Tech Briefs

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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Solar Pumped Fiber Laser for Solar Sail Propulsion and Remote Power Transfer

The photovoltaic capability of any instrument can be enhanced by delivering extra power via a space-based, broadband laser beam. Goddard Space Flight Center, Greenbelt, Maryland A new method has been developed to create coherent laser light efficiently with direct optical coupling of the Sun’s energy into the gain medium for multiple uses. New advances in solar cell photovoltaic (PV) technologies have greatly improved their efficiencies, mostly by improving their ability to convert many wavelengths or wider bands of the solar spectrum to electricity. New advances in actively doped fibers and optical glasses have been shown to produce very broad, multi-line absorption bands as well as stimulated emission lines, or laser lines. By designing the optical cavity system to feed back all emission bands into the gain media for amplification, a multi-wavelength source can be generated requiring no electronics.

Posted in: Tech Briefs, Physical Sciences, Photonics, Briefs

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ELID Grinding of Large Aspheres

Goddard Space Flight Center, Greenbelt, Maryland This work focused on a manufacturing process to produce silicon carbide optical surfaces with low mid-spatial surface errors. Mid-spatial frequency (MSF) and high-spatial frequency (HSF) surface errors in the grinding of fast aspheres are amplified in hard ceramics like silicon carbide due to cyclic tool wear rates, vibration, and tool deformation.

Posted in: Tech Briefs, Photonics, Briefs

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Systems and Methods for Localized Surface Plasmon Resonance Sensing

This innovation uses an optical fiber having a metallic dot array on its tip, a light source coupled to the optical fiber via a light coupler, and a spectrometer coupled to the optical fiber via the coupler. Marshall Space Flight Center, Alabama Recently, there is widespread interest in the development of chemical and biochemical sensors based on plasmonic resonance of metallic nanostructures. In the localized surface plasmon resonance (LSPR) for nanometer-sized metallic structures, a resonant oscillation of the conduction electrons within the metallic nanostructures gives rise to an enhanced scattering and absorption of light. The LSPR sensing requires simpler instrumentation than surface plasmon resonance (SPR).

Posted in: Tech Briefs, Photonics, Briefs

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Designing Reliable Robots for Moon Exploration

Simulation plays a key role in developing robots to explore the Moon. Astrobotic Technology, Inc., Pittsburgh, Pennsylvania Equipment for space exploration is almost impossible to test on Earth. Testing is expensive and cannot replicate the conditions of launch, cruise, landing, and travel across a planetary surface. As space exploration shifts to the private sector, Astrobotic Technology, Inc. is taking the lead in delivering affordable robotic technology. The company uses ANSYS technology to stay competitive, virtually testing its lunar robots on time and under budget.

Posted in: Mechanical Components, Software, Briefs

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Designing Smaller Magnets for the Large Hadron Collider

CERN designs a smaller and more powerful superconducting accelerator magnet using ANSYS multiphysics tools. FEAC Engineering, Ioannina, Greece The European Organization for Nuclear Research (CERN) requires new magnets that are smaller than their predecessors to accommodate new instrumentation. Because of their size, these magnets need to generate a 24 percent stronger magnetic field and the structure must provide for near-zero deformation of the conductor. Even a small deformation could increase the electrical resistance and raise the temperature enough to cause the conductor to lose its superconducting state. Engineers addressed this challenge using ANSYS electromagnetic, thermal, and structural simulation tools. Coupling the multiphysics domains in the ANSYS® Workbench® environment allowed the team to optimize the design by simultaneously considering all of the physics.

Posted in: Physical Sciences, Software, Briefs

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