• 한국자기학회지
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• 제3권3호
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• pp.201-207
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• 1993

$Pr_{15}Fe_{77}B_{8}$ 조성의 합금을 Ar분위기에서 유도용해로를 이용하여 주조하 였다. 이 합금을 석영관에 넣어 고주파 유도로를 이용하여 용해한 후 0.6 nm의 분출구를 통해 회전하는 Cu wheel위에 분사하여 비본형태로 제조하였다. 이 리본을 열간변형하여 결정방향성을 주었는데 이를 위 해 먼저 $680^{\circ}C$에서 $21.8\;kg/mm^{2}$의 압력으로 hot-press하여 92%의 densification을 갖는 시편을 얻을 수 있었다. 이 시편을 다양한 조건하에서 die-upset을 행하였다. 변형율이 높을 수록 $_{i}H_{c}$는 저하되었으나, $B_{r}$은 현저하게 증가되었으며, XRD 분석 결과(006)면에서의 회절강도가 증가되었다. 따라서 압축방향으로 자화용이축이 형성되었음을 알 수 있었다. Die-upset시의 변형속도가 빠를 수록 $_{i}H_{c}$는 증가되었으나, $B_{r}$은 감소되었다. 가공온도에 따른 $B_{r}$의 변화는 $750^{\circ}C$ 까지 상승한 후 감소되었다. 이 조성의 $4{\pi}M_{s}$는 11.8 kG였고 $750^{\circ}C$에서 0.05 mm/sec의 가공속도로 변형률 0.8로 die-upset한 경우에는 $B_{r}$이 11.0 kG로 우수한 자기이방성을 가지고 있으나, die-upset후에 $_{i}H_{c}$가 낮은 문제점이 있다.

• 한국식품과학회지
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• 제25권6호
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• pp.769-774
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• 1993

Fluidized bed opposed jet mill을 사용하여 초미세분쇄한 후 Turboplex classifier로 공기분급한 탈지미강분말의 입도는 air classifying wheel speed (ACWS)가 낮아짐에 따라 입자의 크기와 표준편차는 증가하고 단위부피당 표면적은 감소하였다. ACWS 21,000rpm에서 분급한 미강분말의 형태는 구형이었으며 입도 median이 $3.7{\mu}m$이었다. ACWS별로 회수된 시료의 단백질, 지방, 회분은 ACWS에 따라 전반적으로 증가하는 경향이었다. Mg, Zn, Fe 및 Mn 함량은 ACWS가 증가할수록 비교적 증가하는 경향을 보였으며, phytic acid함량은 중간 ACWS에서 약간 높은 값을 보였다. 식이섬유함량은 $25.2{\sim}31.5%$의 값을 보였고, ACWS 15,000rpm에서 최대값을 나타내었다. ACWS에 따른 시료의 색도는 ACWS가 높을수록 백색도(L)가 증가하였고, 적색도(a)와 황색도(B)는 감소하는 경향을 나타내었다. 보수력(WHC)은 12,000rpm에서 2.88g/g solid로 가장 높았고 ACWS가 높아짐에 따라 감소하는 추세를 보였으나, 보유력은 반대로 ACWS에 따라 약간 증가하는 경향을 보였다. 분급된 미강분말 현탁액의 유동특성은 Bingham body에 속하였으며 농도와 ACWS가 증가함에 따라 항복응력 및 점도가 상승하였다. 분급된 미강분말을 5% 수준으로 대체하여 케이크를 제조한 경우 대조구보다 케이크의 높이와 부피가 증가하였다.

• 대한기계학회논문집A
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• 제37권11호
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• pp.1437-1443
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• 2013

현재 국내선로에서 운전규정에 따른 곡선반경별 속도제한을 실행하고 있으나 기존선 속도 향상과 관련하여 실제로 탈선 발생 없이 운행 가능한 곡선부 최대 통과속도에 대한 연구가 필요하다. 또한, 철도차량의 주행안전성에 영향을 미치는 요인으로서는 차량측면과 궤도측면으로 나눠질 수 있는데, 본 연구에서는 탈선 안전도 향상에 영향을 미치는 매개변수 중 레일 경좌 변화에 따른 주행안전성을 해석하고자 하였다. 탈선의 위험도가 높은 곡선부 통과하는 열차의 고속향상을 도모하기 위하여 실제 선로조건인 남성현${\leftrightarrow}$청도 상 하행 구간의 곡선부 구간별 통과시 레일 경좌와 주행속도 변화에 따른 주행안전성 해석을 수행하였다.

• Journal of Biosystems Engineering
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• 제41권4호
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• pp.281-287
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• 2016

Purpose: The purpose of this study is to develop a walking-type two-row sesame reaper, which can simultaneously perform the cutting and collecting of sesame plants and other crops like perilla and soybean. Methods: The factors involved in reaping sesame were determined experimentally in order to design a prototype of the sesame reaper. The prototype is made up of four parts for cutting, conveying, collecting, and running. The height of two disc-plate saw blades on the cutting part is adjusted by an adjusting wheel, and peripheral speed is adjusted in accordance with the running speed. The conveying belt of the conveying part can be tilted from $0^{\circ}$ to $90^{\circ}$. The collecting part extracts a predetermined amount of transferred sesame plants. The prototype was used to evaluate the performance at different working speeds, so that the work efficiency can be calculated. Results: The center of gravity of the sesame plants was 900 mm, measured from the end of the cut stem. The diameter of the disc-plate saw blade was determined to be 355 mm, peripheral speed was 20.4-32.7 m/s, and the picking height of the conveying belt for sesame was 130 mm. The performance of transfer and collection of the sesame, when the insertion angles were $60^{\circ}$ and $90^{\circ}$, proved to be excellent. However, when the angle was over $120^{\circ}$, the performance was only 75-80%. The performance was at 100% efficiency when the ratio between running speed and conveying belt speed of the prototype was 1:2, which seems to be the ideal ratio for the sesame reaper. Conclusions: A sesame reaper was developed, which can integrate the processes of cutting, conveying, and collecting, by investigating and considering various factors involved in the reaping process. The sesame reaper can reduce the costs for yielding and producing sesame due to its highly efficient performance.

• 대한토목학회논문집
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• 제26권5D호
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• pp.831-838
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• 2006

본 연구에서는 차량의 주행속도, 차축하중 그리고 타이어 압력변화에 따른 아스팔트 포장의 주요 응답 특성을 분석하고자 하였다. 시험도로 아스팔트 포장 중 기층의 두께가 서로 다른 A5(180mm)와 A8(280mm)단면을 선정하여 표준 3축 덤프트럭에 의한 아스팔트의 변형률과 수직응력의 변화를 계측하였다. 모든 주행시험은 각 포장 단면의 주행차로에서 진행되었으며 실제 주행속도와 이동경로는 레이저 원더링 시스템을 적용하여 실시간으로 관찰, 기록하였다. 아스팔트 포장의 변형률은 차량의 주행속도가 증가할수록 그 크기가 감소하는 일반적인 점탄성 거동을 보였다. 특히 수직응력은 차축하중 뿐만 아니라 주행속도에도 영향을 받는 것으로 보아 속도별 차량의 운동특성이 각 차축으로 전달되는 연직하중의 크기에 많은 영향을 주고 있음을 알 수 있었다. 일반적으로 타이어 공기압이 증가하고 차축하중이 증가할수록 아스팔트 하부의 최대 인장변형률은 증가하였다. 두 아스팔트 포장 단면에서 다층탄성해석을 수행한 결과 변형률은 계측된 결과보다 크게 예측되었으며 수직응력은 수치해석결과가 계측결과보다 작게 평가되었다.

• 로봇학회논문지
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• 제12권3호
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• pp.297-305
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• 2017

As the development of autonomous vehicles becomes realistic, many automobile manufacturers and components producers aim to develop 'completely autonomous driving'. ADAS (Advanced Driver Assistance Systems) which has been applied in automobile recently, supports the driver in controlling lane maintenance, speed and direction in a single lane based on limited road environment. Although technologies of obstacles avoidance on the obstacle environment have been developed, they concentrates on simple obstacle avoidances, not considering the control of the actual vehicle in the real situation which makes drivers feel unsafe from the sudden change of the wheel and the speed of the vehicle. In order to develop the 'completely autonomous driving' automobile which perceives the surrounding environment by itself and operates, ability of the vehicle should be enhanced in a way human driver does. In this sense, this paper intends to establish a strategy with which autonomous vehicles behave human-friendly based on vehicle dynamics through the reinforcement learning that is based on Q-learning, a type of machine learning. The obstacle avoidance reinforcement learning proceeded in 5 simulations. The reward rule has been set in the experiment so that the car can learn by itself with recurring events, allowing the experiment to have the similar environment to the one when humans drive. Driving Simulator has been used to verify results of the reinforcement learning. The ultimate goal of this study is to enable autonomous vehicles avoid obstacles in a human-friendly way when obstacles appear in their sight, using controlling methods that have previously been learned in various conditions through the reinforcement learning.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 2017년도 춘계공동학술대회
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• pp.17-17
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• 2017

In electric agricultural machine the gearhead is needed to convert the high speed low torque rotation motion generated by DC motor to lower speed high torque motion used by the vehicle. The gearhead consist of several spur gears works as reduction gears. Spur gear have straight tooth and are parallel to the axis of the wheel. Spur gears are the most easily visualized gears that transmit motion between two parallel shafts and easy to produce. The modeling and simulation of spur gears in DC motor gearhead is important to predict the actual motion behavior. A pair of spur gear tooth in action is generally subjected to two types of cyclic stress: contact stress and bending stress including bending fatigue. The stress may not attain their maximum values at the same point of contact fatigue. These types of failure can be minimized by analysis of the problem during the design stage and creating proper tooth surface profile with proper manufacturing methods. To improve its life expectation in this study modal and stress analysis of gearhead is simulated using ansys work bench software based on finite element method (FEM). The modal analysis was done to understand gearhead deformation behaviour when vibration occurs. FEM static stress analysis is also simulated on gearhead to simulate the gear teeth bending stress and contact stress behavior. This methodology serves as an approach for gearhead design evaluation, and the study of gear stress behavior in DC motor gearhead which is needed in the small workshop scale industries.

• 한국항공우주학회지
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• 제38권10호
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• pp.973-978
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• 2010

본 논문에서는 유격을 고려한 항공기 전방 착륙 장치의 쉬미 현상을 연구하였다. 쉬미는 항공기의 이착륙 시 랜딩기어가 주행도중 측방향과 조향방향으로 진동에 놓이는 현상이다. 이 현상은 스트럿의 낮은 강성, 랜딩기어 내부의 마찰과 유격, 휠의 불균형이나 마모된 부품 등으로 인해 발생하며, 항공기의 안정성을 저하시킨다. 유격은 비선형 요소이기 때문에 기술 함수로 선형화 하여 주파수 영역에서 안정성해석을 수행하였고, 4차 Runge - Kutta를 이용하여 시간영역에서 안정성해석을 수행하였다. 본 연구에서는 수치적인 해석법을 통해 쉬미현상의 선형 동특성과 비선형 동특성을 조사하였다. 유격을 고려한 비선형 수치 해석결과, 선형 임계속도보다 낮은 속도에서 제한주기진동이 발생하는 등, 유격으로 인해 쉬미 안정성이 저감되는 결과를 관찰하였다.

• 수산해양기술연구
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• 제52권1호
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• pp.56-64
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• 2016

This study analyzed characteristics of officers' watch-keeping during fishing operation at the fisheries training ship KAYA (GT: 1,737 tons, Pukyong National University). It observed fishing works of three officers in wheel house of KAYA. The observations were carried out at the fishing ground 45 miles away from east of Jeju from 7 to 8 January 2010. The works and movements of the officers were recorded with three common video cameras and a 4-channel MPEG-4 Triplex DVR. Recorded data of the working circulation was analyzed by using the post-processing method. As a result of the traffic lines, the average (${\pm}S.D$) of working hour (min) and moving frequency (times), distance (m) and speed (m/min) during setting the net was 11.8 (0.9), 43.7 (8.1), 133.9 (35.8) and 10.5 (0.6), respectively. During trawling the net, it was 100, 241 (39.8), 615.7 (194.6) and 5.2 (1.6), respectively. During hauling the net, it was 17.6 (1.4), 41.0 (7.2), 196.9 (37.6) and 10.7 (0.8), respectively. In addition, it has a different tendency of the instrument usage frequency by the fishing works. During setting, the usage priority was CCTV, ECDIS, RPM and pitch controller, net monitor, GPS plotter, chart room, X-band radar, fish finder and public addressor. During trawling, it was CCTV, ECDIS, fish finder, X-band radar, net monitor, chart room, GPS plotter, RPM and pitch controller, auto pilot and steering, interphone, wind speed and direction indicator, No.1. VHF, navigation light control panel and public addressor. During hauling, it was CCTV, RPM and pitch controller, GPS plotter, public addressor, chart room, net monitor, X-band radar, auto pilot and steering and fish finder.

• 대한치과교정학회지
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• 제22권1호
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• pp.123-131
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• 1992

This study was done to evaluate the changes of enamel surface by interproximal stripping and recovery of it by polishing. The number of 34 1st premolars which had extracted for orthodontic treatment were selected as samples. Interproximal stripping was performed by hand with metal strip and strip placer (Dentaurum Co., Germany) and low speed handpiece with diamond disk (Superdiaflex, Germany). Polishing was performed by hand with plastic strip (3M Col) and low speed handpiece with whip-mix, DCPA (Dicalcium Phosphate, Anhydrous, $CaHPO_4$) powder and Sof-lex (3M Co. U.S.A.) polishing kit. Each groups were examined under the scanning electron microscope (JEOL Co., JSM-840A, Japan) and the following results were obtained: 1. The stripped group performed by metal strip and diamond disk altogether showed deep furrow on the enamel surface as wide as about $10{{\mu}m}$. 2. There could be seen more irregular scratched line in the group stripped by metal strip than that by diamond disk. 3. The polished group performed by plastic strip and DCPA powder showed slight smoothening of the edge of stripped furrow on the enamel surface without relation to the stripping method. 4. The polished group performed by Sof-lex progressive polishing kit could not avoid the formation of the furrows on the enamel surface according to the particle size without relation to the stripping method. 5. The polished group performed by the superfine polishing wheel, the final stage of Sof-lex polishing method showed shallow scratched line as wide as within about $2{{\mu}m}$ on the enamel surface without relation to the stripping method. 6. The interproximal stripped enamel surface could not recover its original surface texture by any kind of polishing methods.