SEARCH · Engineering Papers

Results for “CONTRACT”

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.

SourceResearch connectionFrom yearThrough year

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

At least 55 records · Page 3

All sources NASA NTRS DOE OSTI

NASA NTRS1987

Experimental evaluation of honeycomb/screen configurations and short contraction section for NASA Lewis Research Center's altitude wind tunnel

An experimental investigation was conducted in the high speed leg of the 0.1 scale model of the proposed Altitude Wind Tunnel to evaluate flow conditioner configurations in the settling chamber and their effect on the flow through the short contraction section. The lowest longitudinal turbulence intensity measured at the contraction-section entrance, 1.2%, was achieved with a honeycomb plus three fine-mesh screens. Turbulence intensity in the test section was estimated to be between 0.1 and 0.2% with the honeycomb plus three fine mesh screens in the settling chamber. Adding screens, however, adversely affected the total pressure profile, causing a small defect near the centerline at the contraction section entrance. No significant boundary layer separation was evident in the short contraction section.

Burley, Richard R.↗

NASA NTRS1994

An analysis of cost overruns on defense acquisition contracts

This article examines the history of cost overruns reported on 64 completed defense contracts. Its purpose is to formally test the observation of the Under Secretary. Results confirm the observation at the 95 percent level of confidence, and were generally insensitive to the contract type (price, cost), the contract phase (development, production), the type of weapon system (air, ground, sea), and the armed forces service (Air Force, Army, Navy) that managed the contract. After a review of terminology, concepts, and related research for those unfamiliar with the area, the methodology, results, and managerial implications are described.

Christensen, David S.↗

NASA NTRS1995

Observational and numerical studies of extreme frontal scale contraction

The general objective of this effort is to increase understanding of how frontal scale contraction processes may create and sustain intense mesoscale precipitation along intensifying cold fronts. The five-part project (an expansion of the originally proposed two-part project) employed conventional meteorological data, special mesoscale data, remote sensing measurements, and various numerical models. First an idealized hydrostatic modeling study of the scale contraction effects of differential cloud cover on low-level frontal structure and dynamics was completed and published in a peer-reviewed journal. The second objective was to complete and publish the results from a three dimensional numerical model simulation of a cold front in which differential sensible heating related to cloud coverage patterns was apparently crucial in the formation of a severe frontal squall line. The third objective was to use a nonhydrostatic model to examine the nonlinear interactions between the transverse circulation arising from inhomogeneous cloud cover, the adiabatic frontal circulation related to semi-geostrophic forcing, and diabatic effects related to precipitation processes, in the development of a density current-like microstructure at the leading edge of cold fronts. Although the development of a frontal model that could be used to initialize such a primitive equation model was begun, we decided to focus our efforts instead on a project that could be successfully completed in this short time, due to the lack of prospects for continued NASA funding beyond this first year (our proposal was not accepted for future funding). Thus, a fourth task was added, which was to use the nonhydrostatic model to test tentative hypotheses developed from the most detailed observations ever obtained on a density current (primarily sodar and wind profiler data). These simulations were successfully completed, the findings were reported at a scientific conference, and the results have recently been submitted to a peer-reviewed journal. The fifth objective was to complete the analysis of data collected during the Cooperative Oklahoma Profiler Studies (COPS-91) field project, which was supported by NASA. The analysis of the mesoscale surface and sounding data, Doppler radar imagery, and other remote sensing data from multi frequency wind profiler, microwave radiometer, and the Radio Acoustic Sounding System has been completed. This study is a unique investigation of processes that caused the contraction of a cold front to a microscale zone exhibiting an undular bore-like structure. Results were reported at a scientific conference and are being prepared for publication. In summary, considerable progress has been achieved under NASA funding in furthering our understanding of frontal scale contraction and density current - gravity wave interaction processes, and in utilizing models and remotely sensed data in such studies.

Koch, Steven E.↗

NASA NTRS2000

Effects of Adrenergic Blockade on Postpartum Adaptive Responses Induced by Labor Contractions

Prenatal exposure to labor contractions augments the expression of postnatal adaptive responses in newborn rats. Near-term rat fetuses exposed prenatally to simulated labor contractions and delivered by cesarean section breath and attach to nipples at greater frequencies than non-stimulated fetuses. Plasma NE (norepinephrine) and EPI (epinephrine) was significantly elevated in newborn rats exposed to vaginal birth or simulated labor contractions (compressions) with cesarean delivery as compared to non-compressed fetuses. In the present study, we investigated adrenergic mechanisms underlying labor-induced postnatal adaptive responses. Following spinal transection of late pregnant rat dams, fetuses were administered neurogenic or non-neurogenic adrenergic blockade: 1) bretylium (10 mg/kg sc) to prevent sympathetic neuronal release, 2) hexamethonium (30 mg/kg) to produce ganglionic blockade, 3) phenoxybenzanune (10mg/kg sc), an a- adrenergic receptor antagonist, 4) ICI-118551, 10 mg/kg sc), a b receptor antagonist, or 5) vehicle alone. Fetuses were either compressed (C) or non-compressed (NC) prior to cesarean delivery. a- and b- adrenergic antagonists reduced respiration and nipple attachment rates while sympathetic and vehicle alone did not. These results provide additional support for the hypothesis that adaptive neonatal effects of labor contractions are mediated by adrenal and extra-adrenal catecholamines.

Ronca, April E.↗

NASA NTRS2002

Labor Contractions Enhance Oxygenation and Behavioral Activity of Newborn Rat Pups

Labor contractions help instigate behavioral responses at birth (viz., breathing and suckling) that are vital for the newborn's adaptation to the extrauterine world (Ronca et al., 1996). In the present study, we analyzed the role of labor contractions in postpartum oxygenation and behavioral activity of newborn rat pups. Newborns were observed following either vaginal (V) or cesarean delivery. For cesarean delivery, day 21 pregnant dams' were administered a spinal transaction to eliminate lower body sensation, a laparotomy was performed and the uterus was maintained in a heated (37.5 C) bath. Four rat fetuses in one of the dams' paired uterine horn were compressed (C) to Simulate labor contractions (20 sec/min for 10 min) while four fetuses in the opposite horn were not compressed (NC). Fetuses were surgically removed from the uterus, stroked with a soft brush to mimic postnatal licking by the dam, the umbilical cord occluded. Pups were exposed to room temperature (22 C) for one hr, then nest temperature (33 C) for one hr. PO2, CO2, and O2, saturation were determined at 0, 30, 60, or 120 min post delivery using a blood gas analyzer. V and C delivered neonates showed comparable rates of PO2, CO2 and O2 saturation whereas NC neonates showed depressed levels at all time points (p<0.05). Respiratory rates of V, C and NC neonates increased significantly (p<0.05) over the first two postpartum hrs and did not differ across groups. Postpartum behavioral activity was significantly greater in V and C conditions and positively correlated with postnatal oxygenation. These findings provide further evidence for importance of labor contractions in early postpartum adaptation.

Mills, N. A.↗

NASA NTRS2016

Magnetic-Island Contraction and Particle Acceleration in Simulated Eruptive Solar Flares

The mechanism that accelerates particles to the energies required to produce the observed high-energy impulsive emission in solar flares is not well understood. Drake et al. proposed a mechanism for accelerating electrons in contracting magnetic islands formed by kinetic reconnection in multi-layered current sheets (CSs). We apply these ideas to sunward-moving flux ropes (2.5D magnetic islands) formed during fast reconnection in a simulated eruptive flare. A simple analytic model is used to calculate the energy gain of particles orbiting the field lines of the contracting magnetic islands in our ultrahigh-resolution 2.5D numerical simulation. We find that the estimated energy gains in a single island range up to a factor of five. This is higher than that found by Drake et al. for islands in the terrestrial magnetosphere and at the heliopause, due to strong plasma compression that occurs at the flare CS. In order to increase their energy by two orders of magnitude and plausibly account for the observed high-energy flare emission, the electrons must visit multiple contracting islands. This mechanism should produce sporadic emission because island formation is intermittent. Moreover, a large number of particles could be accelerated in each magneto hydro dynamic-scale island, which may explain the inferred rates of energetic-electron production in flares. We conclude that island contraction in the flare CS is a promising candidate for electron acceleration in solar eruptions.

Guidoni, S. E.↗

DOE OSTI2026

Voltage Service Limits Smart Contract Using Distributed Ledger Technology for Electrical Utility Grid with Customer-Owned Generator

Modern electrical grids face growing stability risks from customer-owned generators, especially at points of common couplings (PCCs). Disruptive behavior from power-electronic sources can cause protective relays to isolate problematic generators, making measurement integrity critical. This article presents a distributed ledger technology (DLT) approach that uses smart contracts to evaluate PCC voltage measurements and trigger backup breaker operations. The approach is framed as a verifiable, multi-organization attestation and audit layer, not as a real-time control security mechanism. In the proposed architecture, voltage measurements from a hardware protective relay are anchored on a DLT through the Cyber Grid Guard (CGG) system for attestation by both the grid utility and customer-owned generator. A Voltage Service Limits (VSLs) smart contract evaluates the on-chain measurements against allowable phase-voltage limits derived from the ANSI C84.1 standard. The framework is validated in a hardware-relay-in-the-loop test bed under sustained-undervoltage, sustained-overvoltage, and transient line-to-line fault scenarios. The results show that the VSL smart contract can process these measurements and issue backup breaker actions consistent with the defined service-limit criteria, demonstrating the DLT potential as a verifiable audit layer at the PCC that complements primary protection.

cyber security↗

DOE OSTI2025

Reduced Contracting Time To Accelerate Construction: A Streamlined Approach for Speed and Scale

In the fast-paced construction world, efficiency isn't just an advantage - it's a necessity. By implementing the Cooperative Construction Contracting Agreement (CCCA), we are transforming how we approach major projects, replacing traditional multistep contracting with a streamlined, one-step process. This innovative contracting approach saves valuable time and resources, enabling us to accelerate delivery across our portfolio of projects. Under the old model, each construction phase required separate competitive solicitations for design, build, and other services. With the CCCA, we've consolidated these steps, working with a trusted partner from start to finish. This results in significant time savings that translate into faster project execution without compromising quality or safety.

collaborative partnerships↗

DOE OSTI2025

On the completeness of contraction map proof method for holographic entropy inequalities

The contraction map proof method is the commonly used method to prove holographic entropy inequalities. Existence of a contraction map corresponding to a holographic entropy inequality is a sufficient condition for its validity. But is it also necessary? In this note, we answer that question in affirmative for all linear holographic entropy inequalities with rational coefficients. We show that the pre-image of a non-contraction map is not a hypercube, but a proper cubical subgraph, and show that this manifests as alterations to the geodesic structure in the bulk, which leads to the violation of inequalities by holographic geometries obeying the RT formula.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2025

Hydrologic Model Data for the East Fork Poplar Creek Watershed Simulated with the Advanced Terrestrial Simulator (ATS): Streamflow and Network Expansion–Contraction Dynamics

This dataset supports hydrologic modeling and stream network expansion–contraction analysis for the East Fork Poplar Creek (EFPC) Watershed in Tennessee. It includes a Jupyter notebook for model setup, model configuration files, simulation outputs, and derived products used to evaluate model performance and investigate stream dynamics under varying hydrologic conditions. The dataset was generated using the Watershed Workflow Python package and the Advanced Terrestrial Simulator (ATS), enabling integrated surface–subsurface hydrologic simulations using a stream-aligned mesh. Outputs include high-resolution time series of streamflow, active network length, water table depth, and related hydrologic variables. Also included are spatially explicit stream persistency indices and classifications of reaches as perennial or non-perennial. These data facilitate reproducibility and support further research on stream intermittency and variability in network extent.The model data archive is organized in following directories:1) model_setup_inputsContains the Watershed Workflow Jupyter notebooks (accessed through any open source code editor), selected input datasets, and resulting ATS input files, including XML files (access through any open source code editor), computational mesh (.exo files can be viewed using Paraview), and meteorological forcing files (.h5 files can be accessed through h5py python package and HDFView open source software). 2) model_outputsIncludes ATS simulation outputs relevant to this study. Time series of spatially integrated or averaged variables (e.g., streamflow, water table depth) are provided as CSV files. Select spatial fields (e.g., ponded depth and water table depth) are saved as pickled Python objects to reduce file size, and can be accessed through pickle package in Python. Key geometry objects from Watershed Workflow—such as the surface mesh and river tree—are also included to support analysis of streamflow persistency and expansion–contraction dynamics. These files can also be accessed through Watershed Workflow Python package.3) model_evaluationProvides observed streamflow time series and field survey-based flow regime classifications used to evaluate model performance. Jupyter notebooks for processing ATS outputs and comparing model predictions with observations to build confidence in the model prior to scientific analysis are also included.4) Q_L_relationshipsContains workflows for generating time series of discharge, active network length, and related hydrologic variables used in the stream network expansion–contraction analysis. Includes routines for delineating baseflow-dominated periods. For each catchment, notebooks and processed data (as pickled DataFrames accessed through Pandas Python package) are provided. 5) figure_scriptsProvides the Jupyter notebooks used to generate the figures presented in the paper.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2026

Stochastic tensor contraction for quantum chemistry

Many computational methods in ab initio quantum chemistry are formulated in terms of high-order tensor contractions, whose cost determines the size of system that can be studied. We introduce stochastic tensor contraction to perform such operations with greatly reduced cost, and present its application to the gold-standard quantum chemistry method, coupled cluster theory with up to perturbative triples. For total energy errors more stringent than chemical accuracy, we reduce the computational scaling to that of mean-field theory, while starting to approach the mean-field absolute cost, thereby challenging the existing cost-to-accuracy landscape. Benchmarks against state-of-the-art local correlation approximations further show that we achieve an order-of-magnitude improvement in both total computation time and error, with significantly reduced sensitivity to system dimensionality and electron delocalization. We conclude that stochastic tensor contraction is a powerful computational primitive to accelerate a wide range of quantum chemistry.

Chemical Physics (physics.chem-ph)↗

NASA NTRS1976

The formation of Saturn's satellites and rings, as influenced by Saturn's contraction history

The paper investigates constraints imposed on the ice content of Saturn's satellites and rings by the planet's high luminosity during the early part of its quasi-equilibrium contraction phase. It is assumed that the addition of ices to the satellites was not completed until after the start of the quasi-equilibrium contraction and that the condensation of ices ceased at the same time within the primordial nebulae of Jupiter and Saturn. Using previously derived limits on the time of condensation cessation for Jupiter's system, the following tentative conclusions are made: (1) Titan is the innermost satellite at whose position a methane-containing ice could condense; (2) water ice could have condensed at the positions of all the satellites; (3) the systematic decrease in the mass of the regular satellites with decreasing distance from the planet may have been caused, in part, by the larger time intervals, for the closer satellites, between the start of contraction and the first condensation of ices at their positions; and (4) ammonia ices, primarily NH4SH, were able to condense at the positions of all but the innermost satellites. It is also shown that water ice could have condensed in the region of the rings near the end of the condensation period.

Pollack, J. B.↗

NASA NTRS1977

Earth resources-regional transfer activity contracts review

A regional transfer activity contracts review held by the Earth Resources Office was summarized. Contracts in the earth resources field primarily directed toward applications of satellite data and technology in solution of state and regional problems were reviewed. A summary of the progress of each contract was given in order to share experiences of researchers across a seven state region. The region included Missouri, Kentucky, Tennessee, Mississippi, Alabama, Georgia, and North Carolina. Research in several earth science disciplines included forestry, limnology, water resources, land use, geology, and mathematical modeling. The use of computers for establishment of information retrieval systems was also emphasized.

Bensko, J., Jr.↗

NASA NTRS1978

Steady flow of a non-Newtonian fluid through a contraction

A steady-state analysis is conducted to examine the basic flow structure of a non-Newtonian fluid in a domain including an inflow region, a contraction region, and an outflow region. A Cartesian grid system is used throughout the entire flow domain, including the contraction region, thus creating an irregular grid cell structure adjacent to the curved boundary. At node points adjacent to the curved boundary symmetry conditions are derived for the different flow variables in order to solve the governing difference equations. Attention is given to the motion and non-Newtonian constitutive equations, the boundary conditions, the numerical modeling of the non-Newtonian equations, the stream function contour lines for the non-Newtonian fluid, the vorticity contour lines for the non-Newtonian fluid, the velocity profile across the contraction, and the shear stress contour lines for the non-Newtonian fluid.

Gatski, T. B.↗

NASA NTRS1979

Generalized disks of contractivity for explicit and implicit Runge-Kutta methods

The A-contractivity of Runge-Kutta methods with respect to an inner product norm was investigated thoroughly by Butcher and Burrage (who used the term B-stability). Their theory is extended to contractivity in a region bounded by a circle through the origin. The largest possible circle is calculated for many known explicit Runge-Kutta methods. As a rule it is considerably smaller than the stability region, and in several cases it degenerates to a point. It is shown that an explicit Runge-Kutta method cannot be contractive in any circle of this class if it is more than fourth order accurate.

Dahlquist, G.↗

NASA NTRS1981

Guidelines for cost control and analysis of cost-type research and development contracts

The cost information which should be obtained from a contractor(s) on a major, cost type research and development contract(s), and the analyses and effective use of these data are discussed. Specific type(s) of information which should be required, methods for analyzing such information, and methods for effectively using the results of such analyses to enhance NASA contract and project management are included. The material presented is based primarily on the principal methods which have been effectively used in the management of major cost type research and development contracts.

Sibbers, C. W.↗

NASA NTRS1985

Role of muscle mass and mode of contraction in circulatory responses to exercise

The roles of the mode of contraction (dynamic or static) and active muscle mass in determining the cardiovascular response to exercise has been investigated experimentally in six normal men. Exercise consisted of static handgrip and dynamic handgrip exercise, and static and dynamic knee extension for a period of six minutes. Observed increases in mean arterial pressure after exercise were similar for each mode of contraction, but larger for knee extension than handgrip exercise. Cardiac output increased more for dynamic than for static exercise and for each mode more for knee exercise than for handgrip exercise. Systemic resistance was found to be lower for dynamic than for static exercise, and to decrease from resisting levels by about one third during dynamic knee extension. It is shown that the magnitude of cardiovascular response is related to active muscle mass, but is independent of the contraction mode. Equalization of cardiovascular response was achieved by proportionately larger increases in cardiac output during dynamic exercise. The complete experimental results are given in a table.

Lewis, S. F.↗

NASA NTRS1986

Short time Fourier analysis of the electromyogram - Fast movements and constant contraction

Short-time Fourier analysis was applied to surface electromyograms (EMG) recorded during rapid movements, and during isometric contractions at constant forces. A portion of the data to be transformed by multiplying the signal by a Hamming window was selected, and then the discrete Fourier transform was computed. Shifting the window along the data record, a new spectrum was computed each 10 ms. The transformed data were displayed in spectograms or 'voiceprints'. This short-time technique made it possible to see time-dependencies in the EMG that are normally averaged in the Fourier analysis of these signals. Spectra of EMGs during isometric contractions at constant force vary in the short (10-20 ms) term. Short-time spectra from EMGs recorded during rapid movements were much less variable. The windowing technique picked out the typical 'three-burst pattern' in EMG's from both wrist and head movements. Spectra during the bursts were more consistent than those during isometric contractions. Furthermore, there was a consistent shift in spectral statistics in the course of the three bursts. Both the center frequency and the variance of the spectral energy distribution grew from the first burst to the second burst in the same muscle. The analogy between EMGs and speech signals is extended to argue for future applicability of short-time spectral analysis of EMG.

Hannaford, Blake↗