• Journal of radiological science and technology
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• v.40 no.3
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• pp.443-451
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• 2017

Mammography is commonly used for screening early breast cancer. However, mammographic images, which depend on the physical properties of breast components, are limited to provide information about whether a lesion is malignant or benign. Although a dual-energy subtraction technique decomposes a certain material from a mixture, it increases radiation dose and degrades the accuracy of material decomposition. In this study, we simulated a breast phantom using attenuation characteristics, and we proposed a technique to enable the accurate material decomposition by applying weighting factors for the dual-energy mammography based on a photon-counting detector using a Monte Carlo simulation tool. We also evaluated the contrast and noise of simulated breast images for validating the proposed technique. As a result, the contrast for a malignant tumor in the dual-energy weighted subtraction technique was 0.98 and 1.06 times similar than those in the general mammography and dual-energy subtraction techniques, respectively. However the contrast between malignant and benign tumors dramatically increased 13.54 times due to the low contrast of a benign tumor. Therefore, the proposed technique can increase the material decomposition accuracy for malignant tumor and improve the diagnostic accuracy of mammography.

• Applied Chemistry for Engineering
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• v.34 no.4
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• pp.404-411
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• 2023

For the direct reforming of biogas, a three-phase gliding arc plasma reformer was designed to expand the plasma discharge region, and the operation conditions of the plasma reformer, such as the S/C ratio, the gas flow rate, and the plasma input power, were optimized. The H₂ production efficiency is increased at a lower specific plasma input energy density, but byproducts such as C_XH_Y and carbon soot are generated along with the increase in H₂ production efficiency. The formation of byproducts is decreased at higher specific plasma input energy densities and S/C ratios. The optimized operation conditions are 5.5 ~ 6.0 kJ/L for the specific plasma input energy density and 3 for the S/C ratio, considering the conversion efficiency, H₂ production, and byproduct formation. It is expected that the H₂ production efficiency will improve with the decrease in fuel consumption in biogas burners because the heat generated from plasma discharge heats up the feed gas to over 500 ℃.

• Journal of Energy Engineering
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• v.14 no.4 s.44
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• pp.241-247
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• 2005

Heat transfer enhancement and pressure loss penalty caused by three-row winglets built in three-row tube-bundles in an in-line arrangement, are compared between 'common flow up' and 'common flow down' winglet configurations. The 'common flow down' winglet-pairs recommended by the previous researchers bring about $10\%$ to $25\%$ increase in heat transfer enhancement and $20\%$ to $35\%$ increase in pressure loss penalty, in comparison with fin-tube bundles without winglets. For the 'common flow up' winglet-pairs, the spanwise distance between the trailing edges (${\Delta}y$) of winglet pairs was changed and investigated. Two types ot winglet are applied for triangular and rectangular shapes. In the triangular winglets with ${\Delta}y$=5 mm in in-line tube bundles, the heat transfer increased up to $10\%$, and simultaneously the pressure loss decreased by $8\%$ to $15\%$ for the Reynolds number (based on two times channel height) ranging from 300 to 2700, when the 'common flow up' winglets were built in. The performance of fin-tube bundles with triangular winglets is much superior to the rectangular one, because of the smaller pressure-loss penalty.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.1
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• pp.27-35
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• 2010

This paper presents the vibration control performance of the smart passive control system to suppress the undesired vibration of the structure subjected to the earthquake loadings. Smart passive control system is the MR damper-based control system augmented with electromagnetic induction(EMI) device which consists of permanent magnets and solenoid coils. According to the Faraday's law of electromagnetic induction, an EMI device produces electrical energy from the mechanical energy due to the reciprocal motions of the structure and provide it to the MR damper. The smart passive control system can be the simple and easy to implement and maintain control system by replacing the feedback control system including sensors, controllers and external power sources of the conventional MR damper-based semiactive control system with the EMI device. The control performance of the smart passive control system is evaluated through the set of shaking table test considering the various historical earthquake loadings.

• Journal of Adhesion and Interface
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• v.21 no.1
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• pp.27-33
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• 2020

Adhesion property of epoxy adhesive was evaluated with different surface roughness of glass fiber reinforced composite (GFRC) and optimized condition of surface roughness was confirmed. Different sizes of alumina (Al2O3) particles were blasted to GFRC to control surface roughness of GFRC using sand blasting method. The surface roughness was measured and quantified via surface roughness tester. Contact angle was measured using four types of different solvents. Surface energies and work of adhesion between epoxy adhesive and GFRCs were calculated with different surface roughness of GFRC. Adhesion property between epoxy adhesive and GFRCs was evaluated using single lap shear test and adhesion property increased with surface roughness of GFRC. The fracture surface of GFRCs was observed to evaluate adhesion property. Finally, the optimized roughness condition of GFRCs was confirmed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.34-40
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• 2006

For a cooling performance research of the combustor operated in a extreme environment of a high temperature and high pressure, we accomplished a cooling performance analysis. Generally a heat transfer characteristic in cooling passage is known well experimentally and theoretically, however heat flux in the combustion chamber isn't. In this study, fluid flow combined with heat transfer and thermal structural analysis is accomplished about a combustor nozzle. We tried to analyze the cooling performance with a heat transfer characteristic of a gas and coolant side in the view point of quantity on the mass flow rate to be supplied to the cooling channel. And finally, evaluation on the thermal and structural safety of nozzle wall material was accomplished.

• Journal of the Korean Society for Marine Environment & Energy
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• v.15 no.4
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• pp.357-362
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• 2012

Despite the Wave observations data is very important information to human life at sea, the technology development and research for wave equipments are lacking. In this study, the wave observation system using GPS was evaluated the quality of wave observation data by comparing of long-term observations. The result of the comparison of the acceleration sensor (Hippy-40) and GPS sensor (Mose-1000), the correlation coefficient of the significant wave height and significant wave periods is 0.997 and 0.990 respectively. Also in case of BIAS, the significant wave height is 0.014 m, the significant wave period is -0.212 sec. It makes no significant differences whether the acceleration sensor (Hippy-40) and GPS sensor (Mose-1000). These results of the wave observation data using GPS quality will be evaluated as very good.

• Korean Journal of Soil Science and Fertilizer
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• v.44 no.6
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• pp.1245-1251
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• 2011

As a result of the growing livestock industry, varieties of organic solid and waste biomass are be generated in swine breeding and slaughtering stages. Anaerobic digestion is a promising alternative for the treatment of livestock waste biomass, as well as for the material recovery and energy production. Objectives of this study were to analyze the biochemical methane potential of swine waste biomasses that were generated from swine pen and slaughterhouse and to investigate the material recovery and methane yield per head. As pig waste biomass, swine slurry, blood, intestine residue, and digestive tract content were collected for investigation from pig farmhouse and slaughterhouse. The $B_{th}$ (Theoretical methane potential) and $B_0$ (Biochemical methane potential) of swine slurry generating in swine breeding stage were 0.525 and $0.360Nm^3\;kg^{-1}-VS_{added}$, the ratio of degradation ($B_0/B_{th}$) was 68.6%. $B_{th}$ of blood, intestine residue, and digestive tract content were 0.539, 0.664, and $0.517Nm^3\;kg^{-1}-VS_{added}$, and $B_0$ were 0.405, 0.213, and $0.240Nm^3\;kg^{-1}-VS_{added}$, respectively. And the ratio of degradation showed 75.1, 32.1, and 46.4% in blood, intestine residue, and digestive tract content. Material yield of swine waste biomass was calculated as TS 73.79, VS 46.75, TN 5.58, $P_2O_5$ 1.94, and $K_2O$ $2.91kg\;head^{-1}$. And methane yield was $16.58Nm^3\;head^{-1}$. In the aspect that slaughterhouse is a large point source of waste biomass, while swine farmhouse is non-point source, the feasibility of an anaerobic digestion using the slaughtering waste biomass need to be assessed in the economical aspect between the waste treatment cost and the profitable effect by methane production.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.2
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• pp.189-196
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• 2011

Recently, research and development of a hybrid system for passenger cars as well as for heavy-duty vehicles has become more intensive. An electric powertrain system using an electric motor can replace conventional gasoline and diesel engines. The electric motor has a higher efficiency, better acceleration performance, and is more comfortable than conventional powertrain systems; however, new methods for assessing power performance and energy convergence efficiency have to be investigated because the characteristics of an electric motor are entirely different from those of an internal combustion engine (ICE). In this study, an experiment was carried out on a motor (PMSM: Permanent Magnet Synchronous Motor) test bench. One simple driving mode and four other driving modes identified from real-world driving data of a city bus were selected to perform the experiment on the motor test bench. Then, methods for assessing the acceleration performance, energy convergence efficiency, regenerative effect, etc., were investigated. It was found that the energy efficiency of PMSM was about 90% and that 40% of demand energy was regenerated.

• Prospectives of Industrial Chemistry
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• v.24 no.5
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• pp.1-14
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• 2021

유무기 하이브리드 금속-할라이드계 페로브스카이트(organic-inorganic metal halide perovskite) 페로브스카이트 반도체 소재는 광전자 소자와 소재 연구에 새로운 연구 흐름을 만들고 있다. 태양전지 성능이 불과 과거 몇 년 사이의 짧은 연구 기간에도 불구하고, 광-전 변환 소자 중에서도 단일 소자와 적층 소자(tandem)에서 높은 광-전 변환 효율을 나타내기 때문이다. 이러한 급격한 연구 성과와 성장에도 불구하고, 페로브스카이트 소재의 다양한 광전자 특성의 평가와 결과에 대한 논의가 필요한 상황이다. 특히 내부 이온 이동이 광전자 원거리 이동 특성 평가와 해석에 영향을 주는 경우, 페로브스카이트 소재를 기반으로 한 다양한 광전자 소자의 성능 향상과 해석에 여전히 모호함을 준다. 달리 얘기하면, 이 소재의 기초 특성을 이해하고자 적용하는 다양한 기존 특성 평가 분석법의 활용과 해석에도 복잡한 영향을 미치고 있다고 할 수 있다. 이러한 페로브스카이트 소재 내에서 광전자 원거리 이동을 측정하는 새로운 방법을 소개하고자 한다. 첫 번째 방법으로, Quasi-steady 상태에서 광전도도를 전기적 특성으로 측정하고, 광조사 하에 투과 및 반사를 광학적으로 측정하여, 전도도와 광전자 밀도를 동시에 평가하는 방법으로, photo-induced transmission and reflection (PITR) 분광분석법이다. 이 분광분석법은 실제 소자의 구동조건을 구현한 상태에서 광전자의 원거리 이동에서 발생하는 광전자 밀도 변화를 반영한 광전자 이동도 특성 평가라는 장점을 가지고 있다. 두 번째 방법으로, 기존의 연속 전압 인가 방법 대신 펄스형 전압 인가 방식을 도입하는 방법으로, pulsed voltage space charge limited current (PV-SCLC) 분석법이다. 이는 펄스형 전압 인가 방법으로 이온의 이동을 최소화하여, 전류-전압 측정에서 히스테리시스가 없고 측정결과의 재현성과 신뢰도가 매우 높은 장점이 있다.