Special Coverage

Transducer-Actuator Systems for On-Machine Measurements and Automatic Part Alignment
Wide-Area Surveillance Using HD LWIR Uncooled Sensors
Heavy Lift Wing in Ground (WIG) Cargo Flying Boat
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

Thermally Driven Josephson Effect

A concept is proposed of the thermally driven Josephson effect in superfluid helium. Heretofore, the Josephson effect in a superfluid has been recognized as an oscillatory flow that arises in response to a steady pressure difference between two superfluid reservoirs separated by an array of submicron-sized orifices, which act in unison as a single Josephson junction. Analogously, the thermally driven Josephson effect is an oscillatory flow that arises in response to a steady temperature difference.

Posted in: Briefs, Physical Sciences, Computational fluid dynamics, Thermodynamics, Thermodynamics, Gases

Determining Concentration of Nanoparticles From Ellipsometry

Counting of particles is not necessary.

A method of using ellipsometry or polarization analysis of light in total internal reflection of a surface to determine the number density of gold nanoparticles on a smooth substrate has been developed. The method can be modified to enable determination of densities of sparse distributions of nanoparticles in general, and is expected to be especially useful for measuring gold-nanoparticle-labeled biomolecules on microarrays.

Posted in: Briefs, Physical Sciences, Nanomaterials

Gold Nanoparticle Labels Amplify Ellipsometric Signals

The ellipsometric method reported in the immediately preceding article was developed in conjunction with a method of using gold nanoparticles as labels on biomolecules that one seeks to detect. The purpose of the labeling is to exploit the optical properties of the gold nanoparticles in order to amplify the measurable ellipsometric effects and thereby to enable ultrasensitive detection of the labeled biomolecules without need to develop more-complex ellipsometric instrumentation.

Posted in: Briefs, Physical Sciences, Amplifiers, Amplifiers, Biomaterials, Materials identification

Perturbation Effects on a Supercritical C₇H₁₆/N₂ Mixing Layer

This report presents a computational-simulation study of effects of perturbation wavelengths and initial Reynolds numbers on the transition to turbulence of a heptane/nitrogen mixing layer at supercritical pressure. The governing equations for the simulations were the same as those of related prior studies reported in NASA Tech Briefs. Two-dimensional (2D) simulations were performed with initially imposed spanwise perturbations whereas three-dimensional (3D) simulations had both streamwise and spanwise initial perturbations.

Posted in: Briefs, Physical Sciences, Computational fluid dynamics, Spacecraft fuel, Turbulence

Schema for Spacecraft-Command Dictionary

An Extensible Markup Language (XML) schema was developed as a means of defining and describing a structure for capturing spacecraft command-definition and tracking information in a single location in a form readable by both engineers and software used to generate software for flight and ground systems. A structure defined within this schema is then used as the basis for creating an XML file that contains command definitions. The schema is divided into three sections:

Posted in: Briefs, Information Sciences, Computer software / hardware, Computer software and hardware, Computer software / hardware, Computer software and hardware, Terminology, Spacecraft

Self-Adjusting Hash Tables for Embedded Flight Applications

A common practice in computer science to associate a value with a key is to use a class of algorithms called a hash-table. These algorithms enable rapid storage and retrieval of values based upon a key. This approach assumes that many keys will need to be stored immediately. A new set of hash-table algorithms optimally uses system resources to ideally represent keys and values in memory such that the information can be stored and retrieved with a minimal amount of time and space. These hash-tables support the efficient addition of new entries. Also, for large data sets, the look-up time for large data-set searches is independent of the number of items stored, i.e., O(1), provided that the chance of collision is low.

Posted in: Briefs, TSP, Information Sciences, Embedded software, Embedded software

Efficient Algorithm for Rectangular Spiral Search

The search pattern is automatically expanded as needed.

An algorithm generates grid coordinates for a computationally efficient spiral search pattern covering an uncertain rectangular area spanned by a coordinate grid. The algorithm does not require that the grid be fixed; the algorithm can search indefinitely, expanding the grid and spiral, as needed, until the target of the search is found. The algorithm also does not require memory of coordinates of previous points on the spiral to generate the current point on the spiral.

Posted in: Briefs, Information Sciences, Mathematical models, Surveillance, Surveillance

Algorithm-Based Fault Tolerance Integrated With Replication

In a proposed approach to programming and utilization of commercial off-the-shelf computing equipment, a combination of algorithm-based fault tolerance (ABFT) and replication would be utilized to obtain high degrees of fault tolerance without incurring excessive costs. The basic idea of the proposed approach is to integrate ABFT with replication such that the algorithmic portions of computations would be protected by ABFT, and the logical portions by replication.

Posted in: Briefs, Information Sciences, Failure analysis, Mathematical models, Computer software / hardware, Computer software and hardware, Computer software / hardware, Computer software and hardware

Targeting and Localization for Mars Rover Operations

A design and a partially developed application framework were presented for improving localization and targeting for surface spacecraft. The program has value for the Mars Science Laboratory mission, and has been delivered to support the Mars Exploration Rovers as part of the latest version of the Maestro science planning tool. It also has applications for future missions involving either surface-based or low-altitude atmospheric robotic vehicles.

Posted in: Briefs, Information Sciences, Architecture, Architecture, Ground vehicle operations, Robotics, Spacecraft

Terrain-Adaptive Navigation Architecture

A navigation system designed for a Mars rover has been designed to deal with rough terrain and/or potential slip when evaluating and executing paths. The system also can be used for any off-road, autonomous vehicles. The system uses more sophisticated terrain analysis, but also converges to computational complexity similar to that of currently deployed navigation systems when the terrain is benign. The system consists of technologies that have been developed, integrated, and tested onboard research rovers in Mars analog terrains, including goodness maps and terrain triage, terrain classification, remote slip prediction, path planning, high-fidelity traversability analysis (HFTA), and slip-compensated path following.

Posted in: Briefs, Information Sciences, Adaptive control, Adaptive control, Terrain, Ground vehicle operations, Spacecraft

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