Sectional velocity model for microseismic source location in tunnels

Microseismic (MS) source location is the foundation of MS monitoring and warning. The accuracy of MS source location depends on the accuracy of the velocities used in the location algorithm. In this work, a suitable sectional velocity model for MS source location in tunnels is proposed. In the model, the velocities from the MS source to the MS sensors in any one group are almost the same but those to different groups of MS sensors may be different. An efficient global optimization algorithm (particle swarm optimization) is applied to search for the MS source location and sectional velocity. Results from a tunnel simulation show that the velocities obtained using the sectional velocity model are close to the actual ones and location accuracy is greatly improved. The average location error is reduced by 78.3% (from 13.05 to 2.83 m). The proposed model was applied to MS source location in the deeply-buried tunnels of the Jinping II hydropower station in China. The case shows that the sectional velocities obtained are in accordance with the geological conditions. The locations of rockburst and MS events in the rockburst development process are clustered in the actual rockburst area. The method is good for rockburst monitoring and warning in the tunnels. In addition, the impact of error in the velocity on MS source location accuracy in tunnels is discussed. In tunnels, error in velocity is found to have a great impact on MS source location accuracy.     

高压大直径天然气-凝析液管流计算模型

前人提出的平界面和曲界面模型大多是基于低压、小管径、水平或接近水平管道空气-水条件的实验数据得来的,如何选择长距离、高压、大直径、起伏地形天然气-凝析液管道水力计算模型是一个需要研究的问题。针对高压、大直径、起伏地形条件下的天然气-凝析液混输管线,运用相态与物性、水力、热力耦合的计算方法对分离流的气-液平界面和曲界面机理模型进行了适用性比较研究。将平界面和曲界面模型下的几何关系和摩阻系数计算相关式运用于实际的高压天然气-凝析液长距离地形起伏管道中,对比水力热力计算结果与实际生产数据,认为平界面模型较曲界面模型能更准确地预测高压、大直径天然气-凝析液两相流管线的压降和积液量。     

遗传算法优化BP神经网络预测上覆岩层破坏范围

对吕梁矿区部分煤矿不同煤层的上邻近层瓦斯卸压范围展开了深入的探究和分析,并提出了遗传算法优化BP神经网络预测上覆岩层破坏范围的模型。通过新旧模型对20组矿井开采情况在训练预测冒落带、裂隙带范围的实际对比,可以发现,优化后的网络模型收敛更快、误差更小、拟合效果更佳。     

Development of 10 kW-scale hydrogen generator using chemical hydride

We have developed a hydrogen generator that generates high purity hydrogen gas from the aqueous solution of sodium borohydride, NaBH₄. This paper discussed the performance testing of the hydrogen generator using a Pt-LiCoO₂-coated honeycomb monolith. The NaBH₄ solution hydrolyzed to generate H₂ and sodium metaborate when it contacted the monolith. The gravimetric and the volumetric H₂ densities of the system were 2 wt.% and 1.5 kg H₂/100 l, respectively. The volumetric density was similar to that of the compressed H₂ at 25 MPa. The hydrogen generator successfully provided a maximum H₂ generation rate of 120 nl/min. Assuming a standard PEM (polymer electrolyte fuel cell, PEFC) fuel cell operated at 0.7 V, generating 120 nl/min was equivalent to12 kW.     

Crystallography of intragranular ferrite formed on (MnS+V(C,N)) complex precipitate in austenite

Crystallography of intragranular ferrite formed on incoherent MnS+V(C,N) complex precipitate in austenite was studied in an Fe–Mn–C hypoeutectoid alloy. As transformation temperature decreases, intragranular ferrite morphology changes from idiomorph to acicular ferrite. Idiomorphic ferrite has no specific orientation relationship with austenite although acicular one holds near Kurdjumov–Sachs relationship.     

一种环保型钻井液絮凝剂的研制与评价

固相含量对钻井液的性能影响很大,往往需要使用化学絮凝方法并结合固控设备来维持适宜的固相含量。为有效去除钻井液中的固相颗粒,研制出了一种高效环保的钻井液絮凝剂——阳离子明胶。并对其絮凝效果和作用机理进行了分析评价。评价过程及结果如下:①通过核磁氢谱和电位测量对合成的产物进行了化学表征;②通过浊度实验、粒度分析、电位测量等方法评价了该絮凝剂的絮凝效果,并对其絮凝机理进行了分析。结果表明:阳离子明胶对高岭土絮凝效果显著,在20 mg/L时可使高岭土分散液的剩余浊度百分率下降至4.0%,可有效包裹、桥联黏土颗粒,使高岭土粒径显著增大。同时,该絮凝剂也可使钻井液中固相颗粒显著增大,结合固控设备可使钻井液固相含量由22.5%降至12.6%,其絮凝效果优于常用的水解聚丙烯酰胺类絮凝剂。      

-18℃下冻土区负温水泥浆水化微观过程研究

极地冷海地区具有重要的油气勘探开发价值,但常规固井水泥浆液相水分在该地区负温环境下会分凝结冰,水化反应无法进行,导致固井工作难以开展。为此,针对极地冷海冻土区负温环境下固井水泥浆不凝固难题开发了一种负温水泥浆体系,并对比研究了其在-18℃和室温环境下水化反应微观产物的区别。实验结果表明:该体系具有优良的负温固化性能,在-18℃下0.5~3 h内固化,24 h抗压强度达3.5~9 MPa,可有效解决负温条件下常规水泥浆不固化无强度难题;微观成分测试发现,-18℃下冻土区负温水泥浆的水化程度较室温下低,但水化产物中Aft含量较室温下高,这对水泥石的机械性能起到了积极作用。      

Scheduling Algorithm with Quality of Service Support in IEEE 802.16 Networks

<正>The MAC layer in IEEE802.16 is designed to differentiate service among traffic categories with different multimedia requirements.In this paper,a scheduling algorithm at MAC layer for multiple connections with diverse QoS requirements is proposed.As for this algorithm,each connection is assigned a priority,which is updated dynamically based on its service status concluding queue characteristic and channel state.A connection with the highest priority is scheduled each time.Analytical model is developed by assuming a Finite State Markov Chain(FSMC)channel model.Simulation results show that the proposed scheduling algorithm can improve the performance of mean waiting time and throughput in broadband wireless networks.     

复合膜法火电厂烟气捕水性能的实验研究

复合膜法捕集火电厂烟气中的水蒸气有望成为火电厂节水的一条有效途径。选用聚醚砜（PES）作为中空纤维膜支撑层材料,磺化聚醚醚酮（SPEEK）作为中空纤维膜涂层材料,制作了用于实验研究的SPEEK- PES中空纤维复合膜;采用模拟烟气（H2O/N2）在实验台上研究了不同磺化度的SPEEK涂层、吹扫气流速、烟气温度等对中空纤维复合膜捕水性能的影响。实验结果表明,复合膜中SPEEK的磺化度不是越高越好;吹扫气流速也存在一个最优值;在实验温度范围（40~70 ℃）内,随着温度的提升,复合膜的捕水性能有所提高。     

The effect of completion strategy on fracture propagation from multiple cluster perforations in fossil hydrogen energy development

The hydraulic fracturing is extensively used to stimulate the production of fossil hydrogen energy. Perforation parameters have a great influence on the performance of hydraulically fractured horizontal wells in fossil hydrogen energy development. In this work, a practical model to study the effect of a completion scheme on simultaneous fracture propagation is proposed, in which the coupling fluid flow and stress interaction is considered, and a fracture propagation uniform index model is used to optimize the completion strategy. Moreover, this model is well validated by Wu's model and Zhang's model. The numerical study results indicate that a uniform completion scheme causes a non-uniform fracture development; an optimal completion method is proposed by reducing the cluster number, non-uniform spacing, and practical limited entry technique in a fracturing stage. Furthermore, the combined use of unequal cluster spacing and a limited entry strategy can significantly reduce the suppression effects between multiple clusters, improve the fluid flow into each cluster, and enhance the uniform propagation to achieve the maximum production. Our present work illustrates a better understanding of the effect of the completion strategy on the multiple fracture propagation, and paves a path for a more optimal completion design for fossil hydrogen energy development.