Tech Briefs

Rapid Development of Process Control Systems Using a Model-Based Approach

Developing an effective control system requires creation of an accurate, system-specific model. Developing a control system rapidly and cost effectively requires a disciplined approach that exposes design limitations early so they can be corrected before the costs and schedule go out of control. A trial-and-error development approach is utilized primarily when the control system is presumed to be simple or when there is insufficient time to conduct a full development cycle. This approach is characterized by a relatively small investment in up-front planning, followed by multiple iterations of build and test.

Posted in: Briefs, Physical Sciences, CAD, CAM, and CAE, Electronic control systems, Product development

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Promoted-Combustion Chamber With Induction Heating Coil

Tests can be done at temperature and pressure combinations not previously attainable. An improved promoted-combustion system has been developed for studying the effects of elevated temperatures on the flammability of metals in pure oxygen. In prior promoted-combustion chambers, initial temperatures of metal specimens in experiments have been limited to the temperatures of gas supplies, usually near room temperature. Although limited elevated temperature promoted- combustion chambers have been developed using watercooled induction coils for preheating specimens, these designs have been limited to low-pressure operation due to the hollow induction coil. In contrast, the improved promoted-combustion chamber can sustain a pressure up to 10 kpsi (69 MPa) and, through utilization of a solid induction coil, is capable of preheating a metal specimen up to its melting point [potentially in excess of 2,000 °F (≈1,100 °C)]. Hence, the improved promoted-combustion chamber makes a greater range of physical conditions and material properties accessible for experimentation.

Posted in: Briefs, Physical Sciences, Metals, Oxygen, Combustion and combustion processes, Test procedures, Thermal testing

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Thermal Spore Exposure Vessels

Thermal masses are minimized to enable rapid heating and cooling. Thermal spore exposure vessels (TSEVs) are laboratory containers designed for use in measuring rates of death or survival of microbial spores at elevated temperatures. A major consideration in the design of a TSEV is minimizing thermal mass in order to minimize heating and cooling times. This is necessary in order to minimize the number of microbes killed before and after exposure at the test temperature, so that the results of the test accurately reflect the effect of the test temperature.

Posted in: Briefs, TSP, Bio-Medical, Medical, Bacteria, Containers, Test equipment and instrumentation, Thermal testing

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Enumerating Spore-Forming Bacteria Airborne With Particles

Complementary data are obtained by use of two instruments and correlated. A laboratory method has been conceived to enable the enumeration of: Cultivable bacteria and bacterial spores that are, variously, airborne by themselves or carried by, parts of, or otherwise associated with, other airborne particles; and Spore-forming bacteria among all of the aforementioned cultivable microbes.

Posted in: Briefs, TSP, Bio-Medical, Medical, Measurements, Particulate matter (PM), Bacteria, Test procedures

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Sequence Detection for PPM Optical Communication With ISI

Inter-symbol interference could be reduced. A method of sequence detection has been proposed to mitigate the effects of inter-slot interference and inter-symbol interference (both denoted “ISI”) in the reception of M-ary pulse-position modulation (PPM) optical signals. The method would make it possible to reduce the error rate for a given slot duration, to use a shorter slot duration (and, hence, to communicate at a higher rate) without exceeding a given error rate, or to use a lower-bandwidth (and, hence, less-expensive) receiver to receive a signal of a given slot width without exceeding a given error rate.

Posted in: Briefs, TSP, Information Sciences, Mathematical models, Architecture, Wireless communication systems

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Algorithm for Rapid Searching Among Star-Catalog Entries

Recursive algorithm utilizes precompiled search structure of spherical coverings. An algorithm searches a star catalog to identify guide stars within the field of view of a telescope or camera. The algorithm is fast: the number of computations needed to perform the search is approximately proportional to the logarithm of the number of stars in the catalog.

Posted in: Briefs, TSP, Information Sciences, Mathematical models, Optics, Identification

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Expectation-Based Control of Noise and Chaos

A proposed approach to control of noise and chaos in dynamic systems would supplement conventional methods. The approach is based on fictitious forces composed of expectations governed by Fokker-Planck or Liouville equations that describe the evolution of the probability densities of the controlled parameters. These forces would be utilized as feedback control forces that would suppress the undesired diffusion of the controlled parameters. Examples of dynamic systems in which the approach is expected to prove beneficial include spacecraft, electronic systems, and coupled lasers.

Posted in: Briefs, TSP, Information Sciences, Adaptive control, Electronic equipment, Lasers, Systems engineering, Noise, Spacecraft

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