我住的地方附近中国人不少，原以为很多中国人会来看这电影，结果放映厅里四成的上座率，只有我一个“老外”，感觉有些奇怪──我在英国人的地盘上，和他们看一部国产的功夫电影。
最不好受的时刻，是片头字幕提到100年前的中国人被称为“东亚病夫”， 在国内看可能不觉得怎样，跟一群英国人同处一室，看见这样的描述，就有些五味杂陈了。也许除了功夫片和经济增长率，中国还应该有其他的方式用来向世界介绍自己。
在国内被人诟病最多的说教，在这里好像倒不是太令人反感……大概是片子被剪了几段的缘故。不过霍元甲之母陈氏的一段大特写说教似乎没动，但是“仁义道德”四字没有翻译。月慈（？）的说教大约也就保留了插秧那一段，不过这么有《读者》风味的话从一个清末苗疆的村姑嘴里说出来，感觉还是有些突兀。其实关于为何习武以及比试的意义何在，我以为在多年前的《精武英雄》里已经 阐释得够清楚。
至于武戏，还是霍元甲与秦爷的较量拍得最为冷峻而有气势。武侠电视剧和电影里的刀剑，在这之前再如何刀光耀眼，剑气纵横，给人的感觉都只是一件道具。《霍元甲》里的这场双刀对决，才拍出了武打片里久违的力量感，才真正显得那是一件可以致命的兵器。演员的表演也不再是像相互喂招，而是真正有了生死相搏的沉重感。后来两人酒窖里的打斗，更是没有半点花招，比《方世玉》的观赏性差了不是一点半点，但这才是以命相搏的感觉。类似的感觉以前看李小龙的时候有一些，不过他的电影里对手似乎都缺乏他的凶狠，谈不上势均力敌，所以紧张感不如《霍元甲》。
其他的武戏，基本上都拍出了各种流派的特点。虽然没有哪一场的紧张激烈程度及得上霍 vs. 秦，也不如十年前的陈真 vs. 藤田刚，但确实无法再苛求太多──要再好看就只有上特技了。
这戏里外国对手们大都很讲体育道德，比许多年前电视剧里的那些外国大力士们好多了，也许不这样就没法在海外发行吧 XD，不过有人说得有道理：一代宗师，他的对手也必然不应该是些狗苟之辈。
一开始小霍元甲练武，农劲荪写字的地方和后来的苗疆，我疑心都是南方的农村，秀丽婉约，我很喜欢。
2006年6月18日星期日
One small tiny grainy milestone
Yesterday I thought I made some sensible results from the model I am working on. However, today I realised that the water head exceeding land surface is a kind of scenario: you have intact peat layers but no vegetation at all, thus no interception of moisture by plants, nor enhanced storage by Sphagnum. Besides, I should assume a constant head layer below all layers so the precipitation can finally be received at this depth. Though adding this layer do not change the flooding at the surface, I think this model illustrates the influence of topography -- some areas with high elevation will eventually go dry.
The most important thing for Sphagnums, cannot be found out at this layer. For them to grow, the peat layer must have water present. The critical problem thus is the water head in the acrotelm. Thus I made another model with only two layers: one acrotelm and one constant head (a reservoir) below it. The simulation shows how deep water draws down in different locations. I'll try tomorrow make it a transient model so I can observe the process.
At this moment I think I will forget about that model for one night and do something else for a change.
The most important thing for Sphagnums, cannot be found out at this layer. For them to grow, the peat layer must have water present. The critical problem thus is the water head in the acrotelm. Thus I made another model with only two layers: one acrotelm and one constant head (a reservoir) below it. The simulation shows how deep water draws down in different locations. I'll try tomorrow make it a transient model so I can observe the process.
At this moment I think I will forget about that model for one night and do something else for a change.
2006年6月14日星期三
Convergence problem becomes frustrating
I guess I am approaching the real cause of the problem. Some cells in simulation have oscillating values. That is to say the water head in these cells change rapidly during simulation.
I tried to reduce oscillation by adjusting DAMP value in the PCG2 solver, but the problem still exists even when the DAMP is as low as 0.00001. At the same time it also leads to imbalance of water budget.
If I exclude the ``bad'' cells with large head change by marking them as inactive cells, other cells will also oscillate to a more staggering extent.
During simulations I noticed that most oscillating cells are in layer 1, 2, 10 and 11, where soils with different transmissivity meet. Besides, cells on borders tend to oscillate.
I need to find some means to reduce the head change in cells. Or change solvers to make the model converge. If I cannot make this I will have to fall back to more simplified models.
I tried to reduce oscillation by adjusting DAMP value in the PCG2 solver, but the problem still exists even when the DAMP is as low as 0.00001. At the same time it also leads to imbalance of water budget.
If I exclude the ``bad'' cells with large head change by marking them as inactive cells, other cells will also oscillate to a more staggering extent.
During simulations I noticed that most oscillating cells are in layer 1, 2, 10 and 11, where soils with different transmissivity meet. Besides, cells on borders tend to oscillate.
I need to find some means to reduce the head change in cells. Or change solvers to make the model converge. If I cannot make this I will have to fall back to more simplified models.
2006年6月13日星期二
给自己泼盆冷水
Don't Become a Scientist!
扩招的压力也许并不仅存在于本科和硕士生中间。虽然现在博士在中国还不是太过剩，但谁也无法断言4年后社会拥有多少 PhD 又需要多少 PhD。
虽然作者讨论的是美国，讨论的是基础研究，但中国的应用科学和工科博士现在也不少了，反倒是基础研究的博士比较少，或者说真正有实力读基础学科的 PhD 的人太少。不知道3、4年后会不会出现博士为了一个普通技术员的岗位争得头破血流的场面。
不过真正把环境科学读到博士的人整个大学本科阶段我也只见过两三位，应该还不会太过剩。
然而读了博士以后，即使不会因为生计所迫当一个又一个的博士后，大概也要为研究经费操心。可能很多时间都不能用来研究而是写一个又一个 proposal 。用现实的眼光看，这些都是投身研究工作必须面对的问题，现在也应该有心理准备。
最后是关于博士和科学家生活的光明面：
American universities train roughly twice as many Ph.D.s as there are jobs for them.
扩招的压力也许并不仅存在于本科和硕士生中间。虽然现在博士在中国还不是太过剩，但谁也无法断言4年后社会拥有多少 PhD 又需要多少 PhD。
虽然作者讨论的是美国，讨论的是基础研究，但中国的应用科学和工科博士现在也不少了，反倒是基础研究的博士比较少，或者说真正有实力读基础学科的 PhD 的人太少。不知道3、4年后会不会出现博士为了一个普通技术员的岗位争得头破血流的场面。
不过真正把环境科学读到博士的人整个大学本科阶段我也只见过两三位，应该还不会太过剩。
然而读了博士以后，即使不会因为生计所迫当一个又一个的博士后，大概也要为研究经费操心。可能很多时间都不能用来研究而是写一个又一个 proposal 。用现实的眼光看，这些都是投身研究工作必须面对的问题，现在也应该有心理准备。
最后是关于博士和科学家生活的光明面：
Science is fun and exciting. The thrill of discovery is unique.
Considerable Progress!
On the base of yesterday's trial, today I reduced the model area to Bleaklow only. Surrounding areas are defined as inactive cells and holes in DTM are filled with elevation data from OS map. The simulation now still cannot converge but the water budget gives good consistency (inconsistency about 0.01%). The map of water head draw down and dry cells also make sense.
The question now I have is why the water table draw down so fast in just one day. I would also like to know the storage coefficient of water in the soil -- absence of this parameter may lead to what I see in the simulation. Maybe I should ask the authors of MODFLOW whether such rapid draw down is normal and if I ignored something in the simulation.
The question now I have is why the water table draw down so fast in just one day. I would also like to know the storage coefficient of water in the soil -- absence of this parameter may lead to what I see in the simulation. Maybe I should ask the authors of MODFLOW whether such rapid draw down is normal and if I ignored something in the simulation.
2006年6月12日星期一
Weird “unable to converge” problem
Today I tried to solve the converge problem which prevent my model from simulating groundwater flow in more than 1 time step or stress period. I deactivated all modules one by one, then tried to adjust time parameters. None of these work.
Then I adjusted layer type. When I set layer 2--11 as type 0: confined, and layer 1 as type 0: confined or type 2: confined/unconfined with constant transmissivity, the simulation can work until stress period 51, time step 9. Otherwise the model cannot converge and simulation stops.
It was found later that both type 0 and type 2 can be assigned to layer 1 and 2, but type 3 and 1 will make converge problems. If type 2 is assigned to other layers, the problem also occurs.
Another model is tested. It has 30x30x3 cells and similar configuration with my working model. Strange enough, this model works well. I doubt the transmissivity settings may lead to the problem of my working model.
Another file gives possible causes of the problem. Some are very possible to present in this simulation. I will need to see to them. If there are questions unsolvable without acceptable changes of the model, I may consider using conceptual models instead of spatial explicit model.
The result of many times of simulation, variable control and trial error: the dry cells generated during simulation is the key reason of convergency difficulties. MODFLOW is not suitable to deal with non-saturate flow. My counter measure thus is to use more carefully designed parameters in the model, do a single-period, single-time-step simulation and identify those cells destined to become dry and exclude them (be assigning them as inactive cells) in consequential multi-period simulations. Besides, there are some ``holes'' in the DEM, if they are in my concerned area, I should define them as inactive cells and pay attention to their adjacent cells to ensure they have correct elevation data.
2006年6月11日星期日
A somewhat better simulation result
After I redefined the boundary conditions, got rid of RIVER package, adjusted STR1 package and gave river cells constant head, I got such simulation result:
CUMULATIVE VOLUMES L**3 RATES FOR THIS TIME STEP L**3/T
------------------ ------------------------
IN: IN:
--- ---
CONSTANT HEAD = 63661356.0000 CONSTANT HEAD = 2092976.1300
DRAINS = 0.0000 DRAINS = 0.0000
RIVER LEAKAGE = 0.0000 RIVER LEAKAGE = 0.0000
ET = 0.0000 ET = 0.0000
RECHARGE = 871753.8130
RECHARGE = 28660.4004
TOTAL IN = 64533108.0000 TOTAL IN = 2121636.5000
OUT: OUT:
---- ----
CONSTANT HEAD = 55723300.0000 CONSTANT HEAD = 1831999.0000
DRAINS = 8146114.5000 DRAINS = 267817.4690
RIVER LEAKAGE = 0.0000 RIVER LEAKAGE = 0.0000
ET = 747962.5630 ET = 24590.5508
RECHARGE = 0.0000 RECHARGE = 0.0000
TOTAL OUT = 64617380.0000 TOTAL OUT = 2124407.0000
IN - OUT = -84272.0000 IN - OUT = -2770.5000
PERCENT DISCREPANCY = -0.13 PERCENT DISCREPANCY = -0.13
The discrepancy of the result is much smaller than previous one (82%). Now I have a model that makes sense.
The next problem would be adjusting parameters using inverse models and make the result converge so multi period simulation is possible.
------------------ ------------------------
--- ---
CONSTANT HEAD = 63661356.0000 CONSTANT HEAD = 2092976.1300
DRAINS = 0.0000 DRAINS = 0.0000
RIVER LEAKAGE = 0.0000 RIVER LEAKAGE = 0.0000
ET = 0.0000 ET = 0.0000
RECHARGE = 871753.8130
RECHARGE = 28660.4004
TOTAL IN = 64533108.0000 TOTAL IN = 2121636.5000
OUT: OUT:
---- ----
CONSTANT HEAD = 55723300.0000 CONSTANT HEAD = 1831999.0000
DRAINS = 8146114.5000 DRAINS = 267817.4690
RIVER LEAKAGE = 0.0000 RIVER LEAKAGE = 0.0000
ET = 747962.5630 ET = 24590.5508
RECHARGE = 0.0000 RECHARGE = 0.0000
PERCENT DISCREPANCY = -0.13 PERCENT DISCREPANCY = -0.13
The discrepancy of the result is much smaller than previous one (82%). Now I have a model that makes sense.
The next problem would be adjusting parameters using inverse models and make the result converge so multi period simulation is possible.
2006年6月10日星期六
MODFLOW: Progress so far and problems
Today I finished inputing parameters to PMWIN and had a first run of the model.
It turns out that some of those characters may not be defined correctly. The water budget for the area do not balance thus the simulation cannot continue after the first time step. My first guess is that the boundary condition of the model is not correct: the rivers and streams should be constant head and the boundary of simulated area may be too low and should not be defined as active cells.
Individual modules may also have problems in their parameters. Tomorrow I will look at the output file and determine the need to change.
It turns out that some of those characters may not be defined correctly. The water budget for the area do not balance thus the simulation cannot continue after the first time step. My first guess is that the boundary condition of the model is not correct: the rivers and streams should be constant head and the boundary of simulated area may be too low and should not be defined as active cells.
Individual modules may also have problems in their parameters. Tomorrow I will look at the output file and determine the need to change.
2006年6月6日星期二
Protected: 牢骚
机房里总是太吵。
GIS 专业的人为什么总是有那么多的 GROUP WORK 要带到机房来做呢？今天早上做了什么完全没有印象，头嗡嗡直响。耳边全是他们的说话声和笑声。
现在完全不想见人，只想一个人呆一会儿。
明天看看本科生的机房里是不是安静一些，不然这活没法干了。
GIS 专业的人为什么总是有那么多的 GROUP WORK 要带到机房来做呢？今天早上做了什么完全没有印象，头嗡嗡直响。耳边全是他们的说话声和笑声。
现在完全不想见人，只想一个人呆一会儿。
明天看看本科生的机房里是不是安静一些，不然这活没法干了。
2006年6月5日星期一
Fieldwork Phase 1
I just come back from it.
I have encountered more sphagnum patches than I expected, though some are rather stressed, especially those on the south-facing slopes. Perhaps it is because of more sunlight and less moisture. Besides, there are very few sphagnum patches larger than 5 metres in any dimension, except some in SK0993 in those gullies.
Besides, I just found that many sphagnum patches can be found in these ESA vegetation types: cottongrass moorland, dry bog heather or non-heather dominated. I'll do a chi-square test to see if the hypothesis is true: that land use type is related to sphagnum presence.
A possible spectral signature can be found using about 20 sphagnum patches I found this time. The problem is the difference between aerial photographs made large-scale classification complicated: you have to identify sphagnum patches one square km by another. This could mean extensive fieldwork next phase.
The validation of these signatures is another problem. I can guess they are pretty good predictions, but this must be verified using more fieldwork data.
I may need to do more study on sphagnum habitats considering elevation and hydrology. I also need to talk with Jack in the coming weeks. For the next period, the main focus will be on hydrology models.
I have encountered more sphagnum patches than I expected, though some are rather stressed, especially those on the south-facing slopes. Perhaps it is because of more sunlight and less moisture. Besides, there are very few sphagnum patches larger than 5 metres in any dimension, except some in SK0993 in those gullies.
Besides, I just found that many sphagnum patches can be found in these ESA vegetation types: cottongrass moorland, dry bog heather or non-heather dominated. I'll do a chi-square test to see if the hypothesis is true: that land use type is related to sphagnum presence.
A possible spectral signature can be found using about 20 sphagnum patches I found this time. The problem is the difference between aerial photographs made large-scale classification complicated: you have to identify sphagnum patches one square km by another. This could mean extensive fieldwork next phase.
The validation of these signatures is another problem. I can guess they are pretty good predictions, but this must be verified using more fieldwork data.
I may need to do more study on sphagnum habitats considering elevation and hydrology. I also need to talk with Jack in the coming weeks. For the next period, the main focus will be on hydrology models.
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