Effect of wave non‐linearity on the standing‐wave‐induced seabed response     

C. P. Tsai  T. L. Lee  J. R. C. Hsu 《国际地质力学数值与分析法杂志》2000,24(11):869-892

A standing wave in front of a seawall may reach a height more than twice of its incident component. When excess pore pressure occurs, it may even induce seabed instability, hence endangering the structure. This issue was studied previously using only linear wave theory. In this paper, standing‐wave theory to a second‐order approximation is applied, in order to demonstrate the differences between these two solutions. The spatial and temporal variations in the instantaneous pore pressure are first calculated, in addition to their vertical distributions. The effects of wave height, water depth and the degree of soil saturation on pore pressure distributions are then discussed, followed by the net pore pressure averaged over one wave cycle. The results suggest the existence of a residual pore pressure in the seabed and its net pore pressure can be used to estimate the wave‐induced liquefaction potential in a soil column. It also indicates that, in deep water, the second‐order solution predicts that a negative pore pressure at an antinode which may be greater than a positive pressure. Overall, the second‐order solution is found to agree better with the experimental results of the pore pressures available, compared to the linear solution. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

Improved time integration for pseudodynamic tests     

Shuenn-Yih Chang  Keh-Chyuan Tsai  Kuan-Chou Chen 《地震工程与结构动力学》1998,27(7):711-730

Converting the second-order differential equation to a first-order equation by integrating it with respect to time once as the governing equation of motion for a structural system can be very promising in the pseudodynamic testing. This was originally found and developed by Chang. The application of this time-integration technique to the Newmark explicit method is implimented and investigated in this paper. The main advantages of using the integral form of Newmark explicit method instead of the commonly used Newmark explicit method in a pseudodynamic test are: a less-error propagation effect, a better capability in capturing the rapid changes of dynamic loading and in eliminating the adverse linearization errors. All these improvements have been verified by theoretical studies and experimental tests. Consequently, for a same time step this time-integration technique may result in less-error propagation and achieve more accurate test results than applying the original form of Newmark explicit method in a pseudodynamic test due to these significant improvements. Thus, the incorporation of this proposed time-integration technique into the direct integration method for pseudodynamic testings is strongly recommended. © 1998 John Wiley & Sons, Ltd.  相似文献   

Liquefaction,building settlement,and residual strength of two residential areas during the 2016 southern Taiwan earthquake     

Tsai  Chi-Chin  Hwang  Yu-Wei  Lu  Chih-Chieh 《Acta Geotechnica》2020,15(6):1363-1379

Acta Geotechnica - On February 6, 2016, a moment magnitude (Mw) 6.4 earthquake struck southern Taiwan and devastated the Tainan area. Although the intensity of ground shaking was only moderate...  相似文献   

Transcriptome Profiling of the Abdominal Skin of <Emphasis Type="Italic">Larimichthys crocea</Emphasis> in Light Stress     

Zhaofang Han  Changhuan Lv  Shijun Xiao  Kun Ye  Dongling Zhang  Huai Jen Tsai  Zhiyong Wang 《中国海洋大学学报(英文版)》2018,17(2):344-354

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Coupled nature of evening-time ionospheric electrodynamics     

L. M. Joshi  L. C. Tsai 《Astrophysics and Space Science》2018,363(4):72

The F region evening electrodynamics in the equatorial region is characterized by a pre-reversal enhancement (PRE) in the zonal eastward electric field. Although the theoretical mechanisms for PRE are known, its variability, particularly day-to-day variability is not fully resolved. PRE is a large scale phenomenon driven by the F region dynamo after the sunset hours. This paper investigates whether the variability of the E region conductivity (particularly the one associated with the sporadic E, Es) has any influence on the F region dynamo and hence on the PRE of zonal electric field. Interestingly, ionosonde observations have indicated a higher occurrence of the blanketing type Es (Esb) over the low latitude on days with highly suppressed PRE of zonal electric field in comparison with the days with significantly larger PRE. Observational evidences presented in this paper suggests that the formation of the Esb in the evening hours is a sovereign process, not always controlled by the sheared F region vertical electric field of equatorial origin, mapping along the magnetic field line on to the low latitude E region. Model computations of the PRE suppression based on the measured Es densities have further substantiated the observational findings presented in this paper. These results clearly indicate that the low latitude Es has the potential to suppress the PRE of zonal electric field and possibly can play a vital role in explaining the PRE variability, particularly the day-to-day variability. Results have been discussed in light of earlier reports on PRE mechanisms and E-F region coupling processes.  相似文献   

Gas seepage, pockmarks and mud volcanoes in the near shore of SW Taiwan   总被引：2，自引：0，他引：2  

Song-Chuen Chen  Shu-Kun Hsu  Ching-Hui Tsai  Chia-Yen Ku  Yi-Ching Yeh  Yunshuen Wang 《Marine Geophysical Researches》2010,31(1-2):133-147

In order to understand gas hydrate related seafloor features in the near shore area off SW Taiwan, a deep-towed sidescan sonar and sub-bottom profiler survey was conducted in 2007. Three profiles of high-resolution sub-bottom profiler reveal the existence of five gas seeps (G96, GS1, GS2, GS3 and GS4) and one pockmark (PM) in the study area. Gas seeps and pockmark PM are shown in lines A and C, while no gas venting feature is observed along line B. This is the first time that a gas-hydrate related pockmark structure has been imaged off SW Taiwan. The relatively high backscatter intensity in our sidescan sonar images indicates the existence of authigenic carbonates or chemosynthetic communities on the seafloor. More than 2,000 seafloor photos obtained by a deep-towed camera (TowCam) system confirm the relatively high backscatter intensity of sidescan sonar images related to bacteria mats and authigenic carbonates formation at gas seep G96 and pockmark PM areas. Water column gas flares are observed in sidescan sonar images along lines A and C. Likewise, EK500 echo sounder images display the gas plumes above gas seep G96, pockmark PM and gas seep GS1; the gas plumes heights reach about 150, 100 and 20 m from seafloor, respectively. Based on multichannel seismic reflection (MCS) profiles, an anticline structure trending NNE-SSW is found beneath gas seep G96, pockmark PM and gas seep GS2. It implies that the gas venting features are related to the anticline structure. A thermal fluid may migrate from the anticline structure to the ridge crest, then rises up to the seafloor along faults or fissures. The seafloor characteristics indicate that the gas seep G96 area may be in a transitional stage from the first to second stage of a gas seep self-sealing process, while the pockmark PM area is from the second to final stage. In the pockmark PM area, gas venting is observed at eastern flank but not at the bottom while authigenic carbonates are present underneath the pockmark. It implies that the fluid migration pathways could have been clogged by carbonates at the bottom and the current pathway has shifted to the eastern flank of the pockmark during the gas seep self-sealing process.  相似文献   

The impact of the Changjiang River plume extension on the nanoflagellate community in the East China Sea     

An-Yi Tsai  Gwo-Ching Gong  Robert W. Sanders  Ciou-Jyu Wang  Kuo-Ping Chiang 《Estuarine, Coastal and Shelf Science》2010

Variation in the summer nanoflagellate community on the continental shelf ecosystem of East China Sea (ECS) is closely coupled with environmental variation due to extension of the Changjiang River plume. Spatial patterns of nanoflagellate abundance were studied in June and August 2003, June 2006 and July 2007 over the ECS shelf. The Changjiang River plume was smaller during the August 2003 and July 2007 cruises than during the rest other 2 cruises. Total nanoflagellates densities varied between 1 and 120 × 10² cells ml⁻¹ with the highest abundances occurring within the Changjiang River plume during large plume periods. In the small plume periods, the range of nanoflagellates abundance was 3–33 × 10² cells ml⁻¹ and the highest abundances were observed during these periods either within the Changjiang River plume or the Yellow Sea Coastal Water (YSCW). During large plume periods, nanoflagellate abundance closely related to changes in salinity and during the small period, abundance was most related to water temperature. The pigmented nanoflagellate community (PNF) within Changjiang River plume, especially in the <3 μm size class, appears to increase in response to terrestrial or anthropogenic inorganic nutrient loading in the discharge of fresh water from the Changjiang River. The PNF abundance pronounced increase caused the variation of nanoflagellate community of ECS in summer. We suggest that the discharge of fresh water from Changjiang River has significant ecological impacts on spatial variations in nanoflagellate community in the ECS.  相似文献   

Stochastic sediment transport: anomalous diffusions and random movement     

Tsai  Christina W.  Hung  Serena Y.  Wu  Tsung-Han 《Stochastic Environmental Research and Risk Assessment (SERRA)》2020,34(2):397-413

Stochastic Environmental Research and Risk Assessment - A sediment particle in a flow not only follows the flow direction but also randomly diffuses through the surrounding fluid, because of the...  相似文献   

The Patuxent: People,pollution and pisces     

Chu-fa Tsai 《Marine pollution bulletin》1971

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Engineering analyses of smart 1 array accelerograms     

C. H. Loh  J. Penzien  Y. B. Tsai 《地震工程与结构动力学》1982,10(4):575-591

Presented are the results of engineering analyses of selected accelerograms recorded by the SMART 1 strong motion array in Taiwan which is described in a companion paper by B. A. Bolt, Y. B. Tsai, K. Yeh and M. K. Hsu, entitled Earthquake Strong Motions Recorded by a Large Near-source Array of Digital Seismographs. These analyses include (1) transformations to principal axes, (2) generation of Fourier amplitude spectra, (3) development of generalized response spectrum ratios for characterizing multi-support excitations and (4) moving window analyses in the time and frequency domains for studying the spatial variations of recorded ground motions.  相似文献