d****n
发帖数: 12461 | 1 脚架干啥？防抖。
出门带两个普通脚架能抵得上一个优质脚架吗？不能。
怎么防抖？看弹性模量。碳素的硬度或者说单位重量的弹性模量高于铝合金
"As an example, a plain-weave carbon fiber reinforced laminate has an
elastic modulus of approximately 6 msi and a volumetric density of about 83
lbs/ft3. Thus the stiffness to weight for this material is 107 ft. By
comparison, the density of aluminum is 169 lbs/ft3, which yields a stiffness
to weight of 8.5 x 106 ft, and the density of 4130 steel is 489 lbs/ft3,
which yields a stiffness to weight of 8.8 x 106 ft. Hence even a b... 阅读全帖 |
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m**x
发帖数: 8454 | 2 I must have forgotten all the modulus stuff...
one last question, how do you get:
both N^(p-1) and N^2 are equal to 1 (mod p), let k = gcd(4, p-1) and we
have N^k = 1 (mod p)
=1 |
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H********g
发帖数: 43926 | 3 碳纳米管又硬又韧
Carbon nanotubes are the strongest and stiffest materials yet discovered in
terms of tensile strength and elastic modulus respectively. This strength
results from the covalent sp2 bonds formed between the individual carbon
atoms. In 2000, a multi-walled carbon nanotube was tested to have a tensile
strength of 63 gigapascals (9,100,000 psi).[41] (For illustration, this
translates into the ability to endure tension of a weight equivalent to 6,
422 kilograms-force (62,980 N; 14,160 lbf) on... 阅读全帖 |
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H********g
发帖数: 43926 | 4 硬度是5（磷灰石似乎本身就是拿来定义硬度5的），超过一般的钢（4-4.5）
Tooth enamel ranks 5 on Mohs hardness scale and has a Young's modulus of 83
GPa |
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a***e
发帖数: 27968 | 5 AZ91 is one of the common Mg alloy, nothing special about it. AZ91 means it
has 9% Al and 1% zinc.
both Mg and Al alloys have yield strength in the range of 100 to 200 MPa,
depending of process. perticularlly, AZ91 is about 150MPa, same as A6063.
in term of Young's modulus, Mg alloy is ~45GPa and Al alloy ~70GPa.
so with same thickness, Mg alloy is actually weaker.
however, density wise, it is 2:3 ratio. so it gains something back.
therefore, under same weight, Al and Mg alloy is close in streng... 阅读全帖 |
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t****t
发帖数: 6806 | 6 "Note that the number of exponent digits in the scientific notation produced
by %e, %E, %g and %G for numbers with the modulus of the exponent less than
100 is system-dependent: it may be three or less (zero-padded as necessary)
. In other words, 1.23 times ten to the 99th may be either ``1.23e99'' or ``
1.23e099''."
so i suggest you do sprintf and do a regexp replacement.
3 |
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a*****g
发帖数: 19398 | 7 Number of legal Go positions
The 361 points on a 19x19 Go board can be colored empty, black, or white.
Only some of the 3^361 possible positions are legal, namely those where
every group of connected stones of the same color has an empty point
adjacent to it. In the position above, black stones at E18 and N9 lack such
``liberties'', making the position illegal. Due to its capture rule, the
positions that can arise in a game of Go are exactly the legal positions. On
Jan 20, 2016, the number of le... 阅读全帖 |
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f*********g
发帖数: 25 | 8 如果convolution之后没有non-linear operation，根据Central-limit theorem，最终
的filter会变成Gaussian Filter。如果有non-linear operation，可以看一下这篇文章
https://www.di.ens.fr/~mallat/papiers/Bruna-Mallat-Pami-Scat.pdf
虽然它里面的non-linear operation用的是Fourier modulus针对的是complex value
filte和CNN的不一样,但是从single processing 和能量传播角度去看这个问题挺有意
思的 |
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g****t
发帖数: 31659 | 9 Before finishing Einstein and Fourier's papers,
why we need to waste time on these papers?
I am old and I usually only checked modern papers' result and test data,
coding, 这些干货。
: 如果convolution之后没有non-linear operation，根据Central-limit
theorem
，最终
: 的filter会变成Gaussian Filter。如果有non-linear operation，可以
看一下
这篇文章
: https://www.di.ens.fr/~mallat/papiers/Bruna-Mallat-Pami-Scat.pdf
: 虽然它里面的non-linear operation用的是Fourier modulus针对的是
complex
value
: filte和CNN的不一样,但是从single processing ... 阅读全帖 |
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a********k
发帖数: 2273 | 10 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 branches in lamellipodia. Cell. 2008 Sep
5;134(5):828-42. PubMed PMID: 18775315; PubMed Central PMCID: PMC2570342.
Cai L, Makhov AM, Bear JE. F-actin... 阅读全帖 |
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r***y
发帖数: 248 | 12 我没有真正干过土工就转专业的，算半个行内人，
你可以歧视我没有PE，SE，
但不可以歧视我的智商，
你可以歧视我的智商，
但不可以歧视我的胸器，
这个部件讲究size & elasticity
论deflection,stiffness,elastic modulus
两娃大妈和未婚女差别大了去了，
你有什么资格拿我的胸器说事？
我彻底闪...... |
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y****o
发帖数: 131 | 13 DL+WL
DL+0.7E
DL+LL
0.6DL (empty tank)+WL
0.6DL+0.7E
for the computer model
build a pad then apply your loads on the three points
find the subgrade modulus
use compression only spring support |
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w****o
发帖数: 8 | 14 Dear all friends, I met a problem when I was using ADINA, which made me cannot
continue my research. When I tried to input the material peoperties for ADINA,
I needed input a random Young's Modulus field, which is a big matrix. But I do
not know how to input such a matrix. I don't even know what format of data do
I need. Would you please do me a great favor to tell me something related to
it if you have experience? Or please recommend any friend around whom I can
ask for. I was stucked here and |
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s*******y
发帖数: 44 | 15 用A%B取模，给我的错误信息是Operator % is only supported when the second
operand is a power of 2.
可我搜到的例子里后一个数什么值都有，难道是我用的这个版本才有这种特殊要求（我
用的是XILINX）？这个问题有什么办法解决么？我必须要用这个运算。 |
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c*******n
发帖数: 1648 | 16 Any people know how to correlate toughness and impact stength together for a
material, and how to correlate modulus and hardness? Thank you! |
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w********h
发帖数: 12367 | 18 welcome.
As to pure polymers, especially monodisperse samples,
you can get a master curve of G' or G",
and in terminal region, G' has a frequency dependence with a power law of 2,
while G" has a power law of 1.
the crossover point of G' and G' reflects the relaxation time, which is one of
the most important parameters for polymers.
Polymers with fillers will show significantly different master curves.
First of all, you will lose the perfect terminal region.
And the plateau modulus will change.
I |
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a***n
发帖数: 578 | 19 Mechanical properties (Vicker's hardness, Young's modulus, and fracture
toughness coefficient) have been studied for the three-dimensionally
polymerized, amorphous, and nanocrystalline diamond-plus-graphite composite
carbon phases prepared from fullerite C-60 by temperature treatment under
pressure. The hardness was found to increase gradually with the synthesis
temperature. The experimental values of hardness are well correlated with the
density of samples regardless of the phase structural nat |
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a***n
发帖数: 578 | 20 The theoretical prediction of 3D polymerized C60 can reach only 70% bulk
modulus of diamond. Since even perfect case can only reach 70% toughness, how
can a real system reach that number?
Physical Review Letters -- September 11, 2000 -- Volume 85, Issue 11, pp.
2328-2331
Personally, I believe that so called breakthough news is a hoax.
Poeple nowaday are interested at that materials for its novel electric and
magnetic properties.
Magnetic carbon
NATURE 413 (6857): 716-718 OCT 18 2001
By the way, |
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w********h
发帖数: 12367 | 21 The questions are rather simple.
Such as:
what's exfoliated clay?
what's the advantage of clay-polymer nanocomposite?
How to use X-ray to determin the exfoliated sturcture
of clay-polymer nanocomposite?
List the methods to prepare clay-polymer
nanocomposite?
What's the chemical composition of typical clay?
What are the thickness and transverse dimensions of a typical clay sheet?
What properties you can improve other than strength and modulus?
How are the clay sheets separated? Are clay sheets us |
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c*******n
发帖数: 1648 | 22 The classic entropy theory of rubber that we learned only gives stress-strain
relationship, modulus can be obtained easily in this way, but the fracture
criteria is hard to find. |
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b**s
发帖数: 589 | 23 聚酰亚胺胶粘剂
http://www.geplastics.com/resins/materials/ultem.html
ULTEM resins offer:
Long-term heat resistance - RTI up to 356°F (180°C)
Dimensional stability
Strength and modulus at elevated temperatures
Hydrolytic and chemical stability
Resistance to wave and vapor soldering
FDA and NSF grades
的 |
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b**s
发帖数: 589 | 24 Find two definition of gel
1. A gel is a colloidal system with a finite, usually rather small, yield
stress. Materials such as silica gel which have passed a gel stage during
preparation, are improperly called gels.
2. Rheologically, a sample is said to form a gel when it acquires a nonzero
shear modulus
on
(or
frequency,
at |
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w********h
发帖数: 12367 | 25 en...
第一个问题：1+1等于几？
第二个问题：PS全称是什么？
第三个问题：写出PS的分子式。
第四个问题：PS的终极Tg是多少？ Tg临界分子量是多少？
第五个问题：PS的Me是多少？Plateau modulus Gn0是多少？之间什么关系？
第六个问题：PS的Rouse区松弛时间和fluid区松弛时间的温度依赖关系相同么？PDMS呢？
他们为什么会这样？
第七个问题：请定义polymer rigidity并且说明什么链结构参数决定rigidity.
第八个问题：为什么PS和PVME是一对相容的共混物？请从热力学和分子结构决定的
dynamics两方面进行解释。
第九个问题：当人类的生命尺度变成1000岁，而不是100岁，我们的物质世界会变成什么
样子。。。 |
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w********h
发帖数: 12367 | 26 en...
第一个问题：1+1等于几？
第二个问题：PS全称是什么？
第三个问题：写出PS的分子式。
第四个问题：PS的终极Tg是多少？ Tg临界分子量是多少？
第五个问题：PS的Me是多少？Plateau modulus Gn0是多少？之间什么关系？
第六个问题：PS的Rouse区松弛时间和fluid区松弛时间的温度依赖关系相同么？PDMS呢？
他们为什么会这样？
第七个问题：请定义polymer rigidity并且说明什么链结构参数决定rigidity.
第八个问题：为什么PS和PVME是一对相容的共混物？请从热力学和分子结构决定的
dynamics两方面进行解释。
第九个问题：当人类的生命尺度变成1000岁，而不是100岁，我们的物质世界会变成什么
样子。。。 |
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f*****n
发帖数: 12 | 27 1)you can not get E'' from Instron tension test.
2)E=Stress/strain, you must measure strain rather than displacement.
3)I have no idea about the transient modulus at 100% or 200%. Sorry.
good luck. |
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c******s
发帖数: 20 | 28 什么曲线？
应力应变曲线，导数外推。
如果试验正确，曲线应该呈现不同的段，代表不同运动状态下的响应。 |
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w********h
发帖数: 12367 | 29 hardness是有特指的,必须有比较严格的测试条件下标定"硬度",
stiffness比较广泛一些,一般的indentation得到的surface modulus就可以表征. |
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a******n
发帖数: 5925 | 30 比如mp3, 手机等
要求强度比较大， 应该比一般的塑料外壳要大，
young's modulus比较大， 不是太容易一压就很大变形
价格比不锈钢便宜
具体的还要算， 但是想问问哪些比较接近
以便缩小选择的范围。
谢谢， 必有包子答谢。 |
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n******t
发帖数: 4406 | 31 This is a famous result called Levy's modulus of continuity.
you can check for more references. |
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w****o
发帖数: 2260 | 34 【 以下文字转载自 JobHunting 讨论区 】
发信人: winhao (勇敢的人), 信区: JobHunting
标 题: 谁给说说juggling algorithm里面的gcd
发信站: BBS 未名空间站 (Sun Apr 1 23:18:04 2012, 美东)
数组大小为N, 要shift by k positions
有关的讨论在：
http://www.mitbbs.com/article_t/JobHunting/32080185.html
这个juggling algorithm,其实就是把数组分成了gcd(N, k)个set,在每个set里的数可
以通过k跳，互相到达，所以他们之间就可以交换。
我的问题是，如何从数学上证明这gcd(N, k)个set之间是没有任何的交集？同时这gcd(
N, k)个set的并集正好就是整个数组？
是不是要从 k modulus N方面来着手？
谢谢！ |
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s*****V
发帖数: 21731 | 35 你好像是专业人士，老张的结果怎么样？
in
modulus
GRH
Re |
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a*****g
发帖数: 19398 | 36 【 以下文字转载自 Programming 讨论区 】
发信人: ananpig (●○ 围棋数学一把抓的安安猪), 信区: Programming
标 题: 19路围棋的所有合法图案终于出来了 Number of legal Go positi
发信站: BBS 未名空间站 (Fri Jan 22 10:38:03 2016, 美东)
Number of legal Go positions
The 361 points on a 19x19 Go board can be colored empty, black, or white.
Only some of the 3^361 possible positions are legal, namely those where
every group of connected stones of the same color has an empty point
adjacent to it. In the position above, black stones at E18 and N9 lack such
``liberti... 阅读全帖 |
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c*******n
发帖数: 1648 | 37 【 以下文字转载自 Engineering 讨论区,原文如下 】
发信人: chenchuan (中组部爱人分配办), 信区: Engineering
标 题: Questions
发信站: The unknown SPACE (Tue Jun 10 10:59:59 2003) WWW-POST
Any people know how to correlate toughness and impact stength together for a
material, and how to correlate modulus and hardness? Thank you! |
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s*******s
发帖数: 133 | 38 最近在用ABAQUS算一个结构, 里面有一些tension-only的cable
用了材料属性里面那个no-compression的选项
发现计算很难稳定, 很难converge. 有没有哪位大侠对此有经验的?
查了一下ABAQUS的用户手册, 关于这个问题手册上说有时候可以
'can be overcomed by overlaying each element that uses the no compression
model with another element that uses a small value of modulus'
这个怎么理解? |
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c*****y
发帖数: 6 | 41 那为什么会软呢？温度升高，atomic bonds 减弱？why? |
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i***y
发帖数: 246 | 47 http://www.matweb.com 上能搜到这个，但好像不是你要的高温状态下的。可能只能搜paper了
Physical Properties Metric English Comments
Density 8.71 g/cc 0.315 lb/in³
Mechanical Properties Metric English Comments
Hardness, Brinell 210 210 HB 30
Hardness, Rockwell B 95 95
Tensile Strength, Ultimate 689 MPa 99900 psi
Tensile Strength, Yield 517 MPa 75000 psi 0.5%
Elongation at Break 13.0 % 13.0 %
Reduction of Area 20.0 % 20.0 %
Modulus of Elasticit |
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s********r
发帖数: 257 | 48 About the damage tolerance, I did some composite struction analysis before.
I decrease the modulus of the element to a very small value when the damage
occur at that element. For instance, when matrix fails, I take E2=0, G23=0.
If fiber breaks, E1=0, G12=0, G13=0....
As I know, it seems your interest is on the micro scale analysis of the
composite (not macro :-) ), Crack analysis of composite is very complicated.
Take cross-ply composite for example, the crack may happens in the
longitudinal-ply |
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a****g
发帖数: 460 | 49 section 前面一步 material 定义一下材料属性
比如Young's Modulus, Poissoon's Ratio。
然后再在定义section时选中定义过的材料
然后再把section 赋予某个part。 |
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