• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2011년도 춘계학술대회 논문집
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• pp.791-796
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• 2011

In order to understand long range wave propagation in railway tracks, it is required to identify how far vibrations can travel along a rail. To answer this question, the attenuation characteristics of the main propagating waves are required as a function of distance. In this work, it is identified which wave types predominantly propagate on various regions of the rail cross-section. Then decay rates of propagating waves in railway tracks are investigated for frequencies up to 80 kHz. A numerical method called the Wavenumber Finite Element (WFE) method is utilized to predict dispersion curves and decay rates for a rail on a continuous foundation. In order to validate the simulated results, measurements have been performed on a test track and an operational railway track. The measured results are compared with the output of the simulations and good agreements are found between them.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2005년도 춘계학술발표대회 개요집
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• pp.171-173
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• 2005

To evaluate the applicability of dissimilar metal friction stir welding in automobile manufacturing process, friction stir welding trials were carried out for typical 5000 and 6000 series aluminum alloy sheets with 2mm thickness. The sound joints of A15052 and A16061-T6 alloys were successfully formed under a wide range of welding condition. Excellent weld ability has been obtained at a condition of rotating speed 2000rpm and travel speed 100mm/min, while a radiographic test also confirmed defect free joint for this condition. Through the Erichsen cup test, the plastic formability of the FSWelded joints was found to be about 83% of base metal.

• Journal of Mechanical Science and Technology
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• 제20권10호
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• pp.1702-1715
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• 2006

The increasing use of nano-positioners in a wide variety of laboratory and industrial applications has created a need for nano-mechatronics education in all engineering disciplines. The subject of nano-mechatronics is broad and interdisciplinary. This article focuses on the way nano-mechatronics is taught in department of mechanical engineering at Korea Advanced Institute of Science and Technology (KAIST). As one model of nano-positioning systems, design and experimental methodology is presented in this article. For design phase, the stiffness and resonant frequencies are found analytically and verified by using a commercial finite element analysis program. Next, for experimental phase, various tests are performed to access the performances of the designed nano-positioner, for example, sine-tracking, multi-step response and travel-range check etc. Finally, the definition of 'separation frequency' is described and some comments are discussed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 G
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• pp.3322-3324
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• 1999

This paper studies on the design and fabrication of a micro in-plane positioning actuator integrated with a microlens. Proposed in-plane actuator is a micro XY-stage which is composed of two linear comb drive actuators being orthogonal to each other. In the fabrication of actuator, the single crystalline silicon substrate anodically bonded with a #7740 glass substrate is used because of simple release and passivation. The structure of actuator is formed on the silicon facet of bonded fixture by chlorine-based deep RIE and then released by isotropic wet etching of glass (#7740) in hydrofluoric acid solution. Fabricated actuator has a large travel range up to $30({\pm}15){\mu}m$ and high resolution less than 0.01f1l1l in each direction. Experimented resonant frequency of this actuator is 630Hz. The micro-Fresnel lens is fabricated on the square-shape glass structure prepared in the center of actuator.

• 산업경영시스템학회지
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• 제23권54호
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• pp.87-95
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• 2000

To constuct the stochastic model for performance evaluation of Multi-AGV, two aspects must be considered. The first is stochastic situation for moving jobs. The second is the dispatching rule of AGV. In this paper, the stochastic model for performance evaluation of Multi-AGV is developed. The case of stochastic model with two AGV is developed. But it difficult to solve in the case of stochastic model with more than three AGV because the model have three-ordered equations. The evaluation factor of the model is utilization and empty travel time of AGV. Using these factors, one can easily evaluate a wide range of handling and layout alternatives from given flow data. Hence, the model would be most effective when used in the early stage of designing to narrow down the number of alternative prior to simuation.

• International journal of advanced smart convergence
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• 제8권1호
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• pp.58-64
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• 2019

In recent years, small mobile devices called personal mobility or smart mobility have attracted attention. Personal mobility refers to electric-driven personal transportation that can travel at close range and medium distance, including small electric vehicles, electric bicycles, electric motorcycles and electric scooters. Most of the electric scooters used in Korea are mainly imported from China. This is due to the fact that the price competitiveness of major components of electric scooters is owned in China. At this point, the domestic research direction is preferable for the composition and design of the electric scooter body rather than cost reduction for the components. In this study, we propose a new model of portable folding structure that is easy to use for electric scooters, which are personal vehicles using electric energy. We also made a prototype for practical use.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2018년도 추계학술대회
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• pp.18-20
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• 2018

본 논문에서는 위치-속도 모드전환 제어기를 제안하고 이 제어기를 활용한 운동범위 제약을 가진 기계의 연착륙 방법을 제시한다. EGR 밸브와 같은 기계제품들은 이동할 수 있는 범위를 가지며 범위 내에서 위치를 제어한다. 위치제어 중 양끝 위치로 이동시 기계는 빠른 속도로 충돌할 수 있다. 속도가 빠르면 빠를수록 충돌 시, 충격력이 커지며, 충격력으로 기구물은 빠르게 마모되고 수명을 단축시킬 수 있다. 따라서 양끝 위치 이동 시, 일시적으로 속도를 제어할 수 있는 제어기가 필요하다. 제안된 위치-속도 모드전환제어기는 Hanus Scheme을 사용하여 모드전환 시, 범프효과로 인한 부작용을 감소시켰으며, 모드전환 이후 모드 전환된 제어기의 지령을 빠르게 추종한다. 마지막으로, EGR 밸브 양끝 위치 학습알고리즘에 적용시켜 시험하였다.

• International Journal of Internet, Broadcasting and Communication
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• 제13권3호
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• pp.56-62
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• 2021

MSRDS(Microsoft Robotics Developer Studio) provides the ability to simulate these technologies. SPL(Simple Programming Language) of MSRDS provides many functions for sensor programming to control autonomous robots. Sensor programming in SPL can be implemented in two types of schemes: procedure sensor notification and while-loop schemes. We considered the three programming schemes to control the robot movement after studying the advantages and disadvantages of the sensor notification procedure and the while-loop scheme. We also created simulation environments to evaluate the performance of the three considered schemes when applied to four different mazes. The simulation environment consisted of a maze and a robot with the most powerful sensor, i.e., the LRF(Laser Range Finder) sensor. We measured the required travel time and robot actions (number of turns and number of collisions) needed to escape the maze and compared the performance outcomes of the three considered schemes in the four different mazes.

• 천문학회보
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• 제46권2호
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• pp.48.3-49
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• 2021

We study the process of panspermia in Milky Way-like galaxies by modeling the probability of successful travel of organic compounds between stars harboring potentially habitable planets. To this end, we apply the modified habitability recipe of Gobat & Hong (2016) to a model galaxy from the MUGS suite of zoom-in cosmological simulations. We find that, unlike habitability, which only occupies narrow dynamic range over the entire galaxy, the panspermia probability can vary be orders of magnitude between the inner (R, b = 1~4 kpc) and outer disk. However, only a small fraction of star particles have very large values of panspermia probability and, consequently, the fraction of star particles where the panspermia process is more effective than prebiotic evolution is much lower than from naïve expectations based on the ratio between panspermia probability and natural habitability. The lunar surface progressively darkens and reddens as a result of sputtering from solar wind particles and bombardment of micrometeoroids. The extent of exposure to these space weathering agents is frequently calculated as the location in a diagram of reflectance at 750 nm

• 대한간호
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• 제32권1호
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• pp.61-76
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• 1993

This study was done in order La provide basic data to a Fee System for hospital based Home Health Care services in Korea in the future. It was done by investigating activities provided to possible Home Health Care clients who could be discharged early from genera] hospitals and then estimating the nursing care fee according to each nursing activity based upon the time used for activity. The subjects of the study were selected by convenience sampling and consisted of 35 clients who might be clients for Home Nursing Care and were presently admitted to a medical- surgical ward of Y University Medical Center located in Seoul, Korea. The data collection period was from September 1, 1991 to September 30, 1991. The research in strum nets utilized for the study were a client selection criterial for Home Health Care developed by Choo(l991) and a check-list of nursing activity developed by researcher. The results of the study were as follows : 1. There were 44 different nursing activities provided in the seven days but the time was calculated for only 25 of the nursing activities. 2. Fees for the 25 different nursing activities were calculated by multipling the median of the average wage of a staff nurse having five years experience in an A grade general hospital to the Lime of the nursing activity. The results were compared with the insurance fee which the government recognized as an appropriate fee for that activity. The nursing activities with a lower calculated fee than the insurance fee were suction, catheterization, exercise education and dressing change. The nursing activities with a higher calculated fee than the government recognized fee were 1M injection and vital sign check. 3. There was a range of 1-15 nursing activities provided daily to the client. For the average number of nursing activities per day of 6.26 events the nursing care fee was calaulated at W 6136 per day. 4. Based upon the results of the study, a recommentdation for a Home Health Care fee per visit based on the nursing activities provided could be formulated for a Home Health Care fee system. It could be formulated as following: 1) Home health Care fee per visit $=[(direct{\;} nursing{\;}fee(direct{\;}nursing{\;}care{\;}time{\;}per{\;}activity{\;}{\times}{\;}average{\;}nursing{\;}wage)+indirect fee]{\times}average$ nursing activity per visit]+management fee+ materials fee+a travel fee In this way a nursing fee could be calculated based upon the result of the study of the nursing fees per visit. 2) Nursing activity fees per visit. = $([direct nursing{\;}care{\;}fee+indirect{\;}nursing{\;}fee]{\times}average$ number of nursing activities provided per visit] (W 6, 136) + travel fee(\ 5, 542) +management fee material $fee({\alpha})\{\;}16, 436+{\alpha}$ The nursing fee per visit as calculated in this research of $\{\;}15, 0000+{\alpha}$ could be adjusted according to the patient's condition or the use of high technology nursing care or according to the amount of time spent for travel. The nursing care fee per visit presented in this study can be validated through a Home Health Care demonstration project.