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  • 1
    Call number: MOP Per 68/B(127)
    In: IFM-GEOMAR report
    Type of Medium: Monograph available for loan
    Pages: 99 S.
    Series Statement: Berichte aus dem Institut für Meereskunde der Universität Kiel 127
    Location: MOP - must be ordered
    Branch Library: GFZ Library
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  • 2
    Call number: ZSP-166-4
    Pages: 29 S. : Ill. : 29 cm
    ISSN: 0931-0800
    Series Statement: Berichte aus dem Fachbereich Geowissenschaften der Universität Bremen 4
    Branch Library: GFZ Library
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 61 (1989), S. 223-232 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract Human observers viewed dichoptic orthogonal sine-wave gratings and indicated when exclusive visibility occurred in either eye. Contrast was held constant in one eye and was increased or decreased in the other eye for a number of alternation cycles (continuous presentation) or for only the duration of a single period of exclusive visibility (synchronous presentation). The synchronous presentation condition allowed us to identify the differing effects of contrast during the suppressed and during the dominant periods. Mixed phases were recorded as distinct from suppressed and dominant phases, and new classifications of compound-dominant and compound-suppressed phases are defined. The results indicate that binocular rivalry responds to stimulus contrast in two ways.1) The duty-cycle of dominance and suppression is determined by the relative image contrast between the two eyes, with dominance of the higher contrast image being favored, and2) the overall rate of alternation is driven by monocular image contrast during the suppressed phase (increased monocular contrast increases the alternation rate) and to a lesser extent by monocular contrast during the dominant phase (increased monocular contrast decreases the rate). A model is developed to reflect these ideas. These results support a reciprocal inhibition oscillator as the underlying mechanism of binocular rivalry.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  The design and calibration of a unique thin unsteady pressure sensor for use on small-scale marine propellers is presented. The Polyvinylidene Fluoride film-based sensor incorporates a miniature interface circuit suitable for use where space is a premium. Sensitivity of the sensor is comparable to high-quality microphones. Calibration is performed using an acoustic source and an industry-standard microphone. Evaluation of the sensor’s performance is presented for white noise unsteady pressure input. Results show excellent agreement between sensor-measured pressures and standard microphone-measured pressures.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Noise radiation from a four bladed, 10 in. diameter propeller operating in air at a rotational speed of 3000 RPM and a freestream velocity of 33 ft/s was experimentally analyzed using hot-wire and microphone measurements in an anechoic wind tunnel. Turbulence levels from 0.2 to 5.5% at the propeller location were generated by square-mesh grids upstream of the propeller. Autobicoherence measurements behind the blade trailing edges near the hub and tip showed regions of high phase-coherence between the blade-passage harmonics and the broadband frequencies. Inflow turbulence reduced this coherence. By relating the fluctuation velocities in the propeller wake to the unsteady blade forces, the primary regions of tonal noise generation have been identified as the hub and tip regions, while the midspan has been identified as a region responsible for broadband noise generation. These measurements were complimented by cross-spectra between the propeller wake-flow and the measured sound. The effect of turbulence on the radiated noise level showed an overall increase of 2 dB in the broadband levels for every 1% increase in turbulence. This effect varied for different frequency bands in the acoustic spectrum.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  Specially-developed Polyvinylidene Fluoride film sensors were used to measure the unsteady surface pressure on a small-scale marine propeller. Pressure response of the propeller blades to a spatially-varying-mean axial velocity flowfield was measured. Raw data were corrected for the thermally-induced sensor output in the nominally stratified flow with the aid of a blade-mounted constant-current anemometer. Corrected pressure measurements showed a phase lag in the blade pressure response relative to the mean velocity cycle. The necessity to consider thermally-induced sensor response was demonstrated.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Experiments in fluids 3 (1985), S. 61-70 
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The role of the flow visualization in providing the necessary insight for the development of theoretical models of complex afterbody and base flows is described. Methods of calculating the turbulent base pressure for axisymmetric configurations are discussed. Emphasis is placed on the treatment of supersonic flows for cylindrical, boattail, and flare bodies as well as sharp and blunt cones and base flow nozzles. The guidance provided by flow visualization in the development of theoretical models for the transonic case is also discussed. The current interests in applying finite difference techniques to these-problems indicate that the extensive use of flow visualization data will continue.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An experimental investigation was conducted on the performance and boundary layer characteristics of the Wortmann FX 63-137 airfoil with and without trip wire roughness. Data were obtained through use of a three-component strain gage force balance and static pressure measurement equipment at a test Reynolds number of R c = 100,000. Emphasis was placed on determining the effect of trip wire placement and size on such performance parameters as (C l /C d )max and (C l 3/2 /C d )max. Prediction of transition location by the criterion due to Tani and Gibbings was found to have limited application. Most trip wire locations resulted in degraded performance, but for some locations, minimum drag was reduced, maximum lift to drag ratio increased, and hysteresis averted.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The results of an investigation of the influence of free stream disturbances on the lift and drag performance of the Lissaman 7769 airfoil are presented. The wind tunnel disturbance environment is described using hot-wire anemometer and sound pressure level measurements. The disturbance level is increased by the addition of a ‘turbulence screen’ upstream of the test section and/or the addition of a flow restrictor downstream of the test section. For the Lissaman airfoil it was found that the problems associated with obtaining accurate wind tunnel data at low chord Reynolds numbers (i.e., below 200,000) are compounded by the extreme sensitivity of the boundary layers to the free stream disturbance environment. The effect of free stream disturbances varies with magnitude, frequency content, and source of the disturbance.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The effects of an accelerating freestream from a nonzero velocity on the transitional separation bubble characteristics were investigated quantitatively. Hot wire anemometry was used to determine the boundary layer velocity profile repsonse to the acceleration at selected chordwise locations on a Wortmann FX 63-137 airfoil at 7 ° angle of attack. Both positive and negative accelerations were studied from base chord Reynolds number of 100,000 and 150,000, respectively. The purpose of this experiment was to verify the trends witnessed in previous research concerning a sinusoidally oscillating freestream velocity by uncoupling the accelerating and decelerating boundary layer effects. The experimental results indicate that as a result of a freestream acceleration, the separation bubble position shifts in the direction opposite to the chordwise direction it would move for a quasi-steady velocity change. The transition location was more responsive to the acceleration than was the separation position. This supports the oscillating freestream experiment conclusions.
    Type of Medium: Electronic Resource
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