• Journal of Korean Society on Water Environment
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• v.25 no.6
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• pp.916-921
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• 2009

This study was aimed to both enhance the fluoride removal and to reduce the phosphorus removal in treating semiconductor wastewater using $Ca(OH)_2$ at low pH so as to facilitate struvite crystallization reaction. The struvite crystallization could be introduced after fluoride removal by retaining the phosphorus source. As the results, the method applied in this study achieved high fluoride removal efficiency (about 91%) with retardation of phosphorus removal at pH 4, compared to conventional methods where the removal of fluoride and phosphorus were done at pH 11. Therefore, the fluoride removal at low pH would contribute to the enhancement of nitrogen and phosphorus removals in a consecutive struvite crystallization reactor. Treatment of semiconductor wastewater at low pH using $Ca(OH)_2$ also had lower (about 20%) water content of precipitated sludge compared to conventional method. As the molar ratio of Ca to F increased the removal efficiencies of fluoride and phosphorus increased. Although the amount of seed dosage didn't affect the removal of fluoride and phosphorus, its increase reduced the water content of precipitated matter. Finally, considering consecutive struvite reaction, the optimum condition for the removal of fluoride and phosphorus was as follow: pH: 4, the molar ratio of Ca:F: 1:1.

• Journal of the Korea Safety Management & Science
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• v.13 no.3
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• pp.55-61
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• 2011

Unit cost for asbestos removal work which have been made out at government contract award for recent three years has been reviewed and shown with table. And the cost have been compared with ones made out by two agencies, American asbestos removal specialists, government ministry for making out comparison tables. First, legal and practical work status survey have been made to determine reasonability of introducing separate contract-awarding system, as a part of ensuring reasonable unit work cost. And then, two different status have been compared and there in introduction possibility of separate contract-awarding system, it is found out. In interior removal work case, it is thought that 50% by owner, 60% unit work cost by the expert of which removal specialist think as reasonable unit cost. the results for exterior and spray work method are shown with almost same context. Impact factors for determining unit work cost such as project mount, project kind, contract-awarding method, subcontract method have been compared with parties. Removal specialist and expert group have almost same ideas for project amount which has been hightestly weighed but owner's recognition has partially lower than specialists idea. There are almost no difference of recognition between three(3) parties for project kind. Idea comparison of reasonable unit work cost for asbestos removal work between three concerned parties has been analyzed and found out that expert group do unit work cost, 65% of which removal specialists estimate, in interior tex removal. And there is almost no difference between them in exterior roof slate removal. But there is considerable difference between them that owner estimates 50% unit cost of specialist one while expert group estimate 50% of specialist idea of unit removal cost.

• Oral Biology Research
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• v.42 no.4
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• pp.222-227
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• 2018

The purpose of this study was to determine the cause and risk factors of removing bone plateby investigating and analyzing 359 patients who underwent reduction of fracture or orthognathic surgery with bone plate insertion over the past 3 years. Patients were evaluated with respect to age, smoking status, reason for insertion of plates, the numbers of inserted plates, sites of insertion, time between insertion and removal, reasons for removal of plates. The removal rate of bone plates was 33.1%. Of these, 17.0% of patients had clinical symptoms which led to remove plates. The removal rate of men was 29.9% and the rate of women was 39.2%. There were high removal rates from less than 20s (45.8%) and 20s (34.4%) those who are relatively young age group. On the other hand people in their 50s had a removal rate of 27.8% which was higher than those in their 60s with a rate of 20.7%. The removal rate of bone plate inserted into the mandible was 33.5%, and the removal rate of bone plate inserted into the maxilla was 34.7%. The mean period between the insertion and removal of bone plate was 10.9 months. The main reason for the removal of bone plate was the patient's requirement (44.5%). The most common cause of clinical symptoms was infection (22.7%). Infection was manifested within about a year and led to the plate being removed. Therefore, lowering the possibility of infection after surgery could decrease the removal rate of bone plate.

• Korean Chemical Engineering Research
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• v.52 no.5
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• pp.620-626
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• 2014

The main focus of this study was the evaluation of arsenic concentration in the ground water of Lahore at different depth and application of different mitigation techniques for arsenic removal. Twenty four hours of solar oxidation gives 90% of arsenic removal as compared to 8 hr. or 16 hr. Among oxides, calcium oxide gives 96% of As removal as compared to 93% by lanthanum oxide. Arsenic removal efficiency was up to 97% by ferric chloride, whereas 95% by alum. Activated alumina showed 99% removal as compared to 97% and 95% removal with bauxite and charcoal, respectively. Elemental analysis of adsorbents showed that the presence of phosphate and silica can cause a reduction of arsenic removal efficiency by activated alumina, bauxite and charcoal. This study has laid a foundation for further research on arsenic in the city of Lahore and has also provided suitable techniques for arsenic removal.

• Journal of Environmental Health Sciences
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• v.7 no.1
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• pp.9-20
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• 1981

This study was performed to determine the correlationship between temperature and overall removals of BOD, SS and to demonstrate the effect of temperature on treatment performance. These data for a period from February 1, 1977 to January 31, 1980 were obtained from the Cheong-Gye Cheon Sewage Treatment plant. The results of correlation and stepwise multiple regression analysis were as follows. 1) Secondary effluent BOD and SS showed negative correlationship with water temperature, with correlation coefficient of -0.1710, and -0.1654 respectively. 2) Correlation coefficient of BOD, SS removal rate and water temperature were 0.1823 and 0.0429 respectively. 3) Regresion equation for estimate of BOD removal rate was as follows $\widehat{Y}_1$ (BOD removal rate)=63.9994+0.5442X(water temperature). And BOD removal rate showed non significant change according to the water temperature. 4) Regression equation for estimate of SS removal rate was as follows $\widehat{Y}_2$ (SS removal rate)=61.6881+0.1514X(Water temperature). And SS removal rate showed non significant change according to the water temperature. 5) According to the Stepwise Multiple Regression analysis, water temperature ranked second order in the BOD removal rate estimation and the equation was as follows $\widehat{Y}_1$ (BOD removal rate)=69.7398+0.2665 $X_1$ (Primary effluent BOD)+0.3562 $X_2$ (Water temperature)-0.0122 $X_3(Flow)+4413.271X_4$ (Organic Loading).

• Journal of the Korean Home Economics Association
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• v.35 no.4
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• pp.257-268
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• 1997

The effects of water-and oil-repellent finishes on the deposition and removal of oily soils from polyseter fabrics were investigated in this study. The polyester fabrics treated with three kinds of fluoropolymers(TG-410H, TG-990) were soiled with mixed oily soils and washed by using Terg-O-Tometer at various conditions. It was found that TG-410H and TG-527 treated polyester fabrics reduced significantly the deposition of oily soils than untreated and TG-990 treated polyester fabrics. The removal of oily soils from polyester fabrics was increased in porportion to increasing of surfactant concentration up to a certain point(0.2% owb) but it levelled off above the point. The removal effect was high in the order of TG-990 treated polyester fabrics > untreated polyester fabrics > TG-527 treated polyester fabrics > TBG-410H treasted polyester fabrics. Especially the removal of oily soils from polyester fabrics was more effectively removed in triton X-100 solution. In general the removal of oily soils from polyester fabrics treated with fluoropolymers was increased up to a miximum near 6$0^{\circ}C$ and than decreased above 6$0^{\circ}C$. And efficient removal could be achieved within relatively short time (30min) The removal of oily soils from polyester fabrics was increased in proportion to increasing of pH range up to a certain point(9.5 or 11.0) but it began to decrease above the point. Furthermore the removal of oily soils was increased with th increase of mechanical agitation, but it began to decrease above 160 rpm.

• Journal of Korean Society of Water and Wastewater
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• v.10 no.3
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• pp.73-82
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• 1996

The removal efficiencies of organic substrates, nitrogen and phosphorus in the anaerobic-aerobic biological phosphorus removal process were investigated by addition of acetic acid, propionic acid and butyric acid which are normal volatile fatty acids contained in anaerobic digester supernatants. Substrate utilization coefficients for the phosphorus release and uptake were also estimated. The effect of a VFA, which showed higher phosphorus removal efficiency than the other VFAs did, was also studied in an anaerobic-aerobic-anoxic biological nutrient removal process. For the anaerobic-aerobic process added by VFA, the phosphorus removal efficiencies were up to about 68%, 55% and 61% for the reactors of acetic acid, propionic acid and butyric acid added, respectively, which indicates the efficiencies were increased by about 8-21%, comparing to that of 47% for the reactor with no VFA added. There were no significant difference in removal efficiencies for organic substrate and $NH_3-N$ without regard to addition of VFA. However, the removal efficiency of total nitrogen was increased in the case of VFA added, since $NO_3-N$ was less produced. For the anaerobic-aerobic-anoxic process added VFA, the removal efficiencies for $NH_3-N$ and $PO{_4}^{3-}-P$ were increased by 5% and 13%, respectively, comparing with them in the reactors not added VFA.

• Journal of Environmental Health Sciences
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• v.26 no.3
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• pp.43-49
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• 2000

A laboratory experiments were performed to investigate the effects of several factors on the phosphorus removal by waste oyster shells. The waste oyster shells used in this experiments were crushed particle, calcined particle and extracted solution. A higher efficiencies of phosphorus removal were observed, when a particle size of crushed and calcined particle were smaller. The effluent concentration of phosphorus was around 1.6mg/ι in continuous column experiment which packed with crushed particle of waste oyster shell at the influent concentration of PO4-P of 10 mg/ι. But the clogging of column occurred with increasing of throughput volume of influent. The efficiency of phosphorus removal increased with increasing of dosage amount of crushed, calcined particle and extracted solution. When the calcined particle which contained only about 1/10~1/100 of crushed particle was used, the efficiency of phosphorus removal was correspondingly equivalent to the removal efficiency obtained from crushed particle. The efficiency of phosphorus removal by calcined particle after 9 runs repeated use was decreased about 21.5% as that of the first run. The removal efficiency of 100% could have been achieved at the HRT of 18 hours during the continuous treatment of phosphorus by the solution extracted from calcined particle.

• Journal of Korean Neurosurgical Society
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• v.40 no.3
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• pp.164-168
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• 2006

Objective : The goal of treatment for spinal cord ependymoma is complete removal without postoperative neurological deficit. The authors analyzed the surgical results and factors influencing the postoperative prognosis. Methods : Fifty-one cases of primary spinal cord ependymoma, surgically treated between 1979 and 2003, were retrospectively analyzed. The mean follow-up period was 44 months. Results : Gross total removal was achieved in 42 patients and incomplete removal in nine. The proportion of complete surgical removals was influenced by tumor location and histology. Disease progression was observed in five cases [9.8%], the mean progression free interval after surgical removal was 48 months and the 5-year progression free rate was 68%. Disease progression was found in none of the 42 cases who underwent complete removal, and in 5 of 9 cases who hadincomplete removal group [P<0.001]. Statistically significant disease-progression factors by multivariate analysis were the surgical extent of removal [P=0.012]. preoperative functional status [P=0.032] the presence of intratumoral cysts [P=0.007] and postoperative radiation therapy [P=0042]. Of those patients who underwent incomplete removal, radiation therapy was found to significantly improve the clinical result [P=0042]. Conclusion : In the surgical treatment of spinal cord ependymoma, preoperative functional status, the presence of intratumoral cysts, the extent of removal, and postoperative radiation therapy were found to be significant prognostic factors of postoperative outcome.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.1006-1011
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• 2010

This study was focused on the reactivity of furnace slag against cadmium to design the vertical drain method with reactive column for improving contaminated sea shore sediment. The removal capacity of furnace slag was analyzed using pseudo-second-order model. And the effective parameters of removal test were initial concentration and initial pH. According to equilibrium removal amount and reactive constant calculated by pseudo-second-order model, the removal capacity was analyzed. Equilibrium removal amount of furnace slag was linearly increased as increasing intial cadmium concentration. Because the pH was around 11, the removal mechanism of furnace slag could be both sorption and precipitation. Therefore the removal amount was increased due to initial concentration. pH was increased to around 11 in the case of "No treat", but the pH were 3.8 in the case of "HAc added" and 0.7 in the case of "HCl added". The removal amount was different 4.8, 1.19 and 0.27 mg/g. This results show the pH was major factor to remove cadmium using furnace slag.