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921.
922.
Chunling Liu Yanping Yao Chunwu Wang Xin Gao Zhongliang Qiao Mei Li Yuxia Wang Baoxue Bo 《中国光学快报(英文版)》2008,6(3)
In order to improve the optical properties of the Ⅲ-Ⅴ laser diodes(LDs) by means of H2S plasma passivation technology,H2S plasma passivation treatment is performed on the GaAs(110) surface.The optimum passivation conditions obtained are 60-W radio frequency(RF)power and 20-min duration.So the laser cavity surfaces axe treated under the optimum passivation conditions.Consequently,compared with unpassivated lasers with only AR/HR-coatings,the catastrophic optical damage (COD) threshold value of the passivated lasers by H2S plasma treatment is increased by 33%,which is almost the same as that of (NH4)2Sx treatment.And the life-test experiment has demonstrated that this passivation method is more stable than(NH4)2Sx solution wet-passivated treatment. 相似文献
923.
The inflow conditions for spatial direct numerical simulation (SDNS) of turbulent boundary layers should reflect the characteristics
of upstream turbulence, which is a puzzle. In this paper a new method is suggested, in which the flow field obtained by using
temporal direct numerical simulation (TDNS) for fully developed turbulent flow (only flow field for a single moment is sufficient)
can be used as the inflow of SDNS with a proper transformation. The calculation results confirm that this method is feasible
and effective. It is also found that, under a proper time-space transformation, all statistics of the fully developed turbulence
obtained by both temporal mode and spatial mode DNS are in excellent agreement with each other, not only qualitatively, but
also quantitatively. The normal-wise distributions of mean flow profile, turbulent Mach number and the root mean square (RMS)
of the fluctuations of various variables, as well as the Reynolds stresses of the fully developed turbulence obtained by using
SDNS, bear similarity in nature.
Supported by the National Natural Science Foundation of China (Grant No. 90205021), the China Postdoctoral Science Foundation
(Grant No. 20060400707), and the Foundation for the Author of National Excellent Doctoral Dissertation of China (Grant No.
200328), and partially supported by Liu-Hui Center of Applied Mathematics, Nankai University and Tianjin University 相似文献
924.
We consider a kinetic BGK model relaxing to isentropic gas dynamics previously introduced by the authors, but with Dirichlet boundary condition on the incoming velocities. We pass to the limit as the relaxation parameter tends to zero by compensated compactness inside the domain, and obtain that the limit satisfies entropy inequalities on the boundary involving weak traces of entropy fluxes. Our method is very general and could be applied to any entropy satisfying BGK model as soon as we have strong compactness of the macroscopic variables inside the domain. 相似文献
925.
11尬roductlonIn this paper;we study the exlstence ofnonneg时Ive solutions ofone dl-menslonal-Lapfaclan boundary value problems一(电N》’二入M;0<x<1,儿1)u’仰二0,*’川十口叫)二0,队2)where入>0md a>0 are parmetersmd f E C’[0,1],屯(。)=I冲-‘。,p>1二This problem ppears In the study ofnon-Newtonlan luids(see[1;2])andnon-Newtonlan iltratlon(see[3]).The quantity p Is a characteristic of*theteristicmadium.Media with p>2 are called dllatantn"ids and those with p<2 arecalled pseudop… 相似文献
926.
Antoine Henrot Henrik Shahgholian 《Transactions of the American Mathematical Society》2002,354(6):2399-2416
Our objective, here, is to generalize our earlier results on the existence of classical convex solution to a free boundary problem with a Bernoulli-type boundary gradient condition and with the -Laplacian as the governing operator. The main theorems of this paper assert that the exterior and the interior free boundary problem with a Bernoulli law, i.e. with a prescribed pressure on the ``free' streamline of the flow, have convex solutions provided the initial domains are convex. The continuous function is subject to certain convexity properties. In our earlier results we have considered the case of constant . In the lines of the proof of the main results we also prove the semi-continuity (up to the boundary) of the gradient of the -capacitary potentials in convex rings, with boundaries.
927.
In functional magnetic resonance imaging (fMRI) studies, an elevation in blood pressure (BP) in individuals with a poor autoregulatory response may increase cerebral blood flow, potentially enhancing the blood oxygenation level dependent response. To investigate the role of BP changes, the cerebral activation to either tonic pain or the infusion of the vasopressor norepinephrine was correlated with the accompanying BP changes in alpha-chloralose anesthetized rats. Immediately after formalin (2%) injection into the forepaw, fMRI detected an activation that was correlated with the BP increase and additional activations that were independent of blood pressure changes 5–40 minutes later. The activation detected with the administration of the vasopressor norepinephrine, which does not cross the blood-brain barrier was correlated to both the amount and rate of increase in BP. The response ranged from being sparse, localized within cortex or widespread during modest, moderate or severe elevations in BP, respectively. The cerebral circulatory effects of hypertension should be considered as contributing to changes in cerebral blood oxygenation in fMRI studies involving increases in BP. 相似文献
928.
During the computation of intervoxel anisotropy features, the inclusion of both eigenvalues and eigenvectors reduces the effect of noise, but spatial averaging blurs the resulting maps. We propose a new adaptive technique that uses data-dependent weights in the averaging process so that the influence of each neighbor in the local window is proportional to the similarity of characteristics of the neighbor considered to those of the reference central voxel. This likeness criterion is based on the multidimensional Euclidian distance using the entire available multispectral information contained in the diffusion-weighted images. This solution is controlled by a single parameter beta that results from a compromise between edge-preserving and noise-smoothing abilities. This Euclidian distance-weighted technique is a generic solution for filtering noise during parametric reconstruction. It was applied to map anisotropy using an intervoxel lattice index (LI) from experimental images of mouse brain in vivo and achieves noise reduction without distorting small anatomical structures. We also show how to employ in the discrimination scheme the images not used in the estimation of the considered feature. 相似文献
929.
In previous papers [1, 2], we presented hyperbolic governing equations and jump conditions for barotropic fluid mixtures. Now we extend our results to the most general case of twocomponent media. We obtain governing equations for each component. This is not a system of conservation laws. Nevertheless, using Hamilton's principle we are able to obtain a complete set of Rankine–Hugoniot conditions. For the twofluid case, the jump relations do not involve the conservation of the total momentum and the total energy.Sommario. In precedenti lavori [1, 2] sono state dedotte equazioni di governo iperboliche e condizioni di salto per miscele fluide barotropiche. I risultati sono estesi al caso più generale di mezzi a due componenti, ottenendo le equazioni di governo per ciascun componente. Questo sistema non è derivabile dalle leggi di conservazione. Nondimeno, usando il principio di Hamilton è possibile ottenere un insieme completo di condizioni di Rankine–Hugoniot. Nel caso dei due fluidi, le condizioni di salto non coinvolgono la conservazione del momento e dell'energia totali. 相似文献
930.
Linear partial differential algebraic equations (PDAEs) of the form Au
t(t, x) + Bu
xx(t, x) + Cu(t, x) = f(t, x) are studied where at least one of the matrices A, B R
n×n
is singular. For these systems we introduce a uniform differential time index and a differential space index. We show that in contrast to problems with regular matrices A and B the initial conditions and/or boundary conditions for problems with singular matrices A and B have to fulfill certain consistency conditions. Furthermore, two numerical methods for solving PDAEs are considered. In two theorems it is shown that there is a strong dependence of the order of convergence on these indexes. We present examples for the calculation of the order of convergence and give results of numerical calculations for several aspects encountered in the numerical solution of PDAEs. 相似文献