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101.
Science China Mathematics - We find a new scaling invariance of the barotropic compressible Navier-Stokes equations. Then it is shown that type-I singularities of solutions with $$\mathop {\lim... 相似文献
102.
103.
In this paper, we first establish a strong convergence criterion of approximate solutions for the 3D steady incompressible Euler equations. For axisymmetric flows, under the assumption that the vorticity is of one sign and uniformly bounded in L1 space, we obtain a sufficient and necessary condition for the strong convergence in of approximate solutions. Furthermore, for one-sign and L1-bounded vorticity, it is shown that if a sequence of approximate solutions concentrates at an isolated point in (r,z)-plane, then the concentration point can appear neither in the region near the axis (including the symmetry axis itself) nor in the region far away from the axis. Finally, we present an example of approximates solutions which converge strongly in by using Hill's spherical vortex. 相似文献
104.
In this paper we study the zero dissipation problem for a general system of conservation laws with positive viscosity. It is shown that if the solution of the problem with zero viscosity is piecewise smooth with a finite number of noninteracting shocks satisfying the entropy condition, then there exist solutions to the corresponding system with viscosity that converge to the solutions of the system without viscosity away from shock discontinuities at a rate of order as the viscosity coefficient goes to zero. The proof uses a matched asymptotic analysis and an energy estimate related to the stability theory for viscous shock profiles. 相似文献
105.
作者在对GCr15钢球/CVDCr_7C_3镀层钢盘摩擦副于大气中滑动干摩擦引起的摩擦振动进行考察分析的基础上,本文又对这种摩擦副在真空(6.67×10~(-3)Pa)中的摩擦振动特性进行了试验研究。试件系统为低刚度和小阻尼的弹性系统。试验信号由微机采集、处理并进行频谱分析。结果表明,真空中摩擦力振动的类型呈准谐波周期性自持振动,其与正压力及拖动速度无关,振动频率接近于系统在水平方向上的固有频率;摩擦副运动的平稳性与平均滑动摩擦系数接近反比例关系;真空中摩擦力的粘着分量是使摩擦振动加剧的主要原因;钢球的磨损体积与摩擦振动特性无关。 相似文献
106.
107.
Jinglei Yuan Ye Yu Can Li Xiaoyuan Ma Yu Xia Jie Chen Zhouping Wang 《Mikrochimica acta》2014,181(3-4):321-327
We have developed a specific method for the visual detection of Staphylococcus aureus based on aptamer recognition coupled to tyramine signal amplification technology. A biotinylated aptamer specific for S. aureus was immobilized on the surface of the wells of a microplate via biotin-avidin binding. Then, the target bacteria (S. aureus), the biotinylated-aptamer-streptavidin-HRP conjugates, biotinylated tyramine, hydrogen peroxide and streptavidin-HRP were successively placed in the wells of the microplate. After adding TMB reagent and stop solution, the intensity of the yellow reaction product can be visually inspected or measured with a plate reader. Under optimized conditions, there is a linear relationship between absorbance at 450 nm and the concentration of S. aureus in the 10 to 107 cfu mL?1 concentration range (with an R2 of 0.9976). The limit of detection is 8 cfu mL?1. Figure
A visual detection method for Staphylococcus aureus was based on aptamer recognition coupled to tyramine signal amplification. The linear range was from 10 to 107 cfu mL-1 and the limit of detection was 8 cfu mL-1. 相似文献
108.
Sensitive flow-injection chemiluminescence determination of terbutaline sulfate based on enhancement of the luminol–permanganate reaction 总被引:2,自引:0,他引:2
A novel and highly sensitive chemiluminescence (CL) method for the determination of terbutaline sulfate, coupled with flow-injection analysis (FIA), is described in this paper. The method is based on enhancement by terbutaline sulfate of the chemiluminescence emission of the luminol–permanganate system under alkaline conditions. Under the conditions selected the concentration of terbutaline sulfate is proportional to CL intensity in the range 5×10–10–5×10–7 g mL–1, with a detection limit of 1.7×10–10 g mL–1 (3). The relative standard deviation is 2.8% for 1×10–8 g mL–1 terbutaline sulfate (n=11). Ninety samples can be determined per hour. The proposed method has been used to determine terbutaline sulfate in pharmaceutical preparations and in plasma and urine samples with satisfactory results. The possible mechanism of the chemiluminescence reaction is discussed briefly. 相似文献
109.
We prove a result of uniqueness of the entropy weak solution to the Cauchy problem for a class of nonlinear hyperbolic systems of conservation laws that includes in particular the p-system of isentropic gas dynamics. Our result concerns weak solutions satisfying the, as we call it, Wave Entropy Condition, or WEC for short, introduced in this paper. The main feature of this condition is that it concerns both shock waves and rarefaction waves present in a solution. For the proof of uniqueness, we derive an existence result (respectively a uniqueness result) for the backward (respectively forward) adjoint problem associated with the nonlinear system. Our method also applies to obtain results of existence or uniqueness for some linear hyperbolic systems with discontinuous coefficients. © 1993 John Wiley & Sons, Inc. 相似文献
110.
M. C. Lopes Filho H. J. Nussenzveig Lopes Zhouping Xin 《Archive for Rational Mechanics and Analysis》2001,158(3):235-257
The main purpose of this work is to establish the existence of a weak solution to the incompressible 2D Euler equations with initial vorticity consisting of a Radon measure with distinguished sign in H ? 1, compactly supported in the closed right half-plane, superimposed on its odd reflection in the left half-plane. We make use of a new a priori estimate to control the interaction between positive and negative vorticity at the symmetry axis. We prove that a weak limit of a sequence of approximations obtained by either regularizing the initial data or by using the vanishing viscosity method is a weak solution of the incompressible 2D Euler equations. We also establish the equivalence at the level of weak solutions between mirror symmetric flows in the full plane and flows in the half-plane. Finally, we extend our existence result to odd L 1 perturbations, without distinguished sign, of our original initial vorticity. 相似文献