• Journal of Advanced Marine Engineering and Technology
• /
• 제20권2호
• /
• pp.116-116
• /
• 1996

This paper is concerned with a method for calibrating five-hole probes of both angle-tube and prismatic geometries to measure local total and static pressures and the magnitude and direction of the mean velocity vector. Descriptions of the calibration technique, the typical calibration data, and an accompanying discussion of the interpolation procedure are included. The flow properties are determined explicitly from measured probe pressures using calibration data. Flow angles are obtained within the deviation angle of 1.0 degree and dynamic pressures within 0.03 with 95% certainty. The variations in the calibration data due to Reynolds number are also discussed. For the range of Reynolds number employed, no effect was detected on the pitch, yaw and total pressure coefficients. However, the static pressure coefficient showed change to cause minor variations in the magnitude of the calculated velocity vector. To account for these variations, average correction factors need to be incorporated into the static pressure coefficient.

• Journal of Advanced Marine Engineering and Technology
• /
• 제20권2호
• /
• pp.48-56
• /
• 1996

This paper is concerned with a method for calibrating five-hole probes of both angle-tube and prismatic geometries to measure local total and static pressures and the magnitude and direction of the mean velocity vector. Descriptions of the calibration technique, the typical calibration data, and an accompanying discussion of the interpolation procedure are included. The flow properties are determined explicitly from measured probe pressures using calibration data. Flow angles are obtained within the deviation angle of 1.0 degree and dynamic pressures within 0.03 with 95% certainty. The variations in the calibration data due to Reynolds number are also discussed. For the range of Reynolds number employed, no effect was detected on the pitch, yaw abd total pressure coefficients. However, the static pressure coefficient showed change to cause minor variations in the magnitude of the calculated velocity vector. To account for these variations, average correction factors need to be incorporated into the static pressure coefficient.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2000년도 춘계학술대회논문집A
• /
• pp.873-878
• /
• 2000

Semiconductor packaging technology is changed rapidly according to the trends of the micro miniaturization of multimedia and information equipment. For I/O limitation and fine pitch limitation, DIP and SOP/QFP are replaced by BGA/CSP. This is one of the surface mount technology(SMT). Solder ball is bumped n the die pad and connected onto mounting board. In ball bump formation, vacuum suction type ball alignment process is widely used, However this type has some problems such as ionization, static electricity and difficulty of fifo(first-input first-out) of solder balls. Seesaw type is reducing these problems and has a structural simplicity and economic efficiency. Ball cartridge velocity and ball aligned plate angle are Important variables to improve the ball alignment Process. In this paper, seesaw-type CSP solder ball loader is developed and the optimal velocity and plate angle are proposed.

• Tribology and Lubricants
• /
• 제8권2호
• /
• pp.26-34
• /
• 1992

This paper suggests a method to predict the flying state of the head slider in a hard disk drive (HDD) by using an optimization technique. The modified Reynolds equation for the hydrodynamic lubrication theory under the slip flow condition is used to describe the air-bearing system and a Finite Volume Method (FVM) is applied to solve the equation. Especially, Augmented Lagrange Multiplier (ALM) method is employed to find the minimum flying height, the pitch angle and the roll angle of the slider, which is shown to be faster and more general than the conventional update schemes. By using the proposed method, the variations of the flying state are analyzed as a function of the slider position in the direction of the disk radius for various disk velocities and skew angles.

• 한국추진공학회지
• /
• 제9권1호
• /
• pp.46-52
• /
• 2005

무인표적기의 성능 향상을 위해 추진시스템인 프로펠러를 재설계하였다. Vortex 이론을 이용한 설계 및 해석 프로그램을 사용하였으며, 설계 변수는 반경 방향에 따른 코드 길이, 블레이드의 반경 변화, 그리고 비틀림각 등이다. 저속과 고속일 때 모두 향상된 추력을 내도록 엔진 회전수 변경을 포함하여 프로펠러를 재설계 하였다.

• 한국기계가공학회지
• /
• 제9권1호
• /
• pp.93-98
• /
• 2010

The metal fastening method is the new technology to repair cracks in the casting material using specially designed reverse screws. In this study, we conduct the finite element analysis to analyze the pulling force characteristic of a reverse screw, the core component of the metal fastening method, with respect to the change of the applying torque, frictional coefficient and front screw angle. The simplified analysis model with single screw pitch is proposed for convergency of the non-linear contact analysis. As a results, the pulling force of a reverse screw increase in proportion to the applying torque but exponentially decrease according to frictional coefficient. And also we can find the optimum front screw angle with the largest pulling force is $20^{\circ}$.

• 설비공학논문집
• /
• 제13권11호
• /
• pp.1141-1148
• /
• 2001

Experiments on the condensation heat transfer and pressure drop in the brazed type plate heat exchangers are performed with refrigerants R410A/R22. To investigate the geometric effect, plate heat exchangers with the same pitch and height but different $45^{\circ},\;35^{\circ}and\;20^{\circ}$ chevron angles are used. Varying the mass flux of refrigerant (13~34 kg/$m^2$), the condensing temperatures ($20^{\circ}C\;and\;30^{\circ}C$) and the vapor quality (from 0.9 to 0.15) at the same constant heat flux ($5kW/m^2$), the condensation heat transfer coefficients and pressure drops are measured. The heat transfer coefficients decrease slightly with increasing the condensing temperature at a given mass flux in all plate heat exchangers. The pressure drop increases with increasing the mass flux and the quality and decreasing the condensing temperature and the chevron angle.

• 한국광학회지
• /
• 제8권3호
• /
• pp.218-222
• /
• 1997

빠른 응답 속도와 높은 콘트라스트 비를 갖는 쌍안정 TN(BTN:Bistable Twisted Nematic)셀을 제작하여 전기 광학 특성을 조사하고 쌍안정 특성을 갖기 위한 BTN셀의 동작 조건 및 인가 파형의 특성을 조사하였다. 인가 파형의 reset펄스와 selection펄스의 크기와 폭이 BTN셀의 쌍안정 특성에 미치는 영향과 메모리 시간을 조사하였다. 또한 rubbing강도에 따라 pretilt각을 변화시켜 쌍안정 특성을 보이는 두께와 pitch와의 비의 범위를 구하였다.

• 대한기계학회논문집
• /
• 제12권6호
• /
• pp.1312-1319
• /
• 1988

본 연구에서는 임의의 내접치차를 가공하기 위한 구형호브를 설계하는데 그 목적이 있으며 GTP를 구하는 방법으로는 CAD의 envelope 이론을 도입하여 근사해법이 아닌 해석적 방법으로 GTP를 구하였으며 이는 여러 오차 해석에서도 유용하게 이용되 었다.또한 호브의 설계를 위한 전산 프로그램을 개발하여 가공하고자 하는 내접치 차의 데이터로 부터 압력각, 이두께 및 피치의 값을 수정하여 호브를 설계함과 동시에 여유면 가공량을 등을 바로 계산할 수 있도록 하였으며 이에 의한 구형 호브의 설계에 를 제시하였다.

• 한국해양공학회:학술대회논문집
• /
• 한국해양공학회 2003년도 춘계학술대회 논문집
• /
• pp.116-120
• /
• 2003

To study the trafficability on soft and cohesive benthic terrain, a tracked vehicle model($670mm(L){\times}750mm(B_c)$) is designed and tested. The pitch and chevron angle of grouser, weight and center of gravity of vehicle, and drawbar pull force are chosen as experimental variables. Slip, sinkage and inclined angle of vehicle are picked as performance values. Strength of soil is considered as noise factor. A preliminary straight-line motion test is performed. Then, DOE(Design of Experiment) is discussed for further research.