A Case of Widespread Cavernous Malformations of the Central Nervous System Associated with Acute Neurologic Deficit

노경철,정성은,이도경 대한자기공명의과학회 2017 Investigative Magnetic Resonance Imaging Vol.21 No.1

A 45-year-old female visited our clinic due to sudden right leg weakness and sensory loss. Brain and spinal cord magnetic resonance imaging showed widespread cavernous malformations. Cavernous malformation in L1 spine area was accompanied by a subacute stage hematoma with perilesional edema. Sensory loss subsided after corticosteroid therapy. Usually, neurologic deficit by spinal cavernous malformation appears more chronically in the adults compared to children. Treatment options are difficult to establish in a case with multiple cavernous malformations. Identifying hemorrhagic lesions by extensive neuroimaging evaluation could be helpful to select the treatment target for cavernous malformation.

High-on-Aspirin Platelet Reactivity Differs Between Recurrent Ischemic Stroke Associated With Extracranial and Intracranial Atherosclerosis

노경철,최혜연,우호걸,장준영,허성혁,장대일,김범준 대한신경과학회 2022 Journal of Clinical Neurology Vol.18 No.4

Background and Purpose Ischemic stroke recurs despite the use of antiplatelet agents. Various mechanisms are involved in recurrence due to intracranial atherosclerosis (ICAS) and extracranial atherosclerosis (ECAS). High-on-aspirin platelet reactivity (HAPR) may differ between recurrent stroke due to ICAS and ECAS. Methods Patients with recurrent ischemic stroke as a result of large-artery atherosclerosis despite taking aspirin were enrolled consecutively. Ischemic stroke was classified as stroke due to ICAS or ECAS according to the location of the culprit stenosis. An aspirin reaction units (ARU) value of >550 IU was defined as HAPR. HAPR and its associated factors were compared between the two groups and also considering the mechanism of stroke. Results Among the 190 patients with recurrent stroke (111 with ICAS and 79 with ECAS), 36 (18.3%) showed HAPR. The ARU value was higher in the ECAS than the ICAS group (492± 83 vs. 465±78, mean±standard deviation; p=0.028), as was the proportion of patients with HAPR (27.8% vs. 12.6%, p=0.008). Being male and having stroke due to ECAS (reference = stroke due to ICAS: odds ratio=5.760; 95% confidence interval=2.154–15.403; p<0.001) was independently associated with HAPR. The ARU value differed according to the stroke mechanism, and was highest in those with artery-to-artery embolism. Artery-to-artery embolism was independently associated with HAPR in both the ICAS and ECAS groups. Conclusions Recurrent stroke due to ECAS was more strongly associated with HAPR and insufficient antiplatelet inhibition than was that due to ICAS. Artery-to-artery embolism was associated with HAPR in recurrent ischemic stroke as a result of ICAS or ECAS.

From Bound Cells Comes a Sound Mind: The Role of Neuronal Growth Regulator 1 in Psychiatric Disorders

노경철,박정철,한정수,이성중 한국뇌신경과학회 2020 Experimental Neurobiology Vol.29 No.1

Cell-to-cell adhesion is important for maintenance of brain structure and function. Abnormal neuronal cell adhesion and loss of its connectivity are considered a main cause of psychiatric disorders such as major depressive disorder (MDD). Various cell adhesion molecules (CAMs) are involved in neuronal cell adhesions and thereby affect brain functions such as learning and memory, cognitive functions, and psychiatric functions. Compared with other CAMs, neuronal growth regulator 1 (Negr1) has a distinct functioning mechanism in terms of its cross-talk with cytokine receptor signaling. Negr1 is a member of the immunoglobulin LON (IgLON) family of proteins and is involved in neuronal outgrowth, dendritic arborization, and synapse formation. In humans, Negr1 is a risk gene for obesity based on a genome-wide association study. More recently, accumulating evidence supports that it also plays a critical role in psychiatric disorders. In this review, we discuss the recent findings on the role of Negr1 in MDD, focusing on its regulatory mechanism. We also provide evidence of putative involvement of Negr1 in other psychiatric disorders based on the novel behavioral phenotypes of Negr1 knockout mice.

Numerical study of the effects of periodic body acceleration (PGZ) and bifurcation angle in the stenosed artery bifurcation

노경철,유홍선 한국유변학회 2009 Korea-Australia rheology journal Vol.21 No.3

This article describes the numerical investigation of blood flow in the stenosed artery bifurcation with acceleration of the human body. Using the commercial software FLUENT, three-dimensional analyses were performed for six simulation cases with different body accelerations and bifurcation angles. The blood flow was considered to be pulsation flow, and the blood was considered to be a non-Newtonian fluid based on the Carreau viscosity model. In order to consider periodic body acceleration, a modified, time-dependent, gravitational-force term was used in the momentum equation. As a result, flow variables, such as flow rate and wall shear stress, increase with body acceleration and decrease with bifurcation angle. High values of body acceleration generate back flow during the diastolic period, which increases flow fluctuation and the oscillatory shear index at the stenosis.

유량 조절 밸브가 탑재된 진동수주형 파력발전장치의 터빈 내 유동해석을 위한 수치해석 연구

노경철 ( Kyoung-chul Ro ),오재원 ( Jae-won Oh ),김길원 ( Gil-won Kim ),이정희 ( Jung-hee Lee ) 한국산업융합학회 2021 한국산업융합학회 논문집 Vol.24 No.6

In this paper, a numerical analysis was conducted on the effect of the flow control valve of a oscillation water column(OWC) type wave power generator turbine. The OWC wave power turbine operates with compressed air in the air chamber according to the change of wave height. When the wave height changes rapidly, a flow control valve is required due to overload of the turbine and reduced efficiency. Therefore, in this paper, a flow control valve with an opening angle of 60 degrees was installed in the front of the turbine, and the pressure drop, torque, and overall performance were calculated according to the change of turbine RPM and flow rate of turbine inlet. In conclusion, the flow control valve with an opening angle of 60 degrees affects when the turbine rotates at low rotation and the inlet flow rate is large. But it does not have a significant effect on overall turbine performance and it is necessary to find the optimal angle in the future works.

[기타] 흡기관 분사식 수소기관의 연소특성에 관한 수치해석적 연구

노경철(Kyoung-chul Ro),김충익(Chung-ik Kim),류홍선(Hong-sun Ryou),이종태(Jong-Tai Lee) 한국자동차공학회 2000 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-

Hydrogen fueled engine with external mixture has higher thermal efficiency than directed injection hydrogen fueled engine. It has not required structural change of an existing gasoline engine. But it has low power output and backfire problem in rich mixture relatively.<br/> Thus the numerical analysis is performed on the hydrogen-fueled engine with external mixture for variable equivalence ratios and it is compared with the experimental and numerical result of gasoline engine with external mixture.<br/> It is found that hydrogen fueled engine with external mixture has very shorter delay of combustion period, higher cylinder pressure and higher cylinder temperature than gasoline engine with external mixture.

점탄성 유체해석용 RANS 기반 난류 모델 개발 및 검증

노경철(Kyoung-Chul Ro) 한국산학기술학회 2017 한국산학기술학회논문지 Vol.18 No.3

대동맥이나 협착된 경동맥에서는 심장수축기에 간헐적으로 난류현상이 발생하고 있으며, 혈액의 점성특성으로 인해 기존 난류모델로는 정확한 해석이 어려운 실정이다. 혈류는 점탄성 유체의 성질을 가지고 있어 유체의 전단 변형률 증가에 따라 점도가 감소하는 점탄성 유체이며, 이러한 점탄성 유체는 난류 유동시 저항 감소 현상이 발생한다. 기존의 난류해석 모델들은 점성변화가 없는 뉴턴 유체에 적합한 모델들이 대부분이기 때문에, 점탄성 유체의 저항 감소 현상을 고려한 비뉴턴 유체 해석에 적합한 난류 모델개발이 필요하다. 본 논문은 난류 모델 가운데 수렴성이 좋고 해석시간이 짧은 표준 k-ε 모델을 기반으로 저항 완충 함수를 이용하여 비뉴턴 유체의 저항감소 현상을 해석할 수 있는 수정된 난류모델을 제시하였으며, 이를 기존 난류모델들과 비교하여 제시된 난류 모델을 검증하였다. 새로 제시된 수정된 난류모델은 벽함수 및 점성저층을 고려하지 않았기 때문에 해석시간이 대폭적으로 감소하였으며, 적은 격자수를 이용하여 효율적으로 비뉴턴 유체의 난류 현상을 해석할 수 있기 때문에 향후 혈류해석 및 점탄성유체 해석에 적용할 예정이다. When the systolic blood pressure is high, intermittent turbulence in blood flow appears in the aorta and carotid artery with stenosis during the systolic period. The turbulent blood flow is difficult to analyze using the Newtonian turbulence model due to the viscous characteristics of blood flow. As the shear rate is increased, the blood viscosity decreases by the viscoelastic properties of blood and a drag reduction phenomenon occurs in turbulent blood flow. Therefore, a new non-Newtonian turbulent model is required for viscoelastic fluid and hemodynamics. The main aims of this study were to develop a non-Newtonian turbulence model using the drag reduction phenomenon based on the standard k-ε turbulent model for a general non-Newtonian fluid. This was validated with the experimental data and has a good tendency for non-Newtonian turbulent flow. In addition, the computation time and resources were lower than those of the low Reynolds number turbulent model. A modified turbulent model was used to analyze various turbulent blood flows.

점탄성 유체의 난류 해석을 위한 수정된 k-ε 난류모델 개발 및 혈류역학에의 적용

노경철(K.C. Ro),유홍선(H.S. Ryou) 한국전산유체공학회 2010 한국전산유체공학회지 Vol.15 No.4

This article describes the numerical investigation of turbulent blood flow in the stenosed artery bifurcation under periodic acceleration of the human body. Numerical analyses for turbulent blood flow were performed with different magnitude of periodic accelerations using a modified turbulence model which was considering drag reduction of non-Newtonian fluid. The blood was considered to be a non-Newtonian fluid which was based on the power-law viscosity. In order to validate the modified k-ε model, numerical simulations were compared with the standard k-ε model and the Malin's low Reynolds number turbulence model for power-law fluid. As results, the modified k-ε model represents intermediate characteristics between laminar and standard k-ε model, and the modified k-ε model showed good agreements with Malin's verified power law model. Moreover, the computing time and computer resource of the modified k-ε model were reduced about one third than low Reynolds number model including Malin's model.

점탄성 유체의 난류 해석을 위한 수정된 k-ε 난류모델 개발 및 혈류역학에의 적용

노경철(K.C. Ro),유홍선(H.S. Ryou) 한국전산유체공학회 2010 한국전산유체공학회 학술대회논문집 Vol.2010 No.5

This article described that a high Reynolds number version of a turbulence model was modified by using drag reduction to analyze the turbulent flows of non-Newtonian fluid with visco-elastic viscosity and it was applied hemodynamics which was representative of visco-elastic fluid. The turbulence characteristics of visco-elastic fluid was expanded viscous sublayer region and buffer layer region by drag reduction phenomenon, and also Newtonian turbulence models does not predict because viscosity was related with shear rate of fluid flow. Hence, numerical simulation using a modified turbulence model was conducted under the same conditions that were applied to obtain the experiment results and previous turbulence models and then the numerical investigation of turbulent blood flow in the stenosed artery bifurcation under periodic acceleration of the human body.

NUFLEX의 상변화, 분무유동 및 MHD 해석

노경철(Kyoung Chul Ro),유홍선(Hong Sun Ryou),강관구(Kwan Gu Kang),허남건(Nahmkeon Hur) 한국전산유체공학회 2007 한국전산유체공학회지 Vol.12 No.2

NUFLEX is a general purpose program for the analysis 3D thermo/fluid flow and pre/post processor in a complex geometry. NUFLEX is composed of various physical models, such as phase change(solidification/melting) and spray, MHD(Magneto Hydraulic Dynamics) models. It is possible to simulate continuous cast iron process and spray droplet breakup/collision phenomenon. For the verification of these models, compared with the experimental data and commercial CFD code's results. The results show good agreements with experimental and comercial CFD codes's results.