• Ocean and Polar Research
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• v.37 no.3
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• pp.189-200
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• 2015

Mesozooplankton biomass including total biomass and size-fractionated biomass and the abundance of major taxonomic groups of copepods were studied in the Northwestern Subtropical Pacific Warm Pool (NSPWP) and the Northern East China Sea (NECS) from 2006 to 2014. Mesozooplankton biomass ranged from 0.69 to $3.08mgC/m^3$ (mean $1.12mgC/m^3$) in the NSPWP and from 10.60 to $69.10mgC/m^3$ (mean $30.33mgC/m^3$) in the NECS with higher values in spring than fall. Percent composition in the biomass of each size group of mesozooplankton varied interannually both in the NSPWP and in the NECS. The smallest size group (0.2~0.5 mm) contributed the least to total biomass in both regions, but significantly higher in the NSPWP than in the NECS. The percent composition in abundance of copepod taxonomic groups (i.e. Calanoida, Cyclopoida, and Poecilostomatoida) also fluctuated interannually. Mean composition of calanoid copepods was higher in the NECS than in the NSPWP, but the opposite pattern was observed for poecilostomatoid copepods. Mesozooplankton biomass both in the NSPWP and in the NECS was negatively correlated with Oceanic $Ni{\tilde{n}}o$ Index (ONI), indicating declines in biomass during El $Ni{\tilde{n}}o$ periods and vice versa during Na $Ni{\tilde{n}}a$ period. The effect of El $Ni{\tilde{n}}o$ on variation of mesozooplankton biomass was more prominent in the NSPWP than in the NECS. These results suggest that mesozooplankton biomass both in the NSPWP and in the NECS responded to El $Ni{\tilde{n}}o$ events, although the biological process that explain the reduced mesozooplankton biomass might be different in both regions.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.48 no.3
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• pp.90-98
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• 2011

The recognition and classification of paddy rice disease are of major importance to the technical and economical aspect of agricultural industry over the world. Computer vision techniques are used to diagnose rice diseases and to efficiently manage crops. Segmentation of lesions is the most important technique to detect paddy rice disease early and accurately. A new Gaussian Mean (GM) method was proposed to segment paddy rice diseases in various color spaces. Different color spaces produced different results in segmenting paddy diseases. Thus, this empirical study was conducted with the motivation to determine which color space is best for segmentation of rice disease. It included five color spaces; NTSC, CIE, YCbCr, HSV and the normalized RGB(NRGB). The results showed that YCbCr was the best color space for optimal segmentation of the disease lesions with 98.0% of accuracy. Furthermore, the proposed method demonstrated that diseases lesions of paddy rice can be segmented automatically and robustly.

• Atmosphere
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• v.16 no.4
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• pp.333-342
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• 2006

The long-term trends of global solar irradiance, air temperature, specific humidity and cloudiness measured at King Sejong station, Antarctica, during the period of 1988-2004, have been investigated. A statistically insignificant decrease, -0.21 $Wm^{-2}yr^{-1}$ (-0.26 %$yr^{-1}$, P<0.5) in global solar irradiance was found in an analysis from the time series of the monthly mean values, except for the increasing trends only in two months of January and June. The trends in irradiance are directly and inversely associated with the cloudiness trends in annual and monthly means. The trends in surface air temperature show a slight warming, $0.03^{\circ}Cyr^{-1}$ (1.88 %$yr^{-1}$, P<0.5) on the annual average, with cooling trend in the summer months and the warming in the winter. The exact relationship, if any, between the irradiance and temperature trends is not known. No significant tendency was found in specific humidity for the same periods. Recent (1996-2004) erythermal ultraviolet irradiance shows decreasing trend in annual mean, -0.15 $mWm^{-2}yr^{-1}$ (-1.18 %$yr^{-1}$, P<0.1) which is about five times the trends of global solar irradiance. The ratio of erythermal ultraviolet to global solar irradiance shows remarkable seasonal variations with annual mean value of 0.01 % and a peak in October and November, showing the increase of ultraviolet irradiance resulting from the Antarctic ozone hole. The sensitivity of global solar irradiance to the change in cloudiness is roughly $13%oktas^{-1}$ which is about twice of the value at the South Pole due to the difference in the average surface reflectance between the two stations. Much more sensitive values of $59%oktas^{-1}$ was found for erythermal UV irradiance than for the global solar irradiance.

• Ocean and Polar Research
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• v.27 no.1
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• pp.1-13
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• 2005

The samples for organic carbon analysis were collected between $5^{\circ}\;and\;17^{\circ}N$ along $131.5^{\circ}W$ in the northeast Pacific KODOS (Korea Deep Ocean Study) area. The mean concentration of total organic carbon (TOC) in the surface mixed layer $({\sim}50 m)$ was $100.13{\pm}2.05{\mu}M-C$, while the mean concentration of TOC in the lower 500m of the water column was $50.19{\pm}4.23{\mu}M-C$. A strong linear regression between TOC and temperature $(r^2=0.70)$ showed that TOC distribution was controlled by physical process. Results from the linear regression between chlorophyll-a and TOC, and between chlorophyll-a and particulate organic carbon (POC), decreasing of dissolved organic carbon (DOC) in the surface layer caused by non-biological photo-oxidation process. Below the surface layer, biological production and consumption occurred. DOC accumulation dominated in the depth range of $30{\sim}50m$ and DOC consumption occurred in the depth range of $50{\sim}200m$. TOC was inversely correlated with apparent oxygen utilization (AOU) and TOC/AOU molar ratios ranged from -0.077 to -0.21. These ratios indicated that TOC oxidation was responsible fur $10.9{\sim}30.1%$ (mean 20.2%) of oxygen consumption in the NE Pacific KODOS area. In the euphotic zone, distributions of dissolved and particulate organic matter were controlled by photo-chemical, chemical, biological and physical processes.

• Ocean and Polar Research
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• v.36 no.2
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• pp.165-177
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• 2014

In an effort to investigate the structure and variability of the coastal current in the East Sea, a moored ADCP observation was conducted off Uljin from late May to mid-October 2006. Owing to the transition of season from summer to autumn, the features of the current and wind can be divided into two parts. Until mid-August (Part-I), a southward flow is dominant at all depths with a mean alongshore velocity of 4.2~8.9 cm/s but northward winds are not strong enough to reverse the near-surface current. During Part-II, a strong northward current occurs frequently in the upper layer but winds are predominantly southward including two typhoons that have deep-reaching influence. Profile of mean velocity has three layers with a northward velocity embedded at 12~28 m depth. The near-surface current of Part-II significantly coheres with winds at 4-8 day periods with a phase lag of about 12 hours. The modal structure of the current obtained by EOF analysis is: (1) Mode-1, having 83.6% of total variance, represents the current in the same direction at all depths corresponding to the southward North Korean Cold Current (NKCC). (2) Mode-2 (11.7%) reveals a two-layer structure that can be explained by the northward East Korean Warm Current (EKWC) in the upper layer and NKCC in the lower. (3) Mode-3 (2.6%) has three layers, in which the EKWC is reversed near the surface by opposing winds. This mode is particularly similar to the mean velocity profile of Part-II.

• Ocean and Polar Research
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• v.27 no.2
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• pp.135-148
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• 2005

Macrobeilthic fauna were collected using a van Veen grab $(0.1m^2)$ to investigate the spatial characteristics of the macrobenthos community at 28 stations near the Nakdong River estuary, Southeast Korea, in September 2001. A total of 203 species were sampled with a mean density of $1,554 ind./m^2$ and a biomass of $252.3 gWWt/m^2$. Annelids were the dominant faunal group in terms of species and density, with 68 species and a mean density of $1,031ind./m^2$, which comprised 33.5% and 66.3% of the total benthic animals, respectively. Based on density, three Polychaetes were dominant Tharyx sp· $(420ind./m^2)$, Lumbrineris longifolia $(143ind./m^2)$, and Sternaspis scutata $(118ind./m^2)$, along with a bivalve Theora fragilis $(129 ind./m^2)$. On cluster analysis, the benthic community was classified into four groups based on the species composition: Group-1 occurred in disturbed areas, Group-II in coastal regions, Group-III in central mariculture grounds, and Group-IV offshore. Environmental factors (mean gain size, organic carbon, and depth) were primarily correlated with the macrobenthos community structure. A benthic pollution assessment based on the macrobenthos community structure showed that Group-I and Group-II were located in a coastal area that had been severely disturbed by construction of Busan new port and various pollutants, Group-III was gradually polluted, while offshore Group-IV was the most stable.

• Ocean and Polar Research
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• v.30 no.2
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• pp.129-140
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• 2008

As a preliminary effort to establish a data assimilative ocean forecasting system, we reviewed the theory of the Ensemble Kamlan Filter (EnKF) and developed practical techniques to apply the EnKF algorithm in a real ocean circulation modeling system. To verify the performance of the developed EnKF algorithm, a wind-driven double gyre was established in a rectangular ocean using the Regional Ocean Modeling System (ROMS) and the EnKF algorithm was implemented. In the ideal ocean, sea surface temperature and sea surface height were assimilated. The results showed that the multivariate background error covariance is useful in the EnKF system. We also tested the sensitivity of the EnKF algorithm to the localization and inflation of the background error covariance and the number of ensemble members. In the sensitivity tests, the ensemble spread as well as the root-mean square (RMS) error of the ensemble mean was assessed. The EnKF produces the optimal solution as the ensemble spread approaches the RMS error of the ensemble mean because the ensembles are well distributed so that they may include the true state. The localization and inflation of the background error covariance increased the ensemble spread while building up well-distributed ensembles. Without the localization of the background error covariance, the ensemble spread tended to decrease continuously over time. In addition, the ensemble spread is proportional to the number of ensemble members. However, it is difficult to increase the ensemble members because of the computational cost.

• Ocean and Polar Research
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• v.41 no.2
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• pp.47-61
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• 2019

The Dokdo coast is known for its high biodiversity. However, few studies have examined the biodiversity and macrobenthic community on the subtidal soft-bottom. Therefore, we collected macrobenthos (> 1 mm) using a Smith-McIntyre grab ($0.1m^2$) at 15 stations along the Dokdo coast in September 2016. The sediments consisted of badly sorted (1.7) coarse sand with gravel and the mean sediment grain size was $-0.4{\phi}$. In total, 177 macrobenthic species were collected; their mean density was $1,566ind./m^2$. The number of species and density of macrobenthic fauna decreased significantly with the mean grain size. The dominant species were the amphipods Melita denticulata (16.5%) and Melita shimizui (5.5%), polychaete Salvatoria clavata (5.4%), bivalve Glycymeris aspersa (4.4%), and ophiuroid Ophionereis dubia (4.3%). The dominant macrobenthos species on the subtidal soft-bottom differed from the coastal areas of the East Sea, suggesting that the difference in the sediment grain size affected the macrobenthos. Cluster analysis was performed to divide the study area into four groups, and environmental factors which correlated with species composition and distribution in the study area were the combination of the four parameters of salinity, dissolved oxygen, total organic carbon and depth. A future seasonal investigation is needed to understand the species composition and characteristics of the Dokdo macrobenthos.

• The Korean Journal of Nuclear Medicine
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• v.25 no.2
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• pp.165-176
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• 1991

The purpose of this study was to assess the ability of quantitative Tl-201 tomography to identify and localize coronary artery disease (CAD). The study population consisted of 41 patients (31 males, 10 females; mean age $55{\pm}7$ yr) including 14 with prior myocardial infarction who underwent both exercise Tl-201 myocardium SPECT and coronary angiography for the evaluation of chest pain. From the short axis and vertical long axis tomograms, stress extent polar maps were generated by Cedars-Sinai Medical Center program, and the % stress defect extent (SDE) was quantified for each coronary artery territory. For the purpose of this study, the coronary circulation was divided into 6 arterial segments, and the "myocardial ischemic score" (MIS) was calculated from the coronary angiogram. Sensitivity for the detection of CAD ($\geq50%$ coronary stenosis by angiography) by angiography) by stress extent polar map was 95% in single vessel disease, and 100% in double and triple vessel deseases. Overall sensitivity was 97%. Sensitivity and specificity for the detection of individual diseased vessels were, respectively, 87% and 90% for the left anterior descending artery (LAD), 36% and 93% for the left circumflex artery (LCX), and 71% and 70% for the right coronary artery (RCA). Concordance for the detection of individual diseased vessels between the coronary angiography and stress polar map was fair for the LAD (kappa=0.70), and RCA (kappa=0.41) lesions, whereas it was poor for the LCX lesions (kappa : 0.32). There were siginificant correlations between the MIS and SDE in LAD (rs=0.56, p=0.0027), and RCA territory (rs=0.60, p=0.0094). No significant correlation was found in LCX territory. When total vascular territories were combined, there was a significant correlation between the MIS and SDE (rs=0.42, p=0.0116). In conclusion, the quantitative analysis of Tl-201 tomograms appears to be accurate for determining the presence and location of CAD.

• Journal of Chest Surgery
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• v.30 no.11
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• pp.1083-1091
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• 1997

This study was purposed to assess the result of coronary artery bypass graft surgery by analyzing and comparing the pre and postoperative myocardial perfusion state quantitatively by using myocardial SPECT. Twenty patients who received coronary artery bypass graft surgery since 1993 underwent both preoperative and postoperative myocardial SPECT and the result were analyzed. The mean age was 56.4$\pm$9.0 years, and the patients were composed of thirteen males and seven females. For quantitative analysis, we used polar maps of SPECT generated by Cedars-Sin i Medical Center program and we calculated perfusion scores, ischemic myocardial area ratios and reperfusion scores from polar maps. Preoperative mean stressfrest perfusion score was 7.3$\pm$ 1.117.7$\pm$ 1.0 and postoperative score was 8.1 $\pm$ 1 118.3$\pm$ 1.1. Preoperative mean stress ischemic myocardial area ratio was 0.32$\pm$0.2 and postoperative ratio was 0.15 $\pm$0.1. Postoperative mean perfusion score was significantly increased but, on the other hand, mean ischemic myocardial area ratio was significantly decreased as compared with preoperative values(p<0.01). Preoperative mean perfusion score of patients with postoperative roper(usion score more than 1.5 was significantly higher(p<0.01) than that of patients with postoperative reperfusion score less than 1.5. Preoperative perfusion scores of coronary artery territories that had fixed perfusion defect at myocardial SPECT were significantly low(4.3 $\pm$0.514.6$\pm$0.6, stresslrest), nevertheless it proved quantitatively that there was improvement in myocardial perfusion after surgery by showing improved perfusion scores postoperatively. In conclusion, myocardial SPECT is useful method for quantitative analysis of the myocardial perfusion state after coronary artery bypass grafting surgery.