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181.
Electrical impedance of partially molten gabbro was measured as a function of the frequency of the applied electric field. The impedance of the partially molten gabbro was mainly controlled by the volume and geometry of partial melt, which were observed with an optical microscope study of the quenched sample. The experimental results are interpreted by a theory that formulates the electrical property of rocks containing partial melt, taking ionic diffusion in the melt into account. The theory evaluates the contributions from two types of melt-geometry distributed in the rock matrix, namely:
- 1. (a) nearly isolated melt pockets, and
- 2. (b) connected melt along grain boundaries.
182.
Tidal triggering of earthquakes in the subducting Philippine Sea plate beneath the locked zone of the plate interface in the Tokai region, Japan 总被引:5,自引:1,他引:5
We found a characteristic space–time pattern of the tidal triggering effect on earthquake occurrence in the subducting Philippine Sea plate beneath the locked zone of the plate interface in the Tokai region, central Japan, where a large interplate earthquake may be impending. We measured the correlation between the Earth tide and earthquake occurrence using microearthquakes that took place in the Philippine Sea plate for about two decades. For each event, we assigned the tidal phase angle at the origin time by theoretically calculating the tidal shear stress on the fault plane. Based on the distribution of the tidal phase angles, we statistically tested whether they concentrate near some particular angle or not by using Schuster's test. In this test, the result is evaluated by p-value, which represents the significance level to reject the null hypothesis that earthquakes occur randomly irrespective of the tidal phase angle. As a result of analysis, no correlation was found for the data set including all the earthquakes. However, we found a systematic pattern in the temporal variation of the tidal effect; the p-value significantly decreased preceding the occurrence of M ≥ 4.5 earthquakes, and it recovered a high level afterwards. We note that those M ≥ 4.5 earthquakes were considerably larger than the normal background seismicity in the study area. The frequency distribution of tidal phase angles in the pre-event period exhibited a peak at the phase angle where the tidal shear stress is at its maximum to accelerate the fault slip. This indicates that the observed small p-value is a physical consequence of the tidal effect. We also found a distinctive feature in the spatial distribution of p-values. The small p-values appeared just beneath the strongly coupled portion of the plate interface, as inferred from the seismicity rate change in the past few years. 相似文献
183.
Hurford G.J. Schmahl E.J. Schwartz R.A. Conway A.J. Aschwanden M.J. Csillaghy A. Dennis B.R. Johns-Krull C. Krucker S. Lin R.P. McTiernan J. Metcalf T.R. Sato J. Smith D.M. 《Solar physics》2002,210(1-2):61-86
The Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) observes solar hard X-rays and gamma-rays from 3 keV to
17 MeV with spatial resolution as high as 2.3 arc sec. Instead of focusing optics, imaging is based on nine rotating modulation
collimators that time-modulate the incident flux as the spacecraft rotates. Starting from the arrival time of individual photons,
ground-based software then uses the modulated signals to reconstruct images of the source. The purpose of this paper is to
convey both an intuitive feel and the mathematical basis for this imaging process. Following a review of the relevant hardware,
the imaging principles and the basic back-projection method are described, along with their relation to Fourier transforms.
Several specific algorithms (Clean, MEM, Pixons and Forward-Fitting) applicable to RHESSI imaging are briefly described. The
characteristic strengths and weaknesses of this type of imaging are summarized. 相似文献
184.
Jiangtao Su Yu Liu Hiroki Kurokawa Xinjie Mao Shangbin Yang Hongqi Zhang Haimin Wang 《Solar physics》2007,242(1-2):53-63
We present new observations of the interactions of two close, but distinct, Hα filaments and their successive eruptions on
5 November 1998. The magnetic fields of the filaments are both of the sinistral type. The interactions between the two filaments
were initiated mainly by an active filament of one of them. Before the filament eruptions, two dark plasma ejections and chromospheric
brightenings were observed. They indicate that possible magnetic reconnection had occurred between the two filaments. During
the first filament eruption, salient dark mass motions transferring from the left erupting filament into the right one were
observed. The right filament erupted 40 minutes later. This second filament eruption may have been the result of a loss of
stability owing to the sudden mass injection from the left filament. Based on the Hα observations, we have created a sketch
for understanding the interactions between two filaments and accompanying activities. The traditional theory of filament merger
requires that the filaments share the same filament channel and that the reconnection occurs between the two heads, as simulated
by DeVore, Antiochos, and Aulanier (Astrophys. J.
629, 1122, 2005; 646, 1349, 2006). Our interpretation is that the external bodily magnetic reconnection between flux ropes of the same chirality is another
possible way for two filament bodies to coalesce.
Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users. 相似文献
185.
Aschwanden Markus J. Metcalf Thomas R. Krucker Säm Sato Jun Conway Andrew J. Hurford G.J. Schmahl Edward J. 《Solar physics》2004,219(1):149-157
We compare the photometric accuracy of spectra and images in flares observed with the Ramaty High-Energy Solar Spectroscopic
Imager (RHESSI) spacecraft. We test the accuracy of the photometry by comparing the photon fluxes obtained in different energy
ranges from the spectral-fitting software SPEX with those fluxes contained in the images reconstructed with the Clean, MEM,
MEM-Vis, Pixon, and Forward-fit algorithms. We quantify also the background fluxes, the fidelity of source geometries, and
spatial spectra reconstructed with the five image reconstruction algorithms. We investigate the effects of grid selection,
pixel size, field of view, and time intervals on the quality of image reconstruction. The detailed parameters and statistics
are provided in an accompanying CD-ROM and web page. We find that Forward-fit, Pixon, and Clean have a robust convergence
behavior and a photometric accuracy in the order of a few percent, while MEM does not converge optimally for large degrees
of freedom (for large field of view and/or small pixel sizes), and MEM-Vis suffers in the case of time-variable sources. This
comparative study documents the current status of the RHESSI spectral and imaging software, one year after launch.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/B:SOLA.0000021801.83038.aa 相似文献
186.
C. Kaito Y. Ojima K. Kamitsuji O. Kido Y. Kimura H. Suzuki T. Sato T. Nakada Y. Saito C. Koike 《Meteoritics & planetary science》2003,38(1):49-57
Abstract— Experimental studies of coalescence between Mg grains and SiO grains in smoke reveal the direct production of crystalline forsterite grains. The present results also show that different materials can be produced by grain‐grain collisions, which have been considered one of the models of grain formation in the interstellar medium. The fundamentals of coalescence growth in smoke, which have been developed in our series of experiments, are presented in this paper. Mg2Si polyhedral grains were obtained in a Mg grain‐rich atmosphere. Mg2SiO4 polyhedral grains were obtained in a SiO grain‐rich atmosphere. The IR spectra of the resultant grains showed the characteristics of crystalline forsterite. 相似文献
187.
The production of Fe2SiO4 (fayalite) crystalline grains was performed by two processes, namely, grain formation in a plasma field by evaporating a mixture powder of Fe and SiO and heat treatment of the product collected on the radio-frequency (RF) electrode side. Fe grains <20 nm in size covered with an amorphous SiO layer selectively formed Fe2SiO4 grains by heating at 800 °C. By heating at 600 °C, in addition to the formation of Fe2SiO4 crystal grains, the FeO phase appeared. The doping effect of excited oxygen in a plasma field into the Fe small grains may be the trigger on the formation of fayalite through the FeO phase formation. The present experimental result suggests that the probability of Fe2SiO4 grain formation in space is low. 相似文献
188.
Sato T. Suzuki Y. Kashiwagi H. Nanjo M. Kakui Y. 《Oceanic Engineering, IEEE Journal of》1978,3(1):1-4
A laser method for the remote detection of oil present as a pollutant in the sea water using Raman backscattering and backscattered fluorescence is discussed. The scattering spectra of oils obtained by using a laser Raman spectrometer that employs a CW Ar laser are described. The backscattering spectra of oils obtained by a laser radar technique in the laboratory and the field are also described. Furthermore, theoretical performance of a laser radar with a CW laser or a pulsed laser for the detection of Raman backscattering of kerosene is discussed. 相似文献
189.
Groundwater is a finite resource that is threatened by pollution all over the world. Shimabara City, Nagasaki, Japan, uses groundwater for its main water supply. During recent years, the city has experienced severe nitrate pollution in its groundwater. For better understanding of origin and impact of the pollution, chemical effects and surface–groundwater interactions need to be examined. For this purpose, we developed a methodology that builds on joint geochemical analyses and advanced statistical treatment. Water samples were collected at 42 sampling points in Shimabara including a part of Unzen City. Spatial distribution of water chemistry constituents was assessed by describing Stiff and Piper diagrams using major ions concentrations. The nitrate (NO3?+?NO2–N) concentration in 45% of water samples exceeded permissible Japanese drinking level of 10 mg L??1. Most of the samples showed Ca–HCO3 or Ca–(NO3?+?SO4) water types. Some samples were classified into characteristic water types such as Na–Cl, (Na?+?K)–HCO3, (Na?+?K)–(SO4?+?NO3), and Ca–Cl. Thus, results indicated salt water intrusion from the sea and anthropogenic pollution. At the upstream of Nishi River, although water chemistry was characterized as Ca–HCO3, ion concentrations were higher than those of other rivers. This is probably an effect of disinfection in livestock farming using slaked lime. Positive correlation between NO3? and SO42?, Mg2+, Ca2+, Na+, K+, and Cl? (r?=?0.32–0.64) is evidence that nitrate pollution sources are chemical fertilizers and livestock waste. Principal component analysis showed that chemistry of water samples can be explained by three main components (PCs). PC1 depicts general ion concentration. PC2 and PC3 share influence from chemical fertilizer and livestock waste. Cluster analyses grouped water samples into four main clusters. One of these is the general river chemistry mainly affected by PC1. The others reflect anthropogenic activities and are identified by the combination of the three PCs. 相似文献
190.
The Inference of Geo-Mechanical Properties of Soft Rocks and their Degradation from Needle Penetration Tests 总被引:2,自引:1,他引:1
Needle penetration tests (NPTs) are used for inferring the uniaxial compressive strength of soft rocks, particularly in tunneling through squeezing rocks and foundations on weathered rocks in Japan. The device measures the applied load and the penetration depth of its needle. The ratio of applied load to penetration depth was originally called the needle penetration index (NPI). In this study, this device has been used to infer the geo-mechanical properties of soft rocks from Japan, Turkey, Indonesia, and Egypt. Various equations are presented to infer the geo-mechanical properties in terms of the NPI and compared with the experimental results. The possibility of evaluating the anisotropy of geo-mechanical properties is shown. Furthermore, the characterization of geo-mechanical properties of fault/fracture and slip (shear) surfaces is explained. Some additional equations are given to consider the degradation of geo-mechanical properties as a function of water content, weathering state, and number of cycles of freezing–thawing. Furthermore, the possibility of evaluating the time-dependency characteristics of soft rocks by needle penetration testing is discussed through experiments. It is shown that the effects of water content, weathering state, and number of cycles of freezing–thawing and time-dependency can be evaluated using the NPT technique. 相似文献