• 설비공학논문집
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• 제13권10호
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• pp.974-981
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• 2001

In this study, the minimum heat flux conditions are experimentally investigated for the spray cooling of hot plate. The hot plates are cooled down from the initial temperature of about$ 900^{\circ}C$, and the local heat flux and surface temperatures are calculated from the measured temperature-time history. The results show that the minimum heat flux point temperatures increase linearly resulting from the propagation of wetting front with the increase of the distance from the stagnation point of spray flow. However, in the wall region, the minimum heat flux point temperature becomes independent of the distance. Also, the velocity of wetting front increases with the increase of the droplet flow rate.

• Membrane and Water Treatment
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• 제2권4호
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• pp.225-237
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• 2011

In this study, response of reversibility of membrane flux during chemically enhanced backwash (CEB) to changes in filtration time, filtration flux and coagulant concentration dosing during ultrafiltration (UF) process was investigated using a regression model. The model was developed via empirical modelling approach using response surface methodology. In developing the model, statistically designed UF experiments were conducted and the results compared with the model output. The results showed that the performance of CEB, evaluated in terms of the reversibility of the membrane flux, depends strongly on the changes in coagulant concentration dosage and the filtration flux. Also the response of the reversibility of membrane flux during CEB is independent of the filtration time. The variance ratio, VR << $F_{value}$ and $R^2$ = 0.98 obtained from the cross-validation experiments indicate perfect agreement of the model output with experimental results and also testify to the validity and suitability of the model to predict reversibility of the membrane flux during CEB in UF operation.

• Environmental Engineering Research
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• 제24권3호
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• pp.418-426
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• 2019

Current available commercial membranes are not robust and are therefore destroyed if left to dry out or handled roughly. Woven fibre microfiltration (WFMF) membranes have advantages over its competitors with respect to durability, thus, favourable for the developing economies and operation during rough conditions. Evaluation of the effects of aeration and brushing as a flux enhancement strategies for WFMF membrane was the purpose of this study. The WFMF membrane was found to be susceptible to pore plugging by colloidal material and adsorption/attachment by microbiological contaminants. This led to a 50% loss in flux. Aeration as a single flux enhancement strategy proved insufficient to maintain high flux successfully. Therefore combined flux enhancement strategies yielded the best results.

• Membrane and Water Treatment
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• 제9권5호
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• pp.335-342
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• 2018

Micelle-Enhanced Ultrafiltration (MEUF) is a membrane separation processes that improving ultrafiltration process with the formation of micelles of the surface active agents. Surface active agents are widely used to improve membrane processes due to the ability to trap organic compounds and metals in the treatment of industrial waste water. In this study, surface active agents are used to improve micelle-enhanced ultrafiltration (MEUF) to reduce chemical oxygen demand (COD), total dissolved solid (TDS), turbidity and clogging the membrane in dairy wastewater treatment. Three important operational factors (anionic surface active agent concentration, pressure and pH) and these interactions were investigated by using response surface methodology (RSM) and Box-Behnken design. Results show that due to the concentration polarization layer and increase the number of Micelles; the anionic surface active agent concentration has a negative effect on the flux and has a positive effect on the elimination of contamination indices. pH, and the pressure have the greatest effect on flux. On the other hand, it could be stated that these percentages of separation are in the percentages range of Nano-filtration (NF). While MEUF process has higher flux than NF process. The results have been achieved at lower pressure while NF process needs high pressure, thus making MEUF is the replacement for the NF process.

• 한국표면공학회지
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• 제49권6호
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• pp.513-520
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• 2016

Many surface protection methods have been developed to apply to constructional steels which have been used under severe corrosive environments. One of these methods, hot dip galvanizing is being widely used to the numerous constructional steels such as a guard rail of high way, various types of structural steel for manufacturing ship and for some other industrial fields etc.. Recently, the cost of zinc is getting higher and higher, thus, it is considered that improvement of hot dip galvanizing process to reduce the cost of production should be developed possibly. In this study, additives such as acid cleaning solution, $NH_4OH$, $Al(OH)_3$ and $H_2O_2$ were added to flux solution, and omission of water washing treatment after acid cleaning was investigated with some types of flux solutions added with some additives mentioned above. The decrement of pH by adding the acid cleaning solution could be controlled due to neutralization reaction with addition of $NH_4OH$. The flux solution added with both $NH_4OH$ and $Al(OH)_3$ exhibited nearly the same color and pH value as those of orignal flux solution with no added, and the sample dipped to the flux solution which was added with additives mentioned above indicated a relatively good corrosion resistance compared to other samples. However, the flux solution added with $NH_4OH$, $Al(OH)_3$ and $H_2O_2$ exhibited a different color, sediment and a bad corrosion resistance. Consequently, it is considered that omission of water washing treatment may be able to perform by adding optimum additives to the original flux solution.

• Membrane and Water Treatment
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• 제8권2호
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• pp.113-123
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• 2017

This study investigated effects of physical and chemical cleaning methods on the initial flux recovery of fouled membrane in membrane distillation process. A laboratory scale direct contact membrane distillation (DCMD) experiment was performed to treat digested livestock wastewater with 3.89 mg/L suspended solids, 874.7 mg/L COD, 543.7 mg/L nitrogen, 15.6 mg/L total phosphorus, and pH of 8.6. A hydrophobic PVDF membrane with an average pore size of $0.22{\mu}m$ and a porosity of 75 % was installed inside a direct contact type membrane distillation module. The temperature difference between feed and permeate side was maintained at $40^{\circ}C$ with the feed and permeate stream velocity of 0.18 m/s. The results showed that the permeate flux decreased from $22.1L{\cdot}m^{-2}{\cdot}hr^{-1}$ to $19.0L{\cdot}m^{-2}{\cdot}hr^{-1}$ after 75 hours of distillation. The fouled membrane was cleaned first by physical flushing and consecutively by chemicals with NaOCl and citric acid. After the physical cleaning the flux was recovered to 92 % as compared with the initial clean water flux of the virgin membrane. Then 94 % of the flux was recovered after cleaning by 2,000 ppm NaOCl for 90 minutes and finally 97 % of flux recovered after 3 % citric acid for 90 minutes. SEM-EDS and FT-IR analysis results presented that the foulants on the membrane surface were removed effectively after each cleaning step. The contact angle measurement showed that the hydrophobicity of the membrane surface was also restored gradually after each cleaning step to reach nearly the same hydrophobicity level as the virgin membrane.

• Korean Chemical Engineering Research
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• 제43권3호
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• pp.407-411
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• 2005

분무용액에 다양한 융제들을 도입하여 분무열분해법에 의해 YAG:Tb($Y_3Al_5O_{12}:Tb$) 형광체들을 합성하였다. 융제의 종류, 유기 첨가물 및 후열처리 온도 등이 YAG:Tb 형광체의 형태, 결정성 및 발광 특성에 미치는 영향 등을 조사하였다. 유기첨가물로 사용된 구연산과 에틸렌 글리콜은 고온의 열처리 과정에서 YAG:Tb 형광체의 형태 파괴 없이 발광 특성을 증대시켰다. 반면에 다량의 융제를 포함한 분무용액으로부터 분무열분해 공정에 의해 합성된 전구체 분말은 $1300^{\circ}C$에서의 후열처리 후에 구형의 형태가 사라졌다. 리튬 탄산염을 융제로 함유한 분무용액으로부터 합성된 YAG:Tb 형광체는 후열처리 후에 미세하면서도 균일한 형태를 가졌다. 융제로서 사용된 리튬 탄산염은 YAG:Tb 형광체의 발광 휘도 개선에도 효과적이었다. 리튬 탄산염을 융제로 첨가한 경우에 합성된 YAG:Tb 형광체의 최적의 발광 세기는 융제를 첨가하지 않은 경우에 합성된 형광체의 발광세기의 189％였다.

• 한국환경과학회지
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• 제24권10호
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• pp.1309-1313
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• 2015

The effects of Houttuynia cordata powder on the growth performance of ducks were investigated. Ninety ducks were assigned into one of three dietary treatments as a completely randomized design for 6 weeks: feeds supplemented with 1% or 2% H. cordata and a control group. No significant difference was observed in feed conversion among the three groups (p > 0.05), but addition of H. cordata had a significantly positive effect (p < 0.05) on initial and final body weight, weight gain, and feed intake of the ducks. Furthermore, the effects of chemical treatment (comprising 50 g and 100 g aluminum chloride [$AlCl_3$] per kilogram litter) on the ammonia ($NH_3$) flux in duck litters were also investigated. Duck litter was treated with $AlCl_3$ at a depth of 8 cm by top-dressing; this resulted in a significant difference on $NH_3$ flux (p < 0.05) during the experimental period (but not at 2 weeks). $NH_3$ flux at 6 weeks were reduced by 25.4% and 37.5% by treatment with 1% and 2% H. cordata, respectively, compared with the control groups. In conclusion, enriching the diets of the ducks with 2% H. cordata and adding 100 g $AlCl_3$ to their litter has beneficial effects on increasing their growth performance and reducing $NH_3$ flux in their environment.

• Journal of Pharmaceutical Investigation
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• 제41권1호
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• pp.9-17
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• 2011

The objective of this work is to study transdermal delivery of calcitonin using iontophoresis and to evaluate various factors which affect the transdermal transport. We have studied the effect of polarity, current density, drug concentration, penetration enhancers (isopropyl myristate [IPM] and ethanol) and laser treatment on transdermal flux and the results were compared. We also investigated the iontophoretic flux from microemulsions containing calcitonin together with oleic acid (OA) or IPM. In vitro flux study was performed at $33^{\circ}C$, using side-by-side diffusion cell and full thickness hairless mouse skin. Anodal delivery at pH 3.0 was much larger than cathodal and passive delivery, due to the positive charge of calcitonin. Cumulative amount delivered (CUM) by cathodal or passive delivery was close to zero for 10 hours. The pretreatment of skin by neat IPM markedly increased the CUM anodically. CUM increased as the current density, drug concentration or the duration of IPM treatment increased. Microemulsion containing IPM or oleic acid was prepared and the phase diagram was constructed. CUM also increased when IPM was incorporated into a microemulsion. OA microemulsion showed similar enhancing effect to IPM microemulsion. The delivery of calcitonin from 70% (v/v) ethanol aqueous solution showed a large increase in flux. Laser treatment of skin before flux experiment exhibited about 2 fold increase in total calcitonin amount transported for 12 hours, when compared to that delivered by IPM microemulsion. Based on these results, we have evaluated the possibility of delivering enough amount of calcitonin to reach the therapeutic level. The data suggest that it is highly possible to deliver clinically effective amount of calcitonin using iontophoresis patch with small area (<10 $cm^2$).

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제17권1호
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• pp.29-45
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• 2013

Central schemes offer a simple and versatile approach for computing approximate solutions of nonlinear systems of hyperbolic conservation laws. However, there are large numerical dissipation in case of contact discontinuity. We study semi-discrete central upwind scheme by changing flux functions to reduce the numerical dissipation and we perform numerical computations for various problems in case of contact discontinuity.