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121.
This paper presents a generic method to automatically segment and characterize solar filaments from various Hα full-disk solar
images, obtained by different solar observatories, with different dynamic ranges and statistical properties. First, a cascading
Hough circle detector is designed to find the center location and radius of the solar disks. Second, polynomial surface fitting
is adopted to correct unbalanced luminance. Third, an adaptive thresholding method is put forward to segment solar filaments.
Finally, for each piece of a solar filament, its centroid location, area, and length are characterized, in which morphological
thinning and graph theory are used for identifying the main skeletons of filaments. To test the performance of the proposed
methods, a dataset composed of 125 Hα images is considered. These images were obtained by four solar observatories from January
2000 to May 2010, one image per month. Experimental results show that the accuracy rate is above 95% as measured by filament
number and above 99% as measured by filament area, indicating that only a few tiny filaments are not detected. 相似文献
122.
123.
D. C.-F. Shih G.-F. Lin 《Stochastic Environmental Research and Risk Assessment (SERRA)》2006,20(4):291-295
Uncertainty of NRC proposed performance assessment for the corrosion depth of storage canister of nuclear spent fuel in time history is preformed using the differential analysis. The method is demonstrated to evaluate uncertainty propagation of a system with incomplete and insufficient data in the preliminary phase of assessment. The result shows that mean corrosion depth presents a non-linear regression while variance demonstrates a first-order linear increase through 1,000-year time history. By incorporating correlation into pitting factor, uniform corrosion factor, oxygen concentration and chlorine concentration, it is found that the covariance of pitting factor and chlorine concentration has the most significant contribution in the variance of total loss. Incorporating assumed covariance into the system, the analytical form of uncertainty and importance for the corrosion depth evaluation can be well demonstrated from the input parameters. 相似文献
124.
Walter W. Chen Ban-jwu Shih Yi-Chih Chen Jui-Huang Hung Howard H. Hwang 《Soil Dynamics and Earthquake Engineering》2002,22(9-12):1209-1214
In order to study the damage patterns of natural gas and water pipelines in the Ji-Ji earthquake, a GIS database and analysis procedures were established. Repair statistics was obtained from major natural gas companies and the Taiwan Water Supply Corporation (TWSC), and entered into the system. Then, repair rates (RR) were calculated. Previously, damage was analyzed without considering the corresponding pipeline material and diameters. In this study, new attempts were made to collect more data including those related to the composition of pipelines to provide a more detailed analysis of the relationship between earthquake forces and the resulting damage. Statistical analysis was also conducted to understand the correlation between RR and seismic parameters such as the peak ground acceleration, peak ground velocity, and spectrum intensity. 相似文献
125.
This paper presents experimental and analytical results on the seismic response of a rigid structure supported on isolation systems that consist of either lead rubber or sliding bearings. Shake table tests are conducted with various levels of isolation damping that is provided from the bearings and supplemental viscous fluid dampers. The table motions originated from recorded strong ground motions that have been compressed to the extent that the mass of the model structure corresponds to the mass of a typical freeway overcrossing. Experimental data are used to validate mechanical idealizations and numerical procedures. The study concludes that supplemental damping is most effective in suppressing displacements of rigid structures with moderately long isolation periods (TI≤3 sec) without affecting base shears. Friction damping is most effective in suppressing displacement amplifications triggered by long duration pulses—in particular, pulses that have duration close to the isolation period. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
126.
This study is to evaluate the applicability of estimating the one-dimensional horizontal hydraulic diffusivity of an unconfined
aquifer with time-dependent fluctuation of lateral head and vertical recharge boundaries using observed water level spectra.
Different models of boundary condition are imposed to evaluate the statistical significance between the calculated hydraulic
diffusivity (ξ′) with the given hydraulic diffusivity (ξ). The auto-spectra of the water level in observation wells tapping the same aquifer
are closely related to those at the disturbed boundaries. For an aquifer with a constant hydraulic diffusivity, the water
level fluctuation in the monitoring wells is linearly related to the water level spectra observed at the boundaries. The spectral
density function of aquifer hydraulic head varies inversely with specific yield (S
y) and directly with recharge. Given small variation in water level spectra at the disturbed boundaries, the water level fluctuation
in the aquifer is affected by the recharge condition and the aquifer spectral density function is sensitive to S
y. Using an iterative technique to estimate ξ from 1400 sets of given parameters, 99% of the ξ′/ξ values deviated within only one order of magnitude with the model length (L) being equal to 1 km and 10 km. For L equal to 100 m, approximately 82% of the ξ′/ξ population falls within two orders of magnitude. Therefore, spectral analysis of aquifer hydraulic head response can be
used to estimate the hydraulic diffusivity of an unconfined aquifer which is affected by periodic variations in recharge and
head at boundaries. 相似文献
127.
Owing to the fixed design parameters in traditional isolation systems, the optimal isolation performance may not always be achieved when a structure is subjected to a nondesign earthquake. At the same time, even though an active isolation system (AIS) can offer a better reduction for different seismic waves, in practice the control energy required still constrains its application. To solve this problem, a novel semi‐active isolation system called the Leverage‐type Stiffness Controllable Isolation System (LSCIS) is proposed in this paper. By utilizing a simple leverage mechanism, the isolation stiffness and the isolation period of the LSCIS can be easily controlled by adjusting the position of the pivot point of the leverage arm. The theoretical basis and the control law for the proposed system were first explained in this work, and then a shaking table test was conducted to verify the theory and the feasibility of the LSCIS. As shown in the experiment, the seismic behavior of the LSCIS can be successfully simulated by the theoretical model, and the isolation stiffness can be properly adjusted to reduce the seismic energy input in the LSCIS system. A comparison of the LSCIS with the other systems including passive isolation and AISs has demonstrated that based on the same limitation of base displacement, better acceleration reduction can be achieved by the LSCIS than by any of the other isolation systems. In addition, the control energy required by the LSCIS is lower than that for an AIS using the traditional LQR control algorithm. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
128.
C.Y. Robert WuD.L. Judge Bing-Ming ChengWen-Hao Shih Tai-Sone YihW.H. Ip 《Icarus》2002,156(2):456-473
Experimental results on the spectral identification of new infrared absorption features and the changes of their absorbances produced through vacuum ultraviolet-extreme ultraviolet (VUV-EUV) photon-induced chemical reactions in the C2H2-H2O mixed ices at 10 K are obtained. To the best of our knowledge, this is the first time that EUV photons have been employed in the study of the photolysis of ice analogues. Two different compositions, i.e., C2H2:H2O=1:4 and 1:1, were investigated in this work. A tunable intense synchrotron radiation light source available at the Synchrotron Radiation Research Center, Hsinchu, Taiwan, was employed to provide the required VUV-EUV photons. In this study, the photon wavelengths selected to irradiate the icy samples corresponded to the prominent solar hydrogen, helium, and helium ion lines at 121.6 nm, 58.4 nm, and 30.4 nm, respectively. The photon dosages used were typically in the range of 1×1015 to 2×1017 photons. Molecular species produced and identified in the ice samples at 10 K resulting from VUV-EUV photon irradiation are mainly CO, CO2, CH4, C2H6, CH3OH, and H2CO. In addition to several unidentified features, we have tentatively assigned several absorption features to HCO, C3H8, and C2H5OH. While new molecular species were formed, the original reactants, i.e., H2O and C2H2, were detectably depleted due to their conversion to other species. The new chemical species produced by irradiation of photons at 30.4 nm and 58.4 nm can be different from those produced by the 121.6-nm photolysis. In general, the product column density of CO reaches saturation at a lower photon dosage than that of CO2. Furthermore, the production yield of CO is higher than that of CO2 in the photon irradiation. In the present study, we also observe that the photon-induced chemical reaction yields are high using photons at 30.4 and 58.4 nm. The results presented in this work are essential to our understanding of chemical synthesis in ice analogues, e.g., the cometary-type ices and icy satellites of planetary systems. 相似文献
129.
The focus of automatic solar-flare detection is on the development of efficient feature-based classifiers. The three principal techniques used in this work are multi-layer perceptron (MLP), radial basis function (RBF), and support vector machine (SVM) classifiers. We have experimented and compared these three methods for solar-flare detection on solar H images obtained from the Big Bear Solar Observatory in California. The preprocessing step is to obtain nine principal features of the solar flares for the classifiers. Experimental results show that by using SVM we can obtain the best classification rate of the solar flares. We believe our work will lead to real-time solar-flare detection using advanced pattern recognition techniques. 相似文献
130.
Lawrence A. Taylor John W. Shervais Robert H. Hunter C.-Y. Shih B.M. Bansal J. Wooden L.E. Nyquist L.C. Laul 《Earth and Planetary Science Letters》1983
The concept that the plutonism of the lunar highlands and the mare-type volcanism are two separate problems in both time (> 4.4 AE versus < 3.95 AE) and space is seriously questioned by the discovery of a 4.23-AE low-Ti mare basalt from Fra Mauro Formation.Apollo 14 breccia 14305 contains a clast (,122) which is an olivine gabbronorite that is texturally and mineralogically similar to several Apollo 12 basalts (e.g., 12005, 12035, 12040). It consists of cumulus olivine (40 modal %; Fo 62–70) and Ti-chromite (2.5 modal %); post-cumulus phases include low-Ca pyroxene (29 modal %; Wo 7–13 En 68–75), augite (10 modal %; Wo 31–40 En 47–50), plagioclase (15 modal %, An 82–93), and ilmenite (4 modal %, 5–7 MgO). The TiO2 content of this rock = 4.3%; CaO/Al2O3 ? 1.0, CaO = 5.1%; MgO/FeO ? 1.0, MgO = 21.9%. The REE pattern, normalized to chondritic abundances, is approximately 30 × Ch and “hump-shaped” with a pronounced Eu depletion and a non-KREEPy signature. A four-point Rb-Sr isochron reveals an age of 4.23 ± 0.05 AE. The sample has a low initial 87Sr/86Sr= 0.69911 ± 3.The data presented here show that non-KREEPy, mare-type volcanism commenced at least as early as 4.2 AE in the Fra Mauro region and probably across much of the lunar surface. Massive bombardment during the “terminal cataclysm” and the subsequent veneer of younger mare basalts has obliturated most of the evidence for these ancient volcanic events. These old, mare-type volcanics may be related to basin-forming events such as made Procellarum (i.e., impact-triggered igneous activity). 相似文献