Amplitude Response of a LCR Gravimeter with Feedback at Periods of Microseisms and Earthquake Waves     

Vladimír Tobyáš  Jan Mrlina  Bohumil Chán 《Studia Geophysica et Geodaetica》1999,43(2):185-193

The amplitude response of a LCR gravimeter with the SRW-E feedback was determined on a vertical vibrating platform. The ink-pen recorder was connected parallel with the digital voltmeter input to obtain an analog response of the gravimeter to the harmonic motion of the base with a peak-to-peak amplitude of 10 m and periods excited in an interval of 4 - 10 s as by the ground motion of meteorological microseisms, and in the interval 10 -100 s as by surface waves of distant strong earthquakes. In the first interval, an unexpected maximum of the amplitude response was observed with the double amplitude of apparent 6,5 Gal (6.5 × 10 _–8 m/s ² ) at a period of 4.8 s, and a baseline shift with the amplitude of–64Gal was observed at the same period. The value of this direct component cannot be separated from the effect of the Earth's gravity field. In the second interval, the amplitude response of the gravimeter displayed one expected maximum at a period of 40 s with the double amplitude of 8.1Gal. At the usual level of microseisms with a peak-to-peak amplitude of up to 2 m the fluctuation of the gravimeter on the direct baseline shifted by –4.9 Gal was estimated at 1 Gal. With typical Rayleigh surface waves with periods of 20 s and double amplitudes of up to 100 m, the fluctuation reached 67 Gal.  相似文献   

Seismic noise at the international gravity point in Prague-Ruzyně (Czechoslovakia)     

Karel Holub  Vladimír Tobyáš  Karel Daviš  Reviewer Z. Šimon 《Studia Geophysica et Geodaetica》1975,19(4):383-388

Summary The vertical component of ground displacement was measured at the Prague - Ruzyn International Gravity Point in the frequency range of 1–300 Hz. The permanent noise, the vibrations caused by the observers during gravimetric observations and by the wind, as well as those due to normal operations at the airport, display maximum peak-to-peak amplitudes of 0.06 µm in the frequency range of 1–50 Hz; with a CG-2 gravimeter this is not detrimental to the accuracy of the observations. The taxiing of turbo-jet and jet aircraft and engine tests of aircraft generate vibrations in frequency ranges of 75–90 and 190–270 Hz. Their amplitudes, according to the results of laboratory tests published for various types of gravity meters (CG-2, GAK-PT, GVP-3, KVG), are of magnitudes which generate errors in tenths of mgl.  相似文献   

Effect of the additional low-sensitivity channel on the amplitude response of the electromagnetic seismograph     

Vladimír Tobyáš  Reviewer J. Buben 《Studia Geophysica et Geodaetica》1980,24(2):136-141

u¶rt;m ¶rt; anum¶rt;-amm aamumu maum a aa nu mummu (). ma¶rt;am aamumu uu mau auma uu am auu a uu aaa aa.  相似文献   

A study of the electric conductivity of the earth's mantle from magnetotelluric measurements of the Budkov (Czechoslovakia) station     

Jana Pěčová  Oldŕich Praus  Marta Tobyášová 《Studia Geophysica et Geodaetica》1966,10(2):184-203

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Identity of the characteristics of electrodynamic seismographs with non-standard periods of seismometers and galvanometers     

Tobyáš  Vladimír  Buben  J. 《Studia Geophysica et Geodaetica》1977,21(1):19-26

Summary The maximum changes of magnification were determined for electrodynamic seismographs with standard characteristics and for some experimental long-period seismographs, the constants of which are given in Tab. 1, when the period of the seismometer or galvanometer has a deviation of not more than 5% from the standard value. Under the assumption of control of the other constants of the seismograph, identical amplitude and phase responses with a small change of the absolute magnification of the seismograph may be achieved with characteristicsAII ( ² >0.2), AIV ( ² 0.4), B ( ² >0.3) Nos28, 32 and33. This deviation can also be compensated by adjusting the optical distance. The procedure of adjusting the identical characteristics is suitable for systems with which an accurate setting of the period is difficult and for systems with an uncontrollable period, provided their values are within the limits of allowed deviations from the standard constants.  相似文献   

Electromagnetic fields in jets     

B. D. Sherwin  D. Lynden-Bell 《Monthly notices of the Royal Astronomical Society》2007,378(2):409-415

The magnetic fields and energy flows in an astronomical jet described by our earlier model are calculated in detail. Though the field distribution varies with the external pressure function   p ( z )  , it depends only weakly on the other boundary conditions. Individual field lines were plotted; the lines become nearly vertical at the bottom and are twisted at the top. An animation of a field line's motion was made, which shows the line being wound up by the accretion disc's differential rotation and rising as a result of this. The distribution of Poynting flux within the jet indicates that much of the energy flows up the jet from the inside of the accretion disc but a substantial fraction flows back down to the outside.  相似文献   

Wind-driven monthly variations in transport and the flow field in the Faroe–Shetland Channel     

Toby J. Sherwin  Sarah L. Hughes  William R. Turrell  Bogi Hansen  & Svein Østerhus 《Polar research》2008,27(1):7-22

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Cave air and hydrological controls on prior calcite precipitation and stalagmite growth rates: Implications for palaeoclimate reconstructions using speleothems   总被引：1，自引：0，他引：1  

Catherine M. Sherwin 《Geochimica et cosmochimica acta》2011,75(14):3915-3929

Hourly resolved cave air P_CO2 and cave drip water hydrochemical data illustrate that calcite deposition on stalagmites can be modulated by prior calcite precipitation (PCP) on extremely short timescales. A very clear second-order covariation between cave air P_CO2 and drip water Ca²⁺ concentrations during the winter months demonstrates the effects of degassing-induced PCP on drip water chemistry. Estimating the strength of the cave air P_CO2 control on PCP is possible because the PCP signal is so clear; at our drip site a one ppm shift in Ca²⁺ concentrations requires a P_CO2 shift of between 333 and 667 ppm. This value will undoubtedly vary from site to site, depending on drip water flow rate, residence time, drip water-cave air P_CO2 differential, and availability of low P_CO2 void spaces in the vadose zone above the cave. High-resolution cave environmental measurements were used to model calcite deposition on one stalagmite in Crag Cave, SW Ireland, and modelled growth over the study period (222 μm over 171 days) is extremely similar to the amount of actual calcite growth (240 μm) over the same time interval, strongly suggesting that equations used to estimate stalagmite growth rates are valid. Although cave air P_CO2 appears to control drip water hydrochemistry in the winter, drip water dilution caused by rain events may have played a larger role during the summer, as evidenced by a series of sudden drops in Ca²⁺ concentrations (dilution) followed by much more gradual increases in drip water Ca²⁺ concentrations (slow addition of diffuse water). This research demonstrates that PCP on stalactites, cave ceilings, and void spaces within the karst above the cave partially controls drip water chemistry, and that thorough characterisation of this process at individual caves is necessary to most accurately interpret climate records from those sites.  相似文献   

Variations of the neutralino elastic cross-section with CP-violating phases     

Toby Falk  Andrew Ferstl  Keith A. Olive   《Astroparticle Physics》2000,13(4)

We analyze the neutralino–nucleus elastic cross-section in the minimal supersymmetric extension of the standard model (MSSM), including contributions from CP-violating phases, using the four-fermi neutralino–quark interaction. Over a wide range of the MSSM parameter space, we show the variations in the cross-sections due to these phases. We further concentrate on the regions which are consistent with constraints from the electric dipole moment of the electron, neutron and mercury atom. In the regions we examine in detail, we find suppressions by up to a factor of two, while enhancements in the cross-sections are no greater than 10%.  相似文献   

Experimental seismic station near kaŝperské hory     

Vít Kárník  Vladimír Tobyáŝ 《Studia Geophysica et Geodaetica》1963,7(1):88-89

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