• Geomechanics and Engineering
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• 제13권2호
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• pp.319-331
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• 2017

This vacuum preloading combined with polyacrylamide (PAM) flocculation was proposed to separating solid-liquid in waste slurry and to improving bearing capacity of soft soil ground. By using waste slurry taken from drilled shaft construction site in Shanghai, China, a series of settling column tests with four typical flocculants and one normal for waste slurry were carried out for comparative analysis. The optimal amounts for each flocculant were obtained from the column tests. Then, model tests on vacuum preloading with anionic polyacrylamide (APAM) flocculation and without flocculants were carried out. The out of water and the settlement of slurry surface ground were monitored during the model tests, and the changes in water content, particle-size and pore-size distributions in different positions after the model tests were measured and discussed. It is found that water content of the waste slurry without APAM flocculation changed from 204 to 195% by 24 hours standing and 15 hours vacuum preloading, while the water content of the waste slurry with APAM flocculation was declined from 163 to 96% by 24 hours standing, and was further reduced into 37% by 136 hours vacuum preloading, which shows that the combined method is feasible and effective.

• 한국수산과학회지
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• 제55권2호
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• pp.146-153
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• 2022

The vertical distribution and abundance of icthyoplankton in the southern waters of Jeju Island during June 2020 were investigated. Fish eggs and larvae were identified using the mitochondrial DNA cytochrome c oxidase subunit I (mtDNA COI) and the 16S rRNA gene. During this period, fish eggs of 23 taxa belonging to 21 families and larvae of 27 taxa belonging to 25 families were collected. Fish eggs were located mostly from the surface to 30 m depth of the water column. Larvae were located from the surface to 80 m depth of the water column. Vertical distributions of fish eggs and larvae were influenced by oceanography conditions such as temperature, salinity, and thermocline depth. No discernible difference in mean thermocline depth was observed between day and night.

• 한국해양공학회지
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• 제36권1호
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• pp.21-31
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• 2022

In recent years, various studies have been conducted on oscillating-water-column-type wave energy converters (OWC-WECs) with multiple chambers with the objective of efficiently utilizing the limited space of offshore/onshore structures. In this study, a numerical investigation based on a numerical wave tank was conducted on single, dual, and triple OWC chambers to examine the hydrodynamic performances and the energy conversion characteristics of the multiple water columns. The boundary value problem with the Laplace equation was solved by using a numerical wave tank based on a finite element method. The validity of the current numerical method was confirmed by comparing it with the measured data in the previous experimental research. We undertook a series of numerical simulations and observed that the water column motion of sloshing mode in a single chamber can be changed into the piston motion of different phases in multiple OWC chambers. Therefore, the piston motion in the multiple chambers can generate considerable airflow at a specific resonant frequency. In addition, the division of the OWC chamber results in a reduction of the time-dependent variability of the final output power from the device. As a result, the application of the multiple chambers leads to an increase of the energy conversion performance as well as a decrease of the variability of the wave energy converter.

• Ocean Science Journal
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• 제41권2호
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• pp.121-124
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• 2006

Argo drifters provide information of the vertical structure in the water column and have a potential for the improvement of understanding phytoplankton primary production and biogeochemical cycles in combination with ocean color satellite data, which can obtain the horizontal distribution of phytoplankton biomass in the surface layer. Our examples show that using Argo drifters with satellite-measured horizontal distribution of phytoplankton biomass at the sea surface allow an improved understanding of the development of the spring bloom. The other possible uses of Argo drifter are discussed.

• 한국식품위생안전성학회지
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• 제11권2호
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• pp.149-157
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• 1996

A procedure for the determination of Aflatoxins in food and grains which utilizes reversed phased liquid chromatographic (LC) analysis with postcolumn derivatization by an electrochemical cell and determination with a fluorescence detector has been evaluated. The LC mobile phase was water-acetonitrile-methanol (6+2+2) with 1mM KBr and 1 mM HNO3 which gave baseline separation for the four Aflatoxins (AfB1, AfB2, AfG1, AfG2). The electrochemical cell set at 7V, generated bromine and derivatized aflatoxins B1 and G1, The derivatives were detected by the fluorescence detector. The aflatoxins in naturally contaminated corn samples were isolated by three different cleanup procedures: the AOAC method I column(CB method), a rapid filtrate column (Romer's column), and an immunoaffinity column. The final extract were quantitated with fluordensitometric TLC and the LC postcolumn derivatization techniques. The results were quite similar, however the LC technique showed less interferences and could be automated. Samples of corn, raw peanuts, peanut butter and dried dates were also analyzed successfully with this procedure.

• Journal of Pharmaceutical Investigation
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• 제30권1호
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• pp.51-54
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• 2000

A column-switching high performance liquid chromatographic method has been developed for the determination of a fluconazole in human plasma. Each plasma sample was centrifuged for 10 min at 5000 g. After an aliqout of the supernatant was taken to nylon microcentrifuge filter, these samples were centrifuged for 10 min at 5000 g. An aliqout of the supernatant was injected directly onto the HPLC column. Deionized water was run for 2 min at a flow rate of 1.0 ml/min to retain fluconazole in an extration column, while proteins and endogenous interferences were eluted to the waste. The analyte was then back-flushed onto an analytical column, $C_{18}$ reversed-phase column. The mobile phase for analytical column, 0.01 M sodium acetate (pH 5.0)-methanol (65:35, v/v), was run at a flow rate of 1.0 ml/min. The column effluent was monitored by ultraviolet detection at 261 nm. The retention time for fluconazole was 11.76 min in human plasma. The detection limit for fluconazole in human plasma was $0.2\;{\mu}g/ml$. No interference from endogenous substances was observed.

• Environmental Engineering Research
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• 제14권1호
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• pp.41-47
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• 2009

Column experiments were performed in this study to investigate humic acid adhesion to iron oxide-coated sand (ICS) under different experimental conditions including influent humic acid concentration, flow rate, solution pH, and ionic strength/composition. Breakthrough curves of humic acid were obtained by monitoring effluents, and then column capacity for humic acid adsorption ($C_cap$), total adsorption percent (R), and mass of humic acid adsorbed per unit mass of filter media ($q_a$) were quantified from these curves. Results showed that humic acid adhesion was about seven times higher in ICS than in quartz sand at given experimental conditions. This indicates that humic acid removal can be enhanced through the surface charge modification of quartz sand with iron oxide coating. The adhesion of humic acid in ICS was influenced by influent humic acid concentration. $C_cap$ and $q_a$ increased while R decreased with increasing influent humic acid concentration in ICS column. However, the influence of flow rate was not eminent in our experimental conditions. The humic acid adhesion was enhanced with increasing salt concentration of solution. $C_cap$, $q_a$ and R increased in ICS column with increasing salt concentration. On the adhesion of humic acid, the impact of CaCl2 was greater than that of NaCl. Also, the humic acid adhesion to ICS decreased with increasing solution pH. $C_cap$, $q_a$ and R decreased with increasing solution pH. This study demonstrates that humic acid concentration, salt concentration/composition, and solution pH should be controlled carefully in order to improve the ICS column performance for humic acid removal from water.

• 한국물환경학회지
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• 제23권5호
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• pp.723-730
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• 2007

This study was conducted to develop a combined method for remediating a Chlorinated Aliphatic Hydrocarbons (CAHs) mixtures-contaminated aquifer. The process is consist of two processes. A chemical process (1st) using natural zinc ores for reducing higher concentrations of CAH mixtures to the level at which biological process is feasible; and A biological process (2nd) using aerobic cometabolism for treating lower concentration of CAH mixtures (less than 1 mg/L). Natural zinc ore showed relatively high transformation capacity, average dehalogenation percentage, and the best economic efficiency in previously our study. To evaluate the feasibility of the process, we operated two columns in series (that is, chemical and biological columns). In the first column filled with natural zinc ore and sand, CAH mixtures were effectively transformed with more than 95% efficiency, the efficiency depends on the Empty Bed Contact Time (EBCT) and the mass of zinc ore packed. Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD) analysis were performed to make sure whether natural zinc ore played an key role in the dechlorination of the CAH mixtures. The characteristics of zinc metal surface changed after exposure to CAHs due to oxidation of $Zn^0$ to $Zn^{2+}$. In the biological column injecting propane, DO and effluent of the chemical column, only 1,1,1-TCA was cometabolically transformed. Consequently, the combined process would be effective to remediate an aquifer contaminated with high concentrations of CAH mixtures.

• 지질공학
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• 제14권3호
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• pp.301-311
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• 2004

다공질매질을 구성하고 있는 다양한 매질들의 전기적 특성 중의 하나인 유전율상수를 이용하여 지하수 유동 및 매질의 구조를 파악하기 위한 새로운 유전율추적자시험법(dielectric tracer test method)을 본 연구에서 제안하였다. 추적자물질로는 비중이 물과 동일한 에탄올혼합액체(ethanol mixing liquid, EML)를 제작하였으며, 각기 다른 공극률을 갖는 포화 표준사 및 강모래 층에 대해 매질의 유전율상수를 측정할 수 있는 FDR system및 측정센서를 적용해 추적자시험을 실시하였다. 또한 이들의 결과와 비교하기 위하여 추적자물질인 염분농도 $3\%$를 갖는 염분수용액의 농도 변화를 electro multi-meter로 측정하여 비교 검토하였다. 두 시험결과에서 EML추적자시험의 경우, 각각의 포화 흙칼럼에서의 EML 농도변화를 명확히 확인할 수 있었으나, 염분수용액을 적용한 시험에서는 이들이 지속적으로 칼럼 내 하단부로 침전되어 염분농도 변화에 의한 물의 침투 이동은 확인할 수 없었다. 이는 염분수용액의 비중이 물보다 무겁기 때문에 포화토 내 물의 이동 속도에 비례하여 지속적으로 하단부로 침전이 이루어지는 것을 알 수 있었다. 따라서 본 연구에서는 물의 비중과 동일한 EML 추적자물질과 이들의 유전율상수 변화를 측정할 수 있는 FDR system을 적용하여 유전율추적자시험의 적용 가능성을 실내추적자시험을 통하여 확인하였다.

• 대한환경공학회지
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• 제39권9호
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• pp.513-518
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• 2017

본 연구는 입상활성탄을 일시에 100% 충진하는 방법과 일회 충진양을 50%, 33%, 20% 및 10%로 나눠서 주기적으로 누적 충진하였을 경우에 대해 THMs과 DOC 처리효율 변화를 비교 평가하기 위해 수행하였다. 일시에 100% 충진하는 방법은 운전 초기에는 THMs와 DOC의 유출농도가 낮았으나 운전기간이 증가할수록 높은 유출수 농도를 나타내었다. 반면 주기적 누적충진 방법을 적용한 경우에는 유출수의 THMs와 DOC 농도가 운전기간 동안 상대적으로 균등하게 유지하였다. THMs 흡착제거에는 주기적 누적 충진법이 전체 충진용량을 일시에 충진하는 방법에 비해 효과적이었으나, 활성탄 공정 유입수 THMs 구성종들 중에서 클로로디브로모메탄이나 브로모포름의 함량이 클로로포름이나 브로모디클로로메탄에 비해 월등히 높은 경우에는 주기적 누적충진법에 비해 전체 충진용량을 일시에 충진하는 방법이 더욱 효과적인 것으로 나타났다. DOC의 제거에서는 충진용량을 일시에 충진하여 운전하는 방법이 주기적 누적충진법에 비해 DOC의 총 흡착량과 유출수의 평균농도 측면에서는 유리하였다. 활성탄 공정 운전기간 동안 THMs와 DOC 제거율의 균등화에는 주기적 누적충진 방법을 적용한 경우가 효과적이었고, 적은 양의 활성탄을 주기적으로 자주 충진하는 방식이 더욱 유리하였다.