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Characteristic Parameters (characteristic + parameter)

Distribution by Scientific Domains

Engineering	46%
Physics and Astronomy	20%
Chemistry	13%

Selected Abstracts

Photothermal and accompanied phenomena of selective nanophotothermolysis with gold nanoparticles and laser pulses

LASER PHYSICS LETTERS, Issue 11 2008
V.K. Pustovalov
Abstract In medical applications of laser and nanotechnology to diagnosis and treat cancer or microorganisms, understanding of lased-induced photothermal (PT) and accompanied phenomena around nanoparticles are crucial for optimization and bringing this promising technology to bedside. We analyzed the main Ptbased effects in and around gold nanoparticles under action of short (nano-, pico-, and femtosecond) laser pulses with focus on photoacoustic effects due to the thermal expansion of nanoparticles and liquid around them, thermal protein denaturation, explosive liquid vaporization, melting and evaporation of nanoparticle, optical breakdown initiated by nanoparticles and accompanied to shock waves and explosion (fragmentation) of gold nanoparticles. Characteristic parameters for these processes such as the temperature and pressures levels, and laser intensity thresholds among others are summarized to provide basis for comparison of different mechanisms of selective nanophotothermolysis and diagnostics of different targets (e.g., cancer cells, bacteria, viruses). (© 2008 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source]

Characteristic parameters for CPWs on a very thin dielectric layer

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 3 2005
Ji-Xiang Zhao
Abstract In this paper, approximate analytical expressions for characteristic parameters of CPWs on a very thin dielectric layer are given. The "crowding phenomenon" that occurs during the process of conformal mapping is overcome. Combining these expressions with the partial-capacitance method, the characteristic parameters for CPWs on a multidielectric layered substrate are computed and are found to agree well with the test data. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 240,241, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20783 [source]

Isoelectric points of viruses

JOURNAL OF APPLIED MICROBIOLOGY, Issue 2 2010
B. Michen
Summary Viruses as well as other (bio-)colloids possess a pH-dependent surface charge in polar media such as water. This electrostatic charge determines the mobility of the soft particle in an electric field and thus governs its colloidal behaviour which plays a major role in virus sorption processes. The pH value at which the net surface charge switches its sign is referred to as the isoelectric point (abbreviations: pI or IEP) and is a characteristic parameter of the virion in equilibrium with its environmental water chemistry. Here, we review the IEP measurements of viruses that replicate in hosts of kingdom plantae, bacteria and animalia. IEPs of viruses are found in pH range from 1·9 to 8·4; most frequently, they are measured in a band of 3·5 < IEP < 7. However, the data appear to be scattered widely within single virus species. This discrepancy is discussed and should be considered when IEP values are used to account for virus sorption processes. [source]

Rendering natural waters taking fluorescence into account

COMPUTER ANIMATION AND VIRTUAL WORLDS (PREV: JNL OF VISUALISATION & COMPUTER ANIMATION), Issue 5 2004
By E. Cerezo
Abstract The aim of the work presented here is to generalize a system, developed to treat general participating media, to make it capable of considering volumetric inelastic processes such as fluorescence. Our system, based on the discrete ordinates method, is adequate to treat a complex participating medium such as natural waters as it is prepared to deal with not only anisotropic but also highly peaked phase functions, as well as to consider the spectral behaviour of the medium's characteristic parameters. It is also able to generate detailed quantitative illumination information, such as the amount of light that reaches the medium boundaries or the amount of light absorbed in each of the medium voxels. First, we present an extended form of the radiative transfer equation to incorporate inelastic volumetric phenomena. Then, we discuss the necessary changes in the general calculation scheme to include inelastic scattering. We have applied all this to consider the most common inelastic effect in natural waters: fluorescence in chlorophyll-a. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Influence of dynamic soil,structure interaction on the nonlinear response and seismic reliability of multistorey systems

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 3 2007
Armando Bárcena
Abstract A set of reinforced concrete structures with gravitational loads and mechanical properties (strength and stiffness) representative of systems designed for earthquake resistance in accordance with current criteria and methods is selected to study the influence of dynamic soil,structure interaction on seismic response, ductility demands and reliability levels. The buildings are considered located at soft soil sites in the Valley of Mexico and subjected to ground motion time histories simulated in accordance with characteristic parameters of the maximum probable earthquake likely to occur during the system's expected life. For the near-resonance condition the effects of soil,structure interaction on the ductility demands depend mainly on radiation damping. According to the geometry of the structures studied this damping is strongly correlated with the aspect ratio, obtained by dividing the building height by its width. In this way, for structures with aspect ratio greater than 1.4 the storey and global ductility demands increase with respect to those obtained with the same structures but on rigid base, while for structures with aspect ratio less than 1.4 the ductility demands decrease with respect to those for the structures on rigid base. For the cases when the fundamental period of the structure has values very different from the dominant ground period, soil,structure interaction leads in all cases to a reduction of the ductility demands, independently of the aspect ratio. The reliability index , is obtained as a function of the base shear ratio and of the seismic intensity acting on the nonlinear systems subjected to the simulated motions. The resulting reliability functions are very similar for systems on rigid or on flexible foundation, provided that in the latter case the base rotation and the lateral displacement are removed from the total response of the system. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Prediction of the Elastic Properties of Polycrystalline Microcomponents by Numerical Homogenization

ADVANCED ENGINEERING MATERIALS, Issue 3 2009
Katja Jöchen
Polycrystalline microcomponents made of Stabilor®G, a dental alloy mainly consisting of gold, are examined in terms of their elastic properties. Finite element calculations of uniaxial tensile tests are carried out with ABAQUS so as to identify the characteristic parameters of the distribution of Young's modulus. It is shown that the statistics of mechanical properties observed experimentally can be estimated by using the finite element method. The findings are generalized to microcomponents consisting of crystals with a cubic symmetry. [source]

A two-step Taylor-characteristic-based Galerkin method for incompressible flows and its application to flow over triangular cylinder with different incidence angles

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 11 2010
Yan Bao
Abstract An alternative characteristic-based scheme, the two-step Taylor-characteristic-based Galerkin method is developed based on the introduction of multi-step temporal Taylor series expansion up to second order along the characteristic of the momentum equation. Contrary to the classical characteristic-based split (CBS) method, the current characteristic-based method does not require splitting the momentum equation, and segregate the calculation of the pressure from that of the velocity by using the momentum,pressure Poisson equation method. Some benchmark problems are used to examine the effectiveness of the proposed algorithm and to compare with the original CBS method, and the results show that the proposed method has preferable accuracy with less numerical dissipation. We further applied the method to the numerical simulation of flow around equilateral triangular cylinder with different incidence angles in free stream. In this numerical investigation, the flow simulations are carried out in the low Reynolds number range. Instantaneous streamlines around the cylinder are used as a means to visualize the wake region behind, and they clearly show the flow pattern around the cylinder in time. The influence of incidence angle on flow characteristic parameters such as Strouhal number, Drag and Lift coefficients are discussed quantitatively. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Neural models for coplanar waveguides with a finite dielectric thickness

INTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 6 2003
Celal Yildiz
Abstract This article presents a new approach based on artificial neural networks (ANNs) to determine the characteristic parameters of symmetric and asymmetric coplanar waveguides with a finite dielectric thickness. ANNs are trained with the use of five training algorithms. The results obtained from neural models are in very good agreement with the theoritical and experimental results available in the literature. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 13: 438,446, 2003. [source]

Modeling, experimenting, and improving skid steering on a 6 × 6 all-terrain mobile platform

JOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 2 2010
J.-C. Fauroux
Multiple-wheel all-terrain vehicles without a steering system must use great amounts of power when skid steering. Skid steering is modeled with emphasis put on the ground contact forces of the wheels according to the mass distribution of the vehicle. To increase steering efficiency, it is possible to modify the distribution of the normal contact forces on the wheels. This paper focuses on two aspects: first, it provides a model and an experimental study of skid steering on an all-road 6 × 6 electric wheelchair, the Kokoon mobile platform. Second, it studies two configurations of the distribution of the normal forces on the six wheels, obtained via suspension adjustments. This was both modeled and experimented. Contact forces were measured with a six-component force plate. The first results show that skid steering can be substantially improved by only minor adjustments to the suspensions. This setting decreases the required longitudinal forces applied by the engines and improves the steering ability of the vehicle or robot. Skid-steering characteristic parameters, such as the position of the center of rotation and absorbed skid power, are also dealt with in this paper. © 2010 Wiley Periodicals, Inc. [source]

Kinetics of separating multicomponent mixtures by nondispersive solvent extraction: Ni and Cd

AICHE JOURNAL, Issue 4 2001
Inmaculada Ortiz
A model for nonsteady metals separation using nondispersive solvent extraction presented explicitly accounts for selective separation of multicomponent solutions and concentration of separated components in a back-extraction phase. The separation process comprises extraction and back-extraction steps carried out in two different hollow-fiber modules, connected through the organic phase, together with three homogenization tanks. The model is based on a set of coupled differential equations describing mass balances of metallic solutes in the fluid phases. To be applied in its simplest form, it requires the knowledge of three characteristic parameters, two parameters related to the chemical reactions, and one mass-transport parameter. The latter describes the mass-transport rate through pores of the hollow-fiber membrane filled with the organic phase. The mathematical model was checked against the kinetic results of the separation of Cd/Ni mixtures working with high-concentration solutions and obtaining the characteristic parameters of this system. [source]

Characteristic parameters for CPWs on a very thin dielectric layer

Analysis of a cylindrical patch antenna fed with coaxial probe using FDTD

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 6 2003
Xiangyu Cao
Abstract The feed model is very important for microstrip antenna analysis using FDTD. In this paper, the feed model with coaxial probe is accurately and efficiently analysed in terms of the contour path technique, driving out the magnetic field modified equations and accomplishing the FDTD procedure. Finally, the characteristic parameters of a cylindrical patch antenna are predicted. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 406,408, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10932 [source]

An upper limit to the central density of dark matter haloes from consistency with the presence of massive central black holes

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY: LETTERS (ELECTRONIC), Issue 1 2010
X. Hernandez
ABSTRACT We study the growth rates of massive black holes in the centres of galaxies from accretion of dark matter from their surrounding haloes. By considering only the accretion due to dark matter particles on orbits unbound to the central black hole, we obtain a firm lower limit to the resulting accretion rate. We find that a runaway accretion regime occurs on a time-scale which depends on the three characteristic parameters of the problem: the initial mass of the black hole, the volume density and velocity dispersion of the dark matter particles in its vicinity. An analytical treatment of the accretion rate yields results implying that, for the largest black hole masses inferred from quasi-stellar object (QSO) studies (>109 M,), the runaway regime would be reached on time-scales which are shorter than the lifetimes of the haloes in question for central dark matter densities in excess of 250 M, pc,3. Since reaching runaway accretion would strongly distort the host dark matter halo, the inferences of QSO black holes in this mass range lead to an upper limit on the central dark matter densities of their host haloes of ,0 < 250 M, pc,3. This limit scales inversely with the assumed central black hole mass. However, thinking of dark matter profiles as universal across galactic populations, as cosmological studies imply, we obtain a firm upper limit for the central density of dark matter in such structures. [source]

Electron-hole complexes localized on the quantum well interface roughnesses

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2007
M. A. Semina
Abstract The localization of two-dimensional electron-hole complexes on the attractive potential of an arbitrary shape is studied theoretically. General method of a simple and vivid trial function construction for calculation of the ground state binding energy for such complexes is suggested. The limiting cases corresponding to different relations between characteristic parameters are analyzed. The developed method is illustrated by the particular calculations for the case of exciton in two-dimensional quantum well with an additional lateral con.nement potential. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Semi-Empirical Equations for the Residence Time Distributions in Disperse Systems , Part 1: Continuous Phase

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 11 2004
J.-H. Ham
Abstract Residence time distributions (RTD) are often described on the basis of the dispersion or the tanks in series models, whereby the fitting is not always good. In addition, the underlying ideas of these models only roughly characterize the real existing processes. Two semi-empirical equations are presented based on characteristic parameters (mean, minimum, maximum residence time) and on an empirical exponent to permit better fitting. The determination of the parameters and their influence on the RTD are discussed. The usefulness of the models is shown in this first part for single-phase systems and for the continuous phase of multiphase systems using data from literature for laminar and turbulent flows in different apparatuses. A comparison with the results of other models is also done. [source]