滑坡稳定分析传递系数法若干问题探讨

滑坡稳定性分析传递系数法有隐式和显式两种解法。当前对这两种解法的认识在稳定系数定义、满足的静力平衡方程类型、稳定系数计算公式表达方式、稳定系数大小关系和稳定系数计算误差等方面存在着不清楚或不一致之处。本文对此逐一进行了分析,并在此基础上提出了传递系数法解法选择的建议。     

南海珠江口盆地工程地质分区与评价

本文根据联合国开发计划署（UNDP）援华项目（CPR/85/044）资料撰写的。划分工程地质区及亚区的目的，在于了解区域工程地质条件的共性与差异性，以求在海洋开发中科学地利用和改造自然。本项研究是在大量地质-地球物理-土工测试基础上进行的，工作扎实，内容丰富，资料准确可靠。根据工程地质条件的相似性与差异性，将珠江口盆地划分为两个大区5个亚区，并研究了各区工程地质特征及主要问题。其中以中陆架混合土亚区工程地质条件最好，外陆架粗粒土亚区工程地质条件较好，上陆坡软土亚区工程地质条件最差，内陆架细粒土亚区和上陆架岩石、礁石亚区工程地质条件较差。本项研究成果为南海海洋开发与总体规划提供了科学依据，同时又促进了海洋工程地质科学的发展。     

Finite Element Formulation of Viscoelastic Constitutive Equations Using Fractional Time Derivatives

Fractional time derivatives are used to deduce a generalization ofviscoelastic constitutive equations of differential operator type. Theseso-called fractional constitutive equations result in improvedcurve-fitting properties, especially when experimental data from longtime intervals or spanning several frequency decades need to be fitted.Compared to integer-order time derivative concepts less parameters arerequired. In addition, fractional constitutive equations lead to causalbehavior and the concept of fractional derivatives can be physicallyjustified providing a foundation of fractional constitutive equations.First, three-dimensional fractional constitutive equations based onthe Grünwaldian formulation are derived and their implementationinto an elastic FE code is demonstrated. Then, parameter identificationsfor the fractional 3-parameter model in the time domain as well as inthe frequency domain are carried out and compared to integer-orderderivative constitutive equations. As a result the improved performanceof fractional constitutive equations becomes obvious. Finally, theidentified material model is used to perform an FE time steppinganalysis of a viscoelastic structure.     

大尺度结构物的二阶波浪荷载

本文提出了一个在有限水深条件下大尺度物体上二阶波浪荷载的数值计算方法。用表面布源法求二阶散射势的特解,提出了有限水深满足非齐次表面边界条件的格林函数,给出了格林函数的积分和级数形式,研究了表面布源范围对解的影响。     

Random distributed feedback fibre lasers

The concept of random lasers exploiting multiple scattering of photons in an amplifying disordered medium in order to generate coherent light without a traditional laser resonator has attracted a great deal of attention in recent years. This research area lies at the interface of the fundamental theory of disordered systems and laser science. The idea was originally proposed in the context of astrophysics in the 1960s by V.S. Letokhov, who studied scattering with “negative absorption” of the interstellar molecular clouds. Research on random lasers has since developed into a mature experimental and theoretical field. A simple design of such lasers would be promising for potential applications. However, in traditional random lasers the properties of the output radiation are typically characterized by complex features in the spatial, spectral and time domains, making them less attractive than standard laser systems in terms of practical applications. Recently, an interesting and novel type of one-dimensional random laser that operates in a conventional telecommunication fibre without any pre-designed resonator mirrors–random distributed feedback fibre laser–was demonstrated. The positive feedback required for laser generation in random fibre lasers is provided by the Rayleigh scattering from the inhomogeneities of the refractive index that are naturally present in silica glass. In the proposed laser concept, the randomly backscattered light is amplified through the Raman effect, providing distributed gain over distances up to 100 km. Although an effective reflection due to the Rayleigh scattering is extremely small (∼0.1%), the lasing threshold may be exceeded when a sufficiently large distributed Raman gain is provided. Such a random distributed feedback fibre laser has a number of interesting and attractive features. The fibre waveguide geometry provides transverse confinement, and effectively one-dimensional random distributed feedback leads to the generation of a stationary near-Gaussian beam with a narrow spectrum. A random distributed feedback fibre laser has efficiency and performance that are comparable to and even exceed those of similar conventional fibre lasers. The key features of the generated radiation of random distributed feedback fibre lasers include: a stationary narrow-band continuous modeless spectrum that is free of mode competition, nonlinear power broadening, and an output beam with a Gaussian profile in the fundamental transverse mode (generated both in single mode and multi-mode fibres).     

Effects of nitrogen-doping configurations with vacancies on conductivity in graphene

We investigate electronic transport in the nitrogen-doped graphene containing different configurations of point defects: singly or doubly substituting N atoms and nitrogen–vacancy complexes. The results are numerically obtained using the quantum-mechanical Kubo–Greenwood formalism. Nitrogen substitutions in graphene lattice are modelled by the scattering potential adopted from the independent self-consistent ab initio calculations. Variety of quantitative and qualitative changes in the conductivity behaviour are revealed for both graphite- and pyridine-type N defects in graphene. For the most common graphite-like configurations in the N-doped graphene, we also consider cases of correlation and ordering of substitutional N atoms. The conductivity is found to be enhanced up to several times for correlated N dopants and tens times for ordered ones as compared to the cases of their random distributions. The presence of vacancies in the complex defects as well as ordering of N dopants suppresses the electron–hole asymmetry of the conductivity in graphene.     

Soft‐X‐ray ARPES facility at the ADRESS beamline of the SLS: concepts,technical realisation and scientific applications

Soft‐X‐ray angle‐resolved photoelectron spectroscopy (ARPES) with photon energies around 1 keV combines the momentum space resolution with increasing probing depth. The concepts and technical realisation of the new soft‐X‐ray ARPES endstation at the ADRESS beamline of SLS are described. The experimental geometry of the endstation is characterized by grazing X‐ray incidence on the sample to increase the photoyield and vertical orientation of the measurement plane. The vacuum chambers adopt a radial layout allowing most efficient sample transfer. High accuracy of the angular resolution is ensured by alignment strategies focused on precise matching of the X‐ray beam and optical axis of the analyzer. The high photon flux of up to 10¹³ photons s^?1 (0.01% bandwidth)^?1 delivered by the beamline combined with the optimized experimental geometry break through the dramatic loss of the valence band photoexcitation cross section at soft‐X‐ray energies. ARPES images with energy resolution up to a few tens of meV are typically acquired on the time scale of minutes. A few application examples illustrate the power of our advanced soft‐X‐ray ARPES instrumentation to explore the electronic structure of bulk crystals with resolution in three‐dimensional momentum, access buried heterostructures and study elemental composition of the valence states using resonant excitation.     

X射线在金-硅界面剂量增强系数与金和硅厚度关系的模拟研究

用蒙特卡罗(Monte Carlo)方法计算不同能量的X射线在金-硅(Au-Si)界面处中产生的剂量增强系数（DEF）与金(Au)和硅(Si)厚度的关系.结果表明：界面一侧Si中的DEF与Au和Si的厚度有关。当Au厚度分别取1μm、2μm、4μm、8μm时,界面处最大剂量增强系数分别为：19.78、24.78、24.78、32.3,界面处的DEF随Au厚度的增加而增大;当Si厚度分别取1μm、2μm、4μm、8μm时,界面处最大剂量增强系数分别为：24.5、25.91、27.84、30.09,界面处的DEF随Si厚度的增加而增大.并且研究了Au为2μm、4μm时界面下不同位置处的DEF随能量的变化关系,界面处的DEF最大,离界面越远剂量增强效应越小.     

Uncertainty of array-based measurement of radiated and absorbed sound intensity

Patch near-field acoustic holography (NAH) coupled with an array of sound intensity probes allows separating the sound field incident on a surface from the one radiated by the surface itself. Although the measurement principle has been successfully used to separate the noise source contribution from disturbing sources and/or noise reflections, the method accuracy has not been investigated in the literature. We describe the results of experiments meant to evaluate the uncertainty in the identification of noise radiated by vibrating panels with different absorption characteristics in presence of an incident acoustic radiation using the statistically optimized near-field acoustic holography. Measurement errors were evaluated through tests performed in controlled acoustic conditions. Results evidenced that the measurement uncertainty depends on the accuracy of the microphone array positioning and on the incident sound field. These conclusions were in agreement with the results obtained by simulations in the phase of instrument optimization.     

Motion blur parameters estimation for image restoration

This paper deals with estimation of parameters for motion blurred images. The objectives are to estimate the length (L) and the blur angle (θ) of the given degraded image as accurately as possible so that the restoration performance can be optimised. Gabor filter is utilized to estimate the blur angle whereas a trained radial basis function neural network (RBFNN) estimates the blur length. Once these parameters are estimated the conventional restoration is performed. To validate the proposed scheme, simulation has been carried out on standard images as well as in real images subjected to different blur angles and lengths. The robustness of the scheme is also validated in noise situations of different strengths. In all situations, the results have been compared with standard schemes. It is in general observed that the proposed scheme outperforms its counterparts in terms of restoration parameters and visual quality.