2,427 research outputs found
Nadere verfijning DUROSTA-model: Toetsing H/Tw-parameter en aanpassing t.b.v. porositeitsverschillen en strandtransporten
No full textTeneinde het DUROSTA-model verder te verbeteren zijn de effecten modellering nader onderzocht en is de schaalgrootheid H/Tw nader bekeken.TAW/EN
Development of a rotor model for the numerical simulation of helicopter exterior flow-fields
No full textIncludes bibliographical references (leaves 84-85).A numerical methodology is developed to model the effect of a rotor on the surrounding flow-field. The model calculates the time-averaged aerodynamic forces exerted on the air by the fan blades within the blade-swept region, and permits the user to specify blade properties such as cross-sectional profile and orientation at a particular radial and azimuthal location. The calculated forces are included as source terms within the Reynolds-averaged Navier-Stokes equations for an incompressible fluid, which are solved by the commercial CFD solver, FLUENT. The effects of turbulence are incorporated through the use of Launder and Spalding's k-g turbulence model. This method is selected as being the most efficient use of the resources available, giving the economic advantages of a steady simulation, while allowing radial and azimuthal variations of rotor characteristics. In order to validate the accuracy of the numerical model for both aligned and non-aligned inflow conditions, results are compared with experimental data reported for an axial flow fan. Agreement between experimental and numerical results is excellent to good. Fan static pressure rise is closely predicted by the numerical solution, while fan power consumption and fan static efficiency are under and over-predicted respectively. This error may be attributed to frictional losses not accounted for in the numerical model. These include physical rotational instabilities, leading to increased mechanical losses, and tip effects due to the clearance between the fan blade tips and the fan casing. Trends are nevertheless consistently predicted by the numerical model for inflow angles up to 45°, and for the range of blade pitch settings used. The adverse effect of off-axis inflow on the fan static pressure rise is numerically predicted, while fan power consumption is found to remain independent of inflow angle, as had been experimentally observed. The rotor model is finally integrated with the fuselage of the CIRSTEL (Combined Infra-Red Suppression and Tail rotor Elimination) prototype in an analysis of the helicopter exterior flow-field. No experimental data for this configuration was available for validation purposes. However, the model is used in the simulation of several common helicopter flight conditions. Results are presented graphically, and generally indicate good agreement with physically observed phenomena
Third body effects in the period changes of two Algol binaries: V342 Aql and TW Lac
Full text link32nd International Physics Congress of Turkish-Physical-Society (TPS) -- SEP 06-09, 2016 -- Bodrum, TURKEYThe O - C diagrams of two Algol-type eclipsing binaries V342 Aql and TW Lac have been analyzed with the least-squares method by using all available minima times. The period changes in their O - C diagrams have been discussed with respect to the Light-Time Effect (LITE) that originates from gravitational influence of a third body. New LITE elements, orbital periods and possible minimum masses of third bodies are given.Turkish Phys So
Increasing science, technology, engineering, and mathematics skills using Project Lead the Way
Full text linkIncludes bibliographical references
Psychological, social and welfare interventions for psychological health and well-being of torture survivors
Full text linkThis is the protocol for a review and there is no abstract. The objectives are as follows: Primary objective 1. To assess beneficial and adverse effects of psychological, social and welfare interventions versus no treatment for the reduction of psychological distress in torture survivors. Secondary objectives 2. To describe the quality and generalisability of the studies evaluating the effects of these treatment approaches on torture survivors, and specifically: • to provide an objective assessment of risk of bias in these studies; • to describe the specific populations evaluated in studies of torture survivors (including demographics, torture experiences and psychological status); • to describe the variety of interventions that have been evaluated in these populations; and • to describe the outcomes evaluated in these intervention studies
High-efficiency supercontinuum generation in solid thin plates at 0.1 TW level
No full text
Supercontinuum generation in a solid-state medium was investigated experimentally. A continuum covering 460 to 950 nm was obtained when 0.8 mJ/30 fs Ti: sapphire laser pulses were applied to seven thin fused silica plates at a 1 kHz repetition rate. The primary processes responsible for spectral broadening were self-phase modulation (SPM) and self-steepening, while SPM and self-focusing were balanced to optimize the spectral broadening and suppress the multi-photon process. The output was compressed to a 5.4 fs and a 0.68 mJ pulse, corresponding to two optical cycles and 0.13 TW of peak power. (C) 2017 Optical Society of America</p
Flow compensation in a MEMS dual-thermal conductivity detector for hydrogen sensing in natural gas
Full text linkConventional thermal conductivity detectors (TCDs) demonstrate a flow dependence. The approach presented here to reduce the flow dependence is based on the on-line flow compensation using two thin-film sensors on membranes in parallel on the same chip that are differentially operated. These are laterally identically, but with a different depth of the detection chamber, resulting in different quasi-static sensitivities to the thermal conductivity of the sample gas. The effects of conduction and convection in the structure have been studied using COMSOL Multiphysics. First prototypes have been fabricated and are presently tested.Accepted Author ManuscriptElectronic Instrumentatio
Two-cycle, 2.5 TW pulse generation at 1.8 \u3bcm via Frequency domain Optical Parametric Amplification
No full textA non-collinear Frequency domain Optical Parametric Amplifier is used to produce a 1.8 \u3bcm, 30 mJ, 13 fs laser source, leading to 2.5 TW peak power. This laser opens the way for high brightness soft X-ray attosecond pulses.Peer reviewed: YesNRC publication: Ye
O znaczeniu fałszywego świadectwa. Przypadek TW „Jakuba” a fikcje operacyjne SB dotyczące tajnych współpracowników
Full text linkThe author analyses the case of the fictitious secret collaborator under the pseudonym Jacob, reconstructing the circumstances of his registration and deregistration, and setting it against the background of other fictional activities in the Security Service (Polish: Służba Bezpieczeństwa, SB). Thanks to the concept of false testimony by Robin G. Collingwood, the problem of fictions and forgeries present in SB operational documents is outlined. In conclusion, the author attempts to synthesise the critical issues of the research discourse centred around the problem of secret collaborators.Autor analizuje przypadek fikcyjnego tajnego współpracownika ps. Jakub, rekonstruując okoliczności rejestracji i wyrejestrowania TW oraz osadzając go na tle innych fikcyjnych działań w Służbie Bezpieczeństwa. Dzięki koncepcji fałszywego świadectwa Robina G. Collingwooda zarysowany zostaje problem fikcji i fałszerstw obecnych w dokumentach operacyjnych SB. W zakończeniu podjęta jest próba syntezy kluczowych problemów dyskursu badawczego skupionego wokół tajnych współpracowników
Time-resolved spectroscopy of the dynamic Stark effect
No full textThis study reports on the ac Stark effect of nitric oxide electron-vibration (vibronic) levels dressed by an intense, bichromatic laser field. The aims of the work are to make quantitative measurements of the magnitude of the ac Stark shift of vibrational levels connected by the A 2Σ+ ← X2Π1/2 transition and to map out the cycle-averaged level separation during the Stark field. In pump-probe experiments at intensities up to 30 TW cm-2, the ac Stark shift of the A2Σ+ vA = 2 ← X2Π1/2 vX = 0 transition is found to be Δε2←0(S)(800nm) = 0.34 \ub1 0.05Up, where Up is the ponderomotive energy. By varying the time delay between component fields, the time dependence of the population in the A2Σ+ vA = 2 state is mapped out under different intensity conditions. Fluorescence monitoring of the upper level serves to identify the Stark-shifted transition and reveals that real population remains in the upper level after interacting with the short-pulse laser fields. Semiclassical calculations of NO irradiated by a bichromatic field indicate the direction of the A2Σ+ and X 2Π1/2 level shifts and show that the population promoted to and retained in the A2Σ+ state is determined predominantly by intra-Rydberg state interactions rather than by multiphoton loss processes. The calculations also indicate that the magnitude of the ac Stark effect of the A2Σ+ ← X 2Π1/2 transition depends on the spatial orientation of the molecule with respect to the linear polarization sense of the applied laser field
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