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The UNLV Libraries provide access to thousands of streaming videos for UNLV use. You can search the catalog to find them, or visit the video collection websites directly. Many of the collection sites allow you to register a personal account for creating and managing clips, playlists, and other customized views of the content.
- Search the catalog
- Licensed Streaming Collections:
- Films on Demand
- Kanopy
- Alexander Street Press
- Ambrose Digital Videos
- Docuseek2
See also:
Search the catalog for streaming videos
You can use the catalog to find streaming videos on various topics. In a keyword search, combine the phrase "streaming video" with a word or phrase, e.g.,
Click the Go button above to see the results, or substitute your word or phrase for "water conservation" in the example and Go. Or, for a comprhensive list of streaming videos sorted by date (most recent first), do a keyword search with just the phrase "streaming video".
Click a title in the results list to see the full record for the streaming video; click on "View streaming video" or "View film" to see it.
Instructors: See the WebCampus Toolkit for tips on linking to streaming media in your courses.
Streaming Video Collections
- Films on Demand Features thousands of full-length videos covering the humanities & social sciences, science, business & economics, health, archival films & newsreels.
- Kanopy This streaming video service provides access to thousands of titles in such areas as the arts, humanities, business, sciences, media/communications, education and more. Source producers include Media Education Foundation, BBC, PBS, Kino Lorber, Documentary Educational Resources Collection, among others.
- Filmakers Library Online (Alexander Street Press) Provides award-winning documentaries with relevance across the curriculum—race and gender studies, human rights, globalization and global studies, multiculturalism, international relations, criminal justice, the environment, bioethics, health, political science and current events, psychology, arts, literature, and more. It presents points of view and historical and current experiences from diverse cultures and traditions world-wide.
- Music Online: Classical Music in Video (Alexander Street Press)The collection features performances of all forms of classical music, including major orchestral performances by leading orchestras, plus chamber music, oratorio, and solo performances, along with masterclasses and interviews with master teachers from around the world.
- Music Online: Opera in Video (Alexander Street Press)Contains five hundred hours of the most important opera performances, captured on video through staged productions, interviews, and documentaries. Selections represent the world's best performers, conductors, and opera houses and are based on a work's importance to the operatic canon.
- Dance in Video: Volume I (Alexander Street Press)Contains five hundred hours of dance productions and documentaries by the most influential performers and companies of the 20th century. Selections cover ballet, tap, jazz, contemporary, experimental, and improvisational dance, as well as forerunners of the forms and the pioneers of modern concert dance
- Theatre in Video (Alexander Street Press)With more than 250 definitive performances of the world's leading plays, together with 100+ film documentaries, this collection represents hundreds of leading playwrights, actors and directors.
- Ambrose Digital VideosAmbrose Video Publishing is a distributor of broadcast-quality documentaries and educational videos to schools, libraries and other institutions. UNLV susbcribes to four packages:
-- Ancient History
-- The BBC Shakespeare Plays
-- A History of American Indian Achievement
-- When the Water Tap Runs Dry
- Docuseek2 Docuseek2 has exclusive academic streaming for films from renowned leaders in documentary film distribution including:
-- Bullfrog Films
-- Collective Eye
-- Fanlight
-- Icarus Films
-- Kartemquin
-- Terra Nova Films
Subject Guide
Contact Info
Head, New Media
Office: LLB 1227
(702) 895-2183
Send Email
Online Movies & Streaming Video
Media Playlist Blog
Featured Collection: Kanopy
Kanopy provides convenient access to thousands of educational and feature films covering a variety of subjects.


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Washington, DC The American College of Preventive Medicine (ACPM) has launched a web page featuring an extensive literature review on lifestyle medicine the practice of changing health behaviors to promote health and prevent and treat disease. The document summarizes scientific evidence supporting lifestyle interventions. It also provides information on related topics such as definitions, reimbursement trends, related practice patterns, and relevant organizations. The appendix summarizes the literature review's evidence by disease and behavior category in chart format. Researchers, policymakers and the public can access the review and other relevant information at http://www.acpm.org/LifestyleMedicine.htm.
"We can trace the root causes of 2 of every 5 deaths in the United States to lifestyle behaviors. Now anyone can learn about the scientific basis for behavior change interventions with the click of a mouse," says David Shih, MD, MS, ACPM senior director for medical affairs
The website also describes ACPM's activities in Lifestyle Medicine, including the formation of the Lifestyle Medicine Task Force and development of a clinical preventive and lifestyle medicine track for the Preventive Medicine 2010 meeting in Washington, DC.
ACPM commissioned the literature review in preparation for hosting a blue ribbon panel of physician experts and representatives from leading primary care and other medical associations on July 27 and 28. This panel reached consensus on a draft set of domains and competencies that define a minimum base of knowledge, skills, and attitudes physicians should possess to effect evidence-based lifestyle approaches to disease management and prevention. The panel will finalize language in the coming weeks and plans to disseminate its findings through publication in a major medical journal.
"This is a landmark event. The principles of lifestyle medi
|Contact: David Shih, M.D., M.S.
202-466-2044 x105
American College of Preventive Medicine

subset: commoncrawl


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- Introduction
- Land
- People
- Economy
- Government and society
- Cultural life
- History
- Prehistory
- The first historical dynasty: the Shang
- The Zhou and Qin dynasties
- The Han dynasty
- The Six Dynasties
- The Sui dynasty
- The Tang dynasty
- The Five Dynasties and the Ten Kingdoms
- The barbarians: Tangut, Khitan, and Juchen
- The Song dynasty
- The Yuan, or Mongol, dynasty
- The Ming dynasty
- The early Qing dynasty
- Late Qing
- The early republican period
- The late republican period
- Establishment of the People's Republic
- The Cultural Revolution, 1966–76
- China after the death of Mao
- Leaders of the People's Republic of China since 1949
Phase three: approaching crisis (1944–45)
China was in crisis in 1944. Japan faced increasing pressure in the Pacific and threats to its supply bases and communications lines in China as well as to nearby shipping. Its response was twofold—first, to attack from Burma toward Assam to cut the supply lines or capture the airfields at the western end of the Hump and, second, to capture the railway system in China from north to south and seize the eastern China airfields used by the United States.
The British and Indian army defeated the Japanese attack on Assam (March–July 1944) with help from transport planes withdrawn from the Hump. But the Japanese campaign in China, known as Ichigo, showed up the weakness, inefficiency, and poor command of the Chinese armies after nearly seven years of war. During April and May the Japanese cleared the Beiping-Hankou railway between the Huang He and the Yangtze. Chinese armies nominally numbering several hundred thousand troops were unable to put up effective resistance. Peasants in Henan attacked the collapsing Chinese armies—only recently their oppressors.
The second phase of the Ichigo campaign was a Japanese drive southward from Hankou and northwestward from Guangzhou to take Guilin and open the communication line to the India-China border. By November the Chinese had lost Guilin, Liuzhou, and Nanning, and the Japanese were approaching Guiyang on the route to Chongqing and Kunming. This was the high-water mark of Japan's war in China. Thereafter, it withdrew experienced divisions for the defense of its overextended empire, and China finally began to benefit from the well-trained X-Force when two divisions were flown in from Burma in December to defend Kunming.
Meanwhile, the Chinese government was involved in a crisis of relations with the United States, which contended that the Chinese army must be reformed, particularly in its command structure, and that lend-lease supplies must be used more effectively. There were also many subsidiary problems. Gen. Joseph Stilwell, the executor of disagreeable U.S. policies in China, had developed an unconcealed disdain for Chiang, whom he nominally served as chief of staff. Stilwell was an effective troop commander, and Roosevelt requested that Chiang place Stilwell in command of all Chinese forces. In the context of Chinese politics, in which control of armies was the main source of power, President Chiang's compliance was virtually inconceivable. He declined the request and asked for Stilwell's recall. Roosevelt agreed, but thereafter his relations with Chiang were no longer cordial. Stilwell was replaced by Gen. Albert Coady Wedemeyer.
Nationalist deterioration
The military weakness in 1944 was symptomatic of a gradual deterioration that had taken place in most aspects of Nationalist Chinese public life. Inflation began to mount alarmingly as the government pumped in large amounts of paper currency to make up its fiscal deficits. Salaries of government employees, army officers, teachers, and all those on wages fell far behind rising prices. For most, this spelled poverty amid growing war-weariness. Dissatisfaction with the government's policies spread among intellectuals. Inflation gave opportunities for some groups to profit through hoarding needed goods, smuggling high-value commodities, black market currency operations, and graft. Corruption spread in the bureaucracy and the armed forces. As the war dragged on, government measures to suppress dissidence grew oppressive. Secret police activity and efforts at thought control were aimed not only against communists but also against all influential critics of the government or the KMT.
Communist growth
The communist armies were growing rapidly in 1943 and 1944. According to U.S. war correspondents visiting the Yan'an area in May 1944 and to a group of U.S. observers that established itself there in July, the communists professed allegiance to democracy and to continued cooperation with the Nationalist government in the war effort. There was convincing evidence that the areas under communist control extended for hundreds of miles behind Japanese lines in northern and central China.
This situation was the result of many factors. Communist troop commanders and political officers in areas behind Japanese lines tried to mobilize the entire population against the enemy. Party members led village communities into greater participation in local government than had been the case before. They also organized and controlled peasants' associations, labour unions, youth leagues, and women's associations. They linked together the many local governments and the mass organizations and determined their policies. Because of the need for unity against Japan, the communist organizers tended to follow reformist economic policies. The party experimented with various forms of economic cooperation to increase production; one of these was mutual-aid teams in which farmers temporarily pooled their tools and draft animals and worked the land collectively. In areas behind Japanese lines, some mutual-aid teams evolved into work-and-battle teams composed of younger peasants: when danger threatened, the teams went out to fight as guerrillas under direction of the local communist army; when the crisis passed, they returned to the fields. The party recruited into its ranks the younger leaders who emerged from populist activities. Thus, it penetrated and to some extent controlled the multitude of villages in areas behind Japanese lines. As the Japanese military grip weakened, the experienced communist armies and political organizers spread their system of government ever more widely. By the time of the CCP's Seventh Congress in Yan'an (April–May 1945), the party claimed to have an army of more than 900,000 and a militia of more than 2,000,000. It also claimed to control areas with a total population of 90,000,000. These claims were disputable, but the great strength and wide geographical spread of communist organization was a fact.
1Statutory number; includes 36 seats allotted to Hong Kong and 12 to Macau.
|Official name
|Zhonghua Renmin Gongheguo (People's Republic of China)
|Form of government
|single-party people's republic with one legislative house (National People's Congress [3,0001])
|Head of state
|President: Xi Jinping
|Head of government
|Premier: Li Keqiang
|Beijing (Peking)
|Official language
|Mandarin Chinese
|Official religion
|Monetary unit
|renminbi (yuan) (Y)
|(2014 est.) 1,364,038,000
|Total area (sq mi)
|Total area (sq km)
|Urban-rural population
|Urban: (2013) 52.6%
Rural: (2013) 47.4%
|Life expectancy at birth
|Male: (2009) 72.4 years
Female: (2009) 76.6 years
|Literacy: percentage of population age 15 and over literate
|Male: (2010) 97.1%
Female: (2010) 91.3%
|GNI per capita (U.S.$)
|(2013) 6,560


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Charlie Trotter's name recognition travels far beyond the Windy City to all corners of the culinary globe. Known for being innovative and progressive in their techniques and presentation, the team of chefs has cemented Charlie Trotter's in Chicago's ri...read more
An aerial dining experience at one of Chicago's best restaurants, Cit� offers 360-degree views of glittering city skyline, 70 stories above ground level. Gourmet meals are prepared by Executive Chef Oscar Omelas and paired with wines from Cit�'s wine s...read more
Mandarin cuisine and sushi are not quite synonymous with Chicago, but Dee's is working to change that misconception with their varied and unique menu offerings under the direction of sushi Chef Mr. Masashi.read more
Chicago has always done things their own way, and their famous pizza is no different — the deep-dish pizza was actually born here.read more
MK features fine dining in an airy and contemporary dining room resembling a barn, creating just the perfect atmosphere for its seasonally-fresh ingredients. Two levels of tables sit under exposed wood trestles and brick walls.read more
For over thirty years, diners in The Windy City have turned to the Morton's name to be blown away by great steaks. Only the finest cuts are served here, cooked to perfection, and delivered by a knowledgeable staff.read more
Moto is like the offspring of a science laboratory coupled with an art gallery, with dishes that wow the eyes as well as the palate. Creative techniques, rare ingredients, and unrivaled presentation make for an experience like no other.read more
The James ChicagoRomantic, Business, Spa, Tourism, Urban
The Westin Chicago NorthwestBusiness, Family Friendly, Tourism, Nightlife
Conrad ChicagoRomantic, Business, Family Friendly, Pet Friendly, Tourism, Nightlife, Culinary
ElysianRomantic, Business, Spa, Pet Friendly, Wedding, Resort, Luxe Superior
Hard Rock Hotel ChicagoRomantic, Business, Luxe Superior, Nightlife


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Our Pastor
Recent Message
Recent Stories
Jesus Breaks Every Chain
On Easter Sunday, the presence of God came down on our service and hundreds made decisions to follow Christ.read more
Mark and Dianne Dougharty's story can only be described with one word: faithful.read more
Homebound Ministry
The Bellevue family has over 170 members that are homebound. It is our goal for each one of them to be visited every week.read more
Our Vision
We believe God has called us to be a catalyst for spiritual awakening in Memphis and beyond, and it starts in you.
Your Next Step
Whether you are new to Bellevue, or a longtime member, take the next step in your journey and join us for one of our Next Step Classes!
Bellevue Appling
Main Campus
2000 Appling Road, Cordova, TN
Worship: 9:20 a.m., 11:00 a.m., 6:00 p.m.
Bellevue Arlington
Meets at Arlington High School
5485 Airline Road, Arlington, TN
Worship: 9:20 a.m
Bellevue Frayser
Serves the Frayser Community
3759 N. Watkins St., Memphis, TN
Worship: 11:00 a.m
Bellevue Bella Vista
Spanish-Speaking Services
700 N. Highland, Memphis, TN
Worship: 10:00 a.m, 2:30 p.m.


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Summerlight Photography: There are worlds to discover in the defining moments of life.
It is an honor to be chosen to take part in the ceremonies and moments so important in life. We are always looking for those shots that capture the moment; a photo that will awaken our emotions years in the future.
We seek to represent the uniqueness of our clients as well. Every person, every couple, every family is different. We want to capture you as you are: real, full of life, energy, and love.


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Secretary General of the NGO National Association of Blind (NAB), K Ramkrishna may have lost his eyesight years ago, but he has managed to keep his other vision strong— his vision to succeed and rise above mediocrity. The 64-year-old has been associated with the institute for the welfare of the visually-impaired for last 30 years now. But that's not all what he has done. After completing his post-graduation and MBA from the SP Jain Institute of Management, the mathematics wizard retired from a prestigious bank as the general manager and joined NAB full-time.
"I lost five years of my education, when I started losing my eyesight at the age of eleven. It was indeed a setback, but RT Vyas and Rahmad Fazalboy, who were associated with the NAB then, encouraged me to take up education again," says Ramkrishna. Once he started his studies again, there was no stopping him. "I had a graphic memory and was good at math. That helped me," he recalls.
Quiz him about his success mantra and he says, "I have always believed in a system, people, policies and processes. And above that, I had this sense of urgency in everything I did." Of course, technology played its part too in helping him, but Ramkrishna believes that if he can achieve such great heights despite having an impairment of sorts, then everybody else can. "The youth today should have that one burning dream, instead of being complacent and happy with mediocrity. There are limited opportunities, but when they come, they should grab it by the jugular and utilise it to the full extent," Ramkrishna asserts.
"The desire to struggle for your dream should come from within. After all, like everything else, you have to pay a price for success too," he says. Ramkrishna signs off with another trick that has worked wonders for him. "You have to stand out and be different from the rest," he says.


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Deeplinks Blog posts about Innovation
Digital Video Recorders, once considered a mortal threat by the entertainment industry, have now become its new best friend. It's just the latest example of how the industry's constant warnings of the dangers of "piracy" frequently turn out to be baseless hysteria.
Remember 2001? Digital Video Recorders ("DVRs") like TiVo and ReplayTV were poised to win mainstream adoption, allowing consumers to fast-forward past advertisements more easily than before. In response, the entertainment industry behaved predictably — it freaked out and filed a bunch of lawsuits.
As the deadline nears for a decision from the Copyright Office on EFF's request for a renewal of the 2006 exemption from DMCA liability for handset unlocking, prepaid phone companies have opened a new front in the war on consumer choice with a bill called the Wireless Prepaid Access Device Enforcement Act of 2009. If passed, this legislation would make it a crime to purchase or "handle" a prepaid handset for the purpose of modifying the software that ties it to the network, or to sell the handset outside the U.S.
UPDATE (9/4/14): The net neutrality landscape has changed in the last few years, and not for the better. Here's a discussion about EFF's updated stance and here's our issue page, with links to our most recent blog posts.
On Thursday, Federal Communications Commission (FCC) Chairman Julius Genachowski is expected to unveil draft rules aimed at imposing network neutrality obligations on Internet Service Providers (ISPs). In the excitement surrounding the announcement, however, many have overlooked the fact that the this rulemaking is built on a shoddy and dangerous foundation – the idea that the FCC has unlimited authority to regulate the Internet.
In the past few years, interesting conversations about new media and innovation have taken place at the South by Southwest (SXSW) conference and festival. Voting for the panels to be featured in 2010 is taking place until September 4 -- here are a few proposals that we think will yield interesting discussions:
UPDATE: Just one day after Judge Patel's ruling against RealDVD, a California appeals court has ruled against Kaleidescape, reversing the lower court and sending that case back for a fresh determination of whether Kaleidescape violated the terms of the DVD-CCA license. More bad news for innovators who want to bring legitimate consumers DVD jukebox products.
Judge Patel (who also handled Napster and Bernstein cases) has granted a preliminary injunction in favor of the major motion picture studios and DVD-CCA in their legal battle with Real Networks over its RealDVD products.
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Deeplinks Topics
- Fair Use and Intellectual Property: Defending the Balance
- Free Speech
- Innovation
- International
- Know Your Rights
- Privacy
- Trade Agreements and Digital Rights
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- State-Sponsored Malware
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- Analog Hole
- Anonymity
- Anti-Counterfeiting Trade Agreement
- Biometrics
- Bloggers' Rights
- Broadcast Flag
- Broadcasting Treaty
- Cell Tracking
- Coders' Rights Project
- Computer Fraud And Abuse Act Reform
- Content Blocking
- Copyright Trolls
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- Defend Your Right to Repair!
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- Uncategorized


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§ 6120
The Congress finds that the use of flexible and compressed work schedules has the potential to improve productivity in the Federal Government and provide greater service to the public.
Regional Offices, Guidances, Policies, Manuals, ULP Process, Forms, Representation, ADR Services, and Training.
Federal Service Impasses Panel
Find Jurisdiction, Statute, Work Schedules Act, Biographical Data, and Contact Information.
Solicitor, Administrative Law Judges, IG & Others
Find General Information about these Offices and Contact Information.


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Teaching Assistantships
Each term the department of Mechanical and Materials Engineering hires graduate teaching assistants to act as graders and lab assistants in our undergraduate program. In the coming year the MME Department will start to hire Teaching Assistants on a yearly basis as opposed to term by term.
Students wishing to apply for an assistantship in the department must meet the following eligibility requirements. Students must also meet all terms and conditions as set forth by the Office of Graduate Studies.
MME Graduate Teaching Assistant Eligibility Requirements
All students receiving a teaching assisantship in Mechanical and Materials Engineering must be:
- Admitted to the university and department (with no University Conditions)
- In good academic standing
- Able to register for 9 graduate credits the term of their assisantship
- Meet the application deadline
- If hired as a lab assistant, be available during the days and times the lab meets
Application Deadlines
Winter 2015 - December 10, 2014
Spring 2015 - March 15, 2015
How to Apply
Students that meet the eligibility requirements and who are interested in being considered must complete the online TA application.


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Elementary Educator Asks: Does Merit Pay Turn Kids into Zombies?
Tap, tap, tap---tap, tap--tap. I'm sending a signal from down here in the muck, down here where the boogers are hard and the shoelaces are eternally untied. HELLO up there? In the 80's words of Def Leopard, "Is anybody out there? Is anybody there?" Call me crazy, but how come I don't see or hear serious discussion about what's going to happen to elementary school students and teachers when teacher evaluation is tied to test scores?
"We're going to pay good teachers more; hold the bad ones accountable." I'm sure you've heard the same thing from the Obama administration. And right from http://www.barackobama.com: "We will recruit an army of new teachers and develop innovative ways to reward teachers who are doing a great job, and we will reform No Child Left Behind so that we are supporting schools that need improvement, rather than punishing them."
So, okay. What happens when Obama's vision here becomes law? And how exactly do they plan to assess all this improvement they expect to see? With budgets the way they are, I can only infer that they'll fall back on standardized tests. And the teacher reward? Tied directly to scores.
I'm not saying that the negative impact of merit pay will be any greater in the elementary grades. All teachers on all levels play a crucial part in a student's development. However, I'm sorry to bring up an old, but very true saying: "First impressions last forever." The pressure to perform will squeeze the life out of the innocence of grade school and crush the curiosity that attracted them there in the first place, students and teachers alike.
The Dominoes Fall and the Zombies Rise
Domino #1: Most elementary standardized tests assess math, reading, and writing. When merit pay is squished into the system, classrooms around the country will morph into a zombie-land of reading, writing, and math (Some already have.) I must read. I must write. I must count. I must read. I must count. I must . . . well, you get the point. This isn't a bad thing, right? Right. BUT, all of this reading and writing and math will be taught solely for the purpose of passing a test. Big money will be spent of prep materials and programs and kids will begin to believe that they are in school to pass a test. Not learning to live life to the fullest. Not learning to be curious or to think. Not learning to learn.
Domino #1 falls and hits Domino #2: There goes science, social studies, technology and any other kind of free-thinking non-test taking creative endeavors. You gotta make room for test prep, more room than ever since merit pay or loss of job is in sight. And then what happens to our country? The art of teaching will disappear and clone teachers will spew out soulless, robotic test takers.
Domino #2 falls and hits Domino #3: While the zombie test takers move across grade levels their level of zombieness will increase and all creativity as we know it will cease to exist. Just like their dead, rotting flesh. That's not good. In a recent Newsweek article: "The Creativity Crisis", a recent IBM poll of 1,500 CEOs identified creativity as the No. 1 "leadership competency" of the future. The article guessed that video games and the lack of creative development in school are two machetes slashing at the heart of creativity. With merit pay in place, creativity hasn't got chance to make a comeback.
Down, down, and down for the count.
Let me remind you that this domino effect will go as low as Pre-K. Everyone's got to be evaluated. It's only fair. I know, their kids can't read. How do you give a standardized test to a kindergartner? What about art, music, and library? Those teachers need to be evaluated too. Speech? Gym? I can go all day. But wait, here's an even larger question. How much money will it take to test, monitor, and score every grade level and special area? That's a lot of money and a lot of time to prepare, practice, and actually take the test.
Is it worth the money? I don't think so. If you want true educational reform you put your money into heavy professional development, my friends. In the words of author, Barry Lane, "You don't fatten a pig by weighing it." I'm not talking about a six-hour workshop. I'm talking about intense national programs like The National Writing Project and The National Science Teacher Association; I'm talking about learning from the best. Invite authors, master teachers and educational thinkers to inspire the teaching population; create learning communities and think tanks within school districts that include teachers, parents, and kids. Just because we teach eight-year-olds doesn't mean we can't sit around and talk theory and philosophy.
So let's assess kids (the ones with with a pulse) instead.
We are pushed as teachers to create well-balanced citizens who will contribute to society. We are encouraged to instill a sense of confidence in our students who will some day harness a career in a field of their choice. We are tending a human garden, not screwing parts together. We are indeed teaching human beings. Human beings have many needs: educational, social, emotional, physiological, and . . . dare I say, creative. Can you test resourcefulness in thirty minutes? Leadership? Hard work? Art? Collaboration? Can you assess being a human? Can you assess the fact that a teacher raised the self-esteem of a student?
What pressures are leaning on you as merit pay leaks into the lower grade levels? Are there ways to do it without a high stakes test?
Comments (41)Sign in or register to postSubscribe to comments via RSS
I hear many people say, "Let's pay the good teachers more." Who decides who is a good teacher? Very difficult to do. So the easy way out is simply to base pay on test scores.
"Let me remind you that this domino effect will go as low as Pre-K." Oh it has! You are so right on with this article. We need more edutopians everywhere! Maybe create an Edutopia for parents, they need to understand and to see what is really going on. Thanks Gaetano!
As a third grade teacher who is required to administer 37 days of district, state, and national assessments over a the course of one school year, I can only say thank you for such a clear picture of the consequences of testing, not teaching.
I couldn't agree more, Gaetan! But I have to wonder...where has this NOT already happened. The Domino and Zombie effects you describe have been my reality since NCLB came into law. Creativity has already been lost in public schools. Solving this problem isn't really just about STOPPING the damage, but cleaning up the damage that has already been done and building structures to prevent further damage.
I disagree with Gloria...I think there are many ways we COULD assess good teaching and I think we MUST do so. Good teachers DO need to be encouraged to stay in the profession and bad teachers DO need to be weeded out. But you are right that test scores aren't the answer. It would involve real professional discussions and think tanks like the ones Gaetan describes. It also means principals and others in charge must get out of offices and stop looking at metrics and really get into the classrooms and watch teachers and students in action.
My daughers (1st and 4th) attend Ohlone Elementary in Palo Alto CA. No grades, no homework, mixed grades, big farm, the WHOLE child. They love it and I love it. AND, my oldest daughter has been abpve 95% in all categories of STAR tests for 2 years. I want it all! The farm and no homework and the focus onthe whole child doesn't mean much if she isn't being taught or is not retaining the basic curriculum. But, Ohlone Elementary proves that kids can have high test scores and a happy, creative, sophisticated education.
You are right that is has already happened. However, my point is that merit pay will only make it worse and will drive the zombie population up by assessing every single teacher all the way down to Pre-K. I've been giving a state test for ten years now, but I've never been evaluated on the results.
Yes, there are ways to evaluate teachers. Don't get me wrong; I'm not blind to the fact that there are teachers out there who are practically stealing a paycheck. I think merit pay can be executed in a somewhat proper manner. Take, for example, the Portland Education Association in Maine. They have been working under a Professional Learning Based Salary System (PLBSS). When teachers participate in some sort of professional development, they can increase their pay. "Our salary system is based on the statement that the best indicator of student learning is teacher learning," says Gary Vines, a guidance counselor in the district who played a crucial role in establishing the merit pay system. Helena, Montana adopted a similar merit pay program with career development plans, professional service commitments, and positive evaluations being the determining factors for pay increases. And teachers don't even have to follow the merit pay scale. It's a personal choice. There are ways to increase teacher performance without hanging the invalid threat of a standardized test over their heads.
Thanks for the posts.
A great blog and great comments! All too often, it seems that the negativity (deserved often) leads to resignation. There ARE better options, some mentioned here. Let's work together to "get it all" for all students. Let's keep the blogs positive and supportive. Let's keep the learning communities engaged scenic not formally organized within school systems and beyond. Let's push administrators and school boards to do the right things - not do the short payback things only. Again, the successful and appropriate programs exist; let's fight for them instead of giving up.
Right on, John. It's about inspiring people to rise up. Not beating them down.
The Folly of Merit Pay
I see a great sea of automaton students, especially when teachers are forced to teach in a particular way due to working in a low performing school, or held so accountable that they fear creativity. Education seems to be at a crossroads, accountability vs. teachability. Unfortunately, the "powers that be" in education as of late all seem to be ex businessmen, not educators. Perhaps it would be best if the businessmen would don the teacher robe, and start experiencing the other end of the spectrum. I am sure it would be enlightening.
blog Full-Time Comeback: A ReflectionLast comment 6 days 18 hours ago in Teacher Leadership
blog Why "Content Coverage" is Over: A Manifesto!Last comment 14 hours 43 min ago in Teacher Leadership
Discussion Grant Wiggins on EdutopiaLast comment 3 days 19 hours ago in Education Trends
blog The Era of the TeacherpreneurLast comment 3 days 19 hours ago in Technology Integration
Discussion How to Overcome Teacher Reluctance to Take on a Leadership Positions?Last comment 6 days 6 hours ago in Teacher Leadership


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Have you thought about...
by Zouch - 7/13/13 3:12 AM
In Reply to: suggestion for DSLR camera for beginner by keepsim
I'm a Canon fan, have been since the mid 70s and film cameras.
Either of the Canon cameras you suggest will be very satisfying - the 100D being MUCH smaller and lighter than the others but still taking EOS lenses. The 100D is relatively new and so doesn't yet have a track record of reliability, etc, while the 700D is the latest in a long line of full size starter DSLRs, whose quality and reliability is excellent.
I think, though, that the 700D may be pushing your budget a little. Have you thought about its immediate predecessor, the 650D or the one before that, the 600D. Here in Australia (never cheap for this stuff!) there is about $50-$150 difference in price for essentially the same camera, less a few bells and whistles. Stock in the stores is limited, especially for the 600D but it might be worth pulling up a feature comparison chart from Canon or one of the photo magazines (where you can compare the Nikons also) and see whether the extra features on the newer models are useful to you.
General advice holds here - get a body that meets your needs and focus any additional cash on the lenses.


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My Other Computer Is a Supercomputer
In November 2002, I was called by Mitch Davis (Executive Director of Academic Technology, ITSS, Stanford University) and Carnet Williams (Director of Academic Technology, ITSS, Stanford University) regarding an aggressive, high-profile project. While I was Director of Network Operations at the Stanford Law School, I had the pleasure of working with both Mitch and Carnet during their respective terms as Associate Dean/CIO of Stanford Law School. They told me Dr Vijay Pande, the principal investigator behind the Folding@home Project, wanted to purchase a large commodity cluster, and they sent my name to Vijay as someone who could manage projects effectively to completion. Instinctively, I agreed. We discussed more details of the project, and right before I hung up, I asked, "How big will it be?" They responded, "300 dual-processor nodes." I thought, "600 CPUs...that should do some damage."
While Mitch, Carnet and Vijay worked with Dell and Intel to negotiate the purchase of the cluster, I sent an e-mail to Vijay Pande, stating that I could assist him with the network and hardware side of the project and that I hoped to learn more about the software side during the process. The last line in my message said, "I want to be part of something great." Vijay responded promptly and welcomed my assistance. We set up our first meeting to discuss the scope of the project.
At that initial meeting, it seemed most things were up in the air. Everyone knew equipment was coming, but no real plans were in place. Vijay said he knew that authentication and filesystem choices had to be made, and of course the opportunity to use existing Stanford services was considered.
Vijay also mentioned running PBS, MPI and MOSIX. I knew very little about any of these, but took notes and, back at my desk, did a Google search for those names along with the words "beowulf" and "cluster". I came across a presentation about building a cluster using an open-source distribution named Rocks from an organization called NPACI (www.rocksclusters.org). The presentation was excellent. It answered so many of my questions, such as, how would we put together such a cluster, how would we manage software on nodes, how would we configure the master node and how would we monitor nodes. Basically, the presentation was a framework for how we would build our cluster. I printed copies of the presentation and brought them to our next meeting. The idea of using a packaged solution was well received.
During the time these two meetings were taking place, the cluster was being racked and stacked by Dell in Stanford's Forsythe Data Center, which took seven days. I was able to download a copy of Rocks version 2.3 and run through the installation process on what is defined as the front-end node in Rocks nomenclature. This task was simple, and I was quite impressed at this point. At our third meeting, my role in the project had expanded from being involved only with hardware and the network, to handling software also, as I already had brought up the front end with Rocks successfully. I felt confident that I could handle the rest of it as well, but at this point I didn't realize the true scope of the project. I was embarking on building the largest-known Rocks cluster.
The first issue I ran into was trying to install compute nodes. A Rocks utility called insert-ethers is used to discover compute nodes' Ethernet MAC addresses, assign them an IP address and hostname and then insert this information into a database, during a negotiated process using PXE and DHCP. Following the node insertion, the node is built and configured as defined in a Red Hat Kickstart file, completing the PXE boot process. Unfortunately, I had problems with the network interface cards in the Dell PowerEdge 2650, as the Broadcom Ethernet controllers did not appear to be supported in Rocks. I sent my issue to the Rocks discussion list, and I also called Dell for support and opened a ticket for service under our Gold support contract. The Rocks developers quickly provided an experimental version of their cluster distribution that contained updated drivers, which solved the problem, and soon I saw my suggestions and observations incorporated into the maintenance release of Rocks version 2.3.1.
The final issue, which was discovered at scale, was the inability to have more than 511 active jobs. My users were screaming about the 100 idle processors, because many of the jobs run on Iceberg are short-lived, one- to two-processor jobs. While working with the Rocks Development team, we looked for a defined constant in the Maui scheduler code. I eventually found it, and under the guidance of the Rocks team, recompiled and restarted Maui. The front end now can schedule as many active jobs as there are processors.
Tools and Technologies for Scale and Reliability
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|My Humble Little Game Collection
|May 28, 2015
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|Non-Linux FOSS: All the Bitcoin, None of the Bloat
|May 26, 2015
|Dr Hjkl on the Command Line
|May 21, 2015
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|May 18, 2015
- My Humble Little Game Collection
- New Linux Based OS Brings Internet of Things Closer to Reality
- Initializing and Managing Services in Linux: Past, Present and Future
- Dr Hjkl on the Command Line
- Using Hiera with Puppet
- Non-Linux FOSS: All the Bitcoin, None of the Bloat
- Gartner Dubs DivvyCloud Cool Cloud Management Vendor
- Infinite BusyBox with systemd
- Goodbye, Pi. Hello, C.H.I.P.
- It's Easier to Ask Forgiveness...


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Plastic Tail Comb
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Tags: Backcomb, Brush, Comb, Hair, Plastic, Tail
With 6 different colours to choose from!
Perfect for backcombing and parting hair.
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Aerowatch: Horological Machine No. 4 Thunderbolt
By Ben Coxworth
December 20, 2010
If you enjoy building model airplanes as a boy, and become a designer of high-end watches as an adult, what do you end up doing? If you're Maximilian Büsser, you create a watch that resembles an airplane – and that costs as much as one, too. That's the story behind the new watch from Switzerland's MB&F (Maximilian Büsser & Friends), the Horological Machine No. 4 Thunderbolt. The 50-jewel titanium and sapphire timepiece looks like it might wrench itself free of your wrist and start performing inside loops in the sky ... given that it sells for a mind-blowing 150,000 euro (US$196,812), however, you'd probably want to keep it close at hand. Read More
The Leica M9 Titanium Special Edition
September 28, 2010
Leica used Photokina 2010 to unveil its beautifully crafted limited edition LEICA M9 'Titanium' digital camera. Created in collaboration with chief designer of the Volkswagen Group, Walter de'Silva, the camera is a reinterpretation of the classic LEICA M9. The special edition is strictly limited to 500 cameras worldwide. Read More
Titanium foam bone replacements on the way
By Ben Coxworth
September 23, 2010
Back in June, those brainy folks over at Germany's Fraunhofer research group announced the development of Resobone, a material designed to replace the titanium plates used to patch holes in peoples' skulls. Now, perhaps a little ironically, they've announced the creation of TiFoam – a titanium foam to be used for replacing injured bone. Unlike Resobone, TiFoam is intended for load-bearing areas, where a balance of strength and flexibility are essential. Like Resobone, however, it's designed to encourage surrounding bone to grow into the implant. Read More
More than 1,000 tons (2.2 million pounds) of titanium devices are implanted in patients worldwide every year with joint replacements one of the more common procedures. Light, strong and totally biocompatible, titanium is one of the few materials that naturally match the requirements for implantation in the human body. Researchers have now developed an improved coating technique that could strengthen the connection between titanium joint-replacement implants with a patient's own bone. The stronger connection – created by manipulating signals the body's own cells use to encourage growth – could allow the implants to last longer. Read More
ID titanium laser mouse - stunning design and a price to match
By Jude Garvey
October 30, 2009
With Apple's new wireless Magic Mouse grabbing headlines this month, and innovations such as the multi-functional GlideTV navigator and Nortek Duplus mini wireless mouse being rolled-out almost weekly, it seems the days of the humble mouse are long gone. Enter Intelligent Design's titanium laser mouse - a hand-crafted device that is anything but humble (or cheap) and while it doesn't have the smarts of Apple's new offering, its certainly lays down a challenge on the design front. Read More
The Titanium and Carbon Fibre Gatling Pocket Flashlight
March 6, 2007
March 7, 2007 Named after that famous weapon of war, the Gatling Gun, the GatLight is part objet d'art, part tactile companion and almost coincidentally is one of the most powerful, compact and functional flashlights available. Lumencraft specialises in designing and manufacturing high end pocket flashlights and their latest evolution of their flagship product, the GatLight V3, made of aerospace grade titanium and carbon fibre composites is just a joy to look at. Since every GatLight is custom made to order, the Gatlight V3 has an estimated delivery time of 3 months with pricing between US$295 and US$370 for the all-titanium version. Read More
Limited Edition Titanium Fireblade
July 3, 2005
July 4, 2005 Honda is releasing a limited edition Titanium version of the CBR1000RR – while it comes with all the breathtaking performance of the MotoGP RC211V-derived 2005 Fireblade, the only difference to the standard machine is the Titanium paint job gracing the latest Fireblade's bodywork which is quite distinctive in 2005 with a sharper and more aggressively angled nose with a lower windscreen. The new Titanium model will be available from July in extremely limited quantities. Read More
PING Moxie Junior Set Features Titanium Driver
February 19, 2005
February 20, 2005 It wasn't that long ago that golf clubs were made from hickory and a 250 metre drive was considered "outta sight." When we heard about the new Moxie junior set being announced this week, complete with a Titanium driver, we couldn't help but reflect how far this game has come in a few short decades. The new Moxie Junior set offers young golfers the benefits of proven technology in a package engineered to match their size, strength and ability. Read More


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I'll take Confounding Quiz Show Moments for $800, Alex.
Thursday night's episode of "Jeopardy!" was one of the most miserable to watch in recent memory as only one of the three contestants made it to the Final Jeopardy round. Yes, eventual winner Kristin Sausville was pretty much guaranteed victory when she entered the final frame as her rivals both finished Double Jeopardy in negative territory.
She didn't have to bet anything for the final category (The U.S. Government), of course, but she did anyway — and saw her total fall to $6,800 from $8,400 after failing to give the correct question to the final clue. Read More »


text: I've actually found Flickr to be an interesting way to get a first edit. If people view, comment or mark as a favorite, that tells you something. It isn't the same as having someone you respect looking at it, but it is unbiased and quantitative. It is pretty clear which ones seem to resonate with people. The trick is to figure out which groups to place them in.


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Take your company's recruiting to the next level...automatically, beautifully. Start attracting and engaging prospective candidates with marketing tools designed specifically for hiring.
At TakeLessons, we've worked hard on building an incredible culture and we want to hire people that naturally share our beliefs, attitudes, and values. Kareer.me allows TakeLessons to showcase our culture and find prospective employees who want to be a part of something great.— Steven Cox, CEO TakeLessons
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The Kareer.me team was extremely easy to work with. They have a great concept to help "sell" the company and enable employers to address the questions that many candidates have about the work environment, location, benefits, and extras that make the company unique and fun.— Dawn Ridz, Sr. Recruiter meLLmo
In just minutes, anyone at your company can build and manage an amazing company profile that showcases your company culture, team, workspace, benefits, buzz, and opportunities. Engage talent and develop a talent pipeline while you sleep.
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Take talent on a tour through your office. Show off that espresso machine, ping pong table, on-site gym, or fancy task chair.
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Your opportunities are automatically promoted through our broad network of social networks, so you can relax.
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Your profile is specifically designed to engage top talent. Build a talent pipeline while you sleep.
The Kareer.me Discover Network is a destination for talent currently employed, and those actively seeking. The browsing experience provides your company and opportunities with additional exposure. Top talent finds your company while you get back to business.
Our suite of recruiting tools makes every aspect of developing your talent pipeline and finding the right talent simple. Adding a single line of code to any web page adds a fully customizeable tab to your site that drives visitors to a special private label version of your profile.
The perfect candidate may have already visited your website, but moved on because the right opportunity wasn't currently available. With Kareer.me, you can engage talent early and announce newly available opportunities.
Take your recruiting strategy to the next level. Identify and connect with potential hires before you need them. Put the most effective recruiting strategies to work for your company automatically.


text:
G2D Games
Most Played Games
New Games
Dressup Games
Makeover Games
Girls Games
Celebrity Games
Cool Games
Cooking Games
Baby Games
Fun Games
Game Name
Make Macaroni
Cooking Games
Click Here to Play
Game Details :
You'll have to make macaroni in sauce. At the end, you'll be judged. cook the ingredients the way your shown intitally in the introduction. To play you press the green button and to cook the food, you use the yellow. Make sure you don't over or under cook it though.
New Games
Cheese Omelet
Farm Girl
Christmas Magic Santa
Strawberry Shortcake R
Flappy Mario
Elsa Hand Surgery
Pou Ice Cream Decorati
Frankie Stein Injury
Pizza Mania
Dora Fly Hitter
Celebrities Pet Shop
Rock Star Kiss


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New on NEP: Virginia Garrard-Burnett on Guatemala's civil war
Posted: December 9, 2011
Not Even Past's feature story for December is online now at this link. Virginia Garrard-Burnett discusses the ways people to remember and try to write histories of the hyper-violent chapter of the Guatemalian civil war in the early 80s. Illustrated with fantastic photos by Jean-Marie Simon.
Founded in 2010 and developed by the Department of History at the University of Texas at Austin, NEP provides dynamic, accessible, short articles on every field of History.
For more information about NEP and to register for regular updates, please visit: http://www.notevenpast.org/about.
Not Even Past can also be found on the web, at:
Amazon's Not Even Past bookstore:
You Tube:


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Buick Somerset Clutches
Take your Buick Somerset's performance to a whole'nother level thanks to a Buick Somerset clutch. Buick Somerset clutches' superior slip-resistance and strength come via friction-enhancing carbon and ceramic fibers. To provide a perfect fit and finely-engineered performance, every Buick clutch is made for your specific car. Best yet, Buick performance clutches at Auto Accessories Garage are easy on the wallet and hassle-free to check out.
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Buick Somerset Performance Clutches at the lowest cost are all at Auto Accessories Garage. We feature great-looking Buick Clutch pics and real customer reviews to supply plenty of details. Buick Somerset Performance Clutches always include totally free shipping. If you want the best Buick Somerset Clutches without breaking the bank nobody beats Auto Accessories Garage.
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We offer Buick Somerset Clutches for the following years:
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elle & blair twilight glitz case for htc evo 4g - zebra amethyst
Elle & Blair Twilight Glitz Case for HTC EVO 4G - Zebra Amethyst
Item #: 48-0080004R
If fashion is your passion then the Twilight Glitz collection will speak your language! Simply in love with the Glitz, this collection is decked with signature crystals for the inner fashionista in us all. With its seamless, diamond-cut design, "Twilight Glitz" vies for attention and will make you the envy of all of your friends!
- An exceptional skinny profile
- Distinctive Elle & Blair style
- Reinvented technology to enhance the durability among the crystals for daily use
- Convenient access to all ports and buttons on your wireless device
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The residential construction industry is making a comeback. According to research firm IBISWorld, the industry will finish out the year with 17.5% profit margins, and analysts predict a 10.2% increase in annualized sales revenue by 2017. One sector that will benefit greatly from this boom is eco-friendly construction materials, as builders become more conscientious of the environment and regulators crack down on building standards. Take a look at the range of business opportunities in this burgeoning sector. --Erin Kim
Green homes start with an eco-friendly design. Architects create a floor plan that makes a home as energy-efficient as possible, whether that's making a more compact space, or incorporating solar panels or superinsulation. At ZeroEnergy Design, managing director and co-founder Stephanie Horowitz says they design a house to make sure they "squeeze every inch of energy out of it as we can." The firm's projects typically use 60-80% less energy than conventional houses.
Many paints used for the interior and exterior of homes contain chemicals that, with too much exposure, could cause physical irritation. Even for experienced painters, oil-based paints could cause problems. After Paul Sek of T. Paul Sek Painting ended up in the hospital from chemical exposure during one of his projects, the firm switched to using 100% non-toxic paints. Even though the industry was hurt by the housing crisis, the business has picked up again; the company expects to make 70% of what it did last year by July.
Installing new carpets can fill the air with volatile organic compounds, so flooring alternatives can help make a household safer and healthier. Rob Hendricksen, owner and founder of Hendricksen Natürlich Flooring, provides natural options that also involve environmentally friendly practices in the creation of the product. Hendricksen says the Sebastopol, California, company's business has grown due to increased interest in his green flooring products--from carpets made from natural fibers to hardwoods certified by the Forest Stewardship Council.
Many companies now offer kitchen countertop surfaces made from recycled paper or bamboo. Gilasi, based in Chicago, actually takes materials that cannot be recycled traditionally, and incorporates them into countertops. The company crushes glass—saving hours worth of energy that went into creating it—and adds it to a cement mixture. The countertop was featured in the Museum of Science and Industry's Smart Home exhibit in 2010.
Insulation can be a great way for a house to go green, as it can help reduce energy consumption--and new materials make insulation products even more environmentally friendly. Eco Tec Insulation uses spray foam to insulate homes; the Icynene spray does not emit chemicals and improves the air quality inside houses, according to the company's website. Once sprayed into the wall, ceiling or floor, the foam expands to fill the area, and it can conserve up to 40% of a home's energy loss.
Read more about the residential construction industry.
[1] http://zeroenergy.com/
[2] http://www.epa.gov/kidshometour/products/lpaint.htm
[3] http://www.greenpaintingcontractor.com/
[4] http://naturalfloors.net/
[5] http://www.gilasi.com/
[6] http://ecotecinsulation.com/
[7] http://www.inc.com/best-industries-2012/erin-kim/residential-construction.html
[8] http://www.inc.com/ss/best-industries-2012/issie-lapowsky/8-big-business-opportunities-in-water-conservation
[9] http://www.inc.com/best-industries-2012/darren-dahl/best-business-opportunities-2012.html
[10] http://www.inc.com/best-industries-2012.html


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60 tablets: Enzymatic Therapy, Item# 06309
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$20.95 each
Save 25%
$15.71 each
Seasonal Freedom's unique ingredients enhance your body's immune system, arming it with the defenses to combat various sensitivities. The formula contains a combination of highly-concentrated polyphenols, including luteolin and apigenin, harvested from caper fruit and olive leaf extract. This combination decreases response to sensitivity triggers by up to 70%.
The extracts in Seasonal Freedom contain powerful phytonutrients, which provide antioxidant protection and support:
By supporting healthy immune function, Seasonal Freedom resets the internal response to unavoidable seasonal and environmental sensitivities.
|Supplement Facts
|Dosage and Use


text:
Nike Men's Purdue Boilermakers Madness Basketball Black Shorts
See Price In Cart
Product Information:
Get in the Purdue team spirit in the Nike® Men's Purdue Boilermakers Madness Basketball Shorts. Featuring a team logo embroidered on the lower right leg and team-colored stripes down the sides, you'll dress like your favorite collegiate athletes in these high-performance shorts. Rule the court with integrated Dri-FIT® technology to help wick moisture away and guarantee comfort even through the toughest workout.
- Nike® Purdue Boilermakers Madness Basketball Shorts
- Team logo embroidered on lower right leg
- Team-colored stripes down sides of the short
- Swoosh™ design trademark on lower left leg
- Dri-FIT® technology wicks moisture away to deliver quick-dry comfort
- Exposed elastic waistband and internal drawcord
- Two side pockets
- 12" inseam (size medium)
- Machine washable
- Officially licensed collegiate product
- Fabric: 100% polyester
- Style: 00029679X-PU1
- Nike
Country of Origin: ImportedWeb ID: 22981476


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This particular website will become a place for Practical, simple medical advice.
Things like, take care of problems when you first notice them. Phone your doctor and ask a question. and hundreds more. I just need some time to gather these things.
As you can tell, the website is being remade into something new.


text:
Deep Throated Singing
Burbank may be reeling from a wrongful-death suit brought by the family of a Burbank Police Department veteran who shot himself on a public street, ongoing FBI and grand-jury investigations into police malfeasance and (of course) the upcoming loss of The Tonight Show, soon headed to New York and that whippersnapper Jimmy Fallon. But at least the bucolic suburb still has the distinguished cultural touchstone of Porn Star Karaoke. Located within the cozy confines of old-school red-leatherette lounge Sardo's, the weekly event is a thoroughly bizarre collision of adult-film stars, fan geeks and horndogs that's fast approaching its 10th anniversary of weekly debauchery. Frequently hosted by empress of erotomania Nicki Hunter and often attended by de facto industry godfather Ron Jeremy, this kaleidoscopic mix of off-key caterwauling, cleavage-jamming body shots, torso-tossing exhibitionism and sheer just-for-the-hell-of-it shenanigans is a wonder unique unto itself. The city proclaims itself "The Town Behind the Tinsel," and at Sardo's, you really get an up-close glimpse of what all, er, goes down back there. Sardo's Grill & Lounge, 259 N. Pass Ave., Burbank; every Tuesday, 9 p.m.; free. (818) 846-8126, sardosbar.com.
Tue., April 23, 9 p.m., 2013
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259 N. Pass Ave.
Burbank, CA 91505
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A receiver that employs inherent characteristics of frequency domain representation of the data symbols. By computing a differential-in-frequency function across a large number of OFDM tones, robust estimates of time and frequency offset are obtained. The obtained time and frequency estimates provide control to sampling and frequency offset elements that are interposed between the reliever input and subsequent receiver stages.
1. A receiver of Orthogonal Frequency Division Multiplexing (OFDM) signals comprising:
a time-sampling element responsive to said OFDM signal;
a frequency offset compensation element responsive to time samples developed by said time-sampling element;
a receiving section responsive to output signals of the frequency compensation element, said receiving section including an element that transforms signals related to said output signals of the frequency compensation element to frequency domain to develop thereby frequency domain signals;
a timing offset and estimation element responsive to said frequency domain signals that develops timing offset control signals and applies the developed timing offset control signals to said time-sampling element; and
a frequency offset and estimation element responsive to said frequency domain signals that develops frequency compensation control signals and applies the developed frequency compensation control signals to said frequency offset compensation element.
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This Application is a continuation of application Ser. No. 11/095,978, filed Mar. 31, 2005, now U.S. Pat. No. 7,310,302 issued Dec. 18, 2007, which is a continuation of application Ser. No. 09/311,562, filed May 14, 1999, now U.S. Pat. No. 6,891,792, issued May 10, 2005. This application is also related to application Ser. No. 09/128,738 filed Aug. 5, 1998 by Alamouti, Stolarz, & Becker entitled "Vertical Antenna Adaptive Array", and U.S. Ser. No. 08/796,584 by Alamouti et al., entitled "Method for Frequency Division Duplex Communications," assigned to AT&T Wireless Services and incorporated herein by reference.
The invention relates to a method to synchronize a multicarrier transmission system.
Synchronization techniques for OFDM have been extensively studied: obtaining good performance under a variety of channel conditions with minimal signal processing is challenging. A good OFDM synchronization technique will be applicable to more than the wireless high speed data communications system currently being studied—OFDM is being used or being considered in a variety of LEC networks in the form of ADSL, in Digital Audio Broadcast systems, in cable modems, and in digital television systems. OFDM is a special case of multicarrier transmission systems. The techniques described herein are generally applicable to other forms of multicarrier systems, e.g., discrete multitone (DMT) systems.
The invention uses inherent characteristics of the frequency domain representation of the data symbols. By computing a differential-in-frequency function across a large number of OFDM tones, robust estimates of time and frequency offset can be easily obtained. The technique also allows the system designer to directly trade performance in the presence of channel impairments against signal processing complexity. Analysis and simulation have shown good performance in the presence of noise and channel delay dispersion, impairments that are the harshest in a wireless environment.
Prior techniques for OFDM synchronization have focussed on the time domain representation of the signal. Those that have recognized the translation of time and frequency offset to the frequency domain have apparently not considered the systematic modification of the signal by the offsets.
The problem of joint timing and frequency offset estimation is critical for the proper operation of a digital transmission system. It is also a difficult problem when it comes to system implementation. The problem is compounded by the fact that timing offset may often create similar looking signal impairments to frequency offset. A number of prior studies have attempted to find timing and frequency offset estimation techniques that are robust in the face of a wide variety of impairments present on a wireless channel.
We focus on the problem of joint timing and frequency offset estimation for an OFDM system. We first present a brief overview of an OFDM system. We review prior work in the area and describe our system's requirements as an specific example of OFDM system design. We conclude by showing the performance of the method in the presence of a variety of channel impairments and describing practical limitations of the technique.
Delay spread, that is the time dispersion of a brief transmitted pulse, is a major impediment to high speed data transmission in the outdoors, high mobility wireless environment. Similarly, signal reflections in the landline telephone copper cable plant or in a TV cable systems coaxial cable plant create similar dispersion and make high speed communications over the local access network difficult. In a wireless system, distant signal reflectors can create several microseconds of delay spread. The high mobility (i.e., high vehicle speeds) environment will create a rapidly changing channel. Adaptive channel equalization techniques have been used to combat some of this effect, but are limited in their ability to deal with large amounts of rapidly changing delay spread, especially when the system is transmitting at the high symbol rates needed to attain high throughput. Conversely, using low symbol rates to mitigate channel dispersion will require dense constellations in single carrier systems. Dense signal constellations will be subject to degradation due to noise, interference, and fading.
In an OFDM system, a single higher speed bit stream is separated into a multiplicity of slower speed bit streams, each of the slower bit streams used to modulate one of a set of carriers. The carriers are chosen within a single bandwidth and, for an OFDM system, with their inter-tone spacing chosen to insure orthogonality of the resulting combined waveforms. Generic multicarrier systems are not bound by the strict othogonality constraints but, for ease of implementation will often use very similar techniques to the OFDM system described herein. By designing the transmission in this way, the benefit of low symbol rates can be attained without the penalty of dense constellations—each individual carrier has a sparse constellation, often QPSK. The total capacity of the OFDM system is determined by the union of a large number of these individually sparse constellations. Typically, the OFDM transmitter would be implemented by generating a series of complex numbers, representing the phase of the individual tones, and using the Inverse Discrete Fourier Transform (IDFT) to convert the series of tones into a time domain waveform. For practical reasons, in order to make the analog reconstruction and antialiasing filters realizable, the size of the IDFT (or more often the Inverse Fast Fourier Transform (IFFT)) is usually larger than the number of tones. In addition, extra samples are prepended and appended to the transformed waveform. These "cyclic prefix" and "cyclic suffix" samples make the transmitted signal more robust against time dispersion and timing offset—as long as the received signal, plus its various delayed copies, are sampled within the cyclic extension, the constant amplitude of the received spectrum will be preserved. At the transmitter, the summation of a large number of sinusoids can generate a signal with a large peak-to-average waveform. A peak control function is used to minimize this effect, relaxing the requirements on RF amplifier stages.
Modulated tones occupy only the first group of input tones to the IFFT (about one third of the total number of tones for the OFDM system here). The rest of the IFFT inputs are set to zero, insuring that the output waveform has no signal energy at higher frequencies and thus oversampling the resulting waveform. As stated above, this simplifies the requirement for antialiasing filtering of the final waveform. Besides this oversampling, other redundant information is added to the OFDM waveform—the IFFT waveform samples are cyclically extended both before and after the desired set of samples. For an N point IFFT, the cyclically extended suffix samples are simply copied from the beginning of the waveform as (In the equations here, upper case letters indicate signal representations in the frequency domain. Lower case letters indicate the time domain):
The cyclic prefix is computed similarly, copying the samples at the end of the waveform to the front of the extended waveform.
Two other segments that are added to the IFFT waveform are the windowed section and the guard interval. The guard interval is a period during which the transmitted samples are all zero. At the expense of a slightly reduced transmission efficiency, the presence of this guard interval helps to insure that the samples received during a given OFDM block are not contaminated with delayed samples from a previous block. Since the OFDM system described here will be used in packet mode, it is expected that the transmitter will be turned on and off during each OFDM burst. To prevent the radiated signal from "splattering" outside of its assigned channel, "windowing" of the OFDM samples is used. By shaping the transmitter ramp up and ramp down with a raised cosine pulse shape, the system bandwidth is confined to little more than the bandwidth occupied by the set of OFDM tones alone. Windowing also reduces the system's sensitivity to frequency offset and doppler by reducing the amplitude of the interference contribution from adjacent tones.
The OFDM receiver structure mirrors the operation of the OFDM transmitter. While the technique described here is applicable to a multicast network, that is, a network with one transmitter and several independent receivers, to simplify the description a simple one transmitter, one receiver network is presented. It can readily be seen that each receiver in a multicast network could individually perform the operations described on a common transmitted signal. In the receiver, extra samples are stripped from the received waveform and the resulting waveform is transformed into the frequency domain. Here, assuming that there was no frequency or timing offset in the time domain waveform, a series of tones are processed, with each conveying one of the lower speed bit streams. If QPSK were used at the OFDM transmitter to modulate each tone, then each OFDM tone burst would convey 2 bits of information per tone in the phase of that tone. A simplified OFDM receiver is shown in
While the relatively long symbol period of the OFDM waveform makes the system resistant to delay spread, incorrect timing phase or frequency offset in the received signal will quickly degrade system performance. Most of the extra samples in the time domain waveform insure that the amplitude of the received OFDM spectrum remains constant in the presence of delay spread and timing offset, due to the cyclic shifting property of the Fourier Transform. However, information is conveyed in the phase of the received tones, so the damaging effects of timing offset must be corrected.
Frequency offset has a different effect on the received waveform. While the OFDM transmitter generated orthogonal tones by creating a specific linear harmonic relationship between all the tones, frequency offset shifts each tone by an equal amount, creating an affine relationship between tone frequencies, thus destroying the linear harmonic structure and creating inter-tone interference. Like inter-symbol interference in a single carrier system, frequency offset allows energy from adjacent tones to "bleed" into a desired tone, reducing system performance.
As an example of a practical system, the OFDM system here is intended to provide peak end user data rates of up to 384 kb/s. As shown in
Schmidtl's and Cox's papers in the IEEE Transactions on Communications and in the Proceedings of the International Communications Conference define techniques for estimating time and frequency offset based on signal processing in the time domain, using 'pilot' signals. While the pilot signals are useful for establishing a reference for calculating synchronization parameters, they require that transmit energy be expended and signal bandwidth be consumed that could have been used to transmit end user information.
Moose's technique similarly requires repetition of an OFDM block, essentially using one of the repetitions as a 'pilot' signal. Frequency offset is computed by comparing samples of the first block to the second in the time domain. This technique is only used for frequency offset estimation. It does not address the need for time synchronization.
The work of Pollet, et. al., describes the degradation in system performance when adequate timing synchronization is not used.
Finally, van der Beek, et. al., describe a timing synchronization technique that relies on inherent redundancy in the OFDM time domain waveform. Because the cyclic extension of the FFT samples are simply ordered copies of other samples in the waveform, this technique relies on computing the time correlation between the repeated samples to estimate the timing offset. [J.-J. van de Beek, M. Sandell, M. Isaksson, and P. Borjesson, "Low-complex frame synchronization in OFDM systems," in Proc. ICUPC, November 1995, pp. 982-986.] There are relatively few cyclically extended samples in the OFDM block, so the robustness to noise may be somewhat limited, processing a single OFDM block.
None of the previous techniques process the signals in the frequency domain as the current scheme does, and none recognize the inherent structure of the frequency domain signals that this scheme relies on. Except for van der Beek's scheme, all require the use of redundant pilot signals.
Frequency offset causes each tone in the OFDM cluster to be shifted in frequency by the same amount. The complex OFDM time domain waveform appears to be rotated on a time-sample by time-sample basis by a continuously rotating phasor. While this effect is instructive to understand how to undo the effect of frequency offset, there is nothing immediately obvious about the time domain waveform that suggests how the frequency offset can be estimated. Timing offset similarly shifts all samples by a fixed time interval which, again by itself, gives little information that allows estimation of the amount of offset when observing the time domain waveform. The current method performs estimation of the time and frequency error in the frequency domain, unlike previous approaches which did their estimation in the time domain. In addition to realizing the other advantages described herein, a frequency domain approach to synchronization simplifies the architecture of the receiver.
Timing Offset Correction
First, consider the effect of timing offset on the OFDM tones.
In contrast,
To understand how timing offset has changed the received signal, first consider an OFDM waveform xn, generated from a series of OFDM tones, Xm:
At the OFDM receiver, the waveform is assumed to have a timing offset, Δt. By the shifting property of the Fourier Transform, a time delayed signal in the time domain
Has as its transform:
So, as demonstrated in
For any adjacent pair of tones, Ri and Ri+1,
This suggests an approach that could be used to estimate the amount of timing offset: measure the differential phase from one tone to the next and adjust the sampling point to compensate. It is instructive to note that as shown in
Two useful characteristics of the algorithm become apparent: (1) that noise effects may be partially or mostly mitigated by the tone-to-tone differential nature of the algorithm and (2) that the essential nature of the algorithm creates a weighting of timing estimates based on the likely validity of each estimate. These observations are explained in greater depth below.
One may think of the process of estimating timing offset as the differential detection of tone phase from one tone to its neighbor, in frequency. For QPSK, individual tone modulation can be removed from the estimate by raising the differentially detected phase to the 4th power. Alternatively, each tone phase could be compared to the transmitted signal constellation and the complex conjugate of the nearest signal used to rotate the signal to the positive real axis. While noise and other impairments will occasionally create incorrect decisions about the transmitted signal and thus the received signal phase, these effects will average out across a number of estimates. As another alternative, if the correct transmitted data sequence were known in advance by the receiver, this information could be used to determine the expected phase of each tone. This information could be used as described to rotate the received signal to the positive real axis. To gain the signal to noise advantage of averaging the tone-to-tone estimates, it is possible to average the phase of each measurement. For N tones in an OFDM block, this approach requires the equivalent of N−1 arctangent calculations, which is prohibitively expensive in a real-time system. A preferred embodiment, which gives better performance under many channel conditions, is to separately average the in-phase and quadrature components of the processed constellation points and calculate the phase of that signal to determine the timing offset correction.
Frequency Offset Correction
Having addressed timing offset, a technique to estimate frequency offset is needed.
As before, assume that a series of samples, xn are generated at the transmitter. With a frequency offset of Δf the received samples, rn are:
or, combining this with the previous expression for the received tones,
As was used for estimating timing offset, frequency offset is similarly estimated by calculating the average phase of the ensemble of the received tones. Again, the 4th power signals may be used to remove the modulation. Alternatively, the other techniques described earlier may be employed to estimate the transmitter phase based on known or inferred transmit data. As was the case for timing offset, it is possible to calculate either the phase of the average signal or the average of the phases of the individual signals. For moderate amounts of frequency offset (less than 70% of the tone spacing), either technique works well. In fact, the lower complexity estimate (phase of the mean signal) tolerates larger frequency offsets well—more than 110% of the tone spacing. For typical OFDM systems, frequency offsets and Doppler shifts will generally be a fraction of the tone spacing.
Phase Offset Correction
Finally, it is necessary to consider the effect of phase offset in the channel. The effect of the phase rotation can be expressed as:
So the received tones are given by:
The constant rotation factor can be factored out of the summation, indicating that a constant phase rotation of the baseband waveform results in a uniform rotation of each of the transformed tones.
A constant phase offset in the channel gives the same appearance to the received signal constellation that frequency offset produces. By measuring the rotation of the constellation and driving that parameter to zero by modifying the baseband rotator's phase updates, both frequency offset as well as phase rotation of the channel will be compensated for. Actually, in terms of the final signal constellation, the phase rotation caused by frequency and phase offset will not be the limiting factors—a system which uses differential (in time) detection of the signal phase is immune to fixed or (moderate amounts of) changing rotation. The most significant degradation caused by frequency offset is the inter-tone interference caused by the loss of orthogonality, which only requires that the frequency offset be approximated—phase lock is not essential.
To determine the utility of the timing and frequency offset estimation algorithm, it is necessary to assess its performance in the presence of a variety of channel impairments. In particular, it is necessary to consider how the algorithm behaves in the presence of the following impairments:
These impairments were simulated using Mathcad both individually and in various combinations. Results are presented below.
First, AWGN was simulated at varying signal to noise ratios. Even when the SNR was 6 dB, giving a 4th power differential in frequency constellation as shown in
It can be seen from these AWGN results that, even in the presence of poor SNRs, the algorithm tracks timing offset well, preserving the direction of adjustment and, even in the worst case, preserving the general magnitude of the adjustment needed. Again, it must be noted that these results are for single OFDM block processing. Averaging estimates over successive blocks improves the estimate in the presence of noise. At least in AWGN, simulation results show that the mean of the phase estimate tracks more closely to the actual timing offset than the phase of the mean estimate. While the former estimate is more costly, from a signal processing perspective, with fewer tones' phases differentially compared and with multi-block averaging, it may be preferable to use this method under some circumstances.
Next, it is instructive to look at the effect that frequency offset has on timing offset estimation. As
While these numbers show the overall performance of the timing offset estimator, it is instructive to examine the signal constellation that the estimator is working with.
Finally, simulations of the timing offset estimator were run with delay spread. In one representative experiment, two equal rays with a spacing of 20.8 μsec (46 samples) were generated. With 10 samples of timing offset, it would be expected that the estimator would indicate that 18 samples of correction was needed1. With a 10 dB SNR and 0.1 tone frequency offset, the timing offset estimator indicated 15.7 samples for the mean of the phase estimate and 19.8 samples for the phase of the mean estimate. As shown by the real-time DSP results, delay spread has minimal effect on the timing recovery algorithm. 1 With 10 samples of timing offset in the opposite direction to the 46 samples delay spread, the centroid of the channel response would be (46−10)/2=18 samples from the initial sampling point.
The frequency offset estimator was next tried under simulated channel conditions. It is first worth noting, however, that it is not possible to estimate the frequency offset in the presence of timing offset. Timing offset creates an ever-increasing rotation of the tone signal constellation, making phase measurements meaningless. So, for the remaining simulations, it is assumed that either the timing offset has been adjusted to zero by adjusting the sample clock or the individual tones have been rotated by the proper amount to compensate for the timing offset.
We have observed from the above that (1) the noise perturbation of the signal phase does not create a significant problem for timing estimation and (2) the algorithm inherently provides a desirable weighting of timing estimates. These ideas are expanded in this section to provide some intuition about why the timing offset algorithm behaves as well as it does.
First consider the effect of noise. In
The wireless delay dispersive channel that this OFDM system must endure creates frequency selective fading. From this, one might suspect that tones which are in the middle of a frequency null will have poor SNR and cannot be relied on to provide accurate phase estimates to drive the timing algorithm. Worse, the attenuation of one tone generally alters two phase estimates—if tonei+1 is near an amplitude null, the phase estimate derived from comparing tonei to tonei+1 as well as the phase estimate obtained from tonei+1 and tonei+2 may both be corrupted. Experimental results have shown remarkable performance in the presence of this frequency selective fading. Even when large clusters of tones are suppressed, the timing recovery algorithm performs well. Understanding why this was so provided additional insight into the power of this algorithm.
As shown, each tone is used to estimate the phase of its neighbor. This is done by multiplying the complex conjugate of the first tone with the second tone. This process preserves amplitude information. By collecting the sums of the real and imaginary parts separately, each differential tone pair adds to the phase estimate with an imaginary component proportional to the phase difference and to the amplitude. Further, each differential tone pair contributes to the real component proportionally to the amplitudes of the two tones. Thus, low amplitude, faded, and, probably noisy tones make a much smaller contribution to the overall timing estimate than do high amplitude, most likely clean tones do. The result is that frequency selective fading (i.e., a time dispersive channel) has little effect on the timing estimate. Further, since this algorithm raises the differential signal to the 4th power to remove QPSK modulation, any amplitude differences between tone pairs will be further accentuated.
In the preceding description, it has been assumed that all of the OFDM tones would be used to do timing estimation. With 189 active tones, this provides 188 differential phase estimates to be averaged. The signal processing, on a per tone pair basis, is moderate, but cannot be neglected. First, to compute the product of a tone with its neighbor's complex conjugate requires 4 real multiplies and two real adds. Then, to raise this signal to the 4th power requires 12 real multiples and 3 adds, so the total number of operations is 16 multiplies and 5 adds. It is likely that this can be improved slightly, but this still will be a moderate amount of signal processing. If all 188 tone pairs are used, the receiver will obviously be in the best position to get a good timing estimate, but it is instructive to see just how few tone pairs were sufficient.
In the presence of noise and other impairments, one tone pair is not sufficient to allow the receiver to properly estimate the proper timing instant. With two or more tone pairs, the noise and interference effects described above are observed. As more and more tones pairs are used, the contribution of each individual tone pair's phase estimate is lessened so any applicable degradation of that estimate is likewise reduced.
In one embodiment of the invention, it is possible to average the phase difference between each tone pair to arrive at an overall phase estimate and then to derive synchronization information from that average phase. In the preferred embodiment of the invention, the real and imaginary components of the differentially detected difference between the tones are each summed to arrive at the real and imaginary parts of an overall correction vector. The phase of this overall correction vector is then calculated, representing the overall synchronization signal. By performing the calculations in this manner a simpler algorithm results, with one arctangent calculation required instead of one arctangent calculation per tone pair.
The resulting invention provides a method for OFDM systems that is capable of separately estimating time and frequency offset in the presence of severe channel impairments, requiring no training sequences or other overhead. The algorithm is capable of deriving high-quality estimates on a single OFDM block or, with lower real-time overhead, could be used to track drift over a series of OFDM blocks.
Various illustrative examples of the invention have been described in detail. In addition, however, many modifications and changes can be made to these examples without departing from the nature and spirit of the invention.
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