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961.
962.
Transpiration is a technique in which extra non-physical normal flows are created on an aerofoil surface in order to form a new streamline pattern such that the surface streamlines no longer follow the aerofoil surface under inviscid flow. The transpiration model is an important technique adopted in aerofoil design either to avoid mesh regeneration when aerofoil profile co-ordinates are adjusted or to find shape corrections in inverse design methods. A first-order approximation (with respect to the normal streamline displacement) to the transpiration model is commonly adopted; it is shown that this can be a poor approximation especially in regions of high curvature. In this paper more accurate approximations are developed to address this problem and improve the accuracy. 相似文献
963.
Summary. We examine the convergence characteristics of iterative methods based on a new preconditioning operator for solving the linear
systems arising from discretization and linearization of the steady-state Navier-Stokes equations. With a combination of analytic
and empirical results, we study the effects of fundamental parameters on convergence. We demonstrate that the preconditioned
problem has an eigenvalue distribution consisting of a tightly clustered set together with a small number of outliers. The
structure of these distributions is independent of the discretization mesh size, but the cardinality of the set of outliers
increases slowly as the viscosity becomes smaller. These characteristics are directly correlated with the convergence properties
of iterative solvers.
Received August 5, 2000 / Published online June 20, 2001 相似文献
964.
M. C. Marguery N. Chouini-Lalanne J. C. Ader N. Paillous 《Photochemistry and photobiology》1998,68(5):679-684
Fenofibrate and ketoprofen (KP) are two drugs of similar structure derived from that of benzophenone. Both are photoallergic and promote cross reactions in patients. However, the cutaneous photosensitizing properties of KP also include phototoxic effects and are more frequently mentioned. To account for this difference in their in vivo properties, their in vitro photosensitizing properties on DNA were compared. First, it was shown that under irradiation at 313 nm, fenofibric acid (FB), the main metabolite of fenofibrate, photosensitized DNA cleavage by a radical mechanism similar to that proposed for KP but with a 50 times lower efficiency. Furthermore, FB did not photosensitize the formation of pyrimidine dimers into DNA in contrast to KP, which did promote this type of DNA damage. Their difference in efficiency as DNA breakers was compared to their relative photochemical reactivity and the quantum yield of FB photolysis was found to be eightfold lower than that of KP. The reactivity of these drugs cannot explain alone the difference in their photosensitizing properties. Other factors such as the magnitude of the ionic character of the pho-todecarboxylation pathway of these benzophenone-like drugs are considered in the discussion. 相似文献
965.
Crack initiation and stable crack growth under monotonic loading in steels has been studied using an elastic-plastic finite element analysis. The fracture criterion used for crack initiation and stable crack growth was the critical strain energy density. In addition the shift core method for the analysis of crack extension was used. In the shift core modelling method, crack advance is simulated by moving the coordinates of the core region which surrounds the crack tip, to obtain the stiffness reduction. Simultaneously the core itself geometrically undergoes a simple rigid-body motion or translation during the crack extension. The analytically calculated and experimentally measured load for crack initiation and the subsequent stable crack growth agreed well. 相似文献
966.
967.
Nitro musks in cosmetic products—determination by headspace solid-phase microextraction and gas chromatography with atomic-emission detection 总被引:1,自引:0,他引:1
Summary The combination of headspace solid-phase microextraction with atomic-emission detection enables highly selective and sensitive
determination of itro musk compounds in cosmetic products. Sample preparation is considerably simplified; there is no solvent
extraction step. Enrichment is influenced by the type and amount of cosmetic product investigated. The lowest amount giving
well detectable peaks is 1 mg musk compound per kg sample. Calibration curves obtained from spiked solutions of selected reference
cosmetics in water show very good linearity. Relative standard deviations of peak areas from repeated measurements are usually
<10%.
Presented at the 21st ISC held in Stuttgart, Germany, 15th–20th September, 1996 相似文献
968.
Cyclic voltammetric studies of certain industrially potential iron chelate catalysts 总被引:1,自引:0,他引:1
For the analysis of infrared spectroscopic bands and complex patterns partial cross correlation functions of a sample spectrum
with reference spectra are calculated. The chosen ranges of the spectra are based on empirical knowledge of infrared spectrum
structure correlations. The normalised maxima of the partial cross correlation functions are interpreted as fuzzy truth values
and are combined by fuzzy logical operators. By application of that procedure larger common substructures will be derived
from the reference spectra than by a maximum common substructure search based on the complete spectra.
Received: 30 October 1996/Revised: 24 February 1997/Accepted: 26 February 1997 相似文献
969.
J.-M. Colet C. Piérart F. Seghi I. Gabric R.N. Muller 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1998,134(2):199-205
The relative contributions of intravascular and intracellular compartments to the proton transverse relaxation of the isolated and excised rat liver were determined during the phagocytosis of superparamagnetic particles. The evolution of the proton transverse magnetization of the organ perfused with increasing doses of starch-coated magnetic microspheres was followed up using a Carr–Purcell–Meiboom–Gill sequence with various echo times. From the multiexponential fit of the echo train, the amplitudes and the relaxation ratesR2of the liver tissue were obtained. The results clearly indicate that shortly after contrast medium administration, an internalization takes place which can be followed by the rapid and biphasic evolution of the transverse relaxation rate of the water protons. A very fast decaying component looking like an initial loss of the magnetization is observed together with an increase of the relaxation rate of the remaining water tissue. This regime is strongly dependent on both the echo time and the iron concentration, a behavior characteristic of the agglomeration of magnetic particles. The examination of the liver tissues by electron microscopy shows that this clustering arises in cytoplasmic vacuoles. 相似文献
970.
Distribution of melamine in polyester–melamine surface coatings cured under nonisothermal conditions
N. J. W. Gamage D. J. T. Hill C. A. Lukey P. J. Pomery 《Journal of polymer science. Part A, Polymer chemistry》2004,42(1):83-91
The influence of experimental cure parameters on the diffusion of reactive species in polyester–melamine thermoset coatings during curing has been investigated with X‐ray photoelectron spectroscopy and attenuated total reflectance Fourier transform infrared. The diffusion of melamine plays a vital role in the curing process and, therefore, in the ultimate properties of coatings. At a low (<20%) hexamethoxymethylmelamine (HMMM) crosslinker concentration, the matrix composition is uniform, but at high HMMM concentrations, excess HMMM rapidly segregates to the air–coating interface. The rate of migration is governed by the difference in the surface free energies of polyester and HMMM and the concentration gradient of HMMM between the bulk and the surface. An increased rate of energy absorption also increases the rate of migration of HMMM to the surface. A physical model has been proposed to explain this surface segregation phenomenon in terms of cocondensation and self‐condensation reactions. It suggests that an appropriate amount of melamine can be segregated on the surface and allowed to self‐condense to form a desired thickness of a melamine topcoat through the control of the binder composition and cure conditions. This technique can be implemented to apply a melamine topcoat during cure. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 83–91, 2004 相似文献