Particles settling studies using ultrasonic techniques

Effects of acoustic velocity and attenuation measurements during settling of 43-, 110- and 168-μm glass beads in water are reported. Ultrasonic waves were generated at a frequency of 3.2 MHz. An abrupt increase in acoustic velocity and a sharp peak in the attenuation characterized the onset of settled bed. The observed attenuation peak at the transition between suspended and settled bed was attributed to dissipation caused by viscous absorption losses. The critical concentration at which increase in acoustic velocity and attenuation peak occurred was estimated for these particle sizes.     

Conditions of detonation initiation by focusing shock waves in a combustible gas mixture

Based on experiments on focusing shock waves in hydrogen-air mixtures and available publications, the critical shock-wave Mach number at which detonation is initiated near the apex of a concave reflector is analyzed as a function of the reflector size and reactivity of the mixture. The effect of the reflector shape and size on the value of this Mach number is studied. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 6, pp. 84–89, November–December, 2007.     

Degradation of polycyclic aromatic hydrocarbons: Model simulation for bioavailability and biodegradation

A mathematical model for a one‐dimensional convective‐dispersive solute transport in a soil matrix is presented. The interplay of linear equilibrium sorption and first order degradation were incorporated into the formulation of the model. The model took into consideration the overall effects of the solid and liquid phase mass transfer resistances. Data from experiments were analysed using the temporal moments method (MOM) and CXTFIT curve‐fitting technique. The functional parameters; dispersion coefficient, first order degradation rate constant and the retardation factor were estimated using both first and second normalised moments. The solution to the model equations was achieved by the use of the backward finite difference scheme. Results obtained showed that naphthalene was more selectively degraded than pyrene and anthracene with a residual concentration of naphthalene 1.12E ? 5 mg/L, 1.48 mg/L; pyrene 3.11E ? 4 mg/L, 1.58 mg/L; and anthracene 7.67E ? 4 mg/L, 1.61 mg/L in the axial and radial directions, respectively. Concisely, the modeling results showed the occlusion of these compounds within the fissures and cavities of the soil particles, which renders them not readily bioavailable and thus inaccessible to microbial degradation.     

An appraisal of tree sulphur content as a long term air pollution gauge

Plant sulphur content of tree annual ring groups is used as an air pollution gauge in the vicinity of the Port Talbot (South Wales) steel works. The results indicate, with regards sulphur dioxide pollution, a recent improvement in air quality. Dendrochronological measurements also indicate this general trend.     

涡轮机二维叶栅形状的数值计算

对定常正问题进行研究,在变分原理的基础上,用有限元方法对叶栅进行了数值计算.将翼型NACA0012和NACA2412作为计算对象,给出翼型的形状,计算出表面速度分布,之后与标准的速度分布进行比较.结果表明理论正确,方法可行.     

汽轮机测速探头碰磨分析及处理

介绍了广东粤电云浮发电厂有限公司”1机组测速探头与测速齿轮碰磨的异常现象以及解体检查情况。对碰磨原因进行了分析，提出了具体的结构改进和防范措施，对同类型机组有借鉴作用。     

浅议液化石油气装车流速及装车口径

通过对液化气装车流速及装车鹤管口径的讨论，提出液化气装车时存在的问题。现行的规范中规定的液化气在管道中的流速对于装车过程显得偏小。     

集中粗选分速精选能提高锑浮选指标

本文介绍了作者在难选锦矿石浮选过程中改变过去传统的选矿流程，采取集中粗选、分选精选的选矿方法，坚持饥饿加药的原则，获得了锑精矿品位为６０．６６％、锑浮选回收率为９０．０５％的较好浮选指标。     

OPTIMIZATION AND NEURAL MODELLING OF PULSE COMBUSTORS FOR DRYING APPLICATIONS

ABSTRACT

Results of investigations of a valved pulse combustor to choose optimal geometry, which covered measurements of the flow rates of air and fuel, pressure oscillations, including pressure amplitude and frequency and flue gas composition are presented in the paper. Experimental studies compsiring the operation of the pulse combustor coupled with a drying chamber and working separately are described. It was found that coupling of the pulse combustor with a drying chamber had no significant effect on the pulse combustion process. Smoother runs of pressure oscillations in the combustion chamber, lower noise level and slightly higher NO_x emission were observed. The velocity flow field inside the drying chamber was measured by LDA technique. Results confirmed a complex character of pulsating flow in the chamber. A large experimental data set obtained from measurements enabled developing a neural model of pulse combustion process. Artificial neural networks were trained to predict amplitudes and frequencies of pressure oscillations, temperatures in the combustion chamber and emission of toxic substances. An excellent mapping performance of the developed neural models was obtained. Due to complex character of the pulse combustion process, the application of artificial neural networks seems to be the best way to predict inlet parameters of a drying agent produced by the pulse combustor     

破片动态飞散速度的计算

导弹攻击TBM等目标时,在中低空遭遇、大脱靶量、高相对速度情况下,战斗部爆炸后破片动态飞散弹道出现弯曲甚至存在多值问题,以往不考虑这一情况的有关破片动态飞散速度的计算模型已不适用.为此,建立了考虑破片弹道弯曲及多值问题,且适用于任意遭遇情况的导弹战斗部破片动态飞散速度计算模型.模型采用了计算机数值搜索求解方法,解决了复杂弹目交会情况下无法获得飞散速度的解析表达式的问题.利用两个算例,对建立的模型进行了验证,仿真计算结果与实际一致,表明模型是合理、正确的.