Boussinesq-type modelling using an unstructured finite element technique

A model for solving the two-dimensional enhanced Boussinesq equations is presented. The model equations are discretised in space using an unstructured finite element technique. The standard Galerkin method with mixed interpolation is applied. The time discretisation is performed using an explicit three-step Taylor–Galerkin method. The model is extended to the surf and swash zone by inclusion of wave breaking and a moving boundary at the shoreline. Breaking is treated by an existing surface roller model, but a new procedure for the detection of the roller thickness is devised. The model is verified using four test cases and the results are compared with experimental data and results from an existing finite difference Boussinesq model.     

Third order contribution to the wave-making resistance of a ship at finite depth of water

This paper presents a potential based boundary element method for solving a nonlinear free surface flow problem for a ship moving with a uniform speed in finite depth of water. The free surface boundary condition is linearized by the systematic method of perturbation in terms of a small parameter up to third order. The surfaces are discretized into flat quadrilateral elements and the influence coefficients are calculated by Morino's analytical formula. Dawson's upstream finite difference operator is used in order to satisfy the radiation condition. The second order solution gives better result than the first or third order solution. So the present method with the second order solution can be adopted as a powerful tool for the hydrodynamic analysis of the thin ship in finite depth of water.     

A new approach for the solution of the two-dimensional guillotine-cutting problem in ship production

A new approach has been developed for the arrangement of rectangular pieces in plates for the guillotine-cutting problem as encountered in ship production and similar manufacturing processes. The algorithm is quite novel in the sense that instead of making preliminary specifications and ignoring all the alternative arrangements, as is the case for most of the current models, it selectively considers feasible arrangements by eliminating the majority of the probable arrangements that render the problem insolvable. Intermediate steps of the algorithm produce results which cannot be obtained through integer programming. Losses are distributed to the minimum number of plates. The number of arrangement plans is also minimized. Overall the solution of the problem has been drastically simplified to allow even hand calculations instead of long computer runs.     

Monotone Regression and Correction for Order Relation Deviations in Indicator Kriging

The indicator kriging (IK) is one of the most efficient nonparametric methods in geo-statistics. The order relation problem in the conditional cumulative distribution values obtained by IK is the most severe drawback of it. The correction of order relation deviations is an essential and important part of IK approach. A monotone regression was proposed as a new correction method which could minimize the deviation from original quintiles value, although, ensuring all order relations.     

制图综合中移位算法概述分析

本文首先对移位算法的发展史进行简要介绍,然后,在其基础上,根据各移位算法的思想特征,对各移位算法进行归纳,将其划分为七类,并对每一类算法的核心思想进行详细论述,最后,对各类移位算法进行评价,分析其优缺点,总结各类算法中的可借鉴思想,为更好地实现移位奠定基础。     

曲靖盆地生物气成藏条件及主控因素分析

曲靖盆地新近系茨营组第三段的晚期生物气藏是新近系沉积之后,喜山运动时期各种成藏条件有效的时空配置的结果.在讨论曲靖盆地构造和沉积演化的基础上,综合分析了生物气源、储集层和盖层、圈闭形成以及天然气输导等成藏条件,阐述了生物气晚期聚集成藏条件的时空匹配关系.指出自第四纪以来,生物气源岩持续高效的产气作用是生物气成藏的物质保障,气藏的形成是生物气连续的补充大于逸散动态平衡的产物;背斜构造、砂岩上倾尖灭和砂岩透镜体圈闭是该区主要的圈闭类型;断裂和不整合面是沟通生物气源岩到圈闭的垂向和侧向输导通道,茨营组的连通砂岩体是生物气近距离运移的输导层.蔡家冲组大套湖相暗色泥岩的生物产气效率、断裂的垂向输导能力和圈闭的保存条件及其在时空上的动态配置是生物气晚期成藏的主控因素.     

Taxonomical and Biogeochemical Investigation of Elements in Holocene Mollusk Shells in the South and Southwestern Marmara Basin,Turkey

Concentrations of some heavy metals and trace elements such as Cr, Ga, Ni, Zn, Mo, Cu, Pb, Yb, Y, Nb, Ti, Sr, Ba, Mn, Sc, Co, V, Zr, Fe, Al, W, Se, Bi, Sb, As, Cd in recent mollusk shells and factors affecting their distribution and deposits collected from various depths in the southern and southwestern parts of the Marmara Sea are investigated. The distribution of the elements in the shells is categorized into four groups. Of these, concentrations of 12 elements （As, Bi, Cd, Co, Ga, Mo, Nb, Sb, Se, Sc, W and Yb） are below zero [（0.053-0.79）×10^-6]; concentrations of seven elements （Cr, Ni, Pb, V, Y, Zr and Cu） are （1.0-6.0）×10^-6; concentrations of four elements （Ti, Mn, Ba and Zn） are 10- 20×10^-6; and concentrations of five elements （Si, Al, Fe, Mg and Sr） are （47.44-268.11）×10^-6. The taxonomic characteristics of the 29 elements were studied separately in mollusk shells such as Chamalea gallina （Linn6）, Pitar rudis （Poli）, Nassarius reticulatus （Linn6）, Venerupis senescens （Coocconi）, Mytilus galloprovincialis （Lamarck）, Mytilaster lineatus （Gemelin in Linne） and Chlamys glabra. It was found that, in mollusk taxonomy, the elements have unique values. In other words, element concentrations in various mollusk shells depend mainly on the taxonomic characteristics of mollusks. In various bionomic environments different element distributions of the same species are attributed to the different geochemical characters of the each environment. Data obtained in this study indicate that the organisms are the most active and deterministic factors of the environment.     

The Bayesian detection of discontinuities in a polynomial regression and its application to the cycle-slip problem

This paper deals with the problem of detecting and correcting cycle-slips in Global Navigation Satellite System (GNSS) phase data by exploiting the Bayesian theory. The method is here applied to undifferenced observations, because repairing cycle-slips already at this stage could be a useful pre-processing tool, especially for a network of permanent GNSS stations. If a dual frequency receiver is available, the cycle-slips can be easily detected by combining two phase observations or phase and range observations from a single satellite to a single receiver. These combinations, expressed in a distance unit form, are completely free from the geometry and depend only on the ionospheric effect, on the electronic biases and on the initial integer ambiguities; since these terms are expected to be smooth in time, at least in a short period, a cycle-slip in one or both the two carriers can be modelled as a discontinuity in a polynomial regression. The proposed method consists in applying the Bayesian theory to compute the marginal posterior distribution of the discontinuity epoch and to detect it as a maximum a posteriori (MAP) in a very accurate way. Concerning the cycle-slip correction, a couple of simultaneous integer slips in the two carriers is chosen by maximazing the conditional posterior distribution of the discontinuity amplitude given the detected epoch. Numerical experiments on simulated and real data show that the discontinuities with an amplitude 2 or 3 times larger than the noise standard deviation are successfully identified. This means that the Bayesian approach is able to detect and correct cycle-slips using undifferenced GNSS observations even if the slip occurs by one cycle. A comparison with the scientific software BERNESE 5.0 confirms the good performance of the proposed method, especially when data sampled at high frequency (e.g. every 1 s or every 5 s) are available.     

评价生物气生成量、生成期的元素平衡法及其应用

生物气的生成期对其成藏有至关重要的制约作用,但目前国内外尚缺少可信、有效方法来对此进行评价。针对这一难题,考虑到无论生物气的生成机理如何,都是一个有机元素之间的物质平衡过程,文章探索并建立了评价生物气生成量的元素平衡法,并利用松辽盆地大量的实际分析数据,对这一评价方法(模型)进行了标定和应用。结果表明,松辽盆地生物气的生成可能主要发生在800m以浅的埋深条件下;区内源岩生物气的生成量约为285.0×1012m3;生物气的主要生成期在嫩江组沉积末期之前。     

Numerical simulation of a stratigraphic model

A multi-lithology diffusive stratigraphic model is considered, which simulates at large scales in space and time the infill of sedimentary basins governed by the interaction between tectonics displacements, eustatic variations, sediment supply, and sediment transport laws. The model accounts for the mass conservation of each sediment lithology resulting in a mixed parabolic, hyperbolic system of partial differential equations (PDEs) for the lithology concentrations and the sediment thickness. It also takes into account a limit on the rock alteration velocity modeled as a unilaterality constraint. To obtain a robust, fast, and accurate simulation, fully and semi-implicit finite volume discre tization schemes are derived for which the existence of stable solutions is proved. Then, the set of nonlinear equations is solved using a Newton algorithm adapted to the unilaterality constraint, and preconditioning strategies are defined for the solution of the linear system at each Newton iteration. They are based on an algebraic approximate decoupling of the sediment thickness and the concentration variables as well as on a proper preconditioning of each variable. These algorithms are studied and compared in terms of robustness, scalability, and efficiency on two real basin test cases.