掺Bi石英光纤的γ射线辐照和温度影响特性

采用改进的化学气相沉积法制备了尺寸为10/130 μm的掺Bi单包层石英光纤, 把光纤分成若干组之后置于不同剂量的⁶⁰Co γ辐射源下辐照, 测试了光纤在辐照前后的吸收谱和荧光谱, 并测试了光纤在全温度范围(-40–70 ℃)下荧光强度的变化. 实验结果表明, 辐照后700, 800 nm处的吸收峰显著增强, 这是由于辐照导致更多Bi 近红外活性中心的生成. 976 nm光抽运不同剂量辐照后的光纤, 中心位于1230 nm的荧光谱没有明显变化, 验证了掺Bi石英光纤用于太空及辐照环境下光通信的可能性. 在全温度范围内, 分析了荧光强度的变化规律, 为今后掺Bi光纤激光器的稳定工作提供了数据基础.     

地下核爆炸作用下岩石物理力学性质的变化特征

对地下核爆炸岩石介质爆前爆后的一些物理、力学和声学参数进行了室内测试，发现它们呈规律性地变化，还分析和讨论了变化的机制。     

Composite patch reinforcement of cracked aircraft upper longeron: analysis and specimen simulation

The use of composite patches on cracked portions of metallic aircraft structures is an accepted means of improving fatigue life and attaining high structural efficiency. As more and more advanced composite materials are beng developed, the wider use of the repair technology is anticipated even for the reinforcement of primary aircraft structure. The objective of this work is to illustrate how the composite patch repair technology can be successfully applied to restore the structural integrity of cracked components.The Phosphoric Acid Anodize (PAA) surface treatment on aluminum when applied in conjunction with the AVI13/HV998 adhesive were essential for achieving the appropriate patch bonding strength. Such a process was done without immersing the component into the PAA tank; dismantling the component from the aircraft was not necessary. Boron/epoxy and carbon/epoxy patches were applied at room temperature to the 7075-T6511 cracked specimens and tested under fatigue simulating the load spectrum for the upper longeron attached to the access door of the electronic equipment bay. Considerable improvement in the fatigue life was observed after the repair. Equivalent flight test hours were increased from approximately two thousand hours at which the component fractured completely when not repired to twelve thousand hours when the repair was made with only a small amount of crack growth. A six times increase fatigue life is obtained. The laboratory developed technique has been applied to several in-service aircraft which have now been flown for more than 700 h without detection of crack growth.     

A quantitative study of the flow around an impulsively started circular cylinder

The detailed flow structure behind an impulsively started circular cylinder has been investigated experimentally. The Reynolds number based on the steady state velocity and the diameter of the cylinder was 500 to 3,000. This work is unique in that unsteady spatial velocities were measured simultaneously by a quantitative visualization technique — Laser Induced Photochemical Anemometry (LIPA). The surface vorticity at g/q = π/2 and vorticity distribution behind the cylinder in the Lagrangian coordinates (i.e. coordinates fixed on the cylinder) were calculated from the measured velocities. The surface vorticity shows in the early stage of flow development a close agreement with the previous results obtained by analytical and numerical approaches. The large-field velocity and vorticity information provides an insight into the formation process of the vortices downstream of the cylinder. In addition to the quantitative information, the results of visualized flow pattern obtained by LIPA technique are also presented. A preliminary version of this paper was presented at the Twelfth Symposium on Turbulence, University of Missouri-Rolla, Sept. 24–26, 1990     

变几何叶片对压气机特性影响的实验研究及分析

利用带导叶的单级轴流压气机实验台，详细测量了进口导叶无预旋、全叶高预旋2度和叶顶端部预旋2度对压气机总性能、基元性能及失速边界的影响。在设计及非设计转速下，通过对比三种导叶几何条件下的性能曲线，探讨了导叶预旋在非设计转速下的扩稳效果及设计转速下对 气机性能的影响，分析了利用端弯技术扩大压气机稳定工作范围的机理，该研究进一步说明了端弯技术是推迟轴流压气机不稳定流动发生的有效手段之一，可以很方便的用于实际轴流压气机中。     

小型高速离心压气机级内部的三维流场分析

利用三维数值模拟技术对微型燃气轮机中的离心压气机部分进行了数值分析,得到了离心压气机设计转速下的级特性曲线和各通流部件中的流动情况。数值分析表明:设计转速下压气机的级特性非常陡峭;整个特性线范围内离心叶轮基本在亚音速情况下工作,而径向扩压器是在跨音速条件下工作,离心压气机整机的最大流量是由径向扩压器的喉部面积决定的;离心压气机级内部各通流部件之间流动的相互干扰是引起流动分离的重要原因,各通流部件之间流动的相互匹配和协调将决定了离心压气机整机的性能和稳定性。     

Isoparametric shear spring element applied to crack patching and instability

In this work the isoparametric shear spring element is applied to the stress and energy analysis of a center-crack panel reinforced by a rectangular patch. In this model, only transverse shears are assumed to prevail in the adhesive layer. The stresses and crack-tip stress intensity factors are obtained for reinforcement on both sides and one side of the panel, and are found to be in agreement with those obtained by previous authors using the triangular shear spring element.Crack stability that tends to vary with patch thickness is determined from the local and global maximum of the minimum strain energy density function denoted, respectively, as [(dW/dV)_min^max]_L at point L and [(dW/dV)_min^max]_G at point G. The distance l between L and G gives the prospective path of subcritical crack growth and its magnitude provides a measure of the degree of crack stability. A patched panel with small l tends to be more stable than that with large l. By increasing the patch thickness beyond a certain value, l can be contained within the patch such that failure, if initiated, will be highly localized. Such a behavior is exhibited. Numerical results are provided to support the foregoing conclusion.     

Study on electrochemical profiles of Valeriana medicinal plants by capillary electrophoresis

The objective of this work was to develop a high-performance capillary electrophoresis with amperometric detection (CE-AD) method for the determination of pharmacologically active ingredients in extracts of Valeriana medicinal plants. The method was validated for linearity, repeatability, limits of detection (LODs) and limits of quantification (LOQs), etc. The LODs and LOQs of eight compounds were found to be in the range from 1.0 × 10^?8 to 1.2 × 10^?7 and 3.3 × 10^?8 to 4.0 × 10^?7 g/mL, respectively. The proposed method was successfully applied for the analyses and comparison of bioactive components in Valeriana samples after a relatively simple extraction procedure, and the resultant “electrochemical profiles” can intuitively demonstrate the content diversity of each electrochemically active ingredient in Valeriana samples from different places and plant parts. It was found the content of bioactive ingredients may vary by an order of magnitude depending on natural conditions, e.g. soil, climate, humidity etc.     

Thermal Proton Transfer Reactions in Ultraviolet Matrix-Assisted Laser Desorption/Ionization

One of the reasons that thermally induced reactions are not considered a crucial mechanism in ultraviolet matrix-assisted laser desorption ionization (UV-MALDI) is the low ion-to-neutral ratios. Large ion-to-neutral ratios (10^–4) have been used to justify the unimportance of thermally induced reactions in UV-MALDI. Recent experimental measurements have shown that the upper limit of the total ion-to-neutral ratio is approximately 10^–7 at a high laser fluence and less than 10^–7 at a low laser fluence. Therefore, reexamining the possible contributions of thermally induced reactions in MALDI may be worthwhile. In this study, the concept of polar fluid was employed to explain the generation of primary ions in MALDI. A simple model, namely thermal proton transfer, was used to estimate the ion-to-neutral ratios in MALDI. We demonstrated that the theoretical calculations of ion-to-neutral ratios exhibit the same trend and similar orders of magnitude compared with those of experimental measurements. Although thermal proton transfer may not generate all of the ions observed in MALDI, the calculations demonstrated that thermally induced reactions play a crucial role in UV-MALDI.

A Coordination Compound of Ge0 Stabilized by a Diiminopyridine Ligand

Reduction of the cationic Ge^II complex [dimpyrGeCl][GeCl₃] (dimpyr=2,6‐(ArN=CMe)₂NC₅H_3, Ar=2,6‐iPr₂C₆H₃) with potassium graphite in benzene affords an air sensitive, dark green compound of Ge⁰, [dimpyrGe], which is stabilized by a bis(imino)pyridine platform. This compound is the first example of a complex of a zero‐valent Group 14 element that does not contain a carbene or carbenoid ligand. This species has a singlet ground state. DFT studies revealed partial delocalization of one of the Ge lone pairs over the π*(C?N) orbitals of the imines. This delocalization results in a partial multiple‐bond character between the Ge atom and imine nitrogen atoms, a fact supported by the X‐ray crystallography and IR spectroscopy data.