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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
331

Control Strategy for Energy Efficient Fluid Power Actuators : Utilizing Individual Metering

Eriksson, Björn January 2007 (has links)
This thesis presents a solution enabling lower losses in hydraulic actuator systems. A mobile fluid power system often contains several different actuators supplied with a single load sensing pump. One of the main advantages is the need of only one system pump. This makes the fluid power system compact and cost-effective. A hydraulic load often consists of two ports, e.g. motors and cylinders. Such loads have traditionally been controlled by a valve that controls these ports by one single control signal, namely the position of the spool in a control valve. In this kind of valve, the inlet (meter-in) and outlet (meter-out) orifices are mechanically connected. The mechanical connection makes the system robust and easy to control, at the same time as the system lacks flexibility. Some of the main drawbacks are The fixed relation between the inlet and outlet orifices in most applications produce too much throttling at the outlet orifice under most operating conditions. This makes the system inefficient. The flow directions are fixed for a given spool position; therefore, no energy recuperation and/or regeneration ability is available. In this thesis a novel system idea enabling, for example, recuperation and regeneration is presented. Recuperation is when flow is taken from a tank, pressurized by external loads, and then fed back into the pump line. Regeneration is when either cylinder chambers (or motor ports) are connected to the pump line. Only one system pump is needed. Pressure compensated (load independent), bidirectional, poppet valves are proposed and utilized. The novel system presented in this thesis needs only a position sensor on each compensator spool. This simple sensor is also suitable for identification of mode switches, e.g. between normal, differential and regenerative modes. Patent pending. The balance of where to put the functionality (hardware and/or software) makes it possible to manoeuvre the system with maintained speed control in the case of sensor failure. The main reason is that the novel system does not need pressure transducers for flow determination. Some features of the novel system: Mode switches The mode switches are accomplished without knowledge about the pressures in the system Throttle losses With the new system approach, choice of control and measure signals, the throttle losses at the control valves are reduced Smooth mode switches The system will switch to regenerative mode automatically in a smooth manner when possible Use energy stored in the loads The load, e.g. a cylinder, is able to be used as a motor when possible, enabling the system to recuperate overrun loads The system and its components are described together with the control algorithms that enable energy efficient operation. Measurements from a real application are also presented in the thesis.
332

Understanding independent environment control officers : learning from major South African construction projects / Johannes Albertus Wessels

Wessels, Johannes Albertus January 2015 (has links)
An independent industry of Environmental Control Officers (ECOs) is active on various construction sites across South Africa. It forms part of a global network of verifiers, such as Environmental Impact Assessment (EIA) and EIA follow-up verifiers. This network authenticates statements about and the implementation of sustainability commitments made during the planning phase of major construction projects. International studies show that the construction industry is experiencing many challenges to deliver sustainability commitments, including inadequate collaboration between role players, illdefined roles and responsibilities, and insufficient use of environmental governance approaches. On-site verifiers like ECOs may aid in restraining these challenges by bridging ineffective governance approaches, such as classic EIA with new governance approaches, for instance self-responsibility (e.g. Environmental Management Systems (EMSs)) and involvement of third parties. Moreover, an “independent from all” verification function may be vital in developing countries such as South Africa, where trust between the government, market and public is particularly fragile due to historical injustices. Interestingly, limited learning has been drawn and shared from this function’s real-world experience. There are also differing views on the role, independence and value of ECOs, due to roles, frequent interaction with persons responsible for delivering sustainability commitments, and collaboration with third parties being ill-defined. The overarching purpose of this study is to advance understanding of independent ECOs in major South African construction projects. Three lines of inquiry are followed. The first is to define what the role is, or ideally should be, of an ECO in the South African compliance monitoring and enforcement effort. The second is to identify what factors might influence the independence of verifiers. The third is to appraise how and to what extent independent EIA follow-up verifiers add value in major construction projects in the developing country context of South Africa. This study’s research assumptions are based on the real world of ECOs and uses a mixed method research approach to draw knowledge from the industry. The strategies of inquiry include a survey, interviews, and multiple case study evaluations. The methods for data collection include literature review, a self-administered survey questionnaire, semi-structured interviews, video material, observations of practice at case studies, and the collection of project documentation. The methods used for data analysis are the categorisation and measuring of opinions and statements of survey participants, the analysis of video material and project documentation, and the nominal categorisation and ordinal scaling of case study results. Three journal articles capture the essence of the research results and form part of the thesis report, as prescribed by the North-West University’s rules for doctoral theses in article format. All three articles were peer-reviewed and published in journals aimed at international audiences. Article 1 of the thesis highlights that an industry of ECOs fulfils numerous roles at various construction sites across South Africa. The results identify the importance of ECOs functioning independently of all role-players, but warn that obsessing about independence may compromise the ability of ECOs to fulfil their roles. The results also show that industry is in need of competence and the regulation thereof, as well as support from all role players. By drawing from the research results, the thesis defines an ECO. Article 2 of the thesis reiterates that independence is central to internationally acclaimed verification fields and important to ensure the credibility of EIA. The study identifies 18 factors that might influence the independence of EIA follow-up verifiers and divides the factors into five categories: financial, commercial, professional, personal, and other. By identifying and sharing these factors, this thesis aids in anticipating and avoiding potential conflict of interest between environmental role players. Article 3 strengthens the continuum between environmental governance approaches by conceptualising a framework for appraising the value of independent EIA follow-up verifiers. The framework provides for inter-linking principles and objectives of sustainability to the performance areas of EIA, EIA follow-up and the EMS. The appraisal results indicate that independent verifiers add most value when they are involved in screening, checking compliance, influencing decisions, community engagement, and integrating environmental governance approaches. The study confirms the benefits of adaptable, proactive, experienced, and independent EIA follow-up verifiers, such as ECOs, on major South African construction projects. / PhD (Geography and Environmental Management), North-West University, Potchefstroom Campus, 2015
333

Understanding independent environment control officers : learning from major South African construction projects / Johannes Albertus Wessels

Wessels, Johannes Albertus January 2015 (has links)
An independent industry of Environmental Control Officers (ECOs) is active on various construction sites across South Africa. It forms part of a global network of verifiers, such as Environmental Impact Assessment (EIA) and EIA follow-up verifiers. This network authenticates statements about and the implementation of sustainability commitments made during the planning phase of major construction projects. International studies show that the construction industry is experiencing many challenges to deliver sustainability commitments, including inadequate collaboration between role players, illdefined roles and responsibilities, and insufficient use of environmental governance approaches. On-site verifiers like ECOs may aid in restraining these challenges by bridging ineffective governance approaches, such as classic EIA with new governance approaches, for instance self-responsibility (e.g. Environmental Management Systems (EMSs)) and involvement of third parties. Moreover, an “independent from all” verification function may be vital in developing countries such as South Africa, where trust between the government, market and public is particularly fragile due to historical injustices. Interestingly, limited learning has been drawn and shared from this function’s real-world experience. There are also differing views on the role, independence and value of ECOs, due to roles, frequent interaction with persons responsible for delivering sustainability commitments, and collaboration with third parties being ill-defined. The overarching purpose of this study is to advance understanding of independent ECOs in major South African construction projects. Three lines of inquiry are followed. The first is to define what the role is, or ideally should be, of an ECO in the South African compliance monitoring and enforcement effort. The second is to identify what factors might influence the independence of verifiers. The third is to appraise how and to what extent independent EIA follow-up verifiers add value in major construction projects in the developing country context of South Africa. This study’s research assumptions are based on the real world of ECOs and uses a mixed method research approach to draw knowledge from the industry. The strategies of inquiry include a survey, interviews, and multiple case study evaluations. The methods for data collection include literature review, a self-administered survey questionnaire, semi-structured interviews, video material, observations of practice at case studies, and the collection of project documentation. The methods used for data analysis are the categorisation and measuring of opinions and statements of survey participants, the analysis of video material and project documentation, and the nominal categorisation and ordinal scaling of case study results. Three journal articles capture the essence of the research results and form part of the thesis report, as prescribed by the North-West University’s rules for doctoral theses in article format. All three articles were peer-reviewed and published in journals aimed at international audiences. Article 1 of the thesis highlights that an industry of ECOs fulfils numerous roles at various construction sites across South Africa. The results identify the importance of ECOs functioning independently of all role-players, but warn that obsessing about independence may compromise the ability of ECOs to fulfil their roles. The results also show that industry is in need of competence and the regulation thereof, as well as support from all role players. By drawing from the research results, the thesis defines an ECO. Article 2 of the thesis reiterates that independence is central to internationally acclaimed verification fields and important to ensure the credibility of EIA. The study identifies 18 factors that might influence the independence of EIA follow-up verifiers and divides the factors into five categories: financial, commercial, professional, personal, and other. By identifying and sharing these factors, this thesis aids in anticipating and avoiding potential conflict of interest between environmental role players. Article 3 strengthens the continuum between environmental governance approaches by conceptualising a framework for appraising the value of independent EIA follow-up verifiers. The framework provides for inter-linking principles and objectives of sustainability to the performance areas of EIA, EIA follow-up and the EMS. The appraisal results indicate that independent verifiers add most value when they are involved in screening, checking compliance, influencing decisions, community engagement, and integrating environmental governance approaches. The study confirms the benefits of adaptable, proactive, experienced, and independent EIA follow-up verifiers, such as ECOs, on major South African construction projects. / PhD (Geography and Environmental Management), North-West University, Potchefstroom Campus, 2015
334

Non-Independent Mate Choice in Female Humans (Homo sapiens) : Progression to the Field

Agnas, Axel Jönses Bernard January 2016 (has links)
There is much evidence that mate-choice decisions made by humans are affected by social/contextual information. Women seem to rate men portrayed in a relationship as more desirable than the same men when portrayed as single. Laboratory studies have found evidence suggesting that human mate choice, as in other species, is dependent on the mate choice decisions made by same-sex rivals. Even though non-independent mate choice is an established and well-studied area of mate choice, very few field studies have been performed. This project aims to test whether women’s evaluation of potential mates desirability is dependent/non-independent of same-sex rivals giving the potential mates sexual interest. This is the first field study performed in a modern human’s natural habitat aiming to test for non- independent mate choice in humans. No desirability enhancement effect was found. The possibilities that earlier studies have found an effect that is only present in laboratory environments or have measured effects other than non-independent mate choice are discussed. I find differences in experimental design to be the most likely reason why the present study failed to detect the effect found in previous studies. This field study, the first of its sort, has generated important knowledge for future experimenters, where the most important conclusion is that major limitations in humans ability to register and remember there surrounding should be taken in consideration when designing any field study investigating human mate choice.
335

Two conjectures on 3-domination critical graphs

Moodley, Lohini 01 1900 (has links)
For a graph G = (V (G), E (G)), a set S ~ V (G) dominates G if each vertex in V (G) \S is adjacent to a vertex in S. The domination number I (G) (independent domination number i (G)) of G is the minimum cardinality amongst its dominating sets (independent dominating sets). G is k-edge-domination-critical, abbreviated k-1- critical, if the domination number k decreases whenever an edge is added. Further, G is hamiltonian if it has a cycle that passes through each of its vertices. This dissertation assimilates research generated by two conjectures: Conjecture I. Every 3-1-critical graph with minimum degree at least two is hamiltonian. Conjecture 2. If G is k-1-critical, then I ( G) = i ( G). The recent proof of Conjecture I is consolidated and presented accessibly. Conjecture 2 remains open for k = 3 and has been disproved for k :::>: 4. The progress is detailed and proofs of new results are presented. / Mathematical Science / M. Sc. (Mathematics)
336

Using Generic Telemetry Prognostic Algorithms for Launch Vehicle and Spacecraft Independent Failure Analysis Service

Losik, Len 10 1900 (has links)
ITC/USA 2010 Conference Proceedings / The Forty-Sixth Annual International Telemetering Conference and Technical Exhibition / October 25-28, 2010 / Town and Country Resort & Convention Center, San Diego, California / Current failure analysis practices use diagnostic technology developed over the past 100 years of designing and manufacturing electrical and mechanical equipment to identify root cause of equipment failure requiring expertise with the equipment under analysis. If the equipment that failed had telemetry embedded, prognostic algorithms can be used to identify the deterministic behavior in completely normal appearing data from fully functional equipment used for identifying which equipment will fail within 1 year of use, can also identify when the presence of deterministic behavior was initiated for any equipment failure.
337

Fri Medias Effekt På Korruption : - En komparativ studie av tillgångens betydelse för fri medias effektivitet i kampen mot korruption

Rassam, Rola, Nilsson, Mattias January 2016 (has links)
This paper aims to study the importance of media accessibility, as it is conceptually defined by current research, for the relationship between free media and corruption. Previous studies have determined that a free, independent media plays a vital role in not only curbing corruption but also in sustaining and monitoring a healthy democracy. They have also confirmed that there is a significant correlation between the degree of press freedom and the degree of corruption, in which a freer press has a negative impact on the conditions for corruption. Nevertheless, press freedom and independent media, as said studies have established, cannot be seen as an easy solution or a “quick fix” when fighting corruption. More recent studies have concluded that accessibility is a dimension that could possibly determine how effective the free, independent media is for fighting and preventing corruption. This paper aims to dig deeper into this theory.   The purpose of the study is to distinguish what kind of role media accessibility plays in maximising the free medias effectiveness in the role as a watchdog towards public power. This study hopes to achieve it’s purpose by analysing what the direct effects and consequences of media revelations surrounding corruption cases has resulted in for different countries in relation to the degree of accessibility. The study will also take into account the distinction between rule-based versus relationship-based cultures and how corruption can be perceived and viewed differently between the two. This perspective is to be seen as a complementary outlook and possible explanation when determining if the potential dissimilarities in the effects of media revelations amongst countries are due to differences in accessibility or due to inherent cross-cultural differences. Our work has shown clear differences in the resulted effects of media revelations. However, it is impossible to identify whether the variations among countries in regard to actual effects depend on the degree of accessibility or due to inherent cross-cultural differences between nations.
338

Investigating the role of APOE-ε4, a risk gene for Alzheimer's disease, on functional brain networks using magnetoencephalography

Luckhoo, Henry Thomas January 2013 (has links)
Alzheimer's disease (AD) is developing into the single greatest healthcare challenge in the coming decades. The development of early and effective treatments that can prevent the pathological damage responsible for AD-related dementia is of utmost priority for healthcare authorities. The role of the APOE-ε4 genotype, which has been shown to increase an individual's risk of developing AD, is of central interest to this goal. Understanding the mechanism by which possession of this gene modulates brain function, leading to a predisposition towards AD is an active area of research. Functional connectivity (FC) is an excellent candidate for linking APOE-related differences in brain function to sites of AD pathology. Magnetoencephalography (MEG) is a neuroimaging tool that can provide a unique insight into the electrophysiology underpinning resting-state networks (RSNs) - whose dysfunction is postulated to lead to a predisposition to AD. This thesis presents a range of methods for measuring functional connectivity in MEG data. We first develop a set of novel adaptations for preprocessing MEG data and performing source reconstruction using a beamformer (chapter 3). We then develop a range of analyses for measuring FC through correlations in the slow envelope oscillations of band-limited source-space MEG data (chapter 4). We investigate the optimum time scales for detecting FC. We then develop methods for extracting single networks (using seed-based correlation) and multiple networks (using ICA). We proceed to develop a group-statistical framework for detecting spatial differences in RSNs and present a preliminary finding for APOE-genotype-dependent differences in RSNs (chapter 5). We also develop a statistical framework for quantifying task-locked temporal differences in functional networks during task-positive experiments (chapter 6). Finally, we demonstrate a data-driven parcellation and network analysis pipeline that includes a novel correction for signal leakage between parcels. We use this framework to show evidence of stationary cross-frequency FC (chapter 7).
339

Connecting with women : the working lives of independent midwives and their perceptions of the mother-midwife relationship

Garratt, Rosemary January 2014 (has links)
This study aimed to explore the lived experience of the working lives of midwives in the UK who practice independently of the NHS. It was designed to understand their motivations for working in this way and to explore their beliefs and values about midwifery care with particular emphasis on their perceptions of building and maintaining relationships with childbearing women. Hermeneutic phenomenology informed the methodology for the study and an adapted biographical narrative interpretive method (Wengraf 2001) was used for data collection. In depth qualitative interviews were carried out with twenty Independent midwives in the UK between 2007 & 2009. Data were analysed using Ricoeur's theory of interpretation (Ricoeur 1981). Keys findings indicate that motivated by a very strong sense of what it means to be 'with woman'; these midwives initially chose a career path in the NHS that enabled them to better enact this philosophy. However, constraints on their ability to enact this philosophy in the NHS combined with a desire to form more meaningful relationships with childbearing women and to support their individual needs informed a final move from the NHS into independent practice. Independent midwifery is experienced as very positive career move which results in considerable job satisfaction and an opportunity to use the full range of midwifery skills. Formation of the mother midwife relationship is perceived as a pivotal midwifery tool which facilitates understanding of individual childbearing women and their needs. Ricoeur's theory of interpretation (1981) is utilized to explain how Independent midwives form relationships with their clients in this context. The concepts of 'time', 'autonomy' and 'risk' are discussed in the light of study findings, contributing a unique insight into the working lives of Independent midwives, the mother midwife relationship and enactment of the 'with woman' philosophy in this context. The study also demonstrates that whilst there are many positive aspects of working as an Independent midwife there are also several constraints and potential vulnerabilities. These include the blurring of work/life boundaries, financial insecurity and the consequences of working with clients who often have very complex needs and particular expectations of the midwife-client relationship. Supporting women's choices, working flexibly to meet the needs of clients and respecting their right to autonomous decision making can place Independent midwives in a position of potential vulnerability and leave them subject to professional criticism.
340

Pedagogiken i tiden : Om framväxten av nya undervisningsformer under tidigt 2000-tal – exemplet Kunskapsskolan / Pedagogy of today : On the development of new teaching methods during the early 2000´s. A case study of Kunskapsskolan

Ståhle, Ylva January 2006 (has links)
The study concerns the new educational activities that emerge within the deregulated school system at the beginning of the 21st century. Which ideas guide the work? How is the activity formed? What does one hope to achieve? The aim of the thesis is to explore these educational practices in one of the larges independent schools in Sweden – Kunskapsskolan. The study was based upon a sociocultural perspective on learning and on twenty situated interviews with seven principals. Tools central for the activity in Kunskapsskolan were used as basis for the interviews. A qualitative analysis has been used; one of the methods for analysis applied is phenomenography. The study shows how the school, with the help of centrally developed tools, organised the teaching and the environments for learning that were implemented in all schools of the company. Individually organised teaching is the foundation for all teaching, where the students are expected to be self-regulated and self-correcting and use the tools provided for their learning. With regards to the students’ learning, the teachers’ role is mainly related to individual tutorial conversations. Thereby the tools intended to create freedom and control for the students, also create problems and obstacles. Students who do not learn to use the tools have difficulties in managing their studies. The new tools also affect the teachers’ work. In comparison with other schools, the teachers are expected to submit to the educational model and a centrally controlled planning. The teaching is centrally planned in subject specific stages or subject integrated courses. Teachers can influence the central planning by working collaboratively in teacher teams but not individually. The main commission of the teachers is to follow the educational model decided by the company. In comparison with the traditional school, both teachers and students are given new roles. When learning is individually organised for the students, the teachers are expected to develop their knowledge collectively. According to the results, both students and teachers have different approaches to the system – they can submit to the system or approach it in a more independent and reflective way.

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