Measurement of Prepl Pwall factors in electron beams and in a 60Co beam for plane-parallel chambers

This paper describes a method to measure the product of Prepl Pwall correction factors for ionization chambers and presents our measured values of Prepl Pwall for Markus plane-parallel chambers in electron beams. It is shown that the measured values of Prepl Pwall can be fitted to an equation, Prepl Pwall = c1 + c2 R50 + c3 (R50)2, for Markus chambers at the new reference depth for electron beams (6 MeV < or = nominal energy E < or = 20 MeV). We also present our measured values of Prepl Pwall for NACP and Markus chambers in a water phantom irradiated in a 60Co beam.     

Automated choice of procedures in computerized structural analysis

An efficient and general computer program for structural analysis allows the user to choose between a number of different procedures. New methods for computerized structural analysis are still being improved at a rapid pace. Consequently only a very few structural analysts can be expected to be well acquainted with all aspects of the technology, and will often find it difficult to use the sophisticated programs that presently are available. If dynamic loading or possible stability failure must be considered, the computer programs are becoming increasingly difficult to use. The trends in future computer programming for structural analysis must include efforts to facilitate the user's burden without significant loss of efficiency. This paper contains a discussion of the difficulties involved in modeling and in the choice of solution procedures. Special emphasis is placed on the possibility of designing computer programs so that sound selection of procedures can be made automatically if the user declines to state a preference.     

Dynamically simulated characters in virtual environments

Animated characters can play the role of teachers or guides, team mates or competitors, or just provide a source of interesting motion in virtual environments. Characters in a compelling virtual environment must have a variety of complex and interesting behaviors, and be responsive to the user's actions. The difficulty of constructing such synthetic characters currently hinders the development of these environments, particularly when realism is required. The authors present one approach to populating virtual environments-using dynamic simulation to generate the motion of characters. They explore this approach's effectiveness with two virtual environments: the border collie environment, in which the user acts as a border collie to herd robots into a corral, and the Olympic bicycle race environment, in which the user participates in a bicycle race with synthetic competitors     

Predicting termination and continuation status in psychotherapy using the transtheoretical model.

Measures from the transtheoretical model of change (TMC) were compared to traditional client characteristic variables as predictors of psychotherapy client termination and continuation. According to the TMC, stages of change, processes of change, decisional balance, and levels of attribution are core dimensions of behavior change in psychotherapy. 60 pairs of therapists (mean age 35 yrs) and 18–71 yr old clients were given questionnaires assessing demographics, distress symptoms, and dimensions of the TMC. Therapists also completed an Assessment of Client's Termination Status questionnaire. Client characteristics were not significant predictors but the transtheoretical variables of stages of change, processes of change, and decisional balance for therapy were excellent predictors. A discriminative function analysis correctly classified 92% of the clients into two groups: (1) premature terminators and (2) appropriate terminators and therapy continuers. Discussion focused on the importance of matching therapy to client's stage of change in order to reduce the average rate of 40% of clients terminating therapy prematurely. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Tribological evaluation of oil pump relief valve coatings compatible with an aluminum oil pump body

Wear can cause automotive relief valves to jam. In order to evaluate and screen candidate coatings for oil pump relief valves for reduction of aluminum pump cylinder bore wear and wear-related sticking, a laboratory reciprocating wear test using production parts has been developed. The coatings on valves include impinged and physical vapor deposited (PVD)-coated molybdenum disulfides, electroplated nickel–phosphorous with polytetrafluoroethylene (Ni–PTFE), electroplated bronze, and electroplated nickel–phosphorous–boron nitride (Ni–P–BN).

The test results showed that the electroplated bronze coating demonstrated the best wear resistance against 380 aluminum pump bores while Ni–PTFE ranked second, PVD-coated MoS₂ third, and Ni–P–BN ranked last. It was observed that the electroplated bronze coating showed only mild oxidative or abrasive wear after 20 h wear test. The Ni–P–BN coating gave the worst wear resistance due to severe abrasive wear, surface scoring, and coating abrasion during the wear test. The major wear mechanisms for valve bore/relief valve can be classified at different levels from mild wear (oxidative wear or surface delamination) to abrasive wear (scoring, scuffing, and ploughing). This paper also reviewed the rooted wear mechanisms of production pump relief valves against aluminum bores based on metallographic observations of worn surfaces after field tests. This tribological investigation of valve coatings has provided insights into the fundamental wear mechanisms which depend on the compatibility of two sliding materials, protective coating composition, hard particle content, and surface interaction. The information will be useful in preventing oil pump relief valves from jamming.