Phase transition studies in polymesomorphic compounds(v): Density studies in N-(p-n-Octyloxy benzylidene)-p-n-butyl aniline

The density, ρ, of N-(p-n-octyloxy benzylidene) p-n-butyl aniline (OBBA) is measured as a function of temperature from the isotropic liquid to the smectic-G phase. The compound is trimorphic, exhibiting three smectic phases, smectic-G, crystal smectic-B, and smectic-A phase. The changes in density across the phase transformations and the calculated thermal expansion coefficients confirm the order of the transitions as first order. Particular importance of the smectic-A to crystal smectic-B transformation, which is of first order, is apparent from the density jump across the transition.     

CO2 laser beam modulating for surface texturing machining

Laser texturing is a novel technique that may be used to texture a cold roller in the process of manufacturing high quality steel sheets. With the aim of improving the quality of the textured roller by using a CO₂ laser, a new laser beam modulating device is proposed. An optical beam expander with a fast rotating chopper system is designed. The laser pulse is split into two parts by the chopper blades; one is the preheating pulse that is reflected onto optical loop mirrors; the other is the directly transmitted pulse that creates the craters at the preheated spots. The preheating beam focus spot size and position can be adjusted. The focusing characteristics and optical parameter compensation for the flying optics are investigated. The heat transfer and melt process of laser texturing are numerically simulated. The effects of the double pulses on the texturing are analyzed. The effect of preheating the sample ahead of the laser texturing pulse is examined. The surface profile and bump hardness show improvements by using this approach.     

70MHz连续波质子束脉冲化装置

为了进行强流回旋加速器关键技术研究, 中国原子能科学研究院建立了一个强流回旋加速器综合试验装置. 中国原子能研究院将在这个回旋加速器综合试验装置上建立强流脉冲化实验装置, 目标是实现几十至百keV量级的强流束的脉冲化. 具体是将70MHz连续波负氢束脉冲化为重复频率1—8MHz, 脉冲宽度约为10ns的脉冲质子束. 脉冲化装置将主要包括束流切割器和聚束器两大系统. 聚束器采用频率为70.487MHz的双间隙单漂移栅网结构, 可以将直流束压缩到±30°的回旋加速器高频接受相宽之内. 束流切割器将采用频率为2.2MHz的正弦波, 切割后的脉冲宽度将小于8ns, 最后得到的脉冲束的重复频率为4.4MHz.     

Riemannian three dimensional molecular spaces

A simple manipulation of the first order density function permits to define a curved 3D Riemannian coordinate set, which can substitute the usual flat 3D Cartesian space, where atoms and molecules are supposed to exist. Several simple models are discussed. Gaussian type orbitals generate a space division with positive and negative curvatures, the later one being near the centre of the functions; contrarily Slater type orbitals provide a positive curvature everywhere.     

The Koszul dual of a weakly Koszul module

We study the so-called weakly Koszul modules and characterise their Koszul duals. We show that the (adjusted) associated graded module of a weakly Koszul module exactly determines the homology modules of the Koszul dual. We give an example of a quasi-Koszul module which is not weakly Koszul.     

Spatially Dependent Kinetics of Electrons and Excited Atoms in the Column Plasma of a He–Xe dc Discharge

The radially varying kinetics of electrons and excited atoms in the cylindrical axially homogeneous positive column of a dc glow discharge in a gas mixture of helium and 2% xenon was studied. The experimental investigations comprise the radially resolved measurements of the isotropic part of the electron velocity distribution function (EVDF) using a single-probe technique and of the densities of atoms in the lower excited states by using a laser diode absorption method. The theoretical investigations are based on the solution of the space-dependent kinetic equation for the EVDF and the balance equations of excited gas atoms. Besides a strict solution, various simplified treatments of the electron kinetics as the conventional homogeneous approach and the nonlocal approach have been applied. The electron kinetic behavior in the helium–xenon column plasma changes remarkably with increasing helium gas pressure from a distinctly nonlocal behavior at a low pressure of 100 Pa to a nearly local behavior at a medium pressure of 600 Pa.     

FeMn掺杂AlN薄膜的制备及其特性研究

采用直流磁控共溅射技术, 以Ar与N₂为源气体, 硅片为衬底成功地制备了Fe, Mn掺杂AlN薄膜. 利用X射线衍射和拉曼光谱研究了工作电流、靶基距离等工艺参数的改变对薄膜结构的影响. 利用扫描电子显微镜和能谱分析仪对薄膜的表面形貌和组成成分进行了分析. 利用振动样品磁强计在室温下对Fe, Mn掺杂AlN薄膜进行了磁性表征. Mn掺杂AlN薄膜表现出顺磁性的原因可能是由于Mn掺杂浓度较高, 在沉积过程部分Mn以团簇的形式存在, 反铁磁性的Mn团簇减弱了体系的铁磁交换作用. Fe掺杂AlN薄膜表现出室温铁磁性, 这可能是AlFeN三元化合物作用的结果. 随着Fe 掺杂AlN薄膜中Fe原子浓度从6.81%增加到16.17%, 其饱和磁化强度M_s由0.27 emu·cm^-3逐渐下降到0.20 emu·cm^-3, 而矫顽力H_c则由57 Oe增大到115 Oe (1 Oe=79.5775 A/m), 这一现象与Fe离子间距离的缩短及反铁磁耦合作用增强有关. 关键词： 直流磁控共溅射 氮化铝薄膜 结构 磁性     

Physical Properties of Zinc Oxide Films Prepared by dc Reactive Magnetron Sputtering at Different Sputtering Pressures

Thin films of zinc oxide were deposited by dc reactive magnetron sputtering onto glass substrates held at a temperature of 663 K and oxygen partial pressure of 1x10^‐3 mbar, and at different sputtering pressures in the range 3x10^‐2 ‐ 10x10^‐2 mbar. The effect of sputtering pressure on the structural, electrical and optical properties of the films were systematically studied. The films were polycrystalline in nature with preferred (002) orientation. The temperature dependence of Hall mobility indicated that the grain boundary scattering of the charge carriers are predominant in these films. The films formed at a sputtering pressure of 6x10^‐2 mbar showed a low electrical resistivity of 6.9x10^‐2 Ohm cm, optical transmittance of 83% with an optical band gap of 3.28 eV.     

Chromatographic retention prediction and octanol-water partition coefficient determination of monobasic weak acidic compounds in ion-suppression reversed-phase liquid chromatography using acids as ion-suppressors

Although simple acids, replacing buffers, have been widely applied to suppress the ionization of weakly ionizable acidic analytes in reversed-phase liquid chromatography (RPLC), none of the previously reported works focused on the systematic studies about the retention behavior of the acidic solutes in this ion-suppression RPLC mode. The subject of this paper was therefore to investigate the retention behavior of monobasic weak acidic compounds using acetic, perchloric and phosphoric acids as the ion-suppressors. The apparent octanol-water partition coefficient (K^″ow) was proposed to calibrate the octanol-water partition coefficient (Kow) of these weak acidic compounds, which resulted in a better linear correlation with log kw, the logarithm of the hypothetical retention factor corresponding to neat aqueous fraction of hydroorganic mobile phase. This log K^″ow−log kw linear correlation was successfully validated by the results of monocarboxylic acids and monohydrating phenols, and moreover by the results under diverse experimental conditions for the same solutes. This straightforward relationship not only can be used to effectively predict the retention values of weak acidic solutes combined with Snyder-Soczewinski equation, but also can offer a promising medium for directly measuring Kow data of these compounds via Collander equation. In addition, the influence of the different ion-suppressors on the retention of weak acidic compounds was also compared in this RPLC mode.