• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.10
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• pp.19-26
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• 2021

In fine-particle injection processing, hard fine particles, such as silicon carbide or aluminum oxide, are injected - using high-pressure air, and a small amount of material is removed by applying an impact to the workpiece by spraying at high speeds. In this study, a two-axis stage device capable of sequence control was developed to spray various shapes, such as circles and squares, on the surface during the micro-particle jetting process to understand the surface-shape micro-particle-processing characteristics. In the experimental device, two stepper motors were used for the linear movement of the two degree-of-freedom mechanism. The signal output from the microcontroller is - converted into a signal with a current sufficient to drive the stepper motor. The stepper motor rotates precisely in synchronization with the pulse-signal input from the outside, eliminating the need for a separate rotation-angle sensor. The major factors of the processing conditions are fine particles (silicon carbide, aluminum oxide), injection pressure, nozzle diameter, feed rate, and number of injection cycles. They were identified using the ANOVA technique on the design of the experimental method. Based on this, the surface roughness of the spraying surface, surface depth of the spraying surface, and radius of the corner of the spraying surface were measured, and depending on the characteristics, the required spraying conditions were studied.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.5
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• pp.547-550
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• 2011

We have developed a laser-based needle-free liquid drug-injection device. A laser beam is focused inside the liquid contained in the rubber chamber of a micro-scale. The focused laser beam causes explosive bubble growth, and the sudden volume increase in a sealed chamber drives a microjet of liquid drug through the micronozzle. The exit diameter of a nozzle is less than 100 ${\mu}m$, and we verify that the injected microjet is fast enough to penetrate soft human tissue. In the experiment, the microjet penetrated a 5% gelatin-water solution that replicates the human thrombus and pork-fat tissue.

• The Korean Journal of Pain
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• v.19 no.1
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• pp.77-80
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• 2006

Background: Painful experiences during procedures such as prolotherapy and intramuscular stimulation are stressful to patients and can affect the treatment outcome. We present a method for relieving pain and increasing the level of patient comfort during the procedure. Methods: Twenty six patients who requested sedation anesthesia during the procedure were examined. All patients were injected with 500 ml of 0.9% normal saline and were monitored by electrocardiography, blood pressure and pulse oximetry. The patients were supplied with oxygen (3 L/min) through a nasal cannula. Midazolam (0.02 mg/kg) and alfentanil ($8{\mu}g/kg$) was injected before the procedure and a bolus injection was administered during the procedure if patients felt any pain. The duration of the procedure, the total amount of drugs, the changes in the systolic blood pressure, heart rate, pulse oxygen saturation, sedation and pain level during procedure, satisfaction scale after the procedure, complications and the incidence of amnesia were evaluated. Results: Twenty one patients had a moderate level of sedation, 15 patients did not feel any pain during the procedure, 17 patients had high level of satisfaction (8-10). No patient experienced complications after the procedure, or unstable vital signs, and 6 patients could not remember the procedure. Conclusions: Sedation anesthesia is a safe method for relieving pain during the procedure, and most patients had a high level of satisfaction.

• Smart Structures and Systems
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• v.3 no.1
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• pp.1-22
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• 2007

The energy efficiency of a self-powered wireless sensing system for pressure monitoring in injection molding is analyzed using Bond graph models. The sensing system, located within the mold cavity, consists of an energy converter, an energy modulator, and a ultrasonic signal transmitter. Pressure variation in the mold cavity is extracted by the energy converter and transmitted through the mold steel to a signal receiver located outside of the mold, in the form of ultrasound pulse trains. Through Bond graph models, the energy efficiency of the sensing system is characterized as a function of the configuration of a piezoceramic stack within the energy converter, the pulsing cycle of the energy modulator, and the thicknesses of the various layers that make up the ultrasonic signal transmitter. The obtained energy models are subsequently utilized to identify the minimum level of signal intensity required to ensure successful detection of the ultrasound pulse trains by the signal receiver. The Bond graph models established have shown to be useful in optimizing the design of the various constituent components within the sensing system to achieve high energy conversion efficiency under a compact size, which are critical to successful embedment within the mold structure.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.3
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• pp.218-223
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• 2007

The dissipation of high-power ultrasonic energy at the faces of the defect causes an increase in temperature. It is resulted from localized selective heating in the vicinity of cracks because of the friction effect. In this paper the measurement of size and direction of crack using UET(Ultrasound Excitation Thermography) is described. The ultrasonic pulse energy is injected into the sample in one side. The hot spot, which is a small area around the crack tip and heated up highly, is observed. The hot spot, which is estimated as the starting point of the crack, is seen in the nearest position from the ultrasonic excitation point. Another ultrasonic pulse energy is injected into the sample in the opposite side. The hot spot, the ending point of the crack, is seen in the closest distance from the injection point also. From the calculation of the coordinates of both the first hot spot and the second hot spot observed, the size and slope of the crack is estimated. In the experiment of STS fatigue crack specimen(thickness 14mm), the size and the direction of the crack was measured.

• JSTS:Journal of Semiconductor Technology and Science
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• v.3 no.2
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• pp.83-88
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• 2003

The reset operation of a CCD image sensor was improved using charge trapping of a MOS structure to realize a loe voltage driving. A DC bias generating circuit was added to the reset structure which sets reference voltage and holds the signal charge to be detected. The generated DC bias is added to the reset pulse to give an optimized voltage margin to the reset operation, and is controlled by adjustment of the threshold voltage of a MOS transistor in the circuit. By the pulse-type stress voltage applied to the gate, the electrons and holes were injected to the gate dielectrics, and the threshold voltage could be adjusted ranging from 0.2V to 5.5V, which is suitable for controlling the incomplete reset operation due to the process variation. The charges trapped in the silicon nitride lead to the positive and negative shift of the threshold voltage, and this phenomenon is explained by Poole-Frenkel conduction and Fowler-Nordheim conduction. A CCD image sensor with $492(H){\;}{\times}{\;}510(V)$ pixels adopting this structure showed complete reset operation with the driving voltage of 3.0V. The resolution chart taken with the image sensor shows no image flow to the illumination of 30 lux, even in the driving voltage of 3.0V.

• Journal of Power Electronics
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• v.16 no.6
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• pp.2109-2118
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• 2016

Based on the space vector pulse width modulation (SVPWM) theory, this paper realizes an easier SVPWM strategy, which is equivalently implemented by CBSPWM with zero-sequence voltage injection. The traditional SVPWM strategy has no effect on controlling the neutral-point voltage balance. In order to solve the neutral-point voltage unbalance problem for neutral-point-clamped (NPC) three-level inverters, this paper proposes a neutral-point voltage balance controller. The proposed controller realizes controlling the neutral-point voltage balance by dynamically calculating the offset superimposed to the three-phase modulation waves of an equivalent SVPWM strategy. Compared with the traditional SVPWM strategy, the proposed neutral-point voltage balance controller has a strong ability to balance the neutral-point voltage, has good steady-state performance, improves the output waveforms quality and is easy for digital implementation. An experiment has been carried out on a NPC three-level inverter prototype based on a digital signal processor-complex programmable logic device (DSP-CPLD). The obtained experimental results verify the effectiveness of the proposed neutral-point voltage balance controller.

• Journal of the Optical Society of Korea
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• v.13 no.1
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• pp.75-79
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• 2009

A four beam interference optical system for laser micro structuring using a pulse laser was demonstrated. The four beam interference optical system using a pulse laser(picosecond laser) can fabricate micro structure on mold material(NAK80) directly. Micro structure on the polymer can be reproduced economically by injection molding of the micro structure on the mold material. The four beam interference optical system was composed by the DOE(Diffractive Optical Element) and two lenses. The laser intensity distribution of four beam interference was explained by an interference optics point of view and by the image optics point of view. We revealed that both views showed the same result. The laser power distribution of a $1{\mu}m$ peak pattern was made by the four beam interference optical system and measured by the objective lens and CCD. A $1{\mu}m$ pitch dot pattern on the mold material was fabricated and measured by SEM(Scanning Electron Microscopy).

• Journal of ILASS-Korea
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• v.10 no.1
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• pp.43-52
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• 2005

The effect of fuel injection spray on engine performance has been known as one of the major concerns for improving fuel economy and reducing emissions. In general, reducing the spray droplet size could prevent HC emission in gasoline engine. As far as PFI (Port Fuel Injection) gasoline engine is concerned, the mixture of air and fuel may not be uniform under a certain condition, because breakup and production of spray droplets are made in a short distance between the fuel injector and intake valve. This study, by constituting PFI gasoline spray system, was performed to study the transient spray characteristics and dynamic behavior of droplets from 2hole 2spray type injector used in DOHC gasoline engine. Mean droplet size and optical concentration in accordance with various conditions were measured by LDPA and CCD camera. Through this study, the variation of drop size and optical concentration could be used for understanding the behavior of unsteady spray was declared and the existing the small droplets between each pulse spray could be estimated caused to the development of wall film was conformed.

• Journal of The Korean Dental Society of Anesthesiology
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• v.3 no.2 s.5
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• pp.87-91
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• 2003

Background: The purpose of this study was to compare the availability of propofol and fentanyl (P + F) with diazepam and morphine (D + M) for intravenous conscious sedation during third molar surgery. Methods: Forty patients without systemic disease were operated under IV conscious sedation administered by either of the two techniques. Monitoring consisted of continuous observation of pulse rate, blood pressure, oxygen saturation, and the respiratory rate and were recorded every 15 minutes. Cooperation score was measured 5 and 15 minutes after induction of IV sedation. Following the operation, the surgeon and patients completed questionnaires including pain visual analog scale, amnesia, and side effects. Results: The P + F group was significantly more cooperative than the D + M group. The side effects of D + M group included pain on injection, nausea/vomiting and abdominal pain. The side effects of P + F group included talkativeness, nausea/vomiting, temporary apnea, pain on injection and vertigo. Conclusions: In this study, there were following benefits in the P + F group; more cooperative status and less pain perception. But respiratory depression developed in some patients.