Engineering topics
Srivastava, S.
Publications and source records attributed to Srivastava, S..
Non-Thermal Removal of Gaseous Pollutants
The removal of fluorine based exhaust gases such as CFC's, PFC's, NF3, and SF6 used for plasma etching of and deposition on semi-conductors is a subject of increasing interest because of safety, air pollution, and global warming issues. Conventional treatment methods for removing exhaust gas pollutants are wet scrubbing, carbon and resin adsorption, catalytic oxidation, and thermal incineration. However, there are drawbacks associated with each of these methods which include difficulties in implementation, problems with the disposal of solid and liquid pollutant waste, large water and fuel consumption, and additional pollutants such as NOx emissions which are generated in thermal incineration processes.
A Segmented Time-of-Flight Mass Spectrometer
A time-of-flight mass spectrometer (TOFMS) is described in which the single flight tube of a conventional TOFMS has been replaced by several cylindrical electrostatic lenses in tandem. By a judicious choice of voltages on these lenses, an improved TOFMS has been realized which has a superior mass and energy resolution, shorter flight lengths, excellent signal-to-noise ratio, and less stringent requirements on the bias voltages.
Absolute Electron Impact Ionization Cross Sections for N(sub 2)O and NO from Threshold up to 1000 eV
Normalized values of cross sections for the production of ions by electron impact on N(sub 2)O and NO have been obtained by utilizing the relative flow technique.
Ionization of C(sub 60) (Buckministerfullerene) by Electron Impact
Utilizing a crossed electron beam-molecular beam collision geometry, mass spectra of C(sub 60) and C(sub 70) ions have been obtained for an electron impact energy range of 20 eV to 600 eV.
Formulation of design guidelines for automated robotic assembly in outerspace
The approach for arriving at design guidelines for assembly by robots in outerspace is illustrated. The use of robots in a zero gravity environment necessitates that extra factors over and above normal design guidelines be taken into account. Besides, many of the guidelines for assembly by robots on earth do not apply in space. However, considering the axioms for normal design and assembly as one set, guidelines for design and robotic assembly as another, and guidelines for design and assembly in space as the third set, unions and intersections of these sets can generate guidelines for two or more of these conditions taken together - say design and manual assembly in space. Therein lies the potential to develop expert systems in the future, which would use an exhaustive database and similar guidelines to arrive at those required by a superposition of these conditions.
Simple ultraviolet calibration source with reference spectra and its use with the Galileo orbiter ultraviolet spectrometer
A simple compact electron impact laboratory source of UV radiation has been developed and is used to obtain calibrated optically thin VUV spectra and synthetic spectral models for important molecular band systems of H2, N2, and the n 1P0 Rydberg series of He. The relative spectral intensity of the electron impact source can be used as the primary calibration standard for VUV instrumentation in the 80-230 nm range and with FWHM of not less than 0.4 nm. The accuracy of the present method is 10 percent in the FUV and 20 percent in the EUV. Results for calibration of the Galileo orbiter ultraviolet spectrometer have been compared with those obtained using other methods.
Cross sections for electron impact excitation of electronic states in UF6 at incident electron energies of 10, 20, and 40 eV
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Autonomous scheduling technology for Earth orbital missions
The development of a dynamic autonomous system (DYASS) of resources for the mission support of near-Earth NASA spacecraft is discussed and the current NASA space data system is described from a functional perspective. The future (late 80's and early 90's) NASA space data system is discussed. The DYASS concept, the autonomous process control, and the NASA space data system are introduced. Scheduling and related disciplines are surveyed. DYASS as a scheduling problem is also discussed. Artificial intelligence and knowledge representation is considered as well as the NUDGE system and the I-Space system.
Recent measurements concerning uranium hexafluoride-electron collision processes
Scattering of electrons by UF6 molecules was studied at impact energies ranging from 5 to 100 eV and momentum transfer, elastic and inelastic scattering cross sections were determined. The measurements also yielded spectroscopic information which made possible to extend the optical absorption cross sections from 2000 angstroms to 435 angstroms. It was found that UF6 is a very strong absorber in the vacuum UV region. No transitions were found to lie below the onset of the optically detected 3.0 eV feature.