• Environmental and Resource Economics Review
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• v.26 no.2
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• pp.173-203
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• 2017

The existence of rebound effect from road extension in Korea has been quantitatively verified using cross-sectional, time series data on four major cities - Seoul, Busan, Daegue and Incheon - between 2000 and 2013. The linear mixed effects model was constructed from six variables: total vehicle miles traveled (VMT), road extension, public transport users, gross regional domestic product (GRDP), regional population and fuel consumption. The main results can be summarized as VMT is positively correlated to road extension while negatively with public transport users. It indicates that the road extension-centered "supply-side" transportation policy induces "additional travel" and create "generated traffic" by enhancing driving efficiencies directly, or degrading other transport modes indirectly. Hence, the ultimate goal of road congestion reduction requires public transport-centered "demand management" rather than current supply-side policies.

• Membrane Journal
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• v.26 no.2
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• pp.126-134
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• 2016

To produce renewable biomethane from biogas, the properties of physical absorbents such as water, methanol, 1-methyl-2-pyrrolidone (NMP), poly(ethylene glycol) dimethylether (PEGDME), and propylene carbonate (PC) were studied, and PC was applied to membrane contactor systems. Among physical absorbents, PC exhibited a high contact angle of $58.3^{\circ}$ on polypropylene surface, and a PC/water mixture (5 wt%) increased the contact angle to $90^{\circ}$. Furthermore, the PC/water mixture presented higher $CO_2$ absorption capacities (0.148-0.157 mmol/g) than that of water (0.121 mmol/g), demonstrating a good property as an absorbent for membrane contactors. Actual operations in membrane contactors using the PC/water mixture resulted in $CO_2$ removal of 98.0-97.8% with biomethane purities of 98.5-98.3%, presenting a strong potential for biogas treatment. However, the PC/water mixture yielded moderate improved in $CO_2$ removal and methane recovery, as compared with water in the membrane contactor operation. This is originated from insufficient desorption processes to reuse absorbent and low $CO_2$ flux of the PC/water absorbent. Thus, it is requiring optimizations of membrane contactor technology including development of absorbent and improvement of operation process.

• Membrane Journal
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• v.28 no.5
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• pp.351-360
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• 2018

In this study, propylene/propane separation mechanism through NaY zeolite membrane was investigated. As permeation temperature increased, both propylene and propane permeances increased, saturated and decreased again, and a maximum selectivity was shown at around 50 to $60^{\circ}C$. Propane permeance in mixed gas experiment was much smaller than that in single gas experiment, and propylene/propane mixed gas selectivity was much larger than single gas permselectivity. As permeation time increased in transient permeation experiment, propylene permeance initially increased and saturated, while propane permeance decreased and saturated. All the experimental results announced that propylene/propane separation through NaY zeolite membrane was from preferentially adsorbed propylene molecules. The adsorbed propylene molecules efficiently prevented propane molecules from permeating through the membrane, and sufae diffused through the membrane. NaY zeolite capillary membrane prepared in the present study showed a high mixed gas selectivity of 12 and high propylene permeance of 497 GPU for a propylene/propane (89 : 11) mixture at $50^{\circ}C$ and 4 bar. Therefore, it was concluded that NaY zeolite membrane is one of promising membrane materials for propylene/propane separation due to the low cost and high separation performance.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2018.04a
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• pp.22-22
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• 2018

실고사리[Lygodium japonicum (Thunb.) Sw.]는 국내 자생하는 덩굴성 양치식물로 유인재배가 용이하여 실내 외 조경 및 관상소재로 활용이 가능하다. 한방에서는 전초를 해금사초, 포자를 해금사, 뿌리와 지하경을 해금사근이라 약재로 사용한다. 본 연구는 관상 및 약재로 이용이 가능한 실고사리의 대량생산을 위한 기내 외 번식방법을 개발하고자 수행되었다. 식물재료는 경상북도 의성군 일대에서 성체를 수집하여 청주의 일반하우스에 식재하여 성숙한 포자를 채취하였다. 포자를 기내 발아시켜 전엽체를 획득한 다음 8주 간격으로 계대하면서 연구의 재료를 확보하였다. 전엽체의 증식과 생육에 적합한 배지를 비교 하고자, 1/4, 1/2, 1, 2MS배지와 Knop배지를 조성하여 배양하였다. 배양방법은 전엽체 300mg을 메스로 균일하게 다져서 배양하는 방법을 이용하였으며, 배양환경은 온도($25{\pm}1.0^{\circ}C$), 광도($30{\pm}1.0{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$), 광주기(16/8h light/dark)로 조절되었다. 연구결과, 모든 처리구의 생체중은 초기접종량 보다 11배 이상 증가하였고, 그 중 1MS배지에서는 전엽체의 생체중이 7.3g으로 가장 많이 증가하였다. 뿐만 아니라, 형태형성도 우수하여 모두 정상적인 전엽체의 형태인 하트형으로 발달이 유도되었다. 전엽체로부터 포자체 형성을 유도하고자, 원예상토, 피트모스, 펄라이트 및 마사토의 혼합비율을 5종류로 달리하여 사각분($7.5{\times}7.5{\times}7.5cm$)에 혼합토양을 충진하였다. 전엽체 1g과 증류수 25mL를 핸드블랜더로 10초간 분쇄하여 사각분의 토양표면에 균일하게 분주하는 방법을 사용하였다. 이후 온도($25{\pm}1.0^{\circ}C$), 광도($43{\pm}2.0{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$), 광주기(16/8h light/dark), 습도($72{\pm}2.0%$)를 유지하면서 10주간 재배되었다. 연구결과, 원예상토 단용, 원예상토와 펄라이트 및 마사토가 2:1(v:v)로 혼합된 토양에서 각 498.0, 402.5, 482.5개의 포자체가 형성되어 사각분 면적대비 7.16개($cm^2$)가 생산되었다. 한편 포자체의 생육은 원예상토와 펄라이트가 2:1(v:v)로 혼합된 토양에서 생체중, 엽장, 엽폭, 근장 및 SPAD value 등이 우수하였다.

• Membrane Journal
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• v.33 no.6
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• pp.439-446
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• 2023

Ceramic membranes are generally used for various industrial processes operating under extreme conditions because of its high thermal and chemical stability. However, due to the trade-off phenomenon of permeability and mechanical strength, preparation of high permeability-high strength membrane is necessary. In this study, the change in characteristics and performances of ceramic membranes was analyzed depending on the type of polymer binder and its mixing ratio. Because the solubility between solvent and polymer binder was higher in PSf (polysulfone) than in PES (polyethersulfone), the viscosity and discharge pressure of the PSf-based dope solution were higher than those of PES-based dope solution. When PSf was used as a polymer binder, ceramic membrane showed high mechanical strength and low water permeability due to the dense structure. On the other hand, in case of PES, the mechanical strength was slightly reduced and the water permeability was increased. It was confirmed that the optimum mixing ratio of the PSf and PES with high water permeability and mechanical strength was 9:1.

• Journal of the Korean Society of Safety
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• v.28 no.4
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• pp.8-13
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• 2013

Fatigue crack growth tests were conducted on urban railway wheel steel under mode I and mixed-mode conditions. Fatigue crack growth rates were evaluated in terms of equivalent stress intensity factor ranges, using both the extended and projected crack lengths. The equivalent stress intensity factor range with the growth rate results obtained under mode I loading conditions can be used to predict the crack growth rate under mixed-mode loading conditions. Extended crack length rather than projected crack length is appropriate for the prediction of the crack growth rate under the mixed-mode loading conditions.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.5
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• pp.1234-1243
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• 1990

Double coaxial are jets(annular and coaxial air jets) between which propane gas is fed was selected to study the structure of diffusion flames in turbulent shear flow. Schlieren and direct photographs are taken to visualize the flame structure. Mean and fluctuating temperatures and ion currents were measured to investigate the macroscopic and the instantaneous flame structure. The objective of this study is to understand the interaction between combustion and mixing process especially in the transition region of turbulent shear flow. The investigation reported in this paper focuses on the macroscopic and the instantaneous structures of three flames obtained. The increased mixing effect resulting from increase of Reynolds number of central air jet makes the flame bluish and short. When the velocity of surrounding air stream is higher than that of central air jet, the instantaneous flame structure is composed of coherent structure. It is considered that the flame structure of transitional region of mixing layer depends on the structure of mixing layer of non-reacting conditions.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.324-324
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• 2010

핵융합의 고체형 증식(Helium Cooled Solid Breeder : HCSB) 블랑켓(Blanket Module)은 삼중수소 증식을 위해서 Li4SiO4, Li2TiO3, Li2O 및 Li2ZrO3 등의 페블이 고려되고 있다. 이러한 페블을 제조하기 위해서는 먼저 각각의 분말 제조가 선행되어야 한다. 한국의 Test Blanket Module(TBM)은 Li4SiO4 페블을 개발을 개발하여 사용할 예정이고 옵션으로 Li2TiO3 페블을 개발하는 것으로 되어 있다. Li4SiO4 페블을 개발하기 위해서 먼저 분말합성이 필수적이다. Li4SiO4 분말을 합성에 하기 위해서는 Lithium 금속염과 실리카 졸을 용매 및 폴리머 캐리어로서의 두 가지 기능을 하는 에틸렌글리콜에 첨가한 후 가열하여 완전히 용해시킨 후 혼합 용액을 건조시켜 겔형의 전구체를 제조한다. 이를 하소한 후 결정화시켜 Silicate 분말을 얻는데 이때의 건조, 하소 및 결정화 온도의 조건에 따른 분말의 크기 및 특성이 각각 다르다. 즉, 바인더 물질의 비율과 합성온도에 따라 특성이 약간씩 다른 분말을 얻을 수 있었다. 이렇게 얻어진 Silicate 분말은 지르코니아 볼을 이용하여 약 24 시간 동안 볼 밀링 과정을 통해 입도가 작은 미세한 Silicate 분말로 만들었다. 합성된 분말은 여러 가지 시험 및 분석을 통해서 검증되었으며, 불순물 등은 관찰되지 않았다.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.3
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• pp.67-75
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• 2019

The laminar burning velocity of endothermic fuel surrogates is measured in this study, in order to investigate combustion characteristics of aviation fuel after being used as coolant in an active cooling system of a hypersonic flight vehicle. A Bunsen burner was manufactured such that the laminar burning velocity can be taken for two types of surrogate fuels, SF-1 and 2. The results showed that the burning velocity of surrogate fuels was faster at high equivalence ratio conditions than that of the reference fuel (RF), and specifically, the velocity of SF-1 had the maximum value at the highest equivalence ratio compared with those of SF-2 and RF.

• Asia Marketing Journal
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• v.12 no.2
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• pp.135-154
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• 2010

This paper considers a duopoly where switching costs exist. The analysis proves that temporal price reductions can be pure strategy equilibrium where firms earn more profit than in a regular price strategy. Greater profits result from price discrimination in temporal price reductions. The equilibrium is contrasted with previous studies, which explain temporal price reductions as a result of mixed strategy. In a given model with an assumption about forming switching cost, firms can control their range of loyal consumers by properly setting their regular and promotional prices. The model shows that temporal price reduction tends to raise the regular price and decrease the range of loyal consumers.