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x*y
发帖数: 364 | 2 Help for reference of the following info.
Bilinear basis function (for 4-node quadrilateral element) yields higher
convergence rate than strict linear basis function (for 3-node triangular
element).
I can't find any book provides the info of the convergence rate for comparing
the linear and bilinear basis function. Could anybody by any chance know this?
Thanks! |
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e***n
发帖数: 286 | 3 Urgent!
For any symmetric definite matrix, for sure we can factor it with Cholesky
method. How about symmetric indefinite matrix? I need factor such a matrix
A exactly into the product form
A = B * B'
where B' is the transpose of B and B is some n x n matrix ( not necessarily
to be triangular).
I know we can factor it with a LDLT method and further get
A = P * P' - Q * Q'
But this is not exactly what I need.
Thank you very much! |
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f*******a
发帖数: 80 | 4 I am looking for a software that is capable of drawing 2 or 3 dimensional
objects and a mesher that can render the drawing in triangular/tetrahedral
elements or rectangular/cubic elements. Any thought? |
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f*******a
发帖数: 80 | 5 Folks,
Is there a software that can convert a picture to a 2D triangular mesh?
Thank you in adv. |
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s**g
发帖数: 66 | 6 Wien-Bridge has decent distortion performance. But the amplitude control may
not be as good as you like to see.
DDS uses high speed DAC with built-in look-up table to generate waveform (
sine/triangular/square). The frequency accuracy is realized by internal
oscillator or PLL referenced to an external crystal; amplitude accuracy is
obtained by the DAC.
Add LPF or BPF to suppress distortion and noise (to meet 1mVrms spec). Add
buffer if you like to scale up swing or to drive considerable load or |
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g****t
发帖数: 31659 | 7 请问为啥Wien-Bridge类型的振幅控制会不好？
我觉得精度不够就是二极管工作区的曲线太陡或者太不陡，
把Wien-Bridge里的二极管接个可调电阻，
然后调一下说不定精度就上去了吧？
Wien-Bridge has decent distortion performance. But the amplitude control may
not be as good as you like to see.
DDS uses high speed DAC with built-in look-up table to generate waveform (
sine/triangular/square). The frequency accuracy is realized by internal
oscillator or PLL referenced to an external crystal; amplitude accuracy is
obtained by the DAC.
Add LPF or BPF to suppress distortion and noise |
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c*******l
发帖数: 4801 | 8 比如方格网叫square grid
三角形网格叫triangular grid.
米字型网格怎么说啊？
thanks. |
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e***n
发帖数: 286 | 9 【 以下文字转载自 Computation 讨论区 】
发信人: erain (红花会大老板), 信区: Computation
标 题: 紧急求问: 是否可以将一个对称不定矩阵 A 分解为 A = B * B'
发信站: BBS 未名空间站 (Sat Apr 21 16:47:52 2007)
Urgent!
For any symmetric definite matrix, for sure we can factor it with Cholesky
method. How about symmetric indefinite matrix? I need factor such a matrix
A exactly into the product form
A = B * B'
where B' is the transpose of B and B is some n x n matrix ( not necessarily
to be triangular).
I know we can factor it with a LDLT method and fur |
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f******k
发帖数: 297 | 10 to be a metric you also need triangular inequality, which i believe LZ does
not care a bit... |
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p*******g
发帖数: 2976 | 11 【 以下文字转载自 Biology 讨论区 】
发信人: albertsmwk (.)(.), 信区: Biology
标 题: 第一批“青年千人计划”生物类@publication列表@
发信站: BBS 未名空间站 (Thu Aug 18 15:04:16 2011, 美东)
花了一个小时，深深的鄙视一下自己的无聊行径！！
125 蔡亮 男 1980年11月 复旦大学 生命
科学 2007年12月毕业于[美国]北卡大学 [美国]加州大学旧金山分校 博士后
Cai L, Mostov K. Polarity is destiny. Cell. 2009 Nov 13;139(4):660-2. PubMed
PMID: 19914162; PubMed Central PMCID: PMC2900917.
Cai L, Makhov AM, Schafer DA, Bear JE. Coronin 1B antagonizes cortactin and
remodels Arp2/3-containing actin branche... 阅读全帖 |
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b***k
发帖数: 2673 | 12 ☆─────────────────────────────────────☆
mw (mw) 于 (Sun Jan 18 10:00:12 2009) 提到:
理论上这种arb应该可以用在任何3个correlated的instrument上面，为什么好像google
了一下大部分都
是用在外汇市场上面？
请问这里有什么原因吗？
请大伙给指点一下，谢谢
☆─────────────────────────────────────☆
pxx (pxx) 于 (Sun Jan 18 11:33:57 2009) 提到:
为什么理论上可以用在任何相关的instruments上？
☆─────────────────────────────────────☆
Icare (土豆自风流) 于 (Sun Jan 18 13:21:27 2009) 提到:
Because each currency is essentially a ratio.
You can get an accurate price of A/B if you know A/C and C/B. |
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s***g
发帖数: 259 | 13 spread, liquidity.
another example is bond + FRA
google |
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p****r
发帖数: 165 | 14 anywhere i could find paper about it? I googled , but cannot find anything. |
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g*******g
发帖数: 59 | 15 key rate duration thomas ho 1992. |
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J**Y
发帖数: 34 | 16 Ok. Suppose the var-cov matrix is V=(a11,a12\a21,a22), define a lower
triangular matrix T=(t11,0\t21,t22). The problem is to solve:
V=T*T'. We can get the following equations:
1. t11^2=a11;
2. t11*t12=a12;
3. t21*t11=a12=a21;
4. t21^2+t22^2=a22;
在 JIAY (拖拉机手) 的大作中提到: 】 |
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B***y
发帖数: 83 | 17
Let's say we have a triangular ABC, with
A = (a1,a2), B= (b1,b2), C= (c1,c2),
also we have a point D = (d1,d2).
then the simplest way to detect whether D lies in the interior of ABC is:
calculate the determinent of the matrix:
( 1 1 1 ) (1 1 1) (1 1 1)
a1 b1 d1 b1 c1 d1 c1 a1 d1
a2 b2 d2 b2 c2 d2 c2 a2 d2 ,
if all three determinents are of the same sigh, all positive or all negative.
then D is in the interior of ABC.
Otherwise it is not. |
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z***e
发帖数: 5600 | 18 Let A = (q^n-1)(q^n -q^2 )...(q^n-q^(n-1))
B = q^{n(n-1)/2} (q-1)^n
Then # of max chains = A/B
Reason: A = # of vector ( e1, ..., en) which spans the whole
space
B = # of vectors in each equivalent class
( 2 such vectors in an equivalent class can be
obtained
from one to another by a linear
transformation, which
happens to be uniquely represented by a
nonsingular
lower triangular matrix).
Example, n=2, # = q+1.
-Z. |
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l*********s
发帖数: 5409 | 19 Obviously it follows triangular distribution with support (-1,1)
short-cut,好像只要改个parameter就行，{ 就像N个iid gamma 相加 }。 |
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a*****3
发帖数: 601 | 20 你展开说说为啥是triangular distribution? 为什么显然？ |
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E**A
发帖数: 85 | 21 知道能做lasso，但现在想对weighted least square（比如用triangular kernel取
weight），做L1 regularization，请问用glmnet能实现吗？怎么编啊？不行的话，用
LARS能做吗？ |
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h*****u
发帖数: 109 | 22 请教各位一个Monte Carlo在engineering里应用的一个问题。方法比较简单。是用
Monte Carlo产生若干个Sample，每一个Sample是系统的输入，然后看输出的性能。最
后统计Average。
问题是需要一个probability distribution来产生Sample。知道的信息只是包括最小值
和最大值。没有一个accepted的distribution。请问怎么办？可以把常用的Normal,
Uniform, Triangular等都用上，然后看结果的sensitivity吗？
多谢各位。 |
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c***z
发帖数: 6348 | 23 Some update: clustering didn't work well
I knew that k-mean won't work since Jaccard doesn't follow triangular
inequality - hence convergence of mean doesn't guarantee convergence of
variance.
I tried hierarchical agglomerative and it didn't work well. I believe the
reason is feature selection - I should have used trigrams and such, instead
of words, as trivial words led to mis-clustering.
I am working on trigrams as well as NN, will keep updating here. Thanks a
lot casact and guys! |
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c***z
发帖数: 6348 | 24 I have been asking the same question to my boss, about the practical use of
this abstract metric...
The reason we can't use k-mean is that these metrics are actually not real
metrics, as they don't follow triangular inequality, and hence the mean
means nothing (convergence of mean doesn't imply convergence of variance).
The only thing I can think of is then hierarchical clustering... |
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c***z
发帖数: 6348 | 25 I have been asking the same question to my boss, about the practical use of
this abstract metric...
The reason we can't use k-mean is that these metrics are actually not real
metrics, as they don't follow triangular inequality, and hence the mean
means nothing (convergence of mean doesn't imply convergence of variance).
The only thing I can think of is then hierarchical clustering... |
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n****e
发帖数: 6292 | 26 看了官网资料，前悬是McPherson concept with triangular wishbones, coil
springs, telescopic shock absorbers, stabilizer bar，说了这么多，是不是仍然
是麦弗逊？
重量居然只比jetta重150磅，比jetta wagon还轻些。同样2.5L发动机，0-60都是8.2秒
，难道因为风阻小？
蛋疼的是裸车默认配钢圈，要想上合金圈，得加好几千的配置。 |
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w*******y
发帖数: 60932 | 28 Amazon has a AAA branded First Aid kit at 60% off.
$12.00 & eligible for free shipping with Amazon Prime
INCLUDES: First aid instructions, scissors, tweezers, 4 vinyl gloves (2 pair
), 1 whistle, 10 cotton tip applicators, 3 sting relief pads, 9 antispetic
towelettes, 20 alcohol prep pads, 2 triangular bandage, 1 5" x 9" combine
dressing, 20 3/8" x 1 1/2" bandages, 20 standard adhesive bandages, 10
butterfly bandages, 1 knuckle bandage, 2 knee/elbow bandage, 1 4" x 4"
sterile gauze pad, 3 3" x 3... 阅读全帖 |
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w*******y
发帖数: 60932 | 29 LINK:
http://www.buy.com/prod/SOG-Gear-Set--Shovel-Axe-Saw/q/loc/17250/219179074.html
1.png
Features
SOG Entrenching Tool (F08)
*Compact folding shovel and pick
All-steel construction entrenching tool uses a tempered steel blade with
teeth cut into one side for cutting and slashing
Triangular handle is strong and fits the hand well
Folded, the entrenching tool takes up about the same space as a stack of
paper plates7.5 x 5 x 2.5 (L x W x H)
Includes nylon sheath
SOG Hand Axe (F09)
Camp axe desig... 阅读全帖 |
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w*******y
发帖数: 60932 | 30 Geomag Kids Panels - 36 pieces
Product Features
* Magnetic construction system
* Thousands of geometric forms possible
* Swiss-made quality
* Includes 12 magnetic rods, 10 chromed steel spheres, 6 square panels
and 8 triangular panels (panel colors include: blue, turquoise and white)
* All components manufactured to stringent European and American safety
standards
|
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w*******y
发帖数: 60932 | 31 Helps build toddlers' creativity, confidence and independence through
creative experiences.
Age appropriate design for children ages 24 months and up
Helps develop fine and gross motor skills
Allows toddler to create original music with their scribbles
Includes 1 Unit, 8 Triangular Crayons and Paper
Manufacturer's Suggested Age: 2 Years and Up
Features: Plays Music
Educational Focus: Memory Skillls
Includes: Paper, Crayons
Dimensions: 2.63 " L x 12.75 " W x 11.5 " H
Crayola Beginnings Color Me A... 阅读全帖 |
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w*******y
发帖数: 60932 | 32 This is the lowest price I've seen for this kit for over a year at $17.66.
Use Subscribe and Save and it drops to $15.01. Prices at other sites seem
to range from $18.69-$24.95.
Adventure Medical Kits Trauma Packwith QuikClot:
http://www.amazon.com/Adventure-Medical-Kits-Packwith-QuikClot/
Great to keep in the car and home. Easy to take on a outdoor trip.
Comes with 1 Dressing, Gauze, Sterile, 2" x 2", Pkg/2; 1 Dressing, Gauze,
Sterile, 4" x 4", Pkg/2; 1 Conforming Gauze, 3"; BLEEDING- 1 Trau... 阅读全帖 |
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l*******e
发帖数: 2431 | 33 这个我有点经验，稍微来聊一点。
我儿子刚开始做加法时，速度极慢。后来玩了一个叫Rat-a-tat（amazon买的）
的游戏，这个游戏就是拿几张牌比大小，中间有点决定换牌翻牌的strategy。他
一向喜欢board games，所以对这个游戏颇迷恋了一阵，加法速度提高很大。当
然他的运算速度一直也算不上快。他还喜欢的几个数字相关的游戏是
rummingcub和monopoly。
他因为在蒙校，学校有number chain，所以他很早就知道数列的概念，在三岁
的时候最着迷，除了加一个固定的数，还有double，以及Fibonacci数列。其实
用数列训练数学思维是最简单的，因为在车上饭桌上都可以随口来说。
快五岁的时候有一天他写了个二维数列。他解释说在数列的第x行，第一个数是x，
接下来每个数都是前面的数加上x，同样在第y列，从y开始，每个数都是前面的数
加上y。这样第x行y列的数，刚好是x乘上y。能够把知识拓展运用，这是数学能力
的一个大进步。
四岁的时候我告诉他奇数、偶数、负数、质数这些概念，还有一些概念比如
square number或triangular number，让他去 |
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E*********e
发帖数: 10297 | 34 zms, i helped u to search some old posts by lazystone
发信人: lazystone (waiting), 信区: K12
标 题: Re: 怎样开拓孩子的数学思维
发信站: BBS 未名空间站 (Fri Jun 4 11:55:48 2010, 美东)
这个我有点经验，稍微来聊一点。
我儿子刚开始做加法时，速度极慢。后来玩了一个叫Rat-a-tat（amazon买的）
的游戏，这个游戏就是拿几张牌比大小，中间有点决定换牌翻牌的strategy。他
一向喜欢board games，所以对这个游戏颇迷恋了一阵，加法速度提高很大。当
然他的运算速度一直也算不上快。他还喜欢的几个数字相关的游戏是
rummingcub和monopoly。
他因为在蒙校，学校有number chain，所以他很早就知道数列的概念，在三岁
的时候最着迷，除了加一个固定的数，还有double，以及Fibonacci数列。其实
用数列训练数学思维是最简单的，因为在车上饭桌上都可以随口来说。
快五岁的时候有一天他写了个二维数列。他解释说在数列的第x行，第一个数是x... 阅读全帖 |
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t********r
发帖数: 4908 | 35 ☆─────────────────────────────────────☆
EnjoyMyLife (实心团子实心人) 于 (Fri Jun 4 10:53:07 2010, 美东) 提到:
不知道题目写的对不对
我觉得传统教学中，题海战术也罢，WORKBOOK也好，都比较死
孩子学起来感觉就是纯粹学“数学”而学数学
其实准确说，我觉得数学不仅仅是简单的计数，加减乘除死记硬背
怎样让孩子觉得数学本身就很FUN呢？怎么拓展孩子的数学思维呢？
昨晚去看了一下国内的，自己小时候没参加过什么澳数竞赛
不知道有什么好的书/经验可以借鉴？
☆─────────────────────────────────────☆
whaleTime (live a little) 于 (Fri Jun 4 10:54:37 2010, 美东) 提到:
是不是“word problem" 比较fun 一些？ 就是我们的应用题？
☆─────────────────────────────────────☆
mark (花生，微爷远爷的爸爸) 于 (Fri Jun 4 10:... 阅读全帖 |
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wh
发帖数: 141625 | 36 你好有文化。
The Kiss (original Der Kuss) was painted by Gustav Klimt, during his ‘
golden period’, and is probably his most famous work. It depicts a couple,
in various shades of gold and symbols, sharing a kiss against a bronze
background.
Two figures are situated at the edge of a flowered escarpment. The man is
wearing neutral coloured rectangles and a crown of vines; the woman wears
brightly coloured tangent circles and flowers in her hair. The twain’s
embrace is enveloped by triangular vining and... 阅读全帖 |
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