• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.5
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• pp.297-308
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• 2022

Most air-breathing aircraft operated in the hypersonic region are equipped with a scramjet engine. In a scramjet engine, a shock wave generated at an inlet acts as a compressor for a general gas turbine engine instead, so total pressure loss caused by the shock wave is considered very important. In this study, to minimize total pressure loss, a method of designing an external compression inlet using isentropic compression surface was proposed, and an external compression inlet with 3-deflection angles and Busemann inlet were designed under the same conditions. After that, through computational analysis, the performance characteristics at off-design conditions were compared. Each inlet shape was truncated according to the length of the 3-ramp external compression inlet, and the boundary layer correction was performed. The isentropic external compression inlet showed superior performance at the design point, but under the off-design conditions, its performance was degraded compared to the 3-ramp external compression inlet.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.9
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• pp.2358-2367
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• 1994

This paper presents techniques for evaluation and compensation of total measuring errors in a commercial CMM. The probe errors as well as the machine geometric errors are assessed from probing of the mechanical artefacts such as shpere, step, and rings. For the error compensation, the integrated volumetric error equations are considered, including the probe error adn the machine geometric error. The error compensation is performed on the absolute scale coordinate system, in order to overcome the redundant degree of freedom in the CMM with multi-axis probe. A interface box and corresponding software driver are developed for data intercepting/correction between the machine controller and machine, thus the volumetric errors can be compensated in real time with minimum interference to the operating software and hardware of a commercial CMM. The developed system applied to a practical CMM installed on the shop floor, and demonstrated its performance.

• Journal of radiological science and technology
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• v.20 no.1
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• pp.35-38
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• 1997

Scintigraphic measurement of gastric emptying time has been reported to be influenced by the variation in depth of radionuclide within the stomach. This study was designed to clarify whether a part of the variability in gastric emptying could be ascribed to a relationship between anterior image, the total anteroposterior Image and the tissue attenuation correction(geometric mean). A dual-head scintillation camera(ADAC, USA) was used to investigate effect of such changes. We were performed 16 normal subject gastric emptying studies with $^{99m}TC$ labelled scramble egg, milk and solid meal(610 Kcal, 300 g) The results are as follows; On anterior Image, $T_{1/2}$ emptying time was delayed by 5 min, 6.5%(range $3{\sim}18\;min,\;5{\sim}31.4%$) compared with the geometric mean. But there was no different gastric emptying time between the total anteroposterior image and geometric mean. Therefore, if will be useful to use the method of geometric mean or the total anteroposterior image to evaluate the gastric emptying time accurately.

• Korean Journal of Veterinary Research
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• v.44 no.1
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• pp.137-141
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• 2004

The purpose of this study was to compare easiness of application of polypropylene external total ring prosthesis (PPTRP, Group A) with that of polyvinylchloride external total ring prosthesis (PVCTRP, Group B), which were used for surgical correction of tracheal collapse in dogs. PPTRP was made from 3 ml syringe and PVCTRP from the drip chamber of intravenous administration set. Prostheses of group A (n=5) and B (n=5) were placed to cervical trachea in clinically normal 10 dogs, respectively weighing between 4 kg and 6 kg. There were mild coughing and swelling in one to three dogs of both groups for 3 days after surgery. No exercise intolerance was observed in both groups after surgery. There were no different results of clinical signs and radiographic views after surgery between group A and group B. The time (mean${\pm}$SD) to make total ring prosthesis, group A took $23.2{\pm}1.9$ minutes which was remarkably longer than that $(4.6{\pm}0.3)$ of group B. Also, the time to place around trachea, group A required $61.8{\pm}8.8$ minutes and group B $38.4{\pm}8.0$ minutes. Conclusionly, PVCTRP was timesaving and easier to make, fix, and suture than those of PPTRP. PVCTRP may be used alternatively to PPTRP for the tracheal collapse to treat in dogs.

• Proceedings of the IEEK Conference
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• 2000.11a
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• pp.337-340
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• 2000

In this paper, I compared some characteristics between HPA and LPA using Feedforward method. Feedforward method is known for best IMD correction. HPA generated 46.5㏈c at 45.5㏈m output power. But, using feedforward linearing method, I could improve IMD to 67.17㏈c at the same output power. IMD could be improved 20.67㏈ at 45.5㏈m output power. I measured average power, IMD, total current, and efficiency of two amplifier at many different power levels. I could get about 70d3c IMD using feedforward method.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.384-387
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• 2000

In this paper Power factor correction circuit of single-phase three-level boost converter is proposed. The advantage of the proposed control scheme for three-level boost converter are low blocking voltage of each power device low THD(Total Harmonic Distortion) and high power factor. The control scheme is based on the current comparator capacitor compensator and region detector, In simulations the proposed system is validated.

• Journal of Chest Surgery
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• v.12 no.4
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• pp.336-338
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• 1979

The electrocardiographic changes produced at surgery in all patients undergoing total correction of tetralogy of Fallot at the Seoul National University Hospital from 1961 through August 1979, were reviewed. Particular attention was directed to the presence of postoperative right bundle branch block combined with left anterior hemiblock and its prognosis. 14 patients [9.4%] out of 149 who were survived for 30 days postoperatively, showed right bundle branch block with left anterior hemiblock pattern in electrocardiography. But no complete heart block was occurred in these l 4 patients during the follow up periods of 2-56 months.

• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.362-365
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• 1999

In this paper, the method of reducing harmonics and correcting of power factor in single PWM converter associated with diode rectifier and boos converter is studied. The ac-dc converter in which the harmonic distortion in the input current is reduced using a third harmonic injected PWM is proposed. A lower switching power loss and easy configuration o control circuit are obtained by adopting discontinuous current mode. Simulation and experimental results of ac-dc converter with 5[KHz] switching frequency are presented and correction of power factor and reduction of total harmonic distortion was established.

• Journal of Chest Surgery
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• v.23 no.4
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• pp.820-824
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• 1990

A very early and effective technique of sternal closure by plastic plates was successfully applied to a 7-months-old infant of tetralogy of Fallot in whom the standard closure of sternum was not possible due to massive generalized edema after cardiopulmonary bypass for total correction. This technique provides not only solid but also permanent closure of the sternum so that any early reoperation for closure of sternum and its accompanying risk of infection in many other known methods can be avoided.

• Proceedings of the IEEK Conference
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• 2002.06e
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• pp.67-70
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• 2002

In this paper, we have researched a Automatic Power Factor Correction and THD reduction System for the multiple connection of CFL. Also in this paper, the power factor has been researched for the design of CFL, found the reason why the power factor is low and THD is too high. This paper has designed the PFC System for the multiple connection of CFL, and then we have increased the power factor and reduced the total harmonic distortion, by implementing them.