Showing papers on "Minimum weight published in 2010"

Ant colony optimization applied to minimum weight dominating set problem

Abstract: In this paper we present an application of ant colony optimization (ACO) to the Minimum Weighted Dominating Set Problem. We introduce a heuristic for this problem that takes into account the weights of vertexes being covered and show that it is more efficient than the greedy algorithm using the standard heuristic. Further we give implementation details of ACO applied to this problem. We tested our algorithm on graphs with different sizes, edge densities, and weight distribution functions and shown that it gives greatly improved results over these acquired by the greedy algorithms.

On the solution of the three forces problem and its application in optimal designing of a class of symmetric plane frameworks of least weight

Abstract: Two problems of minimum weight design of plane trusses are dealt with. The first problem concerns construction of the lightest fully stressed truss subject to three self-equilibrated forces applied at three given points. This problem has been solved analytically by H.S.Y. Chan in 1966. This analytical solution is re-derived in the present paper. It compares favourably with new numerical solutions found here by the method developed recently by the first author. The solution to the three forces problem paves the way to half-analytical as well as numerical solutions to the problem of minimum weight design of plane symmetric frameworks transmitting two symmetrically located vertical forces to two fixed supports lying along the line linking the points of application of the forces.

Multiobjective optimization of orthogonally stiffened cylindrical shells for minimum weight and maximum axial buckling load

Abstract: In the present research, the weight and axial buckling optimization of orthogonally stiffened cylindrical shells is carried out by the Genetic Algorithm. Constraints include two nondimensional functions of weight and buckling load in such a way that the stiffened shell has no increase in the weight and no decrease in the buckling load with respect to the initial unstiffened shell. In analytical solution, the Rayleigh–Ritz energy procedure is applied and the stiffeners are treated as discrete members. The optimization is implemented for shells with simply supported end conditions stiffened by four shapes of stiffeners including rectangular-, cee-, I-, and hat-shaped ones. The results show that the I-section and rectangular-section stiffeners are, respectively, the most and the least efficient in designing stiffened cylindrical shells for minimum weight and maximum critical axial buckling load.

Surface code quantum error correction incorporating accurate error propagation

Abstract: The surface code is a powerful quantum error correcting code that can be defined on a 2-D square lattice of qubits with only nearest neighbor interactions. Syndrome and data qubits form a checkerboard pattern. Information about errors is obtained by repeatedly measuring each syndrome qubit after appropriate interaction with its four nearest neighbor data qubits. Changes in the measurement value indicate the presence of chains of errors in space and time. The standard method of determining operations likely to return the code to its error-free state is to use the minimum weight matching algorithm to connect pairs of measurement changes with chains of corrections such that the minimum total number of corrections is used. Prior work has not taken into account the propagation of errors in space and time by the two-qubit interactions. We show that taking this into account leads to a quadratic improvement of the logical error rate.

Comparison of different topologies for island-based multi-colony ant algorithms for the minimum weight vertex cover problem

Abstract: The aim of this paper is compare the effect of using different topologies or connections between separate colonies in island based parallel implementations of the Ant Colony Optimization applied to the Minimum Weight Vertex Cover Problem. We investigated the sequential Ant Colony Optimization algorithms applied to the Minimum Weight Vertex Cover Problem before. Parallelization of population based algorithms using the island model is of great importance because it often gives super linear increase in performance. We observe the behavior of different parallel algorithms corresponding to several topologies and communication rules like fully connected, replace worst, ring and independent parallel runs. We also propose a variation of the algorithm corresponding to the ring topology that maintains the diversity of the search, but still moves to areas with better solutions and gives slightly better results even on a single processor with threads.

Ranking search results based on word weight

Abstract: Ranking search results, comprises retrieving search results that include target strings that relate to a query string; segmenting the query string and each of the target strings; pairing segments in the query string with respective segments in the target strings to form combinations; retrieving weights that correspond to the combinations; and determining a weighted word length based on the weights corresponding to each of the target strings; and ranking the target strings based on their respective weighted word lengths Alternatively, ranking search results includes determining a minimum weight of each inserted word with respect to segments in the query string; determining a minimum weight of each deleted word with respect to segments in the target strings; determining a total edit distance for each target string; and ranking the target strings based on the total edit distances

Traffic condition predicting device and pathway exploration device

Abstract: The invention provides a device for pathway exploration by utilizing predicted traffic data, which comprises a Link path forming unit, a segmenting unit, a weight calculation unit and a selection unit, wherein the Link path forming unit is used for forming all Link paths from an own vehicle to the destination, and the segmenting unit is used for segmenting the geographic region into a plurality of different regions which take the own vehicle as the center; the weight calculation unit is used for aiming at each Link path to calculate the weight of the Link path, and the selection unit is used for selecting the Link path with a minimum weight to be used as an optimal path; when the weight of the Link patch is calculated, the weight calculation unit uses real-time traffic data in a first region nearest to the own vehicle, and uses the predicted traffic data at the corresponding time in other regions.

Minimum weight design for toroidal pressure vessels using Differential Evolution and Particle Swarm Optimization

Abstract: In this paper, Differential Evolution and Particle Swarm Optimization methods have been applied to the design of minimum weight toroidal shells subject to internal pressure. Constraints are first yield pressure, plastic pressures, plastic instability pressure and volume contained by the toroid. Optimality includes geometry and wall thickness, which is constant or variable. The optimization process is performed by FORTRAN routines coupled with finite element analysis code ABAQUS. Depending on geometry parameters of the toroid, the material saving can be as high as 72%. The results also show that Differential Evolution outperforms the Particle Swarm Optimization in most of cases.

An optimal method for seismic drift design of concrete buildings using gradient and Hessian matrix calculations

Abstract: This paper describes a novel seismic optimal design method for the reinforced concrete frame. First, an optimal mathematical model with time-dependent constraints, i.e., inter-story drift constraints, is established for achieving minimum weight design. Second, the inequality constraint problem with time-dependent constraints is converted into a sequence of appropriately formed unconstrained problems using the integral interior point penalty function method. Third, an efficient algorithm of the first and second derivatives of the inter-story drift with respect to design variables is formulated based on Newmark-β method. Gradient and Hessian matrix of the integral interior penalty function are also computed. Fourth, Marquardt’s method is employed to solve a sequence of unconstrained problems. Finally, the minimum weight design of a three-story, two-bay planar frame is demonstrated using the new optimization method and the augmented Lagrange multiplier method. The comparative results show the seismic optimal design method presented in this paper is more efficient than the augmented Lagrange multiplier method in terms of computational time. The proposed new method is an effective and efficient approach for minimum weight design of the reinforced concrete frames subjected to earthquake excitation.

Optimal design of metallic sandwich tubes with prismatic cores to internal moving shock load

Abstract: Prismatic metallic sandwich tubes subject to internal moving shock loads are optimally designed for minimum weight. The stretching-dominated core topologies are considered, and the effective stiffness matrices of prismatic cores are predicted via homogenization procedure. Failure mechanisms are estimated on the basis of structural responses that are obtained by using the multi-layer sandwich model considering the shear deformation and compressibility of the core. In present study, the constraint functions on failure mechanisms are not explicit expressions, leading to the discontinuity of the optimization problem; hence, the genetic algorithm is invoked. The optimum parameters and minimum weight are evaluated. Meanwhile, the optimal designs are validated by finite element simulations. The results demonstrate that the rectangular core is preferred among three core topologies, and the rectangular core with four layers of cells is most weight-efficient at high load indices, but one layer at lower load indices. The effect of the number of unit cells in circumferential direction on the minimum weight design is slight. In addition, the optimal sandwich tubes are inferior to the optimal monolithic tubes at selected load indices, from a weight-efficiency standpoint, attributed to the fact that face yielding induced by circumferential tension primarily dominates the minimum weight design.

Minimum average routing path clustering problem in multi-hop 2-D underwater sensor networks

Abstract: In this paper, we introduce a new clustering problem in underwater sensor networks, namely minimum average routing path clustering problem (MARPCP). To deal with the high complexity of MARPCP, we relax it to a special case of minimum weight dominating set problem (MWDSP). We show an existing algorithm for MWDSP can produce an approximate solution for MARPCP. Also, we design a constant factor approximation algorithm for MARPCP, which is much faster than the first method.

LDPC codes associated with linear representations of geometries

Abstract: We look at low density parity check codes over a finite field $\mathbb K$ associated with finite geometries $T$2*$(\mathcal K)$, where $\mathcal K$ is any subset of PG$(2,q)$, with $q=p$h, $p$≠char$\mathbb K$. This includes the geometry $LU(3,q)$D, the generalized quadrangle $T$2*$(\mathcal K)$ with $\mathcal K$ a hyperoval, the affine space AG$(3,q)$ and several partial and semi-partial geometries. In some cases the dimension and/or the code words of minimum weight are known. We prove an expression for the dimension and the minimum weight of the code. We classify the code words of minimum weight. We show that the code is generated completely by its words of minimum weight. We end with some practical considerations on the choice of $\mathcal K$.

ACT Payload Shroud Structural Concept Analysis and Optimization

Abstract: Aerospace structural applications demand a weight efficient design to perform in a cost effective manner. This is particularly true for launch vehicle structures, where weight is the dominant design driver. The design process typically requires many iterations to ensure that a satisfactory minimum weight has been obtained. Although metallic structures can be weight efficient, composite structures can provide additional weight savings due to their lower density and additional design flexibility. This work presents structural analysis and weight optimization of a composite payload shroud for NASA s Ares V heavy lift vehicle. Two concepts, which were previously determined to be efficient for such a structure are evaluated: a hat stiffened/corrugated panel and a fiber reinforced foam sandwich panel. A composite structural optimization code, HyperSizer, is used to optimize the panel geometry, composite material ply orientations, and sandwich core material. HyperSizer enables an efficient evaluation of thousands of potential designs versus multiple strength and stability-based failure criteria across multiple load cases. HyperSizer sizing process uses a global finite element model to obtain element forces, which are statistically processed to arrive at panel-level design-to loads. These loads are then used to analyze each candidate panel design. A near optimum design is selected as the one with the lowest weight that also provides all positive margins of safety. The stiffness of each newly sized panel or beam component is taken into account in the subsequent finite element analysis. Iteration of analysis/optimization is performed to ensure a converged design. Sizing results for the hat stiffened panel concept and the fiber reinforced foam sandwich concept are presented.

Structural optimization with limited number of element properties

Abstract: This note investigates the weight lost of a structure that presents a limited number of cross-sections for its members. A combined genetic algorithm-gradient approach is used to obtain the minimum weight structure for various numbers of cross-sections. The problem is investigated for the well known ten-bar truss structure. Results show that decreasing the number of cross-sections from nine to four has a small impact on the weight of approximately 5.3%.

Notice of Retraction Dynamic Feedback Equalization Algorithm for Minimum Weight

Abstract: The paper analyzes the existing Linux virtual server (LVS) cluster load balancing algorithm and its inadequacies that not real-time dynamic full makes an appraisal to the load on the each server node, designs a new Dynamic Feedback Equalization Algorithm for Minimum Weight. The algorithm considers real-time load and response capacity of each server node, makes pre-load rate of the server combined with response time, dynamic generates server node weights by real-time feedback and conducts adjust to the load balancing of server cluster by using Minimum weight balancing algorithm. This algorithm has done a comparison with the Weighted Least Connections, theory analysis and experimental results show that the improved dynamic load balancing algorithm is more effective than Weighted Least Connections.

An efficient model for information gain of sequential pattern from web logs based on dynamic weight constraint

Abstract: Data mining is the task of discovering interesting patterns from large amounts of data. There are many data mining tasks, such as classification, clustering, association rule mining, and sequential pattern mining. Many frequent sequential traversal pattern mining algorithms have been developed which mine the set of frequent subsequences traversal pattern satisfying a minimum support constraint in a session database. However, previous frequent sequential traversal pattern mining algorithms give equal weightage to sequential traversal patterns while the pages in sequential traversal patterns have different importance and have different weightage. Another main problem in most of the frequent sequential traversal pattern mining algorithms is that they produce a large number of sequential traversal patterns when a minimum support is lowered and they do not provide alternative ways to adjust the number of sequential traversal patterns other than increasing the minimum support. In this paper, we propose a frequent sequential traversal pattern mining with weights constraint. Our main approach is to add the weight constraints into the sequential traversal pattern while maintaining the downward closure property. A weight range is defined to maintain the downward closure property and pages are given different weights and traversal sequences assign a minimum and maximum weight. In scanning a session database, a maximum and minimum weight in the session database is used to prune infrequent sequential traversal subsequence by doing downward closure property can be maintained. Our method produces a few but important sequential traversal patterns in session databases with a low minimum support, by adjusting a weight range of pages and sequence.

Blocking sets in finite projective spaces and coding theory

Abstract: A small minimal k-blocking set is a point set B in the finite projective space PG(n,q), meeting every (n-k)-space, where |B| < 3(q^k+1)/2, and such that no proper subset of B is a k-blocking set. The first chapter provides an extensive overview of the notions that will be used in the dissertation. In the second chapter, we derive a new bound on the size of a minimal k-blocking set and show a unique reducibility result for k-blocking sets of size at most 2q^k. The linearity conjecture for blocking sets states that all small minimal blocking sets are linear sets. In the third chapter, we investigate linear sets on a line, and prove a result on the intersection of a linear set with a subline, that will be used in the fourth chapter to prove the linearity conjecture for k-blocking sets in PG(n,p^3), where p is prime. In the fifth chapter, we turn our attention to partial covers of PG(n,q). These are sets of hyperplanes, covering almost all points of the projective space; dually, they are almost 1-blocking sets. Assuming that there is at least one hyperplane that is not blocked by an almost 1-blocking set D, we deduce the minimum number of hyperplanes that are not blocked by D and extend this result to almost k-blocking sets. In the last two chapters, we deal with the codes arising from finite geometric structures. We first study the code of points and hyperplanes in PG(n,q), and show, using the theory of blocking sets, that there are no codewords with weight larger than the weight of a hyperplane and smaller that the difference of two hyperplanes. We extend this result for the code of points and k-spaces in PG(n,q) and investigate the dual code, deducing a new upper bound on the minimum weight. Finally, we investigate the LDPC codes arising from linear representations and polar spaces; we deduce bounds on the minimum weight, and characterise codewords of small and large weight using geometric techniques.

A Particle Swarm Optimization Algorithm for Minimization Analysis of Cost-Sensitive Attack Graphs

Abstract: To prevent an exploit, the security analyst must implement a suitable countermeasure In this paper, we consider cost-sensitive attack graphs (CAGs) for network vulnerability analysis In these attack graphs, a weight is assigned to each countermeasure to represent the cost of its implementation There may be multiple countermeasures with different weights for preventing a single exploit Also, a single countermeasure may prevent multiple exploits We present a binary particle swarm optimization algorithm with a time-varying velocity clamping, called SwarmCAG-TVVC, for minimization analysis of cost-sensitive attack graphs The aim is to find a critical set of countermeasures with minimum weight whose implementation causes the initial nodes and the goal nodes of the graph to be completely disconnected This problem is in fact a constrained optimization problem A repair method is used to convert the constrained optimization problem into an unconstrained one A local search heuristic is used to improve the overall performance of the algorithm We compare the performance of SwarmCAG-TVVC with a greedy algorithm GreedyCAG and a genetic algorithm GenNAG for minimization analysis of several large-scale cost-sensitive attack graphs On average, the weight of a critical set of countermeasures found by SwarmCAG-TVVC is 6:15 percent less than the weight of a critical set of countermeasures found by GreedyCAG Also, SwarmCAG-TVVC performs better than GenNAG in terms of convergence speed and accuracy The results of the experiments show that SwarmCAG-TVVC can be successfully used for minimization analysis of large-scale cost-sensitive attack graphs

On Dual Extremal Maximal Self-orthogonal Codes Of Type I-IV

Abstract: For a Type $T \in${I, II, III, IV} of codes over finite fields and length $N$ where there exists no self-dual Type $T$ code of length $N$, upper bounds on the minimum weight of the dual code of a self-orthogonal Type $T$ code of length $N$ are given, allowing the notion of dual extremal codes. It is proven that for $T \in${II, III, IV} the Hamming weight enumerator of a dual extremal maximal self-orthogonal Type $T$ code of a given length is unique.

Optimization of stepped shells

Abstract: Problems of analysis and optimization of axisymmetric shells of piece wise constant thickness are studied. The cases of quasistatic and dynamic loading are considered separately whereas the shells may be manufactured from both, elastic and inelastic materials. Minimum weight designs of inelastic shells of piece wise constant thickness are established under the condition that the limit load is fixed. Also the designs of maximum load carrying capacity are determined for given weight (material volume) of the shell. Necessary optimality conditions are derived with the aid of variational methods of the theory of optimal control. Particular cases of maximization of the load carrying capacity of spherical caps and conical shells are studied in a greater detail in the cases of von Mises and Hill's materials.

Topology optimization of structures with stress constraints: Aeronautical applications

Abstract: Topology optimization of structures is nowadays the most active and widely studied branch in structural optimization. This paper develops a minimum weight formulation for the topology optimization of continuum structures. This approach also includes stress constraints and addresses important topics like the efficient treatment of a large number of stress constraints, the approach of discrete solutions by using continuum design variables and the computational cost. The proposed formulation means an alternative to maximum stiffness formulations and offers additional advantages. The minimum weight formulation proposed is based on the minimization of the weight of the structure. In addition, stress constraints are included in order to guarantee the feasibility of the final solution obtained. The objective function proposed has been designed to force the convergence to a discrete solution in the final stages of the optimization process. Thus, near discrete solutions are obtained by using continuum design variables. The robustness and reliability of the proposed formulation are verified by solving application examples related to aeronautical industry.

A Dynamic RWA Algorithm for Optical Networks with Wavelength Conversion Capacity

Abstract: Aimed at optical networks with wavelength conversion capacity, an algorithm for dynamic routing and wavelength assignment named WIC-RWA was proposed. Extended the layered-graph model to optical networks with limited-range wavelength conversion and limited-count wavelength converters; Designed key degree and influence weight value for links in order to allocate the network resources reasonably; At the same time reduced the blocking probability of the network and the number of wavelength converters by setting wavelength conversion cost weight value and computing the path of minimum weight value. The simulation results showed that the new algorithm can effectively reduce the blocking probability of the entire network and limit the used number of wavelength converters.

Globally optimal triangulations of minimum weight using Ant Colony Optimization metaheuristic

Abstract: Globally optimal triangulations are difficult to be found by deterministic methods as, for most type of criteria, no polynomial algorithm is known. In this work, we consider the Minimum Weight Triangulation (MWT) problem of a given set of n points in the plane. Our aim is to show how the Ant Colony Optimization (ACO) metaheuristic can be used to search for globally optimal triangulations of minimum weight. We present an experimental study for a set of instances for MWT problem. We create these instances since no reference to benchmarks for this problem were found in the literature. We assess through the experimental evaluation the applicability of the ACO metaheuristic for MWT problem.