bluuebunny/crossref_metadata_2025 huggingface dataset:
Firing transformations of an argentinean calcareous commercial clay
Authors: Serra M. F. , Conconi M.S. , Suarez G. , Agietti E. F. , Rendtorff N. M.
Published: September 2013

Mineralogical transformations caused by firing are usually studied by XRD methods only semi-quantitatively. In this work the original mineral disappearance and the neo-mineralization were evaluated quantitatively. Furthermore an indirect non crystalline phase quantification was performed under 1100 ºC was also carried out using the quartz content as internal standard. This study specifically discusses the behavior of an Argentinean white calcareous earthenware commercial when subjected to traditional ceramic firing, besides the technological importance of this particular material, it acts as a model for other clay based ceramic materials. Materials were subjected to thermal treatments between 700 ºC and 1100 ºC. A preliminary sintering characterization was carried out by contraction and porosity evolution. Simultaneous thermogravimetric and differential thermal analysis (TG-DTA) was carried out to elucidate the actual temperature at which the chemical changes occur. Finally, a quantitative analysis based on the Rietveld refinement of the X-ray diffraction patterns was performed to characterize the crystalline phases present in both the clay and in the materials obtained after different thermal treatments. The actual chemical reactions are proposed. The phases identified after firing at traditional working temperature (1040 ºC) are quartz, plagioclase, and the Spinel type alumino-silicate, accompanied by the non-diffracting un-reacted metakaolin and some amount of amorphous glassy phase. At intermediate temperatures (900 ºC) the presence of gehlenite was also detected. The carbonates (calcite and dolomite) presence and decomposition were also evaluated and demonstrated to determine the sintering characteristics of this material.
Caracterização da perovskita CaCu3Ti4O12 consolidada por sinterização assistida por campo elétrico
Authors: Carvalho E. de , Bertolete M. , Machado I. F. , Muccillo E. N. S.
Published: September 2013

A perovskita CaCu3Ti4O12 foi consolidada pela técnica se sinterização assistida por campo elétrico. Foi investigada a influência do tempo e da temperatura de sinterização na estrutura cristalina, na microestrutura e nas propriedades dielétricas da cerâmica policristalina. As amostras foram sinterizadas entre 750 e 930 °C, por tempos de 1 a 8 min. Os pós foram calcinados a 900 °C durante 18 h. As pastilhas foram caracterizadas por difração de raios X, microscopia eletrônica de varredura e por espectroscopia de impedância. O padrão da difração de raios X apresenta a estrutura do tipo perovskita e o parâmetro de rede calculado é de 7,40 Å. A densidade hidrostática aumenta com o aumento do tempo e da temperatura de sinterização. A observação das imagens do microscópio eletrônico de varredura revelam uma microestrutura heterogênea para todas as amostras. As perdas dielétricas são inferiores aos valores apresentados por outras técnicas de consolidação. A permissividade dielétrica é aproximadamente 10³ a 1 kHz. O aumento do tempo e da temperatura de sinterização torna as amostras friáveis.
Influência de diferentes níveis de salinidade nas características sensoriais do tomate
Authors: Eloi Waleska M. , Duarte Sergio N. , Soares Tales M. , Silva Ênio F. de F. e
Published: September 2013

Objetivou-se, com este trabalho, avaliar o efeito de diferentes níveis de salinidade no solo provocados pelo uso da fertirrigação, nas características sensoriais de frutos do tomateiro. O experimento foi conduzido em duas etapas, a primeira desenvolvida em laboratório e a segunda realizada em estufa plástica. A primeira etapa consistiu de testes preliminares que possibilitaram a construção de curvas artificiais de salinização, visando à realização do processo de salinização artificial do solo; na segunda etapa estudou-se a evolução dos diferentes níveis iniciais de salinidade do solo, implementados por meio da aplicação de fertilizantes, de acordo com a marcha de absorção de nutrientes pela cultura. Os níveis iniciais de salinidade utilizados foram: 1,5; 2,5; 3,5; 4,5; 5,5 e 6,5 dS m-1. Para a análise sensorial dos frutos realizou-se o teste hedônico com 39 provadores. Verificou-se que os índices de salinidade utilizados não interferiram na aceitação do produto.
Impacto da salinidade no desenvolvimento e crescimento de mudas de carnaúba (Copernicia prunifera (Miller) H.E.Moore)
Authors: Holanda Samia J. R. , Araújo Francisca S. de , Gallão Maria I. , Medeiros Filho Sebastião
Published: September 2013

Identificar o impacto da salinidade no desenvolvimento e crescimento de espécies resistentes a altas concentrações salinas é de fundamental importância para a recuperação de áreas salinizadas do semiárido nordestino brasileiro. Visando contribuir para a resolução desta problemática, o presente trabalho avaliou o efeito de diferentes níveis de salinidade para o desenvolvimento e o crescimento da carnaúba, espécie nativa e de extremo valor econômico para a região. Os níveis analisados foram: 0, 25, 50, 100 mM de NaCl, correspondente a uma condutividade elétrica de 2.0, 4.6, 7.1, 9.6, 12 dS m-1, respectivamente. Utilizou-se o delineamento inteiramente casualisado, com cinco tratamentos e quatro repetições, e se analisaram as variáveis altura da parte aérea, largura da parte aérea da folha, comprimento da raiz principal, peso da matéria seca, razão da matéria seca parte aérea/raiz e taxa de sobrevivência. Os tratamentos com 25 e 50 mM de NaCl não afetaram a sobrevivência inicial da planta. Concentrações maiores ou iguais que 75 mM de NaCl reduziram a produção de biomassa e a taxa de sobrevivência, em quase 50%; portanto, a produção de plantas nesses níveis de sal não é recomendada.
Características agronômicas e índice de colheita de diferentes genótipos de amendoim submetidos a estresse hídrico
Authors: Duarte Elizabeth A. A. , Melo Filho Péricles de A. , Santos Roseane C.
Published: September 2013

Objetivou-se, com este trabalho, avaliar os componentes agronômicos e o índice de colheita de genótipos de amendoim ereto e rasteiro submetidos a 27 dias de suspensão hídrica, no inicio da fase vegetativa. O experimento foi conduzido em casa de vegetação sob o delineamento inteiramente casualizado com esquema fatorial 8 x 2 (genótipos x tratamentos hídricos) com cinco repetições. As variáveis analisadas foram: peso seco da planta total, peso seco das raízes, altura da haste principal, produção de vagens planta-1, índice de colheita e índice de tolerância à seca. Verificou-se que os genótipos eretos apresentaram melhor ajuste fisiológico quando submetidos ao estresse hídrico prolongado destacando-se genotipo 55 437 como mais tolerante. Todos os genótipos rasteiros foram sensíveis ao estresse hídrico, porém LViPE-06 foi menos sensível, sendo o mais promissor para geração de populações divergentes.
Aclimatização de mudas de cana-de-açúcar em ambiente protegido sob dois tipos de malhas de sombreamento
Authors: Guiselini Cristiane , Pandorfi Heliton , Barros Andréa C. B. , Silva Luzia F. da , Silva Neto Sinval P. O. da
Published: September 2013

Objetivou-se, com este trabalho, analisar a radiação solar global, a temperatura do ar e seus efeitos no crescimento e desenvolvimento de mudas de cana-de-açúcar em aclimatização sob dois tipos de cobertura em ambiente protegido. A pesquisa foi conduzida na área experimental do Centro de Tecnologias Estratégicas do Nordeste, Igarassu, PE. O ambiente protegido foi coberto com plástico leitoso associado a dois tipos de malhas de sombreamento: malha termorrefletora e malha preta; as variáveis estudadas foram: meteorológicas (radiação solar, temperatura do ar) e biométricas (comprimento do colmo, diâmetro do colmo, comprimento da folha, número de folhas, altura da planta e área foliar). Utilizaram-se 12 bandejas sendo escolhidos, aleatoriamente, quatro tubetes por bandeja por tratamento para o acompanhamento biométrico. O delineamento experimental foi inteiramente casualizado utilizando-se o teste de Tukey (p < 0,05) para comparação entre as médias das variáveis biométricas. O ambiente com malha termorrefletora proporcionou os melhores resultados de desenvolvimento das mudas em decorrência da maior disponibilidade de radiação solar global nesse ambiente de produção.
Produção e qualidade de melancia cultivada com água de diferentes salinidades e doses de nitrogênio
Authors: Costa Andréa R. F. C. da , Medeiros José F. de , Porto Filho Francisco de Q. , Silva José S. da , Costa Fabricia G. B. , Freitas Djanira C. de
Published: September 2013

O uso de águas salinas na agricultura é um dos principais fatores que limitam a produção e a qualidade dos frutos no Estado do Rio Grande do Norte, sendo a seleção de híbridos tolerantes à salinidade e a utilização de adubação nitrogenada, alternativas para se evitar perdas de rendimento e qualidade desses frutos. Assim, o objetivo com este trabalho foi avaliar o comportamento produtivo e a qualidade dos frutos de três cultivares de melancia (Quetzali, Shadow e Leopard) submetidas a diferentes salinidades da água de irrigação e doses de nitrogênio, na região de Mossoró, RN. Os tratamentos consistiram em aplicação de água de irrigação com cinco condutividades elétricas (0,57; 1,36; 2,77; 3,86 e 4,91 dS m-1) e três doses de nitrogênio (48, 96 e 144 kg ha-1), delineados em blocos casualizados, com quatro repetições. Foram avaliados a produtividade, o número e o peso médio dos frutos e o teor de sólidos solúveis. O peso médio e o número de frutos influenciaram as perdas de rendimento das cultivares de melancia estudadas; apenas a cultivar Shadow apresentou o teor de sólidos solúveis dos frutos alterado com a salinidade da água de irrigação.
Modelagem matemática do processo de secagem da massa fibrosa de mandioca
Authors: Castiglioni Gabriel L. , Silva Flávio A. da , Caliari Márcio , Soares Júnior Manoel S.
Published: September 2013

O presente trabalho teve por objetivo elaborar um modelo matemático para o processo de secagem da massa fibrosa de mandioca e compará-lo com modelos da literatura. O método dos mínimos quadrados foi usado para ajustar os valores experimentais a um modelo semi-empírico. Os resultados experimentais e preditos foram avaliados estatisticamente por análise de variância, para verificar diferenças significativas. As variáveis estudadas foram temperatura e fluxo de ar em secador de bandeja. O modelo construído e o de Page apresentaram valores de erro relativo médio inferiores a 6%, podendo ser utilizados para a predição da cinética de secagem nas condições.
Comparação entre as técnicas de vibrocompressão e de aumento do fluxo expiratório em pacientes traqueostomizados
Authors: Castro Antonio Adolfo Mattos de , Rocha Swiany , Reis Cléia , Leite José Renato de Oliveira , Porto Elias Ferreira
Published: September 2013

A fisioterapia respiratória tem papel fundamental nos casos de complicações pelo excesso de secreção broncopulmonar. Manobras de remoção de secreção brônquica como a vibrocompressão e o aumento do fluxo expiratório (AFE) garantem a perviabilidade das vias aéreas. O objetivo deste trabalho foi avaliar o efeito das manobras de AFE e vibrocompressão para remoção de secreção e suas repercussões hemodinâmicas e ventilatórias em pacientes traqueostomizados. Participaram 20 pacientes (com 18 a 73 anos) de ambos os sexos com diagnóstico fisioterapêutico de hipersecreção e/ou retenção de muco brônquico, submetidos à aplicação dessas técnicas e à remoção de secreção, que foram avaliados antes e depois da intervenção quanto a parâmetros hemodinâmicos e respiratórios. Com a aplicação da técnica de vibrocompressão foi verificada queda significativa (p<0,05) nas pressões arteriais (PA) diastólica e média de 82,2±13,4 para 77,4±13,3 mmHg e de 104,3±18,2 para 90,9±9,07 mmHg, respectivamente; o mesmo ocorreu com a PA média (p<0,05) após a aplicação da técnica de AFE, de 103,5±13,2 para 94,1±9,0 mmHg. Não houve diferença entre as técnicas aplicadas quanto ao volume de secreção removida (p=0,60). Pacientes traqueostomizados apresentaram pois redução da pressão arterial após 30 minutos da aplicação das técnicas fisioterapêuticas, mas não houve diferença entre as técnicas utilizadas quanto ao volume de secreção removida.
Comparação entre o uso de bocal e máscara facial na avaliação de volumes pulmonares e capacidade vital em indivíduos saudáveis
Authors: Fregadolli Patrícia , Sasseron Ana Beatriz , Lanzoni Kelly Cristiane , Figueiredo Luciana Castilho de , Cardoso Andrea Luciana , Lima Núbia Maria Freire Vieira
Published: September 2013

Testes de função pulmonar são usados para determinar a gravidade, as conseqüências funcionais e o progresso de disfunções pulmonares e neuromusculares. As variações metodológicas com o bocal e a máscara facial e a cooperação do paciente podem interferir no desempenho das manobras e afetar as medidas. O objetivo deste estudo foi comparar os valores de volumes pulmonares (volume corrente [Vc], volume-minuto [Vm]), freqüência respiratória (FR) e capacidade vital (CV) em indivíduos saudáveis quando avaliados por meio do bocal e da máscara facial. Participaram do estudo 60 voluntários saudáveis, 14 homens e 46 mulheres, com média de idade de 22,9±7,1 anos. Para a avaliação com bocal, utilizou-se uma peça semirrígida descartável e clipe nasal; a máscara usada foi facial plástica com borda pneumática inflável. As medidas obtidas foram comparadas estatisticamente (nível de significância 5%). Os valores obtidos com o bocal e com a máscara facial foram, respectivamente: FR, 15 rpm x 13 rpm (p<0,01); Vm, 14,87 l/min x 10,02 l/min (p<0,01); Vc, 0,93 l x 0,8 l (p<0,01); CV, 3,85 l x 3,52 l (p<0,01). Os valores de volumes pulmonares e capacidade vital mostraram-se pois significativamente inferiores quando avaliados com a máscara facial em comparação ao bocal.
Instrumentos clínicos de avaliação funcional do tornozelo: revisão sistemática
Authors: Moreira Tarcísio Santos , Sabino George Schayer , Resende Marcos Antônio de
Published: September 2013

A entorse lateral do tornozelo é umas das lesões mais comuns em atletas e adultos fisicamente ativos. A utilização de instrumentos de avaliação confiáveis e válidos é fundamental na determinação da intervenção terapêutica adequada e, portanto, do sucesso do tratamento. O objetivo deste trabalho foi fazer um levantamento crítico, por meio de uma análise sistemática da literatura, dos instrumentos de medida adequados (questionários e escalas funcionais) disponíveis para a avaliação dos indivíduos que sofreram entorse lateral do tornozelo. Após busca nos bancos de dados Medline e Scielo foram incluídos 11 questionários para avaliação funcional do tornozelo. A escala funcional de extremidade inferior LEFS (Lower extremity functional scale) e a medida funcional de pé e tornozelo FAAM (Foot and ankle ability measure) foram as que apresentaram melhor qualidade metodológica, além de mais informações sobre suas propriedades de medida e suas aplicações práticas - mas não foram traduzidas para o português. Foram encontrados dois questionários traduzidos e adaptados para a população brasileira, o instrumento de instabilidade de tornozelo CAIT (Cumberland Ankle Instability Tool) e a escala de tornozelo e retropé AOFAS (American Orthopaedic Foot and Ankle Society - ankle-hindfoot scale). A AOFAS apresentou uma análise mais completa de suas propriedades, sendo portanto o instrumento mais recomendado para avaliação funcional do complexo pé-tornozelo atualmente no Brasil.
Arte verbal e música na língua Gavião de Rondônia: metodologia para estudar e documentar a fala tocada com instrumentos musicais
Authors: Meyer Julien , Moore Denny
Published: September 2013

Em uma língua com tom e prolongamento distintivos, como Gavião de Rondônia, a primeira questão sobre a fala tocada com instrumentos musicais é a relação entre as melodias e a fonologia suprassegmental das palavras correspondentes na fala cantada e na fala normal. A forma cantada serve para aprender e explicar os toques musicais. Ela é influenciada pelos recursos fonológicos da forma falada e pelos recursos musicais da forma instrumental, sendo intermediária entre as duas. Esta arte é executada com vários instrumentos musicais tradicionais na cultura Gavião de Rondônia. O papel da fala cantada instrumental é artístico, para acompanhar festas, e também prático, para ajudar a manter o patrimônio oral de uma cultura não escrita. Esta prática representa um patrimônio sociocultural do substrato tradicional das culturas da Amazônia, pouco estudado e ameaçado de extinção. Na Terra Indígena Igarapé Lourdes, usamos uma metodologia original para documentar este fenômeno nos instrumentos musicais identificados como 'falantes' ou 'cantantes' pelos colaboradores Gavião. As sessões de gravação e de transcrição necessárias para esse tipo de trabalho foram explicadas aqui. Elas revelaram a relação de iconicidade acústica que existe entre as palavras e a música. A análise linguística permite entender a natureza fonética e fonológica da iconicidade.
O jovem Milton: a individuação entre a igreja e a educação social
Authors: Leão Geraldo , Carrano Paulo César Rodrigues
Published: September 2013

O artigo discute os processos de transição para a vida adulta da juventude contemporânea, a partir de um caso escolhido entre os dados de um estudo sobre percursos biográficos de jovens participantes de um projeto social. O corpus empírico foi constituído por entrevistas biográficas aprofundadas, acompanhamento longitudinal das atividades cotidianas, desenhos de mapas de percursos por parte dos jovens e um grupo de discussão. A análise da trajetória do jovem Milton revela a formulação de estratégias para a superação de provas existenciais possibilitadas por aprendizagens que lhe permitiram constituir um capital social individualizado que o lançou para além das condições objetivas do seu contexto social.
Log Evaluation in Low Resistivity Formation of Tomsk Region Oil Fields
Authors: Evdokimova Elena
Published: September 2013

According to the generalized Western Siberia statistics only 25-30 % of low resistivity reservoirs are successfully identified and evaluated using log dataset. The main purpose of the investigation is development the appropriate wireline log interpretation methodology which helps to identify the low-resistivity J1 1 formation of Z oil field. First of all the common causes of the low resisitivity pay occurance were investigated using published literature sources. Then the wells where the productive J1 1 formation was characterized by anomaly low resistivity (Rt<5 Ohm*m) was determined. Then the concentration of conductive minerals was applied using Ezhova A.S.chart. For the purpose of exact estimation of Rt the conductivity that was not registrated by induction tool was calculated for each wells. This value was used for correct formation resistivity determination. As a result of the work performed the suggested methodology was succcessfuly implemented and recommened for using for Saturation evaluation throughout the low-resistivity pay in the Z oil field
Waxy Crude Oil Characterization and Experimental Study of the Restart of a Line Blocked with Gelled Waxy Crude
Authors: Luthi Ivana Flores
Published: September 2013

Subsea deepwater flowlines transporting crudes are subjected to shutdowns for operational or emergency reasons. For waxy crudes, the low temperature of the surrounding seawater may lead the oil to cool below its pour point. In this situation, a gelled structure composed of paraffin crystals distributed through a viscous matrix is formed, blocking the flowline. The formation of this gel, as well as its aging, present serious complications for the flow restart process, because the required pumping pressure becomes greater than the normal operating pressure. The restart of waxy crude flowlines has close connection with the complex rheological properties of gelled crudes and startup pressure propagation. To better understand the restart process, rheological tests and restart pressure measurements in a pipe were performed. Using a rheometer, essential parameters that describe the behavior of the waxy crude oils, such as WAT (Wax Appearance Temperature), flow curves, yield stress and thixotropy were characterized. Yield stress measurements can be used to estimate the minimum pressure required to restart the flow. However, as the yielding process is time-dependent, phenomena such as thixotropy, shrinkage, compressibility, thermal effects and aging are enormously relevant for the gel breakup. Furthermore, the time required to restart a line blocked with gelled waxy oil depends mainly on the applied pressure and viscosity that decreases with time. Thus, start-up tests were also performed in a horizontal pipeline blocked with gelled waxy crude oil, once when these phenomenas are not considered, the use of conservative pressure values would lead to unnecessary costs for the restart process.
Log Based Stress Modeling and Wellbore Stability Studies
Authors: Omotunde Omokayode
Published: September 2013

One of the major drilling problems encountered during oilfield exploration and development phases is wellbore instability. This largely occurs as a result of mechanical failure of the subsurface underlying rocks; with problems such as stuck pipe incidences, lost circulation, clay swelling accounting for about 5%-10% of total drilling expenses and resulting in non-productive time (NPT) and equipment loss and environmental concerns.

To address these concerns, a geomechanical model is defined. Geomechanical Modeling involves the study of in-situ stresses induced in rock, due to well drilling, completion, fluid injection, temperature changes and the associated deformations and failure that occurs. It takes into account the rock strength and the pore pressure whilst describing the behavior of rock under mechanical disturbance. Typically, a Geomechanical model comprises of six components: Unconfined Compressive Strength (UCS), Pore Pressure (Pp), Vertical Stress, Minimum and Maximum Horizontal Stress and the orientations of the horizontal stresses.

Log-based Stress Modeling offers a practical approach to characterize in-situ stress state profile of the subsurface formations. The knowledge of the mechanical properties and in-situ stresses of the subsurface formations is important, as it provides insights to the determination of optimal mud weight window, stable well trajectories, casing set points so as to minimize wellbore stability related problems. The data required is obtained from a suite of logs such as density, sonic, porosity, caliper and image logs. Stress magnitude information is needed as a continuous function of depth to proper characterization. Information about Stress orientation and constraining its magnitude is based on the observation of failure at the borehole wall which can also be detected by borehole logging tools.

This dissertation employs series of techniques to characterize the magnitude of in-situ stresses. A one-dimensional geomechanical model is developed, by combining the stress information obtained, rock mechanical properties, formation pressures, observation of wellbore failure and defining the failure criteria for both borehole collapse and fracture breakdown. A wellbore stability study was done to determine an optimal mud weight window and the sensitivity of the obtained mud weight window to the minimum and maximum horizontal stresses was investigated.
A Study On Horizontal Well Efficiency With Reference To Improved Oil Recovery Of The Fractured Basement Reservoir In The Cuu Long Basin, Vietnam
Authors: Lu Vi Dinh , Nguyen Quy Minh , Mai Lan Cao , Tran Dao Xuan
Published: September 2013

After several discoveries of oil and gas in fractured basement reservoir such as White Tiger, Dragon, Aurora and Ruby in 1990s, the basement on the continental shelf of Vietnam has become a major target for domestic and foreign oil companies. Oil produced from basement is accounted for more than 90% of the total produced oil. Despite of lesser and lesser new discoveries and most of the big oil fields are in declining phase, fast economic growth of Vietnam needs more energy. Among the Improved Oil Recovery (IOR) techniques, horizontal wells appeared to be a promising one in both short and long term of reservoir life.

Horizontal wells have a higher productivity and pay contact per well than that of vertical wells, thereby reducing the number of wells required to drain the reservoir. Horizontal wells allow operators to take advantage of highly heterogeneous reservoirs, especially those with fractures, or water and gas coning problems. As an injection well, a long horizontal well provides a large contact area, and therefore enhances well injectivity, which is highly desirable for enhanced oil recovery (EOR) applications. In this study, the efficiency of horizontal well will be evaluated by analyzing horizontal well performance. Both the advantages and disadvantages will be compared with those of vertical well. In assessment of the efficiency of horizontal well, both analytical and numerical solutions will be investigated.
Statistical Decision Making: Improving the Decision Process in the Oil and Gas Industry
Authors: Jovic Mia
Published: September 2013

Success is one of the key drivers of an industry, and success is aided by good decision making. In the oil and gas industry, success is remaining competitive and profitable. This takes good decision making regarding company-wide programs. However, these key decisions are often based on Excel graphs that compare several variables over time. While this method can give a good overview, it fails to capture both the dependency of the variables on each other, and the probability that the results were derived by chance. There are several statistical analysis tools, including Multivariate Linear Regression, Spearman R, and the Analysis of Variance, which can be used to increase the chance of making the most profitable decision, by numerically measuring if the results were derived by chance, and if the variables are statistically dependant on each other. These statistical analysis tools need to be better incorporated in daily decision making to ensure that variable relations are not due to chance, and that all the possible variables are considered. By including this additional analysis, companies can help drive their own success by making the decisions that help them keep their competitive edge.
The Trapping Capacity of Nanofluids on Migrating Fines in Sand
Authors: Ogolo Naomi Amoni
Published: September 2013

Fines Migration in reservoirs during hydrocarbon production has posed a big challenge to the oil and gas industry. Various methods have been tried but a lasting solution to the problem seems elusive. The application of nanotechnology to solve fines migration problem in reservoirs is still under investigation. This paper is focused on identifying the type of nanoparticles and dispersant that can effectively trap migrating fines in sand, thus prevent particle migration through the pore spaces of sand. Nine types of nanoparticles were experimented with using four kinds of fluid in the absence and in the presence of crude oil. The amount of fines that 3g/l of each nanofluid can trap before breakthrough of fines occurred was determined. The pH values of the nanoparticles in aqueous solutions were determined and the zeta potentials of the nanofluids were inferred.

The obtained laboratory results show that aluminum oxide nanoparticles is the most effective that can trap migrating fines and prevent them from further migration in sand. The estimated mass of fines captured by aluminium oxide nanoparticles in about 80cm3 volume of sand in distilled water, brine, ethanol and diesel were about 0.63g, 0.52g, 0.8g and 0.94g respectively in the presence of crude oil. The results also revealed that the presence of crude oil affects the performance of the nanoparticles because in the absence of crude, the results were better. The pH of aluminum oxide nanoparticles in aqueous solutions gave the lowest values ranging from 2.5 to 3.6 and this could partly be responsible for the good performance of the compound in trapping migrating fines in sand.
Derivative-Free Generalized Field Development Optimization
Authors: Isebor Obiajulu J.
Published: September 2013

Given the substantial costs and potential rewards associated with petroleum field development and reservoir management, it is essential that these operations be performed as close to optimally as possible. This paper addresses problems where the goal is to simultaneously determine the optimal number and type of new wells, the sequence in which they should be drilled, as well as their corresponding locations and time-varying controls. The optimization is posed as a mixed-integer nonlinear programming (MINLP) problem involving categorical, integer and real-valued variables. The formulation handles bound, linear, and nonlinear constraints, with the latter treated using filter-based techniques. Noninvasive derivative-free approaches are applied for the optimizations. Methods considered include Mesh Adaptive Direct Search (MADS, a local pattern search method), Particle Swarm Optimization (PSO, a global search technique), a PSO-MADS hybrid and Branch and Bound (B&B, a rigorous search procedure that requires relaxation of the categorical variables). Two example cases involving channelized reservoir models are presented. The PSO-MADS hybrid is shown to outperform the standalone MADS and PSO procedures. In the example case in which B&B is applied, the PSO-MADS approach is shown to give comparable solutions but at much lower computational cost. This is significant since B&B provides near-exhaustive search capabilities. It is concluded that the methodology presented here appears to be applicable for realistic petroleum field development and reservoir management.
Integrated Evaluation of Thermo-Chemical Injection in Carbonate Reservoirs
Authors: Karbouj Omar M.
Published: September 2013

This paper provides an integrated evaluation study of thermo-chemical injection in heavy oil carbonate reservoirs. The objective of this study that is established through an optimum development plan is to appraise the possibility of improving the recovery factor and production rate of these reservoirs in an economic way, which will help to extend the productive life and profits of many neglected heavy oil reservoirs. This paper will share the work flow of planning, designing, and evaluating the experimental work and simulation studies of the project.

Within the study, a reservoir example of a large carbonate Middle Eastern reservoir that may utilize advanced production of heavy oil using thermo-chemical flooding is presented. Thorough investigations are carried out by employing several analyses to the aforementioned technique as it is considered the scope of this project. To approach this goal, a number of core flooding experiments are conducted on oil and rock samples obtained from the reservoir under the same conditions of the pressure and temperature measurements. Specific equipment required for the experiments are designed and assembled in order to accomplish these operations.

Fluid characterization is done for the oil, and the prepared chemical solutions. Along with this, rock properties of the used core samples are examined. The performed experiments are operated with different chemical concentrations that are analyzed to determine the best combination based on the economic studies. The applicability of thermal process during the chemical injection has been also examined by several experimental runs. Implementing this type of techniques will give an extra benefit to the reservoir by reducing its oil viscosity. This reduction will yield to a substantial increment in the oil production and therefore will maximize the oil recovery.

In order to clarify the impact of the used techniques on the reservoir, the rock sample properties are checked intensively throughout the flooding processes. Several geological tests are also conducted on the cores before and after the application of the experiments to determine whether the samples are affected or not.
Experimental Investigation of the Influence of Molecular Surface Interactions on Imbibition in Shale Nano-Pore Proxies
Authors: Kelly Shaina
Published: September 2013

Applicable flow regimes and diffusion as well as nano-pore capillary and surface force interactions are topics of great interest for fluid flow in unconventional reservoirs. Liquid flows in shale nano-pores have been wholly less subject to investigation than gas flows. Yet, the study of liquid and multi-component flows at the nano-scale is very important for understanding the interaction of free and bound water with hydrocarbons in shale systems, liquid-driven core analysis methods, and the fate of injected liquids (such as "fracking fluids") into the reservoir. The Young-Laplace equation for capillary pressure and the Washburn equation for imbibition rate are successfully applied in conventional media and have been applied to shale as well. Pore sizes are on the order of nanometers in shale, a scale that is theorized to mark a threshold for new transport phenomena considerations. This work investigates imbibition with various fluids - ketones, alcohols, aqueous solutions, and alkanes - at the nano-scale and reveals compelling evidence that long range intermolecular, electrostatic, and solvation surface interactions play a significant role in nano-capillary imbibition. Experiments are conducted in a pore size distribution of unconnected, fabricated silica and borosilicate glass nanochannels, which serve as a proxy for water-wet nano-pores in shale. The calculated capillary pressures based on the directly measured experimental results for imbibition lengths differ from the macroscopically predicted results by one order of magnitude. Additionally, in many fluid cases, the trend of the capillary pressure curves derived from the data show a decrease in capillary pressure with a decrease in channel size, or a "dewetting trend." This trend is contradictory to the prediction of the Young-Laplace formula. Accordingly, as the size of the pores decreases the relative scale of surface interactions increases, possibly leading to a departure from a regime dominated by Laplacian pressure to one strongly influenced by disjoining pressure. A positive correlation is found between the saturation of the imbibing fluid into the bundle of nanochannels and the calculated, unique disjoining pressure of the fluid.
New Comprehensive Equation to Predict Liquid Loading
Authors: Luo Shu
Published: September 2013

Liquid loading occurs in most of marginal natural gas wells. Many models have been developed to predict the inception of liquid loading. Detailed review of these models and comparison between droplet model and film models are presented in the paper. The results show that film model is more accurate for predicting liquid loading than droplet model. This indicates that film reversal may be the main reason of liquid accumulation in the wellbore. A new model is developed, which includes non-uniform film thickness around pipe. The model is able to improve the prediction of liquid loading, especially for inclined wells.

Different models are examined using both field and lab data. Film model shows much better agreement with the data than droplet model. The effect of inclination angle is validated using Veeken's field data. The new film model shows a significant improvement compared to droplet model as well as other film models.
Experimental Analysis on Bidispersed Cuttings Transport in Laminar Pipe Flow
Authors: Mulchandani Vijay Ashok
Published: September 2013

Abstract

In drilling operations, cuttings transport is one of the crucial tasks performed by the drilling fluid. To be able to predict the true volumetric flow rate of the cuttings it is necessary to understand how the momentum is transferred from the fluid to the particles. This has been the subject of research for more than a century. However, there are still open questions. Due to high apparent viscosities of the fluid, cuttings are typically transported under laminar flow conditions. Moreover, the particle equivalent diameters are far from uniform and polydispersed suspensions and non-Newtonian fluids need to be considered. Many empirical correlations have been obtained to predict the transport of cuttings. However, the results are limited to flow systems similar to the ones analyzed. A better understanding of the transport mechanisms would help to obtain more general predictive tools.

In this contribution, we present an experimental setup used to measure fluid velocities and bidispersed particle velocities and position distributions. The particle image velocimetry (PIV) and the particle tracking velocimetry (PTV) methods are used to obtain flow fields of several bidispersed suspensions with varying particle diameter ratio and concentration. The results supply locally averaged fluid and particle velocity profiles and fluctuations of the particle velocities in the axial directions. These allow us to evaluate the effect of polydispersity on momentum transfer. Furthermore, histograms of the particle positions are used to investigate the effect of velocity gradients on the lateral distributions of semi-dilute suspensions. The results will be used for the development and validation of constitutive relations used in multiphase numerical methods such as the two-fluid model.
The Impact of International Large-Scale Assessments on Work-related Educational Monitoring and Policy-making in Germany
Authors: Seeber Susan , Lehmann Rainer
Published: September 2013

Germany has relied on its well-established tradition of preparing the workforce through the so-called dual system of practical in-firm training (apprenticeships) and theoretical foundations conveyed by vocational schools. Believing in the high quality of academic school programmes that prepare a small elite for university studies, the German public remained convinced until well into the 1990s that there was little need for innovation and improvement in German education. Although there had been earlier signs of concern, this conviction remained unchanged until the publication of the outcomes of the International Association for the Evaluation of Educational Achievement (IEA) Third International Mathematics and Science Study (TIMSS) in 1996. The ‘TIMSS shock’, reinforced by later studies, has resulted in a host of changes in educational policy, perhaps best characterised by the late Hermann Lange as the ‘turn towards evidence-based educational policy making’. Hallmarks of this trend were the decision by all 16 federal states in Germany to participate regularly in international large-scale assessments (ILSAs), including interstate comparisons (taken in 1997); the decision to define standards of educational performance (corresponding to the federally recognised school leaving certificates); the initiation of academic study programmes intended to foster the development of the required advanced technical skills; and the founding and/or expansion of agencies for quality management (including systems of reports on the state of education, both at the federal and the state levels). In this article, the role of ILSAs (including both IEA and others) in these policy changes are described and examined from a critical perspective.
The Impact of Large-Scale International Assessments: A Case Study of How the Ministry of Education in Namibia Used SACMEQ Assessments to Improve Learning Outcomes
Authors: Makuwa Demus K. , Maarse Jan
Published: September 2013

This article highlights the rationale for Namibia's participation in three studies which were conducted under the auspices of the Southern and Eastern Africa Consortium for Monitoring Educational Quality (SACMEQ) during the period 1995–2007. The article provides some of the innovative ways in which the results of the first (SACMEQ I, 1995) and second (SACMEQ II, 2000) studies were disseminated throughout the country. It highlights the analysis of reading and mathematics achievement scores of grade 6 learners at three intervals (1995, 2000 and 2007), and explains how the Ministry of Education used the achievement results from the first two studies (1995 and 2000) to mobilise resources for targeted interventions which contributed to improvements in reading and mathematics achievement during the third SACMEQ study in 2007. The article concludes that participation in well-designed international assessment studies that take the local contexts into account can, when well managed, contribute to improvements in learning outcomes.
Secretion of Glucose-Dependent Insulinotropic Polypeptide in Patients With Type 2 Diabetes
Authors: Calanna Salvatore , Christensen Mikkel , Holst Jens J. , Laferrère Blandine , Gluud Lise L. , Vilsbøll Tina , Knop Filip K.
Published: September 2013

OBJECTIVE

To investigate glucose-dependent insulinotropic polypeptide (GIP) secretion in patients with type 2 diabetes and nondiabetic control subjects during oral glucose or meal tests.

RESEARCH DESIGN AND METHODS

Eligible trials were identified by The Cochrane Library, MEDLINE, Embase, and Web of Science. Data were retrieved and random-effects models for the primary meta-analysis, random-effects meta-regression, and subgroup and regression analyses were applied.

RESULTS

Random-effects meta-analysis of GIP responses in 23 trials during 28 different stimulation tests showed that patients with type 2 diabetes (n = 363) exhibited no significant differences (P = not significant) in peak plasma GIP, total area under the curve (tAUC), time-corrected tAUC (tAUC × min−1), and time-corrected incremental area under the curve (iAUC × min−1) in comparison with nondiabetic control subjects (n = 325) but had lower GIP responses as evaluated from iAUC (weighted mean difference, −648 pmol/L × min; 95% CI, −1,276 to −21). Fixed-effects models meta-analyses confirmed most of the results of the primary meta-analysis but showed iAUC × min−1 to be reduced and showed tAUC and tAUC × min−1 to be higher in diabetic patients. Random-effects meta-regression of the primary meta-analysis showed that age (peak GIP, tAUC, iAUC, and iAUC × min−1), BMI (tAUC, iAUC, and iAUC × min−1), and HbA1c (iAUC and iAUC × min−1) predicted some of the GIP outcomes. Post hoc subgroup analysis showed a negative influence of age and of HbA1c on GIP responses and showed a positive influence of BMI on GIP responses.

CONCLUSIONS

Our results suggest that patients with type 2 diabetes are characterized by preserved GIP secretion in response to oral glucose and meal tests. They also suggest that high BMI is associated with increased GIP responses but increasing age and HbA1c are associated with reduced GIP secretion.
Antidepressant Medication as a Risk Factor for Type 2 Diabetes and Impaired Glucose Regulation
Authors: Barnard Katharine , Peveler Robert C. , Holt Richard I.G.
Published: September 2013

OBJECTIVE

Antidepressant use has risen sharply over recent years. Recent concerns that antidepressants may adversely affect glucose metabolism require investigation. Our aim was to assess the risk of type 2 diabetes associated with antidepressants through a systematic review.

RESEARCH DESIGN AND METHODS

Data sources were MEDLINE, Embase, PsycINFO, The Cochrane Library, Web of Science, meeting abstracts of the European Association for the Study of Diabetes, American Diabetes Association, and Diabetes UK, Current Controlled Trials, ClinicalTrials.gov, U.K. Clinical Research Network, scrutiny of bibliographies of retrieved articles, and contact with relevant experts. Relevant studies of antidepressant effects were included. Key outcomes were diabetes incidence and change in blood glucose (fasting and random).

RESULTS

Three systemic reviews and 22 studies met the inclusion criteria. Research designs included 1 case series and 21 observational studies comprising 4 cross-sectional, 5 case-control, and 12 cohort studies. There was evidence that antidepressant use is associated with type 2 diabetes. Causality is not established, but rather, the picture is confused, with some antidepressants linked to worsening glucose control, particularly with higher doses and longer duration, others linked with improved control, and yet more with mixed results. The more recent, larger studies, however, suggest a modest effect. Study quality was variable.

CONCLUSIONS

Although evidence exists that antidepressant use may be an independent risk factor for type 2 diabetes, long-term prospective studies of the effects of individual antidepressants rather than class effects are required. Heightened alertness to potential risks is necessary until these are complete.
Effects of pneumoperitoneum induced at various pressures on cardiorespiratory function and working space during laparoscopy in cats
Authors: Mayhew Philipp D. , Pascoe Peter J. , Kass Philip H. , Shilo-Benjamini Yael
Published: September 2013

Objective—To evaluate the effect of pneumoperitoneum on cardiorespiratory variables and working space during experimental induction of 3 intra-abdominal pressures (IAPs) in cats.

Animals—6 healthy young adult neutered male domestic shorthair cats.

Procedures—All cats were anesthetized through use of a standardized protocol. A catheter was placed in the right femoral artery for blood pressure and blood gas monitoring. A thermodilution catheter was placed in the right jugular vein via fluoroscopic guidance. Cardiopulmonary variables were measured before (baseline) and 2 and 30 minutes after initiation of pneumoperitoneum at IAPs of 4, 8, and 15 mm Hg; these were created through the use of a mechanical insufflator. At each IAP, abdominal dimensions (height, width, and circumference) were measured at a standardized location.

Results—At 4 mm Hg and 8 mm Hg IAP, no clinically important changes were identified in cardiorespiratory values. Heart rate, cardiac index, and stroke volume index remained unchanged throughout the study at all IAPs. Mean arterial blood pressure began to increase at 8 mm Hg and was significantly higher, compared with baseline, at both time points at 15 mm Hg. At 15 mm Hg, Paco2 was significantly higher and cats were more acidotic than at baseline. Working space was subjectively greater at 8 mm Hg than at 4 mm Hg IAP; however, at 15 mm Hg, no clinically important enlargement of the working space was identified, compared with at 8 mm Hg.

Conclusions and Clinical Relevance—Values of cardiopulmonary variables were largely unchanged by induction of pneumoperitoneum in healthy cats up to an IAP of 8 mm Hg, and no clinically important increases in working space were evident at an IAP of 15 versus 8 mm Hg. These findings provide little justification for use of IAPs > 8 mm Hg in healthy cats undergoing laparoscopic procedures; however, whether the situation is similar in diseased or elderly cats remains to be determined.