3,894 research outputs found
User modeling techniques for enhanced usability of OPSMODEL operations simulation software
The PC based OPSMODEL operations software for modeling and simulation of space station crew activities supports engineering and cost analyses and operations planning. Using top-down modeling, the level of detail required in the data base can be limited to being commensurate with the results required of any particular analysis. To perform a simulation, a resource environment consisting of locations, crew definition, equipment, and consumables is first defined. Activities to be simulated are then defined as operations and scheduled as desired. These operations are defined within a 1000 level priority structure. The simulation on OPSMODEL, then, consists of the following: user defined, user scheduled operations executing within an environment of user defined resource and priority constraints. Techniques for prioritizing operations to realistically model a representative daily scenario of on-orbit space station crew activities are discussed. The large number of priority levels allows priorities to be assigned commensurate with the detail necessary for a given simulation. Several techniques for realistic modeling of day-to-day work carryover are also addressed
Miscellaneous Notes on Collecting in Georgia
Volume: 18Start Page: 82End Page: 8
The Movement Toward Unemployment Insurance in the United States
The subject of unemployment insurance legislation is a timely and highly controversial one. In order to evaluate the movement it is desirable to understand the development of the theory and to investigate the early attempts to secure unemployment legislation in America and in Europe
Device for quickly sensing the amount of O2 in a combustion product gas
A sensing device comprising an O2 sensor, a pump, a compressor, and a heater is provided to quickly sense the amount of O2 in a combustion product gas. A sample of the combustion product gas is compressed to a pressure slightly above one atmosphere by the compressor. Next, the heater heats the sample between 800 C and 900 C. Next, the pump causes the sample to be flushed against the electrode located in O2 sensor 6000 to 10,000 times per second. Reference air at approximately one atmosphere is provided to the electrode of O2 sensor. Accordingly, the O2 sensor produces a voltage which is proportional to the amount of oxygen in the combustion product gas. This voltage may be used to control the amount of O2 entering into the combustion chamber which produces the combustion product gas
Productivity of Florida Springs: first semi-annual report to Biology Division, Office of Naval Research, progress from June 1, 1952 to January 31, 1953
Work has begun on studying the factors responsible for productivity
in the Florida springs, which are nearly constant temperature, constant
chemical, steady state giant laboratories. Progress has been made on five
aspects: qualitative description, quantitative description, completion
of knowledge of chemical factors, measurement of productivity , development
of productivity theory.
Measurement of the primary productivity in Silver Springs and Green
Cove Springs by two new methods: the raising of organisms in cages, and the
measurement of night & day differences in oxygen downstream agree roughly.
Production in these springs is greater than previous production figures reported
for marine, fresh water, and land areas. Instantaneous measures of production
show large variations with season, time of day, cloud cover. Production
estimates range from 11,000 lbs per acre per year to 70,000 lbs. glucose per
acre per year during daylight hours.
Essential stability of the springs environment has been shown with
respect to temperature, phosphorus, and plant cover. A correlation of species
number with lack of stability has been shown with insects. Quantitative
studies have shown very large plant base to pyramids of mass. Correlation
of marine invasion with chlorinity has been shown. The essential aspects of
pH regulated phosphorus geochemistry in Florida have been outlined. Some
theoretical ideas on productivity have been evolved. Mapping of sessile
organisms in springs and taxonomic identification of dominants are half
completed. Plans for second six months include measurement of herbivore
and carnivore production rates and completion of food chain efficiency
determinations in Silver Springs as a preparation for subsequent
comparisons between springs. (34pp.
Filament wound metal lined propellant tanks for future Earth-to-orbit transports
For future Earth-to-orbit transport vehicles, reusability and lighter weights are sought for the main propellant tanks. To achieve this, a filament wound tank with a metal liner and an intermediate layer of foam-filled honeycomb is proposed. A hydrogen tank is used as an example. To accommodate mismatches in the expansion of liner and overwrap a design is proposed wherin the liner is configured so that the extension of the liner under pressure matches the expected contraction of the same liner due to the presence of a cryogen. In operation, the liner is pressurized at a rate such that the pressure strain matches the contraction due to decrease in temperature. As an alternate approach, compressive pre-stress is placed in the liner such that it will not separate from the overwrap. A finite element program is used to show stresses in the liner and overwrap for various tank pressures for the pre-stressed liner concept. A fracture mechanics analysis is made of the liners to determine tank life. The tank concept shown has a similar weight to the Shuttle external hydrogen tank, but the filament wound tank is expected to be reusable. Integration of the propellant tanks into a future transport vehicle is discussed
Oscillation pressure device for dynamic calibration of pressure transducers
Method and apparatus for obtaining dynamic calibrations of pressure transducers. A calibration head (15), a flexible tubing (23) and a bellows (20) enclose a volume of air at atmospheric pressure with a transducer (11) to be calibrated subject to the pressure inside the volume. All of the other apparatus in the drawing apply oscillations to bellows (20) causing the volume to change thereby applying oscillating pressures to transducer (11) whereby transducer (11) can be calibrated
Complements and Meat Demand in the U.S.
In this study we estimated the price elasticities among meats, vegetables, grains, and potatoes and the impact that different levels of income have on the demand for these commodities. The 2005 Nielsen retail home scan data were used to construct a censored demand system of 14 equations. Results revealed that the uncompensated cross-price elasticities for both low and high-incomes suggest both substitution and complement relationships, while the compensated price elasticities are dominated primarily by substitution relationships. Our findings also revealed that expenditure elasticities among both low and high-income households differ for most commodities.censored dependent variables, meats, poultry, fish, vegetables, sample selection model, two-step estimation, Demand and Price Analysis, Livestock Production/Industries, C25, D12, Q11,
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