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Abstract The objective of this study is to describe the properties of dosing weight in the neonatal intensive care unit (NICU). Infants were identified from a database of very low birth weight infants. Before regaining birth weight (BW), dosing and birth weight% difference was described. After regaining BW, dosing and measured weight% difference and frequency of dosing weight updates were described. Associations with infant characteristics including comorbid conditions, serum biochemistries, fluid intake, and urine output were evaluated. There were 115 infants over 4,643 infant-days with a median BW of 1060 g (interquartile range [IQR]: 750, 1300) and median time to regain BW of 10 days (IQR: 8, 13). After regaining BW, dosing weight was 4.2% less than measured weight. The gap widened with increasing creatinine and narrowed with increasing urine output. The only factor associated with the frequency of dosing weight updates was day of the week. Dosing weights in the NICU appear to fall into one of three categories: BW prior to regaining BW, practical weight to facilitate medication and nutrition ordering, and “dry” weight, adjusting for fluid overloaded states. We recommend using measured weight to avoid a 4% daily loss in nutrition intake once BW is regained.

Abstract Corrosion remains a critical concern in various industries, particularly in applications involving aluminum alloys due to their widespread usage as light structural materials. This work provides a comprehensive overview of the recent advances in modeling techniques for better understanding the corrosion behavior of aluminum alloys. The present study encompasses the state‐of‐the‐art of computational approaches, highlighting their strengths and limitations. Special attention is given to transport models, galvanic couples, localized corrosion, and the incorporation of different factors, such as pH variations, electrolyte thicknesses and dynamic electrolytes into corrosion models. Furthermore, the review delves into both bulk and atmospheric corrosion models. On the other hand, this work also emphasizes a clear differentiation between models designed for bare aluminum alloys and those tailored for coated ones. Additionally, it addresses certain challenges associated with the experimental validation of such models. This review concludes with perspectives on both sophisticated transport models to bridge the gap between industrial and academic investigations, as well as the integration of machine learning and artificial intelligence techniques in corrosion modeling, offering promising directions for future research in this field.

In the present work, the influence of alkali ions (Li, Na, K) on the structural and spectroscopic properties of silica glasses doped with Sm3+ was investigated. Infrared and Raman spectroscopy techniques were used to investigate the structural properties of the alkali silicate glasses. The optical absorption showed bands characteristic of Sm3+ ions in alkali silicate glasses, and this was investigated. The Judd–Ofelt theory was applied to evaluate the phenomenological intensity parameters (Ω2, Ω4, and Ω6) of the optical absorption measurements. The multi-channel visible and near infrared emission transitions originating from the 4G5/2-emitting state of the Sm3+ in alkali silicate glasses with a maximum phonon energy of ~1050 cm−1 were investigated. From the evaluated Judd–Ofelt parameters, radiative parameters such as spontaneous emission probabilities, radiative lifetimes, branching ratios, and stimulated emission cross-sections were calculated. The recorded luminescence spectra regions revealed intense green, orange, red, and near-infrared emission bands, providing new traces for developing tunable laser and optoelectronic devices.

Background: For several years, two of the major concerns of logistics managers are (i) the visibility of global supply chains and (ii) the uncertainty in deciding which existing logistics security program is the most appropriate according to the security levels for their organization. This last decision is needed to ensure traceability and visibility of the supply chain. The purpose of this paper is to present an analysis of the main public and private supply chain security management programs in Latin America and the Caribbean. Methods: A qualitative and quantitative research methodology based on thematic content analysis is followed. The four main existing security programs in Latin America and the Caribbean are systematically compared and a common general framework is developed. Results: The analysis shows a high degree of similarity between the levels of security contained in the selected programs. Conclusions: We found that there is little guidance available for companies interested in managing security risks in their supply chains through these logistics’ security programs. This article contributes to the literature on logistics security programs that is currently gaining momentum in managing security risks in global supply chains and provides academic insights into the choice and/or complementarity of one or more logistics security programs.

The Radio Frequency Quadrupole (RFQ) is a linear accelerator that focuses, bunches, and accelerates a continuous input of charged particles while preserving the beam emittance. This paper focuses on the study of the transverse acceptance of an RFQ and how this concept can be used in the design of frontend structures. A simple and fast system to qualify a source and low energy transfer line has been developed in terms of the number of particles delivered in the RFQ acceptance. Multi-particle simulation results show a dependence of the RFQ transverse acceptance on the particle phase in the radio frequency period. The usually referred-to acceptance value is, in fact, just an average value over the 360° phase range, whereas a modulation has been found between more and less favorable phase values, with different patterns depending on the specific structure. We use as a study case three RFQs designed and operated at CERN to investigate such correlations.

To improve the effectiveness and the sustainability of logistics, the Physical Internet paradigm proposes disruptive solutions. This implies developing an ecosystem of tech-based logistics solutions and supporting methodologies that enable all players in global trade to cooperate. The purpose of this paper is to investigate systematic literature review (SLR) studies to gain detailed insight into how innovative transport technologies, and digitalization initiatives around the Physical Internet development impact supply chains. This paper presents the results of a tertiary study that systematically identified more than twelve thousand articles and selects to review 74 secondary studies on the application of disruptive technologies and the Physical Internet initiative on supply chains from a management perspective. This is complementary to previous reviews, since no one provides a comprehensive and consolidated approach towards the relationship of these three fields. The five-stage systematic review process proposed by Denyer and Tranfield (2009) is followed. As a result, we identify the key activities, knowledge areas and strategies in the supply chain field where the Physical Internet and disruptive technologies interact and are game-changing. Also, we present a conceptual framework that summarises the relationships that exist between relevant disruptive technologies, the physical internet topics, and supply chain key activities. The framework is helpful for researchers and practitioners to find potential technologies to invest in, to assess the potential effects on companies of their implementation, and to support strategic decision-making. The paper concludes with an outlook on future research opportunities from operational, tactical, and strategic perspectives.

ABSTRACT At each stage of the HIV life cycle, host cellular proteins are hijacked by the virus to establish and enhance infection. We adapted the virus packageable HIV-CRISPR screening technology at a genome-wide scale to comprehensively identify host factors that affect HIV replication in a human T cell line. Using a smaller, targeted HIV Dependency Factor (HIVDEP) sublibrary, we then performed screens across HIV strains representing different clades and with different biological properties to define which T cell host factors are important across multiple HIV strains. Nearly 90% of the genes selected across various host pathways validated in subsequent assays as bona fide host dependency factors, including numerous proteins not previously reported to play roles in HIV biology, such as UBE2M, MBNL1, FBXW7, PELP1, SLC39A7, and others. Our ranked list of screen hits across diverse HIV-1 strains form a resource of HIV dependency factors for future investigation of host proteins involved in HIV biology. IMPORTANCE With a small genome of ~9.2 kb that encodes 14 major proteins, HIV must hijack host cellular machinery to successfully establish infection. These host proteins necessary for HIV replication are called “dependency factors.” Whole-genome, and then targeted screens were done to try to comprehensively identify all dependency factors acting throughout the HIV replication cycle. Many host processes were identified and validated as critical for HIV replication across multiple HIV strains.

Kingella kingae is an emerging pediatric pathogen and is increasingly recognized as a leading etiology of septic arthritis, osteomyelitis, and bacteremia and an occasional cause of endocarditis in young children. The pathogenesis of K. kingae disease begins with colonization of the upper respiratory tract followed by breach of the respiratory epithelial barrier and hematogenous spread to distant sites of infection, primarily the joints, bones, and endocardium. As recognition of K. kingae as a pathogen has increased, interest in defining the molecular determinants of K. kingae pathogenicity has grown. This effort has identified numerous bacterial surface factors that likely play key roles in the pathogenic process of K. kingae disease, including type IV pili and the Knh trimeric autotransporter (adherence to the host), a potent RTX-family toxin (epithelial barrier breach), and multiple surface polysaccharides (complement and neutrophil resistance). Herein, we review the current state of knowledge of each of these factors, providing insights into potential approaches to the prevention and/or treatment of K. kingae disease.

ABSTRACT Kingella kingae is a leading cause of bone and joint infections and other invasive diseases in young children. A key K. kingae virulence determinant is a secreted exopolysaccharide that mediates resistance to serum complement and neutrophils and is required for full pathogenicity. The K. kingae exopolysaccharide is a galactofuranose homopolymer called galactan and is encoded by the pamABC genes in the pamABCDE locus. In this study, we sought to define the mechanism by which galactan is tethered on the bacterial surface, a prerequisite for mediating evasion of host immune mechanisms. We found that the pamD and pamE genes encode glycosyltransferases and are required for synthesis of an atypical lipopolysaccharide (LPS) O-antigen. The LPS O-antigen in turn is required for anchoring of galactan, a novel mechanism for association of an exopolysaccharide with the bacterial surface. IMPORTANCE Kingella kingae is an emerging pediatric pathogen and produces invasive disease by colonizing the oropharynx, invading the bloodstream, and disseminating to distant sites. This organism produces a uniquely multifunctional exopolysaccharide called galactan that is critical for virulence and promotes intravascular survival by mediating resistance to serum and neutrophils. In this study, we established that at least some galactan is anchored to the bacterial surface via a novel structural interaction with an atypical lipopolysaccharide O-antigen. Additionally, we demonstrated that the atypical O-antigen is synthesized by the products of the pamD and pamE genes, located downstream of the gene cluster responsible for galactan biosynthesis. This work addresses how the K. kingae exopolysaccharide can mediate innate immune resistance and advances understanding of bacterial exopolysaccharides and lipopolysaccharides.

Gravitational models are currently a commonly used methodology to analyze the behavior of countries' trade flows. These studies typically seek to measure the impact of distance and the size of economies as factors that increase or decrease the propensity to trade between countries. Instead of using the traditional model, this paper introduces two distance variables which are built as modernity factors of culture and productive and institutional apparatus that give some evidence the importance of the economic and institutional stability of the countries to favor trade flows. The new model is tested using historical data of Colombia foreign trade between 1995 and 2015 (which is the most updated year publicly available).

The fast and sharp corrosion potential change from the active state to the passive state, that pure zinc plates immersed in calcium hydroxide saturated solutions with and without chlorides spontaneously exhibit at the early stage of passivation, was studied. The corrosion behavior was investigated by corrosion potential monitoring, anodic polarization curves and electrochemical impedance spectroscopy. The zinc surface was characterized by scanning electron microscopy and X-ray energy dispersive spectroscopy. Experimental results show that the presence of chlorides increases the rate of change of potential by 10-fold in the early stage of passivation, producing a porous passivating film of corrosion products mainly made of calcium hydroxy-zincate Ca(Zn(OH)3)2· 2 H2O, with a less protective barrier effect than the non-porous film formed without chlorides. On the other hand, a modeling approach was achieved by solving the transient 2D Nernst–Planck equations and considering 12 chemical species. Numerical results confirm that the composition of the chemical products generated on the Zn surface certainly depends on the concentration of Cl¯ ions: Simonkolleite and hidroxides become unstable in the presence of high Cl¯ concentrations, whereas calcium hydroxyl-zincate is the main chemical compound generated on the Zn surface. However, the presence of the latter compound is much more important in electrolytes with very low concentration of Cl¯ ions.

BackgroundThe use of oral contraceptives (OCs) has been associated with increased incidences of anxiety and depression, for which adolescents seem to be particularly vulnerable. Rather than looking at singular outcomes, we examined whether OC use is associated with depressive and anxiety symptom trajectories from early adolescence into early adulthood.Materials and MethodsData from 178 girls were drawn from the Research on Adolescent Development and Relationships (RADAR-Y) younger cohort study. We used assessments on 9 waves from age 13 until 24. Developmental trajectories of ratings on the Reynolds Adolescent Depression Scale (RADS-2) and the Screen for Child Anxiety Related Emotional Disorders (SCARED) were compared between never and ever users of OCs.ResultsNever users showed increases in depressive and anxiety symptoms in late adolescence, whereas OC users showed a stable level of symptoms throughout adolescence. This effect remained after adjusting for baseline differences between groups in romantic relationships, sexual debut, educational level, smoking, drinking, and drug use. Age of OC use onset did not significantly predict symptom development.ConclusionsOC use in adolescence was related to an altered developmental trajectory of internalizing symptoms, in which OC users did not show an increase in depressive and anxiety symptoms in late adolescence, whereas never users did. The question remains whether this altered symptom trajectory can be considered a protective effect of OC use on psychopathology. Additional research is needed to improve our understanding of the long-term consequences of OC use on mental health.

Studies that use rivers in a last-mile delivery context are scarce. This research considers the first multimodal alternative based on a barge for parcel delivery activities. It proposes two sustainable network designs for a two-echelon distribution. The efficiency of scenarios is assessed through performance indicators. A three-stage decomposition heuristic is used. Allocation of the customers to the closest satellite at the first stage uses a non-supervised machine learning clustering method, 2D-k-means. The last two stages, comprising the two echelons routing, are solved using a heuristic based on the nearest neighbor procedure. The fixed costs decrease by 41% and energy consumption by 92% when applying a river transportation mode and e-cargo bikes in the distribution network’s first and second echelon, respectively. Future research avenues are to render the results more realistic with the consideration of other costs and a larger network.

Background: Military logistics has been present from the moment a soldier was created, and its evolution has been influenced by the technology used. Indeed, it has been observed over time that every military revolution was intrinsically caused by a military logistics revolution, directly promoted by the technology applied to the manner of making war. Few papers have been written about military logistics in relation to the development of war itself. Its application was conceptualized in two dimensions: as an art and as a science, interdependent on decision-making. With the evolution of human beings, the way of making war also evolved and therefore a transformation was generated. This makes it necessary to deepen the application of mathematical modeling, statistics, and new technologies in military logistics, promoting the application of concepts based on technology to improve the effectiveness of armies. The aim of this paper is to review the evolution of military logistics. Methods: A systematic approach to the literature review is followed. The backgrounds of the military logistics thought, key authors, trends and a new definition of military logistics is presented, among others. Results: The findings allow us to identify a set of 21 definitions of military logistics since 1792.

The tourism sector represents an opportunity for economic growth in countries with tourism potential. However, new trends in global tourism require efficiency in tourism supply chain management. One of the main changes is the trend of personalized tourism, which includes the management of itineraries by the tourist. The tourist trip design problem is the problem associated with personalized trip design. This problem has been modeled in the field of Operations Research in different ways, being the Orienteering Problem the most widely applied in the specialized literature. The objective of this paper is to carry out a systematic review of the contributions made to the tourist trip design problem. A review taxonomy is proposed to analyze the main variants, objectives, and solution techniques. Also, future research lines are analyzed and proposed to enrich the literature and provide new solutions to real problems.

In traditional scheduling problems, job processing times are considered constant and known in advance. This assumption is, however, a simplification when it comes to hand-intensive real-life production contexts because workers usually induce variability in the job processing times due to several factors such as learning, monotony, fatigue, psychological factors, etc. These effects can decrease or increase the actual processing time when workers execute a job. The academic literature has reported several modeling and resolution approaches to deal with the phenomenon in a variety of configurations. However, there is no comprehensive review of these research outputs to the best of our knowledge. In this paper, we follow a systematic approach to review relevant contributions addressing the scheduling problem with learning and deterioration effects. Modeling approaches for learning and deterioration effects, objective functions, and solution methods employed in the literature are the main topics for the taxonomy proposed in this review. A total of 455 papers from 1999 to 2021 are included and analyzed. Different areas of interest are presented, and some opportunities for future research are identified.

Poor urban planning and traffic congestion lead to excessive delays in workers’ transit times and decrease their quality of life, especially in emerging countries. Several medium and large companies have a need to hire a transport service for their staff. In this type of transportation system, there is a heterogeneous fleet of vehicles, which are assigned to a set of predefined routes. However, the total transport delay can be even greater if the private transportation system is inefficient or not controlled. The approach proposed in this study seeks to optimize the private transport service by defining the best allocation of its fleet to its routes. A mathematical model is proposed to minimize user wait times. This approach is validated using real data obtained from a transport company in Co-lombia. The results demonstrate the quantitative benefits that can be achieved when the proposed approach is implemented, represented by a considerable reduction in user wait times.

The contributions of Operations Research (OR) in the healthcare field have been extensively studied in the scientific literature since the 1960s, covering decision support tools with operational, tactical, and strategic approaches. The aim of this article is to analyze the historical development of the application of OR models in healthcare. The application trends for optimization, planning, and decision- making models are studied through a descriptive literature review and a bibliometric analysis of scientific papers published between 1952 and 2016. An upward trend in the usage of operational models is observed with the predominance of resource optimization approaches and strategic decision-making for public health.

In this work the Richard's equation with proper boundary conditions was solved by the Finite Element Method in order to simulate the capillary water entrance in mortar. On the boundaries subjected to free water, a constant Dirichlet boundary condition was imposed assuming permanent saturation water content, on the insulated boundaries a nil flux of water was fixed. Meanwhile on the boundaries in contact with a controlled external atmosphere, a physicochemical model was used in order to simulate the water evaporation process. Three special sample geometries, with and without cracks, were studied. Findings identified the initial water content as a very important parameter in the water uptake phenomenon. Once the model for the water entrance was tested with pure water, a governing equation for the chloride transport was coupled with the Richard's equation in order to simulate both the water and chloride transport into simulated mortar samples in contact with sea water. The borders were subjected to different physical conditions for the sake of a better understanding of the role of boundary conditions in the transport of chloride. The governing equation takes into account the convective effect of the water entrance, the diffusion process, and the chloride binding reaction.

An electrochemical model was developed to predict the transient distribution of species generated during corrosion of a carbon steel/AA7075 aluminum alloy galvanic couple. Both metals were set under a confined electrolyte layer of thickness 50 μm containing ten interacting chemical species. The model was solved by the finite element method. The main contribution of the model is the use of an extra source term within some governing equations to avoid solving for the O2 concentration in extremely thin domains. The solution is rendered as top-view instead of the usual cross-sectional one.The whole model provides both a light computational code and a robust approach to the phenomenon under study.Transient experimental pH measurements were achieved with the help of an innovative setup implemented for micrometric electrolyte layers. The experimental and predicted pH fronts had an acceptable level of agreement. Keywords: Galvanic corrosion, Atmospheric corrosion, Computational and theoretical electrochemistry

Summary: Tripartite motif-containing protein 5α (TRIM5α) is a cellular antiviral restriction factor that prevents early events in retrovirus replication. The activity of TRIM5α is thought to be limited to retroviruses as a result of highly specific interactions with capsid lattices. In contrast to this current understanding, we show that both human and rhesus macaque TRIM5α suppress replication of specific flaviviruses. Multiple viruses in the tick-borne encephalitis complex are sensitive to TRIM5α-dependent restriction, but mosquito-borne flaviviruses, including yellow fever, dengue, and Zika viruses, are resistant. TRIM5α suppresses replication by binding to the viral protease NS2B/3 to promote its K48-linked ubiquitination and proteasomal degradation. Importantly, TRIM5α contributes to the antiviral function of IFN-I against sensitive flaviviruses in human cells. Thus, TRIM5α possesses remarkable plasticity in the recognition of diverse virus families, with the potential to influence human susceptibility to emerging flaviviruses of global concern. : The antiviral activity of TRIM5α is thought to be limited to retroviruses as a result of highly specific interactions with capsid lattices. Here, Chiramel et al. demonstrate that TRIM5α restricts replication of specific flaviviruses by binding and degrading the viral protease. Keywords: TRIM5α, flavivirus, retrovirus, interferon, restriction factor, retrovirus, interferon stimulated genes, tick-borne encephalitis virus

The main concern in city logistics is the need to optimize the movement of goods in urban contexts, and to minimize the multiple costs inherent in logistics operations. Inspired by an application in a medium-sized city in Latin America, this paper develops a bi-objective mixed linear integer programming (MILP) model to locate different types of urban logistics spaces (ULS) for the configuration of a two-echelon urban distribution system. The objective functions seek to minimize the costs associated with distance traveled and relocation, in addition to the costs of violation of time windows. This model considers heterogeneous transport, speed assignment, and time windows. For experimental evaluation, two operational scenarios are considered, and Pareto frontiers are obtained to identify the efficient non-dominated solutions to select the most feasible ones from such a set. A case study of a distribution company of goods for supermarkets in the city of Barranquilla, Colombia, is also used to validate the proposed model. These solutions allow decision-makers to define the configuration of ULS networks for urban product delivery.

This paper proposes a hybridized simheuristic approach that couples a greedy randomized adaptive search procedure (GRASP), a Monte Carlo simulation, a Pareto archived evolution strategy (PAES), and an analytic hierarchy process (AHP), in order to solve a multicriteria stochastic permutation flow shop problem with stochastic processing times and stochastic sequence-dependent setup times. For the decisional criteria, the proposed approach considers four objective functions, including two quantitative and two qualitative criteria. While the expected value and the standard deviation of the earliness/tardiness of jobs are included in the quantitative criteria to address a robust solution in a just-in-time environment, this approach also includes a qualitative assessment of the product and customer importance in order to appraise a weighted priority for each job. An experimental design was carried out in several study instances of the flow shop problem to test the effects of the processing times and sequence-dependent setup times, obtained through lognormal and uniform probability distributions with three levels of coefficients of variation, settled as 0.3, 0.4, and 0.5. The results show that both probability distributions and coefficients of variation have a significant effect on the four decision criteria selected. In addition, the analytical hierarchical process makes it possible to choose the best sequence exhibited by the Pareto frontier that adjusts more adequately to the decision-makers’ objectives.

The location routing problem integrates both a facility location and a vehicle routing problem. Each of these problems are NP-hard in nature, which justifies the use of heuristic-based algorithms when dealing with large-scale instances that need to be solved in reasonable computing times. This paper discusses a realistic variant of the problem that considers facilities of different sizes and two types of uncertainty conditions. In particular, we assume that some customers’ demands are stochastic, while others follow a fuzzy pattern. An iterated local search metaheuristic is integrated with simulation and fuzzy logic to solve the aforementioned problem, and a series of computational experiments are run to illustrate the potential of the proposed algorithm.

This contribution describes the latest milestones of a multiyear program to build and operate a compact -300 kV dc high voltage photogun with inverted insulator geometry and alkali-antimonide photocathodes. Photocathode thermal emittance measurements and quantum efficiency charge lifetime measurements at average current up to 4.5 mA are presented, as well as an innovative implementation of ion generation and tracking simulations to explain the benefits of a biased anode to repel beam line ions from the anode-cathode gap, to dramatically improve the operating lifetime of the photogun and eliminate the occurrence of micro-arc discharges.

In the present work, the influence of alkali ions (Li, Na, K) on the structural and spectroscopic properties of silica glasses doped with Sm3+ was investigated. Infrared and Raman spectroscopy techniques were used to investigate the structural properties of the alkali silicate glasses. The optical absorption showed bands characteristic of Sm3+ ions in alkali silicate glasses, and this was investigated. The Judd–Ofelt theory was applied to evaluate the phenomenological intensity parameters (Ω2, Ω4, and Ω6) of the optical absorption measurements. The multi-channel visible and near infrared emission transitions originating from the 4G5/2-emitting state of the Sm3+ in alkali silicate glasses with a maximum phonon energy of ~1050 cm−1 were investigated. From the evaluated Judd–Ofelt parameters, radiative parameters such as spontaneous emission probabilities, radiative lifetimes, branching ratios, and stimulated emission cross-sections were calculated. The recorded luminescence spectra regions revealed intense green, orange, red, and near-infrared emission bands, providing new traces for developing tunable laser and optoelectronic devices. [ABSTRACT FROM AUTHOR]

The school bus routing problem (SBRP) seeks to plan an efficient schedule of a fleet of school buses that must pick up students from various bus stops and deliver them by satisfying various constraints: maximum capacity of the bus, maximum riding time of students, time window to arrive to school. In this paper, we consider a case study of SBRP for a school in Bogotá, Colombia. The problem is solved using ant colony optimization (ACO). Computational experiments are performed using real data. Results lead to increased bus utilization and reduction in transportation times with on-time delivery to the school. The proposed decision-aid tool has shown its usefulness for actual decision-making at the school: it outperforms current routing by reducing the total distance traveled by 8.3 % and 21.4 % respectively in the morning and in the afternoon.El problema de ruteo de buses escolares (SBRP) busca encontrar el programa más eficiente para una flota de buses escolares que deben recoger y despachar estudiantes en varias paradas de bus satisfaciendo varias restricciones: capacidad máxima del bus, máximo tiempo de recorrido de los estudiantes, ventanas de tiempo para la llegada al colegio. En este artículo se considera un caso de estudio de un problema SBRP para un colegio en Bogotá, Colombia. El problema se resuelve usando la metaheurística de colonia de hormigas (ACO). Los experimentos computacionales se realizan empleando datos reales. Los resultados muestran el incremento en el nivel de utilización de los buses y una reducción en los tiempos de transporte con despacho a tiempo en el colegio. La herramienta ha mostrado su utilidad para la planeación regular de buses en el colegio: se redujo la distancia total recorrida en 8,3 % en la mañana y en 21,4 % en la tarde.O problema de roteamento de ônibus escolares (SBRP) busca encontrar o programa mais eficiente para uma frota de ônibus escolares que devem recolher e despachar estudantes em várias paradas de ônibus satisfazendo várias restrições: capacidade máxima do ônibus, máximo tempo de percurso dos estudantes, janelas de tempo para a chegada ao colégio. Em este artigo considera-se um caso de estudo de um problema SBRP para um colégio em Bogotá, Colômbia. O problema resolve-se usando a meta-heurística de colônia de formigas (ACO). Os experimentos computacionais realizam-se empregando dados reais. Os resultados mostram o incremento no nível de utilização dos ônibus e uma redução nos tempos de transporte com despacho a tempo no colégio. A ferramenta tem mostrado sua utilidade para o planejamento regular de ônibus no colégio: reduziu-se a distância total percorrida em 8,3 % na manhã e em 21,4 % na tarde.

La programación de proyectos con recursos restringidos (RCPSP, por su nombre en inglés) es un problema clásico e importante en la gerencia de proyectos, y que ha recibido mucha atención de parte de los investigadores. Este artículo considera el caso en el cual se desea minimizar el costo de las actividades. Esta variante del problema se encuentra principalmente en la gerencia de cadenas de suministro para proyectos de construcción. Sus características muestran que la función es no-regular y que el problema es NP-completo. Este artículo presenta un algoritmo memético pare resolver el problema. Experimentos computacionales son ejecutados empleando las famosas instancias de la librería PSPLIB. Los resultados obtenidos validan la efectividad y eficiencia del algoritmo propuesto.

Este artículo estudia un problema de programación de la producción en el corto plazo inspirado de sistemas de fabricación reales en los cuales se tiene un conjunto de tareas (órdenes de producción) tanto en una configuración de una máquina como en máquinas paralelas idénticas con el objetivo de minimizar el lapso de fabricación o tiempo máximo de terminación de todos los trabajos. Las tareas están sujetas a fechas de disponibilidad diferentes y existen tiempos de preparación de las máquinas dependientes de la secuencia de procesamiento. Puesto que este problema es conocido como fuertemente NPcompleto, incluso para el caso de una máquina simple, este artículo propone un algoritmo heurístico para resolverlo. El algoritmo emplea una estrategia de generación aleatoria de varias secuencias de procesamiento de los trabajos y luego selecciona el mejor de estos programas. Se desarrollaron experimentos computacionales empleando datos generados aleatoriamente. Los resultados muestran que el procedimiento propuesto se desempeña muy bien comparado con la solución óptima o con cotas inferiores, requiriendo un menor tiempo de cálculo.

Este artículo presenta un procedimiento alternativo para resolver el problema de enrutamiento de vehículos con limitaciones de capacidad y flota homogénea (CVRP). Se propone un algoritmo metaheurístico que consta de la combinación de dos fases: diseño de rutas y planificación de la flota. La primera fase está compuesta de procedimientos heurísticos y metaheurísticos donde se construye una solución inicial que es mejorada mediante búsqueda tabú obteniendo soluciones no dominadas en tiempo de cálculo polinomial. Para la segunda fase, correspondiente a la planificación (scheduling) de la flota, se propone abordar el problema partiendo de una analogía con el problema de programación de máquinas paralelas idénticas. Este procedimiento tiene como función objetivo minimizar el costo fijo causado por la utilización de la capacidad instalada. Esta alternativa se aplicó sobre una instancia generada aleatoriamente y una instancia real arrojando resultados significativos al compararse con las heurísticas evaluadas.Este artigo apresenta um procedimento alternativo para resolver o problema de roteamento de veículos com limitações de capacidade e frota homogênea (CVRP). Propõe-se um algoritmo metaheurístico que consta da combinação de duas fases: desenho de rotas e planejamento da frota. A primeira fase está composta de procedimentos heurísticos e metaheurísticos onde se constrói uma solução inicial que é melhorada mediante busca tabu obtendo soluções não dominadas em tempo de cálculo polinomial. Para a segunda fase, correspondente ao planejamento (scheduling) da frota, se propõe abordar o problema partindo de uma analogia com o problema de programação de máquinas paralelas idênticas. Este procedimento tem como função objetivo minimizar o custo fixo causado pela utilização da capacidade instalada. Esta alternativa se aplicou sobre uma instância gerada aleatoriamente e uma instância real dando resultados significativos ao se comparar com as heurísticas avaliadas.This paper presents an alternative procedure to solve the Capacitated Vehicle Routing Problem (CVRP) with homogeneous fleet. The paper proposes a two-phase metaheuristic algorithm: routes design and fleet scheduling. The first phase is based on heuristics and metaheuristics procedures in order to build an initial solution that is then improved using tabu search to obtain non-dominated solutions in polynomial computational time. For the second phase, corresponding to fleet scheduling, the problem is approached using an analogy with the identical parallel machine scheduling problem. This procedure looks for the minimization of the fixed cost of using installed capacity as the objective function. The proposed procedure was tested using both a random-generated instance and real data, giving competitive results in comparison with other heuristics tested.

En la actualidad la implementación de estrategias de cooperación entre los eslabones de una cadena logística ha tomado mucha importancia para lograr optimizaciones en sus indicadores de desempeño, con el fin de ser más reactivos y flexibles en el mercado altamente competitivo y cambiante en el que se desarrollan sus actividades económicas. Sin embargo, pocos estudios se han focalizado en la cuantificación del impacto que tienen dichas estrategias de cooperación en uno de los niveles más bajos de toma de decisiones a corto plazo: la programación de taller. En este artículo se estudia el impacto de las estrategias de cooperación entre los miembros de una cadena logística en el nivel operacional en un contexto dinámico. La cadena logística analizada es de tipo direct sell, ampliamente utilizada por vendedores de computadores por Internet, donde la producción se realiza por pedido y no existe inventario de productos terminados. Inicialmente se presenta una descripción del problema y la estructura analizada, luego se hace un análisis crítico de los algoritmos de programación de tareas que permiten tener en cuenta la información anticipada y, por último, se realiza un estudio de simulación que permite validar las hipótesis del estudio. Los resultados sugieren mejoras interesantes en los indicadores de gestión de la cadena logística cuando existe cooperación entre los miembros.Nowadays implementing cooperation strategies between the members of the supply chain has been an important research topic in order to obtain a more reactive and flexible supply chain in the highly and competitive markets. However, few studies have been done on the impact of such cooperation strategies at one of the lower short-term decision levels: production scheduling. This paper is devoted to the study of information sharing between the members of the supply chain in a dynamic context. We consider a typical make-to-order direct sell supply chain without finished products inventory, similar to that implemented by Internet PC sellers. We compare various scheduling algorithms that are able to take into account future information from forward member of the supply chain. A simulation study is developed in order to get some insights about the impact of information sharing on the performance of the chain. Our results suggest improvement in the performance that shows the importance of collaboration and information sharing between the members of the chain.

La modélisation des systèmes de production est difficile en raison du nombre et de la diversité des paramètres à prendre en compte et de la complexité des relations entre ces paramètres. Dans cet article, nous nous intéressons à l´étude d´une unité complètement automatisée de fabrication de wafers semi-conduc-teurs (fab). Dans la littérature, leur analyse est très souvent réalisée en utilisant des modèles de simulation à événements discrets, mais ces travaux ne présentent pas une véritable conceptualisation du modèle utilisé. L´objectif de cet article est de conceptualiser, à travers des méthodologies formelles, tous les composants d´une unité de production microélectronique: au niveau macro, le système physique de production et son système de supervision, ainsi que, au niveau micro, le processus de fabrication. Ces approches nous aideront à identifier les objets du modèle et leurs interactions permettant ensuite de développer un programme de simulation pour l´analyser du fonctionnement dynamique du system.La modelación de los sistemas de producción es una tarea difícil debido al número y diversidad de variables que deben tenerse en cuenta y a la complejidad de las relaciones entre dichas variables. En este artículo, nos interesamos en el estudio de una unidad completamente automatizada para la fabricación de "wafers" semiconductores (llamada "fab"). En la literatura, el análisis se realiza comúnmente empleando modelos de simulación de eventos discretos, pero esos trabajos no presentan una verdadera conceptualización del modelo empleado. El objetivo de este artículo es conceptualizar, por medio de metodologías formales de modelación, todos los componentes de una planta de fabricación microelectrónica: en el nivel macro, el sistema físico de producción y su sistema de control, así como, en el nivel micro, el proceso de fabricación. Estos enfoques nos ayudarán a identificar los objetos del modelo y sus interacciones para permitir así el desarrollo de un programa de simulación para analizar el funcionamiento dinámico del sistema.The modelling of industrial systems is a very hard task because of both the number and diversity of parameters to take into account, and the complex relations between these parameters. In this paper, we are interested on the study of a fully automated Integrated Circuit (IC) semiconductor manufacturing plant (fab). In the semiconductor literature, fab behaviour analysis has very often been performed using discrete-event simulation models, but little work has been devoted to the conceptualisation of the modelling approach. Other works focus on the analysis of single parts of the fab, by simplifying the relations between its components. In such a context, the aim of this paper is to use formal methodologies to model all the components of a wafer fab, that is, its physical and control systems, as well as the fabrication process. This model specification can then be used to build a simulation model for the dynamic factory behaviour analysis.

Se estudió la variabilidad de 2 genes nucleares, el intrón 4/5 del gen de Calmodulina (CaM) por amplificación PCR y la región ITS (Internal Transcribed Spacers) del ADNr, por PCR y digestión en 139 ejemplares de E. ringens provenientes de las costas de Iquique (20°13'S; 70°09'W) y Talcahuano (36°41'S; 73°06'W). Para CaM se identificaron 8 genotipos en las muestras de Talcahuano y 7 en Iquique, presentando 1 a 3 fragmentos amplificados de 550 a 1.100 pb. En la digestión del fragmento ITS amplificado, sólo la endonucleasa TaqªI detectó 3 diferentes genotipos, 2 presentes en Talcahuano y 3 en Iquique. Se discuten las frecuencias observadas para cada gen y área de estudio. Los resultados llevan a confirmar la existencia de un solo stock, desde un punto de vista genéticoThe genetic variability of two nuclear genes, the 4/5 intron of the Calmodulin (CaM) and the ITS (Internal Transcribed Spacers) of the DNAr were studied. The methodology applied in 139 anchovies (E. ringens) from Iquique and Talcahuano, were the PCR amplification for CaM samples and the PCR amplification and digestion, for ITS samples. The results exhibited 8 genotypes for CaM in Talcahuano, and 7 were identified in Iquique. The size of the fragments founded (1-3), ranged from 550 to 1100 bp. The ITS amplification and digestion of a fragment determined the existence of 3 genotypes, 2 in Talcahuano and 3 in Iquique. But in the digestion of the ITS amplifications, only the TaqªI endonuclease showed diferences in the restriction profiles. The genotypic frequencies are discussed for each gene and study area, as well as the presence of only one stock from a genetic point of view