Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Independent”

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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

EISA (Energy Independence and Security Act) compliant ethanol fuel from corn stover in a depot-based decentralized system

Cellulosic biofuels face significant problems of feedstock aggregation and logistics leading to poor economies of scale. The current model is based on relatively small biorefineries using locally-gathered feedstocks. Here, we examine the potential capacity of a hypothetically distributed, depot-based, biorefinery system to produce cellulosic ethanol from corn stover in the United States Midwest. The local depots serve to aggregate, pretreat and densify biomass (via pellets), which are collected, transported, and fed to a few very large, cellulosic ethanol biorefineries. We found that a corn stover-based depot system would help establish one or two very large-scale biorefineries capable of processing about 8-12% of total corn stover available in the United States Midwest. About 55-153 depots could supply the pretreated pellets to each distributed biorefinery leading to an annual production of 1.02 - 2.91 billion liters of cellulosic ethanol. Most of the participating depots would be located in Illinois and Iowa. The ethanol selling price in this depot-based biorefinery system would varys between U$S 0.67 and U$S 0.72 liter-1. The estimated range of GHG savings from cellulosic ethanol in the depot system compared to gasoline was 3.35-4.84 Tg CO2 year-1. In addition of being economically competitive, a distributed, depot-based, biorefinery system could meet the 60% GHG reduction requirement of the U.S. Energy Independence and Security Act (EISA).

Biorefinery, Cellulosic biofuel, Corn stover, Dist↗
DOE OSTI2013

Independent confirmation of global land warming without the use of station temperatures

Confidence in estimates of anthropogenic climate change is limited by known issues with air temperature observations from land stations. Station siting, instrument changes, changing observing practices, urban effects, land cover, land use variations, and statistical processing have all been hypothesized as affecting the trends presented by the Intergovernmental Panel on Climate Change and others. Any artifacts in the observed decadal and centennial variations associated with these issues could have important consequences for scientific understanding and climate policy. We use a completely different approach to investigate global land warming over the 20th century. We have ignored all air temperature observations and instead inferred them from observations of barometric pressure, sea surface temperature, and sea-ice concentration using a physically based data assimilation system called the 20th Century Reanalysis. This independent data set reproduces both annual variations and centennial trends in the temperature data sets, demonstrating the robustness of previous conclusions regarding global warming.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

An independent analysis of bias sources and variability in wind plant pre-construction energy yield estimation methods

The wind resource assessment community has long had the goal of reducing the bias between wind plant pre-construction energy yield assessment (EYA) and the observed annual energy production (AEP). This comparison is typically made between the 50% probability of exceedance (P50) value of the EYA and the long-term corrected operational AEP (hereafter OA P50), and is known as the P50 bias. The industry has critically lacked an independent analysis of bias reduction investigated across multiple consultants to identify the greatest sources of uncertainty and variance in the EYA process and the best opportunities for uncertainty reduction. The present study addresses this gap by benchmarking consultant methodologies against each other and against operational data at a scale not seen before in industry collaborations. We consider data from 10 wind plants and evaluate discrepancies between eight consultancies in the steps taken from estimates of gross to net energy. Consultants tend to overestimate the gross energy produced at the turbines and then compensate by further overestimating downstream losses, leading to a mean P50 bias near zero, still with significant variability among the individual wind plants. Within our data sample, we find that consultant estimates of all loss categories, except environmental losses, tend to reduce the project-to-project variability of the P50 bias. The disagreement between consultants, however, remains flat throughout the addition of losses. Finally, we find that differences in consultants’ estimates of project performance can lead to differences up to $10/MWh in the levelized cost of energy for a wind plant.

Todd, Austin C.↗
DOE OSTI2020

Distribution System Segmented Model Simplification with Independent Dynamically Changing End-Use Loads

With more emerging technologies in power distribution systems, to support quasi-static time-series (QSTS) simulation over short time frames, accurately modeling the dynamic behavior of end-use load under various conditions is im- portant. However, time and cost can be a burden for the QSTS simulation of thousands of houses representing dynamic load behaviors on large distribution feeders. There are two main contributions of this paper in order to reduce the QSTS simulation complexity. First, the paper presents a method to stochasti- cally model the dynamic behavior of end-use load for QSTS simulations. Second, using the stochastically modeled load behavior as an input to a distribution sys- tem, and building on our previous QSTS simulation simplification/acceleration method that relies on uniform load behavior, this paper presents a segment substitution approach for the simplification of distribution system models with independent dynamically changing end-use loads. Our numerical results show that compared to GridLAB-D, a software tool that simulates end-use load be- havior through physical models, the proposed stochastic modeling approach achieved an 89.3% simulation time reduction for end-use loads, while accurately capturing the temporally changing total load behavior. Moreover, the QSTS simulation of a large test distribution system through OpenDSS showed that the proposed simplification method decreased the feeder simulation time by a factor of three at less than 0.3% voltage error. Compared to our previous method with independent dynamic loads, the voltage error is reduced by a factor of four.

Power distribution system modeling, stochastic pro↗
DOE OSTI2022

Quaternary structure independent folding of voltage-gated ion channel pore domain subunits

Every voltage-gated ion channel (VGIC) has a pore domain (PD) made from four subunits, each comprising an antiparallel transmembrane helix pair bridged by a loop. The extent to which PD subunit structure requires quaternary interactions is unclear. In this report we present crystal structures of a set of bacterial voltage-gated sodium channel (BacNa V ) 'pore only' proteins that reveal a surprising collection of non-canonical quaternary arrangements in which the PD tertiary structure is maintained. This context-independent structural robustness, supported by molecular dynamics simulations, indicates that VGIC-PD tertiary structure is independent of quaternary interactions. This fold occurs throughout the VGIC superfamily and in diverse transmembrane and soluble proteins. Strikingly, characterization of PD subunit-binding Fabs indicates that non-canonical quaternary PD conformations can occur in full-length VGICs. Together, our data demonstrate that the VGIC-PD is an autonomously folded unit. This property has implications for VGIC biogenesis, understanding functional states, de novo channel design, and VGIC structural origins.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2015

Halo-independent tests of dark matter direct detection signals: local DM density, LHC, and thermal freeze-out

From an assumed signal in a Dark Matter (DM) direct detection experiment a lower bound on the product of the DM-nucleon scattering cross section and the local DM density is derived, which is independent of the local DM velocity distribution. This can be combined with astrophysical determinations of the local DM density. Within a given particle physics model the bound also allows a robust comparison of a direct detection signal with limits from the LHC. Furthermore, the bound can be used to formulate a condition which has to be fulfilled if the particle responsible for the direct detection signal is a thermal relic, regardless of whether it constitutes all DM or only part of it. We illustrate the arguments by adopting a simplified DM model with a Z{sup ′} mediator and assuming a signal in a future xenon direct detection experiment.

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

First model-independent Dalitz analysis of B 0 → DK* 0 , D→K$^{0}_{S}$π + π – decay

We report a measurement of the amplitude ratio r S of B 0 → D 0 K* 0 and B 0 → D 0 ¯K* 0 decays with a Dalitz analysis of D → K$^{0}_{S}$π + π – decays, for the first time using a model-independent method. We set an upper limit rS<0.87 at the 68\% confidence level, using the full data sample of 772×10 6 BB¯ pairs collected at the Υ(4S) resonance with the Belle detector at the KEKB e + e – collider. This result is obtained from observables x–= +0.4$^{+1.0+0.0}_{–0.6–0.1}$ ± 0.0, y– = –0.6$^{+0.8+0.1}_{–1.0–0.0}$ ± 0.1, x + = +0.1$^{+0.7+0.0}_{–0.4–0.1}$ ± 0.1 and y + = +0.3$^{+0.5+0.0}_{–0.8–0.1}$ ± 0.1, where x ± = r S cos(δ S ± Φ 3 ), y ± = r S sin(δ S ± Φ 3 ) and Φ 3 (δ S ) is the weak (strong) phase difference between B 0 → D 0 K* 0 and B 0 → D¯ 0 K* 0 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Stochastically estimated covariance matrices for independent and cumulative fission yields in the ENDF/B-VIII.0 and JEFF-3.3 evaluations

A Monte-Carlo method for the generation of correlation and covariance matrices for independent and cumulative fission yields has been developed. The method uses a constrained Monte-Carlo resampling structure in order to vary evaluated fission yield libraries in a way that meets basic conservation principles. This results in the generation of correlation/covariance matrices with limited model bias and uncertainty; the matrices are primarily reflective of the evaluated fission yield uncertainties and correlations that arise from the evaluation process. This method has been applied to generate correlation and covariance matrices for all of the fissioning systems of the ENDF/B-VIII.0 and JEFF-3.3 evaluations, marking the first time such matrices have been generated for all of these systems. These covariance matrices have been published online for immediate public use. These correlation and covariance matrices can be used to improve uncertainty estimation in calculations of reactor antineutrino emission rates, decay heat problems, and nuclear forensics.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗