S********t
发帖数: 4402 | 1 "Import license or permit is required for clearance."FedEx说需要"Radio
Frequency License".
以前也遇到这种情况。不过都是buyer自己解决了。 |
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c******g
发帖数: 2323 | 2 看了一阵，没找到 sensitivity 和 frequency response, 板上有人知道吗？ |
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c*****r
发帖数: 108 | 3 我今天恰好也在向这个题目 下面是我的想法。
MapReduce 把每个search term发送到不同的peer服务器上。这样每个服务器负责累加
一系列的search term。同时每个服务器上maintain一个大顶堆负责记录本服务器上最
frequent的terms。堆的大小为该服务器所负责的search term数量。
时事的发送堆顶的10个search term给一个masternode。masternode负责筛选各个机器
上发来的单词 更具frequency再选出10个display |
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s*w
发帖数: 729 | 4 要有人觉得有所帮助，给发个包子
【 以下文字转载自 Programming 讨论区 】
发信人: saw (句子熊), 信区: Programming
标 题: Re: 一道count frequency of all words的面试题 (转载)
发信站: BBS 未名空间站 (Mon Sep 23 00:28:12 2013, 美东)
又琢磨了两天，看了不少相关东西，终于搞定了，觉得自己对这个多线程的理解加强了
很多。思考比单纯的看人说原理更刻骨铭心。
这个问题我设计的用一个 producer 多个 consumer 的架构，上个版本的是两头用
condition_variable, 一个通知 producer 有空间了开始干活生产，另一个通知
consumer 有库存了开始消费。参见上篇里面的 wait 和 notify_all,notify_one 语
句。 这个思路对于单 producer 单 consumer 没问题，可是不适用于 多 consumer.
因为所有的 consumer 可能同时睡觉（没空存），同时醒来（有库存）,结果只有一个
能抢占mutex(拿到库存)，... 阅读全帖 |
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r******9
发帖数: 566 | 5 刷完这些Google有frequency的，我准备把400以前漏掉的补上。然后再进行400-600的
冲刺。 |
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l*******r
发帖数: 3799 | 6 【 以下文字转载自 Quant 讨论区 】
发信人: spatiaI (spatial), 信区: Quant
标 题: high frequency trading shop面经
发信站: BBS 未名空间站 (Thu Feb 26 21:53:43 2009)
纽约downtown的一家prop trading firm，300多人，有一个小team，做高频交易的。公
司CEO提供strategies, blackbox models，greybox models。两个trader编程序交易，
完全靠commission过活，无底薪。按照ceo的说法，the two guys may be the best
paid programmers in the world. 一个老美，一个澳大利亚人。又按照ceo的说法，是
全澳大利亚最聪明的人！！！比较搞笑。
面试过程两轮，技术问题不多，包括多线程，并行计算，socket/TCPIP，不考具体语言
。虽然他们用C++.
主要是两轮考试，每次一小时，基本上是数论题，类似高中数学竞赛题的东西。
说一个记得的吧。存在整数n, 使得(n+1) |
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p****a
发帖数: 4829 | 7 what is your definition of High Frequency Trading? |
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m********i
发帖数: 298 | 8 Google for: High Frequency Trading Sharpe Ratio. |
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k*********u
发帖数: 2897 | 9 散户最大的优势就是资金相对便宜，借钱炒股的除外，
耐操。跌掉80%,都可以不斩仓，只要有信心。
而且散户，有的是时间，和耐心，只要你能做到，
捂他个3年5年，没什么大不了，可以拿时间换空间。
但是，大户就不行了，他耗不起。
发信人: rim (可乐会捂帮帮主), 信区: Stock
标 题: Re: 阐述为什么要做High Frequency Trading
发信站: BBS 未名空间站 (Fri Jan 7 16:47:30 2011, 美东)
一般散户第一没条件做，
第二这么做也是以己之短攻敌之长， 何苦来着？ |
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D*****l
发帖数: 554 | 10 Are you doing high frequency trading? If so, can I do that kind of fancy
trading with TD Ameritrade? |
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j*****h
发帖数: 3292 | 11 顶，好文
如果学术界真出了研究报告，和上面的结论一样，那是大杀器
小散们可以洗洗睡了,世上再无小散
完全是mutual fund, hedge fund, high frequency trading，直接买公司控股的大户
之间的博杀了 |
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R*********r
发帖数: 38 | 12 SPY QQQ的options有high frequency trading吗？ |
|
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b*******e
发帖数: 6389 | 14 1. HFT有8%的交易赚钱，2%的交易赔钱，其它不赚不赔。
2. 算法交易algorithmic trading比高频交易high frequency trading要更复杂。
3. 他们从来不用stop order or market order，他们有自己的execution engine来执
行自己的下单逻辑order logic。甚至对不同的交易所exchange用不同的引擎。
这点前面发了两个用程序下单的帖子讨论过，可惜几个大牛出来说，IB提供了stop
and trail为什么要自己写程序。
对大牛我无从解释，只好把老外的帖子翻出来给大牛们读。专业交易员只用limit
order。写一个下单执行引擎需要至少一人月的时间，大约上万行c++代码。
另外最好用c++写交易程序，速度真的很重要，而c++比java和c#都快不少。内存垃圾处
理更是游刃有余。
more |
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r*******t
发帖数: 8550 | 15 high frequency 现在是老中的天下 |
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l********5
发帖数: 1833 | 16 I am using a ASTC TV tuner but I can not find the channel. Can someone
please tell me the frequency? Thank you so much! |
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n***y
发帖数: 15001 | 17 What's the frequency, Kenneth? |
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w*******e
发帖数: 902 | 18 是啊，但是
for international frequency only (800/1900) not for US (ATT TMOBILE).
不知道国内能用不 |
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t*******7
发帖数: 4758 | 19 AT&T/Tmobile operates at a network frequency of 850/1900 MHz. That means a phone without 850 might get no service in some areas where AT&T doesn't have 1900mhz coverage.
In China, we use 900/1800 MHz. For Europe, they use 900/1800/1900. |
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w*******e
发帖数: 902 | 20 是啊，但是
for international frequency only (800/1900) not for US (ATT TMOBILE).
不知道国内能用不 |
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t*******7
发帖数: 4758 | 21 AT&T/Tmobile operates at a network frequency of 850/1900 MHz. That means a phone without 850 might get no service in some areas where AT&T doesn't have 1900mhz coverage.
In China, we use 900/1800 MHz. For Europe, they use 900/1800/1900. |
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G**Y
发帖数: 33224 | 22 【 以下文字转载自 PhotoGear 讨论区 】
发信人: GGYY (唧唧歪歪), 信区: PhotoGear
标 题: 万佛，请推荐word frequency tool？
发信站: BBS 未名空间站 (Thu Dec 16 00:24:04 2010, 美东)
MS Word
和
Acrobat PDF
的，
统计一片文章里，词汇频率的工具。
谢谢。 |
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q**********0
发帖数: 335 | 23 Which next-generation DNA sequencing methods is the best for measuring
nuclotide frequency in sequencing, Roche/454 FLX pyrosequencer, Illumina
genome analyzer,Applied Biosystem SOLid sequencer? Thanks. |
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l****6
发帖数: 6 | 24 Is there a study on meiosis recombination frequency in the genome level?
We have a model to address the question, but we are not in the field, is it
an important biology question?
Thanks for inputs! |
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l****6
发帖数: 6 | 25 Thanks for your response.
My question: how important if I can show in genome level, the meiosis
recombination frequency? Have similar work been done? |
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r**********e
发帖数: 587 | 26 For example look at the picture below, T vs C, if I see such peak height
ratio
difference, can I claim there's a change for allele frequency?
区别 |
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B******e
发帖数: 16928 | 27 I would prefer Barclays. MER, which is now a BAC unit, has a relatively more
commercial banking atmosphere which is not very good for the career of high
frequency traders.
is
sense |
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x*x
发帖数: 46 | 28 我两年前恰好搞的和这个差不多，说说我个人的理
解吧。（个人意见，仅供参考）。希望信息不是太
落伍：）
其实所有这些都是将信号进行TFD（Time-Frequency
Distribution)后再分析，也就是信号的一种表示方
法，即时频表示。小波的scale也就是频带了，事实
上，Short-time Fourier Transform(STFT)也是用的
窗函数。而ambiguity function(AF)其实也就是WVD的
2-D Fourier Transform，where WVD is Wigner-Ville
Distribution。WVD是Cohen类时频表示中的一种，由于
其权函数为1，所以具有最好的时频分辨率，当然也有
缺点，就是交叉项过于明显了。
再回到STFT、WT和AF的比较上来，STFT是一次型时频表
示，其能量化二次型表示就是平常我们一直用来显示的
谱图(spectrogram)了；WT的能量二次型就是尺度图scalogram，
尺度图是谱图的仿射(affine)对等体；AF就是WVD的二
次型Fourier Transform，而谱图可以看作是对WVD |
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f*****0
发帖数: 489 | 29 you wanted an analog amplifier that has a frequency response from 0.1hz -
1hz, but a cut-off at 0hz.
such a thing has not been invented and will probably never be invented.
you are much better off rethinking your whole architecture or using a
computer on the back-end to solve that problem.
two potential but dumb solutions:
1) use a manually generated DC potential to offset the DC content in the
input signal. the opamp remains a DC amplifier.
2) use a servo (with extremely long time constant) to |
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s******e
发帖数: 2181 | 30 Thank you upstairs!
Can I increase the input capacitor to 22 uF so that the impedience for low
frequency attenuates? The original input capacitor was 1 uF. |
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s******e
发帖数: 2181 | 31 Thank you upstairs!
Can I increase the input capacitor to 22 uF so that the impedience for low
frequency attenuates? The original input capacitor was 1 uF. |
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s******e
发帖数: 2181 | 32 Thank you upstairs!
Can I increase the input capacitor to 22 uF so that the impedience for low
frequency attenuates? The original input capacitor was 1 uF. |
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g******i
发帖数: 25 | 33 Frequency drift的中文是叫频率漂移还是频率抖动。应该如何测量。 |
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b***n
发帖数: 13455 | 34 it 号称它的input signal can be as small as -30dBm. 我们的一个SB 法国
Technical
Lead非说要达到它的这个要求而不用buffer...我说首先PLL里的frequency divider 用
dBm来度
量input signal level就是个weird的事; 还有这个-30dBm input 几乎可以肯定是还需要
buffer才能到divider input的... 欢迎大家谈谈... |
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x***y
发帖数: 830 | 35
需要
when you are getting -30dBm input, you probablly will see the frequency
division, but won't have rail to rail swing at output and your phase noise
will be degraded. |
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b***n
发帖数: 13455 | 36 Thanks! Yes there may still be frequency division, but just not at the
desired ratio...
noise |
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s******u
发帖数: 142 | 37 This guy tested the divider separately, so they use dBm for the input.
But it's weird for me to see a digital divider paper to put fig. 6, since
min input power vs. frequency curve is usually for ILFD. In a real PLL, you
will not get an input signal as small as -30dBm. Even if -30 dBm can work,
you don't need that small if you don't use the divider separately. |
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c**e
发帖数: 5555 | 38 带宽问题。frequency synthesizer主要抑制片上噪声，带宽较大；clock recovery抑
制reference噪声，带宽较小。 |
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b******y
发帖数: 107 | 39 Hi,
I want to find the close form expression of the following filter
H(z) = z(1-alpha)^2/(z^2-2*alpha*z+alpha^2)
where alpha is a real parameter alpha = 1=2^(-k)
How to express the cutoff frequency of the filter in terms of alpha?
Can suggestions?
Thank you |
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b********n
发帖数: 181 | 40 把z换成e(jw),然后求模等于-3dB处， 如果你的cut off frequency是指-3dB
oh, 你问closed form,我觉得无解吧。这是个数学问题了 |
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f*******y
发帖数: 421 | 41 【 以下文字转载自 EE 讨论区 】
发信人: futureway (30), 信区: EE
标 题: 如何找到一个图片的dominant frequency?
发信站: BBS 未名空间站 (Wed Jan 6 09:42:41 2010, 美东)
就是想知道一个图片里面那个频率最重要，如何做？2d fft? 多谢。 |
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m*****2
发帖数: 9 | 42 最近一个project需要用到structural dynamics 和信号处理的知识, 但对以下几个问题
感到迷惑,
1) 对结构进行动力学分析,为什么有时在time domain, 有时在frequency domain.
2) 如何比较这两种方法的优缺点和联系.
谢谢 |
|
f*******y
发帖数: 421 | 43 【 以下文字转载自 EE 讨论区 】
发信人: futureway (30), 信区: EE
标 题: 如何找到一个图片的dominant frequency?
发信站: BBS 未名空间站 (Wed Jan 6 09:42:41 2010, 美东)
就是想知道一个图片里面那个频率最重要，如何做？2d fft? 多谢。 |
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c********6
发帖数: 658 | 44 Gradients act to setup a one-to-one correspondence between frequency and
spatial position. |
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n**********s
发帖数: 275 | 45 一般都有哪些high frequency options trading strategies??? thx |
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m*********y
发帖数: 127 | 46 Quant Role for High Frequency Algo Trading!
How are you?
I am contacting you regarding an opportunity I have available with a
PRESTIGIOUS Hedge Fund in Downtown Manhattan! Below you will find all the
details!
I have an EXCELLENT relationship with this hiring manager and he is looking
for talented and motivated individuals !
This is a dynamic position requiring both Development and Quant Analysis
skills working with teams in a extremely profitable business!
I NEED YOUR HELP!!!! DO YOU KNOW THE PE |
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s*****I
发帖数: 23 | 47 high frequency trading不需要太多金融知识。 |
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M********t
发帖数: 1718 | 48 Finally, someone knows the high frequency trading industry stands up and
tells the other side of the story. Flash trading has never been a
significant part of HF trading. To the strategies I know, it is actually a
headache... Flash orders might initially target on ECNs such as DirectEdge's
ELP program, which is a favorite boy to HFMMs. But I don't see ELP can
cause such moral problems like those flash orders have done. |
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