Orientation dependence of the substructure characteristics in a Ni-30Fe austenitic model alloy deformed in hot plane strain compression

The present work examines in detail the substructure and texture characteristics in a Ni-30Fe austenitic model alloy subjected to deformation by plane strain compression (PSC) at temperatures between 700 and 900 °C to strains between 0.2 and 1 using a strain rate of 1 s⁻¹. The flow curves display characteristics typical of limited dynamic recrystallization. The deformed matrix texture is similar to that expected for rolling/PSC deformation of face-centred cubic metals while the comparatively weaker dynamic recrystallization texture is dominated by the Cube component. The non-Cube deformed matrix grains contain “organized”, self-screening arrays of microbands aligned along the slip planes with high Schmid factors. By contrast, the Cube deformed matrix grains exhibit more “random” cell substructure with a low density of superimposed larger-angle dislocation walls. These walls are related to {1 1 1} slip planes at low strains, but tend to follow the rigid body rotation toward the compression plane at large strains.     

Fractal pattern formation in thermal grooving at grain boundaries in Ag films on Si(111) surfaces

Growth of Ag films on Br- and H-passivated Si(111) surfaces and the annealing behaviour have been investigated by Rutherford backscattering spectrometry, scanning electron microscopy and photoemission electron microscopy techniques. Upon annealing the phenomenon of thermal grooving was observed in the Ag films. Depending on the annealing temperature, at an intermediate annealing time Ag depletion (evaporation) from the grain boundaries produces fractal patterns of Ag-depleted regions. Continued annealing eventually produces a percolated network of Ag-depleted regions (thermal grooves) along the grain boundaries and isolated Ag grains appear as the depth of the grooves reaches the substrate. For the fractal structures produced by thermal grooving, the fractal dimension has been estimated to be 1.60 ± 0.04. Observation of a fractal pattern in thermal grooving was not hitherto reported. A thorough analysis of the experimental results has been carried out in the context of current theories. These theories are inadequate to describe the experimental results.     

Growth of single-phase Mg0.3Zn0.7O films suitable for solar-blind optical devices on RS-MgO substrates

Single-phase rock-salt Mg_0.3Zn_0.7O film was fabricated on MgO (100) substrate by radio-frequency plasma assisted molecular beam epitaxy. A smooth surface was observed by in-situ reflection high-energy electron diffraction and ex-situ atomic force microscopy. X-ray diffraction characterization demonstrated a high-quality single-phase structure with highly (200) orientation and cube-on-cube epitaxial relationship. Zn fraction in the single-phase rock-salt Mg_0.3Zn_0.7O film was determined by Rutherford backscattering spectrometry. Optical property of the film was investigated by reflectance spectroscopy, which indicated a solar-blind band gap of 255.5 nm. The reason why Zn solubility limit is greatly enhanced in non-polar (100) film compared with (111) polar epilayer is tentatively discussed in this work, suggesting MgO (100) is more suitable for the synthesis of single-phase rock-salt MgZnO with high Zn content towards solar-blind opto-device applications.     

高速精密球轴承钢球三维运动状态检测

提出了通过在装有一个磁化钢球的轴承外圈及保持架侧面配置霍尔传感器,测量钢球三维运动的新方法,阐述了该测试方法的基本原理;设计开发了相关的检测试验装置,并介绍了其基本原理和结构。     

如何提高云状的观测质量

云的形态是复杂多变的,云的观测准确性将直接影响到天气预报的准确率。本文阐述了根据云的成因及外形特征和演变规律,并结合当时的天气现象和天空状况以及对相似云的比较,从而进行云状的准确判断。     

国产GPS探空系统的业务化运用

采用GPS技术实现高空气象探测是国际上气象探空系统发展的重要趋势,而我国高空气象探测系统还比较落后。在我国探空系统中采用GPS技术,使之与国际探空技术同步发展势在必行。本文阐述了国产GPS探空系统的基本工作原理,并对其业务化工作流程进行了探索,指出了在业务运用中的不足之处,旨在促进国产GPS探空系统业务化的运用。     

天然气水合物的近海底直流电测深响应

 本文介绍了利用近海底直流电阻率测深法勘查海底天然气水合物的理论与视电阻率响应特征,近海底直流电阻率响应可采用埋藏点电流源进行模拟。数值模拟结果表明,天然气水合物的存在能够引起近海底直流电测深视电阻率的变化。进一步的计算显示,厚度为10m的薄层天然气水合物引起的视电阻率相对变化率能达到2%,而厚度为100m的厚层天然气水合物引起的视电阻率相对变化率可达10%。偶极—偶极测深装置、四极测深和三极测深装置模拟结果表明,偶极—偶极装置对天然气水合物的分辨能力要高于对称四极装置。同时,电极的相互配置关系、电极系相对海底的距离等对视电阻率曲线形状影响很大,但对于由天然气水合物造成的视电阻率相对变化影响较小。因此利用近海底直流电阻率测深法进行水合物勘查是可行的。     

改进的大地电磁与地震资料联合反演方法在黔中隆起区的适用性研究

为了解决复杂地质问题以及大地电磁(MT)与地震资料联合反演存在的问题,结合已有研究成果,利用基于不同物性参数随机分布共网格模型的大地电磁与地震资料同步联合反演技术,对黔中隆起地震资料品质低,且构造复杂的典型地段的实际资料进行了联合反演。根据研究区实际情况,利用两种地质解释方案建立了联合反演的初始速度模型和电性模型,并进行了联合反演和综合解释。将反演结果与已有方法得到的结果进行对比表明,改进的联合反演方法适用于物性剧烈变化的复杂地质模型条件,在先验信息的约束下,改进后的联合反演方法在确定复杂物性条件下的电性和速度结构方面能够提供更合理的解释方案和物性参数,为目前研究区难以推断的古生界目的层的分布及基本构造特征的判断提供了参考依据和技术手段。     

填土质量控制应推崇的方法

本文阐述了在填土质量控制中,室内试验存在的不足之处及利用轻便触探仪测试的快速性、直观性,提出了应推广的方法,既规范又适用。     

基于软件无线电技术的雷达系统接收通道设计

基于伪随机码调相脉冲压缩体制的电离层斜向返回探测系统可得到电离层的双时响应、散射函数、多径展宽等有用信息，是一种新型的电离层探测系统。该文重点讨论该系统中接收通道的开发与实现。该接收通道的设计基于软件无线电思想，以DSP技术为核心，具有处理方式灵活、实时处理能力强、稳定性好、升级空间大等优点。雷达系统的探测实验结果表明，该接收通道可以满足电离层斜向返回探测需要。