Detecting massive green algae (Ulva prolifera) blooms in the Yellow Sea and East China Sea using Geostationary Ocean Color Imager (GOCI) data   总被引：2，自引：0，他引：2  

Young Baek Son  Jee-Eun Min  Joo-Hyung Ryu 《Ocean Science Journal》2012,47(3):359-375

The historically massive bloom of the green macroalgae Ulva prolifera reported in June?CAugust 2008 around the Qingdao, Yellow Sea, East China Sea and Japan coasts has recurred in a similar season and region. On June 13, 2011, around Qingdao, China, the world??s first Geostationary Ocean Color Imager (GOCI) detected an enormous bloom of floating green algae, which originated from the nearshore Subei Bank, China. The large floating green algae patches were observed along and across the Yellow Sea and in the East China Sea during 2011 summer by various oceanic cruises. To detect the massive macroalgae blooms from space, we analyzed their spectral characteristics from in situ optical measurements and satellite-derived green algae spectra. An ??Index of floating Green Algae for GOCI?? (IGAG) was developed from the multiple spectral band ratios using three wavelengths (555, 660, 745 nm), which the spectral response of green algae reflected at 555, 745, and 865 nm and absorbed at 660 and 680 nm. The results were compared with those obtained by the normalized difference vegetation index (NDVI), enhanced vegetation index (EVI), and Korea Ocean Satellite Center (KOSC) approaches. An advantage of the IGAG method was that muted or subtle signals of floating green algae were enhanced and separated from surrounding complex water signals. Although maps of floating green algae derived by the other approaches delineated dense green algae, they were less sensitive to subtle (less dense) features and in cases of nearby cloudy or complex water conditions. The floating green algae maps from IGAG provided a more robust estimate of wide floating green algae blooms than those derived using NDVI, EVI, or KOSC approaches. The IGAG approach should be useful for tracing and monitoring changes in green algae blooms on regional and global scales.  相似文献   

Initial validation of GOCI water products against in situ data collected around Korean peninsula for 2010–2011     

Jeong-Eon Moon  Young-Je Park  Joo-Hyung Ryu  Jong-Kuk Choi  Jae-Hyun Ahn  Jee-Eun Min  Young-Baek Son  Sun-Ju Lee  Hee-Jeong Han  Yu-Hwan Ahn 《Ocean Science Journal》2012,47(3):261-277

This paper provides initial validation results for GOCI-derived water products using match-ups between the satellite and ship-borne in situ data for the period of 2010?C2011, with a focus on remote-sensing reflectance (R _rs ). Match-up data were constructed through systematic quality control of both in situ and GOCI data, and a manual inspection of associated GOCI images to identify pixels contaminated by cloud, land and inter-slot radiometric discrepancy. Efforts were made to process and quality check the in situ R _rs data. This selection process yielded 32 optimal match-ups for the R _rs spectra, chlorophyll a concentration (Chl_a) and colored dissolved organic matter (CDOM), and with 20 match-ups for suspended particulate matter concentration (SPM). Most of the match-ups are located close to shore and thus the validation should be interpreted limiting to near-shore coastal waters. The R _rs match-ups showed the mean relative errors of 18?C33% for the visible bands with the lowest 18?C19% for the 490 nm and 555 nm bands and 33% for the 412 nm band. Correlation for the R _rs match-ups was high in the 490?C865 nm bands (R²=0.72?C0.84) and lower in the 412 nm band (R²=0.43) and 443 nm band (R²=0.66). The match-ups for Chl_a showed a low correlation (<0.41) although the mean absolute percentage error was 35% for the GOCI standard Chl_a. The CDOM match-ups showed an even worse comparison with R²<0.2. These match-up comparison for Chl_a and CDOM would imply the difficulty to estimate Chl_a and CDOM in near-shore waters where the variability in SPM would dominate the variability in R _rs . Clearly, the match-up statistics for SPM was better with R²=0.73 and 0.87 for two evaluated algorithms, although GOCI-derived SPM overestimated low concentration and underestimated high concentration. Based on this initial match-up analysis, we made several recommendations -1) to collect more offshore under-water measurements of the R _rs data, 2) to include quality flags in level-2 products, 3) to introduce an ISRD correction in the GOCI processing chain, 4) to investigate other types of in-water algorithms such as semianalytical ones, and 5) to investigate vicarious calibration for GOCI data and to maintain accurate and consistent calibration of field radiometric instruments.  相似文献   

Permeability dependence of streaming potential coefficient in porous media          下载免费PDF全文

Luong Duy Thanh  Rudolf Sprik 《Geophysical Prospecting》2016,64(3):714-725

In theory, the streaming potential coefficient depends not only on the zeta potential but also on the permeability of the rocks that partially determines the surface conductivity of the rocks. However, in practice, it is hard to show the permeability dependence of streaming potential coefficients because of the variation of zeta potential from sample to sample. To study permeability dependence of streaming potential, including the effects of the variation of the zeta potential and surface conductance due to the difference in mineral compositions between samples, we perform measurements on 12 consolidated samples, including natural and artificial samples saturated with 7 different NaCl solutions to determine the streaming potential coefficients. The results have shown that the streaming potential coefficients strongly depend on the permeability of the samples for low fluid conductivity. When the fluid conductivity is larger than than 0.50 S/m for the natural samples or 0.25 S/m for the artificial ceramic samples, the streaming potential coefficient is independent of permeability. This behavior is quantitatively explained by a theoretical model.  相似文献   

Phylogenetic,histological and age determination for investigation of non-native tropical black-lip pearl oyster, <Emphasis Type="Italic">Pinctada margaritifera</Emphasis>, settled in jeju,Korea     

Chulhong Oh  Jin-Kyoung Kim  Young-Baek Son  Se-Jong Ju  Hee-Do Jeung  Hyun-Sung Yang  Kwang-Sik Choi  Gilles Le Moullac  Do-Hyung Kang 《Ocean Science Journal》2017,52(4):593-601

This study reports the first finding of tropical blacklip pearl (BLP) oyster, Pinctada margaritifera, in Korean waters. One BLP oyster was found and sampled from Beom-seom islet (33°13′N, 126°33′E) in the southern coast of Jeju Island, Korea in February, 2011. The taxonomic status of the specimen was confirmed by nucleotide sequences of the mitochondrial gene cytochrome oxidase I and 28S ribosomal DNA. Oxygen isotopic analysis (δ¹⁸O_sh) and histology were used to determine the specimen’s age and reproductive stage, which were 3.5 years and ripe male, respectively. This BLP oyster most likely originated in an area in the subtropics or tropics, such as the Okinawa archipelagic or Micronesian regions. We suggest that intensive monitoring surveys are necessary for confirming the northward expansion of BLP oyster in Korean waters in the near future.  相似文献   

Influence of the spatial variability of shear strength parameters on rainfall induced landslides: a case study of sandstone slope in Japan     

Thanh Son Nguyen  Suched Likitlersuang  Hiroyasu Ohtsu  Takafumi Kitaoka 《Arabian Journal of Geosciences》2017,10(16):369

Rainfall-induced landslides frequently occur in humid temperate regions worldwide. Research activity in understanding the mechanism of rainfall-induced landslides has recently focused on the probability of slope failure involving non-homogeneous soil profiles. This paper presents probabilistic analyses to assess the stability of unsaturated soil slope under rainfall. The influence of the spatial variability of shear strength parameters on the probability of rainfall-induced slope failure is conducted by means of a series of seepage and stability analyses of an infinite slope based on random fields. A case study of shallow failure located on sandstone slopes in Japan is used to verify the analysis framework. The results confirm that a probabilistic analysis can be efficiently used to qualify various locations of failure surface caused by spatial variability of soil shear strength for a shallow infinite slope failure due to rainfall.  相似文献   

A dual-porosity model for the study of chemical effects on the swelling behaviour of MX-80 bentonite     

Li  Zhenze  Su  Grant  Zheng  Quinn  Nguyen  Thanh Son 《Acta Geotechnica》2020,15(3):635-653

Significant chemical influence on the swelling potential of MX-80 bentonite was observed during swelling tests where specimens were hydrated with highly concentrated brine. The maximum swelling pressure for specimens hydrated with brine was about 30% of the maximum swelling pressure for the same specimens hydrated with de-ionized water. The maximum swelling pressure was attained within tens of hours of brine infiltration and further decreased by half within a year. A fully coupled hydro–mechanical–chemical (HMC) dual-porosity model is proposed in this paper to interpret the swelling behaviour of MX-80 when infiltrated with brine. The dependence of hydraulic and mechanical properties on such factors as porosity, salinity and water content was investigated. A nonlinear elastic constitutive model was proposed to correlate the swelling pressure with the variation in the microporosity. The chemical effects on the mechanical behaviour were coupled at the micropore level. A number of relationships have been developed for MX-80, i.e. micropore permeability as a function of void ratio, water retention characteristics of micropores and macropores, micropore dependence on water content and the diffusion coefficients of the two types of pore structure. The proposed model was successful in reproducing both quantitatively and qualitatively the experimental results from two sets of infiltration experiments on compacted MX-80 bentonite.

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A fractal model for streaming potential coefficient in porous media          下载免费PDF全文

Luong Duy Thanh  Phan Van Do  Nguyen Van Nghia  Nguyen Xuan Ca 《Geophysical Prospecting》2018,66(4):753-766

Streaming potential is the result of coupling between a fluid flow and an electric current in porous rocks. The modified Helmholtz–Smoluchowski equation derived for capillary tubes is mostly used to determine the streaming potential coefficient of porous media. However, to the best of our knowledge, the fractal geometry theory is not yet applied to analyse the streaming potential in porous media. In this article, a fractal model for the streaming potential coefficient in porous media is developed based on the fractal theory of porous media and on the streaming potential in a capillary. The proposed model is expressed in terms of the zeta potential at the solid?liquid interface, the minimum and maximum pore/capillary radii, the fractal dimension, and the porosity of porous media. The model is also examined by using another capillary size distribution available in published articles. The results obtained from the model using two different capillary size distributions are in good agreement with each other. The model predictions are then compared with experimental data in the literature and those based on the modified Helmholtz–Smoluchowski equation. It is shown that the predictions from the proposed fractal model are in good agreement with experimental data. In addition, the proposed model is able to reproduce the same result as the Helmholtz–Smoluchowski equation, particularly for high fluid conductivity or large grain diameters. Other factors influencing the streaming potential coefficient in porous media are also analysed.  相似文献   

A damage model for structures with degrading response          下载免费PDF全文

Thanh. N. Do  Filip. C. Filippou 《地震工程与结构动力学》2018,47(2):311-332

The paper presents a hysteretic damage model for the response simulation of structural components with strength and stiffness deterioration under cyclic loading. The model is based on 1D continuum damage mechanics and relates any 2 work‐conjugate response variables such as force‐displacement, moment‐rotation, or stress‐strain. The strength and stiffness deterioration is described by a continuous damage variable. The formulation uses a criterion based on the hysteretic energy and the maximum or minimum deformation for damage initiation with a cumulative probability distribution function for the damage evolution. A series of structural component response simulations showcase the ability of the model to describe different types of hysteretic behavior. The relation of the model's damage variable to the Park‐Ang damage index is also discussed. Because of its consistent and numerically robust formulation, the model is suitable for the large‐scale seismic response simulation of structural systems with strength and stiffness deterioration.  相似文献   

Sedimentary Basin Analysis and Petroleum Potential of the Cretaceous Yuchon Group In Haenam Depression, SW Korea     

Son Jin-Dam 《世界地质(英文版)》2000,3(2)

The Yuchon Group in the Late Cretaceous of Haenam and Mokpo area on the southwest coast of Korea peninsula can be divided into two Formations: (1) the intermediate volcanic Formation (Hwawon Formation), about 500m thick, (2)the acidic volcanic Formation (Hwangsan Formation), about 400m thick in ascending order.The former comprises intermediate volcaniclastics interlayered with volcanic rocks, and red mudrock and tuffaceous sandstone indicating fluvial deposits. The latter is subdivided into the upper part (Hwangsan Tuff Member) consisting of subaerial pyroclastics and intercalated rhyolites, and the lower part (Byeongonri Member) including subaqueous volcaniclastics, lake deltaic sandstone and gravelstone, lacustrine black shale and limestone and chert, and lake turbidite sandstone.The Late Cretaceous basin including Haenam subbasin in southwest Korea was largely formed of extensional nonmarine depressions (volcano- tectonic) bounded by NE- SW sinistral fault system.The thermal maturation based on geochemical and mineralogical studies for the black shales and tuffaceous sandstones reached the late stage of oil generation zone or gas generation stage. It seems that black shales and limestones are fairly good as source rock. The porosity of potential reservoir sandstone and tuff ranges from 5 % to 11%, but their permeability except the fractured rocks is very low ( ＜1md) because of fine pore throats reduced by diagenetic cementation of tuffaceous sandstones. Numerous potential traps might have been formed by the later folding and faulting along with lateral facies change and abundant mudrocks and volcaniclastics should make excellent seals.  相似文献   

Distribution and Variability of the Meiobenthic Assemblages near the Korean Polymetallic Nodule Claim Area of the Clarion-Clipperton Fracture Zone (Subequatorial NE Pacific)     

Won-Gi Min  Dongsung Kim  Hyun Soo Rho  Sang Bum Chi  Seung-Kyu Son 《Ocean Science Journal》2018,53(2):315-336

This study was carried out as part of a baseline long-term environmental project in the proposed mining areas for an environmental impact assessment of future mining in the Clarion-Clipperton Fracture Zone (CCFZ). The community structure and distributional pattern of meiobenthos were investigated in the deep-sea bottom of the Clarion-Clipperton Fracture Zone of the northeastern Pacific in July 1998, 1999, 2001, 2003 and August 2004, 2005. Twenty one meiobenthic groups were found at the stations in the study area. The most abundant meiobenthos comprised nematodes followed by benthic foraminiferans and harpacticoid copepods. The maximum density of meiobenthos was 306 ind/10 cm² at the station located at 11°N (water depth, 4833 m), and the minimum density was 6 ind/10 cm² at the station located at 14°N (water depth, 5037 m). Oligotrophic conditions in the CCFZ seem to directly reflect the lower standing stocks of meiobenthos in the CCFZ compared to other deep-sea plains of similar depth. The latitudinal distribution pattern of meiobenthos in the study area seemed to be related with surface water primary productivity, which was connected to the water circulation pattern of the Pacific Ocean near the Equator, diverging at 8ºN latitude and converging at 5°N. The horizontal distribution of meiobenthic organisms in the study area showed high densities at the stations within 135–136°W. The densities of meiobenthic organismas within the CCFZ were high at stations with few manganese nodules on the sediment surface at low-latitude sites. In 1998, the observed relative high values of meiobenthic abundance were at stations from 5° to 6°N. Other stations from 7° to 10°N showed no significant fluctuations during the interannual sampling periods. It is considered that the inter-annual fluctuation of meiobenthos abundance is intimately related with a regime shift that may have occurred in the north Pacific between 1998 and 1999, the El Niño period. Vertical distribution of meiobenthic organisms showed the highest individual numbers in the surface sediment layers of 0～2 cm depth and a steep decreasing trend as sediment becomes deeper at the stations of high latitude located in 16～17°N. Size distribution analyses showed that organisms that fit into the sieve mesh size of 0.063 mm were abundant.  相似文献