隧道浅埋段的超前地质预报与监控量测

隧道超前地质预报与监控量测是新奥法施工不可缺少的一部分,能够准确预报掌子面前方一定距离内围岩质量的好坏,并实时通过围岩变形的监测与分析检验围岩是否稳定及支护是否合理。结合杉溪隧道工程实例,通过对隧道浅埋段的超前地质预报和监控量测数据进行分析研究,得出隧道浅埋段围岩变形速率受施工干扰影响较大,钢支撑内力及围岩压力与围岩断面变形量变化趋势基本一致。通过研究隧道浅埋段的围岩变形规律和支护结构受力特征,可为以后类似项目积累经验,提供施工依据。     

端粒长度检测及其在辐射损伤研究中的应用

介绍了端粒长度主要检测方法TRF、Q-FISH、FlowFISH、Q-PCR、STELA的基本原理及其优缺点,端粒检测在辐射损伤研究及辐射流行病学调查和临床研究中的应用,以及本实验室改进后的Q-PCR方法及其应用。     

Effects of refractory elements on the microstructure and creep behaviour of nickel-base cast superalloys strengthened with high volume fraction gamma-prime phase

Microstructural observations and creep measurements at elevated temperatures were carried out on nickel-base cast superalloys strengthened by 0.65 atomic fraction gamma-prime (y'J phase with varied concentrations of Ta, Wand Mo and with elements commonly used in practice. The variations in the amounts of the refractory elements considerably altered the morphologies and the quantities of carbides as well as γ and γ’ eutectics. The steady-state creep rate for these alloys was related to lattice mismatch between the γ and γ’ phases as well as to the aluminium concentration in the γ’ phase. The effect of the elements on creep rupture life was in the order W>Ta>Mo.     

Uncertainty analysis for multiphase flow: A case study for horizontal air-water flow experiments

This work describes the procedure used to define the measurement uncertainties of horizontal two-phase air-water flow experiments conducted to determine influences due to pipe diameter on pressure gradient on such flows. These experiments were performed with 4 different pipe diameters, always using the same test section length, therefore varying the length-to-diameter (L/D) ratio. Several parameters were measured, such as volumetric/mass flow rate, pressures, temperatures and pressure drop; other parameters were calculated, such as the superficial velocities of each fluid, as well as their corresponding properties. The main parameters studied were the flow patterns for different velocity configurations and the two-phase pressure drop to be used for model improvement, thus the importance of uncertainties analysis. The sources of uncertainty were defined, detailed, systematically studied and quantified. Also, the reproducibility capacity of the experimental setups were analysed through the uncertainty analysis and proving them to be able for future similar studies. The flow maps with their uncertainties could help understand the thresholds for each defined flow pattern region, and the plots of two-phase pressure drop variation with diameter confirmed the homogeneous model as a possible approach to calculate pressure drop if the uncertainties are considered.     

Experimental assessment of the effects of cross-traffic on Wi-Fi video streaming

Wi-Fi networks are the first and sometimes only choice for the video streaming in homes, airports, malls, public areas and museums. However, Wi-Fi networks are vulnerable to interference, noise and have bandwidth limitations. Due to the intrinsic vulnerability of the communication channel, and the large number of variables involved, simulation alone is not enough in the evaluation of the performance of wireless networks. Actually, there is a tendency to give experimental tests a central role in the assessment of Wi-Fi networks performance.The paper presents an experimental analysis of the effects of cross traffic on the performance of video streaming over Wi-Fi, based on cross-layer measurements. Experiments are carried out in a semi-anechoic chamber, to prevent the results from being influenced by external factors. The experimental results permit to analyze the influence of cross traffic characteristics on cross layer measures and objective video quality metrics evaluated through a standardized approach.     

An investigation of slewing-crane dynamics during slewing motion—development and verification of a mathematical model

Information about the dynamic loading of a steel structure is important for its static design as well as for an assessment of its fatigue life. In the case of tower cranes, these loads are mainly caused by vibrations and load sway, which occurs as a result of the slewing motion of the jib around the vertical axis and from the radial movement of the load's suspension point. In this paper, only the slewing motion that produces the spatial motion of the pendulum is considered, because this kind of motion has received much less attention than the translation of the suspension point. In order to achieve this, a non-linear mathematical model of the load sway during the slewing motion was formulated, and the non-linear nature of the swinging motion for large angles and the non-linearity of the power transmission were considered. The structure's elasticity and damping, the friction in the main bearing, and the air resistance were also taken into account. The dynamic forces acting on the steel structure of the crane during payload transport were obtained. In order to confirm the mathematical model, an actual model of a crane was built and used as the basis for measurements. A comparison of the results shows good agreement between the predicted and the measured values.     

中国消防实施“科技强消”战略探讨

本文提出了实施“科技强消”战略的论断,指出了实施该战略的客观必要性和迫切性,提出了实施该战略的基本思路和所要达到的目标、实现途径及对策。     

同步辐射与分析测试

本文介绍一种大科学装置——同步辐射装置。这是一种数百人可同时在其上进行不同的科学技术实验的设备，其可达到的水平比实验室的极限水平高许多，从某些角度代表了国家的科学和技术水平。本文扼要介绍了同步辐射的特性，同步辐射装置的构造及一些主要的分析测试技术，如：X射线吸收精细结构光谱，X射线散射，高分辨X射线衍射，能量色散与时间分辨技术，聚集与微分析，成像与显微放大，综合测试原位测试及作铯对标定等。     

Nonintrusive Method for Detecting Particle Movement Characteristics near Threshold Flow Conditions

Bed-load measurements comprise an important component in the development of reliable formulas, in an effort to obtain the necessary constitutive relations between the amount of transported material and flow parameters. The uncertainty of such measurements is rather well known, being much more pronounced at lower transport rates. This uncertainty stems from the multitude of factors affecting bed-load transport and the lack of available trustworthy measuring technologies. Predictions of the limiting case of nearly zero bed-load transport, typically reported in literature as threshold of motion or critical condition, are even more challenging. The purpose of this contribution is twofold. First, to examine the sensitivity of bed-load transport measurements at conditions moderately higher than critical, to the presence of a rather unobtrusive trap, designed through several iterations. Even under relatively simple laboratory flume channel and flow conditions, it proved difficult to measure the bed-load transport rate in a completely unbiased way. Second, to develop a methodology, together with the appropriate instrumentation, for determining the condition of incipient motion. The nonintrusive approach described here proved to be reliable in detecting even the slightest movements of a particle. At the same time, it demonstrates the complexity of the problem due to the highly fluctuating nature of turbulent flow.     

Analysis of Magnetic Take-Up Roll Employed in Amorphous Alloy Ribbon Production Line

A novel magnetic take-up roll used in amorphous alloy ribbon formation lines is introduced in this paper. The finite element method was used to calculate two different magnetic models for a selected amorphous ribbon. The simulation result showed that magnetic adhesion force can make the ribbon move toward and stay on the magnetic take-up roll. The tests indicated that the results measured complied with simulation ones. Moreover, the final design prototype test successfully satisfy the main objective of the project – to take up the ribbon – with a high success rate.