무기체계 개발단계에서 신뢰도 향상방안

최충현(Chung-Hyun Choi),박상은(Sang-Eun Park) 한국신뢰성학회 2015 신뢰성응용연구 Vol.15 No.1

This note suggests three approaches to improve reliability in developing weapon systems. The high complexity of the weapon systems make it hard to analyze and predict of those reliability. Current situations of the reliability have been reviewed in terms of logistics support analysis (LSA), warranty policy, maintenance and development. Three suggestions are notified to improve the reliability considering the complexity of the weapon systems.

2006년~2009년 새만금호에서 식물플랑크톤 군집과 환경요인의 변화

최충현 ( Chung Hyun Choi ),정승원 ( Seung Won Jung ),윤석민 ( Suk Min Yun ),김성현 ( Sung Hyun Kim ),박종규 ( Jong Gyu Park ) 한국환경생물학회 2013 환경생물 : 환경생물학회지 Vol.31 No.3

본 연구는 한국해양과학기술원의 기본연구과제 (과제번호 PE98988)에 의해 수행되었음. Between May 2006 and November 2009, we investigated the relationship between fluctuations in environmental factors and phytoplankton communities in Saemangeum Artificial Lake, South Korea. Nutrient concentrations in the lake increased because of the inflow of water from Mankyung and Dongjin Rivers during the summer rainy season; in particular, high concentrations were detected at an inner zone close to the estuaries. During the summer rainy season, salinity at the inner zone reduced more rapidly than that at the other zones, and it was similar to the changes in nutrient concentrations. Variations in phytoplankton communities were caused by fluctuations in environmental factors: the abundance of phytoplankton at the inner zone was higher than that at the other zones. Diatoms were the dominant species in the phytoplankton communities. A small centric diatom, Skeletonema costatum like species, was predominant, with a mean abundance of 19.5% in Saemangeum lake. Because of accelerated eutrophication in the lake, phytoplankton abundance increased continuously and the total number of species present in the community decreased. In particular, some dinoflagellates could intermittently cause red tides during low temperature and salinity conditions (at the inner zone). In 2006~2007, a red tide-forming dinoflagellate, Prorocentrum minimum, was the predominant species, while Heterocapsa triquetra, Karlodinium veneficum, and Heterocapsa rotundata were the newly recorded species in late 2008 to early 2009. Therefore, the dynamics of phytoplankton communities under the perennially eutrophic conditions in Saemangeum lake appear to be primarily affected by changes in water temperature and salinity. In particular, the growth of harmful algae may have been accelerated by the low salinity and temperature conditions during the spring season at the inner zone.

말기암환자에서 임박사건 간 48시간 임종예측도 비교

황인철,최충현,김경곤,이경식,서희선,심재용,Hwang, In-Cheol,Choi, Chung-Hyun,Kim, Kyoung-Kon,Lee, Kyoung-Shik,Suh, Heuy-Sun,Shim, Jae-Yong 한국호스피스완화의료학회 2011 한국호스피스.완화의료학회지 Vol.14 No.1

목적: 임박사건(impending event)에 대한 인지는 보호자와의 보다 효과적인 의사소통을 위해 필요할 뿐 아니라, 임종실로 옮기는 시점을 결정하는데 있어서 매우 중요하다. 이 주제에 대한 지금까지의 연구는 대부분 임종 48시간을 전후한 시점에서 이미 '발생되어 있는' 증상의 나열에 불과하였다. 이에 '변화'의 시점에서 사망까지의 시간을 기준으로 하여 임박사건 간 48시간 이내 임종예측도를 비교하였다. 방법: 인천소재 완화의료병동에서 임종을 맞이한 160명의 환자 중 임종 전 일주일 동안의 의무기록이 있는 80명을 대상으로 하였다. 환자 및 보호자가 호소하는 주관적 증상 9가지와 의료인에 의해 관찰되는 객관적 징후 8가지를 선정하고 각 항목에 대한 '의미 있는 변화'의 기준을 사전에 정하였다. 결과: 증상에서는 수면량의 증가(53.8%), 징후에서는 혈압의 감소(87.5%)가 가장 높은 발생빈도를 보였다. 임종까지의 평균시간은 증상의 경우 안정 시 호흡곤란(46.8시간)이, 징후의 경우 산소포화도의 감소(13.6시간)와 혈압의 감소(36.9시간)가 48시간 이내였다. 48시간 임박사건으로서의 예측도는 증상의 경우, 양성예측도는 안정 시 호흡곤란이 가장 높았고(83%) 음성예측도는 안정 시 호흡곤란과 의식혼탁/섬망의 조합이 가장 높았으며(86%), 징후의 경우 양성 예측도는 모두 95% 이상이었고 음성예측도는 혈압의 감소와 산소포화도 감소의 조합에서 가장 높았다(60%). 증상과 징후의 발생양상은 유의한 차이를 보였다. 결론: 증상에서는 안정 시 호흡곤란과 의식혼탁/섬망이, 징후에서는 산소포화도나 혈압의 감소가 임종임박을 예측하는데 가장 유용한 임상지표로 생각된다. Purpose: Recognition of impending death is crucial not only for efficient communication with the caregiver of the patient, but also determination of the time to refer to a separate room. Current studies simply list the events 'that have already occurred' around 48 hours before the death. This study is to analyze the predictability of each event by comparing the time length from 'change' to death. Methods: Subjects included 160 patients who passed away in a palliative care unit in Incheon. The analysis was limited to 80 patients who had medical records for the last week of their lives. We determined 9 symptoms and 8 signs, and established the standard of 'significant change' of each event before death. Results: The most common symptom was increased sleeping (53.8%) and the most common sign was decreased blood pressure (BP) (87.5%). The mean time to death within 48 hours was 46.8% in the case of resting dyspnea, 13.6% in the ease of low oxygen saturation, and 36.9% in the case of decreased BP. The symptom(s) which had the highest positive predictive value (PV) for death within 48 hours was shown to be resting dyspnea (83%), whereas the combination of resting dyspnea and confusion/delirium (65%) had the highest negative PV. As for the most common signs before death within 48 hours, the positive PVs were more than 95%, and the negative PV was the highest when decreased BP and low oxygen saturation were combined. The difference in survival patterns between symptoms and signs was significant. Conclusion: The most reliable symptoms to predict the impending death are resting dyspnea and confusion/delirium, and decline of oxygen saturation and BP are the reliable signs to predict the event.

스테인레스 강 제조공정의 산회수 및 처리수 재활용을 위한 막조합 공정

이기완 ( Lee Ki-wan ),최충현 ( Choi Chung-hyun ),이남경 ( Lee Nam-kyoung ) 한국환경기술학회 2001 한국환경기술학회지 Vol.2 No.1

스테인레스 제조공정에서 산폐수와 산세정폐수의 산회수 및 재활용을 위하여 Variable Pore Micro Filter(VPMF)/Reverse Osmosis(RO)/Nanofiltration(NF) 공정을 도입하였다. 세정폐수처리 공정의 전처리 장치인 VPMF는 처리수의 SS를 1 ppm이하로 유지할 수 있었으며 후속공정인 1단과 2단 RO에서 질산의 제거율은 94, 91 %, 불화수소산은 77, 66 %의 제거율을 나타내어 RO의 최종 처리수는 공업용수로의 재사용이 가능함을 확인하였다. 또한 산세액 처리시 NF에서 99 %의 금속이온 제거율과 99 %의 산화수가 가능하였고, 95 % 농축 산회수액중의 금속이온 함유농도는 재활용에 충분한 수준이었다. Variable Pore Micro Filter(VPMF)/Reverse Osmosis(RO)/Nanofiltration(NF) process was applied to the water reusing and acid recovery from the pickling liquor and pickling wastewater in stainless steel manufacturing factory. As results of experimental and field study, it was found that the pickling wastewater could be improved to SS of 1 ppm by VPMF only. In the 1st and the 2nd RO process following Microfiltration(MF), rejection ratios of chemical components were 94% and 91% for nitric acid, 77% and 66% for hydrofluoric acid. Effluent from the 2nd RO was suitable to quality of process water for the steel industry. NF process had a same efficiency of 99% for the acid recovery and metal rejection to pickling liquor. Metallic contents of the 95% concentrated acid were enough to reuse.

화재에 노출된 철근콘크리트 내력벽의 내화성능

이차돈(Chadon Lee),김현(Hyun Kim),최충현(Chung-Hyun Choi) 한국구조물진단유지관리학회 2010 한국구조물진단학회 학술발표회논문집 Vol.2010 No.2

The research performed in this study aimed to experimentally and theoretically investigate the responses and structural behavior of the bearing walls with both sides being exposed to the fire. From the experiments, it was found that the walls with both sides being exposed to the fire could be severely damaged and led to a complete collapse. The developed model, which could reasonably simulate the wall behavior in fire, predicted that wall thickness and the ratio of the axial load to the nominal strength of the wall section are the most influential factors affecting the fire resistance rate.

소나체계의 OMS/MP 설정과 유사체계 운용실적 분석을 통한 RAM 목표값 설정 방안 연구

송기훈,박영만,홍순국,민승식,유재우,최충현,Song, Ki-Hoon,Park, Young-Man,Hong, Soon-Kook,Min, Seung-Sik,You, Jea Woo,Choi, Chung Hyun 한국군사과학기술학회 2015 한국군사과학기술학회지 Vol.18 No.1

In this research, items and contents of SONAR were derived from investigation of OMS/MP of previously-operated submarines and domestic and international references related to weapon system. Such items and contents were established in detail and were categorized into four separate groups after consulting system design experts and specialists in the field of SONAR's operation. Ultimately, based on wartime and peacetime scenario and operation concept of SONAR, RAM values were obtained through various methods using submarine-operating records and maintenance records for the past eleven years.

통계적 검정력을 이용한 임상시험 자원자 수 타당성 검증

권민경(Min Kyung Kwon),양동인(Dong In Yang),남기창(Ki Chang Nam),최충현(Chung Hyun Choi),김덕원(Deok Won Kim) 대한전기학회 2010 정보 및 제어 심포지엄 논문집 Vol.2010 No.10

임상시험 연구에서 가장 중요한 사항 중의 하나가 자원자 수를 결정하는 문제이다. 일반적으로 검정력 분석 (power analysis)은 연구를 시작하기 전에 필요한 자원자 수를 결정하기 위해 시행하지만, 임상시험 연구 종료 후 그 결과의 타당성을 입증하기 위해 시행하는 경우도 있다. 하지만 대부분의 기존 연구에서는 자원자 수만 제시하고, 통계적 검정력(statistical power)을 제시하지 않고 있다. 본 연구에서는 자기장 인체 영향연구를 위한 자원자 임상시험에 있어서, 자원자 수가 적절하게 결정되었는지를 고찰해 보았다. 일반인 19명과 전자파 과민증 환자(electrohypersensitivity: EHS)임을 주장하는 18명을 연구대상으로 각 그룹마다 총 4가지 인자들(호흡수, 심박변이도, 피부온도, 자각증상)에 대해서 통계적 검정력을 계산해 보았다. 그 결과 자각증상을 제외한 3가지 인자들의 통계적 검정력은 0.8 이상으로 연구계획이 잘 수립되었다고 볼 수 있었다. 또한 모든 분석 인자들의 검정력을 높이기 위해서 일반인 그룹에서 26명 이상의 자원자가 필요함을 확인하였다. 따라서 연구 결과의 타당성을 증명하기 위해서는 자원자수 뿐 만 아니라 통계적 검정력을 제시하는 깃이 필요하다.

시뮬레이션 기반 함정의 신뢰도와 보전도 설정

한영진(Young Jin Han),윤원영(Won Young Yun),유재우(Jea Woo You),최충현(Chung Hyun Choi),김희욱(Hee Wook Kim) 대한산업공학회 2013 대한산업공학회지 Vol.39 No.6

탐지체계의 RAM 분석을 위한 시뮬레이션 모델링 연구

윤원영 ( Won Young Yun ),한영진 ( Young Jin Han ),박고은 ( Go Eun Park ),최충현 ( Chung Hyun Choi ),정덕재 ( Duk Jae Jung ) 한국품질경영학회 2011 품질경영학회지 Vol.39 No.3

RAM(Reliability, Availability and Maintainability) is one of the important indicators to show the performance of weapon systems. For analyzing RAM characteristics, RAM simulation is useful and powerful as mathematical techniques. However, it is necessary to build the simulation model to express about the operation environment of weapon systems, and obtain detail input data for reliability and maintainability about the system to get accurate results by RAM simulation. In this paper, we propose a procedure to analyze RAM of the searching system consisting in weapon systems by RAM simulation and we estimate searching system availability by a commercial simulation program, AvSim.

한국청소년에서 자가비만인식도와 정신건강과의 관련성

황인철(In Cheol Hwang),이경식(Kyoung Shik Lee),박동균(Dong Kyun Park),정은영(Eun-Young Jung),최충현(Chung-Hyun Choi),조성진(Seong-Jin Cho),배승민(Seung-Min Bae) 대한소아청소년정신의학회 2011 소아청소년정신의학 Vol.22 No.2

Objectives:Obesity has been linked to various psychological problems as well as medical complications, especially among adolescents. Previous studies have suggested an association between body weight and depression or self-esteem ; however, there has been little evidence on self-perception of weight and mental health. The aim of this study was to examine the association of perceptional weight status with mental health in Korean adolescents. Methods:This study was based on data obtained from the third Korean National Health and Nutritional Examination Survey (2005). The study sample consisted of 583 adolescents (268 boys, 315 girls) aged 12-18 years, who had completed the health survey, the health examination, and the nutritional survey. Participants were divided into two groups based on the actual or perceptional weight status: non-obese and obese. Questionnaires for stress, depressive mood, and suicidal thoughts were utilized as mental health indicators. Results:The agreement between actual and perceptional weight status was moderate (κ value, 0.585 ; p<0.01). The influencing factors for the discrepancy between actual and perceptional weight status were body mass index of subjects and their parents’ education. The obese group was likely to have higher stress levels and more experience of depressive mood or suicidal ideation in regard to both actual and perceptional weight status. A multiple logistic regression analysis revealed that girls who had perceived themselves as obese were more likely to have an experience of depressive mood than other girls (unadjusted OR, 4.98 ; adjusted OR, 5.15). Conclusion:An experience of depressive mood was significantly associated with the perception of weight status and not actual weight status in Korean female adolescents.