• Applied Chemistry for Engineering
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• v.18 no.4
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• pp.386-390
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• 2007

In this study, polyurethane prepolymers were synthesized from polycaprolactonediol (PCDs. M.W. 530, 830, 1000, 1250, and 2000) and polycaprolactonetriol (PCTs. M.W. 300 and 900), and hexamethylenediisocyanate (HMDI). Polyurethane beads was prepared from the different prepolymers by a two-step suspension polymerization. The particle size of polyurethane beads was investigated by particle size analyzer. The beads were $10{\sim}30{\mu}m$ in size. The structure of beads was confirmed by FT-IR spectrometer. Their thermal properties were analyzed by TGA. Glass transition temperatures ($T_g$) of the beads were in the range of $-23{\sim}-53^{\circ}C$ and decreased with the increase of the PCD molecular weight. In order to prevention the cohesion of beads, the beads were coated with tetraethoxysilane (TEOS).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.202-202
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• 2009

대전제어제를 이용하여 전하량을 가지는 토너 입자를 제조하고, 입자의 유동성을 부여하기 위하여 입자의 표면처리를 하였다. 제조된 토너 입자의 크기는 약 $8{\mu}m$정도이며, 표면 처리를 위해 크기가 약 14nm 정도인 nano-silica를 사용하였다. 대전제어제가 첨가된 토너 입자의 평균 전하질량비는 30.9uC/g이고, 표면처리를 한 입자의 전하질랑비는 외첨 시간이 증가함에 따라 점차적으로 감소하는 것을 관찰 할 수 있었다. 또한 표면처리가 된 입자의 유동성은 표면처리를 하지 않은 입자 보다 우수하다는 것을 관찰 할 수 있었다.

• Journal of Biomedical Engineering Research
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• v.30 no.4
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• pp.311-317
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• 2009

An automatic control system is proposed and implemented for a miniaturized DNA extraction system using magnetic bead. A host-local system is employed for the accommodation of the graphical user interface and the basic control function. The functional partitioning into the local and the host system is discussed. The control functions are classified and formalized for the flexible control scenario, which is the input of the proposed system. As the proposed scenario is consists of the sequence of the user-centric actions, the user goal can be easily programmed and modified. The DNA extraction performance of the implemented system was compared with the existing silica-membrane-based method, resulting in the comparable concentration and purity of the extracted DNA. The proposed system is currently being utilized for the development of the DNA extraction system only changing scenario, without any alteration of the system.

• Journal of Korea Soil Environment Society
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• v.4 no.2
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• pp.103-111
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• 1999

This study is on the mathematical modeling and its verification of the retardation phenomenon of gas migration in an unsaturated zone of very little moisture content The adsorption of VOCs onto the surface of the dry medium was taken into account, which has not been usually considered in the conventional models. The trichloroethylene(TCE) gas migration predicted from the mathematical model developed in this study fits the experimental results obtained from a dry glass-bead column and a dry silica sand column very well The model developed in this study gave much better prediction than did a coventional model.

• Annals of Clinical Microbiology
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• v.19 no.1
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• pp.20-23
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• 2016

In the RNA-based study, it is important to extract high-quality RNA. However, RNA extraction from Mycobacterium tuberculosis is problematic due to its thick, waxy cell wall rich in mycolic acid, which renders the cells resistant to lysis. Using TRIzol reagent and several powerful bead-beating steps, a high quantity of RNA was obtained.

• Journal of the Korean Ceramic Society
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• v.54 no.1
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• pp.49-54
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• 2017

In this study, based on hydrolysis and condensation via $St{\ddot{o}}ber$ process of sol-gel method, synthesis of mono-dispersed silica nanoparticles was carried out with hydrophilic solvent. This operation was expected to be a more simplified process than that with organic solvent. Based on the sol-gel method, which involves simply controlling the particle size, the particle size of the synthesized silica specimens were ranged from 30 to 300 nm by controlling the composition of tetraethylorthosilicate (TEOS), DI water and ammonia solution, and by varying the stirring speeds while maintaining a fixed amount of ethanol. Increasing the content of DI water and decreasing the content of ammonia caused the particle size to decrease, while controlling the stirring speed at a high level of RPMs enabled a decrease of the particle size. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) were utilized to investigate the success factors for synthesizing process; Field emission scanning electron microscopy (FE-SEM) was used to study the effects of the size and morphology of the synthesized particles. To analyze the dispersion properties, zeta potential and particle size distribution (PSD) analyses were utilized.

• KSBB Journal
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• v.8 no.4
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• pp.313-319
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• 1993

Methyl fructoside was synthesized from sucrose and methanol using an immobilized invertase. The enzyme was covalently bound by glutaraldehyde on porous silica coated with polyethyleneimine to give loading capacity of 120mg of invertase per one gram of dry porous silica and effective activity of 100U per one milligram of bound invertase. Polyethyleneimine coating imparted a hydrophillic character, good activity retention and high loading capacity to the surface of porous silica as well as hydrophillic microenviroment in the vicinity of bound invertase. The immobilized enzyme was formed into an alginate-enclosed silica bead to have enough activity for methyl fructoside synthesis from aqueous methanol-sucrose solution. Using the alginate-enclosed biocatalyst the yield of methyl fructoside was obtained as high as 55.9% from aqueous 30% (v/v) methanol and 0.291mo1/l sucrose with 2U/ml activity at $25^{\circ}C$, pH 4.8.

• Microbiology and Biotechnology Letters
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• v.43 no.3
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• pp.300-305
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• 2015

The glutamate decarboxylase gene (gadB) from Lactobacillus plantarum WCFS1 was cloned and expressed as an N-terminal hexa-histidine-tagged fusion protein in Escherichia coli BL21 (DE3) as the host strain. Purified glutamate decarboxylase (GAD) was immobilized onto porous silica beads by covalent coupling. The pH dependence of activity and stability of the immobilized GAD was significantly altered, when compared to those of the free enzyme. Immobilized GAD was stable in the range of pH 3.5 to 6.0. The resulting packed-bed reactor produced 41.7 g of γ-aminobutyric acid/l·h at 45℃.

• Clean Technology
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• v.17 no.2
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• pp.150-155
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• 2011

The removal process of heavy metal ion in aqueous solution by the functionalized silica bead was simulated using the finite difference method. Equilibrium model and non-equilibrium model were proposed and the effects of dimensionless groups and various parameters were investigated. Freundlich isotherm was used in equilibrium model and 1st order adsorption rate expression was assumed in non-equilibrium model. The comparison results by the predictions of equilibrium and non-equilibrium models showed good agreement. The predictions of equilibrium model were compared with experimental results reported in literature and showed the marginal agreement.

• Applied Chemistry for Engineering
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• v.1 no.2
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• pp.133-139
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• 1990

Methacrylate functional silanes with different methylene spacer groups have been synthesized and the orientation effect and absorption behavior of these silane coupling agent were investigated by Fourier transform infrared spectroscopy(FT-IR). The mechanical properties of glass bead/polyester composites are found to be dependent on the spacer group of treated silane coupling agent. The absorption rate of the silane coupling agent onto the fumed silica surface decreases with increasing the number of the methylene spacer in methacrylate functional silanes. Silane molecules containing long spacer groups are adsorbed onto silica slightly bowed with respect to the substrate surface. The relationship between silane molecular structure and mechanical properties of polymer composites is also investigated in order to improve hot/wet properties of glass fiber/polyester composites.