30,203 research outputs found
Mean flow generation by Görtler Vortices in a rotating annulus with librating side walls
No full textLongitudinal libration of the cylinder side walls of a rotating annulus in the supercritical regime induces a centrifugally unstable Stokes boundary layer which generates Görtler vortices only in a portion of a libration cycle. We show for the first time that these vortices propagate into the fluid bulk and generate an azimuthal mean flow which is retrograde (prograde) over the outer (inner) cylinder side wall. Direct numerical simulations (DNS) are carried out and Reynolds-averaged equations and kinetic energy budget of mean and fluctuating flow are used as diagnostic equations to discuss the generation mechanism and scaling behavior of the azimuthal mean flow in the fluid bulk
Mean Flow generation due to longitudinal librations of side-walls of a rotating annulus
No full textLaboratory experiments with rotating annuli are reported that reveal a prograde jet, which is adjacent either to a (longitudinally) librating inner straight cylinder or to a librating inner truncated cone (frustum), whereas the outer cylindrical wall and bottom and top lids rotate with constant angular velocity. In the frustum case, the jet is located on a straight cylindrical surface which is circumscribed about the frustum and joins the bottom lid. These findings are supported by direct numerical simulations which show good agreement between experimental data and numerical results and, when the centrifugal instability of the Stokes boundary layer near the oscillating sidewall does not set in, highlight the important role of local dynamical processes in the corners, between the inner cylinder and the lids, in producing the prograde jet
DNS of inertial wave attractors in a librating annulus with height-dependent gap width
No full textDirect numerical simulations (DNS) of inertial wave attractors have been carried out in a librating Taylor-Couette system with broken mirror symmetry in the radial-axial cross-section. The inertial wave excitation mechanism and its localisation at the edges was clarified by applying boundary layer theory. Additional resonance peaks in the simulated response spectra were found to agree with low-order wave attractors obtained by geometric ray tracing. Numerics and theory are in qualitative agreement with recent lab experiments
Integral Facade Construction: Towards a new product architecture for curtain walls
No full textCurtain wall constructions are one of the most applied facade constructions today. Independently attached to the primary load bearing structure of the building they protect the building’s interior from external climate conditions and allow great design freedom. With continuously rising requirements in terms of energy savings the constructional principle has reached its limits and strategies for improvement are needed. Incrementally evolved over time it is closely related to the architectural design and building processes. Based on literature research and stakeholder interviews the dissertation maps out the traditional and craftsmanship related facade design and construction process currently employed. In a next step, future challenges for facade constructions to cope with a changing market environment are identified. A facade function tree is developed and the theory of product architecture is applied to create a comparative basis for analysing different historical and contemporary facade products and systems. The function tree as well as the analysis clearly show how the fragmented market structures has influenced contemporary facade construction and leads to extremely modular product architectures. Numerous case studies for a new approach are conducted and summarised in several matrices. The case studies show how different modular and integral constructional strategies can respond to the future challenges. The pros and cons of different facade solutions, their potential for innovation and robustness in terms of market conditions are investigated. The dissertation concludes that a greater diversity of fa.ade types with a more integral construction is needed to meet the sometimes conflicting future challenges. If this can be realised, a greater diversity of more integral design and construction processes will evolve simultaneously. The role of the different stakeholders will change and a new way of educating architects or facade specialists will be required in order to meet the needs of the future building market: Away from a purely application oriented towards a product architecture driven approach, which clearly includes the implications of facade product architecture on the structure of the design and construction process.Building TechnologyArchitectur
Determination of the Interatomic Potential of Krypton. U. Buck, M.G. Dondi, U. Valbusa, M.L. Klein and G. Scoles, Phys. Rev.8, 2409-2416 (1973).
No full textFamilie und agrarisch-heimgewerbliche Verflechtung : eine demographische Studie zu Spenge (Ravensberg) 1768 - 1868
No full textKlein P. Familie und agrarisch-heimgewerbliche Verflechtung : eine demographische Studie zu Spenge (Ravensberg) 1768 - 1868. IBS-Materialien. Vol 35. Bielefeld: Inst. für Bevölkerungsforschung u. Sozialpolitik; 1993
A psychoanalytic concept illustrated: Will, must, may, can — revisiting the survival function of primitive omnipotence
No full textThe author explores the linear thread connecting the theory of Freud and Klein, in terms of the central significance of the duality of the life and death instinct and the capacity of the ego to tolerate contact with internal and external reality. Theoretical questions raised by later authors, informed by clinical work with children who have suffered deprivation and trauma in infancy, are then considered. Theoretical ideas are illustrated with reference to observational material of a little boy who suffered deprivation and trauma in infancy. He was first observed in the middle of his first year of life while he was living in foster care, and then later at the age of two years and three months, when he had been living with his adoptive parents for more than a year
Baryons in Dark Matter Halos
No full textThe existence of Dark Matter (DM) has been known since the 30's of the last century. The first cognitions from motions of galaxies in clusters and by the kinematics of individual galaxies were followed by systematic investigations, primarily via galaxy rotation curves. Since the mid 90's, observations can be confronted with models defined in specific galaxy formation scenarios, in particular with the output of numerical simulations performed in the framework of (Lambda) Cold Dark Matter (CDM). The great success of these models is that they reproduce the large-scale structure with great success, while they - maybe not surprisingly - seem to fail to be equally successful in describing the evolution of the universe on smaller, i.e. cluster and galaxy scales. These developments were parallelled by breathtaking advancements in cosmology. Since the precision measurement of the spectrum of the cosmic microwave background (CMB) with COBE, subsequent experiments devoted to the CMB anisotropy (Boomerang, WMAP) have led to what is called 'precision cosmology'. This implies that we are in the position of validating (numerical) models to a high degree. At the same time, we are witnessing amazing developments in observational astronomy, which allow to explore the universe back into the epoch of re-ionization, thereby subjecting models to further critical and crucial tests, the last steps expected to be taken in the near future. All of this looking nice at first glance, it does not mean that we may comfortably sit back and consider most of the riddles solved. In fact, it must be a worry to any astrophysicist that both, DM and Dark Energy remain nothing but hypotheses as long as no particle has been detected in lab experiments yet. Are they just 'epicycles' like those resorted to prior to Kepler to explain the motions of planets? Nearly ten years of critical validation of CDM models have, apart from a lot of success, resulted in what has been coined as the "first and second CDM crisis", i.e. the failure of theory to explain the mass spectrum of dark satellites around big galaxies on large scales, and the (partial) absence of cusps in the dense inner part of galaxy halos. This obviously calls for continuing efforts in both, observational and theoretical fields. The conference Baryons in Dark Matter Halos we announce here is jointly organized by the Bochum /Bonn graduate research school "Galaxy Groups as Laboratories of Baryonic and Dark Matter" and SISSA is meant to bring together experts from the whole world working in the fields outlined above, trying to make a critical assessment of what has been achieved and to identify the problems that we are faced with. Invited reviews will be given to summarise the state-of-the-art, in particular to the participating graduate students and to scientists working in these fields. The event will provide the participating students with the opportunity to present their own work and advertise it to other participants. Their activity should also be understood as a stimulus for future collaborations or intensify the existing ones. In this sense, the event is meant to be between a summer school and a workshop. We would like that this meeting, that takes place in the inviting and picturesque location of Cittanova/Novigrad, Istria, will be featured by the same spirit present in many of the previous meetings and workshops of the graduate school. Our first aim for the five-day meeting is that the so-called "paradigm of hierarchical structure formation" be subjected to a lively and critical discussion (with strong involvement of the students!). A second aim is to identify future directions of research leading to further progress in our understanding of structure formation and evolution of galaxies. It is our aim that during the five-day meeting that the so-called paradigm of hierarchical structure formation will be subjected to a lively and critical discussion (with strong involvement of the students!), with the cosmological concordance model in the background. Future directions of research shall be identified that will lead to further progress in understanding structure formation and the evolution of galaxies. We hope that this meeting, taking place in the inviting location of Cittanova/Novigrad at the picturesque Istrian coast of Croatia, will be featured by the same spirit as was present in many of the previous meetings and workshops of the graduate school
La ligne u=v sur la triple bouteille de Bonan-Jeener-Klein et un ruban
No full textThe u=v line on the Bonan-Jeener's triple Klein bottle and a strip (La ligne u=v sur la triple bouteille de Bonan-Jeener-Klein et un ruban
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