Simple heuristics for the assembly line worker assignment and balancing problem

We propose simple heuristics for the assembly line worker assignment and balancing problem. This problem typically occurs in assembly lines in sheltered work centers for the disabled. Different from the classical simple assembly line balancing problem, the task execution times vary according to the assigned worker. We develop a constructive heuristic framework based on task and worker priority rules defining the order in which the tasks and workers should be assigned to the workstations. We present a number of such rules and compare their performance across three possible uses: as a stand-alone method, as an initial solution generator for meta-heuristics, and as a decoder for a hybrid genetic algorithm. Our results show that the heuristics are fast, they obtain good results as a stand-alone method and are efficient when used as a initial solution generator or as a solution decoder within more elaborate approaches.Comment: 18 pages, 1 figur

On the use of a single site approximation to describe correlation in pure metals

The magnetic properties of pure transition-like metals are discussed within the single site approximation, to take into account the electron correlation. The metal is described by two hybridized bands one of which includes the Coulomb correlation. Our results indicate that ferromagnetism follows from adequate values of the correlation and hybridization.Comment: 2 pages and 2 figure

Solution Of The Urban Traffic Problem With Fixed Demand Using Inexact Restoration

Congested traffic has become a part of the day-to-day for the residents of big metropolitan centers. From an economic viewpoint, this problem has been causing huge financial damage and strategic measures must be taken to tackle it. An alternative means of solving the problem is the inclusion of toll charges on routes with a view to decongesting the road network. The mathematical formulation of this alternative involves the solving of an optimization problem with equilibrium constraints (MPEC). This work proposes an algorithm for the solution of this problem based on the strategy of inexact restoration.837-4019071918Andreani, R., Castro, S.L.C., Chela, J.L., Friedlander, A., Santos, S.A., Aninexact-restoration method for nonlinear bilevel programming problems (2009) Comput. Optim. Appl., 43, pp. 307-328Andreani, R., Martinez, J.M., Svaiter, B.F., On the Regularization of mixed complementarity problems (2000) Numerical Functional Analysis and Optimization, 21, pp. 589-600Andreani, R., Martinez, J.M., On the reformulation od Nonlinear Complementarity Problems using the Fischer-Burmeister function (1999) Applied Mathematics Letters, 12, pp. 7-12Andreani, R., Friedlander, A., Bound Constrained Smooth Optimization for Solving Variational Inequalities and Related Problems (2002) Annals of Operations Research, 116, pp. 179-198Arnott, R., Small, K., (1994) The economics of traffic congestion, , Boston College Working Papers in Economics 256, Boston College, Department of EconomicsBazarra, M.S., Sherali, H.D., Shetty, C.M., (1993) Nonlinear Programming: Theory and Algoritms, , Second Edition, John Wiley & Sons, New YorkBonnans, J.F., Shapiro, A., (2000) Perturbation Analysis of Optimization Problems, , Springer Series in Operations Research, SpringerBrotcorne, L., Labbé, M., Marcotte, P., Savard, G., A Bilevel Model for Toll Optimization on a Multicommodity Transportation Network (2001) Transportation Science, 35 (4), pp. 345-358Calamai, P.H., Vicente, L.N., Generating quadratic bilevel programming test problems (1994) ACM Transactions on Mathematical Software, 20, pp. 103-119Chela, J.L., (2006) Resolução do problem a de programao matemática com restrições de equilíbrio usando restauração inexata, , PhD thesis, University of CampinasFerrari, P., Road network toll pricing and social welfare (2002) Trans. Res. B, 36, pp. 471-483Harker, P.T., Pang, J.S., Existence of optimal solutions to mathematical programs with equilibrium constraints (1988) Operations Research Letters, 7 (2), pp. 61-64Hearn, D.W., (1980) Bounding Flows in Traffic Assignment Models, , Research report N.80-4, Dept. of Industrial and Systems Enginnering, University of Florida, Gainesville, FL 32611Hearn, D.W., Ramana, M.V., Solving congestion toll princing models (1998) Equilibrium and Advanced Transportation Modelling, pp. 109-124. , P. Marcotte, S. Nguyen (eds), Kluwer Academic Publisher, Boston, The NetherlandsHearn, D.W., Yildirim, M.B., A toll pricing framework for traffic assignment problems with elastic demands (2001) Current Trends in Transportation and Network Analysis: Miscellanea in Honor of Michael Florian, , M. Gendreau, P. Marcotte(eds), Kluwer Academic Publisher, Dordrecht, The NetherlandsHearn, D.W., Lawphongpanich, S., An MPEC approach to second-best toll pricing (2004) Mathematical Programming Series B, 101, pp. 33-55Hearn, D.W., Bergendorff, P., Ramana, M.V., Congestion Toll Pricing of Traffic Networks, Network Optimization (1997) Lecture Notes in Economics and Mathematical Systems, 450, pp. 51-71. , P. M. Pardalos, D.W. Hearn and W.W. Hager (Eds.), Springer-VerlagJohansson-Stenman, O., Sterner, T., What is the scope for environmental road pricing? (1998) Road pricing Traffic Congestion and Environment, , K.J. Button, E.T. Verhoef (eds.), Edward Elgar Publishing Limited, London, EnglandLabbé, M., Marcotte, P., Savard, G., A bilevel model of taxation and its application to optimal highway pricing (1998) Manage. Sci, 44 (12), pp. 1608-1622Migdalas, A., Bilevel Programming in traffic planning: models, methods and challenge (1994) Journal of Global Optimization, 4, pp. 340-357Patriksson, M., Rockafellar, R.T., A Mathematical model and descent algorithm for bilevel traffic management (2002) Trans. Sci, 36, pp. 271-291Solodov, M.V., Svaiter, B.F., A New Projection Method for Variational Inequality Problems (1999) SIAM Journal Control Optimization, 37, pp. 765-77

Non-Scissors-Mode Behaviour of Isovector Magnetic Dipole Orbital Transitions Involving Isospin Transfer

We study the response of isovector orbital magnetic dipole (IOMD) transitions to the quadrupole-quadrupole ($Q \cdot Q$) interaction, to the isospin-conserving pairing interaction (ICP) and to combinations of both. We find qualitatively different behaviours for transitions in which the final isospin differs from the initial isospin versus cases where the two isospins are the same. For $N=Z$ even-even nuclei with $J^{\pi}=0^+, T=0$ ground states such as $^8Be$ and $^{20}Ne$, the summed $T=0 \to T=1$ IOMD from the ground state to all the $J=1, T=1$ states in the $0 \hbar \omega$ space does not vanish when the $Q \cdot Q$ interaction is turned off. The pairing interaction (ICP) alone leads to a finite transition rate. For nuclei with $J=0^+, T=1$ ground states such as $^{10}Be$ and $^{22}Ne$, the summed $T=1 \to T=1$ IOMD $does$ vanish when the $Q \cdot Q$ interaction is turned off, as is expected in a good scissors-mode behaviour. However this is not the case for the corresponding sum of the $T=1 \to T=2$ IOMD transitions. In $^{22}Ne$ (but not in $^{10}Be$) the sum of the $T=1 \to T=2$ IOMD transitions is remarkably insensitive to the strengths of both the $Q \cdot Q$ and the ICP interactions. In $^{22}Ne$ an energy weighted-sum is similarly insensitive. All our calculations were carried out in the $0 \hbar \omega$ space.Comment: 19 pages (including 5 figures). submitted to Nucl. Phys.

Evaluation of the AR4 CMIP3 and the AR5 CMIP5 model and projections for precipitation in northeast Brazil

This article compares the sensitivity of IPCC CMIP3-AR4 and CMIP5-AR5 models used on the latest reports from the Intergovernmental Panel on Climate Change (IPCC) in representing the annual average variations (austral summer and autumn) on three regions in Northeastern Brazil (NNEB) for the periods 1979–2000 using the CMAP (Climatology Merged Analysis of Precipitation) data as reference. The three areas of NNEB chosen for this analysis were the semiarid, eastern, and southern regions. The EOF analysis was performed to investigate how the coupled models resolve the temporal variability of the spatial modes in the Tropical Atlantic Sea Surface Temperature (SST), which drives the interannual variations of the rainfall in the Northeastern Brazil. CMIP3-AR4 and CMIP5-AR5 models presented a good representation of the annual cycle of precipitation. Results from correlation and mean absolute error analysis indicate that both CMIP3 and CMIP5 models produce large errors and barely capture the interannual rainfall variance during austral summer and autumn in Northeast Brazil, this features is closely related to the poor representation of the modes of SST variability in the Tropical Atlantic Ocean. For the summer and autumn rainfall projections (2040–2070) in the semiarid region, there was no convergence between the CMIP3 and CMIP5 models. During the summer and autumn in the eastern sector, both the CMIP3 and CMIP5 models projected rainfall above the mean for the 2040–2070 period

Detection of different Mycoplasma bovis genetic subtypes in Argentina

Mycoplasma bovis is the most important cause of mycoplasmal mastitis in dairy cows and has been\ndiagnosed in our country and worldwide. MLVA analysis seems to be a suitable tool to type this\npathogen, for epidemiological studies of outbreaks. In the present work, 7 strains of M. bovis were\nanalyzed. They had been obtained from 2 different herds (milk samples from bulk tank milk and\nmammary quarters of cows with and without mastitis´s clinical signs) and had been previously\nidentified. Four tandem repeat regions (TR) were studied. Among the TR loci studied, variability\nwas found in only one of them (TR52), in which 2 possible alleles were observed in samples from\ncows with clinical mastitis. According to the author´s knowledge this is the first report of the use of\nMLVA for the genetic subtyping of M. bovis strains in Argentina.Fil: Estanguet, A.A. Universidad Nacional de Río Cuarto. Facultad de Agronomía y Veterinaria. Departamento Patología Animal. Río Cuarto, ArgentinaFil: Tamiozzo, P.J. Universidad Nacional de Río Cuarto. Facultad de Agronomía y Veterinaria. Departamento Patología Animal. Río Cuarto, ArgentinaFil: Tamiozzo, P.J. CONICET. ArgentinaFil: Raviolo, J. Universidad Nacional de Río Cuarto. Facultad de Agronomía y Veterinaria. Departamento Producción Animal. Río Cuarto, ArgentinaFil: Giraudo, J. Universidad Nacional de Río Cuarto. Facultad de Agronomía y Veterinaria. Departamento Patología Animal. Río Cuarto, ArgentinaFil: Ambrogi, A. Universidad Nacional de Río Cuarto. Facultad de Agronomía y Veterinaria. Departamento Patología Animal. Río Cuarto, ArgentinaMycoplasma bovis es el mycoplasma causante de mastitis más importante en vacas lecheras y ha sido\ndiagnosticado en nuestro país así como a nivel mundial. Para realizar estudios epidemiológicos de\nbrotes, el análisis por MLVA parece ser una herramienta adecuada para la tipificación genética del\npatógeno. En el presente trabajo se analizaron 7 cepas de M. bovis provenientes de 2 tambos distintos\n(muestras de leche de tanque de enfriado, y cuartos mamarios de vacas con y sin signos de mastitis)\nque habían sido previamente identificadas. Se estudiaron por PCR 4 regiones que comprenden\nsecuencias repetidas en tándem (TR). Dentro de los loci TR analizados, sólo se encontró variabilidad\nen TR 52, en el cual se observaron 2 posibles alelos en muestras que provenían de vacas con mastitis\nclínica. Según el conocimiento de los autores es la primera vez que se informa la utilización del\nanálisis MLVA para detectar subtipos genéticos entre cepas de M. bovis en Argentina

Super-diffusive Transport Processes in Porous Media

The basic assumption of models for the transport of contaminants through soil is that the movements of solute particles are characterized by the Brownian motion. However, the complexity of pore space in natural porous media makes the hypothesis of Brownian motion far too restrictive in some situations. Therefore, alternative models have been proposed. One of the models, many times encountered in hydrology, is based in fractional differential equations, which is a one-dimensional fractional advection diffusion equation where the usual second-order derivative gives place to a fractional derivative of order α, with 1 < α ≤ 2. When a fractional derivative replaces the second-order derivative in a diffusion or dispersion model, it leads to anomalous diffusion, also called super-diffusion. We derive analytical solutions for the fractional advection diffusion equation with different initial and boundary conditions. Additionally, we analyze how the fractional parameter α affects the behavior of the solutions

Investment in the long-tail of biodiversity data: from local research to global knowledge

In business, the "long-tail economy" refers to a market strategy where the gravity center shifts from a few high-demand products to many, varied products focused on small niches. Commercialization of individually low-demand products can be profitable as long as their production cost is low and, all taken together, they aggregate into a big chunk of the market. Similarly, in the "business" of biodiversity data acquisition, we can find several mainstream products that produce zillions of bits of information every year and account for most of the budget allocated to increase our primary data-based knowledge about Earth's biological diversity. These products play a crucial role in biodiversity research. However, along with these large global projects, there is a constellation of small-scale institutions that work locally, but whose contribution to our understanding of natural processes should not be dismissed. These information datasets can be collectively referred to as the "long-tail biodiversity data"