관류 강조 자기공명 영상을 이용한 소아 모야모야 환아의 뇌 혈역학 분석

장원석,김태곤,이승구,최중언,김동석,Chang, Won-Seok,Kim, Tae-Gon,Lee, Seung-Koo,Choi, Jung-Uhn,Kim, Dong-Seok 대한신경외과학회 2005 Journal of Korean neurosurgical society Vol.37 No.3

Objective: Classically, single photon emission tomography is known to be the reference standard for evaluating the hemodynamic status of patients with moyamoya disease. Recently, T2-weighted perfusion magnetic resonance(MR) imaging has been found to be effective in estimating cerebral hemodynamics in moyamoya disease. We aim to assess the utility of perfusion-weighted MR imaging for evaluating hemodynamic status of moyamoya disease. Methods: The subjects were fourteen moyamoya patients(mean age: 7.21 yrs) who were admitted at our hospital between Sep. 2001 to Sep 2003. Four normal children were used for control group. Perfusion MR imaging was performed before any treatment by using a T2-weighted contrast material-enhanced technique. Relative cerebral blood volume(rCBV) and time to peak enhancement(TTP) maps were calculated. Relative ratios of rCBV and TTP in the anterior cerebral artery(ACA), middle cerebral artery(MCA) and basal ganglia were measured and compared with those of the posterior cerebral artery(PCA) in each cerebral hemispheres. Using this data, we analysed the hemodynamic aspect of pediatric moyamoya disease patients in regarding to the age, Suzuki stage, signal change in FLAIR MR imaging, and hemispheres inducing symptoms. Results: The mean rCBV ratio of ACA, MCA did not differ between normal children and moyamoya patients. However the significant TTP delay was observed at ACA, MCA territories (mean = 2.3071 sec, 1.2089 see, respectively, p < 0.0001). As the Suzuki stage of patients is advanced, rCBV ratio is decreased and TTP differences increased. Conclusion: Perfusion MR can be applied for evaluating preoperative cerebral hemodynamic status of moyamoya patients. Furthermore, perfusion MR imaging can be used for determine which hemisphere should be treated, first.

임계치 이상의 전류자극에 대한 생체의 반응 연구

장원석,최규식,Chang, Won-Seok,Che, Gyu-Shik 한국정보통신학회 2010 한국정보통신학회논문지 Vol.14 No.12

임계치 이하의 자극이 주어지면 흥분막은 어떤 특이한 반응을 나타내지 않으나 어느 정도 이상이 되면 아주 다른 양상을 띄게 된다. 흥분막에는 이러한 특성이 있다는 것이 진작부터 알려져 있었고, 일부 연구자들이 이러한 현상을 전기적인 회로를 이용하여 정량적으로 해석하려 노력하였으나 그것은 임계치 이하의 경우에 대한 것에 불과하다. 특히 임계치 이상의 자극에 대한 반응을 정량적으로 연구한 경우는 극히 드물다. 그런데 전기회로와 생체는 비슷한 점도 있지만 다른 면도 많아서 그대로 이를 적용하기에는 무리가 있다. 이러한 이유로 인하여 본 논문에서는 생체막이 임계치 이상의 자극을 받았을 때에 어떠한 현상을 나타내는가를 전기적인 관점에서 정량적으로 연구하였다 When the inferiorthreshold potential is applied on the membrane, the resting status membrane does not display any specific reaction, in the meanwhile if it receives somewhat higher voltages then it shows entirely different configuration. The fact that there is this kind of characteristics on the exciting membrane has been known for a long time, and some researchers have tried to analyze this situation using the electrical circuits but only limitted to inferiorthreshold potential case. The quantitative studies of especially for transthreshold stimulus is extremely rare up to now. The direct application of electrical circuit to biostatus is somewhat uneasonable because there may be much differences between them. We studied the electrical reaction quantitatively of biomembrane when it receives the transthreshold stimulus in point of electricity in this paper.

LNG 발전배가스 농축 CO₂를 이용한 액화 실증기술의 개발

최창식(Chansgik Choi),박수남(Su-nam Park),이혜성(Hye-sung Lee),박동규(Dong Kyoo Park),장원석(Won- seok Chang),남궁형규(Hyeong-gyu Namgung) 한국환경에너지공학회 2023 한국열환경공학회 학술대회지 Vol.2023 No.2

Liquified carbon dioxide (LCO₂) is a promising alternative to fossil fuels that can be used to reduce greenhouse gas emissions. There is growing research into the use of liquefied CO₂ (LCO₂) to reduce CO₂ emissions, which can be transported deep underground for carbon capture and storage (CCS) and LCO₂ for enhanced oil recovery (EOR). It can be used to extract additional oil by injecting it into oil fields, and can also be used as a raw material and refrigerant for the production of various fuels. This study attempted to conduct an empirical study on the production of LCO₂ with a purity of 90% or higher targeting concentrated CO₂ from LNG flue gas. This study was designed to secure empirical process development technology applicable to existing LNG power generation infrastructure and reduce greenhouse gas emissions in the future and reduce cliinate change. It is expected that it will make a significant contribution to mitigating the impact.

불균일 촉매를 이용한 시안화물의 고도산화처리

장원석(Won Seok Chang),박대원(Dae Won Park),홍석원(Seok Won Hong),윤운영(Woon Young Yoon) 大韓環境工學會 2000 대한환경공학회지 Vol.22 No.8

수직성장된 탄소나노튜브의 선택적 패터닝

장원석(Won Seok Chang) 대한기계학회 2012 大韓機械學會論文集B Vol.36 No.12

실리콘 기판 위에 플라즈마 기상층착법을 이용하여 합성된 탄소나노튜브를 화학적인 방법이나 전자빔 혹은 이온빔과 같은 진공 챔버 내에서의 공정없이 펨토초레이저를 이용하여 선택적으로 패터닝 하는 방법을 구현하였다. 플라즈마 기상층착법으로 합성된 탄소나노튜브는 수직성장이 가능하며 탄소나노튜브 간의 간격을 조절하여 성장이 가능하다. 이러한 장점으로 전계방출소자, 바이오센서 등의 응용을 위하여 이용되는 합성 방법이다. 이러한 응용을 위하여 선택적으로 나노튜브를 제거하고 탄소나노튜브 끝의 촉매금속을 제거하는 것이 응용의 효율을 높이는데 매우 중요하다. 본 연구에서는 탄소나노튜브의 전기적, 구조적 특성에 영향을 줄 수 있는 화학적인 방법을 사용하지 않고 펨토초레이저를 사용하여 패터닝과 촉매금속을 제거하는 방법을 구현하였다. The selective patterning of a carbon nanotube (CNT) forest on a Si substrate has been performed using a femtosecond laser. The high shock wave generated by the femtosecond laser effectively removed the CNTs without damage to the Si substrate. This process has many advantages because it is performed without chemicals and can be easily applied to large-area patterning. The CNTs grown by plasma-enhanced chemical vapor deposition (PECVD) have a catalyst cap at the end of the nanotube owing to the tip-growth mode mechanism. For the application of an electron emission and biosensor probe, the catalyst cap is usually removed chemically, which damages the surface of the CNT wall. Precise control of the femtosecond laser power and focal position could solve this problem. Furthermore, selective CNT cutting using a femtosecond laser is also possible without any phase change in the CNTs, which is usually observed in the focused ion beam irradiation of CNTs.

개별 수직성장된 나노튜브와 금속의 복합 구조체 제작 및 분석

장원석(Won Seok Chang),황준연(Jun Yeon Hwang),한창수(Chang Soo Han) 대한기계학회 2012 大韓機械學會論文集B Vol.36 No.1

탄소나노튜브의 기계적 특성과 금속의 전기적 특성을 이용할 수 있는 나노 복합구조체의 특성은 두 재료 사이의 계면이 중용한 역할을 한다. 본 연구에서는 나노임프린트 패터닝을 이용하여 촉매금속을 패턴하고 이를 이용한 개별 성장된 탄소나노튜브 위에 증기증착법을 이용하여 니켈을 증착한 나노구조체의 계면을 조사하였다. 이를 위하여 고해상의 투사전자현미경과 3 차원 원자 프로브 분석기를 이용하였다. 탄소나노튜브 위에서 성장된 나노결정의 경우 준 안정 상태인 조밀입방구조의 Ni3C 를 형성하는 것으로 나타났다. 이러한 특성을 이용한 나노복합체의 응용가능성을 살펴보았다. The properties of carbon nanotube-metal hybrid nanostructures are critically dependent on the structure and chemistry of the metal-carbon nanotube interface. In this study, the interface between nickel and multi-walled carbon nanotubes (CNTs) has been investigated using physical vapor-deposited (sputter-deposited) nickel onto the surface of freestanding carbon nanotube arrays processed by nano-imprint lithography (NIL). These interfaces have been characterized by transmission electron microscopy and 3D atom probe tomography. In the nickel nanocrystals growing on the CNT surface, a metastable hexagonal Ni3C-types phase appears to be stabilized. The structural stability of the nickel-CNT interface is also discussed and related to potential implications for the properties of these nanocomposites.

임상 : 뇌종양 환자에서 관류강조 자기공명영상의 유용성 및 한계점

장원석 ( Won Suk Chang ),강정한 ( Jeong Han Kang ),조진모 ( Jin Mo Cho ),김진아 ( Jin Na Kim ),김응엽 ( Eung Yeop Kim ),안정용 ( Jung Yong Ahn ),김동석 ( Dong Seok Kim ),장종희 ( Jong Hee Chang ) 대한뇌종양학회 2009 대한뇌종양학회지 Vol.8 No.1

Introduction:Accurate diagnosis and grading of brain tumors are critical to determine the specific treatment planning and prognosis of each tumor type. Evaluation of tumor status during treatment to assess therapeutic response and treatmentrelated complications is also important. Recent developments in the field of magnetic resonance imaging(MRI) have been adopted with varying success in the management of brain tumors. We studied the usefulness and limitation of perfusion MRI, one of new MRI techniques, in patients with a brain tumor. Materials and Methods:We analyzed 100 perfusion MR images in 72 patients who treated between December 2005 to August 2006. The type of lesions was glioma in 62 patients, lymphoma in 11, metastasis in 6, other tumor in 7, and nontumorous lesion in 14. The perfusion MR images were obtained by 3.0T MRI using dynamic contrast enhanced method. We calculated relative cerebral blood volume(rCBV) with dedicated software program. Results:The mean rCBV of high grade gliomas(WHO grade III-IV) was significantly higher than that of astrocytic low grade gliomas(WHO grade II). Additionally, rCBV of glioma and tumor grading showed positive linear correlation. However, the value of rCBV is not correlated with the tumor grade in glioma with oligodendroglioma component. While there was no statistically significant difference of rCBV between low grade gliomas, and lymphomas or metastatic brain tumors, the rCBV of high grade gliomas was higher than that of lymphomas or metastatic brain tumors. The perfusion MRI was also helpful for distinguishing recurrence of high grade gliomas from radiation necrosis, and the rCBV was higher in recurrent cases. Conclusion:Even though perfusion MRI has several limitations such as susceptibility artifact, low resolution, the possibility of errors during interpretation, no absolute diagnostic values, and less effectiveness in hypervascular benign tumors or oligodendroglial tumors, this new MRI technique could be a useful method for preoperative diagnosis of brain mass lesion and assessing the results of treatment.

미국은 얼마나 민주적인가: 로버트 달(Robert A. Dahl)의 미국 헌법 비판 검토

장원석 ( Won Seok Chang ) 서울대학교 한국정치연구소 2004 韓國 政治 硏究 Vol.13 No.1

LNG발전소 저농도 CO₂의 컴팩트 포집 및 탄소자원화와 폐열활용기술 개발

장원석(Won-Seok Chang),장미희(Me-Hee Jang),남궁형규(Hyeong-Gyu Namgung),강경수(Gyung-Soo K) 한국에너지기후변화학회 2023 한국에너지기후변화학회 학술대회 Vol.2023 No.5

미국 민주주의의 위기론 일고

장원석 ( Won Seok Chang ) 한국정치평론학회 2012 정치와 평론 Vol.10 No.-

The American face different challenges that result from poor constitution and power, The author argues that the current constitution does not grant the citizens the necessary rights they need and that American citizens are not equally represented, Most citizens do not understand democracy and this makes it difficulty for them to overcome the challenges. Hudson`s introduction offers a review of the history of democratic theory in terms of four models of democracy, giving the reader a set of criteria against which to evaluate the challenges discussed later in the book. Then Hudson explores of what he considers are the major challenges to American democracy: separation of powers, the imperial judiciary, radical individualism, citizen participation, trivialized elections, the privileged position of business, inequality, the national security state. He emphasizes such critical and topical issues as the persistence of economic inequality despite the economic prosperity of the late 1990s, the Clinton scandals and the impeachment controversy, the impact of globalization on business, the role of soft money in election campaigns. He wants to engage the reader in thinking critically about these challenges rather than presenting the neutral and objective discussion common to most textbooks. But his discussion about American presidential system shows a kind of systematic prejudice against the theory of separation of power.