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1.
Containerless rapid solidification of undercooled Cu_Co peritectic alloys   总被引:12,自引:0,他引:12  
Droplets of Co-16%Cu and Co-71.6%Cu peritectic alloys were solidified during containerless processing in a 3_m drop tube. The microstructures of Co-16%Cu alloy droplets were characterized by dendritic or equiaxed α-Co phase with a small amount of Cu-rich solid solution distributed on α-Co phase boundaries. Two thresholds of droplet diameter were observed for Co-16%Cu alloy at which "equiaxed-dendritic-equiaxed" morphological transitions occur to primary α-Co phase. This conspicuous refinement of primary α-Co grains results from the fragmentation of α-Co dendrites caused by recalescence effect. For Co-71.6%Cu alloy, the primary α-Co phase forms as coarse columnar dendrites in large droplets and equiaxed dendrites in small droplets. Theoretical calculations indicate that Marangoni migration contributes more to the growth of disperse Co-rich spheres by stimulating collision and coalescence than Stokes motion caused by the residual gravity in the falling Co-71.6%Cu alloy droplets.  相似文献
2.
Generalized expression of exergy in the thermodynamics   总被引:6,自引:0,他引:6  
Exergy is the ability of the maximum work done to the objective (relative) outside when the system changes from any state to its dead state. Exergy stems from the gaps of intensive properties between its present state and its dead state. Generalized differential expression of exergy is advanced without any premise conditions, which is composed of generalized intensive and extensive (additive) properties. Any form of exergy can be deduced out from this generalized expression, only if its characteristic intensive and extensive parameters are known. That the exergy of any closed system is never below zero has been proved.  相似文献
3.
Dichromatic Polynomials and Potts Models Summed Over Rooted Maps   总被引:6,自引:0,他引:6  
We consider the sum of dichromatic polynomials over non-separable rooted planar maps, an interesting special case of which is the enumeration of such maps. We present some known results and derive new ones. The general problem is equivalent to the q-state Potts model randomized over such maps: it remains an open question whether this model exhibits a phase transition or critical behaviour.  相似文献
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Summary We consider two classes of measure-valued diffusion processes; measure-valued branching diffusions and Fleming-Viot diffusion models. When the basic space is R 1, and the drift operator is a fractional Laplacian of order 1<α≦2, we derive stochastic partial differential equations based on a space-time white noise for these two processes. The former is the expected one by Dawson, but the latter is a new type of stochastic partial differential equation.  相似文献
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Random number generation using a chaotic circuit   总被引:1,自引:0,他引:1  
Summary A simple method to generate pseudorandom numbers is presented. The basic part of the circuit consists of two identical nonautonomous chaotic oscillators, which are driven by an external clock signal. The well-known chaotic circuits are extremely simple, as they are composed only of an inductor and a capacitance diode, and thus it is easy to get the generator to work reliably. The output of the oscillators is discretized by a comparator, and these signals are mixed together using a D flip-flop. The distribution, the spectrum, the return map, and the autocorrelation of random numbers obtained by this circuit are shown. We have studied the system also using the correlation integral method and the local prediction technique. The results of these analyses demonstrate that the number sequence is highly random.  相似文献
8.
Summary We consider a time evolution of unbounded continuous spins on the real line. The evolution is described by an infinite dimensional stochastic differential equation with local interaction. Introducing a condition which controls the growth of paths at infinity, we can construct a diffusion process taking values inC(). In view of quantum field theory, this is a time dependent model ofP()1 field in Parisi and Wu's scheme.  相似文献
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Summary We shall investigate two dimensional diffusion processes occurring in population genetics. In order to construct such processes, we shall consider a martingale problem and discuss its uniqueness problem. Though the standard methods are not applicable in our case, we obtain the uniqueness in a fairly general case.  相似文献
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