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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

Förhindra sönderfall av AOD-slagg under svalning genom förändrad sammansättning

Myckelberg, Pontus January 2018 (has links)
AOD-slag at Sandvik Materials Technology in Sandviken is disintegrating to a fine powder during cooling as a consequence of a volume increase caused by a phase transformation. The slag becomes a powder that's hard to handle because of dusting, the environment that is closeby take a beating. On top of that the slag must be landfilled and cannot be used as secondary material. In general most slags have a great potential to be used in as construction material in different applications around the society after used by the steel industry. In Sandviks case the disintegration stops that from being possible. To prevent disintegration of AOD-slag serveral things can be done, such as new additives or change of slag composition. In this project a new composition of the slag has been obtained from a decrease of lime addition. Then the slag composition can be moved outside of the area of disintegration by the volume increase. The change had to be done without jeopardize the quality of the steel or the lining material in the AOD. Potential steels were choosen for trials with lowered addition of lime after a present value analysis were established. The early analysis was conducted by slag samples from different steels in the AOD, these samples created the foundation of method further on. The full scale tries were conducted in three campaigns with different follow-ups. The results shows that there is possible to reduce the lime addtive to the AOD and by that receive a solid slag and at the same time produce high quality steel. With reduced lime addition the basicity is lowered. With lowered basicity the results shows that the sulphur removal gets worse as well as the reduction of chromium. The method established in this thesis does no go well with all steels except some pinpointed steel types with less demands on high sulphur removal. / AOD-slaggen vid Sandvik Materials Technology i Sandviken sönderfaller till ett fint pulver under svalning som en konsekvens av en fasomvandling av dikalciumsilikat där en volymexpansion sker. Slaggen som blir pulver blir svårhanterlig på grund av att den dammar, närmiljön försämras till följd. Dessutom måste slaggen deponeras och kan inte användas som ett sekundärt material. Generellt anses slagg har stor potential att användas till andra applikationer i samhället efter användning i stålindustrin. I Sandviks fall sätter sönderfallet stopp för det. För att undvika sönderfall av AOD-slaggen kan en rad olika saker göras som tillsatser eller ändring av sammansättning. I det här projektet har en ny slaggsammansättning uppnåtts genom minskning av kalktillsatsen till slaggen. Då kunde slaggens sammansättning flyttas från området för sönderfall genom volymexpansion. Förändringen var tvungen att ske utan att äventyra stålets kvalité eller infodringen i AOD:n. Potentiella stålsorter valdes ut för försök med mindre kalktillsats efter att en nuvärdesbild hade etablerats. Nuvärdesbilden bestod av provtagning av slagg från charger i AOD:n och den bidrog till metoden för försöken. Fullskaleförsöken utfördes i tre kampanjer med olika typer av uppföljning. Resultaten visar att det är möjligt att minska kalkmängden till AOD:n och därmed få en stabil slagg och samtidigt producera ett fullgott stål. Genom minskad kalktillsats sänks basiciteten och det gör slaggen mindre basisk. Resultaten visar att svavelraffineringen blev sämre. Kromreduceringen blev också något sämre. Metoden framtagen i det här projektet fungerade inte för alla stålsorter utan det är framförallt några utvalda stål med lägre krav på svavelrening.
12

A Geographical Comparison of the Relationship Between Aerosol Optical Depth and Fine Particulate Matter in Indiana / A Geographic Comparison between AOD and PM2.5 in Indiana

Douglas, April D. 05 1900 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / This study looked at the time period of June through mid-October, 2013, based on the results of earlier studies that the strongest correlation between the PM2.5 and AOD data sets occurs during the summer and fall. Terra satellite data was used in this study due to availability of images for the geographic area of the state of Indiana during the time period of the study. PM2.5 measurements from 12 IDEM continuous monitoring sites, which were collected at noon local time, were compared with MODIS AOD data. Despite the limitations of useful data and smaller data sets, this study shows encouraging results, and illustrates that there is a relationship between remotely sensed MODIS AOD data and fine particulate matter (PM2.5) data collected from ground sensors within the geographic region of the state of Indiana. It is believed that this topic should be studied further and expanded upon.
13

Mathematical modelling of chemical kinetics and rate phenomena in the AOD Process

Visuri, V.-V. (Ville-Valtteri) 07 November 2017 (has links)
Abstract Argon-oxygen decarburisation (AOD) is the most common unit process for refining stainless steel. The AOD process consists of multiple stages, in which the rate of processing is determined by complex reaction mechanisms. The main objective of this work was to study the chemical rate phenomena in selected process stages. For this purpose, an extensive literature review was conducted to clarify the main assumptions of the existing reaction models. Based on the literature review, a new categorisation of the models was proposed. In addition, a literature review was conducted to identify the main phenomena that affect the reaction kinetics in the AOD process. In this work, based on the law of mass action, a novel kinetic approach and its application for modelling of parallel mass transfer controlled reactions were studied. The developed approach enables the simultaneous solution of the chemical equilibrium and mass transfer rate which controls it. A simplified reaction model was employed for studying the effect of mass transfer rates and residual affinity on the constrained equilibrium at the reaction interface. An earlier-proposed AOD model was extended with two phenomenon-based sub-models. The top-blowing model is based on the assumption that reactions take place simultaneously at the surface of the cavity formed by the momentum of the gas jet and on the surface of the metal droplets caused by the shear force of the gas jet. The reduction model describes the reactions during the reduction stage of the AOD process by assuming that all reactions take place between the metal bath and emulsified slag droplets. The results obtained with the models were in good agreement with the measurement data collected from a steel plant. Owing to their phenomenon-based structure, the developed models are well-suited for the analysis of both existing and new production practices. / Tiivistelmä Argon-happimellotus (AOD) on yleisin ruostumattoman teräksen valmistamiseen käytettävä yksikköprosessi. AOD-prosessi koostuu useista vaiheista, joissa prosessointinopeutta määrittävät monimutkaiset reaktiomekanismit. Tutkimuksen päätavoitteena oli tutkia kemiallisia nopeusilmiöitä valituissa prosessivaiheissa. Tähän liittyen tehtiin kattava kirjallisuuskatsaus, jonka tavoitteena oli tunnistaa olemassa olevien reaktiomallien pääoletukset. Kirjallisuuskatsauksen pohjalta esitettiin uusi mallien kategorisointi. Lisäksi tehtiin kirjallisuuskatsaus, jonka tavoitteena oli tunnistaa tärkeimmät reaktiokinetiikkaan vaikuttavat ilmiöt AOD-prosessissa. Tässä työssä tutkittiin uudenlaista massavaikutuksen lakiin perustuvaa lähestymistapaa sekä sen soveltamista rinnakkaisten aineensiirron rajoittamien reaktioiden mallinnukseen. Kehitetty lähestymistapa mahdollistaa kemiallisen tasapainotilan sekä sitä rajoittavan aineensiirron samanaikaisen ratkaisun. Aineensiirtonopeuksien ja jäännösaffiniteetin vaikutusta reaktiopinnalla vallitsevaan rajoitettuun tasapainotilaan tutkittiin käyttämällä yksinkertaistettua reaktiomallia. Aiemmin kehitettyä AOD-mallia laajennettiin kahdella ilmiöpohjaisella alimallilla. Lanssipuhallusmalli perustuu oletukseen, että reaktiot tapahtuvat samanaikaisesti kaasusuihkun liikemäärän muodostaman tunkeuman ja kaasusuihkun leikkausvoiman aiheuttamien metallipisaroiden pinnalla. Pelkistysmalli kuvaa AOD-prosessin pelkistysvaiheen aikana tapahtuvia reaktioita olettaen, että kaikki reaktiot tapahtuvat terässulan ja emulgoituneiden kuonapisaroiden välillä. Malleilla saadut tulokset vastasivat hyvin terästehtaalta kerättyä mittausaineistoa. Ilmiöpohjaisen rakenteensa ansiosta kehitetyt mallit soveltuvat hyvin sekä olemassa olevien että uusien tuotantopraktiikoiden analysoimiseen.
14

Climatologie du transport des aérosols désertiques au-dessus de l'Atlantique vers la région Caraïbe. / Climatology of desert oust transportation over the Atlantic toward Caribbean area

Euphrasie-Clotilde, Lovely 09 May 2018 (has links)
La région Caraïbe est régulièrement survolée par des masses d'air chargées en poussières désertiquesd'origines saharienne et sub-saharienne. Pour quatre îles de l'arc antillais : Porto Rico, Guadeloupe, Martinique etBarbade; nous avons évalué l'origine de la pollution particulaire et son impact sur la qualité de l'air, en effectuant uneétude statistique des évènements de poussière qui s'appuie sur les réseaux de mesure de qualité de l'air implantés surchacune des îles, sur le réseau international de mesures photométriques AERONET et sur les données deradiosondages réalisés localement. La première étape de notre travail, a visé à définir ce que l'on pouvait qualifier« d'épisode de poussières désertiques» dans notre région en établissant des critères utilisant le jeu de données dontnous disposions. Deuxièmement, nous avons réalisé une étude climatologique des évènements poussiéreux dans laCaraïbe au cours de la dernière décennie (2006-2016). Le troisième axe de la thèse repose sur la caractérisation de lataille des particules afin de mettre en relief les effets du transport à longue distance. Nous avons clôturé notre étudepar la description de la structure verticale de l'atmosphère de la zone tropicale en situation de « brumes de poussièredésertique » afin d'observer les effets thermodynamiques des aérosols minéraux sur la couche atmosphérique. Ladéfinition des évènements de brumes désertique que nous avons adoptée nous a permis de prendre en considérationune grande partie des évènements poussiéreux affectant l'arc antillais, ce qui nous a amené à mieux cerner le cycle detranspon des poussièl'es désertiques au terme d'une étude basée sur onze années de données. / The Caribbean region is regularly flown over by desert dust air masses (Saharan Air Layer) corne fromSaharan and sub-Saharan area. For four islands of the West Indies arc: Puerto Rico, Guadeloupe, Martinique andBarbados; we assessed the origin of polluting particles and their impact on air quality, by performing a statistical andclimatological study of desert dust events. We therefore based on the air quality measurement networks, theinternational AEronet RObotic NETwork (AERONET) photometric measurements installed on each of these islands.And finally, this study builds on sounding data produced locally.The first step in our work was to define and describe an "desert dust episode" in the tropical region. Thus, we studiedthe relationship of correlation between Aerosols Optical Depth (AOD), Angstrom Exponent (AE, characterizing theparticle size) and Particulate Matter 10 microns or Jess in diameter (PM10 data). On the other hand, the radiativeproperties (Single Scattering Albedo, refractive indexes) have been used to highlight sea sait contribution (coarseparticle just as dust particle) that significantly influences PM10 measurement due to the geographical context ofCaribbean islands. Our investigations led us to propose a daily PM 10 threshold at 35 μg m·3 that mainly associatedwith desert dust phenomenon. This latter is more suited for the Lesser Antilles compared to the European PM10threshold related to desert dust events: 50 μg m·3.As a result, a climatological study of dusty events in the Caribbean during the last decade (2006-2016) is carried out.Four dust seasons were identified: the high dust season (May to August), the low dust season (November to February,and two intermediate periods (March to April, September to October). We then examine dust exportation fromAfrican coasts toward the Lesser Antilles (Puerto Rico, Guadeloupe Martinique and Barbados) by mean of backtrajectories[Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) mode\] displaying atmosphericcirculation day-to-day over the Atlantic Ocean.This analysis enabled us to better understand the seasonal cycle of desert dust transportation, specific to each island(Puerto Rico, Guadeloupe, Martinique, Barbados); while most of the previous studies treats average data including thewhole Caribbean zone. lt emerges that islands are not affected by dust events similarly, i.e. by intensity of events andits includes some variation in dust periods.Lastly, we describe the vertical structure of the tropical zone atmosphere in situation of "desert dust events" and"Non-desert dust event" to observe the thermodynamic effects of minerai aerosols on the Caribbean atmosphericlayer. This analysis allowed us to consider desert dust aerosols effects on the thermodynamic parameters(Temperature and humidity) during the dry-season (November to April) named "câreme" and the wet season (May toOctober) named "hivernage".
15

Study of antenna arrays for direction finding / Studie av antennmatriser för riktningsidentifiering

Eriksson Selin, William January 2021 (has links)
The new Bluetooth standard (Bluetooth 5.1) contains direction finding specifications. Specifications for received signal strength indicator(RSSI) using measures of signal strength in order to give a sense of how far away an object is has been present in earlier versions. It will now be accompanied with the possibility of angle of arrival estimation(AoA). AoA estimation in Bluetooth utilizes antenna arrays. Antenna arrays are formations of many individual antenna elements working together. The difference between the measured data at each antenna is dependent on the orientation and position of the antenna elements as well as on phase of an incoming electromagnetic signal. By looking at the phase shifts between the antenna elements in an antenna array it is possible to find an estimation of the direction of where the incoming signal is coming from.  The goal of this thesis is to investigate if the NicheTM antenna(concept developed by Proant AB) is applicable for AoA estimation. In the project we have simulated the different characteristics of the Niche antenna and done extensive simulations of different types of configurations of an Niche antenna array. The commercial electromagnetics simulator CST MW studio suite has been used for simulations. A formation that works well with regards to stability and mutual coupling has been found. The simulated results have also been confirmed by measurements on a mechanically constructed antenna array. Measurements have been carried out in an anechoic chamber. We have done full radiation pattern measurements of the antenna array. The antenna array that we have created can estimate the angle of arrival of an incoming signal with an accuracy of 2.7o with a certainty of one standard deviation. For increased accuracy in the AoA estimation a MATLAB code utilizing the MUSIC(MUltiple SIgnal Classification) algorithm with our variant of the steering vector has been written.
16

Caractérisation, modélisation et validation du transfert radiatif d'atmosphères non standard : impact sur les corrections atmosphériques d'images de télédétection

Zidane, Shems January 2012 (has links)
Cette étude est basée sur des données multi-altitudes aéroportées acquises en juillet 2004 lors d'un événement atmosphérique inhabituel dans la région de Saint-Jean-sur-Richelieu. Nous entendons en cela une atmosphère dont la distribution des aérosols ne respecte pas les variations habituellement implémentée dans les codes de transfert radiatifs. Les surfaces au sol imagées pendant cette campagne de terrain couvraient une variété spectrale assez diversifiée, à savoir des surfaces agricoles, des plans d'eau et des zones urbaines et forestières. L'aspect multi-altitude de cette acquisition de données a permis de caractériser les mêmes cibles au sol avec des contributions de l'atmosphère variant en fonction de l'altitude considérée afin de caractériser au mieux la perturbation observée durant cette campagne et de permettre une meilleure caractérisation de la perturbation apportée par une variation non-standard (panache de fumée). La transformation de la luminance apparente aux trois altitudes en réflectance apparente et l'implémentation de la perturbation apportée par le panache de fumée dans un modèle classique a permis une correction atmosphérique appliquée aux deux altitudes les plus hautes. Les résultats ont démontré une cohérence avec les réflectances apparentes de validation qui confirmait la véracité de notre modélisation du cas non-standard. Ces résultats ont d'autant plus étés pertinent [i.e. pertinents] pour la plus haute altitude de 3,17km : la réflectance apparente à cette altitude est au dessus de la majeur [i.e. majeure] partie du panache de fumée et intègre une bonne proportion de la perturbation apportée par ce panache, ce qui représente un test probant de notre capacité à corriger adéquatement l'influence de cette perturbation. Les perturbations atmosphériques standard sont évidemment prises en compte dans la majorité des modèles atmosphériques, mais ceux-ci sont souvent basés sur des variations monotones des caractéristiques physiques de l'atmosphère avec l'altitude. Lorsque la radiation atmosphérique est perturbée, par un panache de fumée ou un événement de pollution atmosphérique local et non standard, cela nécessite une modélisation et une modification adéquate des modèles existants en fonction des paramètres que l'on pourra obtenir sur ladite perturbation. Les intrants principaux de cette étude étaient ceux normalement utilisés lors d'une correction atmosphérique classique à savoir les luminances apparentes mesurées par un imageur aéroporté mais à trois altitudes différentes et l'épaisseur optique des aérosols (AOD) qui était acquise depuis le sol. La méthodologie que nous avons employé [i.e. employée] utilise aussi un code de transfert radiatif (CAM5S, pour Canadian Modified 5S, qui vient directement du code de transfert radiatif 5S dans le visible et proche infrarouge). Cependant il nous faudra aussi avoir recours à d'autres paramètres et données afin de modéliser correctement la situation atmosphérique particulière présente sur les images multi-altitude acquises pendant la campagne de terrain à Saint-Jean-sur-Richelieu. Nous avons alors élaboré un protocole de modélisation de perturbation atmosphérique non standard où une gamme de données auxiliaires disponibles est venue compléter nos données principales. Cela a permis l'élaboration d'une méthodologie robuste et relativement simple adaptée à notre problématique. Ces données auxiliaires, à savoir des données météorologiques, des profils LEDAR, différentes images satellites et des données de photomètres solaires qui ont permis la détermination de la fonction de phase des aérosols, ont été suffisantes pour établir une modélisation adéquate du panache de fumée observé en terme de distribution verticale non monotone des paramètres physiques relevés lors de cette campagne. Cette distribution non-standard à été par la suite interprétée en terme de profil spécifique de l'AOD qui a remplacé les profils des AOD employés dans le modèle de correction atmosphérique CAM5S. En fonction de cette modélisation, nous montrons que l'erreur entre les réflectances apparentes au sol obtenu [i.e. obtenue] par le processus de correction atmosphérique et les réflectances apparentes au sol provenant du processus de validation dR*(0), moyenné quadratiquement à travers les bandes visibles, reste majoritairement dans une gamme inférieure à 0,01 d'erreur quadratique moyenne des R*(0) après avoir modélisé la perturbation non-standard, ce qui permet une estimation plus acceptable des réflectances multi-altitude et du biais existant entre la prise en compte et la non prise en compte de cette perturbation dans le modèle atmosphérique. D'importants écarts ont néanmoins été observés, majoritairement attribuables à la difficulté apportée par les conditions d'acquisition, les grandes disparités observées entre l'échantillonnage des mêmes surfaces aux trois altitudes, et probablement des erreurs de modélisation et/ou de calibration. La nécessité d'améliorer le processus d'acquisition, de modélisation et de prévision de telle perturbation est largement décrit dans ce document afin de permettre à l'avenir d'établir un protocole d'acquisition plus adapté grâce notamment à une surveillance et un suivi des perturbations atmosphériques maintenant possible grâce aux outils décrits. L'originalité de cette étude réside dans une nouvelle approche de la caractérisation de ces perturbations atmosphériques par l'incorporation d'une structure non standard dans un modèle de correction atmosphérique opérationnel et de démontrer que cette approche présente des améliorations significatives des résultats par rapport à une approche qui ignore la perturbation du profil vertical standard tout en utilisant des valeurs d'AOD totaux correctement mesurés. Le modèle de profil que nous avons employé était simple et robuste, mais a capturé suffisamment de caractéristiques du panache pour réaliser des améliorations significatives en termes de précision de correction atmosphérique. Le processus global d'aborder tous les problèmes rencontrés dans l'analyse de notre perturbation des aérosols nous a aidé à construire une méthodologie appropriée pour caractériser ces événements sur la base de la disponibilité des données, distribué gratuitement et accessibles à la communauté scientifique. Cela rend cette étude adaptable et exportable à d'autres problématiques du même genre.
17

Aerosol optical depth model assessment with high resolution multiple angle sensors

Martin, Joseph S. 12 1900 (has links)
Approved for public release, distribution is unlimited / This thesis assesses the performance of the Naval Postgraduate School Aerosol Optical Depth (NPS AOD) model utilizing very high spatial resolution QuickBird (QB) satellite data. QuickBird derived AOD results are compared to other satellite and ground based AOD results, specifically, AErosol RObotic NETwork (AERONET), MODerate resolution Imaging Spectroradiometer (MODIS), Multi-angle Imaging SpectroRadiometer (MISR), and Advanced Very High Resolution Radiometer (AVHRR). Data is collected around Sir Bu Nuair Island, United Arab Emirates in September 2004 as part of the UAE2 Campaign. Satellite measured radiances are calibrated and due to spatial resolution differences between sensors, modal radiances are calculated for areas matching the highest resolution sensor. The AOD model is based on AVHRR wavelengths; hence, the modal satellite measured radiances are linearly extrapolated to the effective wavelengths of AVHRR. Results show application of the NPS AOD model to QuickBird data yields findings that are consistent with other satellite and ground based retrievals. In general, the NPS AOD model works well for nadir and near-nadir view angles, but not for high zenith angles. / Lieutenant Commander, United States Navy
18

A dinâmica da ajuda externa japonesa: análise empírica sobre os determinantes da assistência oficial para o desenvolvimento de 1961 a 2015 / The dynamics of Japanese foreign aid: an empirical analysis of the determinants of official development assistance from 1961 to 2015

Okamoto, Julia Yuri 06 December 2018 (has links)
Este trabalho busca estudar a alocação da assistência oficial para o desenvolvimento (ODA) do Japão no período de 1961 a 2015. A Agência de Cooperação Internacional Japonesa (JICA) tem apontado como motivações da ajuda externa o desenvolvimento econômico e a redução da pobreza em países menos desenvolvidos. A literatura em Relações Internacionais, no entanto, enxerga com ceticismo que os valores humanitários sejam, por si só, determinantes do nível de generosidade do doador, apontando para a importância de elementos domésticos, de fatores normativos internacionais e de considerações político-estratégicas na explicação dos programas de ajuda. Utilizando análise regressiva, esta pesquisa buscará evidências empíricas da importância relativa de diferentes variáveis explicativas da ajuda externa japonesa. Os resultados mostram que os interesses econômicos e político-estratégicos exercem maior influência sobre o programa de assistência do Japão que o nível de pobreza ou o regime democrático nos países beneficiários. Nossas estimativas indicam, ainda, que o Japão tende a concentrar a ajuda em países em desenvolvimento de renda relativamente mais alta, menos populosos e com menores índices de corrupção. / The purpose of this research is to study Japan\'s official development assistance (ODA) between 1961 and 2015. Japan International Cooperation Agency (JICA) has cited economic development and poverty reduction in less-developed countries as reasons for providing external aid. However, literature on International Relations is skeptical of humanitarian motives being, on their own, the determinants of donor\'s level of generosity, pointing out the influence of domestic aspects, international statutes, and political and strategical considerations on explaining aid programs. By using regressive analysis, this research will look for empirical evidence of the relative significance of different variables that explain Japanese external aid. The results show that economic and political-strategic interests exert more influence over Japan\'s assistance program than the level of poverty or democratic regime in the beneficiary countries. Our estimates also show that Japan tends to focus aid on relatively higher income developing countries, less populous countries and countries with lower levels of corruption.
19

A dinâmica da ajuda externa japonesa: análise empírica sobre os determinantes da assistência oficial para o desenvolvimento de 1961 a 2015 / The dynamics of Japanese foreign aid: an empirical analysis of the determinants of official development assistance from 1961 to 2015

Julia Yuri Okamoto 06 December 2018 (has links)
Este trabalho busca estudar a alocação da assistência oficial para o desenvolvimento (ODA) do Japão no período de 1961 a 2015. A Agência de Cooperação Internacional Japonesa (JICA) tem apontado como motivações da ajuda externa o desenvolvimento econômico e a redução da pobreza em países menos desenvolvidos. A literatura em Relações Internacionais, no entanto, enxerga com ceticismo que os valores humanitários sejam, por si só, determinantes do nível de generosidade do doador, apontando para a importância de elementos domésticos, de fatores normativos internacionais e de considerações político-estratégicas na explicação dos programas de ajuda. Utilizando análise regressiva, esta pesquisa buscará evidências empíricas da importância relativa de diferentes variáveis explicativas da ajuda externa japonesa. Os resultados mostram que os interesses econômicos e político-estratégicos exercem maior influência sobre o programa de assistência do Japão que o nível de pobreza ou o regime democrático nos países beneficiários. Nossas estimativas indicam, ainda, que o Japão tende a concentrar a ajuda em países em desenvolvimento de renda relativamente mais alta, menos populosos e com menores índices de corrupção. / The purpose of this research is to study Japan\'s official development assistance (ODA) between 1961 and 2015. Japan International Cooperation Agency (JICA) has cited economic development and poverty reduction in less-developed countries as reasons for providing external aid. However, literature on International Relations is skeptical of humanitarian motives being, on their own, the determinants of donor\'s level of generosity, pointing out the influence of domestic aspects, international statutes, and political and strategical considerations on explaining aid programs. By using regressive analysis, this research will look for empirical evidence of the relative significance of different variables that explain Japanese external aid. The results show that economic and political-strategic interests exert more influence over Japan\'s assistance program than the level of poverty or democratic regime in the beneficiary countries. Our estimates also show that Japan tends to focus aid on relatively higher income developing countries, less populous countries and countries with lower levels of corruption.
20

Modeling of Gas Flows in Steelmaking Decarburization Processes

Song, Zhili Jack January 2013 (has links)
The purpose of the current study is to increase the understanding of different steelmaking processes at the decarburization stages by use of mathematical modeling. More specifically, two De-Laval nozzles from a VOD (Vaccum Oxygen Decarburization) process, which is used for producing stainless steels with ultra-low carbon grades, was investigated for different vessel pressures. Moreover, the post combustion phenomena in a BOF or LD (Linz-Donawitz) process as well as an AOD (Argon Oxygen Decarburization) process were studied focusing on the decarburization stage. Two industrial VOD nozzles were numerically studied and compared at different temperatures and ambient pressures. Flow patterns of the oxygen jet under different ambient pressures were predicted and the flow information at different positions from the nozzle was analyzed. In addition, the effects of different ambient temperatures on the jet velocity and the dynamic pressure were compared. The predictions revealed that a little under-expansion is somewhat helpful to improve the dynamic pressure. The jet dynamic pressure and its width for the specific nozzle geometry were also studied. It was observed that a variation in the ambient pressure can influence the jet momentum and its width. In addition, a high ambient temperature was found to have a positive effect on the improvement of the jet dynamic pressure. Furthermore, it was found that a change in ambient pressure has a stronger effect on the jet force than a change in the ambient temperature. In addition, it was proved that the profiles of the dynamic pressure at a certain blowing distance fit well to Multi-Gaussian distribution. Post combustion in a BOF/LD and an AOD process during decarburization was also studied. Two mathematical models were created to show the post combustion phenomenon inside the converters, respectively. For the CFD modeling of the two processes, the realizable k-ɛ model, the species transport model and the discrete ordinate were adopted to calculate the turbulence, gas reaction and radiation present in the gas phase in the converter. For the BOF/LD modeling, a series of plant tests were conducted to collect data, which were used in the current model. These include the off-gas information, emissivity data, oxygen blowing parameters and the chemical composition of steel. After the simulation, the predicted flow pattern and detailed information of the gases taking part in the post combustion were compared to plant data. Specifically, the off-gas data from the plant was used for the model verification. The measured CO2 concentration was 15-20 wt% and the predicted value from the modeling was 16.7 wt%. For the AOD converter of interest in the current work, a fan is installed in the end of the AOD flue to help extract the off-gas from the converter. The influence of different fan gauge pressures as well as temperatures of the gas mixture, containing the generated CO and argon, on the post combustion in the whole AOD system was studied. It was indicated from the modeling results that the post combustion was only present in the flue for the present modeling conditions. Moreover, a critical fan gauge pressure (approx.. -550 Pa) was found which could yield a maximum post combustion in the flue gas. For both two models (BOF/LD and AOD), simulations indicated that a change of the converter temperature from 1500 to 1700 °C did not influence the post combustion reaction to a large degree. In addition, these two models can be regarded as the first step for a future more in-depth modeling work of the post combustion. / <p>QC 20130913</p>

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