The Earth’s natural pulse electromagnetic field data consists typically of an underlying variation tendency of intensity and irregularities.The change tendency may be related to the occurrence of earthquake disasters.Forecasting of the underlying intensity trend plays an important role in the analysis of data and disaster monitoring.Combining chaos theory and the radial basis function neural network,this paper proposes a forecasting model of the chaotic radial basis function neural network to conduct underlying intensity trend forecasting by the Earth’s natural pulse electromagnetic field signal.The main strategy of this forecasting model is to obtain parameters as the basis for optimizing the radial basis function neural network and to forecast the reconstructed Earth’s natural pulse electromagnetic field data.In verification experiments,we employ the 3 and 6 days’data of two channels as training samples to forecast the 14 and 21-day Earth’s natural pulse electromagnetic field data respectively.According to the forecasting results and absolute error results,the chaotic radial basis function forecasting model can fit the fluctuation trend of the actual signal strength,effectively reduce the forecasting error compared with the traditional radial basis function model.Hence,this network may be useful for studying the characteristics of the Earth’s natural pulse electromagnetic field signal before a strong earthquake and we hope it can contribute to the electromagnetic anomaly monitoring before the earthquake. 相似文献
Unreinforced masonry infill walls are widely used as non-structural partitions in RC frames. The effects of infills on the structural responses are often ignored in the design process since they are generally considered as expendable elements. However, recent studies have shown that not only shear damage can be inflicted to the columns braced by the infill walls, but also that the structural stability can be jeopardised by the fall-off of the infills. This paper presents the development of new detailing methods for the infill walls, which features slit panels, isolation gaps between the infills and columns, and anchorage of the infills. The proposed detailing methods were tested and verified experimentally using shake-table tests on five 1/3-scale infilled RC frame specimens with different combinations of the features stated above. The design and construction of the shake-table test specimens have taken into account the similitude requirements. The test results indicate that the proposed detailing method effectively reduced the undesirable interaction between column and infill walls. And the use of proper anchorage could prevent the fall off of infills from the bounding frame. Furthermore, the specimens with slit infill walls displayed better seismic performances, which could be attributed to the rocking behaviour of the sub-panels with increased aspect ratios. 相似文献
We discuss here the issues faced by earth scientists in analyzing and visualizing large datasets over a GRID-like setup from a client-server perspective. We approach this problem by using a remote, web-based visualization and data analysis framework, called WEB-IS, and by employing second-generation wavelets as a means for reducing the amount of data transferred and for extracting coherent features in complex geophysical flows and surface faulting patterns. As an example, we describe how onboard processors on satellites can function as a server for beaming down extracted information to the client computer on the ground, thus exemplifying WEB-IS as a viable middleware on a GRID network for geosciences.Reviewed by: Prof. I.D. Clemens, Prof. L. Hanyk 相似文献
Surface wave methods have received much attention due to their efficient, flexible and convenient characteristics. However, there are still critical issues regarding a key step in surface wave inversion. In most existing methods, the number of layers is assumed to be known prior to the process of inversion. However, improper assignment of this parameter leads to erroneous inversion results. A Bayesian nonparametric method for Rayleigh wave inversion is proposed herein to address this problem. In this method, each model class represents a particular number of layers with unknown S-wave velocity and thickness of each layer. As a result, determination of the number of layers is equivalent to selection of the most applicable model class. Regarding each model class, the optimization search of S-wave velocity and thickness of each layer is implemented by using a genetic algorithm. Then, each model class is assessed in view of its efficiency under the Bayesian framework and the most efficient class is selected. Simulated and actual examples verify that the proposed Bayesian nonparametric approach is reliable and efficient for Rayleigh wave inversion, especially for its capability to determine the number of layers.
Singapore has witnessed rapid urban development in the last thirty years. Its landscape has changed from one of slums and
squatters in the immediate post-war years to a city of gardens and high-rise high-density housing. The concept of a `garden
city' was introduced to guide the development of a city-state with abundant greenery. In the process, many parks and gardens
were created including park connectors which are green linkages between parks and other land uses. This paper presents the
findings of an ongoing research into park connectors. It reports on that part of the survey results which examine the views
of residents towards nature provision in park connectors and suggest some design options to enhance the planning of park connectors.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
Summary Dubbed Ice Storm ’98, an extreme weather event characterized by two synoptic systems in succession dropped about 70–100 mm
(in terms of water equivalent) of freezing precipitation over southeastern Ontario, southwestern Quebec and northeastern New
York during a 6-day period from January 5 to 10 in 1998. Individually, the two synoptic systems were not dramatically more
extreme in freezing precipitation than other major freezing rain events (4 since 1961) which occurred in the past over the
affected area. Some regions in the target area, however, were impacted more by the second system. Based on an analysis of
the 500 hPa vorticity field during the ’98 event, we suggest that the 1997/98 El Ni?o had a role in creating a flow environment
conducive to the rapid formation of the second synoptic system. In contrast, other major freezing rain events in the last
30 years involved only one synoptic system per event lasting no more than 3 days, and producing 20–50 mm of precipitation.
We have also found that, 3 out of 4 past major freezing rain events since 1958 were associated with the positive phase of
the North Atlantic Oscillation (NAO). Consistent with this usual past association between the NAO and a major freezing rain
event, Ice Storm ’98 also occurred when the phase of the NAO was positive. Analysis of these 3 past and the ’98 events also
indicates an apparent connection between the positive phase of the NAO and the northern Quebec high pressure system, which
is an essential synoptic feature of a major freezing rain occurrence over the southcentral region of Canada. As measured by
their respective indices, the maximum positive NAO state leads the maximum northern Quebec high by about 2 days (5 days in
the ’98 event). There is some suggestive evidence to indicate that the persistence of the northern Quebec high pressure system
is connected to the persistence of the positive phase of the NAO.
Received January 17, 2000 相似文献