Physical Sciences

Tiger Fibers for Enhanced Optical Sensing of Volatiles

Striped polymer coats on optical fibers would induce gratings upon exposure to analytes. Improved fiber-optic transducers, denoted tiger fibers, have been proposed for sensing volatile compounds. Tiger fibers are so named because, as described below, their sensitive portions would be coated with periodically alternating stripes of different polymers, reminiscent of a tiger’s stripes.

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Using Laser Diodes to Characterize Force and Pressure Sensors

A proposed method of characterizing microphones and other pressure and force sensors would exploit the temporally varying forces of impingement of amplitude-modulated light beams from inexpensive laser diodes. What makes the method likely to be practical is the surprising fact that these forces, albeit small, are nevertheless large enough to enable quantification of the noise floors, sensitivities, and frequency responses of many modern pressure sensors. The time-averaged force of impingement of a pulsed beam of light on a surface is given by F = SDP/c, where S ranges from 1 for a totally absorptive (black) to 2 for a perfectly reflective surface, D is the pulse duty cycle, P is the peak power of the beam, and c is the speed of light. Hence, if one knows S, D, and P, it may be possible to determine the absolute sensitivity of the sensor. Even if one does not know one or more of these parameters, it should be possible to determine the relative sensitivities of different sensors by measuring their responses to the same modulated beam, or to determine the relative frequency response of a given sensor by measuring its output while sweeping the modulation frequency.

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Thermocouple Rakes for Measuring Boundary-Layer Flows

Flows can be measured extremely close to surfaces. Thin-film devices that comprise heaters in combination with thermocouples have been developed for measuring flow velocities extremely close to solid surfaces, at several distances from the surface of interest. Devices that perform this function are denoted generally as “boundary-layer rakes.” The measurement data acquired by boundary-layer rakes are needed for calculating viscous shear forces, for developing mathematical models of turbulence to be used in computational fluid dynamics, and as feedback in some flow-control systems.

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Boundary Conditions for Computing Flows of Real Gas Mixtures

It is possible to suppress errors that arise in a simplistic formulation. An improved formulation of equations of flow of a general gas mixture includes consistent boundary conditions that are applicable to real gases. An analysis of prior formulations, with focus on boundary conditions, led to the conclusion that boundary conditions based on ideal mixtures and/or perfect gases can lead to errors in computed flows of real gases. The improved formulation makes it possible to achieve greater accuracy in computation of flows of real (including chemically reactive) gas mixtures, and is expected to be especially beneficial in computing flows of supercritical fluids like those in diesel engines, gas turbine engines, rocket engines, supercritical-fluid extraction processes, and crude oil under high pressure.

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Seed-Wing Flyers for Exploration

Scientific instruments would be dispersed from aloft by use of miniature autogyros. Small instrumented, free-flying (unpowered) rotary aircraft have been proposed for use in gathering scientific data from hazardous or inaccessible terrain on remote planets as well as on Earth. These aircraft are called “seed-wing flyers” because they would resemble winged seeds (e.g., maple seeds) in both appearance and aerodynamic behavior.

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Long-Life Stratospheric Balloon System With Altitude Control

There would be no venting of helium or dropping of ballast. A proposed improved balloon system for carrying scientific instruments in the stratosphere would include a lightweight, ambient-pressure helium balloon and a vented infrared Montgolfiere (see figure). [An infrared Montgolfiere is an ambient-pressure warm-air balloon, named after the familiar fire-heated hot-air balloons invented by the Montgolfier brothers. An infrared Montgolfiere is heated primarily by the Sun during the day, and/or by infrared radiation from relatively warm surface of the Earth at night.] The system would feature controllability of altitude for taking scientific data, landing, or taking advantage of favorable winds for relocation. The system would be designed for long life, but would weigh less (and therefore cost less) than do previously developed long-life balloon systems.

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Direct Methanol Fuel Cells With Aerosol Feed

Relative to liquid feed, aerosol feed would result in less methanol crossover. Direct methanol fuel cells that would function with aerosol feed (instead of all-gas or all-liquid feed) have been proposed. As explained below, aerosol feed would afford the advantages of liquid feed, while reducing or eliminating some of the disadvantageous effects of liquid feed.

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