可预见的无故障切削

每一个加工工艺的目标应该是在保持高生产率和低生产成本的同时,尽可能提高安全性和可预见性。为此,需要考虑以下几个因素：工件的材料、形状和尺寸、机床、CAM系统、工件和刀具的夹紧、切削刀具的选择及使用情况（见图1）。     

整平推进阻力及支腿钢垫板摩擦系数实测试验

为完成离岸深水港抛石基床整平关键技术研究课题,设计制作了专用试验装置,对采用料仓摊铺方式进行整平的推进阻力和钢质垫板与抛石基床之间的摩擦系数进行了实测,总结了试验结果,为整平机的设计提供参数.     

Coming Soon to a Fjord Near You: Future Jellyfish Scenarios in a Changing Climate

Over the last decades, a dense population of the deep-sea/oceanic scyphozoan jellyfish Periphylla periphylla has established itself as top predator in the Trondheimsfjord in Norway, which has caused the traditional fisheries in this fjord to suffer. This was, however, not the first fjord this jellyfish invaded, and data suggest that it will not be the last one, either. With warmer temperatures, the jellyfish is moving northward in Norway, but not all fjords are created equal, and it is not thriving or taking up residence just anywhere. The current article explores three fjords in which Periphylla periphylla has become the top predator and outcompeted former ones. The main question of interest is why the jellyfish becomes dominant in one fjord and not another. The next question is which other Norwegian fjords further north exist with similar characteristics where we therefore would expect Periphylla periphylla to proliferate in the future. The latter is important from a policy and adaptation perspective for the local community of people, since the proliferation of the species unmistakably leads to fewer fish for commercial harvest and potentially less attractive waters for tourism purposes. Results show that three northern fjords, the Skjerstadfjorden the Holandsfjorden, and Stordjupna in the Vestfjord appear to be particularly vulnerable to a future Periphylla periphylla invasion.     

Revisiting port pricing; a proposal for seven port pricing principles

A review of seven large landlord port authorities around the world reveals a notable diversity of pricing structures. While port authorities increasingly act as commercial undertakings, port pricing often seems to be not driven by commercial considerations. In this paper, we argue that ports can be regarded as “business ecosystems” with multiple users. This provides a valuable perspective on pricing and raises the question of whether ports can be regarded as two-sided markets. We argue this is not the case. The business ecosystem perspective provides a basis for deducing seven pricing principles for port authorities that are detailed in the paper and illustrated with cases these principles. These pricing principles are broadly follow a direct user pays approach; capture value from “non-core” tenants; price aggressively for activities with a high strategic value; differentiate pricing based on price elasticity and connectivity improvements; maximize revenue from long-term lease agreements, price port dues competitively; critically consider differentiation of charges based on environmental performance; and finally use incentives to align interests of terminal operators and shipping lines. We conclude that the ecosystem perspective is central to the understanding of pricing decisions of port authorities and that various pricing issues deserve more attention.     

Using high sampling-rate ADCP for observing vigorous processes above sloping [deep] ocean bottoms

Above sloping bottoms in the ocean mixing processes are not predominantly generated by shear-induced turbulence via bottom friction. Instead, the restratifying buoyancy forces and internal waves create a highly non-linearly varying environment including ‘stratified turbulence’. Most of the resulting vigorous mixing processes that dominate sediment resuspension occur during the passage of frontal bores or solitary boluses, ‘solibores’. Here, the observed evolution of different forms of highly non-linear strictly upslope moving ‘waves’, bores or boluses are reviewed from various NIOZ projects at deep sloping bottom sites ranging from 500 to 3000 m.Such fronts pass a fixed site within a few minutes, extending some 60 ± 30 m above the bottom and occurring over much larger periods at once per subinertial or meso-scale period or approximately, but not exactly, once per tidal harmonic period. In order to observe the details of such solibore one needs specific, high-sampling rate equipment. A suitable piece of equipment is a bottom-mounted 4-beam 300 kHz acoustic Doppler current profiler (ADCP), provided it samples at a rate of about once per second over a period of at least several weeks. Not just the three components of current velocity [u,v,w] are monitored over a range of some 80 m at 1 m intervals, but also the relative ‘echo intensity’ dI, which is a measure for suspended matter and stratified turbulence. Such ADCP-observations are combined and compared with high-resolution temperature measurements. Fine details show a turbulent inner core with more or less laminar streamlines outside it. Whether a front or a bolus, the bore is never observed as a completely closed contour, as swept up turbulent material is sucked into the core at the rear end.     

交流伺服系统的串级滑模变结构控制仿真研究

针对永磁同步电机交流伺服系统,提出了串级滑模控制方案。在速度环滑模控制器中引入了 积分环节,减小了转矩的脉动,位置环采用了准滑模控制方案,极大地抑制了位置输出的抖动。仿真研 究表明,该控制方案具有较强的抗参数摄动和抗干扰能力,表现出良好的控制性能。     

论船舶安全检查的质量船制度

基于现代控制理论的四种控制系统的有机组合作用,提出质量船制度的概念,并对质量船制度的理论依据、基本构架、质量船标准、评价指标体系模型、权重系数设定的数学方法和检查官制度等问题进行了系统的阐述。     

便携式自基准天文定位仪

该文介绍了基于两星或三星等多天体定位位原理,运用二维倾斜传感器与测角传感器测量天体瞄准线与水平面之间的天然体高度角,研制出一种新型便携式自基准天文定位仪。并较全面地介绍了该仪器的组成,测量原理、误差及校正等。     

A cluster analysis of cyclists in Europe: common patterns,behaviours, and attitudes

Transportation - This study uses cluster analysis on a sample of regular cyclists from six European countries (the U.K., the Netherlands, Sweden, Hungary, Italy, and Spain) to shed light on common...     

The value of travel time savings in freight transport: a meta-analysis

Transportation - The value of freight travel time savings (VFTTS) is a monetary value that is considered an important input into cost–benefit analysis and traffic forecasting. The VFTTS is...