• Current Optics and Photonics
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• v.1 no.3
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• pp.228-232
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• 2017

We propose a reflector-type perfect absorber with double absorption lines using electric and magnetic dipoles of Mie resonances in an array of silicon nanospheres on a silver substrate. In the visible range, hundreds of nanometer-sized nanospheres show strong absorption lines up to 99%, which are enhanced by the interference between Mie scattering and reflections from the silver substrate. The air gap distance between the silicon particles and silver substrate controls this interference, and the absorption wavelengths can be controlled by adjusting the diameter of the silicon particles over the entire range of visible wavelengths. Additionally, our structure has a filling factor of 0.322 when the absorbance is nearly 100%.

• 제어로봇시스템학회:학술대회논문집
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• 1987.10b
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• pp.658-663
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• 1987

The new controller developed here, which is the facility with only one measurement, is a new concept for the level controller of the existing nuclear steam generator. A MACS (Microcomputer-based Adaptive Control System of a Steam Generator) is quite practical and efficient, and has also simple structure and higher flexibility in the installment for actual plant. A key ingredient of this system is adaptive regulator which can calculate adaptive, optimal valve position in response to changes in the dynamics of the process and the disturbances. In spite of many difficulties in the steam generator water level control at low power, it can be concluded from the experimental and simulation results, that the MACS can provide optimal, robust steam generator level control from zero to full power. The amount of the control input effort can be reduced by adjusting the weighting factor. However, the steady state water level errors are generated. To avoid the steady errors, the different adaptive algorithm should be investigated in the future. The 3 second sampling time is acceptable for this system. However, action should be taken to shorten the sampling time for better digital control.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.107-108
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• 2008

The temperature rise of GIS (Gas Insulated Switchgear) busbar system is a vital factor that affects its performance. In this paper, a two-dimensional model is presented by commercial code CFX11 for the evaluation of natural convection in the busbar system. In the model, SF6 (Sulfur Hexafluoride) is used to insulate the high voltage device and improves the heat transfer rate. The power losses of a busbar calculated by the magnetic field analysis are used as the input data to predict the temperature rise by the nature convection analysis. The heat-transfer coefficients on the boundaries are analytically calculated by applying the Nusselt number considering material property and model geometry for the natural convection. The temperatures of the tank and conductors from CFX simulation and the experiment were compared. The results show a good agreement. In the future, we will calculate the 3-D model and try to reduce the temperature by adjusting some dimensional parameters.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.603-607
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• 2002

Cavity pressure is a factor of what is occurring inside the mold and is used as one of the process parameters that control the overall injection molding cycle. The insight of cavity pressure is able to predict part quality and optimum process condition. In this paper, it is adapted ejector pin sensor to measure the cavity pressure and investigates the flow balance and the cavity pressure according to different runner thickness for adjusting the flow balance. Flow balance is very important to have not the poor results such as flash and warpage in the family mold. This paper predicted flow balance and cavity pressure using CAE analysis tool and compared with the test results. The results of analysis and test have a good agreement with the cavity pressure profile and flow pattern of the test.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.28 no.1
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• pp.14-16
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• 2017

Pop singers frequently use breathy voice to express diverse emotion. Such method is the major factor that divides vocalization in pop and classical music. Using breathy voice too much for a long time could make singer short-winded, which might cause the voice injured. In order to prevent the problem, singers need to find resonance balance between high notes and low notes and among vowels. Moreover, they should take more attention when producing resonance in consonants with much air flow. Along with finding resonance balance, if skilled at controlling the volume of voice, singers can use the breathy voice selectively at the desired part, adjusting close quotient freely. Through this kind of approach, pop singers can develope their unique style of vocalization and avoid the vocal damage.

• Design & Manufacturing
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• v.10 no.1
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• pp.31-35
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• 2016

In sheet metal forming process, drawing is typical process. And the key factor of drawing is blank holding force (BHF) A low BHF can cause wrinkling, whereas a high BHF can cause fracture during a deep drawing process. Thus, formability can be influenced by application appropriate BHF. In this study, a variable blank holding force (VBHF) is applied to extend the forming limit by avoiding both wrinkling and fracture. To determine VBHF in drawing process, numerical simulations and statistical analysis are carried out using commercial FEM software.

• Journal of Power Electronics
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• v.9 no.4
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• pp.575-581
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• 2009

In this paper two modes of operating a wound rotor induction machine as a generator at sub-and super-synchronous speeds in wind energy conversion systems are investigated. In the first mode, known as double fed induction generator (DFIG), the rotor circuit is fed from the ac mains via a controlled rectifier and a forced commutated inverter. Adjusting the applied rotor voltage magnitude and phase leads to machine operation as a generator at sub-synchronous speeds. In the second mode, the machine is operated in a slip recovery scheme where the slip energy is fed back to the ac mains via a rectifier and line commutated inverter. This mode is described as double output induction generator (DOIG) leading to increase the efficiency of the wind-to electrical energy conversion system. Simulated results of both modes are presented. Experimental verification of the simulated results are presented for the DOIG mode of operation, showing larger amount of power captured and better power factor when compared to conventional induction generators.

• Journal of Applied Reliability
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• v.11 no.3
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• pp.281-291
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• 2011

This paper presents an accelerated life test of booster pump for home water purifier. The failure analysis shows that decreased flux due to the plastic deformation of bypass spring adjusting pressure is the predominant failure mechanism. An accelerated life test is designed and implemented to estimate the lifetime of the booster pump. Temperature, water pressure and voltage are selected as accelerating variables through the technical review about failure mechanism. It is assumed that the lifetimes of booster pumps follow lognormal distribution and the combination model of temperature and non-thermal stresses holds. The life-stress relationship, acceleration factor, and $B_{10}$ life at design condition are estimated by analyzing the accelerated life test data.

• Phonetics and Speech Sciences
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• v.3 no.1
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• pp.111-116
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• 2011

The purpose of this study was to analyze the association between self-reported voice problems and voice disorders in the Korean adult population. Data were collected from the 4th Korea National Health and Nutritional Examination Survey (2008) from 3,135 subjects (1,310 men and 1,825 women) aged 19 years and older. Multi-nominal logistic regression analyses were used to examine the association between self-reported voice problems and voice disorders in the Korean adult population. Adjusting for covariates (age, sex, education level, job, smoking, alcohol drinking, thyroid disorders, pain and discomfort during the last 2 weeks), self-reported voice problems included independently associated functional voice disorders (OR=4.70, 95% CI: 3.14-7.03) and organic voice disorders (OR=3.89, 95% CI: 1.57-9.65). The results of the present study verified that self-reported voice problems are valuable indicators for voice disorders. Further research is needed to ascertain the effect of self-reported voice problems on voice disorder in adults.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.6
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• pp.372-379
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• 2004

Most of the loads in industrial power distribution systems are balanced and connected to three power systems. However, in the user power distribution systems, most of the loads are single ＆ three phase and unbalanced, generating voltage unbalance. Rotating machines operating on an unbalanced voltage will draw a highly unbalanced current. As a result, the three-phase currents may differ considerably, thus resulting in an increased temperature rise in the machine. This paper presents a scheme on steady states of a three-phase induction motor under unbalanced voltages. The three-phase voltages applied to the stator winding of the studied induction motor are controlled by respectively adjusting the magnitude and phase angle of each phase. The voltage unbalanced factor(VUF) of the three-phase source voltages can then be varied to examine the different values of VUF on machine's operation characteristics.