Solving a generalized traveling salesperson problem with stochastic customers

In this paper, a probabilistic generalized traveling salesperson problem (PGTSP) is introduced to address several applications. In the PGTSP, each customer belongs to a cluster that consists of a set of customers. Whether or not any given customer will be present during actual operations is known a priori only probabilistically. The PGTSP seeks the minimum expected length tour to visit a subset of all customers such that the tour traverses each cluster at least once. If when implementing the tour it is revealed that there is no demand for service within the cluster to which a customer stop belongs, that stop will be skipped. An exact solution algorithm based on the integer L-shaped method and three tour construction-based heuristics for quickly solving this problem are described in the paper. Computational experiments were conducted to assess computational requirements and solution quality of the proposed solution techniques. These experiments show that the exact method is able to solve small- and moderate-size problems to optimality. In addition, one of the proposed heuristics (the MMI heuristic), in particular, gives good approximate solutions (often a few percent from optimal) in very reasonable computational time.     

The national — esa soyuz missions andromède, marco polo, odissea, cervantes, delta and eneide

From the autumn of 2001 till spring of 2005 a series of six flights to the International Space Station, ISS, were conducted using the Russian Soyuz manned launcher. These flights initially known as ‘taxi-missions’, were characterized by the participation and co-funding from both the European Space Agency, ESA, and the five national delegations from France, Italy, Belgium, Spain, and the Netherlands. The national participation was reflected both in the flight of a cosmonaut/astronaut, originating from the country co-sponsoring the flight as well as in the origin of the majority of experiments and other activities carried out during these missions. In these six Soyuz missions: Andromède (October 2001), Marco Polo (April 2002), Odissea (October 2002), Cervantes (October 2003), DELTA (April 2004) and Eneide (April 2005), some more than one hundred experiments were carried out. These experiments covered the areas of basic and applied research and technology in biology, human physiology, fluid and plasma physics, material science and Earth observation. Also a significant number of education activities were part of these missions. This paper gives a complete overview of these missions, of all science, education and related activities performed. The perspectives of these activities in the light of the space exploration programs in the XXI century and some of the uncertainties and paradoxes are discussed.     

Failure of Adhesive Bonds at Constant Strain Rates

Shear strengths of adhesive bonds using AF126 and two thicknesses of aluminum were measured at constant rate of crosshead separation. It was found that the shear strength could be related to temperature and strain rate or failure time over the range of deformation rates used.     

Microstructure and protein digestibility of beef: The effect of cooking conditions as used in stews and curries

Beef meat was cooked at 373 K for 10 and 30 min to investigate the effect of the cooking conditions generally used during beef stew and curry preparation on protein digestibility. The cooked meats, along with a raw control, were digested using an in vitro digestion model to simulate gastric and small-intestinal conditions. Samples taken at different digestion times were analyzed using SDS-PAGE, RP-HPLC, ninhydrin assays for amino N and transmission electron microscopy. Simulated gastric conditions quickly led to the loss of basic sarcomere structure in raw meat myofibrils whereas the sarcomere structure of the compact cooked meat myofibrils remained intact after 30 min of gastric digestion. Prolonged cooking of meat (30 min) resulted in incomplete digestion of small MW (<10 kDa) peptides, as observed from SDS-PAGE. This agreed with the amount of ninhydrin-reactive amino N released during digestion, which decreased with an increase in cooking time. The RP-HPLC peak areas of the major identified amino acids (tryptophan, tyrosine and phenylalanine) also decreased with an increase in cooking time. This suggested the formation of “limit peptides” during prolonged cooking of beef, which were not further broken down into free amino acids by digestive enzymes and therefore might not be bioavailable.     

Preparatory processes in the task-switching paradigm: Evidence from the use of probability cues.

The purpose of the investigations was to dissociate processes of task preparation from task execution in the task-switching paradigm. The basic assumption was that task repetitions have 2 advantages over task shifts: an activation advantage as a result of the execution of the same task type in the pretrial, and an expectation advantage, because participants, in general, implicitly expect a repetition. In Experiments 1-3, the authors explicitly manipulated expectancies by presenting cues that announced a shift and/or a repetition with probabilities of 1.00, .75, .50, or .25. Increasing latencies with decreasing probability for shifts and repetitions show that the expectation advantage can be equalized by preparation. However, the activation advantage represented by constant shift costs between tasks of the same probability is not penetrable by preparation. In Experiments 4 and 5, the authors found evidence that preparation involves activation of the expected task and inhibition of distracting tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cancer Stem Cells: Biological Functions and Therapeutically Targeting

Almost all tumors are composed of a heterogeneous cell population, making them difficult to treat. A small cancer stem cell population with a low proliferation rate and a high tumorigenic potential is thought to be responsible for cancer development, metastasis and resistance to therapy. Stem cells were reported to be involved in both normal development and carcinogenesis, some molecular mechanisms being common in both processes. No less controversial, stem cells are considered to be important in treatment of malignant diseases both as targets and drug carriers. The efforts to understand the role of different signalling in cancer stem cells requires in depth knowledge about the mechanisms that control their self-renewal, differentiation and malignant potential. The aim of this paper is to discuss insights into cancer stem cells historical background and to provide a brief review of the new therapeutic strategies for targeting cancer stem cells.     

Configuration for mass customization: how to extend product configuration towards requirements and process configuration

In order to develop mass customization, many companies use configuration software to customize their products. Although many studies already exist about Product Configuration, Requirements and Process Configuration have not been studied in detail. As all these three aspects must be considered for mass customization, the aim of this paper is to show how Product Configuration, when considered as a constraint satisfaction problem, can be extended upstream towards Requirements Configuration and downstream towards Process Configuration. Product Configuration basics are first reviewed thanks to a constraint based approach, and an analysis of industrial configuration situations is done in order to clarify mass customization needs in terms of configuration. Then upstream Requirements Configuration and downstream Process Configuration are defined and generic models are proposed. It is shown that the proposed elements allow a global and consistent flow of configuration activities. A detailed example illustrates the different configuration problems and a discussion terminates the paper.     

Determination of the henrian activity coefficient of sodium in liquid magnesium

The temperature-dependent Henrian activity coefficient of Na in liquid Mg in the very dilute range has been determined from measurements of equilibrium concentrations of Na in liquid Mg in contact with NaCl-MgCl₂ melts of different compositions and temperatures in the range 650 to 790 °C. The term A in the equation RT in γ _Na = A was fitted to the experimental results using the equilibrium constant for the reaction 2NaCl (l) + Mg (l) = MgCl₂ (l) + 2Na (l) and thermodynamic data for the NaCl-MgCl₂ melt. The obtained γ _Na is compared to previously measured activity coefficients and activity coefficients calculated from existing solubility data for the Na-Mg system.     

Delineation of the genomics field by hybrid citation-lexical methods: interaction with experts and validation process

In advanced methods of delineation and mapping of scientific fields, hybrid methods open a promising path to the capitalisation of advantages of approaches based on words and citations. One way to validate the hybrid approaches is to work in cooperation with experts of the fields under scrutiny. We report here an experiment in the field of genomics, where a corpus of documents has been built by a hybrid citation-lexical method, and then clustered into research themes. Experts of the field were associated in the various stages of the process: lexical queries for building the initial set of documents, the seed; citation-based extension aiming at reducing silence; final clustering to identify noise and allow discussion on border areas. The analysis of experts’ advices show a high level of validation of the process, which combines a high-precision and low-recall seed, obtained by journal and lexical queries, and a citation-based extension enhancing the recall. This findings on the genomics field suggest that hybrid methods can efficiently retrieve a corpus of relevant literature, even in complex and emerging fields.     

Properties of poly(butylene terephthatlate) polymerized from cyclic oligomers and its composites

The high viscosity of thermoplastic matrices hampers fiber impregnation. This problem can be overcome by using low viscous polymeric precursors such as cyclic butylene terephthalate (CBT^® resins), which polymerize to form a thermoplastic matrix. This allows thermoset production techniques, like resin transfer molding (RTM), to be used for the production of textile reinforced thermoplastics. Due to the processing route and more specifically the time-temperature profile, inherent to the RTM process, the crystallites of the matrix consist out of well-defined, thick and well-oriented crystal lamellae. Together with a high overall degree of crystallinity and a low density of tie molecules, these large and perfect crystals cause polymer brittleness. Matrix brittleness lowers the transverse strength of unidirectional composites to below the matrix strength, but leaves the mechanical properties in the fiber direction unaffected. Although not a valid option for the RTM production route, crystallization from a truly random melt and at a sufficiently high cooling rate would substantially improve the ductility.