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권순억,박노열,김준오,정태건,Gwon, Sun-Eok,Park, No-Yeol,Kim, Jun-O,Jeong, Tae-Geon 대한기계학회 2000 大韓機械學會論文集A Vol.24 No.12
We obtain the mathematical model of the hard disk drive actuator system the system response data of the finite element analysis or experimental results. The model is base on the Rayleigh-Ritz method to approximate the dynamic response of the actuator system. The basic idea is to use the curve-fit technique to obtain the approximation coefficients. It allows the dynamic analysis of the actuator system without resort to the repetitive finite element modeling work. Even though the dynamic characteristics of the system of the system are affected somewhat by the structural modification and the change of the material properties, we can use the modified size and dynamic properties of the actuator system in the mathematical model to some extent. In this study, we express the mathematical model of the simplified rectangular plate first and then proceed to the actual hard disk drive actuator system.
권순억 대한뇌졸중학회 2000 Journal of stroke Vol.2 No.1
Background and Purpose : The natural history of intracranial arterial stenoses remains unknown. To investigate the natural course of the stenoses in the intracranial cerebral arteries and the possible role of clinical prognostic factors, we conducted a prospective study using transcranial Doppler (TCD)ultrasonography. Methods : We performed TCD study on 83 stroke patients with angiographically documented stenosis of middle cerebral artery (MCA) or basilar artery (BA). The findings were compared to repeat TCD studies conducted more than 2 months apart with respect to changes in mean flow velocities (mFV) of the stenotic segment. We analyzed the clinical data of all patients including risk factors of atherosclerosis, electrocardiogram, echocardiogram, and patterns of stenosis, which may affect the natural history of arterial stenosis. Results : Ninety seven arteries (47 left MCA, 31 right MCA, and 19 BA) from 83 patients (65 men and 18 women; mean age 56.6 years) were serially examined. During a mean follow-up period of 364 days, 23 (23.7%) arteries had TCD evidence of stenosis progression and 26 (26.8%) showed stenosis regression. BAs more often showed stenosis regression than did MCAs (p〈0.05), and arteries with symptomatic stenosis more often regressed than those not causing neurological symptoms (p〈0.05). Age, sex, or any risk factors of atherosclerosis were not associated with the course of the stenosis. Conclusion : These findings suggest that stenoses of intracranial arteries are dynamically changed, and that they may progress or regress within a relatively short period of time. Atherosclerotic risk factors are not related to the progression or regression of the stenoses whereas symptomatic (versus asymptomatic) stenosis and BA (versus MCA) involvement are factors related to regression of the stenosis. Korean Journal of Stroke 2000;2(1): 53~56
뇌졸중 최신지견 2009: 뇌졸중의 급성기 치료 및 이차예방
권순억 대한뇌졸중학회 2010 Journal of stroke Vol.12 No.1
There were several positive clinical trials with new anticoagulants and antiplatelet agents which will affect on the guideline of the secondary stroke prevention. Dabigatran, an oral direct thrombin inihibitor, had better clinical outcomes than warfarin in the prevention of cardiovascular events in the patients with atrial fibrillation. Ticagrelor and prasugrel are new antiplatelet agents. They successfully reduced cardiovascular events after acute myocardial infarction without increase bleeding complications compared to clopidogrel. The effects of platelet inhibition of those thienopyridine antiplatelet agents were influenced by the usage of proton pump inhibitor owever, there are no direct supporting evidences to avoid concomitant use of prohibition of proton pump inhibitors and thienopyridines. Genetic polymorphisms of cytochrome P450 2C19, which affects on the metabolism of thienopyridines, affect on the antiplatelet effects of thienopyridines and clinical outcomes. One small clinical trial showed that niacin was better in the prevention of progression of intima-medial thickness of common carotid artery than ezetimibe.
권순억,김범준,김성래,김동억,김한영,이주헌,배희준,한문구,강동화,나정호,김종성 대한신경과학회 2013 Journal of Clinical Neurology Vol.9 No.4
Background and Purpose Intracranial atherosclerotic stenosis (ICAS) is considered as a major cause of stroke. The carotid intima-media thickness (CIMT), which accurately reflects the burden of generalized atherosclerosis, is also associated with stroke. The aim of this study was to determine the association between the CIMT and ICAS responses to medical treatment. Methods This study constituted part of the “Trial of cilostazol in symptomatic intracranial arterial stenosis”-2 that evaluated the ICAS response after randomized antiplatelet treatment. Magnetic resonance angiography and CIMT measurement were performed at baseline and after 7 months of treatment. CIMT was measured using semiautomated software, and was presented as maximum (CIMT-max) and average (CIMT-ave) values. The change in CIMT was compared relative to the ICAS response (i.e., progression, no-change, and regression). Ordinal logistic regression and analysis of covariance (ANCOVA) were used to analyze the association between the responses. Results Among the 101 enrolled patients, 85 underwent follow-up CIMT measurement. CIMT increased most in the ICAS progression group (CIMT-max: 0.09±0.23, CIMT-ave: 0.04±0.12), and to a lesser degree in the no-change group (CIMT-max: 0.02±0.16, CIMT-ave: 0.02±0.11), but decreased in patients with ICAS regression (CIMT-max: -0.04±0.11, CIMT-ave: -0.03±0.07; CIMT-max: p=0.010, CIMT-ave: p=0.015). Ordinal logistic regression analysis demonstrated that the change in CIMT-max was independently associated with the ICAS response (p=0.032). However, the ANCOVA revealed that the reverse was not true, in that the ICAS response was not independently associated with the change in CIMT after adjusting for confounding factors. Conclusions The ICAS response may be associated with the CIMT response to medical treatment.