Colored Traveling Salesman Problem.
Li, Jun; Zhou, MengChu; Sun, Qirui; Dai, Xianzhong; Yu, Xiaolong
2015-11-01
The multiple traveling salesman problem (MTSP) is an important combinatorial optimization problem. It has been widely and successfully applied to the practical cases in which multiple traveling individuals (salesmen) share the common workspace (city set). However, it cannot represent some application problems where multiple traveling individuals not only have their own exclusive tasks but also share a group of tasks with each other. This work proposes a new MTSP called colored traveling salesman problem (CTSP) for handling such cases. Two types of city groups are defined, i.e., each group of exclusive cities of a single color for a salesman to visit and a group of shared cities of multiple colors allowing all salesmen to visit. Evidences show that CTSP is NP-hard and a multidepot MTSP and multiple single traveling salesman problems are its special cases. We present a genetic algorithm (GA) with dual-chromosome coding for CTSP and analyze the corresponding solution space. Then, GA is improved by incorporating greedy, hill-climbing (HC), and simulated annealing (SA) operations to achieve better performance. By experiments, the limitation of the exact solution method is revealed and the performance of the presented GAs is compared. The results suggest that SAGA can achieve the best quality of solutions and HCGA should be the choice making good tradeoff between the solution quality and computing time.
On Labeled Traveling Salesman Problems
Couetoux, Basile; Gourves, Laurent; Monnot, Jerome
2008-01-01
We consider labeled Traveling Salesman Problems, defined upon a complete graph of n vertices with colored edges. The objective is to find a tour of maximum (or minimum) number of colors. We derive results regarding hardness of approximation, and analyze approximation algorithms for both versions...... of the problem. For the maximization version we give a -approximation algorithm and show that it is APX-hard. For the minimization version, we show that it is not approximable within n 1 − ε for every ε> 0. When every color appears in the graph at most r times and r is an increasing function of n the problem...... is not O(r 1 − ε )-approximable. For fixed constant r we analyze a polynomial-time (r + H r )/2-approximation algorithm (H r is the r-th harmonic number), and prove APX-hardness. Analysis of the studied algorithms is shown to be tight....
The Destined Death of the Travelling Salesman
何苗
2015-01-01
Death of a Travelling Salesman is a short story with heated discussion and dispute. Death, as the title of the story presents, has always been the center of criticism. This paper aims to dissect this short story, and to discuss the destined death of the travelling salesman.
Solving traveling salesman problems by genetic algorithms
无
2003-01-01
The gene section ordering on solving traveling salesman problems is analyzed by numerical experiments. Some improved crossover operations are presented. Several combinations of genetic operations are examined and the functions of these operations are analyzed. The essentiality of the ordering of the gene section and the significance of the evolutionary inversion operation are discussed. Some results and conclusions are obtained and given, which provide useful information for the implementation of the genetic operations for solving the traveling salesman problem.
The General Traveling Salesman Problem
Kleiman, Howard
2011-01-01
This is concerned with essentially two ways in which to construct algorithms for obtaining both approximate and exact solutions to the general traveling salesman problem (GTSP)(the triangle equality need not be satisfied). The first uses an arbitrary n-cycle to permute the columns of an n X n matrix with weighted entries. In doing so, we obtain negative entries. Using these entries, we from negative cycles. We give a formula for the length of cycles necessary to obtain an n-cycle by patching. Using patching of negative cycles, we obtain an n-cycle. The second portion of the algorithm gives procedures for obtain an exact solution to the GTSP. Our second algorithm uses the average arc-value (aav) of a path. We first obtain an n-cycle in a manner similar to that in the first algorithm. Call this T_UPPERBOUND. We then construct paths each of which has an aav less than that of T_UPPERBOUND. Using parallel programming, we construct all paths whose values are less than that of T_UPPERBOUND. Then either we obtain an ...
Saad, Shakila; Wan Jaafar, Wan Nurhadani; Jamil, Siti Jasmida
2013-04-01
The standard Traveling Salesman Problem (TSP) is the classical Traveling Salesman Problem (TSP) while Multiple Traveling Salesman Problem (MTSP) is an extension of TSP when more than one salesman is involved. The objective of MTSP is to find the least costly route that the traveling salesman problem can take if he wishes to visit exactly once each of a list of n cities and then return back to the home city. There are a few methods that can be used to solve MTSP. The objective of this research is to implement an exact method called Branch-and-Bound (B&B) algorithm. Briefly, the idea of B&B algorithm is to start with the associated Assignment Problem (AP). A branching strategy will be applied to the TSP and MTSP which is Breadth-first-Search (BFS). 11 nodes of cities are implemented for both problem and the solutions to the problem are presented.
A new Lagrangean Approach for the Travelling Salesman Problem
2015-01-01
In this paper, we use a reformulation of the symmetric and the asymmetric travelling salesman problem more suitable for Lagrangean relaxation and analyse the new approach on examples from TSP Lib. Furthermore the Lagrangean relaxed subproblems are travelling salesman alike which means that almost all that is known on the travelling salesman polytope can be used when the subproblems are to be solved.
The cost-constrained traveling salesman problem
Sokkappa, P.R.
1990-10-01
The Cost-Constrained Traveling Salesman Problem (CCTSP) is a variant of the well-known Traveling Salesman Problem (TSP). In the TSP, the goal is to find a tour of a given set of cities such that the total cost of the tour is minimized. In the CCTSP, each city is given a value, and a fixed cost-constraint is specified. The objective is to find a subtour of the cities that achieves maximum value without exceeding the cost-constraint. Thus, unlike the TSP, the CCTSP requires both selection and sequencing. As a consequence, most results for the TSP cannot be extended to the CCTSP. We show that the CCTSP is NP-hard and that no K-approximation algorithm or fully polynomial approximation scheme exists, unless P = NP. We also show that several special cases are polynomially solvable. Algorithms for the CCTSP, which outperform previous methods, are developed in three areas: upper bounding methods, exact algorithms, and heuristics. We found that a bounding strategy based on the knapsack problem performs better, both in speed and in the quality of the bounds, than methods based on the assignment problem. Likewise, we found that a branch-and-bound approach using the knapsack bound was superior to a method based on a common branch-and-bound method for the TSP. In our study of heuristic algorithms, we found that, when selecting modes for inclusion in the subtour, it is important to consider the neighborhood'' of the nodes. A node with low value that brings the subtour near many other nodes may be more desirable than an isolated node of high value. We found two types of repetition to be desirable: repetitions based on randomization in the subtour buildings process, and repetitions encouraging the inclusion of different subsets of the nodes. By varying the number and type of repetitions, we can adjust the computation time required by our method to obtain algorithms that outperform previous methods.
Parameterized Traveling Salesman Problem: Beating the Average
Gutin, G.; Patel, V.
2016-01-01
In the traveling salesman problem (TSP), we are given a complete graph Kn together with an integer weighting w on the edges of Kn, and we are asked to find a Hamilton cycle of Kn of minimum weight. Let h(w) denote the average weight of a Hamilton cycle of Kn for the weighting w. Vizing in 1973 asked
A Study of Travelling Salesman Problem
无
2001-01-01
The Travelling Salesman Problem (TSP) is one of the mostdifficult problems that many scholars all over the world are studying. This paper points out the disparity between the definition and the classical solution to TSP and its practical applications, and then presents a new definition of TSP and its effective algorithm conforming to practical applications, thus making TSP practically more valuable.
Quantum heuristic algorithm for traveling salesman problem
Bang, Jeongho; Lim, James; Ryu, Junghee; Lee, Changhyoup; Lee, Jinhyoung
2010-01-01
We propose a quantum heuristic algorithm to solve a traveling salesman problem by generalizing Grover search. Sufficient conditions are derived to greatly enhance the probability of finding the tours with extremal costs, reaching almost to unity and they are shown characterized by statistical properties of tour costs. In particular for a Gaussian distribution of the tours along the cost we show that the quantum algorithm exhibits the quadratic speedup of its classical counterpart, similarly to Grover search.
A Novel Metaheuristic for Travelling Salesman Problem
Vahid Zharfi
2013-01-01
Full Text Available One of the well-known combinatorial optimization problems is travelling salesman problem (TSP. This problem is in the fields of logistics, transportation, and distribution. TSP is among the NP-hard problems, and many different metaheuristics are used to solve this problem in an acceptable time especially when the number of cities is high. In this paper, a new meta-heuristic is proposed to solve TSP which is based on new insight into network routing problems.
The traveling salesman problem a computational study
Applegate, David L; Chvatal, Vasek; Cook, William J
2006-01-01
This book presents the latest findings on one of the most intensely investigated subjects in computational mathematics--the traveling salesman problem. It sounds simple enough: given a set of cities and the cost of travel between each pair of them, the problem challenges you to find the cheapest route by which to visit all the cities and return home to where you began. Though seemingly modest, this exercise has inspired studies by mathematicians, chemists, and physicists. Teachers use it in the classroom. It has practical applications in genetics, telecommunications, and neuroscience.
Diffusive behavior of a greedy traveling salesman
Lipowski, Adam; Lipowska, Dorota
2011-06-01
Using Monte Carlo simulations we examine the diffusive properties of the greedy algorithm in the d-dimensional traveling salesman problem. Our results show that for d=3 and 4 the average squared distance from the origin is proportional to the number of steps t. In the d=2 case such a scaling is modified with some logarithmic corrections, which might suggest that d=2 is the critical dimension of the problem. The distribution of lengths also shows marked differences between d=2 and d>2 versions. A simple strategy adopted by the salesman might resemble strategies chosen by some foraging and hunting animals, for which anomalous diffusive behavior has recently been reported and interpreted in terms of Lévy flights. Our results suggest that broad and Lévy-like distributions in such systems might appear due to dimension-dependent properties of a search space.
Adapting the traveling salesman problem to an adiabatic quantum computer
Warren, Richard H.
2013-04-01
We show how to guide a quantum computer to select an optimal tour for the traveling salesman. This is significant because it opens a rapid solution method for the wide range of applications of the traveling salesman problem, which include vehicle routing, job sequencing and data clustering.
FACES WITH LARGE DIAMETER ON THE SYMMETRICAL TRAVELING SALESMAN POLYTOPE
SIERKSMA, G; TIJSSEN, GA
1992-01-01
This paper deals with the symmetric traveling salesman polytope and contains three main theorems. The first one gives a new characterization of (non)adjacency. Based on this characterization a new upper bound for the diameter of the symmetric traveling salesman polytope (conjectured to be 2 by M. Gr
Ant colonies for the travelling salesman problem.
Dorigo, M; Gambardella, L M
1997-01-01
We describe an artificial ant colony capable of solving the travelling salesman problem (TSP). Ants of the artificial colony are able to generate successively shorter feasible tours by using information accumulated in the form of a pheromone trail deposited on the edges of the TSP graph. Computer simulations demonstrate that the artificial ant colony is capable of generating good solutions to both symmetric and asymmetric instances of the TSP. The method is an example, like simulated annealing, neural networks and evolutionary computation, of the successful use of a natural metaphor to design an optimization algorithm.
On the Core of Multiple Longest Traveling Salesman Games
Estevez Fernandez, M.A.; Borm, P.E.M.; Hamers, H.J.M.
2003-01-01
In this paper we introduce multiple longest traveling salesman (MLTS) games. An MLTS game arises from a network in which a salesman has to visit each node (player) precisely once, except its home location, in an order that maximizes the total reward.First it is shown that the value of a coalition of
State transition algorithm for traveling salesman problem
Chunhua, Yang; Xiaojun, Zhou; Weihua, Gui
2012-01-01
Discrete version of state transition algorithm is proposed in order to solve the traveling salesman problem. Three special operators for discrete optimization problem named swap, shift and symmetry transformations are presented. Convergence analysis and time complexity of the algorithm are also considered. To make the algorithm simple and efficient, no parameter adjusting is suggested in current version. Experiments are carried out to test the performance of the strategy, and comparisons with simulated annealing and ant colony optimization have demonstrated the effectiveness of the proposed algorithm. The results also show that the discrete state transition algorithm consumes much less time and has better search ability than its counterparts, which indicates that state transition algorithm is with strong adaptability.
The Quadratic Selective Travelling Salesman Problem
Thomadsen, Tommy; Stidsen, Thomas K.
2003-01-01
complication that each pair of nodes have an associated profit which can be gained only if both nodes are visited. The QSTSP is a subproblem when constructing hierarchical ring networks. We describe an integer linear programming model for the QSTSP. The QSTSP is solved by two construction heuristics...... solutions at a cost of much higher running time. All problems with up to 50 nodes are solved within one hour.......A well-known extension of the Travelling Salesman Problem (TSP) is the Selective TSP (STSP): Each node has an associated profit and instead of visiting all nodes, the most profitable set of nodes, taking into account the tour cost, is visited. The Quadratic STSP (QSTSP) adds the additional...
Parallel tempering for the traveling salesman problem
Percus, Allon [Los Alamos National Laboratory; Wang, Richard [UCLA MATH DEPT; Hyman, Jeffrey [UCLA MATH DEPT; Caflisch, Russel [UCLA MATH DEPT
2008-01-01
We explore the potential of parallel tempering as a combinatorial optimization method, applying it to the traveling salesman problem. We compare simulation results of parallel tempering with a benchmark implementation of simulated annealing, and study how different choices of parameters affect the relative performance of the two methods. We find that a straightforward implementation of parallel tempering can outperform simulated annealing in several crucial respects. When parameters are chosen appropriately, both methods yield close approximation to the actual minimum distance for an instance with 200 nodes. However, parallel tempering yields more consistently accurate results when a series of independent simulations are performed. Our results suggest that parallel tempering might offer a simple but powerful alternative to simulated annealing for combinatorial optimization problems.
Solving traveling salesman problems using generalized chromosome genetic algorithm
Jinhui Yang; Chunguo Wu; Heow Pueh Lee; Yanchun Liang
2008-01-01
Generalized chromosome genetic algorithm (GCGA) was proposed for solving generalized traveling salesman problems (GTSP) as reported in the authors' earlier work. Theoretically, the GCGA could also be used to solve the classical traveling salesman problem (CTSP), which has not been reported by others. In this paper, the generalized chromosome characteristics are analyzed and the feasibility for consistently solving the GTSP and CTSP is verified. Numerical experiments show the advantages of the GCGA for solving a large-scale CTSP.
STUDI TENTANG TRAVELLING SALESMAN DAN VEHICLE ROUTING PROBLEM DENGAN TIME WINDOWS
I Nyoman Sutapa; I Gede Agus Widyadana; Christine Christine
2003-01-01
The article shows the study of model development of travelling salesman problem. Three models are studied, i.e. travelling salesman problem with time windows, vehicle routing problem, and vehicle routing problem with time windows. Abstract in Bahasa Indonesia : Dalam artikel ini dipaparkan kajian mengenai pengembangan model travelling salesman problem. Ada tiga model yang dikaji yaitu travelling salesman problem dengan time windows, vehicle routing problem, serta vehicle routing problem denga...
List-Based Simulated Annealing Algorithm for Traveling Salesman Problem.
Zhan, Shi-hua; Lin, Juan; Zhang, Ze-jun; Zhong, Yi-wen
2016-01-01
Simulated annealing (SA) algorithm is a popular intelligent optimization algorithm which has been successfully applied in many fields. Parameters' setting is a key factor for its performance, but it is also a tedious work. To simplify parameters setting, we present a list-based simulated annealing (LBSA) algorithm to solve traveling salesman problem (TSP). LBSA algorithm uses a novel list-based cooling schedule to control the decrease of temperature. Specifically, a list of temperatures is created first, and then the maximum temperature in list is used by Metropolis acceptance criterion to decide whether to accept a candidate solution. The temperature list is adapted iteratively according to the topology of the solution space of the problem. The effectiveness and the parameter sensitivity of the list-based cooling schedule are illustrated through benchmark TSP problems. The LBSA algorithm, whose performance is robust on a wide range of parameter values, shows competitive performance compared with some other state-of-the-art algorithms.
SMALL AND LARGE TSP - 2 POLYNOMIALLY SOLVABLE CASES OF THE TRAVELING SALESMAN PROBLEM
VANDAL, R; VANDERVEEN, JAA; SIERKSMA, G
1993-01-01
The problem of minimizing and maximizing the objective function of the Traveling Salesman Problem (TSP) is discussed. In particular, we consider two special cases of the TSP, namely the small TSP and the large TSP, for which both a minimum and a maximum of the objective function can be obtained in
On semidefinite programming relaxations of the traveling salesman problem
de Klerk, Etienne; Sotirov, Renata; 10.1137/070711141
2009-01-01
We consider a new semidefinite programming (SDP) relaxation of the symmetric traveling salesman problem (TSP) that may be obtained via an SDP relaxation of the more general quadratic assignment problem (QAP). We show that the new relaxation dominates the one in [D. Cvetkovic, M. Cangalovic, and V. Kovacevic-Vujcic, Semidefinite programming methods for the symmetric traveling salesman problem, in Proc. 7th Int. IPCO Conference, Springer, London, 1999, pp. 126--136]. Unlike the bound of Cvetkovic et al., the new SDP bound is not dominated by the Held-Karp linear programming bound, or vice versa.
Local Search Algorithms for the Generalized Traveling Salesman Problem
Karapetyan, Daniel
2010-01-01
The Generalized Traveling Salesman Problem (GTSP) is a well-known combinatorial optimization problem with a host of applications. It is an extension of the Traveling Salesman Problem (TSP) where the set of cities is divided into so-called clusters, and the salesman have to visit each cluster exactly once. While GTSP is a very important combinatorial optimization problem and is well-studied in many aspects, researches still did not pay enough attention to GTSP specific local search and mostly use simple TSP heuristics with basic adaptations for GTSP\\@. This paper aims at thorough and deep investigation of the neighborhoods specific for GTSP and algorithms that can explore these neighborhoods quickly. We formalize the procedure of adaptation of a TSP neighborhood for GTSP and propose efficient algorithms to explore the obtained neighborhoods. We also generalize all other existing and some new GTSP neighborhoods. Apart from these theoretical results, we also provide the results of a thorough experimental analysi...
New Integer Programming Formulations of the Generalized Travelling Salesman Problem
P. C. Pop
2007-01-01
Full Text Available The Generalized Travelling Salesman Problem, denoted by GTSP, is a variant of the classical travelling salesman problem (TSP, in which the nodes of an undirected graph are partitioned into node sets (clusters and the salesman has to visit exactly one node from every cluster. In this paper we described six distinct formulations of the GTSP as an integer programming. Apart from the standard formulations all the new formulations that we describe are 'compact' in the sense that the number of constraints and variables is a polynomial function of the number of nodes in the problem. In order to provide compact formulations for the GTSP we used two approaches using auxiliary flow variables beyond the natural binary edge and node variables and the second one by distinguishing between global and local variables. Comparisons of the polytopes corresponding to their linear relaxations are established.
STUDI TENTANG TRAVELLING SALESMAN DAN VEHICLE ROUTING PROBLEM DENGAN TIME WINDOWS
I Nyoman Sutapa
2003-01-01
Full Text Available The article shows the study of model development of travelling salesman problem. Three models are studied, i.e. travelling salesman problem with time windows, vehicle routing problem, and vehicle routing problem with time windows. Abstract in Bahasa Indonesia : Dalam artikel ini dipaparkan kajian mengenai pengembangan model travelling salesman problem. Ada tiga model yang dikaji yaitu travelling salesman problem dengan time windows, vehicle routing problem, serta vehicle routing problem dengan time windows. Kata-kunci: travelling salesman problem, vehicle routing problem, time windows.
OPTIMIZING MULTIPLE TRAVELLING SALESMAN PROBLEM CONSIDERING THE ROAD CAPACITY
Ranjana Ponraj
2014-01-01
Full Text Available The Multiple Travelling Salesman Problems (MTSP can be used in a wide range of discrete optimization problems. As the solution to this problem has wide applicability in many practical fields, this NP Hard problem highly raises the need for an efficient solution. The problem is determining a set of routes for the salesmen that jointly visit a set of given cities which are facing difficulty because of road congestion. Selection of proper route is based on the road capacity, which is the deciding factor in the opt vehicle usage. The objective of the study is to optimize the vehicle utilization and minimize the time of travel by salesman based on the road capacity. The solution to this problem is achieved in 3 steps; the first step is by assigning addresses to cities by Ad-assignment algorithm. The second step is by assigning cities and vehicles to salesman by Sl-assignment algorithm. The third step is by using Parallel Shortest Path Multiple Salesman (PSPMS algorithms to obtain the shortest path. The PSPMS algorithm runs in parallel for each salesman. The solutions to the problem are known to possess an exponential time complexity. From the result we observe that PSPMS is one of the best approximate algorithms used to solve MTSP.
Approximation algorithms for multi-criteria traveling salesman problems
Manthey, Bodo; Shankar Ram, L.
We analyze approximation algorithms for several variants of the traveling salesman problem with multiple objective functions. First, we consider the symmetric TSP (STSP) with $\\gamma$-triangle inequality. For this problem, we present a deterministic polynomial-time algorithm that achieves an
The pickup and delivery traveling salesman problem with handling costs
Veenstra, Marjolein; Roodbergen, Kees Jan; Vis, Iris F.A.; Coelho, Leandro
2017-01-01
This paper introduces the pickup and delivery traveling salesman problem with handling costs (PDTSPH). In the PDTSPH, a single vehicle has to transport loads from origins to destinations. Loading and unloading of the vehicle is operated in a last-in-first-out (LIFO) fashion. However, if a load must
Solving the k-best traveling salesman problem
van der Poort, ES; Libura, M; Sierksma, G; van der Veen, JAA
Although k-best solutions for polynomial solvable problems are extensively studied in the literature, not much is known for NP-hard problems. In this paper we design algorithms for finding sets of k-best solutions to the Traveling Salesman Problem (TSP) for some positive integer k. It will be shown
Development of the PEBLebl Traveling Salesman Problem Computerized Testbed
Mueller, Shane T.; Perelman, Brandon S.; Tan, Yin Yin; Thanasuan, Kejkaew
2015-01-01
The traveling salesman problem (TSP) is a combinatorial optimization problem that requires finding the shortest path through a set of points ("cities") that returns to the starting point. Because humans provide heuristic near-optimal solutions to Euclidean versions of the problem, it has sometimes been used to investigate human visual…
Solving the k-best traveling salesman problem
Poort, van der E.S.; Libura, M.; Sierksma, G.; Veen, van der J.A.A.
1999-01-01
Although k-best solutions for polynomial solvable problems are extensively studied in the literature not much is known for NP-hard problems. In this paper we design algorithms for finding sets of k-best solutions to the Traveling Salesman Problem (TSP) for some positive integer k. It will be shown
Approximation algorithms for multi-criteria traveling salesman problems
Manthey, B.; Shankar Ram, L.
2009-01-01
We analyze approximation algorithms for several variants of the traveling salesman problem with multiple objective functions. First, we consider the symmetric TSP (STSP) with $\\gamma$-triangle inequality. For this problem, we present a deterministic polynomial-time algorithm that achieves an approxi
Dynamic Programming Approaches for the Traveling Salesman Problem with Drone
P. Bouman (Paul); N.A.H. Agatz (Niels); M.E. Schmidt (Marie)
2017-01-01
markdownabstractA promising new delivery model involves the use of a delivery truck that collaborates with a drone to make deliveries. Effectively combining a drone and a truck gives rise to a new planning problem that is known as the Traveling Salesman Problem with Drone (TSP-D). This paper
Hybrid ant colony algorithm for traveling salesman problem
无
2003-01-01
A hybrid approach based on ant colony algorithm for the traveling salesman problem is proposed, which is an improved algorithm characterized by adding a local search mechanism, a cross-removing strategy and candidate lists. Experimental results show that it is competitive in terms of solution quality and computation time.
Finding the Minimum Ratio Traveling Salesman Tour by Artificial Ants
马良; 崔雪丽; 姚俭
2003-01-01
Ants of artificial colony are able to generate good solutions to the famous traveling salesman problem (TSP).We propose an artificial ants algorithm for solving the minimum ratio TSP, which is more general than the standard TSP in combinatorial optimization area. In the minimum ratio TSP, another criterion concerning each edge is added, that is,the traveling salesman can have a benefit if he travels from one city to another. The objective is to minimize the ratio between total costs or distances and total benefits. The idea of this type of optimization is in some sense quite similar to that of traditional cost-benefit analysis in management science. Computational results substantiate the solution quality and efficiency of the algorithm.
The Ordered Clustered Travelling Salesman Problem: A Hybrid Genetic Algorithm
Zakir Hussain Ahmed
2014-01-01
Full Text Available The ordered clustered travelling salesman problem is a variation of the usual travelling salesman problem in which a set of vertices (except the starting vertex of the network is divided into some prespecified clusters. The objective is to find the least cost Hamiltonian tour in which vertices of any cluster are visited contiguously and the clusters are visited in the prespecified order. The problem is NP-hard, and it arises in practical transportation and sequencing problems. This paper develops a hybrid genetic algorithm using sequential constructive crossover, 2-opt search, and a local search for obtaining heuristic solution to the problem. The efficiency of the algorithm has been examined against two existing algorithms for some asymmetric and symmetric TSPLIB instances of various sizes. The computational results show that the proposed algorithm is very effective in terms of solution quality and computational time. Finally, we present solution to some more symmetric TSPLIB instances.
The ordered clustered travelling salesman problem: a hybrid genetic algorithm.
Ahmed, Zakir Hussain
2014-01-01
The ordered clustered travelling salesman problem is a variation of the usual travelling salesman problem in which a set of vertices (except the starting vertex) of the network is divided into some prespecified clusters. The objective is to find the least cost Hamiltonian tour in which vertices of any cluster are visited contiguously and the clusters are visited in the prespecified order. The problem is NP-hard, and it arises in practical transportation and sequencing problems. This paper develops a hybrid genetic algorithm using sequential constructive crossover, 2-opt search, and a local search for obtaining heuristic solution to the problem. The efficiency of the algorithm has been examined against two existing algorithms for some asymmetric and symmetric TSPLIB instances of various sizes. The computational results show that the proposed algorithm is very effective in terms of solution quality and computational time. Finally, we present solution to some more symmetric TSPLIB instances.
A HYBRID HEURISTIC ALGORITHM FOR THE CLUSTERED TRAVELING SALESMAN PROBLEM
Mário Mestria
2016-04-01
Full Text Available ABSTRACT This paper proposes a hybrid heuristic algorithm, based on the metaheuristics Greedy Randomized Adaptive Search Procedure, Iterated Local Search and Variable Neighborhood Descent, to solve the Clustered Traveling Salesman Problem (CTSP. Hybrid Heuristic algorithm uses several variable neighborhood structures combining the intensification (using local search operators and diversification (constructive heuristic and perturbation routine. In the CTSP, the vertices are partitioned into clusters and all vertices of each cluster have to be visited contiguously. The CTSP is -hard since it includes the well-known Traveling Salesman Problem (TSP as a special case. Our hybrid heuristic is compared with three heuristics from the literature and an exact method. Computational experiments are reported for different classes of instances. Experimental results show that the proposed hybrid heuristic obtains competitive results within reasonable computational time.
THE DUBINS TRAVELING SALESMAN PROBLEM WITH CONSTRAINED COLLECTING MANEUVERS
Petr Váňa
2016-11-01
Full Text Available In this paper, we introduce a variant of the Dubins traveling salesman problem (DTSP that is called the Dubins traveling salesman problem with constrained collecting maneuvers (DTSP-CM. In contrast to the ordinary formulation of the DTSP, in the proposed DTSP-CM, the vehicle is requested to visit each target by specified collecting maneuver to accomplish the mission. The proposed problem formulation is motivated by scenarios with unmanned aerial vehicles where particular maneuvers are necessary for accomplishing the mission, such as object dropping or data collection with sensor sensitive to changes in vehicle heading. We consider existing methods for the DTSP and propose its modifications to use these methods to address a variant of the introduced DTSP-CM, where the collecting maneuvers are constrained to straight line segments.
Improved mapping of the travelling salesman problem for quantum annealing
Troyer, Matthias; Heim, Bettina; Brown, Ethan; Wecker, David
2015-03-01
We consider the quantum adiabatic algorithm as applied to the travelling salesman problem (TSP). We introduce a novel mapping of TSP to an Ising spin glass Hamiltonian and compare it to previous known mappings. Through direct perturbative analysis, unitary evolution, and simulated quantum annealing, we show this new mapping to be significantly superior. We discuss how this advantage can translate to actual physical implementations of TSP on quantum annealers.
2D and 3D Traveling Salesman Problem
Haxhimusa, Yll; Carpenter, Edward; Catrambone, Joseph; Foldes, David; Stefanov, Emil; Arns, Laura; Pizlo, Zygmunt
2011-01-01
When a two-dimensional (2D) traveling salesman problem (TSP) is presented on a computer screen, human subjects can produce near-optimal tours in linear time. In this study we tested human performance on a real and virtual floor, as well as in a three-dimensional (3D) virtual space. Human performance on the real floor is as good as that on a…
2D and 3D Traveling Salesman Problem
Haxhimusa, Yll; Carpenter, Edward; Catrambone, Joseph; Foldes, David; Stefanov, Emil; Arns, Laura; Pizlo, Zygmunt
2011-01-01
When a two-dimensional (2D) traveling salesman problem (TSP) is presented on a computer screen, human subjects can produce near-optimal tours in linear time. In this study we tested human performance on a real and virtual floor, as well as in a three-dimensional (3D) virtual space. Human performance on the real floor is as good as that on a…
Novel Local Search Method for the Traveling Salesman Problem
Huang Wenqi; Wang Lei
2005-01-01
A new local search method for the traveling salesman problem based on an original greedy representation of solution space and neighborhood structure is proposed. First, a partial closed route that only consists of three cities is given; then other cities are added to this route by a greedy procedure successively. Implemented on a personal computer, this algorithm finds optimal solutions for 24 out of 27 standard benchmarks, and outperforms the Full Subpath Ejection Algorithm (F-SEC) proposed by Rego in 1998.
LP-Based Approximation Algorithms for Traveling Salesman Path Problems
An, Hyung-Chan
2011-01-01
We present a (5/3 - epsilon)-approximation algorithm for some constant epsilon>0 for the traveling salesman path problem under the unit-weight graphical metric, and prove an upper bound on the integrality gap of the path-variant Held-Karp relaxation both under this metric and the general metric. Given a complete graph with the metric cost and two designated endpoints in the graph, the traveling salesman path problem is to find a minimum Hamiltonian path between these two endpoints. The best previously known performance guarantee for this problem was 5/3 and was due to Hoogeveen. We give the first constant upper bound on the integrality gap of the path-variant Held-Karp relaxation, showing it to be at most 5/3 by providing a new analysis of Hoogeveen's algorithm. This analysis exhibits a well-characterized critical case, and we show that the recent result of Oveis Gharan, Saberi and Singh on the traveling salesman circuit problem under the unit-weight graphical metric can be modified for the path case to compl...
List-Based Simulated Annealing Algorithm for Traveling Salesman Problem
Shi-hua Zhan
2016-01-01
Full Text Available Simulated annealing (SA algorithm is a popular intelligent optimization algorithm which has been successfully applied in many fields. Parameters’ setting is a key factor for its performance, but it is also a tedious work. To simplify parameters setting, we present a list-based simulated annealing (LBSA algorithm to solve traveling salesman problem (TSP. LBSA algorithm uses a novel list-based cooling schedule to control the decrease of temperature. Specifically, a list of temperatures is created first, and then the maximum temperature in list is used by Metropolis acceptance criterion to decide whether to accept a candidate solution. The temperature list is adapted iteratively according to the topology of the solution space of the problem. The effectiveness and the parameter sensitivity of the list-based cooling schedule are illustrated through benchmark TSP problems. The LBSA algorithm, whose performance is robust on a wide range of parameter values, shows competitive performance compared with some other state-of-the-art algorithms.
Mak, Vicky; Thomadsen, Tommy
2006-01-01
This paper considers the cardinality constrained quadratic knapsack problem (QKP) and the quadratic selective travelling salesman problem (QSTSP). The QKP is a generalization of the knapsack problem and the QSTSP is a generalization of the travelling salesman problem. Thus, both problems are NP...
Stability aspects of the traveling salesman problem based on k-best solutions
Libura, M; van der Poort, ES; Sierksma, C; van der Veen, JAA
1998-01-01
This paper discusses stability analysis for the Traveling Salesman Problem (TSP). For a traveling salesman tour which is known to be optimal with respect to a given instance (length vector) we are interested in determining the stability region, i.e. the set of all length vectors for which the tour
A quantum heuristic algorithm for the traveling salesman problem
Bang, Jeongho; Ryu, Junghee; Lee, Changhyoup; Yoo, Seokwon; Lim, James; Lee, Jinhyoung
2012-12-01
We propose a quantum heuristic algorithm to solve the traveling salesman problem by generalizing the Grover search. Sufficient conditions are derived to greatly enhance the probability of finding the tours with the cheapest costs reaching almost to unity. These conditions are characterized by the statistical properties of tour costs and are shown to be automatically satisfied in the large-number limit of cities. In particular for a continuous distribution of the tours along the cost, we show that the quantum heuristic algorithm exhibits a quadratic speedup compared to its classical heuristic algorithm.
Fuzzy Inspired Hybrid Genetic Approach to Optimize Travelling Salesman Problem
Bindu
2012-06-01
Full Text Available One of the category of algorithm Problems are basically exponential problems. These problems are basically exponential problems and take time to find the solution. In the present work we are optimising one of the common NP complete problem called Travelling Salesman Problem. In our work we have defined a genetic approach by combining fuzzy approach along with genetics. In this work we have implemented the modified DPX crossover to improve genetic approach. The work is implemented in MATLAB environment and obtained results shows the define approach has optimized the existing genetic algorithm results
Improved extremal optimization for the asymmetric traveling salesman problem
Chen, Yu-Wang; Zhu, Yao-Jia; Yang, Gen-Ke; Lu, Yong-Zai
2011-11-01
This paper presents an improved extremal optimization (IEO) algorithm for solving the asymmetric traveling salesman problem (ATSP). At each update step, the IEO algorithm proceeds through two main steps: extremal dynamics and cooperative optimization. As an improvement of extremal optimization (EO), the IEO provides a general combinatorial optimization framework by emphasizing the step of cooperative optimization. In the paper, an effective cooperative optimization strategy with combination of greedy search and random walk is designed in terms of the microscopic characteristics of the ATSP solutions. Simulation results on a set of benchmark ATSP instances show that the proposed IEO algorithm provides satisfactory performance on computational effectiveness and efficiency.
Solving the Travelling Salesman Problem Using the Ant Colony Optimization
Zuzana Čičková
2011-12-01
Full Text Available In this article, we study a possibility of solving the well-known Travelling Salesman Problem (TSP, which ranges among NP-hard problems, and offer a theoretical overview of some methods used for solving this problem. We discuss the Ant Colony Optimization (ACO, which belongs to the group of evolutionary techniques and presents the approach used in the application of ACO to the TSP. We study the impact of some control parameters by implementing this algorithm. The quality of the solution is compared with the optimal solution.
The Electric Traveling Salesman Problem with Time Windows
Roberti, Roberto; Wen, Min
2016-01-01
integer linear formulation that can solve 20-customer instances in short computing times and a Three-Phase Heuristic algorithm based on General Variable Neighborhood Search and Dynamic Programming.Computational results show that the heuristic algorithm can find the optimal solution in most small......To minimize greenhouse gas emissions, the logistic field has seen an increasing usage of electric vehicles. The resulting distribution planning problems present new computational challenges.We address a problem, called Electric Traveling Salesman Problem with Time Windows. We propose a mixed...
An Improved Particle Swarm Optimization for Traveling Salesman Problem
Liu, Xinmei; Su, Jinrong; Han, Yan
In allusion to particle swarm optimization being prone to get into local minimum, an improved particle swarm optimization algorithm is proposed. The algorithm draws on the thinking of the greedy algorithm to initialize the particle swarm. Two swarms are used to optimize synchronously. Crossover and mutation operators in genetic algorithm are introduced into the new algorithm to realize the sharing of information among swarms. We test the algorithm with Traveling Salesman Problem with 14 nodes and 30 nodes. The result shows that the algorithm can break away from local minimum earlier and it has high convergence speed and convergence ratio.
Solving constrained traveling salesman problems by genetic algorithms
WU Chunguo; LIANG Yanchun; LEE Heowpueh; LU Chun; LIN Wuzhong
2004-01-01
Three kinds of constrained traveling salesman problems (TSP) arising from application problems, namely the open route TSP, the end-fixed TSP, and the path-constrained TSP, are proposed. The corresponding approaches based on modified genetic algorithms (GA) for solving these constrained TSPs are presented. Numerical experiments demonstrate that the algorithm for the open route TSP shows its advantages when the open route is required, the algorithm for the end-fixed TSP can deal with route optimization with constraint of fixed ends effectively, and the algorithm for the path-constraint could benefit the traffic problems where some cities cannot be visited from each other.
Optimization Approaches for the Traveling Salesman Problem with Drone
Agatz, Niels; Bouman, Paul; Schmidt, Marie
2016-01-01
textabstractThe fast and cost-efficient home delivery of goods ordered online is logistically challenging. Many companies are looking for new ways to cross the last-mile to their customers. One technology-enabled opportunity that recently has received much at- tention is the use of a drone to support deliveries. An innovative last-mile delivery concept in which a truck collaborates with a drone to make deliveries gives rise to a new variant of the traveling salesman problem (TSP) that we call...
On the Min-cost Traveling Salesman Problem with Drone
Ha, Quang Minh; Deville, Yves; Pham, Quang Dung; Hà, Minh Hoàng
2015-01-01
Over the past few years, unmanned aerial vehicles (UAV), also known as drones, have been adopted as part of a new logistic method in the commercial sector called "last-mile delivery". In this novel approach, they are deployed alongside trucks to deliver goods to customers to improve the quality of service and reduce the transportation cost. This approach gives rise to a new variant of the traveling salesman problem (TSP), called TSP with drone (TSP-D). A variant of this problem that aims to m...
Branch-and-cut-and-price for the traveling salesman problem with time windows
Røpke, Stefan; Madsen, Oli B.G.
In the traveling salesman problem with time windows (TSPTW) one is given a depot and a set of nodes to be visited by a salesman. The salesman starts his trip at the depot and must visit all nodes while respecting time windows at the nodes. The objective of the problem is to minimize the total...... distance traveled by the salesman. The TSPTW is formulated as a set-partitioning problem which is solved by using combined cut and column generation. The pricing sub problem in the column generation procedure is a shortest path problem with time window constraints and 2-cycle elimination. A standard column...
Complexity indices for the travelling salesman problem and data mining
Dragos Cvetković
2012-03-01
Full Text Available In this survey paper we extend our previous work on complexity indices for the travelling salesman problem (TSP, summarized in cite{CvCK3}, using graph spectral techniques of data mining. A complexity index is an invariant of an instance $I$ by which we can predict the execution time of an exact algorithm for TSP for $I$. We consider the symmetric travelling salesman problem with instances $I$ represented by complete graphs $G$ with distances between vertices (cities as edge weights (lengths. Intuitively, the hardness of an instance $G$ depends on the distribution of short edges within $G$. Therefore we consider some short edge subgraphs of $G$ (minimal spanning tree, critical connected subgraph, and several others as non-weighted graphs and several their invariants as potential complexity indices. Here spectral invariants (e.g. spectral radius of the adjacency matrix play an important role since, in general, there are intimate relations between eigenvalues and the structure of a graph. Since hidden details of short edge subgraphs really determine the hardness of the instance, we use techniques of data mining to find them. In particular, spectral clustering algorithms are used including information obtained from the spectral gap in Laplacian spectra of short edge subgraphs.
Traveling Salesman Approach for Solving Petrol Distribution Using Simulated Annealing
Zuhaimy Ismail
2008-01-01
Full Text Available This research presents an attempt to solve a logistic company's problem of delivering petrol to petrol station in the state of Johor. This delivery system is formulated as a travelling salesman problem (TSP. TSP involves finding an optimal route for visiting stations and returning to point of origin, where the inter-station distance is symmetric and known. This real world application is a deceptive simple combinatorial problem and our approach is to develop solutions based on the idea of local search and meta-heuristics. As a standard problem, we have chosen a solution is a deceptively simple combinatorial problem and we defined it simply as the time spends or distance travelled by salesman visiting n cities (or nodes cyclically. In one tour the vehicle visits each station just once and finishes up where he started. As standard problems, we have chosen TSP with different stations visited once. This research presents the development of solution engine based on local search method known as Greedy Method and with the result generated as the initial solution, Simulated Annealing (SA and Tabu Search (TS further used to improve the search and provide the best solution. A user friendly optimization program developed using Microsoft C++ to solve the TSP and provides solutions to future TSP which may be classified into daily or advanced management and engineering problems.
The Traveling Salesman Problem Under Squared Euclidean Distances
de Berg, Mark; Sitters, René; Woeginger, Gerhard J; Wolff, Alexander
2010-01-01
Let $P$ be a set of points in $\\mathbb{R}^d$, and let $\\alpha \\ge 1$ be a real number. We define the distance between two points $p,q\\in P$ as $|pq|^{\\alpha}$, where $|pq|$ denotes the standard Euclidean distance between $p$ and $q$. We denote the traveling salesman problem under this distance function by TSP($d,\\alpha$). We design a 5-approximation algorithm for TSP(2,2) and generalize this result to obtain an approximation factor of $3^{\\alpha-1}+\\sqrt{6}^{\\alpha}/3$ for $d=2$ and all $\\alpha\\ge2$. We also study the variant Rev-TSP of the problem where the traveling salesman is allowed to revisit points. We present a polynomial-time approximation scheme for Rev-TSP$(2,\\alpha)$ with $\\alpha\\ge2$, and we show that Rev-TSP$(d, \\alpha)$ is APX-hard if $d\\ge3$ and $\\alpha>1$. The APX-hardness proof carries over to TSP$(d, \\alpha)$ for the same parameter ranges.
Assessing Different Crossover Operators for Travelling Salesman Problem
Imtiaz Hussain Khan
2015-10-01
Full Text Available Many crossover operators have been proposed in literature on evolutionary algorithms, however, it is still unclear which crossover operator works best for a given optimization problem. In this study, eight different crossover operators specially designed for travelling salesman problem, namely, Two-Point Crossover, Partially Mapped Crossover, Cycle Crossover, Shuffle Crossover, Edge Recombination Crossover, Uniform Order-based Crossover, Sub-tour Exchange Crossover, and Sequential Constructive Crossover are evaluated empirically. The select crossover operators were implemented to build an experimental setup upon which simulations were run. Four benchmark instances of travelling salesman problem, two symmetric (ST70 and TSP225 and two asymmetric (FTV100 and FTV170, were used to thoroughly assess the select crossover operators. The performance of these operators was analyzed in terms of solution quality and computational cost. It was found that Sequential Constructive Crossover outperformed other operators in attaining 'good' quality solution, whereas Two-Point Crossover outperformed other operators in terms of computational cost. It was also observed that the performance of different crossover operators is much better for relatively small number of cities, both in terms of solution quality and computational cost, however, for relatively large number of cities their performance greatly degrades
Simulated annealing with probabilistic analysis for solving traveling salesman problems
Hong, Pei-Yee; Lim, Yai-Fung; Ramli, Razamin; Khalid, Ruzelan
2013-09-01
Simulated Annealing (SA) is a widely used meta-heuristic that was inspired from the annealing process of recrystallization of metals. Therefore, the efficiency of SA is highly affected by the annealing schedule. As a result, in this paper, we presented an empirical work to provide a comparable annealing schedule to solve symmetric traveling salesman problems (TSP). Randomized complete block design is also used in this study. The results show that different parameters do affect the efficiency of SA and thus, we propose the best found annealing schedule based on the Post Hoc test. SA was tested on seven selected benchmarked problems of symmetric TSP with the proposed annealing schedule. The performance of SA was evaluated empirically alongside with benchmark solutions and simple analysis to validate the quality of solutions. Computational results show that the proposed annealing schedule provides a good quality of solution.
Hierarchical Approach in Clustering to Euclidean Traveling Salesman Problem
Fajar, Abdulah; Herman, Nanna Suryana; Abu, Nur Azman; Shahib, Sahrin
There has been growing interest in studying combinatorial optimization problems by clustering strategy, with a special emphasis on the traveling salesman problem (TSP). TSP naturally arises as a sub problem in much transportation, manufacturing and logistics application, this problem has caught much attention of mathematicians and computer scientists. A clustering approach will decompose TSP into sub graph and form cluster, so it may reduce problem size into smaller problem. Impact of hierarchical approach will be investigated to produce a better clustering strategy that fit into Euclidean TSP. Clustering strategy to Euclidean TSP consist of two main step, there are; clustering and tour construction. The significant of this research is clustering approach solution result has error less than 10% compare to best known solution (TSPLIB) and there is improvement to a hierarchical clustering algorithm in order to fit in such Euclidean TSP solution method.
Modified reactive tabu search for the symmetric traveling salesman problems
Lim, Yai-Fung; Hong, Pei-Yee; Ramli, Razamin; Khalid, Ruzelan
2013-09-01
Reactive tabu search (RTS) is an improved method of tabu search (TS) and it dynamically adjusts tabu list size based on how the search is performed. RTS can avoid disadvantage of TS which is in the parameter tuning in tabu list size. In this paper, we proposed a modified RTS approach for solving symmetric traveling salesman problems (TSP). The tabu list size of the proposed algorithm depends on the number of iterations when the solutions do not override the aspiration level to achieve a good balance between diversification and intensification. The proposed algorithm was tested on seven chosen benchmarked problems of symmetric TSP. The performance of the proposed algorithm is compared with that of the TS by using empirical testing, benchmark solution and simple probabilistic analysis in order to validate the quality of solution. The computational results and comparisons show that the proposed algorithm provides a better quality solution than that of the TS.
New Variations of Order Crossover for Travelling Salesman Problem
Kusum Deep
2011-01-01
Full Text Available Davis presented the order crossover operator for solving the travelling salesman problem (TSP using genetic algorithm and has described two basic variants of this order crossover operator. In order to improve the efficiency and validity of these variants, in this paper three new variations of the order crossover operator are presented. These are programmed in C++ and implemented on a set of benchmark test problems taken from TSPLIB.The analysis of results based on the numerical and graphical analysis indicated that the new variations of the order crossover proposed in this paper have a definite supremacy over the existing variants for TSP with number of cities less than or equal to 100 as well as greater than 100 for some instances.
Variant of partially mapped crossover for the Travelling Salesman problems
Kusum Deep
2012-01-01
Full Text Available In this paper a variant of partially mapped crossover (VPMX is designed using cut point positions and is tested for its performance with the existing partially mapped crossover (PMX.In order to test the performance ,two mutation operators are used. These mutation operators are inverted displacement and inversion mutations. Partially mapped crossover (PMX with inversion and with inverted displacement and a variant of partially mapped crossover (VPMX with inversion and with inverted displacement are programmed in C++ and implemented on a set of ten benchmark problems taken from the Travelling salesman problem library (TSPLIB. The results indicate that the designed variant of PMX is superior by showing a better performance in eight instances in combination with the inverted displacement mutation. In two instances PMX has obtained a better result. One is PMX with inversion mutation and the other is PMX with inverted displacement mutation.
Phase Transitions and Backbones of the Asymmetric Traveling Salesman Problem
Zhang, W
2011-01-01
In recent years, there has been much interest in phase transitions of combinatorial problems. Phase transitions have been successfully used to analyze combinatorial optimization problems, characterize their typical-case features and locate the hardest problem instances. In this paper, we study phase transitions of the asymmetric Traveling Salesman Problem (ATSP), an NP-hard combinatorial optimization problem that has many real-world applications. Using random instances of up to 1,500 cities in which intercity distances are uniformly distributed, we empirically show that many properties of the problem, including the optimal tour cost and backbone size, experience sharp transitions as the precision of intercity distances increases across a critical value. Our experimental results on the costs of the ATSP tours and assignment problem agree with the theoretical result that the asymptotic cost of assignment problem is pi ^2 /6 the number of cities goes to infinity. In addition, we show that the average computation...
Solving large scale traveling salesman problems by chaotic neurodynamics.
Hasegawa, Mikio; Ikeguch, Tohru; Aihara, Kazuyuki
2002-03-01
We propose a novel approach for solving large scale traveling salesman problems (TSPs) by chaotic dynamics. First, we realize the tabu search on a neural network, by utilizing the refractory effects as the tabu effects. Then, we extend it to a chaotic neural network version. We propose two types of chaotic searching methods, which are based on two different tabu searches. While the first one requires neurons of the order of n2 for an n-city TSP, the second one requires only n neurons. Moreover, an automatic parameter tuning method of our chaotic neural network is presented for easy application to various problems. Last, we show that our method with n neurons is applicable to large TSPs such as an 85,900-city problem and exhibits better performance than the conventional stochastic searches and the tabu searches.
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.
Introducing convex layers to the Traveling Salesman Problem
Liew, Sing
2012-01-01
In this paper, we will propose convex layers to the Traveling Salesman Problem (TSP). Firstly, we will focus on human performance on the TSP. Experimental data shows that untrained humans appear to have the ability to perform well in the TSP. On the other hand, experimental data also supports the hypothesis of convex hull i.e. human relies on convex hull to search for the optimal tour for the TSP. Secondly, from the paper published by Bonabeau, Dorigo and Theraulaz, social insect behavior would be able to help in some of the optimizing problems, especially the TSP. Thus, we propose convex layers to the TSP based on the argument that, by the analogy to the social insect behavior, untrained humans' cognition should be able to help in the TSP. Lastly, we will use Tour Improvement algorithms on convex layers to search for an optimal tour for a 13-cities problem to demonstrate the idea.
Alternative Method for Solving Traveling Salesman Problem by Evolutionary Algorithm
Zuzana Čičková
2008-06-01
Full Text Available This article describes the application of Self Organizing Migrating Algorithm (SOMA to the well-known optimization problem - Traveling Salesman Problem (TSP. SOMA is a relatively new optimization method that is based on Evolutionary Algorithms that are originally focused on solving non-linear programming problems that contain continuous variables. The TSP has model character in many branches of Operation Research because of its computational complexity; therefore the use of Evolutionary Algorithm requires some special approaches to guarantee feasibility of solutions. In this article two concrete examples of TSP as 8 cities set and 25 cities set are given to demonstrate the practical use of SOMA. Firstly, the penalty approach is applied as a simple way to guarantee feasibility of solution. Then, new approach that works only on feasible solutions is presented.
A Multi-Agent Approach for Solving Traveling Salesman Problem
ZHOU Tiejun; TAN Yihong; XING Lining
2006-01-01
The traveling salesman problem (TSP) is a classical optimization problem and it is one of a class of NP-Problem. This paper presents a new method named multi-agent approach based genetic algorithm and ant colony system to solve the TSP. Three kinds of agents with different function were designed in the multi-agent architecture proposed by this paper. The first kind of agent is ant colony optimization agent and its function is generating the new solution continuously. The second kind of agent is selection agent, crossover agent and mutation agent, their function is optimizing the current solutions group. The third kind of agent is fast local searching agent and its function is optimizing the best solution from the beginning of the trial. At the end of this paper, the experimental results have shown that the proposed hybrid approach has good performance with respect to the quality of solution and the speed of computation.
Using 2-Opt based evolution strategy for travelling salesman problem
Kenan Karagul
2016-03-01
Full Text Available Harmony search algorithm that matches the (µ+1 evolution strategy, is a heuristic method simulated by the process of music improvisation. In this paper, a harmony search algorithm is directly used for the travelling salesman problem. Instead of conventional selection operators such as roulette wheel, the transformation of real number values of harmony search algorithm to order index of vertex representation and improvement of solutions are obtained by using the 2-Opt local search algorithm. Then, the obtained algorithm is tested on two different parameter groups of TSPLIB. The proposed method is compared with classical 2-Opt which randomly started at each step and best known solutions of test instances from TSPLIB. It is seen that the proposed algorithm offers valuable solutions.
Implementation of Travelling Salesman Problem Using ant Colony Optimization
Gaurav Singh,
2014-04-01
Full Text Available Within the Artificial Intelligence community, there is great need for fast and accurate traversal algorithms, specifically those that find a path from a start to goal with minimum cost. Cost can be distance, time, money, energy, etc. Travelling salesman problem (TSP is a combinatorial optimization problem. TSP is the most intensively studied problem in the area of optimization. Ant colony optimization (ACO is a population-based metaheuristic that can be used to find approximate solutions to difficult optimization problems. There have been many efforts in the past to provide time efficient solutions for the problem, both exact and approximate. This paper demonstrates the implementation of TSP using ant colony optimization(ACO.The solution to this problem enjoys wide applicability in a variety of practical fields.TSP in its purest form has several applications such as planning, logistics, and manufacture of microchips, military and traffic.
Helsgaun, Keld
2015-01-01
The equality generalized traveling salesman problem (E-GTSP) is an extension of the traveling salesman problem (TSP) where the set of cities is partitioned into clusters, and the salesman has to visit every cluster exactly once. It is well known that any instance of E-GTSP can be transformed...... instances in a well-known library of benchmark instances, GTSPLIB, could be solved to optimality in a reasonable time. In addition, it was possible to solve a series of new very-large-scale instances with up to 17,180 clusters and 85,900 vertices. Optima for these instances are not known...
In Pursuit of the Traveling Salesman Mathematics at the Limits of Computation
Cook, William J
2011-01-01
What is the shortest possible route for a traveling salesman seeking to visit each city on a list exactly once and return to his city of origin? It sounds simple enough, yet the traveling salesman problem is one of the most intensely studied puzzles in applied mathematics--and it has defied solution to this day. In this book, William Cook takes readers on a mathematical excursion, picking up the salesman's trail in the 1800s when Irish mathematician W. R. Hamilton first defined the problem, and venturing to the furthest limits of today's state-of-the-art attempts to solve it. Cook examines
Combination of Chaotic Neurodynamics with the 2-opt Algorithm to Solve Traveling Salesman Problems
Hasegawa, M.; Ikeguchi, T.; Aihara, K.
1997-09-01
We propose a novel approach for combinatorial optimization problems. For solving the traveling salesman problems, we combine chaotic neurodynamics with heuristic algorithm. We select the heuristic algorithm of 2-opt as a basic part, because it is well understood that this simple algorithm is very effective for the traveling salesman problems. Although the conventional approaches with chaotic neurodynamics were only applied to such very small problems as 10 cities, our method exhibits higher performance for larger size problems with the order of 102.
Branch-and-cut-and-price for the traveling salesman problem with time windows
Røpke, Stefan; Madsen, Oli B.G.
In the traveling salesman problem with time windows (TSPTW) one is given a depot and a set of nodes to be visited by a salesman. The salesman starts his trip at the depot and must visit all nodes while respecting time windows at the nodes. The objective of the problem is to minimize the total...... distance traveled by the salesman. The TSPTW is formulated as a set-partitioning problem which is solved by using combined cut and column generation. The pricing sub problem in the column generation procedure is a shortest path problem with time window constraints and 2-cycle elimination. A standard column...... generation process converges slowly for the problem and therefore a stabilization procedure is implemented. Valid inequalities expressed in the original, arc-based variables are added to the LP relaxation to strengthen the lower bound. The proposed algorithm is compared to exact algorithms based on other...
Solving the Traveling Salesman's Problem Using the African Buffalo Optimization
Odili, Julius Beneoluchi; Mohmad Kahar, Mohd Nizam
2016-01-01
This paper proposes the African Buffalo Optimization (ABO) which is a new metaheuristic algorithm that is derived from careful observation of the African buffalos, a species of wild cows, in the African forests and savannahs. This animal displays uncommon intelligence, strategic organizational skills, and exceptional navigational ingenuity in its traversal of the African landscape in search for food. The African Buffalo Optimization builds a mathematical model from the behavior of this animal and uses the model to solve 33 benchmark symmetric Traveling Salesman's Problem and six difficult asymmetric instances from the TSPLIB. This study shows that buffalos are able to ensure excellent exploration and exploitation of the search space through regular communication, cooperation, and good memory of its previous personal exploits as well as tapping from the herd's collective exploits. The results obtained by using the ABO to solve these TSP cases were benchmarked against the results obtained by using other popular algorithms. The results obtained using the African Buffalo Optimization algorithm are very competitive. PMID:26880872
An Analysis of the Fitness Landscape of Travelling Salesman Problem.
Tayarani-N, Mohammad-H; Prügel-Bennett, Adam
2016-01-01
The fitness landscape of the travelling salesman problem is investigated for 11 different types of the problem. The types differ in how the distances between cities are generated. Many different properties of the landscape are studied. The properties chosen are all potentially relevant to choosing an appropriate search algorithm. The analysis includes a scaling study of the time to reach a local optimum, the number of local optima, the expected probability of reaching a local optimum as a function of its fitness, the expected fitness found by local search and the best fitness, the probability of reaching a global optimum, the distance between the local optima and the global optimum, the expected fitness as a function of the distance from an optimum, their basins of attraction and a principal component analysis of the local optima. The principal component analysis shows the correlation of the local optima in the component space. We show how the properties of the principal components of the local optima change from one problem type to another.
The traveling salesman problem on cubic and subcubic graphs
Boyd, Sylvia; van der Ster, Suzanne; Stougie, Leen
2011-01-01
We study the Travelling Salesman Problem (TSP) on the metric completion of cubic and subcubic graphs, which is known to be NP-hard. The problem is of interest because of its relation to the famous 4/3 conjecture for metric TSP, which says that the integrality gap, i.e., the worst case ratio between the optimal values of the TSP and its linear programming relaxation (the subtour elimination relaxation), is 4/3. We present the first algorithm for cubic graphs with approximation ratio 4/3. The proof uses polyhedral techniques in a surprising way, which is of independent interest. In fact we prove constructively that for any cubic graph on $n$ vertices a tour of length 4n/3-2 exists, which also implies the 4/3 conjecture, as an upper bound, for this class of graph-TSP. Recently, M\\"omke and Svensson presented a randomized algorithm that gives a 1.461-approximation for graph-TSP on general graphs and as a side result a 4/3-approximation algorithm for this problem on subcubic graphs, also settling the 4/3 conjectur...
PERANCANGAN APLIKASI PENJADWALAN TRAVELING SALESMAN PROBLEM DENGAN ALGORITMA GENETIKA
Hendy Tannady
2012-11-01
Full Text Available Supply chain management plays an important role in enhancing the efficiency and effectiveness of manufacturing industry business process. In this research, the problem is taken from a sales division in a company in determining the optimal sequence when delivering goods into nine cities. This problem is often referred as travelling salesman problem. This problem is considered important since the optimal sequence can cut off operational cost. Creating an artificial intelligence for the company in determining the location and the optimal sequence of delivering goods is the main objective of this research. A genetic algorithm is utilized to determine the location and the optimal sequence. While for processing the data and concluding the result, researcher designed a Java-based application that provides the capability of automatic computing. The result of this computation is a sequence of locations with a fitness number for each. The best fitness number for the sequence location will be used for the final result and the conclusion to answer the companys problem.
Producer-Scrounger Method to Solve Traveling Salesman Problem
M. A. H. Akhand
2015-02-01
Full Text Available Algorithms inspired from natural phenomena are seem to be efficient to solve various optimization problems. This paper investigates a new technique inspiring from the animal group living behavior to solve traveling salesman problem (TSP, the most popular combinatorial optimization problem. The proposed producer-scrounger method (PSM models roles and interactions of three types of animal group members: producer, scrounger and dispersed. PSM considers a producer having the best tour, few dispersed members having worse tours and scroungers. In each iteration, the producer scans for better tour, scroungers explore new tours while moving toward producer‘s tour; and dispersed members randomly checks new tours. For producer‘s scanning, PSM randomly selects a city from the producer‘s tour and rearranges its connection with several near cities for better tours. Swap operator and swap sequence based operation is employed in PSM to update a scrounger towards the producer. The proposed PSM has been tested on a large number of benchmark TSPs and outcomes compared to genetic algorithm and ant colony optimization. Experimental results revealed that proposed PSM is a good technique to solve TSP providing the best tours in most of the TSPs.
Solving the Traveling Salesman's Problem Using the African Buffalo Optimization.
Odili, Julius Beneoluchi; Mohmad Kahar, Mohd Nizam
2016-01-01
This paper proposes the African Buffalo Optimization (ABO) which is a new metaheuristic algorithm that is derived from careful observation of the African buffalos, a species of wild cows, in the African forests and savannahs. This animal displays uncommon intelligence, strategic organizational skills, and exceptional navigational ingenuity in its traversal of the African landscape in search for food. The African Buffalo Optimization builds a mathematical model from the behavior of this animal and uses the model to solve 33 benchmark symmetric Traveling Salesman's Problem and six difficult asymmetric instances from the TSPLIB. This study shows that buffalos are able to ensure excellent exploration and exploitation of the search space through regular communication, cooperation, and good memory of its previous personal exploits as well as tapping from the herd's collective exploits. The results obtained by using the ABO to solve these TSP cases were benchmarked against the results obtained by using other popular algorithms. The results obtained using the African Buffalo Optimization algorithm are very competitive.
Fast marching methods for the continuous traveling salesman problem
Andrews, J.; Sethian, J.A.
2008-12-01
We consider a problem in which we are given a domain, a cost function which depends on position at each point in the domain, and a subset of points ('cities') in the domain. The goal is to determine the cheapest closed path that visits each city in the domain once. This can be thought of as a version of the Traveling Salesman Problem, in which an underlying known metric determines the cost of moving through each point of the domain, but in which the actual shortest path between cities is unknown at the outset. We describe algorithms for both a heuristic and an optimal solution to this problem. The order of the heuristic algorithm is at worst case M * N logN, where M is the number of cities, and N the size of the computational mesh used to approximate the solutions to the shortest paths problems. The average runtime of the heuristic algorithm is linear in the number of cities and O(N log N) in the size N of the mesh.
Sequential and parallel local search for the time-constrained travelling salesman problem
G.A.P. Kindervater (Gerard); J.K. Lenstra; M.W.P. Savelsbergh (Martin)
1990-01-01
textabstractLocal search has proven to be an effective solution approach for the traveling salesman problem. We consider variants of the TSP in which each city is to be visited within one or more given time windows. The travel times are symmetric and satisfy the triangle inequality; therobjective is
Stability of Solutions to Classes of Traveling Salesman Problems.
Niendorf, Moritz; Kabamba, Pierre T; Girard, Anouck R
2016-04-01
By performing stability analysis on an optimal tour for problems belonging to classes of the traveling salesman problem (TSP), this paper derives margins of optimality for a solution with respect to disturbances in the problem data. Specifically, we consider the asymmetric sequence-dependent TSP, where the sequence dependence is driven by the dynamics of a stack. This is a generalization of the symmetric non sequence-dependent version of the TSP. Furthermore, we also consider the symmetric sequence-dependent variant and the asymmetric non sequence-dependent variant. Amongst others these problems have applications in logistics and unmanned aircraft mission planning. Changing external conditions such as traffic or weather may alter task costs, which can render an initially optimal itinerary suboptimal. Instead of optimizing the itinerary every time task costs change, stability criteria allow for fast evaluation of whether itineraries remain optimal. This paper develops a method to compute stability regions for the best tour in a set of tours for the symmetric TSP and extends the results to the asymmetric problem as well as their sequence-dependent counterparts. As the TSP is NP-hard, heuristic methods are frequently used to solve it. The presented approach is also applicable to analyze stability regions for a tour obtained through application of the k -opt heuristic with respect to the k -neighborhood. A dimensionless criticality metric for edges is proposed, such that a high criticality of an edge indicates that the optimal tour is more susceptible to cost changes in that edge. Multiple examples demonstrate the application of the developed stability computation method as well as the edge criticality measure that facilitates an intuitive assessment of instances of the TSP.
Graph traversals, genes, and matroids: An efficient case of the travelling salesman problem
Gusfield, D.; Stelling, P.; Wang, Lusheng [Univ. of California, Davis, CA (United States); Karp, R. [Univ. of Washington, Seattle, WA (United States)
1996-12-31
In this paper the authors consider graph traversal problems that arise from a particular technology for DNA sequencing - sequencing by hybridization (SBH). They first explain the connection of the graph problems to SBH and then focus on the traversal problems. They describe a practical polynomial time solution to the Travelling Salesman Problem in a rich class of directed graphs (including edge weighted binary de Bruijn graphs), and provide a bounded-error approximation algorithm for the maximum weight TSP in a superset of those directed graphs. The authors also establish the existence of a matroid structure defined on the set of Euler and Hamilton paths in the restricted class of graphs. 8 refs., 5 figs.
Compact Formulations of the Steiner Traveling Salesman Problem and Related Problems
Letchford, Adam N; Theis, Dirk Oliver
2012-01-01
The Steiner Traveling Salesman Problem (STSP) is a variant of the Traveling Salesman Problem (TSP) that is particularly suitable when dealing with sparse networks, such as road networks. The standard integer programming formulation of the STSP has an exponential number of constraints, just like the standard formulation of the TSP. On the other hand, there exist several known {\\em compact} formulations of the TSP, i.e., formulations with a polynomial number of both variables and constraints. In this paper, we show that some of these compact formulations can be adapted to the STSP. We also briefly discuss the adaptation of our formulations to some closely-related problems.
The Random Link Approximation for the Euclidean Traveling Salesman Problem
Cerf, N. J.; Boutet de Monvel, J.; Bohigas, O.; Martin, O. C.; Percus, A. G.
1997-01-01
The traveling salesman problem (TSP) consists of finding the length of the shortest closed tour visiting N “cities”. We consider the Euclidean TSP where the cities are distributed randomly and independently in a d-dimensional unit hypercube. Working with periodic boundary conditions and inspired by a remarkable universality in the kth nearest neighbor distribution, we find for the average optimum tour length voyageur de commerce (TSP) consiste à trouver le chemin fermé le plus court qui relie N “villes”. Nous étudions le TSP euclidien où les villes sont distribuées au hasard de manière décorrélée dans l'hypercube de côté 1, en dimension d. En imposant des conditions aux bords périodiques et guidés par une universalité remarquable de la distribution des kièmes voisins, nous trouvons la longueur moyenne du chemin optimal <~ngle L_Erangle = β_E(d)N^{1-1/d}[1+O(1/N)] , avec β_E= 0,7120 ± 0,0002 et β_E(3)= 0,6979 ± 0,0002. Nous établissons ensuite des prédictions analytiques sur ces quantités à l'aide de l'approximation de liens aléatoires, où les longueurs entre les villes sont des variables aléatoires indépendantes. Grâce aux équations “cavité” développées par Krauth, Mézard et Parisi, nous obtenons dans le cas de liens aléatoires les valeurs, β_RL(d), analogues à β_E(d). Pour d= 1, 2, 3, les résultats numériques confirment que l'approximation de liens aléatoires est bonne, conduisant à un écart inférieur à 2,1% entre β_E(d) et β_RL(d). Pour d grand, nous donnons des arguments montrant que cette approximation est exacte jusqu'à l'ordre 1/d^2 et nous proposons une conjecture pour β_E(d), exprimée en fonction d'une série en 1/d, dont on donne les deux premiers ordres.
On the Symbolic Theme of Death of a Travelling Salesman
肖莉; 袁继红
2012-01-01
The death of the salesman is a masterpiece of Arthur Miller. This thesis simply analyzes the tragedy. What have been discussed in the thesis implies that the author uses the tactics of symbolism to describe a vivid picture of our futile struggle. It also suggests that life means choice.
Mak, Vicky; Thomadsen, Tommy
2004-01-01
A well-known extension of the Travelling Salesman Problem (TSP) is the Selective (or Prize-collecting) TSP: In addition to the edge-costs, each node has an associated reward (denoted the node-reward) and instead of visiting all nodes, only profitable nodes are visited. The Quadratic Selective TSP...
How to make a greedy heuristic for the asymmetric traveling salesman problem competitive
Goldengorin, B.; Jäger, G.
2005-01-01
It is widely confirmed by many computational experiments that a greedy type heuristics for the Traveling Salesman Problem (TSP) produces rather poor solutions except for the Euclidean TSP. The selection of arcs to be included by a greedy heuristic is usually done on the base of cost values. We
Hemert, J.I. van; Urquhart, N.B.
2004-01-01
This paper introduces a generator that creates problem instances for the Euclidean symmetric travelling salesman problem. To fit real world problems, we look at maps consisting of clustered nodes. Uniform random sampling methods do not result in maps where the nodes are spread out to form identifiab
Human Performance on the Traveling Salesman and Related Problems: A Review
MacGregor, James N.; Chu, Yun
2011-01-01
The article provides a review of recent research on human performance on the traveling salesman problem (TSP) and related combinatorial optimization problems. We discuss what combinatorial optimization problems are, why they are important, and why they may be of interest to cognitive scientists. We next describe the main characteristics of human…
On the Equivalence between some Local and Global Chinese Postman and Traveling Salesman Graphs
Granot, D.; Hamers, H.J.M.
2000-01-01
A connected graph G=(V,E), a vertex in V and a non-negative weight function defined on Ecan be used to induce Chinese postman and traveling salesman (cooperative) games. A graph G=(V,E) is said to be locally (respectively, globally) Chinese postman balanced (respectively, totally balanced, submodula
A return to the traveling salesman model: a network branch and bound approach
Elias Munapo
2013-02-01
Full Text Available This paper presents a network branch and bound approach for solving the traveling salesman problem. The problem is broken into sub-problems, each of which is solved as a minimum spanning tree model. This is easier to solve than either the linear programming-based or assignment models.
Chemotaxis can provide biological organisms with good solutions to the travelling salesman problem
Reynolds, A. M.
2011-05-01
The ability to find good solutions to the traveling salesman problem can benefit some biological organisms. Bacterial infection would, for instance, be eradicated most promptly if cells of the immune system minimized the total distance they traveled when moving between bacteria. Similarly, foragers would maximize their net energy gain if the distance that they traveled between multiple dispersed prey items was minimized. The traveling salesman problem is one of the most intensively studied problems in combinatorial optimization. There are no efficient algorithms for even solving the problem approximately (within a guaranteed constant factor from the optimum) because the problem is nondeterministic polynomial time complete. The best approximate algorithms can typically find solutions within 1%-2% of the optimal, but these are computationally intensive and can not be implemented by biological organisms. Biological organisms could, in principle, implement the less efficient greedy nearest-neighbor algorithm, i.e., always move to the nearest surviving target. Implementation of this strategy does, however, require quite sophisticated cognitive abilities and prior knowledge of the target locations. Here, with the aid of numerical simulations, it is shown that biological organisms can simply use chemotaxis to solve, or at worst provide good solutions (comparable to those found by the greedy algorithm) to, the traveling salesman problem when the targets are sources of a chemoattractant and are modest in number (n < 10). This applies to neutrophils and macrophages in microbial defense and to some predators.
Mladenović Nenad
2013-01-01
Full Text Available General Variable Neighborhood Search (GVNS is shown to be a powerful and robust methodology for solving travelling salesman and vehicle routing problems. However, its efficient implementation may play a significant role in solving large size instances. In this paper we suggest new GVNS heuristic for solving Travelling salesman problem with time windows. It uses different set of neighborhoods, new feasibility checking procedure and a more efficient data structure than the recent GVNS method that can be considered as a state-of-the-art heuristic. As a result, our GVNS is much faster and more effective than the previous GVNS. It is able to improve 14 out of 25 best known solutions for large test instances from the literature.
An analogue approach to the travelling salesman problem using an elastic net method.
Durbin, R; Willshaw, D
The travelling salesman problem is a classical problem in the field of combinatorial optimization, concerned with efficient methods for maximizing or minimizing a function of many independent variables. Given the positions of N cities, which in the simplest case lie in the plane, what is the shortest closed tour in which each city can be visited once? We describe how a parallel analogue algorithm, derived from a formal model for the establishment of topographically ordered projections in the brain, can be applied to the travelling salesman problem. Using an iterative procedure, a circular closed path is gradually elongated non-uniformly until it eventually passes sufficiently near to all the cities to define a tour. This produces shorter tour lengths than another recent parallel analogue algorithm, scales well with the size of the problem, and is naturally extendable to a large class of optimization problems involving topographic mappings between geometrical structures.
Bruno Avila Leal de Meirelles Herrera
2015-12-01
Full Text Available ABSTRACT The Traveling Salesman Problem (TSP is one of the most well-known and studied problems of Operations Research field, more specifically, in the Combinatorial Optimization field. As the TSP is a NP (Non-Deterministic Polynomial time-hard problem, there are several heuristic methods which have been proposed for the past decades in the attempt to solve it the best possible way. The aim of this work is to introduce and to evaluate the performance of some approaches for achieving optimal solution considering some symmetrical and asymmetrical TSP instances, which were taken from the Traveling Salesman Problem Library (TSPLIB. The analyzed approaches were divided into three methods: (i Lin-Kernighan-Helsgaun (LKH algorithm; (ii LKH with initial tour based on uniform distribution; and (iii an hybrid proposal combining Particle Swarm Optimization (PSO with quantum inspired behavior and LKH for local search procedure. The tested algorithms presented promising results in terms of computational cost and solution quality.
Khalid. W. Magld
2012-07-01
Full Text Available The Traveling salesman problem (TSP is to find a tour of a given number of cities (visiting each city exactly once where the length of this tour is minimized. Testing every possibility for an N city tour would be N! Math additions. Genetic algorithms (GA and Memetic algorithms (MA are a relatively new optimization technique which can be applied to various problems, including those that are NPhard. The technique does not ensure an optimal solution, however it usually gives good approximations in a reasonable amount of time. They, therefore, would be good algorithms to try on the traveling salesman problem, one of the most famous NP-hard problems. In this paper I have proposed a algorithm to solve TSP using Genetic algorithms (GA and Memetic algorithms (MA with the crossover operator Edge Assembly Crossover (EAX and also analyzed the result on different parameter like group size and mutation percentage and compared the result with other solutions.
A 3/2-Approximation Algorithm for Multiple Depot Multiple Traveling Salesman Problem
Xu, Zhou; Rodrigues, Brian
As an important extension of the classical traveling salesman problem (TSP), the multiple depot multiple traveling salesman problem (MDMTSP) is to minimize the total length of a collection of tours for multiple vehicles to serve all the customers, where each vehicle must start or stay at its distinct depot. Due to the gap between the existing best approximation ratios for the TSP and for the MDMTSP in literature, which are 3/2 and 2, respectively, it is an open question whether or not a 3/2-approximation algorithm exists for the MDMTSP. We have partially addressed this question by developing a 3/2-approximation algorithm, which runs in polynomial time when the number of depots is a constant.
Solving a four-destination traveling salesman problem using Escherichia coli cells as biocomputers.
Esau, Michael; Rozema, Mark; Zhang, Tuo Huang; Zeng, Dawson; Chiu, Stephanie; Kwan, Rachel; Moorhouse, Cadence; Murray, Cameron; Tseng, Nien-Tsu; Ridgway, Doug; Sauvageau, Dominic; Ellison, Michael
2014-12-19
The Traveling Salesman Problem involves finding the shortest possible route visiting all destinations on a map only once before returning to the point of origin. The present study demonstrates a strategy for solving Traveling Salesman Problems using modified E. coli cells as processors for massively parallel computing. Sequential, combinatorial DNA assembly was used to generate routes, in the form of plasmids made up of marker genes, each representing a path between destinations, and short connecting linkers, each representing a given destination. Upon growth of the population of modified E. coli, phenotypic selection was used to eliminate invalid routes, and statistical analysis was performed to successfully identify the optimal solution. The strategy was successfully employed to solve a four-destination test problem.
Elitist Ant System with 2-opt Local Search for the Traveling Salesman Problem
MARTINOVIC, G.
2012-02-01
Full Text Available The Traveling Salesman Problem is one of the most famous problems in combinatorial optimization. The paper presents an algorithm based upon the elitist ant system for solving the traveling salesman problem. 2-opt local search is incorporated in the elitist ant system, and it is used for improvement of a given number of solutions previously constructed by artificial ants. A simple mechanism for avoiding a too early stagnation of the search is also proposed. The aforementioned is based on depositing strong pheromones on solution edges of randomly selected ants called random elitist ants. The aim is to encourage exploration in a greater area of the solution space. Experimental analysis shows how high-quality solutions can be achieved by using the considered algorithm instead of the usual elitist ant system with incorporated 2-opt local search.
On the stability of the Travelling Salesman Problem algorithm of Hopfield and Tank.
Wilson, G V; Pawley, G S
1988-01-01
The application of the method of Hopfield and Tank to the Travelling Salesman Problem (1985) has been re-examined in an effort to find a procedure for scaling to system sizes of real interest. As this failed, methods were tried to improve the algorithm, recognizing the importance of a "silicon implementation". No satisfactory refinement was found, and the reasons for algorithm failure have been identified.
An efficient approach to the travelling salesman problem using self-organizing maps.
Vieira, Frederico Carvalho; Dória Neto, Adrião Duarte; Costa, José Alfredo Ferreira
2003-04-01
This paper presents an approach to the well-known Travelling Salesman Problem (TSP) using Self-Organizing Maps (SOM). The SOM algorithm has interesting topological information about its neurons configuration on cartesian space, which can be used to solve optimization problems. Aspects of initialization, parameters adaptation, and complexity analysis of the proposed SOM based algorithm are discussed. The results show an average deviation of 3.7% from the optimal tour length for a set of 12 TSP instances.
An argument for abandoning the travelling salesman problem as a neural-network benchmark.
Smith, K
1996-01-01
In this paper, a distinction is drawn between research which assesses the suitability of the Hopfield network for solving the travelling salesman problem (TSP) and research which attempts to determine the effectiveness of the Hopfield network as an optimization technique. It is argued that the TSP is generally misused as a benchmark for the latter goal, with the existence of an alternative linear formulation giving rise to unreasonable comparisons.
Petersen, Hanne Løhmann; Madsen, Oli B.G.
2009-01-01
This paper introduces the double travelling salesman problem with multiple stacks and presents four different metaheuristic approaches to its solution. The double TSP with multiple stacks is concerned with determining the shortest route performing pickups and deliveries in two separated networks...... different neighbourhood structures are developed for the problem and used with each of three local search metaheuristics. Additionally some simpler removal and reinsertion operators are used in a Large neighbourhood search framework. Finally some computational results are given along with lower bounds...
The Voronoi Diagram for the Euclidean Traveling Salesman Problem Is Piecemeal Quartic and Hyperbolic
1990-06-01
ceiling function is of cubic order as predicted by the analysis. Acknowledgments The research has greatly benefited from discussions with Gerald ...The Science of Computing. Exploring tole Nature and Power of Algorithms. Addison-Wesley. Reading MA. � 1989 [H21 Held, M . and R M Karp , "The...34Traveling salesman cycles are not always subgrapris of Voronoi duals", Information Processing .etters 16(l):11-12. January 1983. (K21 Karp , R.M
Liew, Sing
2012-01-01
The author would like to propose a simple but yet effective method, convex layers, nearest neighbor and triangle inequality, to approach the Traveling Salesman Problem (TSP). No computer is needed in this method. This method is designed for plain folks who faced the TSP everyday but do not have the sophisticated knowledge of computer science, programming language or applied mathematics. The author also hopes that it would give some insights to researchers who are interested in the TSP.
Ant-cycle based on Metropolis rules for the traveling salesman problem
Gong Qu; He Xian-yang
2005-01-01
In this paper, recent developments of some heuristic algorithms were discussed. The focus was laid on the improvements of ant-cycle (AC) algorithm based on the analysis of the performances of simulated annealing (SA) and AC for the traveling salesman problem (TSP). The Metropolis rules in SA were applied to AC and turned out an improved AC. The computational results obtained from the case study indicated that the improved AC algorithm has advantages over the sheer SA or unmixed AC.
Solving the Traveling Salesman Problem Using New Operators in Genetic Algorithms
Naef T. Al Rahedi; Jalal Atoum
2009-01-01
Problem statement: Genetic Algorithms (GAs) have been used as search algorithms to find near-optimal solutions for many NP problems. GAs require effective chromosome representations as well as carefully designed crossover and mutation operators to achieve an efficient search. The Traveling Salesman Problem (TSP), as an NP search problem, involves finding the shortest Hamiltonian Path or Cycle in a graph of N cities. The main objective of this study was to propose a new representation method o...
A neural-network-based approach to the double traveling salesman problem.
Plebe, Alessio; Anile, Angelo Marcello
2002-02-01
The double traveling salesman problem is a variation of the basic traveling salesman problem where targets can be reached by two salespersons operating in parallel. The real problem addressed by this work concerns the optimization of the harvest sequence for the two independent arms of a fruit-harvesting robot. This application poses further constraints, like a collision-avoidance function. The proposed solution is based on a self-organizing map structure, initialized with as many artificial neurons as the number of targets to be reached. One of the key components of the process is the combination of competitive relaxation with a mechanism for deleting and creating artificial neurons. Moreover, in the competitive relaxation process, information about the trajectory connecting the neurons is combined with the distance of neurons from the target. This strategy prevents tangles in the trajectory and collisions between the two tours. Results of tests indicate that the proposed approach is efficient and reliable for harvest sequence planning. Moreover, the enhancements added to the pure self-organizing map concept are of wider importance, as proved by a traveling salesman problem version of the program, simplified from the double version for comparison.
The A-priori Traveling Salesman Problem with Time Windows
Larsen, Allan; Madsen, Oli B.G.; Solomon, Marius M.
2004-01-01
In this paper we examine the traveling saleman problem with time windows for various degrees of dynamism. In contrast to the static problem, where the dispatcher can plan ahead, in the dynamic version, part or all of the necessary information becomes available only during the day of operation. We...... seek to minimize lateness and examine the impact of this criterion choice on the distance traveled. Our focus on lateness is motivated by the problem faced by overnight mail service providers. We propose a real-time solution method that requires the vehicle, when idle, to wait at the current customer...... the least extra distance to be traveled among the relocation policies....
The A-priori Traveling Salesman Problem with Time Windows
Larsen, Allan; Madsen, Oli B.G.; Solomon, Marius M.
2004-01-01
In this paper we examine the traveling saleman problem with time windows for various degrees of dynamism. In contrast to the static problem, where the dispatcher can plan ahead, in the dynamic version, part or all of the necessary information becomes available only during the day of operation. We...
Double evolutsional artificial bee colony algorithm for multiple traveling salesman problem
Xue Ming Hao
2016-01-01
Full Text Available The double evolutional artificial bee colony algorithm (DEABC is proposed for solving the single depot multiple traveling salesman problem (MTSP. The proposed DEABC algorithm, which takes advantage of the strength of the upgraded operators, is characterized by its guidance in exploitation search and diversity in exploration search. The double evolutional process for exploitation search is composed of two phases of half stochastic optimal search, and the diversity generating operator for exploration search is used for solutions which cannot be improved after limited times. The computational results demonstrated the superiority of our algorithm over previous state-of-the-art methods.
Ant Colony Optimization with Memory and Its Application to Traveling Salesman Problem
Wang, Rong-Long; Zhao, Li-Qing; Zhou, Xiao-Fan
Ant Colony Optimization (ACO) is one of the most recent techniques for solving combinatorial optimization problems, and has been unexpectedly successful. Therefore, many improvements have been proposed to improve the performance of the ACO algorithm. In this paper an ant colony optimization with memory is proposed, which is applied to the classical traveling salesman problem (TSP). In the proposed algorithm, each ant searches the solution not only according to the pheromone and heuristic information but also based on the memory which is from the solution of the last iteration. A large number of simulation runs are performed, and simulation results illustrate that the proposed algorithm performs better than the compared algorithms.
Exact Solutions to the Double Travelling Salesman Problem with Multiple Stacks
Petersen, Hanne L.; Archetti, Claudia; Speranza, M. Grazia
2010-01-01
In this paper we present mathematical programming formulations and solution approaches for the optimal solution of the Double Travelling Salesman Problem with Multiple Stacks (DTSPMS). A set of orders is given, each one requiring transportation of one item from a customer in a pickup region...... to a customer in a delivery region. The vehicle available for the transportation in each region carries a container. The container is organized in rows of given length. Each row is handled independently from the others according to a LIFO (Last In First Out) stack policy. The DTSPMS problem consists...
On the Solutions to the Travelling Salesman Problem using Nature Inspired Computing Techniques
Hifza Afaq
2011-07-01
Full Text Available This paper attempts to bring forward various newly emerged natural computing techniques to a common platform. Six such techniques are compared among each other which have been used to solve a well known classical problem, the travelling salesman problem. The techniques discussed in this paper are Ant Colony Optimization (ACO, Particle Swarm Optimization (PSO, Bacterial Foraging Optimization Algorithm (BFOA, Gravitational Search Algorithm (GSA, Intelligent Water Drops (IWD, and River Formation Dynamics (RFD. In the end, some important results have been tabularized.
A Hybrid Genetic Algorithm for the Traveling Salesman Problem with Pickup and Delivery
Fang-Geng Zhao; Jiang-Sheng Sun; Su-Jian Li; Wei-Min Liu
2009-01-01
In this paper,a hybrid genetic algorithm (CA) is proposed for the traveling salesman problem (TSP) with pickup and delivery (TSPPD).In our algorithm,a novel pheromone-based crossover operator is advanced that utilizes both local and global information to construct offspring.In addition,a local search procedure is integrated into the GA to accelerate convergence.The proposed GA has been tested on benchmark instances,and the computational results show that it gives better convergence than existing heuristics.
Abdoun, Otman
2012-01-01
Genetic algorithm includes some parameters that should be adjusting so that the algorithm can provide positive results. Crossover operators play very important role by constructing competitive Genetic Algorithms (GAs). In this paper, the basic conceptual features and specific characteristics of various crossover operators in the context of the Traveling Salesman Problem (TSP) are discussed. The results of experimental comparison of more than six different crossover operators for the TSP are presented. The experiment results show that OX operator enables to achieve a better solutions than other operators tested.
Efficient cryptographic substitution box design using travelling salesman problem and chaos
Musheer Ahmad
2016-09-01
Full Text Available Symmetric encryption has been a standout amongst the most reliable option by which security is accomplished. In modern block symmetric cyphers, the substitution-boxes have been playing a critical role of nonlinear components that drives the actual security of cyphers. In this paper, the travelling salesman problem and piece-wise linear chaotic map are explored to synthesize an efficient configuration of 8 × 8 substitution-box. The proposed anticipated design has the consistency which is justified by the standard performance indexes. The statistical results manifest that the prospective substitution-box is cryptographically more impressive as compared to some recent investigations.
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.
Abdoun, Otman; Abouchabka, Jaafar
2012-01-01
In this paper, we present a new mutation operator, Hybrid Mutation (HPRM), for a genetic algorithm that generates high quality solutions to the Traveling Salesman Problem (TSP). The Hybrid Mutation operator constructs an offspring from a pair of parents by hybridizing two mutation operators, PSM and RSM. The efficiency of the HPRM is compared as against some existing mutation operators; namely, Reverse Sequence Mutation (RSM) and Partial Shuffle Mutation (PSM) for BERLIN52 as instance of TSPLIB. Experimental results show that the new mutation operator is better than the RSM and PSM.
Nur Ariffin Mohd Zin
2012-01-01
Full Text Available This paper discusses on a comparative study towards solution for solving Travelling Salesman Problem based on three techniques proposed namely exhaustive, heuristic and genetic algorithm. Each solution is to cater on finding an optimal path of available 25 contiguous cities in England whereby solution is written in Prolog. Comparisons were made with emphasis against time consumed and closeness to optimal solutions. Based on the experimental, we found that heuristic is very promising in terms of time taken, while on the other hand, Genetic Algorithm manages to be outstanding on big number of traversal by resulting the shortest path among the others.
Martin Macík
2015-09-01
Full Text Available High level of competition on postal market increases demands on reliability of postal services and lowering of transport costs. This can be achieved by optimizing the routing of postal vehicles. The article discusses the possibilities of such optimization by using graph theory. It describes basic methods of finding optimal routes using a graph. The approach, used in this article, assesses the possibility of applying meta-heuristic solution to the traveling salesman problem in the postal sector. Simulation of methods described has been applied on a regional postal network. Results showed that the software used proves to be sufficiently functional for the field of postal transport networks.
A Primal Dual Algorithm for a Heterogeneous Traveling Salesman Problem
Bae, Jungyun
2011-01-01
Surveillance applications require a collection of heterogeneous vehicles to visit a set of targets. In this article, we consider a fundamental routing problem that arises in these applications involving two vehicles. Specifically, we consider a routing problem where there are two heterogeneous vehicles that start from distinct initial locations, and a set of targets. The objective is to find a tour for each vehicle such that each of the targets is visited at least once by a vehicle and the sum of the distances traveled by the vehicles is a minimum. We present a primal-dual algorithm for a variant of this routing problem that provides an approximation ratio of 2.
ITO-based evolutionary algorithm to solve traveling salesman problem
Dong, Wenyong; Sheng, Kang; Yang, Chuanhua; Yi, Yunfei
2014-03-01
In this paper, a ITO algorithm inspired by ITO stochastic process is proposed for Traveling Salesmen Problems (TSP), so far, many meta-heuristic methods have been successfully applied to TSP, however, as a member of them, ITO needs further demonstration for TSP. So starting from designing the key operators, which include the move operator, wave operator, etc, the method based on ITO for TSP is presented, and moreover, the ITO algorithm performance under different parameter sets and the maintenance of population diversity information are also studied.
Yurtkuran, Alkın; Emel, Erdal
2014-01-01
The traveling salesman problem with time windows (TSPTW) is a variant of the traveling salesman problem in which each customer should be visited within a given time window. In this paper, we propose an electromagnetism-like algorithm (EMA) that uses a new constraint handling technique to minimize the travel cost in TSPTW problems. The EMA utilizes the attraction-repulsion mechanism between charged particles in a multidimensional space for global optimization. This paper investigates the problem-specific constraint handling capability of the EMA framework using a new variable bounding strategy, in which real-coded particle's boundary constraints associated with the corresponding time windows of customers, is introduced and combined with the penalty approach to eliminate infeasibilities regarding time window violations. The performance of the proposed algorithm and the effectiveness of the constraint handling technique have been studied extensively, comparing it to that of state-of-the-art metaheuristics using several sets of benchmark problems reported in the literature. The results of the numerical experiments show that the EMA generates feasible and near-optimal results within shorter computational times compared to the test algorithms.
Alkın Yurtkuran
2014-01-01
Full Text Available The traveling salesman problem with time windows (TSPTW is a variant of the traveling salesman problem in which each customer should be visited within a given time window. In this paper, we propose an electromagnetism-like algorithm (EMA that uses a new constraint handling technique to minimize the travel cost in TSPTW problems. The EMA utilizes the attraction-repulsion mechanism between charged particles in a multidimensional space for global optimization. This paper investigates the problem-specific constraint handling capability of the EMA framework using a new variable bounding strategy, in which real-coded particle’s boundary constraints associated with the corresponding time windows of customers, is introduced and combined with the penalty approach to eliminate infeasibilities regarding time window violations. The performance of the proposed algorithm and the effectiveness of the constraint handling technique have been studied extensively, comparing it to that of state-of-the-art metaheuristics using several sets of benchmark problems reported in the literature. The results of the numerical experiments show that the EMA generates feasible and near-optimal results within shorter computational times compared to the test algorithms.
Kusrini Kusrini
2007-01-01
Full Text Available There are plenty well-known algorithms for solving Travelling Salesman Program (TSP, such as: Linear Programming (LP, Genetic Algorithm (GA, Nearest Neighbourhood Heuristic (NNH and Cheapest Insertion Heuristic (CIH. This paper will talk about TSP implementation by using CIH algorithm. The writer uses Borland Delphi 6 and Interbase 6 as tool for implementing TSP. CIH algorithm has been implemented successfully. By determining count of connected cities and distances between them, the traveled route and total route length to visit all cities in a cities network were obtained. However, this algorithm implementation has not yet be able to solve route searching if there are two cities have different load or there are 2 cities that is not connected. Abstract in Bahasa Indonesia : Ada banyak algoritma untuk memecahkan masalah Travelling Salesman Problem (TSP, diantaranya: Linear Programming (LP, Algoritma Genetik, Nearest Neighbourhood Heuristic (NNH and Cheapest Insertion Heuristic (CIH. Makalah ini akan membahas tentang implementasi algoritma CIH untuk menyelesaikan TSP. Penulis menggunakan Borland Delphi 6 dan Interbase 6 sebagai tool dalam implementasi TSP. Algoritma CIH telah berhasil diimplementasikan. Dengan mengetahui jumlah kota yang terhubung dan jarak diantaranya, rute perjalanan dan total panjang rute untuk mengunjungi semua kota dalam jaringan dapat diketahui. Namun demikian, implementasi algoritma belum mampu menyelesaikan masalah pencarian rute jika ada 2 kota yang mimiliki bobot yang berbeda dengan melihat arahnya dan jika ada 2 buah kota yang tidak terhubung. Kata kunci: TSP, cheapest, insertion, heuristics, basis data.
S. Patvichaichod
2011-01-01
Full Text Available Problem statement: This study deals with the pickup and delivery traveling salesman problem with traffic conditions (PDTSPTW, an extension of the pickup and delivery traveling salesman problem (PDTSP where each customer to be served is associated with two quantities of product to be collected and delivered. Almost PDTSP problems uses distance between each point of customers as Euclidean Distance and are not concerned with other parameters to find minimal cost. Approach: The PDTSPTC concerns more parameters, such as street network and vehicle speed, which results it closer to the real world condition. The study also proposes the developed genetic algorithm called Hybrid Encoding Genetic Algorithm (HEGA. The concept is to combine binary encoding and integer encoding together, causing the in complexity of the algorithm structure and the ease of implementation. Results: the HEGA can save the travel cost about 26-57%. It is obviously seen that HEGA in the PDTSPTC test problems result the fast convergence that is about 12-43% and in all, the computational time is under 6 seconds. Conclusion: The HEGA performs quite well when testing a test problem. Computation times are small in all case. The PDTSPTC is closer to real-world conditions than PDTSP. This problem can be applied in logistics immediately if the distance of streets, traffic conditions (average vehicle speed in each street and vehicle conditions (fuel consumption rate and vehicle capacity are known.
Lin-Kernighan Heuristic Adaptation for the Generalized Traveling Salesman Problem
Karapetyan, Daniel
2010-01-01
Lin-Kernighan heuristic is known to be one of the most successful heuristics for the Traveling Salesman Problem (TSP). It has also proven its efficiency in application to some other problems. However, it was never applied to the the Generalized Traveling Salesman Problem (GTSP) though it has the same nature as TSP. In this paper we discuss possible adaptations of TSP heuristics for GTSP and focus on the case of Lin-Kernighan algorithm. At first, we provide an easy-to-understand description of the original Lin-Kernighan heuristic. Then we propose several adaptations, both trivial and complicated ones. Finally, we conduct a fair competition between all the variations of Lin-Kernighan adaptation and some other GTSP heuristics. It appears that our adaptation of Lin-Kernighan algorithm for GTSP reproduces the success of the original heuristic. Different variations of our adaptation outperform all other heuristics in a wide range of tradeoffs between solution quality and running time, making Lin-Kernighan the state...
Aras, N; Oommen, B J.; Altinel, I K.
1999-11-01
In this paper we introduce a new self-organizing neural network, the Kohonen Network Incorporating Explicit Statistics (KNIES) that is based on Kohonen's Self-Organizing Map (SOM). The primary difference between the SOM and the KNIES is the fact that every iteration in the training phase includes two distinct modules-the attracting module and the dispersing module. As a result of the newly introduced dispersing module the neurons maintain the overall statistical properties of the data points. Thus, although in SOM the neurons individually find their places both statistically and topologically, in KNIES they collectively maintain their mean to be the mean of the data points, which they represent. Although the scheme as it is currently implemented maintains the mean as its invariant, the scheme can easily be generalized to maintain higher order central moments as invariants. The new scheme has been used to solve the Euclidean Travelling Salesman Problem (TSP). Experimental results for problems taken from TSPLIB [Reinelt, G. (1991). TSPLIB-A travelling salesman problem library. ORSA Journal on Computing, 3, pp. 376-384] indicate that it is a very accurate NN strategy for the TSP-probably the most accurate neural solutions available in the literature.
Ant Colony Optimization ACO For The Traveling Salesman Problem TSP Using Partitioning
Alok Bajpai
2015-08-01
Full Text Available Abstract An ant colony optimization is a technique which was introduced in 1990s and which can be applied to a variety of discrete combinatorial optimization problem and to continuous optimization. The ACO algorithm is simulated with the foraging behavior of the real ants to find the incremental solution constructions and to realize a pheromone laying-and-following mechanism. This pheromone is the indirect communication among the ants. In this paper we introduces the partitioning technique based on the divide and conquer strategy for the traveling salesman problem which is one of the most important combinatorial problem in which the original problem is partitioned into the group of sub problems. And then we apply the ant colony algorithm using candidate list strategy for each smaller sub problems. After that by applying the local optimization and combining the sub problems to find the good solution for the original problem by improving the exploration efficiency of the ants. At the end of this paper we have also be presented the comparison of result with the normal ant colony system for finding the optimal solution to the traveling salesman problem.
A hybrid genetic algorithm for solving bi-objective traveling salesman problems
Ma, Mei; Li, Hecheng
2017-08-01
The traveling salesman problem (TSP) is a typical combinatorial optimization problem, in a traditional TSP only tour distance is taken as a unique objective to be minimized. When more than one optimization objective arises, the problem is known as a multi-objective TSP. In the present paper, a bi-objective traveling salesman problem (BOTSP) is taken into account, where both the distance and the cost are taken as optimization objectives. In order to efficiently solve the problem, a hybrid genetic algorithm is proposed. Firstly, two satisfaction degree indices are provided for each edge by considering the influences of the distance and the cost weight. The first satisfaction degree is used to select edges in a “rough” way, while the second satisfaction degree is executed for a more “refined” choice. Secondly, two satisfaction degrees are also applied to generate new individuals in the iteration process. Finally, based on genetic algorithm framework as well as 2-opt selection strategy, a hybrid genetic algorithm is proposed. The simulation illustrates the efficiency of the proposed algorithm.
Mizuno, Shinya; Iwamoto, Shogo; Yamaki, Naokazu
Various methods have been proposed to solve the traveling salesman problem, referred to as the TSP. In order to solve the TSP, the cost metric (e.g., the travel time and distance) between nodes is needed. As we do not always have specific criterion for the cost metric we are proposing using a new computation environment that is used all over the world—Google Maps. We think a cost metric obtained from Google maps is a good, impartial value with little room for variation, making it easier and more efficient to make map information visible. Moreover, a scalable computation environment can be prepared by using cloud computing technology. We can even expand the TSP and calculate routes taken by multiple people. The numerical results show this computation environment to be effective.
Large neighborhood search for the double traveling salesman problem with multiple stacks
Bent, Russell W [Los Alamos National Laboratory; Van Hentenryck, Pascal [BROWN UNIV
2009-01-01
This paper considers a complex real-life short-haul/long haul pickup and delivery application. The problem can be modeled as double traveling salesman problem (TSP) in which the pickups and the deliveries happen in the first and second TSPs respectively. Moreover, the application features multiple stacks in which the items must be stored and the pickups and deliveries must take place in reserve (LIFO) order for each stack. The goal is to minimize the total travel time satisfying these constraints. This paper presents a large neighborhood search (LNS) algorithm which improves the best-known results on 65% of the available instances and is always within 2% of the best-known solutions.
Barron-Romero, Carlos
2011-01-01
This paper presents the differences between two NP problems. It focuses in the Euclidian 2 Dimension Travelling Salesman Problems and General Assign Problems. The main results are the triangle reduction to verify the solution in polynomial time for the former and for the later the solution to the Noted Conjecture of the NP-Class, NP is not P.
F.J. Srour (Jordan); R.A. Zuidwijk (Rob)
2008-01-01
textabstractIn this paper we derive the worst-case ratio of an online algorithm for the Traveling Salesman Problem (TSP) with two disclosure dates. This problem, a variant of the online TSP with release dates, is characterized by the disclosure of a job’s location at one point in time followed by
A O(n^8) X O(n^7) Linear Programming Model of the Traveling Salesman Problem
Diaby, Moustapha
2008-01-01
In this paper, we present a new linear programming (LP) formulation of the Traveling Salesman Problem (TSP). The proposed model has O(n^8) variables and O(n^7) constraints, where n is the number of cities. Our numerical experimentation shows that computational times for the proposed linear program are several orders of magnitude smaller than those for the existing model [3].
An Efficient Combined Meta-Heuristic Algorithm for Solving the Traveling Salesman Problem
Majid Yousefikhoshbakht
2016-08-01
Full Text Available The traveling salesman problem (TSP is one of the most important NP-hard Problems and probably the most famous and extensively studied problem in the field of combinatorial optimization. In this problem, a salesman is required to visit each of n given nodes once and only once, starting from any node and returning to the original place of departure. This paper presents an efficient evolutionary optimization algorithm developed through combining imperialist competitive algorithm and lin-kernighan algorithm called (MICALK in order to solve the TSP. The MICALK is tested on 44 TSP instances involving from 24 to 1655 nodes from the literature so that 26 best known solutions of the benchmark problem are also found by our algorithm. Furthermore, the performance of MICALK is compared with several metaheuristic algorithms, including GA, BA, IBA, ICA, GSAP, ABO, PSO and BCO on 32 instances from TSPLIB. The results indicate that the MICALK performs well and is quite competitive with the above algorithms.
An Efficient Combined Meta-Heuristic Algorithm for Solving the Traveling Salesman Problem
Majid Yousefikhoshbakht
2016-08-01
Full Text Available The traveling salesman problem (TSP is one of the most important NP-hard Problems and probably the most famous and extensively studied problem in the field of combinatorial optimization. In this problem, a salesman is required to visit each of n given nodes once and only once, starting from any node and returning to the original place of departure. This paper presents an efficient evolutionary optimization algorithm developed through combining imperialist competitive algorithm and lin-kernighan algorithm called (MICALK in order to solve the TSP. The MICALK is tested on 44 TSP instances involving from 24 to 1655 nodes from the literature so that 26 best known solutions of the benchmark problem are also found by our algorithm. Furthermore, the performance of MICALK is compared with several metaheuristic algorithms, including GA, BA, IBA, ICA, GSAP, ABO, PSO and BCO on 32 instances from TSPLIB. The results indicate that the MICALK performs well and is quite competitive with the above algorithms.
The Traveling Salesman Problem: Low-Dimensionality Implies a Polynomial Time Approximation Scheme
Bartal, Yair; Krauthgamer, Robert
2011-01-01
The Traveling Salesman Problem (TSP) is among the most famous NP-hard optimization problems. We design for this problem a randomized polynomial-time algorithm that computes a (1+eps)-approximation to the optimal tour, for any fixed eps>0, in TSP instances that form an arbitrary metric space with bounded intrinsic dimension. The celebrated results of Arora (A-98) and Mitchell (M-99) prove that the above result holds in the special case of TSP in a fixed-dimensional Euclidean space. Thus, our algorithm demonstrates that the algorithmic tractability of metric TSP depends on the dimensionality of the space and not on its specific geometry. This result resolves a problem that has been open since the quasi-polynomial time algorithm of Talwar (T-04).
Fault-tolerance of a neural network solving the traveling salesman problem
Protzel, P.; Palumbo, D.; Arras, M.
1989-01-01
This study presents the results of a fault-injection experiment that stimulates a neural network solving the Traveling Salesman Problem (TSP). The network is based on a modified version of Hopfield's and Tank's original method. We define a performance characteristic for the TSP that allows an overall assessment of the solution quality for different city-distributions and problem sizes. Five different 10-, 20-, and 30- city cases are sued for the injection of up to 13 simultaneous stuck-at-0 and stuck-at-1 faults. The results of more than 4000 simulation-runs show the extreme fault-tolerance of the network, especially with respect to stuck-at-0 faults. One possible explanation for the overall surprising result is the redundancy of the problem representation.
RESEARCH ON SOLVING TRAVELLING SALESMAN PROBLEM USING RANK BASED ANT SYSTEM ON GPU
Khushbu Khatri
2015-10-01
Full Text Available Ant Colony Optimization (ACO is meta-heuristic algorithm inspired from nature to solve many combinatorial optimization problems such as Travelling Salesman Problem (TSP. There are many versions of ACO used to solve TSP like, Ant System, Elitist Ant System, Max-Min Ant System, Rank based Ant System algorithm. For improved performance, these methods can be implemented in parallel architecture like GPU, CUDA architecture. Graphics Processing Unit (GPU provides highly parallel and fully programmable platform. GPUs which have many processing units with an off-chip global memory can be used for general purpose parallel computation. This paper presents a parallel Rank Based Ant System algorithm to solve TSP by use of Pre Roulette Wheel Selection Method.
A population-based algorithm for the multi travelling salesman problem
Rubén Iván Bolaños
2016-04-01
Full Text Available This paper presents the implementation of an efficient modified genetic algorithm for solving the multi-traveling salesman problem (mTSP. The main characteristics of the method are the construction of an initial population of high quality and the implementation of several local search operators which are important in the efficient and effective exploration of promising regions of the solution space. Due to the combinatorial complexity of mTSP, the proposed methodology is especially applicable for real-world problems. The proposed algorithm was tested on a set of six benchmark instances, which have from 76 and 1002 cities to be visited. In all cases, the best known solution was improved. The results are also compared with other existing solutions procedure in the literature.
Anuradha.D
2013-04-01
Full Text Available The investigation of metrics in multiple perspectives is dealt in this paper for a bi-criteria travelling salesman problem (BTSP. By representing the problem in a graphical view, its corresponding metrics in terms of graph theory is estimated. With the programming viewpoint a program using Java programming language is implemented to solve a BTSP. The development of efficient software requires metrics, which is measured to highlight the performance of the software. The application can also be viewed in management perspective through which the solutions in reality are discussed. These approaches can be served as an essential device for the decision makers when they are dealing different varieties of logistics problems comprising two criterions.
Navjot Kaur Dalip
2011-11-01
Full Text Available This paper, proposes a solution for Travelling Salesman Problem (TSP [1], using Genetic Algorithm (GA. The proposed algorithm works on data sets of latitude and longitude coordinates of cities and provides optimal tours in shorter time; giving convergence that is fast and better. To improve the solution few heuristic improvements are applied to prevent converging to local optima. The principleof natural selection here is based on both survival and reproduction capacities; that accelerate the convergence speed. Various factors affect the performance of GA(s, such as genetic operators,population etc. As the performance of GA is greatly affected by the initial population, the initial population for the algorithm is sorted first, using Quick Sort, this preserves the better fit population. Also, GA parameters such as selection and mutation probabilities are varied, to obtain enhanced and better performance. The computational results are compared with symmetric problems for some benchmark TSP LIB instances.
A Data-Guided Lexisearch Algorithm for the Asymmetric Traveling Salesman Problem
Zakir Hussain Ahmed
2011-01-01
Full Text Available A simple lexisearch algorithm that uses path representation method for the asymmetric traveling salesman problem (ATSP is proposed, along with an illustrative example, to obtain exact optimal solution to the problem. Then a data-guided lexisearch algorithm is presented. First, the cost matrix of the problem is transposed depending on the variance of rows and columns, and then the simple lexisearch algorithm is applied. It is shown that this minor preprocessing of the data before the simple lexisearch algorithm is applied improves the computational time substantially. The efficiency of our algorithms to the problem against two existing algorithms has been examined for some TSPLIB and random instances of various sizes. The results show remarkably better performance of our algorithms, especially our data-guided algorithm.
A high-performance genetic algorithm: using traveling salesman problem as a case.
Tsai, Chun-Wei; Tseng, Shih-Pang; Chiang, Ming-Chao; Yang, Chu-Sing; Hong, Tzung-Pei
2014-01-01
This paper presents a simple but efficient algorithm for reducing the computation time of genetic algorithm (GA) and its variants. The proposed algorithm is motivated by the observation that genes common to all the individuals of a GA have a high probability of surviving the evolution and ending up being part of the final solution; as such, they can be saved away to eliminate the redundant computations at the later generations of a GA. To evaluate the performance of the proposed algorithm, we use it not only to solve the traveling salesman problem but also to provide an extensive analysis on the impact it may have on the quality of the end result. Our experimental results indicate that the proposed algorithm can significantly reduce the computation time of GA and GA-based algorithms while limiting the degradation of the quality of the end result to a very small percentage compared to traditional GA.
Application of Imperialist Competitive Algorithm on Solving the Traveling Salesman Problem
Shuhui Xu
2014-05-01
Full Text Available The imperialist competitive algorithm (ICA is a new heuristic algorithm proposed for continuous optimization problems. The research about its application on solving the traveling salesman problem (TSP is still very limited. Aiming to explore its ability on solving TSP, we present a discrete imperialist competitive algorithm in this paper. The proposed algorithm modifies the original rules of the assimilation and introduces the 2-opt algorithm into the revolution process. To examine its performance, we tested the proposed algorithm on 10 small-scale and 2 large-scale standard benchmark instances from the TSPLIB and compared the experimental results with that obtained by two other ICA-based algorithms and six other existing algorithms. The proposed algorithm shows excellent performance in the experiments and comparisons.
YAN Shiliang; WANG Yinling
2007-01-01
Travelling Salesman Problem (TSP) is a classical optimization problem and it is one of a class of NP-Problem. The purposes of this work is to apply data mining methodologies to explore the patterns in data generated by an Ant Colony Algorithm (ACA) performing a searching operation and to develop a rule set searcher which approximates the ACA'S searcher. An attribute-oriented induction methodology was used to explore the relationship between an operations' sequence and its attributes and a set of rules has been developed. At the end of this paper, the experimental results have shown that the proposed approach has good performance with respect to the quality of solution and the speed of computation.
Keivan Borna
2015-12-01
Full Text Available Traveling salesman problem (TSP is a well-established NP-complete problem and many evolutionary techniques like particle swarm optimization (PSO are used to optimize existing solutions for that. PSO is a method inspired by the social behavior of birds. In PSO, each member will change its position in the search space, according to personal or social experience of the whole society. In this paper, we combine the principles of PSO and crossover operator of genetic algorithm to propose a heuristic algorithm for solving the TSP more efficiently. Finally, some experimental results on our algorithm are applied in some instances in TSPLIB to demonstrate the effectiveness of our methods which also show that our algorithm can achieve better results than other approaches.
Analyzing the Performance of Mutation Operators to Solve the Travelling Salesman Problem
Abdoun, Otman; Tajani, Chakir
2012-01-01
The genetic algorithm includes some parameters that should be adjusted, so as to get reliable results. Choosing a representation of the problem addressed, an initial population, a method of selection, a crossover operator, mutation operator, the probabilities of crossover and mutation, and the insertion method creates a variant of genetic algorithms. Our work is part of the answer to this perspective to find a solution for this combinatorial problem. What are the best parameters to select for a genetic algorithm that creates a variety efficient to solve the Travelling Salesman Problem (TSP)? In this paper, we present a comparative analysis of different mutation operators, surrounded by a dilated discussion that justifying the relevance of genetic operators chosen to solving the TSP problem.
Rubén Iván Bolaños
2015-06-01
Full Text Available This paper considers a multi-objective version of the Multiple Traveling Salesman Problem (MOmTSP. In particular, two objectives are considered: the minimization of the total traveled distance and the balance of the working times of the traveling salesmen. The problem is formulated as an integer multi-objective optimization model. A non-dominated sorting genetic algorithm (NSGA-II is proposed to solve the MOmTSP. The solution scheme allows one to find a set of ordered solutions in Pareto fronts by considering the concept of dominance. Tests on real world instances and instances adapted from the literature show the effectiveness of the proposed algorithm.
Generalized Traveling Salesman Problem and Its Solution%广义旅行商问题及其求解
赵曦; 叶和平
2007-01-01
广义旅行商问题(Generalized Traveling Salesman Problem,简称GTSP)是比旅行商问题(Traveling Salesman Problem,简称TSP)更为复杂的一类组合优化问题,TSP可视为GTSP的特例.GTSP较TSP能提供更精确的实际问题模型,有着更广泛的应用领域,但相对于TSP的研究而言,至今GTSP的研究成果甚少.详细介绍了GTSP问题的定义与背景,应用领域及其求解方法,着重介绍了最新的GCGA算法,并对GTSP未来的研究提出了建议.
无
2007-01-01
Let G = (V, E) be a complete undirected graph with vertex set V, edge set E, and edge weights I(e)satisfying the triangle inequality. The vertex set V is partitioned into clusters V1, V2 Vk. The clustered traveling salesman problem (CTSP) seeks to compute the shortest Hamiltonian tour that visits all the vertices, in which the vertices of each cluster are visited consecutively. A two-level genetic algorithm (TLGA) was developed for the problem, which favors neither intra-cluster paths nor inter-cluster paths, thus realized integrated evolutionary optimization for both levels of the CTSP. Results show that the algorithm is more effective than known algorithms. A large-scale traveling salesman problem (TSP) can be converted into a CTSP by clustering so that it can then be solved by the algorithm. Test results demonstrate that the clustering TLGA for large TSPs is more effective and efficient than the classical genetic algorithm.
Tachibana, Toshihiro; Adachi, Masaharu
An asymmetric traveling salesman problem is one in which the costs for travel between one city and another are not symmetric. In this paper, we propose a method for solving such problems based on chaotic search method. It uses block-city exchange method, block insertion method, and 2-opt exchange as exchanging methods. In the block-city exchange method, we consider several cities as a block, and the whole block is exchanged with other city. In the block insertion method, we consider several cities as a block, and the block is inserted at the specified location. In the proposed method, a switching between two exchange methods is determined by chaotic neurodynamics. In the proposed method, the block-city exchange method uses one of exchange method for any instance. The other exchange method is selected from the 2-opt exchange and block insertion methods according to the standard deviations of the costs city-wise and that of all branches in the instance. The proposed method obtains better or equivalent solutions with the conventional heuristic methods for asymmetric TSPs.
An Overview of Multiple Traveling Salesman Problem%多旅行商问题研究综述
俞庆生; 林冬梅; 王东
2012-01-01
多旅行商问题是经典旅行商问题的一种泛化,加上某些特定的附加条件,则能够演化成一些较现实的问题,因而具有较高的理论研究和应用价值.在多旅行商问题中,一个任务由多位旅行商共同完成,其问题的求解难度较经典旅行商问题更大,用于经典旅行商问题求解的方法或策略不能简单地应用于多旅行商问题的求解,有关该问题的研究成果远比经典旅行商问题少,本文针对目前有关多旅行商问题的研究进展情况进行综述.%Multiple traveling salesman problem is a generalization of classic traveling salesman problem. It could be converted to real problems while appending some specific constraints, so the problem has high value of the theoretical research and application. A task will be completed by multiple traveling salesman together in multiple traveling salesman problem, therefore the problem is more difficult than the classic one. Those methods or strategies used to the classic one could not be applied to the problem after being updated simply. The achievements for the problem are less than the classic one. In this paper, the research progress of the problem will be overviewed.
Plum, Christian Edinger Munk; Pisinger, David; Salazar-González, Juan-José
2012-01-01
commercial constraints. Inspiration for formulation and solution method is taken from the rich research done within pickup and delivery problems. The problem, the multicommodity one-toone pickup and delivery traveling salesman problem with path duration limits is, to the best of out knowledge, considered...... for the first time. An arc flow and a path flow model are presented. A Branch and Cut and Price solution method is proposed and implemented....
Chen, Hongwei; Kong, Xi; Chong, Bo; Qin, Gan; Zhou, Xianyi; Peng, Xinhua; Du, Jiangfeng
2011-03-01
The method of quantum annealing (QA) is a promising way for solving many optimization problems in both classical and quantum information theory. The main advantage of this approach, compared with the gate model, is the robustness of the operations against errors originated from both external controls and the environment. In this work, we succeed in demonstrating experimentally an application of the method of QA to a simplified version of the traveling salesman problem by simulating the corresponding Schrödinger evolution with a NMR quantum simulator. The experimental results unambiguously yielded the optimal traveling route, in good agreement with the theoretical prediction.
Automatic Combination of Operators in a Genetic Algorithm to Solve the Traveling Salesman Problem
2015-01-01
Genetic algorithms are powerful search methods inspired by Darwinian evolution. To date, they have been applied to the solution of many optimization problems because of the easy use of their properties and their robustness in finding good solutions to difficult problems. The good operation of genetic algorithms is due in part to its two main variation operators, namely, crossover and mutation operators. Typically, in the literature, we find the use of a single crossover and mutation operator. However, there are studies that have shown that using multi-operators produces synergy and that the operators are mutually complementary. Using multi-operators is not a simple task because which operators to use and how to combine them must be determined, which in itself is an optimization problem. In this paper, it is proposed that the task of exploring the different combinations of the crossover and mutation operators can be carried out by evolutionary computing. The crossover and mutation operators used are those typically used for solving the traveling salesman problem. The process of searching for good combinations was effective, yielding appropriate and synergic combinations of the crossover and mutation operators. The numerical results show that the use of the combination of operators obtained by evolutionary computing is better than the use of a single operator and the use of multi-operators combined in the standard way. The results were also better than those of the last operators reported in the literature. PMID:26367182
A Discrete Fruit Fly Optimization Algorithm for the Traveling Salesman Problem
Jiang, Zi-bin; Yang, Qiong
2016-01-01
The fruit fly optimization algorithm (FOA) is a newly developed bio-inspired algorithm. The continuous variant version of FOA has been proven to be a powerful evolutionary approach to determining the optima of a numerical function on a continuous definition domain. In this study, a discrete FOA (DFOA) is developed and applied to the traveling salesman problem (TSP), a common combinatorial problem. In the DFOA, the TSP tour is represented by an ordering of city indices, and the bio-inspired meta-heuristic search processes are executed with two elaborately designed main procedures: the smelling and tasting processes. In the smelling process, an effective crossover operator is used by the fruit fly group to search for the neighbors of the best-known swarm location. During the tasting process, an edge intersection elimination (EXE) operator is designed to improve the neighbors of the non-optimum food location in order to enhance the exploration performance of the DFOA. In addition, benchmark instances from the TSPLIB are classified in order to test the searching ability of the proposed algorithm. Furthermore, the effectiveness of the proposed DFOA is compared to that of other meta-heuristic algorithms. The results indicate that the proposed DFOA can be effectively used to solve TSPs, especially large-scale problems. PMID:27812175
Combined Mutation Operators of Genetic Algorithm for the Travelling Salesman Problem
Kusum Deep
2011-01-01
Full Text Available In this study two combined mutation operators have been developed to increase the performance of Genetic Algorithm that helps to find the minimum cost in the known Travelling Salesman problem (TSP.In order to do this the combined mutation operators which are named as Inverted Exchange and Inverted Displacement are compared with four existing mutation operators. These are programmed in C++ and algorithms, ten bench mark test problems and five variations of order crossover are used. Based implemented on a set of benchmark test problems taken from the TSPLIB.The crossover operator used here is the order crossover using two of its existing and three of its new variations. In general six mutation on the numerical and graphical analysis it indicates that the Inverted Displacement has a definite supremacy over the existing four mutations except for few instances considered here. The Inversion mutation is second best performer. All optimal values found in the six mutations are obtained when the new variations of order crossover are used.
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.
Traveling salesman problems with PageRank Distance on complex networks reveal community structure
Jiang, Zhongzhou; Liu, Jing; Wang, Shuai
2016-12-01
In this paper, we propose a new algorithm for community detection problems (CDPs) based on traveling salesman problems (TSPs), labeled as TSP-CDA. Since TSPs need to find a tour with minimum cost, cities close to each other are usually clustered in the tour. This inspired us to model CDPs as TSPs by taking each vertex as a city. Then, in the final tour, the vertices in the same community tend to cluster together, and the community structure can be obtained by cutting the tour into a couple of paths. There are two challenges. The first is to define a suitable distance between each pair of vertices which can reflect the probability that they belong to the same community. The second is to design a suitable strategy to cut the final tour into paths which can form communities. In TSP-CDA, we deal with these two challenges by defining a PageRank Distance and an automatic threshold-based cutting strategy. The PageRank Distance is designed with the intrinsic properties of CDPs in mind, and can be calculated efficiently. In the experiments, benchmark networks with 1000-10,000 nodes and varying structures are used to test the performance of TSP-CDA. A comparison is also made between TSP-CDA and two well-established community detection algorithms. The results show that TSP-CDA can find accurate community structure efficiently and outperforms the two existing algorithms.
A GPU Implementation of Local Search Operators for Symmetric Travelling Salesman Problem
Juraj Fosin
2013-06-01
Full Text Available The Travelling Salesman Problem (TSP is one of the most studied combinatorial optimization problem which is significant in many practical applications in transportation problems. The TSP problem is NP-hard problem and requires large computation power to be solved by the exact algorithms. In the past few years, fast development of general-purpose Graphics Processing Units (GPUs has brought huge improvement in decreasing the applications’ execution time. In this paper, we implement 2-opt and 3-opt local search operators for solving the TSP on the GPU using CUDA. The novelty presented in this paper is a new parallel iterated local search approach with 2-opt and 3-opt operators for symmetric TSP, optimized for the execution on GPUs. With our implementation large TSP problems (up to 85,900 cities can be solved using the GPU. We will show that our GPU implementation can be up to 20x faster without losing quality for all TSPlib problems as well as for our CRO TSP problem.
Narwadi, Teguh; Subiyanto
2017-03-01
The Travelling Salesman Problem (TSP) is one of the best known NP-hard problems, which means that no exact algorithm to solve it in polynomial time. This paper present a new variant application genetic algorithm approach with a local search technique has been developed to solve the TSP. For the local search technique, an iterative hill climbing method has been used. The system is implemented on the Android OS because android is now widely used around the world and it is mobile system. It is also integrated with Google API that can to get the geographical location and the distance of the cities, and displays the route. Therefore, we do some experimentation to test the behavior of the application. To test the effectiveness of the application of hybrid genetic algorithm (HGA) is compare with the application of simple GA in 5 sample from the cities in Central Java, Indonesia with different numbers of cities. According to the experiment results obtained that in the average solution HGA shows in 5 tests out of 5 (100%) is better than simple GA. The results have shown that the hybrid genetic algorithm outperforms the genetic algorithm especially in the case with the problem higher complexity.
The co-adaptive neural network approach to the Euclidean Travelling Salesman Problem.
Cochrane, E M; Beasley, J E
2003-12-01
In this paper we consider the Euclidean Travelling Salesman Problem (ETSP). This is the problem of finding the shortest tour around a number of cities where the cities correspond to points in the Euclidean plane and the distances between cities are given by the usual Euclidean distance metric. We present a review of the literature with respect to neural network (NN) approaches for the ETSP, and the computational results that have been reported. Based upon this review we highlight two areas that are, in our judgement, currently neglected/lacking in the literature. These are: failure to make significant use of publicly available ETSP test problems in computational work, failure to address co-operation between neurons. Drawing upon our literature survey this paper presents a new Self-Organising NN approach, called the Co-Adaptive Net, which involves not just unsupervised learning to train neurons, but also allows neurons to co-operate and compete amongst themselves depending on their situation. Our Co-Adaptive Net algorithm also includes a number of algorithmic mechanisms that, based upon our literature review, we consider to have contributed to the computational success of previous algorithms. Results for 91 publicly available standard ETSP's are presented in this paper. The largest of these problems involves 85,900 cities. This paper presents: the most extensive computational evaluation of any NN approach on publicly available ETSP test problems that has been made to date in the literature, a NN approach that performs better, with respect to solution quality and/or computation time, than other NN approaches given previously in the literature. Drawing upon computational results produced as a result of the DIMACS TSP Challenge, we highlight the fact that none of the current NN approaches for the ETSP can compete with state of the art Operations Research heuristics. We discuss why we consider continuing to study and develop NN approaches for the ETSP to be of value.
On the Optimization and Parallelizing Little Algorithm for Solving the Traveling Salesman Problem
V. V. Vasilchikov
2016-01-01
Full Text Available The paper describes some ways to accelerate solving the NP-complete Traveling Salesman Problem. The classic Little algorithm belonging to the category of ”branch and bound methods” can solve it both for directed and undirected graphs. However, for undirected graphs its operation can be accelerated by eliminating the consideration of branches examined earlier. The paper proposes changes to be made in the key operations of the algorithm to speed up its execution. It also describes the results of an experiment that demonstrated a significant acceleration of solving the problem by using an advanced algorithm. Another way to speed up the work is to parallelize the algorithm. For problems of this kind it is difficult to break the task into a sufficient number of subtasks having comparable complexity. Their parallelism arises dynamically during the execution. For such problems, it seems reasonable to use parallel-recursive algorithms. In our case the use of the library RPM ParLib developed by the author was a good choice. It allows us to develop effective applications for parallel computing on a local network using any .NET-compatible programming language. We used C# to develop the programs. Parallel applications were developed as for basic and modified algorithms, the comparing of their speed was made. Experiments were performed for the graphs with the number of vertexes up to 45 and with the number of network computers up to 16. We also investigated the acceleration that can be achieved by parallelizing the basic Little algorithm for directed graphs. The results of these experiments are also presented in the paper.
A novel constructive-optimizer neural network for the traveling salesman problem.
Saadatmand-Tarzjan, Mahdi; Khademi, Morteza; Akbarzadeh-T, Mohammad-R; Moghaddam, Hamid Abrishami
2007-08-01
In this paper, a novel constructive-optimizer neural network (CONN) is proposed for the traveling salesman problem (TSP). CONN uses a feedback structure similar to Hopfield-type neural networks and a competitive training algorithm similar to the Kohonen-type self-organizing maps (K-SOMs). Consequently, CONN is composed of a constructive part, which grows the tour and an optimizer part to optimize it. In the training algorithm, an initial tour is created first and introduced to CONN. Then, it is trained in the constructive phase for adding a number of cities to the tour. Next, the training algorithm switches to the optimizer phase for optimizing the current tour by displacing the tour cities. After convergence in this phase, the training algorithm switches to the constructive phase anew and is continued until all cities are added to the tour. Furthermore, we investigate a relationship between the number of TSP cities and the number of cities to be added in each constructive phase. CONN was tested on nine sets of benchmark TSPs from TSPLIB to demonstrate its performance and efficiency. It performed better than several typical Neural networks (NNs), including KNIES_TSP_Local, KNIES_TSP_Global, Budinich's SOM, Co-Adaptive Net, and multivalued Hopfield network as wall as computationally comparable variants of the simulated annealing algorithm, in terms of both CPU time and accuracy. Furthermore, CONN converged considerably faster than expanding SOM and evolved integrated SOM and generated shorter tours compared to KNIES_DECOMPOSE. Although CONN is not yet comparable in terms of accuracy with some sophisticated computationally intensive algorithms, it converges significantly faster than they do. Generally speaking, CONN provides the best compromise between CPU time and accuracy among currently reported NNs for TSP.
Traveling Salesman Problems on China%关于中国旅行商问题的探讨
徐艳; 野金花
2011-01-01
China＇s traveling salesman problem is discussed.Firstly,ant colony algorithm is used to get the most short-circuit travel program of Chinese traveling salesman;Secondly,in most programs,based on the short trip,consider the most economical travel costs,we established a travel in the optimization model without constraints,while costs have been minimal;Finally,considering the money,save time and facilitate the constraints,we have established a travel in a balanced multi-objective optimization model,and software programming using Lingo finally get a more reasonable travel booking solution.%对中国旅行商问题进行了探讨。首先,我们运用蚁群算法得到了中国旅行商的最短路旅行方案;其次,在最短路旅行方案的基础上,再考虑最经济的旅行花费问题,我们建立了旅行问题的无约束条件优化模型,同时得到了最小花费;最后,综合考虑省钱、省时又方便的约束条件,我们建立了旅行问题的均衡多目标优化模型,并运用Lingo软件编程最终得到了较合理的旅行订票方案。
求解旅行商问题的人工蜂群算法%Artificial Bee Colony Algorithm for Solving Traveling Salesman Problem
黄秋菀; 王志刚; 夏慧明
2013-01-01
The article uses artificial bee colony algorithm to solve traveling salesman problems, gives the specific solutions of artificial bee colony algorithm for solving traveling salesman problem, and makes simulation experiment for the different traveling salesman. The results show that the algorithm can efficiently and quickly find optimal solutions to small problems.% 采用人工蜂群算法对旅行商问题进行求解，给出了人工蜂群算法求解该问题的具体方案，对不同的旅行商问题算例进行了仿真实验。结果表明，算法可以有效、快速地找到较小规模问题的最优解。
广义旅行商问题与旅行商问题的转化%Generalized Traveling Salesman Problem and Its Solving
赵曦
2007-01-01
广义旅行商问题(Generalized Traveling Salesman Problem,简称GTSP)是比旅行商问题(Traveling Salesman Problem,简称TSP)更为复杂的一类组合优化问题,TSP可视为GTSP的特例.GTSP的应用领域更广,但相对于TSP的研究而言,GTSP的研究成果很少.本文介绍了GTSP问题的定义与背景,研完了GTSP与TSP的转化,提出了转化的优缺点和研究方向.
Ramadhani, T.; Hertono, G. F.; Handari, B. D.
2017-07-01
The Multiple Traveling Salesman Problem (MTSP) is the extension of the Traveling Salesman Problem (TSP) in which the shortest routes of m salesmen all of which start and finish in a single city (depot) will be determined. If there is more than one depot and salesmen start from and return to the same depot, then the problem is called Fixed Destination Multi-depot Multiple Traveling Salesman Problem (MMTSP). In this paper, MMTSP will be solved using the Ant Colony Optimization (ACO) algorithm. ACO is a metaheuristic optimization algorithm which is derived from the behavior of ants in finding the shortest route(s) from the anthill to a form of nourishment. In solving the MMTSP, the algorithm is observed with respect to different chosen cities as depots and non-randomly three parameters of MMTSP: m, K, L, those represents the number of salesmen, the fewest cities that must be visited by a salesman, and the most number of cities that can be visited by a salesman, respectively. The implementation is observed with four dataset from TSPLIB. The results show that the different chosen cities as depots and the three parameters of MMTSP, in which m is the most important parameter, affect the solution.
Kubota, N. [Osaka Inst. of Technology, Osaka (Japan); Fukuda, T. [Nagoya University, Nagoya (Japan)
1998-05-31
This paper deals with virus evolutionary genetic algorithm. The genetic algorithms (GAs) have been demonstrated its effectiveness in optimization problems in these days. In general, the GAs simulate the survival of fittest by natural selection and the heredity of the Darwin`s theory of evolution. However, some types of evolutionary hypotheses such as neutral theory of molecular evolution, Imanishi`s evolutionary theory, serial symbiosis theory, and virus theory of evolution, have been proposed in addition to the Darwinism. Virus theory of evolution is based on the view that the virus transduction is a key mechanism for transporting segments of DNA across species. This paper proposes genetic algorithm based on the virus theory of evolution (VE-GA), which has two types of populations: host population and virus population. The VE-GA is composed of genetic operators and virus operators such as reverse transcription and incorporation. The reverse transcription operator transcribes virus genes on the chromosome of host individual and the incorporation operator creates new genotype of virus from host individual. These operators by virus population make it possible to transmit segment of DNA between individuals in the host population. Therefore, the VE-GA realizes not only vertical but also horizontal propagation of genetic information. Further, the VE-GA is applied to the traveling salesman problem in order to show the effectiveness. 20 refs., 10 figs., 3 tabs.
Probe Model for Solving Travelling Salesman Problem%探针机模型求解旅行商问题
沙莎; 陈玉华
2016-01-01
The traveling salesman problem is a typical NP-complete problem which has wide applications in engineering practice,such as circuit board layout,and vehicle scheduling.Probe machine model,as a new computing model is more efficienct than turing machine model in calculation.Compared to other conventional algorithms,the probe machine calculation model with strong ability of bottom full parallel computing,can solve traveling salesman problem in lower time complexity.%旅行商问题是典型的NP-完全问题，其在电路板布局、车辆调度等工程实践中有着广泛的应用。探针机模型是一种新兴的计算模型，在解决众多困难问题方面，其运算有效性优于图灵机模型。相比常规算法求解旅行商问题，探针机计算模型具有强大的底层全并行性，可在较低的时间复杂度内解决此问题。
Milan Djordjevic
2012-01-01
Full Text Available Background: The Travelling Salesman Problem is an NP-hard problem in combinatorial optimization with a number of practical implications. There are many heuristic algorithms and exact methods for solving the problem. Objectives: In this paper we study the influence of hybridization of a genetic algorithm with a local optimizer on solving instances of the Travelling Salesman Problem. Methods/ Approach: Our algorithm uses hybridization that occurs at various percentages of generations of a genetic algorithm. Moreover, we have also studied at which generations to apply the hybridization and hence applied it at random generations, at the initial generations, and at the last ones. Results: We tested our algorithm on instances with sizes ranging from 76 to 439 cities. On the one hand, the less frequent application of hybridization decreased the average running time of the algorithm from 14.62 sec to 2.78 sec at 100% and 10% hybridization respectively, while on the other hand, the quality of the solution on average deteriorated only from 0.21% till 1.40% worse than the optimal solution. Conclusions: In the paper we have shown that even a small hybridization substantially improves the quality of the result. Moreover, the hybridization in fact does not deteriorate the running time too much. Finally, our experiments show that the best results are obtained when hybridization occurs in the last generations of the genetic algorithm.
Asymptotic experimental analysis for the Held-Karp traveling salesman bound
Johnson, D.S. [AT& T Bell Laboratories, Murray Hill, NJ (United States); McGeoch, L.A. [Amherst College, MA (United States); Rothberg, E.E. [Silicon Graphics, Mountain View, CA (United States)
1996-12-31
The Held-Karp (HK) lower bound is the solution to the linear programming relaxation of the standard integer Programming formulation of the traveling salesman problem (TSP). For numbers of cities N up to 30,000 or more it can be computed exactly using the Simplex method and appropriate separation algorithms, and for N up to a million good approximations can be obtained via iterative Lagrangean relaxation techniques first suggested by Held and Karp. In this paper, we consider three applications of our ability to compute/approximate this bound. First, we provide empirical evidence in support of using the HK bound as a stand-in for the optimal tour length when evaluating the quality of near-optimal tours. We show that for a wide variety of randomly generated instance types the optimal tour length averages less than 0.8% over the HK bound, and even for the real-world instances in TSPLIB the gap is almost always less than 2%. Moreover, our data indicates that the HK bound can provide substantial {open_quotes}variance reduction{close_quotes} in experimental studies involving randomly generated instances. Second, we estimate the expected HK bound as a function of N for a variety of random instance types, based on extensive computations. For example, for random Euclidean instances it is known that the ratio of the Held-Karp bound to {radical}N approaches a constant C{sub HK}, and we estimate both that constant and the rate of convergence to it. Finally, we combine this information with our earlier results on expected HK gaps to obtain estimates for expected optimal tour lengths. For random Euclidean instances, we conclude that C{sub OPT}, the limiting ratio of the optimal tour length to {radical}N, is .7124 +- .0002, thus invalidating the commonly cited estimates of .749 and .765 and undermining many claims of good heuristic performance based on those estimates. For random distance matrices, the expected optimal tour length appears to be about 2.042.
A selective ensemble method for traveling salesman problems%旅行商问题的一种选择性集成求解方法
王立宏; 李强
2016-01-01
针对大型 TSP（traveling salesman problem）实例很难找到最优解的问题，提出了一种选择性集成求解方法。首先通过扩大路径法来选择集成多个较好解，构造出若干个极大路径；然后采用顶点插入法将剩余顶点和这些极大路径连接成一个哈密顿回路；最后使用2-opt 方法对该回路进行提升。试验结果表明，算法在5个 TSP 实例上得出的最好解的最大偏差为1.69％，说明本算法可以有效求解 TSP。%To solve the problem of finding the optimum solution of very large TSP (traveling salesman problem),a selective ensemble method was proposed.Firstly,expanding path method was used to selective integrate some high quality solutions,and several maximum paths were obtained.And then vertex insertion method was employed to connect these paths and the remainder vertices to form a Hamiltonian tour.Finally,the tour was improved by 2-opt method.Experimental results on 5 TSP instances showed that the maximal bias was 1.69%,and the effectiveness was proved.
Ant Colony Optimization for Solving Traveling Salesman Problem Based on MATLAB%基于MATLAB的蚁群算法求解旅行商问题
黄丽韶; 朱喜基
2012-01-01
The traditional method for solving the traveling salesman problem is a genetic algorithm, which is slow convergence and can not obtain the optimal solution. In order to strike the optimal solution of the traveling salesman problem, this paper described the basic principles of ant colony optimization, the model as well as the basis of the process of solving the traveling salesman problem. The other, an ant colony optimization is built for solving the traveling salesman problem based on MATLAB, and finaly through the simulation to obtain the best solution which is the best one currently.%旅行商问题的传统求解方法是遗传算法,此算法收敛速度慢,并不能获得问题的最优解。为了求取旅行商问题的最优解,本文在阐述蚁群算法的基本原理、模型以及在旅行商问题中的实现过程的基础上,提出了一种以蚁群算法构建的基于MATLAB的求解旅行商问题的方法,并最后通过仿真实验获得了目前已知的最好解。
球面旅行商问题常数及其实验分析%Spherical traveling salesman problem constant and its experimental analysis
王刚; 骆志刚
2011-01-01
This paper gave an upper bound of the optimal value to the random spherical traveling salesman problem, and also a lower bound of the expectation of the optimal value. Conjectured that there exists a spherical traveling salesman problem con-stant whose value is the same as the plane traveling salesman problem constant. Two numerical experiments support the conjec-ture. And they also show that the sphere surface is a better test bed than the plane square for the 2-dimensional traveling sales-man problem constant.%给出了球面随机旅行商问题最优值的一个上界以及最优值期望的一个下界.猜想球面旅行商问题常数存在且与平面旅行商问题常数相等.所做两组数值实验支持该猜想,且显示球面比平面正方形更适宜作为二维旅行商问题常数的测试床.
Majid Yousefikhoshbakht
2016-07-01
Full Text Available The TSP is considered one of the most well-known combinatorial optimization tasks and researchers have paid so much attention to the TSP for many years. In this problem, a salesman starts to move from an arbitrary place called depot and after visits all of the nodes, finally comes back to the depot. The objective is to minimize the total distance traveled by the salesman. Because this problem is a non-deterministic polynomial (NP-hard problem in nature, a hybrid meta-heuristic algorithm called REACSGA is used for solving the TSP. In REACSGA, a reactive bone route algorithm that uses the ant colony system (ACS for generating initial diversified solutions and the genetic algorithm (GA as an improved procedure are applied. Since the performance of the Metaheuristic algorithms is significantly influenced by their parameters, Taguchi Method is used to set the parameters of the proposed algorithm. The proposed algorithm is tested on several standard instances involving 24 to 318 nodes from the literature. The computational result shows that the results of the proposed algorithm are competitive with other metaheuristic algorithms for solving the TSP in terms of better quality of solution and computational time respectively. In addition, the proposed REACSGA is significantly efficient and finds closely the best known solutions for most of the instances in which thirteen best known solutions are also found.
最小比率旅行商问题的引力搜索算法求解%Gravitational Search Algorithm for Minimum Ratio Traveling Salesman Problem
刘勇; 马良
2013-01-01
The objective of the tradition traveling salesman problem is to minimize the total distances. But in fact, the salesman often considers the benefit. In this paper, minimum ratio traveling salesman problem is studied. In this problem, the objective function is the ratio between the total distances and total benefits. The objective function of minimum ratio traveling salesman problem is nonlinear while the objective function of traveling salesman problem is linear. So, it is much more difficult to solve minimum ratio traveling salesman problem. To solve this problem, a gravitational search algorithm is proposed. The algorithm is an optimization method inspired from the law of universal gravitation and Newton's Second Law. The calculation model based on speed and position is used. By random key method, the continuous positions of searching agents are converted to discrete orders of city visit. The implementation of the algorithm is given. The results of emulation and comparison experiment verify the feasibility and effectiveness of this algorithm in optimizing minimum ratio traveling salesman problem.%经典旅行商问题的目标函数是总路程最小,而在实际情况中往往会考虑旅行商的收益问题,研究了以总路程和总收益之比为目标函数的最小比率旅行商问题.由于该问题的目标函数是非线性的,比求解目标函数是线性的旅行商问题更为困难,为有效求解该问题,提出一种引力搜索算法.算法基于万有引力定律和牛顿第二定律进行寻优,并采用速度和位置的计算模型.同时结合随机键的编码方法,将搜索个体的连续位置转换为离散的城市访问顺序.给出了算法的具体实现方案,并通过仿真和比较实验验证算法的优化性能.实验结果表明该算法可以有效求解最小比率旅行商问题.
Syed Tauhid Zuhori
2012-02-01
Full Text Available The traveling salesman problem (TSP is one of the most widely studied NP hard combinatorial optimization problems and has already solved in the semi-optimal manners using numbers of different methods. Among them, Genetic Algorithms (GA are pre-dominating. In this paper I solve the problem with a new operator, Inver-over, for an evolutionary algorithm for the TSP. This operator outperforms all other 'genetic' operators, whether unary or binary, which was first introduced by Guo Tao and Zbigniew Michalewicz. I also propose a new algorithm for solving TSP. To get a comparative idea of the performance of these algorithms I solve same problems with the two algorithms. The performance analysis shows that my proposed algorithm produces relatively better solutions in the case of the tour length every time. But when we increase the cities it takes more time to solve than the Inver-Over operator for TSP.
Marek Antosiewicz
2013-04-01
Full Text Available We compare six metaheuristic optimization algorithms applied to solving the travelling salesman problem. We focus on three classical approaches: genetic algorithms, simulated annealing and tabu search, and compare them with three recently developed ones: quantum annealing, particle swarm optimization and harmony search. On top of that we compare all results with those obtained with a greedy 2-opt interchange algorithm. We are interested in short-term performance of the algorithms and use three criteria to evaluate them: solution quality, standard deviation of results and time needed to reach the optimum. Following the results from simulation experiments we conclude that simulated annealing and tabu search outperform newly developed approaches in short simulation runs with respect to all three criteria. Simulated annealing finds best solutions, yet tabu search has lower variance of results and converges faster.
Yousefikhoshbakht, Majid; Rahmati, Farhad
2012-01-01
This article presents a new algorithm which is a modified version of the elite ant system (EAS) algorithm. The new version utilizes an effective criterion for escaping from the local optimum points. In contrast to the classical EAC algorithms, the proposed algorithm uses only a global updating, which will increase pheromone on the edges of the best (i.e. the shortest) route and will at the same time decrease the amount of pheromone on the edges of the worst (i.e. the longest) route. In order to assess the efficiency of the new algorithm, some standard traveling salesman problems (TSPs) were studied and their results were compared with classical EAC and other well-known meta-heuristic algorithms. The results indicate that the proposed algorithm has been able to improve the efficiency of the algorithms in all instances and it is competitive with other algorithms.
魏超
2014-01-01
The traveling salesman problem (TSP) is one of the classical combinatorial optimization problems. Artificial bee colony algorithm is a new heuristic algorithm proposed in recent years. According to the model of the traveling salesman problem, artificial bee colony algorithm was designed to simulate an example solution. Compare artificial colony algorithm and genetic algorithm at the same time, the results show that the artificial colony algorithm can effectively solve the traveling salesman problem and has a certain advantage in terms of speed of convergence, computational efficiency and stability than genetic algorithm.%旅行商问题(TSP)是经典的组合优化问题之一。人工蜂群算法是近年来被提出的一种新的智能启发式算法。根据旅行商问题的模型特点，设计人工蜂群算法对算例进行仿真求解。同时将人工蜂群算法与遗传算法进行对比，结果表明：人工蜂群算法可以有效的求解旅行商问题，在收敛速度、计算效率、稳定性方面相对遗传算法具有一定的优势。
Application of Improved Prim Algorithm to Traveling Salesman Problem%改进的Prim算法在求解旅行商问题中的应用
刘朝霞
2015-01-01
Traveling salesman problem is a typical combinatorial optimization problem in graph theory , which has many similarities to the minimum cost spanning tree problem description of the problem .In some cases , the shortest tour path can be path formed by the minimum spanning tree to obtain the traveling salesman problem .This paper gives Prim algorithm , and the algorithm is improved , the improved Prim algorithm successfully solves the traveling salesman problem .%旅行商问题是图论中一个典型的组合优化问题，它的问题描述与图论中最小生成树问题的描述具有很多相似之处，在一些情形下，可以用最小生成树形成的路径来获得旅行商问题的最短巡回路径。首先给出了最小生成树Prim算法，然后对其算法进行了改进，通过改进的Prim算法成功求解了旅行商问题。
Death of the (traveling) salesman: primates do not show clear evidence of multi-step route planning.
Janson, Charles
2014-05-01
Several comparative studies have linked larger brain size to a fruit-eating diet in primates and other animals. The general explanation for this correlation is that fruit is a complex resource base, consisting of many discrete patches of many species, each with distinct nutritional traits, the production of which changes predictably both within and between seasons. Using this information to devise optimal spatial foraging strategies is among the most difficult problems to solve in all of mathematics, a version of the famous Traveling Salesman Problem. Several authors have suggested that primates might use their large brains and complex cognition to plan foraging strategies that approximate optimal solutions to this problem. Three empirical studies have examined how captive primates move when confronted with the simplest version of the problem: a spatial array of equally valuable goals. These studies have all concluded that the subjects remember many food source locations and show very efficient travel paths; some authors also inferred that the subjects may plan their movements based on considering combinations of three or more future goals at a time. This analysis re-examines critically the claims of planned movement sequences from the evidence presented. The efficiency of observed travel paths is largely consistent with use of the simplest of foraging rules, such as visiting the nearest unused "known" resource. Detailed movement sequences by test subjects are most consistent with a rule that mentally sums spatial information from all unused resources in a given trial into a single "gravity" measure that guides movements to one destination at a time.
Pei-Chann Chang; Wei-Hsiu Huang; Zhen-Zhen Zhang
2012-01-01
In this research,we introduce a new heuristic approach using the concept of ant colony optimization (ACO)to extract patterns from the chromosomes generated by previous generations for solving the generalized traveling salesman problem.The proposed heuristic is composed of two phases.In the first phase the ACO technique is adopted to establish an archive consisting of a set of non-overlapping blocks and of a set of remaining cities (nodes) to be visited.The second phase is a block recombination phase where the set of blocks and the rest of cities are combined to form an artificial chromosome.The generated artificial chromosomes (ACs) will then be injected into a standard genetic algorithm (SGA) to speed up the convergence.The proposed method is called "Puzzle-Based Genetic Algorithm" or "p-ACGA".We demonstrate that p-ACGA performs very well on all TSPLIB problems,which have been solved to optimality by other researchers.The proposed approach can prevent the early convergence of the genetic algorithm (GA) and lead the algorithm to explore and exploit the search space by taking advantage of the artificial chromosomes.
旅行商问题的人工免疫算法%An Artificial Immune Algorithm for Travelling Salesman Problem
李茂军; 舒宜; 童调生
2003-01-01
This paper presents an Artificial Immune Algorithm (AIA)simulating the biological immune systems, andoffers its basic principle and approach. Comparing AIA with Genetic Algorithm (GAs)simulating the biological evolu-tion process, the paper points out that the method producing new antibodies in AIA is more versatile than the oneproducing new individuals in GAs. AIA reflects mechanism of natural selection better than GAs does, as AIA selectseffective antibodies from all antibodies by the appetency between an antibody and an antigen and by the repulsion be-tween an antibody and another, while GAs selects new individuals of next colony by the proportion of individual fit-ness. For Travel Salesman Problem (TSP), this paper brings forward how to describe antibodies artificially, how toproduce original antibodies, how to compute the appetency between an antibody and an antigen and the repulsion be-tween an antibody and another, and works out several artificial immune operators producing new antibod-ies. Simulating examples show that AIA is a very effective method for TSP.
Jorge A. Ruiz-Vanoye
2012-07-01
Full Text Available In this paper, we show a survey of meta-heuristics algorithms based on grouping of animals by social behavior for the Traveling Salesman Problem, and propose a new classification of meta-heuristics algorithms (not based on swarm intelligence theory based on grouping of animals: swarm algorithms, schools algorithms, flocks algorithms and herds algorithms: a The swarm algorithms (inspired by the insect swarms and zooplankton swarms: Ant Colony Optimization algorithm – ACO (inspired by the research on the behavior of ant colonies, Firefly Algorithm (based on fireflies, Marriage in Honey Bees Optimization Algorithm - MBO algorithm (inspired by the Honey Bee, Wasp Swarm Algorithm (inspired on the Parasitic wasps, Termite Algorithm (inspired by the termites, Mosquito swarms Algorithm – MSA (inspired by mosquito swarms, zooplankton swarms Algorithm - ZSA (inspired by the Zooplankton and Bumblebees Swarms Algorithm – BSA (inspired by Bumblebees. b The school algorithms (inspired by the fish schools: The Particle Swarm Optimization algorithm – PSO (inspired by social behavior and movement dynamics of fish or schooling. c The flock algorithms (inspired by the bird flocks: the flocking algorithm, and the Particle Swarm Optimization algorithm (inspired on the dynamics of the birds, d The herd and pack Algorithms (inspired by the mammal herds and packs: bat algorithm (inspired by bat, wolf pack search algorithm - WPS (inspired by wolfs, Rats herds algorithm - RATHA (inspired by Rats, Dolphins Herds Algorithm - DHA (inspired by Dolphins and the feral-dogs herd algorithm - FDHA (inspired by feral-dogs herd.
Dubins Traveling Salesman Problem with Neighborhoods: A Graph-Based Approach
Jason T. Isaacs
2013-02-01
Full Text Available We study the problem of finding the minimum-length curvature constrained closed path through a set of regions in the plane. This problem is referred to as the Dubins Traveling Salesperson Problem with Neighborhoods (DTSPN. An algorithm is presented that uses sampling to cast this infinite dimensional combinatorial optimization problem as a Generalized Traveling Salesperson Problem (GTSP with intersecting node sets. The GTSP is then converted to an Asymmetric Traveling Salesperson Problem (ATSP through a series of graph transformations, thus allowing the use of existing approximation algorithms. This algorithm is shown to perform no worse than the best existing DTSPN algorithm and is shown to perform significantly better when the regions overlap. We report on the application of this algorithm to route an Unmanned Aerial Vehicle (UAV equipped with a radio to collect data from sparsely deployed ground sensors in a field demonstration of autonomous detection, localization, and verification of multiple acoustic events.
An Investigation of Starting Point Preferences in Human Performance on Traveling Salesman Problems
MacGregor, James N.
2014-01-01
Previous studies have shown that people start traveling sales problem tours significantly more often from boundary than from interior nodes. There are a number of possible reasons for such a tendency: first, it may arise as a direct result of the processes involved in tour construction; second, boundary points may be perceptually more salient than…
Zhu, Liping; Aono, Masashi; Kim, Song-Ju; Hara, Masahiko
2013-04-01
A single-celled, multi-nucleated amoeboid organism, a plasmodium of the true slime mold Physarum polycephalum, can perform sophisticated computing by exhibiting complex spatiotemporal oscillatory dynamics while deforming its amorphous body. We previously devised an "amoeba-based computer (ABC)" to quantitatively evaluate the optimization capability of the amoeboid organism in searching for a solution to the traveling salesman problem (TSP) under optical feedback control. In ABC, the organism changes its shape to find a high quality solution (a relatively shorter TSP route) by alternately expanding and contracting its pseudopod-like branches that exhibit local photoavoidance behavior. The quality of the solution serves as a measure of the optimality of which the organism maximizes its global body area (nutrient absorption) while minimizing the risk of being illuminated (exposure to aversive stimuli). ABC found a high quality solution for the 8-city TSP with a high probability. However, it remains unclear whether intracellular communication among the branches of the organism is essential for computing. In this study, we conducted a series of control experiments using two individual cells (two single-celled organisms) to perform parallel searches in the absence of intercellular communication. We found that ABC drastically lost its ability to find a solution when it used two independent individuals. However, interestingly, when two individuals were prepared by dividing one individual, they found a solution for a few tens of minutes. That is, the two divided individuals remained correlated even though they were spatially separated. These results suggest the presence of a long-term memory in the intrinsic dynamics of this organism and its significance in performing sophisticated computing. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.
Daniel E Acuña
Full Text Available Humans need to solve computationally intractable problems such as visual search, categorization, and simultaneous learning and acting, yet an increasing body of evidence suggests that their solutions to instantiations of these problems are near optimal. Computational complexity advances an explanation to this apparent paradox: (1 only a small portion of instances of such problems are actually hard, and (2 successful heuristics exploit structural properties of the typical instance to selectively improve parts that are likely to be sub-optimal. We hypothesize that these two ideas largely account for the good performance of humans on computationally hard problems. We tested part of this hypothesis by studying the solutions of 28 participants to 28 instances of the Euclidean Traveling Salesman Problem (TSP. Participants were provided feedback on the cost of their solutions and were allowed unlimited solution attempts (trials. We found a significant improvement between the first and last trials and that solutions are significantly different from random tours that follow the convex hull and do not have self-crossings. More importantly, we found that participants modified their current better solutions in such a way that edges belonging to the optimal solution ("good" edges were significantly more likely to stay than other edges ("bad" edges, a hallmark of structural exploitation. We found, however, that more trials harmed the participants' ability to tell good from bad edges, suggesting that after too many trials the participants "ran out of ideas." In sum, we provide the first demonstration of significant performance improvement on the TSP under repetition and feedback and evidence that human problem-solving may exploit the structure of hard problems paralleling behavior of state-of-the-art heuristics.
Lee, M D; Vickers, D
2000-01-01
MacGregor and Ormerod (1996) have presented results purporting to show that human performance on visually presented traveling salesman problems, as indexed by a measure of response uncertainty, is strongly determined by the number of points in the stimulus array falling inside the convex hull, as distinct from the total number of points. It is argued that this conclusion is artifactually determined by their constrained procedure for stimulus construction, and, even if true, would be limited to arrays with fewer than around 50 points.
基于遗传算法求解旅行商问题%Solution of Traveling Salesman Problem Based on Genetic Algorithm
王水平; 陆华; 赵广宇
2008-01-01
从应用的角度讨论了基于遗传算法的旅行商问题(Travelling Salesman Problem,简称TSP)的求解方法,并结合实例给出了求解过程和计算机仿真结果.在算法的仿真中,改进后的算法明显优于传统的遗传算法.这表明,该算法具有良好的可行性和实用性.
Application of Ant Colony Algorithm in K- person Traveling Salesman Problem%蚁群算法在K-TSP问题中的应用
黄席樾; 胡小兵
2004-01-01
针对K-TSP(K-person Traveling Salesman problem)问题,该文提出了一种利用蚁群算法求解该问题的新思路.该算 法采用k只蚂蚁共同构造问题的一个解,并通过多组(每组k只)蚂蚁相互协作最终达到搜索最优解的目的.实验结果显示,该算法行之有效,是一种求解K-TSP问题的有效算法.
Theoretical analysis of two ACO approaches for the traveling salesman problem
Kötzing, Timo; Neumann, Frank; Röglin, Heiko
2012-01-01
Bioinspired algorithms, such as evolutionary algorithms and ant colony optimization, are widely used for different combinatorial optimization problems. These algorithms rely heavily on the use of randomness and are hard to understand from a theoretical point of view. This paper contributes...... to the theoretical analysis of ant colony optimization and studies this type of algorithm on one of the most prominent combinatorial optimization problems, namely the traveling salesperson problem (TSP). We present a new construction graph and show that it has a stronger local property than one commonly used...
改进蚁群优化方法求解立体表面TSP问题%Improved ant optimization method for travelling salesman problems on cuboid
徐华丽; 苏守宝
2011-01-01
给出立体表面TSP问题的数学模型,提出一种改进的蚁群优化算法,用于解决立体表面TSP问题.该算法能快速找到最优路径或近似最优路径,得到的解质量较高且计算时间短.实验方法表明,改进后的蚁群算法在TSP的求解中,收敛速度和全局寻优能力均得到较大的提高.%This paper gives a mathematical model for solving travelling salesman problems on a cuboid and proposes an improved Ant Colony Optimization algorithom(ACO) to solve the travelling salesman problems on a cuboid.The improved algorithm can obtain the global optimal solution or an approximate solution which is greatly close to the optimal solution,and propose the high-quality solutions within shortest time.The experimental results demonstrate that this improved method has much higher convergence speed than that of the basic ant colony algorithm, and can jump over the region of the local minimum, and escape from the trap of a local minimum successfully.
Genetic Algorithm Based Immigrants for Dynamic Travelling Salesman Problem%基于移民策略求解动态TSP问题的遗传算法
付兴武; 张剑光
2011-01-01
在标准遗传算法(SGA)中加入移民策略可以丰富种群多样性,使SGA能够更好的适应环境的变化.为了改善基于移民策略的遗传算法在搜索空间内的探索能力,受原对偶映射思想的启发,设计了基于原对偶映射的移民策略(Primal-Dual based Immigrants,PDI),并将这种策略加入到遗传算法中,求解动态旅行商问题(Dynamic Travelling Salesman Problem,DTSP).仿真结果表明,与基于其他移民策略的遗传算法相比,PDIGA能够更好的适应环境的变化.%Add immigrants in the standard genetic algorithm can enrich the population diversity, so that SGA can better adapt to environment changes. In order to improve the space exploration search capabilities of genetic algorithm based on immigrants, inspired by primal-dual, designed Primal-Dual based Immigrants(PDI), and add PDI to SGA to solve the Dynamic Travelling Salesman Problem(DTSP). Simulation results show that PDIGA is better able to adapt to environment changes to other genetic algorithms based on immigrants.
蚁群和遗传混合算法求解旅行商问题%Hybrid Algorithm of Generation and Ant Colony on Traveling Salesman Problem
金晓龙
2014-01-01
Traveling salesman is a widely used optimized combined question. The ant colony and geneic hybrid algorithm is adopted to solve the traveling salesman problem. The problem that ant colony algorithm is prone to local optima is solved by using crossover and mutation mechanism of genetic algorithm.The hybrid algorithm is debugged in VBA.Finally, the hybrid algorithm is proved to be better than ant colony algorithm and geneic algorithm by comparing running data.%旅行商是应用广泛的优化组合问题，采用蚁群和遗传混合算法解决旅行商问题，利用遗传算法的交叉、变异机制解决蚁群算法易出现局部最优解的问题，将混合算法在VBA环境调试运行。混合算法与蚁群算法、遗传算法仿真数据比较，混合算法具有较好改进效果。
Hasegawa, M.
2011-03-01
The aim of the present study is to elucidate how simulated annealing (SA) works in its finite-time implementation by starting from the verification of its conventional optimization scenario based on equilibrium statistical mechanics. Two and one supplementary experiments, the design of which is inspired by concepts and methods developed for studies on liquid and glass, are performed on two types of random traveling salesman problems. In the first experiment, a newly parameterized temperature schedule is introduced to simulate a quasistatic process along the scenario and a parametric study is conducted to investigate the optimization characteristics of this adaptive cooling. In the second experiment, the search trajectory of the Metropolis algorithm (constant-temperature SA) is analyzed in the landscape paradigm in the hope of drawing a precise physical analogy by comparison with the corresponding dynamics of glass-forming molecular systems. These two experiments indicate that the effectiveness of finite-time SA comes not from equilibrium sampling at low temperature but from downward interbasin dynamics occurring before equilibrium. These dynamics work most effectively at an intermediate temperature varying with the total search time and thus this effective temperature is identified using the Deborah number. To test directly the role of these relaxation dynamics in the process of cooling, a supplementary experiment is performed using another parameterized temperature schedule with a piecewise variable cooling rate and the effect of this biased cooling is examined systematically. The results show that the optimization performance is not only dependent on but also sensitive to cooling in the vicinity of the above effec-tive temperature and that this feature is interpreted as a consequence of the presence or absence of the workable interbasin dynamics. It is confirmed for the present instances that the effectiveness of finite-time SA derives from the glassy relaxation
Integer Programming Modeling for the Problems of Traveling Salesman%旅行售货员问题的整数规划建模研究
冯俊文
2009-01-01
本文分别基于无向图和有向图,建立了旅行售货员问题(Traveling Salesman Problem)的显式整数规划模型,应用整数规划软件包求解之可以方便地确定出售货员的最优售货旅行路线.进一步,本文还讨论了随机旅行售货员问题,建立了相应的确定型等价模型.通过举例说明了各种模型的有效性.最后,本文还讨论了旅行售货员问题的可能推广及其建模问题.
基于遗传算法的旅行商问题仿真实现%Application Research of Genetic Algorithm in the Traveling Salesman Problem
胡玉兰
2002-01-01
从应用的角度讨论了基于遗传算法的旅行商问题(Travelling Salesman Problem,简称TSP)的求解方法,在应用遗传算法求解旅行商问题时,参数值的不同设定对解有不同的影响,结合旅行商问题具体实例,对参数值的变化进行了观察,当选择p\\-c=0.5,p\\-m=0.001时,得到了较为理想的最短旅行路径.
旅行商问题(TSP)的现代优化算法研究%Modern Optimization of Traveling Salesman Problem
蔡晨晓; 漆宇星
2008-01-01
TSP(Traveling Salesman Problem)旅行商问题是一类典型的NP完全问题,遗传算法是解决NP问题的一种较理想的方法.通过介绍基本遗传算法的基本原理;针对TSP问题,给出遗传算法在选择算子、交叉算子和变异算子等方面的编码实现.并就TSP问题的一个具体城市算例,进行了计算验证.在此基础上,对交叉算子和变异算子提出了改进,大量的计算数据验证了改进方法的有效性.
An Efficient Hybrid Genetic Algorithms for Traveling Salesman Problem%一种求解旅行商问题的高效混合遗传算法
姜昌华; 胡幼华
2004-01-01
旅行商问题(Travelling Salesman Problem TSP)是一个典型的组合优化难题,论文提出一种求解旅行商问题的高效混合遗传算法.该算法结合遗传算法和2-opt邻域搜索优化技术,并针对旅行商问题的特点,提出K近邻点集以缩减搜索空间从而加快求解速度.基于典型实例的仿真结果表明,此算法的求解效率比较高.
解旅行商问题的一个新进化算法%A Novel Evolutionary Algorithm for Travelling Salesman Problem
覃锦华; 谢作党; 王宇平
2007-01-01
旅行商问题(Travelling Salesman Problem,TSP)是一个著名的组合优化问题.提出用进化算法求解该问题.算法采用自然编码方式表示个体,设计了一种利用种群的边产生后代个体的新交叉策略.采用随机DoubleBridge变异策略,最后设计了结合2-交换和特殊3-交换的局部搜索算子改善解(个体)的质量.数值模拟实验表明,该算法是有效的.
一种求解函数优化问题的单亲遗传算法%A Partheno Genetic Algorithm for Traveling Salesman Problem
王斌; 李元香; 王治
2003-01-01
In this paper, a kind of Partheno Genetic Algorithm (PGA) based on Path Representation scheme is proposed for solving Traveling Salesman Problem (TSP). This algorithm employs only mutation and selection operators to produce the offspring,instead of traditional crossover operator. A specfiic mutation operator is designed combining the insertion operator with reversion operator,which ensures its strong searching capability. This algorithm simulates the recurrence of nature evolution process, while providing fewer control parameters. Experiments based on Ciunese 144 cities(CHN144)and 7 instances selected from TSPLIB are used to test the performance of this algorithm. They prove that it can reach the satisfying optimization at a faster speed. Especially,for the CHN144,the best path it finds is better than any other available one.
A Partheno Genetic Algorithm for Traveling Salesman Problem%一种求解TSP问题的单亲遗传算法
王斌; 李元香; 王治
2003-01-01
In this paper, a kind of Partheno Genetic Algorithm(PGA)based on Path Representation scheme is pro-posed for solving Traveling Salesman Problem(TSP). This algorithm employs only mutation and selection operatorsto produce the offspring, instead of traditional crossover operator. A specific mutation operator is designed combiningthe insertion operator with inversion operator, which ensures its strong searching capability. This algorithm simu-lates the recurrence of nature evolution process, while providing fewer control parameters. Experiments based onChinese 144 cities(CHN144)and 7 instances selected from TSPLIB are used to test the performance of this algorithm.They prove that it can reach the satisfying optimization at a faster speed. Especially, for the CHN144, the best pathit finds is better than any other available one.
Rodrigo A. Gómez-Montoya
2015-01-01
Full Text Available This paper has as its main objective the use of the TSP (Traveling Salesman Problem with graph theory in order to design routing strategies in a distribution network, looking forward an efficient way to be made in regard to distance and time used for attending the customer’s requirements. Additionally, the paper develops a case of application of the methodology in a Meat Company located in the city of Medellín. As a result, we find that the use of TSP with graph produces a route with the minimum distance in the distribution network; it was demonstrated in the case of application. Keywords: Distribution, graph, routing, transport, TSP
基于蚁群算法的旅行商问题的研究%Research for Solving Traveling Salesman Problem Based on Ant Colony Optimization
李辉
2015-01-01
It provides a powerful method of the design of distributed control and optimization for computer scientists that the study of social insect behavior. Research on swarm intelligence to ant colony algorithm as the representative has gradually become a research hotspot. Ant colony algorithm is very useful in real life, such as solving the traveling salesman problem, this paper introduces a solution of complex of the ant colony algorithm TSP, expounds the basic principle and realization process of the algorithm, and trys to use the coding form to be the basic ant colony algorithm applied to solve the traveling salesman problem.%群居性昆虫行为的研究为计算机科学家提供了设计分布式控制和优化算法的有力方法。对以蚁群算法为代表的群集智能的研究已经逐渐成为一个研究热点。蚁群算法在实际的生活中有很大的用处，比如求解旅行商问题，文章介绍了一种求解复杂TSP的蚁群算法，阐述了该算法的基本原理及实现过程，并且在本文中尝试用编码的形式将基本蚁群算法应用到求解旅行商问题中去。
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.
周辉仁; 唐万生; 牛犇
2009-01-01
针对最小化单个旅行商路程的多旅行商问题,提出了一种递阶遗传算法和矩阵解码方法.该算法根据问题的特点,采用一种递阶编码方案,此编码与多旅行商问题一一对应.用递阶遗传算法优化多旅行商问题不需设计专门的遗传算子,操作简单,并且解码方法适于求解距离对称和距离非对称的多旅行商问题.计算结果表明,递阶遗传算法是有效的,能适用于优化多旅行商问题.%In order to solve a kind of longest-path-shortest multiple traveling salesman problem, a hierarchi-cal genetic algorithm and decoding method with matrix is proposed. Its coding method is simple and can effec-tively reflect the traveling policy, and the methods of crossover and mutation are not special to design. By this method, symmetric and asymmetric multiple traveling salesman problems can be easily solved. The computa-tional results show that the hierarchical genetic algorithm is efficient and fits for multiple traveling salesman problems.
董敏; 汤建钢
2011-01-01
Traveling Salesman Problem（TSP）is a typical NP-complete problem.In combination with the advantages of sticker and delection models,which are two basic kinds of DNA computing models,the sticker-delection model has been formulated,and a new DNA algorithm for TSP based on this model has been proposed.%旅行商问题（Traveling Salesman Problem,TSP）是一个典型的NP完全问题.粘贴和删除模型是DNA计算的两个基本计算模型.结合上述两个模型的优点,构造粘贴-删除模型,并利用该模型给出求解旅行商问题一种新的DNA算法.
旅行商问题中巡回路径的数据结构%Data Structure of Tour for Traveling Salesman Problem
宗德才; 王康康
2014-01-01
The data structure of tour for the traveling salesman problem plays a critical role in the efficiency of local heuristic algorithms. The data structure of tour must permit queries about the relative order of cities in the tour and must allow sections of the tour to be re-versed. The implementation and time complexity of several basic operations when the tour is represented by array,splay tree and two-lev-el tree are analyzed. The array-based representation of a tour permits the relative order of cities to be determined in small constant time, but requires worst-caseΩ( n) time to implement a reversal,which renders it impractical for large instances. For the data structure based on splay tree,all queries and updates take amortized time O( logn) ,which is available for extremely large-scale traveling salesman problem. For the data structure based on two-level tree representation,the worst-case time for each update operation is O( n0. 5 ) ,which is available for large-scale traveling salesman problem.%旅行商问题中巡回路径的数据结构对局部启发式算法的效率起着非常关键的作用。巡回路径的数据结构必须能够查询一条回路中每个城市的相对顺序，并且能够将一条回路中的部分城市逆序。分析了数组表示法、伸展树表示法和两级树表示法表示巡回路径时各种基本操作的实现过程及时间复杂度。数组表示法能够在常数时间内确定一条回路中每个城市的相对顺序，但是最坏情况下完成逆序操作需要Ω( n)时间，不适用于大规模的旅行商问题。伸展树表示法执行查询和更新操作的平摊时间复杂度是O( logn)，适用于极大规模的旅行商问题。而两级树表示法在最坏情况下每一个更新操作的时间复杂度是O( n0. 5 )，适用于大规模的旅行商问题。
Muhammad Ali Ismail
2011-08-01
Full Text Available With the arrival of multi-cores, every processor has now built-in parallel computational power and that can be fully utilized only if the program in execution is written accordingly. This study is a part of an on-going research for designing of a new parallel programming model for multi-core processors. In this paper we have presented a combined parallel and concurrent implementation of Lin-Kernighan Heuristic (LKH-2 for Solving Travelling Salesman Problem (TSP using a newly developed parallel programming model, SPC3 PM, for general purpose multi-core processors. This implementation is found to be very simple, highly efficient, scalable and less time consuming in compare to the existing LKH-2 serial implementations in multi-core processing environment. We have tested our parallel implementation of LKH-2 with medium and large size TSP instances of TSBLIB. And for all these tests our proposed approach has shown much improved performance and scalability.
均匀设计在求解TSP问题中的应用%Applying Uniform Design to Solve Traveling Salesman Problem
赵曦; 李颖
2011-01-01
利用均匀设计抽样的理论和方法,针对遗传算法解决旅行商问题.将遗传算法基本模型的参数设定问题描述成均匀设计中多因素多水平的试验设计.确定参数后再运用均匀设计产生初始种群.用TSP问题库内的基准问题进行仿真实验.证明了该方法是有效的.%The principle and method of Uniform design are used to determine the parameters of genetic algorithm to solve Traveling Salesman Problem by convert the problem into the experimental design of multi-factor and multilevel.Uniform design is applied again to produce the initial population.The method applied to the benchmark problems of TSPLIB shows it's effectiveness.
求解旅行商问题的二阶段演化算法%Two-stage evolutionary algorithm for traveling salesman problem
王玉亭; 孙剑; 李俊青; 潘全科
2010-01-01
对Inver-over算子进行了改进,提出了1st-Inver-over算子和2nd-Inver-over算子,实现了求解TSP问题的基于改进Inver-over算子的二阶段演化算法(Two-stage Inver-over EA).在算法前期,只采用1st-Inver-over算子来保证算法的收敛速度;在算法后期,根据种群的多样性自适应地选取1st-inver-over算子和2nd-Inver-over算子来协调算法的收敛速度和种群的多样性.在TSPLIB(Traveling Salesman Problem Library)中的典型实例上的实验结果表明,Two-stage Inver-over EA比经典的GT算法具有更好的收敛性和搜索效率.
基于求解 TSP 问题的改进贪婪算法%An Improved Greedy Heuristic Based on Solving Traveling Salesman Problem
饶卫振; 金淳
2012-01-01
分析了求解旅行商问题(Traveling Salesman Problem,TSP)的经典贪婪算法(Greedy Heuristic,GR)的特点,发现影响 GR 求解质量的主要因素是在构造后期添加的边过长,从而导致最终求解质量不高.为此,借鉴Held Karp 模型的思路,构造了一种新的距离矩阵改造法(Transforming Distance Matrix, TDM). GR 结合 TDM 得到的改进贪婪算法 GR-TDM 能够有效地克服传统 GR 在构造后期添加长边的缺点.通过计算来自 TSP 算例标准库和 TSP 世界挑战赛网站中的40个算例表明,GR-TDM 耗时较 GR 仅增加了0.5~2%,然而 GR-TDM 的求解质量较传统的 GR 提高了43%.另外,通过与当前构建型算法比较发现,GR-TDM 的求解性能达到一流构建型算法水平.
模糊人工蜂群算法的旅行商问题求解%Fuzzy artificial bees colony algorithm for solving traveling salesman problem
柳寅; 马良
2013-01-01
Aiming at the premature convergence problem in traditional intelligent optimization algorithm,this paper proposed a fuzzy artificial bees colony algorithm,it based on the principles of fuzzy processing and bees colony behavior.It introduced fuzzy inputs and fuzzy outputs into the algorithm to maintain dynamic updates of the nectar access probability.According to effective adjustment on nectar access probability during the different stages of algorithm calculation,the algorithm avoided local optima.Simulation tests of traveling salesman problem and comparisons with other algorithms show the performance of proposed algorithm.The computational results prove the algorithm is feasible and effective.%针对传统人工智能算法早熟收敛问题,基于模糊化处理和蜂群寻优的特点,提出一种模糊人工蜂群算法,将模糊输入/输出机制引入到算法中来保持蜜源访问概率的动态更新.根据算法计算过程中的不同阶段对蜜源访问概率有效调整,避免算法陷入局部极值.通过对旅行商问题的仿真实验和与其他算法的比较来验证算法的性能.计算结果表明,该算法有良好的鲁棒性和有效性.
求解大规模旅行商问题的改进大洪水算法%Modified Great Deluge Algorithm for Large-scale Travelling Salesman Problem
盛虹平; 马良
2012-01-01
Great deluge algorithm is one of heuristics by simulating the process of flood rising to search global optimization. r-Opt algorithm is usually applied in path optimization. For the travelling salesman problem, this paper gives a modified great deluge algorithm which mainly combines great deluge algorithm with r-opt algorithm, and it can be used to solve the large-scale and super large-scale travelling salesman problem. The algorithm is programmed in Delphi 7, and is tested through series of standard instances from TSPLIB. The errors between the algorithm results and the best results published in TSPLIB are almost below \\%. The algorithm is proved to be a kind of new method to solve the difficult large-scale travelling salesman problem.%大洪水算法是通过模拟洪水上涨过程来进行全局寻优的启发式算法,r-opt算法是一类常用的路径改进算法.本文针对旅行商问题,提出一种将二者有机融合的改进大洪水算法,可用于快速求解大规模和超大规模的TSP问题.算法在Delphi7环境下编程实现,经过大量TSPLIB中的数据实例进行测试和验证,求解结果与已公布的最好结果误差基本都在1％以下,为困难的大规模旅行商问题提供了新的求解手段.
Solutions to Traveling Salesman Problem (TSP) Based on Self-Organizing Maps (SOM)%基于自组织网络的货郎担问题解决方案
田胜
2005-01-01
货郎担问题(Traveling Salesman Problem,TSP)作为组合数学中的经典问题,具有一定的研究价值.首先陈述了基于自组织网络(Self-Organizing Maps,SOM)的TSP问题的解决方案,然后着重分析为什么SOM网络能够体现这样的计算智能,并探讨了如何将其应用到其它的优化问题当中.
Esquivel E, J.; Ordonez A, A. [Universidad Autonoma del Estado de Mexico, Facultad de Ingenieria, Cerro de Coatepec s/n, Toluca, Estado de Mexico (Mexico); Ortiz S, J. J. [Departamento de Sistemas Nucleares, ININ, Carretera Mexico-Toluca s/n, Ocoyoacac 52750, Estado de Mexico (Mexico)
2008-07-01
In this paper we present some results obtained during the development of optimization systems that can be used to design refueling and patterns of control rods in a BWR. These systems use ant colonies and Greedy search. The first phase of this project is to be familiar with these optimization techniques applied to the problem of travel salesman problem (TSP). The utility of TSP study is that, like the refueling design and pattern design of control rods are problems of combinative optimization. Even, the similarity with the problem of the refueling design is remarkable. It is presented some results for the TSP with the 32 state capitals of Mexico country. (Author)
刘欣欣; 陈宝兴
2014-01-01
The traveling salesman problem (TSP) is a NP-hard problem which widely studied in combinatorial optimization dom-ain. A new operator, named gene fragment inserting, is proposed in this paper. By using this operator, an evolution algorithm for solving travel salesman problem is presented. Experiment results show that the proposed algorithm can find an approximate optimal solution for TSP with a high probability.%旅行商问题是组合优化中一个广泛研究的NP-hard问题。本文引入了一种新的运算方式：基因片段插入，并利用此运算给出了一种求解旅行商问题的演化算法。实验结果表明，此算法能以较高的概率找到旅行商问题的近似最优解。
党建武; 陈轶星
2001-01-01
提出了一种模拟生物遗传的进化算法，并将该算法应用于旅行商问题得到了较好的结果.根据达尔文进化论的优化过程，结合自然选择原则提出了启发式算法，该算法的时间复杂性与快速排序策略相当.在文中利用该算法求解中国旅行商问题得到目前的最佳结果.%A genetic algorithm simulating evolution is proposed to yieldnear-optional solution to the Travelling Salesman Problem. Noting that Darwinian Evolution is itself optimization process, we propose a heuristic algorithm that incorporates the tents of natural selection. The time complexity of this algorithm is equivalent to the fastest sorting scheme. The alogrithm is used to solve the China-Travelling Salesman Problem, the shortest route is obtained in this paper.
董改芳; 付学良
2013-01-01
In order to effectively improve the calculation results of hybrid optimization algorithm for large-scale traveling salesman problem ( traveling salesman problem, TSP ) instances, a parallel algorithm is developed and a visual parallel computing platform is provided. The platform can realize batch calculation, call the Java corresponding packets to achieve SSH2 protocol, use a remote Linux command to realize task submission, obtain results data stream, connect Excel to achieve results statistics, and make results visualization. The simulation results show that the method is feasible and has better performance than the corresponding serial algorithm.%为有效提高混合优化算法对大规模旅行商问题实例的计算效果,开发了并行算法,提供了一个可视化并行计算平台.该平台可实现批量实例计算,调用Java相应的包实现SSH2协议,利用远程Linux命令实现任务提交,获取计算结果数据流,连接Excel实现计算结果统计,并将结果可视化.仿真结果表明:该方法可行,且性能优于相应的串行算法.
陈明华; 周本达; 任哲
2011-01-01
0引 言 旅行商问题(Traveling Salesman Problem：TSP)是十分重要的组合优化问题,它在计算机科学、运筹学及工程等领域都有着广泛的应用.巡回旅行商问题即给定一组N个城市和它们两两之间的直达距离,寻找一条闭合的旅程,使得每个城市刚好经过一次且总的旅行距离最短.%It is well known that the GA is a guided random search and the guiding direction always aims at the family whose ancestors have schemata with high fitness. Based on the results, the crossover operation in GA is redesigned by using the principle of Latin Hypercube Sampling and combining the 2-opt locale search strategy. Then a new GA called Genetic Algorithm based on Latin Hypercube Sampling is presented. The new GA is applied to solving the Traveling Salesman Problem. Compared to simple GA and Good Point GA for solving this problem, the simulation results show that the new GA has superiority in speed, accuracy and overcoming premature.
Application of particle filter algorithm in traveling salesman problem%利用粒子滤波求解旅行商问题
吴新杰; 黄国兴
2012-01-01
The existing optimization algorithm for solving the Traveling Salesman Problem (TSP) easily falls into local extremum. To overcome this shortcoming, a new optimization method based on the particle filter, which regarded the searching process of the best route of TSP as a dynamic time-varying system, was brought forward. The basic ideas using particle filter principle to search the best route of TSP were enunciated, and its implementation procedures were given. In order to reduce the possibility of sinking into local extreme, the crossover and mutation operator of Genetic Algorithm ( GA) was introduced into the new optimization algorithm to enhance the variety of particles in the sampling process. Finally, the simulation experiments were performed to prove the validity of the new method. The new optimization method based on particle filter can find better solutions than those of other optimisation algorithms.%针对现有优化算法求解旅行商问题(TSP)时容易陷入局部极值的缺点,提出一种基于粒子滤波的优化搜索算法,该算法将TSP最优路径的搜索过程看成是一个动态时变系统.阐述了利用粒子滤波求解TSP最优路径的基本思想,给出了该方法的具体实现步骤.为了增强算法跳出局部极值的能力,在采样过程中引入了遗传算法的交叉和变异操作来丰富样本的多样性.最后为了验证新算法的有效性,进行了仿真实验,结果表明基于粒子滤波的优化算法能够找到比其他优化算法更好的解.
朱玲湘; 廖芹; 邹亮
2004-01-01
介绍了TSPPC(Traveling Salesman Problem with Precedence Constraint),并指出了普通遗传算法对于求解TSPPC的局限性及在算法过程中产生大量非可行解,从而降低了算法的搜索效率.提出了基于TSPPC中约束条件的种群初始化、交叉操作以及变异操作.由于运用这些遗传操作在算法过程中不会产生非可行解,因此大大提高了算法的搜索效率.最后通过定理和算例验证了本文中提出的遗传算法.
赵曦; 林健良; 卢修泉; 黄翰
2006-01-01
按照费用函数满足约束条件的不同,可以把广义旅行商问题(Generalized Traveling Salesman Problem,简称GTSP)分为两类.目前,对GTSP解法的研究主要是面向费用函数满足三角不等式的第一类问题,而对于费用函数不满足三角不等式的第二类问题,则研究的比较少.文章针对第二类GTSP问题,提出了在广义染色体中加入虚顶点的新遗传算法.经过14个TSP问题库内的基准问题的测试表明,新算法是有效的.
蒋望东; 林士敏
2007-01-01
基于遗传算法的求解TSP(Traveling Salesman Problem)研究是近几年的研究热点.设计高效的遗传算法求解,有重要的理论意义和实用价值.本文考察了基于整数编码的遗传算法的选择算子、交叉算子、变异算子,运用选择性集成的思想,将几种算子集成,随进化的进程对交叉概率和变异概率做自适应调整,用Matlab编写遗传算法程序,求解中国31城市TSP问题,获得了优于目前同类工作的结果.
杨丽; 李平; 秦亚玲
2006-01-01
针对量子进化算法(Quantum-inspired Evolutionary Algorithm,QEA),在解决实际问题中遇到的困难,提出一种改进的量子进化算法,应用于求解旅行商问题(Travelling Salesman Problem,TSP),并提出了TSP中的Hamilton圈的随机搜索编码技术.通过求解TSP问题库中的部分问题,表明改进的算法比经典的量子进化算法及免疫遗传算法具有更快的收敛速度和更好的全局寻优能力.
Dynaseareh Algorithms for Solving Time Dependent Traveling Salesman Problem%用动态搜索算法求解时间依赖型旅行商问题
李妍峰; 李军; 赵达
2008-01-01
为解决基于时段的时间依赖型旅行商问题(time-dependent traveling salesman problem,TDTSP),提出处 理跨时段的方法,并建立了相应的数学模型.用动态搜索算法ds-k-opt(k=2,2.5,3)分别求解该问题.仿真算例表明,动态搜索算法中部分ds-2.5-opt解和绝大部分ds-3-opt解优于动态规划启发式算法,且能求解更大规模的TDTSP问题.动态搜索算法的解随k的增大而更优,但运算时间也更长.
童行行; 王凌; 何京芮
2002-01-01
旅行商问题(Traveling Salesman Problem,TSP)是典型的NP-hard问题.通过对已有以最近插入法为代表的构造性算法的分析,提出了一种具有多项式时间性能的基于参考点的相邻插入法及其改进策略,其时间复杂度分别为O(n2)和O(n3),同时基于典型算例的仿真研究验证所提出算法的有效性和高效性.
Two-level degradation hybrid algorithm for multiple traveling salesman problem%一种求解多旅行商问题双层降解混合算法
林冬梅; 王东; 李娅
2011-01-01
This paper put forward a new two-level degradation hybrid algorithm for quickly solving the multiple traveling salesman problems. Top-level degradation divided the original problem into some sub-class problems according to the distribution property of the problem space. Low-level degradation converted these sub-class problems to some corresponding classical traveling salesman problems. The difficulty solving these sub-class problems would be cut down while decreasing the initial edge number of these problems. Finally, could solve high-quality solutions by exact algorithm. The contrast experiments with the same type algorithms show that the computation time of the new algorithm is shorter and the solving quality of the new algorithm is higher. This shows that the new algorithm is effective and efficient.%为了能快速近似求解多旅行商问题,提出了双层降解混合算法.首层降解根据问题空间展布特性,利用聚类技术将问题分解为若干子类问题,底层降解将子类问题转换为经典的旅行商问题,通过缩减子类问题初始状态下的边数量,使得子类问题求解难度得到再度降低,最终利用精确算法进行求解能够得到高质量优化解.对比实验表明双层降解混合算法具有计算时间短和求解质量高的优势,说明了新算法的有效性和高效性.
Antonio Augusto Chaves
2007-08-01
Full Text Available O Problema do Caixeiro Viajante com Coleta de Prêmios (PCVCP pode ser associado a um caixeiro que coleta um prêmio em cada cidade visitada e paga uma penalidade para cada cidade não visitada, com um custo de deslocamento entre as cidades. O problema encontra-se em minimizar o somatório dos custos da viagem e penalidades, enquanto inclui na sua rota um número suficiente de cidades que lhe permita coletar um prêmio mínimo preestabelecido. Este trabalho contribui com o desenvolvimento de metaheurísticas híbridas para o PCVCP, baseadas em GRASP e métodos de busca em vizinhança variável (VNS/VND para solucionar aproximadamente o PCVCP. De forma a validar as soluções obtidas, propõe-se uma formulação matemática a ser resolvida por um solver comercial, objetivando encontrar a solução ótima para o problema, sendo este solver aplicado a problemas de pequeno porte. Resultados computacionais demonstram a eficiência da abordagem híbrida proposta, tanto em relação à qualidade da solução final obtida quanto em relação ao tempo de execução.The Prize Collecting Traveling Salesman Problem (PCTSP can be associated to a salesman who collects a prize in each city visited and pays a penalty for each city not visited, with travel costs among the cities. The objective is to minimize the sum of the travel costs and penalties, including in the tour enough number of cities that allow collecting a minimum prize. This paper contributes with the development of a hybrid metaheuristic to PCTSP, based on GRASP and search methods in variable neighborhood (VNS/VND to solve PCTSP approximately. In order to validate the obtained solutions, we proposed a mathematical formulation to be solved by a commercial solver to find the best solution to the problem, being this solver applied to small problems. Computational results demonstrate the efficiency of the proposed method, as much in relation to the quality of the obtained final solution as in relation
李锋
2011-01-01
多目标旅行商问题(MOTSP)是经典旅行商问题的扩展,其优化目标包含了距离、成本、收益及风险等多个相互冲突的指标.本文提出了一种基于偏好的Pareto演化算法p-PEA用于建模并求解此NP-hard问题.该优化算法建立在MOTSP的智能体仿真模型之上,从而解决了数学建模不能真实再现实际MOTSP中众多影响因素的问题.通过仿真的方法,算法能够得到MOTSP可行解的各项评价指标值.在此基础士,通过设计演化算法搜索问题的Pareto优化解集.其中,将决策者的决策偏好信息引入到Pareto优化解集的求解过程中,所得结果将更合理.最后,以一个130个城市的旅行商问题为例验证了算法的有效性.%The multi-objective traveling salesman problems (MOTSP) are a generalization of the well-known traveling salesman problem where multiple conflicting objectives include optimizing distance, cost, profit, risk of the tour, etc. This paper proposes a preference-based Pareto evolutionary algorithm, named p-PEA, to model and solve this NP-hard problem. The algorithm is built on framework of agent-based simulation model, where MOTSP is represented as an agent model. In this way, various factors of practical MOTSP are easier involved in the model, than the mathematics approaches. Based on agent simulation, multi-objective data of feasible solutions are collected from simulation output. Furthermore, an evolutionary algorithm is adopted to search Pareto-optimal solutions. In the p-PEA algorithm, preference information of decision-maker is introduced to search preferred Pareto-optimal solutions. Finally, the proposed p-PEA algorithm is applied to a bi-objective TSP instance with 130 cities to demonstrate its validity and effectiveness.
吴婷; 陈玉旺; 汪烨
2010-01-01
旅行商问题(traveling salesman problem,TSP)具有很强的理论研究和工程应用价值.在定义离散状态变量和局部适应度的基础上,分析了TSP优化解的微观特征;将自组织临界(self-organized criticality,SOC)的概念引入到组合优化领域,提出了一种基于极值动力学的自组织优化算法.该算法利用快速下降和间断涨落的动态搜索过程,高效地遍历解空间中的局部最优解.针对TSPLIB中典型实例,计算结果表明其求解效率和优化性能均优于模拟退火和遗传算法等优化方法.文中算法提供了一种全新的思路,有助于从系统角度理解组合优化问题的复杂性,并分析合理的优化动力学过程.
米永强
2014-01-01
蚁群算法是一种求解组合优化问题较好的方法。在蚁群算法的基本原理基础上，以旅行商问题为例，介绍了该算法求解TSP的数学模型及具体步骤，并通过仿真实验与粒子群优化算法等方法比较分析，表明了该算法在求解组合优化问题方面具有良好的性能。%Ant colony algorithm is a kind of good methods to solve the combinatorial optimization problems. Based on the basic principle of ant colony algorithm, for traveling salesman problem as an example this paper, this paper introduced the mathematical model of the algorithm to solve TSP and specific steps, through the simulation experiments and comparative analysis with particle swarm optimization algorithm and others, it showed the algorithm has good performance in solving combinatorial optimization problems.
Forest Fire Patrol Path Optimization Based on the Traveling Salesman Problem%基于旅行商问题的森林防火巡逻路径优化
强添纲; 任亚平
2015-01-01
在对传统TSP(traveling salesman problem,旅行商问题)模型进行研究的基础上,通过传统TSP模型和森林防火巡逻路径模型的比较,提出一种新的森林防火巡逻路径模型,并根据该模型对TSP算法进行第一次改进.然后,又在第一改进的前提下,首次将三维空间概念引入TSP算法,实现TSP算法的二次改进.随后对两次不同程度的改进分别进行了测试和分析.结果表明,两次改进优化效果都十分明显,第一次测试的路径优化效率达到61.6％,第二次测试的优化效率也达到47.9％.
饶卫振; 金淳; 陆林涛
2013-01-01
分析了贪婪算法(Greedy algorithm,GRA)求解欧几里德旅行商问题(Euclidean Traveling Salesman Problem,ETSP)的求解质量和求解耗时的特点,发现边位置信息是影响GRA的求解质量和求解耗时的主要因素,在Michael模型基础上提出了一种考虑添加边所在位置信息的改进贪婪算法(Improved Greedy algorithm,IMGRA),并阐述了IMGRA的设计思想和相应的构造方法.分别采用IMGRA和GRA求解了90个算例,结果表明:固定参数下的IMGRA平均求解质量较GRA提高55％,求解耗时降低20％.为此,对IMGRA比GRA求解质量更高和求解耗时更短的原因进行了分析.
冀俊忠; 黄振; 刘椿年; 代启国
2010-01-01
针对蚁群算法在求解大规模旅行商问题(Traveling Salesman Problems,TSP)中时间性能方面的不足,提出了一种快速的求解算法.首先,从TSP问题描述入手,给出了一种新的多粒度的问题描述模型;然后,基于该模型,设计了包括基于密度聚类的粒度划分、粗粒度的蚁群寻优、粒度间的连接、细粒度的蚁群寻优、粒度间可行解的合成以及循环分段优化6个阶段在内的求解算法.算法的复杂度分析及在中、大规模TSP问题上的实验表明:本算法的时间性能不仅比经典的蚁群算法有显著的提高,而且与近年来的一些同类算法相比也具有一定的优势,显示了快速求解大规模TSP问题的能力.
刘萍; 高军; 丁筱玲
2012-01-01
针对工业钢构打字加工路径的组合优化目标，为尽量减少换刀次数和优化刀具移动轨迹，使走刀时间最短，提出建立基于旅行商问题（TSP）的非确定型多项式数学模型，并应用遗传算法（GA）对钢构打字刀具路径的优化问题进行分析、研究和解答。通过合理安排工序和换刀、走刀路径，在不改变机床硬件的前提下，尽可能缩短加工时间。经MATLAB工具箱仿真实验证明，该研究能很好地解决目前我国钢构打字路径寻优问题，使打字过程中的定位精度和加工效率都得到较大提高。%Industrial steel typing processing path optimization goal, to minimize the number of tool changing and optimizing tool moving trajectory, so that the tool path with the shortest time, proposed the establishment based on the traveling salesman problem （TSP） of nondeterministic polynomial mathematical models, and the application of genetic algorithms （GA） on steel typing tool path optimization of analysis, research and solve. Through reasonable arrangement of process and tool, tool path, without changing the machine hardware under the premise, as far as possible to shorten the processing time. The MATLAB toolbox simulation experiments, the study can well solve at present our country steel typing route optimization problem, so that the typing process precision and processing efficiency has been greatly improved.
赵敬和; 谢玲
2011-01-01
针对旅行商问题（TSP）具有的易于描述却难以处理的NP完全难题、其可能的路径数目与城市数目是呈指数型增长的、求解困难的特点。本文首次采用LabVIEW仿真实现模拟退火算法来求解该问题。仿真结果表明LabVIEW独有的数组运算规则可有效的实现该算法求解TSP问题，相比较其它方法，该方法更简单、实用、计算精度高、速度快，并且适合任意城市数目的TSP问题。%For the NP-complete hard problem which is easy to be described,but hard to be solved and the possible amounts of path increase exponentially with the amounts of city in Traveling Salesman Problem ,both resulting TSP is difficult to solve,this paper uses Simulated Annealing based on LabVIEW simulation to solve the problem for the first time. LabVIEW simulation results show that its unique array algorithms can effectively implement the Simulated annealing for TSP.Compared to other methods,this method is more simple,more practical and more precise.In addition, it has higher speed and is suitable for the TSP with any number of cities.
Discrete bat algorithm for solving minimum ratio traveling salesman problem%求解最小比率旅行商问题的离散蝙蝠算法
李枝勇; 马良; 张惠珍
2015-01-01
研究了以总路程与总收益之比为目标函数的最小比率旅行商问题，提出了求解该问题的离散蝙蝠算法。介绍了蝙蝠算法的基本思想，重新定义了位置与位置的减法操作算子、实数与位置的乘法操作算子以及速度与位置的加法操作算子，引入了城市子序列逆序策略来对线路进行局部搜索。给出了算法的具体实现方案，并通过仿真和比较实验验证算法的优化性能，实验结果表明该算法可以有效求解最小比率旅行商问题。%This paper studied minimum ratio traveling salesman problem(MRTSP),which objective function was the ratio be-tween the total distances and total benefits,and presented a discrete bat algorithm for solving MRTSP.In this improved bat al-gorithm,on the one hand,it redefined the subtraction operator of location and location,the multiplication operator of real number and location,and the addition operator of velocity and location.On the other hand,it introduced the reversing the city subsequence in order to perform the route’s local search.The experimental results show that this improved bat algorithm is feasible and can effectively solve the MRTSP instances.
Traveling salesman problem of the graph of which the vertices may have the same names%结点可同名图的旅行商问题
胡广朋; 韦余娟; 郁甲; 章睿
2013-01-01
With the rapid development of economy,tourism is getting popular.The general visitors' the time and money is limited and how to spend the least amount of time and money to play all the citys that the visitors want to go is traveling salesmen' the most difficult problem.For this problem,this paper puts forward an algorithm for solving the TSP that based on the graph of which the vertices may have the same names.Firstly,allocate all the cities into several specific classifications for this TSP.Then,choose one city from every classification and calculate its total distance.At last,choose the optimal road.This algorithm is easy to implement and fast to operate.Thus time and money is saved.%随着经济的快速发展,旅游业也大量兴起.但是一般游客的时间和金钱有限,怎么才能花最少的时间和金钱游玩所有想去的城市成了旅行商为大的难题.基于此问题,提出了基于结点可同名求解TSP的算法,首先将旅行商要走的所有城市分成几类,然后在每类城市中选取一个城市来走,并计算出总的距离,最后选取出一条最优的路径.算法实现容易,运行速度快,解决了一类新的TSP问题.在很大程度上给旅行商节约了时间和金钱.
强宁; 康凤举
2015-01-01
To overcome the premature convergence of the standard particle swarm optimization (PSO)in solving multiple travelling salesman problems (MTSP),a new acceleration particle swarm optimization is constructed.Rely on the idea of mechanics,the movement of particle is de-scribed as search motion driving by force in solution space.The particle is attracted by personal best force,global best force and repelled by local best force.Thus the acceleration of particle de-pends on the resultant of forces.Using convergence criterions to estimate premature conver-gence,the local best will repel all the particles when premature convergence occurs,so the parti-cle swarm can jump out the local best and continue to search.In order to improve the efficiency of the algorithm,a dimensional learning strategy of particle and a new coding method are designed for MTSP.The simulation results show that the proposed algorithm can effectively overcome the premature convergence,and improve the quality and stability of solutions.Thus it provides a fea-sible method for MTSP.%标准粒子群算法（PSO）在求解多旅行商问题（MTSP）时易发生早熟收敛，为此提出一种新的加速度粒子群算法。借鉴力学思想将粒子的运动描述为受力以后在解空间中的搜索运动，粒子受个体最优、全局最优的牵引力，并受局部最优的排斥力，加速度由粒子所受的合力决定。通过审敛操作判断早熟收敛，当发生早熟时局部最优对所有粒子产生的排斥力使种群跳出局部最优继续搜索。为进一步提高算法效率，针对 MTSP 问题的特点设计了基于维度的粒子学习策略和编解码方法。仿真结果表明，该算法能够有效克服早熟收敛，从而提高解的收敛性和稳定性，为 MTSP 问题提供了一种可行的方法。
虞先玉; 胡桂开; 徐辉
2009-01-01
神经网络方法求解流动推销员问题(Travel Salesman Problem,简称TSP问题)时,往往产生不满足TSP的单回路约束的不可行解.基于协同神经网络的方法解决TSP,并设计了一个回路合并算法,确保得到满足TSP的单回路约束的解.通过算例进行数值模拟,并且比较了新算法、标准遗传算法和标准模拟退火算法的求解结果.实验结果表明,说明该方法在求解TSP 问题上是行之有效的.
蔚承建; 何振亚; 张毅锋; 杨绿溪
2000-01-01
本文扩展了基于人口的增量学习算法使其每个基因可呈现多个品质值，这反映了自然演化系统中基因型和表现型的多向性和多源性，提出了用熵来判断进化过程的可进化性.用该方法求解典型的组合优化问题—旅行推销员问题，多数结果优于最好的进化算法结果.%In this paper the population-based incremental learning method is extended to a form of multiple traits for one gene to reflect pleiotropic and polygenic characters in natural evolved systems and the entropy of a probability distribution is used to decide the evolvability of the system.This method is used to solve a typical combinatorial optimization problem- the symmetric traveling salesman problem.Some results are better than the best existing algorithm of evolutionary algorithms for the problem.
Furbish, David J.; Schmeeckle, Mark; Schumer, Rina; Fathel, Siobhan L.
2016-01-01
We describe the most likely forms of the probability distributions of bed load particle velocities, accelerations, hop distances, and travel times, in a manner that formally appeals to inferential statistics while honoring mechanical and kinematic constraints imposed by equilibrium transport conditions. The analysis is based on E. Jaynes's elaboration of the implications of the similarity between the Gibbs entropy in statistical mechanics and the Shannon entropy in information theory. By maximizing the information entropy of a distribution subject to known constraints on its moments, our choice of the form of the distribution is unbiased. The analysis suggests that particle velocities and travel times are exponentially distributed and that particle accelerations follow a Laplace distribution with zero mean. Particle hop distances, viewed alone, ought to be distributed exponentially. However, the covariance between hop distances and travel times precludes this result. Instead, the covariance structure suggests that hop distances follow a Weibull distribution. These distributions are consistent with high-resolution measurements obtained from high-speed imaging of bed load particle motions. The analysis brings us closer to choosing distributions based on our mechanical insight.
Optimization Approaches for the Traveling Salesman Problem with Drone
N.A.H. Agatz (Niels); P. Bouman (Paul); M. Schmidt (Marie)
2016-01-01
textabstractThe fast and cost-efficient home delivery of goods ordered online is logistically challenging. Many companies are looking for new ways to cross the last-mile to their customers. One technology-enabled opportunity that recently has received much at- tention is the use of a drone to suppor
Traveling Salesman Problem for Surveillance Mission Using Particle Swarm Optimization
2010-07-26
or more sets of (probably) overlapping chromosomes. It is fairly easy to see how a meiosis operator might then reduce these sets of chromosomes to a...organisms in that an individual in a population typically has only one chromosome. Meiosis -the process in which the chromosomes In a loose sense, EAs...that use sexual operators model in a haploid organism are reduced into a meiosis . It is possible to imagine a diploid EA in which the gamete, which is
Optimization Approaches for the Traveling Salesman Problem with Drone
N.A.H. Agatz (Niels); P.C. Bouman (Paul); M.E. Schmidt (Marie)
2016-01-01
textabstractThe fast and cost-efficient home delivery of goods ordered online is logistically challenging. Many companies are looking for new ways to cross the last-mile to their customers. One technology-enabled opportunity that recently has received much at- tention is the use of a drone to
The Travelling Salesman Polytope and (0,2)-Matchings.
1981-02-01
characterizing those graphs having perfect 1-mat- chings is the following: Theorem 2.8 ( Tutte [16]). G has a perfect 1 -matching if and only if for every...graphs is polynomially equivalent to the more general problem. An interestinz feature of the results of the previous sections is that they do apply... Tutte , "The factorization of linear graphs", Journal of the London Mathematical Society 22 (1947) 107-111. LI a . n Ud nt.. . R E A D - REj) i E3ORT
Unusual Maths clock or Reverse Traveling Salesman Problem
Valerij F. Ochkov
2014-01-01
Full Text Available The article discusses some of the mathematical problem, attached to the clock. We show how to use the clock in the classroom for mathematics to illustrate some mathematical problems
well solved cases of probabilistic traveling salesman problem
Bellalouna, Monia; Paschos, Vangelis,; Khaznaji, Walid
2010-01-01
International audience; Le problème du voyageur de commerce est généralement NP-Hard. Notre but est de chercher des cas qui sont "Faciles", càd résolubles en temps polynomial. Le Problème du Voyageur de Commerce Petit illustre bien ces cas, notre étude comporte deux volets, d'abord nous donnons la relation entre le problème déterministe et son homologue probabiliste, ensuite nous montrons un résultat remarquable, à savoir : ce problème est stable : la perturbation par l'absence de certaines d...
Chen, Wei-Sheng; Lee, Chien-Chih; Chu, Fang-Dar; Su, Shin-Yi
2011-03-01
This study employs a digisonde and a GPS receiver at Wuhan (30.5°N, 114.4°E), China to observe spread F, GPS phase fluctuations, and medium-scale traveling ionospheric disturbances (MSTIDs) at nighttime in 2000. The MSTIDs are derived from the perturbations of total electron content (TEC). In this study, we explored the seasonal and nighttime occurrence rates as well as the one-to-one correspondences for these phenomena. The results show that, for the seasonal variations, three phenomena all are highly active in summer, which confirms that irregularities over Wuhan mainly relate to MSTIDs. Moreover, all spread F types have a minor occurrence peak in winter but none for the MSTIDs and the GPS phase fluctuations. Besides, none of large GPS phase fluctuations event had occurred during observation periods, which indicates that the strength of irregularities related to MSTIDs are weaker than that of equatorial plasma bubbles. For the nighttime variations, the frequency spread F occurs earlier than other spread F types which implies that disturbances start at the altitude near the F-region peak. For the one-to-one correspondences, the occurrence rates of each spread F type and GPS phase fluctuations are low during MSTIDs occurred. This implies that smaller scale irregularities which are observed as spread F or GPS phase fluctuations may only appear in some phase of MSTIDs.
Oedipus Complex in Death of a Salesman
黄云
2012-01-01
Death of a Salesman depicts the painful conflicts among the members of a family, examines the American citizen’s values and analyzes people’s prize they paid and the tragedy it brought ab-out for blinding believing in American Dream. This paper aims to analyze the work from the aspect of Oedipus complex which was put forward by psychoanalyst Freud, including Oedipus complex’s influ-ence on literature works and on Biff in this drama. Only in this way can we better understand the tragedy cause of this family.
Death of a Salesman:an Aristotelian Tragedy
刘丽明
2013-01-01
Death of a Salesman is Arthur Miller's most famous tragedy and caused great repercussions in the East-West literary. Aristotle is an outstanding representative of the early Western literary theory, and his Poetics epitomizes his theory of tragedy and marked the beginning of western tragedy theory. Based on Aristotle’s part theory of tragedy, a detailed analysis is made on the tragedy of Death of a Salesman.
The Flute Music in Death of a Salesman
方丹霞
2014-01-01
Arthur Miller’s Death of a Salesman takes advantage of the flute music to strengthen the atmosphere of stage, thus acoustically making people immerse the scene of the drama. The paper explores the conflicts and connections in this drama through the flute music, such as work and family, agriculture and business, work and family.
Awakening of Biff and Happy in Death of a Salesman
田烨
2014-01-01
Death of a Salesman is one of the classic works written by Arthur Miller,an American modern dramatist.When the protagonist Willy Loman’s suicide,Biff and Happy eventually awaken in different ways,and understand in different angles who they are and what is their father’s dream.
Fuzzy Synthetic Evaluation for Quality of Clothing Industry's Salesman
WANG Jian-ping; FANG Fei
2002-01-01
It is essential for the human resource management to establish a scientific and efficient evaluation system for the clothing industry. This paper discusses the evaluation system for the quality of clothing industry's salesman, using fuzzy set theory from the following five aspects: basic quality,work attitude, knowledge level,work ability and work achievement. A just and useful way for the human resource manager to evaluate employees' quality is elaborated.
Multiple Traveling Salesmen in Asymmetric Metrics
Friggstad, Zachary
2011-01-01
We consider some generalizations of the Asymmetric Traveling Salesman Path problem. Suppose we have an asymmetric metric G = (V,A) with two distinguished nodes s,t. We are also given a positive integer k. The goal is to find k paths of minimum total cost from s to t whose union spans all nodes. We call this the k-Person Asymmetric Traveling Salesmen Path problem (k-ATSPP). Our main result for k-ATSPP is a bicriteria approximation that, for some parameter b >= 1 we may choose, finds between k and k + k/b paths of total length O(b log |V|) times the optimum value of an LP relaxation based on the Held-Karp relaxation for the Traveling Salesman problem. On one extreme this is an O(log |V|)-approximation that uses up to 2k paths and on the other it is an O(k log |V|)-approximation that uses exactly k paths. Next, we consider the case where we have k pairs of nodes (s_1,t_1), ..., (s_k,t_k). The goal is to find an s_i-t_i path for every pair such that each node of G lies on at least one of these paths. Simple appro...
基于蚁群算法的Traveling Salesman Problem研究%Research of Ant Colony Algorithm on Traveling Salesman Problem
王琛
2008-01-01
本文介绍了一种求解复杂组合优化问题的新的拟生态算法--蚁群算法.阐述了该算法的基本原理以及蚁群算法在TSP问题上的应用,并提出了改进算法,使得算法有更好的全局性.
On Willy' s Loss in Death of a Salesman
崔凤霞
2011-01-01
In Death of a Salesman,Miller depicts Willy' s daydreams,private conversations and soliloquies,to unveil Willy' s past family expectations,betrayals and lies,and elaborate Willy' s road to destruction led by those past experiences,intertwined with the present.From the perspective of loss,the thesis analyzes the existing plight of Willy and inevitability of his death.Willy' s tragedy reminds us to distinguish between fantasy and reality,and establish the correct values.
Schroeder, Alex
2015-11-01
The Connected Traveler project is a multi-disciplinary undertaking that seeks to validate potential for transformative transportation system energy savings by incentivizing efficient traveler behavior. This poster outlines various aspects of the Connected Traveler project, including market opportunity, understanding traveler behavior and decision-making, automation and connectivity, and a projected timeline for Connected Traveler's key milestones.
Travelers' Health: Pregnant Travelers
... Zika is present and take precautions to avoid sexual transmission of the virus. If travel cannot be avoided, pregnant women should strictly follow steps to prevent mosquito bites. Additional information, including the most current list of countries and territories where Zika virus is a risk, ...
Ouchi, Kazunobu
2011-09-01
The number of Japanese oversea travelers has gradually increased year by year, however they usually pay less attention to the poor physical condition at the voyage place. Many oversea travelers caught vaccine preventable diseases in developing countries. The Vaccine Guideline for Oversea Travelers 2010 published by Japanese Society of Travel Health will be helpful for spreading the knowledge of travelers' vaccine and vaccine preventable diseases in developing countries. Many travelers' vaccines have not licensed in Japan. I hope these travelers' vaccines, such as typhoid vaccine, meningococcal vaccine, cholera vaccine and so on will be licensed in the near future.
2016-06-01
The Connected Traveler framework seeks to boost the energy efficiency of personal travel and the overall transportation system by maximizing the accuracy of predicted traveler behavior in response to real-time feedback and incentives. It is anticipated that this approach will establish a feedback loop that 'learns' traveler preferences and customizes incentives to meet or exceed energy efficiency targets by empowering individual travelers with information needed to make energy-efficient choices and reducing the complexity required to validate transportation system energy savings. This handout provides an overview of NREL's Connected Traveler project, including graphics, milestones, and contact information.
The traveling salesman problem for lines and rays in the plane
Dumitrescu, Adrian
2012-01-01
In the Euclidean TSP with neighborhoods (TSPN), we are given a collection of $n$ regions (neighborhoods) and we seek a shortest tour that visits each region. In the path variant, we seek a shortest path that visits each region. We present several linear-time approximation algorithms with improved ratios for these problems for two cases of neighborhoods that are (infinite) lines, and respectively, (half-infinite) rays. Along the way we derive a tight bound on the minimum perimeter of a rectangle enclosing an open curve of length $L$.
Bellingeri, Michele; Agliari, Elena; Cassi, Davide
2015-10-01
The best strategy to immunize a complex network is usually evaluated in terms of the percolation threshold, i.e. the number of vaccine doses which make the largest connected cluster (LCC) vanish. The strategy inducing the minimum percolation threshold represents the optimal way to immunize the network. Here we show that the efficacy of the immunization strategies can change during the immunization process. This means that, if the number of doses is limited, the best strategy is not necessarily the one leading to the smallest percolation threshold. This outcome should warn about the adoption of global measures in order to evaluate the best immunization strategy.
Optimal tree for Genetic Algorithms in the Traveling Salesman Problem (TSP)
Liew, Sing
2012-01-01
In this paper, the author proposes optimal tree as a "gauge" for the generation of the initial population at random in the Genetic Algorithms (GA) to benchmark against the good and the bad parent tours. Thus, without having the so-called bad parent tours in the initiate population, it will speed up the GA. The characteristics of the gauge (algorithm, complexity time, trade-off, etc.) will be discussed in this paper as well.
Parallel local search for the time-constrained traveling salesman problem
G.A.P. Kindervater (Gerard); J.K. Lenstra; M.W.P. Savelsbergh (Martin)
1989-01-01
textabstractIn the time-constrained TSP, each city has to be visited within a given time interval. Such `time windows' often occur in practice. When practical vehicle routing problems are solved in an interactive setting, one needs algorithms for the time-constrained TSP that combine a low running
Report on article The Travelling Salesman Problem: A Linear Programming Formulation
Hofman, Radoslaw
2008-01-01
This article describes counter example prepared in order to prove that linear formulation of TSP problem proposed in [arXiv:0803.4354] is incorrect (it applies also to QAP problem formulation in [arXiv:0802.4307]). Article refers not only to model itself, but also to ability of extension of proposed model to be correct.
Niazi, M. Khalid Khan; Hemminger, Jessica; Kurt, Habibe; Lozanski, Gerard; Gurcan, Metin
2014-03-01
Vascularity represents an important element of tissue/tumor microenvironment and is implicated in tumor growth, metastatic potential and resistence to therapy. Small blood vessels can be visualized using immunohistochemical stains specific to vascular cells. However, currently used manual methods to assess vascular density are poorly reproducible and are at best semi quantitative. Computer based quantitative and objective methods to measure microvessel density are urgently needed to better understand and clinically utilize microvascular density information. We propose a new method to quantify vascularity from images of bone marrow biopsies stained for CD34 vascular lining cells protein as a model. The method starts by automatically segmenting the blood vessels by methods of maxlink thresholding and minimum graph cuts. The segmentation is followed by morphological post-processing to reduce blast and small spurious objects from the bone marrow images. To classify the images into one of the four grades, we extracted 20 features from the segmented blood vessel images. These features include first four moments of the distribution of the area of blood vessels, first four moments of the distribution of 1) the edge weights in the minimum spanning tree of the blood vessels, 2) the shortest distance between blood vessels, 3) the homogeneity of the shortest distance (absolute difference in distance between consecutive blood vessels along the shortest path) between blood vessels and 5) blood vessel orientation. The method was tested on 26 bone marrow biopsy images stained with CD34 IHC stain, which were evaluated by three pathologists. The pathologists took part in this study by quantifying blood vessel density using gestalt assessment in hematopoietic bone marrow portions of bone marrow core biopsies images. To determine the intra-reader variability, each image was graded twice by each pathologist with two-week interval in between their readings. For each image, the ground truth (grade) was acquired through consensus among the three pathologists at the end of the study. A ranking of the features reveals that the fourth moment of the distribution of the area of blood vessels along with the first moment of the distribution of the shortest distance between blood vessels can correctly grade 68.2% of the bone marrow biopsies, while the intra- and inter-reader variability among the pathologists are 66.9% and 40.0%, respectively.
Can rats solve a simple version of the traveling salesman problem?
Bures, J; Buresová, O; Nerad, L
1992-12-31
Whereas correct tours through the radial arm maze are almost equally long, free choice mazes with multiple goals scattered in an open field allow the animal to select the shortest one from a multitude of correct tours. Thirteen rats were trained (at 10 trials per day) to visit an array of cylindrical feeders in an open field (40 x 100 cm) with reward available only when visiting the last feeder of the set. In Expt. 1 with eight feeders arranged in five different configurations the rats made after 10 days of training 1 error in the first 8 choices and incidence of errorless trials was about 20%. In Expt. 2. the use of six feeders in a rectangular (A) or double triangle (B) configuration increased the incidence of errorless trials to 60%. Expt. 3 showed that performance in the 6-feeder maze was significantly impaired by 6 mg/kg ketamine or 0.25 mg/kg scopolamine but not by lower dosages of these drugs. Tours generated on errorless trials (each feeder visited only once) during 10 days of Expt. 2 were analyzed. Six places can be visited in 6! = 720 different closed tours the lengths of which (in arbitrary units) range from 6.00 to 10.12 for A and from 6.83 to 10.47 for B. Whereas random generation of correct routes yielded only 5% of the shortest tours, they were clearly preferred by rats (41% in A and 45% in B). The apparent proficiency of rats in this optimization problem is probably not due to cognitive comparison of the possible correct routes but rather to following a simple rule 'Always go to the nearest not yet visited feeder'.
Online heuristic for the Multi-Objective Generalized traveling salesman problem
Pinxten, J. van; Geilen, M.; Basten, T.; Waqas, U.; Somers, L.
2016-01-01
Today’s manufacturing systems are typically complex cyber-physical systems where the physical and control aspects interact with the scheduling decisions. Optimizing such facilities requires ordering jobs and configuring the manufacturing system for each job. This optimization problem can be describe
Towards a 4/3 Approximation for the Asymmetric Traveling Salesman Problem
Carr, Robert; Vempala, Santosh
1999-06-10
A long-standing conjecture in combinatorial optimization says that the integrality gap of the famous Held-Karp relaxation of the symmetric TSP is precisely 4/3. In this paper, we show that a slight strengthening of this conjecture implies a tight 4/3 integrality gap for a linear programming relaxation of the asymmetric TSP. This is surprising since no constant-factor approximation is known for the latter problem. Our main tools are a new characterization of the integrality gap for linear objective functions over polyhedra, and the isolation of ''hard-to-round'' solutions of the relaxations.
A New Bio-inspired Approach to the Traveling Salesman Problem
Feng, Xiang; Lau, Francis C. M.; Gao, Daqi
The host-seeking behavior of mosquitoes is very interesting. In this paper, we propose a novel mosquito host-seeking algorithm (MHSA) as a new branch of biology-inspired algorithms for solving TSP problems. The MHSA is inspired by the host-seeking behavior of mosquitoes. We present the mathematical model, the algorithm, the motivation, and the biological model. The MHSA can work out the theoretical optimum solution, which is important and exciting, and we give the theoretical foundation and present experiment results that verify this fact.
Analyzing the Performance of Mutation Operators to Solve the Travelling Salesman Problem
Abdoun, Otman; Abouchabaka, Jaafar; Tajani, Chakir
2012-01-01
The genetic algorithm includes some parameters that should be adjusted, so as to get reliable results. Choosing a representation of the problem addressed, an initial population, a method of selection, a crossover operator, mutation operator, the probabilities of crossover and mutation, and the insertion method creates a variant of genetic algorithms. Our work is part of the answer to this perspective to find a solution for this combinatorial problem. What are the best parameters to select for...
Solving the Traveling Salesman Problem Using New Operators in Genetic Algorithms
Naef T. Al Rahedi; Jalal Atoum
2009-01-01
... near-optimum solutions for the TSP. Approach: A proposed genetic algorithm, that employed these new methods of representation and crossover operator, had been implemented using DELPHI programming language on a personal computer...
Chełmińska, Katarzyna; Jaremin, Bogdan
2002-01-01
During the past several decades, the number of both business and tourist travels has greatly increased. Among them are persons suffering from chronic diseases, including diabetics for whom travels pose the additional health-hazard. Irrespective of better education, self-control and constantly improving quality of specialistic equipment available, diabetics still are the group of patients requiring particular attention. In the case of travelling diabetics, problems may occur concerning the transport and storage of insulin, as well as control of glycaemia, all caused by irregularity of meals, variable diet, physical activity, stress, kinetosis (sea voyages), and the change of time zones. The travel may as well evoke ailments caused by the change of climate and concomitant diseases such as traveller's diarrhoea, malaria, etc. Apart from avoiding glycaemia fluctuations, important for retaining health of diabetics is the prevention of other diseases and carrying the necessary drugs.
Travelers' Health: Travel and Breastfeeding
... I J K L M N O P Q R S T U V W X Y Z # ... search/groups ). Mothers who plan to use a breast pump while traveling may need an electrical current ... during travel because exclusive breastfeeding means feeding only breast milk, no other foods or drinks, which protects ...
Schubert, S; Grimm, M
2009-07-01
Travel medicine deals with travellers' diseases. The target group is therefore distinct from tropical medicine. It has gained in significance due to the increase in tourism and professional work abroad in the last 50 years. Dangerous and widespread diseases in tropical countries, in particular tropical malaria, have come into focus in industrialized countries because of their appearance in travellers. Travel medicine deals not only with infectious or transmittable diseases, but also with the ability of patients with chronic diseases to travel, the medical aspects of flying, as well as the health hazards of professional work or high-risk sports abroad. The risk of disease as a result of travelling can be minimized by advice and prophylactic measures, such as vaccinations and drug prophylaxis against malaria, if indicated. On return, medical symptoms should be investigated promptly to ensure early detection of life-threatening disease courses, particularly tropical malaria, as well as to prevent the occurrence of small-scale epidemics. A small number of diseases can also emerge after several years, such as benign types of malaria, amoebic liver abscess and visceral leishmaniasis (kala-azar). Aids also belongs to these diseases. Therefore, in this era of HIV pandemic travellers concerned should be made aware of the risks.
无
2010-01-01
Mauritius Travel From August 31 to September 6, a high- level government delegation from Mauritius visited China. The delegation was headed by the President of Mauritius, Sir Anerood Jugnauth, and included the Minister of Tourism,
Simonsen, Karen-Margrethe
2013-01-01
Review of "Travelling Concepts, Metaphors, and Narratives: Literary and Cultural Studies in an Age of Interdisciplinary Research" ed. by Sibylle Baumgarten, Beatrice Michaelis and Ansagar Nünning, Trier; Wissenschaftlicher Verlag Trier, 2012......Review of "Travelling Concepts, Metaphors, and Narratives: Literary and Cultural Studies in an Age of Interdisciplinary Research" ed. by Sibylle Baumgarten, Beatrice Michaelis and Ansagar Nünning, Trier; Wissenschaftlicher Verlag Trier, 2012...
Vila, Jordi; Oliveira, Ines; Zboromyrska, Yuliya; Gascon, Joaquim
2016-11-01
Traveller's diarrhoea (TD) is acquired primarily through ingestion of food and drinks contaminated with pathogens that cause diarrhoea. They can be bacteria, protozoa, helminths, and viruses. Globally, the most common causes of TD are two pathotypes of Escherichia coli (enterotoxigenic and enteroaggregative) and Campylobacter, although there are significant variations by geographic area visited. Most TD occurs in individuals traveling to low-middle income countries. The type of travel, length of stay, traveller's age, and the presence of certain underlying conditions are important risk factors to consider for the acquisition of TD. While TD is usually a mild and self-limiting disease, half of travellers with TD experience some limitation of activities during their trip, while up to 10% will experience persistent diarrhoea or other complications. The purpose of this article is to provide an updated microbiological, epidemiological, and clinical profile of traveller's diarrhoea, including known risk factors, as well as to make recommendations on the prevention and treatment of TD. Copyright © 2016 Elsevier España, S.L.U. and Sociedad Española de Enfermedades Infecciosas y Microbiología Clínica. All rights reserved.
Travelers' Health: Cruise Ship Travel
... vectorborne diseases such as malaria, dengue, yellow fever, Japanese encephalitis, and Zika are endemic. New diseases might ... environmental conditions, as well as unaccustomed changes in diet and physical activity. Foreign travel may increase the ...
Travelers' Health: Cruise Ship Travel
... Water Disinfection Infographics for Travelers MERS Health Advisory poster Food and Water: What's Safer Health Advisory: MERS ... cruise ships can vary widely depending on ship size, itinerary, length of cruise, and passenger demographics. Generally, ...
无
2011-01-01
China to become the world’s No.1 tourist destination by 2015 May 19 is a special day in China’s history. On that day 400 years ago,Xu Xiake (1587-1641),wellknown geographer,traveler and explorer of the Ming Dynasty (1368-1644),started a lifelong journey,leading to the publication of the monumental Xu Xiake’s Travel Notes,known for its detailed and accurate geographical information. The book also provided valuable insight into local customs and habits.
A Tragedy of a Common Man in Arthur Miller's Death of a Salesman
梁花
2009-01-01
@@ 1. Arthur Miller and Death of a Salesman 1.1 Arthur Miller,One of the Greatest American Playwrights of the Twentieth Century Arthur Miller was one of the most preeminent playwrights of the twentieth century and one of America's most distinguished men of letters.He was born in October of 1915 in New York City. His plays continued the realistic tradition that began in the United States in the period between the two World Wars.
Deser, Stanley D; Deser, Stanley; Jackiw, Roman
1992-01-01
To travel into the past, to observe it, perhaps to influence it and correct mistakes of one's youth, has been an abiding fantasy of mankind for as long as we have been aware of a past. Here are described some recent scientific investigations on this topic.
... probably safe to eat or drink the following:Soft drinks that are carbonated (such as cola).Hot drinks, ... for Staying HealthyInternational travel has its share of health and safety challenges. Talk to your doctor about the area ...
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...
2006-01-01
10 April 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a dust devil traveling across a plain west-southwest of Schiaparelli Crater, in far eastern Sinus Meridiani. The dust devil is casting a shadow toward the northeast, just south (below) of an egg-shaped crater. Location near: 6.4oS, 349.3oW Image width: 3 km (1.9 mi) Illumination from: lower left Season: Southern Summer
... Events Advocacy For Patients About ACOG Travel During Pregnancy Home For Patients Search FAQs Travel During Pregnancy ... Pregnancy FAQ055, February 2016 PDF Format Travel During Pregnancy Pregnancy When is the best time to travel ...
Nielsen, Ulla S; Jensen-Fangel, Søren; Pedersen, Gitte
2013-01-01
We aimed to describe travel patterns, extent of professional pre-travel advice and health problems encountered during travel among HIV-infected individuals.......We aimed to describe travel patterns, extent of professional pre-travel advice and health problems encountered during travel among HIV-infected individuals....
The Concept of Blindness in Sophocles' King Oedipus and Arthur Miller's Death of a Salesman
Md. Ziaul Haque; Fahmida Kabir Chowdhury
2013-01-01
In King Oedipus (429 B.C.E) by Sophocles and Death of a Salesman (1949 A.D) by Arthur Miller, the central characters Oedipus and Willy Loman take extreme pride in their professions; their pride blinds them from seeing the reality of their circumstances, and it eventually brings their ruin. At he same time, the other characters also display their figurative blindness in both the tragedies. However, it is demonstrated that the protagonists do not succeed in executing their responsibilities as l...
2010-04-01
... performed by retail commission salesman. 31.3402(j)-1 Section 31.3402(j)-1 Internal Revenue INTERNAL REVENUE... EMPLOYMENT TAXES AND COLLECTION OF INCOME TAX AT SOURCE Collection of Income Tax at Source § 31.3402(j)-1.... (2) Section 3402(j) and this section are not applicable with respect to wages paid to the...
Travelers' Health: Water Disinfection for Travelers
... Chapter 2 - Food Poisoning from Marine Toxins Water Disinfection for Travelers Howard D. Backer RISK FOR TRAVELERS ... of iodine and chlorine (see Halogens below). Chemical Disinfection HALOGENS The most common chemical water disinfectants are ...
Travel/Travelers and Parasitic Diseases
... care providers. Health departments, the travel industry, multinational corporations, missionary and volunteer organizations, and travelers can also ... PPT, MPEG) on this site? Adobe PDF file Microsoft PowerPoint file Microsoft Word file Microsoft Excel file ...
Travelers' Health: HIV Infection
... Last-Minute Travel Long-Term Travel Mass Gatherings Medical Tourism Mental Health Motion Sickness Natural Disasters Pregnant Travelers ... for purposes of medical treatment (see Chapter 2, Medical Tourism ), the blood and blood products used in the ...
... submit Start of Search Controls Search Form Controls Travelers' Health Note: Javascript is disabled or is not ... FAQ Stamaril clinics Disease Directory Resources Resources for Travelers Adventure Travel Animal Safety Blood Clots Bug Bites ...
Travelers' Health: Motion Sickness
... Disease Directory Resources Resources for Travelers Adventure Travel Animal Safety Blood Clots Bug Bites Business Travel Cold ... motion sickness. Adding distractions—controlling breathing, listening to music, or using aromatherapy scents such as mint or ...
Young, Stanley
2017-04-24
The Connected Traveler project is a multi-disciplinary undertaking that seeks to validate potential for transformative transportation system energy savings by incentivizing energy efficient travel behavior.
Travel time and travel cost in European air travel
Dusek, Tamas
2012-01-01
The aim of the study is to examine two issues of consumer air travel accessibility in Europe, namely flight time and ticket costs. The first part of the paper discusses the various methodological problems of creating time matrix and cost matrix of air travel. Because of problems of conceptualizing of the air travel network and the modifiable areal unit problem the analysis is conducted on several spatial levels. The smallest network consists of 15 busiest airports and the largest network has ...
Childhood and Travel Literature.
Espey, David
If children are not present in most travel literature--precisely because the genre has most typically been the domain of solitary male travelers who are escaping domestic obligation, routine, the familiar, and the family--they nevertheless are an integral part of the genre. The traveler is in many ways a child, an innocent abroad. Traveler writers…
Ziegler, Carol C
2013-06-01
Travel abroad for business and pleasure should be safe and meaningful for the traveler. To assure that safe experience, certain processes should be considered before travel. A thorough pretravel health assessment will offer patients and health care providers valuable information for anticipatory guidance before travel. The destination-based risk assessment will help determine the risks involved in travel to specific locations and guide in the development of contingency plans for all travelers, especially those with chronic conditions. Diseases are more prevalent overseas, and immunizations and vaccinations are all important considerations for persons traveling abroad.
Death of a Salesman and The Glass Menagerie: A Phenomenological Reduction
Bakhtiar Naghdipour
2013-05-01
Full Text Available Tennessee Williams and Arthur Miller were two memory playwrights who searched the memory or the collective unconscious of their generation for the lost dreams of an unspoiled myth as well as the genuine ideals of love, humanity and dignity. These authors employed techniques and mechanisms such as poetic language and expressionistic stage directions to translate the inner workings of their characters into artistic projection. This paper employs the phenomenological principles of Geneva School of criticism with the aim of reducing the immediate consciousness of Williams and Miller, projected as stories of Tom and Willy, in search for the playwrights’ attitudes towards some basic concepts of life in the modern era. Keywords: Death of a Salesman, The Glass Menagerie, memory play, phenomenological reduction
Gautret, Philippe; Parola, Philippe
2014-03-01
Most cases of rabies in travelers are associated with dog bites and occur in adults who are commonly migrants. The incidence of injuries to travelers caused by potentially rabid animals is approximately 0.4 % per month of stay. Dogs account for 51 % of cases, but nonhuman primates are the leading animals responsible for injuries in travelers returning from Southeast Asia. Travel to Southeast Asia, India and North Africa, young age, and traveling for tourism are risk factors for potential exposure. More than 70 % of travelers are not immunized prior to departing and do not receive adequate care when injured. The intradermal vaccination route has been proven economical, safe and immunogenic in travelers. The immunity provided by the three-dose series is long-lasting and should be considered an investment for future travel. Abbreviated schedules may be used for last-minute travelers.
... Home » Health Info » Hearing, Ear Infections, and Deafness Travel Inside the Ear Video When sound waves reach ... are smaller than an orange seed. It then travels into the inner ear, which is filled with ...
Traveling Safely with Medicines
... Medications Safely My Medicine List How to Administer Traveling Safely with Medicines Planes, trains, cars – even boats ... your trip, ask your pharmacist about how to travel safely with your medicines. Make sure that you ...
Travelers' Health: Yellow Fever
... Drugs Cruise Ship Travel Families with Children Fish Poisoning in Travelers Food and Water Getting Health Care ... removal of their thymus or have had indirect radiation therapy in the distant past, these people can ...
US Agency for International Development — E2 Solutions is a web based end-to-end travel management tool that includes paperless travel authorization and voucher document submissions, document approval...
Zheng, F.
2011-01-01
Urban travel times are intrinsically uncertain due to a lot of stochastic characteristics of traffic, especially at signalized intersections. A single travel time does not have much meaning and is not informative to drivers or traffic managers. The range of travel times is large such that certain tr
Zheng, F.
2011-01-01
Urban travel times are intrinsically uncertain due to a lot of stochastic characteristics of traffic, especially at signalized intersections. A single travel time does not have much meaning and is not informative to drivers or traffic managers. The range of travel times is large such that certain
... Emergency Room? What Happens in the Operating Room? Traveling and Asthma KidsHealth > For Kids > Traveling and Asthma A A A What's in this ... t have to get in the way of travel fun. Let's find out how to be prepared ...
Travel epidemiology. WHO perspective.
Gezairy, Hussein A
2002-12-01
International travel is undertaken by large, and ever increasing numbers of people for professional, social, recreational and humanitarian purposes, and this upward trend looks set to continue. Travelers are exposed to a variety of health risks of the unfamiliar environment of the visited area. The risk of exposure is determined by destination, duration of the visit, purpose of the visit, behavior of the traveler and underlying physical and biological status of the traveler. However, most risks can be minimized by suitable precautions taken before, during and after travel. Travelers can themselves, also, easily introduce any infectious agents they may harbor to the visited area. Many infectious diseases have been introduced in many parts of the world through travel and trade. Travel has been identified as a prime factor in the global spread of infectious diseases. In a world of rapid air travel, no country is safe from infectious diseases. An outbreak in one country can easily and rapidly be transmitted across long distances to affect other countries through travel and trade. The World Health Organization devotes great attention to prevention and control of global spread of infectious diseases and minimizing the negative effect of international travel on health. The main strategies of the World Health Organization for minimizing the negative effects of expanding travel on global health security include developing the necessary strategies, rules and regulations; strengthening global communicable diseases surveillance and response; dissemination of related information throughout the world and strengthening national capacity for communicable diseases surveillance and response.
Zheng, F.
2011-01-01
Urban travel times are intrinsically uncertain due to a lot of stochastic characteristics of traffic, especially at signalized intersections. A single travel time does not have much meaning and is not informative to drivers or traffic managers. The range of travel times is large such that certain tr
Maximum gain of Yagi-Uda arrays
Bojsen, J.H.; Schjær-Jacobsen, Hans; Nilsson, E.
1971-01-01
Numerical optimisation techniques have been used to find the maximum gain of some specific parasitic arrays. The gain of an array of infinitely thin, equispaced dipoles loaded with arbitrary reactances has been optimised. The results show that standard travelling-wave design methods are not optimum....... Yagi–Uda arrays with equal and unequal spacing have also been optimised with experimental verification....
Travelers' Health: Water Disinfection for Travelers
... Water Disinfection Infographics for Travelers MERS Health Advisory poster Food and Water: What's Safer Health Advisory: MERS ... prevent recontamination during storage Table 2-10. Microorganism size and susceptibility to filtration ORGANISM AVERAGE SIZE (µm) ...
Comprehensive care of travelers.
Pust, R E; Peate, W F; Cordes, D H
1986-12-01
Travel, especially if it is international, often means major changes for the family. Family physicians should assess the epidemiologic risk and psychosocial significance of travel or relocation in light of the family's life-cycle stage and antecedent health. Using core references, which are kept current in partnership with public health agencies, family physicians are able to provide comprehensive immunization, medications, and patient education for all travel risks. Families are given medical record summaries and recommended sources of care at their destination. Eight weeks after their return patients are reassessed for newly acquired illness and helped to integrate the perspectives gained during the travel into the family's future dynamics. Taking advantage of growing travel medicine opportunities, family medicine educators should base the care of travelers and teaching of residents on defined competence priorities. Travelers' health provides a mutually rewarding model of shared care with public health consultants in the community medicine curriculum.
A Brief Analysis of Willy Loman’s Tragic Fate in Death of a Salesman
丁瑾
2014-01-01
Arthur Miller was considered as the most famous dramatist in America after the World War II, and his representative work Death of a Salesman was recognized as the best play in America during the post-war years. It was also considered to be one of the best three plays in the history of American drama; with A Streetcar Named Desire and Long Day's Journey into Night. Through the failure of two generations, this play addressed the painful conflicts within one family, and it also tackled greater is⁃sues regarding to Americans’national values.As an average person, Willy Loman had experienced hopes and pains, struggles and frustrations as well as dreams and disillusions, at last he chose to commit suicide. Based on the existent materials, the predecessor ’s researches as well as her own thinking, the author of this paper gives a brief analysis of the leading role ’s tragic fate, which mainly elaborates three important stages of Willy Loman’s tragic life:disillusion of the American Dream, the abandonment and the be⁃trayal, aiming to decode the root of Loman’s tragedy from the perspectives of society, family and the protagonist’s character. In conclusion, the paper tries to explore Arthur Miller’s inner world and the resources of his creation as far as possible, hoping to give readers of this paper certain inspiration.
Highway travel time estimation with data fusion
Soriguera Martí, Francesc
2016-01-01
This monograph presents a simple, innovative approach for the measurement and short-term prediction of highway travel times based on the fusion of inductive loop detector and toll ticket data. The methodology is generic and not technologically captive, allowing it to be easily generalized for other equivalent types of data. The book shows how Bayesian analysis can be used to obtain fused estimates that are more reliable than the original inputs, overcoming some of the drawbacks of travel-time estimations based on unique data sources. The developed methodology adds value and obtains the maximum (in terms of travel time estimation) from the available data, without recurrent and costly requirements for additional data. The application of the algorithms to empirical testing in the AP-7 toll highway in Barcelona proves that it is possible to develop an accurate real-time, travel-time information system on closed-toll highways with the existing surveillance equipment, suggesting that highway operators might provide...
Grand, Karina Lykke
2017-01-01
and experienced and how he interpreted this knowledge, visually and in words. Rørbye is my primary research focus, but his artistic struggles are very similar to other artists travelling in Italy at the time. I therefore use Martinus Rørbye’s Italian sojourn as a prism of interpretation.......The Danish painter Martinus Rørbye was among of the Danish artists to reinvent the traditions of the genre of travel painting in the 1830s. His changes and developments of a new complex pictorial strategy were in many ways an answer to the changes in society, especially the advent of tourism....... The new travel image had its focus on concurrency, everyday life and the secular world, resulting in images that anticipated the photographic travel image, the snapshot and the travel postcard. The advent of this new strategy proved to have a very long after-life, as tourists and travellers of today still...
Histoplasmosis in Israeli travelers.
Segel, Michael J; Rozenman, Judith; Lindsley, Mark D; Lachish, Tamar; Berkman, Neville; Neuberger, Ami; Schwartz, Eli
2015-06-01
Histoplasmosis is a common endemic human mycoses acquired mostly in the Americas. We reviewed 23 cases of histoplasmosis in Israeli travelers; 22 had traveled to Central or South America and one to North America. Fourteen cases had been exposed to bat habitats and were symptomatic, presenting ≤ 3 months after their return. Asymptomatic patients (N = 9) were diagnosed during the evaluation of incidental radiological findings or because a travel partner had been suspected of Histoplasma infection, 16-120 months after their return. Serological testing was positive in 75% of symptomatic cases but only 22% of asymptomatic cases. Histoplasmosis should be considered in travelers returning from the Americas with respiratory or febrile illness within weeks of return, particularly if exposed to bat habitats. Travel history is essential in patients presenting with pulmonary nodules, even years after travel to endemic countries.
Human Resources Division
2002-01-01
Administrative procedures for : Travel to the home station and home leave (hl) Additional travel to the home station (at) Travel to the home station and home leave for family reasons (hlf) As part of the process of simplifying administrative procedures, HR and AS Divisions have devised a new, virtually automatic procedure for payment of travel expenses to the home station. The changes are aimed at rationalising administrative procedures and not at reducing benefits. The conditions of eligibility are unchanged. The new procedure, which will be operational with effect from 1st June 2002, will greatly simplify the administrative processing of claims for travel expenses and the recording of home leaves. Currently, requests for payment are introduced manually into the Advances and Claims system (AVCL) by divisional secretariats. All travel to the home station starting prior to 1st June 2002 will be processed according to the existing system whereas that starting on 1st June and after will be processed accordi...
Moisã Claudia Olimpia
2011-01-01
Taking into account the suite of motivation that youth has when practicing tourism, it can be said that the youth travel takes highly diverse forms. These forms are educational tourism, volunteer programs and “work and travel”, cultural exchanges or sports tourism and adventure travel. In this article, we identified and analyzed in detail the main forms of youth travel both internationally and in Romania. We also illustrated for each form of tourism the specific tourism products targeting you...
论《推销员之死》的悲剧性%On the Tragedy of Death of a Salesman
吕方源
2007-01-01
Death of a Salesman was the masterpiece of Arthur Miller.Arthur Miller broke the mold of the formulaic tragedies of previous era since Aristotle and redefined that the common people was as apt a subject for tragedies in its highest sense as kings were,which made Death of a Salesman a modern tragedy.The tragic flaws in Willy Loman - his stubborn pursuit of and his false faith in the American dream,which finally caused his death - made him a tragic hero.In this play,Arthur Miller showed his optimistic view on life in tragedy.
Weber, Carol J
2005-10-01
As an international traveler, contact your health care provider at least 4 to 6 weeks before departure to obtain needed vaccinations and prophylactic medications. Be aware of the occurrence of any disease outbreaks in the countries you are visiting. While traveling, don't forget that one of the most important practices in preventing illness from infections is handwashing. Wash your hands carefully and frequently with soap and water, and if soap and water are not available use an alcohol-based hand rub. Be a responsible traveler by becoming informed about health risks and what to do to avoid them before you travel.
Reality,Fantasy and Memory——A Tentative of the Stage Techniques in Death of a Salesman
王丽
2008-01-01
Death of Salesman is,to a great extent,a memory play.By using lots of literary techniques and displaying a mixture of the flash back of the past life and the reality as well as the fantasy of the hero,this play successfully presents a unique style of realism a nd expressionism,through which,the author unfolds before us the tragic life of Willy Loman,the ma in character of the play.[Keywords]literary technique reality fantasy memory
Information for travellers' physicians.
Allison, D J; Blinco, K
1990-07-01
Physicians can obtain advice about international travel for their patients from many different sources of information. The authors review some of the most common sources based on their experience at the International Travellers' Clinic operated by the New Brunswick Department of Health and Community Services in Fredericton. They identify readily available handbooks and periodicals and compare two computer software programs.
Information for Travellers' Physicians
Allison, David J; Blinco, Kimberley
1990-01-01
Physicians can obtain advice about international travel for their patients from many different sources of information. The authors review some of the most common sources based on their experience at the International Travellers' Clinic operated by the New Brunswick Department of Health and Community Services in Fredericton. They identify readily available handbooks and periodicals and compare two computer software programs.
2006-01-01
CARLSON WAGONLIT TRAVEL informs you that our agency will be closed from 22 December 2006 at 16:30 until 8 January 2007 at 8:30. For all URGENT MATTERS you can contact our CARLSON WAGONLIT TRAVEL branch at W.H.O. (Mr Pierre Plumettaz), phone: 022 791 55 95. We wish you already a Merry Christmas and a Happy New Year!
... What Happens in the Operating Room? Traveling and Asthma KidsHealth > For Kids > Traveling and Asthma A A A What's in this article? Pack ... Or how about sleepover camp? If you have asthma , you'll be packing more than your clothes ...
Braae, Ellen Marie; Diedrich, Lisa; Lee, Gini
2013-01-01
conditions, correspond to the fields of natural sciences and to spatial aesthetics. The Travelling Transect method, inspired by Alexander von Humboldt’s method of transareal travelling and transversal collecting of ephemeral information from site, informs our exploratory fieldwork in the water landscapes...
Traveler response to information
Chorus, C.G.
2007-01-01
The past few years have witnessed an impressive progress in the capabilities of travel information services. It is expected that in a few years, travelers will be constantly informed, pre-trip as well as en-route, about their optimal departure time, route and transport mode. The information is based
Bill, Jan; Roesdahl, Else
2007-01-01
On the interrelationship between travel, transport and society; on land transport, sea and river transport, and on winter transport; on the related technologies and their developments......On the interrelationship between travel, transport and society; on land transport, sea and river transport, and on winter transport; on the related technologies and their developments...
... let them inspect it. Small jars of baby food travel well. They make little waste and you can dispose of them easily. Air ... not eat raw fruits or vegetables. Eat only food that is hot and has been cooked ... and hotels for guidance and assistance. For foreign travel, check ...
Epidemiology of traveler's diarrhea.
Castelli, F; Carosi, G
1995-01-01
Annually, over 75 million international passengers travel to tropical areas, more than 20 million of whom come from industrialized countries. They experience a high rate of traveler's diarrhea (TD), varying from 20 to 56%, which may result in serious limitations to their activities. The cause of TD is considered to be infectious in the overwhelming majority of cases and, apart from differences in relative importance, the list of responsible microbial agents is fairly constant regardless of geographic origin. The ingestion of contaminated food or water is considered to be the principal mode of transmission of the enteric pathogens of TD. Several factors have been proposed as playing a role in the etiogenesis of diarrhea in travelers, including personal (age, socioeconomic status, body weight, preexisting gastrointestinal illnesses), behavioral (mode of travel, standard of accommodation, eating in public places, dietary errors) and travel-related (destination, duration of stay, country of origin, season) factors, which are reviewed in detail.
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...
Understanding taxi travel patterns
Cai, Hua; Zhan, Xiaowei; Zhu, Ji; Jia, Xiaoping; Chiu, Anthony S. F.; Xu, Ming
2016-09-01
Taxis play important roles in modern urban transportation systems, especially in mega cities. While providing necessary amenities, taxis also significantly contribute to traffic congestion, urban energy consumption, and air pollution. Understanding the travel patterns of taxis is thus important for addressing many urban sustainability challenges. Previous research has primarily focused on examining the statistical properties of passenger trips, which include only taxi trips occupied with passengers. However, unoccupied trips are also important for urban sustainability issues because they represent potential opportunities to improve the efficiency of the transportation system. Therefore, we need to understand the travel patterns of taxis as an integrated system, instead of focusing only on the occupied trips. In this study we examine GPS trajectory data of 11,880 taxis in Beijing, China for a period of three weeks. Our results show that taxi travel patterns share similar traits with travel patterns of individuals but also exhibit differences. Trip displacement distribution of taxi travels is statistically greater than the exponential distribution and smaller than the truncated power-law distribution. The distribution of short trips (less than 30 miles) can be best fitted with power-law while long trips follow exponential decay. We use radius of gyration to characterize individual taxi's travel distance and find that it does not follow a truncated power-law as observed in previous studies. Spatial and temporal regularities exist in taxi travels. However, with increasing spatial coverage, taxi trips can exhibit dual high probability density centers.
[Thromboembolism in travelers].
Bihari, I; Sándor, T
2001-11-11
The association between long haul travel and the risk of venous thromboembolism are suspected for long time. Mostly air travel related thrombosis series have been reported in the literature. Risk factors can be classified as: 1. travel related factors (coach position, immobilization, prolonged air travel, narrow seat and room, diuretic effect of alcohol, insufficient fluid intake, dehydration, direct pressure on leg veins, rare inspiration). 2. air plane related risk factors (low humidity, relative hypoxia, stress). 3. patient related factors (hereditary and acquired thrombophylia, previous deep venous thrombosis, age over 40, recent surgery or trauma, gravidity, puerperium, oestrogen containing pills, varicosity, chronic heart disease, obesity, fever, diarrhoea, vomiting, smoking). No patient related factors were found in some cases. To reduce the hazards air travellers are rightly concerned to know the level of the risk and the airlines should be responsible for this information. People should discuss with their physician what prophlylactic measures should be taken, such as compression stockings or low molecular weight heparin. Not only flight but car, bus and train travellers are also at risk of developing venous thromboembolism. Long haul travel alone is a separate risk factor for venous thromboembolism.
[Traveling with immunosuppression].
Birkenfeld, G
2014-03-01
The rapidly increasing number of patients with immunosuppression is followed by their expectation to lead-as much as possible-a "normal" life, including long-distance travel. The advice and preventive measures for diseases associated with travelling depend overall on the mode of the patient's immunosuppression. This report explains the individual preventive possibilities, limits and risks for travellers with asplenia, common variable immunodeficiency, chronic inflammatory bowel and rheumatic diseases, HIV, as well as for patients having undergone solid organ or bone marrow transplantation or chemotherapy.
... a CDC Malaria Branch clinician. malaria@cdc.gov Malaria and Travelers Recommend on Facebook Tweet Share Compartir ... may be at risk for infection. Determine if malaria transmission occurs at the destinations Obtain a detailed ...
Carlson Wagonlit Travel
2005-01-01
Dear customers, On 3 January we informed you that the airlines had decided to cease paying commission to travel agencies in Switzerland. This measure has since been progressively introduced, with rare exceptions. Consequently, in agreement with CERN, we are obliged to apply new transaction fees for private travel, with immediate effect. Carlson Wagonlit Travel (CWT) offers: A personalized, professional and competent consultancy service To seek the most economical and best solution adapted to your needs Neutrality in comparing prices and benefits Additional information concerning e.g. visa regulations, insurance, vaccinations, etc. Support in the event of problems We draw your attention to the fact that, in spite of the increase, these prices remain very competitive on today's market. Thank you for your trust and understanding. Yours truly, Carlson Wagonlit Travel CERN agency
Travelers' Health: Cryptosporidiosis
... cryptosporidiosis was associated with travel to Asia, particularly India, and Latin America. Another study found a 6. ... 22. Lalonde LF, Gajadhar AA. Effect of storage media, temperature, and time on preservation of Cryptosporidium parvum ...
... from rabies in a UK traveller returning from India. Euro Surveill. 2005 Jul;10(30):E050728 5. ... Follow CDC Email Recommend Tweet Post RSS CDC Media Listen Watch YouTube About CDC Employment Newsroom Training/ ...
Full Text Available ... Info » Hearing, Ear Infections, and Deafness Travel Inside the Ear Video When sound waves reach your ear, ... heard a soft sound or a loud sound. The sound passes through the outer ear and is ...
Full Text Available ... stirrup. These are the smallest bones in your body. Together they are smaller than an orange seed. It then travels into the inner ear, which ... organizations Related Topics ...
Hietala, Vincent M.; Vawter, Gregory A.
1993-01-01
The traveling-wave photodetector of the present invention combines an absorptive optical waveguide and an electrical transmission line, in which optical absorption in the waveguide results in a photocurrent at the electrodes of the electrical transmission line. The optical waveguide and electrical transmission line of the electrically distributed traveling-wave photodetector are designed to achieve matched velocities between the light in the optical waveguide and electrical signal generated on the transmission line. This velocity synchronization provides the traveling-wave photodetector with a large electrical bandwidth and a high quantum efficiency, because of the effective extended volume for optical absorption. The traveling-wave photodetector also provides large power dissipation, because of its large physical size.
... Traveler Registration During Trip After Your Trip CDC-TV Videos Resources For Clinicians In-Clinic Quick Links ... toxoid vaccine before departure. After a childhood primary series and a booster dose during adolescence, routine booster ...
Helles, Rasmus; Lai, Signe Sophus
2017-01-01
The article presents a quantitative content analysis (Krippendorff, 2013) of the first episode of the 32 Danish drama series produced between 2005 and 2014. A number of these have experienced unprecedented, international success, with series such as Borgen (2010-13) and The Killing (2007......-12) travelling to multiple countries on several continents. The article shows that there are systematic differences in terms of formal characteristics, themes, and characters’ communicative style between the series that travel and the series that do not. Especially, the analysis finds that the presence of strong...... female lead characters is systematically linked to the positive travel patterns of the series, and that this cuts across different genres of series. The analysis also finds that series, which have explicitly low production values and simple narrative structure, systematically travels poorer....
Travelers' Health: Leishmaniasis, Cutaneous
... Water Disinfection Infographics for Travelers MERS Health Advisory poster Food and Water: What's Safer Health Advisory: MERS ... noise, they are small (approximately one-third the size of mosquitoes), and their bites might not be ...
... Water Disinfection Infographics for Travelers MERS Health Advisory poster Food and Water: What's Safer Health Advisory: MERS ... weight may be small in relation to the size and number of wounds. RIG is difficult to ...
... healthy snacks, like fresh or dried fruit, veggies, trail mix, or granola bars.Other helpful carry-on ... phone number with you in case of an emergency. If you have a severe food allergy, travel ...
Travelers' Health: Leishmaniasis, Cutaneous
... Climates Humanitarian Aid Workers Humanitarian Aid Workers in Ecuador Insurance International Adoption Jet Lag Last-Minute Travel ... military personnel, construction workers, and people who do research outdoors at night or twilight. However, even short- ...
Tini Garske
Full Text Available The spread of infectious disease epidemics is mediated by human travel. Yet human mobility patterns vary substantially between countries and regions. Quantifying the frequency of travel and length of journeys in well-defined population is therefore critical for predicting the likely speed and pattern of spread of emerging infectious diseases, such as a new influenza pandemic. Here we present the results of a large population survey undertaken in 2007 in two areas of China: Shenzhen city in Guangdong province, and Huangshan city in Anhui province. In each area, 10,000 randomly selected individuals were interviewed, and data on regular and occasional journeys collected. Travel behaviour was examined as a function of age, sex, economic status and home location. Women and children were generally found to travel shorter distances than men. Travel patterns in the economically developed Shenzhen region are shown to resemble those in developed and economically advanced middle income countries with a significant fraction of the population commuting over distances in excess of 50 km. Conversely, in the less developed rural region of Anhui, travel was much more local, with very few journeys over 30 km. Travel patterns in both populations were well-fitted by a gravity model with a lognormal kernel function. The results provide the first quantitative information on human travel patterns in modern China, and suggest that a pandemic emerging in a less developed area of rural China might spread geographically sufficiently slowly for containment to be feasible, while spatial spread in the more economically developed areas might be expected to be much more rapid, making containment more difficult.
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2000-01-01
"WHY Chinese Women Travel Alone" was the theme of a special edition of "Truth Talk" a popular talk show on China Central Television (CCTV), which focused on a few middle-aged women from different cultural backgrounds, social classes, and various educational backgrounds who had all branched out on their own for one reason or another. Each woman spoke of her experiences and feelings while travelling alone. They were all
Freedom of Movement (Common Travel Area) (Travel Documentation) Bill 2014
Butler, Graham; Hunt, Brian; Flanagan, Terence
2014-01-01
Private Members' Bill (legislation) introduced in Dáil Éireann (House of Deputies), Houses of the Oireachtas (Irish Parliament). An Act to reinforce the Common Travel Area by providing for passport-free travel for persons who are entitled to travel within the Common Travel Area without a passport...
Freedom of Movement (Common Travel Area) (Travel Documentation) Bill 2014
Butler, Graham; Hunt, Brian; Flanagan, Terence
2014-01-01
Private Members' Bill (legislation) introduced in Dáil Éireann (House of Deputies), Houses of the Oireachtas (Irish Parliament). An Act to reinforce the Common Travel Area by providing for passport-free travel for persons who are entitled to travel within the Common Travel Area without a passport...
[Vaccination for international travelers].
Arrazola, M Pilar; Serrano, Almudena; López-Vélez, Rogelio
2016-05-01
Traveler's vaccination is one of the key strategies for the prevention of infectious diseases during international travel. The risk of acquiring an infectious disease is determined in each case by the characteristics of the traveler and the travel, so the pre-departure medical advice of the traveler must be individualized. The World Health Organization classifies travelerś vaccines into three groups. - Vaccines for routine use in national immunization programs: Haemophilus influenzae type b, hepatitis B, polio, measles-mumps-rubella, tetanus-diphtheria-whooping a cough, and chickenpox. - Vaccinations required by law in certain countries before to enter them: yellow fever, meningococcal disease and poliomyelitis. - Vaccines recommended depending on the circumstances: cholera, japanese encephalitis, tick-borne encephalitis, meningococcal disease, typhoid fever, influenza, hepatitis A, hepatitis B, rabies and BCG. This review is intended to introduce the reader to the field of international vaccination. Copyright © 2016 Elsevier España, S.L.U. y Sociedad Española de Enfermedades Infecciosas y Microbiología Clínica. All rights reserved.
Travels in Architectural History
Davide Deriu
2016-11-01
Full Text Available Travel is a powerful force in shaping the perception of the modern world and plays an ever-growing role within architectural and urban cultures. Inextricably linked to political and ideological issues, travel redefines places and landscapes through new transport infrastructures and buildings. Architecture, in turn, is reconstructed through visual and textual narratives produced by scores of modern travellers — including writers and artists along with architects themselves. In the age of the camera, travel is bound up with new kinds of imaginaries; private records and recollections often mingle with official, stereotyped views, as the value of architectural heritage increasingly rests on the mechanical reproduction of its images. Whilst students often learn about architectural history through image collections, the place of the journey in the formation of the architect itself shifts. No longer a lone and passionate antiquarian or an itinerant designer, the modern architect eagerly hops on buses, trains, and planes in pursuit of personal as well as professional interests. Increasingly built on a presumption of mobility, architectural culture integrates travel into cultural debates and design experiments. By addressing such issues from a variety of perspectives, this collection, a special 'Architectural Histories' issue on travel, prompts us to rethink the mobile conditions in which architecture has historically been produced and received.
Risk assessment in travel medicine.
Leggat, Peter A
2006-01-01
Risk assessment is an integral part of pre-travel and post- assessment. Risk assessment largely determines what health and safety advice and interventions are given within the relevant prevailing travel health guidelines. Risk assessment needs time and depends on information, including that given by the traveller. Risk assessment also needs to be documented. Risk assessment of the traveller preferably starts before they enter the consulting room, where travellers may complete a pre-travel health questionnaire. Armed with this information, risk assessment may be assisted by access to computerised travel health databases and the published literature. Experience of travel to the destination may also assist in risk assessment and the tour operator, overseas employer or agency, the traveller or even the travel health advisers themselves may provide this information.
[Counsel for traveling children].
Sorge, F; Gendrel, D
2013-01-01
Consultation of child traveler has two main objectives: to assess of health risk related to the child's health status and history and also the risk related to travel environment; to counsel and prescribe preventive measure to reduce these travel health risks. The evaluation is based on physical examination and a detailed interview including personal history and information regarding the regions of proposed travel. Up to date knowledge of the epidemiology of visited sites, preventive measures and presumptive treatment is required. Essential health recommendations include, in case of exposure, prevention of malaria, arthropod borned diseases and vaccine preventable diseases. For all destinations advice regarding prevention of diarrhea, accident risks and aggravation of preexisting chronic diseases is needed. Universal primary prevention counselling is valuable for all travellers regardless of their age. In the case of children, special attention must be given to food and water hygiene, sun and heat exposure, swimming risks and transports security measures. Evaluation of risk and health education take time and often several visits are needed to complete the immunization schedule before departure.
Walentiny, C
2009-03-01
The second trimester is the safest time for travelling, because the pregnant woman feels generally most at ease and the risk of spontaneous abortion and pre-term labour is very low. Possible risks must be discussed with the obstetrician before travelling. If the pregnancy is uncomplicated most airlines allow flying up to the 36th (domestic flights) and 35th (international flights) week of gestation. Unless the fetal oxygen supply is already impaired at ground level due to an underlying disease, flying does not pose a risk of fetal hypoxia. Radiation exposure during a long distant flight is low compared to the average annual exposure dosage, but the risk of thrombosis is increased. Altitudes up to 2,500 m pose no problem. Sufficient time to acclimatize must be taken when travelling to high altitudes and exercise kept to a minimum. Scuba diving is contraindicated. Since only a few drugs are completely safe during pregnancy a thorough risk/benefit evaluation is mandatory. Treatment of infections can be considerably complicated, but any necessary treatment should not be withheld because of the fear of potential fetal injury. Good knowledge of local medical resources is essential before travelling. Several personal protective measures minimize the risk of infection: food and water precautions, protection from insect bites and avoidance of crowds, unsafe sex and, if need be, freshwater. Many vaccinations are recommended for travellers. However, live vaccines are contraindicated in pregnant women because of theoretical considerations. Exceptionally a yellow fever vaccination may be given after the first trimester. Killed, inactivated or polysaccharide vaccines can be given after the first trimester after a thorough risk/benefit evaluation. Because of the potentially devastating effect of malaria to the mother and the child, travelling to endemic malaria regions should be avoided. If the risk of infection is high chemoprophylaxis with mefloquine is indicated. In low
Stewart, L; Leggat, P A
1998-06-01
As travel has become easier and more affordable, the number of people traveling has risen sharply. People travel for many and varied reasons, from the business person on an overseas assignment to backpackers seeking new and exotic destinations. Others may take up residence in different regions, states or countries for family, business or political reasons. Other people are fleeing religious or political persecution. Wherever they go and for whatever reason they go, people take their culture with them. Culture, like language, is acquired innately in early childhood and is then reinforced through formal and complex informal social education into adulthood. Culture provides a framework for interpersonal and social interactions. Therefore, the contact with a new culture is often not the exciting or pleasurable experience anticipated. When immersed in a different culture, people no longer know how to act when faced with disparate value systems. Contact with the unfamiliar culture can lead to anxiety, stress, mental illness and, in extreme cases, physical illness and suicide. "Culture shock" is a term coined by the anthropologist Oberg. It is the shock of the new. It implies that the experience of the new culture is an unpleasant surprise or shock, partly because it is unexpected and partly because it can lead to a negative evaluation of one's own culture. It is also known as cross-cultural adjustment, being that period of anxiety and confusion experienced when entering a new culture. It affects people intellectually, emotionally, behaviorally and physically and is characterized by symptoms of psychological distress. Culture shock affects both adults and children. In travelers or workers who have prolonged sojourns in foreign countries, culture shock may occur not only as they enter the new culture, but also may occur on their return to their original culture. Children may also experience readjustment problems after returning from leading sheltered lives in expatriate
Pickover, Clifford A
1998-01-01
""Bucky Fuller thought big,"" Wired magazine recently noted, ""Arthur C. Clarke thinks big, but Cliff Pickover outdoes them both."" In his newest book, Cliff Pickover outdoes even himself, probing a mystery that has baffled mystics, philosophers, and scientists throughout history--What is the nature of time? In Time: A Traveler's Guide, Pickover takes readers to the forefront of science as he illuminates the most mysterious phenomenon in the universe--time itself. Is time travel possible? Is time real? Does it flow in one direction only? Does it have a beginning and an end? What is eternity? P
Malaria prevention in travelers.
Genton, Blaise; D'Acremont, Valérie
2012-09-01
A common approach to malaria prevention is to follow the "A, B, C, D" rule: Awareness of risk, Bite avoidance, Compliance with chemoprophylaxis, and prompt Diagnosis in case of fever. The risk of acquiring malaria depends on the length and intensity of exposure; the risk of developing severe disease is primarily determined by the health status of the traveler. These parameters need to be assessed before recommending chemoprophylaxis and/or stand-by emergency treatment. This review discusses the different strategies and drug options available for the prevention of malaria during and post travel.
Koski, Olivia; Rosin, Mark; Guerilla Science Team
2014-03-01
The Intergalactic Travel Bureau is an interactive theater outreach experience that engages the public in the incredible possibilities of space tourism. The Bureau is staffed by professional actors, who play the role of space travel agents, and professional astrophysicists, who play the role of resident scientists. Members of the public of all ages were invited to visit with bureau staff to plan the vacation of their dreams-to space. We describe the project's successful nine day run in New York in August 2013. Funded by the American Physical Society Public Outreach and Informing the Public Grants.
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...
Travel health. Part 1: preparing the tropical traveller.
Carroll, Bernadette; Daniel, Amanda; Behrens, Ron H
The health threats of modern day travel change as population, wealth and tourism increase across the world. A series of three articles have been written to describe the spectrum of health issues associated with travel. Pre-travel health advice has become more focused on risk assessment and educating the traveller about infectious disease and the more frequent non-infectious hazards associated with travel, while ensuring they are not unnecessarily exposed to injury from vaccines and drugs. In part one, the role of the health advisor and the needs of the traveller are examined. The importance of risk assessment during a consultation is described and factors that influence recommendations and prescribing are explored. As most travel-associated morbidity and mortality is non-vaccine preventable, the focus of the pre-travel consultation should be on educating the traveller and influencing behaviour change. The second article in this series deals with the highest risk group of travellers--residents who visit friends and relatives. It highlights their specific problems and special needs and how to influence their risk of disease by addressing their health beliefs and their cultural dimension of risk. The third article explores the common, and not so common, clinical problems found in returned travellers. Nurses have to deal with a large range of clinical problems and diagnostic dilemmas when attending to the returned traveller. The review provides a perspective on the frequency and severity of problems and how nurses should manage travel associated disease.
Full Text Available ... Search form Search A–Z Index Español Menu Home Health Info Hearing, Ear Infections, and Deafness Balance ... Committees Contact Us Get Involved You are here Home » Health Info » Hearing, Ear Infections, and Deafness Travel ...
2010-12-13
This podcast explains the ways people can stay healthy and avoid the flu when traveling this winter. Created: 12/13/2010 by National Center for Emerging and Zoonotic Infectious Diseases (NCEZID). Date Released: 12/13/2010.
Gulliver's Travels. [Lesson Plan].
Rooks, Kirsten; McLean, Mary
Based on Jonathan Swift's novel "Gulliver's Travels," this lesson plan presents activities designed to help students understand that Swift comments on undesirable outcomes of advances in science; and other authors have also warned against abuse of science. The main activity of the lesson involves students developing a poster illustrating views of…
Philyaw, Henry; And Others
This minicourse guide for teachers of French is intended to help motivate and prepare students for travel in France. Activities are outlined in eleven related areas, including (1) planning for the trip, (2) currency, (3) going through customs, (4) tipping, (5) shopping, (6) guided tours, (7) touring on your own, (8) social life and entertainment,…
ROBERT T.TUOHEY
2010-01-01
@@ Dally travel within Beijing need not be anymore troublesome than going about any major metropolis.Simply,certain basic facts need to be kept in mind,and ordinary precautions taken.Essentially,it's the same situation as midtown Manhattan or downtown Tokyo,except everyone's speaking Chinese.
ROBERT; T.TUOHEY
2010-01-01
Daily travel within Beijing need not be anymore troublesome than going about any major metropolis.Simply,certain basic facts need to be kept in mind,and ordinary precautions taken.Essentially,it’s the same situation as midtown Manhattan or downtown Tokyo,except everyone’s speaking Chinese.
Travelers' Health: Hepatitis A
... total anti-HAV result and a negative IgM anti-HAV result indicate past infection or vaccination and immunity. The presence of serum IgM anti- ... the risk for adverse effects, screening for total anti-HAV before travel can be ... Postvaccination testing for serologic response is not indicated. ...
Ahmad, Othman; Chekima, Ali
2011-01-01
It is fundamentally possible to travel with zero energy based on Newton Laws of Motion. According to the first law of motion, a body will continue to travel for infinite distance unless it is acted upon by another force. For a body in motion, the force which stops perpetual motion is friction. However, there are many circumstances that friction is zero, for example in space, where there is vacuum. On earth, gravity makes objects to be in constant contact with each other generating friction but technology exists to separate them in the air using powerful magnetic forces. At low speeds, the friction caused by air is minimal but we can create vacuum even on land for high speed travel. Another condition for travelling is for it to stop at its destination. On land, we can recover the kinetic energy back into electrical energy using brushless permanent magnet generators. These generators can also convert electric energy into kinetic energy in order to provide motion. This article reviews technologies that will allo...
A Learning Algorithm of Elastic Net for Multiple Traveling Salesmen Problem
Wang, Jiahai; Tang, Zheng; Cao, Qiping; Wang, Ronglong
The Multiple Traveling Salesmen Problem (MTSP) is extension of the Traveling Salesman Problem (TSP). This problem is widely applied to many real routing and scheduling problems. This paper proposes a gradient ascent learning algorithm of the elastic net approach for the MTSP. The learning model has two phases: an elastic net phase, and a gradient ascent phase. The elastic net phase tries to find the minimum of total distances. This procedure is equivalent to gradient descent of an energy function, and leads to a local minimum of energy that represents a good solution to the problem. Once the elastic net gets stuck in local minima, the gradient ascent phase attempts to fill up the valley by modifying parameters in a gradient ascent direction of the energy function. Thus, these two phases are iterated until the elastic net gets out of local minima. The simulations are conducted on a series of standard data in order to investigate the performance of the proposed algorithm. The proposed algorithm is shown to be capable of escaping from the elastic net local minima and generating superior solution in all instances compared to the original elastic net.
Valuation of Travel Time and TravelIer Information
Rietveld, Piet
2003-01-01
The value of travel time plays an important role in cost benefit analysis of infrastructureprojects. However, the issue of uncertainty on travel times and the implications this has forestimations of travel time values has received much less attention in the literature. In thispaper we compare
Valuation of Travel Time and TravelIer Information
Rietveld, Piet
2003-01-01
The value of travel time plays an important role in cost benefit analysis of infrastructureprojects. However, the issue of uncertainty on travel times and the implications this has forestimations of travel time values has received much less attention in the literature. In thispaper we compare variou
2010-04-01
... operators of hotels, restaurants or other firms whose main business is furnishing food or lodging or both... facilities used to do the work. Facilities include such things as a place to work, storage space, equipment, machinery and office furniture. However, facilities do not include tools, equipment or clothing of the kind...
Improved shuffled frog-leaping algorithm for traveling salesman problem%求解TSP问题的改进混合蛙跳算法
张敬敏; 马丽; 李媛媛
2012-01-01
针对TSP问题的特点,设计了一种求解TSP问题的改进的混合蛙跳算法.该算法改进了子种群青蛙个体优化的方式,而不仅是对最坏个体进行优化,这种方式可以有效提高算法的收敛速度.提出了青蛙个体翻转时依赖于全局最优解的“导优”概率和依赖于子种群局部最优解的“导次优”概率,进一步提高了算法寻找最优解的能力.在多个TSPLIB上的实验结果表明,该算法是可行有效的.%According to the TSP character, an improved shuffled frog-leaping algorithm is designed. The algorithm improves the child population frog individual optimization way, not just the worst individual optimization. This way can improve the convergent speed of the algorithm effectively. In order to enhance the ability of searching, "guide optimal" probability and "guide suboptimal" probability are put forward. The "guide optimal" probability represents the global optimum solution probability that the individual reversal depends on. The "guide suboptimal" probability represents the subpopulation optimum solution probability that the individual reversal depends on. Through experiments to multiple problems of the TSPLIB, the results show that the algorithm is feasible and effective.
基于遗传算法的一类多旅行商问题研究%Study on multiple traveling salesman problem based on genetic algorithm
王海龙; 周辉仁; 魏颖辉
2009-01-01
旅行商问题是一个经典的NP完全问题,对多人旅行商问题的求解则更具有意义.以往对求解多人旅行商问题的研究局限于以所有旅行商路径总和最小为优化标准,而对所有旅行商路径最大值最小的多旅行商一类问题研究的相对较少.针对所有旅行商路径最大值最小的多旅行商一类问题,用遗传算法优化,并且提出了矩阵解码方法.该方法适于距离对称和非对称的多旅行商问题求解.以距离非对称的多旅行商问题的实例进行了仿真,并对不同交叉算子性能进行了比较.
Genetic Algorithm Based Solution of Multiple Travelling Salesman Problem%基于遗传算法的多人旅行商问题求解
代坤; 鲁士文; 蒋祥刚
2004-01-01
旅行商问题是一个经典的NP完全问题,多人旅行商问题的求解则更具挑战性.以往对求解多人旅行商问题的研究局限于以所有成员路径总和最小为优化标准,而对以所有成员路径最大值最小为优化标准的另一类多人旅行商问题却未加注意.文章给出了这两类多人旅行商问题的形式化描述,探讨了利用遗传算法求解这两类多人旅行商问题的基本思想和具体方案,进行了仿真实验验证.仿真实验数据表明,这是一种高效而且适应性强的多人旅行商问题求解方法.
基于遗传算法的多旅行商问题研究%Study on multiple traveling salesman problem based on genetic algorithm
王海龙; 周辉仁; 郑丕谔; 唐万生
2009-01-01
针对所有旅行商路径总和最小为优化标准的多旅行商一类问题,用遗传算法优化,并提出了矩阵解码方法.对距离非对称的多旅行商问题的实例进行了仿真,并对不同交叉算子性能进行了比较.结果表明,该算法是有效的,适用于距离对称和非对称的多旅行商问题求解.
Traveler's Health: Avoid Bug Bites
... Blood Clots Bug Bites Business Travel Cold Climates Counterfeit Drugs Cruise Ship Travel Families with Children Fish ... insect repellents that contain at least 20% DEET (products include Cutter Backwoods and Off! Deep Woods) for ...
Epidemic spreading by objective traveling
Tang, Ming; Liu, Zonghua; Li, Baowen
2009-07-01
A fundamental feature of agent traveling in social networks is that traveling is usually not a random walk but with a specific destination and goes through the shortest path from starting to destination. A serious consequence of the objective traveling is that it may result in a fast epidemic spreading, such as SARS etc. In this letter we present a reaction-traveling model to study how the objective traveling influences the epidemic spreading. We consider a random scale-free meta-population network with sub-population at each node. Through a SIS model we theoretically prove that near the threshold of epidemic outbreak, the objective traveling can significantly enhance the final infected population and the infected fraction at a node is proportional to its betweenness for the traveling agents and approximately proportional to its degree for the non-traveling agents. Numerical simulations have confirmed the theoretical predictions.
2010-07-26
... Campaign Travel AGENCY: Federal Election Commission. ACTION: Announcement of effective date. SUMMARY: On... of the Honest Leadership and Open Government Act governing campaign travel on noncommercial aircraft.... SUPPLEMENTARY INFORMATION: On December 7, 2009, the Commission published final rules governing campaign...
Knowledge Representation in Travelling Texts
Mousten, Birthe; Locmele, Gunta
2014-01-01
Today, information travels fast. Texts travel, too. In a corporate context, the question is how to manage which knowledge elements should travel to a new language area or market and in which form? The decision to let knowledge elements travel or not travel highly depends on the limitation...... and the purpose of the text in a new context as well as on predefined parameters for text travel. For texts used in marketing and in technology, the question is whether culture-bound knowledge representation should be domesticated or kept as foreign elements, or should be mirrored or moulded—or should not travel...... at all! When should semantic and pragmatic elements in a text be replaced and by which other elements? The empirical basis of our work is marketing and technical texts in English, which travel into the Latvian and Danish markets, respectively....
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 ...
On the maximum sufficient range of interstellar vessels
Cartin, Daniel
2011-01-01
This paper considers the likely maximum range of space vessels providing the basis of a mature interstellar transportation network. Using the principle of sufficiency, it is argued that this range will be less than three parsecs for the average interstellar vessel. This maximum range provides access from the Solar System to a large majority of nearby stellar systems, with total travel distances within the network not excessively greater than actual physical distance.
CARLSON WAGONLIT TRAVEL
2004-01-01
CARLSON WAGONLIT TRAVEL would like to remind you of the entry formalities applicable to those travelling to the United States. Nationals of Switzerland and of the following countries : Andorra, Australia, Austria, Belgium, Brunei, Denmark, Finland, France, Germany, Iceland, Ireland, Italy, Japan, Liechtenstein, Luxemburg, Monaco, Netherlands, New Zealand, Norway, Portugal, San Marino, Singapore, Slovenia, Spain, Sweden and the United Kingdom, entering the United States under the Visa Waiver Program (no visa requirement), must be in possession of an machine-readable passport that is valid for at least six months after the date of the return trip. Children, including infants, must have their own passport. An entry in the parents' passport is not sufficient. For entry into the United States, an e-ticket (fax or e-mail confirmation or passenger receipt) or a return ticket to the departure point or a ticket to a subsequent onward destination (valid for 90 days) must be presented together with the green ...
Lund, Rebecca; Tienari, Janne
2013-01-01
In this chapter we offer insights into the social construction of diversity in Finnish organizations and society. In Finnish organizations, gender is highlighted while other markers of diversity are blotted out. 'Non-Finns' become subject to cultural assimilation. The US-based concept of Diversity...... Management becomes adopted and adapted in particular ways. Standardized concepts of diversity and its management do not travel, rather they become translated locally. In organizational practice, globalization is slow and laborious....
2008-05-15
Malaria is a serious mosquito-borne disease that can lead to death. This podcast discusses malaria risk when traveling to tropical areas, as well as how to protect yourself and your family from malaria infection. Created: 5/15/2008 by National Center for Zoonotic, Vector-Borne, and Enteric Diseases (NCZVED). Date Released: 5/29/2008.
Mohler, S. R.
1982-01-01
The matter of aging and its relation to space vehicle crewmembers undertaking prolonged space missions is addressed. The capabilities of the older space traveler to recover from bone demineralization and muscle atrophy are discussed. Certain advantages of the older person are noted, for example, a greater tolerance of monotony and repetitious activities. Additional parameters are delineated including the cardiovascular system, the reproductive system, ionizing radiation, performance, and group dynamics.
[Traveling with small children].
Olivier, C
1997-01-01
Traveling with children especially in the tropics requires special planning. Contraindications are rare but care providers should obtain information about medical and transfusional facilities at the destination. Children should receive all vaccinations required for international travel and for specific countries, taking into account age, location, duration of stay, and purpose of trip. A first aid kit should be packed containing a thermometer, bandages, antiseptic agents, a total sunscreen preparation, a mosquito net, sterile compresses, tablets for water disinfection, and indispensable medications (antimalarial agents, antipyretics, oral rehydration solutions, antiemetics, and eye wash). The main indication for chemoprophylaxis is malaria. Chloroquine is recommended for most locations but proguanil may be necessary in areas of resistance. Special attention must be paid to skin care in infants: maintaining cleanliness, avoiding cuts insofar as possible, and treating any wounds. Clothing must be carefully laundered and adequate to prevent overexposure to sunlight and insect bites. Insect bites must also be prevented by applying repellents, using mosquito nets, and wearing insecticide-treated garments. Handwashing by people who prepare meals and by the children before eating is important to prevent food poisoning. Breast feeding is advisable for infants. Thorough cooking of meats, rinsing of fresh produce, drinking of bottled beverages, and sterilization of water are also important food safety measures. These precautions are usually adequate to allow safe travel with children.
Pickover, Clifford A.
1999-09-01
"Bucky Fuller thought big," Wired magazine recently noted, "Arthur C. Clarke thinks big, but Cliff Pickover outdoes them both." In his newest book, Cliff Pickover outdoes even himself, probing a mystery that has baffled mystics, philosophers, and scientists throughout history--What is the nature of time?In Time: A Traveler's Guide , Pickover takes readers to the forefront of science as he illuminates the most mysterious phenomenon in the universe--time itself. Is time travel possible? Is time real? Does it flow in one direction only? Does it have a beginning and an end? What is eternity? Pickover's book offers a stimulating blend of Chopin, philosophy, Einstein, and modern physics, spiced with diverting side-trips to such topics as the history of clocks, the nature of free will, and the reason gold glitters. Numerous diagrams ensure readers will have no trouble following along.By the time we finish this book, we understand a wide variety of scientific concepts pertaining to time. And most important, we will understand that time travel is, indeed, possible.
2006-01-01
Carlson Wagonlit Travel wishes to remind you of the following conditions concerning travel to the USA. Passport conditions Since 26 October 2004, nationals of the countries covered by the US Visa Waiver Programme have been required to present a valid machine-readable passport when entering the United States. Failing this, they require a valid US non-immigrant visa in addition to their passport. Passports issued after 25 October 2005 must also bear a digital photograph. Passports issued after 25 October 2006 must contain biometric data to allow visa-free entry to the US. Advanced Passenger Information System (APIS) form Since 4 October 2005, all non-US citizens travelling to the USA have been required to complete the APIS form before departure and present it when they check in. This new procedure will certainly increase the time it takes to check in. We therefore advise passengers to present themselves at the respective check-in desk in good time. The APIS form can be downloaded from our homepage: w...
CERN Bulletin
2010-01-01
For the first time the new CERN travelling exhibition has gone abroad. The venue is Torino, in Italy, where it is being shown at the Museum of Natural Science in the framework of the activities of the EuroScience Open Forum (ESOF 2010). Soon after the event, the exhibition will fly to Copenhagen. The CERN traveling exhibition was inaugurated in 2009. The new ‘Accelerating Science’ exhibition was inaugurated in 2009 as part of the celebrations to mark the 450th anniversary of the University of Geneva. “CERN’s travelling exhibition is an important tool for outreach in our Member states as it carries the main messages that constitute the backbone of the Laboratory’s education and communication policy”, explains Rolf Landua, head of the Education Group, which manages the exhibition. “The 2010 European Science Open Forum in Torino will gather a lot of experts and visitors from the general public who will be able to experience in an ...
Superluminal travel requires negative energies
Olum, Ken D.
1998-01-01
I investigate the relationship between faster-than-light travel and weak-energy-condition violation, i.e., negative energy densities. In a general spacetime it is difficult to define faster-than-light travel, and I give an example of a metric which appears to allow superluminal travel, but in fact is just flat space. To avoid such difficulties, I propose a definition of superluminal travel which requires that the path to be traveled reach a destination surface at an earlier time than any neig...
Stickel, L.F.; King, John A.
1968-01-01
The concept of home range was expressed by Seton (1909) in the term 'home region,' which Burr (1940, 1943) clarified with a definition of home range and exemplified in a definitive study of Peromyscus in the field. Burt pointed out the ever-changing characteristics of home-range area and the consequent absence of boundaries in the usual sense--a finding verified by investigators thereafter. In the studies summarized in this paper, sizes of home ranges of Peromyscus varied within two magnitudes, approximately from 0.1 acre to ten acres, in 34 studies conducted in a variety of habitats from the seaside dunes of Florida to the Alaskan forests. Variation in sizes of home ranges was correlated with both environmental and physiological factors; with habitat it was conspicuous, both in the same and different regions. Food supply also was related to size of home range, both seasonally and in relation to habitat. Home ranges generally were smallest in winter and largest in spring, at the onset of the breeding season. Activity and size also were affected by changes in weather. Activity was least when temperatures were low and nights were bright. Effects of rainfall were variable. Sizes varied according to sex and age; young mice remained in the parents' range until they approached maturity, when they began to travel more widely. Adult males commonly had larger home ranges than females, although there were a number of exceptions. An inverse relationship between population density and size of home range was shown in several studies and probably is the usual relationship. A basic need for activity and exploration also appeared to influence size of home range. Behavior within the home range was discussed in terms of travel patterns, travels in relation to home sites and refuges, territory, and stability of size of home range. Travels within the home range consisted of repeated use of well-worn trails to sites of food, shelter, and refuge, plus more random exploratory travels
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...
Rabies vaccination for international travelers.
Gautret, Philippe; Parola, Philippe
2012-01-05
Rabies prevention in travelers is a controversial issue. According to experts, the decision to vaccinate results from an individual risk assessment based on the duration of stay, the likelihood of engagement in at-risk activities, the age of the traveler, the rabies endemicity and access to appropriate medical care in the country of destination. However, no detailed information is available regarding the last two determinants in many regions. Twenty-two cases of rabies were reported in tourists, expatriates and migrant travelers over the last decade, including three cases following short-term travel of no more than two weeks. Studies on rabies post-exposure prophylaxis (PEP) in travelers show that overall, 0.4% (range 0.01-2.3%) of travelers have experienced an at-risk bite per month of stay in a rabies-endemic country, while 31% of expatriates and 12% of tourists were vaccinated against rabies before traveling. The main reason cited by travelers for not being vaccinated is the cost of the vaccine. The majority of patients who sustained a high risk injury was not vaccinated against rabies before traveling and were not properly treated abroad. From available studies, the following risk factors for injuries sustained from potentially rabid animals may be identified: traveling to South-East Asia, India or North Africa, young age, and traveling for tourism. The duration of travel does not appear to be a risk factor. It should be noted that "at-risk activities" have not been addressed in these studies. Detailed rabies distribution maps and information on the availability of rabies biologics are urgently needed in order to identify those travelers who need pre-travel vaccination. Meanwhile, cost-minimization of rabies pre-exposure vaccination may be achieved in several ways, notably by using the intra-dermal method of vaccination.
Fellow travellers: Working memory and mental time travel in rodents.
Dere, Ekrem; Dere, Dorothea; de Souza Silva, Maria Angelica; Huston, Joseph P; Zlomuzica, Armin
2017-03-19
The impairment of mental time travel is a severe cognitive symptom in patients with brain lesions and a number of neuropsychiatric disorders. Whether animals are also able to mentally travel in time both forward and backward is still a matter of debate. In this regard, we have proposed a continuum of mental time travel abilities across different animal species, with humans being the species with the ability to perform most sophisticated forms of mental time travel. In this review and perspective article, we delineate a novel approach to understand the evolution, characteristics and function of human and animal mental time travel. Furthermore, we propose a novel approach to measure mental time travel in rodents in a comprehensive manner using a test battery composed of well-validated and easy applicable tests. Copyright © 2017. Published by Elsevier B.V.
Southworth, Frank [ORNL; Garrow, Dr. Laurie [Georgia Institute of Technology
2011-01-01
This chapter describes the principal types of both passenger and freight demand models in use today, providing a brief history of model development supported by references to a number of popular texts on the subject, and directing the reader to papers covering some of the more recent technical developments in the area. Over the past half century a variety of methods have been used to estimate and forecast travel demands, drawing concepts from economic/utility maximization theory, transportation system optimization and spatial interaction theory, using and often combining solution techniques as varied as Box-Jenkins methods, non-linear multivariate regression, non-linear mathematical programming, and agent-based microsimulation.
Cliff, Andrew; Haggett, Peter
2004-01-01
The collapse of geographical space over the last 200 years has had profound effects on the circulation of human populations and on the transfer of infectious diseases. Three examples are used to illustrate the process: (a) the impact of the switch from sail to steamships in importing measles into Fiji over a 40-year period; (b) changes in measles epidemic behaviour in Iceland over a 150-year period; and (c) changes in the spread of cholera within the United States over a 35-year period. In each case, the link between time, travel and disease has been an intimate one.
Robert; Louis; Stevenson
2005-01-01
The sun is not a-bed, when I At night upon my pillow lie; Stilt round the earth his Way he takes, And morning after morning makes. White here at home, in shining day, We round the sunny garden play, Each tittle Indian sleepy - head Is being kissed and put to bed. And When at eve I rise from tea, Day dawns beyond the Atlantic Sea; And all the children in the West Are getting up and being dressed.The SUN'S TRAVELS@Robert Louis Stevenson
Health hazards of international travel.
Cossar, J H; Reid, D
1989-01-01
The growth of travel and the increasing numbers of those affected by travel-related illnesses, some of a serious nature, will cause this subject to demand the attention of the medical profession, the travel trade, travellers themselves and the health authorities of countries receiving tourists. Provision of appropriate advice for the traveller is a shared responsibility, best channelled mainly through travel agencies; it can moreover be shown to be cost-beneficial. Continued monitoring of illness in travellers and provision of information systems geared to this problem and its prevention are fully justified. They should be based on traditional channels of communication and currently-available modern technology, and be readily accessible to medical and related workers. Increased collaboration between medical workers, health educators and those involved in the travel trade would be a positive and useful contribution towards the reduction of illness and discomfort among travellers and the associated expense incurred by the various national health services concerned. There are clearly economic benefits from the development of international tourism, but these have to be balanced in countries accepting tourists by attention to the prevention of illnesses associated with travel.
The Ethical Concerns in Death of Salesman%《推销员之死》的伦理关怀
刘胜利; 薛家宝
2014-01-01
叶推销员之死》是阿瑟·米勒的代表作。本文试图从伦理的视角来分析主人公失败的原因。威利是传统伦理文化和资本主义文化的混合体，而这两者之间充满了矛盾性，从而导致了主人公以自杀来无意识地维护和实践传统文化中对儿子成功的观念和维护自己尊严。%Death of a Salesman is the representative work of Arthur Miller. This essay analyzes the reason of the characters' failure from the perspective of the ethics. Willy is the hybrid of the traditional ethnics and the capitalism one, but these two kinds are full of contradictions. Therefore, it causes that Willy maintains his dignity and the brief that her sons will succeed by committing suicide.
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....
Kory, Carol L.
1998-01-01
The traveling-wave tube (TWT) is a vacuum device invented in the early 1940's used for amplification at microwave frequencies. Amplification is attained by surrendering kinetic energy from an electron beam to a radio frequency (RF) electromagnetic wave. The demand for vacuum devices has been decreased largely by the advent of solid-state devices. However, although solid state devices have replaced vacuum devices in many areas, there are still many applications such as radar, electronic countermeasures and satellite communications, that require operating characteristics such as high power (Watts to Megawatts), high frequency (below 1 GHz to over 100 GHz) and large bandwidth that only vacuum devices can provide. Vacuum devices are also deemed irreplaceable in the music industry where musicians treasure their tube-based amplifiers claiming that the solid-state and digital counterparts could never provide the same "warmth" (3). The term traveling-wave tube includes both fast-wave and slow-wave devices. This article will concentrate on slow-wave devices as the vast majority of TWTs in operation fall into this category.
Gleick, James
2016-01-01
From the acclaimed author of The Information and Chaos, here is a mind-bending exploration of time travel: its subversive origins, its evolution in literature and science, and its influence on our understanding of time itself. The story begins at the turn of the previous century, with the young H. G. Wells writing and rewriting the fantastic tale that became his first book and an international sensation: The Time Machine. It was an era when a host of forces was converging to transmute the human understanding of time, some philosophical and some technological: the electric telegraph, the steam railroad, the discovery of buried civilizations, and the perfection of clocks. James Gleick tracks the evolution of time travel as an idea that becomes part of contemporary culture—from Marcel Proust to Doctor Who, from Jorge Luis Borges to Woody Allen. He investigates the inevitable looping paradoxes and examines the porous boundary between pulp fiction and modern physics. Finally, he delves into a temporal shift that...
Murabona Oduori, Susan
2015-08-01
The telescope has been around for more than 400 years, and through good use of it scientists have made many astonishing discoveries and begun to understand our place in the universe. Most people, however, have never looked through one. Yet it is a great tool for cool science and observation especially in a continent and country with beautifully dark skies. The Travelling Telescope project aims to invite people outside under the stars to learn about those curious lights in the sky.The Travelling Telescope aims to promote science learning to a wide range of Kenyan schools in various locations exchanging knowledge about the sky through direct observations of celestial bodies using state of the art telescopes. In addition to direct observing we also teach science using various hands-on activities and astronomy software, ideal for explaining concepts which are hard to understand, and for a better grasp of the sights visible through the telescope. We are dedicated to promoting science using astronomy especially in schools, targeting children from as young as 3 years to the youth, teachers, their parents and members of the public. Our presentation focuses on the OAD funded project in rural coastal Kenya.
Webb, G M; Ao, X; Zank, G P
2013-01-01
Models for travelling waves in multi-fluid plasmas give essential insight into fully nonlinear wave structures in plasmas, not readily available from either numerical simulations or from weakly nonlinear wave theories. We illustrate these ideas using one of the simplest models of an electron-proton multi-fluid plasma for the case where there is no magnetic field or a constant normal magnetic field present. We show that the travelling waves can be reduced to a single first order differential equation governing the dynamics. We also show that the equations admit a multi-symplectic Hamiltonian formulation in which both the space and time variables can act as the evolution variable. An integral equation useful for calculating adiabatic, electrostatic solitary wave signatures for multi-fluid plasmas with arbitrary mass ratios is presented. The integral equation arises naturally from a fluid dynamics approach for a two fluid plasma, with a given mass ratio of the two species (e.g. the plasma could be an electron pr...
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
CONCEPTUAL CLARIFICATIONS REGARDING YOUTH TRAVEL
Lect. Ph.D Student Moisa Claudia Olimpia
2010-01-01
Currently, there is no clear definition for the youth travel concept. This concept emerged much latter than the first forms of manifestation of tourism for young people, namely the beginning of the ’90s when the first studies regarding youth travel were also conducted. No doubt, the concept of youth travel ensues from three notions, namely: youth, tourism and vacation – in the sense of free time. All the definitions used by tourism organizations, by various national tourism administrations an...
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.
Travel opinion leaders and seekers
Yoo, Kyung-Hyan; Gretzel, Ulrike; Zach, Florian
2011-01-01
While opinion leadership has been recognized as important in tourism, there has been very little empirical research investigating the phenomenon. Given new developments in social media technologies, it is especially important to understand whether travel opinion leadership and seeking are drivers...... media use. The findings suggest that travel opinion leadership and seeking are distinct but connected. Both opinion leaders and seekers are technology savvy, young, educated, involved in travel planning and engaged in social media use for travel. What distinguishes opinion leaders is their greater...
Communication from Carlson Wagonlit Travel
2008-01-01
Entry requirements for the USA: "ESTA" (Electronic System for Travel Authorization) online registration The requirement to register before entering the USA announced by the Department of Homeland Security (DHS) is to be introduced on 12 January 2009. Visitors to the USA will then be required to register their personal data and travel data online not less than 72 hours prior to travel. https://esta.cbp.dhs.gov/ General information on entry requirements for the USA are also available on the Carlson Wagonlit Travel website under the heading „CWT informs": http://www.carlsonwagonlit.ch
Communication from Carlson Wagonlit Travel
2009-01-01
Entry requirements for the USA: "ESTA" (Electronic System for Travel Authorization) online registration The requirement to register before entering the USA announced by the Department of Homeland Security (DHS) is to be introduced on 12 January 2009. Visitors to the USA will then be required to register their personal data and travel data online not less than 72 hours prior to travel. https://esta.cbp.dhs.gov/ General information on entry requirements for the USA is also available on the Carlson Wagonlit Travel website under the heading „CWT informs": http://www.carlsonwagonlit.ch
Single Wave Overtopping Volumes and their Travel Distance for Rubble Mound Breakwaters
Andersen, Thomas Lykke; Burcharth, Hans F.; Gironella, F. X.
2009-01-01
In the present paper small and large scale overtopping data for rubble mound structures have been analysed with respect to single wave overtopping volumes and their travel distance. The analysis has led to formulae for estimation of maximum single wave overtopping volumes and their travel distance...
Russell, C. T.
A useful rule of thumb in solar terrestrial studies is that the solar wind travels 4 Earth radii (RE) per minute. Long-term studies of solar wind velocity [e.g., Luhmann et al., 1993; 1994] show that the median velocity is about 420 km/s, corresponding to 3.96 RE min-1. The quartiles are about 370 km/s and 495 km/s, corresponding to 3.48 Re min-1 and 4.66 Re min-1 respectively. This number helps estimate the delays expected when observing a discontinuity at a solar wind monitor; one example is ISEE-3 when it was at the forward libration point (about 60 min). It is also helpful for estimating how much time passes before the dayside magnetosphere is compressed as denser solar wind flows by (about 2.5 min).
Novita Lavi N
2013-05-01
Full Text Available The sun exposure brings negative effects on the skin such like early aging, spots and skin cancer as the most terrible effect. To reduce the adverse effects of the sun, it is not enough just to behavioral therapy, but also had no protection from the outside. Especially for travellers that exposed by the sun excessively. There is sunscreen, product specially formulated to absorb or deflect ultraviolet rays. A sunscreen preparation contains chemical compounds that can absorb, scatter or reflect sunlight on the skin. This writing contains about effect of ultraviolet, skin protection from ultraviolet from behavioral aspect, variaty and contents of sunscreen and sunscreen application for travellers. Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table 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:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;}
International Travelers' Sociodemographic, Health, and Travel Characteristics: An Italian Study.
Troiano, Gianmarco; Mercone, Astrid; Bagnoli, Alessandra; Nante, Nicola
Approximately the 8% of travelers requires medical care, with the diagnosis of a vaccine-preventable disease. The aim of our study was to analyze the socio-demographic, health and travel characteristics of the Italian international travelers. We conducted a cross sectional study from January 2015 to June 2016, at the Travel Medicine Clinic of Siena, asking the doctor to interview patients who attended the Clinic, recording socio-demographic and travel information, malaria prophylaxis, vaccinations. The data were organized in a database and processed by software Stata®. We collected 419 questionnaires. Patients chose 71 countries for their travels; the favorite destinations were: India (6.31%), Thailand (6.31%), and Brazil (5.10%). The mean length of stay was 36.17 days. Italians, students, and freelancers tended to stay abroad for a longer time (mean: 36.4 days, 59.87 days and 64.16 days respectively). 33.17% of our sample used drugs for malaria chemoprophylaxis: 71.9% of them used Atovaquone/Proguanil (Malarone®), 26.6% used Mefloquine (Lariam®), 1.5% other drugs. The vaccinations that travelers mostly got in our study were to prevent hepatitis A (n = 264), the typhoid fever (n = 187), the Tetanus + Diphtheria + Pertussis (n = 165), the Yellow fever (n = 118) and the cholera (n = 78). Twenty-eight (6.68%) refused some recommended vaccinations. The vaccines mostly refused were for Typhoid fever (n = 20), hepatitis a (n = 9), and cholera (n = 9). Our results demonstrated that Italian international travelers are at-risk because of their poor vaccinations adherence. This implies that pre-travel counseling is fundamental to increase the knowledge of the risks and the compliance of future travelers. Copyright © 2016 Icahn School of Medicine at Mount Sinai. Published by Elsevier Inc. All rights reserved.
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.
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].
Carlson Wagonlit Travel is moving
2013-01-01
The renovation of the Main Building continues! Because of this, Carlson Wagonlit Travel will move from building 62 to building 510 on 4 October and the agency will be closed in the afternoon. An emergency service will be organised for official travels only. Phone: 022 799 75 73 & 022 799 75 78 / e-mail: cern@carlsonwagonlit.ch
Monitoring Travel Time Reliability on Freeways
Tu, Huizhao
2008-01-01
Travel time and travel time reliability are important attributes of a trip. The current measures of reliability have in common that in general they all relate to the variability of travel times. However, travel time reliability does not only rely on variability but also on the stability of travel
Monitoring Travel Time Reliability on Freeways
Tu, Huizhao
2008-01-01
Travel time and travel time reliability are important attributes of a trip. The current measures of reliability have in common that in general they all relate to the variability of travel times. However, travel time reliability does not only rely on variability but also on the stability of travel ti
Lihoreau, Mathieu; Chittka, Lars; Raine, Nigel E
2010-12-01
Animals collecting resources that replenish over time often visit patches in predictable sequences called traplines. Despite the widespread nature of this strategy, we still know little about how spatial memory develops and guides individuals toward suitable routes. Here, we investigate whether flower visitation sequences by bumblebees Bombus terrestris simply reflect the order in which flowers were discovered or whether they result from more complex navigational strategies enabling bees to optimize their foraging routes. We analyzed bee flight movements in an array of four artificial flowers maximizing interfloral distances. Starting from a single patch, we sequentially added three new patches so that if bees visited them in the order in which they originally encountered flowers, they would follow a long (suboptimal) route. Bees' tendency to visit patches in their discovery order decreased with experience. Instead, they optimized their flight distances by rearranging flower visitation sequences. This resulted in the development of a primary route (trapline) and two or three less frequently used secondary routes. Bees consistently used these routes after overnight breaks while occasionally exploring novel possibilities. We discuss how maintaining some level of route flexibility could allow traplining animals to cope with dynamic routing problems, analogous to the well-known traveling salesman problem.
Baron, Danielle M; Ramirez, Alejandro J; Bulitko, Vadim; Madan, Christopher R; Greiner, Ariel; Hurd, Peter L; Spetch, Marcia L
2015-01-01
Visiting multiple locations and returning to the start via the shortest route, referred to as the traveling salesman (or salesperson) problem (TSP), is a valuable skill for both humans and non-humans. In the current study, pigeons were trained with increasing set sizes of up to six goals, with each set size presented in three distinct configurations, until consistency in route selection emerged. After training at each set size, the pigeons were tested with two novel configurations. All pigeons acquired routes that were significantly more efficient (i.e., shorter in length) than expected by chance selection of the goals. On average, the pigeons also selected routes that were more efficient than expected based on a local nearest-neighbor strategy and were as efficient as the average route generated by a crossing-avoidance strategy. Analysis of the routes taken indicated that they conformed to both a nearest-neighbor and a crossing-avoidance strategy significantly more often than expected by chance. Both the time taken to visit all goals and the actual distance traveled decreased from the first to the last trials of training in each set size. On the first trial with novel configurations, average efficiency was higher than chance, but was not higher than expected from a nearest-neighbor or crossing-avoidance strategy. These results indicate that pigeons can learn to select efficient routes on a TSP problem.
Travel Writing on the Edge: An Intermedial Approach to Travel Books and Travel Blogs
Calzati Stefano
2015-08-01
Full Text Available After discussing the limits and potentialities of the definitions of travel writing proposed by Paul Fussell (1980. Patrick Holland and Graham Huggan (1998 and Jan Borm (2004, the article presents a characterization of travel writing both as a genre with a precise rhetorical status, as well as a praxis of knoivledge, which derives from the interplay between travelling and writing. Building on this, a comparison between two Italian travel books and two Italian travel blogs about China is proposed. Specifically, by considering these texts as “intermedial transpositions” (Wolf 2008 that realize the same generic and epistemological matrix (i.e. travel writing, a Multimodal Critical Discourse Analysis (MCDA is conducted in order to assess: 1 how the book and the blog, as different medial formats, interpret the rhetorical features of the travel writing genre: and 2 to what extent the gnoseological and cross-cultural potentials of travel writing, as a praxis of knowledge, is affected by the process of transposition.
Carlson Wagonlit Travel
2005-01-01
Chères clientes, chers clients, Le 3 janvier dernier, nous vous avons informé de la décision des compagnies aériennes de supprimer les commissions versées aux agences de voyages suisses. Cette mesure a été introduite progressivement pour être appliquées maintenant par toutes les compagnies, à quelques rares exceptions près. En conséquence, en accord avec le CERN, nous serons dans l'obligation d'appliquer une nouvelle liste de prix de nos transactions pour les voyages privés. Elle sera applicable dès le lundi 25 juillet 2005. Carlson Wagonlit Travel (CWT) vous propose : Son service de conseil personnalisé, professionnel et compétent Sa recherche de la solution la plus économique et la mieux adaptée à vos besoins Sa neutralité dans les comparaisons de prix et prestations Des informations com...
Paintball velocity as a function of distance traveled
Pat Chiarawongse
2008-06-01
Full Text Available The relationship between the distance a paintball travels through air and its velocity is investigated by firing a paintball into a ballistic pendulum from a range of distances. The motion of the pendulum was filmed and analyzed by using video analysis software. The velocity of the paintball on impact was calculated from the maximum horizontal displacement of the pendulum. It is shown that the velocity of a paintball decreases exponentially with distance traveled, as expected. The average muzzle velocity of the paint balls is found with an estimate of the drag coefficient
Paintball velocity as a function of distance traveled
Pat Chiarawongse
2008-06-01
Full Text Available The relationship between the distance a paintball travels through air and its velocity is investigated by firing a paintball into a ballistic pendulum from a range of distances. The motion of the pendulum was filmed and analyzed by using video analysis software. The velocity of the paintball on impact was calculated from the maximum horizontal displacement of the pendulum. It is shown that the velocity of a paintball decreases exponentially with distance traveled, as expected. The average muzzle velocity of the paint balls is found with an estimate of the drag coefficient.
Knowledge Representation in Travelling Texts
Mousten, Birthe; Locmele, Gunta
2014-01-01
and the purpose of the text in a new context as well as on predefined parameters for text travel. For texts used in marketing and in technology, the question is whether culture-bound knowledge representation should be domesticated or kept as foreign elements, or should be mirrored or moulded—or should not travel...... at all! When should semantic and pragmatic elements in a text be replaced and by which other elements? The empirical basis of our work is marketing and technical texts in English, which travel into the Latvian and Danish markets, respectively....
Last-Minute Travel Application
Hubner, Andre; Lenz, Mario; Borch, Roman; Posthoff, Michael
2000-01-01
In this article, we present a last-minute travel application as part of a complete virtual travel agency. Each year, a significant amount of tour packages are sold as last minute tours in Germany. It is impossible for a travel agent to keep track of all the offered tour packages. Electronic-commerce applications might present the best possible tour package for a specific customer request. Traditional database-driven applications, as used by most of the tour operators, are not sufficient enoug...
Lateralization of travelling wave response in the hearing organ of bushcrickets.
Arun Palghat Udayashankar
Full Text Available Travelling waves are the physical basis of frequency discrimination in many vertebrate and invertebrate taxa, including mammals, birds, and some insects. In bushcrickets (Tettigoniidae, the crista acustica is the hearing organ that has been shown to use sound-induced travelling waves. Up to now, data on mechanical characteristics of sound-induced travelling waves were only available along the longitudinal (proximal-distal direction. In this study, we use laser Doppler vibrometry to investigate in-vivo radial (anterior-posterior features of travelling waves in the tropical bushcricket Mecopoda elongata. Our results demonstrate that the maximum of sound-induced travelling wave amplitude response is always shifted towards the anterior part of the crista acustica. This lateralization of the travelling wave response induces a tilt in the motion of the crista acustica, which presumably optimizes sensory transduction by exerting a shear motion on the sensory cilia in this hearing organ.
Lateralization of travelling wave response in the hearing organ of bushcrickets.
Palghat Udayashankar, Arun; Kössl, Manfred; Nowotny, Manuela
2014-01-01
Travelling waves are the physical basis of frequency discrimination in many vertebrate and invertebrate taxa, including mammals, birds, and some insects. In bushcrickets (Tettigoniidae), the crista acustica is the hearing organ that has been shown to use sound-induced travelling waves. Up to now, data on mechanical characteristics of sound-induced travelling waves were only available along the longitudinal (proximal-distal) direction. In this study, we use laser Doppler vibrometry to investigate in-vivo radial (anterior-posterior) features of travelling waves in the tropical bushcricket Mecopoda elongata. Our results demonstrate that the maximum of sound-induced travelling wave amplitude response is always shifted towards the anterior part of the crista acustica. This lateralization of the travelling wave response induces a tilt in the motion of the crista acustica, which presumably optimizes sensory transduction by exerting a shear motion on the sensory cilia in this hearing organ.
Knudsen, Mette Aagaard
2014-01-01
.g. socio-economic variables. The analysis of Danish travel activities described in the three different travel surveys has outlined detailed information on Danish travel behaviour at an aggregated level during the past two decades. It has above all revealed the significant role of leisure travel. Private...... in a study of leisure travel, with an analysis of the income elasticity of this travel segment. Due to the different survey methodologies, the samples of leisure activities describe the whole span from daily leisure travel activities embedded into people’s daily routines to the infrequent holiday activities....... The applied model describes the travel distance of leisure travel including the probability of having leisure activities or not. The study finds increasing income elasticities of travelling or not and increasing income elasticities of travel distances as the leisure purposes become less frequently completed...
Catchment mixing processes and travel time distributions
Botter, Gianluca
2012-01-01
...) of travel, residence and evapotranspiration times, which are comprehensive descriptors of the fate of rainfall water particles traveling through catchments, and provide key information on hydrologic...
Ben Iannotta
2015-01-01
Here, Iannotta discusses the future of air travel. Among other things, safety technologies that seemed exotic will become the norm, like the auto industry's hands-free Bluetooth systems and side-curtain airbags...
Mosquito Bite Prevention For Travelers
... and parasites that can cause diseases like chikungunya, dengue, Zika, and malaria. If you are traveling to an area where malaria is found, talk to your healthcare provider about malaria prevention medication that may be available. Protect yourself and ...
DCHA Travel & Mission Support System
US Agency for International Development — DTRAMS is a travel data collection system for DCHA that collects information on both the basic details of an employee's trips (destination, length, purpose, etc.)...
PPL Travel & Mission Support System
US Agency for International Development — PTRAMS is a travel data collection system for PPL that collects information on both the basic details of an employee's trips (destination, length, purpose, etc.) and...
GH Travel & Mission Support System
US Agency for International Development — HTRAMS is a travel data collection system for GH that collects information on both the basic details of an employee's trips (destination, length, purpose, etc.) and...
Travelers' Health: Viral Hemorrhagic Fevers
... Climates Humanitarian Aid Workers Humanitarian Aid Workers in Ecuador Insurance International Adoption Jet Lag Last-Minute Travel ... Landry ML, Warnock DW, editors. Manual of Clinical Microbiology. 10th ed. Washington, DC: ASM Press; 2011. p. ...
Transmedia storytelling on travel stories
Adolfo Baltar Moreno
2016-01-01
Full Text Available Travel stories form part of a great tradition inside Western Culture which has served historically to describe, to understand and to imagine other cul - tures and communities, far or near, being constituted into a real narra - tive genre. This type of story has been and is a reflection of the perception of the world based on the imaginary worlds created by the travelling narrators. How do modern authors of travel stories take advantage of the opportunities offered by transmedia storytelling? The present article explores the potential of these types of stories as a privileged object of study for transmedia storytelling studies, from the analysis of a sample of 80 narrative productions based on experiences of travel and presented in diverse editions of the Festival Le Grand Bivouac (France. It also shows the existence of a new contemporary trend inside this narrative form that transcends its literary nature.
Applications of Discrepancy Theory in Multiobjective Approximation
Glaßer, Christian; Witek, Maximilian
2011-01-01
We apply a multi-color extension of the Beck-Fiala theorem to show that the multiobjective maximum traveling salesman problem is randomized 1/2-approximable on directed graphs and randomized 2/3-approximable on undirected graphs. Using the same technique we show that the multiobjective maximum satisfiablilty problem is 1/2-approximable.
Christensen, Linda
2014-01-01
This paper presents an overview of the Dane’s long distance travel. It is a part of the Drivers and Limits project about long distance travel. Long distance travel is in the project defined as infrequent travel with overnight stay. Danes 15-85 years-old travel in average 5.5 long distance travel...... per year og which a third is for international destinations, a third is for domestic second homes and a third are other domestic trips. However, 87% of the kilometres are for international destinations and only 4% are for domestic second homes. Travel activity is very uneven distributed with only half...... of the population having had a journey during the last three month. At the other hand 60% have travelled internationally during the last year and only 2% have never travelled abroad. The paper presents among other things how the travel activity is distributed on travel purpose and mode and how the mode choice...
Sequentially pulsed traveling wave accelerator
Caporaso, George J.; Nelson, Scott D.; Poole, Brian R.
2009-08-18
A sequentially pulsed traveling wave compact accelerator having two or more pulse forming lines each with a switch for producing a short acceleration pulse along a short length of a beam tube, and a trigger mechanism for sequentially triggering the switches so that a traveling axial electric field is produced along the beam tube in synchronism with an axially traversing pulsed beam of charged particles to serially impart energy to the particle beam.
A model of multidestination travel
Morisugi, H.; Tussyadiah, Iis; Kono, T.
2006-01-01
, specifically address the choice of a single destination. This article is intended to explain multiple destination choice using Lancaster's characteristics model and a discussion of model implications of some marketing strategies for destinations as well as for tour operators. The model developed herein...... explains that packages of multiple destinations can create preferable combinations of characteristics for certain travelers. Furthermore, the model provides useful strategies for tour operators in combining destinations into a travel menu or package. © 2006 Sage Publications....
Infectious Risks of Traveling Abroad.
Chen, Lin H; Blair, Barbra M
2015-08-01
A popular leisure activity, international travel can be associated with some infections. The most common travel-related illnesses appear to be gastrointestinal, dermatologic, respiratory, and systemic febrile syndromes. The pretravel medical consultation includes immunizations, malaria chemoprophylaxis, self-treatment for traveler's diarrhea, and advice on the prevention of a myriad of other infectious causes including dengue, chikungunya, rickettsiosis, leptospirosis, schistosomiasis, and strongyloidiasis. Travel to locations experiencing outbreaks such as Ebola virus disease, Middle East respiratory syndrome, avian influenza, and chikungunya call for specific alerts on preventive strategies. After travel, evaluation of an ill traveler must explore details of exposure, including destinations visited; activities; ingestion of contaminated food or drinks; contact with vectors, animals, fresh water, or blood and body fluids; and other potential exposures. Knowledge of the geographic distribution of infectious diseases is important in generating the differential diagnoses and testing accordingly. Empiric treatment is sometimes necessary when suspicion of a certain diagnosis is strong and confirmatory tests are delayed or lacking, particularly for infections that are rapidly progressive (for example, malaria) or for which timing of testing is prolonged (such as leptospirosis).
Knudsen, Mette Aagaard; Rich, Jeppe; Nielsen, Otto Anker
2014-01-01
Historically there has been a lack of knowledge with respect to long distance travel. Due to the considerable contribution of long distance travel to total travelled kilometres and the related energy consumption from the transport sector and derived impacts on greenhouse emissions, this is problematic. The average travel distance has steadily increased during the latest decades together with the increasing motorisation of daily travel and international aviation. Previously most focus has been...
A relational approach to analysing leisure travel
Ettema, D.F.; Schwanen, T.
2012-01-01
Leisure travel makes up a very significant part of daily travel and therefore needs to be considered in any travel demand management or general land use and transportation policy. Yet, research into leisure mobility has tended to ignore important aspects of leisure travel, such as its joint characte
CULTURAL TRANSFER IN TRAVEL GUIDE TRANSLATION: DISCOURSE APPROACH
Novikova Elina Yuryevna
2014-09-01
Full Text Available Intercultural communication and dialogue between various social and political structures and their globalized conditions immediately lead to the development of tourism and services market in this area, including translation services. The study of linguocultural characteristics of a travel guide in terms of pragmatically adequate translation is an interesting aspect for the analysis of the development and functioning of logics of modern interaction planes because the mass tourism participants' communicative characteristics are determined, on the one hand, by the universal, global, economic, social and cultural programmes of mass tourism and, on the other hand, by the local and national peculiarities of tourism discourse in general. The choice of linguistic means in travel guides is determined by their communicative and pragmatic as well as ethno-cultural characteristics that form the main discourse oriented translation programme. The translation of the travel guide texts to German supposes significant differences at out- and in-text levels to achieve maximum compliance with the potential recipients' expectations. The analysis of the two translations of the Russian-language travel guide made to German by the native German speaker and the non-native German speaker let define the so-called sharp edges in the cultural transfer of the information important for the discourse. The travel guide is characterized by the specific features of the touristics discourse, on the one hand, and by the interesting experience of translating, on the other hand.
Practical advice for perioperative travel nurses.
Brumley, Cindy L
2002-10-01
Travel nursing presents unique opportunities that permanent employees may never experience. Today's nursing shortage allows travel nurses to fill temporary staff positions while experiencing the sights, culture, and cuisine of a location of their choosing. This creates a beneficial situation for travel nurses, hospitals, travel companies, and, ultimately, patients. Knowledgeable, flexible nurses and traveler-friendly hospitals can extend contracts if mutually agreeable, thus prolonging the benefits. Before beginning the adventure, however, travelers must have realistic expectations. Many disappointed travelers may have been more successful had they done better research.
TRAVELING MACHINE DRIVEN BY PIEZOELECTRIC BIMORPH
HUA Shunming; CHENG Guangming; FAN Zunqiang; YANG Zhigang; SUZUKI Katsiyoshi
2007-01-01
A rectangular bimorph will vibrate in bending mode under alternating current (AC) electric field. If two opposite tips along longitudinal direction are both clamped, the maximum magnitude of bending displacement occurs on the short center line. Using bimorph type vibrators forementioned as actuators, an invention of simple traveling machine based on stick-slip principle is presented. The machine can not only move along both x and y direction within horizontal working plane, furthermore, excellent bearing ability and agile response as well as stable step are also proved. In addition, the machine can work on stepping mode and scanning mode at the same time, hence the contradiction between long stroke and high precise positioning is solved. Therefore, it meets the needs of micro/nanometer precise positioning under long stroke and is desired to be used as carrying stage for micro-assembling system and locomotive mechanism for miniature robot system.
The value of travel time variance
Fosgerau, Mogens; Engelson, Leonid
2011-01-01
This paper considers the value of travel time variability under scheduling preferences that are defined in terms of linearly time varying utility rates associated with being at the origin and at the destination. The main result is a simple expression for the value of travel time variability...... that does not depend on the shape of the travel time distribution. The related measure of travel time variability is the variance of travel time. These conclusions apply equally to travellers who can freely choose departure time and to travellers who use a scheduled service with fixed headway. Depending...... on parameters, travellers may be risk averse or risk seeking and the value of travel time may increase or decrease in the mean travel time....
Dynamics of a multi-mode maximum entangled coherent state over an amplitude damping channel
A. E1 Allati; Y. Hassouni; N. Metwally
2011-01-01
The dynamics of the maximum entangled coherent state traveling through an amplitude damping channel is investigated.For small values of the transmissivity rate,the traveling state is very fragile to this noise channel,which suffers from the phase flip error with high probability. The entanglement decays smoothly for larger values of the transmissivity rate and speedily for smaller values of this rate.As the number of modes increases,the traveling state over this noise channel quickly loses its entanglement.The odd and even states vanish at the same value of field intensity.
Dynamics of multi-modes maximum entangled coherent state over amplitude damping channel
Allati, A El; Metwally, N
2012-01-01
The dynamics of maximum entangled coherent state travels through an amplitude damping channel is investigated. For small values of the transmissivity rate the travelling state is very fragile to this noise channel, where it suffers from the phase flip error with high probability. The entanglement decays smoothly for larger values of the transmissivity rate and speedily for smaller values of this rate. As the number of modes increases, the travelling state over this noise channel loses its entanglement hastily. The odd and even states vanish at the same value of the field intensity.
Observational Study of Travelers' Diarrhea.
Meuris
1995-03-01
Background: European air travelers returning from Algeria, Egypt, Mexico, Morocco, and Tunisia were interviewed about their experience of travelers' diseases upon arrival in Brussels. Diarrhea was mentioned by 37% of the adults and 27% of the children. These subjects were questioned about the types of measures taken, type and duration of drug treatment (if any), and about duration of diarrhea and side effects experienced. Methods: Final analysis was performed based on 2160 interviews. The largest proportion of diarrhea was reported in the age group 15-24 years (46%). Results: The majority of the 2160 subjects had opted for drug treatment (81%): 927 subjects for loperamide alone, 235 for loperamide in combination with nifuroxazide, and 178 for nifuroxazide alone. Other drugs had been used less frequently. The median time to recovery was 2.4 days with loperamide compared to 3.2 days with nifuroxazide and to 3.4 days for the no-treatment group. Conclusions: A stratification of the results by severity of the diarrhea suggests a rank of antidiarrheal potency as follows: loperamide > nifuroxazide > no-drug treatment. The side effect with the highest incidence was constipation (2.4% with loperamide). (J Travel Med 2:11-15, 1995) Travelers' diarrhea is usually defined as the passage of at least three unformed stools per day or any number of such stools when accompanied by fever, abdominal cramping, or vomiting. The definition may be broadened to include more trivial bowel disturbance.1,2 The duration of this self-limited disease generally is 3 to 5 days. Medical intervention aims at shortening the duration of disease, thus allowing the sufferer to resume his or her usual activities at an early stage. A shortened period of recovery to physical well-being has obvious favorable economic implications if the traveler is on business and may help the maintenance of a desired level of quality of life while a traveler is on holiday. An observational study of various medical
Choosing between travel agencies and the Internet
2015-01-01
M.A. (Tourism and Hospitality Management) Travel agents have been traditionally seen as the key intermediary between suppliers of travel services and the traveller. Developments in the field of information technology offer consumers an alternative to booking via a travel agent - the option to plan and arrange holidays online. Due to the ever developing nature of technology, travellers have the luxury of a multitude of choices in their everyday life - particularly so in making decisions reg...
Poliomyelitis--prevention in travellers.
Mayer, Cora A; Neilson, Amy A
2010-03-01
This article is the second in a series providing a summary of prevention strategies and vaccination for infections that may be acquired by travellers. The series aims to provide practical strategies to assist general practitioners in giving travel advice, as a synthesis of multiple information sources which must otherwise be consulted. Poliomyelitis is a potentially fatal viral illness, which may cause acute flaccid paralysis and permanent central nervous system damage. Ongoing global efforts to eradicate poliomyelitis have been under way since 1988. Travellers are at risk of infection in countries with endemic wild poliomyelitis virus or imported cases, and can spread the infection to areas where poliomyelitis has been eradicated. While all adults should be immune to poliomyelitis, it is important that at-risk travellers are vaccinated appropriately. Vaccine options and regions currently reporting poliomyelitis are presented from a number of sources, which may facilitate the process of giving travel advice in a general practice setting, although it is also important to seek up-to-date epidemiological information.
陈亮; 李畅
2013-01-01
针对蚁群算法在求解旅行商问题(traveling salesman problem,TSP)性能方面的不足,提出了一种基于知识的快速求解旅行商问题的蚁群算法.利用delaunay triangulation知识建立基于DT候选列表,提高了巡游路径质量;采用基于适应度曲面的距离测度分析建立的局部搜索策略,增强局部寻优能力.2种改进策略使用不同的搜索邻域,扩大了搜索空间,提高了搜索效率.
Future Trends in Business Travel Decision Making
Mason, Keith J.
2002-01-01
This research surveys twenty large companies and their travellers to identify and evaluate the effects of pressures on the business travel market in the future. The influence of the following areas on the decision making process are addressed: (1) Corporate travel policies and increasing professionalism in corporate purchasing; (2) The development of global strategic airline alliances; (3) The emergence of low cost airlines on short haul markets; and (4) The development of internet based booking tools and travel agency IT. The survey shows differences in views between travel managers, and travellers with regard to corporate travel policies. While travel managers see policy rules, travellers interpret these as guidelines, indicating travel managers will need to take further actions to exercise true control of travel budgets. The data shows that companies are more likely to prescribe a class of airline ticket, than the choice of airline itself. Corporate hierarchical bias in travel policies is still common both for short and particularly long haul flying. Other findings show that while travel managers believe that their companies are likely to sign global deals with strategic airline groups within a five year period in a bid to consolidating spending, they also believe that nearly a third of short haul flying will be taken with low cost carriers, indicating further penetration in this business travel market by these carriers. The paper also provides other predictions about the business travel market, based on the survey findings.
Toxoplasmosis as a travel risk.
Sepúlveda-Arias, Juan C; Gómez-Marin, Jorge E; Bobić, Branko; Naranjo-Galvis, Carlos A; Djurković-Djaković, Olgica
2014-01-01
Toxoplasma gondii is a protozoan parasite with worldwide distribution that infects more than one third of the global population. Primary infection in immunocompetent individuals is usually asymptomatic; however, different organs can be affected in immunocompromised individuals leading to the development of encephalitis, myocarditis or pneumonitis. The prevalence of infection with Toxoplasma as well as its genetic structure varies geographically and for that reason travel may be considered as a risk factor to acquire the infection. As toxoplasmosis is a foodborne disease, health care providers should give health education on prevention measures to all prospective travelers in order to decrease the risk of infection in endemic areas. This review presents an overview of the infection with T. gondii with some considerations for travelers to and from endemic zones.
Fundamental Travel Demand Model Example
Hanssen, Joel
2010-01-01
Instances of transportation models are abundant and detailed "how to" instruction is available in the form of transportation software help documentation. The purpose of this paper is to look at the fundamental inputs required to build a transportation model by developing an example passenger travel demand model. The example model reduces the scale to a manageable size for the purpose of illustrating the data collection and analysis required before the first step of the model begins. This aspect of the model development would not reasonably be discussed in software help documentation (it is assumed the model developer comes prepared). Recommendations are derived from the example passenger travel demand model to suggest future work regarding the data collection and analysis required for a freight travel demand model.
Elasticity of Long Distance Travelling
Knudsen, Mette Aagaard
2011-01-01
With data from the Danish expenditure survey for 12 years 1996 through 2007, this study analyses household expenditures for long distance travelling. Household expenditures are examined at two levels of aggregation having the general expenditures on transportation and leisure relative to five other...... aggregated commodities at the highest level, and the specific expenditures on plane tickets and travel packages at the lowest level. The Almost Ideal Demand System is applied to determine the relationship between expenditures on transportation and leisure and all other purchased non-durables within...... packages has higher income elasticity of demand than plane tickets but also higher than transportation and leisure in general. The findings within price sensitiveness are not as sufficient estimated, but the model results indicate that travel packages is far more price elastic than plane tickets which...
Travel epidemiology: the Saudi perspective.
Memish, Ziad A; Venkatesh, S; Ahmed, Qanta A
2003-02-01
The Kingdom of Saudi Arabia occupies four-fifths of the Arabian Peninsula, with a land area of 2 million square kilometres. Saudi Arabia holds a unique position in the Islamic world, as the custodian of the two holiest places of Islam, in Mecca and Medina. Annually, some 2 million Muslims from over 140 countries embark on Hajj. This extraordinary en masse migration is a unique forum for the study of travel epidemiology since the Hajj carries various health risks, both communicable and non-communicable, often on a colossal scale. Non-communicable hazards of the Hajj include stampede and motor vehicle trauma, fire-related burn injuries and accidental hand injury during animal slaughter. Communicable hazards in the form of outbreaks of multiple infectious diseases have been reported repeatedly, during and following the Hajj. Meningococcal meningitis, gastroenteritis, hepatitis A, B and C, and various zoonotic diseases comprise some of the possible infectious hazards at the Hajj. Many of these infectious and non-infectious hazards can be avoided or averted by adopting appropriate prophylactic measures. Physicians and health personnel must be aware of these risks to appropriately educate, immunize and prepare these travellers facing the unique epidemiological challenges of Hajj in an effort to minimize untoward effects. Travel epidemiology related to the Hajj is a new and exciting area, which offers valuable insights to the travel specialist. The sheer scale of numbers affords a rare view of migration medicine in action. As data is continually gathered and both national and international policy making is tailored to vital insights gained through travel epidemiology, the Hajj will be continually safeguarded. Practitioners will gain from findings of travel related epidemiological changes in evolution at the Hajj: the impact of vaccinating policies, infection control policies and public health are afforded a real-world laboratory setting at each annual Hajj, allowing us to
[Travel time and distances to Norwegian out-of-hours casualty clinics].
Raknes, Guttorm; Morken, Tone; Hunskår, Steinar
2014-11-01
Geographical factors have an impact on the utilisation of out-of-hours services. In this study we have investigated the travel distance to out-of-hours casualty clinics in Norwegian municipalities in 2011 and the number of municipalities covered by the proposed recommendations for secondary on-call arrangements due to long distances. We estimated the average maximum travel times and distances in Norwegian municipalities using a postcode-based method. Separate analyses were performed for municipalities with a single, permanently located casualty clinic. Altogether 417 out of 430 municipalities were included. We present the median value of the maximum travel times and distances for the included municipalities. The median maximum average travel distance for the municipalities was 19 km. The median maximum average travel time was 22 minutes. In 40 of the municipalities (10 %) the median maximum average travel time exceeded 60 minutes, and in 97 municipalities (23 %) the median maximum average travel time exceeded 40 minutes. The population of these groups comprised 2 % and 5 % of the country's total population respectively. For municipalities with permanent emergency facilities(N = 316), the median average flight time 16 minutes and median average distance 13 km.. In many municipalities, the inhabitants have a long average journey to out-of-hours emergency health services, but seen as a whole, the inhabitants of these municipalities account for a very small proportion of the Norwegian population. The results indicate that the proposed recommendations for secondary on-call duty based on long distances apply to only a small number of inhabitants. The recommendations should therefore be adjusted and reformulated to become more relevant.
Le Masurier, P.; Polak, J.; Pawlak, Janet
2015-01-01
A team of specialist market researchers and Value of Time experts comprising members from SYSTRA, Imperial College London and the Technical University of Denmark has conducted a formal audit and peer review of research undertaken by Arup/ITS Leeds/Accent to derive Value of Travel Time Savings...... Preference (RP) models that were used to derive final Values of Travel Time (VTT). This report contains the findings of our audit and peer review of the procedures adopted by the research team during data collection of the three surveys (SP, RP and Employers Surveys); a peer review of the reported approach...
Black Holes: A Traveler's Guide
Pickover, Clifford A.
1998-03-01
BLACK HOLES A TRAVELER'S GUIDE Clifford Pickover's inventive and entertaining excursion beyond the curves of space and time. "I've enjoyed Clifford Pickover's earlier books . . . now he has ventured into the exploration of black holes. All would-be tourists are strongly advised to read his traveler's guide." -Arthur C. Clarke. "Many books have been written about black holes, but none surpass this one in arousing emotions of awe and wonder towards the mysterious structure of the universe." -Martin Gardner. "Bucky Fuller thought big. Arthur C. Clarke thinks big, but Cliff Pickover outdoes them both." -Wired. "The book is fun, zany, in-your-face, and refreshingly addictive." -Times Higher Education Supplement.
Traveling-Wave Membrane Photomixers
Wyss, R. A.; Martin, S. C.; Nakamura, B. J.; Neto, A.; Pasqualini, D.; Siegel, P. H.; Kadow, C.; Gossard, A. C.
2001-01-01
Traveling-wave photomixers have superior performance when compared with lumped area photomixers in the 1 to 3 THz frequency range. Their large active area and distributed gain mechanism assure high thermal damage threshold and elimination of the capacitive frequency roll-off. However, the losses experienced by the radio frequency wave traveling along the coplanar strips waveguide (due to underlying semi-infinite GaAs substrate) were a serious drawback. In this paper we present device designs and an experimental setup that make possible the realization of photomixers on membranes which eliminate the losses.
2007-10-01
Each year over 55,000 people die because of rabies, mostly from being bitten by rabid dogs. Over half of all rabies infections occur in children under the age of 15 who live in developing countries, but travelers are not immune. This podcast discusses some of the activities that put travelers at risk for rabies and describes ways to prevent infection. Created: 10/1/2007 by National Center for the Prevention, Detection and Control of Infectious Diseases (NCPDCID). Date Released: 10/5/2007.
Hematospermia in a returned traveler.
Lang, Raynell; Minion, Jessica; Wong, Alexander
2017-01-01
Hematospermia is a common complaint among patients seen in outpatient urology clinics. The differential diagnosis is broad and includes inflammatory, infectious, neoplastic, structural, systemic, and traumatic causes. The most common infectious causes are uropathogens and sexually transmitted infections. However, with increasing global travel, physicians must maintain a high clinical suspicion for pathogens not endemic to their region, including Echinococcus, Mycobacterium tuberculosis, and Schistosoma.1 We present a case of hematospermia in a traveler returning from Eastern Africa with exposure to Lake Malawi. The patient's microscopic analysis of semen was positive for Schistosoma haematobium, revealing a rare presentation of S. haematobium infection.
Safe travels? HIV transmission among Britons travelling abroad.
Rice, B; Gilbart, V L; Lawrence, J; Smith, R; Kall, M; Delpech, V
2012-05-01
The aim of the study was to identify and describe the characteristics of persons born in the UK who acquire HIV infection abroad. Analyses using case reports and follow-up data from the national HIV database held at the Health Protection Agency were performed. Fifteen per cent (2066 of 13 891) of UK-born adults diagnosed in England, Wales and Northern Ireland between 2002 and 2010 acquired HIV infection abroad. Thailand (534), the USA (117) and South Africa (108) were the countries most commonly reported. As compared with UK-born adults acquiring HIV infection in the UK, those acquiring HIV infection abroad were significantly (P sex with a commercial sex worker (5.6% vs. 1%, respectively). Among men infected in Thailand, 11% reported sex with a commercial sex worker. A substantial number of UK-born adults are acquiring HIV infection in countries with generalized HIV epidemics, and in common holiday destinations. Of particular concern is the high proportion of men infected reporting sex with a commercial sex worker. We recommend HIV prevention and testing efforts be extended to include travellers abroad, and that sexual health advice be provided routinely in travel health consultations and in occupational health travel advice packs, particularly to those travelling to high HIV prevalence areas and destinations for sex tourism. Safer sex messages should include an awareness of the potential detrimental health and social impacts of the sex industry. © 2012 British HIV Association.
Travelers' Health: Traveling Safely with Infants and Children
... be used with caution in the presence of children to avoid burns and inadvertent ingestion. For more information about repellent ... above. These seats often must be carried from home, since availability of ... abroad. In general, children are safest traveling in the rear seat; no ...
Environmental Impact of Long Distance Travel
Christensen, Linda
2016-01-01
This paper presents an analysis of the CO2 emission resulting from long distance travel by Danes. The emissions are analysed as the Danes’ footprint the whole way from Denmark to the final destination. International travel represents 31% of the Danes’ CO2 emission from passenger travel and the cl......This paper presents an analysis of the CO2 emission resulting from long distance travel by Danes. The emissions are analysed as the Danes’ footprint the whole way from Denmark to the final destination. International travel represents 31% of the Danes’ CO2 emission from passenger travel...... and the climate burden from long overseas distances is especially high even though only few travel overseas. The travel activity is furthermore increasing much more for long distances than for European destinations. Domestic travel activity with overnight stay is nearly stagnating. The study furthermore shows...
The value of travel time variance
Fosgerau, Mogens; Engelson, Leonid
2010-01-01
This paper considers the value of travel time variability under scheduling preferences that are de�fined in terms of linearly time-varying utility rates associated with being at the origin and at the destination. The main result is a simple expression for the value of travel time variability that does not depend on the shape of the travel time distribution. The related measure of travel time variability is the variance of travel time. These conclusions apply equally to travellers who can free...
Communication from Carlson Wagonlit Travel
2009-01-01
We are pleased to inform our customers that the range of tourist guides and roadmaps on sale in our offices has now been extended. We aim to help you prepare your upcoming holiday or business trip in any way we can. Please do not hesitate to contact us should you need any further information. The team at CARLSON WAGONLIT TRAVEL
Writing Travel in the Anthropocene
Graulund, Rune
2016-01-01
by a rapid increase in the mobility of people, goods and information, but primarily examine the impact of the Anthropocene on the notion of travel. For in a world in which the peak of Mount Everest is littered with toilet paper and the Great Pacific Garbage Patch is potentially twice the size of the US...
无
2012-01-01
This summer holiday,I had travelled to Hong Kong with many other students.We went to Hong Kong by plane.Hong Kong is very small,but there are many people living there. In Hong Kong,all of the buildings are very tall.There are lots of shops there and
Twitter for travel medicine providers.
Mills, Deborah J; Kohl, Sarah E
2016-03-01
Travel medicine practitioners, perhaps more so than medical practitioners working in other areas of medicine, require a constant flow of information to stay up-to-date, and provide best practice information and care to their patients. Many travel medicine providers are unaware of the popularity and potential of the Twitter platform. Twitter use among our travellers, as well as by physicians and health providers, is growing exponentially. There is a rapidly expanding body of published literature on this information tool. This review provides a brief overview of the ways Twitter is being used by health practitioners, the advantages that are peculiar to Twitter as a platform of social media, and how the interested practitioner can get started. Some key points about the dark side of Twitter are highlighted, as well as the potential benefits of using Twitter as a way to disseminate accurate medical information to the public. This article will help readers develop an increased understanding of Twitter as a tool for extracting useful facts and insights from the ever increasing volume of health information. © International Society of Travel Medicine, 2016. All rights reserved. Published by Oxford University Press. For permissions, please e-mail: journals.permissions@oup.com.
CITM: Asian's Largest Travel Show
无
2007-01-01
@@ Jointly hosted by China National Tourism Administration, Yunnan Provincial People's Government and General Administration of Civil Aviation of China, China International Travel Mart (CITM) is a major step to develop inbound tourism, to increase tourism receipts in foreign exchanges, and to enhance the international status of China's tourism industry.
Bacterial infec tions in travellers
This review will concentrate on common infections, namely bacterial ... as pyrexia of unknown origin. ... cause of fever without lung involvement (Pontiac fever). Gram- negative ... Frequent use of DEET-based insect repel- lants .... No firm evidence for chemoprophylaxis, but some studies show benefit in short-term travellers.
Your Travel Dollar. Money Management.
Baran, Nancy H., Ed.
This illustrated guide was designed to familiarize consumers with planning a vacation trip, whether domestic or abroad. The guide covers setting up a budget; package tours; cruises and charter flights; travel agencies and clubs; and arranging stays in hotels/motels, rental condominiums, bed-and-breakfasts, hostels, campsites, and private…