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Tech Beat - September 3, 2013

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Editor: Michael Baum
Date created: September 3, 2013
Date Modified: September 3, 2013 
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NIST Ytterbium Atomic Clocks Set Record for Stability

A pair of experimental atomic clocks based on ytterbium atoms at the National Institute of Standards and Technology (NIST) has set a new record for stability. The clocks act like 21st-century pendulums or metronomes that could swing back and forth with perfect timing for a period comparable to the age of the universe.

yb clock
NIST's ultra-stable ytterbium lattice atomic clock. Ytterbium atoms are generated in an oven (large metal cylinder on the left) and sent to a vacuum chamber in the center of the photo to be manipulated and probed by lasers. Laser light is transported to the clock by five fibers (such as the yellow fiber in the lower center of the photo).
Credit: Burrus/NIST
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NIST physicists report in the Aug. 22 issue of Science Express that the ytterbium clocks' tick is more stable than any other atomic clock.* Stability can be thought of as how precisely the duration of each tick matches every other tick. The ytterbium clock ticks are stable to within less than two parts in 1 quintillion (1 followed by 18 zeros), roughly 10 times better than the previous best published results for other atomic clocks.

This dramatic breakthrough has the potential for significant impacts not only on timekeeping, but also on a broad range of sensors measuring quantities that have tiny effects on the ticking rate of atomic clocks, including gravity, magnetic fields, and temperature. And it is a major step in the evolution of next-generation atomic clocks under development worldwide, including at NIST and at JILA, the joint research institute operated by NIST and the University of Colorado Boulder.

"The stability of the ytterbium lattice clocks opens the door to a number of exciting practical applications of high-performance timekeeping," NIST physicist and co-author Andrew Ludlow says.

Each of NIST's ytterbium clocks relies on about 10,000 rare-earth atoms cooled to 10 microkelvin (10 millionths of a degree above absolute zero) and trapped in an optical lattice—a series of pancake-shaped wells made of laser light. Another laser that "ticks" 518 trillion times per second provokes a transition between two energy levels in the atoms. The large number of atoms is key to the clocks' high stability.

The ticks of any atomic clock must be averaged for some period to provide the best results. One key benefit of the very high stability of the ytterbium clocks is that precise results can be achieved very quickly. For example, the current U.S. civilian time standard, the NIST-F1 cesium fountain clock, must be averaged for about 400,000 seconds (about five days) to achieve its best performance. The new ytterbium clocks achieve that same result in about one second of averaging time.

Given this high level of stability the ytterbium clocks can make measurements extremely rapidly—in real time in many cases—which could be important in rapidly changing application settings, such as the factory floor and the natural environment.

A key advance enabling the milestone performance of the ytterbium clocks was the recent construction of a second version of the clock to measure and improve the performance of the original, developed since 2003. Along the way, NIST scientists have made several improvements to both clocks, including the development of an ultra-low-noise laser used to excite the atoms, and the discovery of a method to cancel disruptive effects caused by collisions between atoms.

The ytterbium clocks' stability record is different from the performance levels previously publicized for NIST-F1, which is traceable to the international system of units, and NIST experimental optical clocks based on single ions, such as the aluminum quantum logic clock or the mercury ion clock.** NIST-F1 and the ion clocks were evaluated based on systematic uncertainty, another important metric for standard atomic clocks. NIST-F1's performance is described in terms of accuracy, which refers to how closely the clock realizes the cesium atom's known frequency, or natural vibration rate. Accuracy is crucial for time measurements that must be traced to a primary standard.

NIST scientists plan to measure the accuracy of the ytterbium clocks in the near future, and the accuracy of other high performance optical atomic clocks is under study at NIST and JILA. The research is funded in part by the Defense Advanced Research Projects Agency and the National Aeronautics and Space Administration (NASA).

*N. Hinkley, J.A. Sherman, N.B. Phillips, M. Schioppo, N.D. Lemke, K. Beloy, M. Pizzocaro, C.W. Oates, A.D. Ludlow. An atomic clock with 10-18 instability. Science Express, Aug. 22, 2013.
**See 2010 NIST press release, "NIST's Second 'Quantum Logic Clock' Based on Aluminum Ion is Now World's Most Precise Clock," at www.nist.gov/pml/div688/logicclock_020410.cfm.

Media Contact: Laura Ost, laura.ost@nist.gov, 303-497-4880

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Knowing Exposure Risks Important to Saving Structures from Wildfires

A recent study of one of California's most devastating wildland fires by the National Institute of Standards and Technology (NIST) and the U.S. Forest Service (USFS) strongly suggests that measures for reducing structural damage and property loss from wildland urban interface (WUI)* fires are most effective when they are based on accurate assessments of exposure risks both for individual structures and the community as a whole.

witch fire
A wooded area aflame during the 2007 Witch Creek/Guejito wildfire in Southern California. A new report from NIST looks at the fire's impact on structures in one community based on their pre-fire exposure risk to direct fire contact and embers (both seen in the photo).
Credit: With permission from Dan Tentler, lightbending.net
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The report also describes how the NIST-USFS WUI Hazard Scale provides a state-of-the-art tool for making such assessments and how that data could be linked to improved building codes, standards and practices that will help communities better resist the threat of wildfires.

The Witch Creek/Guejito WUI fire (commonly known as the Witch Fire) was the largest of a series of wildfires that began burning across Southern California on Oct. 20, 2007. It affected areas north and northeast of San Diego, starting in Witch Creek Canyon near Santa Ysabel and quickly spreading westward toward the coast because of strong Santa Ana winds. The Witch Fire burned some 80,000 hectares (nearly 200,000 acres), destroyed more than 1,600 structures, caused an estimated $1.8 billion in property damages and cost $18 million to fight. It also was responsible for two civilian deaths and 39 firefighter injuries.

A NIST-USFS WUI team worked in collaboration with the California Department of Forestry and Fire Protection (CAL FIRE) and the City of San Diego to collect post-incident data within the Witch Fire perimeter. The team focused its effort on The Trails development at Rancho Bernardo, north of San Diego. There were 274 homes in The Trails, with 245 within the fire perimeter. Seventy-four homes were completely destroyed and 16 were partly damaged. Field measurements made by the NIST team included structure particulars, specifically roof type; proximity of combustibles to the structure; and damage to wildland and residential vegetation. Documentation included more than 11,000 photographs.

The data collected and analyzed were used in two separate NIST-USFS reports. The first, issued in 2009, created a detailed timeline of the Witch Fire, tracked its impact on the community, and documented defensive actions taken by homeowners and first responders. The latest study evaluates the effectiveness of those mitigation techniques addressing exposure risks—as defined by the WUI Hazard Scale—associated with direct fire contact and ignition by embers.

"This is the first time anyone has looked at wildfire impact by evaluating pre-event exposure risks throughout an entire community and how those risks affected the defensive actions that were in place," says Alexander Maranghides, lead author of both Witch Fire reports.

What the researchers found was that the majority of defensive strategies used in The Trails were effective and that the level of effectiveness was correlated to fire and ember exposure. Damage and destruction were more prevalent in structures assessed by the WUI Hazard Scale as having been at highest risk from fire and embers. Accordingly, defensive actions were more than twice as effective in saving structures in low-exposure sections of the community as compared to high-risk areas.

Maranghides says that a pre-event knowledge of exposure risks also may be helpful in determining how firefighters attack a WUI fire. "Our data show that it's probably best to fight fires in low-exposure areas because there's a greater chance that they can be suppressed and with less danger to the crews," he explains. "It may be better to sacrifice structures in high-exposure areas than risk the loss of firefighter lives in unwinnable situations."

Useful links:

*USFS defines the wildland urban interface, or WUI, as an "area where structures and other human development meet or intermingle with undeveloped wildland or vegetative fuels."

Media Contact: Michael E. Newman, michael.newman@nist.gov, 301-975-3025

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Air Conditioner "Evolves" in Novel NIST Study

Played out on a computer over hundreds of generations, a survival-of-the-fittest programming method adapted by National Institute of Standards and Technology (NIST) researchers has spawned, of all things, the design for a more efficient rooftop air-conditioning system.

air conditioner
A new NIST tool combining principles of engineering with those of natural evolution yielded the design for a more energy-efficient roof-top air-conditioning unit.
Credit: © pedrosala - Fotolia.com

The evolutionary tack optimized the sequence of connections within the snaking arrangement of cooling tubes in the air conditioner's heat exchanger. The unit's U.S. manufacturer subsequently implemented the changes as a prototype for NIST. The computer-generated design yielded a 3 percent gain in overall performance, confirming the results of prior analysis by NIST researchers.

That amount of improvement could be enough for a manufacturer to achieve compliance with increasingly stringent energy efficiency standards. It also could translate into material savings—a reduction in the amount of costly copper tubing in a heat exchanger without sacrificing performance.

"What we're doing is identifying the best possible route through the heat exchanger for the refrigerant to follow so that it achieves the highest efficiency" explains NIST researcher David Yashar. "Given that the unit we studied has 144 tubes, the number of possible routes determined by a sequence of tube connections is astronomical, impossible for a human to explore using traditional methods."

The new NIST approach optimizes the connections among refrigerant-containing tubes so that maximum cooling occurs. This entails matching characteristics of incoming air, especially its temperature and velocity, with the temperature and other characteristics of the refrigerant.

"The objective is to optimally pair air and refrigerant at every location in the heat exchanger," Yashar explains. That kind of matchmaking can be extraordinarily difficult, he says, largely because the flow of air over the winding circuitry often is very uneven.

The proof-of-concept experiment* with the rooftop unit—like the ones used to cool office and apartment buildings—demonstrated the practical utility of the NIST approach of combining principles of engineering with those of natural evolution.

Yashar and colleague Sunil Lee first used a laser-based method to map how much and how fast air flows over the original refrigerant circuitry. These data were grist for a NIST computer model that simulates heat-exchanger performance. The team used this model with an algorithm that mimics the laws of evolution. The algorithm develops a population of tubing arrangements and the model evaluates the performance of each design in the population. The best potential tubing circuitries from one population served as the starting set for the next generation. After the number-crunching for several hundred generations of circuitry options was completed, a top choice emerged.

The ultimate solution was a circuitry design that increased the heat exchanger's potential cooling capacity by 8 percent and, when used to replace the existing design, boosted the entire system's energy efficiency by 3 percent.

In upcoming studies, the NIST researchers will test their optimization method on a window air-conditioning unit and a full-house, central air-conditioning system.

*D. Yashar and S. Lee, Improving the Performance of a Roof Top Air-Conditioning Unit by Refrigerant Circuitry Optimization (NIST Technical Note 1806), July 2013. Downloadable from: www.nist.gov/manuscript-publication-search.cfm?pub_id=914090

Media Contact: Mark Bello, mark.bello@nist.gov, 301-975-3776

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Limestone Powder Enhances Performance of 'Green' Concrete

Adding limestone powder to "green" concrete mixtures—those containing substantial amounts of fly ash, a byproduct of coal-burning power plants—can significantly improve performance, report* researchers from the National Institute of Standards and Technology (NIST) and the Federal Highway Administration (FHWA).

The promising laboratory results suggest a path to greatly increasing the use of fly ash in concrete, leading to sizable reductions in greenhouse gas emissions, energy use, construction costs and landfill volumes. Global production of cement for concrete accounts for 5 to 8 percent of human-caused greenhouse gas emissions.

Currently, fly ash accounts, on average, for about 15 percent of the binder powders in the ready-made concrete used in the United States. To produce a more green concrete, NIST is researching new material combinations and procedures that could help the industry use fly ash to routinely replace 40 to 50 percent of the ordinary portland cement (OPC), the main binding and hardening agent in concrete.

Because of delays in setting times and questions about its strength in the first few days after application that both "impact its constructability," says NIST chemical engineer Dale Bentz, "green concrete has been a tough sell in large parts of the construction industry." However, Bentz and his FHWA colleagues found that a "judicious combination of fine limestone powder" can help to put these concerns to rest.

So-called high-volume fly ash "ternary" mixtures (including some limestone) that replace between 40 percent and 60 percent of the cement portion not only set at rates comparable to those for typical concrete, but also were superior in terms of key properties.

Initially, the strength of the green concrete mixtures after 28 days slightly lagged that of concrete without any fly ash. However, the team was able to tweak their fly ash-limestone-OPC mixture to overcome the gap, primarily by lowering the water-to-powder ratio and switching to a different standard composition of OPC (ASTM Type III).

Today, global production of OPC totals about 3.5 billion metric tons (3.85 billion tons) annually. Generation of each ton of OPC emits about a ton of carbon dioxide into the atmosphere.

Greater use of high-volume fly ash mixtures could significantly reduce this environmental burden and, at the same time, reduce costs for concrete construction, says Bentz.

For Bentz and his team, the next research challenge is to test their limestone-enhanced mixtures in the field, where curing conditions can vary.

*D.P. Bentz, J. Tanesi and A. Ardani. Ternary blends for controlling cost and carbon content. Concrete International, August 2013.

Media Contact: Mark Bello, mark.bello@nist.gov, 301-975-3776

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Power of 10: Organizations Move Closer to 2013 Baldrige Award

Ten U.S. organizations are this year’s top candidates for the Malcolm Baldrige National Quality Award, the nation's highest recognition for organizational performance excellence. The Baldrige Panel of Judges selected eight organizations in the health care category, one in education and one nonprofit for the final review stage for the 2013 award. Starting this month, teams of experts will make site visits to these organizations to clarify questions and verify information submitted in award applications.

The Baldrige Performance Excellence Program (BPEP) received 22 applications in 2013.* All of the applicants were evaluated rigorously by an independent board of examiners in seven areas defined by the Baldrige Criteria for Performance Excellence: leadership; strategic planning; customer focus; measurement, analysis and knowledge management; workforce focus; operations focus; and results. Examiners will provide around 1,000 hours of review to each applicant receiving a site visit, and all applicants will receive a detailed report on the organization's strengths and opportunities for improvement.

The 2013 Baldrige Award recipients are expected to be named in late November, 2013. The awardees will be honored at a ceremony during the Quest for Excellence conference, April 7-9, 2014, in Baltimore, Md.

The Baldrige Award was established by Congress in 1987. The BPEP is managed by the National Institute of Standards and Technology (NIST) in cooperation with the private sector. It also is a partner in the Baldrige Enterprise, which includes the private-sector Foundation for the Malcolm Baldrige National Quality Award, the Alliance for Performance Excellence—a body made up of the 30-plus state, local, regional and sector-specific Baldrige-based programs serving nearly all 50 states; and ASQ, an international organization promoting quality.

The program helps U.S. organizations succeed in today’s competitive marketplace by providing organizational assessment tools and criteria; educating leaders in businesses, schools, health care organizations, and government and nonprofit organizations about the practices of national role models; and recognizing them with the Baldrige Award in six categories: manufacturing, service, small business, health care, education and nonprofit.

The Baldrige Award is not given for specific products or services. Since 1988, 93 organizations have received the award.

For more information on the Baldrige Performance Excellence Program and the Baldrige Award, see www.nist.gov/baldrige.

*See “2013 Baldrige Award Process Kicks Off with New Applicants” at www.nist.gov/public_affairs/tech-beat/tb20130611.cfm#baldrige.

Media Contact: Michael E. Newman, michael.newman@nist.gov, 301-975-3025

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Learn About Navigating the National Cybersecurity Education Interstate Highway at NIST, Sept. 17-19

The National Initiative for Cybersecurity Education (NICE) is hosting its fourth annual “Shaping the Future of Cybersecurity Education Workshop” September 17-19, 2013, at the National Institute of Standards and Technology (NIST) laboratories in Gaithersburg, Md.

NICE is a national campaign designed to improve the cyber behavior, skills and knowledge of every segment of the population, enabling a safer cyberspace.

The workshop, “Navigating the National Cybersecurity Education Interstate Highway,” will highlight cybersecurity education concepts, tools and best practices with a focus on achievements at the state and federal levels. The goal is to highlight cybersecurity awareness, education and training programs that can be adopted, copied, used or built-on by small businesses, educational institutions, industry and government to advance the strategic goals of NICE.

The September workshop offers four tracks: Awareness; Formal Education; Professionalization, Certifications, Training and Maintaining a Competitive Cybersecurity Workforce; and the Role of States in the National Cybersecurity Interstate Highway—Competitions, CAE Schools and Students. Topics will include what’s happening at the community college and state level, to free federal training resources to small business security best practices. The track 4 offering, “Defense Against the Dark Arts,” is a must for all cybersecurity experts who are Harry Potter fans.

State-of-the-art techniques will be highlighted, including training and mentoring in virtual environments, as well as using competitions to advance cybersecurity education. In addition to picking up new techniques that attendees can use on the job, experts will provide updates on NIST initiatives, including Executive Order 13636 “Improving Critical Infrastructure Cybersecurity” and Cybersecurity in the Cloud.

For more information, or to register, see the workshop Web page at www.nist.gov/itl/csd/4th-annual-nice-workshop-september-17-19-2013.cfm.

Media Contact: Evelyn Brown, evelyn.brown@nist.gov, 301-975-5661

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NIST October Workshop to Explore Intersection of Cloud Computing and Mobility

As part of its ongoing cloud computing forum and workshop series, the National Institute of Standards and Technology (NIST) is hosting “The Intersection of Cloud and Mobility,” October 1-3, 2013, at its Gaithersburg, Md., campus. The workshop will bring together experts in the field of cloud and mobility for plenary talks, panel discussion, facilitated breakout discussions and networking.

cloud
Credit: ©belekekin-Fotolia.com

The audience of leaders in cloud computing and mobility from industry, government and academia will explore the advantages of using low-end mobile devices to access sophisticated cloud-based resources.

On day one, agency executives will address federal perspectives and visions for cloud and mobility. Panels will illuminate the current state of cloud and mobile, and share near and future applications and technologies.

The task of the second day is to discuss current challenges at the intersection of cloud and mobility and to share lessons learned. Presentations will explore key challenges such as privacy, security, business/economic and behavioral issues. Another session will focus on the challenges to the fields of finance, first responders, and defense and intelligence.

Developing a path forward based on the discussion of the first two days is the goal of day three. At the end of each day, participants will work together in breakout sessions focused on the day’s business.

As with past cloud computing workshops, the first day of the meeting also will cover progress on the U.S. Government Cloud Computing Technology Roadmap Priority Action Plans. The session will focus on metrics, standards, service level agreements and security reference architecture.

The workshop and forum is introducing a new discussion topic this year. NIST now hosts a public working group on cloud and accessibility. The goal of the working group is to enable individuals to access information resources in a format of their choice from a broad range of devices. This adds ease-of-use to electronic devices. Several breakout sessions will discuss this extension of accessibility.

For more information on “The Intersection of Cloud and Mobility,” or to register, see www.nist.gov/itl/cloud/intersection-of-cloud-and-mobility.cfm.

Media Contact: Evelyn Brown, evelyn.brown@nist.gov, 301-975-5661

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Two Experts Named to Earthquake Advisory Board

Two earthquake authorities from academia and the private sector have been appointed by Patrick Gallagher, Under Secretary of Commerce for Standards and Technology and Director of the National Institute of Standards and Technology (NIST), to serve on the Advisory Committee on Earthquake Hazards Reduction (ACEHR) of the National Earthquake Hazards Reduction Program (NEHRP).

Established by the Earthquake Hazards Reduction Act of 1977, NEHRP is the federal government’s program to reduce the risks to life and property from earthquakes. NEHRP consists of four federal agencies: the Federal Emergency Management Agency (FEMA), the National Science Foundation (NSF), the United States Geological Survey (USGS) and NIST, which serves as lead agency.

The new ACEHR members, whose terms extend to July 31, 2016, are: James Goltz, branch chief emeritus, Earthquake, Tsunami and Volcanic Hazards Program, California Emergency Management Agency, South Pasadena, Calif., and Peter May, distinguished professor and chair, Department of Political Science, University of Washington, Seattle, Wash. They join a group of 10 previously appointed academic, industry and government experts on the ACEHR.

The committee’s responsibilities include assessing:

  • Trends and developments in the science and engineering of earthquake hazards reduction;
  • The effectiveness of NEHRP in performing its statutory activities (improved design and construction methods and practices; land use controls and redevelopment; prediction techniques and early-warning systems; coordinated emergency preparedness plans; and public education and involvement programs);
  • Any need to revise NEHRP; and
  • The management, coordination, implementation and activities of NEHRP.

More information on NEHRP and the ACEHR can be found at www.nehrp.gov.

Media Contact: Mark Bello, mark.bello@nist.gov, 301-975-3776

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