【正文】 s plan contribution must meet certain minimum standards as to employee participation and vesting and employer funding. ERISA also approved the use of individual retirement accounts (IRAs) to encourage taxdeferred retirement savings by individuals. The Economic Recovery Tax Act of 1981 (ERTA) provided the largest tax cut up to that time, reducing the maximum individual rate from 70 percent to 50 percent (Pub. L. No. 9734, Aug. 13, 1981, 95 Stat. 172). The most sweeping tax changes since world war ii were enacted in the Tax Reform Act of 1986. This bill was signed into law by President ronald reagan and was designed to equalize the tax treatment of various assets, eliminate tax shelters, and lower marginal rates. Conservatives wanted th。 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 Congress about the high level of taxation, stated, The present system is a failure. It was an emergency measure, adopted under the pressure of war necessity and not to be counted upon as a permanent part of our revenue structure…. The high rates put pressure on taxpayers to reduce their taxable ine, tend to destroy individual initiative and enterprise, and seriously impede the development of productive business…. Ways will always be found to avoid taxes so destructive in their nature, and the only way to save the situation is to put the taxes on a reasonable basis that will permit business to go on and industry to develop. Consequently, the Revenue Act of 1924 reduced the maximum individual tax rate to 43 percent (Revenue Acts, June 2, 1924, ch. 234, 43 Stat. 253). In 1926 the rate was further reduced to 25 percent. The Revenue Act of 1932 was the first tax law passed during the Great Depression (Revenue Acts, June 6, 1932, ch. 209, 47 Stat. 169). It increased the 手機(jī)后蓋注塑模的設(shè)計 31 individual maximum rate from 25 to 63 percent, and reduced personal exemptions from $1,500 to $1,000 for single persons, and from $3,500 to $2,500 for married couples. The national industrial recovery act of 1933 (NIRA), part of President franklin d. roosevelt39。 loan amp。 Science, 2021. 45(3): p. 325332. [17] Pouzada, ., . Ferreira, and . Pontes, Friction properties of moulding thermoplastics. Polymer Testing, 2021. 25(8): p. 10171023. [18] Pontes, . and . Pouzada, Ejection force in tubular injection moldings. Part I: Effect of processing conditions. Polymer Engineering and Science, 2021. 44(5): p. 891897. 手機(jī)后蓋注塑模的設(shè)計 30 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。 由于本人實踐經(jīng)驗與理論水平有限，盡管設(shè)計時小心慎重，加之時間較短促，論文中的缺點和不足之處敬請老師批評指正。在利用AutoCAD、 Pro/E 兩種方式造型以及最后采用澆注方法時也得到了王老師的指導(dǎo)，再次表示感謝。 模具總裝配圖如下 81 所示： 手機(jī)后蓋注塑模的設(shè)計 27 圖 81 模具裝配圖 手機(jī)后蓋注塑模的設(shè)計 28 致 謝 本次畢業(yè)設(shè)計自 2021 年 12 月開始，課題名稱為“手機(jī)后蓋注塑模的設(shè)計”，要求設(shè)計出注塑模具一套，生產(chǎn)的塑料制品應(yīng)達(dá)到一定的質(zhì)量要求，設(shè)計出的模具應(yīng)結(jié)構(gòu)合理、工藝性好、出模方便、安全可靠、便于維修。至此，整個開模過程完成。相信通過本次設(shè)計，鍛煉了自己的毅力和耐心，豐富了自己的理論知識和實踐的認(rèn)知能力，對以后的學(xué)習(xí)生活會給予很高的幫助。在設(shè)計斜頂?shù)倪^程中，反反復(fù)復(fù)的畫圖設(shè)計斜頂?shù)念^部形狀，下了很大的功夫。繪圖設(shè)計進(jìn)行的很慢，在后期的操作中對軟件的熟悉逐步加快了速度。在計算機(jī)輔助軟件上，又一次的鍛煉了繪畫和設(shè)計的能力，更深層次的對 AutoCAD 及其燕秀工具箱和 Proe 的認(rèn)知，了解到了以前沒有使用的一些功能。 本次設(shè)計水道水路的直徑為 4mm，它們位置之間的分布情況如圖 73 手機(jī)后蓋注塑模的設(shè)計 25 圖 73 水路分布 手機(jī)后蓋注塑模的設(shè)計 26 8 結(jié)論 在對手機(jī)后蓋注塑模的設(shè)計過程中 ，參閱和查找了許多的文獻(xiàn)和資料，也向?qū)熣髑罅嗽S多的意見和想法。 設(shè)計及其細(xì)節(jié) 在實際的設(shè)計之中，也應(yīng)該注意一些設(shè)計中的小細(xì)節(jié)，使得設(shè)計的冷卻水道能夠更好的位系統(tǒng)服務(wù)。水冷卻有直通式水路、階梯式水路、隔板式水路、盤旋式水路等。 常見的冷卻方法有水冷卻，油冷卻，壓縮空氣冷卻等。 手機(jī)后蓋注塑模的設(shè)計 23 7 冷卻系統(tǒng)設(shè)計 常用冷卻方法 在注塑過程中，熔料的溫度一般會達(dá)到 200℃ 左右，模具 的溫度會持續(xù)保持一個高溫的狀態(tài)，而頂出塑件時溫度卻只有 5060℃ 左右，這個時候就必須有個機(jī)構(gòu)讓模具的文帝在一個很短的時間內(nèi)冷卻，就是冷卻系統(tǒng)，由于冷卻系統(tǒng)的出現(xiàn)更方便了模具的加工生產(chǎn)。具體分布如圖 63 示 手機(jī)后蓋注塑模的設(shè)計 22 圖 63 頂針分布圖 頂出行程的計算 頂出行程是指產(chǎn)品在開模的時候被頂出的距離，也就是說要有多少距離，才能使產(chǎn)品順利脫模。設(shè)計頂出機(jī)構(gòu)的時候應(yīng)該盡量使其留在動模上；保證產(chǎn)品的外觀沒有變形或者出現(xiàn)毛邊；設(shè)計的機(jī)構(gòu)應(yīng)簡單容易操作；復(fù)位時沒有差錯。如圖 62 手機(jī)后蓋注塑模的設(shè)計