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Critical Properties (critical + property)

Distribution by Scientific Domains

Polymers and Materials Science	40%
Chemistry	40%

Selected Abstracts

Processing Dependence of Texture, and Critical Properties of YBa2Cu3O7,, Films on RABiTS Substrates by a Non-Fluorine MOD Method

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2006
Y. Xu
YBa2Cu3O7,, (YBCO or Y123) films on rolling-assisted biaxially textured substrates (RABiTS) were prepared via a fluorine-free metallorganic deposition (MOD) through spin coating, burnout, and high temperature anneal. The effects of substrate texture and surface energy of the CeO2 cap layer were investigated. Except for the commonly accepted key factors, such as the textures of substrate and buffer layers, we found some other factors, for example, the deposition temperature of the cap layer, are also critical to the epitaxial growth of Y123 phase. With the CeO2 cap layer deposited at relative high temperature of 700°C, a critical current density, Jc, over 1 MA/cm2 has been demonstrated for the first time on Ni-RABiTS by a fluorine-free MOD method. Whereas for samples with CeO2 cap layers deposited at a lower temperature of 600°C, even though XRD data showed a better texture on these buffer layers, texture degradations of YBCO grains under the optimized processing conditions were observed and a lower oxygen partial pressure around 40 ppm was necessary for the epitaxial growth of Y123 phase. As a result, Jc fell to 0.45 MA/cm2 at 77 K. The observed phenomena points to the change of surface energy and reactivity of the CeO2 cap layer with respect to the CeO2 deposition temperature. In this paper, the YBCO phase diagram was also summarized. [source]

A New Group Contribution Method based on Equation of State Parameters to Evaluate the Critical Properties of Simple and Complex Molecules

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2006
José O. Valderrama
Abstract A new group contribution method to evaluate the critical properties (temperature, pressure and volume) is presented and applied to estimate the critical properties of biomolecules. Similar to other group contribution methods, the one proposed here divides the molecule into conveniently defined groups and evaluates the properties as the sum of the different contributions according to a specified model equation for each of the properties. The proposed method consists of a one-step calculation that uses simple model equations and does not require additional data besides the knowledge of the structure of the molecule, except for isomers. For these substances the normal boiling temperature, the molecular mass and the number of atoms in the molecule are used to distinguish among isomers. The method is applicable to high molecular weight compounds, as most biomolecules and large molecules present in natural products. On présente une nouvelle méthode de contribution de groupe pour évaluer les propriétés critiques (température, pression et volume) de biomolécules. Comme dans le cas d'autres méthodes de contribution de groupe, celle qu'on présente ici divise la molécule en groupes définis de manière pratique et évalue les propriétés comme la somme des différentes contributions selon une équation de modèle spécifique pour chacune des propriétés. La méthode proposée consiste en un calcul en une étape qui utilise des équations de modèle simple et, excepté pour les isomères, ne requiert pas de données supplémentaires hormis la structure de la molécule. Pour ces substances, on utilise la température d'ébullition normale, la masse moléculaire et le nombre d'atomes dans la molécule pour distinguer entre les isomères. La méthode est applicable à des composés de poids moléculaire élevé, comme la plupart des biomolécules et des molécules larges présentes dans les produits naturels. [source]

Critical properties and stability of stationary solutions in multitransonic pseudo-Schwarzschild accretion

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2006
Soumini Chaudhury
ABSTRACT For inviscid, rotational accretion flows, both isothermal and polytropic, a simple dynamical system analysis of the critical points has given a very accurate mathematical scheme to understand the nature of these points, for any pseudo-potential by which the flow may be driven on to a Schwarzschild black hole. This allows us for a complete classification of the critical points for a wide range of flow parameters, and shows that the only possible critical points for this kind of flow are saddle points and centre-type points. A restrictive upper bound on the angular momentum of critical solutions has been established. A time-dependent perturbative study reveals that the form of the perturbation equation, for both isothermal and polytropic flows, is invariant under the choice of any particular pseudo-potential. Under generically true outer boundary conditions, the inviscid flow has been shown to be stable under an adiabatic and radially propagating perturbation. The perturbation equation has also served the dual purpose of enabling and understanding the acoustic geometry for inviscid and rotational flows. [source]

Wet and Dry Adhesion Properties of Self-Selective Nanowire Connectors

ADVANCED FUNCTIONAL MATERIALS, Issue 19 2009
Hyunhyub Ko
Abstract Here, the wet and dry adhesion properties of hybrid Ge/parylene nanowire (NW) connectors are examined. The ability of the NW connectors to bind strongly even under lubricating conditions, such as mineral oil, sheds light on the dominant role of van der Waals interactions in the observed adhesion. The superhydrophobic surface of the NW connectors enables the wet, self-cleaning of contaminant particles from the surface, similar to the lotus effect. In addition, the effect of NW length on the shear adhesion strength, repeated usability, and robustness of the connectors, all critical properties for applications that require reversible binding of components, is examined. [source]

Metamagnetism Seeded by Nanostructural Features of Single-Crystalline Gd5Si2Ge2

ADVANCED MATERIALS, Issue 37 2009
James D. Moore
Gd5Si2Ge2 belongs to the class of materials known as metamagnets that show promise for application in room-temperature magnetic refrigeration using a phenomenon known as the magnetocaloric effect. Here we image the metamagnetic transition using a local scanning Hall probe and reveal how the microstructure controls the critical properties. [source]

Volume-translated equations of state: Empirical approach and physical relevance

AICHE JOURNAL, Issue 6 2003
Leonid V. Yelash
The volume translation technique is widely applied in chemical engineering modeling of phase behavior and thermodynamic properties. This empirical correction of the molar volume improves the correlation of liquid densities when cubic equations of state are employed. Based on a recently proposed method of analyzing equations of state, the influence of the volume translation on the properties obtained from an equation of state, such as virial coefficients, as well as on the phase behavior, critical properties, the isobaric thermal expansion coefficient, and the heat capacities of pure substances is investigated. The influence of different kinds of temperature-dependent volume translations is investigated and compared to approaches that originate from theoretical considerations. The investigation shows that empirical as well as theoretical approaches for the development of equations of state can exhibit nonphysical behavior. However, the understanding of the reasons for such problems can help to develop reliable equations of state based on both kinds of method. [source]

Critical behavior in quenched random structures: Mean-field lattice-gas approach

AICHE JOURNAL, Issue 2 2001
S. De
A new mean-field equation-of-state model is proposed for predicting the critical behavior of fluids confined in porous, random structures. The approach is based on a lattice-gas formalism and incorporates effects of both fluid confinement and energetically heterogeneous interactions between fluid molecules and pore surfaces. The model was used to predict a variety of thermodynamic properties in these systems, including the dependence of the confined fluid's critical properties on the porosity and relative strength of fluid,fluid and fluid,pore interaction energies. The study of suface-energy heterogeneities show that they significantly affect the critical temperature of the confined fluid, at a given porosity, compared to the uniform energy case. Comparison of the model performance with both grand canonical Monte Carlo simulation results and a set of adsorption data in a silica gel suggest that the approach taken here provides a useful analytic method for calculating physical properties in complex systems of this kind. [source]

Wood-thermoplastic composites manufactured using beetle-killed spruce from Alaska

POLYMER ENGINEERING & SCIENCE, Issue 1 2009
Vikram Yadama
The primary objectives of the study were to characterize the critical properties of wood flour produced using highly deteriorated beetle-killed spruce for wood-plastic composite (WPC) production and evaluate important mechanical and physical properties of WPC extruded using an industry standard formulation. Chemical composition analysis indicated no significant differences in wood constituents between highly deteriorated and sound wood. Preliminary investigation with Fourier transform infrared spectroscopy (FTIR), however, indicated partial degradation or depolymerization of carbohydrate components in highly deteriorated wood compared to sound wood from green trees; effects of these changes could be seen in cell collapse and poor interaction between thermoplastic matrix and deteriorated wood fiber. Physical and mechanical properties of extruded WPCs manufactured from highly deteriorated material were comparable to WPC properties produced using pine wood flour that served as a control material. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers [source]

A New Group Contribution Method based on Equation of State Parameters to Evaluate the Critical Properties of Simple and Complex Molecules

Process vs resource-oriented Petri net modeling of automated manufacturing systems,

ASIAN JOURNAL OF CONTROL, Issue 3 2010
NaiQi Wu
Abstract Since the 1980s, Petri nets (PN) have been widely used to model automated manufacturing systems (AMS) for analysis, performance evaluation, simulation, and control. They are mostly based on process-oriented modeling methods and thus termed as process-oriented PN (POPN) in this paper. The recent study of deadlock avoidance problems in AMS led to another type of PN called resource-oriented PN (ROPN). This paper, for the first time, compares these two modeling methods and resultant models in terms of modeling power, model complexity for analysis and control, and some critical properties. POPN models the part production processes straightforwardly, while ROPN is more compact and effective for deadlock resolution. The relations between these two models are investigated. Several examples are used to illustrate them. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society [source]