• 한국주조공학회지
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• 제25권1호
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• pp.40-50
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• 2005

A series of heavy section ductile cast iron ingots with the cube length of 250mm were systematically investigated as functions of casting parameters of sand casting. Abnormal graphite formation was specially observed with the variation of Si content and Bi or Sb addition. Effects of chilling during casting and adaptation of riserless system were also examined, and proved to be effective for the prevention of both shrinkage and abnormal graphite such as chunky one. The formation of chunky graphite was effectively prevented by low Si content despite the promotion of pearlite matrix structure. The ferritic matrix was encouraged to form by high Si content and chunky graphite formation was effectively suppressed by the addition of Bi and Sb. Bi addition, however, was not good enough to control the microstructure owing to the sensitive cooling rate dependent inoculation behavior and relative low ability of nodulization. Sb addition, on the other hand, was proved to be effective for the microstructural control and enhancement of various mechanical properties such as strength, elongation, and impact energy. It may be suggested that optimized casting parameters should be applied to produce heavy section ductile cast iron with reliability.

• 한국산업융합학회 논문집
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• 제22권1호
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• pp.61-69
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• 2019

All the parts of lotus, including the seed, rhizome, leaf, stalk, petal, anther, pericarp, and fruit receptacle, have been used in traditional medicine system as a health beneficial supplement. However the most usually used from lotus plant is only the root. Therefore in this study, it will be discussed more the utilization of other parts of the lotus, namely the flower of lotus. The petals and stamens of lotus actually are also rich in bioactive components such as flavonoids and alkaloids, are used in the treatment of tissue inflammation, cancer, skin disease, and also for us as antidotes. One of the biotechnological process that can be used to improve the nutritional content, sensory, and also antioxidant activities is fermentation process. The final product desired from the fermentation process in this study is vinegar. The microbial strain powder used is Uinkin fermented powder with three variations of fermentation. The variations given in this study were initial sugar 32%, 24%, and 14% with the same fermentation temperature, $35^{\circ}C$ for 3 months. The results obtained showed that the pH value and sugar content of products during the fermentation process were decreasing during the fermentation process, with total polyphenol content of $283.7{\pm}97.6mg/100g\;QAE$, and total flavonoid content of $3.3{\pm}0.0mg/100g\;QAE$. For the DPPH radical scavenging ability of the fermentation product also increased in a concentration dependent manner, with ORAC activity of the product showed a high activity of $20.7{\pm}0.41{\mu}M$ TE. Therefore, fermentation process can be the one of method for improving the product. The efficiency of lotus flower vinegar fermentation can be reached with an initial sugar condition of 25% (sample B).

• International journal of advanced smart convergence
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• 제12권4호
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• pp.260-267
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• 2023

Due to the development of science and technology in the 4th Industrial Revolution, a variety of content is being developed and utilized through educational courses linked to digital textbooks. Students use smart devices to engage in realistic virtual learning experiences, interacting with the content in digital textbooks. However, while many realistic contents offer visual and auditory effects like 3D VR, AR, and holograms, olfactory content that evokes actual sensations has not yet been introduced. Therefore, in this paper, we designed and implemented 4D educational content by adding the sense of smell to existing content. This implemented content was tested in classrooms through a curriculum-based evaluation. Classes taught with olfactory-enhanced content showed a higher percentage of correct answers compared to those using traditional audio-visual materials, indicating improved understanding.

• 한국산학기술학회논문지
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• 제6권6호
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• pp.502-505
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• 2005

e-러닝에서 멀티미디어콘텐트의 사용이 증가함에 따라 e-러닝 시스템에서 제공하는 콘텐트의 크기 편차가 증가하고 있으며, 이는 e-러닝 사용자에 대한 응답시간의 편차를 크게 하여 학습의 효율성을 떨어뜨리는 요인이 되고 있다. 따라서 멀티미디어콘텐트를 활용한 e-러닝 시스템에서 사용자의 응답시간 편차 개선에 대한 연구가 필요하다. 본 연구의 목적은 e-러닝 사용자의 응답시간의 편차를 줄이는 것이며 이를 위해 다중 계층 구조의 혼합형 e-러닝 시스템을 설계하였다. 또한 실험을 통해 편차 개선을 확인하였다.

• 한국산업정보학회논문지
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• 제11권3호
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• pp.69-81
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• 2006

In this paper, an adaptive algorithm is proposed in streaming MPEG-4 contents with fluctuating resource amount such as throughput of network conditions. In the area of adaptive streaming issue, a lot of researches have been made on how to represent encoded media(such as video) bitstream in scalable way. By contrast, MPEG-4 supports object-based multimedia content which is composed of various types of media streams such as audio, video, image and other graphical elements. Thus, it can be more effective to provide individual media streams in scalable way for streaming object-based content to heterogeneous environment. The proposed method provides the multiple media streams corresponding to an object with different qualities and bit rate in order to support object based scalability to the MPEG-4 content. In addition, an optimal selection of the multiple streams for each object to meet a given constraint is proposed. The selection process is adopted a multiple choice knapsack problem with multi-step selection for the MPEG-4 objects with different scalability levels. The proposed algorithm enforces the optimal selection process to maintain the perceptual qualities of more important objects at the best effort. The experimental results show that the set of selected media stream for presenting objects meets a current transmission condition with more high perceptual quality.

• 열처리공학회지
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• 제36권4호
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• pp.223-229
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• 2023

This work was intended to investigate the effects of Zn content on microstructure and hardness of discontinuous precipitates (DPs) produced by continuous cooling (CC) in Mg-8%Al-X%Zn alloys with 0%, 0.5% and 1% of Zn contents (wt%). The DPs in the alloys possessed a wide range of (α+β) interlamellar spacings, which is attributed to the different transformation temperatures during CC. The higher Zn content resulted in the lower level of interlamellar spacings of the DPs, along with thinner and larger volume fraction of β phase layer in the DPs. It is noted that the DPs in the alloy with higher Zn content exhibited higher hardness, and that the ratio of increase in hardness of the DPs to that of the as-cast state was also increased with increasing Zn content. The reason was discussed on the basis of microstructural differences of the DPs in the Mg-8%Al-X%Zn alloys.

• 한국약용작물학회지
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• 제26권3호
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• pp.227-232
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• 2018

Background: Angelica gigas Nakai is a perennial herb belonging to the family Umbelliferae. Its roots are utilized in traditional medicine. The aim of this study was to increase the yield of and the content of two indicator components (decursin and decursinol angelate) in A. gigas Nakai. Methods and Results: The roots of A. gigas Nakai were harvested 4-times from late August to late October in 2017. Two agents (trace element-TE, and plant hormone-HM) were applied 4 times at intervals of 2 weeks. The content of the two indicator components were analyzed by high performance liquid chromatography. The HM treatment showed the greatest increase in underground part yield and root diameter. The content of the two indicator components in the control (non-treatment) group was the highest in the underground part, but was higher in the aerial parts in the agent treatment group. After treatment with the agents, the content of the indicator components tended to decrease in the underground part. However, the total content of the indicator components in the two agent treatment groups exceeded the level of 6% set by the Korean Pharmacopoeia. Conclusions: The highest underground part yield was found in the HM treatment group, while the highest content of decursin and decursinol angelate were found in the control group. This study provides basic information for yield improvement in A. gigas.

• 한국건설순환자원학회논문집
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• 제8권3호
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• pp.294-301
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• 2020

본 연구에서는 클링커의 고Al₂O₃화를 통한 에너지 절감형 시멘트 제조 가능성을 확인하기 위해, Al₂O₃ 함량이 높은 OPC 조합원료를 실험실 전기로에서 소성하여 C₃A 함량이 높은 클링커를 제조한 후 XRD 리트벨트 분석 및 광학 현미경을 통해 클링커의 소성성을 평가하고, 제조된 클링커에 혼합재를 첨가하여 얻어진 시멘트의 미소수화열 및 압축강도 측정을 통해 시멘트 반응성을 평가하고자 하였다. 그 결과 Al₂O₃ 함량을 일반 OPC보다 증가시켜 제조한 시멘트는 OPC에 비해 소성성이 뛰어나 시멘트 제조 에너지 절감에 기여할 수 있으며, OPC에 비해 C₃A(alite) 광물의 함량이 감소하였음에도 불구하고 압축강도가 오히려 향상되는 등 긍정적으로 작용할 수 있다. 유동성 저하, 수화열 증가와 같은 문제에 대해서도 석고 첨가량 및 분말도 조정, 혼합재 첨가와 같은 방법으로 제어할 수 있을 것으로 기대되어 적극적인 연구가 필요하다.

• 한국환경농학회지
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• 제4권1호
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• pp.52-56
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• 1985

아황산(亞黃酸)가스가 배출(排出)되는 공단주변(工團周邊)에서 재배(栽培)되는 배나무와 수도(水稻)의 엽내(葉內) 류황함량(硫黃含量) 및 감수율(減收率)을 조사(調査)하여 아황산(亞黃酸)가스가 수량(收量) 및 엽내(葉內) 류황(硫黃) 축적에 미치는 영향과 이들간의 관계(關係)를 규명하기 위해 실시한 실험(實驗)의 결과(結果)를 요약(要約)하면 다음과 같다. 1) 배나 수도(水稻) 공(共)히 대조지점(對照地點)에 비해 피해지점(被害地點)의 엽내(葉內) 류황함량(硫黃含量)이 높고 감수(減收)가 되는 경향을 보였다. 2) 배나 수도(水稻) 모두 엽내(葉內) 류황함량(硫黃含量)과 감수율간(減收率間)에는 매우 높은 유의상관(有意相關)을 보여 공해(公害)의 영향(影響)으로 감수(減收)가 된다는 것을 보여 주었다. 3) 류황산화물(硫黃酸化物)(SOx)을 주로 배출(排出)하는 공단주변(工團周邊)에 재배(栽培)되는 배나 수도(水稻)의 공해피해(公害被害)에 의한 보상(補償)을 위(爲)해서는 엽내(葉內) 류황함량(硫黃含量)과 실감수율(實減收率)과의 회귀식(回歸式)을 아황산(亞黃酸)가스 피해지(被害地)에서의 수량감수율(收量減收率) 조사(調査)에 참고(參考)함이 좋을 것으로 생각된다.

• 한국산학기술학회논문지
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• 제18권10호
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• pp.603-610
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• 2017

탄약을 포함한 다양한 산업 분야에서 사용되는 철강 재료는 부식에 취약하므로, 표면 그대로 사용하는 것은 바람직하지 않다. 따라서 도금, 도장, 화성처리와 같은 표면 처리 이후 사용하여야 하는데, 탄약 제조 과정에서는 주로 아연계 인산염 피막 처리가 사용되고 있다. 표면 처리 기법 중 하나인 아연계 인산염 피막은 금속 표면을 화학적으로 처리하여 안정성이 높은 화합물 층을 표면에 고착시키는 방법으로, 크게 도장 하지용 경인산염 피막과 부식 방지용 중인산염 피막으로 나뉘어지는데, 아연계 인산염 피막은 전산도, 철 함량과 같은 여러 가지 인자에 의해 피막의 품질과 내식성이 결정된다. 본 연구에서는 전산도 및 철 함량이 탄약 부식 방지 목적으로 사용되는 아연계 중인산염 피막의 중량 및 내식성에 미치는 영향에 대하여 알아보았다. 철 함량에 따라 피막의 구조가 치밀해지며, 내식성이 향상되는 결과를 확인할 수 있었으나, 전산도는 피막의 두께와 중량에만 영향을 주고 내식성에는 큰 영향을 주지 못하였다. 위 결과를 토대로 탄약 제조 과정에서 사용되는 인산염 피막 처리 공정의 최적 제어 수준을 제시하였다.