采坑型滑坡涌浪参数计算——以贵州小坝滑坡为例

采坑型滑坡高速入水激起的涌浪能量巨大,涌浪运动的初始速度极快,运动距离长。本文采用美国土木工程学会建议的推算法计算最大初始涌浪值,运动学公式计算涌浪向前的最大运动速度和最大传播距离,并结合泥石流防治规范计算运动过程中的冲击能量。以贵州小坝滑坡为例对涌浪的初始浪高和传播距离以及传播过程中所产生的冲击能量进行计算。得出涌浪的初始浪高为33.8 m,涌浪最大初始水平运动速度为60 m/s,涌浪最大运动距离为180 m,在运动过程中产生的能量对距涌浪发生点160 m内的建筑物均造成破坏。该计算结果可为采坑型滑坡涌浪预测及其风险评价提供参考。     

煤矿作家群现象研究

煤矿作家群是煤矿涌现出的作家群体,这些作家以自己的文学作品提高了所在煤矿的知名度,也引起了中国文坛的关注。煤矿作家群的形成、组成和成就都值得深入研究和关注,对这些现象的分析有助于这个群体健康、有序地发展。     

Experimental correlation between photoemission matrix elements and LEED intensities in superperiodic structures

A direct comparison between photoemission measurements and band structure calculations is sometimes tricky. Matrix element effects may affect considerably the spectral weight of the electronic states and prevent the expected translational symmetry of the band structure from being observed. We show how matrix element effects can be qualitatively described to a certain extent by making an analogy between photoemission and low energy electron diffraction. We have tested this approach in two superperiodic systems. We have first explained the intensity distribution in different Brillouin zones of a surface state in Si(1 1 1)-(7 × 7), where the surface state spectral intensity does not exhibit the (7 × 7) symmetry. We have also compared the LEED intensity of superperiodic LEED spots with the energy dependence of bulk bands on a facetted Si surface as measured by photoemission.     

What does an ideal wall look like?

This paper deals with the interface between a solid and an ideal gas. The surface of the solid is considered to be an ideal wall, if the flux of entropy is continuous, i.e., if the interaction between wall and gas is non-dissipative. The concept of an ideal wall is discussed within the framework of kinetic theory. In particular it is shown that a non-dissipative wall must be adiabatic and does not exerts shear stresses to the gas, if the interaction of a gas atom with the wall is not influenced by the presence of other gas atoms. It follows that temperature jumps and slip will be observed at virtually all walls, although they will be negligibly small in the hydrodynamic regime (i.e., for small Knudsen numbers).     

Real-time monitoring of ethane in human breath using mid-infrared cavity leak-out spectroscopy

We report on spectroscopic real-time analysis of ethane traces in exhaled human breath. Ethane is considered the most important volatile marker of free-radical induced lipid peroxidation and cell damage in the human body. Our measurements were carried out by means of mid-infrared cavity leak-out spectroscopy in the 3 μm region, a cw variant of cavity ring-down spectroscopy. The spectrometer is based on a CO overtone laser with tunable microwave sidebands. The resulting system proved to be an unique tool with high sensitivity and selectivity for rapid and precise breath testing. With a 5 s integration time, we achieved a detection limit on the order of 100 parts per trillion ethane in human breath. Thus, sample preconcentration is unnecessary. Time-resolved monitoring of the decaying ethane fraction in breath after smoking a cigarette is demonstrated. Received: 13 March 2001 / Published online: 9 May 2001     

Isotopic ratio measurement of methane in ambient air using mid-infrared cavity leak-out spectroscopy

We report on infrared laser spectroscopic measurements of the isotopic composition of methane (¹²CH₄, ¹³CH₄) in natural air samples with a cavity ring-down technique. A CO overtone sideband laser is utilized to excite a high-finesse cavity which provides an effective optical absorption path length of 3.6 km. We achieved a detection limit of 105 ppt methane in ambient air using an integration time of 20 s. This corresponds to a minimum detectable absorption of 1.9×10^-9 /cm. Rapid determination of the ¹³C/¹²Cisotopic ratio of methane in ambient air without sample preconcentration or gas processing is realized. The present system requires only few minutes for an isotopic ratio measurement with a precision of 11%o . Received: 14 July 2000 / Revised version: 25 October 2000 / Published online: 6 December 2000     

Leakage current and capacitance characteristics of Si/SiO2/Si single-barrier varactor

We investigate, both experimentally and theoretically, current and capacitance (I–V/C–V) characteristics and the device performance of Si/SiO₂/Si single-barrier varactor diodes (SBVs). Two diodes were fabricated with different SiO₂ layer thicknesses using the state-of-the-art wafer bonding technique. The devices have very low leakage currents (about 5×10^-2 and 1.8×10^-2 mA/mm²) and intrinsic capacitance levels of typically 1.5 and 50 nF/mm² for diodes with 5-nm and 20-nm oxide layers, respectively. With the present device physical parameters (25-mm² device area, 760-μm modulation layer thickness and ≈10¹⁵-cm^-3 doping level), the estimated cut-off frequency is about 5×10⁷ Hz. With the physical parameters of the present existing III–V triplers, the cut-off frequency of our Si-based SBV can be as high as 0.5 THz. Received: 9 February 2001 / Accepted: 9 February 2001 / Published online: 23 March 2001     

具有无限时滞中立型泛函微分方程零解的渐近性态

本文利用 D算子的某些性质及 Liapunov泛函的方法 ,研究了具有无限时滞中立型泛函微分方程零解的一致稳定性与一致渐近稳定性 ,得到了新的结果 .     

Polarization observables in elastic electron deuteron scattering including parity- and time-reversal-violating contributions

The general formalism for polarization observables in elastic electron deuteron scattering is extended to incorporate parity- and time-reversal-violating contributions. Parity-violating effects arise from the interference of γ and Z exchange as well as from the hadronic sector via a small parity-violating component in the deuteron. In addition we have allowed for time-reversal-invariance-violating contributions in the hadronic sector. Formal expressions for the additional structure functions are derived, and their decomposition into the various multipole contributions are given explicitly. Received: 19 December 2000 / Accepted: 14 February 2001