The role of melt superheat in splat-quenching

The influence of experimental parameters in the gun splat-quenching technique is briefly discussed. The effect of initial melt temperature on cooling rate as manifested by lamellar spacing measurements in eutectic aluminium-copper alloy is small. Foils quenched from just above the melting point are generally thicker than those quenched from higher temperatures and thus there is a slight decrease in cooling rate with decrease in melt superheat. Increase in the temperature of quenching increases the proportion of degenerate eutectic microstructure obtained.     

Crack propagation in an amine-cured epoxide resin

Crack propagation has been studied in a DGEBA epoxide resin cured with two different series of amine hardeners. Both series produced a cured resin in which cracks propagated in a stick-slip manner in a series of jumps. With a primary diamine hardener, the initiation energy depended on the molecular weight of the hardener, but with a mixed amine hardener the initiation energy was independent of molecular weight. There were also significant differences in fracture surface morphologies between the two series. The effect of temperature and testing rate on the fracture energy and fracture surface morphology of ethylene diamine cured resin has also been studied. The fracture initiation energy increased with increasing temperature and decreasing testing rate and there is some indication of a peak occurring in the 22° C data. Long term static loading experiments have failed to show the occurrence of a static fatigue effect. Different batches of nominally identical resin produced different results, leading to problems of irreproducibility of behaviour.     

Prayer as a coping strategy for chronic pain patients.

Prayer as a coping mechanism was examined in a group of 105 persons (average age 45 yrs) experiencing chronic pain for an average of 4.3 yrs. Previous research suggested that prayer may actually be associated with increased disability among individuals who develop a permanent, painful condition of 6 mo duration or longer. Assessment instruments included the Medical Coping Modes Questionnaire and 2 subscales of the West Haven-Yale Multidimensional Pain Inventory; prayer was measured by the Diverting Attention/Praying-Hoping Subscale of the Coping Strategies Questionnaire. Consistent with previous research, individuals who endorsed a greater use of prayer to cope with their pain also reported a greater degree of disability. Follow-up statistical analyses suggested that prayer was associated with avoidance suggestive of a passive coping response. Additional research is needed to clarify the relationship of prayer to avoidance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

New derivation of the equivalent noise generators of ideal p?n-junction and vacuum diodes

Noise is usually identified as either Johnson or shot noise in its nature. Since both types of noise are produced by nonuniform velocity distributions in charge-carrier plasmas, the average available noise-power spectral density is in both cases determined by the plasma temperature alone, p?n-junction and vacuum diodes are used to demonstrate this theory.     

Comparison of university mental health needs priorities identified by professionals and students.

A random and representative sample of 457 undergraduate and graduate students completed the Needs Assessment Questionnaire that required each respondent to rate on a 5-point scale the seriousness of 24 mental health problems among university students and their families. A similar questionnaire was completed by 30 university-employed mental health professionals. A comparison of the ratings given to specific mental health problems by student and professional groups revealed extensive between-groups differences. The students rated problems of substance abuse as most serious, whereas the professionals rated problems of an academic and neurotic nature as most serious. The results have important implications for the validity and utility of needs assessment strategies. (3 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Energy trade-offs between intensive biomass utilization, site productivity loss, and ameliorative treatments in loblolly pine plantations

Loblolly pine plantations are the most important source of forest products in the US and the slash remaining after conventional harvest represents a significant potential source of bioenergy. However, slash removal in intensive harvests might, under some circumstances, reduce site productivity by reducing soil organic matter and associated nutrients. Two complimentary studies in the Gulf Coastal Plain of the southeastern US were designed to test whether harvest intensity (level of biomass removal) could have a negative long-term impact on site productivity. Harvesting tree crowns in addition to the merchantable bole had a negative impact (18%) on pine biomass accumulation by age 7–10 years on 15 of 19 research blocks. Sites at risk of harvest-induced reductions in productivity were relatively unproductive prior to harvest and had low soil phosphorus (P) concentrations. Intensive harvesting, fertilization, and chemical control of non-crop vegetation were all energy efficient; the additional biomass energy gained through these practices was two-orders of magnitude greater than the energy needed to conduct the activities. Harvest of slash for bioenergy in the Gulf Coastal Plain of the southeastern US has the potential to reduce productivity on infertile soils, but fertilization has the potential to restore and even improve productivity on those sites in an energy-efficient way.     

Toward a real-time model-based training system

This article describes the development of a real-time model-based training system that provides adaptive “over-the-shoulder” (OTS) instructions to trainees as they learn to perform an Anti-Air Warfare Coordinator (AAWC) task. The long-term goal is to develop a system that will provide real-time instructional materials based on learners’ actions, so that eventually the initial set of instructions on a task can be strengthened, complemented, or overridden at different stages of training. The training system is based on the ACT-R architecture, which serves as the theoretical background for the cognitive model that monitors the learning process of the trainee. An experiment was designed to study the impact of OTS instructions on learning. Results showed that while OTS instructions facilitated short-term learning, (a) they took time away from the processing of current information, (b) their effects tended to decay rapidly in initial stages of training, and (c) their effects on training diminished when the OTS instructions were proceduralized in later stages of training. A cognitive model that learned from both the upfront and OTS instructions was created and provided good fits to the learning and performance data collected from human participants. Our results suggest that to fully capture the symbiotic performance between humans and intelligent training systems, it is important to closely monitor the learning process of the trainee so that instructional interventions can be delivered effectively at different stages of training. We proposed that such a flexible system can be developed based on an adaptive cognitive model that provides real-time predictions on learning and performance.