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고유전 (Ba, Sr) $TiO_3$ 박막 커패시터의 저전계 영역에서의 전기전도기구
장훈,장병탁,차선용,이희철,Jang, Hoon,Jang, Byung-Tak,Cha, Seon-Yong,Lee, Hee-Chul 대한전자공학회 1999 電子工學會論文誌, D Vol.d36 No.6
High density DRAM의 cell capacitor로 촉망 받고 있는 고유전체 BST박막 커패시터의 저 전계(<0.2MV/cm) 영역에서의 전기전도 현상을 분석하였다. 저 전계 영역에서 Pt/BST/Pt구조의 MIM 커패시터에 일정 전계를 인가한 후 전류를 측정하는 I(t)방법을 이용하여 유전완화전류와 누설전류를 분리해내어 박막의 측정온도 변화, 전계의 크기, 인가방향 변화, 후속 열처리에 따른 BST 박막의 전기전도 기구를 분석하였다. 그 결과, 유전완화전류는 Hoppiong process에 의한 BST박막내부의 trap된 전자들의 이동에 의한 전하재배치로 설명되어지며, 누설전류도 박막내의 trap에 의한 poole-Frenkel process에 의한 것임을 알 수 있었다. 그리고 각 전류성분에 기억하고 있는 trap이 BST박막내의 산호 결핍임을 추정하였다. The electrical conduction mechanism of high dielectric $(Ba,Sr)TiO_3$ (BST) thin film capacitor, which is the promising cell capacitor for high density DRAM, was investigated in low field region (<0.2MV/cm). It is known that the current in the low field region consists of dielectric relaxation current and leakage current. The current-time (I-t) measurement technique under the constant voltage was used for extracting successfully each current component. The conduction mechanism of the BST capacitor was deduced from the dependency of the current on the measurement temperature, strength of electric field, the polarity of applied electric field and post annealing process. From these results, it was suggested that the dielectric relaxation current and the leakage current are originated from the redistribution of internally trapped electron by hopping process and Pool-Frenkel conduction mechanism, respectively. It was also concluded that traps causing these two current components are due to oxygen vacancies within the BST film.
장훈식(Hoon-Sik Jang),권성환(Sung-Hwan Kwon),이윤희(Yun-Hee Lee),백운봉(Un-Bong Baek),김엄기(Am-Kee Kim),남승훈(Seung-Hoon Nahm) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
??The response of multi walled carbon nanotube(MWNT) to mechanical strain applied with an nano-manipulator were investigated inside scanning electron microscope (SEM). MWNT were produced by arc-discharge method and specimens for tensile test were selected among the MWNT which has rectilinearity and purity above 40%. The average diameter of MWNT was approximately 15㎚. In order to measure the resistance of MWNT during tensile test, an individual MWNT was attached at the tungsten (W) tip using electron beam induced deposition. The contact resistance between MWNT and W tip decrease during the exposure of electron beam. The W tip were manipulated and controlled by nano-manipulator and personal computer. We observed that resistance of samples was significantly changed until the MWNT fracture.
장훈식(Hoon-Sik Jang),이윤희(Yun-Hee Lee),백운봉(Un-Bong Baek),박종서(Jong-Seo Park),남승훈(Seung-Hoon Nahm) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
Carbon nanotubes (CNTs) have attracted an increasing attention due to their superior mechanical properties and potential application in industries. The strength of CNT has been predicted or calculated through several simulation techniques but actual experiments on stress-strain behavior are rare due to its dimensional limit, nanoscale positioning/manipulation, and instrumental resolution. We have attempted to observe straining responses of a multi-walled carbon nanotube (MWNT) with different growth methods by performing an in-situ tensile testing in a scanning electron microscope. Linear deformation and fracture behaviors of MWNT were successfully observed and its force-displacement curve was also measured from the bending stiffness and displacement of the force sensor and manipulator. We also obtained different tensile load of carbon nanotube with different growth methods.
Effects of RetroMTA on osteoblastic differentiation in MC3T3-E1 cells
Hyo-Il Lee(이효일),Sung-Hyeon Choi(최성현),Ji-Hyun Jang(장지현),Hoon-Sang Chang(장훈상),Yun-Chan Hwang(황윤찬),In-Nam Hwang(황인남),Bin-Na Lee(이빈나),Won-Mann Oh(오원만) 대한치과재료학회 2018 대한치과재료학회지 Vol.45 No.2
Mineral trioxide aggregate (MTA) provides a very good sealing, acceptable biocompatibility, dentin bridge formation and osteo-inductive effect. However, MTA has a few drawbacks. RetroMTA including calcium-zirconia complex has been developed to overcome drawbacks of MTA, especially long setting time and difficult handling characteristics. Therefore, the aim of this study was to evaluate the effects of RetroMTA on biocompatibility, osteogenic differentiation and mineralization in MC3T3-E1 cells compared with conventional MTA. Cytotoxicity was assessed by WST-1 assay. The gene expression of osteogenic markers was detected by real-time PCR. ALP activity and mineralization behavior were evaluated using ALP and alizarin red staining. There was no statistically significant difference between ProRoot MTA and RetroMTA with material extracts at dilutions of 1/4, 1/10 and 1/50 in cell viability assay. Expression of osteogenic markers in both ProRoot MTA and RetroMTA groups was significantly higher than in control group. In the mineralization assay, RetroMTA showed significantly higher formation of mineralized nodules than in control. In conclusion, RetroMTA promotes osteogenic differentiation and potential mineralization. It appears to be a potential alternative to ProRoot MTA as a root-end filling material.
장철훈(Chul-Hoon Jang),장동길(Dong-Gil Jang),이빈나(Bin-Na Lee),장훈상(Hoon-Sang Chang),황윤찬(Yun-Chan Hwang),오원만(Won-Mann Oh),황인남(In-Nam Hwang) 대한치과재료학회 2021 대한치과재료학회지 Vol.48 No.3
The objective of present study was to compare the color stability of esthetic materials after application of fluoride varnishes. Esthetic restorative materials including composite resin (Filtek Z350 XT, 3M ESPE, MN, USA), resin modified glass-ionomer (RMGI, Fuji II LC, GC Co., Tokyo, Japan), and giomer (Beautifil Flow Plus F00, Shofu Inc., Kyoto, Japan) were used in this study. Cavity shield (3M ESPE, MN, USA) and V-varnish premium (Vericom, Seoul, Korea) were used as the fluoride varnishes. 30 samples of each restorative materials were prepared, which were divided into 10 each, among three groups. Group I were stored in distilled water, which were used as the control, Group II were applied with Cavity shield and Group III were applied with V-varnish premium. All specimens were stored in the distilled water at 60 ℃ for 30 days for the accelerated test. Samples were then subjected to colorimetric analysis. Data collected was statistically analyzed using one way ANOVA and Tukeys post-hoc test (p=0.05). The color change before and after application of varnish was observed in all experimental groups. Especially RMGI showed highest ΔE * value (p<0.05). The color change according to the accelerated test showed no significant difference in the varnish application group and the control group. Giomer and RMGI applied with Cavity shield showed more color change than V-varnish applied group, despite no significant differences. Present study concludes that color stability of esthetic restoration materials can be affected by application of fluoride varnish. Especially, RMGI showed a large color change compared to the composite resin and giomer, which suggested that careful attention should be paid to clinical application.
Bonding efficacy of cured or uncured dentin adhesives in indirect resin
장지현,이빈나,장훈상,황윤찬,오원만,황인남,Jang, Ji-Hyun,Lee, Bin-Na,Chang, Hoon-Sang,Hwang, Yun-Chan,Oh, Won-Mann,Hwang, In-Nam The Korean Academy of Conservative Dentistry 2011 Restorative Dentistry & Endodontics Vol.36 No.6
연구목적: 본 연구는 간접 레진수복시 상아질 접착제의 중합 여부가 레진인레이와 상아질간의 미세인장결합강도와 결합계면의 형태에 미치는 영향을 공초점 현미경 관찰을 통하여 평가하고자 하였다. 연구 재료 및 방법: 24개의 발거된 대구치를 절단하여 교합면 상아질을 노출시켰다. 수복 방법에 따라 크게 간접 레진수복과 직접 레진수복의 두 군으로 나누었다. 간접 레진수복군은 임시 수복하여 1주일 후, 상아질 접착 과정에 따라 4군(OB-C와 OB-NC군, OS-C와 OS-NC군)으로 나누었다. 간접 레진수복군은 산부식 처리된 상아질면에 OptiBond FL (Kerr) 또는 One-Step (Bisco) 상아질 접착제를 중합 여부에 따라 나누어 적용하였다. 처리된 상아질면에 제작된 3 mm 높이의 레진 인레이(Tescera, Bisco)를 Variolink II (Ivoclar Vivadent)를 사용하여 제조사의 지시에 따라 합착하였다. 직접 레진수복군은 산부식 처리된 상아질면에 상아질 접착 후, 복합레진 (Estelite${\Sigma}$, Tokuyama)으로 즉시 수복하였다(OB-D군, OS-D군). 수복을 마친 모든 치아는 24시간 후, 미세인장 결합 강도 평가와 공초점 레이저 주사 현미경 관찰(CLSM)을 시행하였다. 결과: 간접 레진수복군은 직접 레진수복군에 비하여 낮은 미세인장결합강도를 나타내었으며, 상아질 접착제를 광중합한 군(OB-C군, OS-C군)이 광중합을 시행하지 않은 군(OB-NC군, OS-NC군)에 비하여 높은 미세인장결합강도를 나타내었다. 접착 계면에 대한 CLSM 관찰에서 상아질 접착제를 광중합한 군에서 더 분명하고 균일한 혼성층이 관찰되었다. 상아질 접착제를 광중합하지 않은 군에서는 혼성층이 불분명하거나 거의 관찰되지 않았다. 결론: 간접 레진수복물의 합착시 레진시멘트의 적용 전에 상아질 접착제의 광중합은 분명하고 균일한 혼성층의 형성하며, 이는 결합강도의 향상에 기여한다. Objectives: This study examined the effect of the uncured dentin adhesives on the bond interface between the resin inlay and dentin. Materials and Methods: Dentin surface was exposed in 24 extracted human molars and the teeth were assigned to indirect and direct resin restoration group. For indirect resin groups, exposed dentin surfaces were temporized with provisional resin. The provisional restoration was removed after 1 wk and the teeth were divided further into 4 groups which used dentin adhesives (OptiBond FL, Kerr; One-Step, Bisco) with or without light-curing, respectively (Group OB-C, OB-NC, OS-C and OS-NC). Pre-fabricated resin blocks were cemented on the entire surfaces with resin cement. For the direct resin restoration groups, the dentin surfaces were treated with dentin adhesives (Group OB-D and OS-D), followed by restoring composite resin. After 24 hr, the teeth were assigned to microtensile bond strength (${\mu}TBS$) and confocal laser scanning microscopy (CLSM), respectively. Results: The indirect resin restoration groups showed a lower ${\mu}TBS$ than the direct resin restoration groups. The ${\mu}TBS$ values of the light cured dentin adhesive groups were higher than those of the uncured dentin adhesive groups (p < 0.05). CLSM analysis of the light cured dentin adhesive groups revealed definite and homogenous hybrid layers. However, the uncured dentin adhesive groups showed uncertain or even no hybrid layer. Conclusions: Light-curing of the dentin adhesive prior to the application of the cementing material in luting a resin inlay to dentin resulted in definite, homogenous hybrid layer formation, which may improve the bond strength.
이윤희(Yun-Hee Lee),허용학(Yong-Hak Huh),장훈식(Hoon-Sik Jang),김용일(Yong-il Kim),남승훈(Seung-Hoon Nahm) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
Although the nanohardness has been a typical property of thin films, this cannot be converted to or compared with other mechanical properties such as yield and tensile strengths. In this study, we proposed a novel strength-measurement technique by combining a depth-sensing indentation curve and its resulting indent morphology. From a three-dimensional morphology investigation of the remnant indent using an atomic force microscope, a dimension of indentation-induced yielded zone was characterized as an in-plane closed loop. By adopting the force equilibrium between the applied indentation load and its supporting force beneath the yielded zone, the yield strengths of 1.0 ㎛-thick Au and TiN thin films were measured. However, the measured strength of Au film was about 1.5 times higher than the result from microtensile test. This phenomenon was attributed to the effects of hard Si substrate and can be modified by proposing new yielded zone morphology.