Cooperative C-H…O H-bonds in ''Bay Area'' and Crystal Structure of 1-(4-Methylphenyl)- 3-(4-methoxyphenyl)-2-propene-1-one

The title compound (C17H16O2, Mr = 252.30) crystallizes in the monoclinic system, space group P21/c with a = 11.5763(14), b = 11.0321(11), c = 11.5094(13) (A),β = 114.581(3)°, V= 1336.7(3) (A)3, Z = 4, Dc = 1.254 g/cm3, μ(MoKa) = 0.081 cm-1 and F(000) = 536.00. The final R and wR are 0.0527 and 0.1285, respectively for 3058 observed reflections (I ＞ 2σ(I)). In the title molecule, two phenyl rings are rotated oppositely with respect to the central part C(1)-C(2)=C(3)- C(4) (plane 3) and the dihedral angle between them is 14.8°. The phenone O(1) atom deviates from plane 3 by 0.291(A). In the crystal the molecules form H-bond chains of R21(6) and R21 (5) types similar crystals are also presented.     

Complex zero; Fundamental Therorem of Algbra

In this section we will find the complex zero of a polynomial function. Since the set of real numbers is a subset of the set of complex numbers, finding all zeros of a function requires finding all zeros of the form a ＋ bi. These zeros will be real if b = 0.     

渐近波形估计技术在三维电磁散射中的应用

将渐近波形估计(AWE)技术运用到矩量法计算宽角度三维导体的雷达散射截面(RCS)中,通过矩量法求解电场积分方程,得到导体在某一给定方向入射波照射下的感应电流,然后使用AWE技术将任意角度入射波照射下的感应电流在给定角度附近展开成Taylor级数,利用Pad啨逼近将Taylor级数转化为有理函数,由此获得三维导体在任意角度入射波照射下的感应电流,进而计算出雷达散射截面。计算结果表明:渐进波形估计技术与矩量法结合完全能够逼近矩量法计算的结果,并且计算效率提高一个数量级.     

POWER FUNCTIONS

<正>A power function of degree n is a function of the form f(x)=ax~n.For large n,it appears that the graph coincide with the x-axis near the origin,but it does not;the graph actually touches the x—axis only at the origin.     

单体滴加法微乳液聚合过程中PMMA物理水凝胶形成的研究

在70℃下,以过硫酸铵(APS)为引发剂,采用单体滴加法,进行微乳液聚合,制得的聚甲基丙烯酸甲酯(PMMA)微乳液可形成几乎透明的物理水凝胶.扫描电镜(SEM)实验表明,这种水凝胶是由大量的聚合物纳米粒子彼此连接而成的物理网络形成的.讨论了影响水凝胶形成的因素,提出了水凝胶形成的机理.     

Comparative study of electrical characteristics for n-type 4H–SiC planar and trench MOS capacitors annealed in ambient NO

The interface properties and electrical characteristics of the n-type 4H-SiC planar and trench metal–oxide–semiconductor(MOS) capacitors are investigated by measuring the capacitance voltage and current voltage. The flat-band voltage and interface state density are evaluated by the quasi-static method. It is not effective on further improving the interface properties annealing at 1250℃ in NO ambient for above 1 h due to the increasing interface shallow and fast states.These shallow states reduce the effective positive fixed charge density in the oxide. For the vertical MOS capacitors on the(1120) and(1100) faces, the interface state density can be reduced by approximately one order of magnitude, in comparison to the result of the planar MOS capacitors on the(0001) face under the same NO annealing condition. In addition, it is found that Fowler–Nordheim tunneling current occurs at an oxide electric field of 7 MV/cm for the planar MOS device.However, Poole–Frenkel conduction current occurs at a lower electric field of 4 MV/cm for the trench MOS capacitor. This is due to the local field crowded at the trench corner severely causing the electrons to be early captured at or emitted from the SiO_2/Si C interface. These results provide a reference for an in-depth understanding of the mobility-limiting factors and long term reliability of the trench and planar SiO_2/Si C interfaces.     

谈高等数学实验课的开设

高等数学实验课的开设很有必要,但应被置于辅助地位,在实际操作中适时适度地与理论学习相协调。     

新型1,2,4-三唑啉酮类化合物的合成及生物活性

以碳酸二甲酯为起始原料, 设计并合成了一系列新颖的1,2,4-三唑啉酮类化合物. 通过1H NMR, MS和元素分析确证了其结构.初步生物活性测定结果表明, 部分化合物具有一定的除草活性.     

Doped Polycrystalline 3C-SiC Films Deposited by LPCVD for Radio-Frequency MEMS Applications

Polycrystalline 3C-SiC films are deposited on SiO2 coated Si substrates by low pressure chemical vapour deposition （LPCVD） with C3H8 and SiH4 as precursors. Controlled nitrogen doping is performed by adding NH3 during SiC growth to obtain the low resistivity 3C-SiC films. X-ray diffraction （XRD） patterns indicate that the deposited films are highly textured （111） orientation. The surface morphology and roughness are determined by scanning electron microscopy （SEM） and atomic force microscopy （AFM）. The surface features are spherulitic texture with average grain size of 100nm, and the rms roughness is 20nm （AFM 5×5 μm images）. Polycrystalline 3C-SiC films with highly orientational texture and good surface morphology deposited on SiO2 coated Si substrates could be used to fabricate rf microelectromechanical systems （MEMS） devices such as SiC based filters.     

星形热弹性网络系统的稳定性及Riesz基性质

研究了一类星形弹性网络系统在热效应影响以及边界反馈作用下的稳定性问题及系统相应（广义）特征向量的Riesz基性质．基于Green和Naghdi第二类热弹性理论,假设在该热弹性系统中热以有限波速传播,并且在传播过程中无能量耗散．证明了该热弹性网络系统能量渐近衰减到零．并进一步通过系统算子谱分析,讨论得出该系统算子的（广义）特征向量构成状态空间的一组Riesz基．