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.
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).
I came to USA in summer and now it's spring.
So, I have experienced all of four seasons in America.
Build up factor depends on (1)source (photons) energy (2)the distance traveled and (3)the nature of the medium. With build up factor, we could calculate the dose more precisely.
In order to satisfy the Requirements for structural shielding for X-ray facilities, we consider the following factors. (1)the maximum voltage that X-ray tube is used. This is related to the incident photos energy. (2)maximum current(mA) of beam current, which relate to flux of radiation. (3)work load of the X-ray tube. (4)the use factor. The fraction of workload that the beam is pointed directly to. (5)the occupancy factor.
For diffusion coefficient, it's weighed by gradient of flux, not flux itself. It is reasonable because the diffusion depends on gradient of flux, not flux.
It's interesting that we have flux dependence( or gradient of flux) , which we have not known yet, in the definition of group constants. This is called a recursive problem. To tackle this, we assume the spatial part and energy part of flux is separable. And then, we further assume that we know the energy dependence. For example, we assume a Maxwellian-Boltzmann distribution for thermal neutrons.
Since the difficulty of group parameter constants are already solved, we can easily write down the two group diffusion equation. What following is similar in one group. We will have two kind of problems, source problems and criticality problems.
Starting from expanding flux dependence to even include direction and energy. ø( position, energy, direction, time), we write down the neutron balance equation. And then, omit direction dependence first and focus on energy dependence from now on.
ø( vector r, E, t)
Notice that not only flux has a energy dependence, some parameters like cross section, velocity or diffusion coefficients are also energy dependent now.
Some changes in neutron balance equation:
1. Fission neutrons come from fission reactions of neutrons of all energy.
2. Losing neutrons by scattering from objective energy to any other energy.
3. Gaining neutrons by scattering from any other energy to objective energy.
Then we define g group of flux ø_g by integrate the flux from E_g to E_g-1. By this, we have the neutron balance equation of group g.
For example, we had taken a look of two group, G=2. Some simplifications are used like up-scattering, fission neutrons being all fast
About one month later, I will jet back to Taiwan.
That also means that it's almost a year for my studying abroad.
I would only say it's the busiest year of my life.
However, there is not too much exciting new things knocking my brain.
Not much research, not much inspiring ideas....
Most courses I took this year were already taken in Taiwan before. Just a improved skill and a better feeling of the subject. I hope I could take more challenging courses next semester.
On the other hand, I found that I studied faster now, but think things less. Do keep in mind that thinking and curiosity is the most important.
The most popular place to go is Newport, town dedicated for tourism and a relaxation of life. We ate Dunkkin Donuts, again, for lunch and then went to a fort that has never been used. Unfortunately, the fort is closed for maintenance. After this, we drove along the coast to Berkeley Mansion. It's so Luxurious. I became wanting to own a mansion like this so much. However, it's said that when the old owner lived there, the family need seventy servants to maintain this mansion, which is unlikely possible nowadays.
It took me a long time to visit each exhibition inside, so I can't complete the whole trail. I visited State house, old south church and old state house. State house has a magnificent outlook and a glamorous ornament as well. The state house is built after funding of USA. There is a wooden cod fish hanging in the house of representative. They said that it is a good luck charm for Boston.
Old south church is a puritan church. Compared to several churches we visited days before, it's stunningly simple. It's almost not ornamented at all, both inside and outside. However it played a crucial role in American Revolution.
Old state house is the political center of Boston in the colony period. Both the governor and representative would use this building. To my surprise, though the independence of American eventually resulting in the eruption of revolution, some democracy system heritage from England were already practiced in colony world.
At last, this trip also answered me a question. Ever wondering why there is so many John Hancock Buildings in cities of USA? Who is this guy John Hancock? The answer is, John Hancock is really something. He is the fist man signing in the declaration of Independence. Besides, he is a Bostonian.
Leaving Champaign 10 p.m. and being transported all along until 10 a.m. next day. It reminds me what we often say " work smart and play hard". This time, I played extremely hard.
Right after taking off the airplane, we were immediately lost in the awful traffics of Boston. Thank god Boston is such a small city, I met my friend in the restaurant on time even though we wasted so much time finding our way.
With two cups of coffee, I was sustained to stand through all destinations today which are Trinity Church, Public Library of Boston, Harvard University and MIT.
Rita, my seiner high schoolmate, studied in fine art. She had been in San Francisco for one year. We enjoyed the whole trip together with her boy friends, Mistu a Japanese. Her roommates are also artists. Hermione from Taiwan graduated in the Institute of Art in Chicago, now working in SF. Kevin from China now studies in the same school as Rita. He had worked in video game industry in Shen-hai for years before being in SF. A-Der is a friend I made when we were in the army. He is now studying in another art school in SF. His goal is to become a director making Taiwanese movies. His roommates are also from Taiwan, studying in movie and media individually.
San Francisco is also a city that has extremely freedom to express opinions. There is Gays/Lasbians area where they speak out their rights through parades every year. Their are area of Hippies where you can see people in long hairs, strange clothes with doggies. When Vienein War, it's historically against the war severely.
On the other hand, San Francisco is a dangerous city. The amount of homeless here is the most I have ever seen. They sleep everywhere in the bus stops, street corners, or under light stands. Some regions is strongly told not to go because of the drugs, robbery and gangsters fighting even in day time.
In the New Year's Eve, we came to the counting and the fireworks. It's so crowded. You can hear people shouting and smell everywhere the cannabis. However it's OK. What's so unfortunate is that we had a robbery report. Kevin is robbed of his camera by a group of black people on our way to the fireworks. I was told that this happened all the time just around the acquainted friends.
I think it's exactly this mixing of the beauty and the dirty, freedom to speak and dangerous to live that makes San Francisco attracted. I haven't known it well and I will be back one day.