• Korean Journal of Optics and Photonics
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• v.5 no.1
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• pp.84-89
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• 1994

A tunable pulsed dye laser was operated in a single longitudinal mode by injection locking with a cw ring dye laser. A doubled Nd:YAG laser was used as the pumping source. Phase sensitive detection technique was applied to maintain the required match between the master laser frequency and the slave resonator cavity length. The fluctuation of the center frequency of the pulsed laser was < 10 MHz, and the pulse duration (FWHM) was 6 ns. The linewidth measured by scanning confocal interferometer was 130 MHz. When pumped by 50 mJ of the doubled Nd:YAG laser, the output energy of the pulsed dye laser was 2 mJ and the peak power was 330 kW. 30 kW.

• 전자공학회논문지 IE
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• v.45 no.3
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• pp.5-12
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• 2008

We propose efficient scan testing method capable of reducing the test data and power dissipation for digital logic circuits. The proposed testing method is based on a hybrid run-length encoding which reduces test data storage on the tester. We also introduce modified Bus-invert coding method and scan cell design in scan cell reordering, thus providing increased power saving in scan in operation. Experimental results for ISCAS'89 benchmark circuits show that average power of 96.7% and peak power of 84% are reduced on the average without fault coverage degrading. We have obtained a high reduction of 78.2% on the test data compared the existing compression methods.

• Journal of Electrical Engineering and Technology
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• v.3 no.4
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• pp.528-537
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• 2008

Primary frequency control(PFC) has the ability to regulate short period random variations of frequency during normal operation conditions and also to respond rapidly to emergencies. However, during the past decade, numerous significant sized blackouts occurred worldwide that resulted in serious economic losses. Therefore, the conclusion has been reached that the ability of the current PFC to meet an emergency is poor, and security of power systems should be improved. An alternative to enhance the PFC and thus security is to store excessive amounts of energy during off-peak load periods in efficient energy storage systems for substituting the primary control reserve. In this sense, superconducting magnetic energy storage(SMES) in combination with a static synchronous compensator(STATCOM) is capable of supplying power systems with both active and reactive powers simultaneously and very rapidly, and thus is able to enhance the security dramatically. In this paper, a new concept of PFC based on incorporating a STATCOM-SMES is presented. A complete detailed model is proposed and a new control scheme is designed, comprising an enhanced frequency control scheme, and a fully decoupled current control strategy in d-q coordinates with a novel controller to prevent dc bus capacitors voltage drift/imbalance. The performance of the proposed control schemes is validated through digital simulation carried out using MATLAB/Simulink.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.12 no.4
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• pp.1-7
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• 2016

This paper presents a design method for the horizontal straight ground heat exchanger (GHE) based on the Kavanaugh design method. In order to examine suitability of the suggested design method, a horizontal line type GHE was installed in a steel box of which the size was $5m{\times}1m{\times}1m$ filled with dried Joomunjin standard, and a thermal response test (TRT) was conducted for 21 hours. A numerical analysis was performed for a simulation of a peak month operation and for its verification by finite element method (FEM). According to the simulation results, it was concluded that the suggested design method for a horizontal straight GHE is reliable for the estimation of a design length.

• Journal of Mechanical Science and Technology
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• v.18 no.10
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• pp.1809-1818
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• 2004

The dependence of the ignition timing in an HCCI engine on intake temperature and pressure, equivalence ratio, and fuel species is investigated with a zero-dimensional model combined with a detailed chemical kinetics. The accuracy of the model is evaluated by comparing measured and computed results in a propane-fueled HCCI engine. It is shown that the peak pressure values are reproduced within 10% and ignition timing within 5$^{\circ}$ CA. The heat loss through the walls is found to affect significantly on the ignition timing for different inlet conditions. It is also shown that for the propane-fueled engine, the tolerance in intake temperatures is 20-25K and the tolerance in intake pressure is about 1 bar for stable operation without misfire or too early ignition. Comparison of propane and heptane fuels indicates that the tendency to misfire when heptane is employed as the fuel is less than that when propane is employed with the same wall temperature conditions. However, the heptane-fueled engine may have a lower compression ratio to avoid too early ignition and hence lower efficiency. For the selected set of engine parameters, stable operations might be achieved for the heptane-fueled engine with twice as much tolerance in intake temperatures as for the propane-fueled engine.

• Journal of Korea Water Resources Association
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• v.48 no.3
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• pp.197-207
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• 2015

Modification of travel time is necessary in all Nakdong river basin because hydrological conditions of Nakdong river basin were changed after major rivers project. Also calculation of flood travel time at between sections of weirs is necessary. In this study, flood travel time was calculated using hydraulic model and the latest topographical data from Changnyeong-Haman weir to Nakdong river estuary bank. Analysis of discharge and stage conditions were carried out. 84 of the scenarios were organized according to flow rate, discharge type, boundary conditions, and tributary conditions. Flood travel time of initial and peak were calculated with discharge and stage conditions, respectively. The results of this study will be available in practical business work such as flood forecast warning and weir operation on algae removal.

• Journal of Electrical Engineering and Technology
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• v.5 no.4
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• pp.606-613
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• 2010

This paper proposes a novel current-based maximum power point tracking (CMPPT) method for a single-phase photovoltaic power conditioning system (PV PCS) by using a modified incremental conductance method. The CMPPT method simplifies the entire control structure of the power conditioning system and uses an inherent current source characteristic of solar cell arrays. Therefore, it exhibits robust and fast response under a rapidly changing environmental condition. Digital phase locked loop technique using an all-pass filter is also introduced to detect the phase of grid voltage, as well as the peak voltage. Controllers of dc/dc boost converter, dc-link voltage, and dc/ac inverter are designed for coordinated operation. Furthermore, a current control using a pseudo synchronous d-q transformation is employed for grid current control with unity power factor. A 3 kW prototype PV PCS is built, and its experimental results are given to verify the effectiveness of the proposed control schemes.

• Journal of Power Electronics
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• v.11 no.4
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• pp.499-506
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• 2011

This paper presents an interleaved active-clamping zero-voltage-switching (ZVS) forward-flyback converter without an output choke. The presented topology has two active-clamping circuits with two separated transformers. Because of the interleaved operation of the converter, the output current ripple will be reduced. The proposed converter can approximately share the total load current between the two secondaries. Therefore, the transformer copper loss and the rectifier diodes conduction loss can be decreased. The output capacitor is made of two series capacitors which reduces the peak reverse voltage of the rectifier diodes. The circuit has no output inductor and few semiconductor elements, such that the adopted circuit has a simpler structure, a lower cost and is suitable for high power density applications. A detailed analysis and the design of this new converter are described. A prototype converter has been implemented and experimental results have been recorded with an ac input voltage of 85-135Vrms, an output voltage of 12V and an output current of 16A.

• Korean Journal of Acupuncture
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• v.25 no.1
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• pp.247-257
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• 2008

Objectives : The warm needling technique is the method in combining the effects of acupuncture needle with the effects of moxibustion. We need to standardize the characteristics of the warm needling technique in order to get more systematic and objective result in operation mechanism and effects and then get more clinical abilities in these fields. Methods : In this study, using of labview system on the warm needling technique we studied about measurement and comparison with partial temperature changes according to the position of ignition. Results & conclusion : When we measured the warm needling's partial temperature according to the position of ignition, the bottom ignition method got the higher result on the peak temperature measured at 2cm below the head than the apex ignition method.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.9 no.1
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• pp.71-78
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• 1998

Type Ⅰ thyuroplasty in conjunction with arytenoid adduction is one of the excellent techniques in the treatment of unilateral vocal fold paralysis. But perioperative objective evaluation of the patients is difficult. With the development of the videostroboscopy and image analysis program, we could quantify the Glottal Area Waveform(GAW) in patients with unilateral vocal fold paralysis and investigated the relationship between the glottal area and aerodynamic and acoustic parameters. Eight female patients who were performed type Ⅰ thyroplasty in conjunction with arytenoid adduction and 5 females with normal vocal function were involved in this study. Preoperative and postoperative videostroboscopy and vocal function study wire performed. GAW was analysed quantitatively with image analysis program (Kay Stroboscope Image analysis, KSIP) Peak Glottal Area(PGA), Baseline Offset(BO), and Closing Phase(CP) were increased in patients with unilateral vocal fold paralysis and they were reduced after the operation. Mean flow Rate (MFR) was well correlated with the PGA in normal control group and unilateral vocal fold paralysis patients. Noise to harmonic ratio(NHR) was correlated with PGA only in preoperative unilateral vocal fold paralysis patients. In conclusion quantitative measurement of the GAW is useful method in evaluation of unilateral vocal f31d paralysis patients.