• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2021년도 가을 학술논문 발표대회
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• pp.170-171
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• 2021

This study compared the characteristics of the newly established JISA 5011-5 coal gasification slag fine aggregate with the characteristics of CGS generated in Korean IGCC through microscopic analysis. As a result of the study, similar results to K_CGS and J_CGS were found

• 한국정밀공학회지
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• 제14권7호
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• pp.22-28
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• 1997

In this paper, We have studied internal quality incluiding chemical compositions, microscopic structure and nonmetalic inclusion of test material. We have analyzed dynamic characteristics of cutting resistence and compared chip treatment of the test material. In analyzing internal quality, all of the test material have typical ferrite+pearlite structure. But, nonmetallic inclusion has oxide and sulfide inclusion has oxide and sulfide inclusion in medium carbon steel, mainly sulfide inclusion is existed in S-free cutting steel. In Ca+S-free cutting steel, calcium aluminate and sulfide complex inclusion, had low-melting point, as deformation of sulfide and oxide inclusion is existed. Machining characteristics, cutting resistence is maximum in medium carbon steel. Chip treatement are excellent in S-free cutting steel, similar to the Ca+S free cutting steel and medium carbon steel.

• Journal of the Korean Wood Science and Technology
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• 제41권6호
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• pp.475-489
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• 2013

본 연구는 낙엽송과 백합나무 톱밥을 이용한 펠릿의 제조 과정에서 바인더로 일정량의 유채박, 커피부산물, 수피, 솔방울, 리그닌 분말을 첨가하여 바인더의 종류 및 첨가량이 내구성을 포함한 펠릿의 품질에 미치는 영향을 알아보기 위하여 수행하였다. 바인더와 함께 제조한 펠릿의 품질은 국립산림과학원에서 고시한 목재 펠릿 품질 규격 1등급 기준을 대부분 상회하였으며, 일부 과다한 양의 바인더를 첨가하여 제조한 펠릿에서만 높은 회분 함량으로 2~3등급 기준을 만족하는 것으로 조사되었다. 바인더 종류 및 첨가량에 따른 펠릿의 내구성은 리그닌, 유채박 그리고 커피부산물을 첨가하여 제조한 펠릿에서 우수하였으며, 백합나무 펠릿은 첨가량의 증가와 함께 내구성도 향상되었다. 한편 낙엽송 펠릿의 경우 첨가량의 증가에 따른 내구성 향상 효과는 크지 않았으며, 수피와 솔방울을 바인더로 사용하였을 때 첨가량의 증가와 함께 내구성이 감소하였다. 제조된 펠릿의 광학/전자현미경 관찰을 통하여 바인더의 종류에 따른 차이를 명확하게 확인할 수 없었으나, 첨가량에 따른 차이는 명확하게 관찰할 수 있었다. 결과를 종합하면, 바인더의 첨가는 목재 펠릿의 품질 향상에 대부분의 항목에서 기여하였으며, 특히 커피부산물을 바인더로 사용하여 제조한 펠릿의 경우 모든 품질에서 뚜렷한 향상을 확인할 수 있었다. 향후 저렴한 바인더의 안정적인 확보가 이루어진다면 바인더의 첨가로 인하여 연료적 품질이 향상된 목재 펠릿의 상용화가 가능할 것으로 확신한다.

• Journal of Forest and Environmental Science
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• 제30권1호
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• pp.56-61
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• 2014

Macroscopic and microscopic characteristics of Yellow-hearted pine and Red pine were investigated. Wood color, annual ring width and latewood percentage were observed by the naked eye. Anatomical properties as the structure of three sections and cell dimensions were examined by an optical microscopy. As a result, the color of bark in Yellow-hearted pine was Reddish-grey, and Red pine showed brown or gray. The color of heartwood and sapwood in Yellow-hearted pine was deep-yellow to brown and creamy-white. And the color of heartwood and sapwood in Red pine was light-brown and light-yellow. The annual ring width of Yellow-hearted pine was narrower than that of Red pine, and the latewood percentage of Yellow-hearted pine was a little higher than that of Red pine. There was no significant difference in the anatomical characteristics between Yellow-hearted pine and Red pine.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.1159-1165
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• 2009

In the present study, the flow and heat transfer characteristics of a large plate heat exchanger are investigated numerically. The flow passages are very complicated due to the grooved corrugation patterns of the plate surface so that the detailed mesh and the large amount of the computation time have to be required in the numerical simulation for the conjugate heat transfer analysis. In order to accomplish the efficient and fast analysis of the heat transfer characteristics in the plate heat exchanger, a semimicroscopic method using the porous media model has been investigated numerically. The results showed that the characteristics of the heat transfer and pressure drop, which are respectively presented with Colburn j-factor and Fanning f-factor, are in a good agreement between the detailed mesh and the porous media model. The results of the present study could be applicable to the numerical analysis of entire flow passages in the large plate heat exchanger using porous media treatment.

• 한국분무공학회지
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• 제11권3호
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• pp.168-175
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• 2006

The static pressure distribution and flow characteristics inside the high-pressure swirl spray were investigated by measuring the static pressure inside the spray and applying the computational fluid dynamics (CFD). The static pressure difference between inner and outer part of spray was measured at different axial locations and operating conditions using a piezo-resislive pressure transducer. To obtain the qualitative value of swirl motion at different operating conditions, the spray impact-pressure at the nozzle exit was measured using a piezo-electric pressure transducer, and the flow angle was measured using a microscopic imaging system. The flow characteristics inside the high pressure swirl spray was simulated by the 1-phase 3-dimensional CFD model. The effect of pressure alternations on spray development was discussed with macroscopic spray images and a mathematical liquid film model. The results showed that the static pressure drop is observed inside the swirl spray as a result of the dragged air motion and the centrifugal force of the air. The recirculation vortex inside the spray was also observed inside the swirl spray as a result of the adverse pressure gradient along the axial locations. The results of analytical liquid film model and macroscopic spray images showed that the static pressure structure is one of the main parameters affecting the swirl spray development.

• 한국자동차공학회논문집
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• 제8권3호
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• pp.28-36
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• 2000

Spray characteristics of diesel fuel injection is one of the most important factors in diesel combustion and pollutant emissions especially in HSDI (High Speed Direct Injection) diesel engines where the interval between the onset of combustion and the evaporation of atomized fuel is relatively short, An investigation into various spray characteristics from different holes of VCO(Valve Covered Orifice) nozzles was performed and its results were compared to standard sac nozzle. The global characteristics of spray, including spray angle, spray tip penetration, and spray pattern were measured from the spray images which were frozen by an instantaneous photography with a spark light source. For better understanding of spray behavior, SMD of the fuel sprays from multi hole nozzles were measured with back light imaging while the sprays from the other holes are covered by a purpose-built nozzle cap. The investigation manifestly reveals the different spray patterns at the beginning of injection produced by VCO nozzles can be identified as three distinct types with their own macroscopic and microscopic characteristics, while macroscopic non-uniformity disappears at 0.9∼1.0ms from the start of injection.

• 동력기계공학회지
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• 제21권4호
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• pp.34-41
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• 2017

Diesel engines with compression-ignition type have superior thermal efficiency, durability and reliability compared to gasoline engine. To control emitted gas from the engines, it can be applied to alternative fuel without any modification to the engine. Therefore, in this study, as a basic study for applying emulsified fuel to the actual diesel engine, analysis of spray behavior characteristics of emulsified fuel was carried out simultaneously by experimental and numerical method. The emulsified fuel consist of diesel, hydrogen peroxide, and surfactant. The surfactant for manufacturing emulsified fuel is comprised of span 80 and tween 80 mixed as 9:1 and fixed with 3% of the total volume of the emulsified fuel. In addition, six kinds of emulsified fuel(EF0, EF2, EF12, EF22, EF32, and EF42) were manufactured according to the mixing ratio of hydrogen peroxide. The droplet and spray experiments were performed to observe the behavior characteristics of the emulsified fuel. The numerical analysis was carried out using ANSYS CFX to confirm the microscopic behavior characteristics. Consequently, rapid mixture formation can be expected due to evaporation of hydrogen peroxide in emulsified fuel, and it is confirmed that Reitz&Diwakar breakup model is most suitable as breakup model to be applied to the numerical analysis.

• International Journal of Reliability and Applications
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• 제17권2호
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• pp.137-147
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• 2016

The engine mount of a car subjected to a pre-load related to the weight of the engine, and acts to insulate the vibration coming from the engine by moving on large or small displacement depending on the driving condition of the car. The vibration insulation of the engine mount is an effect obtained by dissipating the mechanical energy into heat by the viscosity characteristic of the rubber and the microscopic behavior of the additive carbon black. Therefore, dynamic stiffness from the intrinsic properties of rubber filled with carbon black at the design stage is an important design consideration. In this paper, we introduced a hyper-elastic, visco-elastic and elasto-plastic model to predict the dynamic characteristics of rubber, and developed a fitting program to determine the material model parameters using MATLAB. The dynamic characteristics analysis of the rubber insulator of the ACTIVE MOUNT was carried out by using MSC.MARC nonlinear structural analysis software, which provides the dynamic characteristics material model. The analysis results were compared with the dynamic characteristics test results of the rubber insulator, which is one of the active mount components, and the analysis results were confirmed to be valid.

• Nuclear Engineering and Technology
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• 제56권1호
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• pp.283-291
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• 2024

Sodium cooled Fast Reactors (SFR) are built with several engineered safety features and hence a severe accident such as a core melt accident is hypothetical with a probability of <10^-6/ry. However, in case of such accidents, the mixture of the molten fuel and structural materials interacts with sodium. This phenomenon is known as Molten Fuel Coolant Interaction (MFCI) and results in fragmentation of the melt due to various instabilities. The fragmented particles settle as a debris bed on the core catcher at the bottom of the reactor vessel, and continue to generate decay heat. Characteristics of the debris particles play a vital role in heat transfer from the bed and need thorough investigation. The size, shape, and physical state of the debris depend on the associated fragmentation mechanism, superheating of the melt, and sodium temperature. Experiments have been conducted by releasing simulated corium, a molten mixture of alumina and iron generated by the aluminothermy process at ~2400 ℃ into liquid sodium, to study the fragmentation phenomena. After the experiment, the fragmented debris was retrieved and the particle size distribution was determined by sieve analysis. The debris was subjected to microscopic investigation for obtaining morphological characteristics. Based on the characteristics of debris, an attempt has been made to assess of fragmentation mechanism of simulated corium in sodium.