• 한국유체기계학회 논문집
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• 제12권4호
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• pp.23-29
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• 2009

For the purpose of high outlet pressure, compactness and low vibration and noise, 2 stage reciprocating air compressors can have various cylinder arrangement: opposed, in-line, and V type. This paper presents an effective method to calculate the inertia forces and to design counter weight. This method is based on the complex representation for the orbital behavior of the compressor shaft. This method helps to find the optimal balancing rate easily to reduce the inertial force or moment. This paper shows that the residual inertia forces of the single throw shafts and the residual inertia moments of the double throw shafts remain to be imbalanced.

• 소성∙가공
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• 제30권3호
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• pp.149-156
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• 2021

Fine blanking is a high-precision process combining principles of metal stamping and cold forming. Unlike conventional metal stamping, fine blanking uses a special triple action such as V-ring force, counter force, shearing force. This study performed the effect of pocket-shaped compression molding on the mold life of the fine blanking using the 7.4mm thick SM45C material. In order to determine the lifespan of the punch and die in the fine blanking molds, a trial mold was manufactured and various punch materials were selected to perform the mold life test. A study on the life of a fine blanking mold by applying a thick plate material was experimentally performed through a mold test.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 A
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• pp.309-311
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• 1996

In this paper, we propose two types of novel discrete time current control methods of modified fixed band hysteresis control and optimal control for Parallel Resonant DC Link Inverters(PRDCLI). Because zero bus voltage intervals are generated on the DC link of PRDCLI, we can obtain the information of counter electromotive force(emf) by a simple estimation strategy. The proposed current controllers predict the currents of the next resonant cycle using the obstained information of counter emf and the average values of DC link voltages. The computer simulation results for a simple equivalent circuit of induction motor show that the proposed control methods are more effective than conventional methods.

• 동력기계공학회지
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• 제21권2호
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• pp.35-40
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• 2017

In this study, the multi-body dynamics model for a wave energy converter is established. The equations of motions for the mechanical parts of the wave energy converter are derived to analyze the dynamic behavior. A spring method with the same performance as the counter weight method is proposed. The counter weight method and spring method are analyzed for evaluating the performance of the wave energy converter. RecurDyn program which is a kind of commercial multi-body dynamics program is used to perform the dynamic simulation of the wave energy converter.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1996년도 춘계학술대회 논문집
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• pp.188-193
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• 1996

This study was performed the blankholding force and vee-ring effects on Blanking characteristics, such as maximum blanking force, burnish, dish-shape, hardness. etc, in fine-blanking die by the experimental method. Two types of aluminum (Al. 1050-0, Al 5052-H) Such as annealed and unannealed materials were used for the experiment. In order to get a hydrostatic pressure effect, the clearance was set to 0.5% of the thickness of strip, and the counter punch and stripper plate with Vee-ring was set-up. While this experiment was carrying out, the average blanking Velocity was constant (37.5mm/sec) As a result of this study, we got a good surface roughness and a glassy shear plane(burnish) of the sheet over 90% thickness, and such as the excellent accuracy of dimensions, the good squareness and the reduction of dish-shape could be obtained, and also the additional results obtained were such that the hardness of shear plane was increased and the maximum blanking force was reduced in the condition of Vee-ring height of 1.0~1.5mm, and blankholding force of 1200kg.

• KSBB Journal
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• 제25권3호
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• pp.205-214
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• 2010

역류크로마토그래피 (counter-current chromatography, CCC)는 일련의 분배과정을 한 개의 튜브 내에서 연속적으로 일어나도록 고안된 시스템으로서 컬럼으로는 polytetrafluoroethylene(PTFE) 튜브가 다층으로 감겨있는 원통형의 홀더 3개가 서로 기어를 통해 물려있으며, 홀더가 회전과 공전을 통해 튜브의 꼬임을 방지하는 rotary seal-free flow centrifuge 시스템으로 되어있다. 역상 HPLC (reverse phase HPLC)에서는 고정상이 실리카에 결합된 유기물단 (organic moiety)이 수용성 이동상 물질에 의해서 용매화 (solvated)되는 반면 CCC는 실리카 대신에 강한 중력장에 의해 분리되는 자유로운 용매가 고정상이 되며 이 고정상의 부피비율은 20-30%에 이른다. 즉 고체담체에 결합된 유기관능기 대신에 물과 섞이지 않는 hexane 같은 유기용제가 고정상으로 사용되는 것이다. 고속역류크로마토그래피 (high-performance countercurrent chromatography, HPCCC)는 CCC의 기능을 향상시킨 분리시스템으로서 높은 중력장하에서 높은 이동상 속도와 높은 분리효율과 짧은 분리시간을 특징으로 하고 있다. 특히 mg 단위에서 kg 단위로의 스케일업이 선형적으로 가능하다는 큰 장점을 지니고 있다. 이 총설에서는 현재까지 개발된 CCC의 일반적인 이론을 간략히 정리하고 최신 HPCCC 장비의 적용 예를 살펴보고 그 응용분야로서 생리활성물질의 분리 및 정제와 관련된 연구동향을 정리하였다.

• 한국운동역학회지
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• 제22권1호
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• pp.25-34
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• 2012

The purpose of this study was to determine the effects of landing height on the lower extremity during a counter movement jump. Fourteen healthy male subjects (age: $27.00{\pm}2.94$ yr, height: $179.07{\pm}5.03$ cm, weight: $78.79{\pm}6.70$ kg) participated in this study. Each subject randomly performed three single-leg jumps after s single-leg drop landing (counter movement jump) on a force platform from a 20 cm and 30 cm platform. Paired t-test (SPSS 18.0; SPSS Inc., Chicago, IL) was performed to determine the difference in kinematics and kinetics according to the height. All significance levels were set at p<.05. The results were as follows. First, ankle and knee joint angles in the sagittal plane increased in response to increasing landing height. Second, ankle and knee joint angles in the frontal plane increased in response to increasing landing height. Third, there were no significant differences in the moment of each segment in the sagittal plane for the jumping height increment. Fourth, ankle eversion moment and knee valgus moment decreased but hip abduction moment increased for the jumping height increment. Fifth, Ankle and knee joint powers increased. In percentage contribution, the ankle joint increased but the knee and hip joints decreased at a greater height. Lastly, as jumping height increased, the power generation at the ankle joint increased. Our findings indicate that the height increment affect on the landing mechanism the might augment loads at the ankle and knee joints.

• 한국운동역학회지
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• 제20권2호
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• pp.155-165
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• 2010

The purpose of this study was to analyze kinematic quantitative factors required of a forehand counter drive in table tennis through 3-D analysis. Four national table tennis players participated in this study. The mean of elapsed time for total drive motion was $1.009{\pm}0.23\;s$. At the phase of impact B1 was the fastest as 0.075 s. This may affect efficiency in the initial velocity and spin of the ball by making a powerful counter drive. The pattern of center of mass showed that it moved back and returned to where it was then moved forward. At the back swing, lower stance made wide base of support and a stronger and safer stance. It may help increasing the ball spin. Angle of the elbow was extended up to $110.75{\pm}1.25^{\circ}$ at the back swing and the angle decreased by $93.75{\pm}3.51^{\circ}$ at impact. Decreased rotation range of swinging arm increased linear velocity of racket-head and impulse on the ball. Eventually it led more spin to the ball and maximized the ball speed. Angle of knee joint decreased from ready position to back swing, then increased from the moment of the impact and decreased at the follow thorough. The velocity of racket-head was the fastest at impact of phase 2. Horizontal velocity was $7796.5{\pm}362\;mm/s$ and vertical velocity was $4589.4{\pm}298.4\;mm/s$ at the moment. It may help increase the speed and spin of the ball in a moment. The means of each ground reaction force result showed maximum at the back swing(E2) except A2. Vertical ground reaction force means suggest that all males and females showed maximum vertical power(E2), The maximum power of means was $499.7{\pm}38.8\;N$ for male players and $519.5{\pm}136.7\;N$ for female players.

• 한국공작기계학회논문집
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• 제11권4호
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• pp.26-33
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• 2002

One characteristic of Fine-Blanking is that the size and the direction of stress and strain are very complex in the plastic flow according to the condition of blanking. Especially, they are affected by the clearance of punch and die, by the force of blanking holder and by the force of counter punch. The purpose of this research is to how the deformation behavior in shear zone more clearly, based on Green & Cauch's large deformation theory. The deformation behavior and cracks were investigated in each step of shear, according to punch penetration increase, the use of V-indenter ring and the hardness of materials. This research found that the transforming behavior was the same as pure discretion and the cracks could be prevented when hardness is low.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2007년도 추계학술대회 및 제23회 정기총회
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• pp.376-382
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• 2007

항로를 횡단하여 건설된 교량은 부근을 지나던 선박의 기관이나 조타기의 고장 또는 비상한 외력의 영향이나 인위적인 판단오류로 인하여 발생할 수 있는 선박과 교각의 충돌을 예방하고 불가피한 충돌의 경우에도 교량의 붕괴를 방지하는 대책을 마련하여야 한다. 충돌이나 간접 충격에 의하여 교량의 상판이 붕괴되는 경우 많은 인명의 손실과 교량으로 연결되는 간선도로의 장기간 폐쇄는 국가적인 재앙이 될 것이기 때문이다.