusion and to direct numerical simulation of compressible, viscous flows. With the Navier-Stokes equations, both homogeneous and inhomogeneous Neumann boundary conditions are demonstrated through external flow around an adiabatic and heated cylinder. Theoretical and numerical examination shows that the error from penalized Neumann and Robin boundary conditions can be rigorously controlled through an a priori penalization parameter η. The error on a transient boundary is found to converge as O
Safi, Seyed Mohammad Amin
2016-01-01
Multiphase flow simulations benefit a variety of applications in science and engineering as for example in the dynamics of bubble swarms in heat exchangers and chemical reactors or in the prediction of the effects of droplet or bubble impacts in the design of turbomachinery systems. Despite all the progress in the modern computational fluid dynamics (CFD), such simulations still present formidable challenges both from numerical and computational cost point of view. Emerging as ...
Wired and Wireless Parallel Simulation of Fluid Flow Problem on Heterogeneous Network Cluster
Fariha Quratulain Baloch
2012-09-01
Full Text Available In this research Homogeneous and Heterogeneous networks will be analyzed using parallel processing technique for highly sophisticated research problem. During the analysis sample networks will be considered and QoS parameters will be observed using simulation for end-to-end services. Analysis of the wireless LAN system is carried out and its efficiency is measured compared to the wired systems, for the purpose of designing and implementing the parallel processing techniques used to solve general purpose engineering problems. The basic purpose for this research is to provide improved QoS in networks for research and academic learning.
Shadid, J.N.; Moffat, H.K.; Hutchinson, S.A.; Hennigan, G.L.; Devine, K.D.; Salinger, A.G.
1996-05-01
The theoretical background for the finite element computer program, MPSalsa, is presented in detail. MPSalsa is designed to solve laminar, low Mach number, two- or three-dimensional incompressible and variable density reacting fluid flows on massively parallel computers, using a Petrov-Galerkin finite element formulation. The code has the capability to solve coupled fluid flow, heat transport, multicomponent species transport, and finite-rate chemical reactions, and to solver coupled multiple Poisson or advection-diffusion- reaction equations. The program employs the CHEMKIN library to provide a rigorous treatment of multicomponent ideal gas kinetics and transport. Chemical reactions occurring in the gas phase and on surfaces are treated by calls to CHEMKIN and SURFACE CHEMKIN, respectively. The code employs unstructured meshes, using the EXODUS II finite element data base suite of programs for its input and output files. MPSalsa solves both transient and steady flows by using fully implicit time integration, an inexact Newton method and iterative solvers based on preconditioned Krylov methods as implemented in the Aztec solver library.
Lattice Boltzmann Model of 3D Multiphase Flow in Artery Bifurcation Aneurysm Problem
Abas, Aizat; Mokhtar, N. Hafizah; Ishak, M. H. H.; Abdullah, M. Z.; Ho Tian, Ang
2016-01-01
This paper simulates and predicts the laminar flow inside the 3D aneurysm geometry, since the hemodynamic situation in the blood vessels is difficult to determine and visualize using standard imaging techniques, for example, magnetic resonance imaging (MRI). Three different types of Lattice Boltzmann (LB) models are computed, namely, single relaxation time (SRT), multiple relaxation time (MRT), and regularized BGK models. The results obtained using these different versions of the LB-based code will then be validated with ANSYS FLUENT, a commercially available finite volume- (FV-) based CFD solver. The simulated flow profiles that include velocity, pressure, and wall shear stress (WSS) are then compared between the two solvers. The predicted outcomes show that all the LB models are comparable and in good agreement with the FVM solver for complex blood flow simulation. The findings also show minor differences in their WSS profiles. The performance of the parallel implementation for each solver is also included and discussed in this paper. In terms of parallelization, it was shown that LBM-based code performed better in terms of the computation time required. PMID:27239221
CFD analyses of flow structures in air-ingress and rod bundle problems
Wei, Hong-Chan
Two topics from nuclear engineering field are included in this dissertation. One study is the air-ingress phenomenon during a loss of coolant accident (LOCA) scenario, and the other is a 5-by-5 bundle assembly with a PWR design. The objectives were to investigate the Kelvin-Helmholtz instability of the gravity-driven stratified flows inside a coaxial pipe and the effects caused by two types of spacers at the downstream of the rod bundle. Richardson extrapolation was used for the grid independent study. The simulation results show good agreements with the experiments. Wavelet analysis and Proper Orthogonal Decomposition (POD) were used to study the flow behaviors and flow patterns. For the air-ingress phenomenon, Brunt-Vaisala frequency, or buoyancy frequency, predicts a frequency of 2.34 Hz; this is confirmed by the dominant frequency of 2.4 Hz obtained from the wavelet analysis between times 1.2 s and 1.85 s. For the rod bundle study, the dominant frequency at the center of the subchannel was determined to be 2.4 Hz with a secondary dominant frequency of 4 Hz and a much minor frequency of 6 Hz. Generally, wavelet analysis has much better performance than POD, in the air-ingress phenomenon, for a strongly transient scenario; they are both appropriate for the rod bundle study. Based on this study, when the fluid pair in a real condition is used, the time which air intrudes into the reactor is predictable.
Lattice Boltzmann Model of 3D Multiphase Flow in Artery Bifurcation Aneurysm Problem.
Abas, Aizat; Mokhtar, N Hafizah; Ishak, M H H; Abdullah, M Z; Ho Tian, Ang
2016-01-01
This paper simulates and predicts the laminar flow inside the 3D aneurysm geometry, since the hemodynamic situation in the blood vessels is difficult to determine and visualize using standard imaging techniques, for example, magnetic resonance imaging (MRI). Three different types of Lattice Boltzmann (LB) models are computed, namely, single relaxation time (SRT), multiple relaxation time (MRT), and regularized BGK models. The results obtained using these different versions of the LB-based code will then be validated with ANSYS FLUENT, a commercially available finite volume- (FV-) based CFD solver. The simulated flow profiles that include velocity, pressure, and wall shear stress (WSS) are then compared between the two solvers. The predicted outcomes show that all the LB models are comparable and in good agreement with the FVM solver for complex blood flow simulation. The findings also show minor differences in their WSS profiles. The performance of the parallel implementation for each solver is also included and discussed in this paper. In terms of parallelization, it was shown that LBM-based code performed better in terms of the computation time required.
Lattice Boltzmann Model of 3D Multiphase Flow in Artery Bifurcation Aneurysm Problem
Aizat Abas
2016-01-01
Full Text Available This paper simulates and predicts the laminar flow inside the 3D aneurysm geometry, since the hemodynamic situation in the blood vessels is difficult to determine and visualize using standard imaging techniques, for example, magnetic resonance imaging (MRI. Three different types of Lattice Boltzmann (LB models are computed, namely, single relaxation time (SRT, multiple relaxation time (MRT, and regularized BGK models. The results obtained using these different versions of the LB-based code will then be validated with ANSYS FLUENT, a commercially available finite volume- (FV- based CFD solver. The simulated flow profiles that include velocity, pressure, and wall shear stress (WSS are then compared between the two solvers. The predicted outcomes show that all the LB models are comparable and in good agreement with the FVM solver for complex blood flow simulation. The findings also show minor differences in their WSS profiles. The performance of the parallel implementation for each solver is also included and discussed in this paper. In terms of parallelization, it was shown that LBM-based code performed better in terms of the computation time required.
de Beer, Joop; Raymer, James; van der Erf, Rob; van Wissen, Leo
2010-11-01
Due to differences in definitions and measurement methods, cross-country comparisons of international migration patterns are difficult and confusing. Emigration numbers reported by sending countries tend to differ from the corresponding immigration numbers reported by receiving countries. In this paper, a methodology is presented to achieve harmonised estimates of migration flows benchmarked to a specific definition of duration. This methodology accounts for both differences in definitions and the effects of measurement error due to, for example, under reporting and sampling fluctuations. More specifically, the differences between the two sets of reported data are overcome by estimating a set of adjustment factors for each country's immigration and emigration data. The adjusted data take into account any special cases where the origin-destination patterns do not match the overall patterns. The new method for harmonising migration flows that we present is based on earlier efforts by Poulain (European Journal of Population, 9(4): 353-381 1993, Working Paper 12, joint ECE-Eurostat Work Session on Migration Statistics, Geneva, Switzerland 1999) and is illustrated for movements between 19 European countries from 2002 to 2007. The results represent a reliable and consistent set of international migration flows that can be used for understanding recent changes in migration patterns, as inputs into population projections and for developing evidence-based migration policies.
Prozan, R. J.; Farmer, R. C.
1985-01-01
The VAST computer code was used to analyze SSME main combustion chamber start-up transients and the IUS flow field for a damaged nozzle was investigated to better understand the gas dynamic considerations involved in vehicle problems, the effect of start transients on the nozzle flow field for the SSME, and the possibility that a damaged nozzle could account for the acceleration anomaly noted on IUS burn. The results obtained were compared with a method of characteristics prediction. Pressure solutions from both codes were in very good agreement and the Mach number solution on the nozzle centerline deviates substantially for the high expansions for the SSME. Since this deviation was unexpected, the phenomenon is being further examined.
ethod of straight lines for a Bingham problem as a model for the flow of waxy crude oils
German Ariel Torres
2005-11-01
Full Text Available In this work, we develop a method of straight lines for solving a Bingham problem that models the flow of waxy crude oils. The model describes the flow of mineral oils with a high content of paraffin at temperatures below the cloud point (i.e. the crystallization temperature of paraffin and more specifically below the pour point at which the crystals aggregate themselves and the oil takes a jell-like structure. From the rheological point of view such a system can be modelled as a Bingham fluid whose parameters evolve according to the volume fractions of crystallized paraffin and the aggregation degree of crystals. We prove that the method is well defined for all times, a monotone property, qualitative behaviour of the solution, and a convergence theorem. The results are compared with numerical experiments at the end of this article.
Cheeseman, Peter; Stutz, John
2005-01-01
A long standing mystery in using Maximum Entropy (MaxEnt) is how to deal with constraints whose values are uncertain. This situation arises when constraint values are estimated from data, because of finite sample sizes. One approach to this problem, advocated by E.T. Jaynes [1], is to ignore this uncertainty, and treat the empirically observed values as exact. We refer to this as the classic MaxEnt approach. Classic MaxEnt gives point probabilities (subject to the given constraints), rather than probability densities. We develop an alternative approach that assumes that the uncertain constraint values are represented by a probability density {e.g: a Gaussian), and this uncertainty yields a MaxEnt posterior probability density. That is, the classic MaxEnt point probabilities are regarded as a multidimensional function of the given constraint values, and uncertainty on these values is transmitted through the MaxEnt function to give uncertainty over the MaXEnt probabilities. We illustrate this approach by explicitly calculating the generalized MaxEnt density for a simple but common case, then show how this can be extended numerically to the general case. This paper expands the generalized MaxEnt concept introduced in a previous paper [3].
Ganji, S. S.; Barari, Amin; Ibsen, Lars Bo
2010-01-01
. In current research the authors utilized the Differential Transformation Method (DTM) for solving the nonlinear problem and compared the analytical results with those ones obtained by the 4th order Runge-Kutta Method (RK4) as a numerical method. Further illustration embedded in this paper shows the ability...
Ganji, S.; Barari, Amin; Ibsen, Lars Bo
2012-01-01
. In current research the authors utilized the Differential Transformation Method (DTM) for solving the nonlinear problem and compared the analytical results with those ones obtained by the 4th order Runge-Kutta Method (RK4) as a numerical method. Further illustration embedded in this paper shows the ability...
Problem of Channel Utilization and Merging Flows in Buffered Optical Burst Switching Networks
Milos Kozak
2013-01-01
Full Text Available In the paper authors verify two problems of methods of operational research in optical burst switching. The first problem is at edge node, related to the medium access delay. The second problem is at an intermediate node related to buffering delay. A correction coefficient K of transmission speed is obtained from the first analysis. It is used in to provide a full-featured link of nominal data rate. Simulations of the second problem reveal interesting results. It is not viable to prepare routing and wavelength assignment based on end-to-end delay, i.e. link's length or number of hops, as commonly used in other frameworks (OCS, Ethernet, IP, etc. nowadays. Other parameters such as buffering probability must be taken into consideration as well. Based on the buffering probability an estimation of the number of optical/electrical converters can be made. This paper concentrates important traffic constraints of buffered optical burst switching. It allows authors to prepare optimization algorithms for regenerators placement in CAROBS networks using methods of operational research.
Johan Soewanda
2007-01-01
Full Text Available This paper discusses the application of Robust Hybrid Genetic Algorithm to solve a flow-shop scheduling problem. The proposed algorithm attempted to reach minimum makespan. PT. FSCM Manufacturing Indonesia Plant 4's case was used as a test case to evaluate the performance of the proposed algorithm. The proposed algorithm was compared to Ant Colony, Genetic-Tabu, Hybrid Genetic Algorithm, and the company's algorithm. We found that Robust Hybrid Genetic produces statistically better result than the company's, but the same as Ant Colony, Genetic-Tabu, and Hybrid Genetic. In addition, Robust Hybrid Genetic Algorithm required less computational time than Hybrid Genetic Algorithm
Geostatistical Sampling Methods for Efficient Uncertainty Analysis in Flow and Transport Problems
Liodakis, Stylianos; Kyriakidis, Phaedon; Gaganis, Petros
2015-04-01
In hydrogeological applications involving flow and transport of in heterogeneous porous media the spatial distribution of hydraulic conductivity is often parameterized in terms of a lognormal random field based on a histogram and variogram model inferred from data and/or synthesized from relevant knowledge. Realizations of simulated conductivity fields are then generated using geostatistical simulation involving simple random (SR) sampling and are subsequently used as inputs to physically-based simulators of flow and transport in a Monte Carlo framework for evaluating the uncertainty in the spatial distribution of solute concentration due to the uncertainty in the spatial distribution of hydraulic con- ductivity [1]. Realistic uncertainty analysis, however, calls for a large number of simulated concentration fields; hence, can become expensive in terms of both time and computer re- sources. A more efficient alternative to SR sampling is Latin hypercube (LH) sampling, a special case of stratified random sampling, which yields a more representative distribution of simulated attribute values with fewer realizations [2]. Here, term representative implies realizations spanning efficiently the range of possible conductivity values corresponding to the lognormal random field. In this work we investigate the efficiency of alternative methods to classical LH sampling within the context of simulation of flow and transport in a heterogeneous porous medium. More precisely, we consider the stratified likelihood (SL) sampling method of [3], in which attribute realizations are generated using the polar simulation method by exploring the geometrical properties of the multivariate Gaussian distribution function. In addition, we propose a more efficient version of the above method, here termed minimum energy (ME) sampling, whereby a set of N representative conductivity realizations at M locations is constructed by: (i) generating a representative set of N points distributed on the
An effective co-evolutionary quantum genetic algorithm for the no-wait flow shop scheduling problem
Guanlong Deng
2015-12-01
Full Text Available This article proposes a competitive co-evolutionary quantum genetic algorithm for the no-wait flow shop scheduling problem with the criterion to minimize makespan, which is a renowned NP-hard combinatorial optimization problem. An innovative coding and decoding mechanism is proposed. The mechanism uses square matrix to represent the quantum individual and adapts the quantum rotation gate to update the quantum individual. In the algorithm framework, the store-with-diversity is proposed to maintain the diversity of the population. Moreover, a competitive co-evolution strategy is introduced to enhance the evolutionary pressure and accelerate the convergence. The store-with-diversity and competitive co-evolution are designed to keep a balance between exploration and exploitation. Simulations based on a benchmark set and comparisons with several existing algorithms demonstrate the effectiveness and robustness of the proposed algorithm.
The Problem of Finding the Maximal Multiple Flow in the Divisible Network and its Special Cases
A. V. Smirnov
2015-01-01
Full Text Available In the article the problem of ﬁnding the maximal multiple ﬂow in the network of any natural multiplicity k is studied. There are arcs of three types: ordinary arcs, multiple arcs and multi-arcs. Each multiple and multi-arc is a union of k linked arcs, which are adjusted with each other. The network constructing rules are described. The deﬁnitions of a divisible network and some associated subjects are stated. The important property of the divisible network is that every divisible network can be partitioned into k parts, which are adjusted on the linked arcs of each multiple and multi-arc. Each part is the ordinary transportation network. The main results of the article are the following subclasses of the problem of ﬁnding the maximal multiple ﬂow in the divisible network. 1. The divisible networks with the multi-arc constraints. Assume that only one vertex is the ending vertex for a multi-arc in k −1 network parts. In this case the problem can be solved in a polynomial time. 2. The divisible networks with the weak multi-arc constraints. Assume that only one vertex is the ending vertex for a multi-arc in s network parts (1 ≤ s < k − 1 and other parts have at least two such vertices. In that case the multiplicity of the multiple ﬂow problem can be decreased to k − s. 3. The divisible network of the parallel structure. Assume that the divisible network component, which consists of all multiple arcs, can be partitioned into subcomponents, each of them containing exactly one vertex-beginning of a multi-arc. Suppose that intersection of each pair of subcomponents is the only vertex-network source x0. If k = 2, the maximal ﬂow problem can be solved in a polynomial time. If k ≥ 3, the problem is NP-complete. The algorithms for each polynomial subclass are suggested. Also, the multiplicity decreasing algorithm for the divisible network with weak multi-arc constraints is formulated.
Reduced-Contrast Approximations for High-Contrast Multiscale Flow Problems
Chung, Eric T.
2010-01-01
In this paper, we study multiscale methods for high-contrast elliptic problems where the media properties change dramatically. The disparity in the media properties (also referred to as high contrast in the paper) introduces an additional scale that needs to be resolved in multiscale simulations. First, we present a construction that uses an integral equation to represent the highcontrast component of the solution. This representation involves solving an integral equation along the interface where the coefficients are discontinuous. The integral representation suggests some multiscale approaches that are discussed in the paper. One of these approaches entails the use of interface functions in addition to multiscale basis functions representing the heterogeneities without high contrast. In this paper, we propose an approximation for the solution of the integral equation using the interface problems in reduced-contrast media. Reduced-contrast media are obtained by lowering the variance of the coefficients. We also propose a similar approach for the solution of the elliptic equation without using an integral representation. This approach is simpler to use in the computations because it does not involve setting up integral equations. The main idea of this approach is to approximate the solution of the high-contrast problem by the solutions of the problems formulated in reduced-contrast media. In this approach, a rapidly converging sequence is proposed where only problems with lower contrast are solved. It was shown that this sequence possesses the convergence rate that is inversely proportional to the reduced contrast. This approximation allows choosing the reduced-contrast problem based on the coarse-mesh size as discussed in this paper. We present a simple application of this approach to homogenization of elliptic equations with high-contrast coefficients. The presented approaches are limited to the cases where there are sharp changes in the contrast (i.e., the high
Approximate maximum-entropy moment closures for gas dynamics
McDonald, James G.
2016-11-01
Accurate prediction of flows that exist between the traditional continuum regime and the free-molecular regime have proven difficult to obtain. Current methods are either inaccurate in this regime or prohibitively expensive for practical problems. Moment closures have long held the promise of providing new, affordable, accurate methods in this regime. The maximum-entropy hierarchy of closures seems to offer particularly attractive physical and mathematical properties. Unfortunately, several difficulties render the practical implementation of maximum-entropy closures very difficult. This work examines the use of simple approximations to these maximum-entropy closures and shows that physical accuracy that is vastly improved over continuum methods can be obtained without a significant increase in computational cost. Initially the technique is demonstrated for a simple one-dimensional gas. It is then extended to the full three-dimensional setting. The resulting moment equations are used for the numerical solution of shock-wave profiles with promising results.
Finite volume numerical solution to a blood flow problem in human artery
Wijayanti Budiawan, Inge; Mungkasi, Sudi
2017-01-01
In this paper, we solve a one dimensional blood flow model in human artery. This model is of a non-linear hyperbolic partial differential equation system which can generate either continuous or discontinuous solution. We use the Lax–Friedrichs finite volume method to solve this model. Particularly, we investigate how a pulse propagates in human artery. For this simulation, we give a single sine wave with a small time period as an impluse input on the left boundary. The finite volume method is successful in simulating how the pulse propagates in the artery. It detects the positions of the pulse for the whole time period.
Statistical fluctuations in Monte Carlo calculations. [for solution of rarefied flow problems
Boyd, I. D.; Stark, J. P. W.
1989-01-01
The time counter and modified Nanbu simulation techniques are analyzed, with emphasis placed on the convergence of the calculations to a steady macroscopic state. Such variables as translational and rotational temperature, and flow velocity, sampled at several points in the flowfield, are considered. Both macroscopic averages and molecular distribution functions are analyzed. The calculation of inelastic collisions, in which transfer of energy between translational and internal energy modes is performed, is achieved through the use of the Larsen-Borgnakke phenomenological model. It is noted that, with reference to translational temperature, the time counter method shows less statistical scatter than that found with the modified Nanbu simulation technique.
Mode decomposition of nonlinear eigenvalue problems and application in flow stability
高军; 罗纪生
2014-01-01
Direct numerical simulations are carried out with different disturbance forms introduced into the inlet of a flat plate boundary layer with the Mach number 4.5. According to the biorthogonal eigenfunction system of the linearized Navier-Stokes equations and the adjoint equations, the decomposition of the direct numerical simulation results into the discrete normal mode is easily realized. The decomposition coefficients can be solved by doing the inner product between the numerical results and the eigenfunctions of the adjoint equations. For the quadratic polynomial eigenvalue problem, the inner product operator is given in a simple form, and it is extended to an N th-degree polynomial eigenvalue problem. The examples illustrate that the simplified mode decomposition is available to analyze direct numerical simulation results.
Optimal design for problems involving flow and transport phenomena in saturated subsurface systems
Mayer, Alex S.; Kelley, C. T.; Miller, Cass T.
Estimation problems arise routinely in subsurface hydrology for applications that range from water resources management to water quality protection to subsurface restoration. Interest in optimal design of such systems has increased over the last two decades and this area is considered an important and active area of research. In this work, we review the state of the art, assess important challenges that must be resolved to reach a mature level of understanding, and summarize some promising approaches that might help meet some of the challenges. While much has been accomplished to date, we conclude that more work remains before comprehensive, efficient, and robust solution methods exist to solve the most challenging applications in subsurface science. We suggest that future directions of research include the application of direct search solution methods, and developments in stochastic and multi-objective optimization. We present a set of comprehensive test problems for use in the research community as a means for benchmarking and comparing optimization approaches.
A free boundary problem describing the saturated-unsaturated flow in a porous medium
Gabriela Marinoschi
2004-01-01
Full Text Available This paper presents a functional approach to a nonlinear model describing the complete physical process of water infiltration into an unsaturated soil, including the saturation occurrence and the advance of the wetting front. The model introduced in this paper involves a multivalued operator covering the simultaneous saturated and unsaturated flow behaviors and enhances the study of the displacement of the free boundary between these two flow regimes. The model resides in Richards' equation written in pressure form with an initial condition and boundary conditions which in this work express the inflow due to the rain on the soil surface on the one hand, and characterize a certain permeability corresponding to the underground boundary, on the other hand. Existence, uniqueness, and regularity results for the transformed model in diffusive form, that is, for the moisture of the soil, and the existence of the weak solution for the pressure form are proved in the 3D case. The main part of the paper focuses on the existence of the free boundary between the saturated and unsaturated parts of the soil, and this is proved, in the 1D case, for certain stronger assumptions on the initial data and boundary conditions.
Two dimensional heat transfer problem in flow boiling in a rectangular minichannel
Hożejowska Sylwia
2015-01-01
Full Text Available The paper presents mathematical modelling of flow boiling heat transfer in a rectangular minichannel asymmetrically heated by a thin and one-sided enhanced foil. Both surfaces are available for observations due to the openings covered with glass sheets. Thus, changes in the colour of the plain foil surface can be registered and then processed. Plain side of the heating foil is covered with a base coat and liquid crystal paint. Observation of the opposite, enhanced surface of the minichannel allows for identification of the gas-liquid two-phase flow patterns and vapour quality. A two-dimensional mathematical model of heat transfer in three subsequent layers (sheet glass, heating foil, liquid was proposed. Heat transfer in all these layers was described with the respective equations: Laplace equation, Poisson equation and energy equation, subject to boundary conditions corresponding to the observed physical process. The solutions (temperature distributions in all three layers were obtained by Trefftz method. Additionally, the temperature of the boiling liquid was obtained by homotopy perturbation method (HPM combined with Trefftz method. The heat transfer coefficient, derived from Robin boundary condition, was estimated in both approaches. In comparison, the results by both methods show very good agreement especially when restricted to the thermal sublayer.
C. Cholet
2017-07-01
Full Text Available The aim of this study is to present a framework that provides new ways to characterize the spatio-temporal variability of lateral exchanges for water flow and solute transport in a karst conduit network during flood events, treating both the diffusive wave equation and the advection–diffusion equation with the same mathematical approach, assuming uniform lateral flow and solute transport. A solution to the inverse problem for the advection–diffusion equations is then applied to data from two successive gauging stations to simulate flows and solute exchange dynamics after recharge. The study site is the karst conduit network of the Fourbanne aquifer in the French Jura Mountains, which includes two reaches characterizing the network from sinkhole to cave stream to the spring. The model is applied, after separation of the base from the flood components, on discharge and total dissolved solids (TDSs in order to assess lateral flows and solute concentrations and compare them to help identify water origin. The results showed various lateral contributions in space – between the two reaches located in the unsaturated zone (R1, and in the zone that is both unsaturated and saturated (R2 – as well as in time, according to hydrological conditions. Globally, the two reaches show a distinct response to flood routing, with important lateral inflows on R1 and large outflows on R2. By combining these results with solute exchanges and the analysis of flood routing parameters distribution, we showed that lateral inflows on R1 are the addition of diffuse infiltration (observed whatever the hydrological conditions and localized infiltration in the secondary conduit network (tributaries in the unsaturated zone, except in extreme dry periods. On R2, despite inflows on the base component, lateral outflows are observed during floods. This pattern was attributed to the concept of reversal flows of conduit–matrix exchanges, inducing a complex water mixing effect
Cholet, Cybèle; Charlier, Jean-Baptiste; Moussa, Roger; Steinmann, Marc; Denimal, Sophie
2017-07-01
The aim of this study is to present a framework that provides new ways to characterize the spatio-temporal variability of lateral exchanges for water flow and solute transport in a karst conduit network during flood events, treating both the diffusive wave equation and the advection-diffusion equation with the same mathematical approach, assuming uniform lateral flow and solute transport. A solution to the inverse problem for the advection-diffusion equations is then applied to data from two successive gauging stations to simulate flows and solute exchange dynamics after recharge. The study site is the karst conduit network of the Fourbanne aquifer in the French Jura Mountains, which includes two reaches characterizing the network from sinkhole to cave stream to the spring. The model is applied, after separation of the base from the flood components, on discharge and total dissolved solids (TDSs) in order to assess lateral flows and solute concentrations and compare them to help identify water origin. The results showed various lateral contributions in space - between the two reaches located in the unsaturated zone (R1), and in the zone that is both unsaturated and saturated (R2) - as well as in time, according to hydrological conditions. Globally, the two reaches show a distinct response to flood routing, with important lateral inflows on R1 and large outflows on R2. By combining these results with solute exchanges and the analysis of flood routing parameters distribution, we showed that lateral inflows on R1 are the addition of diffuse infiltration (observed whatever the hydrological conditions) and localized infiltration in the secondary conduit network (tributaries) in the unsaturated zone, except in extreme dry periods. On R2, despite inflows on the base component, lateral outflows are observed during floods. This pattern was attributed to the concept of reversal flows of conduit-matrix exchanges, inducing a complex water mixing effect in the saturated zone
Nassar, M.; Ginn, T.
2012-12-01
The purpose of this study is to investigate the effect of the computational error on the solution of the inverse problem connecting with density-dependent flow problem. This effect will be addressed by evaluating the uniqueness of the inverse via monitoring objective function surface behavior in two dimensions parameter space, hydraulic conductivity and longitudinal dispersivity. In addition, the Pareto surface will be generated to evaluate the trade-offs between two calibration objectives based on head and concentration measurement errors. This is conducted by changing the aspects of forward model solution scheme, Eulerian and Lagrangian methods with associated variables. The data used for this study is based on the lab study of Nassar et al (2008). The seepage tank is essentially 2D (in an x-z vertical plane) with relatively homogenous coarse sand media with assigned flux in the upstream and constant head or assigned flux boundary condition at the downstream. The forward model solution is conducted with SEAWAT and it is utilized jointly with the inverse code UCODE-2005. This study demonstrates that the choice of the different numerical scheme with associated aspects of the forward problem is a vital step in the solution of the inverse problem in indirect manner. The method of characteristics gives good results by increasing the initial particles numbers and/ or reducing the time step. The advantage of using more particles concept over decreasing the time step is in smoothing the objective function surface that enable the gradient based search technique works in efficient way. Also, the selected points on the Pareto surface is collapsed to two points on the objective function space. Most likely they are not collapsed to a single point in objective function space with one best parameter set because the problem is advection dominating problem.
张宏远; 席裕庚; 谷寒雨
2005-01-01
There are many flow shop problems of throughput (denoted by FSPT) with constraints of due date in real production planning and scheduling. In this paper, a decomposition and coordination algorithm is proposed based on the analysis of FSPT and under the support of TOC (theory of constraint). A flow shop is at first decomposed into two subsystems named PULL and PUSH by means of bottleneck. Then the subsystem is decomposed into single machine scheduling problems,so the original NP-HARD problem can be transferred into a serial of single machine optimization problems finally. This method reduces the computational complexity, and has been used in a real project successfully.
Fraggedakis, D.; Papaioannou, J.; Dimakopoulos, Y.; Tsamopoulos, J.
2017-09-01
A new boundary-fitted technique to describe free surface and moving boundary problems is presented. We have extended the 2D elliptic grid generator developed by Dimakopoulos and Tsamopoulos (2003) [19] and further advanced by Chatzidai et al. (2009) [18] to 3D geometries. The set of equations arises from the fulfillment of the variational principles established by Brackbill and Saltzman (1982) [21], and refined by Christodoulou and Scriven (1992) [22]. These account for both smoothness and orthogonality of the grid lines of tessellated physical domains. The elliptic-grid equations are accompanied by new boundary constraints and conditions which are based either on the equidistribution of the nodes on boundary surfaces or on the existing 2D quasi-elliptic grid methodologies. The capabilities of the proposed algorithm are first demonstrated in tests with analytically described complex surfaces. The sequence in which these tests are presented is chosen to help the reader build up experience on the best choice of the elliptic grid parameters. Subsequently, the mesh equations are coupled with the Navier-Stokes equations, in order to reveal the full potential of the proposed methodology in free surface flows. More specifically, the problem of gas assisted injection in ducts of circular and square cross-sections is examined, where the fluid domain experiences extreme deformations. Finally, the flow-mesh solver is used to calculate the equilibrium shapes of static menisci in capillary tubes.
Yin, W.; Peyton, A. J.; Stefani, F.; Gerbeth, G.
2009-10-01
A completely contactless flow measurement technique based on the principle of EM induction measurements—contactless inductive flow tomography (CIFT)—has been previously reported by a team based at Forschungszentrum Dresden-Rossendorf (FZD). This technique is suited to the measurement of velocity fields in high conductivity liquids, and the possible applications range from monitoring metal casting and silicon crystal growth in industry to gaining insights into the working of the geodynamo. The forward problem, i.e. calculating the induced magnetic field from a known velocity profile, can be described as a linear relationship when the magnetic Reynolds number is small. Previously, an integral equation method was used to formulate the forward problem; however, although the sensitivity matrices were calculated, they were not explicitly expressed and computation involved the solution of an ill-conditioned system of equations using a so-called deflation method. In this paper, we present the derivation of the sensitivity matrix directly from electromagnetic field theory and the results are expressed very concisely as the cross product of two field vectors. A numerical method based on a finite difference method has also been developed to verify the formulation. It is believed that this approach provides a simple yet fast route to the forward solution of CIFT. Furthermore, a method for sensor design selection based on eigenvalue analysis is presented.
Yang, Haijian
2016-07-26
Fully implicit methods are drawing more attention in scientific and engineering applications due to the allowance of large time steps in extreme-scale simulations. When using a fully implicit method to solve two-phase flow problems in porous media, one major challenge is the solution of the resultant nonlinear system at each time step. To solve such nonlinear systems, traditional nonlinear iterative methods, such as the class of the Newton methods, often fail to achieve the desired convergent rate due to the high nonlinearity of the system and/or the violation of the boundedness requirement of the saturation. In the paper, we reformulate the two-phase model as a variational inequality that naturally ensures the physical feasibility of the saturation variable. The variational inequality is then solved by an active-set reduced-space method with a nonlinear elimination preconditioner to remove the high nonlinear components that often causes the failure of the nonlinear iteration for convergence. To validate the effectiveness of the proposed method, we compare it with the classical implicit pressure-explicit saturation method for two-phase flow problems with strong heterogeneity. The numerical results show that our nonlinear solver overcomes the often severe limits on the time step associated with existing methods, results in superior convergence performance, and achieves reduction in the total computing time by more than one order of magnitude.
Zhangxin Chen
1999-12-01
Full Text Available This is the third paper of a three-part series where we develop and analyze a finite element approximation for a degenerate elliptic-parabolic partial differential system which describes the flow of two incompressible, immiscible fluids in porous media. The approximation uses a mixed finite element method for the pressure equation and a Galerkin finite element method for the saturation equation. It is based on a regularization of the saturation equation. In the first paper cite{RckA} we analyzed the regularized differential system and presented numerical results. In the second paper cite{RckB} we obtained error estimates. In the present paper we describe a perturbation analysis for the saturation equation and numerical experiments for complementing this analysis.
Numerical solution of the problem on the constant current flow around a dielectric plate
Stadnik, I.P.
1977-01-01
The problem of a harmonic field circumvention of a plate of arbitrary form is reduced to a second species integral equation for the density of a binary layer. A feature of this integral equation is that the integration is performed along the entire plate except the circle contained in the center of the observation point. The method's agreement with sequential approximations is proven. An examination is made of the plane-parallel case and an example illustrating good agreement in results for the plane-parallel case which were obtained by the proposed method and method of conformal depictions. 2 references, 4 figures.
Turbomachine blading with splitter blades designed by solving the inverse flow field problem
Luu, T. S.; Viney, B.; Bencherif, L.
1992-04-01
The paper presents an inverse method for the turbomachine blading design in incompressible non viscous flow in order to avoid cavitation and gives a new approach of the boundary conditions to be settled in relation with bound vorticity distribution on the blades. Treating first the 2D cascade design, it shows how the blade must be generated with the given thickness distribution and must be loaded in order to obtain the desired outlet flow angle. The 3D design is analysed by two steps S2-S1 approach proposed by Wu[1]. For the meridian flow (S2 approach), the blade thickness is taken into account by the modification of metric tensor in the continuity equation. The governing one is provided by the hub to shroud equilibrium condition and the meridian stream function is choosen to define the flow field. This step leads to the determination of axisymmetrical stream sheets as well as the approximate camber surface of the blades. In the second step, blade to blade flow (S1 approach) is analyzed. The governing equation is deduced from the momentum equation which implies that the vorticity of the absolute velocity must be tangential to the stream sheet. The bound vorticity distribution must be the same one as in S2 approach and the residual flux crossing over the blade be conservative (transpiration model). These two relations constitute the boundary conditions for the S1 flow. The detection of this residual flux due to the normal component of the relative velocity on the blade surface leads to the rectification of the camber surface. The optimized design of the blading of a centifugal impeller with splitter blades is presented. Pour définir la géométrie des aubages, les méthodes conventionnelles prennent la distribution de vitesse sur les deux faces de l'aube comme données initiales. En appliquant cette approche, on perd le contrôle de l'épaisseur de l'aube. Pour y remédier, la présente méthode suggère une méthode inverse en représentant les aubes par une
Mathematical modeling and numerical simulation of two-phase flow problems at pore scale
Paula Luna
2015-11-01
Full Text Available Mathematical modeling and numerical simulation of two-phase flow through porous media is a very active field of research, because of its relevancy in a wide range of physical and technological applications. Some outstanding applications concern reservoir simulation and oil and gas recovery, fields in which a great effort is being paid in the development of efficient numerical methods. The mathematical model used in this work is written as a system comprising an elliptic equation for pressure and a hyperbolic one for saturation. Our aim is to obtain the numerical solution of this model by combining finite element and finite volume techniques, with a second-order non-oscillatory reconstruction procedure to build the values of the velocities at the cell interfaces of the FV mesh from pointwise values of the pressure at the FE nodes. The numerical results are compared to those obtained using the commercial code ECLIPSE showing an appropriate behavior from a qualitative point of view. The use of this FE-FV procedure is not the usual numerical method in petroleum reservoir simulation, since the techniques most frequently used are based on finite differences, even in standard commercial tools.
Farahmand-Mehr Mohammad
2014-01-01
Full Text Available In this paper, a hybrid flow shop scheduling problem with a new approach considering time lags and sequence-dependent setup time in realistic situations is presented. Since few works have been implemented in this field, the necessity of finding better solutions is a motivation to extend heuristic or meta-heuristic algorithms. This type of production system is found in industries such as food processing, chemical, textile, metallurgical, printed circuit board, and automobile manufacturing. A mixed integer linear programming (MILP model is proposed to minimize the makespan. Since this problem is known as NP-Hard class, a meta-heuristic algorithm, named Genetic Algorithm (GA, and three heuristic algorithms (Johnson, SPTCH and Palmer are proposed. Numerical experiments of different sizes are implemented to evaluate the performance of presented mathematical programming model and the designed GA in compare to heuristic algorithms and a benchmark algorithm. Computational results indicate that the designed GA can produce near optimal solutions in a short computational time for different size problems.
Flows in networks under fuzzy conditions
Bozhenyuk, Alexander Vitalievich; Kacprzyk, Janusz; Rozenberg, Igor Naymovich
2017-01-01
This book offers a comprehensive introduction to fuzzy methods for solving flow tasks in both transportation and networks. It analyzes the problems of minimum cost and maximum flow finding with fuzzy nonzero lower flow bounds, and describes solutions to minimum cost flow finding in a network with fuzzy arc capacities and transmission costs. After a concise introduction to flow theory and tasks, the book analyzes two important problems. The first is related to determining the maximum volume for cargo transportation in the presence of uncertain network parameters, such as environmental changes, measurement errors and repair work on the roads. These parameters are represented here as fuzzy triangular, trapezoidal numbers and intervals. The second problem concerns static and dynamic flow finding in networks under fuzzy conditions, and an effective method that takes into account the network’s transit parameters is presented here. All in all, the book provides readers with a practical reference guide to state-of-...
Use of a mixed layer model to investigate problems in operational prediction of return flow
Lewis, J. M.
2006-12-01
Inaccuracy in the numerical prediction of the moisture content of return-flow air over the Gulf of Mexico continues to plague operational forecasters. At the Environmental Modeling Center/National Centers for Environmental Prediction (EMC/NCEP) in the United States, the prediction errors have exhibited bias — typically too dry in the early-1990s and too moist from the mid-1990s to present. This research explores the possible sources of bias by using a Lagrangian formulation of the classic mixed-layer model. Justification for use of this low-order model rests on careful examination of the upper-air thermodynamic structure in a well- observed event during the Gulf of Mexico Experiment (GUFMEX). The mixed-layer constraints are shown to be appropriate for the first phase of return flow, viz., the outflow phase. The research begins by evaluating the model's estimates of sensitivity — the change in the model output (at the termination point of outflow) in response to inaccuracies in the elements of the control vector (the initial conditions, the boundary conditions, and the physical and empirical parameters). This evaluation is accomplished by recourse to a known analytic solution to the mixed-layer equations (a special case). Results indicate that the fourth-order Runge-Kutta integration scheme produces extremely accurate evolutions of the fields, and equally important, delivers accurate measures of the sensitivity. Further, the dynamical system is shown to be `weakly nonlinear', i. e., solutions that result from perturbations to the control vector are well approximated by the first-order terms in the Taylor series expansion about the base state. The second stage of research examines the relative importance of elements of the control vector on the moisture forecast for the general case. Results indicate that inaccuracies in the initial conditions are significant, yet they are secondary to inaccuracies in the boundary conditions and physical/empirical parameters. The
H. Gong; L. Tang; C.W. Duin
2010-01-01
Motivated by applications in iron and steel industry, we consider a two-stage flow shop scheduling problem where the first machine is a batching machine subject to the blocking constraint and the second machine is a discrete machine with shared setup times. We show that the problem is strongly NP-ha
Gong, H.; Tang, L.; Duin, C.W.
2010-01-01
Motivated by applications in iron and steel industry, we consider a two-stage flow shop scheduling problem where the first machine is a batching machine subject to the blocking constraint and the second machine is a discrete machine with shared setup times. We show that the problem is strongly
Determination of the modular elliptic function in problems of free-flow filtration
Anakhaev, K. N.
2016-09-01
The calculated dependences in elementary functions for determining the modular elliptic function λ(τ) =λ1 + iλ2 obtained on the basis of consecutive (six) conformal mappings of a curvilinear triangle to a complex half-plane are presented. Comparison of the values of λ(τ) from the proposed dependences with the results of the Hamel-Gunter exact analytical solution for the boundary contour of the curvilinear triangle, i.e., the real axis of the complex half-plane, gives a very close coincidence (with the largest error of ≤1%). The use of the complex values of the function λ(τ) for the entire internal region of the curvilinear triangle makes it possible to solve one of the most difficult problems of the theory of filtration (filtration through a rectangular dam) in the direct formulation and, for the first time, to construct the pattern of an equal filtration-rate field (the family of isotaches) over the entire internal region of the dam. In this case, the boundary values of filtration rates for special cases (along the sides and along the base of the dam) completely coincide with the results of the Masket exact analytical calculations.
王光臣; 吴臻
2007-01-01
In this paper, we mainly study a kind of risk-sensitive optimal control problem motiwted by a kind of portfolio choice problem in certain financial market. Using the classical convex variational technique, we obtain the maximum principle for this kind of problem. The form of the maximum principle is similar to its risk-neutral counterpart. But the adjoint equation and the variational inequality heavily depend on the risk-sensitive parameter γ. This is one of the main difference from the risk-neutral case. We use this result to solve a kind of optimal portfolio choice problem. The optimal portfolio strategy obtained by the Bellman dynamic programming principle is a special case of our result when the investor only invests the home bond and the stock. Computational results and figures explicitly illustrate the relationships between the maximum expected utility and the parameters of the model.
庄宏; 严宗毅; 吴望一
2002-01-01
A new three-dimensional fundamental solution to the Stokes flow was proposedby transforming the solid harmonic functions in Lamb' s solution into expressions in terms ofthe oblate spheroidal coordinates. These fundamental solutions are advantageous in treatingflows past an arbitrary number of arbitrarily positioned and oriented oblate spheroids. Theleast squares technique was adopted herein so that the convergence difficulties oftenencountered in solving three-dimensional problems were completely avoided. The examplesdemonstrate that present approach is highly accurate, consistently stable andcomputationally efficient.The oblate spheroid may be used to model a variety of particle shapes between acircular disk and a sphere. For the first time, the effect of various geometric factors on theforces and torques exerted on two oblate spheroids were systematically studied by using theproposed fundamental solutions. The generality of this approach was illustrated by twoproblems of three spheroids.
Jiuping Xu
2012-01-01
Full Text Available The aim of this study is to deal with a minimum cost network flow problem (MCNFP in a large-scale construction project using a nonlinear multiobjective bilevel model with birandom variables. The main target of the upper level is to minimize both direct and transportation time costs. The target of the lower level is to minimize transportation costs. After an analysis of the birandom variables, an expectation multiobjective bilevel programming model with chance constraints is formulated to incorporate decision makers’ preferences. To solve the identified special conditions, an equivalent crisp model is proposed with an additional multiobjective bilevel particle swarm optimization (MOBLPSO developed to solve the model. The Shuibuya Hydropower Project is used as a real-world example to verify the proposed approach. Results and analysis are presented to highlight the performances of the MOBLPSO, which is very effective and efficient compared to a genetic algorithm and a simulated annealing algorithm.
Maximum Autocorrelation Factorial Kriging
Nielsen, Allan Aasbjerg; Conradsen, Knut; Pedersen, John L.; Steenfelt, Agnete
2000-01-01
This paper describes maximum autocorrelation factor (MAF) analysis, maximum autocorrelation factorial kriging, and its application to irregularly sampled stream sediment geochemical data from South Greenland. Kriged MAF images are compared with kriged images of varimax rotated factors from an ordinary non-spatial factor analysis, and they are interpreted in a geological context. It is demonstrated that MAF analysis contrary to ordinary non-spatial factor analysis gives an objective discrimina...
Mushtaq, Ammar; Mustafa, Meraj; Hayat, Tasawar; Alsaedi, Ahmed
2014-12-01
The steady laminar three-dimensional magnetohydrodynamic (MHD) boundary layer flow and heat transfer over a stretching sheet is investigated. The sheet is linearly stretched in two lateral directions. Heat transfer analysis is performed by utilizing a nonlinear radiative heat flux in Rosseland approximation for thermal radiation. Two different wall conditions, namely (i) constant wall temperature and (ii) prescribed surface temperature are considered. The developed nonlinear boundary value problems (BVPs) are solved numerically through fifth-order Runge-Kutta method using a shooting technique. To ascertain the accuracy of results the solutions are also computed by using built in function bvp4c of MATLAB. The behaviours of interesting parameters are carefully analyzed through graphs for velocity and temperature distributions. The dimensionless expressions of wall shear stress and heat transfer rate at the sheet are evaluated and discussed. It is seen that a point of inflection of the temperature function exists for sufficiently large values of wall to ambient temperature ratio. The solutions are in excellent agreement with the previous studies in a limiting sense. To our knowledge, the novel idea of nonlinear thermal radiation in three-dimensional flow is just introduced here.
Nassar, Mohamed K.; Ginn, Timothy R.
2014-08-01
We investigate the effect of computational error on the inversion of a density-dependent flow and transport model, using SEAWAT and UCODE-2005 in an inverse identification of hydraulic conductivity and dispersivity using head and concentration data from a 2-D laboratory experiment. We investigated inversions using three different solution schemes including variation of number of particles and time step length, in terms of the three aspects: the shape and smoothness of the objective function surface, the consequent impacts to the optimization, and the resulting Pareto analyses. This study demonstrates that the inversion is very sensitive to the choice of the forward model solution scheme. In particular, standard finite difference methods provide the smoothest objective function surface; however, this is obtained at the cost of numerical artifacts that can lead to erroneous warping of the objective function surface. Total variation diminishing (TVD) schemes limit these impacts at the cost of more computation time, while the hybrid method of characteristics (HMOC) approach with increased particle numbers and/or reduced time step gives both smoothed and accurate objective function surface. Use of the most accurate methods (TVD and HMOC) did lead to successful inversion of the two parameters; however, with distinct results for Pareto analyses. These results illuminate the sensitivity of the inversion to a number of aspects of the forward solution of the density-driven flow problem and reveal that parameter values may result that are erroneous but that counteract numerical errors in the solution.
Chang, Chien-Chieh; Chen, Chia-Shyun
2002-06-01
A flowing partially penetrating well with infinitesimal well skin is a mixed boundary because a Cauchy condition is prescribed along the screen length and a Neumann condition of no flux is stipulated over the remaining unscreened part. An analytical approach based on the integral transform technique is developed to determine the Laplace domain solution for such a mixed boundary problem in a confined aquifer of finite thickness. First, the mixed boundary is changed into a homogeneous Neumann boundary by substituting the Cauchy condition with a Neumann condition in terms of well bore flux that varies along the screen length and is time dependent. Despite the well bore flux being unknown a priori, the modified model containing this homogeneous Neumann boundary can be solved with the Laplace and the finite Fourier cosine transforms. To determine well bore flux, screen length is discretized into a finite number of segments, to which the Cauchy condition is reinstated. This reinstatement also restores the relation between the original model and the solutions obtained. For a given time, the numerical inversion of the Laplace domain solution yields the drawdown distributions, well bore flux, and the well discharge. This analytical approach provides an alternative for dealing with the mixed boundary problems, especially when aquifer thickness is assumed to be finite.
Mani, Karthik
Adjoint methods have found applications in several key areas of computational fluid dynamics (CFD), namely, shape optimization and goal based adaptive solutions. CFD has become an essential tool in the design process by enabling the rapid testing of multiple designs, and currently it is normal practice to use CFD in conjunction with optimization algorithms for design improvement. In the context of shape optimization problems based on CFD, adjoint methods offer the significant advantage of computing sensitivity derivatives of the optimization cost function with respect to the set of design parameters, at a cost that is essentially independent of the number of design parameters. Adjoint methods reduce the cost of obtaining the complete gradient vector at any point in the design space equivalent to that of a single flow solution at the same point in the design space. This immediately enables the use of all gradient based optimization algorithms and lifts any restrictions on the number of design parameters required for the adequate definition of the optimization problem. Adaptive techniques in CFD constitute the other aspect where adjoint methods have have made great inroads. Typical adaptive solutions of the governing flow equations rely on estimating the local error in an evolving solution to target regions of the computational mesh for increased discrete resolution. The main goal of any adaptive solution method is the overall increase in solution accuracy with minimal increase in computational cost. However, targeting local error in the solution does not translate into efficient use of computational resources, since ultimately it is the accurate estimation of boundary integrated functional quantities such as load coefficients that are of importance to the user. Contrary to local error-based methods, adjoint methods allow the adaptation of the computational mesh specifically for the improvement of functionals such as load coefficients. This is achieved by
Model Selection Through Sparse Maximum Likelihood Estimation
Banerjee, Onureena; D'Aspremont, Alexandre
2007-01-01
We consider the problem of estimating the parameters of a Gaussian or binary distribution in such a way that the resulting undirected graphical model is sparse. Our approach is to solve a maximum likelihood problem with an added l_1-norm penalty term. The problem as formulated is convex but the memory requirements and complexity of existing interior point methods are prohibitive for problems with more than tens of nodes. We present two new algorithms for solving problems with at least a thousand nodes in the Gaussian case. Our first algorithm uses block coordinate descent, and can be interpreted as recursive l_1-norm penalized regression. Our second algorithm, based on Nesterov's first order method, yields a complexity estimate with a better dependence on problem size than existing interior point methods. Using a log determinant relaxation of the log partition function (Wainwright & Jordan (2006)), we show that these same algorithms can be used to solve an approximate sparse maximum likelihood problem for...
Generic maximum likely scale selection
Pedersen, Kim Steenstrup; Loog, Marco; Markussen, Bo
2007-01-01
The fundamental problem of local scale selection is addressed by means of a novel principle, which is based on maximum likelihood estimation. The principle is generally applicable to a broad variety of image models and descriptors, and provides a generic scale estimation methodology. The focus...... on second order moments of multiple measurements outputs at a fixed location. These measurements, which reflect local image structure, consist in the cases considered here of Gaussian derivatives taken at several scales and/or having different derivative orders....
Optimal Control of Polymer Flooding Based on Maximum Principle
Yang Lei
2012-01-01
Full Text Available Polymer flooding is one of the most important technologies for enhanced oil recovery (EOR. In this paper, an optimal control model of distributed parameter systems (DPSs for polymer injection strategies is established, which involves the performance index as maximum of the profit, the governing equations as the fluid flow equations of polymer flooding, and the inequality constraint as the polymer concentration limitation. To cope with the optimal control problem (OCP of this DPS, the necessary conditions for optimality are obtained through application of the calculus of variations and Pontryagin’s weak maximum principle. A gradient method is proposed for the computation of optimal injection strategies. The numerical results of an example illustrate the effectiveness of the proposed method.
Maximum likely scale estimation
Loog, Marco; Pedersen, Kim Steenstrup; Markussen, Bo
2005-01-01
A maximum likelihood local scale estimation principle is presented. An actual implementation of the estimation principle uses second order moments of multiple measurements at a fixed location in the image. These measurements consist of Gaussian derivatives possibly taken at several scales and/or ...
雷苏娇; 李俊; 吴海博; 冯宗明
2014-01-01
Multipath routing is a new feature in CCN (Content-Centric Networking) which can be used to enhance the efifciency of network resources usage and balance network congestion. Based on the minimum cost maximum flow theory, we propose a multipath routing algorithm which aims to minimize delay and maximize bandwidth. It can choose different routing paths automatically according to the difference of network bandwidth environment and delay between links to achieve optimal bandwidth utilization of the entire network. The simulation experiment shows that our algorithm can reduce packet loss rate, decrease the bottleneck link load by approximately 60%, and alleviate network congestion.%在CCN (Content-Centric Networking，内容中心网络)中，多路径路由是一个新的特性，采用多路径路由可以更高效地利用网络资源，平衡网络拥塞。本文基于最小费用最大流理论，提出了一种适用于CCN网络的最小时延最大带宽多路径路由算法。该算法可以根据网络链路的带宽差异和链路的时延来选择不同的路由路径,达到整个网络的带宽最优利用。仿真实验表明，该算法与最短路径算法相比可以减少网络丢包，将瓶颈链路的负载量降低60%左右，缓解网络拥塞。
Yuan-Hong Jiang
Full Text Available OBJECTIVES: The aim of this study was to investigate the predictive values of the total International Prostate Symptom Score (IPSS-T and voiding to storage subscore ratio (IPSS-V/S in association with total prostate volume (TPV and maximum urinary flow rate (Qmax in the diagnosis of bladder outlet-related lower urinary tract dysfunction (LUTD in men with lower urinary tract symptoms (LUTS. METHODS: A total of 298 men with LUTS were enrolled. Video-urodynamic studies were used to determine the causes of LUTS. Differences in IPSS-T, IPSS-V/S ratio, TPV and Qmax between patients with bladder outlet-related LUTD and bladder-related LUTD were analyzed. The positive and negative predictive values (PPV and NPV for bladder outlet-related LUTD were calculated using these parameters. RESULTS: Of the 298 men, bladder outlet-related LUTD was diagnosed in 167 (56%. We found that IPSS-V/S ratio was significantly higher among those patients with bladder outlet-related LUTD than patients with bladder-related LUTD (2.28±2.25 vs. 0.90±0.88, p1 or >2 was factored into the equation instead of IPSS-T, PPV were 91.4% and 97.3%, respectively, and NPV were 54.8% and 49.8%, respectively. CONCLUSIONS: Combination of IPSS-T with TPV and Qmax increases the PPV of bladder outlet-related LUTD. Furthermore, including IPSS-V/S>1 or >2 into the equation results in a higher PPV than IPSS-T. IPSS-V/S>1 is a stronger predictor of bladder outlet-related LUTD than IPSS-T.
Pankaj Kumar SRIVASTAVA; Manoj KUMAR
2012-01-01
A numerical algorithm is developed for the approximation of the solution to certain boundary value problems involving the third-order ordinary differential equation associated with draining and coating flows.The authors show that the approximate solutions obtained by the numerical algorithm developed by using nonpolynomial quintic spline functions are better than those produced by other spline and domain decomposition methods.The algorithm is tested on two problems associated with draining and coating flows to demonstrate the practical usefulness of the approach.
Piest, Jürgen
1989-06-01
This is the first of a series of three papers which report on an theoretical turbulence investigation. In the present part, the Reynolds equation for the mean velocity field in turbulent shear flow is derived in a systematic way starting from established physical knowledge. A basic problem of contemporary turbulence theory is that, at the hydrodynamic level, there seems to be no way presently to derive systematically the initial probability distribution of the fluctuating momentum density. For this reason, N-particle statistical mechanics is employed in this investigation. The closure problem of continuum turbulence theory is avoided by this method. The technique of deriving transport equations from the Liouville equation by projection operator methods is used for the derivation. Stationary constant density/temperature processes are considered only. The dissipative term of the momemtum transport equation is analyzed in order to obtain the formulas for the laminar and turbulent friction forces. The latter is obtained as a second-order convolution in the mean velocity field. The kernel function is a time integral of an equilibrium triple correlation function; it constitutes a physical “constant” of the fluid which is needed in addition to the viscosity constant. Its calculation has been the object of a separate investigation which will be reported in the second paper. The third paper describes the numerical evaluation and comparison with experiment for the spherical case of the circular jet. In the present state, the theoretical formula does not reproduce the experimental data. This is considered a preliminary result which, in view of the systematic nature of the derivation, offers the possibility to trace it back to the spots where the theoretical structure is still not adequate.
Alternative Multiview Maximum Entropy Discrimination.
Chao, Guoqing; Sun, Shiliang
2016-07-01
Maximum entropy discrimination (MED) is a general framework for discriminative estimation based on maximum entropy and maximum margin principles, and can produce hard-margin support vector machines under some assumptions. Recently, the multiview version of MED multiview MED (MVMED) was proposed. In this paper, we try to explore a more natural MVMED framework by assuming two separate distributions p1( Θ1) over the first-view classifier parameter Θ1 and p2( Θ2) over the second-view classifier parameter Θ2 . We name the new MVMED framework as alternative MVMED (AMVMED), which enforces the posteriors of two view margins to be equal. The proposed AMVMED is more flexible than the existing MVMED, because compared with MVMED, which optimizes one relative entropy, AMVMED assigns one relative entropy term to each of the two views, thus incorporating a tradeoff between the two views. We give the detailed solving procedure, which can be divided into two steps. The first step is solving our optimization problem without considering the equal margin posteriors from two views, and then, in the second step, we consider the equal posteriors. Experimental results on multiple real-world data sets verify the effectiveness of the AMVMED, and comparisons with MVMED are also reported.
Boundary condition effects on maximum groundwater withdrawal in coastal aquifers.
Lu, Chunhui; Chen, Yiming; Luo, Jian
2012-01-01
Prevention of sea water intrusion in coastal aquifers subject to groundwater withdrawal requires optimization of well pumping rates to maximize the water supply while avoiding sea water intrusion. Boundary conditions and the aquifer domain size have significant influences on simulating flow and concentration fields and estimating maximum pumping rates. In this study, an analytical solution is derived based on the potential-flow theory for evaluating maximum groundwater pumping rates in a domain with a constant hydraulic head landward boundary. An empirical correction factor, which was introduced by Pool and Carrera (2011) to account for mixing in the case with a constant recharge rate boundary condition, is found also applicable for the case with a constant hydraulic head boundary condition, and therefore greatly improves the usefulness of the sharp-interface analytical solution. Comparing with the solution for a constant recharge rate boundary, we find that a constant hydraulic head boundary often yields larger estimations of the maximum pumping rate and when the domain size is five times greater than the distance between the well and the coastline, the effect of setting different landward boundary conditions becomes insignificant with a relative difference between two solutions less than 2.5%. These findings can serve as a preliminary guidance for conducting numerical simulations and designing tank-scale laboratory experiments for studying groundwater withdrawal problems in coastal aquifers with minimized boundary condition effects.
Maximum Multiflow in Wireless Network Coding
Zhou, Jin-Yi; Jiang, Yong; Zheng, Hai-Tao
2012-01-01
In a multihop wireless network, wireless interference is crucial to the maximum multiflow (MMF) problem, which studies the maximum throughput between multiple pairs of sources and sinks. In this paper, we observe that network coding could help to decrease the impacts of wireless interference, and propose a framework to study the MMF problem for multihop wireless networks with network coding. Firstly, a network model is set up to describe the new conflict relations modified by network coding. Then, we formulate a linear programming problem to compute the maximum throughput and show its superiority over one in networks without coding. Finally, the MMF problem in wireless network coding is shown to be NP-hard and a polynomial approximation algorithm is proposed.
Maximum information photoelectron metrology
Hockett, P; Wollenhaupt, M; Baumert, T
2015-01-01
Photoelectron interferograms, manifested in photoelectron angular distributions (PADs), are a high-information, coherent observable. In order to obtain the maximum information from angle-resolved photoionization experiments it is desirable to record the full, 3D, photoelectron momentum distribution. Here we apply tomographic reconstruction techniques to obtain such 3D distributions from multiphoton ionization of potassium atoms, and fully analyse the energy and angular content of the 3D data. The PADs obtained as a function of energy indicate good agreement with previous 2D data and detailed analysis [Hockett et. al., Phys. Rev. Lett. 112, 223001 (2014)] over the main spectral features, but also indicate unexpected symmetry-breaking in certain regions of momentum space, thus revealing additional continuum interferences which cannot otherwise be observed. These observations reflect the presence of additional ionization pathways and, most generally, illustrate the power of maximum information measurements of th...
Andreas Wierschem
2007-09-01
Full Text Available The spatially periodic Kuramoto-Sivashinsky equation (pKS $$ partial_t u=-partial_x^4 u-c_3partial_x^3 u-c_2partial_x^2 u+2 deltapartial_x(cos( xu-partial_x(u^2, $$ with $u(t,xinmathbb{R}$, $tgeq 0$, $xinmathbb{R}$, is a model problem for inclined film flow over wavy bottoms and other spatially periodic systems with a long wave instability. For given $c_2,c_3inmathbb{R}$ and small $deltageq 0$ it has a one dimensional family of spatially periodic stationary solutions $u_s(cdot;c_2,c_3,delta,u_m$, parameterized by the mass $u_m=frac 1 {2pi}int_0^{2pi} u_s(x ,{ m d} x$. Depending on the parameters these stationary solutions can be linearly stable or unstable. We show that in the stable case localized perturbations decay with a polynomial rate and in a universal nonlinear self-similar way: the limiting profile is determined by a Burgers equation in Bloch wave space. We also discuss linearly unstable $u_s$, in which case we approximate the pKS by a constant coefficient KS-equation. The analysis is based on Bloch wave transform and renormalization group methods.
A Note on k-Limited Maximum Base
Yang Ruishun; Yang Xiaowei
2006-01-01
The problem of k-limited maximum base was specified into two special problems of k-limited maximum base; that is, let subset D of the problem of k-limited maximum base be an independent set and a circuit of the matroid, respectively. It was proved that under this circumstance the collections of k-limited base satisfy base axioms. Then a new matroid was determined, and the problem of k-limited maximum base was transformed to the problem of maximum base of this new matroid. Aiming at the problem, two algorithms, which in essence are greedy algorithms based on former matroid, were presented for the two special problems of k-limited maximum base. They were proved to be reasonable and more efficient than the algorithm presented by Ma Zhongfan in view of the complexity of algorithm.
JiahongGUO; XinHong
1999-01-01
In this paper,two dimensional unsteady flow and energy equations are employed for simulation of the flow and heat transfer in round billet continuous casting A numerical method is developed,by using finite volume method and equivalent specific heat method to solve the equations of flow and heat transfer with solidification.The numerical result shows that the method of this paper is efficient for analyzing the flow and heat transfer with solidification of round billet continuous casting.
Triadic conceptual structure of the maximum entropy approach to evolution.
Herrmann-Pillath, Carsten; Salthe, Stanley N
2011-03-01
Many problems in evolutionary theory are cast in dyadic terms, such as the polar oppositions of organism and environment. We argue that a triadic conceptual structure offers an alternative perspective under which the information generating role of evolution as a physical process can be analyzed, and propose a new diagrammatic approach. Peirce's natural philosophy was deeply influenced by his reception of both Darwin's theory and thermodynamics. Thus, we elaborate on a new synthesis which puts together his theory of signs and modern Maximum Entropy approaches to evolution in a process discourse. Following recent contributions to the naturalization of Peircean semiosis, pointing towards 'physiosemiosis' or 'pansemiosis', we show that triadic structures involve the conjunction of three different kinds of causality, efficient, formal and final. In this, we accommodate the state-centered thermodynamic framework to a process approach. We apply this on Ulanowicz's analysis of autocatalytic cycles as primordial patterns of life. This paves the way for a semiotic view of thermodynamics which is built on the idea that Peircean interpretants are systems of physical inference devices evolving under natural selection. In this view, the principles of Maximum Entropy, Maximum Power, and Maximum Entropy Production work together to drive the emergence of information carrying structures, which at the same time maximize information capacity as well as the gradients of energy flows, such that ultimately, contrary to Schrödinger's seminal contribution, the evolutionary process is seen to be a physical expression of the Second Law.
The strong maximum principle revisited
Pucci, Patrizia; Serrin, James
In this paper we first present the classical maximum principle due to E. Hopf, together with an extended commentary and discussion of Hopf's paper. We emphasize the comparison technique invented by Hopf to prove this principle, which has since become a main mathematical tool for the study of second order elliptic partial differential equations and has generated an enormous number of important applications. While Hopf's principle is generally understood to apply to linear equations, it is in fact also crucial in nonlinear theories, such as those under consideration here. In particular, we shall treat and discuss recent generalizations of the strong maximum principle, and also the compact support principle, for the case of singular quasilinear elliptic differential inequalities, under generally weak assumptions on the quasilinear operators and the nonlinearities involved. Our principal interest is in necessary and sufficient conditions for the validity of both principles; in exposing and simplifying earlier proofs of corresponding results; and in extending the conclusions to wider classes of singular operators than previously considered. The results have unexpected ramifications for other problems, as will develop from the exposition, e.g. two point boundary value problems for singular quasilinear ordinary differential equations (Sections 3 and 4); the exterior Dirichlet boundary value problem (Section 5); the existence of dead cores and compact support solutions, i.e. dead cores at infinity (Section 7); Euler-Lagrange inequalities on a Riemannian manifold (Section 9); comparison and uniqueness theorems for solutions of singular quasilinear differential inequalities (Section 10). The case of p-regular elliptic inequalities is briefly considered in Section 11.
Maximum Likelihood Associative Memories
Gripon, Vincent; Rabbat, Michael
2013-01-01
Associative memories are structures that store data in such a way that it can later be retrieved given only a part of its content -- a sort-of error/erasure-resilience property. They are used in applications ranging from caches and memory management in CPUs to database engines. In this work we study associative memories built on the maximum likelihood principle. We derive minimum residual error rates when the data stored comes from a uniform binary source. Second, we determine the minimum amo...
Maximum likely scale estimation
Loog, Marco; Pedersen, Kim Steenstrup; Markussen, Bo
2005-01-01
A maximum likelihood local scale estimation principle is presented. An actual implementation of the estimation principle uses second order moments of multiple measurements at a fixed location in the image. These measurements consist of Gaussian derivatives possibly taken at several scales and....../or having different derivative orders. Although the principle is applicable to a wide variety of image models, the main focus here is on the Brownian model and its use for scale selection in natural images. Furthermore, in the examples provided, the simplifying assumption is made that the behavior...... of the measurements is completely characterized by all moments up to second order....
Economics and Maximum Entropy Production
Lorenz, R. D.
2003-04-01
Price differentials, sales volume and profit can be seen as analogues of temperature difference, heat flow and work or entropy production in the climate system. One aspect in which economic systems exhibit more clarity than the climate is that the empirical and/or statistical mechanical tendency for systems to seek a maximum in production is very evident in economics, in that the profit motive is very clear. Noting the common link between 1/f noise, power laws and Self-Organized Criticality with Maximum Entropy Production, the power law fluctuations in security and commodity prices is not inconsistent with the analogy. There is an additional thermodynamic analogy, in that scarcity is valued. A commodity concentrated among a few traders is valued highly by the many who do not have it. The market therefore encourages via prices the spreading of those goods among a wider group, just as heat tends to diffuse, increasing entropy. I explore some empirical price-volume relationships of metals and meteorites in this context.
Mi Gan
2014-01-01
Full Text Available The multiproduct two-layer supply chain is very common in various industries. In this paper, we introduce a possible modeling and algorithms to solve a multiproduct two-layer supply chain network design problem. The decisions involved are the DCs location and capacity design decision and the initial distribution planning decision. First we describe the problem and give a mixed integer programming (MIP model; such problem is NP-hard and it is not easy to reduce the complexity. Inspired by it, we develop a transformation mechanism of relaxing the fixed cost and adding some virtual nodes and arcs to the original network. Thus, a network flow problem (NFP corresponding to the original problem has been formulated. Given that we could solve the NFP as a minimal cost flow problem. The solution procedures and network simplex algorithm (INS are discussed. To verify the effectiveness and efficiency of the model and algorithms, the performance measure experimental has been conducted. The experiments and result showed that comparing with MIP model solved by genetic algorithm (GA and Benders, decomposition algorithm (BD the NFP model and INS are also effective and even more efficient for both small-scale and large-scale problems.
Krukovsky, P.G. [Institute of Engineering Thermophysics, National Academy of Sciences of Ukraine, Kiev (Ukraine)
1997-12-31
The description of method and software FRIEND which provide a possibility of solution of inverse and inverse design problems on the basis of existing (base) CFD-software for solution of direct problems (in particular, heat-transfer and fluid-flow problems using software PHOENICS) are presented. FRIEND is an independent additional module that widens the operational capacities of the base software unified with this module. This unifying does not require any change or addition to the base software. Interfacing of FRIEND and the base software takes place through input and output files of the base software. A brief description of the computational technique applied for the inverse problem solution, same detailed information on the interfacing of FRIEND and CFD-software and solution results for testing inverse and inverse design problems, obtained using the tandem CFD-software PHOENICS and FRIEND, are presented. (author) 9 refs.
Liu, Chen; Wang, Qinxue; Yang, Yonghui; Wang, Kelin; Ouyang, Zhu; Li, Yan; Lei, Alin; Yasunari, Tetsuzo
2012-03-30
To diagnose problems that threaten regional sustainability and to devise appropriate treatment measures in China's agro-ecosystems, a study was carried out to quantify the nitrogen (N) flow in China's typical agro-ecosystems and develop potential solutions to the increasing environmental N load. The analysis showed that owing to human activity in the agro-ecosystems of Changjiang River Basin the mean total input of anthropogenic reactive N (i.e. chemical fertiliser, atmospheric deposition and bio-N fixation) increased from 4.41 × 10(9) kg-N in 1980 to 7.61 × 10(9) kg-N in 1990 and then to 1.43 × 10(10) kg-N in 2000, with chemical fertiliser N being the largest contributor to N load. Field investigation further showed that changes in human behaviour and rural urbanisation have caused rural communities to become more dependent on chemical fertilisers. In rural regions, around 4.17 kg-N of per capita annual potential N load as excrement was returned to farmlands and 1.38 kg-N directly discharged into river systems, while in urbanised regions, around 1.00 kg-N of per capita annual potential N load as excrement was returned to farmlands and 5.62 kg-N discharged into river systems in urban areas. The findings of the study suggest that human activities have significantly altered the N cycle in agro-ecosystems of China. With high population density and scarce per capita water resources, non-point source pollution from agro-ecosystems continues to put pressure on aquatic ecosystems. Increasing the rate of organic matter recycling and fertiliser efficiency with limited reliance on chemical fertilisers might yield tremendous environmental benefits. Copyright © 2011 Society of Chemical Industry.
F. TopsÃƒÂ¸e
2001-09-01
Full Text Available Abstract: In its modern formulation, the Maximum Entropy Principle was promoted by E.T. Jaynes, starting in the mid-fifties. The principle dictates that one should look for a distribution, consistent with available information, which maximizes the entropy. However, this principle focuses only on distributions and it appears advantageous to bring information theoretical thinking more prominently into play by also focusing on the "observer" and on coding. This view was brought forward by the second named author in the late seventies and is the view we will follow-up on here. It leads to the consideration of a certain game, the Code Length Game and, via standard game theoretical thinking, to a principle of Game Theoretical Equilibrium. This principle is more basic than the Maximum Entropy Principle in the sense that the search for one type of optimal strategies in the Code Length Game translates directly into the search for distributions with maximum entropy. In the present paper we offer a self-contained and comprehensive treatment of fundamentals of both principles mentioned, based on a study of the Code Length Game. Though new concepts and results are presented, the reading should be instructional and accessible to a rather wide audience, at least if certain mathematical details are left aside at a rst reading. The most frequently studied instance of entropy maximization pertains to the Mean Energy Model which involves a moment constraint related to a given function, here taken to represent "energy". This type of application is very well known from the literature with hundreds of applications pertaining to several different elds and will also here serve as important illustration of the theory. But our approach reaches further, especially regarding the study of continuity properties of the entropy function, and this leads to new results which allow a discussion of models with so-called entropy loss. These results have tempted us to speculate over
Maximum mutual information regularized classification
Wang, Jim Jing-Yan
2014-09-07
In this paper, a novel pattern classification approach is proposed by regularizing the classifier learning to maximize mutual information between the classification response and the true class label. We argue that, with the learned classifier, the uncertainty of the true class label of a data sample should be reduced by knowing its classification response as much as possible. The reduced uncertainty is measured by the mutual information between the classification response and the true class label. To this end, when learning a linear classifier, we propose to maximize the mutual information between classification responses and true class labels of training samples, besides minimizing the classification error and reducing the classifier complexity. An objective function is constructed by modeling mutual information with entropy estimation, and it is optimized by a gradient descend method in an iterative algorithm. Experiments on two real world pattern classification problems show the significant improvements achieved by maximum mutual information regularization.
Ilyas Khan
Full Text Available The present work is concerned with exact solutions of Stokes second problem for magnetohydrodynamics (MHD flow of a Burgers' fluid. The fluid over a flat plate is assumed to be electrically conducting in the presence of a uniform magnetic field applied in outward transverse direction to the flow. The equations governing the flow are modeled and then solved using the Laplace transform technique. The expressions of velocity field and tangential stress are developed when the relaxation time satisfies the condition γ = λ²/4 or γ> λ²/4. The obtained closed form solutions are presented in the form of simple or multiple integrals in terms of Bessel functions and terms with only Bessel functions. The numerical integration is performed and the graphical results are displayed for the involved flow parameters. It is found that the velocity decreases whereas the shear stress increases when the Hartmann number is increased. The solutions corresponding to the Stokes' first problem for hydrodynamic Burgers' fluids are obtained as limiting cases of the present solutions. Similar solutions for Stokes' second problem of hydrodynamic Burgers' fluids and those for Newtonian and Oldroyd-B fluids can also be obtained as limiting cases of these solutions.
Khan, Ilyas; Ali, Farhad; Shafie, Sharidan
2013-01-01
The present work is concerned with exact solutions of Stokes second problem for magnetohydrodynamics (MHD) flow of a Burgers' fluid. The fluid over a flat plate is assumed to be electrically conducting in the presence of a uniform magnetic field applied in outward transverse direction to the flow. The equations governing the flow are modeled and then solved using the Laplace transform technique. The expressions of velocity field and tangential stress are developed when the relaxation time satisfies the condition γ = λ²/4 or γ> λ²/4. The obtained closed form solutions are presented in the form of simple or multiple integrals in terms of Bessel functions and terms with only Bessel functions. The numerical integration is performed and the graphical results are displayed for the involved flow parameters. It is found that the velocity decreases whereas the shear stress increases when the Hartmann number is increased. The solutions corresponding to the Stokes' first problem for hydrodynamic Burgers' fluids are obtained as limiting cases of the present solutions. Similar solutions for Stokes' second problem of hydrodynamic Burgers' fluids and those for Newtonian and Oldroyd-B fluids can also be obtained as limiting cases of these solutions.
Pudasaini, Shiva P.; Fischer, Jan-Thomas; Mergili, Martin
2017-04-01
Debris flows are gravity driven mixture flows of soil, sand, rock and water. The solid particles and viscous fluid governs the rheological properties, and their coupling significantly influences the dynamics. For example, debris flows can dramatically increase their volume and destructive potential, and become exceptionally mobile by entraining bed material. The mixture composition can evolve to strikingly change the spatial distribution of particles and fluid, and thus frictional and viscous resistance. So, erosion-deposition and phase-separation between solid and fluid, which strongly depend on material composition, play a critical role in debris flow dynamics. Proper understanding of these complex physical processes is very important in accurate description of impact forces, inundation areas, landscape evolution and developing reliable mitigation plans. Predicting the underlying processes of erosion, phase-separation and deposition in debris flow are long-standing challenges. However, due to lack of data and suitable models, there exists no runout prediction method that includes observed processes of erosion of dry and saturated beds, entrainment and diffusion of eroded material, grain sorting, phase-separation, levee/lobe formation and evolution of deposition patterns. Based on innovative mechanical models for erosion-deposition (Pudasaini and Fischer, 2016a) and phase-separation (Pudasaini and Fischer, 2016b) that explicitly consider changes in local flow compositions, and their basic/potential validations, we present a novel, unified, efficient and fully coupled solution method to these true multi-phase, three-dimensional mass flow problems. As debris flows are better described by a three-phase mixture that include viscous fluid, and fine and coarse grains as compared to often used single-phase models, we propose model extensions that consists of three-phases including yield strength. Thus, we present an advanced mass flow simulation model aiming to
Effective soil hydraulic conductivity predicted with the maximum power principle
Westhoff, Martijn; Erpicum, Sébastien; Archambeau, Pierre; Pirotton, Michel; Zehe, Erwin; Dewals, Benjamin
2016-04-01
Drainage of water in soils happens for a large extent through preferential flowpaths, but these subsurface flowpaths are extremely difficult to observe or parameterize in hydrological models. To potentially overcome this problem, thermodynamic optimality principles have been suggested to predict effective parametrization of these (sub-grid) structures, such as the maximum entropy production principle or the equivalent maximum power principle. These principles have been successfully applied to predict heat transfer from the Equator to the Poles, or turbulent heat fluxes between the surface and the atmosphere. In these examples, the effective flux adapts itself to its boundary condition by adapting its effective conductance through the creation of e.g. convection cells. However, flow through porous media, such as soils, can only quickly adapt its effective flow conductance by creation of preferential flowpaths, but it is unknown if this is guided by the aim to create maximum power. Here we show experimentally that this is indeed the case: In the lab, we created a hydrological analogue to the atmospheric model dealing with heat transport between Equator and poles. The experimental setup consists of two freely draining reservoirs connected with each other by a confined aquifer. By adding water to only one reservoir, a potential difference will build up until a steady state is reached. From the steady state potential difference and the observed flow through the aquifer, and effective hydraulic conductance can be determined. This observed conductance does correspond to the one maximizing power of the flux through the confined aquifer. Although this experiment is done in an idealized setting, it opens doors for better parameterizing hydrological models. Furthermore, it shows that hydraulic properties of soils are not static, but they change with changing boundary conditions. A potential limitation to the principle is that it only applies to steady state conditions
周波; 刘文强; 乔付; 韩娜
2013-01-01
The paper introduces a dynamic programming method of maximum sub-segment sum problem in the course of design and analysis of algorithm. The solution procedure is to solve the maximum sub-segment sum of each element used as the tail element in a given sequence firstly, and then one of the largest is the maximum sub-seg-ment sum of the whole sequence. The paper analyzes the construction method of the optimal solution of the maximum sub-segment sum problem from two different facet, and presents the dynamic program-ming algorithm of the maximum sub-segment sum problem, also analyzes the time complexity of the algorithm. Through the explana-tion of this problem, it wil help the students clear the solving steps of the dynamic programming method and master the design step of the dynamic programming algorithm.%介绍算法设计与分析课程中最大子段和问题的动态规划解法，其求解思想是先求给定序列中以每一个元素为尾元素的最大子段和，然后其中的最大者便是整个序列的最大子段和。从两个不同的角度分析最大子段和问题最优解的构造方法，给出最大子段和问题的动态规划算法，并分析算法的时间复杂度。通过这一问题的讲解，有助于学生明确动态规划方法的解题步骤，掌握动态规划算法的设计步骤。
Equalized near maximum likelihood detector
2012-01-01
This paper presents new detector that is used to mitigate intersymbol interference introduced by bandlimited channels. This detector is named equalized near maximum likelihood detector which combines nonlinear equalizer and near maximum likelihood detector. Simulation results show that the performance of equalized near maximum likelihood detector is better than the performance of nonlinear equalizer but worse than near maximum likelihood detector.
Numerical optimization using flow equations.
Punk, Matthias
2014-12-01
We develop a method for multidimensional optimization using flow equations. This method is based on homotopy continuation in combination with a maximum entropy approach. Extrema of the optimizing functional correspond to fixed points of the flow equation. While ideas based on Bayesian inference such as the maximum entropy method always depend on a prior probability, the additional step in our approach is to perform a continuous update of the prior during the homotopy flow. The prior probability thus enters the flow equation only as an initial condition. We demonstrate the applicability of this optimization method for two paradigmatic problems in theoretical condensed matter physics: numerical analytic continuation from imaginary to real frequencies and finding (variational) ground states of frustrated (quantum) Ising models with random or long-range antiferromagnetic interactions.
Maximum Matchings via Glauber Dynamics
Jindal, Anant; Pal, Manjish
2011-01-01
In this paper we study the classic problem of computing a maximum cardinality matching in general graphs $G = (V, E)$. The best known algorithm for this problem till date runs in $O(m \\sqrt{n})$ time due to Micali and Vazirani \\cite{MV80}. Even for general bipartite graphs this is the best known running time (the algorithm of Karp and Hopcroft \\cite{HK73} also achieves this bound). For regular bipartite graphs one can achieve an $O(m)$ time algorithm which, following a series of papers, has been recently improved to $O(n \\log n)$ by Goel, Kapralov and Khanna (STOC 2010) \\cite{GKK10}. In this paper we present a randomized algorithm based on the Markov Chain Monte Carlo paradigm which runs in $O(m \\log^2 n)$ time, thereby obtaining a significant improvement over \\cite{MV80}. We use a Markov chain similar to the \\emph{hard-core model} for Glauber Dynamics with \\emph{fugacity} parameter $\\lambda$, which is used to sample independent sets in a graph from the Gibbs Distribution \\cite{V99}, to design a faster algori...
On the maximum-entropy method for kinetic equation of radiation, particle and gas
El-Wakil, S.A. [Mansoura Univ. (Egypt). Phys. Dept.; Madkour, M.A. [Mansoura Univ. (Egypt). Phys. Dept.; Degheidy, A.R. [Mansoura Univ. (Egypt). Phys. Dept.; Machali, H.M. [Mansoura Univ. (Egypt). Phys. Dept.
1995-02-01
The maximum-entropy approach is used to calculate some problems in radiative transfer and reactor physics such as the escape probability, the emergent and transmitted intensities for a finite slab as well as the emergent intensity for a semi-infinite medium. Also, it is employed to solve problems involving spherical geometry, such as luminosity (the total energy emitted by a sphere), neutron capture probability and the albedo problem. The technique is also employed in the kinetic theory of gases to calculate the Poiseuille flow and thermal creep of a rarefied gas between two plates. Numerical calculations are achieved and compared with the published data. The comparisons demonstrate that the maximum-entropy results are good in agreement with the exact ones. (orig.).
Egidi, Nadaniela; Giacomini, Josephin; Maponi, Pierluigi
2016-06-01
Matter of this paper is the study of the flow and the corresponding heat transfer in a U-shaped heat exchanger. We propose a mathematical model that is formulated as a forced convection problem for incompressible and Newtonian fluids and results in the unsteady Navier-Stokes problem. In order to get a solution, we discretise the equations with both the Finite Elements Method and the Finite Volumes Method. These procedures give rise to a non-symmetric indefinite quadratic system of equations. Thus, three regularisation techniques are proposed to make approximations effective and ideas to compare their results are provided.
1D and 2D Numerical Modeling for Solving Dam-Break Flow Problems Using Finite Volume Method
Szu-Hsien Peng
2012-01-01
Full Text Available The purpose of this study is to model the flow movement in an idealized dam-break configuration. One-dimensional and two-dimensional motion of a shallow flow over a rigid inclined bed is considered. The resulting shallow water equations are solved by finite volumes using the Roe and HLL schemes. At first, the one-dimensional model is considered in the development process. With conservative finite volume method, splitting is applied to manage the combination of hyperbolic term and source term of the shallow water equation and then to promote 1D to 2D. The simulations are validated by the comparison with flume experiments. Unsteady dam-break flow movement is found to be reasonably well captured by the model. The proposed concept could be further developed to the numerical calculation of non-Newtonian fluid or multilayers fluid flow.
S. Borazjani
2014-01-01
Full Text Available Analytical solutions for one-dimensional two-phase multicomponent flows in porous media describe processes of enhanced oil recovery, environmental flows of waste disposal, and contaminant propagation in subterranean reservoirs and water management in aquifers. We derive the exact solution for 3×3 hyperbolic system of conservation laws that corresponds to two-phase four-component flow in porous media where sorption of the third component depends on its own concentration in water and also on the fourth component concentration. Using the potential function as an independent variable instead of time allows splitting the initial system to 2×2 system for concentrations and one scalar hyperbolic equation for phase saturation, which allows for full integration of non-self-similar problem with wave interactions.
Krieg, R.; Hailfinger, G.
1980-02-01
In Part I a singularity method - also called boundary integral equation method or panel method - has been developed that is applicable especially to highly transient internal flow problems with any three-dimensional geometry including walls wetted on both sides. The boundary conditions are prescribed in terms of pressures and/or accelerations. The method is primarily based on a recently developed dipole element treatment for incompressible fluids. Such elements (panels) can be fitted to the fluid boundary or any enveloping surface. Also, point sources may be included. The applicability of the method is demonstrated by two different examples: the incipient flow in a T-joint and the oscillating flow in the pressure suppression system of a boiling water reactor.
Moretti, G.; Bleich, G.
1968-09-01
The three-dimensional flow field around blunted bodies traveling at supersonic speed is computed using a time-dependent technique. The problem is mathematically well posed, the technique is stable and its accuracy increases with the fineness of the mesh. Values at points within the shock layer are computed by a method closely related to the Lax-Wendroff technique. Values at shock points and body points are computed by a four-dimensional method of characteristics.
Ambarita, Himsar; Kishinami, Koki; Daimaruya, Mashashi; Tokura, Ikuo; Kawai, Hideki; Suzuki, Jun; Kobiyama, Mashayosi; Ginting, Armansyah
The present paper is a study on the optimum plate to plate spacing for maximum heat transfer rate from a flat plate type heat exchanger. The heat exchanger consists of a number of parallel flat plates. The working fluids are flowed at the same operational conditions, either fixed pressure head or fixed fan power input. Parallel and counter flow directions of the working fluids were considered. While the volume of the heat exchanger is kept constant, plate number was varied. Hence, the spacing between plates as well as heat transfer rate will vary and there exists a maximum heat transfer rate. The objective of this paper is to seek the optimum plate to plate spacing for maximum heat transfer rate. In order to solve the problem, analytical and numerical solutions have been carried out. In the analytical solution, the correlations of the optimum plate to plate spacing as a function of the non-dimensional parameters were developed. Furthermore, the numerical simulation is carried out to evaluate the correlations. The results show that the optimum plate to plate spacing for a counter flow heat exchanger is smaller than parallel flow ones. On the other hand, the maximum heat transfer rate for a counter flow heat exchanger is bigger than parallel flow ones.
Marylin Aroche Quintana
2003-12-01
Full Text Available Introduction: The studies of the lung function are essential for the diagnosis, classification and treatment of the Bronchial Asthma and inside them the mensuration of the flow maximum expiratory (FEM it provides a quantitative value of the obstruction of the air roads. Methods: It was carried out a study in two stages, the first one descriptive in which was included the 15 year-old patients and more with diagnostic of Bronchial Asthma and belonging to the CMF #26 of the Policlínico Area V of the Municipality Cienfuegos, with the objective of determining the modifications of the value of the FEM according to outline of treatment used intercrisis. The sample was constituted for 37 patients, to those that were applied a form of data where it was included the age, sex, clinical characteristics of its illness and the current treatment. In the second stage two groups were created selected by the simple random method. The first one received treatment with Intal Spray (four aplications per day and the second with Ketotifeno (tab. 1 mg. /2tab par day egining to make mensurations from FEM to the three, six, nine and twelve months of having implemented the treatment. Results: They in our patient prevailed the ages of 15- 24 years and of 25- 34 years and the feminine sex, the Salbutamol was the more utilized in the previous treatments, initially the greater number of asthmatic they were classified like moderates and upon concluding the 12mo month the 72.9% they of the total of the pattern behaved like light; they with both treatments improved the courages of FEM, although the group of patient that you received treatment with Intal you showed an improvement in statements security much more rapid. Conclusions: That patient that they utilized Intal had a more rapid elevation of the FEM.
Introducción: Los estudios de la función pulmonar son
Rinto Yusriski
2015-09-01
Full Text Available This research discusses an integer batch scheduling problems for a single-machine with position-dependent batch processing time due to the simultaneous effect of learning and forgetting. The decision variables are the number of batches, batch sizes, and the sequence of the resulting batches. The objective is to minimize total actual flow time, defined as total interval time between the arrival times of parts in all respective batches and their common due date. There are two proposed algorithms to solve the problems. The first is developed by using the Integer Composition method, and it produces an optimal solution. Since the problems can be solved by the first algorithm in a worst-case time complexity O(n2n-1, this research proposes the second algorithm. It is a heuristic algorithm based on the Lagrange Relaxation method. Numerical experiments show that the heuristic algorithm gives outstanding results.
Maximum Profit Configurations of Commercial Engines
Yiran Chen
2011-01-01
An investigation of commercial engines with finite capacity low- and high-price economic subsystems and a generalized commodity transfer law [n ∝ Δ (P m)] in commodity flow processes, in which effects of the price elasticities of supply and demand are introduced, is presented in this paper. Optimal cycle configurations of commercial engines for maximum profit are obtained by applying optimal control theory. In some special cases, the eventual state—market equilibrium—is solely determined by t...
Suprayogi Suprayogi; Senator Nur Bahagia; Yudi Thaddeus
2016-01-01
This paper considers a location problem in a supply chain network. The problem addressed in this paper is motivated by an initiative to develop an efficient supply chain network for supporting the agricultural activities. The supply chain network consists of regions, warehouses, distribution centers, plants, and markets. The products include a set of inbound products and a set of outbound products. In this paper, definitions of the inbound and outbound products are seen from the region’s poin...
Brickner, Daniel R.; McCombs, Gary B.
2004-01-01
In this article, the authors provide an instructional resource for presenting the indirect method of the statement of cash flows (SCF) in an introductory financial accounting course. The authors focus primarily on presenting a comprehensive example that illustrates the "why" of SCF preparation and show how journal entries and T-accounts can be…
Brickner, Daniel R.; McCombs, Gary B.
2004-01-01
In this article, the authors provide an instructional resource for presenting the indirect method of the statement of cash flows (SCF) in an introductory financial accounting course. The authors focus primarily on presenting a comprehensive example that illustrates the "why" of SCF preparation and show how journal entries and T-accounts can be…
Maximum entropy production in daisyworld
Maunu, Haley A.; Knuth, Kevin H.
2012-05-01
Daisyworld was first introduced in 1983 by Watson and Lovelock as a model that illustrates how life can influence a planet's climate. These models typically involve modeling a planetary surface on which black and white daisies can grow thus influencing the local surface albedo and therefore also the temperature distribution. Since then, variations of daisyworld have been applied to study problems ranging from ecological systems to global climate. Much of the interest in daisyworld models is due to the fact that they enable one to study self-regulating systems. These models are nonlinear, and as such they exhibit sensitive dependence on initial conditions, and depending on the specifics of the model they can also exhibit feedback loops, oscillations, and chaotic behavior. Many daisyworld models are thermodynamic in nature in that they rely on heat flux and temperature gradients. However, what is not well-known is whether, or even why, a daisyworld model might settle into a maximum entropy production (MEP) state. With the aim to better understand these systems, this paper will discuss what is known about the role of MEP in daisyworld models.
McHugh, P.R.
1995-10-01
Fully coupled, Newton-Krylov algorithms are investigated for solving strongly coupled, nonlinear systems of partial differential equations arising in the field of computational fluid dynamics. Primitive variable forms of the steady incompressible and compressible Navier-Stokes and energy equations that describe the flow of a laminar Newtonian fluid in two-dimensions are specifically considered. Numerical solutions are obtained by first integrating over discrete finite volumes that compose the computational mesh. The resulting system of nonlinear algebraic equations are linearized using Newton`s method. Preconditioned Krylov subspace based iterative algorithms then solve these linear systems on each Newton iteration. Selected Krylov algorithms include the Arnoldi-based Generalized Minimal RESidual (GMRES) algorithm, and the Lanczos-based Conjugate Gradients Squared (CGS), Bi-CGSTAB, and Transpose-Free Quasi-Minimal Residual (TFQMR) algorithms. Both Incomplete Lower-Upper (ILU) factorization and domain-based additive and multiplicative Schwarz preconditioning strategies are studied. Numerical techniques such as mesh sequencing, adaptive damping, pseudo-transient relaxation, and parameter continuation are used to improve the solution efficiency, while algorithm implementation is simplified using a numerical Jacobian evaluation. The capabilities of standard Newton-Krylov algorithms are demonstrated via solutions to both incompressible and compressible flow problems. Incompressible flow problems include natural convection in an enclosed cavity, and mixed/forced convection past a backward facing step.
Well-Posed Stokes/Brinkman and Stokes/Darcy Problems for Coupled Fluid-Porous Viscous Flows
Angot, Philippe
2010-09-01
We present a well-posed model for the Stokes/Brinkman problem with a family of jump embedded boundary conditions (J.E.B.C.) on an immersed interface with weak regularity assumptions. It is issued from a general framework recently proposed for fictitious domain problems. Our model is based on algebraic transmission conditions combining the stress and velocity jumps on the interface Σ separating the fluid and porous domains. These conditions, well chosen to get the coercivity of the operator, are sufficiently general to get the usual immersed boundary conditions on Σ when fictitious domain methods are concerned: Stefan-like, Robin (Fourier), Neumann or Dirichlet… Moreover, the general framework allows to prove the global solvability of some models with physically relevant stress or velocity jump boundary conditions for the momentum transport at a fluid-porous interface. The Stokes/Brinkman problem with Ochoa-Tapia & Whitaker (1995) interface conditions and the Stokes/Darcy problem with Beavers & Joseph (1967) conditions are both proved to be well-posed by an asymptotic analysis. Up to our knowledge, only the Stokes/Darcy problem with Saffman (1971) approximate interface conditions was known to be well-posed.
Arbogast, Todd
2012-01-01
Motivated by possible generalizations to more complex multiphase multicomponent systems in higher dimensions, we develop an Eulerian-Lagrangian numerical approximation for a system of two conservation laws in one space dimension modeling a simplified two-phase flow problem in a porous medium. The method is based on following tracelines, so it is stable independent of any CFL constraint. The main difficulty is that it is not possible to follow individual tracelines independently. We approximate tracing along the tracelines by using local mass conservation principles and self-consistency. The two-phase flow problem is governed by a system of equations representing mass conservation of each phase, so there are two local mass conservation principles. Our numerical method respects both of these conservation principles over the computational mesh (i.e., locally), and so is a fully conservative traceline method. We present numerical results that demonstrate the ability of the method to handle problems with shocks and rarefactions, and to do so with very coarse spatial grids and time steps larger than the CFL limit. © 2012 Society for Industrial and Applied Mathematics.
2006-04-17
solution and the right-hand side K(T,Tv) are functions of two variables); 65 • ill-posedness and nonuniqueness of the solution (this issue will be...investigation on plume contamination and surface effects. FTR Univ. Hamburg TRI-ESA-1987. 4. SUMMARY All research engineering and technical...component nozzle flow (model validation),” Proc. European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS 2004
Bogaers, Alfred EJ
2016-09-01
Full Text Available closed via the fluid equations. The fluid velocity in the cells between the two surfaces in contact is forced to be equal to the adjoining interface velocities. This allows for the small gap to remain, while the effect on the flow profile... slightly improved coupling performance, on average requiring fewer coupling iterations (see for example [17]). The BN Jacobians further provide an approximation of the sensitivities between interface forces and displacements, which can be reused. See...
Sparsest cuts and concurrent flows in product graphs
Bonsma, Paul
2004-01-01
A cut [S.S] is a sparsest cut of a graph G if its cut value [S][S]/[S.S] is maximum (this is the reciprocal of the well-known edge-density of the cut). In the (undirected) uniform concurrent flow problem on G, between every vertex pair of G flow paths with a total flow of 1 have to be established. T
S. Vignesh
2017-04-01
Full Text Available Flow based Erosion – corrosion problems are very common in fluid handling equipments such as propellers, impellers, pumps in warships, submarine. Though there are many coating materials available to combat erosion–corrosion damage in the above components, iron based amorphous coatings are considered to be more effective to combat erosion–corrosion problems. High velocity oxy-fuel (HVOF spray process is considered to be a better process to coat the iron based amorphous powders. In this investigation, iron based amorphous metallic coating was developed on 316 stainless steel substrate using HVOF spray technique. Empirical relationships were developed to predict the porosity and micro hardness of iron based amorphous coating incorporating HVOF spray parameters such as oxygen flow rate, fuel flow rate, powder feed rate, carrier gas flow rate, and spray distance. Response surface methodology (RSM was used to identify the optimal HVOF spray parameters to attain coating with minimum porosity and maximum hardness.
Bilello, J C; Liu, J M
1978-06-21
Progress in an investigation of the application of microdynamics and lattice mechanics to the problems in plastic flow and fracture is described. The research program consisted of both theoretical formulations and experimental measurements of a number of intrinsic material parameters in bcc metals and alloys including surface energy, phonon-dispersion curves for dislocated solids, dislocation-point defect interaction energy, slip initiation and microplastic flow behavior. The study has resulted in an improved understanding in the relationship among the experimentally determined fracture surface energy, the intrinsic cohesive energy between atomic planes, and the plastic deformation associated with the initial stages of crack propagation. The values of intrinsic surface energy of tungsten, molybdenum, niobium and niobium-molybdenum alloys, deduced from the measurements, serve as a starting point from which fracture toughness of these materials in engineering service may be intelligently discussed.
Plotting positions via maximum-likelihood for a non-standard situation
D. A. Jones
1997-01-01
Full Text Available A new approach is developed for the specification of the plotting positions used in the frequency analysis of extreme flows, rainfalls or similar data. The approach is based on the concept of maximum likelihood estimation and it is applied here to provide plotting positions for a range of problems which concern non-standard versions of annual-maximum data. This range covers the inclusion of incomplete years of data and also the treatment of cases involving regional maxima, where the number of sites considered varies from year to year. These problems, together with a not-to-be-recommended approach to using historical information, can be treated as special cases of a non-standard situation in which observations arise from different statistical distributions which vary in a simple, known, way.
Mixed integer linear programming for maximum-parsimony phylogeny inference.
Sridhar, Srinath; Lam, Fumei; Blelloch, Guy E; Ravi, R; Schwartz, Russell
2008-01-01
Reconstruction of phylogenetic trees is a fundamental problem in computational biology. While excellent heuristic methods are available for many variants of this problem, new advances in phylogeny inference will be required if we are to be able to continue to make effective use of the rapidly growing stores of variation data now being gathered. In this paper, we present two integer linear programming (ILP) formulations to find the most parsimonious phylogenetic tree from a set of binary variation data. One method uses a flow-based formulation that can produce exponential numbers of variables and constraints in the worst case. The method has, however, proven extremely efficient in practice on datasets that are well beyond the reach of the available provably efficient methods, solving several large mtDNA and Y-chromosome instances within a few seconds and giving provably optimal results in times competitive with fast heuristics than cannot guarantee optimality. An alternative formulation establishes that the problem can be solved with a polynomial-sized ILP. We further present a web server developed based on the exponential-sized ILP that performs fast maximum parsimony inferences and serves as a front end to a database of precomputed phylogenies spanning the human genome.
Liu, Weibo; Jin, Yan; Price, Mark
2016-10-01
A new heuristic based on the Nawaz-Enscore-Ham algorithm is proposed in this article for solving a permutation flow-shop scheduling problem. A new priority rule is proposed by accounting for the average, mean absolute deviation, skewness and kurtosis, in order to fully describe the distribution style of processing times. A new tie-breaking rule is also introduced for achieving effective job insertion with the objective of minimizing both makespan and machine idle time. Statistical tests illustrate better solution quality of the proposed algorithm compared to existing benchmark heuristics.
Maximum Segment Sum, Monadically (distilled tutorial
Jeremy Gibbons
2011-09-01
Full Text Available The maximum segment sum problem is to compute, given a list of integers, the largest of the sums of the contiguous segments of that list. This problem specification maps directly onto a cubic-time algorithm; however, there is a very elegant linear-time solution too. The problem is a classic exercise in the mathematics of program construction, illustrating important principles such as calculational development, pointfree reasoning, algebraic structure, and datatype-genericity. Here, we take a sideways look at the datatype-generic version of the problem in terms of monadic functional programming, instead of the traditional relational approach; the presentation is tutorial in style, and leavened with exercises for the reader.
Integer Programming Model for Maximum Clique in Graph
YUAN Xi-bo; YANG You; ZENG Xin-hai
2005-01-01
The maximum clique or maximum independent set of graph is a classical problem in graph theory. Combined with Boolean algebra and integer programming, two integer programming models for maximum clique problem,which improve the old results were designed in this paper. Then, the programming model for maximum independent set is a corollary of the main results. These two models can be easily applied to computer algorithm and software, and suitable for graphs of any scale. Finally the models are presented as Lingo algorithms, verified and compared by several examples.
Maximum entropy signal restoration with linear programming
Mastin, G.A.; Hanson, R.J.
1988-05-01
Dantzig's bounded-variable method is used to express the maximum entropy restoration problem as a linear programming problem. This is done by approximating the nonlinear objective function with piecewise linear segments, then bounding the variables as a function of the number of segments used. The use of a linear programming approach allows equality constraints found in the traditional Lagrange multiplier method to be relaxed. A robust revised simplex algorithm is used to implement the restoration. Experimental results from 128- and 512-point signal restorations are presented.
Ancalla, Lourdes Pilar Zaragoza
2005-04-15
The reconstruction of the distribution of density of potency pin upright in a heterogeneous combustible element, of the nucleus of a nuclear reactor, it is a subject that has been studied inside by a long time in Physics of Reactors area. Several methods exist to do this reconstruction, one of them is Maximum Entropy's Method, that besides being an optimization method that finds the best solution of all the possible solutions, it is a method also improved that uses multipliers of Lagrange to obtain the distribution of the flows in the faces of the combustible element. This distribution of the flows in the faces is used then as a contour condition in the calculations of a detailed distribution of flow inside the combustible element. In this work, in first place it was made the homogenization of the heterogeneous element. Soon after the factor of the multiplication executes and the medium values of the flow and of the liquid current they are computed, with the program NEM2D. These values medium nodal are, then, used upright in the reconstruction of the distribution pin of the flow inside the combustible element. The obtained results were acceptable, when compared with those obtained using fine mesh. (author)
The effect of maximum open height on operating characteristics of polymer injected pump poppet valve
Zhang, S. C.; Chen, X. D.; Deng, H. Y.
2012-11-01
Reciprocating polymer injected pump is the key injection equipment of tertiary oil recovery, the poppet valve in it exists the problem of large vibration noise, low efficiency and short life when transportation high viscosity medium. So the CFD technique is adopted to simulate and analyze the inner flow fields of fluid end poppet valve. According to the practical structure of the poppet valve, a simplified 2D axis-symmetry geometry model of the flow field is established. Combined with pump speed, plunger stroke and plunger diameter, given the boundary condition of the inlet valve, then the numerical simulation of flow field under six different maximum open heights is done depending on software Fluent. The relationship between open height to valve gap flow velocity, hydraulic loss and lag angle is obtained. The results indicate that, with the increase of open height, the valve gap flow velocity decreases, inlet outlet pressure differential decreases and hydraulic loss decreases. But the lag angle is continuously increasing with the increase of maximum open height, the valve has a good work performance when the open height is 1, 1.5, 2, 2.5, 3mm, but when it reaches 3.5mm, the valve performance becomes poor. The study can offer certain reference to understand operating characteristics of poppet valve, help to reduce the hydraulic losses and raise volume efficiency of the pump.
Christian F. Janßen
2015-07-01
Full Text Available This contribution is dedicated to demonstrating the high potential and manifold applications of state-of-the-art computational fluid dynamics (CFD tools for free-surface flows in civil and environmental engineering. All simulations were performed with the academic research code ELBE (efficient lattice boltzmann environment, http://www.tuhh.de/elbe. The ELBE code follows the supercomputing-on-the-desktop paradigm and is especially designed for local supercomputing, without tedious accesses to supercomputers. ELBE uses graphics processing units (GPU to accelerate the computations and can be used in a single GPU-equipped workstation of, e.g., a design engineer. The code has been successfully validated in very different fields, mostly related to naval architecture and mechanical engineering. In this contribution, we give an overview of past and present applications with practical relevance for civil engineers. The presented applications are grouped into three major categories: (i tsunami simulations, considering wave propagation, wave runup, inundation and debris flows; (ii dam break simulations; and (iii numerical wave tanks for the calculation of hydrodynamic loads on fixed and moving bodies. This broad range of applications in combination with accurate numerical results and very competitive times to solution demonstrates that modern CFD tools in general, and the ELBE code in particular, can be a helpful design tool for civil and environmental engineers.
HE Long-min; SUN Shi-jie; CHENG Ming-bao
2008-01-01
This paper considers a hybrid two-stage flow-shop scheduling problem with m identical parallel machineson one stage and a batch processor on the other stage.The processing time of job Jj on any of m identical parallel machines is aj≡a(j∈N),and the processing time of job Jj is bj(j∈N)on a batch processor M.We take makespan(Cmax)as our minimization objective.In this paper,for the problem of FSMP-BI(m identical parallel machines on the first stage and a batch processor on the second stage),based on the algorithm given by Sung and Choung for the problem of l I rj,BI I Cmax under the constraint of the given processing sequence,we develop an optimal dynamic programming Algorithm H1 for it in max{O(nlogn),O(nB)} time.A max{O(nlogn),O(nB)} time symmetric Algorithm H2 is given then for the problem of BI-FSMP(a batch processor on the first stage and m identical parallel machines on the second stage).
Computing Rooted and Unrooted Maximum Consistent Supertrees
van Iersel, Leo
2009-01-01
A chief problem in phylogenetics and database theory is the computation of a maximum consistent tree from a set of rooted or unrooted trees. A standard input are triplets, rooted binary trees on three leaves, or quartets, unrooted binary trees on four leaves. We give exact algorithms constructing rooted and unrooted maximum consistent supertrees in time O(2^n n^5 m^2 log(m)) for a set of m triplets (quartets), each one distinctly leaf-labeled by some subset of n labels. The algorithms extend to weighted triplets (quartets). We further present fast exact algorithms for constructing rooted and unrooted maximum consistent trees in polynomial space. Finally, for a set T of m rooted or unrooted trees with maximum degree D and distinctly leaf-labeled by some subset of a set L of n labels, we compute, in O(2^{mD} n^m m^5 n^6 log(m)) time, a tree distinctly leaf-labeled by a maximum-size subset X of L that all trees in T, when restricted to X, are consistent with.
基于OpenCL的并行方腔流加速性能分析%Performance analysis of OpenCL parallel acceleration on cavity flow problem
李森; 李新亮; 王龙; 陆忠华; 迟学斌
2011-01-01
This paper proposed a new approach to accelerate cavity flow problem using OpenCL technology. This paper transformed the cavity flow problem into N-S equation and solved it by finite difference method. During this procedure, used local memory and other techniques to accelerate the code. This paper ran the program on both NVIDIA and ATI platforms. The experiment shows a 30x times speed up.%提出了一种使用OpenCL技术对方腔流问题进行加速计算的方法.在计算方腔流问题时,将其转换为N-S方程通过空间有限差分和龙格库塔时间差分求解,并使用局部缓存等技术进行GPU优化.实验在NVIDIA和ATI平台对所给算法进行评测.结果显示,OpenCL相对其串行版本加速约30倍左右.
Zahr, M. J.; Persson, P.-O.
2016-12-01
The fully discrete adjoint equations and the corresponding adjoint method are derived for a globally high-order accurate discretization of conservation laws on parametrized, deforming domains. The conservation law on the deforming domain is transformed into one on a fixed reference domain by the introduction of a time-dependent mapping that encapsulates the domain deformation and parametrization, resulting in an Arbitrary Lagrangian-Eulerian form of the governing equations. A high-order discontinuous Galerkin method is used to discretize the transformed equation in space and a high-order diagonally implicit Runge-Kutta scheme is used for the temporal discretization. Quantities of interest that take the form of space-time integrals are discretized in a solver-consistent manner. The corresponding fully discrete adjoint method is used to compute exact gradients of quantities of interest along the manifold of solutions of the fully discrete conservation law. These quantities of interest and their gradients are used in the context of gradient-based PDE-constrained optimization. The adjoint method is used to solve two optimal shape and control problems governed by the isentropic, compressible Navier-Stokes equations. The first optimization problem seeks the energetically optimal trajectory of a 2D airfoil given a required initial and final spatial position. The optimization solver, driven by gradients computed via the adjoint method, reduced the total energy required to complete the specified mission nearly an order of magnitude. The second optimization problem seeks the energetically optimal flapping motion and time-morphed geometry of a 2D airfoil given an equality constraint on the x-directed impulse generated on the airfoil. The optimization solver satisfied the impulse constraint to greater than 8 digits of accuracy and reduced the required energy between a factor of 2 and 10, depending on the value of the impulse constraint, as compared to the nominal configuration.
Doisneau, François; Arienti, Marco; Oefelein, Joseph C.
2017-01-01
For sprays, as described by a kinetic disperse phase model strongly coupled to the Navier-Stokes equations, the resolution strategy is constrained by accuracy objectives, robustness needs, and the computing architecture. In order to leverage the good properties of the Eulerian formalism, we introduce a deterministic particle-based numerical method to solve transport in physical space, which is simple to adapt to the many types of closures and moment systems. The method is inspired by the semi-Lagrangian schemes, developed for Gas Dynamics. We show how semi-Lagrangian formulations are relevant for a disperse phase far from equilibrium and where the particle-particle coupling barely influences the transport; i.e., when particle pressure is negligible. The particle behavior is indeed close to free streaming. The new method uses the assumption of parcel transport and avoids to compute fluxes and their limiters, which makes it robust. It is a deterministic resolution method so that it does not require efforts on statistical convergence, noise control, or post-processing. All couplings are done among data under the form of Eulerian fields, which allows one to use efficient algorithms and to anticipate the computational load. This makes the method both accurate and efficient in the context of parallel computing. After a complete verification of the new transport method on various academic test cases, we demonstrate the overall strategy's ability to solve a strongly-coupled liquid jet with fine spatial resolution and we apply it to the case of high-fidelity Large Eddy Simulation of a dense spray flow. A fuel spray is simulated after atomization at Diesel engine combustion chamber conditions. The large, parallel, strongly coupled computation proves the efficiency of the method for dense, polydisperse, reacting spray flows.
Doisneau, François, E-mail: fdoisne@sandia.gov; Arienti, Marco, E-mail: marient@sandia.gov; Oefelein, Joseph C., E-mail: oefelei@sandia.gov
2017-01-15
For sprays, as described by a kinetic disperse phase model strongly coupled to the Navier–Stokes equations, the resolution strategy is constrained by accuracy objectives, robustness needs, and the computing architecture. In order to leverage the good properties of the Eulerian formalism, we introduce a deterministic particle-based numerical method to solve transport in physical space, which is simple to adapt to the many types of closures and moment systems. The method is inspired by the semi-Lagrangian schemes, developed for Gas Dynamics. We show how semi-Lagrangian formulations are relevant for a disperse phase far from equilibrium and where the particle–particle coupling barely influences the transport; i.e., when particle pressure is negligible. The particle behavior is indeed close to free streaming. The new method uses the assumption of parcel transport and avoids to compute fluxes and their limiters, which makes it robust. It is a deterministic resolution method so that it does not require efforts on statistical convergence, noise control, or post-processing. All couplings are done among data under the form of Eulerian fields, which allows one to use efficient algorithms and to anticipate the computational load. This makes the method both accurate and efficient in the context of parallel computing. After a complete verification of the new transport method on various academic test cases, we demonstrate the overall strategy's ability to solve a strongly-coupled liquid jet with fine spatial resolution and we apply it to the case of high-fidelity Large Eddy Simulation of a dense spray flow. A fuel spray is simulated after atomization at Diesel engine combustion chamber conditions. The large, parallel, strongly coupled computation proves the efficiency of the method for dense, polydisperse, reacting spray flows.
Solution of the Problem of the Couette Flow for a Fermi Gas with Almost Specular Boundary Conditions
Bedrikova, E. A.; Latyshev, A. V.
2016-06-01
A solution of the Couette problem for a Fermi gas is constructed. The kinetic Bhatnagar-Gross-Krook (BGK) equation is used. Almost specular boundary conditions are considered. Formulas for the mass flux and the heat flux of the gas are obtained. These fluxes are proportional to the difference of the tangential momentum accommodation coefficients of the molecules. An expression for the viscous drag force acting on the walls of the channel is also found. An analysis of the macroparameters of the gas is performed. The limit to classical gases is taken. The obtained results are found to go over to the known results in this limit.
Solution for Travelling Salesman Problem Based on Flowing Water Algorithm%基于流水算法的旅行商问题求解
王庆; 刘学鹏
2014-01-01
为了求解旅行商问题，本文借用“水无常形，水往低处流，水流千里归大海”的自然规律，提出新型元启发式求解算法：流水算法。新算法主要包括流水局部搜索、水漫溢出、流水凿洞、蒸发-下雨4个算子，同时具有禁忌搜索和正反馈机制特点，兼顾全局搜索和局部搜索能力。最后，本文应用MATLAB平台对算例进行仿真，并与其他经典的元启发式算法进行比较，结果表明流水算法是求解旅行商问题的有效方法，具有较好的收敛性。%To solve the travelling salesman problem, this paper proposes a novel meta-heuristics algorithm, called Flowing Water Algorithm, by borrowing the natural laws of “water has no unchanging shape”, “water flows downwards” and“water flows eventually into sea” and integrating the concept of self-adaptation and elite solution strategy. The new proposed FWA integrates mainly four operators including local search operator, overflowing operator, drilling water tunnel operator and evaporation-rain operator. This algorithm has global and local search capabilities as well as functions of tabu search and positive feedback. By simulating the cases based on MATLAB and analyzing the simulation results, this paper proves the effectiveness of FWA in the application of the travelling salesman problem. Besides, this novel algorithm has better convergence.
Solution of the Pierce problem near a corner of a rectilinear flow with a polygonal cross-section
Kotelnikov, Igor A
2014-01-01
An ill-posed problem of synthesis of the Pierce electrodes for a cylindrical beam with a polygonal cross-section is considered. It is assumed that a beam of charged particles is extracted from a space-charge-limited planar diode and the Pierce electrodes outside of the beam ensure its zero angular divergence. A mathematical statement of the problem presumes a computation of the electrostatic potential outside of the beam that should match the Child-Langmuir 1D potential inside of the beam. An exact solution is first obtained for the potential outside of the beam near its right angle. The solution involves double analytic continuation and a numerical integration of the hypergeometric function and can be used as a benchmark for testing numerical codes. It is shown that equipotential surfaces have fractures that can be pushed away from the corner of the beam by means of smoothing the beam corners. This solution is then generalized to an angle of arbitrary magnitude.
On the effect of standard PFEM remeshing on volume conservation in free-surface fluid flow problems
Franci, Alessandro; Cremonesi, Massimiliano
2017-07-01
The aim of this work is to analyze the remeshing procedure used in the particle finite element method (PFEM) and to investigate how this operation may affect the numerical results. The PFEM remeshing algorithm combines the Delaunay triangulation and the Alpha Shape method to guarantee a good quality of the Lagrangian mesh also in large deformation processes. However, this strategy may lead to local variations of the topology that may cause an artificial change of the global volume. The issue of volume conservation is here studied in detail. An accurate description of all the situations that may induce a volume variation during the PFEM regeneration of the mesh is provided. Moreover, the crucial role of the parameter α used in the Alpha Shape method is highlighted and a range of values of α for which the differences between the numerical results are negligible, is found. Furthermore, it is shown that the variation of volume induced by the remeshing reduces by refining the mesh. This check of convergence is of paramount importance for the reliability of the PFEM. The study is carried out for 2D free-surface fluid dynamics problems, however the conclusions can be extended to 3D and to all those problems characterized by significant variations of internal and external boundaries.
Babaee, Hessam; Choi, Minseok; Sapsis, Themistoklis P.; Karniadakis, George Em
2017-09-01
analyze the performance of the method in the presence of eigenvalue crossing and zero eigenvalues; (ii) stochastic Kovasznay flow: we examine the method in the presence of a singular covariance matrix; and (iii) we examine the adaptivity of the method for an incompressible flow over a cylinder where for large stochastic forcing thirteen DO/BO modes are active.
Nasri Abdelfatah
2011-01-01
Full Text Available The Reactive power flow’s is one of the most electrical distribution systems problem wich have great of interset of the electrical network researchers, it’s cause’s active power transmission reduction, power losses decreasing, and the drop voltage’s increase. In this research we described the efficiency of the FLC-GAO approach to solve the optimal power flow (OPF combinatorial problem. The proposed approach employ tow algorithms, Fuzzy logic controller (FLC algorithm for critical nodal detection and gentic algorithm optimization (GAO algorithm for optimal seizing capacitor.GAO method is more efficient in combinatory problem solutions. The proposed approach has been examined and tested on the standard IEEE 57-bus the resulats show the power loss minimization denhancement, voltage profile, and stability improvement. The proposed approach results have been compared to those that reported in the literature recently. The results are promising and show the effectiveness and robustness of the proposed approach.
OECD Maximum Residue Limit Calculator
With the goal of harmonizing the calculation of maximum residue limits (MRLs) across the Organisation for Economic Cooperation and Development, the OECD has developed an MRL Calculator. View the calculator.
ON RESERVES, STABILITY AND THE MAXIMUM SUSTAINABLE YIELD PROBLEM
Arild Wikan
2013-01-01
Full Text Available Due to the fact that several species of commercial interest have been overexploited throughout the years it is important to understand how harvest and other factors like introducing reserves influence the dynamic behaviour of a population with respect to stability and possible extinction. Therefore, simple one-population models are analysed and it is shown that harvest acts in a strong stabilizing fashion in the sense that it may transfer a population which exhibits chaotic oscillations to a state where the equilibrium population is stable. Moreover, if we divide the habitat of the population into a reserve and a harvest zone we find that increased harvest as well as migration between the two areas act stabilizing but that the former turns out to be the dominating one. If age structure is included in the population model harvest may not necessarily play the same role, especially if the number of age classes become large. Regarding MSY, we demonstrate that it is indeed possible to obtain the same MSY in the case where the habitat is split into a reserve and a harvest zone as in case of no reserve.
Constrained Graph Optimization: Interdiction and Preservation Problems
Schild, Aaron V [Los Alamos National Laboratory
2012-07-30
The maximum flow, shortest path, and maximum matching problems are a set of basic graph problems that are critical in theoretical computer science and applications. Constrained graph optimization, a variation of these basic graph problems involving modification of the underlying graph, is equally important but sometimes significantly harder. In particular, one can explore these optimization problems with additional cost constraints. In the preservation case, the optimizer has a budget to preserve vertices or edges of a graph, preventing them from being deleted. The optimizer wants to find the best set of preserved edges/vertices in which the cost constraints are satisfied and the basic graph problems are optimized. For example, in shortest path preservation, the optimizer wants to find a set of edges/vertices within which the shortest path between two predetermined points is smallest. In interdiction problems, one deletes vertices or edges from the graph with a particular cost in order to impede the basic graph problems as much as possible (for example, delete edges/vertices to maximize the shortest path between two predetermined vertices). Applications of preservation problems include optimal road maintenance, power grid maintenance, and job scheduling, while interdiction problems are related to drug trafficking prevention, network stability assessment, and counterterrorism. Computational hardness results are presented, along with heuristic methods for approximating solutions to the matching interdiction problem. Also, efficient algorithms are presented for special cases of graphs, including on planar graphs. The graphs in many of the listed applications are planar, so these algorithms have important practical implications.
文建国; 崔林刚; 孟庆军; 任川川; 李金升; 吕宇涛; 张艳
2012-01-01
目的 比较尿流加速度(UFA)和最大尿流率(Qmax)诊断膀胱出口梗阻(BOO)的价值. 方法 分别选取50例前列腺增生(BPH)患者和50例健康者进行前列腺体积、UFA和Qmax测定.以P-Q图梗阻区作为参考标准,比较UFA和Qmax诊断BOO的灵敏度和特异性. 结果 BPH组UFA明显低于非BPH组(P＜0.05).以UFA＜2 ml/s2和Qmax＜10 ml/s作为诊断BOO参考标准,灵敏度和特异度分别为88％、75％与81％、63％,与参考标准P-Q图提示梗阻一致性分析Kappa值分别为0.55比0.35. 结论 UFA可以作为诊断BPH患者BOO的依据之一.%Objective To assess the value of the urine flow acceleration(UFA)versus maximum urinary flow rate (Qmax) for diagnosis of bladder outlet obstruction (BOO) in benign prostate hyperplasia (BPH).Methods A total of 50 men with BPH and 50 normal men were included in this study.Urodynamic examinations were performed in all patients according to the recommendations of the International Continence Society.Prostate volume,UFA and Qmax of each patient were analyzed and the results were compared between two groups.Results The UFA and Qmax of BPH group were much lower than that of the control group [(2.05±0.85)ml/s2 vs.(4.60±1.25)ml/s2 ; (8.50±1.05)ml/s vs.(13.00±3.35)ml/s,P＜0.05].The prostate volume in BPH group was increased compared with control group [(28.6±9.8) ml vs.(24.2±7.6)ml,P＜0.05].As diagnosis standard of UFA＜2.05 ml/s2 and Qmax＜ 10 ml/s,the sensitivity and specificity of UFA and Qmax in diagnosing BOO were (88％,75 ％)vs.(81％,63％).While compared with the result of P-Q chart,the Kappa values in correspondence analysis were 0.55 vs.0.35.The sensitivity,specificity and Kappa value of UFA in diagnosing BOO in BPHs were slightly higher than that of Qmax in comparison with the gold standard (BOO diagnosed by P-Q figure).Conclusions The UFA is a useful urodynamics parameter in diagnosing BOO of BPH.
Maximum Profit Configurations of Commercial Engines
Yiran Chen
2011-06-01
Full Text Available An investigation of commercial engines with finite capacity low- and high-price economic subsystems and a generalized commodity transfer law [n ∝ Δ (P m] in commodity flow processes, in which effects of the price elasticities of supply and demand are introduced, is presented in this paper. Optimal cycle configurations of commercial engines for maximum profit are obtained by applying optimal control theory. In some special cases, the eventual state—market equilibrium—is solely determined by the initial conditions and the inherent characteristics of two subsystems; while the different ways of transfer affect the model in respects of the specific forms of the paths of prices and the instantaneous commodity flow, i.e., the optimal configuration.
Maximum ceasing angle of inclination and flux formula for granular orifice flow%颗粒孔洞流的最大休止倾角和流量公式
彭政; 蒋亦民
2011-01-01
This work measured mass flux of a granular sample (glass beads) discharged from an inclined orifice for various inclination angles and orifice diameters. It is found that irrespective the orifice sizes, the fluxes all vary linearly with cosine of the inclination angle, and the linearly extrapolated angle of zero-flux, namely the critical angle of flow ceasing,increases linearly with ratio between grain and orifice diameter, tends to the angle of repose in the limit of infinite orifice diameter within an approximation of the Bagnold angle. The results show that the flux formula varying linearly with cosine of inclination angle is capable to reveal behaviors of the critical ceasing angle, a property that the Beverloo formula of which parameters vary with cosine of inclination angle can not describe.%实验测量了重力驱动下的玻璃珠颗粒样品通过不同倾角和孔径的圆形孔洞的卸载流量.发现无论孔径大小,流量均与倾角的余弦呈良好的线性关系;线性外推得到的零流量角,即流量休止临界角随颗粒粒径与孔洞直径之比的减小而线性增加;在无穷大孔径极限下,此临界角在Bagnold角的误差范围内与样品的安息角一致.这些结果表明流量随倾角余弦线性变化的经验公式能揭示临界角的行为和特性,这是参数随倾角变化的Beverloo公式所不能描述的.
On the sufficiency of the linear maximum principle
Vidal, Rene Victor Valqui
1987-01-01
Presents a family of linear maximum principles for the discrete-time optimal control problem, derived from the saddle-point theorem of mathematical programming. Some simple examples illustrate the applicability of the main theoretical results...
Statistical Inverse Formulation of Optical Flow with Uncertainty Quantification
Sun, Jie
2016-01-01
Optical flow refers to the visual motion observed between two consecutive images. Since the degree of freedom is typically much larger than the constraints imposed by the image observations, the straightforward formulation of optical flow inference is an ill-posed problem. By setting some type of additional "regularity" constraints, classical approaches formulate a well-posed optical flow inference problem in the form of a parameterized set of variational equations. In this work we build a mathematical connection, focused on optical flow methods, between classical variational optical flow approaches and Bayesian statistical inversion. A classical optical flow solution is in fact identical to a maximum a posteriori estimator under the assumptions of linear model with additive independent Gaussian noise and a Gaussian prior distribution. Unlike classical approaches, the statistical inversion approach to optical flow estimation not only allows for "point" estimates, but also provides a distribution of solutions ...
On the sufficiency of the linear maximum principle
Vidal, Rene Victor Valqui
1987-01-01
Presents a family of linear maximum principles for the discrete-time optimal control problem, derived from the saddle-point theorem of mathematical programming. Some simple examples illustrate the applicability of the main theoretical results......Presents a family of linear maximum principles for the discrete-time optimal control problem, derived from the saddle-point theorem of mathematical programming. Some simple examples illustrate the applicability of the main theoretical results...
Ghiyasvand Mehdi
2016-01-01
Full Text Available In this paper, a new problem on a directed network is presented. Let D be a feasible network such that all arc capacities are equal to U. Given a t > 0, the network D with arc capacities U - t is called the t-network. The goal of the problem is to compute the largest t such that the t-network is feasible. First, we present a weakly polynomial time algorithm to solve this problem, which runs in O(log(nU maximum flow computations, where n is the number of nodes. Then, an O(m2n time approach is presented, where m is the number of arcs. Both the weakly and strongly polynomial algorithms are inspired by McCormick and Ervolina (1994.
Sergey G. Chefranov
2013-11-01
Full Text Available Leonardo da Vinci perhaps was the first who paid attention to the energetic efficiency of existence of vortices emerging near sines of Valsalva and defining normal functioning (opening of aortal valve. However up to now a fundamental problem of defining of mechanisms of mysterious energetic efficiency of functioning of cardio-vascular system (CVS of blood feeding of the organism is still remaining significantly not solved and this is, for example, one of the main restriction for the creation of artificial heart and corresponding valve systems. In the present paper, results witnessing possible important role of the very hydro-mechanical mechanism in the realization of the noted energetic efficiency of CVS due to formation in the CVS of spiral structural organization of the arterial blood flow observed by methods of MRT and color Doppler-measuring in the left ventricular of the heart and in aorta.
Rashidi Mohammad Mehdi
2015-01-01
Full Text Available The similar solution on the equations of the revised Cheng-Minkowycz problem for natural convective boundary layer flow of nanofluid through a porous medium gives (using an analytical method, a system of non-linear partial differential equations which are solved by optimal homotopy analysis method. Effects of various drastic parameters on the fluid and heat transfer characteristics have been analyzed. A very good agreement is observed between the obtained results and the numerical ones. The entropy generation has been derived and a comprehensive parametric analysis on that has been done. Each component of the entropy generation has been analyzed separately and the contribution of each one on the total value of entropy generation has been determined. It is found that the entropy generation as an important aspect of the industrial applications has been affected by various parameters which should be controlled to minimize the entropy generation.