• Journal of Advanced Navigation Technology
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• v.10 no.3
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• pp.256-262
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• 2006

This paper proposes a new predistortion linearizer to compensate for AM/AM and AM/PM in the nonlinear characteristics of amplifier. This consists of common-emitter amplifier and schottky diode that is connected between emitter and ground. When effective resistance of the schottky diode with bias condition varies, common-emitter amplifier with series feedback has a increase of amplitude and expansion of phase. This makes a amplifier nonlinear characteristics are to be improved. The proposed linearizer and amplifier has been manufactured and tested to operate in cellular base station frequency (869~894MHz). The test results show that third order intermodulation distortion (IMD3) cab be removed by more than 10.4dB in case of CW 2-tone signals ${\Delta}f$=1MHz, and the adjacent channel power ratio (ACPR) also can be improved by more than 9.6dB for CDMA IS-95 1FA signals.

• Journal of the Korea Society for Simulation
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• v.28 no.2
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• pp.169-177
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• 2019

LVC(Live-Virtual-Constructive) training system is drawing attention due to changes in battlefield situation and the development of advanced information and communication technologies. The ROKAF(Republic of Korea Air Force) plans to construct LVC training system capable of scientific training. This paper analyzes the results of V-C interoperability test with three fighter simulators as virtual systems and a theater-level wargame model as a constructive system. The F-15K, KF-16, and FA-50 fighter simulators, which have different interoperable methods, were converted into a standard for simulation interoperability. Using the integrated field environment simulator, the fighter simulators established a mutually interoperable environment. In addition, the Changgong model, which is the representative training model of the Air Force, was converted to the standard for simulation interoperability, and the integrated model was implemented with optimized interoperability performance. Throughput experiments, It was confirmed that the fighter simulators and the war game model of the ROKAF could be interoperable with each other. The results of this study are expected to be a good reference for the future study of the ROKAF LVC training system.

• Computers and Concrete
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• v.27 no.4
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• pp.319-332
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• 2021

The performance of gene expression programming (GEP) in predicting the compressive strength of bacteria-incorporated geopolymer concrete (GPC) was examined in this study. Ground-granulated blast-furnace slag (GGBS), new bacterial strains, fly ash (FA), silica fume (SF), metakaolin (MK), and manufactured sand were used as ingredients in the concrete mixture. For the geopolymer preparation, an 8 M sodium hydroxide (NaOH) solution was used, and the ambient curing temperature (28℃) was maintained for all mixtures. The ratio of sodium silicate (Na2SiO3) to NaOH was 2.33, and the ratio of alkaline liquid to binder was 0.35. Based on experimental data collected from the literature, an evolutionary-based algorithm (GEP) was proposed to develop new predictive models for estimating the compressive strength of GPC containing bacteria. Data were classified into training and testing sets to obtain a closed-form solution using GEP. Independent variables for the model were the constituent materials of GPC, such as FA, MK, SF, and Bacillus bacteria. A total of six GEP formulations were developed for predicting the compressive strength of bacteria-incorporated GPC obtained at 1, 3, 7, 28, 56, and 90 days of curing. 80% and 20% of the data were used for training and testing the models, respectively. R2 values in the range of 0.9747 and 0.9950 (including train and test dataset) were obtained for the concrete samples, which showed that GEP can be used to predict the compressive strength of GPC containing bacteria with minimal error. Moreover, the GEP models were in good agreement with the experimental datasets and were robust and reliable. The models developed could serve as a tool for concrete constructors using geopolymers within the framework of this research.

• Journal of the Korea Convergence Society
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• v.13 no.3
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• pp.33-41
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• 2022

In this article, we proposed to predict natural gas (NG) leakage levels through feature selection based on a factor analysis (FA) of the integrating the Korean Meteorological Agency data and natural gas leakage data for considering complex factors. The paper has been divided into three modules. First, we filled missing data based on the linear interpolation method on the integrated data set, and selected essential features using FA with OrdinalEncoder (OE)-based normalization. The dataset is labeled by K-means clustering. The final module uses four algorithms, K-nearest neighbors (KNN), decision tree (DT), random forest (RF), Naive Bayes (NB), to predict gas leakage levels. The proposed method is evaluated by the accuracy, area under the ROC curve (AUC), and mean standard error (MSE). The test results indicate that the OrdinalEncoder-Factor analysis (OE-F)-based classification method has improved successfully. Moreover, OE-F-based KNN (OE-F-KNN) showed the best performance by giving 95.20% accuracy, an AUC of 96.13%, and an MSE of 0.031.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.6
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• pp.143-151
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• 2007

This study presents the experimental results of frost durability including resistance to freezing-thawing and surface scaling of concrete. Mixing design was proportioned with the various water-binder ratio between 0.37 and 0.47 and three different binder compositions corresponding to Type I cement without any supplementary cementitious materials(OPC), Type II cement with 50% blast-furnace slag replacement(BFS50), and ternary cement with Type III cement, 15% fly ash, and 35% slag replacement (BFS35%+FA15%). Test results showed that the mixing design with BFS50% and BFS35%+FA15% exhibited higher durability factor than that made with OPC only. Finally, the use of blend cement containing slag can be used effectively in terms of frost durability of the concrete exposed to severe condition under coastal environment like as flying salt, sea water spray, etc.

• Journal of the East Asian Society of Dietary Life
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• v.20 no.4
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• pp.536-542
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• 2010

In this study, we determined the fat content, total fatty acid composition, trans fatty acid (tFA) content, and acid value of twenty samples of sweet-and-sour pork and fifteen samples of used frying oils collected from Chinese restaurants in Seoul. After the extraction of crude fat by the Folch method, the total fat content of the twenty sweet-and-sour porks ranged from 9.93 to 20.04%. The total unsaturated fatty acid content ranged from 50.05 to 81.22%, which mostly consisted of oleic and linoleic acid, while those of total saturated fatty acids were 18.06~49.26%. The tFA content of all of the twenty sweet-and-sour porks tested was less than 0.24 g per 100 g of food. The acid values of the fat extracted from the twenty sweet-and-sour porks ranged from 0.44 to 4.37. In the used frying oils, the ranges of the major compositional fatty acids were as follows: palmitic acid, 4.47~20.28%; oleic acid, 23.43~77.45%; linoleic acid, 5.6~53.06%; stearic acid, 1.81~7.38%. The tFA content in all of the fifteen used frying oils was less than 0.98 g per 100 g of fat, while the acid values of the fifteen used frying oils ranged from 0.27 to 2.41.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.10
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• pp.1046-1054
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• 2006

The raw water DOC contained 39.3% of hydrophilics, 42.9% of hydriophobic, and 17.8% of transphilic. The hydrophobic fraction in this raw water was mostly fulvic acid. Fulvic acid comprised of 62% and the rest was humic acid(38%). There was more carboxylic acid functional group(64%) than phenolic group(36%). HPI-N and HPI-C comprised of 17% and 22% in the hydrophilic portion, respectively. The fouling mechanisms on the membrane surface and into its porous structure were analyzed in terms of several kinetic models. In order to analyze the fouling kinetics, the various kinetic models described in this paper were used to fit the experimental results. The kinetic models and kinetic constants obtained for each operation condition. The permeate flux was rapidly declined by simultaneous pore blocking and cake formation. Also, the permeate flux declined with decreasing internal pore size resulted from organic deposition into the membrane pore. The results of the membrane fouling test using UF membrane according to NOM fractions. HPI-N caused more fouling than HPI-C. Humic acid caused more fouling than fulvic acid probably due to higher adsorption capacity. Since humic acid has higher adsorption capacity than fulvic acid, it would be more adsorbed onto the membrane pores.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.3C
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• pp.95-104
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• 2012

Due to current interest in creation of urban space and urban landscape, more emphasis has been placed on underground space development. With increasing number of underground power cables and its importance, a study of backfill materials for pipe is now imperative. Backfill materials require outstanding thermal characteristics since breakdown of cable insulation can be caused if heat generated from transmission of underground power cables had not been effectively discharged through backfill materials. Also, coal ash, which are industrial by-products, is being produced in high volume every year. Among them, ponded ash (PA) is not recycled and instead, mostly buried. Therefore in this study, thermal conductivity test based on mixture ratio (PA, ponded ash : FA, fly ash) was performed to evaluate the thermal conductivity characteristics of CLSM (controlled low strength materials) with coal ash. The results indicate that the mixture ratio (PA, ponded ash : FA, fly ash) of 80:20, water contents of 28~30%, and cement contents of 7-11% showed the highest conductivity at 0.796~0.884W/mK and thus, considered optimal in terms of recycling ponded ash (PA) as well as for maximizing utilization as backfill materials for pipe in underground.

• Journal of the Korean Society of Food Science and Nutrition
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• v.38 no.10
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• pp.1353-1361
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• 2009

This study investigated the effect of waxy barley on the incorporation trans fat (tFA) into plasma lipid and lipid profile through 6 weeks trial. 39 healthy volunteers were divided into 2 groups and fed waxy barley bread (WBG) or wheat bread (WG) containing equivalent amounts of tFA (elaidic acid rich, 3.75 g/day), respectively. Plasma lipid profiles and fatty acid composition at 0, 2, 4, 6 weeks after a respective bread were studied. Plasma lipid was extracted by the method of Folch, esterified by acid transmethylation and analyzed by gas chromatography. The fatty acid composition reflected the fatty acid proportion of the test fat. However, consumption of waxy barley bread with tFA for 6 weeks affected plasma fatty acid composition including tFA. Incorporation of tFA into plasma lipid was significantly lowered compared to WBG than in WG after 6 weeks of consumption. Furthermore, saturated fatty acids such as C16:0 and C18:0 levels were also significantly lowered in WBG than in WG. Furthermore, plasma total cholesterol level and TG/HDL-cholesterol ratio were also significantly lowered in WBG compared to WG at 2, 4 and 6 weeks. These results suggest that waxy barley bread with high $\beta$-glucan lowered plasma trans, saturated fatty acid and total cholesterol levels though the inhibition of lipid absorption.

• Korean Journal of Veterinary Research
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• v.28 no.1
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• pp.89-97
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• 1988

Twenty-eight porcine rotavirus were isolated from piglets with diarrhoea in chonnam province. According to the age, 41 to 60 day old pigs showed the highest isolation frequency among the post weaning pigs. The characteristics of the field isolates were determined by electronmicroscopy(EM), immunofluorescent assay(FA), and electrophoretic migration patterns of the genome profiles. Some of the isolates showed remarkable haemagglutination activity against rabbit and dog erythrocytes, ranged from 4 to 2848, respectively. At least 3 serotypes of porcine rotavirus were recognized by serum neutralization test using serotype specific rotavirus hyperimmune sera.