直眼掏槽爆破技术在硬岩掘进中的应用

直眼掏槽眼都垂直于工作面，各炮眼之间保持平行，采用中、深孔爆破，爆破后岩石块度均匀。先打4个不装药的空眼，位置布置在巷道中部，作为爆破时的附加自由面。     

三山岛金矿辅助斜坡道光面爆破方案研究

采用先施工导硐、后施工光爆层的二次成巷方案,通过合理地优化爆破设计以及多次对现场光面爆破方案进行总结和完善,使得光面爆破在三山岛金矿辅助斜坡道施工中得到成功的应用,提高了斜坡道施工进度,确保了该矿资源开采的安全性.     

分段装药的间隔长度计算

1 引言传统的露天矿台阶爆破中,炮孔装药多是采用连续装填结构,即先装药后填塞。这一方式的最大优点就在于工艺简单,省时,     

城市浅埋隧道爆破开挖施工技术研究

武汉地铁二号线宝通寺站地下过街通道修建中需要进行爆破开挖施工,作业点上方为城市主干道,车流量大,周边建筑密集,对采用爆破法开挖施工提出了更严格的要求。爆破施工中通过对通道周边商业区、古建筑、地下管线等重点保护区域的振动数据监测,对爆破方案予以优化,发现采用"台阶法—抬炮法"相结合的小进尺循环掘进,多断面渐次开挖的方案能提高爆破施工的安全性;一次断面起爆分三个区,采用"先中间、后两边"的起爆顺序,一方面爆破振动降低了20%~30%,另一方面对于隧道轮廓面的控制效果也十分显著。     

厂房和150m烟囱爆破拆除减振技术分析

针对热电厂烟囱、厂房同时爆破拆除,振动危害大等问题,采用烟囱先爆破,2s后厂房再进行爆破,最终烟囱倒塌在厂房废墟上的方案设计,以减小爆破振动对周围环境的影响。实时监测了拆除过程产生的爆破振动和触地振动,并进行了分析。结果表明,采取这种倒塌方案设计,结合减振沟、减振堤坝等防护措施,有效保证了周围建筑物的安全。可为此类多种结构同时爆破的工程提供经验和参考,减少爆破产生的振动危害。     

炼铁高炉炉衬爆破拆除

本文介绍靶钢炼铁厂１１＾＃高炉大修工程中爆破拆除高炉炉衬的过程。采用爆破方法先破坏炉衬环型砌体结构,再爆破冷却壁之上衬砖,使衬砖局部悬空,在重力作用下脱落,达到安全,快速拆除衬砖的目的。     

一次性爆破拆除1O栋楼房的总体方案设计

介绍了10栋楼房的一次性爆破拆除方案,采用了楼体内特殊结构先爆破、小高度切口控制楼房后坐塌落以及有效的防护措施等技术手段,在周边环境特别恶劣的条件下取得较好的爆破效果。     

岩石介质中双孔爆破效应的数值模拟研究

基于动力分析软件LS-DYNA及Langrange-Euler耦合算法,数值模拟研究了双炮孔同时起爆和微差起爆(微差时间分别为0.05 ms、0.1 ms、0.3 ms和5 ms)时爆炸冲击波在岩石介质中的传播规律和爆破对炮孔周围岩体振动效应的影响。研究表明:双炮孔同时起爆初期,损伤破碎区的扩展类似于单孔爆破;当爆炸冲击波相互叠加后,两炮孔中间纵向单元和药柱内外两侧横向近区单元的压力和等效应力随爆心距的增大而减小,而自由面上单元呈现出先增后减的变化趋势,且在距药柱10 cm外出现内侧单元的压力和应力值均高于外侧;微差起爆可缓解爆破振动和改善爆破效果,以同时起爆药柱完全引爆所需时间0.3 ms为例,当微差小于0.3 ms时,随着微差时间的延长,微差起爆对周围岩体单元的压力和等效应力峰值的降低幅度越大,同时缓解岩体纵向爆破隆起和z方向的振动效应也越明显,但超过0.3 ms后则微差起爆的改善效果受到一定限制。     

电厂大型厂房大解体式爆破拆除

焦作电厂老厂主厂房结构复杂,相邻构筑物多,拆除工期紧.决定采用大解体控制爆破拆除技术进行拆除.主体拆除前,先对一些结构进行了预拆除.采用非电加强双向多回路网格式爆破网路,一次起爆了1.5万个药包和686 kg炸药,成功地爆破拆除了3万多m2主厂房.爆破后解体充分,爆破震动小,爆堆高度1～3 m,为后期的清运提供了良好的条件.     

6幢不同结构大楼的一次爆破拆除

在城市中心环境十分复杂的情况下,一次起爆6幢5万m^2的楼房,这在江苏还是第一次。这6幢楼房相距间隔不大,结构截然不同,高宽比相差较大,倒塌方向各异。6幢楼同时起爆、同时倒塌。既要把爆破地震、塌地振动控制在允许的范围内,又要合理控制网路的延时时间,使各楼着地时间错开,还要防止先爆楼房产生的飞石和冲击波破坏后爆楼房的网路。因此进行有效的预处理,合理的选择爆破参数、切口高度、起爆顺序和延时时间,并进行有效的防护是这次爆破成功的关键。     

浅议广东省高校国库集中支付

国库集中支付制度是我国财政制度改革的重要举措之一，文章根据广东省省属高等院校在国库集中支付过程中的工作实践，分析了广东省高校国库集中支付过程中存在的问题以及应采取的措施。     

大截面差空心件内高压成形研究

截面周长差较大的空心零件的内高压成形需要解决膨胀区的轴向补料问题和预成形问题,才能获得壁厚分布较为均匀的合格零件.以某轿车转向节臂零件的成形过程为例,对上述问题进行了试验研究.首先设计、试制了瓶形预制件,在预成形中利用"有益起皱"实现了大量的补料,获得了壁厚分布符合要求的预制件;然后在终成形前使零件截面具有合理的形状,再进行终成形,既保证了圆角部位的外形尺寸,又提高了壁厚均匀性.采用本文介绍的方法实现了截面周长差达70%的瓶形预制件的制备,从而获得了壁厚、外形尺寸均满足设计要求的转向节臂零件.     

Fabrication of melt-texture growth YBCO samples using a simple muffle furnace

In our previous work we showed that gradients of temperatureT inside the heating chamber andT/t are the necessary conditions for growing oriented crystal layers inside bulk samples. Using a simple muffle furnace, we have successfully fabricated layers of YBCO samples. Powder layers of Y-123 and Y-211 in different structures were compressed to make sample pellets before heat treatment in order to create internal temperature gradients inside the samples when they were heated. SEM observation proved that the crystal layers grew from both the top and bottom surfaces of the sample independently of the original powder layers before heat treatment. Moreover, we found that the crystal layers are not true layers but bulk crystal with gap lines. EDX analysis confirmed that the 123 and 211 phases coexist in almost all of the samples. Using the concept of internal temperature gradients, we show that it is possible to carry out modified melt-texture growth even in a muffle furnace.     

Ultrasonic study of the temperature and pressure dependences of the elastic properties of a single-crystal Heusler structure Cu41Mn20Al39 alloy

Pulse-echo-overlap measurements of ultrasonic wave velocity have been used to determine the elastic-stiffness tensor components Cu and the adiabatic bulk modulus, BS, of a ferromagnetic Heusler structure Cu41Mn20Al39 at % alloy single crystal as functions of temperature in the range 14–300 K and hydrostatic pressure up to 0.2 GPa at room temperature. At 295 K the elastic stiffnesses are: C11=133 GPa, C44=92 GPa, C (=(C11–C12)/2)=17 GPa, C12=99 GPa, CL(=C11+C44–C)=205 GPa, and BS (=C11–4C/3)=106 GPa. Cu41Mn20Al39 is a comparatively soft material elastically because its elastic properties are influenced strongly by magnetoelastic effects. The results of measurements of the effects of hydrostatic pressure on the ultrasonic wave velocity have been used to obtain the hydrostatic-pressure derivatives of the elastic – stiffness tensor components. At 295 K (C11/P)P=0, (C44/P)P=0, (C/P)P=0, (C12/P)P=0, (CL/P)P=0, and (BS/P)P=0 are 5.0±0.1, 3.0±0.1, 1.0±0.2, 3.0±0.3, 7.7±0.4 and 3.7±0.4, respectively. Application of hydrostatic pressure does not induce acoustic-mode softening: the pressure derivatives (CIJ/P)P=0 and (BS/P)P=0 and the acoustic-mode Grüneisen parameters are positive. An interesting feature of the non-linear acoustic behaviour of this alloy is that the value obtained for (C/P)P=0, associated with the softer shear mode propagated along the [1 1 0] direction and polarized along the [1 1 0] direction, is small in comparison with those of the other shear and longitudinal modes. The Grüneisen parameter of this mode, and hence its vibrational anharmonicity, is much larger than those of the other long-wavelength acoustic phonon modes. © 1998 Kluwer Academic Publishers     

The Positive Magnetic Susceptibility for Rb3C60 Superconductor and the Differential Paramagnetic Effect

AC magnetic susceptibility of Rb₃C₆₀ superconductor as a function of temperature was measured in an applied static magnetic field perpendicular to the AC magnetic field. The peaks in real part of AC susceptibility curves located in the transitional temperature indicate that there may exist the differential paramagnetic effect (T) = dM/dH > 0 in the specimen. The amplitude of the peak and the temperature of diamagnetic onset are proportional to intensity of the applied field, and upon cooling the peaks occur before the transition temperature of zero field. Through discussing and comparing our experimental result with those reported previously, we have put forward a new opinion on producing condition of the differential paramagnetic effect (DPE).     

Integral results for nonlinear diffusion equations

We show how to construct integral results for the multi-dimensional nonlinear diffusion equation c/t=·(D(c)c) and for some generalisations of this. For appropriate boundary conditions these become integral invariants. An application of these results to determining the large-time behaviour of some radially symmetric problems is indicated.     

用AutoCAD自动拆图方法的探讨

以实例说明如何创建适合用AutoCAD2000自动生成零件视图的装配图绘图环境以及绘制该装配图的具体方法和步骤。指出了自动生成零件视图的实现过程和操作技巧;对用一般方法绘制的机械装配图提出了分层处理的解决方案,并提供了用AutoCAD2000目标选择集等相关命令快速处理的方法;最后总结说明了该方法在拆画零件图和零件结构设计过程中的诸多优点。     

Superconductivity in bulk A15 Nb3Si under pressure

We have determined the effect of hydrostatic pressureP on the superconducting transition temperatureT _c of bulk, A15 Nb₃Si. For 0P20 kbar (2 GPa),T _c decrease linearly with increasing pressure at a rate T _c/P=–2.67×10^–5 K/bar. From an estimate of T _c/P obtained using recent band structure calculations for the density-of-electronic-states change as a function of lattice parameter in Nb₃Si, we conclude that the pressure dependence of the electron-phonon interaction primarily determines T _c/P.Work performed under the auspices of the U.S. DOE.     

Thermal pressure coefficients of ethanenitrile,propanenitrile, and butanenitrile in the region 295–395 K

The thermal pressure coefficient (p/T) _v has been measured for ethanenitrile from 299 to 364 K, for propanenitrile from 295 to 377 K, and for butanenitrile from 297 to 398 K. The results are discussed in terms of the diminishing role of polarity in the alkanenitrile series and of a corresponding-states approach using gas-liquid critical properties as reduction factors. Although (p/T) _v varies unevenly with chain length, the reduced quantity shows a more regular behavior similar to that of the related quantity the cohesive energy density.     

Effects of cavity surface temperature on reinforced plastic part surface appearance in rapid heat cycle moulding

The influences of the cavity surface temperature just before filling on surface appearance and texture of the moulded reinforced plastic parts in rapid heat cycle moulding (RHCM) are investigated. Two typical reinforced plastics including ABS/PMMA/nano-C_aCO₃ and 20% fibre reinforced polypropylene (FRPP) are tested in experiments. The roughness, gloss and morphology of the part surface are characterized with white light interferometer, gloss meter, and optical microscope, respectively. It is observed that the cavity surface temperature just before filling has a significant influence on part surface appearance. With the increase of the cavity surface temperature just before filling, aesthetic quality of the moulded part can be greatly improved. There is a critical value of the cavity surface temperature just before filling for each plastic. As the cavity surface temperature reaches the critical value, part surface appearance will reach the optimal level with low roughness and high gloss. The weld mark for ABS/PMMA/nano-C_aCO₃ has a V-shaped structure while that for FRPP has a hump-shaped structure. With the increase of the cavity surface temperature just before filling, the width of the V-shaped weld mark reduces gradually until it disappears completely while the height of the hump-shaped weld mark decreases firstly and then increases. The mechanisms for the improvement of surface appearance by increasing cavity surface temperature just before filling and the generation of the V-shaped and hump-shaped weld mark are disclosed.