• Journal of the Korean Society for Aviation and Aeronautics
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• v.29 no.1
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• pp.1-8
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• 2021

Low level wind shear, which often occurs at Jeju International Airport, is a phenomenon that occurs when the topological location and topographical characteristics of Jeju Island are combined with weather characteristics. Low level wind shears, which are caused by rapid changes in wind direction and wind speed, pose a threat to aircraft safety and also cause abnormal situations, such as aircraft go-around, diversion, and cancellation. Many meteorological studies have been conducted on weather patterns, occurrence periods and frequency of low level wind shears. However, researches related to aircraft operations are limited where here we study the similarities and differences between strong southwest winds and bidirectional tailwind type low level wind shears based on aircraft go-around cases at Jeju International Airport. The results are expected to be used to enhance safety when operating to Jeju International Airport, which includes pilot training that reflects the characteristics generated by wind changes, pilot prior notification, providing pilots with latest trends, and increasing extra fuel.

• Journal of Families and Better Life
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• v.6 no.1
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• pp.51-69
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• 1988

This study was mainly concerned with providing a basis of the development of low-income consumer education program. The purpose of this study was to investigate the level of their consumer skill and the degree of consumer problems' perception. For the purpose of this study, 480 questionnaire were distributed to the housewives in Seoul. The 320 data were analyzed by Frequency, Percentage, ANOVA, Duncan's Multiple Rang Test, Multiple Classification Analysis, and Pearson's Correlation . The major findings of this study were as follows; 1) The socio-demographic variables indicating significant relation to the level of consumer skill are income level, housewife's age , and housewife's education level. The independent influence of all the variables affecting consumer skill was analyzed. It result is in confirming the income as the most influential one. 20 The socio-demographic variables indicating significant relation to the degree of consumer problem's perception are income level, and housewife's education level. The independent influence of all the variables affecting consumer problem's perception was analyzed. It results in confirming the income as the most influential one. 3) Consumer skill level differs significantly at the 0.001 level, according toe the degree of consumer problems' perception. The higher level of consumer skill, the lower degree of consumer problems' perception. The result of this study implies that a consumer education should be given to the low-income consumers, on the basis of their consumer skill level. Further research regarding the consumer skill and problems ' perception of the low-income consumers should be conducted.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.601-604
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• 1996

It is well known that steam generator water level control at low power operation has many difficulties in a PWR (pressurized water reactor) nuclear power plant. The reverse process responses known as shrink and swell effects make it difficult to control the steam generator water level at low power. A new automatic control logic to remove the reverse process responses is proposed in this paper. It is implemented in PLC (programmable logic controller) and evaluated by using test equipment in Korea Atomic Energy Research Institute. The simulation test shows that the performance requirements is met at low power (below 15%). The water level control by new control logic is stabilized within 1% fluctuation from setpoint, while the water level by YGN 3 and 4 control logic is unstable with the periodic fluctuation of 25% magnitude at 5% power.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.890-893
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• 2008

In this paper, we present a low complexity modified multi-level sphere decoder (SD) for multiple-input multiple-output (MIMO) systems employing quadrature amplitude modulation (QAM) signals. The proposed decoder, exploiting the multi-level structure of the QAM signal scheme, first decomposes the high-level constellation into low-level 4-QAM constellations, so-called sub-constellations. Then, it deploys SD in the sub-constellations in parallel. In addition, in the searching stage, it uses the optimal low-complexity sort method. Computer simulation results show that the proposed decoder can provide near optimal maximum-likelihood (ML) performance while it significantly reduces the computational load.

• Journal of Families and Better Life
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• v.7 no.2
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• pp.31-43
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• 1989

The purposes of this study were to identify the overall levels of consumer problem, consumer competencies and purchase pattern of urban low-income consumers and to examine the factors affecting the consumer problem and the subareas-market environment problem(MEP) and transaction relation problem(TRP). The related factors, that is, independent variables were competencies-related factors(consumption-oriented attitude, attitude on consumerism, consumer knowledge), purchase pattern-related factors (search pattern, credit pattern, peddler pattern) and socio-demorgraphic factors(age, educational level, family size). For this purpose, a survey was conducted by interview using questionaires on 198 homemakers that lived in the poor areas of Seoul. Statistics used for data analysis were Frequency Distribution, Percentile, Mean, Pearson's Correlation, One-way ANOVA, Scheffe-test, Breakdown and Multiple Classification Analysis. Major findings were as follows: 1) In the level of consum r problem were in the middle level and the level of MEP were higher than that of TRP. The attitude on consumption-orientation was so negative, while attitude on consumerism was positive. The level of consumer knowledge was in the middle level. The urban low-income consumers searched a little and depended on credit and peddler in the low level. 2) Consumer problem perceived by urban low-income consumers differed significantly according to attitude on consumerism, credit pattern, monthly charge of peddler purchase. The MEP depended on attitude on consumerism and monthly charge of peddler purchase, and the TRP was affected by credit pattern and attitude on consumerism. Resulting from MCA, the most influencial variable was attitude on consumerism and credit pattern in the consumer problem, and attitude on consumerism in the MEP, and credit pattenr in the TRP.

• Asian-Australasian Journal of Animal Sciences
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• v.7 no.2
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• pp.207-212
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• 1994

Effects of dietary cellulose and protein levels on nutrient utilization in chickens were investigated. Four experimental diets containing 5% (low cellulose) or 20% (high cellulose) cellulose in combination with 10% (low protein) or 20% (high protein) protein of 70 g/day were alternatively forced-fed to eight colostomized White Leghorn cockerels once a day to make $4{\times}4$ Latin-square design. The digestibilities of DM and energy decreased with the increase in cellulose level, but not affected by dietary protein level. Ether extract digestibility was higher in the high cellulose diets than in the low cellulose protein level. Ether extract digestibility was higher in the high cellulose diets than in the low cellulose diets. The digestibility of nitrogen free extract had the same trend with the digestibility of DM and energy. The digestibility of acid detergent fiber was not so much different among the diets, but the NDF digestibility was lower in the high cellulose diets than in the low cellulose diets, due to the low hemicellulose digestibility. The true digestibility of protein was influenced by both of the dietary protein and cellulose levels, and their interaction was found. The dietary protein level affected the biological value of protein but the dietary cellulose level did not, and consequently the biological value of protein in the low protein diets was lower than in the high protein diets.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.10
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• pp.693-700
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• 2000

A direct torque control algorithm for 3-level inverter-fed induction motors is presented. Conventional voltage selection methods provoke some problems such as stator flux drooping phenomenon and undersirable torque control appeared especially at the low speed operation. To overcome these problems, a proposed method uses intermediate voltage vectors, which are inherently generated in 3-level inverters. In the proposed algorithm, both subdivision of the basic switching sectors and applications of tntermediated voltages improve the low speed operation characteristics. This algorithm basically considers applications in which direct torque controlled induction motors are fed by 3-level inverters with low switching frequency around 500Hz. An adaptive observer is also employed to bring better responses at the low speed operation, by estimating some state-variables, motor speed and motor parameters which take a deep effect on the performance of the low speed operation. Simulation and experiment results verify effectiveness of the proposed algorithm.

• Educational Technology International
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• v.19 no.1
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• pp.93-122
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• 2018

It is crucial to understand the characteristics of learner questioning due to the effects it has on learning. This study focuses on the effects of middle school students questioning on their academic achievement in an online inquiry learning environment. A survey of 827 middle school students was conducted; the students took part in an online math and science program offered by a center for the gifted. Throughout the survey, learner questioning was analyzed, and its correlation with academic achievement was investigated. An analysis was based on questioning categories of a low- and high-level questions from previous studies. Through the survey, it was found that the number of learner questions asked in the online environment was small, but the number of low- and high-level questions were almost equal. Secondly, the higher the academic achievement level of the student, the higher the possibility they would ask either low- or high-level questions. Lastly the group of students in both low- and high-levels of questioning earned the highest average scores on formative evaluations and inquiry tasks. This indicates that regardless of the level of questions, the act of questioning itself is highly related to the academic achievement. However, in the case of advanced learning projects, the quality of questioning and high-level questioning affected the academic achievement of students. Based on these results, implications for the encouragement of learner questioning and support for asking high-level question are suggested.

• Journal of Practical Agriculture & Fisheries Research
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• v.20 no.1
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• pp.175-185
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• 2018

This study was conducted to evaluate the physiological and ecological characters of rice cultivars suitable for low fertilized condition. 5 rice cultivars(Jinmibyeo, Sobibyeo, Hwayeongbyeo, Nagdongbyeo and Junambyeo) were cultivated for selection under 3 different nitrogen application levels, and 1 cultivars were selected. The results obtained are summarized as follows ; High yielded rice cultivars under low N application level were Junambyeo, Jinheng and Sobibyeo. Also these cultivars were yielded highly under conventional level(11kg/10a). Milled rice yield under conventional level(11kg/10a) was positively correlated with them under low N levels. Milled rice yield was most affected by no. of grain/m². Rice cultivars that were high crop growth rate(CGR) before heading stage were Junambyeo, Sobibyeo and Nagdongbyeo. Grain filling rate was increased mostly until 20 days after heading, and decreased after this stage. Nitrogen use efficiency was higher under low N level(5.5kg/10a) than conventional level(11kg/10a). Especially, Junambyeo was most low in Apparent recovery of applied N(AR) under low N application level, but most high in Agronomic N use efficiency(ANUE). This characteristics of Junambyeo will to be useful for selection of variety suitable for growing under low fertilized condition.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.4
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• pp.25-32
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• 1997

In this paper, we propose an adaptive BTC algorithm using the characteristics of the error signals. The BTC algorithm has a avantage that it is low computational complexity, but a disadvantage that it produces the ragged edges in the reconstructed images for th esloping regions beause of coding the input with 2-level signals. Firstly, proposed methods classify the input into low, medium, and high activity blocks based on the variance of th einput. Using 1-level quantizer for low activity block, 2-level for medium, and 4-level for high, it is adaptive methods that reduce bit rates and the inherent quantization noises in the 2-level quantizer. Also, in case of processing high activity block, we propose a new quantization level allocation algorithm using the characteristics of the error signals between the original signals and the reconstructed signals used by 2-level quantizer, in oder that reduce bit rates superior to the conventional 4-level quantizer. Especially, considering the characteristics of input block, we reduce the bit rates without incurrng the visual noises.