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1
Hall, Nicola Jane. "An Exploration of Military Doctoral Students' Journey to Degree Completion." ScholarWorks, 2019. https://scholarworks.waldenu.edu/dissertations/7227.
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Little is known about the experiences of doctoral students who are active duty military or veterans seeking a degree in counselor education and supervision (CES). The purpose of this research was to positively impact the counseling profession by ensuring adequate representation of military-competent counselors through an exploration of the academic journey of military students. This research sought to highlight military students' perceptions of barriers and contributors to degree completion. Selection criteria for participants involved any United States military personnel classified as active or inactive. These military personnel had to have earned within the past 12 months or were currently enrolled in a counselor education and supervision PhD program at an institution accredited by the Council for Accreditation of Counseling and Related Educational Programs. This research adopted a phenomenological hermeneutic theoretical approach to explore the lived experiences of 6 military students on their journey to degree completion in a CES doctoral program. The central research question focused on the lived experiences of military CES students related to their journey towards degree completion. Key results emerged in the form of themes that contributed to degree completion such as helping other veterans/giving back and programmatic fit. Themes that showed prevalent barriers to degree completion included professional identity development, military students and degree completion, environmental factors, and access to military counselors. The implications of this study for social change include supporting academic institutions in reducing the attrition rates of military CES students.
2
Philip, Croné. "Thermo-Elasto-Hydrodynamic lubrication modeling of Tilting Pad Journal Bearings." Licentiate thesis, Luleå tekniska universitet, Maskinelement, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-71105.
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The journal bearing is a critical machine element typically used to support rotating motion in high speed machinery. Through the generation of a hydrodynamic pressure in its thin lubricant film,which is usually in the order of 10-100μmthick depending on the diameter of the journal itself, the bearing is able to withstand large loads, both statically and dynamically, while having a very low rate of wear. It is of course essential that these components provide for a safe operation with as little wear and frictional losses as possible and it is therefore of great interest to develop simulation models of constantly increasing accuracy. Typical relevant quantities when designing a bearing are the load carrying capacity, metal/oil temperature, minimum film thickness, stiffness, damping and power loss. Classical lubrication theory builds upon the Navier-Stokes equations which, with the thin film approximation, can be reduced to a single equation which governs the hydrodynamic pressure build up in the lubricant. Since the problem now has been reduced to solving a single non linear partial differential equation in 2 dimensions, a significant advantage in terms of simulation time compared to the full set of Navier-Stokes equations can be enjoyed with an, in most cases, insignificant error of approximation. However, with time, as the need for bearings capable of operating at higher loads,speeds and with new designs involving more complex geometries, such as, for example, textured surfaces, the applicability of classic thin film theory should not be taken for granted, especially not when there is an increasing amount of turbulence involved. The purpose of the work contained in this thesis is to develop and asses the performance of a state of the art 3D TEHD model using the commercial finite element multi physics software COMSOL Multiphysics. Of special interest is the assessment of the Menter Shear Stress Transport (SST) turbulence model, which is a widely used, standard, 2-equation RANS eddy viscosity model, in predicting characteristic values for a bearing operating in the transition range between laminar and turbulent flow. A comparative study is carried out where the present model is benchmarked against experimental data on a large 4 pad tilting pad journal bearing. The present model is also compared to one of the classic models based on thin film theory. The present model is also used to study the influence of the geometry that constitutes the leading edge groove in a tilting pad journal bearing on the turbulence levels. Finally the possibility of using a shear thinning lubricant for reducing the bearing power loss is investigated. The calculations were all performed using the resources of the super computer cluster at HPC2N at Ume ̊a University. The results clearly show the inadequacy of the SST turbulence model when performing calculations on a bearing operating in the transition range between laminar and turbulent flow. Moreover, the model predicts slightly higher average values of turbulence in a leading edge grooved bearing compared to a conventional one, yet a higher maximum value in the latter.
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Harris, Joel Mark. "Static characteristics and rotordynamic coefficients of a four-pad tilting-pad journal bearing with ball-in-socket pivots in load-between-pad configuration." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-3194.
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Ferguson, Larry T. Myers Jamie. "Voice, power, technology joining the Technology Literacy Club via a journey from the projects to a Ph.D. /." [University Park, Pa.] : Pennsylvania State University, 2008. http://etda.libraries.psu.edu/theses/approved/WorldWideIndex/ETD-2457/index.html.
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Campbell, Thomas Michael. ""The Highwayman" : redefining the hero's journey /." Available to subscribers only, 2007. http://proquest.umi.com/pqdweb?did=1328057801&sid=20&Fmt=2&clientId=1509&RQT=309&VName=PQD.
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Fingerhut, Aaron. "Drug dealers : a journey to crime /." Available to subscribers only, 2008. http://proquest.umi.com/pqdweb?did=1559853391&sid=9&Fmt=2&clientId=1509&RQT=309&VName=PQD.
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Michelson, Helena. "I. Music and poetic word : the romances of Sergei Rachmaninoff ; II. A journey metamorphosed for orchestra /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2003. http://uclibs.org/PID/11984.
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Weyland, Sandra. "Translation models and model translations : a journey across languages, time and cultures." Thesis, University of Aberdeen, 2000. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=217102.
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This thesis studies the effectiveness of existing translation models in the context of everyday translation and proposes a new translation model. The thesis reviews a number of approaches to the process of translation from the Roman times to the present before focusing on contemporary translation theory and the representation of the translation process by means o f translation models. The thesis introduces - and comments on - a number of existing translation models and then proceeds to develop a new model of the process, which aims to present a more holistic view of the process than the models discussed. The second part of the thesis concentrates on the testing of the model. Two very practical tests are applied to the model in order to assess the accuracy of the representation and the usability of the model in the context o f everyday translation. The first test applied to the model has, however, another function. It aims to provide a contemporary readership with a readable English translation of a Renaissance Latin text, the first book of the Instructiones historico-theologicae de doctrina Christiana et vario rerum statua temporibus Apostolici, ad tempora usque seculi decimi septime prior a (1645) by John Forbes o f Corse. This enables a wide audience with very little or no knowledge o f Latin to gain access to the complex theological argument contained in the specimen text. The commentary on the English translation, and on extracts of the German and French translations of this work serves to test the applicability of the model in the context of translation into more than one language. The second test concentrates on the translation from English into German and German into English. For this test, two groups of students from the Universities of Trier and Rostock in Germany were asked to carry out the same translation exercise. The study o f the work received from these students allows me to assess the usability o f the model as a guideline for translators. The thesis concludes by saying that the model has proved successful on both occasions, and by offering suggestions for further study.
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Luetkenhaus, Jeffrey M. ""The Taming of the Shrew" : a journey of discovery /." Available to subscribers only, 2007. http://proquest.umi.com/pqdweb?did=1324373831&sid=1&Fmt=2&clientId=1509&RQT=309&VName=PQD.
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Harangozo, Andrew Vilmos. "An investigation into the effects of lubrication methods on the performance of the tilting-pad journal bearing." Thesis, Brunel University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.257671.
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Sabnavis, Giridhar. "Test Results for Shaft Tracking Behavior of Pads in a Spherical Pivot Type Tilting Pad Journal Bearing." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/32574.
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Most tilting pad journal bearing dynamic characteristics estimation methodologies assume perfect shaft tracking by the pads. In other words, they neglect pivot friction. In case of pads having point or line contact that operate under most normal load conditions, the pad tilting is due to a rocking motion which is not greatly influenced by friction. Hence this simplifying assumption might be acceptable. Heavier loading conditions, such as those typically encountered in gearboxes, demand the use of spherical pivots to avoid pivot failure. The spherical pivot is very attractive for this reason, but the tilting motion is rather a sliding action that must occur in the precision ball socket. A valid concern exists for verifying the soundness of assumed shaft tracking by the pads of such bearings. A â fixed test bearing, floating shaftâ type of test rig previously built for determining the dynamic characteristics of bearings was accordingly modified to facilitate the testing of shaft tracking for a spherical pivot bearing.
This thesis describes the modifications carried out on the rig. The special instrumentation and data acquisition systems implemented to observe the minute pad motion are also discussed. Some preliminary results of the tests are presented for various loading conditions. They show excellent shaft tracking by the pads. More detailed testing and analysis of data is required to fully understand the pad motion and tracking ability of the spherical pivot design.Master of Science
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Defenbaugh, Nicole L. "Sites of discovery : a narrative journey of the IBD body /." Available to subscribers only, 2007. http://proquest.umi.com/pqdweb?did=1490072291&sid=1&Fmt=2&clientId=1509&RQT=309&VName=PQD.
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Balbahadur, Avinash Chetnand. "A Thermoelastohydrodynamic Model of The Morton Effect Operating in Overhung Rotors Supported by Plain or Tilting Pad Journal Bearings." Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/26369.
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Unlike most instabilities, which are non-synchronous in nature, the Morton Effect is a synchronous phenomenon. This thermal instability occurs primarily in overhung rotors that are supported by fluid film bearings and is caused by differential viscous shearing within the bearing lubricant. The Morton Effect has also gained much attention within the last decade.
Prior studies of the Morton Effect have used complex analysis in the frequency domain to model this instability. However, such an approach makes it difficult to develop a user-friendly design tool for engineers. The current research employs a steady-state analysis to predict the onset of the Morton Effect, and it uses an instability criterion which is based on a threshold unbalance caused by a force equal to 15% of the weight of the rotor. It is hoped that this method will provide a more easily adaptable platform for design and analytical purposes.
The current model has demonstrated good agreement with other theoretical models and experimental data. This agreement applies to rotors that are supported by either plain or tilting pad journal bearings and it was found that a worse case scenario for the Morton Effect would involve centered, circular and large-amplitude bearing orbits.
A test rotor was also designed and built. Initial experimental data revealed an unusual instability that might have been caused by the Morton Effect.Ph. D.
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Manous, Michael Lee. "Travel stunts and literary performances the wager journey in England, 1579-1653 /." Diss., UC access only, 2009. http://proquest.umi.com/pqdweb?did=1974746341&sid=1&Fmt=7&clientId=48051&RQT=309&VName=PQD.
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Thesis (Ph. D.)--University of California, Riverside, 2009.Includes abstract. Includes bibliographical references (leaves 556-579). Issued in print and online. Available via ProQuest Digital Dissertations.
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Meyer, Patricia. ""We're Just Women Who Like To Ride:" An Ethnographic Journey On A Woman's Motorcycle." Available to subscribers only, 2009. http://proquest.umi.com/pqdweb?did=1879047041&sid=4&Fmt=2&clientId=1509&RQT=309&VName=PQD.
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Thesis (Ph. D.)--Southern Illinois University Carbondale, 2009."Department of Speech Communication." Keywords: Gender, Motorcycle, Women. Includes bibliographical references (p. 143-157). Also available online.
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Cubillo, Adrian. "Physics-based approach to detect metal-metal contact in the hydrodynamic bearing of a planetary transmission." Thesis, Cranfield University, 2016. http://dspace.lib.cranfield.ac.uk/handle/1826/11585.
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Health condition monitoring, commonly referred as Integrated Vehicle Health Management (IVHM) for fleets or vehicles, studies the current and future health state of a system. Health monitoring techniques based on data driven approaches have proven successful in several areas and are easily scalable; however they do not rely on the understating of the physics of failure; whereas Physics-based Model (PbM) approaches require expert knowledge of the failure modes and are based on the understanding of the component behaviour and degradation mechanisms. The development of IVHM is particularly challenging for legacy aircraft due to the restrictive regulations of the aerospace industry. This thesis proposes a novel PbM technique to detect metal-metal contact in hydrodynamic bearings. The planetary transmission of an aircraft’s Integrated Drive Generator (IDG) is used as a case study. Research on the detection of metal-metal contact in hydrodynamic bearings has focused on data driven approaches using vibration or acoustic emissions rather than on PbMs. The proposed technique estimates metal-metal contact by modelling the physical phenomena involved in the failure mechanism and only the speed, load and temperature are required as inputs, all of them available in the IDG and not requiring any additional sensors. The study of metal-metal in hydrodynamic bearings in the field of tribology has focused on mixed lubrication models of the whole bearing, or computational models accounting for local effect under the hydrodynamic lubrication region. In addition to the IVHM technique, this thesis contributes to the field of tribology by proposing a computational mixed lubrication model capable of studying metal-metal contact locally along the lubricated surface of the bearing. Experimental results of a plain journal bearing have been used to validate the PbM and a replica of the transmission of the IDG has been tested to evaluate the effectiveness of the proposed technique at detecting metal-metal contact.
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Rowan, D. "Design and development of a high-speed test facility and the measurement of the fluid film characteristics of journal bearings." Thesis, Cranfield University, 1998. http://dspace.lib.cranfield.ac.uk/handle/1826/11357.
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In the theoretical analysis of high speed rotor bearing systems, it is common to use
four displacement and four velocity based coefficients, which characterise the
behaviour of the lubricating fluid film. Although a great deal of work has been
published establishing theoretical models of all types of hydrodynamic journal bearings,
the large amount of experimental work has centred on relatively low speed conditions.
This work presents a contribution to the experimental study of the static and dynamic
characteristics of oil films in journal bearings used in high-speed rotating machinery.
The main objectives of the work are:
• To devise new experimental techniques for the measurement of dynamic
coefficients suitable for use at high rotational speeds
• To design, manufacture, assemble and commission a test facility to measure
the static and dynamic characteristics of journal bearings at speeds up to
30000 rpm
• To determine the static and dynamic characteristics of a 5 Pad Tilting Pad
Journal Bearing Unit of 80 mm diameter at speeds up to 25 000 rpm using the
said test facility.
New techniques are particularly necessary for the measurement of velocity coefficients
because these invoke the necessity of imposing a velocity on to the bearing housing
and previous techniques have utilised synchronous motion of the bearing.
Consequently a new experimental procedure for measuring the four velocity or
damping coefficients of an oil film journal bearing from imposed dynamic "orbits" has
been devised called the "double pulse" technique. All four velocity coefficients are
derived from one imposed journal centre dynamic orbit and, therefore may be regarded
as being obtained at the same time. The method requires the production of a "cross-
over" point similar to that of a "figure of eight" shaped orbit and utilises the "cross-over"
point therein.
Coefficients are initially evaluated in a co-ordinate system, which is chosen to align with
the designated parts of the measured orbit. Each coefficient is then evaluated from
single values of instantaneous imposed force and resulting journal centre velocity.
Coefficients are them converted into any other desired axes system. The result is a
simpler experimental procedure, with reduced uncertainty compared to hitherto existing
methods.
The use of non-sinusoidal excitation of the oil film was explored, in the form of applying
a step-pulse train load pattern to produce a cross-over pattern in the journal
displacement ·orbit'.
Experimental tests were completed on a tilting pad bearing at speeds up to 15 000 rpm
inclusive. At speeds above this, the bearing exhibited a vibrational response, which
precluded the accurate measurement of journal centre displacement.
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Dufka, Zbyněk. "Webový systém pro správu elektronických dokumentů." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2015. http://www.nusl.cz/ntk/nusl-220379.
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The aim of this diploma thesis is to provide a systematic study of Open Journal System, which is designed for electronic research papers publishing. Due to the nature of information published in this system, there is an elaborate approval process controlled by the editor. The main objective of this thesis is the realization of a system module, which would, at the end of the approval process, implement a stamp incorporating metadata of the source magazine to individual electronic documents. The thesis gives insight into the development of the structure of the Open Journal System and, briefly, describes the possibility of implementing this system. Another part of the work focuses on the sub-steps of the stamping module which was implemented into the system. This module allows editors to stamp individual electronic PDF documents that are published within the magazine and its various volumes. The module is designed to simplify the editing process of the journal with no prolongation or any other additional time required. Among other things, the reader learns how it is possible to create a block module, which can be used in the sidebar to display any system information. The work, also, previews the possibility to customize the user interface. Each implemented part contains solution proposals and, further, the implementation method and technical description is described in more detail. For better understanding and integrity of the work, stretches of the given code are also included, this might serve as an inspiration for users‘ modifications of the system.
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Plantegenet, Thibaud. "Analyse expérimentale de l'effet Morton." Thesis, Poitiers, 2019. http://www.theses.fr/2019POIT2319.
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Cette thèse a pour objectif d’étudier expérimentalement l’effet Morton pour différents types de paliers et un rotor rigide ou flexible. L’effet Morton est un phénomène d’instabilité thermique se produisant dans les paliers hydrodynamiques qui a pour conséquence d’influencer le comportement vibratoire du système rotor-palier. L’introduction permet d’évoquer les différents phénomènes d’instabilité thermique, en se concentrant dans un premier temps sur l’effet Newkirk pour en décrire mathématiquement son fonctionnement et comprendre la philosophie des phénomènes d’instabilité thermique. L’étude bibliographique de l’effet Morton est ensuite détaillée (cas industriels, modélisation numérique et analyse expérimentale). La première analyse expérimentale est réalisée pour un rotor rigide supporté par un palier cylindrique. Avant l’analyse des essais dans cette configuration, le banc d’essais est détaillé, les caractéristiques dynamiques du palier sont identifiées expérimentalement. Les essais réalisés à vitesse constante montrent la présence de l’effet Morton « stable ». La seconde étude est conduite avec un rotor flexible et permet de mettre en évidence l’influence du temps de démarrage sur l’apparition d’un comportement instable. La dernière étude expérimentale est réalisée avec le rotor flexible supporté par un palier à patins oscillants à pivots flexibles. Le palier étant d’une conception particulière, une étude bibliographique permet de comprendre son fonctionnement, ses points forts et ses applications. Sa conception, son dimensionnement et sa caractérisation expérimentale sont ensuite détaillés, puis les résultats expérimentaux montrent l’influence du balourd initial sur la stabilité. Pour finir, les résultats expérimentaux de chaque configuration sont comparés et permettent de mieux appréhender le comportement de l’effet Morton dans les paliers hydrodynamiques et son influence sur la dynamique du rotorThe main goal of this thesis is the experimental study of the Morton effect in hydrodynamic bearing for rigid and flexible rotors. The Morton effect is a thermally induced increase of the synchronous vibration phenomenon that appears in journal bearing. The introduction part permits to describe the thermal instabilities with firstly a focus on the Newkirk effect and its mathematical description to understand the philosophy of thermal instabilities. Bibliography study of the Morton effect is fully described (case studies, numerical analyses, experimental analyses). The first experimental analysis is conduct for a rigid rotor on a plain journal bearing. In this configuration, the test rig is detailed, the dynamic characteristics of the bearing are experimentally identified and then the tests at constant rotational speed show the “stable” Morton effect. The second study is achieved with a flexible rotor and permits to show the influence of the start-up time on the Morton effect stability. The last experimental study is realized with the flexible rotor on a tilting pad journal bearing with flexible pivot. This bearing being of a particular design, a bibliography allows to understand its principles, its pros and cons and its applications. Its design and its experimental characterization are detailed and then the experimental results show the unbalance influence on stability. To conclude, experimental results are compared and allow a better understanding of the Morton effect in the journal bearing and its influence on the rotordynamic
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"While on my Journey: A Life Story Analysis of African American Women in Pursuit of their Doctoral Degrees in the Southwest." Doctoral diss., 2013. http://hdl.handle.net/2286/R.I.18168.
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abstract: The purpose of this study is to explore the lived experiences of African American women in pursuit of doctoral degrees in the southwest, their challenges and motivations, and plans for the their next chapter. Drawing from critical race theory and a sociocultural framework, this qualitative study uses Dan McAdams' Life Story Interview (McAdams, 2005) to explore the journeys of these high achieving minority women and how achievement is conceptualized in their stories. Particular emphasis is placed on their critical events, challenges, and alternative futures. Seven separate themes (parental support and advocacy in early education, improved experiences among other African American students, perseverance through struggles/experiences led to purpose, poor department support, family support, impact of spirituality, and relocation and desire to give back) emerged that address three main research questions. Implications for findings and suggestions for future research are offered.Dissertation/Thesis
Ph.D. Educational Psychology 2013
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Davis, Francis G. "Amanda's journey." 2008. http://proquest.umi.com/pqdweb?did=1559857551&sid=1&Fmt=2&clientId=14215&RQT=309&VName=PQD.
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Thesis (Ph.D.)--University of Nebraska-Lincoln, 2008.Title from title screen (site viewed Dec. 15, 2008). PDF text: v, 91 p. ; 409 KB. UMI publication number: AAT 3310977. Includes bibliographical references. Also available in microfilm and microfiche formats.
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Cloud, Charles Hunter. "Stability of rotors supported by tilting pad journal bearings /." 2007. http://wwwlib.umi.com/dissertations/fullcit/3248087.
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Lin, Heng Yi, and 林恒毅. "Design and Manufacturing of Pivoted Tilting Pad Journal Bearing." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/07348840212130445052.
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碩士南開科技大學
車輛與機電產業研究所
99
This paper conducts a research on the design and manufacture of the tilting pad journal bearing. The heat-transfer problems associated with the high capability and high-speed spinning of tilting pad journal bearing lead to the need of well lubrication cooling in the bearing system. The main consideration is the flow runner design of lubricant oil. The important parameters in the design include (1) numbers and layouts of tilting pad, (2) design of preload, (3) amount and flow runners of lubricant oil, (4) cooling types of bearing, and (5) sensing of bearing temperature. During the manufacture of bearing, a layer of 0.5mm Babbitt metal is applied on the tilting pad for increasing lubricity and wear-resistance. In order to produce high hydrodynamic oil pressure between the pad and the bearing, a bearing clearance at the order of a few micrometers is manufactured accompanied with highly fine surface roughness and product quality. The results show that the tilting pad journal bearing possesses the capabilities of high rigidity and high buffering to effectively raise the whirl threshold of the pad bearing, which accordingly makes the rotating spindle operates in a good and stable running condition. Also the new design of the oil runner in this paper provides a good lubricated effect at a lower oil consumption as the pad bearing is performed
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Wilkes, Jason Christopher. "Measured and Predicted Rotor-Pad Transfer Functions for a Rocker-Pivot Tilting-Pad Journal Bearing." Thesis, 2011. http://hdl.handle.net/1969.1/ETD-TAMU-2011-12-10366.
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Many researchers have compared predicted stiffness and damping coefficients for tilting-pad journal bearings (TPJBs) to measurements. Most have found that direct damping is consistently overpredicted. The thrust of this research is to explain the difference between measured and predicted stiffness and damping coefficients for TPJBs, and to provide some confidence to designers that TPJB dynamic coefficients can be accurately predicted.
Most analytical models for TPJBs are based on the assumption that explicit dependence on pad motion can be eliminated by assuming harmonic rotor motion such that the amplitude and phase of pad motions resulting from radial and transverse rotor motions are predicted by rotor-pad transfer functions. In short, these transfer functions specify the amplitude and phase of pad motion (angular, radial, translational, etc.) in response to an input rotor motion.
A new pad perturbation model is developed including the effects of angular, radial, and circumferential pad motion and changes in pad clearance due to pad bending compliance. Though all of these pad variables have previously been included in different analyses, there are no publications containing perturbations of all four variables. In addition, previous researchers have only perturbed the journal, while both the bearing and journal motions are perturbed in the present analysis, and the applicability of comparing rotor-perturbed bearing impedance predictions to impedances measured on a bearing-perturbed test rig is discussed. This perturbation model was implemented in a Reynolds-based TPJB code to predict the frequency-dependent bearing impedances and rotor-pad transfer functions.
Direct measurements of pad motion during test excitation were recorded to produce measured transfer functions between rotor and pad motion, and a comparison between these measurements and predictions is given. Motion probes were added to the loaded pad (having the static load vector directed through its pivot) of a 5-pad TPJB to obtain accurate measurement of pad radial and tangential motion, as well as tilt, yaw, and pitch. Strain gages were attached to the side of the loaded pad to measure static and dynamic bending strains, which were then used to determine static and dynamic changes in pad curvature (pad clearance).
Good agreement was found between the amplitude of the measured and predicted transfer functions concerning radial and transverse pad motions throughout the range of speeds and loads tested, while pad tilt was moderately underpredicted.
For the bearing investigated, radial pad motions resulting from pivot compliance were as large as 60% of the radial component of shaft motion when operating at 4400 rpm under heavily loaded conditions. Hence, if a dynamic load applied to the shaft resulted in a shaft displacement of 25 microns (1 mil), the pad would displace radially 15 microns (0.6 mils), and the fluid film height would only decrease by 10 microns (0.4 mils). The consequence of this pad motion is that fluid film stiffness and damping forces produced by relative rotor-pad motions are significantly reduced, resulting in a bearing having significantly less direct stiffness and damping than predicted. A similar effect occurs when shaft motions produce significant changes in pad clearance due to pad compliance. For the pad tested here, the measurements show that predicting TPJB stiffness and damping coefficients without accounting for pad and pivot compliance will produce large errors, and is not advised.
Transverse pad motion was predicted and observed. Based on phase measurements, this motion is lightly damped, and appears to be caused by pivot deflection instead of slipping. Despite observing a lightly damped phase change, an increase in magnitude at this natural frequency was not observed.
Predicted direct stiffness and damping for unit loads from 0-3200 kPa (0-450 psi) fit through 1.5× running speed are within 18% of measurements at 4400 rpm, while predictions at 10200 rpm are within 10% of measurements. This is a significant improvement on the accuracy of predictions cited in literature.
Comparisons between predictions from the developed bearing model neglecting pad, pivot, and pad and pivot flexibility show that predicted direct stiffness and damping coefficients for a model having a rigid pad and pivot are overestimated, respectively, by 202% and 811% at low speeds and large loads, by 176% and 513% at high speeds and high loads, and by 51% and 182% at high speeds and light loads. While the reader is likely questioning the degree to which these predictions are overestimated in regard to previous comparisons, these predictions are based on measured operating bearing clearances, which are 20-30% smaller than the cold bearing clearances that previous comparisons were based on.
The effect of employing a full bearing model (retaining all of the pad degrees of freedom) versus a reduced bearing model (where only journal degrees of freedom are retained) in a stability calculation for a realistic rotor-bearing system is assessed. For the bearing tested, the bearing coefficients reduced at the frequency of the unstable eigenvalue (subsynchronously reduced) predicted a destabilizing cross-coupled stiffness coefficient at the onset of instability within 1% of the full model, while synchronously reduced coefficients for the lightly loaded bearing required 25% more destabilizing cross-coupled stiffness than the full model to cause system instability. This overestimation of stability is due to an increase in predicted direct damping at the synchronous frequency over the subsynchronously reduced value. This increase in direct damping with excitation frequency was also seen in highly loaded test data at frequencies below approximately 2×running speed, after which direct damping decreased with increasing excitation frequency. This effect was more pronounced in predictions, occurring at all load and speed combinations.
The same stability calculation was performed using measured stiffness and damping coefficients at synchronous and subsynchronous frequencies at 10200 rpm. It was found that both the synchronously measured stiffness and damping and predictions using the full bearing model were more conservative than the model using subsynchronously measured stiffness and damping. This outcome contrasts with the comparison between models using synchronously and subsynchronously reduced impedance predictions, which showed the subsynchronously reduced model to be the most conservative. This contrast results from a predicted increase in damping with increasing excitation frequency at all speeds and loads, while this increase in damping with increasing excitation frequency was only measured at the most heavily loaded conditions.
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Napoleon, Anona K. Nāʻone. "ʻIke hoʻoponopono the journey /." Thesis, 2004. http://proquest.umi.com/pqdweb?index=0&did=765924031&SrchMode=1&sid=3&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1233713324&clientId=23440.
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Tao, Yujiao 1988. "A Novel Computational Model for Tilting Pad Journal Bearings with Soft Pivot Stiffnesses." Thesis, 2012. http://hdl.handle.net/1969.1/148299.
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A novel tilting pad journal bearing model including pivot flexibility as well as temporal fluid inertia effects on the thin film fluid flow aims to accurately predict the bearing forced performance. The predictive model also accounts for the thermal energy transport effects in a TPJB. A Fortran program with an Excel GUI models TPJBs and delivers predictions of the bearing static and dynamic forced performance. The calculation algorithm uses a Newton-Raphson procedure for successful iterations on the equilibrium pad radial and transverse displacements and journal center displacements, even for bearings pads with very soft pivots.
The predictive model accounts for the effect of film temperature on the operating bearing and pad clearances by calculating the thermal expansion of the journal and pad surfaces. The pad inlet thermal mixing coefficient (lambda) influences moderately the predicted fluid film temperature field.
Pad pivot flexibility decreases significantly and dominates the bearing stiffness and damping coefficients when the pivot stiffness is lower than 10% of the fluid film stiffness coefficients (with rigid pivots). Pivot flexibility has a more pronounced effect on reducing the bearing damping coefficients than the stiffness coefficients. Pad pivot flexibility may still affect the bearing behavior at a light load condition for a bearing with a large pad preload.
Pad pivot flexibility, as well as the fluid inertia and the pads’ mass and mass moment of inertia, could influence the bearing impedance coefficients, in particular at high whirl frequencies. The stiffness and damping coefficients of a TPJB increase with a reduction in the operating bearing and pad clearances.
The work delivers a predictive tool benchmarked against a number of experimental results for test bearings available in the recent literature. The static and dynamic forced performance characteristics of actual TPJBs can not be accurately predicted unless their pad flexibility and pivot flexibility, fluid film temperature, pad inlet thermal mixing coefficient, operating bearing and pad clearances, among others are well known in advance. However, the extensive archival literature showcasing test procedures and experimental results for TPJBs does not report the above parameters. Thus, reasonable assumptions on the magnitude of certain elusive parameters for use in the predictive TPJB model are necessary.
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Tschoepe, David 1987. "Measurements Versus Predictions for the Static and Dynamic Characteristics of a Four-pad Rocker-pivot, Tilting-pad Journal Bearing." Thesis, 2012. http://hdl.handle.net/1969.1/148049.
Full textAbstract:
Measured and predicted static and dynamic characteristics are provided for a four-pad, rocker-pivot, tilting-pad journal bearing in the load-on-pad and load-between-pad orientations. The bearing has the following characteristics: 4 pads, .57 pad pivot offset, 0.6 L/D ratio, 60.33 mm (2.375in) pad axial length, 0.08255 mm (0.00325 in) radial clearance in the load-on-pad orientation, and 0.1189 mm (0.00468 in) radial clearance in the load-between-pad orientation. Tests were conducted on a floating test bearing design with unit loads ranging from 0 to 2903 kPa (421.1 psi) and speeds from 6.8 to 13.2 krpm.
For all rotor speeds, hot-clearance measurements were taken to show the reduction in bearing clearance due to thermal expansion of the shaft and pads during testing. As the testing conditions get hotter, the rotor, pads, and bearing expand, decreasing radial bearing clearance. Hot-clearance measurements showed a 16-25% decrease in clearance compared to a clearance measurement at room temperature.
For all test conditions, dynamic tests were performed over a range of excitation frequencies to obtain complex dynamic stiffness coefficients as a function of frequency. The direct real dynamic stiffness coefficients were then fitted with a quadratic function with respect to frequency. From the curve fit, the frequency dependence was captured by including a virtual-mass matrix [M] to produce a frequency independent [K][C][M] model.
The direct dynamic stiffness coefficients for the load-on-pad orientation showed significant orthotropy, while the load-between-pad did not. The load-between-pad showed slight orthotropy as load increased. Experimental cross-coupled stiffness coefficients were measured in both load orientations, but were of the same sign and significantly less than direct stiffness coefficients.
In both orientations the imaginary part of the measured dynamic stiffness increased linearly with increasing frequency, allowing for frequency independent direct damping coefficients.
Rotordynamic coefficients presented were compared to predictions from two different Reynolds-based models. Both models showed the importance of taking into account pivot flexibility and different pad geometries (due to the reduction in bearing clearance during testing) in predicting rotordynamic coefficients. If either of these two inputs were incorrect, then predictions for the bearings impedance coefficients were very inaccurate. The main difference between prediction codes is that one of the codes incorporates pad flexibility in predicting the impedance coefficients for a tilting-pad journal bearing.
To look at the effects that pad flexibility has on predicting the impedance coefficients, a series of predictions were created by changing the magnitude of the pad's bending stiffness. Increasing the bending stiffness used in predictions by a factor of 10 typically caused a 3-11% increase in predicted Kxx and Kyy, and a 10-24% increase in predicted Cxx and Cyy. In all cases, increasing the calculated bending stiffness from ten to a hundred times the calculated value caused slight if any change in Kxx, Kyy, Cxx, and Cyy. For a flexible pad an increase in bending stiffness can have a large effect on predictions; however, for a more rigid pad an increase in pad bending stiffness will have a much lesser effect.
Results showed that the pad's structural bending stiffness can be an important factor in predicting impedance coefficients. Even though the pads tested in this thesis are extremely stiff, changes are still seen in predictions when the magnitude of the pad?s bending stiffness is increased, especially in Cxx, and Cyy. The code without pad flexibility predicted Kxx and Kyy much more accurately than the code with pad flexibility. The code with pad flexibility predicts Cxx more accurately, while the code without pad flexibility predicted Cyy more accurately. Regardless of prediction Code used, the Kxx and Kyy were over-predicted at low loads, but predicted more accurately as load increased. Cxx, and Cyy were modeled very well in the load-on-pad orientation, while slightly overpredicted in the load-between-pad orientation. For solid pads, like the ones tested here, both codes do a decent job at predicting impedance coefficients
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Wong, Shih Ming, and 翁士茗. "The static performance of hydrostatic journal bearing for multi-recess and multi-pad." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/4v7676.
Full textAbstract:
碩士國立清華大學
動力機械工程學系
103
In order to achieve high precision machining, hydrostatic journal bearing is widely adopted by machine tool manufacturers in recent years. There are various of system parameters that will affect the performance of bearings respectively. Geometry parameters include bearing length, inner diameter, recess size and number of recess. Operating parameters include restrictor type, lubricant viscosity, supply pressure and eccentricity. However, most previous studies tended to discuss the effects of operating parameters on the performance of hydrostatic journal bearings at given bearing dimensions like length and inner diameter. Consequently, this study investigates the static performance (such as load capacity, stiffness and flow) about various dimensions of multi-pad and multi-recess type hydrostatic journal bearings with constant-resistant restrictor compensation. According to the results, recess size of better stiffness for multi-recess type is relates to the ratio of bearing length to inner diameter. Also, comparative result shows that multi-recess type’s flow is neerly half of multi-pad type’s. Keywords: finite difference method, system parameter, multi-recess, multi-pad
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"A qualitative retrospective study of lesbian youth: The journey toward the resilient self." Tulane University, 2001.
Find full textAbstract:
Much research has examined pathological attributes of lesbians. This qualitative inquiry focused on strengths and non-pathological behaviors exhibited by lesbian youth in the face of homophobia and adversity. Focus group interviews were utilized to gather data from 22 adult lesbians who live in the New Orleans metropolitan area. The analysis shows that those lesbian youth who were better adept at coping and manifested a resilient self had viable social support systems, demonstrated healthy constitutional factors, perceived benefit from adversity, and had self-labeled and self-disclosedacase@tulane.edu
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Shi, Wenying. "A journey towards professional integration experiences of immigrant Ph. D. students in breaking down barriers to enter Canadian academia." Phd thesis, 2010. http://hdl.handle.net/10048/1602.
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This dissertation investigates the internal and external barriers and successes in career preparation of a small group of immigrant doctoral students. Through three cycles of a four-year action research investigation that integrates interviews, surveys, participant reflections and autoethnography, the data was interpreted through the lenses of critical pedagogy, socio-cultural theory, ecological theory and dialectic theory. The study reveals some of the intercultural transformations that take place in order to reconstruct professional autonomy and perceptions of empowerment during the process of breaking downing internal and external barriers. In order for immigrant doctoral students to achieve professional integration the study presents recommendations to university leaders, graduate supervisors and graduate students themselves. The primary goals are to deepen the understanding of various barriers experienced by professional immigrant Ph.D. students and to identify the changes that occurred in reconstructing their professional autonomy and in their perception of empowerment during the process of breaking downing various external and internal barriers towards professional integration. This study should provide new understandings of what Canadian doctoral education means to professional immigrants, where gaps exist in universities programs of studies and their implementation, and between students career preparation needs and the services provided through university career support. In light of Canadas aggressive immigration policy, the findings point to the need to build an integrated career support system for immigrant doctoral students academic career transition success and encourage Canadian
universities to reflect upon the humanistic and democratic values and approaches embedded in the internationalization of education. In addition, immigrant doctoral students may feel empowered by the stories being told and inspired by the insights and strategies revealed.
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Speck, Christopher E. Eiseley Loren C. "Loren Eiseley's timeless journey through the sacred universe. /." 2007. http://proquest.umi.com/pqdweb?did=1417814671&sid=1&Fmt=2&clientId=10361&RQT=309&VName=PQD.
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Agnew, Jeffrey Scott. "Rotordynamic Performance of a Flexure Pivot Pad Bearing with Active and Locked Integral Squeeze Film Damper Including Predictions." Thesis, 2011. http://hdl.handle.net/1969.1/ETD-TAMU-2011-12-10429.
Full textAbstract:
Tests are performed on a flexure-pivot-pad tilting-pad bearing with a series integral squeeze film damper in load-between-pads configuration, with both active and locked damper. The damper effects are negated when locked, resulting in a flexure-pivot-pad bearing only. Experimental tests provide static performance data and dynamic stiffnesses from which rotordynamic coefficients are extracted. The following two excitation schemes are implemented: (1) multi-frequency, single direction excitation and (2) single-frequency, rotating load excitation (or "circular excitation"). The XLTRC2 Rotordynamics Software Suite provides stiffness and damping coefficient, eccentricity, and power loss predictions for the locked damper bearing. Test conditions include the rotor-speed range of 4000-12000 rpm and the unit-load range of 0-862 kPa (0-125 psi).
Dynamic tests utilizing the multi-frequency excitation for the locked and active damper bearing configurations both show that the real portion of the dynamic stiffness is well modeled by a quadratic curve fit, and the imaginary portion representing the damping is a linear function of excitation frequency. This means that frequency independent coefficients can be obtained when an added mass term is included. While stiffness coefficients are lower for the active damper bearing, damping coefficients remain almost constant between the locked and active damper configurations. A simulation shows that, although the damping coefficients do not change significantly, the reduced stiffness provided by the damper results in greater effective damping.
Static performance tests for the locked and active damper bearing indicate low cross-coupling, as shown by the eccentricity and low attitude angle measurements. Pad metal temperature measurements show a smaller temperature differential along the pad arcs for the active damper bearing, than observed for the locked damper case. Frictional power loss is estimated based on lubricant temperature rise and does not differ significantly for the two bearing configurations.
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Chaffin, Carol. "On sacred ground : a qualitative exploration of the journey of self discovery /." 2005. http://proquest.umi.com/pqdweb?did=888839851&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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Schoening, Anne M. "The journey from bedside to classroom making the transition from nurse to nurse educator /." 2009. http://proquest.umi.com/pqdweb?did=1686181371&sid=17&Fmt=2&clientId=14215&RQT=309&VName=PQD.
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Thesis (Ph.D.)--University of Nebraska-Lincoln, 2009.Title from title screen (site viewed May 5, 2009). PDF text: x, 146 p. : ill. (some col.) ; 1 Mb. UMI publication number: AAT 3344653. Includes bibliographical references. Also available in microfilm and microfiche formats.
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Auger, Manon. ""Mademoiselle Dessaulles" : adaptation scénaristique du Journal (1874-1881) d'Henriette Dessaulles ; suivie de Le statut sémiologique du personnage dans le journal intime : l'exemple du Journal (1874-1881) d'Henriette Dessaulles /." 2004. http://proquest.umi.com/pqdweb?did=974397241&sid=3&Fmt=2&clientId=9268&RQT=309&VName=PQD.
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Stenson, Matthew Scott. "Lifting up the serpent in the wilderness the reader's journey through John Milton's "Paradise Lost", an intertextual study /." 2009. http://proquest.umi.com/pqdweb?did=1697328671&sid=3&Fmt=2&clientId=14215&RQT=309&VName=PQD.
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Thesis (Ph.D.)--University of Nebraska-Lincoln, 2009.Title from title screen (site viewed July 21, 2009). PDF text: iv, 361 p. ; 2 Mb. UMI publication number: AAT 3350457. Includes bibliographical references. Also available in microfilm and microfiche formats.
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Lee, Jung Gu. "A Nonlinear Transient Approach for Morton Synchronous Rotordynamic Instability and Catcher Bearing Life Predictions." Thesis, 2012. http://hdl.handle.net/1969.1/ETD-TAMU-2012-05-10981.
Full textAbstract:
This dissertation deals with three research topics; i) the catcher bearings life prediction method, ii) the Morton effect, and iii) the two dimensional modified Reynolds equation.
Firstly, catcher bearings (CB) are an essential component for rotating machine with active magnetic bearings (AMBs) suspensions. The CB's role is to protect the magnetic bearing and other close clearance component in the event of an AMB failure. The contact load, the Hertzian stress, and the sub/surface shear stress between rotor, races, and balls are calculated, using a nonlinear ball bearing model with thermal growth, during the rotor drop event. Fatigue life of the CB in terms of the number of drop occurrences prior to failure is calculated by applying the Rainflow Counting Algorithm to the sub/surface shear stress-time history. Numerical simulations including high fidelity bearing models and a Timoshenko beam finite element rotor model show that CB life is dramatically reduced when high-speed backward whirl occurs.
Secondly, the theoretical models and simulation results about the synchronous thermal instability phenomenon known as Morton Effect is presented in this dissertation. A transient analysis of the rotor supported by tilting pad journal bearing is performed to obtain asymmetric temperature distribution of the journal by solving variable viscosity Reynolds equation, energy equation, heat conduction equation, and equations of motion for rotor. The tilting pad bearing is fully nonlinear model. In addition, thermal mode approach and staggered integration scheme are utilized in order to reduce computation time. The simulation results indicate that the temperature of the journal varies sinusoidally along the circumferential direction and linearly across the diameter, and the vibration envelope increased and decreased, which considers as a limit cycle that is stable oscillation of the envelope of the amplitude of synchronous vibration.
Thirdly, the Reynolds equation plays an important role to predict pressure distribution in the fluid film for the fluid film bearing analysis. One of the assumptions on the Reynolds equation is that the viscosity is independent of pressure. This assumption is still valid for most fluid film bearing applications, in which the maximum pressure is less than 1 GPa. In elastohydrodynamic lubrication (EHL) which the lubricant is subjected to extremely high pressure, however, the pressure independent viscosity assumption should be reconsidered. With considering pressure-dependent viscosity, the 2D modified Reynolds equation is derived in this study. The solutions of 2D modified Reynolds equation is compared with that of the classical Reynolds equation for the plain journal bearing and ball bearing cases. The pressure distribution obtained from modified equation is slightly higher pressures than the classical Reynolds equations.PDF file replaced 10-21-2012 at the request of the Thesis Office.
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Hayes, Lisa. "Theatricalizing oral history how British and American theatre artists explore current events and contemporary politics in the journey from interview to performance /." 2008. http://proquest.umi.com/pqdweb?did=1542153011&sid=51&Fmt=2&clientId=39334&RQT=309&VName=PQD.
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Thesis (Ph.D.)--State University of New York at Buffalo, 2008.Title from PDF title page (viewed on Feb. 13, 2009) Available through UMI ProQuest Digital Dissertations. Thesis adviser: Frisch, Michael Includes bibliographical references.
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English, Sarah Collard. "The use of dialogic electronic journal writing to develop students' understanding of chemical bonding." 2006. http://proquest.umi.com/pqdweb?did=1147196591&sid=4&Fmt=2&clientId=39334&RQT=309&VName=PQD.
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Thesis (Ph.D.)--State University of New York at Buffalo, 2006.Title from PDF title page (viewed on Oct. 24, 2006) Available through UMI ProQuest Digital Dissertations. Thesis adviser: Liu, Xiufeng. Includes bibliographical references.
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Dufour, Monique. "Étude de l'influence de la prise de bêta-bloquants sur la fréquence cardiaque d'exercice en fonction de la période de la journée chez des patients atteints d'une maladie coronarienne /." 2003. http://proquest.umi.com/pqdweb?did=766850421&sid=11&Fmt=2&clientId=9268&RQT=309&VName=PQD.
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