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In Squeeze Film Dampers, (SFD), grooves (deep or shallow) are used to feed oil into the damper and prevent oil starvation within the fluid film lands. In oil seals with film land of clearance c, short shallow grooves (depth ≤ 15c, length ≤ 30c) are machined to reduce the cross-coupled stiffness coefficients, and thus improve the seal stability characteristics. Moreover, test stands for these devices can also incorporate grooves or recesses as part of oil feeding/ discharge arrangements. A common assumption is that these grooves do not influence the test system forced response. However, unexpected large added mass coefficients are reported in these configurations and not adequately predicted. In the case of grooved oil seals, experimental results also show that circumferential grooves do aid to reduce cross-coupled force coefficients but to a lesser extent than predictions otherwise indicate. A linear fluid inertia model for analysis of multiple-groove SFD or oil seal configurations is advanced. A perturbation analysis for small motion about a journal centered and off-centered position yields zeroth and first order flow equations defined at each individual flow region (land and grooves) of constant clearance ( c ).The analysis considers both the circumferential and axial dynamic pressure variations across the groove and land regions. At the groove regions, an effective groove depth ( dη ) and effective clearance (c d c η η = + ) are defined based on qualitative observations of the laminar flow pattern through annular cavities. This depth differs from the actual physical groove depth. The boundary conditions at the inlet and exit plane are a function of the geometric configuration. Integration of the resulting dynamic pressure fields on the journal surface yields the force coefficients (stiffness, damping, and inertia). Comparisons between predicted and experimental force coefficients for a grooved oil seal and a SFD show excellent correlation over a narrow range of effective groove depths. The results confirm that large added mass coefficients are associated to the feed/discharge grooves in the scrutinized test configurations. Furthermore, predictions, benchmarking experimental data, corroborate that short inner land grooves in an oil seal do not isolate the pressure field of the adjacent film lands, and hence contribute greatly to the force response of the seal.

Thesis (D. SC.)--University of Michigan. / "Photo-lithoprint." Bibliography: p. 37.

Study of the dynamics of strings and filaments has broad applications, for instance, macroscopic coil motion in petroleum engineering and microscopic one-armed swimmers in biological science. In this work, we study the motions of flexible strings and thin filaments in two different regimes, inertial and viscous, theoretically and experimentally. Quantitative experiments on the whirling string show that steady motion exists only when the string whirls at its natural frequencies and that whirling motions for other frequencies exhibit rich dynamics. Furthermore, three kinds of response have been observed experimentally for the planar excitation: planar steady oscillation; two-dimensional (2D) to three-dimensional (3D) transient response; 3D steady whirling motion. These phenomena repeat as the driving frequency is increased. The forced response of a string subjected to planar excitation is analyzed through a perturbation technique and multiple time scale method. The steady-state whirling motion of linear elastic filaments under self-weight with rotary excitation at one end and free at the other has been examined; specifically, the effect of bending stiffness has been investigated both theoretically and experimentally. The theoretical predictions have been compared with the experimental results for thin filaments with different bending stiffness to demonstrate the effect of bending stiffness directly. The dynamic response of thin filaments under planar excitation has also been studied experimentally. The two-dimensional dynamics of an Euler elastica in low-Reynolds number regime has been studied. Tension effects have been shown to be either comparable to or dominant over the bending contributions for the microscopic one-armed swimmers. Hence one may change the tension in situ through the externally or internally generated forces, thus changing the effective bending stiffness, and as a consequence controlling the swimming velocity and the propulsion efficiency. Finally, the low-Reynolds-number dynamics of a micro-string has been studied, in order to understand the physics underpinning eukaryotic sperm flagellar swimming. Both linear analysis of small-amplitude swimming and fully numerical simulations show that time-reversal symmetry is broken, which leads to the propulsion. Numerical studies have been performed for different boundary conditions and different forcing levels. Comparison with previous bending model illustrated that, for the same equivalent bending stiffness, the micro-string has higher propulsion efficiency with similar swimming velocity. Excellent agreement between the simulation predictions and the experimentally observed flagellar wave-forms has been obtained. With this theoretical model, observations of swimming characteristics of the sperm of different species are reconciled into a single scaling relationship, characterized by the so-called \string sperm number". Our results imply that tension plays a crucial role in flagellar elasticity and provides impetus for studying a different model underlying the physics of flagellar swimming. For example, it is possible to postulate alternate hypotheses for active force generation by the dynein motors; it also enables the formulation of a different role to the micro-filaments in general, one based on tension rather than one based on bending.

The first coal-fired power plant in Sri Lanka was successfully connected to the national grid in year 2011. The proposal of implementing coal-fired power plants in Sri Lanka has been appearing in power sector master plans since year 1985. It was delayed for many years, mainly due to public protests and indecision of the political leadership of the country. This research analyzes the social and economic barriers faced during the implementation stage. Operation of the plant in terms of system inertia, reliability and stability is discussed. This is the single largest power sector investment in Sri Lanka and returns on the investment were analyzed in this study. As this is the first coal-fired power plant in Sri Lanka, success of this project will create the platform for the public acceptance of future coal-fired power plants. There were some technical failures during the initial years of operation of the plant, and now it records a higher reliability. Furthermore, it is important to summarize the lessons learnt after implementing this project. Future plans of the utility, energy policy of the country and the political agenda of a country should reflect the experience with this project. This is a good example that teaches the lesson; projects which require to be implemented in the national interest should not be postponed or cancelled due to the protest by small groups of people perceived to be affected by the project. It is highlighted that system stability is improved in many cases due to the increase of power system inertia, to which this power plant makes the largest contribution. System inertia is improved in six out of nine scenarios, which were analyzed in this study. Economic benefits gained by the power plant were examined and the study proves that this power plant will have a significant positive effect on the national economy. Loss incurred delaying the project was calculated and it proves the importance of this project.

No description available.

The newspaper industry has in the last few decades experienced a gradual but steady decline. The cause of this decline and potential ways of counteraction have been under considerable debate recently both in the industry and in academia. For the last decade and a half, the digitization of news has emerged as a much debated challenge and been perceived by the industry as both its inevitable future and its biggest threat. Taking its starting-point in this complex situation, this dissertation particularly focuses on how the organizational culture of regional, ideologically driven newspaper organizations affects propensity for change. Particular focus is placed on the regional newspaper industry, and an ethnographical case study has been conducted of a Swedish county covered by two independent, competing newspaper organizations. The purpose of the study is to develop a theoretical concept to describe the kind of organizational inertia currently experienced by the regional newspaper industry. Combining semi-structured interviews, observations and analysis of public documentation, it is shown that both regional organizations in the study are struggling to reconcile a steadily declining print edition with the pressures of publishing news online. The regional newspaper industry is expected to deliver online news content to a growing audience without a profitable business model. Since the late 1990s, when the first of the organizations’ websites appeared, the Internet’s potential as a financially justifiable publishing platform has been put into question. Sixteen years later, the websites and the questions remain. The study shows how organizational memory and the act of remembrance are used along with certain aspects of corporate history and culture to legitimize long term strategizing that in turn have significant effects on the propensity for change. Dimensions of “spectrality” and the concept of “spectral organizations” are introduced as theoretical concepts to describe these particular types of organizations that are haunted by their past to the extent that they exhibit strategic entrenchment or even altogether an inability to progress and adapt to their environment. The contribution of the study is to increase the understanding of why the regional newspaper industry is experiencing inertia, and of the ideological forces that make implementing paradigmatic change so difficult. / Baksidestext: The newspaper industry has in the last few decades experienced a gradual but steady decline. The cause of this decline and potential ways of counteraction have been under considerable debate recently both in the industry and in academia. For the last decade and a half, the digitization of news has emerged as a much debated challenge and been perceived by the industry as both its inevitable future and its biggest threat. Taking its starting-point in this complex situation, this dissertation particularly focuses on how the organizational culture of regional, ideologically driven newspaper organizations affects propensity for change. Particular focus is placed on the regional newspaper industry, and an ethnographical case study has been conducted of a Swedish county covered by two independent, competing newspaper organizations. The end result is a theoretical concept that describes, and aids the understanding of, the kind of organizational inertia currently experienced by the regional newspaper industry. / <p>ISBN of the printed version refers to the 2nd edition of the book.</p>

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Thesis (M.S.)--California Polytechnic State University, 2009. / Mode of access: Internet. Title from PDF title page; viewed on March 17, 2009. Major professor: Robert D. Clark, Ph.D. "Presented to the faculty of California Polytechnic State University, San Luis Obispo." "In partial fulfillment of the requirements for the degree [of] Master of Science in Kinesiology." "March 2009." Includes bibliographical references (p. 41-44). Also available on microfiche.

The Large-scale Semi-Geostrophic Equations (LSGE, Salmon[73]) are three-dimensional equations valid for an ocean with a rigid lid and length scales much greater than the internal deformation radius (about 40km). In this thesis I reduce the LSGE to a pair of two-dimensional equations via the ansatz that the temperature is independent of the vertical co-ordinate. I refer to these as the Depth-Independent-Temperature (DIT) equations. Whilst this is regarded as a paradigm for the entire ocean, the reduction is similar in spirit to that utilised by many authors for modelling the mixed layer of the ocean. The equations of this thesis differ from the work of such mixed layer models because they involve no ad hoc vertical averaging and so solutions to these equations are also solutions to the full three-dimensional LSGE. The DIT are arguably the simplest equations for ocean circulation to include the effects of inertia, topography and baroclinicity. The DIT are studied both analytically and numerically. It is shown that the model exhibits baroclinic instabilities and analogies are drawn with classical Rayleigh-Benard convection. It is shown that both viscosity and thermal diffusivity are required to avert an ultra-violet catastrophe. Numerical simulations of turbulence demonstrate that the long-time behaviour resembles barotropic flow and that the temperature is reduced to the role of a passive tracer unless large-scale thermal structure is imposed externally on the flow. One of the advantages of the current model over the more widely used quasi-geostrophic models is that there is no restriction on the vertical extent of the bottom topography. This allows the simulation of idealised oceanic basin circulations in which the depth of the ocean vanishes smoothly at boundaries. These ocean simulations are used to study the sensitivity of the model to the Rossby Number, Ekman Number and forcing parameters. Comparison of a barotropic and a DIT ocean reveals the influence of baroclinicity in the latter model. Characteristic features of the Gulf Stream such as meandering, recirculation gyres and the shedding of warm and cold core rings are reproduced by the DIT model and the simple nature of the equations permits an interpretation of these features.