帕米尔─西昆仑地震带强震活动的规律性特征

分析了帕米尔─西昆仑带的强震活动规律，指出该带强震活动在时间轴上可划为６个活动幕，在空间上可划为３个优势分布区域，地震活动水平呈西强东弱态势，并且存在强震从帕米尔向东南方向沿地震带作定向迁移规律，文章对此现象作出了物理解释．     

A laboratory study of directional spectra with maximum likelihood method─I Developing wind wave

INTRODUCTIONDirectionalspectraofwind-generatedwavesareveryimportanttotheresearchrelatedto1.InstituteofPhysicalOceanography,OceanUniversityofQingdao,Qingdao266003,China2.ResearchinstituteforAppliedMechanics,KyUshuUniversity,Kasuga816,Japanwindwaves.Theyfindapplicationinfieldsasdiverseasbasicair-seainteraction,practicalwaveforecasting,satellitesurveillanceandengineeringdesignofmarinestructuresandvehicles.Sincethepioneeringworkofthestereowaveobservationproject(Coteetal.11960),alotofeff…     

海浪方向谱估计方法的比较

分别利用数值模拟和实测资料对目前被认为分辨力较高的最大似然法(MLM)、扩展本征矢方法(EEV)、扩展最大滴方法(EMEP)以及贝叶斯方法(BDM)等四种海浪方向谱估计方法的可靠性进行了分析,从不同频率、不同噪声水平和不同方向集中度三个角度检验其再现性、稳定性和实用性,结果表明MLM、EEV和BDM大致给出相同的方向分布,其中BDM的再现性最好,但实用性逊于MLM和EEV,EMEP由于稳定性差,不适用于实测资料的分析.     

Directional spectrum of ocean waves from array measurements using phase/time/path difference methods

Wave direction has for the first time been consistently, accurately and unambiguously evaluated from array measurements using the phase/time/path difference (PTPD) methods of Esteva in case of polygonal arrays and Borgman in case of linear arrays. We have used time series measurements of water surface elevation at a 15-gauge polygonal array, in 8 m water depth, operational at the CERC's Field Research Facility at Duck, North Carolina, USA. Two modifications have been made in the methodology. One modification is that we use the true phase instead of the apparent phase, the other modification being that estimates of wave direction are registered only if the relevant gauges in the array are coherent at 0.01 significance level. PTPD methods assume that in a spectral frequency band the waves approach from a single direction, and are simple, expedient and provide redundant estimates of wave direction. Using Esteva's method with the above modifications, we found that at Duck: (i) the directions of swell and surf beat, when energetic swell is present, conform to the schematic diagram of surf beat generation given by Herbers et al., (ii) surf beat of remote origin occurs when the significant wave height, H_mo, falls below 0.41 m, (iii) the surf beat of remote origin is not normally incident at the shore contrary to Herbers et al. In fact we found that the surf beat of remote origin is incident at angles in excess of 45° with respect to the shore normal, and (iv) the surf beat of remote origin is largely trans-oceanic in origin.     

Simulation of directional waves in a numerical basin by a desingularized integral equation approach

A numerical solution is developed to investigate the generation and propagation of small-amplitude water waves in a semi-infinite rectangular wave basin. The three-dimensional wave field is produced by the prescribed “snake-like” motion of an array of segmented wave generators located along the wall at one end of the tank. The solution technique is based on the boundary element approach and uses an appropriate three-dimensional Green function which explicitly satisfies the tank-wall boundary conditions. The Green function and its derivatives which appear in the integral equation formulation can be shown to be slowly convergent when the source and field points are in close proximity. Therefore, when computing the velocity potentials on the wave generators, the source points are chosen outside the fluid domain, thereby ensuring the rapid convergence of these functions and rendering the integral equations non-singular. Numerical results are shown which illustrate the influence of the various wavemaker and basin parameters on the generated wave field. Finally, the complete wave field produced by the diffraction of oblique waves by a vertical circular cylinder in a basin is presented.     

Modelling of multipeaked directional wave spectra

An approach for modelling of multipeaked directional wave spectra is proposed. For model identification, a numerical optimization technique that uses the random linear search algorithm is applied. This technique allows the fitting of spectral models to measured or hindcast data. The HIPOCAS hindcast data for North Atlantic are used for an application study.     

基于偏微分方程的定向插值在偏移成像中的应用

对于射线类偏移成像来说,求解射线追踪系统中所涉及的属性值不在网格节点上的插值计算问题是一个非常重要的环节,它影响到求解走时、路径和振幅信息的计算效率和精度,进而影响到整个偏移成像的质量和效率.本研究根据速度模型的空间梯度特点,考虑被插值点处速度的梯度在横向和纵向的分布特征,构建基于速度梯度空间变化的偏微分方程算法,将近...     

定向钻进技术的发展与应用

定向钻进技术已有近百年的历史,随着的资源钻采井孔深度的不断增加,近几年该技术发展很快。讨论定向钻进技术包括基本内涵与最新拓展,对于更好的理解与推广应用这项技术具有重要意义。论文讨论了定向钻进的定义,概述了钻孔设计、测斜技术、测斜数据计算、测斜数据传输,特别是纠斜新技术的发展如自动垂直与自动导向钻进新技术等。简要介绍了目前定向钻进技术的应用领域与钻孔类型。提出了适用于深部地质钻探的定向钻进全孔轨迹主动控制的概念与实施措施。     

View-illumination effects on hyperspectral vegetation indices in the Amazonian tropical forest

Because of the pointing capability of the Hyperion/Earth Observing-One (EO-1) to improve the revisit time of the scene, temporal series of narrowband vegetation indices (VIs) can be generated to study the phenology of the Amazonian tropical forests. In this study, 10 selected narrowband VIs calculated from Hyperion nadir and off-nadir data and from different view directions (forward scattering and backscattering) were analyzed for their sensitivity to view-illumination effects along the dry season on the Seasonal Semi-deciduous Forest. Data analysis was also supported by PROSAIL modeling to simulate the spectral response of this forest type in both directions. Hyperion and PROSAIL results showed that the Enhanced Vegetation Index (EVI) and Photochemical Reflectance Index (PRI) were the two more anisotropic VIs, whereas the Normalized Difference Vegetation Index (NDVI), Structure Insensitive Pigment Index (SIPI) and the Vogelmann Red Edge Index (VOG) were comparatively less sensitive to view-illumination effects. When compared to the other VIs and because of the greater dependence on the near-infrared (NIR) reflectance, EVI showed a different spectral behavior. EVI increased from forward scattering to backscattering and with decreasing solar zenith angle (SZA) towards the end of the local dry season, due to reduction in shading and enhancement of the illumination effects. On the other hand, PRI was higher with increasing shading in the forward scattering direction, as deduced from the PROSAIL simulation. Results emphasized the importance of taking into account bidirectional effects when analyzing temporal series of VIs collected over tropical forests by imaging spectrometers with pointing capability or even by multispectral sensors with large field-of-view (FOV).     

水平定向钻穿越施工钻井液压力分析

孔壁稳定是水平定向钻进铺管成败的关键。影响孔壁稳定的主要因素是钻井液压力及其性能。通过对水平孔中钻井液和地层压力平衡机理以及孔壁周围应力位移的分析,结合摩尔强度准则得出了孔壁稳定时钻井液的允许压力区间公式,并对该区间进行修正得出了地层不单一以及地下水存在情况下的钻井液允许压力区间公式。通过对公式的计算分析得出孔壁稳定的钻井液允许压力区间的宽度随孔深的增加而扩大。