Low-energy cathodoluminescence microscopy for the characterization of nanostructures

Abstract

Spatially and spectrally resolved low-energy cathodoluminescence (CL) microscopy was applied to the characterization of nanostructures. CL has the advantage of revealing not only the presence of luminescence centers but also their spatial distribution. The use of electrons as an excitation source allows a direct comparison with other electron-beam techniques. Thus, CL is a powerful method to correlate luminescence with the sample structure and to clarify the origin of the luminescence. However, caution is needed in the quantitative analysis of CL measurements. In this review, the advantages of cathodoluminescence for qualitative analysis and disadvantages for quantitative analysis are presented on the example of nanostructures.     

超高层建筑转换梁节点“L型”角钢连接器的应用

泰山基业（财富中心）工程在建筑标高100 m处设置转换层，型钢梁多向相交、钢筋纵横贯穿。通过分析、对比转换梁腰筋与型钢梁的连接方式，确定采用“L型”角钢连接器的方式，可以保证转换梁腰筋与型钢梁的连接质量。     

厚薄承台界定的新方法和梁式模型法的修正

大量的试验与研究结果均表明,梁式模型法适用于多桩薄承台设计,对于厚承台并不适用。通过对国内外桩基承台试验数据统计,确定空间桁架方法和梁式模型方法应用于承台的界限,也即如何定义"薄"承台和"厚"承台;并且通过对试验数据的数学统计,考虑承台底层纵筋对抗剪和抗冲切的有利作用,对梁式模型法的冲切和剪切公式进行了修正。     

微射流驱动弯曲测试法测量微结构的弹性模量

提出了一种新颖的用于测量微结构力学性能的弯曲测试法——微射流驱动的弯曲测试法(microjet-driving microbending test method,JDBT)。该方法利用气体微射流连续冲击微结构,使之发生弯曲变形,通过获取结构的尺寸参数和形变位移,并代入结构的变形公式,从而反解出材料的力学性能参量。利用动量定理推导了微射流作用力公式,对某型号石英摆片式加速度计的敏感结构进行了理论建模,并用COMSOL MULTIPHYSICS有限元软件对理论公式进行了修正,接着通过JDBT实验得到了不同流量下的结构位移,最后将结构尺寸和结构形变位移代入修正后的理论公式,从而得到了石英玻璃的弹性模量约为71GPa,比纳米压痕仪测试的结果要小14%左右,与文献中提到的结果吻合较好。     

综采切眼锚梁网支护技术研究与实践

该文详细介绍了朱庄煤矿综采切眼使用的锚梁网支护技术。通过现场实例,介绍了综采切眼大断面巷道锚杆支护参数的选择、施工工艺以及注意事项,并通过矿压监测来验证支护形式的选择与支护参数设计的合理性,可靠性。论文还将锚梁网支护与传统的架设工字钢支护从材料成本、劳动强度、安全保障等方面进行了比较分析,得出了锚梁网支护技术的优越性以及该技术在矿井安全高效运行中的重要作用。     

在结构受拉区设置钢板的抗裂机理分析

采用经典层合梁理论分析了钢板在结构中对裂缝阻碍的作用，证明了在结构受拉区设置钢板可以更充分的发挥钢材的作用，使得钢板与混凝土共同受力，起到阻碍受拉区域混凝土裂缝产生的作用。     

Analysis of cohesive failure in adhesively bonded joints with the SSPH meshless method

Adhesives have become the method of choice for many structural joining applications. Therefore, there is a need for improved understanding of adhesive joint performance, especially their failure, under a variety of loading conditions. Various numerical methods have been proposed to predict the failure of adhesive bonded material systems. These methods generally use a cohesive zone model (CZM) to analyze crack initiation and failure loci. The CZM incorporates a traction–separation law which relates the jump in surface tractions with the jump in displacements of abutting nodes of the cohesive segment; the area under the curve relating these jumps equals the energy release rate which is determined from experimental data. Values of parameters in the CZM are usually obtained through the comparison of results of numerical simulations with the experimental data for pure mode I and mode II deformations. Here a numerical approach to simulate crack initiation and propagation has been developed by implementing CZM in the meshless method using the symmetric smoothed particle hydrodynamics (SSPH) basis functions, and using the design of experiments technique to find optimal values of CZM parameters for mode I failure. Unlike in the finite element method where a crack generally follows a path between element boundaries, in the meshless method a crack can follow the path dictated by the physics of the problem. The numerical technique has been used to study the initiation and propagation of a crack in a double cantilever beam under mode I and mixed mode in-plane loadings. Computed results are found to agree well with the corresponding experimental findings. Significant contributions of the work include the determination of optimum values of CZM parameters, and simulating mode I, mode II and mixed mode failures using a meshless method with the SSPH basis functions.     

Influences of the three‐phase boundary on the electrochemical corrosion characteristics of carbon steel under droplets

The potential/current distributions of carbon steel were investigated under 0.001 M sodium chloride droplets of various sizes using a wire beam electrode. During the corrosion process, carbon steel exhibited heterogeneous electrochemical characteristics with the major anodes located near the edge of the droplets. The three‐phase boundary (TPB) plays a vital role in determining the electrochemical distribution and the corrosion degree of carbon steel. With the increase of droplet size, the average anodic current density and the corrosion degree decreased, which is believed to be due to the decrease of the TPB length per unit area.     

Molecular beam epitaxy growth of peak wavelength-controlled InGaAs/AlGaAs quantum wells for 4.3-μm mid-wavelength infrared detection

InGaAs/AlGaAs multiple quantum wells used for 4.3 μm mid-wavelength infrared quantum well infrared detectors were grown by molecular beam epitaxy. In composition loss was observed and quantitatively studied by high-resolution X-ray diffraction technology. By this In composition loss effect, the energy band engineering on the photo-response wavelength is not easily achieved. A thin AlGaAs barrier grown at low temperature is used to suppress the In atom desorption, and this growth process was verified to be able to adjust the photo-response wavelength as designed by energy band engineering in the photocurrent spectrum.     

钢管步进式冷床齿形设计方法及其应用

介绍了Ф159mm连轧管机组步进式冷床的生产工艺及其动作原理,推导出一套适用于该类型冷床齿形设计的公式。利用该公式可从理论上和设计实例上优化冷床齿形设计,并可借助Excel表格进行齿形验算分析,既方便又快捷。