Integer programming models for the pre-marshalling problem

[EN] The performance of shipping companies greatly depends on reduced berthing times. The trend towards bigger ships and shorter berthing times places severe stress on container terminals, which cannot simply increase the available cranes indefinitely. Therefore, the focus is on optimizing existing resources. An effective way of speeding up the loading/unloading operations of ships at the container terminal is to use the idle time before the arrival of a ship for sorting the stored containers in advance. The pre-marshalling problem consists in rearranging the containers placed in a bay in the order in which they will be required later, looking for a sequence with the minimum number of moves. With sorted bays, loading/unloading operations are significantly faster, as there is no longer a need to make unproductive moves in the bays once ships are berthed. In this paper, we address the pre-marshalling problem by developing and testing integer linear programming models. Two alternative families of models are proposed, as well as an iterative solution procedure that does not depend on a difficult to obtain upper bound. An extensive computational analysis has been carried out over several well-known datasets from the literature. This analysis has allowed us to test the performance of the models, and to conclude that the performance of the best proposed model is superior to that of previously published alternatives.This study has been partially supported by the Spanish Ministry of Education, Culture, and Sport, FPU Grant A-2015-12849 and by the Spanish Ministry of Economy and Competitiveness, under projects DPI2014-53665-P and DPI2015-65895-R, partially financed with FEDER funds.Parreño-Torres, C.; Alvarez-Valdes, R.; Ruiz García, R. (2019). Integer programming models for the pre-marshalling problem. European Journal of Operational Research. 274(1):142-154. https://doi.org/10.1016/j.ejor.2018.09.048S142154274

Inhibidores del comercio electronico en las Pymes

103 p.El comercio electrónico ha experimentado un importante crecimiento en el mundo hace varios años, previo a esto ha debido enfrentar diversos factores que han inhibido su crecimiento. Nuestro país no es una excepción, se ha producido una brecha entre el inmenso desarrollo de estas tecnologías por parte de las grandes empresas y, las pequeñas y medianas que han visto distanciarse el horizonte de los negocios en línea. El objetivo de la presente investigación es identificar los factores (inhibidores) que han frenado la incorporación al comercio electrónico en las PyMEs de Chile. Con este trabajo se pretende contribuir a la investigación de los negocios sobre la Web, además se intenta generar documentación para futuras investigaciones complementarias a esta, a fin de establecer acciones que sirvan para enmendar el efecto negativo que ejercen los inhibidores del comercio electrónico. El procedimiento que se realizó para conseguir el objetivo general y los específicos fue una investigación de mercado, que comenzó por un estudio exploratorio y seguido de uno del tipo concluyente, a través de una encuesta que se aplicó a 200 empresas de diversas industrias en la zona centro y centro sur del país. De este estudio se concluye que existen diversos inhibidores que afectan la incorporación de las Pymes al comercio electrónico, siendo el más relevante la Seguridad en el comercio electrónico, seguido de factores como la Confianza entre los participantes y la Carencia de modelos de negocios. También se concluyó que los inhibidores afectan de manera diferente a las empresas dependiendo de su tamaño (medido en facturación anual), industria, entre otras características

A branch and bound approach for large pre-marshalling problems

[EN] The container pre-marshalling problem involves the sorting of containers in stacks so that there are no blocking containers and retrieval is carried out without additional movements. This sorting process should be carried out in as few container moves as possible. Despite recent advancements in solving real world sized problems to optimality, several classes of pre-marshalling problems remain difficult for exact approaches. We propose a branch and bound algorithm with new components for solving such difficult instances. We strengthen existing lower bounds and introduce two new lower bounds that use a relaxation of the pre-marshalling problem to provide tight bounds in specific situations. We introduce generalized dominance rules that help reduce the search space, and a memoization heuristic that finds feasible solutions quickly. We evaluate our approach on standard benchmarks of pre-marshalling instances, as well as on a new dataset to avoid overfitting to the available data. Overall, our approach optimally solves many more instances than previous work, and finds feasible solutions on nearly every problem it encounters in limited CPU times.The authors thank the Paderborn Center for Parallel Computation (PC2) for the use of the Arminius cluster for the computational study in this work. This work has been partially supported by the Spanish Ministry of Science, Innovation, and Universities FPU Grant A-2015-12849 and by the Spanish Ministry of Economy and Competitiveness, under projects DPI2014-53665-P and DPI2015-65895-R, partially financed with FEDER funds.Tanaka, S.; Tierney, K.; Parreño-Torres, C.; Alvarez-Valdes, R.; Ruiz García, R. (2019). A branch and bound approach for large pre-marshalling problems. European Journal of Operational Research. 278(1):211-225. https://doi.org/10.1016/j.ejor.2019.04.005S211225278

Halocline water modification and along slope advection at the Laptev Sea continental margin

A general pattern in water mass distribution and potential shelf–basin exchange is revealed at the Laptev Sea continental slope based on hydrochemical and stable oxygen isotope data from the summers 2005–2009. Despite considerable interannual variations, a frontal system can be inferred between shelf, continental slope and central Eurasian Basin waters in the upper 100 m of the water column along the continental slope. Net sea-ice melt is consistently found at the continental slope. However, the sea-ice meltwater signal is independent from the local retreat of the ice cover and appears to be advected from upwind locations. In addition to the along-slope frontal system at the continental shelf break, a strong gradient is identified on the Laptev Sea shelf between 122° E and 126° E with an eastward increase of riverine and sea-ice related brine water contents. These waters cross the shelf break at ~ 140° E and feed the low-salinity halocline water (LSHW, salinity S < 33) in the upper 50 m of the water column. High silicate concentrations in Laptev Sea bottom waters may lead to speculation about a link to the local silicate maximum found within the salinity range of ~ 33 to 34.5, typical for the Lower Halocline Water (LHW) at the continental slope. However brine signatures and nutrient ratios from the central Laptev Sea differ from those observed at the continental slope. Thus a significant contribution of Laptev Sea bottom waters to the LHW at the continental slope can be excluded. The silicate maximum within the LHW at the continental slope may be formed locally or at the outer Laptev Sea shelf. Similar to the advection of the sea-ice melt signal along the Laptev Sea continental slope, the nutrient signal at 50–70 m water depth within the LHW might also be fed by advection parallel to the slope. Thus, our analyses suggest that advective processes from upstream locations play a significant role in the halocline formation in the northern Laptev Sea

ANÁLISE SUSTENTÁVEL DO MODELO DE CICLO DE VIDA. SITUAÇÃO E PERSPECTIVAS DE IXTAPAN DE LA SAL, MÉXICO

Cuando se busca entender la evolución de un destino turístico, el análisis del ciclo de vida es una de las herramientas de gestión y planeación más utilizadas. Sin embargo, existen para su medición, variables limitadas que generalmente se basan en la cantidad de turistas y en el tiempo en que se ha desarrollado la actividad, lo cual deja en un segundo plano la sustentabilidad. En este trabajo, se formula un esquema alternativo de análisis mediante el cual se integran variables de sustentabilidad para establecer los impactos económicos, ambientales y sociales de los turistas actuales y futuros. Así también, se presenta una metodología que estima la curva de evolución de los destinos, para aquellos lugares que no cuentan con información suficiente. Finalmente se concluye que el destino de Ixtapan de la Sal, en México, hoy en día no es sustentable, y un mayor número de turistas solo pondría en riesgo su competitividad

Estimulación magnética trascraneal en el desempeño motor en enfermedades del sistema nervioso central : Revisión Sistemática

Introducción: El uso de la estimulación cerebral no invasiva en procesos de rehabilitación es de gran interés, por cuanto con mediación tecnológica se generan nuevas posibilidades de recuperación motora, a partir de la activación de la corteza cerebral. El objetivo del estudio es establecer la evidencia del uso terapéutico de la EMT, relacionado con el desempeño motor de pacientes con enfermedades del sistema nervioso central. Metodología: Se realizó una revisión sistemática de la literatura. Se incluyeron 10 estudios en el análisis cualitativo que incluyó la evaluación de calidad con la escala de Jadad y del riesgo de sesgo con la herramienta Cochrane. Fueron excluidos 1613 estudios. Se aplicó el protocolo del estudio para la extracción, revisión y validez de los estudios incluidos. Resultados: La evidencia disponible muestra resultados positivos del uso terapéutico de la EMT en el desempeño motor en aspectos como la aceleración, la fuerza de pinza y de agarre, la estabilidad y la fuerza muscular, así como una mejor velocidad de la marcha y una disminución en la frecuencia y severidad de los espasmos. Discusión: La EMT puede constituir una estrategia terapéutica para mejorar el desempeño motor en pacientes con ECV, Lesión Medular y enfermedad de Parkinson, que requiere más investigación por la heterogeneidad de los diseños y medidas de descenlace utilizados, así como por la alta variabilidad interindividual que hace complejo estandarizar los protocolos de su uso terapéutico.Introduction: To include the trascraneal magnetic stimulation in neurorehabilitation process is interesting inasmuch as the use of the technology contributes to create new possibilities of motor recovery by means of cerebral cortex activation. The purpose of this study is to establish the evidence of the therapeutic use of TMS related to motor performance of patients with central nervous system diseases. Methodology: It was conducted a systematic review, that includes ten studies in qualitative analysis with the Jadad scale and the risk of bias using the Cochrane tool. 1613 studies were excluded. Was applied the protocol for the collection, review and validity of the included studies. Results: The evidence shows positive results of the therapeutic use of TMS motor performance in aspects such as acceleration, pinch strength and grip, stability and muscle strength, as well as improved gait velocity and a decrease in the frequency and severity of spams. Discussion: TMS may constitute a therapeutic strategy to improve motor performance in patients with Stroke, Parkinson´s disease and Spinal Cord Injury. It requires further research by the heterogeneity of the designes and outcomes measures used as well as the high variability interindividual makes complex the standardization of protocols for therapeutic use

Inflammatory mediators and immune response in Mexican adolescents

Introduction: Low-grade inflammation and increased immunity related to cardiovascular diseases have been described in children and adults, however, studies in Mexican adolescents are being done at present. Objective: To evaluate inflammatory proteins and indicators of immunity in adolescents by gender and body mass index. Material and methods: 115 Mexican adolescents, 15-18 years old (36 men), were divided into non-overweight, risk of overweight and overweight by CDC pediatric criteria by body mass index. Serum concentrations of ceruloplasmin, C3 and C4 were quantified by nephelometry; IL-6 and TNF-α from stimulated supernatant were analyzed with Human Th1-Th2 cytokine CBA II kit (BD Biosciences Pharmigen, San Diego, CA), and detected by flow cytometry. Data were analysed by Mann-Whitney U. Results: Gender differences were found in C3 (men: median 118.8, mean rank: 41.0; women: median: 143.9, mean rank: 65.7, p = 0.001) and ceruloplasmin (men: median: 31.01, mean rank: 47.06; women: median: 31.0, mean rank: 62.9, p = 0.015). Differences by BMI were found in C3 (women non-overweight: median: 137.00 mena rank: 36.52; women with risk of overweight/overweight: median: 175.80, mean rank: 57.69, p = 0.002) and C4 (men non-overweight: median: 23.40, mean rank: 16.60; men with risk of overweight/overweight: median: 26.40, mean rank: 26.36, p = 0.028; women non-overweight: median: 24.25, mean rank: 37.16 and women with risk of overweight/overweight: median: 32.80, mean rank: 54.42, p = 0.013). Conclusion: Inflammatory proteins are increased in adolescents with risk of overweight and overweight, particularly in women

Comparison of Upper Neck Loading in Young Adult and Elderly Volunteers During Low Speed Frontal Impacts

Cervical pain and injuries are a major health problem globally. Existing neck injury criteria are based on experimental studies that included sled tests performed with volunteers, post-mortem human surrogates and animals. However, none of these studies have addressed the differences between young adults and elderly volunteers to date. Thus, this work analyzed the estimated axial and shear forces, and the bending moment at the craniocervical junction of nine young volunteers (18–30 years old) and four elderly volunteers (>65 years old) in a low-speed frontal deceleration. Since the calculation of these loads required the use of the mass and moment of inertia of the volunteers' heads, this study proposed new methods to estimate the inertial properties of the head of the volunteers based on external measurements that reduced the error of previously published methods. The estimated mean peak axial force (Fz) was −164.38 ± 35.04 N in the young group and −170.62 ± 49.82 N in the elderly group. The average maximum shear force (Fx) was −224.42 ± 54.39 N and −232.41 ± 19.23 N in the young and elderly group, respectively. Last, the estimated peak bending moment (My) was 13.63 ± 1.09 Nm in the young group and 14.81 ± 1.36 Nm in the elderly group. The neck loads experienced by the elderly group were within the highest values in the present study. Nevertheless, for the group of volunteers included in this study, no substantial differences with age were observed

Low-Dimensional Assemblies of Magnetic MnFe2O4 Nanoparticles and Direct In Vitro Measurements of Enhanced Heating Driven by Dipolar Interactions: Implications for Magnetic Hyperthermia

Magnetic fluid hyperthermia (MFH), the procedure of raising the temperature of tumor cells using magnetic nanoparticles (MNPs) as heating agents, has proven successful in treating some types of cancer. However, the low heating power generated under physiological conditions makes it necessary a high local concentration of MNPs at tumor sites. Here, we report how the in vitro heating power of magnetically soft MnFe2O4 nanoparticles can be enhanced by intracellular low-dimensional clusters through a strategy that includes: (a) the design of the MNPs to retain Neel magnetic relaxation in high-viscosity media, and (b) culturing MNP-loaded cells under magnetic fields to produce elongated intracellular agglomerates. Our direct in vitro measurements demonstrated that the specific loss power (SLP) of elongated agglomerates (SLP = 576 +/- 33 W/g) induced by culturing BV2 cells in situ under a dc magnetic field was increased by a factor of 2 compared to the SLP = 305 +/- 25 W/g measured in aggregates freely formed within cells. A numerical mean-field model that included dipolar interactions quantitatively reproduced the SLPs of these clusters both in phantoms and in vitro, suggesting that it captures the relevant mechanisms behind power losses under high-viscosity conditions. These results indicate that in situ assembling of MNPs into low-dimensional structures is a sound possible way to improve the heating performance in MFH

Increasing nutrient fluxes and mixing regime changes in the eastern Arctic Ocean

Primary productivity in the Arctic Ocean is experiencing dramatic changes linked to the receding sea ice cover. The vertical transport of nutrients from deeper water layers is the limiting factor for primary production. Here, we compare coincident profiles of turbulence and nutrients from the Siberian Seas in 2007, 2008, and 2018. In all years, the water column structure in the upstream region of the Arctic Boundary Current promotes upward nutrient transport, in contrast to the regions further downstream, and there are first indications for an eastward progression of these conditions. In summer 2018, strongly enhanced vertical nitrate flux and primary production above the continental slope were observed, likely related to a remote storm. The estimated contribution of these elevated fluxes above the slope to the Pan-Arctic vertical nitrate supply is comparable with the basin-wide transport, and is predicted to increase with declining sea ice cover in the future