We test possible lensing scenarios of the JVAS system B2114+022, in which two galaxies at different redshifts ('G1' at z 1=0.3157 and 'G2' at z 2=0.5883) are found within 2 arcsec of quadruple radio sources. For our investigation, we use possible lensing constraints derived from a wealth of data on the radio sources obtained with VLA, MERLIN, VLBA and EVN as well as HST imaging data on the two galaxies, which were presented recently in Augusto et al. In the present study, we focus on reproducing the widest separated, observationally similar radio components A and D as lensed images. We first treat G2 (which is the more distant one from the geometric centre) as a shear term, and then consider two-plane lensing explicitly including G2's potential at the z 2 plane as the first case of two-plane lens modelling. Our modelling results not only support the hypothesis that the system includes gravitationally lensed images of a higher-redshift extragalactic object, but they also show that the explicit inclusion of G2's potential at the second lens plane is necessary in order to fit the data with astrophysically plausible galaxy parameters. Finally, we illustrate a natural consequence of a two-plane lens system, namely the prediction of distortion as well as shift and stretching of G2's isophotes by G1's potential, which can in principle be measured by subtracting out G1's light distribution in an image of high signal-to-noise ratio and good angular resolution, especially a multicolour one. 相似文献
Canceling magnetic features are commonly believed to result from magnetic reconnection in the low atmosphere. According to the Sweet–Parker type reconnection model, the rate of flux cancellation in a canceling magnetic feature is related to the converging speed of each pole. To test this prediction observationally, we have analyzed the time variation of two canceling magnetic features in detail using the high-resolution magnetograms taken by the Michelson Doppler Imager (MDI) on the Solar and Heliospheric Observatory (SOHO). As a result, we have obtained the rate and converging speed of flux cancellation in each feature: 1.3×1018 Mx hr–1 (or 1.1×106 G cm s–1 per unit contact length) and 0.35 km s–1 in the smaller one, and 3.5×1018 Mx hr–1 (1.2×106 G cm s–1) and 0.27 km s–1 in the bigger one. The observed speeds are found to be significantly bigger than the theoretically expected ones, but this discrepancy can be resolved if uncertainty factors such as low area filling factor of magnetic flux and low electric conductivity are taken into account. 相似文献
To investigate the urban groundwater contamination by eight trace metals and 69 volatile organic compounds (VOCs) in relation
to land use in Seoul, a total of 57 groundwater samples collected from wells were examined using a non-parametric statistical
analysis. Land use was classified into five categories: less-developed, residential, agricultural, traffic, and industrial.
A comparison of analyzed data with US EPA and Korean standards for drinking water showed that some metals and VOCs exceeded
the standards in a few localities, such as Fe (N=5), Mn (N=6), Cu (N=1), TCE (N=6), PCE (N=8), 1,2-DCA (N=1), and 1,2-dichloropropane (N=1). Among the 69 investigated VOCs, 19 compounds such as some gasoline-related compounds (e.g., toluene) and chlorinated
compounds (e.g., chloroform, PCE, TCE) were detected in groundwater. Non-parametric statistical analysis showed that the concentrations
of most trace metals (Fe, Mn, As, Cr, Pb, Cd) and some VOCs (especially, TCE, PCE, chloroform; toluene, carbon tetrachloride,
bromodichloromethane, CFC113) are significantly higher in the industrial, residential, and traffic areas (P<0.05), indicating that anthropogenic contamination of urban groundwater by those chemicals is growing. Those chemicals can
be used as effective indicators of anthropogenic contamination of groundwater in urban areas and therefore a special attention
is warranted for a safe water supply in those areas. The results of this study suggest that urban groundwater quality in urban
areas is closely related with land use. 相似文献
In sedimentology, stratigraphic sequences and cycles are ordered by time spans and physical scales, such as thickness, and bounded by discontinuities, including unconformities or flooding surfaces. Spectral analysis based on wavelet transform (WT) maxima is proposed and used as a quantitative tool to identify multi-order stratigraphic boundaries and cycles in well log data. The proposed spectral analysis is based on quantitative analysis on the center frequencies and resolutions of Gaussian wavelets in time and frequency, and uses a combination of the WT maxima based on both the first order Gaussian wavelet having a high time resolution and the seventh order Gaussian wavelet having a high frequency resolution. WT maxima spectra, which can characterize the evolution of WT maxima across scales and periods along WT maxima lines concerned with sequence boundaries, are used to detect dominant spectral peaks corresponding to the time-period domain WT maxima and to determine WT maxima spectral slopes. The WT maxima spectral slopes are helpful for discriminating sequence boundaries from intrasequence cyclic variations in well log data, and the time-period domain WT maxima are used to relate the detected boundaries to relevant cycles. The interval WT maxima spectra and the stationary index, related to the WT maxima spectra, are introduced as indicators that can be used for the hierarchical ordering of the boundaries and cycles. Application of the proposed method to well log data shows that the suggested method is efficient in identifying multi-order sequences that relate well to the Milankovitch cycles.
It is well known that real‐time hybrid simulation (RTHS) is an effective and viable dynamic testing method. Numerous studies have been conducted for RTHS during the last 2 decades; however, the application of RTHS toward practical civil infrastructure is fairly limited. One of the major technical barriers preventing RTHS from being widely accepted in the testing community is the difficulty of accurate displacement control for axially stiff members. For such structures, a servo‐hydraulic actuator can generate a large force error due to the stiff oil column in the actuator even if there is a small axial displacement error. This difficulty significantly restricts the implementation of RTHS for structures such as columns, walls, bridge piers, and base isolators. Recently, a flexible loading frame system was developed, enabling a large‐capacity real‐time axial force application to axially stiff members. With the aid of the flexible loading frame system, this paper demonstrates an RTHS for a bridge structure with an experimental reinforced concrete pier, which is subjected to both horizontal and vertical ground motions. This type of RTHS has been a challenging task due to the lack of knowledge for satisfying the time‐varying axial force boundary condition, but the newly developed technology for real‐time force control and its incorporation into RTHS enabled a successful implementation of the RTHS for the reinforced concrete pier of this study. 相似文献
The vertically-integrated effect of interaction between waves and wave-induced currents on wave transformation over a submerged elliptic shoal was investigated based on numerical simulations of the Vincent and Briggs experiment [Vincent, C.L., Briggs, M.J., 1989. Refraction- diffraction of irregular waves over a mound. Journal of Waterway, Port, Coastal and Ocean Engineering, 115(2), pp. 269–284.]. The numerical simulations were performed using two numerical wave-current model systems: one, a combination of the wave model SWAN and the current model SHORECIRC, and the other, a combination of the wave model REF/DIF and the same current model. A time-dependent, phase-resolving wave and current model, FUNWAVE, was also utilized to simulate the experiment. In the simulations, the developed wave-induced currents defocused waves behind the shoal and brought on a wave shadow zone that showed relatively low wave height distributions. For the breaking case of monochromatic waves, the wave heights computed using FUNWAVE showed good agreement with the measurements and the resulting wave-induced currents showed a jet-like velocity distribution in transverse direction. And the computed results of the two model combinations agreed better with the measurements than the computed results obtained by neglecting wave-current interaction. However, it was found that for the case in which transverse interference pattern caused by refracted waves was strong, REF/DIF-SHORECIRC did not correctly evaluate radiation stresses, the gradients of which generate wave-induced currents. SWAN-SHORECIRC, which cannot deal with the interference patterns, predicted a jet-like wave-induced current. For breaking random wave cases, the computed results of the two model combinations and FUNWAVE agreed well with the measurements. The agreements indicate that it is necessary to take into account the effect of wave-induced current on wave refraction when wave breaking occurs over a submerged shoal. 相似文献