Browsing by Subject "bidirectional"

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    Examining the relationship of dieting behavior and substance use among female adolescents
    (2018-05) Rowe, Alia T.; Zapolski, Tamika C.B.
    The problem behavior theory suggests that the engagement in one problematic behavior increases the likelihood of engagement in another problematic behavior. Previous research has found among youth an increasing probability of co-occurring dieting and substance use behavior, particularly among girls. However, to date findings are inconclusive on the temporal ordering of these behaviors. Further, limited research has been conducted to explore whether the temporal ordering of the two behaviors exist similarly between White and Black youth. The present study will use a cross-lagged panel design across one year to examine the temporal ordering between dieting behavior and substance use among a sample of 2,016 adolescent females (grade mean=7; 77.2% White; 22.8% Black). We hypothesized that a bidirectional relationship would be observed between the two behaviors. However, given no published studies on this relationship by race, no a priori hypotheses were made for this second aim. Result showed that within the full sample dieting behavior significantly predicted substance use one year later, but the inverse relationship was not found. Additionally, this effect was replicated in the White sample but null effects in both directions was found among Black youth. These findings provide support for a temporal relationship between dieting behavior and substance use, such that the former predicts risk for the latter. Moreover, although there is evidence of race differences in the risk pathway, further research is needed to confirm this effect. Future studies are also needed to determine whether this observed temporal relationship is present among adolescent females of other racial/ethnic groups, as well as if the relationship varies as a function of other demographic variables, such as age (e.g., early, mid, or late-adolescence).
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    PV Based Converter with Integrated Battery Charger for DC Micro-Grid Applications
    (2014) Salve, Rima; Santos Jr., Euzeli C. dos
    This thesis presents a converter topology for photovoltaic panels. This topology minimizes the number of switching devices used, thereby reducing power losses that arise from high frequency switching operations. The control strategy is implemented using a simple micro-controller that implements the proportional plus integral control. All the control loops are closed feedback loops hence minimizing error instantaneously and adjusting efficiently to system variations. The energy management between three components, namely, the photovoltaic panel, a battery and a DC link for a microgrid, is shown distributed over three modes. These modes are dependent on the irradiance from the sunlight. All three modes are simulated. The maximum power point tracking of the system plays a crucial role in this configuration, as it is one of the main challenges tackled by the control system. Various methods of MPPT are discussed, and the Perturb and Observe method is employed and is described in detail. Experimental results are shown for the maximum power point tracking of this system with a scaled down version of the panel's actual capability.