Closed-loop control of a SCR system using a NOx sensor cross-sensitive to NH3

This paper proposes a control strategy for an automotive selective catalytic reduction (SCR) system using a NO_x sensor in a feedback loop. As is representative of real world applications, the employed NO_x sensor is cross-sensitive to NH₃, which induces several complexities. In particular the ambiguity of the measurements could be detrimental to the closed loop response, as it generates multiple equilibrium points (artefacts), besides the point of practical interest. A study of the closed-loop dynamics is performed in the vicinity of each point, which shows that the closed loop system naturally converges to the point of interest not to the artefacts. Experimental results obtained after a detailed calibration method illustrate the relevance and performance of the proposed approach.     

氧化还原电位对低煤阶煤生物甲烷生成的影响

氧化还原电位（Eh）是煤层生物甲烷生成的重要控制因素之一。为了解其对煤层生物甲烷产出的影响以及产甲烷的动力学过程，在实验室采用-102 mV、-153 mV、-208 mV、-284 mV、-315 mV这5个氧化还原电位值，对河南义马低煤阶煤样品进行了生物甲烷模拟产出实验，采用气相色谱仪对不同反应阶段生成气体的成分及生成量进行检测，同时对菌种源中微生物进行培养计数。结果表明：①不同Eh条件下的实验均有甲烷的生成，氧化还原电位较低时产甲烷菌的繁殖更加快速，在-284 mV时生物甲烷的浓度最大，-102 mV时最小；②通过平板计数法，分析了产甲烷过程和细菌生长动力学机理--整个产甲烷生成过程也是微生物生长代谢的过程，间接证明了产气量大小变化的原因。结论认为，Eh对于煤层生物甲烷的生成具有重要的控制作用。     

远程下保护层开采被保护层防突技术研究

针对平煤十矿丁5,6卸压区域内的煤层和未卸压区域内的煤层区域制定合理的防突措施,并对区域措施效果进行了检验和验证.同时对局部煤层的情况实施了综合防突措施,最后对反向风门、压风自救系统、避难硐室、爆破作业等安全防护措施进行了论述.     

Dynamic failure in coal seams: Implications of coal composition for bump susceptibility

As a contributing factor in the dynamic failure (bumping) of coal pillars, a bump-prone coal seam has been described as one that is “uncleated or poorly cleated, strong…that sustains high stresses.” Despite extensive research regarding engineering controls to help reduce the risk for coal bumps, there is a paucity of research related to the properties of coal itself and how those properties might contribute to the mechanics of failures. Geographic distribution of reportable dynamic failure events reveals a highly localized clustering of incidents despite widespread mining activities. This suggests that unique, contributing geologic characteristics exist within these regions that are less prevalent elsewhere. To investigate a new approach for identifying coal characteristics that might lead to bumping, a principal component analysis (PCA) was performed on 306 coal records from the Pennsylvania State Coal Sample database to determine which characteristics were most closely linked with a positive history of reportable bumping. Selected material properties from the data records for coal samples were chosen as variables for the PCA and included petrographic, elemental, and molecular properties. Results of the PCA suggest a clear correlation between low organic sulfur content and the occurrence of dynamic failure, and a secondary correlation between volatile matter and dynamic failure phenomena. The ratio of volatile matter to sulfur in the samples shows strong correlation with bump-prone regions, with a minimum threshold value of approximately 20, while correlations determined for other petrographic and elemental variables were more ambiguous. Results suggest that the composition of the coal itself is directly linked to how likely a coal is to have experienced a reportable dynamic failure event. These compositional controls are distinct from other previously established engineering and geologic criteria and represent a missing piece to the bump prediction puzzle.     

补偿强反光体表面红外测温误差的算法研究

针对运动强反光体表面温度实时测量困难、精度低这一难点,本文从红外测温原理入手,分析并揭示了红外测温精度易受到被测物体反射率、测量距离、测量环境、红外入射角等因素的影响。根据铝板材加工设备轧辊表面测温实际需要设计了一种利用红外传感器实现对强反光体表面温度点对点测量的方案。通过对测量数据的研究分析建立了一种基于斯忒藩定律的红外入射角度补偿算法,以此减小因红外入射角度变化产生的测温误差。实验结果证明本方法能较好地弥补红外入射角度变化产生的测温误差,提高测温精度。该补偿算法运算简单,适应性强,为改善入射角度变化对测温精度影响提供了新的方法。     

Analysis of roof and pillar failure associated with weak floor at a limestone mine

A limestone mine in Ohio has had instability problems that have led to massive roof falls extending to the surface. This study focuses on the role that weak, moisture-sensitive floor has in the instability issues.Previous NIOSH research related to this subject did not include analysis for weak floor or weak bands and recommended that when such issues arise they should be investigated further using a more advanced analysis. Therefore, to further investigate the observed instability occurring on a large scale at the Ohio mine, FLAC3 D numerical models were employed to demonstrate the effect that a weak floor has on roof and pillar stability. This case study will provide important information to limestone mine operators regarding the impact of weak floor causing the potential for roof collapse, pillar failure, and subsequent subsidence of the ground surface.     

Microcracks size growth prediction based on microdefects nucleation number

The mechanical reason for rock and concrete failure is trans-scale fracture, which can be divided into three phases: (1) microcrack evolution, (2) macrocrack nucleation, (3) macrocrack growth and run-through. Using the idea that a microcrack could be regarded as a well-organized aggregation of nucleated microdefects, the size growth model of the largest microcrack based on the accumulated number of microdefect nucleation is established. In order to test the validity of the model, trans-scale fracture of a plate made of heterogeneous material is numerically simulated to display the microcrack’s evolution. Statistical analysis of the number and sizes of the microcracks indicates that the predicted size of the largest microcrack according to the model is in close agreement with the measured crack size prior to peak stress, but not at all close to the measured values after the peak. At the end of the paper, some remaining problems are proposed for the further work.     

岩土工程可靠度分析的拉格朗日乘数法

基于可靠指标标准正态空间计算的数学模型,运用拉格朗日乘数法,提出了计算岩土工程设计验算点和可靠指标的方法.该方法适用于任何概率分布的相关变量,不必计算当量正态均值和方差、相关变量独立变换,也适用于功能函数为高度线性时采用JC法计算可靠指标迭代不能收敛的情况.通过建立构造函数,然后求其对各个变量的一阶偏导并与结构的功能函数联立求解出验算点坐标,之后求出可靠性指标.由于标准正态分布函数的反函数表达式不能给出,在求解其导数时可使用有理多项式法求解.通过二个算例分析表明该方法简单、可靠和有效,值得在工程实践中推广.     

结合MNF变换和Canny算子的遥感影像变化检测

针对大面积区域的多时相遥感影像变化检测的需求，提出了一种基于最小噪声分离（MNF）的Canny边缘检测提取影像变化信息的检测方法。对多时相影像采用多种变换组合成具有多维波段信息的影像，采用最小噪声分离法分离噪声并得到单波段差异图，通过Canny边缘检测法计算梯度幅值，采用高低双阈值法细化边缘，从而提取差异图变化边缘，有效突出了变化信息。以1995年和2003年加扎勒河的两期遥感影像为例，利用两时相影像进行土地覆被变化检测。实验结果表明，该方法适用于监测大面积区域内地物的突变情况。在数据基础上进行最小噪声分离可以有效解决传统Canny边缘检测提取边缘时造成的伪边缘现象，同时采用高低双阈值法有效去除伪边缘点，从而获得更加精确、直观的变化检测效果，在自然地理变化监测、地理国情灾害监测等有很好的应用价值。     

Study on “triangle” water-inrush mode of strong water-guide collapse column

The water-inrush mechanism of strong water-guide collapse column in coal seam is studied based on the establishment of geological and mathematical models of "triangle" water-inrush mode. The geological background of Shuangliu mine is considered a prototype, similar simulation tests are adopted to analyze the water-inrush rules under this model, and the formation of water-guide channel and water-inrush process is investigated by examining the changes in rock resistivity. This work also uses the coupled cloud image derived from numerical simulation software to verify the results of simulation test. Results show that the numerical simulation of "triangle" water-inrush mode is consistent with the similar simulation. The "triangle" seepage area, which is located at the bottom of collapse columns and is connected to aquifer, is caused by the altered seepage direction and strengthened seepage actions after the overlapping of hydraulic transverse seepage in collapse column and hydraulic vertical seepage flow in aquifer. Under "triangle"water-inrush model, water-guide channel is formed by the communication between plastic failure zone of working face baseplate and"triangular" seepage area. Accordingly, the threatening water-inrush distance between working face and collapse column increases by 20 m compared with that of theoretical calculation.