• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.3
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• pp.86-93
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• 2008

This paper presents a design of the reticle stage for lithography using VCM(Voice Coil Motor) and kinematic analysis. The stage has three axes for X,Y,${\theta}_z$, those actuated by three VCM's individually. The reticle stage has cross coupled relations between X,Y,${\theta}_z$ axes, and the closed solution of the forward/inverse kinematics were solved to get an accurate reference position. The reticle stage for lithography was designed for reaching both high accuracy and long stroke, which was $0.1{\mu}m$ (X,Y)/ $1{\mu}rad({\theta}_z)$ accuracies and relatively long strokes about 2mm (X,Y) and 2 degrees(${\theta}_z$). Also this research presents a rotational compensation algorithm for the precision gap sensor for the stage. Simulation results show the overall performance of the whole algorithm and the improvement quantity of the rotational compensation algorithm.

• Proceedings of the KIEE Conference
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• 2007.11a
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• pp.173-174
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• 2007

본 논문에서는 scan 전극과 common 전극 사이에 보조 전극을 가진 PDP에서 asymmetry, long gap mode 와 같은 새로운 구동방법을 제안한다. asymmetry mode에서 주전극의 가운데 부분에 위치한 보조전극은 리셋, 어드레스, 서스테인의 모든 구간동안 scan 또는 common 전극에 연결되어 있다. long gap mode에서는 전기적으로 끊어져있거나 초기 몇 개의 서스테인 펄스를 제외하고 서스테인 구간동안 Vs/2의 전압으로 유지된다. 제안된 조와 구동 방법에서 전력에너지소비를 최소화함으로써 더 높은 발광효율을 얻을 수 있다. 새로운 구동방법의 효용은 다양한 Xe분압상태에서도 연구되었다.

• Journal of Digital Contents Society
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• v.11 no.2
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• pp.265-276
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• 2010

The purpose of this study was to investigate the Korean Local Government's recognition on the educational gap among regions in the filed of adult learning including vocational education and life long-learning. The study also tried to figure out the local government's recognition and infrastructure of e-Learning which is suggested as one of the solutions on the regional gap of educational opportunities and quality. This study took 12 HRD(Human Resources Development) centers funded and operated by the Korean Local Governments except Seoul and Kyong-Gi classified by the metropolitan areas in Korea. As a result, firstly it was found that the local governments had perception on the difference and gap of educational opportunities and quality among regions in the area of adult education. Especially, the perception was relatively more serious on quality than quantity. Secondly, the result showed the large gap among regions on the area of opening educational and training programs, the quality of teachers and tutors, the effectiveness and outcomes of educational programs. Thirdly, they perceived more serious educational gap on face-to-face classes rather than e-Learning in the context of educational methodology. It also revealed that the local governments had relatively better foundations on physical systems than other infrastructures and resources such as human-ware, culture-ware and soft-ware(contents, programs etc.). It was recommended to consider these findings in developing and implementing future educational policies to solve the problem of regional gap on education.

• Transactions on Electrical and Electronic Materials
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• v.18 no.3
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• pp.125-128
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• 2017

This study is on how ohmic area etching affects the buffer breakdown voltage of AlGaN/GaN HEMT. The surface morphology of the ohmic metal can be improved by whole etching on the ohmic area. The buffer breakdown voltages of the samples with whole etching on the ohmic area were improved by the suppression of the metal spikes formed under the ohmic contact regions during high-temperature annealing. The samples with selective etching on the ohmic area were investigated for comparison. In addition, the buffer leakage currents were measured on the different radii of the wafer, and the uniformity of the buffer leakage currents on the wafer were investigated by PL mapping measurement.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.314-314
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• 2016

In this paper, the effects of carrier concentration on dielectric constant of ITO films were investigated by spectroscopic ellipsometry. From SE results, we find the pronounced shift of the ${\varepsilon}1$ peaks toward high energy with concentration; while contrarily, the ${\varepsilon}2$ values at low energy region increases with decreasing concentration. These shifts are attributed to the Burstein-Moss and free-carrier absorption effects within ITO films. With increases carrier concentration, the values of extinction coefficients show quite different behaviors in range of wavelength from 200 to 1200 nm. The reduction in k at ${\lambda}{\leq}500nm$, while increasing at ${\lambda}{\geq}500nm$ was observed. The QE of HJ solar cells behaviors can be roughly classified into two regions: short-wavelengths (${\leq}650nm$) and long-wavelengths region (${\geq}650nm$). With increasing carrier concentration as well as energy band gap, QE shows improvement at short-wavelength, while at long-wavelength QE shows opposite trend. Widening band gap energy due to Burstein-Moss shift is the key to improve QE in short-wavelength; simultaneously FCA effect due to optical scattering is attributed to the reduction in QE at long-wavelength. In spite of band gap extension, Jsc calculated from QE decreases from 34.7 mA/cm2 to 33.2 mA/cm2 with increasing carrier concentration. It demonstrated that FCA effect may more govern Jsc in the HJ solar cells.

• Journal of Chest Surgery
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• v.30 no.2
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• pp.236-240
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• 1997

The management of neonate with long gap atresia without a fistula(type A) is complex and controversial. Various esophageal reconstruction include use of native esophagus or replacement with colon, stomach and small bowel. A severe premature male, at 28 weeks gestation weighing 1.2kg, was born with type A esophageal atresia in Chonnam University Hospital. Initial treatment consisted of gastrostomy under the local anesthesia and suctioning of proximal pouch, and than underwent delayed esophageal end to end anastomosis. A minimal leakage and mediastinitis ocurred postoperatively, but was treated by adequate drainage and negative suction from the leakage site through the gastrostomy. The patient was discharged in good general condition and normal weight of 5.4kg after 4 months after the surgery.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• v.25 no.6
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• pp.453-460
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• 2022

Purpose: Esophageal atresia (EA) with or without tracheoesophageal fistula (TEF) is a congenital anomaly that can cause frequent digestive and nutritional problems, even after repair. The most common complication is anastomotic stricture, for which reoperation or balloon dilatation is performed. This study aimed to evaluate the postoperative complications of EA and the role of endoscopic balloon dilatation (EBD) in cases of anastomotic stricture. Methods: We retrospectively analyzed patients diagnosed with EA with or without TEF between January 2000 and February 2021. Patients' baseline characteristics, associated anomalies, and postoperative complications were reviewed. Results: Among 26 patients, 14 (53.8%) were male, 12 (46.2%) had coexisting anomalies, and the median follow-up was 6.1 years (range, 1.2-15.7 years). In univariate analysis, prematurity, low birth weight, and long-gap EA were associated with postoperative complications in 12 (46.2%) patients. Among the 10 (38.5%) patients with anastomotic stricture, nine (90.0%) required EBD. Regarding the first EBD, it was performed at a median of 3.3 months (range, 1.2-7.6 months) post-repair, while the average patient weight was 4.6 kg. The mean diameter ranged from 3.3 to 9.1 mm without major complications. In univariate analysis, long-gap EA alone was significantly associated with EBD. Conclusion: Approximately half of the patients experienced complications after EA repair. In particular, patients with a long-gap EA had a significantly increased risk of complications, such as anastomotic strictures. EBD can be safely used, even in infants.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.6
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• pp.7-13
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• 2008

Through two-dimensional numerical simulations, we analyzed the effects of new cell structure for the luminous efficacy improvement in an ac plasma display panel. In the new structure with 5 electrodes, two auxiliary electrodes are arranged between X and Y electrodes with long gap. Through the application of adequate auxiliary pulse on the address electrode, the luminous efficacy in the new cell structure showed the improvement of 52[%] in comparison with that of conventional cell structure with short gap between X and Y electrodes. Consequently, as the short gap discharge between auxiliary electrodes decreases and the long gap discharge between X and Y electrodes increases, the result of VUV generation efficacy shows higher improvement. The reliability of simulation result could he confirmed by the experimental result in the test panel.

• Tunnel and Underground Space
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• v.27 no.1
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• pp.12-25
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• 2017

In local underground mines heavily depending on the natural ventilation, ducted fan auxiliary ventilation system is strongly recommended instead of the total mine ventilation system requiring large capital and operating costs. Optimizing the installation of ducted fans in series in long large-opening mines is required to assure the economy and efficiency of the ventilation system. The two most critical design parameters for optimization are the wall separation distance and gap length between adjoining ducts. This study aims at deriving the optimal values for those two parameters concerning the economic and environmental aspects through the extensive CFD analysis, which minimizes pressure loss, leakage and entrainment of the contaminated air in the gap space. The ranges of the wall separation distance and gap length for study are selected by taking into consideration the existing recommendations and guidelines. The ultimate goal is to optimize the auxiliary ventilation system using ducted fans in series to provide a reliable and efficient solution to maintain clean and safe workplace environment in local long underground mines.

• Wind and Structures
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• v.12 no.5
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• pp.413-424
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• 2009

A series of wind tunnel free-decay sectional model dynamic tests were conducted to examine the effects of torsional-to-vertical natural frequency ratio of 2DOF bridge dynamic systems on the aerodynamic and dynamic properties of bridge decks. The natural frequency ratios tested were around 2.2:1 and 1.2:1 respectively, with the fundamental vertical natural frequency of the system held constant for all the tests. Three 2.9 m long twin-deck bridge sectional models, with a zero, 16% (intermediate gap) and 35% (large gap) gap-to-width ratio, respectively, were tested to determine whether the effects of frequency ratio are dependent on bridge deck cross-section shapes. The results of wind tunnel tests suggest that for the model with a zero gap-width, a model to approximate a thin flat plate, the flutter derivatives, and consequently the aerodynamic forces, are relatively independent of the torsional-to-vertical frequency ratio for a relatively large range of reduced wind velocities, while for the models with an intermediate gap-width (around 16%) and a large gap-width (around 35%), some of the flutter derivatives, and therefore the aerodynamic forces, are evidently dependent on the frequency ratio for most of the tested reduced velocities. A comparison of the modal damping ratios also suggests that the torsional damping ratio is much more sensitive to the frequency ratio, especially for the two models with nonzero gap (16% and 35% gap-width). The test results clearly show that the effects of the frequency ratio on the flutter derivatives and the aerodynamic forces were dependent on the aerodynamic cross-section shape of the bridge deck.