Influence of temperature on acoustic emission source location accuracy in underground structure

An acoustic emission (AE) experiment was carried out to explore the AE location accuracy influenced by temperature. A hollow hemispherical specimen was used to simulate common underground structures. In the process of heating with the flame, the pulse signal of constant frequency was stimulated as an AE source. Then AE signals received by each sensor were collected and used for comparing localization accuracy at different temperatures. Results show that location errors of AE keep the same phenomenon in the early and middle heating stages. In the later stage of heating, location errors of AE increase sharply due to the appearance of cracks. This provides some beneficial suggestions on decreasing location errors of structural cracks caused by temperature and improves the ability of underground structure disaster prevention and control.     

爆破位置对深凹露天矿山炮烟扩散的影响研究

深凹露天矿山由于其特殊的结构,爆破产生的炮烟扩散稀释较为困难,严重危害生产作业人员的生命安全与健康。基于实际矿山构建了深凹露天矿山的二维物理及数学模型,采用非稳态数值分析方法研究了不同爆破位置下,深凹露天矿山采坑内爆破炮烟的扩散规律。研究结果表明：不同爆破位置下,露天采坑内均出现复环流,爆破点位置是影响露天采坑内风流结构特征的重要因素；露天采坑内的炮烟最高浓度均随着时间变化而逐渐下降,但下降的速率逐步减小,呈现三个阶段的下降趋势；爆破位置位于背风侧时露天采坑内的炮烟最高浓度和降至安全浓度所需时间远高于迎风侧三个爆破位置；随着背风侧爆破点距采坑底部距离的减小,炮烟最高浓度及降至安全浓度所需时间先降低后增加,炮烟最高浓度及降至安全浓度所需时间随着迎风侧爆破位置距采坑底部距离的减小而增加。研究结果对于指导深凹露天矿山企业合理组织爆破后的生产作业和保障作业人员安全具有重要意义。     

The effect of biomass feeding location on rice husk gasification for hydrogen production

The objective of this study is to investigate the impact of biomass feeding location on rice husk gasification for hydrogen production. By comparing the results between top-feed and bottom-feed of the feedstock of the fluidized bed biomass gasification at the reaction temperature between 600～1000 °C and ER = 0.2, 0.27, and 0.33 without steam, the optimum low heating value was increase by 2.35 kJ/g-rice husk by the top-feed to gasifier. Although the yield of hydrogen was decreased by 42% for the rice husk gasification by the top-feed operation, the yield of CO, CO2, and CH4 were highly increased, which enhancing the heating value of the effluent gas. The study results suggested the potential route of the biomass gasification at the different feeding location.     

YOLSO: You Only Look Small Object

Small object detection is challenging and far from satisfactory. Most general object detectors suffer from two critical issues with small objects: (1) Feature extractor based on classification network cannot express the characteristics of small objects reasonably due to insufficient appearance information of targets and a large amount of background interference around them. (2) The detector requires a much higher location accuracy for small objects than for general objects. This paper proposes an effective and efficient small object detector YOLSO to address the above problems. For feature representation, we analyze the drawbacks in previous backbones and present a Half-Space Shortcut(HSSC) module to build a background-aware backbone. Furthermore, a coarse-to-fine Feature Pyramid Enhancement(FPE) module is introduced for layer-wise aggregation at a granular level to enhance the semantic discriminability. For loss function, we propose an exponential L1 loss to promote the convergence of regression, and a focal IOU loss to focus on prime samples with high classification confidence and high IOU. Both of them significantly improves the location accuracy of small objects. The proposed YOLSO sets state-of-the-art results on two typical small object datasets, MOCOD and VeDAI, at a speed of over 200 FPS. In the meantime, it also outperforms the baseline YOLOv3 by a wide margin on the common COCO dataset.     

新型地锚张弦梁式泥石流格栅坝构件受力的简化计算方法

针对常见泥石流防治结构被冲击破坏的问题，基于“柔性消能”理念，结合张弦梁结构和竖向预应力锚杆技术，提出一种既能改善结构受力性能、增加结构整体抗冲击能力、保证结构安全可靠，又能减小结构构件截面尺寸、节约成本、便于现场施工组装和后期运营维护的新型地锚张弦梁式泥石流格栅坝，并阐述其技术原理。根据泥石流荷载分布和新型地锚张弦梁式泥石流格栅坝的受力特征，给出其简化的内力计算方法；并利用SAP2000建立新结构有限元模型，分析了结构的整体受力，验证了构件简化计算方法的合理性；结合Python语言和Qt De? signer软件开发了相应的设计计算软件，对新型地锚张弦梁式泥石流格栅坝的内力进行求解。结果表明：提出的新结构抗冲击性能好，构件受力均匀；以后设计中应关注竖杆的剪切脆性破坏和立柱偏心受力情况，保证结构安全；变形协调仅使底层张弦梁与竖杆内力偏大，实际工程应用时，应着重验算底层构件，防止其破坏；文中提出的简化计算方法能较准确的反映结构的受力特性，具有一定的合理性，研究可为新型地锚张弦梁式泥石流格栅坝的设计计算和推广应用提供理论依据和技术支持。     

基于机器学习识别与标记分水岭分割的盲道图像定位

视觉导盲仪是一种旨在解决盲人出行困难的导盲设备，为了实现视觉导盲仪诱导盲人找到盲道并沿盲道行走，提出了一种基于机器学习识别与标记分水岭分割的盲道图像定位算法，通过离线训练与在线的识别、分割来定位盲道区域。首先对盲道图像进行视角变换的预处理，根据盲道的地面方程将变化的倾斜视角转换为固定的俯视视角，消除射影变换带来的失真；然后利用局部二进制模式描述子提取鸟瞰图的纹理特征，以自适应增强学习算法离线训练盲道识别分类器；进而利用分类器对鸟瞰图像进行在线识别，粗略确定盲道区域；最后将识别结果进行形态学处理后作为标记，利用标记分水岭算法得到精确分割的盲道区域并定位盲道中心线。在研制的视觉导盲仪上进行验证，结果表明盲道定位准确率达到了95.44%，速度平均每秒8帧，具有高准确率的同时达到实时性要求，为盲道的准确三维定位提供了必要条件。     

Location Privacy in Device-Dependent Location-Based Services: Challenges and Solution

With the evolution of location-based services (LBS), a new type of LBS has already gain a lot of attention and implementation, we name this kind of LBS as the Device-Dependent LBS (DLBS). In DLBS, the service provider (SP) will not only send the information according to the user’s location, more significant, he also provides a service device which will be carried by the user. DLBS has been successfully practised in some of the large cities around the world, for example, the shared bicycle in Beijing and London. In this paper, we, for the first time, blow the whistle of the new location privacy challenges caused by DLBS, since the service device is enabled to perform the localization without the permission of the user. To conquer these threats, we design a service architecture along with a credit system between DLBS provider and the user. The credit system tie together the DLBS device usability with the curious behaviour upon user’s location privacy, DLBS provider has to sacrifice their revenue in order to gain extra location information of their device. We make the simulation of our proposed scheme and the result convince its effectiveness.     

相对冲击位置和补片层数对胶接修理CFRP复合材料层合板抗冲击性能的影响

本文针对碳纤维增强聚合物（CFRP）复合材料修补结构，基于连续损伤力学和粘结单元模型，在ABAQUS软件中对低速冲击载荷下不同冲击位置和补片层数的CFRP复合材料层合板内部和层间损伤进行了数值分析，并与试验结果进行了对比。选择相对冲击位置为0 mm、10 mm、20 mm、30 mm和40 mm时对应的五种修补结构，通过数值计算和试验，获得了修补结构在低速冲击过程中的冲击力、冲击能量等数据。在保持补片单层厚度不变的前提下，使补片层数从1层增加到5层，计算获得了修补结构的低速冲击响应。研究结果表明：冲头接触修补结构时会对补片造成较大的损伤，补片可以提高含孔损伤母板的抗冲击性能；冲击点离修补结构损伤孔越近，结构受冲击所产生的分层损伤越严重；增加补片的层数可以提高修补结构的抗冲击性能；通过对补片层数进行优化，得到优化层数为2，其对应的修补结构与无修补结构相比分层损伤面积减少了19.9%，较好地提升了母板的抗冲击性能。     

机抽—速度管复合排水采气新工艺

为了提高目前常用的排水采气工艺的适应性,同时降低由排采工艺调整带来的额外的成本开销,利用空心抽油杆对机抽工艺进行了改进,结合应用所研发的空心防气排水采气专用泵,形成了机抽—速度管复合排水采气工艺,并在鄂尔多斯盆地苏里格气田某产水气井进行了现场试验。研究结果表明:①该工艺实现了机抽与速度管柱、气举、泡排等多种排采工艺的自由组合,并且可根据气井产水特点灵活调整适合的排采工艺,提高了工艺的适应性;②采用的游动阀及固定阀均依靠抽油机动力和空心抽油杆重力实现强制启闭,避免了气锁和砂卡引起的机抽失效;③该工艺的选井原则为气井初期产气量较高(大于1×10~4m~3/d)、产水量相对较高(介于3～30 m~3/d),且井口到液面的距离小于2500m;④针对产气量分别为2×10~4m~3/d、1×10~4m~3/d的气井,需采用外径为36 mm、壁厚为6 mm或外径为38 mm、壁厚为6 mm的空心抽油杆进行速度管排水采气,针对产气量为0.6×10~4m~3/d的气井,需采用外径为34 mm、壁厚为5.5 mm的空心抽油杆进行速度管排水采气。结论认为,该工艺可以明显提高产水气井的稳产气量,实现产水气井的连续、稳定生产,应用效果好。