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高技术用混合气体节制冷循环吴沛宜,许名尧(西安交通大学动力系西安710049)关键词:技术,气体,制冷循环。THETHROTTLINGREFRIGERATIONCYCLESUSINGMIXINGGASESUSEDINHIGHTECHNIQUE¥WuP... 相似文献
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(GdO)3BO3:Eu^3+的合成及其荧光与结构的关系 总被引:2,自引:0,他引:2
以Li2CO3为助熔剂合成了(GdO)3BO3纯物相,并利用多晶X射线衍射研究了(GdO)3BO3的结构,根据(GdO)3BO3所属空间群中等效点系的对称性及Eu^3+的荧光光谱,推断出Gd^3+在(GdO)3BO3中所处格位的点对称性为C1,C2或C3。 相似文献
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本成功地合成了一系列新型Pb-1222相层状铜氧化物(Pb0.5Cd0.5)(Sr0.9R0.1)2(R‘0.7Ce0.3)2Cu2Oz,R=R’=Y,Pr,Sm,Eu,Gd,Dy,Ho以有(R,R‘)=(La,Eu),Sm,Gd),(Sm,Eu),(La,Gd),(Eu,Gd),(Nd,Dy),(Nd,Y),(Nd,Er)。 相似文献
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意大利和荷兰联合发射的卫星BeppoSAX在1997年2月28日探测到γ暴GRB970228的X射线余辉,随后的地面和哈勃空间望远镜的观测证实在该位置上有一光学瞬变源。哈勃空间望远镜在此光学变源方位观测到一暗的河外天体。 相似文献
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本文成功地合成了一系列新型Pb-1222相层状铜氧化物(Pb0.5Cd0.5)(Sr0.9R0.1)2(R'0.7Ce0.3)2。Cu2Ox,R=R'=Y,Pr,Sm,Eu,Gd,Dy,Ho以及(R,R’)=(La,Eu),(Sm,Gd),(Sm,Eu),(La,Gd),(Eu,Gd),(Nd,Eu),(Nd,Dy),(Nd,Y),(Nd,Er).X-射线衍射和电子衍射表明它们属于四方晶系,其结构与(Pb,CU)-1222相结构相似.其中(R',R')=(Eu,Gd)的样品在氧气中成相得到23K的超导转变临界温度. 相似文献
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本文研究了PEG2000铬菁R(NH4)2SO4体系对Co(Ⅱ)、Ni(Ⅱ)的非有机溶剂萃取行为。指出在pH=5的(NaAcHAc)水溶液中,有(NH4)2SO4存在下,Ni(Ⅱ)可被PEG相几乎完全萃取,而Co(Ⅱ)则基本上不被萃取。从而获得了Co(Ⅱ)与Ni(Ⅱ)混合离子的定量分离。 相似文献
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Solitary Wave in Linear ODE with Variable Coefficients 总被引:1,自引:0,他引:1
In this paper, the linear ordinary differential equations with variable coefficients are obtained from thecontrolling equations satisfied by wavelet transform or atmospheric internal gravity waves, and these linear equationscan be further transformed into Weber equations. From Weber equations, the homoclinic orbit solutions can be derived,so the solitary wave solutions to linear equations with variable coefficients are obtained. 相似文献
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O. AKSOGANA.H. SOFIYEV 《Journal of sound and vibration》2002,254(4):693-702
In this study, the dynamic buckling of an elastic cylindrical shell with variable thickness, subject to a uniform external pressure which is a power function of time, has been considered. Initially, the fundamental relations and Donnell-type dynamic buckling equation of an elastic cylindrical shell with variable thickness have been obtained. Then, employing Galerkin's method, these equations have been reduced to a time-dependent differential equation with variable coefficients. Finally, applying a special Ritz-type method, the critical static and dynamic loads, the corresponding wave numbers and dynamic factor have been found analytically. Using those results, the effects of the variation of the thickness with a linear, a parabolic or an exponential function in the axial direction and the effect of the variation of the power of time in the external pressure expression are studied using pertinent computations. It is observed that these effects change appreciably the critical parameters of the problem. The present method has been verified, comparing the results of the present work and those of previous works in the literature, for a shell with constant thickness subject to a uniform external pressure varying linearly with time. 相似文献
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This paper deals with the free axisymmetric vibrations of orthotropic circular plates with linear variation in thickness. The analysis is based on a set of two differential equations derived by an extension of Mindlin's shear theory for plates. On simplification and algebraic manipulation, one of the dependent variables is eliminated from the governing equations of motion, giving rise to a fourth order linear differential equation with variable coefficients. The resulting differential equation is solved numerically by the Chebyshev collocation technique. Frequencies and mode shapes for the first five modes of vibration are computed for different plates. 相似文献
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There are many interesting methods can be utilized to construct special solutions of nonlinear differential equations with constant coefficients. However, most of these methods are not applicable to nonlinear differential equations with variable coefficients. A new method is presented in this Letter, which can be used to find special solutions of nonlinear differential equations with variable coefficients. This method is based on seeking appropriate Bernoulli equation corresponding to the equation studied. Many well-known equations are chosen to illustrate the application of this method. 相似文献
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提出了一种基于边界元法求解变系数瞬态热传导问题的特征正交分解(POD)降阶方法,重组并推导出变系数瞬态热传导问题适合降阶的边界元离散积分方程,建立了变系数瞬态热传导问题边界元格式的POD降阶模型,并用常数边界条件下建立的瞬态热传导问题的POD降阶模态,对光滑时变边界条件瞬态热传导问题进行降阶分析.首先,对一个变系数瞬态热传导问题,建立其边界域积分方程,并将域积分转换成边界积分;其次,离散并重组积分方程,获得可用于降阶分析的矩阵形式的时间微分方程组;最后,用POD模态矩阵对该时间微分方程组进行降阶处理,建立降阶模型并对其求解.数值算例验证了本文方法的正确性和有效性.研究表明:1)常数边界条件下建立的低阶POD模态矩阵,能够用来准确预测复杂光滑时变边界条件下的温度场结果;2)低阶模型的建立,解决了边界元法中采用时间差分推进技术求解大型时间微分方程组时求解速度慢、算法稳定性差的问题. 相似文献
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By introducing displacement functions as well as stress functions, two independent state equations with variable coefficients are established from the three-dimensional equations of a radially inhomogeneous spherically isotropic piezoelastic medium. By virtue of the laminated approximation method, the state equations are then transformed into the ones with constant variables in each layer, and the state variable solutions are presented. Based on the solutions, linear algebraic equations about the state variables only at the inner and outer spherical surfaces are derived by utilizing the continuity conditions at each interface. Frequency equations corresponding to two independent classes of vibrations are finally obtained from the free surface conditions. Numerical calculations are presented and the effect of the material gradient index on natural frequencies is discussed. 相似文献