Expert Systems in the Fighter of the 1990s

In the Advanced Tactical Fighter (ATF) to be deployed in the 1990s, the role of expert systems will enhance mission success. This paper discusses the utilization of two expert systems for handling multisensor data fusion and situation assessment. In multisensor data fusion, each sensor operates over a different region of the surveillance volume asynchronously and provides different measurements. In some instances, more than one sensor may yield the same measurement but with a different measurement accuracy. In this regard, the paper describes, in layman's terms, a system block diagram for processing the autonomous sensor track files and the possible need for a ``smart' fusion processor. This expert system is shown to manage the sensor outputs in both the temporal and spatial domains to maximize target identification confidence as well as kinematic state vector accuracy. The paper delineates the features needed by the fusion expert in order to assign a quality factor to each composite track file entry. A second expert system uses the output from fusion and other mission-related data to formulate the best picture of the surveillance volume at hand. This second expert system will show how historical data and real-time sensor data are merged for purposes of display parameters to the pilot, weapon cueing, countermeasures response management, and feedback to the fusion expert processor for individual sensor communication and data collection direction. The paper concludes with a tabular summary of the subprocesses of which these two expert systems may consist.     

Vegetation and the atmospheric cycling of mercury

Beyond their role in the cycling of the major elements, carbon, nitrogen, oxygen, etc., little is known about geobiological interactions involving plants with the elements of lower abundance. Plants influence the distribution of volcanic mercury by uptake from the atmosphere and soil fluids, transport to the shoot and re-release as Hg° into the atmosphere. Release rates as high as 2.5 × 10^?4 g.h^?1 per kg are known but even at more typical rates, fluxes far greater than the Environmental Protection Agency calculated U.S. average annual degassing rate of 130 × 10^?6 g.m^?2 should exist. On a global basis, the presence or absence of vegetative cover may be a significant regulator of Hg° transport between land surfaces and the atmosphere.     

Spectra of fresh photo-electrons in the Martian atmosphere

In this paper the latest neutral and ionospheric models of the upper Martian atmosphere, created on the Viking data are used. For the calculations of the photoelectron spectra the Hinteregger's measurements of the solar flux together with the theoretical photoelectron distribution are also used.     

Spectroscopic study of plasma parameters for solar active regions and flares

Results are given of the study of active regions and flares by a high resolution Mg XI ion spectra obtained aboard rockets and a satellite. It is shown that there is a noticable similarity in the physical conditions in the plasma of active regions and flares. Plasma of both sources consists okf a thermal component with the temperature T ～ 2.?3.10⁶K for active regions and T ～ 1.5?2.5.10⁷K for flares and in both cases of a relatively small number (～ 1–5%) of suprathermal electrons with an energy E ～ 3–6 kT.     

Particle and Joule heating of the neutral polar thermosphere in cusp region using Atmosphere Explorer-C satellite measurements

Simultaneous measurements taken by instruments on the Atmosphere Explorer - C satellite were used to compare electron and proton particle energy deposition, Joule heating, and neutral density perturbations in the region of the cusp.Altitude profiles of Joule heating, electron energy deposition, and electron density are derived using measurements taken by the satellite as input to a computer model. Electric fields are calculated using ion drift measurements. Figures are presented for a representative orbital pass.A peak Joule heating rate of 0.059 Wm^?2 occurred in the cusp region with a peak of 0.025 Wm^?2 in the evening auroral electrojet. Peak volume heating rates corresponding to these regions were 1.4 × 10^?6Wm^?3 and 7.10^?7 Wm^?3, both occurring at an altitude of 115 km. Particle energy deposition was about an order of magnitude less than Joule heating. Large neutral density perturbations are related to regions of heating.     

Forces acting on a foreign particle near a solidification front

The interaction of inert foreign particles and a solid-liquid interface during solidification is considered. The viscous drag on the particle which produces a force on the interface is calculated under general assumptions as well as the disjoining force for small particles and the buoyancy force for large ones.     

A review of long drop tubes as a supplement/alternative to space experiments

The 100 meter high drop tube at the Marshall Space Flight Center has proven to be a viable facility for studies of containerless solidification. Advantages are that experiments are inexpensive and large numbers of specimens can be processed rapidly. It would not be unusual to run ten specimens in a day. Another significant advantage is that the undercooling behavior can be followed with sufficient sensitivity to easily detect the onset of recalescence and subsequent events.Disadvantages are the restrictions on specimen sizes and types of alloys that can be run in a microgravity environment. Practical specimen sizes range between 50 mg and 500 mg depending on the type of furnace being used. Refractory alloys can be processed in a vacuum (about 10^?5 torr) and therefore at microgravity. Non-refractory alloys demand an atmosphere (about 200 torr) to obtain appreciable undercooling before impact at the bottom of the tube. Under these conditions significant g forces result.Because of the present limitations of the 100 meter drop tube, the most definitive work has been done on niobium based alloys. Large amounts of undercooling have been observed routinely and the effects of undercooling on microstructure have been characterized in detail. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy have been used to determine types of phases, amounts of phases, and compositions of phases. It is clear, as would be expected, that the results bear some resemblance to rapid solidification processing by quenching. However, there are dissimilarities due to the uniqueness of solidification by deep undercooling without quenching in long drop tubes and accompanying recalescence effects.