Automated flare forecasting using a statistical learning technique     

Yuan Yuan  Frank Y.Shih  Ju Jing  Hai-Min Wang 《中国天文和天体物理学报》2010,10(8)

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Unsupervised fuzzy neural network structural active pulse controller     

Shih‐Lin Hung  C. M. Lai 《地震工程与结构动力学》2001,30(4):465-484

Applying active control systems to civil engineering structures subjected to dynamic loading has received increasing interest. This study proposes an active pulse control model, termed unsupervised fuzzy neural network structural active pulse controller (UFN‐SAP controller), for controlling civil engineering structures under dynamic loading. The proposed controller combines an unsupervised neural network classification (UNC) model, an unsupervised fuzzy neural network (UFN) reasoning model, and an active pulse control strategy. The UFN‐SAP controller minimizes structural cumulative responses during earthquakes by applying active pulse control forces determined via the UFN model based on the clusters, classified through the UNC model, with their corresponding control forces. Herein, we assume that the effect of the pulses on structure is delayed until just before the next sampling time so that the control force can be calculated in time, and applied. The UFN‐SAP controller also averts the difficulty of obtaining system parameters for a real structure for the algorithm to allow active structural control. Illustrative examples reveal significant reductions in cumulative structural responses, proving the feasibility of applying the adaptive unsupervised neural network with the fuzzy classification approach to control civil engineering structures under dynamic loading. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

Isotopic and REE studies of lunar basalt 12038: implications for petrogenesis of aluminous mare basalts     

L.E. Nyquist  J.L. Wooden  C.-Y. Shih  H. Wiesmann  B.M. Bansal 《Earth and Planetary Science Letters》1981,55(3):335-355

We report Sr, Nd, and Sm isotopic studies of lunar basalt 12038, one of the so-called aluminous mare basalts. A precise internal Rb-Sr isochron yields a crystallization age of 3.35±0.09 AE and initial⁸⁷Sr/⁸⁶Sr=0.69922?2 (2σ error limits, 1AE=10⁹ years, λ(⁸⁷Rb)=0.0139AE^?1). An internal Sm-Nd isochron yields an age of 3.28±0.23AE and initial¹⁴³Nd/¹⁴⁴Nd=0.50764?28. Present-day¹⁴³Nd/¹⁴⁴Nd is less than the “chondritic” value, i.e. ?(Nd, 0)=?2.3±0.4 where ?(Nd) is the deviation of¹⁴³Nd/¹⁴⁴Nd from chondritic evolution, expressed as parts in 10⁴. At the time of crystallization ?(Nd, 3.2AE)=1.5±0.6.We have successfully modeled the evolution of the Sr and Nd isotopic compositions and the REE abundances within the framework of our earlier model for Apollo 12 olivine-pigeonite and ilmenite basalts. The isotopic and trace element features of 12038 can be modeled as produced by partial melting of a cumulate mantle source which crystallized from a lunar magma ocean with a chondrite-normalized REE pattern of constant negative slope. Chondrite-normalized La/Yb=2.2 for this hypothetical magma ocean pattern. A plot of I(Sr) versus ?(Nd) for the Apollo 12 basalts clearly shows the influence of varying proportions of olivine, clinopyroxene, orthopyroxene, and plagioclase in the basalt source regions. A small percentage of plagioclase (～5%) in the 12038 source apparently is responsible for low I(Sr) and ?(Nd) in this basalt. Aluminous mare basalts from Mare Crisium (Luna 24) and by inference Mare Fecunditatis (Luna 16) occupy locations on the I(Sr)-?(Nd) plot similar to that of 12038, implying that some basalts from three widely separated lunar regions came from plagioclase-bearing source regions. A summary of model calculations for mare basalts shows a record of lunar mantle solidification during the period when REE abundances in the lunar magma ocean increased from ～20× chondritic to >100× chondritic. Although there is a general trend from olivine to clinopyroxene-dominated source regions with progressive magma ocean evolution, significant mineralogical heterogeneities in mantle composition apparently formed at any given stage of evolution, as evidenced in particular by the three Apollo 12 magma types.  相似文献   

Automatic Solar Flare Tracking Using Image-Processing Techniques   总被引：1，自引：0，他引：1  

Ming Qu  Frank Shih  Ju Jing  Haimin Wang 《Solar physics》2004,222(1):137-149

Measurement of the evolution properties of solar flares through their complete cyclic development is crucial in the studies of Solar Physics. From the analysis of solar H images, we used Support Vector Machines (SVMs) to automatically detect flares and applied image segmentation techniques to compute their properties. We also present a solution for automatically tracking the apparent separation motion of two-ribbon flares and measuring their moving direction and speed in the magnetic fields. From these measurements, with certain assumptions, we inferred the reconnection of the electric field as a measure of the rate of the magnetic reconnection in the corona. The automatic procedure is a valuable tool for real-time monitoring of flare evolution.  相似文献   

Energy-based probabilistic evaluation of soil liquefaction   总被引：3，自引：0，他引：3  

Y.R. Chen  S.C. Hsieh  J.W. Chen  C.C. Shih 《Soil Dynamics and Earthquake Engineering》2005,25(1):55-68

This paper presents a seismic wave energy-based method with back-propagation neural networks to assess the liquefaction probability. An empirical equation and Fourier spectrum of acceleration are employed, respectively, to calculate the seismic wave energy. Discriminant analysis is used to determine the equation of the boundary curve separating the data points with and without liquefaction. The proposed method shows capability in evaluating the probability of soil liquefaction based on the boundary curve and a logarithm normal distribution.  相似文献   

Application of the new international geomagnetic reference field (IGRF80) to large sets of marine magnetometer data     

R. Macnab  K.G. Shih  S.P. Srivastava 《Physics of the Earth and Planetary Interiors》1985,37(1):5-11

Measurements of the magnetic field made over an interval of time must be corrected for secular variation before the data can be merged. The older versions of International Geomagnetic Reference Field (IGRF) failed to model secular variation adequately, and compilation of magnetic anomaly maps from different data sets often required numerous ad-hoc adjustments. With the superiority of the new IGRF at modelling secular variation, the merging of multi-year data sets has become much more practicable. This has been demonstrated in the consolidation of nearly 400 000 data points collected between 1972 and 1980 during 10 different survey cruises in the southwest Labrador Sea.Improvements in the IGRF have been achieved at a substantial cost in computing overhead. The new reference field expressions are more complicated than the old, and hence are slower to evaluate on digital computers. When processing large data sets, this can cause unacceptable delays. A third degree polynomial technique has been devised that approximates the total field portion of the full IGRF expression for a limited time and region. The method reduces processing time by a factor of 40, with little sacrifice in accuracy.  相似文献   

The age of Dar al Gani 476 and the differentiation history of the martian meteorites inferred from their radiogenic isotopic systematics     

Lars E. Borg  Larry E. Nyquist  Chi-Yu Shih 《Geochimica et cosmochimica acta》2003,67(18):3519-3536

Samarium-neodymium isotopic analysis of the martian meteorite Dar al Gani 476 yields a crystallization age of 474 ± 11 Ma and an initial ε_Nd¹⁴³ value of +36.6 ± 0.8. Although the Rb-Sr isotopic system has been disturbed by terrestrial weathering, and therefore yields no age information, an initial ⁸⁷Sr/⁸⁶Sr ratio of 0.701249 ± 33 has been estimated using the Rb-Sr isotopic composition of the maskelynite mineral fraction and the Sm-Nd age. The Sr and Nd isotopic systematics of Dar al Gani 476, like those of the basaltic shergottite QUE94201, are consistent with derivation from a source region that was strongly depleted in incompatible elements early in the history of the solar system. Nevertheless, Dar al Gani 476 is derived from a source region that has a slightly greater incompatible enrichment than the QUE94201 source region. This is not consistent with the fact that the parental magma of Dar al Gani 476 is significantly more mafic than the parental magma of QUE94201, and underscores a decoupling between the major element and trace element-isotopic systematics observed in the martian meteorite suite.Combining the ε_Nd¹⁴²-ε_Nd¹⁴³ isotopic systematics of the martian meteorites yields a model age for planetary differentiation of 4.513_+0.033^−0.027 Ga. Using this age, the parent/daughter ratios of martian mantle sources are calculated assuming a two-stage evolutionary history. The calculated sources have very large ranges of parent/daughter ratios (⁸⁷Rb/⁸⁶Sr = 0.037-0.374; ¹⁴⁷Sm/¹⁴⁴Nd = 0.182-0.285; ¹⁷⁶Lu/¹⁷⁷Hf = 0.028-0.048). These ranges exceed the ranges estimated for terrestrial basalt source regions, but are very similar to those estimated for the sources of lunar mare basalts. In fact, the range of parent/daughter ratios calculated for the martian meteorite sources can be produced by mixing between end-members with compositions similar to lunar mare basalt sources. Two of the sources have compositions that are similar to olivine and pyroxene-rich mafic cumulates with variable proportions of a Rb-enriched phase, such as amphibole, whereas the third source has the composition of liquid trapped in the cumulate pile (i.e. similar to KREEP) after ∼99% crystallization. Correlation between the proportion of trapped liquid in the meteorite source regions and estimates of f_O2, suggest that the KREEP-like component may be hydrous. The success of these models in reproducing the martian meteorite source compositions suggests that the variations in trace element and isotopic compositions observed in the martian meteorites primarily reflect melting of the crystallization products of an ancient magma ocean, and that assimilation of evolved crust by mantle derived magmas is not required. Furthermore, the decoupling of major element and trace element-isotopic systematics in the martian meteorite suite may reflect the fact that trace element and isotopic systematics are inherited from the magma source regions, whereas the major element abundances are limited by eutectic melting processes at the time of magma formation. Differences in major element abundances of parental magma, therefore, result primarily from fractional crystallization after leaving their source regions.  相似文献   

Periodic variability during the X-ray decline of 4U 1636-53     

I. C. Shih  A. J. Bird  P. A. Charles  R. Cornelisse  D. Tiramani 《Monthly notices of the Royal Astronomical Society》2005,361(2):602-606

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Influence of river channel geometry in stream flow modelling and guidelines for field investigation          下载免费PDF全文

Hongbo Zhang  Fan Zhang  Xiaonan Shi  Chen Zeng  Dong‐Sin Shih  Gour‐Tsyh Yeh  Daniel R. Joswiak 《水文研究》2014,28(4):2630-2638

Fully physics‐based, process‐level, distributed fluid flow and reactive transport hydrological models are rarely used in practice until recent years. These models are useful tools to help understand the fundamental physical, chemical, and biological processes that take place in nature. In this study, sensitivity analyses based on a mountain area river basin modelling study are performed to investigate the effect of river channel geometric characteristics on downstream water flow. Numerical experiments show that reduction in the river channel geometric measurement interval may not significantly affect the downstream water stage simulation as long as measurement accuracy at special nodes is guaranteed. The special upstream nodes include but are not limited to 1) nodes located close to the observation station, 2) nodes near the borders of different land covers with considerable riverbed roughness changes, 3) nodes at entering points of tributaries causing discharge jump and 4) nodes with a narrow cross‐section width that may control the flow conditions. This information provides guidelines for field investigation to efficiently obtain necessary geometric data for physics‐based hydrological modelling. It is especially useful in alpine areas such as the Tibetan Plateau where field investigation capability is limited under severe topography and climate condition. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Estimating anisotropic aquifer parameters by artificial neural networks     

Hsien‐Tsung Lin  Kai‐Yuan Ke  Chu‐Hui Chen  Shih‐Ching Wu  Yih‐Chi Tan 《水文研究》2010,24(22):3237-3250

In recent years, many approaches have been developed using the artificial neural networks (ANN) model incorporated with the Theis analytical solution to estimate the effective hydrological parameters for homogeneous and isotropic porous media, such as the Lin and Chen approach (ANN approach) and the principal component analysis (PCA)‐ANN approach. The above methods assume a full superimposition of the type curve and the observed drawdown and try to use the first time‐drawdown data as a match point to make a fine approximation of the effective parameters. However, using first time‐drawdown data or early time‐drawdown data does not always allow for an accurate estimation of the hydrological parameters, especially for heterogeneous and anisotropic aquifers. Therefore, this article corrects the concept of the superimposed plot by modifying the ANN approach and the PCA‐ANN approach, as well as incorporating the Papadopoulos analytical solution, to estimate the transmissivities and storage coefficient for anisotropic, homogeneous aquifers. The ANN model is trained with 4000 training sets of the well function, and tested with 1000 sets and 300 sets of synthetic time‐drawdown generated from the homogeneous and heterogeneous parameters, respectively. In situ observation data from the time‐drawdown at station Shi‐Chou on the Choushui River alluvial fan, Taiwan, is further adopted to test the applicability and reliability of the proposed methods, as well as provide a basis for comparison with the Straight‐line method and the Type‐curve method. Results suggest that both of the modified methods perform better than the original ones, and using late time‐drawdown to optimize the effective parameters is shown to be better than using early time‐drawdown. Additionally, results indicate that the modified ANN approach is better than the modified PCA‐ANN approach in terms of precision, while the efficiency of the modified PCA‐ANN approach is approximately three times better than that of the modified ANN approach. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献