ABSTRACT
Space levitation processing allows researchers to conduct benchmark tests in an effort to understand the physical phenomena involved in rapid solidification processing, including alloy thermodynamics, nucleation and growth, heat and mass transfer, solid/liquid interface dynamics, macro- and microstructural evolution, and defect formation. Supported by ground-based investigations, a major thrust is to develop and refine robust computational tools based on theoretical and applied approaches. This work is accomplished in conjunction with experiments designed for precise model validation with application to a broad range of industrial processes.
ABSTRACT
Transitions from the liquid to the solid state of matter are omnipresent. They form a crucial step in the industrial solidification of metallic alloy melts and are greatly influenced by the thermophysical properties of the melt. Knowledge of the thermophysical properties of liquid metallic alloys is necessary in order to gain a tight control over the solidification pathway, and over the obtained material structure of the solid. Measurements of thermophysical properties on ground are often difficult, or even impossible, since liquids are strongly influenced by earth's gravity. Another problem is the reactivity of melts with container materials, especially at high temperature. Finally, deep undercooling, necessary to understand nucleus formation and equilibrium as well as non-equilibrium solidification, can only be achieved in a containerless environment. Containerless experiments in microgravity allow precise benchmark measurements of thermophysical properties. The electromagnetic levitator ISS-EML on the International Space Station (ISS) offers perfect conditions for such experiments. This way, data for process simulations is obtained, and a deeper understanding of nucleation, crystal growth, microstructural evolution, and other details of the transformation from liquid to solid can be gained. Here, we address the scientific questions in detail, show highlights of recent achievements, and give an outlook on future work.
ABSTRACT
PURPOSE: The purpose of this review is to determine whether incentive-based programs conducted at worksites increase participation and long-term smoking cessation rates. METHODS: Published studies of workplace smoking cessation programs involving incentives and competition were identified through all available years up to winter of 1992 in MEDLINE (1966-1992), Psychlit (1967-1992), Smoking and Health (1960-1992), and Combined Health Information (1973-1992) computer databases and article reference lists. Programs were considered incentive programs when they involved either cash or other prizes paid to the participant for quitting smoking. Incentive competition programs typically involve groups contesting for prizes by having the greatest smoking cessation rates. Thirty studies were found, out of which 15 quasi-experimental and experimental studies are reviewed. The 15 studies that did not have comparison groups were excluded from this report. RESULTS: Only eight studies had a comparison group in which the effects of incentives and competition were separated from the effects of other interventions. Only one study separated the effects of competition from incentives. Five of these studies evaluated smoking rates after six months, and three after 12 months from the program start. Three of these studies showed that incentives increased participation rates, and five enhanced smoking reduction. No study showed, however, that incentives and/or competition enhanced smoking cessation past six months. CONCLUSIONS: It appears that incentives/competition may be useful for increasing participation and smoking reduction. Further research needs to be conducted to determine whether incentives and/or competition enhance long-term quit rates, and what are the most effective types of incentive procedures.
