ALBERT

Description: The first Clouds and the Earth's Radiant Energy System (CERES) instrument will be launched on the Tropical Rainfall Measuring Mission (TRMM) spacecraft from a Japanese launch site in November 1997. This instrument is a follow-on to the Earth Radiation Budget Experiment (ERBE) begun in the 1980's. The instrument will measure the radiation budget - incoming and outgoing radiant energy - of the Earth. It will establish a baseline and look for climatic trends. The major feature of interest is clouds, which play a very strong role in regulating our climate. CERES will identify clear and cloudy regions and determine cloud physical and microphysical properties using imager data from a companion instrument. Validation efforts for the remote sensing algorithms will be intensive. As one component of the validation, the S'COOL (Students' Cloud Observations On-Line) project will involve school children from around the globe in making ground truth measurements at the time of a CERES overpass. Their observations will be collected at the NASA Langley Distributed Active Archive Center (DAAC) and made available over the Internet for educational purposes as well as for use by the CERES Science Team in validation efforts. Pilot testing of the S'COOL project began in January 1997 with two local schools in Southeastern Virginia and one remote site in Montana. This experience is helping guide the development of the S'COOL project. National testing is planned for April 1997, international testing for July 1997, and global testing for October 1997. In 1998, when the CERES instrument is operational, a global observer network should be in place providing useful information to the scientists and learning opportunities to the students.

Description: Current and future earth observation programs depend on satellite measurements of radiance to retrieve the properties of clouds on a global basis. At present, this retrieval is made assuming that the clouds in the instrument field of view are plane parallel and independent of adjacent pixels. While this assumption is known to be false except in very limited cases, its impact can be evaluated, and if possible corrected, based on emerging theoretical techniques. In this study, the Spherical Harmonic Discrete Ordinate Method (SHDOM, Evans, 1996) has been used to assess the sensitivity of the retrieval to a variety of cloud parameters. SHDOM allows the plane parallel assumption to be relaxed and makes 2D and even 3D radiative solutions practical. A previous study (Chambers et al., 1996) assessed the effect of horizontal inhomogeneity in 45 LANDSAT scenes of boundary layer clouds over ocean. The four scenes studied here represent overcast, broken, scattered and strongly thermally forced cloud fields and are used to perform sensitivity studies to a wider variety of parameters. Comparisons are made at three solar zenith angles (theta (sub 0) = 0, 49, and 63 degrees) to avoid ambiguity in the results due to solar zenith angle.

Description: Active and passive multiplication of RC time constants for subaudio frequency integrated filters

Description: Compound diode-transistor structure with current gain invariant with temperature

Description: A computer-based analysis of the dynamic effects of spur gear systems is presented. The method of analysis with its associated computer code is capable of determining the dynamic response of spur gear systems having involute tooth profiles and standard contact ratios. Various parameters affecting the system dynamic behavior are examined. Numerical results of the analysis are compared with semi-empirical formulae, AGMA (American Gear Manufacturers Association) formulae, and experimental data. A close correlation with the experimental data is obtained.

Description: The effect of load speed on straight and involute tooth forms is studied using several finite-element models. It is found that for rapidly rotating gears and sprockets, the load speed along the tooth surface can significantly affect the tooth vibration. Indeed, it is found that for sufficiently high load speeds and for sufficiently slender tooth forms, the tooth deflection can, at times, be directed opposite to the load direction. Comparisons are made of various dynamic models of gear and sprocket teeth. It is shown that for stubby tooth forms there is considerable difference between results obtained with finite element models and results obtained with Timoshenko beam models. Finally, it is shown that gear or sprocket vibrations can be induced by the shape of the tooth form itself. This effect becomes increasingly significant at higher speeds.

Description: An electrostatic shield for complementary MOS integrated circuits was developed to minimize the adverse effects of stray electric fields created by the potentials in the metal interconnections. The process is compatible with silicon gate technology. N-doped polycrystalline silicon was used for all the gates and the shield. The effectiveness of the shield was demonstrated by constructing a special field plate over certain transistors. The threshold voltages obtained on an oriented silicon substrate ranged from 1.5 to 3 V for either channel. Integrated inverters performed satisfactorily from 3 to 15 V, limited at the low end by the threshold voltages and at the high end by the drain breakdown voltage of the n-channel transistors. The stability of the new structure with an n-doped silicon gate as measured by the shift in C-V curve under 200 C plus or minus 20 V temperature-bias conditions was better than conventional aluminum gate or p-doped silicon gate devices, presumably due to the doping of gate oxide with phosphorous.

Description: As part of NASA's Mission to Planet Earth, the first Clouds and the Earth's Radiant Energy System (CERES) instrument will be launched on the Tropical Rainfall Measuring Mission (TRMM) spacecraft from the Tanegashima launch site in Japan in November 1997. The instrument will measure the radiation budget incoming and outgoing radiant energy - of the Earth. The major feature of interest is clouds, which play a very strong role in regulating our climate. CERES will identify clear and cloudy regions and determine cloud physical and microphysical properties using imager data from a companion instrument. Validation efforts for the remote sensing algorithms will be intensive. As one component of the validation, the S'COOL (Students' Cloud Observations On-Line) project will involve school children around the globe in making ground truth measurements at the time of a CERES overpass. They will report cloud type, height, fraction, and opacity, as well as the local surface conditions. Their observations will be collected at the NASA Langley Distributed Active Archive Center (DAAC) and made available over the Internet for educational purposes as well as for use by the CERES Science Team in validation efforts. Pilot testing of the S'COOL project began in January 1997 with two local schools in Southeastern Virginia and one remote site in Montana. National testing in April 1997 involved 8 schools (grades 3 to high school) across the United States. Global testing will be carried out in October 1997. Details of the S'COOL project, which is mainly Internet-based, are being developed in each of these phases according to feedback received from participants. In 1998, when the CERES instrument is operational, a global observer network should be in place providing useful information to the scientists and learning opportunities to the students. Broad participation in the S'COOL project is planned, both to obtain data from a wide range of geographic areas, and to involve as many students as possible in learning about clouds and atmospheric science. This paper reports on the development phase of the S'COOL project, including the reaction of the teachers and students who have been involved. It describes the operational state of the S'COOL network, and identifies opportunities for additional participants.

Description: Epitaxially grown Si contact for area reduction of MOS transistor circuits

Description: An analytical computer simulation program for dynamic modeling of low-contact-ratio spur gear systems is presented. The procedure computes the static transmission error of the gears operating under load and uses a fast Fourier transform to generate the frequency spectrum of the static transmission error at various tooth profile modifications. The dynamic loading response of an unmodified (perfect involute) gear pair was compared with that of gears with various profile modifications. Correlations were found between various profile modifications and the resulting dynamic loads. An effective error, obtained from frequency domain analysis of the static transmission error of the gears, gave a very good indication of the optimum profile modification to reduce gear dynamic loading. Design curves generated by dynamic simulation at various profile modifications are given for gear systems operated at various loads. Optimum profile modifications can be determined from these design curves for improved gear design.