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  • MECHANICAL ENGINEERING  (11)
  • GEOPHYSICS  (5)
  • Chemical Engineering  (4)
  • COMPOSITE MATERIALS  (3)
  • 2005-2009
  • 1990-1994  (23)
  • 1970-1974
  • 1992  (23)
  • 1
    Electronic Resource
    Electronic Resource
    Two-dimensional finite element analysis of microwave heating (1992)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 1577-1592 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Transient temperature profiles for long rods of lossy dielectric materials with thermally-dependent dielectric properties exposed to uniform plane waves are obtained. Maxwell's equation and the heat equation are simultaneously solved using the finite element method to predict the power absorbed and the resulting temperature rise in samples of square and circular cross-section. Following the method introduced recently, we derive an exact radiation boundary condition which is independent of the rod cross-section. For a cylindrical sample, the boundary condition is imposed on the cylinder itself. For a square rod, the boundary condition is imposed on a cylinder containing the rod. The temperature dependence of dielectric properties and sample dimensions appreciably influence heating patterns. For square samples, the edges focus radiation, causing preferential heating at the edges. This effect is pronounced for larger samples. In addition, the incident wave polarization influences the heating of the rod. For waves where the electric field is polarized along the long axis of the sample (TMz polarization) the power absorbed is higher than when the electric field is perpendicular to the axis (TEz polarization). A case involving runaway heating is also investigated.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690381009
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    Paper (German National Licenses)
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  • 2
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    Technology integration box beam failure study (1992)
    In:  Other Sources
    Details
    Publication Date: 2013-08-29
    Description: Composite structures have the potential to be cost effective, structurally efficient primary aircraft structures. As part of the Advanced Composite Technology (ACT) program to exploit this potential for heavily loaded aircraft structures, the design and fabrication of the technology integration box beam (TIBB) was completed. The TIBB is an advanced composite prototype structure for the center wing section of the Lockheed C-130 aircraft. The TIBB was tested for downbending, upbending, torsion, and combined upbending and torsion load conditions to verify the design. The TIBB failed at 83 percent of design ultimate load for the combined upbending and torsion load condition. Current analytical and experimental results are described for a study of the mechanisms that led to the failure of the TIBB. Experimental results include load, strain, and deflection data. An analytical study was conducted of the TIBB structural response. Analytical results include strain and deflection results from a global analysis of the TIBB.
    Keywords: COMPOSITE MATERIALS
    Type: Second NASA Advanced Composites Technology Conference; p 99-111
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
    Electronic Resource
    Electronic Resource
    Unbiased estimation of gross errors in process measurements (1992)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 563-572 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new approach to gross error detection provides unbiased estimates and 100(1-α)% simultaneous confidence intervals of process variables when biased process measurements and process leaks exist. Presented in this article are estimation equations for process variables, as well as equations that help identify biased measurements and process leaks. These equations include the power function for a global test, and two types of α-level component tests and their power functions. Important strengths and weaknesses of this approach are compared to those of the serial compensation strategy, in particular, by varying the significance level (α), the variance-covariance matrix (Σ), the size of measurement bias (δ), the number of biased variables, and the sample size (N). Accuracy of δ estimation and performance in detecting the presence of process leaks (γ) are also evaluated and compared. The proposed approach has unique features that can provide a basis for improving the reconciliation of variables in process operations.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690380410
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  • 4
    Electronic Resource
    Electronic Resource
    Affinity membranes: Their chemistry and performance in adsorptive separation processes. By Elias Klein, Wiley, New York, 152 pp., 1991 (1992)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 1997-1998 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690381219
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  • 5
    Electronic Resource
    Electronic Resource
    Continuous flow methods in organic synthesis. By P. Tundo, Ellis Horwood Ltd., 310 pp., 3 Appendices, hardback, 1991 (1992)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 1999-2000 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690381222
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  • 6
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    Overview of the ACT program (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: NASA's Advanced Composites Program (ACT) was initiated in 1988. A National Research Announcement was issued to solicit innovative ideas that could significantly contribute to development and demonstration of an integrated technology data base and confidence level that permits cost-effective use of composite primary structures in transport aircraft. Fifteen contracts were awarded by the Spring of 1989 and the participants include commercial and military airframe manufacturers, materials developers and suppliers, universities, and government laboratories. The program approach is to develop materials, structural mechanics methodology, design concepts, and fabrication procedures that offer the potential to make composite structures cost-effective compared to aluminum structure. Goals for the ACT program included 30-50 percent weight reduction, 20-25 percent acquisition cost reduction, and provided the scientific basis for predicting materials and structures performance. This paper provides an overview of the ACT program status, plans, and selected technical accomplishments. Sixteen additional papers, which provide more detailed information on the research and development accomplishments, are contained in this publication.
    Keywords: COMPOSITE MATERIALS
    Type: FAA, Ninth DOD(NASA)FAA Conference on Fibrous Composites in Structural Design, Volume 2; p 577-59
    Format: application/pdf
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  • 7
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    Large-gap magnetic positioning system having advantageous configuration (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: A magnetic configuration was devised in which the positioned object is maintained in a stable orientation and position on one side of an opaque plane surface entirely by means of magnetic components on the other side of the plane. The system is effective with or without gravity, and can operate in any orientation. In this system, the positioned object need only contain a simple dipole magnet. The positioning components consist of a group of permanent magnets creating a magnetic field configuration which stabilizes the levitated dipole in all but one degree of freedom, and a magnetic position sensing and force feedback system to actively stabilize the object in the one unstable direction. The system utilizes very low power at equilibrium and can maintain gaps of 50 mm.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Langley Research Center, International Symposium on Magnetic Suspension Technology, Part 2; p 941-953
    Format: text
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  • 8
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    Coarse-fine residual gravity cancellation system with magnetic levitation (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: Aircraft flight along parabolic trajectories have been proposed and executed in order to achieve low cost, near free fall conditions of moderate duration. This paper describes a six degree of freedom experiment isolation system designed to cancel out residual accelerations due to mechanical vibrations and errors in aircraft trajectory. The isolation system consists of a fine motion magnetic levitator whose stator is transported by a conventional coarse motion stage. The levitator uses wide gap voice coil actuators and has the dual purpose of isolating the experiment platform from aircraft vibrations and actively cancelling residual accelerations through feedback control. The course motion stage tracks the levitated platform in order to keep the levitator's coils centered within their matching magnetic gaps. Aspects of system design, an analysis of the proposed control strategy and simulation results are presented. Feasibility experiments are also discussed.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Langley Research Center, International Symposium on Magnetic Suspension Technology, Part 1; p 473-492
    Format: text
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  • 9
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    Reduction of Marine Magnetic Data for Modeling the Main Field of the Earth (1992)
    In:  CASI
    Details
    Publication Date: 2014-09-25
    Description: The marine data set archived at the National Geophysical Data Center (NGDC) consists of shipborne surveys conducted by various institutes worldwide. This data set spans four decades (1953, 1958, 1960-1987), and contains almost 13 million total intensity observations. These are often less than 1 km apart. These typically measure seafloor spreading anomalies with amplitudes of several hundred nanotesla (nT) which, since they originate in the crust, interfere with main field modeling. The source for these short wavelength features are confined within the magnetic crust (i.e., sources above the Curie isotherm). The main field, on the other hand, is of much longer wavelengths and originates within the earth's core. It is desirable to extract the long wavelength information from the marine data set for use in modeling the main field. This can be accomplished by averaging the data along the track. In addition, those data which are measured during periods of magnetic disturbance can be identified and eliminated. Thus, it should be possible to create a data set which has worldwide data distribution, spans several decades, is not contaminated with short wavelengths of the crustal field or with magnetic storm noise, and which is limited enough in size to be manageable for the main field modeling. The along track filtering described above has proved to be an effective means of condensing large numbers of shipborne magnetic data into a manageable and meaningful data set for main field modeling. Its simplicity and ability to adequately handle varying spatial and sampling constraints has outweighed consideration of more sophisticated approaches. This filtering technique also provides the benefits of smoothing out short wavelength crustal anomalies, discarding data recorded during magnetically noisy periods, and assigning reasonable error estimates to be used in the least square modeling. A useful data set now exists which spans 1953-1987.
    Keywords: GEOPHYSICS
    Type: NASA. Goddard Space Flight Center, Types and Characteristics of Data for Geomagnetic Field Modeling; p 149-202
    Format: text
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  • 10
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    Extraterrestrial surface propulsion systems (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Lunar traction systems, Mars oxygen production, and Mars methane engine operation were the three topics studied during 1992. An elastic loop track system for lunar construction operations was redesigned and is being tested. A great deal of work on simulating the lunar environment to facilitate traction testing has been reported. Operation of an oxygen processor under vacuum conditions has been the focus of another design team. They have redesigned the processor facility. This included improved seals and heat shields. Assuming methane and oxygen can be produced from surface resources on Mars, a third design team has addressed the problem of using Mars atmospheric carbon dioxide to control combustion temperatures in an internal combustion engine. That team has identified appropriate tests and instrumentation. They have reported on the test rig that they designed and the computer-based system for acquiring data.
    Keywords: MECHANICAL ENGINEERING
    Type: USRA, Proceedings of the 8th Annual Summer Conference: NASA(USRA Advanced Design Program; p 209-215
    Format: application/pdf
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