【文章內(nèi)容簡介】 速、智能化控制的電梯一定會提供優(yōu)質(zhì)良好的服務(wù)。無機(jī)房、無齒輪、電磁兼容性、遠(yuǎn)程監(jiān)控、使用新材料等技術(shù)將是電梯工業(yè)今后幾年的主要研究方向。 由于國外先進(jìn)的安裝技術(shù)和維護(hù)保養(yǎng)技術(shù)的引進(jìn)，目前電梯安裝，特別是提升高度較高的電梯安裝，普遍采用無腳手架安裝法進(jìn)行電梯的安裝。同時(shí)，與電梯相關(guān)的基礎(chǔ)工業(yè)的進(jìn)步、現(xiàn)代化管理手段的貫徹和安裝工人的技術(shù)能力的培養(yǎng)， 為電梯安裝的快捷、準(zhǔn)確提供了方便。為提高維護(hù)保養(yǎng)工作的質(zhì)量， 及時(shí)解決和預(yù)防電梯在使用過程中的突發(fā)故障和運(yùn)行隱患，一些電梯企業(yè)借助計(jì)算機(jī)網(wǎng)絡(luò)建立了電梯監(jiān)視或監(jiān)控系統(tǒng) ,有效地提高在用電梯的完好率 ,及時(shí)排除電梯所發(fā)生的故障，最大限度地維護(hù)電梯用戶的權(quán)利。 雖然目前中國是世界上最大的電梯市場，但是，各類電梯使用普及率與國外發(fā)達(dá)國家相比，還存在相當(dāng)?shù)陌l(fā)展空間。即使達(dá)到了國外發(fā)達(dá)國家的水平，每年電梯的更新，也具有相當(dāng)?shù)臄?shù)量。 目前電梯在國際上發(fā)展的比較迅速，特別是在某些特殊場合和有發(fā)展前景，而國產(chǎn)電梯在性能上存在著一些問題，因此加強(qiáng)電梯的研究成果很有必要， 研究運(yùn)用高級控制，傳 感器的提高以此來彌補(bǔ)元件的不足 ,達(dá)到更好的運(yùn)行性能，將中國國產(chǎn)的電梯推向國際市場。因此，充分了解電梯發(fā)展趨勢，掌握其中的核心技術(shù)，創(chuàng)建含有自主知識產(chǎn)權(quán)的民族品牌，任重而道遠(yuǎn)。 第 13 頁 共 19 頁 參考文獻(xiàn)： [1]吳中俊，黃永紅 .可編程控制器原理及應(yīng)用 [2]. 北京 : 機(jī)械工業(yè)出版社 ,2021 [2]陳立定 ,吳玉香 ,蘇開才 .電氣控制與可編程控制器 [M].廣州 :華南理工大學(xué)出版社 ,2021 [3]鄭學(xué)偉 .基于 PLC的電梯控制系統(tǒng) [DB].中國優(yōu)秀碩士學(xué)位論文全文數(shù)據(jù)庫 ,2021 [4]黃立培 .變頻器應(yīng)用技術(shù)及電動機(jī)調(diào)速 [M].北京 :人民郵電出版社 ,1997 [5]張燕賓 .SPWM變頻調(diào)速應(yīng)用技術(shù) [M]. 北京 :機(jī)械工業(yè)出版社 ,1997 [6]李秧耕 ,何喬治 ,何峰 .電梯基本原理及安裝維修全書 [M].北京：機(jī)械工業(yè)出版社， 2021 [7]劉裁文 .電梯控制系統(tǒng) [M].北京 :電子工業(yè)出版社 ,1996 [8]賀玲芳 .基于 PLC控制的全自動變頻恒壓供水系統(tǒng) [J].西安：西安科技學(xué)院學(xué)報(bào) ,2021 [9]林小峰 .可編程控制器原理及應(yīng)用 [M]. 北京 : 高等教育出版社 , 1991 [10]張曉峰，張靜．電氣控制與可編程控制技術(shù)及應(yīng)用［ M］ ．北京：國防工業(yè)出版社， 2021 第 14 頁 共 19 頁 附錄 附錄一 完整程序匯總 第 15 頁 共 19 頁 第 16 頁 共 19 頁 第 17 頁 共 19 頁 第 18 頁 共 19 頁 第 19 頁 共 19 頁 附錄二 實(shí)驗(yàn)接線圖 第 20 頁 共 19 頁 請刪除以下內(nèi)容， O(∩ _∩ )O 謝謝?。。?The origin of taxation in the United States can be traced to the time when the colonists were heavily taxed by Great Britain on everything from tea to legal and business documents that were required by the Stamp Tax. The colonists39。 disdain for this taxation without representation (socalled because the colonies had no voice in the establishment of the taxes) gave rise to revolts such as the Boston Tea Party. However, even after the Revolutionary War and the adoption of the . Constitution, the main source of revenue for the newly created states was money received from customs and excise taxes on items such as carriages, sugar, whiskey, and snuff. Ine tax first appeared in the United States in 1862, during the Civil War. At that time only about one percent of the population was required to pay the tax. A flatrate ine tax was imposed in 1867. The ine tax was repealed in its entirety in 1872. Ine tax was a rallying point for the Populist party in 1892, and had enough support two years later that Congress passed the Ine Tax Act of 1894. The tax at that time was two percent on individual ines in excess of $4,000, which meant that it reached only the wealthiest members of the population. The Supreme Court struck down the tax, holding that it violated the constitutional requirement that direct taxes be apportioned among the states by population (pollock v. farmers39。 loan amp。 trust, 158 . 601, 15 S. Ct. 912, 39 L. Ed. 1108 [1895]). After many years of debate and promise, the sixteenth amendment to the Constitution was ratified in 1913, providing Congress with the power to lay and collect taxes on ine without apportionment among the states. The objectives of the ine tax were the equitable distribution of the tax burden and the raising of revenue. Since 1913 the . ine tax system has bee very plex. In 1913 the ine tax laws were contained in eighteen pages of legislation。 the explanation of the tax reform act of 1986 was more than thirteen hundred pages long (Pub. L. 99514, Oct. 22, 1986, 100 Stat. 2085). Commerce Clearing House, a publisher of tax information, released a version of the Internal Revenue Code in the early 1990s that was four times thicker than its version in 1953. Changes to the tax laws often reflect the times. The flat tax of 1913 was later replaced with a graduated tax. After the United States entered world war i, the War Revenue Act of 1917 imposed a maximum tax rate for individuals of 67 percent, pared with a rate of 13 percent in 1916. In 1924 Secretary of the Treasury Andrew W. Mellon, speaking to