Ju Sun (孙举)

Dedicated to my research and life

海风中骑行:Manhattan Waterfront Greenway

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弄到手头这辆自行车之后,心里就一直痒着要牵出去溜溜。网上查到这个Greenway 之后,忍不住激动,拉着车就出发了!(哥也是有车的人啦!哈哈哈)

按官方的说法,这条Greenway 全长32 Miles (约51.2 公里)。西边沿Hudson River 一直蜿蜒至Battery Park, 远眺自由女神后,折向东北,继而继续蜿蜒前行,经Manhattan Bridge, Willamburg Bridge, 联合国, 至Harlem River 上游。

我从West 103 街的入口,取道Riverside Park。时值下午3点左右,众多的New Yorkers在公园里玩弄时光:跑步的人最多好像,然后慢性散步的,脱了上衣晒太阳的,轮滑的,当然也有谈请说爱的。哥关注玩Soccer的小朋友们

从一座天桥下穿过后,Hudsen River已尽在眼前。来去匆匆的跑步的和骑行者,点缀着这座都市的一个典型周末。河风,在单车旁拍打,渗透,直至心灵。好清爽的下午!河上的泛舟者,伴着偶尔的帆船,让人们诉说风中点点惺味的来由。

CVX Annouced Version 2 (Beta)

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CVX has become an indispensable tool for modeling and prototyping in various scientific disciplines, in particular where optimization play significant roles.  It provides a most intuitive modeling interface that bridges complex formulation and the underlying numerical solvers, saving the user abundant time for thinking.

Version 2 of CVX has featured extended support for commercial solvers, MOSEK and Gurobi. This is really good news for academic users, since 1) both solvers provide free licenses to academic users; and 2) both solvers are mostly more optimized than the free solvers currently bundles with CVX, namely, SDPT3 and SeDuMi. Related part of the announcement as follows:

  • Academic users may utilize the CVX Professional capability at no charge.

  • Users with a valid academic license for Gurobi 5.0 or later may use it with CVX without obtaining a CVX Professional license. This is because CVX is able to detect the presence of an academic Gurobi license.

  • In order to use MOSEK, a CVX Professional license is required. We intend to provide such licenses at no charge, but we have not yet completed the licensing architecture. We will make an announcement once this has been completed.

In addition, mailing list support has changed into a Q&A forum (StackExchange style …) and the documentation has changed to online html version with better cross references.

Battery Problem With Nikon Coolpix L100

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Nikon Coolpix L100 is a compact Megazoom digital camera, coming with 15x optical zooming capacity and wide view angle - ideal for amateur photo-takers like me . The price is also not bad, at about $400 Singapore dollars when I bought one in 2009. The only pitfall is with its batteries: at the outset, it simply doesn’t accept rechargeable batteries, such as the typical Ni-MH’s - even you’re not a doctrine environmentalist, it may bother you a lot whenever you have to head for stores for batteries.

In fact, Nikon has added in rechargeable support not long after this camera was released. You can follow these steps to get your L100 live well with the rechargeable:

  1. Firmware Version. Press the MENU botton, and go to Set Up –> Firmware version. If the firmware is COOLPIX L100 Ver.1.0, you will need to update your firmware to V1.1. following these instructions (Coolpix L100 1.1 firmware update from Nikon website).

  2. Battery Type. After the updating, one has to select Set up –> Battery type –> COOLPIX (Ni-MH) to enable this lovely feature.

Now you should be able to power your L100 with your rechargeable batteries (and also still be able to use the disposable)!

Shapiro and Mudd …

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冒个泡:CU 本办公楼叫Shapiro, 旁边那个叫Mudd。某西北女将前者念的像“傻x 楼”, 后者回“妈的” 。。。 对掐中。。。

PS: 今天presentation 把without loss of generality 说成 without loss of generosity 。。。被John 掐住好,很肿的补了句 Anyway we cannot lose it …

A Tight Lower Bound for Finite Sum of Arctangents

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Days ago we ran into a need to lower bound \(\sum_{j=1}^k \pi/2 - \arctan j = \sum_{j=1}^k \arctan 1/j\).

One possibility is observe the non-negativity and continuity of the function \(\arctan x\) over \(j \in {\mathbb Z}_+\) and apply an integral lower bound: \[ \begin{align*} & \sum_{j=1}^k \arctan \frac{1}{j} \newline \geq \; & \int_{1}^{k+1} \arctan 1/x \; dx = \left. x\arctan 1/x + \frac{1}{2} \ln \left(1+x^2\right) \right|_{x = 1}^{k+1} \newline = \; & \frac{1}{2}\ln \left[\left(k+1\right)^2 +1\right] + \left(k+1\right) \arctan \frac{1}{k+1} - \frac{\pi}{4} - \frac{1}{2} \ln 2 \newline \geq \; & \frac{1}{2}\ln \left[\left(k+1\right)^2 +1\right] + \left(k+1\right) \left(\frac{1}{k+1} - \frac{1}{3} \frac{1}{\left(k+1\right)^3}\right) - 1.132 \newline = \; & \frac{1}{2}\ln \left[\left(k+1\right)^2 +1\right] - 0.132 - \frac{1}{3} \frac{1}{\left(k+1\right)^2}, \end{align*} \] where in the third line we have retained the first two terms of series expansion for \(\arctan x\) for \(\left|x\right| \leq 1\). The integral approximation gives very messy terms and a somewhat loose lower bound. We can obtain a much neater one: \[ \begin{align} \sum_{j=1}^k \arctan \frac{1}{j} \geq \log \left(k+1\right). \end{align} \]

Finals, QE and Ahead

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I’m finished with my finals, after interrupted study and broken rest time for several days – you must pay afterwards even with unmindful procrastination on the move.

Qualification Exam is ahead within two plus weeks. It’s the time to get refreshed my mind with the concepts of circuits, Fourier transformation, registers, and bit error probability, pretty everything a typical electrical engineering graduate needs to know. Yuh… another fighting! Of course the words your professor would often spend on this issue is > make sure you pass, but not spend too much time! It’s an interesting balance a graduate student most likely always tries to strike…

Visits to this blog keep roll up, even after my absence in the past few months. I’m pleased to be noticed of the 20,000 hits by the system. I’ve decided to put reasonable amount of time in future to update this blog with more technical expositions and discussions. This would considerably improve my ability to understand technical materials, which I would need to sharpen as soon as possible.

I was just having a Christmas dinner with John and one master student. It’s pretty fun! We consumed some 1.5 bottles of red wines. And John was asking one theorem for each bottle we had for next semester, jokingly …

CV Meeting – Frontiers in Computer Vision

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Prof. Alan Yuille (UCLA) in parter with others is organizing a special workshop for exploring frontiers in vision, a good chance for researchers to pause a while and look backward and forward.

Frontiers in Computer Vision

From the cyber-discussion being fired there, some interesting disagreements amongst these top vision researchers are already significant: conservatism versus radicalism, and pragmatism versus idealism. For a research community as ambitious and diverse and young as vision, nevertheless, consensus rarely occurs and ideological debates prevail – it is not surprising; in fact, this signals an active research field in my opinion. But my humble mind is really seeking some fuels the workshop could potentially generate for these topics:

  1. Object recognition
  2. Culture of scholarship in vision

The former has been central on the spot for the past 10 years with least success, while the latter has partially contributed to the dismal stagnation.

【转】史上最狠的论文评审意见

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2010年Environmental Microbiology杂志刊登了一部分杂志的审稿意见,让人在学术研究严肃、认真的前提下充分体会了下,审稿人的幽默与诙谐,有的审稿意见甚至让人啼笑皆非,下面列举了一部分经典的审稿意见,让大家也见识一下史上最狠的评审意见,其他的内容见文后附件,有兴趣的可以继续寻找。

PS:翻译纯属搞笑,不喜勿拍!

This paper is desperate. Please reject it completely and then block the author’s email ID so they can’t use the online system in future.

这文章太不给力了…请万勿发表。此外,建议锁定该作者的电子邮件ID,避免此人日后继续投稿。。。