• 한국정밀공학회지
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• 제13권12호
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• pp.78-85
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• 1996

The determination of the optimum biarc curve passing through a given set of points along involute curve is studied. The method adopted is that of finding the optimum no. of span and the optimum length of the span such that the error between the biarc curve and involute curve is minimum. Irregular curve span method is effectively used to describe the involute curve with reduced length of NC-Code.

• 사상체질의학회지
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• 제14권1호
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• pp.51-66
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• 2002

The main purpose of this study is to differentiate Sasang Constitutions of men and women by measuring 5 parts of the body. By the definitions about Four Chos(四焦) in ${\ulcorner}$The Discourse on Viscera and Bowels(臟腑論)${\lrcorner}$, the body is divided into four parts and sets up the five borderlines. They are Top-line, Bosom-line, Stomach-line, Navel-line and Bottom-line. Top-line(第一線) is the horizontal distance between Rt. & Lt. Coracoid processes passing through the acupuncture point CV-22(天突穴) or the horizontal distance between Rt. & Lt. beginning points of Axillary lines. Bosom-line(第二線) is the horizontal distance passing through Rt.& Lt. Nipples. Stomach-line(第三線) is the horizontal distance passing through Rt.& Lt. acupuncture point ST-19(不容穴). Navel-line(第四線) is the horizontal distance passing through the navel(CV-8; 神闕穴) and the acupuncture point ST-25(天樞穴). Bottom-line(第五線) is the horizontal distance between Rt. & Lt. Anterior Superior Iliac Spine(ASIS). The measured numerical values of Five Lines are the most important factors to classify the Four Constitutions(Taeyangin, Taeumin, Soyangin, Soeumin). Among the five lines, Stomach-line(Middle-line) is the base line to decide Yin and Yang. As a result, I could differentiate the four Constitutions as follows. 1. Taeyangin's Top-line is more than 36cm long. Top-line is the longest. Bottom-line is the shortest. The length-difference between Top-line and Bottom-line is more or less 10cm long. 2. In case of Taeumin, Navel-line is the longest. The numerical values of Middle and Bottom lines are almost the same or Bottom-line is shorter than Middle-line by 1 or 2 cm long. In some special case, the five lines are all the same and the body just looks like a log. 3. In case of Soyangin, just like Taeyangin, Top-line is the longest. Bottom-line is the shortest. The length of Top-line is ranged between 30cm to 35cm long. From Top-line to Bottom-line, the length gradually diminishes each by 2cm: for example, 34-32-30-28-26. 4. In case of Soeumin, the longest one is Bottom-line. Specially, Navel-line is shorter than Middle-line. Bottom-line is longer than the Middle.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.687-690
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• 2002

Multimode boundary-layer transition on a NACA0012 airfoil is experimentally investigated under periodically passing wakes and the moderate level of free-stream turbulence. The periodic wakes are generated by rotating circular cylinders clockwise or counterclockwise around the airfoil. The free-stream turbulence is produced by a grid upstream of the rotating cylinder, and its intensity(Tu) at the leading edge of the airfoil is $0.5\;or\;3.5\;{\%}$. The Reynolds number ($Re_c$) based on chord length (C) of the alrfoil is $2.0{\times}10^5$, and Strouhal number ($St_c$) of the passing wake is about 0.7. Time- and phase-averaged streamwise mean velocities and turbulence fluctuations are measured with a single hot-wire probe, and especially, the corresponding wall skin friction is evaluated using a computational Preston tube method. The wake-passing orientation changes pressure distribution on the airfoil in a different manner irrespective of the free-stream turbulence. Regardless of free-stream turbulence level, turbulent patches for the receding wakes propagate more rapidly than those for the approaching wake because adverse pressure gradient becomes larger. The patch under the high free-stream turbulence ($Tu=3.5{\%}$) grows more greatly in laminar-like regions compared with that under the low background turbulence ($Tu=0.5{\%}$) in laminar regions. The former, however, does not greatly change the original turbulence level in the very near-wall region while the latter does it. At further downstream, the former interacts vigorously with high environmental turbulence inside the pre-existing transitional boundary layer and gradually lose his identification, whereas the latter keep growing in the laminar boundary layer. The calmed region is more clearly observed under the lower free-stream turbulence level and for the receding wakes. The calmed region delays the breakdown further downstream and stabilizes more the boundary layer.

• 수산해양기술연구
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• 제52권4호
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• pp.308-317
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• 2016

The tail flip of the decapod shrimp is a main feature in escaping behavior from the mesh of the codend in the trawl. The characteristics of tail flip in target prawn was observed and analyzed in a water tunnel in respect of flow condition and mesh penetration by a high speed video camera (500 fps). The tail bending angle or bending time in static water was significantly different than in flow water (0.7 m/s) and resultantly the angular velocity in static water was significantly higher than in flow water when carapace was fixed condition. When escaping through vertical traverse net panel in water flow the relative moving angle and relative passing angle to flow direction during tail flip, it significantly decreases the number of shrimps escaping than the case of blocking shrimp. The bending angles of tail flip between net blocking and passing through mesh were not significantly different while the bending time of shrimp passing through mesh was significantly longer than when shrimp blocking on the net. Accordingly the angular velocity of passing through mesh was significantly slower than blocking on the net although the angular velocity of the tail flip was not significantly related with carapace length. The main feature of tail flip for mesh penetration was considered as smaller diagonal direction as moving and passing angle in relation to net panel as right angle to flow direction rather than the angular velocity of tail flip.

• 대한교통학회지
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• 제24권5호
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• pp.7-18
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• 2006

신뢰성 있는 통행시간정보제공과 교통정보센터의 효율적인 운영을 위해 통상 국내에서는 5분 주기로 통행시간자료를 수집하고 있다. 그러나 주기 단위로 수집할 경우 수집주기내에 링크를 통과하지 못하는 데이터는 사용할 수 없으며, 특히 혼잡시 이러한 데이터가 많이 발생하므로 혼잡정보가 늦게 제공되는 문제점이 있다. 본 연구에서는 이러한 문제점을 해결하기 위해 대기행렬소멸길이와 신호현시 등을 추정하여 링크통행시간 추정하는 기법을 개발하였다 현장실험을 기반으로 MAPE와 MAE를 사용하여 평가한 결과 제안기법의 정확도는 1.98%, 4.75초로 실측치와 큰 차이를 보이지 않았다. 제안기법은 혼잡할 경우에 GPS기반으로 부족한 데이터의 절대량을 보족해 줄 수 있는 대안으로 기대된다.

• 대한기계학회논문집B
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• 제24권1호
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• pp.132-142
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• 2000

The objective of this study is to experimentally investigate the noise propagating characteristics, the noise reduction mechanism and the performance of a slotted tube attached at the exit plane of a circular convergent nozzle. The experiment is performed through the systematic change of the jet pressure ratio and the slot length under the condition of two kinds of open area ratios, 25% and 51%. The open area ratio calculated by the tube length equivalent for the slot length is defined as the ratio of the total slot area to the surface area of a slotted tube. The experimental results for the near and far field sound, the visualization of jet structures and the static pressure distributions in the jet passing through a slotted tube are presented and explained in comparison with those for a simple tube. The propagating characteristics of supersonic jet noises from the slotted tube is closely connected with the slot length rather than the open area ratio, and its propagating pattern is similar to the simple tube. It is shown that the slotted tube has a good performance to suppress the shock-associated noise as well as the turbulent mixing noise in the range of a limited jet pressure and slot dimension. The considerable suppression of the shock‘associated noise is mainly due to the pressure relief caused by the high-speed jets passing through the slots on the tube. Both the strength of shock waves and the interval between them in a jet plume are decreased by the pressure relief. Moreover, the pressure relief is divided into the gradual and the sudden relief depending upon the open area ratio of the slotted tube. Consequently, the shock waves in a jet plume are also changed by the type of pressure relief. The gradual pressure relief caused by the slotted tube with the open area ratio 25% generates the weak oblique shock waves. On the contrary, the weak normal shock waves appear due to the sudden pressure relief caused by the slotted tube with the open area ratio 51%.

• 상하수도학회지
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• 제26권2호
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• pp.257-264
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• 2012

The concept of a non-contact type of UV disinfection system was introduced in this study. UV lamps and their quartz sleeves hang over the water surface and there is no interface between the sleeve and water. Obviously, there is no fouling. Based on optical laws and other UV distribution models, a detail mathematical model for a non-contact type UV disinfection system was developed in this study. Pathway length of UV light in a non-contact type photoreactor is longer than that in a submerged type photoreactor because the light is more refractive while passing through 3 interfaces of medium. But the pathway length passing through the water media is not significantly longer than that in a submerged type photoreactor so, the absorption of UV light by water is not significantly different from the other system. Due to the reflection effect, UV intensity is rapidly decreased as the horizontal distance from the light source is increased. The reflective attenuation in a non-contact type photoreactor is higher than that in a submerged type photoreactor. These mean that the short photoreactor is advantageous than the narrow-long photoreactor for the non-contact type photoreactor in an optical point of view.

• Journal of Mechanical Science and Technology
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• 제14권8호
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• pp.867-878
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• 2000

In order to study unsteady aerodynamic loads on high speed trains passing by each other 350km/h, three-dimensional flow fields around trains during the crossing event are numerically simulated using three-dimensional Euler equations. Roe's FDS with MUSCL interpolation is employed to simulate wave phenomena. An efficient moving grid system based on domain decomposition techniques is developed to analyze the unsteady flow field induced by the restricted motion of a train on a rail. Numerical simulations of the trains passing by on the double-track are carried out to study the effect of the train nose-shape, length and the existence of a tunnel on the crossing event. Unsteady aerodynamic loads-a side force and a drag force-acting on the train during the crossing are numerically predicted and analyzed. The side force mainly depends on the nose-shape, and the drag force depends on tunnel existence. Also. a push-pull (i.e.impluse force) force successively acts on each car and acts in different directions between the neighborhood cars. The maximum change of the impulsive force reaches about 3 tons. These aerodynamic force data are absolutely necessary to evaluate the stability of high speed multi-car trains. The results also indicate the effectiveness of the present numerical method for simulating the unsteady flow fields induced by bodies in relative motion.

• 해양환경안전학회:학술대회논문집
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• 해양환경안전학회 2003년도 추계학술발표회
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• pp.59-65
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• 2003

시계 불량시 교량하 항로를 교각과 충돌없이 안전하게 통항하기 위하여 충분히 떨어진 곳에서 레이더로 교각을 탐지하는 것이 매우 중요하다. 본 연구에서는 이론 검토 및 레이더 실험을 통하여 교각인식을 위하여 필요한 교각 돌출량을 도출하였다. 교량하 항로를 통과하는 최대선박의 전장과 통항조건별로 필요치를 제시함으로써 교량 설계시 그 해역의 교통 환경에 적합한 교각방호시설의 설계가 가능하도록 하였다.

• 한국산학기술학회논문지
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• 제9권4호
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• pp.1030-1038
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• 2008

교통량조사 방법은 루프검지기와 피에조센서를 주로 많이 사용하여 차량의 숫자만을 파악하여 교통주기를 계산하는 방법을 사용하나 교통량을 파악하는 방법은 단순한 교통량에만 국한되는 것이 아니라 다중교통특성인 진입로의 길이, 도로의 폭, 보행자의 수, 통과차량수, 지체차량수 등 관련되는 교통대안을 총 망라하여 새로운 교통량인 혼잡도라는 개념을 대표대안으로 선정하면 바로 교통주기에 적용할 수 있다. 본 논문에서는 서로 관련성이 없는 교통대안들을 AHP 방법을 사용하여 교통주기 계산에 즉시 사용할 수 있는 공통 분모인 새로운 교통대안을 찾아내는 알고리즘을 개발하고 이를 새로운 교통량 개념인 혼잡도라는 교통량을 찾아내는 퍼지센서 알고리즘을 구성하는데 적용한다. 시뮬레이션을 통해 타 교통제어방법과 비교하여 지체차량시간이 줄어듬을 보여준다.