• 한국강구조학회 논문집
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• 제23권2호
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• pp.159-167
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• 2011

최근 강구조물의 건설이 지속적으로 증가되고 있고, 이에 따른 모니터링 시스템의 중요성이 더욱 부각되고 있는 실정이다. 강구조물의 노화로 인한 피로균열 및 부식은 강구조물의 수명저하에 가장 큰 요인이 된다. 구조물이 큰 교량의 경우에는 사람의 접근이 어렵고, 균열 측정 방법 또한 시간이 오래 걸리며, 많은 비용이 소비된다. 따라서, 초기에 균열을 발견하고 보수, 보강 작업을 수행함으로써 비용을 절감할 수 있는 모니터링 시스템의 개발이 절실히 요구된다. 본 연구에서는 강부재의 전위차법(EPDM : Electric Potential Drop Method)에 의한 모니터링 기법에 의해 쉽게 관찰되지 않는 피로균열의 발생 및 진전 상황을 추적하고 또한 잔여수명을 예측하였다.

• 한방안이비인후피부과학회지
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• 제17권2호
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• pp.81-86
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• 2004

Objective: This study was designed to investigate clinical features of chronic urticaria and assess Korean traditional medical therapy on that. Methods: The ratio of male and female, duration of symptoms, personal history and family history of allergic diseases, serum IgE level, and suspected causes and provocation factors were investigated in 41 patients with chronic urticaria. And frequency of wheals, duration of wheals, number of wheals, itch severity, and antihistamine counts of 6-point(0-5) score was assessed in 26 patients. The change of total scores between baseline and follow up were analyzed using Wilcoxon signed-rank test(p〈0.05). Results: 1. The ratio of male and female was 1:1.28 and the mean duration of symptoms was 26.0 months. 2. The frequency of personal history and family history of allergic diseases was each 53.7$\%$ and 48.8$\%$ and 30.6$\%$ had over 200 IU／mL serum IgE level. 3. The suspected causes were none(43.9$\%$), foods(29.3$\%$), drugs(9.8$\%$) and stress(7.3$\%$). 4. The suspected provocation factors were foods(39.0$\%$), none(19.5$\%$), fatigue(17.0$\%$), heat and sweating(l4.6$\%$), pressure(12.2$\%$) and stress(9.8). 5. The total scores between baseline and follow up of 26 patients was lowered from 14.85${\pm}$3.80 to 7.65${\pm}$4.31 and it was significant statistically. Conclusions: Korean traditional medical therapy was proved to be effective on the chronic urticaria and we need to consider foods as important factor in both treatment and patient education of urticaria.

• Safety and Health at Work
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• 제9권1호
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• pp.42-52
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• 2018

Background: Maintenance operations on-board ships are highly demanding. Maintenance operations are intensive activities requiring high man-machine interactions in challenging and evolving conditions. The evolving conditions are weather conditions, workplace temperature, ship motion, noise and vibration, and workload and stress. For example, extreme weather condition affects seafarers' performance, increasing the chances of error, and, consequently, can cause injuries or fatalities to personnel. An effective human error probability model is required to better manage maintenance on-board ships. The developed model would assist in developing and maintaining effective risk management protocols. Thus, the objective of this study is to develop a human error probability model considering various internal and external factors affecting seafarers' performance. Methods: The human error probability model is developed using probability theory applied to Bayesian network. The model is tested using the data received through the developed questionnaire survey of >200 experienced seafarers with >5 years of experience. The model developed in this study is used to find out the reliability of human performance on particular maintenance activities. Results: The developed methodology is tested on the maintenance of marine engine's cooling water pump for engine department and anchor windlass for deck department. In the considered case studies, human error probabilities are estimated in various scenarios and the results are compared between the scenarios and the different seafarer categories. The results of the case studies for both departments are also compared. Conclusion: The developed model is effective in assessing human error probabilities. These probabilities would get dynamically updated as and when new information is available on changes in either internal (i.e., training, experience, and fatigue) or external (i.e., environmental and operational conditions such as weather conditions, workplace temperature, ship motion, noise and vibration, and workload and stress) factors.

• Nuclear Engineering and Technology
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• 제39권3호
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• pp.193-206
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• 2007

The Korea Atomic Energy Research Institute has developed an advanced fast reactor concept, KALIMER-600, which satisfies the Generation IV reactor design goals of sustainability, economics, safety, and proliferation resistance. The concept enables an efficient utilization of uranium resources and a reduction of the radioactive waste. The core design has been developed with a strong emphasis on proliferation resistance by adopting a single enrichment fuel without blanket assemblies. In addition, a passive residual heat removal system, shortened intermediate heat-transport system piping and seismic isolation have been realized in the reactor system design as enhancements to its safety and economics. The inherent safety characteristics of the KALIMER-600 design have been confirmed by a safety analysis of its bounding events. Research on important thermal-hydraulic phenomena and sensing technologies were performed to support the design study. The integrity of the reactor head against creep fatigue was confirmed using a CFD method, and a model for density-wave instability in a helical-coiled steam generator was developed. Gas entrainment on an agitating pool surface was investigated and an experimental correlation on a critical entrainment condition was obtained. An experimental study on sodium-water reactions was also performed to validate the developed SELPSTA code, which predicts the data accurately. An acoustic leak detection method utilizing a neural network and signal processing units were developed and applied successfully for the detection of a signal up to a noise level of -20 dB. Waveguide sensor visualization technology is being developed to inspect the reactor internals and fuel subassemblies. These research and developmental efforts contribute significantly to enhance the safety, economics, and efficiency of the KALIMER-600 design concept.

• 한국도로학회논문집
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• 제2권2호
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• pp.139-148
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• 2000

외국의 포장가속시험기는 대부분 아스팔트포장의 시험을 주된 목적으로 개발되었다. 그러나, 국내의 고속도로는 콘크리트포장과 아스팔트포장이 거의 같은 연장을 유지하고 있는 실정으로 콘크리트포장의 활용이 예상되어 콘크리트 포장의 시험을 위한 독자적인 포장가속시험시설의 개발이 요구되고 있다. 따라서 한국의 실정에 알맞은 콘크리트/아스팔트포장 '시험용 포장가속 시험시설'을 개발하기 위하여 1997년부터 1999년 동안의 3년간 연구를 수행하였다. 1차 연도에서는 포장가속시험시설을 제작하는데 필요한 기본적인 사양과 기본 시스템 설계에 관한 기초연구가 이루어 졌고, 2$\sim$3차 년도에는 KALES의 전체구조, 하중작용, 현가장치 및 구동장치 등에 대한 상세설계를 수행하였다. 실모델을 제작하기 전단계로 모형시험기를 만들어 시험을 수행하여 작동성 및 하중분배기구 등을 검토하였다. 피로해석 검토결과 제안된 KALES 시스템은 내구성이 있으며 실제차량을 잘 모사할 수 있는 시험기로 판명되었다.

• Journal of Chest Surgery
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• 제18권4호
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• pp.872-880
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• 1985

Myasthenia gravis is a neuromuscular transmission disorder characterized by fatigue and weakness of voluntary muscles. Although the pathogenesis is known as reduction of available acetylcholine receptors at neuromuscular junctions by autoimmune attack, the thymic role in myasthenia gravis is still unclear and under investigation. But thymectomy in the management of myasthenia gravis has become increasingly important since the first successful operation with remission of symptoms in 1939 by Blalock. From January 1983 to June 1985, authors performed 17 thymectomies for patients with myasthenia gravis. Among them, 12 patients were free from thymoma [Croup A] and 5 were coupled with thymoma [Group B]. The results were as follows: 1] Sex distribution was 11 females and 6 males. Mean age of the patients was 32.2 year old. Sex and age distribution by the Group A and B are shown Table 1. 2] Clinical manifestations of ocular symptoms were seen in 5 patients [88.2%], extremity weakness in 13 patients, bulbar weakness in 12 patients and dyspnea in 6 patients. According to the Osserman`s classification, 5 patients were in group IIA, 6 in IIB and 6 in IIC. 3] Pre-operatively, all patients were positive response to the anti-cholinesterase test and 12 patients [92.3%] revealed positive findings in electromyography [EMC] which was done in 13 patients. 4] The postoperative complications were respiratory distress in 3 patients, myasthenic crisis in 2 patients and wound disruption in one patients. 5] Pathologic examination of the thymus showed hyperplasia in 10 patients [90%] and thymoma in 5 patients, of which 4 were mixed type with invasion to the adjacent tissues and one lymphocytic type without invasion. Normal thymus was noticed in only 2 patients. 6] In postoperative evaluations, among the 12 patients c free from thymoma [Group A], complete remission of symptoms was noticed in 3 patients and improvement in 7 patients. But among the 5 patients coupled with thymoma [Group B], only one patients showed improvement [Table 8]. Therefore, remission and clinical improvement were noticed in 11 patients [64.7%] of the all and complete remission was noticed in 3 patients [17.6%].

• 대한교통학회지
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• 제31권5호
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• pp.48-59
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• 2013

본 연구에서는 도로투자 사업으로 인한 편익 중 일반적으로 계상하고 있는 통행시간 절감 및 차량운행비용 절감 등 직접적인 편익 이외에 추가적으로 이용자입장에서 체감할 수 있는 도로 주행 중 운전쾌적성 편익을 산정하고자 운전쾌적성의 정의를 마련하였고 운전쾌적성 산정방법론을 개발하였다. 도로특성(도시부/지방부) 및 차량 밀도(차간거리)에 따른 이용자의 지불용의액을 CVM 방법 중 가장 최근에 활발히 활용되고 있는 이중양분선택형(double-bounded dichotomous choice)질문법을 활용하여 설문조사한 후 그 결과를 로짓모형에 적용하여 운전쾌적성 가치를 도출하였다. 도시부 및 지역간 도로에서 공히 지불용의액의 크기는 전반적으로 기존 차간거리가 짧을수록 큰 것으로 분석되었고, 도로의 차간거리 변화가 같더라도 사업 전의 차간거리와 사업 후의 차간거리에 따라 지불용의액이 다른 것으로 나타났다. 즉, 도로의 차간거리가 증가하더라도 기존 차간거리가 어느 정도인지에 따라 지불용의액이 다르게 나타나 지불용의액이 기존 차간거리에 영향을 받는 것으로 분석되었다.

• Journal of Welding and Joining
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• 제7권3호
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• pp.19-27
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• 1989

Both the SS41 steel and the M.E.F(martensite encapsulated islands of frrite) dual phase steel made of SS41 steel by heat treatment were welded by friction welding, and then manufactured machinemade Vnotch standard Charpy impact specimens and precracked with a fatigue system at BM(base metal), HAZ(heat affected zone) and WZ(weld interface Zone). The impact test of them was performed with an instrumented impact test machine at a number of temperatures in constant loading velocity and the dynamic fracture characteristics were studied on bases of the absorbed energy, dynamic fracture toughness and fractography from the test. The results obtained are as follows; At the room temperature, the absorbed energy is HAZ.geq.WZ.geq.BM in case of the M.E.F. dual phase steel: BM.geq.HAZ.geq.WZ in case of the SS41 steel, HAZ.geq.BM.geq.WZ at the low temperature. The absorbed energy is decreased markedly with the temperature lowering; it is highly dependent on the temperature. The dynamic fracture toughness of the M.E.F. dual phase steel is HAZ.geq.WZ.geq.BM at the room temperature; BM.geq.WZ.geq.HAZ below-60.deg. C. Therefore the reliability of friction welding is uncertain at the low temperature(below-60.deg. C). The dynamic fracture toughness of the SS41 steel; HZA.geq.WZ.geq.BM at overall temperature region. The flaw formed by rotational upsetting pressure was shown y SEM; in this region. The absorbed energy per unit area and dynamic fracture toughness were low relative to other region.

• 한국재료학회지
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• 제11권2호
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• pp.151-154
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• 2001

상부전극, Pt, Ir, 그리고 $IrO_2$, 에 따라 수소 열처리전과 후, 그리고 회복열처리시 누설전류특성을 고찰하였다. Pt/PLZT/Pt 케페시터는 수소열처리 후에 다시 회복열처리를 수행하면 완전히 이력곡선의 회복을 보이며 또한 피로특성도 거의 회복 된다. Pt과 IrO$_2$ 상부전극의 경우의 진 누설전류 특성은 열처리조건에 관계없이 강한 시간 의존성을 갖는 space-charge influenced injection모델에 적합하다. 반면에 Ir 상부전극의 경우는 Ir과 PLZT 사이의 계면에 헝성된 전도성 상인 $IrO_2$로 인해 높은 누설전류 밀도를 보이면서 relaxation current 영역이 없이 steady state 영역을 보이는, 주로 Schottky barrier 모델에 의해 설명된다.

• 대한기계학회논문집A
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• 제36권9호
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• pp.979-984
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• 2012

Antiroll-bar Assembly는 철도 차량의 롤링을 제어하도록 설계된 정밀 부품이고 안전과 편안한 승차감을 위해 중요하다. Antiroll-bar Assembly의 주부품인 토션바는 소모품으로써 프랑스에서 전량 수입되고 있다. 따라서 비용절감과 성능향상을 위해 국내 환경에 적합한 토션바 국산화 개발이 필요하다. 본 연구에서는 국내 철도에서 측정된 로드 히스토그램을 활용하여 개발된 토션바에 대한 해석 및 시험을 진행하였고, 수입품과의 비교 시험 결과 만족할만한 결과를 얻었다. 또한 토션바의 부식현상을 방지하기 위해서 스테인리스강 소재의 Ring cover를 씌울 수 있도록 설계를 변경하였다. 변경된 설계 안전성은 CAE해석과 마모시험을 통해서 검증하였다. 이 결과 설계변경에 의한 정적 및 피로에 대한 안전성은 큰 차이가 없었다. 그리고 2종류의 스테인리스강 중에서 내마모성이 우수한 소재를 채택하였다.