• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2001.04a
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• pp.28-33
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• 2001

Screw conveyors are used extensively in industrial for conveying and elevating materials. Despite their apparent simplicity, the mechanics of the conveying action is very complex. so many engineers depend on experiential data. Capacities of screw are pumping, steady flow of polymer melts, steady volumetric throughput etc. they are affected by geometry of screw, heat flux, pressure on inside barrel, rotating velocity, friction coefficient at screw surface etc. by computation volumetric efficiency increases as rotating velocity increases and decreases as friction coefficient increases. also it decreases with short pitch length. and double flight screw is more effective than single flight screw. The temperature of polymer melts by heating pad and injection pressure play a very important role in the injection molding machine. so in this paper we analyze thermal distortion and stress of screw includes pressure and temperature distributions by finite element analysis to understand what design factors influence on volumetric throughput efficiency of the screw and thermo-mechanical characteristics of screw.

• International Journal of Precision Engineering and Manufacturing
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• v.7 no.2
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• pp.52-55
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• 2006

The OLEDs(Organic Light-Emitting Diodes) structure organizes the bottom layer using glass, ITO(indium thin oxide), hole injection layer, hole transport layer, emitting material layer, electron transport layer, electron injection layer and cathode using metal. OLED has various advantages. OLEDs research has been divided into structural side and emitting material side. The amount of emitting light and luminescence efficiency has been improved by continuing effort for emitting material layer. The emitting light mechanism of OLEDs consists of electrons and holes injected from cathode and anode recombination in emitting material layer. The mobilities of injected electrons and holes are different. The mobility of holes is faster than that of electrons. In order to get high luminescence efficiency by recombine electrons and holes, the balance of their mobility must be set. The more complex thin film structure of OLED becomes, the more understanding about physical phenomenon in each interface is needed. This paper observed what the thickness change of hole transport layer has an affection through the below experiments. Moreover, this paper uses numerical analysis about carrier transport layer thickness change on the basis of these experimental results that agree with simulation results.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1994-1996
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• 2002

This paper reports a novel high-speed fluid injection system employing a simple magnetic micoractuator. This magnetic microacutator consists of current carrying copper beams and permanent magnet under the beams. There were many efforts to magnetic microactuator realization using conducting coils [1-2]. Even though many of magnetic microactuators were successfully fabricated and tested, it is true that most them suffer complex fabrication processes and thus higher production costs than electrostatic counterparts. In this research, efforts were concentrated on the microactuator realization that has simple structure, low production cost, and mass production possibility.

• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.1
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• pp.72-75
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• 2018

An initial rotor position estimation method is proposed in this study for an interior permanent-magnet synchronous motor without a resolver or an absolute encoder. This method uses least squares approximation to estimate the initial rotor position. The magnetic polarity is identified by injection of short pulses. The proposed estimation process is robust because it does not require complex signal processing that depends on the performance of a digital filter. In addition, it can be applied to various servo systems because it does not require additional hardware. Experimental results validate the effectiveness of the proposed method using a standard industrial servomotor with interior-permanent magnets.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.04a
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• pp.83-84
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• 2006

ITO/4, 4', 4"-tris (N -3 - methylphenyl - N - phenyl - amino) - triphenylamine, [m-MTDATA] / Terbium Iris - (1 - phenyl - 3 - methyl - 4 - (tertiarybutyryl) - pyrazol - 5 - one) triphenylphosphine oxide [$(tb-PMP)_3Tb-(Ph_3PO)$] / Mg:Ag devices were made to investigate its electrical and light emission properties. The thickness of m-MTOATA layer was varied from 0 to 80 nm. There was a threshold thickness for the sufficient hole injection. The insertion of 20 nm thick m-MTDATA layer between ITO and Tb-complex resulted in the right shift of current-voltage curve because of the insufficient hole injection. The low operating voltage can be obtained above the 40 nm of m-MTDATA layer. The insertion of m-MTDATA induced the increase of the background in the electroluminescence spectrum which was dependent on the current density of the devices.

• Korean Journal of Optics and Photonics
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• v.14 no.5
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• pp.521-529
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• 2003

For complex-coupled (CC) DFB lasers, we found that there might be little correlation between the single mode yields at threshold and above threshold. At threshold, the single mode yield considering f number of in-phase (IP) CC DFB lasers is the same as that of anti-phase (AP) CC DFB lasers. However, the single mode yield as a function of injection current above threshold of IP CC DFB lasers is much different from that of AP CC DFB lasers. In the case of IP CC DFB lasers, the single mode yield increases as the coupling coefficient ratio (CR) increases, while, in the case of AP CC DFB lasers, the single mode yield decreases rapidly regardless of CR as the injection current increases. In the case of AR-HR combinations, the effect of AR ref1ectivity on the single mode yield increases as the coupling strength decreases. As the coupling strength decreases, the CR at which the increase rate of the single mode yield starts to decrease, increases, and the maximum single mode yield increases. Single mode yields of AR-HR and AR-AR combinations are larger than those of AR-CL and CL-CL combinations.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.8
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• pp.99-106
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• 1999

The present study deals with the effect of combustion chamber shape on in-cylinder soot oxidation characteristics of a D.I . diesel engine. The analysed combustion chambers were a toroidal and a reentrant with a projection(Complex). The two-color method was used to measure in-cylinder flame temperature and KL value which is approximately proportional to the soot amount along the optical path. In addition, heat release rate was calculated from the in-cylinder pressure data. From these investigations , the soot oxidation of the reentrant and the complex which were strengthen squish flows went worse in late combustion period under heavy-load operation compared to that of the toroidal at retarded fuel injection timing . It might be the cause of the flame holding that squish lip depress the outflow of flame from the bowl to the entire combustion space.

• Journal of The Korean Astronomical Society
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• v.29 no.spc1
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• pp.331-332
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• 1996

We present 3 rare subtypes of the FFSs observed with high temporal resolution at 4-frequency (1.42, 2.13, 2.84 and 4.2G GHz). The various FFSs occurred during the main and post-flare phase can demonstrate that coronal nonthermal electron acceleration/injection may go through the whole development process of flares, and deduce that there may exist the re-forming of loop-like structures in the post-flare phase, and the complex multi-type magnetic structures in corona.

• Journal of The Korean Astronomical Society
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• v.34 no.4
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• pp.289-291
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• 2001

To study the structure and dynamics of a cosmic-ray-plasma system, hydrodynamic approach is a fairly good approximation. In this approach, there are three basic energy transfer mechanisms: work done by the plasma flow against pressure gradients, cosmic ray streaming instability and stochastic acceleration. The interplay between these mechanisms gives a range of structures. We present some results of different version of the hydrodynamic approach, e.g., flow structure, injection, instability, acceleration with and without shocks.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.2
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• pp.199-204
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• 2013

Owing to the global energy crisis, studies have strongly focused on realizing energy savings through vehicle weight reduction using light metal alloys or polymer composites. Polymer composites afford many advantages including enabling the fabrication of complex shapes by injection molding, and glass and carbon fibers offer improved mechanical properties. However, the high temperature in an engine room and the high humidity during the rainy season can degrade the mechanical properties of the polymer. In this study, the mechanical properties of injection-molded glass-fiber-reinforced polymer were assessed at a temperature of $85^{\circ}C$ and the maximum moisture absorption conditions. The result showed a 23% reduction in the maximum tensile strength under high temperature, 30% reduction under maximum moisture absorption, and 70% reduction under both heat and moisture conditions. For material selection during the design process, the effects of high temperature and high humidity should be considered.