Zeiada W.A.,Mansoura University |
Underwood B.S.,ArizonaState University |
Kaloush K.E.,ArizonaState University
International Journal of Pavement Engineering | Year: 2016
Many well-constructed Hot Mix Asphalt pavements have been in service for 40 or more years without any evidence of fatigue cracking. This field experience suggests that there exists a strain level, known as the fatigue endurance limit (FEL), below which an asphalt concrete pavement will not exhibit fatigue cracks. Several studies have been conducted to define and verify this limit. Each of these methods is associated with certain assumptions regarding the nature of the FEL and heretofore a comprehensive comparison of each has not been made using a consistent set of mixtures. Likewise, the impact of any observed differences in FEL on the predicted pavement performance has not been made. This paper investigates and compares six different methods for identifying the FEL: NCHRP 9–44A approach, simplified viscoelastic continuum damage model, smeared-healing with continuum damage model, plateau value approach, pseudo-strain analysis method, and reduced cycles method. Each method is found to yield different values ranges from approximately 30–170 microstrains at 21.1 °C. The predicted FEL from each of the six methods are then used with the mechanistic empirical design algorithm to evaluate their effects on predicted pavement performance. Simulation outputs show different pavement performance and perpetual pavement structural design thicknesses from each of the methods. The study outcomes are expected to benefit future field verification research of FEL as it provides comprehensive analyses using six different methods. This future verification research may indicate the method that best represents actual perpetual pavement design and performance. © 2016 Taylor & Francis
PubMed | ArizonaState University
Type: Journal Article | Journal: Journal of pediatric health care : official publication of National Association of Pediatric Nurse Associates & Practitioners | Year: 2012
The current study aimed to investigate the relationship between individual and familial characteristics of HIV-infected mothers and their psychological health as it relates to parenting as well as their parenting beliefs/abilities.A descriptive correlational design was used. Seventeen HIV-infected mothers and their infants were recruited from a university clinic in Alabama. Assessments were gathered at the infants pediatric clinic appointments (approximately 6 weeks after delivery) and included a demographic questionnaire, the Beck Depression Inventory-II, the Maternal Confidence Questionnaire, the Parenting Stress Index-Short Form, and the Questionnaire About Physical Contact.Dysfunctional parent-child interactions significantly correlated with maternal confidence, parent stress, and overall feeling about physical contact. Difficult child temperament correlated with overall and current feelings of physical contact and parent stress. Significant correlations were found between parent distress, parent stress, and maternal depression.Beyond the need to assist HIV-infected mothers with stress and depression, an intervention is needed to facilitate optimal parent-child interactions and improve both child psychosocial and cognitive outcomes.
PubMed | ArizonaState University
Type: Journal Article | Journal: Developmental psychology | Year: 2011
Mexican American adolescents have higher rates of externalizing problems than their peers from other ethnic and racial groups. To begin the process of understanding factors related to externalizing problems in this population, this study used the social development model (SDM) and prospective data across the transition to junior high school from 750 diverse Mexican American families. In addition, the authors examined whether familism values provided a protective effect for relations within the model. Results showed that the SDM worked well for this sample. As expected, association with deviant peers was the primary predictor of externalizing behaviors. There was support for a protective effect in that adolescents with higher familism values had slower rates of increase in association with deviant peers from 5th to 7th grades than those with lower familism values. Future research needs to determine whether additional culturally appropriate modifications of the SDM would increase its usefulness for Mexican American adolescents.