一种基于微波谐振测量Sagnac效应的新方案

目前光学陀螺的主要工作原理是Sagnac效应, 如何提高Sagnac效应的测量精度是提高陀螺精度的一个重要研究课题. 传统的光学陀螺利用光短波长的特性来提高检测精度. 但考虑到微波的相位(频率)检测精度远高于光波的相位(频率)检测精度, 如果能够利用微波实现Sagnac效应的检测, 就能得到比光学陀螺更高的检测精度, 从而为实现高精度的微波陀螺提供了可能. 利用基于光电振荡器的光载微波结构实现了微波Sagnac效应的检测. 实验结果证明了微波检测Sagnac效应的可行性, 为将来实现高精度的微波谐振陀螺打下基础.     

超材料谐振子间的电耦合谐振理论与实验研究

通过将两个金属开口环谐振器口对口地放置, 实现了超材料谐振子间的电耦合谐振. 对电耦合谐振的微波等效电路进行了理论分析和数值计算, 结果表明耦合后的超材料谐振子能产生两个谐振频率, 其中一个随耦合强度的增加逐渐向低频方向移动, 而另一个固定在单谐振子的谐振频率处不变. 微波透射谱的实验测试和电磁仿真结果表明, 两个谐振峰随耦合强度的增加分别向低频和高频方向移动. 分析表明: 低频谐振峰的位置主要是由超材料谐振子间的电耦合强度决定的; 高频谐振偏离单谐振子的谐振频率主要是由不可避免的磁耦合引起的, 而且在耦合间距越小时磁耦合影响越大. 提出的基于超材料谐振子间的电磁耦合实现的双频谐振及其可调性极大地增加了超材料的设计与应用空间.     

纯相稀土硫化物红色发光材料的高温微波合成及其光谱性质

采用工业频率为2.45 GHz的高温微波法制备了纯基质相的CaS∶Eu2+红色发光材料,激发波段为410~580 nm,发射峰值波长为654 nm。在微波输入功率为1.0~1.1 k W的条件下,可以获得纯基质相CaS∶Eu2+发光材料;在1.2~1.3 k W功率范围,获得的样品中含有Ca O杂质相,且颗粒团聚严重。其中,1.1 k W制备的CaS∶Eu2+样品相纯度最高,发光性能最优。微波功率的变化本质上揭示了固体颗粒的介电损耗因子及其加热特性的变化,体系涉及的非平衡反应机制促使了纯基质相的形成,并影响材料晶相结构、粒径、形貌和发光性能。结果显示,高温微波制备技术通过控制输入功率及其物料的介电损耗性质,能够获得纯基质相并且颗粒小、团聚少的荧光粉。     

Simultaneous Determination of Sn and S in Methyltin Mercaptide by Microwave-Assisted Acid Digestion and ICP-OESSCIEI北大核心CSCD

Methyltin mercaptide is widely used as one of the best heat stabilizer in the polyvinylchloride (PVC) thermal processing due to its excellent stability, good transparency, high compatibility and weather resistance. The content of sulfur and tin significantly affects its quality and performance, so it is of great significance to develop an analytical method for the simultaneous determination of sulfur and tin. Inductively coupled plasma atomic emission spectrometry (ICP-OES) has been a powerful analytical tool for a myriad of complex samples owing to its advantages of the low detection limits, rapid and precise determinations over wide dynamic ranges, freedom from chemical inter-element interferences, the high sample throughput and above all, simultaneous multi-elements analysis. Microwave technique as a well-developed method for sample preparation can dramatically reduce the digestion time and the loss of volatile elements compared with the traditional open digestion. Hereby, a microwave-assisted acid digestion (MW-AAD) procedure followed by inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis was developed for the simultaneous determination of Sn and S in methyltin mercaptide. This method has the advantages of simplicity, rapidness, good accuracy, green and less use of samples. Parameters affecting the MW-AAD such as the digestion solution and digestion time were optimized by using a chemical analyzed reference sample (DX-181) to attain tin and sulfur quantitative recoveries. HNO3-HCl-HClO4(v/v/v=9 : 3 : 1) and 10 min were the optimum digestion solution and digestion time, respectively. Under optimum conditions, the standard addition method and the standard calibration curve method were both been used to detect Sn and S in DX-181. There was no significant difference between two methods and the relative deviations to the chemical analysis values were both less than 2%. Additionally, the accuracy of the MW-AAD method was examined by analyzing three methyltin mercaptide samples (DX-181, DX-990, DX-960). The results were satisfactory with the relative deviations (<3%) and the recoveries of standard addition (99%-102%).     

Determination of Trace Elements in Marine Cetaceans by ICP-MS and Health Risk AssessmentSCIEI北大核心CSCD

The liver, kidney and muscle samples from seven cetaceans were digested by microwave digestion, and trace elements amounts of V, Cd, Cu, Zn, As, Cr, Ni, Mn, Se, Hg and Pb were determined by inductively coupled plasma mass spectrometry (ICP-MS), and the health risk assessment for Zn, Cu, Cd, Hg, Se in the liver was conducted. The results of international lobster hepatopancreas standard (TORT-2) showed acceptable agreement with the certified values, and the relative standard deviation (RSD) of eleven kinds of trace elements were less than 3.54%, showing that the method is suitable for the determination of trace elements in cetaceans. The experimental results indicated that different tissues and organs of the dolphins had different trace elements, presenting the tissue specificity. There is a certain inter-species difference among different dolphins about the bioaccumulation ability of the trace elements. The distribution of trace elements in whales presented a certain regularity: the contents of most elements in liver, kidney were much higher than the contents of muscle tissues, Cu, Mn, Hg, Se, and Zn exhibit the higher concentrations in liver, while Cd was mainly accumulated in kidney. And according to the health risk assessment in liver, the exceeding standardrate of selenium and copper in seven kinds of whales was 100%, suggesting that these whales were suffering the contamination of trace elements. The experimental results is instructive to the study of trace elements in cetaceans, while this is the first report for the concentrations in organs of Striped dolphin, Bottlenose dolphin, Fraser's Dolphin and Risso's dolphin in China, it may provide us valuable data for the conservation of cetaceans.     

THERMODYNAMIC AND PARTICLE-DYNAMIC STUDIES ON SYNTHESIS OF SILICA NANOPARTICLES USING MICROWAVE-INDUCED PLASMA CVD

1. Introduction1.1 Silica nanoparticles and synthesis methods Silica (SiO2) nanoparticles are widely used in industry asan active filler for polymer reinforcement, a rheologicaladditive in fluids, a free flow agent in powders, and anagent for chemical mechanical polishing during IC (inte-grated circuit) fabrication (Sniegowski & de Boer, 2000).Silica powder is also used for producing silicon carbide(Koc & Cattamanchi, 1998) or opaque silica aerosols (Leeet al., 1995). Many methods can …     

遥感技术用于固体力学实验研究的新成果

在岩石、混凝土和钢材加载直到破坏的过程中用红外和微波遥感技术进行了观测研究．发现这些材料在加载过程中其红外和微波辐射温度、红外辐射波谱及红外热像均随应力的变化而变化．材料破坏前这些变化表现出某些前兆性特征．研究表明遥感技术可作为固体力学研究的一种新手段，并可望在工程上得到应用     

HMDS/KI a simple,a cheap and efficient catalyst for the one-pot synthesis of N-functionalized pyrimidines

The syntheses of N-Alkylpyrimidine derivatives by reacting pyrimidin-2,4-diones with appropriate alkyl halide under microwave irradiation at 400?W were compared to the conventional synthesis route. These methodologies are regioselective and compatible with numerous substrates and furnish the corresponding N-alkylpyrimidines in good yields using a cheap catalyst HMDS/KI in MeCN. A comparison study between these two different modes of heating was investigated.     

消毒灭菌的电离辐射与电磁辐射等物理技术比较分析北大核心CSCD

消毒灭菌技术广泛应用于食品工业、医疗领域、水处理等方面。相对于传统化学和热效应的消毒灭菌方法,γ射线、X射线、电子束、微波、低温等离子体、紫外线、高压脉冲电场等物理手段具有不污染环境、消毒灭菌温度低、没有化学残留物等优点而日益受到重视。但这些物理技术手段各有不同,本文首先介绍了γ射线、X射线、电子束、微波、低温等离子体、紫外线、高压脉冲电场等消毒灭菌的技术原理,然后对比了各自优缺点和应用领域。每种方法都有优势和不足,应针对不同的消毒灭菌对象而选择不同的方式。最后,展望了消毒灭菌的发展方向,提出了消毒灭菌在家庭日常消毒、医疗垃圾处理、有人状态下的室内空气消毒等方面的迫切需求。