Algorithme de branch-and-price-and-cut pour le problème de conception de réseaux avec coûts fixes, capacités et un seul produit

De nombreux problèmes liés aux domaines du transport, des télécommunications et de la logistique peuvent être modélisés comme des problèmes de conception de réseaux. Le problème classique consiste à transporter un flot (données, personnes, produits, etc.) sur un réseau sous un certain nombre de contraintes dans le but de satisfaire la demande, tout en minimisant les coûts. Dans ce mémoire, on se propose d'étudier le problème de conception de réseaux avec coûts fixes, capacités et un seul produit, qu'on transforme en un problème équivalent à plusieurs produits de façon à améliorer la valeur de la borne inférieure provenant de la relaxation continue du modèle. La méthode que nous présentons pour la résolution de ce problème est une méthode exacte de branch-and-price-and-cut avec une condition d'arrêt, dans laquelle nous exploitons à la fois la méthode de génération de colonnes, la méthode de génération de coupes et l'algorithme de branch-and-bound. Ces méthodes figurent parmi les techniques les plus utilisées en programmation linéaire en nombres entiers. Nous testons notre méthode sur deux groupes d'instances de tailles différentes (gran-des et très grandes), et nous la comparons avec les résultats donnés par CPLEX, un des meilleurs logiciels permettant de résoudre des problèmes d'optimisation mathématique, ainsi qu’avec une méthode de branch-and-cut. Il s'est avéré que notre méthode est prometteuse et peut donner de bons résultats, en particulier pour les instances de très grandes tailles.

Optimization models and methods for real-time transportation planning in forestry

Lors du transport du bois de la forêt vers les usines, de nombreux événements imprévus peuvent se produire, événements qui perturbent les trajets prévus (par exemple, en raison des conditions météo, des feux de forêt, de la présence de nouveaux chargements, etc.). Lorsque de tels événements ne sont connus que durant un trajet, le camion qui accomplit ce trajet doit être détourné vers un chemin alternatif. En l’absence d’informations sur un tel chemin, le chauffeur du camion est susceptible de choisir un chemin alternatif inutilement long ou pire, qui est lui-même "fermé" suite à un événement imprévu. Il est donc essentiel de fournir aux chauffeurs des informations en temps réel, en particulier des suggestions de chemins alternatifs lorsqu’une route prévue s’avère impraticable. Les possibilités de recours en cas d’imprévus dépendent des caractéristiques de la chaîne logistique étudiée comme la présence de camions auto-chargeurs et la politique de gestion du transport. Nous présentons trois articles traitant de contextes d’application différents ainsi que des modèles et des méthodes de résolution adaptés à chacun des contextes. Dans le premier article, les chauffeurs de camion disposent de l’ensemble du plan hebdomadaire de la semaine en cours. Dans ce contexte, tous les efforts doivent être faits pour minimiser les changements apportés au plan initial. Bien que la flotte de camions soit homogène, il y a un ordre de priorité des chauffeurs. Les plus prioritaires obtiennent les volumes de travail les plus importants. Minimiser les changements dans leurs plans est également une priorité. Étant donné que les conséquences des événements imprévus sur le plan de transport sont essentiellement des annulations et/ou des retards de certains voyages, l’approche proposée traite d’abord l’annulation et le retard d’un seul voyage, puis elle est généralisée pour traiter des événements plus complexes. Dans cette ap- proche, nous essayons de re-planifier les voyages impactés durant la même semaine de telle sorte qu’une chargeuse soit libre au moment de l’arrivée du camion à la fois au site forestier et à l’usine. De cette façon, les voyages des autres camions ne seront pas mo- difiés. Cette approche fournit aux répartiteurs des plans alternatifs en quelques secondes. De meilleures solutions pourraient être obtenues si le répartiteur était autorisé à apporter plus de modifications au plan initial. Dans le second article, nous considérons un contexte où un seul voyage à la fois est communiqué aux chauffeurs. Le répartiteur attend jusqu’à ce que le chauffeur termine son voyage avant de lui révéler le prochain voyage. Ce contexte est plus souple et offre plus de possibilités de recours en cas d’imprévus. En plus, le problème hebdomadaire peut être divisé en des problèmes quotidiens, puisque la demande est quotidienne et les usines sont ouvertes pendant des périodes limitées durant la journée. Nous utilisons un modèle de programmation mathématique basé sur un réseau espace-temps pour réagir aux perturbations. Bien que ces dernières puissent avoir des effets différents sur le plan de transport initial, une caractéristique clé du modèle proposé est qu’il reste valable pour traiter tous les imprévus, quelle que soit leur nature. En effet, l’impact de ces événements est capturé dans le réseau espace-temps et dans les paramètres d’entrée plutôt que dans le modèle lui-même. Le modèle est résolu pour la journée en cours chaque fois qu’un événement imprévu est révélé. Dans le dernier article, la flotte de camions est hétérogène, comprenant des camions avec des chargeuses à bord. La configuration des routes de ces camions est différente de celle des camions réguliers, car ils ne doivent pas être synchronisés avec les chargeuses. Nous utilisons un modèle mathématique où les colonnes peuvent être facilement et naturellement interprétées comme des itinéraires de camions. Nous résolvons ce modèle en utilisant la génération de colonnes. Dans un premier temps, nous relaxons l’intégralité des variables de décision et nous considérons seulement un sous-ensemble des itinéraires réalisables. Les itinéraires avec un potentiel d’amélioration de la solution courante sont ajoutés au modèle de manière itérative. Un réseau espace-temps est utilisé à la fois pour représenter les impacts des événements imprévus et pour générer ces itinéraires. La solution obtenue est généralement fractionnaire et un algorithme de branch-and-price est utilisé pour trouver des solutions entières. Plusieurs scénarios de perturbation ont été développés pour tester l’approche proposée sur des études de cas provenant de l’industrie forestière canadienne et les résultats numériques sont présentés pour les trois contextes.

Procedure di Programmazione Dinamica per Determinare le K Migliori Soluzioni del Knapsack Problem 0-1 e dello Shortest Path Problem

In questa tesi viene trattata la problematica di determinare le migliori K soluzioni per due problemi di ottimizzazione, il Knapsack Problem 0-1 e lo Shortest Path Problem. Tali soluzioni possono essere impiegate all'interno di metodi di column generation per la risoluzione di problemi reali, ad esempio Bin Packing Problems e problemi di scheduling di veicoli ed equipaggi. Sono stati implementati, per verificarne sperimentalmente le prestazioni, nuovi algoritmi di programmazione dinamica, sviluppati nell’ambito di un programma di ricerca. Inizialmente, per entrambi i problemi, è stato descritto un algoritmo che determinasse le migliori K soluzioni per ogni possibile sottoproblema; partendo da uno zaino con capacità nulla, nel caso del Knapsack Problem 0-1, e dalla determinazione di un cammino dal vertice sorgente in se stesso per lo Shortest Path Problem, l’algoritmo determina le migliori soluzioni di sottoproblemi via via sempre più grandi, utilizzando le soluzioni costruite per gli stati precedenti, fino a ottenere le migliori soluzioni del problema globale. Successivamente, è stato definito un algoritmo basato su un approccio di ricorsione backward; in questo caso si utilizza una funzione ricorsiva che, chiamata a partire dallo stato corrispondente al problema globale, viene richiamata solo sugli stati intermedi strettamente necessari, e per ognuno di essi non vengono determinate soluzioni superflue.

Chirality in the new generation of antidepressants: stereoselective analysis of the enantiomers of mirtazapine, N-demethylmirtazapine, and 8-hydroxymirtazapine by LC-MS.

Mirtazapine is an antidepressant that acts specifically on noradrenergic and sertonergic receptors. A LC-MS method was developed that allows the simultaneous analysis of the R-(-)- and S-(+)-enantiomers of mirtazapine (MIR), demethylmirtazapine (DMIR), and 8-hydroxymirtazapine (8-OH-MIR) in plasma of MIR-treated patients. The method involves a 3-step liquid-liquid extraction, an HPLC separation on a Chirobiotic V column, and MS detection in electrospray mode. The limit of quantification (LOQ) for all enantiomers was 0.5 ng/mL, and the intra- and interday CVs were within 3.3% to 11.7% (concentration ranges 5-50 ng/mL). A method is also presented for the quantitative analysis of glucuroconjugated MIR and 8-OH-MIR. S-(+)-8-OH-MIR is present in plasma mainly as its glucuronide. Preliminary data suggest that in all patients, except in those comedicated with CYP2D6 inhibitors such as fluoxetine and thioridazine, R-(-)-MIR concentrations were higher than those of S-(+)MIR. Moreover, fluvoxamine seems also to inhibit the metabolism of MIR. Therefore, this method seems to be suitable for the stereoselective assay of MIR and its metabolites in plasma of patients comedicated with MIR and other drugs for routine and research purposes.

Nylon wool column: a tool for obtaining monokine-rich eluates in the absence of serum

Diverse conditions for stimulating human mononuclear cells to release thymocyte costimulatory factors were tested for their contribution to the generation of supernatants high titers of these monokines. Activity titers increased with LPS concentration, reaching a plateau between 1 and 10 microng/ml. Indomethacin did not modify the monokine, but the assay for thymocyte costimulatory activity was substantially affected by inhibitory substances produced by the monocytes in the absence of indomethacin. The use of nylon wool columns to trap the cells was shown to be effective in raising cellular densities without decreasing activity titers. As result, the yield per cell could be maintained even in the absence of serum, an important step toward the goal of purifiying bioactive from crude broths.

Separation of astaxanthin from cells of Phaffia rhodozyma using colloidal gas aphrons (CGA) in a flotation column

The aim of this study is to investigate the separation of astaxanthin from the cells of Phaffia rhodozyma using colloidal gas aphrons (CGA), which are surfactant stabilized microbubbles, in a flotation column. It was reported in previous studies that optimum recoveries are achieved at conditions that favor electrostatic interactions. Therefore, in this study, CGA generated from the cationic surfactant hexadecyl trimethyl ammonium bromide (CTAB) were applied to suspensions of cells pretreated with NaOH. The different operation modes (batch or continuous) and the effect of volumetric ratio of CGA to feed, initial concentration of feed, operating height, and flow rate of CGA on the separation of astaxanthin were investigated. The volumetric ratio was found to have a significant effect on the separation of astaxanthin for both batch and continuous experiments. Additionally, the effect of homogenization of the cells on the purity of the recovered fractions was investigated, showing that the homogenization resulted in increased purity. Moreover, different concentrations of surfactant were used for the generation of CGA for the recovery of astaxanthin on batch mode; it was found that recoveries up to 98% could be achieved using CGA generated from a CTAB solution 0.8 mM, which is below the CTAB critical micellar concentration (CMC). These results offer important information for the scale-up of the separation of astaxanthin from the cells of P. rhodozyma using CGA.

Low generation triazine-based dendrimers-synthesis, characterzation and in vitro biological activity

In the present study, two low generation triazine-based dendrimers, G1.0(Cl)4 dendrimer and G1.5(OH)8 dendrimer, were synthesized and their cytotoxicity were tested by using the NIH 3T3 and the A2780 cell lines. In the synthesis process of the G1.0(Cl)4 dendrimer, cyanuric chloride (CAC) which has high reactivity chlorine atom was connected to the terminal of triethylene glycol (TEG) via nucleophilic substitution by controlling temperature. The prepared G1.0(Cl)4 dendrimer was purified by silica gel column chromatography. Then the four chlorine atoms in the G1.0(Cl)4 dendrimer were substituted by diethanolamine (DEA) to give dendrimer with the hydroxyl terminal group G1.5(OH)8. The starting materials, CAC, G1.0(Cl)4 dendrimer and G1.5(OH)8 dendrimer were analyzed by one-dimensional NMR, FTIR and MS techniques. The two dendrimers, G1.0(Cl)4 and G1.5(OH)8, showed perfect stability in the air environment at room temperature. However, G1.0(Cl)4 is not soluble in water while the G1.5(OH)8 dendrimer is a water soluble compound. Furthermore, cell biological evaluation at the studied concentrations showed that the CAC, as well as the prepared G1.0(Cl)4 and G1.5(OH)8 dendrimers, have no cytotoxicity towards the NIH 3T3 and A2780 cell lines.

The role of the vagus nerve in the generation of cardiorespiratory interactions in a neotropical fish, the pacu, Piaractus mesopotamicus

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

On-line redox speciation analysis of antimony using L-proline immobilized on controlled pore glass and hydride generation inductively coupled plasma optical emission spectrometry for detection

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Aperfeiçoamento do método clause-column table para a geração eficiente de implicantes primos

Pós-graduação em Engenharia Elétrica - FEIS

Assimilation of Meteosat Second Generation (MSG) satellite data in a regional numerical weather prediction model using a one-dimensional variational approach

The quality of temperature and humidity retrievals from the infrared SEVIRI sensors on the geostationary Meteosat Second Generation (MSG) satellites is assessed by means of a one dimensional variational algorithm. The study is performed with the aim of improving the spatial and temporal resolution of available observations to feed analysis systems designed for high resolution regional scale numerical weather prediction (NWP) models. The non-hydrostatic forecast model COSMO (COnsortium for Small scale MOdelling) in the ARPA-SIM operational configuration is used to provide background fields. Only clear sky observations over sea are processed. An optimised 1D–VAR set-up comprising of the two water vapour and the three window channels is selected. It maximises the reduction of errors in the model backgrounds while ensuring ease of operational implementation through accurate bias correction procedures and correct radiative transfer simulations. The 1D–VAR retrieval quality is firstly quantified in relative terms employing statistics to estimate the reduction in the background model errors. Additionally the absolute retrieval accuracy is assessed comparing the analysis with independent radiosonde and satellite observations. The inclusion of satellite data brings a substantial reduction in the warm and dry biases present in the forecast model. Moreover it is shown that the retrieval profiles generated by the 1D–VAR are well correlated with the radiosonde measurements. Subsequently the 1D–VAR technique is applied to two three–dimensional case–studies: a false alarm case–study occurred in Friuli–Venezia–Giulia on the 8th of July 2004 and a heavy precipitation case occurred in Emilia–Romagna region between 9th and 12th of April 2005. The impact of satellite data for these two events is evaluated in terms of increments in the integrated water vapour and saturation water vapour over the column, in the 2 meters temperature and specific humidity and in the surface temperature. To improve the 1D–VAR technique a method to calculate flow–dependent model error covariance matrices is also assessed. The approach employs members from an ensemble forecast system generated by perturbing physical parameterisation schemes inside the model. The improved set–up applied to the case of 8th of July 2004 shows a substantial neutral impact.

Low generation triazine-based dendrimers-synthesis, characterzation and in vitro biological activity

In the present study, two low generation triazine-based dendrimers, G1.0(Cl)4 dendrimer and G1.5(OH)8 dendrimer, were synthesized and their cytotoxicity were tested by using the NIH 3T3 and the A2780 cell lines. In the synthesis process of the G1.0(Cl)4 dendrimer, cyanuric chloride (CAC) which has high reactivity chlorine atom was connected to the terminal of triethylene glycol (TEG) via nucleophilic substitution by controlling temperature. The prepared G1.0(Cl)4 dendrimer was purified by silica gel column chromatography. Then the four chlorine atoms in the G1.0(Cl)4 dendrimer were substituted by diethanolamine (DEA) to give dendrimer with the hydroxyl terminal group G1.5(OH)8. The starting materials, CAC, G1.0(Cl)4 dendrimer and G1.5(OH)8 dendrimer were analyzed by one-dimensional NMR, FTIR and MS techniques. The two dendrimers, G1.0(Cl)4 and G1.5(OH)8, showed perfect stability in the air environment at room temperature. However, G1.0(Cl)4 is not soluble in water while the G1.5(OH)8 dendrimer is a water soluble compound. Furthermore, cell biological evaluation at the studied concentrations showed that the CAC, as well as the prepared G1.0(Cl)4 and G1.5(OH)8 dendrimers, have no cytotoxicity towards the NIH 3T3 and A2780 cell lines.

On thermodynamics in the primary power conversion of oscillating water column wave energy converters

The paper presents an investigation to the thermodynamics of the air flow in the air chamber for the oscillating water column wave energy converters, in which the oscillating water surface in the water column pressurizes or de-pressurises the air in the chamber. To study the thermodynamics and the compressibility of the air in the chamber, a method is developed in this research: the power take-off is replaced with an accepted semi-empirical relationship between the air flow rate and the oscillating water column chamber pressure, and the thermodynamic process is simplified as an isentropic process. This facilitates the use of a direct expression for the work done on the power take-off by the flowing air and the generation of a single differential equation that defines the thermodynamic process occurring inside the air chamber. Solving the differential equation, the chamber pressure can be obtained if the interior water surface motion is known or the chamber volume (thus the interior water surface motion) if the chamber pressure is known. As a result, the effects of the air compressibility can be studied. Examples given in the paper have shown the compressibility, and its effects on the power losses for large oscillating water column devices.

Cold vapour generation electrothermal atomic absorption spectrometry and solid phase extraction based on a new nanosorbent for sensitive HG determination in environmental samples (sea water and river water)

Mercury is not an essential element for plant or animal life and it is a potential environmental toxic because of its tendency to form covalent bonds with organic molecules and the high stability of the Hg-C bond. Reports estimate a total mercury concentration in natural waters ranging from 0.2 to 100 ng L-1. Due to this fact, highly sensitive methods are required for direct determination of such extremely low levels. In this work, a rapid and simple method was developed for separation and preconcentration of mercury by flow injection solid phase extraction coupled with on-line chemical vapour generation electrothermal atomic absorption spectrometry. The system is based on chelating retention of the analyte onto the mini column filled with a mesoporous silica functionalized with 1,5 bis (di-2-pyridyl) methylene thiocarbohydrazide. The main aim of this work was to develop a precise and accurate method for the determination of the Hg. Under the optima conditions and 120 s preconcentration time, the detection limit obtained was 0.009 μg L-1, with RSDs 3.7 % for 0.2 μg L-1, 4.8 % for 1 μg L-1 and enrichment factor 4, Furthermore, the method proposed has permitted the determination of Hg with a reduction in the analysis time, the sample throughput was about 18 h-1, low consumption of reagents and sample volume. The method was applied to the determination of Hg in sea water and river water. For the quality control of the analytical performance and the validation of the newly developed method, the analysis of two certified samples, TMDA 54.4 Fortified Lake, and LGC6187 River sediment was addressed. The results showed good agreement with the certified values.