Tesi sul tema "Entrainment"
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1
McDowell, David W. "Determining entrainment rate and the role of entrainment in stratocumulus clouds". Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1999. http://handle.dtic.mil/100.2/ADA366842.
Testo completoAbstract (sommario):
Thesis (M.S. in Meteorology and Physical Oceanography) Naval Postgraduate School, June 1999."June 1999". Thesis advisor(s): Wing Wang. Includes bibliographical references (p. 63-65). Also available online.
2
Dwivedi, Ambuj. "Mechanics of sediment entrainment". Thesis, University of Auckland, 2010. http://hdl.handle.net/2292/5854.
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3
Gilani, Mohammad Nejad Hamzeei. "CFD of droplet entrainment". Thesis, Imperial College London, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.542939.
Testo completo
4
Stone, Rebecca E. "Deep mixed layer entrainment". Monterey, California. Naval Postgraduate School, 1997. http://hdl.handle.net/10945/8198.
Testo completoAbstract (sommario):
Approved for public release; distribution is unlimited.A bulk turbulence-closure mixed layer model is generalized to allow prediction of very deep polar sea mixing. The model includes unsteady three- component turbulent kinetic energy budgets. In addition to terms for shear production, pressure redistribution, and dissipation, special attention is devoted to realistic treatment of thermobaric enhancement of buoyancy flux and to Coriolis effect on turbulence. The model is initialized and verified with CTD data taken by R/V Valdivia in the Greenland Sea during winter 1993-1994. Model simulations show (1) mixed layer deepening is significantly enhanced when the thermal expansion coefficient's increase with pressure is included; (2) entrainment rate is sensitive to the direction of wind stress because of Coriolis; and (3) the predicted mixed layer depth evolution agrees qualitatively with the observations. Results demonstrate the importance of water column initial conditions, accurate representation of strong surface cooling events, and inclusion of the thermobaric effect on buoyancy, to determine the depth of mixing and ultimately the heat and salt flux into the deep ocean. Since coupling of the ocean to the atmosphere through deep mixed layers in polar regions is fundamental to our climate system, it is important that regional and global models be developed that incorporate realistic representation of this coupling
5
Spolander, Bruce John. "Entrainment in Saldanha Bay". Master's thesis, University of Cape Town, 1996. http://hdl.handle.net/11427/19819.
Testo completoAbstract (sommario):
Bibliography: pages 64-67.Saldanha Bay is located lOOkm north of Cape Town, along the south western coast of South Africa, at a latitude of approximately 33° S. In 1975 major harbour works, including the construction of an iron ore jetty, divided Saldanha Bay into two distinct bays. The bay to the north of the jetty has become known as Small Bay, while the bay to the south is commonly referred to as Big Bay. Big Bay is connected at its southern end to the shallow Langebaan Lagoon system, and to the west with the Benguela upwelling system (see figure 1.1). The oceanography of the shelf outside the bay is dominated by the coastal upwelling system (Shannon 1985). The equatorward winds which predominate for much of the year, drive an offshore flux of surface water, which is replaced near the coast by nutrient-rich water from deeper layers. These winds are the result of an interplay between the South Atlantic High Pressure Cell, a thermal low that forms over southern Africa in summer, coastal lows, and eastward moving extra tropical cyclones (Shannon 1985). In summer, the band of extra tropical cyclones associated with the jetstream moves to the south of its winter position, while the South Atlantic High intensifies and moves approximately 6° to the south (Preston-Whyte and Tyson 1988), creating a pressure gradient over the Benguela region. The presence of the thermal low over the adjacent subcontinent increases the existing pressure gradient, and enhances the equatorward air flow. This seasonal modulation of upwelling favourable winds results in an upwelling season that extends from about September to March (Shannon 1985). During this period, there is also synoptic modulation, provided by wind relaxation or reversal events. These events are either associated with the passage of a cyclone to the south of the continent, or with a coastal low passing along the coast (Shannon 1985).
6
Chen, Chi-Shao. "Equatorial entrainment zone simulations". Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA237234.
Testo completoAbstract (sommario):
Thesis (M.S. in Physical Oceanography)--Naval Postgraduate School, June 1990.Thesis Advisor(s): Garwood, Roland W. Second Reader: Chu, Pecheng. "June 1990." Description based on signature page as viewed on October 19, 2009. DTIC Identifier(s): Air water interactions, ocean models, ocean currents, entrainment, ocean circulation, heat flux, wind velocity, mathematical prediction, equatorial regions, theses. Author(s) subject terms: Air-sea interaction, equatorial circulation. Includes bibliographical references (p. 73-75). Also available in print.
7
Huang, Danlan. "Entrainment in Pulsing plumes". Thesis, The University of Sydney, 2019. http://hdl.handle.net/2123/21168.
Testo completoAbstract (sommario):
The main contribution of this work is to investigate the entrainment in plumes with constant and time-varying source conditions experimentally. The study aims to build up an experiment rig to conduct the bulk entrainment measurement in plumes. Secondly, the study aims to examine the influences the forcing frequency and amplitude have on entrainment in pulsing plumes, where the flow rate, momentum and buoyancy are sinusoidal functions of time. Finally, the study aims to investigate the validity of the integral model for pure plumes with constant source conditions established by Morton et al. (Proc R Soc Lond A 234(1196):1–23, 1956) in pulsing plumes, as well as the virtual origin correction method for lazy plumes proposed by Hunt and Kaye (J Fluid Mech 435:377–396, 2001) in both constant source plumes and pulsing plumes. Experiments were conducted to verify the pulses in pulsing plumes. Plumes are formed by issuing saline fluid downwards into a less dense uniform environment from a round pipe. The pulsing flow is generated by a programmable ISMATEC gear pump. The evolution of the pulses in pulsing plumes is revealed by applying the light-attenuation method with high frequency imaging. Pulsing is shown to affect the development of the flow, as the forcing frequency at the source dominates the frequency of the flow downstream. To study the bulk entrainment in pulsing plumes, turbulent axisymmetric lazy plumes with constant source conditions were examined initially. The bulk dilution and entrainment measurements were achieved by using the experimental approach of Hunt and Kaye (J Fluid Mech 435:377–396, 2001). The integral relationship for the local flow rate Q(z) and local momentum M(z) from the model established by Morton et al. (Proc R Soc Lond A 234(1196):1–23, 1956) for constant source plumes was used to determine the average local entrainment. Experiments with pulsing plumes were carried out with a flow rate amplitude ranged from 33% to 80% and the non-dimensional frequency - Strouhal number 〖St=fD/U〗_0 ranged from 0.012 to 1.2, where the maximum frequency f of this pulsing plume is in the order of the eddy turnover time scale at the source, D is the source diameter and U_0 is the average velocity at the source. The entrainment coefficient was determined in pulsing plumes and was found within the range of the entrainment values in plumes with constant source conditions. The influence of the forcing frequency and amplitude is examined, and found to be very small over the entire range of source conditions considered. The virtual origin correction method of Hunt and Kaye (J Fluid Mech 435:377–396, 2001) is found to give a reasonably good estimation in predicting the virtual origin in pulsing plumes. The results suggest that the local entrainment velocity is proportional to the time-average local plume velocity even in pulsing plumes where the local velocity is varying with time. This supports the application of the integral model of Morton et al. (Proc R Soc Lond A 234(1196):1–23, 1956) to building ventilation problems and environmental flows where these conditions exist.
8
Thompson, Keith B. "Entrainment Zone Characteristics and Entrainment Rates in Cloud-Topped Boundary Layers from DYCOMS-II". Thesis, Monterey, California. Naval Postgraduate School, 2012. http://hdl.handle.net/10945/6881.
Testo completoAbstract (sommario):
The major objective of this thesis is to understand entrainment zone properties and the cloud-top entrainment rates using in situ aircraft measurements. The entrainment zone is defined objectively using a new method based on turbulence perturbations from high-rate turbulence samplings taken during the Dynamics and Chemistry of Marine Stratocumulus (DYCOMS-II) field study. The Entrainment Interfacial Layer (EIL) of the stratocumulus-topped boundary layer (STBL) is defined as the region near the cloud top where mixing occurs between dry free-troposphere air and moist turbulent air. Although the concept of the entrainment zone is clear, defining the top and bottom altitudes of the EIL from vertical profiles of tracer variables is complicated by many factors including an insufficient number of sounding profiles to provide good statistics. This issue is further complicated by the presence of multiple interfaces near the cloud top often used as a substitute for the EIL. As a result, the region that comprises the entrainment zone is not clearly defined. This study examines the characteristics of several important interfaces such as the cloud top, the inversion layer, the interface between turbulent and non-turbulent layers, and the EIL. The relative heights and depths of these interfaces are studied using a large number of sounding profiles from five DYCOMS-II flights. The characteristics of the EIL jump conditions were also analyzed; their variability illustrates the complexity of the jumps and therefore the uncertainty in entrainment rate calculations. Entrainment rates were estimated from jump conditions obtained in this thesis and compared to previous studies.
9
Boga, Gabriele. "Numerical Experiments on Turbulent Entrainment". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/20559/.
Testo completoAbstract (sommario):
The aim of this thesis work is the study of the turbulent entrainment phenomenon in jets through numerical experiments. More specifically, an attempt to study the effect of engulfment and nibbling mechanisms separately was made. The flow chosen for the numerical experiments is the temporal planar jet. The idea behind these experiments is to study the spreading and the mixing of a passive scalar under the effect of two modified velocity fields. The first is a large-scale velocity field obtained through a filtering operation, while the second is a small-scale velocity field obtained subtracting the large-scale velocity field from the total one and then adding the mean velocity.
Initially, the post-processing of a spatially developing planar jet, performed by Doctor Andrea Fregni and Professor Andrea Cimarelli, has been carried out in order to analyse the main features of spatially evolving jets compared with the temporal ones. A co-flow and a passive scalar are present in the simulation. The Reynolds number is set to Re = 3000 and the Schmidt number is Sc = 1. After this first step, a benchmark DNS of a temporal planar jet with Re = 3000 and Sc = 1 has been performed in order to evaluate the main differences with respect to the spatially evolving jet. Once the settings were validated, the numerical experiments with large and small scale velocity fields have been performed. The filter used in all the experiments is the box filter. The results of two different filter lengths are presented, the first is Δ = 1.5λcl and the second is Δ = 3λcl. Since λcl is function of time, the two filter lengths are themselves varying in time. The results of the experiments were then compared with those of the unfiltered solution. The passive scalar spread approximatively the same amount under the effect of the large-scale velocity fields and under the effect of the unfiltered velocity. On the other hand, the small-scale fluctuations have been proved to be important in the mixing process.
10
Lohmann, Frank Cord. "Entrainment processes during plume ascent". [S.l.] : [s.n.], 2006. http://e-diss.uni-kiel.de/diss_1693/d1693.pdf.
Testo completo
11
Singh, Jaswant. "Gas entrainment by liquid sprays". Thesis, University of Leeds, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.432173.
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12
Smith, Karen Lynn. "Entrainment of the circadian clock". Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624358.
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13
Pilippu, Hewage Eranga Dulanjalee. "Erosion and entrainment during landslides". Thesis, The University of Sydney, 2022. https://hdl.handle.net/2123/28901.
Testo completoAbstract (sommario):
The main focus of this thesis is to experimentally investigate the effect of grain size on the mechanism of erosion during landslides using small-scale laboratory experiments. Specifically, we have focused on the effect of the grain size of the flowing and erodible bed materials on the erosion rate. We experimentally investigated a flow of particles over an erodible base in a laboratory-scale inclined flume with different particle size combinations for the flow and the erodible substrate. The dynamics of the flow-erodible bed interface was captured with X-ray radiography. The evolving erosion depths were estimated from the well-established critical velocity-based method and a novel particle size-based method.
The erosion rates estimated from the two techniques gave contradictory conclusions. The normalized erosion rate increases with the flow to bed grain size ratio in the critical-velocity-based erosion rate estimation, whereas the erosion rates estimated from the particle-size-based approach encounter the opposite trend. To further investigate this behaviour, we have developed a one-dimensional continuum model which incorporates the kinematics of the flowing system. The observed erosion behaviour interpreted from the bidisperse calibration method is reproduced with this model reasonably well. The effect of size-based segregation in these flows is found to be minimal, however overall, we observed reverse segregation in the flow system.
In this research, we successfully captured the internal micromechanics of the flow field with X-ray radiography. This imaging methodology allows us to probe deeply within the flowing material, avoiding limitations in data capturing only near sidewalls that are prevalent with other imaging methods. In contrast to the critical velocity-based technique, the newly developed bidisperse calibration technique precisely determined the flow-erodible bed interface.
14
Mc, Laughlin Declan T. "Gas entrainment into viscous polymer solutions". Thesis, Queen's University Belfast, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252316.
Testo completo
15
Rigobon, Daniel E. "Models of entrainment of human walking". Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/119940.
Testo completoAbstract (sommario):
Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 39-40).
Stable human locomotion may be described as a non-linear limit cycle oscillator. This claim has been supported through the observation of dynamic entrainment and phase-locking to external mechanical perturbations applied at the ankle. Simple models have been developed in attempts to understand these behaviors, but have been unsuccessful at replicating experimental studies. In this manuscript, an energy-based controller was implemented on a single degree-of-freedom model, adjusting its leading leg angle at heel strike and consequently the energy dissipation of the model. Stochasticity was applied to the controller to simulate the variability which has been observed and quantified in walking. The results indicate that energy control may be responsible for entrainment in human walking, but a revised model may be required to match the experimental coefficients of variation in step duration and velocity.
by Daniel E. Rigobon.
S.B.
16
Beard, Robert L. "Oceanic mixed layer entrainment zone dynamics". Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA240896.
Testo completoAbstract (sommario):
Thesis (M.S. in Meteorology and Physical Oceanography)--Naval Postgraduate School, September 1990.Thesis Advisor(s): Garwood, R. W. Second Reader: Chu, P. C. "September 1990." Description based on title screen viewed on December 16, 2009. DTIC Descriptor(s): Marine meteorology, thermoclines, thickness, production, predictions, models, energy, theses, turbulence, temperature gradients, vertical orientation, heating, kinetic energy, budgets, oceans, weather stations, entrainment, north pacific ocean, shear properties, transients. DTIC Identifier(s): Mixed layer (marine) air sea interaction, entrainment shear production, mixed layer. Author(s) subject terms: air-sea interaction, entrainment shear production, mixed layer. Includes bibliographical references (p. 46-47). Also available in print.
17
Bahner, Mark A. "A reduced-turbulence, reduced-entrainment electrostatic precipitator". Thesis, This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-03122009-040702/.
Testo completo
18
Wlodarczak, Marcin [Verfasser]. "Temporal entrainment in overlapping speech / Marcin Wlodarczak". Bielefeld : Universitätsbibliothek Bielefeld, 2014. http://d-nb.info/1047666359/34.
Testo completo
19
Hancock, Peter. "Metal entrainment in continuous liquid phase drosses". Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=28772.
Testo completoAbstract (sommario):
A comprehensive characterization of silver and bismuth refining crusts produced during the pyrometallurgical refining of lead was undertaken. Parameters such as intermetallic crystal size and composition, and degree of metal entrainment were determined. Silver crust was found to be composed mostly of the $ epsilon$-phase (AgZn$ sb3$) with an average particle size of 50 $ mu$m. Liquid lead entrainment of 80 volume percent was measured. The intermetallic phase in bismuth crust was composed entirely of CaMg$ rm sb2Bi sb2$ crystals with an average diameter of 50 $ mu$m. Lead entrainment in bismuth crust was approximately 90 volume percent. The high degree of metal entrainment observed in both silver and bismuth crusts was not adequately explained through a capillary model of liquid metal entrainment in a static bed of solid particles. The models used to predict swelling in colloidal particle systems (such as clay soils) were found to better approximate the high degree of liquid entrainment.Experiments were performed in which particle beds of $ gamma$-phase ($ rm Ag sb5Zn sb8$) intermetallic compound were infiltrated with liquid lead under controlled conditions and examined under the optical microscope. Image analysis revealed pronounced swelling of fine particle beds relative to coarse. The effect was most noticeable for average particle diameters less than 100 $ mu$m where the solids volume fraction decreased from 50 to 30 vol.%. Data showed samples LO exhibit a constant increase in inter-particle spacing of approximately 50 $ mu$m. The increase in spacing explained the degree of swelling at low particle diameters and was also used to develop an expression to predict height of capillary rise.
Based on an osmotic pressure analogy in colloidal particle systems, a swelling pressure term was defined to explain the increase in inter-particle spacing. The swelling pressure was defined as equal and opposite to the capillary pressure tending to force particles to random packing. It was concluded that swelling was related to mass transfer at the solid-liquid interface of the intermetallic crystals giving a reduced static pressure due to a localized minimization of Gibbs energy. The static pressure change (swelling pressure) was attributed to overlap of mass transfer boundary layers where mid-point static liquid metal pressure is less than the pressure in the bulk liquid. For the system studied, the mass transfer boundary layer was estimated to be approximately 100 $ mu$m in thickness.
Further experiments, using the sessile drop technique, were used to support the study findings by showing rapid spreading of liquid lead on Ag-Zn intermetallic substrates. The rapid spreading was attributed to mass transfer at the solid-liquid interface giving a reduced interfacial energy, $ gamma sb{ rm s1}$ due to a localized reduction in Gibbs energy.
The analysis of experimental results led to the development of two new industrial processes in the lead industry aimed at reducing lead loss to silver and bismuth crusts. Tests employing continuous agitation during bismuth removal from lead promoted the growth of large $ rm CaMg sb2Bi sb2$ crystals. The larger crystals minimized the effect of mass transfer boundary layer overlap and reduced lead entrainment from 90 to 80 volume percent. The addition of a low melting point KCl-ZnCl$ sb2$ salt during silver crust formation was found to remove up to 90% of entrained lead by the salt preferentially wetting Ag-Zn intermetallic particles. This was found to eliminate surface forces which retained liquid in the system of solid particles.
20
Harrison, Roger. "Entrainment of Air into Thermal Spill Plumes". Thesis, University of Canterbury. Civil and Natural Resources Engineering, 2009. http://hdl.handle.net/10092/2865.
Testo completoAbstract (sommario):
The design of smoke management systems for buildings such as atria, covered
shopping malls and sports arenas require appropriate calculation methods to predict the volume of smoky gases produced in the event of a fire. The volume of smoke must be calculated in order to determine the required fan capacity or ventilator area for a smoke management system.
In design, consideration is often given to entrainment of air into a smoke flow from a compartment opening that subsequently spills and rises into an adjacent atrium void. This type of plume is commonly known as a thermal spill plume. There has been much controversy over the validity of various entrainment calculation methods for the spill plume and there are considerable differences in the calculated smoke production
rates using these methods. There are also scenarios involving the spill plume where design guidance is very limited. Whilst over-sizing of the required smoke exhaust can be uneconomical, under-sizing can compromise the design objectives.
This work attempts to rigorously characterises thermal spill plume entrainment using new data obtained from an extensive series of 1/10th physical scale modelling experiments, supported by numerical modelling using Computational Fluid Dynamics.
Spill plume behaviour and subsequent entrainment appears to be specifically
dependent on the characteristics of the layer flow below spill edge, particularly in terms of the width and the depth of the flow. Plumes generated from narrow, deep layer flows entrain air at a greater rate with respect to height compared to plumes generated from wide, shallow layers. The findings of this work go some way to explain and reconcile differences in entrainment reported between previous studies.
New guidance has been developed for the thermal spill plume in smoke management
design, in the form of a range of new simplified design formulae,improvements to analytical calculation methods and an initial assessment of the use of numerical modelling using Computational Fluid Dynamics.
21
Balaji, Ravishankar. "Breathing Entrainment and Mechanical Ventilation in Rats". Case Western Reserve University School of Graduate Studies / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=case1307743446.
Testo completo
22
Bouvet, Cécile. "Auditory-motor entrainment : behavioural and cerebral dynamics". Thesis, Montpellier, 2020. http://www.theses.fr/2020MONT4002.
Testo completoAbstract (sommario):
Nous synchronisons nos mouvements avec les rythmes auditifs présents dans notre environnement sans même en avoir l’intention. Cette coordination, qui influence la stabilité du mouvement produit, s’est avéré bénéfique dans des contextes sportifs et thérapeutiques. À ce jour, la recherche a atteint un large consensus sur les mécanismes sous-tendant les processus de coordination sensori-motrice intentionnelle, mais explore toujours les mécanismes d’entraînement audio-moteur spontanés. Cette thèse aborde la dynamique de synchronisation non-intentionnelle pour différentes relations de fréquence entre un mouvement périodique et un rythme auditif. À travers quatre études complémentaires, ce travail questionne le rôle de multiples niveaux de graduation temporelle et de leur accentuation dans l’émergence et la stabilité de formes simples vs. complexes de synchronisation. La 1ère étude confirme quantitativement l’émergence d’une synchronisation audio-motrice spontanée, différente d’une relation de fréquence de 1:1. La 2ème étude introduit le bénéfice de l’addition d’un patron d’accentuation congruent pour l’émergence de synchronisation à différents rapports de fréquence. Elle permet également d’observer qu’un patron d’accentuation ternaire est plus favorable à la synchronisation qu’un patron d’accentuation binaire. La 3ème étude s’intéresse à cette découverte via l’enregistrement Électroencéphalographique des réponses neurales aux différents patrons d’accentuation, confirmant une différence de réponse aux stimulations binaires et ternaires, liée aux performances comportementales. La 4ème étude se concentre sur le bénéfice des patrons d’accentuation sur la production de mouvement plus complexe. Elle considère également les réponses neurales aux différents patrons d’accentuation en prenant en compte la congruence avec la coordination motrice produite, démontrant l’influence des systèmes sensoriels et moteur sur la perception rythmique. En résumé, ces résultats démontrent qu’un entraînement audio-moteur spontané peut émerger à différents ratios de fréquences en conformité avec les prédictions de l’approche des systèmes dynamiques de l’action et de la perception. De plus, l’entraînement audio-moteur spontané est modulé (i.e., promu ou dégradé) par l’addition de patrons d’accentuation, selon leur congruence avec le mode de fréquence audio-moteur et les réponses neurales. D’autre part, des formes plus complexes de coordination répondent de façon similaire à la présence d’accentuation, soutenues par le couplage audio-moteur et les processus de perception rythmique auditive. Ainsi, les conclusions de cette thèse ouvrent de nouvelles pistes de recherche sur la synchronisation audio-motrice spontanée et son application à l’entraînement et la réhabilitation des performances motricesWe often synchronise our movements to auditory rhythms in our environment without the intention to do so. Such coordination influences the stability of movement performance, and, therefore, can be used to our benefit in sport and therapeutic contexts. Research to date has largely reached a consensus about the mechanisms underlying intentional sensory-motor coordination, but spontaneous auditory-motor entrainment is still under exploration. This thesis addresses the dynamics of unintentional synchronisation towards various frequency relationships between periodic movement and auditory rhythm frequencies. It presents four complementary studies questioning the role of multiple metrical levels and their accentuation on the emergence and stability of simple vs. complex synchronisation in healthy adults. The 1st study confirms quantitatively the emergence of spontaneous synchronisation at frequency ratios different from 1:1. The 2nd study introduces the benefit of a congruent accentuation pattern on the emergence of various frequency ratios. It leads to the observation that a ternary accentuation pattern facilitates synchronisation more than a binary accentuation pattern. The 3rd study examines this new finding through the recording of neural responses to various accented patterns using Electroencephalography, confirming a differential response to ternary and binary patterns linked to behavioural performance. The 4th study focuses on the benefit of accentuation patterns for the production of a more complex type of movement coordination. It also measured neural tracking of the accentuation pattern relative to the congruence of the motor coordination performed, showing that both sensory and motor systems influenced rhythm perception. All together, these results demonstrate that spontaneous auditory-motor entrainment can emerge at various frequency ratios in accordance with the predictions of the dynamical systems approach to action and perception. Furthermore, spontaneous auditory-motor entrainment is modulated (i.e., increased or decreased) by the addition of simple accentuation patterns, depending on congruence with the auditory-motor frequency mode and the neural response to the accents. In addition, more complex multi-limb motor coordination performance responds similarly to accentuation, underpinned by auditory-motor coupling and sensory processing of the auditory rhythms. Therefore, the findings of this thesis open new avenues for future research on spontaneous auditory-motor coordination and its application in the training and rehabilitation of motor performance
23
Awin, Layth Ali M. "Structure and Entrainment of Forced Turbulent Fountains". Thesis, The University of Sydney, 2021. https://hdl.handle.net/2123/27276.
Testo completoAbstract (sommario):
In this PhD thesis, the primary focus is to numerically investigate the entrainment in forced turbulent fountains. The study also aims to establish a benchmark to examine the fountain properties, specifically the detailed structure of fountains in the forced turbulent regime. Previous research primarily focuses on developing integral and scaling models to estimate the bulk flow properties, which are validated against experimental results, mainly for the estimation of fountain rise height. The hypothesis implicit in such models is that the fountain flow is self-similar and the entrainment can be estimated using simple jet/plume scalings with constant entrainment coefficients. There have been, however, no reasonable attempts by numerical simulations either to tackle the entrainment problem or to undertake detailed study of forced turbulent fountain flows over a range of source conditions.
Computational fluid dynamics (CFD) simulations of the incompressible Navier-Stokes equations in dimensionless form were carried out to describe the three dimensional fountain flow for developing and fully developed flow. The fountains were formed by projecting a dense flow upwards from a circular source into a less dense environment. The numerical simulations were conducted for Reynolds and Froude numbers in the ranges 2000 ≤ Re ≤ 3500 and 2 ≤ Fr ≤ 24 based on the fountain source properties. The simulations were capable of capturing full details of the turbulent structure, entrainment and mixing in forced round fountains. The total entrainment rate and associated entrainment coefficients were determined and found to be larger than that for jets and plumes. The structure of the fountain including height and width was also predicted and assessed for the inner and outer flows. Results show that all quantities are dependent, predominantly, on the Froude number, with regression analysis used to quantify the scaling relations.
24
Hadjerioua, Boualem. "Air entrainment and oxygenation by overfalling nappes". Diss., The University of Arizona, 1994. http://hdl.handle.net/10150/186852.
Testo completoAbstract (sommario):
This research analyzes air entrainment and flow conditions of overfalling nappes and the behavior of bubbles in the plunge pools leading to oxygenation of the water. A literature search indicated that these phenomena have never been analyzed as a whole. An experimental/analytical/numerical approach is used to estimate the rate of oxygenation by nappes over weirs. The experimental investigation was done at the Tennessee Valley Authority (TVA) Engineering Laboratory, Norris, Tennessee. An air-water concentration probe (developed by Lamb and Killen, 1950) was calibrated and used to determine contours of air concentration in the plunge pool. Representative bubble sizes were determined using high-speed photography. The air set in motion by the nappe was computed analytically by integrating the momentum and continuity equations over the air boundary layer. Comparison with the air in the plunge pool established the fraction of the boundary entering the plunge pool. A three-dimensional, fluid flow solver was used to compute a representative water flow field in the plunge pool. Using that water flow field, the trajectory and residence time of bubbles in the plunge pool were then computed by solving the two-dimensional Lagrangian equations of motion. Included in this calculation is the mass transfer of air from the bubble over its trajectory using an empirical mass transfer coefficient. From this calculation, the rate of oxygenation was determined for the overall plunge pool. The analytical results show good agreement with the experimental data collected by the author and with other findings documented in the literature.
25
Martín, Buldú Javier. "Entrainment of semiconductor lasers : noise, modulation and synchronization". Doctoral thesis, Universitat Politècnica de Catalunya, 2003. http://hdl.handle.net/10803/6603.
Testo completoAbstract (sommario):
El objetivo de esta tesis es el estudio de la dinámica de los láseres de semiconductor (LS) con realimentación óptica, tanto desde el punto de vista experimental como numérico. La reflexión de la luz emitida por el láser, debida a la presencia de un espejo externo, es capaz de inducir una dinámica caótica en su intensidad de salida. Concretamente, cuando el láser es bombeado cerca de su corriente umbral, puede entrar en el régimen de fluctuaciones de baja frecuencia (LFF), caracterizado por repentinas caídas de su intensidad a tiempos irregulares. El comportamiento pulsado, y caótico, en este régimen es de especial interés desde el punto de vista de la dinámica de sistemas no-lineales, pero también por sus aplicaciones en comunicaciones ópticas.Si queremos resumir los resultados de esta tesis ordenados cronológicamente,debemos empezar hablando de ruido. El efecto de el ruido en un sistema no-lineal puede ser de gran ayuda en la obtención de una respuesta más regular, efectos como la resonancia coherente o la resonancia estocástica han dado buena prueba de ello. Con el objetivo de observar ambos fenómenos en el comportamiento pulsado de un láser en régimen de LFF, se realizan simulaciones numéricas a partir del modelo de Lang-Kobayashi (LK), que describe la evolución del campo eléctrico y los portadores en un LS. Los resultados obtenidos demuestran que añadiendo cierta cantidad de ruido externo a través de la corriente de bombeo, los pulsos observados en la intensidad de salida se vuelven más regulares, que es la característica típica de la resonancia de coherencia (RC). Si la corriente de bombeo está modulada con una señal periódica de cierta frecuencia, se puede observar cómo el ruido externo ayuda al sistema a seguir dicha frecuencia, lo que se refleja en la intensidad de salida con unas caídas no sólo más regulares, sino también a la frecuencia de forzamiento. Este fenómeno, observado en diversos sistemas no-lineales, se conoce como resonancia estocástica (SR). Los estudios realizados permiten observar que no sólo la amplitud del ruido es importante, sino también su tiempo de correlación, debiéndose ajustar ambos parámetros para poder observar dichas resonancias. En relación con el efecto del ruido en estos sistemas, se estudia (experimental y numéricamente) el caso de un láser en LFF cuando es modulado con dos frecuencias, observando resonancia a frecuencias no presentes en el sistema. Estos resultados son la primera evidencia experimental de este fenómeno, bautizado como resonancia fantasma (GR), el cual sólo habia sido predicho teóricamente hasta el momento.
Paralelamente, se analizan los efectos del acoplamiento de dos sistemas caóticos, en nuestro caso dos láseres en régimen de LFF. Los resultados demostran que el acoplamiento puede incrementar la respuesta de un sistema no lineal a un señal periódica externa.
Se profundiza también en el estudio del comportamiento multimodo de los láseres de semiconductor con realimentación óptica. Se presentan resultados experimentales y numéricos del comportamiento de los modos longitudinales en el régimen de LFF, observándose como, cuando la intensidad total cae, se activan modos laterales que hasta el momento permanecian apagados. Finalmente, y continuando con el estudio de la dinámica multimodo, se analiza la sincronización de dos láseres multimodo mediante una extensión del modelo de LK, observándose sincronización generalizada y anticipada, tanto de la intensidad total, como entre los modos longitudinales de cada láser. Estos resultados sugieren la utilización de este tipo de láseres para la transmisión de mensajes multiplexados.
26
Veverka, Peter John. "An investigation of interfacial instability during air entrainment". Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/5800.
Testo completo
27
Bhutani, Supriya. "Natural entrainment of the drosophila melanogaster circadian clock". Thesis, University of Leicester, 2009. http://hdl.handle.net/2381/7881.
Testo completo
28
Barrack, Duncan. "Modelling cell cycle entrainment during cortical brain development". Thesis, University of Nottingham, 2010. http://eprints.nottingham.ac.uk/11318/.
Testo completoAbstract (sommario):
Radial glial cells play an important role during embryonic development in mammals. They are not only important for neural production but help to organise the architecture of the neocortex. Glial cells proliferate during the development of the brain in the embryo, before differentiating to produce neurons at a rate which increases towards the end of embryonic brain development. Glial cells communicate via Adenosine tri-phosphate (ATP) mediated calcium waves, which may have the effect of locally synchronising cell cycles, so that clusters of cells proliferate together, shedding cells in uniform sheets. Hence radial glial cells are not only responsible for the production of most neocortical neurons but also contribute to the architecture of the brain. It has been argued that human developmental disorders which are associated with cortical malfunctions such as infantile epilepsies and mental retardation may involve defects in neuronal production and/or architecture and mathematical modelling may shed some light upon these disorders. This thesis investigates, among other things, the conditions under which radial glial cells' cell cycles become `phase locked', radial glia proliferation and stochastic effects. There are various models for the cell cycle and for intracellular calcium dynamics. As part of our work, we marry two such models to form a model which incorporates the effect of calcium on the cell cycle of a single radial glial cell. Furthermore, with this achieved we consider populations of cells which communicate with each other via the secretion of ATP. Through bifurcation analysis, direct numerical simulation and the application of the theory of weakly coupled oscillators, we investigate and compare the behaviour of two models which differ from each other in the time during the cell cycle at which ATP is released. Our results from this suggest that cell cycle synchronisation is highly dependent upon the timing of ATP release. This in turn suggests that a malfunction in the timing of ATP release may be responsible for some cortical development disorders. We also show how the increase in radial glia proliferation may mostly be down to radial glial cells' ability to recruit quiescent cells onto the cell cycle. Furthermore, we consider models with an additive noise term and through the application of numerical techniques show that noise acts to advance the onset of oscillatory type solutions in both models. We build upon these results and show as a proof of concept how noise may act to enhance radial glia proliferation.
29
Maa'd, Abdil-Ghani Shehab. "Entrainment and boiling limits in the heat pipe". Thesis, University of Reading, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283274.
Testo completo
30
Whyte, Kenneth K. "Entrainment and mixing in rivers, estuaries and reservoirs". Thesis, University of Liverpool, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.400129.
Testo completo
31
Jackson, Derek William Thomas. "Aeolian entrainment of surface beach and dune settlements". Thesis, University of Ulster, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242047.
Testo completo
32
Williams, Jonathan Jowett. "Aeolian entrainment thresholds in a developing boundary layer". Thesis, Queen Mary, University of London, 1986. http://qmro.qmul.ac.uk/xmlui/handle/123456789/28966.
Testo completoAbstract (sommario):
The aeolian threshold condition is identified as defining the critical state between a static sediment bed and active aeolian transport. Disparities in reported mean threshold shear velocities (U*T) are attributed to variation in: (a) flow regimes; (b) entrainment criteria; (c) particle characteristics and exposures; and (d) techniques for measurement of 1*T The relative significance of these factors is assessed for strips and beds of ballotini, aeolian sand, salt crystals and sugar crystals using the controlled, reproducible flow conditions of the developing boundary layer over a flat plate. Such a plate was covered with a non-erosive layer of grains to simulate a flat sediment bed and was positioned in a wind tunnel. values were calculated using the momentum integral method. In a separate study, threshold conditions on impervious and permeable beds were compared directly. Analysis of entrainment from strips and beds on the plate shows that the threshold condition is principally determined by a critical degree of overlap between the probability distributions of local shear velocity, P ( U ), and of grain threshold shear velocity, P(U*T). Characteristic P(U*T) distributions for test materials were determined and two objective definitions of U*T were devised. Experimental *T values agree well with published data and are used to resolve the data scatter associated with both 'restricted' and 'universal' threshold curves. Rates of aeolian entrainment over a range of values are found to be an inverse exponential function of time and wind speed. Different erosion rates were found to result from skewness of P(U) and degree of overlap between P(U) and P(U*T). Fluid sweeps in the turbulent bursting cycle are considered to be the primary entrainment mechanism. Medium/high-speed cine film gave insight into initiation processes. Grain oscillation due to vortex shedding and initial motion characterized by a progressive rolling and bouncing were observed. Bed permeability was not found to affect aeolian threshold values.
33
Seidel, Tobias, Dirk Lucas e Matthias Beyer. "TOPFLOW-Experiments on Direct Condensation and Bubble Entrainment". Helmholtz-Zentrum Dresden - Rossendorf, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-197715.
Testo completoAbstract (sommario):
Direct Contact Condensation between steam and water as well as bubble entrainment below the water surface play an important role in different accident scenarios for light water reactors. One example is the emergency core cooling water injection into a two-phase mixture. It has to be considered for example to evaluate potential pressurized thermal shock phenomena.
This report documents experiments conducted in flat basin inside the TOPFLOW pressure chamber aiming on the generation of a database useful for CFD model development and validation. It comprises 3 different setups: condensation at a stratified flow of sub-cooled water, condensation at a sub-cooled water jet and a combination of both phenomena with steam bubble entrainment. The documentation includes all details on the experimental set up, on experimental conditions (experimental matrices), on the conduction of the experiments, on measuring techniques used and on data evaluation procedures. In addition, selected results are presented.
34
Terrill, Eric J. "Acoustic measurements of air entrainment by breaking waves /". Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 1998. http://wwwlib.umi.com/cr/ucsd/fullcit?p9907829.
Testo completo
35
Galvanin, Silvia. "Circadian Clock Study Through Frequency-Encoded Entrainment Stimulations". Doctoral thesis, Università degli studi di Padova, 2018. http://hdl.handle.net/11577/3422301.
Testo completoAbstract (sommario):
Circadian clocks are intrinsic, time-tracking systems that enable organisms to maintain their physiological state and their synchrony with the 24-hour rotation of the Earth, by partitioning behavioural and metabolic processes according to time of day within each tissue. They are entrained to the external environment by light/dark cycles and by food timing, which act as clock synchronizers. Emerging evidence suggests that circadian regulation is intimately linked to metabolic homeostasis and that dysregulation of circadian rhythms can contribute to disease. Conversely, metabolic signals also feed back into the circadian system, modulating circadian gene expression and behaviour.
Conventional experimental approach of circadian clock in vitro studies is based on single-pulse stimulation of only one metabolite or hormone, while in vivo peripheral tissues are exposed to periodic oscillating stimuli of a large number of metabolites and hormones, whose variations are in most cases interconnected, as for example glucose and insulin. Moreover, only one or few clock genes are generally considered, while it is known that a large number of genes, thus biological processes, are under circadian regulation.
Therefore, this Ph.D. research work is aimed at the development of technologies and data analysis tools to investigate the entrainment of peripheral mammalian circadian clock to frequency-encoded metabolic stimuli, which well mimic physiological oscillations at which peripheral tissues are exposed in vivo. Technologies, and, more specifically, microtechnologies have been developed to investigate the effects of periodic metabolic entrainment, showing that in murine fibroblasts oscillatory periodic metabolic stimulations entrain the expression of Per2, one of the core genes of the circadian molecular mechanism. Moreover, it has been proven that only by metabolic oscillations it is possible to completely reset the phase of cell-autonomous clocks. In order to develop a physiological and pathological in vitro model, achieving a high spatio-temporal control of cell culture microenvironment, frequency-encoded perturbations have been automated in a newly designed microfluidic platform for circadian applications.
Finally, to broaden the description of genes expressed with a circadian temporal pattern, a new data analysis method has been proposed and characterized, that allows to identify circadian genes in whole transcriptome data, to group genes based on the phase of their expression, to visualize transcriptome data at a glance and clearly identifying modifications at the transcriptome level from one biological condition to another one.I ritmi circadiani sono meccanismi biologici di organizzazione temporale intrinseci e autosostenuti, che consentono agli organismi di anticipare i cambiamenti ambientali e permettono loro di adattare il loro comportamento e la loro fisiologia nell’arco della giornata. L’orologio circadiano è sincronizzato dai cicli luce/buio e dall’ora dei pasti. La funzione biologica essenziale del ritmo circadiano è mantenere lo stato fisiologico dell’organismo e la sua sincronia comportamentale e metabolica con l’ambiente esterno. Recentemente è stato dimostrato che l’orologio circadiano garantisce il mantenimento dell’omeostasi metabolica, e che una distruzione del ritmo circadiano è causa di numerose malattie. L’approccio sperimentale convenzionale per lo studio dell’orologio circadiano in vitro è basato su una singola stimolazione di un solo metabolita o ormone, mentre in vivo i tessuti sono esposti in continuo a stimoli oscillatori periodici di una grande vastità di metaboliti e ormoni, le cui variazioni sono spesso interconnesse, come nel caso di glucosio e insulina. Inoltre, nell’analisi sperimentale convenzionale, sono studiati solo uno o pochi geni noti per essere implicati nell’orologio circadiano, mentre è noto che un elevato numero di geni sono espressi in modo circadiano. Lo scopo di questo progetto di ricerca è quindi sviluppare tecnologie e metodi di analisi per studiare l’effetto di stimoli metabolici in frequenza sull’orologio circadiano di tessuti periferici. Questi stimoli riproducono infatti in vitro le oscillazioni metaboliche a cui i tessuti sono esposti in vivo. Tecnologie, e più nello specifico, microtecnologie sono state sviluppate per studiare gli effetti di stimoli metabolici oscillatori, ed è stato dimostrato che in fibroblasti murini l’espressione di Per2 (uno dei geni principali del meccanismo molecolare dell’orologio circadiano) è sincronizzata da stimoli metabolici oscillatori. Inoltre, è stato dimostrato che le oscillazioni metaboliche sono di per sé sufficienti per allineare l’orologio circadiano nei tessuti periferici. Per sviluppare un modello che riproducesse in vitro condizioni sia fisiologiche che patologiche, raggiungendo un controllo spazio-temporale preciso del microambiente cellulare, le stimolazioni in frequenza sono state automatizzate in un dispositivo microfluidico progettato in modo dedicato per studi del ritmo circadiano. Infine, per estendere lo studio ai geni espressi con un pattern temporale circadiano, un nuovo metodo di analisi è stato proposto e caratterizzato. Il metodo permette di identificare geni circadiani da dati di trascrittomica, di suddividere i geni basandosi sulla fase della loro espressione, di visualizzare dati di trascrittomica nel loro complesso e di individuare rapidamente e in modo semplice modifiche a livello trascrizionale da una condizione biologica ad un’altra.
36
Gallagher, Michael William. "Coherent flow structures over mixed grain sized surfaces and their role in sediment transport". Thesis, University of Aberdeen, 1998. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU105984.
Testo completoAbstract (sommario):
The prediction of grain entrainment rates in river flows is of great importance to an engineer, as the movement of sediment can cause permanent changes to the form and character of a river. One of the key elements in achieving accurate prediction of grain entrainment rates is the understanding of the near bed flow regime, as research has revealed the existence of a number of organised flow structures which are thought to control the magnitude of shear stress applied to the bed surface. However, most of the knowledge gained on these turbulent flow structures has been from experiments conducted over smooth walls often at low Reynolds numbers. Many geophysical flows differ greatly from this scenario, having flows with high Reynolds numbers and boundaries which are rough and deformable. A series of flume experiments have therefore been conducted to investigate whether the flow structures identified over smooth walls are also present over mixed grain sized sediment beds. The first experiment used a new flow measurement technique known as particle image velocimetry to record flow field measurements over a fixed bed. Both horizontal and vertical planes of the flow were investigated (at different times) in order to obtain an understanding of the three dimensional nature of the flow. A second set of experiments was conducted over the same fixed bed, but also involved the introduction of sediment grains into the flow upstream of the measurement area. The same techniques were used to examine the flow in this case, thus enabling significant differences between the circumstances to be identified. A third set of experiments was conducted over a natural sediment and in this case flow field measurements were taken at periods of high and low transport rates, a difference in transport rate being associated with bed armouring. A short time series of near instantaneous velocity field measurements were recorded for each experimental condition to aid the identification of the flow structures. Visual inspection of the time series revealed that sweeps and ejections occur at different scales, the smallest scaling with grain size or bed features and the largest scaling with flow depth.
37
Ditas, Jeannine. "On the small-scale dynamics of cloud edges". Doctoral thesis, Universitätsbibliothek Leipzig, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-144262.
Testo completoAbstract (sommario):
Clouds are one of the major uncertainties in climate change predictions caused by their complex structure and dynamics. Numerous cloud processes are acting from cloud-scale down to mm-scale and interplay with each other as well as with atmospheric processes. This complexity on the one hand and the high spatial resolution required to analyse the small scale processes on the other hand cause difficulties in cloud research. One important and until now insufficiently understood process in cloud microphysics is the entrainment process. It defines the turbulent transport of sub-saturated environmental air into the cloud region. Subsequent mixing leads to the evaporation of cloud droplets resulting in negatively buoyant air at cloud edge. One distinguishes between two types of entrainment processes: cloud top and lateral entrainment. While the first type is mostly detected at the top of stratiform clouds, lateral entrainment plays an important role for the dynamics of cumulus clouds.
Within in this thesis, highly-resolved measurements with a resolution down to the centimeter scale performed with the helicopter-borne measurement payload ACTOS (Airborne Cloud Turbulence Observation System) are used to study both types of entrainment processes. Shear-induced cloud top entrainment leads to a turbulent inversion layer (TIL) atop of a stratocumulus layer consisting of clear air. The TIL seems to be coupled with the underlying cloud layer due to the turbulence intensity. With increasing thickness of the TIL the turbulence inside is damped monotonically leading to a maximum layer thickness and inhibiting direct mixing between cloud top and free troposphere. At the edges of shallow trade wind cumuli, shear-induced lateral entrainment generates a subsiding shell. Its evolution is analysed based on detailed measurements in continuously developing shallow cumuli. With the cloud evolution, the subsiding shell grows at the expense of the cloud core region and an increasing downdraft velocity is observed within this region. These observations are confirmed with the simulation of an idealised subsiding shell.
The results present unique observations at the edges of clouds and are an appreciable progress in cloud research which decisively influence future research.
38
Verney, John Parker. "Rhythmic perception and entrainment in 5-year-old children". Thesis, University of Cambridge, 2013. https://www.repository.cam.ac.uk/handle/1810/244940.
Testo completoAbstract (sommario):
Phonological awareness is an important component of early literacy and many children struggle to master its key elements, such as the ability to hear syllables and rhymes within the speech stream. The hypothesis explored within this study is that since music and language have parallel auditory perceptual mechanisms then training in rhythmic activities, such as music, could lead to increased understanding of the rhythmic nature required to decode early language and literacy skills. Previous research investigating the relationship between the constructs of music perception and phonological awareness has been promising, but generally inconclusive. Within the study I examine whether there is a link between the temporal processing required to process rhythmic entrainment in both phonological awareness skills and music. The data are interpreted with respect to a theoretical framework linking music and language based on temporal sampling. The ‘temporal sampling theory’ (Goswami, 2011) suggests that the decoding of both language and music is linked to the perception of accent and beat, and that the ability to hear the onset of these accents is critical within a stream of auditory events. To this end rhythmic entrainment tasks were presented in a range of musical activities including drumming along to music and singing nursery songs and rhymes. The musical and rhythmic activities were given in several different forms, to see which would be most effective in showing the children’s ability to synchronise to a beat. These were all presented at four pulse rates (400 ms, 500 ms, 666 ms, 1000 ms). Data were collected over a period of 2 years commencing in November 2009. In Study1 93 4 and 5-year-old children were tested and in Study 2 data were collected from a further 99. In addition to psychometric tests for IQ, Word Recall, teachers from the schools provided information from the children’s Foundation Stage profiles. Phonological awareness skills (syllable and rhyme) were also measured, as was reading development. Overall, children showed greater temporal accuracy (rhythmic entrainment) in keeping time with a musical piece than in keeping time with a metronome. Entrainment accuracy was greatest at the 500 ms rate, the only rate for which entrainment was as accurate with music and metronome. Individual differences in rhythmic entrainment whilst drumming were not linked to I.Q. Children were more temporally accurate when singing than in the rhythmic entrainment tasks and temporal accuracy at pulse rates of 500 ms (2 Hz) and 666 ms (1.5 Hz) showed some significant links to rhyme awareness and to reading. Temporal accuracy in singing a rhyming word on time was also greatest at 500 ms, although simply singing along to music did not show a preferred rate. Unexpectedly, temporal accuracy in singing was linked to I.Q., and was not linked independently to syllable and rhyme awareness. However, temporal accuracy in singing at the 500 ms rate was linked to reading. In Sample 2 of the PhD I report on the results of a seven-week three group matched intervention study of 99 children. The intervention was designed to investigate whether a short intervention of either music or ‘rhythmic speech’ based around the preferred rate of 500ms would lead to improved phonological awareness skills. Group 1 was given a programme of music games and songs, and group 2 was given a matched programme of games and ‘rhythmic speech’, without musical accompaniment or singing, to promote syllable and rhyme awareness. A third group, who received no additional training acted as a control. The results show that an intervention based on rhythmic structure in either a rhythmic speech form or in musical form can be successful in improving children’s phonological awareness skills. The rhythmic speech programme proved to be a more successful vehicle than the music intervention in improving the phonological skills of this group of 90 children. Both interventions were successful in improving both rhyme and syllable awareness, but the greatest improvements came in the syllable tests. There was further evidence that an intervention in either rhythmic speech or music would impact on the children’s future reading skills. Both interventions produced significantly higher correlations with a Word Reading test than the control group. There was no evidence to suggest that a musical intervention based on tapping along to a beat was of more benefit than one based on rhythmic speech. Overall the evidence gathered from the data in this study does suggest that there are direct links between rhythmic awareness, as measured by tapping to an isochronous beat, and the children’s capacity to decode phonological information. The favoured rate at which the brain processes information in both domains, thus linking them together, is at a pulse rate with an Inter Onset Interval set to 500ms. This study’s results could be used to support the development of rhythmic based interventions, in both a rhythmic speech and musical form in support of early literacy skills in 4 and 5 –year –old children.
39
Mickett, John B. "Turbulent entrainment fluxes within the eastern Pacific warm pool /". Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/11005.
Testo completo
40
Bock, Elinor Rae. "Common Ground| A Look at Entrainment in Romantic Relationships". Thesis, The New School, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3566429.
Testo completoAbstract (sommario):
Past research has shown that entrainment facilitates social bonding in intimates and strangers. The current study investigated if synchronicity in romantic couples is disrupted by relationship discord. Rocking chair movements were used as an objective measure of synchronicity. Couples rocked together for 3 minutes to assess their baseline synchronicity, and again for 3 minutes after inducing a threat to the relationship in one member of each couple. It was hypothesized that satisfied couples would be more entrained than dissatisfied couples at baseline, as well as after inducing a relationship threat. Results indicated no significant difference in rocking between satisfied and dissatisfied couples at baseline. However, results supported that synchronicity was significantly disrupted in dissatisfied couples, but not satisfied couples, after the threat was induced. These results suggest that relationship satisfaction acts as a buffer to relationship threats and/or that satisfied couples are more likely to remain entrained even in the face of hardship.
41
Breda, Carlo. "Temperature and light entrainment of the Drosophila circadian clock". Thesis, University of Leicester, 2010. http://hdl.handle.net/2381/9743.
Testo completoAbstract (sommario):
Drosophila melanogaster locomotor activity responds to seasonal conditions by modulating the “evening” activity component. During simulated winters of cold temperature and short days an advanced evening locomotor peak occurs with more daytime locomotor activity; on the other hand long photoperiods and warm temperatures give a delay in the evening peak, thereby avoiding a possible desiccation during the hottest times of the day. This pattern of activity is related to a thermosensitive splicing event that occurs in a 3’ intron in the period gene, with a higher level of splicing and earlier accumulation of PERIOD in short days and low temperatures. A mutation in norpA which encodes a phospholipase C, generates a high level of spliced per at warmer temperature, so mutants behave as if it is colder than it actually is. The relation between norpA, per splicing and the circadian neurons has been analysed. Initially, norpA expression has been investigated via in situ hybridisation and immunocytochemistry. norpA transcript has been localised among the clock pacemakers but not NORPA. Subsequently, norpA expression has been knocked-down by RNAi in specific subset of neurons. The resulting locomotor behaviour shows seasonally related effects implicating the photoreceptors, lateral and dorsal clock neurons as structures involved in timing the locomotor behaviour. In parallel, the thermal role of a second PLCβ, plc21C, has been investigated via RNAi among circadian pacemakers. It has been possible to show that plc21C expression in the photoreceptors, lateral and dorsal neurons is required to set different locomotor behaviours at different temperatures, but not via per and tim splicing. Finally, in contrast to reports that the double photoreceptor mutants involving glass and cryptochrome are “circadian blind”, these flies have been observed to entrain to light-dark cycles at moderate temperatures. Candidate orphan G protein coupled receptors have been screened in order to identify a further set of putative circadian-relevant photoreceptors contributing to this residual entrainment in glass60jcryb mutants. In constant light conditions, the RNAi of CG7497 and CG16958 generates rhythmic or arrhythmic flies depending on the genetic background tested.
42
Pan, Jin. "Gas Entrainment in Two-Phase Gas-Liquid Slug Flow". Thesis, Imperial College London, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.516177.
Testo completo
43
O'Connell, Aileen. "Observations of air entrainment and the limits of coatability". Thesis, Heriot-Watt University, 1989. http://hdl.handle.net/10399/915.
Testo completo
44
Blenkinsopp, Christopher Edwin. "Air entrainment, splash and energy dissipation in breaking waves". Thesis, University of Southampton, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.435725.
Testo completo
45
Fung, Po Kan. "A fundamental study of air entrainment in steam condensers". Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.253839.
Testo completo
46
Iaccarino, Hannah Frances. "Gamma frequency entrainment attenuates amyloid load and modifies microglia". Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/109020.
Testo completoAbstract (sommario):
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Brain and Cognitive Sciences, February 2017.Cataloged from PDF version of thesis. "January 2016."
Includes bibliographical references (pages 101-107).
Gamma oscillations (20-50 Hz), a common local field potential signature in many brain regions, are generated by a resonant circuit between fast-spiking (FS)-parvalbumin (PV)-interneurons and pyramidal cells. Changes in gamma oscillations have been observed in several neurological disorders. However, the relationship between gamma oscillations and cellular pathologies of these disorders is unclear. Here, we investigated this relationship using the 5XFAD mouse model of Alzheimer's disease (AD) and found reduced behaviorally driven gamma activity before the onset of plaque formation or evidence of cognitive decline. Because of the early onset of gamma deficits, we aimed to determine if exogenous gamma manipulations could influence disease pathology progression. We discovered that optogenetically driving FS-PV-interneurons at gamma frequency (40 Hz) reduced levels of amyloid-[beta] (A[beta])₁-₄₀ and A[beta] ₁-₄₂ isoforms in the hippocampus of 5XFAD mice. Neither driving FS-PV-interneurons at other frequencies, nor driving excitatory neurons, reduced A[beta] levels. Furthermore, driving FS-PV-interneurons at 40 Hz reduced enlarged endosomes and amyloid precursor protein (APP) cleavage intermediates in hippocampus. Gene expression profiling revealed an induction of microglia specific genes associated with morphological transformation of microglia and increased A[beta] phagocytosis by microglia. Inspired by these observations, we designed a non-invasive light-flickering paradigm that induced 40 Hz activity in visual cortex. The light-flickering paradigm profoundly reduced A[beta]₁-₄₀ and A[beta]₁-₄₂ levels in the visual cortex of pre-depositing mice and mitigated plaque load in aged, depositing mice. A GABAA antagonist completely blocked this effect; further evidence that GABAergic signaling is essential for this neuroprotective gamma activity. Finally, we showed that 40 Hz activity reduced tau phosphorylation in the TauP301S mouse model. Overall, our findings uncover a previously unappreciated function of the brain's gamma rhythms in neuroprotection by recruiting both neuronal and glial responses to mitigate AD-associated pathology.
by Hannah Frances Iaccarino.
Ph. D.
47
Lamarre, Eric. "An experimental study of air entrainment by breaking waves". Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/12685.
Testo completo
48
Witz, Matthew J. "Mechanics of particle entrainment in turbulent open-channel flows". Thesis, University of Aberdeen, 2015. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=225690.
Testo completoAbstract (sommario):
An advanced understanding of particle entrainment is required to optimise the design and maintenance of numerous open channel hydraulic systems and structures placed in these systems; including river channels and canals. This study is on particle entrainment (defined as the movement of a particle from a stationary position to being mobile in the flow). Three aspects of particle entrainment were identified as the focus of this work: First, the waiting time for an exposed particle to entrain under constant flow conditions. Second, the flow features responsible for the entrainment of an individual exposed particle. Third, the motion of an entrained particle immediately after entrainment. Waiting time was found to be highly sensitive to protrusion, with a small increase in protrusion resulting in a significant decrease in waiting time. Contrary to previous suggestions the waiting time to entrainment was found to be poorly described by an exponential distribution; instead Weibull or gamma distributions provide an improved fit in both qualitative and quantitative terms. Ensemble averaged flow fields at the point of entrainment were computed to determine the features responsible for entrainment. The data from the transverse vertical PIV plane indicated the presence of two counter-rotating vortices, with the boundary between the vortices located directly over the entrainment particle. The streamwise vertical PIV measurements showed the presence of a structure extending for a considerable distance in the streamwise direction, the length of which appeared to be independent of submergence. Further, the inclination of the downstream end of the structure appeared to increase with submergence. From the point of entrainment particle dffusion in all three coordinate directions displays an exponent significantly greater than that of ballistic diffusion. From the point of entrainment particle diffusion in all three coordinate directions displays an exponent significantly greater than that of ballistic diffusion. The results highlight the clear difference in the local scale between the diffusion of an already mobile particle with one starting from a position of rest.
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Kallingal, George J. "The Role of Gastrin-releasing Peptide in Photic Entrainment". Kent State University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=kent1208972062.
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Kishore, Aravind. "Laminar Plunging Jets - Interfacial Rupture and Inception of Entrainment". University of Cincinnati / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1397476562.
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