• Korean Journal of Materials Research
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• v.24 no.5
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• pp.271-276
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• 2014

Silica nano-powder (SNP) is an inorganic material able to provide high-performance in various fields because of its multiple functions. Methods used to synthesize high purity SNP, include crushing silica minerals, vapor reaction of silica chloride, and a sol-gel process using TEOS and sodium silicate solution. The sol-gel process is the cheapest method for synthesis of SNP, and was used in this study. First, we investigated the shape and the size of the silica-powder particles in relation to the variation of HCl and sodium silicate concentrations. After drying, the shape of nano-silica powder differed in relation to variations in the HCl concentration. As the pH of the solution increased, so did the density of crosslinking. Initially, there was NaCl in the SNP. To increase its purity, we adopted a washing process that included centrifugation and filtration. After washing, the last of the NaCl was removed using DI water, leaving only amorphous silica powder. The purity of nano-silica powder synthesized using sodium silicate was over 99.6%.

• Convergence Security Journal
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• v.21 no.3
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• pp.31-38
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• 2021

Tor, known as Onion Router, guarantees strong anonymity. For this reason, Tor is actively used not only for criminal activities but also for hacking attempts such as rapid port scan and the ex-filtration of stolen credentials. Therefore, fast and accurate detection of Tor traffic is critical to prevent the crime attempts in advance and secure the organization's information system. This paper proposes a novel classification model that can detect Tor traffic and classify the traffic types based on CNN(Convolutional Neural Network). We use UNB Tor 2016 Dataset to evaluate the performance of our model. The experimental results show that the accuracy is 99.98% and 97.27% in binary classification and multiclass classification respectively.

• Membrane and Water Treatment
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• v.10 no.5
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• pp.331-338
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• 2019

This study aimed to investigate the membrane fouling and sludge characteristics in a pilot-scale submerged membrane bioreactor (MBR) operated under low temperature ($7^{\circ}C$). To elucidate the mechanisms of membrane fouling at low temperature, we studied the correlation between MBR performances and physicochemical properties of sludge including extracellular polymeric substance (EPS), relative hydrophobicity (RH) and floc size during long-term operation. The MBR was shown able to remove chemical oxygen demand (COD) stably and efficiently (>90 %) in the case of overgrowth of filamentous bacteria (bulking sludge) at low temperature. On the other hand, the occurrence of filamentous bulking greatly accelerated membrane fouling, as indicated by membrane filtration period of 14 days for filamentous bulking at $7^{\circ}C$, in comparison with that of 27 days for non-bulking sludge at $24^{\circ}C$ The overgrowth of filamentous bacteria resulting from low-temperature condition led to an increased release of EPS, higher RH, smaller floc size and lower fractal dimension of sludge. These factors accelerated the formation of compact cake layer on membrane surface in association with performance diminution in terms of increase in transmembrane pressure (TMP) of the membrane and thus the decrease in membrane permeability.

• Clean Technology
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• v.27 no.3
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• pp.217-222
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• 2021

Although monolayer black phosphorus (BP) and few-layer BP nanosheets (NSs) have been extensively studied as promising alternatives to graphene, research has focused primarily on atomically thin-layered BP in an isolated form. In order to realize the practical applications of BP-related devices, a BP film based on continuous networking of few-layer BP NSs should be developed. In this study, a transparent BP film with high quality was fabricated via a vacuum filtration method. An oxygen-free water solvent was used as an exfoliation medium to avoid significant oxidation of the few-layer BP NSs in liquid-phase exfoliation. The exfoliation efficiency from bulk BP to the few-layer BP NSs was estimated at 22%, which is highly efficient for the production of continuous BP film. The characteristics of the high-quality BP film were determined as 98% transparency, minimum oxidation of 18%, structural stability, and an appropriate bandgap of about 1.8 eV as a semiconductor layer. In order to demonstrate the potential of the BP film for photocatalytic activity, we performed photoelectrochemical water oxidation of the transparent BP film. Although its performance should be improved for practical applications, the BP film could function as a photoanode, which offers a new potential semiconductor in water oxidation. We believe that if the BP film is adequately engineered with other catalysts the photocatalytic activity of the BP film will be improved.

• Journal of applied mathematics & informatics
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• v.41 no.1
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• pp.95-105
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• 2023

To make the network energy efficient and to protect the network from malignant user's energy efficient grid based secret key sharing scheme is proposed. The cost function is evaluated to select the optimal nodes for carrying out the data transaction process. The network is split into equal number of grids and each grid is placed with certain number of nodes. The node cost function is estimated for all the nodes present in the network. Once the optimal energy proficient nodes are selected then the data transaction process is carried out in a secured way using malicious nodes filtration process. Therefore, the message is transmitted in a secret sharing method to the end user and this process makes the network more efficient. The proposed work is evaluated in network simulated and the performance of the work are analysed in terms of energy, delay, packet delivery ratio, and false detection ratio. From the result, we observed that the work outperforms the other works and achieves better energy and reduced packet rate.

• Membrane and Water Treatment
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• v.13 no.2
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• pp.105-110
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• 2022

Al₂O₃ positively charged nanofiltration composite membrane was successfully prepared with aluminate coupling agent (ACA) as modifier, sodium bisulfite (NaHSO₃) and potassium persulfate (K₂S₂O₈) as initiator and methacryloyloxyethyl trimethylammonium chloride (DMC) as crosslinking monomer. The surface of the membrane before grafting and after polymerization were characterized by SEM and FT-IR. Three factor and three-level orthogonal experiments were designed to explore the optimal conditions for membrane preparation, and the optimal group was successfully prepared. The filtration experiments of different salt solutions were carried out, and the retention molecular weight was determined by polyethylene glycol (PEG). The results showed that the polymerization temperature had the greatest effect on the rejection rate, followed by the reaction time, and the concentration of DMC had the least effect on the rejection rate. The rejection rates of CaCl₂, MgSO₄, NaCl and Na₂SO₄ in the optimal group were 83.8%, 81.3%, 28.1% and 23.6% (average value), respectively. The molecule weight cut-off of 90% (MWCO) of the optimal group was about 460, which belongs to nanofiltration membrane.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.751-756
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• 2009

In the perspective of saving energy in buildings, the high performance of insulation and air tightness for improving the heating and the cooling efficiency, has brought economically positive effects. However, these building energy saving technologies cause the lack of ventilation, which is the direct cause of increasing the indoor contaminants, and is also very harmful to the residents, because they spend over 90% of their time indoors. Therefore, the ventilation is important to keep the indoor environment clean and it can also save the energy consumption. In this study, a HEPA type nano ceramic filter is designed as a passive ventilation system to collect airborne particles and to supply fresh outdoor air. The double layer filter, which has $30{\mu}m$ in diameter at the conditions of 10wt% of concentration and 3kV/cm of the electric intensity, is produced by electrospinning. The filtration coating technology is confirmed in the solution with $SiO_2$ nano particles using polymer nano fibers. Also double layer filters are coated with $SiO_2$ nano particles and finally the porous construction materials are made by sintering in the electric furnace at $200{\sim}1400^{\circ}C$. The efficiency is measured 96.67% at the particle size of $0.31{\mu}m$, which is slightly lower than HEPA filter. However the efficiency is turned out to be sufficient.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.21 no.3
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• pp.99-110
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• 2018

Compared to yellow dust coming from China or particulate matter created naturally in spring due to Total Suspended Particulate(TSP), particulate matter in winter season have much more serious effect on human body as they penetrate cell membranes. Although such particulate matter are becoming a social issue, there are no concrete plans on how to reduce them. Air-purifying plants are limited in maintaining the indoor air quality of large area because it is usually difficult to quantify their performance. In order to improve this, a bio-filter that can be connected to air conditioner is suggested as an option. This study seeks to improve air conditioning model-based monitoring method for bio-filters from prior studies and objectify correlations between applied vegetation and growing environment into quantitative indicators. By doing so, this study seeks to provide criteria on plants applied to artificial soil-based vegetation bio-filters and basic information to set air-conditioning features. The study results confirmed significant tendency on the growing stability of each purifying plant in mechanical air-conditioning environment. Among three models selected for bio-filter vegetation models, epipremnum aureum showed high performance in quantitative indicators, including soil moisture, EC, and leaf temperature, etc., indicating that it would assure the highest growing stability in this test air-conditioning environment.

• Membrane Journal
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• v.20 no.4
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• pp.320-325
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• 2010

This paper was carried out to study the preparation condition and the permeation flux of reinforced poly(vinylidene fluoride) (PVDF) hollow fiber microfiltration (MF) membrane with the solvent, additive, second miscible polymer, and preparation condition used poly(vinylidene fluoride) (PVDF) such as a material with the excellent chemical stability and the milder preparation condition. The performance of the reinforced MF membrane prepared obtained the average $0.3{\mu}m$ pore size, $42kg_f/cm^2$ tensile strength, and the high water flux of 600 LMH. The change of membrane performance with various additives was considerably affected on the water flux and rejection. For hydrophilic modification of hydrophobic PVDF MF membrane, the MF membrane might be prepared with a prefer water flux and rejection by addition of hydrophilic poly(methyl methacrylate) (PMMA).

• The Korean Journal of Nuclear Medicine
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• v.23 no.1
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• pp.55-61
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• 1989

While cisplatin has been widely used in the treatment of a variety of cancers, nephrotoxicity is one of the major problems which frequently limit clinical usefulness of cisplatin. This study has been conducted to investigate nephrotoxicity of cisplatin in terms of changes in glomerular filtration rate (GFR) and effective renal plasma flow (EFPF) measured by the simultaneous use of $^{99m}Tc-DTPA$ and $^{131}I-OIH$, before and after administration of cisplatin, in 12 patients with lung cancer and four patients with esophageal cancer. Cisplatin was administrated at total doses of $75\sim100mg/m^2$ with two hour hydration and diuresis method. GFR determined by the use of $^{99m}Tc-DTPA$ had a good correlation with 24-hour creatinine clearance rate (r=0.77, p<0.001). GFR and filtration fraction decreased immediately after administration of cisplatin, however, they showed a tendency to be in completely recovered four weeks after administration. ERPF was not changed immediately after and four weeks after administration of cisplatin. GFR before and immediately after administration of cisplatin were analyzed with regard to age, sex, performance status, previous adminstration of cisplatin and method of administration. None of these factors had any influence on the rate of decrease in GFR except method of administration. Administration of cisplatin as a single dose lowered GFR more compared with that as divided doses. In this study, we have also demonstrated that the simultaneous use of $^{99m}Tc-DTPA$ and $^{131}I-OIH$ was a useful tool for the measurement of GFR and ERPF respectively.