• 한국태양에너지학회 논문집
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• 제38권5호
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• pp.75-84
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• 2018

The most crucial point of reducing building energy is application of high performance envelope. The amount of heat exchange through window is highest in comparison of other envelopes so that heat exchange through window influence directly with building energy consumption. The window energy performance can be define with thermal, leakage and optical performance. In previous study we can confirmed that not only thermal performance but also optical performance are considered, 11% to 15% of building energy consumption can be reduced. Smart window system has potential of energy saving so that many industry field use smart window system including architectural area and these aspect causes smart window market continuous growth year by year. In this study, building energy consumption has been analyzed which consist of smart window that dynamically control optical states. The consideration of standard commercial building model for research, the reference medium size commercial building model of DOE (Department Of Energy, USA) has been used. The building energy simulation result of 4 axis in 8 regions in Korea shows 8% to 22% reduction of building energy consumption by application of smart window system.

• Smart Structures and Systems
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• 제24권1호
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• pp.15-26
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• 2019

Over the past decades, a great variety of dampers have been developed and applied to mechanical, aerospace, and civil structures to control structural vibrations. This study is focused on two emerging damper types, namely, eddy current dampers (ECDs) and electromagnetic damper (EMDs), both of which are regarded as promising alternatives to commonly-applied viscous fluid dampers (VFDs) because of their similar mechanical behavior. This study aims to enhance the damping densities of ECDs and EMDs, which are typically lower than those of VFDs, by proposing new designs with multiple improvement measures. The design configurations, mechanisms, and experimental results of the new ECDs and EMDs are presented in this paper. The further comparison based on the experimental results revealed that the damping densities of the proposed ECD and EMD designs are comparable to those of market-available VFDs. Considering ECDs and EMDs are solid-state dampers without fluid leakage problems, the results obtained in this study demonstrate a great prospect of replacing conventional VFDs with the improved ECDs and EMDs in future large-scale applications.

• Natural Product Sciences
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• 제24권4호
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• pp.219-224
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• 2018

During the screening for cytotoxic compounds from plants grown in Korea, Betula platyphylla (BP) showed potent activity against the adenocarcinomic human alveolar basal epithelial A549 cell line. To identify the cytotoxic components from BP, the $CH_2Cl_2$ fraction with the most significant cytotoxic effect was applied to the column chromatographies. Seven compounds were isolated: lupeol (1), betulinic acid (2), (-)-rhododendrol (3), platyphyllenone (4), platyphyllone (5), (-)-centrolobol (6), and oleanolic acid (7). Among them, three diarylheptanoids (4 - 6) exhibited cytotoxicity toward A549 cells. Especially, $50{\mu}M$ of 4 reduced A549 cell viability to $18.93{\pm}0.82%$ compared to control ($100.00{\pm}21.48%$). Lactate dehydrogenase (LDH) leakage and intracellular reactive oxygen species (ROS) production were also induced by $50{\mu}M$ 4. This is the first report on the cytotoxic effect of BP-derived diarylheptanoids 4-6 against A549 cells. The compound 4 may be useful for the development of early hit compounds for non-small cell lung carcinoma, but the consideration about selectivity of 4 is required since 4 also showed the cytotoxicity in the human normal lung epithelial BEAS-2B cell line.

• 전기전자학회논문지
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• 제23권3호
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• pp.988-993
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• 2019

지난 수십 년간 반도체 업계에서는 반도체 소자의 성능을 높이고 높은 밀도로 반도체 소자를 칩 위에 집적하기 위해 끊임없이 그 크기를 축소해 왔다. 하지만, 게이트 제어의 감소, 높아진 누설 전류, 그리고 단 채널 효과와 같은 다양한 문제점에 직면하면서 이를 극복할 수 있는 차세대 반도체에 점점 더 많은 관심을 보이고 있다. 본 논문에서는 다음 반도체 세대를 이끌 후보로 관심을 받고 있는 CNTFET(Carbon NanuTube Field Effect Transistor)을 활용하여 디지털 회로를 디자인하는 방법에 대해 논하고자 한다. CNTFET이 분명 구조적으로 기존 MOSFET과 다른 구조를 가진 만큼, CNTFET을 활용하여 디지털 회로를 디자인할 때, 기존 디지털 회로 기법을 어떻게 활용할 수 있는지 자세히 알아보고 시뮬레이션을 통해 두 소자의 성능 차이를 확인해 보고자 한다.

• 융합보안논문지
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• 제17권5호
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• pp.71-76
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• 2017

오늘날은 다수의 정보자산 내 중요 데이터를 다수의 사용자가 필요에 의해, 필요한 만큼 접근하여 열람하고 있는 정보화 사회이다. 이러한 복잡함 속에서 중요 정보 자산에 대해 허가된 사용자의 접근을 확인하고, 사용 이력을 관리하기 위해 계정관리 관련 기술이 적용되고 있다. 그러나 계정을 이용해 중요/민감 정보를 열람할 수 있다는 점은 이것이 탈취 당했을 때 공격자에게 정보 절취의 길을 열어줄 수 있게 된다는 단점이 있다. 따라서 본 논문에서는 계정 소유주의 근태에 기반하여 계정의 사용 유무를 통제할 수 있으면서도, 보안성은 높였고, 편의성 저해도 없는 안전한 계정관리시스템을 제안하였다. 제안된 시스템은 계정 소유주가 업무 목적으로만 계정을 사용할 수 있도록 허가된 기간 내에 2-Factor 인증을 통해 로그인을 허용한다. 이를 통해 계정 유휴 기간 내 발생할 수도 있는 정보 유출을 사전에 차단할 수 있다.

• ETRI Journal
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• 제42권6호
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• pp.943-950
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• 2020

We propose 8.2-GHz band radar RFICs for an 8 × 8 phased-array frequency-modulated continuous-wave receiver developed using 65-nm CMOS technology. This receiver panel is constructed using a multichip solution comprising fabricated 2 × 2 low-noise amplifier phase-shifter (LNA-PS) chips and a 4ch RX front-end chip. The LNA-PS chip has a novel phase-shifter circuit for low-voltage operation, novel active single-to-differential/differential-to-single circuits, and a current-mode combiner to utilize a small area. The LNA-PS chip shows a power gain range of 5 dB to 20 dB per channel with gain control and a single-channel NF of 6.4 dB at maximum gain. The measured result of the chip shows 6-bit phase states with a 0.35° RMS phase error. The input P1 dB of the chip is approximately -27.5 dBm at high gain and is enough to cover the highest input power from the TX-to-RX leakage in the radar system. The gain range of the 4ch RX front-end chip is 9 dB to 30 dB per channel. The LNA-PS chip consumes 82 mA, and the 4ch RX front-end chip consumes 97 mA from a 1.2 V supply voltage. The chip sizes of the 2 × 2 LNA-PS and the 4ch RX front end are 2.39 mm × 1.3 mm and 2.42 mm × 1.62 mm, respectively.

• 드라이브 ㆍ 컨트롤
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• 제18권4호
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• pp.84-90
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• 2021

Viscosity of hydraulic oils decreases due to loss reduction and efficiency increase of fluid power systems. However, low viscosity is not always appropriate due to the induction of large leakage and small lubricity. Therefore, a detailed study on the optimum viscosity of hydraulic oils is necessary. In this study, based on the thermohydrodynamic lubrication theory, numerical simulation was conducted using the slipper model of swashplate-type axial piston pumps and motors. The viscosity grades' (VG) effects of oils on power losses are mainly discussed numerically in fluid film lubrication, including changes in temperature and viscosity. The simulation results reveal that the flow rate increases and the friction torque decreases as VG decreases. The film temperature and power loss were minimised for a specific oil with a VG. The minimum conditions regarding the temperature and loss were different and closed. Under various operating conditions, the film temperature and power loss were minimised, suggesting that an optimum hydraulic oil with a specific VG could be selected for given operating conditions of pressure and speed. Otherwise, a preferable operating condition must be established to determine a specific VG oil.

• Corrosion Science and Technology
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• 제21권5호
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• pp.327-339
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• 2022

The water-jet technique started by Bridgman can cut metal and alloys without harmful gas and fume. However, while this technique is convenient to cut metals and alloys, in the case of coated pipe, water jet induces the degradation of coatings on the pipes, and may facilitate structural failure, leakage, and loss of products. While there are many reports on the effect of water jet on cut metals and the damage of metallic materials, research on the effect of water impingement on the epoxy coatings has been little studied. In this work, we therefore control the velocity of water jet, distance between nozzle and specimen, and water temperature, and discuss the effect of water impingement on the epoxy coatings. Increasing water velocity and water temperature and reducing nozzle distance increased the degradation rates of three epoxy coatings were increased. Among three test parameters - water velocity, nozzle distance and water temperature, water temperature was relatively effective to increase the degradation rate of epoxy coatings.

• Nuclear Engineering and Technology
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• 제53권3호
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• pp.732-740
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• 2021

Scattering resonance of medium mass nuclides leads complex spectrum in the fast reactor, which requires thousands of energy groups in the spectrum calculation. When the broad-group cross sections are collapsed, reaction rate cannot be completely conserved. To eliminate the error from energy collapsing, the Super-homogenization method in energy collapsing (ESPH) was employed in the fast reactor code SARAX. An ESPH factor was derived based on the ESPH-corrected SN transport equation. By applying the factor in problems with reflective boundary condition, both the effective multiplication factor and reaction rate were conserved. The fixed-source iteration was used to ensure the stability of ESPH iteration. However, in the energy collapsing process of SARAX, the vacuum boundary condition was adopted, which was necessary for fast reactors with strong heterogeneity. To further reduce the error caused by leakage, an additional conservation factor was proposed to correct the neutron current in energy collapsing. To evaluate the performance of ESPH with conservation factor, numerical benchmarks of fast reactors were calculated. The results of broad-group calculation agreed well with the direct full-core Monte-Carlo calculation, including the effective multiplication factor, radial power distribution, total control rod worth and sodium void worth.

• 한국안전학회지
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• 제37권6호
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• pp.25-31
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• 2022

In this study, the spill and leak system is developed to provide real-time remote monitoring of industrial complexes where chemical accidents have been occurring every year. The spill and leak monitoring system uses IR-RCD equipment mounted on a 70m-high steel tower to detect chemical substances, thereby detecting chemical accidents such as leaks, fires, and explosions in real time. If IR-RCD equipment can actually detect chemical substances at a long distance, accurate and rapid initial response can be expected. Therefore, in order to confirm that IR-RCD equipment can detect chemical leakage accidents occurring at a long distance, acetone was selected as the experimental substance and a detection experiment was designed. The experiment was conducted using the acetone pool evaporation method at the wharf which was located 1.5 km away from IR-RCD equipment, and it was confirmed whether IR-RCD equipment could detect acetone in real time through the control monitor.