多环城市环隧连接道纵向排烟方案研究

总结国内部分城市环隧的建设规模以及排烟方式,分析连接道对多环城市环隧纵向排烟的影响。以采用纵向排烟方式的北京市某多环城市环隧为例,采用FLUENT软件对多环城市环隧连接道进行烟气模拟,并根据模拟结果提出多环城市环隧连接道纵向排烟的烟控方案。

多环道城市环隧纵向排烟模拟研究

分析多环城市地下交通联系隧道排烟设计难点,以某城市环隧为例,分别介绍在发生主隧道火灾、主隧道连接道火灾、出入口隧道火灾、车库连接道火灾等的情况下的纵向排烟方案设计。采用CFX软件模拟分析排烟方案的有效性。在此基础上对此类隧道的纵向排烟提出建议措施。

“日”形地下环隧施工风险因素综合分析

为了研究复杂环境对城市地下空间建设过程中的安全影响,以某在建城市地下“日”形环隧工程为研究对象,基于模糊层次分析法结合专家经验与统计分析法对该工程进行综合风险因素定性与定量分析。将城市环隧建设风险划分为地质环境风险、建筑环境风险、建筑设计风险和施工建设风险四类,并将每种风险细分为两层指标因素。研究表明,该工程建设过程中具有较高风险。根据权重计算结果,建设过程中要着重注意包括临近建筑、地下管网、管线分布等因工程所处复杂建筑环境带来的建筑设计与施工建设风险;两指标层中的风险指标按照权重大小划分为主要、中等、次要影响因素三类,并给出了相应的风险防控对策。研究结果可为未来城市环隧工程建设风险控制与管理提供理论指导。

纵向通风排烟模式下城市环隧的疏散设计

分析了城市环隧的特点以及发展现状,提出了纵向排烟条件下城市环隧的疏散设计难点。结合实际工程案例,采用计算机仿真模拟技术分析了城市环隧疏散设计方案的可行性,并得出了结论和建议。通过分析城市环隧纵向排烟时烟气流动特性,对比人行疏散方式及车行疏散方式的特点,提出应在条件允许的情况下尽量采用车行疏散。

纵向通风排烟模式下城市环隧的疏散设计

根据城市环隧发展状况及特点对纵向排烟通风模式疏散设计进行探讨,并结合实例,利用计算机模拟仿真技术对疏散设计的可行性进行分析,与车行、人行疏散方式特点进行对比,认为采用车行疏散方式相对合适。

地铁、环隧对建筑空间的影响——世界侨商中心建筑设计难点解析

在北京通州核心区,拥有地铁上盖、地下环隧交通组织的世界侨商中心项目,体现了建筑与交通的融合。本文将分别从与城市外部交通的接驳、连接空间的节点设计、商业流线引导三个方面对交通与建筑一体化的空间组织进行了详细的分析。

超高层地下室与既有环隧衔接施工技术

环隧与新建建筑地下室对接涉及有限空间内原支护结构加固及破除、环隧底板地基处理、新旧环隧对接等问题,以实际案例为依托,针对支护结构采用绳锯切割,与环隧对接处采用植筋并设置变形缝的施工方法,采用中埋+外贴橡胶止水带的方式安全有效地完成采用中埋+外贴橡胶止水带的方式解决新旧混凝土间变形缝防水问题,,实现地下空间连通的目的,为后续类似项目提供施工借鉴。

基于ISM模型的地下环形隧道通行能力影响因素研究

在地面土地利用趋于饱和、交通拥堵问题日益严重的形势下,地下道路逐渐得到广泛的研究和应用。文中通过对城市地下环隧通行能力影响因素的分析,梳理出具体的12项影响因素,并据此构建城市地下环隧通行能力的解释结构(ISM)模型,再对影响因素进行划分并找出各因素之间的相互关系。研究结果表明,12个影响地下环隧通行能力的因素可被划分为3个层级,根据层级关系可将其划分为车流特性因素、环境因素与天气因素。

基于多元矩阵的俱乐部物品的有效供给——以武汉市“六桥一隧一环”为例

本文首先从武汉市"六桥一隧一环"的供给现象出发,确定了"六桥一隧一环"的俱乐部物品的性质——部分竞争性和部分排他性。其次列举政府供给、市场供给和第三部门供给三种供给方式的利弊并以此为基础构建了多元矩阵模型。再次对政府无偿供给、政府供给行政化收费、政府供给市场化收费三种可能的供给方式进行有效性分析。并最终得出政府无偿供给无效,政府供给市场化收费相对有效,政府供给行政化收费最有效的结论。

北京奥林匹克公园中心区地下交通联系通道防水设计与施工技术

以北京奥林匹克公园中心区地下交通联系通道工程为例,介绍了其防水设计原则和防水等级,分析了该防水工程的特点,并重点阐述了混凝土结构自防水和柔性全包防水层施工技术,以及施工缝、变形缝、后浇带、穿墙管等特殊部位的防水措施。

Fast Secret Key Generation Based on Dynamic Private Pilot from Static Wireless Channels

In static or quasi-static wireless channel environments, secret key generation(SKG) based on wireless channels is vulnerable to active attacks due to the openness and invariance of public pilot, especially man-inthe-middle(MITM) attacks, where attacker acts as a transparent relay to manipulate channel measurements and derive the generated keys. In order to fight against this attack, a dynamic private pilot is designed, where both private pilot and secret key are derived from the characteristics of wireless channels and private to third party. In static or quasi-static environments, we use singular value decomposition techniques to reconstitute the wireless channels to improve the randomness of the wireless channels. Private pilot can encrypt and authenticate the wireless channels, which can make channel state information intercepted by MITM attacker reduced to zero and the SKG rate close to that without attacks. Results of analysis and simulation show the proposed SKG scheme can withdraw the MITM attacks.

Tunneling Radiation from a Static Spherically Symmetric Black Hole Surrounded by Quintessence

By extending the Parikh-Wilczek tunneling framework,we investigate the tunneling radiation of unchargedmassless particles from a static spherically symmetric black hole surrounded by quintessence.The results are consistentwith an underlying unitary theory.

Wireless Channel Parameter Estimation Algorithms: Recent Advances and Future Challenges

Temporal and three-dimensional(3 D) spatial information is important for the characterization of wireless channels. In this paper, the commonly used array signal processing(ASP) methods to estimate channel parameters are summarized. Firstly, algorithms that can be used to estimate azimuth angle of arrival(AAo A) and elevation Ao A(EAo A) are introduced. They include multiple signal classification(MUSIC), estimation of signal parameter via rotational invariance techniques(ESPRIT), and Unitary ESPRIT algorithms. Secondly, algorithms that can be used to jointly estimate delay, AAo A, and EAo A are given. They include joint angle and delay estimation(JADE) MUSIC, JADE ESPRIT, shift-invariance(SI) JADE, and space-alternating generalized expectation-maximization(SAGE) algorithms. We also propose an improved SIJADE algorithm to further reduce computation complexity by incorporating with the Unitary ESPRIT algorithm. Performance of the above algorithms to extract only spatial information and to jointly extract temporal and spatial information is compared in both synthetic and 60 GHz real channel environments. Simulation results show that with the inclusion of delay estimation, the joint temporal and spatial estimation algorithms can provide better resolution than algorithms estimating only angles.Measurement data processing results show that MUSIC algorithm can provide comparable results with SAGE algorithm in estimating AAoA and EAoA. SI-JADE and the improved SI-JADE algorithms are also applicable to process 60 GHz channel measurement data.However, MUSIC, SI-JADE, and the improved SI-JADE algorithms can greatly reduce computational burden compared with SAGE algorithm. At last, some future directions are pointed out.

Research on the closure and creep mechanism of circular tunnels

A numerical code called Rock Failure Process Analysis (RFPA2D) was em- ployed to investigate the closure,damage and failure behavior of the horizontal tunnels.In this code the time-dependent deformation was described in terms of evolution of meso- scopic structure,leading to progressive degradation of elastic modulus and failure strength of material.In terms of material degradation,a series of numerical simulations were per- formed to study the convergence and subsequent failure in circular tunnels.The numerical results provide a complete illumination for the closure,damage and failure behavior with different loading conditions.It is shown that the depth and the ratio of far field stresses play an important role in the creep behavior of tunnels.Creep failure is expected to occur in the direction of the smallest far field stress component,which means that rheological failure of tunnels is influenced not only by the rock characteristic around the tunnels but also by the orientation and distribution of far field stress on a global scale.

Visual fatigue relief zone in an extra-long tunnel using virtual reality with wearable EEG-based devices

Long-time driving and monotonous visual environment increase the safety risk of driving in an extra-long tunnel. Driving fatigue can be effectively relieved by setting the visual fatigue relief zone in the tunnel. However, the setting form of visual fatigue relief zone, such as its length and location, is difficult to be designed and quantified. By integrating virtual reality(VR) apparatus with wearable electroencephalogram(EEG)-based devices, a hybrid method was proposed in this study to assist analyzers to formulate the layout of visual fatigue relief zone in the extra-long tunnel.The virtual environment of this study was based on an 11.5 km extra-long tunnel located in Yunnan Province in China.The results indicated that the use of natural landscape decoration inside the tunnel could improve driving fatigue with the growth rate of attention of the driver increased by more than 20%. The accumulation of driving fatigue had a negative effect on the fatigue relief. The results demonstrated that the optimal location of the fatigue relief zone was at the place where driving fatigue had just occurred rather than at the place where a certain amount of driving fatigue had accumulated.

Tunneling Through Black Rings

Hawking radiation of black ring solutions to 5-dimensional Einstein-Maxwell-dilaton theory is analyzed by use of the Parikh-Wilczek tunneling method. To get the correct tunneling amplitude and emission rate, we adopt and develop the Angheben-Nadalini-Vanzo Zerbini covariant approach to cover the effects of rotation and electronic discharge all at once, and the effect of back reaction is also taken into account. This constitutes a unified approach to the tunneling problem. Provided the first law of thermodynamics for black rings holds, the emission rate is proportional to the exponential of the change of Bekenstein-Hawking entropy. Explicit calculation for black ring temperatures agrees exactly with the results obtained via the classical surface gravity method and the quasi-local formalism.

Performance analysis of wireless local area networks(WLAN) in a coal-mine tunnel environment

In order to establish an effective wireless communication system in an underground coal-mine environment, the propagation of radio waves through a rectangular-like mine tunnel was investigated by jointly, considering both the dielectric constant and the reflectance of a mine tunnel. By combining free space and modified waveguide propagation models, we propose a new hybrid propagation model based on ray tracing. Simulation results have shown the effectiveness of establishing a wireless Local Area Network (LAN) in this coal-mine environment. The results of this research will be very useful as a guide in the design and development of tunnel wireless LAN systems.

Study on mechanism of circumferential cracks in cold-region tunnels

There exists frost damage in cold-region tunnels. The circumferential cracks affect the function of tunnels. Using three-dimensional finite element method, the authors analyzed the mechanism of circumferential cracks in cold-region tunnels It is proved that the internal thermal stress in lining exceeds the tensile strength of concrete, which is the direct cause for circumferential cracks occurring. The laws of thermal stress in lining induced by parameters such as temperature drop, horizontal drag coefficient and length of lining are analyzed. The conclusions are valuable to the design and construction of cold-region tunnels considering the thermal stress.

Ring-Polymer Molecular Dynamics Studies of Thermal Rate Coefficients for Reaction F+H2O→HF+OH

The prototype tetra-atomic reaction F+H2O→HF+OH plays a significant role in both atmospheric and astronomical chemistry.In this work,thermal rate coefficients of this reaction are determined with the ring polymer molecular dynamics(RPMD)method on a full-dimensional potential energy surface(PES).This PES is the most accurate one for the title reaction,as demonstrated by the correct barrier height and reaction energy,compared to the benchmark calculations by the focal point analysis and the high accuracy extrapolated ab initio thermochemistry methods.The RPMD rate coefficients are in excellent agreement with those calculated by the semiclassical transition state theory and a two-dimensional master equation technique,and some experimental measurements.As has been found in many RPMD applications,quantum effects,including tunneling and zero-point energy effects,can be efficiently and effectively captured by the RPMD method.In addition,the convergence of the results with respect to the number of beads is rapid,which is also consistent with previous RPMD applications.

Wave Motion of Smoke in Subway Fire Environment

Wave motion in subway or tunnel fire is an intrinsic property of smoke.As the pressure of smoke changes with mass of certain power,a kind of linear wave equation for smoke can be derived from the conservation equations of its mass and momentum,under nearly homogeneous zone assumption.The smoke movement of 4 subway fires was simulated with Airpak.By fitting the pressure-mass functions to the simulated data,wave equations of the smoke were derived,and wave motions of smoke were thus validated.It can be seen that smoke wave is a kind of mass wave,whose velocity is inversely proportional to smoke mass,and wave of a bigger fire propagates slower.