William ghes Technical Center

Atlantic City, NJ, United States

William ghes Technical Center

Atlantic City, NJ, United States
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Weatherall J.C.,Battelle | Yam K.,Battelle | Barber J.,William ghes Technical Center | Smith B.T.,William ghes Technical Center | And 2 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2017

Millimeter wave imaging is employed in Advanced Technology Imaging (AIT) systems to screen personnel for concealed explosives and weapons. AIT systems deployed in airports auto-detect potential threats by highlighting their location on a generic outline of a person using imaging data collected over a range of frequency. We show how the spectral information from the imaging data can be used to identify the composition of an anomalous object, in particular if it is an explosive material. The discriminative value of the technique was illustrated on military sheet explosive using millimeter-wave reflection data at frequencies 18-40 GHz, and commercial explosives using 2-18 GHz, but the free-space measurement was limited to a single horn with a large-Area sample. This work extends the method to imaging data collected at high resolution with a 18-40 GHz imaging system. The identification of explosives is accomplished by extracting the dielectric constant from the free-space, multifrequency data. The reflection coefficient is a function of frequency because of propagation effects associated with the material's complex dielectric constant, which include interference from multiple reflections and energy loss in the sample. The dielectric constant is obtained by numerically fitting the reflection coefficient as a function of frequency to an optical model. In principal, the implementation of this technique in standoff imaging systems would allow threat assessment to be accomplished within the scope of millimeter-wave screening. © 2017 SPIE.

Borst C.W.,University of Louisiana at Lafayette | Tiesel J.-P.,La Well GmbH | Best C.M.,William ghes Technical Center
IEEE Transactions on Visualization and Computer Graphics | Year: 2010

We present and evaluate a new approach for real-time rendering of composable 3D lenses for polygonal scenes. Such lenses, usually called volumetric lenses, are an extension of 2D Magic Lenses to 3D volumes in which effects are applied to scene elements. Although the composition of 2D lenses is well known, 3D composition was long considered infeasible due to both geometric and semantic complexity. Nonetheless, for a scene with multiple interactive 3D lenses, the problem of intersecting lenses must be considered. Intersecting 3D lenses in meaningful ways supports new interfaces such as hierarchical 3D windows, 3D lenses for managing and composing visualization options, or interactive shader development by direct manipulation of lenses providing component effects. Our 3D volumetric lens approach differs from other approaches and is one of the first to address efficient composition of multiple lenses. It is well-suited to head-tracked VR environments because it requires no view-dependent generation of major data structures, allowing caching and reuse of full or partial results. A Composite Shader Factory module composes shader programs for rendering composite visual styles and geometry of intersection regions. Geometry is handled by Boolean combinations of region tests in fragment shaders, which allows both convex and nonconvex CSG volumes for lens shape. Efficiency is further addressed by a Region Analyzer module and by broad-phase culling. Finally, we consider the handling of order effects for composed 3D lenses. © 2006 IEEE.

Baldwin W.C.,William ghes Technical Center | Felder W.N.,U.S. Federal Aviation Administration | Sauser B.J.,Stevens Institute of Technology
International Journal of Industrial and Systems Engineering | Year: 2011

Systems engineers are responsible for systems ranging from the very simple to the extremely complex. The various types of systems create a need for differentiation of properties and identification using some common nomenclature. While other system taxonomies exist, we propose a unique classification mechanism which utilises a finite set of characteristics. Welldefined attributes provide a basis to develop unambiguous mathematical descriptions in future work. Application of the classification scheme will help employ the appropriate systems engineering methodology to systems in development. Copyright © 2011 Inderscience Enterprises Ltd.

Patel P.,University of Central Lancashire | Hull T.R.,University of Central Lancashire | Lyon R.E.,William ghes Technical Center | Stoliarov S.I.,University of Maryland College Park | And 3 more authors.
Polymer Degradation and Stability | Year: 2011

Conventional thermally durable materials such as metals are being replaced with heat resistant engineering polymers and their composites in applications where burn-through resistance and structural integrity after exposure to fire are required. Poly aryl ether ether ketone (PEEK) is one such engineering polymer. Little work has been published with regards to the flammability of PEEK and its filled composites. The current study aims to assess the flammability and fire behaviour of PEEK and its composites using thermogravimetric analysis, pyrolysis combustion flow calorimetry, limiting oxygen index, a vertical flame resistance test, and fire (cone) calorimetry. © 2010 Elsevier Ltd. All rights reserved.

Li Q.,SRA International, Inc. | Garg N.,William ghes Technical Center
Airfield and Highway Pavements 2015: Innovative and Cost-Effective Pavements for a Sustainable Future - Proceedings of the 2015 International Airfield and Highway Pavements Conference | Year: 2015

In order to provide adequate support to the surface layer of airfield pavement, the base, subbase and subgrade must be compacted to high density. Generally, the pavement materials are compacted by roller in the longitudinal direction. It may cause property variance between longitudinal and transverse directions. Portable Seismic Pavement Analyzer for Soils (D-PSPA) was used to evaluate the effect of rolling direction on unbound material modulus. A series of D-PSPA tests were conducted on subgrade, subbase and base materials at the National Airport Pavement Test Facility (NAPTF) in both longitudinal and transverse directions. Single factor analysis of variance (ANOVA) was performed on test results to investigate whether there is a significant difference between two directions. The preliminary data analysis indicates that the seismic modulus measured in longitudinal direction is higher than transverse direction for subbase. Higher seismic modulus was obtained in transverse direction for base. Subgrade, on the other hand, appears to be not affected by the rolling direction. © ASCE.

Patel P.,University of Central Lancashire | Hull T.R.,University of Central Lancashire | Stec A.A.,University of Central Lancashire | Lyon R.E.,William ghes Technical Center
Polymers for Advanced Technologies | Year: 2011

The relationship between physical properties and fire performance as measured in the cone calorimeter is not well understood. A number of studies have identified relationships between the physical and chemical properties of polymeric materials and their gasification behavior which can be determined through numerical pyrolysis models. ThermaKin, a one-dimensional pyrolysis model, has recently been employed to predict the burning behavior in fire calorimetry experiments. The range of thermal, chemical, and optical properties of various polymers have been utilized to simulate the processes occurring within a polymer exposed to a uniform heat flux, such as in a cone calorimeter. ThermaKin uses these material properties to predict the mass flux history in a cone calorimeter. Multiplying the mass flux history by the heat of combustion of the fuel gases gives the HRR history and these have been calculated for cone calorimeter experiments at 50kWm-2 incident heat flux for the lowest, average, and highest values of physical parameters exhibited by common polymers. In contrast with actual experiments in fire retardancy, where several parameters change on incorporation of an additive, this study allows for the effect of each parameter to be seen in isolation. The parameters used in this study are grouped into physical properties (density, heat capacity, and thermal conductivity), optical properties (absorption and reflectivity), and chemical properties (heat of decomposition, kinetic parameter, and heat of combustion). The study shows how the thermal decomposition kinetic parameters effect the surface burning (pyrolysis) temperature and resulting heat release rate history, as well as the relative importance of other properties directly related to the chemical composition. It also illustrates the effect of thermal inertia (the product of density, heat capacity, and thermal conductivity) and of the samples' ability to absorb radiant heat. © 2011 John Wiley & Sons, Ltd.

Lyon R.E.,William ghes Technical Center
Review of Scientific Instruments | Year: 2015

The thermal dynamics of bomb calorimeters are modeled using a lumped heat transfer analysis in which heat is released in a pressure vessel/bomb immersed in a stirred water bath that is surrounded by a static air space bounded by an insulated (static) jacket, a constant/controlled temperature jacket (isoperibol), or a changing temperature (adiabatic) jacket. The temperature history of the water bath for each of these boundary conditions (methods) is well described by the two-term solution for the calorimeter response to a heat impulse (combustion), allowing the heat transfer coefficients and thermal capacities of the bomb and water bath to be determined parametrically. The validated heat transfer model provides an expression for direct calculation of the heat released in an arbitrary process inside a bomb calorimeter using the temperature history of the water bath for each of the boundary conditions (methods). This result makes possible the direct calculation of the heat of combustion of a sample in an isoperibol calorimeter from the recorded temperature history without the need for semi-empirical temperature corrections to account for non-adiabatic behavior. Another useful result is that the maximum temperature rise of the water bath in the static jacket method is proportional to the total heat generated, and the empirical proportionality constant, which is determined by calibration, accounts for all of the heat losses and thermal lags of the calorimeter. © 2015 U.S. Government.

Mahoney C.M.,U.S. National Institute of Standards and Technology | Fahey A.J.,U.S. National Institute of Standards and Technology | Steffens K.L.,U.S. National Institute of Standards and Technology | Benner Jr. B.A.,U.S. National Institute of Standards and Technology | Lareau R.T.,William ghes Technical Center
Analytical Chemistry | Year: 2010

The application of surface analytical techniques such as time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS) is explored as a means of differentiating between composition C4 plastic explosives (C-4). Three different C-4 samples including U.S. military grade C-4, commercial C-4 (also from the United States), and C-4 from England (PE-4) were obtained and analyzed using both ToF-SIMS and XPS. ToF-SIMS was able to successfully discriminate between different C-4 samples with the aid of principal component analysis, a multivariate statistical analysis approach often used to reduce the dimensionality of complex data. ToF-SIMS imaging was also used to obtain information about the spatial distribution of the various additives contained within the samples. The results indicated that the samples could potentially be characterized by their 2-D chemical and morphological structure, which varied from sample to sample. XPS analysis also showed significant variation between samples, with changes in the atomic concentrations, as well as changes in the shapes of the high-resolution C 1s and O 1s spectra. These results clearly demonstrate the feasibility of utilizing both ToF-SIMS and XPS as tools for the direct characterization and differentiation of C-4 samples for forensic applications. © 2010 American Chemical Society.

Levitt I.,William ghes Technical Center
AIAA/IEEE Digital Avionics Systems Conference - Proceedings | Year: 2012

Total and uncompensated latency are important performance parameters associated with data moving through a system architecture. Often, multiple temporal notions are required to specify system latency, which introduces potential for imprecise specification or confusion to system designers. In this paper, a model of system latency is provided which can be used to formally define latency in a system architecture. The modeling is applied to ADS-B OUT system latency. © 2012 IEEE.

Lai H.,Florida International University | Leung A.,William ghes Technical Center | Magee M.,William ghes Technical Center | Almirall J.R.,Florida International University
Analytical and Bioanalytical Chemistry | Year: 2010

This study demonstrates the use of solid-phase microextraction (SPME) to extract and pre-concentrate volatile signatures from static air above plastic explosive samples followed by detection using ion mobility spectrometry (IMS) optimized to detect the volatile, non-energetic components rather than the energetic materials. Currently, sample collection for detection by commercial IMS analyzers is conducted through swiping of suspected surfaces for explosive particles and vapor sampling. The first method is not suitable for sampling inside large volume areas, and the latter method is not effective because the low vapor pressure of some explosives such as RDX and PETN make them not readily available in the air for headspace sampling under ambient conditions. For the first time, headspace sampling and detection of Detasheet, Semtex H, and C-4 is reported using SPME-IMS operating under one universal setting with limits of detection ranging from 1.5 to 2.5 ng for the target volatile signatures. The target signature compounds n-butyl acetate and the taggant DMNB are associated with untagged and tagged Detasheet explosives, respectively. Cyclohexanone and DMNB are associated with tagged C-4 explosives. DMNB is associated with tagged Semtex H explosives. Within 10 to 60 s of sampling, the headspace inside a glass vial containing 1 g of explosive, more than 20 ng of the target signatures can be extracted by the SPME fiber followed by IMS detection. © 2010 Springer-Verlag.

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