• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.4
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• pp.143-147
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• 2018

Water levels are measured in various fields such as sewage treatment plants, water treatment plants, rivers, dams, factory storages' tanks. Ultrasonic instruments for water level measurement are expensive and are used for industrial field. Rapid advances in electronics have made it possible to build a wide variety of measurement, monitoring and control functions at low cost. This study was started to make ultrasonic level measurement system at low price. The system was constructed with an Arduino, an ultrasonic sensor and a temperature sensor for use in the experiment. The ultrasonic sensor measures the time from the sensor to the liquid surface. The temperature sensor measures the atmospheric temperature and improves the accuracy of the ultrasonic distance measurement by correcting the sound speed. Arduino controls measurements and calculates the water level. All components of the system are assembled into a device holder. Experiments with this system show that the water level measured by the system is very close to the actual value. This system is also inexpensive and easy to install and maintain, making it suitable for laboratory use.

• Journal of Digital Convergence
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• v.16 no.10
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• pp.453-463
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• 2018

This study investigated the effects of an Augmented Reality(AR) implemented book on flow of reading, interest in history, and acquisition of history knowledge. Perceptions of AR infused books were investigated as well. Researchers provided a history book implementing AR and the same book without any AR content respectively to an experiment group(n=15) and a control group(n=15) composed of $3^{rd}$ and $4^{th}$ grade elementary school children. Results indicate that AR implemented reading had a positive effect on the flow of reading and interest in history, but not on acquisition of history knowledge. Also, AR-based contents were attractive to learners due to its amusing characters, sound, realistic visual motions, and vivid three-dimensional effects. Lastly, students preferred amusing interesting characters, lengthier animations and subtitles, and AR that could be seen without holding smart devices for a long while.

• Journal of Industrial Technology
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• v.23 no.A
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• pp.149-156
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• 2003

The development and maintenance of a sound bond are essential requirements of concrete repair and replacement. The bond property of a overlay to its substrate concrete during the lifetime is one of the most important performance requirements which should be quantified. A standard or a verified bond strength measurement method is required at field for screening, selecting materials and quality control for overlay or repair materials, but no test method has been adopted as a standard. In this study, a concrete pull off bond strength measurement method for field application is proposed and evaluated. This study compares the splitting tensile test, slant shear test, nipple pipe direct tensile test, flexural adhesion test, briquette tensile test, jumbo nail pull-out test and core pull-off test with their test procedures. From these comparison and investigation, core pull-off test is selected as a main topic of this study because of it's suitability for in situ testing, simplicities in field application and clearness at interface boundary condition. Thus, the proposed core pull off test is evaluated to be the most appropriate method for field application in a simple manner. The fracture surface and fracture mode could be easily determined by visual observation of failure surface of the field specimen. The core pull off test was found to be sensitive to surface condition and latex contents at latex modified concrete.

• Journal of the korean academy of Pediatric Dentistry
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• v.29 no.1
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• pp.30-37
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• 2002

Bacterial microleakage around restorations is considered the principal cause of pulpal inflammation associated with restorations. The rationale for using cavity disinfectant is based on its antimicrobial properties but the cavity disinfectant may leave debris on dentin surfaces. The purpose of this study was to evaluate the effect of 2% chlorhexidine on shear bond strength and microleakage of adhesive restoration. 45 sound bovine teeth were used for the shear bond strength test and 30 for the micorleakage. For the experimental groups, 2% chlorhexidine was applied before the restorations, and was not for the control groups. The result from the this study can be summarized as follows; 1. No significant difference could be found in shear bond strength of each group. 2. No significant difference could be found in microleakage of each group.

• Journal of the korean academy of Pediatric Dentistry
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• v.29 no.1
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• pp.11-18
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• 2002

Compomer, like resin composite, undergoes shrinkage during setting. But, due to the structure of glass ionomers and their hydrophilic nature, water sorption and subsequent expansion may lead to compensation of the shrinkage. The purpose of this study was to, evaluate the change of mliroleakage after 30day-water-storage of compomer and composite resin. 40 sound third molars were used for the microleakage test. Z-100 resin was used for the control groups(Group I and III), Dyract AP for the experimental groups(Group II and IV). The storage time was 1 day in Group I, II and 30days in Group III, IV. The result from the this study can be summarized as follows; 1. No significant difference could be found in microleakage of occlusal margin between each group(p>0.05). 2. In microleakage of gingival margin, no significant difference could be found between group I and II, and between group I and III (p>0.05). 3. Group IV was showed less microleakage than group II and group III in gingival margin(p<0.05).

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.05a
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• pp.656-659
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• 2017

In this paper, we propose a digital method for transmitting audio signals using LED visible light communication system. In the proposed method, we compare the method for transmitting audio signal in analog signal and the method for transmitting by digital signal. When amplifying the audio sound and transmitting the analog signal using the LED visible light communication, attenuation corresponding to the transmission distance occurs, and there is a disadvantage that it is noisy. In order to overcome this, we propose a method for transmitting digital audio signals. The proposed method has the advantage of reducing the influence of noise, but it turned out that it is affected much by the LED blinking speed. Various methods to overcome this need to be continuously studied.

• The Journal of Fisheries Business Administration
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• v.34 no.1
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• pp.137-156
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• 2003

Increasingly, leisure time is being used for outdoor recreational activities, and fishing is one of the principal forms of marine recreation. Marine recreational fishing is a popular activity in Korea and this activity has led to the development of a sector of substantial social and economic value. Also it is considered as one of the important outdoor leisure industries in Korea. With rising of income level and development of marine outdoor leisure industries, social, economic demand increase of marine recreational fishing are showing us new advance ability of marine aquatic bio-industry. However the recreational use of fish stocks has become an important consideration in the public and environmental economic analysis of management aspect of fishing, having grown considerably over recent years to reach a level in Korea where the fish stocks and coastal ecosystem has become a significant management problem. we are inevitably facing marine environmental deterioration and overfishing in marine recreational fishing. In this study, not only resources and environmental problems which are occurred by recreational fishers, but also illegal fishing behaviors and other problems such as market's failure are going to analyze basic management theories and methods of recreational fishing through mathematical principals and economic rents which maximize net social benefits. In view of the likelihood of marine recreational fishers adopting high rates of discount, the conservation of fish resources would appear to require continual public surveillance and control of the physical yield and condition of the fish stocks and the optimal use level. The institutional management of recreational fisheries is the way of escaping the collapse of recreational fisheries just like as the situation of management's failure of commercial fisheries worldwide. One of the effective management measure is a license system. In this system, optimal fee is paid by recreational fishers, which prevent them from overfishing, environmental problems to some extents and carry out the optimal number of outings. And money obtained by license fee should be spent for more improvement fishing culture and welfare for marine recreational fishing. Marine recreational fishing is to be promoted under sound conservation and management principles.

• Journal of the Ergonomics Society of Korea
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• v.28 no.4
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• pp.147-154
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• 2009

The tactical computer is currently being developed and installed in armored vehicles and tanks for reinforcement. With the tactical computer, Korea Army will be able to grasp the deployment status of our forces, enemy, and obstacles under varying situations. Furthermore, it makes the exchange of command and tactical intelligence possible. Recent studies showed that the task performance is greatly affected by the user interface. The U.S. Army is now conducting user-centered evaluation tests based on C2 (Command & Control) to develop tactical intelligence machinery and tools. This study aims to classify and regroup subordinate menu functions according to the user-centered task performance for the Korea Army's tactical computer. Also, the research suggests an ergonomically sound layout and size of main touch buttons by considering human factors guidelines for button design. To achieve this goal, eight hierarchical subordinate menu functions are initially drawn through clustering analysis and then each group of menu functions was renamed. Based on the suggested menu structure, new location and size of the buttons were tested in terms of response time, number of error, and subjective preference by comparing them to existing ones. The result showed that the best performance was obtained when the number of buttons or functions was eight to conduct tactical missions. Also, the improved button size and location were suggested through the experiment. It was found in addition that the location and size of the buttons had interactions regarding the user's preference.

• Journal of the Korean Dietetic Association
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• v.12 no.3
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• pp.299-306
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• 2006

The purpose of this study was to analyze effect of nutrition education after executing education nutrition with the nutrition education textbook, reconstructed 12 units, focused on older elementary school children and to evaluate interest and understanding of textbook. The subjects were 4th grade children. The results were as follows. The most interesting lesson contents was 'obesity(16.3%)', and the next were 'food poisoning' (13.3%), 'kimchi'(13.3%), and 'Korean table manners'(10.2%) in the 12 unit. Children who attended education nutrition answered 'interesting'(94.1%), 'understand easily'(97.1%) about the developed textbook. With regard to change in nutrition knowledge after education, the percentage of correct answers was increased in most of question except 'reason of snack' and 'weight-control'. And the total score of nutrition knowledge was risen(p<0.01), because the ratio of correct answer of 'importance of breakfast'(p<0.05) and 'nutrition labeling'(p<0.01) was improved especially. The ratio of desirable snack time 'between lunch and dinner' was higher after education(91.2%) than before(55.2%)(p<0.01). After education, the choice of 'Fruit and vegetable' of which desirable snack food was increased. Both the choice of 'bread' and 'fast food', a factor of oversupply calorie, was decreased. And after education, the percentage of sound snack place 'home' was improved. In regard of a meal environment, the percentage of 'every wash hand before eating' is 65.1% and there is scarcely change after education. Before education, children answered 'use it rightly'(82.4%) about 'how to eat with spoon and chopsticks', but it is lower after education. The ratio of 'leave food sometimes or always' is 47.1% before education, and the ratio of leftover food tend to decreased in school lunch. Relate to reason of leftover, the percentage of 'because of hate food' tend to decrease. This results suggests that the activity-centered nutrition education can help to change food behaviors and increase nutrition knowledge level of school children.

• Journal of Digital Convergence
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• v.11 no.1
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• pp.309-314
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• 2013

This study aimed to identify the effect of chronic mind-body function decline on health-related activities of daily living. Data collection was surveyed using interview and questionnaires by 148 subjects in a general hospital located in Seoul from June 8 to July 13, 2011. The results were as follows: First, based on exercise habit, patient group who do exercise regularly showed in male(26.7%) and female(22.7%), respectively. The risk ratio of it was 0.25 times. On the other hand, control group who do exercise regularly showed in male(42.2%) and female(31.8%), respectively. The risk ratio of it was 0.61 times. Secondly, the risk ratio of social factor in male was 45.18 times(p=.04) while the risk ratio of physical factor in female was 237.1 times(p=.001). In conclusion, to prevent declining of chronic mind-body function, it is necessary to solve stress through sound life rhythm maintenance, immunity enhancing food intake and continuous exercise.