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.

Risk and resilience factors associated with delinquent behavior among African -American adolescent males

Juvenile crime is a social problem of increasing concern to many citizens in the United States. In 2000, there were an estimated 2.4 million juvenile arrests for a variety of crimes ranging from misdemeanors to violent felony offenses. African American males are disproportionately represented among juvenile offenders in the United States. In 2000, black youth were approximately 16% of the U.S. population between the ages of 10–17; however, they accounted for 42% of juvenile arrests for violent crime. ^ This study explored putative factors associated with juvenile offending among a sample of African American adolescent males. The independent variables in this study were academic achievement, religiosity, parenting styles and discrimination. The dependent variables were delinquent behavior and arrest. The data used in this study were from a larger NIDA funded longitudinal study that included approximately 425 African American youths. The data collection method involved structured interviews and questionnaires. The participants for the original study were selected via random sampling from all students attending middle school in Miami-Dade County. The study examined the hypotheses that African American males retrospectively reporting (a) high academic achievement, (b) high religiosity, (c) authoritarian parenting and (d) low perceptions of discrimination are less likely to be involved in delinquent behavior and are also less likely to be arrested. ^ Results indicated that among African American adolescent males, delinquent behavior had a significant relationship (p < .05) with academic achievement, perceived discrimination and the interaction between perceived discrimination and experienced discrimination. Arrest was significantly related to academic achievement (p < .001), religious perception (p < .05), and church attendance (p < 05). Neither dependent variable was significantly related to parenting styles. ^ The findings indicated that experimental studies are needed to clarify cause and effect relationship among the variables associated with juvenile offending among African American males, which may differ from those associated with juvenile offending among other groups. ^

Integrated construction project delivery system in the U.S. public sector: An information modeling framework

Integrated project delivery (IPD) method has recently emerged as an alternative to traditional delivery methods. It has the potential to overcome inefficiencies of traditional delivery methods by enhancing collaboration among project participants. Information and communication technology (ICT) facilitates IPD by effective management, processing and communication of information within and among organizations. While the benefits of IPD, and the role of ICT in realizing them, have been generally acknowledged, the US public construction sector is very slow in adopting IPD. The reasons are - lack of experience and inadequate understanding of IPD in public owner as confirmed by the results of the questionnaire survey conducted under this research study. The public construction sector should be aware of the value of IPD and should know the essentials for effective implementation of IPD principles - especially, they should be cognizant of the opportunities offered by advancements in ICT to realize this.^ In order to address the need an IPD Readiness Assessment Model (IPD-RAM) was developed in this research study. The model was designed with a goal to determine IPD readiness of a public owner organization considering selected IPD principles, and ICT levels, at which project functions were carried out. Subsequent analysis led to identification of possible improvements in ICTs that have the potential to increase IPD readiness scores. Termed as the gap identification, this process was used to formulate improvement strategies. The model had been applied to six Florida International University (FIU) construction projects (case studies). The results showed that the IPD readiness of the organization was considerably low and several project functions can be improved by using higher and/or advanced level ICT tools and methods. Feedbacks from a focus group comprised of FIU officials and an independent group of experts had been received at various stages of this research and had been utilized during development and implementation of the model. Focus group input was also helpful for validation of the model and its results. It was hoped that the model developed would be useful to construction owner organizations in order to assess their IPD readiness and to identify appropriate ICT improvement strategies.^

Risk and resilience factors associated with delinquent behavior among African American adolescent males

Juvenile crime is a social problem of increasing concern to many citizens in the United States. In 2000, there were an estimated 2.4 million juvenile arrests for a variety of crimes ranging from misdemeanors to violent felony offenses. African American males are disproportionately represented among juvenile offenders in the United States. In 2000, black youth were approximately 16% of the U.S. population between the ages of 10-17; however, they accounted for 42% of juvenile arrests for violent crime. This study explored putative factors associated with juvenile offending among a sample of African American adolescent males. The independent variables in this study were academic achievement, religiosity, parenting styles and discrimination. The dependent variables were delinquent behavior and arrest. The data used in this study were from a larger NIDA funded longitudinal study that included approximately 425 African American youths. The data collection method involved structured interviews and questionnaires. The participants for the original study were selected via random sampling from all students attending middle school in Miami-Dade County. The study examined the hypotheses that African American males retrospectively reporting (a) high academic achievement, (b) high religiosity, (c) authoritarian parenting and (d) low perceptions of discrimination are less likely to be involved in delinquent behavior and are also less likely to be arrested. Results indicated that among African American adolescent males, delinquent behavior had a significant relationship (p The findings indicated that experimental studies are needed to clarify cause and effect relationship among the variables associated with juvenile offending among African American males, which may differ from those associated with juvenile offending among other groups.

Integrated Construction Project Delivery System in the U.S. Public Sector: An Information Modeling Framework

Integrated project delivery (IPD) method has recently emerged as an alternative to traditional delivery methods. It has the potential to overcome inefficiencies of traditional delivery methods by enhancing collaboration among project participants. Information and communication technology (ICT) facilitates IPD by effective management, processing and communication of information within and among organizations. While the benefits of IPD, and the role of ICT in realizing them, have been generally acknowledged, the US public construction sector is very slow in adopting IPD. The reasons are - lack of experience and inadequate understanding of IPD in public owner as confirmed by the results of the questionnaire survey conducted under this research study. The public construction sector should be aware of the value of IPD and should know the essentials for effective implementation of IPD principles - especially, they should be cognizant of the opportunities offered by advancements in ICT to realize this. In order to address the need an IPD Readiness Assessment Model (IPD-RAM) was developed in this research study. The model was designed with a goal to determine IPD readiness of a public owner organization considering selected IPD principles, and ICT levels, at which project functions were carried out. Subsequent analysis led to identification of possible improvements in ICTs that have the potential to increase IPD readiness scores. Termed as the gap identification, this process was used to formulate improvement strategies. The model had been applied to six Florida International University (FIU) construction projects (case studies). The results showed that the IPD readiness of the organization was considerably low and several project functions can be improved by using higher and/or advanced level ICT tools and methods. Feedbacks from a focus group comprised of FIU officials and an independent group of experts had been received at various stages of this research and had been utilized during development and implementation of the model. Focus group input was also helpful for validation of the model and its results. It was hoped that the model developed would be useful to construction owner organizations in order to assess their IPD readiness and to identify appropriate ICT improvement strategies.