Physical Sciences

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:

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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.

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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.

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Characterization of a MEMS Directional Sound Sensor

There is a wide range of potential military applications in which ambiguity in bearing occurs with respect to sound. For example, autonomous unmanned aerial vehicles (UAVs) could employ a sensor to determine the bearing of an explosion and conduct battle damage assessment (BDA) on it. With existing sensors this is difficult to do because the explosion is too short in duration to use the Doppler effect to determine the bearing. Also, an autonomous underwater vehicle (AUV) acting as a quiet platform to tow a short, omni-directional hydrophone array must contend with bearing ambiguity.

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Two-Camera Imaging System for Kinematic Measurements

A high-speed imaging system has been devised as a noninvasive means of collecting data on the kinematics of working models of developmental underwater or aerial vehicles that would utilize flapping fins or flapping wings for propulsion. The system includes two high-speed digital electronic cameras aimed along orthogonal axes that acquire snapshots of a model simultaneously in rapid succession. The data from successive images are postprocessed to obtain three-dimensional coordinates of points of interest on the model as functions of time. In the case of a flapping appendage, the points of interest are tips on the appendage, and the temporal evolution of the tip coordinates through multiple flapping cycles is utilized, in conjunction with computational fluid dynamics and other analytical tools, in an iterative process of testing and design directed toward improving the swimming or flying performance of the model. The system can, of course, be used as a noninvasive means of kinematic testing of models other than those of vehicles utilizing flapping appendages.

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Synthesizing Pseudo-Finer-Resolution MODIS Data Products

A document discusses a methodology for synthesizing finerresolution data products from outputs of the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments aboard NASA's Terra and Aqua satellites. Typical MODIS ocean color data have 1-km resolution, but those in five wavelength bands have 500-m resolution and those in two wavelength bands have 250-m resolution. Finer-resolution bio-optical-property data products improve our capability for monitoring coastal ocean and estuarine processes.

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Nanostructured Ferromagnetic-Wire/Insulator Composites

A research and development effort now in progress is focused on nano-structured ferromagnetic- wire/insulator composite materials to be used as the magnetic-core materials of sensors for measuring weak magnetic fields. Figure 1 schematically depicts an example of such a sensor — a flux-gate magnetometer that resembles a traditional orthogonal flux-gate magnetometer except that, instead of a single cylindrical ferromagnetic core, there are multiple parallel ferromagnetic wire cores packed together with insulating material between them. An overriding consideration in the design, fabrication, and operation of such a magnetometer is that high effective magnetic permeability of the core is necessary as one of the prerequisites for obtaining high sensitivity.

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Robot Vision System for Precise Object Retrieval in Unmanned Systems

Automating large-scale material handling systems that involve picking up or retrieving items via cranes or robot arms can yield big benefits, particularly in harsh or hard-to-access environments. The Automatic Launch & Recovery System (AutoLARS) is being developed for the U.S. Navy by Allied Systems and Concept Systems. The Navy required a system for retrieving unmanned vessels and placing them aboard Navy ships. The problem is how to guide a robot that is affixed to a ship so that it can attach a line or fixture to an unmanned floating vehicle, and how to accomplish this while both are tossing at sea.

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Advanced Concepts for Space Access

A paper summarizes commonly proposed advanced launch concepts, including both concepts that employ propellant and propellant-less concepts. A wide range of advanced launch concepts have been proposed in an effort to revolutionize space access through either a significant reduction in launch costs or significant improvements in launch performance. These revolutionary concepts aren't necessarily required to be in the propulsion arena. For example, materials that can dramatically reduce the inert mass fraction will also aid in a launch vehicle's ability to place more payload into orbit with existing propulsion systems.

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Time-Coding of Asynchronous Data Transmissions

A method for providing a time code for multiple streams of simultaneously received data has been developed in order to allow reconstruction of the data after asynchronous transfer. It is often desirable to transmit data collected from a plurality of sensors. When the data is received, it is desirable that the original signal be reconstructed to have the same timing as the originally received data.

Posted in: Briefs, Physical Sciences, Data exchange, Data management, Identification
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