1,768 research outputs found
Interview With P.C. Hodgell
No full textP.C. Hodgell, author of God Stalk and Dark of the Moon, was one of the many authors who attended Mythcon XIX in Berkeley last summer. She was good enough to meet with the Mythic Circle writers\u27 roundtable and share some of her experiences with us. The following is transcribed from a low-quality tape; when it was possible to recognize a speaker’s voice I have identified them - others are noted as ct. Hope you enjoy it
Comments on 'Modelling the morphodynamic impact of offshore sandpit geometry' by Roos et al. (2008)
No full textThis brief comment of Roos et al.'s [Roos, P.C., Hulscher, S.J.M.H. &
de Vriend, H.J., 2008. Modelling the morphodynamic impact of offshore
sandpit geometries. Coast. Eng. doi:10.1016/j.coastaleng.2008.02.019]
paper is aimed at supporting the validity of idealized process-based models
as a valuable tool for the design of sand pits. The discussion moves from a
brief description of the capabilities of an already existing idealized
process-based model [Blondeaux, P. and Vittori, G. 2005a Morphological
development of shallow sand pits. Proceedings 29th International
Conference Coastal Engineering 2004, World Scientific (Jane McKee
Smith ed) ISBN 981-256-995-2 pp. 2581–2593; Blondeaux, P. and
Vittori, G., 2005b. Flow and sediment transport induced by tide
propagation: part 2: the wavy bottom case. J. Geophys. Res., Vol.
110, No. C8, C08003] which can predict the morphological time
development of sand pits. Then, the differences between Blondeaux
& Vittori's model and Roos et al.'s model are analysed to give to the
potential user an idea of the range of applicability of the different
models, also in relation to practical applications
Perception of emotional facial expressions at different intensities in early-symptomatic Huntington's disease
No full textItem does not contain fulltextBACKGROUND: While there is abundant evidence that patients with Huntington's disease (HD) have an impairment in the recognition of the emotional facial expression of disgust, previous studies have only examined emotion perception using full-blown facial expressions. OBJECTIVE: The current study examines the perception of facial emotional expressions in HD at different levels of intensity to investigate whether more subtle deficits can be detected, possible also in other emotions. METHOD: We compared early symptomatic HD patients with healthy matched controls on emotion perception, presenting short video clips of a neutral face changing into one of the six basic emotions (happiness, anger, fear, surprise, disgust and sadness) with increasing intensity. Overall face perception ability as well as depressive symptoms were taken into account. RESULTS: A specific impairment in recognizing the emotions disgust and anger was found, which was present even at low emotion intensities. CONCLUSION: These results extend previous findings and support the use of more sensitive emotion perception paradigms, which enable the detection of subtle neurobehavioral deficits even in the pre- and early symptomatic stages of the disease.4 p
Nonequilibrium and classical dissipation scalings in DNS of homogeneous isotropic decaying turbulence
No full textWe present data from direct numerical simulations of homogeneous isotropic decaying turbulence showing both the non-equilibrium and the classical dissipation scalings reported in wind-tunnel experiments of both regular and fractal grid-generated turbulence, i.e. Cε ∼ (Re0/Reλ)n with n of order unity and Cε ∼ constant, respectively (Re0 and Reλ are global and local Reynolds numbers). These two dissipation behaviours lead to different power-law decay exponents in both regimes also in accord with the experiments. Finally, we show that in both regimes the maximum non-linear energy cascade flux, Π, reasonably satisfies the classical expectation that Π ∼ K3/2/l
Horizontally viscous effects in a tidal basin: Extending Taylor’s problem
No full textThe classical problem of Taylor (Proc. Lond. Math. Soc., vol. 20, 1921, pp. 148–181) of Kelvin wave reflection in a semi-enclosed rectangular basin of uniform depth is extended to account for horizontally viscous effects. To this end, we add horizontally viscous terms to the hydrodynamic model (linearized depth-averaged shallow-water equations on a rotating plane, including bottom friction) and introduce a no-slip condition at the closed boundaries. In a straight channel of infinite length, we obtain three types of wave solutions (normal modes). The first two wave types are viscous Kelvin and Poincaré modes. Compared to their inviscid counterparts, they display longitudinal boundary layers and a slight decrease in the characteristic length scales (wavelength or along-channel decay distance). For each viscous Poincaré mode, we additionally find a new mode with a nearly similar lateral structure. This third type, entirely due to viscous effects, represents evanescent waves with an along-channel decay distance bounded by the boundary-layer thickness. The solution to the viscous Taylor problem is then written as a superposition of these normal modes: an incoming Kelvin wave and a truncated sum of reflected modes. To satisfy no slip at the lateral boundary, we apply a Galerkin method. The solution displays boundary layers, the lateral one at the basin’s closed end being created by the (new) modes of the third type. Amphidromic points, in the inviscid and frictionless case located on the centreline of the basin, are now found on a line making a small angle to the longitudinal direction. Using parameter values representative for the Southern Bight of the North Sea, we finally compare the modelled and observed tide propagation in this basin.Delft Institute of Applied MathematicsElectrical Engineering, Mathematics and Computer Scienc
Reinforcing glass with glass: Application of transport reinforcement in structural glass beams
No full textDue to the increasing demand of transparency in buildings, it is no longer unusual to apply transparent elements into the bearing structure. Glass is a strong but very brittle material, which means safety is rather problematic should it break. Safety is an issue that has to be improved before glass can be considered suitable for structural elements. Earlier studies have shown that reinforcing glass beams will provide reasonable residual load-bearing capacity, which could provide this safety. Glass fibre is suitable as reinforcement material when the transparency is regarded as important. In February 2009 at the Faculty of Architecture at Delft University of Technology, P.C. Louter designed and tested a laminated glass beam with embedded glass fibre rods. The bonding interlayer consisted of SentryGlas foil, developed by DuPont and often applied for lamination in hurricane-resistant windows. The results were promising and the concept showed high potential for further research. The study of this thesis project is focussed on improving the concept of embedding reinforcement in laminated glass beams.Design and ConstructionCivil Engineering and Geoscience
The influence of basin geometry on equilibrium and stability of double inlet systems
No full textThis study investigates the influence of basin geometry on the cross-sectional stability of double inlet systems. The inlet is in equilibrium when the amplitude of the inlet velocities equals the equilibrium velocity (~1 m s-1). This equilibrium is stable when after a perturbation the cross-sections of both inlets return to their original equilibrium value. The necessary amplitudes of the inlet velocities are obtained using an idealized 2DH hydrodynamic that calculates tidal elevation and flow in a geometry consisting of several adjacent rectangular compartments. Model results suggest that regardless of the inclusion or exclusion of bottom friction in the basin, stable equilibrium states exist. Qualitatively, the influence of basin geometry does not change the presence of stable equilibrium. Quantitatively, however, taking a basin surface area of 1200 km2, equilibrium values can differ up to a factor 2 depending on the geometry of the basin.Hydraulic EngineeringCivil Engineering and Geoscience
Influence of liquefaction on scour around offshore monopile foundations
No full textScour hole formation around offshore monopile foundations is a threat for the structure’s stability. Large uncertainty leads to conservatism in design codes and hence to high construction costs. Under the same hydrodynamic loading as for scour hole formation the soil can liquefy due to structural vibrations or waves. The aim of this study is to determine the effect of liquefaction from vibrations of offshore monopile foundations on scour by performing scaled flume experiments, where liquefaction is induced by a monotonic excess pore water pressure (EPWP). Liquefaction is known to be caused by EPWP build up under cyclic loading and normally lasts for limited time, because the built up pore water pressure drains off to the bed surface. Therefore, monotonic EPWP is introduced at the bottom of a pile, which is placed in a flume filled with fine sand. During the experiments a current is used to induce scour, while the EPWP is used as independent variable. In the experiments the EPWP gradient is observed to take some time to bring the sediment into liquefaction. First the soil is lifted, but as soon as the vertical resistance of the sand is lost a current breaks through. Subsequently, the flow concentrates in one feeder and sediment is transported as if it is in suspension. When this occurs depends on the magnitude of the EPWP. During the scour experiments this resulted in a sudden collapse of the scour hole. The scour depth decreased and a new balance arises between slope sliding and erosion due to the horseshoe and lee-wake vortices. It is concluded that under liquefaction the equilibrium scour depth decreases for a larger negative excess pore water pressure gradient. Furthermore, the angle of repose is decreased. The equalising effect of liquefaction on the scour hole is also expected in field situations, but the extent is unknown. The potential gain of the decreased scour depth to the structure’s stability is limited, since the liquefied area may not be expected to provide any contribution to the stability of the structure.Structural MechanicsStructural EngineeringCivil Engineering and Geoscience
Three-dimensional semi-idealized model for tidal motion in tidal estuaries
No full textIn this paper, a three-dimensional semi-idealized model for tidal motion in a tidal estuary of arbitrary shape and bathymetry is presented. This model aims at bridging the gap between idealized and complex models. The vertical profiles of the velocities are obtained analytically in terms of the first-order and the second-order partial derivatives of surface elevation, which itself follows from an elliptic partial differential equation. The surface elevation is computed numerically using the finite element method and its partial derivatives are obtained using various methods. The newly developed semi-idealized model allows for a systematic investigation of the influence of geometry and bathymetry on the tidal motion which was not possible in previously developed idealized models. The new model also retains the flexibility and computational efficiency of previous idealized models, essential for sensitivity analysis. As a first step, the accuracy of the semi-idealized model is investigated. To this end, an extensive comparison is made between the model results of the semi-idealized model and two other idealized models: a width-averaged model and a three-dimensional idealized model. Finally, the semi-idealized model is used to understand the influence of local geometrical effects on the tidal motion in the Ems estuary. The model shows that local convergence and meandering effects can have a significant influence on the tidal motion. Finally, the model is applied to the Ems estuary. The model results agree well with observations and results from a complex numerical model.Delft Institute of Applied MathematicsElectrical Engineering, Mathematics and Computer Scienc
- …
