2,902 research outputs found
Skylab 3 and 4 science demonstrations: Preliminary report
Twelve science demonstrations were accomplished on the Skylab 3 and 4 missions. These were defined in response to crew requests for time-gap fillers and were designed to be accomplished using onboard equipment. The following 12 are described and the preliminary results are given: liquid floating zone; diffusion in liquids; ice melting; immiscible liquids; liquid films; gyroscope; Rochelle salt growth; deposition of silver crystals; fluid mechanics series; neutron environment; orbital mechanics; and charged particle mobility
Commerce Laboratory: Mission analysis payload integration study
A mission model which will accommodate commercial users and provide a basic data base for further mission planning is reported. The data bases to be developed are: (1) user requirements; (2) apparatus capabilities and availabilities; and (3) carrier capabilities. These data bases are synthesized in a trades and analysis phase along with the STS flight apparatus, and optimum missions will be identified. The completed work is reported. The user requirements data base was expanded to identify within the six scientific disciplines the areas of investigation, investigation categories and status, potential commercial application, interested parties, process, and experiment requirements. The scope of the apparatus data base was expanded to indicate apparatus status as to whether it is ground or flight equipment and, within both categories, whether the apparatus is: (1) existing, (2) under development, (3) planned, or (4) needed. Applications for the apparatus are listed. The methodology is revised in the areas of trades and analysis and mission planning. The carrier capabilities data base was updated and completed
A microscopic study of solid/liquid phase change in several members of the paraffin family
Microscopic study of solid/liquid phase change in several members of paraffin famil
Pegasus thermal design
Electronic and micrometeoroid detector panels for Pegasus thermal desig
Water production rates and activity of interstellar comet 2I/Borisov
We observed the interstellar comet 2I/Borisov using the Neil Gehrels-Swift
Observatory's Ultraviolet/Optical Telescope. We obtained images of the OH gas
and dust surrounding the nucleus at six epochs spaced before and after
perihelion (-2.56 AU to 2.54 AU). Water production rates increased steadily
before perihelion from molecules s on Nov. 1,
2019 to molecules s on Dec. 1. This rate of
increase in water production rate is quicker than that of most dynamically new
comets and at the slower end of the wide range of Jupiter-family comets. After
perihelion, the water production rate decreased to
molecules s on Dec. 21, which is much more rapidly than that of all
previously observed comets. Our sublimation model constrains the minimum radius
of the nucleus to 0.37 km, and indicates an active fraction of at least 55% of
the surface. calculations show a variation between 57.5 and 105.6
cm with a slight trend peaking before the perihelion, lower than previous and
concurrent published values. The observations confirm that 2I/Borisov is
carbon-chain depleted and enriched in NH relative to water.Comment: 12 pages, 3 figures, 2 tables, submitted to ApJ
Land tenure and the adoption of agricultural technology in Haiti:
There has long been an active debate in Haiti - as in many other developing countries - over whether or not the customary tenure system constrains technology adoption and agricultural development, and whether cadaster and land titling should be national priorities. This paper contributes to this debate by reviewing and interpreting the body of literature and new empirical evidence concerning the relationship between land tenure and the adoption of technology in rural Haiti. The findings suggest that (a) formal title is not necessarily more secure than informal arrangements, (b) informal arrangements based on traditional social capital resources assure affordable and flexible access to land for most people, and (c) perceived stability of access to land-via stability of personal and social relationships-is a more important determinant of technology adoption than mode of access. The paper concludes that there is no definitive relationship between tenure and technology adoption by peasants; peasants are preoccupied more by political and economic insecurity than insecure tenure; and rather than tinkering with formalizing tenure, policy makers should prioritize other more fundamental rural sector reforms. The paper ends by considering some of the implications for theory and suggests several avenues for future research on land policy.
Consequences of a Distant Massive Planet on the Large Semi-major Axis Trans-Neptunian Objects
We explore the distant giant planet hypothesis by integrating the large
semi-major axis, large pericenter Trans-Neptunian Objects (TNOs) in the
presence of the giant planets and an external perturber whose orbit is
consistent with the proposed distant, eccentric, and inclined giant planet, so
called planet 9. We find that TNOs with semi-major axes greater than 250 au
experience some longitude of perihelion shepherding, but that a generic outcome
of such evolutions is that the TNOs evolve to larger pericenter orbits, and
commonly get raised to retrograde inclinations. This pericenter and inclination
evolution requires a massive disk of TNOs (tens of M_\Earth) in order to
explain the detection of the known sample today. Some of the highly inclined
orbits produced by the examined perturbers will be inside of the orbital
parameter space probed by prior surveys, implying a missing signature of the
9th planet scenario. The distant giant planet scenarios explored in this work
do not reproduce the observed signal of simultaneous clustering in argument of
pericenter, longitude of the ascending node, and longitude of perihelion in the
region of the known TNOs
Problems related to the integration of fault tolerant aircraft electronic systems
Problems related to the design of the hardware for an integrated aircraft electronic system are considered. Taxonomies of concurrent systems are reviewed and a new taxonomy is proposed. An informal methodology intended to identify feasible regions of the taxonomic design space is described. Specific tools are recommended for use in the methodology. Based on the methodology, a preliminary strawman integrated fault tolerant aircraft electronic system is proposed. Next, problems related to the programming and control of inegrated aircraft electronic systems are discussed. Issues of system resource management, including the scheduling and allocation of real time periodic tasks in a multiprocessor environment, are treated in detail. The role of software design in integrated fault tolerant aircraft electronic systems is discussed. Conclusions and recommendations for further work are included
- …