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heuristic-methods
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Extended haessler heuristic algorithm for cutting stock problem: a case study in film industry
, Article Australian Journal of Basic and Applied Sciences ; Volume 3, Issue 4 , 2009 , Pages 3944-3953 ; 19918178 (ISSN) ; Mohammadi, A ; Sharif University of Technology
2009
Abstract
The cutting stock problem is an important problem in the field of combinational optimization. In classic versions of this problem, the aim is to find a solution for cutting some equal-width mother rolls into smaller parts with given width so that the amount of trim-loss become as small as possible. There are plenty of works which addressed the classic cutting stock problem. However in real world applications there are usually some constraints which make the problem different form classical version and make it harder to solve. In this paper we investigate a special cutting stock problem in film industry and show that it can not be solved by using previous methods. We propose a new hybrid...
A heuristic homotopic path simplification algorithm
, Article Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), 20 June 2011 through 23 June 2011 ; Volume 6784 LNCS, Issue PART 3 , June , 2011 , Pages 132-140 ; 03029743 (ISSN) ; 9783642219306 (ISBN) ; Ghodsi, M ; Sharif University of Technology
2011
Abstract
We study the well-known problem of approximating a polygonal path P by a coarse one, whose vertices are a subset of the vertices of P. In this problem, for a given error, the goal is to find a path with the minimum number of vertices while preserving the homotopy in presence of a given set of extra points in the plane. We present a heuristic method for homotopy-preserving simplification under any desired measure for general paths. Our algorithm for finding homotopic shortcuts runs in O( mlog(n + m) + nlogn log(nm) + k) time, where k is the number of homotopic shortcuts. Using this method, we obtain an O(n 2 + mlog(n + m) + nlogn log(nm)) time algorithm for simplification under the Hausdorff...
Hybridizing harmony search algorithm with sequential quadratic programming for engineering optimization problems
, Article Computer Methods in Applied Mechanics and Engineering ; Volume 197, Issue 33-40 , 2008 , Pages 3080-3091 ; 00457825 (ISSN) ; Mahdavi, M ; Minary Jolandan, M ; Alizadeh, Y ; Sharif University of Technology
2008
Abstract
This study presents a hybrid harmony search algorithm (HHSA) to solve engineering optimization problems with continuous design variables. Although the harmony search algorithm (HSA) has proven its ability of finding near global regions within a reasonable time, it is comparatively inefficient in performing local search. In this study sequential quadratic programming (SQP) is employed to speed up local search and improve precision of the HSA solutions. Moreover, an empirical study is performed in order to determine the impact of various parameters of the HSA on convergence behavior. Various benchmark engineering optimization problems are used to illustrate the effectiveness and robustness of...
A metaheuristic approach to the graceful labeling problem of graphs
, Article 2007 IEEE Swarm Intelligence Symposium, SIS 2007, Honolulu, HI, 1 April 2007 through 5 April 2007 ; 2007 , Pages 84-91 ; 1424407087 (ISBN); 9781424407088 (ISBN) ; Eshghi, K ; Sharif University of Technology
2007
Abstract
In this paper, an algorithm based on Ant Colony Optimization metaheuristic is proposed for finding solutions to the well-known graceful labeling problem of graphs. Despite the large number of papers published on the theory of this problem, there are few particular techniques introduced by researchers for gracefully labeling graphs. The proposed algorithm is applied to many classes of graphs, and the results obtained have proven satisfactory when compared to those of the existing methods in the literature. © 2007 IEEE
Planning by guided hill-climbing
, Article 6th Mexican International Conference on Artificial Intelligence, MICAI 2007, Aguascalientes, 4 November 2007 through 10 November 2007 ; Volume 4827 LNAI , 2007 , Pages 1067-1077 ; 03029743 (ISSN); 9783540766308 (ISBN) ; Ghassem Sani, G ; Sharif University of Technology
Springer Verlag
2007
Abstract
This paper describes a novel approach will be called guided hill climbing to improve the efficiency of hill climbing in the planning domains. Unlike simple hill climbing, which evaluates the successor states without any particular order, guided hill climbing evaluates states according to an order recommended by an auxiliary guiding heuristic function. Guiding heuristic function is a self-adaptive and cost effective function based on the main heuristic function of hill climbing. To improve the performance of the method in various domains, we defined several heuristic functions and created a mechanism to choose appropriate functions for each particular domain. We applied the guiding method to...
An intelligent nuclear reactor core controller for load following operations, using recurrent neural networks and fuzzy systems
, Article Annals of Nuclear Energy ; Volume 30, Issue 1 , 2003 , Pages 63-80 ; 03064549 (ISSN) ; Ghofrani, M. B ; Lucas, C ; Yazdanpanah, M. J ; Sharif University of Technology
2003
Abstract
In the last decade, the intelligent control community has paid great attention to the topic of intelligent control systems for nuclear plants (core, steam generator). Papers mostly used approximate and simple mathematical SISO (single-input-single-output) model of nuclear plants for testing and/or tuning of the control systems. They also tried to generalize theses models to a real MIMO (multi-input-multi-output) plant, while nuclear plants are typically of complex nonlinear and multivariable nature with high interactions between their state variables and therefore, many of these proposed intelligent control systems are not appropriate for real cases. In this paper, we designed an on-line...
Solving Detour-Based Fuel Stations Location Problems
, Article Computer-Aided Civil and Infrastructure Engineering ; Volume 31, Issue 2 , 2016 , Pages 132-144 ; 10939687 (ISSN) ; Aashtiani, H. Z ; Ghamami, M ; Marco Nie, Y ; Sharif University of Technology
Blackwell Publishing Inc
Abstract
This article studies the problem of locating fuel stations to minimize the extra cost spent in refueling detours, which belongs to a class of discretionary service facility location problems. Unlike many studies of similar problems in the literature, the proposed model considers capacity constraints and compares different ways to incorporate them in the formulation. Note that ignoring the capacity constraint results in nonoptimal and unrealistic solutions. The proposed models are solved using both an off-the-shelf solver (CPLEX) and a specialized meta-heuristic method (Simulated Annealing) developed in this study. The solution methods are tested and compared in two case studies; a test...
A novel deterministic model for simultaneous weekly assignment and scheduling decision-making in operating theaters
, Article Scientia Iranica ; Volume 24, Issue 4 , 2017 , Pages 2035-2049 ; 10263098 (ISSN) ; Fatemi Ghomi, S. M. T ; Hooshangi Tabrizi, P ; Sharif University of Technology
Abstract
This paper studies a simultaneous weekly assignment and scheduling decisionmaking problem in operating theaters with elective patients. Because of limited recourses in hospitals, considering assignment and scheduling decisions simultaneously can help mangers exploit the available resources more efficiently and make the work-load uniformly distributed during the planning horizon. This procedure can significantly reduce hospital costs and increase satisfaction of patients and personnel. This paper formulates the mentioned problem as a Mixed Integer Linear Program (MILP) considering applicable assumptions like finite recovery beds and limitation of equipment. Since the problem is NP-hard, in...
Superpoly algebraic normal form monomial test on Trivium
, Article IET Information Security ; Volume 7, Issue 3 , 2013 , Pages 230-238 ; 17518709 (ISSN) ; Salmasizadeh, M ; Mohajeri, J ; Sharif University of Technology
2013
Abstract
Recently, AIDA/cube testers have been revealed to be useful in building distinguishers for several cryptography schemes. χ2 tests, on the other hand, are well known and extensively used for distinguishing purposes. In this study, the notion of multi-χ2 test and AIDA/cube testers are utilised to introduce the superpoly algebraic normal form monomial test through which the output of reduced round Trivium is distinguished from being random. The test successfully distinguishes the keystream of Trivium with 830 out of 1152 initialisation rounds with a complexity of 239 operations, which is the most effective distinguisher on reduced Trivium thus far. Applying algebraic IV differential attack...
Fast forward planning by guided enforced hill climbing
, Article Engineering Applications of Artificial Intelligence ; Volume 23, Issue 8 , 2010 , Pages 1327-1339 ; 09521976 (ISSN) ; Ghassem Sani, G ; Sharif University of Technology
Abstract
In recent years, a number of new heuristic search methods have been developed in the field of automated planning. Enforced hill climbing (EHC) is one such method which has been frequently used in a number of AI planning systems. Despite certain weaknesses, such as getting trapped in dead-ends in some domains, this method is more competitive than several other methods in many planning domains. In order to enhance the efficiency of ordinary enforced hill climbing, a new form of enforced hill climbing, called guided enforced hill climbing, is introduced in this paper. An adaptive branch ordering function is the main feature that guided enforced hill climbing has added to EHC. Guided enforced...
Solving the discrete time/resource trade-off problem in project scheduling with genetic algorithms
, Article Applied Mathematics and Computation ; Volume 191, Issue 2 , 2007 , Pages 451-456 ; 00963003 (ISSN) ; Kianfar, F ; Sharif University of Technology
2007
Abstract
In this paper, we develop a metaheuristic procedure for solving the discrete time/resource trade-off problem in the field of project scheduling. In this problem, a project contains activities interrelated by finish-start-type precedence constraints with a time lag of zero, which require a single constrained renewable resource. Each activity has a specified work content and can be performed in different modes, i.e. with different durations and resource requirements; as long as the required work content is met. The objective is to schedule each activity in one of its modes in order to minimize the project makespan. To tackle this problem, we use a genetic algorithm in which a new method based...
Service level based capacity rationing procedure for make-to-order manufacturing systems
, Article International Journal of Engineering, Transactions A: Basics ; Volume 20, Issue 1 , 2007 , Pages 1-16 ; 17281431 (ISSN) ; Modarres, M ; Sharif University of Technology
Materials and Energy Research Center
2007
Abstract
We extend a heuristic method within the framework of "dynamic capacity apportionment procedure" (DCAP) to allocate an existing capacity among the classes with different profit contributions. In general, DCAP is applied when some capacity shortage exists and can not be enhanced in short - run. Our proposed approach is constructed for a make - to - order manufacturing system that produces a variety of products while experiences a burst of demand in excess of capacity. Although, a higher level of profit can be gained by accepting more orders from higher priority classes at the expense of rejecting some or all of orders of lower priority classes, it may result in elimination of an existing...
An ACO algorithm for graph coloring problem
, Article 2005 ICSC Congress on Computational Intelligence Methods and Applications, Istanbul, 15 December 2005 through 17 December 2005 ; Volume 2005 , 2005 ; 1424400201 (ISBN); 9781424400201 (ISBN) ; Eshghi, K ; Sharif University of Technology
2005
Abstract
Ant Colony Optimization (ACO) is a well-known metaheuristic in which a colony of artificial ants cooperate in exploring good solutions to a combinatorial optimization problem. In this paper, an ACO algorithm is presented for the graph coloring problem. This ACO algorithm conforms to Max-Min Ant System structure and exploits a local search heuristic to improve its performance. Experimental results on DIMACS test instances show improvements over existing ACO algorithms of the graph coloring problem
An improved model for optimal under voltage load shedding: Particle swarm approach
, Article 2006 IEEE Power India Conference, New Delhi, 10 April 2006 through 12 April 2006 ; Volume 2005 , 2005 , Pages 723-728 ; 0780395255 (ISBN); 9780780395251 (ISBN) ; Mozafari, B ; Ranjbar, A. M ; Sharif University of Technology
2005
Abstract
Under voltage load shedding is one of the most important tools to avoid voltage instability. In this paper an optimal load shedding algorithm is developed. This approach is based on the concept of the static voltage stability margin and its sensitivity value at the maximum loading point or the collapse point. The traditional load shedding objective is extended to incorporate both technical and economical effects of load shedding. The voltage stability criterion is modeled as a soft constraint into load shedding scheme. The proposed methodology is implemented over the IEEE14 bus system and solved using a mathematical (GAMS/CONOPT) and two heuristic (P.S.O & GA) methods. © 2006 IEEE
Flowshop-scheduling problems with makespan criterion: A review
, Article International Journal of Production Research ; Volume 43, Issue 14 , 2005 , Pages 2895-2929 ; 00207543 (ISSN) ; Saghafian, S ; Sharif University of Technology
2005
Abstract
This paper is a complete survey of flowshop-scheduling problems and contributions from early works of Johnson of 1954 to recent approaches of metaheuristics of 2004. It mainly considers a flowshop problem with a makespan criterion and it surveys some exact methods (for small size problems), constructive heuristics and developed improving metaheuristic and evolutionary approaches as well as some well-known properties and rules for this problem. Each part has a brief literature review of the contributions and a glimpse of that approach before discussing the implementation for a flowshop problem. Moreover, in the first section, a complete literature review of flowshop-related scheduling...
Optimizing a Flowshop Model with the Objective of Minimizing Total Weighted Tardiness while Considering due Dates on All Machines
, M.Sc. Thesis Sharif University of Technology ; Ghassemi Tari, Farhad (Supervisor)
Abstract
Minimizing completion time of tasks in a flowshops has always attracted attention of researchers since it was introduced by Johnson, 1954. If all jobs are processed in the same order, the sequence is called a permutation sequence. Tardiness factor is one of important factors in permutation flowshop sequencing problem. Minimizing this factor brings about increase in service level of the shop and is helpful in meeting customer’s needs. Since, minimizing tardiness in PFSP in among NP-hard problems, computational efforts in this area has focused on heuristic approaches. However, the researches has always considered due dates only on the last machine. It means, always it has been assumed that due...
A Hybrid Simulated Annealing Algorithm For Winner Determination problem In Combinatorial Auction
, M.Sc. Thesis Sharif University of Technology ; Kianfar, Farhad (Supervisor)
Abstract
One of the most important issues that an organization faced with is resource management. The proper resource management has the great rule in organization cost reduction. One of the most efficient processes in resource allocation is auction and there is different auction with different mechanism and goals. In an auction there is a set of items and a set of bids, and the task of auctioneer is matching items with suitable bids. Each bid consist of desirable items and the bidder value of that items. In an auction process, after mechanism design of auction and auction implementation we must identify the winners of auction and this is a hard problem even in simple auction.
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Multi-user opportunistic spectrum access with channel impairments
, Article AEU - International Journal of Electronics and Communications ; Volume 67, Issue 11 , 2013 , Pages 955-966 ; 14348411 (ISSN) ; Salehkaleybar, S ; Pakravan, M. R ; Sharif University of Technology
2013
Abstract
In this paper, we study the impact of sensing error and channel fading on the decision process of a multiple secondary user network in a primary network whose channel occupancy states are modelled as a Bernoulli process. We present a randomized access strategy to maximize total secondary network throughput. The proposed method guarantees that the probability of collision between primary and secondary users in each channel is less than the predefined value of P c = ξ. To find the optimal access strategy, we formulate secondary network throughput as an optimization problem. Then, using the KKT method to find the solution, we break the original problem into multiple sub-problems. Then, we...
A heuristic complexity-based method for cost estimation of aerospace systems
, Article Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering ; Volume 227, Issue 11 , 2013 , Pages 1685-1700 ; 09544100 (ISSN) ; Jafari, M. H ; Sharif University of Technology
2013
Abstract
Cost estimation plays an essential role in the development of aerospace systems that are perhaps the most complex, time- and labor-consuming ones. Regarding this matter, it is unavoidable to take a systematic approach to build a realistic model through a deliberative, heuristical and easy-to-do process in the early stages of design. In the current study, complexity index theory is utilized to develop a heuristic complexity-based method to estimate various costs of aerospace systems. This method promises to be logically and practically more reliable and accurate than classical parametric methods. Logically, manipulating a group of parameters, instead of only one or two, reduces the...
Discrete kinematic synthesis of discretely actuated hyper-redundant manipulators
, Article Robotica ; Volume 31, Issue 7 , 2013 , Pages 1073-1084 ; 02635747 (ISSN) ; Zohoor, H ; Korayem, M. H ; Sharif University of Technology
2013
Abstract
Discrete kinematic synthesis of discretely actuated hyper-redundant manipulators is a new practical problem in robotics. The problem concerns with determining the type of each manipulator module from among several specific types, so that the manipulator could reach several specified target frames with the lowest error. This paper suggests using a breadth-first search method and a workspace mean frame to solve this problem. To reduce errors, two heuristic ideas are proposed: two-by-two searching method and iteration. The effectiveness of the proposed method is verified through several numerical problems