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Kvalitetsjämförelse av markmodeller skapade med digital fotogrammetri : En jämförelse av mätosäkerhet på markmodeller med bilder ifrån olika UAVs / Quality comparison of surface models created by digital photogrammetry : An accuracy comparison of terrain models using photos from two different UAV modelsSebastian, Olsson January 2022 (has links)
In recent years, the technical progress of Unmanned Aerial Vehicles (UAV) has increased rapidly. This has made it economically possible for tasks where one earlier needed helicopters or airplanes. By equipping UAVs with high-quality cameras, the utility has expanded. With detailed photos from a UAV together with digital photogrammetry, special software can be used to create point clouds, 3D-models, elevation models and ortomosaics over smaller geographic areas. Due to the easy access and that the use of UAVs has increased among private users, the Swedish transport agency has set up rules that determine how UAVs should be used. In these regulations, UAVs are separated into different groups from A1 to A3 based on the weight of the aircraft. The regulations make it illegal to fly a UAV heavier than 250 g over people who are not informed about the flight. Since there are several industries where it could be interesting to fly over people, DJI has manufactured a UAV-model called DJI Mini 2. This UAV weighs 249 g and can therefore be flown over people. In this project, two different flights have been carried out. One with the DJI Mini 2 weighing 249 g and one with the DJI Mavic 2 Pro weighing just under 1 kg. During the flight, overlapping pictures were captured and orthomosaic and elevation models were created from those. The purpose of the project was to investigate if the same accuracy can be achieved with a mini-UAV as with a larger UAV. The study also investigated whether the models were accurate enough to use as a ground model along roads and railroads. In the Dronelink software, two different flight routs were created over Örsholmens IP in the eastern part of Karlstad, Sweden. Dronelink created the flightpath based on the UAVs different specifications and the overlap between images that were acquired. A geodetic control network was created using GNSS-technology. Five points were measured twice with 45 minutes in between and calculated in SBG GEO. The next day, a surveying total station was established centrally between the points in the geodetic control network. Thereafter 19 ground control points were measured, and 398 ground points distributed in 20 different control profiles. After the points were measured, the flights were carried out. A total of two flights by each UAV model were made the same day. Then the flight with the best results were used for further processing. The photos taken were processed in Agisoft Metashape. In the software, point clouds, elevation models and orthomosaic were created. The elevation model was then compared to the measured control profiles. The orthomosaic was used to compare the ground control points. The results showed that the elevation model created with Mavic 2 Pro was within the SIS tolerance on all different types of surfaces to be used for modelling along roads and railways. The elevation model from the DJI Mini 2 was withing the tolerance on grass and asphalt but not on gravel surface. The mean deviation on gravel was -1,37 cm outside the tolerance. The planar comparison showed that both models were withing the tolerance to achieve HMK level 3 standard. / Den tekniska utvecklingen av obemannade flygfarkoster har de senaste åren utvecklats i snabb takt. Flygfarkosterna som ofta benämns UAV (Unmanned Aerial Vehicle) har gjort det möjligt att till en låg kostnad genomföra uppdrag som tidigare krävt helikopter eller flygplan. Genom att utrusta en UAV med en högkvalitativ kamera så ökar dess användningsområde. Med hjälp av detaljerade digitala bilder tagna med UAV, och digital fotogrammetri i specialprogramvaror kan punktmoln, 3D-modeller, höjdmodeller och ortomosaik över mindre geografiska områden framställas. På grund av att UAV-användningen ökat snabbt så har Transportstyrelsen tagit fram ett regelverk för hur en UAV får användas. I detta regelverk så delas olika UAV-modeller in i grupper från A1 till A3 baserat på vikten. Regelverket gör att en UAV som är tyngre än 250 g inte får flygas över människor som inte är informerade om att flygningen pågår. Eftersom det i flera branscher kan vara intressant att flyga över platser där människor rör sig fritt så har DJI tillverkat en UAV-modell som heter DJI Mini 2. Denna UAV väger 249 g och får därför flygas över människor. I detta projekt har två olika flygningar gjorts med DJI Mini 2 som väger 249 g och med Mavic 2 Pro som väger knappt 1 kg. Under flygningen togs överlappande bilder och höjdmodeller och ortomosaik skapades från dessa. Syftet med arbetet är att undersöka om lika hög noggrannhet kan uppnås med en mini-UAV som med en större modell. Studien undersökte även om modellerna uppnår kraven i SIS-TS 21144:2016 och HMK för att få användas till att skapa markmodell längs väg och järnväg. I programvaran Dronelink så skapades två flygrutter över Örsholmens IP i den östra delen av Karlstad. Dronelink skapade rutterna baserat på de olika UAV-specifikationerna och bildöverlappet som valdes för flygningarna. På platsen skapades ett nytt stomnät med hjälp av GNSS-teknik. Fem punkter mättes in två gånger med 45 minuters mellanrum och beräknades i SBG GEO. Dagen efter etablerades en totalstation centralt mellan punkterna mot stomnätet. Därefter mättes 19 markstöd in och 398 punkter fördelat i 20 olika kontrollprofiler. Efter att punkterna var inmätta genomfördes flygningarna. Totalt gjordes två flygningar med de olika UAV-modellerna på samma dag. Därefter valdes de flygningar som visade bäst resultat för vidare bearbetning. Bilderna som togs bearbetades i programvaran Agisoft Metashape och punktmoln, höjdmodell och ortomosaik genererades. Höjdmodellen användes sedan för att jämföras mot de inmätta kontrollprofilerna. Ortomosaiken jämfördes med de inmätta kontrollpunkterna. Resultatet visade att höjdmodellen som skapades med Mavic 2 Pro var inom SIS-TS 21144:2016 toleranserna på samtliga underlag för att få användas för modellskapande på väg och järnväg. Höjdmodellen som skapades med DJI Mini 2 var inom toleransen på gräs och asfalt men inte på grusunderlag. Medelavvikelsen på grus var -1,37 cm utanför toleransen. Vid jämförelsen i plan visade resultatet att båda modellerna var inom HMKs toleranser för att uppnå HMK-standardnivå 3.
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Sustainability and development impacts of off-grid electrification in developing countries : An assessment of South Africa's rural electrification program / Hållbarhet och utvecklingseffekter av off-grid elektrifiering i utvecklingsländer : En bedömning av Sydafrikas elektrifiering av landsbygden programmetAzimoh, Chukwuma Leonard January 2016 (has links)
Previous studies have shown that provision of sustainable electricity supply to rural households is essential to bring development to off-grid populations. For this reason, most developing countries put large efforts into rural electrification programs to stimulate development and reduce poverty. However, to be sustainable these programs need to recover costs, which poses a challenge to remote low income populations. This often forces governments and other institutions involved in rural electrification to subsidize the electricity production. It also affects the choice of technology and places a barrier on the level of energy provided in line with the ability to pay for services. As a result of this, most programs have failed to achieve the desired objectives, as the technologies used often do not support income generating activities that could increase the payment capabilities of the beneficiaries and contribute to development. This thesis is focused on the rural electrification program of South Africa, the country in sub-Saharan Africa that has the highest access to electricity. It investigates the success elements that influence the sustainability of rural electrification programs and their contributions to socio-economic development. This was achieved by evaluating the South African program that provides solar home systems to off-grid communities, and a hybrid solar-wind mini-grid project in South Africa. The study also draw lessons from other rural electrification programs in neighbouring countries, i.e. an evaluation of a hybrid solar-diesel mini-grid system in Namibia, and a review of two systems, a hybrid solar-biomass mini-grid project in Botswana and a hydro mini-grid program in Lesotho. The study revealed that hydro based hybrid mini-grid systems provide the most cost effective way of bringing energy services to rural settlements. Regardless of technology, successful programs depend on adequate support from the government, implementation of a progressive tariff system that allows the high consuming high income earners and businesses, to cross subsidize the low consuming , low income users. It shows that it is more likely for rural electrification programs to survive if the design considers the existing businesses, population growth and the corresponding load increase. The thesis further shows that provision of sufficient energy to induce income generating activities is essential to decrease the need for subsidies and to ensure the sustainability of programs. In addition, availability of spare parts and a capable management team is essential for the successful operations and maintenance of these systems.
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Procédés de régularisation de problèmes d'optimisation et de mini-maxBehar, Isak 14 February 1974 (has links) (PDF)
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小三通與金門住民生活需求、滿意度之研究 / Study of Kinmen Residents’ Livelihood Demand and Satisfaction with the “Mini Three Links”王水彰, WANG SHUI CHANG Unknown Date (has links)
金門位處福建省南海岸與廈門、漳州、泉州對口的孤島,住民沿習中華閩南文化生活,自1949年大陸國共兩黨內戰成為台灣反共前哨,長年來的兩岸歷史恩怨,隨著歷史的變遷,時局的更迭,兩岸的敵對關係逐漸轉為緩和,進而共謀發展,其具體表徵之一為金門與廈門實施「小三通」。而小三通之實施,對於金門人來說,為前所未有之經驗,此項措施對於金門人來說,帶來何種衝擊,金門人真正需要的是什麼,自小三通實施以後,金門人的感受又是如何?此項課題值得深究,而研究者為金門的一份子,基於長年以來對於鄉土的熱愛,以學術的角度,對此議題加以研究,是理所當然亦是職責所在。
本研究為瞭解「小三通」與金門住民生活需求及滿意度,事涉受訪者主觀經驗詮釋,本文採用深度訪談法,以40歲以上金門原住民13位在不同職業、性別、年齡、居住地作為訪談對象。研究發現:
一、「小三通」以來金門住民環境依賴對岸。金門需要擴張港口基礎整建。教育環境:採認開放承認大陸學歷、規劃金門為大學城。醫療環境:開放與廈門醫院合作醫療健保。消費娛樂:提升更多元化的優質休閒管道。產業環境:創造有利的投資環境,開放陸資進駐金門、設置免稅區,提升觀光人口增加創業就業。
二、金門住民對「小三通」的生活滿意度:
(一)、交通改善最大受益是台商。
(二)、地方建設看不到實質的成效。
(三)、在文化親情方面呈一致性的滿意。
(四)、在生活品質上持正面的看法與滿意。
三、金門住民對「小三通」經濟滿意度:
(一)、對金門的復活商機呈現不滿意。
(二)、金門的資源條件遠不如廈門。
(三)、產業成長:金門酒廠除外百業萎縮,惟有旅遊業與特產業有微幅成長。
四、依據本研究發現提供以下建議
(一)、加速修正落實「離島建設條例」。
(二)、落實民生基礎建設、交通建設、水資源開發政策。
(三)、觀光產業配套:金門重新定位、流程法令鬆綁、提升觀光基礎建設內涵、實施兩岸交流合作。
(四)、落實醫療環境軟硬體設施。
(五)、落實金門設為大學島構思,作雙學歷採認制度。 / Situated as an offshore island on the Southern coast of Fujian Province and opposite to Xiamen, Changzhou and Quanzhou, Kinmen inherited Chinese culture from the South Min and its residents were thus imbued. Kinmen has become Taiwan’s outpost against China since the Civil War between KMT and the Chinese Communists in 1949. In recent years, the long-term aversion and hostility between Taiwan and China has been fading with the pass of time and change of cross-Strait political tides. In this regard, further cooperation and development are mutual concerns for both sides of the Strait, and one of the concrete symbolic policies is the so-called Kinmen-Xiamen “Mini Three Links”. For the people of Kinmen, the policy is an unprecedented experience; therefore, it is important to understand what impact will be brought forth, and what Kinmen’s residents exactly need and how they feel after the implementation. Being a local resident of Kinmen, the author tends to pay more attention and enthusiasm to this homeland; moreover, it is thus the responsibility as well for the author to concentrate on the study in the context of “Mini Three Links”.
The objective of the study is to understand Kinmen residents’ livelihood demand and satisfaction with the “Mini Three Links”. A semi-structured interview method was applied and conducted in this study, focusing on 13 local residents of different occupations, genders, ages, and townships. The findings of this study are as follows:
1. For Kinmen’s residents, their living environment deeply relies on the Mainland after the implementation of the “Mini Three Links”. Thus it is necessary for Kinmen to expand its infra-structure on harbor construction. With reference to education, it is suggested that Chinese educational system and degrees should be recognized, and a university community should be established in Kinmen. In the medical-care environment, future cooperation in health insurance with Xiamen hospitals is highly recommended. With respect to consuming and recreational conditions, it is indispensable that a pluralistic channel for upgrading leisure and recreation development has to be explored. As to the industrial environment, the policies such as creating a better investment surrounding, openness of Chinese funds in Kinmen, setting up a duty-free zone, and increasing tourists to Kinmen are also highly recommended.
2. Kinmen residents’ livelihood satisfaction with the “Mini Three Links”:
a. Taiwanese businesspeople benefit the most from the improvement of traffic.
b. Local infra-structure and construction is not substantially upgraded.
c. Residents have overall satisfaction with cultural and fraternal relations.
d. Positive opinion and satisfaction with living quality.
3. Kinmen residents’ satisfaction with economy:
a. Dissatisfaction with likely rehabilitation of Kinmen’s economy.
b. Kinmen’s resource conditions are much worse than that of Xiamen.
c. Excluding Kinmen’s liquor company, business industries have been declining. However, tourism industry and local specialties are slightly flourishing.
4. Suggestions:
a. Speeding up revision of the “Offshore Island Construction Act”.
b. Substantiating policies of infra-structure, traffic, and water resources exploration and development.
c. Repositioning Kinmen’s role in the cross-Strait relations, enhancing in-depth infra-structure in tourism industry, and strengthening cross-Strait interflow and cooperation.
d. Building up medical-care surrounding and hardware and software facilities.
e. Constructing Kinmen an Island of Universities, and bilaterally recognizing educational degrees and diplomas with China.
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Assessment controls on reservoir performance and the affects of granulation seam mechanics in the Bredasdorp Basin, South Africa.Schalkwyk, Hugh Je-Marco January 2006 (has links)
<p>The Bredasdorp Basin is one of the largest hydrocarbon producing blocks within Southern Africa. The E-M field is situated approximate 50 km west from the FA platform and was brought into commission due to the potential hydrocarbons it may hold. If this field is brought up to full producing capability it will extend the lifespan of the refining station in Mosselbay, situated on the south coast of South Africa, by approximately 8 to 10 years. An unexpected pressure drop within the E-M field caused the suite not to perform optimally and thus further analysis was imminent to assess and alleviate the predicament. The first step within the project was to determine what might have cause the pressure drop and thus we had to go back to cores drilled by Soekor now known as Petroleum South Africa, in the early 1980&rsquo / s.</p>
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</br>Analyses of the cores exposed a high presence of granulation seams. The granulation seams were mainly subjected within sand units within the cores. This was caused by rolling of sand grains over one another rearranging themselves due to pressure exerted through compaction and faulting, creating seal like fractures within the sand. These fractures caused these sand units to compartmentalize and prohibit flow from one on block to the next. With advance inquiry it was discovered that there was a shale unit situated within the reservoir dividing the reservoir into two main compartments. At this point it was determined to use Petrel which is windows based software for 3D visualization with a user interface based on the Windows Microsoft standards. This is easy as well as user friendly software thus the choice to go with it. The software uses shared earth modeling tool bringing about reservoir disciplines trough common data modelling. This is one of the best modelling applications in the available and it was for this reason that it was chosen to apply within the given aspects of the project A lack of data was available to model the granulation seams but with the data acquired during the core analyses it was possible to model the shale unit and factor in the influences of the granulation seams to asses the extent of compartmentalization. The core revealed a thick shale layer dividing the reservoir within two sections which was not previously noted. This shale layer act as a buffer/barrier restricting flow from the bottom to the top halve of the reservoir. This layer is thickest at the crest of the 10km² / domal closure and thins toward the confines of the E-M suite. Small incisions, visible within the 3 dimensional models could serve as a guide for possible re-entry points for future drilling. These incisions which were formed through Lowstand and Highstand systems tracts with the rise and fall of the sea level. The Bredasdorp Basin consists mainly of tilting half graben structures that formed through rifting with the break-up of Gondwanaland. The model also revealed that these faults segregate the reservoir further creating bigger compartments. The reservoir is highly compartmentalized which will explain the pressure loss within the E-M suite. The production well was drilled within one of these compartments and when the confining pressure was relieved the pressure dropped and the production decrease. As recommendation, additional wells are required to appraise the E-M structure and determine to what extent the granulation seems has affected fluid flow as well as the degree of sedimentation that could impede fluid flow. There are areas still containing untapped resources thus the recommendation for extra wells.</p>
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The Diagnostic Suitability of Goldberg's Rule for the Mini-MultRoberts, Dan Haynes 12 1900 (has links)
This study was undertaken to determine whether the Mini-Mult is able to function as well as the MMPI for a limited clinical purpose, the discrimination of psychosis and neurosis by Goldberg's rule. The smaller size of the Mini-Mult (71 items) allows conservation of time .and energy by subjects and professionals. Thirty male residents of the Austin State Hospital completed two standard MMPIs and one oral Mini-Mult. A fourth set of scores was obtained by extracting Mini-Mult from the first MMPI. Correlations and tests of significance were computed for raw scores and Goldberg's index scores. Results indicate no significant differences in the discrimination of psychosis and neurosis between the MMPI and the Mini-Mult.
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Sedimentology of a Lower Middle Pleistocene Reservoir in Garden Banks Area, Northern Gulf of Mexico: Integration of 3D Seismic, Cores, and Well LogsO'Brien, Sean P. 14 May 2010 (has links)
Garden Banks field 236, known as Pimento, is part of a lower middle Pleistocene submarine-fan deposit in the north central Gulf of Mexico. Pimento field represents a classic example of a prograding fan across the continental shelf continuing across the continental slope filling and spilling minibasins. Channel complexes cut through the field as sediment migrated across the shelf and slope to the basin floor. This thesis consists of two papers which utilized donated 3D seismic data on six of the blocks in Pimento field. Public domain data was incorporated with these data to explore the producing reservoir sand in the field. Mapped horizons revealed the overall structural elements of the field including the fill and spill facies of the minibasin that directly influences the deposition of the field. In these papers, channel complexes have been resolved using seismic geomorphological techniques and cross sections. Two potential drilling targets have also been discovered and one has been initially investigated as a drilling target.
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Influência da proximidade entre o mini-implante e as raízes dentárias sobre o grau de estabilidade / Influence of miniscrew dental root proximity on the stability degreeGigliotti, Mariana Pracucio 12 March 2009 (has links)
O objetivo deste trabalho foi avaliar a influencia da proximidade entre miniimplantes autoperfurantes e as raizes dentarias sobre a estabilidade destes dispositivos de ancoragem. A amostra consistiu de 40 mini-implantes inseridos entre as raizes do primeiro molar e segundo pre-molar superiores de 21 pacientes, como recurso de ancoragem para retracao anterior. A largura do septo no local de insercao (LSI) e a menor distancia da cabeca do mini-implante a raiz dentaria (MDR) foram mensuradas nas 40 radiografias pos-cirurgicas. Sob este aspecto, os miniimplantes foram divididos em duas categorias de grupos: de acordo com a largura do septo no local de insercao, grupos G1L (LSI3mm) e G2L (LSI>3mm), e de acordo com a proximidade do mini-implante a raiz adjacente, grupos G1P (MDR0mm) e G2P (MDR>0mm). A estabilidade dos mini-implantes foi avaliada mensalmente pela quantificacao do grau de mobilidade, e a partir desta variavel foi calculada a proporcao de sucesso. Tambem foi avaliada a influencia das seguintes variaveis sobre o grau de estabilidade: caracteristica do tecido mole no local de insercao, o grau de sensibilidade, a quantidade de placa, a altura de insercao e o periodo de observacao. As duas categorias de grupos foram comparadas quanto ao grau de mobilidade e proporcao de sucesso por meio do teste de Mann-Whitney e do teste Exato de Fisher, respectivamente. Adicionalmente, avaliou-se a influencia das demais variaveis sobre a estabilidade deste sistema de ancoragem atraves do teste t e do teste do Qui-quadrado. Os resultados obtidos demonstraram que não houve diferenca estatisticamente significante para o grau de mobilidade e proporção de sucesso entre os mini-implantes inseridos em septos do grupo G1L e G2L. A proximidade entre os mini-implantes avaliados e as raizes dentarias adjacentes (grupos G1P e G2P) tambem nao influenciou na estabilidade e proporcao de sucesso deste sistema de ancoragem. A proporcao de sucesso total encontrada foi de 90% e nenhuma variavel demonstrou estar relacionada ao insucesso dos miniimplantes. No entanto, observou-se maior sensibilidade nos pacientes cujos miniimplantes apresentavam mobilidade, e que a falha destes dispositivos de ancoragem ocorria logo apos sua insercao. / The purpose of this study was to evaluate the influence of the proximity between self-drilling miniscrews and dental roots on the stability degree. The sample consisted of 40 miniscrews inserted in the interradicular septum between maxillary second premolars and first molars to provide skeletal anchorage for anterior retraction. The forty post-surgical radiographs were used to measure the septum width in the insertion site (SWI) and the smallest distance between miniscrew head and dental root (SDR). In this regard, the miniscrews were divided in two categories of groups: according to the septum width in the insertion site, groups G1W (SWI 3mm) and G2W (SWI>3 mm), and according to the miniscrew dental root proximity, groups G1P (SDR0mm) and G2P (SDR>0mm). The mobility degree (MD) was monthly quantified to determine miniscrew stability, and the success rate of these devices was calculated. This study also evaluated the influence of following variables on the stability degree: soft tissue characteristics in the insertion site (attached gingiva, mucogingival junction and alveolar mucosa), sensitivity degree during miniscrew load, plaque amount around miniscrew, insertion height, and total evaluation period. All the groups were compared regarding mobility degree and success rate using t test and Fisher exact test, respectively. The results showed no significant difference in mobility degree and success rate between groups G1W and G2W. The miniscrew dental root proximity did not influence the stability and success rate of this anchorage system when G1P and G2P were compared. The total success rate found was 90% and no variable was associated with the miniscrew failure. Nevertheless, the results showed that greater patient sensitivity degree was associated to the miniscrews mobility and the failure of these anchorage devices happened in a short time after their insertion.
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Desenvolvimento local e avaliação de políticas públicas: análise de viabilidade para construção de um índice de desenvolvimento local para o município de São José do Rio Preto / Local Development and Public Politics Evaluation: Analysis of the viability of creation of un index of local development for the city of São José do Rio Preto.Borges, Claudia Moreira 21 June 2007 (has links)
O objetivo deste trabalho é analisar os impactos gerados pelo Programa dos Minidistritos Industriais e de Serviços, implantado em São José do Rio Preto, com a construção de um ferramental quantitativo para verificar as influências no desenvolvimento local. Para realização deste estudo, foram delineadas etapas de pesquisa qualitativa e documental, orientadas por Gil (2002) entre outros autores, e uma etapa quantitativa de acordo com Hair et al (2005a). Na etapa qualitativa o programa dos minidistritos foi analisado a partir de uma visão histórica e identificados as principais repercussões, atores e incentivos dados para o município de Rio Preto. Por meio da análise, e outros modelos construídos, foi desenhado o modelo de desenvolvimento local baseado no Programa dos Minidistritos Industriais e de Serviços, intitulado Modelo de Desenvolvimento Integrado Local Industrial (DILI). Na etapa quantitativa foram aplicados testes de agrupamento e discriminante e utilizados dados por setores censitários disponibilizados pelo IBGE. Os setores foram classificados com o auxílio do teste de agrupamento e foi gerada uma função que possibilita verificar as diferenças de desenvolvimento entre as regiões que possuem minidistritos e as que não possuem. Os resultados obtidos demonstram que os setores onde estão localizados os minidistritos são os mais carentes de renda e educação e possuem maior aglomeração populacional, em conseqüência da quantidade de minidistritos. / This work has the objective of analyse the impacts generated by Industrial and Services Minidistricts, implanted in São José do Rio Preto, with the the construction of a quantitative toolto verify the influences in the local development. In order to reach this objective, there were delineated stages of research: qualitative and documental, both oriented by Gil (2002) among others, and quantitative, according to Hair et al. (2005). In the qualitative stage, the program of Mini-districts was analysed under a historical view and the main repercussions, actors and incentive data were identified for the city of São José do Rio Preto. Through the analysis and other built models, the local development model was created based on the Program of Industrial and Services Mini-districts, entitled Local-Industrial Integrated Development Model (LIID). In the quantitative stage there were applied grouping and discriminant tests and the sector census data disposable by the IBGE. The sectors were classified in clusters with the help of the grouping test. It was generated a function which enables to verify the developmental differences between the regions have and the ones that have not mini-districts. The results reveal that the sectors where the mini-districts are located are the ones that lack in high output and education, and are also the most populous ones, being this last encouraged by the Mini-districts.
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Estudo da inferência de carregamento em histórias de vôos simulados na liga de Al aeronáutico SAE-AMS 7475 T7351 / Loading study of inference in a simulated flights history using an SAE-AMS 7475 T7351 aluminum alloy.Ruchert, Cassius Olivio Figueiredo Terra 28 March 2007 (has links)
Este trabalho discutiu o estudo da inferência de carregamento e a reconstrução fratográfica da taxa de propagação da trinca por fadiga em histórias de vôos simulados do tipo Twist, mini-Twist, Falstaff e mini-Falstaff. O material estudado foi uma liga de alumínio de grau aeronáutico SAE-AMS 7475 T7351 na qual foram obtidas as propriedades mecânicas a partir dos ensaios de tração e dureza, análise química, metalográfica. Foram realizados ensaios de amplitude constante de carregamento em corpos de prova com geometria tipo C(T) extraídos de um bloco e ensaios de amplitude variável em corpos de prova com geometria tipo M(T) extraídos de uma placa. Corpos de prova do tipo C(T) foram extraídos da orientação L-T e T-L, à temperatura ambiente com diferentes espessuras para a realização de ensaios de propagação de trinca por fadiga (da/dN vs. ΔK) com distintos valores de razão de carregamento,R (0,1;0,3; 0,5; 0,7 e 0,8) de acordo com a norma ASTM-E647 (1993). Foram realizados dois tipos de ensaios de fadiga com amplitude constante de carregamento. Primeiro, o ensaio com ΔP constante para obtenção dos dados dos estágios II e III das curvas da/dN vs. ΔK para distintos valores de R e, posteriormente, o ensaio com ΔK constante e R crescente para ser utilizado no estudo da inferência de carregamento de amplitude constante a partir da relação entre a morfologia da estria, H/s e a razão de carregamento R. Adicionalmente foram realizados ensaios de tenacidade à fratura, nas direções L-T e T-L, conforme a norma ASTME1820 (1999). As taxas de propagação macroscópica e microscópica foram comparadas e boas correlações foram obtidas para um intervalo entre 0,1 a 1,0 μm/ciclo, mesmo com distintos R. Através da técnica proposta por Berkovitz (1995), o espectro de carregamento foi estimado para distintos valores de R, através da técnica de parametrização do fator K e os resultados foram comparados ao espectro de carregamento real imposto pela máquina de ensaio. Após os ensaios de amplitude constante de carregamento foram realizados ensaios de amplitude variável com a aplicação em corpos de prova M(T) de espectros de vôos simulados padronizados pela NLR do tipo Twist e Falstaff e seus vôos reduzidos, mini-Twist e mini- Falstaff, em uma máquina servohidráulica de ensaios dinâmicos. A partir destes ensaios notou-se que suprimir os vôos com os carregamentos menos severos influencia muito a vida da propagação da trinca de fadiga, quando vôos simulados do tipo Twist e mini-Twist, fato este não observado para o Falstaff e mini-Falstaff. Foi possível observar também o efeito da aceleração e desaceleração da trinca por fadiga observando os gráficos de d2a/dvôo vs. a obtidos dos ensaios de amplitude variável. Foi realizado um estudo da superfície de fratura do CP05 por meio da técnica fractográfica do reconhecimento de blocos marcadores sendo possível mostrar uma satisfatória reconstituição da taxa de propagação da trinca por fadiga de vôo simulado do tipo Falstaff por meio de medidas das marcações na superfície de fratura dos vôos mais severos, realizadas em imagens obtidas por MEV. / The loading inference and the fractographic reconstruction of fatigue crack propagation rate in simulated flight stories, as Twist, mini-Twist, Falstaff and mini-Falstaff were investigated in this work. The studied material was an aluminum alloy SAE-AMS 7475 T7351. Tensile and hardness tests were carried out in order to determine mechanical properties, as well as chemical and microstructure analysis of the material. C(T) specimens were extracted from a block of material for constant amplitude load testing and M(T) specimens were extracted from a plate and were tested in variable amplitude loading. The curves (da/dN vs. ΔK) for constant-amplitude loading were obtained from fatigue crack propagation tests performed in L-T and T-L directions in C(T) specimens for R (0.1; 0.3; 0.5; 0.7 and 0.8), at room temperature, according to ASTM-E647 (1993). Two different constant loading fatigue tests were performed. At constant ΔP and distinct values of R for obtaining data of stages II and III of da/dN - ΔK curves; and at constant ΔK and increasing the R ratio to be used in the inference of constant amplitude loading in the relation of H/s striation morphology (obtained from fractographic images) and the loading ratio, R. Additionally, fracture toughness tests were executed in T-L and L-T directions, according to ASTM-E1820 (1999). The macroscopic and microscopic fatigue crack propagations were compared and good correlation was obtained for the range 0.1-1.0 μm/cycle, for all R values. By using the K factor parametrization method, Berkovitz (1995), the loading spectrum was estimated for the distinct R-values and the results were compared to the actual spectrum imposed by the test machine. Variable amplitude tests were performed in M(T) specimens by applying simulating flight spectra normalized by NLR, as Twist, mini-Twist, Falstaff and mini-Falstaff, in a servohydraulic test machine MTS, in which a Flextest GT controller was coupled. The suppression of less severe loading flights showed a great influence in fatigue crack propagation life, in simulated flight tests Twist and mini-Twist, but not in Falstaff and mini-Falstaff. The acceleration and slowing down of fatigue crack were observed in the d2a/dflight - a curve obtained from variable loading tests. The fractured surfaces of some samples were examined by the fractographic technique of blocking marks recognition. A good reconstitution of fatigue crack propagation rate of a simulated flight like Falstaff was obtained by the measurements of marks in the fracture surfaces of the more severe flights, in MEV images.
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