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Results for “effectiveness factor”

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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS2010

Effects of Buckling Knockdown Factor, Internal Pressure and Material on the Design of Stiffened Cylinders

A design study was conducted to investigate the effect shell buckling knockdown factor (SBKF), internal pressure and aluminum alloy material selection on the structural weight of stiffened cylindrical shells. Two structural optimization codes were used for the design study to determine the optimum minimum-weight design for a series of design cases, and included an in-house developed genetic algorithm (GA) code and PANDA2. Each design case specified a unique set of geometry, material, knockdown factor combinations and loads. The resulting designs were examined and compared to determine the effects of SBKF, internal pressure and material selection on the acreage design weight and controlling failure mode. This design study shows that use of less conservative SBKF values, including internal pressure, and proper selection of material alloy can result in significant weight savings for stiffened cylinders. In particular, buckling-critical cylinders with integrally machined stiffener construction can benefit from the use of thicker plate material that enables taller stiffeners, even when the stiffness, strength and density properties of these materials appear to be inferior.

Lovejoy, Andrew E.↗
NASA NTRS1999

Combined effects of space flight factors and radiation on humans

The probability that a dose of ionizing radiation kills a cell is about 10,000 times the probability that the cell will be transformed to malignancy. On the other hand, the number of cells killed required to significantly impact health is about 10,000 times the number that must be transformed to cause a late malignancy. If these two risks, cell killing and malignant transformation, are about equal, then the risk that occurs during a mission is more significant than the risk that occurs after a mission. The latent period for acute irradiation effects (cell killing) is about 2-4 weeks; the latent period for malignancy is 10-20 years. If these statements are approximately true, then the impact of cell killing on health in the low-gravity environment of space flight should be examined to establish an estimate of risk. The objective of this study is to synthesize data and conclusions from three areas of space biology and environmental health to arrive at rational risk assessment for radiations received by spacecraft crews: (1) the increased physiological demands of the space flight environment; (2) the effects of the space flight environment on physiological systems; and (3) the effects of radiation on physiological systems. One physiological system has been chosen: the immune response and its components, consisting of myeloid and lymphoid proliferative cell compartments. Best-case and worst-case scenarios are considered. In the worst case, a doubling of immune-function demand, accompanied by a halving of immune capacity, would reduce the endangering dose to a crew member to around 1 Gy.

Non-NASA Center↗
NASA NTRS1992

Fatigue mechanisms in patients with cancer: effects of tumor necrosis factor and exercise on skeletal muscle

Fatigue is a common adverse effect of cancer and its therapy. However, the specific mechanisms underlying cancer fatigue are unclear. One physiologic mechanism may involve changes in skeletal muscle protein stores or metabolite concentration. A reduction in skeletal muscle protein stores may result from endogenous tumor necrosis factor (TNF) or from TNF administered as antineoplastic therapy. This muscle wasting would require patients to exert an unusually high amount of effort to generate adequate contractile force during exercise performance or during extended periods of sitting or standing. This additional effort could result in the onset of fatigue. Additionally, cancer fatigue may develop or become exacerbated during exercise as a consequence of changes in the concentration of skeletal muscle metabolites. These biochemical alterations may interfere with force that is produced by the muscle contractile proteins. These physiologic changes may play a role in the decision to include exercise in the rehabilitation plans of patients with cancer. They also may affect ideas about fatigue.

Review, Tutorial↗
NASA NTRS1939

The Calculated Effect of Various Hydrodynamic and Aerodynamic Factors on the Take-Off of a Large Flying Boat

Present designs for large flying boats are characterized by high wing loading, high aspect ratio, and low parasite drag. The high wing loading results in the universal use of flaps for reducing the takeoff and landing speeds. These factors have an effect on takeoff performance and influence to a certain extent the design of the hull. An investigation was made of the influence of various factors and design parameters on the takeoff performance of a hypothetical large flying boat by means of takeoff calculations. The parameters varied in the calculations were size of hull (load coefficient), wing setting, trim, deflection of flap, wing loading, aspect ratio, and parasite drag. The takeoff times and distances were calculated to the stalling speeds and the performance above these speeds was studied separately to determine piloting technique for optimum takeoff. The advantage of quick deflection of the flap at high water speeds is shown.

Olson, R.E.↗
NASA NTRS1980

Conceptual model of turbulent flameholding for scramjet combustors

New concepts and approaches to scramjet combustor design are presented. Blowoff was from failure of the recirculation-zone (RZ) flame to reach the dividing streamline (DS) at the rear stagnation zone. Increased turbulent exchange across the DS helped flameholding due to forward movement of the flame anchor point inside the RZ. Modeling of the blowoff phenomenon was based on a mass conservation concept involving the traverse of a flame element across the RZ and a flow element along the DS. The scale required to achieve flameholding, predicted by the model, showed a strong adverse effect of low pressure and low fuel equivalence ratio, moderate effect of flight Mach number, and little effect of temperature recovery factor. Possible effects of finite rate chemistry on flameholding and flamespreading in scramjets are discussed and recommendations for approaches to engine combustor design as well as for needed research to reduce uncertainties in the concepts are made.

Huber, P. W.↗
NASA NTRS1997

Temperature Induced Alpha Factor

Temperature effects can be important in short pulse propagation or in CW operation of VCSELs. In those cases, the optical susceptibility function is, in general, a function of carrier density and plasma and/or lattice temperature(s). Just as there is an alpha factor induced by the density change (density alpha), there are alpha factors induced by lattice or plasma temperature change (temperature alphas). The density alpha factor has been studied quite extensively, while the temperature alpha factors have not been computed for any structure. I will report on my first calculations of alpha factors induced by the plasma and lattice temperature change for GaAs/AlGaAs quantum wells using microscopic theory. Besides, the temperature dependence of the density alpha factor is also considered.

Ning, C. Z.↗
DOE OSTI2023

Pair breaking in superconductors with strong spin-orbit coupling

Here we study the influence of symmetry-breaking perturbations on superconductivity in multiorbital materials, with a particular focus on an external magnetic field. We introduce the field-fitness function which characterizes the pair-breaking effects of the perturbation on a given superconducting state. For even-parity superconductors we find that this field-fitness function for an external magnetic field is one, implying that the paramagnetic response is controlled only by a generalized effective g factor. For odd-parity superconductors, the interplay of the effective g factor and the field-fitness function can lead to counterintuitive results. We demonstrate this for p-wave pairing in the effective j = $\frac{3}{2}$ electronic states of the Luttinger-Kohn model.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS2009

SDBI 1904: Human Factors Assessment of Vibration Effects on Visual Performance during Launch

The primary objective of the of Human Factors Short Duration Bioastronautics Investigation (SDBI) 1904 is to determine visual performance limits during operational vibration and g-loads, specifically through the determination of minimal usable font sizes using Orion-type display formats. Currently there is little to no data available to quantify human visual performance under these extreme conditions. Existing data on shuttle vibration magnitude and frequency is incomplete, does not address seat and crew vibration in the current configuration, and does not address human visual performance. There have been anecdotal reports of performance decrements from shuttle crews, but no structured data has been collected. The SDBI is a companion effort to the Detailed Test Objective (DTO) 695, which will measure shuttle seat accelerations (vibration) during ascent. Data from the SDBI will serve an important role in interpreting the DTO vibration data. This data will be collected during the ascent phase of three shuttle missions (STS-119, 127, and 128). Both SDBI1904 and DTO 695 are low impact with respect to flight resources, and combined they represent an efficient and focused problem solving approach. The SDBI and DTO data will be correlated to determine the nature of perceived visual performance under varying vibrations and g-loads. This project will provide: * Immediate data for developing preliminary human performance vibration requirements * Flight validated inputs for ongoing and future ground-based research * Information of functional needs that will drive Orion display format design decisions

Shelby G Thompson↗
NASA NTRS1951

Determination and Use of the Local Recovery Factor for Calculating the Effectiveness Gas Temperature for Turbine Blades / Jack B. Esgar and Alfred L. Lea

In an in experimental investigation of local recovery factors for a blade having a pressure distribution similar to that of a typical reaction-type turbine blade, it a was found that the recovery factors were essentially independent of Mach number, Reynolds number, pressure gradient, and position on the blade surface except for regions where the boundary layer was probably in the transition range from laminar to turbulent. The recommended value of local subsonic recovery factor for use in calculating the effective gas temperature for gas turbine blades was 0.89.

HEAT TRANSFER, CASCADES↗
DOE OSTI2024

Investigation of the Impact of TSL Data Libraries and Geometry Variations on the MSRE Benchmark

The increasing demand for green, low-carbon energy solutions has amplified the focus on advanced nuclear reactor technologies. Among these, Molten Salt Reactors (MSRs) have been spotlighted because of their special features. Historically, Oak Ridge National Laboratory (ORNL) started the Molten Salt Reactor Experiment (MSRE) in 1956. Later, ORNL and the University of California, Berkeley (UCB) jointly developed the MSRE benchmark. This was then reviewed by the International Reactor Physics Experiment Evaluation Project (IRPhEP) committee and added to their 2019 handbook. In the current study, the benchmark model was recreated via the Serpent code. The calculated effective multiplication factor was 1.02087 ± 0.00019, which gives a deviation of about 2000 pcm compared to the benchmark/experimental result. At North Carolina State University (NCSU), recent evaluations were conducted on thermal scattering cross sections for molten salt FLiBe and 20% porous nuclear graphite, anticipated for incorporation in the ENDF/B-VIII.1 library. The influences of these thermal scattering law (TSL) data and geometry changes on the multiplication factor were examined using the ENDF/B-VII.1 and ENDF/B-VIII.0 libraries. Introducing the TSL data for FLiBe and 20% porous graphite resulted in an effective multiplication factor of +270 pcm compared to the reference value obtained with ENDF/B-VII.1 in this study. The adjustment of the reactor vessel dimensions resulted in decrease of -448 pcm in the calculated effective multiplication factor.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2022

Integer quantum Hall effect and enhanced g factor in quantum-confined Cd 3 As 2 films

Here, we investigate the integer quantum Hall effect in Cd 3 ⁢As 2 thin films under conditions of strong to moderate quantum confinement (thicknesses of 10, 12, and 15 nm). In all the films, we observe the integer quantum Hall effect in the spin-polarized lowest Landau level (filling factor v = 1) and at spin-degenerate higher index Landau levels with even filling factors (v = 2,4,6). With increasing quantum confinement, we also observe a lifting of the Landau-level spin degeneracy at v = 3, manifest as the emergence of an anomaly in the longitudinal and Hall resistivities. Tight-binding calculations show that the enhanced g factor likely arises from a combination of quantum confinement and corrections from nearby subbands.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Effect Laws of Different Factors on Levitation Characteristics of High-T{sub c} Superconducting Maglev System with Numerical Solutions

The interaction between the high-temperature superconducting (HTS) bulk and permanent magnet guideway (PMG) has been a topic among the existing HTS magnetic levitation systems. Up to now, the theories about the electromagnetic and force characteristics have been relatively consummated. Here, using the finite element model by COMSOL Multiphysics 5.3a, we investigated the impact of the intrinsic and external factors on the levitation characteristics of HTS maglev systems, the application laws are concluded. Factors including the critical current density and geometric dimensions of the bulk superconductor, as well as the moving velocity, are discussed. The effects of the multiple back and forth movements are also analyzed. By comparing calculation results of the distributions of the induced current and the levitation force of the bulk superconductor, we can clearly confirm the effect laws of various factors on the electromagnetic characteristics and levitation force. These observations support the physical parameters that are difficult to be tested by experiments. And they also have a significant contribution to the experimental condition selections and optimization of the high-temperature superconducting magnetic levitation.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS2002

Developmental regulation of the effects of fibroblast growth factor-2 and 1-octanol on neuronogenesis: implications for a hypothesis relating to mitogen-antimitogen opposition

Neocortical neurons arise from a pseudostratified ventricular epithelium (PVE) that lies within the ventricular zone (VZ) at the margins of the embryonic cerebral ventricles. We examined the effects of fibroblast growth factor-2 (FGF-2) and 1-octanol on cell output behavior of the PVE in explants of the embryonic mouse cerebral wall. FGF-2 is mitogenic and 1-octanol antimitogenic in the PVE. Whereas all postmitotic cells migrate out of the VZ in vivo, in the explants some postmitotic cells remain within the VZ. We refer to these cells as the indeterminate or I fraction, because they neither exit from the VZ nor reenter S phase as part of the proliferative (P) fraction. They are considered to be either in an extremely prolonged G(1) phase, unable to pass the G(1)/S transition, or in the G(0) state. The I fate choice is modulated by both FGF-2 and 1-octanol. FGF-2 decreased the I fraction and increased the P fraction. In contrast, 1-octanol increased the I fraction and nearly eliminated the P fraction. The effects of FGF-2 and 1-octanol were developmentally regulated, in that they were observed in the developmentally advanced lateral region of the cerebral wall but not in the medial region. Copyright 2002 Wiley-Liss, Inc.

NASA Discipline Developmental Biology↗