On the determination of the laminar burning velocity from closed vessel gas explosions

A methodology to determine the laminar burning velocity from closed vessel gas explosions is explored. Unlike other methods which have been used to measure burning velocities from closed vessel explosions, this approach belongs to the category which does not involve observation of a rapidly moving flame front. Only the pressure–time curve is required as experimental input. To verify the methodology, initially quiescent methane–air mixtures were ignited in a 20-l explosion sphere and the equivalence ratio was varied from 0.67 to 1.36. The behavior of the pressure in the vessel was measured as a function of time and two integral balance models, namely, the thin-flame and the three-zone model, were fitted to determine the laminar burning velocity. Data on the laminar burning velocity as a function of equivalence ratio, pressure and temperature, measured by a variety of other methods have been collected from the literature to enable a comparison. Empirical correlations for the effect of pressure and temperature on the laminar burning velocity have been reviewed and two were selected to be used in conjunction with the thin-flame model. For the three-zone model, a set of coupled correlations has been derived to describe the effect of pressure and temperature on the laminar burning velocity and the laminar flame thickness. Our laminar burning velocities are seen to fall within the band of data from the period 1953–2003. A comparison with recent data from the period 1994–2003 shows that our results are 5–10% higher than the laminar burning velocities which are currently believed to be the correct ones for methane–air mixtures. Based on this observation it is concluded that the methodology described in this work should only be used under circumstances where more accurate methods can not be applied.     

基于BP神经网络不同输入变量的爆破振速预测

以某隧道爆破开挖为实例,利用BP神经网络解决复杂非线性函数逼近问题的能力,以最大段药量、爆心距、爆破分段数、泊松比、岩石基本质量指标作为影响爆破振动速度的主要因素,选取不同维数的输入变量建立BP神经网络模型来预测爆破振动速度。对比分析各组预测值与实测值之间的相对误差,选取合理维数的输入变量建立了爆破振动危害预测的BP神经网络模型。     

加卸荷条件下岩石力学特性与声发射特征

为了探究真三轴复杂应力变化条件下岩石强度及破坏模式,通过真三轴卸荷扰动测试系统对砂岩试件进行不同第二主应力加卸荷试验,讨论在加卸荷过程中岩石的力学特性及声发射特征。试验结果表明:第二主应力的增加对试件的承载能力起到先增强后弱化的效果;不同第二主应力加卸荷声发射能量及累计振铃计数变化趋势大体一致,耗散能量比在载荷达到岩石损伤强度时突增;声发射能量峰值提前于试件轴向应力跌落,声发射能量和累计振铃计数大幅突增可作为岩石破坏的前兆;在低载荷下岩石中活动主要是裂隙压密与发育,在达到岩石损伤强度后岩石中的活动主要是裂纹贯通形成破裂面,砂岩试件声发射定位点集中区域与试件主要破裂面基本吻合。     

On the parameterization of the roughness length for the air-sea interface in free convection

The roughness length at the air-sea interface during free convection (z_0fc) is mainly related to the convective velocity (w_*) rather than the friction velocity (u_*). The parameterization of z_0fc with w _* ² /g as proposed by Abdella and DAlessio in 2003 is evaluated. It is shown that their proposed formula is consistent with field measurements. In order to avoid self-correlation by using u_*, a new parameterization of w_* with wind speed (U_z) at height z and stability parameter (z/L, where L is the buoyancy length) is proposed. This new formula for w_* is in agreement with an independent field result.     

大气污染源监测采样技术

依据气态污染源共同的排放特性及平均排放浓度，排放速率的概念，导出气态污染源监测中常用的三种采样方法：积分法、分部积分法、有限加合近似法。根据分析化学的要求，提出样品采集时间的设计方法。由此得出不同类型排放源的监测时间和采样频率确定方法。     

Flow Dynamics in Eccentrically Rotating Flasks Used for Dispersant Effectiveness Testing

The evaluation of dispersant effectiveness used for oil spills is commonly done using tests conducted in laboratory flasks. We used a Hot Wire Anemometer (HWA) to characterize mixing dynamics in the Swirling Flask (SF) and the Baffled Flask (BF), the latter is being considered by the EPA to replace the prior to test dispersant effectiveness in the laboratory. Five rotation speeds of the orbital shaker carrying the flasks were considered, Ω = 50, 100, 150, 175 and 200 rpm. The radial and azimuthal water speeds were measured for each Ω. It was found that the flow in the SF is, in general, two-dimensional changing from horizontal at low Ω to axi-symmetric at high Ω. The flow in the BF appeared to be three-dimensional at all rotation speeds. This indicates that the BF is more suitable for representing the (inherently) 3-D flow at sea. In the SF, the speeds and energy dissipation rates ɛ increased gradually as the rotation speed increased. Those in the BF increased sharply at rotation speeds greater than 150 rpm. At 200 rpm, the Kolmogorov scale (i.e., size of smallest eddies) was about 250 and 50 μm in the SF and BF, respectively. Noting that the observed droplet sizes of dispersed oils range from 50 to 400 μm (hence most of it is less than 250 μm), one concludes that the mixing in the SF (even at 200 rpm) is not representative of the vigorous mixing occurring at sea.     

切断位置对赤子爱胜蚓再生速度的影响

将赤子爱胜蚓从脑、生殖环部位和总体节的 1/ 2和 3/ 4的位置切断 ,得到有头无尾、无头无尾、无头有尾 3种类型 16个处理体段 ,在 (2 0± 1)℃人工气候箱中培养 ,测定其再生速度 .结果表明 ,赤子爱胜蚓切断的位置不同 ,其再生速度不同 .其中 ,脑部的存在与否 ,对再生速度没有显著的影响 .但是生殖环存在的处理比切除生殖环的处理再生速度快 ,且存活率高 .无头无尾体段再生前部和再生后部的比较表明 ,再生前部比再生后部慢 .体节的损失越少 ,再生的速度越快 .图 6表 3参 11     

Among- and within-population variation in sperm quality in the simultaneously hermaphroditic land snail Arianta arbustorum

Sperm competition models on the evolution of sperm size assume associations with another sperm quality trait, sperm longevity. Sperm length can also provide an indication of possible mechanisms affecting motility and thus fertilization success. Despite their importance, however, detailed mechanisms of sperm competition at the gamete level are poorly understood. In simultaneously hermaphroditic land snails, sperm traits and cryptic female choice are assumed to be crucial in determining fertilization success. We examined the variation in sperm length and number among individuals from four natural populations of the land snail Arianta arbustorum, a species with multiple mating and long-term sperm storage. We also assessed variation in velocity, motility and longevity of sperm in snails from two of the four populations. Independent of shell size, sperm length differed among populations and, to a minor extent, even among individuals within populations. Mean sperm length of a snail was not correlated with the number of sperm delivered in a spermatophore. The mean sperm velocity (=VCL) did not differ between snails from two populations. However, VCL varied among snails. Percentage motility and longevity of sperm differed between snails from the two populations. No correlations were found between length, velocity, percentage motility and longevity of sperm. To conclude, individual snails differed in sperm quality, and this variation may partly explain the differential fertilization success between A. arbustorum snails. Moreover, our findings did not support the positive association between sperm length and longevity assumed by sperm competition models for internally fertilizing species.     

锅炉温控炉拱的设计及燃烧技术性能

论述了将小型链条炉排工业锅炉的炉拱设计成在运行中可以全量调节的结构,以适应燃用多种煤种的需要,并减少与固定拱操作有关的意外伤亡事故。这项技术有创新性,适用性和推广价值     

HKB—1型磁化率仪研制及计算机联机的实现

本文介绍了一种新研制的磁化率仪,它可测定自然界中大多数物质(良导体除外)的初始磁化率,特别适合于岩石的磁化率及其各向异性(AMS)测量。仪器工作磁场300A/m,频率920Hz,样机总磁化率测量灵敏度达到 2×10~(-12)m~3,读数采用数字显示方式并具有自动锁定功能。与计算机的联机采用了标准EIARS-232C串行接口,因此具有良好的通用性。在软件的控制下,计算机可自动完成测量数据的采集、计算处理、座标转换以及成图或存贮等工作,AMS参数的测量效率得到很大提高。