Calcium species evolution mechanism during coal pyrolysis and char gasification in H2O/CO2

The release mechanism of Ca during coal pyrolysis and char gasification in H₂O, CO₂ and their mixtures was studied. Sequential chemical extraction was used to determine the modes of occurrence of Ca in coal and char. The released Ca from coal pyrolysis and char gasification were captured and analyzed by activated carbon adsorption and X-ray photoelectron spectroscopy (XPS). Model compounds CaS and CaSO₄ were adopted to further reveal the released form of Ca under different atmospheres. The results indicate that Ca in coal is mainly released as CaCl₂ during the pyrolysis process, and the possible migration mechanism of Ca during pyrolysis was proposed. Ca in coal is mainly released in the form of CaCl₂, CaCO₃, and CaSO₄ during the gasification, and Ca is released as CaCl₂ under all conditions. In addition, Ca will be released as CaCO₃ under CO₂ atmosphere, as CaSO₄ under H₂O and H₂O/CO₂ atmospheres at 800 °C and 900 °C, released as CaSO₄ under all conditions at 1000 °C. This is closely related to the formation of CaO₂ intermediates during the gasification process.     

裂隙岩体小净距超大断面隧道围岩非连续变形分析

由于现有隧道规范不足与设计、施工经验匮乏,裂隙岩体中小净距超大断面隧道的围岩稳定性分析与中夹岩柱变形破坏特征及其支护方案优化仍是大型隧道工程建设中遇到的棘手难题。以济南市东南二环绕城高速大岭超大断面隧道为工程依托,通过对掌子面岩体结构信息的精细化描述,获取各评定指标分布概型,并应用Monte Carlo法生成符合围岩等级评价指标分布概型的大量随机数,通过归纳统计获得隶属各围岩亚级分级的概率分布,由此对岩体质量进行了稳健评估。此外,用改进的非连续变形分析(DDARF)法对大岭隧道浅埋小净距段围岩的变形破坏规律及裂隙演化过程进行了数值模拟;以裂隙扩展破碎区贯通与否作为中夹岩柱稳定性的评定依据,分别针对无锚、有锚支护条件下的围岩稳定性状况及变形特征进行了对比分析。结果表明:无锚支护条件下,隧道后行洞开挖对先行洞的裂隙扩展及变形有一定影响,但不明显;而锚杆支护则可显著约束围岩尤其是中夹岩柱的裂隙扩展及贯通,锚杆支护条件下二次扰动后先行洞围岩的裂隙扩展情况、变形破坏特征与单洞开挖无异,且系统锚杆支护与中夹岩柱水平加长锚杆支护对裂隙演化的控制效应无较大区别。研究结果对裂隙岩体中小净距超大断面隧道围岩的支护方案优化有实际指导意义。     

施氮方式对烤烟氮素吸收积累及品质的影响

试验研究了不同施氮量和基追肥比例对烟株氮素吸收累积、土壤硝态氮、品质及产量的影响。结果表明,不同处理对烤烟生长前期干物质积累量、烟株氮素含量和氮素累积量无明显影响,减少氮肥用量与基肥用量降低了成熟期叶片氮素含量和氮素累积量,减少氮肥用量显著降低了生长前期和后期的土壤硝态氮含量。随施氮量的增加,烤后烟叶还原糖含量、糖碱比表现为下降趋势,而总植物碱、总氮含量表现为增加趋势。相同施氮量基追肥比例为30:70处理的还原糖含量、糖碱比较大,总植物碱含量、总氮含量较小,香气质、余味得分较高。施纯氮90 kg/hm²,基追肥比例为50:50和30:70的处理经济效益明显增加。本试验条件下,兼顾烟叶产量与品质的最佳氮肥运筹模式为施纯氮90 kg/hm²,基追肥比例为30:70。     

层层自组装多糖微胶囊的制备及其缓释型纯棉织物修饰应用

为制备生物相容性功能纺织材料,采用层层自组装技术将带有不同电荷的海藻酸钠(Alg)、壳聚糖(Chi)、透明质酸(HA)组装到碳酸钙模板上,利用乙二胺四乙酸(EDTA)去除模板,得到Alg/ Chi/ HA生物多糖微胶囊;利用超景深三维显微镜、扫描电子显微镜、红外光谱、综合热分析仪研究了微胶囊的形貌结构及热稳定性。结果表明:Alg/Chi/HA多糖微胶囊具有很好的中空结构及较强的稳定性;考察了多糖微胶囊吸附释放行为及其随pH值的变化规律,发现Alg/Chi/HA多糖微胶囊具有良好的pH值响应性;进一步将Alg/Chi/HA多糖微胶囊整理至棉纤维上,以制备缓释型功能纺织材料,为功能纺织品开发提供有益的实践经验与技术储备。     

化学沉淀法制备磷酸铁锂正极材料的研究进展

磷酸铁锂(LiFePO4)是一种非常有应用前景的锂离子电池正极材料,化学沉淀法是制备这种材料的理想方法。本文从不同的前驱体合成路线角度出发,针对金属离子掺杂和表面碳包覆这两种改性手段,对化学沉淀法制备LiFePO4正极材料国内外的研究进行综述,对当前研究过程中存在的问题和未来的研究方向进行了评论和展望,为LiFePO4正极材料的研究提供了参考。     

变形协调情况下土钉墙内力和位移的计算方法

 土钉墙的内力主要包括土钉轴力、钉土剪力和面层受力,而土钉墙变形的过程是土钉、面层和土体之间相互协调共同作用的过程,传统的计算模型都是从力矩平衡的力学角度出发,不能合理解释土钉内力和变形的相互关系。通过对土钉墙受力和变形机制的分析,利用Mindlin解计算在虚拟开挖应力和钉土剪力共同作用下土体侧向位移,结合钉土剪力和钉土相对位移的线性关系以及钉土剪力在最危险滑动面位置等于0的特点,计算土钉轴力、钉土剪力和土钉墙在开挖面位置的变形。土钉被动区段钉土剪力超出其极限值的部分转移至面层,假定面层受力增量呈三角形分布,根据静力平衡得到面层受力分布。通过与工程实测资料的对比分析,初步验证土钉墙内力和变形计算方法的合理性和可行性。     

青城凸起中生界内幕断层及油气运聚特征

针对青城凸起断裂系统复杂,油气运聚成藏规律认识不清的问题,在研究高青—平南断层连通性以及中生界主要断层封闭能力和输导能力的基础上,对高青地区油气运聚特征进行模拟。结果表明,高青—平南断层整体具有良好的输导能力,而中生界内幕断层平均连通概率均小于0.6,整体输导能力较差,油气主要沿断层—砂体进行垂向、侧向运移。高青地区油气优势运移路径为沿高青断层向西、西南方向运移;油气运移指向主要受构造形态和砂体控制,油气沿断层和骨架砂体向鼻状构造脊部运移,运移距离受北东向鼻状构造控制,而构造脊部的西侧地层西倾,油气无法沿骨架砂体继续运移。因此,在高15—高52—高46井南北向鼻状构造带油气运移通畅,是有效的含油带。     

水平井砾石充填SLCH防砂工艺矿场试验

砾石充填是适用于疏松砂岩油藏水平井的一种较好的防砂方法，但由于在充填过程中水平段容易形成砂桥导致防砂失败，长期以来在中国缺乏成功的矿场应用实践。介绍了水平井砾石充填SLCH防砂工艺，详细阐述了该工艺的基本原理、防砂管柱结构、施工流程、施工参数和矿场试验情况。矿场试验证实，SLCH防砂工艺能够较好地应用于疏松砂岩油藏水平井防砂，具有良好的推广应用前景。     

Investigations of water inrushes from aquifers under coal seams

In many coal mines, limestone-confined aquifers underlie coal seams. During coal extraction from these mines, water inrushes occur frequently with disastrous consequences. This paper introduces the hydrogeological conditions of the coal mines and the potential water inrush disasters from aquifers under coal seams. It then presents the water inrush mechanism. The main factors which control water inrushes include strata pressure, mining size, geologic structures and the water pressure in the underlying aquifer. Analysis shows that reduction of confinement due to mining is the major cause of the water-conducting failure in the floor strata. The depth of the failure zone is strongly dependent on the mining width. This paper also presents field observation results of the water-conducting failure in the floor strata, and applies the finite element method coupled with stress-dependent permeability to analyze hydraulic conductivity enhancement due to coal extraction. Finally, theoretical and empirical methods to predict water inrushes are given, and technical measures for improving mine design and safety for coal extraction over aquifers are presented. These measures include fault and fracture grouting and mining method modification such as changing long-wall to short-wall mining.     

Data aggregation in wireless sensor network using SVM-based failure detection and loss recovery

Abstract

In wireless sensor network, data aggregation can cause increased transmission overhead, failures, data loss and security-related issues. Earlier works did not concentrate on both fault management and loss recovery issues. In order to overcome these drawbacks, in this paper, a reliable data aggregation scheme is proposed that uses support vector machine (SVM) for performing failure detection and loss recovery. Initially, a group head, selected based on node connectivity, splits the nodes into clusters based on their location information. In each cluster, the cluster member with maximum node connectivity is chosen as the cluster head. When the aggregator receives data from the source, it identifies node failures in the received data by classifying the faulty data using SVM. Furthermore, a reserve node-based fault recovery mechanism is developed to prevent data loss. Through simulations, we show that the proposed technique minimises the transmission overhead and increases reliability.