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71.
M. Brando N. Büttgen V. Fritsch J. Hemberger H. Kaps H.-A. Krug von Nidda M. Nicklas K. Pucher W. Trinkl A. Loidl E.W. Scheidt M. Klemm S. Horn 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,25(3):289-298
We present susceptibility, microwave resistivity, NMR and heat-capacity results for Li1-xZnx(V1-yTiy)2O4 with 0 ?
x
? 0.3 and 0 ?
y
? 0.3. For all doping levels the susceptibility curves can be fitted with a Curie-Weiss law. The paramagnetic Curie-Weiss temperatures
remain negative with an average value close to that of the pure compound Θ≈ - 36 K. Spin-glass anomalies are observed in the susceptibility, heat-capacity and NMR measurements for both type of dopants.
From the temperature dependence of the spin-lattice relaxation rate we found critical-dynamic behavior in the Zn doped compounds
at the freezing temperatures. For the Ti-doped samples two successive freezing transitions into disordered low-temperature
states can be detected. The temperature dependence of the heat capacity for Zn-doped compounds does not resemble that of canonical
spin glasses and only a small fraction of the total vanadium entropy is frozen at the spin-glass transitions. For pure LiV2O4 the spin-glass transition is completely suppressed. The temperature dependence of the heat capacity for LiV2O4 can be described using a nuclear Schottky contribution and the non-Fermi liquid model, appropriate for a system close to
a spin-glass quantum critical point. Finally an (
x
/
y
,
T
)-phase diagram for the low-doping regime is presented.
Received 16 March 2001 and Received in final form 30 October 2001 相似文献
72.
G. Tiana M.H. Jensen K. Sneppen 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(1):135-140
A feedback mechanism that involves the proteins p53 and mdm2, induces cell death as a controlled response to severe DNA damage.
A minimal model for this mechanism demonstrates that the response may be dynamic and connected with the time needed to translate
the mdm2 protein. The response takes place if the dissociation constant k between p53 and mdm2 varies from its normal value. Although it is widely believed that it is an increase in k that triggers the response, we show that the experimental behaviour is better described by a decrease in the dissociation
constant. The response is quite robust upon changes in the parameters of the system, as required by any control mechanism,
except for few weak points, which could be connected with the onset of cancer.
Received 8 May 2002 / Received in final form 9 July 2002 Published online 17 September 2002 相似文献
73.
74.
Existence and Uniqueness of Endemic States for the Age-structured MSEIR Epidemic Model 总被引:1,自引:0,他引:1
Geni Gupur 《应用数学学报(英文版)》2002,18(3):441-454
The existence and uniqueness of positive steady states for the age-structured MSEIR epidemic model with age-dependent transmission coefficient is considered. Threshold results for the existence of endemic states are established; under certain conditions, uniqueness is also shown. 相似文献
75.
We investigate an operator renormalization group method to extract and describe the relevant degrees of freedom in the evolution of partial differential equations. The proposed renormalization group approach is formulated as an analytical method providing the fundamental concepts of a numerical algorithm applicable to various dynamical systems. We examine dynamical scaling characteristics in the short-time and the long-time evolution regime providing only a reduced number of degrees of freedom to the evolution process. 相似文献
76.
从立方抛物线谈起(1)--余弦型振动,椭圆余弦型振动与双曲线型非周期运动 总被引:1,自引:1,他引:0
从立方抛物线的特性谈起 ,用较初浅的方法 ,借助于雅可比椭圆函数求椭圆方程的解来说明一大类一维保守系统的余弦振动、椭圆余弦型振动与双曲线型非周期运动 .并以杜芬振子、单摆、倒摆、转动圆环上的小环运动为典型实例作了详细讨论 相似文献
77.
We establish the existence and stability of multidimensional transonic shocks for the Euler equations for steady potential compressible fluids. The Euler equations, consisting of the conservation law of mass and the Bernoulli law for the velocity, can be written as a second-order, nonlinear equation of mixed elliptic-hyperbolic type for the velocity potential. The transonic shock problem can be formulated into the following free boundary problem: The free boundary is the location of the transonic shock which divides the two regions of smooth flow, and the equation is hyperbolic in the upstream region where the smooth perturbed flow is supersonic. We develop a nonlinear approach to deal with such a free boundary problem in order to solve the transonic shock problem. Our results indicate that there exists a unique solution of the free boundary problem such that the equation is always elliptic in the downstream region and the free boundary is smooth, provided that the hyperbolic phase is close to a uniform flow. We prove that the free boundary is stable under the steady perturbation of the hyperbolic phase. We also establish the existence and stability of multidimensional transonic shocks near spherical or circular transonic shocks.
78.
79.
Equilibrium Problems with Applications to Eigenvalue Problems 总被引:5,自引:0,他引:5
In this paper, we consider equilibrium problems and introduce the concept of (S)+ condition for bifunctions. Existence results for equilibrium problems with the (S)+ condition are derived. As special cases, we obtain several existence results for the generalized nonlinear variational inequality studied by Ding and Tarafdar (Ref. 1) and the generalized variational inequality studied by Cubiotti and Yao (Ref. 2). Finally, applications to a class of eigenvalue problems are given. 相似文献
80.
根据环形管通道内流体流动和换热的特点,以Kirillov和Smogalev提出的干涸点理论模型假设为基础,从最基本的质量守恒方程出发,并引入临界液膜厚度等相应的辅助模型,得到了双面加热环形通道内流动沸腾干涸点的理论模型。同时针对间隙为1.0mm和1.5mm的环形窄缝进行了低压低质量流速工况下干涸点的实验研究。比较发现理论模型预测值与实验结果基本相符。说明本文提出的理论模型适用于低压低流量条件下的窄环形通道。实验同时发现:环状流临界热流密度在系统压力为2.2MPa达到最大值,临界含汽量随质量流速的增大呈缓慢下降趋势。 相似文献