• Tribology and Lubricants
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• v.15 no.3
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• pp.278-286
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• 1999

To predict the behavior of the intravascular micro active endoscope in the real human vascular system, a human mock circulation system was developed. The intravascular micro active endoscope which consists of micro active bending catheter and micro drug infusion catheter was driven in the velocity, Re number and temperature controlled flow. The three SMA (Shape Memory Alloy) zigzag type spring in the micro active bending catheter was heated by the electric current generated by PWM controller, and the shape memory effect made the actuator bend to any direction. The micro drug infusion catheter was driven through the inner hole of the micro active bending catheter. A mock circulation system is shaped from Ascending Arota to Femoral artery according to a human data (the data contains many vascular sizes and hydrographs of many control points). We developed a vascular model with glass and silicone tubes, and set the flow system with circulation parts, flow settling parts, and lots of valves. The heater and heat-controller was added to the How system to centre! the temperature of the How at 36.5$^{\circ}C$. The result showed that the developed intravascular micro active endoscope could be induced to any point in the vascular model.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.51 no.3
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• pp.120-125
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• 2002

The switching-mode power converter has been widely used because of its features of high efficiency and small weight and size. These features are brought by the ON-OFF operation of semiconductor switching devices. However, this switching operation causes the surge and EMI(Electromagnetic Interference) which deteriorate the reliability of the converter themselves and entire electronic systems. This problem on the surge and noise is one of the most serious difficulties in AC-to-DC converter. In the switching-mode power converter, the output voltage is generally controlled by varying the duty ratio of main switch. When a converter operates in steady state, duty ratio of the converter is kept constant. So the power of switching noise is concentrated in specific frequencies. Generally, to reduce the EMI and improve the immunity of converter system, the switching frequency of converter needs to be properly modulated during a rectified line period instead of being kept constant. Random Pulse Width Modulation (RPWM) is performed by adding a random perturbation to switching instant while output-voltage regulation of converter is performed. RPWM method for reducing conducted EMI in single switch three phase discontinuous conduction mode boost converter is presented. The more white noise is injected, the more conducted EMI is reduced. But output-voltage is not sufficiently regulated. This is the reason why carrier frequency selection topology is proposed. In the case of carrier frequency selection, output-voltage of steady state and transient state is fully regulated. A RPWM control method was proposed in order to smooth the switching noise spectrum and reduce it's level. Experimental results are verified by converter operating at 300V/1kW with 5%~30% white noise input. Spectrum analysis is performed on the Phase current and the CM noise voltage. The former is measured with Current Probe and the latter is achieved with LISN, which are connected to the spectrum analyzer respectively.

• Journal of Korean Academy of Nursing
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• v.23 no.4
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• pp.528-543
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• 1993

Vitamin E, which has its advocates in the treatment of diabetes mellitus. autoimmune disease, cancer and peripheral vascular and thromboembolic disease, has now been alleged to have a powerful antioxident effect and to affect various biological activities such as fertility factor, inhibition of human platelet aggregation and stabilization of biological membranes. The present study was designed to test whether vitamin I(alpha-tocopherol) can : (1) enhance the hemagglutinin response to sheep red blood cells (SRBC), (2) modulate Arthus and delayed type hypersensitivity(DTH) to SRBC and contact hypersensitivity to dinitrofluorobenzene (DNFB). (3) enhance the mitogenic response of murine splenocyte, (4) decrease the recovery of Cryptococcus neoformans from brain, lung, liver, spleen and kidney of infected mice and (5) have an inhibitory or enhancing effect on the induction of active systemic anaphylaxis(ASA) induced by chicken-gamma globulin (CGG) in mice. Mice were given either intramuscular injections of 0.3ml (300mg) of vitamin I before immunization or were infection for 10 consecutive days or were given by vitamin I esophageal intubation, 0.1ml(100mg), for 20 days before sacrifice for the mitogenic response experiments. It was found that vitamin E treated mice showed a significant enhancement in hemagglutinin response, Arthus reaction and DTH to SRBC and contact hypersensitivity to DNFB. There was no significant difference in the mitogenic response to phytohemagglutinin(PHA), but the response to concanavalin A(ConA) or pokeweed mitogem(PWM) was increased in vitamin E-treated mice. Interestingly, the vitamin E administration before C. neoformans infection decreased significantly the recovery of C. neoformans from brain lung, liver, spleen and kidney of the infected mice as compared with that of the control mice, strongly suggesting that vitamin E pretreatment may increase the resistance of mice to the fungal infection. Unexpectedly, vitamin E administration enhanced the production of CGG -induced ASA. Taken together, it can be concluded that vitamin I administration may in-crease the humoral and cellular immune response and resistance. to C. neoformans infection, but enhance the induction of ASA to CGG. Further studies are necessary to clarify the underlying mechanism accounting for these effects.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.5
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• pp.1019-1025
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• 2003

There are many kinds of seam trackers in the industrial welding field. We are proposed the contact seam tracking sensor applying strain gauges kind of contact sensor that mostly used in welding part now. For this seam tracking experiment, we made the strain gauges sensor by ourselves and tested how well the sensor tracks the seam. The experiment device consist of strain gauges sensor, amplifier circuit of strain gauges signal, saw wave generator, MOSFET power diving circuit and X-Y slide by moved DC motor. The tracking areas are X-Y planes(left, right, up and down) and the change of strain gauge resistance causes to move DC motor that connected to X-Y slide. As a result of experiment, we confirmed that the strain gauges sensor tracks a seam well, and X-Y slide DC motor was controlled by PWM control.

• Journal of the Korean Institute of Telematics and Electronics
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• v.9 no.3
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• pp.1-8
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• 1972

The characteristics of tunnel diode pair circuit biased within the negative resistance region has also the voltage-control type negative resistance region, and the voltage at the center point of negative resistance region is described as the square-wave relaxation oscillation. In this paper, the period T, positive duration T1, negative duration T2 of the pulse are obatined from the characteristic curve T, positive duration T1, negative duration T2 of the pulse are obtained from the characteristic curve and observed actually, considring the fact that the pulse width and the period of square-wave at the center point of the negative resistance region is able to be controlle dby the blas volgate. Mereover, the relationship between T, T1 or T2 and circuit parameters is searched for and the Circuit parameters that satisfy the conditions of T1-T2 being proportional to the variation of bias voltage with Teonstant are determined. Thereafter, the bias voltage and the signal voltage are inserted serially to the PWM circuit and the characteristics of that circuit is analyzed.

• International Journal of Automotive Technology
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• v.4 no.2
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• pp.65-75
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• 2003

A HEV evaluation program, funded by ADEME, was carried out by a group of Laboratories of different specialties in order to evaluate and compare consumption, emission and component technologies of the three first HEVs put on the market (Toyota Prius, Nissan Tino and Honda Insight). This paper presents the results obtained until now. These results show good consumption and emission performance of the tested vehicles compared to conventional ones. The energy management seems to be globally the same for the three vehicles excepting for cold stans where the Insight allows a very earlier stop of the engine compared to the Tino and especially to the Prius. A mapping of the engine consumption of the Prius and the Insight was performed in order to furnish data for the simulation models. The Permanent Magnet motors of the Prius and Tino have different number of pair poles and then different emf at a given speed. The low emf values of the Prius allow operation at high speed with less field weakening control than for the Tino. The inverters of the Prius and the Tino, controlled by a PWM at respectively 5 kHz and 7 kHz switching frequency, are made of IGBTs with high commutation performances.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.2
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• pp.175-181
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• 2016

In the conventional E-bike, a 42 V/10 A Li-ion battery drives a 24 V/10 A BLDC motor via a 6-switch PWM DC/AC inverter. The major problems of the conventional battery-fed motor drive systems are listed as follows. To charge the battery, an external battery charger (adapter) is required, which degrades the portability of E-bike users. In addition, given the high-frequency operation of the motor drive inverter, the switching losses are significant, which degrades the whole power efficiency. High-voltage batteries (42 V) require a complex battery management system (BMS), which degrades the reliability of the battery pack. In this paper, an embedded boost-converter battery charger for E-bikes is proposed. The variable output boost converter, which converts 16.8 V battery voltage to the required variable voltage of the inverter input, can use a low-voltage battery and thus improve the reliability of batteries. By varying the inverter input voltage via boost converter, a DC link voltage control method can be applied to reduce the switching frequency of the inverter, which improves the whole power efficiency. Given that the function of a flyback charger is integrated in the proposed boost converter, the portability of the E-bike user can be maximized by excluding an external adapter. The validity of the proposed circuit will be confirmed by operation mode analysis and simulation. Moreover, experimental results of integrative charger using Li-ion battery and 200 W motor test will be showed with a prototype sample as well.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.10
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• pp.581-586
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• 2002

To improve the current waveform of diode rectifiers, we propose a new operating principle for the voltage-doubler diode rectifiers. In the conventional voltage-doubler rectifier circuit, relatively large capacitors are used to boost the output voltage, while the proposed circuit uses smaller ones and a small reactor not to boost the output voltage but improve the input current waveform. A circuit design method is shown by experimentation and confirmed simulation. The experimental results of the proposed diode rectifier satisfies the harmonic guide lines. A high input power factor of 97(%) and an efficiency of 98[%] are also obtained. The new rectifier with no controlled switches meet the harmonic guide lines, resulting in a simple, reliable and low-cost at-to dc converters in comparison with the boost-type current-improving circuits. This paper proposes a nonlinear impedance circuit composed by diodes and inductors or capacitors. This circuit needs no control circuits and switches, and the impedance value is changed by the polarity of current or voltage. And this paper presents one of these applications to improve the input current of capacitor input diode rectifiers. The rectifier using the nonlinear impedance circuit is constructed with four diodes and four capacitors in addition to the conventional rectifiers, that is, it has eight diodes and five capacitors, including a DC link capacitor. It makes harmonic components of the input current reduction and the power factor improvement. Half pulse-width modulated (HPWM) inverter was explained compared with conventional pulse width modulated(PWM) inverter. Proposed HPWM inverter eliminated dead-time by lowering switching loss and holding over-shooting.

• Journal of the Semiconductor & Display Technology
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• v.12 no.2
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• pp.13-17
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• 2013

In lighting system where several large-area organic light-emitting diode (OLED) lighting panels are involved, panel aging may appear differently from each other, resulting in a falling-off in lighting quality. To achieve uniform light output across large-area OLED lighting panels, we have employed an optical feedback circuit. Light output from each OLED panel is monitored by the optical feedback circuit that consists of a photodiode, I-V converter, 10-bit analogdigital converter (ADC), and comparator. A photodiode generates current by detecting OLED light from one side of the glass substrate (i.e., edge emission). Namely, the target luminance from the emission area (bottom emission) of OLED panels is monitored by current generated from the photodiode mounted on a glass edge. To this end, we need to establish a mapping table between the ADC value and the luminance of bottom emission. The reference ADC value corresponds to the target luminance of OLED panels. If the ADC value is lower or higher than the reference one (i.e., when the luminance of OLED panel is lower or higher than its target luminance), a micro controller unit (MCU) adjusts the pulse width modulation (PWM) used for the control of the power supplied to OLED panels in such a way that the ADC value obtained from optical feedback is the same as the reference one. As such, the target luminance of each individual OLED panel is unchanged. With the optical feedback circuit included in the lighting system, we have observed only 2% difference in relative intensity of neighboring OLED panels.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.11 no.6
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• pp.64-73
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• 1997

RPWM(Random Pulse Width Modulation) techniques have been attracting an interest as an excellent reduction method of acoustic noise on the inverter drive system. Using randomly changed switching fre-quency of the inverter, the power spectrum of the electromagnetic acoustic noise can be spread out into the wide-band area. The wide band noise is much more comfortable and less annoying than the narrow-band one. This paper describes an implementationof the triangular carrier frequency modultde RPWM inverter drive system The poweer soedtrum of the noise emittde from the induction motro was measured in the anechoic chamber. The analysis of the sources for the acoustic noise and the effects of the noise reduction are confirmed by the ceasured dpectra of the noise. Real-time RPWM along with the speed control was achieved by high speed DSP(Digital Signal Processor ) TmS320C31, By changing the center frequency and the bandwidth of the carrier, theis real-time RPWM scheme can be used as an efficient switching frequency band acoustic noise reduction method for the inverter system with variant load conditions.