• Journal of Convergence Society for SMB
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• v.6 no.2
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• pp.37-43
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• 2016

Due to the remarkable improvement of ICT, with the popularization of mobile devices and every sector of society connected by networks, an era, in which peer to peer, peer to thing, thing to thing can be connected to one another everywhere, has begun. As all the electronic devices are connected to Internet, they have become more intellectualized and automated, making convergence and process of information through the connection of the devices possible to provide a lot better services. However, those devices communicate mutually to send information and they are exposed to various security threats. Therefore, this study analyzes ZigBee, CoAP, MQTT, XMPP, which are communication-related technology of IoT, draws security threats they have, and suggests requirements that components of IoT should have. Plus, it examines real cases about security threats in IoT, and suggests a countermeasure so as to contribute to establishment of a basis for IoT to be used much more safely in the future.

• Journal of the Korea Society of Computer and Information
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• v.19 no.12
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• pp.91-100
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• 2014

In this paper, we categorize existing human gesture recognition technologies to camera-based, additional hardware-based and frequency-based technologies. Then we describe several representative techniques for each of them, emphasizing their strengths and weaknesses. We define important performance issues for human gesture recognition technologies and analyze recent technologies according to the performance issues. Our analyses show that camera-based technologies are easy to use and have high accuracy, but they have limitations on recognition ranges and need additional costs for their devices. Additional hardware-based technologies are not limited by recognition ranges and not affected by light or noise, but they have the disadvantage that human must wear or carry additional devices and need additional costs for their devices. Finally, frequency-based technologies are not limited by recognition ranges, and they do not need additional devices. However, they have not commercialized yet, and their accuracies can be deteriorated by other frequencies and signals.

• Progress in Superconductivity
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• v.2 no.2
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• pp.86-91
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• 2001

Temperature dependences of the unloaded Ｑ(Ｑ$_{0}$) and the resonant frequency ( $f_{0}$) of YB $a_2$C $u_3$ $O_{7-{\delta}}$ (YBCO) microstrip ring resonators and rutile-loaded cylindrical cavity resonators were measured at low temperatures. Dc magnetron-sputtered YBCO films grown on Ce $O_2$-buffered r-cut sapphire (CbS) substrates were used fur this purpose. The surface resistances ( $R_{s}$) of YBCO films measured by both a microstrip ring resonator and a TE $01\delta$/ mode rutile-loaded cylindrical cavity resonator are compared with each other. It turned out that the values of $R_{s}$ measured by the microstrip resonator technique are comparable to those by the rutile-loaded resonator technique at temperatures lower than ~50 K. However, above 50 K, the $R_{s}$ measured by the microstrip resonator technique appeared higher according to the temperature. Our results show that the current crowding effects near the edge of a microstrip resonator become more significant at temperatures near the critical temperature.emperature.e.e.e.e.e.e.

• Journal of Digital Convergence
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• v.13 no.3
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• pp.193-199
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• 2015

PUSH technology is a technology that can transfer server information without user's request and it is very useful in various areas along with mobile applications. This paper suggest a suitable application model that can utilizes the PUSH technology and mobile devices by finding a useful area. For this, AdMan, a mobile application which can utilize the PUSH technology and mobile devices has been developed. AdMan is a mobile application that developed once and can be able to run on both Android and iOS based mobile devices, since it was developed by using a tool called m-Bizmaker. AdMan is a customer management and advertisement system that can bring big efficiency by utilizing the PUSH technology and mobile application under the today's mobile environment, and it is a good model of ICT technology application of modern society. As an application that can maximize the utilization of the PUSH technology and mobile devices, AdMan can realize better effectiveness if it run on a PUSH server.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.5
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• pp.779-785
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• 2015

Recently, home energy management system (HEMS) for power consumption reduction has been widely used and studied. The HEMS performs electric power consumption control for the indoor electric device connected to the HEMS. However, a traditional HEMS is used for passive control method using some particular power saving devices. Disadvantages with this traditional HEMS is that these power saving devices should be newly installed to build HEMS environment instead of existing home appliances. Therefore, an HEMS, which performs with existing home appliances, is needed to prevent additional expenses due to the purchase of state-of-the-art devices. In this paper, an intelligent inference algorithm for EMS at home for non-power saving electronic equipment, called legacy devices, is proposed. The algorithm is based on the adaptive network fuzzy inference system (ANFIS) and has a subsystem that notifies retraining schedule to the ANFIS to increase the inference performance. This paper discusses the overview and the architecture of the system, especially in terms of the retraining schedule. In addition, the comparison results show that the proposed algorithm is more accurate than the classic ANFIS-based EMS system.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.10 no.6
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• pp.522-528
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• 2017

In this paper, we propose a multi-band antenna for wearable devices using metal frame coupling. The proposed antenna has a $45mm{\times}35mm$ antenna using metal frame and a ground dual coupling structure. The proposed multi-band antenna in this paper is optimized for small devices such as wearable devices. By using the metal frame as a part of the antenna, the volume of the antenna is reduced and satisfies under VSWR 3:1 impedance bandwidth of 70 MHz (870 ~ 940 MHz) in low frequency band, 280 MHz (1600 ~ 1880 MHz) and 280 MHz (1900 ~ 2170 MHz) in high frequency band. It also verified the applicability of wearable devices by measuring wireless performance indicators such as TRP/TIS.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.257-257
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• 2010

One of the critical issues for applications of flexible organic thin film transistors (OTFTs) for flexible electronic systems is the electrical stabilities of the OTFT devices, including variation of the current on/off ratio ($I_{on}/I_{off}$), leakage current, threshold voltage, and hysteresis, under repetitive mechanical deformation. In particular, repetitive mechanical deformation accelerates the degradation of device performance at the ambient environment. In this work, electrical stabilities of the pentacene organic thin film transistors (OTFTs) employing multi-stack hybrid encapsulation layers were investigated under mechanical cyclic bending. Flexible bottom-gated pentacene-based OTFTs fabricated on flexible polyimide substrate with poly-4-vinyl phenol (PVP) dielectric as a gate dielectric were encapsulated by the plasma-deposited organic layer and atomic layer deposited inorganic layer. For cyclic bending experiment of flexible OTFTs, the devices were cyclically bent up to $10^5$ times with 5mm bending radius. In the most of the devices after $10^5$ times of bending cycles, the off-current of the OTFT with no encapsulation layers was quickly increased due to increases in the conductivity of the pentacene caused by doping effects from $O_2$ and $H_2O$ in the atmosphere, which leads to decrease in the $I_{on}/I_{off}$ and increase in the hysteresis. With encapsulation layers, however, the electrical stabilities of the OTFTs were improved significantly. In particular, the OTFTs with multi-stack hybrid encapsulation layer showed the best electrical stabilities up to the bending cycles of $10^5$ times compared to the devices with single organic encapsulation layer. Changes in electrical properties of cyclically bent OTFTs with encapsulation layers will be discussed in detail.

• Journal of Positioning, Navigation, and Timing
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• v.7 no.4
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• pp.217-226
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• 2018

According to the Korea Coast Guard's maritime disaster statistics (Korea Coast Guard 2017, Korean Statistical information Service 2018), an average of 2,140 marine accidents occurred every year for the past 6 years and the number of accidents is increasing every year. Among them, maritime accidents of fishing vessels are the most frequent, and recently accidents involving fishing boat and leisure vessels are rapidly increasing as well. In particular, the number of accidents involving leisure vessels increased to about one-third of the accidents of fishing vessels, and emergency rescue requests are increasing every year accordingly. However, the number of crash accidents involving users of small vessels and marine leisure activities are increasing because of the difficulties of installing navigation equipment and electronic navigation charts. Recently, the demand for precise positioning using mobile devices is increasing in the fields of maritime safety, piloting support, and coastal survey. Although various applications of smart devices provide location-based services for users, the measurement results are discontinuous when using the position coordinates of the National Marine Electronics Association (NMEA) calculated by smartphone. Recently, Google announced that they will provide GPS raw data to developers from Android 7.0 Nougat. As a result, developers have an opportunity to receive precise carrier phase and code measurements to make more accurate positioning according to the performance of Android devices. This study analyzed GPS positioning performance using Android devices, and compared and analyzed the positioning performance at sea with high-performance GPS receivers.

• Korean Journal of Materials Research
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• v.31 no.3
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• pp.132-138
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• 2021

Electrochromic devices (ECDs) have been drawing great attention due to their high color contrast, low power consumption, and memory effect, and can be used in smart windows, automatic dimming mirrors, and information display devices. As with other electronic devices such as LEDs (light emitting diodes), solar cells, and transistors, the mechanical flexibility of ECDs is one of the most important issue for their potential applications. In this paper, we report on flexible ECDs (f-ECDs) fabricated using an all-in-one EC gel, which is a mixture of electrolyte and EC material. The f-ECDs are compared with rigid ECDs (r-ECDs) on ITO glass substrate in terms of color contrast, coloration efficiency, and switching speed. It is confirmed that the f-ECDs embedding all-in-one gel show strong blue absorption and have competitive EC performance. Repetitive bending tests show a degradation of electrochromic performance, which must be improved using an optimized device fabrication process.

• Electronics and Telecommunications Trends
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• v.36 no.3
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• pp.53-64
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• 2021

As the 5G service market is expected to grow rapidly, the development of high-power, high-efficiency power amplifiers for the 5G communication infrastructure is indispensable. Gallium nitride (GaN) is attracting great interest as a key device in power devices and integrated circuits due to its wide bandgap, high carrier concentration, high electron mobility, and high-power saturation characteristics. In this study, we investigate the technology trends of Ka-band GaN radio frequency (RF) power devices and integrated circuits for operation in the millimeter-wave band of recent 5G mobile communication services. We review the characteristics of GaN RF high electron mobility transistor (HEMT) devices to implement power amplifiers operating at frequencies around 28 GHz and compare the technology of foreign companies with the device characteristics currently developed by the Electronics and Telecommunication Research Institute (ETRI). In addition, the characteristics of Ka-band GaN monolithic microwave integrated circuit (MMIC) power amplifiers manufactured using various GaN HEMT device technologies are reviewed by comparing characteristics such as frequency band, output power, and output power density of integrated circuits. In addition, by comparing the performance of the power amplifier developed by ETRI, the current status and future direction of domestic GaN power devices and integrated circuit technology will be discussed.