Carbon monolith: Preparation,characterization and application as microextraction fiber

A carbon monolith was synthesized via a polymerization–carbonization method, styrene and divinylbenzene being adopted as precursors and dodecanol as a porogen during polymerization. The resultant monolith had bimodal porous substructure, narrowly distributed nano skeleton pores and uniform textural pores or throughpores. The carbon monolith was directly used as an extracting fiber, taking place of the coated silica fibers in commercially available solid-phase microextraction device, for the extraction of phenols followed by gas chromatography–mass spectrometry. Under the studied conditions, the calibration curves were linear from 0.5 to 50 ng mL⁻¹ for phenol, o-nitrophenol, 2,4-dichlorophenol and p-chlorophenol. The limits of detection were between 0.04 and 0.43 ng mL⁻¹. The recoveries of the phenols spiked in real water samples at 10 ng mL⁻¹ were between 85% and 98% with the relative standard deviations below 10%. Compared with the commercial coated ones (e.g. PDMS, CW/DVB and DVB/CAR/PDMS), the carbon monolith-based fiber had advantages of faster extraction equilibrium and higher extraction capacity due to the superior pore connectivity and pore openness resulting from its bimodal porous substructure.     

旋流阻塞与旋流扩散复合内消能泄洪洞的壁面压强特性

结合雅砻江两河口水电站3#导流洞改建的水工模型试验,研究了新型旋流阻塞和旋流扩散复合内消能泄洪洞的壁面压强特性。研究结果表明:在淹没堰流流态时,壁面压强在进口的堰面、竖井段和旋流洞段因阻塞的顶托作用整体增大;在起旋器出口下游侧的旋流洞的顶部仍然存在局部范围的低压区或负压区;在旋流阻塞段,流速增大,壁面压强减小,水流空化数降低;在旋流扩散段,壁面压强略大于或小于大气压。     

Si/SiO_2和Si/SiN_x/SiO_2超晶格的能带结构

利用Kronig-Penney模型从理论上计算了Si/SiO2和Si/SiNx/SiO2多层膜结构中量子阱的能带结构,进一步分析了各亚层薄膜厚度对能带结构和有效质量的影响.结果发现,适当减少亚层的厚度都能使得纳米Si薄膜的带隙发生明显宽化.在Si/SiO2超晶格中,Si量子阱层带隙能量随着Si层厚度的变化符合EPL(eV)=1.6+0.7/d2关系,与我们的计算结果十分吻合.在Si/SiNx/SiO2超晶格系统中,可以通过控制各亚层厚度,尤其是Si和SiNx层厚度,均能够有效地控制发光.     

二氧化锡薄膜的PECVD制备和特性

用ＰＥＣＶＤ方法制备出二氧化锡薄膜，利用双探针技术诊断出等离子体反应器内电子密度的分布，并分析了它对薄膜电阻的影响．透射电镜分析表明随沉积温度升高，二氧化锡薄膜从非晶态转变为多晶态，其电阻率随之减小．掺锑的二氧化锡薄膜对石油液化气和酒精具有良好的气敏效应     

固体火箭发动机自动化设计系统与AutoCAD的"无缝"联结及应用

探讨了固体火箭发动机自动化设计系统与AutoCAD软件的捆绑方式,并对发动机设计在CAD下的二次开发与设计系统的实现作了详细的应用分析,完成了较好的基于Windows的发动机设计CAD应用软件,说明在自动化设计系统中可以利用CAD强大的图型绘制功能来完成相应的设计要求。     

Effect of crystal form and particle size of titanium dioxide on the photodegradation behaviour of ethylene-vinyl acetate copolymer/low density polyethylene composite

The photodegradation behaviour of ethylene-vinyl acetate copolymer (EVA)/low density polyethylene (LDPE) composite containing four different types of titanium dioxide (TiO₂) was investigated through colour difference, Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and mechanical tests. The results showed that the performance losses of composites were qualitatively correlated with the degradation degree. The vinyl acetate (VA) groups in EVA were sensitive to UV light and the photodegradation mainly occurred in the amorphous region. The chain scission and annealing effect facilitated the secondary crystallization of composites. The heterogeneous nucleation effect of TiO₂ on the crystallization of composites was related to the particle size of TiO₂. The micro rutile TiO₂, micro anatase TiO₂ and their mixture (rutile/anatase = 13/87) exhibited a photo-stabilising effect, while the nano mixed crystals TiO₂ (rutile/anatase = 20/80) had an opposite effect.     

中央电视塔气动弹性风洞模拟试验

按照空气动力弹性相似性准则设计了中央电视塔准仿气动弹性模型，在大气边界层风洞中进行了实验。应用应变仪测定了塔根部的动态弯矩，利用光纤－光点摄影摄像法测定了塔楼和天线顶端的风振运动轨迹，从而得到了中央电视塔对风响应的有关动态特性。     

DEVELOPMENT OF A NEW TIME SCALE FOR THEQUATERNARY CLIMATE IN THE CHINESE LOESS PLATEAU BASED ON Rb CONCENTRATIONS

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Structure and optical properties of GeGaS films deposited by thermal evaporation

Amorphous GeGaS thin films have been successfully deposited onto glass slides at room temperature by the thermal evaporation technique. The structural units of the films were studied using Raman spectroscopy. In addition to the basic structural units of GeS₄ tetrahedra, there are some SS and GeGe homopolar bonds which exist in the films. The increase in Ge atoms leads to the replacement of SS bonds by GeGe bonds, and the isolated Ge(Ga)S₄ tetrahedra units transform into corner-sharing or edge-sharing Ge(Ga)S₄ tetrahedra units in the films. The refractive index and optical band gap were derived from transmission spectra of films. The values of optical band gap decrease while the refractive indices increase with increasing Ge content. Composition dependence of optical band gap and refractive index has also been interpreted in terms of the variation in the structure of films based on Raman spectra.