Information Science

Non-Binary Protograph-Based LDPC Codes for Short Block Lengths

The constrained protograph-based LDPC codes are a new class of codes proposed for low-complexity implementation of decoders. NASA’s Jet Propulsion Laboratory, Pasadena, California Short block codes are in demand by international space agencies for transmission of command and control data to spacecraft in the uplink channel. Codes that outperform currently used binary codes with the same block lengths and code rates are desirable. A design method constructs non-binary LDPC (low-density parity-check) codes both for unconstrained non-binary protograph-based codes and the new class of constrained protograph-based codes. The non-binary short block codes outperform the binary version by at least 1 dB for the same block size and code rate.

Posted in: Information Sciences, Electronics & Computers, Briefs

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Method Resolves Algebraic Loops While Improving Accuracy and Reducing Runtime

Higher accuracies are achieved while running at the lower base sample rate. Armstrong Flight Research Center, Edwards, California A method has been developed for resolving algebraic loops that occur in closed-loop systems when using MathWorks Simulink modeling and simulation tools. This variable fidelity method improves accuracy and reduces runtime significantly for users of Simulink Coder applications. The method improves the Simulink Coder tool’s ability to more efficiently and quickly generate C code based on algorithms modeled in the simulation tool. By replacing transfer functions that require high sampling rates with embedded function integration schemes, users can achieve continuous transfer function accuracy at almost no computational cost. The innovation also enables computationally intensive block diagrams to run faster in real time, and satisfies Nyquist frequency requirements in models. Algebraic loops are resolved through fast sampling, making the innovation especially applicable to high-speed systems with saturation limits, dead-bands, and other constraints that create fast dynamics.

Posted in: Information Sciences, Electronics & Computers, Briefs

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Simulation and Visualization of Elastodynamics in Time- Evolving Generalized Curvilinear Coordinates

Deforming grids and stresses can be visualized as the solution proceeds in time. Ames Research Center, Moffett Field, California This innovation unifies an earlier innovation and a new solution method based on finite differences to simulate structural dynamic phenomena over time-varying grids in generalized curvilinear coordinates. The methodology is based on physics-based first principles partial differential equations of elastodynamics in the space-time domain. It provides a powerful, yet simple methodology to compute structural dynamic variables of interest such as stresses over an entire grid mapped over or inside a given body of interest directly in the time domain. The grid can be allowed to deform in time as the solution evolves. The simulation (deforming grids and stresses) can be visualized as the solution proceeds in time; the simulation can be suspended at any point in time based on the visualization of the state of the system, and the simulation can be resumed/terminated altogether as the evolving solution proceeds within/outside the expectation bounds dictated by physics. The attractiveness of the innovation lies in the intuitiveness of the approach where the physical variables such as stresses and the displacements can be visualized directly in space and time as the simulation proceeds.

Posted in: Information Sciences, Electronics & Computers, Software, Briefs

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3D Finite Element Model of Magnetic Mirror and Nano Antenna

Simulations are considerably cheaper and faster than the fabrication process. Goddard Space Flight Center, Greenbelt, Maryland A 3D finite element mathematical model has been developed for representing a behavior of a magnetic mirror and nano antenna subject to polarized incident light. This model represents the fourth generation of magnetic mirror with the goal of suppressing the diffraction.

Posted in: Information Sciences, Electronics & Computers, Software, Briefs

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Toolbox for Modeling and Analysis of Thermodynamic Systems (T-MATS)

Tools are included to make model creation easier than before. John H. Glenn Research Center, Cleveland, Ohio T-MATS is an open-source Simulink library for use in modeling and simulation of thermodynamic systems. It provides a user friendly graphical MATLAB/Simulink-compatible toolbox along with tools to increase ease of model creation. It also includes a generic nonlinear solver that allows the designer to ensure that all conservation equations are respected at every time step.

Posted in: Information Sciences, Electronics & Computers, Software, Briefs

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Advanced Numerical Tools for Design and Analysis of In-Space Valve and Feed Systems

Marshall Space Flight Center, Alabama A high-fidelity numerical simulation software (CRUNCH CFD®) predicts the transient performance of flight valve designs, provides design support by supplementing current empirical rules, and diagnoses system anomalies. Currently, transient analysis of valves is difficult to simulate because of the requirement to dynamically deform the grid due to the valve motion. For complex, transient problems such as engine startup or shutdown that also involve dynamic sealing of fluid flow paths due to valve/solid surface contact, it becomes nearly impossible to deform the grid in an automated fashion.

Posted in: Information Sciences, Electronics & Computers, Software, Briefs

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Global Elevation Data Adaptive Compression Algorithms

These algorithms can be used in applications requiring large databases of graphical information that are deployed via restricted environments, such as tablets and smartphones. Armstrong Flight Research Center, Edwards, California The Global Elevation Data Adaptive Compression Algorithms (GEDACA) were developed to provide compression and rapid decompression of digital terrain maps (DTMs) in constrained computing environments. The primary purpose of these algorithms is to create and utilize highly compressed digital terrain data representing the geographical areas of the entire world to enable Automatic Ground Collision Avoidance Systems (Auto-GCAS) for high-performance fighter aircraft. The data is formatted to be accessible anywhere in the world in real time, and also allows for control of data resolution to support the complete range of high-performance aircraft operations. Other uses include applications that require large databases of graphical information and are deployed via restricted environments, such as tablets and smartphones.

Posted in: Information Sciences, Electronics & Computers, Software, Briefs

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