• Proceedings of the KOSOMBE Conference
• /
• v.1997 no.11
• /
• pp.126-130
• /
• 1997

In the development of the totally implantable artificial heart (TAH), the information of the preload condition is important to ind appropriate condition or the automatic control of the heart. Our TAH configuration consists of two artificial ventricles, and brushless DC motor within actuator. The pressure between ventricles could indicate the preload condition during the TAH operation. If we can measure accurately inspite of the noise induced from TAH and environmental condition. We suggested integrating a feedback loop to remove an unexpected DC drift. NPI 19-series Nova sensor was used which could measure pressure in gas and liquid. This method and sensor enabled us to develop the pressure transducer compact so (that) the systems can be implanted with TAH into patient. This system has been verified in vitro and in vivo test. This results showed that the output waveform of this system was stable irrespective of animal condition.

• Food Science and Biotechnology
• /
• v.16 no.6
• /
• pp.1051-1054
• /
• 2007

An edible wild perennial plant with extremely potent antimicrobial activity was found and identified as apiifolia Virgin's Bower (Clematis apiifolia DC) which is easily found around wet wildernesses. Fresh fruit extract of C. apiifolia exhibited minimum inhibitory concentrations (MIC) in the vicinity of 0.1% against various yeasts and of less than or equal to 0.4% for non-lactic acid bacteria. MICs against lactic acid bacteria were about 2.0%. The antimicrobial activity of C. apiifolia fruit was even more potent than that of garlic which has been known for its potent antimicrobial activity. The principal antimicrobial compound of fruit extract of C. apiifolia was isolated and identified by high performance liquid chromatography and gas chromatography as protoanemonin (a gamma lactone of 4-hydroxy-2,4-pentadienoic acid). The antimicrobial activity of C. apiifolia was stable at high temperatures, and the activity was maintained after heating at $121^{\circ}C$ for 10 min. The antimicrobial compound of C. apiifolia was supposed to inhibit microorganisms by reacting with sulfhydryl groups of cellular proteins.

• Proceedings of the KIEE Conference
• /
• 1998.07f
• /
• pp.2148-2150
• /
• 1998

This paper proposes a constant frequency controlled zero voltage switching method that can reduce switching losses caused by emf on inductance in DC motor. The zero voltage switching method is used more than a zero current switching method because of reducing switching losses by capacitance of depletion region of MOSFET. To simplify the controller circuit, we propose constant frequency controlled zero voltage switching method in the paper. The control method is more stable than a variable frequency control method because it can optimize bandwidth of a closed-loop and reactances. Therefore, we construct a constant frequency controlled zero voltage switching converter and improve zero switching losses in high switching frequency. In the process, we can control low-losses in full range on variable voltage and load. We simulate the proposed converter with P-SPICE and compare results obtained through the experiment.

• Proceedings of the KIEE Conference
• /
• 2006.07b
• /
• pp.998-999
• /
• 2006

포항가속기 연구소의 선형가속기에는 22개의 솔레노이드 전자석, 16개의 사극전자석 그리고 전자빔의 궤도 조절을 위한 16개의 2극 전자석이 있다. 선형가속기의 빔을 저장링으로 공급해주는 빔 전송선에는 22개의 사극전자석과 13개의 빔 궤도 조절용 이극 전자석이 있다. 전자빔의 정밀 제어를 위하여 전자석의 전원장치는 출력전류 분해능은 16bit 이상이고 출력전류의 안정도는 최대출력에 대하여 ${\pm}50ppm$ 이하의 고정밀 고안정도가 요구된다. 이를 위하여 풀-브릿지 4상한 DC/DC 컨버터를 이용한 전자석전원장치를 개발 하였다. 전원장치의 입력전압 직류 40V이고 출력전류는 단방향 전원장치는 최대 50A/50V 이고 양방향 전원장치는 ${\pm}20A/20V$이다. 스위칭 주파수는 50 kHz이다. 전원장치의 출력부에 필터가 없으면 출력전류에는 스윗칭과 관련된 주파수 성분이 포함 되고 전자빔은 이들 주파수 성분에 대하여 영향을 받게 된다. 이러한 이유로 출력 필터의 cut-off 주파수는 5 kHz 이하가 되어야 한다. 본 논문에서는 고정밀 고안정 스윗칭 전자석전원장치를 위한 출력필터의 설계, 제작 그리고 이를 적용한 전자석전원장치에 대하여 논의 하고자 한다.

• Journal of the Korean institute of surface engineering
• /
• v.39 no.3
• /
• pp.98-104
• /
• 2006

Al-doped ZnO (AZO) films were deposited on the plastic substrate by inductively coupled plasma (ICP) assisted DC magnetron sputtering. The AZO films were produced by sputtering a metallic target (Zn/Al) in a mixture of argon and oxygen gases. AZO films with an electrical resistivity of ${\sim}10^3\;{\Omega}cm$ and an optical transmittance of 80% were obtained even at a low deposition temperature. In-situ process control methods were used to obtain stable deposition conditions in the transition region without any hysteresis effect. The target voltage was controlled either at a constant DC power. It was found that the ratio of the zinc to oxygen emission intensity, I (O 777)/I (Zn 481) decreased with increasing the target voltage in the transition region. The $Ar/O_2$ plasma treatment improve the adhesion strength between the polycarbonate substrate and AZO films.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.32 no.12
• /
• pp.907-914
• /
• 2008

This study is mainly focused on the assessment of return, semi return, and returnless fuel supply system for an LPi engine. In order to compare the return type with returnless one with various LPG blends, combustion analysis and cyclic THC emission characteristic were tested at the part load operating condition of the LPi engine. Considering heat balance of each fuel supply systems, pressure and temperature increment of return type showed lower at the fuel rail during idle warm up operation. However, those of returnless type at LPG tank maintained stable and slow increment because the heat transfer from the LPi engine was minimized. Finally, hot restartability of each fuel supply systems were evaluated with the various LPG blends and fuel temperatures. As a result, semi return type has equivalent performance to return type considering combustion and emission characteristic, hot restartability performance for LPi engine.

• Journal of Power Electronics
• /
• v.15 no.1
• /
• pp.202-215
• /
• 2015

This paper investigates the stability and performance of model predictive controlled active-front-end (AFE) rectifiers for energy storage systems, which has been increasingly applied in power distribution sectors and in renewable energy sources to ensure an uninterruptable power supply. The model predictive control (MPC) algorithm utilizes the discrete behavior of power converters to determine appropriate switching states by defining a cost function. The stability of the MPC algorithm is analyzed with the discrete z-domain response and the nonlinear simulation model. The results confirms that the control method of the active-front-end (AFE) rectifier is stable, and that is operates with an infinite gain margin and a very fast dynamic response. Moreover, the performance of the MPC controlled AFE rectifier is verified with a 3.0 kW experimental system. This shows that the MPC controlled AFE rectifier operates with a unity power factor, an acceptable THD (4.0 %) level for the input current and a very low DC voltage ripple. Finally, an efficiency comparison is performed between the MPC and the VOC-based PWM controllers for AFE rectifiers. This comparison demonstrates the effectiveness of the MPC controller.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.18 no.5
• /
• pp.448-457
• /
• 2013

This paper proposes a control method under stand-alone operating mode for distributed-module type photovoltaic power conditioners. In conventional schemes, there are some problems of a controller saturation in the DC-link (or load) voltage controller when overly-heavy load, light load, and the generated PV power reduction occurs, as well as when a transition occurs from an overly-loaded to normal conditions. To overcome these problems, the proposed controller method switches the main control target from DC-link voltage to the maximum power point, which is closer to the stable operating point when it returns to normal operating conditions. For the analysis, a state-plane trajectory was given and the circuit analysis by PSIM simulation was done. For the verification, a prototype hardware with 110[W] and 50[W] dual photovoltaic modules has been implemented. From the results, it can be seen that PV power tracking is successfully done with the proposed method even under a stand-alone operation mode.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.25 no.1
• /
• pp.21-28
• /
• 2020

Integrated bidirectional OBC/LDC was developed to reduce the volume for elements, avoid space restriction, and increase efficiency in EV vehicles. In this study, a DC-DC converter in integrated OBC/LDC circuits was composed of an SRC circuit with a stable output voltage relative to an LLC circuit using a theoretical method and simulation. The resonant network of the selected circuit was optimized to minimize the power loss and element volume under constraints for the buck converter and the battery charging range. Moreover, the validity of the optimal model was verified through an analysis using a theoretical method and a numerical analysis based on power loss at the optimized resonant frequency.

• Journal of Power Electronics
• /
• v.15 no.2
• /
• pp.327-337
• /
• 2015

This study discusses the design of a parallel-operated DC-DC single-ended primary-inductor converter (SEPIC) for low-voltage application and current sharing with a constant output voltage. A coupled inductor is used for parallel-connected SEPIC topology. Generally, two separate inductors require different ripple currents, but a coupled inductor has the advantage of using the same ripple current. Furthermore, tightly coupled inductors require only half of the ripple current that separate inductors use. In this proposed work, tightly coupled inductors are used. These produce an output that is more efficient than that from separate inductors. Two SEPICs are also connected in parallel using the coupled inductors with a single common controller. An analog control circuit is designed to generate pulse width modulation (PWM) signals and to fulfill the closed-loop control function. A stable output current-sharing strategy is proposed in this system. An experimental setup is developed for a 18.5 V, 60 W parallel SEPIC (PSEPIC) converter, and the results are verified. Results indicate that the PSEPIC provides good response for the variation of input voltage and sudden change in load.