MEMs

Mechanical Response of an Al-PTFE Composite to Uniaxial Compression Over a Range of Strain Rates and Temperatures

Reactive materials can be loosely categorized as composites of inert solid materials which, when subjected to a violent mechanical stimulus such as an impact, react exothermally with a rapid release of energy. This reaction, while aptly described as “explosive,” differs from a true detonation or deflagration in that it requires a mechanical stimulus to not only initiate the reaction but also to sustain it. Such materials can also be fairly robust mechanically and can serve as substantial structural components. Because of these properties, reactive materials have a number of potential ordnance applications. Various compositions have been investigated to tailor properties of reactivity, strength, and density to suit particular needs.

Posted in: Briefs, Materials, Composite materials, Materials identification, Materials properties, Impact tests, Thermal testing
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Novel Conductive Coatings of Carbon Nanotubes

Carbon nanotubes (CNTs) are the material of ever-increasing concern due to their excellent electronic and physicochemical properties. Currently, research has been focused towards their applications for use in chemical and biological sensors as well as their use in optoelectronic devices. One of the major challenges is the construction of flexible electronic devices.

Posted in: Briefs, Materials
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Water Mist System for Shipboard Machinery Space Fires

Water mist has been determined to be a preferred alternative to Halon 1301 total flooding to extinguish fires occurring in ship machinery spaces and pump rooms, because it is toxicologically and physiologically inert. Water mist systems produce a drop size distribution with a range of drop sizes under 1000 μm, while the more conventional sprinkler systems produce much coarser particles. The smaller particle sizes have greater cooling efficiencies because evaporation and cooling are controlled by surface area, and the surface area of a large number of small droplets is greater than that of a small number of large droplets of the same total volume.

Posted in: Briefs, Mechanical Components
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Axial Field Electric Motor

An axial field electric motor comprises one or more elements such as a rotor mounted for rotation and multiple axial flux permanent magnets carried by the rotor. The axial flux permanent magnets are oriented such that an associated magnetic flux produced thereby is at least substantially axially oriented. The axial flux permanent magnets are positioned around the rotor with alternating orientations of flux direction so that a flux direction of adjacent magnets is at least substantially axially oriented but opposite in direction. The radial flux permanent magnets are also carried by the rotor and oriented so that an associated magnetic flux produced is at least substantially radially oriented.

Posted in: Briefs, Mechanical Components
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Miniature Rotorcraft Flight Control Stabilization System

Autonomous rotorcraft provide improved capability in performing military missions such as reconnaissance, targeting, border patrol, and environmental sensing. A common difficulty in applying miniature rotorcraft to these areas is the complexity and specialization of the control. In general, rotorcraft have extreme vibration that make miniature inertial measurement difficult. Sources of vibration include the main rotor, tail rotor, and blade flapping dynamics. Typical sensors include MEMS accelerometers, which are sensitive to vibration. Inclusion of alternative and or redundant sensors may be used to reduce vibration sensitivity and add useful additional feedback.

Posted in: Briefs, Physical Sciences
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Studies of Dynamic Fracture in Brittle Materials

A program of research spanning several years ending in November 2005 was dedicated primarily to formulation and analysis of canonical boundary- value problems in mathematical modeling of dynamic fracture in brittle materials. The sub-topics within the broad topic of dynamic fracture in brittle materials that were studied, and the accomplishments in each sub-topic, are summarized as follows:

Posted in: Briefs, Physical Sciences
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Acceleration Strain Transducer Containing Cantilever Flaps

A recently invented acceleration strain transducer is based on the principle of a conventional spring-and-mass acceleration transducer combined with a linear strain sensor that measures the acceleration-induced deflection of the spring. The invention is compatible with any of a variety of linear strain sensors, including conventional foil resistance strain gauges, fiber-optic and fiber-laser strain sensors, and electrically-conductive-liquid strain sensors.

Posted in: Briefs, Physical Sciences
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Simulation of Airflow Through a Test Chamber

A computational-simulation study of the flow of air through a thermo-anemometer chamber was performed to resolve what originally seemed to be an anomaly in the measurement data obtained by use of the chamber. The thermo-anemometer chamber is a test chamber used to measure the rate of generation of heat by a device placed within it. In the original application that produced the apparent anomaly that prompted this study, the chamber was used to measure the power dissipation (as manifested by heating) in an operating power-supply inductor. The apparent anomaly was that the heating of the inductor as calculated from the measurements made by use of the chamber seemed unrealistically high.

Posted in: Briefs, Physical Sciences
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Study of Submodeling of a Small Component in a Structure

A study was performed to evaluate the accuracy achievable in the use of submodeling in finite-element modeling of the mechanical response of a structural system that includes components embedded in a larger structure that is subjected to a large transient load. The specific system studied was a simplified model of a “smart” projectile containing a substructure that supported an electronic-circuit board on which were mounted two capacitors and an eight-lead integrated circuit (see figure). The main body or shell of the projectile was represented as a cylindrical ring supporting the substructure. The dimensions of the various components were chosen to be typical of “smart” munitions. The transient load condition was represented by a velocity-versus-time boundary condition, typical of the velocity versus time of a projectile at launch, imposed at the lower surface of the cylindrical ring.

Posted in: Briefs, Information Technology
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Next-Generation Information Systems Architectures

A document describes a paradigm in which low-altitude unmanned aerial vehicles (UAVs) with wireless communication capability are used to assist networking among a set of ground stations. This new paradigm is attractive because UAVs can be dynamically deployed in a wide variety of geographical territories. Furthermore, UAVs often have high-quality line-of-sight communication links with other UAVs, and ground stations as aerial links usually suffer relatively little shadowing compared with their terrestrial counterparts.

Posted in: Briefs, Information Technology
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