【文章內(nèi)容簡介】 the first two nights, but on the third night, a storm blew up. A gust of wind swept the bed off the roof and sent it crashing into the courtyard below. The young man did not wake up until the bed had struck the ground. Although the bed was smashed to pieces, the man was miraculously unhurt. When he woke up, he was still on the mattress. Glancing at the bits of wood and metal that lay around him, the man sadly picked up the mattress and carried it into his house. After he had put it on the floor, he promptly went to sleep again.Lesson50 Taken for a ride 乘車兜風(fēng)I love travelling in the country, but I don39。t like losing my way. I went on an excursion recently, but my trip took me longer than I expected. 39。 I39。m going to Woodford Green,39。 I said to the conductor as I got on the bus,39。 but I don39。t know where it is.39。 39。 I39。ll tell you where to get off,39。 answered the conductor. I sat in the front of the bus to get a good view of the countryside. After some time, the bus stopped. Looking round, I realized with a shock that I was the only passenger left on the bus.39。 You39。ll have to get建立計量標(biāo)準(zhǔn)技術(shù)報告計量標(biāo)準(zhǔn)名稱精密壓力表標(biāo)準(zhǔn)器組代碼12415100準(zhǔn)確度等級177。%開展檢定項目~4級一般壓力表建立計量標(biāo)準(zhǔn)負責(zé)人建立計量標(biāo)準(zhǔn)單位 年 月 日一、建立計量標(biāo)準(zhǔn)的目的意義壓力計量儀器儀表，絕大多數(shù)為強制檢定的計量器具，直接影響著產(chǎn)品的質(zhì)量和生產(chǎn)設(shè)備與人身的安全，為了加強計量器具的強檢工作、保證產(chǎn)品質(zhì)量和生產(chǎn)安全，特建立壓力表標(biāo)準(zhǔn)裝置。二、選用的計量標(biāo)準(zhǔn)器及主要配套設(shè)備計 量 標(biāo) 準(zhǔn) 器名 稱型號規(guī)格編 號準(zhǔn)確度等級檢定證書號精密壓力表Y150精密壓力表Y150精密壓力表Y150精密壓力表Y15004MPa精密壓力表Y150010MPa精密壓力表Y150016MPa配 套 設(shè) 備壓力表校驗器三、檢定方法及原理本單位一般工作壓力表直接比較法本單位精密壓力表%上級計量行政部門二等標(biāo)準(zhǔn)活塞壓力計177。5104直接比較法壓力表是根據(jù)帕斯卡定律，以流體靜力學(xué)的平衡原理為基礎(chǔ)進行壓力計量的，利用壓力校驗器造成的壓力并經(jīng)導(dǎo)管將該壓力同時傳遞給精密壓力表和被測壓力表，使二者在同一壓力下進行示值比對。四、實驗室環(huán)境條件環(huán) 境 參 數(shù)要 求實 測 結(jié) 果結(jié) 論溫 度20177。5℃22℃符 合濕 度≤85%80%符 合五、計量標(biāo)準(zhǔn)的誤差分析及總不確定度壓力表檢定裝置的誤差來源： 二等標(biāo)準(zhǔn)器量值傳遞誤差△1≤177。5104 精密表讀數(shù)誤差△2≤177。104 精密表刻度誤差△3≤177。104 精密表溫度影響誤差△4≤177。12104 精密表的彈性后效和彈性遲滯誤差△5≤177。103經(jīng)上述分析找到各項誤差限。由于各項誤差彼此獨立，在誤差合成上，采用方和根法，即總不確定度U=177。=177。104=177。%所以總不確定度為177。%，小于檢定規(guī)程中的規(guī)定要求。六、計量標(biāo)準(zhǔn)的測量重復(fù)性序號 Xi (MPa)U=XiU210023456007008910任選一只壓力表040MPa，，在40Mpa處，在同等條件下，對受檢點40MPa反復(fù)檢10次，各項測值如下：=U2=S=177。=177。=177。七、計量標(biāo)準(zhǔn)總不確定度的驗證標(biāo)準(zhǔn)壓力值計量部門檢定結(jié)果（MPa）本裝置檢定結(jié)果（MPa）比對差值0000510203040選定一只040 Mpa壓力表經(jīng)自檢測一組數(shù)據(jù)與法定計量部門的一組數(shù)據(jù)比對檢定結(jié)果如下： MPa，未超過被檢表允許極限誤差的三分之二。即此裝置的總不確定度得到驗證。八、結(jié)論該裝置的合成總不確定度為177。%，符合檢定規(guī)程的要求，可開展一般工作壓力表的檢定工作。九、附錄 國家計量檢定規(guī)程 計量器具檢定合格證書 說明書操作規(guī)范into the cave hoping to find buried treasure. The leader of the party was examining the soil near the entrance to the cave when the machine showed that there was gold under the ground. Very excited, the party dug a hole two feet deep. They finally found a small gold coin which was almost worthless. The party then searched the whole cave thoroughly but did not find anything except an empty tin trunk. In spite of this, many people are confident that 39。The Revealer39。 may reveal something of value fairly soon.Lesson56 Faster than sound! 比聲音還快！Once a year a race is held for old cars. A lot of cars entered for this race last year and there was a great deal of excitement just before it began. One of the most handsome cars was a RollsRoyce Silver Ghost. The most unusual car was a Benz which had only three wheels. Built in 1885, it was the oldest car taking part. After a great many loud explosions, the race began. Many of the cars broke down on the course and some drivers spent more time under their cars than in them ! A few cars, however, pleted the race. The winning car reached a speed of forty miles an hourmuc