Crystal Structure,Phase Transition and Ferroelastic Properties of [N(CH3)4]3[As2Cl9]

The crystal structure of [N(CH₃)₄]₃[As₂Cl₉] is determined at 293 K. It crystallizes in trigonal space group P31c: a = 9.2199(8), c = 21.065(3)Å, Z = 2, R₁ = 0.0505, wR₂ = 0.1283. The crystal is built of the discrete bioctahedral [As₂Cl₉]^3— anions and the deformed tetramethylammonium cations. A structural phase transition in [N(CH₃)₄]₃[As₂Cl₉] is detected by the DSC and dilatometric techniques at 146/151 K (on cooling/heating). Dielectric relaxation studies in the frequency range 75 kHz — 5 MHz indicate reorientations of the tetramethylammonium cations within the high temperature phase. Optical observations show the existence of the ferroelastic domain structure below 146 K. The possible mechanism of phase transition is discussed on the basis of the presented results.     

Catalytic Hydrosilylation of Furan, Thiophene, and Pyridine Aldimines

The addition of hydrosilanes (HSiEt₃, HSiMe₂Ph, H₂SiPh₂) to the CH=N bond of heterocyclic azomethines has been studied in the presence of monovalent complexes of rhodium and palladium. The effect on the reaction of the CF₃ group of the aldimines, which were obtained from O-, S-, and N-heteroaromatic aldehydes and 2-trifluoromethylaniline, has been clarified, as were other regularities of the processes being studied. A series of corresponding furans, thiophenes, and pyridine amines has been synthesized.     

Transition‐metal‐catalyzed reactions of 5‐methylene‐2‐oxazolidinone and 5‐methylene‐1,3‐thiazolidine‐2‐thione with isocyanates

5‐Methylene‐2‐oxazolidinone (1) and 5‐methylene‐1,3‐thiazolidine‐2‐thione (4) react with various isocyanates to give the corresponding urethanes 3 and 5 in high yields in the presence of palladium(0) or palladium(II) catalyst under mild reaction conditions. A mechanism is proposed. Copyright © 2003 John Wiley & Sons, Ltd.     

利用相干渡越辐射测量电子束团长度的分析与计算

利用相干渡越辐射(CTR)测量短和超短电子束团长度是国际上束测领域新发展的频域测量技术.文中理论分析和数值计算了北京自由电子激光装置的皮秒级的射频电子束团序列产生的CTR,当辐射波长在长于束长(4ps)时,渡越辐射发生相干增强效应;与非相干渡越辐射相比,当λ≥2πσz时,增强的倍数约等于束团中粒子的数目(10⁸);CTR从亚毫米波到毫米波段呈宽带连续谱特性;渡越辐射能量主要集中在轴线附近,宏脉冲辐射能量高达几毫焦.设计采用偏振型束团长度测量系统,利用CTR自相关技术,实验测量该束团序列的纵向长度,并藉助傅里叶变换光谱法,推求束团电子分布.     

向列液晶表面弹性能K13项的物理效应及检验方法

通过解析推导和数值计算的方法，得到了平衡态指向矢满足的微分方程和边界条件.研究了表面弹性能K13项对磁场作用下的弱锚定向列液晶盒Fréedericksz转变性质的影响.结果表明，表面弹性能K13项的存在对液晶系统的自由能有很大的影响，从而改变转变的性质，诱导液晶盒在阈值点发生一级Fréedericksz转变.给出了发生一级转变的物理条件，它除了与液晶的结构和材料有关外，还依赖于液晶表面弹性能K13项，同时给出了由此判断K13项是否存在的检验方法. 关键词： 表面弹性能K13项 弱锚定 Fréedericksz转变     

Thermal degradation of two liquid fuels and detonation tests for pulse detonation engine studies

The use of liquid fuels such as kerosene is of interest for the pulse detonation engine (PDE). Within this context, the aim of this work, which is a preliminary study, was to show the feasibility to initiate a detonation in air with liquid-fuel pyrolysis products, using energies and dimensions of test facility similars to those of PDEs. Therefore, two liquids fuels have been compared, JP10, which is a synthesis fuel generally used in the field of missile applications, and decane, which is one of the major components of standard kerosenes (F-34, Jet A1, ...). The thermal degradation of these fuels was studied with two pyrolysis processes, a batch reactor and a flow reactor. The temperatures varied from 600°C to 1,000°C and residence times for the batch reactor and the flow reactor were, respectively, between 10–30 s and 0.1–2 s. Subsequently, the detonability of synthetic gaseous mixtures, which was a schematisation of the decomposition state after the pyrolysis process, has been studied. The detonability study, regarding nitrogen dilution and equivalence ratio, was investigated in a 50 mm-diameter, 2.5 m-long detonation tube. These dimensions are compatible with applications in the aircraft industry and, more particularly, in PDEs. Therefore, JP10 and decane were compared to choose the best candidate for liquid-fuel PDE studies. This paper was based on work that was presented at the 20th International Colloquium on the Dynamics of Explosions and Reactive Systems, Montreal, Canada, July 31 – August 5, 2005.     

Nonparametric estimation and adaptive control in a class of finite Markov decision chains

We consider a class of Markov decision processes withfinite state and action spaces which, essentially, is determined by the following condition: The state space isirreducible under the action of any stationary policy. However, except by this restriction, the transition law iscompletely unknown to the controller. In this context, we find a set of policies under which thefrequency estimators of the transition law are strongly consistent and then, this result is applied to constructadaptive asymptotically discount-optimal policies.Dedicated to Professor Truman O. Lewis, on the occasion of his sixtieth birthdayThis research was supported in part by the Third World Academy of Sciences (TWAS) under Grant TWAS RG MP 898-152, and in part by the Consejo Nacional de Ciencia y Tecnología (CONACYT) under Grant A128CCOEO550 (MT-2).     

关于三维各向同性谐振子径向矩阵元计算的讨论

根据广义Laguerre多项式的数学性质，导出了较为简单的三维各向同性谐振子径向矩阵元的普遍公式,并在这基础上计算了一些重要特殊情形的径向矩阵元: 矢径r整数次幂的平均值，电偶极跃迁矩阵元和电四极跃迁矩阵元. 关键词： 三维各向同性谐振子 径向矩阵元 广义Laguerre多项式 偶极跃迁 四极跃迁     

Notes on Sublattice-Lattices

We prove that directly reducible lattices and selfdual subdirectly irreducible lattices of locally finite length are determined by their sublattice-lattices. As a corollary we obtain that splitting varieties are closed under the isomorphism of sublattice-lattices iff they are selfdual. A class of selfdual non-closed varieties is given too.     

用玻色子组态混合和玻色子表面δ相互作用研究核谱

用玻色子组态混合波函数和玻色子表面δ相互作用研究了三玻色子核⁴⁶Ti和⁵⁴Cr的sdgIBMI的能谱和E2跃迁概率,理论计算结果令人满意,比sdIBMI能拟合出更多的能级和E2跃迁概率,而且它们的误差更小. 说明g玻色子在振动区也起着重要的作用,同时进一步证明了这种玻色子组态混合模型是成功的.