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

A constraint programming approach for the premarshalling problem

[EN] The enormous amount of containers handled at ports hampers the efficiency of terminal operations. The optimization of crane movements is crucial for speeding up the loading and unloading of vessels. To this end, the premarshalling problem aims to reorder a set of containers placed in adjacent stacks with a minimum number of crane movements, so that a container with an earlier retrieval time is not below one with a later retrieval time. In this study, we present a series of constraint programming models to optimally solve the premarshalling problem. Extensive computational comparisons show that the best proposed constraint programming formulation yields better results than the state-of-the-art integer programming approach. A salient finding in this paper is that the logic behind the model construction in constraint programming is radically different from that of more traditional mixed integer linear programming models.Acknowledgements This study has been partially supported by the Spanish Ministry of Science and Innovation under predoctoral grant PRE2019-087706 and the project 'OPTEP-Port Terminal Operations Opti-mization' (No. RTI2018-094940-B-I00) financed with FEDER funds.Jiménez-Piqueras, C.; Ruiz, R.; Parreño-Torres, C.; Alvarez-Valdes, R. (2023). A constraint programming approach for the premarshalling problem. European Journal of Operational Research. 306(2):668-678. https://doi.org/10.1016/j.ejor.2022.07.042668678306

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

Problemas de fugas a través del karst en la Presa de Tous (España) (Análisis estructural, previsión del comportamiento y recomendeciones)

In the present work, the problems of leakages happened in Tous’s dam (Valencia-Spain) are studied. Tous’s dam is built on karstic terrains with the existence of caverns and strike-slip faults that at the same time become karstic. In this study the techniques of structural geology are applied, so, we deduct the karstic drainage directions, by using determined hypothesis of work. The confirmation of these hypotheses in the course of our fieldwork has permitted to quantify the probability of those leakages for each direction we found. This circumstance has permitted to foretell the places where it would be possible to expect leakages with the increase of the height of the dam foreseen for a second phase of building

Long-term outcome of patients with acromegaly and congestive heart failure

Cardiovascular complications are a major cause of morbidity and mortality in patients with acromegaly. Normalization of GH secretion is associated with an improvement in structural and functional cardiac abnormalities. However, the long-term cardiac effects of treatment for acromegaly have not been studied in patients who have already developed chronic congestive heart failure (CHF). We reviewed the charts of 330 consecutive patients with acromegaly treated in two French and Belgian centers since 1985. Ten patients with both acromegaly and CHF (eight men, two women, mean age 49.7 yr) were studied retrospectively. One of them was excluded because CHF was due to severe aortic stenosis. CHF ( New York Heart Association stages III-IV and echocardiography showing dilated hypokinetic cardiomyopathy with left ventricular systolic dysfunction and a left ventricular ejection fraction less than 45%) was diagnosed before, concomitantly, or after acromegaly in, respectively, two, five, and two patients. Three patients were referred with terminal heart failure requiring transplantation. One patient had transient CHF associated with a hypertensive crisis. The other eight patients had symptomatic chronic CHF. Control of GH hypersecretion failed, totally or partially, in three patients: one had a long-term survival, and the two others died at 1 and 5 yr. Good GH control was achieved in five patients: four of these are still alive 2-16 yr after diagnosis of CHF, their clinical status is stable or improved, and their quality of life is good. Overall, the 1- and 5-yr mortality ( or transplantation) rates for patients with chronic symptomatic CHF were 25% ( 2 of 8 patients) and 37.5% ( 3 of 8 patients), respectively. In conclusion, less than 3% of acromegalic patients developed CHF in this study. Although effective treatment of acromegaly improved short-term cardiovascular status, its impact on long-term survival is questionable

A Collaborative Environment for Engaging Novices in Scientific Inquiry

We describe the design, implementation, and evaluation of GreenTouch, a collaborative environment that enables novice users to engage in authentic scientific inquiry. Green-Touch consists of a mobile user interface for capturing data in the field, a web application for data curation in the “cloud, ” and a tabletop interface for exploratory analysis of heterogeneous data. This paper contributes: 1) the design, implementation, and validation of a collaborative environment which allows novices to engage in scientific data capture, curation, and analysis; 2) empirical evidence for the feasibility and value of integrating interactive surfaces in college-level education based on an in situ study with 54 undergraduate students; and 3) insights collected through iterative design, providing concrete lessons and guidelines for designing multi-touch interfaces for collaborative inquiry of complex domains. AUTHOR KEYWORDS Tabletop; multi-touch interaction; collaborative learning