정신분열병 환자에서 자기공명영상 구획화를 이용한 전두엽 하위구조와 구조적 이상 관찰

김재진,권준수,강도형,윤탁,한문희,장기현 大韓神經精神醫學會 2002 신경정신의학 Vol.41 No.6

연구목적 : 정신분열병 환자를 대상으로 한 구조적 뇌영상 연구들은 국소적 전두피질(prefrontal cortex)의 이상에 대하여 상당히 다양한 결과들을 보고하였다. 본 연구는 정확한 해부학적 구획화를 바탕으로 한 관심영역 체계를 통해 정신분열병에서 전두피질의 구조적 이상 유무를 탐색하고자 시행되었다. 방 법 : 12명의 정신분열병 환자와 12명의 나이 및 성별 분포가 동일한 정상인들을 대상으로 뇌 자기공명 영상을 획득한 후, 지형학적 표지물을 이용하여 8개의 전두엽 하위구조 구획 작업을 실시하였다. 구획된 전두엽 하위구조들의 용적을 측정하여 두 군간에 차이가 있는가 관찰하였고, 하위구조 용적과 정신분열 증상의 심각도 간의 상관관계를 살펴보았다. 결 과 : 상당 수의 전두엽 하위구조들의 용적이 정상인에 비해 정신분열병 환자들에서 작은 경향을 보였고, 특히 우측 부운동영역(supplementary motor area)이 통계적으로 유의하게 작은 용적을 보였다(p<0.003). 또 이러한 전두엽 하위구조들의 용적 감소는 정신분열병 음성 증상의 심각도와 밀접한 상관성을 보였고, 이러한 현상은 우측 상전두이랑(superior frontal gyrus)에서 가장 대표적이었다(γ=-0.704, p=0.01). 결 론 : 이러한 결과는 정신분열병에서 전두엽기능저하의 바탕이 되는 구조적 결함의 존재 가능성을 시사한다. 이러한 전두피질의 구조적 결함은 정신분열병에서의 인지기능결핍과 신경회로의 장애 소견과 연결될 수 있다. Objectives : Although most of the functional and structural neuroimaging studies have reported the association of the that cognitive deficits in patients with schizophrenia with the pathophysiology of the prefrontal cortex, their findings vary considerably. Based on the precise parcellation methods, this study was designed to investigate substructural abnormalities of the prefrontal cortex in patients with schizophrenia. Methods : The subjects consisted of twelve patients with schizophrenia and 12 age- and sex-matched normal volunteers. Magnetic resonance images were obtained in all subjects, and parceled into 8 frontal substructures using the topographic landmarks. The frontal substructural volumes were compared between the two groups, and their correlations with the schizophrenic symptom severity were analysed in the patient group. Results : In the comparison of substructural volumes, most frontal substructures of the patient group tended to be smaller than those of the normal comparison group ; particularly the right supplementary motor area was significantly smaller(p<0.003). Negative symptoms tended to be inversely correlated with the frontal substructural volumes, particularly with the right superior frontal gyral volume(γ=-0.70, p=0.01). Conclusion : These findings suggest the possibility of structural defects related to 'hypofrontality' in schizophrenia. These frontal structural defects may be the basis of neurocognitive deficits and neural circuital dysfunction in schizophrenia.

Field measurement of local ice pressures on the ARAON in the Beaufort Sea

Tak-Kee Lee,Jong-Hyun Lee,Heungsub Kim,Chae Whan Rim 대한조선학회 2014 International Journal of Naval Architecture and Oc Vol.6 No.4

This study conducted four field measurements of local ice pressure during the icebreaking voyage of the icebreaking research vessel “ARAON” in the Chukchi and Beaufort seas from July to August of 2010. For measurements, 14 strain gauges, including 8 strain gauge rosettes, were set on the bow of the port side. Influence coefficients were determined using a finite element model of the instrumented area and they were used to convert the measured strains on the hull structure to local ice pressures. The converted maximum pressure was calculated as 2.12 MPa on an area of 0.28 m2. Pressure-area curves were developed from the surveyed pressure data and the results were compared with previously measured data. The study results are expected to provide an understanding of local ice pressures and thus be useful in the structural design of ice class ships.

Review of Ice Characteristics in Ship-Iceberg Collisions

Tak-Kee Lee,Hyun-Jin Park 한국해양공학회 2021 韓國海洋工學會誌 Vol.35 No.5

The International Ice Patrol (IIP) was established after the Titanic collided with an iceberg off the eastern coast of Canada in 1912 and sank, killing more than 1,500 people. Recently, the IIP has analyzed satellite images and provided safe operation information to vessels by tracking the occurrence and movement of icebergs. A large number of recent arctic studies mainly deal with sea ice formed by freezing seawater related to sea routes and resource development. The iceberg that collided with the Titanic was land-based ice that dislodged from a glacier and fell into the sea. The properties of these two types of ice are different. In addition, vessels operating in ice-covered waters such as the Arctic sea have an ice-breaking function or minimum ice-strengthened functions. Ships operating on transatlantic routes including the eastern coast of Canada do not necessarily require ice-strengthened functions. Hundreds to thousands of icebergs are discovered each year near the area where the Titanic sank. In this study, the status of ship-iceberg collision accidents was investigated to provide useful information to researchers, and the physical and mechanical characteristics of icebergs were investigated and summarized.

잔류응력을 고려한 용접부의 피로강도 평가 모델

이탁기(Tak-Kee Lee),남용윤(Yong-yun Nam),한승호(Seung-ho Han),신병천(Byung-Chun Shin) 대한기계학회 2001 대한기계학회 춘추학술대회 Vol.2001 No.8

This paper reports a new model for the fatigue strength assessment of welded joints with residual stresses. The effects of residual stresses are assumed to be equivalent to those of mean stresses However residual stresses are released during cyclic loadings. The proposed model consists of three ingredients, a hot-spot stress approach, a residual stress relaxation mechanism, and an equivalent stress. The equivalent stress is modeled by stress ranges and the ratios between mean stresses and the ultimate stress of material. Once being tuned with two specific fatigue tests, this model can be applied to arbitrary stress ratios and many kinds of welded joints. Three fatigue tests were carried out under a constant amplitude loading and two variable amplitude loadings, and the results were putted together with those of present model. The two results are going quite closely.

선박의 좌초발생 확률에 대한 고찰

이탁기(Tak-Kee Lee) 한국해양환경·에너지학회 2003 한국해양환경·에너지학회 학술대회논문집 Vol.2003 No.-

서해 도서지역의 풍력-디젤 하이브리드 발전에 대한 경제성 분석

이탁기(Tak Kee Lee),남용윤(Yong Yun Nam),김재동(Jae Dong Kim),한정우(Jeong Woo Han) 한국항해항만학회 2011 한국항해항만학회지 Vol.35 No.5

본 연구에서는 최대 발전량이 500kW인 서해 도서의 풍력-디젤 하이브리드 발전시스템에 대한 경제성 분석을 수행하였다. 이를 위해 해당 도서에 대한 연간 전력 부하 변동치와 바람 데이터를 수집하고 분석하였으며, 풍력을 포함하여 신재생 에너지에 대한 하이브리드 최적화 모델로 미국의 NREL에서 개발한 Homer 프로그램을 이용하였다. 풍력-디젤 하이브리드 발전시스템의 경제성을 판단하기 위해 풍속과 경유 가격을 변수로 하는 민감도 해석도 수행하였다. 그 결과, 현재의 조건에서는 경제성이 낮았으나, 풍속이 초속 3미터가 넘거나 경유 가격이 리터당 2.4달러를 초과할 경우 대상지역에도 풍력-디젤 하이브리드 발전시스템이 경제성을 갖는 것으로 평가되었다. In this paper, an economic feasibility study of wind-diesel hybrid power systems for an island in the Yellow Sea, where the maximum power generation is about 500kW, was performed. For the study, annual electric load variation and wind resource data of the island were collected and analyzed. HOMER program - a typical hybrid optimization model for electric renewables including wind resource, developed by the National Renewable Energy Laboratory - was used. Wind speed and diesel price were picked out as variables for the sensitivity analysis in order to find the economic accountability for the wind-diesel hybrid power system. As the result, even though it is not feasible economically under the present condition, if mean wind speed is over 3 m/sec. or diesel price goes up to 2.4 $ per liter, the wind-diesel hybrid power system for the island becomes a prospective candidate.

북극해 계측자료에 기초한 아라온호의 국부 빙압력 계산 연구

이탁기(Tak-Kee Lee),김태욱(Tae-Wook Kim),임채환(Chae Whan Rim),김성찬(Sungchan Kim) 한국해양공학회 2013 韓國海洋工學會誌 Vol.27 No.5

The icebreaking research vessel (IBRV) ARAON had her second ice trial in the Arctic Ocean in the summer season of 2010. During the voyage, the local ice loads acting on the bow of the side were measured using 14 strain gauges. These measurements were carried out in three icebreaking performance tests. To convert the measured strains into the local ice pressures, a finite element model of the instrumented area was developed. The influence coefficient method (ICM), which uses the influence coefficient from the finite element model, and the direct method, which uses the measured strain, were selected as the conversion methods. As a result, the maximum measured pressure was 1.236MPa, and the average difference between ICM and the direct method was about 5% for an area of 0.2㎡. The pressure-area relationship of the measurement falls below the range of the existing pressure-area curve, which is due to the low ice strength of melted ice in the summer.

Damping Effect of Reinforced Polyurethane Foam under Various Temperatures

Lee, Tak-Kee,Kim, Myung-Hyun,Rim, Chae-Whan,Chun, Min-Sung,Suh, Yong-Suk Korean Society of Ocean Engineers 2011 International journal of ocean system engineering Vol.1 No.4

Reinforced polyurethane foam (RPUF) is one of the important materials of Mark III type insulation systems used in liquefied natural gas (LNG) cargo containment systems. However, RPUF is the most difficult material to use with regard to its safety assessment, because there is little public and reliable data on its mechanical properties, and even some public data show relatively large differences. In this study, to investigate the structural response of the system under compressive loads such as sloshing action, time-dependent characteristics of RPUF were examined. A series of compressive load tests of the insulation system including RPUF under various temperature conditions was carried out using specimens with rectangular section. As a result, the relationship between deformation of RPUF and time is linear and dependent on the loading rate, so the concept of strain rate could be applied to the analysis of the insulation system. Also, we found that the spring constant tends to converge to a value as the loading rate increases and that the convergence level is dependent on temperature.

북극해에서 계측된 국부 빙하중에 대한 선속 및 빙두께 영향

이탁기(Tak-Kee Lee),이종현(Jong-Hyun Lee),임채환(Chae-Whan Rim),최경식(Kyungsik Choi) 한국해양공학회 2013 韓國海洋工學會誌 Vol.27 No.5

The icebreaking research vessel ARAON conducted her second ice trial in the Arctic Ocean during the summer season of 2010. During this voyage, the local ice loads acting on the bow of the port side were measured using 14 strain gauges. The measurement was carried out during icebreaking while measuring the thickness of the ice very 10 m. The obtained strain data were converted to the equivalent stress values, and the effects of the ship speed and ice thickness on the ice load were investigated. As a result, it was found that a faster speed produced a larger stress, according to the variation in the peak values below an ice thickness on the ice load was not clear.

Effects of the Welding Residual Stress on the Grounding Damage Analysis of a Tanker

Lee, Tak Kee,Rim, Chae Whan,Han, Dae Suk,Kim, B.H. Trans Tech Publications, Ltd. 2007 Key Engineering Materials Vol.353-358 No.3

<P>Vessels are rarely subjected to accidental loads such as the collision, grounding and stranding. But these accidental loads cause a lot of damages to hull structure including a large deformation, fracture, tearing and so on. In case of carrying dangerous goods such as crude oil, these accidents can induce a serious environmental pollution. All ocean-going vessels were made by welding. The welding residual stress is a significant shortcoming of welding remains at the hull structure, even though welding technology in shipbuilding field has provided a variety of advantages, e.g. remarkable shortening of the shipbuilding time. The aim of this paper is to investigate the effects of the residual stress in a grounding accident. When a ship runs aground against a sea-obstacle like a rock, this accident can be classified as a grounding. Among parameters of grounding accident scenarios such as the ship speed, the initial striking point, and loading conditions of the ship, only ship speed varies from 10 to 15 knots under ballast condition with/without consideration of residual stress(this sentence is not clear to the read). The initial striking point is at the bow of the center line of ship. A series of nonlinear numerical simulations with large deformation and fracture were carried out using LS-DYNA. As a result, two cases with residual stress have longer damage length. The difference seems to be relatively small, but not negligible.</P>