• Proceedings of the Optical Society of Korea Conference
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• 2006.02a
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• pp.87-88
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• 2006

Bragg fibers, consisting of a low index core (including air) surrounded by a series of periodic layers of alternate high and low refractive index materials, each being higher than that of the core, form a 1D photonic bandgap (PBG). In view of the multitude of individual physical parameters that characterize a Bragg fiber, they offer a wide choice of parametric avenues to tailor their propagation characteristics. Owing to their unique PBG guidance mechanism, Bragg fibers indeed exhibit unusual dispersion characteristics that are otherwise nearly impossible to achieve in conventional silica fibers. Solid core Bragg fibers, amenable to fabrication by the highly mature MCVD technology, could be designed to realize broadband supercontinuum light. This talk would review our recent works on modeling of propagation characteristics, dispersion tailoring in them for applications as metro as well as dispersion compensating fibers and also as supercontinuum light generators.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.855-857
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• 2003

A slotless Permanent Magnet Linear Synchronous Motor (PMLSM) has good control ability but thrust density is low. So, this paper proposes inserted core type of slotless PMLSM to improve its low thrust density. Inserting the core between windings of each phase, detent force is generated by the difference of magnetic resistance in an air gap. To minimize detent force and maxize thrust, this paper applies the neural network to inserted core type of slotless PMLSM.

• The Transactions of the Korean Institute of Power Electronics
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• v.15 no.2
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• pp.119-126
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• 2010

An integrated magnetic (IM) transformer is proposed for a phase shifted full bridge (PSFB) converter with zero voltage switching (ZVS). In a proposed IM transformer, the transformer is located on the center leg of E-core and the output inductor is wound on two outer legs with air gap. The proposed IM transformer is analyzed by using the magnetic capacitor model. For reducing the core size, EE core is redesigned. The proposed IM transformer is experimentally verified on a 1.2 kW prototype converter. The converter efficiency with the proposed IM transformer is about 93 % at full load and its volume size can be reduced. It can be expected that the power density can be largely increased with the proposed IM transformer.

• Proceedings of the KIEE Conference
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• 1994.11a
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• pp.86-88
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• 1994

In this paper, we present the design procedure and analysis the fundamental characteristics for Linear DC motor using permeance method and finite element method. Designed LDM is made of two permanent magnets, three iron core and amateur windings. For the design the LDM, first of all it is nessary to calculate the air gap flux density and thrust force, after that to determine core size, the numbers of winding turns, winding width, motor cross section area and losses in the coil. Also, we analysis the fundamental characteristics for implemented LDM according to proposed design procedure, and we find that the implemented LDM generated constant thrust force for costant current as long as iron of core is not saturated. Finally, we find that the proposed design procedure in this paper is effective to design and implementation of LDM.

• Proceedings of the KIEE Conference
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• 2001.07d
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• pp.2042-2044
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• 2001

The jumping ring apparatus of the type described in this study is used to demonstrate and educate the effects of electromagnetic induction. Placing an aluminum ring over the core and switching on AC source causes the ring to jump in the air due to induced currents in the ring producing a magnetic field opposed to that produced in the core. If the AC current is slowly increased from zero or ring is placed over the core when AC is already flowing the ring floats due to the balance between its weight and the upward electromagnetic force. Pentimum computer is used to display this value to screen and generate control signal.

• 대한예방의학회:학술대회논문집
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• 2005.10a
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• pp.31-44
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• 2005

In summary, air pollution issues in the United States are addressed by a core group of regulations supplemented by active Interventions as needed by public health agencies. The strategies employed by public health officials must be flexible and innovative to address the needs of the citizens, As you can see from the examples cited above, the collaboration of public health agencies can be critical in protecting communities from adverse exposures. In the US state and local governments have the primary responsibility for health and safety issues, including those associated with air pollution. The federal agencies have responsibilities when activities between states are involved and or the issues are of national significance. Significant challenges and opportunities remain to identify the relationship to air pollution and other environmental factors and the incidence of disease, and hence develop and implement Intervention strategies.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.2
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• pp.87-94
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• 2003

To reduce the air side pressure drop in air-cooled heat exchanger, tow-in type winglet vortex generators are applied. A specially designed multiple-channel test core was used in the experiments for the various geometry of winglet vortex generators. The proposed tow-in type vortex generator gives significant separation delay, reduces form drag, and removes the zone of poor heat transfer from near-wake of the tubes. The results show the significant pressure drop reduction for the tow-in win91e1 vortex generators with the similar enhancement of the heat transfer as other vortex generator applications in heat exchanger. In the range of Reynolds number of 350 to 2100 the pressure drop decrease 8∼15% and 34∼55% for the in-line and staggered tube banks, respectively, compared to those without vortex generators.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.6 no.1
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• pp.54-65
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• 1994

Performance of naturally circulating cooling system of $SF_6$ gas charged transformer was simulated and the variations of gas flow rate, maximum coil temperature, gas temperature and cooling air temperature were investigated with respect to the height of radiator, interplates distance and heat generation rate at core. The results show that the height of radiator most significantly affects the performance of natural circulating cooling system of transformer.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.3 no.1
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• pp.61-68
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• 1991

The purpose of this study is to investigate the heat transfer characteristics and the flow structure in the case of rectangular air jet impinging vertically on the flat heating surface. The maximum value of Nusselt number at stagnation point is observed at H/B=10. It is found that this trend has been caused by the effect of stretching of large scale vortex in the stagnation region. For potential core region the Nusselt number distribution in the downstream of the stagnation point decreases gradually and begins to increase at about X/B=3. From the flow visualization it could be seen that small eddy produced from the nozzle edge grows in large scale and that large scale eddy disturbed the thermal boundary layer on the heating plate. The local average Nusselt number becomes maximum at X/B=0.5 regardless of H/B variation.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.491-498
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• 2004

Lift Fan Engines of JAXA's conceptual Jet VTOL aircraft have a very small bellmouse shape air intake, which make some differences in aerodynamic design of the blades. To obtain a better rotor or stator blade design, this paper performs a numerical analysis of the throughflow on a lift fan as a two-dimensional axisymmetrical flow. Based on the last report focusing on the air intake's influence on the throughflow, a more realistic bellmouse air intake case is treated to reconsider the influence on the throughflow by the small bellmouse air intake. Three work input patterns are tested to reduce some problematic influences on the throughflow or blade designs. The obtained result shows one of acceptable blade designs for the lift fan engine.