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Work-related low back disorders (WRLBDs) are common and costly in the U.S. and numerous interventions aiming to reduce WRLBD risk have been developed.  In one approach, training programs incorporating the work strategies (or work methods) of experienced workers have often been proposed as a training model or a behavior target of training.  However, both the specific role of work experience in contributing to WRLBDs and the effectiveness of such an intervention approach are not well understood.  In the current research, differential work strategies of experienced workers and associated WRLBD risk were identified, in the context of several common occupational activities.  Three experiments were completed, in which both experienced workers and matched novices participated.  These experiments involved relatively short duration repetitive lifts/lowers, more prolonged lifts/lowers that induced fatigue, and dynamic pushes/pulls.  Diverse aspects of work strategies were quantified, emphasizing torso kinematics/kinetics, balance maintenance, and/or torso movement stability.  During short-term repetitive lifts/lowers, experienced workers exhibited higher torso kinematics and kinetics, suggestive of a higher risk for WRLBDs, though better balance maintenance and torso stability were evident in this group.  Thus, experienced workers may trade off an increased risk for WRLBDs to achieve better balance and torso stability.  Fatigue modified work methods during repetitive lifts/lowers in both the novice and experienced groups, though the associated contribution to WRLBDs was unclear due to opposite changes in torso kinematics vs. kinetics.  More consistently, fatigue decreased balance maintenance during lifts/lowers.  Fatigue also modified work methods adopted by experienced workers, leading to higher torso kinetics, that were suggestive of a higher risk for WRLBDs during lifts/lowers.  For dynamic pushes/pulls, experienced workers used lower torso kinematics and kinetics, suggestive of a lower risk for WRLBDs.  As a whole, these results suggest that work methods are distinct between novices and experienced workers.  Further, work experience may not consistently reduce WRLBD risk, and the influences of experience may be task specific.  Such findings can help guide the development of future interventions, particularly training, targeting the control of WRLBDs. / Ph. D.

<div> <p>TiB₂particulate reinforced aluminum matrix composites (TiB₂/Al-MMCs) have received extensive attention due to a great potential in a wide variety of applications. Nano-TiB₂/Al-MMCs have also received attention from scholars with the development of nanotechnology in recent years. However, obstacles like agglomeration of nanoparticles in the matrix, and the difficulty of preparation of nanoparticulate reinforced metal matrix composites (PRMMNCs) still need to be resolved. This study summarizes the research progress of Al-matrix composites (Al-MMCs) in recent years and exemplifies the common preparation methods. Experiments were designed to study the common problems in the preparation of composite materials.</p> <p> </p> <p>Two experiments were designed and completed in this study. First, TiB₂/Al-4.5Cu composites were synthesized through a mixed salt reaction method. The distribution of reinforcing particle in the aluminum matrix was observed. The predictive model of particle behavior in Al-4.5wt. %Cu matrix based on thermodynamic laws was re-examined. The experiment results are inconsistent with the prediction from a classic prediction model. Regardless of the rate of solidification and critical velocity (V_C), the most of the particles are rejected by advancing solid-liquid interface. Through review of classic particle pushing theory, this study attempts to derive a new boundary condition used to predict the behavior of reinforcing particles in a metal matrix during solidification based on the diffusion convection equations. </p> <p> </p> <p>Second, nano-TiB₂/Al composites with a variety of volume fractions were synthesized by ultrasound assistance in a stirring method. The research has focused on optimization and improvement of preparation methods. High-energy ball milling (HEBM) and high-intensity ultrasound (HIU) were introduced into the fabrication process. Furthermore, a forging post-treatment process is used to process as-cast samples prepared by the experiment, so that the reinforcing particles in the composite material can be redistributed. The experiment results show that HEBM facilitates the mixing of nano-TiB₂ particles with salts. HIU helps distribute particles evenly throughout the matrix. The Vickers hardness and tensile strength of the composites were tested. The results indicated that the forging treatment has great influence on the mechanical properties of composite materials.</p> </div> <b><br></b>

Ring oscillators provide a central role in timing circuits for today?s mobile devices and desktop computers. Increased integration in these devices exacerbates switching noise on the supply, necessitating improved supply resilience. Furthermore, reduced voltage headroom in submicron technologies limits the number of stacked transistors available in a delay cell. Hence, conventional single-loop oscillators offer relatively few design options to achieve desired specifications, such as supply rejection. Existing state-of-the-art supply-rejection- enhancement methods include actively regulating the supply with an LDO, employing a fully differential or current-starved delay cell, using a hi-Z voltage-to-current converter, or compensating/calibrating the delay cell. Multiloop ring oscillators (MROs) offer an additional solution because by employing a more complex ring-connection structure and associated delay cell, the designer obtains an additional degree of freedom to meet the desired specifications. Designing these more complex multiloop structures to start reliably and achieve the desired performance requires a systematic analysis procedure, which we attack on two fronts: (1) a generalized delay-cell viewpoint of the MRO structure to assist in both analysis and circuit layout, and (2) a survey of phase-noise analysis to provide a bank of methods to analyze MRO phase noise. We distill the salient phase-noise-analysis concepts/key equations previously developed to facilitate MRO and other non-conventional oscillator analysis. Furthermore, our proposed analysis framework demonstrates that all these methods boil down to obtaining three things: (1) noise modulation function (NMF), (2) noise transfer function (NTF), and (3) current-controlled-oscillator gain (KICO). As a case study, we detail the design, analysis, and measurement of a proposed multiloop ring oscillator structure that provides improved power-supply isolation (more than 20dB increase in supply rejection over a conventional-oscillator control case fabricated on the same test chip). Applying our general multi-loop-oscillator framework to this proposed MRO circuit leads both to design-oriented expressions for the oscillation frequency and supply rejection as well as to an efficient layout technique facilitating cross-coupling for improved quadrature accuracy and systematic, substantially simplified layout effort.

Chemists use the electron-pushing formalism to rationalize, analyze, and explain how a chemical reaction occurs on an electronic level. The electron pushing formalism (EPF) is the curved arrows representing electron movement. Some research on undergraduate organic chemistry students’ understanding of the electron pushing formalism has presented evidence that some students do not find the electron-pushing formalism meaningful. Research at the University of Ottawa found that the EPF symbolism is meaningful to the participants because they interpret EPF arrows and use charges and mapping to problem-solve. At the University of Ottawa, the organic chemistry curriculum was changed in 2012 to have students learn and interpret reactions based on similar reactivity patterns. The goal of the redesign was to give students the tools to analyze, predict, and explain how reactions occur instead of memorizing. An initial section of the curriculum is dedicated to teaching the electron-pushing formalism before any reaction. An exam analysis was conducted to see the new curriculum's effect by looking at students' drawn structures and EPF arrows. Students demonstrated minimal errors when drawing the EPF arrows and scored higher on familiar and unfamiliar reactions following the new curriculum, which suggests students found the EPF arrows meaningful. The following think-aloud interview study better captured student interpretations of the EPF arrows to determine what features students found relevant and whether the students who could explain a conceptual understanding of the EPF arrows could express a deeper understanding. The think-aloud interviews found that students do place meaning into organic chemistry representations as students were thinking about how to draw the EPF arrows based on prior knowledge. The data from the two previous studies were collected near the end of the course when students had a significant amount of experience, while students’ initial interpretations of the EPF arrows are needed. The primary focus of this thesis is to understand how students initially interpret the electron-pushing formalism arrows and look further into previous findings, which include electron movement, bond-forming and breaking processes, mapping, charges, stepwise reasoning, and transplanting electrons. Twelve students were recruited from Organic Chemistry I and interviewed over three weeks after being taught the electron-pushing formalism. The interviews were conducted using a think-aloud procedure to capture students’ thoughts, and each interview lasted approximately 1 hour. The instrument consisted of six organic chemistry questions, specifically chosen, as students would not encounter them in the class and would have to interpret the representations. The transcripts were analyzed with respect to the previous studies' findings and compared among participants to explore students’ interpretations and use of the EPF arrows. The findings from this study suggest participants found the EPF arrows meaningful because participants interpreted the representations as electron-movement, bond-forming, and bond-breaking processes which contrasts some prior research that reported students do not find the EPF arrows meaningful (Bhattacharyya and Bodner, 2005; Graulich, 2015). Participants connected the EPF arrows to electron movement, bond-forming, and bond-breaking processes. Participants compared surface features to determine how to draw the EPF arrows. Participants’ visualization and how they approached the reactions differed. Participants’ visualizations of the organic chemistry reaction were divided between a stepwise or concerted visualization. Most participants approached the EPF arrows stepwise as a problem-solving tool as it was easier for them to understand. Participants correctly interpreted most bond-breaking EPF arrows, but some participants relocated the electron pair onto a different atom instead of forming a bond. Participants mainly mapped the carbon atoms with numeric labels and found implicit atom-type questions challenging. Participants interpreted charges as an important surface feature and used charges to help them solve the question. Participants viewed charges as a reactive location where bonds break and form and compared the number of charges between reactants and products to check whether their answers were correct. The results suggest the participants in the study found the EPF arrows and made meaningful connections at the submicroscopic level with minimal experience. Mastering the EPF arrows at the beginning of the course appears beneficial to student learning because participants interpreted the EPF arrows as a meaningful representation suggesting that the EPF arrows are less of a barrier when learning and mastering organic chemistry, under the University Of Ottawa’s organic chemistry curriculum as intended. Since the EPF arrows are less of a barrier, students can focus on other organic chemistry concepts and can be more successful which is seen in the first exam analysis where minimal errors were seen. The first exam analysis observed minor pentavalent atoms and errors with the EPF arrows (Flynn and Featherstone, 2017). The following interview study found students described mapping, charges, stepwise, and chemistry reasoning when discussing electron movement (Galloway et al., 2017). The findings from this work demonstrated the EPF arrows as a representation are meaningful to participants as they interpreted the EPF arrows after being recently taught. Similar findings at a different institution using a revised curriculum that focuses on the EPF at the beginning of the course found students were more likely to use the EPF arrows and were more likely to provide the correct answer than their counterparts (Crandell et al., 2018; Houchlei et al., 2021). Research at institutions adopting the functional group curriculum reported that students did not find the EPF meaningful (Bhattacharyya and Bodner, 2005; Ferguson and Bodner, 2008; Grove, Cooper, and Rush, 2012). The findings suggest that the time spent mastering the EPF arrows at the beginning of the course is beneficial when learning organic chemistry because the symbols are less likely to be a hindrance through misinterpretation, and students can focus on mastering organic chemistry concepts. Implications for teaching and learning include providing clarity on interpreting the EPF arrows and using the transplanting processes to demonstrate other chemical possibilities. Participants demonstrated comparing reactants and products when problem-solving. When students face difficulty, they should compare the products of chemical processes (bond-forming, bond-breaking, or electrons moving). The correct process has the EPF arrow starting from electrons and point to an atom or bond, maintains the conservation of atoms, and electrons stay with one of the originating atoms. The other processes will not follow one of the above principles, thus making them illogical. Future work could further explore if students interpret the EPF arrows as a whole or if they interpret the arrowhead and arrow tail. Why do some students face difficulty keeping electrons on an originating atom? Why do some students face difficulty conserving atoms, electrons, and charges throughout a reaction? Whether the findings are generalizable by expanding the sample size. In the context of the new curriculum, it appears students' have acquired a better understanding of the EPF. The results are promising because participants with minimal experience interpreted the EPF arrows and found them meaningful as a symbolic representation aligned with the curriculum's intentions.

The stability of the spine can be estimated from kinematic variability and nonlinear analyses of seated balance tasks. However, processing methods require sufficient signal duration and test-retest experiments require that the assessment must be reliable. Our goal was to characterize the reliability and establish the trial duration for spine stability assessment. Stationarity, kinematic variability and nonlinear dynamic stability were quantified from kinetic and kinematic data collected during balance performance. Stationarity results showed that a minimum 30 seconds test duration is necessary. Intra-session reliability was excellent, however inter-session reliability needed more test trials to achieve excellent reliability. Few studies have investigated the spinal stability during pushing and pulling exertions. Past studies suggest that the spine can be stabilized by paraspinal muscle stiffness as well as reflexes. We hypothesized that the stability of the spine decreases with exertion force and decreases during pushing more than during pulling exertion. Kinematic variability and nonlinear dynamic stability measurements were quantified from the balance performance during isometric pushing and pulling tasks. Results demonstrated that spinal stability decreased with exertion force and decreased a greater amount during pushing task than during pulling task. Stiffness alone may be insufficient to stabilize the trunk. Results may be able to be explained by slower reflex delay. The results suggested that pushing and pulling exertions have a potential risk of low-back disorders. / Master of Science

This qualitative study explores midwifery practice during the second stage of labour focusing specifically on whether midwives adopt a directed or physiological approach to maternal pushing. It was undertaken against the backdrop of research findings suggesting that there is no proven benefit to directing a woman's pushing efforts but anecdotal evidence suggests that this remains a routine and accepted part of midwifery practice in the United Kingdom (UK). Semi- structured interviews were undertaken with ten midwives who had recent experience of caring for women during the second stage of labour, ten women who had recently given birth and four obstetricians. A form of thematic analysis was undertaken. Findings were viewed through a lens of critical social theory (CST) and drew on feminist principles to provide a deeper understanding of the emergent themes. Findings indicated that a directed approach to second stage pushing was the norm in this UK Maternity Unit and was deeply embedded within the cultural context of what it meant to be a midwife that involved ' doing' rather than 'being'. Reasons explaining why midwives continue to use directed pushing were grouped into themes; ' time passing and watching the clock' 'different worlds' , 'different women', 'midwives take charge', 'growth of confidence and changing practice' and 'conflict'. When viewed from a CST perspective midwives undertaking directed pushing is seen as an example of institutionalised oppressive behaviour symbolising the way in which knowledge and rationality are disregarded in favour of a risk averse practice that is paradoxically the opposite of what evidence recommends. Midwives are identified as being oppressed by the dominant biomedical model to the extent that they do not view directed pushing as an intervention. In order to promote a more physiological approach with its' associated benefits, a return to a social model of midwifery with a focus on salutogenesis rather than pathogenesis is called for. Recommendations for midwifery education, practice and research are provided in order to support the transformational shift in midwifery culture that is needed if such a change is to become a reality.

The context of this report and the IRIDIA laboratory are described in the preface. Evolutionary Robotics and the box-pushing task are presented in the introduction.The building of a test system supporting Evolutionary Robotics experiments is then detailed. This system is made of a robot simulator and a Genetic Algorithm. It is used to explore the possibility of evolving box-pushing behaviours. The bootstrapping problem is explained, and a novel approach for dealing with it is proposed, with results presented.Finally, ideas for extending this approach are presented in the conclusion.

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