• 대한치과교정학회지
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• 제45권5호
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• pp.268-272
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• 2015

Clear thermoplastic retainers have been widely used in daily orthodontics; however, they have inherent limitations associated with thermoplastic polymer materials such as dimensional instability, low strength, and poor wear resistance. To solve these problems, we developed a new type of clear orthodontic retainer that incorporates multi-layer hybrid materials. It consists of three layers; an outer polyethylenterephthalate glycol modified (PETG) hard-type polymer, a middle thermoplastic polyurethane (TPU) soft-type polymer, and an inner reinforced resin core. The resin core improves wear resistance and mechanical strength, which prevent unwanted distortion of the bucco-palatal wall of the retainer. The TPU layer absorbs impact and the PETG layer has good formability, optical qualities, fatigue resistance, and dimensional stability, which contributes to increased support from the mandibular dentition, and helps maintain the archform. This new type of vacuum-formed retainer showed improved mechanical strength and rate of water absorption.

• 한국분말재료학회지
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• 제14권1호
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• pp.44-49
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• 2007

In the fabrication of dye-sensitized solar cells (DSSCs), carbon counter electrode has been tested for replacing the platinum counter electrode which has two drawbacks: limited surface area and high material cost. Poor mechanical stability of carbon layer due to weak bonding strength to electrically conductive TCO (transparent conducting oxide) glass substrate is a crucial barrier for practical application of carbon counter electrode. In the present study a carbon counter electrode with high conversion efficiency, comparable to Pt counter electrode, could be fabricated by adaption of a bonding layer between particulate carbon material and TCO substrate.

• 한국정밀공학회지
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• 제18권11호
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• pp.132-137
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• 2001

Application of ceramics, carbide, ferrite has grown considerably due to their mechanical properties such as high degree hardness, chemical stability, super wear resistance. Despite these characters, the use of advanced material has not increased because of poor machinability. The application of metal bonded wheel was proposed. But it is difficult that metal bond wheel can be dressed. Recently, to solve this problem, the technology of in-process electrolytic dressing is developed. This method need wheel for electrolytic dressing, power supply and electrolyte. The aim of this study is development of CIB-D wheel for electrolytic and its evaluation of electrolytic characteristics, and achieve ultra-precision lapping of carbide, optic glass.

• Journal of the Korean Wood Science and Technology
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• 제33권2호통권130호
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• pp.17-23
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• 2005

Juvenile and transitional-juvenile wood samples from loblolly pine (Pinus taeda) were immersed in water to investigate longitudinal and tangential swelling properties. Increment cores from twenty-six loblolly pine trees were sampled at breast height (1.37 m). Earlywood rings 5 and 9 were separated from the core, extracted, oven-dried and immersed in water at room temperature. The variance in longitudinal swell was significant for ring 5 compared to ring 9 (p = 0.001). It was found that tangential swell might predict longitudinal swelling of juvenile wood at ring 9 but not at ring 5. Poor correlation in ring 5 suggests that swelling response in younger juvenile wood may differ. The swell response at ring 5 did not follow the shrinkage models discussed in the literature while ring 9 adhered to the expected curve.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.696-702
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• 2006

Flutter characteristics of composite curved wing were investigated in this study. The efficient and robust system for the flutter optimization of general composite curved wing models has been developed using the coupled computational method based on both the standard genetic algorithm and the micro genetic algorithms. Micro genetic algorithm is used as an alternative method to overcome the relatively poor exploitation characteristics of the standard genetic algorithm. The present results show that the micro genetic algorithm is more efficient in order to find optimized lay-ups for a composite curved wing model. It is found that the flutter stability of curved wing model can be significantly increased using composite materials with proper optimum lamination design when compared to the case of isotropic wing model under the same weight condition.

• Journal of Microbiology
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• 제34권1호
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• pp.82-89
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• 1996

Purine nucleoside phosphorylase (PNP) was purified in Micrococcus luteus (M. luteus) using streptomycin sulfate and amomonium sulfate fractionation, three times by a Sephadex G-100 gel filtration and a DEAE-Sephadex A-50 ion exchange chromatography. The enzyme was purified 72 folds with a 11% recovery and showed a single band in a nondenaturing gel electrophoresis. The M. W. of PNP turned out to be 1.35 * 10$^{5}$ delton in G-150 gel filtration chromatography. The stability of the enzyme was increased by treatment with both substrates, MgCI$_{2}$ or CaCI$_{2}$, but not significantly kcal/mol. M. luteus PNP catalyzed the phosphorolysis of inosine, deoxyinosine, guanosine and deoxyguanosine with the Km value of 1.5 * 10$^{-3}$ M, 3.0 * 10$^{-3}$ M, 5.0 * 10$^{-4}$ M, respectively. The enzyme was reacted with adenosine, 1-methylnosine and 1-methylguanosine as substrates, which were shown to be poor substrates for mammalian enzyme.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2018년도 춘계 학술논문 발표대회
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• pp.124-125
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• 2018

The objective of this study is analyzing of requirements for improvement of the work-life balance of construction managers working in Korean construction companies. A survey has been conducted to analyze the requirements for improvement of construction managers. The survey was conducted on construction managers working in the field of architectural construction. 59 field managers working in 18 Korean construction companies responded to the survey. Upon analysis of the survey, the working hours were excessive and recreational time was very poor for the construction managers. There were differences in the answers regarding the areas that require improvement in the working conditions based on the age groups of the construction managers. A majority of young technicians selected that the recreational time and content of work require improvement, and technicians with a lot of experience selected that the stability of occupation and wage require improvement.

• Journal of Electrochemical Science and Technology
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• 제8권2호
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• pp.162-168
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• 2017

$LiNi_xCo_yMn_zO_2$ cathode materials have been the focus of much attention because of their high specific capacity. However, because of the poor interfacial stability between cathodes and electrolytes, the cycling performance of these materials fades rapidly, especially at high temperatures. In the present paper, we propose the use of tris(trimethylsilyl) phosphate (TMSPO), which contains phosphate and silyl functional groups, as a functional additive in electrolytes. The addition of TMSPO resulted in the formation of cathode electrolyte interphase (CEI) layers on the surfaces of the cathodes and effectively suppressed electrolyte decomposition reactions, even at high temperatures. As a result, cells cycled with TMSPO exhibited remarkable capacity, which remained after 50 cycles (82.0%), compared to cells cycled without TMSPO (64.6%).

• 대한조선학회지
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• 제26권1호
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• pp.63-72
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• 1989

Container선의 선미부 선형 설계에 있어서 pram의 wideness를 증가시킴에 따라 발생될 수 있는 여러 사항을 조사하였다. $KM_T$의 증가로 인한 정수중의 복원력 향상 및 상갑판위에 화물적재의 양을 늘일 수 있다는 점과 더불어 항해중 복원성능의 변화, 선체변동압력의 증대, 저항추진성능에 미치는 영향 그리고 선체구조 측면에서의 고려사항등을 검토하였다.

• 대한화장품학회지
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• 제22권2호
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• pp.89-98
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• 1996

A novel polymeric sunscreen agent was developed. It was prepared by the coupling reaction of 2-ethylhexyl 4-hydroxycinnamate with poly vinylbenzyl chloride(PVBC, average MW 6,500). In this reaction the reactivity was mostly affected by catalyst. In the absence of catalyst the yield was approximately 55% and in the presence of tetrabutylammonium bromide the yield was about 65%, but in the presence of tetrabutylammonium iodide the yield was 100% to give a average molecular weight 20,000 polymeric sunscreen agent. There were no side reactions, and its structure and purity were confirmed by various analytical methods, such as NMR, IR, and so on. UV radiation absorption efficiency is more than 70% compared with that of octyl methoxycinnamate. The solubility in polar oil, for example C12-15 alkylbenzoate and caprylic/capric triglyceride, is more than 50%. It showed high stability in the time course of test including acceleration test. This polymer is safe to skin because of poor permeability to skin, no side products in the process of preparing, and easy elimination of excess starting materials.