畢業(yè)論文-3D打印ABS材料的條件探究及其機械性能測定

1、PAGE 152015屆本科畢業(yè)論文(設計) 2015屆本科畢業(yè)論文（設計）3D打印ABS材料的條件探究及其機械性能測定學 院：專業(yè)班級：學生姓名：指導教師：（副教授） 答辯日期：2015年5月17日 8888888888888 新疆師范大學2012屆本科畢業(yè)論文（設計） PAGE 17目 錄TOC o 1-3 h u HYPERLINK l _Toc15634 1. 前言 PAGEREF _Toc15634 1 HYPERLINK l _Toc15147 2. 實驗部分3 HYPERLINK l _Toc25058 2.1 實驗儀器、材料3 HYPERLINK l _Toc18154 2.2

2、 3D打印建模 3 HYPERLINK l _Toc6078 2.3 3D打印機操作及模型的打印3 2.4 模型的剝離4 2.5 機械性能的測定5 HYPERLINK l _Toc15104 3. 結(jié)果與討論6 HYPERLINK l _Toc18515 3.1 不同打印溫度下機械性能測定7 HYPERLINK l _Toc4631 3.2 不同填充密度機械性能測定8 HYPERLINK l _Toc27076 3.3 不同層高機械性能測定9 HYPERLINK l _Toc25921 3.4 不同底部/底部厚度機械性能測定11 HYPERLINK l _Toc26752 4. 結(jié)論 PAGE

3、REF _Toc26752 12致 謝 HYPERLINK l _Toc5313 13 HYPERLINK l _Toc691 參考文獻 PAGEREF _Toc691 14新疆師范大學2015屆本科畢業(yè)論文(設計)3D打印ABS材料的條件探究及其機械性能測定摘要：3D打印技術是采用三維噴墨打印技術，通過分層加工與疊加成形相結(jié)合的方式，逐層打印增加材料來增加材料來生成3D實體，達到與激光成型等其他3D模型制造技術相同3D真實物體的數(shù)字制造技術。其最大優(yōu)勢在于能擴展設計人員的想象空間，只要能在計算機上設計成三維圖形的東西，無論是造型各異的服裝，精美的工藝品，還是個性化的車子，只要解決了材料的問題

4、，都可以實現(xiàn)3D打印。因此實驗主要是使用基于熔融沉積制造技術的3D打印機，關于ABS材料的條件探究及其機械性能測定，主要通過制作國標下10804的長方形，改變3D打印機上的打印溫度、填充密度、層高、頂部/底部厚度等參數(shù)，測定不同參數(shù)對ABS產(chǎn)品的機械性能測定。大大減少因溫度等原因下原材料的浪費，節(jié)省成本，提高制作精度，提高產(chǎn)品的硬度。使3D打印能更好的應用于人們的日常生活中。得出樣品在打印溫度220、填充密度80%、層高0.2mm、頂部/底部厚底0.4mm的條件下，其機械性能最佳。關鍵詞：3D打印機；ABS材料；熔融；機械性能3D print ABS material condition in

5、quiry and its mechanical property determinationAbstracts: 3D printing technology is the use of three dimensional ink-jet printing technology, the way of the combination of the layering processing and superposition forming, printing material layer by layer increased to increase the material to genera

6、te the 3D entity, and the other to the laser forming 3D model manufacturing technology as the real object of digital manufacturing technology 3D. Its biggest advantage is that can be extended to design personnels imagination, as long as can be designed into a 3D graphics in computer, whether differe

7、nt styles of clothing, fine arts and crafts, or personalized car, as long as the solution to the problem of material, can achieve 3D print. Therefore, this experiment is the use of fused deposition manufacturing technology based on the ABS 3D printer, the condition of material and mechanical propert

8、ies were determined by national standard, the main production of rectangular 10804, change the 3D printer to print the temperature, packing density, height, top / bottom thickness, determination of different parameters on the mechanical properties of ABS product. Reduce waste, the temperature of the

9、 raw materials and other reasons to save cost, improve the manufacturing accuracy, improve the hardness of products. The 3D print can be better used in peoples daily life. The samples in a temperature of 220 DEG C, print density, filling conditions 80% storey 0.2mm, top / bottom thickness of 0.4mm,

10、the best mechanical properties.Key words: 3D ABS printer; materials; melting; mechanical properties;新疆師范大學2015屆本科畢業(yè)論文(設計)1. 前言 3D打印技術與3D印刷是兩個完全不同的概念，3D印刷是將圖片分離成不同角度的紅、藍兩張圖片，然后將兩張圖片按照規(guī)定的距離印在一起，并用特殊眼睛觀察看來形成3D視覺效果，或者將圖片經(jīng)過特殊處理后，直接印刷在特殊的光柵板上，從而呈現(xiàn)3D視覺效果的印刷技術，而3D打印技術是指采用三維噴墨打印技術，通過分層加工與疊加成形相結(jié)合的方式，逐層打印增加材料來

11、增加材料來生成3D實體，達到與激光成型等其他3D模型制造技術相同3D真實物體的數(shù)字制造技術。3D打印機按照所使用技術的不同，其工作原理分為基于三維打印技術的3D打印機和基于熔融沉積制造技術的3D打印機。 近年來3D打印技術持續(xù)發(fā)展，成本的大幅降低使其已經(jīng)從研發(fā)的消腫空間向主流市場進軍，發(fā)展勢頭不可阻擋，已經(jīng)成為社會廣泛關注、民用市場迅速崛起的新領域。3D打印制作的模型、禮品、紀念品乃至工藝品的應用，極大吸引了社會關注及投入，發(fā)展加速，市場開始呈現(xiàn)量與質(zhì)的雙飛躍。據(jù)預測，2020年3D打印成品將占產(chǎn)品生產(chǎn)總量的50%。3D打印技術的最大優(yōu)勢在于能擴展設計人員的想象空間，只要能在計算機上設計成三維

12、圖形的東西，無論是造型各異的服裝，精美的工藝品，還是個性化的車子，只要解決了材料的問題，都可以實現(xiàn)3D打印。目前3D打印技術支持多種材料，可以廣泛應用在工業(yè)設計、建筑、汽車、航天、牙科、醫(yī)療甚至美食等不同領域。3D打印機的快速成型技術使之在市場上獨其優(yōu)勢，在生產(chǎn)應用上潛力巨大，目前已在工業(yè)、醫(yī)學、日常生活上有了一定的應用。然而3D打印面臨著的最大的技術難題分為：材料的限制對3D打印技術應用范圍形成一大難題；價格成本的制約導致設備尋求量難有爆發(fā)性增長。因此對與3D打印技術的材料研究已成為不可缺少的項目。而目前ABS可以說是3D打印機中最常用的打印材料，有多種顏色可以選擇，是消費級3D打印機用戶最

13、喜愛的打印材料，ABS材料:（丙烯腈-丁二烯-苯乙烯共聚物，ABS是Acrylonitrile Butadiene Styrene的首字母縮寫）是一種強度高、韌性好、易于加工成型的熱塑型高分子材料結(jié)構(gòu)。又稱ABS樹脂.，其綜合性能較好，有極好的沖擊強度、電性能、耐磨性、抗化學藥品性、染色性、成型加工和機械加工較好。且具有高韌性，低重量，不透明的特點，產(chǎn)品成型效果非常好，光滑細膩?；瘜W性質(zhì)穩(wěn)定，被廣泛應用與工業(yè)機械塑料配件、模型機械、電子電器、儀器儀表等工業(yè)領域。ABS材料通常是細絲盤裝，通過3D打印噴嘴加熱溶解打印。由于噴嘴噴出之后需要立即凝固，不同的3D打印的打印溫度、填充密度、層高、底部/

14、頂部厚度的改變，將決定打印的產(chǎn)品耗材、外觀、機械性能和穩(wěn)定性。本實驗主要使用了基于熔融沉積制造技術的3D打印機，其工作原理是先在3D打印機的控制軟件中導入由Cura生成的實物數(shù)據(jù)，經(jīng)處理生成支撐材料和熱噴頭的運動路徑，及相關參數(shù)如：打印溫度、填充密度、層高、頂部/底部厚度等。然后熱噴頭會在計算機的控制下根據(jù)實物的截面輪廓信息在打印平面上進行平面運動，同時熱塑性絲狀材料由供絲機構(gòu)送至熱噴頭，并在噴頭中加熱和熔化成半溶態(tài)后擠壓出，并噴涂在相應的工作臺上，噴涂熱塑性材料快速冷卻后在平臺上形成一層厚度約0.1mm的輪廓薄片，形成了一個3D打印截面，將這個作業(yè)過程不斷循環(huán)，承載工作臺高度隨之不斷降低，一

15、層層的熔覆3D打印截面而形成多層堆疊，最終獲得所需的三維實物。通過使用基于熔融沉積制造技術的3D打印機，關于ABS材料的條件探究及其機械性能測定，主要通過制作國標（GB-T 9341-2008）下10*80*4的長方形，改變3D打印機上的打印溫度、填充密度、層高、頂部/底部厚度等參數(shù)，測定不同參數(shù)對ABS產(chǎn)品的機械性能測定。大大減少因溫度等原因下原材料的浪費，節(jié)省成本，提高制作精度，提高產(chǎn)品的硬度。使3D打印能更好的應用于人們的日常生活中。2. 實驗部分2.1實驗儀器、材料制備儀器：H1-204GT-0弘瑞3D打印機（北京匯天威科技有限公司）制圖軟件：Cura（中國科學技術大學先進技術研究院研

16、發(fā)） Autodesk 3ds Max 2012 64-bit - Simplified Chinese測試儀器：三思縱橫電子萬能試驗機UTM6104（出廠編號UTM14513）實驗材料：三綠國維ABS材料（glow in dark ABS condctive） 3M2214汽車噴漆美紋膠帶（駿業(yè)辦公天貓專營店）試劑：丙酮 CH3COCH3 分析純（天津市致遠化學試劑有限公司）2.2實驗內(nèi)容2.2.1 3D打印參數(shù)設定本實驗通過使用基于熔融沉積制造技術的3D打印機，關于ABS材料的條件探究及其機械性能測定，主要通過制作國標（GB-T 9341-2008）下10804的長方形，改變3D打印機上的

17、參數(shù)一：【打印溫度】 不同的打印溫度會影響ABS材料的溶解與揮發(fā)程度，因此不同的打印溫度下的產(chǎn)品其相關機械性能會有所不同，確立打印溫度必不可少。ABS材料的溶解溫度與機器的最高承受溫度在200260之間參數(shù)二：【填充密度】 不同填充密度的產(chǎn)品，其打印填充的量的不同，會直接影響其外觀和承受力，以及其耗材的多少，因此填充密度的確定亦不可或缺。其密度為100%、90%、80%、70%、60%、50%、40%、30%、20%。10%產(chǎn)品無法成立。參數(shù)三：【層高】 層高決定了每一層的打印厚度及出料的粗細程度與打印時間的長短。常規(guī)打印層高為0.06mm、0.1mm、0.15mm、0.2mm、0.25mm。

18、參數(shù)四：【頂部/底部厚度】 控制底部層與頂部層的厚度。實心層的量由切層厚度和這個數(shù)值決定，它是與壁厚相接近來得到一個健壯的部分，機器的控制值在0.1mm到0.5mm之間。為0.1mm、0.2mm、0.3mm、0.4mm、0.5mm。 測定不同參數(shù)對ABS產(chǎn)品的機械性能測定。大大減少因溫度等原因下原材料的浪費，節(jié)省成本，提高制作精度，提高產(chǎn)品的硬度。使3D打印能更好的應用于人們的日常生活中。2.2.2 3D打印建模利用3Dmax2012制作國標（GB-T 9341-2008：見附錄）塑料 彎曲性能的測定模型10mm80mm4mm的長方形，再使用Cura對模型進行參數(shù)的設定。如圖2-1、圖2-1所

19、示。圖2-1：3Dmax2012截面 圖2-2：Cura的制作截面2.2.3 3D打印機操作及模型的打印 將已經(jīng)制備完成的模型10mm80mm4mm的長方形，存于儲存卡中。在3D打印機中打開，點擊運行即可。模型的打印是基于熔融沉積的制造技術，通過分層加工、疊加成型而完成打印。2.2.4 模型的剝離因玻璃的導熱系數(shù)偏低，導致ABS材料前期起翹。我尋求了許多新的解決方案。包括打印或不打印底座，升高加熱臺的溫度、用丙酮來清洗藍色膠帶，密封內(nèi)部空間保留熱量、升高或降低噴頭的溫度。調(diào)整了所有能調(diào)解的參數(shù)，但是始終無法解決翹邊的問題。之前那些聲稱能解決該問題的辦法：使用新型的加熱板和藍膠帶、用玻璃板、創(chuàng)造

20、真空條件、使用新型膠帶等等，都被一一驗證失敗了。所以我的解決方案也就隨之而來了，它已被證實便宜、迅速、簡單、100%可靠。步驟一： 把ABS廢料和丙酮混在錐形瓶里第一步就是將ABS廢料（底座、支撐或打印失敗的作品）和少許丙酮溶液混合在一起。讓混合物放置幾個小時后，它們已經(jīng)充分的溶解了，然后取較薄一層的溶液。步驟二：在加熱臺上涂一層薄的混合液（圖2-3）在加熱臺上先粘貼一層藍色膠帶，然后涂一層薄的ABS、丙酮混合液（圖2-3）用玻璃棒引流在藍膠帶上涂上薄薄一層的混合液。步驟三： 打印作品選擇打印時去掉底座，直接在那層溶液上打印。然后你會發(fā)現(xiàn)當作品的厚度在增加時就不會產(chǎn)生翹邊的情況了，該層混合液會

21、產(chǎn)生薄薄的一層ABS，這層底座會和加熱盤很好的貼合，即使打印很長或很大的物體也不會出現(xiàn)翹邊的情況了。步驟四： 剝離作品（圖2-4）薄薄的ABS溶液和加熱盤吸附較好。當作品比較大的時候，需要取下藍膠帶，重要的是小心別傷害作品。 圖2-3：ABS材料與丙酮的混合液涂于藍色膠帶上 圖 2-4：產(chǎn)品已基本不起翹，順利剝離 2.2.5 機械性能的測定 將制作打印好的10*80*4mm的長方形放至三思縱橫電子萬能試驗機UTM6104中進行其機械強度的測定。 圖2-5：三思縱橫電子萬能試驗機UTM61043. 結(jié)果與討論3.1 不同打印溫度 設定打印溫度為變量，填充密度為100%，層高，底部/頂部厚度為定量

22、，打印10mm80mm4mm的長方形，質(zhì)量變化圖3-1所示，在200時由于溫度過低，導致出料不均勻，使其質(zhì)量偏低，而210到250之間的質(zhì)量比較穩(wěn)定，且重復性較好。而260時，質(zhì)量的突然下降主要是因為溫度過高，熔絲后，流動性過快，粘稠度減小，出絲過細造成的質(zhì)量下降。 再從樣品的直觀可以，可以看出在220時表面更加光滑且平整，200,260時打印有明顯參差不齊。從質(zhì)量的變化程度和外觀上判斷打印溫度初步定于210到250之間。 圖3-1：不同打印溫度下產(chǎn)品質(zhì)量的變化 圖3-2：不同打印溫度下最大力的比較如圖3-2所示，可以明顯的看出在220比起其他打印溫度而言時最大力最佳且穩(wěn)定性最好。綜上可以得出

23、：在其他條件不變的情況下，打印溫度在220時，ABS材料的機械性能穩(wěn)定性最優(yōu)。3.2 不同填充密度 將填充密度定為變量，溫度設為220，層高，底部/頂部厚度保持不變的條件下，打印10*80*4mm的長方形質(zhì)量比較圖如下： 圖3-3：不同填充密度下質(zhì)量變化圖 如圖3-3所示，隨著填充密度的增加，質(zhì)量呈線性變化，變化穩(wěn)定，表明在220打印溫度下不同填充密度的質(zhì)量變化均勻且打印穩(wěn)定性好。 圖3-4：不同填充密度下最大力的變化如圖3-4所示，隨著填充密度的增加，最大力呈上升趨勢，在80%時有一個上升的拐點，且80%所對應的最大力為92.8213N，用于我們?nèi)粘Ｉ钪校?0N的力已相對足夠，且比較90%

24、與100%，最大力雖然較好，但質(zhì)量也隨之上升，相對比較耗費材料。 圖3-5：不同填充密度下產(chǎn)品展示如圖3-5所示,80%到100%時，產(chǎn)品的表面更加光滑且平整，重復性更好，結(jié)合前兩張圖形，可以得出填充密度為80%時它的耗材，產(chǎn)品外觀及最大力都達到了最佳。綜上可以得出：在打印溫度為220，其他條件不變的情況下，填充密度為80%時產(chǎn)品的機械性能達到最佳。3.3 不同層高將層高設為變量，打印溫度設為220，填充密度設為80%，底部/頂部厚度為定量時。打印10*80*4mm的長方形，其質(zhì)量變化如下圖所示：31min38min48min108min69min 圖3-6：不同層高下產(chǎn)品質(zhì)量變化圖 如圖3-

25、6所示，不同層高下產(chǎn)品質(zhì)無明顯變化，而在0.05，0.1mm的層高時，因為每層的打印過細，出料不均勻，打印時空隙較多，導致質(zhì)量偏低。0.15mm到0.25mm質(zhì)量變化不明顯。0.10mm時質(zhì)量最低。因此可以初步取得層高的范圍為0.15mm到0.25mm之間。且在這期間的打印耗時也較短。一定程度上節(jié)省了時間。 圖3-7：不同層高下在最大力的變化如圖3-7所示；可以明顯看出隨著層高的不斷增高，其最大力呈上升后又下降的趨勢。在層高為0.2mm時達到最大。在不同的打印層高下產(chǎn)品顯示出，在0.15mm到0.25mm時產(chǎn)品的表面光滑且平整，而0.2mm時達到最佳（圖3-9）。綜上可以得出：在打印溫度為22

26、0、填充密度為80%時，樣品在層高為0.2mm時其機械性能達到最佳。 圖3-8：不同層高下產(chǎn)品的展示3.4不同頂部 底部厚度 將底部/頂部厚度設為變量，打印溫度設為220，填充密度設為80%，層高設為0.2mm時。打印10*80*4mm的長方形，其質(zhì)量變化如下圖所示： 圖3-9：不同底部/底部厚度下質(zhì)量的變化 圖3-10：不同底部/頂部厚度下最大力的變化 如圖3-9所示，在不同底部/頂部厚度質(zhì)量的變化無太多明顯的變化。說明底部/頂部厚度的改變對樣品的質(zhì)量無太多影響。而在圖3-10可以明顯看出，隨著底部/頂部厚度的變化，樣品的最大力呈逐漸上升后下降的趨勢。在底部/頂部厚度為0.4mm時，最大力達

27、到最大。4.結(jié)論 本實驗主要是使用基于熔融沉積制造技術的3D打印機，對ABS材料的條件探究及其機械性能測定，主要通過制作國標（GB-T 9341-2008）10*80*4的長方形，通過改變3D打印機上的打印溫度、填充密度、層高、頂部/底部厚度等參數(shù)，測定不同參數(shù)對ABS產(chǎn)品的機械性能測定。以達到減少因溫度等原因下原材料的浪費，節(jié)省成本，提高制作精度，提高產(chǎn)品的硬度。使3D打印能更好的應用于人們的日常生活中。 在填充度為100%的長方形10*80*4中，當打印溫度為220度時。其機械性能最佳；在打印溫度在220度的條件下打印10*80*4的長方形時，填充度為80%時，其外觀，機械性能較優(yōu)在打印溫

28、度為220度，填充度為80%的條件下打印10*80*4的長方形時，層高為0.2mm時，其外觀，最大力及打印時間均最佳。 綜上得出樣品在打印溫度220、填充密度80%、層高0.2mm、頂部/底部厚底0.4mm的條件下，其機械性能最佳。致 謝 本論文是在王帥老師的悉心指導下完成的，王老師嚴謹?shù)闹螌W態(tài)度和淵博的知識使我們在做論文期間受益匪淺。在做畢業(yè)論文期間關老師對我們認真負責，從論文的查閱、開題報告的撰寫，以及撰寫開題報告的注意事項，都耐心得指導我們。對于每一個細節(jié)，每一個我們不理解的地方都為我們悉心得講解。實驗部分，當我們遇到問題的時候，老師耐心得給我們講解。王老師淵博的專業(yè)知識，嚴謹?shù)闹螌W態(tài)度

29、，精益求精的工作作風，誨人不倦的高尚師德，嚴以律己、寬以待人的崇高風范，樸實無華、平易近人的人格魅力對我影響深遠。不僅使我樹立了遠大的學術目標、掌握了基本的研究方法，還使我明白了許多待人接物與為人處世的道理。本論文從選題到完成，每一步都是在導師的指導下完成的，傾注了導師大量的心血。在此，謹向?qū)煴硎境绺叩木匆夂椭孕牡母兄x！ 本論文的順利完成，也離不開搭檔史錦榮的幫助。當我們對實驗儀器的操作有什么問題的時候，他總是能耐心的查找相關文獻并努力的解決在實驗中出現(xiàn)的各種難題。因為有了搭檔的幫助與努力才使得我們的實驗能夠更快更好的完成。本論文的也完成離不開各位老師，學姐和朋友們的關心和幫助。在此感謝王老

30、師、班主任的指導，感謝他們的關心、支持和幫助。參考文獻：1孫建明 童澤平 殷志平 3D打印技術的市場及發(fā)展前景分析 2014.（5）2王雪瑩 3D打印技術及其產(chǎn)業(yè)發(fā)展的前景預見 2012.（4）3王忠宏 李揚帆 3D打印產(chǎn)業(yè)的實際態(tài)勢困境擺脫與可能走向 2013（2）4左世全 我國3D打印發(fā)展戰(zhàn)略與對策研究 2014（1）27-15王柏通 3D打印噴頭的溫度分析及控制策略研究2014（3）6林湖彬 杜崇銘 張姿 鄧淑玲 林志丹 3D打印材料的發(fā)展現(xiàn)狀 2013（10）41-277蔣紀國 王奇 毛春屏 我國ABS樹脂生產(chǎn)現(xiàn)狀及發(fā)展趨勢 2009（2）8談敦禮 李談 陳紅 常見ABS樹脂的性能對比

31、2009 24-39張玉蓉 王建軍 唐開菲 沈國春 論復合材料彎曲試驗 1998（4）4-410 ISO國際標準目錄 世界標準信息 1001-2853（2007）02-0043-07請刪除以下內(nèi)容，O(_)O謝謝！ The term autism refers to a cluster of conditions appearing early in childhood. All involve severe impairments in social interaction, communication, imaginative abilities, and rigid, repetitiv

32、e behaviors. To be considered an autistic disorder, some of these impairments must be manifest before the age of three. The reference book used by mental health professionals to diagnose mental disorders is the Diagnostic and Statistical Manual of Mental Disorders , also known as the DSM. The 2000 e

33、dition of this reference book (the Fourth Edition Text Revision known as DSM-IV-TR ) places autism in a category called pervasive developmental disorders . All of these disorders are characterized by ongoing problems with mutual social interaction and communication, or the presence of strange, repet

34、itive behaviors,interests, and activities. People diagnosed with these disorders are affected in many ways for their entire lives. Description Each child diagnosed with an autistic disorder differs from every other, and so general descriptions of autistic behavior and characteristics do not apply eq

35、ually to every child. Still, the common impairments in social interaction, communication and imagination, and rigid, repetitive behaviors make it possible to recognize children with these disorders, as they differ markedly from healthy children in many ways. Many parents of autistic children sense t

36、hat something is not quite right even when their children are infants. The infants may have feeding problems, dislike being changed or bathed, or fuss over any change in routine. They may hold their bodies rigid, making it difficult for parents to cuddle them. Or, they may fail to anticipate being l

37、ifted, lying passively while the parent reaches for them, rather than holding their arms up in return. Most parents of autistic children become aware of the strangeness of these and other behaviors only gradually. Impairments in social interaction are usually among the earliest symptoms to develop.

38、The most common social impairment is a kind of indifference to other people, or aloofness, even towards parents and close care-givers. The baby may fail to respond to his or her name being called and may show very little facial expression unless extremely angry, upset, or happy. Babies with autism m

39、ay resist being touched, and appear to be lost in their own world, far from human interaction. Between seven and 10 months of age, most infants often resist being separated from a parent or well-known caregiver, but these infants may show no disturbance when picked up by a stranger. Other children w

40、ith autism may be very passive, although less resistant to efforts by others to interact. However, they do not initiate social interaction themselves. Still others may attempt to engage with adults and peers, but in ways that strike others as inappropriate, or odd. In adolescence and adulthood, some

41、 of the higher-functioning individuals with autistic disorders may appear overly formal and polite. They may react with little spontaneity, as if social interaction doesnt come naturally or easily to them, and so they are trying to follow a pre-determined set of rules. Some individuals with autism h

42、ave normal intelligence, and many have special talents in areas such as music or memory. However, individuals with autism may have other mental or emotional problems that co-exist with their autism. Some of these other disorders may include impulse control disorders, obsessive-compulsive disorder ,

43、mood and anxiety disorders, and mental retardation . PSYCHOLOGICAL AND FAMILY FACTORS. Although Henry Maudsley, in the late 1800s, was the first psychiatrist to focus on very young children with mental disorders, it was the psychiatrist Leo Kanner who coined the phrase early infantile autism in 1943

44、. Kanner believed that the parents of children with autistic behaviors were emotionally cold and intellectually distant. He coined the term refrigerator parents to describe them. His belief that parental personality and behavior played a powerful role in the development of autistic behaviors left a

45、devastating legacy of guilt and self-blame among parents of autistic children that continues to this day. Recent studies are unequivocal, however, in demonstrating that parents of autistic children are no different from parents of healthy children in their personalities or parenting behaviors. In fa

46、ct, many families with an autistic child also have one or more perfectly healthy children. Because autistic children can be extremely sensitive to change, any change within the family situation can be potentially traumatic to the autistic child. A move, divorce, birth of a sibling or other stressors

47、 that occur in the lives of most families may evoke a more extreme reaction from an autistic child. While there is no single neurological abnormality found in children with autistic disorders, some research using non-invasive brain imaging techniques such as magnetic resonance imaging (MRI) suggests

48、 that certain areas of the brain may be involved. Several of the brain areas being researched are known to control emotion and the expression of emotion. These areas include the temporal lobe (large lobe of each side of the brain that contains a sensory area associated with hearing), the limbic syst

49、em, the cerebellum, the frontal lobe, the amygdala, and the brain stem, which regulates homeostasis (body temperature and heart rate). Recent research has focused particularly on the temporal lobe because of the finding that previously healthy people who sustain temporal lobe damage may develop auti

50、stic-like symptoms. In animal research, when the temporal lobe is damaged, social behavior declines, and restless, repetitive motor behaviors are common. When measured by MRI, total brain volume appears to be greater for those with autistic disorders. Other neurological factors include lesions to th

51、e brain, congenital rubella, undiagnosed and untreated phenylketonuria (PKU), tuberous sclerosis, and Retts disorder (a related condition in which the baby develops in an apparently normal manner through age five months, and then begins to lose communicative and social interaction skills). There is

52、also evidence of a higher proportion of perinatal complications (complications arising around the time of giving birth) among children with autistic symptoms. These complications include maternal bleeding after the first trimester and meconium in the amniotic fluid. (Meconium is a substance that acc

53、umulates in the bowel of the developing fetus and is discharged shortly after birth.) Some evidence suggests that the use of medications during pregnancy may be related to the development of autistic symptoms. As newborns, children with autistic behaviors show a higher rate of respiratory illness an

54、d anemia than healthy children. ALLERGIES, INFECTIONS, AND IMMUNIZATIONS. Some professionals believe that autistic disorders may be caused by allergies to particular fungi, viral infections, and various foods. No controlled studies have supported these beliefs, but some parents and professionals rep

55、ort improvement when allergens and/or certain foods are eliminated from the diet. Viral infections of the mother, such as rubella, or of the young child, such as encephalitis, mumps, and measles, occasionally appear to cause autistic disorders. The common childhood immunization series known as MMR (

56、measles, mumps, rubella) has recently come under scrutiny as a possible cause of some autistic conditions.Basketball can make a true claim to being the only major sport that is an American invention. From high school to the professional level, basketball attracts a large following for live games as

57、well as television coverage of events like the National Collegiate Athletic Association (NCAA) annual tournament and the National Basketball Association (NBA) and Womens National Basketball Association (WNBA) playoffs. And it has also made American heroes out of its player and coach legends like Mic

58、hael Jordan, Larry Bird, Earvin Magic Johnson, Sheryl Swoopes, and other great players. At the heart of the game is the playing space and the equipment. The space is a rectangular, indoor court. The principal pieces of equipment are the two elevated baskets, one at each end (in the long direction) o

59、f the court, and the basketball itself. The ball is spherical in shape and is inflated. Basket-balls range in size from 28.5-30 in (72-76 cm) in circumference, and in weight from 18-22 oz (510-624 g). For players below the high school level, a smaller ball is used, but the ball in mens games measure

60、s 29.5-30 in (75-76 cm) in circumference, and a womens ball is 28.5-29 in (72-74 cm) in circumference. The covering of the ball is leather, rubber, composition, or synthetic, although leather covers only are dictated by rules for college play, unless the teams agree otherwise. Orange is the regulati