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Showing papers on "Wave power published in 1994"


Journal ArticleDOI
TL;DR: In this paper, the authors investigated wave propagation in a superlattice consistent of dielectric material with a nonlinear Kerr coefficient and found gaps in the propagating properties of the medium that depend critically on the injected wave power.
Abstract: We investigate wave propagation in a superlattice consistent of dielectric material with a nonlinear Kerr coefficient. We find gaps in the propagating properties of the medium that depend critically on the injected wave power. This property can be used for transmission of information.

15 citations


Journal ArticleDOI
TL;DR: In this article, the effects of the accessibility condition on lower hybrid current drive (LHCD) were investigated in JT-60U, where the wave intensity on the plasma periphery, which is detected by a Langmuir probe located on the divertor plate, is also consistent with an inaccessible power fraction going into the plasma interior.
Abstract: The effects of the wave accessibility condition on lower hybrid current drive (LHCD) are investigated in JT-60U. The density dependence of the detectable maximum photon energy of hard X rays in LHCD plasmas is consistent with that of the maximum electron energy which is limited by the accessibility condition. The current drive efficiency and the driven current profile are affected by the accessibility condition. Inaccessible wave power enhances impurity content, particle recycling and main plasma radiation loss, and in extreme cases triggers a MARFE. The wave intensity on the plasma periphery, which is detected by a Langmuir probe located on the divertor plate, is also consistent with an inaccessible power fraction going into the plasma interior. A ray trace analysis taking account of toroidal effect indicates that the inaccessible wave power is localized on the plasma periphery and finally propagates into the divertor plasma region

13 citations


Journal ArticleDOI
TL;DR: In this paper, a nonlinear coupling mechanism between the primary wave and a lower-frequency wave is explored to explain the presence of the sideband emissions, and the theoretical results with the wave data confirm this mechanism as a viable explanation for the observed sidebands.
Abstract: Sideband wave emissions are secondary peaks in wave power observed at frequencies above and below the primary peak. Observed sideband amplitudes are usually reduced compared to the primary wave amplitude. During the recent CHARGE 2B ionospheric rocket mission, sideband waves were observed during an electron beam injection experiment. The beam current was modulated causing a peak in wave power at the modulation frequency and at certain times sidebands were observed along with the primary wave emission. A nonlinear coupling mechanism between the primary wave and a lower-frequency wave is explored here to explain the presence of the sideband emissions. Comparison of the theoretical results with the wave data confirm this mechanism as a viable explanation for the observed sidebands.

13 citations



Patent
04 Oct 1994
TL;DR: In this article, a reeds-shaped piezoelectric elements are mounted to a wall of a power-generating box 8 that is communicated with the air chamber 2 through a duct 5.
Abstract: PURPOSE:To make generation of electricity possible by flexure deformation caused by oscillation of piezoelectric elements in a power generation apparatus activated by wave power. CONSTITUTION:A cavity 20, communicated with the outside water through an opening 1b of a wall body 1, is provided and an air chamber 2 is formed above the water level 3 in the cavity 20. A number of power-generating units 9 are mounted to a wall of a power-generating box 8 that is communicated with the air chamber 2 through a duct 5. The power-generating units 9 are equipped with reeds-shaped piezoelectric elements 13 that oscillate by airflow flowing through the duct 5 and the inside of the box 8 in accordance with rise and fall of the water level 3.

5 citations


Patent
07 Jun 1994
TL;DR: In this paper, a novel operational principle is used, wherein a large variation of impedance of a strip line, provided for converting electro-magnetic waves into magneto-static waves in the vicinity of saturation of the magnetostatic wave.
Abstract: To overcome conventional increase of insertion loss and conventional discrepancy of phase characteristic of an S/N enhancer provided for increasing S/N of an electro-magnetic wave to be converted into a magneto-static wave by utilizing saturation of magneto-static wave power propagating through a ferrite thin film, a novel operational principle is used, wherein a large variation of impedance of a strip line, provided for converting electro-magnetic waves into magneto-static waves in the vicinity of saturation of the magneto-static wave. The electro-magnetic wave reflected from the input terminal of the strip line is selectively derived as an output wave through a directional coupling device. As a result, particularly for an electro-magnetic wave applied with wide-band FM modulation, S/N can be remarkably increased without any increase of insertion loss or any influence of phase characteristic discrepancy.

5 citations


Journal ArticleDOI
TL;DR: In this article, an axially magnetized cold plasma column contained in a dielectric tube, surrounded by a vacuum and shielded by a metallic cylinder, was considered and closed-form analytical expressions for the wave dispersion relation, wave power, absorbed power and wave attenuation coefficient of the right-hand circularly polarized dipolar electromagnetic waves were given.
Abstract: We consider an axially magnetized cold plasma column contained in a dielectric tube, surrounded by a vacuum and shielded by a metallic cylinder. Closed-form analytical expressions for the wave dispersion relation, wave power, absorbed power and wave attenuation coefficient of the right-hand circularly polarized dipolar electromagnetic waves are given. In view of plasma production by such waves their phase diagrams are discussed. The external DC magnetic field is found to facilitate the column sustainment, especially at low values of the product plasma radius*wave frequency, and can remove occasionally occurring wave reflections from the column end. In the presence of a metallic shield one can observe fast wave propagation at higher powers. The axial structure of plasma columns sustained by the fundamental plasma mode HEII has been obtained under a free-fall/diffusion gas-discharge regime. In the limit of an infinite metallic cylinder radius the results for the wave phase and attenuation coefficients coincide with those derived numerically by Margot and Moisan (1991).

3 citations


Journal ArticleDOI
TL;DR: In this article, an oscillating water column-type (OWC) wave power converter was developed by the Coastal Development Institute of Technology (CDIT) for the Japanese Ministry of Transport.
Abstract: Commissioned by the Japanese Ministry of Transport, the Coastal Development Institute of Technology has developed an oscillating water column-type (OWC) wave power converter. The wave power extract...

3 citations


31 Dec 1994
TL;DR: In order to save money to build a Pendulor Wave Power Converter, a new Pendulors was invented and studied as discussed by the authors, and the results obtained by the studies, design for remodeling of Muroran Wave Test Plant was accomplished.
Abstract: In order to save money to build a Pendulor Wave Power Converter, a new Pendulor was invented and studied. Applying the results obtained by the studies, design for remodeling of Muroran Wave Test Plant was accomplished. The feature occupies less space, provides easy installation and is safer against storms. The new plant will be completed in May 1994. The Pendulor utilizes pendular motion excited by ocean waves and then the motion is altered to a generator running by means of an oil pump/motor set.

3 citations


Patent
15 Apr 1994

2 citations


Patent
15 Jul 1994

01 Jan 1994
TL;DR: In this article, a particle-in-cell simulation of wave-particle interactions in a space environment has been proposed to identify correlations between the phase of the wave-field and the fluxes of energetic particles.
Abstract: Langmuir emissions in space are reported to be clumpy and intermittent. The high-frequency wave power appears concentrated in spatial packets, whether amidst the solar wind or on auroral field lines. Due to the plasma motion relative to the spacecraft, determining the source for the wave free energy in the three-dimensional electron distribution function has always been difficult, since the unstable features pass by the detector in presumably too short time to be measured. The range of unstable phase velocities and growth rates have generally been estimated rather than determined by unequivocal measurements. The analysis of wave-particle interactions in a space environment has taken recently a new turn with the development of wave correlators on board rockets and satellites. Such instruments seek to identify correlations between the phase of the wave-field and the fluxes of energetic particles. The data interpretation is complex, however, it must be backed by a detailed theoretical understanding of the wave-particle interaction, including the phase relation for inhomogeneous packets. To this end Langmuir packets interacting with fast electrons can be studied in the appropriate regime by means of particle-in-cell simulations, provided that one succeeds in reducing the level of the fluctuations, enhancing the signal-to-noise ratio, and incorporating the appropriate boundary conditions. The first results of such simulations are presented here as a test and expansion of previous analysis.


Patent
29 Nov 1994
TL;DR: In this article, a rocking body is installed around the axial center of a turning shaft pivotally supported in a gap with a wall, and a windmill and an air hole are installed on an upper part in an air tank 1E installed in the structure, while a power generating means, which converts a rotary motion by an air flow to be produced by a rokcing motion due to waves of the rocking body 3 and a sea surface variation in the windmill 4 into electricity, is installed in this floating structure 1 as the constitution.
Abstract: PURPOSE:To provide a wave activated generating set that improves the recovery efficiency of wave energy, reducing the cost of production, and gets maintenance facilitated. CONSTITUTION:A rocking body 3 is installed, as being rocking motion around the axial center of a turning shaft 3A pivotally supported in a gap with a wall 1A, in each paritioned part 1B of a floating structure 1 to be formed by the partioned wall 1A radially installed from the central part, and a windmill 4 and an air hole 6 are installed on an upper part in an air tank 1E installed in the structure 1, while a power generating means, which converts a rotary motion by an air flow to be produced by a rokcing motion due to waves of the rocking body 3 and a sea surface variation in the windmill 4 into electricity, is installed in this floating structure 1 as the constitution. Accordingly, as plural pieces of rocking bodies 3 are set up on the circumference of this structure 1, wave energy is effectively recoverable even if a sense of waves is varied by a wind direction or the like, and further a mooring system is adopted, so that it can be easily set up in an optional position, whereby the cost of installation is reducible and simultaneously maintenance is also achievable in an easy manner.

Patent
05 Apr 1994
TL;DR: In this article, the authors proposed an inexpensive wave power apparatus which can always extract a constant amount of power from waves substantially irrespective of wave changes, which can be constructed over a coastal gully, so that waves can cause the water level to rise and fall in the chamber, and so cause air to flow to and fro in a duct.
Abstract: PURPOSE: To provide an inexpensive wave power apparatus which can always extract a constant amount of power from waves substantially irrespective of wave changes. CONSTITUTION: A wave power apparatus 10 includes a chamber 16 which may be constructed over a coastal gully 12 so that waves 14 cause the water level to rise and fall in the chamber, and so cause air to flow to and fro in a duct 32. A Wells-type biplane turbine 34 in the duct 32 drives a generator 36. The turbine 34 comprises two turbine discs 45 which left 0.5 m, each defining a hub, a plurality of airfoil section straight blades 80, and an out ring 56. The ring 56 is sufficiently massive to act as an energy-storage flywheel, and has a greater moment of inertia than the hub and the blades. Each turbine disc 45 might have a kinetic energy of at least 1 MJ when rotating at 1650 rpm.

01 Jan 1994
TL;DR: In this article, a new analysis method based on time series fitting using a nonlinear optimization technique was developed in order to study the hydrodynamic and restoring force characteristics from full scale free decaying test data.
Abstract: This paper deals with simulation and statistical prediction of total second order responses, including slow drift motions caused by waves and wind, of a full scale floating offshore structure. A new analysis method based on time series fitting using a nonlinear optimization technique was development in order to study the hydrodynamic and restoring force characteristics from full scale free decaying test data. To investigate the second order force characteristics and the contribution of wind fluctuations to slow drift motions, cross bi-spectral analysis of motion and waves, multi-input analysis of motion, waves, instantaneous wave power and wind fluctuations were carried out. With respect to the second order forces, a comparison between analyzed results and numerical results calculated by the potential theory is made. On a basis of these investigations, a comparison between measured time history of slow drift motion and simulations is carried out. Relating to statistical estimates of the probability density function and the extreme response, a new prediction method is developed to take account both second order wave forces and varying wind loads. At-sea measured sample data, the statistical prediction based on the Rayleigh distribution, e.e. the so-called Cartwright-Longuet-Higgins' estimates and the results obtained from the present method are compared.

Patent
07 Feb 1994

Proceedings ArticleDOI
15 Oct 1994
TL;DR: In this paper, the acceleration of electrons up to energies in the MeV range has been observed in JET during combined application of Lower Hybrid and Fast Wave in fully non-inductively driven discharges.
Abstract: Acceleration of electrons up to energies in the MeV range has been observed in JET during combined application of Lower Hybrid and Fast Waves in fully non‐inductively driven discharges. Without Fast Wave, the energy of the fast electrons remains below 200 keV. Up to 18% of the Fast Wave power has been estimated to be coupled to the fast electron population. This additional acceleration of electrons is defined as synergy between LH and Fast Wave. Specific experiments have indicated that the most likely responsible mechanism is the damping on fast electrons of an Ion Berstein Wave generated after mode conversion of the Fast Wave. The new JET RF systems, which are being prepared, (10 MW of Lower Hybrid and up to 20 MW of ICRF power at arbitrary phasing) will allow to assess if this synergism can be used to achieve the current drive efficiencies required in a reactor.

Journal ArticleDOI
TL;DR: In this article, a bidimensional explicit finite-difference simulation of a river delta growth, based on Pelnard-considere continuity equation, considering long-shore sediment transport as given by CERC formula, has been developed and fed by sets of marine events generated by means of a general Markovian-process simulator.
Abstract: A bidimensional explicit finite-difference simulation of a river delta growth, based on Pelnard-Considere continuity equation, considering long-shore sediment transport as given by CERC formula, has been developed and fed by sets of marine events generated by means of a general Markovian-process simulator. The simulation was restricted to the final stage of the sea-beach interaction, remaining it limited, seaward, to the consideration of pairs of values representing wave power and direction of wave motion. This kind of formulation allowed a computationally efficient way to represent persistent phenomena. River sand supply has been modelled by means of a simply stationary stochastic process. The operativeness of the model has been evaluated on some fixed conditions:a) beach length 20 km;b) non-erodible edges;c) river supply in the middle. In general, wave power ranged up to some unit·103 W/m, while sand river supply up to near 7·10−2 m3/s. Some models were left to evolve for 500 y, a time interval in which some significant event should occur. The results show how: 1) for long-time estimations a spatial resolution of 500 m could be a reasonable choice; 2) time step should be kept as small as possible, even in the absence of numerical instability; 3) wave-approaching angles simulation scheme impacts on final delta morphology; 4) sea status persistence strongly influences the final results; 5) even a simple (t/const) time adimensionalization may influence the results when high river sand supply meets low wave power conditions; 6) neglecting on/off-shore sediment transport reflects in a marked triangular equilibrium delta shapes; 7) the cuspate aspect of a river delta could be an indication of a non-erosion-dominated stage or of a growing one. Although for predictive engineering purpose 2D longshore formulations appear to be less attractive than 3D ones, it has been pointed out how some hypotheses can be tested, in an earth science operating context, using either moderate-complexity software or easily avilable computing devices.