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31.
An analytical model for high damping elastomeric isolation bearings is presented in this paper. The model is used to describe mathematically the damping force and restoring force of the rubber material and bearing. Ten parameters to be identified from cyclic loading tests are included in the model. The sensitivity of the ten parameters in affecting the model is examined. These ten parameters are functions of a number of influence factors on the elastomer such as the rubber compound, Mullins effect, scragging effect, frequency, temperature and axial load. In this study, however, only the Mullins effect, scragging effect, frequency and temperature are investigated. Both material tests and shaking table tests were performed to validate the proposed model. Based on the comparison between the experimental and the analytical results, it is found that the proposed analytical model is capable of predicting the shear force–displacement hysteresis very accurately for both rubber material and bearing under cyclic loading reversals. The seismic response time histories of the bearing can also be captured, using the proposed analytical model, with a practically acceptable precision. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
32.
Abstract An analytical electron microscope study of almandine garnet from a metamorphosed Al–Fe‐rich rock revealed detailed composition profiles and defect microstructures of resorption zoning along fluid‐infiltrated veins and even into the garnet/ilmenite (inclusion) interface. This indicates a limited volume diffusion for the cations in substitution (mainly Ca and Fe) and an interface‐controlled partition for the extension of a composition‐invariant margin. A corrugated interface between the Ca‐rich margin/zone and the almandine garnet core is characterized by dislocation arrays and recovery texture further suggesting a resorption process facilitated by diffusion‐induced recrystallization, diffusion‐induced dislocation migration and diffusion–induced grain boundary migration. Integrated microstructural and chemical studies are essential for understanding the underlying mechanisms of processes such as garnet zoning and its modification. Without this understanding, it will not be possible to reliably use garnet compositions for thermobarometry and other applications that rely on garnet chemical information. 相似文献
33.
This paper is a follow-up to a previous paper on the subject of liquefaction potential index (LPI), a parameter that is often used to characterize the potential for surface manifestation of liquefaction at a given site subjected to a given shaking level (represented by a pair of peak ground surface acceleration amax and moment magnitude Mw). In the previous paper by Juang and his coworkers, the LPI was re-calibrated for a piezocone penetration test (CPTU) model, and a simplified model based on LPI was created for computing the conditional probability of surface manifestation of liquefaction (PG). In this paper, the model for this conditional probability PG is extended into a complete framework for assessing the probability of surface manifestation of liquefaction in a given exposure time at a given site subjected to all possible ground motions at all seismic hazard levels. This new framework is formulated and demonstrated with an example site in 10 different seismic regions in the United States. 相似文献
34.
Estimation of Contamination of ERS-2 and POSEIDON Satellite Radar Altimetry Close to the Coasts of Australia 总被引:4,自引:0,他引:4
It is broadly acknowledged that the precision of satellite-altimeter-measured instantaneous sea surface heights (SSH) is lower in coastal regions than in open oceans, due partly to contamination of the radar return from the coastal sea-surface state and from land topography. This study investigates the behavior of ERS-2 and POSEIDON altimeter waveform data in coastal regions and estimates a boundary around Australia's coasts in which the altimeter range may be poorly estimated by on-satellite tracking software. Over one million 20 Hz ERS-2 (March to April 1999) and POSEIDON (January 1998 to January 1999) radar altimeter waveform data were used over an area extending 350 km offshore Australia. The DS759.2 (5'resolution) ocean depth model and the GSHHS (0.2 km resolution) shoreline model were used together to define the coastal regions. Using the 50% threshold retracking points as the estimates of expected tracking gate, we determined that the sea surface height is contaminated out to maximum distance of between about 8 km and 22 km from the Australian shoreline for ERS-2, depending partly on coastal topography. Using the standard deviation of the mean waveforms as an indication of the general variability of the altimeter returns in the Australian coastal region shows obvious coastal contamination out to about 4 km for both altimeters, and less obvious contamination out to about 8 km for POSEIDON and 10 km for ERS-2. Therefore, ERS-2 and POSEIDON satellite altimeter data should be treated with some caution for distances less than about 22 km from the Australian coast and probably ignored altogether for distances less than 4 km. 相似文献
35.
36.
Wei-Chia Hung Cheinway Hwang Chung-Pai Chang Jiun-Yee Yen Chih-Hsi Liu Wan-Huei Yang 《Environmental Earth Sciences》2010,59(7):1535-1548
During 1992–2007, excessive pumping of groundwater caused large-scale aquifer-system compaction and land subsidence in the
Choshui River Alluvial Fan, especially in the area of Yunlin county. The subsidence impedes surface-water runoff and endangers
the operation of Taiwan High Speed Rail. Leveling, Global Positioning System (GPS), multi-level compaction monitoring well,
and Differential Interferometric Synthetic Aperture Radar (DInSAR) are used to study the extent of subsidence in Yunlin and
its mechanism. These sensors complement each other in spatial and temporal resolutions. A leveling network totaling 434 km
in length was deployed to derive subsidence at every 1.5 km along the routes, and the result is accurate to few mm and shows
a basin-like subsidence pattern centering at Tuku Township. Four multi-level compaction monitoring wells, co-located with
GPS pillars, detect compactions at different depths, showing that the aquifer-system compaction (the cause of subsidence)
occurs mostly below depths >200 m, where reduction of groundwater pumping is most needed. The vertical displacements from
GPS and leveling agree to within 1 cm, and are larger than the cumulative compaction detected by the compaction-monitoring
wells, suggesting that compaction also occurs below 300 m (the depth of the wells). The vertical displacements derived using
DInSAR and 8 ENVISAT SAR images agree with the leveling result to 1–2 cm. 相似文献
37.
Jeomshik Hwang Ellen R.M. Druffel Daniel J. Repeta 《Geochimica et cosmochimica acta》2006,70(20):5162-5168
A major fraction of particulate organic carbon (POC) in the deep ocean remains molecularly uncharacterized. In an effort to determine the chemical characteristics and source(s) of sinking POC, we studied a nonhydrolyzable fraction of sinking POC using 13C NMR (nuclear magnetic resonance) spectroscopy and analytical pyrolysis. 13C NMR spectra and products from analytical pyrolysis of the nonhydrolyzable fraction exhibit a strongly aliphatic character that is distinct from that of bulk POC. The aliphatic nature of this fraction is consistent with its low stable carbon isotope values. We hypothesize that the nonhydrolyzable fraction derives to a significant extent from a refractory component of organisms that selectively accumulates, resulting in its manifestation as a major part of POC sinking to the deep ocean and in underlying sediments. 相似文献
38.
Yeonsang Hwang Martyn P. Clark Balaji Rajagopalan 《Stochastic Environmental Research and Risk Assessment (SERRA)》2011,25(7):957-972
Among other sources of uncertainties in hydrologic modeling, input uncertainty due to a sparse station network was tested.
The authors tested impact of uncertainty in daily precipitation on streamflow forecasts. In order to test the impact, a distributed
hydrologic model (PRMS, Precipitation Runoff Modeling System) was used in two hydrologically different basins (Animas basin
at Durango, Colorado and Alapaha basin at Statenville, Georgia) to generate ensemble streamflows. The uncertainty in model
inputs was characterized using ensembles of daily precipitation, which were designed to preserve spatial and temporal correlations
in the precipitation observations. Generated ensemble flows in the two test basins clearly showed fundamental differences
in the impact of input uncertainty. The flow ensemble showed wider range in Alapaha basin than the Animas basin. The wider
range of streamflow ensembles in Alapaha basin was caused by both greater spatial variance in precipitation and shorter time
lags between rainfall and runoff in this rainfall dominated basin. This ensemble streamflow generation framework was also
applied to demonstrate example forecasts that could improve traditional ESP (Ensemble Streamflow Prediction) method. 相似文献
39.
Evidence for significant clockwise rotations of the Korean Peninsula during Cretaceous 总被引:1,自引:0,他引:1
Youn Soo Lee Hyun-Chul Han Jae Ha Hwang Weon-Seo Kee Bok Chul Kim 《Gondwana Research》2011,20(4):904-918
In an effort to evaluate the Cretaceous magnetostratigraphy for the Korean Peninsula and to establish the tectonic coherence of its various elements, we collected paleomagnetic data from 121 samples from 20 sites within the Chilgok Formation (108.3–109.9 Ma) in the Gyeongsang Basin. Together with previously published data, we evaluate the results from a total of 163 sites in the basin.We combine our age model with results from recent stratigraphic, paleomagnetic and radiometric geochemical studies. In this study, we found that two distinct declination shifts decrease with younging direction, indicating two clockwise rotational events of the Korean Peninsula with respect to the Eurasia continent. The earlier event took place during 130–100 Ma (Phase I, newly termed “Goguryeo Disturbance”) and a later one during 80–50 Ma (Phase III, belonging to “Bulguksa Orogeny”). The mean rotation rate in the interval from 115.2 to 103.8 Ma (Phase I) is about 0.74°/Ma, while the rate from 90.9 to 79.8 Ma (Phase II) is 0.19°/Ma. Based on paleolatitude change during Phase I, we infer that the Korean Peninsula (eastern part of the Sino-Korea Block) migrated southward about 300 km after the complete amalgamation of the Sino-Korea Block into the Eurasian continent resulting in N–S compression within the Korean peninsula and Manchuria. Large-scale strike-slip faults (e.g., Tan-Lu Fault, Okcheon Boundary Fault) were probably rejuvenated in the Sino-Korea Block during Phase I. 相似文献
40.