• The Journal of the Korea institute of electronic communication sciences
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• v.19 no.3
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• pp.497-506
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• 2024

In this paper, medium-power wireless power transmission is implemented using the commercial power frequency (60 Hz). Since general magnetic induction wireless power transmission devices use more than several tens of kHz, the commercial power frequency (60 Hz) cannot be used as is. Therefore an AC/DC converter is used to convert the 60 Hz power frequency into DC, and a high-frequency power amplifier is used to convert DC into several tens of kHz. In magnetic induction wireless power transmission, the AC/DC converter and high-frequency power amplifier are removed, and a extremely low frequency wireless power transmission(ELF-WPT) system using commercial frequency consisting of only transmitting resonance tank, transmitting coil, receiving resonance tank, and receiving coil is implemented, and verified through wireless power transmission experiments.

• The Journal of the Korea institute of electronic communication sciences
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• v.19 no.4
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• pp.763-770
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• 2024

Currently, land-based fish farms utilizing seawater have introduced and are utilizing various equipment such as real-time water quality monitoring systems, facility automation systems, and automated dissolved oxygen supply devices. Furthermore, data collected from various equipment in these fish farms produce structured and unstructured big data related to water quality environment, facility operations, and workplace visual information. The big data generated in the operational environment of fish farms aims to improve operational and production efficiency through the development and application of various methods. This study aims to develop a system for effectively analyzing and visualizing big data produced from land-based fish farms. It proposes a data visualization process suitable for use in a fish farm big data analysis system, develops big data visualization tools, and compares the results. Additionally, it presents intuitive visualization models for exploring and comparing big data with time-series characteristics.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.5
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• pp.500-506
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• 2024

The transparent electrode characteristics of the SnO₂/AgNi/SnO₂ (OMO) multilayer structures prepared by sputtering were investigated according to the annealing temperature. Ni-doped Ag of various compositions was selected as the metal layer and heat treatment was performed at 100~300℃ to evaluate the thermal stability of the metals. The manufactured OMO multilayer structures were heat treated for 6 hours at 400~600℃ in an N₂ atmosphere. The structural, electrical, and optical properties of the OMO structures before and after annealing were evaluated and analyzed using a UV-VIS spectrophotometer, 4-point probe, XPS, FE-SEM, etc. OMO with Ni-doped Ag shows improved performance due to the reduction of structural defects of Ag during annealing, but OMO structure with pure Ag shows degradation characteristics due to Ag diffusion into the oxide layer during high-temperature annealing. The figure of merit (FOM) of SnO₂/Ag/SnO₂ was highest at room temperature and gradually decreased as the heat treatment temperature increased. On the other hand, the FOM value of SnO₂/AgNi/SnO₂ mostly showed its maximum value at high temperature(~550℃). In particular, the FOM value of SnO₂/Ag-Ni (3.2 at%)/SnO₂ was estimated to be approximately 2.38×10^-2 Ω^-1. Compared to transparent electrodes made of other similar materials, the FOM value of the SnO₂/Ag-Ni (3.2 at%)/SnO₂ multilayer structure is competitive and is expected to be used as an alternative transparent conductive electrode in various devices.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.6
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• pp.657-661
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• 2024

Gallium oxide (Ga₂O₃) is emerging as a next-generation power semiconductor material due to its excellent electrical properties, including an ultra-wide bandgap of approximately 4.8 eV and a breakdown electric field of about 7 MV/cm. However, its low thermal conductivity of around 0.13 W/cmK presents significant challenges to the performance and reliability of Ga₂O₃-based devices. In this study, we employed the Silvaco TCAD simulator to analyze the thermal and electrical characteristics of Ga₂O₃ Schottky barrier diodes (SBDs) with heat sinks of varying thermal conductivities. The results demonstrate that heat sinks with higher thermal conductivity effectively mitigate the temperature rise in the device, leading to an increase in current density. The limitation in heat dissipation due to parasitic on-state resistance not only affects device performance but also impacts long-term reliability. Therefore, this study contributes to the development of effective thermal management strategies for Ga₂O₃-based power semiconductors.

• The Journal of the Korea institute of electronic communication sciences
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• v.19 no.5
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• pp.903-910
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• 2024

Complex semantic segmentation tasks are primarily performed in server environments equipped with high-performance graphics hardware such as GPUs and TPUs. This cloud-based AI inference method operates by transmitting processed results to the client. However, this approach is dependent on network communication and raises concerns about privacy infringement during the process of transmitting user data to servers. Therefore, this paper proposes a Generalized On-Device Framework for Semantic Segmentation that can operate in mobile environments with high accessibility to people. This framework supports various semantic segmentation models and enables direct inference in mobile environments through model conversion and efficient memory management techniques. It is expected that this research approach will enable effective execution of semantic segmentation algorithms even in resource-constrained situations such as IoT devices, autonomous vehicles, and industrial robots, which are not cloud computing environments. This is expected to contribute to the advancement of real-time image processing, privacy protection, and network-independent AI application fields.

• The Journal of the Korea institute of electronic communication sciences
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• v.19 no.5
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• pp.835-844
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• 2024

The rapid expansion of the real-time streaming industry is driven by the widespread adoption of portable devices and the growth of video platforms. Consequently, the demand for transmitting and receiving large volumes of content has increased, leading to traffic congestion and inefficiency in traditional IP address-based networks. To address these issues, Contents Centric Networking (CCN) is being researched as an alternative. CCN is a network architecture based on content names (what) rather than IP addresses (where), where each node has a cache space called Content Store (CS) to alleviate server bottlenecks and traffic congestion. However, in a CCN environment, the departure of intermediate nodes between clients and servers can lead to packet loss and degradation of service quality. Therefore, research on managing the departure of intermediate nodes in real-time environments is essential. This study proposes a new method for detecting the departure of intermediate nodes through RSSI (Received Signal Strength Indicator) monitoring and for efficiently creating backup paths.

• The Journal of the Korea institute of electronic communication sciences
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• v.19 no.5
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• pp.927-932
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• 2024

In this paper, the waveguide filter is realized by using the 3D printing and electroplating process. The waveguide filter is consisted of the resonator and the inductive window. The resonator is made small by putting vertical pillar inside the cavity. In case of in/output, the pin of SMA connector is connected to the pillar using the tapped-line method. Designed filter has the volume of 24.0 x 58.0 x 38.0 mm3 that is about 91% reduced compared to general cavity filter. Designed filter is modeled divided into upper part that has the inductive window and lower part that has the pillar. Printed filter by the ABS plastic is plated with 10㎛ thick copper over nickel electrodes. Fabricated filter is measured with the center frequency of 2.397GHz and bandwidth of 4.76%. Also, the insertion loss of filter has 0.15dB and return loss is shown under the 20dB. Suggested waveguide filter with pillar and manufacturing process allows the waveguide devices to be made small, lightweight, and low-cost and can be applied to various RF system.

• The Journal of the Korea institute of electronic communication sciences
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• v.19 no.5
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• pp.959-966
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• 2024

Recently, various IoT devices are being developed to suit the user's lifestyle in our daily lives. In this paper, a smart coffee machine using IoT technology was implemented through an application and an ESP-01 WiFi module. The implemented smart coffee machine is different from existing coffee machines with alarm functions in that it can manage the desired date and time with an application by combining IoT. The application uses Android Studio to input data and transmits appropriate information to the smart coffee machine. An Arduino-based circuit was configured to control the coffee machine and MP3 module so that coffee is extracted at the desired time and an alarm sound is heard through the speaker. The extracted coffee can be divided into three stages: hot, warm, and lukewarm depending on the temperature. Finally, the suitability of the implemented smart coffee machine was confirmed through an experiment on the change in coffee temperature according to the amount of water and time.

• Archives of Metallurgy and Materials
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• v.67 no.4
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• pp.1469-1473
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• 2022

Tungsten diselenide (WSe₂) is one of the promising transition metal dichalcogenides (TMDs) for nanoelectronics and optoelectronics. To enhance and tune the electronic performance of TMDs, chemical functionalization via covalent and van der Waals approaches has been suggested. In the present report, the electric and structural transition of WSe₂ oxidized by exposure to O₃ is investigated using scanning tunneling microscopy. It is demonstrated that the exposure of WSe₂/high-ordered pyrolytic graphite sample to O₃ induces the formation of molecular adsorbates on the surface, which enables to increase in the density of states near the valence band edge, resulting from electric structural modification of domain boundaries via exposure of atomic O. According to the work function extracted by Kelvin probe force microscopy, monolayer WSe₂ with the O₃ exposure results in a gradual increase in work function as the exposure to O₃. Therefore, the present report demonstrates the potential pathway for the chemical functionalization of TMDs to enhance the electric performance of TMDs devices.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.251-252
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• 2012

Recently, the growing interest in organic microelectronic devices including OLEDs has led to an increasing amount of research into their many potential applications in the area of flexible electronic devices based on plastic substrates. However, these organic devices require a gas barrier coating to prevent the permeation of water and oxygen because organic materials are highly susceptible to water and oxygen. In particular, high efficiency OLEDs require an extremely low Water Vapor Transition Rate (WVTR) of $1{\times}10^{-6}g/m^2$/day. The Key factor in high quality inorganic gas barrier formation for achieving the very low WVTR required ($1{\times}10^{-6}g/m^2$/day) is the suppression of defect sites and gas diffusion pathways between grain boundaries. In this study, we developed an $Al_2O_3$ nano-crystal structure single gas barrier layer using a Neutral Beam Assisted Sputtering (NBAS) process. The NBAS system is based on the conventional RF magnetron sputtering and neutral beam source. The neutral beam source consists of an electron cyclotron Resonance (ECR) plasma source and metal reflector. The Ar+ ions in the ECR plasma are accelerated in the plasma sheath between the plasma and reflector, which are then neutralized by Auger neutralization. The neutral beam energies were possible to estimate indirectly through previous experiments and binary collision model. The accelerating potential is the sum of the plasma potential and reflector bias. In previous experiments, while adjusting the reflector bias, changes in the plasma density and the plasma potential were not observed. The neutral beam energy is controlled by the metal reflector bias. The NBAS process can continuously change crystalline structures from an amorphous phase to nano-crystal phase of various grain sizes within a single inorganic thin film. These NBAS process effects can lead to the formation of a nano-crystal structure barrier layer which effectively limits gas diffusion through the pathways between grain boundaries. Our results verify the nano-crystal structure of the NBAS processed $Al_2O_3$ single gas barrier layer through dielectric constant measurement, break down field measurement, and TEM analysis. Finally, the WVTR of $Al_2O_3$ nano-crystal structure single gas barrier layer was measured to be under $5{\times}10^{-6}g/m^2$/day therefore we can confirm that NBAS processed $Al_2O_3$ nano-crystal structure single gas barrier layer is suitable for OLED application.