46700m~2楼房一次爆破拆除

东北汽配城为框架结构,总建筑面积46700m2,周边环境非常复杂。该建筑物共有260根柱子,断面尺寸不尽相同。按建筑伸缩缝将楼房分为5个部分,分别采用了原地坍塌、定向倾倒、折叠倾倒一次控制爆破技术,并将土石方爆破的斜线起爆技术用于拆除爆破。由于爆破设计、施工及安全措施得当,爆破获得圆满成功。     

西湖第一高楼定向爆破拆除

采用定向控制爆破拆除22层钢筋混凝土框筒结构办公楼。介绍了爆破方案、爆破部位、破坏高度和破坏程度,以及倾倒可靠性校核;同时,阐述了炮孔装药参数、装药结构、起爆顺序和网路。实践证明,要降低高层框筒结构定向倒塌带来的触地振动危害,采用分组延时爆破、铺设缓冲层和开挖减震沟是有效的。     

茅台酒厂26层剪力墙结构大楼爆破拆除

根据茅台酒厂钟楼的结构特性、周围环境特点及爆破要求,分析该栋26层高楼的爆破拆除控制要点,采用了单向三折叠的爆破方案。通过爆破方法预先拆除切口内部分剪力墙,有效地降低爆破总药量;通过切口间开设铰链,使大楼在空中充分解体,减小了塌落体的触地块度,从而降低了触地冲击;采用胶皮网覆盖和敷设减振带等防护措施,有效地控制了爆破飞石及触地振动。结合高速摄影对钟楼倒塌后坐造成排污管及排污沟破坏的原因进行了分析,可为类似工程提供参考。     

A mini-scale modeling approach to natural daylight utilization in building design

This paper purposes on shading devices as natural daylight utilization component for building design. It was proved that a proper setting for shading device could conspicuously promote the room lighting performance. Natural daylight which includes directional sunlight, diffused skylight and reflected light can also exert as a perspective of energy conservation in buildings. In order to verify a simple approach can also be workable, a mini-scale model (1:20) is employed in this study. It reveals that when a suitable altitude and azimuth is maintained, in regards to the vertical shading device and the sun position, not only is shading achieved, but the area of the daylight zone can also be substantially increased. The experiment investigated and analyzed the details of this modeling data and subsequently proposed relevant design criterion for vertical shading devices that both users and designers can apply. Namely, it proved that a mini-scale model could also assist in natural daylight utilization and building energy-conservation design.     

民航中波NDB导航信号监测方法探讨

本文主要研究了民航无线电导航信号监测方法,结合日常监测的工作经验,以乌鲁木齐国际机场NDB导航台为例多次测试分析,详细给出了针对NDB系统导航信号进行监测的技术方法。     

Fast Directional Handoff and lightweight retransmission protocol for enhancing multimedia quality in indoor WLANs

More and more mobile devices such as smartphones are being used with IEEE 802.11 wireless LANs (WLANs or Wi-Fi). However, mobile users are still experiencing poor service quality on the move due to the large handoff delay and packet loss problem. In order to reduce the delay, a new handoff scheme using the geomagnetic sensor embedded in mobile devices is proposed in this paper. The proposed scheme predicts the movement direction of a Mobile Station (MS) from the currently associated Access Point (AP) and performs active scanning with a reduced number of channels. In terms of the packet loss, a lightweight retransmission protocol is also proposed to minimize lost packets on Wi-Fi without producing a lot of acknowledgement packets. The proposed approaches are implemented on Android smartphones, and their performance is evaluated in a real indoor WLAN environment. The evaluation results demonstrate that the proposed schemes maintain seamless quality for real-time video even in an environment with frequent handoffs. Note that the proposed schemes are a client-only solution and do not require modification of the existing APs, which renders them very practical.     

Directional hydraulic fracturing to control hard-roof rockburst in coal mines

Hard roof is the main factor that induces rock-burst.In view of the present obvious weakness of control measures for hard roof rockburst in domestic collieries,the mechanism and field application of di...     

Quantitatively comparing phase-field modeling with direct real time observation by synchrotron X-ray radiography of the initial transient during directional solidification of an Al-Cu alloy

The initial transient during directional solidification of an Al-4 wt.% Cu alloy was simulated by a quantitative phase-field model solved with the adaptive finite element method. The simulated solidification process was compared with the related analytical theory and in situ and real time observations by means of X-ray radiography at the European Synchrotron Radiation Facility. The simulated velocity of the planar interface and solute profile ahead of the solidification front in the liquid are close to the predictions of the Warren-Langer model of the initial planar solidification transient, but in fair quantitative agreement with experimental results only at early stages of planar solidification. After the accelerated flat interface lost its stability a transition to cellular solidification was initiated. The initial cell spacing predicted by the phase-field simulation agreed well with the experimental observations in the region where the cell growth direction was perpendicular to the fluid flow, whereas a discrepancy was obvious in the corners where the fluid flow was parallel to growth. An analytical relation describing the wavelength of the initial solid-liquid interface corrugations under diffusion-limited transport is screened out by comparing the phase-field simulation data with expressions based upon the Mullins-Sekerka linear stability analysis theory or derived for primary spacing. The gravity-driven natural convection in the experiment resulted in misfits between the phase-field predictions and the experimental observations in the late stage of planar solidification, onset and development of morphological instability.     

Precipitation behaviour of oxide in directionally solidified aerospace bearing steel

The directional solidification enables independently control of the holding temperature and withdrawal rate over a given range. This technology was used to investigate the precipitation behaviour of oxide in aerospace bearing steel M50NiL. Most of the oxides are Si–Al–Mn–Ti–O complex inclusions with spherical shape. With the increase of withdrawal rate, the size and volume fraction of oxides decrease. In contrast, the diameter and volume fraction increase remarkably with the increase of holding temperature. The composition of oxides with different sizes varies with holding temperature. The holding temperature of 1550°C accompanied with a cooling rate over 95.7°C?min^?1 is deemed as the optimal solidification parameters for M50NiL steel, which can significantly reduce the size and volume fraction of oxides.     

Formation of methane hazard in longwall coal mines with increasingly higher production capacity

Directional drilling has been established in the coal industry as a viable means of gas drainage, exploration and water management. But the environment in and around coal seams is not always conducive to stable conditions while drilling and borehole stability after the drilling has been completed. This paper identifies the conditions which cause unstable drilling conditions and the various means which are used to attempt to manage or bypass those conditions. Ultimately, equipment does become bogged in these adverse environments and requires recovery by over-coring.