Barrier and compensation layers in the East China Sea

Climatology of the isothermal layer depth （ILD） and the mixed layer depth （MLD） has been produced from in-situ temperaturesalinity observations in the East China Sea （ECS） since 1925. The methods applied on the global are used to compute the ILD and the MLD in the ECS with a temperature criterion AT=0. 8 ℃ for the ILD, and a density criterion with a threshold △σθ corresponding to fixed △T=0. 8 ℃ for the MLD, respectively. With the derived climatology ILD and MLD, the monthly variations of the barrier layer （BL） and the compensation layer （CL） in the ECS are analyzed. The BL mainly exists in the shallow water region of the ECS during April-June with thickness larger than 15 m. From December to next March, the area along the shelf break from northeast of Taiwan Island to the northeast ECS is characterized by the CL. Two kinds of main temperature - salinity structures of the CL in this area are given.     

Motion compensation system for ocean profiling

The vertical profiles of ocean temperature and salinity measured with instruments lowered by cable from surface ships can be seriously affected by the nonuniform drop rate caused by ship motion. This paper describes a motion compensation system developed for conductivity, temperature, and depth profilers that significantly reduces the effect of ship motion on profiler drop rates, thereby enhancing the measurement capabilities of vertical profilers.     

Ecosystem services assessment and compensation costs for installing seaweed farms

In a global context of promotion and expansion of blue growth initiatives, the development of activities such as aquaculture calls for the assessment of the potential impacts on biodiversity at different levels and associated services. This paper presents an assessment of the potential impact of the installation of seaweed farms on ecosystem services and the induced compensation costs. Biophysical and socioeconomic indicators have been developed for helping decision makers to select the most suitable locations. The approach considers a multi-criteria approach based on Geographical Information Systems (GIS) and Habitat Equivalency Analysis (HEA). The former is used to obtain biophysical ecosystem services and socioeconomic indicators and the latter to evaluate the costs required to compensate the loss of cultural and provisioning ecosystem services. A case-study in the Normand-Breton (Saint Malo) Gulf, France, illustrates this method through the analysis of hypothetical locations of seaweed farms. Results highlight the differences between alternative locations regarding biophysical constraints (in terms of distance and depth), potential risks of conflicts with existing uses, impacts on habitats and the ecosystem services delivered, and compensation costs. This case-study illustrates the flexibility of this approach which can be further adapted to include other indicators in order to deliver integrated information to coastal planners.     

上海市湿地损失补偿机制博弈分析

我国河口湿地保护与开发之间的矛盾非常突出,针对长江口地区人地矛盾,采用博弈论的方法探讨长江口湿地补偿问题,并以上海市南汇边滩为例,基于多层博弈模型,从湿地补偿资金的来源、运作方式、投向及产生的生态补偿效益进行一个全过程研究。在第一层博弈分析中提出上海市通过圈围滩涂湿地解决人地矛盾,只有通过降低造地成本才能不违反国家相关政策,风险最小。第二层博弈的结果是基层湿地管理单位力图节约造地成本,并获得来自上海市政府的激励性补偿。第三层博弈带来上海市和基层单位在利益上的双赢,但是却损害了湿地的环境功能。为了弥补环境损失,第四层博弈把南汇边滩造地收益中降低的成本用于补偿其它具有湿地功能的湿地,表面上是补偿湿地面积,实质是补偿生态系统的平稳过渡。通过连续分层博弈过程给予了一个处理河口湿地补偿问题的可选方案。     

Active heave compensation on drill-ships in irregular waves

This paper investigates a possible method for heave compensation on board deep-water drill-ships subjected to irregular-wave excitation. The proposed system exploits favorable interaction of coupled oscillators to achieve the desired results. This study examines an actively controlled compensator which performs well over a large wave-frequency bandwidth. Performance under certain operating conditions is investigated using a dynamic model. Simple mathematical arguments and frequency-domain computations in an irregular wave spectrum show the proposed heave compensation system to be effective within the bounds of linearity.     

Nonlinear control of an active heave compensation system

Heave motion of a vessel or a rig has an adverse impact on the response of a drill-string or a riser. To compensate for heave motion, passive and active devices are usually used. Active heave compensators, in which a control system is an essential part, allow conducting operations under more extreme weather conditions than passive ones. This paper presents a constructive method to design a nonlinear controller for an active heave compensation system using an electro-hydraulic system driven by a double rod actuator. The control system reduces the effect of the heave motion of the vessel on the response of the riser by regulating the distance from the upper end of the riser to the seabed. The control development is based on Lyapunov's direct method and disturbance observers. The paper also includes a method to select the control and disturbance observer gains such that actuator saturations are avoided. Stability of the closed loop system is carefully examined. Simulation results illustrate the effectiveness of the proposed control system.     

A novel CFAR tonal detector using phase compensation

A novel tonal detector is presented in this paper. The detector uses phase compensation for detecting sinusoidal signal with unknown amplitude, frequency, and phase in complex Gaussian noise with unknown variance. We analyze the statistical properties of the discrete Fourier transform (DFT) of the observations and consider the leakage effect. Then we develop the detector by using generalized likelihood ratio test (GLRT). The new detector fully utilizes the phase information of the signal and achieves constant false alarm rate (CFAR) property. Theoretical analysis and simulation results show its improvement in detection performance.     

Heave compensation and formation strength evaluation from downhole acceleration measurements while coring

In order to evaluate the efficiency of heave compensation in the Ocean Drilling Program, we developed a device measuring the acceleration of the core barrels. First results show that heave compensation limits bit motion to 10% of the surface heave. We also use the acceleration data to characterize the formation. On rotary corers, acceleration amplitudes decrease with increasing hardness of the formation. Comparison with geophysical logs shows that this relationship can resolve cm-scale features. On piston corers, the maximum acceleration is characteristic of the sediment shear strength. Easy and fast to deploy, this tool allows to characterize formations before any sample analysis.     

水下机器人主动升沉补偿系统研究

介绍一种基于水下机器人常规液压收放绞车的主动升沉补偿系统,利用加速度传感器获得母船的升沉运动信号,控制绞车的运转来降低母船的升沉运动对水下机器人的影响。通过理论计算建立主动升沉补偿系统的数学模型,仿真分析绞车运动对水下机器人升沉运动的补偿效果,并利用主动升沉补偿系统实验台验证基于常规液压收放绞车的主动升沉补偿方案的可行性。     

A computationally efficient Doppler compensation system forunderwater acoustic communications

A Doppler compensation system is presented which is suitable for high-data-rate acoustic communication between rapidly moving platforms such as autonomous underwater vehicles. The proposed approach provides a generic preprocessor to conventional adaptive receiver structures with only a marginal increase in computational load and hardware cost. The preprocessor employs a novel Doppler estimation technique and efficient sample rate conversion to remove Doppler shift induced by platform velocity and acceleration. Performance predicted by simulation is compared to that of sea trials of a prototype communication system in the North Sea. Successful communication is demonstrated at 16 kbit/s with a transmitting platform moving at up to ±2.6 m/s     

A comparison between the international and US regimes regulating oil pollution liability and compensation

Despite its search for a universal oil spill liability and compensation regime, the maritime community continues to face the dichotomy between the US approach and that adopted by the rest of the world. Both regimes have a two-tier structure that is composed of a liability scheme and a fund scheme. However, the significant differences between the two regimes can be found in the liability limit of a responsible party and the scope of recoverable damages. This explains the reasons why the US took a unilateral approach instead of participating in the international one. In the short term, it seems that the current dual system will continue. In the long term, however, it would be desirable to establish a unified international regime which would enable all actors to direct their energies toward handling oil spills rather than grappling with unilateral legislation in individual jurisdictions of the world. Even before an establishment of a unified international regime, harmonization between the two regimes would not only be helpful for the ultimate unification, but also desirable for transactions of the industries concerned under the current dual system.     

海洋绞车主动升沉补偿控制系统建模与仿真分析

针对海洋绞车主动升沉补偿系统的控制要求,通过对主动升沉补偿系统的控制机理进行分析,于Simulink软件中搭建海洋绞车主动升沉补偿控制系统的仿真模型。根据负载所处不同海况,设置相应仿真参数,得出负载在不同海况下主动升沉补偿控制系统的补偿特性,绘制了负载在升沉补偿作用下的位移响应曲线及补偿时电机转速响应曲线,并与无升沉补偿作用下的仿真结果进行对比。仿真结果表明,该主动升沉补偿控制系统具备理想的补偿精度。将主动升沉补偿控制系统应用于海洋绞车进行模拟试验,得到了电驱动海洋绞车主动升沉补偿控制系统在四级模拟海况下的试验数据。试验结果表明该主动升沉补偿控制系统满足补偿能力设计要求。研究可为海洋绞车主动升沉补偿控制系统补偿性能的改进与完善提供参考。     

海底电缆鬼波压制及陷频补偿方法研究

受到海底、自由表面等强反射界面的影响, 在海底电缆采集的地震资料中鬼波干扰往往非常发育, 在频谱中表现为明显的陷频现象, 严重影响地震剖面的质量, 给后期的处理解释带来困难。为克服这一困难, 根据海底电缆双检(陆检和水检)对下行波场的不同响应, 在深入研究伪多道匹配滤波技术的基础上提出了伪多道双检合成方法。与传统的求取反射系数的双检合成方法不同, 该方法完全数据驱动。在合成数据和渤海地震资料的实际应用中, 鬼波成分得到了明显的压制, 同时拓宽频带, 补偿陷频, 证明了该方法的有效性。     

水下拖曳升沉补偿系统水动力数学模型研究

建立变缆长的水下拖曳升沉补偿系统水动力学偏微分方程组和边界条件.拖缆动力学模型基于Ablow and Schechter模型,拖体采用水下运载体六自由度方程模拟,运用有限差分法离散偏微分方程组和牛顿迭代法计算变缆长情况下拖体深度与拖缆各点张力的动态取值.数值计算结果表明采用收放拖缆的升沉补偿方法能够有效削弱母船升沉运动对拖体深度和拖缆张力的影响.     

Improvements in acoustic sediment concentration profiling using anLMS compensation algorithm

In sediment concentration profiling, sound attenuation becomes important for high-frequency acoustic backscattering systems (ABSS) when sediment concentration is high and/or the range of remote sensing is long. In the present study, a test of a least mean square (LMS) compensation algorithm was performed in order to determine the advantages over the more frequently used iteration algorithm. Numerical simulation and laboratory experiments in a mixing tank as well as an open channel suggest that the new algorithm is much more robust to white Gaussian noise and fixed-echo noise, and errors do not accumulate along the profiling path. Good linearity of this instrument in concentrations up to 20 kg/m^-3 is found by comparison with a suction-sampler. In the mixing tank, backscattering intensity profiles in concentrations up to 120 kg/m^-3 vary little along a propagation path of 40 cm and fit well to the expected homogeneous concentration. Furthermore, by using the oscillation errors in the LMS solution, a procedure has been developed to compensate for the errors in the instrument constants evaluated from the attenuation between the transducer and the first measuring volume. The feasibility of the proposed instrument-constant compensation is verified by experiments. This allows instantaneous correction of the influence of sediment deposition on the transducer surface which is important when the system is applied to coastal investigation     

具有运动补偿高精度海洋气象多参数模拟仪的研制

针对船舶气象仪的综合检查过程中检测周期长、人工排查效率低以及传统的自动气象站传感器信号模拟器的模拟精度低,没有相关运动补偿算法导致此类系统不适应海洋船舶应用环境的问题,对气象要素传感器的高精度信号采样电路、信号输出、软件滤波和运动补偿等方面进行了研究。通过分析传感器和船舶气象仪的原理,设计了各个气象参数的采样电路、信号模拟电路、触摸屏、GPS和电子罗盘采样与模拟电路,并在近海测试过程中进行了运动补偿模型测试,并基于STM32微控制器进行了该仪器的系统检测实验。研究测试结果表明：该系统具有低功耗、高可靠性、高精度的特点,能应用于海上环境,同时具有对船舶实时定位、气象要素实时模拟和采集、运动补偿多项功能。并且本系统精度在运动补偿后,系统测量方差为0.019 3 m/s,精度提高至接近真实值,均符合《海洋调查规范第3部分：海洋气象观测》的标准。     

Fourier频率域随机谱隐秘信息加载与增量补偿系统

提出一种基于光学原理的Fourier频率域随机谱隐秘信息加载与增量补偿系统,并给出一种隐秘信息的加载方式,可实现光学图像信息隐藏.宿主图像经过随机相位调制后进行Fourier变换得到频率域的随机谱,在此随机谱上加载隐秘信息,同时,系统对由隐秘信息的加入所产生的影响进行补偿.利用该系统所得到的载体图像未经正确的密钥-随机相位-调制时,隐秘信息将弥散在载体图像的Fourier频率域空间,具有较好的不可检测性.此外,即使攻击者知道隐秘信息的存在甚至知道隐藏方法,但在不知道密钥的情况下,依然无法破解隐秘信息的内容