• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2003.11a
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• pp.299-306
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• 2003

The SCM420 used mainly to automobile transmission gear has problems that it costs transmission gear maker much money in carburizing treatment. For this, it needs to alternate the existing material and heat treatment to new gear material and surface modification. For this, friction and wear experiment according to sliding speed and applied load was carried out to evaluate the wear resistance of two transmission gear materials with oxidation nitrocarburising and non-oxidation nitrocarburising NT100, The presumed wear volume was calculated with the image processing for evaluation of wear resistance of two transmission gear materials. The results show that the oxidation nitrocarburising has a distinguished wear resistance than non-oxidation nitrocarburising.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1993.04a
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• pp.55-55
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• 1993

Farnesyl Protein transferase(FPT)는 발암유전자 ras의 단백질 산물인 p$^{21}$의 post-translational modification의 첫 단계인 ras-farnesylation에 관여하는 효소로 본 연구에서는 정제된 FPT와 E. coli에서의 발현 system을 이용하여 FPT의 구조와 기능을 밝히고 이를 FPT 방해제의 설계에 이용하고자 한다. Bovine testis에 존재하는 FPT를 30%-50%의 Ammonium sulfate로 fractionation하고, DEAE-Sephacel, Sephacryl S-300 column을 통과시킨 후 peptide(KKCVIM) affinity column을 이용하여 순수 정제하였다. 정제된 효소의 분자량은 gel-filtration에 의해 100KDa으로 추정되었고 SDS-PAGE 결과 49KDa과 46KDa의 두 subunit로 구성되었음이 확인되었다. 효소활성에는 $Mg^{2＋}$ 와 $Zn^{2＋}$가 필수적이며 최적 pH는 7.0이었다. Yeast의 FPT의 두 subunit 유전자는 Yeast genomic DNA를 template로 사용하고 각 subunit에 specific한 합성된 primer들과 vent polymerase를 이용하여 Polymerase chain reaction을 통하여 얻었다. 두 유전자를 pBluescriptII SK＋ vector를 변형시킨 두 vector, pBSK＋4와 pBChl＋4에 재조합 시킨 후 E.coli에 transformation시켜 발현시켰다. 현재 정제된 Bovine FPT와 E. coli에서 발현된 Yeast FPT의 chemical modification과 site-directed mutagenesis를 통하여 FPT의 active site와 substrate binding site에 관한 연구를 진행시키고 있다.

• International Journal of Precision Engineering and Manufacturing
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• v.9 no.4
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• pp.71-73
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• 2008

The development of polymer/inorganic nanocomposites has attracted a great deal of interest due to the improved hybrid properties derived from the two different components. Various nanoscale fillers have been used to enhance polymer mechanical and thermal properties, such as toughness, stiffness, and heat resistance. The effects of the filler on the final properties of the nanocomposites are highly dependent on the filler shape, particle size, aggregate size, surface characteristics, polymer/inorganic interactions, and degree of dispersion. In this paper, we describe the influence of different $CaCO_3$ dispersion methods on the thermal properties of polyethylene terephthalate (PET)/$CaCO_3$ composites: i.e., the adsorption of $CaCO_3$ on the modified PET surface, and the hydrophobic modification of the hydrophilic $CaCO_3$ surface. We prepared PET/$CaCO_3$ nanocomposites using a twin-screw extruder, and investigated their thermal properties and morphology.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.5
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• pp.441-449
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• 2014

Thermoplastic fusion bonding is widely used to seal polymer microfluidic devices and optimal bonding protocol is required to obtain a successful bonding, strong bonding force without channel deformation. Besides, UV modification of the PMMA (poly-methyl methacrylate) is commonly used for chemical or biological application before the bonding process. However, study of thermal bonding for the UV modified PMMA was not reported yet. Unlike pristine PMMA, the optimal bonding parameters of the UV modified PMMA were $103^{\circ}C$, 71 kPa, and 35 minutes. A very low aspect ratio micro channel (AR=1:100, $20{\mu}m$ depth and $2000{\mu}m$ width) was successfully bonded (over 95%, n>100). Moreover, thermal bonding of multi stack PMMA chips was successfully demonstrated in this study. The results may applicable to fabricate a complex 3 dimensional microchannel networks.

• Macromolecular Research
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• v.16 no.7
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• pp.659-662
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• 2008

A new and useful poly(ethylene oxide)-based pH-sensitive block copolymer is introduced. Poly(ethylene oxide-b-N-phenylmaleimide) was first synthesized by anionic polymerization of N-phenylmaleimide (N-PMI) using mixed alkali metal polymeric alkoxide by sequential monomer addition method in the mixture of benzene/THF/DMSO (10/5/3, v/v/v) at room temperature. Reductive deimidation of the resulting block copolymer was performed using hydrazine monohydrate leading to the formation of the corresponding pH-sensitive poly(ethylene oxide-b-maleic acid).

• Journal of Electrochemical Science and Technology
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• v.2 no.3
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• pp.143-145
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• 2011

Metal-binding antibiotics are very attractive choices as cation selective ionophores. The ability of tetracycline (TC) antibiotics to bind to metal ions has obtained much attention. TCs exhibit the potentiometric performance changes for various cations dependant on several experiment conditions. In this report, we investigated the potentiometric performance changes of TC as the modification of TC's possible metal binding site. We found that the selectivity alter with the blocking main binding site of ionophores for cations. And, additionally it is possible to control the selectivity of sensors with chemical modification of ionophores.

• Journal of Pharmaceutical Investigation
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• v.30 no.2
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• pp.73-83
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• 2000

Polyethylene glycol (PEG) is a water soluble, biocompatible, non-toxic polymer and PEGylation is a well established technique for the modification of therapeutic proteins and peptides. PEG-protein drugs have been extensively studies in relation to therapies for various diseases: cancer, inflammation and others. The covalent attachment of PEG to proteins and peptides prolonged plasma half-life, reduced antigenicity and immunogenicity, increased thermal and mechanical stability, and prevented degradation by enzymes. Several chemical groups for general and site specific conjugation have been exploited to activate PEG for amino group, carboxyl group, and cysteine groups. PEGylation of many proteins and peptides have been studied to enhance their properties for the potential uses. Also, the different positional isomers in several PEG-proteins have shown the difference in vivo stability and biological indicating that the site of PEG molecule attachment is one of the important factor to develop PEG-proteins as potential therapeutic agents.

• Journal of the Korean Society of Clothing and Textiles
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• v.4 no.1_2
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• pp.19-24
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• 1980

To study possible modification of acrylic fiber, Cashmilon SF was treated with hexamethylene-diamine(HMDA) in toluene at elevated temperature. Physico-chemical properties of treated fiber were tested by dyeing with benzyl scarlet BS and by measuring tensile strength of the fiber. Following results were obtained from this experiment. 1) HMDA and fiber were condensed at above $120^{\circ}C$. 2) Treated samples could be dyed with acidic dyes. 3) Treatment with HMDA decreased tensile strength of the fiber. This study therefore suggests that HMDA can be used to modify the properties of the fiber.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.05a
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• pp.101-101
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• 2015

Photoelectrochemical water splitting is considered as a promising method of transforming solar energy into chemical energy stored in the type of hydrogen. An n-type $WO_3$ semiconductor is one of the most promising photoanodes for hydrogen production from water splitting. Films annealed at lower temperatures consisted of amorphous, whereas films annealed above $500^{\circ}C$ comprised solely of monoclinic $WO_3$. In this study, we observed photoactivity of $WO_3$ as increasing thickness of $WO_3$. And it shows good photoacivity as thickness increases. Also we tried to improve photoactivity through surface modification and bulk modification by using hydrogen treatment and conducting polymer. The photocurrent was measured in potentiostatic method with the three electrode system. A Pt wire and Ag / AgCl electrode were used as the counter electrode and the reference electrode, respectively. photocurrent-time (I-T) curve was measured at a bias potential of 0.79 V.

• Macromolecular Research
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• v.16 no.6
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• pp.524-531
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• 2008

The mitigation or elimination of methanol crossover for perfluorosulfonic acid fuel cell membranes has been investigated extensively for direct methanol fuel cell applications with the aim of increasing the electrochemical performance and enhancing the utilization rate of methanol. Self-assembly modifications by applying an oppositely charged polyelectrolyte to Nafion membranes were attempted in order to block or reduce methanol crossover while maintaining the other advantageous properties of Nafion membranes. It was reported that anionic polyallylamine hydrochloride (PAH) was the most efficient polyelectrolyte in reducing methanol crossover, and considerable cell performance was obtained even at a methanol feed concentration of 10 M.