May 01
Scientists Create First Memristor: Missing Fourth Electronic Circuit Element
By Bryan Gardiner 
April 30, 2008 | 12:03:41 PMCategories: Research
Researchers at HP Labs have built the first working prototypes of an important new electronic component that may lead to instant-on PCs as well as analog computers that process information the way the human brain does.
The new component is called a memristor, or memory resistor. Up until today, the circuit element had only been described in a series of mathematical equations written by Leon Chua, who in 1971 was an engineering student studying non-linear circuits. Chua knew the circuit element should exist -- he even accurately outlined its properties and how it would work. Unfortunately, neither he nor the rest of the engineering community could come up with a physical manifestation that matched his mathematical expression.
Thirty-seven years later, a group of scientists from HP Labs has finally built real working memristors, thus adding a fourth basic circuit element to electrical circuit theory, one that will join the three better-known ones: the capacitor, resistor and the inductor.
Researchers believe the discovery will pave the way for instant-on PCs, more energy-efficient computers, and new analog computers that can process and associate information in a manner similar to that of the human brain.
According to R. Stanley Williams, one of four researchers at HP Labs' Information and Quantum Systems Lab who made the discovery, the most interesting characteristic of a memristor device is that it remembers the amount of charge that flows through it.
Indeed, Chua's original idea was that the resistance of a memristor would depend upon how much charge has gone through the device. In other words, you can flow the charge in one direction and the resistance will increase. If you push the charge in the opposite direction it will decrease. Put simply, the resistance of the devices at any point in time is a function of history of the device –- or how much charge went through it either forwards or backwards. That simple idea, now that it has been proven, will have profound effect on computing and computer science.
"Part of what's going to come out of this is something none of us can imagine yet," says Williams. "But what we can imagine in and of itself is actually pretty cool."
For one thing, Williams says these memristors can be used as either digital switches or to build a new breed of analog devices.
For the former, Williams says scientists can now think about fabricating a new type of non-volatile random access memory (RAM) – or memory chips that don't forget what power state they were in when a computer is shut off.
That's the big problem with DRAM today, he says. "When you turn the power off on your PC, the DRAM forgets what was there. So the next time you turn the power on you've got to sit there and wait while all of this stuff that you need to run your computer is loaded into the DRAM from the hard disk."
With non-volatile RAM, that process would be instantaneous and your PC would be in the same state as when you turned it off.
Scientists also envision building other types of circuits in which the memristor would be used as an analog device.
Indeed, Leon himself noted the similarity between his own predictions of the properties for a memristor and what was then known about synapses in the brain. One of his suggestions was that you could perhaps do some type of neuronal computing using memristors. HP Labs thinks that's actually a very good idea.
"Building an analog computer in which you don't use 1s and 0s and instead use essentially all shades of gray in between is one of the things we're already working on," says Williams. These computers could do the types of things that digital computers aren't very good at –- like making decisions, determining that one thing is larger than another, or even learning.
While a lot of researchers are currently trying to write a computer code that simulates brain function on a standard machine, they have to use huge machines with enormous processing power to simulate only tiny portions of the brain.
Williams and his team say they can now take a different approach: "Instead of writing a computer program to simulate a brain or simulate some brain function, we're actually looking to build some hardware based upon memristors that emulates brain-like functions," says Williams.
Such hardware could be used to improve things like facial recognition technology, and enable an appliance to essentially learn from experience, he says. In principle, this should also be thousands or millions of times more efficient than running a program on a digital computer.
The results of HP Labs teams findings will be published in a paper in today's edition of Nature. As far as when we might see memristors actually being used in actual commercial devices, Williams says the limitations are more business oriented than technological.
Ultimately, the problem is going to be related to the time and effort involved in designing a memristor circuit, he says. "The money invested in circuit design is actually much larger than building fabs. In fact, you can use any fab to make these things right now, but somebody also has to design the circuits and there's currently no memristor model. The key is going to be getting the necessary tools out into the community and finding a niche application for memristors. How long this will take is more of a business decision than a technological one."
Image: An atomic force microscope image of a simple circuit with 17 memristors lined up in a row. Each memristor has a bottom wire that contacts one side of the device and a top wire that contacts the opposite side. The devices act as 'memory resistors', with the resistance of each device depending on the amount of charge that has moved through each one. The wires in this image are 50 nm wide, or about 150 atoms in total width. Image courtesy of J. J. Yang, HP Labs.
科学家创造了第一个Memristor：遗失的第四种电子电路元件
作者: Bryan Gardiner
翻译：apollo_maverick
注：memristor来自于memory resistor（记忆电阻器），还没有正式的译法，以下都译为忆阻器）
HP Labs的研究者已经制造了一种重要的新电子组件的第一个可以工作的原形，这种电子组件可能使即开型PC（instant-on PCs）以及以像人类大脑处理信息的方式的模拟式计算机（analog computers）成为可能。
这种新组件被叫做忆阻器，或记忆电阻器（memory resistor）。直到今天以前，这种电路元件都只是被Leon Chua写的一组数学方程式描述的，在1971年，Leon Chua是一个研究非线性电路的工程学生。Chua知道这种电路元件应该存在——他甚至精确地描述了它的特性和它如何工作。不幸的是，他以及其他的工程团体都未能搞出符合他的数学表达的物理实现。
37年后，HP Labs的一组科学家最终造出了真正的可以工作的忆阻器，因此把第四种基本电路元件加入了电子电路理论，另外三个广为所知的是：电容器，电阻器和电感器。
根据R. Stanley Williams，HP Labs信息与量子系统实验室搞出这个发现的四位研究者之一，的说法，忆阻器器件的最有趣特征是它可以记忆流经它的电荷数量。
研究者相信这个发现将为即开型PC、更高能效的计算机和以人类大脑类似方式处理和联系信息的模拟式计算机铺平道路。
的确，Chua起初的想法是忆阻器的电阻取决于多少电荷经过了这个器件。也就是说，你能让电荷以一个方向流过，电阻会增加。如果你让电荷以反向流动，电阻就会减小。简单地说，这种器件在任一时刻的电阻是时间的函数（译者注：原文为“the resistance of the devices at any point in time is a function of history of the device”）——或多少电荷向前或向后经过了它。那个简单的想法，现在已经被证实，并将对计算及计算机科学产生深远的影响。
“这将导致什么出现是任何人都还无法想像的，”Williams说，“但我们可以想像的是这个东西本身确实很酷。”
举个例子，Williams说这些忆阻器可以用于数字式开关（digital switches）或制造新型的模拟器件（a new breed of analog devices）。
相较于过去，Williams说科学家现在可以考虑构造新型的非易失性随机存取存储器（RAM）——或当计算机关闭后不会忘记它们曾经所处的能量状态的存储芯片。
那是今天的DRAM所面临的大问题，他说。“当你关闭你的PC电源，DRAM就忘记了那里曾有过什么。所以下次打开计算机电源你就必须坐在那儿等到所有需要运行计算机的东西都从硬盘装入到DRAM。”
有了非易失性RAM，那个过程将是瞬间的并且你的PC会回到你关闭时的相同状态。
科学家也预想制造其他类型的电路，忆阻器在其中可以用作模拟器件（analog device）。
的确，Leon自己注意到了在他自己预言的忆阻器的特性与他知道的大脑的突触之间的相似性。他的一个建议是你可能用忆阻器做某种类型的神经计算。HP Labs认为那确实是个非常好的想法。
“制造一个模拟式计算机，在其中不用1和0的，而代之的是用就像明暗不同的灰色之中的几乎所有状态（instead use essentially all shades of gray in between），这是我们正在做的事情中的一件，”Williams说。这些计算机可以做许多种数字式计算机不很擅长的事情——比如做决策，判定一个事物比另一个大，或甚至学习。
当前就有许多研究者试图编写在标准机器上运行的计算机代码来模拟大脑功能，他们必须使用大量的有巨大处理能力的机器来模拟仅仅是大脑的很小的部分。
Williams和他的团队说他们现在能用一种不同的方式：“不同于写计算机程序来模拟大脑或模拟大脑的某种功能，我们事实上依靠构造某种基于忆阻器的仿真类大脑功能的硬件，”Williams说。
这样的硬件可以用来改进一些事情，比如脸部识别技术，并且使本质上从经验来学习的装置可用，他说。基本上，这也应该是比在数字式计算机上运行程序要快几千到几百万倍。
HP Labs团队发现的结果将被公布在一篇今天的《自然》杂志论文中。直到我们可以看到忆阻器真正被用于实际的商业器件中，Williams说相较于技术上的限制，限制更多来自于商业上。
最终，这个问题将与投入到设计忆阻器电路的时间和努力有关，他说。“投资到电路设计上的钱的确比建造工厂多得多。事实上，你现在就可以用任何工厂来做这些东西，但是也必须设计电路而且目前还没有忆阻器的模型。关键是搞出必要的工具并且为忆阻器找到合适的应用。这要多久更多的是个商业决策问题较于技术问题。”
图片：原子力显微镜下的一个有17个忆阻器排列成一排的简单电路的图像。每个忆阻器有一个底部的导线与器件的一边接触，一个顶部的导线与另一边接触。这些器件起“记忆寄存器（memory registors）”的作用，每个器件的电阻取决于通过每个器件上的电荷数量。这幅图中的这些导线是50nm宽，或总共大约150个原子宽。图片由J. J. Yang, HP Labs许可。
转自：http://blog.wired.com/gadgets/2008/04/scientists-prov.html
April 19
English Requirements
Any applicant whose first language is not English must certify proficiency in English when applying to UCLA, and, if admitted, upon arrival.
Such applicants must submit scores received on the Test of English as a Foreign Language (TOEFL) or the International English Language Testing System (IELTS) as part of their application. The TOEFL is administered by the Educational Testing Service (ETS). Applications may be obtained from ETS, Box 6151, Princeton, New Jersey 08541-6151. IELTS is administered by local IELTS test centers throughout the world. Applicants should consult www.ielts.org for the nearest IELTS test center. The results of these tests help applicants determine whether they are prepared to undertake graduate study conducted in English before making extensive plans for graduate study in the U.S.
A TOEFL score of at least 560 on the paper and pencil test or 220 on the computer based test is the minimum required for applicants to graduate programs at UCLA; some majors may require higher scores as noted.
For the internet-based TOEFL (TOEFL iBT), the following are minimum passing scores for each section and the minimum total passing score:
- Writing: 25
- Speaking: 24
- Reading: 21
- Listening: 17
- Total minimum passing score: 87
An IELTS overall band score of at least 7.0 is the minimum required.
Applications are not considered complete without the test scores.
TOEFL scores should be sent to your major department. IELTS scores should be sent to your major department and the Graduate Division.
Please note that TOEFL scores are considered valid for only two years, and that if several scores are submitted, only the most recent is considered.
Admitted applicants are required, upon arrival at UCLA, to take the UCLA English as a Second Language Placement Examination (ESLPE), an English diagnostic test, before being permitted to register. Depending on the results of the ESLPE, you may be required to complete English as a Second Language courses beginning in your first term at UCLA. If English courses are required, you should anticipate spending a longer period of time at the University. Admission is canceled for those who do not pass the ESLPE.
Please note that you must sit for the ESLPE regardless of your score obtained on the TOEFL, IELTS or any other English proficiency test.
Applicants who hold a bachelor’s or higher degree from a university located in the United States or in another country in which English is both the spoken language and the medium of instruction, or who have completed at least two years of full-time study at such an institution, are exempted from both the TOEFL/IELTS requirement and the ESLPE. Please be sure to include such information in your application.
February 19
Ten years ago, on 10 February 1998, W3C published Extensible Markup Language (XML) 1.0 as a W3C Recommendation. W3C is marking the ten-year anniversary of XML by celebrating "XML10" and extending thanks to the dedicated communities -- including people who have participated in W3C's XML groups and mailing lists, the SGML community, and xml-dev -- whose efforts have created a successful family of technologies based on the solid XML 1.0 foundation. The success of XML is a strong indicator of how dedicated individuals, working within the W3C Process, can engage with a larger community to produce industry-changing results. "Today we celebrate the success of open standards in preserving Web data from proprietary ownership," said Jon Bosak, who led the W3C Working Group that produced XML 1.0.
评论：XML成为标准10年了，作为全球被广泛采用的信息交换标准，如今已成为我们整个现代生活的基础之一。也许不能直接看到，但是当我们在ATM/CDM上取款/存款时，当我们在超市结帐时，当我们浏览网页时，当我们打电话时，几乎都在发生着XML数据交换。
October 14
土共又开大会了。到处泛滥着八股文，泛滥着土不拉叽的红色。这些显然不是科学发展的表现。不爽。不过实际上也不关我啥事，发发牢骚而已。
October 09
Intel IDF 2007这几天正在进行，这次IDF展示了'08,'09年计划推出的新平台，其中最具革命性的可能要数这个'09年推出的代号为"Moorestown"的MID/UMPC平台，SOC(System On Chip，即单芯片系统，中央处理器、图形处理器、内存控制器、通讯模块等等通通集成在一块芯片上)设计，由此带来的是超低的功耗，并且性能完全满足日常需要。据信电池可以使用24小时。最重要的是x86架构，也就是说可以跑Windows，这样就可以使用全功能Internet浏览器，比如IE, Opera, Firefox。而尺寸却可以像手机一样大小，电池也可以使用24小时了。再加上WWAN（无线广域网）由于3G/3.5G/4G的应用而接入带宽暴涨。这样，WAP推出时宣称的Internet in hand，就真正被新平台实用化了，而WAP只是昙花一现，大家需要的还是全功能的互联网内容(HTML, Javascript, AJAX, Flash, Silverlight)支持。
又带来了多少新的机会~
就像视频中说的，这是个big deal！
following video is the "Moorestown" demo, enjoy it
September 22
1997年5月8日，中国南方航空有限公司深圳公司波音７３７-３００型Ｂ２９２５号飞机执行重庆深圳３４５６航班任务，着陆过程中失事。机上旅客６５人，其中死亡３３人，重伤８人，轻伤２０人；空勤组９人，其中死亡２人，重伤１人，轻伤６人。飞机第一次接地时就听机长大声喊：”加油门，复飞！加油门，复飞！......”飞机在地面跳了三下后复飞，每次弹跳都是前起落架着地。飞机在空中盘旋后，第二次反向着陆时只听见副驾驶大叫了一声：”下降率太高啦！”（这也是他人生最后的一句呐喊）驾驶舱就是一阵轰鸣声。
当天，２９２５号机１９：４５自重庆江北机场起飞，预计２１：３０到达深圳黄田机场，２１：０７与深圳机场进近管制建立联系，按正常程序向３３号跑道进近。２１：１７与塔台建立联系。塔台告诉机组“五边雨比较大，看见跑道叫”。２１：１８：０７机组报告“已建立盲降”，２１：１８：５３机组报告“看到引进灯”，塔台指挥飞机“检查好可以着陆”。在飞机过近台附近，塔台看见飞机着陆灯，但雨中灯光不清楚，地面雷达显示，飞机航迹、下滑高度正常。２１：１９：３３飞机第一次在跑道南端接地，接地后飞机跳了三跳，然后复飞。复飞后左转上升到１２００米，塔台提醒机组开应答机，但二次雷达上一直没有显示。２１：２３：５７，机组报告在三边位置，要求其它飞机避让，２１：２３：４０，机组再次要求其它飞机避让，并报告“有紧急情况”，驾驶舱内出现多种警告。塔台告诉已让其它飞机避让。２１：２４：５８机组要求落地后用消防车、救护车，塔台告诉机组都已经准备了。接着飞机又转了一圈，并报告准备向南落地，塔台同意向南落地，并告诉２９２５号机组，“前面落地的机组反映北面天气好，南面五边雨大”，机组回答明白，并说“我准备落地了”。２１：２８：３０飞机着陆，着陆后飞机解体、起火。
最后那一句“下降率太大啦！”撕心裂肺的绝望的叫喊让人心惊肉跳。接着就是坠毁的轰鸣……
Tools 
