Effects of Tooth Whitening and Topical Fluoride Application on Shade and Translucency Changes in Tooth with Early Caries Lesion

류현,김정숙,이명구,김용성 대한예방치과학회 2010 International Journal of Clinical Preventive Denti Vol.6 No.1

Objective: The purpose of this study was to evaluate shade and translucency change by means of various topical fluoride application after tooth whitening on teeth with artificial caries lesions. Materials and method: 84 extracted anterior teeth were selected and induced to artificial caries by 0.1 M lactic acid-sodium hydroxide buffer solution, then tooth whitening treatment were performed for 2 weeks. Topical fluoride application was sequentially applied for 4 times. Improvement of shade and translucency were checked by Shadescan and evaluated according to types of whitening agents, topical fluoride agents and application methods. Results: By application of tooth whitening agent, translucency seemed to be increased in all groups (p<0.05), but after 2 weeks, there was no significant difference within group and also between group comparisons (p>0.05). Except of 22% carbamide peroxide gel application group, value difference ratio was decreased significantly and value difference between the lesion and normal tooth area seemed to be increased (p<0.05). At the beginning of fluoride application, translucency was improved significantly in 0.1% sodium fluoride strip group and fluoride varnish application groups (p<0.05) ; at 4 weeks, all groups showed the significantly increased translucency (p<0.05). There was no significant difference between groups comparisons (p>0.05). Control group and 2% sodium fluoride strip application group showed constant increasing of value difference ratio between the lesion and normal tooth area (p<0.05) ; 0.1% sodium fluoride strip group seemed to be steady state ; fluoride varnish group showed continuous recovery of value difference ratio (p<0.05). Conclusion: It seemed that demineralized area of tooth with early caries was remineralized without any treatment, in addtion fluoride application could make it possible to accelerate recovery of tooth shade and translucency. Clinically in case of patient showed incipient caries in their anterior teeth, just applying whitening agent had any alternative plan could make additional inconsistency and demineralization. It was suggested that fluoride application after whitening to such patients could make more desirable improvement of shade and advanced remineralization.

유기농 아이 외 1편

류현 천년의시작 2018 (계간)시작 Vol.17 No.3

고분해능 투과전자현미경을 이용한 $A^{2+}$(Mg$_{1/3}$Nb$_{2/3}$)O$_3$,(A$^{2+}$=Sr$^{2+}$ and $Ca^{2+}$) 세라믹스의 구조연구

류현,남산,변재동,이확주,박현민,Ryu, Hyun,Nahm, Sahn,Byun, Jae-Dong,Lee, Hwack-Joo,Park, Hyun-Min 한국세라믹학회 1999 한국세라믹학회지 Vol.36 No.7

The crystal structure of A2+(Mg1/3Nb2/3)O3,(A2+=Sr2+ and Ca2+)ceramics was studied usig X-ray diffraction (XRD) and high resolution transmission electrion microscopy(HRTEM). Ba(Mg1/3Nb2/3)O3 (SMN) has the 1:2 ordered monoclinic structure which has the anti-phase tilt of octahedra. The type of tilting in SMN was considered to be a$^{\circ}$a$^{\circ}$c- or a­a­c$^{\circ}$ Ca(Mg1/3Nb2/3)O3 (CMN) also has the 1:2 ordered monoclinic structure which was distorted by the anti-phase tilt or in-phsae tilt of octahedra. A unit cell containing both the in-phase tilt axis and anti-phase tilt axis was not observed in the CMN. Therefore CMN has the mixed phase consisting of the 1:2 ordered monoclinic phase with anti-phase tilt of octahedra and the one with in -phase tilt of ocatahedra,. The anti-parallel shift of cation was also observed in the CMN.

시각장애학교 중등학생의 수학적 성향 분석

류현,이해균 한국시각장애교육&재활학회 2013 시각장애연구 Vol.29 No.2

The Purpose of this study is to analyze mathematical disposition of secondary course students in schools for the blind. It offers basic materials to develope methods and strategies that can enhance their interest and motivation in learning mathematics. To carry out the purpose, secondary course students attending 12 schools for the blind throughout the nation were categorized as gender, course, time at onset of the visual impairment, primary literacy medium for learning, and experience of general education. Questionnaire was distributed and analyzed on behalf of their mathematical disposition. Confidence, adaptability, continuity, interest, self-monitoring and awareness of mathematical applicability were contained in mathematical disposition. The results on mathematical disposition and its components from this investigation were as follows. The mathematical disposition level of secondary course students attending schools for the blind is revealed average. Awareness of mathematical applicability indicates highest level in the mathematical disposition components. Male students indicate higher level than female students do in the mathematical disposition of secondary course students attending schools for the blind. Male students indicate higher level than female students do in their adaptability, continuity, interest of mathematics and awareness of mathematical applicability. Middle school course students indicate higher level than high school course students do in their continuity of mathematics. Braille users indicate higher level than regular print (including regular-sized, large-sized, and enlarged materials) users do in their mathematical adaptability. Students who had taken general education indicate higher level than those who had not taken general education in their mathematical confidence. 본 연구는 시각장애학교 중등학생의 수학 교과 관련 학습 특성을 파악하기 위하여 전국 12개 시각장애학교 중등학생 319명을 대상으로 수학적 성향에 관하여 분석하였다. 이를 수행하기 위해 수학적 성향의 하위 6개요인 24문항의 설문지를 구성하여 도출한 연구 결과를 요약하면 다음과 같다. 첫째, 시각장애학교 중등학생의 수학적 성향은 보통 수준이었고, 하위 요인 중 수학의 가치 인식이 가장 높았다. 둘째, 시각장애학교 중등학생 중 남학생이 여학생보다 수학적 성향이 더 높았으며, 사고 과정의 융통성, 문제 해결에 대한 의지, 수학적 호기심, 수학의 가치 인식도 더 높았다. 중학생이 고등학생보다 문제 해결에 대한 의지가 더 높았고, 사용하는 문자매체가 점자인 학생이 묵자인 학생보다 사고 과정의 융통성이 더 높았다. 일반학교 재학 경험이 있는 학생이 없는 학생보다 수학에 대한 자신감이 더 높았다. 이러한 연구결로 시각장애학교 중등학생의 수학적 성향은 보통의 수준이며, 성별ㆍ과정별 차이는 정안학생과 유사함을 할 수 있다. 이를 중심으로 후속 연구에 필요한 제언을 하였다.

순 방향 DC-DC 변환기의 간단하고 효과적인 동기 정류기에 대한 연구

柳鉉,朴鍾伯 조선대학교 생산기술연구소 1997 生産技術硏究 Vol.19 No.1

A simple and efficient MOSFET synchronous rectiflcation circuit suitable for forward DC-DC converters is proposed. The main feature of this circuit is the addition of a capacitor in parallel with the drain-source of the MOSFET used as a rectifying device. This capacitor extends the conduction period of the MOSFET used as a freewheeling device. As a result, a 92% efficiency at 5V for 10A output is achieved.

[당선작] 교양 외 4편

류현 천년의시작 2018 (계간)시작 Vol.17 No.1

접지판과 방사 패치 사이의 간격 변화에 따른 QMSA의 특성 연구

류현,박성교,박종백,Ryu, Hyun,Park, Sung-Kyo,Park, Chong-Baek 한국음향학회 1999 韓國音響學會誌 Vol.18 No.4

본 논문에서는 CHUKOH사의 CGP-500 PTFE 기판상에(유전율 2.6, 두께 1.6mm(±0.08)) 접지판의 폭과 방사 패치의 폭이 동일한 850MHz 대의 QMSA(Quarter-Wavelength Microstrip Antenna)를 설계·제작하였다. 실험에 의하여 가장 양호한 급전점을 선정하여 프로브 급전한 다음, 방사 패치와 그라운드 판과의 간격 L₃을 단계적으로 5mm씩 잘라가면서 QMSA의 공진 주파수와 반사 손실을 측정하였다. 그 결과, 간격 L₃이 좁아질수록, 특히 10mm 이하에서는 예상과 달리 공진 주파수는 증가하고 반사 손실은 감소하는 것을 알 수 있었다. In this paper, we designed and fabricated QMSA(Quarter-Wavelength Microstrip Antenna) for 850MHz band on the CGP-500 PTFE substrate(by CHUKOH company) with ε/sub r/=2.6, H=1.6mm(±0.08), where width of the radiation patch is .identical with that of the ground plane. A well matched feed point was obtained by experiments and this QMSA was fed by using prove feed method. The resonant frequencies and the return losses were mcasured by cutting the gap L₃ between the radiation patch and the ground plane, with a 5mm cutting length, step by step. As a result, we found that the measured return losses were decreased and the resonant frequencies were increased when the gap L₃ was shorter, especially under 10mm, unlike we had expected.

자기구동 동기 정류의 공진 토플로지 응용에 대한 연구

柳鉉,朴鍾伯 조선대학교 생산기술연구소 1996 生産技術硏究 Vol.18 No.2

The MOSFET devices are driver in a resonant fashion by the power circuit, resulting in partial recovery of the energy stored in the parasitic capacitances. The necessity of developing high efficiency-low output voltage converters with very high efficiency for distributed power supply systems, leads to the substitution of the recifier diodes of the output stage by synchronous rectifiers. Resonanl synchronous rectification is, when feasible, the best synchronous rectification technique in high switching frequency resonant topologies. The main feature of this circuit is the addition of a capacitor in parallel with the drain-source of the MOSFET used as a rectifying device. A selection of the resonant topologies where it can be implemented and considerations about the resonant synchronous rectifier are presented in this paper. To verify the utility of these techniques. a 100W(SV,20A)Forward ZVS-MRC has been built and tested, obtaining efficiency over 87%. This converter has also been tested at 3.3V, obtaining efficiency of 84%.

국제 학술지 분석을 통한 시각장애학생의 학습 관련 보조공학 도구 연구 동향 조사

류현,이해균 한국특수교육학회 2014 한국특수교육학회 학술대회 Vol.2014 No.1

도심 고등학교의 온실가스 인벤토리 작성 및 저감 시나리오 효과 분석

류현,김정우,고우형,이윤영,심혜철,위대현 한국환경교육학회 2012 한국환경교육학회 학술대회 자료집 Vol.2012 No.12