Tesi sul tema "Cohesive bed"
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Shaker, Amjad Hamed. "An investigation of erosion and deposition of fine cohesive sediments". Thesis, University of Southampton, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242460.
Letter, Joseph V. "Significance of probabilistic parameterization in cohesive sediment bed exchange". [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0022613.
Ockelford, Anne-Marie. "The impact of stress history on non cohesive sediment bed stability and bed structure". Thesis, University of Glasgow, 2011. http://theses.gla.ac.uk/2577/.
Ebisa, Fola Miressa. "Downstream hydraulic geometry of clay-dominated cohesive bed stream channels". Thesis, University of Ottawa (Canada), 2007. http://hdl.handle.net/10393/27838.
Lintern, David Gwyn. "Influences of flocculation on bed properties for fine-grained cohesive sediment". Thesis, University of Oxford, 2003. http://ora.ox.ac.uk/objects/uuid:f26b7e9d-9de2-4ab0-8090-feef8c3bac9b.
Llull, Marroig Antoni Ignaci. "Ship propeller induced scour of non-cohesive sediment in low bed-clearance conditions". Doctoral thesis, Universitat Politècnica de Catalunya, 2022. http://hdl.handle.net/10803/673563.
Els vaixells que maniobren en condicions de calat reduït poden provocar erosió local del llit de sediments a causa del raig d'aigua d'alta velocitat generat per les hèlix. L'erosió causa inestabilitat en les estructures dels molls, danys a la protecció del llit i pot crear grans àrees d'acreció, posant en risc la seguretat en la navegació. Aquest fenòmen està relacionat en gran mesura amb l'augment de les dimensions dels vaixells comercials en les darreres dècades i és àmpliament reconegut en les guies actuals de gestió portuària. Aquesta tesi presenta, en primer lloc, el treball experimental realitzat per estudiar els efectes erosius provocats per dos dels sistemes de propulsió més comuns: hèlix convencional i sistema de doble hèlix. A continuació, s'utilitza l'anàlisi d'un cas pràctic per avaluar l'impacte de les maniobres dels vaixells sobre el fons marí en una dàrsena portuària concreta. A la primera part de la tesi es presenten i s'analitzen en un conjunt de mesures experimentals de velocitat del flux d'aigua a la sortida de l'hèlix i de tensions de tall sobre un llit horitzontal. La distribució de velocitats axials es caracteritza a partir de mesures puntuals preses amb un sistema de tub de Pitot-estàtic acoblat a sensors de pressió diferencial. Posteriorment es realitzen mesures directes de les tensions de tall al llit amb una placa de tensions (shear plate) a tres velocitats de rotació de l'hèlix i dues distàncies verticals sobre el llit. Les mesures de la velocitat i la tensió de tall es relacionen amb un coeficient de fricció empíric que és dependent de la distància al llit. A la segona part d'aquest treball es presenta un nou conjunt d'experiments en erosió local per sistemes de doble hèlix confinats. La profunditat màxima d'erosió s'estudia en funció de la distància al sòl, la distància a la paret i la velocitat de sortida del raig d'aigua. Amb l'objectiu de reproduir maniobres de vaixells en entorns portuaris, s'analitza l'erosió generada pels sistemes de doble hèlix en règim combinat, és a dir, avant i invertit. Els resultats mostren diferències respecte els experiments tradicionals en què només es considera la rotació avant. Per estimar l'evolució temporal de la màxima profunditat d'erosió es proposen dos models empírics, un per a cada règim de rotació. De l'anàlisi de Pi de Buckingham s'obté un nou paràmetre adimensional que, proposat com a nombre de Froude del mur, permet establir un llindar d'erosió. Els resultats experimentals també mostren que la distància al mur vertical està més relacionada amb les majors profunditats d'erosió que amb la distancia al sòl. La darrera part de la tesi presenta un cas d'estudi en què les maniobres del vaixell es relacionen amb els canvis en la morfologia portuària observada al llarg del temps. El vaixell d'estudi s'obté a partir de les estadístiques d'ús de les dàrsenes portuàries. L'evolució morfològica del fons marí s'analitza mitjançant estudis hidrogràfics de la darrera dècada, que permet caracteritzar el patró d'erosió. A través de dades AIS, s'analitza la maniobra del vaixell d'estudi i s'utilitza com a model de maniobra en un simulador. La maniobra es reprodueix al simulador, d'on se n'extreu el comportament dels motors principals i de les hèlix de maniobra. El patró de maniobra i el comportament dels motors s'utilitzen per avaluar les seccions de maniobra més perjudicials, que resulten ser l'aproximació lateral del vaixell al moll d'atrac, durant la maniobra d'arribada, i les primeres etapes de la maniobra de sortida.
Enginyeria nàutica, marina i radioelectrònica naval
Mooneyham, Christian David. "Interaction of Clay Wash Load With Gravel Beds". Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/84547.
Master of Science
Harsanto, Puji. "Erosion Characteristics of Cohesive Sediment Bed and Bank, and Their Effects on River Morphology". 京都大学 (Kyoto University), 2012. http://hdl.handle.net/2433/160989.
Thompson, Charlotte E. L. "The role of the solid-transmitted bed shear stress of mobile granular material on cohesive bed erosion by unidirectional flow". Thesis, University of Southampton, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398824.
Rangel, Roberto Carlos. "Evolution of a non-cohesive granular bed subject to a succession of erosive turbidity currents". Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36712.
Includes bibliographical references (leaf 18).
An experiment was performed to study the evolution of a non-cohesive granular bed subject to a succession of erosive turbidity currents to evaluate the applicability of a proposed interface model that prescribes a relationship between the bed shear stress and the local bed elevation and local bed slope. This study considered only the relationship between the local bed elevation and the shear stress by using non-cohesive plastic particles as bed sediment that was laid down in a subaqueous straight channel. The elevation of the plastic bed was measured before and after it was subjected to two erosive salt water turbidity currents using a high resolution displacement laser mapping system. These changes in elevation of the sediment bed are compared to determine whether a correlation exists between local bed elevation and bed erosion. The results from this experiment display a weak correlation between the erosion of the plastic bed and the initial local bed elevation when the initial elevation height is small relative to the thickness of the turbidity currents.
(cont.) However, a strong correlation exists when the initial elevation height is approximately 2% to 6% of the turbidity current thickness. The strength of this correlation also depends upon the window size of the analysis which is shown to be associated with the downstream variability in bed roughness.
by Roberto Carlos Rangel.
S.B.
Patterson, Shelley M. "The effects of ballistic impact of littorinid shells on the erosion of a cohesive clay bed". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ58430.pdf.
Papenmeier, Svenja [Verfasser]. "Properties and dynamics of suspended load and near-bed fine cohesive sediments in highly impacted estuaries. Case studies from the Weser, Ems and Elbe estuaries (Germany) / Svenja Papenmeier". Kiel : Universitätsbibliothek Kiel, 2012. http://d-nb.info/1029457085/34.
Ralaiarisoa, Velotiana Jean-Luc. "Influence de la cohésion sur le transport éolien de particules : application au sable humide et à la neige". Thesis, Rennes 1, 2020. http://www.theses.fr/2020REN1S065.
This thesis deals with the cohesion effect on the aeolian grain transport. We consider the sand and snow case. A numerical approach to the erosion process by impact allows us to quantify the cohesion effect on the Splash process. Then we adopt wind tunnel experiment to study the effect of the cohesion on the transport. We show over a dry sand bed a transition from the saltation regime to a collision one at a Shields number of 0.3. Over a wet sand bed, the aerodynamic threshold increases with the water content whereas the impact threshold is in the same order of magnitude compare to the dry case. Over a hard snow bed, the characteristic decay height shows a quadratic dependence with the air friction speed and increases with the particle diameter. The characteristics of the aeolian transport over a cohesive snow bed are close to those over a hard one. There is a sharp decrease of the transported snow flux which can increase significantly when the wind tunnel is fed with an incoming snow flux. Our results indicate the mass flow rate aims to a saturation. However the saturation is not reached with the wind-tunnel length we work over wet sand and cohesive snow bed
Zaidan, Jana. "Scοur investigatiοn arοund a bridge pier fοunded in cοhesive sοil". Electronic Thesis or Diss., Normandie, 2023. http://www.theses.fr/2023NORMLH22.
Local scour is considered to be one of the main causes of bridge failure and collapse. Laboratory experiments are a crucial and important approach for the scour process investigation. Yet, there is no robust and standard instrumentation for tracking the evolution of this physical phenomenon in laboratory studies. There are several flume-based studies of scour around a circular bridge pier on cohesionless soil. However, the bed of natural alluvial channels often contains cohesive sediments. Comparatively, there is a limited research on local scour around circular pier founded in cohesive beds that has been documented. In this PhD research, a 3D Laser Scanner is used to monitor scour around a circular pier. The results obtained with this technique, in line with previous research, in particular that carried out on a sandy bed, demonstrate its effectiveness. The technique offers advantages such as continuous spatiotemporal monitoring, but also many limitations. In a next step, the study focused on the effect of the type and proportion of fines in the sediment mixture on the depth and the shape of the scour hole and the temporal propagation of scour process around a circular pier. Results show that increasing the clay in the fine fraction reduce significantly the scour. The mixture with a range around 7.5-10 % of clay fines content provides the threshold composition for coherent soil behavior in scouring process. In addition, scour depth prediction for bridge piers in cohesive soil is not yet fully developed. In engineering practice, scour depth estimation methods currently used are those proposed for sand bed. Many researches aimed to adress a method to optimize the design of bridge piers in the case of cohesive soil. Among the different methods, the one based on the use of the EFA (Erosion Function Apparatus) erodimeter and called SRICOS (Scour Rate In COhesive Soil) was examined as part of this work in order to predict the deepest scour in cohesive bed
COLETTO, MAURICIO MIGUEL. "Atmospheric Freeze Drying of Food in Fluidized Beds - Practical aspects and CFD simulation". Doctoral thesis, Politecnico di Torino, 2015. http://hdl.handle.net/11583/2588248.
Israel, Devadason Benjamin Praisy. "Contraction scour in compound channels with cohesive soil beds". Texas A&M University, 2007. http://hdl.handle.net/1969.1/85810.
Putta, Sriram. "Elastodynamic Numerical Characterization of Adhesive Interfaces Using Spring and Cohesive Zone Models". The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu156338398610629.
Skipworth, Peter John. "The erosion and transport of cohesive-like sediment beds in sewers". Thesis, University of Sheffield, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245698.
Yin, Daowei. "Genesis and evolution of bedforms on cohesive mud beds and simulated bedrock channels". Thesis, University of Leeds, 2013. http://etheses.whiterose.ac.uk/6358/.
Schumacher, Martin Robert [Verfasser], e Andrei [Akademischer Betreuer] Lupas. "Cohesin-assoziierte Proteine und ihre Funktion bei der Schwesterchromatid-Kohäsion / Martin Robert Schumacher ; Betreuer: Andrei Lupas". Tübingen : Universitätsbibliothek Tübingen, 2012. http://d-nb.info/1162843616/34.
Braziulytė, Asta. "Karių, dalyvavusių tarptautinėje misijoje Afganistane, potrauminio streso sąsajos su patiriamais stresogeniniais įvykiais bei subjektyviai vertinamu grupės sutelktumu". Master's thesis, Lithuanian Academic Libraries Network (LABT), 2009. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2009~D_20091222_104451-94115.
Aiming to assess the psychological condition of soldiers, who have returned from an international mission in Afghanistan, the incurred stressogenic events, to find out what stressful situations cause post-traumatic stress, the stressogenic events they have experienced as well as development of post-traumatic stress and unit cohesion are the scope of analysis of this paper. 111 soldiers, who had returned from an international mission, were interviewed using the following surveys: Soldiers' Stress Survey, Mississippi Scale for Post-traumatic Stress, Unit Cohesion. The results demonstrated that the soldiers, who had experienced more stressogenic events and evaluated the unit cohesion with a lower grade, had a deeper post-traumatic stress symptoms than those, who had experienced the same number of stressogenic events but gave a better evaluation of the unit cohesion. It has been established that in the event of lower unit cohesion, soldiers experience deeper post-traumatic stress symptoms, regardless of incurred stressogenic events. The depth of post-traumatic stress symptoms did not vary between groups of soldiers having higher education degree and those who did not, as well as between older and younger or the ones, with bigger stressogenic event experience.
Raghavan, Sathyanarayanan. "Experimental and theoretical study of on-chip back-end-of-line (BEOL) stack fracture during flip-chip reflow assembly". Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/54298.
Chen, Xingnian. "Numerical Study of Abutment Scour in Cohesive Soils". 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2008-12-225.
Yang, Shie-Chen, e 楊士震. "Dynamic Behavior of Cohesive Granular Materials in a Vibrated Bed". Thesis, 2000. http://ndltd.ncl.edu.tw/handle/96227848453209178607.
國立中央大學
機械工程研究所
89
This thesis examines the dynamic behaviors of granular materials subjected to external vertical vibration. The cohesionless and cohesive materials are considered in this thesis. Two-dimensional discrete element computer simulation is used to study the flow behaviors, self-diffusion and mixing of vibration granular flows. Experiment was also performed to supplement the simulation results of the current study. The flow behaviors of convection cells of cohesionless materials under vertical vibration are first investigated by simulation. The flow pattern and velocity vectors are consistent with the former experimental results. The profiles of solid fractions and the granular temperatures with the altitude of granular bed are studied with different vibration conditions. A power law relation exists between the convection flow rate and the dimensionless vibration velocity. The influences of flow parameters on self-diffusion in the vibrated granular bed are studied by simulation and experiment. Employing the image processing technology and particle tracking method, the local displacements and velocities of particles are measured. The self-diffusion coefficients are determined from the history of particles’ diffusive displacements. The DEM simulation is performed to calculate the particles’ self-diffusive displacements with the same flow parameters and material properties as the experiment. The simulation results are compared to the experimental tests. The flow behaviors of convection cell are strongly related to the self-diffusion of particles induced by the energy input from the vertical external vibration. The velocity fluctuations, granular temperature and self-diffusions are anisotropic with greatest components in the vertical direction. The dependence of the diffusion coefficients on the dimensionless acceleration, vibration amplitude, vibration frequency, solid fraction, velocity fluctuations, restitution coefficient and granular temperature are discussed carefully. The wet particles with the effect of liquid bridge are used as the cohesive granular materials. Three types of viscous liquids with different tension and viscosity are used in this thesis. A simplified model of dynamic bridge strength based on the superposition of lubrication and circular capillary force approximation is incorporated in the DEM model. The energy dissipations during vertical vibration are generated from the friction and inelasticity between particles, viscous resistance and liquid bridge bond rupture due to the liquid bridge. For cohesive granular materials, the energy dissipation is mainly associated with the viscous force, the interparticle friction and the inelasticity of collision, rather than with the capillary force of liquid bridge. The liquid bridge force due to surface tension and viscosity interacts with frictional force mutually to determine the strength of the convection flow rate. The energy dissipation increases monotonously with the increase of the dimensionless interstitial liquid volume, and the distributions of the energy dissipation are strongly influenced by the properties of viscous liquids. The self-diffusion motions for cohesive materials are faster than those of cohesionless materials. The mixing of vibrated granular flow is strongly dependent on the self-diffusivity of particles and is related to the magnitude of interstitial liquid volume between particles.
Glasbergen, Kenneth. "The Effect of Coarse Gravel on Cohesive Sediment Entrapment in an Annular Flume". Thesis, 2014. http://hdl.handle.net/10012/8288.
Galvagno, Giampiero. "A study of scour below Ruskin Dam spillway using a non-cohesive bed hydraulic model". Thesis, 1998. http://hdl.handle.net/2429/7672.
Morozowa, Julia. "Adhäsionsentstehung, Adhäsionsprophylaxe bei Myomektomien (mit 2 prospektiv randomisierten Studien Adhibit (Cohesion) und Spraygel (Confluent)". 2005. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=014907413&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
Rodrigues, Bárbara da Costa Carlos de Almeida. "Liderança, coesão e desempenho e bem-estar das equipas desportivas". Master's thesis, 2019. http://hdl.handle.net/10400.12/7297.
O presente estudo tem como objetivo principal compreender se a liderança do treinador tem influência no desempenho e bem-estar da equipa, e ainda compreender se essa relação é mediada pela coesão. A amostra é constituída por 110 jogadores de futebol e rugby, em que 90 pertenciam ao sexo masculino e 20 ao sexo feminino, com idades compreendidas entre os 14 e superior ou igual a 25 anos (M=19,3; DP=3,8). Para avaliar as variáveis em estudo foram utilizados quatro instrumentos: a escala Multidimensional de Liderança no Desporto, de Gomes e Resende (2014); o questionário de Perceção de Rendimento Desportivo, de Gomes (2016); a Warwick-Edinburgh Mental Well-being Scale (WEMWBS), de Kammann e Flett (1980), e ainda, a escala Group Environment Questionnaire, de Carron, Brawley e Widmeyer (1985). Os resultados obtidos demonstram que as hipóteses de estudo foram suportadas, constatando que existe uma relação significativa entre a liderança transformacional e o desempenho percebido e bem-estar da equipa. Além disso, testemunhou-se que existe impacto significativo da liderança transformacional no desempenho percebido, tal como no bem-estar da equipa, por meio da coesão.
The main objective of this study is to understand if coach leadership has influence on team performance and well-being, and also to understand if this relationship is mediated by cohesion. The sample is composed by110 soccer and rugby players, in which 90 were male and 20 female, with a range of age14 to over 25 years old (M = 19.3; SD = 3.8). In order to evaluate the variables in this study, four instruments were used: the Multidimensional Sport Leadership scale, by Gomes and Resende (2014); the Sports Perception Questionnaire, by Gomes (2016); the Warwick-Edinburgh Mental Well-being Scale (WEMWBS) by Kammann and Flett (1980); and the Group Environment Questionnaire, by Carron, Brawley and Widmeyer (1985). The results reveal that the study hypotheses were supported, showing that there is a significant relationship between transformational leadership and perceived performance and well-being of the team. Besides that, it has been witnessed that there is a significant impact of transformational leadership on perceived performance as well as team well-being, through cohesion.
Santos, Rita Menezes dos. "Exigências laborais associadas ao stress profissional e bem-estar laboral: O papel moderador da coesão grupal percebida". Master's thesis, 2010. http://hdl.handle.net/10071/4996.
The organizational world is constantly changing, whether due to globalization, increased competition, economic crises that follow, which makes it possible for organizations and their employees are subject to extreme demands. In this sense, is of increasing relevance in studies of stress and well-being at work, and that this study proposes to examine the relationship between job demands and occupational stress and perceived psychological well-being, as well as check the moderating role that perceived group cohesion has on the relationship between perceived job demands and perceived occupational stress and psychological well-being. The sample consists of 158 individuals belonging to a hotel group, and the questionnaires occurred electronically and personally. The results allowed to demonstrate that there is a strong relationship between the job demands of time with either perceived occupational stress, either psychological well-being, and in this second case the strongest correlation. Furthermore, perceived group cohesion had a moderating role between job demands and occupational stress and perceived psychological well-being, and yet a strong predictor of psychological well-being.