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세포-신경계-혈류역학 시스템 통합모델에 의한 심장역학 분석
전형민(Hyung Min Jun),심은보(Eun Bo Shim) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
A model of the cardiovascular system coupling cell, hemodynamics and autonomic nervecontrol function is proposed for analyzing heart mechanics. We developed a comprehensive cardiovascular model with multi-physics and multi-scale characteristics that simulates the physiological events from membrane excitation of a cardiac cell to contraction of the human heart and systemic blood circulation and ultimately to autonomic nerve control. Using this model, we delineatedthe cellular mechanism of heart contractility mediated by nerve control function. To verify the integrated method, we simulated a 10% hemorrhage, which involves cardiac cell mechanics, circulatory hemodynamics, and nerve control function. The computed and experimental results were compared. Using this methodology, the state of cardiac contractility, influenced by diverse properties such as the afterload and nerve control systems, is easily assessed in an integrated manner.
노화에 따른 동맥벽 탄성도 저하가 심실세포의 Cross-bridge 동역학에 미치는 영향에 대한 수치적 연구
전형민(Hyung Min Jun),심은보(Eun Bo Shim) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.11
본 연구에서는 심장의 세포 변화에서부터 혈류 순환의 시스템 변화까지 일련의 과정을 시뮬레이션 할 수 있는 통합모델을 개발하였다. 본 통합 모델을 이용하여 대동맥의 탄성도 변화 따른 Pulse Wave Velocity를 추정하였으며 심근의 수축 Mechanics의 변화를 시뮬레이션 하였다. 심장은 단순한 구 형상으로 모델링 되었다. 특히 동맥순환의 특성인 Wave propagation 과 Wave deflection의 현상을 모델링하기 위해 기존 모델에서 사용된 동맥계 순환 모델을 수정하였다. 즉 기존의 동맥 모델을 1차원의 운동방정식과 연속방정식을 기반으로 하는 Distributed arterial model로 대체하였다. Distributed arterial model은 혈액의 점성에 의한 에너지 손실, 혈관의 점탄성 효과 그리고 분지 되는 혈관에서의 에너지 손실을 포함하는 정교한 동맥 순환 모델이다. 정교한 동맥계 순환 모델의 동맥 탄성도 값을 조절함으로써 탄성도 변화에 대한 PWV를 계산 할 수 있었다. 이러한 수치적 방법을 사용하여 노화에 따른 동맥벽 탄성도의 저하가 심근세포의 Cross-bridge 동역학에 미치는 영향을 시뮬레이션 하였다.
전형민(Hyung Min Jun),김현우(Hyunwoo Kim),여재익(Jai-ick Yoh) 한국추진공학회 2018 한국추진공학회 학술대회논문집 Vol.2018 No.5
연소실 내부의 연료 분포를 실시간으로 측정하는 목적을 가진 소형화 장비인 LIBS plug가 개발 및 제작 되었다. LIBS plug는 레이저 유도 플라즈마 분광분석법 (Laser-induced breakdown spectroscopy : LIBS)를 응용한 장비로, 기존의 LIBS 결과인 전체 스펙트럼에서 당량비와 깊게 관여하는 두 개의 파장(H: 656.3 nm, O: 777 nm)만을 선정하여 측정할 수 있도록 하였다. 렌즈와 밴드패스 필터, 포토다이오드로 구성된 본 장비로 수집한 결과에 대한 분석이 이루어졌으며, 액체(가솔린)와 기체(LPG) 연료와 공기의 혼합물에서의 당량비 측정이 이루어졌다. LIBS plug, a simplified laser-induced breakdown spectroscopy(LIBS) device with the purpose of measuring the fuel distribution inside the combustion chamber was developed and manufactured. LIBS plug received only two wavelengths (H:656.3 nm, O: 777 nm) that are deeply related to the equivalence ratio in the overall spectrum. Calibration curve between the LIBS plug’s signal and equivalence ratio was constructed and fuel distribution of gasoline-air mixture and LPG-air mixture was measured with the LIBS plug.
스케일 법칙을 기반으로 하는 에너지-심혈관 시스템 모델의 개발
전형민(Jun Hyung Min),심은보(Shim Eun Bo) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
In this study, we developed a combined model of circulation and energy systems in human body. Cardiovascular system is approximated by a lumped parametric model. The hemodynamics of vessels can be represented by the relationship between blood pressure and blood flow rate in the cardiovascular system. For energy system of human body, we derive a mathematical model of body-mass regulation integrating the metabolic scaling law, temperature homeostasis, and energy conservation. In the energy system model, body mass change is determined from the difference between energy intake and totalenergy expenditure. We simulate an obesity case by assuming a gradual decrease in heat production rate. The computational results show that body weight increase is induced by a long term adaptation due to the decrease in body heat production, which eventually induces a long term increase of arterial blood pressure.
심근세포를 기반으로 한 심혈관 혈류역학 시스템 모델의 개발
전형민(Jun Hyung Min),심은보(Shim Eun Bo) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11
In this paper we developed an integrated model of cardiovascular system for the analysis of circulatory hemodynamics. Excitation contraction coupling in cardiac cells are implemented by the membrane potential (excitation) and cross-bridge dynamics models. By combining this ventricular cell model with a lumped circulation model, we examined how blood pressure dynamics in the atrium, ventricle and aorta are related to the cellular processes. The time courses of the hemodynamic properties, as well as the volume-pressure trajectory of the left ventricle, were well reproduced. Our multi-scale cardiovascular model, which covers from cardiac cells to the circulatory system, simulates the typical characteristics of heart mechanics, such as the pressure-volume relationship, stroke volume, and the effect of the increased maximum free calcium concentration on cardiovascular hemodynamics.
전형민(Hyung Min Jun),심은보(Eun Bo Shim),최성욱(Sung Uk Choi) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
Respiratory quotient (RQ) refers to the ratio of the volume of carbon dioxides versus the volume of oxygen that human body breathes in. However, measuring the volumes of expiratory oxygen and inspiratory carbon dioxides poses many difficulties. Therefore, we developed a new RQ measuring device that used an algorithm that obtained the respiratory quotient by the measurement of concentrations of oxygen and carbon dioxide during expiration independently from their expiratory and inspiratory volumes. A mouthpiece of the device is composed of a chamber and three valves that were used to obtain the concentrations of oxygen and carbon dioxide during expiration. It was designed in such a way that only expiratory air can enter the expiration chamber in which oxygen and carbon dioxide sensors are placed. The inlet and outlet valves of the chamber isolate external air. This study analyzed human metabolism on the basis of the measured respiratory quotient, weight, and height data.
후부하 증가에 의한 심근비대 시 심근세포의 역학적 변화에 대한 가설
심은보(Eun Bo Shim),전형민(Hyung Min Jun) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
The intrinsic increase of heart contractility induced by afterload increase is important in cardiac mechanics. However, its cellular mechanism is not well explained. In this study, we try to delineate the cellullar mechanics by using the model coupling the cardiovascular system dynamics with the cellular excitation-contraction. The ventricular pressure and cross-bridge generated force were elevated by the afterload increase and the change of cross-bridge elongation was reduced during contraction when the afterload increased. This phenomenon is believed to be originated from the force-velocity relationship of cardiac cell.
심은보(Eun Bo Shim),전형민(Hyung Min Jun) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
In this study, we developed an arterial network model to simulate the arterial pressures and PWV (pulse wave velocity) in arteries. The model is based upon a numerical solution of the one-dimensional equations of motion in a geometrically accurate branching network of the arterial system including energy losses at bifurcations. For validation of the present method, the computed pressure waves are compared with the existing experimental observations. The pulse wave velocities for normal and stiffened arteries are obtained to assess the effect of arterial wall stiffness. Variations of systole and diastole blood pressures according to arterial wall stiffness in aorta are also delineated. We simulate that a gradual increase of wall stiffness in arteries can induce ventricular hypertrophy.