丹东地区健康小学生发样中Zn、Fe、Cu、Ca和Mg等微量元素的测定

本文通过原子吸收光谱法对丹东地区万余名6-13岁健康小学生发样中Zn、Fe、Cu、Ca、Mg等微量元素的含量状况进行了分析,结果表明丹东地区6-13岁健康小学生普遍缺Zn,且以男学生尤为明显,其他微量元素在各不同年龄阶段也有不同程度的缺乏.同时获得了一系列相关数据,从而为丹东小学生的健康生长发育提供了极有价值的参考资料和科学依据.     

Development of new triangular elements for free surface flows

New finite elements have been developed to simulate steady and unsteady two-dimensional free surface flows. The depth-averaged velocity components with the free surface elevation have been used as independent variables in the model. The differences between the various elements presented lie in the choice of velocity approximation. The Newton–Raphson method has been used to solve the non-linear system of equations. Emphasis is put on bench-mark examples to assess the accuracy and efficiency of the elements. A simple stable new element tested herein shows promising advantages for industrial finite element codes.     

ICP－AES法同时测定磷铁中的主含量元素和杂质

本文研究用ＩＣＰ－ＡＥＳ法同时测定磷铁的主含量元素Ｐ和杂质元素Ｓｉ、Ｍｎ、Ｔｉ、Ｖ、Ｃｒ的方法。采用碱熔酸化分解试样，选Ｂ为测Ｐ的内标元素，回收率为９６％－１０２％，最大相对标准偏差为８．６０％，大多数结果的相对标准偏差小于５％。     

ICP-AES法同时测定饮用水中Pb, As等11种金属元素

本文建立了ICP AES(电感耦合等离子体发射光谱仪 )法同时测定生活饮用水中的铅、砷、铜、铁、锌、锰、铬、镉、银、铝、硒的分析方法 ,采用超声波雾化器 ,提高了雾化效率 ,同时提高分析的灵敏度。优化了ICP工作参数 ,研究了酸度对测定的影响 ,并进行了元素分析线的选择、背景扣除方式和共存元素干扰的试验。该法相关性好 (r为 0 9993～ 0 9998) ,线性范围广 ,精密度RSD <9 8% ,准确度好 ,样品加标回收率为 90 0 %～ 10 9 7% ,检出限低 ,具有分析速度快 ,多元素同时测定 ,操作简便等优点。应用于实际样品的测定 ,结果满意。     

Effect of microstructure of MgO buffer layer on BaTiO3 grown on silicon substrates

MgO ultrathin films were grown on Si(1 0 0) substrates as buffer layers for the growth of ferroelectric BaTiO₃ thin films by laser molecular beam epitaxy (L-MBE). The deposition process of MgO buffer layers grown on silicon was in situ monitored by reflection high-energy electron diffraction (RHEED). The structure of BaTiO₃ films fabricated on MgO buffers was investigated by X-ray diffraction. Biaxially textured MgO was obtained at high laser energy density, but when the laser energy was lowered, MgO buffer was transformed to the form of texture with angular dispersion with the increase of the film thickness. BaTiO₃ films grown on the former buffer were completely (0 0 1) textured, while those on the latter were (0 0 1) preferred orientated. Furthermore, the fabricated MgO buffers and BaTiO₃ films had atomically smooth surface and interface. All these can reveal that the quality of textured MgO buffer is a key factor for the growth of BaTiO₃ films on silicon.     

Influences of Pressure and Substrate Temperature on Epitaxial Growth of γ-Mg2SiO4 Thin Films on Si Substrates

An epitsucial γ-Mg2SiO4 thin film can be a good buffer between the Si substrate and some oxide thin films. For high temperature superconducting multilayer structures, hopefully it can be taken as an insulating layer to replace the widely used MgO film. To explore such possibilities, we carry out systematic studies on the influences of pressure and substrate temperature on the epitaxy of γ-Mg2SiO4 thin films grown on Si （100） substrates using rf magnetron sputtering with an Mg target of purity of 99.95 percent. With the substrate temperature kept at 500℃ and the pressure changing from lO Pa to 15 Pa, in the XRD spectra the 7-Mg2SiO4 （400） peak grows drastically while the MgO （200） peak is suppressed. Keeping the pressure at 15Pa and increasing the temperature from 500℃ to 570℃ further can improve the film epitaxy, while working at 780℃ and 11Pa seems to give very good results. X-ray photoelectronic spectroscopy and φ scan are used to characterize the stoichiometry, crystallinity, and in-plane growth of the samples.     

Molecular Dynamics Simulation of Myoglobin Collision with Low Energy Ions

Collisions of a low energy heavy ion with a myoglobin in water are simulated by molecular dynamics model. The increase of total energy is very small. The mean squared fluctuation decreases at 300 K and increases at 250K. This is an important novel cooling effect that protects the protein from ion damage. The possible collision side effect is the change of tertiary structure that blocks the normal functions of the myoglobin.     

Approach to a Cauchy Problem in Stability Study of the Schwarzschild Black Hole

Generally, the Schwarzschild black hole is proven to be stable by two different methods： the mode-decomposition method and the integral method. We show that the integral method can only apply to the initial data vanishing at both the horizon and the spatial infinity. It can not treat the initial data only vanishing at the spatial infinity. We give an example to show the misleading information caused by the use of tortoise coordinates in the perturbation equations. Subsequently, the perturbation equations in the Schwarzschild coordinates are shown to be insuftlcient for the stability study.     

火焰原子吸收光谱法测定铁树中微量元素

采用干式灰化法对铁树叶进行灰化处理,将其残渣溶于HNO3溶液中,用火焰原子吸收分光光度计测定了铁树中的Cd、Co、Mn、Zn、Mg、Ca、Fe、Pb、Cu、Ni等10种微量元素的含量.实验表明,铁树中Ca、Mg、Fe和Zn含量较丰富.     

Flip-Chip GaN-Based Light-Emitting Diodes with Mesh-Contact Electrodes

GaN-based light-emitting diodes （LEDs） with mesh-contact electrodes have been developed. The p-type ohmic contact layer is composed of oxidized Ni/Au mesh and NiO overlay （20A）. An Ag （3000A） omni-directional reflector covers the p-type contact. The n-type contact is a Ti/AI planar film with a 10-μm-width Ti/AI stripe. The Ti/AI stripe surrounds the centre of LED mesa. With a 20-mA current injection, the light output power of GaN-based LEDs with mesh-contact electrodes is 23% higher than that of the conventional LEDs.