• Journal of KIISE:Databases
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• v.31 no.4
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• pp.384-394
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• 2004

Recently, to relieve the performance degradation caused by the bottleneck between CPU and main memory, cache conscious multi-dimensional index structures have been proposed. The ultimate goal of them is to reduce the space for entries so as to widen index trees and minimize the number of cache misses. The existing index structures can be classified into two approaches according to their entry reduction methods. One approach is to compress MBR keys by quantizing coordinate values to the fixed number of bits. The other approach is to store only the sides of minimum bounding regions (MBRs) that are different from their parents partially. In this paper, we propose a new index structure that exploits the properties of the both techniques. Then, we investigate the existing multi-dimensional index structures for main memory database system through experiments under the various work loads. We perform various experiments to show that our approach outperforms others.

• Journal of Elementary Mathematics Education in Korea
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• v.10 no.1
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• pp.1-19
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• 2006

It is generally accepted that fostering creative thinking is a core in mathematics education and accumulating research products on that topic is really needed. In this study, I hoped to investigate and verify that in mathematics education it was possible to cultivate creative thinking through various and divergent activities, For this purpose, I delat with some illustrations, in which students learned mathematics through the operational activities using teaching tools, problem solving and problem posing activities, and finally they seemed to foster creative mathematical thinking. In conclusion of this paper, I have suggested that in math education those activities should be used to cultivate students' creative thinking in kindergarten or early elementary school. Also I asserted that it is urgently need to store up research products about various materials and methods for those mathematics teaching and learning.

• Korean Journal of Community Nutrition
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• v.24 no.5
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• pp.408-421
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• 2019

Objectives: This study compared the dietary behaviors of single-person households when eating alone according to the employment pattern and age. Methods: A total of 566 people aged 20~59 years old were collected from the status of workers and classified into three groups according to their employment pattern (regular, non-regular workers and business owner). The subjects were collected by purposive quota sampling on a Gallup panel from June to November in 2017. The dietary behavior and perception of eating alone of the subjects were surveyed via online and self-reported questionnaires. Results: The frequency of eating alone was significantly higher in the regular group than the non-regular group and business group (p<0.01). The place of eating alone was significantly higher in the regular and non-regular group in the convenience store, and business group in the office (p<0.001). Ramen, the menu when eating alone, was significantly higher in the non-regular group than the other groups (p<0.01). The preference for eating alone was lower in the older age group (p<0.05). The young aged group (aged 20~30) ate more fast food and felt more convenience than the older aged group aged 40~50 years (p<0.05). Conclusions: Single-person households with a non-regular job have poorer dietary behavior in eating alone than those who had regular employment. In a situation of an increasing number of non-regular workers aged in their 20s and 30s, there is a high likelihood of social problems, such as health and poverty. This study highlights the need for a healthy food selection environment to improve the dietary life of single-person households with non-regular jobs for the diverse types of single-person households.

• Korean Institute of Interior Design Journal
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• v.26 no.1
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• pp.114-123
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• 2017

The objective of this paper is to investigate problems associated with the storehouse affiliated with rural housing for the elderly engaged in farming activities, and to suggest improvements with the examples of storehouse floor plans. The elderly in rural area still engage in farming even though they are suffering from aging problems. Therefore, the planning of storehouse which has relevance to agriculture is very important. The methods employed were a field survey and interviews with residents. 12 houses belonging to elderly people (60's and over) were selected by the convenient sampling in Cheonan, Chungcheongnam-do. The results are as follows. First, at least more than 3 storehouses have to be planned to store the goods separatedly according to their kinds and characteristics. Second, storehouses should be placed near or directly connected with the main house to support the accessibility of the elderly. Third, the open space has to be planned in front of the storehouse to park a truck for loading goods directly. Fourth, the storage equipments such as shelves should be planned inside of the storehouse for the space efficiency and user convenience. Fifth, the width of the door should be wide enough to carry agricultural products and goods. It is recommended to use double hinged doors or double pocket doors. Besides, the thresholds of the doors should be removed and, rather than using direct lighting system, it is better to use indirect lightings and task lightings together to minimize glare and to provide enough illumination.

• Journal of KIISE
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• v.42 no.1
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• pp.23-32
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• 2015

In the Android market, a large portion of the market share consists of third party applications, but not much research has been performed in this respect. Of these applications, mobile Voice Over IP (VoIP) applications are one of the types of applications that are used the most. In this paper, we focus on user authentication methods for three representative applications of the Google Voice service, which is a famous mobile VoIP application. Then, with respect to the Android file system, we developed a method to store and to send user information for authentication. Finally, we demonstrate a vulnerability in the mechanism and propose an improved mechanism for user authentication by using hash chaining and an elliptic curve Diffie-Hellman key exchange.

• Journal of KIISE:Databases
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• v.32 no.1
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• pp.1-11
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• 2005

An aggregation query computes aggregate information over a data cube in the query range specified by a user Existing methods based on the prefix-sum approach use an additional cube called the prefix-sum cube(PC), to store the cumulative sums of data, causing a high space overhead. This space overhead not only leads to extra costs for storage devices, but also causes additional propagations of updates and longer access time on physical devices. In this paper, we propose a new prefix-sum cube called 'SPEC' which drastically reduces the space of the PC in a large data warehouse. The SPEC decreases the update propagation caused by the dependency between values in cells of the PC. We develop an effective algorithm which finds dense sub-cubes from a large data cube. We perform an extensive experiment with respect to various dimensions of the data cube and query sizes, and examine the effectiveness and performance ot our proposed method. Experimental results show that the SPEC significantly reduces the space of the PC while maintaining a reasonable query performance.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.9 no.5
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• pp.865-872
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• 2019

In this paper, we describe the Solar Car, Woongbi, which was created to participate in the World Solar Challenge(WSC) at the team NeulHaeRang of Korea National University of Transportation. The WSC is the world's largest solar car racing competition and has a separate automobile regulation and must be manufactured to meet the regulations. Therefore, the key point of the solar car design is to optimize the energy efficiency based on the regulations. The solar car's drive system consists of a solar array to convert solar energy into electric energy, a maximum power point tracker (MPPT) controller to track the converted electric energy to maximum output power, a battery to store the produced electric energy, a BLDC (Brushless DC) motor for driving the vehicle by converting energy into mechanical energy, and a motor controller for controlling the BLDC. The optimal design methods for solar energy conversion and electric driving system of battery, motor are presented in this paper.

• Journal of Navigation and Port Research
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• v.43 no.2
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• pp.79-85
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• 2019

Climate change is a very vital issue that can be no longer avoided. Korea has been a top-level country Iin dealing with carbon dioxide emissions since 1960. Many studies have been conducted to suppress or eliminate carbon dioxide emissions, which account for a large portion of greenhouse gases. Carbon Capture and Storage (CCS), the most practical method of them, plays a significant role. However, these methods have the disadvantage of the limits of geographical distribution and high possibility of re-emission into the atmosphere. Recently, ocean storage has been studied using Accelerated Weathering of Limestone (AWL), a technique for storing carbon dioxide in the ocean as an alternative to CCS, an underground storage. AWL is a method of converting carbon dioxide into concentrated water in the form of bicarbonate ion and discharging it to the ocean to dilute and store it. It does not cause re-emission to the atmosphere, and the discharged concentrated water increases the alkalinity of the ocean to prevent marine acidification. The objective of this study was to understand the behavior of DIC (Dissolved Inorganic Carbon) including carbon dioxide during the ocean discharge of bicarbonate ion concentrated water in AWL method. This study area was set near Ulleung-do where sufficient water depth and operational efficiency were secured. CORMIX model was used to calculate the material diffusion by submerged discharge using ship.

• Journal of the Korea Convergence Society
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• v.10 no.6
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• pp.121-128
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• 2019

Fashion display is a part of fashion brand marketing strategy. Today, due to the improvement of consumers' aesthetics, consumers' requirements for display and decoration in fashion stores are also increasing. And color design plays an important psychological role in the display. In this study, the color design of the display is taken as the center, and the status quo, emotional characteristics, psychological and physiological functions of the color design of the display are taken care of. After analyzing specific examples through previous studies, the methods and rules of color design are explored on the basis of these studies, and the principles of color matching beauty are studied to prompt the color design that follows in the display. First, there should be some emphasis on the overall color allocation. Second, the structure of the store needs to be considered. Third, we need to emphasize scientific and reasonable color matching sequence. To sum up, judging this research is of positive significance to the later research on color design.

• Clinical and Experimental Pediatrics
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• v.62 no.3
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• pp.102-107
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• 2019

Purpose: This study compared the iron statuses of small for gestational age (SGA) and appropriate for gestational age (AGA) infants at birth. Methods: The clinical data of 904 newborn infants admitted to the neonatal intensive care unit were reviewed. Blood samples were drawn from the infants within 24 hours after birth. Serum ferritin level was used as a marker of total iron status. Results: In this study, 115 SGA (GA, $36.5{\pm}2.9weeks$; birth weight [BW], $1,975{\pm}594.5g$) and 717 AGA (GA, $35.1{\pm}3.5weeks$; BW, $2,420.3{\pm}768.7g$) infants were included. The SGA infants had higher hematocrit levels ($50.6%{\pm}5.8%$ vs. $47.7%{\pm}5.7%$, P<0.05) than the AGA infants. No difference in serum ferritin level (ng/mL) was found between the groups (mean [95% confidence interval]: SGA vs. AGA infants, 139.0 [70.0-237.0] vs. 141.0 [82.5-228.5]). After adjusting for gestational age, the SGA infants had lower ferritin levels (147.1 ng/mL [116.3-178.0 ng/mL] vs. 189.4 ng/mL [178.0-200.8 ng/mL], P<0.05). Total body iron stores were also lower in the SGA infants than in the AGA infants (185.6 [153.4-211.7] vs 202.2 [168.7-241.9], P<0.05). Conclusion: The SGA infants had lower ferritin and total body iron stores than the AGA infants. The SGA infants affected by maternal hypertension who were born at late preterm had an additional risk of inadequate iron store. Iron deficiency should be monitored in these infants during follow-up.