• Clean Technology
• /
• v.19 no.4
• /
• pp.355-369
• /
• 2013

Economic feasibility is one of the most important factors in energy production from regenerative biomass. From the aspect, biogas from anaerobic digestion of wastewater sludge is regarded as the most economical because of its cheap substrate and additional income from the disposal of waste sludge. Sludge hydrolysis has been regarded as the rate limiting step of anaerobic digestion and many sludge pre-treatment technologies have been developed to accelerate anaerobic sludge digestion for enhanced biogas production. Various sludge pre-treatment technologies including biological, thermo hydrolysis, ultrasonic, and mechanical methods have been applied to full-scale systems. Sludge pre-treatment increased the efficiency of anaerobic digestion by enhancing hydrolysis, reducing residual soilds, and increasing biogas production. This paper introduces the characteristics of various sludge pre-treatment technologies and the energy balance and economic feasibility of each technology were compared to prepare a guideline for the selection of feasible pre-treatment technology. It was estimated that thermophilic digestion and thermal hydrolysis were most economical technology followed by Cell rupture$^{TM}$, OpenCEL$^{TM}$, MicroSludge$^{TM}$, and ultrasound. The cost for waste sludge disposal shares the biggest portion in the economic analysis, therefore, water content of the waste sludge was the most important factor to be controlled.

• Polymer(Korea)
• /
• v.26 no.3
• /
• pp.344-352
• /
• 2002

In this work, two thermal cationic latent catalysts, i.e., triphenyl benzyl phosphonium hexafluoroantimonate (TBPH) and benzyl 2-methylpyrazinium hexafluoroantimonate (BMPH) were newly synthesized. And the thermal and mechanical properties of difunctional epoxy (diglycidylether of bisphenol h, DGEBA) resins initiated by 1 phr of either TBPH or BMPH catalyst were investigated. As experimental results, the epoxy/TBPH system showed higher curing temperature and critical stress intensity factor ($K_{IC}$) than those of epoxy/BMPH. This could be interpreted in terms of slow thermal diffusion rate and bulk structure of four phenyl groups in TBPH. However, the decomposed activation energy determined from Coats-Redfern method was lower in the case of epoxy/TBPH. This result was probably due to the fact that broken short chain structure was developed by steric hindrance of TBPH.

• Journal of the Korean earth science society
• /
• v.43 no.2
• /
• pp.265-282
• /
• 2022

This study analyzes the impact of long-range transport of biomass burning emissions from northeastern China on the concentration of particulate matter of diameter less than 10 ㎛ (PM₁₀) in Korea using the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem). Korea was impacted by anthropogenic emissions from eastern China, dust storms from northern China and Mongolia, and biomass burning emissions from northeast China between April 4-and 7, 2020. The contributions of long-range PM₁₀ transport were calculated by separating biomass burning emissions from mixed air pollutants with anthropogenic emissions and dust storms using the zeroing-out method. Further, the radiation energy budget over land and sea around the Korean Peninsula was analyzed according to the distribution of biomass burning emissions. Based on the WRF-Chem simulation during April 5-6, 2020, the contribution of long-range transport of biomass burning emissions was calculated as 60% of the daily PM₁₀ average in Korea. The net heat flux around the Korean Peninsula was in a negative phase due to the influence of the large-scale biomass burning emissions. However, the contribution of biomass burning emissions was analyzed to be <45% during April 7-8, 2020, when the anthropogenic emissions from eastern China were added to biomass burning emissions, and PM₁₀ concentration increased compared with the concentration recorded during April 5-6, 2020 in Korea. Furthermore, the net heat flux around the Korean Peninsula increased to a positive phase with the decreasing influence of biomass burning emissions.

• Composites Research
• /
• v.26 no.3
• /
• pp.189-194
• /
• 2013

This paper deals with the study of mechanical properties and impact energy absorbed by composites, made by using thermoplastic and thermoset as matrix, flax fiber and nanoclay as reinforcements. The nanoclay was sprayed on the fiber laminate directly after mixing with ethanol. This experiment designed by Taguchi method and have variable factors, i.e three types of fiber direction(F), three different nanoclay wt%(N) and three spray gun hole shapes(S). According to these conditions, composites were made and the optimum conditions were found to be F1N3S1, F1N2S1, F1N2S1 and F3N2S1 for thermoplastic, and F1N3S2, F1N3S2, F1N2S2 and F3N2S1 for thermoset which were matched with tensile strength, modulus, total impact absorbed energy and heat release rate respectively.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.13 no.1
• /
• pp.43-46
• /
• 2010

As one of the methods for recycling the FRP used for the small and medium-sized waste ships, separation of the roving layer from the mat has some merit in a sense of the recycling energy and the environmental effects. Similar characteristics between the roving and the mat make the mechanically automatic differentiation difficult. They, however, contain different ratio of the resin and the glass and the thickness. In this study photo physical differentiation between the two layers has been made using (1) boiling concentrated sulfuric acid which can dissolve the resin in the FRP layer and (2) hydrogen fluoride(HF) solution which can reacts with $SiO_2$ fragments of the glass. Furthermore coloring the FRP sample with water-soluble dye following the HF treatment makes the roving layer more distinguishable photophysically. The implementation of HF treatment has been successfully tested in this study.

• Composites Research
• /
• v.30 no.6
• /
• pp.371-378
• /
• 2017

In this study, hygroelastic behavior of thermosetting epoxy is predicted by molecular dynamics simulations. Since consistent exposures to humid environments lead to macroscopic degradation of polymer composite, computational simulation study of the hygroscopically aged epoxy cell is essential for long-time durability. Therefore, we modeled amorphous epoxy molecular unit cell structures at a crosslinking ratio of 30, 90% and with the moisture weight fraction of 0, 4 wt% respectively. Diglycidyl ether of bisphenol F (EPON862) and triethylenetetramine (TETA) are chosen as resin and curing agent respectively. Incorporating equilibrium and non-equilibrium ensemble simulation with a classical interatomic potential, various hygroelastic properties including diffusion coefficient of water, coefficient of moisture expansion (CME), stress-strain curve and elastic modulus are predicted. To establish the structural property relationship of pure epoxy, free volume and internal non-bond potential energy of epoxy are examined.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.19 no.4
• /
• pp.322-331
• /
• 2016

Oil budget calculator identifies the removal pathways of spilled oil by both natural and response methods, and estimates the remaining oil required response activities. A oil budget calculator was newly developed as a response tool for Deepwater Horizon oil spill incident in Gulf of Mexico in 2010 to inform clean up decisions for Incident Comment System, which was also successfully utilized to media and general public promotion of oil spill response activities. This study analyzed the theoretical background of the oil budget calculator and explored its future application to Korea. The oil budge calculation of four catastrophic marine pollution incidents indicates that 3~8% of spilled oil was removed mechanically by skimmers, 1~5% by in-situ burning, 4.8~16% by chemical dispersion due to dispersant operation, and 37~56% by weathering processes such as evaporation, dissolution, and natural dispersion. The results show that in-situ burning and chemical dispersion effectively remove spilled oil more than the mechanical removal by skimming, and natural weathering processes are also very effective to remove spilled oil. To apply the oil budget calculator in Korea, its parameters need to be optimized in response to the seasonal characteristics of marine environment, the characteristics of spilled oil and response technologies. A new algorithm also needs to be developed to estimate the oil budget due to shoreline cleanup activities. An oil budget calculator optimized in Korea can play a critical role in informing decisions for oil spill response activities and communicating spill prevention and response activities with the media and general public.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.15 no.1
• /
• pp.47-53
• /
• 2012

As one of the methods for recycling the FRP from the waste ships, separation of roving layer from the mat has some merits in a sense of the eco-friendly and economical recycling process. Similar characteristics, however, between the roving and the mat even with different ratio of the resin and the glass and the thickness of the roving, much thinner than the mat, make the mechanically automatic differentiation difficult. In this study spectrochemical differentiation between the two layers has been made using boiling concentrated sulfuric acid, methanol and isopropanol solution saturated with KOH, or hydrogen fluoride (HF) solution. Furthermore efficiently coloring water-soluble dye following the HF treatment makes the roving layer more distinguishable photophysically. The layer differentiation and the automatic layer distraction move up the date of simple and automatic separation process for the waste FRP.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.8 no.4
• /
• pp.1-13
• /
• 2005

In the process of a hydrology circulation, evapotranspiration is considered a very important factor to build a plan for the development of water resources and to operate water resources system. This study purposes to estimate daily potential evapotranspiration quantity in consideration of energy factors of the surface by using spatial information such as Landsat TM (ETM+) data, DEM and Landcover. Kyounan-cheon, Han River is selected as a target area, and landcover is divided by vegetation and non-vegetation covered area. Penman-Monteith equation which considers leaf-area index is used to estimate potential evapotranspiration quantity of vegetation covered area. The combination method (energy burget and aerodynamic method) is used in non-vegetation covered area. Among the input data for estimating potential evapotranspiration, NDVI, SR and Albedo is formed by Landsat, TM and ETM+ from 1986 through 2002. ground heat flux is estimated by using NDVI distribution map, LAI distribution map is drawn by using SR distribution map. The result of estimation shows that the average potential evapotranspiration in the whole basin is about 1.8-3.2mm/day per each cell. THe results of estimating potential evapotranspiration quantity by each landcover are as follows; water surface 3.6-4.9mm/day, city 1.4-3.1mm/day, bareland 1.4-3.5mm/day, grassland 1.7-3.7mm/day, forest 1.7-3.0mm/day and farmland 1.8-3.6mm/day. The potential evapotranspiration quantity is underestimated in comparison with observed evaporation data by evaporation pan, but it is considered that it has physical propriety.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 1999.10a
• /
• pp.1-2
• /
• 1999

시간과 공간의 구애를 받지 않는 양질의 음성, 화상, 문자정보의 교환을 위한 노력으로 디지털 휴대폰과 휴대용 컴퓨터가 등장하면서 음성과 문자정보의 교환분야에 커다란 진보를 이룩하였다. 그러나 현재는 휴대폰이 음성정보에 문자정보교환이 추가된 상황이기 때문에, 아직도 관련 정보교환기술 및 기기개발이 진행되고 있다. 앞으로 휴대폰과 휴대용 컴퓨터의 기능을 통합하고 화상정보까지 결합된 휴대용 정보기기를 위해서는 전자회로의 집적화 및 통신속도 증대가 필수적이다. 또한 이들 휴대용 정보기기를 구동시키기 위한 전력도 증가될 것으로 예측되기 때문에, 현재 전원으로 사용되는 2차전지보다 에너지 밀도가 더욱 증패된 전지가 요구될 것으로 예상된다. 그리고 내연기관의 배기에 의해 발생되는 환정오염문제를 해결하기 위한 방법중의 일환으로 전기자동차 개발이 진행되고 있으며, 이들 전기자동차에 2차전지를 장착하기 위해서 경제성이 있고, 고속충전이 가능하고, 안전성이 높은 고에너지 밀도의 2차 전지 개발이 요구되고 있다. 현재 2차전지는 음극재료나 양극재료에 따라 낚축전지, 니켈/카드륨(Ni/Cd) 전지, 니켈/수소(Ni/MH) 전지, 라륨 2 차전지등이 있으며, 전극재료의 고유특성에 의해 전위와 애너지 밀도가 결정된다. 특히 리튬 2차전지는 리튬의 낮은 산화환원전위와 분자량으로 인해 에너지 밀도가 높기 때문에 앞에서 언급한 휴대용 전자기기의 구동전원으로 많이 사용되고 있다. 리튬 2차전지는 음극 재료가 금속리튬인 경우는 리튬금속으로, 탄소재료인 경우는 리튬이온이라 하며, 한편으로 전해질이 고체 고분자이거나 혹은 역체 유기용매와 리튬염을 고분자와 혼성시킨 겔(gel)인 경우는 고분자로, 전해짙이 리튬염이 전리되어 있는 유동성 액체일 경우는 고분자를 생략하여 구분하고 있다. 즉 리튬금속 2 차전지(LB), 리튬이온 2 차전지(LIB), 리튬금속 고분자 2차전지(LPB), 리튬 이온 고분자 2차전지(LIPB)로 크게 구분된다. 금속리듐을 음극으로 사용하고 전해질로는 리튬염이 전리되어 있는 액체유기용매 를 사용한 리튬금속 2차전지는, 금속리튬전극이 충방전 과정을 반복하면서, 전리된 리튬이 균일하게 산화환원되지 못하고 표변에서 양극방향으로 성장하는 수지상 (dendrite) 현상으로 인해 안전성 확보에 문게가 있었다. 리튬과 알루미늄 합금형태로 음극에 사용한 동전형 전지는 상용화 되었지만, 이러한 단점을 개선하기 위해 리튬이온이 금속으로 석활되는 환원반응전위보다 높은 전위에서 전극재료가 충전되면서 리튬이온이 저장되고, 방전되면서 배출되는 탄소를 음극재료로, 그리고 리튬이온이 충방 전시 가역적으로 삼입 탈리되는 층상의 리튬금속산화물을 양극으로 구성하고, 엑체 전해질과 다공성 고분자 분리막을 사용한 것이 LIB이다. LIB에서 리튬이온의 이동이 가능한 액체전해질의 가능을 고분자 전해질이 대신함으로서 보다 높은 안정성을 확보 한 전지가 LIPB 이다. 또한 고분자 전해질을 사용한 경우 금속리튬상에서의 수지상 성장이 저하되는 현상이 관찰됨으로서, 이론용량이 3,860mAh/g 에 달하는 리튬금속 혹은 합금을 고분자 전지에서 음극으로 사용하고자 하는 2 차전지가 LPB 이다. 리튬 2차전지는 비록 1989년 액체전해질을 사용한 금속리튬 2차전지의 실패전력을 안고있지만 궁극적으로는 이론적으로 최대의 에너지밀도를 가지고 있는 LPB를 지 향할 것으로 예상되지만 가까운 장래에 실현되기는 어려울 것이다. 따라서 향후의 라튬 2차전지의 전개방향은 현재의 LIB를 고분자 전해질을 채용하는 LIPB로 진행시커면서 저가의 전극재료개발을 지속적으로 추진할 것으로 예상된다. 현재 리튬 2차전지는 소형전지에 국한되고 있지만 전기자동차나 전력저장용으로 이를 대형화시커기 위해서는 열적특성이 우수하고 저가인 전극재료개발이 선행되야하기 때문에, 저가의 탄소재료와 코발트산화물을 대신할 수 있는 철, 망칸 또는 니켈산 화물의 개발이 필요하다.