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Fabricating Composite-Material Structures Containing SMA Ribbons

Repeatable, predictable structures can be fabricated. An improved method of designing and fabricating laminated composite-material (matrix/fiber) structures containing embedded shape-memory-alloy (SMA) actuators has been devised. Structures made by this method have repeatable, predictable properties, and fabrication processes can readily be automated.

Posted in: Manufacturing & Prototyping, Briefs, TSP

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Pressure-Sensor Assembly Technique

An essential underfilling step can be performed without compromising a diaphragm. Nielsen Engineering & Research (NEAR) recently developed an ultrathin data acquisition system for use in turbomachinery testing at NASA Glenn Research Center. This system integrates a microelectro- mechanical-systems- (MEMS-) based absolute pressure sensor [0 to 50 psia (0 to 345 kPa)], temperature sensor, signal-conditioning application-specific integrated circuit (ASIC), microprocessor, and digital memory into a package which is roughly 2.8 in. (7.1 cm) long by 0.75 in. (1.9 cm) wide. Each of these components is flip-chip attached to a thin, flexible circuit board and subsequently ground and polished to achieve a total system thickness of 0.006 in. (0.15 mm). Because this instrument is so thin, it can be quickly adhered to any surface of interest where data can be collected without disrupting the flow being investigated.

Posted in: Manufacturing & Prototyping, Briefs

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Wafer-Level Membrane-Transfer Process for Fabricating MEMS

This process is well suited for structures fabricated on dissimilar substrates. A process for transferring an entire wafer-level micromachined silicon structure for mating with and bonding to another such structure has been devised. This process is intended especially for use in wafer-level integration of microelectro- mechanical systems (MEMS) that have been fabricated on dissimilar substrates.

Posted in: Manufacturing & Prototyping, Briefs, TSP

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A Reactive-Ion Etch for Patterning Piezoelectric Thin Film

Gaseous mixtures BCl3 and Cl2 are highly selective for etching PbZr1-xTixO3 films. Reactive-ion etching (RIE) under conditions described below has been found to be a suitable means for patterning piezoelectric thin films made from such materials as PbZr1-xTixO3 or BaxSr1-xTiO3. In the original application for which this particular RIE process was developed, PbZr1-xTixO3 films 0.5 μm thick are to be sandwiched between Pt electrode layers 0.1 µm thick and Ir electrode layers 0.1 μm thick to form piezoelectric capacitor structures. Such structures are typical of piezoelectric actuators in advanced microelectromechanical systems now under development or planned to be developed in the near future.

Posted in: Manufacturing & Prototyping, Briefs, TSP

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Numerical Modeling of Nanoelectronic Devices

Nanoelectronic Modeling 3-D (NEMO 3-D) is a computer program for numerical modeling of the electronic structure properties of a semiconductor device that is embodied in a crystal containing as many as 16 million atoms in an arbitrary configuration and that has overall dimensions of the order of tens of nanometers. The underlying mathematical model represents the quantum-mechanical behavior of the device resolved to the atomistic level of granularity. The system of electrons in the device is represented by a sparse Hamiltonian matrix that contains hundreds of millions of terms. NEMO 3-D solves the matrix equation on a Beowulf-class cluster computer, by use of a parallel-processing matrix×vector multiplication algorithm coupled to a Lanczos and/or Rayleigh-Ritz algorithm that solves for eigenvalues. In a recent update of NEMO 3-D, a new strain treatment, parameterized for bulk material properties of GaAs and InAs, was developed for two tight-binding submodels. The utility of the NEMO 3-D was demonstrated in an atomistic analysis of the effects of disorder in alloys and, in particular, in bulk InxGal–xAs and in In0.6Ga0.4As quantum dots.

Posted in: Software, Briefs, TSP

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Advances in Thrust-Based Emergency Control of an Airplane

It should be possible to land safely after a primary-flight-control failure. Engineers at NASA's Dryden Flight Research Center have received a patent on an emergency flight-control method implemented by a propulsion-controlled aircraft (PCA) system. Utilizing the pre-existing auto-throttle and engine-pressure-ratio trim controls of the airplane, the PCA system provides pitch and roll control for landing an airplane safely without using aerodynamic control surfaces that have ceased to function because of a primary-flight- control-system failure. The installation of the PCA does not entail any changes in pre-existing engine hardware or software. [Aspects of the method and system at previous stages of development were reported in "Thrust-Control System for Emergency Control of an Airplane" (DRC-96-07), NASA Tech Briefs, Vol. 25, No. 3 (March 2001), page 68 and "Emergency Landing Using Thrust Control and Shift of Weight" (DRC-96-55), NASA Tech Briefs, Vol. 26, No. 5 (May 2002), page 58.]

Posted in: Mechanical Components, Briefs, TSP

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Ultrasonic/Sonic Mechanisms for Drilling and Coring

These mechanisms imitate burrowing actions of gophers and crabs. Two apparatuses now under development are intended to perform a variety of deep-drilling, coring, and sensing functions for subsurface exploration of rock and soil. These are modified versions of the apparatuses described in "Ultrasonic/Sonic Drill/Corers With Integrated Sensors" (), NASA Tech Briefs, Vol. 25, No. 1 (January 2001), page 38. In comparison with the drilling equipment traditionally used in such exploration, these apparatuses weigh less and consume less power. Moreover, unlike traditional drills and corers, these apparatuses function without need for large externally applied axial forces.

Posted in: Mechanical Components, Briefs, TSP

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