辐射损伤潜径迹的纳米尺度观测研究

综述了近年来用扫描隧道显微镜 (STM )和扫描力显微镜 (SFM)在原子水平上观测辐射损伤潜径迹的研究及进展。详述了辐射损伤潜径迹的形貌、损伤范围、损伤数密度、损伤几率等 ,对损伤潜径迹直径与能损的关系、损伤过程及各种可能的损伤机制进行了分析和讨论。     

Measuring the Electron’s Charge and the Fine-Structure Constant by Counting Electrons on a Capacitor

The charge of the electron can be determined by simply placing a known number of electrons on one electrode of a capacitor and measuring the voltage, V_s, across the capacitor. If V_s is measured in terms of the Josephson volt and the capacitor is measured in SI units then the fine-structure constant is the quantity determined. Recent developments involving single electron tunneling, SET, have shown bow to count the electrons as well as how to make an electrometer with sufficient sensitivity to measure the charge.     

量子力学中电子隧穿势垒的时间

简要地介绍各种形式的粒子隧穿势垒时间的定义,并且评论了它们的适用范围.同时介绍有关电子隧穿势垒时间方面的实验测量和结果.     

量子阱中电子隧穿逃逸时间的研究

用波包方法计算了电子从量子阱中的隧穿逃逸时间随外加偏压的变化，与实验结果符合良好，通常半经典近似模型与实验结果偏离较大，通过对两者的比较给出了改进的半经典模型，大大简化了隧穿逃逸时间的计算。     

AlAs and InAs mode LO phonon emission assisted tunneling in (InGa)As/(AlIn)As double barrier structures

WE present a magnetospectral analysis of the different scattering processes involved in the tunneling current of an MBE grown (InGa)As/(AlIn)As double barrier diode. At zero magnetic field, the I(V) characteristics of the sample show a replica peak. We demonstrate that this peak is associated to the tunneling of electrons from the emitter to the quantum well, assisted by the emission of an AlAs mode LO phonon. The presence of InAs mode LO phonon emission processes is also revealed at high magnetic fields. At a field B where the crossing between InAs and AlAs mode phonon emission processes occurs, a change in the B-dependent behavior of the peak voltage positions is observed, that we attribute to a change in the dominant process. The higher probability for InAs mode LO phonon emission processes is explained by the stronger coupling of electrons to this mode in this system, in agreement with previous results on (InGa)As/(AlIn)As single heterojunctions.     

山西省中部引黄工程深埋长隧洞施工方案的比选

隧洞施工方法分为钻爆法和TBM法,其主要是依据工程地质和水文地质条件,并结合地形条件、隧洞长度和施工技术水平等因素综合考虑分析确定,文中主要从技术经济和施工工期等方面对山西省中部引黄工程深埋长隧洞施工方案进行了比选,最终推荐了钻爆法.     

盾构隧道开挖三维数值模拟方法研究

盾构隧道开挖的模拟方法是对隧道-土-结构物相互作用进行三维数值分析的重要考虑因素。对两种典型的模拟方法进行了探讨,一种是更接近真实施工过程的分步开挖法,另一种则是简化的一步通长开挖应力释放法。对比分析表明,两种方法对于地面沉降的预测结果比较接近,而对于邻近桩基础的预测结果之间的差异也不是太大。同时,一步通长开挖应力释放法能得到不同的地层损失,并且建模简单,能够较好地用于分析隧道开挖对地面建筑物及周边地下结构物的影响。     

Combining scanning tunneling microscopy and synchrotron radiation for high-resolution imaging and spectroscopy with chemical, electronic, and magnetic contrast

The combination of high-brilliance synchrotron radiation with scanning tunneling microscopy opens the path to high-resolution imaging with chemical, electronic, and magnetic contrast. Here, the design and experimental results of an in-situ synchrotron enhanced x-ray scanning tunneling microscope (SXSTM) system are presented. The system is designed to allow monochromatic synchrotron radiation to enter the chamber, illuminating the sample with x-ray radiation, while an insulator-coated tip (metallic tip apex open for tunneling, electron collection) is scanned over the surface. A unique feature of the SXSTM is the STM mount assembly, designed with a two free-flex pivot, providing an angular degree of freedom for the alignment of the tip and sample with respect to the incoming x-ray beam. The system designed successfully demonstrates the ability to resolve atomic-scale corrugations. In addition, experiments with synchrotron x-ray radiation validate the SXSTM system as an accurate analysis technique for the study of local magnetic and chemical properties on sample surfaces. The SXSTM system's capabilities have the potential to broaden and deepen the general understanding of surface phenomena by adding elemental contrast to the high-resolution of STM.     

An approach for cross-data querying and spatial reasoning of tunnel alignments

In mechanized tunneling projects, finding a low-risk and cost-effective alignment is an important task. Several alignment variants are usually created and each one is intensely scrutinized. Variants often have individual advantages and disadvantages and can lead to different constructive designs of a tunnel. In order to find the best alignment possible the variants have to be analyzed and evaluated based on requirements and evaluation criteria, such as safety, cost, built environment and operational requirements. To perform this evaluation and to enable comprehensive decision making, a holistic planning environment is examined that includes documents and models of different domains. In general, these domain specific data differ schematically and semantically, which consequently makes it challenging to combine and compare such diverse data. For this purpose, information from different sources must be linked and evaluated in a structured way. In particular, spatial relationships have to be investigated. Therefore, in this paper, ontology databases are utilized to merge BIM and GIS at data level to create an integrated model of the entire tunneling project. Relevant information for decision-making can then be derived, such as the location of private and public buildings that are in a certain vicinity of the planned alignment. On the one hand, the implementation of queries is a popular and frequently used approach to check for semantic properties. On the other hand, using a query language to derive information from geometric data can be challenging, due to the necessity of processing geometric data prior to and during query execution. Additionally, geometric definitions can differ in the considered coordinate reference system, the dimension or the structure. To handle geometry information by employing query languages, representations are methodically transformed to well-known text literals. A simplified and uniform geometric representation can be utilized for spatial reasoning, for example by adopting GeoSPARQL methods.