• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.4
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• pp.392-397
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• 2022

We present the structural and optical properties of Au@TiO₂ core-shell microsphere structure prepared by a hydrothermal synthesis method. As a way to improve the efficiency of organic solar cells, the Au@TiO₂ core-shell microsphere was synthesized to use the local surface plasmon resonance (LSPR) phenomenon. The synthesized results were confirmed to have the Au@TiO₂ core-shell structure using a high-resolution transmission electron microscopy. An absorption was observed to occur at 527 nm belonging to the visible light region using a visible light spectroscopy, which supports the LSPR phenomenon. We suggest that the Au@TiO₂ core-shell microsphere is highly likely to be applied to organic solar cells including dye-sensitized solar cells. In addition, we expect it to be widely used not only in the energy but also in the bio as well as in the environmental fields.

• Journal of the Society of Naval Architects of Korea
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• v.59 no.6
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• pp.439-446
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• 2022

Efforts to reduce carbon dioxide(CO₂) emissions are being carried out due to climate environmental problems. Eco-friendly ships are also being developed, and various energy saving measures have been developed and applied. In ships, researches have been conducted in various fields such as electric propulsion system and energy saving devices. In addition, the development of ships using various renewable energy, such as kite using wind power and wind power generation, has been carried out. This paper proposes a plan to use renewable energy for ships by applying wave generators to small ships. In 2016, 130 small domestic ships drifted by sea due to discharge of starting storage batteries, and discharge cases accounted for the largest portion of the causes of domestic ship accidents. This is due to the excessive use of storage batteries for starting the main engine by departing in a weak storage battery state for small ships. Accordingly, two type wave power generators - opened flow wave power generator and enclosed vibrator type wave power generator - are developed for charging a starting storage battery when the ships are stationary at sea or port. Opened flow wave power generator utilizes the flow of fluid in the ship by using wave induced ship motion. Enclosed vibrator type wave power generator utilizes the pendulum kinetic energy located in a ship due to wave induced ship motion.

• Nuclear Engineering and Technology
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• v.55 no.8
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• pp.2723-2733
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• 2023

Transuranic nuclides (such as ²³⁸Pu, ²⁵²Cf, ²⁴⁹Bk, etc.) have a wide range of application in industry, medicine, agriculture, and other fields. However, due to the complex conversion chain and remarkable fission losses in the process of transuranic nuclides production, the generation amounts are extremely low. High flux reactor with high neutron flux and flexible irradiation channels, is regarded as the promising candidate for producing transuranic nuclides. It is of great significance to increase the conversion ratio of transuranic nuclides, resulting in higher efficiency and better economy. In this paper, we perform an optimization design evaluation of producing transuranic nuclides in high flux reactor, which includes optimization design of irradiation target and influence study of reactor core loading. It is demonstrated that the production rate increases with appropriately determined target material and target structure. The target loading scheme in the irradiation channel also has a significant influence on the production of transuranic nuclides.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.4
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• pp.555-562
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• 2023

The Railway Safety Act of 2014 strengthened the 'Railway Safety Management System' to establish autonomous safety management for railway operators and railway facility managers. Accordingly, it is required to establish and implement risk assessment and safety measures for risk management. However, the current risk assessment system is carried out at the fragmented safety management level within individual fields, which has caused difficulties in establishing and implementing risk assessment and safety measures. In addition, the technical standards of the safety management system stipulate that risk assessment of railway operators is mandatory, so standardized standards for risk assessment of railway facilities and railway vehicle maintenance are needed. Therefore, in this paper, we first verified railway risks by analyzing railway accident data for the last 10 years, and proposed a standardized framework to effectively assess and manage risks through a case study of a condition-based smart maintenance system developed based on railway vehicle maintenance data.

• Journal of Korea Society of Industrial Information Systems
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• v.29 no.1
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• pp.31-48
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• 2024

The domestic automotive industry must consider a strategic shift from traditional automotive component manufacturing to align with future trends such as connectivity, autonomous driving, sharing, and electrification. This research conducted topic modeling on R&D projects in the future automotive sector funded by the Ministry of Trade, Industry, and Energy from 2013 to 2021. We found that topics such as sensors, communication, driver assistance technology, and battery and power technology remained consistently prominent throughout the entire period. Conversely, topics like high-strength lightweight chassis were observed only in the first period, while topics like AI, big data, and hydrogen fuel cells gained increasing importance in the second and third periods. Furthermore, this research analyzed the areas of concentrated investment for each period based on topic-specific government investment amounts and investment growth rates.

• Korean Journal of Food Science and Technology
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• v.31 no.6
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• pp.1529-1535
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• 1999

This study was done for the extraction of carotenoid from Phaffia rhodozyma in combination with PEF and other methods. PEF treatment conditions were $30{\sim}80\;kV/cm,\;100{\sim}1000\;Hz\;and\;100{\sim}1000\;{\mu}s$. In order to increase permeability of yeast cell wall, various methods such as freezing-thawing, mechanical treatment, solvents, permeabilizing agents, and yeast cell wall lytic enzyme were used before PEF treatment. The combination of PEF $(50\;kV/cm,\;300\;Hz,\;1000\;{\mu}s)$ and conventional methods such as solvent and freezing-thawing pre-treatment had no effects on the extraction of carotenoid pigments. The extent of extracted carotenoid by the PEF $treatment(50\;kV/cm,\;300\;Hz,\;1000\;{\mu}s)$ combined with yeast cell wall lytic enzyme and mechanical pre-treatment increased 52% and 69.8% more than the sum of that by each treatment, respectively. Permeabilizing agents, especially Tween 20 and capric acid, enhanced the extraction efficiency of carotenoid pigments from P. rhodozyma cells. These results indicated the feasibility for the continuous extracting carotenoid pigments from P. rhodozyma by PEF combined with other permeabilizing methods.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.2
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• pp.94-101
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• 1989

Transport properties of 2DEG at AlGaAs/GaAs interface such as average electron energy, flight distance, each valley occupancy ratio, average electron velocity for various fields are investigated by MONTE-CARLO method. As the electric field increases, more electrons transit drastically from (000) valley to (000) upper valley. This phenomenon shows the nonstationary effect such as velocity overshoot. The duration of the transient decreases from about 1.4 psec for electric field E = 7KV/cm to about 0.7 psec for 12KV/cm. The average electron velocity during transient transport in 2DEG is about 8 times the steady-state velocity for E = 12KV/cm at room temperature. In comparison with bulk GaAs the peak velocity in the 2DEG is higher than that in even pure bulk GaAs at electric field E = 7 KV/cm. On the basis of the fact that the electrons in the 2DEG have larger peak velocity and shorter transient time of velocity than those in the bulk GaAs, it is suggested that the device with 2DEG may obtain higher mobility than that with bulk GaAs.

• The Journal of the Acoustical Society of Korea
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• v.39 no.6
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• pp.568-575
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• 2020

Ultrasound has been widely used in various industrial fields. One of challenging application areas is cooling microelectronics. Ultrasonic cooling systems can work with air, argon (Ar) and nitrogen (N₂) instead of conventional refrigerant such as freon gas, which can cause global warming. Furthermore, ultrasonic systems do not have moving parts, thus high durability can be obtained. So it is necessary to develop ultrasonic cooling systems due to environmental issues and durability points. In this paper, the design and fabrication processes are explained. When designing the system, a feasibility test was performed with a prototype cooler. Based on the result, finite element analysis with ANSYS software was performed. The predicted anti-resonance frequency for a piezoelectric actuator was 34.8 kHz, which was in good agreement with the experimental result of 34.6 kHz with 0.6% error. In addition, the predicted anti-resonance frequency for the ultrasonic waveguide was 39.4 kHz, which also agreed well with the experimental value of 39.8 kHz with 1.0% error. Based on these results, the developed ultrasonic waveguide might be applicable in microchip cooling.

• Journal of the Korean Society for Nondestructive Testing
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• v.36 no.5
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• pp.399-405
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• 2016

Recently, fiber optic sensors, which have many advantages are being applied in various fields by replacing conventional electric sensors. To transmit the light signals between an interrogator and a sensor head, optical components such as an optical adaptor and optical jumper cords are generally used. When signals are transmitted using an adaptor, the end surface of each jumper cord is faced together. If alien substances exist on the core surface of an optical fiber, those can cause light transmission loss and signal disappearance. For this reason, non-contact fiber jumper cords are developed to overcome the problems that require continual attention. The light transmission performance of non-contact fiber jumper cords are also evaluated. From the test results, conventional fiber jumper cords are unable to transmit the signals over 2 mm cavity between the ends of both cords. Otherwise, non-contact fiber jumper cords can transmit the signals with stability up to the cavity of 7 mm though they have more transmission loss than the conventional ones. Consequently, non-contact fiber jumper cords that have better signal stability than conventional ones in environments are highly recommended in field applications, especially if they play a role as a cable for signal transmission between fiber optic sensors.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.6
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• pp.1-8
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• 2016

Current sensors are used widely in the fields of current control, monitoring, and measuring. They have become more popular with the increasing demand for smart grids in a power network, generation of renewable energy, electric cars, and hybrid cars. Although open loop Hall effect current sensors have merits, such as low cost, small size, and weight, they have low accuracy. This paper describes the design and fabrication of a 300A open loop current sensor that has high accuracy and temperature performance. The core of the current sensor was calculated numerically and the signal conditioning circuits were designed using circuit analysis software. The characteristics of the manufactured open loop current sensor of 300 A class was measured at currents up to 300 A. According to the test of the current sensor, the accuracy error and linearity error were 0.75% and 0.19%, respectively. When the temperature compensation was carried out with the relevant circuit, the temperature coefficients were less than $0.012%/^{\circ}C$ at temperatures between $-25^{\circ}C$ and $85^{\circ}C$.