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常微分方程具有一般数学的特点:抽象性、严密性,又具有本身的特点,即与工程技术紧密相连,实用性强.而常数变易法是解线性微分方程行之有效的一种方法。 相似文献
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This paper presents the uncertainty modelling of experimental results for a physical model of a tanker moored to a terminal inside a port. The physical model was built for an oil terminal at the port of Leixões in Portugal. The model incorporates the new modified port layout, as well as a future 300 m extension of the port outer north breakwater to enhance operational conditions. The physical model tests were performed on a scale of 1:80 in the Portuguese Civil Engineering Laboratory (LNEC). A generic mooring system of four mooring lines and two fenders is simulated using a nonlinear spring system. Decay tests are carried out to evaluate the natural periods of the moored model. Then, tests are carried out for the moored model in waves. The major aim of the experimental study is to obtain novel results for the wave elevation and direction at various locations inside the port, the ship motions at six degrees of freedom, and loads on mooring lines and fenders including the modified port layout. As the physical model measurements are subjected to different types of uncertainties, a systematic uncertainty analysis is carried out here, following ITTC guidelines and recommendations, to quantify all possible sources of uncertainties. The results are discussed, and several conclusions are reached. Based on the experimental results, the presented physical model study may replicate the results for waves and motions with uncertainties less than 9% of the significant amplitudes. The assessment of the applied nonlinear spring model reveals load predictions on the moorings, with uncertainties less than 4% of the maximum mooring loads. 相似文献
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麦哲伦(Magellan,Ferdinand),葡萄牙著名航海家和探险家.先后为葡萄牙(1505~1512)和西班牙(1519—1521)作航海探险。5个多世纪以来,人们对麦哲伦崇拜得很,都把他看作是世界英雄,因为他是第一个完成环球航行的航海家。这一创举实际上以无可争辩的事实证明了地圆说。从这个意义上讲,麦哲伦的确是 相似文献
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为优化某船用柴油机的燃烧室的"油-气-室"匹配,降低有害物排放,运用AVL Fire对原型燃烧室改用不同燃烧室进行额定工况模拟.结果表明,高低型双涡流室双缩口燃烧室能在上涡流室形成"飞轮效应",相对于原型燃烧室,不仅能增加功率,而且能降低Nox和SOOT的排放.对高低型双涡流室双缩口燃烧室设置不同的高低涡流室的半径比r/R和喷油夹角进行计算.结果表明:随着r/R从0.3增加到1.3,Nox和SOOT的排放量均先减少后增多;当r/R为0.7时,Nox和SOOT的排放量均最少.当喷油夹角为140°~165°时,随着喷油夹角的增大,Nox的排放量先减少后增加,随后再减少,最后又升高;SOOT排放量先减小后增大,随后再减小. 相似文献
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Characteristics of a bubble jet near a vertical wall 总被引:1,自引:0,他引:1
A numerical model of a coupled bubble jet and wall was built on the assumption of potential flow and calculated by the boundary integral method. A three-dimensional computing program was then developed. Starting with the basic phenomenon of the interaction between a bubble and a wall, the dynamics of bubbles near rigid walls were studied systematically with the program. Calculated results agreed well with experimental results. The relationship between the Bjerknes effect of a wall and characteristic parameters was then studied and the calculated results of various cases were compared and discussed with the Blake criterion based on the Kelvin-impulse theory. Our analyses show that the angle of the jet's direction and the pressure on the rigid wall have a close relationship with collapse force and the bubble's characteristic parameters. From this, the application range of Blake criterion can be determined. This paper aims to provide a basis for future research on the dynamics of bubbles near a wall. 相似文献
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G. C. Pereira M. M. F. Oliveira L. P. Andrade R. P Espíndola K. G. van Hecke N. F. F. Ebecken 《Journal of Marine Science and Technology》2016,21(4):651-662
Coastal zones are among the most productive areas in the world, offering a wide variety of valuable habitats and ecosystems services. Despite the low population density in the Brazilian coastal zone, their distribution is quite concentrated near some coastal cities and state capitals. This concentration places enormous pressure on coastal resources. Therefore, the main objective of this paper is to present an overview on the current status of SiMoCo (Sistema de Monitoramento Costeiro, or Coastal Monitoring System in English) project as a possible early warning system that can be integrated to the Brazilian Coastal Management Information System. This prototype platform provides a real-time access to the composition, organization and simulation of planktonic communities. First, our results demonstrate such a system detecting a target dinoflagellate; second, we apply structural and functional indexes to compare and characterize the ecological networks from two different coastal areas. Conclusions are made about SiMoCo’s feasibility and its possible contribution to the decision-making process within integrated coastal zone management (ICZM) strategies. 相似文献
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Eiji Shintaku Yukio Fujimoto Kunihiro Hamada Tetsuya Takeuchi 《Journal of Marine Science and Technology》2000,5(1):40-47
This paper describes a stress sensor using a piezoelectric element which was developed to monitor features of the stress
history of a structural member. The sensor is 90 mm long, 60 mm wide, and 25 mm thick. A stress-level meter can turn on and
off different colored light-emitting diodes (LED) according to the changes in a stress level. A stress-level cross counter
can display the number of cycles which exceeds a specified stress level during a monitoring period. The sensor is bonded onto
a structural member using an adhesive agent. In order to see the performance of the prototype sensor, experiments were carried
out using a fatigue-testing machine. The sensor was bonded onto a smooth specimen and multiple repeated stresses were applied
to that specimen. There were three main findings. (1) The sensor can operate under a stress range from −150 MPa to 150 MPa,
and a frequency from 0.05 Hz to 5 Hz. (2) The stress-level meter can turn the lights of the LED on and off accurately under
any stress amplitude and frequency. (3) When the stress frequency is 1 Hz or less, the stress-level cross counter can count
accurately the number of cycles which exceed the predetermined stress levels.
Received: February 25, 2000 / Accepted: April 11, 2000 相似文献
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某船用大型可拆卸式滚动轴承设计 总被引:1,自引:0,他引:1
《中国修船》2019,(5):12-14
文章以船用滚动轴承为研究对象,针对该滚动轴承工作中存在的缺点和不足,设计了一种船用可拆卸式滚动轴承,说明了该滚动轴承的工作原理和主要零部件,并利用三维建模软件UG进行了该滚动轴承的零部件及装配体建模,最后进行了滚动轴承装配体的干涉检查,结果表明,所设计的船用大型可拆卸式滚动轴承运行良好。 相似文献
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文章分析了传统故障诊断系统的特点,介绍了一种高分辨率谱估计算法-MUSIC算法,并针对该算法特点,提出了一种基于ARM微处理器的异步电动机嵌入式故障诊断系统,重点阐述了系统硬件电路和软件系统的设计,并进行了实验验证。结果表明系统具有硬件电路简单、可操作性较强、实时性可靠等优点。 相似文献
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This paper presents a preliminary technical feasibility study on a new methodology proposed for installing a monopile-based bottom supported offshore wind turbine structure. The concept is developed to address the problem of “waiting for a suitable weather window” which is commonly faced by the existing installation methods that uses a typical jack-up platform. In the methodology, a floating vessel along with a floatable subsea structure fitted with a hull on the top, hereafter named SSIP (subsea structure for installing a pile), is proposed first to install a monopile. Then the same structure is used to carry an FIUS (fully integrated upper structure) of an offshore wind turbine, which is characterized by a telescopic tower, and install it over the monopile by using an FOP (float-over-pulling) arrangement. Here, the installation methodologies are first briefly described along with the critical load cases associated with them. These load cases are then numerically studied for a significant wave height (HS) of 2.5 m, and the results are summarized. For installing a fully integrated offshore wind turbine upper structure on a monopile foundation by the FOP method, two installation schemes are presented, and their dynamic characteristics are compared. It is shown that the proposed methodologies have potential to provide installation solutions which can be environmentally more robust compared to the existing method for installing an offshore wind turbine. 相似文献
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本文描述了一个简单的基于神经网络的小型帆船自适应舵的控制方案.该方案采用了两个简单的双层神经网络:一个使用在线的BP算法来学习未知的帆船动态;另一个则利用前一个所学到的知识来调整它的连接权系数和偏差权系数以产生控制信号.仿真结果表明,与仔细调整过的PID控制器相比较,神经网络控制器在航向保持上与PID近乎相同,但却具有好得多的鲁棒特性. 相似文献