p*t
发帖数: 1210 | 1 How to let Matlab read a plot? I am trying to transfer a scanned plot to Excel
format. thanks. |
|
f*******r
发帖数: 204 | 2 For yourpurpose, it is simpler to find some software to digitize a curve
(by hand :)). I currrently use Grapher for digitizing. If you don't hav
e this software, try searching digitize in google to see whether there's
some free ware.
If using matlab, you can use "imread" to read the image into a matrix an
d write a program to find the profile by detecting the color change in t
he image. If the plot only have a single curve, it is better to scan the
plot into Black/White form; and then you will s |
|
p*t
发帖数: 1210 | 3 thanks, very helpful.
Excel
定 |
|
q****g
发帖数: 1190 | 4 在算Radius of gyration的时候，要 I (moment of inertia) 除以面积 A，然后开根
号。但是这个时候面积 A ，应该是什么？？？ 比如一个中空的tube，外半径R，内半
径r，这个时候A是 piR^2呢还是 pi(R^2-r^2)呢，高手说一下，谢谢 |
|
h****g
发帖数: 74 | 5 不应该是面积把，moment of inertia 得定义是r^2 dm, 我认为如果你是一个3D得问题
，这个dm就该是对整个体积的积分得到mass。然后去radius of gyration的话，mk^2.
这个m也应该是整个物体的质量。
不知道有没有理解错你的题意 |
|
a******n
发帖数: 98 | 6 Already solved my problem: there is a command of "inertia relief" in both of
ANSYS and Nastran. |
|
g******s
发帖数: 733 | 7 用 omega_r = sqrt( stiffness / moment of inertia) 计算出来的谐振频率是first
mode还是second mode?
先谢了！ |
|
l********e
发帖数: 214 | 8 quasi-static不考虑inertia，加速度带来的效应被忽略了。当然还有其它区别。 |
|
s******e
发帖数: 207 | 9 Sorry, can't input chinese from work computer...
I am EE, not have too much experience on the motor control, however needs to
redesign a motor contol board to protect the motor in the rotor lock state.
The motor is too old to have built-in thermal protection.
It is DC Brushless Motor, max load current rated at 0.77A, there is no other
valuable parameter I can find for the motor. Even the vendor does not know.
I searched on the internet, some one listed parameter like
IA/IN
MA/MN
MK/MN
someone cl... 阅读全帖 |
|
p*******k
发帖数: 50 | 10 第6题洞挖在中间尽量保证inertia值不变? |
|
s********1
发帖数: 581 | 11 转轴加速平动时torque=I*alpha还成立吗？例如当圆球沿着斜面滚下来的时候。如果力
矩，moment of inertia和角加速度都绕球心计算，torque=I*alpha还成立吗？此时，
球的转动动能还是(1/2)*I*omega^2吗？ |
|
m********8
发帖数: 123 | 12 what the hell is “运动滞
后力”
if “inertia” is nonsense，
why the hell your 运动滞后力 is not a nonsese
您的“运动滞后力”高明在哪里？？？
藕的思维那么好，也不敢搞物理，只好做机械工程
物理是很需要思考、思辨的
您这种浆糊脑袋， 居然自不量力。。。
倪不适合搞物理这种需要思辨的学问，您还是干别的去吧 |
|
p***e
发帖数: 402 | 13 箱子有没有滑动,采取的求法有什么不同?
对于没有滑动的情况,我初步打算用moment of inertia 来表示动能,然后重力势能转发
为动能.能量在初始位置和最后位置
的都是守恒的....很久没看多classical mechanics,都忘光了,现在大脑一片混乱,各位
大佬救命呀...路过的给一点点小小的提
示... |
|
m********e
发帖数: 1156 | 14 我还算有知的，无论深度还是广度，奈何世界上的知识太多。
有人贴出老爱的几百篇论文，我一看大多数是德文，不知道，无法判断。
您瞅一眼，看看有多少是真正的科研论文？
1913 Einige Argumente für die Annahme einer molekular Agitation beim
absoluten Nullpunkt Annalen der Physik(ser. 4), 40, 551–560, link
Some Arguments for the Assumption of Molecular Agitation at Absolute
Zero
1913 Déduction thermodynamique de la loi de l'équivalence
photochimique Journal de physique (ser. 5), 3, 277–282
Thermodynamic Deduction of the Law of Photoche... 阅读全帖 |
|
s********1
发帖数: 581 | 15 转轴加速平动时torque=I*alpha还成立吗？例如当圆球沿着斜面滚下来的时候。如果力
矩，moment of inertia和角加速度都绕球心计算，torque=I*alpha还成立吗？此时，
球的转动动能还是(1/2)*I*omega^2吗？ |
|
l***y
发帖数: 1166 | 16 Components
组成部分
This theory is a logical extension of the rotating magnetic field model.
According to the Swami Vivekananda,
这个理论是旋转磁场模型的一个合理延伸。根据斯瓦米·维韦卡南达：
"the Vedantic Prana and Akasha and the Kalpas, which according to [Tesla was
] the only theories modern science can entertain [... he] thinks he can
demonstrate that mathematically that force and matter are reducible to
potential energy" (Grotz, 1997)
“根据（特斯拉说的），吠檀多的能量、阿卡萨和劫，只有现代科学的理论才能容纳（
……他），认为他可以用数学来论证，力和物质可约简成势能” (Grotz, 1997)
Tesla ele... 阅读全帖 |
|
l**n
发帖数: 67 | 17 I cannot be better than Goldstein in this case. It's in his book
'classical mechanics' section "eigenvalues of the inertia tensor"
In simple words,
In maths, what you want to solve is a similar transformation.
Under such a transformation(3-D rotation), your S tensor becomes
diagonal. To proof that this can always be done for a hermitian
tensor(matrix) needs one page. Just skip it here. And then
the problem simply reduced to find the eigenvectors and eigen-
values for the orginal tensor. You put |
|
c********s
发帖数: 123 | 18
~~~~~first of all, what is this?
2nd, how do you compare v and c?
3rd, where do you compare v and c?
That discussion answers these 3 questions and tells you such a comparison
is not meaningful. And indeed, in its local inertia reference frame, moon
moves much slower than c. |
|
c*w
发帖数: 4736 | 19 Well, maybe I should give you guys a little hint :)
The ball is going to move in a circle, at a const speed.
So what is the angular velocity of the ball is related
to the angular velocity of the turntable?
The problem is:
A turntable rotates with const angular speed Omiga. A ball
rolls on it, without slipping. The moment of inertia of the
ball is (2/3)M(R^2), and the mass of the ball is sphereically
evenly distributed.
This is an undergrad phys competition problem, few student really
worked it o |
|
d****z
发帖数: 9503 | 20 Firstly, there is NO minimal length in QM. A minimal length would mean a
maximum energy. There is clearly no up limit on energy in current QM. Why? For
any object you observe, you can always choose a reference frame which has a
relative speed of 0.9999999999999999999999c with respect to the object.
Current QM assumes the principle of relativity, which means it should describe
the physics in that frame the same way as in any other inertia frame. In that
frame, the energy of the object could be at |
|
|
i*********5
发帖数: 19210 | 22 腿和打水
常见打水错误
Top Freestyle Flutter Kick Mistakes
GoSwim - Top Freestyle Flutter Kick Mistakes
TheRaceClub - Secret Tip Legs
Inertia
Stabilizing Force
Lift
Propulsion |
|
y*******n
发帖数: 10103 | 23 恩，的确，除非这个汽缸能变压缩比～～。ILMOR这个idea其实就是实现这个
最近看书，intake valve close的timing比想象中滞后很多（至少是摩托车、赛车
engine），以前高中物理学的，进气valve关闭应该正好在BDC的时候，但实际上由于空
气的inertia，即使活塞开始上升后，即在BDC之后很久
还有很多空气再往汽缸里涌。4 valve机器机器valve在50-60度after BDC才关闭。 2
valve的甚至在80度 After BDC才关闭上。当然这是在高rpm下，空气速度很快的时候。
这些机器在低转下，intake这么晚关，应该是会排出不少进气的，也算是miller循环了
吧。
环了 |
|
c*********r
发帖数: 19468 | 24 usually the drive shaft is made of carbon fiber, and its radius is
relatively small
so compared with that of the fly wheel, its moment of inertia may not be
that huge |
|
k**0
发帖数: 19737 | 25 直接贴一段GOOGLE来的东西吧! 去睡了.
OHV means OverHead Valve - an engine design where the camshaft is installed
inside the engine block and valves are operated through lifters, pushrods
and rocker arms (an OHV engine also known as "Pushrod" engine). Although an
OHV design is a bit outdated, it has been successfully used for decades. An
OHV engine is very simple, has more compact size and proven to be durable.
Downside: it's difficult to precisely control the valve timing at high rpm
due to higher inertia cau |
|
p*********e
发帖数: 32207 | 26 看了一下wiki的介绍
"
Thompson coupling[edit]
Thompson coupling from U.S. Patent 7,442,126. Note: drawing on the right
omits certain components in order to illustrate the control yoke's spherical
pantograph.
The Thompson constant velocity joint (TCVJ), also known as a Thompson
coupling, assembles two cardan joints within each other to eliminate the
intermediate shaft. A control yoke is added to keep the input and output
shafts aligned. The control yoke uses a spherical pantograph scissor
mechanism to bi... 阅读全帖 |
|
V***b
发帖数: 3419 | 27 我也没看明白，涉及多个变量都要积分的事情真要静下心仔细计算。当然我只想知道结
论。其实BMW自己说过，用单个turbo实现两个小turbo的boost的话，single-turbo的
inertia大，是个劣势，但针对N55的需求single-turbo就行了，排量再大或者boost再
高的话还得twin-turbo。 |
|
w********e
发帖数: 664 | 28 汽车行业的moment of inertia要比手机大许多许多....
musk搞的那些东西都是靠一般人拿不到的资源。。。他的实力是能把这些资源用到极致
火箭说白了是他花纳税人的钱，以一种合法和间接的方式，技术全是NASA的
搞汽车，Tesla能活到今天财政上是靠卖碳排放指标，不过他能把这个玩儿转
不过我觉着他应该不会很想趟这个浑水了，等花街的热度下来一点之后，加州那一摊子
应该会卖给偷油塔。。。或者戴姆勒。。。 |
|
w********e
发帖数: 664 | 29 汽车行业的moment of inertia要比手机大许多许多....
musk搞的那些东西都是靠一般人拿不到的资源。。。他的实力是能把这些资源用到极致
火箭说白了是他花纳税人的钱，以一种合法和间接的方式，技术全是NASA的
搞汽车，Tesla能活到今天财政上是靠卖碳排放指标，不过他能把这个玩儿转
不过我觉着他应该不会很想趟这个浑水了，等花街的热度下来一点之后，加州那一摊子
应该会卖给偷油塔。。。或者戴姆勒。。。 |
|
q**j
发帖数: 10612 | 30 polar mass of inertia小？ |
|
B*Z
发帖数: 7062 | 31 前两天猫猫提出了M235的分布是53：47，比较吃惊。好像其他人也没有接下去继续讨论
。我还是问一下吧。这个wd的重要性在哪里？因为我的车也是这个比例，看上去不是非
常理想。可是评论却说handle好，不会开玩笑吧？
1. 直线跑，当然是50：50或者更靠后比较好，后轮加速比较有劲。可是这个又有一个问
题，就是到底多少就到头了？后驱是不是要35：65。考虑到GTR是53:47，是否awd就是这
个比例比较好？
2. 曲线跑，是否是50：50比较好？但是这时候还有个问题，就是50：50可以是大部分质
量在中间，也可以是像扁担一样两头重。这时候好像有个指标叫P(olar) M(ass) of I(
inertia)。感觉PMI比wd更加合理。
当然我说不清楚，以上是我的疑问。不知道wd最根本的意义是什么。多谢。 |
|
p*********e
发帖数: 32207 | 32 ☆─────────────────────────────────────☆
carbonfiber (碳纤维) 于 (Tue Aug 11 10:49:08 2009, 美东) 提到:
http://www.ilmor.co.uk/concept_5-stroke_1.php
3缸涡轮增压汽油机，其中两缸（高压气缸）工作方式类似普通的4冲程引擎
但是废气是排到第三缸（低压气缸），继续做功一个冲程
第三缸的排气凸轮轴转速与曲轴同速（也就是比通常的凸轮轴转速加倍）
所以一个低压气缸可以配套两个高压气缸
低压气缸的存在使得膨胀比（决定内燃机理论热效率）和压缩比（汽油机的终极瓶颈）
分离
在较低的压缩比的前提下达到14.5以上的膨胀比
（相比之下，目前即便是直喷涡轮增压汽油机的膨胀比也不过是9.5-10.5）
同时低压缩比意味着高增压，所以功率密度也不是问题
不过我觉得这个方案的油门响应可能不好，因为涡轮迟滞可能会恶化
☆─────────────────────────────────────☆
wawat (娃々頭) 于 (Tue Aug 11 15:13:24 20... 阅读全帖 |
|
p*********e
发帖数: 32207 | 33 ☆─────────────────────────────────────☆
fatboat (極.品.飛.車) 于 (Fri Aug 28 11:45:47 2009, 美东) 提到:
前两天去看了一辆porsche 944
我查了一下,transmission在rear axe以后了
导致trunk很浅
这样对weight distribution不是很有好处么？除了trunk会变小点
现在的FR车是不是变速箱都在前轴后面？
☆─────────────────────────────────────☆
owenxguo (特别丑) 于 (Fri Aug 28 11:48:41 2009, 美东) 提到:
corveete还是后面吧，现在车的材料和设计都更先进，全部放在前面也可以很好的平衡
前后车重，基本没啥必要放后面。
☆─────────────────────────────────────☆
pandamalone (0000~史前圣灵猫熊) 于 (Fri Aug 28 11:49:07 2009, 美东) 提到:
简单的说，基于成本的考虑
... 阅读全帖 |
|
B*Z
发帖数: 7062 | 34 这样做成了扁担了也不好。虽然是50:50，但是polar mass inertia会增加。最合理的
办法就是把发动机往后面挪，不要第二排。这样就完美了。而且前面还长一些，更好看
。可惜还真的有人喜欢哪个第二排。 |
|
e********y
发帖数: 350 | 35 polar moment of inertia 低很多啦~ |
|
B*Z
发帖数: 7062 | 36 toyota真牛
Combining cam-changing VVT and cam-phasing VVT may satisfy the requirement o
f both top-end power and flexibility throughout the whole rev range, though
it is inevitably more complex. At the time of writing, only Toyota and Porsc
he have such designs. However, I believe in the future more and more sports
cars will adopt this kind of VVT.
Toyota’s VVTL-i is the most sophisticated VVT design yet
Toyota joined the CVVL club in 2008 with its Valvematic technology. Compare
with BMW Valvetron... 阅读全帖 |
|
v******d
发帖数: 227 | 37 轴距长的车polar moment of inertia更大所有整体会更稳定，车身不太容易旋转，轴
距短的车很容易rotate，极限开高速弯就有点吓人吧。 |
|
w*******y
发帖数: 60932 | 38 Walmart has the Schwinn 420 Elliptical for $487 (reg. $599) compared to the
lowest price shown on google at $597 and free site to store shipping.
Don't forget to use cashback sites to make it even better.
Schwinn 420 Elliptical:
http://www.walmart.com/ip/Schwinn-420-Elliptical-Machine/125346
Rated "Best Buy" by a leading consumer magazine. This Schwinn Elliptical
Machine is designed to deliver a comfortable workout with maximum results.
The BioGlide motion technology has a natural elliptical st... 阅读全帖 |
|
X*****s
发帖数: 2767 | 39 http://online.barrons.com/article/SB500014240531119043319045773
First, let's get this out of the way - I fought the trend and the trend won.
Despite my bearish pronouncements, the stock market rumbled its way higher
in the first quarter of the year with nary a hiccup. The Standard & Poor's
500 index's gain of 12% was indeed the best opening to a year since 1998.
And the Nasdaq beat that with an 18% increase.
But expecting the performance of the second quarter to come close to the
performance of ... 阅读全帖 |
|
A******e
发帖数: 655 | 40 如果你depression的主要原因是你和老板的关系不好，那我建议你趁早走人
这个不单单是communication的问题，有的时候就是personality 不match
有时候你讨厌他，也许只不过是mirroring他对你的成见，不信任，等等
人生苦短，快乐是那么不容易的事，何必陷在这个泥沼里苦苦挣扎
如果你depresssion是令有原因，比如说和心上人分手，离婚，
或者出了车祸之类的，那么我认为你可以和你老板坦诚地谈一谈
想一个比较好的解决办法，
闹翻了，其实是好事，古时兵法上有置之死地而后生，
现在的说法是改变你生活和old habits的inertia,然后才会有change |
|
r***l
发帖数: 36 | 41 可以用covariance matrix或者inertia matrix的特征值 |
|
P*****a
发帖数: 392 | 42 http://www.nytimes.com/2002/07/15/international/15WEB-CHIN.html?pagewanted=1
China Juggles the Conflicting Pressures of a Society in Transition
By CRAIG S. SMITH
Stability in China can seem reassuringly deep, anchored by the inertia of an
older generation worn out from decades of politically driven chaos and a
younger generation transfixed by the promise of material gain.
But Chinese society is still only midstream in its difficult transition from a
centrally planned economy to a market driven o |
|
