Stress Effect on Ultrasonic Wave Propagation Through the Solid-Solid and Liquid-Solid Plane Interface

Ultrasonic wave propagation in prestressed materials has been studied extensively in the last 40 years. Most of this work was concentrated on the effect of stress on the velocities of different types of ultrasonic waves in homogeneous materials. Actually stresses affect not only wave velocities but also the boundary conditions at the interface. Many practical applications of ultrasonic stress characterization involve wave propagation through the interface between fluid and solid or two solids. In immersion measurements one needs to consider the effect of stress on wave propagation from fluid to solid. This leads to change in propagation direction and energy redistribution. Also additional modes could be excited leading to stress-induced birefringence. These are all important phenomena which require rigorous quantitative description since the stress effect in general is very small. Another important problem is ultrasonic characterization of residual stresses in composite materials [1]. It involves wave propagation through an interface between layers with different properties and stress levels

Dynamic dictionary matching revisited

Over 40% of the nation’s bridges have been classified as structurally deficient or functionally obsolete, with the estimated cost of repairs running in the billions of dollars [1]. It would not be economically feasible to replace all of these structures. Therefore, quantitative assessment of bridge condition is needed to determine which structures need replacing and which are safe

Predictors and correlates of maternal role competence and satisfaction

BACKGROUND: Developing a sense of competence and satisfaction in the maternal role enhances positive parenting and healthy development of the child. There is limited longitudinal research on the predictive factors influencing maternal role competence and satisfaction. OBJECTIVES: The aim of this study was to determine the predictive and concurrent associations of prenatal perceived maternal role competence, learned resourcefulness, social support, stress, and depression to perceived maternal role competence and satisfaction at 6 weeks postpartum. METHOD: A longitudinal, descriptive design was used. A convenience sample of 184 first-time pregnant women with a singleton and uneventful pregnancy were recruited from two regional public hospitals in Hong Kong. The Parenting Sense of Competence Scale, Self-control Schedule, Medical Outcomes Study Social Support Survey, Social Readjustment Rating Scale, and Edinburgh Postnatal Depression Scale were used to assess maternal role competence and satisfaction, learned resourcefulness, social support, stress, and depressive symptoms, respectively. Data were collected during pregnancy and at 6 weeks postpartum. RESULTS: Multiple regression analysis showed that perceived maternal role competence and satisfaction at 6 weeks postpartum were predicted by prenatal perceived maternal role competence and learned resourcefulness and were associated with postnatal learned resourcefulness and depression. Social support and stress were not associated directly with perceived maternal role competence and satisfaction at 6 weeks postpartum. DISCUSSION: The present findings suggest that maternal learned resourcefulness and depression are important factors affecting perceived maternal role competence and satisfaction at postpartum. Culturally competent healthcare should be developed to promote the psychological well-being of women and to equip women with the learned resourcefulness skills to facilitate maternal role taking and enhance women's sense of competence and satisfaction in the maternal role. Copyright © 2010 Lippincott Williams and Wilkins.link_to_subscribed_fulltex

Groupwork and computers: Task type and children's performance

In the majority of British primary schools, children use the computer in groups of two or three. This is partly due to the lack of resources, that is, most classrooms still only have one or two computers to share between around 30 children. Groupwork on computers is also justified for pedagogic reasons. Previous research comparing children working in groups or alone has revealed an advantage for children working in groups although the work undertaken has generally been problem solving tasks. This investigation examined the performance of pairs and individual 6-year old children on a drill and practice program using a pre-test, intervention, post-test design. In comparison to the problem solving evidence, individuals were found to have a significant advantage over pairs during the computer-based task.link_to_subscribed_fulltex