Multisorbent tubes sampling used in thermal desorption cold trap injection with gas chromatography-mass spectrometry for C2–C6 hydrocarbon measurements in an urban atmosphere

Three solid adsorbents (Carbotrap, Carbotrap C, and Carbosieve III) were evaluated for sampling trace non-methane hydrocarbons in urban atmospheres. The sampled atmosphere was pumped through a multisorbent tube containing the three sorbents separated by a small amount of silanized glass wool. The trapped compounds were recovered by thermal desorption and analysed by combining cryogenic enrichment with gas chromatography and mass spectrometry. Adsorption/thermal desorption and breakthrough experiments were performed to test their ability to quantitatively trap the light hydrocarbons. The technique was suitable for determination of low ppbv concentrations of these compounds. Ambient atmospheric sampling was conducted in Vitoria-Gasteiz (Basque Country, Spain), and the measurements cover a period of one year (2001–2002). Fifteen C₂–C₆ hydrocarbons are identified and quantified, and seasonal trends are discussed.     

小口径管扭转模态导波在线检测

采用扭转模态导波T(0,1)开展了小口径管在线检测研究。考虑管线服役环境及其结构特征,研制了一种适用于小口径管线在线检测的新型传感器阵列。传感器采用剪切型压陶瓷晶片作为敏感元件,具有柔性、轻质的特点。实验表明,环向布置的传感器阵列能够在管线中高效激励T(0,1)模态导波;通过提取回波信号中的各模态导波信息,实验系统能有效辨识管线中缺陷的状态变化;对于含有支撑结构的小口径管,比较并分析管线中导波散射信号及特征结构处回波信号的变化有助于辨识支撑结构附近区域损伤的产生及扩展。     

On the ground state of Yang–Mills theory

We investigate the overlap of the ground state meson potential with sets of mesonic-trial wave functions corresponding to different gluonic distributions. We probe the transverse structure of the flux tube through the creation of non-uniform smearing profiles for the string of glue connecting two color sources in Wilson loop operator. The non-uniformly UV-regulated flux-tube operators are found to optimize the overlap with the ground state and display interesting features in the ground state overlap.     

苯乙烯协助水热制备高催化活性ZnO管(英文)

采用苯乙烯微球为模板水热合成了直径为1~2μm,管壁厚度约200nm的ZnO管。用SEM和XRD对制得的样品进行表征,结果表明,醋酸锌浓度和水热时间在ZnO管的制备过程中起到重要作用。在实验结果的基础上,提出了ZnO管的形成机理。紫外-可见吸收光谱计算出ZnO管的禁带宽度为2.96eV,合成的ZnO管对罗丹明B具有很高的紫外光催化活性。     

Experimental investigation of heat transfer and pressure drop characteristics of flow through spirally fluted tubes

Spirally fluted tubes are used extensively in the design of tubular heat exchangers. In previous investigations, results for tubes with flute depths e/D_vi < 0.2 were reported, with most correlations applicable for Re ≥ 5000. This paper presents the results of an experimental investigation of the heat transfer and pressure drop characteristics of spirally fluted tubes with the following tube and flow parameter ranges: flute depth e/D_vi = 0.1−0.4, flute pitch p/D_vi = 0.4−7.3, helix angle θ/90° = 0.3−0.65, Re = 500−80,000, and Pr = 2−7. The heat transfer coefficients inside the fluted tube were obtained from measured values of the overall heat transfer coefficient using a nonlinear regression scheme. The friction factor data obtained consisted of 507 data points. The proposed correlation for the friction factor predicts 96% of the database within ±20%. The heat transfer correlation for the range 500 ≤ Re ≤ 5000 predicts 76% of the database (178 data points) within ±20%, and the correlation for the higher Re range predicts 97% of the 342 data points within ±20%. Comparison of heat transfer and friction data show that these tubes are most effective in the laminar and transition flow regimes. The present results show that the increase of flute depth in the range considered does not improve heat transfer.     

单色显示管的工作特性分析

本文详细介绍了二种条件下显示管的工作特性,并指出其优缺点、相互转换及应用前景,同时又给出了不同的调制方式下工作特性的相互转换。最后推荐了一种新条件下的工作特性。     

Drag measurements in a hypervelocity expansion tube

A technique is described for the measurement of aerodynamic drag in a hypervelocity expansion tube in which the test flow period may be as short as 50 s. The technique is an application of the stress wave force balance first proposed by Sanderson and Simmons (1991). The experiments were conducted in a test flow of partially dissociated Carbon Dioxide where the flow speed was in excess of 7 kms. The validity of the technique is first demonstrated by comparing the forces measured on a range of sharp cones with those expected theoretically. Agreement to within 10% is achieved. Two re-entry type heat shield geometries were then tested with the experimental drag forces being compared with a Modified-Newtonian prediction. In both cases agreement to within 11% was obtained. Received 12 December 1995 / Accepted 29 April 1996     

真空微电子毫米波器件

介绍了真空微电子分布放大器和真空微电子微波管两类器件，对其优点和问题进行了探讨，并就我国发展真空微电子毫米波器件提出了看法．     

Length-independent inter-tube conductance in double-wall carbon nanotubes

Conductance due to inter-tube transfer in incommensurate double-wall tubes is numerically studied. The conductance is usually much smaller than e²/π and its average and fluctuation are independent of the length. This behavior arises because the inter-tube transfer oscillate around zero in a complex plain as a function of position in a quasi-periodic manner and therefore cancel each other when being summed up except near tube edges.     

斯特林型高频脉冲管制冷机的现状与样机研制

首先介绍了国际上高频脉冲管制冷机的研究现状及未来发展趋势 ,表明高效高频脉冲管制冷机的产品和样机在国际上已日趋成熟。然后简要介绍了作者近几年在德国研制的高频脉冲管制冷机样机的性能和特点。作者获得的性能和国际上最好性能的比较表明 ,作者获得的性能结果已处于世界先进行列