• 상하수도학회지
• /
• 제20권4호
• /
• pp.617-626
• /
• 2006

Compared with the sludge from gravity sedimentation, it is difficult for operations to settle the sludge occurred from dissolved-air-flotation (DAF). Even though there are some problems in treating DAF sludge with conventional gravity thickeners, those has been used until now. In this study, Solid Flux theory for gravity thickening was applied to the Solid Flux of DAF sludge through flotation in order to develop new methodology for treatment of DAF sludge. Also, characteristics of DAF sludge were investigated. From the experiment results, it was revealed that the higher the polymer dosage, at fixed the solid concentration, the greater the rising velocity becomes. When we applied solid flux theory, the relationship, which is similar to that of gravity thickening, has been achieved. Also, we could find the proper polymer dosage from the rising velocity is about 50 mg/L. Consequently, the limiting solid flux can be derived from the relationship between the total solid flux and the withdrawal velocity of DAF sludge. Furthermore, the factors, such as solid concentrations, bubble volume, pH, zeta potential, and temperature, have effects on the flotation and sedimentation for DAF sludge treatment.

• Journal of Welding and Joining
• /
• 제34권2호
• /
• pp.11-15
• /
• 2016

FE analyses for weldment of ship structure are required for various reasons such as stress concentration for bead tow, residual stress and distortion after welding, and hydrogen diffusion for prediction of low temperature crack. These analyses should be done by solid element modeling, but most of ship structures are modeled by shell element. If we are able to make solid element in the shell element FE modeling it is easily to solve the requirement for solid elements in weld analysis of large ship structures. As the nodes of solid element cannot take moments from nodes of shell element, these two kinds of element cannot be used in one model by conventional modeling. The PSCM (Perpendicular shell coupling method) can connect shell to solid. This method uses dummy perpendicular shell element for transferring moment from shell to solid. The target of this study is to develop a FE pre-processing system applicable at welding at ship structure by using PSCM. We also suggested glue-contact technique for controlling element numbers and element qualities and applied it between PSCM and solid element in automatic pre-processing system. The FE weldment modeling through developed pre-processing system will have rational stiffness of adjacent regions. Then FE results can be more reliable when turn-over of ship-block with semi-welded state or ECA (Engineering critical assessment) of weldment in a ship-block are analyzed.

• Journal of the Korean Wood Science and Technology
• /
• 제41권1호
• /
• pp.1-11
• /
• 2013

본 연구에서는 은수원사시나무의 산 당화공정에서 생성되는 고형 부산물의 화학적, 구조적 특성을 관찰하였다. 산 가수분해는 황산과 염산을 사용하였고, 1차 가수분해농도를 72%, 36%, 18%로 변화를 주었고, 2차 가수분해에서 4%로 동일하게 희석하였다. 가수분해 후 액상 가수분해액과 고형 부산물을 각각 분리하였고 고형 부산물을 각각 RS72, RS36, RS18, RC36, RC18이라고 하였다. 황산의 농도가 높아짐에 따라 생성된 고형부산물은 감소(71.2~21.4%)하였지만, 염산의 농도는 고형 부산물의 생성량(65.0~67.0%)에 큰 영향을 주지 않았다. 또한 RS36과 RS18은 고형 부산물 질량 대비 23.6%, RC36과 RC18은 각각 25.6%, 27.3%가 리그닌으로 이루어져 있었다. 고형 부산물의 열분해산물 분석 결과 Levoglucosan, Furfural 등 탄수화물 유래 물질과 리그닌 유래 물질인 Guaiacol, Syringol 등이 검출되었지만 RS72에서는 리그닌 유래 물질만이 검출되었다. 또한 열중량분석결과 고형 부산물 내 리그닌 함량이 높아질수록 다량의 탄이 생성되고 최대 중량 감소율이 감소하여 염산에 비해 황산이, 또한 산의 농도가 높을수록 화학적으로 축합된 구조를 형성하는 것을 확인하였다.

• 한국환경과학회지
• /
• 제19권9호
• /
• pp.1119-1127
• /
• 2010

The behavior of copper throughout the whole process of wastewater treatment plant that uses the activated sludge process to treat the wastewater of petrochemical industry that contains low concentration of copper was investigated. Total inflow rate of wastewater that flows into the aeration tank was $697\;m^3$/day with 0.369 mg/L of copper concentration, that is, total copper influx was 257.2 g/day. The ranges of copper concentrations of the influent to the aeration tank and effluent from the one were 0.315 ~ 0.398 mg/L and 0.159 ~ 0.192 mg/L, respectively. The average removal rate of copper in the aeration tank was 50.8 %. The bioconcentration factor (BCF) of copper by microbes in the aeration tank was 3,320. The accumulated removal rate of copper throughout the activated sludge process was 71.3%, showing a high removal ratio by physical and chemical reactions in addition to biosorption by microbes. The concentration of copper in the solid dehydrated by filter press ranged from 74.8 mg/kg to 77.2 mg/kg and the concentration of copper by elution test of waste was 2.690 ~ 2.920 mg/L. It was judged that the copper concentration in dehydrated solid by bioconcentration could be managed with the control of that in the influent.

• Journal of Radiation Protection and Research
• /
• 제22권4호
• /
• pp.243-250
• /
• 1997

공기 중의 라돈 농도를 측정하기 위한 고체비적검출기의 상대교정법을 개발하였으며, 상대 교정된 CN-85를 이용하여 15층 아파트 층 별로 실내 공기 중의 라돈 농도를 측정한 후 피폭 선량을 계산하여 보았다. 측정 결과 아파트 실내 공기 중에서의 라돈 농도는 대체적으로 상층으로 올라갈수록 감소하는 경향이 있었으나, 환기 횟수에 크게 영향을 받음을 알 수 있었다. 측정값의 평균은 $1.50{\pm}0.51pCi/1$ 였으며, 최대값과 최소값은 각각 $2.68{\pm}0.32pCi/l$, $0.69{\pm}0.16pCi/l$였다.

• Transactions on Electrical and Electronic Materials
• /
• 제2권4호
• /
• pp.24-29
• /
• 2001

GaN films were grown for various Mg doping concentrations in metal-organic chemical vapor deposition. Below the Mg concentration of 10$^{19}$ ㎤, the thermally annealed sample shows the compensated phase to n-type GaN in Hall measurement. In the MB concentration of 4$\times$10$^{19}$ ㎤ corresponding to the hole carrier concentration of 2.6$\times$1$^{19}$ ㎤ there exists a photoluminescence center of the donor and the acceptor pair transition of the 3.28-eV band. This center is correlated with the defects for a shallow donor of the $V_{Ga}$ and for an acceptor of $Mg_{Ga}$ . The acceptor level shows the binding energy of 0.2-0.25 eV, which was observed by the photon energy of the photocurrent signal of 3.02-3.31 eV. Above the Mg concentration of 4$\times$10$^{19}$ ㎤, both the Mg doping level and Mg concentration were saturated and there Is a photoluminescence center of a deep donor and an acceptor pair transition of the 2.76-eV blue band.

• 약학회지
• /
• 제36권6호
• /
• pp.563-569
• /
• 1992

The sorption and desorption properties of four different solid adsorbents were evaluated for the trace enrichment of ibuprofen from biological samples. Chromosorb 107 gave the highest dynamic adsorption coefficient. Among the organic solvents examined, acetone gave the highest desorption coefficient. Using the Chromosorb 107 column, the optimum elution volume of the eluting solvent was evaluated from the breakthrough curve of ibuprofen. The usefulness of Chromosorb 107 as the solid adsorbent and acetone as the eluting solvent was examined for the solid-phase extraction of ibuprofen from serum in the concentration range of $20{\sim}40\;{\mu}g/ml$.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2008년도 춘계학술대회논문집
• /
• pp.369-372
• /
• 2008

An experimental study is carried out to study two-phase vertically upward hydraulic transport of solid particles by water in a vertical and inclined (0${\sim}$60 degree) concentric annulus with rotation of the inner cylinder. Rheology of particulate suspensions in shear-thinning fluids is of importance in many applications such as particle removal from surfaces, transport of proppants in fractured reservoir and cleaning of drilling holes, and so on. Annular fluid velocities varied from 0.2 m/s to 1.5 m/s for the actual drilling operational condition. Macroscopic behavior of solid particles, averaged flow rate, and particle rising velocity are observed. Main parameters considered in this study were radius ratio, inner-pipe rotary speed, fluid flow regime, and particle injection rate. For both water and CMC solutions, the higher the concentration of the solid particles is, the larger the pressure gradients become

• 약학회지
• /
• 제36권2호
• /
• pp.120-125
• /
• 1992

Ths sorption and desorption properties of four different solid adsorbents were evaluated for the trace enrichment of diphenylhydantoin from biological samples. Graphitized carbon black(GCB) gave the highest adsorption coefficient. And among the organic solvents examined, methanol gave the highest desorption coefficient. Using the GCB column, the optimum elution volume of the eluting solvent was evaluated from the breakthrough curve of diphenylhydantoin. The usefulness of GCB as the solid adsorbent was examined for the solid-phase extraction of diphenylhydantoin from serum in the concentration range of $20-50\;{\mu}g/ml$.

• KSBB Journal
• /
• 제8권4호
• /
• pp.382-389
• /
• 1993

초산이온이 대장균 성장을 저해하는 현상을 규명 하기 위해서 M9 배지, LB 배지를 사용해서 플라스 크, 발효조 배양을 수행하였다. 대장균의 초산 생성 은 높은 포도당 초기 농도, LB 배지와 같은 복합 배 지에서 활발하였고, 플라스크 배양과 같은 pH 조절 이 되지 않는 배양방법에셔는 초산의 생성에 따른 pH 감소에 따라 세포성장이 많이 저해되었다. 초산 을 외부에서 첨가하여 세포성장에 마치는 영향을 조 사하여 보았는데 LB 배지를 사용한 플라스크 배양 에서는 첨가된 초산의 농도가 2g/l 이상, M9 배지 를 사용한 플라스크 배양에서는 초산의 농도가 4g/l 이상, 그리고 M9 배지를 사용한 발효조 배양에 셔는 8g/l 이상에서 초산의 성장 저해효과가 나타 다. LB 한천 배지를 볕에 깐 LB 액체 배지의 플라스 크 배양을 수행하였다. LB 한천의 양이 증가함에 따라서 한천에서 포도당의 방출이 일어나 최종 대장 균 세포 O.D.가 증가하였다.