Finite element method for strong reflection of water waves     

Yong-Sik Cho  Woo-Chang Jeong  Seung-Buhm Woo   《Ocean Engineering》2004,31(5-6):653-667

In this study, the propagation of monochromatic water waves over an arbitrarily varying topography is numerically investigated. A finite element model is developed by formulating the diffraction of waves caused by depth changes. Not only the propagating mode but also the evanescent modes are included in the model. The model developed is applied to the study of strong reflection of monochromatic waves over a sinusoidally varying topography. Predicted reflection coefficients are compared with those of available laboratory experiments and the eigenfunction expansion method. A very good agreement is observed.  相似文献   

The primary sector in economic development: Lundahl, M. (ed.) London and Sydney: Croom Helm, 1985. 408 pp. £25.00 hardback.     

George Cho 《Applied geography (Sevenoaks, England)》1986,6(4)

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Rubber movements in a marketing network: smallholders in Peninsular Malaysia     

George Cho 《Applied geography (Sevenoaks, England)》1982,2(3):189-206

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Effects of oil spill on seawater infiltration and macrobenthic community in tidal flats   总被引：1，自引：0，他引：1  

Chung IY  Cho KJ  Hiraoka K  Mukai T  Nishijima W  Takimoto K  Okada M 《Marine pollution bulletin》2004,49(11-12):959-963

Tidal flat ecosystem simulators are used to clarify the effects of stranded fuel oil on tidal flat ecosystems. Results show that oil spills increase the periphyton on sediment by decreasing the predation stress caused by deposit feeders. About a month after an oil spill, the total population density of the macrobenthos recovered. The oxidation-reduction potential in the surface sediment drops to a negative value after the oil spill, and the anaerobic condition throughout the sediment seems to be responsible for the decrease in the population density of the macrobenthos. The infiltration volume of seawater into the oil-stranded sediment decreases to a third of that without the oil spill. The recovery of infiltration volume after about a month coincides with the recovery of the population density of the macrobenthos. This result suggests that the macrobenthic population is highly dependent on the infiltration of seawater.  相似文献   

Origin and transport of sedimentary organic matter in the Yalujiang estuary,North China     

Ying?WuEmail author  Jing?Zhang  Ki?Woong?Cho  Gi?Hoon?Hong  Chang?Soo?Chung 《Estuaries and Coasts》2004,27(4):583-592

The biogeochemistry of organic matter (OM) in a macrotidal estuary, the Yalujiang River, was studied during two cruises: the flood season in August 1994 and the dry season in April 1996. Surface sediments were collected in the riverine zone (RZ), the turbidity maximum zone (TMZ), and the marine zone (MZ). The molecular distribution of the n-alkanes and fatty acid series and bulk sediment characteristics, such as C:N and δ¹³C, were used to assess differences in OM source and transport from the river upstream to the marine end member. Higher C:N values typical for terrestrial sources were observed at the upper reach for both seasons. The δ¹³C of OM in surface sediments varied from −27.3‰ to −21.6‰ in the flood season and from −26.8‰ to −31‰ in the dry season. The concentrations of n-alkanes varied between 0.3–21.4 μg g⁻¹ and the variation of fatty acids was 4.8–32.9 μg g⁻¹. The data showed mixing of terrestrial and autochthonous OM in the middle and lower reaches. The distribution of lipids (n-alkanes and Carbon Preference Index) encountered in this study confirmed the importance of terrestrial OM in the sediment samples from degraded soil material. The distribution of fatty acids suggested important phytoplankton, zooplankton, and microbial signals (short-chain and unsaturated acids; ≤C₂₀). Branched fatty acids, such as the iso- and anteiso-C₁₅ and C₁₇ compounds, relfect bacterial contributions. All samples were characterized by a high proportion of mixture inputs in both seasons. A slight decreasing trend was observed with increasing salinity except for the highest percentage of mixed fatty acids in the TMZ of the flood season. Terrestrial fatty acids were approximately 20% in the flood season and 27–46% in the dry season. Differences in hydrological conditions and primary production between the TMZ, RZ, and MZ resulted in different OM distributions, which are reflected in the sources and degree of diagenesis of the sedimentary OM. Seasonal variation may be strongly influenced by hydrological characteristics rather than primary productivity and anthropogenic activities in the Yalujiang region.  相似文献   

Estimation of green grass/herb biomass from airborne hyperspectral imagery using spectral indices and partial least squares regression   总被引：7，自引：0，他引：7  

Moses Azong Cho  Andrew Skidmore  Fabio Corsi  Sipke E. van Wieren  Istiak Sobhan   《International Journal of Applied Earth Observation and Geoinformation》2007,9(4):414-424

The main objective was to determine whether partial least squares (PLS) regression improves grass/herb biomass estimation when compared with hyperspectral indices, that is normalised difference vegetation index (NDVI) and red-edge position (REP). To achieve this objective, fresh green grass/herb biomass and airborne images (HyMap) were collected in the Majella National Park, Italy in the summer of 2005. The predictive performances of hyperspectral indices and PLS regression models were then determined and compared using calibration (n = 30) and test (n = 12) data sets. The regression model derived from NDVI computed from bands at 740 and 771 nm produced a lower standard error of prediction (SEP = 264 g m⁻²) on the test data compared with the standard NDVI involving bands at 665 and 801 nm (SEP = 331 g m⁻²), but comparable results with REPs determined by various methods (SEP = 261 to 295 g m⁻²). PLS regression models based on original, derivative and continuum-removed spectra produced lower prediction errors (SEP = 149 to 256 g m⁻²) compared with NDVI and REP models. The lowest prediction error (SEP = 149 g m⁻², 19% of mean) was obtained with PLS regression involving continuum-removed bands. In conclusion, PLS regression based on airborne hyperspectral imagery provides a better alternative to univariate regression involving hyperspectral indices for grass/herb biomass estimation in the Majella National Park.  相似文献   

A pseudo‐force iterative method with separate scale factors for dynamic analysis of structures with non‐proportional damping     

Feng‐Bao Lin  Yung‐Kuo Wang  Young S. Cho 《地震工程与结构动力学》2003,32(2):329-337

Dynamic equilibrium equations of structural systems with non‐proportional damping are coupled through the damping terms. Such coupling invalidates application of the classical modal superposition method. In this paper, a mode‐superposition pseudo‐force method is proposed. The coupled equilibrium equations are solved by an iterative process in which the coupling terms are treated as pseudo‐forces. A scale factor for each mode of the system is obtained by optimizing the iteration convergence. Through these uniquely solved scale factors, the modified modal equations not only converge much faster but also yield results with higher accuracy. A proof of the convergence of the iterative process is also presented. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Toward the optimization of PC-based training     

Kohei Cho  Shunji Murai 《ISPRS Journal of Photogrammetry and Remote Sensing》1997,52(6):247-252

Since 1992, the National Space Development Agency of Japan (NASDA) and the Economic and Social Commission for Asia and the Pacific (ESCAP) have been co-organising the Regional Remote Sensing Seminar on Tropical Ecosystem Management (Program Chairman: Prof. Shunji Murai) every year in some country in Asia. In these seminars, the members of the ISPRS Working Group VI/2 ‘Computer Assisted Teaching’ have been performing a PC-based hands-on-training on remote sensing and GIS for beginners. The main objective of the training was to transfer not only knowledge but also the technology of remote sensing and GIS to the beginners. The software and CD-ROM data set provided at the training were well designed not only for training but also for practical data analysis. This paper presents an outline of the training and discusses the optimisation of PC-based training for remote sensing and GIS.  相似文献   

Artificial neural networks for predicting DGPS carrier phase and pseudorange correction   总被引：2，自引：2，他引：0  

Arif Indriyatmoko  Taesam Kang  Young Jae Lee  Gyu-In Jee  Yong Beom Cho  Jeongrae Kim 《GPS Solutions》2008,12(4):237-247

Artificial neural networks (ANNs) were used to predict the differential global positioning system (DGPS) pseudorange and carrier phase correction information. Autoregressive moving average (ARMA) and autoregressive (AR) models were bounded with neural networks to provide predictions of the correction. The neural network was employed to realize time-varying implementation. Online training for real-time prediction of the carrier phase enhances the continuity of service of the differential correction signals and, therefore, improves the positioning accuracy. When the correction signal from the DGPS was lost, the artificial neural networks predicted the correction data with good accuracy for the navigation system during a limited period. Comparisons of the prediction results using the two models are given.

Young Jae LeeEmail:

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A hydraulic model of the Korea Strait bottom cold current     

Young-Gyu Park  Yang-Ki Cho  Kuh Kim 《Journal of Oceanography》1995,51(6):713-727

A one and a half layer inviscid hydraulic model was introduced to study the dynamics of the flow that brings the bottom cold water southward into the Korea Strait. Two different channel geometries were considered; a rectangular channel and a channel with a sloping western wall, which represents the continental slope near the Korean coast. The lower layer water in the rectangular channel separates from the eastern wall when the depth of the channel,H _o, becomes shallower than a critical value donwstream. Hydraulic control of the flow is possible after the flow separation, if the channel becomes shallow enough. Before hydraulic control, the width of the flow decreases asH _o decreases, but the effect of the slope of the western wall is negligible. After the control, however, the width increases asH _o decreases or the slope becomes weaker. If the slope becomes weak enough or the channel becomes deep enough, which is determined by upstream conditions, the lower layer is observed only over the sloping western wall. This simple model shows that the continental slope between the East Sea (Japan Sea) and the Korea Strait makes the southward flowing North Korean Cold Water bank against the Korean coast in the Korea Strait. The model also shows that the sloping bottom near the Korean coast makes the bottom cold water of the Korea Strait appear only over the continental slope away from the trough of the strait.  相似文献