• 한국시뮬레이션학회논문지
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• 제10권1호
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• pp.13-24
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• 2001

We propose a divide-conquer method of Petri nets under the condition of one-boundedness for all the Petri nets. We introduce the P-invariant transitive matrix of Petri nets and relationship between them. The feature of the P-invariant transitive matrix is that each element stands for the transitive relationship between input place and output place through the firing of the enable transition.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2001년도 봄 학술발표회 논문집
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• pp.489-494
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• 2001

This paper deals with a dynamic modeling of artillery system loaded by gun charge explosion during firing condition. Geometric and elastic gun data are used to modify a projectile interaction model. The maximum impact force on gun barrel was 15,000 N and the gun barrel moved about 1.3 m. A cannon bal] was presented to travel in the flexible gun, the traveling distance was about 23,000 m, and the angular velocity was about 10rad/sec. The artillery dynamic system using the multi-body dynamics enables us to obtain the data for the fatigue analysis.

• Tribology and Lubricants
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• 제34권4호
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• pp.146-159
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• 2018

This paper presents a wear analysis procedure for calculating the wear of journal bearings of a four-strokes and four-cylinder engine operating at a constant angular crank shaft speed during firing conditions. To decide whether the lubrication state of a journal bearing is in the possible region of wear scar, we utilize the concept of the centerline average surface roughness to define the most oil film thickness scarring wear (MOFTSW) on two rough surfaces. The wear volume is calculated from the wear depth and wear angle, determined by the magnitude of each film thickness on a set of oil films with thicknesses lower than the MOFTSW at every crank angle. To calculate the wear volume at one contact, the wear range ratio during one cycle is used. The total wear volume is then determined by accumulating the wear volume at every contact. The fractional film defect coefficient, asperity load sharing factor, and modified specific wear rate for the application of the mixed-elasto-hydrodynamic lubrication regime are used. The results of this study show that wear occurs only at the connecting-rod big-end bearing. Thus, simulation results of only the big-end bearing are illustrated and analyzed. It is shown that the wear volume of each wear scar group occurs consecutively as the crank angle changes, resulting in the total accumulated wear volume.

• 보존과학회지
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• 제35권4호
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• pp.331-343
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• 2019

The purpose of this study was to investigate the material characteristics of black wares excavated from Yongyeon-ri, Damyang and to clarify the correlation of the factors that develop black coulor compared with black wares excavated from other regions. As a results of absorption rate, colour coordinate, compositional mineral, section analysis and contents showed high correlation between the kilns and the waste dumplings, indicating that they were made using the same materials. Second, comparing the microtextures and contents of the glaze layer with the excavated sherds from other kilns, a characteristic coagulation phenomena of iron oxides were not observed in Yongyeon-ri and Gilmyeong-ri, and it was considered that the material, mixing ratio, and firing environment were different from those of Bonggok-dong. In addition, statistical analysis using the major components revealed that the bodies of Yongyeon-ri were highly correlated with those of Bonggok-dong, which is nearest to the region, and similar to Gilmyeong-ri in the glaze layer. The characteristics of colorant were different depending on Fe₂O₃ content and K₂O content also contributed to the classification of the composition of each excavated kiln. Conclusionally, it can be seen from the scientific analysis that the colour of black wares excluded from different regions is materially different from that of iron oxide, the coloring condition, and the firing environment.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2007년도 제29회 추계학술대회논문집
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• pp.125-130
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• 2007

추력 30톤급 액체로켓엔진의 실물형 연소기에 케로신을 이용한 재생냉각 방식을 적용하여 연소시험을 수행하였다. 30톤급 실물형 연소기로는 처음으로 연소기 헤드와 연소실이 일체형으로 제작되었으며, 연소성능 및 재생냉각 성능, 그리고 연소기 내구성 확인을 위하여 여러 차례 연소시험이 수행되었다. 본 논문에서는 연소압력 68 bar 혼합비 2.8의 탈설계점 조건과 연소압력 60 bar, 혼합비 2.5의 설계점 조건을 적용한 연소시험의 성능결과에 대하여 기술하였다. 각각의 연소시험 결과 연소성능 및 연소안정성, 그리고 연소기 내구성 측면에서 충분히 성공적인 데이터를 얻었으며, 이로써 30톤급 액체로켓엔진 케로신 재생냉각 연소기 개발의 기술적인 검증을 완료했다는 의미를 부여할 수 있게 되었다.

• Tribology and Lubricants
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• 제34권3호
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• pp.93-107
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• 2018

The purpose of Part I of this study is to find the potential region of wear scarring on engine journal bearings operating at a constant angular crank shaft velocity under firing conditions. To do this, we calculate the applied loads and eccentricities of a big-end journal bearing installed on a four-stroke and four-cylinder engine at every crank angle. Then, we find potential wear regions, such as a minimum oil film thickness, at every crank angle below most oil film thickness scarring wear (MOFTSW) obtained based on the concept of the centerline average surface roughness. Thus, the wear region is defined as a set of each film thickness below the MOFTSW at every crank angle. In this region, the wear volume changes according to the wear depth and wear angle, depending on the minimum oil film thickness at every crank angle. The total wear volume is the summation during one cycle. Graphical views of the region in the two-dimensional coordinates show the crank angle and bearing angle along the journal center path, indicating the position of the minimum oil film thickness. The results of wear analysis show that the possible wear region is located at a few tens of angles behind the upper center of a big-end bearing at maximum power rpm.

• 보존과학회지
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• 제29권2호
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• pp.111-125
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• 2013

이 연구에서는 화성 발안리 유적에서 출토된 원삼국과 백제 토기의 용도와 제작기법에 대하여 고찰하였다. 각 주거지에서 수습한 토기시료는 중도식 무문토기와 타날문 토기 및 백제토기로서 정련상태와 비짐물질의 첨가 등 광물학적 특성에 따라 형태가 구분되며 사용용도가 달라진다. 중도식 무문토기와 장란형토기는 대부분 황갈색을 띠며 취사용기로 사용되었고, 타날문 토기는 회청색을 띠며 저장용기로 사용되었던 것으로 보인다. 중도식 무문토기와 백제토기는 $900{\sim}940^{\circ}C$의 소성을 거쳤고 타날문 토기는 $900{\sim}1,100^{\circ}C$ 정도의 소성을 거쳤을 것으로 판단된다. 따라서 토기의 소성조건은 용도에 따라 조절하여 사용하였을 것으로 해석된다. 한편 모든 토기들은 유사한 지구화학적 거동특성을 갖는 것으로 보아 모두 같은 기원의 태토를 사용하였을 것으로 추정된다.

• 한국재료학회지
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• 제23권5호
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• pp.271-275
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• 2013

Cobalt (Co) compounds have been used for centuries to impart rich blue color to glass, glazes and ceramics. Cobalt monoxide (CoO), an oxide of Co, is an inorganic compound that has long been used as a coloring agent in the ceramic industry. Unlike other coloring agents, CoO can be used to develop colors other than blue, and several factors such as its concentration in the glaze and firing condition have been suggested as possible mechanisms. For example, CoO produces a typical blue color called "cobalt blue" at very low concentrations such as 1 wt% in both oxidation and reduction firing conditions; a higher concentration of CoO (5 wt%) develops a darker blue color under the same firing conditions. Interestingly, CoO also develops a purple color at high concentrations above 10 wt%. In this study, we examined the applicability and mechanism of a novel purple glaze containing cobalt(II, III) oxide, one of the well characterized cobalt oxides. Experimental results show that an Augite crystal isoform (Augite-Fe/Co) in which Fe was replaced with Co is the main component contributing to the formation of the purple color. Based on these results, we developed a glaze using chemically synthesized Augite-Fe/Co crystal as a color pigment. Purple color glaze was successfully developed by the addition of 6~15 wt% of $Co_3O_4$ to magnesia lime.

• 한국추진공학회지
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• 제25권6호
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• pp.45-52
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• 2021

본 연구에서는 액체 추진제 소형로켓엔진의 개발을 위한 선행연구로 연료과농 조건의 기체메탄-기체산소 연소시험 결과를 제시한다. 다양한 당량비에 대한 연소특성을 비교하기 위해 산소 공급 유량을 12 g/s로 설정하고 메탄 공급 유량을 변화시켰다. 시험 결과, 연소시험 중 형성되는 정상상태 특성속도가 후반에서 급작스럽게 증가하는 현상이 관측되었으며, 그 변화량은 당량비에 비례하여 커지는 경향을 확인할 수 있었다. 이를 바탕으로 특성속도의 변이특성에 종속하는 당량비 구간을 총 3가지 연소 범주로 구분하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.304.1-304.1
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• 2016

We have investigated the effect of plasma nitridation of atomic layer deposited-Al2O3 films of monocrystalline Si wafers and the thermal properties of nitridated Al2O3 films. Nitridation was performed on Al2O3 to form aluminum oxynitride (AlON) using NH3 plasma treatment in a plasma-enhanced chemical vapor deposition and it was conducted at temperature of $400^{\circ}C$ with various plasma power condition. After nitridation, we performed firing and forming gas annealing (FGA). For each step, we have observed the minority carrier lifetime and the implied Voc by using quasi-Steady-State photoconductance (QSSPC). We confirmed a tendency to increase the minority carrier lifetime and the implied Voc after the nitridation. On the other hand, the minority carrier lifetime and the implied Voc was decreased after Firing and forming gas annealing (FGA). To get more information, we studied properties of the plasma treated Al2O3 films by using Secondary Ion Mass Spectroscopy (SIMS) and X-ray Photoelectron Spectroscopy (XPS).