Power Electronic Converters in Low-Voltage Direct Current Distribution – Analysis and Implementation

Over the recent years, smart grids have received great public attention. Many proposed functionalities rely on power electronics, which play a key role in the smart grid, together with the communication network. However, “smartness” is not the driver that alone motivates the research towards distribution networks based on power electronics; the network vulnerability to natural hazards has resulted in tightening requirements for the supply security, set both by electricity end-users and authorities. Because of the favorable price development and advancements in the field, direct current (DC) distribution has become an attractive alternative for distribution networks. In this doctoral dissertation, power electronic converters for a low-voltage DC (LVDC) distribution system are investigated. These include the rectifier located at the beginning of the LVDC network and the customer-end inverter (CEI) on the customer premises. Rectifier topologies are introduced, and according to the LVDC system requirements, topologies are chosen for the analysis. Similarly, suitable CEI topologies are addressed and selected for study. Application of power electronics into electricity distribution poses some new challenges. Because the electricity end-user is supplied with the CEI, it is responsible for the end-user voltage quality, but it also has to be able to supply adequate current in all operating conditions, including a short-circuit, to ensure the electrical safety. Supplying short-circuit current with power electronics requires additional measures, and therefore, the short-circuit behavior is described and methods to overcome the high-current supply to the fault are proposed. Power electronic converters also produce common-mode (CM) and radio-frequency (RF) electromagnetic interferences (EMI), which are not present in AC distribution. Hence, their magnitudes are investigated. To enable comprehensive research on the LVDC distribution field, a research site was built into a public low-voltage distribution network. The implementation was a joint task by the LVDC research team of Lappeenranta University of Technology and a power company Suur-Savon S¨ahk¨o Oy. Now, the measurements could be conducted in an actual environment. This is important especially for the EMI studies. The main results of the work concern the short-circuit operation of the CEI and the EMI issues. The applicability of the power electronic converters to electricity distribution is demonstrated, and suggestions for future research are proposed.

Société mutualiste : dite... / statuts [types]Ministère du travail et de la participation

Collection : Journal officiel de la République française ; brochure 1171

The quality of the mother-child relationship during collaborative problem solving /

The quality of the mother-child relationship was examined in relation to joint planning, maternal teaching strategies, maternal emotional support, mutual positive affect and attachment security. Fifty-five grade five children and their mothers participated in a laboratory session comprised of various activities and completed questionnaires to evaluate attachment security. Joint planning and social problem solving were assessed observationally during an origami task. Problem solving effectiveness was unrelated to maternal teaching strategies, maternal encouragement and mutual positive affect. A marginally significant relationship was found between maternal encouragement and active child participation. Attachment security was found to be significantly related to sharing of responsibility during local planning, but only for child autonomous performance. An examination of conditional probabilities revealed that mutual positive affect did not increase the likelihood of subsequent mother-child dyadic regulation. However, mutual positive affect was found to be significantly related to both active child participation and dyadic regulation. The hypothesis predicting a mediational model was not supported. The implications of these findings in the theoretical and empirical literature were considered and suggestions for future research were made.

Registered nurses' perceptions of factors impacting on their continuing education /

This qualitative study examined the effects of hospital restructuring on a group of nurses at a community hospital. Eleven nurses were asked questions in order to gain insight into their experience in this situation. Ten of these participants were female, and one was male. The intent was to gather information about how restructuring has affected their lives, including, their motivational factors and barriers to participation in continuing education, and their descriptions of their workplace environment. Audiotaped interviews were conducted on two occasions to obtain this data. Emergent themes included the nurses' comments about continuing education, motivational factors, barriers that included geography and time, reactions of co-workers, restructuring, the College of Nurses' Quality Assurance Program including peer feedback, and performance appraisals. The literature review compares the barriers and motivational factors to the previous research findings. Thus, this study gave voice to the experience of this group of nurses, working in a healthcare setting that is involved in restructuring. This information is important to the healthcare system, since many areas are involved in restructuring. The whole process, if it is to be successful, depends on the frontline workers, namely the nurses. Thus, if there is anything to be learned from this group of people, that could be used to improve this progression, everyone would benefit from this information, were it to be implemented. Everyone is a stakeholder in the quality of healthcare in our province. The frontline workers are the ones that hold the vantage point to be able to provide suggestions for the changes needed to successful. These nurses are not just motivated by work issues however, and educating them and motivating them will also improve the care provided through increased knowledge and enhanced self-esteem.

The role of motivational systems in community service involvement : initiating and sustaining factors and quality of experience /

Community service participation can have a positive impact on development, especially for youth. Although researchers have found positive outcomes, there has been a notable decline in youth participation over the past few years (Statistics Canada, 2000). Given the positive outcomes and current decline, it has been argued that youth should be encouraged to get involved in service activities. In the present study, quantitative and qualitative data were collected to determine factors that would help youth to initiate and sustain service, along with examining the quality of their experience. Eighty-two university undergraduate students (23 men), ranging in age from 17-20 years completed a 60-minute self-report questionnaire. Initiating and sustaining factors, motivational systems (similar to approach and avoidance dimensions), activity dimensions {Structure, Supportive Social Environment), quality of experience {Positive, Stress-Challenge), and future intention to participate in community service were measured. Eight participants also completed a 20-minute telephone interview to complement and expand on the quantitative data collected. Some initiating and sustaining factors were specific to individuals higher on the avoidance dimension, while others were relevant to those higher on the approach dimension. Several factors also were important to individuals regardless of their motivational system orientation. Positive quality of experience was related positively to experiencing a supportive social environment. In addition, women rated their community service as more positive than did men. A predicted interaction between the avoidance dimension and Structure in predicting positive quality of experience was not supported; however, positive quality of experience was predicted by the interaction of the approach dimension and Structure. A tested interaction between the avoidance dimension and Supportive Social Environment in predicting positive quality of experience was not supported. Similarly, a predicted interaction between the approach dimension and Supportive Social Environment in predicting positive experience quality was not supported. However, Supportive Social Environment was positively related to positive quality of experience. No support was found for a mediational role for positive quality of experience or stress-challenge quality of experience in exploring the relation between motivational orientation and fiiture intention to engage in service activities. The results of this study suggest that participating in a service environment that is supportive and provides the opportunity for social interactions with others would promote positive quality of experience and help youth sustain involvement. Thus, to help youth have positive experiences and to remain active in service, it is important for service agencies to promote these types of environments. In addition, some initiating and sustaining factors were specific to youth higher on the avoidance dimension and some were relevant to youth higher on the approach dimension. Therefore, service agencies may need to consider using different recruitment and retention strategies, depending on the type of youth they wish to recruit.

A physical activity intervention in a workplace setting

Physical inactivity poses a huge burden on Canada's health care system and is detrimental to the health of Canadians (Katzmarzyk & Janssen, 2004). Walking is a viable option for individuals to become physically active on a daily basis and is in fact the most commonly reported leisure time physical activity. It has been associated with many health benefits including weight loss/weight control, reduced risk of coronary artery disease and diabetes, lowered blood pressure, and improved psychological wellbeing (Brisson & Tudor-Locke, 2004). Specifically, individuals' stage of change, selfefficacy and health related quality of life (HRQL) are three psychological constructs that can be greatly improved with increased physical activity (Dishman, 1991; Penedo & Dahn, 2005; Poag & McAuley, 1992). Public health physical activity recommendations exist but many individuals find these difficult to meet due to overly busy lifestyles (Public Health Agency of Canada, 2003). Pedometers are inexpensive devices that can monitor individual bouts of walking so that the incorporation of physical activity into one's daily life is more plausible. They are also excellent tools for motivation, goalsetting, and immediate feedback (Brisson & Tudor-Locke, 2004). Since many people spend a large proportion of their time at their places of employment, workplaces have begun to be a common site for the development of physical activity interventions. These programs have been growing in popUlarity and have shown numerous benefits for both employees and employers (Voit, 2001). The purpose of the current study was to implement and evaluate the use of a pedometer-based physical activity intervention incorporating goal-setting and physical activity logs in a workplace setting, and to examine the relationship between different types of self-efficacy (task, barrier, and scheduling) and different phases of the intervention. Twenty male participants from a local steel manufacturing plant who exhibited health risk factors (e.g. hypertension, diabetes, etc.) were assigned to one of two groups (group A or group B). All participants were asked to wear pedometers on their waists, record their daily steps, set goals that were outlined on a step-tracking sheet (detennined by their baseline number of steps), and keep track of their work days, wakelbed time, sedentary time, and time spent doing other physical activity. Group A began the intervention immediately following the baseline measures, whereas group B continued with their regular routine for 4 weeks before beginning. Physiological measures (height, weight, blood pressure, relative body fat, waist and hip circumference, and body mass index) were taken and a battery of questionnaires that assessed barrier, task and scheduling self-efficacy, HRQL, and stage of change administered at baseline, week 5 (end of intervention for group A), week 9 (end of intervention for group B; follow-up for group A) and week 13 (follow-up for both groups). Results showed that this workplace physical activity intervention was successful at increasing the participants' daily steps, that task self-efficacy is a significant predictor of participants' exercise adherence during the initial stages of participation (intervention phase), and that the participants felt that this intervention was effective. Finally, further exploratory analyses showed that this intervention was effective for all participants, but most valuable for participants most in need of improvement - that is, those who were most sedentary prior to the intervention. This intervention is an inexpensive use of simple and effective tools (e.g. pedometers), has the potential to attract a wide variety of participants and become a pennanent part of any health promotion initiative.

What children value : a scale to guide health promotion programs

Objective. Physical activity is important for the health of all human beings. Although it is important to develop good health promotion programs for children to increase participation in physical activity, to date there appear to be no programs based on what kids value beyond health and physical activity itself. This study proposed to create a scale with strong content and face validity that could uncover what any given population of children value in life regardless of their participation in physical activity and that experts feel could be related to physical activity. These findings will allow the development of targeted health promotion programs to increase children's participation in regular physical activity. Method In this study, a combination of qualitative and quantitative approaches was used. Data were gathered from seven experts in the field, sixty-seven children in grades three to five, five parents, and three teachers. From these data response groupings were created and sent to four experts to be given single word names. The resulting nine theme names were re-worked into "child-friendly" language. Four children were then asked to discuss theme names to see if they liked and understood them. The next step involved asking children and experts to rank order the nine themes, the children in general and the experts in terms of relevance to physical activity. From these results, possible versions of the scale were then created using the combined expert/children rankings. Each version was examined for content validity. Two versions of a scale resulted. These were sent to experts, parents, teachers and children in order to determine which one they liked better and to suggest any foreseeable problems. Once this information was collected, a beta (final prototype) version of the scale was created. Results. Nine common theme names were created from the response groupings. All four children agreed that they did understand and like each of the nine theme names. Experts and teachers agreed that full coverage of the content had been achieved. Children suggested a single wording change from "Being Accepted" to "Being Included". Five themes were selected for inclusion. The beta version of the scale included 12 forced choice statements, the first ten comparing all themes against one another followed by two anchor statements. Conclusion. At the outset it was recognized that it is essential to know what children think is important in their lives in order to serve as potential benefits in the development of effective physical activity promotion programs. This study developed a scale which could be used to determine what a population of children feel is important in order to focus health promotion programs for physical activity. The scale has strong face and content validity.

Academics as parents--parents as academics : a study of the integration of intellectual and child-care labours /

Discussions concerning the challenges of combining work and family are certainly not new, and still actively continue. There is, however, a silence in the related literature regarding a comprehensive description of integrating specifically university academic ~. work and family responsibilities. This silence is especially evident for men who are parents as well as academics. With the participation of 4 key informants, this qualitative research study gave voice to men and women who participate in the academic labour of a Canadian university as professors, and as graduate students, along with the parenting labour of at least 1 child under the age of7. Methodology was developed to reveal in-depth perspectives regarding the work practices employed by 4 key informants as they combined intellectual and child-care responsibilities. Multiple data collection methods included journal reflections, day time observation sessions, a focus group, and a final evaluation questionnaire. Using research findings, together with information extrapolated from Three Models of the Family (Eichler, 1997), this study also took steps toward developing a Proposed "Three Models of the University," to offer explanation for the work practices of the key informants as academics/parents, and also for future consideration in university policy formation.

From Fordism to neoconservatism : free trade and Canadian industrial policy in an era of globalism /

Nothing today affects the lives of people in countries throughout the industrialized and developing world as much as international trade. Nowhere is this more true than in Canada. Canada's involvement in international trade has a long history dating back to 1854 when it was a British colony. As a major trading country, Canada has always adopted a proactive industrial policy which has been largely responsible for its relative economic prosperi ty. But, wi th businesses now free to invest and divest under the terms of the CUFTA and the NAFTA, the most fundamental concerns for Canadians, in a borderless world, are what powers will the Canadian government have to shape industrial policy, and to what extent can Canada continue as a viable nationstate if it can no longer control its national economy? These are important concerns because, in world without borders, the adjustment process becomes more volatile and more difficult to manage. The CUFTA and the NAFTA not only create the rules for conducting trade, but they also establish a set of new rules for the Canadian government that will diminish its power. As a member of a new North American trading bloc, Canada will find itself subject to a set of forces requiring analysis beyond participation in a conventional free trade area. Because many of the traditional levers of government will now be subject to external control imposed by these agreements, Canada will not be able to mount certain policies in the future that it has relied on in the past. This reality limits the pro-active role of the Canadian state to use policies and programmes for the country's immediate national development. What this thesis attempts is an examination of the evolution of Canadian industrial policy, in effect, the transi tion from Fordism to Neoconservatism, and an assessment of Canada's future as a nation-state as it tries to find security and improved access in a free trade arrangement. Unless Canada takes steps to neutralize the asymmetry of power between itself and the United States through adjustment programmes, it is the contention of this thesis that its economic future is anything but stable.