压缩小波变换和非线性阈值技术压制磁共振尖峰噪声方法研究

地面磁共振是一种新的地球物理探测方法,能够通过探测地下水中氢质子丰度获取地下水含量、孔隙度等水文地质信息.然而,磁共振信号甚为微弱,仅达到纳伏级(10~(-9)V),极易受到噪声干扰.其中,尖峰噪声对磁共振信号影响最为严重,亟待研究有效的噪声抑制方法.小波多尺度分解硬阈值是近两年国际磁共振领域专家提出的尖峰噪声有效消除方法,但硬阈值算法设定阈值的固有缺陷会引发信号震荡,出现伪吉布斯效应,导致信号损失.基于此,本文提出压缩小波变换(Synchrosqueezing Wavelet Transform,SWT)和非线性國值处理(Nonlinear Thresholding,NT)算法联合消除磁共振信号尖峰噪声干扰.首先选择Morlet小波作为基小波,使得信号与噪声数据具有更高的时频集中性,利于尖峰噪声消除.其次,基于压缩小波系数进行非线性处理,可以弥补利用硬阈值和软阈值进行噪声消除时所引起的信号损失.仿真数据和实际数据结果表明,SWT联合NT方法可以利用单次采集数据有效消除尖峰噪声干扰并还原信号.本文提出的消噪方法将为磁共振数据后续反演解释,如多指数弛豫反演,奠定坚实的基础.     

基于压缩感知的多跳地震数据采集技术与方法

随着油气地震勘探目标的复杂程度日益提高,地震数据采集系统的道容量也需要得到进一步的提升.本文根据压缩感知、稀疏表示等理论,提出了一种多跳恒传输量的数据采集框架,以减少每条测线上地震数据的传输量,进而提升采集系统的道容量.为了能够明显地提高带道能力,设计了基于有序并行原子更新的字典学习算法,该算法能够在计算量较小的前提下有效的得到相应数据的稀疏变换矩阵.基于压缩感知的多跳地震数据采集方法已能够在吉林大学研制的无缆自定位地震仪中实现.本文最后使用一组仿真数据和一组实测数据进行测试,其结果表明,数据采集信噪比控制在14 dB以上(引入噪声约18%)时,最多可以将系统的道容量提高3倍以上.     

基于三元伪随机编码的冲击夯可控震源控制系统设计

冲击夯可控震源具有移动方便、质量轻、输出力大等优点,在城市工程勘察以及中浅层地震勘探等领域具有一定的应用前景.其激励信号主要基于二元伪随机编码技术,由于旁瓣效应导致相关干扰严重、地震记录信噪比低等问题,制约了冲击夯震源的推广应用.本文针对传统控制方法的不足,开展了基于三元伪随机的冲击夯可控震源编码技术和编码匹配控制方法研究,并在此基础上设计和实现了相应的控制系统.野外实验结果表明:相比于二元伪随机编码控制方法,三元伪随机编码控制方法得到的地震子波的主旁瓣比提高了4.04 dB;震源信号穿透力强,在测线远端处能量约为30磅锤击震源的100倍,约为二元伪随机方法的4倍;单炮地震记录中干扰抑制能力强,信噪比显著提升,子波频带宽,提高了分辨率,在一定程度上提高了地震勘探效果.     

薄壁型钢管/胶合竹板复合柱抗震性能试验

对9根带约束拉杆的方形薄壁型钢管/胶合竹板复合空芯柱(SBCCB)试件进行低周反复拟静力测试,考察SBCCB的破坏过程和形态,分析试件的长细比、胶合竹净横截面面积、截面组合方式对其受力和抗震性能影响。结果表明:SBCCB破坏形态主要为柱脚胶合面的开裂破坏和胶合竹板断裂破坏,截面组合方式对其破坏模式有显著影响。SBCCB试件有较好的弹性变形能力和抗震耗能性能,增大复合柱截面尺寸和长细比能改善抗震性能;约束拉杆有效保证了试件的整体性,抑制基体开胶破坏,间接提高了抗震性能。     

青海湖嗜盐微生物筛选分离与生长特性

为全面获得青海湖嗜盐菌种质资源,构建种群系统发育树和确定种群进化定位.采用高盐选择性培养基筛选,分离从20份青海湖水样中获得35株青海湖嗜盐微生物.耐盐梯度实验表明:水体中以中度嗜盐菌为主,约占62.85%,轻度嗜盐菌约占22.85%,非嗜盐菌与耐盐菌约占14.28%.青海湖中度嗜盐微生物能在10～45℃,pH 5.5～11.0的范围内生长,与地区盐碱化环境相关,具有嗜盐兼嗜碱微生物的特性.     

三峡水库156m蓄水前后澎溪河回水区藻类多样性变化特征

为了解156 m蓄水前后三峡水库次级河流藻类多样性变化特征,对2007年7月至2008年1月澎溪河回水区的藻类种群结构的变化进行连续监测.基于三峡水库水位调度特点,将监测期划分为蓄水前、中、后三个时段,即7-9月、10月、11月至翌年1月,应用Shannon-Weaver多样性指数H’对藻类多样性进行评价,通过Connell中度扰动假说理论结合优势藻种探讨蓄水过程水动力变化及藻类多样性的变化特征.结果表明:2007年7-9月蓄水前H’均值为3.466±0.317,10月蓄水期则降为3.246±0.338,而11月蓄水后高水位阶段H’均值上升为3.431±0.352.蓄水前澎溪河回水区具有河流型特征,流量与降雨作为主要的物理扰动因子影响水体扰动强度,进而引起多样性变化.10月蓄水期间水位突升、流量骤降导致水体扰动强度加剧,较蓄水前藻类多样性下降.自11月蓄水后的高水位阶段,降雨较小、流量趋于稳定,水体扰动降低,多样性回升并维持在相对稳定的状态.     

THE PRELIMINARY STUDY ON THE SEISMOGENIC STRUCTURE OF THE HUTUBI MS6.2 EARTHQUAKE

Based on the phase report of Xinjiang Seismic Network, the Hutubi M_S6.2 earthquake sequence M_L ≥ 1.0 was relocated by the HypoDD method. The results show that the aftershocks were distributed along NE and NW direction. The aftershocks were in the depths of 5~15km. In addition, by using the digital waveforms of Xinjiang Seismic Network, the best double-couple focal mechanism of the main shock and some aftershocks of M_S ≥ 3.8 were determined by the CAP method. Based on the above studies, the source depth, focal mechanism and aftershock distribution of the Hutubi M_S6.2 earthquake were analyzed and the seismogenic structure was discussed. The nodal plane parameters of the best double-couple focal mechanism are strike 144°, dip 26°, rake 118°, and strike 293°, dip 67°, rake 77°, respectively. The moment magnitude M_W is about 5.9, with centroid depth of 15.2km. These show that the main shock was a thrust type. Most focal mechanism solutions of the aftershocks were shown as a thrust type, which are similar to the main shock. It is speculated that the possible seismogenic fault of this earthquake is the Huorgosi-Manas-Tugulu Fault.     

2018年9月12日陕西宁强5.3级地震震害特征及发震构造背景

2018年9月12日在陕西省汉中市宁强县与四川省广元市交界处(32.75°N,105.69°E)发生5.3级地震。现场调查结果表明,此次地震最高烈度为Ⅵ(6)度。Ⅵ度区等震线呈椭圆状,其长轴呈北东走向,主要涉及到陕西省和四川省广元市的13个乡镇。部分震区房屋建筑出现轻微破坏现象。这次地震的发震断层是龙门山断裂带中的青川断裂。     

EARTHQUAKE LOCATION AND VELOCITY STRUCTURE IN YIBIN AREA,SICHUAN

Small earthquakes have been recorded in Yibin area, Sichuan Province since 1970, the frequency and intensity of seismicity have shown an increasing trend in recent ten years, and the earthquakes are distributed mainly in Changning, Gongxian and Junlian areas. Based on the seismic data from January 2008 to May 2015 recorded by Sichuan and Yunnan regional networks and Yibin local network, seismicity analysis, precise location and velocity structure inversion for earthquakes in Yibin area are carried out, the three-dimensional spatial distribution of seismic activity and the velocity structure at different depths in this region are investigated, trying to analyze the seismic activity law and seismogenic mechanism in Yibin area. The earthquake relocation result shows that the spatial cluster distribution of earthquakes is more obvious in Yinbin area, the earthquakes are concentrated in Changning-Gongxian and Gongxian-Junlian regions. The seismic activity presents two dominant directions of NW and NE in Changning-Gongxian region, and shows asymmetric conjugate distribution, the long axes of NW-trending and NE-trending seismic concentration area are about 30km and 12km respectively, and the short axes are about 5km. There is a seismic sparse segment near Gongxian, the frequency and intensity of seismicity in the southeast side are obviously higher than that in the northwest side, and the earthquakes with larger magnitude are relatively deep, the focal depth is gradually shallower with the distance away from Gongxian. Seismic activity is sparse in the west and dense in the east in Gongxian-Junlian region, the predominant direction of earthquakes in the seismic dense area of the eastern segment is NE. Seismic activity extends in opposite direction in the easternmost part of the two earthquake concentrated area. The P-wave velocity structure at different depths in the study area is obtained using joint inversion method of source and velocity structure. In view of the predominant focal depth in this region, this paper mainly analyzes the velocity structure of the upper crust within 10km. Within this study area, the P-wave velocity of earthquake concentration areas is relatively high within 10km of the predominant focal depth, especially in the northwest of Gongxian and eastern Junlian area, the P-wave velocity on the southeast of Gongxian increases gradually with depth, especially at 6km depth. These high-velocity zones are generally related to brittle and hard rocks, where the stress is often concentrated. Comparing earthquake distribution and velocity structure, seismic activity in this area mainly occurs in high-low velocity transition areas, the inhomogeneity of velocity structure may be one of the factors controlling earthquake distribution. The transition zone of high and low velocity anomalies is not only the place where stress concentrates, but also the place where the medium is relatively fragile, such environment has the medium condition of accumulating a large amount of strain energy and is prone to fracture and release stress.     

基于RIA的网络地理信息系统的设计与实现

通过分析与研究目前网络G IS存在的不足,引入R IA概念模型,设计并实现了一个基于丰富互联网应用程序(R IA)的网络G IS。实验表明,该模型增强了客户端的用户体验感,减轻了服务器的压力,极有可能成为未来网络G IS发展的主流。