Publications

The Waste Isolation Pilot Plant (WIPP), located in southeastern New Mexico of the United States (U.S.), has been developed by the U.S. Department of Energy (DOE) for the geologic disposal of transuranic (TRU) waste. The DOE demonstrates compliance with the WIPP containment requirements by means of performance assessment (PA) calculations. WIPP PA calculations estimate the probability and consequence of potential radionuclide releases from the repository to the accessible environment for a regulatory period of 10,000 years after facility closure. WIPP PA models are used (in part) to support the repository recertification process that occurs at five-year intervals following the receipt of the first waste shipment at the site in 1999. The PA executed in support of the 2014 Compliance Recertification Application (CRA-2014) for WIPP includes a number of parameter, implementation, and repository feature changes. Among these changes are the incorporation of a new panel closure system design, additional mined volume in the north end of the repository, a refinement to the PA representation of WIPP waste shear strength, and a gas generation rate refinement. These changes are briefly discussed, as is their cumulative impact on regulatory compliance for the facility. The federal recertification status of the WIPP is also discussed.

Shales have small pore and throat sizes ranging from nano to micron scales, low porosity and limited permeability. The poor permeability and complex pore connectivity of shales pose technical challenges to (a) understanding flow and transport mechanisms in such systems and, (b) in predicting permeability changes under dynamic saturation conditions. This study presents quantitative experimental evidence of the migration of water through a generic shale core plug using micro CT imaging. In addition, in-situ measurements of gas permeability were performed during counter-current spontaneous imbibition of water in nano-darcy permeability Marcellus and Haynesville core plugs. It was seen that water blocks severely reduced the effective permeability of the core plugs, leading to losses of up to 99.5% of the initial permeability in experiments lasting 30 days. There was also evidence of clay swelling which further hindered gas flow. When results from this study were compared with similar counter-current gas permeability experiments reported in the literature, the initial (base) permeability of the rock was found to be a key factor in determining the time evolution of effective gas permeability during spontaneous imbibition. With time, a recovery of effective permeability was seen in the higher permeability rocks, while becoming progressively detrimental and irreversible in tighter rocks. These results suggest that matrix permeability of ultra-tight rocks is susceptible to water damage following hydraulic fracturing stimulation and, while shut-in/soaking time helps clearing-up fractures from resident fluid, its effect on the adjacent matrix permeability could be detrimental.

Conventional structural metals suffer from fatigue-crack initiation through dislocation activity which forms persistent slip bands leading to notch-like extrusions and intrusions. Ultrafine-grained and nanocrystalline metals can potentially exhibit superior fatigue-crack initiation resistance by suppressing these cumulative dislocation activities. Prior studies on these metals have confirmed improved high-cycle fatigue performance. In the case of nano-grained metals, analyses of subsurface crack initiation sites have indicated that the crack nucleation is associated with abnormally large grains. However, these post-mortem analyses have led to only speculation about when abnormal grain growth occurs (e.g., during fatigue, after crack initiation, or during crack growth). In this study, a recently developed synchrotron X-ray diffraction technique was used to detect the onset and progression of abnormal grain growth during stress-controlled fatigue loading. This study provides the first direct evidence that the grain coarsening is cyclically induced and occurs well before final fatigue failure—our results indicate that the first half of the fatigue life was spent prior to the detectable onset of abnormal grain growth, while the second half was spent coarsening the nanocrystalline structure and cyclically deforming the abnormally large grains until crack initiation. Post-mortem fractography, coupled with cycle-dependent diffraction data, provides the first details regarding the kinetics of this abnormal grain growth process during high-cycle fatigue testing. Precession electron diffraction images collected in a transmission electron microscope after the in situ fatigue experiment also confirm the X-ray evidence that the abnormally large grains contain substantial misorientation gradients and sub-grain boundaries.

The Waste Isolation Pilot Plant (WIPP) transuranic waste repository located east of Carlsbad, New Mexico, USA, consists of 10 waste panels located in the southern end and operations and experimental areas located in the northern end. Waste panels are to be separated from each other and from the northern areas by panel closure systems that consist of run-of-mine-salt that will compact and reconsolidate over time along with the creep closure of open areas of the repository. To more fully assess the sensitivity of predicted repository releases to currently implemented material parameters, the application of modified parameters in the operations and experimental (non-waste) areas of the repository is undertaken to simulate an accelerated (instantaneous) creep closure, the inclusion of capillary pressure effects on relative permeability, and an increase in initial/residual brine saturation and residual gas saturation in the operations and experimental areas of the repository. The resulting sensitivity analysis (CRA14-SEN2) is then compared to the most recent compliance recertification application results presented for CRA-2014 PA (CRA14). The modifications to the repository model result in increased pressures and decreased brine saturations in waste areas and increased pressures and brine saturations in the operations and experimental areas. The slight pressure increases in repository waste regions yield very slightly decreased brine saturations (on average) in those areas. Brine flows up the borehole during a hypothetical drilling intrusion are nearly identical to those found in the CRA14. Brine flows up the repository shaft are decreased as compared to CRA14 due to restricted flow within the operations and experimental areas. The modified operations and experimental area parameters essentially halt the flow of gas from the southern waste areas of the repository to the northern non-waste areas, except as transported through the marker beds and anhydrite layers. The combination of slightly increased waste region pressure (on average) and very slightly decreased brine saturations result in a modest increase in spallings and no significant effect on direct brine releases due to the pressure/saturation trade-off. Total releases from the Culebra and cuttings and cavings releases are not affected. Overall, the effects on total high-probability (P(R) > 0.1) mean releases from the repository are entirely insignificant, with total low-probability (P(R) > 0.001) mean releases minimally increased (~4%) and the associated 95% confidence level on the mean reduced (~20%). It is concluded that the baseline modeling assumptions associated with the operations and experimental areas of the repository have an insignificant effect on the prediction of total releases from the repository and/or adequacy of the current (CRA14) model to demonstrate compliance with the regulatory limits.

In this work we use estimates of ionic transport properties obtained from molecular dynamics to rank lithium electrolytes of different compositions. We develop linear response methods to obtain the Onsager diffusivity matrix for all chemical species, its Fickian counterpart, and the mobilities of the ionic species. We apply these methods to the well-studied propylene carbonate/ethylene carbonate solvent with dissolved LiBF4 and O2. The results show that, over a range of lithium concentrations and carbonate mixtures, trends in the transport coefficients can be identified and optimal electrolytes can be selected for experimental focus; however, refinement of these estimation techniques is necessary for a reliable ranking of a large set of electrolytes.

The MagLIF (Magnetized Liner Inertial Fusion) concept [Slutz et al., Phys. Plasmas 17, 056303 (2010)] has demonstrated fusion-relevant plasma conditions [Gomez et al., Phys. Rev. Lett. 113, 155003 (2014)] on the Z accelerator using external field coils to magnetize the fuel before compression. We present a novel concept (AutoMag), which uses a composite liner with helical conduction paths separated by insulating material to provide fuel magnetization from the early part of the drive current, which by design rises slowly enough to avoid electrical breakdown of the insulators. Once the magnetization field is established, the drive current rises more quickly, which causes the insulators to break down allowing the drive current to follow an axial path and implode the liner in the conventional z-pinch manner. There are two important advantages to AutoMag over external field coils for the operation of MagLIF. Low inductance magnetically insulated power feeds can be used to increase the drive current, and AutoMag does not interfere with diagnostic access. Also, AutoMag enables a pathway to energy applications for MagLIF, since expensive field coils will not be damaged each shot. Finally, it should be possible to generate Field Reversed Configurations (FRC) by using both external field coils and AutoMag in opposite polarities. This would provide a means to studying FRC liner implosions on the 100 ns time scale.

Bolted joints are prevalent in most assembled structures; however, predictive models for their behavior do not exist. Calibrated models, such as the Iwan model, are able to predict the response of a jointed structure over a range of excitations once calibrated at a nominal load. The Iwan model, though, is not widely adopted due to the high computational expense of implementation. To address this, an analytical solution of the Iwan model is derived under the hypothesis that for an arbitrary load reversal, there is a new distribution of dry friction elements, which are now stuck, that approximately resemble a scaled version of the original distribution of dry friction elements. The dry friction elements internal to the Iwan model do not have a uniform set of parameters and are described by a distribution of parameters, i.e., which internal dry friction elements are stuck or slipping at a given load, that ultimately governs the behavior of the joint as it transitions from microslip to macroslip. This hypothesis allows the model to require no information from previous loading cycles. Additionally, the model is extended to include the pinning behavior inherent in a bolted joint. Modifications of the resulting framework are discussed to highlight how the constitutive model for friction can be changed (in the case of an Iwan–Stribeck formulation) or how the distribution of dry friction elements can be changed (as is the case for the Iwan plasticity model). The reduced Iwan plus pinning model is then applied to the Brake–Reuß beam in order to discuss methods to deduce model parameters from experimental data.

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We discuss upsets in erased floating gate cells, due to large threshold voltage shifts, using statistical distributions collected on a large number of memory cells. The spread in the neutral threshold voltage appears to be too low to quantitatively explain the experimental observations in terms of simple charge loss, at least in SLC devices. The possibility that memories exposed to high energy protons and heavy ions exhibit negative charge transfer between programmed and erased cells is investigated, although the analysis does not provide conclusive support to this hypothesis.

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The development of scramjet engines is an important research area for advancing hypersonic and orbital flights. Progress towards optimal engine designs requires both accurate flow simulations as well as uncertainty quantification (UQ). However, performing UQ for scramjet simulations is challenging due to the large number of uncertain parameters involved and the high computational cost of flow simulations. We address these difficulties by combining UQ algorithms and numerical methods to the large eddy simulation of the HIFiRE scramjet configuration. First, global sensitivity analysis is conducted to identify influential uncertain input parameters, helping reduce the stochastic dimension of the problem and discover sparse representations. Second, as models of different fidelity are available and inevitably used in the overall UQ assessment, a framework for quantifying and propagating the uncertainty due to model error is introduced. These methods are demonstrated on a non-reacting scramjet unit problem with parameter space up to 24 dimensions, using 2D and 3D geometries with static and dynamic treatments of the turbulence subgrid model.

Materials subject to cyclic loading have been studied extensively and experimentally determined comparisons of stress to number of cycles are used to estimate fatigue life under various loading scenarios. Fatigue data are traditionally presented in the form of S-N curves. Normally, S-N data are derived from cyclic loading but the S-N results are also applicable to random vibration loading and, to some extent, shock. This paper presents an alternate presentation of fatigue data in terms of input energy and number of cycles to failure. In conjunction with this study, a series of shock tests was conducted on 3D printed cantilever beams using a 6-DOF shaker table. All of the beams were tested to failure at shock levels in the low-cycle fatigue regime. From these data, a nominal fatigue curve in terms of input energy and number of shocks to failure was generated and compared with the theoretical developments.

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The efficiency of discrete ordinates transport sweeps depends on the scheduling algorithm, the domain decomposition, the problem to be solved, and the computational platform. Sweep scheduling algorithms may be categorized by their approach to several issues. In this paper we examine the strategy of domain overloading for mesh partitioning as one of the components of such algorithms. In particular, we extend the domain overloading strategy, previously defined and analyzed for structured meshes, to the general case of unstructured meshes. We also present computational results for both the structured and unstructured domain overloading cases. We find that an appropriate amount of domain overloading can greatly improve the efficiency of parallel sweeps for both structured and unstructured partitionings of the test problems examined on up to 105 processor cores.

As MIL-STD-810G, Environmental Engineering Considerations and Laboratory Tests, and subsequent versions have incorporated multiple-degree-of-freedom (MDOF) vibration test methodologies, it is important to understand the history and factors that drove the original decision in MIL-STD-810 to focus on single-degree-of-freedom (SDOF) vibration testing. Examining the thought process behind early MIL-STD-810 vibration test methods is useful when considering MDOF testing now that it is feasible with today's technology and documented in MIL-STD-810. This paper delves into the details of the decision made in the 1960s to develop the SDOF vibration testing standards in MIL-STD-810 beyond the limitations of technology at the time. This paper also considers the implications for effective test planning today considering the advances in test capabilities and improvements in understanding of the operational environment.

The 3D Scanning Laser Doppler Vibrometer (3D SLDV) has the ability to scan a large number of points with high accuracy compared to traditional roving hammer or accelerometer tests. The 3D SLDV has disadvantages, however, in that it requires line-of-sight from three scanning laser heads to the point being measured. This means that multiple scans can become necessary to measure large or complex parts, and internal components cannot typically be measured. In the past, large aerospace structures tested at Sandia National Laboratories typically have used a handful of accelerometer stations and instrumented internal components to characterize these test articles. This work describes two case studies that explore the advantages and difficulties in using a 3D SLDV to measure the same test articles with a much higher resolution scan of the exterior. This work proposes strategies for combining a large number of accelerometer channels with a high resolution laser scan. It explores the use of mirrors and laser head mounts to enable efficient re-alignment of the lasers with the test article when many scans are necessary, and it discusses the difficulties and pitfalls inherent with performing such a test.

Researchers present a Li-ion synaptic transistor for analog computation (LISTA). LISTA is an all solidstate, nonvolatile redox transistor (NVRT) with a resistance switching mechanism based upon the intercalation of Li-ion dopants into a channel of Li1-xCoO2. The researchers also demonstrate that an NVRT device is advantageous for neuromorphic applications because it utilizes the low energy process of ion insertion/extraction for resistance switching while maintaining nonvolatility.

We designed and produced optical coatings for broad bandwidth high reflection (BBHR) of femtosecond (fs) pulses for high energy petawatt (PW) lasers. These BBHR coatings consist of TiO2/SiO2 and/or HfO2/SiO2 layer pairs formed by reactive E-beam evaporation with ion-assisted deposition in Sandia's Large Optics Coating Facility. Specifications for the HR band and center wavelength of the coatings are for 45° angle of incidence (AOI), P polarization (Ppol), with use of the coatings at different AOIs and in humid or dry/vacuum environments providing corresponding different HR center wavelengths and spectral widths. These coatings must provide high laserinduced damage threshold (LIDT) to handle the PW fluences, and also low group delay dispersion (GDD) to reflect fs pulses without distortion of their temporal profiles. We present results of LIDT and GDD measurements on these coatings. The LIDT tests are at 45° or 65° AOI, Ppol in a dry environment with 100 fs laser pulses of 800 nm line center for BBHR coatings whose HR band line centers are near 800 nm. A GDD measurement for one of the BBHR coatings whose design HR center wavelength is near 900 nm shows reasonably low and smoothly varying GDD over the HR band. Our investigations include BBHR coatings designed for 45° AOI, Ppol with HR bands centered at 800 nm in dry or vacuum environments, and featuring three options: all TiO2/SiO2 layer pairs; all HfO2/SiO2 layer pairs; and TiO2/SiO2 inner layer pairs with 5 outer HfO2/SiO2 layer pairs. LIDT tests of these coatings with 100 fs, 800 nm line center pulses in their use environment show that replacing a few outer TiO2 layers of TiO2/SiO2 BBHR coatings with HfO2 leads to ∼ 80% higher LIDT with only minor loss of HR bandwidth.

Using III-V dielectric metasurfaces, we experimentally demonstrate resonantly enhanced harmonic generations up to the 4th order. Moreover, we observe large enhancements and spectral tailoring of the photoluminescence of quantum dots embedded inside dielectric metasurfaces. © OSA 2017.

Emerging novel architectures for shared memory parallel computing are incorporating increasingly creative innovations to deliver higher memory performance. A notable exemplar of this phenomenon is the Multi-Channel DRAM (MCDRAM) that is included in the Intel® XeonPhi™ processors. In this paper, we examine techniques to use OpenMP to exploit the high bandwidth of MCDRAM by staging data. In particular, we implement double buffering using OpenMP sections and tasks to explicitly manage movement of data into MCDRAM. We compare our double-buffered approach to a non-buffered implementation and to Intel’s cache mode, in which the system manages the MCDRAM as a transparent cache. We also demonstrate the sensitivity of performance to parameters such as dataset size and the distribution of threads between compute and copy operations.

Accident scenarios in nuclear power plants that bypass containment have the potential for large and early releases of radionuclides. They are typically guarded against using means such as redundant valves arranged in series and interlocks for systems that interface with the high pressure reactor coolant system. Some of these preventative arrangements rely on active systems that may fail in unique ways with the introduction of digital instrumentation and control. A hypothetical scenario in a pressurized water reactor plant is examined in which the digital controllers for the residual heat removal system intake valves are subjected to a common cause failure. This failure may cause simultaneous unintended valve opening while the reactor is at power, which has the potential to overpressurize and damage piping in the residual heat removal system and cause a leak of primary system water past containment into the auxiliary building (interfacing system loss of coolant accident). If the controllers are in a persistent fault condition, plant personnel will have to traverse the potentially contaminated auxiliary building to override at least one controller and close its associated valve. A dynamic case is assembled and run using the ADAPT dynamic event tree driver and the MELCOR severe accident analysis code in which uncertainties in the progression of the accident as well as mitigating operator actions are explored for an interfacing systems loss of coolant accident initiator. The results are assessed using recently-developed tools to gain insight into the likely outcomes and key events.

We experimentally investigate a new class of quasi-aperiodic structures for improving the emission pattern in nanowire arrays. Efficient normal emission, as well as lasing, can be obtained from III-nitride photonic crystal (PhC) nanowire arrays that utilize slow group velocity modes near the G-point in reciprocal space. However, due to symmetry considerations, the emitted far-field pattern of such modes are often 'donut'-like. Many applications, including lighting for displays or lasers, require a more uniform beam profile in the far-field. Previous work has improved far-field beam uniformity of uncoupled modes by changing the shape of the emitting structure. However, in nanowire systems, the shape of nanowires cannot always be arbitrarily changed due to growth or etch considerations. Here, we investigate breaking symmetry by instead changing the position of emitters. Using a quasi-aperiodic geometry, which changes the emitter position within a photonic crystal supercell (2x2), we are able to linearize the photonic bandstructure near the G-point and greatly improve emitted far-field uniformity. We realize the III-nitride nanowires structures using a top-down fabrication procedure that produces nanowires with smooth, vertical sidewalls. Comparison of room-temperature micro-photoluminescence (μ-PL) measurements between periodic and quasi-aperiodic nanowire arrays reveal resonances in each structure, with the simple periodic structure producing a donut beam in the emitted far-field and the quasi-aperiodic structure producing a uniform Gaussian-like beam. We investigate the input pump power vs. output intensity in both systems and observe the simple periodic array exhibiting a non-linear relationship, indicative of lasing. We believe that the quasi-aperiodic approach studied here provides an alternate and promising strategy for shaping the emission pattern of nanoemitter systems.

We have integrated an ultrahigh mobility twodimensional electron gas with a high-quality-factor terahertz photonic cavity. With a quantizing magnetic field and at low temperatures, we demonstrated collective nonperturbative coupling of the electron cyclotron resonance with terahertz cavity photons with a high cooperativity. Due to the suppression of superradiance-induced broadening of cyclotron resonance by the high-quality-factor cavity, our hybrid quantum system exhibited unprecedentedly sharp polariton lines and a large vacuum Rabi splitting simultaneously.

Time-resolved particle image velocimetry (PIV) was conducted at 40 kHz using a pulse-burst laser in the supersonic wake of a wall-mounted hemisphere. Velocity fields suggest a recirculation region with two lobes in which flow moves away from the wall near centerline and recirculates back towards the hemisphere off centerline. Spatio-temporal cross-correlations and conditional ensemble averages relate the characteristic behavior of the unsteady shock motion to the flapping of the shear layer. At Mach 1.5, oblique shocks form associated with vortical structures in the shear layer and convect downstream in tandem; a weak periodicity is observed. Shock motion at Mach 2.0 appears somewhat different, wherein multiple weak disturbances propagate from shear layer turbulent structures to form an oblique shock that ripples as these vortices pass by. Bifurcated shock feet coalesce and break apart without evident periodicity. Power spectra show a preferred frequency of shear layer flapping and shock motion for Mach 1.5, but at Mach 2.0 a weak preferred frequency is found only for the oblique shock motion and not the shear layer unsteadiness.

Optical coatings deposited using electron beam evaporation are subject to aging effects that change the spectral characteristics of the optical coating. The aim of this study was to determine whether aging effects can also negatively impact the laser damage resistance of an optical coating. Maintaining high resistance to laser damage is particularly important for the performance of high fluence laser systems. In 2013, we deposited different high reflection coatings for 1054 nm containing HfO2/TiO2/SiO2 layers. For this study, we re-measured the laser damage thresholds of these coatings at 3.5 ns to determine if aging effects cause the laser damage threshold to decline, and to compare whether HfO2 or TiO2 is superior in terms of long-term laser damage resistance.

With the growing complexity and scale of high performance computing (HPC) systems, application performance variation has become a significant challenge in efficient and resilient system management. Application performance variation can be caused by resource contention as well as software- and firmware-related problems, and can lead to premature job termination, reduced performance, and wasted compute platform resources. To effectively alleviate this problem, system administrators must detect and identify the anomalies that are responsible for performance variation and take preventive actions. However, diagnosing anomalies is often a difficult task given the vast amount of noisy and high-dimensional data being collected via a variety of system monitoring infrastructures. In this paper, we present a novel framework that uses machine learning to automatically diagnose previously encountered performance anomalies in HPC systems. Our framework leverages resource usage and performance counter data collected during application runs. We first convert the collected time series data into statistical features that retain application characteristics to significantly reduce the computational overhead of our technique. We then use machine learning algorithms to learn anomaly characteristics from this historical data and to identify the types of anomalies observed while running applications. We evaluate our framework both on an HPC cluster and on a public cloud, and demonstrate that our approach outperforms current state-of-the-art techniques in detecting anomalies, reaching an F-score over 0.97.

The Craig-Bampton approach for component mode synthesis in structural dynamics has been widely used to reduce the order of large, detailed finite element models made from linear elastic materials. This methodology separates the full order model into smaller subcomponents and reduces the equations of motion with a truncated set of fixed-interface modes and static constraint modes. A drawback of this approach is that the model has one constraint mode for every interface degree-of-freedom, which may result in a large and prohibitively costly superelement. Previous work has addressed this issue via characteristic constraint modes, which reduces the number of interface degrees-of-freedom by performing a secondary modal analysis on the interface partition. The current work extends the Craig-Bampton approach with interface reduction to include subcomponents with linear viscoelastic materials modeled using a Prony series. For substructures containing materials such as foams or polymers, the viscoelastic constitutive law more accurately represents the material energy dissipation compared to traditional viscous or modal damping. The new approach will be demonstrated on the assembly of two composite plates with fixed boundary conditions along one edge.

Abstract not provided.

During 2016, nuclear criticality safety (NCS) practitioners from SNL and code developers from LANL collaborated in several areas of interest to the DOE/NNSA Nuclear Criticality Safety Program (NCSP). This collaboration involved. Testing of the preliminary release of the MCNP6- Whisper methodology, with feedback to the developers, Sharing of the benchmark catalogs (the collection of MCNP input files and benchmark results), with 1101 cases from LANL and 866 cases from SNL, Comparison and analysis of 357 benchmarks common to both catalogs, Investigation of the impact of the different benchmark catalogs on sensitivity-uncertainty based NCS validation results from MCNP6-Whisper, Investigation of the impact of randomized selections from the benchmark catalog on sensitivity-uncertainty based validation results from MCNP6-Whisper. Investigation of the use of MCNP6-Whisper in selecting benchmarks for use in NCS validation for unique, nonstandard, legacy fuel applications. This paper summarizes the collaboration work and initial results. It must be noted that the results described herein are preliminary and need further research and detailed analysis. However, the initial results are very interesting, and it is important to share them with the NCSP community.

The reaction of OH with H2 is a crucial chain-propagating step in the H2-O2 system thus making the specification of its rate, and its uncertainty, important for predicting the high-temperature combustion of hydrocarbons. In order to obtain an uncertain representation of this reaction rate in the absence of actual experimental data, we perform an inference procedure employing maximum entropy and approximate Bayesian computation methods to discover hypothetical data from a target shock-tube experiment designed to measure the reverse reaction rate. This method attempts to invert the fitting procedure from noisy measurement data to parameters, with associated uncertainty specifications, to arrive at candidate noisy data sets consistent with these reported parameters and their uncertainties. The uncertainty structure of the Arrhenius parameters is obtained by fitting each hypothetical data set in a Bayesian framework and pooling the resulting joint parameter posterior densities to arrive at a consensus density. We highlight the advantages of working with a data-centric representation of the experimental uncertainty with regards to model choice and consistency, and the ability for combining experimental evidence from multiple sources. Finally, we demonstrate the utility of knowledge of the joint Arrhenius parameter density for performing predictive modeling of combustion systems of interest.

Optical coatings deposited using electron beam evaporation are subject to aging effects that change the spectral characteristics of the optical coating. The aim of this study was to determine whether aging effects can also negatively impact the laser damage resistance of an optical coating. Maintaining high resistance to laser damage is particularly important for the performance of high fluence laser systems. In 2013, we deposited different high reflection coatings for 1054 nm containing HfO2/TiO2/SiO2 layers. For this study, we re-measured the laser damage thresholds of these coatings at 3.5 ns to determine if aging effects cause the laser damage threshold to decline, and to compare whether HfO2 or TiO2 is superior in terms of long-term laser damage resistance.

Although many optical-quality glass materials are available for use in optical systems, the range of polymeric materials is limited. Polymeric materials have some advantages over glass when it comes to large-scale manufacturing and production. In smaller scale systems, they offer a reduction in weight when compared to glass counterparts. This is especially important when designing optical systems meant to be carried by hand. We aimed to expand the availability of polymeric materials by exploring both crown-like and flint-like polymers. In addition, rapid and facile production was also a goal. By using UV-cured thiolene-based polymers, we were able to produce optical materials within seconds. This enabled the rapid screening of a variety of polymers from which we down-selected to produce optical flats and lenses. We will discuss problems with production and mitigation strategies in using UV-cured polymers for optical components. Using UV-cured polymers present a different set of problems than traditional injection-molded polymers, and these issues are discussed in detail. Using these produced optics, we integrated them into a modified direct view optical system, with the end goal being the development of drop-in replacements for glass components. This optical production strategy shows promise for use in lab-scale systems, where low-cost methods and flexibility are of paramount importance.

Here we report for the first time the feasibility of using metal-organic frameworks (MOFs) as electrodes for aqueous Na-ion batteries. We show that Fe-MIL-100, a known redox-active MOF, is electrochemically active in a Na aqueous electrolyte, under various compositions. Emphasis was placed on investigating the electrode-electrolyte interface, with a focus on identifying the relationship between additives in the composition of the working electrode, particle size and overall performance. We found that the energy storage capacity is primarily dependent on the binder additive in the composite; the best activity for this MOF is obtained with Nafion as a binder, owing to its hydrophilic and ion conducting nature. Kynar-bound electrodes are clearly less effective, due to their hydrophobic character, which impedes wetting of the electrode. The binder-free systems show the poorest electrochemical activity. There is little difference in the overall performance as function of particle size (micro vs. nano), implying the storage capacities in this study are not limited by ionic and/or electronic conductivity. Excellent reversibility and high coulombic efficiency are achieved at higher potential ranges, observed after cycle 20. That is despite progressive capacity decay observed in the initial cycles. Importantly, structural analyses of cycled working electrodes confirm that the long range crystallinity remains mainly unaltered with cycling. These findings suggest that limited reversibility of the intercalated Na ions in the lower potential range, together with the gradual lack of available active sites in subsequent cycles is responsible for the rapid decay in capacity retention.

The intent of this work is to highlight the role of differential and integral data evaluation to address issues in connection with criticality safety applications. Demonstration is made by using, as an example, differential data measurements and evaluation, and the benchmark integral experiments for titanium. Energy-differential data are measured analyzed and evaluated to produce nuclear data libraries for criticality safety applications. Alternatively, integral experiments are performed at critical facilities, small experimental reactors, and play an important part in the validation of the differential nuclear data. The demonstration provided here for titanium gives its importance to criticality safety. Titanium is an effective neutron absorber that serves as baseline material for chemical separation in high-activity waste solutions in US. Titanium has not been considered for use in nuclear applications such as reactor design and analysis. Rather, it appears as a structural material that may be present in fuel cycle facilities or canisters for transport and disposition of nuclear waste. Criticality safety evaluations of systems in which titanium is present require an understanding of the nuclear data and its uncertainty.

A simple procedure has been developed to create palladium (Pd) films on the surface of several common polymers used in commercial fused deposition modeling (FDM) and stereolithography (SLA) based three-dimensional (3D) printing by an electroless deposition process. The procedure can be performed at room temperature, with equipment less expensive than many 3D printers, and occurs rapidly enough to achieve full coverage of the film within a few minutes. 3D substrates composed of dense logpile or cubic lattices with part sizes in the mm to cm range, and feature sizes as small as 150 μm were designed and printed using commercially available 3D printers. The deposition procedure was successfully adapted to show full coverage in the lattice substrates. The ability to design, print, and metallize highly ordered three-dimensional microscale structures could accelerate development of a range of optimized chemical and mechanical engineering systems.

Manufacturing of integrated circuits (ICs) using a split foundry process expands design space in IC fabrication by employing unique capabilities of multiple foundries and provides added security for IC designers [1] Defect localization and root cause analysis is critical to failure identification and implementation of corrective actions. In addition to split-foundry fabrication, the device addressed in this publication is .comprised of 8 metal layers, aluminum test pads, and tungsten thru-silicon vias (TSVs) making the circuit area > 68% metal. This manuscript addresses the failure analysis efforts involved in root cause analysis, failure analysis findings, and the corrective actions implemented to eliminate these failure mechanisms from occurring in future product.

Abstract not provided.

One of the more common forms of passive vibration isolation in mechanical systems has been the use of elastomeric or foam pads. Cellular silicone foam is one such example which has been used for vibration isolation and mitigating the effects of mechanical shock. There are many desirable properties of cellular silicone, including its resilience and relative insensitivity to environmental extremes. However, there is very little test data that is useful for understanding its dynamic characteristics or for the development of a predictive finite element model. The problem becomes increasingly difficult since foam materials typically exhibit nonlinear damping and stiffness characteristics. In this paper we present a test fixture design and method for extraction of a few dynamic properties of one type of cellular silicone foam pad. The nonlinear damping characteristics derived from the experimental testing are then used to attempt to improve the predictive capability of a linear finite element model of the system. Difficulties and lessons learned are also presented.

One nearly ubiquitous, but often overlooked, source of measurement error in Digital Image Correlation (DIC) arises from imaging through heat waves. “Heat waves” is a colloquial term describing a heterogeneous refractive index field caused by temperature (and thus density) gradients in air. Many sources of heat waves exist in a typical DIC experiment, including hot lights, a heated sample, sunlight, or even a hot camera. This paper presents a detailed description of the error introduced to DIC measurements as a result of heat sources being present in the system. We present characteristic spatial and temporal frequencies of heat waves, and explore the relationships between the location of the heat source, the focal length of the lens, and the stand-off distance between the camera and the imaged object. Finally, we conclude with suggested methods of mitigating the effects of heat waves first by careful design of the experiment and second through data processing. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration under contract No. DE-AC04-94AL85000.

Predicted lateral power device performance as a function of alloy composition is characterized by a standard lateral device figure-of-merit (LFOM) that depends on mobility, critical electric field, and sheet carrier density. The paper presents calculations of AlGaN electron mobility in lateral devices such as HEMTs across the entire alloy composition range. Alloy scattering and optical polar phonon scattering are the dominant mechanisms limiting carrier mobility. Due to the significant degradation of mobility from alloy scattering, at room temperature Al fractions greater than about 85% are required for improved LFOM relative to GaN using a conservative sheet charge density of 1 × 1013 cm−2. However, at higher temperatures at which AlGaN power devices are anticipated to operate, this “breakeven” composition decreases to about 65% at 500 K, for example. For high-frequency applications, the Johnson figure-of-merit (JFOM) is the relevant metric to compare potential device performance across materials platforms. At room temperature, the JFOM for AlGaN alloys is predicted to surpass that of GaN for Al fractions greater than about 40%.

The finite element method has revolutionized structural analysis since its inception over 50 years ago, by enabling the computer analysis of geometrically complex structures. The main requirement of the finite element method is that an appropriate partition, or mesh, of the structure be created first. The elements of the partition typically have standard shapes, such as the hexahedron, pentahedron, and tetrahedron. While this small library of standard element shapes is sufficient for many applications, there is a growing need for more general polyhedral shapes, ones that can have an arbitrary number of vertices, edges, and faces, and ones that can be non-convex. In this chapter, we discuss current and possible future applications of polyhedral finite elements in solid mechanics. These applications include rapid engineering analysis through novel meshing and discretization techniques, and fracture and fragmentation modeling. Several finite element formulations of general polyhedra have been developed. In this chapter we use a polyhedral formulation based on the use of harmonic shape functions. Harmonic shape functions are one example of several possible generalized barycentric coordinates, as discussed in Chapter 1.

Previous research at Sandia National Laboratories showed the potential advantages of using light-trapping features which are not currently used in direct tubular receivers. A horizontal bladed receiver arrangement showed the best potential for increasing the effective solar absorptance by increasing the ratio of effective surface area to the aperture footprint. Ray-tracing analyses using SolTrace were performed to understand the light-trapping effects of the bladed receivers, which enable re-reflections between the fins that enhance the effective solar absorptance. A parametric optimization study was performed to determine the best possible configuration with a fixed intrinsic absorptivity of 0.9 and exposed surface area of 1 m². The resulting design consisted of three vertical panels 0.584 m long and 0.508 m wide and 3 blades 0.508 m long and 0.229 m wide with a downward tilt of 50 degrees from the horizontal. Each blade consisted of two panels which were placed in front of the three vertical panels. The receiver was tested at the National Solar Thermal Test Facility using pressurized air. However, the receiver was designed to operate using supercritical carbon dioxide (sCO2) at 650 °C and 15 MPa for 100,000 hours following the ASME Boiler and Pressure Vessel Code Section VIII Division 1. The air flowed through the leading panel of the blade first, and then recirculated toward the back panel of the blade before flowing through one of the vertical back panels. The test results of the bladed receiver design showed a receiver efficiency increase over a flat receiver panel of ∼5 - 7% (from ∼80% to ∼86%) over a range of average irradiances, while showing that the receiver tubes can withstand temperatures > 800 °C with no issues. Computational fluid dynamics (CFD) modeling using the Discrete Ordinates (DO) radiation model was used to predict the temperature distribution and the resulting receiver efficiencies. The predicted thermal efficiency and surface temperature values correspond to the measured efficiencies and surface temperatures within one standard deviation. In the near future, an sCO2 flow system will be built to expose the receiver to higher pressure and fluid temperatures which could yield higher efficiencies.

Broad bandwidth coatings allow angle of incidence flexibility and accommodate spectral shifts due to aging and water absorption. Higher refractive index materials in optical coatings, such as TiO2, Nb2O5, and Ta2O5, can be used to achieve broader bandwidths compared to coatings that contain HfO2 high index layers. We have identified the deposition settings that lead to the highest index, lowest absorption layers of TiO2, Nb2O5, and Ta2O5, via e-beam evaporation using ion-assisted deposition. We paired these high index materials with SiO2 as the low index material to create broad bandwidth high reflection coatings centered at 1054 nm for 45 deg angle of incidence and P polarization. High reflection bandwidths as large as 231 nm were realized. Laser damage tests of these coatings using the ISO 11254 and NIF-MEL protocols are presented, which revealed that the Ta2O5/SiO2 coating exhibits the highest resistance to laser damage, at the expense of lower bandwidth compared to the TiO2/SiO2 and Nb2O5/SiO2 coatings.

A conceptual model for turbulent ignition in high-pressure spray flames is presented. The model is motivated by first-principles simulations and optical diagnostics applied to the Sandia n-dodecane experiment. The combined analysis established a conceptual model for turbulent ignition in high-pressure spray flames which is based on a set of identified characteristic time scales. The suddenly forming steep gradients from successful high-temperature ignition initiate the propagation of a turbulent flame. It rapidly ignites the entire spray head on time scales which are generally significantly smaller than the corresponding cool flame wave time scales.

The efficiency of discrete ordinates transport sweeps depends on the scheduling algorithm, the domain decomposition, the problem to be solved, and the computational platform. Sweep scheduling algorithms may be categorized by their approach to several issues. In this paper we examine the strategy of domain overloading for mesh partitioning as one of the components of such algorithms. In particular, we extend the domain overloading strategy, previously defined and analyzed for structured meshes, to the general case of unstructured meshes. We also present computational results for both the structured and unstructured domain overloading cases. We find that an appropriate amount of domain overloading can greatly improve the efficiency of parallel sweeps for both structured and unstructured partitionings of the test problems examined on up to 10⁵ processor cores.

We propose, theoretically investigate, and numerically validate an algorithm for the Monte Carlo solution of least-squares polynomial approximation problems in a collocation framework. Our investigation is motivated by applications in the collocation approximation of parametric functions, which frequently entails construction of surrogates via orthogonal polynomials. A standard Monte Carlo approach would draw samples according to the density defining the orthogonal polynomial family. Our proposed algorithm instead samples with respect to the (weighted) pluripotential equilibrium measure of the domain, and subsequently solves a weighted least-squares problem, with weights given by evaluations of the Christoffel function. We present theoretical analysis to motivate the algorithm, and numerical results that show our method is superior to standard Monte Carlo methods in many situations of interest.

Motivated by applications in risk management of computational systems, we focus our attention on a special case of the partial vertex cover problem, where the underlying graph is assumed to be a tree. Here, we consider four possible versions of this setting, depending on whether vertices and edges are weighted or not. Two of these versions, where edges are assumed to be unweighted, are known to be polynomial-time solvable. However, the computational complexity of this problem with weighted edges, and possibly with weighted vertices, has not been determined yet. The main contribution of this paper is to resolve these questions by fully characterizing which variants of partial vertex cover remain intractable in trees, and which can be efficiently solved. In particular, we propose a pseudo-polynomial DP-based algorithm for the most general case of having weights on both edges and vertices, which is proven to be NP-hard. This algorithm provides a polynomialtime solution method when weights are limited to edges, and combined with additional scaling ideas, leads to an FPTAS for the general case. A secondary contribution of this work is to propose a novel way of using centroid decompositions in trees, which could be useful in other settings as well.

Ubiquitous in rotating machinery, flywheels smooth the flow of energy in rotary systems ranging from small engines to large reciprocating machines. A new class of standalone flywheel energy storage system has been in use since the late 20th century. These systems are electrically connected to the applications that they serve. They may be found in applications as diverse as uninterruptible power supplies, racecars, and large physics research facilities. This chapter presents the theoretical and practical foundations of flywheel design, the history of flywheels from ancient times to the present, flywheel subsystem technology, and a survey of applications where flywheel energy storage systems are currently in service.

Product formation, in particular ketohydroperoxide formation and decomposition, were investigated in time-resolved, Cl-atom initiated neopentane oxidation experiments in the temperature range 550-675 K using a photoionization time-of-flight mass spectrometer. Ionization light was provided either by Advanced Light Source tunable synchrotron radiation or ∼10.2 eV fixed energy radiation from a H2-discharge lamp. Experiments were performed both at 1-2 atm pressure using a high-pressure reactor and also at ∼9 Torr pressure employing a low-pressure reactor for comparison. Because of the highly symmetric structure of neopentane, ketohydroperoxide signal can be attributed to a 3-hydroperoxy-2,2-dimethylpropanal isomer, i.e. from a γ-ketohydroperoxide (γ-KHP). The photoionization spectra of the γ-KHP measured at low- and high pressures and varying oxygen concentrations agree well with each other, further supporting they originate from the single isomer. Measurements performed in this work also suggest that the "Korcek" mechanism may play an important role in the decomposition of 3-hydroperoxy-2,2-dimethylpropanal, especially at lower temperatures. However, at higher temperatures where γ-KHP decomposition to hydroxyl radical and oxy-radical dominates, oxidation of the oxy-radical yields a new important channel leading to acetone, carbon monoxide, and OH radical. Starting from the initial neopentyl + O2 reaction, this channel releases altogether three OH radicals. A strongly temperature-dependent reaction product is observed at m/z = 100, likely attributable to 2,2-dimethylpropanedial.

Transported probability density function (TPDF) methods are an attractive modeling approach for turbulent flames as chemical reactions appear in closed form. However, molecular micro-mixing needs to be modeled and this modeling is considered a primary challenge for TPDF methods. In the present study, a new algebraic mixing rate model for TPDF simulations of turbulent premixed flames is proposed, which is a key ingredient in commonly used molecular mixing models. The new model aims to properly account for the transition in reactive scalar mixing rate behavior from the limit of turbulence-dominated mixing to molecular mixing behavior in flamelets. An a priori assessment of the new model is performed using direct numerical simulation (DNS) data of a lean premixed hydrogen–air jet flame. The new model accurately captures the mixing timescale behavior in the DNS and is found to be a significant improvement over the commonly used constant mechanical-to-scalar mixing timescale ratio model. An a posteriori TPDF study is then performed using the same DNS data as a numerical test bed. The DNS provides the initial conditions and time-varying input quantities, including the mean velocity, turbulent diffusion coefficient, and modeled scalar mixing rate for the TPDF simulations, thus allowing an exclusive focus on the mixing model. The new mixing timescale model is compared with the constant mechanical-to-scalar mixing timescale ratio coupled with the Euclidean Minimum Spanning Tree (EMST) mixing model, as well as a laminar flamelet closure by Pope and Anand (1984). It is found that the laminar flamelet closure is unable to properly capture the mixing behavior in the thin reaction zones regime while the constant mechanical-to-scalar mixing timescale model under-predicts the flame speed. The EMST model coupled with the new mixing timescale model provides the best prediction of the flame structure and flame propagation among the models tested, as the dynamics of reactive scalar mixing across different flame regimes are appropriately accounted for.

Energy storage (ES) is a pivotal technology for dealing with the challenges caused by the integration of renewable energy sources. It is expected that a decrease in the capital cost of storage will eventually spur the deployment of large amounts of ES. These devices will provide transmission services, such as spatiotemporal energy arbitrage, i.e., storing surplus energy from intermittent renewable sources for later use by loads while reducing the congestion in the transmission network. This paper proposes a bilevel program that determines the optimal location and size of storage devices to perform this spatiotemporal energy arbitrage. This method aims to simultaneously reduce the system-wide operating cost and the cost of investments in ES while ensuring that merchant storage devices collect sufficient profits to fully recover their investment cost. The usefulness of the proposed method is illustrated using a representative case study of the ISO New England system with a prospective wind generation portfolio.

In this column, the guest editors introduce the six articles in the special issue on Architectures for the Post-Moore Era.

In various applications with recirculation, liquid droplets can be immersed in gases that may have a wide range of possible compositions, from pure air to hot combustion products. In order to gain fundamental understanding of the behaviour of individual droplets in vitiated air, numerical simulations of kerosene single droplet evaporation, autoignition, and combustion in conditions relevant to gas turbines have been performed. The droplet autoignition behaviour has been analysed in both physical and mixture fraction space for a wide range of vitiated air compositions and initial droplet diameters. Results show that the autoignition time delay decreases with increasing level of dilution with hot combustion products and decreasing initial droplet diameter. Chemistry is confined up to a radius of almost 10 initial droplet diameters and the location of autoignition is influenced by both the initial droplet diameter and the level of dilution. The time evolution of species in the gaseous phase after autoignition shows similar trends for all the diameters and dilution levels investigated here with the peak of temperature and OH mass fraction moving towards the droplet surface as a consequence of the balance between fuel production and consumption. In mixture fraction space, the location of the peaks of temperature and OH mass fraction after autoignition do not change in time whereas other intermediate species such as CH2O and pyrolysis products still exhibit a quite variable behaviour. The long-time flame structure has been compared with gaseous laminar counterflow simulations and, although qualitatively similar, the flame structure in the two configurations has differences with implications for flamelet combustion models used in spray combustion. The droplet evaporation, autoignition, and combustion behaviour has been summarized through a regime diagram showing the evaporation and autoignition time delays as a function of both initial droplet diameter and vitiated air dilution. This allows the identification of different states in the droplet combustion scenario and the introduction of critical values of dilution and initial droplet diameter beyond which single droplet rather than cloud combustion can occur, which can be exploited in the design of lean burn gas turbine combustion systems. The approach presented here can be easily extended to other conditions and fuels allowing the generation of regime diagrams for various operating conditions.

The synthesis of a series of lanthanide trifluoroacetic acid (H-TFA) derivatives which contain only the TFA and its conjugate acid has been developed. From the reaction of Ln(N(SiMe3)2)3 with an excess amount of H-TFA, the products were identified as: [Ln(μ-TFA)3(H-TFA)2]n (Ln = Y, Ce, Sm, Eu, Gd, Tb, Dy), [Ln(μ-TFA)3(μ-H-TFA)]n·solv (Ln·solv = Pr·2 H-TFA, H3O+, Ho·2py, Er·py, Yb·py, H-TFA), 3[H][(TFA)La(μ-TFA)3La(TFA)(μ-TFA)2(μc-TFA)2]n ½(H2O) ½(H2O, H-TFA) (La·½(H2O) ½(H2O, H-TFA)), [(k2-TFA)Nd(μ-TFA)3]n·H-py+ (Nd·H-py+), [(py)2Tm(μ-TFA)3]n (Tm), or [Lu(μ-TFA)4Lu(μ-TFA)3·H3O+]n (Lu·H3O+). The majority of samples formed long chain polymers with 3 or 4 μ-TFA ligands. Tm was isolated with py coordinated to the metal, whereas Ho, Er, and Yb were isolated with py located within the lattice. Select samples from this set of compounds were used to generate nanomaterials under solvothermal (SOLVO) conditions using pyridine (py) or octylamine at 185 °C for 24 h. The SOLVO products were isolated as: (i) from py: La – fluocerite (LaF3, PDF 98-000-0214, R = 9.64%, 35(0) nm), Tb – terbium fluoride (TbF3, PDF 00-037-1487, R = 4.76%, 21(2) nm), Lu lutetium oxy fluoride (LuOF, PDF 00-052-0779, R = 8.24%, 8(2) nm); (ii) from octylamine: La – fluocerite/lanthanum oxide carbonate (LaF3, PDF 98-000-0214, R = 7.47%, 5(0) nm; La2O2(CO3), PDF 01-070-5539, R = 12.32%, 12(0) nm), Tb – terbium oxy fluoride (TbOF, PDF 00-008-0230, R = 7.01%, 5(0) nm); Lu – lutetium oxide (Lu2O3, PDF 00-012-0728, R = 6.52%, 6(1) nm).

A detailed kinetic model comprising low- and high-temperature reaction pathways capable of predicting the combustion characteristics of cyclopentane was studied. The simulations reproduced the unique reactivity trend of cyclopentane and the measured concentration profiles of intermediate and product species. Simulation results agreed with the experiments and both showed an increase in reactivity with increasing temperature at φ = 0.5 1.0 and 1.5. For richer conditions cyclopentane concentration profiles exhibit inhibition of reactivity between 850 and 1000 K.

SymPy is an open source computer algebra system written in pure Python. It is built with a focus on extensibility and ease of use, through both interactive and programmatic applications. These characteristics have led SymPy to become a popular symbolic library for the scientific Python ecosystem. This paper presents the architecture of SymPy, a description of its features, and a discussion of select domain specific submodules. The supplementary materials provide additional examples and further outline details of the architecture and features of SymPy.

Transported probability density function (TPDF) methods are an attractive modeling approach for turbulent flames as chemical reactions appear in closed form. However, molecular micro-mixing needs to be modeled and this modeling is considered a primary challenge for TPDF methods. In the present study, a new algebraic mixing rate model for TPDF simulations of turbulent premixed flames is proposed, which is a key ingredient in commonly used molecular mixing models. The new model aims to properly account for the transition in reactive scalar mixing rate behavior from the limit of turbulence-dominated mixing to molecular mixing behavior in flamelets. An a priori assessment of the new model is performed using direct numerical simulation (DNS) data of a lean premixed hydrogen–air jet flame. The new model accurately captures the mixing timescale behavior in the DNS and is found to be a significant improvement over the commonly used constant mechanical-to-scalar mixing timescale ratio model. An a posteriori TPDF study is then performed using the same DNS data as a numerical test bed. The DNS provides the initial conditions and time-varying input quantities, including the mean velocity, turbulent diffusion coefficient, and modeled scalar mixing rate for the TPDF simulations, thus allowing an exclusive focus on the mixing model. The new mixing timescale model is compared with the constant mechanical-to-scalar mixing timescale ratio coupled with the Euclidean Minimum Spanning Tree (EMST) mixing model, as well as a laminar flamelet closure by Pope and Anand (1984). It is found that the laminar flamelet closure is unable to properly capture the mixing behavior in the thin reaction zones regime while the constant mechanical-to-scalar mixing timescale model under-predicts the flame speed. The EMST model coupled with the new mixing timescale model provides the best prediction of the flame structure and flame propagation among the models tested, as the dynamics of reactive scalar mixing across different flame regimes are appropriately accounted for.

The mechanism(s) of low salinity water flooding (LSWF) must be better understood at high temperatures and pressures if the method is to be applied in high T/P kaolinite-bearing sandstone reservoirs. We measured contact angles between a sandstone and an oil (acid number, AN = 3.98 mg KOH/g, base number, BN = 1.3 mg KOH/g) from a reservoir in the Tarim Field in western China in the presence of various water chemistries. We examined the effect of aqueous ionic solutions (formation brine, 100X diluted formation brine, and softened water), temperature (60, 100 and 140 °C) and pressure (20, 30, 40, and 50 MPa) on the contact angle. We also measured the zeta potential of the oil/water and water/rock interfaces to calculate oil/brine/rock disjoining pressures. A surface complexation model was developed to interpret contact angle measurements and compared with DLVO theory predictions. Contact angles were greatest in formation water, followed by the softened water, and low salinity water at the same pressure and temperature. Contact angles increased slightly with temperature, whereas pressure had little effect. DLVO and surface complexation modelling predicted similar wettability trends and allow reasonably accurate interpretation of core-flood results. Water chemistry has a much larger impact on LSWF than reservoir temperature and pressure. Low salinity water flooding should work in high temperature and high pressure kaolinite-bearing sandstone reservoirs.

Mg(BH4)2 is a promising solid-state hydrogen storage material, releasing 14.9 wt% hydrogen upon conversion to MgB2. Although several dehydrogenation pathways have been proposed, the hydrogenation process is less well understood. Here, we present a joint experimental-theoretical study that elucidates the key atomistic mechanisms associated with the initial stages of hydrogen uptake within MgB2. Fourier transform infrared, X-ray absorption, and X-ray emission spectroscopies are integrated with spectroscopic simulations to show that hydrogenation can initially proceed via direct conversion of MgB2 to Mg(BH4)2 complexes. The associated energy landscape is mapped by combining ab initio calculations with barriers extracted from the experimental uptake curves, from which a kinetic model is constructed. The results from the kinetic model suggest that initial hydrogenation takes place via a multi-step process: molecular H2 dissociation, likely at Mg-terminated MgB2 surfaces, is followed by migration of atomic hydrogen to defective boron sites, where the formation of stable B-H bonds ultimately leads to the direct creation of Mg(BH4)2 complexes without persistent BxHy intermediates. Implications for understanding the chemical, structural, and electronic changes upon hydrogenation of MgB2 are discussed.

In recent years a rich variety of emergent phenomena have been observed when suspensions of magnetic particles are subjected to alternating magnetic fields. These particle assemblies often exhibit vigorous dynamics due to the injection of energy from the field. These assemblies include surface and interface phenomena, such as highly organized, segmented "snakes" that can be induced to swim by structural symmetry breaking, and "asters" and "anti-asters," particle assemblies that can be manipulated to capture and transport cargo. In bulk suspensions of magnetic platelets subjected to multiaxial alternating fields, advection lattices and even vortex lattices have been created, and a variety of biomimetic dynamics-serpents, bees and amoebas-have been discovered in magnetic fluids suspended in an immiscible liquid. In this paper several new driven phases are presented, including flying chevrons, dense spinning clusters, filaments, and examples of phase coexistence in driven phases. These observations broaden the growing field of driven magnetic suspensions and present new challenges to those interested in simulating the dynamics of these complex systems.

Recent Magnetized Liner Inertial Fusion experiments at the Sandia National Laboratories Z pulsed power facility have featured a PDV (Photonic Doppler Velocimetry) diagnostic in the final power feed section for measuring load current. In this paper, we report on an anomalous pressure that is detected on this PDV diagnostic very early in time during the current ramp. Early time load currents that are greater than both B-dot upstream current measurements and existing Z machine circuit models by at least 1 MA would be necessary to describe the measured early time velocity of the PDV flyer. This leads us to infer that the pressure producing the early time PDV flyer motion cannot be attributed to the magnetic pressure of the load current but rather to an anomalous pressure. Using the MHD code ALEGRA, we are able to compute a time-dependent anomalous pressure function, which when added to the magnetic pressure of the load current, yields simulated flyer velocities that are in excellent agreement with the PDV measurement. We also provide plausible explanations for what could be the origin of the anomalous pressure.

Robust time-averaged molecular dynamics has been developed to calculate finiteerature elastic constants of a single crystal. We find that when the averaging time exceeds a certain threshold, the statistical errors in the calculated elastic constants become very small. We applied this method to compare the elastic constants of Pd and PdH0.6 at representative low (10 K) and high (500 K) temperatures. The values predicted for Pd match reasonably well with ultrasonic experimental data at both temperatures. In contrast, the predicted elastic constants for PdH0.6 only match well with ultrasonic data at 10 K; whereas, at 500 K, the predicted values are significantly lower. We hypothesize that at 500 K, the facile hydrogen diffusion in PdH0.6 alters the speed of sound, resulting in significantly reduced values of predicted elastic constants as compared to the ultrasonic experimental data. Literature mechanical testing experiments seem to support this hypothesis.

Ionic liquids containing lanthanide halide anions give the opportunity to investigate magnetic behaviour in non-ordered systems. Reported herein is the synthesis and characterization of ionic liquids containing a series of lanthanide halide anions, with the resulting materials displaying unusual behaviour below 50 K. Specifically, the ionic liquid structural glass formation appears to drive magnetic behaviour due to cluster formation of the anions during rapid cooling. This system presents a possible probe to study the dynamics of glass forming materials.

Time-resolved particle image velocimetry recently has been demonstrated in high-speed flows using a pulse-burst laser at repetition rates reaching 50 kHz. Turbulent behavior can be measured at still higher frequencies if the field of view is greatly reduced and lower laser pulse energy is accepted. Current technology allows image acquisition at 400 kHz for sequences exceeding 4,000 frames, but for an array of only 128 × 120 pixels, giving the moniker of “postage-stamp PIV.” The technique has been tested far downstream of a supersonic jet exhausting into a transonic crossflow. Two-component measurements appear valid until 100 kHz at which point a noise floor emerges dependent upon the reduction of peak locking. Stereoscopic measurement offers three-component data for turbulent kinetic energy spectra, but exhibits a reduced signal bandwidth and higher noise in the out-of-plane component due to the oblique camera images. The resulting spectra reveal two regions exhibiting power-law dependence describing the turbulent decay. One is the well-known inertial subrange with a slope of -5/3 at high frequencies. The other displays a -1 power-law dependence for a decade of mid-range frequencies corresponding to the energetic eddies measured by PIV, which appears to have been previously unrecognized for high-speed free shear flows.

The purpose of this report is to briefly survey the major contributions of the FY14- FY16 LDRD project titled “An Advanced Decision Framework for Power Grid Resiliency”. The primary contributions of the project are described in detailed technical reports and journal articles, references to which we provide in a bibliography.

The objective of this project is to measure the hydrogen-affected fracture properties of structural welded metals exposed to hydrogen isotopes. The main goal of FY16 was to evaluate low-temperature effects on fracture properties of stainless steel welds pre-charged with hydrogen. Forged stainless steels consisting of 316L, 304L, and 21-6-9 welded with 308L filler metal were pre-charged and tested at 223 K at select displacement rates to evaluate fracture behavior over the lower STS temperature range. Reductions in fracture thresholds were observed for all stainless steel welds when samples were precharged with hydrogen; however, temperature effects were not observed in the 304L and 21-6-9 welds. Only 316L exhibited enhanced degradation at 223 K. In addition to fracture testing, tensile specimens were extracted from the weld region and tested at 296 K and 223 K in the hydrogen pre-charged condition. A slight increase in yield strength was measured in the pre-charged condition at 296K and 223 K for the three different welds. A reduction in total elongation of 3-11% was observed at 296 K, whereas reductions in total elongation from 50-64% were observed at 223 K. Microhardness and ferrite numbers were measured in the weld regions to try to elucidate the factors affecting fracture. Lastly, in collaboration with Savannah River National Laboratory (SRNL), weld and heat-affected zone bend specimens extracted from forged 304L and 21-6-9 stainless steel were supplied to SRNL and are in the final stages of sample preparation for subsequent tritium exposure, aging, and fracture testing. The collection of testing completed and planned between Sandia and SRNL contributes to the development of a comprehensive database of properties for materials as a function of hydrogen-isotope concentrations.

The objectives of this work are to (1) Develop a detailed understanding of the performance characteristics of current chromate conversion coatings utilized in the stockpile, (2) Develop a detailed understanding of the performance characteristics of non-chromate conversion coatings proposed to replace their chromate containing counterparts, (3) Provide an informed assessment of the aforementioned coatings and a recommended course of action for the replacement of chromate containing coatings, and (4) establish subject matter expertise in the area of replacement coatings to provide as a resource to the systems organization. These tasks will be accomplished by performing a battery of traditional corrosion performance tests (in accordance with the relevant MIL specifications governing chemical conversion coatings), combined with more detailed analytical evaluation of the materials. Coatings will be evaluated in the as-received and artificially aged condition. Four different coating systems were evaluated on four different aluminum alloys in FY16. The focus this year was to continue populating the test matrix initiated in previous years, evaluating key coatings in the as received and thermally stressed condition, as compared to the baseline chromate conversion coating (Bonderite (formerly Alodine) 1200S). The non-chromate conversion coatings included Bonderite T 5900, Chemeon TCP-HF, Luster-On Aluminescent, and MacDermid-Enthone Iridite NCP. A second effort that was completed this year was to address a bottleneck that existed for the electrical evaluation of the coatings, assessing their conformance with the MIL specification. An electromechanical test system was assembled and automated, eliminating the need to rely on an already heavily utilized mechanical test system and operator in Materials Mechanics and Tribology.

The overall objectives are to provide the science-base needed by industry to understand how emerging alternative fuels impact highly efficient DISI light-duty engines being developed by industry and how engine design and operation can be optimized for most efficient use of future fuels.

The overall objectives are to provide the science-base needed by industry stakeholders to understand how engine design and operation can be co-optimized with future fuels for highest overall system efficiency.

This report requests a non-explosive hazard classification of trace explosives in solution. UN Series 1 and 2 explosive hazard classification tests were performed on a simulated worst-case waste stream of five (5) percent by weight of explosive (CL-20) dissolved in a solvent solution (acetone) for transport and storage. The explosive hazard classification test results reported the sample to be non-explosive and the report provides the necessary data for the Department of Transportation to determine and assign the appropriate hazard class for five (5) percent or less of trace explosive in solvent solutions when being shipped and/or stored. Based on the test results, this report requests that the Department of Transportation assign a hazard class of 3, Desensitized explosive liquid, n.o.s. for this type of substance.

The Bird project explored the use of big data analytics tool to improve the findability of information within the Sandia internal network. We were able to perform query classification utilizing the supervised learning algorithms in the Apache Spark library. By relying on the distributed processing capabilities provided by the Apache Hadoop framework, we successfully processed the large query log files needed to train the models in this effort. The capabilities developed in this project are being used to enhance the effectiveness of the enterprise search engine.

This report summarizes the outcome of an expert panel review of a key degradation phenomenon identified for atmospherically exposed austenitic stainless steel containers used for the interim dry storage of used nuclear fuel - specifically, chloride induced stress corrosion cracking due to the presence of atmospherically deposited salts. The expert panel consisted of Dr. Peter Andresen (GE Corp Research & Development), Dr. Robert G. Kelly (University of Virginia), Dr. John R. Scully (University of Virginia), and Dr. Alan Turnbull (National Physical Laboratory) and was moderated by Dr. David G. Enos (Sandia National Laboratories). In addition to the above subject matter experts, participants from Sandia National Laboratories, Savannah River National Laboratory, Pacific Northwest National Laboratory, and the Southwest Research Institute will be present. Input from the panel members for a series of preliminary questions dealing with the subject area, along with the meeting minutes, presentation materials, and final recommendations are included here.

This document describes a conceptual Data Model for use in the IDC Re-Engineering development project.

The thermal degradation of two polyurethane elastomers was investigated via thermal gravimetric analysis coupled with gas chromatography/ma ss spectrometry. Decomposition occur s in a multi - step fashion with similar onset temperatures for both materials. Apparent activation energy plots were calculated inside Model - Free Kinetics software and utilized to construct conversion and isothermal conversion tables . These tables predicted material degradation as a function of temperature and time. Isothermal experiments were performed and found to be in good agreement with the predictions made from the Model - Free Kinetic s software package. Volatile products evolved during the multistep decomposition were captured at various times and analyzed using the coupled gas chromatography/mass spectrometry system . This analysis demonstrated strong correlation between the degradation products and known decomposition mechanisms for polyurethanes.

Abstract not provided.

We recently developed an enzymatically active, ultra-thin, nano-stabilized liquid membrane for CO₂ separation from a mixture of gases, which was recognized by an international R&D 100 Award in 2015. The separation membrane is an approximately 18-nm thick water layer stabilized by capillary condensation within a hydrophilic mesoporous silica film and embedded with the metallo-enzyme carbonic anhydrase. The enzyme speeds CO₂ uptake and release from the membrane by catalyzing the rapid inter-conversion of carbon dioxide and water to bicarbonate and a proton. The membrane separates CO₂ from 1:1 gas mixtures at a rate of 2600 GPU with CO₂/N₂ and CO₂/H₂ selectivities exceeding 788 and 1500, the highest combined flux and selectivity yet reported. That membrane performance exceeds, for the first time, the U.S. Department of Energy standards for CO₂ capture technology. CO₂ flux depends sensitively on nanopore surface chemistry in the active region. To understand that dependence, we applied molecular simulations to interrogate enzyme behavior in the presence of varied surface chemistries. The results indicate that a polar surface chemistry within the membrane nanopores prevents aggregation of enzymes that would otherwise occur in both bulk liquid solution and non-polar nanopores. Additionally, the enzyme active site maintains a stable structure, even when the overall protein structure deforms within the nanopores. In summary, confinement in the ultra-thin layer of water within mesoporous silica nanopores facilitates a 15x higher enzyme concentration than in bulk conditions, without affecting the structure of the enzyme active site, when the nanopore surfaces are covered with polar functional groups. Thus, confinement of the carbonic enzymes in the membrane water-filled nanopores facilitates higher rates of CO₂ uptake and release than achievable in bulk solutions.

SNL’s IDC Reengineering Phase 2 team developed 12 Use Case Realizations (UCRs) during the Elaboration phase. This document describes the changes made to these UCRs after their initial delivery to the IDC.

Sandia National Laboratories has a large cybersecurity research program supporting the Department of Energy as well as other federal departments and agencies. Fundamental research helps us stay ahead of threats. Sandia’s research efforts in cybersecurity are focused in three broad areas: 1. Trusted hardware, software, and systems 2. Networks and systems architectures and analysis 3. Effective cyber defense systems Research is conducted in state-of-the-art facilities with extensive computing and information science capabilities, which range from architectures and algorithms to advanced modeling and simulation. Three areas of active research most applicable to connected vehicle security are: Red Team Assessments, Emulytics™, and Supply Chain Risk Management.

Lithium niobate, due to its material properties, is often used for optical waveguides, optical modulators, and other linear and nonlinear optical applications. In this research, we present monolithically integrated microdisk resonators with an integrated ground plane fabricated from a commercially purchased lithium niobate on insulator wafer. Using this architecture, we demonstrate excitation of a 167MHz mechanical resonance as well as electro-optic modulation of a 1.93THz optical mode in a free-standing whispering gallery mode (WGM) resonator. By hovering a signal probe above the disk while grounding the device using the integrated ground plane, an electric field can be applied across the device which both induces an electro-optic effect as well as drives mechanical motion via the piezoelectric effect. Detection of the mechanical mode and electro-optic shift was performed by coupling to the high quality factor (Q = 454,000) optical modes of the microresonator using a tapered optical fiber.

Understanding the stability of the zircaloy-4 liner, which is used in the Tritium- Producing Burnable Absorber Rod, is important for predicting the maximium reasonable life time and failure mechanisms of this essential component for tritium production. In this year-long study, a combination of in-situ ion irradiation transmission electron microscopy and thermal desorption measurements were used to explore the structural stability of Zr-4 as a function of sequential and concurrent displacement damage, helium implantation, and molecular deuterium implantation at the temperature of interest for reactor operation. Under the limited conditions explored, the liner alloy appeared to be relatively stable based on the direct TEM observation of the microstructure.

This study examined a concept for improving the nation's ability to detect unauthorized transport of radiological and nuclear material that involves detecting not the radiological or nuclear material itself, but rather the anomalous presence of materials, such as lead and tungsten, typically used to shield such illicit materials from detection. Specifically, the project studied a potentially inexpensive, non-intrusive, and fast method of detecting anomalous shielding: use of magnetic induction sensors to measure currents induced in conductors by a driver coil. The first phase of this work, documented in this report, identified the signatures of materials of interest, assessed the usefulness of measured signatures for discrimination between materials, and then benchmarked models and calculations. The next task involved assessing the strength of these signatures when the materials of interest were enclosed within other materials, such as aluminum and steel, of various thicknesses. A final task mimicked a real-world scenario by testing the ability to detect material signatures of interest at a scale of a vehicle or cargo vessel against a cluttered backdrop, with and without the shielding of another material, such as aluminum or steel. This final task raised doubts regarding whether this detection scheme will be useful under real-world conditions.

The Sandia National Laboratories, California (SNL/CA) site comprises approximately 410 acres and is located in the eastern portion of Livermore, Alameda County, California. The property is owned by the United States Department of Energy and is being operated by Sandia Corporation. The facility location is shown on the Site Map(s) in Appendix A. This Stormwater Pollution Prevention Plan (SWPPP) is designed to comply with California’s General Permit for Stormwater Discharges Associated with Industrial Activities (General Permit) Order No. 2014-0057-DWQ (NPDES No. CAS000001) issued by the State Water Resources Control Board (State Water Board) (Ref. 6.1). This SWPPP has been prepared following the SWPPP Template provided on the California Stormwater Quality Association Stormwater Best Management Practice Handbook Portal: Industrial and Commercial (CASQA 2014).

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The purpose of this document is to give further details on modeling than requested in the Excel sheets To analyze the results and draw any conclusion with respect to the vibration modeling purpose.

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This document contains the system specifications derived to satisfy the system requirements found in the IDC System Requirements Document for the IDC Re-Engineering Phase 2 project. This System Specification Document (SSD) defines waveform data processing requirements for the International Data Centre (IDC) of the Comprehensive Nuclear Test Ban Treaty Organization (CTBTO). The routine processing includes characterization of events with the objective of screening out events considered to be consistent with natural phenomena or non-nuclear, man-made phenomena. This document does not address requirements concerning acquisition, processing and analysis of radionuclide data but does include requirements for the dissemination of radionuclide data and products.

This System Requirements Document (SRD) defines waveform data processing requirements for the International Data Centre (IDC) of the Comprehensive Nuclear Test Ban Treaty Organization (CTBTO). The IDC applies, on a routine basis, automatic processing methods and interactive analysis to raw International Monitoring System (IMS) data in order to produce, archive, and distribute standard IDC products on behalf of all States Parties. The routine processing includes characterization of events with the objective of screening out events considered to be consistent with natural phenomena or non-nuclear, man-made phenomena. This document does not address requirements concerning acquisition, processing and analysis of radionuclide data, but includes requirements for the dissemination of radionuclide data and products.

This document contains the glossary of terms used for the IDC Re-Engineering Phase 2 project. This version was created for Iteration E3. The IDC applies automatic processing methods in order to produce, archive, and distribute standard IDC products on behalf of all States Parties.

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The following report describes work performed under the LDRD program at Sandia National Laboratories October 2014 and September 2016. The work presented demonstrates the ability of Sandia Labs to develop state-of-the-art photonic devices based on thin film lithium niobate (LiNbO₃ ). Section 1 provides an introduction to integrated LiNbO₃ devices and motivation for developing thin film nonlinear optical systems. Section 2 describes the design, fabrication, and photonic performance of thin film optical microdisks fabricated from bulk LiNbO₃ using a bulk implantation method developed at Sandia. Sections 3 and 4 describe the development of similar thin film LiNbO₃ structures fabricated from LiNbO₃ on insulator (LNOI) substrates and our demonstration of optical frequency conversion with state-of-the-art efficiency. Finally, Section 5 describes similar microdisk resonators fabricated from LNOI wafers with a buried metal layer, in which we demonstrate electro-optic modulation.

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This document contains 4 use case realizations generated from the model contained in Rational Software Architect. These use case realizations are the current versions of the realizations originally delivered in Elaboration Iteration 3.

This document summarizes an analysis that was performed to identify the conditions for safe operation of the SWiFT V27 rotors during the FY16/17 wake steering experimental campaign.

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We establish an atomistic view of the high- and low-temperature phases of iron/steel as well as some elements of the phase transition between these phases on cooling. In particular we examine the 4 most common orientation relationships between the high temperature austenite and low-temperature ferrite phases seen in experiment. With a thorough understanding of these relationships we are prepared to set up various atomistic simulations, using techniques such as Density Functional Theory and Molecular Dynamics, to further study the phase transition, in particular, quantities needed for Phase Field Modeling, such as the free energies of bulk phases and the phase transition front propagation velocity.

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This study presents a conceptual framework for capturing the spatial and temporal aspects of non-market dimensions of value (DOV) and how they vary as the result of policy changes for hydropower generation and developed water uses. The foundation of this project is a literature review that reveals that focused, sector specific valuations are no longer adequate if the goal is to provide decision makers with a complete understanding of their decisions. Rather, estimates of non-market values for informing decisions regarding dam operations and/or other water management alternatives must consider the entire spectrum of market and non-market values, and the tradeoffs (both positive and negative) between those values over time and space, while considering shifting preferences in an uncertain environment. This document describes the history and reasoning for these conclusions and presents a conceptual framework for understanding non-market values as a function of changes to hydropower operations and water resources management.

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Sandia National Laboratories has prepared a budgetary cost estimate for planning for the IDC Re-engineering Phase 3 effort, based on leveraging a fully funded, Sandia executed NDC Modernization project. This report provides the budgetary cost estimate and describes the methodology, assumptions, and cost model details used to create the budgetary cost estimate.

This document contains a description of the system architecture for the IDC Re-Engineering Phase 2 project.

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This report gives information on the following topics related to Sandia National Laboratories: site leadership's vision, condition, footprint management, major gaps and risks, and proposed investment plan.

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International trade and related economic activities in Central and South Asia are increasing as developing economies, particularly India and Pakistan, grow. China continues to emerge as a major regional and global power and has embarked upon numerous regional economic and political initiatives . A major development is the China - Pakistan Economic Corridor (CPEC), a host of infrastructure and trade projects worth over 40 billion American dollars . This report analyzes CPEC a nd its potential regional effects, including the trade security implications of the port and land infrastructure developments . As trade increase s in the reg ion and the major CPEC infrastructure projects are completed, there will be numerous implications on trade security and geopolitics within South Asia. CPEC projects uniquely intersect numerous regional situations, including territorial disputes in Kashmir, the Afghanistan/Pakistan border, and Chinese foreign policy a mbitions. A nuanced understanding of these effects can influence future policy adjustments in this region . The views expressed in this report are those of the author and do not necessarily reflect the position of Sandia National Laboratories or the author's current and past institutions.

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This memo concerns the transmission of mechanical signals through silicone foam pads in a compression Kolsky bar set-up. The results of numerical simulations for four levels of pad pre-compression and two striker velocities were compared directly to test measurements to assess the delity of the simulations. The nite element model simulated the Kolsky tests in their entirety and used the hyperelastic `hyperfoam' model for the silicone foam pads. Calibration of the hyperfoam model was deduced from quasi-static compression data. It was necessary, however, to augment the material model by adding sti ness proportional damping in order to generate results that resembled the experimental measurements. Based on the results presented here, it is important to account for the dynamic behavior of polymeric foams in numerical simulations that involve high loading rates.

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Detection of cultural artifacts from airborne remotely sensed data is an important task in the context of on-site inspections. Airborne artifact detection can reduce the size of the search area the ground based inspection team must visit, thereby improving the efficiency of the inspection process. This report details two algorithms for detection of cultural artifacts in aerial long wave infrared imagery. The first algorithm creates an explicit model for cultural artifacts, and finds data that fits the model. The second algorithm creates a model of the background and finds data that does not fit the model. Both algorithms are applied to orthomosaic imagery generated as part of the MSFE13 data collection campaign under the spectral technology evaluation project.

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Central to protecting our nation's critical infrastructure is the development of methodologies for prioritizing action and supporting resource allocation decisions associated with risk-reduction initiatives. Toward this need a web-based risk assessment framework that promotes the anonymous sharing of results among water utilities is demonstrated. Anonymous sharing of results offers a number of potential advantages such as assistance in recognizing and correcting bias, identification of 'unknown, unknowns', self-assessment and benchmarking for the local utility, treatment of shared assets and/or threats across multiple utilities, and prioritization of actions beyond the scale of a single utility. The constructed framework was demonstrated for three water utilities. Demonstration results were then compared to risk assessment results developed using a different risk assessment application by a different set of analysts.

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This document contains 21 use cases generated from the model contained in Rational Software Architect.

This document contains 21 use cases generated from the model contained in Rational Software Architect.

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