Página 1 dos resultados de 69 itens digitais encontrados em 0.026 segundos

‣ Otimização de sistemas de faixas adicionais em aclives de rodovias de pista simples; Optimization of climbing lanes system on two-lane highways

Lima, Francisco Arcelino Araújo
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 02/08/2010 Português
Relevância na Pesquisa
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O objetivo desta pesquisa foi propor um método capaz de estabelecer a sequência de implantação de um conjunto de faixas adicionais que maximize os benefícios do investimento nos aclives das rodovias de pista simples. O método proposto consiste em: (i) definir os aclives mais longos que o comprimento crítico; (ii) definir os aclives que satisfazem os critérios técnico-econômicos para implantação das faixas adicionais no horizonte de projeto; (iii) determinar as faixas adicionais que devem ser implantadas a cada ano do projeto, em função do crescimento do tráfego; e (iv) determinar a sequência ótima para implantação das faixas, em função do benefício global e do valor disponível para investimento a cada ano. Dentre os critérios técnicos que indicam a necessidade de faixa adicional, optou-se por utilizar a adaptação das diretrizes da AASHTO para as condições das rodovias brasileiras proposta por Melo e Setti (2003). Para quantificar os benefícios proporcionados pelas reduções dos custos operacionais e dos tempos de viagem, optou-se por utilizar modelos desenvolvidos por pesquisas nacionais; para quantificar os benefícios da redução dos acidentes, foi utilizado o modelo do HDM-4. Custos típicos de construção por quilômetro de faixa adicional (serviços de terraplenagem...

‣ Impacto da divulgação das notas no Enem na concorrência entre escolas

Azevedo Marques, Bruno Amato de
Fonte: Fundação Getúlio Vargas Publicador: Fundação Getúlio Vargas
Tipo: Dissertação
Português
Relevância na Pesquisa
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A partir 2006, o INEP (Instituto Nacional de Estudos e Pesquisa) passou a divulgar anualmente as notas das escolas no Exame Nacional do Ensino Médio (Enem). Tal divulgação já faz parte do calendário das escolas, professores, jornais e revistas que cobrem o setor educacional e até de pais de alunos. Este estudo visa analisar o impacto da divulgação dessas notas na competição entre as instituições de ensino médio e, mais especificamente, avaliar o efeito da nota média das escolas concorrentes na nota de uma dada escola, em relação aos anos anteriores à divulgação. A concorrência será analisada do ponto de vista espacial, de modo que, o peso atribuído à nota de uma instituição na estimação da nota de outra escola é inversamente proporcional à distâncias entre as mesmas. Essa análise empírica de instituições públicas e privadas foi realizada por meio da estimação em mínimos quadrados, utilizando-se variáveis de controle relacionadas às instituições e ao perfil socioeconômico dos alunos. Para tanto, foram utilizadas as bases de microdados do Censo Escolar e do Enem no período de 2004 à 2011. Os resultados indicam a existência de competição entre as escolas, com aumento no grupo de escolas públicas no período posterior à divulgação.; From 2006...

‣ Articulação curricular e (in)sucesso educativo na disciplina de Inglês : um estudo exploratório

Barbosa, Elsa de Jesus Monteiro Magalhães
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Dissertação de Mestrado
Publicado em //2010 Português
Relevância na Pesquisa
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Dissertação de mestrado em Ciências da Educação (área de especialização em Desenvolvimento Curricular); O presente estudo incide em concepções e percepções de professores sobre (in)sucesso na disciplina de Inglês e a sua relação com a articulação curricular horizontal e vertical, intradisciplinar e interdisciplinar. Pressupondo-se que a articulação curricular pode promover o sucesso educativo dos alunos, auscultou-se um conjunto de professores de uma escola sobre as suas representações de (in)sucesso e as suas percepções sobre a presença e importância de um conjunto de práticas de articulação curricular, assim como sobre o papel dos projectos de escola e do plano anual de actividades na promoção do sucesso. O estudo, de carácter exploratório e de índole quantitativo e qualitativo, foi efectuado numa escola EB 2,3 da região Norte e reporta-se ao ano lectivo de 2008/2009. A recolha de informação foi feita através de um questionário administrado às 14 professoras de Inglês dos 2º e 3º ciclos da escola, e ainda uma entrevista efectuada a quatro actores-chave: Director do Agrupamento, Coordenadora do Departamento de Línguas e Sub-Coordenadoras de Inglês do 2º e 3º ciclos. Foi ainda realizada a análise documental de cinco documentos orientadores do agrupamento-alvo: o Plano Anual de Actividades...

‣ Para uma avaliação do projeto testes intermédios

Ferreira, Maria Antonieta da Costa Mourão Lima, 1967-
Fonte: Universidade de Lisboa Publicador: Universidade de Lisboa
Tipo: Dissertação de Mestrado
Publicado em //2015 Português
Relevância na Pesquisa
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Dissertação de mestrado, Ciências da Educação (Área de Especialização em Avaliação em Educação), Universidade de Lisboa, Instituto de Educação, 2015; Este estudo teve como objetivo a descrição e caracterização da participação das escolas no Projeto Testes Intermédios, no período 2010-2013, sistematizando informação e interpretando as taxas de adesão e a composição anual do elenco de testes intermédios. Pretendeu-se caracterizar o universo de escolas que aderiram ao Projeto e a natureza dessa adesão. Desenvolveu-se uma investigação de cariz quantitativo, centrada na análise do comportamento das escolas perante a oferta de testes intermédios dirigida ao 3.º ciclo do ensino básico e ao ensino secundário, tendo como fonte primária os dados referentes à inscrição das escolas no período acima indicado. A análise partiu do conjunto inicial de variáveis de caracterização das escolas, a que acresceram as variáveis relativas aos anos de participação no Projeto e ao elenco de testes selecionado, como forma de identificar padrões de adesão. Enquanto contribuição para a avaliação do Projeto Testes Intermédios, o estudo constitui-se como uma avaliação de uma intervenção de política pública educativa. Os resultados evidenciaram uma participação muito expressiva...

‣ Childhood Predictors of Adolescent Marijuana Use: Early Sensation Seeking, Deviant Peer Affiliation, and Social Images

Hampson, Sarah E.; Andrews, Judy A.; Barckley, Maureen
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
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This study examined psychosocial mechanisms by which children’s early sensation seeking may influence their later marijuana use. In a longitudinal study, 4th and 5th grade elementary school children (N = 420) were followed until they were in 11th and 12th grades in high school with annual or biennial assessments. Sensation seeking (assessed over the first 4 assessments) predicted affiliating with deviant peers and level of favorable social images of kids who use marijuana (both assessed over the subsequent 3 assessments). Affiliation with deviant peers and the growth in social images predicted marijuana use in 11th and 12th grades. Affiliation with deviant peers mediated the effect of early sensation seeking on subsequent marijuana use. The theoretical and applied significance of this influence of early sensation seeking is discussed.

‣ Creating a Developmentally Sensitive Measure of Adolescent Alcohol Misuse: An Application of Item Response Theory

Edelen, Maria Orlando; McCaffrey, Daniel M.; Ellickson, Phyllis L.; Tucker, Joan S.; Klein, David J.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em //2009 Português
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This study, funded by the US National Institute of Drug Abuse, evaluates the usefulness of item response theory (IRT) to create a developmental alcohol misuse scale. Data were collected during 1997–2006 from 5828 Midwestern US students who completed annual surveys at Grades 7 through 11 and two and four years after high school. Seventeen alcohol misuse items were calibrated with IRT and examined for differential item functioning (DIF) across five study waves. Eight items displayed DIF; in most cases, properties for items assessed two years after high school were different from those assessed in grades 8–11. Implications and suggestions for future research are discussed.

‣ Relationships Between Level and Change in Family, School, and Peer Factors During Two Periods of Adolescence and Problem Behavior at Age 19

Fleming, Charles B.; Catalano, Richard F.; Haggerty, Kevin P.; Abbott, Robert D.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
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While prior research has examined family, school, and peer factors as potential predictors of problem behavior, less attention has been given to studying when these factors are most predictive of problems and if and when changes in these factors signal risk. Using annual data on a community sample of 1,040 individuals (47% female; 81% White), this study models growth in risk and protective factors during two developmental periods (Grades 5–8 and Grades 9–12) in order to predict substance misuse and crime at age 19. For protective factors of positive relationships with family and positive bonds to school, both the levels of these factors at Grade 5 and change between Grade 5 and Grade 8 predicted substance misuse and crime in early adulthood. Higher likelihoods of both forms of problem behavior also were predicted by increases in the risk factor of exposure to negative peers between 5th and 8th grade. In the late adolescent period, levels at 9th grade of all risk and protective factors examined predicted both substance misuse and crime. Also, increases in exposure to negative peers in late adolescence predicted greater likelihoods of both forms of problem behavior, while greater risk of substance misuse was predicted by decreases in school bonding and academic achievement...

‣ The Development and Correlates of Academic Interests from Childhood through Adolescence

Dotterer, Aryn M.; McHale, Susan M.; Crouter, Ann C.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 01/05/2009 Português
Relevância na Pesquisa
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Study goals were to assess: (1) the development of academic interests from middle childhood through late adolescence, (2) the degree to which junior high and high school transitions, parents’ educational expectations, interests, and education, were related to changes in academic interests, and (3) the longitudinal links between youth’s academic interests and school grades. Participants were mothers, fathers, and two siblings from 201, White, working and middle class families who were interviewed in their homes on up to 9 annual occasions. Multi-level model analyses revealed overall declines in youth’s interests over time, with boys showing more rapid decline than girls. Mothers’ educational expectations were positively related to youth’s interests, and youth’s interests declined less when fathers had more education. The transition to junior high, but not high school, was linked to decline in interests, but this was buffered by mothers’ academic interests. Declines in youth’s academic interests were linked to declines in school grades.

‣ Adolescent Work Intensity, School Performance, and Substance Use: Links Vary by Race/Ethnicity and Socioeconomic Status

Bachman, Jerald G.; Patrick, Jeremy Staff; O’Malley, M.; Freedman-Doan, Peter
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Português
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High school students who spend long hours in paid employment during the school year are at increased risk of lower grades and higher substance use, although questions remain about whether these linkages reflect causation or prior differences (selection effects). Questions also remain about whether such associations vary by socioeconomic status (SES) and race/ethnicity. This study examines those questions using nationally representative data from two decades (1991–2010) of annual Monitoring the Future surveys involving about 600,000 students in 10th and 12th grades. White students are consistently more likely than minority students to hold paid employment during the school year. Among White and Asian-American students, paid work intensity is negatively related to parental education and grade point averages (GPA), and positively related to substance use. Also among Whites and Asian Americans, students with the most highly educated parents show the strongest negative relations between work intensity and GPA, whereas the links are weaker for those with less educated parents (i.e., lower SES levels). All of these relations are less evident for Hispanic students, and still less for African-American students. It thus appears that any costs possibly attributable to long hours of student work are most severe for those who are most advantaged – White or Asian-American students with highly educated parents. Working long hours is linked with fewer disadvantages among Hispanic students and especially among African-American students. Youth employment dropped in 2008–2010...

‣ Bone marrow fibrosis in 66 patients with immune thrombocytopenia treated with thrombopoietin-receptor agonists: a single-center, long-term follow-up

Ghanima, Waleed; Geyer, Julia Turbiner; Lee, Christina S.; Boiocchi, Leonardo; Imahiyerobo, Allison A.; Orazi, Attilio; Bussel, James B.
Fonte: Ferrata Storti Foundation Publicador: Ferrata Storti Foundation
Tipo: Artigo de Revista Científica
Publicado em /05/2014 Português
Relevância na Pesquisa
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Thrombopoietin-receptor agonists increase platelet counts by stimulating the thrombopoietin receptor. Bone marrow fibrosis has been reported in patients receiving thrombopoietin-receptor agonists. This study determined the extent of myelofibrosis, its clinical relevance, and incidence of phenotypic or karyotypic abnormalities in patients with immune thrombocytopenia treated with thrombopoietin-receptor agonists. The grade of myelofibrosis was assessed before (n=15), during (n=117) and after (n=9) treatment in bone marrow biopsies from 66 patients. The proportion of bone marrow biopsies showing no fibrosis (myelofibrosis grade 0) decreased from 67% pre-treatment to 22% at last biopsy, of which 59% had grade 1 myelofibrosis and 18% had grade 2 myelofibrosis. The median duration of treatment with thrombopoietin-receptor agonists to last bone marrow biopsies was 29 months; patients who had two or more biopsies significantly more frequently had myelofibrosis grades 2/3 in the last bone marrow biopsies as compared to the first. Older age was associated with higher grades of fibrosis. No differences in blood counts or lactate dehydrogenase levels were found between patients with myelofibrosis grades 0/1 and those with grade 2. No clonal karyotypic or immunophenotypic abnormalities emerged. This study found that thrombopoietin-receptor agonists induce myelofibrosis grades 2/3 in approximately one-fifth of patients with immume thrombocytopenia...

‣ Rethinking School Feeding Social Safety Nets, Child Development, and the Education Sector

Bundy, Donald; Burbano, Carmen; Grosh, Margaret; Gelli, Aulo; Jukes, Matthew; Drake, Lesley
Fonte: World Bank Publicador: World Bank
Português
Relevância na Pesquisa
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This review highlights three main findings. First, school feeding programs in low-income countries exhibit large variation in cost, with concomitant opportunities for cost containment. Second, as countries get richer, school feeding costs become a much smaller proportion of the investment in education. For example, in Zambia the cost of school feeding is about 50 percent of annual per capita costs for primary education; in Ireland it is only 10 percent. Further analysis is required to define these relationships, but supporting countries to maintain an investment in school feeding through this transition may emerge as a key role for development partners. Third, the main preconditions for the transition to sustainable national programs are mainstreaming school feeding in national policies and plans, especially education sector plans; identifying national sources of financing; and expanding national implementation capacity. Mainstreaming a development policy for school feeding into national education sector plans offers the added advantage of aligning support for school feeding with the processes already established to harmonize development partner support for the education for all-fast track initiative.

‣ Addressing Educational Disparity : Using District Level Education Development Indices for Equitable Resource Allocations in India

Jhingran, Dhir; Sankar, Deepa
Fonte: Banco Mundial Publicador: Banco Mundial
Português
Relevância na Pesquisa
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The challenge of development work in the social sector in India today is one of bridging huge disparities across regions of the country, gender and social groups. Unless national and state policies specifically target resources to address these disparities, achieving higher level outcomes in an inclusive manner, which is the real goal for human development in education and health, will be a distant dream. This paper takes up the case of the Indian government s Elementary Education for All Mission to understand how this flagship program relates investments to spatial and social disparities. For identifying the most deprived districts in terms of educational inputs, outputs and overall development, the authors estimate district level education development indices for 2003-2004. The contribution of the largest investment program is measured by "per child allocations" and expenditures at the state and district levels for 2005-2006. An analysis of comparing the ratio of allocations to expenditures with the ratio of district level indices to sub-dimensional indices shows that there is an apparent disconnect between the "real investment needs" of the districts...

‣ Community Participation in Public Schools : The Impact of Information Campaigns in Three Indian States

Pandey, Priyanka; Goyal, Sangeeta; Sundararaman, Venkatesh
Fonte: World Bank, Washington, DC Publicador: World Bank, Washington, DC
Português
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This study evaluates the impact of a community-based information campaign on school performance from a cluster randomized control trial. The campaign consisted of eight to nine public meetings in each of 340 treatment villages across three Indian states to disseminate information to the community about its state mandated roles and responsibilities in school management. The findings from the first follow-up 2-4 months after the campaign show that providing information through a structured campaign to communities had a positive impact in all three states. In two states there was a significant and positive impact on reading (14-27 percent) in one of the three grades tested; in the third state there was a significant impact on writing in one grade (15 percent) and on mathematics in the other grade tested (27 percent). The intervention is associated with improvement in teacher effort in two states. Some improvements occurred in the delivery of certain benefits entitled to students (stipend, uniform, and mid day meal) and in process variables such as community participation in each of the three states. Follow-up research needs to examine whether there is a systematic increase in learning when the impact is measured over a longer time period and whether a campaign sustained over a longer time is able to generate greater impact on school outcomes.

‣ Universal Secondary Education (USE) in Guyana

World Bank
Fonte: Washington, DC Publicador: Washington, DC
Português
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In 2002, Guyana adopted a broadly-based five year plan (2003-2007) to achieve universal secondary education (USE), with a strategy to convert secondary classes in primary schools and grade 7-10 community high schools into General Secondary Schools (GSS) in which all students could present for the Caribbean Examination Certificate (CXC) or an alternative competency-based Certificate. Current status of secondary education (chapter one) summarizes the performance of public schools in Guyana against the Ministry of Education (MOE) policy on universal secondary education (2002), trends evident in the annual statistical digests, and the broad issues presented to Senior MOE officers on 13 December and to the Minister on 19 December 2007. Improving secondary student participation (chapter two) examines national and regional trends in population, enrollment, low levels of apparent transition from primary to secondary schools, poor secondary school entry examination (SSEE) results and issues related to the "size" of secondary schools. Upgrading and qualifying teachers (chapter three) identifies small school enrollment issues in earlier chapters with the enrollment required to offer a viable secondary curriculum...

‣ Former Yugoslav Republic of Macedonia : Student Assessment

World Bank
Fonte: Washington, DC Publicador: Washington, DC
Tipo: Publications & Research :: Working Paper; Publications & Research
Português
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In 2001, FYR Macedonia embarked on a new education policy agenda. One of the goals of this agenda was to improve the country's student assessment system. In order to gain a better understanding of the strengths and weaknesses of its existing assessment system, FYR Macedonia decided to benchmark this system using standardized tools developed under The World Bank's Systems Approach for Better Education Results (SABER) program. SABER is an evidence-based program to help countries systematically examine and strengthen the performance of different aspects of their education systems. SABER-student assessment is a component of the SABER program that focuses specifically on benchmarking student assessment policies and systems. The goal of SABER-student assessment is to promote stronger assessment systems that contribute to improved education quality and learning for all. The importance of assessment is linked to its role in: providing information on levels of student learning and achievement in the system; monitoring trends in education quality over time; supporting educators and students with real-time information to improve teaching and learning; and holding stakeholders accountable for results. The SABER-student assessment framework is built on the available evidence base for what an effective assessment system looks like. The framework provides guidance on how countries can build more effective student assessment systems. The framework is structured around two main dimensions of assessment systems: the types/purposes of assessment activities and the quality of those activities. Assessment systems tend to be comprised of three main types of assessment activities...

‣ Explaining recent increases in students' marijuana use: impacts of perceived risks and disapproval, 1976 through 1996.

Bachman, J G; Johnson, L D; O'Malley, P M
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /06/1998 Português
Relevância na Pesquisa
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OBJECTIVES: Marijuana use among high school seniors increased during most of the 1970s, decreased throughout the 1980s, and has been increasing again during the 1990s. Earlier analyses of the classes of 1976 through 1986 attributed the historic trends during that period to specific changes in views about marijuana. This study examined whether recent increases in marijuana use among seniors and among students in earlier grades reflect similar processes. METHODS: Multivariate regression analyses were conducted on data from large annual nationwide surveys of high school seniors from 1976 through 1996 (approximate n = 61,000) and 8th and 10th graders from 1991 through 1996 (n's = 87,911 and 82,475, respectively). RESULTS: Individual lifestyle factors (grades, truancy, religious commitment, evenings out for recreation) correlated substantially with marijuana use but did not explain the historic changes in marijuana use. Rather, decreases in perceived risk of harmfulness and in disapproval can account for the recent increases in all 3 grades and for earlier decreases among seniors. CONCLUSIONS: These findings indicate that perceived risks and disapproval are important determinants of marijuana use. Accordingly, prevention efforts should include realistic information about risks and consequences of marijuana use.

‣ Self-reports on students' learning processes are academic metacognitive knowledge

Gomes,Cristiano Mauro Assis; Golino,Hudson Fernandes
Fonte: Curso de Pós-Graduação em Psicologia da Universidade Federal do Rio Grande do Sul Publicador: Curso de Pós-Graduação em Psicologia da Universidade Federal do Rio Grande do Sul
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2014 Português
Relevância na Pesquisa
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The current study postulates that students' self-reported perceptions on their academic processes are a type of metacognition: academic metacognitive knowledge (AMcK). We investigated, using Structural Equation Modeling (SEM), three hypotheses: (a) AMcK explains the variance of factor scores of students' learning approaches (SLA) and academic motivation (AM); (b) AMcK is distinct from working metacognition (WMC); and (c) AMcK has incremental validity, beyond WMC, on the explanation of general academic achievement (GAA) variance. Two tests (indicators of WMC) and two scales (indicators of AMcK) were administered to 684 ten-to-eighteen-year-old Brazilian children and adolescents. Annual grades in Math, Portuguese, Geography and History were used as indicators of GAA. The results show that none of the three hypotheses can be refuted.

‣ An Assessment of the Effectiveness and Usage of the Surfrider Foundation Annual State of the Beach Report

Bain, John
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Masters' project Formato: 2508944 bytes; application/pdf
Português
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Every year since 2000, the Surfrider Foundation has released the State of the Beach Report. This annual report uses a suite of coastal health indicators to rate coastal state management information availability and status. After eight years, the Surfrider Foundation wanted to know how well the State of the Beach Report was measuring coastal health and to what extent it was utilized in creating coastal policy. I used three separate metrics to assess the State of the Beach Report. First, using the Handbook for measuring the progress and outcomes of Integrated Coastal and Ocean Management (UNESCO, 2006), I created a hierarchy of those many aspects of beach health of interest to the Surfrider Foundation. By coding the various indicators used in the State of the Beach Report I was able to determine that the report directly addressed 32 of the 34 subcategories and thus is an appropriate measure of coastal health. Secondly, I analyzed data from each of the previous eight State of the Beach Reports to determine where changes in indicator grades signified a trend. Once these trends were identified I identified the cause of each change. The majority of these changes were the result of states increasing the amount and availability of information related to coastal zone issues. The BEACH Act...

‣ Faixas adicionais para aclives de rodovias brasileiras; Climbing lanes on upgrades of Brazilian highways

Melo, Ricardo Almeida de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 10/06/2002 Português
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O objetivo da tese foi adaptar, para as condições das rodovias brasileiras, as diretrizes da AASHTO para projetos de faixas adicionais de subida. Esta adaptação foi feita através de três aspectos: (i) geração de curvas de desempenho para caminhões típicos brasileiros; (ii) determinação da redução admissível de velocidade para caminhões; e (iii) estimativa do fluxo e da porcentagem de caminhões no tráfego que justifiquem economicamente a construção da faixa adicional. Quanto ao primeiro aspecto, constatou-se que as relações massa/potência encontradas para caminhões brasileiros (variam de 100 a 380 kg/kW) são significativamente maiores que a dos caminhões norte-americanos (120 kg/kW), o que inviabiliza o uso das curvas de desempenho que constam do livro verde da AASHTO. Nesta pesquisa, um modelo de locomoção de veículos foi calibrado e validado, logo após foram geradas curvas de desempenho para sete categorias de caminhões brasileiros. No segundo aspecto, as relações entre as diferenças de velocidade entre automóveis e caminhões, e índices de envolvimento de caminhões em acidentes foram obtidas. Para atingir esse objetivo, foram coletados dados sobre acidentes envolvendo caminhões, velocidade de veículos em aclives e volume diário médio. As relações foram comparadas com a utilizada nas diretrizes da AASHTO e as diferenças encontradas sugerem que a redução admissível na velocidade dos caminhões brasileiros deve ser de 20 km/h...

‣ Mine to metal: a practical balance for a large platinum producer

Bartlett,H.E.; Liebenberg,M.J.
Fonte: Journal of the Southern African Institute of Mining and Metallurgy Publicador: Journal of the Southern African Institute of Mining and Metallurgy
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2014 Português
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This paper deals with the sampling and mass measurement for ore delivered from a shaft to a processing plant and the contribution of the data from these measurements to the metal balances from shaft deliveries to final metal production. Accurate measurement of the grade and tonnage of run-of-mine ore is important for four main reasons; ► It enables the measurement of the production from different profit centres to within statistically determined confidence limits for daily, monthly, or annual averages. The profit centres could be individual shafts within a mining complex or ore treated on a toll basis ► The monthly production at shaft head is compared to the grades and tonnage determined from underground sampling and mass measurement in terms of a shaft call factor ► The sum of the production from the shafts is the input to concentrators. This input is a major part of the total input into a complex with concentrators, smelters, and refineries. In terms of the Codes of Practice for Metal Accounting the inputs are compared to outputs and inventory changes to assess the efficiencies and unaccounted losses or gains at the various stages in the flow of metal from source to market ► On a daily or daily moving average basis...