• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1997년도 춘계학술대회
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• pp.150-155
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• 1997

Modelling and Simulation of the activation process for the myocardium is meaningful to understand special excitation conduction system in the heart and to study cardiac functions. In this paper, we propose two dimensional cellular automata model for the activation process of the myocardium and simulated by means of discrete time and discrete event algorithm. In the model, cells are classified into anatomically similar characteristic parts of heart; SA node, internodal tracks, AV node, His bundle, bundle branch and four layers of the ventricular muscle, each of which has a set of cells with preassigned properties, that is, activation time, refractory duration and conduction time between neighbor cell. Each cell in this model has state variables to represent the state of the cell and has some simple state transition rules to change values of state variables executed by state transition function. Simulation results are as follows. First, simulation of the normal and abnormal activation process for the myocardium has been done with discrete time and discrete event formalism. Next, we show that the simulation results of discrete time and discrete event cell space model is the same. Finally, we compare the simulation time of discrete event myocardium model with discrete time myocardium models and show that the discrete event myocardium model spends much less simulation time than discrete time myocardium model and conclude the discrete event simulation method Is excellent in the simulation time aspect if the interval deviation of event time is large.

• 한국재료학회지
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• 제10권9호
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• pp.593-600
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• 2000

본 연구에서는 도핑하지 않은 다이아몬드 박막에서의 전류전도 경로를 체계적으로 규명하고 다이아몬드 박막의 전도기구에 대해 조사하였다. 도핑되지 않은 다결정 다이아몬드 박막에서 두께와 측정방향에 따른 교류 임피던스법에 의해 측정된 저향값이 기존의 표면전도 모델과는 일치하지 안니하였다. 다이아몬드 박막에 구리를 전기도금한 결과 구리는 결정립계에만 불연속적으로 도금되었고 다이아몬드 박막 위에 은을 증착한 후 전지에칭을 한 결과 결정립계가 우선 에칭이 되어 전류가 결정립계를 통하여 흐름을 확인하였다. 또, 리본형 다이아몬드 박막의 표면을 절연층으로 형성시킨 후 박막 내부의 결정립계를 통하여 전류가 흘러 전기도금이 되는 것으로부터 다결정 다이아몬드 박막의 주요 전기전도 경로는 결정립계임을 확인하였다. 높은 전기전도도를 보여주는 다이아몬드 박막은 전도 활성화 에너지가 45meV 정도이었고 dangling bond 밀도는 낮았다. 그러나 산소 열처리나 수소플라즈마처리가 Si passivation 이론과는 반대로 dangling bond 밀도를 증가시키면서 전기전도성을 떨어뜨렸다. 이 결과들과 표면의 탄소화학결합을 연결시켜 높은 전도성을 야기시키는 결합은 H-C-C-H 결합임을 추론하였다.

• Journal of Acupuncture Research
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• 제30권4호
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• pp.125-138
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• 2013

Objectives : This study aimed to investigate temperature characteristics by heat transfer type of therapeutic modalities. Methods : We selected heating and cooling modalities that are frequently used in clinical by heat transfer type: conduction, convection, radiation, and conversion. We used ham as tissue model, and applied the modalities for 30 minutes. We measured real-time changed temperature($^{\circ}C$) of the surface, 2, 4, 6, 8, 10, 12, and 14 mm depth. Results : 1. In conduction-using hot pack, ice pack, and CryoStamp heating-cooling combination therapy unit($40^{\circ}C/{\sim}15^{\circ}C$), the surface temperature sharply rose close to equilibrium in first 5 minutes. 2. In convection-using smokeless moxa, temperature slowly rose to the maximum at 25-minute elapsed time. But in another convection-using CRAiS cryotherapy device, result was similar to that of conduction. 3. In radiation-using infrared lamp, result was similar to that of conduction, but not reached equilibrium during applying time. 4. In conversion-using ultrasound device, temperature was the highest at 6 mm depth, and not reached equilibrium during applying time. Conclusions : We could comprehend temperature characteristics and proper use of modalities by heat transfer type. It would be necessary to consider in vivo physical conditions in further studies.

• KSTLE International Journal
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• 제1권1호
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• pp.63-68
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• 2000

Angular contact ball bearings are mainly used in the spindle, which requires high speed and stiffness. The heat generation is studied by experiments and simulations using a pair of angular contact ball bearings. The temperature variation of inner and outer races and the temperature increment distribution are measured by using thermocouples for the rotational speed, preload, viscosity of lubricant. The measured values from experiments are used to estimate the heat conduction rate. The method of oil-air lubrication is used for the experiment. The amount of conduction heat transfer to the test spindle and the convection heat transfer coefficients long the spindle are computed by using inverse method with temperature increment distribution. Total heat generation rate is estimated with the heat partition rate which is calculated from temperatures of inner and outer races. In addition, the empirical factor of oil-air lubrication method for Palmgren's heat generation model is suggested. The empirical friction coefficients, which are obtained from the experiments, depend on the preload condition, and can give us more accurate estimation of the heat generation in ball bearings.

• KSTLE International Journal
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• 제2권2호
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• pp.142-145
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• 2001

The electrorheology of the chitosan adipnate suspension in silicone oil was investigated. Chitosan adipnate suspension showed a typical ER response (Bingham flow behavior) upon application of an electric field. The shear stress for the chitosan adipnate suspension exhibited a linear dependence on the volume fraction of particles and an electric field power of 1.88. The experimental results for the chitosan adipnate suspension correlated with the conduction models and this suspension was found to be an anhydrous ER fluid.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.592-594
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• 1998

In order to analysis high frequency interference conduction in transformer, this paper constructs a equivalent network based on P.I. Fergested transformers physical model. A method of calculating self and mutual leakage inductance of windings sections is presented and a calculating example is given.

• Multiscale and Multiphysics Mechanics
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• 제1권2호
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• pp.171-188
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• 2016

Gradient enhanced theories of crystal plasticity enjoy great research interest. The focus of this work is on thermodynamically consistent modeling of grain size dependent hardening effects. In this contribution, we develop a model framework for damage coupled to gradient enhanced crystal thermoplasticity. The damage initiation is directly linked to the accumulated plastic slip. The theoretical setting is that of finite strains. Numerical results on single-crystalline metal showing the development of damage conclude the paper.

• Nuclear Engineering and Technology
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• 제41권7호
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• pp.885-892
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• 2009

This manuscript will discuss a numerical method where the six equations of two-phase flow, the solid heat conduction equations, and the two equations that describe neutron diffusion and precursor concentration are solved together in a tightly coupled, nonlinear fashion for a simplified model of a nuclear reactor core. This approach has two important advantages. The first advantage is a higher level of accuracy. Because the equations are solved together in a single nonlinear system, the solution is more accurate than the traditional "operator split" approach where the two-phase flow equations are solved first, the heat conduction is solved second and the neutron diffusion is solved third, limiting the temporal accuracy to $1^{st}$ order because the nonlinear coupling between the physics is handled explicitly. The second advantage of the method described in this manuscript is that the time step control in the fully implicit system can be based on the timescale of the solution rather than a stability-based time step restriction like the material Courant limit required of operator-split methods. In this work, a pilot code was used which employs this tightly coupled, fully implicit method to simulate a reactor core. Results are presented from a simulated control rod movement which show $2^{nd}$ order accuracy in time. Also described in this paper is a simulated rod ejection demonstrating how the fastest timescale of the problem can change between the state variables of neutronics, conduction and two-phase flow during the course of a transient.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권8호
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• pp.404-410
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• 2006

Toward the practical applications, on operation of conduction-cooled HTS SMES at temperatures well below 40[K] should be investigated, in order to take advantage of a greater critical current density of HTS and considerably reduce the size and weight of the system. In order to take advantage of a greater critical current density of high temperature superconducting (HTS) and considerably reduce the size and weight of the system, conduction-cooled HTS superconducting magnetic energy storage (SMES) at temperatures well below 40[K] should be investigated. This work focuses on the breakdown and flashover phenomenology of dielectrics exposed in air and/or vacuum for temperatures ranging from room temperature to cryogenic temperature. Firstly, we summarize the insulation factors of the magnet for the conduction cooled HTS SMES. And Secondly a surface flashover as well as volume breakdown in air and/or vacuum with two kind insulators has been investigated. Finally, we will discuss applications for the HTS SMES including aging studies on model coils exposed in vacuum at cryogenic temperature. The commercial application of many conduction-cooled HTS magnets, however, requires refrigeration at temperatures below 40[K], in order to take advantage of a greater critical current density of HTS and reduce considerably the size and weight of the system. The magnet is driven in vacuum condition. The need to reduce the size and weight of the system has led to the consideration of the vacuum as insulating media. We are studying on the insulation factors of the magnet for HTS SMES. And we experiment the spacer configure effect in the dielectric flashover characteristics. From the results, we confirm that our research established basic information in the insulation design of the magnet.

• 설비공학논문집
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• 제7권2호
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• pp.266-275
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• 1995

A numerical investigation on the conduction-natural convection-surface radiation conjugate heat transfer in the enclosure having substrate and chips has been performed. A 2-dimensional simulation model is developed by considering heat transfer by conduction, convection and radiation. The solutions to the equation of radiative transfer are obtained by the discrete ordinates method using S-4 quadrature. The effects of Rayleigh number and the substrate-fluid thermal conductivity ratio on the cooling of chip are analyzed. The result shows that radiation is the dominant heat transfer mode in the enclosure.