• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.693-696
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• 2008

The biaxial tensile strength of concretes was measured by the Biaxial Flexure Test(BFT) which was recently developed to measure the biaxial tensile strength of concretes. From the test result, The circular specimen is generally fractured after 1${\sim}$3 of the initial crack were formed on the top of specimen. The direction and number of the initial crack was completely arbitrary. As the specimen was larger, the number of the crack increased. And, the strengths of the different radii and thickness of specimens were calculated by the commercial finite element program to study the size effect of the biaxial tensile strength like the uniaxial tensile strength. The parameters such as radii to the support and to the load point, were studied using the program. The results of the FE analysis were entirely consistent with the predictive solution, when b/a>0.4, and the thickness of the specimens were increased. On the other hands, those with lesser free length showed good results.

• International Journal of Precision Engineering and Manufacturing
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• v.8 no.2
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• pp.44-48
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• 2007

In recent years, the size of plane substrates and semiconductor wafers has increased. As conventional contact transportation systems composed of, for example, carrier rollers, belt conveyers, and robot hands carry these longer and wider substrates, the increased weight results in increased potential for fracture. A noncontact transportation system is required to solve this problem. We propose a new noncontact transportation system combining acoustic viscous and aerostatic forces to provide damage-free transport. In this system, substrates are supported by aerostatic force and transported by acoustic viscous streaming induced by traveling wave deformation of a disk-type stator. A ring-type piezoelectric transducer bonded on the stator excites vibration. A stator with a high Q piezoelectric transducer can generate traveling vibrations with amplitude of $3.2{\mu}m$. Prior to constructing a carrying road for substrates, we clarified the basic properties of this technique and stator vibration characteristics experimentally. We constructed the experimental equipment using a rotational disk with a 95-mm diameter. Electric power was 70 W at an input voltage of 200 Vpp. A rotational torque of $8.5\times10^{-5}Nm$ was obtained when clearance between the stator and disk was $120{\mu}m$. Finally, we constructed a noncontact transport apparatus for polycrystalline silicon wafers $(150(W)\times150(L)\times0.3(t))$, producing a carrying speed of 59.2 mm/s at a clearance of 0.3 mm between the stator and wafer. The carrying force when four stators acted on the wafer was $2\times10^{-3}N$. Thus, the new noncontact transportation system was demonstrated to be effective.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.10 s.89
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• pp.969-976
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• 2004

The wide and growing use of cellular phones has raised the question about the possible health risks associated with radio-frequency electromagnetic fields. It would be helpful for phone users to blow the exposure levels during cellular phone use. But it is very difficult to recognize the amount of exposure, because measuring accurate level of RF is a difficult matter. In this study, we developed a model to estimate the exposure level and the individual risk of exposure by utilizing the available informations that we can get. We used such parameters as usage time a day, total using period, distance between cellular phone and head, slope of cellular phone, hands-free usage, antenna pulled out or not SAR(Specific Absorption Rate) of cellular phone, and flip or folder type. We proposed a model presenting individual risk of RF exposure from level 0 to 10 by using a neural network.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.4
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• pp.624-633
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• 2018

While the multimedia lecture system has been getting smart using immerging technology, the microphone still relies on the classical approach such as holding in hand or attaching on the body. In this paper, we propose a ceiling mounted array microphone system that allows a wide reception coverage and instructors to move freely without attaching microphone. The proposed system adopts cell and handover of mobile communication instead of a complicated beamforming method and implements a wide range microphone over several cells with low cost. Since the characteristics of unvoiced speech is similar to Pseudo Noise it is shown that soft handover are possible with 3 microphones connected to delay-sum multipath receiver. The proposed system is tested in $6.3{\times}1.5m$ area. For real-time processing the correlation range can be reduced by 82% or more, and the output latency delay can be improved by using the delay adaptive filter.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.10a
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• pp.259-263
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• 2014

In the ICT field, one among the remarkable issue of in 2014 is the "Wear computer", that is, the opening of "Wearable Device" age. The Samsung galaxy gear and products like Google glass and Apple watch are done as the wearable device. According to the definition of MIT Media Lab, the wearable device adheres to the body and is included till the application which names all things doing the computing action and can perform the partial computing function. And the wearable device is one brain. If the wearable device is popularized, it will be changed many things. First of all, 2 hands become free. My body is due to be connected to 24 hours Internet. It is not level that it adheres the Smart phone or device to the body and the brain role in which the device is connected outside directly, the human body is done. In this paper, the related companies analyze the technical elements of this wearable device especially.

• The Journal of the Korea Contents Association
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• v.21 no.10
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• pp.172-183
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• 2021

The current study delves into millennial consumers' attitude toward 'undisclosed ads' and 'disclosed ads' through in-depth interviews. More specifically, this study explores how millennial consumers think of undisclosed ads and celebrity endorsers as well as influencers through interviewing 12 millennial consumers. In addition, this study also deals with millennial consumers' attitude toward disclosed ads and celebrity endorsers as well as influencers. Study results suggest that millennial consumers perceive 'undisclosed ads' as deceiving ads and hold negative attitude toward celebrity endorsers as well as influencers who are involved in 'undisclosed ads'. Interestingly, millennial consumers hold both positive and negative attitude toward 'disclosed ads'. 'Disclosed ads' could be delivered to millennial consumers without any reservation when it is integrated as an entertaining factor into contents. On the other hands, negative feelings could occur when 'disclosed ads' is frequently employed and is forcibly embedded in contents, making millennial consumers feel that it is imperative to watch 'disclosed ads' in order to enjoy free contents. In the discussion section practical implications are provided.

• Design Convergence Study
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• v.17 no.3
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• pp.1-19
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• 2018

Hand rehabilitation training tools are used in hospitals and at home for patients and users who require recovery of disabled hands and improvement in overall hand function. However, existing training tools are not organized into a progressive system, and they lead to repeatability operations over a period of time. As a result, patients feel free and cannot be motivated by rehabilitation, and continuous rehabilitation training is difficult. Based on this argument, the study combines one of the elements of the game called the "Cat's cradle" to enable the user to feel achievement through play and to achieve natural rehabilitation through unconsciousness. After examining the characteristics of the tool, the user's environment, the relevance of the Cat's cradle game to the training tool and to the patient's continued rehabilitation was established. And design elements were derived through professional interviews. Later, design guidelines and prototypes have been created to complement the problems associated with guidelines and prototypes by conducting usability testing and design element assessment.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.7 no.7
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• pp.935-944
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• 2017

As augmented reality technology has developed, various augmented reality contents can be seen in real life, and the performance of mobile device is improved, so augmented reality technology can be used even without special device. As a result, a training system, guidance system and a museum art guide system based on augmented reality technology are emerging, and interest in augmented reality is also increasing. However, the existing guidance systems using a single mobile device have limitations in terms of the user experience (UX) because the camera of the device limits the field of view or the two hands are not free and the user input is difficult. In this paper, we compare augmented reality based guidance systems for Rubik's Cube using tablet and HMD to improve the constraint of user experience of such a single mobile device, and find elements that positively improve user experience. After that, we evaluate whether the user experience is actually improved through the user experience comparison test and the questionnaire.

• Communications of Mathematical Education
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• v.31 no.3
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• pp.241-255
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• 2017

The 4th industrial revolution is coming. In order to prepare for the new learning environment with it, we may need digital mathematics textbooks that fully utilize all possible technologies. So various attempts have been made in elementary and middle school mathematics education. However, despite the importance of higher mathematics, we haven't seen a best possible math digital textbooks yet in Korea. In this paper, we introduce our new model of interactive math digital textbook about Linear Algebra/ Calculus/ Differential Equations/ Statistics/ Engineering Math. Especially, this manuscript focuses on our experience of using digital contents and interactive labs for developing a new model for linear algebra digital textbook. We introduce our works on linear algebra digital textbooks which include pdf e-book, web contents, video clips of lectures, interactive lab. Using this linear algebra digital textbook, students can freely use any mobile devices to access diverse learning materials, lessons, and hands-on exercises without any limitations. Also, times saved in the computation, coding, and typing process can be used to have more discussions for deeper understanding of mathematical concepts. This type of linear algebra digital textbook, which contains all interactive free cyber-lab with codes and all lectures for each sections, can be considered as a new model for the next generation of math digital textbook.

• Journal of Broadcast Engineering
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• v.18 no.3
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• pp.425-434
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• 2013

Observers usually experience visual fatigue when they watch contents displayed on 3D display. There has been various research on visual fatigue incurred in stereoscopic displays that use 3D glasses, but relatively less studies have been done in the area of autostereoscopic displays. i3D system refers to interactive 3D system that makes it possible for users to interact with contents using their hands. Current research measured visual fatigue that users experience from i3D under various visual environments. We examined the effects of viewing distance, disparities and visual orientation on visual fatigue in i3D. The results indicated that visual fatigue decreased with longer distance and smaller disparity. Visual fatigue increased with angle when 3D fusion was unstable. In addition, there was an interaction effect between angle and distance in which visual fatigue increased with distance under stable 3D fusion but there was no difference in visual fatigue as a function of distance when 3D fusion was unstable. These results would be importantly used to develop autostereoscopic displays that minimize visual fatigue.