Numerical simulations of the seasonal/latitudinal variations of atomic oxygen and nitric oxide in the lower thermosphere and mesosphere

A 2-Dimensional zonally-averaged thermospheric model and the global University College London (UCL) thermospheric model have been used to investigate the seasonal, solar activity and geomagnetic variation of atomic oxygen and nitric oxide. The 2-dimensional model includes detailed oxygen and nitrogen chemistry, with appropriate completion of the energy equation, by adding the thermal infrared cooling by O and NO. This solution includes solar and auroral production of odd nitrogen compounds and metastable species. This model has been used for three investigations; firstly, to study the interactions between atmospheric dynamics and minor species transport and density; secondly, to examine the seasonal variations of atomic oxygen and nitric oxide within the upper mesosphere and thermosphere and their response to solar and geomagnetic activity variations; thirdly, to study the factor of 7 to 8 peak nitric oxide density increase as solar F sub 10.7 cm flux increases from 70 to 240 reported from the Solar Mesospheric Explorer. Auroral production of NO is shown to be the dominant source at high latitudes, generating peak NO densities a factor of 10 greater than typical number densities at low latitudes. At low latitudes, the predicted variation of the peak NO density, near 110 km, with the solar F sub 10.7 cm flux is rather smaller than is observed. This is most likely due to an overestimate of the soft X-ray flux at low solar activity, for times of extremely low support number, as occurred in June 1986. As observed on pressure levels, the variation of O density is small. The global circulation during solstice and periods of elevated geomagnetic activity causes depletion of O in regions of upwelling, and enhancements in regions of downwelling

Control system designs for the shuttle infrared telescope facility

The Shuttle Infrared Telescope Facility (SIRTF) image motion compensation system is described in detail and performance is analyzed with respect to system noise inputs, environmental disturbances, and error sources such as bending and feedforward scale factor. It is concluded that the SIRTF accuracy and stability requirements can be met with this design

Reference manual for the Langley Research Center flight simulation computing system

The researchers at the Langley Research Center Flight Simulation Computing System are provided with an advanced real-time digital simulation capability. This capability is controlled at the user interface level by the Real Time Simulation Supervisor. The Supervisor is a group of subprograms loaded with a simulation application program. The Supervisor provides the interface between the application program and the operating system, and coordinates input and output to and from the simulation hardware. The Supervisor also performs various utility functions as required by a simulation application program

The re-emission spectrum of digital hardware subjected to EMI

The emission spectrum of digital hardware under the influence of external electromagnetic interference is shown to contain information about the interaction of the incident energy with the digital circuits in the system. The generation mechanism of the re-emission spectrum is reviewed, describing how nonlinear effects may be a precursor to the failure of the equipment under test. Measurements on a simple circuit are used to demonstrate how the characteristics of the re-emission spectrum may be correlated with changes to the digital waveform within the circuit. The technique is also applied to a piece of complex digital hardware where Similar, though more subtle, effects can be measured. It is shown that the re-emission spectrum can be used to detect the interaction of the interference with the digital devices at a level well below that which is able to cause static failures in the circuits. The utility of the technique as a diagnostic tool for immunity testing of digital hardware, by identifying which subsystems are being affected by external interference, is also demonstrated

Flame-Retardant Treatment Of Wood With A Diisocyanate and An Oligomer Phosphonate

An oligomer phosphonate and isophorone diisocyanate, in a chloroform or dichloromethane solution, were impregnated into wood and cured at 105 C. The leach resistance and thermal degradation of treated wood specimens were evaluated. Leaching milled specimens removed up to 49% of the phosphorus and 12% of the nitrogen. The average weight percent gain of solid specimens leached with three 4-day cycles of running water was reduced from 23% to 17% during the first cycle and from 17% to 16% during the second and third cycles. Toluene: ethanol extraction did not remove the reacted chemicals from the wood. Acetone extraction resulted in a 1% to 2% reduction of the weight percent gain values. Thermal analysis showed that the flame-retardant treatment reduced the temperature at maximum rate of pyrolysis approximately 80 C and increased the amount of residual char to about 30%. Leaching raised the temperature on the average 8 C at the maximum rate of pyrolysis and decreased the amount of residual char an average of 3%. The temperature at maximum rate of pyrolysis and amount of residual char indicate the potential effectiveness of this treatment as a leach-resistant, flame-retardant treatment for wood