r***n
发帖数: 553 | 1 Three Are Accused of Impeding Boston Bombing Inquiry
They were perhaps Dzhokhar Tsarnaev’s closest friends during his two years
at college, an American classmate from high school and two Russian-speaking
students from Kazakhstan. The Kazakhs seemingly had money and drove
expensive cars. They entertained Mr. Tsarnaev at their off-campus apartment,
and he partied with them in New York. One of them lent Mr. Tsarnaev a black
BMW after he smashed his Honda Civic in an accident.
And in the wake of the... 阅读全帖 |
|
G**Y
发帖数: 33224 | 2 似乎美国人民也受不了了：
beekeeper6wrote:
8:02 AM PST
"impeded democracy"? We helped protesters overthrow a democratically elected
government! I thought Obama was going to be Mr. UN, not going at it alone
cowboy-style? Looks like the more things have changed...
AnnsThoughtresponds:
8:05 AM PST
I think what the White House means by impeding democracy is that after the
2010 election in the Ukraine, the winners immediately began to help
themselves to the nation's treasury, which caused the people to riot in
re... 阅读全帖 |
|
t**x
发帖数: 20965 | 3 The Mitutoyo Case: Will Japan Learn from Its Mistakes or Repeat Them?
Introduction
In the last few years, a number of Japanese companies have been implicated
in export control violations that have highlighted deficiencies in Tokyo's
ability to control the spread of sensitive dual-use technologies. One of the
most prominent and egregious cases is that of the Mitutoyo Corporation, a
leading precision measuring device manufacturer. The charges in this case
revolved around the illegal transfer of fi... 阅读全帖 |
|
a*****y
发帖数: 33185 | 4 贴一个washingtonpost的：
"China’s continued economic development will bring the country increasingly
into direct competition with the United States, which is why Trump has
explicitly stated the proposed U.S. tariffs are designed to impede the Made
in China 2025 program. But this strategy is unlikely to be effective and
risks undermining rather than boosting U.S. manufacturing."
https://www.washingtonpost.com/news/monkey-cage/wp/2018/05/03/what-is-made-
in-china-2025-and-why-is-it-a-threat-to-trumps-t... 阅读全帖 |
|
b**u
发帖数: 2761 | 5 http://en.wikipedia.org/wiki/Short_track_speed_skating
There are several actions that will result in skaters being disqualified (DQ
) from a race, and having their time rendered invalid.
* Impeding (DQI): Pushing, blocking, or otherwise causing an impediment
for another skater
* Cross-tracking (DQX): Deliberately cutting in front of a competitor
who is attempting to pass
裁判判的是韩国队impeding。
规把 |
|
g*****1
发帖数: 666 | 6 由于bz的Cross-tracking 造成的 Impeding
* Impeding (DQI): Pushing, blocking, or otherwise causing an impediment
for another skater
Pushing, blocking, BZ都做了，也造成了SLL的impediment |
|
l****z
发帖数: 29846 | 7 ＝＝＝＝＝＝＝＝＝＝＝
James Williams, an attorney for Ms. Johnson, called the attempts to “impede
Justice Johnson’s ascension to the Chief Justice position… a racially
divisive maneuver
＝＝＝＝＝＝＝＝＝＝＝
反正你ｔｍｄ的不同意我老黑的就是种族歧视．
The unusual contest to determine who should be the next chief justice of the
Louisiana Supreme Court isn’t over just yet.
Lawyers for Louisiana Gov. Bobby Jindal on Friday filed notice that they
planned to appeal U.S. District Court Judge Susie Morgan’s ruling last week
that settled the is... 阅读全帖 |
|
l****z
发帖数: 29846 | 8 The Left Doesn’t Really Believe in Climate Change
Jon Gabriel, Ed.
May 27, 2014 at 1:37 pm ( 23 hours ago )
The sky is always falling. If the new ice age doesn’t do us in, the ozone
hole will. The instant DDT is banned, aerosols must follow. Global warming
is replaced by climate change is replaced by “global weirding.”
And what is the solution to these often-contradictory scenarios? We
anachronists who retain a bias toward the hard sciences would employ very
different measures to prevent a fr... 阅读全帖 |
|
y*******7
发帖数: 579 | 9 网络上看了很多关于这个网站的推介，http://www.gototrafficschool.com/
就注册去上课了，发现价格已经改了，是$19，
不过用promotion code (X2B-C8B-A94) 依然可以减少$2。
现在已经不能只是开着电脑耗时间了，我试着开机，但出去了3-4个小时，回来就要求
重新log in了。而且也不能直接参加final exam，必须答对各章的所有试题才能到达
final exam，而且各章的题目之后还有一题“security question”，就是问关于前面
学习材料中的图片、录像中的内容，所以还不得不点击看看，总共也需要不少时间。不
过有个节约时间的方法，就是先到问题的一页，看完问题再点击“previous”回到前一
页寻找答案，利用IE的“编辑”菜单下“查找（在当前页）”的功能可以快速定位。如
果中途log off再回来log in，得一页页翻过之前做过的章节，不过不需要重新做题就
是。到达上次退出地方，就自动加载之前这一章的内容。
欢迎大家使用promotion code：X2B-C8B-A94
http://www.gototraff... 阅读全帖 |
|
g********d
发帖数: 19244 | 10 可以得到一张impeding traffic
但不会得到一张driving below minimum speed limit
而且 开的超过45迈 也不能保证不会得到 impeding traffic的票子 |
|
f*******e
发帖数: 8974 | 11 嗯，这是琴谱的数据，我那套东西的数据晚上找找
Input Power
110V-240V AVAILABLE
Output Tube
16.5W×2 (8Ω RMS)
Vacuum Tube
6N3 x2
Harmonic Distortion
< 2%
Crosstalk Attenuation
>50dB
Frequency
20Hz-50kHz
Signal/Noise Ratio
>80dB (A weight)
Overloading Level
>20V
Input Impedance
10KΩ
Input sensitivity
450mV
Load Impedance
8ohms
Audio Output
2 groups speaker out, 1 x 3.5 mini jack out (Line/Phone)
Audio Input
1 x RCA, 1 x Aux, 1 x MP3/I-pod |
|
a*****o
发帖数: 246 | 12 Why is that headphone with higher impedance is harder to drive while speaker
with lower impedance is harder to drive?
How about a preamplifer as a headphone amp? |
|
J*****s
发帖数: 110 | 13 我有一个bookshelf音响，想找一个合适的功法。一直没搞懂选择怎么样的功放。
音响：
Cambridge Soundworks Model Six Bookshelf Speaker：
http://store.cambridgesoundworks.com/Model-Six-Bookshelf-Speake
Pair/M/B0034ZZ5W6.htm
参数概要：
One 3/4-inch cone tweeter with a center dome and an 8-inch woofer
FREQUENCY RESPONSE 50HZ - 20KHZ
MIN/MAX POWER 15 WATTS / 150 WATTS
SENSITIVITY 90DB
NOMINAL IMPEDANCE 8 OHMS
发现Amazon上有一个功放：
Pioneer GM-D8500M Class-D Mono Amplifier with 1200 Watts Max. Power
http://www.amazon.com/exec/obidos/... 阅读全帖 |
|
D**********s
发帖数: 3139 | 14 local有一对mcintosh xrt25，样子见图。和卖家商量了一下差不多1200 self-pickup。不是日本的分体版本，16个高音单元是固定在woofer上面的，搬运起来极其麻烦，包装也是个问题，一共120多公斤，suv肯定是装不下了。以前麦家的小旗舰，三分频。
Crossover frequencies: 250Hz and 1500Hz
Impedance: 4 ohms
Output: 85dB @1w/1m [88dB @ 2.83v]
Power rating: 1000w
Overload protection: none
Size: 84"H including tweeter section. bass section 14-1/2"W and 19"D
价格倒是还可以，但是上面还有xrt26，分体的，好搬运，好价格的也经常出现。四分
频，20个高音单元，见图。
Crossover frequencies: 100Hz, 250Hz and 1500Hz.
Impedance: 4 ohms.
Output: 84dB @1w/1m [87dB @ 2.83... 阅读全帖 |
|
s******g
发帖数: 15854 | 15 有点想搞个胆机放在客厅里，一边听，一边做装饰，看这个港产的Audio Space AS-3i
我就想知道他能不能推动JBL L830这种音箱
音箱的spec是
Speakers Maximum Output Power: 300 Watts
Speakers Response Bandwidth: 48 - 40000 Hz
胆机的spec是
Input Impedance: > 100Kohm (RCA)
Output Impedance: 4, 8 ohm
Output Power: 32Wx2 Class AB2 P-P (Ultralinear) 16Wx2 Class AB2 P-P (Triode)
Damping Factor: > 5
Frequency Response: 20Hz - 30KHz / -1dB
T.H.D.: < 1% 20Hz-20KHz (Ref. Output)
懂的给号号脉，包子酬谢 |
|
J********e
发帖数: 42 | 16 Nevermind. Sometimes low impedance headphones need even better amp to feed
them with high current and large undistorted power, like ATH 2002, grado RA1.
I believe D5000 is very suitable for mp3 and portable output. Look at the
1st curves below, D5000 is way louder than D7000 even with the same
impedance.
The reason why people said about Denon used ATH drivers was because they
behaved incredibly similar for many kinds of music. In the 2nd figure, A900
is quite the same as the response of D7000. I... 阅读全帖 |
|
J********e
发帖数: 42 | 17 Nevermind. Sometimes low impedance headphones need even better amp to feed
them with high current and large undistorted power, like ATH 2002, grado RA1.
I believe D5000 is very suitable for mp3 and portable output. Look at the
1st curves below, D5000 is way louder than D7000 even with the same
impedance.
The reason why people said about Denon used ATH drivers was because they
behaved incredibly similar for many kinds of music. In the 2nd figure, A900
is quite the same as the response of D7000. I... 阅读全帖 |
|
d******0
发帖数: 22800 | 18 你说你自己的果果版吧。。 这里除了这个比较新的女ID，那有啥啥bose粉啊。
看这个urban dictionary给bose的解释吧。
http://www.urbandictionary.com/define.php?term=Bose
1. Bose 530 up, 179 down
Highly overrated company that manufactures inferrior audio components that
fail to compete with equipment in a pricerange that undercuts many Bose
products tenfold.
Paper cones, 'secret' frequency response, and wide gaps in the crossover
dynamics make for muddy and empty sound with high distortion in the upper
ranges coupled with limited bass respon... 阅读全帖 |
|
d*******n
发帖数: 2078 | 19 是你太小看的80年代好的卡座了。好的卡座是有amp的。卡座的耳机插孔是，录音监听
的最后一步，很重要的，不是什么简单衰减或者变阻一下就输出了。
洋人论坛讨论这个挺多的：
“Most cassette deck headphone outputs are designed for low impedance
headphones. However, I have used the headphone output from a Sony TCK-611s
and more recently on my Nakamichi CR-7 with great success, and I think you
would be surprised how good these sound compared to a dedicated headphone
amp (of which I have quite a few). I wouldn't use them for your 600 ohm
Beyers, but for Grados, the low impedance Denons, ... 阅读全帖 |
|
y**i
发帖数: 357 | 20
well，不能ignore the fact很多公司用ESS Sabre 9018做DAC，得到的review很好。
sacd和cd是不同的format。要还原好CD很难。
http://thewelltemperedcomputer.com/Intro/SQ/USB_SPDIF.htm
Async USB: In asynchronous mode the DAC tells the PC how many data to send.
This allows for using a fixed clock at the DAC. allows for a
implementation with a very low intrinsic jitter.
SPDIF: SPDIF is real time, any fluctuation in the clock of the sender
translates into input jitter.
我觉得前级的作用是：1.present correct output impedance 2. present low input
... 阅读全帖 |
|
t**s
发帖数: 156 | 21 有没有用过的请评论一下？
另外， 这两个箱子用yamaha rx-a700 可以推的好吗？ 多谢了！
jamo c803:
Frequency Response (Hz, +/-3dB): 45 - 24,000
Power (W, long/short term): 125 / 250
Impedance (Ohm): 6
Sensitivity (dB, 2.8V/1m): 87
Crossover Frequency: 2 kHz
Kef q300:
Frequency Response ±3dB: 42Hz - 40kHz
Crossover Frequency: 2.5kHz
Amplifier requirements: 15 - 120W
Sensitivity (2.83V/1m): 87dB
Maximum output (SPL): 110dB
Impedance: 8Ω
yamaha rx-a700:
Rated Output Power (20Hz-20kHz, 2ch driven): 90W (8ohms, 0.08%... 阅读全帖 |
|
G****o
发帖数: 229 | 22 我在听，目前主要是讲如何推箱子
project是做 guitar amp 估计都是重点在做音箱吧
Week 1
Lesson 1: Introduction to wave propagation, simple oscillating systems,
sound pressure, sound waves, the speed of sound, wavelength, frequency and
wavenumber, sound pressure level, and auditory directional cues.
Lesson 2: Electronics fundamentals - charge, current, voltage, resistance,
Ohm’s law, DC circuits, finding currents and voltages in simple circuits
Week 2
Lesson 1: Reflection and absorption of sound, resonances in air columns,
res... 阅读全帖 |
|
w*****g
发帖数: 4298 | 23 It's BACK! For those of you who missed out on the first round of group-buy
for the Aune T1 on Massdrop, it has been re-added and the price is already
at the 119.99 tier. That's 45% off the MSRP of $219. Much better sound than
e17 since it has tube.
If 200 people total join (94 more at the time of writing) the price drops
even lower to 109.99!
Product Features:
Frequency response: 20hz-20khz
Signal to noise Ratio: >=120db
Line out: 2Vrms
Suitable headphone impedance: 30 ohm ~ 600 ohm
Headphone Am... 阅读全帖 |
|
s******d
发帖数: 2568 | 24 用speaker selector驱动multi-room speakers只能说是没有办法的办法。
市面上的speaker selector基本上都是无源设备。 就是没有电源和任何有源电路的。
靠几个按键开关来接通speakers.
那问题就来了， 如果每个room的speaker阻抗是8欧姆， 四个房间同时接通的阻抗是多
少？八个房间同时接通的阻抗又是多少？ 这不是分分秒秒要烧功放吗？
为了满足某些人非要同时按好多个speakers，又避免烧机的悲剧，大多数speaker
selector都加保护功能 ，名曰impedance matching ，或 Impedance protection, 或
Protection Circuit 。。。 等等。听起来挺好， 但打开机子看看， 不外乎串上几个
大水泥电阻。 这样不管接几个喇叭，反正有功率串联电阻扛着，烧机的概率就大大降
低了。
要是你花了功夫研究喇叭线要用多粗， 或者多出点血用无氧铜喇叭线， 把功放到喇叭
的阻抗降那么几十分之一欧姆，串上这几个几欧姆的水泥电阻， 那阻尼系数啥的全可
忘了。 或者买个音质如何好， 功率XXX瓦r... 阅读全帖 |
|
g*****9
发帖数: 4125 | 25 An accepted guideline is that the wire impedance should not exceed 5% of the
entire circuit. For a given material, resistance is a product of length and
thickness. For this reason, lower impedance speakers require lower
resistance speaker wire.Longer cable runs need to be even thicker. Once the
5% guideline is met, thicker wire will not provide any improvement.
Maximum wire lengths for two conductor copper speaker wire
Wire size 2 Ω load 4 Ω load 6 Ω load 8 Ω load |
|
|
W******e
发帖数: 3319 | 27 1. Introduction
My interest in studying creativity was inspired by the frustrations that I
felt as a student, then as a professor. I wanted to know how I could
encourage creativity in myself, my students, and my colleagues.
Politicians, industrial managers, academic administrators, and other leaders
often say that innovation is critical to the future of civilization, our
country, their company, etc. But in practice, these same people often act as
if innovation is an evil that must be suppressed,... 阅读全帖 |
|
a*****g
发帖数: 19398 | 28 The common-core math standards require that students learn the standard
algorithm for multi-digit adding and subtracting—you know, the process in
which you line the numbers up vertically to add or subtract and regroup as
needed—by the end of 4th grade.
But waiting until then to teach the algorithm is a big waste of time for
some students, writes Tom Loveless, a senior fellow at the Brookings
Institution.
Students begin learning to add and subtract in 1st grade under the common
standards. So teac... 阅读全帖 |
|
a*****g
发帖数: 19398 | 29 我一直说 common core 出的问题，现在终于有其他人出文章了
http://www.theatlantic.com/education/archive/2015/11/math-showi
Common Core-era rules that force kids to diagram their thought processes can
make the equations a lot more confusing than they need to be.
Rogelio V. Solis / AP
At a middle school in California, the state testing in math was underway via
the Smarter Balanced Assessment Consortium (SBAC) exam. A girl pointed to
the problem on the computer screen and asked “What do I do?” The proctor
read the instruc... 阅读全帖 |
|
e*i
发帖数: 10288 | 30 General answer : NO.
Unless your lot is 1 acre or more.
I did some research for my daughter last year. :P
ARTICLE 2.01 GENERAL PROVISIONS*
Sec. 2.01.001 Dangerous wild animals
Dangerous wild animals, as defined in V.T.C.A., Health and Safety Code,
section 822.101, shall be regulated in accordance with the provisions of V.T
.C.A, Health and Safety Code, chapter 822, subchapter E, section 822.101 et
seq. (Ordinance adopting Code)
ARTICLE 2.02 LIVESTOCK AND FOWL*
Division 1. Generally
S... 阅读全帖 |
|
e*i
发帖数: 10288 | 31 General answer : NO.
Unless your lot is 1 acre or more.
I did some research for my daughter last year. :P
ARTICLE 2.01 GENERAL PROVISIONS*
Sec. 2.01.001 Dangerous wild animals
Dangerous wild animals, as defined in V.T.C.A., Health and Safety Code,
section 822.101, shall be regulated in accordance with the provisions of V.T
.C.A, Health and Safety Code, chapter 822, subchapter E, section 822.101 et
seq. (Ordinance adopting Code)
ARTICLE 2.02 LIVESTOCK AND FOWL*
Division 1. Generally
S... 阅读全帖 |
|
g****t
发帖数: 31659 | 32 这个progress的意思是,你先跑了,或者先跳了,
然后我伸胳膊.这才存在impede什么的问题.
现在问题是,例如你和我都没动,我伸着胳膊,我没推你,没抓住你.
然后你跳起来做投篮动作,我没来得及收胳膊,你碰到了我.这样要罚球么?
以前都是防守方不跳,蹭犯规就不成立.
你看下Tmac 35秒蹭Duncan 3+1那个球.
那时候我记得解说就是这么说的:Duncan跳了.
这个是有道理的.make sense
因为进攻方先跳,就有了progress的概念了,
这种情况下,防守方不能有新动作.如果防守方跳了,接触肯定算防守方的.
a. A player shall not hold, push, charge into, impede the progress of an
opponent by
extending a hand, arm, leg or knee or by bending the body into a position
that is not normal.
Contact that results in the re-routing of an opponen |
|
c******t
发帖数: 1733 | 33 Common errors performing classic lifts.
by Sergey Rudnev,IKSFA Master Coach
a) JERK 1. Error: feet are wider than shoulder width Consequences: reduction
of the distance and speed of acceleration of the bells, worsening of the
efficiency of the leg work. Causes: low mobility in the hip joints or lack
of knowledge of physics. Correction: in the former case I recommend rocking
in gymnastic bridge or static rack holds (1-5 minutes). In the latter I
recommend revising the section of physics entitled ... 阅读全帖 |
|
c******t
发帖数: 1733 | 34 Common errors performing classic lifts.
by Sergey Rudnev,IKSFA Master Coach
a) JERK 1. Error: feet are wider than shoulder width Consequences: reduction
of the distance and speed of acceleration of the bells, worsening of the
efficiency of the leg work. Causes: low mobility in the hip joints or lack
of knowledge of physics. Correction: in the former case I recommend rocking
in gymnastic bridge or static rack holds (1-5 minutes). In the latter I
recommend revising the section of physics entitled ... 阅读全帖 |
|
H*****r
发帖数: 764 | 35 http://claytravis.net/wordpress/?p=1298
Ohio State Is Screwed (But You Wouldn’t Know It Based On Media Coverage)
You’re not hearing anything about Ohio State at all from most sports media
which is why I took a break from two top-secret longer form writing projects
to let you know what you need to know about Ohio State and Jim Tressel.
The immediate takeaway is simple — and salty — Ohio State and Jim Tressel
are fucked. (I used screwed in the headline so y’all wouldn’t get busted
at work).
Last n... 阅读全帖 |
|
c****n
发帖数: 21367 | 36 impede的必要条件是俩人都离球很远吧...
你说的意大利和澳大利亚的点球是06年那个么？那个不是impede...
罚下 |
|
h*****8
发帖数: 2667 | 37 网上有个人问了个类似的问题，我把问答都贴了：
Q：I have a new Shure SM57 mic, and I want to do recording on my laptop mic
jack. I've got a low-impedence in/high-impedence out XLR to quarter-inch (
guitar amp plug) converter. But if I use another converter to convert to the
small plug in my laptop, the sound vlume is very low and noisy. As I
understand, its because the line-in voltage on music amps and my laptop is
very different, so I need a pre-amp? Is this correct, do I need a pre-amp to
record mic to laptop? Where c... 阅读全帖 |
|
g**o
发帖数: 3033 | 38
~~~~~~~~~~~~~~~~~~~~~~~~
this is correct, but make sure you are using stereo, not mono plugs.
stereo plugs are more common, many headphones come with one.
For impedence checking, just use some cheap earphones, which are 8ohms,
typically. If you can't get normal volume out of those earphones, it may
because your current headphone has higher impedence. Check with a multimeter
if you have. In this case, you need to invest a headphone amp.
But I really doubt a roland keyboard can't work well with a... 阅读全帖 |
|
s******g
发帖数: 15854 | 39 有点想搞个胆机放在客厅里，一边听，一边做装饰，看这个港产的Audio Space AS-3i
我就想知道他能不能推动JBL L830这种音箱
音箱的spec是
Speakers Maximum Output Power: 300 Watts
Speakers Response Bandwidth: 48 - 40000 Hz
胆机的spec是
Input Impedance: > 100Kohm (RCA)
Output Impedance: 4, 8 ohm
Output Power: 32Wx2 Class AB2 P-P (Ultralinear) 16Wx2 Class AB2 P-P (Triode)
Damping Factor: > 5
Frequency Response: 20Hz - 30KHz / -1dB
T.H.D.: < 1% 20Hz-20KHz (Ref. Output)
懂的给号号脉，包子酬谢 |
|
r***n
发帖数: 553 | 40 Three Are Accused of Impeding Boston Bombing Inquiry
They were perhaps Dzhokhar Tsarnaev’s closest friends during his two years
at college, an American classmate from high school and two Russian-speaking
students from Kazakhstan. The Kazakhs seemingly had money and drove
expensive cars. They entertained Mr. Tsarnaev at their off-campus apartment,
and he partied with them in New York. One of them lent Mr. Tsarnaev a black
BMW after he smashed his Honda Civic in an accident.
And in the wake of the... 阅读全帖 |
|
j*****y
发帖数: 1916 | 41 Science. 2013 Aug 30;341(6149):976-80. doi: 10.1126/science.1238041.
Poverty impedes cognitive function.
Mani A1, Mullainathan S, Shafir E, Zhao J.
Author information
Abstract
The poor often behave in less capable ways, which can further perpetuate
poverty. We hypothesize that poverty directly impedes cognitive function and
present two studies that test this hypothesis. First, we experimentally
induced thoughts about finances and found that this reduces cognitive
performance among poor but not i... 阅读全帖 |
|
z*****n
发帖数: 7639 | 42 Actually this is not simple question.
1. The physical layer sensing first starts to work:
When a transceiver(e.g., your PC's LAN card) is not connected (plugged in),
the transmitter output is open and giving infinite impedance (zero current),
when the port is connected to another transceiver such as a port of router.
The transmitter is connected to a receiver circuits thus the impedance is c
hanged. This change can be sensed by the transmitter circuits and as the res
ult, it marks a signal to Da |
|
s********n
发帖数: 235 | 43 Title: ELECTRON-ENERGY LEVELS IN SEMICONDUCTOR ELECTROCHEMISTRY
Author(s): GOMES WP; CARDON F
Source: PROGRESS IN SURFACE SCIENCE Volume: 12 Issue: 2 Pages: 155-215
DOI: 10.1016/0079-6816(82)90002-8 Published: 1982
Title: DIFFERENTIAL CAPACITANCE OF N-TYPE AND P-TYPE GALLIUM-ARSENIDE
ELECTRODE
Author(s): LAFLERE WH; CARDON F; GOMES WP
Source: SURFACE SCIENCE Volume: 44 Issue: 2 Pages: 541-552 DOI: 10.
1016/0039-6028(74)90136-8 Published: 1974
Title: APPLICATION OF KRAMERS-KRONI... 阅读全帖 |
|
a*****g
发帖数: 19398 | 44 The common-core math standards require that students learn the standard
algorithm for multi-digit adding and subtracting—you know, the process in
which you line the numbers up vertically to add or subtract and regroup as
needed—by the end of 4th grade.
But waiting until then to teach the algorithm is a big waste of time for
some students, writes Tom Loveless, a senior fellow at the Brookings
Institution.
Students begin learning to add and subtract in 1st grade under the common
standards. So teac... 阅读全帖 |
|
a*****g
发帖数: 19398 | 45 我一直说 common core 出的问题，现在终于有其他人出文章了
http://www.theatlantic.com/education/archive/2015/11/math-showi
Common Core-era rules that force kids to diagram their thought processes can
make the equations a lot more confusing than they need to be.
Rogelio V. Solis / AP
At a middle school in California, the state testing in math was underway via
the Smarter Balanced Assessment Consortium (SBAC) exam. A girl pointed to
the problem on the computer screen and asked “What do I do?” The proctor
read the instruc... 阅读全帖 |
|
C*******g
发帖数: 82 | 46 for RF applications Rin is not a problem since people can use matching
network or transformers to tune the input impedances so that optimal power
gain can be achieved. Besides sometimes people use the 1/gm property of CG
stage to form a wideband input match to 50Ω.
In low frequency designs when people just connect the input of the second
stage to the output of the first stage it is a problem if the input
impedance of the following stage is too low. |
|
z*****n
发帖数: 7639 | 47 Are you talking about impedance of the cable?
I hope you know the difference between
resistance and impedance for a RF cable. |
|
c*******l
发帖数: 4801 | 48 这个电路的cross over freq是50k左右，好像
如果你的op-amp输出impedance大的话，比如几k,cross over附近的phase会掉下来，
就没有phase margin了
看看你的output impedance. |
|
f*****0
发帖数: 489 | 49
in your circuit, the output should have a dc content of 1/2Vdd because
the opamp is powered by a single rail, and you shouldn't read 0 on the
scope.
a regular DMM shouldn't read out a 500Khz noise so that's OK.
that's never the issue.
the most likely issue is the circuit's output impedance mismatch vs.
that of the probe, or a defective probe. if the signal you are
amplifying is really a high frequency signal, opamp's output impedance
does go up with frequency. but unless you are using some weir |
|
l****o
发帖数: 184 | 50 you can find the transfer function in "improved synthesis of gain boosted
regulated cascode CMOS stage using symbolic analysis and gm/ID methodology"
Very complicated including all the capacitors.
But intuitively, the first non-dominate pole is due to the output impedance
of the additional amplifier, right?
Another question is, is the output impedance of the additional amplifier
affected by the negative loop? |
|
