Effect of combined bending strain and thermal cycling on the voltage-current characteristic curves of Bi-2223 tapes

High critical temperature superconductors are evolving from a scientific research subject into large-scale application devices. In order to meet this development demand they must withstand high current capacity under mechanical loads arising from thermal contraction during cooling from room temperature down to operating temperature (usually 77 K) and due to the electromagnetic forces generated by the current and the induced magnetic field. Among the HTS materials, the Bi2Sr2Ca2Cu3Ox, compound imbedded in an Ag/AgMg sheath has shown the best results in terms of critical current at 77 K and tolerance against mechanical strain. Aiming to evaluate the influence of thermal stress induced by a number of thermal shock cycles we have evaluated the V-I characteristic curves of samples mounted onto semicircular holders with different curvature radius (9.75 to 44.5 mm). The most deformed sample (epsilon = 1.08%) showed the largest reduction of critical current (40%) compared to the undeformed sample and the highest sensitivity to thermal stress (I-c/I-c0 = 0.5). The V-I characteristic curves were also fitted by a potential curve displaying n-exponents varying from 20 down to 10 between the initial and last thermal shock cycle.

Fetal Pulmonary Response After Fetoscopic Tracheal Occlusion for Severe Isolated Congenital Diaphragmatic Hernia

OBJECTIVE: To estimate the response in lung growth and vascularity after fetal endoscopic tracheal occlusion for severe congenital diaphragmatic hernia in the prediction of neonatal survival.METHODS: Between January 2006 and December 2010, fetal lung parameters (observed-to-expected lung-to-head ratio; observed-to-expected lung volume; and contralateral lung vascularization index) were evaluated before fetal tracheal occlusion and were evaluated longitudinally every 2 weeks in 72 fetuses with severe isolated congenital diaphragmatic hernia. Thirty-five fetuses underwent fetal endoscopic tracheal occlusion and 37 cases did not.RESULTS: Survival rate was significantly higher in the fetal endoscopic tracheal occlusion group (54.3%) than in the no fetal endoscopic tracheal occlusion group (5.4%, P<.01). Fetal endoscopic tracheal occlusion resulted in a significant improvement in fetal lung size and pulmonary vascularity when compared with fetuses that did not go to the fetal intervention (increase of the observed-to-expected lung-to-head ratio, observed-to-expected total lung volume, and contralateral pulmonary vascularization index 56.2% compared with 0.3%, 37.9% compared with 0.1%, and 98.6% compared with 0.0%, respectively; P<.01). Receiver operating characteristic curves indicated that the observed-to-expected total fetal lung volume was the single best predictor of neonatal survival before fetal endoscopic tracheal occlusion (cutoff 0.23, area under the curve [AUC] 0.88, relative risk 5.3, 95% confidence interval [CI] 1.4-19.7). However, the contralateral lung vascularization index at 4 weeks after fetal endoscopic tracheal occlusion was more accurate in the prediction of neonatal outcome (cutoff 24.0%, AUC 0.98, relative risk 9.9, 95% CI 1.5-66.9) with the combination of observed-to-expected lung volumes and contralateral lung vascularization index at 4 weeks being the best predictor of outcome (AUC 0.98, relative risk 16.6, 95% CI 2.5-112.3).CONCLUSION: Fetal endoscopic tracheal occlusion improves survival rate by increasing the lung size and pulmonary vascularity in fetuses with severe congenital diaphragmatic hernia. The pulmonary response after fetal endoscopic tracheal occlusion can be used to predict neonatal survival. (Obstet Gynecol 2012; 119: 93-101) DOI: 10.1097/AOG.0b013e31823d3aea

Effect of mechanical loading on the I-c degradation behavior of Bi-2223 tapes

During the winding process of HTS coils the tapes of Bi-2223 are subjected to the influence of bending strain, axial strain, compressive force and torsional deformation resulting in I-c degradation. In the literature the effects of the individual strain components are separately analyzed in spite of during coil winding and energizing the strain-stress effects are combined. In this work using commercial tapes of Bi-2223 Ag/AgMg with and without stainless steel reinforcement several samples were wound on cylindrical FRP G-10 holder in which different combined strains are applied. Measurements of I - V characteristic curves are done to determine the degree of critical current degradation and the operational limits. The results are compared with the I, values of short samples and other specimens subjected to deformation generated by loading types such as tensile and bending strain.

Critical current degradation of Bi-2223 composite tapes induced by cyclic deformation and fatigue-related effects

Application of high temperature superconductor Bi2Sr2Ca2Cu3Ox. (Bi-2223) compound embedded in an Ag matrix requires the knowledge of critical current as a function of mechanical properties. Commercial tapes available in different types have been developed in industrial production scale in which a combination of small diameter filaments, long tape lengths and a ductile matrix results in a conductor with low crack formation and good tolerance against strain. The measurement of critical current and the evaluation of n-index from V-I characteristic curves of Bi-2223/Ag composite tapes subjected to an initial bending strain as a function of number of thermal cycles were done for two types of Bi-2223/Ag composite tapes: with and without steel tape reinforcement. The results showed that tapes with reinforcement presented small critical current degradation as a function of the number of thermal cycles whereas tapes without reinforcement exhibited steadily critical current degradation caused by the propagation of cracks. The n-index followed the same critical current behavior.

Estudo teórico e experimental das curvas características de um ventilador axial aplicado em pulverização agrícola

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo de filmes supercondutores para aplicações em dispositivos eletrônicos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Avaliação do processo de infiltração da água em solo residual de Biotita-gnaisse para superfícies com diferentes declividades utilizando lisímetros

Pós-graduação em Engenharia Civil e Ambiental - FEB

Distribuição espacial e plano de amostragem seqüencial de ácaros fitófagos na cultura da seringueira [Hevea brasiliensis (Wild. Ex Adr. de Juss.) Müell.Arg.]

Pós-graduação em Agronomia - FEIS

Modelo Matemático para redimensionamento de motores elétricos trifásicos superdimensionados

Pós-graduação em Agronomia (Energia na Agricultura) - FCA

Novas configurações de interferômetros de quadratura e de técnicas de detecção de fase óptica baseadas em phase unwrapping

Pós-graduação em Engenharia Elétrica - FEIS

Theoretical and experimental study of agricultural spraying using CFD

This paper presents a computational fluid dynamics (CFD) application about the axial fan design used in an agricultural spraying system with a theoretical and experimental analysis of comparative results between the characteristic curves of a fan for several rotations and numerical results for the influence of blade attack angle variation and optimization of the spraying system, both for a same rotation. Flow was considered three-dimensional, turbulent, isothermal, viscous and non-compressible in a steady state, disregarding any influence of the gravity field. The average turbulent field was obtained from the application of time average where the turbulence model required for closing the set of equations was the k-E model. Resolution of all connected phenomena was achieved with the help of a fluid dynamics computer, CFX, which uses the finite volumes technique as a numerical method. In order to validate the theoretical analysis, an experiment was conducted in a circular section of a horizontal wind tunnel, using a Pitot tube for pressure readings. The main results demonstrate that the methodology used, based on CFD techniques, is able to reproduce the phenomenological behavior of an axial fan in a spraying system because results were very reliable and similar to experimentally measured ones.

Electrical and Superconducting Properties in Lap Joints for YBCO Tapes

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Analysis of criteria for metabolic syndrome in a population-based study of Japanese-Brazilians

Objective: Criteria for metabolic syndrome (MS) differ particularly regarding the definition of central obesity and consequently, there could be differences in the assessment of cardiovascular risk. We estimated the prevalence of metabolic syndrome, compared the agreement of the World Health Organization (WHO) criteria with the standard and a modified National Cholesterol Education Program (NCEP) criterion and investigated whether additional factors were associated with the diagnosis of the syndrome in a Japanese descendant population.Methods: In this cross-sectional, population-based survey, 1166 Japanese-Brazilians (533 men, 633 women) aged 57.4 +/- 12.4 years with mean body mass index (BMI) and waist of 25.2 +/- 4.0 kg/m(2) and 84.5 +/- 10.6 cm, respectively, were included. McNemar and kappa statistics were used to assess the concordance between WHO criteria with the standard and a modified NCEP criteria (waist of 90 and 80 cm, for men and women, respectively). in logistic regression analysis, a number of metabolic variables and albumin-to-creatinine ratio were included to test independent associations with metabolic syndrome defined by the modified NCEP criteria.Results: According to WHO, 55.4% (95% Cl 52.5-58.2%) of the subjects had MS and to NCEP 47.4% (95% Cl 44.6-50.0%). WHO criterion detected 48.3% of central obese subjects while NCEP only 14.0%. Kappa statistics showed a good strength of agreement (k = 0.67, p < 0.01) between WHO and NCEP standard definitions of MS. Using the modified NCEP criterion for Asians, more subjects with metabolic syndrome were identified (58%) and agreement with WHO was improved (k = 0.72, p < 0.001). However, similar Framingham risk scores were attributed to the subsets of subjects classified by any of the three criteria. Areas under the receiver operating characteristic curves, obtained for the modified waist values to diagnose metabolic syndrome according to WHO, were > 0.80 and corresponded, respectively, to sensitivity and specificity of 63 and 83% for men and 77 and 72% for women. In final logistic regression model, age, male sex, BMI and homeostasis model assessment-insulin resistance but not with albumin-to-creatinine ratio (ACR) were independently associated with the syndrome.Conclusions: High prevalence of MS, independent of the criterion considered, was found in this Japanese-Brazilian population. The replacement of waist cutoff by those proposed by WHO for Asians lead to this diagnosis in a higher number of subjects with elevated cardiovascular risk. Our data did not support that ACR should be included in the classical definition of MS in Japanese descendants as previously suggested by WHO.

Estudo de causas de falhas em selos mecânicos de bombas centrífugas para circulação de óleo térmico

This study is about a heating line that uses thermal oil. It is located in a facility that produces interlayers used in cars windshields. A plastic resin is melted and is sent to a matrix called DIE where the interlayers are produced. The DIE needs to receive heat from the circulation of thermal oil in four different regions of its interior, to ensure the correct thickness of the interlayer. The thermal energy is provided by electric heaters and the flow of thermal oil is impelled by four mechanically sealed centrifugal pumps (one per region). The key point of this study is the fact that these four pumps of the system have reported successive failures in the mechanical seals. Apparently, a poorly designed project has burdened the system intermittently. The pumps operation condition is located in a region of low efficiency, according to the characteristic curves. This fact is the source of the noticeable reduced time between failures. Changes in the configuration of the facility and in the number of pumps will be proposed, aiming to achieve higher operational efficiency. The proposals will be mathematically analyzed according to the Hydraulic Institute criteria. At the same time, we will also keep focus on an in-depth study of a heating system structure, starting with a detailed approach for each component and discussion about its real need and economic viability. At the end of this paper it is shown that the gain in efficiency achieved with the new proposed configuration reflects not only in the reduction of maintenance costs, but also a potential improvement in energy efficiency. It is shown that these two aspects are closely related and together form the basis for the design of a reliable and efficient pumping system

Análise do método suvrel na expressão diferencial a partir da matriz de contagens gerada com dados de RNA-SEQ

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)