• Journal of the Korea Society for Simulation
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• v.30 no.1
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• pp.11-20
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• 2021

As unmanned underwater systems have recently emerged, a high-speed underwater channel modeling technique, which is one of the most important techniques in the system, has received a lot of attention. In this paper, we proposed a high-speed sound propagation model and verified the applicability through quantitative performance analyses. We used a high-order finite difference method (FDM) for wave propagation modeling in the water, and a domain decomposition method was adopted using multiple general-purpose graphics processing units (GPUs) to increase the calculation efficiency. We compared the results of the model we proposed with the analytic solution in the half-infinite media and results of the Virtual Timeseries Experiment (VirTEX) model, which is based on the ray method. Finally, we analyzed the performance of the model quantitatively using numerical examples. Through quantitative analyses of the improvement in computational performance, we confirmed that the computational speed increases linearly as the number of GPUs increases. The computation times are increased by 2 times and 8 times, respectively, when the domain size of computation and the maximum frequency are doubled. We expect that the proposed high-speed underwater channel modeling technique is able to contribute to the enhancement of national defense as an underwater communication channel model and analysis tool to develop the underwater communication technique for the unmanned underwater system.

• Journal of the Korean Society of Food Science and Nutrition
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• v.34 no.10
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• pp.1566-1571
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• 2005

Consumer's perception and consumption pattern of fresh-cut agri-food Products were surveyed to Provide basic information for quality enhancement. The results are summarized as follows: The respondents had a preference for a discount store (60.5$\%$) to purchase fruits and vegetables and the frequency of purchase was one time Per week (46.1$\%$). Fruits and vegetables were purchased frequently by full-time housewives compared with workers. The reasons for purchasing fresh-cut agri-food generally resulted from a consideration of the saving in cooking time, the ease of handling and the desire to serve appropriate portions. On the other hand, the reasons for not purchasing fresh-cut agri-food Products were the comparatively high price, a perception of unsanitary handling. Freshness was considered to be the most important factor when purchasing these products. The preferred price for the fresh-cut agri-food products were approximately 110 $\∼$ 140$\%$ of that for the unprocessed products. 87.7$\%$ of respondents answered that they will purchase fresh-cut agri-food products continuously if some problems that they considered, would be improved.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.6D
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• pp.775-789
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• 2008

The Office for Government Policy Coordination announced in 2006, september that a scheme of pre-signal would show remarkable outcome to reduce traffic accidents. Therefore, the Ministry recommended applying preferentially the pre-signal scheme to enhancement projects for high accident frequency areas. In case that the suggested pre-signal was unilaterally introduced to the enhancement projects at intersections, it might rather cause a big trial and error in terms of traffic safety. Hence, on the basis of quantitative analysis, this study was to indicate a pre-signal's effectiveness to reduce the traffic accidents, to illustrate a trend of the accident type due to the pre-signal, and to introduce intersection type that could be appropriate for the pre-signal. The methodology adopted Comparison-Group Method which was developed by Hauer. Through this methodology, overall effectiveness to reduce the accidents is considered positive but individual effectiveness by intersection and by accident case was different. All cases of the accidents at small scale intersection demonstrated positive results to reduce its accidents, while in case of frontal collision and side-right angle collision out of the accident types, the installation of pre-signal rather caused a negative result increasing the accident in terms of the traffic safety. I hope that this study would be a useful reference for future development of the estimation of accident effectiveness. Thus, when the pre-signal is being installed in the big intersection, it is recommended operating the installation concerning carefully improvements about muliple aspects as traffic operation, traffic facility, human factor etc.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.11
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• pp.1959-1975
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• 2011

Adaptive Bit Loading (ABL) in Multiple-Input Multiple-Output Orthogonal Frequency-Division Multiplexing (MIMO-OFDM) is often used to achieve the desired Bit Error Rate (BER) performance in wireless systems. In this paper, we discuss some of the bit loading algorithms, compare them in terms of the BER performance, and present an effective and concise Adaptive Grouped Loading (AGL) algorithm. Furthermore, we propose a "weight factor" for loading algorithm to converge rapidly to the final solution for various data rate with variable Signal to Noise Ratio (SNR) gaps. In particular, we consider the bit loading in near optimal Singular Value Decomposition (SVD) based MIMO-OFDM system. While using SVD based system, the system requires perfect Channel State Information (CSI) of channel transfer function at the transmitter. This scenario of SVD based system is taken as an ideal case for the comparison of loading algorithms and to show the actual enhancement achievable by our AGL algorithm. Irrespective of the CSI requirement imposed by the mode of the system itself, ABL demands high level of feedback. Grouped Loading (GL) would reduce the feedback requirement depending upon the group size. However, this also leads to considerable degradation in BER performance. In our AGL algorithm, groups are formed with a number of consecutive sub-channels belonging to the same transmit antenna, with individual gains satisfying predefined criteria. Simulation results show that the proposed "weight factor" leads a loading algorithm to rapid convergence for various data rates with variable SNR gap values and AGL requires much lesser CSI compared to GL for the same BER performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.2B
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• pp.345-351
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• 2010

It has been growing interests that convergence services of broadcasting and telecommunication services such as DMB 2.0 and Mobile IPTV etc. Unicast type is difficult to service broadcasting due to limits of capacity and poor receiving environments, WiBro supports broadcast service with MBS. MBS is transmission method that base stations belong to same the MBS zone transmit the all users who request broadcasting service. Terminals are received resources from all base station in the MBS zone and SINR can be improved because of macro diversity. If terminals are located at edge of the MBS zone, complement algorithm are needed beacause received SINR is very low. In this paper, MIMO STBC, Relay and FFR are introduced to improve the throughputs using high MCS. The basic simulation environment is assumed to be SISO. Transparent relay and FFR applicable on MBS are divided by SISO and MIMO STBC environment and evaluate the performance.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.4
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• pp.290-296
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• 2009

$Bi_{4}Ti_{3}O_{12}$ (BiT) thin films were grown on the Pt/Ti/$SiO_2$/si substrate using a metal organic decomposition (MOD) method. Effects of oxygen annealing on the structural properties and dielectric properties of the BiT thin films were investigated. The BiT films were well developed when rapid thermal annealed at $>500^{\circ}C$ in oxygen ambient. For the film annealed at $700^{\circ}C$, no crystalline phase was observed under oxygen free annealing atmosphere while its crystallinity was significantly enhanced as the oxygen pressure increased. The BiT film also exhibited a smooth surface with defect free grains. A high dielectric constant and a low dielectric loss were achieved satisfactory in the frequency range from 75 kHz to 1 MHz. Especially, the BiT film, annealed at $700^{\circ}C$ and 10 torr oxygen pressure, showed good dielectric properties: dielectric constant of 51 and dielectric loss of 0.2 % at 100 kHz. Its leakage current was also considerably improved, being as $0.62\;nA/cm^2$ at 1 V. Therefore, it is considered that the oxygen annealing has effects on an enhancement of crystallinity and dielectric properties of the BiT films.

• Journal of Environmental Science International
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• v.20 no.2
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• pp.231-239
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• 2011

Diethyl phthalate (DEP) and nonylphenol (NP) are widely spread in the natural environment as an endocrine disruption chemicals (EDs). Therefore, in this study, ultrasound (US) and ultraviolet (UVC), including $TiO_2$, as advanced oxidation processes (AOPs) were applied to a DEP and NP contaminated solution. When only the application of US, the optimum frequency for significant DEP degradation and a high rate of hydrogen peroxide ($H_2O_2$) formation was 283 kHz. We know that the main mechanism of DEP degradation is radical reaction and, NP can be affected by both of radical reaction and pyrolysis through only US (sonolysis) process and combined US+UVC (sonophotolysis) process. At combined AOPs (sonophotolysis/sonophotocatalysis) such as US+UVC and US+UVC+$TiO_2$, significant degradation of DEP and NP were observed. Enhancement effect of sonophotolysis and sonophotocatalysis system of DEP and NP were 1.68/1.38 and 0.99/1.17, respectively. From these results, combined sonophotocatalytic process could be more efficient system to obtain a significant DEP and NP degradation.

• Child Health Nursing Research
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• v.7 no.2
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• pp.161-178
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• 2001

The purpose of this study was to identify nursing interventions performed by neonatal nursing unit nurses. For data collection this study used the taxonomy of Nursing Intervention Classification(NIC : 486 nursing intervention) which was modified by McCloskey & Bulecheck(2000). The new 58 nursing interventions was translated into Korean, and then modified by pannel group, which consist of clinical experts and nursing scholars and finally the 419 nursing interventions was selected. The data were collected from 112 nurses. 168 nursing interventions were performed at least monthly by 50％ or more of the nurses. The high frequency of performed nursing interventions were Family domain. 37 nursing interventions were performed at least once a day. The nursing interventions receiving the highest item mean score were neonatal care, neonatal monitoring, photo-therapy; neonate, bottle feeding and temperature regulation. 56 nursing interventions were rarely performed by 90％ or more of the nurses. Most of them were in the behavioral domain. The rarely used interventions were urinary bladder training, art therapy, religious addiction prevention, religious ritual enhancement and bladder irrigation. Therefore, neonatal nursing units nurses used interventions in the Physiological: basic domain most often on a daily basis and the interventions in the behavioral domain least often. These findings will help in building of a standardized language for the neonatal nursing units and enhance the quality of nursing care. Further study will be needed to classify each intervention class and nursing activity and validate NIC in pediatric care unit.

• Journal of Energy Engineering
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• v.29 no.1
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• pp.75-84
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• 2020

This study investigates a simple, yet effective and affordable, manufacturing method to increase the electrical efficiency by triboelectric generator (TEG) applying 3D printers. In this study, we propose the newly manufacturing method for producing a macroscale surface patterning. Overall experiments were conducted in designed test-bed chamber system which can control the magnitude and frequency of the frictional force and the relative humidity. Furthermore, we can demonstrate the voltage enhancement of macroscale surface patterns about 1.6-fold. The peak voltage producing by TEG was as high as 18 V. In comparison with conventional process that employ micro- and nanoscale patterns, the proposed process by 3D printer is faster and more suitable for mass production.

• Journal of Sensor Science and Technology
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• v.8 no.2
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• pp.163-170
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• 1999

A programmable A/D converter for an embedded fiber-optic combustion pressure sensor has been designed with 8 N and P channel MOSFETs, respectively. A local field enhancement for reducing programming voltage during writing as well as erasing an EEPROM device is introduced. In order to observe linear programmability of the EEPROM device during programming mode, a cell is developed with a $1.2\;{\mu}m$ double poly CMOS fabrication process in MOSIS. It is observed that the high resolution, of say 10mVolt, is valid in the range 1.25volts to 2volts. The experimental result is used for simulating the programmable 8 bit A/D converter with Hspice. The A/D converter is demonstrated to consume low power, $37\;{\mu}W$ by utilizing a programming operation. In addition, the converter is attained at the conversion frequency of 333 MHz.