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금속 촉매를 적용한 물의 subcritical 조건하에서 폐식용유의 가수분해공정에 대한 연구
김태하,( Md. Sufi Ullah Siddik Bhuyan ),송광현,신명철,이루리,최소아,서용찬,주영환 한국폐기물자원순환학회(구 한국폐기물학회) 2014 한국폐기물자원순환학회 춘계학술발표논문집 Vol.2014 No.-
화석연료의 고갈에 따른 대체 연료의 등장에 대한 필요로 인하여 바이오디젤에 대한 연구가 활발하게 진행되고 있다. 현재 바이오디젤의 원료로 일반적으로 사용되는 식물성 오일의 경우 식용 오일을 연료로 사용함에 따르는 도덕적 문제와 더불어 높은 원료 가격으로 인한 생산비용의 상승문제 등의 문제점이 지적되고 있다. 이러한 문제점을 해결하기위한 방법으로 사용후 버려지는 폐식용 오일을 이용한 바이오 디젤 생산에 대한 연구가 활발하게 진행되고 있다. 폐식용유내에 존재하는 유리지방산(FFAs ; Free Fatty acids)을 제거하기위한 별도의 고순도화 공정없이 폐식용유를 바이오디젤을 생산하는 원료로 곧바로 투입할 수 있는 기술중의 하나로 폐식용유를 물의 subcritical 조건(150℃<T<370℃,0.4<p<22Mpa)에서 가수분해시켜 FFAs (Free Fatty Acids)로 변환시킨후 에스테르화 반응을 통해 바이오디젤을 생산하는 기술이 최근 소개되고 있다. 이 공정의 경우 반응조건(온도 및 압력)이 실제 공정을 구현하기에 가혹하다는 문제점이 지적되고 있다. 따라서 본 연구에서는 폐식용유를 물의 subcritical 조건에서 가수분해 시키는데 있어서 다양한 금속 촉매들을 반응 공정에 적용함을 통해 반응 조건을 완화시킬 수 있는 방법을 제안하고자한다. 각각의 방법에서 생성된 FFAs 의 분석을 위하여 산가(Acid Value), 비누화가(Saponification Value)를 측정하였고 이를 통해 FFAs의 전환율을 구하였다. 또한 생산된 FFAs의 성분 분석을 위해 기체크로마토그래피(GC - FID) 분석을 실시하였다.
의사결정 집중화 수준과 불확실성이 실물옵션 활용에 미치는 영향에 대한 연구 : 국내 중소기업 클라우드 서비스 도입에 대한 연구
김태하,남승현,양희동 한국데이터전략학회 2017 Journal of information technology applications & m Vol.24 No.4
We question whether Korean IT managers consider real options to reduce risks of cloud service implementation. This work investigates the impact of technology risk, relationship risk, economy risk, security risk upon the intention of IT managers to utilize abandon & expansion options. We also analyze moderation effect of centralization level of decision making between these risks and the utilization of real options. Using the survey questionnaire, we empirically find that technology risk, relationship risk and security risk have significant effect upon abandon option and technology risk, relationship risk, and economy upon expansion option. We also find the evidence that centralization level moderates some risks and the direction of moderation effect is to offset the effect of risks on intention to utilize real options.
적응적 신호 크기 예측을 이용한 G.711 패킷 손실 은닉 알고리즘의 성능향상
김태하,이인성,Kim, Tae-Ha,Lee, In-Sung 한국음향학회 2015 韓國音響學會誌 Vol.34 No.5
본 논문에서는 G.711 패킷 손실 은닉 알고리즘의 성능향상을 위해 적응적 신호 크기 예측을 사용하는 패킷 손실 알고리즘을 제안한다. 기존의 방법은 연속 손실이 발생하였을 때 20 %의 감쇠인자를 가지고 이득조절을 수행하였다. 그러나 이 방법은 신호의 변화를 고려하지 않기 때문에 신호가 왜곡되는 경우가 발생한다. 따라서 Least Mean Square(LMS) 예측기를 사용하여 이전과 이후 프레임의 정보를 통한 적응적 신호 크기 예측으로 이득을 조절하는 것을 제안한다. 제안된 알고리즘의 성능 평가는 Perceptual Evaluation of Speech Quality(PESQ) 평가를 통하여 나타내었다. In this paper, we propose Packet Loss Concealment (PLC) method using adaptive signal scale estimation for performance improvement of G.711 PLC. The conventional method controls a gain using 20 % attenuation factor when continuous loss occurs. However, this method lead to deterioration because that don't consider the change of signal. So, we propose gain control by adaptive signal scale estimation through before and after frame information using Least Mean Square (LMS) predictor. Performance evaluation of proposed algorithm is presented through Perceptual Evaluation of Speech Quality (PESQ) evaulation.
Economic Evaluation of IT Investments for Emergency Management:A Cost-centric Control Model
김태하,이영재 한국데이터전략학회 2008 Journal of information technology applications & m Vol.15 No.3
In an emergency management case, evaluating the economic value of information technology investments is a challenging problem due to the effects of decision making, uncertainty of disasters, and difficulty of measurements. Risk assessment and recovery process, one of the major functions in emergency management, consists of (1) measurement of damages or losses, (2) recovery planning, (3) reporting and approving budgets, (4) auctioning off recovery projects to constructors, and (5) construction for the recovery. Specifically and of our interest, measurement of damages or losses is often a costly and time-consuming process because the wide range of field surveys should be performed by a limited pool of trained agents. Managers, therefore, have to balance accuracy of the field survey against the total time to complete the survey. Using information technologies to support field survey and reporting has great potential to reduce errors and lowers the cost of the process. However, existing cost benefit analysis framework may be problematic to evaluate and justify the IT investment because the cost benefit analysis often include the long-run benefit of IT that is difficult to quantify and overlook the impact of managerial control upon the investment outcomes. Therefore, we present an alternative cost-centric control model that conservatively quantifies all cost savings to replace benefits in cost benefit analysis and incorporate the managerial control. The model provides a framework to examine how managerial decision making and uncertainty of disaster affect the economic value of IT investments. The current project in Emergency Agency in South Korea is introduced as a case to apply the cost-centric control model. Our work helps managers to better evaluate and justify IT-related investment alternatives in emergency management.
김태하,박용철,이효진,김동화,박준건,김성준,이미연 한국환경과학회 2004 한국환경과학회지 Vol.13 No.12
Seasonal variation of biogeochemical characteristics was determined in Lake Shihwa from October 2002 to August 2003. When the lake was artificially constructed for the freshwater reservoir in 1988, the development of the strong haline density stratification resulted in two-layered system in water column and hypoxic/anoxic environment prevailed in the bottom layer due to oxidation of accumulated organic matters in the lake. Recently, seawater flux to the lake through the sluice has been increased to improve water quality in the lake since 2000, but seasonal stratification and hypoxic bottom layer of the lake still developed in the summer due to the nature of artificially enclosed lake system. As the lake is still receiving tremendous amount of organic matters and other pollutants from neighboring streams during the rainy summer season, limited seawater flux sluicing into the lake may not be enough for the physical and biogeochemical mass balance especially in the summer. The excess of accumulated organic matters in the bottom layer apparently exhausted dissolved oxygen and affected biogeochemical distributions and processes of organic and inorganic compounds in the stratified two-layered environment in the summer. During the summer, ammonia and dissolved organic carbon remarkably increased in the bottom layer due to the hypoxic/anoxic condition in the bottom layer. Phosphate also increased as the result of benthic flux from the bottom sediment. Meanwhile, dissolved organic carbon showed the highest value at the upstream area and decreased along the salinity gradient in the lake. In addition to the sources from the upstream, autochthonous origin of particulate organic carbon from algal bloom in the lake might be more important for sustaining aggravated water quality and development of deteriorated bottom environment in the summer. The removal of trace metals could be attributed to scavenging by strong insoluble metal-sulfide compounds in the hypoxic/anoxic bottom layer in the summer.