Scaling forces to asteroid surfaces: The role of cohesion

The scaling of physical forces to the extremely low ambient gravitational acceleration regimes found on the surfaces of small asteroids is performed. Resulting from this, it is found that van der Waals cohesive forces between regolith grains on asteroid surfaces should be a dominant force and compete with particle weights and be greater, in general, than electrostatic and solar radiation pressure forces. Based on this scaling, we interpret previous experiments performed on cohesive powders in the terrestrial environment as being relevant for the understanding of processes on asteroid surfaces. The implications of these terrestrial experiments for interpreting observations of asteroid surfaces and macro-porosity are considered, and yield interpretations that differ from previously assumed processes for these environments. Based on this understanding, we propose a new model for the end state of small, rapidly rotating asteroids which allows them to be comprised of relatively fine regolith grains held together by van der Waals cohesive forces.Comment: 54 pages, 7 figure

U.S. Tax Law as an Expert System

Tax law is a particular application well-suited for an expert system because of the large among of knowledge and the many variables involved. The following presents the results of implementing a small portion of tax code, with a brief look at whether or not it can be fully recreated in an accurate system with an acceptable response time. The actual prototype implementation has been done using the expert shell NEXPERT, making use of the IF/THEN rule construct which seems to fall naturally from the tax code

Building a Collaboration for Youth Development: The Club-Within-a-Club

This article describes the experiences of Ohio 4-H Youth Development and the Boys & Girls Clubs of Columbus, Inc. to incorporate 4-H clubs within the Boys & Girls Clubs setting. The purpose of the study was to inform the continued collaboration of the two organizations. Staff and youth interviews, participant observation, and review of program records were conducted to gain insight into program implementation. Benefits, challenges, and keys to success were derived. The authors conclude that perception of benefits, compatibility of missions, and the new audience for 4-H outweigh the challenges. Communication through regular meetings is deemed essential

An integrated approach to rotorcraft human factors research

As the potential of civil and military helicopters has increased, more complex and demanding missions in increasingly hostile environments have been required. Users, designers, and manufacturers have an urgent need for information about human behavior and function to create systems that take advantage of human capabilities, without overloading them. Because there is a large gap between what is known about human behavior and the information needed to predict pilot workload and performance in the complex missions projected for pilots of advanced helicopters, Army and NASA scientists are actively engaged in Human Factors Research at Ames. The research ranges from laboratory experiments to computational modeling, simulation evaluation, and inflight testing. Information obtained in highly controlled but simpler environments generates predictions which can be tested in more realistic situations. These results are used, in turn, to refine theoretical models, provide the focus for subsequent research, and ensure operational relevance, while maintaining predictive advantages. The advantages and disadvantages of each type of research are described along with examples of experimental results