Coherence-coefficient-based Markov random field approach for building segmentation from high-resolution SAR images

Building segmentation from high-resolution synthetic aperture radar (SAR) images has always been one of the important research issues. Due to the existence of speckle noise and multipath effect, the pixel values change drastically, causing the large intensity differences in pixels of building areas. Moreover, the geometric structure of buildings can cause strong scattering spots, which brings difficulties to the segmentation and extraction of buildings. To solve of these problems, this paper presents a coherence-coefficient-based Markov random field (CCMRF) approach for building segmentation from high-resolution SAR images. The method introduces the coherence coefficient of interferometric synthetic aperture radar (InSAR) into the neighborhood energy based on traditional Markov random field (MRF), which makes interferometric and spatial contextual information more fully used in SAR image segmentation. According to the Hammersley-Clifford theorem, the problem of maximum a posteriori (MAP) for image segmentation is transformed into the solution of minimizing the sum of likelihood energy and neighborhood energy. Finally, the iterative condition model (ICM) is used to find the optimal solution. The experimental results demonstrate that the proposed method can segment SAR building effectively and obtain more accurate results than the traditional MRF method and K-means clustering.

Coherence cube enhancement based on local histogram specification

Coherence analysis is a powerful tool in seismic interpretation for imaging geological discontinuities such as faults and fractures. However, subtle faults or fractures of one stratum are difficult to be distinguished on coherence sections （time slices or profiles） due to interferences from adjacent strata, especially these with strong reflectivity. In this paper, we propose a coherence enhancement method which applies local histogram specification （LHS） techniques to enhance subtle faults or fractures in the coherence cubes. Unlike the traditional histogram specification （HS） algorithm, our method processes 3D coherence data without discretization. This method partitions a coherence cube into many sub-blocks and self-adaptively specifies the target distribution in each block based on the whole distribution of the coherence cube. Furthermore, the neighboring blocks are partially overlapped to reduce the edge effect. Applications to real datasets show that the new method enhances the details of subtle faults and fractures noticeably.

The Coherence Cube Computing Method with Self-adaptive Time Window Based on Wavelet Transform

The coherence cube technology has become an important technology for the seismic attribute interpretation, which extracts the discontinuities of the events through analyzing the similarities of adjacent seismic channels to identify the fault form. The coherence cube technology which uses constant time window lengths can not balance the shallow layers and the deep layers, because the frequency band of seismic data varies with time. When analyzing the shallow layers, the time window will crossover a lot of events, which will lead to weak focusing ability and failure to delineate the details. While the time window will not be long enough for analyzing deep layers, which will lead to low accuracy because the coherences near the zero points of the events are heavily influenced by noise. For solving the problem, we should make a research on the coherence cube technology with self-adaptive time window. This paper determines the sample points＆#39; time window lengths in real time by computing the instantaneous frequency bands with Wavelet Transformation, which gives a coherence computing method with the self-adaptive time window lengths. The result shows that the coherence cube technology with self-adaptive time window based on Wavelet Transformation improves the accuracy of fault identification, and supresses the noise effectively. The method combines the advantages of long time window method and short time window method.

Application of the third generation of coherent cube in recognizing faults and fractures

Three-dimensional coherent cube is an extremely effective new technique for interpreting seismic data. It has obvious advantages in many aspects compared with the conventional 3D data volume, such as recognizing faults and fractures, interpreting ancient channels, and edge detection of oil-gas reservoir. Coherent cube is to condense and extract information around a certain point in 3D data volume, and then highlight the original characteristics of the geologic body at this point. Therefore, in terms of its essence, coherent cube is a special seismic attribute cube and those points having rather small coherent value are related to the discontinuity of geologic body. In practical production, people often interpret horizontal slices or layer slices of coherent cube, and this provides advantageous foundations for resolving special problems in oil-gas exploration.……

Advances in high-resolution nuclear magnetic resonance methods in inhomogeneous magnetic fields using intermolecular multiple quantum coherences

Strong and extremely homogeneous static magnetic field is usually required for high-resolution nu-clear magnetic resonance (NMR). However, in the cases of in vivo and so on, the magnetic field inho-mogeneity owing to magnetic susceptibility variation in samples is unavoidable and hard to eliminate by conventional methods such as shimming. Recently, intermolecular multiple quantum coherences (iMQCs) have been employed to eliminate inhomogeneous broadening and obtain high-resolution NMR spectra, especially for in vivo samples. Compared to other high-resolution NMR methods, iMQC method exhibits its unique feature and advantage. It simultaneously holds information of chemical shifts, multiplet structures, coupling constants, and relative peak areas. All the information is often used to analyze and characterize molecular structures in conventional one-dimensional NMR spec-troscopy. In this work, recent technical developments including our results in this field are summarized; the high-resolution mechanism is analyzed and comparison with other methods based on interactions between spins is made; comments on the current situation and outlook on the research directions are also made.

Utility of high-resolution anterior segment optical coherence tomography in the diagnosis and management of sub-clinical ocular surface squamous neoplasia

Background:To evaluate the frequency and characteristics of sub-clinical ocular surface squamous neoplasia(OSSN)detected by high-resolution anterior segment tomography(HR-OCT)in patients with clinically unapparent disease following topical treatment.Methods:A retrospective chart review of patients with OSSN identified through a pharmacy database at the Bascom Palmer Eye Institute from January 2013 to December 2018 was conducted.Patients undergoing primary therapy with topical 5-fluorouracil 1%(5-FU)(4 times a day for 7 days with a 21-day break)or interferon-alpha-2b(IFN)(4 times a day)were reviewed.Patients were separated into two groups.Group 1 included individuals whose clinical resolution of OSSN aligned with complete resolution on HR-OCT.Group 2(sub-clinical OSSN group)included individuals with clinical OSSN resolution but with features of persistent disease on HR-OCT.Patients excluded included those treated at an outside institution and those who used topical therapy as a surgical adjunct.Results:A total of 95 patients(95 eyes)were reviewed.Sub-clinical OSSN was detected at a frequency of 17%in our study patients(n=16 patients,9 treated with 5-FU and 7 treated with IFN).In the 16 individuals,the mean time to clinical resolution was 3.6±1.0 cycles for 5-FU and 4.0±0.0 months for IFN.An additional 2.1±0.8 cycles for 5-FU and 1.2±0.4 months for IFN were needed to achieve HR-OCT resolution of OSSN.Recurrence in Group 1 was noted in 10 patients(12%)while no recurrences occurred in Group 2,the cohort with subclinical disease that received the extended medical therapy.The mean follow-up was 24.0±17.9 months.Conclusion:We found that at least 17%of individuals with apparent clinical resolution of OSSN have sub-clinical disease detected on HR-OCT.This information can be used to optimize treatment and extend therapy past the point of clinical resolution.

High-resolution subsurface articular cartilage imaging based on Fourier-domain common-path optical coherence tomography

We demonstrate the subsurface imaging of an articular cartilage using Fourier-domain common-path optical coherence tomography. The bare fiber probe integrated with a hypodermic needle provides the rigidness required to perform lateral scanning with less microscale bending. By submerging both the probe and the specimen into saline solution, we not only reduce the beam divergence, but also increase the signal-to-noise ratio compared with the measurement in free space. Our system can differentiate the characteristic cartilage zones and identity various micro-structured defects in an ex vivo chicken knee cartilage, thus demonstrating that it could be used to conduct early arthritis diagnosis and intraoperative endo-microscopy.

RFI Detection for Multichannel HRWS SAR System Based on Spatial Cross Correlation

Multichannel high-resolution and wide-swath(HRWS)imaging is an advanced digital beamforming technique for future synthetic aperture radar(SAR)systems.However,radio frequency interference(RFI)is a critical concern for HRWS SAR missions,which distorts measure-ments and produces image artifacts.In this paper,the spatial cross-correlation coefficients of multichannel HRWS SAR signals are investigated for RFI detection.It is found when the two channels are correlated,RFI-polluted areas present lower coherence values than non-polluted areas in the same scenarios,which makes previous methods fail.Further,this paper studies the case of two fully decorrelated channels to maximize the coherence difference among RFI and target echoes,and RFI detection is realized by exploiting the anomaly value of coherence.Experimental results of real air-borne multichannel SAR data demonstrate that the RFI can be detected successfully.

相干体技术及其在油气勘探中的应用

相干体技术是近几年才发展完善的一项用于辅助解释的分析技术,主要用于解决复杂断裂带的断裂性质和预测裂缝发育带等地质问题。利用相干体技术预测出了塔里木盆地桑塔木、塔里木盆地克拉2和松辽盆地大情字井三维地震工区的碳酸盐岩裂缝发育带,识别出了岩性异常体的边界、小断层和断层间的关系,准确而有效地解决了常规地震解释中遇到的断裂组合问题。

基于小波变换的地震相干体算法研究

基于计算相干体算法 ,提出了用模拟地震子波的小波函数 (或高分辨导数小波函数 )的小波变换 ,得到分频瞬时相位 ,再计算相干体的相干体算法 1和用小波变换得到的实、虚部 (相当Hilbert变换 )计算相干体的相干体算法 2 .在油田构造解释中 ,为了突出小断层特征 ,用分频计算出的相干体进行重构 .实际资料计算表明 ,相干体算法 2较K .J.Marfurt相干体算法抗噪声能力强 ;相干体算法 1较相干体算法 2在实际应用中效果更明显 .

C_1相干算法及其在三维地震勘探解释中的应用

作者在文中详细讨论了二维和三维 C1相干算法。根据三维 C1相干算法的特点 ,结合三维地震数据体的特点 ,考虑到三维地震勘探在各大矿区的全面普及 ,针对三维地震资料开发出了一套实用的应用程序进行相干处理和解释。通过对实际三维地震资料的处理 ,分析结果表明 ,C1相干技术对三维地震资料的构造。

基于小波变换的地震相干体算法的应用

基于 Bahorich M和 Marfurt K J的相干算法 ,本文提出了利用小波域分频计算瞬时特征参数计算相干体的方法。根据研究的断层特征 ,用分频计算相干体进行重构。

相干体技术算法改进及其在TJH地区的应用

相干体技术是近年来地震勘探在资料解释方面的重要突破。与原来揭示地下异常体的方法相比 ,相干体可以更清楚地识别断层和地层特征。由于相干体是通过三维地震数据体计算得到 ,用传统方法计算需要运行较长时间。笔者在理论分析的基础上 ,提出了改进的相干体算法 ,开发了相应的软件 ,并在大港油田TJH地区得到了成功应用。

趋势面分析与相干体技术在火山岩预测中的应用

根据近年来的研究成果,火山岩顶面在形态上主要呈穹窿状,形成局部隆起的构造圈闭,可利用趋势面分析的方法寻找火山口隆起的分布.火山岩气藏往往是复合型气藏,它不仅受火山口的构造控制,还与有利的火山岩储层密切相关,可利用相于体切片技术来圈定有利储层的分布范围.通过这两种技术的结合,既可确定火山口的分布又可圈定有利储层的分布范围,成为近期井位部署的重要技术手段,对火山岩气藏的预测具有普遍意义.

断裂系统精细分析技术

断裂系统精确解释是精确构造和岩性分析的基础。概要介绍了利用地震资料断裂系统解释的多种方法的演变过程和相互联系 ,分析了它们的优缺点 ,阐述了三代相干体、倾角、方位角、方差及混沌等增强不连续的属性计算方法 ,给出了属性计算结果细线化的具体算法与应用实例。最后 。

相干体技术在火山岩预测中的应用

火山岩气藏地质特征复杂,岩相变化快,物性变化大,地震响应特征复杂,规律性差,预测困难。三维相干技术可以通过检测同相轴的不连续性,对断层、特殊岩性体进行识别。在松辽盆地北部徐家围子断陷深层火山岩的研究中,利用体属性多算子相干分析技术计算了高分辨率相干体、倾角体和方位角体,并采用HLS(色调、光亮度和饱和度)彩色模型显示这些地震属性体;然后结合三维可视化技术对火山岩的分布范围进行了预测。在相干体切片上,断层清楚,火山口和火山岩体分布范围清晰。

利用地震数据分频相干技术检测火山岩裂缝

针对在全频带地震剖面上小断层特征不明显,而在单频地震剖面上断层特征非常明显的特点,本文采用分频相干数据体分析技术,基于单频相干解释,借鉴信号重构的部分思路,提出了地震数据分频相干技术。主要内容包括:分频数据的处理、解释,分频相干数据的处理、解释,分频相干数据的融合、重构。利用地震数据分频相干技术对XS井区火成岩储层裂缝进行了检测。结果表明,利用分频相干数据体的多尺度分辨率特性可以识别一些常规数据难以发现的小断裂和裂缝发育带,且高频相干数据体对裂缝的反映更为清晰、准确,相干融合数据反映了更丰富的裂缝发育带信息,且与HTI各向异性裂缝检测结果相吻合。

煤田采区三维地震精细构造解释方法

虽然煤田三维地震勘探已经过了十多年的发展,但构造解释问题仍是目前需要解决的主要问题之一.随着三维地震资料解释方法的不断发展,小波分析技术、相干体技术、地震属性技术、图像处理等提高解释精度的方法相继在地震勘探领域中得到应用.另一方面,由于煤矿采区三维地震勘探资料一般具有高信噪比和高分辨率的特点,为做好三维地震资料精细构造解释提供了物质基础.本文结合小波分析技术、相干体技术、地震属性技术等多种方法,结合两个采区的实例,对小断层和小规模陷落柱做了精细构造解释.解释结果显示联合使用以上几种解释技术,能提高三维地震资料的构造解释精度和可靠信.

多属性分析技术在桑塔木油田断块油气藏中的应用

桑塔木油田三叠系T_Ⅲ油组经过二十多年开发,近年来注水生产效果差,同一断块内单井原始油水界面不一致的矛盾日益凸显,导致油田挖潜难度大。通过GeoEast解释系统多窗口倾角扫描、构造导向滤波、相干体、方差体、构造体曲率、边缘检测等多属性综合分析,进行桑塔木油田微小断层精细解释。经动态试井资料验证,断层解释精度高、可靠性好。根据断层精细刻画结果,对桑塔木油田断块重新划分,解决了桑塔木油田以往同一断块内单井油水界面不一致的问题。对断块油藏进行评价,结合GeoEast系统烃类检测属性,部署完钻5口井,均获成功。