• IEIE Transactions on Smart Processing and Computing
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• 제2권2호
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• pp.77-85
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• 2013

this study examined hybrid Time of Arrival/Angle of Arrival (TOA/AOA) localization technique in a cellular network. Based on the linearized equations from the TOA and AOA measurements, the weighted least square (WLS) method is proposed to obtain the location estimation of a mobile station (MS) by analyzing the statistical properties of the error vector in Line of Sight (LOS) and Non-line of Sight (NLOS) environments, respectively. Moreover, the precise expression of the Cramer-Rao lower bound (CRLB) for hybrid TOA/AOA measurements in different LOS/NLOS conditions was derived when the LOS error is a Gaussian variable and the NLOS error is an exponential variable. The idea of cooperative localization is proposed based on the additional information from short-range communication among the MSs in fourth generation (4G) cellular networks. Therefore, the proposed hybrid TOA/AOA WLS method can be improved further with the cooperative scheme. The simulation results show that the hybrid TOA/AOA method has better performance than the TOA only method, particularly when the AOA measurements are accurate. Moreover, the performance of the hybrid TOA/AOA method can be improved further by the cooperative scheme.

• 한국정밀공학회지
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• 제33권7호
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• pp.565-570
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• 2016

This paper presents the characteristics related to needle insertion of a robotic device for the automated biopsy procedure. The automated biopsy device, a main component of the robotic needle insertion type intervention system, allows performance of the full biopsy procedure, except for anesthesia, without direct handling of a radiologist or a tele-operated control. In this study, the needle length parameters corresponding to various insertion depths and precision for needle insertion of the automated biopsy device, are discussed. There were two combinations of needle length parameters for appropriate needle insertion and motion capture-based measurement was performed; 0.156 mm error for the 90 mm length commanded insertion displacement was measured. The pre-defined goal is a maximum 1 mm error and thus our measured error is within the acceptable range. In the repeatability check, it was also shown that the device can implement a highly accurate insertion.

• 한국전자통신학회논문지
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• 제10권4호
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• pp.507-512
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• 2015

거리 측정정보를 사용하는 무선위치추정시스템에서 추정기법으로 반복기법기반 근사해를 주로 많이 사용하고 있으나 지역최소문제 및 계산량을 고려해 대안으로 선형 닫힌 형태의 해가 연구되어 왔다. 그러나 각 닫힌 형태의 해는 별도의 특성을 가진 오차요인을 갖고 있으며 이 문제로 인해 그 사용이 제한되기도 한다. 본 논문에서는 대표적인 두 닫힌 형태의 해를 융합하여 각 해가 갖는 오차요인을 서로 상쇄시키는 기법을 제안한다. 두 해를 융합하기 위한 가중치를 각 오차요인이 갖는 오차 특성 기반 퍼지 기법으로 결정하는 방법을 사용한다. 제안된 기법의 성능은 시뮬레이션 기반으로 검증한다.

• 대한기계학회논문집A
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• 제38권11호
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• pp.1299-1307
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• 2014

본 논문은 감도가 낮고 정밀한 족적센서의 특성에 대하여 연구한 논문이다. 이를 위하여 센서의 형상 변수 조절 범위를 낮게 선정하였다. 센서의 감도 해석으로 2차원 해석 모델을 사용할 경우 실험값과 비교한 결과 오차가 많이 나는 것을 확인하였다. 따라서 이 오차를 개선하기 위하여 3D 기반의 새로운 해석 모델을 적용시켜 재해석 하였고, 이를 실험값과 비교한 결과 오차가 개선되었음을 확인할 수 있었다.

• Near Infrared Analysis
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• 제1권1호
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• pp.1-7
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• 2000

A convenient algorithm for optimizing wavelength selection in multiple linear regression (MLR) has been developed. MOP (MLP Optimization Program) has been developed to test all possible MLR calibration models in a given spectral range and finally find an optimal MLR model with external validation capability. MOP generates all calibration models from all possible combinations of wavelength, and simultaneously calculates SEC (Standard Error of Calibration) and SEV (Standard Error of Validation) by predicting samples in a validation data set. Finally, with determined SEC and SEV, it calculates another parameter called SAD (Sum of SEC, SEV, and Absolute Difference between SEC and SEV: sum(SEC+SEV+Abs(SEC-SEV)). SAD is an useful parameter to find an optimal calibration model without over-fitting by simultaneously evaluating SEC, SEV, and difference of error between calibration and validation. The calibration model corresponding to the smallest SAD value is chosen as an optimum because the errors in both calibration and validation are minimal as well as similar in scale. To evaluate the capability of MOP, the determination of benzene content in unleaded gasoline has been examined. MOP successfully found the optimal calibration model and showed the better calibration and independent prediction performance compared to conventional MLR calibration.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.600-603
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• 2009

We compared relative importance of thermal conductivity and initial ground temperature in designing borehole heat exchanger network and also we test accuracy of ground temperature estimation in thermal response test using a proven 3-D T-H modeler. The effect of error in estimating ground temperature on calculated total length of borehole heat exchanger was more than 3 times larger than the case of thermal conductivity in maximum 20% error range. Considering 10% of error in estimating thermal conductivity is generally acceptable, we have to define the initial ground temperature within 5% confidence level. Utilizing the mean annual ground surface temperature and the geothermal gradient map compiled so far can be a economic way of estimating ground temperature with some caution. When performing thermal response test for estimating ground temperature as well as measuring thermal conductivity, minimum 100 minutes of ambient circulation is required, which should be even more in case of very cold and hot seasons.

• 제어로봇시스템학회논문지
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• 제17권9호
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• pp.941-946
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• 2011

The Loran-C, a radio navigation system based on TDOA measurements is enhanced to eLoran using TOA measurements instead of TDOA measurements. Many error factors such as PF, SF, ASF, clock errors and unknown biases are included in eLoran TOA measurements. Because these error factors can cause failure in eLoran navigation algorithm, these errors must be compensated for high accuracy eLoran navigation results. Compensation of ASF and unknown biases are difficult to calculate, while the others such as PF and SF are relatively easy to eliminate. In order to compensate all errors in eLoran TOA measurements, a simple GPS aided bias compensation method is suggested in this paper. This method calculates the bias as the difference of TOA measurement and the range between eLoran transmitters and the receiver whose position is determined using GPS. The real data measured in Europe are used for verification of suggested method and navigation algorithm.

• 전기전자학회논문지
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• 제18권1호
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• pp.37-44
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• 2014

In this paper we present an LDO based on an error amplifier. The designed error amplifier has a gain of 89.93dB at low frequencies. This amplifier's Bandwidth is 50.8MHz and its phase margin is $59.2^{\circ}C$. Also we proposed a BGR. This BGR has a low output variation with temperature and its PSRR at 1 KHz is -71.5dB. For a temperature variation from $-40^{\circ}C$ to $125^{\circ}C$ we have just 9.4mV variation in 3.3V LDO output. Also it is stable for a wide range of output load currents [0-200mA] and a $1{\mu}F$ output capacitor and its line regulation and especially load regulation is very small comparing other papers. The PSRR of proposed LDO is -61.16dB at 1 KHz. Also we designed it for several output voltages by using a ladder of resistors, transmission gates and a decoder. Low power consumption is the other superiority of this LDO which is just 1.55mW in full load. The circuit was designed in $0.35{\mu}m$ CMOS process.

• KIEAE Journal
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• 제4권1호
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• pp.11-20
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• 2004

Innovative daylighting systems in buildings in various climatic zones around the world have been developed under the IEA SHC Task21. The performance assessment were obtained by monitoring the most systems using full-scale test model rooms or actual buildings under real sky conditions. This study aims to analyze the configuration and monitoring system of the nine Mock-up models of the IEA SHC Task21 comparatively. For the purpose, the geometry of the test rooms (length, width, height, window area, glazed area and occupied), reflectance of walls, floor and ceiling, transmittance of glazing (transmittance for hemispherical irradiation, normal irradiation and U-value) were compared. And equipment for measurement (manufacturer, range, calibration, maximum calibration error, cosine response error, fatigue error), and data acquisition system (manufacturer, type, number of differential analogue input channels, A/D converter resolution in bits, data acquisition software) were also analyzed comparatively. Some findings of these experimental methodology of standard monitoring have been proven to be a valuable one for future assessment of advanced daylighting systems in our country.

• 동력기계공학회지
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• 제14권2호
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• pp.34-39
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• 2010

Recently, technical trend for machine tools is focused on enhancement of speed and accuracy. High speedy processing causes thermal and structural deformation of objects from the machine tools. Water cooler has to be applied to machine tools to reduce the thermal negative influence with accurate temperature controlling system. Existing On-Off control type can't control temperature accurately because compressor is operated and stopped repeatedly and causes increment of power consumption and decrement of the expected life of compressor. The goal of this study is to minimize temperature error in steady state. In addition, control period of an electronic expansion valve were considered to increment of lifetime of the machine tools and quality of product with a water cooler. PI controller is designed using type of hot-gas bypass for precise control of temperature. Gain of PI is decided easily by method of critical oscillation response, excellent performance of control is shown with 4.24% overshoot and ${\pm}0.2^{\circ}C$error of steady state. Also, error range of temperature is controlled within $0.2^{\circ}C$although disturbance occurs.