a-Si∶H中光致亚稳缺陷产生的弛豫过程:HCR和DCR模型的实验检验

国家自然科学基金

Effect of rapid thermal annealing on the Raman spectrum of Si0.33Ge0.67/Si (100) alloy

The effect of thermal annealing on the Raman spectrum of Si0.33Ge0.67 alloy grown on Si (100) by molecular beam epitaxy is investigated in the temperature range of 550-800 degrees C. For annealing below 700 degrees C, interdiffusion at the interface is negligible and the residual strain plays the dominant role in the Raman shift. The strain-shift coefficients for Si-Ge and Ge-Ge phonon modes are determined to be 915 +/- 215 cm(-1) and 732 +/- 117 cm(-1), respectively. For higher temperature annealing, interdiffusion is significant and strongly affects the Raman shift and the spectral shape.

人工湿地塘床系统净化污水的机理研究

人工湿地处理污水实验场经过多年的运行已形成了较稳定的具有多 种生物种类的适合污水处理的生态系统，活水公园人工湿地塘床系统运行时间仅一年，初步显示了湿地生态系统的生物多样性特点。筛选出了菖蒲、芦苇、茭白、香蒲、水竹、马蹄莲、凤眼莲、浮萍、睡莲等适合本地人工湿地塘床系统种植的湿地植物。人工湿地塘床系统是由各种湿地单元与各种各样的高、低等生物和所处的开放式的环境共同构成了较为完整的具有净化污水功能的生态系统，因此，与生物滤池相比，把人工湿地塘床系统称为生态滤池显得更为合适。其出水具有生物安全性。实验结果表明，实验场对生活污水中的COD_(Cr)、BOD_5、TP的去除率在80％以上，对TN的去除率为60.60% ～ 86.4%，细菌总数的去除率为86.9% ～ 99.6%，总大肠菌群的去除率为94.6% ～ 99.7%，其出水水质能够满足二级污水处理的要求。活水公园对枯水期府河水中的COD_(Cr)、BOD_5、TN、TP的去除率在85％以上，总大肠菌群的去除率为99.97%，其净化效果能够满足污水深度处理的需要。湿地植物光合作用向水体供氧能力的试验研究结果表明，在几种光照控制条件静态试验和现场试验中，菖蒲、香蒲、茭白、水竹、凤眼莲等植物植株水面以上的茎、叶在光照条件下进行光合作用时并没有引起根层区水体内溶解氧浓度的升高（氧增），反出现下降（氧亏）。说明这些植物水上部分光合作用对水体DO没有贡献。浮萍光合作时引起氧增的作用较弱，仅维持低水平，试验期间9:00 ～ 15:00的氧增幅度在0.11 ～ 1.13mg/L之间，平均为0.44mg/L。芦苇在9:00 ～ 15:00光合作用时根层区水体氧增幅在-0.20 ～ 1.07mg/L之间，平均为0.30mg/L。上述这些植物植株的水面以下的根、根茎、茎、叶如果暴露在光照条件下时，会进行光合作用，产生的氧直接释放到水体并引起氧增的作用非常明显，试验期间9:00 ～ 15:00的氧增幅度在1.91 ～ 16.1mg/L之间。人工湿地处理污水系统植物床基质内各测点的上、下层COD_(Cr)值虽有一定的差别，但经过成对平均数比较分析发现这种差别并未形成明显的趋势。污水在植物床基质中流动时，随着迁移距离的延长，其中的COD_(Cr)的降解速率呈现先快后慢的趋势，根据动态变化规律，建立了COD_(Cr)在植物床基质层内沿程水平迁移降解动态变化模型：C_L = C_o exp(4.629 * 10~(-5)L~2-0.01567L，0 ≤ L ≤ 100。经验证，模型预测值与实际监测值呈非常显著相关（r ≥ 0.9946 > r_(0.0005(4))，r_(0.0005(4)) = 0.9741)。在人工湿地塘床系统运行监测过程中，发现处于光照下的水体中的pH呈周期性变化，与DO的变化规律相似，在试验期间，9:00 ～ 15:00的pH和DO都呈上升趋势，两者呈协同周期性变化。经相关性回归分析，pH的变化规律与DO呈非常显著相正关，植物床表层渍水区pH与DO的回归关系相关系数r = 0.9129 > r_(0.01(70))(r_(0.01(70)) = 0.302)，植物塘内的pH与DO的相关系数r = 0.8584 > r_(0.01(60))(r_(0.01(60)) = 0.325)，植物床基质层内的pH与DO之间的相关性较差。相关分析结果表明，DO变化幅度大的水体中，pH的变化幅度也就越大，两者之间的相关性也就越显著，这可能与水体中氧化还原电位和水生植物光合作用伴随的代谢活动有关。这种相关性和协同周期性变化具有一定的生态学意义，并会给净化污水的效果产生影响。

Experimental Setup for Assessing the Energetic Materials Deflagration Propagation under High Temperature and High Pressure Conditions

The technology of "explosion in fractures" is one of new synthetic engineering methods used in low permeability reservoirs. The most important problem arose from the technology is to assess the deflagration propagation capability of milky explosives in rock fractures. In order to investigate detailed this problem in the laboratory, an experimental setup was designed and developed in which different conditions can be simulated. The experimental setup mainly includes two parts. One is the experimental part and the other is the measurement part. In the experimental setup, the narrow slots with different width can be simulated; meanwhile, different initial pressures and initial temperatures can be loaded on the explosives inside the narrow slots. The initial pressure range is from 0-60 MPa, and the initial temperatures range is from room temperature to 100 V. The temperature and the velocity of deflagration wave can be measured; meanwhile the corresponding pressure in the narrow slot is also measured. In the end, some typical measurement results are briefly presented and discussed.

Sand storms: CFD analysis of Reynolds stress and collision stress of particles near sand bed

Sand storm is a serious environmental threat to humans. Sand particles are transported by saltation and suspension, causing soil erosion in one place and deposition in another. In order to prevent and predict sand storms, the causes and the manners of particle motions must be studied in detail. In this paper a standard k-epsilon model is used for the gas phase simulation and the discrete element method (DEM) is used to predict the movements of particles using an in-house procedure. The data are summarized in an Eulerian-Eulerian regime after simulation to get the statistical particle Reynolds stress and particle collision stress. The results show that for the current case the Reynolds stress and the air shear stress predominate in the region 20-250 mm above the initial sand bed surface. However, in the region below 3 mm, the collision stress must be taken into account in predicting particle movement. (C) 2010 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.