Accélération de méthodes de résolution classiques par l'utilisation de stratégies de séparation locale comme outil d'hybridation

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal

Reduced cost-based variable fixing in two-stage stochastic programming

The explicit consideration of uncertainty is essential in addressing most planning and operation issues encountered in the management of complex systems. Unfortunately, the resulting stochastic programming formulations, integer ones in particular, are generally hard to solve when applied to realistically-sized instances. A common approach is to consider the simpler deterministic version of the formulation, even if it is well known that the solution quality could be arbitrarily bad. In this paper, we aim to identify meaningful information, which can be extracted from the solution of the deterministic problem, in order to reduce the size of the stochastic one. Focusing on two-stage formulations, we show how and under which conditions the reduced costs associated to the variables in the deterministic formulation can be used as an indicator for excluding/retaining decision variables in the stochastic model. We introduce a new measure, the Loss of Reduced Costs-based Variable Fixing (LRCVF), computed as the difference between the optimal values of the stochastic problem and its reduced version obtained by fixing a certain number of variables. We relate the LRCVF with existing measures and show how to select the set of variables to fix. We then illustrate the interest of the proposed LRCVF and related heuristic procedure, in terms of computational time reduction and accuracy in finding the optimal solution, by applying them to a wide range of problems from the literature

A Vehicle Routing Problem with Multiple Service Agreements

We consider a logistics service provider which arranges transportation services to customers with different service agreements. The most prominent feature of this service agreement is the time period in which these customers send their orders and want to retrieve delivery information. After customers place their orders, they require information about the driver and an early indication of the arrival times. At the moment, this information needs to be provided. The order information of other customers with a different service agreement that needs to be serviced in the same period might still be unknown. Ultimately all customers have to be planned, constrained by the information provided to the customers in the earlier stage. In this paper, we investigate how the logistic service provider plans its routes and communicates the driver and arrival time information in the phase where not all customers are known (stage 1). Once all customer orders are known (stage 2), the final routes can be determined, which adhere to the already communicated driver and arrival time information from stage 1, minimizing total routing cost. For this problem, an exact algorithm is presented. This problem is solved using a novel tractable branch-and-bound method and re-optimization in stage 2. Detailed results are presented, showing the improvements of using re-optimization. We show that integrating the planning of the customers with the different service agreements leads to significant cost savings compared to treating the customers separately (as is currently done by most logistics service providers).</p

Capacity Planning with Uncertainty on Contract Fulfillment

This paper focuses on the tactical planning problem faced by a shipper which seeks to secure transportation and warehousing capacity, such as containers, vehicles or space in a warehouse, of different sizes, costs, and characteristics, from a carrier or logistics provider, while facing different sources of uncertainty. The uncertainty can be related to the loads to be transported or stored, the cost and availability of ad-hoc capacity on the spot market in the future, and the availability of the contracted capacity in the future when the shipper needs it. This last source of uncertainty on the capacity loss on the contracted capacity is particularly important in both long-haul transportation and urban distribution applications, but no optimization methodology has been proposed so far. We introduce the Stochastic Variable Cost and Size Bin Packing with Capacity Loss problem and model that directly address this issue, together with a metaheuristic to efficiently address it. We perform a set of extensive numerical experiments on instances related to long-haul transportation and urban distribution contexts and derive managerial insights on how such capacity planning should be performed

Differences in Obstetric Care Between Japan and the US: A Qualitative Analysis of Blogs

Aim To investigate patient-reported differences in obstetric care between Japan and the US by characterizing the information Japanese immigrants and expatriates share online

Herpes vírus simples e carcinoma cérvico-uterino

An important role has been ascribed to the herpes-vírus simplex (HSV) in the etiology of uterine cervical cancer. We have studied 60 women, 30 of them with cervical uterine cancer and another 30 without them. We performed clinicai, cytological, cytophatic and sorological studies. The last one permited to conclude past infections and the others the presence of the virus concomitantly. The clinical study found out the antecedents of the women and their partners concerned signs and symptoms of the disease. In addition we performed a careful gynecological exam in order to detect the viral disease. By the other hand we searched cytological alterations characteristical of the presence of the virus in cervical smears. The cytopathic effects was observed in rabbit cornea culture cells (SIRC-cells). The sorological study consisted in a complement fixation microtechnics againt antigen of the herpes virus (50% of hemolysis). We compared statistically the results of the two groups and did not find any significative difference relatively of the various parameters studied.Nos últimos anos tem-se imputado relevante papel ao herpes vírus simples (HSV), como agente etiológico do carcinoma cérvico-uterino. Tal premissa baseia-se em dados epidemiológicos, similares em ambas as condições: a infecciosa e a neoplásica. Sabendo-se da possibilidade,comprovada experimentalmente e, às vezes clinicamente, de vírus constituirem-se em agentes neoplásicos, aventou-se a hipótese acima referida. No intuito de colaborar no esclarecimento de tão importante questão, procuramos, em nosso meio, pesquisar essa possibilidade. Efetuamos estudos clínico-anamnésticos, citológico, virológicos e sorológicos em portadoras de câncer comparando-as a mulheres de grupo controle. As três primeiras pesquisas objetivaram surpreender a presençamomentânea do vírus; e a última permitiu intuir uma possível infecção pregressa, que possivelmente possa ter induzido à oncogênese. A análise suscinta clínico-anamnéstica pesquisou sintomas e sinais de infecção presente e passada na mulher e no parceiro. O estudo citológico, demonstrando características celulares típicas de doença herpética, autorizou-nos, com certa precisão, detectar a presença do vírus. Igualmente o estudo virológico, através de efeitos indiretos citopáticos em culturas de células, acarretados pelo herpes, denunciou a presença de tal micro-organismo. O estudo sorológico procurou detectar no sangue periférico, anti-corpos anti-SHV, por meio de uma reação de fixação de complemento. Os nossos estudos não demonstraram que as cancerosas eram mais assíduamente suspeitas de infecção herpética atual ou passada

Enhanced triacylglycerol catabolism by carboxylesterase 1 promotes aggressive colorectal carcinoma

The ability to adapt to low-nutrient microenvironments is essential for tumor cell survival and progression in solid cancers, such as colorectal carcinoma (CRC). Signaling by the NF-κB transcription factor pathway associates with advanced disease stages and shorter survival in patients with CRC. NF-κB has been shown to drive tumor-promoting inflammation, cancer cell survival, and intestinal epithelial cell (IEC) dedifferentiation in mouse models of CRC. However, whether NF-κB affects the metabolic adaptations that fuel aggressive disease in patients with CRC is unknown. Here, we identified carboxylesterase 1 (CES1) as an essential NF-κB–regulated lipase linking obesity-associated inflammation with fat metabolism and adaptation to energy stress in aggressive CRC. CES1 promoted CRC cell survival via cell-autonomous mechanisms that fuel fatty acid oxidation (FAO) and prevent the toxic build-up of triacylglycerols. We found that elevated CES1 expression correlated with worse outcomes in overweight patients with CRC. Accordingly, NF-κB drove CES1 expression in CRC consensus molecular subtype 4 (CMS4), which is associated with obesity, stemness, and inflammation. CES1 was also upregulated by gene amplifications of its transcriptional regulator HNF4A in CMS2 tumors, reinforcing its clinical relevance as a driver of CRC. This subtype-based distribution and unfavorable prognostic correlation distinguished CES1 from other intracellular triacylglycerol lipases and suggest CES1 could provide a route to treat aggressive CRC