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1
Pankaj, Rajesh Kumar. "A threshold strategy for a first in first out heteregeneous two server queueing system." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/14756.
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Shi, Haijian. "Best-first Decision Tree Learning." The University of Waikato, 2007. http://hdl.handle.net/10289/2317.
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In best-first top-down induction of decision trees, the best split is added in each step (e.g. the split that maximally reduces the Gini index). This is in contrast to the standard depth-first traversal of a tree. The resulting tree will be the same, just how it is built is different. The objective of this project is to investigate whether it is possible to determine an appropriate tree size on practical datasets by combining best-first decision tree growth with cross-validation-based selection of the number of expansions that are performed. Pre-pruning, post-pruning, CART-pruning can be performed this way to compare.
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Wright, SCD, and JE Maree. "First year Baccalaureate nursing students: Reasons for drop-out?" University of South Africa Press, 2007. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1001041.
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Improving throughput in the B. Tech. Nursing Sciences programme is a complex issue as not only the theoretical but also the practical component and undefined inner strengths of the student influence success. The purpose of this article is to report factors in the prospective students’ social background, their perceptions of nursing and nurses and their motivation that could influence their academic success in the first year of study. The research design was contextual, qualitative and exploratory. Triangulation of data gathering methods was obtained by using two instruments, a targeted selection interview and a written instrument. Data analysis was done through Tesch’s approach. The results indicate that prospective students perceive a nurse to be functioning from the affective domain, and that they judge themselves to be strong in the affective domain. The cognitive domain was rarely mentioned (7%). Due to the myths regarding the nursing profession, the profession continue to attract students who are interested in the myth and not the reality.
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Ang, Li-Minn. "Depth-first search embedded wavelet algorithm for hardware implementation." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2001. https://ro.ecu.edu.au/theses/1047.
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The emerging technology of image communication over wireless transmission channels requires several new challenges to be simultaneously met at the algorithm and architecture levels. At the algorithm level, desirable features include high coding performance, bit stream scalability, robustness to transmission errors and suitability for content-based coding schemes. At the architecture level, we require efficient architectures for construction of portable devices with small size and low power consumption. An important question is to ask if a single coding algorithm can be designed to meet the diverse requirements. Recently, researchers working on improving different features have converged on a set of coding schemes commonly known as embedded wavelet algorithms. Currently, these algorithms enjoy the highest coding performances reported in the literature. In addition, embedded wavelet algorithms have the natural feature of being able to meet a target bit rate precisely. Furthermore work on improving the algorithm robustness has shown much promise. The potential of embedded wavelet techniques has been acknowledged by its inclusion in the new JPEG2000 and MPEG-4 image and video coding standards.
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Friedman, Susan. "Changing the subject : first-person narration in and out of the classroom." [Tampa, Fla] : University of South Florida, 2007. http://purl.fcla.edu/usf/dc/et/SFE0001943.
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Winikoff, Steven M. "Incorporating the simplicity first methodology into a machine learning genetic algorithm." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ39118.pdf.
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Schardl, Tao Benjamin. "Design and analysis of a nondeterministic parallel breadth-first search algorithm." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/61575.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2010.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 75-77).<br>I have developed a multithreaded implementation of breadth-first search (BFS) of a sparse graph using the Cilk++ extensions to C++. My PBFS program on a single processor runs as quickly as a standard C++ breadth-first search implementation. PBFS achieves high workefficiency by using a novel implementation of a multiset data structure, called a "bag," in place of the FIFO queue usually employed in serial breadth-first search algorithms. For a variety of benchmark input graphs whose diameters are significantly smaller than the number of vertices - a condition met by many real-world graphs - PBFS demonstrates good speedup with the number of processing cores. Since PBFS employs a nonconstant-time "reducer" - a "hyperobject" feature of Cilk++ - the work inherent in a PBFS execution depends nondeterministically on how the underlying work-stealing scheduler load-balances the computation. I provide a general method for analyzing nondeteriministic programs that use reducers. PBFS also is nondeterministic in that it contains benign races which affect its performance but not its correctness. Fixing these races with mutual-exclusion locks slows down PBFS empirically, but it makes the algorithm amenable to analysis. In particular, I show that for a graph G = (V, E) with diameter D and bounded out-degree. this data-race-free version of PBFS algorithm runs in time O((V +E)/P+DIg[supercript 3] (V/D)) on P processors, which means that it attains near-perfect linear speedup if P < (V +E)/DIg[supercript 3] (V/D).<br>by Tao Benjamin Schardl.<br>M.Eng.
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Martin, Georgianna LaNelle. "Getting out, missing out, and surviving: the social class experiences of White, low-income, first-generation college students." Diss., University of Iowa, 2012. https://ir.uiowa.edu/etd/2937.
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The purpose of this study was to understand how White students from low socioeconomic status backgrounds (operationalized as students who are both low income and of the first generation in their family to attend college) experience and navigate social class during college. This was a qualitative research study employing a phenomenological research methodology. A critical theoretical lens was used to illuminate systemic issues of power and privilege related to social class present in the experiences of these participants. This study was guided by the following research question: How do White, low SES students experience and navigate social class during college? Participants in this study had many similar experiences to one another related to their social class. However, there also existed a variety of individual differences in how students understood and experienced their social class during college. Overall, participants expressed a limited awareness of their social class growing up, but all became keenly aware of it during college. In particular, during college, students became aware of how their own social class differed from the dominant middle class to upper class social class represented on campus. Participants minimized the salience of social class as an aspect of their identity with many of them expressing that they did not want their social class to define them. While participants largely did not feel as if social class was an important aspect of their identity, it became clear through their stories that this aspect of their identity influenced how they viewed themselves, the world around them, and their higher SES peers in college. For example, participants readily acknowledged the frustration and resentment that set them apart from their college peers. The students who participated in this study exhibited ethics of hard work, self-sufficiency, and financial responsibility. These values and attitudes also were evident in students' practices and behaviors (e.g., their judicious spending habits, their long hours working for pay). It also became clear that the long hours most participants in this study worked in order to afford college meant missing out on opportunities for involvement in activities outside of the classroom. Finally, participants' experiences interacting with their high SES peers played a pivotal role in their awareness of their social class during college. Participants were often frustrated by the attitudes, values, and behaviors of their higher SES peers, and for some, these social class differences led to social isolation. Overall, these findings illuminate a variety of issues and areas for concern, directly related to social class, experienced by low-income, first-generation college students in higher education.
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Cottrill, Virginia M. "Life After Drop-Out: An Examination of Rural, Appalachian, First-Generation Non-Persisters." Ohio University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1395160206.
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ALAHMADI, ABDULRAHMAN M. "ENHANCED FIRST-FIT DECREASING ALGORITHM FOR ENERGY-AWARE TASK SCHEDULING IN CLOUD." OpenSIUC, 2014. https://opensiuc.lib.siu.edu/theses/1381.
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With the emergence of many new data centers around the globe, large-scale commercial and scientific applications executed in the cloud call for efficient cloud resource management strategies to save energy without compromising the performance. According to the statistics from the Data Centre Dynamic (DCD) organization, the expected energy consumption by computer servers would increase by 19% in 2013 compared with 2012. Such a trend may continue for many years. Moreover, the estimated energy consumption of computers in the U.S. was about 2% out of the total energy consumption in 2010, which makes the IT industry the second largest pollution contributor after aviation. In this paper, a novel approach for scheduling, sharing and migrating Virtual Machines (VMs) for a bag of cloud tasks is designed and developed to reduce energy consumption within a certain execution time and high system throughput. This approach is derived from an Enhanced First Fit Decreasing (EFFD) algorithm combined with our VM reuse strategy. Furthermore, a virtual machine migration method is introduced to dynamically monitor the cloud situation for necessary migration. Our simulation results using the open source CloudReport show that EFFD with our VM reuse strategy could gain a higher resource utilization rate and lower energy consumption than regular Greedy, Round Robin (RR) and FDD without VM reuse.
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Rene, Mario Jean. "EQUITABLE SHORTEST JOB FIRST: A PREEMPTIVE SCHEDULING ALGORITHM FOR SOFT REAL-TIME SYSTEMS." OpenSIUC, 2014. https://opensiuc.lib.siu.edu/theses/1388.
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The Shortest Job First algorithm gives the optimal average turnaround time for a set of processes, but it suffers from starvation for long processes. Starvation occurs when a long process is denied processor resources because the resources are occupied by short processes, thus, causing the long process to potentially never finish its task. This thesis considers that the short processes are soft real time processes. It presents the designer with a choice to select an algorithm that provides close to optimal average turnaround time within the soft deadline for short processes as compared to the Shortest Job First algorithm which results in decreased average turnaround time for long processes. The proposed algorithm improves drawback, related to long job starvation, in Preemptive-Shortest Job First by providing protection to a process through prioritization. A priority is assigned to a process based on a percentage of its burst time to completion, by introducing the parameter Theta, or the time spent by the process in the waiting queue, by introducing the parameter Lambda. Theta protects a current running process from being preempted when its execution time reaches a percentage of its total computing time. Lambda gives priority to a process when it exceeds a certain amount of time in the waiting queue. Four variants of the proposed scheduling methodology, each using a different theta and lambda, have been developed. The performances of these variants are compared against Highest Response Ratio Next (HRRN), Railroad, Enhanced Shortest Job First (ESJF), and Alpha scheduling algorithms that have been previously proposed. Experimental results show that our proposed algorithm performs better in terms of reducing the average turnaround time of the long processes while maintaining the turnaround time on the short processes at low desired levels, as those required for soft real time tasks.
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Reid, M. Jeanne. "First-generation urban college students speaking out about their secondary school preparation for postsecondary education." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1180403873.
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Wu, Chun Andy, and 胡俊. "The effectiveness of dispatcher-assisted cardio-pulmonary resuscitation on survival of out-of-hospital cardiac arrest: a literature review." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B48426507.
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Background
According to data from Department of Health, in 2011 heart diseases was the second commonest leading cause of death in Hong Kong [13]. Shortening the time from cardiac arrest to Cardio-pulmonary Resuscitation (CPR) could increase the chance of survival. If the brain of the patient who suffers from cardiac arrest does not receive oxygen within 4 minutes, severe brain damage might occur [14]. In some countries like US and Finland, dispatcher will give CPR instruction to caller when cardiac arrest is recognized. Therefore, the patient could receive early CPR before the arrival of paramedics. If dispatcher-assisted CPR is implemented in Hong Kong, the chance of survival of out-of-hospital cardiac arrest (OHCA) patient could be increased.
Objective
1. To evaluate whether it is evident that dispatcher-assisted CPR and dispatcher instruction [22] would improve survival of OHCA.
2. To evaluate whether these measures could be implemented in Hong Kong.
Data Source
PubMed was searched for articles in English language with no limit set for time of the study. The keywords were dispatcher-assisted CPR and out of hospital. No inclusion criteria were set on the publication type and other details.
Results
Initial PubMed search resulted in 24 articles. After reviewing the abstracts, 10 articles were selected for full-text assessment. Finally, four relevant articles were selected for the literature review. Of the four papers, two were retrospective cohort studies; one was before-after comparison study while the remaining one was randomized control trial.
Three papers (Rea et al, Eisenberg et al, and Kuisma et al.) used the survival to hospital discharge as the effect measure for the primary outcome to evaluate the effectiveness of dispatcher-assisted CPR. The remaining paper (Hallstrom et al.) mainly studied the potential benefit and harm from dispatcher-assisted CPR.
Using no bystander CPR as the reference group, the multivariate adjusted odds ratio of survival was 1.45 (95% CI, 1.21, 1.73) for dispatcher-assisted bystander CPR and 1.69 (95% CI, 1.42, 2.01) for bystander CPR without dispatcher assistance [2]. The percentage of total bystander-initiated CPR increased from 45% to 56% after the programme (difference: 11.1%, 95% CI, ±9.3%). Besides, the percentage discharged for dispatcher-assisted CPR group after the programme was 15% higher than that before the programme [6]. The most important findings are related to the number of cardiac arrest calls in that when the dispatcher handled on less than 4 Ventricular Fibrillation (VF) calls during the study period, the survival to hospital discharge was 22.1% compared to 38.2% and 39.4% when the dispatcher handled 4 to 9 calls or more than 9 calls (p = 0.0227 for the three groups) [8]. With telephone guided CPR, the survival to hospital discharge was 43.1% compared with 31.7% when CPR instructions were not provided (p = 0.0453) [8]. In patients (n = 3,320) receiving advanced cardiac life support (ACLS) a total of 993 (29.9%) was found to be benefited from dispatcher-assisted CPR [7].
Conclusion
Instructions by dispatcher can improve bystander CPR rates, which in turn increases the chance of survival [26]. Dispatcher-assisted CPR is worth considering to be recommended to all callers reporting a patient in cardiac arrest in Hong Kong.<br>published_or_final_version<br>Public Health<br>Master<br>Master of Public Health
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Renlund, Henrik. "Recursive Methods in Urn Models and First-Passage Percolation." Doctoral thesis, Uppsala universitet, Matematisk statistik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-145430.
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This PhD thesis consists of a summary and four papers which deal with stochastic approximation algorithms and first-passage percolation. Paper I deals with the a.s. limiting properties of bounded stochastic approximation algorithms in relation to the equilibrium points of the drift function. Applications are given to some generalized Pólya urn processes. Paper II continues the work of Paper I and investigates under what circumstances one gets asymptotic normality from a properly scaled algorithm. The algorithms are shown to converge in some other circumstances, although the limiting distribution is not identified. Paper III deals with the asymptotic speed of first-passage percolation on a graph called the ladder when the times associated to the edges are independent, exponentially distributed with the same intensity. Paper IV generalizes the work of Paper III in allowing more edges in the graph as well as not having all intensities equal.
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Moos, Aziza. "First-year students' perceptions of the influence of social integration on academic performance." Thesis, University of the Western Cape, 2009. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_1031_1367480725.
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<p>During Apartheid, South African education policies were largely based on a system of <br>racial segregation, resulting in unequal educational opportunities between black and white students. <br>Current education policies centred on Access and Equity have been ratified to address the education issues of the past. However, there still remains a concern about the poor performance and <br>consequently, the high drop out rate, particularly amongst black South African university students. The findings of various studies have shown that the factors that contribute to poor academic performance range from inadequate pre-university schooling and financial issues to poor language proficiency, inadequate social support and insufficient social integration. The present study employed a qualitative approach to explore first-year students&rsquo<br>perceptions of the influence of social integration on academic performance. Tinto&rsquo<br>s Student Integration Model provided the conceptual basis for the conduction of the study. Three focus groups were used to collect the data which were analysed according to thematic analysis procedures. The main finding of the study <br>was that academic and social experiences were intrinsically linked in the first year of study. Moreover, the findings indicate that friends, belonging to nonacademic organisations and lecturer-student interaction (as three indicators of social integration) influenced first-year students&rsquo<br>academic performance. South African contextual factors such as socio-economic status and language <br>were found to be a potential hindrance to good academic performance. The implications of these findings are discussed.</p>
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Ismail, Arif. "First Principles and Genetic Algorithm Studies of Lanthanide Metal Oxides for Optimal Fuel Cell Electrolyte Design." Thèse, Université d'Ottawa / University of Ottawa, 2011. http://hdl.handle.net/10393/20198.
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As the demand for clean and renewable energy sources continues to grow, much
attention has been given to solid oxide fuel cells (SOFCs) due to their efficiency and low
operating temperature. However, the components of SOFCs must still be improved
before commercialization can be reached. Of particular interest is the solid electrolyte,
which conducts oxygen ions from the cathode to the anode. Samarium-doped ceria (SDC)
is the electrolyte of choice in most SOFCs today, due mostly to its high ionic
conductivity at low temperatures. However, the underlying principles that contribute to
high ionic conductivity in doped ceria remain unknown, and so it is difficult to improve
upon the design of SOFCs. This thesis focuses on identifying the atomistic interactions in
SDC which contribute to its favourable performance in the fuel cell.
Unfortunately, information as basic as the structure of SDC has not yet been
found due to the difficulty in experimentally characterizing and computationally
modelling the system. For instance, to evaluate 10.3% SDC, which is close to the 11.1%
concentration used in fuel cells, one must investigate 194 trillion configurations, due to
the numerous ways of arranging the Sm ions and oxygen vacancies in the simulation cell.
As an exhaustive search method is clearly unfeasible, we develop a genetic algorithm
(GA) to search the vast potential energy surface for the low-energy configurations, which will be most prevalent in the real material.
With the GA, we investigate the structure of SDC for the first time at the DFT+U
level of theory. Importantly, we find key differences in our results from prior calculations of this system which used less accurate methods, which demonstrate the importance of accurately modelling the system. Overall, our simulation results of the structure of SDCagree with experimental measurements. We identify the structural significance of defects in the doped ceria lattice which contribute to oxygen ion conductivity. Thus, the structure
of SDC found in this work provides a basis for developing better solid electrolytes, which
is of significant scientific and technological interest.
Following the structure search, we perform an investigation of the electronic properties of SDC, to understand more about the material. Notably, we compare our calculated density of states plot to XPS measurements of pure and reduced SDC. This allows us to parameterize the Hubbard (U) term for Sm, which had not yet been done. Importantly, the DFT+U treatment of the Sm ions also allowed us to observe in our
simulations the magnetization of SDC, which was found by experiment.
Finally, we also study the SDC surface, with an emphasis on its structural similarities to the bulk. Knowledge of the surface structure is important to be able to understand how fuel oxidation occurs in the fuel cell, as many reaction mechanisms occur on the surface of this porous material. The groundwork for such mechanistic studies is provided in this thesis.
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Lander, Dorothy Agnes. "Telling tales out of school : author-ising the university as a service organ-isation for first year students." Thesis, University of Nottingham, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339604.
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Lee, Yin Lam. "A Qualitative Study of Out-of-class Learning Opportunities among First Year ESL Freshmen in a College Town." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1339531130.
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Mann, Kimberly Lynn. "The First Thing Out the Window: Race, Radical Feminism, and Marge Piercy's "Woman on the Edge of Time"." W&M ScholarWorks, 2009. https://scholarworks.wm.edu/etd/1539626579.
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Arvola, Bjelkesten Kim. "Feasibility of Point Grid Room First Structure Generation : A bottom-up approach." Thesis, Blekinge Tekniska Högskola, Institutionen för kreativa teknologier, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-15721.
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Context. Procedural generation becomes increasingly important for videogames in an age where the scope of the content required demands bot a lot of time and work. One of the fronts of this field is structure generation where algorithms create models for the game developers to use. Objectives. This study aims to explore the feasibility of the bottom-up approach within the field of structure generation for video games. Methods. Developing an algorithm using the bottom-up approach, PGRFSG, and utilizing a user study to prove the validity of the results. Each participant evaluates five structures giving them a score based on if they belong in a video game. Results. The participants evaluations show that among the structures generated were some that definitely belonged in a video game world. Two of the five structures got a high score though for one structure that was deemed as not the case. Conclusions. A conclusion can be made that the PGRFSG algorithm creates structures that belong in a video game world and that the bottom-up approach is a suitable one for structure generation based on the results presented.
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Dyke, Felicia Delphine. "What is the Impact of a Transition Program and Traditional Program of Study on Over Age First Time Ninth Grade Students." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/26907.
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The purpose of this study is to determine if a transition program has a greater success rate, as measured by GPA, number of students recycled, attendance, and conduct, than a traditional program of study for over age, first time ninth grade students by the end of first semester of the ninth grade. Some of the typical outcomes during the transition to high school from grade 8 to grade 9 are high failure rates, lack of Algebra I readiness, and poor attendance. These concerns contribute to drop-out rates and the level of competitiveness students will have when facing the workforce. This is a timely issue as we continue to address Standards of Learning (SOL) and No Child Left Behind (NCLB) Act and the initiatives to rethink our high schools as they attempt to prepare students for the ongoing changes of the economy, workforce, and expectations of colleges and universities.<br>Ph. D.
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Packard, Ashley. "Infringement or impingement? : carving out a First Amendment defense for sysops held strictly liable for their subscribers' copyright infringements /." free to MU campus, to others for purchase, 1997. http://wwwlib.umi.com/cr/mo/fullcit?p9841178.
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Crawford, Aria. "The Seemingly Downward Spiral of a First Year Teacher That Actually Turns Out Alright in the End: A Case Study." Scholarship @ Claremont, 2019. https://scholarship.claremont.edu/cgu_etd/143.
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My first year as an educator has followed a tumultuous pattern. Not only was I exploring who I was becoming as an educator, but I was also a full-time graduate school student. I attempted to collect student data through a variety of ways, including formal and informal assessments and listening to student anecdotes, which proved to be more difficult than anticipated. When I began writing this narrative, I had yet to step foot into a classroom and work with children. I had a different idea and perspective than I did after becoming a teacher of record. Throughout the year, my mental and physical health was altered multiple times. There were times when I let my own school work suffer in favor of my work with my students and vice versa. There were times when I fantasized about dropping out of graduate school and quit my job, and there were times when I thoroughly enjoyed working on my homework and going to work. This narrative is a reflection of those ups and downs and tracks the progress of myself and the students I have interacted with. What follows is a yearlong exploration of myself, my environment, and my students who have proven to be simultaneous sources of stress and comfort.
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Reddy, Lucina Jacqueline. "Evaluating the first year roll-out of the Imibala Gifted And Talented Enrichment Programme of the Imibala Trust in The Western Cape." Master's thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/21796.
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The following dissertation details an evaluation conducted on a giftedness programme. The introduction of giftedness programmes can be traced as far back as 1922 where Terman was one of the first people to document and formalise the link between one's innate ability and their performance on a number of outcomes. Since then many other theorists Renzulli (1977) and Subotnik, Olszewski-Kubilius, and Worrell (2011) have expanded on the definition of giftedness to include not only one's innate ability but development of potential through a specialised environment that encourages the gifted learner to enhance their ability. In 2013, a programme evaluation student at the University of Cape Town, Reitumetse Mogorosi, conducted research for the Imibala Trust to assist with the design of the Gifted and Talented Enrichment (GATE) Programme. The Imibala Trust had for some time (with the support of the Metropole East Education Department) decided to pilot such a programme that aimed to serve gifted disadvantaged children in the Helderberg region. As a result of Mogorosi's work the GATE personnel were provided with an evaluation report that detailed a plausible programme theory for their programme; the activities that the GATE programme should include in its design; the selection process to be followed to recruit the identified target audience; and the importance of engaging relevant stakeholders in the programme. Following Mogorosi's (2014) report, the GATE programme was piloted in 2014. In 2014, a second masters' student from the University of Cape Town evaluated the pilot implementation of the GATE programme. This dissertation is an account of that evaluation study. The evaluator conducted two forms of evaluation, namely a process evaluation and a short-term outcome evaluation. The process evaluation aimed to establish whether the GATE personnel had implemented the programme as planned; while the short-term outcome evaluation aimed to determine whether the participants in the GATE programme perceived any changes as a result of the programme.
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Stoddart, Mark Christopher John. "Making meaning out of mountains : skiing, the environment and eco-politics." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/934.
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This research provides a sociological analysis of skiing as a form of outdoor recreation and nature tourism in British Columbia, Canada. A qualitative multi-method approach is used, combining discourse analysis, interviews with skiers, and unobtrusive field observation at Whistler Blackcomb and Whitewater ski resorts. Through a focus on discourse, embodied interactions among humans and non-humans, and flows of power, this research describes an environmental ambiguity at the centre of skiing. There is a tension between interpretations of skiing as an environmentally-sustainable practice and notions of skiing as an environmental and social problem. Skiing is based on the symbolic consumption of nature and is understood by many participants as a way of entering into a meaningful relationship with the non-human environment. However, interpretations of skiing as a non-consumptive use of non-human nature are too simple. Social movement groups disrupt pro-environmental discourses of skiing by challenging the sport’s ecological and social legitimacy. Many skiers also articulate a self-reflexive environmental critique of their sport. In these instances, skiing is brought into the realm of politics. Recreational forms of interaction with the non-human environment tend to be at the periphery of environmental sociology. At the same time, sport sociologists tend to focus on the social dimensions of outdoor recreation, while bracketing out non-human nature. This research brings these two fields of inquiry into dialogue with each other, thereby addressing this double lacuna.
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Sun, Yi. "New matching algorithm -- Outlier First Matching (OFM) and its performance on Propensity Score Analysis (PSA) under new Stepwise Matching Framework (SMF)." Thesis, State University of New York at Albany, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3633233.
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<p> An observational study is an empirical investigation of treatment effect when randomized experimentation is not ethical or feasible (Rosenbaum 2009). Observational studies are common in real life due to the following reasons: a) randomization is not feasible due to the ethical or financial reason; b) data are collected from survey or other resources where the object and design of the study has not been determined (e.g. retrospective study using administrative records); c) little knowledge on the given region so that some preliminary studies of observational data are conducted to formulate hypotheses to be tested in subsequent experiments. When statistical analysis are done using observational studies, the following issues need to be considered: a) the lack of randomization may lead to a selection bias; b) representativeness of sampling with respect to the problem under consideration (e.g. study of factors influencing a rare disease using a nationally representative survey with respective to race, income, and gender but not with respect to the rare disease condition).We will use the following sample to illustrate the challenges of observational studies and possible mitigation measures. </p><p> Our example is based on the study by Lalonde (1986), which evaluated the impact of job training on the earnings improvement of low-skilled workers in 1970's (In Paper 1 section 1.5.2, we will discuss this data set in more detail). The treatment effect estimated from the observational study was quite different from the one obtained using the baseline randomized "National Supported Work (NSW) Experiment" carried out in the mid-1970's. Now we understand the treatment effect which is the impact of job training. Selection bias may contaminate the treatment effect, in other words, workers who receive the job training may be fundamentally different from those who do not. Furthermore, the sample of control group selected for observational study by Lalonde may not represent the sample of control group from the original NSW experiment. </p><p> In this study, we address the issue of lack of randomization by applying a new matching algorithm (Outlier First Matching, OFM) which can be used in conjunction with the Propensity Score Analysis (PSA) or other similar methods to achieve the convincible treatment effect estimation in observational studies. </p><p> This dissertation consists of three papers. </p><p> Paper 1 proposes a new "Stepwise Matching Framework (SMF)" and rationalizes its usage in causal inference study (especially for PSA study using observational data). Furthermore, under the new framework of SMF, one new matching algorithm (Outlier First Matching or OFM in short) will be introduced. Its performance along with other well-known matching algorithms will be studied using the cross sectional data. </p><p> Paper 2 extends methods of paper 1 to correlated data (especially to longitudinal data). In the circumstance of correlated data (e.g. longitudinal data), besides the selection bias as in cross-sectional observational data, the repeated measures bring out the between-subject and within-subject correlation. Furthermore, the repeated measures can also bring out the missing value problem and rolling enrollment problem. All of above challenges from correlated data complexity the data structure and need to be addressed using more complex model and methodology. Our methodology calculate the variant p-score of control subjects at each time point and generate the p-score difference from each control subject to every treatment subject at treatment subject's time point. Then such p-score differences are summarized to create the distance matrix for next step analysis. Once again, the performance of OFM and other well-established matching algorithms are compared side by side and the conclusion will be summarized through simulation and real data applications. </p><p> Paper 3 handles missing value problem in longitudinal data. As we have mentioned in paper 2, the complexity of data structure of longitudinal data often comes with the problem of missing data. Due to the possibility of between subject and within subject correlation, the traditional imputation methodology will probably ignore the above two correlations so that it may lead to biased or inefficient imputation of missing data. We adopt one missing value imputation strategy introduced by Schafer and Yucel (2002) through one R package "pan" to handle the above two correlations. The "imputed complete data" will be treated using the similar methodology as paper 2. Then MI results will be summarized using Rubin's rule (1987). The conclusion will be drawn based on the findings through simulation study and compared to what we have found in complete longitudinal data study in paper 2. </p><p> In last section, we conclude the dissertation with the discussion of preliminary results, as well as the strengths and limitations of the present research. Also we will point out the direction of the future study and provide suggestions to practice works.</p>
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Johnson, Ludwig, and Lukas Mårtensson. "Assessing HTTP Security Header implementations : A study of Swedish government agencies’ first line of defense against XSS and client-side supply chain attacks." Thesis, Blekinge Tekniska Högskola, Institutionen för datavetenskap, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-21725.
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Background. Security on the web is a fundamental requirement as it becomes a bigger part of society and more information than ever is shared over it. However, as recent incidents have shown, even Swedish government agencies have had issues with their website security. One such example is when a client-side supply chain for several governmental websites was hacked and malicious javascript was subsequently found on several governmental websites. Hence this study is aimed at assessing the security of Swedish government agencies’ first line of defense against attacks like XSS and client-side supply chain. Objectives. The main objective of the thesis is to assess the first line of defense, namely HTTP security headers, of Swedish government agency websites. In addition, collecting statistics of what HTTP security headers are actually used by Swedish government agencies today were gathered for comparison with similar studies. Methods. To fulfill the objectives of the thesis, a scan of all Swedish government agency websites, found on Myndighetsregistret, was completed and an algorithm was developed to assess the implementation of the security features. In order to facilitate tunable assessments for different types of websites, the algorithm has granular weights that can be assigned to each test to make the algorithm more generalized. Results. The results show a low overall implementation rate of the various HTTP security headers among the Swedish government agency websites. However, when compared to similar studies, the adoption of all security features are higher among the Swedish government agency websites tested in this thesis. Conclusions. Previous tools/studies mostly checked if a header was implemented or not. With our algorithm, the strength of the security header implementation is also assessed. According to our results, there is a significant difference between if a security header has been implemented, and if it has been implemented well, and provides adequate security. Therefore, traditional tools for testing HTTP security headers may be inefficient and misleading.
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Dalpiaz, Anthony. "Social Media Use, Media Literacy, and Anxiety in First-Year College Students." University of Dayton / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1597137716516134.
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Zimmermann, Christoph [Verfasser]. "Towards a first precision measurement of the mass of the W-boson with the ATLAS detector at root out s = 7 TeV / Christoph Zimmermann." Mainz : Universitätsbibliothek Mainz, 2016. http://d-nb.info/111079083X/34.
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Goold, Jeremy C. "Improving Routing Security Using a Decentralized Public Key Distribution Algorithm." Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd797.pdf.
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Shields, Kieran Patrick. ""Standing up not standing out" : an ethnographic study of the educational experiences of Irish Traveller children in their first year of primary education in rural Northern Ireland." Thesis, Queen's University Belfast, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709818.
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This study explores the early educational experiences of a small group of Irish Traveller children as they transitioned into the first year of their formal primary school education in a rural primary school in Northern Ireland. Informed in part by some theoretical concepts associated with the work of Bourdieu, Jenkins and the sociology of childhood, the study aimed to better understand how young Traveller children lived out and experienced their first days of school. Using an ethnographic approach that involved some classroom observations of and interviews with Traveller children, the study highlights the interface between the school culture and aspects of the Traveller children’s culture and the challenges and complexities for both them and their teachers in finding an accommodation between the two. Through specific examples in the school setting the study shows the challenges and complexities for teachers as they strive to meet organisational imperatives while also attempting to attend to the individual needs presented by some Traveller children. The study also shows how normative school teacher practices, the school culture and ethos aim to support Traveller children and yet, sometimes in practice, can have unintended less positive impacts. The indicates a concern that the twin aims of inclusion, which is perceived and practiced as integration, versus respect for diversity and difference may appear incompatible and yet there are a number of small changes that could be made within the school setting to bridge the gap between these two positions. The thesis ends by outlining these suggested changes to policy and practice.
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Lindblom, Anne. "Stepping out of the shadows of colonialism to the beat of the drum : The meaning of music for five First Nations children with autism in British Columbia, Canada." Doctoral thesis, University of Eastern Finland, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-48442.
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This dissertation set out to examine the meaning of music for First Nations childrenwith autism in BC, Canada. The research questions addressed were: How can thediagnosis of ASD be seen through a First Nations lens? How do the First Nationschildren with ASD use music? In which ways is music used in different domains?In which ways is music used to facilitate inclusion? How is traditional music used?The dissertation is based on four original articles that span over the issues of under-detection of autism among First Nations children in BC, ethnographic fieldwork,and the paradigmatic shift to Indigenist research methodologies, the role of music insocial inclusion and a First Nations lens on autism, the use of Indigenous music withFirst Nations children with autism, put in context with First Nations children’s rights.Material was collected during six week periods in two consecutive years, generatingdata from conversations, follow-up conversations, observations, video-filmed observations,and notes. Post-colonial BC, Canada is the context of the research, and issuesof social inclusion and children’s rights are addressed. During the research process,a journey that began with an ethnographic approach led to an Indigenist paradigm.It was found that colonial residue and effects of historical trauma can influenceFirst Nations children being under-detected for autism. The First Nations childrendiagnosed with autism in this study use music in similar ways to typically developingchildren and non-Indigenous individuals with autism. These uses include for communicationand relaxation, for security and happiness, to soothe oneself and whenstudying. However, music interventions in school settings are not culturally sensitive.Music as a tool for inclusion is overlooked and Indigenous music not utilizedoutside of optional Aboriginal classes. The most important lesson of the study wasthe significance of reciprocal experience, emphasized by the Indigenist paradigm. Itcan be suggested that carefully designed, culturally sensitive music interventions,in collaboration with traditional knowledge holders and Elders, would be beneficialfor the development of First Nations children with autism. Consequently, culturallysensitive music interventions could have potential to ensure that the children’s rightsare respected. For these interventions to be culturally adequate, specific IndigenousKnowledge must be the foundation.
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Alpuche, Aviles Jorge Edmundo. "The Development and Validation of a First Generation X-Ray Scatter Computed Tomography Algorithm for the Reconstruction of Electron Density Breast Images Using Monte Carlo Simulation." Journal of X-ray Science and Technology, IOS Press, 2011. http://hdl.handle.net/1993/4970.
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Breast CT is a promising modality whose inherent scatter could be used to reconstruct electron density (rho_e) images. This has led us to investigate the benefits of reconstructing linear attenuation coefficient (mu) and (rho_e) images of the breast. First generation CT provides a cost-effective and simple approach to reconstruct (rho_e) images in a laboratory but is limited by the anisotropic probability of scatter, attenuation, noise and contaminating scatter (coherent and multiple scatter).
These issues were investigated using Monte Carlo (MC) simulations of a first generation breast scatter enhanced CT (B-SECT) system. A reconstruction algorithm was developed for the B-SECT system and is based on a ring of detectors which eliminates the scatter dependence on the relative position of the scattering centre. The algorithm incorporates an attenuation correction based on the (mu) image and was tested against analytical and MC simulations. MC simulations were also used to quantify the dose per scan.
The ring measures a fraction of the total single incoherent scatter which is proportional to ray integrals of (rho_e) and can be quantified even when electron binding is non negligible. The algorithm typically reconstructs accurate (rho_e) images using a single correction for attenuation but has the capability for multiple iterations if required. MC simulations show that the dose coefficients are similar to those of cone beam breast CT. Coherent and multiple scatter can not be directly related to (rho_e) and lead to capping artifacts and overestimated (rho_e) by a factor greater than 2. This issue can be addressed using empirical corrections based on the radiological path of the incident beam and result in (rho_e) images of breast soft tissue with 1% accuracy, 3% precision and a mean glandular dose of 4 mGy for a 3D scan. The reconstructed (rho_e) image was more accurate than the (rho_e) estimate derived from the (mu) image. An alternative correction based on the thickness of breast traversed by the beam provides an enhanced contrast image reflecting the breast scatter properties. These results demonstrate the feasibility of detecting small (rho_e) changes in the intact breast and shows that further experimental evaluation of this technique is warranted.
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Nyberg, Angelica, and Jonas Hartman. "Evaluation of EDF scheduling for Ericsson LTE system : A comparison between EDF, FIFO and RR." Thesis, Linköpings universitet, Programvara och system, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-131551.
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Scheduling is extremely important for modern real-time systems. It enables several programs to run in parallel and succeed with their tasks. Many systems today are real-time systems, which means that good scheduling is highly needed. This thesis aims to evaluate the real-time scheduling algorithm earliest deadline first, newly introduced into the Linux kernel, and compare it to the already existing real-time scheduling algorithms first in, first out and round robin in the context of firm tasks. By creating a test program that can create pthreads and set their scheduling characteristics, the performance of earliest deadline first can be evaluated and compared to the others.<br>Schemaläggning är extremt viktigt för dagens realtidssystem. Det tillåter att flera program körs parallellt samtidigt som deras processer inte misslyckas med sina uppgifter. Idag är många system realtidssystem, vilket innebär att det finns ett ytterst stort behov för en bra schemaläggningsalgoritm. Målet med det här examensarbetet är att utvärdera schema-läggningsalgoritmen earliest deadline first som nyligen introducerats i operativsystemet Linux. Målet är även att jämföra algoritmen med två andra schemaläggningsalgoritmer (first in, first out och round robin), vilka redan är väletablerade i Linux kärnan. Det här görs med avseende på processer klassificerade som firm. Genom att skapa ett program som kan skapa pthreads med önskvärda egenskaper kan prestandan av earliest deadline first algoritmen utvärderas, samt jämföras med de andra algoritmerna.
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Atsalakis, Mihalis. "Prediction of initial involvement of first grade Greek school children in an out-of-school, organized, community physical activity programme : an application of the theory of planned behaviour." Thesis, University of Hull, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262408.
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Touray, Barra. "Energy-efficient routing algorithms for wireless sensor networks." Thesis, Liverpool John Moores University, 2013. http://researchonline.ljmu.ac.uk/4352/.
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A wireless sensor network (WSN) is made of tiny sensor nodes usually deployed in high density within a targeted area to monitor a phenomenon of interest such as temperature, vibration or humidity. The WSNs can be employed in various applications (e.g., Structural monitoring, agriculture, environment monitoring, machine health monitoring, military, and health). For each application area there are different technical issues and remedies. Various challenges need to be considered while setting up a WSN, including limited computing, memory and energy resources, wireless channel errors and network scalability. One way of addressing these problems is by implementing a routing protocol that efficiently uses these limited resources and hence reduces errors, improves scalability and increases the network lifetime. The topology of any network is important and wireless sensor networks (WSNs) are no exception. In order to effectively model an energy-efficient routing algorithm, the topology of the WSN must be factored in. However, little work has been done on routing for WSNs with regular patterned topologies, except for the shortest path first (SPF) routing algorithms. The issue with the SPF algorithm is that it requires global location information of the nodes from the sensor network, which proves to be a drain on the network resources. In this thesis a novel algorithm namely, BRALB (Biased Random Algorithm for Load Balancing) is proposed to overcome the issues faced in routing data within WSNs with regular topologies such as square-base topology and triangle-based topology. It is based on random walk and probability. The proposed algorithm uses probability theory to build a repository of information containing the estimate of energy resources in each node, in order to route packets based on the energy resources in each node and thus does not require any global information from the network. It is shown in this thesis by statistical analysis and simulations that BRALB uses the same energy as the shortest path first routing as long as the data packets are comparable in size to the inquiry packets used between neighbours. It is also shown to balance the load (i.e. the packets to be sent) efficiently among the nodes in the network. In most of the WSN applications the messages sent to the base station are very small in size. Therefore BRALB is viable and can be used in sensor networks employed in such applications. However, one of the constraints of BRALB is that it is not very scalable; this is a genuine concern as most WSNs deployment is large scale. In order to remedy this problem, C-BRALB (Clustered Biased Random Algorithm for Load Balancing) has been proposed as an extension of BRALB with clustering mechanism. The same clustering technique used in Improved Directed Diffusion (IDD) has been adopted for C-BRALB. The routing mechanism in C-BRALB is based on energy biased random walk. This algorithm also does not require any global information apart from the initial flooding initiated by the sink to create the clusters. It uses probability theory to acquire all the information it needs to route packets based on energy resources in each cluster head node. It is shown in this thesis by using both simulations and statistical analysis that C-BRALB is an efficient routing algorithm in applications where the message to be sent is comparable to the inquiry message among the neighbours. It is also shown to balance the load (i.e. the packets to be sent) among the neighbouring cluster head nodes.
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Papoutsellis, Evangelos. "First-order gradient regularisation methods for image restoration : reconstruction of tomographic images with thin structures and denoising piecewise affine images." Thesis, University of Cambridge, 2016. https://www.repository.cam.ac.uk/handle/1810/256216.
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The focus of this thesis is variational image restoration techniques that involve novel non-smooth first-order gradient regularisers: Total Variation (TV) regularisation in image and data space for reconstruction of thin structures from PET data and regularisers given by an infimal-convolution of TV and $L^p$ seminorms for denoising images with piecewise affine structures. In the first part of this thesis, we present a novel variational model for PET reconstruction. During a PET scan, we encounter two different spaces: the sinogram space that consists of all the PET data collected from the detectors and the image space where the reconstruction of the unknown density is finally obtained. Unlike most of the state of the art reconstruction methods in which an appropriate regulariser is designed in the image space only, we introduce a new variational method incorporating regularisation in image and sinogram space. In particular, the corresponding minimisation problem is formed by a total variational regularisation on both the sinogram and the image and with a suitable weighted $L^2$ fidelity term, which serves as an approximation to the Poisson noise model for PET. We establish the well-posedness of this new model for functions of Bounded Variation (BV) and perform an error analysis through the notion of the Bregman distance. We examine analytically how TV regularisation on the sinogram affects the reconstructed image especially the boundaries of objects in the image. This analysis motivates the use of a combined regularisation principally for reconstructing images with thin structures. In the second part of this thesis we propose a first-order regulariser that is a combination of the total variation and $L^p$ seminorms with $1 < p \le \infty$. A well-posedness analysis is presented and a detailed study of the one dimensional model is performed by computing exact solutions for simple functions such as the step function and a piecewise affine function, for the regulariser with $p = 2$ and $p = 1$. We derive necessary and sufficient conditions for a pair in $BV \times L^p$ to be a solution for our proposed model and determine the structure of solutions dependent on the value of $p$. In the case $p = 2$, we show that the regulariser is equivalent to the Huber-type variant of total variation regularisation. Moreover, there is a certain class of one dimensional data functions for which the regularised solutions are equivalent to high-order regularisers such as the state of the art total generalised variation (TGV) model. The key assets of our regulariser are the elimination of the staircasing effect - a well-known disadvantage of total variation regularisation - the capability of obtaining piecewise affine structures for $p = 1$ and qualitatively comparable results to TGV. In addition, our first-order $TVL^p$ regulariser is capable of preserving spike-like structures that TGV is forced to smooth. The numerical solution of the proposed first-order model is in general computationally more efficient compared to high-order approaches.
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Leos, Zamorategui Arturo. "On the interface between physical systems and mathematical models : study of first-passage properties of fractional interfaces and large deviations in kinetically constrained models." Thesis, Sorbonne Paris Cité, 2017. http://www.theses.fr/2017USPCC183/document.
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La thèse décrit les propriétés d’équilibre et hors d’équilibre de modèles mathématiques stochastiques de systèmes physiques. À l’aide de simulations numériques, on étudie les fluctuations des différentes quantités mais on s’interesse aussi aux grands déviations dans certains systèmes. La première partie de la thèse se concentre sur l’étude des interfaces rugueuses observées dans des processus de croissance. Ces interfaces sont simulées avec des nouvelles techniques de programmation en parallèle qui nous permettent d’accéder à des systèmes de très grande taille. D’une part, on discute le cas diffusif, représenté par l’équation d’Edward-Wilkinson dans des interfaces périodiques, pour lequel on obtient une solution exacte de l’équation discrète dans l’espace de Fourier. Avec cette solution on déduit le facteur de structure associé aux amplitudes des modes et l’expression exacte est comparée avec les valeurs numériques. De plus, on fait le lien entre les propriétés de premier passage des interfaces et le mouvement Brownien. On mesure la distribution des longueurs des intervalles et on compare les résultats avec une version modifiée du théorème de Sparre-Andersen. D’autre part, on étudie le cas général qui inclut les cas sous-diffusif et superdiffusif avec des conditions de bord périodiques. On étudie pour ces interfaces fractionnaires des propriétés de premier passage liées aux zéros des interfaces. Dans l’état stationnaire, on étudie également les premiers cumulants et propriétés d’échellement de la longueur des intervalles et de la densité de zéros. De plus, on mesure la largeur typique de l’interface et ses propriétés d’échellement. Finalement, on analyse le comportement de ces observables dans les interfaces hors d’équilibre et on discute leur dépendance en la taille du système. On discute également les conditions de stabilité des solutions del’équation discrète, importantes pour les simulations des interfaces. Dans une deuxième partie, on étude la transition de phase dynamique dans des modèles cinétiquement contraints afin d’étudier la transition vitreuse observée dans des verres structuraux. Pour un modèle en dimension un, on étudie la géométrie spatio-temporelle des bulles d’inactivité qui caractérisent les hétérogénéités dynamiques observées dans les verres. On trouve que les directions spatiales et temporelles des bulles ne sont pas liées par un comportement diffusif. En contraste, on confirme l’échellement de l’aire et d’autres quantités attendues pour un système, a priori diffusif. De plus, grâce à la théorie des grandes déviations et l’algorithme de clonage, on identifie la transition de phase dynamique dans des systèmes en deux dimensions spatiales. D’abord on mesure l’énergie libre dynamique pour différentes valeurs du paramètre λ. Après, on conjecture des valeurs critiques λ c = Σ/K, avec Σ la tension surface d’une ı̂le de sites actifs entourée par des sites inactifs dans un modèle effectif et K l’activité moyenne du système, pour laquelle la transition de phase a lieu dans la limite de taille infinie. En mesurant l’activité du système et le nombre d’occupation, on observe la dépendance de ces observables avec la taille des systèmes étudiés loin de la transition. Finalement, on mesure la propagation du front des sites actifs dans tout les systèmes. Pour l’un des systèmes étudiés, on identifie une vitesse balistique du front qui nous permet d’observer la transition de phase d’un point de vue dynamique<br>This thesis investigates both equilibrium and nonequilibrium properties of mathematical stochastic models that as a representation of physical systems. By means of extensive numerical simulations we study mean quantities and their fluctuations. Nonetheless, in some systems we are interested also in large deviations. The first part of the thesis focuses on the study of rough interfaces observed in growth processes. These interfaces are simulated with state-of-the-art simulations based on parallel computing which allow us to study very large systems. On the one hand, we discuss the diffusive case given by the Edward-Wilkinson equation in periodic interfaces. For the discrete version of such an equation, we obtain an analytic solution in Fourier space. Fur-ther, we derive an exact expression of the structure factor related with the modes amplitudes describing the interface and compare it with the numerical values. Moreover, using a mapping between stationary interfaces and the Brownian motion, we relate the distribution of the intervals generated by the zeros of the interface with the first-passage distribution given by a the Sparre-Andersen theorem in the case of the Brownian motion. As a generalization of the results obtained in the diffusive case, we study a linear Langevin equation with a Riesz-Feller fractional Laplacian of order z used to simulate sub- and super-diffusive interfaces. In this general case, we identify three regimes based on the scaling behaviour of the cumulants of the intervallengths, the density of zeros and the width of the interface. Finally, we study the evolution in time of some of the observables introduced before. In the second part of the thesis, we study the dynamical phase transition in kinetically constrained models (KCMs) in order to get some insight on the glass transition observed in structural glasses. In a one-dimensional KCM we study the geometry of the bubbles of inactivity in space-time for systems at different temperatures. We find that the spatial length of the bubbles does not scale diffusively with its temporal duration. In contrast, we confirm a vidiffusive behaviour for other quantities studied. Further, by means of large deviation theory and cloning algorithms, we identify the dynamical phase transition in two-dimensional systems. To start with, we measure numerically the dynamical free energy both by measuring the largest eigenvalue of the evolution operator,for small systems, and via the cloning algorithm, for larger systems. We conjecture a value λ c = Σ/K, with Σ the surface tensionof a bubble of activity surrounded by a sea of inactive sites in an effective interfacial model and K the mean activity of the system, for each of the systems studied. For the activity of the system and the occupation number we discuss their scaling properties far from the phase transition. Starting from an empty system subject to different boundary conditions, we investigate the front propagation of active sites. We argue that the phase transition in this case can be identified by the abrupt slowing-down of the front. This is done by measuring the ballistic speed of the front in the simplest case studied. Finally, we propose an effective model following the Feynman-Kac formula for a moving front.-proprietés de premier passage, interface rugueuse, diffusion fractionnaire , système hors d'équilibre, transition de phase dynamique, modèle cinétiquement contraint, grandes déviations.-first-passage properties, rough interface, fractional diffusion, out-of-equilibrium system, dynamical phase transition, kinetically constrained model, large deviations
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Mahaffey, Cynthia Jo. "Wearing the Rainbow Triangle: The Effect of Out Lesbian Teachers and Lesbian Teacher Subjectivities on Student Choice of Topics, Student Writing, and Student Subject Positions in the First-Year Composition Classroom." Connect to this title online, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=bgsu1100110069.
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Gemmrich, Simon. "A first-kind boundary integral study to solve the Laplace-Beltrami equation on a subsurface of the unit sphere and a multigrid algorithm for the acoustic single layer equation." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66653.
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This dissertation is a study of two independent problems from the common research area of boundary element methods used to solve elliptic boundary value problems. Both topics focus mainly on a single layer approach. For the first project we consider the Laplace-Beltrami Dirichlet problem on a subsurface of the unit sphere in R^3. We derive and analyze a boundary element method for a first-kind integral equation to solve this boundary value problem. The method can be used to study the motion of point vortices on a sphere with impenetrable walls; we compare our approach with previous methods in this field. We derive rigorous error estimates for approximations of the solution to the integral equation in appropriate Sobolev spaces which yield global error estimates for the solution of the boundary value problem. Moreover, we support the theoretical results with numerical evidence gathered from test cases. The second project is concerned with a multigrid preconditioning strategy for the acoustic single layer equation in two dimensions. As proposed in [6], we reformulate the boundary element method in a weaker base inner product and then use a V-cycle multigrid scheme with a Richardson type smoother. We provide a full convergence analysis for the proposed multigrid algorithm based on an analogous result for the single layer equation corresponding to the Laplace operator. Numerical experiments underline the performance of the algorithm. Moreover, we conduct a numerical study of the effect of the weak inner product on the oscillatory behavior of the corresponding eigenfunctions.<br>Cette dissertation est une étude de deux problèmes indépendants provenant du domaine commun de la recherche des méthodes d'éléments finis de frontière pour résoudre des problèmes aux limites elliptiques. Les deux sujets portent principalement sur l'approche de l'opérateur simple couche.Pour le premier projet nous considérons le problème de Laplace-Beltrami Dirichlet sur une sous-surface de la sphère de rayon 1. Nous dérivons et analysons une méthode à équations intégrales du premier type pour résoudre ce problème aux limites. Cette méthode peut être utilisée pour étudier le mouvement de tourbillons ponctuels sur une sphère avec des murs impénétrables; nous comparons notre approche avec d'autres méthodes connues pour ce problème. Nous dérivons rigoureusement des estimations d'erreur pour les équations intégrales dans les espaces de Sobolev appropriés, ce qui donne des estimations globales de l'erreur pour la solution du problème aux limites. De plus, nous appuyons ces résultats théoriques grâce à des simulations numériques obtenues à partir de tests.Le deuxième projet porte sur une stratégie de préconditionnement multigrille pour l'équation de simple couche acoustique en deux dimensions. Tel que proposé dans [6], nous transférons la formulation en termes d'éléments finis de frontière à un produit scalaire plus faible et utilisons par la suite une méthode multigrille V-cycle avec un lisseur de type Richardson. Nous fournissons une analyse complète de convergence pour l'algorithme proposé basée sur un résultat analogue pour l'équation de simple couche correspondant à l'opérateur de Laplace. Des simulations numériques soulignent la performance de l'algorithme. De plus, nous faisons une étude numérique de l'effet du produit scalaire faible sur le comportement oscillatoire des fonctions propres correspondantes.
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Martinez, Sergio Elias Gavilan. "Aplicação do ensaio APULOT na determinação da resistência à compressão in loco do concreto nas primeiras idades." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/172081.
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A presente pesquisa propõe analisar, avaliar e validar o uso de ensaios de aderência açoconcreto para estimativa da resistência à compressão axial do concreto in loco nas primeiras idades em canteiros de obras, como alternativa ao controle de qualidade tradicional. Alguns pesquisadores propuseram a utilização de um ensaio de aderência modificado, que denominaram Appropriate Pull-Out Test (APULOT), como uma adaptação do método pullout test (POT) tradicional, normalizado pela norma EN12504-3. Para viabilizar o uso do ensaio APULOT como ensaio que possa ser implementado na prática do controle tecnológico do concreto em canteiros de obras e seja representativo da resistência in loco é necessário definir um padrão para o mesmo. O presente trabalho desenvolveu um molde específico para o ensaio, analisou a influência do processo da cura nos resultados da tensão máxima de aderência, estudou como a medição da maturidade no concreto pôde auxiliar na determinação do momento certo para fazer o ensaio de arrancamento e comparou resultados dos ensaios feitos em corpos de prova para teste de aderência com ensaios de arrancamento de barras de aço em painéis de concreto. Para tanto foram feitos nove concretagens empregando diferentes tamanhos e configurações de corpos de prova, ensaios de arrancamento, extrações de testemunhos de painéis de concreto, ensaios à compressão simples e medições de maturidade dos concretos empregados. Também se realizaram registros de temperatura ambiente e velocidade do vento na vizinhança dos painéis, buscando estabelecer relações entre a maturidade e as condições ambientais do canteiro. Os ensaios descritos anteriormente realizaram-se às idades de 3, 5, 7 e 28 dias. Os resultados obtidos mostram que, sob condições padronizadas de ensaio, existe ótima correlação entre a tensão máxima de aderência e a resistência à compressão do concreto e por tanto o ensaio de aderência pode ser utilizado para fazer uma estimativa da resistência à compressão do concreto in loco nas primeiras idades.<br>This research aims to analyze, evaluate and validate the use of steel-concrete bond tests to estimate the axial compression strength of in situ concrete at early ages on construction sites, as alternative to conventional strength control tests. Some researchers have proposed the use of a modified bond test, named Appropriate Pull-Out Test (APULOT), as an adaptation of the traditional pull-out test method (POT) standardized by the EN12504-3. To implement the APULOT as a strength control procedure for concrete on construction site, standardization is needed. This study developed a specific mold for the test; analyzed the influence of curing process on the results of the maximum bond stress; studied how measuring the maturity in the concrete could help to determine when is the right time to make the pull-out test; compared results of tests made on cores for testing the bond and pull-out tests on steel bars in concrete panels. Therefore, it have been made nine concrete events, pull-out tests using different sizes and configurations of cylindrical concret specimen, pull-out tests and extraction of cores from concrete panels, compressive test and maturity measurements of specific employees. Also, temperature and wind speed records have been performed in the panel´s sourrundings, seeking to establish relationships between maturity and ambiental conditions on construction site. The tests described above were carried out at 3, 5, 7 and 28 days. The results show that, under standardized test conditions, a correlation between the maximum bond stress and the concrete compression strength exists, and therefore, bond test can be used to estimate the in situ compression strength of the concrete in the first ages.
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Popelka, Lukáš. "Internetové uživatelské rozhraní pro tvorbu elektronických schémat." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2009. http://www.nusl.cz/ntk/nusl-217939.
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The diploma thesis deals with creating of electronic schematics in editor using web interface. The editor generates electrical circuit text file according to Spice netlist specification. The program has been created in Java and takes an advantage of object oriented programming language. The editor is a part of a web page and is executable as an applet. The diploma thesis describes a programming language selection, program layout and implementation. Thesis contains programming code examples, window illustration and component drawings. Depth-first search algorithm has been used for nodes number assignment. An OrCAD PSpice reference guide was used for netlist.
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Takiyama, Felipe Iwao. "Algoritmos de inferência exata para modelos de primeira ordem." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/3/3152/tde-23122014-145932/.
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Este trabalho descreve a implementação de algoritmos de inferência para modelos de primeira ordem. Três algoritmos foram implementados: ve, c-fove e ac-fove. Este último e o estado da arte no calculo de probabilidades em Redes Bayesianas Relacionais e não possua nenhuma implementação disponível. O desenvolvimento foi feito segundo uma metodologia ágil que resultou em um pacote de software que pode ser utilizado em outras implementações. Mostra-se que o software criado possui o desempenho esperado em teoria, embora apresente algumas limitações. Esta dissertação contribui também com novos tópicos teóricos que complementam o algoritmo.<br>In this work, we describe the implementation of inference algorithms for first order models. Three algorithms were implemented: ve, c-fove and ac-fove. The latter is the state of the art in probability calculations for Relational Bayesian Networks and had no implementation available. The development was done according to an agile methodology, which resulted in a software that can be used in other packages. We show that the resulting software has the expected performance from the theory, although with some limitations. This work also contributes with new theoretical topics that complement the algorithm.
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Karlsson, Albin. "Evaluation of the Complexity of Procedurally Generated Maze Algorithms." Thesis, Blekinge Tekniska Högskola, Institutionen för kreativa teknologier, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-16839.
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Background. Procedural Content Generation (PCG) in Video Games can be used as a tool for efficiently producing large varieties of new content using less manpower, making it ideal for smaller teams of developers who wants to compete with games made by larger teams. One particular facet of PCG is the generation of mazes. Designers that want their game to feature mazes also need to know how to evaluate their maze-complexity, in order to know which maze fits the difficulty curve best. Objectives. This project aims to investigate the difference in complexity between the maze generation algorithms recursive backtracker (RecBack), Prim’s algorithm (Prims), and recursive division (RecDiv), in terms completion time, when solved using a depth-first-search (DFS) algorithm. In order to understand which parameters affect completion time/complexity, investigate possible connections between completion time, and the distribution of branching paths, distribution of corridors, and length of the path traversed by DFS. Methods. The main methodology was an implementation in the form of a C# application, which randomly generated 100 mazes for each algorithm for five different maze grid resolutions (16x16, 32x32, 64x64, 128x128, 256x256). Each one of the generated mazes was solved using a DFS algorithm, whose traversed nodes, solving path, and completion time was recorded. Additionally, branch distribution and corridor distribution data was gathered for each generated maze. Results. The initial results showed that mazes generated by Prims algorithm had the lowest complexity (shortest completion time), the shortest solving path, the lowest amount of traversed nodes, and the lowest proportion of 2-branches, but the highest proportion of all other branch types. Additionally Prims had the highest proportion of 4-6 length paths, but the lowest proportion of 2 and 3 length paths. Later mazes generated by RecDiv had intermediate complexity, intermediate solving path, intermediate traversed nodes, intermediate proportion of all branch types, and the highest proportion of 2-length paths, but the lowest proportion of 4-6 length paths. Finally mazes generated by RecBack had opposite statistics from Prims: the highest complexity, the longest solving path, the highest amount of traversed nodes, the highest proportion of 2-branches, but lowest proportion of all other branch types, and the highest proportion of 3-length paths, but the lowest of 2-length paths. Conclusions. Prims algorithm had the lowest complexity, RecDiv intermediate complexity, and RecBack the highest complexity. Increased solving path length, traversed nodes, and increased proportions of 2-branches, seem to correlate with increased complexity. However the corridor distribution results are too small and diverse to identify a pattern affecting completion time. However the corridor distribution results are too diverse to make it possible to discern a pattern affecting completion time by just observing the data.
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Gomes, Wagner de Paula. "Programação de tripulantes de aeronaves no contexto brasileiro." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/3/3138/tde-21122009-170008/.
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Esta pesquisa trata o Problema de Programação de Tripulantes (PPT), presente no planejamento operacional das empresas aéreas. O principal objetivo do PPT é atribuir um conjunto de tarefas aos tripulantes, considerando as regulamentações trabalhistas, as regras de segurança e as políticas das empresas, de tal maneira que o custo da tripulação seja mínimo. O PPT é normalmente dividido em dois subproblemas, resolvidos sequencialmente: Problema de Determinação das Viagens (PDV) e Problema de Atribuição de Escalas (PAE). No PDV, determina-se um conjunto de viagens que cubra todos os voos planejados. Em seguida, no PAE, as escalas, compostas pelas viagens escolhidas e outras atividades como folgas, sobreavisos, reservas, treinamentos e férias, são atribuídas aos tripulantes. Esta decomposição justifica-se pela natureza combinatória do PPT, porém não incorpora as disponibilidades e as preferências dos tripulantes em ambos os subproblemas (PDV e PAE), gerando assim custos extras relacionados aos conflitos que surgem durante a atribuição das escalas aos tripulantes no PAE. Além disso, as estimativas de custos adotadas no PDV não possuem caráter global, já que o custo real da programação só pode ser obtido após a atribuição das escalas. O estado da arte envolve a solução integrada do PPT, em que se elimina a necessidade de resolver inicialmente o PDV, provendo assim uma melhor estimativa de custo e uma programação final com melhor qualidade, por considerar os custos da tripulação, as disponibilidades e preferências dos tripulantes de forma global. O problema, no entanto, é NP-Difícil. Assim sendo, a metodologia proposta nesta pesquisa objetiva a solução do PPT de forma integrada, através de um Algoritmo Genético Híbrido (AGH) associado a um procedimento de busca em profundidade, levando em conta as particularidades da legislação brasileira. A metodologia foi testada, com sucesso, para a solução de instâncias baseadas na malha real de uma empresa aérea brasileira.<br>This master of science research treats the Crew Scheduling Problem (CSP), as part of the airlines operational planning. The main aim of the CSP is to assign a set of tasks to crew members, considering the labor regulations, safety rules and policies of companies, such that the crew cost is minimal. The CSP is divided into two subproblems, solved sequentially: Crew Pairing Problem (CPP) and Crew Rostering Problem (CRP). First, CPP provides a set of pairings that covers all the planned flights. Then, in the CRP, the rosters, encompassing the pairings and other activities such as rest periods, alert duties, reserve duties, training times and vacations, are assigned to the crew members. This decomposition is justified by the combinatorial nature of the CSP, but it not incorporates the crew members availabilities and preferences in both subproblems (CPP and CRP), generating extra costs related to conflicts that arise during the assignment of rosters to the crew members in the CRP. Besides, the costs estimations adopted in the CPP does not have a global character, since the real cost of the global schedule can be only obtained after the assignment of the rosters. The state of the art involves the integrated solution of CSP, where the CPP does not need to be solved, thus providing a better estimated cost and a better schedule quality, considering crew costs and also crew members availabilities and preferences globally. The problem, however, is NP-Hard. Therefore, the methodology proposed in this master of science research aims to obtain an integrated solution of the CSP, through an hybrid algorithm genetic associated with a depth-first search procedure, taking into account the Brazilian legislation. The methodology was tested, with success, to solve instances related a real network of a Brazilian airline.
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Miro, Panades Ivan. "Conception et implantation d'un micro-réseau sur puce avec garantie de service." Paris 6, 2008. http://www.theses.fr/2008PA066195.
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Ce travail de thèse porte sur la conception et implantation physique d’un micro-réseau sur puce avec garantie de service. Ces études reposent sur le micro-réseau sur puce DSPIN développé au Lip6. Dans un premier temps, nous étudions l’incorporation des communications avec garantie de service dans ce micro-réseau. Ce type de communications est très utilisé dans les systèmes ayant de fortes contraintes temporelles comme, par exemple, les traitements de flux vidéo ou audio. La solution proposée est capable d’offrir des garanties de latence et de bande passante à faible coût matériel. Dans un deuxième temps, nous analysons une FIFO qui permet d’interconnecter des systèmes synchrones qui n’ont pas le même domaine d’horloge. Ce type de FIFO est optimisé pour des profondeurs faibles ainsi que pour faciliter son implantation dans des architectures compatibles avec l’approche Globalement Asynchrone, Localement Synchrone. Sa conception repose sur des cellules standard sans utiliser des cellules spécifiques ni asynchrones. Enfin, nous présentons une implantation matérielle du micro-réseau DSPIN dans la plate-forme FAUST développée par le CEA-Léti. Toute la chaîne de conception, depuis la synthèse de l’architecture jusqu’au dessin des masques, est décrite en détail pour illustrer la façon dont la technologie DSPIN s’intègre dans un flot de conception industriel. Ainsi, le circuit final est testé avec des données réelles.
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Feng, Le. "An in-depth examination of two-dimensional Laplace inversion and application to three-dimensional holography." University of Dayton / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1406814392.
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Nel, Celeste. "Die oorgang van skool na universiteit : 'n teoretiese raamwerk vir 'n pre-universitêre intervensie." Thesis, Stellenbosch : University of Stellenbosch, 2008. http://hdl.handle.net/10019.1/3175.
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Thesis (PhD (Education )--University of Stellenbosch, 2008.<br>352 leaves, preliminary pages xxiii and numbered pages 1-329. Includes bibliography and a list of figures.<br>ENGLISH ABSTRACT: The South African school system is increasingly producing students who do not make the grade in higher education. Universities are concerned about the quality of the students who register as first-years at higher education institutions. The findings of various studies have clearly shown that more and more students are inadequately prepared and therefore not ready for higher education. In South Africa the problems resulting
from the gap between school and university have been exacerbated by the inequalities that exist in the secondary school system, and which are still part of the legacy of apartheid. Within the context of learners’increasing unpreparedness for university studies, their difficult transition from school to university and the concomitant high drop-out figures in higher education, this study investigated the extent to which universities – with Stellenbosch University as a case in point – can contribute towards preparing students for university studies from as early as school level, and thus facilitate their transition from school to university. Taking this research question into account, the researcher investigated the extent to which specific variables played a part both in the pre-university phase and after admission. In addition, the study also focused on the extent to which students’ school background (previously disadvantaged privileged school) influences students’ preparedness, and to what extent academic standards (amongst others final examination results)are related to success in the first year at university. The research design was a case study of black newcomer first-year students who participated in a Stellenbosch University bursary project (the Merit Bursary project) in their Grade 12 year. The data generation consisted of two phases, namely a quantitative
approach in the pre-university phase and a qualitative approach, after admission, in the transitional phase. The research findings have revealed that the inequalities in the South African schooling system influence the transition from school to university. The classification of schools (previously disadvantaged or privileged school) plays a crucial role in students’ preparedness and how they handle the transition from school to
university. There are various academic, social, emotional, cultural and financial factors that impact on this transition. However, the factors are interdependent – no one factor can be regarded as being more important than another. Universities must adopt a holistic approach to the transition that newcomer students are required to make. It was concluded in the study that universities have a responsibility to ensure that the diminishing pool of potential students in higher education be expanded. Universities should also ontribute
towards preparing prospective students more effectively so that the transition process will be less challenging. It is believed that this will also improve the throughput rate. In this regard the study proposes a theoretical framework for a pre university intervention.<br>AFRIKAANSE OPSOMMING: Die Suid-Afrikaanse skoolstelsel lewer toenemend studente wat nie die mas in hoër onderwys opkom nie en universiteite is bekommerd oor die kwaliteit van die studente wat as eerstejaars aan hoëronderwysinstellings registreer. Uit die bevindinge van verskeie studies het dit geblyk dat studente toenemend nie voldoende voorbereid en gereed is vir hoër onderwys nie. In die Suid-Afrikaanse konteks word die gaping tussen skool en universiteit vergroot deur ongelykhede in die sekondêre skoolstelsel as gevolg van die land se apartheidsgeskiedenis. In die konteks van leerders se toenemende onvoorbereidheid
vir universiteitstudie, die moeilike oorgang van skool na universiteit en die gepaardgaande hoe uitvalsyfers in hoër onderwys, het hierdie studie ondersoek ingestel na die mate waarin universiteite - met die Universiteit Stellenbosch as spesifieke geval - reeds op skoolvlak ’n rol kan speel om voornemende studente beter vir universiteitstudie voor te berei en sodoende die oorgang van skool na universiteit te vergemaklik.
Met die navorsingsingsvraag in ag genome, het die navorser die mate waarin spesifieke veranderlikes ’n rol speel in die pre-universitêre fase asook die fase na toetrede tot universiteit, ondersoek. In samehang hiermee, het die studie ook gefokus op die invloed van skoolagtergrond (voorheen benadeelde of bevoorregte skole) op die voorbereidheid van studente en die mate waarin akademiese maatstawwe op skool (onder meer eindeksamenresultate) verband hou met sukses in die eerste universiteitsjaar. Die
navorsingsontwerp was ’n gevallestudie van swart nuwelingeerstejaarstudente wat in hulle graad 12-jaar aan ’n beursprojek (die Verdienstelikheidsbeursprojek) van die Universiteit Stellenbosch deelgeneem het. Die data-generering het uit twee fases bestaan, naamlik ’n kwantitatiewe benadering in die pre-universitêre fase en ’n kwalitatiewe benadering na toetrede in die oorgangsfase. Die ondersoek het gevind dat die ongelykhede in die Suid-Afrikaanse skoolstelsel die oorgang van skool na universiteit beinvloed. Skoolklassifikasie (voorheen benadeelde of bevoorregte skole) speel ’n bepalende rol
in die voorbereidheid van studente en ook in die wyse waarop studente die oorgang hanteer. Daar is ’n verskeidenheid akademiese, sosiale, emosionele, kulturele en finansiële faktore wat ’n rol speel in die oorgang van skool na universiteit. Die faktore is egter interafhanklik van aard – geen een kan uitgesonder word as belangriker as die ander nie. Universiteite moet die oorgang van nuwelingstudente holisties
benader. Hierdie ondersoek kom verder tot die slotsom dat dit ook die verantwoordelikheid van universiteite is om te sorg dat die krimpende poel potensiele studente vir hoër onderwys vergroot en beter voorbereide studente toegelaat word om sodoende die oorgangsproses te vergemaklik en deurvloeikoerse te verhoog. In die lig hiervan stel die studie ’n teoretiese raamwerk vir ’n pre-universitêre intervensie voor.
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Larson, Kajsa. "On perfect simulation and EM estimation." Doctoral thesis, Umeå : Department of Mathematics and Mathematical Statistics, Umeå University, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-33779.
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Deprez, Romain. "Optimisation perceptive de la restitution sonore multicanale par une analyse spatio-temporelle des premières réflexions." Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4746/document.
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L'objectif de cette thèse est l'optimisation de la qualité perçue de la reproduction sonore par un système audio multicanal, dans un contexte de salle d'écoute domestique. Les travaux de recherche présentés s'articulent selon deux axes. Le premier concerne l'effet de salle, et plus particulièrement les aspects physiques et perceptifs liés aux premières réflexions d'une salle. Ces éléments sont décrits spécifiquement, et une expérience psychoacoustique a été menée afin d'étendre les données disponibles quant à leur perceptibilité, c'est à dire leur capacité à modifier la perception du son direct, que ce soit en termes de timbre ou de localisation. Les résultats mettent en évidence la dépendance du seuil en fonction du type de stimulus, ainsi que son évolution en fonction de la configuration spatiale de l'onde directe et de la réflexion. Pour une condition donnée, le seuil de perceptibilité est décrit comme une fonction de directivité dépendant de l'incidence de la réflexion.Le deuxième axe de travail concerne les méthodes de correction de l'effet de la salle de reproduction. Les méthodes numériques classiques sont d'abord étudiées. Leur principale lacune réside dans l'absence de prise en compte du rôle spécifique des propriétés temporelles et spatiales des première réflexions. Le travail de thèse se termine par la proposition d'une nouvelle méthode de correction utilisant un algorithme itératif de type FISTA modifié afin de prendre en compte la perceptibilité des réflexions. Le traitement est implémenté dans une représentation où l'information spatiale est analysée sur la base des harmoniques sphériques<br>The goal of this Ph. D. thesis is to optimize the perceived quality of multichannel sound reproduction systems, in the context of a domestic listening room. The presented research work have been pursued in two different directions.The first deals with room effet, and more particularly with physical and perceptual aspects of first reflections within a room. These reflections are specifically described, and a psychoacoustical experiment have been carried out in order to extend the available data on their perceptibility, i.e. their potency in altering the perception of the direct sound, whether in its timbral or spatial features. Results exhibit the variation of the threshold depending on the type of stimulus, as well as on the spatial configuration of the direct sound and the reflection. For a given condition, the perceptibility threshold is given as a directivity function depending on the direction of incidence of the reflection.The second topic deals with room correction methods. Firstly, state-of-the art digital methods are investigated. Their main drawback is that they don't consider the specific impact of the temporal and spatial attributes of first reflections. A new correction method is therefore proposed. It uses an iterative algorithm, derivated from the FISTA method, in order to take into account the perceptibility of the reflections. All the processing is carried out in a spatial sound representation, where the spatial properties of the sound are analysed thanks to spherical harmonics