Briefs : Information Technology
Improved Design of Adaptive Feedforward Tracking Systems

An improved method of analysis and design offers the potential to enhance the performances of adaptive feedforward tracking systems. The method can, in principle, make it possible to increase such performance measures as rates of convergence and noise-cancellation ratios, without need for...

Briefs : Mechanical & Fluid Systems
Flexible Actuators for Small, Mobile, Special-Purpose Robots

A report discusses flexible microactuators for a proposed generation of small, mobile, special-purpose robots. Aspects of this topic were discussed in two previous articles in NASA Tech Briefs: "Thin-Film, Light-Energized Bimorph Micromechanical Actuators" (NPO-19607), Vol. 20, No. 8...

Briefs : Electronics & Computers
Sight-to-Touch Translator

The sight-to-touch translator (ST3) is a conceptual electronic apparatus that would generate a tactile representation of visible objects in its vicinity. The ST3 would be worn by a blind person; the tactile display would help the wearer to visualize nearby obstacles and act to avoid them. Thus,...

Briefs : Software
Software for Tooth-Contact Analysis of Spiral Bevel Gears

The SBGTAPER computer program implements a method for design and generation of spiral bevel gears that feature tapered teeth with localized bearing contact and a low level of transmission errors. The influence of misalignment on transmission errors and shift of bearing contact were...

Briefs : Information Technology
Expressing Object-Oriented Concepts in Fortran 90

A methodology for object-oriented programming in Fortran 90 has been developed. The methodology provides for emulation of the most important object-oriented concepts of C++; namely, classes (including abstract data types, encapsulation, and function overloading), inheritance, and dynamic...

Briefs : Mechanical & Fluid Systems
Gas Buffer Seal

The figure presents a simplified view of a shaft seal that provides a small flow of neutral buffer gas to prevent contact between different gases contained in two adjacent regions along the shaft. In the original application, the shaft couples a hydrogen-burning turbine with a high-pressure oxygen pump, and helium is used as the...

Briefs : Electronics & Computers
Optical Horizontal-Displacement Sensors for Crane Payloads

Sensors made largely of commercially available optical and electronic components are being developed for use in measuring small horizontal displacements of payloads suspended below cranes at the ends of nominally vertical cables. The outputs of these sensors would be used in...

Briefs : Physical Sciences
Equations of State for Fluid Mixtures at High Pressures

A method that includes the use of modified equations of state has been developed to enable noniterative, efficient computation of the thermodynamic behaviors of gases and liquids at temperatures >100 K and pressures from 1 to 100 MPa. The method is intended to be particularly useful for...

Briefs : Materials
Coating SiC Fiber Tows With Polymer/Silicon Slurries

The figure schematically illustrates an apparatus and process in which a continuous tow of silicon carbide fibers is coated and infiltrated with a polymer/silicon slurry. A compact of such coated, infiltrated fiber tows is subsequently heated to a temperature > 1,200 °C in nitrogen to...

Briefs : Manufacturing & Prototyping
Removable Fillers for VPS Fabrication of Closed Channels

An improved process has been devised for making closed channels (e.g., coolant channels) in a heat-exchanger liner or a similar metal object. The process involves the following steps: First, grooves destined to become closed channels are machined into the object from one surface. Next, a...

Briefs : Mechanical & Fluid Systems
Latch-Release Pin Puller With Shape-Memory-Alloy Actuator

The figure illustrates one of several related pin-puller mechanisms that harness the recovery characteristics of a shape-memory alloy (SMA). Like some other SMA-actuated mechanisms described previously in NASA Tech Briefs, this pin puller is suitable for use in place of a pyrotechnically...

Briefs : Electronics & Computers
Coplanar-Stripline Transition and Band-Stop Filters

Three coplanar-stripline circuits have been designed to perform coupling and filtering functions in microwave systems. These circuits could be incorporated into feed networks for microwave antennas, for example. One of the circuits comprises two back-to-back coplanar-strip-to-microstrip...

Briefs : Electronics & Computers
Transmitting Data Signals via Fiber-Optic Power Lines

Data signals can be transmitted via the same optical fibers that are used to transmit power from base stations to remote stations containing sensors and associated circuitry. [A prototype system based on fiber-optic transmission of data and power is described in "General-Purpose Optically...

Briefs : Physical Sciences
Oscillating-Flow Heat-Transfer and Pressure-Drop Test Rig

The figure illustrates an apparatus for measuring heat-transfer and pressure-drop characteristics of porous plug specimens in oscillating flows. The apparatus is built around an oscillating-flow test rig that was originally designed for pressure-drop (but not heat-transfer) measurements...

Briefs : Materials
Testing Corrosion Prevention in Reinforced Concrete

An accelerated-testing method has been developed for evaluating the effectiveness of various measures taken to prevent the corrosion of steel reinforcing bars ("rebars") cast into concrete. Such measures can include chemical admixtures incorporated into the concrete, coatings, penetrants,...

Briefs : Medical
Compact, Noncontact Fiber-Optic Probe for Diagnosis of Eye Diseases

A compact fiber-optic probe has been found to be useful for noncontact diagnosis of interior parts of eyes. The probe was originally developed for performing dynamic-light-scattering measurements to determine transport properties of submicron particles suspended in fluids in...

Briefs : Photonics/Optics
Multicolor Transceiver for Optoelectronic Communication

A great increase in the effectiveness of fiber optic systems is possible with a device that allows for simultaneous two-way signalling of multiple data streams on a single optical fiber. By using a highly efficient multijunction solar cell to emit as well as detect two or more distinct...

Briefs : Physical Sciences
Generalized Mathematical Model of Pyrolysis of Biomass

A generalized mathematical model has been devised for use in analyzing the pyrolysis of arbitrarily specified (but typical) biomass feedstocks at atmospheric pressure. The model represents both the microparticle (kinetically controlled) and macroparticle (diffusion-limited) types of...

Briefs : Mechanical & Fluid Systems
Wheel Drive of Mars Rover

A brief report summarizes the design of the lightweight, high-torque wheel drive of a small robotic vehicle used to explore the surface of Mars. Planetary gearing was selected for compactness and high torque capability. The input stages were fitted with ball bearings to survive the cold (down to -100 °C) Martian...

Briefs : Electronics & Computers
Antiovershoot Position Control for Motors Run at Full Speed

An improved motor controller provides a circuit that will allow a motor to run at full speed while traveling from point A to point B, and still be able to obtain the desired damping coefficient when reaching point B. Previously, a motor would overshoot its desired stopping point when...

Briefs : Motion Control
Precision Actuator Positions Laser Grating

The tunable external cavity diode laser is an important new tool used to evaluate and test the latest fiber-optic components and building blocks of modern telecommunications systems. A key factor enabling operation of this type of laser is the ability to angle-tune the wavelength-dependent key component...

Briefs : Materials
Highly Selective Gas-Phase Etching of Silicon

A technique of gentle, highly selective gas-phase etching of silicon has been devised to enable the fabrication of microelectromechanical devices integrated with electronic circuits. For example, newly fabricated complementary metal oxide/semiconductor (CMOS) integrated-circuit chips can be...

Briefs : Materials
High-Performance Thermal Insulation for a Racing Car

Thermal-insulation blankets developed for use aboard the space shuttle can be adapted to a racing car to protect the driver against excessive cockpit heating. [Also see an earlier article under "Mission Accomplished," NASA Tech Briefs, Vol. 20, No. 8 (August 1996) page 20.] Thermal protection...

Briefs : Electronics & Computers
Signaling-and-Detection Scheme for Beacon Monitoring

A signaling-and-detection scheme has been proposed for use in conjunction with the remote-monitoring concept described in "Beacon Monitoring Would Reduce Interactions With Remote Systems" (NPO-19706), NASA Tech Briefs, Vol. 21, No. 5 (May 1997), page 54. To recapitulate: A remote system (a...

Briefs : Robotics, Automation & Control
Manipulator System for a Robotic Vehicle

A prototype manipulator system that includes two different arms has been tentatively selected for use on a semiautonomous robotic vehicle called Rocky 7 (see figure). [A previous version of this vehicle with a single manipulator arm was described in "High-Performance Robotic Vehicle" (NPO-19921) NASA Tech...

Briefs : Physical Sciences
Automated Window Inspection Device

The Automated Window Inspection Device (AWID) is a prototype apparatus for computer-controlled, noncontact inspection of windows, with reproducible positioning and electronic recording of data on the locations, sizes, and depths of flaws. The AWID was developed to accelerate and facilitate (1) postflight...

Briefs : Photonics/Optics
Multimode Optical Fiber as Imaging Probe

A proposed electro-optical image-processing system would enable remote viewing of an object through a multimode optical fiber, as though the fiber were a conventional image-transmitting optic like a lens or prism. Ordinarily, it would be impractical to use a multimode optical fiber as an imaging probe or...

Briefs : Mechanical & Fluid Systems
High-Wind Masts for Meteorological Instruments

Rigid, guyed masts of a proposed type for supporting meteorological instruments would be designed to withstand considerably stronger winds than those conventionally used. The proposed fairings would also help minimize perturbations of airflows and thereby minimize the contaminating effects of the...

Briefs : Physical Sciences
Mathematical Model of Pyrolysis of Biomass Particles

A mathematical model of a special class of solid/fluid chemical reactions has been developed for use in analyzing the pyrolysis of particles of cellulose, wood, and similar biomass materials. Although it involves some simplifying assumptions (as do all models of chemical and physical...

Briefs : Physical Sciences
Mathematical Model of a Direct-Contact Pyrolysis Reactor

A mathematical model has been developed for use in assessing the performances of direct-contact pyrolysis reactors used to convert particles of raw biomass materials (usually small wood chips) into char, tar, and gas. The optimal designs are here considered to be those that maximize the...

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