A hierarchical model for the location of perinatal facilities in the municipality of Rio de Janeiro

We present a 3-level hierarchical model for the location of maternal and perinatal health care facilities in Rio de Janeiro. Relaxations and heuristics are developed for this model and computational results are given for problems available in the literature, for networks ranging from 10 to 400 vertices. The quality of the solutions produced by the procedures we developed do not differ significantly among themselves. The model is also applied to a case study corresponding to real 1995 data of the municipality of Rio de Janeiro.     

Alternative targets for data envelopment analysis through multi-objective linear programming: Rio de Janeiro Odontological Public Health System Case Study

In the last 10 years much has been written about the drawbacks of radial projection. During this time, many authors proposed methods to explore, interactively or not, the efficient frontier via non-radial projections. This paper compares three families of data envelopment analysis (DEA) models: the traditional radial, the preference structure and the multi-objective models. We use the efficiency analysis of Rio de Janeiro Odontological Public Health System as a background for comparing the three methods through a real case with one integer and one exogenous variable. The objectives of the study case are (i) to compare the applicability of the three approaches for efficiency analysis with exogenous and integer variables, (ii) to present the main advantages and drawbacks for each approach, (iii) to prove the impossibility to project in some regions and its implications, (iv) to present the approximate CPU time for the models, when this time is not negligible. We find that the multi-objective approach, although mathematically equivalent to its preference structure peer, allows projections that are not present in the latter. Furthermore, we find that, for our case study, the traditional radial projection model provides useless targets, as expected. Furthermore, for some parts of the frontier, none of the models provide suitable targets. Other interesting result is that the CPU-time for the multi-objective formulation, although its endogenous high complexity, is acceptable for DEA applications, due to its compact nature.     

A two-phase greedy algorithm to locate and allocate hubs for fixed-wireless broadband access

We study a two-phase, budget-constrained, network-planning problem with multiple hub types and demand scenarios. In each phase, we install (or move) capacitated hubs on selected buildings. We allocate hubs to realized demands, under technological constraints. We present a greedy algorithm to maximize expected demand covered and computationally study its performance.     

Residual currents and corridor of flow in the Rio de la Plata

The Rio de la Plata is a large and shallow water body that discharges onto the Atlantic Ocean. The main driving forces for the river flow are the bathymetry, tides, the outflow from the Paraná and Uruguay rivers and the winds. A numerical model covering the entire river was set up with the objective of increasing our understanding of the hydrographical features and morphological dynamics in the Estuary. The simulations revealed a counter-clockwise residual circulation in the Samborombón Bay and an eastward net flow near the Uruguayan coast. The residual flow is forced by both the tides and the bathymetry. The residence time for the entire river ranges from 40 to 80 days. However, residence times above 120 days was found in the Samborombón Bay. Three corridors of flow have been identified.     

An alternative to the Bathe algorithm

This paper presents a new composite sub-steps algorithm for solving reliable numerical responses in structural dynamics. The newly developed algorithm is a two sub-steps, second-order accurate and unconditionally stable implicit algorithm with the same numerical properties as the Bathe algorithm. The detailed analysis of the stability and numerical accuracy is presented for the new algorithm, which shows that its numerical characteristics are identical to those of the Bathe algorithm. Hence, the new sub-steps scheme could be considered as an alternative to the Bathe algorithm. Meanwhile, the new algorithm possesses the following properties: (a) it produces the same accurate solutions as the Bathe algorithm for solving linear and nonlinear problems; (b) it does not involve any artificial parameters and additional variables, such as the Lagrange multipliers; (c) The identical effective stiffness matrices can be obtained inside two sub-steps; (d) it is a self-starting algorithm. Some numerical experiments are given to show the superiority of the new algorithm and the Bathe algorithm over the dissipative CH-α algorithm and the non-dissipative trapezoidal rule.     

求解应急医疗设施分层递进式选址问题的改进免疫算法

针对应急医疗设施的特点,提出分层递进式选址方法,对应急医疗设施进行合理选址.首先,通过熵权法对选址所需要考虑的因素进行权重计算,并进行初步选址;其次,考虑设施点的服务容量、重大公共卫生事件下轻重症患者的治疗与转移的实际情况,建立双层级整数规划模型;再次,根据模型的具体特点,设计改进的免疫优化算法对其进行求解;最后,以湖...     

Help! to the rescue in Rio Rancho

This paper analyzes the problem of locating the optimal positions of two emergency facilities in the hypothetical township of Rio Rancho based on the given data of emergency distributions in the township for 1985. To solve this problem, we designed two models to estimate the expected response time for a given pair of facility locations. One model assumed that the emergencies occured in the center of the blocks, while the other supposed a uniform distribution of emergencies along the streets bordering the blocks. Both models considered only corners as possible locations for the emergency facilities, and neither considered obstacles. However, not accounting for the obstacles did not affect the final solutions because the routes from the points chosen as the optimal locations would not be lengthened by a consideration of these barriers. In the discussion of the strengths and weaknesses of the models, it appears that the only serious weakness of the two models is the data upon which both are based. (The data may be incomplete since they cover only the year 1985). Finally, although we believe that Model II is the stronger of the two models, we feel that since both give the same results, our recommendations for the locations were truly the optimal positions for the facilities.     

An economic theory of public facilities in space

This paper deals with the determination of the number and locations of facilities in which a public service is made available to consumers. The solutions obtained by planning and voting are characterized and compared for both a benefit taxation, based on consumers' locations, and an income taxation.     

An optimal algorithm to generate tilings

We produce an algorithm that is optimal with respect to both space and execution time to generate all the lozenge (or domino) tilings of a hole-free, general-shape domain given as input.We first recall some useful results, namely the distributive lattice structure of the space of tilings and Thurston's algorithm for constructing a particular tiling. We then describe our algorithm and study its complexity.     

An improved algorithm to test copositivity

Copositivity plays a role in combinatorial and nonconvex quadratic optimization. However, testing copositivity of a given matrix is a co-NP-complete problem. We improve a previously given branch-and-bound type algorithm for testing copositivity and discuss its behavior in particular for the maximum clique problem. Numerical experiments indicate that the speedup is considerable.     

A reduced model to locate low contrast inclusions in poroelastic media

This paper introduces a numerical method to localize inclusions having slightly different elastic coefficients than those of a fully saturated poroelastic matrix, whose detection is often difficult. This method can be used to find weakly stiffer or softer objects in saturated soils or diseased biological tissues at early stages. To this end, we propose a reduced model from the Biot’s equations by splitting the fluid pressure into two parts: one embedded into an elasticity model and the other one used as a corrector term. By applying the small amplitude homogenization method, we can successfully retrieve the position and extension of inclusions in poroelastic media employing this simplified model. Numerical results show a good agreement for the location of inclusions when the contrast is below 30% stiffer or softer than the matrix, and for a noise level up to 5% for frequencies below 50 Hz.     

An efficient approach to updating simplex multipliers in the simplex algorithm

The simplex algorithm computes the simplex multipliers by solving a system (or two triangular systems) at each iteration. This note offers an efficient approach to updating the simplex multipliers in conjunction with the Bartels–Golub and Forrest–Tomlin updates for LU factors of the basis. It only solves one triangular system. The approach was implemented within and tested against MINOS 5.51 on 129 problems from Netlib, Kennington and BPMPD. Computational results show that the new approach improves simplex implementations. Project 10371017 supported by National Natural Science Foundation of China.     

An algorithm to solve the proportional network flow problem

The proportional network flow problem is a generalization of the equal flow problem on a generalized network in which the flow on arcs in given sets must all be proportional. This problem appears in several natural contexts, including processing networks and manufacturing networks. This paper describes a transformation on the underlying network that reduces the problem to the equal flow problem; this transformation is used to show that algorithms that solve the equal flow problem can be directly applied to the proportional network flow problem as well, with no increase in asymptotic running time. Additionally, computational results are presented for the proportional network flow problem demonstrating equivalent performance to the same algorithm for the equal flow problem.     

An algorithm to generate the ideals of a partial order

Generating the ideals of a partially ordered set is an important, frequently occurring problem in scheduling, reliability, sensitivity analysis for network flows and other combinatorial optimization problems. In this paper we present an algorithm which generates all the ideals of a partial order on n elements in O(n) time per ideal.     

An algorithm to Cyclic Path Covering Number

In this paper we develop an algorithm to find Cyclic Path covering number of any graph, by finding the Cyclic Path covering number of a tree graph.     

An algorithm to recognize a middle graph

A graph F is called middle if there exists a graph G such that there is a one-to-one correspondence between the vertices of F and the vertices and edges of G such that two vertices of F are adjacent if and only if the corresponding elements (considered as subsets of the set of vertices) have a non-empty intersection.In this paper we present a linear time algorithm for the recognition of the middle graphs. The algorithm is based on a computer-oriented characterization of middle graphs. We show also how the algorithm can be generalized to recognize the middle graphs of hypergraphs.     

An efficient algorithm to allocate shelf space

Shelf space is one of the most important resources of a retail firm. This paper formulates a model and proposes an approach which is similar to the algorithm used for solving a knapsack problem. Subject to given constraints, the proposed heuristic allocates shelf space item by item according to a descending order of sales profit for each item per display area or length. Through the use of simulations, the performances of objective value and the computational efficiency of this method are evaluated. Three options are also proposed for improving the heuristics. Compared to an optimal method, the improved heuristic is shown to be a very efficient algorithm which allocates shelf space at near-optimal levels.