Superconducting gravimeter observations without a tilt compensation system     

Sachiko Iwano  Yoichi Fukuda 《Physics of the Earth and Planetary Interiors》2004,147(4):343-351

This paper examines the possibility of using superconducting gravimeter (SG) observations without a tilt compensation system. SG data obtained at Syowa Station, Antarctica, were recorded without tilt compensation from April 5, 2001 to January 4, 2002, however, tilt signals were registered during this time period. A tilt correction was applied to gravity data from August 2, 2001 to January 4, 2002. After the tilt correction, errors of tidal parameters were dramatically reduced and tidal parameters themselves almost coincide with those from the same length of tilt-controlled gravity data recorded in 2000, when tilt compensation system was used. The noise level of the thermal leveler in the seismic band was also investigated. Averaged power spectra of gravity from 15 quiet days each in 2000 and 2001 recorded with and without the tilt compensation system, respectively, were compared. ‘Quiet’ in this case, means very low earthquake activity and calm wind conditions. No significant difference in the seismic band, except at the frequency of 2 mHz, was noticed. The difference at 2 mHz occurred because of room temperature variations caused by the water cooler, which cools down a compressor by automatically switching on and off.  相似文献   

The application of commutative algebra to geodesy: two examples     

J. L. Awange  E.W. Grafarend  Y. Fukuda  S. Takemoto 《Journal of Geodesy》2005,79(1-3):93-102

Algebra, in particular commutative algebra, is applied here to provide a general unified solution to nonlinear systems of equations encountered in geodesy. Starting with the “Abelian group”, the “polynomial ring” is defined and used to form generators of ideals. By applying Buchberger or polynomial resultant algorithms, these generators are reduced to simple structures often comprising a univariate polynomial in one of the unknowns. The advantage of the proposed unified approach is that it provides exact solutions to geodetic nonlinear systems of equations without the traditional requirements of linearization, iterations or approximate starting values. The commutative algebraic approach therefore alleviates the need for isolated exact solutions to various geodetic nonlinear systems of equations. The procedure is applied to GPS meteorology to compute refraction angles, and Helmert’s one-to-one mapping of topographical points onto the reference ellipsoid.  相似文献   

A geophysical interpretation of the secular displacement and gravity rates observed at Ny-Ålesund, Svalbard in the Arctic—effects of post-glacial rebound and present-day ice melting     

Tadahiro Sato  Jun'ichi Okuno  Jacques Hinderer  Daniel S. MacMillan  Hans-Peter Plag †  Olivier Francis ‡  Reinhard Falk  Yoichi Fukuda 《Geophysical Journal International》2006,165(3):729-743

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Magnetic and electric field observations during the 2000 activity of Miyake-jima volcano, Central Japan   总被引：1，自引：0，他引：1  

Yoichi Sasai  Makoto UyeshimaJacques Zlotnicki  Hisashi UtadaTsuneomi Kagiyama  Takeshi HashimotoYuji Takahashi 《Earth and Planetary Science Letters》2002,203(2):769-777

Magnetic and electric field variations associated with the 2000 eruption of Miyake-jima volcano are summarized. For about 1 week prior to the July 8 phreatic explosion, significant changes in the total intensity were observed at a few stations, which indicated uprising of a demagnetized area from a depth of 2 km towards the summit: this non-magnetic source can be regarded as a vacant space itself. Electric and magnetic field variations were observed simultaneously associated with the tilt-step event, which was the abrupt (∼50 s) inflation at a few km depth within the volcano followed by gradual recovery (∼several hours). The electric field is ascribed to the electrokinetic effect most probably due to forced injection of fluids from the source, while the magnetic field to the piezomagnetic effect due to increased pressure. Large magnetic variations amounting to a few tens of nT were observed at several stations since July 8, and they turned almost flat after the August 18 largest eruption. Magnetic changes are explained mostly by the vanishing of magnetic mass in the summit and additionally by the thermal demagnetization at a rather shallow depth. A large increase in the self-potential by 130 mV was also observed near the summit caldera associated with the August 18 eruption, which suggests that the hydrothermal circulation system sustained within the volcano for the past more than 10 years was destroyed by this eruption.  相似文献   

Microbiological and Chemical Studies in the Seas of Hiuchi and Bingo—II     

Yoichi Yoshida  Masao Kimata 《Journal of Oceanography》1970,26(1):6-10

The distribution of inorganic nitrogen compounds and the metabolic rates of these compounds by microorganisms as a whole were investigated in the Seas of Hiuchi and Bingo. The results obtained are as follows:

1. Of inorganic nitrogen compounds, the contents in sea water, those in bottom muds, the uptake or liberation rates of microorganisms as a whole in sea water, and the liberation rates from bottom muds to sea water are 0.2～4.0 μg at. N/l, 3～60 μg at.N/100 g, 0.01～0.5 μg at.N//lhr, and 0.3～1.9 μg at.N/100 cm²/hr, respectively, and these contents or rates of ammonia usually are the largest of these inorganic nitrogen compounds.
2. From the above-mentioned results and the others, it is suggested that the nitrogen in the seas circulates mainly in sea water itself and the course of nitrogen cycle, which passes through bottom muds, is not so important, and further that, of the cycle of inorganic nitrogen compounds, the main course is the course which ammonia is liberated from organic nitrogen compounds and it is immediately uptaked by microorganisms, and the course which it is oxidized to nitrate and the others are not so important.

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Piezomagnetic potentials due to an inclined rectangular fault in a semi-infinite medium   总被引：2，自引：0，他引：2  

Mitsuru Utsugi  Yasunori Nishida  & Yoichi Sasai 《Geophysical Journal International》2000,140(3):479-492

Analytical solutions for the piezomagnetic potentials are derived for strike-slip, dip-slip and tensile-opening fault motions with arbitrary dip and strike angles, so as to be applicable in various types of earthquakes. These solutions are expressed as the composition of elementary functions which are identical to the magnetic potentials produced by magnetic dipoles, quadrupoles and octupoles distributed on the fault plane and other planes. Therefore, the geomagnetic field changes due to the piezomagnetic effect are expressed by the superposition of the fields produced by these equivalent sources.
Examples of calculated results show characteristic features for various types of fault motions as follows: (1) the pattern of the geomagnetic field changes becomes significantly different depending on the strike direction, although the maximum amplitude is almost the same for all directions; (2) the geomagnetic field change reaches a maximum at a dip angle of 90° for strike-slip and tensile-opening fault motions and at 45° for dip-slip fault motion.  相似文献   

New radioisotope-free method for measuring bacterial production using [15N5]-2′-deoxyadenosine and liquid chromatography mass spectrometry (LC–MS) in aquatic environments     

Kenji Tsuchiya  Tomoharu Sano  Nobuyuki Kawasaki  Hideki Fukuda  Noriko Tomioka  Koji Hamasaki  Yuya Tada  Shinji Shimode  Tatsuki Toda  Akio Imai 《Journal of Oceanography》2015,71(6):675-683

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Snowmelt and the hydrological interaction of forest–grassland ecosystems in Central Yakutia,eastern Siberia          下载免费PDF全文

M. L. Lopez Caceres  F. Takakai  G. Iwahana  A. N. Fedorov  Y. Iijima  R. Hatano  M. Fukuda 《水文研究》2015,29(14):3074-3083

In the last two decades the major focus of study in forest water and carbon balances in eastern Siberia has been on the effect of rain during the growing season. Little attention has been paid to the contribution of snowmelt water. The results of the present study indicate that weather conditions during the snowmelt period as well as the soil moisture conditions carried from the previous year's growing season strongly determined the water availability for the forest ecosystem at the beginning of the next growing season. In the forest–grassland intermingled ecosystem of lowland Central Yakutia, gradual snowmelt water flow from the forest into the adjacent grassland depressions increased when soil moisture was high and air temperature was low, whereas low soil moisture and high air temperatures accelerated soil thawing and consequently snowmelt water infiltration into the forest soil. We found that snow depth did not determine the volume of snowmelt water moving to the grassland depression since the thermokarst lake water level in the adjacent grassland was about 25 cm lower in 2005 than in May 2006, even though maximum snow depth reached 57 cm and 43 cm in the winter of 2004–05 and 2005–06, respectively. The contribution of snowmelt water to forest growth as well as the flow of water from the forest to the grasslands showed a strong annual variability. We conclude that warmer springs and high variability in precipitation regimes as a result of climate change will result in more snowmelt water infiltration into the forest soil when the previous year's precipitation is low while more snowmelt water will flow into the thermokarst lake when the previous year's precipitation is high. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Water molecules in beryl and cordierite: high-temperature vibrational behavior,dehydration, and coordination to cations     

J. Fukuda  K. Shinoda 《Physics and Chemistry of Minerals》2011,38(6):469-481

Natural samples of typical cyclosilicates beryl and cordierite include water and carbon dioxide molecules in channels formed by the open cavities. Water molecules in the channels have two forms that are distinguished by whether they coordinate to extra-framework cations (type II) or not (type I). We measured polarized infrared (IR) spectra for thin sections of the (100) plane of beryl or the (100) and (010) planes (cb and ca planes) of cordierite under various temperature conditions. The spectral features of major bands clearly showed the distinguishable behavior of types I and II water molecules under high temperature as follows. Over the temperature range from room temperature to 800°C where rapid dehydration did not occur, the decrease in band heights for type II water molecules were smaller than those for type I, and band shifts were more predominant for type II water molecules. The decrease in band heights and band shifts of type I/II bands differed also for beryl and cordierite, which arises from the different ways in which water molecules are fixed in the channels. Dehydration was enhanced at 850°C. The IR spectra at room temperature quenched from 850°C both for beryl and cordierite showed that the vibrational bands related to type II water molecules were stable after those related to type I water molecules disappeared. In addition, frequency changes of type II bands were observed, possibly because of changes of coordination states of type II water molecules to extra-framework cations in the channels.  相似文献   

The Structure of Young Stellar Jets and Winds Revealed by High Resolution [Fe II] λ1.644μm Line Observations     

Tae-Soo Pyo  Masahiko Hayashi  Naoto Kobayashi  Alan T. Tokunaga  Hiroshi Terada  Miwa Goto  Takuya Yamashita  Yoichi Itoh  Hideki Takami  Naruhisa Takato  Yutaka Hayano  Wolfgang Gaessler  Yukiko Kamata  Yosuke Minowa  Masanori Iye 《Astrophysics and Space Science》2003,287(1-4):21-24

We present high angular resolution spectra taken along the jets from L1551 IRS 5 and DG Tau obtained with the Subaru Telescope. The position-velocity diagrams of the [Fe II] λ 1.644 μmemission line revealed remarkably similar characteristics for the two sources, showing two distinct velocity components separated from each other in both velocity and space with the entire emission range blueshifted with respect to the stellar velocity. The high velocity component (HVC) has a velocity of –200 ––300 km s^-1 with a narrow line width, while the low velocity component (LVC) is around –100 km s^-1 exhibitinig a broad line width. The HVC is located farther away from the origin and is more extended than the LVC. Our results suggest that the HVC is a well-collimated jet originating from the region close to the star, while the LVC is a widely-opened wind accelerated in the region near the inner edge of the accretion disk.  相似文献