• 보존과학회지
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• 제37권5호
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• pp.545-556
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• 2021

본 연구에서는 정선 아우라지 유적에서 출토된 신석기시대 및 청동기시대 토기 총 11점을 대상으로 재료학적 특성을 연구하였다. 불석결과, 청동기시대 조기 토기의 염기성 및 산성 성분은 신석기시대 토기와 청동기시대 전기 토기의 중간 영역에서 분포하였지만, 각 제작시기에 따른 큰 차이는 확인되지 않았다. 이미 연구되었던 강원지역 출토 토기와 비교해본 결과, 정선 아우라지 출토 토기는 영동지역 출토 토기보다 산성 성분이 적은 경향성을 보였으며, 염기성 성분은 출토유적에 따라 차이가 있었다. 희토류 원소 분포 패턴에서는 분석대상 토기 모두 유사한 패턴 결과를 나타내어 태토원료의 모암이 동일기원임을 확인하였으며, 기 연구되었던 타 유적 토기 태토와의 비교를 통하여 정선 아우라지 출토 토기 태토의 특성을 확인하였다. 미세구조 불석결과 분석대상 토기는 대체로 점토입자 및 공극의 분포가 불규칙하며, 기질이 느슨하여 치밀한 소성이 이루어지지 못했다. 신석기시대 토기에서는 부정형 공극이 많이 확인되었으며, 점토기질과 함께 장석을 포함한 알루미노 규산염의 배열이 관찰된 반면, 청동기시대 전기 토기의 공극은 미정질 입자와 입방체 결정 등으로 채워진 부분이 다수 확인되었다. 정선 아우라지 출토 토기 태토의 주된 광물상은 제작시기와는 별개로 각 토기의 특성에 따른 광물 조성이 검출되기도 했지만, 전체적으로 유사한 조성을 나타내었다. 따라서 토기의 소성온도에는 큰 차이가 없었던 것으로 확인되며, 약 750~850℃ 범위에서 저온소성된 것으로 추정된다.

• 한국재료학회지
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• 제30권10호
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• pp.550-557
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• 2020

Used in the ceramic tile market as a representative building material, relief ceramic tile is showing increased demand recently. Since ceramic tiles are manufactured through a sintering process at over 1,000 ℃ after uniaxial compression molding by loading granule powders into a mold, it is very important to secure the flowability of granular powders in a mold having a relief pattern. In this study, kaolin, silica, and feldspar are used as starting materials to prepare granule powders by a spray dryer process; the surface of the granule powders is subject to hydrophobic treatment with various concentrations of stearic acid. The effect on the flowability of the granular powder according to the change of stearic acid concentration is confirmed by measuring the angle of repose, tap density, and compressibility, and the occurrence of cracks in the green body produced in the mold with the relief pattern is observed. Then, the green body is sintered by a fast firing process, and the water absorption, flexural strength, and durability are evaluated. The surface treatment of the granule powders with stearic acid improves the flowability of the granule powders, leading to a dense microstructure of the sintered body. Finally, the hydrophobic treatment of the granule powders makes it possible to manufacture relief ceramic tiles having a flexural strength of 292 N/cm, a water absorption of 0.91 %, and excellent mechanical durability.

• Journal of Platform Technology
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• 제9권4호
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• pp.60-70
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• 2021

본 논문은 2채널 이상의 다중 카메라를 사용하는 곡면 스크린 사격 시스템에서 패턴 레이저 영상의 좌표를 안정적으로 추적할 수 있는 방법을 제안하였다. 이 방법은 HMD 사격 방식을 대체할 수 있는 다중 스크린 사격 방식에 적용시 매우 효과적으로 타겟점을 추적 및 획득할 수 있다. 개별 카메라로부터 획득한 변형이 심한 곡면 스크린의 영상을 영상 정규화, 영상 이진화 및 노이즈 제거를 통해 보정한다. 이 보정된 영상을 매칭점을 기준으로 사격의 탄착점 추적에 용의한 유클리드 공간 맵으로 생성하여 적용한다. 실험한 결과, 곡면 스크린 사격 시스템에서 패턴 레이저의 영상 좌표를 안정적으로 추출하였고, 실세계 좌표 위치와 광대역 유클리드 맵의 타켓점 위치 오차를 최소화하였다. 실험을 통해 제안한 방법의 신뢰성을 확인하였다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 추계학술대회 초록집
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• pp.43.1-43.1
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• 2010

In the crystalline silicon solar cells, the full area aluminum_back surface field(BSF) is routinely achieved through the screen-printing of aluminum paste and rapid firing. It is widely used in the industrial solar cell because of the simple and cost-effective process to suppress the overall recombination at the back surface. However, it still has limitations such as the relatively higher recombination rate and the low-to-moderate reflectance. In addition, it is difficult to apply it to thinner substrate due to wafer bowing. In the recent years, the dielectric back-passivated cell with local back contacts has been developed and implemented to overcome its disadvantages. Although it is successful to gain a lower value of surface recombination velocity(SRV), the series resistance($R_{series}$) becomes even more important than the conventional solar cell. That is, it is a trade off relationship between the SRV and the $R_{series}$ as a function of the contact size, the contact spacing and the geometry of the opening. Therefore it is essential to find the best compromise between them for the high efficiency solar cell. We have investigated the optimal design for the local back contact by using PC1D simulation.

• 한국세라믹학회지
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• 제44권3호
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• pp.157-161
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• 2007

Line width under $100\;{\mu}m$ with good resolution is difficult to achieve using conventional thick-film process utilizing screen printing method. However combined with lithography technology finer line and space for miniaturization and highly integrated package is achievable. In this study, photosensitive Ag paste of optimum formulation used for thick film lithography technology was fabricated by various Ag powder, glass powder and additives. As the result, line width of $30\;{\mu}m$ with good definition and reduced mismatch during co-firing with LTCC substrate was acquired. Formulated Ag paste was used to pattern embedded fine line inductor with over 90% yield.

• 한국군사과학기술학회지
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• 제15권3호
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• pp.257-265
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• 2012

This paper presents a study on characteristics of precession motion of a smart munition. It's a kind of the Sensor Fuzed Weapon. The particular thing for the smart munition is that it has precession motion in the air while the sensor is searching the ground to detect ground vehicles such as tanks. The smart munition has a cylindrical shape and has a sensor attached on its side. Due to its non-uniform mass distribution, its center of gravity(CG) is located away from the center of volume(CV). In order for the smart munition to detect the target effectively, the ground searching pattern of sensor should have an uniform circular form, and for this, the precession motion of smart munition should be in its steady-state. Finally, it is necessary to choose the right initial conditions at the moment of firing, for the steady-state precession motion during flight.

• 터널과지하공간
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• 제20권3호
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• pp.183-193
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• 2010

이 논문은 석회석 광산의 발파 중에 일어나는 파쇄도 관련 문제들에 대하여 고찰한 것이다. 먼저 실 규모 발파 시에 발파 결과를 크게 달리 할 수 있는 중요 발파설계변수를 추출하였다. 또 현장에서 간편하게 적용할 수 있는 발파 성과 평가 방법을 제시하였다. 이는 저자들이 시멘트 제조를 위한 석회석 광산에서 다양한 규모로 설계, 시공, 평가 한 경험에 근거한 것이다.

• 한국재료학회지
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• 제27권11호
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• pp.583-589
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• 2017

Ceramic ink-jet printing has become a widespread technology in ceramic tile and ceramicware industries, due to its capability of manufacturing products on demand with various designs. Generally, thermally stable ceramic inks of digital primary colors(cyan, magenta, yellow, black) are required for ink-jet printing of full color image on ceramic tile. Here, we synthesized an aqueous glass-ceramic ink, which is free of Volatile organic compound(VOC) evolution, and investigated its inkjet printability. $CoAl_2O_4$ inorganic pigment and glass frit were dispersed in aqueous solution, and rheological behavior was optimized. The formulated glass-ceramic ink was suitably jetted as single sphere-shaped droplets without satellite drops. After ink-jet printing and firing processes, the printed glass-ceramic ink pattern on glazed ceramic tile was stably maintained without ink spreading phenomena and showed an improved scratch resistance.

• 한국세라믹학회지
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• 제44권1호
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• pp.32-36
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• 2007

Zinc gallate $(ZnGa_2O_4)$ thin film phosphors have been formed on ITO glass substrates by a sol-gel spinning coating method. For the formation of the film phosphors, the starting materials of zinc acetate dihydrate, gallium nitrate hydrate and 2-methoxyethanol as a solution were used. The thin films deposited were firstly dried at $100^{\circ}C$ and fired at $500^{\circ}C\;or\;600^{\circ}C$ for 30 min and then, annealed $500^{\circ}C\;or\;600^{\circ}C$ at for 30 min under an annealing atmosphere of 3% $H_2/Ar$. The thin films deposited on ITO glass plates showed the (220), (222), (400), (422), (511), and (440) peaks of spinel structure as well as the (311) peak indicating a standard powder diffraction pattern. The surface morphologies of the thin film phosphors were observed with a firing and an annealing condition. The $ZnGa_2O_4$ film phosphors showed the blue emission spectra around 410 nm as well as the emission spectra in the UV region (360-380 nm).

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.255-258
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• 2002

Liquid rocket engines using liquefied natural gas (LNG) or methane as a fuel is known to have several good characteristics, such as high specific impulse compared to other hydrocarbon fuels, environment-friendly exhaust gas, low production cost, and re-usability with low soot generation in the cooling channel. In this study, experimental combustion chambers capable of using LNC and $CH_{4}$ are being researched through experimental firing tests, and within easy range of eyes' inspection, there are the periodical existence of soot or discoloration in the chamber wall surface. This result means that mixture ratio of oxidizer and fuel fluctuates periodically between outer-row injectors in the mixing head in the circumferential direction. Therefore, based on this phenomenon, the variation of mixture ratio near the chamber wall caused by the spill pattern of a shear coaxial injector was analyzed quantitatively and the thermal heat flux Into the cooling channel is modified. Then, the calculated and modified results are compared with the measured ones.