• Journal of the korean society of oceanography
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• 제35권1호
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• pp.16-33
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• 2000

In order to measure the vertical fluxes of particles and reactive radionuclides such as thorium and polonium isotopes, Dunbar-type sediment traps were freely deployed at the Ulleung Basin and in warm and cold water masses around the polar front of the East Sea. We estimated the ratios of the catched (F) to the predicted $^234$Th fluxes (P) using natural tracers pair $^234$Th-$^238$U. The F/P ratios are decreased with increasing water depth. Whereas the concentrations of suspended particles are homogeneous in water column, the mass fluxes are also decreased with increasing water depth like the F/P ratios. These facts indicate that organic matters of settling particles are destructed within the euphotic layer due to decomposition. Whereas regenerations of sinking particles are negligible in the cold water mass, about 80% of them are regenerated in the warm water mass during falling of large particles. These downward mass fluxes are closely correlated with their primary productions in euphotic zone. The activities of $^234$Th, $^228$Th and $^210$Po in the sinking material were increased with water depth. Because $^234$Th steadily produced in the water column are cumulatively adsorbed on the surface of sinking particles, vertical $^234$Th fluxes were observed to increase with water depth. Therefore, these sinking particles play important roles in transporting the particle reactive elements like thorium from surface to the deep sea. The scavenging processes including adsorption and settling reactions generate radio-disequilibrium between daughter and parent nuclides in water column. The activity ratios of $^234$Th/$^238$U and $^228$Th/$^228$Ra were observed to be < 1.0 in the surface water and approached to be equilibrium below the thermocline. The extent of the deficiency of daughter nuclides compared to the parents nuclide was highly correlated with the vertical particle flux. Because most of the $^210$Po in the surface water are scavenged on a labile phase and are recycled at sub-surface depths (< 200 m), the $^210$Po are always observed to be excess activities compared to $^226$Ra in surface water.

• 한국자동차공학회논문집
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• 제23권2호
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• pp.199-207
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• 2015

Solid materials of ammonia sources with SCR have been considered for the application of lean NOx reduction in automobile industry, to overcome complex problems of liquid urea based SCR. These solid materials produce ammonia gas directly with proper heating and can be packaged by compact size, because of high volumetric ammonia density. Among ammonium salts and metal ammine chlorides, calcium ammine chloride was focused on this paper due to low decomposition temperature. In order to make calcium ammine chloride in lab-scale, simple reactor and glove box was designed and built with ammonium gas tank, regulator, and sensors. Basic test conditions of charging ammonia gas to anhydrous calcium chloride are chosen from equilibrium vapor pressure by Van't Hoff plot based on thermodynamic properties of materials. Synthetic method of calcium ammine chloride were studied for different durations, temperatures, and pressures with proper ammonia gas charged, as a respect of ammonia gas adsorption rate(%) from simple weight calculations which were confirmed by IC. Also, lab-made calcium ammine chloride were analyzed by TGA and DSC to clarify decomposition step in the equations of chemical reaction. To understand material characteristics for lab-made calcium ammine chloride, DA, XRD and FT-IR analysis were performed with published data of literature. From analytical results, water content in lab-made calcium ammine chloride can be discovered and new test procedures of water removal were proposed.

• Korean Chemical Engineering Research
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• 제55권6호
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• pp.854-860
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• 2017

본 연구에서는 di-(2-ethylhexyl)-phosphoric acid (D2EHPA)와 carbon nanotubes (CNTs)를 polysulfone (PSf)에 고정화시켜 PSf/D2EHPA/CNTs 비드를 제조하였으며, 제조한 비드에 의한 Sr(II)의 제거특성을 살펴보았다. Scanning electron microscopy (SEM), Fourier transform infrared spectrometer (FTIR) 및 Thermo gravimetric analysis (TGA) 분석을 통하여 PSf/D2EHPA/CNTs 비드의 형태적 특성들을 조사하였다. PSf/D2EHPA/CNTs 비드에 의한 Sr(II)의 제거는 운전시간 60 min 정도에서 평형에 도달하였으며, 속도 실험결과는 유사 2차 속도식에 잘 부합하는 것으로 나타났다. 또한 PSf/D2EHPA/CNTs 비드에 의한 Sr(II)의 제거에서 Langmuir 식으로부터 구한 최대 제거량은 4.75 mg/g이었다. PSf/D2EHPA/CNTs 비드에 의한 Sr(II)의 제거효율은 추출제 D2EHPA 만을 사용하는 경우보다 CNTs를 첨가함으로써 Sr(II)의 제거량이 2.5배 정도 향상되는 결과를 보였다.

• 한국식품저장유통학회지
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• 제12권1호
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• pp.54-61
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• 2005

건조분말두부의 열풍, 진공 및 동결 건조방법에 따른 흡습특성과 평형수분함량 예측의 회귀식을 도출하였다. 단분자층 수분함량은 GAB식이 더 높은 유의성을 보였으며 수분흡습을 위한 엔탈피, 자유에너지, 엔트로피의 변화는 큰 차이는 없었으나 수분활성도가 0.11에서 0.93으로 증가할수록 흡습엔탈피의 값은 감소하였으며 등온흡습곡선의 경우 수분활성도가 증가할수록 수분함량이 높아졌으며 수분 활성도가 높을수록 필요로 하는 흡습에너지가 낮아져 흡습이 쉽게 이루어짐을 알 수 있다. 평형수분함량 예측은 수분 활성도를 독립변수로 평형수분함량을 종속변수로 하여 3차 회귀분석을 하였고, 건조방법에 관계없이 5, 15, $25^{\circ}C$ 온도조건에서 모두 결정계수가 0.98이상의 높은 값을 보였다. 등온흡습곡선의 적합도가 가장 높은 모델은 Caurie, Oswin, Henderson 순이였으며, 결정계수(R-square)값이 $0.94\~0.99$이상으로 높은 적합도를 나타내었으며 편차도는 Oswin식이 낮은 편차를 나타내었으며, 동결건조의 경우에는 Caurie식이 가장 낮은 편차를 나타내었다.

• 한국환경과학회지
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• 제11권3호
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• pp.241-246
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• 2002

One of the Musty and earthy smell compounds in raw water is generally attributed to 2-methylisoborneol (2-MIB). It is well known that activated carbon and oxidants such as $O_3$, Cl $O_2$, are effective ways to control 2-MIB. In isotherm equilibrium experiments, 2-MIB in distilled water was much more adsorbed to the activated carbon(A/C) than raw water containing dissolved organic carbon (DOC). The Freundlich constants(k) of distilled water and raw water were 3.36 and 0.049, and 1/n values were 0.80 and 0.42, respectively. The 2-MIB residual rate were Y = $e^{-0}$.55x/~ $e^{-0}$.54x/ with Ozone( $O_3$) dose by 5 minutes contact time at the 241 and 353 ng/L initial concentrations. The 2-MIB residual rate were Y = $e^{-0}$.32x/~ $e^{-0}$.35x/ with Chlorine dioxide(Cl $O_2$) dose by 15 minutes contact time at the 89 and 249 ng/L initial concentrations. 2-MIB was decreased from 1911 ng/L to 569ng/L by post-ozonation(70%removal efficiency) and removal efficiencies of 2-MIB by the following 4 kinds Granular Activated Carbon(GAC) process such as coal base, coconut base, wood base and zeolite＋carbon base were 95.8, 89.5, 88.4, and 93.7% respectively.ely.

• 한국지하수토양환경학회지:지하수토양환경
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• 제19권6호
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• pp.72-79
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• 2014

Cavitation generated by ultrasonic irradiation can enhance the diffusional transport of organic contaminants from soil surfaces or pores. Therefore, ultrasound soil washing can be an alternative of traditional soil washing process. In this study, soil was artificially contaminated with n-tetradecane, n-hexadecane and phenanthrene. A plate type ultrasonic reactor at 25 kHz frequency and 1000W power was used for laboratory soil washing experiments. Ultrasonic soil washing efficiency was compared with those of traditional soil washing using mechanical mixing. Various operational parameter such as soil/liquid ratio, irradiation time, particle size, and soil organic matter content was tested to find out the optimum condition. It was found that ultrasonic soil washing demonstrates better performance than mechanical soil washing. Optimum soil:liquid ratio for ultrasonic soil washing was 1 : 5. Desorption of organic contaminants from soils by ultrasonic irradiation was relatively fast and reached equilibrium within 10 minute. However, decrease in the soil particle sizes by ultrasonic irradiation results in re-adsorption of contaminants to soil phase. It was also observed that soil particle size distribution and soil organic matter content have significant effects on the efficiency of ultrasonic soil washing.

• 공업화학
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• 제34권2호
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• pp.199-205
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• 2023

Arsenic is a highly toxic element, and its contamination is widespread around the world. The natural materials with high selectivity and efficiency toward pollutants are important in wastewater treatment technology. In this study, the mesoporous synthetic hectorite was synthesized by facile hydrothermal crystallization of gels comprising silica, magnesium hydroxide, and lithium fluoride. Additionally, the naturally available clay was modified using zirconium at room temperature. Both synthetic and modified natural clays were employed in the removal of arsenate from aquatic environments. The materials were fully characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), and Fourier transform-infrared (FT-IR) analyses. The synthesized materials were used to remove arsenic (V) under varied physicochemical conditions. Both materials, i.e., Zr-bentonite and Zr-hectorite, showed high percentage removal of arsenic (V) at lower pH, and the efficiency decreased in an alkaline medium. The equilibrium-state sorption data agrees well with the Langmuir and Freundlich adsorption isotherms, and the maximum sorption capacity is found to be 4.608 and 2.207 mg/g for Zr-bentonite and Zr-hectorite, respectively. The kinetic data fits well with the pseudo-second order kinetic model. Furthermore, the effect of the background electrolytes study indicated that arsenic (V) is specifically sorbed at the surface of these two nanocomposites. This study demonstrated that zirconium intercalated synthetic hectorite as well as zirconium modified natural clays are effective and efficient materials for the selective removal of arsenic (V) from aqueous medium.

• Applied Biological Chemistry
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• 제17권3호
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• pp.219-234
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• 1974

인산고정능(燐酸固定能)이 대단(大端)히 큰 것으로 알려진 제주도(濟州道) 화산회토양(火山灰土壞)에서 시용인산(施用燐酸)의 동태(勳態)를 파악(把握)코저 재배년수(栽培年數)가 다른 감귤원(柑橘園)에서 채취(探取)한 토양(土壤)에 대(對)하여 인산(燐酸)의 분별정량(分別定量)을 행(行)하고 각(各) 토양인산(土壤燐酸)의 축적형태(蓄積形態), 그의 토심(土深)에 따른 변화(變化) 및 이들에 영향(影響)을 미치는 토양(土壤)의 이화학적(理化學的) 성질(性質)과의 관계(關係)를 비교검토(比較檢討)함과 아울러 인산흡착실험(燐酸吸着實驗)을 행(行)하여 인산흡착(燐酸吸着)에 대(對)한 등온흡착식(等溫吸着式) 및 인산시용량(燐酸施用量) 결정기준(決定基準)인 인산흡수계수(燐酸吸收係數)에 대(對)한 검사(檢討)를 하였던 바 다음과 같은 결과(結果)를 얻었다. 1. 무기인산(無機燐酸)의 분별정량(分別定量)을 Chang & Jackson 법(法)에 의(依)하여 행(行)한 결과 형태별(形態別) 함량(含量)은 Water-soluble p

• 공업화학
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• 제25권5호
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• pp.520-525
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• 2014

본 연구에서는 기존 에폭시수지에 에폭시 콩기름(Epoxidized soybean oil : ESBO)과 실란처리 되어진 실리카가 첨가된 에폭시 접착제의 접착특성에 대하여 고찰하였다. 실리카의 표면처리는 실란커플링제인 ${\gamma}$-methacryloxy propyl trimethoxy silane (MPS), ${\gamma}$-glycidoxy propyl trimethoxy silane (GPS), 그리고 ${\gamma}$-mercapto propyl trimethoxy silane (MCPS)을 사용하였다. 실리카 첨가 에폭시 접착제의 표면특성과 구조특성은 scanning electron microscope (SEM)과 Fourier transform infrared spectroscopy (FT-IR)을 이용하여 관찰하였으며 T-peel 시험법에 의한 접착특성은 universal testing machine (UTM)를 이용하여 분석하였다. 실란처리에 따른 실리카의 평형 확산압력, 표면자유에너지, 비표면적은 BET법을 이용한 $N_2$/77 K 기체 흡착을 통하여 관찰하였다. 결과로서, 에폭시 접착제의 접착박리강도는 미처리에 비해 접착제 내 실란처리된 실리카가 함유됨에 따라 증가하였다. 이러한 결과는 실란커플링제가 에폭시 접착제의 분산을 증가시키는 중요한 역할이라고 판단된다. 그리고 MCPS로 실란처리한 에폭시 접착제의 경우 GPS와 MPS에 비해 가장 우수한 접착력을 나타냄을 확인하였다.

• 한국수산과학회지
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• 제33권1호
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• pp.60-65
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• 2000

우리나라 인근해안에서 서식하고 있는 해조류 23종에 대하여 Cr 및 Pb의 흡착성능을 조사한 결과, Sargassum 종이 Cr에 대하여 흡착능이 가장 높았다. Sargassum 종 4종을 이용하여 Cr 및 Pb의 생체흡착 실험을 수행하여 흡착 평형에는 Cr은 $30{\~}60$분, Pb는 30분 정도 소요 되었다. Cr 및 Pb 최대 흡착량은 136mg Cr/g biomass 및 232.5mg Pb/g biomass 였다. Pb흡착 및 탈착과정을 6회 반복한 결과 S. thunbergii는 재생성이 매우 효과적인 바이오 흡착제 였다. S. thunbergii를 자유 충전시킨 충전층 반응기를 이용하여 50mg/L Pb 용액의 연속적인 제거 실험을 수행한 결과 유입되는 Pb가 완전히 제거되는 구간은 HRT 10분에서 약 300 bed volume, HRT 5분에서 약 200 bed volume정도였다. 1회 흡착시 Pb 제거량은 HRT 10분에서 165 mg/g biomass, HRT 5분에서 112 mg/g biomass 였으나 흡착 완결까지의 소요 시간이 각각 112시간 및 52시간으로 HRT 5분일때가 더욱 효과적이라는 것을 알 수 있었다. 0.1 M HCl을 이용한 Pb 회수 실험에서 회수율은 $95{\%}$이상이었다. HRT 10분 및 5분에서 탈착 후 재흡착이 3회 반복되어도 흡착량은 다소 감소하였지만 계속적인 Pb의 제거가 가능하여 S. thunbergii는 바이오 흡착제로 사용이 가능함을 알 수 있었다.