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김종연 서울대학교 지리교육과 1996 地理敎育論集 Vol.36 No.1
The purpose of this study is to discover out the characteristics of the channel bed forms in Su-ip stream, Yangpyong, Kyonggi province. Channel bed form reflects the characteristics of the flow and sediments which are transported by the stream, and the interaction between the fluvial systems and its environments. The study was restricted to the areas consisting of bed rock cliff and talus slopes, in lateral movement of the channel. Bed-rock channel and gravel-bed channel can be differentiated between by its forming material and the material supply from the slope, nearest to channel, effected to channel bed forma. A series of field measurements reveals that the riffle-pool sequences were formed in studied reach, but the regularity, reported by other researchers who studied the gravel-bed river, was not found at all. The irregularity of the riffle-pool sequences in this reach were caused by the large bed rock obstacles from the slopes. The step-pool sequences, which dissipate the fluvial energy and minimize the stream power per unit area, were found, and all of them were formed by the bed rock. The material size of the riffle period is larger than that of the nearest pool and run period. It can be regarded as not only the geometric feature of the channel bed, but also the spatial sorting of the bed forming material. So, the riffle period includes the roughness elements, increased resistance to the flow. In the run period, the armoured layer was found to be not a static armour, but a dynamic armour, which moves downstream during a flood. In this reach, if combined with the riffle, the mid channel bar and the point bar were found. And the material size of the bar is smaller than that of the nearest riffle period. According to the material size characteristics, the bar does its role as a temporary sediment storage. The cluster bed form was found on the surface of the bar and shut stream. The bed forms like the riffle-pool sequences and the bar, and are combined with the large bed rock obstacle that is transported from the nearest slope. According to these results, the channel bed form characteristics of this reach strongly influenced by the material transport from the slope.
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김종연 대한예방의학회 2012 예방의학회지 Vol.45 No.1
Objectives: This study was performed to consider the association between Internet using time for non-educational purposes and adolescent health, and to examine how health status differs between Internet users and non-users. Methods: We analyzed 2009 data from the Korea Adolescent Risk Behavior Web-Based Survey, conducted on a nationally representative sample of students in grades 7 to 12. A total of 75 066 adolescents were categorized into four groups according to their Internet using time excluding using for educational purposes: non-Internet users (NIUs),occasional Internet users (OIUs) (<1 h/d), moderate Internet users (MIUs) (≥1 and <2 h/d), and heavy Internet users (HIUs) (≥2 h/d). Health factors included eight health risk behavior indices, four mental health indices and six physical health indices. Results: The distribution of Internet use was as follows: NIUs 17.4%, OIUs 68.1%, MIUs 12.7%, and HIUs 1.7%. In multivariate analysis, using OIUs as a reference, U- or J-shaped associations were observed for five health risk behavior indices (current smoking, current drinking, drug abuse, sexual intercourse, sedentary behavior on weekdays) and four mental health indices (stressed, depressed, suicidal ideation, attempted suicide) in both genders. After removing confounding effects, including age, region, school type, subjective school record, subjective economic status, presence of parents, living with family, and sedentary behavior, these associations were still observed. Conclusions: Health professionals should consider both Internet non-users (for non-educational purposes) and heavy users to be high-risk groups in terms of health status. Also, more well-designed studies are needed to clarify what factors are working in these nonlinear associations.
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한강살리기사업에의한 한강 여주 구간의 하천 지형 변화 고찰
김종연 한국지형학회 2020 한국지형학회지 Vol.27 No.2
In this study, changes in the fluvial landforms of the Yeoju section of the Han River, which was made up of the Han River Restoration Project, were examined through existing previous research data, government’s environmental impact assessment data, satellite images, and field observations. For example, In the vicinity of Dori Island, the most upstream part of the study section, the location of the confluence of the Han River and Cheongmi Stream was changed, and it was found that a significant portion of the sand sedimentary layer disappeared. In the Bawuinupgubi area, the wetland, which is the first class in the ecological nature, was greatly modified, and the elevation of the ground rose as Gangcheon island and it was completely separated from the river by dredging The confluence of Geumdangcheon and the point bar of Yeonyang-ri in the south were also dredged, turned into an artificial waterfront park, and a chute channel remained in the form of a wetland was also developed as a recreational park. The deposional forms around Baekseok-ri islands also disappeared as dredging was carried out. Among the areas adjacent to the confluence of Bokcheon and Yangchon-ri Island, some sedimentay forms remains, but the abandonned channel between Yangchon-ri and the northern river bank has been changed into a riverside reservoir through dredging and embankment construction, and the waterway of the tributary river(Yazoo) has been greatly changed.
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김종연,나형용,박희철 대한금속재료학회(대한금속학회) 1995 대한금속·재료학회지 Vol.33 No.4
Vibration damping capacity(i.e Specific Damping Capacity, SDC) of extruded bars of both casted and Powder Metallurgy(PM) Al-Zn alloys was investigated in relation to their Zn compositions and heat treatment conditions. The effect of α/β interface area on SDC was studied. The SDC is found to increase with increasing Zn content. The SDC of specimens heat treated at 250℃ for 1 hour is smaller than that of as-extruded bars because their α/β interface area decreases. In the case of extruded bars of PM Al-78wt%Zn alloy heat treated at 250℃ and 310℃ for 1 hour, SDC and lamellar spacing are 12.8% and 0.5㎛, 25.6% and 0.1㎛, respectively. This large difference in SDC is believed due to the disappearance of retained α phase as well as much finer lamellar spacing by heat treating at 310℃. The SDC of extruded bars of PM alloys is about 3% larger than that of extruded bars of casting.
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망막정맥폐쇄 및 당뇨병에 의한 황반부종 환자에서 유리체강내 베바시주맙 주입술의 단기효과
김종연,권의용,이동욱,조남천.Jong Youn Kim. M.D.. Eui Yong Kweon. M.D.. Dong Wook Lee. M.D.. Nam Chun Cho. M.D. 대한안과학회 2008 대한안과학회지 Vol.49 No.8
Purpose: To evaluate the short-term effect and safety of intravitreally injected bevacizumab in patients with macular edema (ME) caused by retinal vein occlusion (RVO) and diabetic macular edema (DME). Methods: We retrospectively evaluated 59 eyes of 51 patients, 29 with ME caused by RVO and 30 with DME, who received intravitreal injection of bevacizumab. Fifty-one consecutive patients (59 eyes) with ME associated with RVO and DME were treated with intravitreal injections of 1.25-2.5 mg (0.05-0.1 ml) of bevacizumab. Ophthalmic evaluation was performed at baseline and at 1, 3, 6 months after each injection. Clinical evidence of toxicity and complications, changes of visual acuity with an ETDRS chart (LogMAR), and central macular thickness (CMT) using optical coherence tomography (OCT), were evaluated. Results: The follow-up period was 7.3 months (7.3±0.31) and the mean number of injections was 1.2. The baseline mean LogMAR was 1.06±0.53 and mean CMT was 479.6±160.4 μm. At 1, 3 and 6 months, the mean LogMAR was 0.90±0.52, 0.80±0.39 and 0.78±0.39, respectively, and the mean CMT was 316.9±86.7 μm, 281.1±67.4 μm and 278.4±64.6 μm, respectively. No adverse incidents were observed, including cataract, retinal detachment, vitreous hemorrhage, and endophthalmitis, although transient increased intraocular pressure was observed. Conclusions: Intravitreal bevacizumab injections are safe and effective in ME caused by RVO and DME. J Korean Ophthalmol Soc 49(8):1275-1282, 2008
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