Home About us Contact
|
Home About us Contact | ||
|
|
||
Constant Velocity (constant + velocity)
Selected AbstractsSpectral analysis and design approach for high force-to-volume extrusion damper-based structural energy dissipationEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 2 2008Geoffrey W. Rodgers Abstract High force-to-volume extrusion damping devices can offer significant energy dissipation directly in structural connections and significantly reduce seismic response. Realistic force levels up to 400,kN have been obtained experimentally validating this overall concept. This paper develops spectral-based design equations for their application. Response spectra analysis for multiple, probabilistically scaled earthquake suites are used to delineate the response reductions due to added extrusion damping. Representative statistics and damping reduction factors are utilized to characterize the modified response in a form suitable for current performance-based design methods. Multiple equation regression analysis is used to characterize reduction factors in the constant acceleration, constant velocity, and constant displacement regions of the response spectra. With peak device forces of 10% of structural weight, peak damping reduction factors in the constant displacement region of the spectra are approximately 6.5,×, 4.0,×, and 2.8,× for the low, medium, and high suites, respectively. At T,=,1,s, these values are approximately 3.6,×, 1.8,×, and 1.4,×, respectively. The maximum systematic bias introduced by using empirical equations to approximate damping reduction factors in design analyses is within the range of +10 to ,20%. The seismic demand spectrum approach is shown to be conservative across a majority of the spectrum, except for large added damping between T,=,0.8 and 3.5,s, where it slightly underestimates the demand up to a maximum of approximately 10%. Overall, the analysis shows that these devices have significant potential to reduce seismic response and damage at validated prototype device force levels. Copyright © 2007 John Wiley & Sons, Ltd. [source] Natural convection of a water-fine particle suspension in a rectangular cell heated and cooled from opposing vertical walls: The effect of distribution of particle sizeHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 8 2001Masashi Okada Abstract A water-fine particle suspension with a uniform initial temperature and concentration in a rectangular cell was heated from a vertical wall and cooled from the opposing vertical wall. The dispersed particles had a distribution in size. In this natural convection, many layers separated by almost-horizontal sharp interfaces were observed. In the beginning many layers appear, and each interface of the layers falls gradually with a constant velocity, and finally all layers vanish. To clarify this phenomenon, concentrations and mean diameters of the particles in each layer and temperature distributions were measured. Moreover, natural convection of the other suspension with particles which had a narrow size distribution was also investigated. © 2001 Scripta Technica, Heat Trans Asian Res, 30(8): 636,647, 2001 [source] Moving element method for train-track dynamicsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 11 2003C. G. Koh Abstract This paper presents a new approach, called the moving element method, for the dynamic analysis of train-track systems. By discretizing the rail beam on viscoelastic foundation into elements that ,flow' with the moving vehicle, the proposed method eliminates the need for keeping track of the vehicle position with respect to the track model. The governing equations are formulated in a co-ordinate system travelling at a constant velocity, and a class of conceptual elements (as opposed to physical elements) are derived for the rail beams. In the numerical study, four cases of moving vehicle are presented taking into consideration the effects of moving load and rail corrugation. The method is shown to work for varying vehicle velocity and multiple contact points, and has several advantages over the finite element method. The numerical solutions compare favourably with the results obtained by alternative methods. Copyright © 2003 John Wiley & Sons, Ltd. [source] A numerical approach revealing the impact of rheological properties on mouthfeel caused by foodINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 6 2007Katrin Mathmann Summary In contrast to the static chemoreceptor-related flavour perception, texture of food capable of flow is detected dynamically with oral mechanoreceptors while the food is manipulated in the mouth. The resulting sensation called mouthfeel strongly depends on the different physical properties of food. Aim of the current study is to determine numerically the occurring fluid mechanical forces in food suspensions using a simplified tongue-palate model system consisting of two parallel plates. For this purpose, the equations of fluid and particle motion are numerically solved by using structured overlapping grids. In the computational experiment, a density neutral fluid system between the plates is compressed by moving the upper plate with constant velocity down to the other one. It has been found that suspended particles move with the fluid flow but have only minor effect on the global flow field in the applied concentration. [source] Abnormal kinetic behavior of uroporphyrinogen decarboxylase obtained from rats with hexachlorobenzene-induced porphyriaJOURNAL OF BIOCHEMICAL AND MOLECULAR TOXICOLOGY, Issue 1 2005Gabriela Chaufan Abstract Uroporphyrinogen decarboxylase is an essential enzyme in all organisms and functions in the heme biosynthetic pathway, catalyzing the decarboxylation of the four acetate groups of uroporphyrinogen to form coproporphyrinogen. This work examines whether the four sequential decarboxylations occur at the same active site, and explores whether hexachlorobenzene-induced porphyria affects the behavior of the enzyme. For this purpose, kinetic competition studies were done with mixtures of uroporphyrinogen III and pentacarboxyporphyrinogen III. With the enzyme from normal rats, a constant velocity was obtained with all the mixtures, indicating that uroporphyrinogen and pentacarboxy-porphyrinogen react at the same active site, i.e. the first and fourth decarboxylations occur at the same site. In contrast, in experiments with enzyme from rats with hexachlorobenzene-induced porphyria, the total rate for mixtures was always lower than the reference rate; and a curve with a deep minimum was obtained, indicating that the two reactions occur at functionally different sites, but with cross-inhibition. This suggests that the modifications induced in the enzyme by hexachlorobenzene cause the two active sites to become nonequivalent and functionally different. The question is discussed how the hexachlorobenzene treatment may produce this abnormal kinetic behavior, and alternative hypotheses are considered. © 2005 Wiley Periodicals, Inc. J Biochem Mol Toxicol 19:19,24, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.20055 [source] Agonist-evoked Ca2+ wave progression requires Ca2+ and IP3JOURNAL OF CELLULAR PHYSIOLOGY, Issue 2 2010John G. McCarron Smooth muscle responds to IP3 -generating agonists by producing Ca2+ waves. Here, the mechanism of wave progression has been investigated in voltage-clamped single smooth muscle cells using localized photolysis of caged IP3 and the caged Ca2+ buffer diazo-2. Waves, evoked by the IP3 -generating agonist carbachol (CCh), initiated as a uniform rise in cytoplasmic Ca2+ concentration ([Ca2+]c) over a single though substantial length (,30,µm) of the cell. During regenerative propagation, the wave-front was about 1/3 the length (,9,µm) of the initiation site. The wave-front progressed at a relatively constant velocity although amplitude varied through the cell; differences in sensitivity to IP3 may explain the amplitude changes. Ca2+ was required for IP3 -mediated wave progression to occur. Increasing the Ca2+ buffer capacity in a small (2,µm) region immediately in front of a CCh-evoked Ca2+ wave halted progression at the site. However, the wave front does not progress by Ca2+ -dependent positive feedback alone. In support, colliding [Ca2+]c increases from locally released IP3 did not annihilate but approximately doubled in amplitude. This result suggests that local IP3 -evoked [Ca2+]c increases diffused passively. Failure of local increases in IP3 to evoke waves appears to arise from the restricted nature of the IP3 increase. When IP3 was elevated throughout the cell, a localized increase in Ca2+ now propagated as a wave. Together, these results suggest that waves initiate over a surprisingly large length of the cell and that both IP3 and Ca2+ are required for active propagation of the wave front to occur. J. Cell. Physiol. 224: 334,344, 2010. © 2010 Wiley-Liss, Inc. [source] The stationary three-dimensional Navier,Stokes equations with a non-zero constant velocity at infinityMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 18 2008Chérif Amrouche Abstract This paper is devoted to some mathematical questions related to the three-dimensional stationary Navier,Stokes equations. Our approach is based on a combination of properties of Oseen problems in ,3. Copyright © 2008 John Wiley & Sons, Ltd. [source] A three-dimensional Brownian motor, realised with symmetric optical latticesPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 5 2009Anders Kastberg Abstract A three-dimensional Brownian motor is realised using lasercooled caesium atoms trapped in a system of two static, and individually symmetric, optical lattices; a so-called double optical lattice. Isotropic fluctuations, emanating from light scattering, are rectified, and the diffusion of the ensemble of atoms is biased, with a resulting constant velocity that is controllable both in direction and magnitude. The working principle of the Brownian motor can be seen as a pulsation between two different potentials, both symmetric but around different points. The correlation between interferometric spatial offsets, and imbalance in optical pumping rates, leads to a spatio-temporal asymmetry sufficient for generating a controlled, directed motion (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||