c*****t
发帖数: 520 | 1 请问版上有没有人仔细读过Alessandra Lunardi关于parabolic PDEs的著作。例如正式
成书的Analytic semigroups and optimal regularity in parabolic problems，以及
他其他的讲义或论文？
我觉得Analytic semigroups and optimal regularity in parabolic problems这本书
不是很容易读。开头插值空间等准备知识非常多，又很难跳过这些，直接看方程相关的
内容。因为有人强烈推荐此书，而且我看到不少引用此书的论文，所以我还是想尽力自
学，希望对除fully nonlinear equations 以外的内容至少有些基本概念。
不知是否有人能提供些自学经验？例如初学时应该重点攻读哪些部分；或者有什么相对
简易的材料可以对照之类。
非常感谢大家的帮助。 |
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c*****t
发帖数: 520 | 2 请教parabolic equation收敛到stationary solution 的条件。
Consider parabolic equation
u_t=Lu. (P)
If we know that the second order elliptic equation
Lu=0, (E)
has unique solution v(x), then v(x) is the unique stationary solution of (P).
(We let (P) and (E) have same boundary conditions.)
Under what condition we can say that the solution u(x,t) of (P) converges to
v(x), as t goes to infinity?
In general, if (E) has several solutions v_1(x),...,v_n(x),... 阅读全帖 |
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c*****t
发帖数: 520 | 3 在很多文献中看到“standard parabolic regularity”这种说法。请问这具体包括哪
些方面的内容？
对于semilinear and quasilinear parabolic equations ，有什么比较简短的讲义概
述其regularity方面的主要结论吗？
非常感谢指点。 |
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c*****t
发帖数: 520 | 4 We consider a parabolic equation: u_t=au_xx+bu_x+cu, x in R, 0
If the coefficients a, b, c have good enough behavior, e.g. analytic, can we
get the following conclusion?
If the solution is not identical constant, then for any 0
R, the set A(t)={x in R: u(x,t)=r} is a discrete subset of R.
Angenent said that if r=0, then this conclusion is trivial. It is Theorem A
of the following paper.
http://www.math.jhu.edu/~js/Math745/angenent.par1.pdf
I do not know how to prove Theore... 阅读全帖 |
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L*******t
发帖数: 2385 | 5 请教一下版上的大牛们。。
coefficient满足什么条件的时候，一个线性的parabolic PDE的解是Smooth的？
谢谢了！ |
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t******l
发帖数: 10908 | 6 另一方面，我觉得 “美式构建式数学教育”，在 代数/前代数/Formal-Operation 阶
段最大的问题，两个：
其一：是在 Formal Operation 阶段，没有考虑 Formal Operation 阶段的特点，照抄
小学阶段 Concrete Operation 的 spiral 教学法。这带来 (a) 教学进度太慢，教授
的基础知识太少，花太多时间在不必要的 spiral 上，(b) 在 Formal Operation 的
spiral 的循序渐进层面，也有问题。
这个原因是 Formal Operation 是有明显的阶段性和结构性的，而 spiral 的时候很难
越过阶段性和结构性的边界。举个例子就是：
Algebra 1 和 "linear" geometry / "linear" analytic geometry，比如 solve
linear equation, solve system equations, complete a square, solve quadratic
equation, equation of line, slope of ... 阅读全帖 |
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n******h
发帖数: 2482 | 7 I couldn't care less on what central banks are buying because this time they
are simply forced to do so. All central banks want to depress the PM price
so that they can print their worthless fiat money to infinity. The reason
they are buying after 2009 is simply because Fed officially started printing
money, aka QE, on the top of zero-interest-rate policy. This direct
currency depreciation is detrimental to us-dollar-nominated foreign reserve
and especially dangerous to countries with a small fo... 阅读全帖 |
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z****i
发帖数: 406 | 8 转自wilmott
mghiggins
Senior Member
Posts: 313
Joined: Nov 2001
Sat Jan 04, 03 01:54 PM
User is offline
Qualitative explanation for why there is a vol smile in stochastic
volatility models from a market-making perspective:
First, let's step back and look at the standard Black-Scholes world. Why do
options have value over intrinsic value? Because they have positive Gamma.
As a market-making trader, you buy an option and Delta-hedge it - now, the
value of your portfolio as a function of the ... 阅读全帖 |
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i**w
发帖数: 71 | 9 parabolic pde with constant coefficients can always be transformed into heat
equation. thus solving heat equation solves all parabolic in some sense.
Transformation from general parabolic with (x,t) dependent coefficients to
heat like equation is not so obvious, but it is probably not so wild to
claim it true. any one from math?
|
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i**w
发帖数: 71 | 10 parabolic pde with constant coefficients can always be transformed into heat
equation. thus solving heat equation solves all parabolic in some sense.
Transformation from general parabolic with (x,t) dependent coefficients to
heat like equation is not so obvious, but it is probably not so wild to
claim it true. any one from math?
|
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S******s
发帖数: 5376 | 11 Jigging Rod Selection
Like I said before I am discussing the Japanese Jerk/Crank style which is
also referred to as vertical jigging, speed jigging and butterfly jigging.
The rods used here are much different than the longer yo-yo style that is
common across the Northeast
Generally because of the rhythm, action & technique involved in this
technique you will need a rod that has the following attributes
FEATURES & BENEFITS …. WHAT TO LOOK FOR
Lightweight – weight is very important, you will need ... 阅读全帖 |
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G***G
发帖数: 16778 | 12 killing ants may be boring.
but it will be an interesting game if you try my method.
1) buy a parabolic mirror
2) under sun, use the parabolic mirror to concentrate the sunlight.
3) ants will die if you shoot the concentrated sunlight into its nest.
enjoy it.
I have killed hundreds of them this morning.
it is efficient. and most importantly, it is green.
Moreover, kids love to play with it.
You watch them while you kill them.
be cautious: when you try this method, wear your sun-proof glass.
Don'... 阅读全帖 |
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T*********s
发帖数: 17839 | 13 These 72 Analysts Believe Gold Will Go Parabolic To Between $2,500 and $15,
000!
By W Lorimer Wilson
Created 19 Jul 2010
Believe it or not but I have identified 72 economists, academics, gold
analysts and market commentators who have developed sound rationale as to
why gold could quite possibly go to a parabolic top of at least $2,500 an
ounce to even as much as an unimaginable $15,000 before the bubble finally
pops!
Believe it or not but I have identified 72 economists, academics, gold
analysts |
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z***o
发帖数: 1254 | 14 我用Bollinger Bands （BB） 和 Parabolic SAR 看盘整和趋势。 BB squeeze 的话进入盘
整准备突破阶段，这很准。 但Parabolic SAR只是个大概的升或降的趋势， 要根据大
盘和其他配合来看。 图中SOHU和BIDU都是进入BB SQUEEZE 收脖子阶段， 准备向上或
向下的大幅突破。 ｓｏｈｕ的下拉大红蜡烛比较明显了， 而ＢＩＤＵ则不明，要等等。 |
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x******g
发帖数: 33885 | 15 5 Analysts See Gold Reaching its Parabolic Peak Sometime in 2011!
1.Bob Kirtley: $10,000;
2.Patrick Kerr: $5,000 – $10,000;
3.Taran Marwah: $3,000;
4.James Dines: $3,000 – $5,000;
5.Jim Sinclair: $3,000 – $5,000 (by June !!)
10 Analysts See Gold Reaching its Peak Before the End of 2012
1.Arnold Bock: $10,000;
2.Porter Stansberry: $10,000;
3.Taran Marwah: $6,000+;
4.Greg McCoach: $5,000+;
5.Robert McEwen: $5,000;
6.Mary Anne and Pamela Aden: $3,000 – $5,000;
7.John Paulson: $2,400 – $4,000;
8.Ian... 阅读全帖 |
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N********n
发帖数: 8363 | 16 CAF went parabolic from Dec to Feb. Any time you see sth parabolic
you do one thing: stay out. If you have profit then lock it with
trailing stops. CAF is now paying back for that insane move.
Those of you owning MSFT since March can use CAF as an example and
better have the necessary trailing stops on. |
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E***r
发帖数: 1037 | 18 I remembered I saw a similar chart somewhere, now I found the source,
despite that McClellan used DJIA. McClellan wrote this blog on Jan 18,
2018, right before the Feb crash. He is the inventor of McClellan
Oscillator, the de facto market breadth indicator.
http://www.mcoscillator.com/learning_center/weekly_chart/ending_how_it_began_parabolically/
Ending How It Began (Parabolically)?
January 18, 2018
There is a lot of talk lately about the market “going parabolic”. Most of
the time when that... 阅读全帖 |
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KV
发帖数: 5728 | 19 VT是相当好的杆子，parabolic，forgiving，而且thin walled高碳混合编，很轻，很
接近century c2，价格只有c2的三分之一左右，距离上不输c2，尤其是在这些高摩擦深
spool轮子上，杆子的loading才是决定距离的主要因素。
s8是ex fast taper，capable of long distance casting，此类杆子的loading需要力
量，我可以打赌，你拿一根vt，再拿一根s8，你用vt扔的一定比s8远，这是因为非
pendulum下，臂长身高不占优势情况下，过顶投掷不能很好地发挥s8的潜力。
对钓鱼而言，parabolic的surf杆在fight鱼的时候，非常forgiving，vt的backbone很
强，除非鱼太大，否则不会有自己战斗自己的无用lifting，而s8在上鱼和fight鱼的时
候，直接作用在你身上的力量远高于vt，不fun。
当然两根都是现阶段市面上顶级一级的高端surf杆子，都不便宜，细微的差别在于你是
否在意，我个人喜欢vt远高于s8，我的s8送给版上某位小兄弟了，他身高比我还高，力
量看着也不小，希望能... 阅读全帖 |
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w********h
发帖数: 12367 | 20 parabolic dependence可以么？
这个parabolic dependence有没有什么特殊的含义？
还是non-monotone dependence好一些？
但是感觉non-monotone包含的东西比较多，
不专门指抛物线。 |
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q*********u
发帖数: 9501 | 22 不是俺马后炮，俺前不久也在这里分析过黄金走势，这些大牛分析黄金竟然错的
离谱到难以置信的程度，俺不得不佩服。
These 72 Analysts Believe Gold Will Go Parabolic To Between $2,500 and $15,
000!
By W Lorimer Wilson
Created 19 Jul 2010
Believe it or not but I have identified 72 economists, academics, gold
analysts and market commentators who have developed sound rationale as to
why gold could quite possibly go to a parabolic top of at least $2,500 an
ounce to even as much as an unimaginable $15,000 before the bubble finally
pops!
Believe it or not but I |
|
h******t
发帖数: 872 | 23 http://finance.fortune.cnn.com/2011/04/28/the-coming-commodity-
The coming commodity price nightmare
Posted by Colin Barr
April 28, 2011 6:34 am
Here's another sign we have much bigger inflation problems than Ben Bernanke.
The commodity price boom we've all been bellyaching about for the past six
months started not in August, when the Fed chief first started talking about
quantitative easing, but a full eight years earlier – when Bernanke was
but a Fed governor and the housing bubble was a mere ... 阅读全帖 |
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w*********g
发帖数: 30882 | 24 Un-White America: Will Blacks and Hispanics lead the USA to ruin
http://www.theburningplatform.com/?p=40398
I think ol’ Fred may be on to something here. Does that make me a racist?
========================
I begin to weary of the endless denunciations of “white privilege;” the
calls to end the dominance of malignant white men; the law suits to abolish
all tests on which white men excel, meaning almost any test of mental
ability; to make universities and police forces and advanced-placement
clas... 阅读全帖 |
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m*****u
发帖数: 23 | 25 “当时的罗马”是什么时候？大概是中国当时的战国末期到汉初这段时间。当时中国建
筑保留至今的为0。赵州桥大概600年的隋朝，又过了好几百年。那时候罗马forum都是
废墟一
片了。
400年的时差怎好一起比。不过确实，西罗马亡后，西欧乱了几百年，欧洲大规模改变
拱的形状要很久以后了，但即使是medeval在1000年以后，欧洲已经在建筑上复兴了。
而全欧洲范围内人力物力财力在建筑上的投入，恐怕以后也后无来者了。因为那时投资
不算回报率
的。有的几百年还在建。
这里是我们说的都是欧洲大规模的建筑吧。比如起初教堂宫殿和故宫的对比。这种建筑
不好和中国的石桥比。如果文章帖子是关于桥的，我也不会起这个头。因为赵州桥也是
我的骄傲。但毕竟，桥梁建筑不是主要建筑文明的表现形式。比如人们去看故宫很少有
人去参观赵州桥。
高层建筑的拱需要考虑平行的推力，没有就塌了。拱如果是弧形，又把房子建得高于
地表，两边很难撑住。桥的话，拱如果从地表以下开始，两边有两个河岸顶着，推力越
大反倒越安
全。如果中国建赵州桥的时候确实去用石头去造宫殿，如果没有其他技术的支持，也不
能把这种不规则的parabolic arc... 阅读全帖 |
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S*********g
发帖数: 24893 | 26 【 以下文字转载自 StephenKing 俱乐部 】
发信人: StephenKing (金博士), 信区: StephenKing
标 题: 不系安全带，John Nash今天车祸死了
发信站: BBS 未名空间站 (Sun May 24 11:17:59 2015, 美东)
John Forbes Nash, Jr.
Born June 13, 1928
Bluefield, West Virginia, U.S.
Died May 23, 2015 (aged 86) [1]
Residence United States
Nationality American
Fields
Mathematics
Economics
Institutions
Massachusetts Institute of Technology
Princeton University
Alma mater
Princeton University
Carnegie Institute of Te... 阅读全帖 |
|
发帖数: 1 | 27 美索不达米亚人已经掌握的技术，古罗马人已经应用得炉火纯青。这些欧洲最基本的常
识，对当时乃至现在的中国人来说，就像天方夜谭一样吧？对于拱形的分类，中国人除
了知道个“券”以外，知识还能粗陋到哪里呢？
Triangular arch
Round arch or Semi-circular arch
Segmental arch or arch that is less than a semicircle
这就是赵州桥的类别属性，古罗马人早就玩得纯熟的技术了。
Unequal round arch or Rampant round arch
Lancet arch
Equilateral pointed arch
Shouldered flat arch -see also jack arch
Trefoil arch, or Three-foiled cusped arch
Horseshoe arch
Three-centered arch
Elliptical arch
Inflexed arch
Ogee arch
Reverse ogee arch
Tudor arch
Para... 阅读全帖 |
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b*********3
发帖数: 1709 | 28 The market stabbed itself in the rectum long ago by going parabolic whenever
Trumped mentioned a "good deal" was right around the corner. So Trump
thought he was in a good bargaining position, and now the market and Trump
both realized they are screwed: the Chinese won't deal now. They'll wait for
submission, either a nice BJ from orange man or the Democrat who replaces
him. "The Art of the Kneel: When You Think You Have them By the Balls, But
It's You who has to clean the Jizz Off Your Face". |
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b*********3
发帖数: 1709 | 29 The market stabbed itself in the rectum long ago by going parabolic whenever
Trumped mentioned a "good deal" was right around the corner. So Trump
thought he was in a good bargaining position, and now the market and Trump
both realized they are screwed: the Chinese won't deal now. They'll wait for
submission, either a nice BJ from orange man or the Democrat who replaces
him. "The Art of the Kneel: When You Think You Have them By the Balls, But
It's You who has to clean the Jizz Off Your Face". |
|
l****z
发帖数: 29846 | 30 http://www.zerohedge.com/news/worlds-largest-solar-plant-21-bil
World's Largest Solar Plant, With Second Largest Ever Department of Energy
Loan Guarantee, Files For Bankruptcy
Tyler Durden's picture
Submitted by Tyler Durden on 04/02/2012 20:14 -0400
Solyndra was just the appetizer. Earlier today, in what will come as a
surprise only to members of the administration, the company which proudly
held the rights to the world's largest solar power project, the hilariously
named Solar Trust of America... 阅读全帖 |
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l****z
发帖数: 29846 | 32 Robot Theory
The battle of robot theory is on. Bank of America paints one picture and
McKinsey another.
Let's investigate both theories.
Automation Will Change Jobs More Than Kill Them
As reported by the New York Times, McKinsey says Automation Will Change Jobs
More Than Kill Them
The report, published on Friday and written by two members of the
McKinsey Global Institute, the consulting firm’s research arm, and another
McKinsey employee, adds a twist to the debate over the likely nature and
... 阅读全帖 |
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S*********g
发帖数: 24893 | 33 【 以下文字转载自 StephenKing 俱乐部 】
发信人: StephenKing (金博士), 信区: StephenKing
标 题: 不系安全带，John Nash今天车祸死了
发信站: BBS 未名空间站 (Sun May 24 11:17:59 2015, 美东)
John Forbes Nash, Jr.
Born June 13, 1928
Bluefield, West Virginia, U.S.
Died May 23, 2015 (aged 86) [1]
Residence United States
Nationality American
Fields
Mathematics
Economics
Institutions
Massachusetts Institute of Technology
Princeton University
Alma mater
Princeton University
Carnegie Institute of Te... 阅读全帖 |
|
|
f*******y
发帖数: 13 | 35 在Santa Monica，买方请上门取（大件可帮你抬上车:)，有意者请站内信，谢谢！
- 2004 Hyundai Accent 90000 miles, first&only owner, followed all
recommended maintenance (every 3000 miles etc.), no accident, white 4dr
automatic, power window/door locks, CD, AC, new battery. 轮胎4年前costco换的
（从买车起未有过爆胎），前面有一个低灯需换灯泡
$2200 (~$12000买入,kbb good to excellent condition:$2790-$3065)
- Toshiba LCD TV 39'' $150（4年前costco～$700买的）
- King-size bed with frame(black), head board(black), mattress, box spring $
150(木质非组装，4年前家具店～$800买的）
- 黑色木质床头柜，两抽... 阅读全帖 |
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n*******l
发帖数: 2911 | 36 Matlab的FFT确实是自动并行多核运行，反正我的iMac的四个核是
基本全速运行。
我现在是在一个512x512的网格上用一个semi-implicit scheme
解一个parabolic equation, 时间步长是10^{-6}, 每步要几次FFT，
时间从0到七八十的样子就要算三个礼拜了。这里面用了个while
循环以及几个if判断，也许时间花在了while循环上？
我把网格变成1024x1024时，花费时间基本上是x4，所以时间似乎
是主要花费在FFT上。
我对于这样规模的问题，在四核iMac上到底应该花费多少时间没有什
么概念。已经多年没有进行严肃的计算了。至于GPU计算，受GPU内
存的限制，对于网格的大小限制也比较大。我看到有文章里说6GB内
存的GPU只能处理128x128x128的三维网格，那就是1024x1024的
二维网格呗？我还想尝试一下2048x2048甚至更大点的网格，GPU可
能有困难。 |
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f*******y
发帖数: 13 | 37 在Santa Monica，买方请上门取（大件可帮你抬上车:)，有意者请站内信，谢谢！
- 2004 Hyundai Accent 90000 miles, first&only owner, followed all
recommended maintenance (every 3000 miles etc.), no accident, white 4dr
automatic, power window/door locks, CD, AC, new battery. 轮胎4年前costco换的
（从买车起未有过爆胎），前面有一个低灯需换灯泡
$2200 (~$12000买入,kbb good to excellent condition:$2790-$3065)
- Toshiba LCD TV 39'' $150（4年前costco～$700买的）
- King-size bed with frame(black), head board(black), mattress, box spring $
150(木质非组装，4年前家具店～$800买的）
- 黑色木质床头柜，两抽... 阅读全帖 |
|
p****e
发帖数: 1028 | 38 i think several others have addressed this topic well, but it can be
summarized briefly as below:
1. some stable economic growth period; with hindsight, people are thinking
we are entering another growth highway
2. asset pricing bubble starts to emerge; wealth effect leads to more
consumption and hence even higher asset valuation
3. speculators start to leverage up
4. ordinary folks start to pile up
5. prices start going parabolic
6. asset valuation goes too high such that at least one of the be... 阅读全帖 |
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k***n
发帖数: 3158 | 39 I agree with your thought of it being the last leg of a bull market
this cyclical bull market since March 2009 has been grinding higher
after a strong initial surge.
most bull markets in the past did not end in the grinding phase
instead, they ended with a parabolic spike
a good example is Nasdaq in 2000
so we could be entering such a euphoria stage of this cyclical bull market
big boys will need such a spike to exit their positions
extra
stocks. |
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G**T
发帖数: 2610 | 41
这不是理想主义。 这是愚昧主义。 :)
你如果学过一些高等数学，就知道所有的PDEs只有三类：elliptic, parabolic,
hyperbolic. 参考这里：http://en.wikipedia.org/wiki/Partial_differential_equation
自然界里各种复杂的体系（包括人类社会），当然有很多目前的科学还没法用ＰＤＥ描
述（太复杂了）, 但这三类系统规律不会被打破 －－ 参考swarm intelligence之类
的研究。
这三类系统的behavior有本质区别，大概（即不严谨地、忽略很多特例和交叉和情况地
）来说，第一类的系统往往是有规律循环的 （数学上称existence & uniqueness of
solutions)； 第二类往往是有规律发散的 （存在不唯一的解）； 第三类往往是无
规律发散的 （没有唯一解） －－ 欢迎专业的来钻牛角尖，但the point is:
存在很多well defined system，给一个很小的initial error，系统演绎下去后，结果
可以相差十万八千里－－俗称误差放大或误差发散系统。... 阅读全帖 |
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t******l
发帖数: 10908 | 42 其实有兼顾函数 condition 和避免用三角函数的办法的。
对这题而言，最简单的就是换元建模时分两段，各段里用二次函数换元来替代三角函数
换元。解析几何图景里就是用两个 parabolic curve 换元，来替代用一个 Sine curve
换元，来避免三角函数计算。
当然这样就不能保持 v_longitude 一直等于 1。但这换元本身的目的只是
computational massage，也没有必要把无穷大直接敲在地板上永远等于 1。
当然总而言之这些都是特么体力活，等我吃饱了撑的时候再说。 |
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t******l
发帖数: 10908 | 43 发现这题还 too 简单，这题的 sin 只用到 0 到 pi/2，一个 parabolic 就完事了，
不用分段了。
其实就一个无穷大点，显然不用分段。刚才想多了。
curve |
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t******l
发帖数: 10908 | 44 Parabolic 换元的 computational massage，避免三角函数，函数 condition
也不错。计算了从 1 圈 到 10 圈的长度。
体力活，call me 雷锋 again。（待会儿贴上推导过程）：
-->4 * integrate('sqrt((1*%pi)^2 * t^4 *(2-t^2) + 1 / (2-t^2))', 't', -1, 0,
1.e-12, 1.e-48)
ans =
6.2625797
-->4 * integrate('sqrt((2*%pi)^2 * t^4 *(2-t^2) + 1 / (2-t^2))', 't', -1, 0,
1.e-12, 1.e-48)
ans =
10.833098
-->4 * integrate('sqrt((3*%pi)^2 * t^4 *(2-t^2) + 1 / (2-t^2))', 't', -1, 0,
1.e-12, 1.e-48)
ans =
15.597487
-->4 * integrate('sqrt((4*%pi)^2 * t^4 *(... 阅读全帖 |
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t******l
发帖数: 10908 | 45 parabolic 换元后得到的积分公式见附图: |
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w*******o
发帖数: 6125 | 46 那你就有必要检讨一下你的模型啰，hehe
既然话都说到这个份上，我也不怕得罪的说一句，
刚开始的时候,因为你老在版上说你的KE系统,
我留意过，不过觉得可能还不如简单的Parabolic SAR
//纯粹探讨,nothing personal
So
a |
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s********u
发帖数: 1054 | 47 This is why AAPL was down
a.) aapl is a very crowded trade
b.) the chart had gone parabolic
c.) everyone trading the stock had stops at 279-280
d.) hedge funds started a rumor about the COO
e.) market makers took out all the stops on the open
f.) everyone else rushed for the exits due to aapl's large weighting
in the nasdaq
that rumors were made up by those scumbags. Do not let them play on your
fears and steal your shares. Just sit tight! |
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N********n
发帖数: 8363 | 48 Stewart Thomson
1. Gold war update from the front lines: The Gold Community retook $1400
last night. Silver is close to retaking $30. I won the battle as to whether
gold would take out $1424 on the upside or $1315 on the downside. Most
thought $1315 would fall. It didn't. Gold soared to $1430 basis dec futures
and many gold stocks continue to exhibit violent upsurges.
2. I don't like losing. So I don't. Don't you throw your gold away either
because of all the correction talk going around.
3. Gol... 阅读全帖 |
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a*****n
发帖数: 89 | 49 If you look at the weekly chart, very much like a parabolic top forming
pattern,wait at least three days to one week for confirmation. |
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a*****n
发帖数: 89 | 50 Note that the parabolic top pattern usually occurs in a shorter time frame,
though. |
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