Interior and its implications for the atmosphere

The bulk composition and interior structure of Titan required to explain the presence of a substantial methane atmosphere are shown to imply the presence of solid CH4 - 7H2O in Titan's primitive material. Consideration of the possible composition and structure of the present atmosphere shows plausible grounds for considering models with total atmospheric pressures ranging from approximately 20 mb up to approximately 1 kb. Expectations regarding the physical state of the surface and its chemical composition are strongly conditioned by the mass of atmosphere believed to be present. A surface of solid CH4, liquid CH4 solid, CH4 hydrate, H2O ice, aqueous NH3 solution, or even a non-surface of supercritical H2O-NH3-CH4 fluid could be rationalized

Preformed stiffeners used to fabricate structural components for pressurized tanks

Process of fabricating stiffened section components of pressurized tanks for aerospace use was developed. A potential use of the fabrication process is the production of gore and quarter-panel sections of hydrogen and oxygen tanks for space vehicle boosters

Hands-On Physical Science for In-Service Teachers

The initiation of the Virginia Commonwealth University B.S. in Science program was reported in this journal Fall 1999 as a program designed to meet the academic content major of a teacher preparation program for elementary and middle school mathematics and science teachers [1]. This paper reports the current status of the interdisciplinary B.S. in Science degree program including program enrollment data and trends. Also described are refinements in the required curriculum, which include a newly developed geometry, a mathematical computing course, and an emerging teaching technology course featuring graphing calculators, CBLs, and computer software applications

Thermal tides in an assimilation of three years of Thermal Emission Spectromenter data from Mars Global Surveyor

Introduction. Thermal tides are particularly prominent in the Mars atmosphere with the result that temperature and wind fields have a strong dependence on local solar time (LT). Tides include westward propagating migrating (sun-synchronous) waves driven in response to solar heating and additional nonmigrating waves resulting from zonal variations in the thermotidal forcing. Zonal modulation of forcing can arise from longitudinal variations of the boundary (topography and surface thermal inertia) and radiatively active aerosols (dust and water ice clouds). Nonmigrating tides appear as diurnally varying upslope/ downslope circulations within the near-surface boundary layer that, like their migrating counterparts, are also able to propagate vertically to aerobraking altitudes in the lower thermosphere. The Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES) has yielded atmospheric temperature profiles with unprecedented latitude and longitude coverage that has provided the basis for characterizing the seasonal evolution of tides and stationary waves [1]. However, the twice-daily observations (2 am and 2 pm LT) are insufficient to unambiguously resolve the sunsynchronous tides. Recently the technique of data assimilation has been sufficiently developed for Mars to yield a dynamically consistent set of thermal and dynamic fields suitable for detailed investigations of various aspects of the martian circulations system [2,3,4,5]. We will refer to this data set an the TES Reanalysis, which represents the current best estimate of the evolving state of the martian atmosphere during the MGS mission. The assimilated thermal and dynamical fields provide a means of assessing circulation variability and transport capability reflecting the variability of the actual Mars atmosphere

Associative memory scheme for genetic algorithms in dynamic environments

Copyright @ Springer-Verlag Berlin Heidelberg 2006.In recent years dynamic optimization problems have attracted a growing interest from the community of genetic algorithms with several approaches developed to address these problems, of which the memory scheme is a major one. In this paper an associative memory scheme is proposed for genetic algorithms to enhance their performance in dynamic environments. In this memory scheme, the environmental information is also stored and associated with current best individual of the population in the memory. When the environment changes the stored environmental information that is associated with the best re-evaluated memory solution is extracted to create new individuals into the population. Based on a series of systematically constructed dynamic test environments, experiments are carried out to validate the proposed associative memory scheme. The environmental results show the efficiency of the associative memory scheme for genetic algorithms in dynamic environments