• 자원ㆍ환경경제연구
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• 제14권3호
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• pp.569-593
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• 2005

유럽배출권가래시장(EU ETS)과 Nord Pool에서 거래되고 있는 탄소배출권 가격자료를 이용하여 일물일가법칙 만족 여부를 검정하였다. 이를 위해 단위근 검정방법과 공적분 검정방법을 이용하였고, 인과성 분석, 충격반응분석과 분산분해 분석을 통해 두 시장간의 동태적 움직임을 분석하였다. 분석 결과 두 시장간 국제 배출권 가격 사이에는 일물일가의 법칙이 성립하며, EU ETS가 Nord Pool의 가격을 선도(lead)하고 EU ETS의 가격이 Nord Pool 가격의 움직임에 영향을 주는 것으로 분석되었다. 또한 Nord Pool은 자체 시장과 타 시장의 변동 모두에 큰 영향을 받는 시장인 반면, EU ETS는 외부의 충격에 큰 영향을 받지 않는 시장으로 분석되었다. 향후 유럽 지역에서의 배출권 시장이 EU ETS를 중심으로 통합되어 하나의 배출권 시장을 형성할 것으로 예측된다.

• 설비공학논문집
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• 제18권10호
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• pp.842-849
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• 2006

In this study, the effect of carbon nanotubes (CNTs) on boiling heat transfer is investigated. Three refrigerants of R22, R123, R134a, and water are used as base working fluids and 1% of CNTs by volume is added to the base fluids to study the effect of CNTs. All data are obtained at the pool temperature of $7^{\circ}C$ for all refrigerants and $100^{\circ}C$ for water in the heat flux range of $10{\sim}80\;kW/m^2$. Test results show that CNTs increase the boiling heat transfer coefficients for all fluids. Especially, large enhancement was observed at low heat flutes. With increasing heat flux, however, the enhancement was suppressed due to vigorous bubble generations. Fouling was not observed during the course of this study. Optimum quantity and type of CNTs and their dispersion should be examined for their application in pool boiling heat transfer.

• 한국습지학회지
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• 제25권4호
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• pp.417-425
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• 2023

생태계는 탄소순환에 있어 매우 중요한 탄소 저장고이다. 기후변화가 점점 심화됨에 따라, 생태계의 이러한 기능을 활용하여 기후변화를 완화하려는 노력들이 진행되고 있다. 본 연구에서는 국내 생태계를 대상으로 생태계 유형(산림, 농경지, 습지, 초지, 정주지) 및 탄소저장고별(지상부·지하부 생체량, 고사목, 낙엽, 토양유기탄소 및 생태계 전체) 탄소 저장 및 거동과 관련된 연구를 목록화 하고 분석하였다. 또한, 선행연구 결과를 모아 각 생태계 유형과 탄소저장고를 대상으로 탄소 저장 및 거동량의 평균값을 산정하였다. 그 결과, 대부분의(66%) 국내 탄소 저장·거동 관련 연구가 산림에서 수행된 것을 확인할 수 있었다. 산림에서 수행된 연구 결과를 토대로 탄소저장고별 저장량을 분석한 결과, 식생의 지상부(4,166.66gC m^-2)와 지하부(3,880.95gC m^-2)와 토양(4,203.16gC m^-2)에 많은 양의 탄소가 저장되어 있는 것을 확인하였다. 특히 산림 지하부에 많은 탄소가 저장되어 있는 것을 확인할 수 있었다. 다른 생태계 유형의 경우, 데이터의 제한으로 탄소저장고별 저장·거동량은 확인이 불가능하였다. 다만, 토양유기탄소 저장의 경우 산림과 초지의 데이터가 비교 가능하였는데, 두 생태계가 상대적으로 비슷한 탄소의 양을 저장하고 있는 것으로 나타났다(각각 4,203.16 gC m^-2, 4,023.23 gC m^-2). 본 연구를 통하여, 상대적으로 다양한 생태계 유형에서의 탄소 연구가 필요함을 확인할 수 있었다.

• Journal of Ecology and Environment
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• 제30권4호
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• pp.281-285
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• 2007

We conducted research to determine the effects of forest tending works (FTW) on forest carbon (C) storage in Korean red pine forests by estimating changes in the quantity and distribution of stored organic C in an approximately 40-year-old red pine stand after FTW. We measured organic C storage (above- and belowground biomass C, forest floor C, and soil C at 50 cm depth) in the Hwangmaesan Soopkakkugi model forest in Sancheonggun, Gyeongsangnam-do before and after the forest was thinned from a density of 908 trees/ha to 367 trees/ha. The total C stored in tree biomass was 69.5 Mg C/ha before FTW and 38.6 Mg C/ha after FTW. The change in total C storage in tree biomass primarily resulted from the loss of 19.9 Mg C/ha stored in stem biomass after FTW. The total C pool in this red pine stand was 276 Mg C/ha before FTW and 245.1 Mg C/ha after FTW. Prior to FTW, 71.5% of the total C pool was stored in mineral soil, 25.2% in tree biomass, and 3.3% in the forest floor, where as after FTW 80.5% of the total C pool was stored in mineral soil, 15.7% in tree biomass and 3.7% in the forest floor. These results suggest that the development of site-specific tending techniques may be required to minimize the loss of tree biomass C storage capacity in red pine stands from FTW.

• 한국태양에너지학회 논문집
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• 제29권5호
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• pp.35-44
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• 2009

In this study, boiling heat transfer coefficients(HTCs) and critical heat flux(CHF) are measured on a smooth square flat copper heater in a pool of pure water with and without carbon nano tubes(CNTs) dispersed at $60^{\circ}C$. Tested aqueous nanofluids are prepared using multi-walled CNTs whose volume concentrations are 0.0001, 0.001, 0.01, and 0.05%. For dispersion of CNTs, polyvinyl pyrrolidone(PVP) is used in distilled water. Pool boiling HTCs are taken from $10kW/m^2$ to critical heat flux for all nanofluids. Test results show that the pool boiling HTCs of the nanofluids are lower than those of pure water in entire nucleate boiling regime. On the other hand, critical heat flux is enhanced greatly showing up to 200% increase at volume concentration of 0.001% CNTs as compared to that of pure water. This is related to the change of surface characteristics by the deposition of CNTs. This deposition makes a thin CNT layer on the surface and the active nucleation sites of heat transfer surface are decreased due to this layer. The thin layer acts as the thermal resistance and also decreases the bubble generation rate resulting in a decrease in pool boiling HTCs. The same layer, however, maintains the nucleate boiling even at very high heat fluxes and reduces the formation of large vapor canopy at near CHF resulting in a significant increase in CHF.

• 한국주조공학회지
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• 제6권4호
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• pp.284-289
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• 1986

Decarburization phenomena have been studied by plasma in stainless steel, plain carbon steel and cast iron. It was also investigated the movement of impurity element P,S in the plasma jet metal pool. The plasma jet was obtained by $Ar\;-\;CO_2$ gas mixture with 5 kVA DC power source. It produced enough temperature to dissociate into activated oxygen atom by reaction of $CO_2{\leftrightarrows}CO+O^+$ and it reacted with ${\underline{C}}$ in metal pool. Decarburization rate was increased about 5 times in comparing with the conventional induction melted metal pool by $CO_2$ gas decarburization. Even under the Ar plasma jet, decarburization was obtained by agitation of metal bath by $Ar^+$ bombardment and dilution phenomena of carbon atom under the very high plasma temperature. But heavy element P and S are not much removed because they are too heavy in mass to be activated by $Ar^+$ion bombardment. Desulphurization was achieved by $Ar\;-\;CO_2$ plasma in plain carbon steel and cast iron by the reaction of $SO_2({\underline{S}}+O^+)$. But dephosphorization could not be obtained by $Ar\;-\;CO_2$ plasma, because gaseous reaction of phosphorous oxide (${\underline{P}}+O^+$) was not existed.

• Journal of Welding and Joining
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• 제31권6호
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• pp.71-76
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• 2013

Gas nitriding is a surface hardening process where nitrogen is introduced into the surface of a ferrous alloy. During fusion welding of nitrided carbon steel, the nitride inside weld metal is dissolved and generates nitrogen gas, which causes porosities - blow holes and pits. In this study, several laser welding processes such as weaving welding, two-pass welding, dual beam welding and laser-arc hybrid welding were investigated to elongate the weld pool to enhance nitrogen gas evacuation. The surface pits were successfully eliminated with elongated weld pool. However blowholes inside the weld metal were effective reduced but not fully disappeared.

• 한국화재소방학회논문지
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• 제19권3호
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• pp.58-63
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• 2005

등유 풀화재의 화염과 연소에 의해 생성되는 연기의 특성에 대해서 조사하였다. 다양한 발열량을 위해 직경을 변하게 할 수 있는 팬버너를 제작하였다. 풀화재를 조사하기 위해 화염 높이와 떨림 주파수를 분석하였다. 실험적으로 풀화염 높이는 이론적 상관관계 증가율과 잘 일치하지만, 정량적으로는 등유의 연소율에 기인하여 과대 평가된 값을 보인다. 연기의 특성을 조사하기 위해 세 가지의 실험방법을 사용하였다. 먼저 가스분석기를 이용하여 연소시 발생되는 주요 가스 농도를 측정하였는데 이산화탄소의 생성과 산소의 소모율은 풀화염의 열방출율에 비례하지만, 일산화탄소의 발생에 대한 경향성은 발견할 수 없었다. 연기의 매연입자를 광감쇄법과 TEM 이미지를 이용하여 특성을 조사하였다 연기밀도는 발열량의 증가에 따라 매우 급격히 증가하였고, 등유 풀화염에서 발생한 매연입자들은 자연적인 연소조건임에도 불구하고 역확산 제트화염에서 생성된 매연과 유사한 형태와 탄화정도를 보임이 관찰되었다.

• 한국안전학회지
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• 제20권3호
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• pp.105-111
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• 2005

An experimental study is performed for extinguishing of n-heptane pool fire by water mist containing potassium acetate as a fire suppression additive. Water mist was generated by a single pressure nozzle in a small-scale chamber. The drop size distribution of water mist was measured using laser diffraction(Malvern particle sizer). The flame temperature, oxygen concentration and carbon monoxide concentration were measured. In case of using additives, the fire extinguishing time was shorter than that of pure water at a given discharge pressure and it was because the momentum of a water droplet containing additives was increased. And also dissociated metal atoms, potassium, were reacted as a scavenger of the major radical species OH, H which were generated for combustion process. Moreover, at a high pressure of 4MPa, the fire was extinguished through blowing effect as well as primary extinguishing mechanisms.

• Design & Manufacturing
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• 제13권1호
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• pp.42-47
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• 2019

Nucleate boiling heat transfer is one of the most important phenomenon in the various industries. Especially, critical heat flux (CHF) refers to the upper limit of the pool boiling heat transfer region. Therefore, many researchers have found that CHF can be significantly increased by adding very small amounts of nanoparticles. In this study, the CHF and heat transfer coefficient were tested under the pool boiling state using copper and multi wall carbon nanotube nanoparticles. The results showed that two different types of nanoparticles deposited on the surface of two specimens made of the same material increased the heat flux in the nanoparticles with high conductivity, and there was no difference in the critical heat flux when the same material nanoparticles were deposited on the two different specimen surfaces.