We investigated a torrential rainfall case with a daily rainfall amount of 379 mm and a maximum hourly rain rate of 77.5 mm that took place on 12 July 2006 at Goyang in the middlewestern part of the Korean Peninsula. The heavy rainfall was responsible for flash flooding and was highly localized. High-resolution Doppler radar data from 5 radar sites located over central Korea were analyzed. Numerical simulations using the Weather Research and Forecasting (WRF) model were also performed to complement the high-resolution observations and to further investigate the thermodynamic structure and development of the convective system. The grid nudging method using the Global Final (FNL) Analyses data was applied to the coarse model domain (30 km) in order to provide a more realistic and desirable initial and boundary conditions for the nested model domains (10 km, 3.3 km). The mesoscale convective system (MCS) which caused flash flooding was initiated by the strong low level jet (LLJ) at the frontal region of high equivalent potential temperature (θe) near the west coast over the Yellow Sea. The ascending of the warm and moist air was induced dynamically by the LLJ. The convective cells were triggered by small thermal perturbations and abruptly developed by the warm θe inflow. Within the MCS, several convective cells responsible for the rainfall peak at Goyang simultaneously developed with neighboring cells and interacted with each other. Moist absolutely unstable layers (MAULs) were seen at the lower troposphere with the very moist environment adding the instability for the development of the MCS. 相似文献
SPT-N-based methods have been adopted for liquefaction assessment of soils during earthquakes for decades. However, there has not been a consistent way of assessing the accuracy and applicability of these methods. The Chi-chi earthquake of 1999, which has been the most serious ground shaking in Taiwan within the century, caused extensive liquefactions in mid-west alluvial deposits of the island. This paper assesses the prediction accuracy of several SPT-N-based methods using liquefaction and non-liquefaction incidents observed during the earthquake. A sensitivity study on commonly adopted parameters shows that the SPT blow count and peak ground acceleration are most sensitive in computing liquefaction potential. By comparing the error in predicting liquefaction and non-liquefaction incidents, this study concludes that Tokimatsu and Yoshimi’s method is more accurate than the other methods. However, the differences between prediction errors of various methods are minimal, indicating all of the methods examined are applicable for the 1999 earthquake in Taiwan. 相似文献
Climate change has altered locally single-type disasters to large-scale compound disasters because of increasing intensity
and frequency of extreme rainfall events. The compound disasters can combine small-scale floods, debris flows, shallow landslides,
deep-seated landslides, and landslide lakes into a large-scale single disaster event. Although simulation models and evaluation
tools are available for single-type disasters, no single model is well developed for compound disasters due to the difficulty
of handling the interrelationship between two successive single-type disasters. This study proposes a structure for linking
available single-type simulation models to evaluate compound disasters and provides a useful tool of decision making for warning
and planning of disaster reduction. 相似文献
We review the first science results from the Arcminute Cosmology Bolometer Array Receiver (ACBAR); a multi-frequency millimeter-wave receiver optimized for observations of the Cosmic Microwave Background (CMB) and the Sunyaev–Zel’dovich (SZ) effect in clusters of galaxies. ACBAR was installed on the 2 m Viper telescope at the South Pole in January 2001 and the results presented here incorporate data through July 2002. We present the power spectrum of the CMB at 150 GHz over the range ℓ=150–3000 measured by ACBAR as well as estimates for the values of the cosmological parameters within the context of ΛCDM models. We find that the inclusion of ΩΛ greatly improves the fit to the power spectrum. We also observe a slight excess of small-scale anisotropy at 150 GHz; if interpreted as power from the SZ effect of unresolved clusters, the measured signal is consistent with CBI and BIMA within the context of the SZ power spectrum models tested. 相似文献
After reviewing the studies on the lateral artificial boundaries in dynamic soil-structure interactions, the free field boundary was theoretically analyzed in asymmetric- and symmetric-matrix forms. First, the lumped mass system was combined with viscous or viscoelastic elements to obtain a lumped mass-free field boundary. Second, typical examples were implemented using the finite element software ABAQUS. The incident shear wave was taken to be perpendicular to the bottom to verify the effectiveness of the lumped mass-free field under various sites: underground structures, uniform sites, and layered sites. Finally, the accuracy of the lumped mass-free field boundary was compared with those of the viscoelastic and roller boundaries on different calculation scales, soil damping ratios, structure sizes, and ground motion characteristics. Subsequently, the engineering design values for different damping ratios are given. The results show that the precision of the lumped mass-free field boundary was reasonable, and the operation was simple within the same engineering application.
Petrological, mineralogical and geochemical studies carried out on kaolinite deposits in Haerwusu surface mine,Jungar Coalfield, northern Ordos Basin, North China, define their characteristics, ore genesis and economic interest. Based on the crystalline size, two different types of kaolinite rocks, cryptocrystalline and grainy, were identified under the microscope. XRD data show that kaolinite is the predominant mineral, associated with boehmite, magnesite, anatase, pyrite,diaspore and calcite. However, high boehmite content(mean 70%) shows up in the middle layers. Kaolinite minerals present homogeneous shape and a good crystallinity(HI = 0.96–1.26). Geochemical studies show that the SiO2/Al2 O3 molar ratio of kaolinite is close to the theoretical value, and the contents of Na2 O, K2 O, CaO, MgO are less, suggesting a strong chemical weathering environment. The REE and Eu anomalies show a close relationship between kaolinite and the Yinshan Oldland granite. A Ce anomaly reflects a continental sedimentary environment with shallow water. A temperature range of26.7–34℃ was calculated on the basis of the isotopic signatures(δ18 O, δD) of the kaolinite rocks. All these data indicate that the formation of the kaolinite is caused mainly by the dissolution, coagulation, precipitation and recrystallization of aluminosilicate clastics in acidic conditions. The formation of boehmite in the middle layers indicates that the source rocks have changed. Boehmite is mainly formed by dehydration and compaction of an aluminum-rich colloid which transported into peat swamp during diagenesis. In addition, it formed by desiliconization of kaolinite under acidic conditions. Due to its high kaolinite content(up to 90%) and low iron mineral content(less than 1%), and good crystallinity, kaolinite deposits occurred at Haerwusu surface mine probably have great economical value in the future. 相似文献
An alternative formulation is proposed for deriving depth-integrated equations for gravity-driven granular avalanches over a non-trivial topography with small curvature. The coordinate system of Bouchut and Westdickenberg (2004Bouchut, F and Westdickenberg, M. 2004. Gravity driven shallow water models for arbitrary topography. Commun. Math. Sci., 2: 359–389. [Crossref], [Google Scholar]) is combined with the unified coordinate (UC) method, so that it can evolve in accordance with the entrainment–deposition processes at the basal surface. The resultant mass and momentum equations are formulated as a conservation system of the Cartesian components of the conservative physical variables. The motion of the flows is driven by the basal topography-induced pressure, pressure gradient, and resisted by the basal friction. The best benefit of this formulation is that it greatly simplifies the computation of the varying coordinate orientations. The features and advantages of this formulation are illustrated by the sliding-mass examples where we simulate the motion of a finite mass of granular material sliding down an inclined chute, running through a transition zone, and being deposited onto a horizontal plane. 相似文献
It is easy for a multi-layered perception (MLP) to fit a stratified spatial interpolation pattern whose form is close to open surface; while it is easy for a radial basis function network (RBFN) to fit a pocket (radial) spatial interpolation pattern whose form is close to closed surface. However, in the real world, the spatial interpolation pattern may consist of stratified and pocket patterns. Neither MLP nor RBFN can fit the pattern easily. To combine their advantages to fit the complex hybrid spatial interpolation patterns, in this article we propose a novel neural network, MLP–RBFN hybrid network (MRHN), whose hidden layer contains sigmoid and Gaussian units at the same time. Although there are two kinds of processing units in MRHN, in this study we used the principle of minimizing the error sum of squares to derive the supervised learning rules for all the network parameters. This research took rainfall distribution in Taiwan as a case study. The results show that (1) the prediction error of the testing dataset outside the training dataset demonstrated that MRHN was the most accurate among the three networks, RBFN was the next best, and MLP was the worst; (2) the MLP model seriously underestimated the values of high observed rainfall; (3) over-learning may be a serious shortcoming of using RBFN in spatial interpolation applications; (4) MRHN may have better generalization learning capacity than RBFN in spatial interpolation applications. 相似文献
Landslides induced by typhoon Morakot during its passage across Taiwan on 7–9 Aug 2009 claimed more than 700 lives and caused heavy economic loss. Unlike earthquake monitoring, precise locations of landslides could not be determined in near-real time because their seismic phases are difficult to identify. Here, we show that large, damaging landslide events are characterized seismically by a distinct waveform pattern of frequent intermixes of P and S waves over a time window of several tens of seconds. The predominant frequency band during these time windows ranges from 0.5 to 5?Hz. The high-frequency content is clearly deficient relative to that of local earthquakes by about one to two orders. We also demonstrate that large landslide events can be located and monitored with algorithms specifically designed for real-time seismic applications. This near-real-time monitoring capability would be particularly useful for emergency responders and government organizations to coordinate effective relief-and-rescue operations. 相似文献