排序方式： 共有49条查询结果，搜索用时 640 毫秒
41.
This paper presents new laboratory experiments carried out in a supertank (300 m × 5 m × 5.2 m) of breaking solitary waves evolution on a 1:60 plane beach. The measured data are employed to re-examine existing formulae that include breaking criterion, amplitude evolution and run-up height. The properties of shoreline motion, underwater particle velocity and scale effect on run-up height are briefly discussed. Based on our analyses, it is evidently found that there exist five zones during a wave amplitude evolution course on the present mild slope. A simple formula which is capable of predicting maximum run-up height for a breaking solitary wave on a uniform beach with a wide range of beach slope (1:15–1:60) is also proposed. The calculated results from the present model agree favorably with available laboratory data, indicating that our method is compatible with other predictive models. 相似文献
42.
This article proposes an improved multi‐run genetic programming (GP) and applies it to estimate the typhoon rainfall over ocean using multi‐variable meteorological satellite data. GP is a well‐known evolutionary programming and data mining method used to automatically discover the complex relationships among nonlinear systems. The main advantage of GP is to optimize appropriate types of function and their associated coefficients simultaneously. However, the searching efficiency of traditional GP can be decreased by the complex structure of parse tree to represent the multiple input variables. This study processed an improvement to enhance escape ability from local optimums during the optimization procedure. We continuously run GP several times by replacing the terminal nodes at the next run with the best solution at the current run. The current method improves GP, obtaining a highly nonlinear meaningful equation to estimate the rainfall. In the case study, this improved GP (IGP) described above combined with special sensor microwave imager (SSM/I) seven channels was employed. These results are then verified with the data from four offshore rainfall stations located on islands around Taiwan. The results show that the IGP generates sophisticated and accurate multi‐variable equation through two runs. The performance of IGP outperforms the traditional multiple linear regression, back‐propagated network (BPN) and three empirical equations. Because the extremely high values of precipitation rate are quite few and the number of zero values (no rain) is very large, the underestimations of heavy rainfall are obvious. A simple genetic algorithm was therefore used to search for the optimal threshold value of SSM/I channels, detecting the data of no rain. The IGP with two runs, used to construct an appropriate mathematical function to estimate the precipitation, can obtain more favourable results from estimating extremely high values. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
43.
Tai-Wen Hsu Shih-Chun Hsiao Shan-Hwei Ou Swun-Kwang Wang Bin-Da Yang Shih-En Chou 《Ocean Engineering》2007,34(5-6):870-883
A numerical model based on the second-order fully nonlinear Boussinesq equations of Wei et al. [1995. Journal of Waterway, Port, Coastal and Ocean Engineering 121 (5), 251-263] is developed to simulate the Bragg reflection of both regular and irregular surface waves scattered by submerged bars. Particularly for incident regular waves, the computed results are observed to agree very well with the existing experimental data as presented by Davies and Heathershaw [1984. Journal of Fluid Mechanics 144, 419-446] and Kirby and Anton [1990. Proceedings of the 22nd International Conference on Coastal Engineering, ASCE, New York, pp. 757–768). In the case of incident irregular waves, the simulated results reveal that the distribution of Bragg reflection from irregular waves becomes more flat than that of regular waves. Due to lack of experimental data, the numerical results for incident irregular waves are compared with those of the evolution equation of the mild-slope equation [Hsu et al., 2002 Proceedings of the 24th Ocean Engineering Conference in Taiwan, pp. 70–77 (in Chinese)]. In addition, several parameters such as the number of bars, the relative height of bars and the spacing of bars affecting Bragg reflection are also discussed. 相似文献
44.
Keh‐Chyuan Tsai Po‐Chien Hsiao Kung‐Juin Wang Yuan‐Tao Weng Min‐Lang Lin Ker‐Chun Lin Chui‐Hsin Chen Jiun‐Wei Lai Sheng‐Lin Lin 《地震工程与结构动力学》2008,37(7):1081-1098
A series of pseudo‐dynamic tests (PDTs) of a full‐scale 3‐story 3‐bay buckling‐restrained braced frame (BRBF) using concrete‐filled tube columns was tested in the Taiwan National Center for Research on Earthquake Engineering using networked PDT techniques in October 2003. During the tests, real‐time experimental responses and video were webcasted to Internet viewers. The input ground motions adopted for the PDTs were chosen from the 1999 Chi‐Chi and the 1989 Loma Prieta earthquakes and scaled to represent three seismic hazard levels. This paper is in two parts, focusing on the investigations of the overall structure and the local members. This paper constitutes Part I and discusses the design, analytical investigations, and key experimental results of the specimen frame, such as the buckling of the brace‐to‐gusset joints. Part II of the paper, the companion paper, describes the gusset stiffening schemes and detailed experimental behavior of the BRBs and their connections. Experimental peak inter‐story drifts of 0.019 and 0.023 radians, prescribed for the design basis and the maximum credible earthquakes, respectively, are within the target design limits of 0.020 and 0.025 radians. These tests confirmed that the PISA3D and OpenSees nonlinear structural analysis computer programs can simulate the experimental peak shears and floor displacements well. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
45.
During a March 1977 experiment, four systems were used to provide wave-direction information offshore of Mission Beach, CA: a synthetic aperature radar (SAR) carried aboard a NASA CV990 aircraft, a coastal imaging radar, a pressure-gauge array offshore, and aerial photography aboard two aircraft. The coastal radar, aerial photographs, and SAR provided wave images. From the coastal radar images and the aerial photographs, the direction and length of the principal wavetrains were measured by a manual analysis. The SAR images were also processed using an FFT to give two-dimensional wave spectra. The array at the Naval Ocean Systems Center (NOSC) tower was used to provide directional wave spectra. Scatter diagrams are presented, which intercompare the measurements from these four systems. In addition, radar image spectral information is compared with the array spectra. The intercomparison of the data from these four systems shows good agreement among the imaging systems. Between the imaging systems and the pressure array there is agreement for the most prominent wavetrains and disagreement for several cases where multiple wavetrains from different directions but with similar periods are present. 相似文献
46.
Special concentrically braced frames (SCBFs) are commonly used as the lateral‐load resisting system in buildings. SCBFs primarily sustain large deformation demands through inelastic action in the brace, including compression buckling and tension yielding; secondary yielding may occur in the gusset plate and framing elements. The preferred failure mode is brace fracture. Yielding, buckling, and fracture behavior results in highly nonlinear behavior and accurate analytical modeling of these frames is required. Prior research has shown that continuum models are capable of this level of simulation. However, those models are not suitable for structural engineering practice. To enable the use of accurate yet practical nonlinear models, a research study was undertaken to investigate modeling parameters for line‐element models, which is a more practical modeling approach. This portion of the study focused on methods to predict brace fracture. A fracture modeling approach simulated the nonlinear, cyclic response of SCBFs by correlating onset of fracture to the maximum strain range in the brace. The model accounts for important brace design parameters including slenderness, compactness, and yield strength. Fracture data from over 40 tests was used to calibrate the model and included single‐brace component, single story frame, and full‐scale multistory frame specimens. The proposed fracture model is more accurate and simpler than other, previously proposed models. As a result, the proposed model is an ideal candidate for practical performance simulation of SCBFs. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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We compare the accuracies of GPS and gravity observations obtained from three airborne gravity surveys over Taiwan Island at altitude 5000 m and over Kuroshio Current, Taiwan Strait, and Dongsha Atoll at altitude 1500 m. A kinematic network adjustment was used to determine the positions of the aircrafts. GPS positioning errors are at the decimeter-level, which are not entirely propagated to velocity and acceleration errors due to cancellation of long wavelength errors. Outliers are downweighted in the Gaussian filtering to improve the gravity accuracy, especially at altitude 1500 m. Compared with the upward-continued gravity, the gravity anomalies from the 1500-m surveys show a consistent accuracy of about 3 mgal; the accuracy from the 5000-m survey is degraded, especially over high mountains. The RMS crossover differences at 1500 m and 5000 m are all below 3 mgal, suggesting flight altitudes do not affect the crossover difference. Coherence analysis suggests that the spatial resolvable wavelengths of the airborne gravity range from 4 km (altitude 1500 m) to 6 km (altitude 5000 m). 相似文献
49.
Chun-Chieh Hsiao J. Y. Liu K.-I. Oyama N. L. Yen Y. A. Liou S. S. Chen J. J. Miau 《GPS Solutions》2010,14(1):83-89
The seismo-ionospheric precursor prior to the Mw7.9 earthquake near Wenchuan, China, on 12 May 2008 was observed by the FORMOSAT-3/COSMIC
satellite constellation. By binning radio occultation observations, the three-dimensional ionospheric structure can be obtained
to monitor the ionospheric electron density variation prior to the earthquake. It has been determined that near the epicenter
the F2-peak height, hmF2, descends about 25 km and the F2-peak electron density, NmF2, decreases about 2 × 105 el/cm3 around noon within 5 days prior to the earthquake. The integrated electron content decreases more than 2 TECU between 250
and 300 km altitude. 相似文献