• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.20 no.1
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• pp.49-59
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• 1984

Optimizing investigation of characteristics of underwater welding by a gravity type arc welding process was experimentally carried out by using six types of domestic coated welding electrodes for welding of domestic marine structural steel plates (KR Grade A-1, SWS41A, SWS41B,) in order to develop the underwater welding techniques in practical use. Main results obtained are summarized as follows: 1. The absorption speed of the coating of domestic coated lime titania type welding-electrode became constant at about 60 minutes in water and it was about 0.18%/min during initial 8 minutes of absorption time. 2. Thus, the immediate welding electrode could be used in underwater welding for such a short time in comparison with the joint strength of in-atmosphere-and on-water-welding by dry-, wet-or immediate-welding-electrode. 3. By bead appearance and X-ray inspection, ilmenite, limetitania and high titanium oxide types of electrodes were found better for underwater-welding of 10 mm KR Grade A-1 steel plates, while proper welding angle, current and electrode diameter were 6$0^{\circ}C$, above 160A and 4mm respectively under 28cm/min of welding speed. 4. The weld metal tensile strength or proof stress of underwater-welded-joints has a quadratic relationship with the heat input, and the optimal heat input zone is about 13 to 15KJ/cm for 10mm SWS41A steel plates, resulting from consideration upon both joint efficiency of above-100% and recovery of impact strength and strain. Meanwhile, the optimal heat input zone resulting from tension-tension fatigue limit above the base metal's of SWS41A plates is 16 to 19KJ/cm. Reliability of all the empirical equations reveals 95% confidence level. 6. The microstructure of the underwater welds of SES41A welded in such a zone has no weld defects such as hydrogen brittleness with supreme high hardness, since the HAZ-bond boundary area adjacent to both surface and base metal has only Hv400 max with the microstructure of fine martensite, bainite, pearlite and small amount of ferrite.

• Korean Security Journal
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• no.53
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• pp.63-79
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• 2017

Defence Security Command is the only military intelligence and investigation agency which is in charge of safeguarding military information and investigating specific crimes such as subversion and disloyalty in military. While the presidential security provided by Defence Security Command, along with Presidential Security Service(PSS) and the police, forms one of three pillars sustaining presidential security, its works and activities have been rarely known to the public due to the military confidentiality. This study looks into some data specialized into the presidential security among works of Defense Security Command by using various resources such as biographies of key people, media reports, and public materials. It reviews the presidential security works in a historical sense that the works have developed and changed in accordance with the historical changes of Defense Security Command, which was rooted in Counter-Intelligence Corps (Teukmubudae in Korean) in 1948 and leads to the present. The study findings are as follows. First, when the Korean War broke out in 1950 and since then the South Korea was under the threat of the North Korean armed forces and left wing forces, Counter-Intelligence Corps(Bangcheopdudae in Korean) took the lead in presidential security more than the police who was in charge of it. Secondly, even after the Presidential Security Office has founded in 1963, the role of the military on presidential security has been extended by changing its titles from Counter-Intelligence Corps to Army Security corps to Armed Forces Security Command. It has developed their provision of presidential security based on the experience at the president Rhee regime when they could successfully guard the president Rhee and the important government members. Third, since the re-establishment into Defence Security Command in 1990, it has added more security services and strengthened its legal basis. With the excellent expertise, it played a pivotal role in the G20 and other state-level events. After the establishment of the Moon Jaeinin government, its function has been reduced or abolished by the National Defense Reform Act. However, the presidential security field has been strengthening by improving security capabilities through reinforcing the organization. This strengthening of the security capacity is not only effective in coping with the current confrontation situation with the hostile North Korean regime, but also is important and necessary in conducting constant monitoring of the military movement and security-threat factors within military during the national security events.

• Journal of the Korean Orthopaedic Association
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• v.56 no.1
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• pp.26-33
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• 2021

Purpose: This study evaluated the results of dual plate fixation for periprosthetic femur fracture after total knee arthroplasty (TKA). Materials and Methods: From October 2007 to February 2013, 23 cases of periprosthetic femur fracture after TKA were treated at the author's hospital. There were 13 cases of fixation using a medial and lateral dual plate when the stability of the fracture site could not be achieved by one side fixation with a follow-up of more than one year. The cases included no loosening of the femoral component in fractures that were categorized as Lewis-Rorabeck classification II and supracondylar comminuted fractures and elongation of the fracture line to the lateral epicondyle of the femur or stem in the medullary canal. The mean age was 72 years (65-82 years), and 11 cases were female. Three cases had a stem due to revision. The mean bone marrow density was -3.2 (-1.7 to -4.4), and the mean period from primary TKA to periprosthetic fractures was 28 months (1-108 months). The mean follow-up period was 23 months (12-65 months). The medial fracture site was first exposed via the subvastus approach. Second, the supplementary plate was fixed on the lateral side of the fracture using a minimally invasive plate osteosynthesis technique. The average union time, complications, and Hospital for Special Surgery Knee Score (HSS) at the last follow-up were evaluated. Results: The mean union time was 17.4 weeks (7-40 weeks). Two cases showed delayed bone union and nonunion occurred in one case, in whom bone union was achieved three months later after re-fixation using a dual plate with an autogenous bone graft. The mean varusvalgus angulation was 1.67 degrees (-1.2-4.9 degrees), and the mean anterior-posterior angulation was 2.86 degrees (0-4.9 degrees) at the last follow-up. The mean knee range of motion was 90 degrees, and the HSS score was 85 points (70-95 points) at the last follow-up. Conclusion: Dual plate fixation for periprosthetic femur fractures that had not achieved stability by one side plate fixation after TKA showed a good clinical result that allowed early rehabilitation.

• The Journal of Engineering Geology
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• v.31 no.4
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• pp.603-620
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• 2021

A land nodal seismic system was employed to acquire seismic reflection data using stand-alone cable-free receivers in a land-river area. Acquiring reliable data using this technology is very cost effective, as it avoids topographic problems in the deployment and collection of receivers. The land nodal airgun system deployed on the mouth of the Hyungsan River (in Pohang, Gyeongsangbuk Province) used airgun sources in the river and receivers on the riverbank, with subparallel source and receiver lines, approximately 120 m-spaced. Seismic data collected on the riverbank are characterized by a low signal-to-noise (S/N) and inconsistent reflection events. Most of the events are represented by hyperbola in the field records, including direct waves, guided waves, air waves, and Scholte surface waves, in contrast to the straight lines in the data collected conventionally where source and receiver lines are coincident. The processing strategy included enhancing the signal behind the low-frequency large-amplitude noise with a cascaded application of bandpass and f-k filters for the attenuation of air waves. Static time delays caused by the cross-offset distance between sources and receivers are corrected, with a focus on mapping the shallow reflections obscured by guided wave and air wave noise. A new time-distance equation and curve for direct and air waves are suggested for the correction of the static time delay caused by the cross-offset between source and receiver. Investigation of the minimum cross-offset gathers shows well-aligned shallow reflections around 200 ms after time-shift correction. This time-delay static correction based on the direct wave is found essential to improving the data from parallel source and receiver lines. Data acquisition and processing strategies developed in this study for land nodal airgun seismic systems will be readily applicable to seismic data from land-sea areas when high-resolution signal data becomes available in the future for investigation of shallow gas reservoirs, faults, and engineering designs for the development of coastal areas.

• (The) Research of the performance art and culture
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• no.43
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• pp.121-143
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• 2021

The Aim of the this paper is to figure out impetus of the Naeseo Traditional Folk art Conservation Association. This Preservation Society derived from Hogaeri farmers' band. Through aging and hollowing out Hogaeri farmers' band got into a period of stagnation. In order to overcome slump villager and people of a township organized a conservation society in 1994. Members restored and directed folk song which from age to age for performance. are designated as cultural asset in 2017. Sutguldeong song is only song in inland area. This song are worthy of notice in . which is consist of various agricultural work songs experienced two changes. Rice-planting songs are characteristic. Especially, Executive playing a central role harden foundation of the Preservation Society. The mainspring of activity is the sense of responsibility. Preservation Society laying emphasis on recruiting new members. Preservation Society is planning to develop curriculum for Jurisdiction elementary and middle school students. This Preservation Society is made up of First generation members and Second generation members. First generation members who are born and bred in Hogaeri have been good friends both in joy and in sorrow Early days of Preservation Society. So, They has a strong family bond. In order to induce membership Members are practicing Nongak, popular folk songs, dancing program. Second generation members are not conversant with a folk song. Nonetheless They have a strong mind on a member line.

• The Korean Journal of Quaternary Research
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• v.14 no.1
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• pp.7-31
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• 2000

Quaternary Geological and geophysical investigation was performed at the Eurimji reservoir of Jaechon City in order to interprete depositional environment and genesis of lake sediments. For this purpose, echo sounding, bottom sampling and columnar sampling by drilling on board and GPR survey were employed for a proper field investigation. Laboratory tests cover grain size population analysis, pollen analysis and $^{14}C$ datings for the lake sediments. The some parts of lake bottom sediments anthropogenically tubated and filled several times to date, indicating several mounds on the bottom surface which is difficult to explain by bottom current. Majority of natural sediments were accumulated both as rolling and suspended loads during seasonal flooding regime, when flash flow and current flow are relatively strong not only at bridge area of the western part of Eurimji, connected to stream valley, but at the several conduit or sewage system surrounding the lake. Most of uniform suspend sediments are accumulated at the lake center and lower bank area. Some parts of bottom sediments indicate the existence of turbid flow and mudflow probably due to piezometric overflowing from the lake bottom, the existence of which are proved by CM patterns of the lake bottom sediments. The columnar samples of the lake sediments in ER-1 and ER-3-1 boreholes indicate good condition without any human tubation. The grain size character of borehole samples shows poorly sorted population, predominantly composed of fine sand and muds, varying skewness and kurtosis, which indicate multi-processed lake deposits, very similar to lake bottom sediments. Borehole columnar section, echo sounding and GPR survey profilings, as well as processed data, indicate that organic mud layers of Eurimji lake deposits are deeper and thicker towards lower bank area, especially west of profile line-9. In addition the columnar sediments indicate plant coverage of the Eurimji area were divided into two pollen zones. Arboreal pollen ( AP) is predominant in the lower pollen zone, whreas non-aboreal pollen(NAP) is rich in the upper pollen zone. Both of the pollen zones are related to the vegetation coverage frequently found in coniferous and deciduous broad-leaved trees(mixed forest) surrounded by mountains and hilly areas and prevailing by aquatic or aquatic margin under the wet temperate climate. The $^{14}C$ age of the dark gray organic muds, ER1-12 sample, is 950$\pm$40 years B.P. As the sediments are anthropogenetically undisturbed, it is assumed that the reliability of age is high. Three $^{14}C$ ages of the dark gray organic muds, including ER3-1-8, ER3-1-10, ER3-1-11 samples, are 600$\pm$30 years B.P., 650$\pm$30 years B.P., 800$\pm$40 years B.P. in the descending order of stratigraphic columnar section. Based on the interpretation of depositional environments and formation ages, it is proved that Eurimji reservoir were constructed at least 950$\pm$40 years B.P., the calibrated ages of which ranges from 827 years, B.P. to 866 years B.P. Ancient people utilize the natural environment of the stream valley to meet the need of water irrigation for agriculture in the local valley center and old alluvium fan area.