• 한국해양공학회지
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• 제25권6호
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• pp.1-8
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• 2011

This paper describes a new method for a digital gas metal arc welding (GMAW) system. The GMAW system is an arc welding process that incorporates the GMAW power source (PS-GMAW) with a wire feed unit (WFU). The PS-GMAW requires an electric power of constant voltage. A constant magnitude is maintained for the arc current by controlling the wire-feed speed of the WFU. A mathematical model is derived, and a self-tuning fuzzy proportional-integral-derivative (PID) controller is designed and applied to control the welding current. The electrode wire feeding mechanism with this controller is driven by a DC motor, which can compensate for both the molten part of the electrode and undesirable fluctuations in the arc length during the welding process. By accurately maintaining the output welding current and welding voltage at constant values during the welding process, excellent welding results can be obtained. Simulation and experimental results are shown to prove the effectiveness of the proposed controller.

• 대한인간공학회지
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• 제34권2호
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• pp.85-101
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• 2015

Objective: The purpose of this study was to develop and evaluate smart secondary controls using iPad for the drivers with physical disabilities in the driving simulator. Background: The physically disabled drivers face problems in the operation of secondary control devices that accept a control input from a driver for the purpose of operating the subsystems of a motor vehicle. Many of conventional secondary controls consist of small knobs or switches that physically disabled drivers have difficulties in grasping, pulling or twisting. Therefore, their use while driving might increase distraction and workload because of longer operation time. Method: We examined the operation time of conventional and smart secondary controls, such as hazard warning, turn signal, window, windshield wiper, headlights, automatic transmission and horn. The hardware of smart secondary control system was composed of iPad, wireless router, digital input/output module and relay switch. We used the STISim Drive3 software for driving test, customized Labview and Xcode programs for interface control of smart secondary system. Nine subjects were involved in the study for measuring operation time of secondary controls. Results: When the driver was in the stationary condition, the average operation time of smart secondary devices decreased 32.5% in the normal subjects (p <0.01), 47.4% in the subjects with left hemiplegic disabilities (p <0.01) and 38.8% in the subjects with right hemiplegic disabilities (p <0.01) compared with conventional secondary devices. When the driver was driving for the test in the simulator, the average operation time of smart secondary devices decreased 36.1% in the normal subjects (p <0.01), 41.7% in the subjects with left hemiplegic disabilities (p <0.01) and 34.1% in the subjects with right hemiplegic disabilities (p <0.01) compared with conventional secondary devices. Conclusion: The smart secondary devices using iPad for people with hemiplegic disabilities showed significant reduction of operation time compared with conventional secondary controls. Application: This study can be used to design secondary controls for adaptive vehicles and to improve the quality of life of the people with disabilities.

• 한국광학회지
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• 제14권1호
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• pp.58-64
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• 2003

대용량 홀로그램 정보저장장치를 현재의 CD-ROM과 같이 디스크 형으로 구현하는데 있어서, 저장된 데이터를 정확하게 읽어내기 위한 픽업 모듈의 서보 컨트롤은 매우 중요하다 디스크 및 회전 모터의 요동에서 오는 기계적 오차를 보정하기 위해, 데이터 재생 시 광축상에 한 장의 평판유리를 사용하는 새로운 서보 컨트롤 방식을 제안하였다. 평판유리를 $\pm$$10^{\circ}$이내에서 회전시킴으로써, $\pm$200 $\mu\textrm{m}$ 정도의 오차범위를 $\pm$150 $\mu\textrm{m}$ 이내로 컨트롤하여 재생오차를 92.5% 이상 줄일 수 있었다.

• 한국산학기술학회논문지
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• 제14권4호
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• pp.1555-1560
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• 2013

칼럼 타입의 전동조향장치(MDPS) 시스템은 차량 안전성과 연료 효율 향상을 보장하기에 승용차에 보편적으로 장착하고 있다. 시스템 해석과 제어기 개발을 위해서는 보통 Mechanical Simulation사에서 제작한 CarSim 프로그램과 매트랩 시뮬링크의 두 프로그램을 이용하여 제어 알고리즘과 차량 모델이 결합되어 하나의 시스템처럼 동시에 동작하도록 시뮬레이션을 수행한다. 매트랩 시뮬링크의 MDPS 제어 시스템과 완전 차량 모델의 동시시뮬레이션 기술개발에 대한 구체적이 방법이 소개된 적이 없기에 본 연구에서 상세히 소개하기로 한다. 본 연구에서는 사인 파형의 조향핸들입력을 이용한 시뮬레이션 결과가 보여 지고 실험결과와 잘 비교되었다. 이러한 동시시뮬레이션 기술은 차량의 핸들링 성능 평가나 CMDPS 평가 수행 및 로직 튜닝을 위해 효과적으로 사용될 수 있다.

• Design & Manufacturing
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• 제11권3호
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• pp.41-45
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• 2017

Drones can be manipulated in a variety of ways. One of the most common controller is joystick method. But joystick controller uses both hands and takes a long time to learn. Particularly, in the case of 8-character flight, it is necessary to use both front and rear flight (pitch), left and right flight (Roll), and body rotation (Yaw). Joystick controller has limitations to intuitively control it. In particular, when the main body rotates, the viewpoint of the forward direction is changed between the drones and the user, thereby causing a mental rotation problem in which the user must control the rotating state of the drones. Therefore, we developed a motion matching controller that matches the motion of the drones and the controller. That is, the movement of the drone and the movement of the controller are the same. In this study, we used a gyro sensor and an acceleration sensor to map the controller's forward / backward, left / right and body rotation movements to drone's forward / backward, left / right, and rotational flight motion. The motor output is controlled by the throttle dial at the center of the controller. As the motions coincide with each other, it is expected that the first drone operator will be able to control more intuitively than the joystick manipulator with less learning.

• Korean Journal of Radiology
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• 제23권2호
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• pp.237-245
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• 2022

Objective: Viscoelasticity is an essential feature of nerves, although little is known about their viscous properties. The discovery of shear wave dispersion (SWD) imaging has presented a new approach for the non-invasive evaluation of tissue viscosity. The present study investigated the feasibility of using SWD imaging to evaluate diabetic neuropathy using the sciatic nerve in a diabetic rat model. Materials and Methods: This study included 11 diabetic rats in the diabetic group and 12 healthy rats in the control group. Bilateral sciatic nerves were evaluated 3 months after treatment with streptozotocin. We measured the nerve cross-sectional area (CSA), nerve stiffness using shear wave elastography (SWE), and nerve viscosity using SWD imaging. The motor nerve conduction velocity (MNCV) was also measured. These four indicators and the histology of the sciatic nerves were then compared between the two groups. The performance of CSA, SWE, and SWD imaging in distinguishing the two groups was assessed using receiver operating characteristic (ROC) analysis. Results: Nerve CSA, stiffness, and viscosity in the diabetic group was significantly higher than those in the control group (all p < 0.05). The results also revealed a significantly lower MNCV in the diabetic group (p = 0.005). Additionally, the density of myelinated fibers was significantly lower in the diabetic group (p = 0.004). The average thickness of the myelin sheath was also lower in the diabetic group (p = 0.012). The area under the ROC curve for distinguishing the diabetic neuropathy group from the control group was 0.876 for SWD imaging, which was significantly greater than 0.677 for CSA (p = 0.030) and 0.705 for SWE (p = 0.035). Conclusion: Sciatic nerve viscosity measured using SWD imaging was significantly higher in diabetic rats. The viscosity measured using SWD imaging performed well in distinguishing the diabetic neuropathy group from the control group. Therefore, SWD imaging may be a promising method for the evaluation of diabetic neuropathy.

• 전력전자학회논문지
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• 제11권1호
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• pp.7-13
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• 2006

근래에 선형전동기로 냉장고 등 냉동기기의 압축기 피스톤을 제어하는 선형압축기가 높은 효율 때문에 많이 주목받고 있다. 선형압축기의 피스톤 스트로크는 LPMSM의 입력 전압 및 전류값을 적분하여 구하며, 이 입력 신호에 직류성분이 포함될 경우 스트로크가 발산된다. 본 연구에서는 고역필터 및 직류 옵셋 보상 방식을 사용하여 입력 전압 및 전류의 직류성분에 의한 스트로크의 발산을 방지하는 기법을 제시하였다. 고역필터의 차단주파수에 대한 스트로크의 크기 및 위상과 스트로크에 포함된 직류옵셋 값의 관계를 유도하고, 직류 옵셋 값을 보상하여 정확한 스트로크를 계산한다. 새로 개발된 스트로크 계산방법의 성능은 16비트 DSP 구현된 선형압축기 시스템의 실험을 통하여 확인하였다.

• 한국산학기술학회논문지
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• 제11권10호
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• pp.3666-3672
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• 2010

본 연구는 옥외 광고를 위한 LCD 패널용 콘솔(이하 콘솔'이라 한다.)"의 내부온도 제어를 위한 냉각장치의 제어기 설계에 관하여 다루고 있다. 콘솔은 본 연구진에 의하여 개발된 것으로 냉각장치는 열전소자를 이용하여 사용조건에 적합하도록 설계하였다. 아울러 본 연구는 콘솔이 우수한 성능을 발휘할 수 있도록 제어전략과 그 방안을 제안하고자 한다. 본 연구의 구성은 먼저 시스템의 구조와 설계조건에 대하여 정의하였다. 이어서 동적 특성을 결정하는 파라미터를 측정한 후 분석을 위하여 시스템을 수식 모델링하였다. 끝으로 제어전략을 수립한 후 수식모형을 이용하여 제어기의 성능 검사를 위한 시뮬레이션을 실시하고 기존의 제어기 성능과 비교분석하였다. 본 연구의 목적은 비교분석을 통하여 보다 개선된 제어방식을 제시하는 것이다.

• 한국자동차공학회논문집
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• 제16권1호
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• pp.8-13
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• 2008

Emissions from automobiles have long been considered a prime source of pollutants involved in smog formation and ozone production. Especially VOCs are associated with serious environmental problems such as photo-chemical smog as well as human health effects. Since motor vehicles are a major source of VOCs, estimating of emission from mobile source is the most important factor to control VOCs. VOCs are emitted from various pollution like motor vehicles, mobile and stationary source that has characteristics of toxicity, cancer-causing, bio-accumulation, durability in air and diffusion can exert a bad influence upon human health and environment. However we don't have any standard or regulation about VOCs emissions. This study is summarized as VOCs emission characteristics from in-use light-duty diesel and LPG fueled vehicles. The vehicle exhaust-gas test mode is CVS cycle and nier-10 cycles that developed on EPA and National Institute of Environmental Research. TO-14 method (Toxic Organic) was chosen for VOCs analysis from EPA in USA. This study results will be useful when make a emission factor and rule making of emission standard about domestic VOCs emission for the improve to air condition.

• Journal of Astronomy and Space Sciences
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• 제15권2호
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• pp.427-436
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• 1998

무궁화위성 $1{cdot}2$호와 앞으로 발사될 무궁화위성 3호의 원지점 궤도천이는 기본적으로 궤도평면을 바꾸는 타원궤도천이인데, 무궁화위성 $1{cdot}2$호의 경우는 고체추진제를 이용하여 천이궤도의 원지점에서 단 한번 분사함으로써 목표 표류궤도로 진입하는 AKM(Apoges Kick Motor)단계를 거치는 반면, 무궁화위성 3호는 액체추진제를 이용하영 원지점에서 여러번 분사를 통해 천이궤도를 바꾸어 나가면서 최종 표류궤도로 진입하는 LAE(Liquid Apogee Engine) 단계를 거치도록 계획되어 있다. 본 연구에서는 액체추진제를 사용한 정지궤도 진입방법과 추진제 제어방법을 연구하여 액체추진제를 사용한 정지궤도 진입 시뮬레이션 툴을 개발하였다. 정밀한 시뮬레이션을 위해 연세대학교 위성궤도공학연구실의 COWELL5 정밀궤도예측 프로그램을 토대로 기본설계를 했으며, 결과는 $STK/VO^{TM}$의 지상궤적 및 3차원 그래픽환경으로 실시간 구현이 가능하도록 했다.