Applying Iterative Method to Solving High-Order Terms of Seafloor Topography

Abstract

We introduce an iterative inversion method to address the problems in high-order seafloor topography inversion using gravity data (gravity anomaly and vertical gravity gradient anomaly), such as the difficulty in computing the equation and the uniqueness of the calculation results. A part of the South China Sea is selected as the experimental area. Considering the coherence and admittance function of gravity topography and vertical gravity gradient topography, the inversion band of the gravity anomaly and vertical gravity gradient anomaly in the study area is 30?km–120?km. Seafloor topography models of different orders are constructed using an iterative method, and the performance of each seafloor topography model is analyzed against ETOPO1 and other seafloor topography models. The experimental results show that as the inversion order increases, the clarity and richness of seafloor topographic expression continuously improve. However, the accuracy of seafloor topography inversion does not improve significantly when the inversion order exceeds a certain value, which is related to the contribution of high-order seafloor topography to gravity information. The results show that the accuracy of BGT4 (inversion model constructed by the gravity anomaly) is slightly poorer than that of BVGGT4 (inversion model constructed by the vertical gravity gradient anomaly) in areas with complex topography, such as multi-seamounts and trenches, and the results are generally better in areas with flat seafloor topography.     

等幅疲劳三参数P—S—N曲线族最优拟合法

对于给定的等幅疲劳成组试验数据 ,利用三参数幂函数方程来描述P -S -N等幅曲线。通过线性拟合相关系数的最优化来确定其中三个系数 ,采用割线法进行最优化求解。该方法具有迭代收敛快、拟合精度高的特点     

预修正快速傅里叶变换高阶边界元方法在波浪对物体作用问题中的应用

边界元方法被广泛应用于波浪对海上婕筑物作用领域,但由于传统边界元方法的存储量和计算量均为未知量的平方量级,很难满足大范围多未知量问题的计算需要.本文基于高阶边界元方法,应用预修正快速傅里叶变换方法,使计算量与存储量分别降低至O(NlogN)和O(N)量级,并得到一个连续的压强分布以适应结构设计的要求,同时可以通过使用满...     

A simple and effective model for Jones matrix to evaluate the transmission performance of Savart polariscope

Starting from the wave normal tracing treatment in the Savart polariscope that relates the Jones matrix to its transmission performance, this paper establishes a simple and effective model for the Jones matrix at an arbitrary incidence in the spatial domain. Analytical expressions of all the matrix components are determined with the consideration of all the main impact factors. This model needs only a few parameters hence it is convenient to be employed to evaluate the propagation performance of any birefringent optical system. The simulated results obtained with it demonstrate that this model gives a precise representation of the characteristic of light propagation in the Savart polariscope. This would provide useful suggestions for the design, calibration, and performance improvement of any other birefringent polarisation element and optical system.     

海水中胶体有机碳的测定──高温燃烧法和紫外/过硫酸钾法的比较

利用切向超滤(cross-flow ultrafiltration)技术对海水中胶体有机碳(COC)和真溶解有机碳(UOC)进行了分离,并分别用高温燃烧法和紫外/过硫酸钾法对胶体有机碳和真溶解有机碳进行了测定。测定结果表明,切向超滤能定量分离海水中的胶体有机碳,高温燃烧法和紫外/过硫酸钾法对胶体有机碳和真溶解有机碳的测定结果没有明显的系统误差,表明这两种方法的氧化效率基本相同,胶体粒子的存在,对紫外/过硫酸钾法的氧化效率没有显着影响。     

An extension of general identities for 3D water-wave diffraction with application to the Diffraction Transfer Matrix

Interaction theories are used in numerous branches of physics to efficiently evaluate wave scattering by multiple obstacles. An example of these interaction theories is the direct matrix method introduced by Kagemoto and Yue [1], which enables fast computation of three-dimensional water-wave multiple-scattering problems. The building block of interaction theories is a mathematical operator that encapsulates the mapping between incident and scattered waves. This operator is generally referred to as T-matrix and satisfies both reciprocity and energy identities. In some branches of physics, such as acoustics and electromagnetism, these identities are well established; in hydrodynamics, however, they have only been derived for a T-matrix that maps two-dimensional incident and scattered water waves. In three dimensions, water waves can be represented as a series expansion of cylindrical eigenfunctions. In this paper, we use this representation of water waves to derive the reciprocity and energy identities satisfied by the T-matrix of the direct matrix method, known as Diffraction Transfer Matrix (dtm). The identities derived herein represent an extension of existing general relations between two diffraction solutions. We show that this extension can be applied to verify the accuracy of the dtm entries, thereby increasing the reliability of existing schemes for computing the dtm. We present results for the dtm of two geometrically different isolated obstacles, as well as for the dtm of an asymmetric array. Finally, we demonstrate that the results presented herein can be extended to floating bodies found in a wide range of ocean engineering problems.     

NURBS高阶面元法在多体水动力分析中应用

当位于海上的多个浮体距离相近时,它们间将产生显著的水动力相互作用。使用NURBS(非均匀有理B样条)高阶面元法进行多体水动力分析,速度势用任意阶的B样条函数近似,物面用NURBS曲面表示,由于水动力与几何表示相分离,就可以方便地实现计算机辅助设计与水动力分析的集成。对截断圆柱与椭球间的水动力相互作用和半潜式平台与箱型驳船间的水动力相互作用的计算显示此种方法可以对多体间的水动力相互作用给出准确的分析,计算时间和占用内存大幅减少。     

Application of potentiometric method using a cell without liquid junction to underway pH measurements in surface seawater

This study evaluated a method to carry out underway pH measurements of surface seawater by means of a cell without liquid junction using glass electrodes for hydrogen and sodium ions as follows:

Glass-electrode-Na+

Test solution (reference solution)

H+-glass-electrode

Full-size table

Table options

     

11.

市场比较法在养殖用海价格评估中的应用初探     

崔东阳  金颖  吴桂敏  唐琳 《海洋科学》2019,43(12)

开展养殖用海基准价格评估,有利于推动海域资源市场化配置,形成良性的养殖用海交易市场。本研究介绍了市场比较法的原理及适用范围,并基于养殖用海的特点,以深圳市开放式养殖用海为评估对象,运用市场比较法测算其海域基准价值,并分析各评估方法在养殖用海评估中的适用性和局限性。     

12.

Assessment of acoustic iterative inverse method for bubble sizing to experimental data     

Bok Kyoung Choi  Bong -Chae Kim  Byoung -Nam Kim  Suk Wang Yoon 《Ocean Science Journal》2006,41(4):195-199

Comparative study was carried out for an acoustic iterative inverse method to estimate bubble size distributions in water. Conventional bubble sizing methods consider only sound attenuation for sizing. Choi and Yoon [IEEE, 26(1), 125–130 (2001)] reported an acoustic iterative inverse method, which extracts the sound speed component from the measured sound attenuation. It can more accurately estimate the bubble size distributions in water than do the conventional methods. The estimation results of acoustic iterative inverse method were compared with other experimental data. The experimental data show good agreement with the estimation from the acoustic iterative inverse method. This iterative technique can be utilized for bubble sizing in the ocean.     

13.

A simple experimental method to regain the mechanical behavior of naturally structured marine clays     

《Applied Ocean Research》2019

Quantitative laboratory studies on the structural behavior of natural intact marine clays require a large number of identical natural samples leading to an expensive and challenging task. This study proposes a simple method to reconstruct an artificial structured marine clay as the state of its natural intact clay at both macro and micro levels. For this purpose, the Shanghai marine clay is selected and mixed with low cement contents (1–6%). The clay-cement slurry is mixed in a container with the ice-covered sides at a low temperature about 0 ± 2 °C to postpone the hydration reactions until consolidation began. The purpose of adding cement is to generate the inter-particle bonding and structure in reconstituted samples. Initially, the reconstituted samples are consolidated under the in situ stress of 98 kPa and then under the pre-consolidation pressure of 50 kPa. Mechanical characteristics such as compression index, yield stress, unconfined compression strength, shear strength ratio, and the stress paths from triaxial tests are compared with natural intact clay accordingly. Scanning electron microscope and mercury intrusion porosimetry analyses are also performed to analyze the microstructure of clays for comparison. Furthermore, the proposed method is also examined by using natural intact marine clays of different locations and characteristics.     

14.

Numerical evaluation of a subsea equipment installation method designed to avoid resonant responses     

《Applied Ocean Research》2019

Several methods have been employed to install the different types of subsea equipment that are required for offshore oil and gas production systems. More recently, the increasing development of oil fields at remote, ultra-deepwater scenarios has been requiring heavier and more complex subsea equipment. In such scenarios the usual installation methods have been facing increasing challenges, including resonance effects associated to the dynamic behavior of the cable-equipment system. In this context, after presenting a review of the state-of-the-art of installation methods for subsea equipment, this work presents a methodology for the design and evaluation of an installation method based on the combination of steel wire and polyester ropes. The goal is to obtain a feasible and safe installation method that can avoid resonance effects along all phases of the lowering procedure, without the need of specialized devices such as heave compensators, and using only simpler installation vessels such as standard tugboats instead of more expensive and specialized vessels (such as drilling rigs). The method is evaluated by numerical simulations for case studies considering representative metocean data for Brazilian ultra-deepwater scenarios, following a methodology that considers the random characteristic of actual sea states by employing an irregular spectral representation. The results indicate that the method may indeed be feasible for the deepwater installation of heavier equipment, potentially being more cost-effective especially for remote locations where other more complex methods might become inefficient.     

15.

A method to calculate design tide levels on the basis of numerical model of tidal current and its application     

WANG Zhen  WEI Youxing  ZHANG Changkuan 《海洋学报(英文版)》2012,31(4):24-30

In order to determine the design tide levels in the areas without measured tide level data, especially in the areas where it is difficult to measure tidal levels, a calculation method based on a numerical model of tidal current is proposed. The essentials of the method are described, and its application is illustrated with an example. The results of the application show that the design tide levels calculated by the method are close to those determined by long-time measured tide level data, and its calculation precision is high, so it is feasible to use the method to determine the design tide levels in the areas.     

16.

冷扩散法提取沉积物中的酸可溶硫化物及其在中国边缘海区的应用   总被引：1，自引：0，他引：1  

蒲晓强  钟少军  刘飞  徐丽君  瞿成利  刘刚  陶小晚 《海洋科学》2006,30(11):93-96

为了快速而有效地对中国边缘海区沉积物中的酸可溶硫化物(AVS)进行研究,冷扩散法被引入。用冷扩散法提取不同体积硫化物溶液中的AVS,所得到的AVS含量与所加溶液体积的相关性较好,说明此方法具有较好的提取效果。在中国边缘海不同典型海域的浅表层沉积物中,利用冷扩散法对AVS进行了分析:胶州湾李村河口AVS的浓度在0.4~120.1μmol/g之间;南黄海西北部陆架在0~11.1μmol/g之间;南海北部陆坡一柱状样沉积物中多数样品<1μmol/g。结果显示不同典型海域沉积物中AVS的分布差别较大,符合不同环境沉积物中AVS含量的一般规律。因此冷扩散法作为一种有效的AVS提取方法,值得在研究中使用与推广。     

17.

等密度面P矢量方法在南海环流诊断研究中的应用   总被引：1，自引：0，他引：1  

王桂华  许建平 《海洋学报》2002,24(1):124-128

海流的直接测量困难而又昂贵,而采用一些数学模式间接获取流场信息也有其局限性,比如初始场、边界条件和黏性参数的确定存在较大的人为性和不确定性等问题.然而,随着海上现场观测资料的增多,近年来利用温盐资料诊断环流的研究工作也越来越多,例如采用β螺旋方法[1]、P矢量方法[2]和改进逆模式方法[3]等等;这些诊断研究成果,在一定程度上弥补了海洋环流研究中,由于海流观测资料不足而带来的缺陷.在众多诊断环流计算方法中,近年来用得较多的是P矢量方法[2,4,5],1).     

18.

深水S-lay管道形态和内力分析的分段解析方法     

梁辉  赵岩  岳前进 《海洋工程》2019,37(1):75-83

考虑深水S型铺设中离散均布托辊对上弯段管道的支撑作用,提出了管道铺设形态和内力的分段解析求解方法,通过迭代搜索算法确定管道最佳反弯点和升离点的位置,结合刚性悬链线理论和欧拉梁弯曲理论,推导了管道的变形和内力的解析表达式。依据所建立的分段解析方法编制了相应的数值计算程序,以某3 000 m水深铺设12英寸管道为例,计算了管道形态和内力响应,与商用有限元软件的数值分析结果进行对比,表明了分段解析方法的准确性和有效性。建立的方法具有较高的计算效率,为进一步开展S型铺设参数的优化或可靠性研究提供了有力的手段。     

19.

A finite difference method for effective treatment of mild-slope wave equation subject to non-reflecting boundary conditions     

《Applied Ocean Research》2015

A numerical model for coastal water wave motion that includes an effective method for treatment of non-reflecting boundaries is presented. The second-order one-way wave equation to approximate the non-reflecting boundary condition is found to be excellent and it ensures a very low level of reflection for waves approaching the boundary at a fairly wide range of the incidence angle. If the Newman approximation is adopted, the resulting boundary condition has a unique property to allow the free propagation of wave components along the boundary. The study is also based on a newly derived mild-slope wave equation system that can be easily made compatible to the one-way wave equation. The equation system is theoretically more accurate than the previous equations in terms of the mild-slope assumption. The finite difference method defined on a staggered grid is employed to solve the basic equations and to implement the non-reflecting boundary condition. For verification, the numerical model is then applied to three coastal water wave problems including the classical problem of plane wave diffraction by a vertical circular cylinder, the problem of combined wave diffraction and refraction over a submerged hump in the open sea, and the wave deformation around a detached breakwater. In all cases, the numerical results are demonstrated to agree very well with the relevant analytical solutions or with experimental data. It is thus concluded that the numerical model proposed in this study is effective and advantageous.     

20.

复经验正交函数方法对湛江南三岛海滩剖面季节变化动态特征研究     

李志强  刘长华  杜健航  吴光林  张会领 《海洋工程》2012,30(2):79-86

利用复经验正交函数(CEOF)分析方法对湛江南三岛2009年2月22日至2010年4月21日期间的实测海滩剖面数据进行了分析。结果表明该海滩的季节变化有3个主要模态:第1模态是海滩风暴剖面和涌浪剖面之间的相互转换,其贡献占总方差的71.18%。其原因是海区侵蚀性风暴大浪和建设性涌浪的交替变化。第2模态是平均高、低潮线之间的地形变化,其原因是由于潮汐变化导致入射波浪冲流活动范围变化,占总方差的14.28%。第3模态是侵蚀大浪过后的水下沙坝向岸迁移,并受潮汐影响在滩面上摆动,占总方差的6.80%。最后指出必须重视风暴对华南海滩演变季节性过程的影响。     

市场比较法在养殖用海价格评估中的应用初探

开展养殖用海基准价格评估,有利于推动海域资源市场化配置,形成良性的养殖用海交易市场。本研究介绍了市场比较法的原理及适用范围,并基于养殖用海的特点,以深圳市开放式养殖用海为评估对象,运用市场比较法测算其海域基准价值,并分析各评估方法在养殖用海评估中的适用性和局限性。     

Assessment of acoustic iterative inverse method for bubble sizing to experimental data

Comparative study was carried out for an acoustic iterative inverse method to estimate bubble size distributions in water. Conventional bubble sizing methods consider only sound attenuation for sizing. Choi and Yoon [IEEE, 26(1), 125–130 (2001)] reported an acoustic iterative inverse method, which extracts the sound speed component from the measured sound attenuation. It can more accurately estimate the bubble size distributions in water than do the conventional methods. The estimation results of acoustic iterative inverse method were compared with other experimental data. The experimental data show good agreement with the estimation from the acoustic iterative inverse method. This iterative technique can be utilized for bubble sizing in the ocean.     

A simple experimental method to regain the mechanical behavior of naturally structured marine clays

Quantitative laboratory studies on the structural behavior of natural intact marine clays require a large number of identical natural samples leading to an expensive and challenging task. This study proposes a simple method to reconstruct an artificial structured marine clay as the state of its natural intact clay at both macro and micro levels. For this purpose, the Shanghai marine clay is selected and mixed with low cement contents (1–6%). The clay-cement slurry is mixed in a container with the ice-covered sides at a low temperature about 0 ± 2 °C to postpone the hydration reactions until consolidation began. The purpose of adding cement is to generate the inter-particle bonding and structure in reconstituted samples. Initially, the reconstituted samples are consolidated under the in situ stress of 98 kPa and then under the pre-consolidation pressure of 50 kPa. Mechanical characteristics such as compression index, yield stress, unconfined compression strength, shear strength ratio, and the stress paths from triaxial tests are compared with natural intact clay accordingly. Scanning electron microscope and mercury intrusion porosimetry analyses are also performed to analyze the microstructure of clays for comparison. Furthermore, the proposed method is also examined by using natural intact marine clays of different locations and characteristics.     

Numerical evaluation of a subsea equipment installation method designed to avoid resonant responses

Several methods have been employed to install the different types of subsea equipment that are required for offshore oil and gas production systems. More recently, the increasing development of oil fields at remote, ultra-deepwater scenarios has been requiring heavier and more complex subsea equipment. In such scenarios the usual installation methods have been facing increasing challenges, including resonance effects associated to the dynamic behavior of the cable-equipment system. In this context, after presenting a review of the state-of-the-art of installation methods for subsea equipment, this work presents a methodology for the design and evaluation of an installation method based on the combination of steel wire and polyester ropes. The goal is to obtain a feasible and safe installation method that can avoid resonance effects along all phases of the lowering procedure, without the need of specialized devices such as heave compensators, and using only simpler installation vessels such as standard tugboats instead of more expensive and specialized vessels (such as drilling rigs). The method is evaluated by numerical simulations for case studies considering representative metocean data for Brazilian ultra-deepwater scenarios, following a methodology that considers the random characteristic of actual sea states by employing an irregular spectral representation. The results indicate that the method may indeed be feasible for the deepwater installation of heavier equipment, potentially being more cost-effective especially for remote locations where other more complex methods might become inefficient.     

A method to calculate design tide levels on the basis of numerical model of tidal current and its application

In order to determine the design tide levels in the areas without measured tide level data, especially in the areas where it is difficult to measure tidal levels, a calculation method based on a numerical model of tidal current is proposed. The essentials of the method are described, and its application is illustrated with an example. The results of the application show that the design tide levels calculated by the method are close to those determined by long-time measured tide level data, and its calculation precision is high, so it is feasible to use the method to determine the design tide levels in the areas.     

冷扩散法提取沉积物中的酸可溶硫化物及其在中国边缘海区的应用

为了快速而有效地对中国边缘海区沉积物中的酸可溶硫化物(AVS)进行研究,冷扩散法被引入。用冷扩散法提取不同体积硫化物溶液中的AVS,所得到的AVS含量与所加溶液体积的相关性较好,说明此方法具有较好的提取效果。在中国边缘海不同典型海域的浅表层沉积物中,利用冷扩散法对AVS进行了分析:胶州湾李村河口AVS的浓度在0.4~120.1μmol/g之间;南黄海西北部陆架在0~11.1μmol/g之间;南海北部陆坡一柱状样沉积物中多数样品<1μmol/g。结果显示不同典型海域沉积物中AVS的分布差别较大,符合不同环境沉积物中AVS含量的一般规律。因此冷扩散法作为一种有效的AVS提取方法,值得在研究中使用与推广。     

等密度面P矢量方法在南海环流诊断研究中的应用

海流的直接测量困难而又昂贵,而采用一些数学模式间接获取流场信息也有其局限性,比如初始场、边界条件和黏性参数的确定存在较大的人为性和不确定性等问题.然而,随着海上现场观测资料的增多,近年来利用温盐资料诊断环流的研究工作也越来越多,例如采用β螺旋方法[1]、P矢量方法[2]和改进逆模式方法[3]等等;这些诊断研究成果,在一定程度上弥补了海洋环流研究中,由于海流观测资料不足而带来的缺陷.在众多诊断环流计算方法中,近年来用得较多的是P矢量方法[2,4,5],1).     

深水S-lay管道形态和内力分析的分段解析方法

考虑深水S型铺设中离散均布托辊对上弯段管道的支撑作用,提出了管道铺设形态和内力的分段解析求解方法,通过迭代搜索算法确定管道最佳反弯点和升离点的位置,结合刚性悬链线理论和欧拉梁弯曲理论,推导了管道的变形和内力的解析表达式。依据所建立的分段解析方法编制了相应的数值计算程序,以某3 000 m水深铺设12英寸管道为例,计算了管道形态和内力响应,与商用有限元软件的数值分析结果进行对比,表明了分段解析方法的准确性和有效性。建立的方法具有较高的计算效率,为进一步开展S型铺设参数的优化或可靠性研究提供了有力的手段。     

A finite difference method for effective treatment of mild-slope wave equation subject to non-reflecting boundary conditions

A numerical model for coastal water wave motion that includes an effective method for treatment of non-reflecting boundaries is presented. The second-order one-way wave equation to approximate the non-reflecting boundary condition is found to be excellent and it ensures a very low level of reflection for waves approaching the boundary at a fairly wide range of the incidence angle. If the Newman approximation is adopted, the resulting boundary condition has a unique property to allow the free propagation of wave components along the boundary. The study is also based on a newly derived mild-slope wave equation system that can be easily made compatible to the one-way wave equation. The equation system is theoretically more accurate than the previous equations in terms of the mild-slope assumption. The finite difference method defined on a staggered grid is employed to solve the basic equations and to implement the non-reflecting boundary condition. For verification, the numerical model is then applied to three coastal water wave problems including the classical problem of plane wave diffraction by a vertical circular cylinder, the problem of combined wave diffraction and refraction over a submerged hump in the open sea, and the wave deformation around a detached breakwater. In all cases, the numerical results are demonstrated to agree very well with the relevant analytical solutions or with experimental data. It is thus concluded that the numerical model proposed in this study is effective and advantageous.     

复经验正交函数方法对湛江南三岛海滩剖面季节变化动态特征研究

利用复经验正交函数(CEOF)分析方法对湛江南三岛2009年2月22日至2010年4月21日期间的实测海滩剖面数据进行了分析。结果表明该海滩的季节变化有3个主要模态:第1模态是海滩风暴剖面和涌浪剖面之间的相互转换,其贡献占总方差的71.18%。其原因是海区侵蚀性风暴大浪和建设性涌浪的交替变化。第2模态是平均高、低潮线之间的地形变化,其原因是由于潮汐变化导致入射波浪冲流活动范围变化,占总方差的14.28%。第3模态是侵蚀大浪过后的水下沙坝向岸迁移,并受潮汐影响在滩面上摆动,占总方差的6.80%。最后指出必须重视风暴对华南海滩演变季节性过程的影响。