Special Coverage

Technique Provides Security for Multi-Robot Systems
Bringing New Vision to Laser Material Processing Systems
NASA Tests Lasers’ Ability to Transmit Data from Space
Converting from Hydraulic Cylinders to Electric Actuators
Automating Optimization and Design Tasks Across Disciplines
Vibration Tables Shake Up Aerospace and Car Testing
Supercomputer Cooling System Uses Refrigerant to Replace Water
Computer Chips Calculate and Store in an Integrated Unit
Electron-to-Photon Communication for Quantum Computing

Compact Ku-Band T/R Module for High-Resolution Radar Imaging of Cold Land Processes

This module can be used in phased-array antennas for radar or communications.

Global measurement of terrestrial snow cover is critical to two of the NASA Earth Science focus areas: (1) climate variability and change and (2) water and energy cycle. For radar backscatter measurements, Ku-band frequencies, scattered mainly within the volume of the snowpack, are most suitable for the SWE (snow-water equivalent) measurements. To isolate the complex effects of different snowpack (density and snowgrain size), and underlying soil properties and to distinctly determine SWE, the space-based synthetic aperture radar (SAR) system will require a dual-frequency (13.4 and 17.2 GHz) and dual-polarization approach.

Posted in: Briefs, Physical Sciences, Antennas, Radar, Cold weather, Soils, Water, Weather and climate

Performance Bounds on Two Concatenated, Interleaved Codes

It is now possible to calculate tight bounds at high SNR.

A method has been developed of computing bounds on the performance of a code comprised of two linear binary codes generated by two encoders serially concatenated through an interleaver. Originally intended for use in evaluating the performances of some codes proposed for deep-space communication links, the method can also be used in evaluating the performances of short-block-length codes in other applications.

Posted in: Briefs, TSP, Information Sciences, Communication protocols, Wireless communication systems, Performance tests, Test procedures

Mission Reliability Estimation for Repairable Robot Teams

An analytical model demonstrates autonomous and intelligent control systems capable of operating distributed, multi-planetary surface vehicles for scouting or construction.

A mission reliability estimation method has been designed to translate mission requirements into choices of robot modules in order to configure a multi-robot team to have high reliability at minimal cost. In order to build cost- effective robot teams for long-term missions, one must be able to compare alternative design paradigms in a principled way by comparing the reliability of different robot models and robot team configurations. Core modules have been created including: a probabilistic module with reliability-cost characteristics, a method for combining the characteristics of multiple modules to determine an overall reliability-cost characteristic, and a method for the generation of legitimate module combinations based on mission specifications and the selection of the best of the resulting combinations from a cost-reliability standpoint.

Posted in: Briefs, TSP, Information Sciences, Mathematical analysis, Fleet management, Cost analysis, Robotics, Reliability

Algorithm for Stabilizing a POD-Based Dynamical System

This algorithm provides a new way to improve the accuracy and asymptotic behavior of a low-dimensional system based on the proper orthogonal decomposition (POD). Given a data set representing the evolution of a system of partial differential equations (PDEs), such as the Navier-Stokes equations for incompressible flow, one may obtain a low-dimensional model in the form of ordinary differential equations (ODEs) that should model the dynamics of the flow. Temporal sampling of the direct numerical simulation of the PDEs produces a spatial time series. The POD extracts the temporal and spatial eigen-functions of this data set. Truncated to retain only the most energetic modes followed by Galerkin projection of these modes onto the PDEs obtains a dynamical system of ordinary differential equations for the time-dependent behavior of the flow.

Posted in: Briefs, Information Sciences, Computational fluid dynamics, Mathematical analysis, Mathematical models

Parameterizing Coefficients of a POD-Based Dynamical System

This parameterization enables accurate prediction of temporal evolution of certain flow dynamics.

A method of parameterizing the coefficients of a dynamical system based of a proper orthogonal decomposition (POD) representing the flow dynamics of a viscous fluid has been introduced. (A brief description of POD is presented in the immediately preceding article.) The present parameterization method is intended to enable construction of the dynamical system to accurately represent the temporal evolution of the flow dynamics over a range of Reynolds numbers.

Posted in: Briefs, Information Sciences, Computational fluid dynamics, Mathematical models

Confidence-Based Feature Acquisition

Selective acquisition of data values enables higher classification performance at lower cost.

Confidence-based Feature Acquisition (CFA) is a novel, supervised learning method for acquiring missing feature values when there is missing data at both training (learning) and test (deployment) time. To train a machine learning classifier, data is encoded with a series of input features describing each item. In some applications, the training data may have missing values for some of the features, which can be acquired at a given cost. A relevant JPL example is that of the Mars rover exploration in which the features are obtained from a variety of different instruments, with different power consumption and integration time costs. The challenge is to decide which features will lead to increased classification performance and are therefore worth acquiring (paying the cost).

Posted in: Briefs, Information Sciences, Artificial intelligence, Cost analysis

Universal Decoder for PPM of any Order

Complexity can be reduced and flexibility increased, at small cost in performance.

A recently developed algorithm for demodulation and decoding of a pulse-position-modulation (PPM) signal is suitable as a basis for designing a single hardware decoding apparatus to be capable of handling any PPM order. Hence, this algorithm offers advantages of greater flexibility and lower cost, in comparison with prior such algorithms, which necessitate the use of a distinct hardware implementation for each PPM order. In addition, in comparison with the prior algorithms, the present algorithm entails less complexity in decoding at large orders.

Posted in: Briefs, Information Sciences, Mathematical models, Computer software and hardware, Cryptography

Metal Vapor Arcing Risk Assessment Tool

The Tin Whisker Metal Vapor Arcing Risk Assessment Tool has been designed to evaluate the risk of metal vapor arcing and to help facilitate a decision toward a researched risk disposition. Users can evaluate a system without having to open up the hardware. This process allows for investigating components at risk rather than spending time and money analyzing every component. The tool points to a risk level and provides direction for appropriate action and documentation.

Posted in: Briefs, Information Sciences, CAD, CAM, and CAE, Metals, Refractory materials, Reliability, Risk assessments

Constant-Differential-Pressure Two-Fluid Accumulator

An improved design does not rely on the spring rate of the accumulator tank.

A two-fluid accumulator has been designed, built, and demonstrated to provide an acceptably close approximation to constant differential static pressure between two fluids over the full ranges of (1) accumulator stroke, (2) rates of flow of the fluids, and (3) common static pressure applied to the fluids. Prior differential-pressure two-fluid accumulators are generally not capable of maintaining acceptably close approximations to constant differential pressures.

Posted in: Briefs, Manufacturing & Prototyping, Springs, Containers, Pumps

Large Cell Ultracapacitors

Maxwell Technologies Inc. (San Diego, CA) has introduced its new K2 series large cell BOOSTCAP ultracapacitors. About the size of a soda can, the K2 series BOOSTCAP cells operate at 2.7 volts and incorporate design and construction enhancements for high performance, durability, and a long operating lifetime.

Posted in: GDM, Products, Products, Energy, Energy Efficiency, Energy Storage, Renewable Energy, Transportation

The U.S. Government does not endorse any commercial product, process, or activity identified on this web site.