Study of carbon nanotube film and shape memory alloys treatment for sensing and structural vibration control

Structural vibration control is of great importance. Current active and passive vibration control strategies usually employ individual elements to fulfill this task, such as viscoelastic patches for providing damping, transducers for picking up signals and actuators for inputting actuating forces. The goal of this dissertation work is to design, manufacture, investigate and apply a new type of multifunctional composite material for structural vibration control. This new composite, which is based on multi-walled carbon nanotube (MWCNT) film, is potentially to function as free layer damping treatment and strain sensor simultaneously. That is, the new material integrates the transducer and the damping patch into one element. The multifunctional composite was prepared by sandwiching the MWCNT film between two adhesive layers. Static sensing test indicated that the MWCNT film sensor resistance changes almost linearly with the applied load. Sensor sensitivity factors were comparable to those of the foil strain gauges. Dynamic test indicated that the MWCNT film sensor can outperform the foil strain gage in high frequency ranges. Temperature test indicated the MWCNT sensor had good temperature stability over the range of 237 K-363 K. The Young’s modulus and shear modulus of the MWCNT film composite were acquired by nanoindentation test and direct shear test, respectively. A free vibration damping test indicated that the MWCNT composite sensor can also provide good damping without adding excessive weight to the base structure. A new model for sandwich structural vibration control was then proposed. In this new configuration, a cantilever beam covered with MWCNT composite on top and one layer of shape memory alloy (SMA) on the bottom was used to illustrate this concept. The MWCNT composite simultaneously serves as free layer damping and strain sensor, and the SMA acts as actuator. Simple on-off controller was designed for controlling the temperature of the SMA so as to control the SMA recovery stress as input and the system stiffness. Both free and forced vibrations were analyzed. Simulation work showed that this new configuration for sandwich structural vibration control was successful especially for low frequency system.

Anxious children who received treatment grow -up: An 8-to-13 year follow-up study

This dissertation examined the long-term efficacy (8-to-13 years, M = 9.54, SD = 1.689) of exposure-based cognitive-behavioral therapy (CBT) for phobic and anxiety disorders in youths. Long-term efficacy was examined in terms of diagnostic recovery, symptom reductions, and clinically significant change. This dissertation also examined predictors of long-term efficacy (e.g., age, gender, and other clinical characteristics) as well as the relative long-term efficacy of CBT for Hispanic/Latino and European American youth. ^ Participants consisted of 67 youth (age range 15–26 years; M = 19.43, SD = 3.02 years at time of follow-up assessment), (47.8% females, 37.3% Hispanic/Latino) who had participated in one of two clinical trials (Silverman et al., 1999a, b). After providing informed consent to participate in the long term follow-up, youths completed a diagnostic interview and a battery of questionnaires. Results indicated that treatment gains were maintained about 9.5 years after treatment was completed. Maintenance of treatment gains was evident in terms of diagnostic recovery, symptom reductions, and clinically significant change. Long-term treatment gains extended to both ethnic groups and the two ethnic groups were functionally equivalent along most indices examined. Analyses of predictors of long-term outcome showed that parent self-reported pre-treatment depression, youth-reported pre-treatment depression, and youths retrospective reports of negative life events were significantly associated with less favorable long-term gains in terms of total symptoms of anxiety at long-term follow-up. In terms of long-term sequelae, youths with less successful post-treatment outcomes reported seeking-out additional treatment as well as using/abused substances and substance dependence significantly more than youths with successful post-treatment outcomes. Results are discussed in terms of the contribution of the present study to knowledge base about the long-term efficacy of exposure-based CBT procedures for phobic and anxiety disorders in youth. Findings also are discussed in terms of the need to modify CBT procedures to target youths with less successful post-treatment outcomes. Limitations and future directions are presented. ^

Individual child cognitive behavioral treatment versus child-parent cognitive behavioral treatments for anxiety disorders in children and adolescents: Comparative outcomes

Anxiety disorders; such as separation anxiety disorder, generalized anxiety disorder, social phobia and specific phobia, are widespread in children and adolescents. Cognitive behavioral therapy (CBT) has been shown to be effective in reducing excessive fears and anxieties in children and adolescents. Research has produced equivocal findings that involving parents in treatment of child anxiety enhances effects over individual CBT (ICBT). The present dissertation study examined whether parental involvement can enhance individual treatment effect if the parent conditions are streamlined by targeting specific parental variables. The first parent condition, Parent Reinforcement Skills Training (RFST), involved increasing mothers' use of positive reinforcement and decreasing use of negative reinforcement. The second parent condition, Parent Relationship Skill Training (RLST), involved increasing maternal child acceptance and decreasing maternal control (or increasing autonomy granting). Results of the present dissertation findings support the use of all three treatment conditions (ICBT, RLST, RFST) for child anxiety; that is, significant reductions in anxiety were found in each of the three treatment conditions. No significant differences were found between treatment conditions with respect to diagnostic recovery rate, clinician rating, and parent rating of child anxiety. Significant differences between conditions were found on child self rating of anxiety, with some evidence to support the superiority of RLST and RFST to ICBT. These findings support the efficacy of individual, as well as parent involved CBT, and provide mixed evidence with respect to the superiority of parent involved CBT over ICBT. The conceptual, empirical, and clinical implications of the findings are discussed. ^

Individual Child Cognitive Behavioral Treatment versus Child-Parent Cognitive Behavioral Treatments for Anxiety Disorders in Children and Adolescents: Comparative Outcomes

Anxiety disorders; such as separation anxiety disorder, generalized anxiety disorder, social phobia and specific phobia, are widespread in children and adolescents. Cognitive behavioral therapy (CBT) has been shown to be effective in reducing excessive fears and anxieties in children and adolescents. Research has produced equivocal findings that involving parents in treatment of child anxiety enhances effects over individual CBT (ICBT). The present dissertation study examined whether parental involvement can enhance individual treatment effect if the parent conditions are streamlined by targeting specific parental variables. The first parent condition, Parent Reinforcement Skills Training (RFST), involved increasing mothers’ use of positive reinforcement and decreasing use of negative reinforcement. The second parent condition, Parent Relationship Skill Training (RLST), involved increasing maternal child acceptance and decreasing maternal control (or increasing autonomy granting). Results of the present dissertation findings support the use of all three treatment conditions (ICBT, RLST, RFST) for child anxiety; that is, significant reductions in anxiety were found in each of the three treatment conditions. No significant differences were found between treatment conditions with respect to diagnostic recovery rate, clinician rating, and parent rating of child anxiety. Significant differences between conditions were found on child self rating of anxiety, with some evidence to support the superiority of RLST and RFST to ICBT. These findings support the efficacy of individual, as well as parent involved CBT, and provide mixed evidence with respect to the superiority of parent involved CBT over ICBT. The conceptual, empirical, and clinical implications of the findings are discussed.