TE03 to TE01 mode converters for use with a 150 GHz gyrotron

Two-step high-power TE03-to-TE01 mode transducers (TE02 is the intermediate mode) were designed to transform the TE03 output mode of the 150 GHz KfK gyrotron into the fundamental circular symmetric TE01 mode for low-loss propagation and further conversion into the linearly polarized quasioptical HE11 mode. The advanced perturbation structures of the ruppled-wall mode converters (with input- and output-diameter D=27.8 mm) were optimized by numerically solving the proper coupled-wave differential equations. The overall TE03-to-TE01 conversion efficiency at 150 GHz was calculated to be ₀=99.1% for a long converter (total length L=2.67 m) and ₀=97.8% for a short converter (L=1.07 m); ohmic attenuation is included. The corresponding theoretical bandwidth (for 95%) is ±1.4 GHz and ±2 GHz, respectively. Low-power experimental data are in excellent agreement with these computed values.     

Eigenmodes of a Toroidal Cavity with a Conducting Separating Wall

The eigenmodes of a toroidal cavity with a separating wall are examined in the light of theory and experiment. Excellent agreement between the predicted resonant frequency of 1.148 GHz corresponding to a 4-period generating function and the experimentally observed frequency is found. The exact solution of Maxwell's equations in toroidal systems with a separating wall is presented and the eigenfrequencies are experimentally measured on a toroidal cavity with major and minor radii of respectively 12.5 cm and 10.0 cm.     

Gas chromatography using a resistively heated column with mass spectrometric detection for rapid analysis of pyridine released from Bacillus spores

Gas chromatography using a resistively heated analytical column with full scan electron impact mass spectrometry (EI-MS) was used to detect pyridine generated from heating Bacillus spores in a custom designed furnace inlet, along with gasoline range aromatic (GRA) hydrocarbons representing an environmental contaminant that could interfere with detection of the biologically-derived compound. Gas phase materials from the furnace inlet were collected onto a section of cooled open tubular column, and carrier gas flow was then routed through the trapping column onto the analytical column. Both sections of column were contained within low thermal mass tubular metal sheaths, with each independently and resistively heated allowing rapid temperature ramps and cooling. An analysis time of 2 min resolved spore-derived pyridine from the other organics, and allowed identification by mass spectrum match. Throughput of 20 analyses per hour was shown to be possible with a 1-min column cool-down time between analyses.     

Miscibility of polymer blends studied by a simplified method of data analysis using light heating modulated temperature DSC

A simple method of application of light heating modulated temperature DSC to a study of miscibility of polymer blends has been developed. In this method only the sample was measured and the standard materials were not used. The total heat flow, the complex heat capacity, the reversing and non-reversing heat flows were obtained as values measured from those quantities in hypothetical glassy state at T>T_g. The values of the hypothetical glassy state were calculated by extrapolation from T<T_g. The present method gives relative values but useful information can be obtained from the results. Some results from miscible and immiscible polymer blends are shown. This revised version was published online in July 2006 with corrections to the Cover Date.     

Synthesis of Compact NaA Zeolite Membrane by Microwave Heating Method

A continuous and dense NaA zeolite membrane was synthesized by microwave heating method while employing a multi-step seeding LTA zeolite with the average size of 120 rim. The gas H2/N2 mixture separating results indicated that the mixture selectivity increased with increasing of synthesis times. In addition, selectivity of the three-step synthesis was higher than the value(3.74) expected from Kundsen diffusion.     

Numerical Study on Hypersonic Flow and Aerodynamic Heating北大核心CSCD

基于有限差分法开发了高超声速流动与换热问题气热耦合仿真求解器,运用该求解器对三种典型高超声速流动与换热问题开展了仿真研究,得到了相应的气动参数、热流密度分布。高超声速后台阶的存在使表面气动参数、热流分布不再连续;随着缝深的提高,缝隙局部流速迅速降低,对流换热效应减弱;高超声速无限长圆管绕流中,边界层外部区域气动参数随时间变化不大,边界层内存在较大的温度梯度,壁面温度随时间升高。三个算例的仿真结果均与试验测量值进行了对比,验证了所开发的求解器的计算能力。     

微波消解石墨炉原子吸收光谱法测定番木瓜酱菜中铅

研究了微波消解石墨炉原子吸收光谱法测定番木瓜酱菜中铅的最佳条件 ,方法简便快速 ,检出限为 0 .0 6 8mg·kg- 1(换算到样品中的最终浓度 ) ,RSD为 1.4 %～ 9.6 % ,样品加标回收率为97.7%～ 10 0 .3%。     

微波场对SrTiO3化学合成中热过程的影响

在分析微波场中 SrTiO3化学合成体系与电磁场相互作用的基础上 ,探讨合成体系在微波场中的加热机制和影响升温的主要因素（如合成体系的介电性质、保温材料的结构、生坯的致密度等） .结果表明 ,TiO2和 SrCO3在低温阶段对体系的升温速率的贡献相接近 ;高温阶段体系升温主要是 TiO2的贡献 ,同时产物对升温有较大的影响 .微波合成与常规合成在加热方式上的明显不同,对合成过程、合成时间等影响较大 .     

ZnO: a versatile agent for benzylic oxidations

Zinc oxide catalyzed oxidation of various alkylbenzenes, naphthalene and 1,2,3,4-tetrahydronaphthalene in air using microwave irradiation or conventional heating in the presence of N,N-dimethylformamide is described.     

Differential thermal analysis under quasi-isothermal, quasi-isobaric conditions (Q-DTA): Part III. Mechanism of congruent and incongruent phase transformations of salt hydrates

By using the “simultaneous Q-DTA, Q-TG measuring technique” elaborated recently, conditions near to the requirements of thermodynamics can be created, thus the “normalized” course of curves taken by this method, their characteristic temperatures or the values measured for the enthalpy change can be considered to be near to the theoretical values.

For testing this new method, CuSO₄·5H₂O, MnSO₄·5H₂O, Mg(NO₃)₂·6H₂O and Na₂SO₄·10H₂O have been investigated. These model substances can be prepared in stoichiometric composition free of impurities, their decomposition mechanism is well-known, thus the effect of the altered experimental conditions by the simultaneous Q-DTA, Q-TG method on the course of their dehydration can be calculated.