Les nuages de glace de type cirrus sont reconnus comme ayant un impact radiatif important mais encore mal déterminé sur le système Terre-atmosphère. Récemment, la constellation de satellites A-Train a efficacement contribué à leur étude, grâce un panel d’instruments en parfaite synergie les uns avec les autres. Dans cette thèse, nous proposons d’utiliser l’instrumentation de l’A-Train afin d’étudier les propriétés optiques et radiatives des cirrus. Dans un premier temps, des données issues de deux campagnes aéroportées sont utilisées, afin d’effectuer une validation des mesures du radiomètre infrarouge spatial IIR. Nous montrons de très bonnes similitudes entre les mesures radiométriques aéroportées et spatiales, ce qui permet de conclure à la validation de ces dernières. Une seconde étude présente un algorithme développé dans le but de restituer l’épaisseur optique des cirrus et la dimension effective des cristaux qui les composent, à partir des mesures de IIR. Nous montrons que ses résultats sont en accord avec des mesures in situ et des produits opérationnels, mais remarquons cependant que leur qualité pourrait être améliorée dans l’hypothèse d’une meilleure connaissance des propriétés de nuages d’eau liquide sous-jacents. Une troisième étude propose donc une amélioration de cet algorithme, permettant de restituer simultanément les propriétés d’une couche de nuage de glace et de deux couches de nuage d’eau liquide. Cet algorithme ’multi-couches’ est appliqué sur un grand nombre de cas, de manière à juger efficacement de la qualité de ses résultats. Des comparaisons avec divers produits opérationnels montrent une bonne cohérence de nos restitutions. / Cirrus are cloud types that are recognized to have a strong but still poorly understood impact on the Earth-atmosphere radiation balance. Recently, the A-Train satellite constellation has efficiently contributed to the study of these clouds, due to a multitude of instruments in perfect synergism. In this PhD research, several A-Train instruments have been used to study the optical and radiative properties of cirrus. Firstly, with the help of the data from two airborne campaigns, we have performed a validation of the measurements from the Infrared Imaging Radiometer (IIR) onboard CALIPSO. We have observed strong similarities between the airborne and space borne radiometric measurements, which allows validating the latter. A second study presents an algorithm developed in order to perform retrievals of the optical thickness of cirrus and the effective size of their ice crystals using IIR measurements. We demonstrate that these retrievals are perfectly coherent with in situ measurements and operational products of IIR. It is nevertheless observed that better constraints on the properties of liquid water clouds underneath cirrus layers could significantly improve the retrievals. Therefore, a third study presents a modification of this algorithm, allowing us to simultaneously retrieve the properties of one cirrus layer and two layers of liquid water clouds underneath. This ‘multi-layer’ algorithm is applied to a large amount of cases in order to assess its effectiveness. Comparisons with several operational products indicate a good coherence of our retrievals.

Estudamos a estrutura de álgebras de potências associativas que são álgebras train. Primeiramente, mostramos a existência de idempotentes, que são todos principais e absolutamente primitivos. Em seguida, vemos as equações train envolvendo a decom- posição de Peirce. Quando a álgebra é de dimensão finita, resulta que a dimensão das componentes de Peirce são invariantes e o limite superior para seus nilndices são es- tudados para alguns idempotentes. Além disso, mostramos que as álgebras localmente train são álgebras train. Damos então uma descrição completa para o conjunto dos idempotentes para obter suas fórmulas explcitas. É voltada uma atenção para o caso de álgebras de Jordan, onde discutimos condições para que álgebras train de potências as- sociativas sejam álgebras de Jordan. Também mostramos que álgebras train de Jordan são de dimensão finita. Para álgebras de Bernstein de ordem n e perodo p, provamos que para termos associatividade nas potências necessitamos p = 1. Neste caso, existem 2 n1 possibilidades de equações train, que são explicitamente descritas. / We study the structure of power associative algebras which are train algebras. First we show the existence of idempotents, which are all principal and absolutely primitive. Then consider the train equations involving the Peirce decomposition. When the alge- bra is finite dimensional, it follows that the size of the Pierce components are invariant and the upper limit for its nil-indexes are studied for some idempotent. Furthermore, we show that locally train algebras are train algebras. Then we get a complete de- scription for the set of idempotents to obtain their explicit formulas. We give attention to the case of Jordan algebras, where we discuss conditions for train power associa- tive algebras be Jordan algebras. We also show that Jordan train algebras are finite dimensional. For Bernstein algebras of order n and period p, we prove that to have associativity in the powers we need p = 1. In this case, there are 2 n1 possibilities of train equations, which are explicitly described.

Thesis (M. Psych.Org.)--University of Queensland, 2002. / Includes bibliographical references.

Heavy haul trains are used to transport mineral resources from inland mines to harbours in South Africa. It is believed that the cost is less with a larger load per car or per train. This has resulted in the use of long heavy haul trains. The increase in train length has posed unprecedented technical challenges. For heavy haul trains, energy consumption, running time and in-train forces between neighbouring cars are of much concern to transportation corporations. The objective of the study is to find optimal driving methodologies for the implementation of a desired speed profile with energy consumption and in-train forces considered. Firstly, three control strategies are proposed in this study for train handling. In view of the characteristics of traditional pneumatic braking systems and the new Electronically Controlled Pneumatic (ECP) braking systems, a simulation study of optimal open loop controllers was undertaken. The result shows that the ECP braking systems demonstrate superb performance compared with pneumatic braking systems, especially together with independent distributed power (iDP) control. Thus, the main focus of the study was the control of heavy haul trains equipped with ECP braking systems. It is shown that there are redundancies in designing an open loop controller. An optimization procedure is applied to schedule cruise control by taking the in-train forces into initial design consideration. Optimal open loop scheduling presents a better starting point for a closed-loop controller design. A type of linear quadratic regulator (LQR) controller with state feedback is simulated to verify the above result. However, the closed-loop control law is designed based on full state feedback, which is not practical since not all the states can be measured. An observer could be designed to supplement the LQR controller if partial states are measured. This is, however, not the approach taken in this study. Instead, the application of output regulation of nonlinear systems with measured output feedback to the control of heavy haul trains is considered. This approach to design is practically feasible and manageable, and by its nature, is also easily integrable with human drivers. In this study, the existing result of output regulation of nonlinear systems is extended. The output regulation problem of nonlinear systems with measured output feedback is formulated in this study and solved for the local version and global version. For its application to train control, some application issues are discussed. Based on the proposed theory, a speed regulator for train control is designed. Simulation results show its applicability. Lastly, this study concentrates on the fault-tolerant capacity of the speed regulator. Two kinds of fault modes are considered. Fault detection and isolation for the sensor fault and braking system fault are exploited. Controller redesign is also given. Simulation results show that such a speed regulator has a fault-tolerant capacity to the corresponding faults. / Thesis (PhD)--University of Pretoria, 2007. / Electrical, Electronic and Computer Engineering / PhD / Unrestricted

Train dispatchers faces lots of challenges due to conflicts which causes delays of trains as a result of solving possible dispatching problems the network faces. The major challenge is for the train dispatchers to make the right decision and have reliable, cost effective and much more faster approaches needed to solve dispatching problems. This thesis work provides detail information on the implementation of different heuristic algorithms for train dispatchers in solving train dispatching problems. The library data files used are in xml file format and deals with both single and double tracks between main stations. The main objective of this work is to build different heuristic algorithms to solve unexpected delays faced by train dispatchers and to help in making right decisions on steps to take to have reliable and cost effective solution to the problems. These heuristics algorithms proposed were able to help dispatchers in making right decisions when solving train dispatching problems.

This study is meant to be an initial study of the possibility to replace the discrete control signal wires over the electrical coupler between train cars with a data bus system. The reason for this is that the electrical coupler is large and heavy due to the high amount of contacts it contains. It is also a problem for manufacturers who are upgrading an existing fleet and need to transfer more signals through a coupler with no spare contacts to use. Except the control signals there are also Ethernet and power signals in the electrical coupler. Some trains also use a bus system for control signals and/or signals containing a large amount of data such as passenger information.This report gives a presentation of some common ways to distribute electrical signals throughout a train used by most manufacturers. It also presents some design recommendations for a system that would collect existing signals to a bus system and two different design proposals that should be considered if such a system is to be developed. The study shows that there are already systems on the market for transferringcontrol signals over a bus but they are more aimed for trains under construction. Forthis reason a new bus system would only be suitable for upgrading existing couplersto free up space in the electrical coupler unit.

No description available.

A l’heure des études sur le changement climatique, un certain nombre d’inconnues subsiste comme la caractérisation des propriétés radiatives des aérosols à l’échelle globale. Différents moyens d’observations, depuis la surface ou l’espace, ont été développés ces dernières années et nous nous focalisons ici sur les mesures spatiales océaniques et notamment sur celles issues de deux instruments, MODIS/AQUA (Moderate Resolution Imaging Spectroradiometer de la NASA) et POLDER/PARASOL (POLarization and Directionality of Earth Reflectances du CNES) qui appartiennent à la constellation de satellites « A-Train ». Ces deux instruments nous permettent, à partir des luminances réfléchies par le système « Terre-Atmosphère », d’observer quotidiennement différents types d’aérosols (brûlis, poussières désertiques, pollution) en fonction de la zone géographique et d’en effectuer le suivi temporel.En première analyse, on peut comparer les résultats obtenus par chaque capteur qui ont des techniques d’observations privilégiant pour l’un, le domaine spectral pour l’autre, le caractère angulaire et polarisé des luminances. Utiliser ensuite en synergie les deux types d’informations nécessite de comparer les mesures brutes des instruments et d’assurer la cohérence des traitements. Nous avons ainsi examiné les étapes nécessaires à cette inversion: étalonnage des instruments, corrections apportées aux mesures et validité des modèles d’aérosols utilisés. Enfin, nous avons sélectionné quelques cas d’études afin d’analyser les caractéristiques des aérosols (quantité, taille, nature) d’origine désertique au-dessus de l’océan Atlantique et leur évolution au cours de leur transport. / Within climatic change issues, one of the unknowns remains the characterization of the aerosol radiative properties at global scale. Different ways of monitoring aerosols from surface or space have been developed during the recent years and our present study is especially focused on observations over ocean from two satellite instruments, MODIS/AQUA (Moderate Resolution Imaging Spectroradiometer of NASA) and POLDER/PARASOL (POLarization and Directionality of Earth Reflectances of CNES), that are both part of the “A-Train” constellation. From the radiances reflected by the “Earth-Atmosphere” system, we can monitor the distribution of different aerosol types (smoke, dust, pollution) over specific regions and with a good temporal frequency.We can first compare results obtained by each sensor that are using different techniques, MODIS favor spectral domain when POLDER considers the angular and polarized character of radiances. In a second step, it looks attractive to combine both data sets into a single inversion scheme. To do so, it requires to ensure that the radiances of the two instruments are consistent and to control the coherency of the assumptions used along the retrieval processing. We analyze the different steps: calibration, gaseous absorption and molecular scattering correction as well as the validity of the aerosol models. Lastly, we select specific events to analyze the evolution of aerosol plumes (content, size, composition) transported over the Atlantic Ocean.

Train-the-trainer is an educational method extensively used by organizations for capacity development. Despite the wide spread use of this method, there is little information regarding its use, role in educating adults, and participant perceptions of its utility. Healthcare service providers’ perceptions of a train-the-trainer educational method was investigated in this qualitative study. A focus group methodology was used. Content analysis revealed themes about participant perceptions. The overall theme identified was the need to address location-specific challenges, specifically, recognition by the trainer of the context of communities and programs in which the training occurs. Organizations using this method need be flexible and willing to revise the training plan based in adult learner needs. Service providers recommended that the provision of strategies and examples for transfer of learning into practice was critical as was the tailoring of train-the-trainer workshops in length, facilitation style, resources, and delivery modality to community capacity and needs. / October 2008

No description available.