• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.7
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• pp.3482-3486
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• 2013

In the case of the Pilot Symbol Assisted Modulation (PSAM) method predicting and compensating amplitude and phases caused on fading channels, there can be severe performance deterioration by Doppler spread on fast fading channels. In this paper, the fading compensation method suggested so as to improve occurring problems as well as analyze them. Doppler spread is the major cause of the bit error rate(BER) performance deterioration. Compared to the existing PSAM method, the more performance deterioration occurs, the larger Doppler spread appears but performance shows well its less $10^{-2}BER$ performance than the existing PSAM method in the suggested method whereas the existing PSAM method has about $10^{-1}BER$ its considerable performance deterioration that caused by Doppler spread within a symbol cycle with the level of delay wave interference.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.11
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• pp.29-34
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• 2008

The propagation characteristics of novel grating-assisted multimode interference (GA-MMI) coupler are explicitly and theoretically investigated by using longitudinal modal transmission-line theory (L-MTLT). The coupling efficiency of GA-MMI coupler is evaluated along the variation of grating thickness and duty cycle, and the spectrum is analyzed numerically. The numerical results reveal that the coupling length and the efficiency of $2{\times}2$ GA-MMI coupler along the variation of grating structure have low tolerance and the bandwidth varies dramatically along the output states.

• Asian Pacific Journal of Cancer Prevention
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• v.13 no.2
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• pp.447-450
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• 2012

Video-assisted thoracic surgery (VATS) has been recommended as more optimal surgical technique than traditional thoracotomy for lobectomy in lung cancer, but it is not well defined. Here, we compared VATS and traditional thoracotomy based on clinical data. From November 2008 to November 2010, 180 patients underwent lobectomy for non-small-cell lung cancer (NSCL) identified by computerized tomography. Of them, 83 cases were performed with VATS and 97 by thoracotomy. Clinical parameters, consisting of blood loss, operating time, number of lymph node dissection, days of pleural cavity drainage, and length of stay were recorded and evaluated with t test. No significant difference was observed between the VATS and thoracotomy groups in the average intraoperative blood loss, number of lymph node dissections, and days of pleural cavity drainage. While the average operating time in the VATS group was significantly longer than that in thoracotomy group, recurrence was only present in one case, as opposed to 7 cases in the thoracotomy group In conclusion, similar therapeutic effects were demonstrated in VATS and thoracotomy for NSCL. However, VATS lobectomy was associated with fewer complications, recurrence and shorter length of stay.

• Journal of Korean Clinical Nursing Research
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• v.24 no.1
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• pp.44-55
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• 2018

Purpose: This study aimed to explore and understand the experience of decision making among women undergoing or forgoing selective fetal reduction who have higher-order multiple pregnancies through assisted reproductive techniques. Methods: A qualitative study was conducted from August 1, to October 30, 2013. Eight participants were interviewed and the interviews were audio-recorded and transcribed verbatim. Six persons participated in in-depth interviews in person and two participated over the telephone. A thematic analysis was conducted. Results: Four themes were identified and carefully named: Confusion after higher-order multiple pregnancy; Obstacles to choice: Uncertain safety; Weighing between reality and ideality and; Influences of medical professionals. Conclusion: The results demonstrated a wide range of factors considered by women when making decisions about selective fetal reduction, and mothers' feelings of conflict and distress in the decision-making process. The results suggest that it is important for nurses to provide emotional support and consolation, in addition to sufficient information. These findings will help nurses improve their counseling techniques by understanding the situation of infertile couples.

• Applied Microscopy
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• v.45 no.4
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• pp.195-198
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• 2015

Gas-assisted etching (GAE) with focused ion beam (FIB) was applied to prepare plan-view specimens of Cu thin-layer on a silicon substrate for transmission electron microscopy (TEM). GAE using $XeF_2$ gas selectively etched the silicon substrate without volume loss of the Cu thin-layer. The plan-view specimen of the Cu thin film prepared by FIB milling with GAE was observed by scanning electron microscopy and $C_S$-corrected high-resolution TEM to estimate the size and microstructure of the TEM specimen. The GAE with FIB technique overcame various artifacts of conventional FIB milling technique such as bending, shrinking and non-uniform thickness of the TEM specimens. The Cu thin film was uniform in thickness and relatively larger in size despite of the thickness of <200 nm.

• Progress in Superconductivity and Cryogenics
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• v.18 no.3
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• pp.1-5
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• 2016

Ion-beam assisted deposition (IBAD) technology has been successfully applied to high-temperature superconductor coated conductors (CC) as textured substrates. Since the coated conductors were proposed as a potential framework for utilizing the superior transport characteristics of $YBa_2Cu_3O_7$ and related cuprate oxides, several methods including rolling-assisted bi-axial textured substrates (RABiTS) and inclined substrate deposition (ISD), as well as IBAD, have been attempted. As of 2016, most companies that are trying to commercialize CC adapt IBAD technology except for American Superconductors who use RABiTS predominantly. For the materials in the IBAD process, initial efforts to use yttria-stabilized zirconia (YSZ) or related fluorites in Fujikura in Japan have quickly given way to MgO which technique was developed by Stanford University in the USA. In this review, we present a historical overview of IBAD technology, in particular, for the application of CC. We describe the key scientific understanding of nucleation, the texturing mechanism, and the growth of large bi-axial grains and discuss some potential new IBAD materials and systems for large-scale production.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.132-132
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• 2015

Virtual metrology (VM) model based on plasma information (PI) parameter for C4F8 plasma-assisted oxide etching processes is developed to predict and monitor the process results such as an etching rate with improved performance. To apply fault detection and classification (FDC) or advanced process control (APC) models on to the real mass production lines efficiently, high performance VM model is certainly required and principal component regression (PCR) is preferred technique for VM modeling despite this method requires many number of data set to obtain statistically guaranteed accuracy. In this study, as an effective method to include the 'good information' representing parameter into the VM model, PI parameters are introduced and applied for the etch rate prediction. By the adoption of PI parameters of b-, q-factors and surface passivation parameters as PCs into the PCR based VM model, information about the reactions in the plasma volume, surface, and sheath regions can be efficiently included into the VM model; thus, the performance of VM is secured even for insufficient data set provided cases. For mass production data of 350 wafers, developed PI based VM (PI-VM) model was satisfied required prediction accuracy of industry in C4F8 plasma-assisted oxide etching process.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.4
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• pp.144-150
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• 2005

Gas-assisted injection molding (GAIM) process is reducing the injection pressure during mold filling required as well as the shrinkage and warpage of the part and cycle time. Despite of these advantages, this process introduces new parameters and makes the application more difficult because the process interacts between gas and melt during injection molding process. Important GAIM factors that involved in this process include gas penetration design, locations of gas injection points, shot size, gas injection delay time as well as common injection molding parameters, gas pressure and gas injection time. In this study, the experiments were conducted to investigate effects of GAIM process variables on the gas penetration for PP and ABS moldings by changing gas injection point. Taguchi method was used fer the design of experiment. When the gas was injected at cavity's center, the most effective factor was shot size. When the gas was injected at cavity's end, the most effective factor was melt temperature. Injection speed was also an effective factor in GAIM process.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.4
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• pp.42-50
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• 2000

Drop size distribution of an air-assisted fuel injector(AAFI) was investigated. Influence of parameters such as ambient air density supply pressure and air-liquid mass ratio(ALR) was examined through both measurement and analysis. The Sauter mean diameter$D_{32}$ varied from 9 to 25$\mu$m throughout all experimental conditions. An empirical correlation for droplet size was obtained. Analytical correlations for predicting $D_{32}$ with respect to operating conditions were also derived through energy consideration and introduction of a simplified model of the from the empirical fitting was adapted to the original equation the proposed correlation in this study matched more closely with measured results. The current correlation exhibited a favorable study matched more closely with measured results. The current correlation exhibited a favorable prediction for $D_{32}$ compared to that by the empirical correlation at selected experimental conditions so that it may be used to predict atomization performance of the AAFI at operating conditions which was not covered in the measurements. After validation the analytical equation was applied to survey the feasible operating conditions for gasoline direct injection application.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.2
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• pp.322-329
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• 2009

Machinability of LAM(Laser Assisted Machining) has been studied for ceramics such as $Al_2O_3$, $Si_3_N4$ and $ZrO_2$ by $CO_2$ laser. It was possible to remove ceramics by PCBN tool because material became softening and deterioration by local laser beam irradiation. The advantage of LAM is the ability to produce larger material removal rates and tool life. But, for cutting of $Al_2O_3$ and $ZrO_2$, stage of laser power control was needed owing to thermal shock with high temperature of workpiece by laser power. And when $Si_3N_4$ was machined by LAM, $N_2$ gas spouted from surface of one cause of high temperature. Characteristics of LAM were analyzed using pyrometer, dynamometer, SEM and EDS to measure temperature of workpiece surface, cutting force, variation of machining surface and structure of lattice respectively. As the result of this study, it was found that machinability of LAM for ceramics in $CO_2$ laser and mechanism of LAM was different according to the kind of ceramics because of properties of materials.