Large-scale simulation of watershed mass transport: a case study of Tsengwen reservoir watershed, southwest Taiwan     

Ko-Fei Liu  Ying-Hsin Wu  Yi-Chin Chen  Yu-Jia Chiu  Shang-Shu Shih 《Natural Hazards》2013,67(2):855-867

We present the large-scale simulation of watershed mass transport, including landslide, debris flow, and sediment transport. A case study of Tsengwen reservoir watershed under the extreme rainfall triggered by typhoon Morakot is conducted for verification. This approach starts with volume-area relation with landslide inventory method to predict temporal and regional landslide volume production and distribution. Then, debris flow model, Debris-2D, is applied to simulate the mass transport from hillslope to fluvial channel. Finally, a sediment transport model, NETSTARS, is used for hydraulic and sediment routing in river and reservoir. Near the water intake at the reservoir dam, the simulated sediment concentration is in good agreement with the measured one. The proposed approach gives good prediction and should help the management of reservoir operation and disaster prevention.  相似文献   

Basin-scale groundwater response to precipitation variation and anthropogenic pumping in Chih-Ben watershed, Taiwan     

Kuo-Chin Hsu  Hsin-Fu Yeh  You-Cheng Chen  Cheng-Haw Lee  Chung-Ho Wang  Feng-Sheng Chiu 《Hydrogeology Journal》2012,20(3):499-517

The sustainable use of groundwater has become increasingly challenging due to extreme hydrological events and anthropogenic activity. In this study, the basin-scale groundwater response to precipitation variation was analyzed using an integrated model that comprises lumped models for land and river recharges and a distributed model for groundwater. The integrated model was applied to the Chih-Ben watershed, Taiwan, using 20?years (1988?C2007) of data. The hydrological data were analyzed for trends using statistical tests. Based on decreasing trends in precipitation and groundwater levels and an increasing trend in stream flow, the oblique-cut method was applied to precipitation and excess infiltration to assess land and streambed recharge. Distributed numerical groundwater modeling was used to simulate the basin-scale groundwater responses to precipitation variation and anthropogenic pumping. The model was calibrated using stable-isotope and groundwater-level data. The safe yields were estimated for the Chih-Ben watershed for dry, wet, and normal precipitation scenarios. The safe yield of groundwater was shown to vary with precipitation, which does not guarantee the sustainable use of groundwater resources. Instead, water resources should be assessed at a basin scale, taking into account the whole ecosystem, rather than only considering water for human consumption in the alluvium.  相似文献   

Thermodynamic approach to the equation of state of a magnetized Fermi gas     

V. Canuto  H. Y. Chiu  L. Fassio-Canuto 《Astrophysics and Space Science》1969,3(2):258-267

In this paper we have rederived the equations of state for a magnetized Fermi gas by generalizing the physical definition of the pressure. We have also given a simplified derivation of the energy eigenvalues of a free electron in a magnetic field, based on the use of simple harmonic oscillators. Physical interpretations of our results are presented. Possible astrophysical applications are also discussed.On leave of absence from Dept. of Physics, C.I.E.A., Ap. Post. 14740, Mexico 14, D.F., Mexico.  相似文献   

A fast method of flood discharge estimation     

Yen‐Chang Chen  Chao‐Lin Chiu 《水文研究》2004,18(9):1671-1684

Discharge, especially during flood periods, is among the most important information necessary for flood control, water resources planning and management. Owing to the high flood velocities, flood discharge usually cannot be measured efficiently by conventional methods, which explains why records of flood discharge are scarce or do not exist for the watersheds in Taiwan. A fast method of flood discharge estimation is presented. The greatest advantage of the proposed method is its application to estimate flood discharge that cannot be measured by conventional methods. It has as its basis the regularity of open‐channel flows, i.e. that nature maintains a constant ratio of mean to maximum velocities at a given channel section by adjusting the velocity distribution and the channel geometry. The maximum velocity at a given section can be determined easily over a single vertical profile, which tends to remain invariant with time and discharge, and can be converted to the mean velocity of the entire cross‐section by multying by the constant ratio. Therefore the mean velocity is a common multiple of maximum velocity and the mean/maximum velocity ratio. The channel cross‐sectional area can be determined from the gauge height, the water depth at the y‐axis or the product of the channel width multiplied by the water depth at the y‐axis. Then the most commonly used method, i.e. the velocity–area method, which determines discharge as the product of the cross‐sectional area multiplied by mean velocity, is applied to estimate the flood discharge. Only a few velocity measurements on the y‐axis are necessary to estimate flood discharge. Moreover the location of the y‐axis will not vary with time and water stage. Once the relationship of mean and maximum velocities is established, the flood estimation can be determined efficiently. This method avoids exposure to hazardous environments and sharply reduces the measurement time and cost. The method can be applied in both high and low flows in rivers. Available laboratory flume and stream‐flow data are used to illustrate accuracy and reliability, and results show that this method can quickly and accurately estimate flood discharges. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Th/U/U and Pa/U ages from a single fossil coral fragment by multi-collector magnetic-sector inductively coupled plasma mass spectrometry     

Richard A. Mortlock  Richard G. Fairbanks  Tzu-chien Chiu 《Geochimica et cosmochimica acta》2005,69(3):649-657

The ²³⁰Th/²³⁴U/²³⁸U age dating of corals via alpha counting or mass spectrometry has significantly contributed to our understanding of sea level, radiocarbon calibration, rates of ocean and climate change, and timing of El Nino, among many applications. Age dating of corals by mass spectrometry is remarkably precise, but many samples exposed to freshwater yield inaccurate ages. The first indication of open-system ²³⁰Th/²³⁴U/²³⁸U ages is elevated ²³⁴U/²³⁸U_initial values, very common in samples older than 100,000 yr. For samples younger than 100,000 yr that have ²³⁴U/²³⁸U_initial values close to seawater, there is a need for age validation. Redundant ²³⁰Th/²³⁴U/²³⁸U and ²³¹Pa/²³⁵U ages in a single fossil coral fragment are possible by Multi-Collector Magnetic Sector Inductively Coupled Plasma Mass Spectrometry (MC-MS-ICPMS) and standard anion exchange column chemistry, modified to permit the separation of uranium, thorium, and protactinium isotopes from a single solution. A high-efficiency nebulizer employed for sample introduction permits the determination of both ²³⁰Th/²³⁴U/²³⁸U and ²³¹Pa/²³⁵U ages in fragments as small as 500 mg. We have obtained excellent agreement between ²³⁰Th/²³⁴U/²³⁸U and ²³¹Pa/²³⁵U ages in Barbados corals (30 ka) and suggest that the methods described in this paper can be used to test the ²³⁰Th/²³⁴U/²³⁸U age accuracy.Separate fractions of U, Th, and Pa are measured by employing a multi-dynamic procedure, whereby ²³⁸U is measured on a Faraday cup simultaneously with all minor isotopes measured with a Daly ion counting detector. The multi-dynamic procedure also permits correcting for both the Daly to Faraday gain and for mass discrimination during sample analyses. The analytical precision of ²³⁰Th/²³⁴U/²³⁸U and ²³¹Pa/²³⁵U dates is generally better than ±0.3% and ±1.5%, respectively (2 Relative Standard deviation [RSD]). Additional errors resulting from uncertainties in the decay constant for ²³¹Pa and from undetermined sources currently limit the ²³¹Pa/²³⁵U age uncertainty to about ±2.5%. U isotope data and ²³⁰Th/²³⁴U/²³⁸U ages agree with National Institute of Standards and Technology (NIST) reference materials and with measurements made by Thermal Ionization Mass Spectrometry (TIMS) in our laboratory.  相似文献   

Refinement of thrust faulting models for the Central New Madrid seismic zone     

Jose Pujol  Arch Johnston  Jer-Ming Chiu  Yung-Tun Yang 《Engineering Geology》1997,46(3-4):281-298

We present the results of the joint relocation of events recorded during 1989–1992 by the PANDA network in the central New Madrid seismic zone. The near-surface material in the study area is a gently-dipping layer of poorly consolidated sediments with low P-wave velocity and high V_p/V_s (estimated values: 1.8 km s⁻¹ and 3). The sediments are underlain by high-velocity Paleozoic rocks. Under the network the difference in sediment thickness is only 0.6 km, but because of the low velocities the location of the events using layered models is affected by errors. Application of the joint hypocentral determination (JHD) technique to a subset of 580 events shows that the single-event locations may be in error by as much as 1 km in depth, depending on where the events are located. Analysis of synthetic data generated for a realistic 3-D velocity model supports the JHD results. The analysis of synthetic data also suggests that a V_p/V_s≤ 2.3 is more appropriate for the post-Paleozoic Mississippi embayment sediments. Based on the JHD locations we present a new interpretation of the seismicity, with two en-echelon SW-dipping thrust faults connected by a west-dipping thrust fault. These faults appear associated with the Reelfoot scarp and its northern extension, the Kentucky bend scarp.  相似文献   

The liberalization of shipping in Taiwan     

Rong-Her Chiu 《Marine Policy》2007

Maritime transport has become well developed in Taiwan, which is located in the western Pacific Rim. Following the model of traditional maritime nations, Taiwan's government enacted some shipping-friendly measures to help the industry in its early expansion stage. Nevertheless, government authorities have taken actions to liberalize the operations of the maritime-transport sector over the past 10 years. This paper focuses on how the liberalization measures were proposed and implemented including the process and reasons behind the formulation of governmental policies, the interaction between domestic shipping operators and the government. In addition, this paper presents a comprehensive review of the liberalization policy's impact on domestic maritime transport operators.  相似文献   

An Experimental Study on Wave-Induced Dynandc Stresses in Seabed     

S. C. Chang L. K. Chien J  G. Lin Y. F. Chiu 《中国海洋工程》2006,20(1):27-44

A series of hydraulic model tests with horizontal movable seabed under regular wave actions have been carried out to investigate the dynamic interactions between water waves and seabed soil. Seabed dynamic stresses from experiments are, tound to differ from theoretical resuhs. The response of p0 in permeable seabed has a small decay and phase shift to the nonlinear wave actions, and the dynamic stresses, σs/p0, σh/p0 and u/p0, contain different phase shift characteristics. Such phenomena will strongly affect the dynamic stress path in seabed. If the phase shifts of σs. and σh are neglected, the stress path will become a straight line; otherwise, it will become an elliptical curve. In phase shift cases, the long axis of the p - q diagram will be shortened when the depth increases, and the short axis will become longer when the phase shift increases. For the p＇ - q＇ diagram, the larger the phase lag of u, the longer the short axis. Relative results offer useful information for the analysis of seabed stability.  相似文献   

Application of polarization analysis in correcting the orientation error of a downhole seismometer     

Hung-Chie Chiu  Huey-Chu Huang  Chun-Long Leu  Shean-Der Ni 《地震工程与结构动力学》1994,23(10):1069-1078

This paper shows that the polarization analysis of later arrivals could be used to estimate the orientation error and the tilt of the downhole accelerometers in the Dahan downhole strong-motion array. This four-level array is located to the north of Hualien city in eastern Taiwan. Polarization analysis of a windowed signal which includes significant phases (e.g. primary S wave) can give a stable major polarization axis. This axis can then be used as the reference direction for correcting the orientation error and the tilt of the downhole seismometers. If the surface instrument is chosen as the reference, the angle between the major polarization axes of the surface and any downhole recordings will be the orientation error needed to be corrected for the downhole accelerograph. This angle is a combination of the tilt and the orientation errors which correspond to the dip and strike of maximum polarization, respectively. At the Dahan downhole strong-motion array, the orientation errors of the seismometers at the depth of 50, 100 and 200 m were 1°, 90° and 84°. These orientation errors were consistent with the horizontal particle-motion analysis. The errors of horizontal plane (tilt) were almost zero. After correction, the coherency of the waveforms between the surface and the downhole recordings was significantly improved.  相似文献   

Interactive effects of hypoxia and polybrominated diphenyl ethers (PBDEs) on microbial community assembly in surface marine sediments     

Yuki Chan  Amy Li  Singaram Gopalakrishnan  Paul K.S. Shin  Rudolf S.S. Wu  Stephen B. Pointing  Jill M.Y. Chiu 《Marine pollution bulletin》2014

Hypoxia alters the oxidation–reduction balance and the biogeochemical processes in sediments, but little is known about its impacts on the microbial community that is responsible for such processes. In this study, we investigated the effects of hypoxia and the ubiquitously dispersed flame-retardant BDE47 on the bacterial communities in marine surface sediments during a 28-days microcosm experiment. Both hypoxia and BDE47 alone significantly altered the bacterial community and reduced the species and genetic diversity. UniFrac analysis revealed that BDE47 selected certain bacterial species and resulted in major community shifts, whereas hypoxia changed the relative abundances of taxa, suggesting slower but nonetheless significant community shifts. These two stressors targeted mostly different taxa, but they both favored Bacteroidetes and suppressed Gammaproteobacteria. Importantly, the impacts of BDE47 on bacterial communities were different under hypoxic and normoxic conditions, highlighting the need to consider risk assessments for BDE47 in a broader context of interaction with hypoxia.  相似文献