Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “STATE VECTOR”

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 1,801 records · Page 100
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Large N-ightmare dark matter

A dark QCD sector is a relatively minimal extension of the Standard Model (SM) that admits Dark Matter (DM) candidates, but requires no portal to the visible sector beyond gravitational interactions: a "nightmare scenario" for DM detection. Here, we consider a secluded dark sector containing a single flavor of light, vector-like dark quark gauged under (N). In the large-N limit, this single-flavor theory becomes highly predictive, generating two DM candidates whose masses and dynamics are described by few parameters: a light quark-antiquark bound state, the dark analog of the η' meson, and a heavy bound state of N quarks, the dark analog of the Δ ++ baryon. We show that the latter may freeze-in with an abundance independent of the confinement scale, forming DM-like relics for N ≲ 10, while the former may generate DM via cannibalization and freeze-out. We study the interplay of this two-component DM system, and determine the characteristic ranges of the confinement scale, dark-visible sector temperature ratio, and N that admit non-excluded DM, once effects of self-interaction constraints and bounds on effective degrees of freedom at the BBN and CMB epochs are included.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2026

Improving missing transverse momentum estimation with a deep neural network

At hadron colliders, the net transverse momentum of particles that do not interact with the detector (missing transverse momentum, $^→_𝑝$$^{miss}_{T}$) is a crucial observable in many analyses. In the standard model, $^→_𝑝$$^{miss}_{T}$ originates from neutrinos. Many beyond-the-standard-model particles, such as dark matter candidates, are also expected to leave the experimental apparatus undetected. This paper presents a novel deep neural network based $^→_𝑝$$^{miss}_{T}$ estimator, DeepMET, developed by the CMS Collaboration at the LHC. The DeepMET algorithm produces a weight for each reconstructed particle based on its properties. The estimator is based on the negative vector sum of the weighted transverse momenta of all reconstructed particles in an event. Compared with other estimators currently employed by CMS, DeepMET improves the $^→_𝑝$$^{miss}_{T}$ resolution by 10%–30%, shows improvement for a wide range of final states, is easier to train, and is more resilient against the effects of additional proton-proton interactions accompanying the collision of interest.

artificial neural networks↗
DOE OSTI2024

Measurement of simplified template cross sections of the Higgs boson produced in association with W or Z bosons in the H → b b ¯ decay channel in proton-proton collisions at s = 13 TeV

Differential cross sections are measured for the standard model Higgs boson produced in association with vector bosons (W, Z) and decaying to a pair of b quarks. Measurements are performed within the framework of the simplified template cross sections. The analysis relies on the leptonic decays of the W and Z bosons, resulting in final states with 0, 1, or 2 electrons or muons. The Higgs boson candidates are either reconstructed from pairs of resolved b-tagged jets, or from single large-radius jets containing the particles arising from two b quarks. Proton-proton collision data at $\sqrt{s}$ =13 TeV, collected by the CMS experiment in 2016–2018 and corresponding to a total integrated luminosity of 138 fb -1 , are analyzed. The inclusive signal strength, defined as the product of the observed production cross section and branching fraction relative to the standard model expectation, combining all analysis categories, is found to be μ = $1.15^{+0.22}_{-0.20}$. This corresponds to an observed (expected) significance of 6.3 (5.6) standard deviations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Constraints on the spin-parity and anomalous HVV couplings of the Higgs boson in proton collisions at 7 and 8 TeV

Our study of the spin-parity and tensor structure of the interactions of the recently discovered Higgs boson is performed using the H→ZZ,Zγ*,γ*γ*→4ℓ, H→WW→ℓνℓν, and H→γγ decay modes. The full data set recorded by the CMS experiment during the LHC run 1 is used, corresponding to an integrated luminosity of up to 5.1 fb -1 at a center-of-mass energy of 7 TeV and up to 19.7 fb -1 at 8 TeV. A wide range of spin-two models is excluded at a 99% confidence level or higher, or at a 99.87% confidence level for the minimal gravitylike couplings, regardless of whether assumptions are made on the production mechanism. Any mixed-parity spin-one state is excluded in the ZZ and WW modes at a greater than 99.999% confidence level. Under the hypothesis that the resonance is a spin-zero boson, the tensor structure of the interactions of the Higgs boson with two vector bosons ZZ, Zγ, γγ, and WW is investigated and limits on eleven anomalous contributions are set. Furthermore, the tighter constraints on anomalous HVV interactions are obtained by combining the HZZand HWW measurements. All observations are consistent with the expectations for the standard model Higgs boson with the quantum numbers J PC =0 ++ .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Electron-Phonon Coupling from Ab Initio Linear-Response Theory within the G W Method: Correlation-Enhanced Interactions and Superconductivity in Ba 1 - x K x BiO 3

We present a new first-principles linear-response theory of changes due to perturbations in the quasiparticle self-energy operator within the GW method. This approach, named GW perturbation theory ( GW PT), is applied to calculate the electron-phonon ( e -ph) interactions with the full inclusion of the GW nonlocal, energy-dependent self-energy effects, going beyond density-functional perturbation theory. Avoiding limitations of the frozen-phonon technique, GW PT gives access to e -ph matrix elements at the GW level for all phonons and scattering processes, and the computational cost scales linearly with the number of phonon modes (wave vectors and branches) investigated. We demonstrate the capabilities of GW PT by studying the e -ph coupling and superconductivity in Ba 0.6 K 0.4 BiO 3 . We show that many-electron correlations significantly enhance the e -ph interactions for states near the Fermi surface, and explain the observed high superconductivity transition temperature of Ba 0.6 K 0.4 BiO 3 as well as its doping dependence.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Incommensurate Magnetism Near Quantum Criticality in CeNiAsO

Here, we report the discovery of incommensurate magnetism near quantum criticality in CeNiAsO through neutron scattering and zero field muon spin rotation. For T < T N 1 = 8.7(3) K, a second order phase transition yields an incommensurate spin density with a wave vector k = (0.44(4),0,0). For T < T N 2 = 7.6(3) K, we find coplanar commensurate order with a moment of 0.37(5)μ B , reduced to 30% of the saturation moment of the |±1/2 > Kramers doublet ground state, which we establish through inelastic neutron scattering. Muon spin rotation in CeNiAs 1–x P x O shows the commensurate order only exists for x ≤ 0.1 so we infer the transition at x c = 0.4(1) is between an incommensurate longitudinal spin density wave and a paramagnetic Fermi liquid.

36 MATERIALS SCIENCE↗
DOE OSTI2025

𝐵 → 𝜌⁢ℓ⁢$\bar{v}$ Resonance Form Factors from 𝐵→ 𝜋⁢𝜋⁢ℓ⁢$\bar{v}$ in Lattice QCD

The decay 𝐵 → 𝜌⁢ℓ⁢$\bar{v}$ is an attractive process for determining the magnitude of the smallest Cabibbo-Kobayashi-Maskawa matrix element, |𝑉 𝑢⁢𝑏 |, and can provide new insights into the origin of the long-standing exclusive-inclusive discrepancy in determinations of this standard-model parameter. This requires a nonperturbative QCD calculation of the 𝐵 → 𝜌 form factors 𝑉, 𝐴 0 , 𝐴 1 , and 𝐴 12 . The unstable nature of the 𝜌 resonance has prevented precise lattice QCD calculations of these form factors to date. Here, we present the first lattice QCD calculation of the 𝐵 → 𝜌 form factors in which the 𝜌 is treated properly as a resonance in 𝑃-wave 𝜋⁢𝜋 scattering. To this end, we use the Lellouch-Lüscher finite-volume formalism to compute the 𝐵 → 𝜋⁢𝜋 form factors as a function of both momentum transfer and 𝜋⁢𝜋 invariant mass, and then analytically continue to the 𝜌 resonance pole. This calculation is performed with 2 + 1 dynamical quark flavors at a pion mass of approximately 320 MeV, and demonstrates a clear path toward results at the physical point.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

SigTime: Learning and Visually Explaining Time Series Signatures

Understanding and distinguishing temporal patterns in time series data is essential for scientific discovery and decision-making. For example, in biomedical research, uncovering meaningful patterns in physiological signals can improve diagnosis, risk assessment, and patient outcomes. However, existing methods for time series pattern discovery face major challenges, including high computational complexity, limited interpretability, and difficulty in capturing meaningful temporal structures. Here, to address these gaps, we introduce a novel learning framework that jointly trains two Transformer models using complementary time series representations: shapelet-based representations to capture localized temporal structures and traditional feature engineering to encode statistical properties. The learned shapelets serve as interpretable signatures that differentiate time series across classification labels. Additionally, we develop a visual analytics system—SigTime—with coordinated views to facilitate exploration of time series signatures from multiple perspectives, aiding in useful insights generation. We quantitatively evaluate our learning framework on eight publicly available datasets and one proprietary clinical dataset. Additionally, we demonstrate the effectiveness of our system through two usage scenarios along with the domain experts: one involving public ECG data and the other focused on preterm labor analysis.

97 MATHEMATICS AND COMPUTING↗
NASA NTRS1973

Fuel-optimal angular momentum vector control for spinning and dual-spin spacecraft.

The problem of fuel-optimal small-angle reorientation of the spin axis of a spinning or dual-spin spacecraft is examined. The results obtained show significant improvements over previously published optimization studies by virtue of the introduction of two innovations: (1) mass-explusion active control is utilized for angular momentum vector pointing only, with passive damping relied upon for stable vehicles to attenuate vehicle coning about the angular momentum vector, so that the task of the active controller changes from spin axis control to angular momentum vector control, and (2) several options are considered for type, number, and location of attitude control jets. The first of these considerations introduces a target set which is a smooth, two-dimensional linear manifold in the four-dimensional state space, whereas previous studies have adopted the origin as the target set. The second innovation amounts to consideration of a spectrum of control restraint sets.

Larson, V.↗
NASA NTRS1977

Navigation simulator for the Space Tug vehicle

A general simulation program (GSP) for state estimation of a nonlinear space vehicle flight navigation system is developed and used as a basis for evaluating the performance of a Space Tug navigation system. An explanation of the iterative guidance mode (IGM) guidance law, derivation of the dynamics, coordinate frames and state estimation routines are given in order to clarify the assumptions and approximations made. A number of simulation and analytical studies are used to demonstrate the operation of the Tug system. Included in the simulation studies are (1) initial offset vector parameter study; (2) propagation time vs accuracy; (3) measurement noise parametric study and (4) reduction in computational burden of an on-board implementable scheme. From the results of these studies, conclusions and recommendations concerning future areas of practical and theoretical work are presented.

Colburn, B. K.↗
NASA NTRS1982

Characteristics of ageostrophic flow in the vicinity of a severe weather outbreak - AVE-SESAME I

GOES satellite data was used to examine the ageostrophic flow in the vicinity of severe weather outbreaks along the Red River between Texas and Oklahoma in April 1979. The observations were part of the NASA AVE-SESAME I data on atmospheric states close to severe weather conditions. The Barnes Objective Analysis Technique was employed to analyze the data on a 100 km grid. The ageostrophic wind was defined on a regional scale from satellite data on different levels of cloud wind vectors, with a height change signalling a short-wave system in a long-wave trough. The percentage of deviation of the subgeostrophic winds from the geostrophic wind was calculated, and maximum departure corresponded with the region of greatest storm development. Time cross sections of additions to the ageostrophic flow were made as a function of pressure at 100 mb intervals from 900-100 mb. The ageostrophic acceleration was consistently twice the geostrophic acceleration.

Arnold, J. E.↗
NASA NTRS1985

Numerical solutions of 3-dimensional Navier-Stokes equations for closed bluff-bodies

The Navier-Stokes equations are solved numerically. These equations are unsteady, compressible, viscous, and three-dimensional without neglecting any terms. The time dependency of the governing equations allows the solution to progress naturally for an arbitrary initial guess to an asymptotic steady state, if one exists. The equations are transformed from physical coordinates to the computational coordinates, allowing the solution of the governing equations in a rectangular parallelepiped domain. The equations are solved by the MacCormack time-split technique which is vectorized and programmed to run on the CDc VPS 32 computer. The codes are written in 32-bit (half word) FORTRAN, which provides an approximate factor of two decreasing in computational time and doubles the memory size compared to the 54-bit word size.

Abolhassani, J. S.↗
NASA NTRS2015

A Vehicle Management End-to-End Testing and Analysis Platform for Validation of Mission and Fault Management Algorithms to Reduce Risk for NASA's Space Launch System

The engineering development of the new Space Launch System (SLS) launch vehicle requires cross discipline teams with extensive knowledge of launch vehicle subsystems, information theory, and autonomous algorithms dealing with all operations from pre-launch through on orbit operations. The characteristics of these spacecraft systems must be matched with the autonomous algorithm monitoring and mitigation capabilities for accurate control and response to abnormal conditions throughout all vehicle mission flight phases, including precipitating safing actions and crew aborts. This presents a large and complex system engineering challenge, which is being addressed in part by focusing on the specific subsystems involved in the handling of off-nominal mission and fault tolerance with response management. Using traditional model based system and software engineering design principles from the Unified Modeling Language (UML) and Systems Modeling Language (SysML), the Mission and Fault Management (M&FM) algorithms for the vehicle are crafted and vetted in specialized Integrated Development Teams (IDTs) composed of multiple development disciplines such as Systems Engineering (SE), Flight Software (FSW), Safety and Mission Assurance (S&MA) and the major subsystems and vehicle elements such as Main Propulsion Systems (MPS), boosters, avionics, Guidance, Navigation, and Control (GNC), Thrust Vector Control (TVC), and liquid engines. These model based algorithms and their development lifecycle from inception through Flight Software certification are an important focus of this development effort to further insure reliable detection and response to off-nominal vehicle states during all phases of vehicle operation from pre-launch through end of flight. NASA formed a dedicated M&FM team for addressing fault management early in the development lifecycle for the SLS initiative. As part of the development of the M&FM capabilities, this team has developed a dedicated testbed that integrates specific M&FM algorithms, specialized nominal and off-nominal test cases, and vendor-supplied physics-based launch vehicle subsystem models. Additionally, the team has developed processes for implementing and validating these algorithms for concept validation and risk reduction for the SLS program. The flexibility of the Vehicle Management End-to-end Testbed (VMET) enables thorough testing of the M&FM algorithms by providing configurable suites of both nominal and off-nominal test cases to validate the developed algorithms utilizing actual subsystem models such as MPS. The intent of VMET is to validate the M&FM algorithms and substantiate them with performance baselines for each of the target vehicle subsystems in an independent platform exterior to the flight software development infrastructure and its related testing entities. In any software development process there is inherent risk in the interpretation and implementation of concepts into software through requirements and test cases into flight software compounded with potential human errors throughout the development lifecycle. Risk reduction is addressed by the M&FM analysis group working with other organizations such as S&MA, Structures and Environments, GNC, Orion, the Crew Office, Flight Operations, and Ground Operations by assessing performance of the M&FM algorithms in terms of their ability to reduce Loss of Mission and Loss of Crew probabilities. In addition, through state machine and diagnostic modeling, analysis efforts investigate a broader suite of failure effects and associated detection and responses that can be tested in VMET to ensure that failures can be detected, and confirm that responses do not create additional risks or cause undesired states through interactive dynamic effects with other algorithms and systems. VMET further contributes to risk reduction by prototyping and exercising the M&FM algorithms early in their implementation and without any inherent hindrances such as meeting FSW processor scheduling constraints due to their target platform - ARINC 653 partitioned OS, resource limitations, and other factors related to integration with other subsystems not directly involved with M&FM such as telemetry packing and processing. The baseline plan for use of VMET encompasses testing the original M&FM algorithms coded in the same C++ language and state machine architectural concepts as that used by Flight Software. This enables the development of performance standards and test cases to characterize the M&FM algorithms and sets a benchmark from which to measure the effectiveness of M&FM algorithms performance in the FSW development and test processes.

Trevino, Luis↗
DOE OSTI2016

Contour Mapping Based Radiation Source Localization by UAS Swarm

The unmanned swarm of aerial systems (UAS) can be used for remote radiation sensing and search for source location. Recently, the cost of developing UAS platforms has dropped drastically partly due to the increase in their popularity. The radiation sensing using multiple UAS has becomes economically viable. Different algorithms for determining the location of a radiation source using simultaneous measurements taken from drones in formation have been studied including gradient-based methods. Generally in order to accomplish contour mapping, the swarm of drones with on board sensors use gradient estimation to determine the direction of steepest gradient which governs a bulk heading vector for the swarm to follow. However, some algorithms and test methods are useful only in a specific set of circumstances with particular initial conditions. Besides, implementation of drones in swarm formation was generally not tested in the context of radiation source detection. The objective of this research is to advance the state-of-the-art by conducting experiments using multiple UAS and radiative sources in an indoor flight test-bed. The dynamic flight characteristic of the UAS swarm were considered in the search and mapping algorithms. In this paper, the radiation source detection using algorithms pertaining to swarm formation of UAS, gradient estimation, contour mapping, and experimental flight test-bed are discussed. In addition, more effective and practical ways of constructing the contour maps are explored. (authors)

42 ENGINEERING↗
DOE OSTI2025

Wireless Patch Antenna Characterization for Live Health Monitoring Using Machine Learning

Temperature monitoring in extreme environments, such as coal-fired power plants, was addressed by designing and testing wireless patch antennas for use in machine learning-aided temperature estimation. The sensors were designed to monitor the temperature and health of boiler systems. Wireless interrogation of the sensor was performed using a Vector Network Analyzer (VNA) and a pair of interrogation antennas to capture resonance behavior under varying thermal and spatial conditions with sensitivities ranging from 0.052 to 0.20 $\frac{𝑀𝐻𝑧}{°C}$. Sensor calibration was conducted using a Long Short-Term Memory (LSTM) model, which leveraged temporal patterns to account for hysteresis effects. The calibration method demonstrated improved performance when combined with an LSTM model, achieving up to a 76% improvement in temperature estimation error when compared with Linear Regression (LR). The experiments highlighted an innovative solution for patch antenna-based non-contact temperature measurement, which addresses limitations with conventional methods such as RFID-based systems, infrared, and thermocouples.

20 FOSSIL-FUELED POWER PLANTS↗
DOE OSTI2021

Critical Review of Platinum Group Metal-Free Materials for Water Electrolysis: Transition from the Laboratory to the Market : Earth-abundant borides and phosphides as catalysts for sustainable hydrogen production

To combat the global problem of carbon dioxide emissions, hydrogen is the desired energy vector for the transition to environmentally benign fuel cell power. Water electrolysis (WE) is the major technology for sustainable hydrogen production. Despite the use of renewable solar and wind power as sources of electricity, one of the main barriers for the widespread implementation of WE is the scarcity and high cost of platinum group metals (pgms) that are used to catalyse the cathodic hydrogen evolution reaction (HER) and the anodic oxygen evolution reaction (OER). Hence, the critical pgm-based catalysts must be replaced with more sustainable alternatives for WE technologies to become commercially viable. This critical review describes the state-of-the-art pgm-free materials used in the WE application, with a major focus on phosphides and borides. Several emerging classes of HER and OER catalysts are reviewed and detailed structure-property correlations are comprehensively summarised. The influence of the crystallographic and electronic structures, morphology and bulk and surface chemistry of the catalysts on the activity towards OER and HER is discussed.

Chemistry↗
DOE OSTI2015

Many-body forces in the equation of state of hyperonic matter

In this work we introduce an extended version of the formalism proposed originally by Taurines et al. that considers the effects of many-body forces simulated by nonlinear self-couplings and meson–meson interaction contributions. In this extended version of the model, we assume that matter is at zero temperature, charge neutral, and in beta-equilibrium, considering that the baryon octet interacts by the exchange of scalar–isoscalar (σ, σ{sup ∗}), vector–isoscalar (ω, ϕ), vector–isovector (ϱ), and scalar–isovector (δ) meson fields. Using nuclear matter properties, we constrain the parameters of the model that describe the intensity of the indirectly density dependent baryon–meson couplings to a small range of possible values. We then investigate asymmetric hyperonic matter properties. We report that the formalism developed in this work is in reasonable agreement with experimental data and also allows for the existence of massive hyperon stars (with more than 2 M{sub ⊙}) with small radii, compatible with astrophysical observations.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2026

Omega-Limit Sets and Input-To-State Stability in Power Grids with Switching Equilibria

This paper studies a power transmission system with both conventional generators (CGs) and distributed energy assets (DEAs) providing frequency control. We consider an operating condition with demand aggregating two dynamic components: one that switches between different values on a finite set, and one that varies smoothly over time. Such dynamic operating conditions may result from protection scheme activations, external cyber-attacks, or due to the integration of dynamic loads, such as data centers. Mathematically, the dynamics of the resulting system are captured by a system that switches between a finite number of vector fields - or modes -, with each mode having a distinct equilibrium point induced by the demand aggregation. To analyze the stability properties of the resulting switching system, we leverage tools from hybrid dynamic inclusions and the concept of ..omega.. -limit sets from sets. Specifically, we characterize a compact set that is semi-globally practically asymptotically stable under the assumption that the switching frequency and load variation rate are sufficiently slow. For arbitrarily fast variations of the load, we use a level-set argument with multiple Lyapunov functions to establish input-to-state stability of a larger set and with respect to the rate of change of the loads. The theoretical results are illustrated via numerical simulations on the IEEE 39-bus test system.

24 POWER TRANSMISSION AND DISTRIBUTION↗

Refine your search to explore more results.