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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
771

Harmonic Reduction IN a Single-Switch Three-Phase Boost Rectifier With Harmonic-Injected PWM

Huang, Qihong 04 February 1997 (has links)
A constant switching frequency with the sixth-order harmonic injection PWM concept is established, and a sixth-order harmonic injection technique is developed for the harmonic reduction of a single-switch three-phase boost rectifier. The approach employs a constant duty cycle with sixth-order harmonic injection to suppress the dominant (fifth-order) harmonic in the input currents. Hence, to meet the THD<10% requirement, the rectifier voltage gain can be designed down to 1.45; to meet the IEC 1000-3-2 (A) standard, the output power can be pushed up to 10 kW for the application with a 3X220 V input and a 800 V output. The results are verified on a 6-kW prototype. The injection principle is graphically explained in current waveforms and mathematically proved. Two injection methods are proposed to meet either the THD requirement or the IEC standard. The injection implementation and design guidelines are provided. The boost inductor design and EMI filter design are discussed. An average small- signal model based on the equivalent multi-module model is developed and experimentally verified. The variations of the small-signal model against load are demonstrated, and the compensator design is discussed. The results show that at no load, the dominant pole of the control-to-output transfer function approaches the origin and causes more phase delay, making the control design difficult. To avoid the no load case and to simplify the control design, a 50-W dummy load (1% of the full load) is added. Finally, a simple nonlinear gain control circuit is presented to mitigate the load effect and reduce the dummy load to 10 W. / Master of Science
772

Development of a Performance Index for Stormwater Pipeline Infrastructure

Bhimanadhuni, Sowmya 28 July 2015 (has links)
With new government regulations and emerging knowledge of the risk to the environment posed by the failure of stormwater pipelines, stormwater infrastructure asset management is becoming increasingly important in the U.S. An essential aspect of asset management practice is the accurate performance assessment of one's assets. This paper presents a weighted factor framework to determine the performance of stormwater pipes. This paper prepares a list of 50 parameters affecting the performance of stormwater pipelines; the list is based on a review of the literature, existing asset management plans, and feedback from utilities. This list is broken down into essential and preferential parameters. Indeed, not all utilities necessarily possess sufficient resources to collect such a large set of parameters. This study also develops a three-level hierarchical structure of the degradation of stormwater pipeline infrastructure. The structure consists of five failure modules and the essential parameters only. On the basis of the survey results gathered from 10 utilities across the EPA regions, the study combines the essential parameters into a performance index. The index is a scale of 1 to 5, similar to the National Association of Sewer Service Companies' Pipeline Assessment and Certification Program grading system. Grade 1 implies excellent condition and Grade 5 implies collapse is imminent. / Master of Science
773

Floristic composition and environmental determinants of roadside vegetation in North England

Akbar, K.F., Hale, William H.G., Headley, Alistair D.D. January 2009 (has links)
No / The roadside vegetation in some counties of north England (north and west Yorkshire) was studied to determine the community structure according to the British National Vegetation Classification (NVC) and main environmental factors influencing its composition. The data from Phytosociological survey (699 quadrats) and from the physico-chemical analyses of 233 soil samples from 35 sites were obtained. Both the classification (TWINSPAN & MATCH) and ordination programs (Canonical Correspondence Analysis) were used. The roadside vegetation is mainly dominated by few grasses (Arrhenatherum elatius, Festuca rubra, Dactylis glomerata, Lolium perenne, Poa trivialis, Elymus repens, Holcus lanatus) and their associated herbs (Cirsium arvense, Heracleum sphondylium, Urtica dioica). Five NVC Mesotrophic grassland communities (Arrhenatheretum elatioris community MG1, Lolium perenne-Cynosurus cristatus grassland MG6, Lolium perenne leys MG7, Holcus lanatus-Deschampsia cespitosa grassland MG9, Festuca rubra-Agrostis stolonifera-Potentilla anserina grassland MG11) and one Upland Festuca ovina-Agrostis capillaris-Galium saxatile grassland, U4 were identified which in general, exhibited good fit with the typical NVC units.
774

Data for proteomic analysis of murine cardiomyocytic HL1 cells treated with siRNA against tissue factor

Brioschi, M., Lento, S., Barcella, S., Nasim, Md. Talat, Tremoli, E., Banfi, C. January 2015 (has links)
Yes / This data article is related to the research article entitled Proteomics of Tissue Factor silencing in cardiomyocytic cells reveals a new role for this coagulation factor in splicing machinery control by Lento et al [1]. Tissue Factor (TF) is the key player in the coagulation cascade, but it has additional functions ranging from angiogenesis, tumor invasion and, in the heart, the maintenance of the integrity of cardiac cells. This article reports the nano-LC-MSE analysis of the cardiomyocytic HL-1 cell line proteome and describes the results obtained from a Gene Ontology analysis of those proteins affected by TF-gene silencing.
775

Dermal adipose tissue secretes HGF to promote human hair growth and pigmentation

Nicu, C., O'Sullivan, J.D.B., Ramos, R., Timperi, L., Lai, T., Farjo, N., Farjo, B., Pople, J., Bhogal, R., Hardman, J.A., Plikus, M.V., Ansell, David, Paus, R. 15 February 2021 (has links)
Yes / Hair follicles (HFs) are immersed within dermal white adipose tissue (dWAT), yet human adipocyte-HF communication remains unexplored. Therefore, we investigated how perifollicular adipocytes affect the physiology of organ-cultured human anagen scalp HFs. Quantitative (immuno-)histomorphometry, microCT and transmission electron microscopy showed that the number and size of perifollicular adipocytes declined during anagen-catagen transition, whilst fluorescence lifetime imaging revealed increased lipid oxidation in adipocytes surrounding the bulge/sub-bulge region. Ex vivo, dWAT significantly stimulated hair matrix keratinocyte proliferation and HF pigmentation. Both dWAT pericytes and PREF1/DLK1+ adipocyte progenitors secreted hepatocyte growth factor (HGF) during human HF-dWAT co-culture, for which the c-Met receptor is expressed in the hair matrix and dermal papilla. These effects were abrogated by an HGF-neutralising antibody, and reproduced using recombinant HGF. Laser capture microdissection-based microarray analysis of the hair matrix showed that dWAT-derived HGF up-regulated KRT27, KRT73, KRT75, KRT84, KRT86 and TCHH. Mechanistically, HGF stimulated Wnt/β-catenin activity in the HM by inhibiting SFRP1 in the dermal papilla, up-regulating matrix AXIN2, LEF1, WNT6 and WNT10B expression. Our study demonstrates that dWAT regulates human hair growth and pigmentation via HGF secretion, and thus identifies important, molecular and cellular targets for therapeutic intervention in disorders of human hair growth and pigmentation.
776

Surface water flow resistance due to emergent wetland vegetation

Hall, Karen 24 May 2012 (has links)
The key to a successful wetland design is duplicating the hydroperiod of the desired wetland type. Dense wetland vegetation affects surface water flow rates by increasing flow resistance. Prior research represented the vegetation as individual stems; however, many wetland species grow in clumps. Therefore, the objectives of this study were to investigate the effect of clumping vegetation on flow resistance and to develop a prediction equation for use in wetland design. A 6-m by 1-m by 0.4-m recirculating flume was planted with mature common rush, Juncus effusus, a common emergent wetland plant. Three different flow rates (3, 4, and 5 L/s) and three different tailgate heights (0, 2.5, and 5 cm) were used to simulate a variety of wetland conditions. Plant spacing and clump diameter were varied (20 and 25 cm, 8 and 12 cm, respectively). Friction factors ranged from 9 to 40 and decreased with increasing plant density. Non-dimensional parameters determined through Buckingham Pi analysis were used in a regression analysis to develop a prediction model. Results of the regression analysis showed that the fraction of vegetated occupied area (P) was most significant factor in determining friction factor. / Master of Science
777

Passive Viscoelastic Constrained Layer Damping Application for a Small Aircraft Landing Gear System

Gallimore, Craig Allen 20 October 2008 (has links)
The main purpose of this report was to test several common viscoelastic polymers and identify key attributes of their applicability to a small aircraft landing gear system for improved damping performance. The applied viscoelastic damping treatment to the gear was of a constrained layer type, promoting increased shear deformation over free surface treatments, and therefore enhanced energy dissipation within the viscoelastic layer. A total of eight materials were tested and analyzed using cyclic loading equipment to establish approximate storage modulus and loss factor data at varying loading frequencies. The three viscoelastic polymers having the highest loss factor to shear modulus ratio were chosen and tested using a cantilever beam system. A Ross, Kerwin, and Ungar analysis was used to predict the loss factor of the cantilever beam system with applied treatment and the predictions were compared to experimental data. Customer requirements often govern the scope and intensity of design in many engineering applications. Limitations and constraints, such as cost, weight, serviceability, landing gear geometry, environmental factors, and manufacturability in regards to the addition of a viscoelastic damping treatment to a landing gear system are discussed. Based on results found from theoretical and experimental testing, application of a damping treatment to a small aircraft landing gear system is very promising. Relatively high loss factors were seen in a cantilever beam for simple single layer constrained treatments for very low strain amplitudes relative to strains seen during loading of the landing gear. With future design iterations, damping levels several times those seen in this document will be seen with a constrained treatment applied to a landing gear system. / Master of Science
778

Essays on Factor Models

Lin, Chun-Wei 16 May 2024 (has links)
This dissertation consists of three chapters describing the applications of factor models in different fields of asset pricing. The first chapter addresses the following issue: Prominent volatility-based factor pricing models focus exclusively on the second moment of asset returns, and hence, tend to identify volatile factors but with little risk premia. This chapter demonstrates that a simple asset return transform can arbitrarily upset the ranking of volatility-based factors, but not their prices of risks. Accordingly, we propose a new framework to identify factors based on their prices of risks, or the so-called principally priced risk factors (PPRFs). We construct these factors by generalizing the standard Sharpe ratio for a single asset to a set of assets, incorporating information from both the first and second moments of asset returns. The PPRF framework improves out-of-sample pricing performance in both equity and currency markets. The second chapter identifies the origins of covariance in institutional trading. Conceptually, we introduce two perspectives: the asset perspective, which prioritizes assets as the key market fundamentals, and the manager perspective, which prioritizes fund managers as the key market fundamentals that drive institutional trading covariance. Empirically, we establish that the asset perspective is the primary driver of covariance in institutional trading. Our analysis documents two further empirical patterns. First, returns stemming from the covariance in institutional trading from the asset perspective have higher volatility, offering valuable insights into the demand-based asset pricing literature. Second, the persistence in trading often breaks down during economic downturns, suggesting potential connections to the uncertainty-based business cycle literature. Finally, the third chapter examines the impact of changes in monetary policy rules on the asset valuations of firms with different profitability. I have the following two empirical findings. First, during periods of hawkish monetary policies, the 'profitability premium'— the expected extra return on investments in more profitable firms — tends to increase. Second, when analyzing the factors mediating this effect, changes in inflation expectations play a more significant role in influencing the profitability premium during transitions to a hawkish monetary regime, compared to the effects of real interest rate adjustments on production costs. These observations suggest a possible mechanism by which monetary policy may have different long-term effects on firms with different characteristics. / Doctor of Philosophy / This dissertation explores factor models in asset pricing across three chapters. The first chapter critiques volatility-based models that focus on asset return variance and introduces a new framework for identifying factors based on risk prices, enhancing pricing performance in equity and currency markets. The second chapter investigates the origins of covariance in institutional trading, emphasizing the asset perspective as the dominant influence and documenting higher volatility and breakdowns in trading persistence during economic downturns. The third chapter examines the effects of monetary policy changes on firm asset valuations, finding that hawkish policies increase the profitability premium, significantly influenced by shifts in inflation expectations rather than changes in real interest rates. These insights highlight the nuanced impacts of market fundamentals and monetary policy on asset pricing and firm profitability.
779

Hyperacusis and Misophonia Discrimination Scale (HMDS): a Validation Study

van Tussenbroek, Fay, Morales Gutiérrez, Silvia Estela January 2024 (has links)
Misophonia and hyperacusis are relatively unknown and misunderstood auditory sensitivityconditions. Misophonia is characterised by strong negative emotional reactions to sounds andsound patterns, depending on the meaning or context of the sound. Hyperacusis is characterizedby negative reactions to sounds, depending on the physical characteristics of the sounds (e.g.,frequency and intensity). Research often fails to distinguish misophonia from hyperacusis, andresearch on both conditions is scare. Moreover, there are insufficient tools available to assessand study misophonia and hyperacusis. The purpose of the current study was topsychometrically validate the Hyperacusis and Misophonia Discrimination Scale (HMDS).The goal of this self-report measure was to discriminate people with hyperacusis from peoplewith misophonia. Various analyses were used to assess the reliability and validity of thequestionnaire. A total of 249 participants completed the online questionnaire. Results indicatedan excellent reliability using Cronbach’s alpha and group and item comparisons showed thediscriminatory effectiveness of the HMDS. However, the results of a factor analysis indicateda complex underlying factor structure which did not provide a sufficient fit to the data,suggesting that the dimensions of the questionnaire require further refinement to effectivelydifferentiate between misophonia and hyperacusis. Based on the results, a revision to theHMDS is presented and future research should explore the psychometric properties of thisrevised scale as well as validate the HMDS with participants who have undergone a clinicalscreening in order to confirm their status. / Misofoni och hyperakusis är relativt okända och missförstådda tillstånd av auditiv känslighet.Misofoni kännetecknas av starka negativa känslomässiga reaktioner på ljud och ljudmönster,beroende på ljudets betydelse eller sammanhang. Hyperakusis kännetecknas av negativareaktioner på ljud, beroende på ljudets fysiska egenskaper (t.ex. frekvens och intensitet).Forskningen misslyckas ofta med att skilja misofoni från hyperakusis, och forskningen ombåda tillstånden är knapphändig. Dessutom finns det inte tillräckligt med verktyg för attbedöma och studera misofoni och hyperakusis. Syftet med den aktuella studien var attpsykometriskt validera Hyperacusis and Misophonia Discrimination Scale (HMDS). Måletmed detta självrapportmått var att skilja personer med hyperakusis från personer med misofoni.Olika analyser användes för att bedöma frågeformulärets tillförlitlighet och giltighet. Totalt249 deltagare fyllde i onlineformuläret. Resultaten visade på en utmärkt tillförlitlighet enligtCronbachs alfa och jämförelser mellan grupper och objekt visade på HMDS diskriminerandeeffektivitet. Resultaten av en faktoranalys indikerade emellertid en komplex underliggandefaktorstruktur som inte gav en tillräcklig passning till data, vilket tyder på att frågeformuläretsdimensioner kräver ytterligare förfining för att effektivt skilja mellan misofoni ochhyperakusis. Baserat på resultaten presenteras en revidering av HMDS och framtida forskningbör utforska de psykometriska egenskaperna hos denna reviderade skala samt validera HMDSmed deltagare som har genomgått en klinisk screening för att bekräfta sin status.
780

Ovulation-inducing factor/nerve growth factor (OIF/NGF) : Immunohistochemical studies of the bovine ovary and the llama hypothalamus

2016 January 1900 (has links)
The overall objective was to elucidate the mechanism of action of ovulation-inducing factor/nerve growth factor (OIF/NGF) in the reproductive function of spontaneous and induced ovulators, using cow and llama as models. In Study 1, the dynamics of trkA, the high affinity receptor for OIF/NGF, were studied during periovulatory period in cows. Unilateral ovariectomies were performed by colpotomy on Days 2, 4 and 6 of the estrous cycle (Day 0= ovulation), and before and after LH administration. Ovarian samples were processed for immunofluorescent detection of trkA. The intensity and area of immuno-positive staining, and the proportion of immuno-positive cells in both the granulosa and theca layers were higher in dominant than in subordinate follicles (P<0.05). Dominant follicles displayed a different intracellular distribution of trkA from subordinate follicles. The number of positive cells was higher in the developing CL (Day 2 and 4) than in the mature or regressing CL (Day 6, Pre-LH, and Post-LH). In Study 2, the distribution of GnRH neurons in the hypothalamus was examined in female llamas (n = 4). Hypothalamic samples were processed for immunohistochemistry for GnRH. The distribution of GnRH neurons had no evident accumulation in specific hypothalamic nuclei. The majority of GnRH neurons were detected in the anterior and medio-basal hypothalamus (P<0.05). The GnRH neuron fibers were detected primarily in the median eminence and in the medio-basal hypothalamus. In Study 3, the relationship between trkA and GnRH neurons in the llama diencephalon was examined in llama brains (n = 4) obtained in Study 2. Samples were stained using double immunofluorescence. TrkA immuno-reactivity was present in most hypothalamic areas examined; the highest density was found in the diagonal band of Broca and the periventricular nuclei. A low percentage of GnRH cells (1%) showed immuno-reactivity to trkA. Close association between immuno-reactive cells (i.e., GnRH and trkA in the same microscopic field) was detected rarely (3/160 GnRH neurons). We concluded that: 1) the high affinity receptor for OIF/NGF is expressed in greater quantities in dominant than subordinate follicles and in the developing CL; 2) GnRH neurons of llamas are concentrated in the anterior and middle hypothalamus, in close relationship to the third ventricle; and, 3) expression of trkA receptors on GnRH neurons was rare, suggesting that the ovulatory effect of OIF/NGF is not via direct interaction with GnRH neurons.

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