Engineering topics
Publications and source records attributed to Park, J..
We report preliminary results for the cosmogenic radionuclides, Cl-36, Al-26, and Be-10 and noble gases in a basaltic shergottite Dhofar 019. We found long terrestrial age of Dhofar 019 even though this meteorite was found in hot desert, Oman. Additional information is contained in the original extended abstract.
A method of optimal 3D viewing based on adaptive displays of stereo images is presented for advanced telemanipulation. The method provides the viewer with the capability of accurately observing a virtual 3D object or local scene of his/her choice with minimum distortion.
Analytical and experimental investigations into the control of noise in the interior of a three-dimensional enclosure with a flexible boundary are presented. The rigid boundaries are constructed from acrylic material, and in the different cases considered the flexible boundary is constructed from either aluminum or composite material. Noise generated by an external speaker is transmitted into the enclosure through the flexible boundary and active control is realized by using Lead Zirconate Titanate (PZT) piezoelectric actuators bonded to the flexible boundary. Condenser microphones are used for noise measurements inside and outside the enclosure. Minimization schemes for global and local noise control in the presence of a harmonic disturbance are developed and discussed. In the experiments, analog feedforward control is implemented by using the harmonic disturbance as a reference signal.
Long wavelength heterojunction internal photoemission infrared detectors have been successfully demonstrated utilizing the growth of degenerately boron doped layers.
Infrared detectors operating from mid IR wavelengths to very long wavelength IR are of great interest for a variety of ground based and space based applications such as night vision, early warning systems, navigation, flight control systems, weather monitoring, and astronomy.
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By incorporating a 1-nm-thick p+ doping spike at the PtSi/Si interface, we have successfullydemonstrated extended cutoff wavelengths of PtSi Schottky infrared detectors in the long wavelengthinfrared (LWIR) regime for the first time. The extended cutoff wavelengths resulted from thecombined effects of an increased electric field near the silicide/Si interface due to the p+ dopingspike and the Schottky image force. The p+ doping spikes were grown by molecular bema epitaxy at450 degrees C using elemental boron as the dopant source, with doping concentrations ranging from 5x 10^(19) to 2 x 10^(20) cm^(-3). Transmission electron microscopy indicated good crystallinequality of the doping spikes. The cutoff wavelengths were shown to increase with increasing dopingconcentrations of the p+ spikes. Thermionic emission dark current characteristics were observed andphotoresponse in the LWIR regime was demonstrated.
This paper reports the results of a study of proton irradiation effects on heterostructures.
The SAFIRE (Spectroscopy of Atmospheric Far Infra-Red Emissions) experiment is discussed with particular reference to the scientific aims and the conceptual instrument design of the project. The principal requirements of the experiment are reviewed, and it is shown how these requirements are met in the instrument concept. In particular, measurements of hydrogen oxides and other important species in the stratosphere require a far infrared limb sounder. Some problems involved in the optical and thermal design of the instrument are examined.
Observational data of the pre- and post-volcanic aerosols from the eruption of the Volcan de Fuego in Guatemala (15 deg N) in October 1974 were used in conjunction with predictions of a 2-D circulation model to gain better understanding of the transport, chemical and sedimentation processes which determine the stratospheric aeosol layer.
Commercial silicon resin was devolatilized by vacuum distillation, cured at room temperature and tested favorably for outgassing criteria. Applications of the devolatilized resin are potting compounds and conformal coatings.