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Mojapelo, Mamokou Margaret. "Reproduction performance of Saanen bucks supplemented with selenium." Diss., University of Pretoria, 2017. http://hdl.handle.net/2263/63294.
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Reproduction potential of farm animals is mainly determined by selection of appropriate strategies that benefit the reproductive performance. The aims of the study were first to evaluate the effect of selenium (Se) supplementation on attainment of puberty and reproductive performance of Saanen bucks and secondly, to evaluate the effect of selenium supplementation on semen yield and quality of Saanen bucks following two semen collection methods and induced stress. The study consisted of three experiments. For experiment 1, goats were allocated into two treatment groups: treatment and control. The treatment group were dosed with sodium selenite at three months interval. In experiment 2, the two groups from experiment one were further subdivided into two groups each based on semen collection method (artificial vagina - AV or electro ejaculator - EE) leading to four groups (Se + AV, Se +EE, Control + AV, Control + EE). For experiment 3, the major two groups (selenium supplemented and control) were subdivided into two groups each based on induced stress (injected with adrenocorticotropic hormone -ACTH) and not, leading to four groups (Se, Se + ACTH, ACTH and control). For the last two experiments, selenium supplementation was done at two months interval. ACTH was administered at three weeks interval. The phenotypic parameters were evaluated every two weeks. For all experiments semen was collected bi-weekly from bucks and evaluated for volume, colour, sperm motility, concentration, viability and morphology. Blood samples were collected at two weeks interval to determine selenium concentration and reproductive hormones. Data collected was analysed using GLM procedures of SAS (2012) and the means were separated by Duncan test. Supplementation with selenium significantly (P < 0.05) improved body weight, testicular measurements and decreased age at puberty. Selenium supplementation led to significantly (P < 0.05) greater ejaculate volume, semen colour and pH, high sperm motility, concentration and viability in the present study. There were lower (P < 0.05) percentages of morphological abnormal sperm from the selenium supplemented bucks than the control. There were also a lower percentage of primary sperm abnormalities from the selenium treated group, compared to the control. The electro-ejaculator method of semen collection had a greater ejaculate volume regardless of the selenium supplementation. The interaction of selenium supplementation and electro-ejaculator method of semen collection showed that when bucks are supplemented with selenium, the electro-ejaculator technique lead to a creamy semen appearance. The electro-ejaculator technique had an advantage of leading to a lower percentage of tertiary sperm abnormalities. Selenium supplementation also reduced the detrimental effects of stress on semen characteristics. Supplementation with selenium lessened the effects of induced stress, improved luteinising hormone and testosterone concentrations. Selenium supplementation enhanced serum blood glutathione peroxidase activity and lowered cortisol level in bucks. The results of the present study confirmed that male goat kids supplemented with selenium attain puberty with enhanced pubertal characteristics. It was observed that if selenium is supplemented and semen is collected frequently, both the electro-ejaculator and artificial vagina semen collection methods yield acceptable semen parameters and, consequently lead to improved semen quality of Saanen bucks.Dissertation (MSc Agric)--University of Pretoria, 2017.
National Research Foundation (NRF)
University of Pretoria
Animal and Wildlife Sciences
MSc (Agric)
Unrestricted
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Pauls, Torben. "Bildung und Praxis Studien zur hermeneutischen Bildungstheorie Günther Bucks." Würzburg Ergon-Verl, 2008. http://d-nb.info/99849884X/04.
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Pauls, Torben. "Bildung und Praxis : Studien zur hermeneutischen Bildungstheorie Günther Bucks." Würzburg Ergon-Verl, 2009. http://d-nb.info/99849884X/04.
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Chavez, Stephen John. "Feeding behaviors and performance measurements in bucks, rams, and bulls." Morgantown, W. Va. : [West Virginia University Libraries], 2008. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=5716.
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Thesis (M.S.)--West Virginia University, 2008.Title from document title page. Document formatted into pages; contains vii, 91 p. : ill. (some col.). Includes abstract. Includes bibliographical references.
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Bendersky, Corinne (Corinne Bernarda) 1973. "Complementarities in employment dispute resolution systems : bigger bang or just bigger bucks?" Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/8436.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, Sloan School of Management, 2002.Includes bibliographical references (p. 133-147).
Organizations face increasing pressure to improve internal conflict management, which has led to experimentation with different types of dispute resolution components. These include: Rights-based processes, in which third-parties determine the outcome of a dispute based on laws, contracts or standards of behavior; Interest-based neutrals, who manage the dispute resolution process and leave decision-making authority to the parties themselves; and Negotiations, which include all efforts by individual disputants to resolve conflicts themselves. Anecdotal evidence suggests that systems combining all three types of dispute resolution components are more effective than any of the individual or pairs of components. To date, however, there is no theoretical explanation or rigorous empirical evidence to justify the regular implementation of full dispute resolution systems by organizational leaders. In this dissertation I present and test two competing theoretical models to explain the benefits of dispute resolution systems over pairs and individual components. The first is an additive model, in which the more types of components that are available, the more types of disputes that can be managed. The second model is a complementarities model, in which none of the components can operate effectively without reinforcement from the other types of components. Thus, performance benefits accrue only when a full system is implemented.
(cont.) I test these competing models in a multi-method quasi-experimental and two supplemental before-and-after field studies. I consistently find evidence contradicting the additive model, and suggestive evidence supporting the complementarities model. The effects of exposing employees to a three-component dispute resolution system are: 1) more positive attitudes towards workplace conflict, 2) less conflict avoidance, 3) more conflict negotiation, and 4) more conflict resolution. When employees are exposed to a two-component system, however, only negotiation behaviors increase. All other outcomes were either non-significant or in the opposite-to-expected direction. Although this study is not conclusive evidence of the complementarities model, the data clearly reject the additive one. This study implies that practitioners should focus on introducing full systems to organizations instead of taking an incremental approach to changing dispute resolution behaviors.
by Corinne Bendersky.
Ph.D.
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Graeff, Michael. "An archive: housing the written history of the citizens of Bucks County, Pennsylvania." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/44423.
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The growth of any community is marked many times over by the coming of progress which may be regarded either with promise or as a threat. The history of Doylestown records the arrival of train travel as an event.
It would be a remarkable change that could put a small town on the map by opening doors of travel and communication in the heart of rural farmland. The tracks entered the town from the southwest and ended a few blocks downhill from the original crossing of Main and State Streets at its center. The rail line would now be the demarcation between town and country - an edge. A passenger station was built as were an array of light industrial and farm trade buildings, splayed out in rows along the lengths of track. The empty lots between center and edge became a weave of streets lined with town houses constructed to acknowledge the train with large front porches open wide welcoming the arrival of both the familiar and the stranger.
The ebb and flow of pedestrians descending and ascending from town to train and train to town became the daily ritual established by such progress. It is in this routine and the willing communication between buildings that lay a complimentary existence defining the character of a neighborhood.
It is a further part of progress that centers of activity with their subsequent community of buildings become obsolete. Yet from obsolescence may be found rebirth, and the rail yard was no exception. Commerce waned and then shifted from industrial and agrarian means to service oriented trade with each vacant structure quietly resurrected under adaptive re-use. The commuter line still operates though continually threatened with closure. A truth made evident by the perpetually locked doors of the station. The only activity that has a direct connection to the rail yard's past is the ritual of the commuting passengers. Pedestrian traffic into town still beats its daily walk up the stairs and sidewalks along the same streets. The numbers are now supplemented though by a stream of vehicles as evidenced by the number of parking spaces fit neatly into the available open nooks of the old freight house. Despite these progressive changes what is of greatest significance is that none has occurred to the detriment of the fabric of the existing neighborhood. It remains a distinctly vibrant edge only because new activities were necessary in offering new opportunities and a feeling of continuum. The site for the archive therefore lies at this edge of town.
Master of Architecture
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Stiefbold, Angela S. "Farming Scenery: Growing Support for Agricultural Land Preservation, Bucks County, Pennsylvania, 1930-1990." University of Cincinnati / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1592133417563856.
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Strawn, Rachel Mayes. "Drivin' trucks, huntin' bucks, and reading Aristotle?: The rural student's college choice dilemma." W&M ScholarWorks, 2014. https://scholarworks.wm.edu/etd/1550154174.
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Schmoyer, Gerald Richard. ""The life of Jesus for children" an evaluation of a Bible study for Bucks Area Home Schoolers /." Theological Research Exchange Network (TREN), 2006. http://www.tren.com/search.cfm?p001-1073.
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Friedman, Gail. "Remembering Del-Aware: Community Activism and Eco-Politics in Bucks County, Pennsylvania in the Age of Reagan." Master's thesis, Temple University Libraries, 2016. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/396215.
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HistoryM.A.
This thesis tells the previously untold story of how environmental activists in Bucks County, Pennsylvania, in the 1980s waged a nearly decade-long and ultimately losing battle against a plan to pump water from the free-flowing Delaware River. As a case study of grassroots community activism during the presidential administration of Ronald Reagan, the struggle known locally as “Dump the Pump” and spearheaded by a nonprofit organization called Del-AWARE supports and provides a regional take on recent scholarship that has illuminated the vibrant underlying dynamics of local civic engagement occurring amid the overshadowing political conservatism of the Reagan years. Also a case study in public history, this thesis demonstrates how collective historical memory fueled not only Del-AWARE’s protracted struggle, but its enduring legacy in public policy and community life. It concludes with suggestions for preserving the history of Del-AWARE before it is lost forever.
Temple University--Theses
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Tolley, Rebecca. "More Bang For Your Book Bucks: The Added Value of Table of Contents (TOC) Record Enhancement [Poster Session]." Digital Commons @ East Tennessee State University, 2002. https://dc.etsu.edu/etsu-works/5749.
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Helge, Adam. "Procedurell Generering - Rum och Korridorer : En jämförelse av BSP och Bucks algoritm som metoder för procedurell generering av dungeons." Thesis, Högskolan i Skövde, Institutionen för informationsteknologi, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-15288.
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Procedurell generering av spelinnehåll är idag ett populärt alternativ för många spelutvecklare då det kan minska kostanden, tiden samt arbetsbördan för mindre bolag. Den här studien har som syfte att undersöka två stycken algoritmer inom procedurell generering där den ena är BSP och den andra är Bucks algoritm. Bucks algoritm är en ny, okänd och tämligen oanvänd algoritm som är av intresse att undersöka för att utvärdera dess användbarhet inom spelutveckling. Resultatet från studien visar att BSP genererar innehåll snabbast och i gengäld skapar Bucks algoritm innehåll med en högre nivå av densitet och relativ storlek.
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Grundy, Martha Paxson. "“In the world but not of it”: Quaker faith and the dominant culture, Middletown Meeting, Bucks County, Pennsylvania, 1750-1850." Case Western Reserve University School of Graduate Studies / OhioLINK, 1990. http://rave.ohiolink.edu/etdc/view?acc_num=case1058985472.
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Hillbrick, Gordon Colin, and kimg@deakin edu au. "THE LIPID COMPOSITION OF CASHMERE GOAT FIBRES." Deakin University, 1994. http://tux.lib.deakin.edu.au./adt-VDU/public/adt-VDU20031205.162817.
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This study examined the differences in the chemical composition, particularly fatty acids, of the lipid extracted from the fibre of bucks, does and castrated goats. The study provides a more detailed understanding of the chemical composition of buck fibre lipid and how it varies throughout the year, and also details the effect of body region and nutrition on the production and chemical composition of lipid from buck fibre.
Lipid was extracted with either petroleum ether (non-polar) or chloroform/methanol azeotrope (polar) and analysed by gas chromatography and gas chromatography-mass spectrometry. The more polar solvent system extracted larger amounts of lipid and more of each individual fatty acid. The following buck specific ethyl branched fatty acids were identified: 2-ethylhexanoic, 4-ethylhexanoic, 2-ethyloctanoic, 4-ethyloctanoic, 6-ethyloctanoic, 2-ethyldecanoic, 4-ethyldecanoic, 2-ethyldodecanoic, 6-ethyldodecanoic, 4-ethyldodecanoic, 2-ethyltetradecanoic, 6-ethyltetradecanoic, 4-ethyltetradecanoic, 2-ethylhexadecanoic and 4-ethyloctadecanoic acids. Of these buck specific fatty acids only 4-ethylhexanoic (T), 4-ethyloctanoic, 4-ethyldecanoic, 4-ethyldodecanoic, 6-ethyldodecanoic (T), 4-ethyltetradecanoic, 2-ethylhexadecanoic (T) and 4-ethylhexadecanoic acids have been previously identified or tentatively identified (T) in buck fibre extracts. This shows that the chemical composition of buck fibre lipid is more complex than previously reported, and that it may be more difficult than previously thought to artificially duplicate the odour of the buck.
Buck fibre samples had lower average
concentrations of 2-methylpropanoic, 2-methylbutanoic, iso-pentadecanoic, anteiso-pentadecanoic, iso-hexadecanoic, anteiso-heptadecanoic, iso-octadecanoic and anteiso-nonadecanoic acids as compared with fibre samples from does, spayed does, or wethers that were castrated at one month of age. The reduced concentrations of these fatty acids in buck fibre extracts were likely to be due to the synthesis of ethyl branched derivatives of iso and anteiso fatty acids. Buck fibre samples had higher concentrations of benzoic acid as compared with fibre samples from does, spayed does, or wethers that were castrated at one month of age. The significance of these results is that non buck specific fatty acids may also make a contribution to the odour of bucks.
When fibre samples were collected at various times throughout the year, it was found that the bucks had increased amounts of lipid and ethyl branched fatty acids in fibre samples shorn from March to September, as compared with fibre samples shorn in November and January. The increase in the amount of lipid and ethyl branched fatty acids corresponded with both the rutting period of the buck and the period when the buck odour was increased. This suggests that ethyl branched fatty acids could be pheromones.
The variation in lipid content and fatty acid composition was also examined between fibre samples collected from different body regions of the buck during April, as alterations in sebaceous gland activity around the neck during rutting have been reported. It was found that the average amount of lipid in the neck region of the bucks was not statistically higher than the average amounts in the midside and hind regions. However, the ethyl branched fatty acid concentrations were statistically higher in the fibre from around the neck as compared with the fibre from the other body regions, which is consistent with the odour of the buck being most pronounced around the head and neck region.
The lipid content and composition of fibre samples from bucks fed high and low quality diets (lucerne and pangola grass, respectively) was examined to determine the effect of nutrition on buck specific components. The high quality diet increased the amount of lipid and ethyl branched fatty acids in fibre samples collected in April from the neck, midside and hind regions, as compared with fibre samples from the corresponding body regions from bucks fed the low quality diet. Thus it may be possible for the pheromone levels of bucks to be increased by simply providing them with good nutrition.
The lipid content and ethyl branched fatty acid concentrations of fibre samples increased earlier in the year for the lucerne fed bucks as compared with the pangola grass fed bucks. The lucerne fed bucks had increased concentrations of ethyl branched fatty acids in fibre samples shorn during December to June (6 months) whereas the pangola grass fed bucks had increased concentrations of ethyl branched fatty acids in fibre samples shorn during April to August (4 months). These observations show that good nutrition can result in both the earlier production of ethyl branched fatty acids and an extended period when ethyl branched fatty acids are produced. This suggests that nutrition can be used to manipulate pheromone levels in the buck. The period when the ethyl branched fatty acids were increased corresponded with the period when the plasma luteinizing hormone (LH) and testosterone concentrations, odour and sebaceous gland volume of the bucks were increased, which supports the assumption that ethyl branched fatty acids are involved in odour production and act as pheromones.
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Katjavivi, Perivi John. "Film and national culture in Namibia: a study and analysis of how the films 100 Bucks and Try have contributed to the creation of post-colonial identity and national culture in independent Namibia." Master's thesis, University of Cape Town, 2016. http://hdl.handle.net/11427/22784.
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I wish to present a study of the different literature regarding national culture, African cinema and postcolonial identity and explore how it relates to local cinema in Namibia. How have Namibian films contributed to this debate? The films 100 Bucks and Try contributed to the creation of postcolonial identity and national culture in independent Namibia. This dissertation will focus primarily on the aesthetics, themes and stories produced in Namibia since 2000 as well as how our storytelling and funding models can learn from other industries throughout the world. I will undertake an examination of past works and writings on the topic of national culture in post colonial African states, nationalism and African identity.
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Sayers, Jeremy H. "The Great Mysterious." University of Akron / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=akron1271258434.
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Cox, Scott Lee Londré Felicia Hardison. "Buck Hoss." Diss., UMK access, 2006.
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Thesis (M.A.)--Dept. of Theatre. University of Missouri--Kansas City, 2006."A thesis in theatre." Typescript. Advisor: Felicia Hardison Londré́. Vita. Title from "catalog record" of the print edition Description based on contents viewed Jan. 26, 2007. Includes bibliographical references (leaves 92-93). Online version of the print edition.
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Müller-Kelwing, Karin. "Hellmuth Buck." Böhlau Verlag, 2020. https://slub.qucosa.de/id/qucosa%3A75035.
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Buck, Anja. "Untersuchungen zur Bedeutung der sal-ähnlichen Gene bei der Maus." [S.l.] : [s.n.], 2001. http://webdoc.sub.gwdg.de/diss/2002/buck/buck.pdf.
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Wei, Jia. "Investigation of High-Input-Voltage Non-Isolated Voltage Regulator Modules Topology Candidates." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/32482.
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Since the early 80s, the computer industry has undergone great expansion. Processors are becoming faster and more powerful. Power management issues in computing systems are becoming more complex and challenging. An evolution began when the high-performance Pentium processor was driven by a non-standard, less-than-5V power supply, instead of drawing its power from the 5V plane on the system board. A so-called Voltage Regulator Module (VRM), is put close to the processor in order to provide the power as quickly as possible. Nowadays, for desktop and workstation applications, VRM input voltage has moved to the 12V output of the silver box. In the meantime, microprocessors will run at very low voltage (below 1V), will consume up to 100A of current, and will have dynamics of about 400A/us.
This work presents an investigation of three 12V VRM topologies: the synchronous buck converter, the tapped-inductor buck converter and the active-clamp couple-buck converter. The limitations of today¡¯s synchronous buck approach are identified. The extreme duty cycle of the current topology makes it difficult to design an efficient VRM with decent transient response.
The tapped-inductor buck and the active-clamp couple-buck converters are discussed as solutions. The transient response and efficiency of each type of converter are compared. Ripple cancellation is also addressed. The analytical and experimental results are presented: The tapped-inductor buck can improve the efficiency, but suffers a voltage spike, which nullifies its candidacy; the active-clamp couple-buck converter can improve the efficiency while maintaining good transient response, and it is therefore a good candidate for 12V VRMs.Master of Science
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Qiu, Yang. "High-Frequency Modeling and Analyses for Buck and Multiphase Buck Converters." Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/29804.
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Future microprocessor poses many challenges to its dedicated power supplies, the voltage regulators (VRs), such as the low voltage, high current, fast load transient, etc. For the VR designs using multiphase buck converters, one of the results from these stringent challenges is a large amount of output capacitors, which is undesired from both a cost and a motherboard real estate perspective. In order to save the output capacitors, the control-loop bandwidth must be increased. However, the bandwidth is limited in the practical design. The influence from the switching frequency on the control-loop bandwidth has not been identified, and the influence from multiphase is not clear, either. Since the widely-used average model eliminates the inherent switching functions, it is not able to predict the converter's high-frequency performance. In this dissertation, the primary objectives are to develop the methodology of high-frequency modeling for the buck and multiphase buck converters, and to analyze their high-frequency characteristics.
First, the nonlinearity of the pulse-width modulator (PWM) scheme is identified. Because of the sampling characteristic, the sideband components are generated at the output of the PWM comparator. Using the assumption that the sideband components are well attenuated by the low-pass filters in the converter, the conventional average model only includes the perturbation-frequency components. When studying the high-frequency performance, the sideband frequency is not sufficiently high as compared with the perturbation one; therefore, the assumption for the average model is not good any more. Under this condition, the converter response cannot be reflected by the average model. Furthermore, with a closed loop, the generated sideband components at the output voltage appear at the input of the PWM comparator, and then generate the perturbation-frequency components at the output. This causes the sideband effect to happen. The perturbation-
frequency components and the sideband components are then coupled through the comparator. To be able to predict the converter's high-frequency performance, it is necessary to have a model that reflects the sampling characteristic of the PWM comparator. As the basis of further research, the existing high-frequency modeling approaches are reviewed. Among them, the harmonic balance approach predicts the high-frequency performance but it is too complicated to utilize. However, it is promising when simplified in the applications with buck and multiphase buck converters. Once the nonlinearity of the PWM comparator is identified, a simple model can be obtained because the rest of the converter system is a linear function.
With the Fourier analysis, the relationship between the perturbation-frequency components and the sideband components are derived for the trailing-edge PWM comparator. The concept of multi-frequency modeling is developed based on a single-phase voltage-mode-controlled buck converter. The system stability and transient performance depend on the loop gain that is affected by the sideband component. Based on the multi-frequency model, it is mathematically indicated that the result from the sideband effect is the reduction of magnitude and phase characteristics of the loop gain. With a higher bandwidth, there are more magnitude and phase reductions, which, therefore, cause the sideband effect to pose limitations when pushing the bandwidth.
The proposed model is then applied to the multiphase buck converter. For voltage-mode control, the multiphase technique has the potential to cancel the sideband effect around the switching frequency. Therefore, theoretically the control-loop bandwidth can be pushed higher than the single-phase design. However, in practical designs, there is still magnitude and phase reductions around the switching frequency in the measured loop gain. Using the multi-frequency model, it is clearly pointed out that the sideband effect cannot be fully cancelled with unsymmetrical phases, which results in additional reduction of the phase margin, especially for the high-bandwidth design. Therefore, one should be extremely careful to push the bandwidth when depending on the interleaving to cancel the sideband effect.
The multiphase buck converter with peak-current control is also investigated. Because of the current loop in each individual phase, there is the sideband effect that cannot be canceled with the interleaving technique. For higher bandwidths and better transient performances, two schemes are presented to reduce the influence from the current loop: the external ramps are inserted in the modulators, and the inductor currents are coupled, either through feedback control or by the coupled-inductor structure. A bandwidth around one-third of the switching frequency is achieved with the coupled-inductor buck converter, which makes it a promising circuit for the VR applications.
As a conclusion, the feedback loop results in the sideband effect, which limits the bandwidth and is not included in the average model. With the proposed multi-frequency model, the high-frequency performance for the buck and multiphase buck converters can be accurately predicted.Ph. D.
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Dey, Sourav. "Large-Signal Analysis of Buck and Interleaved Buck DC-AC Converters." Wright State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=wright1409578634.
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Rahman, Muhammad Saad. "Buck Converter Design Issues." Thesis, Linköping University, Department of Electrical Engineering, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-9713.
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Switch Mode Power Supplies are very important components in present day electronics and have continued to thrive and grow over the past 25 years. This thesis looks inside how the SMPS have evolved over the passage of years with special emphasis to the Synchronous Buck Converter. It also discusses why there is a strong potential to further the study related to designs based around a Synchronous Buck Converter for portable applications. The main objective of the thesis is to look into the controller design for minimizing size, enhancing efficiency and reliability of power converters in portable electronic equipment such as mobile phones and PDAs. The thesis aims to achieve this using a 90 nm process with an input voltage of 1.55V and an output of 1V with a power dissipation of 200mW.
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Buck, David Hidden. "Promoting more effective student questions through specific questioning strategies." Montana State University, 2011. http://etd.lib.montana.edu/etd/2011/buck/BuckD0811.pdf.
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This project addresses the question "Do students understand key scientific concepts better with training in the use of specific questioning strategies?" Students were trained specifically in composing questions using the cognitive domain of Bloom's Taxonomy, as well as in developing experiments, inventions and models using Cothron's Four Question Strategy. Students engaged in several inquiry activities, both independently and in large and small groups, to practice these strategies and approaches. The results of this research suggest that there is a strong correlation between employing these strategies to improve students' questioning skills and the students' understanding of key concepts surrounding questioning and inquiry.
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Olivar, Gerard. "Chaos in the buck converter." Doctoral thesis, Universitat Politècnica de Catalunya, 1997. http://hdl.handle.net/10803/5841.
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Esta tesis estudia el fenómeno del caos en las ecuaciones que modelan un convertidor buck con control PWM. Desde el punto de vista matemático, contribuye al estudio de los sistemas lineales a trozos tridimensionales, con émfasis en las perspectivas geométrica y de cálculo numérico. Se consiguen resultados analíticos pero, finalmente, deben emplearse métodos numéricos para calcular efectivamente las órbitas periódicas, bifurcaciones, variedades invariantes y cuencas de atracción. Desde el punto de vista de la ingeniería, esta tesis contribuye, por una parte, a dilucidar ciertas cuestiones acerca del comportamiento observado en el circuito electrónico experimental, y por otra parte, plantea nuevas preguntas que debe responder la comunidad científica dedicada a la ingeniería. Entre ellas, la búsqueda experimental de fenómenos secundarios detectados en las simulaciones numéricas y la posibilidad de implementar algunos de los métodos de control de caos deducidos en un prototipo experimental.El capítulo 2 resume la información básica sobre convertidores conmutados de corriente contínua, y también sobre qué tipo de comportamiento cabe esperar de un sistema dinámico no lineal. Se discuten las referencias más relevantes sobre circuitos no lineales, y en concreto, las que atañen a circuitos caóticos en electrónica de potencia.
Los sistemas de ecuaciones diferenciales lineales a trozos con dos topologías se introducen en el capítulo 3. Como caso particular, se dan las ecuaciones que rigen la dinámica del convertidor buck con control PWM, y se establecen algunas propiedades básicas de las soluciones. La técnica general para obtener órbitas periódicas se particulariza para las soluciones T-periódicas y 2T-periódicas, y se establecen resultados para algunos tipos específicos de las nT-periódicas.
En el capítulo 4 se detalla el análisis de la aplicación estroboscópica. Este capítulo está orientado geométricamente, aunque el cálculo numérico es también imprescindible para obtener resultados específicos. Se halla también una región de atrapamiento para el sistema, en la cual se encuentra una aplicación de tipo horseshoe. La herramienta principal de este capítulo es la continuidad de la aplicación de Poincaré asociada, que permite deducir analíticamente como se transforman las diferentes regiones del espacio de fases.
El capítulo 5 está dedicado a las bifurcaciones secundarias halladas conjuntamente con el atractor principal. En este capítulo, el cálculo numérico es esencial para hallar los diagramas de bifurcaciones, las variedades invariantes y las cuencas de atracción. Como las soluciones son conocidas analíticamente a trozos, los algoritmos se benefician de ello en rapidez y sencillez. Se encuentran bifurcaciones suaves y no suaves. Se dan también expresiones exactas para los multiplicadores característicos, lo cual representa una gran ventaja cuando se calculan las bifurcaciones.
El capítulo 6 se aparta ligeramente del espíritu general de la tesis. En lugar de describir el comportamiento caótico del sistema, se sugieren algunos métodos de control de caos y se simulan éstos para comprobar si producen los efectos deseados. En concreto, se dan tres opciones: primero, se concreta el método OGY para las ecuaciones del convertidor buck ; segundo, se sugieren varios esquemas de control de realimentación con retardos, y tercero, se propone un método de control de lazo abierto. El control del comportamiento caótico en este circuito es importante, puesto que reduce el rizado de salida y por tanto, amplia el rango operacional del convertidor.
Algunas sugerencias para seguir el estudio de estos sistemas dinámicos se dan en el capítulo 7. Algunas simulaciones se han hecho con una versión suavizada del sistema de ecuaciones diferenciales con el software standard AUTO. También se proponen aproximaciones de la aplicación de Poincaré, que pueden proporcionar un tratamiento más analítico y simulaciones más rápidas.
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Олейник, Н. Г., and Юрий Иванович Подъячий. "Исследование корректоров мощности BUCK/BOOST." Thesis, Национальный технический университет "Харьковский политехнический институт", 2017. http://repository.kpi.kharkov.ua/handle/KhPI-Press/44600.
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Bozzo, Closas Bernat. "Superconducting joining of melt textured YBCO bulks." Doctoral thesis, Universitat Autònoma de Barcelona, 2016. http://hdl.handle.net/10803/369047.
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La obtenció de ceràmiques superconductores de YBa2Cu3O7 porta implícita una limitació en les dimensions i forma de les peces. Per tal de superar aquesta limitació, s’ha proposat un mètode de soldadura basat en l’ús d’una làmina de plata com a decapant.
Aquest treball de Tesi està enfocat en:
• El perfeccionament de la tècnica de soldadura de YBCO per tal de resoldre una sèrie de problemàtiques presents en el moment de començar aquest treball.
• Caracterització de la microestructura de les mostres soldades.
• El desenvolupament d’eines d’anàlisi quantitatiu per avaluar la qualitat de la soldadura des del punt de vista de les propietats magnètiques i elèctriques.
• La expansió del mètode de soldadura per incloure soldadures on existeix una desorientació cristal·logràfica entre les dues peces unides i estudi de la influència d’aquesta desorientació en les propietats magnètiques i elèctriques.
El primer pas seguit fou la construcció d’un forn equipat amb un sistema d’observació òptica in-situ. Aquest sistema va permetre obtenir gravacions de l’evolució de la mostra durant el tractament tèrmic. Aquests vídeos van permetre detectar la presència de dos tipus de líquids que eren arrossegats fora de la zona de soldadura. L’estudi de la microestructura de la soldadura van indicar que aquesta pèrdua de líquid afavoria l’aparició de defectes microestructurals. Una modificació del porta-mostres emprat solucionà el problema.
Es van realitzar estudis de la microestructura més detallats per tal de poder entendre millor els mecanismes que en fan possible la seva formació amb la idea de postular-ne un possible model.
Un estudi adequat de les propietats magnètiques també fou necessari, ja que l’objectiu final del mètode de soldadura és el d’unir diverses peces de YBCO, tot mantenint les propietats superconductores a la zona soldada. Per aquest motiu, es van realitzar mesures d’imatge magnètica, basades en una Sonda d’Efecte Hall. A partir dels mapes de magnetització local de les mostres, es va obtenir la distribució de densitats de corrent crítica, emprant un programari especialitzat. Per tal d’entendre millor aquests mapes de densitat de corrent i, també, per extreure’n informació útil, es va desenvolupar un programari de simulació i els coneixements adquirits, es van poder obtenir les densitats de corrent intergranular i intragranular (JcGB i JcG).
Es va estudiar la dependència del quocient entre JcGB i JcG amb l’angle de desorientació cristal·lina. En principi s’esperava una dependència semblant a la que es troba en el cas de les cintes superconductores. No obstant, la dependència que es va trobar era més fluixa que la del cas model considerat.
Aquesta dependència es va comprar, llavors, amb la d’altres estudis similars, fets amb fronteres de gra artificials en mostres superconductores volumètriques, revelant un comportament semblant entre elles, indicant que el valor del quocient JcGB/JcG era potencialment intrínsec al grau de desorientació. Aquesta hipòtesi es va confirmar quan es van comparar mostres de YBCO amb qualitats diferents, però amb el mateix angle de desorientació.
Es van realitzar mesures dels mapes de magnetització en funció del camp magnètic per tal de determinar els règims d’ancoratge de vòrtexs presents en les mostres i es van comparar amb el cas de les cintes superconductores. Tot i que els règims d’ancoratge en la zona de soldadura són similars als de les fronteres de gra per una cinta superconductora, els règims en zones fora de la soldadura difereixen entre els dos casos.
Finalment, es van realitzar mesures de nanoindentació per tal de correlacionar les propietats mecàniques amb les elèctriques. Concretament, es va avaluar la duresa del material en la zona de soldadura i fora d’aquesta zona. El quocient entre les dues dureses mostraven una gran correlació amb el valor del quocient JcGB/JcG.The obtention of bulk YBa2Cu3O7 tiles by the Top Seeded Melt Growth method carries and implicit limitation on the shape and size of the pieces. In order to overcome this limitation a joining method based on the use of an Ag foil as a welding agent has been proposed. This thesis work was focused in the following aspects: • The refinement of the welding methodology for YBCO pellets in order to solve the issues present. • Characterization of the microstructure of welded pellets. • The development of suitable quantitative analysis tool for evaluating the weld quality in terms of its superconducting behavior. • The expansion of the methodology to include welds with crystallographic misorientation and study the influence of such a crystallographic misorientation on the electric and magnetic properties The first step was to develop a furnace bundled with an in-situ observation video setup that allowed visually record the evolution of the sample during the thermal process. Those videos revealed the existence of two types of liquids that were dragged out from the weld position. The microstructural study carried out on the welded samples indicated that this loss of liquid was the source of microstructural malformations at the weld position. A modification on the sample holder was required and solved the issue. All the studied samples were analyzed under the scope of their micro-structural characteristics and their magnetic properties. For the case of the micro-structural characterization, a basic study was carried out in order to determine the successfulness of the weld formation and it was used as a feedback parameter for fine-tuning the thermal process. The weld microstructure was further investigated in order to obtain more information about its characteristics and in order to obtain a better understanding about the mechanisms that make the weld formation possible. A proper study of the magnetic and electric properties was also required, since the final objective of the superconducting welding technology is to join several YBCO tiles while maintaining the superconducting properties at the weld position. For that purpose, magnetic imaging Hall Effect based measurements were performed on the specimens under study. From the local magnetization maps, current density distribution maps were obtained by using specialized software. In order to understand and obtain useful information from those current density maps, a simulation software piece was developed and the knowledge acquired from those simulations allowed obtaining the inter- and intra-granular critical current density values (JcGB and JcG) from each sample. The ratio between JcGB and JcG was studied as a function of the misorientation angle. In principle, a behavior similar to coated conductors was expected. However, the dependence found was weaker than the considered model case. That determined dependence was compared with similar studies on grain boundaries in bulk YBCO, revealing a similar behavior and indicating that the JcGB/JcG ratio value was potentially intrinsic to the misorientation angle. This hypothesis was confirmed when several samples with different YBCO grain characteristics but with the sample misorientation were compared. Field dependence measurements of the magnetization maps were also performed in order to determine the vortex pinning regimes present at the samples and to compare them with the thin film case. Despite the weld pinning regimes were similar, the behavior at the grain was slightly different. Finally, the superconducting properties were correlated with the mechanical properties. The hardness of the material was evaluated by using nano-indentation techniques at different positions. The ratio between the hardness at the weld and away from the weld exhibited a high correlation with the JcGB/JcG ratio.
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Buck, Imke. "Der späte Zola als politischer Schriftsteller seiner Zeit." Mannheim : MATEO, Universität Mannheim, 2003. http://www.uni-mannheim.de/mateo/verlag/diss/buck/buckabstract.html.
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Beugly, Jayson S. "Fish and invertebrate communities in agricultural headwater streams." Virtual Press, 2008. http://liblink.bsu.edu/uhtbin/catkey/1391472.
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Agricultural practices may influence stream biological communities by removing riparian vegetation and modifying stream channel morphology, both which may reduce water retention time. I collected benthic invertebrates and fishes in seven headwater agriculturally-influenced streams in central Indiana, to quantify controls on invertebrate and fish community assemblage variation. Invertebrates were collected at 14 sites and fish were collected at 12 sites in Buck Creek watershed. The abundances of invertebrates and fishes were analyzed in Detrended Correspondence Analyses (DCA) in PC-ORD software and correlated with abiotic and biotic factors. The sites located in close proximity to Buck Creek have increased stability of biotic (fish assemblages) and abiotic (flow and water depth) factors. Abundances of invertebrates of headwater streams in east-central Indiana agricultural landscapes are influenced by distance between sites, distance to Buck Creek, and presence of fish species. Abundances of fishes were correlated with water quality and distance to Buck Creek.Department of Biology
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Cazzell, Gregory A. "Output Impedance in PWM Buck Converter." Wright State University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=wright1247006982.
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Chadha, Ankit. "Tapped-Inductor Buck DC-DC Converter." Wright State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=wright1578488939749599.
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Buck, Sandra Franziska [Verfasser]. "Genetik paranoiden Denkens / Sandra Franziska Buck." Halle, 2017. http://d-nb.info/1144955270/34.
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Barbagallo, Mariano. "HV Interleaved Multiphase DcDc Buck-Boost Converter." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017.
Find full textAbstract:
in electric vehicle (ev) systems, bi-directional dc-dc converters are used to interface the rechargeable energy storage system (ress) such as the battery bank with the high voltage dc-link of the inverter. currently multi-cell batteries used in automotive systems, such as ev or hev, are subject to a higher failure rate than single cell batteries. the more cells are used in series, the greater the opportunities to fail and the worse the reliability. when a cell has failed the entire string or even worse the battery must be replaced, which is extremely costly [1]. so, to have less cells in series increases the reliability of the system, which also leads to a lower voltage of the dc link. for this reason and many others, in a hybrid or electric vehicle powertrain, a boost dc-dc converter enables optimization of the battery system.
this work aims to investigate all the benefits that come with interleaving technique in dc-dc converters for automotive systems. indeed, these kind of converters for use in high-performance and high-power applications have received increasing interest in recent years. in particular this research work, done with sevcon ltd focuses on the theory behind bi-directional multiphase interleaved (imc) converter and how it could be used to interface a rechargeable energy storage system (ress) to the powertrain of a hybrid or electric vehicle.
more specifically, it was investigated if it is possible to use (after appropriate hardware and software amendments) a standard three phase ac motor inverter as a multiphase interleaved converter. for this purpose two motor controller, produced by sevcon have been analysed. both the gen4 size 10 and the hvlp inverters were considered for use as a dc-dc converter. the voltage can step up or down based on the power flow direction. each phase is indeed a bi-directional buck or boost converter, which is composed of a bridge of power switches and inductor.
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Dageryd, Marcus. "A Comprehensive Buck-Passing Account of Value." Thesis, Umeå universitet, Institutionen för idé- och samhällsstudier, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-105631.
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Yang, Shun. "Modelling and control of a Buck converter." Thesis, Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-2207.
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DC/DC buck converters are cascaded in order to generate proper load voltages. Rectified line voltage is normally converted to 48V, which then, by a bus voltage regulating converter also called the line conditioner converter, is converted to the bus voltage, e.g. 12V. A polynomial controller converter transforms the 12V into to a suitable load voltage, a fraction of or some few voltages. All cascaded converters are individually controlled in order to keep the output voltage stable constant. In this presentation focusing on the polynomial controller converter implemented as Ericsson’s buck converter BMR450. In this paper modeling, discretization and control of a simple Buck converter is presented. For the given DC-DC-Converter-Ericsson BMR 450 series, analyzing the disturbance properties of a second order buck converter controllers by a polynomial controller. The project is performed in Matlab and Simulink. The controller properties are evaluated for measurement noise, EMC noise and for parameter changes.+46-762795822
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Buck, Alexander [Verfasser]. "Simulation von Bremsenquietschen (Brake Squeal) / Alexander Buck." Aachen : Shaker, 2008. http://d-nb.info/1161305882/34.
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Galigekere, Veda Prakash N. "SiC Schottky Diodes and Polyphase Buck Converters." Wright State University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=wright1190064950.
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Borges, Altamir Ronsani. "Retificador trifásico buck-boost de estágio único." Florianópolis, 2012. http://repositorio.ufsc.br/xmlui/handle/123456789/96385.
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Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia Elétrica.Made available in DSpace on 2012-10-26T11:31:11Z (GMT). No. of bitstreams: 1 310449.pdf: 21721330 bytes, checksum: c168d93cdf83455b450594dd9b356bfd (MD5)
Este trabalho apresenta uma nova topologia de retificador trifásico de estágio único com característica Buck-Boost. Inicialmente é apresentada uma revisão bibliográfica envolvendo as publicações mais relevantes na área de estudo. Na sequencia são apresentadas a motivação para o trabalho e as contribuições da Tese. A topologia proposta é apresentada sendo descritas a sua origem e seus modos de operação de interesse. São analisados então os modos de condução descontínua (MCD) e contínua (MCC). No MCC são analisados os modos de operação Buck, Buck+Boost e Boost. As etapas do estudo de cada modo de operação compreendem a descrição das etapas de operação, análise teórica estudos por simulação numérica, definição das equações de projeto e resultados experimentais.
This work presents a new topology of three-phase rectifier with singlestage and Buck-Boost characteristic. Initially a literature review is presented which brings the most important publications in the study area. Following it is presented the motivation for the work and the contributions of this thesis. The proposed topology is then presented, with descriptions of their origin and their operation modes of interest. Are then analyzed the discontinuous (DCM) and continuous (CCM) conduction modes. At MCC, we analyze the operation modes Buck, Boost and Buck + Boost. The study stages of each mode of operation include the description of the operation stages, theoretical analysis, numerical simulation studies, definition of design equations and experimental results.
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Costa, Levy Ferreira. "Conversor CC-CC buck+boost multinível bidirecional." reponame:Repositório Institucional da UFSC, 2013. https://repositorio.ufsc.br/handle/123456789/107621.
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Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-graduação em Engenharia Elétrica, Florianópolis, 2013Made available in DSpace on 2013-12-06T00:38:59Z (GMT). No. of bitstreams: 1 318751.pdf: 7406463 bytes, checksum: 49c6f8f030e730434043622025a67275 (MD5) Previous issue date: 2013
Este trabalho apresenta uma nova topologia de conversor cc-cc Buck+Boost bidirecional multinível, adequado para aplicação em alta tensão. Esta topologia é gerada a partir da associação de um conversor Buck e um conversor Boost, ambos bidirecionais e multiníveis. As topologias multinível são obtidas a partir da generalização dos conversores Buck e Boost de três níveis. As principais características do conversor Buck+Boost proposto são: redução dos esforços de tensão nos semicondutores e capacitores,- tornando-o possível para aplicação em alta tensão; capacidade de processamento de fluxo bidirecional de energia; frequência de operação dos magnéticos múltipla da freqüência de comutação dos interruptores. Além disso, o conversor Buck+Boost proposto apresenta oito capacitores, cujas tensões devem ser balanceadas para a correta operação do conversor. Portanto, uma estratégia de balanço das tensões nos capacitores da topologia é apresentada e uma técnica de controle utilizando uma ação de feedforward é proposta. Para validar a análise teórica, um protótipo com especificação de 10 kW de potência de saída, tensão de entrada de 1 kV e de saída de 750 V foi construído e avaliado experimentalmente. Os resultados experimentais comprovaram as vantagens do conversor cc-cc proposto e da técnica de controle proposta para balanço das tensões nos capacitores
Abstract: This work presents a novel topology of a Buck+Boost bidirectional multilevel dc-dc converter suitable for high voltage applications. The proposed topology is constructed by cascading a Buck-type and a Boost-type converter, both bidirectional and multilevel. The multilevel topologies are derived from standard three level topologies. The main features of the proposed Buck+Boost converter are: reduced voltage stress across the semiconductors, allowing its use in high voltage; bidirectional power flow; frequency operation of the inductor is a multiple of the switching frequency. Moreover, the proposed Buck+Boost topology presents eight capacitors, which their voltage must be controlled for proper operation of the converter. Therefore, a strategy to balance the voltages across these capacitors is presented and a complete feedback control technique with an inductor current feedforward action is proposed. In order to validate the theoretical analysis, a prototype with 10 kW output power capability, 1 kV to 750 V input-to-output voltage was constructed and experimented. The results attest the advantages of the new dc-dc topologies and developed feeback control.
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Murase, John Takeshi. "Investigation of Buck Converter Radiated Emissions (150 kHz - 30 MHz) Measured according to CISPR 25." Thesis, KTH, Elektroteknisk teori och konstruktion, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-140954.
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Electromagnetic compatibility and compliance with relevant standards is imperative for commercial success for any type of electronic equipment. Since more and more electronics are constantly added into today’s vehicles, this is a highly significant matter in the automotive business. The primary source of electric energy in an on-road vehicle is typically a 12 or 24 volt battery; this makes voltage step down converters ubiquitous in virtually any automotive electronic system. In strive for ever more environmental friendly and energy efficient solutions a switch mode power supply is most often the given choice when it comes to the task of voltage conversion. However, the use of switch mode power supplies presents a new set of challenges when it comes to successfully comply with the electromagnetic emission standards. Knowledge and understanding about how different design parameters impact on EMC performance is key when few prototype runs and short time to market lies in focus. This text will investigate just how different layout design parameters affect the radiated emissions from a buck converter. Emphasis lies on radiated emissions in the lower frequency range up to a few MHz. Both computer simulations and practical measurements indicate the same thing; in the lower part of the frequency spectrum, when measured according to CISPR 25, radiated emissions from buck converters are dominated by voltage driven mechanisms. Along the way we will see how PCB layout alone can be responsible for differences in measured radiated emission levels of well over 20 dB.
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Dooley, Tadhg. "Remembering Buck v. Bell: its history and contemporary relevance." Thesis, Boston University, 2003. https://hdl.handle.net/2144/27639.
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Boston University. University Professors Program Senior theses.PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you.
2031-01-02
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Dong, Yan. "Investigation of Multiphase Coupled-Inductor Buck Converters in Point-of-Load Applications." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/28469.
Full textAbstract:
Multiphase interleaving buck converters are widely used in todayâ s industrial point-of-load
(POL) converters, especially the microprocessor voltage regulators (VRs). The issue of todayâ s
multiphase interleaving buck converters is the conflict between the high efficiency and the fast
transient in the phase inductor design. In 2000, P. Wong proposed the multiphase coupledinductor
buck converter to solve this issue. With the phase inductors coupled together, the
coupled-inductor worked as a nonlinear inductor due to the phase-shifted switching network, and
the coupled-inductor has different equivalent inductances during steady-state and transient. One
the one hand, the steady state inductance is increased due to coupling and the efficiency of the
multiphase coupled-inductor buck converter is increased; on the other hand, the transient
inductance is reduced and the transient performance of the multiphase coupled-inductor buck is
improved. After that, many researches have investigated the multiphase coupled-inductor buck
converters in different aspects. However, there are still many challenges in this area: the
comprehensive analysis of the converter, the alternative coupled inductor structures with the
good performance, the current sensing of converter and the light-load efficiency improvement.
They are investigated in this dissertation.
The comprehensive analysis of the multiphase coupled-inductor buck converter is
investigated. The n-phase (n>2) coupled-inductor buck converter with the duty cycle D>1/n
hasnâ t been analyzed before. In this dissertation, the multiphase coupled-inductor buck converter
is systematically analyzed for any phase number and any duty cycle condition. The asymmetric
multiphase coupled-inductor buck converter is also analyzed.
The existing coupled-inductor has a long winding path issue. In low-voltage, high-current
applications, the short winding path is preferred because the winding loss dominates the inductor
total loss and a short winding path can greatly reduce the winding loss. To solve this long
winding path issue, several twisted-core coupled-inductors are proposed. The twisted-core
coupled-inductor has such a severe 3D fringing effect that the conventional reluctance modeling
method gives a poor result, unacceptable from the design point of view. By applying and
extending Sullivanâ s space cutting method to the twisted core coupled inductor, a precise
reluctance model of the twisted-core coupled-inductor is proposed. The reluctance model gives
designers the intuition of the twisted-core coupled-inductors and facilitates the design of the
twisted-core coupled-inductors. The design using this reluctance model shows good correlation
between the design requirement and the design result. The developed space cutting method can
also be used in other complex magnetic structures with the strong fringing effect.
Today, more and more POL converters are integrated and the bottleneck of the integrated
POL converters is the large inductor size. Different coupled-inductor structures are proposed to
reduce the large inductor size and to improve the power density of the integrated POL converter.
The investigation is based on the low temperature co-fire ceramic (LTCC) process. It is found
that the side-by-side-winding coupled-inductor structure achieves a smaller footprint and size.
With the two-segment B-H curve approximation, the proposed coupled-inductor structure can be
easily modeled and designed. The designed coupled-inductor prototype reduces the magnetic
size by half. Accordingly, the LTCC integrated coupled-inductor POL converter doubles the
power density compared to its non-coupled-inductor POL counterpart and an amazing 500W/in3
power density is achieved.
In a multiphase coupled-inductor converter, there are several coupled-inductor setups. For
example, for a six-phase coupled-inductor converter, three two-phase coupled inductors, two
three-phase coupled-inductors and one six-phase coupled inductors can be used. Different
coupled-inductor setups are investigated and it is found that there is a diminishing return effect
for both the steady-state efficiency improvement and the transient performance improvement
when the coupling phase number increases.
The conventional DCR current sensing method is a very popular current sensing method for
todayâ s multiphase non-coupled-inductor buck converters. Unfortunately, this current sensing
method doesnâ t work for the multiphase coupled-inductor buck converter. To solve this issue,
two novel DCR current sensing methods are proposed for the multiphase coupled-inductor buck
converter.
Although the multiphase coupled-inductor buck converters have shown a lot of benefits,
they have a low efficiency under light-load working in DCM. Since the DCM operation of the
multiphase coupled-inductor buck converter has never been investigated, they are analyzed in
detail and the reason for the low efficiency is identified. It is found that there are more-than-one
DCM modes for the multiphase coupled-inductor buck converter: DCM1, DCM2 â ¦, and DCMn.
In the DCM2, DCM3â ¦, and DCMn modes, the phase-currents reach zero-current more-thanonce
during one switching period, which causes the low efficiency of the multiphase coupledinductor
buck converter in the light load. With the understanding of the low efficiency issue, the
burst-in-DCM1-mode control method is proposed to improve the light load efficiency of the
multiphase coupled-inductor buck converter. Experimental results prove the proposed solution.Ph. D.
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Ganapathy, Shunmugam. "Apparent diffusion coefficients of carbon dioxide through grain bulks." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0001/NQ41611.pdf.
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Doss, Gary Richard Jr. "Novel Intelligent Power Supply Using A Modified Pulse Width Modulator." Wright State University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=wright1253576739.
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Pierleoni, Enrico. "Analisi e progetto del Z-Source Buck Converter." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/16305/.
Full textAbstract:
I convertitori elettronici di potenza operanti in commutazione generalmente operano a partire da sorgenti o di tensione o di corrente. Recentemente si sono studiati convertitori che all’ingresso includono una rete puramente reattiva e priva di perdite (un filtro) in grado di modificare l’impedenza di uscita della sorgente di potenza. L’introduzione di questa rete amplia il numero di configurazioni possibili per gli interruttori del convertitore, dato che l’impedenza di sorgente impedisce le distruttive sovracorrenti legate ai possibili stati di Shoot-Through che, anzi, diventano utili per generare il boost della tensione in ingresso. Poiché le forme d’onda e il modo di funzionamento subiscono drastici cambiamenti, a questo tipo di conversione ci si riferisce con il termine Z-Source.
In questa tesi prenderemo in considerazione la forma più elementare di convertitore dc-dc (il leg commutatore del Chopper‑Buck) e vedremo come l’applicazione della Z-Source consenta una conversione di tensione di tipo salita/discesa, a patto di modificare opportunamente la generazione dei comandi agli interruttori.
Si è potuto verificare a simulazione che il convertitore è effettivamente in grado di operare sia in salita che in discesa.
La complessità delle forme d’onda generate però è tale che è quasi impossibile evitare la comparsa di stati indesiderati non appena si esce dal funzionamento nominale di corrente sul carico o per variazioni dei Duty-cycle dei comandi.
In particolare, si sono riscontrate possibili instabilità che possono far aumentare indefinitamente la tensione sui condensatori del Z‑Source portandola a livelli pericolosamente alti. Inoltre, la presenza del diodo di free-wheeling sull’interruttore low-side può provocare imprevisti stati di Shoot-Through che modificano il Duty‑cycle effettivo in uscita, rendendo di non facile predicibilità il guadagno di tensione del convertitore.
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Allen, Kirk D. "Practical implementation of the hard switched buck chopper." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1997. http://handle.dtic.mil/100.2/ADA331788.
Full text
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Kilic, Umit Erdem. "Design Of Buck Converter For Educational Test Bench." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/2/12608153/index.pdf.
Full textAbstract:
In this thesis a buck converter has been developed to be used as a test bench in power electronics laboratory. For this purpose, first, steady-state and small-signal analyses of a buck converter is carried out, then open-loop and closed-loop control of the converter are developed and simulated. Then, the circuit is manufactured and tested. The test results are compared with the simulation results. Finally, an experimantal
procedure is prepared to enable the students to perform the experiment in the laboratory with the test bench developed.
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"Evaluation of E-Bucks: A Simulated Classroom Economy." Doctoral diss., 2010. http://hdl.handle.net/2286/R.I.8706.
Full textAbstract:
abstract: ABSTRACT The purpose of this study was to investigate the effects of E Bucks, a simulated classroom economy (a token economy system), in business classes on students' grades, absences, and tardiness. The study compared these variables in classes using E Bucks to those in similar classes before E Bucks was initiated. The following research questions were addressed: (a) How did the mean term grades in business classes that included E Bucks compare to those in similar classes prior to the E Bucks implementation? (b) How did the mean number of student absences in business classes that included E Bucks compare to those in similar classes prior to the E Bucks implementation? (c) How did the mean number of student tardies in business classes that included E Bucks compare to those in similar classes prior to the E Bucks implementation? Four teachers in 3 high schools in Phoenix, Arizona, participated in the study that included 22 sections of business classes with a total of 568 students. All participating teachers implemented the token economy voluntarily, although some implemented the program more consistently than others. All of the teachers administered district-aligned assessments with the same terms/occasions throughout the district. Archival data (term grades, attendance, and tardies) from 3 years of business, technology, and marketing courses were collected and analyzed. The results of 4 analyses of variance examining the dependent variables of grades, absences, and tardies were mixed. The results demonstrated significance for some but not all of the teachers' classes on all 3 dependent variables. In 1 of the 4 analyses 2 teachers had approached significant increases in grades when students were "paid" for grades. The same two teachers had nonsignificant decreases in the mean number of student absences during the grading period students were "paid" for grades. Recommendations included studying a larger number of students and measuring the impact of gender and socioeconomic status on the effects of the E Bucks simulation.Dissertation/Thesis
Ed.D. Educational Leadership and Policy Studies 2010
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Chang, Shao-Chih, and 張紹智. "Seasonal change of semen characteristic in dairy goat bucks." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/83543183700711572273.
Full textAbstract:
碩士國立中興大學
畜產學系
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Seasonal Changes of Semen Characteristics in Dairy Goat Bucks Shao-Chih Chang Abstract The purpose of this study was to investigate the effect of photoperiod and season on fresh semen characteristics and frozen semen quality of dairy goat bucks. Seven healthy and sexually matured dairy goat bucks were used in this study. Scrotal circumference were measured and semen samples were collected with an artificial vagina once weekly during a year. Semen volume, mass activity score and motility score of sperm, percentage of abnormal sperm and dead sperm, sperm concentration and total sperms per ejaculation were measured respectively. Semen with 3.0 or higher score of mass activity of sperm were diluted with 10％ skim milk extender biweekly and cryopreserved for one week and three months respectively. Afterward, the post-thawed motility score and viability of sperm in frozen semen were evaluated. The natural photoperiod was divided into long-daylight period（＞12 hrs）and short-daylight period（＜12 hrs）groups, and the year was divided into：spring, summer, autumn and winter seasons. The result showed that the percentage of abnormal sperm（7.18±0.28 vs.5.81± 0.26％）, sperm concentration（4.11±0.07 vs.3.65±0.06 ×109 sperms/ml）and total sperms per ejaculation（4.67±0.09 vs.4.16±0.10 ×109 sperms）of long-daylight period group were higher than those in short-daylight period group（P＜0.05）.There were no significant difference（P＞0.05）in scrotal circumference, semen volume, mass activity score and motility score of sperm and the percentage of dead sperm between two photoperiods groups. The maximal scrotal circumference of dairy goat bucks occurred in autumn（30.27±0.08 cm）and was significantly higher than those in other seasons（P＜0.05）. Semen volume was higher in autumn（1.30±0.03 ml）, lower in spring（1.03±0.02ml）and it showed significantly seasonal difference （P＜0.05）. The mass activity and motility score of sperms in spring （3.90±0.07 and 2.87±0.07）were significantly lower than those in the other seasons（P＜0.05）. The highest percentage of dead sperms presented in spring （25.54±1.41％）and it was significantly higher than those in the summer （21.10±0.64％）and winter（21.12±1.10％），but there were no significantly difference between spring and autumn（P＞0.05）. The percentage of abnormal sperms was highest in the autumn and lowest in the winter. Sperm concentration in winter（3.46±0.06×109 sperm/ml）was significantly lower than those in other seasons（P＜0.05）. Total sperms per ejaculation in summer （4.76±0.12×109 sperms）and autumn（4.77±0.12×109 sperms）were significantly higher than those in the spring（4.18±0.09×109 sperms） and winter（3.93±0.14×109 sperms）（P＜0.05）。 Post-thawed motility score of sperm in frozen semen cryopreservated for one week was significantly higher in short-daylight period group（2.07±0.25）than those in long-daylight period group（1.83±0.0l）（P＜0.05）,and it was lower in spring（1.67±0.05）than those in other seasons. There were no significantly difference in viability of sperms between two daylight period groups and between seasons. Semen cryopreservated for three months showed significant difference on post-thawed motility score of sperms between different daylight period groups（P＜0.05）,and it also showed significantly seasonal difference（P＜0.05）, But there was no significantly difference in viability of sperms between two daylight period groups and seasons. It was concluded that, the semen characteristics of dairy goat bucks in central Taiwan showed significantly seasonal variation, and the frozen semen quality was in accordance with the seasonal variation of fresh semen. Keyword：Dairy goat bucks, semen characteristics, frozen semen, season.
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Nethenzheni, Livhuwani Pertunia. "Effect of bioxcell and triladyl extenders and removal of seminal plasma of equilibrated and cryopreserved goat semen." Diss., 2017. http://hdl.handle.net/11602/691.
Full textAbstract:
MSCAGR (Animal Science)Department of Animal Science
The objectives of the study were to evaluate the effect of two extenders (Triladyl® and Bioxcell®) and the removal of seminal plasma on goat buck semen. Six ejaculates were collected from six indigenous bucks by means of electro-ejaculator method, and semen was pooled, and replicated 10 times. Raw semen were randomly allocated into six groups as follows: (i) Raw non-washed, (ii) Raw washed, (iii) Triladyl®-washed, (iv) Triladyl®-non-washed, (v) Bioxcell®-washed and (vi) Bioxcell®-non-washed. All six groups were analysed for spermatozoa motility rates using computer-aided sperm analysis (CASA). The spermatozoa viability for all groups were assessed using Eosin-Nigrosin, acrosome integrity using Spermac, chromatin structure using Acridine Orange, and mitochondria using JC-1 staining solutions. Both the Triladyl® and Bioxcell® washed semen groups were diluted (1:4) with Phosphate Buffered Saline (PBS) then centrifuged at 1500 x g for ten min and seminal plasma was aspirated using 1 mL sterile plastic pipette. Semen samples were diluted (1:4) as follows: Triladyl® (washed and non-washed) or Bioxcell® (washed and non-washed) and then equilibrated at 5 ºC for 2 hours. Following equilibration, semen parameters were analysed. Thereafter, the semen samples were loaded into straws and placed 5 cm above a liquid nitrogen vapour for 10 min, and then stored at -196 ºC until use. Following one month of storage, frozen semen straws per treatment group were thawed at 37 ºC for 30 seconds, then semen parameters were analysed again. Significant differences among the mean values of semen parameters were determined by Tukey’s test using ANOVA, GLM procedure of SAS version 12.1 of 2010. Total Spermatozoa motility rate of Bioxcell® (92.5±4.6), (68.2±13.5) and Triladyl® (94.9±5.5), (63.1±15.1) were significantly reduced (P < 0.05) following equilibration and freeze-thawing process, respectively on washed semen groups. Live and normal spermatozoa percentages were drastically reduced in Bioxcell® (5.2±4.9) and Triladyl® (6.9±8.6) washed semen groups, following freeze-thawing. There was a significantly lower number of spermatozoa with high mitochondrial membrane potential in non-washed semen extended with Triladyl® (68.7±26.8) compared to non-washed semen extended with Bioxcell® (49.8±20.1) following the freeze-thawing process. In conclusion, the freezing-thawing process did reduce the indigenous buck semen parameters irrespective of removal or non-removal of seminal plasma. However, Bioxcell® extender was found to be more suitable for preserving spermatozoa during equilibration and freezing/thawing process of buck semen.