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로소나이트(Lawsonite)의 압력에 따른 등방성 압축거동 연구
임준혁,이용재,Im, Junhyuck,Lee, Yongjae 대한자원환경지질학회 2016 자원환경지질 Vol.49 No.1
자연산 로소나이트(Ca-Lawsonite, $CaAl_2Si_2O_7(OH)_2{\cdot}H_2O$) 분말의 압력증가에 따른 변화와 구조적 특성을 소형 압력 발생장치인 다이아몬드 앤빌셀과 실시간 싱크로트론 X-선 회절실험을 통하여 확인하였다. 본 연구에서 시료에 적용한 압력은 1 기압에서 8 GPa 까지였으며 메탄올, 에탄올, 물의 혼합 용액을 압력 매개체로 하여 상온조건에서 실험하였고, 특이한 상전이나 압력하 부피변화의 이상현상은 발견되지 않은 가역적 압축특성을 관찰하였다. 최고압력까지 로소나이트는 결정성을 잃지 않는 것으로 확인되었고 압력증가에 따른 체적감소를 통해 체적탄성률($B_0$)을 계산해 본 결과 146(6) GPa로 도출되었다. 체적탄성률과 함께 계산된 선형압축률은 a-, b-, c-축에서 각각 0.0022, 0.0024, $0.0020GPa^{-1}$로 압력에 의한 부피감소는 대체적으로 3축이 같은 비율로 감소하는 것을 확인하였다. Powder samples of natural lawsonite (Ca-lawsonite, $CaAl_2Si_2O_7(OH)_2{\cdot}H_2O$) was studied structurally up to 8 GPa at room temperature using monochromatic synchrotron X-ray powder diffraction and a diamond anvil cell (DAC) with a methanol : ethanol : water (16 : 3 : 1 by volume) mixture solution as a penetrating pressure transmitting medium (PTM). Upon pressure increase, lawsonite does not show any apparent pressure induced expansion (PIE) or phase transition. Pressure-volume data were fitted to a second-order Birch-Murnaghan equation of state using a fixed pressure derivative of 4 leading to a bulk modulus ($B_0$) of 146(6) GPa. This compression is further characterized to be isotropic with calculated linear compressibilities of ${\beta}^a=0.0022GPa^{-1}$, ${\beta}^b=0.0024GPa^{-1}$, and ${\beta}^c=0.0020GPa^{-1}$.
터널 내 소화기 표시등 검출을 이용한 3D LIDAR 기반 차량정밀측위
임준혁(Jun-Hyuck Im),임성혁(Sung-Hyuck Im),지규인(Gyu-In Jee) 제어로봇시스템학회 2018 제어·로봇·시스템학회 논문지 Vol.24 No.8
Vehicle localization is essential for autonomous driving. Basically, the position information of the autonomous vehicle is obtained from the Global Positioning System (GPS). More accurate localization can be performed by using maps and various sensors that are mounted on the autonomous vehicle. GPS receivers cannot receive GPS signals in tunnels, so dead reckoning (DR) is used for vehicle localization. However, the error from DR continuously accumulates. Therefore, this error must be corrected by using vehicle-mounted sensors, such as Light Detection and Ranging (LIDAR) and cameras. Tunnels have very specific shape information, which is usually an ellipse, and several emergency facilities exist in tunnels. Some facilities are separated from the tunnel wall, which can be detected by using 3D LIDAR. In particular, fire extinguisher lamps are periodically installed at intervals of 50 m, which can serve as good landmarks. First, the point cloud for the tunnel wall must be removed to effectively detect fire extinguisher lamps. This process can be easily conducted by using shape information. After this removal, we detect the fire extinguisher lamps. In this paper, we propose a 3D LIDAR-based vehicle-localization method that uses ellipse parameters and fire extinguisher lamps in road tunnels. These experiments are conducted at the Maseong tunnel in South Korea. The experimental results show that the root mean square (RMS) position errors in the lateral and longitudinal directions were 0.06 m and 0.23 m, respectively, exhibiting precise localization accuracy.
임준혁(Jun-Hyuk Im),박준규(Jun-Kyu Park),이승태(Seung-Tae Lee),정채림(Chae-Lim Jeong),허진(Jin Hur) 대한전기학회 2018 전기학회논문지 Vol.67 No.4
This study proposes the mitigation method of shaft voltage by varying the parasitic capacitance. First, the shaft voltage explained. Second, the parasitic capacitances causing shaft voltage are analyzed respect to geometry of motor and windings. Then, the equivalent circuit is established to obtain the shaft voltage and output torque characteristic and develope appropriate motor structure. Finally, simulation and experiment are conducted to verify that modified motor suppress the shaft voltage. This novel model does not require additional hardware.
축 전압 저감 구조 모터의 축 전압 주파수 응답 특성 분석
임준혁(Jun-Hyuk Im),박준규(Jun-Kyu Park),허진(Jin Hur) 대한전기학회 2020 전기학회논문지 Vol.69 No.3
In PWM based inverter driven motor, shaft voltages usually cause bearing fault. Many methods to mitigate the shaft voltages have been proposed. Since the high frequency components are hazardous to bearing, it is necessary to analyze the frequency responses for each shaft voltage mitigation method. In this paper, frequency responses of three shaft voltage mitigation methods are analyzed and compared. First, equivalent circuit models regarding geometric shape of motor are presented. Second, modified models of each equivalent circuit containing shaft voltage reduction methods are proposed. Finally, the comparison of the frequency responses for each shaft voltage mitigation method is presented.
임준혁(Jun-Hyuck Im),임성혁(Sung-Hyuck Im),김우현(Woo-Hyun Kim),지규인(Gyu-In Jee) 제어로봇시스템학회 2010 제어·로봇·시스템학회 논문지 Vol.16 No.2
With GPS being the primary navigation system, Loran use is in steep decline. However, according to the final report of vulnerability assessment of the transportation infrastructure relying on the global positioning system prepared by the John A. Volpe National Transportation Systems Center, there are current attempts to enhance and re-popularize Loran as a GPS backup system through the characteristic of the ground based low frequency navigation system. To advance the Loran system such as Loran-C modernization and eLoran development, research is definitely needed in the field of Loran-C receiver signal processing as well as Loran-C signal design and the technology of a receiver. We have developed a set of Matlab tools, which implement a software Loran-C receiver that performs the receiver’s position determination through the following procedure. The procedure consists of receiving the Loran-C signal, cycle selection, calculation of the TDOA and range, and receiver’s position determination through the Least Square Method. We experiences the effect of an incorrect cycle selection and various error factors (ECD, ASF, sky wave, CRI, etc.) from the result of the Loran-C signal processing. It is apparent that researches which focus on the elimination and mitigation of various error factors need to be investigated on a software Loran-C receiver. These aspects will be explored in further work through the method such as PLL and Kalman filtering.