抽运激光在光靶中的局域及其对X射线激光特性的影响

新型X射线靶设计为:由SiO2和TiO2组成具有12个周期的一维光子晶体,在它的中间嵌入光靶材料层作为缺陷层,SiO2,TiO2和光靶层的光学厚度分别为λ4、λ4和λ2,λ为抽运激光波长.与普通平板光靶相比,当抽运光垂直照射到这种光靶时,靶层内部的光强将提高2个数量级,所以抽运激光的阈值强度将降低2个数量级,这有利于X射线激光的小型化.在同样的抽运激光照射下,X射线激光的强度将提高4个数量级,转换效率也将提高约4个数量级.由于平均电离度随抽运激光强度的提高而提高,所以采用这种光靶有利于使X射线激光向短波长推进. 关键词： X射线激光 光子晶体 光波局域     

液晶显示器用衬垫料的扫描电镜图像

论述了液晶显示器 (LCD)用衬垫料的作用和性能要求。给出了液晶显示器用衬垫料的扫描电镜图像。该图像对观测衬垫料的粒径分布和控制液晶显示器的盒厚均匀程度 ,消除液晶显示器的底色差异具有一定的意义。实验所得图像为从事液晶显示器的工程技术人员提供了清晰的衬垫料图像 ,为排除衬垫料的不均匀因素所造成的液晶屏的质量问题提供了依据。     

非保守力学系统Nielsen方程的形式不变性

研究非保守力学系统Nielsen方程的形式不变性.给出非保守力学系统Nielsen方程的形式不变性的定义和判据,研究形式不变性和Noether对称性的关系,并举例说明结果的应用 关键词： 非保守力学系统 Nielsen方程 形式不变性 Noether对称性     

ICP-AES测定饮用水源中的Cu、Mn、Pb、Cd、Zn

用ICP－AES法同时测定饮用水源中的Cu、Mn、Pb、Cd、Zn等重金属元素，具有基体效应小、测量范围宽等优点。检出限为0．2－4．0μg/L，回收率为91．5％－103．9％，相对标准偏差为0．29％－1．5％，测定密码样与实际样品，结果令人满意。     

Synthesis of a Novel Aromatic Diamino-bridged Bis（β-cyclodextrin） and its Inclusion Complexation with Dyes Molecules

Bridged bis(β-cyclodextrin)s (CDs), as a very important family of CD derivatives, have been known that they can significantly alter the molecular binding ability and selectivity toward a variety of guests in comparison with parent cyclodextrin. Their two…     

Two New Eremophilenolides from Ligularia muliensis

Many Ligularia species have long been used as traditional folk medicine for theirantibiotic, antiphlogistic and antitussive activities1, and were found to be an importantsource of eremophilane. In the course of our search for bioactive sesquiterpenoids, w…     

一些特殊图类乘积的离散度

连通图的离散度是用s(G)来表示的,s(G)=max{ω(G-S)-|S|:ω(G-S)>1,SV(G)}.给出了两个完全图乘积的和一个完全图与路的乘积的离散度.还给出了两个完全图乘积的坚韧度.     

Paper-like Microfibrous Nickel Catalyst for Hydrogen Production via NH3 Decomposition in Fuel Cell Applications

Recently, miniature H2 generator to power fuel cells for portable/micro electronic devices and passenger propulsion has been the focus of intense research activities1-3. One of the strategies is to find simple CO-free H2 production with novel microreactor…     

Microwave synthesis of magnetic Fe3O4 nanoparticles used as a precursor of nanocomposites and ferrofluids

Methods to synthesize magnetic Fe₃O₄ nanoparticles and to modify the surface of particles are presented in the present investigation. Fe₃O₄ magnetic nanoparticles were prepared by the co-precipitation of Fe³⁺ and Fe²⁺, NH₃·H₂O was used as the precipitating agent to adjust the pH value, and the aging of Fe₃O₄ magnetic nanoparticles was accelerated by microwave (MW) irradiation. The obtained Fe₃O₄ magnetic nanoparticles were characterized by Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and vibrating sample magnetometer (VSM). The average size of Fe₃O₄ crystallites was found to be around 8–9 nm. Thereafter, the surface of Fe₃O₄ magnetic nanoparticles was modified by stearic acid. The resultant sample was characterized by FT-IR, scanning electron microscopy (SEM), XRD, lipophilic degree (LD) and sedimentation test. The FT-IR results indicated that a covalent bond was formed by chemical reaction between the hydroxyl groups on the surface of Fe₃O₄ nanoparticles and carboxyl groups of stearic acid, which changed the polarity of Fe₃O₄ nanoparticles. The dispersion of Fe₃O₄ in organic solvent was greatly improved. Effects of reaction time, reaction temperature and concentration of stearic acid on particle surface modification were investigated. In addition, Fe₃O₄/polystyrene (PS) nanocomposite was synthesized by adding surface modified Fe₃O₄ magnetic nanoparticles into styrene monomer, followed by the radical polymerization. The obtained nanocomposite was tested by thermogravimetry (TG), differential scanning calorimetry (DSC) and XRD. Results revealed that the thermal stability of PS was not significantly changed after adding Fe₃O₄ nanoparticles. The Fe₃O₄ magnetic fluid was characterized using UV–vis spectrophotometer, Gouy magnetic balance and laser particle-size analyzer. The testing results showed that the magnetic fluid had excellent stability, and had susceptibility of 4.46×10⁻⁸ and saturated magnetization of 6.56 emu/g. In addition, the mean size d (0.99) of magnetic Fe₃O₄ nanoparticles in the fluid was 36.19 nm.     

Liquid phase oxidation of p-chlorotoluene to p-chlorobenzaldehyde over cobalt-doped mesoporous titania with a crystalline framework

Cobalt-doped mesoporous titania with a crystalline framework synthesized by surfactant templating method presented highly selective (99%) and reasonable conversion rate (49%) of catalytic oxidation of para-chlorotoluene to para-chlorobenzaldehyde in acetic acid using aqueous hydrogen peroxide as oxidant for the first time. Recycling of the catalyst indicates that the catalyst can be used a number of times without losing its activity to a greater extent. By contrast, cobalt-doped mesoporous titania without a crystalline structure and cobalt doped the commercial titania, Degussa P25 prepared by impregnation method with the similar concentration of cobalt were found inactive. The effects of catalyst concentration, reaction time, reaction temperature, and solvents on the performance of the catalyst were also investigated.