Application of Graphite Foam Heat Exchangers in Neutron Sample Environment Systems. NATHAN PORTER (Utah State University Logan, UT 84321) LOUIS J. SANTODONATO (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

Temperature control is crucial for many neutron scattering measurements. The demand for cryogenic systems which operate over a wide temperature range and rapidly lock into a set point is growing furiously. The scope of this research is evaluation and implementation of graphite foam to enhance the thermal performance (i.e. ability to promptly reach the temperature extremes) and set point performance (i.e. the ability to rapidly alter and stabilize on a desired temperature) of a closed cycle helium gas refrigerator system. The work involves an inter-division ORNL collaboration between the Spallation Neutron Source and Metals and Ceramics Division. Measurements of special graphite foam developed at ORNL provided thermal conductivity values throughout the temperature range of interest (3 to 300 K). The conductivity of the foam was measured in a conductance test by placing the foam between two isolated copper blocks. The thermal conductivity measurement came from a calculation of the temperature difference between these blocks. The measurements indicated a high conductivity (greater than 100 W/ m?K at 20 K). These results warranted the design, fabrication, and testing of a graphite foam heat exchanger module. A heating module, also fabricated with graphite foam, is incorporated in the design for rapid stabilizing and raising temperatures. A first generation prototype was produced and installed within a "pilot plant" cryogenic system. Testing shows set point stabilization is greatly enhanced, and that the thermal performance weakens being critically dependent on the details of the installation. However, enhancements transpired with the testing of each new configuration refinement within the testing apparatus.

Attachments for Remote Tools and Equipment for Remote Operations. ADAM CARROLL (University of Arizona Tucson, AZ 85719) CRAIG BRADLEY (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

The Spallation Neutron Source (SNS) will be a facility with the capability of creating large quantities of neutrons for material science research. The neutrons are generated by high energy protons hitting a mercury target, releasing neutrons and high radiation. The Target Cell, a heavily shielded room for maintenance of the mercury target, contains four pairs of through-the-wall manipulators and one pair of servomanipulator arms attached to a bridge crane to perform maintenance in the Target Cell. The manipulators function best with tools modified for their grippers. Some recent Target Cell projects have been directly related to the development of attachments to everyday tools to be operated by manipulators. For example, there are three pneumatic torque wrenches used remotely in the Target Cell to torque nuts and bolts. In order for the larger torque wrench to be properly positioned for the mercury target bolts, the torque wrench must be capable of being held by a hoist hook in both horizontal and vertical directions. To solve this problem a stainless steel handling bail was attached to both ends of the wrench. Special bends are added to hold the hook in place over the center of gravity in both directions. The hoist hook, with help from the manipulator's arm, will move between both positions. The two smaller pneumatic torque wrenches require a remotely attachable reaction bar to counter the torquing force applied to a nut or bolt. The small wrenches need several reaction bars of various lengths and shapes for torquing different bolts throughout the Target Cell. Another example of a Target Cell project involves the mercury piping supports. The mercury pipe is held in support cradles. Some cradles are adjustable in both horizontal and vertical directions while most only in the vertical direction. All support cradles help align the pipes when being remotely replaced. The adjustments to the cradles are made by turning hex nuts on threaded rods connected to a plate that holds the pipe. Once the adjustments are completed and the pipe connected the nuts must be locked since the vibration of the mercury flowing through the pipe can slowly loosen the nuts and lower the pipe. A removable attachment was designed to be placed over the nuts. The attachment reacts against the side of the cradle keeping the pipe in the correct position. The SNS Hot Cell requires both modified tools and other adaptations for remote operations in its unique environment.

Beam Impulse Dynamics: Transient Behavior in Microcantilevers. SARIT BARHEN (Washington University in St Louis Saint Louis, MO 63130) DR. THOMAS THUNDAT (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

The microcantilever of an atomic force microscope is a dynamic system that exhibits useful resonance behavior. Although best known for its service in sensing applications, the microcantilever is gaining popularity in external applications as its unique probing capabilities continue to improve and secure recognition. Theoretically, this system can be modeled in a variety of forms, with one of the most common schemes treating the system as a single mass attached to a spring with a dashpot (the point-mass model). In this case only the temporal aspects of the system are considered and the cantilever's motion is modeled via a second order ordinary differential equation. Such models however, are somewhat unrealistic in that they have a single degree of freedom and ignore the physical extension of the cantilever. Thus, to more accurately portray the microcantilever system, the beam equation is considered. As a fourth-order partial differential equation, the beam equation involves both the temporal and spatial attributes of the system, with the ensuing eigenvalues and eigenfunctions representing the cantilever frequencies and their corresponding modes. Of particular interest is the effect of a short duration impulse applied to the microcantilever of an atomic force microscope. This impulse is observed to create a phenomenon of beats which occur within the system's oscillations. This is verified experimentally for a triangular cantilever, and modeled theoretically as both the analytical and numerical solutions to a fourth-order partial differential equation for the spatial and temporal attributes of the cantilever.

Conceptual Design of Isotope Separator On-Line Target for Rare Isotope Accelerator. ADAM CARROLL (University of Arizona Tucson, AZ 85719) CRAIG BRADLEY (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

Isotope Separator On-Line (ISOL) is one of the two types of targets that are being conceptually designed for the Rare Isotope Accelerator (RIA); a 400 kW accelerator for ions from hydrogen to uranium, with the goal of providing a better understanding of exotic nuclei. The ISOL target is composed of a main target, the tungsten core and a secondary target of 133 uranium carbide disks that surrounds the tungsten. Three essential design objectives of the ISOL target were evaluated, (1) cooling the target during beam operation, (2) analyzing the beam window, and (3) ease of replacement with remote handling equipment. The secondary target is thermally cooled by water flowing through two sets of pipes that spiral around the uranium carbide disks. The tungsten is directly cooled by water flowing through small spiraling channels in the tungsten. This is achieved by encasing the tungsten inside a pipe to force the water through the channels at 300 psi. The ion beam goes through the pipe to contact the tungsten making the pipe the target beam window. To ensure that the pipe can manage both the internal pressure of the water and the thermal gradient created by the beam passing through it, Mechanica, a finite element analysis program, was implemented to calculate the theoretical stresses the pipe will experience. By analyzing a range of wall thickness from 0.5 to 1.5 millimeters with two materials, stainless steel and aluminum, it was discovered that aluminum at 1.5 mm allows the greatest factor of safety. The ISOL target needs to be replaced frequently because of the high level of energy the tungsten receives, making the target radioactive to the point it must be handled completely remotely. To make the process simple the target only has four Hiltap water connections. The electrical power connects automatically when the target is placed in the base of the target module. Handles, hook plates, and alignment pins are also added to guide the target in and out of the target module to make replacement less difficult. The ISOL target is a continually changing design as new ideas are modeled and analyzed. With every small change or addition the ISOL conceptual target becomes a little closer to becoming a reality.

Condensed Science Matter Division. Measuring and analyzing the transport properties in Superconducting films. BRANDON KILLIAN (North Carolina Agricultural and Technical State University greensboro, NC 27408) ALBERT GAPUD (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

This project is part of ORNL ongoing progress in developing high temperature superconductors (HTS) for industrial applications, most especially to eventually replace conventional conductors in transmission lines with HTS wires. This accomplishment would allow transmission of current with significantly fewer energy losses. HTS are materials that have no resistance to the flow of electricity below transition temperature, Tc, and where Tc is above the boiling point of liquid nitrogen (77K). Transport properties were measured, specifically the resistivity and critical current density, Jc, on thin films of the HTS material YBa2Cu3O7 (YBCO) made here at ORNL and at North Carolina A & T (NCAT) in order to assess the quality of films and to determine the effects of enhancing magnetic flux pinning. Effective flux pinning prevents current-induced dissipative motion of the quantized magnetic flux lines (vortices) within a superconductor, thereby potentially elevating Jc. Since flux pinning can arise from nanoscale defects in the superconductor, we examined samples in which were added nanoscale impurities. Measurements were made in cryogenic systems with a superconducting magnet capable of supplying a large applied magnetic field (up to 14 Tesla) and varying the field orientation over a wide range. The samples are cooled to controlled temperatures from Tc to as low as 4K (boiling point of liquid helium). At each fixed temperature, the samples were measured at different applied magnetic fields (H), and at different angular orientations ( ) of the sample in the field. We have found that introduction of oxide nanostructures with sufficient lattice mismatch dramatically elevates Jc over a broad range of fields and field orientations; therefore this kind of film processing should be very promising for HTS applications. Furthermore, we have found this information to be critical to the optimization of processing conditions for the development of superior-quality YBCO film at NCAT.

Cyber Security Issues within the Engineering Science and Technology Division (ESTD). SHANE MORRISON (Bevill State Community College Fayette, AL 35555) TERRY HEATHERLY (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

Information systems have become one of the most used and necessary tools in today's society. During the course of a normal day, the majority of the world's population interacts with some type of computerized system. Whether it is a computer, PDA, cell phone, automobile, shopping (Debit and Credit cards) or a medical system, people are going to interact with some type of computer system. From the infancy of the ARPANET in 1968, the first prototype of today's Internet, there have been cyber security concerns because neither business nor individual wants to lose sensitive data. In more current times, these types of concerns are no different today at the Oak Ridge National Laboratory (ORNL). With the escalating rate of more complex viruses as well as the propagation of spy-ware, identity theft, system failures and the loss of sensitive data have unfortunately become more probable. Therefore, the main goal of this project is to research the evolving methods required to resolve dynamic cyber security issues. In conjunction, various software applications were used to detect, quarantine and remove different types of active cyber security vulnerabilities. Thus, cyber security specialists apply this research by electronically scanning and monitoring information systems within their responsible organizations. Upon finding issues, we use numerous methods to resolve and help to prevent future vulnerabilities from reoccurring. Therefore, continuous cyber security research is a necessity. Routine monitoring and the correction of the problems help to prevent damage to sensitive data and mission critical systems. This proactive cyber security strategy contributes not only to daily dividends that can be measured economically, but also to the world-class research occurring at ORNL.

Design of Mock-up Target for the Spallation Neutron Source. RYDER WINCK (Rice University Houston, TX 77005) ERIC CRAIG BRADLEY (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

The Spallation Neutron Source is a research facility currently under construction at Oak Ridge National Laboratory. The facility will produce neutrons by bombarding a mercury target with a beam of protons. The mercury is contained in a stainless steel vessel that must be replaced several times a year. The Mercury Target must be removed remotely due to high radiation. During Integrated System Testing, operators will practice removal and installation of the Mercury Target. A mock-up of the Mercury Target was needed to avoid potential damage to the Mercury Target that costs about one million dollars and would take months to reproduce. The objective of this project was to design a mock-up target of the real Mercury Target. A basic mock-up target existed at the start of the project. However, it differed significantly from the Mercury Target in many critical dimensions. The Mock-up Target was modified to mimic the Mercury Target in dimensions corresponding to transportation and placement. Before physically modifying the Mock-up Target, a computer aided design program, Pro/Engineer Wildfire 2.0 (Pro/E), was used to digitally model the initial Mock-up Target, compare it to the Mercury Target, and make drawings of the Mock-up Target to give to the fabricators. The Mock-up Target is considered as a "below hook lifting device" and is designed to comply with DOE Standard 1090, Section 14.2.1, which states that lifting devices must have a factor of safety of three based on the yield strength of the material. To check for this, a sub-program of Pro/E, Mechanica, was used to run finite element stress analysis on the part of the Mock-up Target that would be receiving the highest stresses. In addition to Mechanica analysis, stress calculations were done by hand. A formal stress analysis report was written to document that the Mock-up Target would comply with the DOE Standard. Although the Mock-up Target is not yet fabricated, the design is successful in that it fulfills the requirements in a safe and inexpensive way by modifying the current Mock-up Target to the proper specifications. The Mock-up Target will allow for remote handling practice that is as realistic as possible without the risk of using the million dollar Mercury Target.

Determination of Top Load Length of a Marconi Antenna to Achieve a Resonant Frequency of 3.2 MHz. WEI TAN (University of Colorado Denver, CO 80202) JOHN WILGEN (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

The Theater Positioning System (TPS) requires choosing a certain type of antenna to operate at 3.2 MHz as a ground wave transmitter. A 50 ft Marconi antenna with a top load is chosen for ease of assembly of five temporary transmitters. The top load consists of the upper portions of four guy wires that intersect at the top of the vertical wire, and which are oriented at an angle of 67 degrees from the horizontal direction. The challenge of this research is to determine the length of these four top load wires so as to realize an antenna that resonates at 3.2 MHz. The determination process has three main steps. The first is to come up with an estimation of length by modeling antennas with a range of top load lengths to see which one has a resonant frequency closest to 3.2 MHz. The simulations are done by running finite different time domain (XFDTD) software. Meanwhile, other parameters of interest are obtained, such as reflection coefficient and the real part of antenna impedance for each antenna with a specific length of top load. The second step is to build a prototype which is 1/100 the size of an actually one, then use a network analyzer to measure the resonant frequency, reflection coefficient and the real part of antenna impedance. The third step is to tabulate and compare the results acquired with computational and experimental methods and explain the discrepancy between them. The computer simulation showed that the length of the top loads from the intersection to the lower end needs to be between 20 ft and 22 ft long-a 2 ft range, in order to make this antenna resonate at 3.2MHz. Since the cell size was set as 2 ft per cell when the FDTD simulation was done, the 2 ft range has reached resolution limitation of the model. Meanwhile, a 1/100 scale prototype was built and network analyzer measurements were completed and compared with the modeling simulation.

Determining the Optical Properties of Biological Tissue Samples Using an Integrating Sphere Method. MARCUS ALLEGOOD (Gainesville College Gainesville, GA 30503) JUSTIN BABA (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

The wavelength dependent interaction of light with biological tissue is an important tool used to determine tissue optical properties. To accurately determine these optical properties for different types of tissue at specific wavelengths would be beneficial for a variety of different biomedical applications. In order to collect the needed data for the multitudes of different wavelengths in a timely and accurate manner, a fully automated computer program and process was developed. The hardware used included an integrating sphere, spectrometer, and a collimated light source. Scattered light intensity inside the sphere was recorded by the spectrometer as either transmitted or reflected light from the tissue sample. LabVIEW was used to write the programs to collect raw intensity data from the spectrometer, to convert the data into a format for C code execution, and to compute the optical properties based on the collected data. To make the process fully automated, the LabVIEW and C code programs were linked together into one single program to allow data to be passed between the two instantly. The automated program was tested using a neutral density filter and the execution of the program was successful. Future work will entail testing of actual known tissue phantoms to check for accuracy before proceeding to utilize the system to characterize actual tissues. Ultimately, the data collection process and algorithms developed through this effort will be applied to build models for light interaction with biological tissue samples.

Developing "Cool Roof" Criteria for Direct Nailed and Vented Roof Decks. BENJAMIN RUDOLPH (Virginia Polytechnic Institute and State University Blacksburg, VA 24551) WILLIAM A. MILLER (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

Solar reflectance and thermal emmitance affect the surface temperature of a roof, which in turn drives the heat transfer penetrating through the roof. A roof with 0.70 solar reflectance and 0.75 thermal emmittance is defined as a "cool roof" by California's Title 24 prescriptive requirements. However, the Title 24 formula has been found to be too restrictive for "cool roofs" in the low emmittance range. In this project, a more accurate prescriptive requirement formula was developed which considered emmittance, reflectance, and the R-value of various roofs across the 16 California climate zones. Running ORNL's STAR roof calculator, a numerical computational tool, a thermal energy balance was developed to approximate the changes required for two different roofs to produce equal heat flow, and thus cooling load, through the roof. The venting of the underside of a roof surface also provides thermal benefits for comfort cooling. Published literature demonstrates a reduction in the daytime heat flux penetrating a counter-batten tile roof as compared to a direct nailed shingle roof, but the energy savings associated with venting are difficult to quantify. Due to the inclusion of a subsurface air channel in many modern roofs, the thermal energy balance must involve natural convection to be complete, which the Tile Roofing Institute is keenly interested in implementing within Title 24. Using CO₂ as a tracer gas, the mass flow of air inside the channel has been calculated to be in the range of .026 lbs/sec. The next step is to develop formulas which relate mass flow to solar irradiance, wind speed, wind direction and outdoor air temperature. In addition to prescriptive requirements considering reflectance, emmittance and R-value, it is hoped that a more comprehensive set of requirements considering air channels will be developed.

EM Ground-Wave Propagation Prediction Using Finite Difference Time Domain (FDTD) Method and Antenna Modeling (100 kHz) for Theater Position System (TPS) Broadcast Applications. WEI TAN (University of Colorado Denver, CO 80120) PAUL EWING (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

The finite difference time domain (FDTD) approach is rapidly becoming a popular computational method in electromagnetic (EM) propagation prediction due to its extreme simplicity, compared to traditional frequency domain approaches, and its capability of modeling antennas of complex geometries that are difficult to analyze by other methods. The challenge of this research is to model various antenna designs with XFDTD software tools and to select the optimum one for transmission of reference signals in a large-area ground-based radiolocation system. The validation process focuses on three main steps. The first is to construct the physical dimensions of these antennas and then simulate their EM field effects. The simulation presents the field propagation in a graphical format, meanwhile calculating the numerical values of the real and imaginary parts of the port impedance. The second step is to compare these results with the ones obtained in a paper published in an IEEE journal paper (James K. Breakkall, Michael W. Jacobs, Alfred E. Resnick, G. Yale Eastman, Milton D. Machalek, Thomas F. King, "A Novel Short AM Monopole Antenna with Low-Loss Matching System", IEEE Broadcast Technology Society 52nd Annual Broadcast Symposium Conference Record, October 9-11, 2002) using the NEC-4.1(Numerical Electromagnetic Code) method of moments code. The final step is to explain the discrepancies between results yielded from these two methods. The results of the simulation will be used to guide the construction of an antenna to be physically built and tested with appropriate equipment at a later time.

Enhancing And Updating The Interactive Envelope Materials Database For Whole-Building Energy Simulation Programs. BRETT CARMICHAEL (Pellissippi State Technical Community College Knoxville, TN 37921) DR. JAN KOSNY (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

Thermal resistance of a wall area is used to calculate the flow of heat from one wall surface to another. Decreasing the flow of heat (either containing the heat in cold weather conditions, or keeping it out in warm weather conditions), becomes the main focus of a more energy efficient building. Vast amounts of research have been done within this area, but accurate assessment of data generated has been a hindrance in the past. This is due to the widely varying composition of different buildings, including the details of the buildings, the different wall technologies used, and even the climate the building resides in. Due to the lack of commercial software which can adequately assess whole-building energy efficiency, creation of a user friendly online application has become the focus of the research. The development of the application focuses on three main areas. The first is the Whole Wall R-value Calculator. This calculator gives developers and builders the ability to easily discover the whole wall R-value for any house they are designing, simply by entering basic geometric dimensions and selecting from a list of tested wall systems. The second area of focus is the Thermal Mass Calculator. It calculates the energy savings of a building based on the configuration of the wall technology and the climate in which the building is located. The final area is the online Hotbox Test R-value Database. This project contains years of hotbox data compiled at the Oak Ridge National Laboratories, and the goal of the database is to present the information in a clear, concise, and user-friendly way. The combination of these three areas helps to incorporate all the aspects needed to make an accurate assessment of whole-building energy efficiency.

Fabrication of Spiral Bio-Reactor Light Sheets. JEANNE DUCE (Florida State University Tallahassee, FL 32302) DUNCAN EARL (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

Hydrogen is typically created from electrolysis or thermo-chemical production. Electrolysis requires large amounts of energy while producing hydrogen at a low efficiency rate. An alternative to these processes is to use algae as a biological means of creating hydrogen from sunlight. Exploiting the photosynthesis and respiratory characteristics of algae, a photobioreactor is envisioned that could produce significant volumes of Hydrogen without the use of electricity. Oak Ridge National Laboratory (ORNL) and the National Renewable Energy Laboratory (NREL) are collaborating to develop a prototype spiral geometry photobioreactor that efficiently captures sunlight to fuel the bioproduction of Hydrogen. A significant component of this prototype is the Spiral Bio-Reactor Light Sheet used to distribute sunlight within the bioreactor. The design of the Spiral Bio-Reactor Light sheet consists of plexi-glass sheets that have been rolled into a spiral shape. Micro-etches on the back of the sheet disperse the sunlight in a uniform and controlled manner. The spiral shape of the light sheet allows the sunlight to be dispersed over a large surface area, allowing for maximum algae illumination and production of Hydrogen. In this way the Spiral-Bio Reactor Light Sheet can create hydrogen in an efficient manner without the use of electricity. Chlamydomonas reinhardtii is one type of algae that is capable of converting sunlight into hydrogen photosynthetically, and would be an excellent choice in the Spiral-Bio Reactor Light Sheet. Depriving sulfur to the growth medium of Chlamydomonas reinhardtii causes oxygen production during photosynthesis to decrease. The culture's consumption of oxygen creates an anaerobic condition which instantaneously induces the production of hydrogen. Hybrid Solar Lighting (HSL) is a light source that utilizes direct sunlight taken from a roof top collector and concentrates the sunlight into optical fibers that are supplied to light fixtures. These optical fibers are feed into the spiral shaped plexi-glass. The Spiral Bio- Reactor is in-cased to allow the Hydrogen to be extracted and stored. Work is still in progress and final results expected by September.

Limitation of YBCO on Heat Transfer and Stability in High Temperature Superconducting Magnets. JENNIFER CARNEY (University of Tennessee Knoxville, TN 37916) ROBERT DUCKWORTH (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

The thermal conductivity of composite YBa2Cu3Ox (YBCO) tapes was measured to better understand heat transfer in the multilayer structures that are often found in high temperature superconducting (HTS) magnets. Knowledge of the conduction heat transfer through the wire's components- buffer layers, substrate, YBCO, and stabilizer- can allow for the efficient selection insulating materials that can provide dielectric strength and improve heat transfer for a second generation (2-G) YBCO tapes. A test setup was designed to measure the effective thermal conductivity of composite YBCO tapes. Various sample stacks that were composed of different materials such as copper, kapton, YBCO, and Apiezon© N grease for example were placed between two platinum thermometers and below a heater bobbin. Through variation of the number and type of materials, the background heat loads were quantified so that the properties of the YBCO and candidate insulation materials were accurately measured. After each sample stack was cooled down in an ice bath (273 K), a heater load was applied and the temperature difference across the sample was measured. From the temperature difference, the total thermal resistance was then used to calculate the effective thermal conductivity of the samples. Additional measurements were done at liquid nitrogen temperatures (77 K) although measurements at 273 K allowed for a broad cross section of data to analyzed quickly without sacrificing a meaningful comparison. The measurement of the thermal conductivity was impacted by the contact pressure and the materials that were used to secure the thermometers to the sample stack. A comparison of the role of these factors on the thermal conductivity measurement will be presented. It was found that the composite YBCO tape results were consistent with known thermal properties of substrate, buffer layers, YBCO, and stabilizer at 273 K. The overall thermal resistance did improve when kapton was replaced with Apiezon© N grease. These results were applied to a series of preliminary experiments where the stability of composite YBCO tapes was characterized and the removal of heat along the length and across the thickness of the composite YBCO tape was studied. The heat transfer across the thickness of the tape can be improved slightly, but additional measurements are needed. This will assure whether candidate insulation materials for HTS coils can provide tangible improvement in the coil stability.

Metrics for the Comparative Analysis of Geospatial Datasets with Applications to High-Resolution Grid-Based Population Models. KATHLEEN ABERCROMBIE (Auburn University Auburn, AL 36849) AUROOP GANGULY (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

Geospatial data sciences have emerged as critical requirements for high-priority application solutions in diverse areas like the mitigation of natural or man-made disasters and the assurance of energy, communication and transportation networks. This research develops metrics for comparative analysis of geospatial datasets, specifically for quantifying the relationships within variables, generating measures of difference among datasets, and measuring the value of data in the context of the end-use. This case study focuses on two high-resolution, grid-based population datasets: the LandScan database available from the Geographic Information and Science Technology (GIST) group at Oak Ridge National Laboratory (ORNL) and the Gridded Population of the World (GPW) database available from the Center for International Earth Science Information Network (CIESIN) group at Columbia University. Metrics for quantifying the spatial relationships within multiple geospatial variables include spatial auto- and cross-correlation as a function of lags. This research computes and displays these metrics as three-dimensional surfaces to visualize the relationship between the LandScan databases and one ancillary variable: nighttime lights from satellite imagery. Quantifying metrics for the difference among multiple datasets include spatially aggregated measures like normalized mean squared differences, fractional area coverage, and analysis of grid-based differences through histograms. The spatial cross-correlation metrics described earlier can also be used as spatially-aware measures of difference when the two datasets are supposed to convey identical information. The third set of metrics was designed to measure the usefulness of the databases in the context of end-use. The metrics are based on the number of times the population exceeds certain threshold values in both or one of the datasets, and include the accuracy, bias score, probability of detection, false alarm ratio, probability of false detection, threat scores, equitable threat scores and receiver operating curves. Case studies appear to suggest that GPW is suitable as a residential population model, while LandScan Global is more suitable as an ambient population model, confirming significant difference in the end-use for man-made or natural disasters, security threat scenarios and impact analysis. The metrics utilized in this research can be easily generalized to other geospatial datasets and application domains.

Monthly CO2 Emissions Due to Natural Gas Flaring/Venting and Cement Manufacture. KIM HAND (Georgia Institute of Technology Atlanta, GA 30332) TJ BLASING (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

Radiatively active "greenhouse" gases, such as carbon dioxide (CO2) and methane (CH4), influence the climate system. Because of its abundance, CO2 is by far the most influential of these gases. Until recently, only annual data on fossil-fuel CO2 emissions were available. However, as numerical models of the carbon cycle, which predict future atmospheric CO2 and CH4, become increasingly sophisticated, the need for sub-annual (e.g. seasonal) values of carbon emissions increases. Monthly CO2 emissions from fossil-fuel consumption in the United States have recently been estimated. Therefore, the work reported here focused on release of natural gas at the well sites (not reported as fuel consumption) and on cement manufacture, which is a major industrial source of CO2 emissions. Values of several parameters had to be obtained to calculate optimally precise emissions estimates. For natural gas, only total amounts released are reported. The fractions combusted to CO2, released as uncombusted CH4, and released as soot were not well known before this study. These fractions are important because CO2, CH4, and soot have substantially different impacts on the environment. The literature review and engineering calculations completed for this project indicated that about 98% of reported flared/vented natural gas is combusted to CO2. In cement manufacture, CO2 is produced when raw material, including limestone, is heated to produce clinker, an intermediate product used to make cement. Calcium and magnesium carbonates (CaCO3 and MgCO3, respectively) release CO2 when heated, and leave the resulting calcium and magnesium oxides (CaO and MgO, respectively) in the clinker. The amounts of CaO and MgO in the clinker indicate how much CO2 was released. On average, 64.6% of the clinker mass is CaO, and about 2% is MgO. However, the error term for MgO is almost as large as the mean, so carbon from MgCO3 is currently disregarded by the United States Environmental Protection Agency and the Intergovernmental Panel on Climate Change. Some clinker is reduced to dust, most of which is recovered and re-used, but an estimated 2% escapes unreported. The reported clinker values are multiplied by 1.02 to account for this. With the above information obtained in this study, and routinely reported data, the optimally precise monthly values of carbon emissions (as CO2) from gas flaring and cement manufacture for the United States were estimated.

Optical Distance Measurement Device for Eye Surgery. EILEEN MCFADDEN (Colorado School of Mines Golden, CO 80401) JUSTIN BABA (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

During a microsurgical procedure called a vitrectomy, surgical equipment is inserted into the eye through 1.4 mm diameter holes in the par plana to repair retinal damage. Currently, surgeons gauge the distance between the surgical tools and the tissue surface using their sense of touch coupled with limited visual feedback from a fiber optic light source. This touch feedback system necessitates the application of adequate contact force to provide a sensation of surface contact, which may lead to unintended surface penetration and tissue damage. Therefore, a fiber optic probe coupled with the surgical tool is needed to aid the surgeon by accurately reporting the distance from the end of the tool to the tissue surface, particularly for delicate surgeries. To accomplish this, an optical approach based on specular reflection from the tissue surface was investigated. Preliminary data was collected on chicken breast tissue and cardboard using three different detector-to-emitter spacing probes, with each probe consisting of a muli-wavelength light emitting diode (LED) source with wavelengths of 660, 810, and 940 nm and a silicon photo-detector. The chicken breast tissue was chosen to represent a birefrignent, i.e. structurally aligned, homogeneous sample and the cardboard to represent a homogeneous non-birefrigent sample with an expectation that the retinal surface will have structural characteristics that fall somewhere in between. Repeatable results using both chicken and cardboard demonstrated trends corresponding to the inverse square law for a Gaussian input beam intensity profile. The reported findings of distance versus intensity show that as the detector-to-emitter spacing decreased, the useful range of the sensor increased, thus supporting the implementation of a fiber optic coupled LED and photo-detector sensor for surgical tool-to-surface distance measurement.

PERFORMANCE ANALYSIS OF A 2ND ORDER S? ADC WITH ELECTRONICS NOISE USING MATLAB AND SIMULINK. JOSH WERRMANN (University of Kentucky Lexington, KY 40506) M. NANCE ERICSON (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

In the field of signal processing, the sigma delta analog to digital converter (SDADC) is particularly useful for high resolution digitizing of signals. This high resolution is accomplished by oversampling and quantization noise shaping. Mathematical representation of SDADCs is difficult, and continues to be problematic. Closed form representation has not been shown in the known literatures. Accordingly, SDADC developments typically involve simulations in which signals are sampled and calculated at some defined time interval. In this manner, long sequences of output data can then be processed in the frequency domain to assess SDADC effectiveness. Furthermore, SDADCs are constructed by utilizing integrated circuit techniques, thus making the fabrication of prototypes not only time consuming, but costly, with costs ranging from a few thousand to greater than $100,000. This renders it advantageous to have a computer simulation readily available to quickly assess ADC performance characteristics with user specific input variables which simulate real world conditions. The focus of this work is the development of tools for assessing SDADC performance based upon MATLAB and SIMULINK. With these tools, an accurate input noise spectra can be generated which represents the dominant electronic noise sources (white noise, 1/f noise), and includes noise folding, enabling evaluation on the effect these sources have on a 2nd order SDADC. These tools can further be used to analyze the effect that any individual component, such as the various gains in the modulator or the input voltage may have on the various performance metrics, including the signal to noise ratio (SNR), dynamic range (DR), and total harmonic distortion (THD). The success of the simulations will be determined based upon how closely the simulations are in accord with theory.

Reactive Power Benefits of CHP Systems. JASON FOSTER (Tennessee Technological University Cookeville, TN 38505) ABDOLREZA ZALTASH (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

Combined Cooling, Heating, and Power (CHP) systems enjoy greater efficiency over individually operated electric and thermally activated (TA) systems by using waste heat from power production as input to TA systems. However, a new benefit of CHP is dynamic reactive power (RP) for voltage regulation. There is a growing deficit of RP reserves due to the changing market. The lack of adequate RP and the inability to transport it from central generation to load is one of the main culprits of the past blackouts. Incorporating functionality into existing or new equipment, RP compensation can be spread over the distribution systems. For mass implementation of CHP-based RP, a standardized control system with minimal communications must be employed and its benefits demonstrated. For the developmental stage, a programmable real-time controller is being used along with mathematical models of the CHP-based RP system and practical test data. The specific technologies being investigated include synchronous motors/generators used as synchronous condensers and prototype inverters for reactive power compensation. In this investigation a 250 hp synchronous motor will interface with the ORNL distribution system. The power inverters will simulate the end-user interface for energy sources such as microturbines and fuel cells. Eventually, several different technologies will be operated in parallel at different injection points. Current methods of RP compensation are mainly based on transporting RP over long distances from central generators or by capacitor banks with expensive switchgear. Also, capacitors cannot provide continuous or dynamic RP and lose their effectiveness at lower voltage when most needed. The project is well suited for ORNL, which owns its distribution system and can make the necessary modifications. Also, ORNL's power supplier, TVA, is one of many project partners. ORNL's facilities division will reduce RP compensation at the substation and operate dynamic loads to provide for more meaningful test results. To gain widespread acceptance by the electric power industry, the benefits and impacts of CHP-based RP must be well understood. Ultimately, this project will lead to the development of "rules of thumb" for operation that can easily and reliably be applied.

Single-Cell Noise Spectrum Analysis for Gene Circuit Characterization. DAR ROY (The Hebrew University of Jerusalem Jerusalem, ISRAEL 91904) MICHAEL L. SIMPSON (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

The capability to characterize natural and engineered gene circuits could be beneficial on both academic and industrial fronts by gaining more understanding of intra- and inter-cellular biological processes and structure-function relationships. To explore the frequency distribution of stochastic processes in gene circuits, Green Fluorescent Protein (GFP) expressing gene circuits were constructed on high copy number plasmids in Escherichia Coli bacterial cells. Experiments concentrated on two different types of circuits: (1) Non-regulated gene constructs differing in protein degradation rates, and (2) Autoregulated negative-feedback gene constructs where gene expression is repressed by the binding of a repressor protein at an operator site in the promoter. Laser confocal microscopy (Leica SP2) with a 488 nm Ar source was used to acquire 4-8 hour time-series fluorescence data (500-550 nm) from excited bacterium populations. Cell doubling time was controlled by varying growth temperatures. Single-cell fluorescent output was extracted from microscopy images by tracking individual cells using computer-imaging software to calculate mean pixel intensity. GFP noise was defined as this output's deviation from the population's mean fluorescence. A common reference point from calculated biased Autocorrelation Functions (ACFs) for this time-series noise data (time lag at which the ACF decayed by ½) was used as a measure of noise bandwidth (Fnbw) for gene circuits. An increase in Fnbw with decreasing cell doubling time was observed for all the gene constructs. In addition, an increased bandwidth of about two-fold was seen for the autoregulated gene circuit as opposed to the unregulated circuit. This increase in bandwidth was predicted by a previous theoretical study for these gene circuits and is consistent with negative feedback theory. Additional spectral measurements and model interpretation may reveal significant information on enzyme kinetics, feedback mechanisms, epigenetic motifs, and kinetic parameter fitting of these gene circuits. Ultimately the physical sciences approach to biological systems may be at the forefront of molecular-scale engineering and help enhance the biologist's tools for discovering underlying structure of gene circuits and networks.

Spark Plug Erosion in Natural Gas Engines. BRYCE HUDEY (University of South Florida Tampa, FL 33620) COLIN MCCLELLAND (Wabash College Crawfordsville, IN 47933) TIM THEISS (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

Spark plugs in industrial natural gas engines demand a longevity and reliability surpassing that of ordinary automotive spark plugs. While current models are designed for 4000 hours of continuous use, demand exists for plugs with an engine lifespan of up to 8000 hours without failure. A critical limiting factor in the lifetimes of these plugs is the erosion of the electrode terminals. In order to characterize possible erosion and failure processes, spectroscopic analyses of breakdown arcs were conducted on ten sets of used plugs. By varying the spark timing and the environment's gas and pressure, spectral signatures from materials such as nickel, calcium, or hydrogen were isolated and examined. Since the sets were each in engines for times ranging between 100 and 5200 hours, material content was compared with plug age and possible trends were scrutinized, but this trend comparison failed to yield any clear conclusions. A vacuum was applied to view hydrogen spectra for plugs from an Exhaust-Gas-Recirculation (EGR) engine to understand their unique erosion characteristics. The increased levels of found in these plugs might be related to their relatively high erosion rates. Computer analysis of the data determined the frequency of the arc's tendency to alternate between two distinct breakdown points on the plug's arcing surfaces. Though suspected of contributing to the erosion pattern, new data shows that each plug's affinity for sparking consecutively on one side varies widely from plug to plug within a common set. This discovery might mean there are more processes at work that are not yet fully understood. This, coupled with the quantity and variety of elements represented in the emission spectrum, may shed some light on the effects of possible erosion processes.