地震旋回体的概念及应用

张军华 ,王永刚 ,杨国权 ,赵勇 ,黄国平 .地震旋回体的概念及应用 .石油地球物理勘探 ,2 0 0 3,38(3) :2 81～ 2 84本文首先研究了理论模型的旋回特征 ,给出了不同模型的时频响应。然后 ,对时频滤波器的设计和显示参数的设置进行了讨论 ,得出采用三角形滤波器、频带取值为 1.2倍频程、优势频率递归取 1.0 5倍频程可以得到理想结果的结论。作为应用实例 ,文中以 TN、QMQ两个不同岩性的工区为例 ,重点对砂泥岩和奥陶系灰岩储层的地震旋回特征进行了分析 ,取得了较好的应用效果。

HHT方法在研究地震旋回体中的应用

HHT(Hilbert-Huang变换)是一种近年才发展起来的非线性信号处理方法,具有明确的物理意义、高度的精确性和自适应性,但在地震信号处理中尚未得到广泛的应用。简要介绍了HHT的方法原理,然后分析了模型信号和地震旋回体的HHT时频谱。结果表明:HHT对模型信号的识别能力强,且不同类型地震旋回体与其HHT时频谱之间存在对应关系,这为地震层序的划分以及进一步的沉积相分析提供理论依据。

短时傅立叶变换在研究沉积旋回地质体中的应用

针对地震波信号通常是非平稳信号,Fourier变换不适用于分析非平稳信号、不能反映局部时间信号的频谱特征的特点,而利用短时Fourier变换能够反映信号在任意局部时间范围的频率特征,以便满足研究信号在不同时间位置局部性质的要求。分别从正反旋回的地质模型出发,通过作理论记录以及用短时Fourier变换分析波在沉积旋回地层中传播时的频率变化来确定沉积旋回的类型。

优选膝关节压缩感知三维体素各向同性快速自旋回波采集序列成像加速系数

目的筛选膝关节压缩感知(CS)三维体素各向同性快速自旋回波采集(VISTA)中等权重序列成像的最优加速系数。方法对9名健康志愿者行左膝CS 3D VISTA中等权重序列成像,分别设定CS加速系数为4、6、8、10、12,比较各组图像膝关节各组织信噪比(SNR)、对比噪声比(CNR)和不同区域解剖结构评分。结果不同CS加速系数CS 3D VISTA图像中,软骨、关节液、肌肉和骨髓SNR差异均有统计学意义(P均<0.05),半月板和韧带SNR差异无统计学意义(P均>0.05);关节液-软骨、关节液-半月板、关节液-韧带和软骨-软骨下骨间CNR差异均有统计学意义(P均<0.05);股胫关节、股骨远端骨髓和膝后部肌肉解剖结构评分差异均有统计学意义(P均<0.001),髌股关节解剖结构评分差异无统计学意义(P>0.05)。CS加速系数为10时,膝关节各部位SNR值及各组织间CNR值均最高;CS加速系数为8及以上时,各部位图像解剖结构评分逐渐降低。结论CS 3D VISTA中等权重序列膝关节成像中,设定CS加速系数为8,可在成像时间、SNR、CNR及图像细节显示等方面达到较好平衡。

潍北凹陷砂砾岩体的地球物理特征研究

潍北凹陷下第三系孔店组沉积中砂砾岩体较为发育,由于地震资料质量较差,砂砾岩体的剖面特征及平面分布一直得不到较好的落实。从原始地震记录人手,分别进行了时频分析技术及均方根振幅(能量)技术处理,获得了相应的时频分析剖面及均方根振幅剖面。由时频特征确定了地震旋回体的存在,旋回体的横向变化揭示了砂砾岩体沉积环境的规律。均方根剖面能量团的变化反映了砂砾岩体的空间分布范围,揭示了研究区砂砾岩体沉积期多水系、多物源、纵向上多期叠置的沉积特征。

壳体地貌初论

壳体地貌是针对传统地貌学存在的基本问题，吸收和运用历史—因果论大地构造学说的理论观点和方法，将地貌成因因素和过程因素综合起来研究的一种地貌学理论和方法。本文运用成因—过程分析法，将地貌及其发展置于大地构造背景下加以研究，提出了地貌四要素和壳体地貌旋回的概念。并主张将侵蚀地貌过程和沉积地貌过程统一起来研究。

西峰油田长8油层组高分辨率层序地层分析

运用高分辨率层序地层学的短期基准面旋回原理,详细分析了鄂尔多斯盆地西峰油田长8油组辫状河三角洲前缘的叠加水下分流河道、复合式河口坝、叠加河口坝、滑塌体及浊积扇砂体短期基准面旋回的叠加样式及储层成因。研究表明这五类砂体明显受到基准面升降、可容纳空间和沉积物补给量比值的控制。在此基础上探讨了不同砂体组合在长8层序地层格架中的展布规律。

高分辨MRI大脑中动脉管壁改变与脑白质高信号相关因素分析

目的对急性脑梗死患者进行头部MRI影像筛查,探讨大脑中动脉管壁改变与大脑白质高信号严重程度的相关性,以及脑血管病相关危险因素对它们的影响。方法连续收集经DWI确诊的急性脑梗死患者86例,并应用头部MRI T_2、FLAIR及大脑中动脉管壁HRMR成像,记录患者病史资料、大脑中动脉管壁改变情况及脑白质高信号程度。依据有无大脑中动脉管壁改变以及脑白质高信号严重程度分别分析两者危险因素,并采用多因素回归分析两者的独立预测因素。结果排除3例图像质量不佳者,83例纳入研究。T_2FLAIR像中存在显著WMH(2分、3分)37例,不存在显著WMH(0分、1分)46例。WMH与年龄、mRs评分、高血压病、糖尿病及大脑中动脉粥样硬化管壁改变呈显著相关性(P<0.05)。多因素回归分析中,高血压病、大脑中动脉粥样硬化管壁改变与WMH密切相关。本研究组中存在严重的大脑中动脉粥样硬化管壁改变(2分、3分)38例,不存在(0分、1分)45例,其与年龄、高血压病和糖尿病差异有统计学意义。多因素回归分析显示年龄与大脑中动脉粥样硬化管壁改变严重程度密切相关。结论 WMH在脑血管病患者中有较高的发病率,并与年龄、mRs评分、高血压病、糖尿病及高分辨下大脑中动脉粥样硬化管壁改变密切相关。早期发现大脑中动脉粥样硬化管壁改变并采取适当的干预措施,对于预防WMH具有重要临床意义。

Sedimentary system characteristics and depositional filling model of Upper Permian——Lower Triassic in South Yellow Sea Basin

In the South Yellow Sea Basin,Mesozoic–Paleozoic marine strata are generally well developed with large thickness,and no substantial breakthroughs have been made in hydrocarbon exploration.Through research,it is believed that the Upper Permian–Lower Triassic can be regarded as a long-term base-level cycle.Based on drilling data,characteristics of the lithology–electric property combination cyclicity,and the special lithology,the long-term base-level cycle was divided into five medium-term base-level cycles(MC1–MC5).On this basis,the Permian–Triassic sedimentary systems and their filling model were analyzed in accordance with the change of base-level cycle and transition of sedimentary environment,as well as characteristics of the drilling sedimentary facies and seismic facies.The results show that there were six sedimentary systems(fluvial,delta,tidal flat,open platform,restricted platform,and continental shelf)developed in the Upper Permian–Lower Triassic,the sedimentary systems were distributed such that the water was deep in the northwest and shallow in the southeast,and there were two base-level cycle filling models(a relatively stable tidal flat facies and a rapidly transgressive continental shelf facies to stable platform facies)developed in the Upper Permian–Lower Triassic.These models can provide a basis for evaluation of the Mesozoic–Paleozoic hydrocarbon geology in the South Yellow Sea Basin.

Friction contact mechanisms of layered surface

In this paper,we firstly review the carbon layered surface prepared with electron cyclotron resonance (ECR) plasma sputtering. Secondly,the friction behavior of carbon layered surface under pin-on-disk testing is described. Furthermore,the contact stress evolution processes of layered surface with and without transfer layer during wear are given for understanding the contact mechanisms. Finally,a three-dimension (3D) local yield map of layered surface is introduced,which is useful to predict the possible contact mechanisms.

Dielectric Behavior of Oblate Spheroidal Particles：Application to Erythrocytes Suspensions

We have investigated the pressure effect on the eletrorotation (ER) spectrum of living cell suspensions byconsidering the particle shape effect. In particular, we consider coated oblate spheroidal particles and present a theoreticalstudy of ER based on the spectral representation theory. Analytic expressions for the characteristic frequency as wellas the dispersion strength can be obtained, thus simplifying the fitting of experimental data on oblate spheroidal cellsthat abound in the literature. From the theoretical analysis, we find that the cellshape, coating as well as materialparameters can change the ER spectrum. We demonstrate a good agreement between our theoretical predictions andexperimental data on human erthrocytes suspensions.

Heteroclinic bifurcations in attitude maneuver of coupled slosh-spacecraft with flexible appendage

In this paper, the chaotic dynamics in an attitude transition maneuver of a slosh-spacecraft coupled with flexible appendage in going from minor axis to major axis spin under the influence of dissipative effects due to fuel slosh and a small flexible appendage constrained to only torsional vibration is investigated. The slosh-spacecraft coupled with flexible appendage in attitude maneuver carrying a sloshing liquid is considered as multi-body system with the sloshing motion modeled as a spherical pendulum. The focus in this paper is that the dynamics of the liquid and flexible appendage vibration are coupled. The equations of motion are derived and transformed into a form suitable for the application of Melnikov’s method. Melnikov’s integral is used to predict the transversal intersections of the stable and unstable manifolds for the perturbed system. An analytical criterion for chaotic motion is derived in terms of system parameters. This criterion is evaluated for its significance to the design of spacecraft. The dependence of the onset of chaos on quantities such as body shape and magnitude of damping values, fuel fraction and torsional vibration frequency of flexible appendage are investigated. In addition, we show that a spacecraft carrying a sloshing liquid, after passive reorientation maneuver, will end up with periodic limit motion other than a final major axis spin because of the intrinsic non-linearity of fuel slosh. Furthermore, an extensive numerical simulation is carried out to validate the Melnikov’s analytical result.

Effects of power-law spectrum behaviors of nonthermal electrons on a ring-beam maser instability

The electron-cyclotron maser （ECM） emission driven by nonthermal electrons is one of the most crucial mechanisms responsible for radio emissions in magnetized planets, for the interplanetary medium （IPM） and for the laboratory microwave generation devices. Major astrophysical observations demonstrate that nonthermal electrons frequently have a negative power-law spectrum with a lower energy cutoff and anisotropic distribution in the velocity space. In this paper, the effects of power-law spectrum behaviors of electrons on a ring-beam maser emission are considered. The results show that the growth rates of O1 and X2 modes decrease rapidly for small A （the dispersion of momentum u）. Because of the lower energy cutoff behavior, the nonthermal electrons with large a still can excite the ECM instability efficiently. The present analysis also includes the effects of parameter β （βu0 is the dispersion of perpendicular momentum ui, u0 the average value of u） on the instability. The growth rate of X2 mode decreases with parameter v0 （v0 = u⊥o/uo, U⊥0 is the average value of u⊥）. But for O1 mode, the relationship between the growth rate and v0 is complicated. It also shows that the growth rates are very sensitive to frequency ratio Ω （frequency ratio of electron cyclotron frequency to plasma frequency）.

Nonadiabatic acceleration of plasma sheet ions related to ion cyclotron waves

The nonadiabatic acceleration of plasma sheet ions is important to the understanding of substorm energetic injections and the formation of ring current. Previous studies show that nonadiabatic acceleration of protons by magnetic field dipolarization is hard to occur at X>–10 RE because the time-scale of dipolarization(several minutes) is much larger than the gyroperiod of protons there(several seconds). In this paper, we present a case of nonadiabatic acceleration of plasma sheet ions observed by Cluster on October 30, 2006 at(XGSM, YGSM)=(-7.7, 4.7) RE. The nonadiabatic acceleration of ions is caused not by previously reported magnetospheric dipolarization but by the ultra low frequency(ULF) waves during magnetospheric dipolarization. The nonadiabatic acceleration of ions generates a new energy flux structure of ions, which is characterized by the usual energy flux increase of ions(28–80 ke V) and a concurrent energy flux decrease of ions in a lower energy range(10 e V–20 ke V). These new observations constitute a complete physical picture: The lower energy ions absorb the wave energy, and thus get accelerated to higher energy. We use a nonadiabatic model to interpret the ion energy flux variations. Both analytic and simulation results are in good agreement with the observations. This indicates that the nonadiabatic acceleration associated with ULF waves superposed on dipolarized magnetic field is an effective mechanism for ion energization in the near-Earth plasma sheet. The presented energy flux structures can be used as a proxy to identify the similar dynamic process.