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The viscosity of liquid R134a

Oliveira, Carla Padrel de; Wakeham, W. A.
Fonte: Plenum Publishing Corporation Publicador: Plenum Publishing Corporation
Tipo: Artigo de Revista Científica
Publicado em //1993 ENG
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36.72%
The paper reports new measurements of the viscosity of liquid R134a over the temperature range 235 to 343 K and pressures up to 50MPa. The measurements have been carried out in a vibrating-wire viscometer calibrated with respect to the viscosity of several liquid hydrocarbons. It is estimated that the uncertainty in the viscosity data reported is +0.6%. The data therefore have a lower uncertainty than that of earlier measurements of the viscosity of this environmentally acceptable regrigerant. The viscosity data have been represented as a function of density by means of a formulation based upon the rigid, hard-sphere theory of dense fluids with a maximum deviation of _+0.3%. This representation allows the present body of experimental data to be extended to regions of thermodynamic state not covered by the measurements.

An industrial reference fluid for moderately high viscosity

Oliveira, Carla Padrel de; Caetano, Fernando J. P.; Fareleira, João M. N. A.; Fröba, Andreas P.; Harris, Kenneth R.; Leipertz, Alfred; Trusler, J. P. Martin; Wakeham, William A.
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Artigo de Revista Científica
Publicado em //2008 ENG
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36.8%
In industrial practice, there is a demand for a reference standard for viscosity that is established for a readily available fluid to simplify the calibration of industrial viscometers for moderately high viscosities [(50 to 125) mPa · s]. Diisodecyl phthalate (DIDP) has been suggested as that reference fluid, and a number of studies of its properties have been carried out in several laboratories throughout the world, within the auspices of a project coordinated by the International Association for Transport Properties. That project has now progressed to the point where it is possible to collate the results of studies of the viscosity of the fluid by a number of different techniques, so as to lead to a proposed standard reference value which will be included in the paper. To support this recommended value, the various measurements conducted have been critically reviewed, and the sample purity and other factors affecting the viscosity have been studied. Density and surface tension measurements have also been performed. This paper does not describe the individual viscosity determinations carried out in independent laboratories because these are the subject of individual publications, but it does describe the ancillary studies conducted and their relevance to the viscosity standard. In addition...

Análise do método de medição de viscosidade de líquidos por ultra-som usando a reflexão de ondas de cisalhamento.; Analisys of ultrasonic measurement of liquids viscosity by means of the shear reflectance method.

Franco Guzmán, Édiguer Enrique
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 14/08/2006 PT
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36.72%
Neste trabalho é analisada a medição de viscosidade de líquidos por ultrasom pelo método da reflexão de ondas de cisalhamento. O método baseiase na medição da magnitude e fase do coeficiente de reflexão quando as ondas de cisalhamento incidem na interface entre um sólido e o líquido testado. Foram analisados os conceitos teóricos do método da medição de viscosidade e desenvolvida a metodologia experimental a fim de evitar a influência indesejada de fatores externos, como a temperatura e a instabilidade da eletrônica, sobre a medição. Foram obtidos resultados com dois óleos alimentícios (azeite de oliva e óleo de milho) e quatro óleos automotivos do tipo SAE (40, 90, 140 e 250). Foi mostrado que para uma freqüência de operação baixa o suficiente para garantir comportamento Newtoniano do líquido, os valores de viscosidade têm excelente concordância numérica com os valores obtidos usando o viscosímetro rotacional, no caso dos óleos menos viscosos. Já no caso dos óleos mais viscosos, foram obtidos valores de viscosidade menores que os obtidos com viscosímetro rotacional, e o aumento no módulo elástico sugere um comportamento mais viscoelástico. Foi mostrado que o método de cálculo simplificado usado por alguns autores...

Viscosity measuring cell using ultrasonic wave mode conversion

Buiochi, F.; Franco, E. E.; Higuti, R. T.; Adamowski, J. C.
Fonte: Taylor & Francis Ltd Publicador: Taylor & Francis Ltd
Tipo: Artigo de Revista Científica Formato: 139-149
ENG
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36.76%
This work presents a cell to measure dynamic viscosity of liquids using ultrasonic wave mode conversion from longitudinal to shear wave. The strategy used to obtain the viscosity is based on the measurement of the complex reflection coefficient of shear waves at a solid-liquid interface. Viscosity measurements of automotive oils (SAE90 and SAE140) were obtained in the frequency range from 1 to 10 MHz. These results are compared with the Maxwell model with two relaxation times, showing the dependency of viscosity with frequency. Several parameters affecting viscosity measurements, including the solid material properties, liquid viscosity, and operating frequency are discussed.

A Simple maxwell Based Model in Order to Represent the frequency-dependent viscosity measured by ultrasound

Franco, Ediguer E.; Adamowski, Julio C.; Higuti, Ricardo T.; Buiochi, Flávio
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Conferência ou Objeto de Conferência Formato: 1905-1907
ENG
Relevância na Pesquisa
36.76%
A previous work showed that viscosity values measured high frequency by ultrasound agreed with the values at low frequency by the rotational viscometer when conditions are met, such as relatively low frequency viscosity. However, these conditions strongly reduce the range of the measurement cell. In order to obtain a measurement range and sensitivity high frequency must used, but it causes a frequency-dependent decrease on the viscosity values. This work introduces a new simple in order to represent this frequency-dependent behavior.model is based on the Maxwell model for viscoelastic , but using a variable parameter. This parameter has physical meaning because it represents the linear behavior the apparent elasticity measured along with the viscosity by .Automotive oils SAE 90 and SAE 250 at 22.5±0.5oC viscosities at low frequency of 0.6 and 6.7 Pa.s, respectively,tested in the range of 1-5 MHz. The model was used in to fit the obtained data using an algorithm of non-linear in Matlab. By including the viscosity at low frequency an unknown fitting parameter, it is possible to extrapolate its . Relative deviations between the values measured by the and extrapolated using the model for the SAE 90 and SAE 250 oils were 5.0% and 15.7%...

Influence of vegetable oil in the viscosity of biodiesel-a review

Tsuji, Fernando Kazushi; Neto, Luiz Daré
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
36.78%
Viscosity is a measure fluid resistance to flowing, affecting the fuel spray in the combustion chamber and, by this way, thus the formation of carbon deposits. The analysis of the influence of vegetable oil viscosity in biodiesel seems appropriate, because biodiesel viscosity is a function of vegetable oil. The increase of the fuel viscosity, promoted by biodiesel, has a major impact on the dynamics of jet fuel, increasing its speed and distance of penetration, obtaining therefore an increase in the amount of turbulent movement of the jet and thus an increase in the rate of preparation of the mixture, air-fuel, when adding biodiesel to diesel oil. The negative effect of this higher fuel viscosity is the increase of the wear of the train of gears, cam shaft, and valve push rod of all the injection pumps due to the higher pressure of injection. The viscosity of biodiesel is influenced by the size of its molecule and by the increase of molecule insaturations, is directly related with its origin vegetable oil or fat. This study is a review of the influence of vegetable oils in viscosity of biodiesel. Copyright © 2008 SAE International.

Influencia da viscosidade sobre o escoamento gas-liquido horizontal intermitente; Influence of viscosity on the gas liquid intermittent flow in the horizontal pipe

Milvio Duarte
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 26/02/2007 PT
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36.72%
Uma mistura de gás e líquido escoando em um tubo para uma larga faixa de vazões tem as fases gás e líquido distribuídas na tubulação de forma intermitente. Esse padrão é caracterizado por uma sucessão de longas bolhas seguidas de pistões de líquido que não ocorrem com tamanhos e periodicidade definidos devido às interações cinemáticas e dinâmicas que ocorrem entre as bolhas e os pistões de líquido. O comprimento, a velocidade e a freqüência das estruturas gás e líquido formadas são influenciados por diversos parâmetros do escoamento podendo-se citar: as vazões de gás e líquido, o diâmetro da linha, a densidade e a viscosidade dos fluidos entre outros. O presente trabalho tem por objetivo analisar o efeito da variação da viscosidade na caracterização das estruturas gás-líquido. O aparato experimental consiste de um misturador gás-líquido posicionado na entrada da seção de testes. Ela consiste de tubo de acrílico transparente de 23,4 m de comprimento, com 26 mm de diâmetro interno, totalizando 900 diâmetros livres. Dois pares de fluidos são testados: ar e água e ar com uma mistura de glicerina. Tomando-se como referência a viscosidade da água, 1 cP, a mistura de glicerina mais água apresenta uma viscosidade de 27 cP. As medidas instantâneas do escoamento tais como comprimentos...

One-dimensional viscoelastic fluid model where viscosity and normal stress coeffients depend on the shear rate

Carapau, Fernando
Fonte: F. Carapau, "One-dimensional viscoelastic fluid model where viscosity and normal stress coeffients depend on the shear rate",Nonlinear Analysis:Real World Applications, Volume 11, Issue 5, pp. 4342-4354, 2010. Publicador: F. Carapau, "One-dimensional viscoelastic fluid model where viscosity and normal stress coeffients depend on the shear rate",Nonlinear Analysis:Real World Applications, Volume 11, Issue 5, pp. 4342-4354, 2010.
Tipo: Artigo de Revista Científica
POR
Relevância na Pesquisa
46.55%
Westudy the unsteady motion of a viscoelastic fluid modeled by a second-order fluid where normal stress coefficients and viscosity depend on the shear rate by using a power-law model. To study this problem, we use the one-dimensional nine-director Cosserat theory approach which reduces the exact three-dimensional equations to a system depending only on time and on a single spatial variable. Integrating the equation of conservation of linear momentum over the tube cross-section, with the velocity field approximated by the Cosserat theory, we obtain a one-dimensional system. The velocity field approximation satisfies both the incompressibility condition and the kinematic boundary condition exactly. From this one-dimensional system we obtain the relationship between average pressure and volume flow rate over a finite section of the tube with constant and variable radius. Also, we obtain the correspondent equation for the wall shear stress which enters directly in the formulation as a dependent variable. Attention is focused on some numerical simulation of unsteady/steady flows for average pressure, wall shear stress and on the analysis of perturbed flows.

Viscosity of gums in vitro and their ability to reduce postprandial hyperglycemia in normal subjects

Brenelli,S.L.; Campos,S.D.S.; Saad,M.J.A.
Fonte: Associação Brasileira de Divulgação Científica Publicador: Associação Brasileira de Divulgação Científica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/1997 EN
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Experiments were carried out in vitro with three viscous polysaccharides (guar gum, pectin, and carboxymethylcellulose (CMC)) of similar initial viscosity submitted to conditions that mimic events occurring in the stomach and duodenum, and their viscosity in these situations was compared to their actions on postprandial hyperglycemia in normal human subjects. Guar gum showed greater viscosity than the other gums during acidification and/or alkalinization and also showed larger effects on plasma glucose levels (35% reduction in maximum rise in plasma glucose) and on the total area under the curve of plasma glucose (control: 20,314 ± 1007 mg dl-1 180 min-1 vs guar gum: 18,277 ± 699 mg dl-1 180 min-1, P<0.01). Pectin, which showed a marked reduction in viscosity at 37oC and after events mimicking those that occur in the stomach and duodenum, did not have a significant effect on postprandial hyperglycemia. The performance of viscosity and the glycemia response to CMC were at an intermediate level between guar gum and pectin. In conclusion, these data suggest that temperature, the process of acidification, alkalinization and exposure to intestinal ions induce different viscosity changes in gums having similar initial viscosity, establishing a direct relationship between a minor decrease of gum viscosity in vitro and a reduction of postprandial hyperglycemia

The viscosity distribution around a rising bubble in shear-thinning non-newtonian fluids

Li,Shaobai; Ma,Youguang; Fu,Taotao; Zhu,Chunying; Li,Huaizhi
Fonte: Brazilian Society of Chemical Engineering Publicador: Brazilian Society of Chemical Engineering
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2012 EN
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36.78%
The viscosity distribution of the liquid around a rising bubble in carboxymethyl cellulose (CMC) aqueous solutions was measured experimentally by particle image velocimetry (PIV). The effect of the concentration of CMC solutions on the viscosity distribution around a bubble and the coupling relations between the viscosity field, flow field and shear stress field were also studied. Results indicated that the specific viscosity (non-dimensionalized by η0) decreases with the increase in CMC solution concentration due to a shear thinning effect. Within the experimental range, similar viscosity distributions of liquids around a rising bubble were found: a hollow cylindrical low viscosity region around the bubble wake and a high viscosity region in the central bubble wake.

Extensional viscosity measurements of concentrated emulsions with the use of the opposed nozzles device

Różańska,S.; Różański,J.; Ochowiak,M.; Mitkowski,P. T.
Fonte: Brazilian Society of Chemical Engineering Publicador: Brazilian Society of Chemical Engineering
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2014 EN
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36.8%
This paper presents results of experimental studies on the apparent extensional viscosity of emulsions. The apparent extensional viscosity measurements were carried out with the use of a customized rheometer which utilizes stagnation flow between two opposing nozzles. Apparent extensional viscosity was determined for emulsions containing 60, 70 and 74 vol.% of dispersed phase. The emulsions were produced using a homogenizer equipped with different dispersing endings that resulted in emulsions characterized by different droplet sizes. The experimental results show that the value of apparent extensional viscosity of the emulsion is significantly influenced by the droplet size and by the concentration of dispersed phase. Apparent extensional viscosity as well as shear viscosity of the emulsions increases with the increase of the dispersed phase concentration and with the decrease of the droplet diameter. It has also been observed that the decrease in the diameter of droplets increases the ratio of the apparent extensional viscosity to the shear viscosity, known as the Trouton ratio.

Viscosity Evaluation of Heavy Oils from NMR Well Logging

Yang, Zheng
Fonte: Universidade Rice Publicador: Universidade Rice
Tipo: Thesis; Text Formato: 188 p.; application/pdf
ENG
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36.84%
Heavy oil is characterized by its high viscosity, which is a major obstacle to both logging and recovery. Due to the loss of T 2 information shorter than the echo spacing ( TE ), estimation of heavy oil properties from NMR T 2 measurements is usually problematic. In this work, a new method has been developed to overcome the echo spacing restriction of NMR spectrometer during the measurement of heavy oil. A FID measurement supplemented the CPMG in an effort to recover the lost T 2 data. Constrained by the initial magnetization ( M 0 ) estimated from the FID and Curie's law and assuming lognormal distribution for bitumen, the corrected T 2 of bitumen can be obtained. This new method successfully overcomes the TE restriction of the NMR spectrometer and is nearly independent on the TE applied in the measurement. This method was applied in the measurement of systems at elevated temperatures (8 ∼ 90 °C) and some important petrophysical properties of Athabasca bitumen, such as hydrogen index ( HI ), fluid content and viscosity were evaluated by using the corrected T 2 . Well log NMR T 2 measurements of bitumen appear to be significantly longer than the laboratory results. This is likely due to the dissolved gas in bitumen. The T 2 distribution depends on oil viscosity and dissolved gas concentration...

Resistance, wave-making and wave-decay of thin ships, with emphasis on the effects of viscosity.

Lazauskas, Leo Victor
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2009
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36.76%
Three interrelated topics in ship hydrodynamics - resistance, wave-making and wave decay - are investigated in an attempt to improve the accuracy of some simple methods used in the preliminary design of thin ships. Several published sets of data from classical and recent boundary layer experiments on flat plates are used to estimate boundary layer quantities such as thicknesses and eddy viscosities. These quantities are subsequently used to modify the hull shape and the free-surface boundary condition as a means of including viscous effects on wave-making and ship-wave decay. A recent technique is used to analyse 161 experimental flat-plate turbulent boundary layer velocity profiles, and a new skin-friction line is derived. Some practical methods are proposed for the numerical quadrature of integrals arising in thin-ship hydrodynamics. We demonstrate that for some integrals, rapid oscillation, rather than being a hindrance to accurate quadrature, can actually be beneficial if appropriate techniques are employed. We find that boundary layer displacement thickness effects on wave resistance are very small and can be safely ignored for full-size vessels. On the other hand, the idea of a detachment layer, an indication of where the boundary layer begins to thicken rapidly...

Adequacy of human milk viscosity to respond to infants with dysphagia: experimental study

Almeida,Mariangela Bartha de Mattos de; Almeida,João Aprígio Guerra de; Moreira,Maria Elisabeth Lopes; Novak,Franz Reis
Fonte: Faculdade De Odontologia De Bauru - USP Publicador: Faculdade De Odontologia De Bauru - USP
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2011 EN
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36.78%
Neonatal nutrition is an important subject in health in the short, medium and long term. In preterm newborns, nutrition assumes a predominant role for the child's overall development. Babies with uncoordinated swallowing or respiration may not have the necessary oral abilities to suck the mother's breast and will need to implement different feeding practices; one of them is changing the consistency of the milk offered. Objectives: Determine viscosity variations of untreated human and pasteurized milk without and with thickening to adapt the diet to the needs of dysphagic infants hospitalized in the Neonatal Intensive Cara Unit (NICU). Material and Methods: The authors altered the viscosity of natural infant powdered milk and, after thickening, determined and adopted a thickening standard for human milk. Untreated human and pasteurized milk was thickened in concentrations of 2%, 3%, 5% and 7% and the viscosity were determined every 20 minutes for a period of 60 minutes at a temperature of 37ºC. Results: The infant lactose formula thickened at concentrations of 2% and 3% produced viscosities of 8.97cP and 27.73 cP, respectively. The increases were significantly different after 1 hour. Inversely, untreated human milk at 2%, 3%, 5% and 7% produced diminished viscosity over time; the changes were more accentuated in the first 20 minutes. In pasteurized human milk...

Adequacy of human milk viscosity to respond to infants with dysphagia: experimental study

Almeida, Mariangela Bartha de Mattos de; Almeida, João Aprígio Guerra de; Moreira, Maria Elisabeth Lopes; Novak, Franz Reis
Fonte: Universidade de São Paulo. Faculdade de Odontologia de Bauru Publicador: Universidade de São Paulo. Faculdade de Odontologia de Bauru
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; ; Formato: application/pdf
Publicado em 01/12/2011 ENG
Relevância na Pesquisa
36.78%
Neonatal nutrition is an important subject in health in the short, medium and long term. In preterm newborns, nutrition assumes a predominant role for the child's overall development. Babies with uncoordinated swallowing or respiration may not have the necessary oral abilities to suck the mother's breast and will need to implement different feeding practices; one of them is changing the consistency of the milk offered. Objectives: Determine viscosity variations of untreated human and pasteurized milk without and with thickening to adapt the diet to the needs of dysphagic infants hospitalized in the Neonatal Intensive Cara Unit (NICU). Material and Methods: The authors altered the viscosity of natural infant powdered milk and, after thickening, determined and adopted a thickening standard for human milk. Untreated human and pasteurized milk was thickened in concentrations of 2%, 3%, 5% and 7% and the viscosity were determined every 20 minutes for a period of 60 minutes at a temperature of 37ºC. Results: The infant lactose formula thickened at concentrations of 2% and 3% produced viscosities of 8.97cP and 27.73 cP, respectively. The increases were significantly different after 1 hour. Inversely, untreated human milk at 2%, 3%, 5% and 7% produced diminished viscosity over time; the changes were more accentuated in the first 20 minutes. In pasteurized human milk...

A study of the effect of ink viscosity on dot gain in offset lithography

Dailey, David
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
EN_US
Relevância na Pesquisa
36.76%
Dot gain is the enlargement which takes place in a dot from the time the dot is captured or generated on the film until it is printed. Dot gain can cause many problems, including color variation and loss of contrast, and if uncontrolled is one of the main contributors to waste in offset lithography. Of the many factors influencing dot gain, inks have been found to be a major contributor. One property recommended for further investigation is ink viscosity, which is the resistance to flow of an ink. The purpose of this study was to investigate the effect of ink viscosity on dot gain in offset lithography. It was found that as ink viscosity increases, dot gain will decrease, and if ink viscosity is optimized, dot gain will be optimized. Experimentation was done on a single color, single impression sheet-fed lithographic press, with five inks of different viscosities. Results of this experiment show that ink viscosity is significant in affecting the amount of dot gain that occurs. Inks with 15 and 20 percent solvent added, which were less than 1000 poise viscosity, were found cause the significant difference. Other factors found to be significant were screen ruling and paper absorbency. The Yates Method of Analysis of Variance and graphing were used to analyze the data.

A MEMS viscosity sensor for conductive fluids

Gan Chau, Luis
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
EN_US
Relevância na Pesquisa
36.76%
MEMS Viscosity sensors are widely used in different applications nowadays. MEMS sensors are created by making them small in size almost penny-like sized. With low power consumption, cheap costs of production, and mass production of the devices. These sensors are able to measure viscosity through three different characteristics, the frequency, amplitude and the quality factor. Each of these describes the fluids viscosity, by using a vibrational type viscometer. The sensor has been proven to work in conductive fluids after a post process fabrication of a protective layer of Parylene C. The sensors performance has been altered due to a thicker membrane, but still operates as expected. The MEMS viscosity sensor has been tested in various glycerol water mixtures to simulate conductive fluids with varying viscosity. The tests had positive outcomes, and the sensors performance was not altered, they worked as predicted. Different tests were accomplished to make sure the sensors performance remained close to normal operations after adding the protective layer of Parylene C. Four distinct oils were chosen to accomplish this variation test. Oil was chosen rather than a conductive liquid in order to prevent the sensor from damaging itself, and having to repackage another sensor and running all the previous tests. With these tests the sensor proved that adding a thin layer of Parylene C does not alter the sensors performance...

A Thermally actuated microelectromechanical (MEMS) device for measuring viscosity

Puchades, Ivan
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Dissertação
EN_US
Relevância na Pesquisa
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A thermally actuated non-cantilever-beam micro-electro-mechanical viscosity sensor is presented. The proposed device is based on thermally induced vibrations of a silicon-based membrane and its damping due to the surrounding fluid. This vibration viscometer device utilizes thermal actuation through an in-situ resistive heater and piezoresistive sensing, both of which utilize CMOS compatible materials leading to an inexpensive and reliable system. Due to the nature of the actuation, thermal analysis was performed utilizing PN diodes embedded in the silicon membrane to monitor its temperature. This analysis determined the minimum heater voltage pulse amplitude and time in order to prevent heat loss to the oil under test that would lead to local viscosity changes. In order to study the natural vibration behavior of the complex multilayer membrane that is needed for the proposed sensor, a designed experiment was carried out. In this experiment, the effects of the material composition of the membrane and the size of the actuation heater were studied in detail with respect to their effects on the natural frequency of vibration. To confirm the validity of these measurements, Finite Element Analysis and white-light interferometry were utilized. Further characterization of the natural frequency of vibration of the membranes was carried out at elevated temperatures to explore the effects of temperature. Complex interactions take place among the different layers that compose the membrane structures. Finally...

Mantle dynamics, postglacial rebound and the radial viscosity profile

Kaufmann, G; Lambeck, Kurt
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
36.8%
We infer the radial viscosity structure of the Earth's mantle from observations of long-wavelength geoid, glacially-induced sea-level changes, and changes in the Earth's rotation and gravitational field. We employ a combination of forward and formal inverse modeling of long-term mantle circulation driven by large-scale density differences deduced from seismic tomography. Based on the resulting unscaled mantle viscosity profiles, we model the time-dependent glacial isostatic adjustment of the Earth related to past and present changes in the ice-ocean mass imbalance and we deduce scaled mantle viscosity profiles, which simultaneously fit the long-wavelength geoid constraint and glacially-induced changes of the Earth's shape. Three mantle viscosity profiles are fitting the observational data equally well. All profiles are characterized by a two order of magnitude variation of viscosity within the Earth's mantle. Variations of viscosity in the upper mantle are less than one order of magnitude. In the lower mantle, the viscosity differs significantly with depth for all models. Average viscosities in the upper and lower mantle are around (2 - 5) x 1020 and (1 - 3) x 1022 Pa s, respectively. (C) 2000 Elsevier Science B.V. All rights reserved.

Glacial isostatic adjustment and the radial viscosity profile from inverse modeling

Kaufmann, Georg; Lambeck, Kurt
Fonte: American Geophysical Union Publicador: American Geophysical Union
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
36.8%
A formal inverse procedure is used to infer radial mantle viscosity profiles from several observations related to the glacial isostatic adjustment process. The data sets consist of Late Pleistocene and Holocene sea level data from Scandinavia, the Barents Sea, Central Europe, Canada, and the far field, as well as observations of changes in the Earth's rotation and gravitational field, and present-day uplift and gravity changes in Scandinavia. Inferences of mantle viscosity are robust against assumptions such as the a priori viscosity model and model discretization. However, the quality of ice sheet reconstruction remains crucial for the inverse inference. The importance to discuss regional mantle viscosity models in view of the lateral variability in mantle properties has been evident. Our inference suggests a two order of magnitude increase of mantle viscosity with depth, and volume-averaged upper and lower mantle viscosities around 7 × 1020 and 2 × 1022 Pa s, respectively. Mantle viscosity does not need to increase sharply across the 660-km seismic discontinuity. The viscosity profiles suggested are also able to reconcile the large-scale geoid anomaly related to mantle convection.