• 공업화학
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• 제29권6호
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• pp.652-656
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• 2018

본 연구에서는 석유계 잔사유를 원료로 피치 합성반응 중 압력변수에 의한 영향을 고찰하였다. 압력변수를 달리하여 두 단으로 나누어 반응을 진행하였다. 실험은 두 단을 연속적으로 진행하였고, 첫 번째 단에 가압, 상압, 감압으로 열처리를 진행하였고, 두 번째 단은 상압과 감압으로 실험하였다. 합성 온도는 $400^{\circ}C$, 합성 시간은 총 2 h으로 피치 합성을 진행하였다. 각 조건에 의해 제조된 피치의 열적 특성과 분자량 분포는 연화점 측정과 MALDI-TOF 분석을 통해 고찰하였다. 또한, GC-SIMDIS를 이용해 피치 합성 반응 중 휘발된 액상 성분에 대한 특성을 고찰하였다. 첫 번째 단에서 가압 조건을 이용한 경우, 저비점 물질들이 상대적으로 다른 두 조건보다 많이 피치 합성 반응에 참여하였으며, 저비점 물질들의 반응참여 효과로 낮은 연화점을 갖는 피치를 얻을 수 있었다. 반대로 첫 번째 단에서 감압 조건을 사용한 경우, 저비점 물질들이 효과적으로 휘발되어 반응기 외부로 빠져나가 낮은 피치 수율을 얻었고, 일부 코크스화가 진행된 결과를 얻을 수 있었다. 압력 공정변수를 제어하여 피치의 수율 및 연화점 등 물성을 효과적으로 조절할 수 있는 공정변수를 도출하였다.

• 한국자동차공학회논문집
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• 제11권4호
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• pp.58-67
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• 2003

An automotive engine cooling system is closely related with overall engine performances, such as reduction of fuel consumption, decrease of air pollution, and increase of engine life. Because of complex reaction between each component, the direct experiment, using a vehicle, takes high cost, long time, and slow response to the system change. Therefore, a computer simulation would provide the designer with an inexpensive and effective tool for design, development, and optimization of the engine cooling system over a wide range of operating conditions. In this work, it has been predicted the thermal performance of the engine cooling system in cases of stationary mode, constant speed mode, and city-drive mode by mathematical modelling of each component and numerical analysis. The components are engine, radiator, heater, thermostat, water pump, and cooling fans. Since the engine model is the most important, that is divided into eight sub-sections. The volume mean temperature of eight sub-sections are simultaneously calculated at a time. For detail calculation, the radiator and heater are also divided into many sub-sections like control volumes in finite difference method. Each sub-section is assumed to consist of three parts, coolant, tube with fin, and air. Hence it has been developed the simulation program that can be used in case of design and system configuration changes. The overall performance results obtained by the program were desirable and the time-traced tendencies of the results agreed fairly well with those of actual situations.

• 한국작물학회지
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• 제38권1호
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• pp.31-37
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• 1993

우리나라 주요 벼 재배품종 및 신육성계통(자포니카: 25품종, 통일형:8품종)에 대한 쌀 알칼리 붕괴성의 품종적 특이성을 분시검토하여 보고자 KOH 농도를 0.8-1.8까지 0.2% 간격으로 처리하여 농도별 쌀의 알칼리 붕괴반응을 조사하고 주성분분석법을 적용하여 품종적 유형을 분류하였다. 주성분분석에서 상위 2개 주성분치의 변이가 전변이량의 92%을 차지하였고 제1 및 제2 주요분치 좌표상의 품종분포에 따라 크게 4개 유형으로 군집화 시킬 수 있었다. 제 I 군에서는 전 KOH 농도에 걸쳐 거의 비슷하게 알칼리 붕괴성(ADV)가 낮은 도봉벼만 유일하게 분포하였고, 제 II군에는 1.4% KOH 농도에서 중간정도의 ADV 이면서 고-저 알칼리 농도 ADV간차가 중도인 백운찰벼, 신선찰벼 및 수원 34002 등 찰벼가 포함되어 있었다. 제 III군에는 1.4% KOH 농도에서 중-중고의 ADV 이면서 저-고 KOH 농도간 ADV 변화가 심했던 대부분의 통일형 품종과 자포니카 조생계가 분포되어 있었고 육도농림찰 001와 한강 찰벼등은 이 유형에 포함되어 있었다. 제 IV군에는 1.4% KOH 농도에서 ADV가 중고이상으로 높으면서 고-저 알칼리 농도 ADV간차가 중-중고인 중생 및 중만생 자포니카 품종들이 주로 분포 하였으며 조생인 금조벼가 이 유형에 속하였다. 여기서 제 1 주성분은 전 알칼리 농도에서 평균적으로 표현되는 붕괴성 정도였고 제 2 주성분은 저-고 KOH 농도의 ADV간 차 또는 KOH 농도에 따른 ADV 변화의 회귀계수와 밀접하게 관련된 요소였다. 1.2%-1.4% KOH 농도에서의 ADV는 저-고 KOH 농도간 ADV차와 2차 곡선 회귀계수를 나타내었다.

• 한국운동역학회지
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• 제20권2호
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• pp.213-219
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• 2010

The purpose of this study is developing a method to analyze and evaluate a golf swing motion using the ground reaction force (GRF) data. Proper weight shifting is essential for a successful shot in golf swing and this could be evaluated by means of the forces between the feet and ground. GRF during the swing were measured from 15 low-handicapped male golfers including professionals. Four clubs(driver, iron 3, iron 5, and iron 7) were selected to analyze the differences due to different characteristics of club. Swings of each subject were taken using a high speed video camera and GRF data were taken simultaneously by two AMTI force platforms. To simplify the GRF data, forces of the three major component of GRF(vertical, lateral, anterior-posterior force) at 10 predefined temporal events for each trial were selected and the mean of each event were calculated and evaluated. Analyzed vertical GRF (VGRF) data could be divided into two different styles, one-legged and two legged. One-legged style shows good weight transfer to the target leg and most of the previous study shows this style as a typical pattern of good players. Therefore the data from the iron 5 swing obtained from 10 one-legged style golfers are provided as criteria for the evaluation of a swing.

• 한국세라믹학회지
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• 제36권4호
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• pp.410-416
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• 1999

The reactivity of three kinds of spinels which CaO-Al2O3-SiO2 slag was investigated in terms of mineral phases and microstructures. New crystal products were not formed by reaction of 12CaO.7Al2O3 in the slag with spinels and free MgO components was preferenctially dissolved into slag for MgO-rich spinel and stoichiometric spinel. Meanwhile mineral phase was changed from 12CaO.7Al2O3 to CaO.Al2O3 to CaO.2Al2O3 finally to CaO.6Al2O3 having high melting point for Al2O3 -rich spinel. The Fe-oxide component of the slag was taken up by only stoichiometric spinel grains within the spinel clinker and the trapped amount of Fe-oxide was independent of MgO content of MgO in spinel clinker the more th resistance to slag corrosion but the less resistance to slag penetration.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2002년도 봄 학술발표회 논문집
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• pp.101-110
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• 2002

This article summarises the traditional method of soil-structure interaction based on the modulus of subgrade reaction and shows its weakness. In order to avoid these weakness, a new soil-structure interaction model is proposed. This model considers the soil as a set of connected springs which enables interaction between springs. Its use is as simple as the traditional model but allows to define the soil properties independently from the structural properties and the loading conditions. Thus, the definition of the modulus of subgrade reaction is unnecessary as each component is defined by its own modulii (Young's modulus and shear modulus). The non-linear soil behaviour for the shear stress versus distortion is also incorporated in the model. This feature allows to pinpoint the arching effect in the ground and shows how the stresses concentrate on stiff materials. Based on these principles, three dimensional program has been developed in order to solve the difficult problem of soil improvement by inclusions (stiff or soft). Also the possibility to take into account a flexible mat and/or a subgrade layer has been implemented. Equations used in the model are developed and a parametric study of the necessary data used in the program is presented. In particular, the Westergaard modulus notion and the arching effect are analysed.

• 대한기계학회논문집B
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• 제39권6호
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• pp.535-540
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• 2015

등판이 기울어지는 사무용 의자에서 등판 회전축 위치를 인체의 엉덩관절에 일치시키면 인체와 등판이 일체화되어 기울어짐으로써 사용성을 향상시킬 수 있다. 그러나 등판 힌지가 외부로 돌출되지 않도록 하기 위해 적용되는 핀인슬롯 조인트에서 기구적인 마찰이 발생해 등을 기울이고 세우는 동안 사용자에 영향을 줄 것으로 예상된다. 본 연구에서는 마찰 정도가 다른 조인트 부품으로서 슬라이더, 롤러 그리고 베어링 세 가지 유형을 적용하고, 등판 기울임 시 대비 복귀 시의 반발력 비율을 측정하였다. 실험 결과 베어링, 롤러, 슬라이더를 적용한 경우 등판 반발력 비율은$[{\pm}SD]$은 각각 $59.7[{\pm}10.3]%$, $47.2[{\pm}13.6]%$, $30.3[{\pm}18.1]%$로 나타나 베어링을 적용할 경우 마찰이 가장 작았다. 그러나 각 부품들은 생산단가 측면에서 차이를 보이기 때문에 부품 선정 시 마찰감소 성능뿐만 아니라 사용자의 주관적인 만족도를 함께 고려할 수 있음을 제시하였다.

• Ocean Systems Engineering
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• 제6권2호
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• pp.191-201
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• 2016

Stern bearing is a key component of marine propulsion plant. Its environment is diverse, working condition changeable, and condition severe, so that stern bearing load is of strong time variability, which directly affects the safety and reliability of the system and the normal navigation of ships. In this paper, three affecting factors of the stern bearing load such as hull deformation, propeller hydrodynamic vertical force and bearing wear are calculated and characterized by random theory. The uncertainty mathematical model of stern bearing load is established to research the relationships between factors and uncertainty load of stern bearing. The validity of calculation mathematical model and results is verified by examples and experiment yet. Therefore, the research on the uncertainty load of stern bearing has important theoretical significance and engineering practical value.

• KSBB Journal
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• 제28권5호
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• pp.275-281
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• 2013

Soil microbial community analysis of farmland soil sprayed with lye in order to use fertilizer in Nigeria was performed. As a control, two kinds of soils not sprayed with lye, located in Eungo and Lagos with general practice in agriculture was selected. Soil sprayed with lye was pH 8.25 through alkalization reaction, while the other soil samples were pH 6.22 and 5.94. Substrate utilization and species diversity index of soil sprayed with lye were low than that of the other soils with the analysis of Biolog ecoplate. As a result of principal component analysis, the relationship between three samples was low. Microbial community analysis was performed by DGGE and most of them were soil uncultured bacterium. Especially, Uncultured Acidobacteria and Uncultured Methylocystis sp., which had been isolated from the rhizosphere of soybean grown in that site were discovered in the soil sprayed with lye.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.836-839
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• 2003

In this paper, we briefly introduce the test bench and test method of RWA micro-vibration. TAMAM RWA (Reaction Wheel Assembly) micro-vibration was measured on a KISTLER dynamic plate which can measure time signals of three orthogonal forces and torques simultaneously up to 400Hz, and test data was analyzed. Measured data were evaluated with respect to the wheel spin rate and the static/dynamic unbalances were estimated from the extracted first harmonic component. The estimated static and dynamic unbalances were 0.79gㆍcm and 17.4gㆍ$\textrm{cm}^2$ respectively. The resonance mode and two rocking modes were observed as a results of its frequency analysis. Several higher order harmonic components were observed, which comes from its rotor shape as well as the wheel bearing.