• Korean Journal of Remote Sensing
• /
• v.39 no.6_1
• /
• pp.1211-1224
• /
• 2023

Clouds cause many difficult problems in observing land surface phenomena using optical satellites, such as national land observation, disaster response, and change detection. In addition, the presence of clouds affects not only the image processing stage but also the final data quality, so it is necessary to identify and remove them. Therefore, in this study, we developed a new cloud detection technique that automatically performs a series of processes to search and extract the pixels closest to the spectral pattern of clouds in satellite images, select the optimal threshold, and produce a cloud mask based on the threshold. The cloud detection technique largely consists of three steps. In the first step, the process of converting the Digital Number (DN) unit image into top-of-atmosphere reflectance units was performed. In the second step, preprocessing such as Hue-Value-Saturation (HSV) transformation, triangle thresholding, and maximum likelihood classification was applied using the top of the atmosphere reflectance image, and the threshold for generating the initial cloud mask was determined for each image. In the third post-processing step, the noise included in the initial cloud mask created was removed and the cloud boundaries and interior were improved. As experimental data for cloud detection, CAS500-1 L2G images acquired in the Korean Peninsula from April to November, which show the diversity of spatial and seasonal distribution of clouds, were used. To verify the performance of the proposed method, the results generated by a simple thresholding method were compared. As a result of the experiment, compared to the existing method, the proposed method was able to detect clouds more accurately by considering the radiometric characteristics of each image through the preprocessing process. In addition, the results showed that the influence of bright objects (panel roofs, concrete roads, sand, etc.) other than cloud objects was minimized. The proposed method showed more than 30% improved results(F1-score) compared to the existing method but showed limitations in certain images containing snow.

• Korean Journal of Environment and Ecology
• /
• v.18 no.1
• /
• pp.75-91
• /
• 2004

Biodiversity and seasonal community composition of benthic macroinvertebrates were studied from Upo wetlands in Gyeongsangnam-do, Korea, comprising Upo (4 sites), Mokpo (2 sites), Sajipo (1 site), Jjokjibeol (1 site), Yeobeol (1 site), and Topyeongcheon (2 sites) areas from October 2002 to August 2003. As a result, it was known that Upo wetlands retained relatively well-preserved littoral zones which may provide good habitats for benthic macroinvertebrates; however, frequent disturbances of littoral zones caused by flood were the major factor affecting on the survival and distribution of benthic macroinvertebrates in the areas. During the study period, a total of 135 species of benthic macroinvertebrates in 10 genera, 59 families, 16 orders, 7 classes, and 3 phyla were collected those of which are the highest degree of diversity of the taxa ever known in Korean wetlands: aquatic insects 103 spp. (Diptera 27 spp., Odonata 24 spp., Coleoptera 19 spp., Hemiptera 16 spp., Ephemeroptera 9 spp., Trichoptera 7 spp., and Collembola 1 sp.), Crustacea 2 spp., Mollusca 19 spp. (Gastropoda 12 spp. and Bivalvia 7 spp.), and Annelids 11 spp. (Oligocaeta 1 sp. and Hirudinea 10 spp.). Sajipo (St.G) and Jjokjibeol (St.H) areas yielded relatively larger numbers of species, 54 spp. and 53 spp., respectively, while more than 40 species occurred at most other sites. Based on quantitative sampling (0.5m${\times}$2m), aquatic insects (88.0％), particularly chironomids in Diptera (61.0％), occupied major proportion of the total individuals of benthic macroinvertebrates, while Mollusca (5.3％), Annelida (3.5％), and Crustacea (3.2％) occupied minor proportions. In standing water areas, diverse groups of benthic macroinvertebrates such as chironomids, demselflies, aquatic bugs, aquatic beetles, crustaceans, and gastropods were dominant in terms of individual number; in the running water areas, on the other hand, chironomids and baetid mayflies were dominant. However, gastropods, i.e. viviparids, were the dominant group of benthic macroinvertebrates in most study areas in terms of biomass. Dominance indices were 0.22-0.51 (mean$\pm$sd 0.42$\pm$0.09) in autumn, 0.31-0.96 (0.02$\pm$0.23) in winter, and 0.30-0.89 (0.57$\pm$0.18) in summer; diversity indices were 3.50-4.26 (3.80$\pm$0.24) in autumn,1.55-4.50 (3.10$\pm$1.01) in winter, and 1.35-3.77 (2.55$\pm$0.09) in summer. Highly movable or true aquatic benthic macroinvertebyates such as aquatic bugs, aquatic beetles, and gastropods recovered earlier after flood. In the study sites of Upo wetlands, Upo and Sajipo areas showed relatively higher values of average diversity index which may indicate a good habitat condition for benthic macroinvertebrates.

• Proceedings of the KOR-BRONCHOESO Conference
• /
• 1981.05a
• /
• pp.7-8
• /
• 1981

Authors observed clinically 34 cases of the corrosive esophagitis caused by various corrosive agents at Kyung Hee University Hospital from Aug. 1978 to Dec. 1980. The results obtained were as follows; 1. Among the 34 patients, male was 19 (55.9%) and female 15(44.1%). Most frequently found age was 3rd decade. 2. 18 cases(52.9%) came to the hospital within 24 hours after ingestion of the agents, and 13 cases(38.2%) within 2 to 7 days. 3. Seasonal distribution showed most frequently in spring(35.3%). 4. The moment of the accident was suicidal attempt in 27 cases(79.4%) and misdrinking in 7 cases(20.6%). 5. Acetic acid was a most commonly used agent, showing 23 cases(67.6%), lye and insecticides were next in order. 6. Common chief complaints were swallowing difficulty and sore throat. 7. The average hospital days was 14.8 days. 8. Esophagogram was performed between 3 to 7 days after ingestion in 13 cases(38.2 %), findings were constrictions on the 1st narrowing portion in 4 cases(30.8%) and within normal limits in 3 cases(23.1%). 9. Esophagoscopy was performed in 31 cases(91.2%) between 2 to 7 days after ingestion, which revealed edema and coating on entrance of the esophagus in 9 cases (29.0 %). Diffuse edema on entire length of the esophagus and within normal limits were next in order. 10. Laboratory results were as follows: Anemia was in 1 cases(2.9%), leukocytosis. in 21 cases (61.8%), increase ESR in 9 cases (26.5%), markedly increased BUN and creatinine in 3 cases (8.8%), and hypokalemia in 1 cases(2.9%). Proteinuria in 10 cases(29.4%) hematuria in 4 cases(l1.8%), and coca cola urine in 3 cases (8.8%). 11. Associated diseases were 3 cases(8.8%) of cancer, 1 cases (2.9%) of diabetes mellitus, and 1 cases(2.9%) of manic depressive illness. 12. Various treatment was given: Esophageal and gastric washing in 23 cases(67.6%) for the emergent treatment, antibiotics in 32 cases(94.1%), steroids in 30 cases(88.2%), bougienation in 5 cases(14.7%), hemodialysis in 1 case(2.9%), and partial esophagectomy with gastrostomy and gastroileal anastomosis in 1 cases(2.9%). 13. Serious complications were observed in 9 cases (26.5%), consisted of 6 cases(17.6%) of esophageal stricture, 1 cases(2.9%), of aute renal failure, 1 cases (2.9%) of pneu momediastinum with pneumonia, and 1 cases (2.9%) of pneumonia.