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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

Using APEX to Model Anticipated Human Error: Analysis of a GPS Navigational Aid

The interface development process can be dramatically improved by predicting design facilitated human error at an early stage in the design process. The approach we advocate is to SIMULATE the behavior of a human agent carrying out tasks with a well-specified user interface, ANALYZE the simulation for instances of human error, and then REFINE the interface or protocol to minimize predicted error. This approach, incorporated into the APEX modeling architecture, differs from past approaches to human simulation in Its emphasis on error rather than e.g. learning rate or speed of response. The APEX model consists of two major components: (1) a powerful action selection component capable of simulating behavior in complex, multiple-task environments; and (2) a resource architecture which constrains cognitive, perceptual, and motor capabilities to within empirically demonstrated limits. The model mimics human errors arising from interactions between limited human resources and elements of the computer interface whose design falls to anticipate those limits. We analyze the design of a hand-held Global Positioning System (GPS) device used for radical and navigational decisions in small yacht recalls. The analysis demonstrates how human system modeling can be an effective design aid, helping to accelerate the process of refining a product (or procedure).

VanSelst, Mark↗
NASA NTRS1998

Employing Simulation to Evaluate Designs: The APEX Approach

The key innovations of APEX are its integrated approaches to task analysis, procedure definition, and intelligent, resource-constrained multi-tasking. This paper presents a step-by-step description of how APEX is used, from scenario development through trace analysis.

Freed, Michael A.↗
NASA NTRS1961

Heat-Transfer Measurements on the Apexes of Two 60 deg Sweptback Delta Wings (Panel Semiapex Angle of 30 deg) Having 0 deg and 45 deg Dihedral at a Mach Number of 4.95

An experimental investigation was conducted to evaluate the heat-transfer rates at the apex of two 60 degree sweptback delta wings (panel semi-apex angle of 30 degrees) having cylindrical leading edges and 0 degrees and 45 degree positive dihedral. The models tested might correspond to the first several feet of a hypersonic reentry vehicle. The tests were conducted at a Mach number of 4.95 and a stagnation temperature of 400 F. nominal test-section unit Reynolds numbers varied from 2 x 10(exp 6) to 12 x 10(exp 6) per foot. The results of the investigation indicated that the laminar heat-transfer distributions (ratio of local to stagnation-line heating rate) about the models normal to the leading edges were in close agreement with two-dimensional blunt-body theory. The three-dimensional stagnation point heat-transfer rate on the 0 degree dihedral model was in excellent agreement with theory and the stagnation-line heat transfer on the straight portion of the leading edge of both models approached a constant level 12 percent above the theoretical stagnation-line level on an isolated swept infinite cylinder. When the heating rates on the 45 degree dihedral model (planform sweep of 69.3 degree) were compared with those on the 0 degree dihedral model (planform sweep of 60 degrees) at equal angles of attack and equal lifts greater than zero, the stagnation-line heating rates on the 45 degrees dihedral model were, in general, considerably lower as a result of the difference in effective sweeps of the leading edges. On the wing panels inboard from the stagnation lines, the differences in heating were very small. The stagnation-line heat-transfer variation with angle of attack, the shift in stagnation-line location, and the reduction in stagnation-line heat transfer resulting from the increase in effective sweep when positive dihedral is incorporated into a constant-panel 0 degree dihedral wing, all agreed with the results of a theoretical study made of highly swept delta wings with large positive dihedral.

Gunn, Charles R.↗
NASA NTRS2003

Changes in vacuolation in the root apex cells of soybean seedlings in microgravity

Changes in the vacuolation in root apex cells of soybean (Glycine max L. [Merr.]) seedlings grown in microgravity were investigated. Spaceflight and ground control seedlings were grown in the absence or presence of KMnO4 (to remove ethylene) for 6 days. After landing, in order to study of cell ultrastructure and subcellular free calcium ion distribution, seedling root apices were fixed in 2.5% (w/v) glutaraldehyde in 0.1 M cacodylate buffer and 2% (w/v) glutaraldehyde, 2.5% (w/v) formaldehyde, 2% (w/v) potassium antimonate K[Sb(OH)6] in 0.1 M K2HPO4 buffer with an osmolarity (calculated theoretically) of 0.45 and 1.26 osmol. The concentrations of ethylene in all spaceflight canisters were significantly higher than in the ground control canisters. Seedling growth was reduced in the spaceflight-exposed plants. Additionally, the spaceflight-exposed plants exhibited progressive vacuolation in the root apex cells, particularly in the columella cells, to a greater degree than the ground controls. Plasmolysis was observed in columella cells of spaceflight roots fixed in solutions with relatively high osmolarity (1.26 osmol). The appearance of plasmolysis permitted the evaluation of the water status of cells. The water potential of the spaceflight cells was higher than the surrounding fixative solution. A decrease in osmotic potential and/or an increase in turgor potential may have induced increases in cell water potential. However, the plasmolysed (i.e. non-turgid) cells implied that increases in water potential were accompanied with a decrease in osmotic potential. In such cells changes in vacuolation may have been involved to maintain turgor pressure or may have been a result of intensification of other vacuolar functions like digestion and storage. c2003 COSPAR. Published by Elsevier Ltd. All rights reserved.

Non-NASA Center↗
NASA NTRS2005

Geometric analysis of Arabidopsis root apex reveals a new aspect of the ethylene signal transduction pathway in development

Structurally, ethylene is the simplest phytohormone and regulates multiple aspects of plant growth and development. Its effects are mediated by a signal transduction cascade involving receptors, MAP kinases and transcription factors. Many morphological effects of ethylene in plant development, including root size, have been previously described. In this article a combined geometric and algebraic approach has been used to analyse the shape and the curvature in the root apex of Arabidopsis seedlings. The process requires the fitting of Bezier curves that reproduce the root apex shape, and the calculation of the corresponding curvatures. The application of the method has allowed us to identify significant differences in the root curvatures of ethylene insensitive mutants (ein2-1 and etr1-1) with respect to the wild-type Columbia.

Arabidopsis/genetics/growth & development↗
NASA NTRS2008

Reaching for the APEX at Ames

The multidimensional design of the APEX program is the result of an extensive research and development effort dating back nearly a decade. "In the late 1990s and early 2000, we were pretty successful at getting new research and technology projects here at the center," Johnson says, "and we had a lack of critical mass of project managers. We were taking people who were primarily researchers and putting them in the position of managing projects." Smith and Johnson held a series of workshops across the center during 2000 and 2001 to gather feedback about how to address this issue. When they briefed the center's senior management on their findings, one of the top recommendations was to establish a project manager development program at Ames. At that point, they cast a wide net for ideas and information. "We did centerwide needs assessment, we did focus groups, we did surveys," Smith says. "We came up with a proposal for what a program would look like, tying in what we knew about the Academy of Program1 Project Leadership (now the Academy for Program/Project and Engineering Leadership, or APPEL), what we've seen at other centers, what other centers have tried. We were always checking to make sure our program mapped to APPEL. We also looked at the PMI [Project Management Institute] model, INCOSE [International Council on Systems Engineering], CMMI [Capability Maturity Model Integration], you name it." "We had a lot of conversations with the Jet Propulsion Lab and Goddard," Johnson adds. "We saw those centers as models for what Ames was aspiring to be in terms of a center for managing space flight missions." Their research confirmed what they already knew-that strong practitioner involvement would be critical to their program design process. 'XPEX is for the practitioner by the practitioner," Smith says. "They have to be a part of designing it. Otherwise there's no way we could design a program that meets their needs." At the same time that they worked at the grassroots level, they also solicited feedback from the center's senior management. "We recognized that in order for anything to succeed here, we needed to have a champion at the center management level," Johnson said. "You have to have champions, and you have to listen to what the senior managers are saying. They have their own ideas." In the case of APEX, one of those ideas fundamentally reshaped the program. "When we originally started, it was a project management development program," Johnson says, "but in our meeting with our center director, he said, 'Project management is important, but we also need to strengthen our systems engineering.' So we basically added that component to the program based on what he wanted."

Kohut, Matthew↗
NASA NTRS2008

APEX-CAMBIUM: A Case Study in Advantages and Challenges of International Cooperation for the International Space Station

It is generally agreed that space science benefits from an international collaboration. There are different mechanisms to make this happen but to recognize opportunities requires a keen awareness of the activities, people and respective strengths. Apex- Cambium is a joint Canadian Space Agency (CSA)-National Aeronautics and Space Administration (NASA) initiative. It was made possible in large part through the good relations and shared willingness to meet a common objective, that of doing exciting science in space. The actual mechanics of bringing an international project together can be divided into two perspectives: programmatic and implementation. The programmatic component includes recognizing complementarities, bringing science together, and the need to have Agencies approve and accept joint responsibility for the mission. The implementation component involves working to define science requirements, available resources and assigning individual responsibilities while keeping the overall success criteria as a collective objective. The APEX-CAMB11.JM mission will be described from the point of view of both CSA and NASA. Suggestions on how to facilitate these types of initiatives will be provided and highlights of the APEX-Cambium collaboration will be provided.

Cox, David↗
NASA NTRSDate not supplied

Leveraging Resonant Terminator Orbits for the Trajectory Design of OSIRIS-APEX at (99942) Apophis

The OSIRIS-REx spacecraft has been approved for an extended mission (OSIRIS-APEX) to visit the asteroid (99942) Apophis. In this paper we outline a potential design for the spacecraft’s trajectory during the variable phase orbit segment of the APEX mission. This phase of the mission, nominally expected to begin in January2030, has the primary goal of collecting image and spectral data of the full asteroid surface at a wide variety of illumination conditions without requiring frequent firing of the spacecraft thrusters. This work will focus on leveraging resonant terminator orbits (RTOs) in order to satisfy these goals and the associated science requirements. Though this segment will occur after Apophis’ closest flyby of Earth in April 2029, the proposed design utilizes the current best estimates of the asteroid’s orbital elements and physical properties at that time when designing the spacecraft’s orbit.

Gavin M Brown↗
NASA NTRS2016

APEX-04 SpaceX-10

APEX is Advanced Plant Experiments on Orbit which is a series of investigations which focus on fundamental plant biology.

POIWG↗
DOE OSTI2025

What's on the menu? Examining native apex‐ and invasive meso‐predator diets to understand impacts on ecosystems

Abstract Understanding how carnivores impact ecological communities is essential for guiding effective management actions and conserving biodiversity. Quantifying predators' diets, including prey selectivity, allows for the assessment of the relative effects native and invasive predators may have on prey populations. In Australia, populations of a native, terrestrial apex predator, the dingo Canis dingo/C. familiaris , and introduced and invasive subordinate mesopredators, the European red fox Vulpes vulpes and feral cat Felis catus , co‐occur, but there is limited understanding of their relative impacts on native and invasive prey in different ecosystems. To assess the possible effects of dingoes, foxes and cats on prey, we examined their diet and prey selectivity across a ~10,000 km 2 semi‐arid mallee ecosystem. Using macroscopic scat analysis, we identified strong dietary niche separation. Larger‐bodied dingoes primarily consumed large marsupial herbivores, whereas foxes and cats primarily consumed smaller prey, including introduced and native rodents and birds. Foxes had the broadest diet, and the greatest dietary overlap with cats ( = 0.81), compared with dingoes ( = 0.50) or between dingoes and cats ( = 0.36). Livestock were identified in 2% of dingo and 7% of fox scats. Cats and foxes consumed more than 15 times the volume of small native mammals compared with dingoes, including threatened species such as fat‐tailed dunnarts Sminthopsis crassicaudata . Cats and foxes also selectively consumed small mammals relative to their estimated availability and consumed fewer large mammals. In contrast, dingoes consumed fewer birds and more echidnas relative to their availability. Our results suggest limited intraguild competition within this semi‐arid ecosystem, as dingoes are primarily exerting top‐down pressure on large herbivores, whereas invasive mesopredators are disproportionately impacting smaller prey, including threatened native mammals. Practical implication . Our findings suggest that ongoing conservation management of dingoes, red foxes and feral cats must consider the variation in diets, impacts on prey and ecological roles of these different predator species, and avoid indiscriminate lethal control methods. Quantifying actual, rather than assumed, impacts of predators on threatened native species, large herbivores and livestock is essential to achieve effective and integrated ecosystem management.

Mason, Rachel T. [School of Life and Environmental↗
DOE OSTI2024

Diocotron modes in pure electron plasmas in the APEX levitating dipole trap

Abstract Observations of persistent toroidal modes in dipole-trapped pure electron plasmas are presented. Non-neutral electron plasmas were confined by the poloidal magnetic field of the APEX (A Positron Electron eXperiment) levitating dipole trap. The negative bias of the electron emitter was gated to control the filling time. Large amplitude, narrow-band oscillations were consistently observed in wall probe measurements after the fill. The oscillatory image-charge currents induced by the trapped electron plasma typically persisted for many seconds with fundamental frequencies, f 0 = 50 to 500 kHz, that scale with the E → × B → drift velocity. We attribute this feature to the dipole-equivalent of the diocotron mode that is commonly observed in non-neutral plasmas in linear traps.

Deller, A. (ORCID:0000000234301501)↗
DOE OSTI2026

Apex Study: Compensating Transient Beam Loading in the RHIC 28 MHZ

With the EIC on the way, it is important that developments and strategies are in place to deal with the very high beam currents that the machine will feature. Specifically, the EIC will collide beams of up to 2.5 A, three times the beam current in RHIC. This higher beam current will cause significant voltage transients in the cavity fields which can lead to longitudinal instabilities and beam loss. In anticipation of these negative effects, studies were carried out on the RHIC 28 MHz cavities using newly developed firmware and software to diagnose and combat beam loading. Diagnostic tools such as the bunch-by-bunch (BbyB) ADC firmware and digital network analyzer (DNA) were used to characterize the closed loop system and transient on the cavity voltage magnitude and phase. Then, a one-turn delay feedback (OTFB) and adaptive feed-forward (aFFWD) were used to minimize the transient beam loading. The studies were carried out with beam during 2 accelerator physics experiements (APEXs) using one of the 28 MHz accelerating cavities here at RHIC.

43 PARTICLE ACCELERATORS↗