• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.6
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• pp.158-163
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• 1996

In the conventional GaAs MESFET circuit simulation, the DC and transient simulation results are often failed due to the discontrinuities of the first and second order derivatives arising from the use of separate C-V models in linear, satruration, and transition regions. In this paper, we propose a unified capacitance model for linear, transition, and saturation regions by using a unified channel length modulation effect that is derived by extending the channel length modulation effect in the saturation region to the linear region. Calculated resutls from the proposed capacitance model agree well with 2-D device simulation resutls. Thus, the proposed model is expected to be useful in circuit simulation.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05b
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• pp.368-373
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• 1996

A simple set of the transition criterion of the condensation regimes and the heat transfer coefficients on the direct contact condensation of the core makeup tank is developed, and implemented in RELAP5/MOD3.1 The condensation regimes are divided into two regimes: supply limit and condensation limit. In mode]ing the transition criterion between two regimes, a large-eddy model developed by Theofanous is used, and the empirical coefficient of the present large-eddy model is close to that of the large-eddy model. It turns out that the modified code better predicts the experimental data, especially the injection flow rate and the water level trend than the original code does.

• Journal of Power System Engineering
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• v.9 no.4
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• pp.187-193
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• 2005

In this paper, we proposes a man-machine interface design for fault diagnosis system with inter-node search method in a Petri net model. First, complicated fault cases are modeled as the Petri net graph expressions. Next, to find out causes of the faults on which we focus, a Petri net model is analyzed using the backward reasoning of transition-invariance in the Petri net. In this step, the inter-node search method algorithm is applied to the Petri net model for reducing the range of sources in faults. Finally, the proposed method is applied to a fault diagnosis of a refrigeration system to confirm the validity of the proposed method.

• Proceedings of the Korea Water Resources Association Conference
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• 2004.05b
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• pp.1331-1334
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• 2004

Wet/Dry phenomena typically incorporate a number of complex flow mechanism. These include a momentum transfer and turbulent mixing caused by the delivery of water. However currently available one dimensional schemes applicable to wet/dry process cannot effectively simulate such process. Two dimensional finite element model, SU/PG, is used to simulate complex flow in this study. The Wetted Area Method in SU/PG allows elements to transition gradually between wet and dry states. The model is applicable to a straight river reach with irregular bathymetry. Wet/dry calculation using the wetted area method can simulate simple numerical test. The computed results of velocity vectors and water depth agree with those of observed. The methodology Presented in this study will contributed to two-dimensional wet/dry analysis in a river in this country.

• Proceeding of EDISON Challenge
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• 2016.03a
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• pp.368-372
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• 2016

In this paper, the physics-based analytical model of transition metal dichalcogenide (TMD)-based double-gate (DG) tunneling field-effect transistors (TFETs) is proposed. The proposed model is derived by using the two-dimensional (2-D) Landauer formula and the Wentzel-Kramers-Brillouin (WKB) approximation. For improving the accuracy, nonlinear and continuous lateral energy band profile is applied to the model. 2-D density of states (DOS) and two-band effective Hamiltonian for TMD materials are also used in order to consider the 2-D nature of TMD-based TFETs. The model is validated by using the tight-binding non-equilibrium Green's function (NEGF)-based quantum transport simulation in the case of monolayer molybdenum disulfide ($MoS_2$)-based TFETs.

• Water for future
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• v.27 no.2
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• pp.85-96
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• 1994

Numerical instability of Preissmann scheme is studied for unsteady flow analysis in a natural river. The solution strategies to overcome the instability problems are presented in this paper. The main causes of numerical instability of Preissmann scheme are transition flow, abrupt change in cross section, in-appropriate roughness coefficients, time step and distance step, rapidly rising hydrograph, dry bed and so on. Transition flow model is proposed for the analysis of the transition flow which changes from subcritical to supercritical or conversely. The subcritical and supercritical reaches are groped in the channel, then appropriate boundary conditions are introduced for each reach. The transition flow analysis produces stable solutions in calculating through the various transition conditions. Verification with an actual river system is necessary in the future.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.10
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• pp.915-920
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• 2013

Payload capacity and transition ability are essential for climbing robots to apply the robots to various applications such as inspection and exploration. This paper presents a new climbing robotic platform with multi-link structure of track-wheel modules to enhance payload capacity and transition ability, and its tracking controller design and experimental results. The compliances between track-wheel modules achieve stable internal and external transitions while the large adhesion area of the track-wheel module enhances the payload capacity of the robot. Kinematic model-based tracking controller is designed and implemented for autonomous internal transition, and the gains of the controller are optimized by experimental design. Experiments on the automatic internal transitions are performed and the results guarantee autonomous internal transition with little tracking error.

• Journal of Information Processing Systems
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• v.15 no.3
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• pp.570-592
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• 2019

The Event-B design pattern is an excellent way to quickly develop a formal model of the system. Researchers have proposed a number of Event-B design patterns, but they all lack formal behavior semantics. This makes the analysis, verification, and simulation of the behavior of the Event-B model very difficult, especially for the control-intensive systems. In this paper, we propose a novel method to transform the Event-B synchronous control flow design pattern into the labeled transition system (LTS) behavior model. Then we map the design pattern instantiation process of Event-B to the instantiation process of LTS model and get the LTS behavior semantic model of Event-B model of a multi-level complex control system. Finally, we verify the linear temporal logic behavior properties of the LTS model. The experimental results show that the analysis and simulation of system behavior become easier and the verification of the behavior properties of the system become convenient after the Event-B model is converted to the LTS model.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.3
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• pp.232-239
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• 2013

This paper proposes an improved stator flux estimator through ensuring conventional PLPF to act as a pure integrator for sensorless control of induction motors. Conventional PLPF uses the estimated synchronous speed as a cut-off frequency and has the gain and phase compensators. The gain and phase compensators are determined on the assumption that the estimated synchronous angular speed is coincident with the real speed. Therefore, if the synchronous angular speed is not same as the real speed, the gain and phase compensation will not be appropriate. To overcome the problem of conventional PLPF, this paper analyzes the relationship between the synchronous speed error and the phase lag error of the stator flux. Based on the analysis, this paper proposes the synchronous speed error compensation scheme. To achieve a start-up without speed sensor, the current model is used as the stator flux estimator at the standstill. When the motor starts up, the current model should be switched into the voltage model. So a stable transition between the voltage model and the current model is required. This paper proposes the simple transition method which determines the initial values of the voltage model and the current model at the transition moment. The validity of the proposed schemes is proved through the simulation results and the experimental results.

• The Korean Journal of Applied Statistics
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• v.27 no.2
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• pp.317-330
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• 2014

Bipolar disorder is a psychopathy characterized by manic and major depressive episodes. It is important to determine the degree of depression when treating patients with bipolar disorder because 810% of bipolar patients commit suicide during the periods in which they experience major depressive episodes. The Hamilton depression rating scale is most commonly used to estimate the degree of depression in a patient. This paper proposes using the Hamilton depression rating scale to estimate the effectiveness of patient treatment based on the linear mixed effects model and the transition model. Study subjects were recruited from the Seoul National University Bundang Hospital who scored 8 points or above in the Hamilton depression rating scale on their first medical examination. The linear mixed effects model and the transition model were fitted using the Hamilton depression rating scales measured at the baseline, six month, and twelve month follow-ups. Then, Hamilton depression rating scale at the twenty-four month follow-up was predicted using these models. The prediction models were then evaluated by comparing the observed and predicted Hamilton depression rating scales on the twenty-four month follow-up.