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201.
The Red Sea continental margin (RSCM) corresponds to a wide hinge zone between Red Sea and Arabian plate. This margin has been studied through geological and geophysical observations primarily in regard to the evolution of Red Sea rift. This margin is characterized by occurrence of thin sediments, significant onshore uplift, tectonic subsidence of the offshore sedimentary basin, active faulting and seismicity. Studies indicate that sedimentary sequences of the margin are deformed by faults and folds resulti... 相似文献
202.
Keisuke Kuroda Takeshi Hayashi Ayako Funabiki An Thuan Do Vu Duc Canh Tran Thi Viet Nga Satoshi Takizawa 《Hydrogeology Journal》2017,25(4):1137-1152
Groundwater pollution by arsenic is a major health threat in suburban areas of Hanoi, Vietnam. The present study evaluates the effect of the sedimentary environments of the Pleistocene and Holocene deposits, and the recharge systems, on the groundwater arsenic pollution in Hanoi suburbs distant from the Red River. At two study sites (Linh Dam and Tai Mo communes), undisturbed soil cores identified a Pleistocene confined aquifer (PCA) and Holocene unconfined aquifer (HUA) as major aquifers, and Holocene estuarine and deltaic sediments as an aquitard layer between the two aquifers. The Holocene estuarine sediments (approximately 25–40 m depth, 9.6–4.8 cal ka BP) contained notably high concentrations of arsenic and organic matter, both likely to have been accumulated by mangroves during the Holocene sea-level highstand. The pore waters in these particular sediments exhibited elevated levels of arsenic and dissolved organic carbon. Arsenic in groundwater was higher in the PCA (25–94 μg/L) than in the HUA (5.2–42 μg/L), in both the monitoring wells and neighboring household tubewells. Elevated arsenic concentration in the PCA groundwater was likely due to vertical infiltration through the arsenic-rich and organic-matter-rich overlying Holocene estuarine sediments, caused by massive groundwater abstraction from the PCA. Countermeasures to prevent arsenic pollution of the PCA groundwater may include seeking alternative water resources, reducing water consumption, and/or appropriate choice of aquifers for groundwater supply. 相似文献
203.
Saeko S. Hayashi 《Astrophysics and Space Science》1989,160(1-2):263-268
From the user's point of view, it is essential to promote collaborations to make full use of large telescopes, by covering the wide range of the wavelengths. To do that efficiently, it is necessary to work with other facilities, often abroad. Other talks in this symposium are concerned about the spatial resolution or the coverage at one wavelength or one to two octaves in wavelength. Though the above is important, that is not enough to attach the mysteries in the Universe, since a considerable amount of energy is emitted in the infrared, and mass exists in molecular gas form. In this paper, two examples of international, multiwavelength work are shown which turned out to be beneficial for the world-wide community. One is the Japan-U.K. arrangement mainly between the radio and infrared facilities, and the other is the arrangement around James Clerk Maxwell Telescope (JCMT), challenging a new regime of the observational astronomy.Paper presented at the Symposium on the JNLT and Related Engineering Developments, Tokyo, November 29–December 2, 1988. 相似文献
204.
Abstract. This study examined the effect of CO2 on NaCl solubility in hydrothermal fluid, with the synthetic fluid inclusion technique. Fluid inclusions of 30–40 wt% NaCl and 5 mol % CO2 were synthesized, and their halite dissolution temperatures, Tm (halite), were measured. The solubilities of NaCl in CO2 -bearing aqueous fluid were obtained at 160–320C under vapor-saturated pressures. The Tm (halite) value in aqueous fluid with 5 mol % CO2 obtained in this study agrees with that of Schmidt et al. (1995), showing that 5 mol % CO2 reduces the solubility of NaCl by about 1 wt%.
Calculation of magnetite solubility suggests that 5–10 mol % CO2 decreases magnetite solubility by 4.5–8.9 % relative to the magnetite solubility in CO2-free solution. Therefore, an increase of CO2 content in ore-forming solutions may cause deposition of iron minerals and produce ore deposits. 相似文献
Calculation of magnetite solubility suggests that 5–10 mol % CO2 decreases magnetite solubility by 4.5–8.9 % relative to the magnetite solubility in CO2-free solution. Therefore, an increase of CO2 content in ore-forming solutions may cause deposition of iron minerals and produce ore deposits. 相似文献
205.
Qiu-Ming Pei Shou-Ting Zhang Ken-ichiro Hayashi Dong Li Li Tang 《International Geology Review》2018,60(9):1172-1194
The Xing’an–Mongolia orogenic belt is located in the southeastern segment of the Central Asian Orogenic Belt. Its tectonic evolution, especially during the Late Palaeozoic to Early Mesozoic, remains controversial. Here, we report new zircon U–Pb dates, whole-rock geochemistry, and Hf isotopes of representative samples from four plutons in the Linxi area of Northeast China to provide new constraints on this issue. Zircon U–Pb dating indicates that the intrusions were emplaced in two stages: (1) Late Permian to Early Triassic (the Banshifangzi and Xinangou plutons (252 ± 3)–(246.3 ± 3.3) Ma); and (2) Late Triassic (the Baoshan and Hada plutons (220.8 ± 2.7)–(211.4 ± 2.6) Ma). Their positive εHf(t) values (6.6–14.1), coupled with their geochemical characteristics, suggest that the provenance of investigated granitoids were most likely to be dominated by juvenile crustal materials. Based on these new data and previous studies, we propose three stages of tectonic evolution during the Late Palaeozoic–Early Mesozoic in the XMOB: (1) Late Carboniferous–Early Permian (330–270 Ma): double-sided subduction of the Palaeo-Asian Ocean; (2) Middle Permian–Middle Triassic (270–237 Ma): the closure of the Palaeo-Asian Ocean and subsequent continent–continent collision between the North China Craton and the South Mongolia Terrane; and (3) Late Triassic (237–211 Ma): post-collisional extension. 相似文献
206.
Youhei Kawamura Ashraf M. Dewan Bert Veenendaal Masahiro Hayashi Takeshi Shibuya Itaru Kitahara 《International Journal of Digital Earth》2014,7(4):279-293
Communications network damage resulting from a large disaster causes difficulties in the ability to rapidly understand the current situation and thus make appropriate decisions towards mitigating problems, such as where to send and dispense emergency supplies. The research outlined in this paper focuses on the rapid construction of a network after a disaster occurs. This study suggests ZigBee and geographic information systems (GIS) technologies to resolve these problems and provide an effective communication system. The experimental results of the ZigBee network system are presented, examples are provided of the mapping and analysis undertaken using GIS for the disaster-stricken area of Tsukuba City, Japan, and the communications node arrangements are determined for this region. These results demonstrate the effectiveness of establishing such a communications system for supporting efforts to relieve disaster-damaged areas. 相似文献
207.
We study properties of waves of frequencies above the photospheric acoustic cut-off of ≈5.3 mHz, around four active regions, through spatial maps of their power estimated using data from the Helioseismic and Magnetic Imager (HMI) and Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO). The wavelength channels 1600 Å and 1700 Å from AIA are now known to capture clear oscillation signals due to helioseismic p-modes as well as waves propagating up through to the chromosphere. Here we study in detail, in comparison with HMI Doppler data, properties of the power maps, especially the so-called “acoustic halos” seen around active regions, as a function of wave frequencies, inclination, and strength of magnetic field (derived from the vector-field observations by HMI), and observation height. We infer possible signatures of (magneto)acoustic wave refraction from the observation-height-dependent changes, and hence due to changing magnetic strength and geometry, in the dependences of power maps on the photospheric magnetic quantities. We discuss the implications for theories of p-mode absorption and mode conversions by the magnetic field. 相似文献
208.
S. K. Gupta J. Christiansen Y. Hayashi A. Jain P. K. Mohanty K. C. Ravindran B. Satyanarayana 《Experimental Astronomy》2013,35(3):507-526
Arrival time of particles in an extensive air shower (EAS) is a key physical parameter to determine its direction. EAS direction is useful for studies of anisotropy and composition of cosmic rays, and search for multi-TeV γ-rays sources. Accurate timing may be used to search exotic phenomena such as production of new particles at extremely high energies available during early stages of development of EAS and also for detecting sub-relativistic hadrons in EAS. Time to digital converters (TDCs) are used to perform this task. Traditional TDCs operate in the START-STOP mode with limited dynamic range and single-hit capability. With the advent of high luminosity collider LHC, need for TDCs with large dynamic range, multi-hit capability and TRIGGERED mode of operation became necessary. A 32 channel TDC was designed for the GRAPES-3 experiment on a CAMAC platform around TDC32, an ASIC developed by micro-electronics group at CERN, Geneva. Four modules were operated in the GRAPES-3 experiment. Here, we present details of the circuit design and their performance over several years. The multi-hit feature of this device was used to study the time structure of particles in the EAS on time scale of ~1 μs. The distribution of time intervals in the multi-hit data shows an exponential profile with a time constant of ~370 ns. These delayed particles are likely to be neutrons produced in the EAS core that were recorded in the scintillator detectors following the relativistic EAS front. 相似文献
209.
A New Method for Polar Field Interpolation 总被引:1,自引:0,他引:1
The photospheric magnetic field in the Sun’s polar region is not well observed compared to the low-latitude regions. Data
are periodically missing due to the Sun’s tilt angle, and the noise level is high due to the projection effect on the line-of-sight
(LOS) measurement. However, the large-scale characteristics of the polar magnetic field data are known to be important for
global modeling. This report describes a new method for interpolating the photospheric field in polar regions that has been
tested on MDI synoptic maps (1996 – 2009). This technique, based on a two-dimensional spatial/temporal interpolation and a
simple version of the flux transport model, uses a multi-year series of well-observed, smoothed north (south) pole observations
from each September (March) to interpolate for missing pixels at any time of interest. It is refined by using a spatial smoothing
scheme to seamlessly incorporate this filled-in data into the original observation starting from lower latitudes. For recent
observations, an extrapolated polar field correction is required. Scaling the average flux density from the prior observations
of slightly lower latitudes is found to be a good proxy of the future polar field. This new method has several advantages
over some existing methods. It is demonstrated to improve the results of global models such as the Wang–Sheeley–Arge (WSA)
model and MHD simulation, especially during the sunspot minimum phase. 相似文献
210.
This paper presents finite element modeling (FEM) to simulate the present-day stress field and crustal deformation using NE-SW structural section in the central Seismic Gap region of the Garhwal Himalaya. Our study deals with the effect of geometrical characteristics and rock layer parameters on the upper crust. Modeling results show that two types of tectonic regimes developed in the central Seismic Gap region: the geotectonics of the northern part has been controlled by regional compression, whereas southern part is characterized by regional extension. Correspondingly, thrust faults are induced in the northern part and normal faults are extensively developed in the southern front. Those evidences noticeably indicate that the compressive tectonic environment of the Himalaya becomes change into the extensional tectonic regime in its front. The computed shear stress accumulation along the northern fiat of Main Himalayan Thrust (MHT) implies that considerable amount of interseismic stress is building up along the MHT system in the Himalaya, which ultimately release through the possible future great Himalayan earthquake (M 〉 8). The comparison between our modeled stress field, faulting pattern and horizontal shortening rate with the distribution of the microseismic events, focal mechanism solutions, active faulting and GPS data in the central Seismic Gap region shows good agreement. 相似文献