On Linear Product Codes and Their Duals Scientific Report No. 4
Tensor products of linear codes, and product codes with dual cyclic component codes
TENSOR FIELD↗
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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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Improving turbo-like codes using iterative decoder analysis
The density evolution method is used to analyze the performance and optimize the structure of parallel and serial turbo codes, and generalized serial concatenations of mixtures of different outer and inner codes. Design examples are given for mixture codes.
turbo codes iterative decoding↗
Upper bounds to error probabilities of coded systems over AWGN and fading channels
A family of upper bounds to error probabilities of coded systems on the additive white Gaussian noise channel was recently proposed by Divsalar. Their calculation depends only on the weight spectrum of the code words. We first elaborate upon these bounds to show how they can be further tightened by using numerical integration instead of a Chernoff bound, and by reducing the number of code words to be included in the bound. Next, we extend them to finding channels.
coded systems↗
NED and SIMBAD Conventions for Bibliographic Reference Coding
The primary purpose of the 'reference code' is to provide a unique and traceable representation of a bibliographic reference within the structure of each database. The code is used frequently in the interfaces as a succinct abbreviation of a full bibliographic reference. Since its inception, it has become a standard code not only for NED and SIMBAD, but also for other bibliographic services.
NED SIMBAD bibliographic reference coding astronom↗
Self-Concatenated Trellis Coded Modulation With Self-Iterative Decoding
Self-concatenated trellis coded modulation with b(q-1) interleavers is a concatenated coded scheme based on only one rate bq/n convolutional code.
Self-Concatenated trellis coded iterative decoding↗
Design of Serially Concatenated Trellis Coded Modulation
Serial concatenation of an outer binary convolutional code with an inner TCM code over a multidimensional Euclidean constellation through an interleaver, allows to extend the extremely good performance of turbo codes to the case of high spectral efficiency.
Serial Concatenated trellis code↗
Automatic Code Generation for Instrument Flight Software
Automatic code generation can be used to convert software state diagrams into executable code, enabling a model- based approach to software design and development. The primary benefits of this process are reduced development time and continuous consistency between the system design (statechart) and its implementation. We used model-based design and code generation to produce software for the Electra UHF radios that is functionally equivalent to software that will be used by the Mars Reconnaissance Orbiter (MRO) and the Mars Science Laboratory to communicate with each other. The resulting software passed all of the relevant MRO flight software tests, and the project provides a useful case study for future work in model-based software development for flight software systems.
state charts↗
A Radiation Solver for the National Combustion Code
A methodology is given that converts an existing finite volume radiative transfer method that requires input of local absorption coefficients to one that can treat a mixture of combustion gases and compute the coefficients on the fly from the local mixture properties. The Full-spectrum k-distribution method is used to transform the radiative transfer equation (RTE) to an alternate wave number variable, g . The coefficients in the transformed equation are calculated at discrete temperatures and participating species mole fractions that span the values of the problem for each value of g. These results are stored in a table and interpolation is used to find the coefficients at every cell in the field. Finally, the transformed RTE is solved for each g and Gaussian quadrature is used to find the radiant heat flux throughout the field. The present implementation is in an existing cartesian/cylindrical grid radiative transfer code and the local mixture properties are given by a solution of the National Combustion Code (NCC) on the same grid. Based on this work the intention is to apply this method to an existing unstructured grid radiation code which can then be coupled directly to NCC.
National Combustion Code↗
Use of a Viscous Flow Simulation Code for Static Aeroelastic Analysis of a Wing at High-Lift Conditions
In this paper, we present a static aeroelastic analysis of a wind tunnel test model of a wing in high-lift configuration using a viscous flow simulation code. The model wing was tailored to deform during the tests by amounts similar to a composite airliner wing in highlift conditions. This required use of a viscous flow analysis to predict the lift coefficient of the deformed wing accurately. We thus utilized an existing static aeroelastic analysis framework that involves an inviscid flow code (Cart3d) to predict the deformed shape of the wing, then utilized a viscous flow code (Overflow) to compute the aerodynamic loads on the deformed wing. This way, we reduced the cost of flow simulations needed for this analysis while still being able to predict the aerodynamic forces with reasonable accuracy. Our results suggest that the lift of the deformed wing may be higher or lower than that of the non-deformed wing, and the washout deformation of the wing is the key factor that changes the lift of the deformed wing in two distinct ways: while it decreases the lift at low to moderate angles of attack simply by lowering local angles of attack along the span, it increases the lift at high angles of attack by alleviating separation.
Aeroelastic↗
Accuracy of RT Code SORD for Realistic Atmospheric Profiles
We discuss accuracy of our recently developed RT code SORD using 2 benchmark scenarios published by the IPRT group in 2015. These scenarios define atmospheres with a complicate dependence of scattering and absorption properties over height (profile). Equal step, dh=1km, is assumed in the profiles. We developed subroutines that split such atmospheres into layers of the same optical thickness, d tau. We provide full text of the subroutines with comments in Appendix. The d tau is a step for vertical integration in the method of successive orders. Modification of the input profiles from "equal step over h" to "equal step over tau" changes input for RT simulations. This may cause errors at or above the acceptable level of the measurement uncertainty. We show errors of the RT code SORD for both intensity and polarization. In addition to that, using our discrete ordinates RT code IPOL, we discuss one more IPRT scenario, in which changes in height profile indeed cause unacceptable errors. Clear understanding of source and magnitude of these errors is important, e.g. for the AERONET retrieval algorithm. SORD is available from ftp://maiac.gsfc.nasa.gov/pub/skorkin/SORD_IP_16B/ or by email request from the first author.
polarization↗
Performance of Variable Coded Modulations over a Nonlinear Channel for VCM Protocol Red Book
This presentation provides a summary of the results obtained from a study which evaluates the performance of variable coded modulations specified in the "Variable Coded Modulation Protocol" CCSDS Red Book, over a nonlinear channel that is currently on the CCSDS Blue Book track. The objectives are to perform simulation that identifies the operating signal-to-noise-power ratio required to achieve a codeword error rate of 1e-4 over the specified nonlinear channel for various modulations (i.e. BPSK, QPSK, 8-PSK) and LDPC coding schemes, and compare against performance over an ideal additive white Gaussian channel. We select a only subset of operating modes to perform the analysis which are based on a number of mitigation techniques to combat the nonlinear distortions. Specifically, transmitter centroidal pre-distortion, phase post-distortion and receiver mean phase estimation are analyzed in this study.
coding↗
Serial Concatenation of Interleaved Codes: Performance Analysis, Design and Iterative Decoding
A serially concatenated code with interleaver consists of the cascade of an outer encoder, an interleaver permuting the outer code words bits, and an inner encoder whose input words are the permuted outer code words.
concatenated↗
Turbo Trellis Coded Modulation with Iterative Decoding for Mobile Satellite Communications
In this paper, analytical bounds on the performance of parallel concatenation of two codes, known as turbo codes, and serial concatenation of two codes over fading channels are obtained.
Parallel↗
Utilizing Code Generation from Models for Electric Aircraft Motor Controller Flight Software
The processes followed to develop and test safety-critical flight software significantly increase development effort and overhead in comparison to both non-safety-critical and non-flight software. Generating code from models can be used to reduce development effort; however, the processes for using code generation to develop flight software are relatively immature. This work presents an approach for developing safety-critical flight software utilizing code generation from models to reduce development time and effort. The presented use-case is of electric aircraft motor control software developed for NASA's X-57 Maxwell aircraft.
flight software↗
Buffer-IPyC separation process in TRISO fuel particles simulated with Bison code
During High Temperature Gas-cooled Reactor (HTGR) operation, tristructural isotropic (TRISO) coated-particle fuel undergoes irradiation-induced changes in morphology and thermomechanical properties. Experimental results from the Advanced Gas Reactor (AGR) Fuel Development and Qualification Program show, among other things, the mechanism of gap formation between the buffer and inner pyrolytic carbon (IPyC) layers, which could be explored further via computational simulations using the Bison code. Two simulation models were developed, the debonding restricted model, where no gap formation between buffer and IPyC layers is permitted, and the debonding enabled model, where the gap between those layers is created. The inputs of the simulated models are based on the irradiation conditions from the AGR-1 experiment. The research included simulations on spherical and aspherical fuel types. Under the specific temperatures and fluences of the AGR-1 irradiation experiment, and the Bison simulations, it was concluded that the most common scenario is a gap formation along the buffer-IPyC interface, while the least possible scenario is the situation where there is no gap formation at the buffer-IPyC junction. The computational results confirmed that the sphericity of the fuel influences the thickness of the gap that occurs at the buffer-IPyC junction, in a way that with increasing aspect ratio the gap thickness increases. The results obtained for spherical and aspherical fuel are nearly identical. Finally, performed simulations match conclusions observed from the AGR-1 experiment, which as such shows that the Bison code is a good computational method for simulating the TRISO fuel. Future simulations will include the validation of performed research and comparison of the results between Bison and PARFUME codes.
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
An adaptable recursive binary entropy coding technique
We present a novel data compression technique, called recursive interleaved entropy coding, that is based on recursive interleaving of variable-to-variable length binary source codes.
data compression entrophy coding biliary adaptive ↗
Benchmarking of massively parallel phase-field codes for directional solidification
We present a detailed benchmark comparing two state-of-the-art phase-field implementations for simulating alloy solidification under experimentally relevant conditions. The study investigates the directional solidification of Al-3wt%Cu under high-velocity solidification conditions and SCN-0.46wt% camphor under microgravity conditions from National Aeronautics and Space Administration (NASA) DECLIC-DSI-R experiments. Both codes, one employing finite-difference discretization with uniform mesh and GPU-acceleration (GPU-PF) and the other one employing finite-element discretization with adaptive-mesh and CPU-parallelization (PRISMS-PF), solve the same quantitative phase-field formulation that incorporates an anti-trapping current for the solidification of dilute alloys. We evaluate the predictions of each code for dendritic morphology, primary spacing, and tip dynamics in both 2D and 3D, as well as their numerical convergence and computational performance. While existing benchmark problems have primarily focused on simplified or small-scale simulations, they do not reflect the computational and modeling challenges posed by employing experimentally relevant time and length scales. Our results provide a practical framework for assessing phase-field code performance as well as validating and facilitating their application in integrated computational materials engineering (ICME) workflows that require integration with realistic experimental data.
36 MATERIALS SCIENCE↗
TRANSP integrated modeling code for interpretive and predictive analysis of tokamak plasmas
This paper provides a comprehensive review of the TRANSP code, a sophisticated tool for interpretive and predictive analysis of tokamak plasmas, detailing its major capabilities and features. It describes the equations for particle, power, and momentum balance analysis, as well as the poloidal field diffusion equations. The paper outlines the spatial and time grids used in TRANSP and details the equilibrium assumptions and solvers. Various models for heating and current drive and radiation, including updates to the NUBEAM model, are discussed. The handling of large-scale events such as sawtooth crashes and pellet injections is examined, along with the predictive capabilities for advancing plasma profiles. The integration of TRANSP with the ITER Integrated Modeling and Analysis Suite (IMAS) is highlighted, demonstrating enhanced data access and analysis capabilities. Additionally, the paper discusses best practices and continuous integration techniques to enhance TRANSP's robustness. The suite of TRANSP tools, designed for efficient data analysis and simulation, further supports the optimization of tokamak operations and coupling with other tokamak codes. Continuous development and support ensure that TRANSP remains a major code for the analysis of experimental data for controlled thermonuclear fusion, maintaining its critical role in supporting the optimization of tokamak operations and advancing fusion research.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗