• KSBB Journal
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• 제4권1호
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• pp.11-14
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• 1989

Tower fermentor를 이용한 연속 알콜발효에서 cell re-cycle과 aeration에 대한 영향을 검토하였다. 균주는 floc-culationg 효모인 Saccharomyces cerecisiae TS4를 를 사용하였다. 15% glucose를 사용한 cell recycle system의 연속 알콜발효에서 cell 농도는 50%/1였고, ethanol productiv는 26.4g EtOH/l-hr로서 cell농도가 가장 높은 값을 나타내었으며, aeration rate는 3.8$\times$ $10^-^3$ VVM이상부터는 ethanol pro-ductivity가 감소하였다.

• 한국음향학회지
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• 제40권5호
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• pp.439-451
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• 2021

본 논문에서는 실제 환경에서의 연속 음성 강화를 위한 딥러닝 기반 온라인 빔포밍 알고리듬과 스펙트럼 감산을 결합한 빔포머를 제안한다. 기존 빔포밍 시스템은 컴퓨터에서 음성과 잡음을 완전히 겹친 방식으로 혼합하여 생성된 사전 분할 오디오 신호를 사용하여 대부분 평가되었다. 하지만 실제 환경에서는 시간 축으로 음성 발화가 띄엄띄엄 발성되기 때문에, 음성이 없는 잡음 신호가 시스템에 입력되면 기존 빔포밍 알고리듬의 성능이 저하된다. 이러한 효과를 경감하기 위하여, 심층 학습 기반 온라인 빔포밍 알고리듬과 스펙트럼 감산을 결합하였다. 잡음 환경에서 온라인 빔포밍 알고리듬을 평가하기 위해 연속 음성 강화 세트를 구성하였다. 평가 세트는 CHiME3 평가 세트에서 추출한 음성 발화와 CHiME3 배경 잡음 및 MUSDB에서 추출한 연속 재생되는 배경음악을 혼합하여 구성되었다. 음성인식기로는 Kaldi 기반 툴킷 및 구글 웹 음성인식기를 사용하였다. 제안한 온라인 빔포밍 알고리듬 과 스펙트럼 감산이 베이스라인 빔포밍 알고리듬에 비해 성능 향상을 보임을 확인하였다.

• 한국물환경학회지
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• 제25권6호
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• pp.922-934
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• 2009

The transport of contaminants and spatial variation in a deep reservoir are certainly governed by the thermal structure of the reservoir. There has been continuous efforts to utilize three-dimensional (3D) hydrodynamic and water quality models for supporting reservoir management, but the efforts to validate the models performance using extensive field data were rare. The study was aimed to evaluate a 3D hydrodynamic model, ELCOM, in Daecheong Reservoir for simulating heat fluxes and stratification processes under hydrological years of 2001, 2006, 2008, and to assess the impact of internal wave on the reservoir mixing. The model showed satisfactory performance in simulating the water temperature profiles: the absolute mean errors at R3 (Hoenam) and R4 (Dam) sites were in the range of $1.38{\sim}1.682^{\circ}C$. The evaporative and sensible heat losses through the reservoir surface were maximum during August and January, respectively. The net heat flux ($H_n$) was positive from February to September, while the stratification formed from May and continued until September. Instant vertical mixing was observed in the reservoir during strong wind events at R4, and the model reasonably reproduced the mixing events. A digital low-pass filter and zero crossing method was used to evaluate the potential impact of wind-driven internal wave on the reservoir mixing. The results indicated that most of the wind events occurred in 2001, 2006, 2008 were not enough to develop persistent internal wave and effective mixing in the reservoir. ELCOM is a suitable 3D model for supporting water quality management of the deep and stratified reservoirs.

• 상하수도학회지
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• 제8권2호
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• pp.43-52
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• 1994

In this paper, the unit processes in the typical water treatment plant, which need to be expanded because the water demand is over the existing water treatment capacity in the near future, were carefully examined to upgrade the water treatment plant. The models were installed in the fields as a distorted model based upon the hydraulic similitudes. The models having the constant discharge ratio in the unit processes between the model and the prototype were installed as two units to compare the treatment efficiencies. The capacity of the individual unit, which is a model of the prototype of $250,000m^3/day$ capacity, was $24m^3/day$. In the mixing and flocculation experiments, the mixing intensity of flocculators G was selected as the main experimental item. The optimal mixing intensities G, which are 65/sec for experimental discharge of $1m^3/hr$ and 85/sec for experimental discharge of $1.3m^3/hr$, are identified based upon the comparison the relative turbidity removal efficiencies. Also, the outlet weir loading was selected as the main experimental item in the sedimentation process. Through the continuous experiments with the main experimental items of the mixing intensity of flocculators G and the outlet loading of the weir in the sedimentation basin, about 20% upgrading compared to the existing water treatment capacity was obtained.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2001년도 추계학술발표회
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• pp.27-30
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• 2001

Flow and transport at fracture intersections, and their effects on network scale transport, are investigated in three-dimensional random fracture networks. Fracture intersection mixing rules complete mixing and streamline routing are defined in terms of fluxes normal to the intersection line between two fractures. By analyzing flow statistics and particle transfer probabilities distributed along fracture intersections, it is shown that for various network structures with power law size distributions of fractures, the choice of intersection mixing rule makes comparatively little difference in the overall simulated solute migration patterns. The occurrence and effects of local flows around an intersection (local flow cells) are emphasized. Transport simulations at fracture intersections indicate that local flow circulations can arise from variability within the hydraulic head distribution along intersections, and from the internal no flow condition along fracture boundaries. These local flow cells act as an effective mechanism to enhance the nondiffusive breakthrough tailing often observed in discrete fracture networks. It is shown that such non-Fickian (anomalous) solute transport can be accounted for by considering only advective transport, in the framework of a continuous time random walk model. To clarify the effect of forest environmental changes (forest type difference and clearcut) on water storage capacity in soil and stream flow, watershed had been investigated.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제30회 춘계학술대회논문집
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• pp.339-342
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• 2008

PSP는 산소��칭원리에 의해 모델표면의 전역적 압력정보를 측정할 수 있는 기법이다. 본 연구는 자유류 마하수 2.5에서 수직 제트 분사와 Cavity를 이용한 스크램제트의 연소실 내부에서의 공기와 연료의 혼합 특성을 알아보기 위해 PSP를 사용하여 표면압력을 측정하였다. 그 결과 Cavity의 크기가 커질수록 공기-연료의 혼합정도가 커지는 것을 알 수 있었다.. 또한 CFD와 압력공을 이용하여 측정 압력값을 비교하였다. 그 결과 충격파의 형태 및 전단경계층의 두께 변화 등의 정성적 결과가 모두 일치하였으며, 압력측정 결과 약간의 오차는 발생하였으나 3D Bow Shock이 위치한 지점에서의 압력 및 Vorticity가 크게 나타나는 경향성이 모두 일치하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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• pp.11-16
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• 2002

The production of Portland cement involves maximum use of resources and energy, which leads to destruction of tile ecological environment, raising in serious environmental issues such as acid rain and the greenhouse effect. In order to combat the arising problems associated with Portland cement, it thus is necessary that a non-clinker cement should be developed. In this study, non-clinker cement is produced by blending granulate blast furnace slag with phosphogypsum as main materials, and small amounts of hydrate lime or waste lime as activators. This paper aims to investigate compressive strength according to various condition of mixing ratio, blame, W/C ratio and curing temperature. Compressive strength of non-clinker cement increases continuously according to increase in curing age and blain. Although the compressive strength is fairly comparable to that of OPC in the early curing age, it reaches a higher lever in the later age than that of OPC due to the optimum mixing ratio and the continuous reaction of slag and phosphogypsum. Results obtained from this study have shown that non-clinker cement could be used as a replacement of OPC.

• Environmental Engineering Research
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• 제23권1호
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• pp.76-83
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• 2018

Spatial moment analysis has been performed on the concentration of the first species in a multispecies solute transport in porous media. Finite difference numerical technique was used in obtaining the solute concentration. A constant continuous source of contaminant was injected at the inlet of the domain. Results suggest that the decaying of solute mass increases as the magnitude of mean fluid velocity increases. The dispersion coefficient is highly time dependent under decaying of solutes with a complex behavior of mixing of solutes. The solute mobility and mixing varies non-linearly with time during its initial period, while the same ceases with higher decay rates of the first species much faster.

• 소성∙가공
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• 제8권3호
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• pp.271-271
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• 1999

A concentration change during grade transition operation in thin slab casting is investigated through computer simulation and the results are compared with experimental measurements. Fluid flow and mixing patterns in various tundish levers and flow rates were analysed by a three-dimensional mathematical model. Based on the contained results, a simple, efficient and accurate computational model is suggested to predict the concentration profile at the outlet of the tundish. Based on the model, mixing in and below the mold was analyzed considering electromagnetic braking force. The predicted concentration profiles show good agreements with the measured values. It is found that the lower vortices in the mold are suppressed by the electromagnetic field and a plug-like flow region develops, which decreases the intermixing of two different grades of steel and shortens the length of transition region.

• 자원리싸이클링
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• 제6권1호
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• pp.17-22
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• 1997

미립의 자성/비자성 입자의 혼합분체로부터 자성 입자만을 연속적으로 분리할 수 있는 전자석 유동층이 제안되었고 본 선별기에 의해 분리된 입자분중 자성 분율에 대한 공탑 가스유속, 혼합분체내 자성 입자의 분율(=100-비자성 입자의 분율) 및 전자석으로 공급되는 전류 세기와 같은 조업변수의 영향이 규명되었다. 전자석 유동층에 의한 자성 분리는 미립의 혼합분체내 자성입자에 작용하는 전자서의 자력이 분체를 유동화시키는 가스흐름으로 인한 유체력보다 클 때 가능함이 밝혀졌다.