A design chart for the plastic collapse of corrugated cylinders under external pressure

The paper presents a theoretical and an experimental investigation into the plastic collapse of circular steel corrugated cylinders under external hydrostatic pressure. The experimental investigation gives a detailed study of 9 steel corrugated cylinders which were tested to destruction. Six of these cylinders failed by plastic non-symmetric bifurcation buckling and three failed by plastic axisymmetric deformation. The results of these tests were used, together with the results obtained from previous tests, to present a design chart for the plastic collapse of these vessels. The design chart was obtained by a semi-empirical approach, where the thinness ratios of the vessels were plotted against their plastic knockdown factors. The process of using the design chart is to calculate the theoretical elastic instability pressure for a perfect vessel by the finite element method and also to calculate the thinness ratio for this vessel. Using the appropriate value of the thinness ratio, the plastic knockdown factors are obtained from the design chart. To obtain the actual collapse pressure of the vessel, the theoretical elastic instability pressure for a perfect vessel is divided by the plastic knockdown factor. This work is of importance in ocean engineering. A large safety factor must also be introduced.     

Plastic buckling of ring-stiffened conical shells under external hydrostatic pressure

The paper describes experimental tests carried out on three ring-stiffened cones that were tested to destruction under external hydrostatic pressure. The cones were carefully machined from EN1A Steel. All three cones failed by plastic non-symmetric bifurcation buckling in a mode commonly known as general instability. In this mode the entire ring-shell combination buckles bodily.The paper also provides a design chart using the results obtained from these three vessels, together with the results of six other vessels obtained from other tests. The design chart allows the possibility of obtaining a plastic knock down factor, so that the theoretical buckling pressures, based on elastic theory, can be divided by the plastic knockdown factor, to give the predicted buckling pressure. This method can also be used for the design of full-scale vessels.     

Inelastic shell instability of thin-walled circular cylinders under external hydrostatic pressure

This paper reports on experimental work carried out on nine thin-walled circular cylinders which were tested to destruction under external hydrostatic pressure. Seven of the cylinders failed through non-symmetric bifurcation buckling and two failed through axisymmetric collapse. The results were used from these tests, together with the results from other experiments, to produce a design chart which could be used for designing against the occurence of elastic and inelastic shell instability.     

调和常数及深度基准面的变化与历元订正

分析和验证了黄海沿岸部分长期验潮站M2分潮振幅的线性变化趋势及深度基准面L值增大趋势,发现了长周期分潮调和常数不稳定性对深度基准面确定的影响。研究表明,在剥离了深度基准面变化趋势后,由年观测数据分析结果确定的深度基准面可达到厘米级的精度水平,而由月分析结果确定的深度基准面存在周期性变化,其深度基准面不宜直接计算确定。论证了对潮汐调和常数附加历元信息的必要性和基本方案。通过研究得出对统一深度基准建立的指导性结论。     

Isobathymetric Line Simplification with Conflict Removal Based on a B-spline Snake Model

This paper introduces a new method for the smoothing of isobathymetric lines for marine chart construction. Specific constraints have to be observed as the chart must be legible and safe for navigation. The method, based on a snake model, respects these constraints of legibility and safety which impose a direction for curve deformation. Conflicts such as self-intersections are also considered. These two points are the main contributions of the paper as current methods cannot deal with such constraints. Several case studies are presented and results obtained on real data are discussed.     

Isobathymetric Line Simplification with Conflict Removal Based on a B-spline Snake Model

This paper introduces a new method for the smoothing of isobathymetric lines for marine chart construction. Specific constraints have to be observed as the chart must be legible and safe for navigation. The method, based on a snake model, respects these constraints of legibility and safety which impose a direction for curve deformation. Conflicts such as self-intersections are also considered. These two points are the main contributions of the paper as current methods cannot deal with such constraints. Several case studies are presented and results obtained on real data are discussed.     

Finding a balance between economic performance and capacity efficiency for sustainable fisheries: Case of the Da Nang gillnet fishery,Vietnam

Marine capture fisheries in Vietnam are small-scale, multi-species, multi-gear, and open access regime. Under numerous governmental promotion programs, Vietnamese fishing fleets have expanded at an uncontrollable rate. This research analyzes the economic performance and capacity efficiency of the Da Nang gillnet fishery. Data were obtained from 45 gillnetters in Da Nang using questionnaires, which were administered between April and July of 2011. The results showed that large-scale vessels (engine power≥90 hp) had better economic performance than small-scale vessels (engine power<90 hp) with average gross revenue flows of 1346.7 and 750.7 million VND, respectively. The large-scale vessels further actualized positive profits (15% gross revenue), while the small-scale vessels demonstrated negative results (−0.4% gross revenue). The main operating costs of fuel and labor accounted for 44% and 26%, respectively, of the total operating expenses. However, the results of the data envelopment analysis (DEA) showed that the Da Nang gillnet fishery did not operate at full capacity and that the unused capacity and the technical inefficiency rates were approximately 21.2% and 10.8%, respectively. The over-use of fuel, net sheets, and number of days at sea in the large-scale vessels were 7%, 10%, and 3%, respectively, while these ratios in the small-scale vessels were 7%, 3%, and 7%, respectively. Overcapacity may be separated into two parts, one part resulting from the optimal technical use of inputs and a second part resulting from enhancing the current policies. As such, feasible policies may include implementing the buyback of small and unprofitable vessels, and reviewing subsidy programs.     

一种新型无人船海洋水深测量技术

在海洋测深中,由于波浪和潮汐的影响,调查船或无人船所测量的瞬时水深不能直接作为海图水深。本文提出了一种新型的无人船海洋水深测量技术,以评估搭载RTK和单波束测深仪的无人船用于海洋水深测量的潜能。首先,使用无人船所搭载RTK的厘米级精度高程数据,通过低通滤波剔除波浪信息,而获得海平面高程。然后,基于潮汐表和无人船海平面高程,构建了一种参考椭球面和海图的两个基准面之差的获取方法;在常规的海洋调查中,该基准面差通常需要由长期的验潮获得。最后,利用海图基准和无人船测量的瞬时水深的转换关系,计算出海图水深。在海南省蜈支洲岛周边海域,利用自研发的无人船“USBV”开展了相关海上实验,以验证所提出的技术方法。实验结果验证了该无人船海洋水深测量技术。     

On the use of the capability polar plots program for dynamic positioning systems for marine vessels

As the capability of polar plots becomes better understood, improved dynamic positioning (DP) systems are possible since the control algorithms greatly depend on the accuracy of the aerodynamic and hydrodynamic models. The measurements and estimation of the environmental disturbances have an important role in the optimal design and selection of a DP system for a marine vessel. The main objective of this work is to present a new software program capable of estimating the environmental forces, thrusters capability calculations, and capability polar plots for marine vessels. A flowchart illustrating the logic and data flow of a developed software program, the Capability Polar Plot Program (CPPP), and the estimated results for two case studies for a scientific drilling vessel and a survey vessel are presented. It is obvious from the obtained results that the developed program has a future potential for the estimation of the Capability Polar Plots for marine vessels. Moreover, the developed software program would be considered as a marine tool for the thrusters' selection and their configuration for marine vessels and floating production units for the Oil and Gas industries.     

选择性压盖技术在纸质海图生产中的应用

利用数字海图数据直接出版纸质海图是提高纸制图生产效率的重要手段,但由于数字海图与纸质海图在编制原则和表现规范上的差异造成由数字图生产纸质图时,需要大量的手工修编,从而增加了工作量,延长了成图周期。采用一种新的制图理念,利用ArcInfo的选择性压盖技术,制作纸质图符号库,选择正确符号化顺序,从而实现纸质海图生产与数字海图生产同步,减少重复劳动,缩短成图周期,提高了工作效率。     

海区形势图的编制方法

如何设计并制作出内容丰富、形式多样、表现合理、清晰实用的海区形势图,是海图编辑人员必须认真思考和设法解决的问题。根据工作经验,就海区形势图的编制规律和特点进行了论述,并研究、归纳出一套海区形势图的编制方法。     

Design of mooring system of vessels inside breakwater

A method of simulation calculation for a mooring system of vessels inside a breakwater is illustrated. Using a simulation program based on the above method, a test design for a mooring system for oil-storage vessels of total 5.6 million kiloliters was conducted.In order to obtain data for the simulation program, various experiments, such as wind tunnel tests to test wind resistance, and wave tank tests to test the waves transmitted through or over the breakwater, and the motions of vessels inside the breakwater due to waves, were conducted.Some proposals concerning design criteria and safety factors are presented.Finally, the results of the test design under estimated sea and weather conditions are shown, and the design is concluded to be both technically and economically feasible.     

基于人机交互方式的海图集一体化分幅

根据海图集制作中分幅设计需要处理的多种情况,提出了海图集一体化分幅方法,采用开放式模块化的方案流程,利用人机交互的方式,使计算数据与矢量数据相结合,结果可以在电脑屏幕上显示出来,使设计者的思想得以充分体现。同时利用批量数据联动处理的方式,提高了图幅设计的效率。     

新版渔业用图的设计

新版渔业用图在数学基础的确定、表示的主要内容和生产方式上都发生了一定变化,针对新版渔业用图的设计特点,介绍了其表示的主要内容、数据结构设计以及版面设计方法.     

Nonlinear meta-models for conceptual seakeeping design of fishing vessels

The scope of this paper is to develop the nonlinear meta-models for seakeeping behaviour, considering the fishing vessels. These models are intended to be inserted either in a multiattribute design selection process or in a comprehensive multiobjective optimization procedure. For this purpose, seakeeping data of fishing vessels in regular head waves are used to develop meta-models of transfer functions of heave, pitch and vertical acceleration by nonlinear analysis. A home-made software considers two databases; the first is composed by the ship dimensions and coefficients of fishing vessels, and the second is their ship motion data obtained by employing a strip-theory calculation. The meta-models are proposed to predict the vertical motion characteristics for given ranges of speed and wave length during the concept design stage. The independent variables are hull size (Δ), main dimensions (L, B, T), and some hydrostatic parameters (C_WP, C_VP, LCB, LCF, etc.). The results estimated by the software show good correspondences with the ones achieved by direct computations. The study provides additional insight on the influence of hull form parameters on seakeeping performance of small vessels having form properties and parametric range corresponding to the investigated vessels.     

Design of Mooring System for Oil Storage Vessels

The floating oil storage system has been proposed as a new facility for Strategic Petroleum Reserve (SPR) in China. Mooring is one of the key technologies to ensure the safety, reliability, and performance of the oil storage system. This paper describes the concept, analysis, design and reliability of the mooring system. For mooring system design of these oil vessels, analysis is essential of the behavior of the vessel in connection with mooring facilities of nonlinear resilience. A nonlinear mathematical model for analyzing a moored vessel is established and solved. Some results of numerical simulations are presented. Assessment of the safety regarding the mooring system in terms of failure probability is carried out. Another simulation model for calculating the failure probability of the mooring system is proposed. The design parameters that have an influence on the characteristics of the failure probability have been identified. The simulation results show that the mooring system has an annual reliab     

海水工厂化养鱼排污水处理的实验研究与工程设计

本文从保护海洋环境出发，论述研究设计海水工厂化养鱼排污水处理工程的重要性，提出用光合细菌（PSB）和海藻试验研究工厂化养鱼排污水处理的效率、特性及副产品的综合利用。通过工程计算，设计出工艺流程图及光合细菌反应池、二沉池和海藻塘的工程容量。     

Seakeeping performance of fishing vessels in irregular waves

A study of the seakeeping performance of a set of fishing vessels is carried out aiming to identify the seakeeping criteria, and vessel conditions that limit the operability of the fishing vessels in certain sea states. Ship motions and derived responses are obtained in fully developed sea states using the transfer functions of the hull forms. Those responses are assessed against the prescribed values, for the chosen criteria, to determine the vessels operational conditions that might result in hazards or seasickness. For the purpose of this study, each fishing vessel is considered operating in sea states 5 and 6, with different Froude numbers and heading angles, and their short term responses are assessed against the most relevant criteria related with the absolute and relative motions, accelerations, slamming and green water on deck. The results obtained show that roll and pitch criteria are most critical for seakeeping performance, and there is a significant influence of the transverse metacentric height, GMt, and the location of the reference checking points in the seakeeping performance of these fishing vessels.     

遥感溢油识别的电子海图设计与功能实现

针对遥感溢油识别的电子海图显示应用系统的开发,进行功能需求分析并提出系统设计方案。在分析了几种常见的电子海图显示平台开发模式的基础上,基于MapObjects组件开发实现了电子海图显示应用平台,具备海图显示、数据叠加、海图分析、添加标注、地图输出等功能。     

BPF法在海图基准面计算中的应用

为了船只航行安全，在海图上所标的水深一般并非指平均海面到海底的距离(平均水深)，而是从低于平均海面的某一个面到海底的距离，这个面叫做海图基准面。基准面的确定并无统一的方法，国际上只有一个原则的规定，即实际海面应当可能但很少可能低于它。这样规定既避免了在海图上给出过分浅的水深数值，又可保证航行的安全。 但世界海洋国家在实际确定基准面深度时方法很不统一，甚至有些并不甚符合上述原则。我国历史上曾采用过国外的许多种方法，十分混乱。五十年代以来曾采用弗拉基米尔斯基方法，但这种方法计算手续相当麻烦，效果有时也不够理想。这里我们将提出一种以 BPF 法为基础的计算海图基准面方法，并将由此得出的面叫做“近最低潮面”。此法计算较简便，用实测资料检验表明，所得结果较为合理。