• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.1
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• pp.69-74
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• 2021

This paper introduces a low-power voltage-controlled oscillator(VCO) with filters that consist of resistors and capacitors. The proposed VCO contains a 5-stage current mode buffer, and each buffer cell has a resistor-capacitor filter that connects input and output terminals. The filter adds a zero to the buffer cell. Because the zero moves the oscillation condition to high frequencies, the proposed VCO can generate a high frequency clock with low power consumption. The proposed circuit has been designed with 0.18 ㎛ CMOS process. The power consumption is 9.83 mW at 2.7 GHz. The proposed VCO shows 3.64 pJ/Hz in our simulation study, whereas the conventional circuit shows 4.79 pJ/Hz, indicating that our VCO achieves 24% reduction in power consumption.

• Journal of radiological science and technology
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• v.44 no.3
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• pp.173-181
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• 2021

The purpose of this study was to reduce dose while maintaining image quality during digital radiographic examination of paranasal sinus by using the automatic exposure control (AEC) system. The tube voltage was set as six stages that increased by about 10 kVp to 70 kVp, 81 kVp, 90 kVp, 102 kVp, 109 kVp and 117 kVp. And then the AEC system conditions were consisted of 9 setting environments, that change mode of the sensitivity (S200, S400, S800) and the density (+2.5, 0, -2.5). We measured automatically exposed tube current (mAs) under 54 conditions with combined these, and assessed SNR and PSNR through the acquired images. In addition, four radiologists performed a qualitative assessment of the acquired images for each combination on a five-point scale of the Likert. As a result, the lowest dose and the highest values of SNR and PSNR in images with a qualitative assessment more than 4 point were the AEC control factors of 90 kVp, S800, D2.5. We applied this condition to the clinical trial, it showed an effect of 83.1% reduction in exposure radiation dose (mR). Therefore, AEC system could be used as dose reduction technology if it understood and used related regulatory factors and physical characteristics.

• Imaging Science in Dentistry
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• v.51 no.1
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• pp.73-80
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• 2021

Purpose: The purpose of this study was to evaluate the cone-beam computed tomographic (CBCT) imaging and histopathological characteristics of osteoradionecrosis(ORN) and medication-related osteonecrosis of the jaw(MRONJ). Materials and Methods: Ten surgical specimens from segmental mandibulectomy (3 ORN and 7 MRONJ) were analyzed using CBCT. The CBCT parameters were as follows: high-resolution mode (tube voltage, 90.0 kV; tube current, 4.00 mA; rotation time, 16.8 s; field of view, 56 mm×56 mm; thickness, 0.099 mm). Histopathological characteristics were evaluated using histological slides of the surgical specimens. The Pearson chi-square test was used to compare ORN and MRONJ in terms of CBCT findings(internal texture, sequestrum, periosteal reaction and cortical perforation) and histopathological characteristics(necrotic bone, inflammatory cells, reactive bone formation, bacteria, Actinomyces, and osteoclasts). A P value less than 0.05 was considered to indicate statistical significance. Results: MRONJ showed periosteal reaction on CBCT more frequently than ORN (7 of 7 [100%] vs. 0 of 3 [0%], P<0.05). Regarding histopathological characteristics, MRONJ showed osteoclasts more frequently than ORN (6 of 7 [85.7%] vs. 0 of 3 [0%], P<0.05). Conclusion: This study evaluated the CBCT imaging and histopathological characteristics of ORN and MRONJ, and the findings suggest that CBCT could be useful for the evaluation of ORN and MRONJ.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.9
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• pp.1202-1208
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• 2020

In line with the current era of the 4th Industrial Revolution, it is necessary to prepare for the future by integrating AI elements in the ship sector. In addition, it is necessary to respond to this in the field of power management for the appearance of autonomous ships. In this study, we propose a battery-linked electric propulsion system (BLEPS) algorithm using machine learning's DNN. For the experiment, we learned the pattern of ship power consumption for each operation mode based on the ship data through LabView and derived the battery status through Python to check the flexibility of the generator and battery interlocking. As a result of the experiment, the low load operation of the generator was reduced through charging and discharging of the battery, and economic efficiency and reliability were confirmed by reducing the fuel consumption of 1% of LNG.

• International Journal of Naval Architecture and Ocean Engineering
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• v.12 no.1
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• pp.241-257
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• 2020

The rapid proliferation of oil/gas drilling and wind turbine installations with jack-up rig-formed structures increases structural safety requirements, due to the greater risks of operational collisions during use of these structures. Therefore, current industrial practices and regulations have tended to increase the required accidental collision design loads (impact energies) for jack-up rigs. However, the existing simplified design approach tends to be limited to the design and prediction of local members due to the difficulty in applying the increased uniform impact energy to a brace member without regard for the member's position. It is therefore necessary to define accidental load estimation in terms of a reasonable collision scenario and its application to the structural response analysis. We found by a collision probabilistic approach that the kinetic energy ranged from a minimum of 9 MJ to a maximum 1049 MJ. Only 6% of these values are less than the 35 MJ recommendation of DNV-GL (2013). This study assumed and applied a representative design load of 196.2 MN for an impact load of 20,000 tons. Based on this design load, the detailed design of a leg structure was numerically verified via an FE analysis comprising three categories: linear analysis, buckling analysis and progressive collapse analysis. Based on the numerical results from this analysis, it was possible to predict the collapse mode and position of each member in relation to the collision load. This study provided a collision strength assessment between attendant vessels and a jack-up rig based on probabilistic collision scenarios and nonlinear structural analysis. The numerical results of this study also afforded reasonable evaluation criteria and specific evaluation procedures.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.2
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• pp.445-466
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• 2022

As everything linking to the internet, people can subscribe to various services from a service provider to facilitate their lives through the Internet of Things (IoT). An obligatory thing for the service provider is that they should push the service data safely and timely to multiple IoT terminal devices regularly after the IoT devices accomplishing the service subscription. In order to control the service message received by the legal devices as while as keep the confidentiality of the data, the public key encryption algorithm is utilized. While the existing public encryption algorithms for push service are too complicated for IoT devices, and almost of the current subscription schemes based on push mode are relying on centralized organization which may suffer from centralized entity corruption or single point of failure. To address these issues, we design a secure subscription-push service scheme based on blockchain and edge computing in this article, which is decentralized with secure architecture for the subscription and push of service. Furthermore, inspired by broadcast encryption and multicast encryption, a new encryption algorithm is designed to manage the permissions of IoT devices together with smart contract, and to protect the confidentiality of push messages, which is suitable for IoT devices. The edge computing nodes, in the new system architecture, maintain the blockchain to ensure the impartiality and traceability of service subscriptions and push messages, meanwhile undertake some calculations for IoT devices with limited computing power. The legalities of subscription services are guaranteed by verifying subscription tags on the smart contract. Lastly, the analysis indicates that the scheme is reliable, and the proposed encryption algorithm is safe and efficient.

• Journal of Biomedical Engineering Research
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• v.43 no.5
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• pp.319-330
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• 2022

In this study, the optimal driving frequency was derived through finite element analysis (FEA) to optimize the developed piezoelectric ultrasonic medical devices(PUMD) for bone surgery. The core of the PUMD is the piezoelectric ceramic (PZT), which is a vibrator that generates vibration energy. The piezoelectric ceramic shows the maximum current value with respect to the input voltage at the resonance frequency, which generates the maximum mechanical vibration. In the past, various studies have been conducted related to the analysis of PUMD, but most of the research so far has been limited to free vibration analysis. However, in order to derive the accurate resonant frequency, the initial stress generated by bolt tightening in the bolt-clamped Langevin type transducer (BLT) must be considered. In this study, after designing a PUMD, the driving performance according to the bolt tightening value was analyzed through FEA, and this was experimentally verified. First, the resonance mode and frequency response were confirmed through modal and harmonic analysis at 20-40 kHz, which is known as the optimal driving frequency band of PUMD for bone surgery. In addition, the design of the PUMD was confirmed by checking the mechanical behavior of the tip and the piezoelectric ceramic at the resonant frequency. Consequentially, the characteristic evaluation was performed, and it was confirmed that the resonant frequency result derived through the FEA was reasonable. Through this study, we presented a more rational FEA method than before for BLT transducers. We expect that this will shorten the time and cost of developing a PUMD, and will enable the development of more stable and high-quality products.

• Current Optics and Photonics
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• v.6 no.5
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• pp.497-505
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• 2022

Topological photonic nanocavities are considered to possess outstanding optical performance, and provide new platforms for realizing strong interaction between light and matter, due to their robustness to impurities and defects. Here hybrid plasmonic topological photonic nanocavities are proposed, by embedding various plasmon nanoantennas such as gold nanospheres, cylinders, and rectangles in a topological photonic crystal corner-state nanocavity. The maximum quality factor Q and minimum effective mode volume V_eff of these hybrid nanocavities can reach the order of 10⁴ and 10^-4 (𝜆/n)³ respectively, and the high figures of merit Q/V_eff for all of these hybrid nanocavites are stable and on the order of 10⁵ (𝜆/n)^-3. The relative positions of the plasmon nanoantennas will influence the coupling strength between the plasmon structures and the topological nanocavity. The hybrid nanocavity with gold nanospheres possesses much higher Q, but relatively large V_eff. The presence of a gold rectangular structure can confine more electromagnetic energy within a smaller space, since its V_eff is smallest, although Q is lowest among these structures. This work provides an outstanding platform for cavity quantum electrodynamics and has a wide range of applications in topological quantum light sources, such as single-photon sources and nanolasers.

• Korean Journal of Materials Research
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• v.32 no.11
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• pp.508-514
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• 2022

Piezoelectric composite films which are enabled by inorganic piezoelectric nanomaterials-embedded polymer, have attracted enormous attention as a sustainable power source for low powered electronics, because of their ease of fabrication and flexible nature. However, the absorption of applied stress by the soft polymeric matrices is a major issue that must be solved to expand the fields of piezoelectric composite applications. Herein, a flexible and porous piezoelectric composite (piezoelectric sponge) comprised of BaTiO₃ nanoparticles and polydimethylsiloxane was developed using template method to enhance the energy conversion efficiency by minimizing the stress that vanishes into the polymer matrix. In the porous structure, effective stress transfer can occur between the piezoelectric active materials in compression mode due to direct contact between the ceramic particles embedded in the pore-polymer interface. The piezoelectric sponge with 30 wt% of BaTiO₃ particles generated an open-circuit voltage of ~12 V and a short-circuit current of ~150 nA. A finite element method-based simulation was conducted to theoretically back up that the piezoelectric output performance was effectively improved by introducing the sponge structure. Furthermore, to demonstrate the feasibility of pressure detecting applications using the BaTiO₃ particles-embedded piezoelectric sponge, the composite was arranged in a 3 × 3 array and integrated into a single pressure sensor. The fabricated sensor array successfully detected the shape of the applied pressure. This work can provide a cost-effective, biocompatible, and structural strategy for realizing piezoelectric composite-based energy harvesters and self-powered sensors with improved energy conversion efficiency.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.3
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• pp.99-104
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• 2022

In the age of convergent media, traditional media and network media are highly integrated, and benefits are shared, which promotes the increase of traditional culture communication channels, the change of communication methods, and the change of the mode of interaction with audiences. This article analyzes the difficulties of traditional culture dissemination by enumerating some excellent cultural programs in China. At the same time, combined with the current situation of convergence media, it discusses how to transform invisible traditional culture into visual digital content, and make it widely disseminated by means of convergence media. It provides reference for the development of traditional culture, and has enlightening significance for creating high-quality cultural programs and spreading mainstream culture.