• 한국표면공학회지
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• 제30권4호
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• pp.285-297
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• 1997

Finned segment, with which are lined inner wall of the turbine combustors, are subject to severe degradation when they are exposed to a hostile environmment at elevated temperature. To protect the finned segment from this environment and to maintain good mechanical properties of components at high temperature, they are preferred to be coated. The most governing factor for the durability of coatings used in the high temperature is the microstructure of coatings; these are splat from, distibution of microcacks, size and distribution of pores, thickness of coating layer, adhesion between coating layer, and oxidation of band coating. In this study, based on the evaluation of the imported finned segment, new finned segment segment was manufactured with optimum plasma spraying parameters, and their properties were examined. Using $ZrO_2(8wt$Y_2O_3)$,/TEX> powder for ceramic coating and 67Ni-22Cr-10Al-0.5Y mixing powder for bond coating, thickness of ceramic and bond coating layer were varied in order to find optimum condition, the results showed that B2T4(bond coating : 100~250$\mu\textrm{m}$, ceramic coating : 250~300$\mu\textrm{m}$) was the best among the specimens tested. Compared to the imported finned segment, B2T4 has better bond strength, hardness, and isothermal and cyclic oxidation resistance.

• 한국전기전자재료학회논문지
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• 제20권12호
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• pp.1039-1043
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• 2007

In this paper, in order to develop low temperature sintering ceramics for multilayer piezoelectric actuator application, PMN-PZN-PZT ceramics were fabricated using $LiCO_3,\;Bi_2O_3$ and CuO as sintering aids. And also, their piezoelectric and dielectric properties were investigated according to the milling time. All the specimens sintered at $930\;^{\circ}C$ showed tetragonal phases without secondary phases. With increasing milling time, piezoelectric and dielectric characteristic of specimens increased up to 60 hours milling time and then decreased due to the agglomeration of fine particle. Accordingly, it seems that 60 hour is optimum milling condition. At the sintering temperature of $930\;^{\circ}C$ and milling time of 60 hour, density, dielectric constant(${\varepsilon}_r$), electromechanical coupling factor (kp), mechanical quality factor (Qm), piezoelectric d constant showed the optimum value of $7.95\;g/m^3$, 1382, 0.546, 1749, 330 pC/N, respectively for multilayer piezoelectric actuator application.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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• pp.354-355
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• 2007

Process variables for manufacturing the $CuInSe_2$ thin film were established in order to clarify optimum conditions for growth of the thin film depending upon process conditions (substrate temperature, sputtering pressure, DC/RF Power), and then by changing a number of vapor deposition conditions and Annealing conditions variously, structural and electrical characteristics were measured. Thereby, optimum process variables were derived. For the manufacture of the $CuInSe_2$, Cu, In and Se were vapor-deposited in the named order. Among them, Cu and In were vapor-deposited by using the sputtering method in consideration of their adhesive force to the substrate, and the DC/RF power was controlled so that the composition of Cu and In might be 1 : 1, while the surface temperature having an effect on the quality of the thin film was changed from 100[$^{\circ}C$] to 300[$^{\circ}C$] at intervals of 50[$^{\circ}C$].

• Transactions on Electrical and Electronic Materials
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• 제11권1호
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• pp.33-36
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• 2010

$MgF_2$ is a current material used for optical applications in the ultraviolet and deep ultraviolet range. Process variables for manufacturing $MgF_2$ thin film were established in order to clarify the optimum conditions for the growth of the thin film, dependant upon the process conditions, and then by changing a number of the vapor deposition conditions, substrate temperatures, and heat treatment conditions, the structural and optical characteristics were measured. Then, optimum process variables were thus derived. Nevertheless, modern applications still require improvement in the optical and structural quality of the deposited layers. In the present work, in order to understand the composition and microstructure of $MgF_2$, single layers grown on a slide glass substrate using an Electron beam Evaporator (KV-660), were analyzed and compared. The surface substrate temperature, having an effect on the quality of the thin film, was changed from $200^{\circ}C$ to $350^{\circ}C$ at intervals of $50^{\circ}C$. The heat treatment temperature, which also has an effect on the thin film, was changed from $200^{\circ}C$ to $400^{\circ}C$ at intervals of $50^{\circ}C$. The physical properties of the thin film were investigated at various fabrication conditions, such as the substrate temperature, the heat treatment temperature, and the heat treatment time, by X-ray diffraction, and field emission-scanning electron microscopy.

• 한국식품영양학회지
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• 제6권4호
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• pp.287-293
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• 1993

This study was carried out to investigate the influences of cultural conditions of koji on the production of organic acid during rice-koji making by Aspergillus awamori var. kawachii which is now widely used as koji-mold in brewing Takju and Yakju in Korea. The optimum temperature for the germination of the conidia of the mold was 35'8, and the time required for germination at this temperature was 8 hours. Rapid germination occurred when the water content of steamed rice was above 40%, but germination retardation occurred markedly below 35%. The optimum cultural temperature for the production of organic acid was 32$^{\circ}C$, and the production of organic acid was markedly restricted at 36$^{\circ}C$ and 4$0^{\circ}C$. It was effective for the high production of both saccharogenic amylase and organic acid to shift the cultural temperature from initial 36$^{\circ}C$ to 32$^{\circ}C$ after 20~25 hours of cultivation. Initial water content suitable to the production of organic acid was 40% in steamed rice, but its production was markedly restricted below 30% of water content. When the quantity of conidial inoculation was too small, the production of organic acid was low in initial phase, but it was retrived at later period. Acid production was markedly restricted together with the increase in koji thickness.

• Geomechanics and Engineering
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• 제33권1호
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• pp.65-75
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• 2023

Recycled concrete aggregate (RCA) is widely used as a construction material in road construction, concrete structures, embankments, etc. However, it has been reported that calcite (CaCO₃) precipitation from RCA can be a cause of clogging when used in drainage applications. An accelerated calcite precipitation (ACP) procedure has been devised to evaluate the long-term geochemical performance of RCA in subsurface drainage systems. While the ACP procedure was useful for the French Drain application, there remained opportunities for improvement. In this study, key factors that control the formation of calcite precipitation were quantitatively evaluated, and the results were used to improve the current prototype ACP method. A laboratory parametric study was carried out by investigating the effects of reaction temperature and time on the formation of calcite precipitation of RCA, with determining an optimum reaction temperature and time which maximizes calcite precipitation. The improved ACP procedure was then applied to RCA samples that were graded for Type I Underdrain application, to compare the calcite precipitation. Two key findings are (1) that calcite precipitation can be maximized with the optimum heating temperature (75℃) and time (17 hours), and (2) the potential for calcite precipitation from RCA is not as significant as for limestone. With the improved ACP procedure, the total amount of calcite precipitation from RCAs within the life cycle of a drain system can be determined when RCAs from different sources are used as pipe backfill materials in a drain system.

• 한국약용작물학회지
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• 제4권2호
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• pp.163-171
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• 1996

Lycoris의 종자발아(種子發芽) 특성(特性)을 구명(究明)하고자 온도(溫度), 채종시기(採種時期)와 파종시기(播種時期), 파종용토(播種用土)과 용토(用土)의 수분량(水分量) 및 광선(光線)의 유무(有無)가 종자발아(種子發芽)에 미치는 영향(影響)을 조사(調査)한 결과(結果)는 다음과 같다. 1. 백양꽃과 개상사화(想思花)는 90% 이상 결실(結實)하였고 종자성숙(種子成熟)은 $9{\sim}10$월 상순(上旬)으로 나타났는데 60% 이상의 발아율(發芽率)을 얻는데는 6개월이 소요되었다. 2. 발아적온(發芽適溫)은 $25^{\circ}C$로 나타났고 변온처리(變溫處理)는 $20,\;25^{\circ}C$에서 효과적(效果的)이었다. 3. 채종적기(採種適期)는 9월(月) 20일(日)경이었고 파종시기(播種時期)는 채종(採種) 즉시 파종(播種)하는 것이 가장 좋았다. 4. 파종용토(播種用土)은 사양토가 가장 좋았고 용토(用土)의 수분량(水分量)은 용토(用土) 400mg당 PF 1. 9가 가장 적당하였다. 4. 종자발아(種子發芽)는 암조건(暗條件)이 명조건(明條件)보다 좋은 것으로 나타났다.

• 한국미생물·생명공학회지
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• 제18권3호
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• pp.251-259
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• 1990

생전분 분해력이 강력한 glucoamylase를 생산하는 균주로서 Asp.usamii IAM 2185를 선정하였다. 밀기울배지에서의 효소생산의 최적 initial pH는 6.0-8.0, 최적 배양온도는 25-$30^{\circ}C$, 최적 배양시간은 72시간이고, 밀기울배지에 ammonuim nitrate와 albumin의 첨가는 효소의 생산을 약간 증가시켰다. 황산암모늄분획, CM-cellulose와 DEAE-cellulose column chromatography에 의하여 효소를 정제하였고, 정제효소의 specific activity는 34.3U/mg.protein, 수율은 10.3 이었다.

• Journal of Biosystems Engineering
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• 제24권1호
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• pp.9-18
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• 1999

This study was performed to investigate the optimum microalgal culture conditions using flask culture and to find the feasibility of using the flue gas of the rice husk incinerator for cultivating the microalgae. The optimum initial pH of media was 4.5 for the microalgae culture, and the intermittently illuminated culture was more effective than the continuous illuminated culture. Thus, the balance between photosynthesis and formative metabolism must be considered thoroughly to cultivate microalgal cells. The optimum CO2 concentrations were in the range of 7 to 10%, and the optimum temperature was about 35$^{\circ}C$ in both the daytime and the nighttime for the culture. When flue gas of the rice husk incinerator was applied to the microalgae culture using stirred photobioreactor, the dry cell weight was 0.026 g dry biomass/hr$.$l. The results obtained in experiments indicated that the flue gas was effective for microalgae culture without any limitations.

• 대한기계학회논문집
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• 제18권5호
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• pp.1117-1125
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• 1994

A UBET program is developed for determining the optimum sizes of preform of a rib-web part in axisymmetric closed-die forging. The program consists of forward and backward tracing processes. In forward process, material flow, degree of die filling, and forging load are predicted. In backward tracing process, the optimum dimensions of initial billet and preform are determined from the final-shape data without flash. The above program is easy to handle input data with and is convenient to visualize the whole process of closed-die forging with. Experiments are carried out with pure plasticine billets at room temperature. The theoretical predictions of the forging load and the flow pattern are in good agreement with the experimental results.