• 한국재료학회지
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• 제25권9호
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• pp.487-491
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• 2015

In photovoltaic power generation where minority carrier generation via light absorption is competing against minority carrier recombination, the substrate thickness and material quality are interdependent, and appropriate combination of the two variables is important in obtaining the maximum output power generation. Medici, a two-dimensional semiconductor device simulation tool, is used to investigate the interdependency in relation to the maximum power output in front-lit Si solar cells. Qualitatively, the results indicate that a high quality substrate must be thick and that a low quality substrate must be thin in order to achieve the maximum power generation in the respective materials. The dividing point is $70{\mu}m/5{\times}10^{-6}sec$. That is, for materials with a minority carrier recombination lifetime longer than $5{\times}10^{-6}sec$, the substrate must be thicker than $70{\mu}m$, while for materials with a lifetime shorter than $5{\times}10^{-6}sec$, the substrate must be thinner than $70{\mu}m$. In substrate fabrication, the thinner the wafer, the lower the cost of material, but the higher the cost of wafer fabrication. Thus, the optimum thickness/lifetime combinations are defined in this study along with the substrate cost considerations as part of the factors to be considered in material selection.

• 한국기계가공학회지
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• 제12권3호
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• pp.7-12
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• 2013

In Die casting process, the problem of die degradation is often issued. In oder to increase of die life the material degradation of die steel was investigated using test core pins. Three test core pins were positioned in front of the gate entry and observed washout and soldering resistance during Mg die casting process. The test parameters are set as different commercial die materials, coatings condition and hardness of die surface. Usign 220t magnesium die casting machine was employed to cast AZ91 magnesium alloys. After 150 shots, macroscopic observation of die surface was carried out. Additional 50 cycles later, test pins were chemically cleaned with 5% HCl aqueous solution to find out the existence of washout and soldering layers. Microstructural characterization of die surface and the die roughness measurement were performed together. Computational simulation using AnyCasting program was also beneficial to correlate the extent of die damage with the position of test pin inside die cavity. As results, the optimal combination of die steel with productive coating as well as its hardness was drawn out. it will be helpful to decide the material and condition considering increasing of tool life.

• Geomechanics and Engineering
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• 제15권6호
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• pp.1143-1151
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• 2018

Loess often causes problems when used as a filling material in the construction of foundations. Therefore, the compaction technique, shear behavior, and bearing capacity of a filled foundation should be carefully considered. A series of tests was performed in this study to obtain effective compaction techniques and construction parameters. The results indicated that loess is strongly sensitive to water. Thus, the soil moisture content should be kept within 12%-14% when it is used as a filling material. The vibrating-dynamic combination compaction technique is effective and has fewer limitations than other methods. In addition, the shear strength of the compacted loess was found to increase linearly with the degree of compaction, and the soil's compressibility decreased rapidly with an increase in the degree of compaction when the degree of compaction was less than 95%. Finally, the characteristic value of the bearing capacity increased with an increase in the degree of compaction in a ladder-type way when the degree of compaction was within 92%-95%. Based on the test data, this paper could be used as a reference in the selection of construction designs in similar engineering projects.

• 한국유체기계학회 논문집
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• 제3권4호
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• pp.7-14
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• 2000

This paper provides integrity evaluation and root cause analysis for defects observed at volute tongue, or cutwater, of the operating centrifugal pump in power plant. The cause of the cracks are analyzed and reviewed from the viewpoint of the operation and maintenance of the pumps, and the sample obtained from the cracked volute tongue of the pump are examined. At first, in-situ hardness test and microstructure examination were performed to understand the cause of cracking at volute tongue. The evaluation of structural integrity and the possibility of the crack propagation is also evaluated. Cracks were typical intergranular cracking and propagated along with prior austenite grain boundary. At easing volute tongue, the hardness was higher than ASTM requirement and a large amount of intergranular Cr carbide was precipitated. These were due to high C content in material. P content was also higher than ASTM requirement. Therefore, Cr carbide precipitation and P segregation at grain boundary, caused by higher C and P content in material, resulted in intergranular cracking of casing volute tongue. This procedure for integrity evaluation and root cause analysis is used to guide, and support the pump designer and manufacturer's material selection and process design to avoid a costly, unplanned outage of plant.

• 한국의류산업학회지
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• 제10권1호
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• pp.92-100
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• 2008

When designing protective clothing, there are something to be considered such as physiological feature of human body, acting range not to restrict physical activity, and effectiveness of material. Because the primary objective of protective clothing is to protect human body from danger and it is designed through complex designing process not likely general clothing design. However, current evaluation techniques-such as the ISO, the ASTM and the CEN, and KS-provide only the standard to evaluate the primary feature of material (testing, performance requirements, material specification, selection and application, test and care, and so on). There are no standard to evaluate influence for the human body while protective clothing put on. Especially, in Korea, there is KS to evaluate protective clothing, but it is partially translated version from ISO because of lack of core technology about this field. However, developed countries recognize it is new competitive means in the time of Global Standards and they are competing to make their own standard to global standard for the protective clothing. Therefore, it can be great opportunity for Korean clothing and textile industry to revitalize if focusing on research and development for protective clothing design based on physical activity of human body, fit evaluation technique and sizing which is currently no global standard for it and developing our standard to global standard.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1988년도 춘계학술대회 논문집
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• pp.33-34
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• 1988

태양전지의 특성분석에 관한 최근의 동향을 고찰해 보기로 한단. 첫째, $CuInSe_2$와 비정질 실리콘 등의 광전압 용도의 태양전지의 재료선택에 관한 일반 규칙을 살펴 보고, 둘째, AM1 조건에서 보다 정확한 전지효율의 측정방법을 조사하며, 셋째, 태양전지의 중요 특성분석방법들을 소개 설명한다. 특히 생산 품질관리의 규모로 까지 확대적용이 가능한 다음과 같은 태양전지의 특성분석방법들의 장치개선 및 컴퓨터제어를 고찰하기로 한다. 전지효율 및 기타 전지특성을 위한 전류-전압 성질 측정장치, 양자효율을 위한 분광반응장치, 소수 이동자의 확산거리를 위한 표면광전압장치, 또한 에너지갭 내의 양자상태밀도를 위한 광열굴절장치 등이다.

• KSBB Journal
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• 제14권4호
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• pp.403-407
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• 1999

식품이나 수질 내의 독성 물질 monitoring을 위해서 발광미생물인 P. phosphoreum이 많이 연구되고 있는데 이 독성 물질측정을 위하여 P. phosphoreum을 더 효과적으로 이요하기 위해 고정화하여 이용하는 방법을 연구하였다. 고정화 방법을 크게 4가지로 나누어서 그 방법에 따라 각각 고정화 물질 한가지씩을 선택하여 P. phosphoreum의 bioluminescence 안정성을 알아보았다. Polvacrylamide나 collagen에서는 bioluminescence가 유지를 못하고 material과 cell을 혼합하자마자 급격히 떨어졌으나 alginate와 k-carrageenan에서는 빛 안정성이 매우 좋았다. 그러나 k-carrageenan은 온도를 높여야 gel이 형성되는 성질을 갖고 있기 때문에 저온성 발광 미생물인 P. phosphoreum에는 적합한 고정화 물질이 되지 못한다. 따라서 P. phosphoreum의 bioluminescence를 안정되게 유지하면서 고정화가 용이한 polymer로는 alginate가 적합하다.

• 복식문화연구
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• 제12권1호
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• pp.73-89
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• 2004

The following is a summary of comparative study on costumes between 『Cheng-Hoe-Jeon-Do』 and 『Chen-De-dang-an』 in Gun-Ryung 41st, 42nd and 43rd yew to find out costume situation actually worn by Emperor Gun-Ryung in Qing dynasty. In Gun-Ryung 41st year, Emperor's costumes showed a sign of royal tour robes. In 42nd year, a phase of mourning robe system came out and a plain side of costumes was shown owing to the mourning. In 43rd year, it showed costume situation worn by Emperor in peaceful year without any particular event. Velvet, material for traveling crown was used in a short time before and after the change of the season besides royal tour and this can be understood as a well-timed and reasonable selection of material. Eventhough robe material, Jik-kyung-Ji-chack-sa(a kind of silk) had been used for summer robes since Gun-Ryung 42nd you. Memorial costumes followed Emperor's court costume system I in 『Cheng-Hoe-Jeon-Do』 and court belt I or II as memorial suit belt was used for the memorial costume of Emperor Gun-Ryung and they properly applied of the costume system in 『Cheng-Hoe-Jeon-Do』 for coats.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 학술대회 및 기술세미나 논문집 디스플레이 광소자
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• pp.54-55
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• 2006

Organic light-emitting diodes(OLEOs) are attractive because of possible application in display with low operating voltage, low power consumption, self-emission and capability of multicolor emission by the selection of emissive material. We investigated the effects of deposition rate on the electrical characteristics, physical characteristics and optical characteristics of OLEOs in the ITO(indium-tin-oxide)/N.N'-diphenyl-N,N'-bis(3-methyphenyl)-1,1'-biphenyl-4,4'-diamine(TPD)/tris(8-hydroxyquinoline)aluminum($Alq_3$)/Al device. We measured current density, luminous flux and luminance characteristics of devices with varying deposition rates of TPD and $Alq_3$. It has been found that optimal deposition rate of TPD and $Alq_3$ were respectively $1.5{\AA}/s$ from the device structure. An AFM measurement results, surface roughness of the deposited film was the lowest when deposition rate was $1.5{\AA}/s$.

• Structural Engineering and Mechanics
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• 제73권5호
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• pp.501-513
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• 2020

In the present work, the optimization of machining parameters to achieve the desired technological parameters such as surface roughness, tool radial vibration and material removal rate have been carried out using response surface methodology (RSM). The hard turning of EN19 alloy steel with coated carbide (GC3015) cutting tools was studied. The main problem faced in manufacturer of hard and high precision components is the selection of optimum combination of cutting parameters for achieving required quality of surface finish with maximum production rate. This problem can be solved by development of mathematical model and execution of experiments by RSM. A face centred central composite design (FCCD), which comes under the RSM approach, with cutting parameters (cutting speed, feed rate and depth of cut) was used for statistical analysis. A second-order regression model were developed to correlate the cutting parameters with surface roughness, tool vibration and material removal rate. Consequently, numerical and graphical optimization were performed to obtain the most appropriate cutting parameters to produce the lowest surface roughness with minimal tool vibration and maximum material removal rate using desirability function approach. Finally, confirmation experiments were performed to verify the pertinence of the developed mathematical models.