Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Distribution”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 649 records · Page 36
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Fault Response of Distributed Energy Resources Considering the Requirements of IEEE 1547-2018

Inverter-based DER responses to faults on the electric power system are different than those of conventional generators and are often poorly understood. Inverter fault responses are largely software-defined, within physics-based constraints. DERs are regulated by standards and grid codes that also constrain their responses. Though fault response of DERs will vary widely, for any DER following any particular standard, a pattern of fault response can be synthesized by observing that particular standard. In this paper, the recently published IEEE 1547-2018 is examined to explore the general fault response of any DER that follows IEEE 1547-2018. Additionally, an IEEE 1547-2018 compliant inverter model is developed and tested in simulation to find the fault response, and that response is compared with the fault response of a commercial off-the-shelf inverter.

41 EE - Solar Energy Technologies Office (EE-4S)↗
DOE OSTI2014

ITAR: A modified TAR method to determine depth dose distribution for an ophthalmic device that performs kilovoltage x-ray pencil-beam stereotaxy

Purpose: New technology has been developed to treat age-related macular degeneration (AMD) using 100 kVp pencil-beams that enter the patient through the radio-resistant sclera with a depth of interest between 1.6 and 2.6 cm. Measurement of reference and relative dose in a kilovoltage x-ray beam with a 0.42 cm diameter field size and a 15 cm source to axis distance (SAD) is a challenge that is not fully addressed in current guidelines to medical physicists. AAPM's TG-61 gives dosimetry recommendations for low and medium energy x-rays, but not all of them are feasible to follow for this modality. Methods: An investigation was conducted to select appropriate equipment for the application. PTW's Type 34013 Soft X-Ray Chamber (Freiburg, Germany) and CIRS's Plastic Water LR (Norfolk, VA) were found to be the best available options. Attenuation curves were measured with minimal scatter contribution and thus called Low Scatter Tissue Air Ratio (LSTAR). A scatter conversion coefficient (C{sub scat}) was derived through Monte Carlo radiation transport simulation using MCNPX (LANL, Los Alamos, NM) to quantify the difference between a traditional TAR curve and the LSTAR curve. A material conversion coefficient (C{sub mat}) was determined through experimentation to evaluate the difference in attenuation properties between water and Plastic Water LR. Validity of performing direct dosimetry measurements with a source to detector distance other than the treatment distance, and therefore a different field size due to a fixed collimator, was explored. A method—Integrated Tissue Air Ratio (ITAR)—has been developed that isolates each of the three main radiological effects (distance from source, attenuation, and scatter) during measurement, and integrates them to determine the dose rate to the macula during treatment. Results: LSTAR curves were determined to be field size independent within the range explored, indicating that direct dosimetry measurements may be performed with a source to detector distance of 20 cm even though the SAD is 15 cm during treatment. C{sub scat} varied from 1.102 to 1.106 within the range of depths of interest. The experimental variance among repeated measurements of C{sub mat} was larger than depth dependence, so C{sub mat} was estimated as1.019 for all depths of interest. Conclusions: Equipment selection, measurement techniques, and formalism for the determination of dose rate to the macula during stereotaxy for AMD have been determined and are strongly recommended by the authors of this paper to be used by clinical medical physicists.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2022

Security Enhancements for Distributed Energy Resource Systems Interconnected with Distribution Networks: Final Technical Report

The revised IEEE 1547 Standard defines new complex communication-adjustable voltage and frequency regulation and ride-through characteristics, while maintaining the general antiislanding requirement for unintentional islanding situations. Unintentional islanding is prohibited while intentional islanding is specifically allowed, thus effectively enabling microgrid operation mode. Further, IEEE 1547-2018 Standard introduces new requirements in terms of interoperability so that the DER plant/circuit segments may be seamlessly integrated with the utility networks but at the same time become vulnerable to a cyber-attack. Traditional cybersecurity measures including encryption, authentication and role-based access control may not be fully implementable to all communication protocols specified in the IEEE 1547 Standard. Therefore, in this project we have identified, researched, implemented and tested several cyberphysical approaches that rely mostly on the behavior of the DER circuit and may help with validating the incoming command and control action potentially coming through an insecure communications channel. Additionally, we have built semantic models and communications profiles for DER facilities and have implemented lightweight IEC 61850 based publisher-subscriber GOOSE messaging mechanism, with security extensions in terms of authentication and encryption. The project proposed information models for integration into UCA OpenFMB 2.0 profiles focusing on grid code compliance.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2011

[Ni(PPh2NBn2)2(CH3CN)]2+ as an Electrocatalyst for H2 Production: Dependence on Acid Strength and Isomer Distribution

[Ni(PPh2NBz2)2(CH3CN)](BF4)2, Ni(PPh2NBz2)22+ (where PPh2NBz2 is 1,5-dibenzyl-3,7-diphenyl-1,5-diaza-3,7-diphosphacyclooctane) has been studied as an electrocatalyst for the production of hydrogen in acetonitrile. Using strong acids, such as p cyanoanilinium, Ni(PPh2NBz2)22+ has been shown to be protonated under catalytic conditions prior to reduction, with an effective pKa of 6.7±0.4. Through multinuclear NMR spectroscopy studies, the nickel(II) complex was found to be doubly protonated without any observed singly protonated species. In the doubly protonated complex, both protons are positioned exo with respect to the metal center and are stabilized by an N-H-N hydrogen bond. The formation of exo protonated isomers is proposed to limit the rate of hydrogen production because the protons are unable to gain suitable proximity to the reduced metal center to generate dihydrogen. Pre-protonation of Ni(PPh2NBz2)22+ has been found to shift the catalytic operating potential to more positive potentials by up to 440 mV, depending upon the conditions. The catalytic rate was found to increase by an order of magnitude by increasing the solution pH or through the addition of water. This material is based upon work supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences.

08 HYDROGEN↗
DOE OSTI2015

A novel system for measurement of the transverse electron momentum distribution from photocathodes

The transverse momentum of electrons produced by a photocathode contributes significantly to the performance of several different types of accelerator-based light sources, such as Free Electron Lasers, as well as systems designed for ultrafast electron diffraction and dynamic transmission electron microscopy. Minimization of the transverse emittance from photocathodes is the subject of intensive research, and therefore measurement of this parameter is of great importance. Here, we describe a simple system that offers real time measurements of transverse emittance and can be easily integrated into the photocathode fabrication process.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2010

Photon parton distributions in nuclei and the EMC effect

Photons, as well as quarks and gluons, are constituents of the infinite momentum frame (IMF) wave function of an energetic particle. They are mostly equivalent photons whose amplitude follows from the Lorentz transformation of the particle rest frame Coulomb field into the IMF and from the conservation of the electromagnetic current. We evaluate in a model independent way the dominant photon contribution {proportional_to}{alpha}{sub em}(Z{sup 2}/A{sup 4/3})ln(1/R{sub A}m{sub N}x) to the nuclear structure functions as well as the term {proportional_to}{alpha}{sub em}Z/A. In addition we show that the definition of x consistent with the exact kinematics of eA scattering (with exact sum rules) works in the same direction as the nucleus field of equivalent photons. Combined, these effects account for the bulk of the hadronic European Muon Collaboration (EMC) effect for x{<=}0.5 where Fermi motion effects are small. In particular, for these x the hadronic mechanism contribution to the EMC effect does not exceed {approx}3% for all nuclei. Also, the A dependence of the hadronic mechanism of the EMC effect for x>0.5 is significantly modified.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗