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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Validation et désagrégation de l’humidité du sol estimée par le satellite SMOS en zones agricoles et forestières des Prairies canadiennes

Djamai, Najib January 2015 (has links)
Résumé : Le satellite Soil Moisture and Ocean Salinity (SMOS), lancé en novembre 2009, est le premier satellite en mode passif opérant en bande-L. Cette fréquence est considérée comme optimale pour estimer l’humidité du sol. SMOS est destiné à cartographier l’humidité de la couche 0-5 cm du sol à l’échelle globale, avec une précision attendue inférieure à 0,04 m3/m3, une répétitivité temporelle inférieure à 3 jours et une résolution spatiale d’environ 40 km. L’objectif de cette thèse est de valider l’humidité du sol de SMOS sur des sites agricoles et forestiers situés au Canada, et de contribuer au développement de méthodes de désagrégation de l’humidité du sol estimée par SMOS dans le but d’exploiter ces données dans les études à l’échelle locale telle qu’en agriculture. Les données de la campagne de terrain CanEx-SM10, effectuée sur un site agricole (Kenaston) et un site forestier (BERMS) situés à Saskatchewan, et celles de la campagne SMAPVEX12, effectuée sur un site majoritairement agricole (Winnipeg) situé au Manitoba, sont utilisées. Les données d’humidité du sol de SMOS ont montré une amélioration de la version v.309 à la version v.551. La version 551 des données d’humidité du sol de SMOS se compare mieux aux mesures in situ que les autres versions, aussi bien sur les sites agricoles que sur le site forestier. Sur les sites agricoles, l’humidité du sol de SMOS a montré une bonne corrélation avec les mesures au sol, particulièrement avec la version 551 (R ≥ 0,58, en modes ascendant et descendant), ainsi qu’une certaine sensibilité à la pluviométrie. Néanmoins, SMOS sous-estime l’humidité du sol en général. Cette sous-estimation est moins marquée sur le site de Kenaston en mode descendant (|biais| ≈ 0,03 m3/m3, avec la version v.551). Sur le site forestier, en raison de la densité de la végétation, les algorithmes d’estimation de l’humidité du sol à partir des mesures SMOS ne sont pas encore efficaces, malgré les améliorations apportées dans la version v.551. Par ailleurs, sur le site agricole de Kenaston et le site forestier de BERMS, les données d’humidité du sol de SMOS ont montré, généralement, de meilleures performances par rapport aux produits d’humidité du sol d’AMSR-E/NSIDC, AMSR-E/VUA et ASCAT/SSM. DISaggregation based on Physical And Theoretical scale Change (DISPATCH), un algorithme de désagrégation à base physique, est utilisé pour désagréger à 1 km de résolution spatiale l’humidité du sol de SMOS (40 km de résolution) sur les deux sites agricoles situés à Kenaston et à Winnipeg. DISPATCH est basé sur l’efficacité d’évaporation du sol (SEE) estimée à partir des données optique/ thermique de MODIS, et un modèle linéaire/non-linéaire liant l’efficacité d’évaporation et l’humidité du sol à l’échelle locale. Sur un site présentant une bonne dynamique spatiale et temporelle de l’humidité du sol (le site de Winnipeg au cours de la campagne de terrain SMAPVEX12), les résultats de DISPATCH obtenus avec le modèle linéaire sont légèrement meilleurs (R = 0,81 ; RMSE = 0.05 m3/m3 et pente = 0,52, par rapport aux mesures in situ) comparés aux résultats obtenus avec le modèle non-linéaire (R = 0,72 ; RMSE = 0.06 m3/m3 et pente = 0,61, par rapport aux mesures in situ). La précision de l’humidité du sol dérivée de DISPATCH, en se basant sur les deux modèles linéaire et non linéaire, décroit quand l’humidité du sol à grande échelle croît. Cette étude a montré, également, que DISPATCH peut être généralisé sur des sites particulièrement humides (le site de Kenaston au cours de la campagne de terrain CanEx-SM10). Cependant, en conditions humides, les résultats dérivés avec le modèle non-linéaire (R > 0,70, RMSE = 0,04 m3/m3 et pente ≈ 0,80, par rapport aux valeurs d’humidité du sol dérivées des mesures aéroportées de la température de brillance en bande L) ont montré de meilleures performances comparées à ceux dérivés avec le modèle linéaire (R > 0,73, RMSE = 0,08 m3/m3 et pente > 1.5, par rapport aux valeurs d’humidité du sol dérivées des mesures aéroportées de la température de brillance en bande L). Ceci est dû à une sous-estimation systématique de la limite sèche Tsmax. Par ailleurs, l’humidité du sol désagrégée présente une forte sensibilité à〖 Ts〗_max, particulièrement avec le modèle linéaire. Une approche simple a été proposée pour améliorer l’estimation de〖 Ts〗_max, dans des zones particulièrement humides. Elle a permis de réduire l’impact de l’incertitude sur〖 Ts〗_max dans le processus de désagrégation. Avec 〖 Ts〗_max améliorée, le modèle linaire aboutit à de meilleurs résultats (R > 0,72, RMSE = 0,04 m3/m3 et pente ≈ 0,80, par rapport aux valeurs d’humidité du sol estimées à partir des mesures aéroportées de la température de brillance en bande-L) que le modèle non-linéaire (R > 0,64, RMSE = 0,05 m3/m3 et pente ≈ 0,3, par rapport aux valeurs d’humidité du sol estimées à partir des mesures aéroportées de la température de brillance en bande-L). Basé sur des données optiques/ thermiques de MODIS, DISPATCH n’est pas applicable pour les journées nuageuses. Pour surmonter cette limitation, une nouvelle méthode a été proposée. Elle consiste à combiner DISPATCH avec le schéma de surface Canadian Land Surface Scheme (CLASS). Les données d’humidité du sol à 1 km de résolution dérivées de DISPATCH pour les journées non nuageuses sont utilisées pour calibrer les simulations de CLASS disponibles continuellement aux heures de passage de SMOS. Une approche de calibration basée sur la correction de la pente entre les valeurs d’humidité du sol dérivées de CLASS et les valeurs d’humidité du sol dérivées de DISPATCH (données de référence) a été mise au point. Les résultats montrent que les données d’humidité du sol à 1 km de résolution dérivées de cette nouvelle approche pour les journées nuageuses se comparent bien aux mesures in situ (R = 0,80 ; biais = -0,01 m3/m3 et pente = 0,74). Pour les journées non nuageuses, les valeurs d’humidité du sol dérivées de DISPATCH seul se comparent mieux aux mesures in situ que les valeurs dérivées en combinant DISPATCH à CLASS. / Abstract : The Soil Moisture and Ocean Salinity (SMOS), launched in November 2009, is the first passive microwave satellite operating in L band which is considered as optimal for soil moisture estimation. It is designed to provide global soil moisture maps at 0 – 5 cm layer from soil surface with a targeted accuracy of 0.04 m3 / m3, revisit time of less than 3 days anda spatial resolution of about 40 km. The objective of this thesis is to validate SMOS soil moisture data over agricultural and forested sites located in Canada, and to contribute to the development of SMOS downscaling methods in order to exploit these data in local scale studies such as agriculture. The data used are collected during the CanEX-SM10 field campaign, conducted over an agricultural site (Kenaston) and a forested site (BERMS) located in Saskatchewan, and during SMAPVEX12 field campaign conducted over a mostly agricultural area (Winnipeg) located in Manitoba. SMOS soil moisture data showed an improvement from the processor versions 309 to 551. Version 551 was found to be closer and more correlated to ground measurements over both agricultural and forested sites. For the agricultural sites, SMOS soil moisture showed high correlation coefficient with ground data especially with version 551(R ≥ 0.58, for ascending and descending overpasses), as well as a certain sensitivity to rainfall events. However, the SMOS soil moisture values were underestimated compared with ground measurements. This underestimation is less pronounced for the descending overpass over the Kenaston site (|bias| viii ≈ 0.03 m3/m3, for version v.551). For the forested site, due to the vegetation density, the SMOS soil moisture estimation algorithms were not very efficient despite the improvements brought to version 551. Moreover, over the agricultural site of Kenaston and the forested site of BERMS, SMOS soil moisture data showed, in general, good performances compared to AMSR-E/NSIDC, AMSR-E/VUA and ASCAT/SSM soil moisture products. DISaggregation based on Physical And Theoretical scale Change (DISPATCH), a physically-based downscaling algorithm, was used to downscale at 1-km spatial resolution the SMOS soil moisture estimates (40-km resolution) over the agricultural sites located in Kenaston and Winnipeg. DISPATCH is based on the Soil Evaporative Efficiency (SEE) derived from optical/thermal MODIS data, and a linear/non-linear model linking the Soil Evaporative Efficiency to the near-surface soil moisture at local scale. Over a site with a good spatial and temporal dynamics of soil moisture (such as Winnipeg’s site during the SMAPVEX12 field campaign), slightly better results were obtained with DISPATCH based on the linear model (R = 0.81, RMSE = 0.05 m3 /m3 and slope = 0.52, with respect to ground data) compared to results obtained from the non-linear model (R = 0.72, RMSE = 0.06 m3 /m3 and slope = 0.61, with respect to ground data). The accuracy of the DISPATCH-derived soil moisture, using both linear and non-linear models, decreases when the large-scale soil moisture increases. This study also showed, also, that DISPATCH can be generalized for very wet soil conditions (Kenaston’s site during the CanEX-SM10 field campaign). However, under wet soil conditions, better results were obtained with DISTACH based on the nonlinear (R > 0.70, RMSE = 0.04 m3/m3 and slope ≈ 0.80, with respect to the estimated soil moisture form L-band airborne brightness temperature) compared to results obtained with ix DISPATCH based on the linear model (R > 0.73, RMSE = 0.08 m3/m3 and slope > 1.5, with respect to the estimated soil moisture form L-band airborne brightness temperature). This is due to a systematic underestimation of the dry edge Tsmax. Furthermore, the downscaling results were found to be very sensitive to 𝑇𝑠𝑚𝑎𝑥, particularly with the linear model. A simple approach was proposed to improve the estimation of Tsmax under very wet soil conditions. It allowed reducing the impact of 𝑇𝑠𝑚𝑎𝑥 uncertainty in the disaggregation process. Using the improved Tsmax value, better results were obtained with the linear model (R > 0.72, RMSE = 0.04 m3/m3 and slope ≈ 0.80, with respect to the estimated soil moisture form L-band airborne brightness temperature) compared to the non-linear model (R > 0.64, RMSE = 0.05m3/m3 and slope ≈ 0.3, with respect to the estimated soil moisture form L-band airborne brightness temperature). Based on optical/thermal MODIS data, DISPATCH is not applicable for cloudy days. To overcome this limitation, a new method was proposed. It involves the combination of DISPATCH with the Canadian Land Surface Scheme (CLASS). DISPATCH-derived soil moisture data for cloud-free days are used to calibrate CLASS soil moisture simulations which are continually available at SMOS overpasses times. A calibration approach based on slope correction between the CLASS-derived and DISPATCH-derived (reference data) soil moisture datasets is considered. Results showed that soil moisture values derived from this newly developed method during cloudy days compare well with in situ data (R = 0.80, RMSE = 0.07 m3/m3 and slope = 0.73). For no-cloudy days, DISTATCH-derived soil moisture data are closer to in situ data than those derived when combining DISPATCH with CLASS.
12

The Research of feasibility of High-level Manpower Dispatch

Sung, Hsiao-li 20 August 2008 (has links)
ABSTRACT The manpower dispatch development in US, Japan and European country, all become mature industrial stage, in Taiwan also gradually develops under this tidal current, and gradually becomes one of frequently strategies adopt by the enterprise human resources department for human flexible scheduling. The manpower dispatch not only may provide the enterprise human resource in response to peak time or obtains the support of special specialized talented person, simultaneously can outside of administration responsibility, exempt from related cost for the employment of permanent staff, lets the enterprise have the extra mental effort to concentrates in its core specialty, therefore the enterprise get much attention and use it, further enhance its development of the enormous potential. The manpower dispatch already is one of 12 prioritizes service industries in "service industry development guiding principle and the course of action" by the Economic Construction Committee of Executive Yuan, according to the industry and commerce general survey that held by DGBAS (Directorate-General of Budget, Accounting and Statistics) in 2001, there are approximately 790 manpower supplies industry, from the experiences of US, the manpower dispatch will be very important in the future duty field. According to the estimates of Economic Construction Committee, the average labor force are 9,900 thousand people in Taiwan, the dispatch laborer population might reach 300 thousand people in the future. But recently, the type of knowledge worker change the manpower dispatch level (Yang Ch'aoan, 2004). Perhaps the dispatches worker's image impression of most people is still the image of low-end manual worker, the administration worker or the sanitation worker, but the nowadays enterprise's demand gradually transformed to technical role in specialist, high-level white-color worker as well as telecommunication ,marketing specialist. At present in practice, some company runs the dispatch of tradition low level affairs or the labor work, some runs the recommendation or dispatch of the high step personnel (commonly knows as¡Ghead hunting) ,as for the high-level manpower dispatch that different from the dispatch of traditional dispatch and head hunting, in Europe/America and Japan had the explicit law definition and business volume, but in Taiwan is whether feasible? In the limit of not having enough literature for reference, this research attempts from the demand of enterprise, the supplies of high-level manpower, the barrier in practical and the economical scale of market, to analyze its feasibility, provides some reference for the dispatch industry. This research discovered that¡G (1) the high-level manpower dispatch truly has its demand in Taiwan, and increases day by day. (2) the supplies of the high-level manpower due to lack of protection of the law, presents recruits difficult and high turnover. (3) the high-level manpower dispatches will match the expectation for both supply and demand sides (for example, the cognition of the employer, the trust, authorization and support to high-level dispatch manpower, and whether is willing to give reasonable service fee for which provides dispatch service) the challenge still many, was the key point of high-level manpower dispatch management. (4) the business volume of high-level manpower dispatch at present in Taiwan is not enough, and is insufficient to support the dispatch industry to run this service only. (5) the high-level manpower dispatch is feasible, and will be supposed to the mainstream of manpower dispatch market for the future. Keyword: the manpower dispatch, the human resources, high-level manpower, dispatch demand enterprise
13

The Effect of Icing on the Dispatch Reliability of Small Aircraft

Gates, Melinda M. 08 December 2004 (has links)
In 2000, the National Aeronautics and Space Administration (NASA) initiated a program to promote the use of small aircraft as an additional option for national public transportation. The Small Aircraft Transportation System (SATS) asserted the idea of everyday individuals piloting themselves on trips, within a specified distance range, using a small (4 person), piston powered, un-pressurized aircraft and small airports in close proximity to their origin and destination. This thesis investigates how one weather phenomenon, in-flight icing, affects the dispatch reliability of this transportation system. Specifically, this research presumes that a route is considered a "no-go" for low time pilots in a small, piston powered aircraft if any icing conditions are forecast along the route at the altitude of the flight during the time the traveler desires to make the trip. This thesis evaluates direct flights between Cleveland and Boston; Boston and Washington, D.C.; and Washington, D.C. and Cleveland during the months of November through May for the years 2001 to 2003 at maximum cruising altitudes of 6,000 feet, 8,000 feet, 10,000 feet, and 12,000 feet above mean sea level (MSL). It was found that the overall probability of a "no-go" for all three flight paths at the normal cruising altitude of 12,000 feet is 56.8%. When the cruising altitude is reduced to 10,000 feet, 8,000 feet, and 6,000 feet the probability of a "no-go" for all three flight paths reduces to 54.6%, 48.5%, and 43.7% respectively. / Master of Science
14

Optimal dispatch in Smart Power Grids with partially known deviation

Basu, Meheli 01 July 2015 (has links)
Power grid is an interconnected system of supplying electricity from the supplier to the consumer, consisting of electricity generating plant, high voltage transmission lines- to carry electricity from the generating plant to the load center, and distribution lines- to carry electricity from load centers to individual consumers. A lot of research is being pursued to develop technologies for improving the next generation of power grid called the Smart Power Grid. The Smart Power Grid will have sophisticated communication infrastructure to improve the efficiency of electricity generation using renewable energy sources like the sun, water, etc and also to inform consumers of their electricity usage pattern. Also, the electricity market is now divided into three sections- generation, transmission and distribution. Private companies are competing with each other to provide electricity at the most competitive market price. We have developed two algorithms to help generating companies achieve their goal of meeting the hourly electricity need of the consumers and to do so at a minimum total cost.
15

Aircraft systems design methodology and dispatch reliability prediction

Bineid, Mansour January 2005 (has links)
Aircraft despatch reliability was the main subject of this research in the wider content of aircraft reliability. The factors effecting dispatch reliability, aircraft delay, causes of aircraft delays, and aircraft delay costs and magnitudes were examined. Delay cost elements and aircraft delay scenarios were also studied. It concluded that aircraft dispatch reliability is affected by technical and non-technical factors, and that the former are under the designer's control. It showed that the costs of aircraft delays are very significant and must be reduced. Cont/d.
16

Aircraft systems design methodology and dispatch reliability prediction

Bineid, Mansour January 2005 (has links)
Aircraft despatch reliability was the main subject of this research in the wider content of aircraft reliability. The factors effecting dispatch reliability, aircraft delay, causes of aircraft delays, and aircraft delay costs and magnitudes were examined. Delay cost elements and aircraft delay scenarios were also studied. It concluded that aircraft dispatch reliability is affected by technical and non-technical factors, and that the former are under the designer's control. It showed that the costs of aircraft delays are very significant and must be reduced. Cont/d.
17

Assessing the Impact of Economically Dispatchable Wind Resources on the New England Wholesale Electricity Market

Goggins, Andrew 01 January 2013 (has links) (PDF)
Among renewable energy resources, wind power is poised to contribute most significantly to meeting future wholesale electricity demand. However, the intermittent nature of wind power makes maintaining system reliability a challenge as the share of installed wind capacity on the grid increases. In New England, wind plants are currently unable to receive automatic dispatch instructions from the regional grid operator, but a centralized wind forecasting system under development will enable wind plants to be dispatched by ISO New England’s automatic dispatch software by 2016. Wind plants will receive an upper bound to their production through so-called Do Not Exceed (DNE) dispatch limits. This study evaluates how the automatic dispatch of wind plants in the ISO New England control area will impact wind plant output, emissions, wholesale energy market prices, and the system-wide generation mix. Wind generation is modeled using 10-minute time-series wind speed data from the National Renewable Energy Laboratory’s Eastern Wind Dataset. Market outcomes for 2020 are then simulated using the spreadsheet-based Oak Ridge Competitive Electricity Dispatch (ORCED) model which mimics the economic dispatch of power plants in deregulated wholesale electricity markets. Results show that imposing DNE dispatch limits reduce total wind generation by a small amount – 6.47% over the course of the study year. The study finds that DNE dispatch limits constrain wind generation often – 28.4% of the year on average – but that the levels of wind generation avoided were typically small – 72.4% of DNE limit curtailment events were at levels below 5% of plant nameplate capacity.
18

A Distributed Algorithm for Optimal Dispatch in Smart Power Grids with Piecewise Linear Cost Functions

Yasmeen, Aneela 01 July 2013 (has links)
We consider the optimal economic dispatch of power generators in a smart electric grid for allocating power between generators to meet load requirements at minimum total cost. We assume that each generator has a piece-wise linear cost function. We first present a polynomial time algorithm that achieves optimal dispatch. We then present a decentralized algorithm where, each generator independently adjusts its power output using only the aggregate power imbalance in the network, which can be observed by each generator through local measurements of the frequency deviation on the grid. The algorithm we propose exponentially erases the power imbalance, while eventually minimizing the generation cost.
19

Estimating Wind Forecast Errors and Quantifying Its Impact on System Operations Subject to Optimal Dispatch

Li, Xiaoguang 14 December 2011 (has links)
Wind power is being added to the supply mix of numerous jurisdictions, and an increasing level of uncertainties will be the new reality for many system operators. Accurately estimating these uncertainties and properly analyzing their effects will be very important to the reliable operation of the grid. A method is proposed to use historical wind speed, power, and forecast data to estimate the potential future forecast errors. The method uses the weather conditions and ramp events to improve the accuracy of the estimation. A bilevel programming technique is proposed to quantify the effects of the estimated uncertainties. It improves upon existing methods by modeling the transmission network and the re-dispatch of the generators by operators. The technique is tested with multiple systems to illustrate the feasibility of using this technique to alert system operators to potential problems during operation.
20

Estimating Wind Forecast Errors and Quantifying Its Impact on System Operations Subject to Optimal Dispatch

Li, Xiaoguang 14 December 2011 (has links)
Wind power is being added to the supply mix of numerous jurisdictions, and an increasing level of uncertainties will be the new reality for many system operators. Accurately estimating these uncertainties and properly analyzing their effects will be very important to the reliable operation of the grid. A method is proposed to use historical wind speed, power, and forecast data to estimate the potential future forecast errors. The method uses the weather conditions and ramp events to improve the accuracy of the estimation. A bilevel programming technique is proposed to quantify the effects of the estimated uncertainties. It improves upon existing methods by modeling the transmission network and the re-dispatch of the generators by operators. The technique is tested with multiple systems to illustrate the feasibility of using this technique to alert system operators to potential problems during operation.

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