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Paradigm Shifts and Design Flaws: Learning from Observations and Evaluation Methods

Explore the impacts of observation, evaluation methods, and design flaws through intriguing stories and important lessons in engineering and design paradigms.

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Paradigm Shifts and Design Flaws: Learning from Observations and Evaluation Methods

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  1. Chapter 0 Design Paradigms

  2. Observation by different person 有三個人搭乘火車，在英國的原野上觀光，一個人是工程師，一個人是物理學家，一個人是數學家。經過一處鄉村，三個人看到窗外草地上站著一隻黑色的羊，一動也不動。工程師首先驚訝開口：「沒有想到英國的羊是黑色的！」物理學家說話了：「我必須要糾正你，你應該說，你所看到的這一隻羊是黑色的。」數學家說話了：「我必須要糾正你，你應該說，你所看到的這一隻羊，這一邊是黑色的！」

  3. 很重要的邏輯概念: 存活者偏差 1941年，第二次世界大戰正打得如火如荼。有一天，美國哥倫比亞大學著名統計學家沃德 教授(Abraham Wald)遇到了一個意外的訪客，那是英國皇家空軍的作戰指揮官來請協助改善這個攸關飛行員生死的難題。依照當時的航空技術，機體裝甲只能局部加強，否則機體過重，會導致起飛困難及操控遲鈍。 沃德將聯軍轟炸機的彈著點資料，描繪成兩張比較表，沃德的研究發現，機翼是最容易被擊中的部位，而飛行員的座艙與機尾，則是最少被擊中的部位。 在研究成果報告的會議上，卻發生一場激辯--應該加強機翼的裝甲or加強飛行員座艙與機尾發動機部位的裝甲。 部長決定接受沃德的建議，立刻加強駕駛艙與機尾發動機的防禦裝甲。不久之後，聯軍轟炸機被擊落的比例，果然顯著降低。 這個案例有兩個特別值得警惕的地方： 第一，死掉或被俘的人無法發表意見，蒐集更多資料，並不會改善決策品質。 第二，召集更多作戰經驗豐富的飛行員來提供專業意見，也不能改善決策品質，因為這些飛行員，正是產生偏誤資料過程中的一環。

  4. Wrong evaluation method所有的蛤蜊都是臭的！ 有一天，母親又買回一包蛤蜊，我熟練的拿出一個大碗，開始我的鑑定工作，出乎意料之外的是：居然「所有的」蛤蜊都是壞掉的？ 我簡直不敢相信我的耳朵，一個一個再敲過一次，竟然仍然「沒有一個」蛤蜊是好的！ 那種感覺就很像一位警察到一部公車上去抓扒手，結果發現一車的人都是扒手！ 我捧著那一大碗被判刑的蛤蜊去稟告母親， 母親很是驚訝：「怎麼會這樣呢？這個賣蛤蜊的從來不會騙我的呀？」 於是母親大人親自動手檢驗，這才發現原來我抓在左手中的那個蛤蜊是壞的！ 難怪敲起來聲音全部不對勁！ 這種「原來如此」的恍然大悟的經驗，往往在孩子心中烙下深刻的溝痕，然後進入記憶的深處，等候生命的唱盤再度轉到那個相似的部位。

  5. Design Reliability Reliability comes from six major sources: • Proper functional design. • Proper safe life design. • Proper fabrication. • Proper QC. • Proper maintenance. • Proper usage.

  6. Failure in Design Example 1-column transportation to Apollo at Selinous (Function design Error) Transportation of a round column

  7. Failure in Design • Transportation of a rectangular column

  8. Failure in Design • Transportation of a rectangular column- a new design

  9. Failure in Design • Example 2 – Kansas city Hyatt Regency (improper fabrication)

  10. Failure in Design • Example 3 – improper safe life design

  11. Failure in Design • Example 4 – improper safe life design

  12. Failure in Design • Example 5 – Wrong Analysis

  13. Failure in Design • Example 6 – Fail of Dee Bridge (not enough safety factor)

  14. Failure in Design • Example 6 –

  15. Failure in Design • Example 6 –

  16. Failure in Design • Example 7 – Columbia disaster (human error)

  17. Failure in Design • Example 7 – Columbia disaster

  18. Failure in Design Lesson should be learned • Failure mode should be recognized. • Engineering Judgment is a important issue to designer. • Human error is incontrovertibly a major cause of design. • Experience is important to mechanical engineer. • success can be replicated virtually without risk, but it can be extrapolated only by a proper application of the engineering method embodied in a proper perspective on failure. • Respect of law of nature. • Engineering history is important.

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