Simulation of the interactions between gravity processes and contour currents on the Algarve Margin (South Portugal) using the stratigraphic forward model Sedsim

The margin of the Gulf of Cadiz is swept by an intermediate current the Mediterranean Outflow Water (MOW) flowing from the Mediterranean to the Atlantic. On the northern margin of the Gulf (Algarve Margin, South Portugal) the MOW intensity is low, and fine-grained contourite drifts are built up with an alongslope alignment. Recent sedimentological studies emphasize the presence of complex process interactions resulting in the formation of a unique depositional architecture. Alongslope processes related to contour currents generate contourite drift, while downslope processes form canyons and channels aligned on deep faults. This paper uses a combined oceanographic and geological dataset to simulate the different types of interactions between gravity processes and contour currents, which were evidenced on this margin. An extrapolation of the contour current intensity has been used based on the present day velocity field and sea-level fluctuations over the simulated geological time-scale. According to our model results, the construction of the contourite drift is closely linked to contour current velocities and directions, the types of sediments transported and the existing topography. Using modern sedimentological understanding of the area, we have correlated gravity flow's strongest activity to sea level lowstand periods mainly due to a closer connection between canyon's mouth and river or deltaic systems. The simulated gravity flows are initialized at different locations and times on the margin depending on the preserved lobes retrieved from seismic analysis. Their resulting morphological features are identified as perched-lobes with volumes and forms close to the ones observed on Portimão and Lagos Drifts. This study provides a process-based understanding of the construction of contourite system and a physical evaluation of the interactions between gravity flows perpendicular to the slope, and alongslope processes. In addition, it shows the influence of autocyclic factors in the construction of contourite sedimentation, which is important to consider in future sedimentary paleo-reconstruction interpretations.     

基于AutoCAD15的等值线圈的自动绘制方法

在AutoCAD15的环境下利用VBA（Visual Basic Application)宏语言编程实现等值线图自动绘制是一个崭新的课题。分析了该课题的意义。介绍了等值线绘制的原理以及方法和过程，并给出了由程序自动绘制的等值线实例。实例表明，该方法能够获得高质量的等值线圈。     

坡地开发中的植物篱技术

论述了植物篱在我国坡地开发中的地位、作用、选取标准及在坡地开发中的其它应用，认为植物篱应是控制川中丘陵遂宁组母质区水土流失的主要手段。     

深水牵引流沉积研究进展与展望

深水牵引流沉积是继深水重力流沉积之后发现的又一种新的深水沉积类型，目前已发现的深水牵引流沉积包括等深流沉积和内潮汐、内波沉积两种类型。综述了深水牵引流沉积的研究历史、现状与进展，指出了其存在的问题及发展趋势。     

Flow Discharge Modeling in Open Canals Using a New Fuzzy Modeling Technique (SMRGT)

The main goal of this study was to research the answer to two important questions in flow modeling; i) how to optimally design the cross‐section of an open channel for a given flow, and ii) in the case of selecting the fuzzy method for modeling, how to construct the membership functions (MFs) and fuzzy rules (FRs) such that the system yields the best results. The first question is answered in order to minimize difficulties in excavation and related costs by using the appropriate flow velocity. To provide the best answer researchers use several methods. The second question is answered in order to minimize model error. For this aim, there are many algorithms proposed by researchers in the literature. In this paper, the fuzzy logic method was used for open canal flow modeling. Furthermore, a simple membership function and fuzzy rule generation technique (SMRGT) is introduced, and used for fuzzy modeling. Two fuzzy models, each for different cross‐sectional shape, are presented in this study as an application of SMRGT. The comparison depends on various statistics, mean absolute relative error, and contour maps showed that the fuzzy models were successful in open channel flow modeling and SMRGT is useful for MF (membership function) and FR (fuzzy rule) generation.     

Historic reconstruction of reservoir topography using contour line interpolation and structure from motion photogrammetry

The geometry of impounded surfaces is a key tool to reservoir storage management and projection. Yet topographic data and bathymetric surveys of average-aged reservoirs may be absent for many regions worldwide. This paper examines the potential of contour line interpolation (TOPO) and Structure from Motion (SfM) photogrammetry to reconstruct the topography of existing reservoirs prior to dam closure. The study centres on the Paso de las Piedras reservoir, Argentina, and assesses the accuracy and reliability of TOPO- and SfM- derived digital elevation models (DEMs) using different grid resolutions. All DEMs were of acceptable quality. However, different interpolation techniques produced different types of error, which increased (or decreased) with increasing (or decreasing) grid resolution as a function of their nature, and relative to the terrain complexity. In terms of DEM reliability to reproduce area–elevation relationships, processing-related disagreements between DEMs were markedly influenced by topography. Even though they produce intrinsic errors, it is concluded that both TOPO and SfM techniques hold great potential to reconstruct the bathymetry of existing reservoirs. For areas exhibiting similar terrain complexity, the implementation of one or another technique will depend ultimately on the need for preserving accurate elevation (TOPO) or topographic detail (SfM).     

地震学预报方法在博克图5.6级地震研究中的应用

应用国家地震局 85 - 0 4 - 0 1课题提供的部分地震学预报地震方法对 1 980年和 1 981年博克图地震进行了研究。结果表明 ,该地震前后某些地震学预报项目出现了明显的异常变化。这些可作为监视该区地震活动的判定指标     

辅助导航中等值线匹配算法仿真试验研究

等值线（ICCP）匹配算法是辅助导航中的一个重要匹配算法,但目前缺乏本算法的系统仿真试验。本文对ICCP算法在地形辅助导航中的应用进行了正交实验设计,按照设计方案进行大量仿真研究。通过对仿真结果的分析,得出等值线匹配精度的主要因素。     

Contour scaling of a sandstone by salt weathering under simulated hot desert conditions

A laboratory study has been used to investigate relationships between salts and contour scaling—a weathering feature commonly observed on rock surfaces in salt-rich environments. Surface disaggregation and essentially surface-parallel cracks were produced in sandstone blocks using 10 per cent solutions of sodium sulphate and magnesium sulphate applied daily to single exposed surfaces for sixty days. A control block soaked once in saturated magnesium sulphate and subsequently wetted daily with distilled water showed extensive surface disaggregation, but no cracking. Both surface disaggregation and subsurface cracking were associated with relative concentrations of microcrystalline salt. A tentative model of contour scaling is proposed, which involves linking together potential cracks by salt-induced fracturing of intervening, crack-stopping grains. Further control blocks treated respectively with 10 per cent and saturated sodium chloride showed no evidence of subsurface cracking and only limited surface disaggregation of the ‘saturated’ block.     

The role of boundary conditions in the simulation of rotating,stratified turbulence

Abstract

In this paper we use the CASL method to explore the role of boundary conditions in determining the long-time behaviour of rotating, stratified, quasi-geostrophic turbulence. We find that initially two-dimensional (sufficiently tall) columns of potential vorticity (PV) break down through three-dimensional instability to give a fully three-dimensional flow consisting of ellipsoidal structures. This is the case both for rigid-lid (isothermal) vertical boundary conditions and for vertically periodic boundaries. However, the rigid boundary case gives rise to semi-ellipsoids at both the top and bottom boundaries, and, for sufficient domain depths, preferred depths for the formation of ellipsoids in the interior. By contrast, in the vertically periodic case, the distribution of ellipsoids is homogeneous in depth.

The role of the horizontal boundaries is indirect, but still significant. In all cases doubly periodic horizontal boundary conditions are imposed. We consider a range of initial conditions where in each case equal numbers of two-dimensional columns of positive and negative vorticity are used, taking up a fixed, but relatively small fraction of the domain (approximately 5%). Thus when there is only a small number of vortices, they have larger radius. When the initial number of vortices is small enough (i.e., when the radius is not small compared with the horizontal domain width), at long time there is a two-dimensionalisation giving rise to a single column of positive PV and a single column of negative PV, as has been observed in some previous simulations. We find the same phenomenon for both vertically periodic and rigid lid boundary conditions, but it occurs over a broader range of initial conditions in the vertically periodic case. However, in all cases fully three-dimensional final states are regained when the number of vortices is increased while keeping the fraction of the domain occupied by vortices fixed, i.e., when the vortex radius/domain width ratio is sufficiently small.