Related Publications

  • A novel application of terrestrial LIDAR to characterize elevation change at human grave surfaces in support of narrowing down possible unmarked grave locations

    Unmarked graves are difficult to locate once the ground surface no longer shows visible evidence of disturbance, posing significant challenges to missing person investigations. This research evaluates the use of terrestrial LIDAR point data for measuring localized elevation change at human grave surfaces. Three differently sized human graves, one control-pit, and surrounding undisturbed ground, were scanned four times between February 2013 and November 2014 using a tripod-mounted terrestrial laser scanner. All the disturbed surfaces exhibited measurable and localized elevation change,...
  • First Six Dimensional Phase Space Measurement of an Accelerator Beam

    This Letter presents the first complete six dimensional phase space measurement of a beam in an accelerator. The measurement was made on the Spallation Neutron Source Beam Test Facility. The data reveal previously unknown correlations in the six dimensional phase space distribution that are not visible in lower dimensionality measurements. The correlations are shown to be intensity dependent.
  • Ecosystem warming extends vegetation activity but heightens vulnerability to cold temperatures

    Shifts in vegetation phenology are a key example of the biological effects of climate change1,2,3. However, there is substantial uncertainty about whether these temperature-driven trends will continue, or whether other factors—for example, photoperiod—will become more important as warming exceeds the bounds of historical variability4,5. Here we use phenological transition dates derived from digital repeat photography6 to show that experimental whole-ecosystem warming treatments7 of up to +9 °C linearly correlate with a delayed autumn green-down and advanced spring green-up of the dominant...
  • NDA Measurement Analysis of Spent Nuclear Fuel Assemblies at the Swedish Clab Facility Using the INDEPTH Code

    A project to research the application of non-destructive assay (NDA) to spent fuel assemblies is underway among a team comprised of the European Commission, DG Energy, Directorate Safeguards; the Swedish Nuclear Fuel and Waste Management Company; Uppsala University; and US national laboratories (Los Alamos National Laboratory, Lawrence Livermore National Laboratory, and Oak Ride National Laboratory). The research goals of this project combine safeguards goals (detection of missing/substituted fuel pins and verification of operator declarations) and non-safeguards goals (estimation of decay...
  • Vibrational Spectroscopy of Water with High Spatial Resolution

    The ability to examine the vibrational spectra of liquids with nanometer spatial resolution will greatly expand the potential to study liquids and liquid interfaces. In fact, the fundamental properties of water, including complexities in its phase diagram, electrochemistry, and bonding due to nanoscale confinement are current research topics. For any liquid, direct investigation of ordered liquid structures, interfacial double layers, and adsorbed species at liquid–solid interfaces are of interest. Here, a novel way of characterizing the vibrational properties of liquid water with high...
  • Are ‘Water Smart Landscapes’ Contagious? An Epidemic Approach on Networks to Study Peer Effects

    We test the existence of a neighborhood based peer effect around participation in an incentive based conservation program called ‘Water Smart Landscapes’ (WSL) in the city of Las Vegas, Nevada. We use 15 years of geo-coded daily records of WSL program applications and approvals compiled by the Southern Nevada Water Authority and Clark County Tax Assessors rolls for home characteristics. We use this data to test whether a spatially mediated peer effect can be observed in WSL participation likelihood at the household level. We show that epidemic spreading models provide more flexibility in...
  • Initial Modeling of Urban Search Measurements

    Detection of illicit nuclear materials in urban environments is difficult due to the large amount of background radiation from naturally occurring radioactive materials (NORM) in the roadways and buildings. Mobile searches suffer from low count rates so the detection algorithms must be carefully balanced between missing real sources and reporting too many false alarms. The Modeling Urban Scenarios and Experiments (MUSE) project aims to create a virtual testbed for the simulation of radiation detection to predict realistic background and threat source detection events, so that detection...
  • Characterization of NORM in an Urban Environment using HPGe Measurements and MCNP6 Simulations

    This work is part of a larger project aimed at producing an operationally relevant, validated simulation environment that can be used as a ‘virtual testbed’ for counterterrorism and counterproliferation efforts. Examples of such efforts include searches for illicit radiation sources before and during large special events, such as the presidential nominating conventions, inaugurations, and large sporting events.1 Once validated by laboratory and field measurements, this testbed can be used to test and validate algorithms and detector systems designed for various search missions in an urban...
  • NORM Concentration Determination in Common Materials in an Urban Environment

    The United States government performs searches for illicit radiation sources before and during large special events, such as State of the Union addresses, presidential inaugurations, or the recent papal visit.1 Clear detection of sources is difficult due to natural background radiation, which can vary greatly throughout a given search area. Background radiation is mostly a function of the materials used in roadways, sidewalks, and building exteriors.2,3 A team of scientists from Oak Ridge National Laboratory (ORNL), Lawrence Livermore National Laboratory (LLNL), the Remote Sensing...
  • Determining Physical Parameters of Shielded Uranium using Gamma Spectroscopy and the DiffeRential Evolution Adaptive Metropolis (DREAM) Method

    Inverse radiation transport is a well-established method for determining unknown parameters within a system that exhibits particle leakage. Two significant challenges of solving inverse transport problems are (1) to determine multiple unknowns without false convergence on local minima and (2) to be able to quantify uncertainty. It was recently demonstrated that the DiffeRential Evolution Adaptive Metropolis (DREAM) method effectively meets both of these challenges [1]. In Bledsoe’s 2014 article [1], the DREAM method was only applied to numerical test cases in which measured data were...
  • Solving Inverse Transport Problems with Neutron Multiplication Measurements and Improved Differential Evolution

    In the problem of inverse radiation transport, measurements of particle leakages from radioactive source/shield systems are used to infer unknown parameters within the systems. This reconstruction can be accomplished by finding the physical parameters of the unknown system that minimize the difference between calculated detector responses and measured detector responses. Recently, the differential evolution (DE) method was shown to be highly adept at solving inverse transport problems in which the measured quantities were leakages of unscattered gammaray lines [1]. In this work, we present an...
  • Fukushima Daiichi Unit 1 Ex-Vessel Prediction: Core-Concrete Interaction

    Lower head failure and corium-concrete interaction were predicted to occur at Fukushima Daiichi Unit 1 (1F1) by several different system-level code analyses, including MELCOR v2.1 and MAAP5. Although these codes capture a wide range of accident phenomena, they do not contain detailed models for ex-vessel core melt behavior. However, specialized codes exist for the analysis of ex-vessel melt spreading (e.g., MELTSPREAD) and long-term debris coolability (e.g., CORQUENCH). On this basis, an analysis was carried out to further evaluate ex-vessel behavior for 1F1 using MELTSPREAD and CORQUENCH....
  • In situ edge engineering in two-dimensional transition metal dichalcogenides

    Exerting synthetic control over the edge structure and chemistry of two-dimensional (2D) materials is of critical importance to direct the magnetic, optical, electrical, and catalytic properties for specific applications. Here, we directly image the edge evolution of pores in Mo1−xW x Se2 monolayers via atomic-resolution in situ scanning transmission electron microscopy (STEM) and demonstrate that these edges can be structurally transformed to theoretically predicted metastable atomic configurations by thermal and chemical driving forces. Density functional theory calculations and ab initio...
  • Numerical simulation of runaway electrons: 3-D effects on synchrotron radiation and impurity-based runaway current dissipation

    Numerical simulations of runaway electrons (REs) with a particular emphasis on orbit dependent effects in 3-D magnetic fields are presented. The simulations were performed using the recently developed Kinetic Orbit Runaway electron Code (KORC) that computes the full-orbit relativistic dynamics in prescribed electric and magnetic fields including radiation damping and collisions. The two main problems of interest are synchrotron radiation and impurity-based RE dissipation. Synchrotron radiation is studied in axisymmetric fields and in 3-D magnetic configurations exhibiting magnetic islands and...
  • Fabrication of highly dense isotropic Nd-Fe-B nylon bonded magnets via extrusion-based additive manufacturing

    Magnetically isotropic bonded magnets with a high loading fraction of 70 vol.% Nd-Fe-B are fabricated via an extrusion-based additive manufacturing, or 3D printing system that enables rapid production of large parts. The density of the printed magnet is ∼ 5.2 g/cm3. The room temperature magnetic properties are: intrinsic coercivity Hci  = 8.9 kOe (708.2 kA/m), remanence Br  = 5.8 kG (0.58 T), and energy product (BH)max = 7.3 MGOe (58.1 kJ/m3). The as-printed magnets are then coated with two types of polymers, both of which improve the thermal stability as revealed by flux aging loss...
  • Additive manufacturing of anisotropic hybrid NdFeB-SmFeN nylon composite bonded magnets

    In this work, we demonstrate a novel method of extrusion-based 3D printing additive manufacturing of bonded magnets comprising 65 vol% anisotropic composite powders of Dy-free magfine Nd-Fe-B and Sm-Fe-N in nylon. The 3D printing was performed using a big area additive manufacturing (BAAM) process. The effects of various post-printing alignment with different magnetic field intensities and temperatures on the properties of the anisotropic bonded Nd-Fe-B + Sm-Fe-N composite magnets were investigated. Remanence increases with alignment magnetic field leading to an increase in energy product, (...
  • Mechanically Robust, Sodium-Ion Conducting Membranes for Nonaqueous Redox Flow Batteries

    Sodium-based batteries are promising for grid-storage applications because of significantly lower cost compared to lithium-based systems. The advancement of solid-state and redox-flow sodium-ion batteries requires sodium-ion exchange membranes with high conductivity, electrochemical stability, and mechanical robustness. This study demonstrates that membranes based on poly(ethylene oxide) (PEO) can meet these requirements. Membranes plasticized with tetraethylene glycol dimethyl ether (TEGDME) achieve high ionic conductivity. Plasticized PEO membranes containing sodium triflate salt (NaTFS)...
  • Sparse Bayesian Regression with Integrated Feature Selection for Nuclear Reactor Analysis

    High-dimensional-nonlinear function estimation using large datasets is a current area of interest in the machine learning community. Applications permeate throughout the analytical sciences, where evergrowing datasets are providing more information to the analyst. This paper leverages the existing relevance vector machine, a sparse Bayesian version of the well-studied support vector machine and expands the method to include integrated feature selection and automatic function shaping. These innovations produce an algorithm that can distinguish variables useful for predicting a response from...
  • A Methodology for Determining the Concentration of Naturally Occurring Radioactive Materials in an Urban Environment

    The detection of radioactive sources in an urban setting is greatly complicated by natural background radiation, which emanates from various materials including roadways, sidewalks, soil, and building exteriors. The method presented and demonstrated here represents an effort to characterize the concentration of naturally occurring radioactive material (NORM) in these types of materials. The location surveyed in this work was the Fort Indiantown Gap Combined Arms Collective Training Facility in Lebanon County, Pennsylvania. Over 70 measurements with a high-purity germanium detector were...
  • Determining initial enrichment, burnup, and cooling time of pressurized-water-reactor spent fuel assemblies by analyzing passive gamma spectra measured at the Clab interim-fuel storage facility in Sweden

    The purpose of the Next Generation Safeguards Initiative (NGSI)–Spent Fuel (SF) project is to strengthen the technical toolkit of safeguards inspectors and/or other interested parties. The NGSI–SF team is working to achieve the following technical goals more easily and efficiently than in the past using nondestructive assay measurements of spent fuel assemblies: (1) verify the initial enrichment, burnup, and cooling time of facility declaration; (2) detect the diversion or replacement of pins; (3) estimate the plutonium mass [which is also a function of the variables in (1)]; (4) estimate the...
  • Search for Neutrinoless Double-β Decay in 76Ge with the Majorana Demonstrator

    The Majorana Collaboration is operating an array of high purity Ge detectors to search for neutrinoless double-β decay in 76Ge . The Majorana Demonstrator comprises 44.1 kg of Ge detectors (29.7 kg enriched in 76Ge ) split between two modules contained in a low background shield at the Sanford Underground Research Facility in Lead, South Dakota. Here we present results from data taken during construction, commissioning, and the start of full operations. We achieve unprecedented energy resolution of 2.5 keV FWHM at Qββ and a very low background with no observed candidate events...
  • Neutron decay correlations in the Nab experiment

    The alpha correlation can be used to extract the quark mixing matrix element Vud, which is used to precisely test our understanding of the electroweak interaction. A non-zero Fierz term would signal the presence of scalar and tensor currents which must come from new physics beyond the Standard Model of Particle Physics. Nab uses an asymmetric spectrometer to determine the proton time-of-flight and the beta energy in order to reconstruct the angular correlation between the electron and antineutrino. The charged particles are detected using thick, large-area, segmented silicon detectors,...
  • Superstretchable, Self-Healing Polymeric Elastomers with Tunable Properties

    Utilization of self-healing chemistry to develop synthetic polymer materials that can heal themselves with restored mechanical performance and functionality is of great interest. Self-healable polymer elastomers with tunable mechanical properties are specially attractive for a variety of applications. Herein, a series of urea functionalized poly(dimethyl siloxane)-based elastomers (U-PDMS-Es) are reported with extremely high stretchability, self-healing mechanical properties, and recoverable gas-separation performance. Tailoring the molecular weights of poly(dimethyl siloxane) or eight ratio...
  • A general method to improve 3D-printability and inter-layer adhesion in lignin-based composites

    We report the utilization of a melt-stable lignin waste-stream from biorefineries as a renewable feedstock, with acrylonitrile-butadiene rubber and acrylonitrile-butadiene-styrene (ABS) polymer to synthesize a renewable matrix having excellent 3D-printability. While the initial low melt viscosity of the dispersed lignin phase induces local thermo-rheological relaxation facilitating the composite's melt flow, thermal crosslinking in both lignin and rubber phases as well as at the lignin-rubber interface decreases the molecular mobility. Consequently, interfacial diffusion and the resulting...
  • Modeling sequential context effects in diagnostic interpretation of screening mammograms

    Prior research has shown that physicians' medical decisions can be influenced by sequential context, particularly in cases where successive stimuli exhibit similar characteristics when analyzing medical images. This type of systematic error is known to psychophysicists as sequential context effect as it indicates that judgments are influenced by features of and decisions about the preceding case in the sequence of examined cases, rather than being based solely on the peculiarities unique to the present case. We determine if radiologists experience some form of context bias, using screening...