• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 58
  • 31
  • 22
  • 8
  • 5
  • 3
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 143
  • 78
  • 29
  • 24
  • 18
  • 15
  • 14
  • 12
  • 12
  • 12
  • 12
  • 11
  • 11
  • 10
  • 10
  • 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.
51

Athletic Surfaces’ Influence on the Thermal Environment: An Evaluation of Wet Bulb Globe Temperature in the Phoenix Metropolitan Area

January 2020 (has links)
abstract: Exertional heat stroke continues to be one of the leading causes of illness and death in sport in the United States, with an athlete’s experienced microclimate varying by venue design and location. A limited number of studies have attempted to determine the relationship between observed wet bulb globe temperature (WBGT) and WBGT derived from regional weather station data. Moreover, only one study has quantified the relationship between regionally modeled and on-site measured WBGT over different athletic surfaces (natural grass, rubber track, and concrete tennis court). The current research expands on previous studies to examine how different athletic surfaces influence the thermal environment in the Phoenix Metropolitan Area using a combination of fieldwork, modeling, and statistical analysis. Meteorological data were collected from 0700–1900hr across 6 days in June and 5 days in August 2019 in Tempe, Arizona at various Sun Devil Athletics facilities. This research also explored the influence of surface temperatures on WBGT and the changes projected under a future warmer climate. Results indicate that based on American College of Sports Medicine guidelines practice would not be cancelled in June (WBGT≥32.3°C); however, in August, ~33% of practice time was lost across multiple surfaces. The second-tier recommendations (WBGT≥30.1°C) to limit intense exercise were reached an average of 7 hours each day for all surfaces in August. Further, WBGT was calculated using data from four Arizona Meteorological Network (AZMET) weather stations to provide regional WBGT values for comparison. The on-site (field/court) WBGT values were consistently higher than regional values and significantly different (p<0.05). Thus, using regionally-modeled WBGT data to guide activity or clothing modification for heat safety may lead to misclassification and unsafe conditions. Surface temperature measurements indicate a maximum temperature (170°F) occurring around solar noon, yet WBGT reached its highest level mid-afternoon and on the artificial turf surface (2–5PM). Climate projections show that WBGT values are expected to rise, further restricting the amount of practice and games than can take place outdoors during the afternoon. The findings from this study can be used to inform athletic trainers and coaches about the thermal environment through WBGT values on-field. / Dissertation/Thesis / Masters Thesis Geography 2020
52

Towards Brains in the Cloud: A Biophysically Realistic Computational Model of Olfactory Bulb

January 2019 (has links)
abstract: The increasing availability of experimental data and computational power have resulted in increasingly detailed and sophisticated models of brain structures. Biophysically realistic models allow detailed investigations of the mechanisms that operate within those structures. In this work, published mouse experimental data were synthesized to develop an extensible, open-source platform for modeling the mouse main olfactory bulb and other brain regions. A “virtual slice” model of a main olfactory bulb glomerular column that includes detailed models of tufted, mitral, and granule cells was created to investigate the underlying mechanisms of a gamma frequency oscillation pattern (“gamma fingerprint”) often observed in rodent bulbar local field potential recordings. The gamma fingerprint was reproduced by the model and a mechanistic hypothesis to explain aspects of the fingerprint was developed. A series of computational experiments tested the hypothesis. The results demonstrate the importance of interactions between electrical synapses, principal cell synaptic input strength differences, and granule cell inhibition in the formation of the gamma fingerprint. The model, data, results, and reproduction materials are accessible at https://github.com/justasb/olfactorybulb. The discussion includes a detailed description of mechanisms underlying the gamma fingerprint and how the model predictions can be tested experimentally. In summary, the modeling platform can be extended to include other types of cells, mechanisms and brain regions and can be used to investigate a wide range of experimentally testable hypotheses. / Dissertation/Thesis / Doctoral Dissertation Neuroscience 2019
53

Information processing in the olfactory system of different amphibian species

Weiss, Lukas 07 September 2020 (has links)
No description available.
54

Limitation Studies of Seed Set in the Onion Allium cepa l. (Liliaceae)

Shasha'a, Nizar Shukri 01 May 1972 (has links)
Two field experiments were carried out. In the first experiment, 13 variables were studied for 3 inbred groups as influenced by genetic differences, source of pollen, soil moisture, fertilizers , and size of bulbs. Path-coefficient analysis was made of var ious insect pollinators influencing seed yield in different inbreds, and of components of seed production in all inbreds together. In the second experiment, 4 variables were studied for one male-sterile inbred and one male-fertile inbred as influenced by soil moisture and fertilizers. Genetic differences among inbreds were the most important source of variation in seed yields. This points out that a major portion of the onion seed problem could be solved through plant breeding. The inbreds differed very significantly in t heir attractiveness to pollinating insects, probably as a result of varying genetic vigor which influenced nectar formation. Most of the inbreds had negative correlation or no correlation between the number of honey bee nectar collectors and seed yield. The separation of correlation with honey bee nectar and pollen collectors into components of direct and indirect effects indicates that the number of pollinating insects was excessive for all inbreds in the experiment. Negative direct effects on seed yield and negative indirect effects through percent fertilized flowers and seeds per fertilized flower disclose some important aspects as possible causes for low onion seed yields: 1. Depletion of assimilated food needed for the development of fertilized ovules through an overdraw on nectar by nectar collectors. 2. Water deficit affecting fertilized developing ovules due to increased transpiration resulting from overhandling of flowers by honey bees, especially by pollen collectors, which through nervous search for pollen on male- sterile lines might cause enough physical damage to increase transpiration even at low visitation levels. At high visitation levels, pollen collectors might also harm male-fertile lines. 3 . Removal of pollen from the stigmas of male-sterile flowers by high populations of pollen collecting honey bees. Compatibility of the pollen parents with the male-sterile inbreds was influenced by soil moisture levels. At high moisture, M611C increased seed yields while B12115-2C decreased them. At low moisture the reverse was true. In the first experiment there was no significant yield response to varying soil moisture levels due to contrasting effects of high soil moisture on compatibility with pollen parents. In the second experiment, the pollen parent B2215C was used and a significant favorable response to high soil moisture was obtained. Salinity aspects and the effects of indiscriminate use of fertilizers were tested through the method of fertilizer placement. While fertilizers reduced seed yield , high soil moisture tended to reduce the negative effects of nitrogen and to produce favorable response to phosphorus. Seed yield followed the trend in plant survival as affected by the induced salinity x moisture relationships. The size of bulbs had a great influence on seed yields, mainly through an increased number of umbels per plant. It seems that the number of umbels per plant had more influence on the number of flowers per row than did the number of flowers per umbel. Path-coefficient analysis of components of onion seed production indicates that the percentage of fertilized flowers is the most important criterion for selection to improve seed yield. It would be ideal to combine both high percentage of fertilized flowers and large number of flowers per umbel, but if compromise has to be made, selection would best be considered on the basis of greater percentage of fertilized flowers in the umbel. Plants which have a large percentage of fertilized flowers can be easily detected at the pre-seed harvest stage.
55

Centrifugal Input Modifies Spontaneous Activity of Olfactory Bulb Neurons

Ford, Neil C. 09 October 2013 (has links)
No description available.
56

Design of DC Light Bulb for the DC House Project

Liang, Kent Chin 01 June 2012 (has links) (PDF)
This thesis focuses on the design and implementation of an economical and energy efficient DC Light Bulb for the DC House Project. For the DC lighting system, emphasis is on the DC-DC LED driver, dimmer circuit, LED lighting array, and physical packing design. In this paper, a DC Light Bulb is designed, simulated, and tested to operate at a wide input voltage ranging from 24 VDC to 72 VDC, to be fully dimmable using pulse-width modulation technique, and to produce lumination intensities equivalent to a standard 100 W A19 incandescent light bulb at one-tenth the total power consumption. The DC Light Bulb’s physical design also takes advantage of the same physical dimensions of a standard A19 incandescent light bulb using an E26 Edison screw base. Results from computer simulations and hardware tests demonstrated the feasibility of the proposed DC Light Bulb in terms of overall efficiency, line regulation, load regulation, power consumption, total lumens, luminous efficacy, and thermal profile.
57

Implementering av variabelt varvtal i vattenkraftsaggregat : en förstudie

Persson, Elin January 2023 (has links)
Detta arbete har utrett möjligheten till att implementera variabelt varvtal hos bulbturbiner. Som utgångspunkt har anläggningar med ett Kaplanlöphjul och en växellåda analyserats där variabelt varvtal ska implementeras med en frekvensomriktare och ett löphjul med fasta skovelblad.  Arbetet har fokuserat på att avgöra vilka huvudkomponenter som krävs till inköp för att kunna implementera variabelt varvtal. Ett ytterligare mål var att avgöra vilken anläggning som kan ge mest producerad energi av en anläggning med fast och variabelt varvtal. Slutligen har lönsamheten för en investering som möjliggör ett variabelt varvtal bedömts. Till grund för beräkningar användes insamlad mätdata från anläggningarna under år 2022 och uppskattningar av verkningsgrad och inköpspris för de olika komponenterna.  Resultatet visar att det är möjligt att implementera variabelt varvtal i anläggningen, både genom att behålla växellådan och genom att bygga bort den. Att behålla växellåda är det alternativ som är enklast att implementera eftersom installationen och ombyggnationen blir mindre omfattande. Vidare kan en anläggning med variabelt varvtal potentiellt leda till en utökning av producerad energi där ökningen är åtminstone 0,8 GWh. Slutligen skulle en investering av denna typ kunna betraktas som lönsam under förutsättningen att man kan få intäkter från stödtjänster.  Dessa slutsatser bygger på en del antaganden som bör valideras med leverantörer. / This work has investigated the opportunities to implement variable speed for bulb turbines. As a reference, facilities with a Kaplan runner and a gearbox have been analyzed were variable speed is introduced with a frequency converter and a runner with non-adjustable blades.  The work has focused on determine which main components are necessary for purchases in order to implement variable speed. Another goal was to determine which facility can produce the most energy comparing a facility with variable and fixed speed. Lastly, the financially profitability of an investment that enable variable speed has been assessed.  The foundation of the calculations were based on measured data from the sites during year 2022 and approximations of efficiency and the price of purchase for the different components. The result shows that it is possible to implement variable speed in the facilities, with and without a gearbox. To keep the gearbox is the alternative that is easiest to implement due to less reconstruction of the facility. Furthermore, a facility with variable could potentially lead to an increase in produced energy where the increase is at least 0.8 GWh. Lastly, an investment of this kind could be considered profitable under the assumption that it is possible to receive revenue from ancillary services.  The conclusions are made on assumptions that needs to be validated with suppliers.
58

Dr

Pressler, Richard T. 24 July 2006 (has links)
No description available.
59

Regional Contributions to Neuronal Diversity in the Developing Mouse Telencephalon

Qin, Shenyue 15 December 2017 (has links)
No description available.
60

Early Information Processing in the Vertebrate Olfactory System : A Computational Study

Sandström, Malin January 2007 (has links)
The olfactory system is believed to be the oldest sensory system. It developed to detect and analyse chemical information in the form of odours, and its organisation follows the same principles in almost all living animals - insects as well as mammals. Likely, the similarities are due to parallel evolution - the same type of organisation has arisen more than once. Therefore, the olfactory system is often assumed to be close to optimally designed for its tasks. Paradoxically, the workings of the olfactory system are not yet well known, although several milestone discoveries have been made during the last decades. The most well-known is probably the disovery of the olfactory receptor gene family, announced in 1991 by Linda Buck and Richard Axel. For this and subsequent work, they were awarded a Nobel Prize Award in 2004. This achievement has been of immense value for both experimentalists and theorists, and forms the basis of the current understanding of olfaction. The olfactory system has long been a focus for scientific interest, both experimental and theoretical. Ever since the field of computational neuroscience was founded, the functions of the olfactory system have been investigated through computational modelling. In this thesis, I present the basis of a biologically realistic model of the olfactory system. Our goal is to be able to represent the whole olfactory system. We are not there yet, but we have some of the necessary building blocks; a model of the input from the olfactory receptor neuron population and a model of the olfactory bulb. Taking into account the reported variability of geometrical, electrical and receptor-dependent neuronal characteristics, we have been able to model the frequency response of a population of olfactory receptor neurons. By constructing several olfactory bulb models of different size, we have shown that the size of the bulb network has an impact on its ability to process noisy information. We have also, through biochemical modelling, investigated the behaviour of the enzyme CaMKII which is known to be critical for early olfactory adaptation (suppression of constant odour stimuli). / Luktsystemet anses allmänt vara det äldsta sensoriska systemet. Det utvecklades för att upptäcka och analysera kemisk information i form av lukter, och det är organiserat efter samma principer hos nästan alla djurarter: insekter så väl som däggdjur. Troligen beror likheterna på parallell evolution -- samma organisation har uppstått mer än en gång. Därför antas det ofta att luktsystemet är nära optimalt anpassat för sina arbetsuppgifter. Paradoxalt nog är luktsystemets arbetssätt ännu inte väl känt, även om flera banbrytande framsteg gjorts de senaste decennierna. Det mest välkända är nog upptäckten av genfamiljen av luktreceptorer, som tillkännagavs 1991 av Linda Buck och Rikard Axel. För detta och efterföljande arbete belönades de med Nobelpriset år 2004. Upptäckten har varit mycket värdefull för både experimentalister och teoretiker, och formar grunden för vår nuvarande förståelse av luktsystemet. Luktsystemet har länge varit ett fokus för vetenskapligt intresse, både experimentellt och teoretiskt. Ända sedan fältet beräkningsbiologi grundades har luktsystemet undersökts genom datormodellering. I denna avhandling presenterar jag grunden för en biologiskt realistisk modell av luktsystemet. Vårt mål är att kunna representera hela luktsystemet. Så långt har vi ännu inte nått, men vi har några av de nödvändiga byggstenarna: en modell av signalerna från populationen av luktreceptorceller, och en modell av luktbulben. Genom att ta hänsyn till nervcellernas rapporterade variationer i geometriska, elektriska och receptor-beroende karaktärsdrag har vi lyckats modellera svarsfrekvenserna från en population av luktreceptorceller. Genom att konstruera flera olika stora modeller av luktbulben har vi visat att storleken på luktbulbens cellnätverk påverkar dess förmåga att behandla brusig information. Vi har också, genom biokemisk modellering, undersökt beteendet hos enzymet CaMKII, som är kritiskt viktigt för adaptering (undertryckning av ständigt närvarande luktstimuli) i luktsystemet.

Page generated in 0.028 seconds