Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “enhancing”

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.

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

At least 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Kinetic friction attributed to enhanced radiation by cyclotron maser instability

Along the auroral field lines, a fraction of the energetic electrons injected from the magnetotail is reflected by the earth's convergent geomagnetic field. The reflected loss-cone electrons are unstable with respect to the cyclotron maser instability, resulting in the auroral kilometric radiation. This paper investigates the kinetic friction force exerted on the energetic electrons by the enhanced radiation field. It is found that the enhanced radiation results in a deceleration of reflected electrons, thereby providing an effective resistivity. In addition, the rate of decrease (increase) of effective perpendicular (parallel) kinetic temperatures is also evaluated. The analysis is carried out over various physical parameters such as the degree of loss cone, average particle energy, and the ratio of plasma frequency to cyclotron frequency.

Yoon, Peter H.↗
NASA NTRS1992

Gas-exposure enhanced Na* emission from Na-rich surfaces

The optical emission attributed to electronically desorbed excited sodium atoms from NaCl and Na-evaporated surfaces is shown to be enhanced by exposure of the surface to gaseous CO2 and N2. This is the first observation of enhancement of electron-simulated desorption of substrate atoms caused by the exposure of surfaces to gaseous molecules which do not contain the desorbed atoms. The large amount of excited-sodium yield at 60 K provides evidence for nonexistence of the secondary-electron excitation of thermally desorbed ground sodium.

Xu, Jun↗
NASA NTRS1992

Enhancement of Thomson scatter by charged aerosols in the polar mesosphere - Measurements with a 1.29-GHz radar

The summer polar mesosphere was observed with the Sondrestrom 1.29-GHz radar with a new high-resolution data acquisition mode. On one occasion, a spatially narrow enhancement in the backscattered power was seen near an altitude of 88 km. Possible explanations are discussed and it is proposed that this layer may be the first example of polar mesosphere summer echoes detected above 1 GHz. Specifically, suggested that these echoes are enhanced Thomson scatter from a layer of charged aerosols, and speculate on the size and charge state.

Cho, John Y. N.↗
NASA NTRS1990

Ductility enhancement from interface dislocation sources in a directionally solidified beta + gamma + gamma-prime Ni-Fe-Al composite alloy

A directionally solidified beta + gamma + gamma-prime Ni-Fe-Al in situ composite alloy of composition Ni50Fe30Al20 has been used to investigate the effect of a plastically soft second phase on the mechanical behavior of a B2 ordered intermetallic alloy. This material exhibits extensive plasticity during compressive deformation at room temperature and fails in shear with extensive gamma + gamma-prime lamellar or rod pullout. The material also exhibits about 10 percent tensile elongation to fracture at room temperature, with final fracture that includes substantial necking of the gamma + gamma-prime lamellae or rods. Observation of slip lines and dislocation substructures discloses that the normally brittle beta matrix undergoes extensive plasticity in order to deform compatibly with the more ductile gamma phase. The plasticity of the beta matrix is accomplished by the generation of glissile dislocations into the beta matrix from the beta/gamma interface region and is enhanced because of a favorable beta-gamma orientation relationship for slip transfer. Ductility enhancement from interface-generated mobile dislocations generated from beta-gamma interfaces is compared to that observed in film-coated beta-NiAl single crystals and FeAl polycrystals.

Larsen, M.↗
NASA NTRS1992

Radiation enhanced dissociation of hydrogen in nuclear rockets

The effect of radiation-induced dissociation of hydrogen gas in nuclear rockets is studied. The dissociation degree is obtained by solving rate equations, which include the fast-ion induced dissociation and ionization of atomic and molecular hydrogens. Analytical formulas are used to estimate a change in the viscosity and the specific impulse. It was found that the fast-ion induced dissociation plays an important role in enhancing the specific impulse for nuclear rocket concepts using hydrogen gas at low pressures (less than 0.1 MPa) and low temperatures (less than 3000 K). It is also shown that the specific impulse is enhanced by mixing helium-3, lithium-6, boron-10, or uranium-235 with hydrogen.

Watanabe, Yoichi↗
NASA NTRS1991

An enhanced Ada run-time system for real-time embedded processors

An enhanced Ada run-time system has been developed to support real-time embedded processor applications. The primary focus of this development effort has been on the tasking system and the memory management facilities of the run-time system. The tasking system has been extended to support efficient and precise periodic task execution as required for control applications. Event-driven task execution providing a means of task-asynchronous control and communication among Ada tasks is supported in this system. Inter-task control is even provided among tasks distributed on separate physical processors. The memory management system has been enhanced to provide object allocation and protected access support for memory shared between disjoint processors, each of which is executing a distinct Ada program.

Sims, J. T.↗
NASA NTRS1993

Image-Enhancement Program

ENHANCETOOL computer program has capabilities for interactive enhancement of digital images. Includes particularly useful combination of algorithms not existing in single interactive program. Software package also provides means through which additional image-enhancement algorithms easily integrated and made available to user. Written in C Language.

Matthews, Christine G.↗
NASA NTRS1992

Mission Control Center enhancement opportunities in the 1990's

The purpose of this paper is to present a framework for understanding the major enhancement opportunities for Air Force Mission Control Center/Test Support Centers (MCC's/TSC's) in the 1990's. Much of this paper is based on the findings of Study 232 and work currently underway in Study 2-6 for the Air Force Systems Command, Space System Division, Network Program Office. In this paper, we will address MCC/TSC enhancement needs primarily from the operator perspective, in terms of the increased capabilities required to improve space operations task performance.

Hartman, Wayne↗
NASA NTRS1993

Robust algebraic image enhancement for intelligent control systems

Robust vision capability for intelligent control systems has been an elusive goal in image processing. The computationally intensive techniques a necessary for conventional image processing make real-time applications, such as object tracking and collision avoidance difficult. In order to endow an intelligent control system with the needed vision robustness, an adequate image enhancement subsystem capable of compensating for the wide variety of real-world degradations, must exist between the image capturing and the object recognition subsystems. This enhancement stage must be adaptive and must operate with consistency in the presence of both statistical and shape-based noise. To deal with this problem, we have developed an innovative algebraic approach which provides a sound mathematical framework for image representation and manipulation. Our image model provides a natural platform from which to pursue dynamic scene analysis, and its incorporation into a vision system would serve as the front-end to an intelligent control system. We have developed a unique polynomial representation of gray level imagery and applied this representation to develop polynomial operators on complex gray level scenes. This approach is highly advantageous since polynomials can be manipulated very easily, and are readily understood, thus providing a very convenient environment for image processing. Our model presents a highly structured and compact algebraic representation of grey-level images which can be viewed as fuzzy sets.

Lerner, Bao-Ting↗
NASA NTRS1993

Resolution-enhanced Mapping Spectrometer

A familiar mapping spectrometer implementation utilizes two dimensional detector arrays with spectral dispersion along one direction and spatial along the other. Spectral images are formed by spatially scanning across the scene (i.e., push-broom scanning). For imaging grating and prism spectrometers, the slit is perpendicular to the spatial scan direction. For spectrometers utilizing linearly variable focal-plane-mounted filters the spatial scan direction is perpendicular to the direction of spectral variation. These spectrometers share the common limitation that the number of spectral resolution elements is given by the number of pixels along the spectral (or dispersive) direction. Resolution enhancement by first passing the light input to the spectrometer through a scanned etalon or Michelson is discussed. Thus, while a detector element is scanned through a spatial resolution element of the scene, it is also temporally sampled. The analysis for all the pixels in the dispersive direction is addressed. Several specific examples are discussed. The alternate use of a Michelson for the same enhancement purpose is also discussed. Suitable for weight constrained deep space missions, hardware systems were developed including actuators, sensor, and electronics such that low-resolution etalons with performance required for implementation would weigh less than one pound.

Kumer, J. B.↗
NASA NTRS1993

The Enhanced-model Ladar Wind Sensor and Its Application in Planetary Wind Velocity Measurements

For several years we have been developing an optical air-speed sensor that has a clear application as a meteorological wind-speed sensor for the Mars landers. This sensor has been developed for aircraft use to replace the familiar, pressure-based Pitot probe. Our approach utilizes a new concept in the laser-based optical measurement of air velocity (the Enhanced-Mode Ladar), which allows us to make velocity measurements with significantly lower laser power than conventional methods. The application of the Enhanced-Mode Ladar to measuring wind speeds in the martian atmosphere is discussed.

Soreide, D. C.↗
NASA NTRS1992

Enhancements to the Design Manager's Aide for Intelligent Decomposition (DeMAID)

This paper discusses the addition of two new enhancements to the program Design Manager's Aide for Intelligent Decomposition (DeMAID). DeMAID is a knowledge-based tool used to aid a design manager in understanding the interactions among the tasks of a complex design problem. This is done by ordering the tasks to minimize feedback, determining the participating subsystems, and displaying them in an easily understood format. The two new enhancements include (1) rules for ordering a complex assembly process and (2) rules for determining which analysis tasks must be re-executed to compute the output of one task based on a change in input to that or another task.

Rogers, James L.↗
NASA NTRS1992

Image enhancement filters significantly improve reading performance for low vision observers

As people age, so do their photoreceptors; many photoreceptors in central vision stop functioning when a person reaches their late sixties or early seventies. Low vision observers with losses in central vision, those with age-related maculopathies, were studied. Low vision observers no longer see high spatial frequencies, being unable to resolve fine edge detail. We developed image enhancement filters to compensate for the low vision observer's losses in contrast sensitivity to intermediate and high spatial frequencies. The filters work by boosting the amplitude of the less visible intermediate spatial frequencies. The lower spatial frequencies. These image enhancement filters not only reduce the magnification needed for reading by up to 70 percent, but they also increase the observer's reading speed by 2-4 times. A summary of this research is presented.

Lawton, T. B.↗
NASA NTRS1992

Enhancing images with Intensity-Dependent Spread functions

The theory of Intensity-Dependent Spread functions (IDS), a model of the human visual system proposed by Cornsweet (1985), is applied to image enhancement. An artificial image is examined which illustrates the characteristics of IDS processing and shows how the theoretical results translate into visual effects. Examples of realistic scenes that have been enhanced by IDS are presented. The system is shown to be particularly useful for bringing out detail in regions of low-contrast images. IDS can be readily implemented on a parallel computer.

Reese, Greg↗
NASA NTRS1994

More About The Enhanced Projection-And-Assembly Method

Report discusses enhanced projection-and-assembly (EP&A) method and its application to Galileo spacecraft. EP&A method and its predecessor, projection-and-assembly (P&A) method, described in "Enhanced Method of Reduction of Mathematical Models" (NPO-18402), and "Two-Stage Reduction of Dynamical Models" (NPO-18723).

Lee, Allen Y.↗
NASA NTRS1993

Enhancement effects in polarimetric radar returns: Phase difference statistics

The probability density functions (pdfs) of the co- and cross-polarized phase differences are derived for backscatter from vegetation using the coherent and incoherent scattering theories. Unlike previous derivations, no assumptions or observations other than the applicability of the Central Limit Theorem (CLT), the low fractional volume of the medium, the reciprocity of the scatterers, and the azimuthal symmetry of the scatterer's orientation statistics are employed. Everything else follows logically via the mathematics. The difference between the coherent theory and the incoherent theory is referred to as the backscatter enhancement effect. The influence of this enhancement effect on the phase difference pdfs is examined and found to be important under combined conditions of scatterer anisotropy and appropriate reflection coefficient values.

Lang, R. H.↗
NASA NTRS1992

Shared visions: Partnership of Rockwell International and NASA Cost Effectiveness Enhancements (CEE) for the space shuttle system integration program

As a result of limited resources and tight fiscal constraints over the past several years, the defense and aerospace industries have experienced a downturn in business activity. The impact of fewer contracts being awarded has placed a greater emphasis for effectiveness and efficiency on industry contractors. It is clear that a reallocation of resources is required for America to continue to lead the world in space and technology. The key to technological and economic survival is the transforming of existing programs, such as the Space Shuttle Program, into more cost efficient programs so as to divert the savings to other NASA programs. The partnership between Rockwell International and NASA and their joint improvement efforts that resulted in significant streamlining and cost reduction measures to Rockwell International Space System Division's work on the Space Shuttle System Integration Contract is described. This work was a result of an established Cost Effectiveness Enhancement (CEE) Team formed initially in Fiscal Year 1991, and more recently expanded to a larger scale CEE Initiative in 1992. By working closely with the customer in agreeing to contract content, obtaining management endorsement and commitment, and involving the employees in total quality management (TQM) and continuous improvement 'teams,' the initial annual cost reduction target was exceeded significantly. The CEE Initiative helped reduce the cost of the Shuttle Systems Integration contract while establishing a stronger program based upon customer needs, teamwork, quality enhancements, and cost effectiveness. This was accomplished by systematically analyzing, challenging, and changing the established processes, practices, and systems. This examination, in nature, was work intensive due to the depth and breadth of the activity. The CEE Initiative has provided opportunities to make a difference in the way Rockwell and NASA work together - to update the methods and processes of the organizations. The future success of NASA space programs and Rockwell hinges upon the ability to adopt new, more efficient and effective work processes. Efficiency, proficiency, cost effectiveness, and teamwork are a necessity for economic survival. Continuous improvement initiatives like the CEE are, and will continue to be, vehicles by which the road can be traveled with a vision to the future.

Bejmuk, Bohdan I.↗
NASA NTRS1993

Enhanced decoding for the Galileo S-band mission

A coding system under consideration for the Galileo S-band low-gain antenna mission is a concatenated system using a variable redundancy Reed-Solomon outer code and a (14,1/4) convolutional inner code. The 8-bit Reed-Solomon symbols are interleaved to depth 8, and the eight 255-symbol codewords in each interleaved block have redundancies 64, 20, 20, 20, 64, 20, 20, and 20, respectively (or equivalently, the codewords have 191, 235, 235, 235, 191, 235, 235, and 235 8-bit information symbols, respectively). This concatenated code is to be decoded by an enhanced decoder that utilizes a maximum likelihood (Viterbi) convolutional decoder; a Reed Solomon decoder capable of processing erasures; an algorithm for declaring erasures in undecoded codewords based on known erroneous symbols in neighboring decodable words; a second Viterbi decoding operation (redecoding) constrained to follow only paths consistent with the known symbols from previously decodable Reed-Solomon codewords; and a second Reed-Solomon decoding operation using the output from the Viterbi redecoder and additional erasure declarations to the extent possible. It is estimated that this code and decoder can achieve a decoded bit error rate of 1 x 10(exp 7) at a concatenated code signal-to-noise ratio of 0.76 dB. By comparison, a threshold of 1.17 dB is required for a baseline coding system consisting of the same (14,1/4) convolutional code, a (255,223) Reed-Solomon code with constant redundancy 32 also interleaved to depth 8, a one-pass Viterbi decoder, and a Reed Solomon decoder incapable of declaring or utilizing erasures. The relative gain of the enhanced system is thus 0.41 dB. It is predicted from analysis based on an assumption of infinite interleaving that the coding gain could be further improved by approximately 0.2 dB if four stages of Viterbi decoding and four levels of Reed-Solomon redundancy are permitted. Confirmation of this effect and specification of the optimum four-level redundancy profile for depth-8 interleaving is currently being done.

Dolinar, S.↗