a*****v
发帖数: 128 | 1 求教各位大侠，
如题，使用bruker的600
如果想用waltz去耦，在哪里找到rf field strength，怎么计算去耦的bandwidth呢？ |
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a*****v
发帖数: 128 | 2 求教各位大侠，
如题，使用bruker的600
如果想用waltz去耦，在哪里找到rf field strength，怎么计算去耦的bandwidth呢？ |
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w*******U
发帖数: 256 | 5 i programmed two codes using staggered and collocated grids to solve the
incompressible N-S equation in a Cartesian box with no-slip boundary
condition (lid driven flow). i used predictor-corrector method to decouple
velocity and pressure and imposed zero normal gradient for pressure boundary
condition in both codes. in the code of staggered grids, everything is fine
whereas in the code of collocated grids the velocity is fine but the
pressure drops always and cannot converge. could anyone help ... 阅读全帖 |
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G****n
发帖数: 145 | 6 No, the author's order is alphabetical. Larry Lang has more citations than
many top Chinese scholars including chaired professors such as Wang Jiang at
MIT, Wang Neng at Columbia, Wang Tan at UBC, Li Kai at UBC and Charles Cao
at Penn State. As a comparison, Li Kai is a chaired Professor at UBC in the
same field as Larry Lang, a few years junior, here is her citation lists for
papers above 100:
Monitoring: Which institutions matter?[PDF] from 163.152.84.199…, J Harford
, K Li - Journal of Financ... 阅读全帖 |
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a*****g
发帖数: 19398 | 7 By Daarel Burnette II
There's heated debate nationally over whether K-12 teachers really are in
short supply and—if so—what's caused the shortage and how widespread it is.
But in a number of states with dwindling supplies of new teachers,
overcrowded classrooms, months-long substitute assignments, and droves of
teachers quitting midyear, activists on both sides of the issue are seizing
the opportunity to push their policy agendas.
Those divisions are on stark display in places like Indiana, Okla... 阅读全帖 |
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w********o
发帖数: 10088 | 8 试验测出的信号是两个周期信号的叠加，想分别找出两个信号的周期，有什么标准的处
理方法么
一共只有5－6个周期的信号，用FFT出来的峰不怎么明显，很宽。。。 |
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D*******a
发帖数: 3688 | 9 我记得信号先要过个kaiser window再fft。。。 |
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w********o
发帖数: 10088 | 10 我google了一下，只找到kaiser window是什么，能说说这个window怎么做么
谢谢 |
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a****l
发帖数: 8211 | 13 do you understand why you need a kaiser window before fft??
Actually, I think in this case, kaiser window will not help, because there
are probabily not enough cycles. |
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J*******r
发帖数: 379 | 14 kaiser窗是为了压制旁瓣吧？但是主瓣会变宽。 |
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a****l
发帖数: 8211 | 17 you should first understand why you are having the problem with your signal,
then decide which method to use to solve the problem. There is no "
universal/omnipotent" solution in signal processing, all techniques are
invented to solve a certain problem. |
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z*****n
发帖数: 7639 | 18 yes. Kaiser window or any other window
make nonsense of signal separation. |
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z*****n
发帖数: 7639 | 19 well, you first need to analyse your signals.
What is the frequency/time domain properties
of these two signals respectively? If they
(at least one of them) have some special pattern
in time domain, you may try correlation.
If they don't overlap in frequency domain,
try FFT/DFT. |
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W***n
发帖数: 11530 | 20
Without your ckt diagram, can't tell. Did you choose the right value for
decoupling cap?
Btw, what's the horizontal scale? |
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g******u
发帖数: 3060 | 21 具体情况具体分析了。
低速低电流的信号就放个小decoupling电容，毛刺时间长的话需要放个低通。如果相对
输入端低阻抗的话还要加个电感。 |
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f*****0
发帖数: 489 | 22 quite a few problems:
1) you don't need a virtual ground. since you are using four batteries, you
can just ground the circuit to the true ground - center of the batteries.
and if you really really want to use the virtural ground for whatever reason
, put a small eletrolytic cap on the resistor and lower their value to no
more than 1k.
2) you absolutely need to have power supply decoupling or your opamp will
likely oscillate. the particular opamp is a pretty fast one (40mhz gbp), so
you may want |
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p*****t
发帖数: 966 | 23 不是一回事情么 ？ 英语叫做decoupling cap |
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F*********n
发帖数: 52 | 24 请问那应该如何计算RF的电流关系呢？
如果射频放大器的输出是接到50ohm传输线，而传输线的另一端接50ohm的负载(先设定是理想状况VSWR=1,不匹配的情况更复杂吧...），那么和直接在放大器输出接50ohm负载的情况应该是一样的把？然后如果是DC decouple的话，那么负载的射频电压和电流应该是同相的，然后就用一般的交流功率来算了吧？如果理解错误，希望指点指点。
另外对于射频的skin effect,应该是指频率越高，电流越聚集在导体的表面把？那样是不是意味着，比起直流，射频电流引起的传输线温度升高应该更严重？如果是的话，那么应该怎么来估算要用多宽的传输线才能够负载相关的射频功率输出了？网上找的布线宽对应电流的公式好像都是直流的...
第一次处理大功率的射频放大器布线，希望有经验的指点以下？ |
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F*********n
发帖数: 52 | 25 没有哪位大虾做过这样的估算？？自己顶一下。。。
定是理想状况VSWR=1,不匹配的情况更复杂吧...），那么和直接在放大器输出接50ohm
负载的情况应该是一样的把？然后如果是DC decouple的话，那么负载的射频电压和电
流应该是同相的，然后就用一般的交流功率来算了吧？如果理解错误，希望指点指点。
是不是意味着，比起直流，射频电流引起的传输线温度升高应该更严重？如果是的话，
那么应该怎么来估算要用多宽的传输线才能够负载相关的射频功率输出了？网上找的布
线宽对应电流的公式好像都是直流的... |
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d****o
发帖数: 1112 | 26 google decoupling capacitors |
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gr
发帖数: 2958 | 27 正解。
关键看功能，有可能是decouple capacitor，有可能是自举电容，等等。
might
mig |
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N*******g
发帖数: 1089 | 28 我知道这些电容是什么， 但是电容值的选择是不是有经验值在里面。 比如decoupling
cap有时候是33nF, 有时候是100nF. 什么时候要选择100nF, 什么时候33nF. 你说看要
求， 我也知道， 可是在设计中，信号还没有检测的时候， 我就要选电容了。这个时
候怎么选？ |
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g******u
发帖数: 3060 | 29 if you are not doing high speed designs, decoupling cap choice is mostly
based on experience and datasheets. |
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n**x
发帖数: 25 | 30
try put some 0402 SMD decoupling capacitors on the back of your PCB, if you
BGA IC uses some vias to fanout. |
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w*****s
发帖数: 433 | 31 最近一个向往已久的Qualcomm的一个电面,职位是 Digital Hardware Design Engineer (Baseband/FFA/SURF/PWB).虽然不是我学的IC的方向,但也非常希望能得到这个job.
这个position要求3年工作经验,我强调了我是new grad,但貌似他们也ok,给了个机会talk.
skill要求如下:
Candidates should have three to ten years experience designing consumer electronics, wireless devices and/or low power platforms. Solid electrical engineering, digital & analog circuit fundamentals and lab skills are a must. Strong written and oral communication and teamwork skills are required. Experience with digital c... 阅读全帖 |
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d*******d
发帖数: 3382 | 32 一般的电话面试，应该没法非常深入，所以至少准备好：
* brief self introduction
* resume上提过的所有东西，都要滚瓜烂熟，每个做过的project，都要有个summary/
story，并能够回答相关的细节
* 相关方面的fundemental。engineering的东西，很多东西万变不离其宗。
* 手头备好纸笔，随时准备开算，备好电脑，准备随时google（注意键盘声别被听到）
。回答面试问题，注意think aloud，把思路说出来，切忌不吭声闷头想花很多时间给
个正确答案，很多时候，面试看思路的方向对不对，intuition好不好。
* 准备一些关于职位公司的相关问题，如果给你机会问问题，可以趁机多了解一些这个
职位的requirement，这样为onsite复习准备的时候能有的放矢；同时要表现出对公司
和职位的兴趣。
Engineer (Baseband/FFA/SURF/PWB).虽然不是我学的IC的方向,但也非常希望能得到这
个job.
会talk.
electronics, wireless devices and/or low powe... 阅读全帖 |
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g******u
发帖数: 3060 | 33 没什么特别简单的办法，除非做反馈。
其实如果layout够好，两边线差不多长，load处接些decoupling电容，大致上也可算平
均分配。 |
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a***x
发帖数: 398 | 34 1. 手机天线是有选通性能的，对不同的频率信号发射的效率差别极大。
2.对于手机来说，电池的负极就是GND， BYPASS， DECOUPLE电容很多，很大，就像个
大水库，小的波浪是看不出来的。
3.手机出厂要测频率泄漏的，这个是有标准的。 |
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t******g
发帖数: 17520 | 35 mixed signal的controller？
不明觉厉，
如果用thermal stream往板子上吹， 能保证整个
模块在控制温度内那？如果往controller 上吹的话， 周边的
元件isolate地好吗？
我猜有可能上面说的jitter， skew， PLL
可能grounding， decoupling， 如果软件硬件没问题，
低温solder joint的问题？
如果是低能片， 这种从睡觉起床时间会不会随着温度变化？
原因可以很多。。。 |
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c*m
发帖数: 40 | 36 ANSYS 没用过，不知道能不能做的出来。
我用的是ABAQUS，而且只用它算 mechanical process，肯定可以算的出来。
thermal process 我是用自己编写的一个小软件算的。我想应该用abaqus 也算的出来。
多
其实计算这个问题不需要知道许多理论公式，因为你是用软件包来计算的。以ABAQUS为
如果两个过程分开算，就叫decoupled，合在一起算就叫coupled。coupled算
过
定
equation.
可
考 |
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h******y
发帖数: 315 | 37 【 以下文字转载自 USTC 讨论区 】
发信人: qwqw (胡瓜), 信区: USTC
标 题: 转帖]中科大再发物理《Nature》
发信站: BBS 未名空间站 (Wed Oct 28 23:59:33 2009, 美东)
http://www.nature.com/nature/journal/v461/n7268/abs/nature08470.html
Letter
Nature 461, 1265-1268 (29 October 2009) | doi:10.1038/nature08470; Received
17 June 2009; Accepted 27 August 2009
Preserving electron spin coherence in solids by optimal dynamical decoupling
Jiangfeng Du1, Xing Rong1, Nan Zhao2, Ya Wang1, Jiahui Yang1 & R. B. Liu2
1 Hefei National Laboratory for Physical S |
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J*******3
发帖数: 1651 | 40 漫谈物理学的过去、现在与未来*
冯 端
摘 要 文章试图对物理学的发展历史作一透视，从而理解其现状，并进而窥测其未
来的前景.我们希望这一看法对于当今从事物理学教学与科研的人士有所助益.由于物理
世界的层次化，诸层次之间既可能存在耦合，又可能出现脱耦.因而大量粒子所构成的
复杂体系中所涌现的各种层展性质就不能简单地还原成个别粒子所服从的规律.我们根
据这一观点并结合物理学的未来前景，讨论了当今物理学研究的若干前沿问题.一切迹
象预示着物理学将有光明的前景.
关键词 物理学，历史，现状，前景，前沿，物理世界的层次化，层展性质
RAMBLING ABOUT THE PAST,PRESENT AND FUTURE OF PHYSICS
Feng Duan
(Department of Physics,Najing University;National Laboratory of
Solid State Microstructures,Najing 210093)
Abstract This paper gives a historical perspective about the ... 阅读全帖 |
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f*******d
发帖数: 339 | 41
long
The photon field would keep its blackbody spectrum during
expansion of the Universe, but it is NOT in thermal
equilibrium! It has decoupled from matter since recombination. The
self-interaction of the photoes are also neglible.
sense.
photon
drops
no
etc.
I am not sure I understand your later statement. The cosmic virial
theorem
relates potential energy and peculiar velocity, but here he is talking
about uniform motion, there is no potential enengy and peculiar
velocity? |
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c**********g
发帖数: 222 | 42
fun.
>>>>Here, I mean that the photon field itself is in thermal
equilibrium. Because
the photon is decoupled from the matter after recombation, it expandes
adaibatically. Its evolution is the same as that of the closed box of
photon
in adaibatic expansion. For this reason I say that it is in thermal
equibrium
with itself though no interaction at all.
a
is
the
not
talking
Yes, you are absolutly right. Because gravity play a cruical role
in cosmology,
I cite the cosmic energy theorem just i |
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l**n
发帖数: 67 | 43 Our discussion of the CMBR is far from completion. And I am still
not 100% convinced where does the energy of the CMB photon go? Let's
take a typical attitude of physicist, find a problem, couldn't solve
it and forget about it:) Commented by the experts, the blackbody
spectrum could be preserved when the photons decoupled from the
matter which acts the wall in the typical black cavity. To us non-
expert we should just be aware of the fact that the space and the
wave-length of the photon are stre |
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L****n
发帖数: 12932 | 44 来自主题: Medicalpractice版 - 医患关系？ well, let me try with a short answer.
First of all, despite all the political correct bs, it has to do with how
much a human life worth. The more human life worth, the more important a
physician is, in turn the more a physician will be paid, and further in turn
, the more strict and regulation on how physician perform. This process may
take years and years. China is just at the beginning of this process.--The
decoupling of the contribution/reward of health-care industry in China is
rampant. As a... 阅读全帖 |
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L****n
发帖数: 12932 | 45 来自主题: Medicalpractice版 - 医患关系？ well, let me try with a short answer.
First of all, despite all the political correct bs, it has to do with how
much a human life worth. The more human life worth, the more important a
physician is, in turn the more a physician will be paid, and further in turn
, the more strict and regulation on how physician perform. This process may
take years and years. China is just at the beginning of this process.--The
decoupling of the contribution/reward of health-care industry in China is
rampant. As a... 阅读全帖 |
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z****e
发帖数: 54598 | 46 jvm也是c写的，最终什么都是c，但是c和汇编都太底层了
跟人的思维接不上，人毕竟是人，不可能完全用机器的思维方式去思考和书写语言
整个计算机系统就是层层封装的结果
并行计算跟分布式计算是两回事
并行计算很多时候对于单机更有意义，共享内存这些
分布式计算一定涉及网络连接，分布式计算不在乎甚至有意识地破坏某些nodes
以测试整个系统的健壮程度，比如chaos monkey，就是要让某些nodes fail掉
看看系统work不work，并行计算用得比较多的是hpc，而不是分布式系统
分布式系统因为nodes上各种乱七八糟的系统什么良莠不齐
所以找到一个统一的平台非常重要，否则每个node都要求定制软件，工作量太大
jvm是目前能找到的最好平台
其他语言要么效率比不过jvm，要么就是兼容性比不过java
hpc上的mpi这些到还真是用c比较多，物理系什么都很喜欢写pbsscript
然后提交hpc排队，执行后看结果，并行计算和分布式计算有一些共性和重叠
但是毕竟不是一个东西，不同的topics
从效率上说，效率提升不只比单线程的效率
是多线程，多进程的效率提升，能并行处理的部分越多，可以... 阅读全帖 |
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z****e
发帖数: 54598 | 47 jvm也是c写的，最终什么都是c，但是c和汇编都太底层了
跟人的思维接不上，人毕竟是人，不可能完全用机器的思维方式去思考和书写语言
整个计算机系统就是层层封装的结果
并行计算跟分布式计算是两回事
并行计算很多时候对于单机更有意义，共享内存这些
分布式计算一定涉及网络连接，分布式计算不在乎甚至有意识地破坏某些nodes
以测试整个系统的健壮程度，比如chaos monkey，就是要让某些nodes fail掉
看看系统work不work，并行计算用得比较多的是hpc，而不是分布式系统
分布式系统因为nodes上各种乱七八糟的系统什么良莠不齐
所以找到一个统一的平台非常重要，否则每个node都要求定制软件，工作量太大
jvm是目前能找到的最好平台
其他语言要么效率比不过jvm，要么就是兼容性比不过java
hpc上的mpi这些到还真是用c比较多，物理系什么都很喜欢写pbsscript
然后提交hpc排队，执行后看结果，并行计算和分布式计算有一些共性和重叠
但是毕竟不是一个东西，不同的topics
从效率上说，效率提升不只比单线程的效率
是多线程，多进程的效率提升，能并行处理的部分越多，可以... 阅读全帖 |
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l**t
发帖数: 10440 | 48 【 以下文字转载自 SanFrancisco 讨论区 】
发信人: coupled (decouple), 信区: SanFrancisco
标 题: Re: 奔（内容血腥暴力残忍无度，儿童不宜老人不宜孕妇不宜所有人都
发信站: BBS 未名空间站 (Mon May 17 01:17:22 2010, 美东)
准备先杀后煎？残忍，没鱼性 |
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c**********9
发帖数: 135 | 49 The Golf R has always used 4MOTION permanent all-wheel drive. The latest
generation system is now being used in the fourth-generation Golf R. Using
refinements such as the Haldex 5 coupling, the 4MOTION system is activated
before any wheelspin occurs, eliminating nearly all traction losses. The
system achieves this by using an advanced control function based on specific
driving conditions. When operating under a relatively low load or when
coasting, the front wheels are driven and the rear axle ... 阅读全帖 |
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c**********9
发帖数: 135 | 50
The balancer shaft had to be omitted due to package and weight reasons. The
more pronounced vibration of the components and the sustained effect on
interior acoustics were already counteracted during the early stages of
design, however. The interior noise level of the 2nd engine order could be
reduced to a low level in comparison to the competition via consistent
vehicle-side sound insulation measures and electrically actuated exhaust
flaps. The driving dynamics requirement could be taken into ... 阅读全帖 |
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