• The Korean Journal of Nuclear Medicine
• /
• v.32 no.3
• /
• pp.238-249
• /
• 1998

Purpose: To localize and compare the neural basis of verbal and visual human working memory, we performed functional activation study using $H_2^{15}O$ PET. Materials and Methods: Repeated $H_2^{15}O$ PET scans with one control and three different activation tasks were performed on six right-handed normal volunteers. Each activation task was composed of 13 match-ing trials. On each trial, four targets, a fixation dot and a probe were presented sequentially and subject's task was to press a response button to indicate whether or not the probe was one of the previous targets. Short meaningful Korean words, simple drawings and monochromic pictures of human faces were used as matching objects for verbal or visual memory. All the images were spatially normalized and the differences between control and activation states were statistically analyzed using SPM96. Results: Statistical analysis of verbal memory activation with short words showed activation in the left Broca's area, promoter cortex, cerebellum and right cingulate gyrus. In verbal memory with simple drawings, activation was shown in the larger regions including where activated with short words and left superior temporal cortex, basal ganglia, thalamus, prefrontal cortex, anterior portion of right superior temporal gyrus and right infero-lateral frontal cortex. On the other hand, the visual memory task activated predominantly right-sided structures, especially inferior frontal cortex, supplementary motor cortex and superior parietal cortex. Conclusion: The results are consistent with the hypothesis of the laterality and dissociation of the verbal and visual working memory from the invasive electrophysiological studies and emphasize the pivotal role of frontal cortex and cingulate gyrus in working memory system.

• Korean Journal of Ecology and Environment
• /
• v.33 no.3 s.91
• /
• pp.187-196
• /
• 2000

This paper describes a simple method that uses differences among Carlson's (1977) trophic state index (TSI) values based on total phosphorus (TP), chlorophyll a (CHL) and Secchi depth (SD) to draw inferences regarding the factors that are limiting to phytoplankton growth and the composition of lake seston. Examples are provided regarding seasonal and spatial patterns in a large subtropical lake (Lake Okeechobee, Florida, USA) and inter- and intra-lake variations from a multilake data set developed from published studies. Once an investigator has collected routine water quality data and established TSI values based on TP, CHL, and SD, a number of inferences can be made. Additional information can be provided where it also is possible to calculate a TSI based on total nitrogen (TN). Where TSI (CHL)<>TSI (SD), light attenuating particles are large (large filaments or colonies of algae), and the phytoplankton may be limited by zooplankton grazing. Other limiting conditions are inferred by different relationships between the TSI values. Results of this study indicate that the analysis is quite robust, and that it generally gives good agreement with conclusions based on more direct methods (e.g., nutrientaddition bioassays, zooplankton size data, zooplankton removal experiments). The TSI approach, when validated periodically with these more costly and time-intensive methods, provides an effective, low cost method for tracking long-term changes in pelagic structure and function with potential value in monitoring lake ecology and responses to management.

• Korean Journal of Ecology and Environment
• /
• v.33 no.3 s.91
• /
• pp.222-229
• /
• 2000

Spatial and temporal variation of phosphorus in response to intensity of summer monsoon was evaluated in Taechung Reservoir during 1993${\sim}$1994. Total phosphorus (TP) averaged 31 ${\mu}$g/l during the study and varied from 6 to 197 ${\mu}$g/l. Concentrations of TP were highest in the headwaters during the monsoon of July${\sim}$August 1993, and these values were mainly made of particulate P and were closely associated (R$^{2}$=0.74, p<0.001) with high inorganic suspended solids (NVSS). In-lake TP in the headwaters was mainly influenced by the watershed runoff and declined toward the dam. Values of TP downlake was only one-fifth of the peak in the headwaters and had no correlation with NVSS. In 1994, inlake TP was markedly lower relative to 1993 and showed low spatial and temporal variation. Maximum TP during monsoon 1994 in the headwaters and mid-lake was 72% and 52% lower, respectively, than in those two zones in 1993 whereas TP downlake was similar between the two years. These results suggest that temporal variation downlake is much less influenced by seasonal inflow compared to the haedwaters. In 1993, mean TP before fall overturn, based on average value for all sites, was significantly (t=5.99, p<0.001) greater than the mean after fall overturn, whereas in 1994 mean TP after fall overturn (32 ${\mu}$g/l) was greater. This outcome indicates that in 1993 major P-input originated from the external source from the watershed during the intense monsoon, whereas in 1994 internal processes dominated during the weak monsoon. Overall data suggest that annual budget of inlake P is regulated by intensity of the summer monsoon, and phosphorus data measured at single site near the dam or headwater zone may not be represent seasonal trends of the system due to large spatial variation of Taechung Reservoir.

• Korean Journal of Ecology and Environment
• /
• v.51 no.1
• /
• pp.60-70
• /
• 2018

The distribution of benthic macroinvertebrates was investigated at 1,157 sites of 7 main water systems in Korea, including 442 sites of Han River system (Namhan River, Bukhan River, Han River main stream, Anseongcheon, etc.), 305 sites of Nakdong River system (Nakdong River, Hyeongsan River, Taehwa River, etc.), 199 sites of Geum River system (Geum River, Sapgyocheon, Mangyeong River, Dongjin River, etc.) 102 sites of Seomjin River system (Seomjin River), 102 sites of Yeongsan River system (Yeongsan River, Tamjin River, etc.), and 7 sites of Jeju stream system. A total of 151 families were found in the whole survey sites, including 141 families in Han River, 122 in Nakdong River, 115 in Geum River, 106 in Seomjin River, 113 in Yeongsan River, and 50 in Jeju. Chironomidae (20.8%) was the most dominant species in Korea, followed by Hydropsychidae (17.1%), Baetidae (12.6%), Tubificidae (10.3%), Heptageniidae (8.6%), Ephemerellidae (6.3%), Asellidae (2.7%), Leptophlebiidae (2.4%), Planariidae (1.7%), and Tipulidae (1.6%). Substrates compositions consisted of large sand (22.6%), large gravel (18.4%), silt (10.5%), and boulder (8.2%). The mean stream width was 133.5 m and the mean watercourse width was 61.7 m. The mean water depth and velocity were 30.2 cm and $33.1cm\;s^{-1}$, respectively. Results of cluster analysis based on distributional characteristics of benthic macroinvertebrates were divided into six groups according to the frequency of benthic macroinvertebrate taxa which appeared in the study area. Finally, altitude, current velocity and substrate composition were the most influencial factors determining the distribution patterns of macroinvertebrate communities.

• Korean Journal of Ecology and Environment
• /
• v.51 no.1
• /
• pp.105-123
• /
• 2018

Currently, satellite images act as essential and important data in water resources, environment, and ecology as well as information of geographic information system. In this paper, we will investigate basic characteristics of satellite images, especially application examples in water resources. In recent years, researches on spatial and temporal characteristics of large-scale regions utilizing the advantages of satellite imagery have been actively conducted for fundamental hydrological components such as evapotranspiration, soil moisture and natural disasters such as drought, flood, and heavy snow. Furthermore, it is possible to analyze temporal and spatial characteristics such as vegetation characteristics, plant production, net primary production, turbidity of water bodies, chlorophyll concentration, and water quality by using various image information utilizing various sensor information of satellites. Korea is planning to launch a satellite for water resources and environment in the near future, so various researches are expected to be activated on this field.

• Korean Journal of Ecology and Environment
• /
• v.53 no.1
• /
• pp.31-45
• /
• 2020

The biological indices based on the community structure with species richness and/or abundance are commonly used to assess aquatic ecosystem health. Meanwhile, recently functional traits-based approach is considered in ecosystem health assessment to reflect ecosystem functioning. In this study, we developed a database of biological traits for 136 taxa consisting of major stream insects (Ephemeroptera, Plecoptera, Trichoptera, Coleoptera, and Odonata) collected at Korean streams on the nationwide scale. In addition, we obtained environmental variables in five categories (geography, climate, land use, hydrology and physicochemistry) measured at each sampling site. We evaluated the relationships between community indices based on taxonomic diversity and functional diversity estimated from biological traits. We classified sampling sites based on similarities of their environmental variables and evaluated relations between clusters of sampling sites and diversity indices and biological traits. Our results showed that functional diversity was highly correlated with Shannon diversity index and species richness. The six clusters of sampling sites defined by a hierarchical cluster analysis reflected differences of their environmental variables. Samples in cluster 1 were mostly from high altitude areas, whereas samples in cluster 6 were from lowland areas. Non-metric multidimensional scaling (NMDS) displayed similar patterns with cluster analysis and presented variation of taxonomic diversity and functional diversity. Based on NMDS and community-weighted mean trait value matrix, species in clusters 1-3 displayed the resistance strategy in the life history strategy to the environmental variables whereas species in clusters 4-6 presented the resilience strategy. These results suggest that functional diversity can complement the biological monitoring assessment based on taxonomic diversity and can be used as biological monitoring assessment tool reflecting changes of ecosystem functioning responding to environmental changes.

• Journal of Preventive Medicine and Public Health
• /
• v.35 no.3
• /
• pp.205-213
• /
• 2002

Objective : Whether exposure to chronic noise induces an increase in blood pressure, or the development of hypertension, has not been established. A cohort study was performed to identify the effects of chronic noise exposure on blood pressure. Methods : 530 males working at a metal manufacturing factory in Busan, Korea were enrolled for the study. They were monitored for 9 consecutive years, from 1991 to 1999, with an annual health check-up. The subjects were divided into 4 groups, which were determines by noise level categories(NLC) according to noise intensity ; NLC-I: office workers, exposed to noise a level below 60dB(A) ; NLC-II: field technical supporters or supervisors, frequently exposed to workplace noise, wearing no hearing protection device; NLC-III: workers, exposed to workplace noise below 85dB(A), wearing ear plugs or muffs; NLC-IV: workers, exposed to workplace noise over 85 dB(A), wearing both ear plugs and muffs. Results : After controlling possible confoundens, such as baseline age, smoking, alcohol intake, exercise, family history of hypertension, systolic(SBP) of diastolic blood pressure(DBP) and changes in BMI (body mass index), the pooled mean for the systolic blood pressures, over the duration of the study period, were 3.8mmHg, 2.0mmHg and 1.7mmHg higher in NLC-IV, NLC-III NLC-II groups, respectively, than in the NLC-I group. There were no significant differences in the diastolic blood pressures between the groups. Conclusion : This study suggests that chronic noise exposure increases systolic blood pressure independently, among male workers.

• Korean Journal of Weed Science
• /
• v.3 no.2
• /
• pp.143-150
• /
• 1983

Red rice (local name "Sore") as a weed has been a serious threat to rice production in direct-seeded rice culture in Ganghwagun, Gyeonggi province. In the Ganghwagun 508 ha out of 1,420 ha in the Samsanmyeon area is infested with red rice. The average lowland rice yield is about 4,300 kg/ha in the Ganghwagun, but the average upland rice yield is about 2,000 kg/ha in infested area. This study was carried out in order to clarify the ecological characteristics of red rice and factors affecting the competitive ability of five red rice varieties, collected from Samsanmyeon in 1981, with rice cultivar. Five varieties-Monggeunsare, Salsare, Ginkaragsare, Galsaegsalsare, Galsaegkaragsare-showed the same morphological characteristics of cultivated Japonica type, Chuncheongbyeo, but red rice tillers more profusely, is taller and lodges more easily than Chucheongbyeo. It shatters easily about 10-15 days after heading date, and at this time the hull is discolored in yellow or dark brown. There are many types of red rice with short or long owns on the spikelet, occasionally with or without own on the spikelet in the same hill, and the grains are short or long. In red reice leaf blast occurs more severely than in cultivated Indica/Japonica type, Teabaegbyeo, particulary serious in Monggeunsare. When red rice invaded in direct-seeded rice, number of panicles of rice became reduced more than other yield components.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.6 no.3
• /
• pp.152-163
• /
• 2001

Based upon the sedimentological, geochemical and micropaleontological analyses of two sediment cores from the Antarctic Peninsula (AP), three distinct lithological units can be recognized: (1) ice-proximal an/or ice-distal diamictons in the lower part of the cores, accumulated just seaward of the grounding line of the ice shlef until 11,000 yrs BP; (2) diatomaceous mud between 6,000 and 2,500 yrs BP in the middle part, resulted from a large influx of organic materials by enhanced production of open marine condition; (3) diatomaceous sandy mud since 2,500 yrs BP, characterized by an increase in sand content and decrease in TOC and diatom abundance in the lower layers, which reflects the formation of more extensive and seasonally persistent sea ice. Based on the C-14 radiocarbon dating, the sub-ice shlef deposition of the diamicton on the AP western shelf completed around 11,000 yrs BP. Colder condition was reinstated between 12,800 and 11,600 BP with a dropin TOC content and diatom abundance, which is coincident with the Younger Dryas event in the North Atlanticregion. At this time, the ice shelf, that is now absent in the study area, appears to advance as evidenced by an abrupt increase in sea-ice taxa. A climatic optimum is recognized between 9,000 and 2,500 BP, coincide witha mid-Holocene climatic optimum 'Hypsithermal Warm Period' from the other Antarctic sites. During this time, diatomaceous mud accumulated by a large influx of organic materials by enhanced production occurred in openmarine condition. Around 2,500 BP, diatomaceous sandy mud reflects the formation of more extensive and seasonally persistent sea ice, coincident with the onset of the Neoglacial in the Antarctic. Our results provide evidence of climatic change from the Antarctic Peninsula`s western shelf that helps in determining the existence and timing of Holocene milennial-scale climatic events in the Southern Hemisphere.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.38 no.4
• /
• pp.363-373
• /
• 2020

During last decades numerous studies generating orthoimage have been carried out. Traditional methods require exterior orientation parameters of aerial images and precise 3D object modeling data and DTM (Digital Terrain Model) to detect and recover occlusion areas. Furthermore, it is challenging task to automate the complicated process. In this paper, we proposed a new concept of true orthoimage generation using DL (Deep Learning). DL is rapidly used in wide range of fields. In particular, GAN (Generative Adversarial Network) is one of the DL models for various tasks in imaging processing and computer vision. The generator tries to produce results similar to the real images, while discriminator judges fake and real images until the results are satisfied. Such mutually adversarial mechanism improves quality of the results. Experiments were performed using GAN-based Pix2Pix model by utilizing IR (Infrared) orthoimages, intensity from LiDAR data provided by the German Society for Photogrammetry, Remote Sensing and Geoinformation (DGPF) through the ISPRS (International Society for Photogrammetry and Remote Sensing). Two approaches were implemented: (1) One-step training with intensity data and high resolution orthoimages, (2) Recursive training with intensity data and color-coded low resolution intensity images for progressive enhancement of the results. Two methods provided similar quality based on FID (Fréchet Inception Distance) measures. However, if quality of the input data is close to the target image, better results could be obtained by increasing epoch. This paper is an early experimental study for feasibility of DL-based true orthoimage generation and further improvement would be necessary.