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Vazão de grãos em um silo cilíndrico: uma atividade experimental; Flow of sugar and grains of rice from a hole in the bottom of cylinder

Linares, Juan Lopez; Pastorello, Isa Mara; Arce, A. I. C.
Fonte: SOC BRASILEIRA FISICA; SAO PAULO Publicador: SOC BRASILEIRA FISICA; SAO PAULO
Tipo: Artigo de Revista Científica
POR
Relevância na Pesquisa
45.49%
O fluxo de materiais granulares é pouco discutido nos livros de física básica, apesar de que sistemas de grãos estão muito presentes na vida cotidiana. Este trabalho mostra o desenvolvimento de um sistema experimental relativamente simples para estudar a vazão de grãos de arroz e de açúcar. O aparelho é constituído por um silo cilíndrico com uma abertura circular no fundo e uma balança. A balança é conectada a um computador para monitorar a massa como função do tempo dos grãos que saem do silo. Foram realizadas medidas para diferentes diâmetros da abertura de saída do silo e diferentes alturas iniciais da coluna de grãos. Para fins didáticos, o mesmo sistema foi usado para medir a vazão de água. Os resultados claramente ilustram as diferenças entre os dois tipos de fluidos e podem ser facilmente reproduzidos em sala de aulas.; In basic physics books practically anything is discussed about the flux of granular materials, even though grains systems are widely present in the everyday life. In this work was developed a relatively simple experimental system to study the flow of rice and sugar grains out of a cylindrical silo with a circular aperture at the bottom. Measurements were repeated at different diameters of the circular holes and different initial heights of the grains column. For didactic motivations...

Medição de propriedades viscoelásticas de líquidos por ultrassom.; Ultrasonic measurement of the viscoelastic properties of liquids.

Franco Guzmán, Ediguer Enrique
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 23/06/2010 PT
Relevância na Pesquisa
45.73%
A medição das propriedades viscoelásticas de líquidos por ultrassom tem sido um tema de pesquisa importante desde meados do século XX, principalmente, pela possibilidade de realizar medições em tempo real da viscosidade. O método de medição baseia-se na determinação do coeficiente de reflexão complexo (magnitude e fase) de ondas de cisalhamento refletidas da interface definida entre um sólido e uma amostra líquida. Enquanto a medição da magnitude é relativamente simples e precisa, a medição da fase é muito difícil devido à forte dependência da temperatura, que gera uma incerteza muito grande. No entanto, na medição da viscosidade em regime newtoniano somente a magnitude é requerida. Ocorre que os resultados experimentais reportados até o momento na literatura não coincidem quantitativamente com a teoria. Neste trabalho, uma nova técnica que permite determinar com boa precisão a magnitude do coeficiente de reflexão e, por conseguinte, a viscosidade de líquidos em regime newtoniano foi desenvolvida. Foi mostrado que a maioria dos líquidos testados apresentam comportamento newtoniano à frequência de trabalho de 1MHz, com exceção de alguns óleos automotivos de alta viscosidade, que possuem claramente comportamento viscoelástico. Desvios menores que 12...

Simulação de escoamentos transientes em dutos de transporte de líquidos; Simulation of transient flow in pipelines for the transportation of liquids

Santos, Fernanda Olegario dos
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 08/07/2010 PT
Relevância na Pesquisa
45.49%
O transporte de fluidos e produtos petroquímicos através de malhas dutoviárias é uma opção extremamente difundida, tanto em aplicações industriais envolvendo longas distâncias quanto em sistemas de distribuição nos quais um determinado fluido deve ser entregue a um grande número de usuários ou processos. Em ambos os casos, para uma operação eficiente e segura da malha, é necessário um sistema de detecção de vazamentos, que detecta e avalia rapidamente a ocorrência de um vazamento, especialmente quando o fluido transportado for tóxico e/ou inflamável. Neste sentido, a análise hidráulica em escoamentos transitórios tem sido particularmente útil aos propósitos de detecção de vazamentos. Sistemas de observação para essa análise podem revelar uma quantidade substancial de informações relativas às propriedades físicas e o nível de integridade do sistema, pois as ondas de pressão resultantes são afetadas pelos diversos dispositivos e fenômenos, incluindo os vazamentos. Este trabalho apresenta a construção e validação de um modelo de simulação numérica adequado para uma nova técnica de detecção de vazamento, baseada na inspeção acústica ativa da tubulação, capaz de detectar vazamentos pré-existentes. Resultados numéricos foram comparados com os obtidos de ensaios experimentais realizados no oleoduto piloto do Laboratório de Escoamentos Multifásicos Industriais da Universidade de São Paulo...

Caracterização por espalhamento de luz de dispersões aquosas de agregados lipídicos aniônicos; Structural characterization of aqueous dispersions of the anionic phospholipid DMPG by light scattering

Enoki, Thaís Azevedo
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 19/11/2010 PT
Relevância na Pesquisa
45.49%
Neste trabalho caracterizamos dispersões aquosas de vesículas lipídicas por espalhamento de luz. Utilizamos os diferentes métodos da técnica: espalhamento de luz estático (SLS) e espalhamento de luz dinâmico (DLS) no estudo desses sistemas. No SLS a intensidade da luz espalhada foi coletada em vários ângulos de espalhamento para diferentes concentrações, e obtivemos os seguintes parâmetros: peso molecular, Mw, raio de giração, Rg, que esta relacionado _a forma do centro espalhador e segundo coeficiente do virial, A2, que está relacionado a interações entre partículas. No DLS a correlação da luz espalhada foi obtida em função do tempo, para vários ângulos e concentrações. As medidas de DLS fornecem o coeficiente de difusão dos centros espalhadores, que estão relacionados a seus diâmetros efetivos. Em especial a técnica de SLS foi amplamente estudada para desenvolvimento de uma apostila coordenada pela Profa. Vera B. Henriques. Nesta apostila a teoria de espalhamento de luz estático está apresentada através de uma abordagem diferente da convencional, sob o ponto de vista da mecânica estatística. O principal objeto de estudo neste trabalho foram as dispersões aquosas de dimiristoil fosfatidil glicerol (DMPG). O DMPG...

Forma de linha do espectro Raman do ânion croconato em diversos ambientes; Line form of the Raman spectrum of croconate anion in diverse environments

Cavalcante, Ary de Oliveira
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 10/06/2003 PT
Relevância na Pesquisa
65.7%
A espectroscopia Raman é utilizada para obtenção de informações dinâmicas de líquidos. A habilidade do ânion croconato como sonda das interações é testada no estudo do processo de transição vítrea no sal croconato de tetra-n-butilamônio (CTBA), [(C4H9)4N]2C5O5.4H2O, um líquido muito viscoso com temperatura de transição vítrea, Tg, em cerca de 298K. As funções de correlação temporais foram obtidas pela transformada de Fourier do contorno dos modos do croconato, C5O5-2. Posteriormente, foram ajustados modelos teóricos para o defasamento vibracional a essas funções de correlação, como o modelo de Kubo. Nesse estudo foi possível encontrar assinaturas espectroscópicas da transição vítrea que são interpretadas do ponto de vista da dinâmica do ânion croconato e das interações deste ânion com o ambiente em que ele se insere. A miscibilidade do CTBA em acetonitrila permitiu que fossem feitos estudos do defasamento do ânion croconato neste solvente. Nestes estudos, nota-se um contraste com os resultados obtidos para a solução aquosa saturada do sal Li2C5O5. O valor encontrado para tempo de correlação da flutuação da freqüência vibracional, τc, na solução diluída em acetonitrila (τc ≈ 0...

Experimental study of the complex reflection coefficient of shear waves from the solid-liquid interface

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: 803-809
ENG
Relevância na Pesquisa
45.77%
The determination of the reflection coefficient of shear waves reflected from a solid-liquid interface is an important method in order to study the viscoelastic properties of liquids at high frequency. The reflection coefficient is a complex number. While the magnitude measurement is relatively easy and precise, the phase measurement is very difficult due to its strong temperature dependence. For that reason, most authors choose a simplified method in order to obtain the viscoelastic properties of liquids from the measured coefficient. In this simplified method, inconsistent viscosity results are obtained because pure viscous behavior is assumed and the phase is not measured. This work deals with an effort to improve the experimental technique required to measure both the magnitude and phase of the reflection coefficient and it intends to report realistic values for oils in a wide range of viscosity (0.092 - 6.7 Pa.s). Moreover, a device calibration process is investigated in order to monitor the dynamic viscosity of the liquid.

Analysis of the fluid-dynamic behavior of fluidized and vibrofluidized bed containing glycerol

Daleffe,R. V.; Freire,J. T.
Fonte: Brazilian Society of Chemical Engineering Publicador: Brazilian Society of Chemical Engineering
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2004 EN
Relevância na Pesquisa
45.67%
The fluid-dynamic characteristics of fluidized and vibrofluidized beds of inert particles in liquids are being widely studied by researchers interested in understanding and modeling the paste drying process. In this work characteristic fluid-dynamic curves of pressure drop versus air velocity were obtained for fluidized and vibrofluidized beds with glycerol. Glycerol was used as a standard fluid to simulate a paste in the bed, and "ballotini" glass spheres were used as inert particles. The fluid-dynamic behavior as well as the quality of the fluidization regimes was analyzed through pressure drop versus air velocity curves and visual observation of the flow patterns in the beds. The results indicated that standard deviation curves are a useful tool for gaining an understanding of the fluid-dynamic behavior of a vibrofluidized bed. They allow detection of changes in the fluid-dynamic behavior which were not observed by analyzing only the pressure drop versus air velocity curves. For fluidized beds (G=0.00), it was also observed that analysis of curves of standard deviations of pressure drop may help in the estimation of more accurate values of minimum fluidization velocities.

Rigidity percolation and the spatial heterogeneity of soft modes in disordered materials

de Souza, Vanessa K.; Harrowell, Peter
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
45.49%
We show how the spatial character of unconstrained motion in a network of bonds can be directly inferred from the topological arrangement of constraints. Relaxation time scales of these soft modes are determined, and from this information we generate spatial maps of the heterogeneous distribution of relaxation times in the disordered network. We show that the nature of the dynamic heterogeneity and its sensitivity to changes in bond configuration depends dramatically on the proximity of the system to the rigidity percolation point.

Spatial dimension and the dynamics of supercooled liquids

Eaves, Joel D.; Reichman, David R.
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
45.7%
Inspired by recent theories that apply ideas from critical phenomena to the glass transition, we have simulated an atomistic model of a supercooled liquid in three and four spatial dimensions. At the appropriate temperatures and density, dynamic density correlation functions in three and four spatial dimensions correspond nearly exactly. Dynamic heterogeneity, quantified through the breakdown of the Stokes–Einstein relationship, is weaker in four dimensions than in three. We discuss this in the context of recent theories for dynamical heterogeneity. Because dimensionality is a crucially important variable, our work adds a stringent test for emerging theories of glassy dynamics.

Fingerprints of order and disorder on the high-frequency dynamics of liquids

Giordano, Valentina M.; Monaco, Giulio
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
55.83%
It is largely accepted that liquids are characterized by a short-range order usually corresponding to that of the solid phase at the same density. It is less clear to what extent dynamic properties of liquids and crystals can be compared. In particular, high-frequency collective excitations reminiscent of phonons in solids exist as well in liquids. They are however traditionally discussed in terms of relaxation processes characteristic of the liquid phase. We report here on a quantitative comparison of the collective excitations in liquid and polycrystalline sodium. We show that liquid sodium exhibits acoustic excitations of both longitudinal and transverse polarization at frequencies strictly related to those of the corresponding crystal. The only relevant difference between the liquid and the polycrystal appears in the broadening of the excitations: An additional disorder-induced contribution comes into play in the case of the liquid, which we show to be related to the distribution of local structures around the average one. These results establish a direct connection between structural and dynamic properties of liquids, with short-range order and overall structural disorder leaving very specific fingerprints.

Cluster formation restricts dynamic nuclear polarization of xenon in solid mixtures

Kuzma, N. N.; Pourfathi, M.; Kara, H.; Manasseh, P.; Ghosh, R. K.; Ardenkjaer-Larsen, J. H.; Kadlecek, S. J.; Rizi, R. R.
Fonte: American Institute of Physics Publicador: American Institute of Physics
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
45.58%
During dynamic nuclear polarization (DNP) at 1.5 K and 5 T, 129Xe nuclear magnetic resonance (NMR) spectra of a homogeneous xenon/1-propanol/trityl-radical solid mixture exhibit a single peak, broadened by 1H neighbors. A second peak appears upon annealing for several hours at 125 K. Its characteristic width and chemical shift indicate the presence of spontaneously formed pure Xe clusters. Microwave irradiation at the appropriate frequencies can bring both peaks to either positive or negative polarization. The peculiar time evolution of 129Xe polarization in pure Xe clusters during DNP can be modelled as an interplay of spin diffusion and T1 relaxation. Our simple spherical-cluster model offers a sensitive tool to evaluate major DNP parameters in situ, revealing a severe spin-diffusion bottleneck at the cluster boundaries and a significant sample overheating due to microwave irradiation. Subsequent DNP system modifications designed to reduce the overheating resulted in four-fold increase of 129Xe polarization, from 5.3% to 21%.

Experimental and theoretical modeling of DNAPL transport in vertical fractured media; Experimental and theoretical modeling of dense, non-aqueous phase liquids transport in vertical fractured media

Levy, Laurent Claude, 1973-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 2 v. (614 p.); 6654704 bytes; 6654459 bytes; application/pdf; application/pdf
ENG
Relevância na Pesquisa
45.62%
In recent years, groundwater contamination by dense, non-aqueous phase liquids (DNAPLs) such as chlorinated solvents and polychlorinated biphenyls (PCBs) has become an important environmental concern in many industrialized areas. Accidental spills, poor storage facilities and inadequate disposal practices are factors contributing to the release of these chemicals into the subsurface environment. The detection and presence of DNAPLs at hazardous waste sites is likely to be a significant limiting factor in the site remediation process. This is especially true for the remediation of complex subsurface formations, such as fractured bedrock. This work has developed a new model describing DNAPL infiltration into a water- saturated, vertical fracture idealized as a circular section capillary tube. A series of laboratory and geotechnical centrifuge experiments of DNAPL infiltration into vertical capillary tubes was performed to demonstrate the validity of the model, and examine the role played by capillary, gravity, viscous, and inertia forces during the infiltration process. The new model can be used to better understand the processes likely to influence DNAPL transport and remediation in real fracture systems.; (cont.) Laboratory infiltration experiments showed that the common assumption of perfect wetting at the DNAPL/water interface is incorrect. Furthermore...

Experimental study of the atomization process for viscous liquids by meniscus perturbation and micro air jet

Lee, Heejin, 1976-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 79 leaves; 4107287 bytes; 4115587 bytes; application/pdf; application/pdf
EN_US
Relevância na Pesquisa
45.68%
An experimental study was performed to understand the atomization process in the specialized printing method which consists of the high frequency oscillating motion of a needle and a micro air jet. Highly viscous liquids, such as glycerin and acrylic paint were successfully printed with this printing method within the line width of 1 mm. High-speed imaging technique was used to observe the evolution and mechanical perturbation of a liquid meniscus which is coated on the oscillating needle. Various parameters which affect print patterns were identified to understand and control the atomization process occurring at the oscillating needle. For time-controlled atomization or printing, a pulse air jet system was implemented to print liquids only when it is demanded, and it was shown that the period of atomization can be controlled by the air jet on-and-off. The inertial coating process was studied to explain the dynamic meniscus profile, compared with static meniscus. Kinematic analysis of the needle motion was performed, which shows that the needle motion is a sinusoidal one undergoing inertial coating. Liquid sheet breakup mechanism in the presence of the air stream was also studied in conjunction with the principle of the air- blast atomizer. Performing as a printing device or a droplet generator...

Slow dynamics in supercooled liquids : matrix formalism, mode coupling and glass transition

Wu, Jianlan, 1976-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 169, [1] p.; 5109951 bytes; 5131120 bytes; application/pdf; application/pdf
EN_US
Relevância na Pesquisa
45.81%
In this thesis, slow dynamics of supercooled liquids are investigated in the framework of the mode-coupling theory (MCT). Following the real-time generalized Langevin equation in Newtonian liquids, the dynamic Gaussian factorization scheme leads to mode-coupling (MC) closures. As an alternative approach to the projection operator technique, the matrix formalism based on the complete basis set is developed for studying dynamics in many-particle systems. In a dissipative system, the MC closures have to be obtained from irreducible memory kernels instead of standard memory kernels. The matrix formalism provides a new explanation of this preference by comparing linear and nonlinear relaxation time scales, and generalizes the irreducible memory kernel to higher orders. A simple kinetic spin model, the East model, is used to test the matrix formalism and the mode-coupling closures, where the dynamic Gaussian factorization scheme is replaced by a linear approximation due to the kinetic constraint. Next, slow dynamics in Brownian liquids is studied and generalization of MC closures is derived for both coherent and incoherent intermediate scattering functions. Predictions of nonergodic parameters for these two correlation functions in a hard-sphere colloidal suspension improve as the order of the MC closure increases. New glass-transition phenomena are revealed by applying the standard MC closure to a two-Yukawa colloidal suspension.; by Jianlan Wu.; Thesis (Ph. D.)--Massachusetts Institute of Technology...

Thermorheological Properties Near the Glass Transition of Oligomeric Poly(methyl methacrylate) Blended with Acrylic Polyhedral Oligomeric Silsesquioxane Nanocages

Kopesky, Edward T.; Boyes, Stephen G.; Treat, Neil; Cohen, Robert E.; McKinley, Gareth H.
Fonte: MIT - Massachusetts Institute of Technology Publicador: MIT - Massachusetts Institute of Technology
Tipo: Pré-impressão Formato: 598728 bytes; application/pdf
EN_US
Relevância na Pesquisa
45.61%
Two distinct oligomeric species of similar mass and chemical functionality (Mw ≈ 2,000 g/mol), one a linear methyl methacrylate oligomer (radius of gyration Rg ≈ 1.1 nm) and the other a hybrid organic-inorganic polyhedral silsesquioxane nanocage (methacryl-POSS, r ≈ 1.0 nm), were subjected to thermal and rheological tests to compare the behaviors of these geometrically dissimilar molecules over the entire composition range. The glass transition temperatures of the blends varied monotonically between the glass transition temperatures of the pure oligomer (Tg = −47.3°C) and the pure POSS (Tg = −61.0°C). Blends containing high POSS contents (with volume fraction φ_POSS ≥ 0.90) exhibited enhanced enthalpy relaxation in DSC measurements, and the degree of enthalpy relaxation was used to calculate the kinetic fragility indices m of the oligomeric MMA (m = 59) and the POSS (m = 74). The temperature dependences of the viscosities were fitted by the free volume-based WLF-VFT framework and a dynamic scaling relation. The calculated values of the fragility from the WLF-VFT fits were similar for the POSS (m = 82) and for the oligomer (m = 76), and the dynamic scaling exponent was similar for the oligomeric MMA and the POSS. Within the range of known fragilities for glass-forming liquids...

Thermorheological properties of nanostructured dispersions

Gordon, Jeremy B
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 149 p.
ENG
Relevância na Pesquisa
45.62%
Nanostructured dispersions, which consist of nanometer-sized particles, tubes, sheets, or droplets that are dispersed in liquids, have exhibited substantially higher thermal conductivities over those of the liquids alone. While it is desirable to synthesize a fluid that has improved heat transfer characteristics, it is necessary that the viscosity remain low, so as not to appreciably increase the pumping power needed to employ these fluids in "real world" applications. To this end, the theological and thermal properties of twenty-six different nanostructured dispersions were examined. In terms of rheometry, both steady flow and creep tests were employed, while the transient hot wire technique was utilized to perform measurements of the thermal conductivity of each fluid. Characterization of the dispersed phase was completed using dynamic light scattering and transmission electron microscopy. In particular, the dispersion properties examined were nanostructure material, nanoparticle size, base fluid material, nanostructure concentration, and presence of a surfactant. It was observed that several of the fluids or nanopowders obtained from commercial manufacturers either contained no particles, had the presence of a relatively large proportion of water in ethylene glycol-based fluids...

Enabling microscopic simulators to perform system-level analysis of viscoelastic flows

Anwar, Zubair
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 261 p.
ENG
Relevância na Pesquisa
45.49%
State-of-the-art methods for simulating viscoelastic flows couple the conservation equations for mass and momentum with a model from kinetic theory that describes the microstructural state of the polymer. Introduction of appropriate numerical discretization and boundary conditions for these equations leads to a hybrid simulation for studying the dynamic behavior of polymeric liquids in complex geometries. This approach represents a rare example of a successful multiscale solution of a physical problem, as it allows investigation of arbitrary models of kinetic theory. The simulations, however, are not amenable to standard numerical techniques for system-level stability, bifurcation, and control analysis as this requires closed form equations. These simulation either use stochastic descriptions for the polymer microstructure that cannot be reduced to closed form, or involve equations for the evolution of a distribution of polymer conformations, which can only be written in closed form by invoking mathematical closure approximations that can have a significant qualitative impact on the predictive ability of these simulations. The focus of this thesis was to develop a novel numerical method that can enable hybrid simulations to perform system-level analysis of polymeric flows. This numerical approach has been applied directly to kinetic theory models and hybrid simulations to obtain stationary states and associated bifurcations and stability information. The method is general in its applicability in that it treats kinetic theory models and hybrid simulations as black boxes that are then used to obtain system-level information without any modification. The methods developed here are illustrated in a variety of problems.; (cont) Steady state results have been obtained for the non-interacting rigid dumbbell model in steady shear...

Ultrafast dynamic ellipsometry of laser driven shock waves

Bolme, Cynthia Anne
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 229 p.
ENG
Relevância na Pesquisa
45.78%
The experimental measurement technique of ultrafast dynamic ellipsometry (UDE) was developed for measuring material motion and changes in optical properties of samples under laser driven shock loading. Ultrafast dynamic ellipsometry, a technique based on space-shifted spectral interferometry, uses the time-dependent frequency of a chirped laser pulse to provide time encoding, allowing the picosecond probing of material dynamics in a single shot. With this technique, the sample is probed at two different incident angles with both s- and p-polarized light, which measures the motion of the material and any change in its complex refractive index. Ultrafast dynamic ellipsometry was first used to ascertain the Hugoniot and the shocked refractive indices of thin polymer films of polycarbonate, poly(methyl methacrylate) (PMMA), poly(chlorotrifluoroethylene-co-vinylidene fluoride) (Kel-F 800), and polydimethylsiloxane (Sylgard 184). Next, UDE was used to measure the Hugoniots of liquid samples over a range of nearly one-dimensional stresses in a single laser shot by capitalizing on the spatial energy distribution of the shock generating laser beam. Using the spatially resolved UDE data, the Hugoniots and shocked refractive indices of cyclohexane...

Estudo comparativo de algumas propriedades dinâmicas de líquidos e grãos na sala de aula; Comparative study of some dynamic properties of liquids and grains in the classroom

LÓPEZ, J.; DEMARCHI, T.; AKAMATSU, M.; VERCIK, A.
Fonte: Sociedade Brasileira de Física Publicador: Sociedade Brasileira de Física
Tipo: Artigo de Revista Científica
POR
Relevância na Pesquisa
65.86%
Visando entender as diferenças entre as propriedades dinâmicas dos materiais granulares e as propriedades dinâmicas dos líquidos, foram realizados experimentos usando água e grãos de arroz e açúcar. Os experimentos requerem poucos recursos e foram pensados para que possam ser desenvolvidos com facilidade na sala de aula ou num laboratório de ensino. Os resultados mostraram que o fluxo de grãos difere significativamente do fluxo de líquidos.; In order to understand the differences in the dynamic properties between granular materials and liquids, experiments using water, rice and sugar grains were performed. The experiments require few material resources and were thought so as to be easily made in a classroom or in a teaching laboratory. The results showed that grain's flow differs significantly from that of liquids.; Banco Santander

Connection between dynamics and thermodynamics of liquids on the melting line

Fragiadakis, D.; Roland, C. M.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 02/03/2011
Relevância na Pesquisa
45.75%
The dynamics of a large number of liquids and polymers exhibit scaling properties characteristic of a simple repulsive inverse power law (IPL) potential, most notably the superpositioning of relaxation data as a function of the variable TV{\gamma}, where T is temperature, V the specific volume, and {\gamma} a material constant. A related scaling law, TmVm{\Gamma}, with the same exponent {\Gamma}={\gamma}, links the melting temperature Tm and volume Vm of the model IPL liquid; liquid dynamics is then invariant at the melting point. Motivated by a similar invariance of dynamics experimentally observed at transitions of liquid crystals, we determine dynamic and melting point scaling exponents {\gamma} and {\Gamma} for a large number of non-associating liquids. Rigid, spherical molecules containing no polar bonds have {\Gamma}={\gamma}; consequently, the reduced relaxation time, viscosity and diffusion coefficient are each constant along the melting line. For other liquids {\gamma}>{\Gamma} always; i.e., the dynamics is more sensitive to volume than is the melting point, and for these liquids the dynamics at the melting point slows down with increasing Tm (that is, increasing pressure).; Comment: 20 pages, 8 figures, 1 table