A model for the coevolution of the genetic code and the process of protein synthesis - Review and assessment
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Lacey, J. C., Jr.↗
SEARCH · Engineering Papers
Results for “L CODES”
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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Three-dimensional upwind parabolized Navier-Stokes code for real gas flows
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Tannehill, John C.↗
Three-dimensional upwind, parabolized Navier-Stokes code for chemically reacting flows
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Buelow, Philip E.↗
Nonsystematic convolutional codes for sequential decoding in space applications.
Description of a class of rate 1/2 nonsystematic convolutional codes with the following desirable properties: (1) an undetected decoding error probability verified by simulation to be much smaller than for the best systematic codes of the same constraint length; (2) computation behavior with sequential decoding verified by simulation to be virtually identical to that of the best systematic codes; (3) a ?quick-look-in' feature that permits recovery of the information sequence from the hard-decisioned received data without decoding simply by modulo-two addition of the received sequences; and (4) suitability for encoding by simple circuitry requiring less hardware than encoders for the best systematic codes of the same constraint length. Theoretical analyses are given. These codes have been adopted for use in several forthcoming space missions.
Massey, J. L.↗
Coordinated design of coding and modulation systems
The joint optimization of the coding and modulation systems employed in telemetry systems was investigated. Emphasis was placed on formulating inner and outer coding standards used by the Goddard Spaceflight Center. Convolutional codes were found that are nearly optimum for use with Viterbi decoding in the inner coding of concatenated coding systems. A convolutional code, the unit-memory code, was discovered and is ideal for inner system usage because of its byte-oriented structure. Simulations of sequential decoding on the deep-space channel were carried out to compare directly various convolutional codes that are proposed for use in deep-space systems.
Massey, J. L.↗
Number of minimum-weight code words in a product code
Consideration is given to the number of minimum-weight code words in a product code. The code is considered as a tensor product of linear codes over a finite field. Complete theorems and proofs are presented.
Miller, R. L.↗
Development of an infrared radiative heating model
Infrared radiative transfer solution algorithms used in global circulation models were assessed. Computation techniques applicable to the Ames circulation model are identified. Transmission properties of gaseous CO2, H2O, and O3 are gathered, and a computer program is developed, using the line parameter tape and Voight profile subroutine, which computes the transmission of CO2, H2O, and O3. A computer code designed to compute atmospheric cooling rates was developed.
Bergstrom, R. W.↗
SPAR improved structure-fluid dynamic analysis capability, phase 2
An efficient and general method of analyzing a coupled dynamic system of fluid flow and elastic structures is investigated. The improvement of Structural Performance Analysis and Redesign (SPAR) code is summarized. All error codes are documented and the SPAR processor/subroutine cross reference is included.
Pearson, M. L.↗
Computer code to interchange CDS and wave-drag geometry formats
A computer program has been developed on the PRIME minicomputer to provide an interface for the passage of aircraft configuration geometry data between the Rockwell Configuration Development System (CDS) and a wireframe geometry format used by aerodynamic design and analysis codes. The interface program allows aircraft geometry which has been developed in CDS to be directly converted to the wireframe geometry format for analysis. Geometry which has been modified in the analysis codes can be transformed back to a CDS geometry file and examined for physical viability. Previously created wireframe geometry files may also be converted into CDS geometry files. The program provides a useful link between a geometry creation and manipulation code and analysis codes by providing rapid and accurate geometry conversion.
Johnson, V. S.↗
Aeroelastic Computations For Wings With Loaded Tips
External fuel tanks or missiles degrade stability because of unsteady aerodynamics. Transonic aeroelasticity of wings with tip stores simulated with improved version of ATRAN3S computer code, previously used to study behavior of clean wings only. Output of code agrees well with wind-tunnel data.
Goorjian, Peter M.↗
The design plan of a VLSI single chip (255, 223) Reed-Solomon decoder
The very large-scale integration (VLSI) architecture of a single chip (255, 223) Reed-Solomon decoder for decoding both errors and erasures is described. A decoding failure detection capability is also included in this system so that the decoder will recognize a failure to decode instead of introducing additional errors. This could happen whenever the received word contains too many errors and erasures for the code to correct. The number of transistors needed to implement this decoder is estimated at about 75,000 if the delay for received message is not included. This is in contrast to the older transform decoding algorithm which needs about 100,000 transistors. However, the transform decoder is simpler in architecture than the time decoder. It is therefore possible to implement a single chip (255, 223) Reed-Solomon decoder with today's VLSI technology. An implementation strategy for the decoder system is presented. This represents the first step in a plan to take advantage of advanced coding techniques to realize a 2.0 dB coding gain for future space missions.
Hsu, I. S.↗
User documentation for the MSK and OMS intelligent tutoring systems
This user's guide describes how to use the Intelligent Tutoring Systems for the Manual Select Keyboard (MSK) and the Orbital Maneuvering System (OMS) and how to use the C code that runs the mockup version of the MSK.
Fink, Pamela K.↗
Simultaneous measurements of temperature and density in air flows using UV laser spectroscopy
The simultaneous measurement of temperature and density using laser-induced fluorescence of oxygen in combination with Q-branch Raman scattering of nitrogen and oxygen is demonstrated in a low-speed air flow. The lowest density and temperature measured in the experiment correspond to the freestream values at Mach 5 in the Ames 3.5-Foot Hypersonic Wind Tunnel for stagnation conditions of 100 atm and 1000 K. The experimental results demonstrate the viability of the optical technique for measurements that support the study of compressible turbulence and the validation of numerical codes in supersonic and hypersonic wind tunnel flows.
Fletcher, D. G.↗
Green's function methods in heavy ion shielding
An analytic solution to the heavy ion transport in terms of Green's function is used to generate a highly efficient computer code for space applications. The efficiency of the computer code is accomplished by a nonperturbative technique extending Green's function over the solution domain. The computer code can also be applied to accelerator boundary conditions to allow code validation in laboratory experiments.
Wilson, John W.↗
Design of a Hypersonic Waverider-Derived Airplane
The paper describes the first assessment study of a waverider-derived Mach 5 aircraft design using fuselage integrated-underslung over/under turboramjets with endothermic fuel. The study is based on a tanker-to-tanker mission, which begins at Mach 0.8 and 30,000 feet, with the vehicle accelerating to Mach 12 at constant altitude and then to Mach 5 while climbing to about 90,000 feet. The paper describes the vehicle, the aerodynamic analysis, and the propulsion system and its installed performance, structure design, and analysis. The mission simulation was run using the CSOTAV code developed by the NASA Langley Research Center.
Pegg, Robert J.↗
Comments regarding two upwind methods for solving two-dimensional external flows using unstructured grids
Steady flow over the leading portion of a multicomponent airfoil section is studied using computational fluid dynamics (CFD) employing an unstructured grid. To simplify the problem, only the inviscid terms are retained from the Reynolds-averaged Navier-Stokes equations - leaving the Euler equations. The algorithm is derived using the finite-volume approach, incorporating explicit time-marching of the unsteady Euler equations to a time-asymptotic, steady-state solution. The inviscid fluxes are obtained through either of two approximate Riemann solvers: Roe's flux difference splitting or van Leer's flux vector splitting. Results are presented which contrast the solutions given by the two flux functions as a function of Mach number and grid resolution. Additional information is presented concerning code verification techniques, flow recirculation regions, convergence histories, and computational resources.
Kleb, W. L.↗
National Transportation Safety Board Aircraft Accident Investigation Supported
The main purpose of this investigation was for NASA to help the National Transportation Safety Board (NTSB) gain better understanding of the events that led to the loss of Comair Flight 3272 over Monroe, Michigan, on January 9, 1997. In-flight icing was suspected as being the primary cause of this accident. Of particular interest to the Safety Board was what NASA could learn about the potential performance degradation of the wing of the Embraer EMB-120 twin-turboprop commuter aircraft with various levels of ice contamination. NASA agreed to undertake (1) ice-accretion prediction computations with NASA s LEWICE program to bound the kind of contaminations that the vehicle may have developed, (2) testing in the NASA Lewis Research Center's Icing Research Tunnel to verify and refine the ice shapes developed by LEWICE, (3) a two-dimensional Navier- Stokes analysis to determine the performance degradation that those ice shapes could have caused, and (4) an examination using three-dimensional Navier-Stokes codes to study the three-dimensional effects of ice contamination.
Reehorst, Andrew L.↗
NASA Environmentally Responsible Aviation High Overall Pressure Ratio Compressor Research Pre-Test CFD
This paper describes a collaborative and cost-shared approach to reducing fuel burn under the NASA Environmentally Responsible Aviation project. NASA and General Electric (GE) Aviation are working together aa an integrated team to obtain compressor aerodynamic data that is mutually beneficial to both NASA and GE Aviation. The objective of the High OPR Compressor Task is to test a single stage then two stages of an advanced GE core compressor using state-of-the-art research instrumentation to investigate the loss mechanisms and interaction effects of embedded transonic highly-loaded compressor stages. This paper presents preliminary results from NASA's in-house multistage computational code, APNASA, in preparation for this advanced transonic compressor rig test.
Celestina, Mark L.↗