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A jet plane may reach a speed of around 3500 km/h but light travels at the speed of 1,071,360,000 km/h (a speed that you and I could not possibly comprehend), so you can imagine the difference in time that would be recorded if the clock were traveling near to that speed.

喷气式飞机能达到3500 km/h，但光速是1，071，360，000 km/h（一个你和我是无法想象的速度），那你想一想，如果那个钟能靠近光速的话，那个时差会有多大。

In order to achieve high-speed machining, not only have high-speed machine tool spindle, but also high-speed servo system, which is not only to increase productivity, but also to maintain high-speed cutting tool of the necessary conditions for normal work.

为了实现高速切削加工，机床不但要有高速主轴，还要有高速的伺服系统，这不仅是为了提高生产效率，也是维持高速切削中刀具正常工作的必要条件。

Then basing the selective thread bar, we can select the speed reducer whose model is XB1-50 . Basing the selective harmonies waves speed reducer ,we can confirm the servo electromotor whose type is 110SZ07 . Then we can design the spindles of every component ,which conclude the spindle of between the speed reducer and electromotor axis, which is a round bond sleeve spindle and the spindle between the speed reducer and the thread bar, which is flat bond sleeve spindle , the bearing , the track whose type is roll track HJG-D25, and the collective structure of the plate.

根据给定的工作台的切削力、传动精度、行程等确定丝杠为滚珠丝杠副FC1-2004-2.5，由丝杠的尺寸及转矩，选择减速器为XB1-50型的谐波减速器，本根据谐波减速器的输入力矩尺寸及减速比，选择伺服电机为直流伺服电机110SZ07，其转速为10000rpm，然后设计元器件间的联轴器，包括减速器与电机轴间的半圆键套筒联轴器、减速器与丝杠间的平键套筒联轴器，设计轴承，导轨为HJG-D25的滚动导轨，及工作台的总体结构。

CNC lathe spindle speed due to very high, for ease of workpiece clamping, multi-use high-speed hydraulic power chuck, because it is in the production plant has passed a strict balance, with a high speed (speed limit up to 4000 ~ 6000r/min), high clamping force (push pull for the largest 2000 ~ 8000N), high-precision, adjusting claw convenience, through-hole, long life and so on.

由于数控车床主轴转速极高，为便于工件夹紧，多采用液压高速动力卡盘，因它在生产厂已通过了严格的平衡，具有高转速（极限转速可达4000~6000r/min）、高夹紧力（最大推拉力为2000~8000N）、高精度、调爪方便、通孔、使用寿命长等优点。

Design and realization of engine speed system According to servocontrol technology of D.C and actual equipment, the paper has designed hardware circuit of engine speed system, drive circuit of simulation speed meter and indicator of simulation speed meter.

依据发动机转速系统的数学模型，给出了软件实现框图；依据有关飞行模拟器验证的国家军用标准，利用A/D转换卡采集到的发动机转速系统转速的仿真数据(稳态转速、加速转速和减速转速)，对发动机转速系统的仿真情况进行了验证。4。

To solve the aerodynamic problems resulted from high-speed trains when they pass through a tunnel, a model experiment system for high-speed trains was set up on the basis of analyzing the relative present experiment systems at home and abroad, and its similarity rules were derived. In this system, compressed air is used to impel a model train, and the speed of this train speed can reach 70 m/s.

为了解决高速列车进出隧道引起的空气动力学问题，基于对目前国内外高速列车模型试验研究现状的分析，建立了模型列车速度可达100 m/s的压缩空气式高速列车模型试验系统，并导出了模型试验的相似准则。

This simulation system will help to improve innovation design level of high-speed cultivation machine such as high-speed plow and high-speed rotary tiller. SPH; back-rotary tilling ; simulation ; soil-tool interaction ; high-speed cutting

因为牵涉到多相、松散和物性分散的耕作土壤在工作部件高速作用下的破坏过程以及破坏后土壤运动状态的描述，用连续体力学理论及其数值解法(有限单元法或者边界元法)很难描述该过程如有限单元法在大变形状况下会发生网

The results show that the zero speed point is located on the arc between two absolute speed zero points of rotation axes, and the necessity of relative speed zero point is demonstrated.

利用程序对相对速度零点的位置进行搜索，发现速度零点处于两轴绝对速度零点之间的圆弧上，从而证明了相对速度零点存在的必然性。

Based on a data collecting system of moving and static test-bed about helicopter airscrew,the paper designed principal axis low speed control system ,namely designed electric control system, speed measuring system of it and researched a debugging shceme about low speed control system.

本文以"直升机旋翼动平衡试验台数据采集工程"为背景，设计了"直升机旋翼动平衡试验台数据采集系统"工程中的主轴低速控制系统，即对低速控制系统中的电控系统和测速系统进行了设计，并结合实际工程给出了系统的调试方案和最后的实验结果。

Regarding the general industrial dust aluminite powder, the firing delay time and the most tremendous pressure rise speed influence is very obvious to its maximum explosion pressure; Its maximum explosion pressure and the maximum pressure rise speed reduces along with the dust granularity increases: And increases the tendency to be obvious; Has a best dust loading, causes its maximum explosion pressure and the maximum pressure rise speed maximizing.

对于一般工业粉尘铝粉来说，点火延迟时间对其最大爆炸压力和最大压力上升速率的影响十分明显；其最大爆炸压力和最大压力上升速率随着粉尘粒度的减小而增加：且增加趋势明显；存在一个最佳粉尘浓度，使其最大爆炸压力和最大压力上升速率达到最大值。

The work of this paper is as follows: 1. Looking back the progressing history of the linear motor, introducing the features of the elevator driven by linear induction motor, radicating the topic of this paper "the digital frequency variable control of the elevator bi-side direct driven by linear induction motor". The research of this paper covers the conventional VVVF control, space vector based VVVF control, vector control and DTC.

本文主要开展了以下几个方面的工作： 1 回顾了直线电机发展历史，电机的驱动技术演变，特别是针对直线电机的驱动，简要介绍了直线感应电机驱动电梯的优点和不同结构类型，对传统的v／f控制，基于空间矢量法的v／f控制，矢量控制，和基于电压空间矢量的直接转矩控制进行了比较，确立了本课题的研究主题：直线感应电机双边直推式驱动电梯的全数字变频控制。

The article combines with the treatment of a superficial civil air defense work to introduce how the grouting method to improve the performance of the backfill soil.

文章从治理漂浮人防工事的角度提出了注浆技术在改善回填土性质方面的应用，并详细阐述了注浆技术的施工流程。