Showing papers on "Minimum weight published in 2013"

Minimum weight perfect matching of fault-tolerant topological quantum error correction in average $O(1)$ parallel time

Abstract: Consider a 2-D square array of qubits of extent $L\times L$. We provide a proof that the minimum weight perfect matching problem associated with running a particular class of topological quantum error correction codes on this array can be exactly solved with a 2-D square array of classical computing devices, each of which is nominally associated with a fixed number $N$ of qubits, in constant average time per round of error detection independent of $L$ provided physical error rates are below fixed nonzero values, and other physically reasonable assumptions. This proof is applicable to the fully fault-tolerant case only, not the case of perfect stabilizer measurements.

Weight optimization of a cooling system composed of fan and extruded fin heat sink

Abstract: This Paper details the weight optimization of forced convection cooling systems, composed of fan and extruded fin heat sink, required for a dc-dc converter of an airborne wind turbine (AWT) system. The presented investigations detail the optimization of the heat sink's fins with respect to minimum weight and the selection of a suitable fan for minimum overall system weight. A new analytical cooling system model is introduced, the calculated results are compared to the results determined with a preexisting analytical model and Finite Element Model (FEM) simulations. The comparison to experimental results demonstrate the accuracy improvements achieved with the proposed methods. Compared to commercially available products a weight reduction of 52% is achieved with the proposed optimization procedure for the required heat sink system with Rth, S-a = 1K/W.

Codes from incidence matrices of graphs

Abstract: We examine the p-ary codes, for any prime p, from the row span over $${\mathbb {F}_p}$$ of |V| × |E| incidence matrices of connected graphs Γ = (V, E), showing that certain properties of the codes can be directly derived from the parameters and properties of the graphs. Using the edge-connectivity of Γ (defined as the minimum number of edges whose removal renders Γ disconnected) we show that, subject to various conditions, the codes from such matrices for a wide range of classes of connected graphs have the property of having dimension |V| or |V| − 1, minimum weight the minimum degree δ(Γ), and the minimum words the scalar multiples of the rows of the incidence matrix of this weight. We also show that, in the k-regular case, there is a gap in the weight enumerator between k and 2k − 2 of the binary code, and also for the p-ary code, for any prime p, if Γ is bipartite. We examine also the implications for the binary codes from adjacency matrices of line graphs. Finally we show that the codes of many of these classes of graphs can be used for permutation decoding for full error correction with any information set.

Minimum Bisection is fixed parameter tractable

Abstract: In the classic Minimum Bisection problem we are given as input a graph $G$ and an integer $k$. The task is to determine whether there is a partition of $V(G)$ into two parts $A$ and $B$ such that $||A|-|B|| \leq 1$ and there are at most $k$ edges with one endpoint in $A$ and the other in $B$. In this paper we give an algorithm for Minimum Bisection with running time $O(2^{O(k^{3})}n^3 \log^3 n)$. This is the first fixed parameter tractable algorithm for Minimum Bisection. At the core of our algorithm lies a new decomposition theorem that states that every graph $G$ can be decomposed by small separators into parts where each part is "highly connected" in the following sense: any cut of bounded size can separate only a limited number of vertices from each part of the decomposition. Our techniques generalize to the weighted setting, where we seek for a bisection of minimum weight among solutions that contain at most $k$ edges.

Optimization of Composite Material System and Lay-up to Achieve Minimum Weight Pressure Vessel

Abstract: The use of composite pressure vessels particularly in the aerospace industry is escalating rapidly because of their superiority in directional strength and colossal weight advantage The present work elucidates the procedure to optimize the lay-up for composite pressure vessel using finite element analysis and calculate the relative weight saving compared with the reference metallic pressure vessel The determination of proper fiber orientation and laminate thickness is very important to decrease manufacturing difficulties and increase structural efficiency In the present work different lay-up sequences for laminates including, cross-ply [0 m /90 n ] s , angle-ply [±θ] ns , [90/±θ] ns and [0/±θ] ns , are analyzed The lay-up sequence, orientation and laminate thickness (number of layers) are optimized for three candidate composite materials S-glass/epoxy, Kevlar/epoxy and Carbon/epoxy Finite element analysis of composite pressure vessel is performed by using commercial finite element code ANSYS and utilizing the capabilities of ANSYS Parametric Design Language and Design Optimization module to automate the process of optimization For verification, a code is developed in MATLAB based on classical lamination theory; incorporating Tsai–Wu failure criterion for first-ply failure (FPF) The results of the MATLAB code shows its effectiveness in theoretical prediction of first-ply failure strengths of laminated composite pressure vessels and close agreement with the FEA results The optimization results shows that for all the composite material systems considered, the angle-ply [±θ] ns is the optimum lay-up For given fixed ply thickness the total thickness of laminate is obtained resulting in factor of safety slightly higher than two Both Carbon/epoxy and Kevlar/Epoxy resulted in approximately same laminate thickness and considerable percentage of weight saving, but S-glass/epoxy resulted in weight increment

Local and global Pareto dominance applied to optimal design and material selection of composite structures

Abstract: The optimal design of hybrid composite structures considering sizing, topology and material selection is addressed in a multi-objective optimization framework. The proposed algorithm, denoted by Multi-objective Hierarchical Genetic Algorithm (MOHGA), searches for the Pareto-optimal front enforcing population diversity by using a hierarchical genetic structure based on co-evolution of multi-populations. An age structured population is used to store the ranked solutions aiming to obtain the Pareto front. A self-adaptive genetic search incorporating Pareto dominance and elitism is presented. Two concepts of dominance are used: the first one denoted by local non-dominance is implemented at the isolation stage of populations and the second one called global non-dominance is considered at age structured population. The age control emulates the human life cycle and enables to apply the species conservation paradigm. A new mating and offspring selection mechanisms considering age control and dominance are adopted in crossover operator applied to age-structured population. Application to hybrid composite structures requiring the compromise between minimum strain energy and minimum weight is presented. The structural integrity is checked for stress, buckling and displacement constraints considered in the multi-objective optimization. The design variables are ply angles and ply thicknesses of shell laminates, the cross section dimensions of beam stiffeners and the variables associated with the material distribution at laminate level and structure level. The properties of the proposed approach are discussed in detail.

Sketching Earth-Mover Distance on Graph Metrics

Abstract: We develop linear sketches for estimating the Earth-Mover distance between two point sets, i.e., the cost of the minimum weight matching between the points according to some metric. While Euclidean distance and Edit distance are natural measures for vectors and strings respectively, Earth-Mover distance is a well-studied measure that is natural in the context of visual or metric data. Our work considers the case where the points are located at the nodes of an implicit graph and define the distance between two points as the length of the shortest path between these points. We first improve and simplify an existing result by Brody et al. [4] for the case where the graph is a cycle. We then generalize our results to arbitrary graph metrics. Our approach is to recast the problem of estimating Earth-Mover distance in terms of an l1 regression problem. The resulting linear sketches also yield space-efficient data stream algorithms in the usual way.

A Characterization of Graphs by Codes from their Incidence Matrices

Abstract: We continue our earlier investigation of properties of linear codes generated by the rows of incidence matrices of k-regular connected graphs on n vertices. The notion of edge connectivity is used to show that, for a wide range of such graphs, the p-ary code, for all primes p, from an n 1 nk incidence matrix has dimension n or n 1, minimum weight k, the minimum words are the scalar multiples of the rows, there is a gap in the weight enumerator between k and 2k 2, and the words of weight 2k 2 are the scalar multiples of the dierences of intersecting rows of the matrix. For such graphs, the graph can thus be retrieved from the code.

Parametric Optimization of Eicher 11.10 Chassis Frame for Weight Reduction Using FEA-DOE Hybrid Modeling

Abstract: The chassis serves as a backbone for supporting the body and different parts of the automobile. It should be rigid enough to withstand the shock, twist, vibration and other stresses. Along with strength, an important consideration in chassis design is to have adequate bending stiffness. The main objective of the research is to obtain the minimum weight of Eicher 11.10 chassis frame. The chassis frame is made of two side members joined with a series of cross members. The number of cross members, their locations, cross-section and the sizes of the side and the cross members becomes the design variables. The chassis frame model is to be developed in Solid works and analyzed using Ansys. Since the no. of parameters and levels are more, the probable models are too many. So, to select optimum parameters among them large no of modeling and analysis work is involved which consumes more time. To overcome this problem TAGUCHI method along with FEA is use. The weight reduction of the side bar is achieved by changing the Parameters using orthogonal array. Then FEA is performed on those models to get the best solution. This method can save material used, production cost and time.

Distribution-Aware Compressed Full-Text Indexes

Abstract: In this paper we address the problem of building a compressed self-index that, given a distribution for the pattern queries and a bound on the space occupancy, minimizes the expected query time within that index space bound. We solve this problem by exploiting a reduction to the problem of finding a minimum weight K-link path in a properly designed Directed Acyclic Graph. Interestingly enough, our solution can be used with any compressed index based on the Burrows-Wheeler transform. Our experiments compare this optimal strategy with several other known approaches, showing its effectiveness in practice.

Structural optimization of mini hydraulic backhoe excavator attachment using fea approach

Abstract: Excavators are heavy duty earthmoving machines and normally used for excavation task. During the excavation operation unknown resistive forces offered by the terrain to the bucket teeth. Excessive amount of these forces adversely affected on the machine parts and may be failed during excavation operation. Design engineers have great challenge to provide the better robust design of excavator parts which can work against unpredicted forces and under worst working condition. Thus, it is very much necessary for the designers to provide not only a better design of parts having maximum reliability but also of minimum weight and cost, keeping design safe under all loading conditions. Finite Element Analysis (FEA) is the most powerful technique for strength calculations of the structures working under known load and boundary conditions. FEA approach can be applied for the structural weight optimization. This paper focuses on structural weight optimization of backhoe excavator attachment using FEA approach by trial and error method. Shape optimization also performed for weight optimization and results are compared with trial and error method which shows identical results. The FEA of the optimized model also performed and their results are verified by applying classical theory.

Minimum weight design of beams against failure under uncertain loading by convex analysis

Abstract: Under operational conditions, some loads acting on a beam are known (deterministic loads), but there usually exist other loads the magnitude and distribution of which are unpredictable (uncertain loads). If the uncertainty in the loading is not taken into account in the design, the likelihood of failure increases. In the present study beams are designed for minimum weight subject to maximum stress and buckling load criteria and under deterministic and uncertain transverse loads. The uncertain load, which is subject to a constraint on its L 2 norm, is determined to maximize the normal stress using a convex analysis. The location of the maximum stress is determined under the combination of deterministic and worst-case uncertain loads. The minimum weight design is obtained by determining the minimum cross-sectional area subject to stress and buckling load constraints. Results are given for a number of problem parameters including the axial load, elastic foundation modulus and uncertainty levels.

Approximating the Girth

Abstract: This article considers the problem of computing a minimum weight cycle in weighted undirected graphs. Given a weighted undirected graph G = (V,E,w), let C be a minimum weight cycle of G, let w(C) be the weight of C, and let wmax(C) be the weight of the maximum edge of C. We obtain three new approximation algorithms for the minimum weight cycle problem: (1) for integral weights from the range [1,M], an algorithm that reports a cycle of weight at most 4 3w(C) in O(n2 log n(log n + log M)) time; (2) For integral weights from the range [1,M], an algorithm that reports a cycle of weight at most w(C) + wmax(C) in O(n2 log n(log n + log M)) time; (3) For nonnegative real edge weights, an algorithm that for any e > 0 reports a cycle of weight at most (4 3 + e)w(C) in O(1 en2 log n(log log n)) time.In a recent breakthrough, Williams and Williams [2010] showed that a subcubic algorithm, that computes the exact minimum weight cycle in undirected graphs with integral weights from the range [1,M], implies a subcubic algorithm for computing all-pairs shortest paths in directed graphs with integral weights from the range [−M,M]. This implies that in order to get a subcubic algorithm for computing a minimum weight cycle, we have to relax the problem and to consider an approximated solution. Lingas and Lundell [2009] were the first to consider approximation in the context of minimum weight cycle in weighted graphs. They presented a 2-approximation algorithm for integral weights with O(n2 log n(log n + log M)) running time. They also posed, as an open problem, the question whether it is possible to obtain a subcubic algorithm with a c-approximation, where c

Sizing Optimization of Sandwich Panels Having Prismatic Core Using Water Cycle Algorithm

Abstract: Due to possessing unique structure, sandwich panels have special characteristics which the most important is having high strength to weight ratio. Sandwich panels having diverse prismatic cores have been investigated and comparisons have been carried out for finding the best design. For this reason, the importance of optimization techniques particularly metaheuristics is understood. Water cycle algorithm (WCA), as a recently developed optimizer, is inspired from water cycle process. The optimum dimensions and the minimum weight have been calculated in order to design ultra-light weight sandwich panels. The imposed constraints in this problem are buckling load and yield stress. The obtained figures and results conclude that the diamond prismatic topology (having corrugation order of 4) is the most weight efficient among other existing designs under specific loading direction.

3-Rainbow Domination Number in Graphs

Abstract: The k-rainbow domination is a location problem in operations research. Give an undirected graph G as the natural model of location problem. We have a set of k colors and assign an arbitrary subset of these colors to each vertex of G. If a vertex which is assigned an empty set, then the union of color set of its neighbors must be k colors. This assignment is called the k-rainbow dominating function, abbreviate as kRDF, of G. The weight of kRDF is the sum of numbers of assigned colors over all vertices of G. The minimum weight of kRDF is defined as the k-rainbow domination number of G. In this paper, we present an exact algorithm and a heuristic algorithm to obtain the 3-rainbow domination number and the weight of 3RDF in graphs, respectively. Then, we test the practical performances of these algorithms, including their run times and solution qualities.

Decomposition algorithms for solving the minimum weight maximal matching problem

Abstract: – We investigate the problem of finding a maximal matching that has minimum total weight on a given edge-weighted graph. Although the minimum weight maximal matching problem is NP-hard in general, polynomial time exact or approximation algorithms on several restricted graph classes are given in the literature. In this article, we propose an exact algorithm for solving several variants of the problem on general graphs. In particular, we develop integer programming (IP) formulations for the problem and devise a decomposition algorithm, which is based on a combination of IP techniques and combinatorial matching algorithms. Our computational tests on a large suite of randomly generated graphs show that our decomposition approach significantly improves the solvability of the problem compared to the underlying IP formulation. © 2013 Wiley Periodicals, Inc. NETWORKS, Vol. 62(4), 273–287 2013

Optimization of Composite Wing Structure for a Flying Wing Aircraft Subject to Multi Constraints

Abstract: This paper presents a minimum weight optimization of a composite wing structure subject to multi constraints including strength, damage tolerance and aeroelastic stability. Based on preliminary design data, the investigation demonstrated an efficient optimization approach of a composite wing structure modeled by FEM in the detailed design phase for a flying wing aircraft. For potential application, the structure modeling and optimization process has been performed by full use of the commercial software MSC Nastran, which is widely employed in aerospace industry. First the wing structure FE model is divided into number of design zones along the span. A pre-process was proposed to group all plies in the same fiber orientation within one zone into a stack laminate and share one design variable. In each zone, the number of design variable in terms of skin ply thickness is reduced to the same number of fiber orientations used in the wing skin laminate. After the optimization, a post process was performed to trim the ply thickness and reset the skin laminate layup under the design and manufacture constraint. To keep the final design on the safe side, the thickness of an optimized ply is normally increased to the standard figure in the trim process. Consequently the trimmed structure weight is slightly increased after the post-process. However a practical optimum design of the composite wing structure in detailed FE model can be obtained. For the composite wing example, numerical results show that the optimized structure weight has been reduced by 16.3%. The results also show that the optimization approach is much efficient with little accuracy penalty.

An improved particle swarm optimizer for steel grillage systems

Abstract: In this paper, an improved version of particle swarm optimization based optimum design algorithm (IPSO) is presented for the steel grillage systems. The optimum design problem is formulated considering the provisions of American Institute of Steel Construction concerning Load and Resistance Factor Design. The optimum design algorithm selects the appropriate W-sections for the beams of the grillage system such that the design constraints are satisfied and the grillage weight is the minimum. When an improved version of the technique is extended to be implemented, the related results and convergence performance prove to be better than the simple particle swarm optimization algorithm and some other metaheuristic optimization techniques. The efficiency of different inertia weight parameters of the proposed algorithm is also numerically investigated considering a number of numerical grillage system examples.

Minimum Weight Design of Pre Engineered Steel Structures Using Built-up Sections and Cold Formed Sections

Abstract: In the past few decades most of the efforts were made to achieve minimum weight of the steel structures by satisfying all the design requirements imposed by various latest building codes and this idea lead towards the concept of pre-engineered steel buildings (PEB). In current research work, minimum weight buildings are targeted with simple fabrication process and easy erection to have maximum structural efficiency. Minimum weight of structure is proportional to the minimum cost and hence lowers seismic and gravitational forces. To achieve above mentioned objectives and to verify the suitability and applicability of concept of PEB, a sample steel industrial building is first analyzed and designed by using conventional steel hot rolled sections and then by using pre-engineered tapered and cold formed sections. Results of analysis were compared in terms of weight and response of structures which clearly indicated that PEB structures are of less weight and structurally more efficient than conventional steel structures.

Improved Fixed-Parameter Algorithm for the Minimum Weight 3-SAT Problem

Abstract: The problem of finding a satisfying assignment for a CNF formula that minimizes the weight (the number of variables that are set to 1) is NP-complete even if the formula is a 2-CNF formula. It generalizes the well-studied problem of finding the smallest hitting set for a family of sets, which can be modeled using a CNF formula with no negative literals. The natural parameterized version of the problem asks for a satisfying assignment of weight at most k.

On efficient design of earthquake resistant moment frames

Abstract: This paper introduces a number of simple findings that lead to the efficient design of system based earthquake resisting moment frames. A system based design is defined as one that leads to minimum drift and minimum weight solutions, for code recognized seismic frameworks, without resorting to complicated numerical analysis. These findings are used to form an algorithm, which in turn leads to closed form solutions for system-specific performance-based design of earthquake resisting moment frames. The results of some of these findings may be summarized as follows;  the efficient design of a representative closed loop sub-frame is one involving beams and columns of equal strength and stiffness,  a design may be said to be efficient when the demand/capacity ratios of all of its members are as close to unity as possible,  the magnitude of a mid-span concentrated load may be considered small if it is less than half its plastic collapse value acting alone on the same beam.

A minimum weight labelling method for determination of a shortest route in a non-directed network

Abstract: This paper proposes a new minimum weight labelling method for determining a shortest route in a non-directed network from a source node to a destination node. It is assumed that all links have positive weights associated with them. The key feature of this method is that for an m node network the algorithm developed finds an optimal solution in at most (m − 1) iterations.

On the support designs of extremal binary doubly even self-dual codes

Abstract: Let D be the support design of the minimum weight of an extremal binary doubly even self-dual [24m,12m,4m+4] code. In this note, we consider the case when D becomes a t-design with t \geq 6.

On the dual minimum distance and minimum weight of codes from a quotient of the Hermitian curve

Abstract: In this paper we study evaluation codes arising from plane quotients of the Hermitian curve, defined by affine equations of the form $$y^q+y=x^m,\,q$$ being a prime power and $$m$$ a positive integer which divides $$q+1$$ . The dual minimum distance and minimum weight of such codes are studied from a geometric point of view. In many cases we completely describe the minimum-weight codewords of their dual codes through a geometric characterization of the supports, and provide their number. Finally, we apply our results to describe Goppa codes of classical interest on such curves.