• 전력전자학회:학술대회논문집
• /
• 전력전자학회 1999년도 전력전자학술대회 논문집
• /
• pp.346-349
• /
• 1999

This paper proposes a new series-connected diode rectifier which draws sinusoidal input currents. The proposed rectifier system is configured by adding an auxiliary circuit to the conventional 12-pulse series-connected diode rectifier and employing a current injection technique. A low kVA (0.02Po (PU) ) active current source injects a triangular current results in near sinusoidal input current from the utility with less than 1% THD. The resulting system is suitable for high voltage and high power applications. Experimental results is provided from a 220VA rectifier system.

• Journal of Electrical Engineering and Technology
• /
• 제13권4호
• /
• pp.1515-1527
• /
• 2018

This paper presents a sensorless speed control of IPMSM (Interior Permanent Magnet Synchronous Motor) using the high-frequency (HF) square wave injection method. In the proposed HF pulsating square wave injection method, injection voltage is applied into the estimated d-axis of rotor and high-frequency induced q-axis current is considered to estimate the rotor position. Conventional square wave injection methods may need complex demodulation process to find rotor position, while in the proposed method, an easy demodulation process based on the rising-falling edge of the injected voltage and carrier induced q-axis current is implemented, which needs less processing time and improves control bandwidth. Unlike some saliency-based sensorless methods, the proposed method uses maximum torque per ampere (MTPA) strategy, instead of zero d-axis command current strategy, to improve control performance. Furthermore, this paper directly uses resultant d-axis current to detect the magnet polarity and eliminates the need to add an extra pulse injection for magnet polarity detection. As experimental results show, the proposed method can quickly find initial rotor position and MTPA strategy helps to improve the control performance. The effectiveness of the proposed method and all theoretical concepts are verified by mathematical equations, simulation, and experimental tests.

• 동력기계공학회지
• /
• 제9권2호
• /
• pp.14-18
• /
• 2005

In this study, the spray characteristics of blended fuels with biodiesel were investigated. The experiments were performed for the effect of mixing ratio and injection pressures on the spray behavior. Conventional diesel fuel and biodiesel fuel and blended fuels were used as test fuels. Through the spray visualization system, composed of a Halogen lamp and High speed camera. The process of spray injection was visualized. Fuel containing biodiesel has different spray pattern on account of the high viscosity and large surface tension. Through this experimental result, we found that, after solenoid driving pulse generates, the increase of injection pressure enables delay time to get shorter, but the increase of mixing ratio makes delay time lengthen.

• 한국광학회:학술대회논문집
• /
• 한국광학회 2009년도 창립 20주년기념 특별학술발표회
• /
• pp.359-360
• /
• 2009

This paper reports experimental results on temporal characteristics of injection-locked polarization switching of a conventional type 1.55-${\mu}m$ wavelength single-mode vertical-cavity surface-emitting laser (VCSEL). The polarization of external injection beam was kept orthogonal to main mode of VCSEL. The relation for variation of intensity of two polarization modes of VCSEL with wavelength detuning for various repetition rates of injection pulse is reported.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
• /
• 제48권11호
• /
• pp.640-645
• /
• 1999

This paper proposes a new series-connected diode rectifier which draws sinusoidal input currents. The proposed rectifier system is configured by adding an auxiliary circuit to the conventional 12-pulse series-connected diode rectifier and employing a current injection technique. A low kVA($0.02P_{\circ}$(PU) ) active current source injects a triangular current into the interphase reactor of the diode rectifier. The current injection results in near sinusoidal input current from the utility with less than 1% THD. The resulting system is suitable for high voltage and high power applications. Experimental and simulation results are provided from a 220V, 3kVA prototype rectifier system.

• Journal of Dental Anesthesia and Pain Medicine
• /
• 제21권4호
• /
• pp.345-355
• /
• 2021

Background: This study aimed to evaluate the efficacy of external vibrating devices and counterstimulation on a child's dental anxiety, apprehension, and pain perception during local anesthetic administration. Methods: This was a prospective, randomized, parallel-arm, single-blinded interventional, clinical trial. One hundred children aged 4-11 years, requiring pulp therapy or extraction under local anesthesia (LA), were recruited and allocated equally into two groups (1:1) based on the interventions used: Group BD (n = 50) received vibration using a Buzzy^® device {MMJ Labs, Atlanta, GE, USA} as a behavior guidance technique; Group CS (n = 50) received counterstimulation for the same technique. Anxiety levels [Venham's Clinical Anxiety Rating Scale (VCARS), Venham Picture Test (VPT), Pulse oximeter {Gibson, Fingertip Pulse Oximeter}, Beijing, China)] were assessed before, during, and after LA administration, while pain perception [Wong-Baker Faces Pain Rating Scale (WBFPS), Visual Analogue Scale (VAS)] was evaluated immediately after injection. Statistical analysis was performed using the Student's t-test to assess the mean difference between the two groups and the repeated measures ANOVA for testing the mean difference in the pulse rates. Statistical significance was set at P < 0.05. Results: Significant differences in mean pulse rate values were observed in both groups. In contrast, the children in the BD group had higher diminution (P < 0.05), whereas the mean VCARS and VPT scores were conspicuous (P < 0.05). Based on the mean WBFPS and VAS scores, delayed pain perception after LA injection was more prominent in the BD group than in the CS group. Conclusion: External vibration using a Buzzy^® device is comparatively better than counterstimulation in alleviating needle-associated anxiety in children requiring extraction and pulpectomy.

• 한국연소학회:학술대회논문집
• /
• 한국연소학회 1997년도 제15회 KOSCO SYMPOSIUM 논문집
• /
• pp.69-76
• /
• 1997

Industrial-scale pulse corona process to remove $SO_2$ and $NO_x$ simultaneously from combustion flue gas has been studied. The pilot plant built in the present study treats 2,000 $Nm^3$/hr of flue gas from a boiler. The geometry of the pulse corona reactor is similar to that of an electrostatic precipitator commonly used in industry, A thyratron switch and magnetic pulse compressors, which can generate up to 130 kV of peak pulse voltage and up to 30 kW of average pulse power, have been used to produce pulsed corona. The removal efficiencies of $S0_2$ and $NO_x$ with the present process are maximum of 95 % and 85 %, respectively. Electrical power consumption to produce the pulsed corona, which has been one of the major difficulties to apply this process to industry, has been evaluated in the present study. The results showed that the power consumption can be reduced significantly by simultaneous addition of hydrocarbon injection and heterogeneous phase reactions to the process.

• 전기전자학회논문지
• /
• 제5권2호
• /
• pp.201-210
• /
• 2001

광 시분할 및 파장분할 다중화에 의한 초고속 광통신 시스템에 적합한 파장 및 반복율 가변 능력을 갖는 초단 펄스열을 고리형 반도체 광섬유 레이저의 광주입 모드잠김에 의해 발생시켰다. 발생된 광 펄스열은 10 GHz, 20 GHz, 30 GHz, 및 40 GHz의 다양한 반복율에서 ${\sim}10$ 피코초 정도의 펄스폭과 30 nm가 넘는 파장 가변능력을 보였다.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2008년도 춘계학술대회논문집
• /
• pp.61-64
• /
• 2008

The present study of these experiments are close examination of spray characteristics that are continuous liquid jet and modulated pressure pulse liquid jet. The experiments were conducted using water, over a range of cross-flow velocities from 42${\sim}$136 m/s, with injection frequencies of 35.7${\sim}$166.2 Hz. Between continuous cross-flow jet and pressure pulsed cross-flow jet for characteristics of penetration, breakup point, spray angle and macro spray shape are investigated experimentally. In cross-flow field, main parameter of liquid jet for breakup was cross-flow stream rather than pressure pulse frequency. As oscillation of the periodic pressure that could make liquid jet moved up and down, the mixing efficiency was increased. Also, a bulk of liquid jet puff was detected at upper field of liquid surface. So, this phenomenon has a good advantage of mixing spray from concentration of center area to outer area. Because of pressure pulsation frequency, an inclination of SMD for the structured layer was evanescent. Cross-sectional characteristics of SMD at downstream area were non-structured distributions. Then cross-sectional characteristics of SMD size were about same tendency over a range that is effect of spray mixing. The tendency of volume flux value for various frequency of pressure pulse was same distribution. And volume flux was decreased when the frequency of pressure pulse increase.

• 한국자동차공학회논문집
• /
• 제8권6호
• /
• pp.51-59
• /
• 2000

In-cylinder spray flow motion plays an important in the adjustment of mixture preparation with a fundamental spray characteristics and in-cylinder flow field well in direct-injection gasoline engine. In this study, the fundamental spray characteristics such as mean drop size, velocity distribution, spray angle were measured and in-cylinder spray flow motion was visualized in order to optimize intake port, piston top land and combustion chamber shapes in the development stage of mass-produced G야 engine. For these experiments, the PDPA measurements and Mie scattering technique were used for detailed spray characteristics and in-cylinder spray motions were obtained by use of ICCD camera through the single-cylinder optical engine. From the experimental results, the test injector shows a good low-end linearity between the dynamic flow and fuel injection pulse width and the fuel spray of 20mm or less in SMD with good spray symmetry. In addition, the in-cylinder tumble flow has more effect on the homogeneous mixture formation than that of in-cylinder swirl flow at early injection mode and the in-cylinder swirl flow plays a better role of stratified mixture preparation than tumble flow at late injection mode.