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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Software development environments: Status and trends

Currently software engineers are the essential integrating factors tying several components together. The components consist of process, methods, computers, tools, support environments, and software engineers. The engineers today empower the tools versus the tools empowering the engineers. Some of the issues in software engineering are quality, managing the software engineering process, and productivity. A strategy to accomplish this is to promote the evolution of software engineering from an ad hoc, labor intensive activity to a managed, technology supported discipline. This strategy may be implemented by putting the process under management control, adopting appropriate methods, inserting the technology that provides automated support for the process and methods, collecting automated tools into an integrated environment and educating the personnel.

Duffel, Larry E.↗
NASA NTRS1991

Solution of geometrically nonlinear statics problems by the p-version of the finite element method

This project is concerned with the possibility of using computers for the simulation of structural systems with the same degree of reliability as full scale physical experiments. Reliable numerical simulation will make it possible to reduce the costs of engineering and improve the quality of engineering decisions based on computed information. An error of idealization is an error between the actual physical quantities on which engineering decisions are based (e.g., maximum principal stress, first natural frequency, etc.) and the same data corresponding to the exact solution of the mathematical model. An error of discretization is an error between the quantities of interest corresponding to the exact and approximate solutions of a mathematical model. A high degree of reliability can be achieved in numerical simulation only if both the errors of idealization and errors of discretization can be shown to be small.

Szabo, Barna A.↗
NASA NTRS1991

Training, Quality Assurance Factors, and Tools Investigation: a Work Report and Suggestions on Software Quality Assurance

Previously, several research tasks have been conducted, some observations were obtained, and several possible suggestions have been contemplated involving software quality assurance engineering at NASA Johnson. These research tasks are briefly described. Also, a brief discussion is given on the role of software quality assurance in software engineering along with some observations and suggestions. A brief discussion on a training program for software quality assurance engineers is provided. A list of assurance factors as well as quality factors are also included. Finally, a process model which can be used for searching and collecting software quality assurance tools is presented.

Lee, Pen-Nan↗
NASA NTRS2006

The Effects of Development Team Skill on Software Product Quality

This paper provides an analysis of the effect of the skill/experience of the software development team on the quality of the final software product. A method for the assessment of software development team skill and experience is proposed, and was derived from a workforce management tool currently in use by the National Aeronautics and Space Administration. Using data from 26 smallscale software development projects, the team skill measures are correlated to 5 software product quality metrics from the ISO/IEC 9126 Software Engineering Product Quality standard. in the analysis of the results, development team skill is found to be a significant factor in the adequacy of the design and implementation. In addition, the results imply that inexperienced software developers are tasked with responsibilities ill-suited to their skill level, and thus have a significant adverse effect on the quality of the software product. Keywords: software quality, development skill, software metrics

Beaver, Justin M.↗
DOE OSTI2022

Carbazole-Based Hole Transport Polymer for Methylammonium-Free Tin-Lead Perovskite Solar Cells with Enhanced Efficiency and Stability

As the most commonly used hole transport material (HTM) in tin-lead (Sn-Pb) perovskite solar cells (PSCs), poly(3,4-ethylenedioxythiophene) polystyrenesulfonate (PEDOT:PSS) limits the power conversion efficiency (PCE) and stability of the PSCs due to its acidic characteristics. Herein, an easily synthesized polymer HTM poly[(phenyl)imino[9-(2-ethylhexyl)carbazole]-2,7-diyl] (CzAn) with a shallow highest occupied molecular orbital (HOMO) level of -4.95 eV is used in a p-i-n structure, methylammonium-free, Sn-Pb PSC to replace PEDOT:PSS. Upon optimization using doping and surface engineering, high quality Sn-Pb PSCs could be successfully fabricated, boosting the PCE to 22.6% (stabilized PCE of 21.3%) compared with 21.2% for PEDOT:PSS. The perovskite films prepared on the modified CzAn HTM possess improved crystallinity, reduced trap-state density, and larger carrier mobility resulting in PSCs with greatly improved stability.

carrier mobility↗
DOE OSTI2016

Stress engineering of high-quality single crystal diamond by heteroepitaxial lateral overgrowth

Here, we describe a method for lateral overgrowth of low-stress single crystal diamond by chemical vapor deposition (CVD). The process is initiated by deposition of a thin (550 nm) (001) diamond layer on Ir-buffered a-plane sapphire. The diamond is partially masked by periodic thermally evaporated Au stripes using photolithography. Lateral overgrowth of the Au occurs with extremely effective filtering of threading dislocations. Thermal stress resulting from mismatch of the low thermal expansion diamond and the sapphire substrate is largely accommodated by the ductile Au layer. The stress state of the diamond is investigated by Raman spectroscopy for two thicknesses: at 10 μm where the film has just overgrown the Au mask and at 180 μm where the film thickness greatly exceeds the scale of the masking. For the 10-μm film, the Raman linewidth shows spatial oscillations with the period of the Au stripes with a factor of 2 to 3 reduction relative to the unmasked region. In a 180-μm thick diamond film, the overall surface stress was extremely low, 0.00 ± 0.16 GPa, obtained from the Raman shift averaged over the 7.5mm diameter of the crystal at its surface. We conclude that the metal mask protects the overgrown diamond layer from substrate-induced thermal stress and cracking. Lastly, it is also responsible for low internal stress by reducing dislocation density by several orders of magnitude.

36 MATERIALS SCIENCE↗
NASA NTRS1980

Flight evaluation of the effect of winglets on performance and handling qualities of a single-engine general aviation airplane

A flight evaluation was conducted to determine the effects of winglets on the performance and handling qualities of a light, single-engine general aviation airplane. The performance measurements were made with a pace airplane to provide calibrated airspeeds; uncalibrated panel instruments in the test airplane were used to provide additional quantitative performance data. These tests were conducted with winglets on and off during the same day to measure relative performance effects. Handling qualities were evaluated by means of pilot comments. Winglets increased cruise speed 8 knots (5.6 percent) at 3962 m (13,000 ft) density altitude and 51 percent maximum continuous power setting. Maximum speed at 3962 m was virtually unchanged. Rate of climb increased approximately 6 percent, or 0.25 m/sec (50 ft/min), at 1524 m (5000 ft). Stall speed was virtually unchanged. Handling qualities were favorably affected.

Holmes, B. J.↗
DOE OSTI2019

Work Plan for the Site-wide SSHAC Level 3 Probabilistic Seismic Hazard Analysis at INL

This work plan provides the overall framework, key activities, key tasks, and schedule for the execution of a probabilistic seismic hazard analysis at Idaho National Laboratory (INL). The probabilistic seismic hazard analysis will follow processes and procedures appropriate for the Senior Seismic Hazard Analysis Committee (SSHAC) Level 3 study provided in U. S. Nuclear Regulatory Commission guidance, NUREG-2213. The SSHAC Level 3 probabilistic seismic hazard analysis (PSHA) is being conducted as an INL site-wide effort. The work plan was developed and revised by participants who will perform the SSHAC Level 3 PSHA. The work plan also includes the quality assurance requirements commensurate with American Society of Mechanical Engineers Nuclear Quality Assurance NQA 1 2008/2009 and 2011 Addendum for design nuclear facilities under the U.S. Department of Energy and U. S. Nuclear Regulatory Commission. The scope of the SSHAC Level 3 PSHA is designed to produce the mean-centered definition of the seismic hazard with the appropriate treatment of uncertainties supported by the associated technical justifications. The SSHAC Level 3 study will properly implement and completely document the activities of evaluation, integration, and documentation. The evaluation process will consider data, models, and methods proposed by the larger technical community that are relevant to the PSHA at INL. The integration process will build seismic-source and ground-motion characterization models that represent the center, body, and range of technically defensible interpretations, taking into consideration the outcomes of the evaluation process. Key tasks and activities—such as a project kickoff meeting, three workshops, four formal working meetings, and a briefing meeting with the Participatory Peer Review Panel—will occur for the seven-member technical integration teams to construct seismic-source and ground-motion-characterization models. Both preliminary and final hazard-input documents will be developed to perform sensitivity analyses and the final PSHA, respectively. The entire study will be thoroughly documented in draft and final reports. The Participatory Peer Review Panel will review the SSHAC Level 3 study from start to finish, including the draft and final INL Site-wide PSHA reports, so they can provide a closure letter documenting the study’s adherence to SSHAC processes and technical adequacy of the final products.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
NASA NTRS1995

Design, analysis, and control of a large transport aircraft utilizing selective engine thrust as a backup system for the primary flight control

A study has been conducted to determine the capability to control a very large transport airplane with engine thrust. This study consisted of the design of an 800-passenger airplane with a range of 5000 nautical miles design and evaluation of a flight control system, and design and piloted simulation evaluation of a thrust-only backup flight control system. Location of the four wing-mounted engines was varied to optimize the propulsive control capability, and the time constant of the engine response was studied. The goal was to provide level 1 flying qualities. The engine location and engine time constant did not have a large effect on the control capability. The airplane design did meet level 1 flying qualities based on frequencies, damping ratios, and time constants in the longitudinal and lateral-directional modes. Project pilots consistently rated the flying qualities as either level 1 or level 2 based on Cooper-Harper ratings. However, because of the limited control forces and moments, the airplane design fell short of meeting the time required to achieve a 30 deg bank and the time required to respond a control input.

Gerren, Donna S.↗
DOE OSTI2018

Modulating Self-Assembly of DNA Crystals with Rationally Designed Agents

This article reports a strategy for controlling the crystallization kinetics and improving the quality of engineered self-assembled 3D DNA crystals. Growing large, high-quality biomacromolecule crystals is critically important for determining the 3D structures of biomacromolecules. It often presents a great challenge to structural biologists. Herein, we introduce a rationally designed agent to modulate the crystallization process. Under such conditions, fewer, but larger, crystals that yield diffraction patterns of modestly higher resolution are produced compared with the crystals from conditions without the modulating agent. We attribute the improvement to a smaller number of nuclei and slow growth rate of crystallization. This strategy is expected to be generally applicable for crystallization of other biomacromolecules.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1993

Summary of the effects of engine throttle response on airplane formation-flying qualities

A flight evaluation was conducted to determine the effect of engine throttle response characteristics on precision formation-flying qualities. A variable electronic throttle control system was developed and flight-tested on a TF-104G airplane with a J79-11B engine at the NASA Dryden Flight Research Facility. This airplane was chosen because of its known, very favorable thrust response characteristics. Ten research flights were flown to evaluate the effects of throttle gain, time delay, and fuel control rate limiting on engine handling qualities during a demanding precision wing formation task. Handling quality effects of lag filters and lead compensation time delays were also evaluated. The Cooper and Harper Pilot Rating Scale was used to assign levels of handling quality. Data from pilot ratings and comments indicate that throttle control system time delays and rate limits cause significant degradations in handling qualities. Threshold values for satisfactory (level 1) and adequate (level 2) handling qualities of these key variables are presented. These results may provide engine manufacturers with guidelines to assure satisfactory handling qualities in future engine designs.

Walsh, Kevin R.↗
DOE OSTI2014

Enamel Matrix Derivative has No Effect on the Chondrogenic Differentiation of Mesenchymal Stem Cells

Background: Treatment of large bone defects due to trauma, tumor resection, or congenital abnormalities is challenging. Bone tissue engineering using mesenchymal stem cells (MSCs) represents a promising treatment option. However, the quantity and quality of engineered bone tissue are not sufficient to fill large bone defects. The aim of this study was to determine if the addition of enamel matrix derivative (EMD) improves in vitro chondrogenic priming of MSCs to ultimately improve in vivo MSC mediated endochondral bone formation. Methods: MSCs were chondrogenically differentiated in 2.0 × 10{sup 5} cell pellets in medium supplemented with TGFβ3 in the absence or presence of 1, 10, or 100 μg/mL EMD. Samples were analyzed for gene expression of RUNX2, Col II, Col X, and Sox9. Protein and glycoaminoglycan (GAG) production were also investigated via DMB assays, histology, and immunohistochemistry. Osteogenic and adipogenic differentiation capacity were also assessed. Results: The addition of EMD did not negatively affect chondrogenic differentiation of adult human MSCs. EMD did not appear to alter GAG production or expression of chondrogenic genes. Osteogenic and adipogenic differentiation were also unaffected though a trend toward decreased adipogenic gene expression was observed. Conclusion: EMD does not affect chondrogenic differentiation of adult human MSCs. As such the use of EMD in combination with chondrogenically primed MSCs for periodontal bone tissue repair is unlikely to have negative effects on MSC differentiation.

60 APPLIED LIFE SCIENCES↗