• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.3
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• pp.256-264
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• 2022

The frequency power control method (FCM) which has a wide operating frequency range is adopted for induction heating (IH) cooktops. When FCM is applied to the full-bridge series resonant converter (FB-SRC) based IH system, high-frequency switching of the inverter is required compared to the half-bridge SRC (HB-SRC)-based IH system. Therefore, the switching loss of the inverter increases, and applying FCM under the condition that the inverter operating frequency range is limited is difficult. Therefore, this paper proposes a control strategy with the phase shift power control method considering that limited frequency conditions are presented. Loss analysis following the control method is performed through simulation and mathematical analysis. In addition, the validity of the proposed control strategy is verified by analyzing the heating performance following the control method through the test results of the 3,200[W] prototype.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.380-383
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• 2000

This paper presents about EL(electro-luminescent) driver with inverter Inverter is constructed by using characteristic of FET and its output characteristics is analysed for the variation of gate bias frequency and load. The optimum operating condition of inverter is that the gate bias frequency of FET equal two resonant frequency of circuit.

• Journal of Korean Academy of Fundamentals of Nursing
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• v.15 no.4
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• pp.566-577
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• 2008

Purpose: Developing a curriculum(DACUM) is a method of analyzing job focused competency, which is obtained from the data of an expert belonging to a certain career. In this study the DACUM method was used to analyze the jobs of operating room nurses. Method: Through the DACUM workshop which was arranged by two DACUM facillitators, a definition of the role of operating room nurses was developed and then duties and tasks of operating room nurses' were identified. For the workshop, a DACUM committee with 10 operating room nurses was organized. Finally, the duties and tasks which were identified were validated by 422 nurses for importance, difficulty and frequency. Results: Thirteen duties and 105 tasks were identified on the DACUM chart, where importance, difficulty, and frequency of tasks were represented by alphabet letters A, B, and C as higher degree of importance. The determinant coefficient(DC) showed that the most important duty was assisting with operations(DC=6.61), and the least, managing operating materials(DC=4.22). For tasks, the most important ones were assisting in orthostatic surgery(DC=7.60), and assisting in thoracic surgery(DC=7.38), and the least important making gauze ball(DC=2.39), and saving of operation site((DC=3.27). Conclusion: The results suggest a need to develop an education program using the DACUM chart as a basis for the development and as a clinical career ladder and for curriculum of operating room nursing.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.3
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• pp.135-140
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• 2019

In this paper, a frequency split type broadband drive amplifier operating in the L, S and C bands was designed and fabricated. Transistor is difficult to efficiently use when the fractional bandwidth of the drive amplifier is more than 100%, In particular, the characteristics of the driving amplifier are important for operating the power amplifier in which the characteristics of the output power and the efficiency are sensitively changed according to the frequency band. A frequency split methods was applied to maximize the bandwidth of a drive amplifier and to divide the output of the drive amplifier into low band and high band so that the transistor of the power amplifier located at the rear of the drive amplifier can be efficiently used. The designed drive amplifier was fabricated in GaAs HBT technology and 9-layer SiP, and verified by the measurements. The fabricated drive amplifier shows a gain of more than 8 dB and an output power of more than 15 dBm in the operating frequency range.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.8
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• pp.1095-1101
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• 2002

An experimental apparatus was prepared to investigate thermal and hydrodynamic characteristics of regenerator at cryogenic temperature under pulsating pressure condition. The regenerator was pressurized and depressurized by a compressor with various operating frequencies. Cold end of the regenerator was maintained around 100 K by means of a liquid nitrogen heat exchanger. Instantaneous gas temperature and mass flow rate were measured at both ends of the regenerator during the whole pressure cycle. Pulsating pressure drop across the regenerator was also measured to see if it could be predicted by a friction factor at steady flow condition. The operating frequency of pressure cycle was varied between 3 and 60 Hz, which are typical operating frequencies of Gifford-McMahon, pulse tube, and Stilting cryocoolers. First, the measured friction factor for typical wire screen mesh regenerator was nearly same as steady flow friction factor for maximum oscillating Reynolds number up to 100 at less than 9 Hz. For 60 Hz operations, however, the discrepancy between oscillating flow friction factor and steady flow one was noticeable if Reynolds number was higher than 50. Second, the ineffectiveness of regenerator was directly calculated from experimental data when the cold-end was maintained around 100 K and the warm-end around 293 K, which simulates an actual operating condition of cryogenic regenerator. Influence of the operating frequency on ineffectiveness was discussed at low frequency range.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.845-850
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• 2003

Unsteady nature of a tip leakage vortex in an axial flow fan operating at a design and off-design operating conditions has been investigated by measuring the velocity fluctuation in a blade passage with a rotating hotwire probe sensor. Two hot-wire probe sensors rotating with the fan rotor were also introduced to obtain the cross-correlation coefficient between the two sensors located in the vortical flow as well as the fluctuating velocity. The results show that the vortical flow structure near the rotor tip can be clearly observed at the quasi-orthogonal planes to a tip leakage vortex. The leakage vortex is enlarged as the flow rate is decreased, thus resulting in the high blockage to main flow. The spectral peaks due to the fluctuating velocity near the rotor tip are mainly observed in the reverse flow region at higher flow rates than the peak pressure operating condition. However, no peak frequency presents near the rotor tip for near stall condition.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.5
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• pp.431-437
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• 2013

Measured acoustic signal from operating high speed train contains frequency change called doppler shift due to its motion. To avoid this doppler shift wind tunnel test is required. But scaledown of model can cause change of source characteristics. And measurements using some part of train cannot reproduce real flow condition. The best way to recognize real noise source characteristics is measurement from operating high speed train but doppler shift makes it hard. So, we developed simple dedopplerization technique for one microphone and applied to field test data of high speed train. Through this, we could capture real frequency of noise from operating high speed train.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.5
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• pp.678-681
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• 2020

In this paper, we analyzed the noise figure of cascode low noise amplifier (LNA) based on the measured data of 65nm CMOS devices. By using the channel thermal noise model of transistors, we expanded noise figure equation and divided the equation into three parts to see its contributions to noise figure. We also varied design parameters such as bias point, transistor gate width, and operating frequency. Our results show that different noise sources dominate at the different operating frequencies. One can easily find the noise transition frequency with device models in ahead of the practical design. Therefore, this research provides a low noise design approach for different operating frequencies.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.75-79
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• 2001

This paper presents a novel version of an active voltage clamped ZVS-PWM high frequency inverter using IGBTs for electromagnetic induction eddy current-based rolling drum heating in new generation copy and printing machines in consumer business use. The operating principle of this inverter circuit and unique features are described herein. Its constant frequency duty cycle (asymmetrical PWM) controlled voltage source quasi-resonant soft switching high frequency inverter employing IGBTs is proposed, which is capable of achieving stable and efficient zero voltage soft switching commutation over a widely specified power regulation range from full power to low power. The operating performances in a steady state of this inverter is discussed and evaluated on basis of simulation and experimental results as an induction heated roller in new generation copy machine.

• Journal of Electrical Engineering and Technology
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• v.10 no.4
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• pp.1518-1526
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• 2015

For now, there are some low frequency oscillations in the power system which feature low frequency oscillation with positive damping and cannot be explained by traditional low frequency oscillation mechanisms. Concerning this issue, the dynamic damping effect is put forward on the basis of the power-angle curve and the study of damping torque in this article. That is, in the process of oscillation, damping will dynamically change and will be less than that of the stable operating point especially when the angle of the stable operating point and the oscillation amplitude are large. In a situation with weak damping, the damping may turn negative when the oscillation amplitude increases to a certain extent, which may result in an amplitude-increasing oscillation. Finally, the simulation of the two-machine two-area system verifies the arguments in this paper which may provide new ideas for the analysis and control of some unclear low frequency phenomena.