Adaptive output feedback control based on DRFNN for AUV

The tracking control problem of AUV in six degrees-of-freedom (DOF) is addressed in this paper. In general, the velocities of the vehicles are very difficult to be accurately measured, which causes full state feedback scheme to be not feasible. Hence, an adaptive output feedback controller based on dynamic recurrent fuzzy neural network (DRFNN) is proposed, in which the location information is only needed for controller design. The DRFNN is used to online estimate the dynamic uncertain nonlinear mapping. Compared to the conventional neural network, DRFNN can clearly improve the tracking performance of AUV due to its less inputs and stronger memory features. The restricting condition for the estimation of the external disturbances and network's approximation errors, which is often given in the existing literatures, is broken in this paper. The stability analysis is given by Lyapunov theorem. Simulations illustrate the effectiveness of the proposed control scheme.     

基于CFD模拟的单点系泊船型网箱浮架结构分析与设计

针对单点系泊(SPM)网箱系泊力大于传统网箱,离岸环境承受风浪时风险更高的问题,研究设计了一种相较传统圆形网箱拥有更小系泊力的船型网箱,运用正交原理制定了三因素三水平的试验方案,对网箱浮架进行了计算机数值模拟,分析网箱在波流共同作用下的水动力特性变化。研究表明,在兼顾经济成本与网箱安全性的条件下,长24 m,宽9 m,头部角度为60°的网箱浮架具有较优良的水动力性能和相对较低的养殖成本。该网箱系统能随着潮流改变方向而在锚点周围移动,从而极大减小网箱底部的养殖残渣堆积并降低锚固安装成本,可为我国深水网箱的发展提供一定的理论参考依据。     

基于STM32的浮标及其定日光伏控制系统设计

为了提高海洋浮标对太阳能的利用率而设计了一种定日光伏系统的控制方案,采用STM32嵌入式单片机作为控制核心,结合浮标的特制外形,其太阳能电池板能够始终向着太阳转动,最大限度地为浮标进行供电。所述的浮标特制外形由带有对称肋板的浮标体和透明保护罩组成,提高了浮标的抗变形能力,减弱了太阳能电池板转动引起的反转及左右摇摆趋势。该系统经试验及仿真分析,达到预期目标,运行稳定可靠,有良好的推广应用价值。     

Impact of seepage flow on sediment resuspension by internal solitary waves: parameterization and mechanism

Sediment incipient motion is the first step in sediment resuspension. Previous studies ignored the effect of seepage flow on the mobility of sediment particles and simplified the seabed surface as a rigid boundary. A flume experiment was designed to innovatively divide the seabed into two parts to control the dynamic response of the seabed and control the seepage conditions. In the experiment, the seabed sediments and the amplitude of internal solitary waves(ISWs) were changed to compare and ana...     

Simulation of turning circle by CFD: Analysis of different propeller models and their effect on manoeuvring prediction

Propeller modelling in CFD simulations is a key issue for the correct prediction of hull-propeller interactions, manoeuvring characteristics and the flow field in the stern region of a marine vehicle. From this point of view, actuator disk approaches have proved their reliability and computational efficiency; for these reasons, they are commonly used for the analysis of propulsive performance of a ship. Nevertheless, these models often neglect peculiar physical phenomena which characterise the operating propeller in off-design condition, namely the in-plane loads that are of paramount importance when considering non-standard or unusual propeller/rudder arrangements. In order to emphasize the importance of these components (in particular the propeller lateral force) and the need of a detailed propeller model for the correct prediction of the manoeuvring qualities of a ship, the turning circle manoeuvre of a self-propelled fully appended twin screw tanker-like ship model with a single rudder is simulated by the unsteady RANS solver χnavis developed at CNR-INSEAN; several propeller models able to include the effect of the strong oblique flow component encountered during a manoeuvre have been considered and compared. It is emphasized that, despite these models account for very complex and fundamental physical effects, which would be lost by a traditional actuator disk approach, the increase in computational resources is almost negligible. The accuracy of these models is assessed by comparison with experimental data from free running tests. The main features of the flow field, with particular attention to the vortical structures detached from the hull are presented as well.     

On the design of a longitudinal motion control system of a fully-submerged hydrofoil craft based on the optimal preview servo system

The current control system of a fully-submerged hydrofoil craft based on optimal feedback control has several problems: it has no good performance of contouring waves and it cannot reduce the effect of wave disturbance. In this paper, we apply the optimal preview servo system to the longitudinal control system of a fully-submerged hydrofoil craft in order to settle the problems of current control system. The control system based on optimal preview servo system is composed of feedback controller and feedforward controller. Also in order to design the control system, the necessary prediction range of future information, the weight function in performance index, the future reference input and wave disturbance are determined. Finally, the validity of the proposed control system in this paper is confirmed by simulation. The simulation results show that the control system has good performance of contouring waves in following seas and is effective to settle the problems of current control system of a fully-submerged hydrofoil craft.     

Multigrain sedimentation/erosion model based on cross-shore equilibrium sediment distribution: Application to nourishment design

In the light of global warming and sea level rise there are many coastal beaches that suffer from erosion. Beach nourishment has become a common practice to maintain the sediment balance on a shore-face. In this paper, a three-dimensional numerical model for evaluating long-term impact of beach nourishment projects has been developed. The model addresses the longstanding complex issue of coastal morphology and sediment grain size distribution from an unconventional angle, which exploits the strong links between grain size distribution and the prevailing transport direction of each sediment constituent under ‘average’ wave and storm action. The present model predicts the redistribution of nourished sediment according to the subtle clues implied by equilibrium distribution curves and latest coastal wave transformation theories. After verification against recent field observations in Terschelling, The Netherlands, the model was used to predict long-term effects of different beach nourishment strategies. It was found that: (a) given the source sediment available in Terschelling the tactics of large volume and less frequent implementation are better than otherwise; and (b) from a pure engineering point of view, waterline nourishment outperforms offshore trough nourishment.The model offers an additional tool for coastal engineers to evaluate the feasibility, effectiveness and the optimization of dumping locations for beach nourishment projects. It is also a useful tool for stratigraphic modelling of shallow-marine sedimentation in conjunction with sea level changes.     

Sulfur diagenesis and burial on the Amazon shelf: Major control by physical sedimentation processes

Early diagenetic properties of Amazon shelf muds are dominated by nonsulfidic Fe and Mn cycling, resulting in relatively little S deposition compared to previously studied marine margin environments. Despite abundant potential reactants typical of sulfidic deposits, authigenic sulfides represent only ~ 10% of diagenetically reduced Fe, and DOP (degree of pyritization) is only ~0.02. The average C/S (wt wt^–1) ratio of buried sediment below the zone of SO₄ ^2- reduction is ~ 7.4, ~ 2.6 times more than the commonly assumed modern shelf average of ~ 2.8. The deltaic burial rate forS is ~ 0.65 × 10⁶ tons yr^–1. Relatively lowS deposition is promoted by terrestrial weathering that delivers reactive oxide debris, but apparently depends most strongly on reoxidation and rapid burial by intense physical reworking and fluid-mud formation. Diagenetic models of S distributions demonstrate rapid sediment reworking (~ 10–100 cm yr^–1 as apparent advection), substantialS reoxidation (84–98%), and in one case, massive sediment deposition of up to ~ 5 m of sediment in ~ 1 year. Extremely low DOP coupled with dominance by nonsulfidic reduced-Fe minerals and lack of biogenic sedimentary structures may be an indicator in marine organic-rich muds of intense physical reworking under oxygenated waters.     

Dysfunction by design: Consequences of limitations on transferability of catch shares in the Alaska pollock fishery

The Eastern Bering Sea fishery for pollock is one of the largest fisheries in the world and has often been touted as an example of sustainable fisheries management. Yet, sustainability requires more than protection of the biological productivity of the targeted fish species. It requires preservation of the flows of net social and economic benefits of the fishery, and flexible governance and management institutions that allow for adaptation to changes in fish abundance as well as changes in consumer demand and in the prices of key inputs. From an economic perspective, the Alaska pollock fishery was unsustainable before passage of the American Fisheries Act (AFA) in 1998. The AFA permanently divided the pollock Total Allowable Catch (TAC) giving a 10% allocation to the Community Development Quota (CDQ) program and partitioning the remainder among four fishing sectors. It allowed CDQ to be leased to any sector but largely prohibited leasing or sale between other sectors. These limits on intersectoral transfers have reduced the ability of sectors to respond to changes in the abundance and distribution of pollock, implementation of management measures intended to benefit other species, and changes in the prices of input factors and products. This paper explores these consequences.     

基于数据挖掘技术探析国医大师熊继柏辨治头痛的特点及组方规律

目的：基于数据挖掘技术研究国医大师熊继柏辨治头痛的特点及组方规律。方法：搜集公开发表的熊老辨治头痛的医案,利用中医传承计算平台进行用药频次、关联度、关联规则等分析。结果：共获得处方 49 首,中药 94 味,药物总频次为618次。高频使用药物排前5位的依次为川芎、甘草、天麻、白芷、僵蚕。治疗头痛主要采用解表药、补虚药、平肝息风药、活血化瘀药。药物四气中,温性>平性>寒性>凉性>热性;五味中,辛味>甘味>苦味>酸味>咸味;归经中以肝经最多,其次为脾、肺二经。常用药物组合主要以高频药物（川芎、天麻、僵蚕、白芷、黄芩、甘草等）两两组合或三者组合为主。有高度关联性的药物有川芎、天麻、白芷、僵蚕、柴胡、白芍、葛根等。获得核心组合3组。结论：熊老治疗头痛有2个特点,一是善用风药和虫药,二是喜用川芎。本研究对头痛的临床治疗颇有裨益。