• Proceedings of the KSME Conference
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• 2003.11a
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• pp.592-597
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• 2003

Thrust vector control using a coflow-counterflow concept is achieved by suction and blowing through a slot adjacent to a primary jet which is shrouded by a suction collar. In the present study, the flow characteristics of thrust vectoring is investigated using a numerical method. The nozzle has a design Mach number of 2.0, and the operation pressure ratio is varied to obtain various flow features of the nozzle flow. Test conditions are in the range of the nozzle pressure ratio from 6.0 to 10.0, and a suction pressure from 90kPa to 35kPa. Two-dimensional, compressible Navier-Stokes computations are conducted with RNG ${\kappa}-{\varepsilon}$ turbulence model. The computational results provide an understanding of the detailed physics of the thrust vectoring process. It is found that an increase in the nozzle pressure ratio leads to increased thrust efficiency but reduces the thrust vector angle.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.10a
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• pp.17-20
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• 2012

In the RFID system, A collision occurs when the multiple tags transmit at the concurrent in slot. Reduce conflicts, in order to maximize the efficiency of the system, the number of tags with the same number of slots are allocated. the number of slots to the next frame determined by the number of contention tags. In this paper, it estimate the number of tags based on the DFSA. Analyzed the performance of the system by the initial set number of tags through simulation.

• International Journal of Precision Engineering and Manufacturing
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• v.6 no.2
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• pp.5-11
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• 2005

Among the micro machining techniques, micro EDM is generally used for machining micro holes, pockets, and micro structures on difficult-cut-materials. Micro EDM parameters such as applied voltage, capacitance, peak current, pulse width, duration time are very important to fabricate the tool electrode and produce the micro structures. Developed micro EDM machine is composed of a 3-axis driving system and RC circuit equipped with pulse generator. In this paper, using micro EDM machine, the characteristics of micro EDM process are investigated and it is applied to micro holes, slots, and pockets machining. Through experiments, relations between machined surface and voltages and between MRR and feedrate are investigated. Also the trends of tool wear are investigated in case of hole and slot machining.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.775-776
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• 2006

Based on the requirement of high power and efficiency in automobile systems, this paper describes an investigation for the optimum design of a permanent magnet reluctance motor(PRM), and then the characteristics of this kind of motor is compared with that of a interior permanent magnet(IPM) motor. The IPM of 4-pole with 6-slot is redesigned into a PRM, which has the same stator and different rotor structure with IPM. Through finite element analysis(FEA) and equivalent circuit method, the PRM has higher salient ratio, higher efficiency at high speed, and lower iron loss compared with IPM.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.660-662
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• 2000

It is demonstrated that the torque performance of the flux barrier type synchronous reluctance motor(SynRM) can be improved in terms of geometric parameters. Torque ana power factor are related to the difference of inductances and the saliency ratio. And these inductance characteristics are determined by the geometric parameters of rotor: the number of layers. the width of iron to the width of flux barrier($K_w$). slot number and shape, airgap, bridge, etc. The relationship between geometric parameters. especially, $K_w$ and motor performance will be studied. This paper shows that torque and power factor are improved through redesign with considering geometric parameters. Performance comparisons of proto type SynRM and improved SynRM are given by FEA(Finite Element Analysis).

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1996.03a
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• pp.18-23
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• 1996

The Job of Milling in the Local Skill Contest in 1996 was to assemble parts into a complete whole of the parts number 1, 3, 4 worded by Milling Machine and the parts number 2 worked by Machining Center. In the parts of Milling Machine, the Job was to work 45$^{\circ}$angle working, T-slot, dovetail, the correct position drilling, rimming, boring, etc. In the Machining Center, there were the way of calculation of point of contact of 'R' contour curved line and lots of working elements. So, it was possible to work the parts and assemble them within the time limit only through the program to be made out in the way to shorten working hours.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2625-2630
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• 2008

Horseshoe vortices are formed at the junction of an object immersed in fluid-flow and endwall plate as a result of three-dimensional boundary layer separation. This study shows preliminary results of the kinematics of such horseshoe vortices around a circular cylinder with a cavity (slot) placed upstream to disturb the primary separation line. Through the cavity, no mass flow addition (blowing) or reduction (suction) is applied. The upstream cavity weakens the adverse pressure gradient before the cavity. With the upstream cavity, a single vortex is found to form immediately upstream of the cylinder whereas a typical two vortex system is observed in the absence of the cavity. Furthermore, the strength of the single vortex tends to be reduced, resulting from the interaction with the separated flow convecting directly towards the leading edge of the cylinder.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.209-212
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• 2002

The wear process of end mill is a so complicated process that a more reliable technique is required for the monitoring and controling the tool life and its performance. This research presents a new tool wear monitoring method based on the sound signal generated on the machining. The experiment carried out continuous-side-milling for 4 cases using the high-speed steel slot drill under wet condition. The sound pressure was measured at 0.5m from the cutting zone by a dynamic microphone, and was analyzed at frequency domain. The tooth passing frequency appears as a harmonics form, and end mill wear is related with the first harmonic. It can be concluded from the result that the tool wear is correlate with the intensity of the measured sound at tooth passing frequency estimation of end mill wear using sound is possible through frequency analysis at tooth passing frequency under the given circumstances.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.11
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• pp.2035-2042
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• 2011

In this paper, we proposed the outer-rotor type of FSPM motor for high speed operation and optimized motor shape. First of all, combinations of pole and slot numbers are examined for the optimal back-EMF and cogging torque, then optimizes the better shape design of the permanent magnet, rotor pole width. Further, The winding turns are obtained by circle of the voltage limit equation and motor parameters to minimize the current and to improve the efficiency. As a result, the performance of the designed model is satisfied, and it is verified through a two-dimensional finite element method (2D-FEA).

• Proceedings of the KIEE Conference
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• summer
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• pp.782-784
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• 2004

The purpose of this paper is the selection of an optimum slot combination minimized the harmonics of air gap flux density and e.m.f., and reduction of the magnetic noise through the theoretical study on the cause and result of the magnetic noise. The analysis method is performed by the magnetic noise equivalent program and the FEM.