VPN隧道封装性能分析与研究

隧道技术是实现VPN的关键技术。本文分析了ESP和AH隧道协议在通道模式和传输模式下的隧道结构，计算了不同隧道的封装开销和开销比例，并对计算的结果进行了分析。     

面向边坡危岩的旋翼机环绕航摄处理与分析

针对小范围危岩在单体类圆台形边坡精细化三维模型生产中的不足,提出一种基于边坡坡度对危岩地段开展环绕框架式加渐进式影像数据采集方法,分层分域采集边坡危岩的影像信息,并运用倾斜摄影技术进行三维重建;同时运用传统模仿五镜头航摄建模方法在桂林某铁路段危岩边坡开展了三维重建对比实验并进行了精度分析。分析表明,该方法可以高质地建立类圆台形边坡危岩的实景三维模型,有利于对危岩隐患进行区域锁定与阶段性监测,并为基础空间体数据采集提供较优选择。     

VPN隧道技术研究

隧道技术是实现VPN的关键技术，常见的隧道协议包括GRE，L2PT和IPSec。不同的隧道协议具有不同的隧道结构，它们在工作模式，多路复用，安全性等方面的支持程度也不同，本文的研究结论为合理选择隧道技术提供了理论依据。     

虚拟现实技术在隧道开挖工程中的应用

针对复杂地质结构与多地质灾害风险的地下隧道开挖安全和科学施工,提出了一种隧道开挖计算机仿真方法。方法首先以地质勘探资料为基础,通过智能推演和人机交互方法进行三维地质建模,然后应用计算机仿真技术虚拟隧道开挖,最终揭示隧道围岩地质结构变化特征,实现隧道开挖过程中的地质灾害风险预警。方法成功地应用于几个大型铁路隧道开挖工程,结果证明该方法能够有效预测隧道围岩地质结构变化与地质灾害可能发生的空间位置、类型与级别。方法为实际隧道科学施工决策、安全开挖提供了可靠依据。     

分体式电缆隧道检测机器人的移动结构研究

随着城市电缆隧道的不断增加,为确保电缆隧道内环境检测和电缆的安全运行,对电缆隧道检测机器人进行研究具有重要意义,而目前国内外对于电缆隧道检测机器人的研究还处于初期发展阶段。介绍了电缆隧道检测机器人的现状,为采集电缆隧道内部环境图像、温度、有毒气体等信息,需要开发适应复杂环境的机器人移动结构。通过对电缆隧道环境类似的管道机器人移动结构现状分析与综合比较,将履带、轮式、多节机器人移动结构作为设计的重点参考对象。通过进一步分析履带、轮式、多节机器人移动结构的特点,提出了多节分体式机器人的研究思路,并设计了分体式机器人移动结构。通过机器人运动分析,验证了该移动结构的优越性。基于分体式电缆隧道检测机器人移动结构研究,为后续电缆隧道检测机器人的研究提供了有益借鉴和参考。     

基于无线自组网测振仪的被动网落石监测系统

山区铁路沿线崩塌落石灾害频发,及时、准确地发现崩塌落石事件并发出报警信息,对铁路运营安全具有重要的意义。通常在一些危岩落石高发地段会设置被动防护网拦截滚石,然而该方式并不能完全防止落石上道。为确保“落石不上道,上道不撞车”,迫切需要研发一套无人值守、全天候实时准确监测铁路沿线被动网落石监测系统。本文研发一种基于三轴MEMS无线自组网测振仪的被动网落石监测系统,通过前端感知振动并对振动信号进行边缘计算处理得到最大加速度值,并调用摄像头对发生振动的被动网预置点进行拍照,将最大加速度值和摄像头拍摄到的照片上传至服务器;最后由服务器及时推送报警信息,实现了铁路沿线被动网落石的自动化监测功能。工程实际应用表明,该系统能满足铁路边坡崩塌落石自动化监测的需求,该研究成果可应用于铁路、公路危岩落石自动化监测领域。     

隧道内细水雾抑制火灾事故的数值仿真

以工业灾害的抑制技术为背景,针对隧道内发生的火灾事故,采用数值仿真技术研究连续喷射水雾阻挡气相物质燃烧的过程.并讨论水雾抑制燃烧的机理.相比于欧拉/欧拉方法,欧拉/拉格朗日方法能较好地描述水雾液滴引起的瞬时流动特性及变化经历,利用欧拉/拉格朗日方法,对气相反应流及水雾扩散过程进行数值研究.应用颗粒随机轨道模型,来考察湍流对水雾液滴扩散的影响.比较了有、无水雾抑制时和水雾不同初始流量下,隧道内流场的温度分布情况,揭示了水雾液滴的运动特性,为火灾事故抑制技术的发展提供理论依据.     

高速公路隧道照明系统的集散控制和监测

本文结合某隧道照明灯的分布及其控制设备,对该隧道内的照明进行集散控制与检测,保证在白天洞外照度与洞内照度的平缓过渡;夜间洞内洞口照明协调。从的安全性上考虑,保证根据应急地点和时机进行应急照明控制。从节能上考虑,保证根据车流量进行照明控制。     

基于视频检测技术的智能隧道交通安全监控系统设计

隧道实时交通安全监控系统是确保隧道安全运营的重要手段.针对隧道环境的特殊性,提出基于差异深度积累的目标检测算法和基于卡尔曼滤波的目标跟踪算法,实现了多运动目标的检测与跟踪,并综合运用图像处理、计算机视觉、模式识别和软件工程等技术设计了基于视频检测技术的智能隧道交通安全监控系统.该系统能准确地检测出各种交通运行参数和交通事件,为隧道交通安全提供了有力保障.     

基于计算机辅助测量的隧道断面测量新方法

介绍了如何将三次参数样条插值法运用到铁路隧道断面轮廓曲线拟合的过程,及如何计算出轮廓曲线的数学表达式,并利用所求方程,对隧道断面面积进行计算,实现了其与标准隧道断面的比较,计算出了实际断面的超、欠挖面积和体积。在算法基础上,设计开发出一个应用系统———计算机辅助隧道断面测量系统,通过实验验证了该方法的正确性。这一方法的应用,将断面量测与洞室位移监测相结合,实现了隧道断面测量的数字化,改进了传统隧道断面的验收工作,降低了其外业难度,提高了测量精度。     

流道引流对风洞试验段轴向静压因数的影响

为改善开口式汽车风洞试验段轴向静压因数分布,应用数值仿真方法研究不同扩散角、收集口角度和流道引流方式对风洞试验段轴向静压因数以及静压梯度的影响.数值仿真得到的轴向静压因数与风洞试验结果一致,验证该计算方法的正确性.研究结果表明：流道引流方法可提高收集口附近的速度,降低当地的静压因数,导致试验段轴向静压因数的降低,从而改善流场品质.从收集口顶部或其两侧引入流道回流的方式都能降低试验段轴向静压因数,且两种方式降低效果相同.对于较大的扩散角,与15°收集口的引流相比,0°收集口的引流改善试验段轴向静压因数的效果更好;对于较小的扩散角,结果相反.     

基于数值计算的高速列车气动阻力风洞试验缩比模型选取方法

为给高速列车气动阻力风洞试验模型选取提供更多的参考依据,通过计算流体力学(Computational Fluid Dynamics,CFD)方法,研究不同比例的高速列车缩比模型对气动阻力风洞试验结果的影响.首先,计算得到开口式风洞测试段的静压系数分布曲线,为高速列车气动阻力测量试验模型的长度选择以及摆放位置提供依据;其次,通过数值计算得到全尺寸模型列车在明线运行时,以及不同比例的模型列车在风洞中运行工况下的气动阻力信息,并从阻塞效应和雷诺数的变化,以及风洞试验段内静压分布的影响这3个方面对列车模型的气动阻力结果进行分析,得到在所研究风洞中较合理的列车缩比模型比例选取范围.这种以CFD为基础进行数值仿真,选取风洞试验中列车模型比例及试验测试位置的方法,为在地面交通工具风洞中进行高速列车模型气动阻力试验的缩比模型选取提供一定依据.     

基于贝叶斯网络的隧道围岩失稳风险预警方法

为了对隧道围岩失稳风险做出准确判断,预防围岩失稳灾害的发生,将贝叶斯网络方法应用于隧道围岩失稳的风险预警。在系统分析隧道支护参数影响围岩稳定性的基础上,通过引入基于贝叶斯网的知识表达和相应的不确定性推理原理,构造了隧道围岩失稳风险预警专家系统;并通过工程案例验证了隧道围岩失稳风险预警专家系统好的适用性。贝叶斯网专家系统可以充分利用专家的先验知识和已有案例提供的或概率分布,可以使推理在输入数据不完备的基础上进行,能够有效地实现围岩失稳风险预警。     

基于特征断面的复杂巷道段三维建模

为解决巷道断面随工程需要及岩层变化不断改变,导致巷道三维建模程序复杂的问题,提出基于特征断面的巷道三维建模思想,通过建立巷道特征断面模型库,实现变化巷道段的三维建模,以期提高复杂巷道段的建模效率。首先阐述建模数据的采集方法,并对巷道断面进行了细化坐标分析;同时提出拐角处断面变化巷道段的平滑处理算法（通过圆弧来圆滑拐角处巷道中心线）,对普通巷道段采用三角剖分形成三角网完成巷道段的建模;而巷道断面发生变化的复杂巷道段存在简单曲面四边形,采用Bézier曲面及曲面的拼接完成巷道段的建模,并在实验中进行了验证     

Surface subsidence and uplift above a headrace tunnel in metamorphic basement rocks of the Swiss Alps as detected by satellite SAR interferometry

Surface subsidence associated with the construction of a headrace tunnel in the Swiss Alps at more than 2000 m above sea level (a.s.l.) has been detected at two locations with satellite differential Synthetic Aperture Radar (SAR) interferometry. At the first location, a subsidence trough of about 4 cm in the satellite line-of-sight direction following the headrace tunnel axes has been measured between August 1995 and August 1996. Similar values from SAR data of ascending and descending orbits indicate displacements in the vertical direction of the movement. In the second case, a symmetric cone of depression with a maximum displacement of about 4 cm between 1995 and 1997 has been observed above the tunnel. Differences in the results from satellite SAR data of ascending and descending orbits indicate that the direction of displacement in this second case was not entirely vertical. Large-scale consolidation associated with pore-pressure reduction in the rock mass arising from tunnel drainage at about 200-400 m depth beneath the topographical surface is believed to be the contributing mechanism (Zangerl et al., 2008a, 2008b). Evidence for this process is based on pore pressure recordings in nearby deep wells. In both areas, the subsidence was followed by a small uplift of about one centimeter between 1997 and 1999, after the tunnel was cased with permeable concrete segments. This partial recovery is also visible in pore pressure records and can be related to the elastic components of rock mass deformation.     

The perception of hazard I. Hazard analysis and the contribution of visual search to hazard perception

Rockfall accidents are an important determinant of safety performance in deep level mining. Previous research which is reviewed suggests that a lack of skill in perceiving warnings of imminent danger may be an important factor contributing to this kind of accident. The perceptual task of mine workers is described briefly and a survey of the visual characteristics of dangerous rock is reported upon. The visual search performance of mine workers in a stope simulator, designed on the basis of the survey results, was studied. The findings show not only that novice mine workers, when compared with experienced men, lack the ability to search adequately in a simulation of dangerous rock, but also that their search skills can be improved significantly by training.     

Numerical study of the injection process in a transonic wind tunnel: The numerical details

Numerical prediction of an injection process was successfully performed. The physical problem corresponds to the mixing of a number of parallel supersonic jets with a subsonic main stream, in the presence of solid walls. In practice, this arrangement is to be used as a boosting device in a transonic wind tunnel, with the ultimate objective of extending the tunnel’s envelope without penalizing the main compressor. Five supersonic nozzles are installed at the floor and five at the ceiling of the transition module’s entrance section. Due to the great difference between cross-sectional typical lengths of nozzles and tunnel, the numerical tool has to have a three-dimensional capability. The core of the code is an adaptation of the finite-difference diagonal algorithm, and turbulence effects are properly tackled by the use of the Spalart and Allmaras one-equation scheme. Some simplifications were adopted in order to render the problem minimally tractable, especially in this initial numerical simulation stage, which is the reporting objective of this article. Albeit this, and due to the magnitude of the problem in hand, these simplifying initiatives were not sufficient to bring the calculations down to a scale of reasonable computer costs. Hence, a sequence of grids, coupled with a division of the computational domain, was adopted. Boundary conditions were thoroughly worked, especially the ones related to the domain of calculation’s entrance plane. This plane is important because of the many viscous gradient regions that project against it. Among the many settings under which a tunnel can operate there is one defined as the “design condition”, or else as the “design point”, as it is sometimes called. For a tunnel equipped with an injection system, the design point asks (besides many other specifications) for equal static pressures at the section where the supersonic jet meets for the first time the main stream coming from the tunnel circuit. We have simulated five different operating settings of the tunnel and among them the design condition. Therefore, we have results for the design as well as for many off-design points. The idea was to simulate the many tunnel settings and also to test the code’s ability to handle all these different situations. The code was duly validated and verified, and in the sequel the steady flow field in the mixing region was calculated. Many interesting and very important results were obtained, among which we would point out the existence of compression and expansion domes at the supersonic regions, the calculation of the many engineering parameters related to the injection process, and especially the determination of the injection’s gain threshold.     

An equivalent method for blasting vibration simulation

Due to the complicated blasting load, the diversified medium models and various constitutive relations of the rock mass, and a huge job for simulating blasting of multiple holes, it is very difficult and costly to simulate the blasting vibration accurately in numerical computation. This paper presents an equivalent simulation method so as to transform this complex dynamic problem into an approximate initial-boundary problem. The equivalent elastic boundary applied by the blasting load was developed for multiple holes according to the spatial distribution of rock damage around each blasthole. The equivalent mechanics process of the complex blasting load was performed through analysis of the expansion of the borehole volume, the growth of cracks, the movement of stemming and the outburst of detonation gases. In combination with the blasting excavation of the tailrace tunnel in the Pubugou Hydropower Station, particle vibration velocities in the surrounding rock at different distances from the explosion source were simulated by applying this equivalent method based on the dynamic finite element method. The comparison with field monitoring data indicates that this equivalent simulation method is applicable to predicting the far-field dynamic response of the ground subjected to blasting load, and the selection of rock mass properties near the equivalent elastic boundary has a significant impact on simulation results.     

压力平衡口对开口式汽车模型风洞驻室流场影响的数值仿真

为尽可能真实地建立汽车测试环境,对开口式汽车模型风洞驻室试验段流场品质进行数值仿真,研究在开设压力平衡口前后的流场品质,并对不同面积和形式的压力平衡口工况进行数值仿真,得到不同试验段内流场品质的计算结果.通过比较分析得出结论:有压力平衡口时,特别是压力平衡口的面积为140 m×140 m时,汽车模型风洞驻室试验段最有利于汽车性能测试.     

FL-26风洞扩散段结构优化分析

针对FL-26风洞原有结构（如扩散段）已出现裂纹,严重影响科研任务的按时完成以及风洞设备运行安全的问题,简介扩散段的结构,分析产生裂纹的原因;对原有结构进行详细的有限元验证计算和分析,得到裂纹产生的基本原因是其结构动态特性太差;基于改善动态特性的指标对多种方案进行比较,确立最终结构改造方案:更换内壳体,材料为16MnR...