• Journal of IKEEE
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• v.24 no.1
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• pp.90-96
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• 2020

As various communication services have emerged due to the development of mobile communication technology, there is a need for a wideband antenna supporting multiple communication services with one antenna. In this paper, we propose a planar slot wideband antenna that can support all the communication services of 3.1~4.99GHz, the low frequency band of 5G, in addition to the existing communication services such as WiFi, LTE 2300/2500, and WiMAX. Through the simulation, the optimized antenna design parameters were obtained, and the antenna was fabricated to implement an antenna with a frequency bandwidth of 1.96~6.01GHz (S11 <-10dB) and presented the radiation pattern and gain of the antenna. The proposed antenna is a multi-band antenna that can provide all the services of LTE, Wifi, WiMAX, and 5G low frequency bands. It can be used as a repeater antenna in radio shadow area such as buildings, dense areas, and ships.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.2
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• pp.466-474
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• 2014

According to wireless network technology and mobile processors performance were improved, the small wireless mobile device such as smart phones has been widely utilized. The mobile devices can be used GPS information, thereby the services based on location information was increased. GPS was impossible to provide location information in indoor and signal shading environment, and the tracking systems based on short distance wireless communication are required infrastructure. The IEEE 802.11 based tracking system is possible estimation using APs, however the tracking device is exhausted battery power seriously. In this paper, we propose IEEE 802.11 based low-power tracking system. We reduced power consumption from channel scanning and network connection. For performance evaluation, we designed and implemented the tracking tag device, and measured power consumption of the device. As the simulation result, we confirmed that the power consumption was reduced 46% compare to the standard execution.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.3
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• pp.465-470
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• 2007

This paper is designed and producted the microstrip patch antenna which used aperture coupled feed structure, and had a comparatively hish gain and headband characteristic with a PCS substitution repeater antenna. The proposed antenna transformed a coupled slot into a H-type in order to improve a characteristic of a general aperture coupled feed antenna. It is this H-type form slot reduces back lobe from the antenna backside at the same time that a coupling between a power feed and patches is iccreased, and to have maximized a gain of an antenna. As a result of having measured the antenna which the VSWR was 1.5 or below and tied up the gain than 7.5dBi in the $1750{\sim}1870$[MHz] that was a PCS substitution, and a beamwidth became in $80^{\circ}$ and radio waves shadow was local, but accomplishment did PCS mobile communication service in building me smoothly, but confirmed what practical use can become.

• Journal of Convergence for Information Technology
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• v.8 no.6
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• pp.243-249
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• 2018

In this paper, we analyzed the effect of modulation scheme and modulation scheme on the dimming level of visible light communication system and studied the effect of distortion due to delayed signal. Currently, the modulation schemes most commonly used in visible light communication result in increasing the communication performance but reducing the brightness of the entire illumination. Continuous Burst Zero Duration will severely degrade lighting. This degrades not only the illumination but also the performance of the whole system and causes Flicker phenomenon. In this paper, we analyze the relationship between modulation technique and illumination - communication performance and investigate the effect of signal delay on visible light communication system. Through simulation, we analyze the performance of IPI-OOK which has the best communication-lighting performance and propose future research directions accordingly.

• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.4
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• pp.571-576
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• 2022

Due to the epochal development of the unmanned technology, the importance of LDT(: Location Detection Technology), which accurately estimates the location of a user or object, is dramatically increased. TOA(: Time of Arrival), which calculates a location by measuring the arrival time of signals, and TDOA(: Time Difference of Arrival) which calculates it by measuring the difference between two arrival times, are representative LDT methods. Based on the signals received from three or more base stations, TOA calculates an intersection point by drawing circles and TDOA calculates it by drawing hyperbolas. In order to improve the radio shadow area problem, a huge number of repeaters have been installed in the urban area, but the signals received through these repeaters may cause the serious error for estimating a location. In this paper, we propose an efficient location estimation technique using the signal received through the repeater. The proposed approach estimates the location of MS(: Mobile Station) employing TOA and TDOA methods, based on signals received from one repeater and two BS(: Base Station)s.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.7
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• pp.22-31
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• 2008

Cognitive radio should imply a proper sensing technique for detecting the presence of licensed users to identify the unused spectrum holes. Besides this, this information should also be used to opportunistically provide communication among secondary users. At the same time the performance of the primary user should not be declined by the secondary users. The detection of licensed users may be significantly difficult for shadowing effect. To prevail over this problem cooperative spectrum sensing, In which the combined observation information gained by multiple secondary users is employed to achieve higher performance of detection, has been inspected. However, the primary challenge of cooperative sensing lays in its ability to detect the presence of licensed user quickly and accurately. In this paper, we have used UltraWideBand (UWB) to detect the presence of licensed users and transmit the sensing information among the nodes of the network. UWB has the capability of transmitting data at a very high rate. It is unique in co-existence capability with narrow band systems. Here, we have shown that the detection probability of licensed user is improved by means of transmitting the spectrum sensing information via UWB. We also have analyzed the throughput of the proposed technique and compared the result with existing sensing method.

• Journal of the Society of Disaster Information
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• v.15 no.1
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• pp.39-48
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• 2019

Purpose: This study aims at developing and implementing Smart Safety Management System based on IoT/ICT Convergence for safety of high-risk groups working at disaster or industrial field. Its functions are as follows. Method: We will develop three devices for keeping the safety of high-risk jobs: Sensor of inactivity, Lora based Refitting technology for communication between high-risk workers, and Lora Gateway for monitoring entire situations. Then we will test three devices in respect of their functions, and propose their applicabilities in the field. Results: The system can send and receive safety tags and danger signals by which sensor technology can detect dangerous state of workers. And its command terminal was developed by low-power wireless communication technology and LoRa Gateway, which can fulfill the lifting functions between safety tags. And, furthermore, the command terminal can monitor dangerous situations of disaster sites in real time and can perform the preemptive rescues. Conclusion: This study proves the functional efficacy of Smart Safety Management System for worker safety in various high-risk occupational groups, and also suggests ways to secure worker safety in disaster area and various high risk industrial sites.

• Journal of the Korea Society for Simulation
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• v.31 no.3
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• pp.55-61
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• 2022

Currently police and fire departments use a Network/Wifi/GPS based emergency location positioning system established by mobile carriers to directly link with the device of the people who request the rescue to accurately position the expected location in the call area. However in the case of mountain rescue it is difficult to rescue the victim in golden time because the location of the search area cannot be limited when the victim is located in a radio shadow area of the mountain or the device power is off and this situation become worse if victim fail to report 911 by himself due to the injury. In this paper, we are expected to solve the previous problem by propose the mobile telecommunication forensic simulator consist of time series of cell information, human mobility model which include some general and specific features (age, gender, behavioral characteristics of victim, etc.) and intelligent infer system. The results of analysis appear in heatmap of polygons on the map based on the probability of the expected location information of the victim. With this technology we are expected to contribute to rapid and accurate lifesaving by reducing the search area of rescue team.

• Journal of the Korean Society of Radiology
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• v.17 no.6
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• pp.957-964
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• 2023

This study focused on hand sanitizer as a medium that can replace ultrasonic gel, which is vulnerable to contamination by bacteria that reside on the hand. Hand sanitizer produces a strong sterilization effect from germs resident on the hands through different sterilization principles depending on the ingredients. Select products of gel type, cream type, and foam type, except for liquid type with low viscosity, and ultrasonically apply one 62% ethanol gel type and one cream type, one benzalkonium chloride 0.066% cream type and one foam type, respectively. Using ATS-539 as a medium, image evaluation was performed on the axial and lateral resolution and penetration depth, and the presence or absence of an air layer between the probe and the phantom. As a result, in the evaluation of the axial and lateral resolution and the depth of penetration, all four experimental groups met the evaluation criteria. However, in the case of the foam type, although it was suitable for the evaluation criteria of resolution and penetration depth, dark shadows appeared on both sides except for the center of observation during image evaluation. Through this experiment, it was possible to confirm the possibility that the remaining three types of hand sanitizers except the foam type could replace the ultrasonic gel.

• Korean Journal of Heritage: History & Science
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• v.52 no.4
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• pp.56-77
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• 2019

Bi-Seok is a treasure trove of funeral rites and an important cultural asset that can shed light on the historical and social history of calligraphy, but research of the topic is still insignificant. In particular, research on the production method of Bi-Seok remains an unproven field. The production of Bi-Seok can be roughly divided into ma-jeong (refining stone), sculpture, and the Buk-chil (process of engraving letters) process. This article reveals some facts: First, performing ma-jeong to the Sang-Seok, Honyu-Seok, Bi-seok, which are known to be God's things. This process is needed because of the change in the perception of the Honyu-Seok due to the settlement and propagation of Confucian ceremonial rituals in the times of hardship in 1592 and 1636. As the crafting process of ma-jeong did not remain concrete, it was only possible to examine the manufacturing process of Bi-Seok through its materials and tools. Second, the rapid proliferation of Oh-Seok and Sa-jeo-chwi-yong (purchase of things made by private citizens) in the Yeongjo era has great importance in social and cultural history. When the Gang-Hwa-Seok of the commodity were exhausted, the Oh-Seok that was used by Sadebu (upper civil class) were used in the tomb of Jangneung, which made Oh-Seok popular among people. In particular, the use of Oh-Seok and the Ma-Jeong process could minimize chemical and physical damage. Third, the writing method of the Bi-seok is Buk-chil. After Buk-Chil of Song Si-Yeol was used on King Hyojong's tomb, the Buk-Chil process ( printing the letters on the back of the stone and rubbing them to make letters) became the most popular method in Korea and among other East Asian countries, and the fact that it was institutionalized to this scale was quite impressive. Buk-Chil became more sophisticated by using red ink rather than black ink due to the black color that results from Oh-Seok. Fourth, the writing method changes in the late Joseon Dynasty. Until the time of Yeongjo's regime, when inscribing, the depth of the angle was based on the thickness of the stroke, thus representing the shade. This technique, of course, did not occur at every Pyo-Seok or Shindobi, but was maintained by outstanding artisans belonging to government agencies. Therefore, in order to manufacture Bi-Seok, Suk-seok, YeonJeong, Ma-jeong, Jeong-Gan, ChodoSeoIp, Jung-Cho, Ip-gak, Gyo-Jeong, and Jang-Hwang, a process was needed to make one final product. Although all of these methods serve the same purpose of paying respects and propagandizing the great work of deceased persons, through this analysis, it was possible to see the whole process of Pyo-Seok based upon the division of techniques and the collaboration of the craftsmen.