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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 955 records · Page 53
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

H–J–B Equations of Optimal Consumption-Investment and Verification Theorems

We consider a consumption-investment problem on infinite time horizon maximizing discounted expected HARA utility for a general incomplete market model. Based on dynamic programming approach we derive the relevant H–J–B equation and study the existence and uniqueness of the solution to the nonlinear partial differential equation. By using the smooth solution we construct the optimal consumption rate and portfolio strategy and then prove the verification theorems under certain general settings.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Numerical implementation, verification and validation of two-phase flow four-equation drift flux model with Jacobian-free Newton–Krylov method

This study presents a numerical investigation on using the Jacobian-free Newton–Krylov (JFNK) method to solve the two-phase flow four-equation drift flux model with realistic constitutive correlations (‘closure models’). The drift flux model is based on Isshi and his collaborators’ work. Additional constitutive correlations for vertical channel flow, such as two-phase flow pressure drop, flow regime map, wall boiling and interfacial heat transfer models, were taken from the RELAP5-3D Code Manual and included to complete the model. The staggered grid finite volume method and fully implicit backward Euler method was used for the spatial discretization and time integration schemes, respectively. The Jacobian-free Newton–Krylov method shows no difficulty in solving the two-phase flow drift flux model with a discrete flow regime map. In addition to the Jacobian-free approach, the preconditioning matrix is obtained by using the default finite differencing method provided in the PETSc package, and consequently the labor-intensive implementation of complex analytical Jacobian matrix is avoided. Extensive and successful numerical verification and validation have been performed to prove the correct implementation of the models and methods. Code-to-code comparison with RELAP5-3D has further demonstrated the successful implementation of the drift flux model.

42 ENGINEERING↗
DOE OSTI2014

Uncertainty Estimation Improves Energy Measurement and Verification Procedures

Implementing energy conservation measures in buildings can reduce energy costs and environmental impacts, but such measures cost money to implement so intelligent investment strategies require the ability to quantify the energy savings by comparing actual energy used to how much energy would have been used in absence of the conservation measures (known as the baseline energy use). Methods exist for predicting baseline energy use, but a limitation of most statistical methods reported in the literature is inadequate quantification of the uncertainty in baseline energy use predictions. However, estimation of uncertainty is essential for weighing the risks of investing in retrofits. Most commercial buildings have, or soon will have, electricity meters capable of providing data at short time intervals. These data provide new opportunities to quantify uncertainty in baseline predictions, and to do so after shorter measurement durations than are traditionally used. In this paper, we show that uncertainty estimation provides greater measurement and verification (M&V) information and helps to overcome some of the difficulties with deciding how much data is needed to develop baseline models and to confirm energy savings. We also show that cross-validation is an effective method for computing uncertainty. In so doing, we extend a simple regression-based method of predicting energy use using short-interval meter data. We demonstrate the methods by predicting energy use in 17 real commercial buildings. We discuss the benefits of uncertainty estimates which can provide actionable decision making information for investing in energy conservation measures.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2016

Accuracy of automated measurement and verification (M&V) techniques for energy savings in commercial buildings

Trustworthy savings calculations are critical to convincing investors in energy efficiency projects of the benefit and cost-effectiveness of such investments and their ability to replace or defer supply-side capital investments. However, today’s methods for measurement and verification (M&V) of energy savings constitute a significant portion of the total costs of efficiency projects. They also require time-consuming manual data acquisition and often do not deliver results until years after the program period has ended. The rising availability of “smart” meters, combined with new analytical approaches to quantifying savings, has opened the door to conducting M&V more quickly and at lower cost, with comparable or improved accuracy. These meter- and software-based approaches, increasingly referred to as “M&V 2.0”, are the subject of surging industry interest, particularly in the context of utility energy efficiency programs. Program administrators, evaluators, and regulators are asking how M&V 2.0 compares with more traditional methods, how proprietary software can be transparently performance tested, how these techniques can be integrated into the next generation of whole-building focused efficiency programs. This paper expands recent analyses of public-domain whole-building M&V methods, focusing on more novel M&V2.0 modeling approaches that are used in commercial technologies, as well as approaches that are documented in the literature, and/or developed by the academic building research community. We present a testing procedure and metrics to assess the performance of whole-building M&V methods. We then illustrate the test procedure by evaluating the accuracy of ten baseline energy use models, against measured data from a large dataset of 537 buildings. The results of this study show that the already available advanced interval data baseline models hold great promise for scaling the adoption of building measured savings calculations using Advanced Metering Infrastructure (AMI) data. Median coefficient of variation of the root mean squared error (CV(RMSE)) was less than 25% for every model tested when twelve months of training data were used. With even six months of training data, median CV(RMSE) for daily energy total was under 25% for all models tested. Finally, these findings can be used to build confidence in model robustness, and the readiness of these approaches for industry uptake and adoption

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2012

Verification and Validation of EnergyPlus Phase Change Material Model for Opaque Wall Assemblies

Phase change materials (PCMs) represent a technology that may reduce peak loads and HVAC energy consumption in buildings. A few building energy simulation programs have the capability to simulate PCMs, but their accuracy has not been completely tested. This study shows the procedure used to verify and validate the PCM model in EnergyPlus using a similar approach as dictated by ASHRAE Standard 140, which consists of analytical verification, comparative testing, and empirical validation. This process was valuable, as two bugs were identified and fixed in the PCM model, and version 7.1 of EnergyPlus will have a validated PCM model. Preliminary results using whole-building energy analysis show that careful analysis should be done when designing PCMs in homes, as their thermal performance depends on several variables such as PCM properties and location in the building envelope.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2017

Application of automated measurement and verification to utility energy efficiency program data

Trustworthy savings calculations are critical to convincing regulators of both the cost-effectiveness of energy efficiency program investments and their ability to defer supply-side capital investments. Today’s methods for measurement and verification (M&V) of energy savings constitute a significant portion of the total costs of energy efficiency programs. They also require time-consuming data acquisition. A spectrum of savings calculation approaches is used, with some relying more heavily on measured data and others relying more heavily on estimated, modeled, or stipulated data. The increasing availability of “smart” meters and devices that report near-real time data, combined with new analytical approaches to quantify savings, offers the potential to conduct M&V more quickly and at lower cost, with comparable or improved accuracy. Commercial energy management and information systems (EMIS) technologies are beginning to offer these ‘M&V 2.0’ capabilities, and program administrators want to understand how they might assist programs in quickly and accurately measuring energy savings. This paper presents the results of recent testing of the ability to use automation to streamline the M&V process. In this paper, we apply an automated whole-building M&V tool to historic data sets from energy efficiency programs to begin to explore the accuracy, cost, and time trade-offs between more traditional M&V, and these emerging streamlined methods that use high-resolution energy data and automated computational intelligence. For the data sets studied we evaluate the fraction of buildings that are well suited to automated baseline characterization, the uncertainty in gross savings that is due to M&V 2.0 tools’ model error, and indications of labor time savings, and how the automated savings results compare to prior, traditionally determined savings results. The results show that 70% of the buildings were well suited to the automated approach. In a majority of the cases (80%) savings and uncertainties for each individual building were quantified to levels above the criteria in ASHRAE Guideline 14. In addition the findings suggest that M&V 2.0 methods may also offer time-savings relative to traditional approaches. Lastly, we discuss the implications of these findings relative to the potential evolution of M&V, and pilots currently being launched to test how M&V automation can be integrated into ratepayer-funded programs and professional implementation and evaluation practice.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2015

First Experience With Real-Time EPID-Based Delivery Verification During IMRT and VMAT Sessions

Purpose: Gantry-mounted megavoltage electronic portal imaging devices (EPIDs) have become ubiquitous on linear accelerators. WatchDog is a novel application of EPIDs, in which the image frames acquired during treatment are used to monitor treatment delivery in real time. We report on the preliminary use of WatchDog in a prospective study of cancer patients undergoing intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) and identify the challenges of clinical adoption. Methods and Materials: At the time of submission, 28 cancer patients (head and neck, pelvis, and prostate) undergoing fractionated external beam radiation therapy (24 IMRT, 4 VMAT) had ≥1 treatment fraction verified in real time (131 fractions or 881 fields). EPID images acquired continuously during treatment were synchronized and compared with model-generated transit EPID images within a frame time (∼0.1 s). A χ comparison was performed to cumulative frames to gauge the overall delivery quality, and the resulting pass rates were reported graphically during treatment delivery. Every frame acquired (500-1500 per fraction) was saved for postprocessing and analysis. Results: The system reported the mean ± standard deviation in real time χ 91.1% ± 11.5% (83.6% ± 13.2%) for cumulative frame χ analysis with 4%, 4 mm (3%, 3 mm) criteria, global over the integrated image. Conclusions: A real-time EPID-based radiation delivery verification system for IMRT and VMAT has been demonstrated that aims to prevent major mistreatments in radiation therapy.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2016

Verification study of an emerging fire suppression system

Self-contained fire extinguishers are a robust, reliable and minimally invasive means of fire suppression for gloveboxes. Moreover, plutonium gloveboxes present harsh environmental conditions for polymer materials; these include radiation damage and chemical exposure, both of which tend to degrade the lifetime of engineered polymer components. Several studies have been conducted to determine the robustness of selfcontained fire extinguishers in plutonium gloveboxes in a nuclear facility, verification tests must be performed. These tests include activation and mass loss calorimeter tests. In addition, compatibility issues with chemical components of the self-contained fire extinguishers need to be addressed. Our study presents activation and mass loss calorimeter test results. After extensive studies, no critical areas of concern have been identified for the plutonium glovebox application of Fire Foe™, except for glovebox operations that use large quantities of bulk plutonium or uranium metal such as metal casting and pyro-chemistry operations.

42 ENGINEERING↗
DOE OSTI2022

Code verification for practically singular equations

We report the method-of-moments implementation of the electric-field integral equation (EFIE) yields many code-verification challenges due to the various sources of numerical error and their possible interactions. Matters are further complicated by singular integrals, which arise from the presence of a Green's function. To address these singular integrals, an approach is presented in wherein both the solution and Green's function are manufactured. Because the arising equations are poorly conditioned, they are reformulated as a set of constraints for an optimization problem that selects the solution closest to the manufactured solution. In this paper, we demonstrate how, for such practically singular systems of equations, computing the truncation error by inserting the exact solution into the discretized equations cannot detect certain orders of coding errors. On the other hand, the discretization error from the optimal solution is a more sensitive metric that can detect orders less than those of the expected convergence rate.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2011

Weekly Verification of Dosimetric Data for Virtual Wedge Using a 2D Diode Detector Array

A linac manufacturer has recommended that users measure virtual wedge (VW) angle and VW factor as a weekly quality assurance (QA) procedure. The purpose of this study was to investigate whether a 2D diode detector array (MapCHECK{sup TM}) is a useful tool for the verification of dosimetric data for VW. Measurements were performed on 2 linear accelerators (4, 6, and 10 MV) at 10-cm depth for a field size of 10 x 10 cm{sup 2} and with wedge angles of 15, 30, 45, and 60{sup o}. To verify the VW dose distributions generated by the treatment planning system (TPS), we confirmed that agreement between TPS data and measurements were {<=}2% dose difference or 2-mm distance-to-agreement based on American Association of Physicists in Medicine Task Group Report 53 (AAPM TG-53). We present here the results of a 1-year evaluation of VW by means of a 2D diode detector array. The maximum 2-fold standard deviation of the measured wedge angle turned out to be within 1.0, and all measured VW factors to be 1.00 {+-} 0.03. Although >95% of the points measured for 6 and 10 MV were generally within the tolerance of the dose distribution as mentioned above, the percentage of agreement between the measured data for 4 MV and TPS data were somewhat below 90%. We also verified generally good reproducibility for the dose distribution. The 2-D diode detector array was thus found to be useful as a tool for weekly VW QA.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2016

A comparison between radiation therapists and medical specialists in the use of kilovoltage cone-beam computed tomography scans for potential lung cancer radiotherapy target verification and adaptation

Target volume matching using cone-beam computed tomography (CBCT) is the preferred treatment verification method for lung cancer in many centers. However, radiation therapists (RTs) are trained in bony matching and not soft tissue matching. The purpose of this study was to determine whether RTs were equivalent to radiation oncologists (ROs) and radiologists (RDs) in alignment of the treatment CBCT with the gross tumor volume (GTV) defined at planning and in delineating the GTV on the treatment CBCT, as may be necessary for adaptive radiotherapy. In this study, 10 RTs, 1 RO, and 1 RD performed a manual tumor alignment and correction of the planning GTV to a treatment CBCT to generate an isocenter correction distance for 15 patient data sets. Participants also contoured the GTV on the same data sets. The isocenter correction distance and the contoured GTVs from the RTs were compared with the RD and RO. The mean difference in isocenter correction distances was 0.40 cm between the RO and RD, 0.51 cm between the RTs, and RO and 0.42 cm between the RTs and RD. The 95% CIs were smaller than the equivalence limit of 0.5 cm, indicating that the RTs were equivalent to the RO and RD. For GTV delineation comparisons, the RTs were not found to be equivalent to the RD or RO. The alignment of the planning defined GTV and treatment CBCT using soft tissue matching by the RTs has been shown to be equivalent to those by the RO and RD. However, tumor delineation by the RTs on the treatment CBCT was not equivalent to that of the RO and RD. Thus, it may be appropriate for RTs to undertake soft tissue alignment based on CBCT; however, further investigation may be necessary before RTs undertake delineation for adaptive radiotherapy purposes.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2022

Experimental demonstration and modeling of a robotic neutron detector with spectral and directional sensitivity for treaty verification

International safeguards and arms control agreements often require labor-intensive, intrusive onsite inspections to perform verification tasks. The ability to localize a neutron source and/or characterize a neutron field may be imperative for identifying anomalies. We are interested in the role of autonomous mobile robots, which, if designed properly, may be more effective and efficient and less intrusive than their human counterparts. Toward developing such a capability, we, for this study, have constructed the N-SpecDir Bot, comprised of three boron-coated straw detectors azimuthally-distributed within a cylinder of high-density polyethylene, which is mounted on an omni-directional robotic platform. Our N-SpecDir Bot is specifically designed to provide spectral and directional sensitivity, in addition to gross counts, by utilizing the signals from the three detectors. The detection system has been extensively characterized by MCNP modeling, which has been benchmarked to experiments conducted at the Princeton Plasma Physics Laboratory. We demonstrate the spectral and directional sensitivity experimentally and in simulation, and provide a simple yet robust method for directional measurements.

98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL P↗
DOE OSTI2025

Optimizing a detection system for fissile material in nuclear disarmament verification

In arms control treaties, verification plays a crucial role in detecting non-compliance, deterring future violations, and building trust between state parties. Neutron interrogation that induces fission reactions in fissile isotopes and measures the resulting fission neutrons, could be employed for this purpose. This study aims to develop a system which can determine the presence of fissile material while intrinsically protecting information. In this paper, we focus on optimizing the system for discriminating between an enriched uranium block from a depleted uranium (DU) block. The system was built and we report on benchmark measurements with DU and 16% enriched uranium blocks. Furthermore, the Excalibur (Experiment for Calibration with Uranium) neutron source, a neutron spectrometer (redBubble Technology Industries (BTI) N-Probe), and superheated droplet detectors were used for these measurements. MCNP simulations provided insights into detector responses to fissile materials with varying isotopic compositions, confirming that the system functioned as designed.

Active neutron interrogation↗
DOE OSTI2013

Experimental verification of the Boltzmann relation in confined plasmas: Comparison of noble and molecule gases

Experimental verification of the Boltzmann relation is performed in argon and oxygen gas inductively coupled plasmas from the measurements of both the spatial electron currents (as a fluid approach) and the electron energy probability functions (EEPFs, as a kinetic approach). At a low gas pressure of 10 mTorr, the measured electron currents are spatially uniform, and the EEPFs in the total electron energy scale are identical, which indicate that the Boltzmann relation is valid at both the argon and oxygen gases. As the gas pressure increases to 30-40 mTorr, however, the Boltzmann relation is broken in the oxygen gas discharge, while the Boltzmann relation is still valid in the argon gas discharge. This different variation in the oxygen gas discharge is mainly due to the presence of various inelastic collisions in the entire electron energy region, which causes the transition of the electron kinetics from a non-local to a local regime.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

Use of daily detector verification data for isotopical half-life determination

In this work, the possibility of using data fromthe daily detector verification routines performed at the Neutron Activation Laboratory of IPEN to determine precise values for the half-lives of {sup 57}Co and {sup 60}Co was evaluated. For this purpose data from 4 of the laboratory's detectors, some spanning for more than 9 years, were inspected, separated in consistent groups, and then analyzed using a robust least-squares fit procedure in order to determine the half-lives. The results allowed for a discussion on the possibilities and limitations of the use of these data for the determination of half-lives.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

Establishment and experimental verification of the photoresist model considering interface slip between photoresist and concave spherical substrate

A thickness distribution model of photoresist spin-coating on concave spherical substrate (CSS) has been developed via both theoretical studies and experimental verification. The stress of photoresist on rotating CSS is analyzed and the boundary conditions of hydrodynamic equation are presented under the non-lubricating condition. Moreover, a multivariable polynomial equation of photoresist-layer thickness distribution is derived by analyzing and deducing the flow equation where the evaporation rate, substrate topography, interface slip between liquid and CSS, and the variation of rotational speed and photoresist parameters are considered in detail. Importantly, the photoresist-layer thickness at various CSS rotational speeds and liquid concentrations can be obtained according to the theoretical equation. The required photoresist viscosity and concentration parameters of different photoresist coating thickness under a certain coating speeds can be also solved through this equation. It is noted that the calculated theoretical values are well consistent with the experimental results which were measured with various CSS rotational speeds and liquid concentrations at steady state. Therefore, both our experimental results and theoretical analysis provide the guidance for photoresist dilution and pave the way for potential improvements and microfabrication applications in the future.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Calibrations and verifications performed in view of the ILA reinstatement at JET

The calibrations and verifications that are performed in preparation of the ITER-Like antenna (ILA) reinstatement at JET are reviewed. A brief reminder of the ILA system layout is given. The different calibration methods and results are then discussed. They encompass the calibrations of the directional couplers present in the system, the determination of the relation between the capacitor position readings and the capacitance value, the voltage probes calibration inside the antenna housing, the RF cables characterization and the acquisition electronics circuit calibration. Earlier experience with the ILA has shown that accurate calibrations are essential for the control of the full ILA close-packed antenna array, its protection through the S-Matrix Arc Detection and the new second stage matching algorithm to be implemented. Finally the voltage stand-off of the capacitors is checked and the phase range achievable with the system is verified. The system layout is modified as to allow dipole operation over the whole operating frequency range when operating with the 3dB combiner-splitters.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Design and verification of distributed logic controllers with application of Petri nets

The paper deals with the designing and verification of distributed logic controllers. The control system is initially modelled with Petri nets and formally verified against structural and behavioral properties with the application of the temporal logic and model checking technique. After that it is decomposed into separate sequential automata that are working concurrently. Each of them is re-verified and if the validation is successful, the system can be finally implemented.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗