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At least 865 records · Page 48

Optimization of an Energy Tuning Assembly for High Explosives Detection

The Portable Isotopic Neutron Spectroscopy (PINS) system, employs neutron-induced gamma-ray spectroscopy and provides a nondestructive method for high explosives detection. In standard operation it uses Californium-252 as a neutron source. Operating PINS with a deuterium-tritium (DT) neutron generator has some advantages over Cf-252, including lifetime and ability to produce high-energy inelastic scattering gamma rays. However, current systems using DT neutron generators suffer from a high environmental background and reduced ability to induce neutron capture, reducing spectral quality and limiting nitrogen sensitivity. Here, this study presents the development of an energy-tuning assembly (ETA) designed to optimize the DT neutron energy spectrum to increase nitrogen reaction rates in a target, thereby improving high explosive detection capabilities. A metaheuristic optimization framework, MultiGNOWEE, coupled with MCNP, was employed to generate two ETA configurations: a single-objective ETA, which maximizes nitrogen capture reactions, and a multi-objective ETA, which balances neutron capture and inelastic scattering. Simulations demonstrated the optimized configurations achieved up to a 10-fold improvement in nitrogen capture rates compared to the bare configuration. Experimental validation was conducted using a DT neutron generator and a high-purity germanium (HPGe) detector. Two prototype ETAs were constructed and assessed on a melamine simulant. Measurements demonstrated improved nitrogen detection for both prototype ETA configurations when compared to the standard system.

97 MATHEMATICS AND COMPUTING↗

Versatile, ultra-low sample volume gas analyzer using a rapid, broad-tuning ECQCL and a hollow fiber gas cell

We describe a versatile mid-infrared (Mid-IR) spectroscopy system developed to measure the concentration of a wide range of gases with an ultra-low sample size. The system combines a rapidly-swept external cavity quantum cascade laser (ECQCL) with a hollow fiber gas cell. The ECQCL has sufficient spectral resolution and reproducibility to measure gases with narrow features (e.g., water, methane, ammonia, etc.), and also the spectral tuning range needed to measure volatile organic compounds (VOCs), (e.g., aldehydes, ketones, hydrocarbons), sulfur compounds, chlorine compounds, etc. The hollow fiber is a capillary tube having an internal reflective coating optimized for transmitting the Mid-IR laser beam to a detector. Sample gas introduced into the fiber (e.g., internal volume = 0.6 ml) interacts strongly with the laser beam, and despite relatively modest path lengths (e.g., L ~ 3 m), the requisite quantity of sample needed for sensitive measurements can be significantly less than what is required using conventional IR laser spectroscopy systems. Example measurements are presented including quantification of VOCs relevant for human breath analysis with a sensitivity of ~2 picomoles at a 1 Hz data rate.

broad-tuning↗

GATEWAY Demonstrations: Tuning Hospital Lighting: Evaluating Tunable LED Lighting at the Swedish Hospital Behavioral Health Unit in Seattle

The GATEWAY program evaluated a tunable LED lighting system installed in the new Swedish Medical Behavioral Health Unit in Seattle that incorporates color-tunable luminaires in common areas, and uses advanced controls for dimming and color tuning, with the goal of providing a better environment for staff and patients. The report reviews the design of the tunable lighting system, summarizes two sets of measurements, and discusses the circadian, energy, and commissioning implications as well as lessons learned from the project.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

Platform for Remote Deployment and Training for Enhanced Building Operation Practices (Building Re-Tuning and On-going Commissioning)

While a building’s energy usage is driven largely by its design and use, building operator behavior has a strong influence on its energy consumption. This project developed and piloted a specific, data-driven coaching methodology to help operators understand how they can adjust operations and/or affect no/low-cost repairs or upgrades to their specific building HVAC systems to reduce energy consumption. Named BuildingCoach, the operational optimization method used is based on the Building Re-tuning approach developed by the Pacific Northwest National Laboratory. A building operations analytics market has matured over the past decade, though its potential to affect energy-saving changes has not been fully realized. Training operators to understand the methods for operational optimization with the explicit approach of using building-system performance data is hypothesized to create a more effective, longer lasting result in building energy efficiency, and this strategy is the fundamental premise of this project. With the support of an Industry Advisory Board, the project succeeded in developing materials and recruiting for and delivering three pilot cohorts. Deliverables included twenty-two self-paced training modules (accessed via a Learning Management System) and a web-based platform that includes access to real-time building system data and a repository for building system documentation. The project set out to have 100 participants from 50 buildings in three pilot cohorts. In the end, there were 28 participants from 17 buildings, i.e., a significant shortfall. The first two pilot cohorts had only two buildings in each, and this was partially due to difficulties in deploying the Building Operator Coaching Solution (“the BOCS”), which is technology that extracts the data from the controls network and presents it as prescribed for coaching. In the third cohort, the project team deployed the BOCS successfully to 13 buildings, the methodology was piloted as intended, and numerous opportunities for optimization were identified. The BuildingCoach business plan charts a path to an economically sustainable effort. However, even with a licensing model captured in the final version of the business plan, the scalability is still limited to keeping less than 1,000 buildings affected by 2033. Even so, there are unexplored paths to greater scalability that are being considered. CUNY BPL is working to perpetuate and grow the use of BuildingCoach. As of this writing, about twenty buildings have either been connected or will be connected with operators coached / to be coached in the NYC municipal portfolio, twelve buildings across four campuses in NY State will use BuildingCoach, a NY upstate county wishes for six or seven buildings to participate with the support of funding from NYSERDA, and others have also expressed interest. In the decades to come, there will be an increasing percentage of large and mid-sized buildings that incorporate automated system optimization (ASO), and the building operators’ role will shift to spend more time on maintenance and monitoring. Meanwhile, programs such as BuildingCoach will play a critical role in optimizing operations. And, regardless of the emergence of ASO, operators will still need to understand how their systems operate so that they can monitor them properly. Within that context, BuildingCoach is an important step towards operators’ understanding of efficient building system operations.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

Model Predictive Control Tuning by Inverse Matching for a Wave Energy Converter

This paper investigates the application of a method to find the cost function or the weight matrices to be used in model predictive control (MPC) such that the MPC has the same performance as a predesigned linear controller in state-feedback form when constraints are not active. This is potentially useful when a successful linear controller already exists and it is necessary to incorporate the constraint-handling capabilities of MPC. This is the case for a wave energy converter (WEC), where the maximum power transfer law is well-understood. In addition to solutions based on numerical optimization, a simple analytical solution is also derived for cases with a short prediction horizon. These methods are applied for the control of an empirically-based WEC model. The results show that the MPC can be successfully tuned to follow an existing linear control law and to comply with both input and state constraints, such as actuator force and actuator stroke.

16 TIDAL AND WAVE POWER↗

Some Issues in Uncertainty Quantification and Parameter Tuning: A Case Study of Convective Parameterization Scheme in the WRF Regional Climate Model

The current tuning process of parameters in global climate models is often performed subjectively, or treated as an optimization procedure to minimize the difference between model fields and observations. The later approach may be generating a set of tunable parameters that approximate the observed climate but via an unrealistic balance of physical processes and/or compensating errors over different regions in the globe. In this study, we run the Weather Research and Forecasting (WRF) regional model constrained by the reanalysis data over the Southern Great Plains (SGP) where abundant observational data from various resources are available for calibration of the input parameters and validation of the model results. Our goal is to quantify the uncertainty ranges and identify the optimal values of five key input parameters in a new Kain-Frisch (KF) convective parameterization scheme incorporated in the WRF model. A stochastic sampling algorithm, Multiple Very Fast Simulated Annealing (MVFSA), is employed to efficiently sample the input parameters in KF scheme based on the skill score so that the algorithm progressively moves toward regions of the parameter space that minimize model errors. The results based on the WRF simulations with 25-km grid spacing over the SGP show that the model bias for precipitation can be significantly reduced by using five optimal parameters identified by the MVFSA algorithm. The model performance is very sensitive to downdraft and entrainment related parameters and consumption time of Convective Available Potential Energy (CAPE). Simulated convective precipitation decreases as the ratio of downdraft to updraft flux increases. Larger CAPE consumption time results in less convective but more stratiform precipitation. The simulation using optimal parameters obtained by only constraining precipitation generates positive impact on the other output variables, such as temperature and wind. By using the optimal parameters obtained at 25 km simulation, both the magnitude and spatial pattern of simulated precipitation are improved at 12-km spatial resolution. The optimal parameters identified from the SGP region have also improved the simulation of precipitation when moving model domain to another region with a different climate regime (i.e. North America monsoon region). These results suggest the improvement of precipitation simulation by using the optimal parameters remains when the model domain or spatial resolution is changed.

54 ENVIRONMENTAL SCIENCES↗

Filter Tuning Using the Chi-Squared Statistic

This paper examines the use of the Chi-square statistic as a means of evaluating filter performance. The goal of the process is to characterize the filter performance in the metric of covariance realism. The Chi-squared statistic is the value calculated to determine the realism of a covariance based on the prediction accuracy and the covariance values at a given point in time. Once calculated, it is the distribution of this statistic that provides insight on the accuracy of the covariance. The process of tuning an Extended Kalman Filter (EKF) for Aqua and Aura support is described, including examination of the measurement errors of available observation types, and methods of dealing with potentially volatile atmospheric drag modeling. Predictive accuracy and the distribution of the Chi-squared statistic, calculated from EKF solutions, are assessed.

Filter Tuning↗

Interoperable Map Services with Performance Tuning for Earth Science Data through API-Tiles and Dynamic API-Styles

NASA’s Goddard Earth Sciences Data and Information Services Center (GES DISC) provides access to a wide range of global climate data from various satellite missions and models. However, the visualization and analysis of these data can be challenging due to their large volume, complex structure, and diverse formats. This study presents the implementation of interoperable map services (API-Maps) with performance tuning using API-Tiles and dynamic API-Styles. API-Maps is a standard for defining and exposing map services through RESTful (representational state transfer) APIs (application programming interfaces). API-Tiles is a technique for generating and delivering map tiles on demand from any data source. API-Styles is a method for dynamically applying styles to map tiles based on user preferences or data attributes. The use of API-Tiles and dynamic API-Styles enhances the performance and scalability of the map services, allowing for smooth and interactive visualization of large datasets. Two types of Earth Science data sources from the NASA GES DISC are used in the experiment: regularly gridded data, such as Global Precipitation Measurement (GPM) precipitation data, and low processing level data, such as low-level data of atmospheric composite measurements from the TROPOspheric Monitoring Instrument (TROPOMI) mission. Re-gridding of swath data (low level data - e.g. Level 2) of atmospheric composites (e.g. TROPOMI products, such as nitrogen dioxide, ozone and aerosol optical depth) is applied to enable the Web-based, interoperable, tiled, and styled mapping (rendering) services of such data. The results demonstrate the effectiveness of the proposed approach in providing fast and efficient access to Earth science data through interoperable map services.

Geographic Information System↗

TUNING SILICON NANORODS FOR ANODES OF LI-ION RECHARGEABLE BATTERIES

Silicon is a promising anode material for Li-ion batteries in regarding of high capacity, low cost and safety, but it suffers poor cycling stability due to the pulverization induced by severe volume expansion/shrinkage (297%) during lithium insertion/extraction. In our previous investigation on aluminum nanorods anodes, it is found the selection of substrates in which Al nanorods grown plays the role in prevention of pulverization resulting in the increase of cycling life. Adapting this knowledge, we investigated the Si based nanorods anodes by tuning its composition and element distribution. Our results show that although the Si nanorods demonstrated higher initial anodic capacity of 1500 mAh/g, it diminished after 50 cycles due to morphology change and pulverization. By codepositing Cu, the Si-Cu composite nanorods demonstrated sustainable capacity of 500 mAh/g in 100 cycles attributing to its flexible and less brittle nature.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Tuning the Limiting Thickness of a Thin Oxide Layer on Al (111) with Oxygen Gas Pressure

We report an x-ray photoelectron spectroscopy study of the oxidation of Al(111) surfaces at room temperature, which reveals that the limiting thickness of an aluminum oxide film can be tuned by using oxygen pressure. This behavior is attributed to a strong dependence of the kinetic potential on the oxygen gas pressure. The coverage of oxygen anions on the surface of the oxide film depends on the gas pressure leading to a pressure dependence of the kinetic potential. Our results indicate that a significantly large oxygen pressure (>1 Torr) is required to develop the saturated surface coverage of oxygen ions, which results in the maximum kinetic potential and therefore the saturated limiting thickness of the oxide film.

36 MATERIALS SCIENCE↗

Tuning Fermilab Heavy Quarks in 2+1 Flavor Lattice QCD with Application to Hyperfine Splittings

We report the nonperturbative tuning of parameters - {kappa}{sub c}, {kappa}{sub b}, and {kappa}{sub crit} - that are related to the bare heavy-quark mass in the Fermilab action. This requires the computation of the masses of D{sub s}{sup (*)} and B{sub s}{sup (*)} mesons comprised of a Fermilab heavy quark and a staggered light quark. Additionally, we report the hyperfine splittings for D{sub s}{sup (*)} and B{sub s}{sup (*)} mesons as a cross-check of our simulation and analysis methods. We find a splitting of 145 {+-} 15 MeV for the D{sub s} system and 40 {+-} 9 MeV for the B{sub s} system. These are in good agreement with the Particle Data Group average values of 143.9 {+-} 0.4 MeV and 46.1 {+-} 1.5 MeV, respectively. The calculations are carried out with the MILC 2+1 flavor gauge configurations at three lattice spacings a {approx} 0.15, 0.12, and 0.09 fm.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

Tuning the Physicochemical Properties of Diverse Phenolic Ionic Liquids for Equimolar CO2 Capture by the Substituent on the Anion

Phenolic ionic liquids for the efficient and reversible capture of CO{sub 2} were designed and prepared from phosphonium hydroxide and substituted phenols. The electron-withdrawing or electron-donating ability, position, and number of the substituents on the anion of these ionic liquids were correlated with the physicochemical properties of the ionic liquids. The results show that the stability, viscosity, and CO{sub 2}-capturing ability of these ionic liquids were significantly affected by the substituents. Furthermore, the relationship between the decomposition temperature, the CO{sub 2}-absorption capacity, and the basicity of these ionic liquids was quantitatively correlated and further rationalized by theoretical calculation. Indeed, these ionic liquids showed good stability, high absorption capacity, and low absorption enthalpy for CO{sub 2} capture. This method, which tunes the physicochemical properties by making use of substituent effects in the anion of the ionic liquid, is important for the design of highly efficient and reversible methods for CO{sub 2}-capture. This CO{sub 2} capture process using diverse phenolic ionic liquids is a promising potential method for CO{sub 2} absorption with both high absorption capacity and good reversibility.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Tuning laser produced electron-positron jets for lab-astrophysics experiment

This paper reviews the experiments on the laser produced electron-positron jets using large laser facilities worldwide. The goal of the experiments was to optimize the parameter of the pair jets for their potential applications in laboratory-astrophysical experiment. Results on tuning the pair jet’s energy, number, emittance and magnetic collimation will be presented.

43 PARTICLE ACCELERATORS↗

Smart Novel Semi-Active Tuned Mass Damper for Fixed-Bottom and Floating Offshore Wind (Paper)

The intention of this paper is to present the results of a novel smart semi-active tuned mass damper (SA-TMD), which mitigates unwanted loads for both fixed-bottom and floating offshore wind systems. The paper will focus on the most challenging water depths for both fixed-bottom and floating systems. A close to 38m Monopile and 55m Tension Leg Platform (TLP) will be considered. A technical development and trade-off analysis will be presented comparing the new system with existing passive non-linear TMD (N-TMD) technology and semi-active. TheSATMD works passively and activates itself with low power source under unwanted dynamic loading in less than 60msec. It is composed of both variable stiffness and damping elements coupled to a central pendulum mass. The analysis has been done numerically in both FAST(NREL) and Orcaflex (Orcina), and integrated in the Wind Turbine system employing CAD/CAE. The results of this work will pave the way for experimental testing to complete the technology qualification process. The load reductions under extreme and fatigue cases reach up significant levels at tower base, consequently reducing LCOE for fixed-bottom to floating wind solutions. The nacelle acceleration is reduced substantially under severe random wind and sea states, reducing the risks of failure of electromechanical components and blades at the rotor nacelle assembly. The SA-TMD system isa new technology that has not been applied previously in wind solutions. Structural damping devices aim to increase offshore wind turbine system robustness and reliability, which eases multiple substructures installations and global stability.

17 WIND ENERGY↗

Open-Loop Control of Adjustable Tuned Mass Dampers for Floating Wind Turbine Platforms: Preprint

Floating offshore wind turbines have several advantages over their land-based counterparts, including access to stronger, more consistent winds and proximity to population centers. However, increased costs from the platform have been a challenge inhibiting their widespread adoption. New damping technologies with tunable target frequencies and damping ratios promise a greater degree of control over platform motions, allowing hulls to be designed smaller and reducing the overall cost of the turbines. In this work, a control strategy is proposed for these adjustable tuned mass dampers (TMDs). A frequency-domain model of the system is developed, from which response amplitude operators (RAOs) for the platform's rigid-body modes can be obtained for different natural frequencies and damping ratios of the dampers. Using these RAOs, and JONSWAP spectrums of operational and extreme sea states, the performance of the various damper settings are compared by evaluating the standard deviation of a rigid-body motion of interest (platform pitch or heave). By finding the optimal damper setting for a range of representative design load cases (DLCs), a lookup function is made to return the damper target frequency given the peak period of the sea state. To determine the current sea state, we propose a simple estimator that uses wave measurements (e.g., from a measurement buoy) to determine the peak period and significant wave height. The significant wave height is determined using the statistics of the past 100 seconds of wave elevation information and the peak period is computed using a frequency locked loop. Initial results show that we can use these estimated values to control the TMD natural frequency with an open loop controller. The controlled system is tested in a range of environmental conditions determined by the International Electrotechnical Commission design load cases (DLCs), which include normal and extreme wind and wave models. In these tests, we compare the performance of 4 cases: (1) no TMD, (2) a constant TMD based on the worst case DLC, (3) a controlled TMD based on known wind and wave environments, and (4) a real-time controlled TMD using estimated wind and wave environments. The effect of hull-based TMD control is also compared to changes in traditional wind turbine control via blade pitch.

control↗

Tuning Microstructure of Mesophase Pitch Carbon Fiber by Altering the Carbonization Ramp Rate

The microstructure of mesophase pitch carbon fibers (CFs) are tuned by varying ramp rates from 1 to 50 °C min –1 up to 1000 °C to study the effect of ramp rate on CFs’ microstructure, thermal and mechanical properties with the goal of offsetting the cost by decreasing cycle time. The ramp rates represent carbonization times ranging from 16.4 to 1.17 h, not including cool down. Differential scanning calorimetry, thermogravimetric analysis, and derivative thermogravimetry are used to investigate the impact ramp rate has on the thermal properties of mesophase pitch. It is found that lower ramp rates are endothermic in nature with a lower temperature onset and maximum weight loss. Higher ramp rates possess an exothermic nature with higher temperatures resulting in maximal weight loss over a smaller range of temperatures. Mechanical testing shows varying CF strengths and moduli dependent on ramp rate and an optimized process is developed to produce the strongest CF. Furthermore, microstructural characterization revealed that faster ramp rates lead to smaller interplanar spacings and larger crystallites but possessed greater disorder.

36 MATERIALS SCIENCE↗