• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.4
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• pp.917-922
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• 2010

In this paper, a new temperature-insensitive CMOS dual-mode current reference for low-voltage low-power mixed-mode circuits is proposed. The temperature independent reference current is generated by summing a proportional to absolute temperature(PTAT) current and a complementary to absolute temperature(CTAT) current. The temperature insensitivity was achieved by the mobility and the other which is inversely proportional to mobility. As the results, the temperature dependency of output currents was measured to be $0.38{\mu}A/^{\circ}C$ and $0.39{\mu}A/^{\circ}C$, respectively. And also, the power dissipation is 0.84mW on 2V voltage supply. These results are verified by the $0.18{\mu}m$ n-well CMOS parameter.

• Journal of the Korean Solar Energy Society
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• v.35 no.1
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• pp.35-43
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• 2015

A numerical simulation on the wake flow of a wind turbine which is a scaled version of a multi-megawatt wind turbine has been performed. Two different inlet conditions of averaged wind speed including one below and one above the rated wind speed were used in the simulation. Steady-state pitch angles of the blade associated with the two averaged wind speeds were imposed for the simulation. The steady state analysis based on the Reynolds averaged Navier-Stokes equations with the method of frame motion were used for the simulation to find the torque of the rotor and the wake field behind the wind turbine. The simulation results were compared with the results obtained from the wind tunnel testing. From comparisons, it was found that the simulation results on the turbine power are pretty close to the experimental values. Also, the wake results were relatively close to the experimental results but there existed some discrepancy in the shape of velocity deficit. The reason for the discrepancy is considered due to the steady state solution with the frame motion method used in the simulation. However, the method is considered useful for solutions with much reduced calculation time and reasonably good accuracy compared to the transient analysis.

• Journal of Navigation and Port Research
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• v.45 no.6
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• pp.284-297
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• 2021

A simple kinematic model for the prediction of ship manoeuvres based on trial data is proposed in this study. The model consists of first order differential equations in surge, sway, and yaw directions which simulate the time series of each velocity component. Actually instead of sea trial data, dynamic model simulations are conducted with randomly varied control inputs such as propeller revolution rates and rudder angles. Based on learning of control inputs and velocity outputs of dynamic model simulations in sufficient time, kinematic model coefficients are optimized so that the kinematic model can be approximately reproduce the velocity outputs of dynamic model simulations with arbitrary control inputs. The resultant kinematic model is verified with new dynamic simulation sets.

• Korean Journal of Optics and Photonics
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• v.11 no.2
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• pp.97-101
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• 2000

We proposed and demonstrated a new scheme for subtracting the source excess noise from the output of the fiber-optic gyroscope. Unlike the previous methods, this scheme has an advantage of not requiring a delaying fiber for source noise detection and can be simply applied to fiber gyroscope operating at the proper frequency. By usmg this scheme. the proper frequency component of the source excess noise was subtracted from the gyroscope output. As a result, we obtained the reduction of noise by 12 dB (electrical) which was measured from the noise floor spectrum in the fiber gyroscope modulated at the proper frequency. We also obtarned !be random walk coefficient of thc gyro output reduced by a factor of 3.5. f 3.5.

• Proceedings of the KIPE Conference
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• 2006.06a
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• pp.342-344
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• 2006

전동기 구동시스템의 사양 결정과 설계를 위해서는 부하의 부하토크, 관성계수, 마찰계수 등의 정보에 의한 부하 모델링이 반드시 필요하다. 전동지게차 시스템의 모델링을 위해서는 차체의 중량과, 바퀴의 제원 등 제한적인 정보를 기초로 하여 번거로운 계산과정을 거쳐야 하지만 정확한 정보를 얻기에는 어려움이 따른다. RecurDyn은 기계시스템의 모델링과 시뮬레이션을 하는 3차원 해석이 가능한 Functionbay사에서 개발한 시뮬레이션 프로그램으로서 3D의 기계적인 형상을 작성하고, 물성을 입력하면 부하토크, 등가 관성계수, 마찰계수를 출력할 수 있어 전동기구동시스템의 시뮬레이션 프로그램인 Matlab/Simulink와 결합하여 시뮬레이션을 수행 할 경우 부하 모델링 없이 전체 구동시스템의 특성 시뮬레이션이 가능하다. 본 논문에서는 영구자석 동기전동기로 구동하는 전동지게차 시스템을 대상으로 RecurDyn 프로그램의 활용을 소개하고 Matlab/Simulink를 이용한 결함 시뮬레이션의 가능성을 보고자 한다.

• Proceeding of EDISON Challenge
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• 2015.03a
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• pp.590-593
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• 2015

항공기 운항 중에 가장 연료가 많이 소모될 때는 순간 고출력이 필요한 이륙 순간이다. 항공기가 이륙시 보다 적은 연료를 이용하여 효율적인 비행을 위해 고양력 장치를 사용하고 있다. 본 연구에서는 항공기가 이륙 시 사용되는 고양력 발생 장치 중 하나인 Slat을 이용하여 Slat의 각도 변화에 따라 가장 효율적인 공력특성을 찾아보았다. Slat의 각도를 $15^{\circ}$, $20^{\circ}$ $25^{\circ}$, $30^{\circ}$로 변화시켜 보면서 공력 특성 값들을 확인한 결과 Slat이 있는 경우 NACA2415만 있는 경우보다 양력계수가 좋아졌으나 Slat 뒷전의 와류에 의해 항력계수가 약간 증가 하는 모습을 보였다. 본 실험 case 중에서는 Slat 각도가 $30^{\circ}$일 때 Slat 뒷전의 와류가 사라져 가장 우수한 공력 특성을 보였다.

• Journal of the Korean Data and Information Science Society
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• v.28 no.5
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• pp.971-980
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• 2017

The varying coefficient regression model has gained lots of attention since it is capable to model dynamic changes of regression coefficients in many regression problems of science. In this paper we propose a varying coefficient regression model that effectively considers the errors on both input and response variables, which utilizes the kernel method in estimating the varying coefficient which is the unknown nonlinear function of smoothing variables. We provide a generalized cross validation method for choosing the hyper-parameters which affect the performance of the proposed model. The proposed method is evaluated through numerical studies.

• Progress in Medical Physics
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• v.22 no.2
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• pp.92-98
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• 2011

This study is to keep the accuracy and stability of the output dose evaluations for linear accelerator photon beams by using the air ionization chambers (TM31010, 0.125 cc, PTW) through the Task Group 51 protocol. The absorbed dose to water calibration factor $N_{dw}{^{Co-60}}$ was delivered from the air kerma calibration factor $N_k$ which was provided from manufacture through SSDL calibration for determination of output factor. The ionization chamber of TM31010 series was reviewed the calibration factor and other parameters for reduce the uncertainty within ${\pm}2%$ discrepancy and we found the supplied $N_{dw}{^{Co-60}}$ which was derived from Nk has shown a -2.8% uncertainty compare to that of PSDL. The authors provided the program to perform the output dosimetry with TG-51 protocol as it is composed same screen of TG-51 worksheets. The evaluated dose by determination of output factor delivered to postal TLD block for comparison the output dose to that of MDACC (RPC) in postal monitoring program. The results have shown the $1.001{\pm}0.013$ for 6 MV and $0.997{\pm}0.012$ discrepancy for 15 MV X rays for 5 years followed. This study shows the evaluated outputs for linear accelerate photon beams are very close to that of international output monitor with small discrepancy of ${\pm}1.3%$ with high reliability and showing the gradually stability after 2010.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.46 no.4
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• pp.42-49
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• 2009

This paper proposes a driving current control method for a back light unit (BLU), consisting of red, green, and blue (RGB) light-emitting diodes (LEDs), whereby an RGB optical sensor is used to check the output color stimulus variation to enable a time-stable color stimulus for light emission by the RGB LED BLU. First, to obtain the present color stimulus information of the RGB LED BLU, an RGB to XYZ transform matrix is derived to enable CIEXYZ values to be calculated for the RGB LED BLU from the output values of an RGB optical sensor. The elements of the RGB to XYZ transform matrix are polynomial coefficients resulting from a polynomial regression. Next, to obtain the proper duty control values for the current supplied to the RGB LEDs, an XYZ to Duty transform matrix is derived to calculate the duty control values for the RGB LEDs from the target CIEXYZ values. The data used to derive the XYZ to Duty transform matrix are the CIEXYZ values for the RGB LED BLU estimated from the output values of the RGB optical sensor and corresponding duty control values applied to the RGB LEDs for the present, first preceding, and second preceding sequential check points. With every fixed-interval check of the color stimulus of the RGB LED BLU, the XYZ to Duty transform matrix changes adaptively according to the present lighting condition of the RGB LED BLU, thereby allowing the RGB LED BLU to emit the target color stimulus in a time-stable format regardless of changes in the lighting condition of the RGB LEDs.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1968-1969
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• 2011

본 논문에서는 패턴 인식을 위한 다중 출력을 가지는 Interval Type-2 퍼지 집합을 이용한 퍼지 집합 기반 퍼지 뉴럴 네트워크를 소개한다. Interval Type-2 퍼지 집합 기반 퍼지 뉴럴 네트워크는 각 입력 변수에 따른 서로 분리된 입력 공간을 분할함으로서 네트워크 및 규칙을 구성한다. 규칙의 전반부는 퍼지 입력 공간을 개별적으로 분할하여 표현하고, 각 공간은 Interval Type-2 퍼지 집합으로 구성된다. 규칙의 후반부는 패턴 인식을 위한 다중 출력을 가지며 Interval 집합을 이용하여 다항식으로서 표현된다. 다항식의 계수인 연결가중치는 오류역 전파 알고리즘을 이용하여 학습한다. 또한 실수 코딩 유전자 알고리즘을 이용하여 제안된 네트워크를 최적화한다. 제안된 네트워크는 표준 모델로서 널리 사용되는 수치적인 예를 통하여 평가한다.