帆船、帆板运动的力学原理简介

帆船、帆板运动是奥运会的比赛项目,这项运动被越来越多的人所喜爱。但要想学会驶帆,必须首先弄清它的力学原理。1 帆船的动力来源 一般人对于帆船往往认为是被风推着跑的。其实风的动力以两种形式作用于帆,如图1、图2所示,帆船的最大动力来源是所谓的“伯努利效应”。     

素体阻值分选机的机械设计

论述了电阻素体阻值分选机的性能、结构及主要部件强度的设计要求、工作原理、传动方案、主要参数设计、凸轮和转盘的受力分析。认为整台设备的关键是采用单片机协调各工作部件运行。     

逆风张帆的力学原理

本刊2004年第4期刊出了《也谈“逆风行舟”的力学解释》(以下简称《也文》)一文，今就文中谈及的问题再作些探讨，对逆风张帆的力学原理谈点个人的浅见．     

《太平广记》里的舟船意象

<太平广记>小说里出现了很多舟船意象,这里主要以前七十卷为文本对象,从舟船的神异功能,民间信仰背景以及叙事功能等几个方面,探讨舟船作为沟通神人的媒介所体现出来的超越意义和探索意义.     

辐射场与太阳帆之间的相互作用

用分子动力理论导出了辐射场施于静止帆和运动帆的压强,并从动力学观点讨论了辐射场与帆之间的能量转换效率,同时指出了文[1]存在的一些问题.     

Propulsion of the putt-putt boat — I

Conclusions The putt-putt boat’s operation has two phases, ejection and suction. During ejection water is thrown out of the pipes, and dur-ing suction an equal quantity of water is injested. Even though the net mass flow is zero, the differences in the flow patterns during outflow and inflow cause a net forward thrust; thrust is mainly produced during ejection phase. Neglecting the suction part of the cycle for dynamic analysis of the boat agrees quite well with the experimental data obtained. Moreover, modeling the boat as a kayak, rather than a flat plate gives a better drag estimate. The diaphragm just makes the puttputt sound and is not involved in the propulsion. In the second part, the thermodynamic process involved in generating the thrust and drag forces will be dealt with.     

The Curtin-Hammett principle

This article qualitatively discusses the Curtin-Hammett principle without mathematical treatment of the kinetic model. We show how the practical application of this principle can be extended to tautomers of several compounds and to explain the diazotization of aniline. The concept of ‘kinetic quenching’ is also discussed as a system where the Curtin-Hammett principle is inapplicable.     

合作原则与礼貌原则在大学英语篇章教学中的运用

Grice的合作原则和Leech的礼貌原则为如何推断人们在语言交际过程中的隐含意思确定了理论基础。把这一理论用于英语篇章教学中，可以正确理解篇章内涵，提高学生的语言运用能力。     

无意识教育的实施原则

本文对无意识教育的具体实施提出了三个原则往复观照--双向投射论;平等参与--角色趋同论画龙点睛--适度启发论.