Defining the concept of stratigraphic grade and applying it to stratal (reservoir) architecture and evolution of the slope-to-basin profile: An outcrop perspective

Stratigraphic grade is the similarity of the morphology of successive slope-to-basin profiles in a genetically related depositional system. In this article we use data collected from regional cross-sections of six depositional systems, stratal architecture derived from outcrops of the Lewis Shale (Wyoming, USA), and the Ross Sandstone (Ireland), and supplementary outcrop and subsurface data from other depositional systems to determine how stratigraphic grade relates to stratal (reservoir) architecture in deepwater systems.Four methods are developed that collectively define stratigraphic grade: (1) regional stacking patterns of fourth-order stratigraphic surfaces, (2) the relationship between the trajectory of the shelf edge (T_se) and the trajectory of the depocenter (T_d) for fourth-order stratigraphic units, (3) morphology of the slope-to-basin profiles of fourth-order stratigraphic surfaces, and (4) the similarity of the morphologies of slope-to-basin profiles of fourth-order surfaces in a system (σ_s, σ_r). Several characteristics of stratigraphic (reservoir) architecture of fourth-order stratigraphic cycles are related to stratigraphic grade: (1) longitudinal distribution of sandstone in fourth-order cycles, (2) location of maximum sandstone relative to the depocenter of fourth-order cycles, (3) lengths of fourth-order submarine fans, and (4) longitudinal and vertical distribution of architectural elements. Stratigraphic grade is thus a predictor of reservoir architecture and can thereby be used to reduce the uncertainty in the interpretation of subsurface data.The concept of stratigraphic grade is useful in understanding the stratigraphic evolution of deepwater systems. Most deepwater systems analyzed in this study initiated as out-of-grade and temporally evolved to graded systems over a time span of millions of years. Systems rarely evolve from graded to out-of-grade. First-order controls on stratigraphic grade are determined to be angle of slope, tectonically forced changes in angle of slope during deposition, and sediment supply.     

Mining online footprints to predict user’s next location

Social media applications are widely deployed in mobile platforms equipped with built-in GPS tracking devices, and these devices have led to an unprecedented collection of geolocated data (geo-tags). Geo-tags, along with place names, offer new opportunities to explore the trajectory and mobility patterns of social media users. However, trajectory data captured by social media are sparsely and irregularly spaced and therefore have varying degrees of resolution in both space and time. Previous studies on next location prediction are mostly applicable for detecting the upcoming location of a moving object using dense GPS trajectories where locations are recorded at regular time intervals (e.g., 1 minute). Additionally, point features are commonly used to represent the locations of visits, but using point features cannot capture the variability of human mobility. This article introduces a new methodology to predict an individual’s next location based on sparse footprints accumulated over a long time period using social networks, and uses polygons to represent the location corresponding to the physical activity area of individuals. First, the density-based spatial clustering algorithm is employed to discover the most representative activity zones that an individual frequently visits on a daily basis, and a polygon-based region is then derived for each representative activity zone. A sparse mobility Markov chain model considering both the movements and online behaviors of the social media user is trained and used to predict the user’s next location. Initial experiments with a group of Washington DC Twitter users demonstrate that the proposed methodology successfully discovers the activity regions and predicts the user’s next location with accuracy approaching 78.94%.     

A framework of spatio-temporal trajectory simplification methods

We present an extensible, generic, spatio-temporal trajectory simplification framework that modularises trajectory simplification into the stages of normalising, ranking, and reduction. We combine a range of ranking strategies and scoring heuristics – some from the literature and some new – into our framework modules and create a variety of spatio-temporal trajectory simplification methods. These trajectory simplification methods are experimented upon using real world and synthetic datasets, measuring running time, geometric displacement, and region-of-interest visitation. The results indicate that our proposed framework creates a number of efficient and effective spatio-temporal trajectory simplification methods.     

2013—2016年海口市空气质量特征及典型个例污染物来源分析

根据海南省环境科学研究院提供的海口站2013—2016年逐日空气污染数据,统计分析了海口市空气质量状况。综合应用高低空环流场、AQI指数结合MODIS卫星蓝光气溶胶厚度图,采用HYSPLIT轨迹聚类分析法、潜在源贡献因子法和浓度权重轨迹分析方法,重点分析了2013年12月海口空气污染的的主要输送路径,并探讨了首要污染物PM_2.5和O₃的潜在源区。结果表明：冬夏季风风向转换是海口发生空气污染的最主要气象原因,且首要污染物为PM_2.5,其次是PM₁₀和O₃;海口市空气质量达标率在97.1%,总体较好,AQI指数呈逐年下降趋势;值得关注的是,O₃呈逐年稳定上升趋势。大气污染物浓度受污染物排放和环流场共同影响,海口污染日对应的地面天气形势主要有3种类型,冷高压、变暖高压脊和台风外围下沉气流。此次污染过程中污染源是来自北方地区污染物长距离输送影响的结果。污染物个例分析中,首要污染物PM_2.5潜在源区主要集中在湖南和江西的交界处、广东沿海地区、广西北部、江西和福建的交界处以及浙江中部地区,这些潜在源区气团沿着轨迹1、2和4通过长距离输送到海口。海口O₃质量浓度贡献较大的区域主要集中在湖南和江西的交界处、粤西一带,主要沿着轨迹2将内陆地区的污染源输送到海口。     

HDD铺管竣工管道轨迹曲线拟合方法

随着社会发展,工程施工中越来越要求文明施工,尤其在一些沿海城市,精确地控制导向钻孔轨迹的非开挖施工已经显示出了强大的生命力。由于非开挖施工的特殊性,验收工作成为了困扰性的问题．如何才能得知施工轨迹是不是和设计要求的轨迹一致,基于此本文提供了一种方法来检验非开挖施工轨迹是否合格。     

Vehicle trajectory modelling with consideration of distant neighbouring dependencies for destination prediction

Vehicle trajectory modelling is an essential foundation for urban intelligent services. In this paper, a novel method, Distant Neighbouring Dependencies (DND) model, has been proposed to transform vehicle trajectories into fixed-length vectors which are then applied to predict the final destination. This paper defines the problem of neighbouring and distant dependencies for the first time, and then puts forward a way to learn and memorize these two kinds of dependencies. Next, a destination prediction model is given based on the DND model. Finally, the proposed method is tested on real taxi trajectory datasets. Results show that our method can capture neighbouring and distant dependencies, and achieves a mean error of 1.08 km, which outperforms other existing models in destination prediction significantly.     

VIV trajectories of an elastically mounted sphere

In this paper, vortex-induced vibrations (VIV) of an elastically mounted sphere with two linear degrees of freedom have been experimentally studied. The dynamic response analysis shows that, for the range of reduced velocity from 2 to 14 here investigated, the sphere exhibits similar amplitudes and frequencies compared to the tethered sphere, and Modes I and II are detected. A new application of the phase average approach allowed extrapolating the periodic trajectory pattern from the experimental trajectories. In particular, more than one dominant harmonic component is observed in the streamwise oscillation, so the sphere trajectories are significantly different from the traditional figure-of-eight shape. The main difference is that these trajectories are not self-intersecting. Based on the experimental observations, an analytical model of the trajectory is built and discussed.     

Design and implementation of time efficient trajectories for autonomous underwater vehicles

This paper discusses control strategies adapted for practical implementation and efficient motion of autonomous underwater vehicles (AUVs). For AUVs we would like efficiency in both the measured time and the energy consumption, the mission dictating the weight to put on each of these cost. As a first approach to this problem, we focus in this paper on time minimization. Based on the structure of the time optimal trajectories and of the pure motions, we develop an algorithm to design time efficient trajectories corresponding to piecewise constant thrust arcs with few actuator switchings. We do that by solving a new optimization problem where the unknowns are the time period between two actuator switchings as well as the values of the constant thrust arcs. We apply a direct method to compute the solutions numerically. With our algorithm, we gain considerable computational time. Moreover, with as few as three actuator switchings, the duration of our trajectories is within 10% of the optimal trajectories. Since our control strategies have a simple structure they can be implemented on a test-bed vehicle. For the experiments displayed in this paper we use a spherical underwater vehicle which exhibits with almost no preference of direction or orientation for movement; this gives us a very controllable and versatile vehicle.     

Trajectory analysis and inferences on geometric relationships of an Early Triassic prograding clinoform succession on the northern Barents Shelf

A sedimentary succession studied along three parallel seismic lines details a platform-edge progradation of 21–36 km in a northwesterly direction across the northwestern Barents Shelf. The intra-shelf clinoform succession is bounded at bottom and top by Base Olenekian and Early Ladinian seismic reflectors. The ca 800 m thick succession can be resolved into seven distinct clinothems. The system is characterized by an early sub-horizontal platform-edge trajectory with extensive progradation, limited relative sea level rise and restricted accommodation. Thereafter the system outlines a largely ascending trajectory, marking a major rise in relative sea level and creation of significant accommodation. The platform-edge appears to back-step along one line suggesting that relative sea level rise out-paced sediment influx and preserved a clinothem with a trajectory characterized by accretionary transgression. Thereafter the trajectory is overall ascending regressive, with some variation of the trajectory angle, culminating in a flat and finally descending trajectory with oblique clinoforms outlining extensive progradation and another period of limited accommodation. The clinoforms downlap onto a succession of basin-floor deposits which appear to comprise at least two separate periods of deposition, forming two separate units. The first five clinothems downlap onto the first basin-floor unit. The shift to downlap onto the second unit occurs around the second period of extensive platform-edge advance, suggesting limited accommodation promoted bypass of significant amounts of sediment to the basin floor.The Gardarbanken High has been considered an obstacle to Early Triassic sediment progradation in this part of the basin. This inference can be corroborated based on the seismic attributes, which show sediment infill and onlap near the High. The influence is also noticeable in the reduced slope relief near the High, indicating that the basin floor was topographically higher. However, other geometric attributes cannot provide any definitive measures of structural influence.The thickness of preserved topsets and the distance from the platform-edge to the toe pinch-out point of each clinothem is found to be inversely proportional. This relationship is most marked in the fully developed sigmoidal clinoforms, whereas the link appears weaker in the oblique clinoforms. A near-perfect correlation between clinothem average vertical thickness (the average sedimentary rock accumulation within the clinothem) and advance of the toe is found, with only a relatively close relationship between clinothem average vertical thickness and advance of the platform-edge. In the studied system it therefore appears the advance of the toe is governed solely by sediment influx while the advance of the platform-edge is also influenced by relative sea level.     

双台风生消过程涡旋能量、水汽输送相互影响的三维物理图像

重点研究“莫拉克”台风发展并登陆台湾,以及“天鹅”台风消亡阶段两者相互作用的问题。通过诊断分析发现“莫拉克”与“天鹅”移动过程存在双台风涡旋互旋、吸引与合并现象。采用双台风中心连线的垂直剖面移动坐标分析法可揭示出双台风涡度、风场三维结构,演变过程中双台风的涡度、动能强度呈反向变化关系,在双台风生消过程中,动能、位涡场分布存在显著“连体”通道特征。并揭示出双台风涡旋各自生、消过程水汽、动能可能存在的相互影响及其涡旋结构变化的内在关联。对“天鹅”消亡、“莫拉克”引发暴雨过程,采用Flexpart-WRF耦合模式模拟“质点群”轨迹,模拟结果再现了双台风生消阶段“天鹅”台风水汽“粒子群”向“莫拉克”低层气旋式输入通道,且在“莫拉克”涡旋高层反气旋式卷出的三维立体动态图像。通过剔除“天鹅”台风涡旋数值模拟试验进一步印证了“天鹅”台风趋于消弱过程其水汽、动能输送为“莫拉克”台风发展与维持做出了一定贡献。基于以上合成分析、轨迹和数值模拟技术综合分析提出了能揭示“天鹅”消亡、“莫拉克”发展过程能量、水汽输送相互影响的三维物理图像。