别具一格的音箱设计——艺龙“抛物线型”系列音箱简评

最近、广州艺龙公司向市场推出了全国首创的抛物线型声场设计的风华系列音箱,其别具一格的音箱设计理念和独特造形引起了业界的瞩目。目前,国内音箱的生产、销售状况比较混乱。由于听觉心理的主观性,对于音箱声音质量的鉴别有一定的离散性和难度,没有经过一定的听觉训练,并不容易区分出质量的高低。这就给音箱生产、销售带来很大的漏洞。

Consistency of Water Production Function Models of Two Crops

On basis of test information, the research performed analysis on water production function models of two crops, which indicated that water model of crops in whole growth stage and water model of crops indifferent growth stages have consistency as well as differences, providing references for optimization of irrigation water. Meanwhile, the research analyzed the deficiency of optimization on irrigation water for crops just by Jensen model.

Symmetry Reductions of Cauchy Problems for Fourth-Order Quasi-Linear Parabolic Equations

This paper is devoted to studying symmetry reduction of Cauchy problems for the fourth-order quasi-linear parabolic equations that admit certain generalized conditional symmetries （GCSs）. Complete group classification results are presented, and some examples are given to show the main reduction procedure.

Existence and Nonexistence of Global Solution for Quasilinear Parabolic Equation

This paper deals with the existence and nonexistence of global positive solutions of the following quasilinear parabolic equations:u t=1m△u m-u n, x∈Ω,t>0 1m·u mv=u p,x∈Ω,t>0 u(x,0)=u 0(x)>0,x∈Ω-where Ω∈R N is a bounded domain with smooth boundary Ω,m,n,p are positive constants, γ is the outward normal vector. The necessary and sufficient conditions for the global existence of solutions are obtained.

Energy Spectrum of a Positronium Negative Ion in a Parabolic Quantum Well

The method of few-body physics is applied to calculating the energy levels of low-lying states ofa positro-nium negative ion in a parabolic quantum well. The results show that the energy levels of a positronium negativeion intwo-dimensional case are lower than those in three-dimensional case.

Oscillation of Solutions of Nonlinear Neutral Parabolic Differential Equations

This paper deals with the oscillatory properties of a class of nonlinear neutralparabolic partial differential equations with several delays. Sufficient criteria for the equa-tion to be oscillatory are obtained by making use of some results of first-order functionaldifferential inequalities. These results fully reveal the essential difference between this typeand that without delays.

Asymptotical Properties for Parabolic Systems of Neutral Type

Asymptotical properties for the solutions of neutral parabolic systems with Robin boundary conditions were analyzed by using the inequality analysis.The oscillations problems for the neutral parabolic systems were considered and some oscillation criteria for the systems were established.

Blow Up for Solutions of Nonlinear Doubly Degenerate Parabolic Equation

This paper studies the conditions of blow up in finite time of solutions of initial boundary value problem for a class nonlinear doubly degenerate parabolic equation.

Asymptotic Behavior of Global Solutions for Double Degenerate Nonlinear Parabolic Equation

In this paper we study the decay estimate of global solutions to the initial-boundary value problem for double degenerate nonlinear parabolic equation by using a dif-ference inequality.

Estimates on Blow-up Rate of Nonlinear Parabolic Systems with Nonlinear Boundary Conditions

In this paper, the estimate on blow-up rate of the following nonlinear parabolic system is considered：{ut=uxx＋u^l 11v^l 12,vt=vxx＋u^l21v^l22,（x,t）∈（0,1）×（0,T）,ux（0,t）=0,vx（0,t）=0,t∈（0,T）,ux（1,t）=（u^p11v^p12）（1,t）,vx（1,t）=（u^p21v^p22）（1,t）,t∈（0,T）,u（x,0）=u0（x）,v（x,0）=v0（x）,x∈（0,1）We will prove that there exist two positive constants such that：c≤max x∈[0,1]u（x,t）（T-t）^r（l1-1）≤C,0〈t〈T,c≤max x∈[0,1] v（x,t）（T-t）^1/（t1-1）≤C,0〈t〈T.where l1=l21α/α2＋l22,r=α1/α2〉1,α1≤α2〈0.

On the Regional Enlarged Observability for Linear Parabolic Systems

In this paper, we study the notion of the enlarged observability for distributed parabolic systems, where the aim is to reconstruct the initial state between two prescribed profiles P1 and P2 in an internal subregion c0 of the evolution domain f2. We give some definitions and properties of this concept, and then we solve the problem of the reconstruction of initial state using the Hilbert Uniqueness Method （HUM）. This leads to several interesting results which are performed through numerical example and simulations.

Asymptotic Behavior of Nonlinear Parabolic Partial Functional Differential Equations

This paper is devoted to the investigation of the asymptotic behavior for a class of nonlinear parabolic partial functional differential equations. The boundedness and stability of the solutions are established by the upper-lower solution method. Some conditions are obtained by using the semigroup theory, the properties of nonnegative matrices and the techniques of inequalities to determine the asymptotically stable region of the equilibrium.

Continuity of Weak Solutions for Quasilinear Parabolic Equations with Strong Degeneracy

The aim of this paper is to study the continuity of weak solutions for quasilinear degenerate parabolic equations of the form： μt-△φ（μ） = 0 ,where φ ε C1（R^1） is a strictly monotone increasing function. Clearly, the above equation has strong degeneracy, i.e., the set of zero points of φ＇（.） is permitted to have zero measure. This is an answer to an open problem in [13, p. 288].

AN INTEGRO-DIFFERENTIAL PARABOLIC VARIATIONAL INEQUALITY ARISING FROM THE VALUATION OF DOUBLE BARRIER AMERICAN OPTION

This paper studies the nonlinear variational inequality with integro-differential term arising from valuation of American style double barrier option. First, the authors use the penalty method to transform the variational inequality into a nonlinear parabolic initial boundary problem(i.e., penalty problem). Second, the existence and uniqueness of solution to the penalty problem are proved by using the Scheafer fixed point theory. Third, the authors prove the existence of variational inequality' solution by showing the fact that the penalized PDE converges to the variational inequality. The uniqueness of solution to the variational inequality is also proved by contradiction.

EXISTENCE AND NONEXISTENCE OF GLOBAL SOLUTION OF NONLINEAR PARABOLIC EQUATION WITH NONLINEAR BOUNDARY CONDITION

This paper deals with the existence and nonexistence of global positive solution of the following equation:where p, q, m, α are parameters with is a bounded domain with Ω smooth enough, The necessary and sufficient conditions for the global existence of solution are obtained.

A link of stochastic differential equations to nonlinear parabolic equations

Using Girsanov transformation,we derive a new link from stochastic differential equations of Markovian type to nonlinear parabolic equations of Burgers-KPZ type,in such a manner that the obtained BurgersKPZ equation characterizes the path-independence property of the density process of Girsanov transformation for the stochastic differential equation.Our assertion also holds for SDEs on a connected differential manifold.

Solution to Nonlinear Parabolic Equations Related to P-Laplacian

Consider the following Cauchy problem：where 1 〈 p 〈 2, 1 〈 m 〈 p_~11, and # is a a-finite measure in N. By the Moser＇s iteration method, the existence of the weak solution is obtained, provided that （M＋1）N 〈 P. In mN＋l contrast, if 〉 p, there is no solution to the Cauchy problem with an initial value δ（X）, where 5（x） is the classical Dirac function.

Modeling of growth stress gradient effect on the oxidation rate at high temperature

A new oxidation kinetics model is established for high-temperature oxidation. We assume that the interface reaction is fast enough and the oxidation rate is controlled by diffusion process at high temperature. By introducing the growth stress gradient we modify the classical oxidation parabolic law. The modified factor of the oxidation rate constant is a function of growth strain, environment oxygen concentration, and temperature. The modeling results show that the stress gradient effect on the oxidation rate cannot be ignored. Growth strain will dominate whether the stress gradient effect promotes or slows down the oxidation process. The stress gradient effect becomes weaker at higher temperature. This effect is amplified at higher concentrations of environmental oxygen. Applied mechanical loads do not affect the oxidation rate. This model is available for high temperature oxidation of metals and alloys.

NONCONFORMING FINITE ELEMENT METHOD FOR NONLINEAR PARABOLIC EQUATIONS

A nonconforming finite element method for the nonlinear parabolic equations is studied inthis paper.The convergence analysis is presented and the optimal error estimate in L^2(‖·‖_h)norm isobtained through Ritz projection technique,where ‖·‖_h is a norm over the finite element space.

RECENT PROGRESS ON CONTROLLABILITY/OB SERVABILITY FOR SYSTEMS GOVERNED BY PARTIAL DIFFERENTIAL EQUATIONS

The main purpose of this paper is to overview some recent methods and results on controllability/observability problems for systems governed by partial differential equations. First, the authors review the theory for linear partial differential equations, including the iteration method for the null controllability of the time-invariant heat equation and the Rellich-type multiplier method for the exact controllability of the time-invariant wave equation, and especially a unified controllability/observability theory for parabolic and hyperbolic equations based on a global Carleman estimate. Then, the authors present sharp global controllability results for both semi-linear parabolic and hyperbolic equations, based on linearization approach, sharp observability estimates for the corresponding linearized systems and the fixed point argument. Finally, the authors survey the local null controllability result for a class of quasilinear parabolic equations based on the global Carleman estimate, and the local exact controllability result for general hyperbolic equations based on a new unbounded perturbation techniaue.