新室友兩個半

第一次看見嘉偉時就有點面善，原來他也是清大工科系畢業的(04級)，很巧。

他在台大唸電子所，不過來UIUC唸的是Finance.

June是韓國人，唸生物方面的大學部。很和氣的一個人，和Michael一起上教會。口頭禪是mess up。

Michael是Matt的combo friends，華裔美國人。異常活潑。雖然晚上常常在客廳大笑害我沒辦法睡覺，但的確是一位相當好的人。因為常常過來我們家，所以是半個室友。口頭禪是fail。

再介紹一下老室友吧

Matt是台大電機所來的交換學生。萬人迷。今年七月就會回去了，但再過一兩年就會回來美國唸博士了。

Adrian，電機博士生三年級。每天早上六點半起床，晚上十二點睡覺。

旅行

大學畢業那年和好友們去新竹湖口玩

途中去朋友姑姑家坐了一下

聊天中不經意聽到的「愛玩」兩字

卻像一把鑰匙開啟了我未來四年出外旅行的日子

當下我默默地下了決定……

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北京、長春、大阪、京都、神戶

印象很深的是第一次從大阪回來的時候

老師說我有改變

自信和講話的氣勢都不一樣了

原來旅行有這種效果?

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北京、長春、大阪、京都、神戶、上海、芝加哥、西雅圖、舊金山、波士頓

去旅行像是在吃藥

憂鬱藥

需要它在下沉中的心情中拉一把

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北京、長春、大阪、京都、神戶、上海、芝加哥、西雅圖、舊金山、波士頓、東京、山形、日光

在台北東區

忠孝東路可能有走過九百九十九遍了

就像呼吸一樣沒有特別的想法

但是轉念一想

如果開始想象我正在旅行

在台北旅行

那車外的街景就變得有趣起來

好像我在國外似的

如果可以的話

把心眼打開

讓每一刻都在旅行

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北京、長春、大阪、京都、神戶、上海、芝加哥、西雅圖、舊金山、波士頓、東京、山形、日光、台北

桃園機場

去過那麼多國外的機場後
才發現我們的桃園機場真的是有待改善
網路上巳經有了相當多的討論

不過我覺得我們機場有兩點倒是相當可愛
一、免費的無線網路
二、免費的行李推車
在國外的機場，這幾乎都是要收費的

但我覺得最可愛的還是入關處一整排的「持中華民國護照」通道
像是家門
在展開雙臂歡迎國人回家

山形第一天

Last time I visited Osaka, I made a conclusion that Japanese girls are not that pretty. They are merely cute, but not pretty. This fact really disappointed me since I had always expected that there should be many beautiful girls in Japan because they are usually pretty in Japanese drama.

But this time in Tokyo, I found these Japanese dramas did not lie. 

In Tokyo station, beautiful office ladies are so many. Maybe the most pretty ones are always gathered in the largest city. Just like the situation in Taipei of Taiwan. The pretty comes and goes. I really want to enjoy appreciating them but I can't do that too apparently. Because my parents are with me. I better be a good boy XD.

And I think this is the most important thing of the day.

Way back home

As I had expected, it's a terribly long trip home.

Getting up at eight, I went to Illini terminals at nine to take Amtrak train. To my disappointment, the train delayed for one hour. Not until today, I have seen the amtrak as the most reliable transportation to Chicago( I wondered if there is an grammar error of this sentence). This reminded me the rail trains in Taiwan which delay all the time. I wondered if I could ask for a ticket fee return.

And then, I took CTA subway to O'Hare airport. I don't know it's because of my unluckiness or what, the train stopped after one or two stops and all passengers were requested to take off. And after several minuets, all passengers were asked to take on the very same train again. Thank god I had pretty adequate buffer for transferring.

With two McDonald's meals for lunch and dinner, I found I always choose McDonald's in airport.

And now I am in LA airport. This is the most uncomfortable airport I have ever been in USA. It's crowded. Many places are under refurnishing or something( or supposed to be?). It's dark in the check-in hall and , especially, in the food court.

Finally, I were home. To my curiosity, I did not feel very excited. Further more, the humid and warm air made me uncomfortable. Maybe I am really not a homesick type of person I think.

class review NPRE 441 5/4

Regulations
ICRP 26/30 Philosophy( dose equivalent (rem or Sv) and effective dose equivalent,Stochastic and Nonstochastic effect.)

Because different radiations cause different biological effect, so we define:
dose equivalent is equal to dose by quality factor.

Because different tissues respond differently to radiations, so we define:
effective dose equivalent is equal to dose equivalent by tissue weighting factor W(tissue). It only applies to stochastic case.

For nonstochastic case, we consider a 50 year organ dose.
For stochastic case, we consider doses upon whole body.

we also have limitation on intake dose( also stochastic and non-stochastic).

NPRE 441 5/1

Photon shielding:

Secondary protection barrier( for scattered photons and leakage radiation), depending on ratio of scattering to incident radiation scattering field size, exposure rate on scatterer....

Distance between "source and scatterer" and "scatterer and objective place" are related to allowable value as well as occupancy factor and others.

Eventually, I want to find the required barrier thickness. Usually we would find K or B, attenuation factor) first, then we can use some table or figure to find the corresponding required wall thickness.

Beta ray shielding:

Gotta consider both electrons  and bremsstrahlung radiation. To calculate the bremsstrahlung part, we first find the fraction of energy emitted as bremsstrahlung. And then to find the required thickness of wall. 

Neutron shielding:

For fast neutron.

Use table 9.5, we could find the relation of neutron energy and neutron flux that cause a 0.01 Sv/h.

Once we know the attenuation cross section, we can know the flux distribution of neutron in the wall. At the end point of wall, the flux of neutron should equal the required value. This is, we could find the required wall thickness.

For thermal neutron.

Gotta consider gamma capture reaction. Usually, we assume a uniformly distributed gamma source. Then we have equation to fine the dose rate on the surface of the sphere. 

So, we have dose rate from fast and thermal neutrons and gamma rays. One way to reduce gamma ray radiation, we could add some lower energy emitter like boron(0,48Mev).