EL Highlights for August 2011
NIST Engineering Laboratory (EL) Researchers Characterize a Large-Area Light Emitting Diode (LED) Based Solar Simulator
Researchers in the Engineering Laboratory's Building Environment Division set up and investigated the performance of a prototype, large-area solar simulator based entirely on individually-controlled LEDs. This simulator is an important step in a series of unique measurement capabilities that are being developed to significantly increase the measurement science capabilities to characterize photovoltaic (PV) cells and modules at NIST.
Advancements in LED technology over the past five years, particularly in increased light output and wavelength selectability, have made it feasible to use LED arrays over the wavelength range of 350 nm to 1100 nm (or beyond) to construct the solar spectrum of any form under indoor testing conditions. The advantages of LEDs over the traditional xenon or sodium arc lamps as light sources are in the long lifetimes, reliability of performance, and precise control over the emission characteristics of individual LEDs. The design of this LED simulator is based on a tapered waveguide constructed from aluminum, with a highly polished and reflective interior surface. An LED array illuminates into each waveguide, which facilitates the mixing of different colors, producing a uniformly illuminated area at the exit plane.
In a recent manuscript, "Towards realization of large-area, LED-based solar simulator", by B. H. Hamadani (EL), K. Chua, J. Roller (EL), M. J. Bennahmias, B. Campbell (EL), H. W. Yoon (EL) and B. Dougherty (EL), submitted for publication in the journal of Progress in Photovoltaics: Research and Applications, the authors outline the results of their measurements with the use of two LED arrays and two waveguides to produce a close version of the standard solar spectrum (AM 1.5) with better than 90 % uniformity over an area of 25 cm by 50 cm. They evaluated the spectral output, the spatial uniformity, and the temporal stability of the simulator in both constant current mode and pulsed-mode LED operation, and compared the data with International Electrotechnical Commission (IEC) standards on solar simulators for class rating. Further improvements and expansion to a larger size with more light intensity are currently in the works; however, these initial results show great promise for the viability of this technology for indoor characterization of PV cells and modules.
CONTACT: Behrang Hamadani (NIST), 301 975 5548
NIST Publishes Final Version of Industrial Control Systems Security Guide
NIST announced the final publication of Special Publication 800-82, Guide to Industrial Control System (ICS) Security. Special Publication 800-82 provides guidance on how to secure industrial control systems, including supervisory control and data acquisition (SCADA) systems, distributed control systems, and other control system configurations such as programmable logic controllers, while addressing their unique performance, reliability, and safety requirements. Special Publication 800-82 provides an overview of industrial control systems and typical system topologies, identifies typical threats and vulnerabilities to these systems, and provides recommended security countermeasures to mitigate the associated risks.
Finalized after three rounds of public review and comment, the guide is directed specifically to federally-owned or operated industrial control systems, including those run by private contractors on behalf of the federal government. However, the guide's potential audience is far larger and more diverse than the federal government. In fact, about 90 percent of the nation's critical infrastructure is privately owned.
The guide responds to responsibilities assigned to NIST under the Federal Information Security Management Act (FISMA). The law directs NIST to develop information security standards and guidelines for non-national security federal information systems. While these FISMA-related specifications are not mandatory for the private sector or state and local governments, many businesses and other organizations have adopted the NIST-developed standards and guidelines. Drafts of the new ICS document have been downloaded more than 1,000,000 times, and the guide already is referenced in industry-specific security publications.
Contact: Keith Stouffer, (301) 975-3877
NIST-Tested Smart Phones Help Save Lives in Afghanistan
A platoon of U.S. soldiers in Afghanistan attributes part of their success in a battle with Taliban forces to the use of NIST-tested smart phones provided to them through the DARPA Transformative Apps program. According to an email report sent from the DARPA Field Service Representative stationed in Afghanistan to the members of the DARPA and NIST team, a section of U.S. soldiers was nearly surrounded by Taliban forces on June 25. A second section was informed of this and used an application on the DARPA-provided Dell Streak smart phone to map the area and accurately determine the distance and location of the enemy forces. With this information, they fired several high explosive rounds at the enemy position, and the firefight died down quickly. According to the mortar team, if they had not used the phone, the U.S. soldiers would have needed to visually estimate the range and their rounds would have been much less accurate.
The goal of the DARPA Transformative Apps program is to place the right mobile software applications ("apps") into the hands of warfighters as they are needed. In the role as the Independent Evaluation Team, NIST staff assessed the capabilities of software apps developed by the program to measure and help advance technical progress, ensuring that the systems provide maximum benefit to the warfighters.
Contact: Craig Schlenoff, (301) 975-3456, and Brian Weiss, (301) 975-4373
NIST Engineering Laboratory (EL) Delivers Zero Gravity Metrology Sensor to NASA
EL Information Systems Division researcher Nick Dagalakis delivered the prototype of a zero gravity volumetric sensor to engineers from the NASA Goddard Space Flight Center (NASA/GSFC). NASA funded the development of this experimental sensor, called "Cryogenic Fuel Gauge for zero gravity environments using capacitance tomography," for the purpose of creating better fuel tank imaging sensors under low gravity operating conditions. NIST designed, fabricated, and performed dynamic testing of the sensor for NASA. Part of the work involved the fabrication of innovative flexible arrays of specially-arranged micro devices by EL guest researcher Dr. Seung Ho Yang. The electronic circuitry was developed with the collaboration of researchers from the PML Quantum Electrical Metrology Division, Dr. Rae Duk Lee and Dr. Yicheng Wang. The sensor was successfully tested and then moved to a new NASA/GSFC laboratory where work will continue in order to make the sensor practical and space-worthy for use in NASA space craft fuel tanks.
Contact: Nick Dagalakis, (301) 975-5845
NIST Engineering Laboratory (EL) Researcher Wins Magazine of Concrete Research Best Paper of 2010 Prize
The journal Magazine of Concrete Research selected Dale Bentz, a researcher in the EL Materials and Construction Research Division, for the Best Paper of 2010 Award for his manuscript, "Blending different fineness cements to engineer the properties of cement-based materials." To support fast track and high rise construction in the U.S., cements have become progressively finer over the years. While finer cements provide higher early-age strengths, this is accompanied by greater autogenous stresses and amplified heat release at early ages, both of which can contribute to an increased propensity for early-age cracking. As cement manufacturers are generally hesitant to produce a wide variety of products, these same fine cements are employed in transportation and other constructions in which durability is generally more critical than achieving high early-age strengths.
The research in the prize-winning paper demonstrated that a set of two cements, one coarse and the other fine, could be systematically blended in varying proportions to provide materials with a wide range of early-age properties. In many cases, the measured properties of the blended systems could be adequately characterized by a simple law of mixtures, enabling the a priori design of blends with desired performance. Several international cement companies currently are pursuing the approaches developed in the paper for blending coarse and fine cements. The prize will be presented to Mr. Bentz at a special luncheon of the Institution of Civil Engineers in London on October 24, 2011.
CONTACT: Dale Bentz (EL), 301 975 5865
NIST Engineering Laboratory (EL) Researcher Wins Best Poster Award at the 13th International Congress on the Chemistry of Cement (ICCC)
Paul Stutzman, a researcher in the EL Materials and Construction Research Division, along with co-authors from academia and industry, has won the Best Poster Award at the 13th International Congress on the Chemistry of Cement (ICCC) for their combined work on developing new quantitative characterization techniques for fly ash, a by-product of burning coal for energy production. The ICCC is a prestigious quadrennial international meeting that draws significant participation from industry, academia, and government.
One new cementitious material showing great potential for use in critical elements of the Nation's physical infrastructure are geopolymers, which can be formed by mixing glassy wastes such as fly ash with alkaline solutions, which themselves may be an industrial by-product. The process is far less energy intensive than that for making Portland cement, the most prevalent cementitious material. A challenge for geopolymers, however, is the rate of strength development required for typical construction practice. Because the composition of fly ash produced by a particular power plant is unique and can vary over time, improved characterization techniques are needed to ensure reliable performance in the field. The award recognized a new technique for combining scanning electron microscopy and X-ray microanalysis with X-ray powder diffraction to develop quantitative assessments of the different types of mineral and glassy phases that can be present in a fly ash.
CONTACT: Paul Stutzman (EL), 301 975 6715
NIST Engineering Laboratory (EL)-DHS Workshop on Homeland Security Modeling and Simulation (M&S)
NIST's Engineering Laboratory (EL) and the U. S. Department of Homeland Security (DHS) Science and Technology Directorate and jointly hosted a Homeland Security Modeling & Simulation (M&S) Workshop on June 14-15, 2011 at NIST in Gaithersburg. The workshop assembled a wide range of individuals from both government and the private sector to exchange information and benchmark knowledge on M&S and M&S-related issues for homeland security. More than 70 attended the workshop, which included experts on technical and operational issues from government, industry, and academia. Representatives came from the U.S., Singapore, and Europe.
Dr. Bert Coursey, Director of Standards, DHS Science and Technology Directorate, and Dr. Vijay Srinivasan, Chief, NIST/EL's Manufacturing Systems Integration Division, gave welcoming addresses. The workshop had three keynote speeches:
- Dr. Keith Holtermann (Director of the DHS Federal Emergency Management Agency (FEMA) National Exercise Division), on "Modeling & Simulation – An Exercise Perspective"
- Dr. William Grosshandler (Deputy Director for NIST/EL Building and Fire Research), on "Disaster-Resilient Buildings, Infrastructure, and Communities"
- Dr. Charles Hutchings (Senior Systems Engineer, DHS Management Directorate, Program Accountability and Risk Management Division), on "Perspective on the Use of Models and Simulations in Problem Solving for Homeland Security"
Four parallel working sessions provided opportunities to identify important domain-specific technical issues and share information on:
- Incident Management
- Critical Infrastructure Systems
- Hazardous Material Releases
- Healthcare Systems
The discussion topics of the working session included: 1) needs and requirements; 2) M&S resources; 3) best practices; 4) limitations, cautions, and warnings; and 5) R&D, standards, and implementation issues. Findings and recommendations from the workshop will be made available to stakeholders and the general public as a joint DHS/NIST workshop proceedings report.
Contact: Y. Tina Lee, 301-975-3550