No description available.

We have developed a probe to measure specific heat of Gd-doped PbMo(_6)S(_8), at low temperatures in high magnetic fields up to 12.5 T using a heat pulse method and an a.c. technique. Comparison between these heat capacity measurements and transport measurements provides critical complimentary information about fundamental thermodynamic properties and granularity m superconductors. We have used a tiny, robust, highly sensitive and broadly field independent Cemox thermometer (CX-1030), eliminating the use of bulky gas thermometry or capacitance thermometry. The diameter of the probe is 20 min which facilitates use in our 17 T high field magnet and in free-standing cryostats. Experiments include accurate measurement of temperature oscillations of 10(^-6)K. The measurements and analysis of the data were made fully computer controlled. Measurements on Cu and NbTi demonstrate we achieved an accuracy of ±0.2 K in temperature and a typical accuracy of -10% m the specific heat values quoted. Gd-doped Lead Chevrel phase material Pb(_1-x)Gd(_x)Mo(_6)S(_8) has been fabricated in a controlled environment using simple sintering methods and a Hot Isostatic Press (HIP) operating at pressures up to 2000 atmospheres. Cp has been measured and the properties of the materials including B(_c2)(T) have been determined. HIP processing improves the materials, increasing Tc ~ 15 K and B(_c2)(0) ~ 60 T. These values are amongst the best reported values for the Chevrel phase materials to date. I am personally responsible for taking all the data and its analysis. The modification of the probe were also undertaken by me. The fabrication of the samples was not my work

No description available.

Indiana University-Purdue University Indianapolis (IUPUI) / In this work we have designed and simulated a thermal bi-directional integrated circuit mass flow sensor. The approach used here was an extension to the gas flow model given by Mayer and Lechner. The design features high precision response received from analog integrated circuits. A computational fluid dynamic (CFD) model was designed for simulations with air and water Using COMSOL Multiphysics. Established mathematical models for the heat flow equations including CFD parameters were used within COMSOL simulation(COMSOL Multiphysics, Sweden). Heat pulses of 55 °C for a period of nearly 120 seconds and 50% duty cycles were applied as thermal sources to the flowstream. The boundary conditions of the heat equations at the solid (heating element) fluid interface were set up in the software for the thermal response. The hardware design included one heating element and two sensing elements to detect the bi-directional mass flow. Platinum sensors were used due to their linear characteristics within 0 ºC to 100 ºC range, and their high temperature coefficient(0.00385 Ω/Ω/ºC). Polyimide thinfilm heater was used as the heating element due to its high throughput and good thermal efficiency. Two bridge circuits were used to sense the temperature distribution in the vicinity of the sensing elements. Three high precision instrumentation low power amplifiers with offset voltage ~2.5μV (50μV max) were used for bridge signal amplification and the difference circuit. The difference circuit was used to indicate the flow direction. A LM555 timer chip was utilized to provide the heat pulse period. Simulation and experimental measurements for heat pulses with different amplitude (temperature) were in good agreement. Also, the sensitivity of the flow sensor was observed to remain unaffected with the change in the duty cycle of the heat operation mode.

É apresentada neste trabalho a Técnica de Pulso Térmico com os aspectos teóricos envolvidos e a montagem do sistema experimental. A técnica é destinada à determinação do potencial de superfície, centróide de carga e carga total em filmes de polímeros. A técnica foi aplicada em conjunto com a de descarga termo estimulada em \"circuito-aberto\'\' ao estudo das propriedades de transporte e armazenamento de cargas em filmes de Teflon FEP (25?m) em diferentes situações: amostras virgens, tratadas termicamente, submetidas a radiação ultra violeta e amostras submetidas à descarga iônica a baixa pressão. Vários problemas foram levantados e alguns deles abordados segundo modelos teóricos simplificados na interpretação dos dados experimentais. / Theoretical experimental aspects of the Heat Pulse Technique (HPT) are presented. The applications were the measurements of surface potentials, charge centroid, and total charge of the film samples. No tentative was made to determinate the spatial distribution of the observed charges. The HPT was used as complement of TSC open circuits measurements in the study of conduction and polarization effects in 25?m Teflon FEP films for different initial conditions of the corona-charged samples: virgin samples, annealed, u.v. irradiated, and samples submitted to ionic glow discharge. Several problems were raised and some of them were treated using very simple theoretical models to interpret the experimental results.

É apresentada neste trabalho a Técnica de Pulso Térmico com os aspectos teóricos envolvidos e a montagem do sistema experimental. A técnica é destinada à determinação do potencial de superfície, centróide de carga e carga total em filmes de polímeros. A técnica foi aplicada em conjunto com a de descarga termo estimulada em \"circuito-aberto\'\' ao estudo das propriedades de transporte e armazenamento de cargas em filmes de Teflon FEP (25?m) em diferentes situações: amostras virgens, tratadas termicamente, submetidas a radiação ultra violeta e amostras submetidas à descarga iônica a baixa pressão. Vários problemas foram levantados e alguns deles abordados segundo modelos teóricos simplificados na interpretação dos dados experimentais. / Theoretical experimental aspects of the Heat Pulse Technique (HPT) are presented. The applications were the measurements of surface potentials, charge centroid, and total charge of the film samples. No tentative was made to determinate the spatial distribution of the observed charges. The HPT was used as complement of TSC open circuits measurements in the study of conduction and polarization effects in 25?m Teflon FEP films for different initial conditions of the corona-charged samples: virgin samples, annealed, u.v. irradiated, and samples submitted to ionic glow discharge. Several problems were raised and some of them were treated using very simple theoretical models to interpret the experimental results.