Showing papers on "Wave power published in 2001"
TL;DR: In this article, the ULF wave drift resonance theory was used to explain relativistic electron phase space density enhancements in the recovery phase of most storms, and the results showed that five out of nine storm events are consistent with the wave-drone resonance mechanism.
Abstract: Using data from the Comprehensive Energetic Particle and Pitch Angle Distribution (CEPPAD)-High Sensitivity Telescope (HIST) instrument on the Polar spacecraft and ground magnetometer data from the 210 meridian magnetometer chain, we test the ULF wave drift resonance theory proposed to explain relativistic electron phase space density enhancements. We begin by investigating changes in electron flux due to the “Dst effect”. The Dst effect refers to the adiabatic response of relativistic electrons to changes in the magnetic field characterized by the Dst index. The Dst effect, assuming no loss or addition of new electrons, produces reversible order of magnitude changes in relativistic electrons flux measured at fixed energy, but it cannot account for the flux enhancement that occurs in the recovery phase of most storms. Liouville's theorem states that phase space density expressed in terms of constant adiabatic invariants is unaffected by adiabatic field changes and thus is insensitive to the Dst effect. It is therefore useful to express flux measurements in terms of phase space densities at constant first, second and third adiabatic invariants. The phase space density is determined from the CEPPAD-HIST electron detector that measures differential directional flux of electrons from 0.7 to 9 MeV and the Tsyganenko 96 field model. The analysis is done for January to June 1997. The ULF wave drift resonance theory that we test proposes that relativistic electrons are accelerated by an m=2 toroidal or poloidal mode wave whose frequency equals the drift frequency of the electron. The theory is tested by comparing the relativistic electron phase space densities to wave power determined at three ground stations with L* values of 4.0, 5.7 and 6.2. Comparison of the wave data to the phase space densities shows that five out of nine storm events are consistent with the ULF wave drift resonance mechanism, three out of nine give ambiguous support to the model, and one event has high ULF wave power at the drift frequency of the electrons but no corresponding phase space density enhancement suggesting that ULF wave power alone is not sufficient to cause an electron response. Two explanations of the anomalous event are investigated including excessive loss of electrons to the magnetopause and wave duration.
61 citations
TL;DR: In this paper, the authors compared the performance of different types of turbines under irregular wave conditions, and found that the running and starting characteristics of the impulse type turbines could be superior to those of the Wells turbine under the irregular wave condition.
46 citations
TL;DR: Alongshore gradients in wave energy and propagation direction were observed near a pier that extends 500 m from the Duck, N.C., shoreline to about 6m water depth as discussed by the authors.
Abstract: Alongshore gradients in wave energy and propagation direction were observed near a pier that extends 500 m from the Duck, N.C., shoreline to about 6-m water depth. When incident waves approached the beach obliquely, wave energy observed near the shoreline 200 m downwave of the pier was as much as 50% lower than observed 400 m downwave, and waves close to the pier were more normally incident than those farther downwave. Alongshore gradients were much smaller 400 m offshore of the shoreline, upwave of the pier, and with nearly normally incident waves, confirming that the gradients are associated with wave propagation under the pier. A spectral refraction model for waves propagating over the measured bathymetry, which includes a depression under the pier, accurately predicts the observations 400 m downwave of the pier, but overpredicts energy near the pier. Refraction model predictions that include partial absorption of wave energy by the pier pilings reproduce the observed alongshore gradients, suggesting that piling-induced dissipation may be important.
44 citations
05 Nov 2001
TL;DR: The Mighty Whale as mentioned in this paper is a floating type wave power device based on an oscillating water column (OWC) principle, which was installed at the test location, the mouth of Gokasho Bay in Mie prefecture, in July 1998.
Abstract: "Mighty Whale" is a floating type wave power device based on an oscillating water column (OWC) principle. The prototype of Mighty Whale was installed at the test location, the mouth of Gokasho Bay in Mie prefecture, in July 1998. The open sea tests were started on September 1998, and we are keeping on measuring many data to show the safety and economic features of the device. This paper shows an interim report of characteristics of wave energy absorption and power generation of the prototype by the open sea tests. The results of data analysis of the open sea tests at this time, average power output is 6-7 kWh and the maximum total energy efficiency is around 15% that is ranging from 6 seconds to 7 seconds of significant wave period. These are approximately similar to the values estimated by the theoretical analysis and water tank experiments before the open sea tests.
34 citations
TL;DR: In this paper, the most intense wave types (most commonly triggering burst mode data collection) are the broadbanded waves which are then studied in detail using the three-dimensional resolution of the EFI.
Abstract: Burst data from the electric field instrument (EFI) on the Polar satellite are used to classify cusp wave properties and the association of the observed waves with particle populations. The most intense wave type (most commonly triggering burst mode data collection) are the broadbanded waves which are then studied in detail using the three-dimensional resolution of the EFI. Finite wavelength effects are removed using two techniques: time-shifting of the sphere potentials to a spacecraft body reference time and spin angle selection. The corrected electric field signal exhibits a uniform spectrum in two dimensions. The wave properties are consistent with two-dimensional turbulence, with phase velocities smaller than the spacecraft velocity and frequency as low as (or lower than) the oxygen gyrofrequency. Owing to their low frequency, we conclude that these waves cannot resonate with and thus heat the ions. The broad k-spectrum and very low frequency in the plasma frame points toward drift or shear instabilities for wave excitation.
22 citations
Patent•
30 Mar 2001
TL;DR: In this paper, a movable offshore floater is provided with a chamber 3 which receives solar power to generate steam by evaporating the seawater, a steam turbine 8 which is actuated by the steam from the chamber 3, and a generator 9 driven by the turbine 8.
Abstract: PROBLEM TO BE SOLVED: To provide a floater type hydrogen and oxygen production system, with which hydrogen and oxygen can be efficiently mass-produced utilizing natural energies of the vast sea, such as solar energy that falls onto the sea surface, wave power, tidal power and wind power. SOLUTION: A movable offshore floater is provided with a chamber 3 which receives solar power to generate steam by evaporating the seawater, a steam turbine 8 which is actuated by the steam from the chamber 3, and a generator 9 driven by the turbine 8. The steam that came through the turbine 8 is cooled by the seawater through a heat exchanger 10 to obtain plain water, which is then stored in a water storage tank 11. Thereafter, the plain water is dissolved into hydrogen and oxygen in a water electrolysis system 26 by the electric power from the generator 9, a wave power generator 5, a wind power generator 6 and a tidal power (water power) generator 7. Thus mass-production of hydrogen and oxygen can be efficiently carried out on the floater utilizing the natural energies.
18 citations
TL;DR: In this article, a model is formulated describing rip current systems as wave pumps, where the incoming wave power is related to the useful pump power of the rip system through the pump efficiency epsilon(rip).
Abstract: Field observations of hydraulic gradients and the corresponding friction factors 0 from rip systems are presented. From a range of field experiments we find f = 0.032 +/- 0.014 in rip feeder channels. A model is formulated describing rip current systems as wave pumps. That is, the incoming wave power is related to the useful pump power of the rip system through the pump efficiency epsilon(rip). The presently available data indicate that epsilon(rip) is almost constant around 0.035. This gives a predictive capability when the wave conditions and certain aspects of the topography are known. We present epsilon(rip)-data from both laboratory and field. In our study mean-water-level-data with centimeter accuracy were effectively collected with simple stilling wells.
18 citations
Patent•
10 Oct 2001
TL;DR: In this paper, an arrival wave number determination part 10 calculates a ratio Er between a maximum value and the next maxim value of the characteristic value of a covariance matrix R of a M-element array reception signal so as to compare it with a predetermined value Dr. When he ratio Er is not less than the predetermined value DR, the number of arrival waves is determined to be one, while the number number of incoming waves M-1 when the ratioEr is less than a value Dr, when DR is more than the value DR.
Abstract: PROBLEM TO BE SOLVED: To precisely estimate the principal wave direction of an arrival wave having high correlation. SOLUTION: An arrival wave number determination part 10 calculates a ratio Er between a maximum value and the next maxim value of a characteristic value of a covariance matrix R of a M-element array reception signal so as to compare it with a predetermined value Dr. When he ratio Er is not less than the predetermined value Dr, the number of arrival waves is determined to be one, while the number of incoming waves is determined to be M-1 when the ratio Er is less than the value Dr. A virtual linear array conversion part 12 converts reception signals ranging from 2-1 to 2-M of a circular array into virtual linear array reception signals. An arrival wave power estimation part 13 estimates arrival wave power at an angular interval Δθ. An arrival direction estimation part 11 computes an incoming direction estimation function F(θ) at an angular interval Δθ while using a matrix ES consisting of S eigenvectors in the covariance matrix R as a signal characteristic spatial matrix and using a matrix EN consisting of (M-S) eigenvectors as a noise characteristic spatial matrix if the incoming wave number determination in the incoming wave number determination part results in an S-wave. A principal wave direction estimation part 14 combines the computed value F(θ) in the arrival direction estimation part 11 and the computed value in the incoming wave power estimation part 13 together so as to determine its maximum value direction as the principal wave direction estimation result.
15 citations
Patent•
02 Aug 2001
TL;DR: In this article, a wave power station converted the linear energy of the movement of water particles into a suitable rotational energy for driving a current generator, which is anchored firmly to the sea bed and transferred the continuously present vertical or circular energy of motion of the water particles in waves into rotational energies via buoyancy bodies or floats with attached arms.
Abstract: The wave power station converts the linear energy of the movement of water particles into a suitable rotational energy for driving a current generator (9). The power station is anchored firmly to the sea bed and transfers the continuously present vertical or circular energy of motion of the water particles in waves into rotational energy via buoyancy bodies or floats (1) with attached arms (2). Only one rotation direction is possible.
14 citations
Patent•
NEC1
TL;DR: In this article, a pilot power control unit is provided to a base station radio unit to control a desired wave power-to-interference wave power ratio of a pilot signal to stay at a preset value.
Abstract: A satisfactory reception environment is secured efficiently regardless of a degree of the traffic intensity. A pilot power control unit is provided to a base station radio unit. The pilot power control unit controls a desired wave power-to-interference wave power ratio of a pilot signal to stay at a preset value. More specifically, upon receipt of a multiplex wave from a multiplexing unit, the pilot power control unit computes a desired wave power-to-interference wave power ratio of a pilot signal. Then, the pilot power control unit transmits a command signal to a coder to change a transmission power value of the pilot signal in an amount corresponding to a difference between the computed desired wave power-to-interference wave power ratio and a set desired wave power-to-interference wave power ratio.
12 citations
TL;DR: In this paper, the authors described the characteristics of wave energy absorption of the prototype by the open sea tests data, and compared the results of the prediction method of electrical output and water tank experiments were compared with open sea test data on the output of air chamber, turbine output and generated output.
Abstract: “Mighty Whale” is an offshore floating type wave power device based on the oscillating water column (OWC) principle. It converts wave energy into electric energy, and produces a relatively calm sea area behind it. These electric energy and calm sea area will be able to utilize for varied applications such as to improve a deteriorated ocean environment and fish farming. JAMSTEC constructed the prototype of Mighty Whale for open sea tests by May 1998, and the open sea tests were started on September 1998 at the mouth of Gokasho Bay in Mie prefecture. This paper describes the characteristics of wave energy absorption of the prototype by the open sea tests data. Particularly the results of the prediction method of electrical output and water tank experiments were compared with open sea tests data on the output of air chamber, turbine output and generated output. The outline of the discussion about these results, the validity of prediction method of generated output was confirmed. And we recognized characteristics of wave energy absorption and wave energy efficiency of floating type wave power device. Based these results, the validity of the design for the prototype was confirmed.
Dissertation•
01 Dec 2001
TL;DR: In this paper, a comprehensive data set has been compiled covering almost a full range of conditions occurring on natural beaches, and virtually all longshore transport formulae have been evaluated against this extensive data set.
Abstract: The process of sand being moved parallel to the coast by wave and current action is called longshore (sediment) transport. Knowledge oflongshore transport is essential for the design of breakwaters at harbour entrances, for navigation channels and for calculating the amount of dredging they require, for beach improvement schemes and for the determination of the stability of inlets and estuaries. Different aspects oflongshore transport have been investigated, namely, (1) analysis offield data, (2) evaluation oflongshore transport formulae and (3) the development of the wave power approach as an alternative method to calculate longshore transport. In the development of a better understanding oflongshore sediment transport, the following has been done for the first time: (1) a comprehensive data set has been compiled covering almost a full range of conditions occurring on natural beaches; and (2) virtually all longshore transport formulae have been evaluated against this extensive data set. A new improved method, the applied wave power approach, has been developed and extensively calibrated against the same data set. Based on this evaluation, guidelines are now available for design engineers as to which are the best bulk and detailed predictors oflongshore sediment transport. These are respectively, the recalibrated Kamphuis formula and the applied wave power approach. Another useful first, is the derivation of confidence intervals for a longshore transport formula, showing what accuracy can be obtained and that accurate predictions are now possible. In addition, it has now been determined what the minimum required measurement period should be and what the most cost-effective way is for obtaining the true long-term mean net longshore transport rate at a particular site. Stellenbosch University http://scholar.sun.ac.za
Patent•
NEC1
TL;DR: In this paper, a pilot power control unit is provided to a base station radio unit to control a desired wave power-to-interference wave power ratio of a pilot signal to stay at a preset value.
Abstract: The present invention has an object to secure a satisfactory reception environment efficiently regardless of a degree of the traffic intensity. The object is achieved by the following. A pilot power control unit is provided to a base station radio unit. The pilot power control unit controls a desired wave power-to-interference wave power ratio of a pilot signal to stay at a preset value. More specifically, upon receipt of a multiplex wave from a multiplexing unit, the pilot power control unit computes a desired wave power-to-interference wave power ratio of a pilot signal. Then, the pilot power control unit transmits a command signal to a coder to change a transmission power value of the pilot signal in an amount corresponding to a difference between the computed desired wave power-to-interference wave power ratio and a set desired wave power-to-interference wave power ratio.
01 Jan 2001
Patent•
19 Jul 2001
TL;DR: In this article, the authors proposed a solution to provide a device and an instrument for SIR measurement which can carry out precise SIR measurements even in environment wherein interference is abruptly caused.
Abstract: PROBLEM TO BE SOLVED: To provide a device and an instrument for SIR measurement which can carry out precise SIR measurement even in environment wherein interference is abruptly caused. SOLUTION: While desirable wave power is detected from a receive signal, interference wave power is detected from the receive signal and temporally successive interference wave power detected values are averaged over a long- section slot and a short-section slot and the quantity of variation of the interference wave power is detected by obtaining the difference between the two mean values and the mean value of the short section when the detected variation quantity of the interference wave power is large and the mean value of the long section when small is selected to obtain the ratio of the selected mean value and desirable wave power.
Patent•
16 Nov 2001
TL;DR: In this paper, a float control device has a first estimation unit for estimating a first wave height as height of a wave and a first direction as direction of the wave on the basis of inputs of several wave height data showing height of the boat, and a second estimation unit is used to estimate the external turbulent force to be applied to the boat.
Abstract: PROBLEM TO BE SOLVED: To accurately estimate characteristics of the wave such as wave direction and wave power on the sea, and to accurately control the movement of a float on the basis of the estimated characteristic of the wave. SOLUTION: This float control device has a first estimation unit 2 for estimating a first wave height as height of the wave and a first direction as direction of the wave on the basis of inputs of several wave height data showing height of the wave and for estimating a first wave power as the wave power of the wave on the basis of the first wave height and the first direction, a first control unit 4 for computing the first thrust as the thrust of a float on the basis of the first wave power, a second estimation unit 3 for estimating the external turbulent force to be applied to the float on the basis of a position data showing position of the float and a speed data showing speed of the float, a second control unit 5 for computing the second thrust as the thrust of the float on the basis of the external turbulent force, and a thrust distribution unit 6 for controlling a float propelling device 7 to generate the first and the second thrust on the basis of the computed first thrust and the computed second thrust.
Patent•
23 Oct 2001
TL;DR: In this paper, the authors proposed an approach to enhance the accuracy of measurement of a ratio between desired wave power and interference wave power by compensating both the desired and the interference wave powers according to radio wave propagation environment using an average value of delay profile, the number of allocated fingers and intensity of the total reception electric fields, etc.
Abstract: PROBLEM TO BE SOLVED: To enhance an accuracy of measurement of a ratio between desired wave power and interference wave power by compensating the desired wave power and the interference wave power according to radio wave propagation environment using an average value of delay profile, the number of allocated fingers and intensity of the total reception electric fields, etc., as parameters. SOLUTION: A compensation value calculating part 118 calculates a desired wave compensation coefficient and an interference wave compensation coefficient for compensating the desired wave power and the interference wave power from the average value calculated by a delay profile average value detecting part 117 and power information outputted by a power measuring part 105, and outputs them to a desired wave compensation value buffer 119 and an interference wave compensation value buffer 120 respectively. The desired wave power is multiplied by the desired wave compensation coefficient by a multiplication part 115, the interference wave power is multiplied by the interference wave compensation coefficient by a multiplication part 116, the ratio between the desired wave power after compensation and the interference wave power after compensation is calculated from multiplication results in a SIR (signal to interference ratio) calculation part 121 and converted into dB values. COPYRIGHT: (C)2003,JPO
TL;DR: In this article, the authors described the composition of wave power generating system with water valve rectifier and presented the results of experimental test for practical use which has been carrying out at Haramachi site since 1996.
Abstract: This paper describes the composition of wave power generating system with water valve rectifier and presents the results of experimental test for practical use which has been carrying out at Haramachi site since 1996 It is confirmed that electric power is generated under both surf and backwash conditions by rectifying the alternative air flow through the water valve A maximum output power of over 130 kW is obtained
Patent•
06 Jun 2001
TL;DR: In this paper, the authors propose a utility model for sea-wave power energy with an air compressor and a hydroturbine, which is composed of a wave-power energy air taking and using device, a water lifting device and an air energy storing and pressure lifting storeroom.
Abstract: The utility model relates to a power generating device using sea-wave power energy with an air compressor and a hydroturbine, which is composed of a wave-power energy air taking and using device, a water lifting device and an air energy storing and pressure lifting storeroom. A floating pier sheathed on a centre peg floats up and down along with sea waves, drives an air compressor to work through the engagement action of a gear and a rack bar and provides high-pressure air for the air energy storing and pressure lifting storeroom, and the high-pressure gas in the pressure lifting storeroom can be used for a steam turbine to work and emit light. The floating pier floats up and down to link the piston type two-way water lifting device to work, water in the water lifting device is pressed to an artificial energy storing reservoir to be used for the work and the electricity generation of a hydroturbine. The utility model has simple structure, and can normally and constantly generate electrictity by means of the great power of the sea waves.
TL;DR: In this article, a parabolic bay is used to focus the waves and a high efficiency turbine is developed to better extract energy under reversing air flows for wave power applications in Australia.
Patent•
11 Jan 2001
TL;DR: In this paper, the system has nine rotatable axles mounted in upper and lower planes in an open casing 5 m wide, 9 m long and 1.5 m high.
Abstract: The system has nine rotatable axles mounted in upper and lower planes in an open casing 5 m wide, 9 m long and 1.5 m high. The casing consists of a mainly open frame (4), e.g. of steel or aluminum tubes, and is transmissive for the waves in the direction of wave motion. Struts maintain the required stability of the frame. Floats (10) or air containers mounted externally on the long sides keep the casing floating horizontally just under the water's surface. It also uses sensors and electromagnets to switch on generators depending on the power of the waves such that even with minimum wave power there is at least one generator switched.
Journal Article•
TL;DR: Based on the repeatedly measured profile data on the beach between headlands of the Liaozuikou Bay in east Guangdong, and measured data of wave and wind are analyzed with cross spectrum as mentioned in this paper, the results show that the profile temporal variations are mostly responsed by the actions that composed of wind stress, wave power and typhoons.
Abstract: Based on the repeatedly measured profile data on the beach between headlands of the Liaozuikou Bay in east Guangdong,and measured data of wave and wind are analyzed with cross spectrum The results show that the profile temporal variations are mostly responsed by the actions that composed of wind stress, wave power and typhoons
Patent•
[...]
15 Mar 2001
TL;DR: In this article, the wave power plant converts the hydro mechanic energy of the waves of sea by means of the sensor tanks connected to the chassis via of bearings that will transfer the energy produced by their movements on the waves, to the hydro motor by pumping mineral oil through pumps.
Abstract: The wave power plant converts the hydro mechanic energy of the waves of sea by means of the sensor tanks (1) connected to the chassis (2) via of bearings (3) that will transfer the energy produced by their movements on the waves, to the hydro motor (7) by pumping mineral oil through pumps (4). Low-pressure hydro accumulator (5) on the suction line of the pump, controls the necessary pressure and flow. The high-pressure hydro accumulator (6) on the pump's pressure line controls the circuit pressure by means of pressure regulators depending on last of the alternator. At the same time the high-pressure hydro accumulator (6) creates the required volume for compensation in the circuit and smoothen the flow. The pressurized mineral oil supplied by the system flows through the hydro motor (7) which drives the alternator (8) to produce electrical energy.
Patent•
13 Jun 2001
TL;DR: In this paper, a pilot power control unit is provided to a base station radio unit to control a desired wave power-to-interference wave power ratio of a pilot signal to stay at a preset value.
Abstract: The present invention has an object to secure a satisfactory reception environment efficiently regardless of a degree of the traffic intensity. The object is achieved by the following. A pilot power control unit is provided to a base station radio unit. The pilot power control unit controls a desired wave power-to-interference wave power ratio of a pilot signal to stay at a preset value. More specifically, upon receipt of a multiplex wave from a multiplexing unit, the pilot power control unit computes a desired wave power-to-interference wave power ratio of a pilot signal. Then, the pilot power control unit transmits a command signal to a coder to change a transmission power value of the pilot signal in an amount corresponding to a difference between the computed desired wave power-to-interference wave power ratio and a set desired wave power-to-interference wave power ratio.
01 Jan 2001
TL;DR: In this article, the authors compared with computational data based on two theoretical models of the ground impedance when the force acts to hard “stamp” placed on the elastic half-space surface and for the other case when the oscillating force action is determined as the normal pressure uniformly distributed by the circle area of ground surface.
Abstract: equency dependence of its inconstancy at the range 50…400 Hz has value not higher than 7 dB. The oscillating displacements of the source work platform and the ground impedance are investigated as the functions of the frequency. The experimental results are compared with computational data based on two theoretical models of the ground impedance – when the force acts to hard “stamp” placed on the elastic half-space surface and for the other case when the oscillating force action is determined as the normal pressure uniformly distributed by the circle area of the ground surface. The report is devoted to the investigation of the important source characteristic – the total elastic wave power radiated by mini seismic source in the ground medium. These mini sources are classified as portable, electrical dynamic kind and controlled by the computer. They are produced in IAP RAS (N.Novgorod) for the near surface geophysical research – seismic probing of the highest ground layers. These high efficiency sources are able to excite the complex oscillations in the wide frequency band 20…800 Hz [1]. The elastic wave energy balance problem is discussed also. It includes the analysis of the wave energy distribution between all types of excited elastic waves because the excitation efficiency by the surface sources of every wave type involved to the probing and near surface layered structure visualization can be essentially different so as the role of these waves. The theoretical calculations in some publications could be used for the elastic waves energy estimations [25] and there are some additional results in more later works [6,7]. But the most insurance data are obtained by the field measurements allowed to get the source-ground system parameters with more accuracy for the certain sample of source placed on some point of ground surface that is useful for the choice of more adequate theoretical model required for the estimation of elastic wave energy balance. Experimental method bases on the measurements of the source platform and also vibrating mass acceleration with their recording to the hard memory. Two measurement series are performed consequently with overlap by the frequency. The constant amplitude signal of the duration of about 19.2 s and with smoothly changed frequency in the ranges 20…200 Hz, 100…1000 Hz is arrived on the source input. The platform vibration amplitudes Ug (pare of curves from 1 group corresponded to both two series) and oscillating mass UM (pare of curves from 2 group) are showed by the continuous lines on fig.1. The amplitude maximum at the frequency 24.8 Hz is indicated rather expressively and this frequency is near to the one of partial resonance for the junction: oscillating mass of value - M and spring of rigidity value – K ωM 2 = K/M. Other peculiar frequency - so called putting resonance frequency is equal to ωu 2 =(K+Kg)/(mpl +mg). This corresponds to partial resonance for the oscillator formed by the junction of common mass of platform mpl and united ground mass mg and common rigidity of the ground Kg and of the spring K. However this maximum is not recognized on the curves Ug ,UM . The indicated circumstance is explained that the second resonance frequency wide band is determined by the common losses at the source R and ground losses Rg=ReZg including the dissipation and elastic wave radiation and the quality of this resonance is small because Rg >> R. The calculation results corresponding to the vibration displacements are showed on fig.1 for the comparison with the experimental data moreover they relate to the two theoretical models of the ground impedance Z1g , Z2g . In the first model the ground impedance Z1g is determined as the ratio of amplitude of the harmonic force normal acting on hard weightless round “stamp” placed on the elastic half-space surface to the complex amplitude of oscillating ground velocity in the round center. Low frequency