• Journal of Korean Neurosurgical Society
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• v.43 no.3
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• pp.139-142
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• 2008

Objective: The purpose of this study was to evaluate the efficacy of spinal implant removal and to determine the possible mechanisms of pain relief. Methods: Fourteen patient~with an average of 42 years (from 22 to 67 years) were retrospectively evaluated. All patients had posterior spinal instrumentation and fusion, who later developed recurrent back pain or persistent back pain despite a solid fusion mass. Patients' clinical charts, operative notes, and preoperative x-rays were evaluated. Relief of pain was evaluated by the Visual Analog Scale (VAS) pain change after implant removal. Clinical outcome using VAS and modified MacNab's criteria was assessed on before implant removal, 1 month after implant removal and at the last clinical follow-up. Radiological analysis of sagittal alignment was also assessed. Results: Average follow-up period was 18 months (from 12 to 25 months). There were 4 patients who had persistent back pain at the surgical site and 10 patients who had recurrent back pain. The median time after the first fusion operation and the recurrence of pain was 6.5 months (from 3 to 13 months). All patients except one had palpation pain at operative site. The mean blood loss was less than 100ml and there were no major complications. The mean pain score before screw removal and at final follow up was 6.4 and 2.9, respectively (p<0.005). Thirteen of the 14 patients were graded as excellent and good according to modified MacNab's criteria. Overall 5.9 degrees of sagittal correction loss was observed at final follow up, but was not statistically significant. Conclusion: For the patients with persistent or recurrent back pain after spinal instrumentation, removal of the spinal implant may be safe and an efficient procedure for carefully selected patients who have palpation pain and are unresponsive to conservative treatment.

• Advances in environmental research
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• v.6 no.2
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• pp.95-111
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• 2017

The valorization of swine manure samples, i.e., de-watered cake (SMc) and solid digestate (SMd), in products with beneficial value, i.e., low cost activated carbons (ACs), is studied. For this purpose slow pyrolysis and steam activation at three different duration times are applied. Additionally, the obtained ACs are characterized and tested towards removal of Cr(VI) from aqueous solutions. It is revealed that BET surface area varies in the range of $236-267m^2/g$ for ACs prepared from SMc sample and in the range of $411-432m^2/g$ for ACs prepared from SMd sample. Despite the low determined surface area of prepared ACs, a high total Cr removal capacity is observed occurring through a "coupled adsorption-reduction" mechanism. Higher Cr(VI) removal capacity is demonstrated for ACs having higher surface area ($q_m$ is 140.9 mg/g according Langmuir modelling). Cr(VI) removal is found to be pH dependent with a maximum at pH 1. However at that pH significant amounts of Cr remain in the solution as Cr(III). At pH 2 lower amount of Cr(VI) is removed compensated by a higher removal of Cr(III) resulting in a higher amount of adsorbed $Cr_{tot}$. Therefore adsorption at pH 2 is found to be appropriate. The removal capacity of the studied ACs towards Cr(VI) is almost independent of activation time.

• Journal of Wetlands Research
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• v.14 no.4
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• pp.629-635
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• 2012

This study was conducted to evaluate the removal behaviors of DOM(dissolved organic matter) and phosphorus in eutrophic lake water by coagulation process with PAC(powdered activated carbon). It was observed that the removal characteristic of soluble matter was different from that of dissolved one, and the removal of DOM was effected by both pH and coagulant dosage. It was founded that PAC could increase the removal efficiency by an adsorption of DOM in coagulation process. A formation of soluble and colloidal matters resulted in the degradation of phosphorus removal efficiency in a chemical precipitation process. The phosphorus removal efficiency could be enhanced by an absorption of colloidal matter and dissolved complex with PAC addition. In addition, the PAC addition caused the increase of floc density in coagulation process, that led to the rise of sedimentation rate, and resulted in a significant improvement of solid-liquid separation efficiency.

• Journal of Korean Society on Water Environment
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• v.22 no.2
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• pp.250-257
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• 2006

The objective of this study is to propose an alternative process for the small sewage treatment plants in rural communities. A biofilter has been used for biological wastewater treatment, which is becoming the alternative to the conventional activated sludge system. The proposed process used in this study, which is packed with floating media (i.e. expanded polystylene), has advantages of biofilter system and alternative flow system and they are incorporated into one process. Pilot and bench scale studies were performed using domestic wastewater. In the results of pilot plant study, it was observed that the stable effluent water quality was achieved and it met the present effluent criteria of suspended solid (SS), organic matters, T-N and T-P. In the study for determination of the cycle of backwashing, it was observed that the cycle of backwashing depended on BOD loading rates of influents. In the BOD loading rates of $0.5kg\;BOD/m^3{\cdot}day$ and $1.0kg\;BOD/m^3{\cdot}day$, the backwashing cycle of 28 hour and 16 hour were needed, respectively. The optimum backwashing time was 120~80 seconds at the media expansion rate of 50%. In the removal of SS, organic matters, T-N and T-P, SS removal was rather achieved by physical filtration than biological mechanism and the removal of organic matters except for SS, T-N and T-P were mainly rather achieved by biological mechanism than physical filtration. In bench-scale study, the effects of recirculation rate was investigated on removal of SS, TCOD, T-N and T-P. It was observed that the recirculation made removal efficiencies of SS, TCOD, T-N and T-P increased. Especially, in T-N removal, the increase of T-N removal efficiency of 40% was observed in the reicirculation rate of 1Q compared with 0Q.

• Applied Chemistry for Engineering
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• v.5 no.5
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• pp.899-903
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• 1994

Chitin was extracted from crab shell by Hackman method and chitosan was prepared to chitin, that was deacetylated under various concentration of NaOH solution and reaction time at constant temperature, $100^{\circ}C$. Samples were A=19%, B=52%, C=70% and D=93% deacetylation's chitosan and they were tested. When deacetylation was increased, $\overline{Mw}$ was decreased and removal rate of suspended solid and removal rate of chemical oxygen demand were increased. Suspended solid and removal rate of chemical oxygen demand showed the better at pH 9 and pH 7 than any other pH range.

• New & Renewable Energy
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• v.19 no.4
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• pp.27-34
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• 2023

In this study, microalgal oil was extracted from Nannochloropsis oceanica cultured in an open raceway pond and converted into biodiesel using a solid acid catalyst. Microalgal oil was extracted from two types of microalgae with and without nitrogen starvation using the KOH-solvent extraction method and the fatty acid content and oil extraction yield from each microalgae were compared. The fatty acid content of N. oceanica was 184.8 mg/g cell under basic conditions, and the oil content increased to 340.1 mg/g under nitrogen starvation conditions. Oil extraction yields were 90.8 and 95.4% in the first extraction, and increased to 97.5 and 98.8% after the second extraction. Microalgal oil extracted by KOH-solvent extraction was yellow in color and had reduced viscosity due to chlorophyll removal. In biodiesel conversion using the catalyst SO₄^2-/HZSM-5, solvent-extracted oil showed a FAME content of 4.8%, while KOH-solvent-extracted oil showed a FAME content of 90.4%. Solid acid catalyst application has been made easier by removal of chlorophyll from microalgal oil. The FAME content increased to 96.6% upon distillation, and the oxidation stability increased to 11.07 h with addition of rapeseed biodiesel and 1,000 ppm butylated hydroxyanisole.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.696-696
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• 2013

Solid Oxide Fuel Cells (SOFCs) have been gaining academic/industrial attention due to the unique high efficiency and minimized pollution emission. SOFCs are an electrochemical system composed of dissimilar materials which operates at relatively high temperatures ranging from 800 to 1000oC. The cell performance is critically dependent on the inherent properties and integration processing of the constituents, a cathode, an electrolyte, an anode, and an interconnect in addition to the sealing materials. In particular, the gas transport, ion transport, and by-product removal also affect the cell performance, in terms of open cell voltages, and cell powers. In particular, the polarization of cathode materials is one of the main sources which affects the overall function in SOFCs. Up to now, there have been studies on the materials design and microstructure design of the component materials. The current work reports the effect of thin film processing on cathode polarization in solid oxide fuel cells. The polarization issues are discussed in terms of dc- and ac-based electrical characterizations. The potential of thin film processing to the applicability to SOFCs is discussed.

• Journal of Magnetics
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• v.16 no.1
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• pp.10-14
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• 2011

This study reports on Co/$Co_2$MnSn two-phase magnets. The Co/$Co_2$MnSn two-phase magnet has Co precipitates in a $Co_2MnSn$ Heusler alloy matrix, in which the two phases are exchange-coupled at the phase boundary. The as-casted Co/$Co_2$MnSn system, which has Co-Mn solid solution precipitates in a $Co_2$MnSn Heusler alloy matrix, showed that the Co solid solution precipitates are crystallographically coherent and there is exchange coupling at the phase boundary. To form pure Co precipitates by removal of Mn solute atoms in Co-Mn solid solution, annealing was carried out 48 hours at $870^{\circ}C$. After annealing, the low $T_c$ and low magnetization phase of the Co-Mn solid solution became a high $T_c$ and high magnetization phase of hexagonal Co.

• Korean Journal of Environmental Biology
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• v.17 no.2
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• pp.183-190
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• 1999

The bioleaching of heavy metals from fly ash was performed by Thiobacillus thiooxidans MET isolated from the enrichment culture of an anaerobically digested sludge. The effect of solid concentrations on the efficiency of metal leaching was studied in shaken flasks. In the range of solid concentrations 20 g.L­$^1$to 100 g.L­$^1$T. thiooxidans MET oxidized S$^{0}$ to sulfate without any lag period. The final pH of slurry solution was decreased to below pH 1, and the final oxide-redox potential (ORP) was increased to over 420 mV in the solid concentrations below 100 g.L­$^1$. However, the initial lag period of 4 to 8 days was required to obtain the pH reduction and ORP increase of the slurry solutions in the range of solid concentrations 150 g.L­$^1$to 300 g.L­$^1$. The sulfur oxidation rate of T. thiooxidans MET in 20~100 g.L­$^1$solid concentrations was 0.70~0.75 g-S.L­$^1$ㆍ d­$^1$, but its sulfur oxidation activity was remarkably inhibited with increasing solid concentration over 150 g.L­$^1$. Increasing fly ash solids concentration in the range of solids concentration 20 g.L­$^1$ to 200 g.L­$^1$decreased the removal efficiency of Zn, Cu, Mn, Cr and Pb. The solubilization of heavy metals from fly ash was strongly correlated with the pH value of slurry solution. When the pH of slurry solution was reduced to 3, the solubilization process of Zn, Cu and Mn started, and their solubilization efficiency of Zn, Cu and Mn was progressively increased below pH 2. However, the solubilization process of Cr and Pb started at pH 2.5 and 2.0, respectively.

• Magazine of the Korean Society of Agricultural Engineers
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• v.45 no.6
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• pp.194-206
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• 2003

A pilot study was performed to examine the feasibility of the pond system for further polishing of treatment wetland effluent to agricultural reuse of reclaimed water. The constructed wetland and pond system was installed in Konkuk University and the effluent from septic tank of school building was used as an influent to the wetland system. The effluent of the wetland was used as an influent to pond systems. The influent concentrations of total coliform(TC), fecal coliform (FC), and E. coli were about $10^5$MPN/100 ml, and they were reduced to less than 10,000 MPN/100 ml on average after wetland treatments, showing over 95 % removal. And they were further reduced to less than 1,000 MPN/100 ml in average, showing over 85∼93 % removal after pond treatment. Turbidity and SS were improved effectively on average and their pond effluent concentration was about 4.5 NTU and 9.8 mg/L in average, respectively Average $BOD^5$ concentrations were also reduced substantially to 9.3 mg/L with about 83 % removal rate after wetland and pond treatment systems. Nutrients removal was relatively low and removal rate for T-N and T-P was less than 43 and 44%, respectively after wetland and pond treatment. Considering stable performance and effective removal of bacterial indicators as well as other water quality parameters, low maintenance, and cost-effectiveness, pond system was thought to be an effective and feasible alternative for agricultural reuse of reclaimed water. This paper describes a preliminary result Iron pilot study and further investigations are recommended on the optimum design parameters before full scale application.