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김병현,권혁춘 大韓齒科保存學會 1998 Restorative Dentistry & Endodontics Vol.23 No.1
The physical properties of polymer are greatly influenced by the extent to which resin cures. The presence of unreacted monomer can have a plasticizing effect on the polymer, thereby altering the physical and mechanical properties of dentin bonding agent(DBA). If the DBA does not polymerize sufficiently, it will leave a weak bonding layer and lead to lower bond strength. The purpose of this study was to evaluate te shear bond strengths(SBS) and the degree of conversion(DC) of 4 commercialy avilable dentin bonding systems which are composed of 2 multi-bottle systems [Scotchbond Multi-Purpose(SMP), AeliteBond(AB)] and 2 one-bottle systems [SingleBond(SB), One-Step(OS)]. For shear bond strength measurement, labial surfaces of freshly extracted bovine incisors were ground with #600 grit SiC paper to expose dentin. Four different groups of samples were formed, with 10 samples being made for each of the 4 commercial DBA in each group according to the curing sequences of DBA and overlayer thickness of composites:Group Ⅰ (standard cure and 1㎜ thick composites):The DBA was light cured and the composites of 1㎜ thickness was applied;Group Ⅱ (standard cure and 2㎜ thick composites):The DBA was light cured and the composites of 2㎜ thickness was applied;Group Ⅲ(simultaneous cure and 1㎜ thick composites):The DBA was not light-cured and simultaneously cured with composites of 1㎜ thickness;Group Ⅳ(simultaneous cure and 2㎜ thick composites):The DBA was not light-cured and simultaneously cured with composites of 2㎜ thickness. The SBS was measured immediately after the composites was bonded to the bovine dentin using an Instron machine. The DC of the DBA as examined in a thin film under simulated conditions of the experimental groups according to the curing sequences and overlayer thickness of composites in the SBS test. using a Fourier transform Infrared(FTIR) spectrometer. The following results were obtained from SBS tests and DC measurements 1. In SBS tests, the multi-bottle DBA(SMP, AB) had a generally higher bond strength values than the one bottle DBA(SB, OS). In DC measurements, the one bottle DBA(SB, OS) had a significantly higher DC than the multi-bottle DBA(SMP, AB). 2. In all DBAs except OS, there was no significant difference between the bond strength of group Ⅰ(standad cure and 1㎜ thick composites) and that of group Ⅲ(simultaneous cure and 1㎜ thick composites). SMP, SB in Group Ⅰ had a significantly higher DC than those in group Ⅲ, but AB, OS in group Ⅰ had a significantly lower DC than those in group Ⅲ 3. All DBAs in Goup Ⅱ(standard cure and 2㎜ thick composites) had significantly higher bond strength and DC than those in Group Ⅳ(simultaneous cure and 2㎜ thick composites). 4. In all DBAs, there was no significantly different SBS and DC between Group Ⅰ and Group Ⅱ, but all DBAs in Group Ⅲ had significantly higher SBS and DC than those in Group Ⅳ.
함포시스템 격침핀 열처리 개선을 통한 사격안정성 향상 연구
김병현,나라별,김병호 국방기술품질원 2022 국방품질연구논집 Vol.4 No.1
본 연구는 76mm 포탄 발사 시 발생하는 격침핀 휨 현상을 해결하기 위한 결과이다. 함포 사격 중 격침핀이 비정상적으로 휘어지는 현상이 발생하였다. 원제작사 제품과 화학성분은 유사하지만, 열처리 공정이 다른 것을 확인하였다. 따라서 열처리 공정을 개선하고 경도를 원제품과 비슷하게 하기 위해 Q/T 처리 후 표면 열처리 방법 중 하나인 고주파 열처리를 통해 선단부와 핀 하단부의 경도를 분류하였다. 개선제품의 효과를 확인하기 위해 실제 사격시험을 실시했으며, 기존 제품은 촬영 후 휘어지는 현상이 있었지만 개선제품은 휘어지는 현상이 없었다. 이를 통해 품질이 향상되었음을 확인할 수 있었다.
김병현,박권하,이상수,성낙원 한국마린엔지니어링학회 2000 한국마린엔지니어링학회지 Vol.24 No.2
A diesel engine has been studied for many years to improve fuel economy and to reduce emissions as important factors governing the emission performance of diesel engines. This study addresses to swirl effects on combustion characteristics in a large diesel engine. The transport equations of flows and chemical reactions are given for fully compressible fluid. The simulations have been done for compression and expansion strokes and the results are given at several crank angles which are the angles at just before injection start, TDC, ATDC 90 and just before exhaust valve open. The results show that the strength of the swirl flow makes many effects on burning fuel and forming emissions.