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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Acta mechanica 100 (1993), S. 241-251 
    ISSN: 1619-6937
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The study of two-dimensional, irrotational, inviscid, incompressible steady state motion generated by a polygonal and a smooth obstruction, is made in terms of the linearized theory. The bottom is represented in integral form using Fourier's double integral theorem. Then following Lamb [1], a linear free-surface profile is obtained for the supercritical and subcritical cases. The results are plotted and discussed for the two cases of the flow for different shapes of the bottom and different values of Froude number,F.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1619-6937
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1619-6937
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The problem considered is a steady, two-dimensional, and irrotational flow of an incompressible and inviscid fluid under the action of gravity. The boundary of the flow domain consists of a free boundary part “C f ” and an analytic solid boundary part “C s ” and they meet in a common endpoint “0”. The flow is determined by the inverse velocity potential functionz=f(w) and the conjugate flow velocity $$u = \frac{{dw}}{{dz}}$$ is given by the reciprocal derivative $$u\left( w \right) = \frac{1}{{f'\left( w \right)}}$$ . Following the method suggested by Carter, we will be able to expressz(w) andu(w) as an infinite asymptotic expansion near the origin in powers ofw 1/2 andw 1/2 lnw. Upon imposing the flow conditions on these expansions we will obtain the expansion of the conjugate velocityu to terms of orderw 3/2 as well as the shape of free streamline. The importance of the results of this problem is that it gives simple, and more accurate, qualitative features of the local flow behaviour. Numerical examples have been considered and the results are given in quantitative diagrams to show the progress of the obtained higher approximation.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1619-6937
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary A theoretical study is made, of an irrotational, inviscid incompressible and steady flow over a two-dimensional trapezoidal obstacle; with disturbing height ε, lying on the bottom of the running stream, in terms of a linearised theory. Particular attention is given to two cases of the flow, the supercritical and the subcritical. The bottom is represented in integral form using Fourier's double-integral theorem. Following the method suggested by Thomson (1886) and Lamb (1932), we obtain a linearised free-surface profile in series form for the two cases of flow. The linearised solution obtained is based on the assumption that the height of the trapezoidal bump, ε, is small compared to the channel depth,h. The nature of the free-surface formed depends on whether the flow is subcritical or supercritical. The results are plotted for the two cases of the flow for different shapes of the bottom and different values of Froude number,F. The effect of the Froude number, the bottom height and the shape of the bottom are discussed.
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  • 5
    ISSN: 1434-6079
    Keywords: 34.00 ; 34.80B ; 34.90
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Precision data on transient magnetic fields (TF) in ferromagnetic Gd and Fe were obtained for oxygen ions at velocities between 2 and 8v 0 (v 0=c/137) using the16O(3−) state as probe. At the high velocities the TF in Gd were found to be twice as large as in Fe which is in contrast to the generally observed scaling with the polarization density of the hosts. Degrees of polarization could be deduced from TF strengths using measured ion fractions of singly occupiedK-shell. The values derived were compared with theoretical estimates based on spin exchange scattering as a possible polarization mechanism.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Boundary layer meteorology 62 (1993), S. 3-20 
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract As a result of several air quality model evaluation exercises involving a large number of source scenarios and types of models, it is becoming clear that the magnitudes of the uncertainties in model predictions are similar from one application to another. When considering continuous point sources and receptors at distances of about 0.1 km to 1 km downwind, the uncertainties in ground-level concentration predictions lead to typical mean biases of about ±20 to 40% and typical relative root-mean-square errors of about 60 to 80%. In fact, in two otherwise identical model applications at two independent sites, it is not unusual for the same model to overpredict by 50% at one site and underpredict by 50% at the second site. It is concluded that this fundamental level of model uncertainty is likely to exist due to data input errors and stochastic fluctuations, no matter how sophisticated a model becomes. The tracer studies that lead to these conclusions and have been considered in this study include: (1) tests of the Offshore and Coastal Dispersion (OCD) model at four coastal sites; (2) tests of the Hybrid Plume Dispersion Model (HPDM) at five power plants; (3) tests of a similarity model for near-surface point source releases at four sites; and (4) tests of 14 hazardous gas models at eight sites including six sets of experiments where dense gases were released.
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  • 7
    ISSN: 1573-269X
    Keywords: liquid sloshing modeling ; impact ; parametric resonance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract The parametric excitation of an elevated water tower experiencing sloshing hydro-dynamic impact is studied using the multiple scales method. The liquid sloshing mass is replaced by a mechanical model in the form of a simple pendulum experiencing impacts with the tank walls. The impact loads are modeled based on a phenomenological representation in the form of a power function with a higher exponent. In this case the system equations of motion include impact nonlinearities (selected to be of fifth power) and cubic structural geometric nonlinearities. When the first mode is parametrically excited the system exhibits hard nonlinear behavior and the impact loading reduced the response amplitude. On the other hand, when the second mode is parametrically excited, the impact loading results in complex response behavior characterized by multiple steady state solutions, where the response switches from soft to hard nonlinear characteristics. Under combined parametric resonance, the system possesses a single steady-state response in the absence and in the presence of impact. However, the system behaves like a soft system in the absence of impact and like a hard system in the presence of impact.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1572-9486
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Preliminary results of measurements of proton energy spectra and search for coincidentp, n pair emission following negative muon capture in12C,16O,27Al are given. A very clear signal for proton emission is found, which can be exploited in future detailed studies.
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  • 9
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Traditionally ferrites have been used in accelerators for tuning rf cavities and in nonreciprocal devices controlling the power flow in rf accelerating systems. Recently, the development of cavity tuners based on perpendicularly biased ferrites has shown good progress. Yttrium iron garnet (YIG) is gradually replacing the traditional Ni Zn ferrites. The use of conventional parallel-biased Ni Zn ferrites for varying the frequency of accelerating cavities has the disadvantage of high saturation magnetization (4πMs). This precludes practical operation in low magnetic loss regions. Different substitutions have been used with YIG to reduce its 4πMs, making it a practical candidate for perpendicular biasing operating in the saturation region. In addition, YIG is known for its low dielectric and magnetic losses. In this paper we give a short review of development in accelerator cavity tuners based on perpendicularly biased iron garnet ferrites. We use the operation of a 52 MHz stripline-based YIG tuner which we have tested at BNL as an example to demonstrate the advantages of using YIG in cavity tuners. We also discuss magnetic tuning techniques based on magnetostriction of Ni.
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5505-5505 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This experimental investigation is concerned with the study of diffraction of magnetostatic waves (MSWs) by surface acoustic waves (SAWs) when both types of waves travel in the same yttrium iron garnet (YIG) film. The SAWs are used to set up a space and time modulation of the medium in which the MSW propagates. Because of their mostly isotropic propagation properties in the plane of the film, magnetostatic forward volume waves are employed in this investigation. In the configuration used, MSW is launched at different angles with respect to the acoustic beam. Different MSW microstrip transducers are used to detect the scattered and unscattered MSW signals. The frequency of the Bragg-diffracted MSW signal is shifted by an amount equal to the SAW frequency. The MSW microstrip transducers are 65-μm-wide and 15-μm-thick copper lines on an RT/duroid substrate of thickness of 5 mils and εr=10.5. A YIG film of 120 μm thickness is placed in contact with the microstrip structure described above. A dc magnetic field is applied normal to the film plane. The SAW is excited using bulk wave transducers (36° Y-cut lithium niobate) placed on plexiglass wedges to convert the bulk acoustic waves into SAW. Our experimental results are in good agreement with calculations based on Bragg's diffraction. Different device applications that employ this effect for spectrum analysis1 and frequency shifting2 have been proposed recently.
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