Large earthquakes during hydraulic stimulations at the geothermal site of Soultz-sous-Forêts

Several deep wells were drilled in the Rhine Graben (Soultz-sous-Forêts, France) to evaluate the geothermal Hot Dry Rock potential of a deep fractured granite reservoir. Three main boreholes, which reached about 5 km depth, intersected a crystalline basement overlain by 1.4 km of Cenozoic and Mesozoic sediments. Stimulations of these three wells were carried out in 2000 for GPK2, 2003 for GPK3 and 2004, and 2005 for GPK4. During these stimulations and other hydraulic activities a seismological surface network was installed in order to monitor the seismicity induced by the massive fluid injection.

Here we analyse the seismicity of magnitude larger than or equal to 1.4, which is the lowest magnitude felt by the population. Based on a spectral analysis of the displacement recorded by a Güralp velocimeter at a depth of 200 m, we know that the source dimensions range from tens to hundreds of metres. We analyse several parts of the reservoir where obvious correlation between the fluid path and tectonic features has been pointed out. Based on seismological arguments such as location and focal mechanisms, we show that this activity is linked with tectonic features, or at least with large fractures that control the behaviour of the geothermal reservoir. To constrain the hypothesis, we study 391 events and focal mechanisms to argue in favour of the existence and stability of tectonic features that can be compared to geological data. We show that the largest events recorded on the site occurred after the shut-in. Their spatial distribution appears not to be random within the reservoir, and the focal mechanisms of these events also confirm the non-randomness of their distribution. Given their source dimensions, the largest events can only occur on large structures, such as tectonic ones. Therefore, the behaviour of the reservoir is controlled by these main fractured zones, which either lead the fluid or hinder its path.     

改进残差神经网络实现心音分类

心音的变化可以较早表征心脏疾病体征,基于深度学习实现心音信号分类具有心脏疾病临床辅助无创诊断作用。秉承特征获取简易和深度学习模型简单理念,设计了融合CBAM注意力机制、Focal Loss损失函数和多尺度特征的ResNet152网络模型对PhysioNet/CinC 2016心音数据集进行深度学习;详细介绍了CBAM注意力机制以及在网络瓶颈结构中的融合方式、Focal Loss损失函数原理、多尺度特征获取方式,并设计了5组对比消融实验和横向对比实验。实验结果表明,CBAM注意力机制、Focal Loss损失函数和多尺度特征提高了ResNet152基线网络模型分类准确率。     

国外红外探测器的发展及其在制导武器中的应用

红外探测器是红外制导武器导引头的核心部件，它的发展深刻影响着红外制导武器的发展。本文介绍了国外械外探测器的发展概况，归纳了现有红外探测器的种类，简述了几种红外探测器采用材料以及它们在制导弹武器中应用，对红外焦平面阵列作了重点介绍。     

红外焦平面技术发展概况

红外焦平面是近期发展较快的一项高技术,具有广泛的应用前景。本文介绍红外焦平面的发展现状和国外各大公司近年来的研究结果;叙述了单片式、混合式、Z 平面焦平面的工作原理,并根据各自的特点指出了可能的应用领域;还介绍了 Z 平面焦平面的近期发展,认为在今后很长时间内,3种焦平面器件将竞相发展,相互间不能取代,在发展单片式、混合式焦平面的同时,应开展 Z 平面技术的研究。     

Secondary radiation in transmission-type X-ray tubes: Simulation, practical issues and solution in the context of X-ray microtomography

In laboratory-based X-ray radiography and computed tomography, the X-rays are assumed to originate from one single focal spot with a finite spot size, which is generated by focussing accelerated electrons on the target material. However, apart from this focal spot, X-rays can also be produced elsewhere in the tube system. A major contribution of this parasitic radiation originates from electrons that are backscattered from the target material, into the X-ray tube system, where they can produce so-called off-focus or secondary X-rays. This phenomenon has been widely studied for rotating anode X-ray tubes in medical imaging systems, but not for transmission-type microfocus X-ray tubes. This paper presents a study on the origin of secondary radiation in this kind of X-ray tubes, which is performed by Monte Carlo simulations and by experimental measurements. The impact of this phenomenon on the imaging process is studied, and two correction methods are proposed, both on the hardware and on the software levels.     

非制冷红外焦平面CMOS读出电路设计

在过去的10年里红外焦平面阵列成像技术逐渐进入了成熟期,从红外焦平面的发展背景出发,简要介绍了一种新颖的非制冷焦平面成像技术,论述了读出电路在红外焦平面信号传输中的作用并介绍了其基本框图,分析了国内外焦平面读出电路的现状,最后提出了一些在红外焦平面阵列读出电路设计中所需要注意的问题。     

改进SSD的输电铁塔鸟窝检测

输电铁塔作为架空输电线的重要组成部分,其安全状况将影响整个电力系统的运行,鸟窝的搭建作为影响输电线路正常运行的重要因素之一,需要对此进行监控.而现有的监控手段不仅效率低,还需要耗费大量的人力物力.本文针对这一现象提出一种基于SSD算法的实时检测方法,并在SSD的网络结构基础上将前置网络VGGNet替换为ResNet-101,提高其特征提取能力,并将Softmax loss用Focal loss代替以改善SSD算法中样本不平衡的问题,并利用数据增广提高数据多样性,以提高模型的鲁棒性.实验结果表明本文所提出的方法检测精度对比原SSD算法在准确度和召回率上分别有3.17%和6.35%的提升.     

CTP输出设备成像参数的设置

计算机直接制版(CTP)设备中激光头的焦距、变焦距、发光功率以及滚筒的转速是影响CTP曝光质量的直接因素。本文使用网屏热敏CTP设备PT-R4100,通过改变激光头的焦距、变焦距、发光功率和滚筒转速进行制版测试,从而确定最佳的成像参数。调整CTP输出设备的成像参数设置将印版分成13个测试条,每个测试条分成13个测试块,制版后通过观察和测定测试条或测试块的颜色和密度值,可以确定成像最清晰的测试条,从而计算出CTP设备最佳的成像参数。测试结果表明,该方法可以快速、准确地测定CTP的各项成像参数。CTP输出设备最佳成像参数为:激光头的焦距为1500puls、变焦距为6700puls、发光功率为90%、滚筒转速为600r/min。     

通过标点恢复提高机器同传效果

在机器同传（MSI）流水线系统中,将自动语音识别（ASR）的输出直接输入神经机器翻译（NMT）中会产生语义不完整问题,为解决该问题,提出基于BERT（Bidirectional Encoder Representation from Transformers）和Focal Loss的模型。首先,将ASR系统生成的几个片段缓存并组成一个词串;然后,使用基于BERT的序列标注模型恢复该词串的标点符号,并利用Focal Loss作为模型训练过程中的损失函数来缓解无标点样本比有标点样本多的类别不平衡问题;最后,将标点恢复后的词串输入NMT中。在英-德和汉-英翻译上的实验结果表明,在翻译质量上,使用提出的标点恢复模型的MSI,比将ASR输出直接输入NMT的MSI分别提高了8.19 BLEU和4.24 BLEU,比使用基于注意力机制的双向循环神经网络标点恢复模型的MSI分别提高了2.28 BLEU和3.66 BLEU。因此所提模型可以有效应用于MSI中。     

厄米双曲余弦高斯光束的焦开关

对双曲余弦高斯光束通过光阑透镜分离系统的轴上光强分布做了详细的数值分析。研究发现,在一定条件下轴上存在两个光强极大值点,并且在这两个极大值点相互竞争中会出现焦点位置的有效置换,即出现焦开关。厄米双曲余弦高斯光束产生焦开关的条件是:光阑与透镜相对间距为1,光束阶数为偶数,光束参数小于其相应的临界值,截断参数在它的两个临界值之间。进一步研究表明,焦点位置相对跃迁量和轴上相对光强下凹量随光束参数的减小而增大,但是随着截断参数的增大焦点位置相对跃迁量和轴上相对光强下凹量将分别出现一个极大值。在大范围调焦的应用中,可利用焦开关实现调焦之目的;在精密聚焦的激光应用中,应控制焦开关的产生。