• Carbon letters
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• 제12권1호
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• pp.44-47
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• 2011

Activated carbon fibers (ACFs) were prepared from cost effective commercial textiles through stabilization, carbonization, and subsequently activation by carbon dioxide. ACFs were characterized for surface area and pore size distribution by physical adsorption of nitrogen at 77 K. ACFs were also examined for various surface characteristics by scanning electron microscopy, Fourier transform infrared spectroscopy, and CHNO elemental analyzer. The prepared ACFs exhibited good surface textural properties with well developed micro porous structure. With improvement in physical strength, the commercial textile grade acrylic precursor based ACFs developed in this study may have great utility as cost effective adsorbents in environmental remediation applications.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2015년도 춘계 학술논문 발표대회
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• pp.243-244
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• 2015

This paper presents a Stochastic Long-Term Maintenance Costs Estimating Method for the Apartment Housing (SLCE). A simulation approach is used for generating the stochastic long-term maintenance cost, and it is based on the defined variability in repair cycle of the individual maintenance elemental within the process. SLCE provides the probability distribution of the budget required to maintain the apartment housing. A case study is presented to demonstrate and to validate the system.

• 한국건설관리학회논문집
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• 제1권1호
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• pp.63-71
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• 2000

건설공사비의 총액을 산정하기 위한 예비 견적은 위험의 정도를 감수하고 있다. 즉 대형 건설공사의 경우 오랜 기간에 걸쳐 수행되어지며 공종에 따른 공사기간별로 초기 계획단계보다 실행견적가에 미달하는 위험과 관련하여 발생되어진다. 이는 신뢰성 있는 유사비용데이터 수집의 어려움과 데이터의 수가 절대적으로 부족할 뿐만 아니라 이러한 수집된 비용데이터 조차도 건설공사의 특성을 충분히 반영하지 못하기 때문이다. 또한 통산 비용산정방법에 있어서 기존에 주로 활용되는 확정론적 비용평가는 다수의 불확실성을 띄고 있는 건설공사의 특수성을 반영하지 못하고 있다. 따라서 국내의 비용평가시 다루어지지 않고 있는 비용의 확률적 개념을 도입함으로서 비용의 위험도를 측정하고 비용요인들간의 상관성과 부위별 비용특성을 반영하여 견적시 과대 과소의 오차합계를 최소화하기 위한 방법을 제시하고자 한다. 여기서 위험도는 예비견적비가 실제 발주자 집행 실행견적가 보다 적게 될 확률로서 정의하고 본 방법의 제시에 따른 사례의 적용을 통해 객관적 인 검증을 연구의 목적으로 한다. 연구의 방법은 첫 번째, 비용 데이터로부터 직접적으로 위험도를 평가하는 통계학적 방법과 두 번째, 몬테칼로 시뮬레이션 방법을 이용하여 비용데이터로부터 간접적으로 위험도 평가방법을 제안하고자한다. 몬테칼로 시뮬레이션 방법은 단위 요소비용의 분포특성과 비용상관성으로부터 총비용의 확률분포를 생성하여 신뢰성 있는 비용 데이터의 확장과 해석이 가능한 방법으로 실제상황에 접근된 위험도 평가가 가능할 것이다.

• Carbon letters
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• 제15권2호
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• pp.105-112
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• 2014

Wastewater from textile industries is a major cause of water pollution in most developing countries. In order to address the issues of water pollution and high cost for treatment processes, the use of an inexpensive and environmentally benign adsorbents has been studied. The objective was to find a better alternative to the conventional methods. Lemon grass waste (ash) collected from a lemon grass stream distillation subunit in Bhutan was tested for dye removal from aqueous solutions. The study investigated the removal of methylene blue using the following operational parameters: initial concentration (100-600 mg/L), contact time, adsorbent dose (0.1-0.55 gm/100 mL), and pH (3-10). It was found that the percentage removal of dye increased with a decrease of the initial concentration and increased contact time and dose of adsorbent. The basic pH solution of dye showed better adsorption capacity as compared to the acidic dye solution. Langmuir and Freundlich adsorption isotherms were fitted to the data well. Data fitted better to Lagergren pseudo 2nd order kinetics than a 1st order kinetic model. Surface morphology was also examined via scanning electron microscopy. An elemental analysis was also carried out and the chemical composition and functional groups were analyzed using energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy techniques, respectively. The obtained results indicate that lemon grass ash could be employed as a low cost alternative to commercial activated carbon in wastewater treatment for the removal of dyes.

• 에너지공학
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• 제12권2호
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• pp.65-73
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• 2003

국내의 HAPs(Hazardous Air Pollutants)중 수은은 아직까지 관심의 대상이 아니지만 머지않아 문제가 될 것으로 예측된다. 본 논문에서는 현재 국내외의 배가스 수은 배출현황과 처리기술에 대해 요약하였다. 미국을 중심으로 구미 각국에서는 대기분야의 연구개발이 수은에 집중되고 있다. 수은 제어 프로그램은 크게 두 가지로 방향을 잡고 있다. 하나는 기존의 WFGD(Wet Flue Gas Desulfurization)를 이용하여 수은을 산화시켜 제거하는 방법이며 다른 하나는 수은 제거효율이 높은 활성탄 또는 다른 novel sorbent (low-cost sorbent)를 사용하는 방법이다. 선진국에서는 2007년에 발전소 수은 제거설비 설치가 의무화 될 것이다. 본 논문에서 제공하는 자료는 국내에서 발전소 수은 규제가 시작될 때 효과적으로 적용될 수 있을 것이다.

• Journal of Microbiology and Biotechnology
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• 제30권1호
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• pp.136-145
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• 2020

Chlorella sp. HS2, which previously showed excellent performance in phototrophic cultivation and has tolerance for wide ranges of salinity, pH, and temperature, was cultivated heterotrophically. However, this conventional medium has been newly optimized based on a composition analysis using elemental analysis and ICP-OES. In addition, in order to maintain a favorable dissolved oxygen level, stepwise elevation of revolutions per minute was adopted. These optimizations led to 40 and 13% increases in the biomass and lipid productivity, respectively (7.0 and 2.25 g l^-1d^-1 each). To increase the lipid content even further, 12 h heat shock at 50℃ was applied and this enhanced the biomass and lipid productivity up to 4 and 17% respectively (7.3 and 2.64 g l^-1d^-1, each) relative to the optimized conditions above, and the values were 17 and 14% higher than ordinary lipid-accumulating N-limitation (6.2 and 2.31 g l^-1d^-1). On this basis, heat shock was successfully adopted in novel Chlorella sp. HS2 cultivation as a lipid inducer for the first time. Considering its fast and cost-effective characteristics, heat shock will enhance the overall microalgal biofuel production process.

• 한국재료학회지
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• 제18권3호
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• pp.153-158
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• 2008

Fe-aluminides have the potential to replace many types of stainless steels that are currently used in structural applications. Once commercialized, it is expected that they will be twice as strong as stainless steels with higher corrosion resistance at high temperatures, while their average production cost will be approximately 10% of that of stainless steels. Self-propagating, high-temperature Synthesis (SHS) has been used to produce intermetallic and ceramic compounds from reactions between elemental constituents. The driving force for the SHS is the high thermodynamic stability during the formation of the intermetallic compound. Therefore, the advantages of the SHS method include a higher purity of the products, low energy requirements and the relative simplicity of the process. In this work, a Fe-aluminide intermetallic compound was formed from high-purity elemental Fe and Al foils via a SHS reaction in a hot press. The formation of iron aluminides at the interface between the Fe and Al foil was observed to be controlled by the temperature, pressure and heating rate. Particularly, the heating rate plays the most important role in the formation of the intermetallic compound during the SHS reaction. According to a DSC analysis, a SHS reaction appeared at two different temperatures below and above the metaling point of Al. It was also observed that the SHS reaction temperatures increased as the heating rate increased. A fully dense, well-bonded intermetallic composite sheet with a thickness of $700\;{\mu}m$ was formed by a heat treatment at $665^{\circ}C$ for 15 hours after a SHS reaction of alternatively layered 10 Fe and 9 Al foils. The phases and microstructures of the intermetallic composite sheets were confirmed by EPMA and XRD analyses.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
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• pp.21-24
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• 2004

Structural performance of the seismic devices made by steel bar and high performance fiber reinforced cement composites(HPFRCCs) was experimentally observed. These dampers will be applied for reducing damage as well as seismic response. The advantages of the HPFRCCs damper is selective structural performance, strength, stiffness, and ductility by changing configuration, bar arrangements and type of materials used. The experimental results indicate that elemental ductility is much increased with decreasing damage when the HPFRCCs are applied to the damper. It means cementitious damper for structural control is available which has much merit in performance and cost.

• 국제학술발표논문집
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• The 1th International Conference on Construction Engineering and Project Management
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• pp.956-961
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• 2005

Delay, cost overrun and inferior quality in public works are common in Nepal and Cambodia. Almost 90 percent of the civil construction engineers working in the industry were one-degree graduates without appropriate training. The civil engineering education had provided elemental engineering knowledge to the graduates however integrated engineering and management knowledge and skill are essential for efficient infrastructure development. ODA in developing countries had been concentrated in hard infrastructure development without improving the quality of higher education. Integrating ODA to engineering education system would help develop qualified technical manpower and appropriate technology domestically, and improve the efficiency in infrastructure development in developing countries.

• Elastomers and Composites
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• 제58권1호
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• pp.44-56
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• 2023

Additive manufacturing (AM) or three-dimensional (3D) printing of metals has been drawing significant attention due to its reliability, usefulness, and low cost with rapid prototyping. Among the various AM technologies, fused deposition modeling (FDM) or fused filament fabrication is receiving much interest because of its simple manufacturing processing, low material waste, and cost-effective equipment. FDM technology uses metal-filled polymer filaments for 3D printing, followed by debinding and sintering to fabricate complex metal parts. An efficient binder is essential for producing polymer filaments and the thermal post-processing of printed objects. This study involved an in-depth investigation of and a fabrication route for a novel multi-component binder system with steel alloy powder (45 vol.%) ranging from filament fabrication and 3D printing to debinding and sintering. The binder system consisted of polyvinyl pyrrolidone (PVP) as a binder and thermoplastic polyurethane (TPU) and polylactic acid (PLA) as a carrier. The PVP binder held the metal components tightly by maintaining their stoichiometry, and the TPU and PLA in the ratio of 9:1 provided flexibility, stiffness, and strength to the filament for 3D printing. The efficacy of the binder system was examined by fabricating 3D-printed cubic structures. The results revealed that the thermal debinding and sintering processes effectively removed the binder/carrier from the cubic structures, resulting in isotropic shrinkage of approximately 15.8% in all directions. The scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) patterns displayed the microstructure behavior, phase transition, and elemental composition of the 3D cubic structure.