• Resources Recycling
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• v.26 no.6
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• pp.20-28
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• 2017

The direct tensile strength of the mortar specimen containing pitch-based carbon fiber was ranged between 1/27~1/22 as compared to the average compressive strength of mortar. It was found that the direct tensile strength of the mortar containing the same amount of PAN-based carbon fiber was around 1/15. While the case of the control specimen without the carbon fiber was around 1/29. One the other hands, the flexural tensile strength of the mortar containing pitch-based carbon fibers was about 1/12 as compared to the average compressive strength. In case of the mortar specimen with PAN-based carbon fiber and control mortar were 1/10 and 1/13.5, respectively. The tensile performance of the mortar with pitch-based carbon fiber was found to be intermediate between control mortar and the reinforced mortar incorporated with the PAN-based carbon fiber.

• Korean Journal of Soil Science and Fertilizer
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• v.43 no.1
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• pp.105-112
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• 2010

Applications of plant residues and green manures generally improve the properties of soil under conventional farming system. Therefore, we investigated the improvement of selected soil physical properties, bulk density, porosity, and water content, soil penetration resistance, and soil microbial biomass carbon (SMBC) content as affected by different management practices: 1) conventional tillage without rice straw or green manure crop treatment (TNT, check plot), 2) no-tillage amended with rice straw (NTRS), 3) no-tillage amended with rye (NTR), 4) no-tillage amended with Chinese milk vetch (NTCMV), 5) no-tillage without rice straw or green manure crop treatment (NTNT), The values of bulk density, porosity, and water content ranged from 1.22 to 1.37 Mg $m^3$, from 48.3 to 54.0%, and from 35.0 to 40.2%, respectively. The management practices might positively influence the changes in the selected soil properties, especially in the second experimental year. The soil penetration resistance and SMBC content were also improved after applying rice straw and green manure crops as comparing with TNT. Therefore, applications of the rice straw and green manure crop management practices under no-tillage system positively influenced soil physical properties and soil microbial activities in paddy field.

• Journal of the Korean Institute of Gas
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• v.27 no.4
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• pp.85-91
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• 2023

In this study, an experimental study was conducted on the flame behavior, combustion dynamics, and NOx emission characteristics for hydrogen co-firing with the EV burner which is the first stage combustor of GT24. It was confirmed that as the hydrogen co-firing rate increases, the NOx emission increases. This change was elucidate to be the result of a combination of changes in penetration depth due to changes in fuel density, reduction in fuel mixing due to changes in flame position due to increased flame propagation speed, and oscillation of fuel mixedness due to combustion instability. Through pressurization tests in the range of 1.3 to 3.1 bar, NOx emission characteristics under high-pressure operating conditions were predicted, and based on this, the hydrogen co-firing limits of the EV burner was evaluated.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.324-324
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• 2013

자동차의 경량화 요구에 따라 비중이 큰 기존의 철계 금속재에서 비중이 낮은 알루미늄 합금 및 마그네슘 합금의 경량 금속 재료로 대체 적용하는 것이 요즘의 추세이다. 마그네슘 판재 성형의 경우 윤활제로 인한 마그네슘 판재의 부식이 발생할 수 있다. 이를 개선하기 위해 윤활제의 사용을 최소화 혹은 제로화가 가능하게 하는 진공 플라즈마 표면처리 기술이 시급하다. 본 연구는 무윤활 마그네슘 판재성형을 위한 금형 표면처리 기술로서 각각 질화처리, 비정질 탄소 코팅 공정기술에 관한 연구를 수행하였다. 플라즈마 질화처리는 기존의 질화방법에 비교하여 비교적 저온에서 짧은 시간에 표면에 백화현상이 발생하지 않는 대면적 플라즈마 질화공정 기술 구현이 가능하였으며, 비정질 탄소 코팅 공정은 모재와의 밀착력을 높이기 위한 공정 조건을 연구하였다. 각각의 표면처리된 금형을 이용하여 성형테스트를 실시하고 이 때의 마그네슘 판재의 성형성을 관찰하였다. 따라서 본 연구의 최종 목표는 무윤활 상태에서 마그네슘 판재가 성형이 가능한 금형 진공 표면처리 방법을 개발하는 것이다.

• Journal of the Korean Vacuum Society
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• v.18 no.1
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• pp.49-53
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• 2009

The chemical properties of SiOC film was studied for inter-layer insulator. SiOC film was formed with non polarity due to the appropriate union by the alkyl and hydroxyl group. An amorphous structure of non polarity can induce the low dielectric constant materials. The chemical properties of thin film can define the bonding structure owing to the ionic variation, and the analysis of chemical properties was researched by the carbon content using the FTIR spectra, and induced the film with non polarity. The electrical properties is the electron flow, and is always not the same as the chemical properties. The electrical properties of SiOC film with various flow rate ratios was analyzed and researched the correlation between the chemical properties. SiOC film showed the increasing of the leakage current after annealing process, and abruptly increased the carbon content at some samples. But the sample with increasing the carbon content decreased the leakage current. It means that the chemical properties is not the same as the electrical properties, and the carbon is related with the variation of the bonding structure, and does not contribute the current flow.

• 한국도로학회:학술대회논문집
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• 2009.11a
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• pp.545-548
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• 2009

• Korean Journal of Organic Agriculture
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• v.20 no.4
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• pp.503-518
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• 2012

Korean type of no-tillage cultivation method which was applied on this study used the ridge and the furrow and constantly recycling them as it was suitable for Korea's weather and farming conditions. This no-tillage cultivation was reported to have little negative impact such as reduction of production (Kwon et al., 1997). In addition, it was found to have a lot of benefits as it requires less agro-materials and energy costs as well as shortened working hours because tillage operation is not needed. (Yang et al., 2012). According to an analysis, no-tillage cultivation can reduce greenhouse gas emissions by $344.7kgCO^2$ (58%) in every 10a ($1,000m^2$) compared to ordinary pepper farming technique (Korea averages). Direct-indirect reduction effects from using fertilizer and using less amount of energy were 92% and 44% respectively both of which can be considered very high. Besides the direct effects of no-tillage cultivation, soil management using no-tillage technique raises carbon sequestration effect on soil as time goes on (West & Marland, 2002), that is why the technique is expected to have constant carbon emission reduction effect. For theses reasons, distribution and expansion of Korean type no-tillage cultivation are expected to play a role as major agro-green technologies for achieving our goal of reducing greenhouse gas emissions in agricultural sector.

• Clean Technology
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• v.18 no.4
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• pp.426-431
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• 2012

Carbon-rich coal can be utilized as a fuel for direct carbon fuel cell (DCFC). However, left-behind ash after the electrochemical oxidation may hinder the electrochemical reactions. In this study, we produced ash-free coal (AFC) by thermal extraction and then tested it as a fuel for DCFC. DCFC was built based on solid oxide electrolyte and the electrochemical performance of AFC mixed with $K_2CO_3$ was compared with AFC only. Significantly enhanced power density was found by catalytic steam gasification of AFC. However, an increase of the power density by catalytic pyrolysis was negligible. This result indicated that a catalyst activated the steam gasification reactions, producing much more $H_2$ and thus increasing the power density, compared to AFC only. Results of a quantitative analysis showed much improved kinetics in AFC with $K_2CO_3$ in agreement with DCFC results. A secondary phase of potassium on yttria-stabilized zirconia (YSZ) surface was observed after the cell operation. This probably caused poor long-term behavior of AFC with $K_2CO_3$. A thin YSZ (30 ${\mu}m$ thick) was found to be higher in the power density than 0.9 mm of YSZ.

• Proceeding of EDISON Challenge
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• 2013.04a
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• pp.111-124
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• 2013

Jianbo Wang의 그룹에서 최근 발표한 무촉매 분자 내 탄소-탄소 결합 형성 반응의 메커니즘을 계산 화학적으로 평가한다. 이 반응은 금속 촉매를 사용하지 않는다는 점과 Bio activity 를 갖는 Hydroxy-substituted Polycyclic Aromatic Compound (PAC)를 손쉽게 합성할 수 있다는 점에서 중요하다. Diazo moiety를 갖는 분자의 반응이 일반적으로 진행할 수 있는 세 가지 반응 경로가 제시되었고, DFT functional을 이용해 중간체 및 전이 상태에 대한 최적화 구조 및 에너지를 얻었다. 탄소-탄소 결합의 원천을 탐구하기 위해 Natural bond orbital charge calculation과 치환기 효과에 대한 계산이 수행되었다. 계산 결과, 중간체로 Triplet carbene을 형성하는 경로가 가장 불안정한 중간체를 형성했고, Tosylate가 해리되기 전 탄소-탄소 결합이 형성되는 경로가 가장 합리적인 반응경로임을 알 수 있었다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.6 s.237
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• pp.860-875
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• 2005

A new meshfree method for the analysis of elasto-plastic deformations is presented. The method is based on the proposed first-order least-squares formulation, to which the moving least-squares approximation is applied. The least-squares formulation for the classical elasto-plasticity and its extension to an incrementally objective formulation for finite deformations are proposed. In the formulation, the equilibrium equation and flow rule are enforced in least-squares sense, while the hardening law and loading/unloading condition are enforced exactly at each integration point. The closest point projection method for the integration of rate-form constitutive equation is inherently involved in the formulation, and thus the radial-return mapping algorithm is not performed explicitly. Also the penalty schemes for the enforcement of the boundary and frictional contact conditions are devised. The main benefit of the proposed method is that any structure of cells is not used during the whole process of analysis. Through some numerical examples of metal forming processes, the validity and effectiveness of the method are presented.