• Fire Science and Engineering
• /
• v.24 no.5
• /
• pp.32-38
• /
• 2010

Multi-dimensional fire dynamics were studied numerically with the change in ventilation conditions in a full-scale ISO 9705 room. Fire Dynamic Simulator (FDS) was used for the identical conditions conducted in previous experiments. Flow rate and doorway width were changed to create over-ventilated fire (OVF) and under-ventilated fire (UVF). From the numerical simulation, it was found that the internal flow pattern rotated in the opposite direction for the UVF relative to the OVF so that a portion of products recirculated to the inside of compartment. Significant change in flow pattern with ventilation conditions may affect changes in the complex process of CO and soot formation inside the compartment due to increase in the residence time of high-temperature products. The fire behavior in the UVF created complex 3D characteristics of species distribution as well as thermal and flow structures. In particular, additional burning near the side wall inside the compartment significantly affected the flow pattern and CO production. The distribution of CO inside the compartment was explained with 3D $O_2$ distribution and flow patterns. It was observed that gas sampling at local positions in the upper layer were insufficient to completely characterize the internal structure of the compartment fire.

• Microbiology and Biotechnology Letters
• /
• v.34 no.3
• /
• pp.257-264
• /
• 2006

An aerobic submerged membrane bioreactor (MBR) treating ammonium wastewater was studied in respect of nitrification characteristics and distribution of nitrification bacteria over a period of 350 days. MBR was fed with ammonium concentration of 500-1000 mg $NH_4-N/L$ at a nitrogen load of $1-2kg\;N/m^3{\cdot}d$. Overall ammonium oxidation rate increased with dissolved oxygen (DO) concentration, temperature, and sludge retention time (SRT). Under a higher concentration of free ammonia ($NH_3-N$) due to the decrease of ammonium oxidation rate, the nitrite ratio ($NO_2-N/NO_x-N$) in the effluent increased. The sudden collapse of nitrification efficiency accompanied by sludge foaming and the increase of sludge volume index (SVI) was observed unexpectedly during the operation. At the later stage of operation, additional carbon source was fed to the MBR and resulted in twice higher value of SVI and the decrease of ammonium oxidation rate. In fluorescence in situ hybridization (FISH) analysis, genus Nitrosomonas which is specifically hybridized with probe NSM156 was initially the dominant ammonia oxidizing bacteria and the amount of Nitrosospira gradually increased. Nitrospira was the dominant nitrite oxidizing bacteria during whole operational period. Significant amount of Nitrobacter was also detected which might due to the high concentration of nitrite maintained in the reactor.

• Journal of the Korean Electrochemical Society
• /
• v.15 no.2
• /
• pp.74-82
• /
• 2012

Proton exchange membrane fuel cell performance is changed by the complicated physical phenomenon. In this study, water discharge performance of proton exchange membrane fuel cell were performed numerically to compare serpentine channel flow fields of 5-pass 4-turn serpentine and 25 $cm^2$ reaction surface between with and without sub-channel at the rib. Through the supplement of sub channel flow field, it is shown from the results that water removal characteristic inside channel improves because the flow direction of under-rib convection is changed into the sub channel. Reacting gases supplied from entrance disperse into sub channel flow field and electrochemical reaction occurs uniformly over the reaction surface. The results obtained that total current density distributions become uniform because residence time of reacting gases traveling to sub-channel flow field is longer than to main channel.

• Journal of the Korean Institute of Gas
• /
• v.14 no.5
• /
• pp.1-6
• /
• 2010

In this work, a numerical investigation is performed for the combustion chamber of domestic gas boiler with 1-stage and 2-stage heat exchangers. The fluid flow and heat transfer performance is simulated with a structure change of heat exchanger. The numerical solution shows that the heat transfer of the 2-stage heat exchanger is about 24% higher than that of the 1-stage heat exchanger, while the pressure loss of the 2-stage heat exchanger increases. The temperature of combustion chamber with 2-stage heat exchanger is lower than that of 1-stage. This effect reduces thermal NOx with decrease of high temperature staying time of the combustion gas.

• Analytical Science and Technology
• /
• v.5 no.1
• /
• pp.83-90
• /
• 1992

The $^{14}C$-warfarin used as rodenticids was identified from various organs of sprague dawley with scintillation counter. And the cytochrome p-450 which was induced by coumarin derivatives was identified with electrophoresis. The distributions of $^{14}C$-warfarin after $14.8{\mu}Ci/kg$ oral application at each organ was as follows; urine-7.5%, blood-0.44%, feces-0.9%, liver-0.66%, lung-0.86%, kidney-0.8%, heart-0.43% and spreen-0.33% after 24hrs. The cytochrome p-450 was purified by Octyl Sepharose CL-4B hydrophobic chromatography and isozymes were 50.8 Kd in control group, 53.3 Kd and 55.2 Kd in coumarin pretreated group and 50.8 Kd, 54.6 Kd and 57.7 Kd in warfarin pretreated group.

• 한국HCI학회:학술대회논문집
• /
• 2007.02b
• /
• pp.136-144
• /
• 2007

1990년대 후반까지 줄곧 광고 시장 점유율 1위를 차지하던 신문광고가 2001년을 기점으로 광고 시장 점유율의 지속적인 하락세를 보이고 있다. 이는 인터넷과 같은 경쟁적인 뉴미디어가 급격히 성장하는 데 그 원인이 있을 뿐만 아니라, 신문의 광고효과를 산출하는 과학적 방법론이 부족하다는 데에도 그 원인이 있다. 이러한 문제의식에서 출발하여, 본 연구에서는 안구운동 추적(eyetracking)을 활용하여 신문광고의 노출효과를 측정했다. 이를 위하여, 기존 신문 구독자의 인구통계학적 분포에 따라 추출된 50명의 표본을 대상으로, 신문의 면내 광고별 체류시간을 헤드 마운트형 안구운동 추적기(head-mounted eyetracker)를 활용하여 측정했다. 실험 결과, 데이터의 95%가 기존의 주의-기억 단계를 따르는 순차적인 정보처리모델과 스타치 구독률 조사(starch readership reports) 결과와 안구운동 추적 결과와 일치했다. 하지만, 5%의 데이터가 주의와 기억 단계의 차이에 기인한 이월 효과(carry-out)로 순차적인 정보처리모델과 일치하지 않는 것으로 나타났다. 즉 5%가량이 광고를 보지 않았음에도 봤다고 표시했다. 또한, 기존에 스타치 구독률 조사와 같은 재인 측정 방법을 통하여 간접적으로 측정하였던 기존의 신문 광고 노출율(보통 30%)에 비하여, 직접 측정한 결과 60%에 달하는 광고 노출율을 보였다. 이는 기존의 인식과 달리, 스타치 구독률 조사가 단순 노출 정도가 아니라, 응답자의 선택적인 기억 결과를 측정한 것임을 보여준다. 이로써, 안구운동 추적을 활용한 노출효과측정은 기존에 스타치 구독률 조사에서 놓치고 있는 부분을 보완할 수 있는 기법임을 보여준다. 또한 이 기법에 의하여 도출된 노출율은 60%에 달하여 기존의 약30%로 제시된 연구결과들이 실제로 측정기법의 한계로 인하여, 기억이 가지고 있는 왜곡을 그대로 반영한 노출율에 관한 자료를 쓰는 것으로 나타났다. 본 연구에서 제안된 노출효과 측정방법론은 기존의 왜곡된 데이터를 보완하고, 신문 광고 시장의 과학적인 측정기법을 발전시키는 데 의미 있는 기여를 할 것으로 기대한다.

• Journal of the Korean association of regional geographers
• /
• v.11 no.6
• /
• pp.517-529
• /
• 2005

Mt. Apsan is well known to be one of the most popular tourist sites around Daegu. Annually, more than 16 million persons visit Mt. Apsan. Although, in the mountain there are varieties of geomorphic and geological resources, there has been less concern to utilize the resources for geo-tourism. For example, there are about 10 valleys within Mt. Apsan and various landforms are scattered around the valleys. In this context, this study, based on field surveys centering around Gosangol valley, Anjiranggol valley and Dalbigol valley, focuses on exploring ways towards developing Mt. Apsan as an example geo-tourist site. The main findings are as follows: 1) The main landforms of Mt. Apsan include river cliff, cavern, free face, mud crack, ripple mark, fold, sheeting joint, talus, alluvial fan, pot hole, fault line, gnamma, columnar joint and metamorphic rock. 2) The guide notes on the landforms are developed. 3) In order to raise a learning effect of visitors on geomorphic resources, 9 nature trails are designed according to valleys and the length of visitor's stay.

• Journal of Korean Society of Environmental Engineers
• /
• v.37 no.5
• /
• pp.285-292
• /
• 2015

In this study, we were clearly identify the behaviour characteristics on particle size distribution of a condensing species by injection condition of HMDS (Hexa Methyl Di-Silazane, silica precursor that is one of liquid adsorbents) to remove condensing gaseous species as using pyroligneous liquor generated during carbonization process of biomass as precursor of condensing gaseous species. When using HMDS to remove the condensing gaseous species by growth machanism of particles, we could be controlled properly particles size such as amount of adsorbent injection, residence time, heating temperature and MFC flux. Especially, in case of using the silica precursor, in consideration of the physical and chemical properties of the boiling point, the specific gravity and the molecular weight, we found that the condensing species could be effectively controlled by particles granulation.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.2
• /
• pp.6-13
• /
• 2017

This study examines the effect of the type and number of orifices in an in-line mixer to improve the mixing performance and pressure loss. Recently, in-line non-power-consuming mixers have been increasingly used to complement mechanical mixers, which have a long dwell time, noise, excessive energy consumption, and high maintenance costs. An in-line mixer with an orifice for efficient mixing in water treatment was examined by numerical analysis using the commercial code FLUENT. The flow characteristics of pressure loss and velocity distribution within the mixer and the mixing efficiency were compared with and without the orifices. The CFD results show that the mixing efficiency was improved, but the pressure loss was increased by the in-line mixer with an orifice. A sensitivity study was also done on the principal parameters.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2018.05a
• /
• pp.449-449
• /
• 2018

최근 국내 하천과 호수에서 수온상승 및 기후변화로 인한 녹조발생이 빈번하게 나타남에 따라 녹조발생원인과 예측에 대한 중요성이 빠르게 인식되어가고 있다. 이에 본 연구에서는 보 구간의 연직 수온분포를 분석하고, 측정된 수온분포와 유해 남조류 세포수를 바탕으로 수체안정화도와 남조류의 발생을 비교하였다. 낙동강수계의 8개보를 선정하여 2015년 1월부터 2016년 12월까지 주 1회, 수심 1m 간격으로 측정한 수온을 분석했으며, 유해 남조류 세포수는 환경부 조류경보제 및 수질예보제에서 측정한 자료를 사용하였다. 수온 모니터링 분석 결과 2015년과 2016년 모두 5월 이후 수온성층이 형성되었고, 8월에 비교적 강한 수온성층이 형성되는 것으로 나타났다. 특히 칠곡보와 강정고령보에서 상대적으로 뚜렷하게 나타났는데 이는 수심이 깊고 체류시간이 긴 지형적 특성에 의한 것으로 판단된다. 형성된 수온성층은 안정된 상태로 지속되지 않고 주로 강우 시에 상 하층간의 수온구배가 줄어들어 혼합되는 전도현상이 관찰되었다. 수체안정화도 산정 결과 역시 2015년, 2016년 모두 수온성층 결과와 비슷하게 5월에 수체안정화도가 급증하다 9월 이후에 크게 감소하는 경향을 보였으며, index별로 Schmidt stability, Bouyancy Frequency 항목에서 이러한 경향이 뚜렷하게 나타났다. 또한 5월 이후 수체안정화도가 증가하는 시기에 남조류 세포수의 현존량도 증가하는 것으로 관찰되어 남조류의 발생과 수체안정화도의 증가는 시기적으로 일치하는 것으로 나타났다. 수체안정화도와 남조류 세포수와의 상관성은 2016년이 높았으며 그중 강정고령보에서 상관계수가 Schmidt stability는 0.78, Bouyancy frequency는 0.65로 높은 상관성을 나타내었다. 하지만 2015년의 경우 9월 이후 수체안정화도와 수온이 감소하였지만 남조류 세포수는 증가하여 경향이 일치하지 않는 것으로 나타났는데, 이는 저수온성의 남조류가 우점했기 때문인 것으로 판단된다. 향후 조류 발생 및 예측 등을 효과적으로 재현하는데 있어 자료로 활용하기 위해서는 지속적인 수질 모니터링 및 기상인자 모니터링이 필요할 것으로 판단된다.