Many bridges are handling heavier loads than those expected at design, making it increasingly necessary to strengthen existing members or conduct repairs on damaged structural members. Carbon Fiber Reinforced Polymer (CFRP) materials have been broadly used to repair and strengthen reinforced concrete structures. Using CFRP materials as the strengthening material is an excellent solution because of their mechanical properties. CFRP has properties of high strength, corrosion resistance, and light weight. CFRP materials are being widely used for shear and flexural strengthening. Most studies have focused on uni-directional layout of CFRP strips in high shear regions of beams. Recent shear tests on full-scale I-girders have shown that the use of bi-directional CFRP layouts with CFRP anchors led to much higher shear strength increases than when using uni-directional layouts. The objective of the study is to determine the mechanism that governs shear strengthening of bridge girders using bi-directional CFRP and, in doing so, demonstrate the feasibility of using bi-directional CFRP for shear strengthening of large bridge I- and U-beams. Small-scale panel tests have been conducted to investigate parameters that influence the shear strength provided by bi-directional CFRP layouts. Panels were tested under compressive forces to simulate the compression struts that develop in the webs of I-beams. The applied loads generated bottle-shaped compressive struts. CFRP anchors were used to prevent early failure due to CFRP strip delamination from the panel surface. The panels, while not fully reproducing the boundary condition of girder webs, were tested ahead of full-scale girders to investigate a wide range of parameters in a cost-effective manner. The variables considered include the amount of CFRP and steel reinforcement, the inclination of CFRP fibers, and the layout and spacing of CFRP strips. The panel tests provide qualitative comparisons between the influence of the various parameters. The relative strength contributions of CFRP strips, steel stirrups, and concrete were evaluated. / text

Each of us has knowledge but it is not complete. When we come together to listen, we learn, we grow in understanding and we can analyze better the course that needs to be taken. One thing I learned over the past several years is that words and their interpretation have power. Grand Bayou community member This dissertation examines the question of change in the non-community people who have interacted or come into contact with the Grand Bayou Participatory Action Research (PAR) project. Who Changes?, a book on institutionalizing participation in development, raises the issu of "where is the change?" in a participatory project (Blackburn1998). Fischer (2000), Forester (1992), and Wildavsky (1979) indicate that a participatory process is beneficial to all stages of planning policy development, and analysis. However, planners, academics, and practitioners who work with high risk communities are often of different cultures, values, and lived experience than those of the community. Despite the best intentions of these professionals, these differences may at times cause a disconnect from or a dismissal of the community's knowledge, values or validity claims as the participatory process transpires. The outside experts often fail to learn from the local communities or use the community's expertise. The Grand Bayou Participatory Action Research (PAR) project, funded in part by a National Science Foundation (NSF) grant, investigated the viability of PAR in a post-disaster recovery project. The NSF report revealed that the community did gain agency and political effectiveness; the study and evaluation, however, did not focus on the outside collaborators and their change. Freirian and Habermasian theories of conscientization and critical hermeneutics would assume that those engaged with the project have changed in some way through their learning experience and that change may be emancipatory. The change builds on a core tenet of PAR in developing relational knowledge while honoring the other. This study used a case study methodology utilizing multiple sources of evidence to explore the answer to this question. A better understanding of the change in outside collaborators in a PAR project can be helpful in developing a more holistic participatory community planning process.

Thesis advisor: Celeste Wells / This study examined the influence of a popular Youtuber in creating social discourse surrounding concepts of health, fitness, and beauty, employing a case study approach of the popular Youtube channel, Blogilates. Both visual and rhetorical analyses were conducted on the titles and thumbnail images of the top 50 most viewed Blogilates videos, and 10 videos were studied in depth. The findings established the concept of a unique power relationship between Youtubers and their viewers, which also explains the marked dissonance between the discourse posited by the channel’s marketing and the discourse posited in the actual video content. / Thesis (BA) — Boston College, 2017. / Submitted to: Boston College. College of Arts and Sciences. / Discipline: Departmental Honors. / Discipline: Communication.

Major depressive disorder is one of the most common mental health conditions in the world while obesity, a condition tied to numerous chronic conditions throughout the lifespan, is at epidemic levels throughout most of the world. Adolescence is a crucial transition period for physical, cognitive, and social-emotional development. Adolescents, particularly girls, are at high risk of developing depression and obesity. Some studies suggest that obesity is a risk factor for the development of depression while others suggest that depression alters health habits, thereby leading to obesity. The overall goal of this work is to examine both of these questions in adolescent girls and further to explore whether the relationship between obesity (and other related risk factors) and depression is a bi-directional one. The National Heart, Lung, and Blood Institute's Growth and Health Study (NGHS) is an observational study of 2379 adolescent black and white girls. Height and weight was measured annually (and used to estimate body mass index) over 10 years from early to late adolescence. Diet and other risk factors were also measured longitudinally over 10 years. Depression was measured twice using the Centers for Epidemiologic Studies Depression Scale (CES-D): first at exam 8 and then at the final exam (exam 10). Multivariable logistic regression and longitudinal (repeated measures) mixed models were used to control for potential confounding by age, socio-economic status, physical activity, hours of television/video watching per day, and dietary factors. The first objective was to determine whether young adolescent girls who were already overweight or obese had a higher risk for developing depression during the follow-up exams in later adolescence. Overall, the prevalence of moderate (or worse) depression was much higher in girls who were classified as obese (474% with depression) than either overweight (37.8%) or normal-weight (34.3%) girls. After adjusting for baseline age, race, SES, television/video hour per day), physical activity level, diet quality (using Healthy Eating Index scores), and percent of energy from protein, obese girls had a 68% increase risk of subsequent depression (95% CI: 1.17 to 2.39) compared with normal weight girls. There was no increased depression risk for overweight girls. The risk of incident depression associated with obesity was the same for blacks and whites in the study. Finally, after controlling further for a measure of self-worth (using the Harter Scales), the effect of obesity was somewhat attenuated. The second objective of the study was to explore other risk factors for depression in these adolescent girls. In these analyses, several factors from the early adolescent years predicted the development of later depression (moderate or worse). These included hours spent watching television (risk increased by 6% for each additional hour watched per day), white race, SES, obesity, and self-worth score. While the self-worth score ranged only from 1 to 4, there was nearly a 60% reduction in risk for each increase of one point in the score. Thus, self-worth was a particularly important predictor, with higher self-worth scores protecting these girls from incident depression. The final objective of this work was to examine the change in behavioral risk factors associated with prevalent depression at exam 8. Depressed (vs. non-depressed) girls who were not obese at exam 8 were approximately 75% more likely to become obese by exam 10. The results of this study support a finding of a bi-directional relationship between obesity and depression in adolescent girls.

This dissertation is divided into two main topics. In the first topic, we study the joint source-channel coding problem of transmitting an analog source over a Gaussian channel in two cases - (i) the presence of interference known only to the transmitter and (ii) in the presence of side information about the source known only to the receiver. We introduce hybrid digital analog forms of the Costa and Wyner-Ziv coding schemes. We present random coding based schemes in contrast to lattice based schemes proposed by Kochman and Zamir. We also discuss superimposed digital and analog schemes for the above problems which show that there are infinitely many schemes for achieving the optimal distortion for these problems. This provides an extension of the schemes proposed by Bross and others to the interference/source side information case. The result of this study shows that the proposed hybrid digital analog schemes are more robust to a mismatch in channel signal-to-noise ratio (SNR), than pure separate source coding followed by channel coding solutions. We then discuss applications of the hybrid digital analog schemes for transmitting under a channel SNR mismatch and for broadcasting a Gaussian source with bandwidth compression. We also study applications of joint source-channel coding schemes for a cognitive setup and also for the setup of transmitting an analog Gaussian source over a Gaussian channel, in the presence of an eavesdropper. In the next topic, we consider joint physical layer coding and network coding solutions for bi-directional relaying. We consider a communication system where two transmitters wish to exchange information through a central relay. The transmitter and relay nodes exchange data over synchronized, average power constrained additive white Gaussian noise channels. We propose structured coding schemes using lattices for this problem. We study two decoding approaches, namely lattice decoding and minimum angle decoding. Both the decoding schemes can be shown to achieve the upper bound at high SNRs. The proposed scheme can be thought of as a joint physical layer, network layer code which outperforms other recently proposed analog network coding schemes. We also study extensions of the bi-directional relay for the case with asymmetric channel links and also for the multi-hop case. The result of this study shows that structured coding schemes using lattices perform close to the upper bound for the above communication system models.

¡@¡@In recent years, the trends in network communication towards mobile network .Traditional network cannot meet the need of new communication challenge. The 802.11 outperforms other new wireless network technique ¡@¡@In this paper, we assume user have wireless NIC devices with Mobile IPv6 protocol module. We use this model to build an environment and use this environment to design our Mobile IPv6 multicast simulation. We do these for two reasons, (1)To analyze how to use multicast over Mobile IPv6 wireless network. (2)To design an experimentation for multicast over wireless LAN. After we get results of the experimentation, we could know why wireless network does not have better quality than wired LAN. ¡@¡@During our implementation, we have a high latency problem and try to solve it by our program. After our improvement, average latency reduces to 27.77% and miss rate reduces to 33.07%. ¡@¡@Our implementation not only provide some useful information when some one need to build Mobile IPv6 environment but also give a solution for solving handover latency problem.

A two-dimensional, finite-element, porous-media flow model is developed to simulate stratified bi-directional flow of brine through the earth embankment carrying the Southern Pacific Railroad across Great Salt Lake. The model is part of a two-year research program whose objective is to develop a computer model of circulation in Great Salt Lake. This overall model is to be used as a predictive device for salinity distributions and circulation patterns in the lake. The porous media flow model is designed to establish flow rates through the Southern Pacific Railroad causeway embankment which traverses the north central part of he lake and divides it into two bodies of water. The study first develops the mathematical equations which describe two-dimensional stratified bi-directional flow of a fluid through porous media. Next , the problem is numerically posed as a boundary value problem in terms of pressure. This formulation is then solved by an iterative finite element scheme which employs quadratic, isoparametric, quadrilateral elements. The study also investigates two possible means of performing an analysis of stratified bi-directional flow with a pressure formulation by either posing the problem as a single boundary value problem with two densities of fluid within, or as two single-density boundary value problems coupled at the density interface. The single boundary formulation did not converge with the techniques attempted due to numerical instability at the density interface. The numerical model developed enables one to calculate fluid flow rates as well as the locations of the free surface and density-interface. The model simulation investigates many lake variables which affect brine flows through the embankment. Realistic model parameters are used which cover the range of actual values observed on the lake for the years 1968 through 1972. The numerical results presented in the study are given in terms of generalized dimensionless variables. The numerical results appeared to be in agreement with previously performed stratified bi-directional Hele-Shaw model studies. The major lake parameters affecting flow rates through the causeway were the free surface head difference, the southside lake surface elevation and the difference in fluid densities between the upper and lower layers of the embankment . The southward density flow was found to be completely cut off for certain combinations of lake parameters. Lack of adequate field data collected on the embankment has left both the geometry and the coefficient of permeability of the fill in question, preventing a rigorous verification of the model' s ability to predict actual flows. More field data are also necessary to establish whether there is stratification on the north side of the embankment which can greatly affect flow calculations. A high Reynold's number was found for flow through the embankment, raising a question as to the validity of the Darcian flow assumption used in the analysis. However, the establishment of the true Reynold's number can only be verified through the collection of more empirical data.

This research is concerned with inheritance as used in object-oriented database. More specifically, partial bi-directional inheritance among classes is examined. In partial inheritance, a class can inherit a proper subset of instance variables from another class. Two subclasses of the same superclass do not need to inherit the same proper subset of instance variables from their superclass. Bi-directional partial inheritance allows a class to inherit instance variables from its subclass. The prototype of an object-oriented database that supports both full and partial bi-directional inheritance among classes was developed on top of an existing relational database management system. The prototype was tested with two database applications. One database application needs full and partial inheritance. The second database application required bi-directional inheritance. The result of this testing suggests both advantages and disadvantages of partial bi-directional inheritance. Future areas of research are also suggested.

Additive manufacturing (AM) offers a way to manufacture highly complex designs with potentially enhanced performance as it is free from many of the constraints associated with traditional manufacturing. However, current design and optimisation tools, which were developed much earlier than AM, do not allow efficient exploration of AM's design space. Among these tools are a set of numerical methods/algorithms often used in the field of structural optimisation called topology optimisation (TO). These powerful techniques emerged in the 1980s and have since been used to achieve structural solutions with superior performance to those of other types of structural optimisation. However, such solutions are often constrained during optimisation to minimise structural complexities, thereby, ensuring that solutions can be manufactured via traditional manufacturing methods. With the advent of AM, it is necessary to restructure these techniques to maximise AM's capabilities. Such restructuring should involve identification and relaxation of the optimisation constraints within the TO algorithms that restrict design for AM. These constraints include the initial design, optimisation parameters and mesh characteristics of the optimisation problem being solved. A typical TO with certain mesh characteristics would involve the movement of an assumed initial design to another with improved structural performance. It was anticipated that the complexity and performance of a solution would be affected by the optimisation constraints. This work restructured a TO algorithm called the bidirectional evolutionary structural optimisation (BESO) for AM. MATLAB and MSC Nastran were coupled to study and investigate BESO for both two and three dimensional problems. It was observed that certain parametric values promote the realization of complex structures and this could be further enhanced by including an adaptive meshing strategy (AMS) in the TO. Such a strategy reduced the degrees of freedom initially required for this solution quality without the AMS.

This thesis is concerned primarily with the optimization of the current regulation in bi-directional ac-dc power converters through the use of appropriate current control methods. Following a review into prior current control technology, current control methods which attempt to achieve Zero Average Current Error (ZACE) in each switching period are presented. A ZACE controlled converter offers independent real and reactive power flow control with negligible low order current harmonics, a relatively narrow switching frequency band, and relative immunity to power circuit parameter variations, including DC link or AC line voltage harmonics. ZACE and other desirable characteristics in a current control method are discussed. The single phase ac and dc ripple current is characterized.Two new types of ZACE current control techniques for directly controlling the inductor current in switched power converters are introduced in this thesis together with variations for certain applications. Slope-generated hysteresis (SGH), the first to be developed, is a hysteresis method which uses the slopes of the current error signal alone to generate a hysteresis band which will result in a fixed switching frequency. Slope-generated hysteresis-clock (SGHC) is presented as an alternative with a dual clock to force a narrow switching frequency band.Ramptime current control is the second type of ZACE current control presented. Developed as an improvement over SGH, ramptime produces ZACE in each switching period by using the timing of a previous switching instant relative to the coincident previous current error signal excursion time to determine each switching instant. The digital current error polarity signal is the only variable input required to produce a pwm output.Variations of ramptime current control are also presented. Polarized ramptime is a subset of ramptime which maintains a narrow ++ / switching frequency band despite switching delays. Dual ramptime is the final enhancement of ramptime where two polarized ramptime regulators are used together to provide the appropriate choice between full-bridge and half-bridge switching in a single phase current controlled full-bridge voltage source inverter with the ac ripple current minimized without compromising the transient response. Using this technique, excellent fidelity and a narrow switching frequency band are demonstrated.The ZACE current control techniques are applied to a three phase voltage source inverter. A "standing phase" system of control for a three wire, three phase inverter is chosen over individual phase control since only two current regulators are required to control two decoupled current error signals, and the effective switching frequency is reduced by one third.The new ZACE methods are found to compare favourably in simulation to existing linear and hysteresis type current control techniques. SGH current control has equivalent fidelity to any other hysteresis control in delivering the reference current waveform, but is prone to noise in the hysteresis band determination requiring filtering. This, combined with the effect of switching delays compromises the narrowness of the switching frequency band. SGHC current control is also prone to noise in the generation of the hysteresis band, and results in a decrease in the fidelity of reproduction of the reference waveform. Ramptime current control is a robust technique, largely immune to power circuit parameter and voltage variances, with good fidelity and a relatively narrow switching frequency band. Polarized ramptime current control is shown to produce excellent fidelity with a narrow switching frequency band.The operation of the ZACE methods in single and three phase prototype converters is demonstrated. A field installation of a ++ / grid-connected ramptime current controlled converter is shown to source 20 kW of real power onto the grid from a photovoltaic array with a maximum power point tracking control, while independently providing grid voltage support through reactive power control.The effect of the synchronization of the current regulators on the ac and dc current ripple are presented. Synchronized polarized ramptime regulators are shown to produce the minimum ripple current in simulation and in the prototype operation.ZACE current control techniques, and ramptime and polarized ramptime in particular, are presented as a significant contribution to the control of current in power electronic converters.