• Restorative Dentistry and Endodontics
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• 제31권6호
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• pp.452-459
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• 2006

와동벽과 복합레진 수복물이 접착될 때, 복합레진의 치질에 대한 접착력과 레진 자체의 중합 시 발생하는 수축응력이 상충하게 된다. 이러한 수축응력의 크기는 와동의 형태요소 (C-factor)와 수복물의 체적에 영향을 받는다. 이에 본 실험에서는 단일 병 접착제를 사용한 복합레진 수복 시 법랑질 변연만으로 이루어진 와동의 C-factor와 체적이 미세누출에 미치는 영향을 미세 전류 측정법을 이용하여 정량적으로 분석하고 평가하였다. 연마기를 이용하여 40개의 건전한 우치 협면에 편평한 법랑질 표면을 형성하였다. 각각 10개의 치아에 원통형 와동을 형성하였으며, 와동의 깊이와 직경에 따라 4개 군으로 분류하였다 ( I군: 1.5 mm ${\times}$ 2.0 mm, II군: 1.5 mm ${\times}$ 6.0 mm, III군: 2.0 mm ${\times}$ 1.72 mm, IV군: 2.0 mm ${\times}$ 5.23 mm). 각기 와동의 C-factor는 4, 5.62, 2, 2.54를 보였다. 산 부식 후 단일 병 접착제인 BC Plus$^{TM}$ (Vericom, Korea)를 제조사의 지시에 따라 적용하고, 미세혼합형 복합레진인 Denfil$^{TM}$(Vericom)을 충전하였다. 40초씩 광중합 후 치아를 실온에서 증류수에 24시간 동안 보관한 다음, Sof-Lex system을 이용하여 연마하였고, 5$^{\circ}$C와 55$^{\circ}$C범위에서 500회 열순환을 시행하였다. 이후 미세전류 측정을 위해 치수강 내에 증류수를 채우고 치근단공을 통해 0.018 stainless wire를 삽입한 후 sticky wax로 근첨부를 밀봉하였으며, nail varnish를 수복물의 변연에서 1 mm를 제외한 전체 치면에 2회 도포하였다. 미세누출의 측정은 전기 화학적 방법을 이용하여 측정하였으며, 통계적 유의성은 95% 유의 수준의 Two-way ANOVA로 검증하여 , 다음과 같은 결과를 얻었다. 1. 복합레진 수복물의 체적이 적은 것이 큰 것에 비해 미세누출도가 적었으나, 통계학적으로 유의한 차이는 없었다. 2. 와동 형태와 연관된 C-factor는 복합레진 수복물의 미세누출도에 영향을 주지 않았다. 법랑질 변연을 갖는 와동에 단일 병 접착제를 사용한 본 실험에서는 복합레진의 중합 시 발생하는 수축응력에 영향을 미치는 것으로 알려진 수복물의 체적과 C-factor가 미세누출도에 영향을 주지 못하였다. 이는 법랑질과 접착시스템과의 강력한 접착력에 기인한 것으로 보이며, 앞으로 이에 대한 더 많은 연구가 필요할 것으로 사료된다.

• 한국유체기계학회 논문집
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• 제17권6호
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• pp.59-63
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• 2014

Object of this study is to see whether the arc-groove on a D-shape bluff body effects the drag reduction or not. To this end, the changes of the boundary layer on the surface of the object, the downstream flow field and wake flow were found by experiments. The experiments are conducted by changing number and depth of the groove, angle of the first groove and Reynolds number(Re). Groove did not effect on the surface in the downstream boundary layer of the object and was minimal impact on the time mean velocity recovery of the wake flow. Also the effects of Groove did not have a significant impact on the structure of the wake and the wake frequency. Therefore it is found that the arc-groove of the drag reduction effect on the D-shape bluff body was smaller.

• 한국광학회:학술대회논문집
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• 한국광학회 2000년도 제11회 정기총회 및 00년 동계학술발표회 논문집
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• pp.276.2-278
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• 2000

In a recent years, a number of approaches have been studied, including passive, active, and hybrid mode-locking of semi-conductor lasers for short pulse generation and research has been devoted to achieve low timing-jitter operation since the timing jitter is unfavorable for system applications. Among the methods of mode locking, passive mode locking does not need external rf drives, and therefore the operation and fabrication procedures are simplified. In spite of these attractive advantages of passive mode-locked laser, it has critical drawbacks such as large timing jitter and the difficulty in synchronization with external circuits. Their inherent large timing jitter value was shown to be suppressed to certain levels by means of hybrid mode-locking technique$^{(1)}$ , where the saturable absorber section was modulated by an external signal with the cavity round trip frequency. Furthermore, the subharmonic mode-locking (SHML) technique alleviates the restrictions of high speed driving electronics. It has been demonstrated experimentally$^{(1)}$ that the hybrid subharmonic mode-locking technique has lead to significant reduction of the timing jitter. (omitted)

• Archives of Reconstructive Microsurgery
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• 제23권2호
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• pp.101-104
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• 2014

Reconstruction of soft tissue defects of the knee has always been a challenging task for plastic surgeons. Various reconstructive choices are available depending on the location, size, and depth of the defect relative to the knee joint. Defects on the knee joint have several characteristic features. The use of a free flap is preferred for reconstructions involving obliteration of large-cavity defects, but recipient pedicle isolation can be difficult because of the extent of the injury zone. Furthermore, the true defect during knee joint flexion is larger than during knee joint extension, and a durable flap is necessary for joint movement. We report for the first time on the use of pedicled perforator flaps for reconstruction of bilateral knee defects in a 76-year-old woman. The operative procedure required skeletonizing the perforators of an antero-lateral thigh flap and antero-medial thigh flap and rotating the flap in the defect. The patient returned to normal daily activity and had a full range of motion two months after the accident. The shorter operating time with decreased donor site morbidity and its durability make this flap a valuable alternative for soft tissue reconstruction of the knee.

• Restorative Dentistry and Endodontics
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• 제14권1호
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• pp.205-210
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• 1989

The purpose of this study was to observe the minim pins of Link plus (which has buttress thread and shoulder stop design) inserted into dentin and the dentin surrounding pin. The gingival walls of class II cavity were prepared with high speed handpiece in molar teeth not elapsed time after teeth were extracted, and pinhole of 2mm in depth was positioned about 1 mm to the dentinoenamel junction and minim pin was inserted with wrench. After initial examination of the specimens, the specimens were sectioned longitudinally and horizontally to the pins with carborundum disc and low speed diamond saw (Isomet Buehler Ltd) All specimens were coated Au of 250-300${\AA}$ in thickness with Ion Sputter JFC 100 and observed under Scanning Electron Microscope (JSM-35) The following results were obtained. 1. The shoulder stop was seated on the enterance of pinhole in gingival wall, and there were the irregular space between the pin and dentin at the enterance to the pin hole and flakes of dentin lifting from the dentin floor. 2. In case of section to pin horizontally or longitudinally, the dentin debris were observed in gap between pin and dentin, and small cracks were often seen in the dentin surrounding minim pins.

• 로봇학회논문지
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• 제3권1호
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• pp.58-67
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• 2008

This study developed a novel augmented reality interface for minimally invasive surgery. The augmented reality technique can alleviate the sensory feedback problem inherent to laparoscopic surgery. An augmented reality system merges real laparoscope image and reconstructed 3D patient model based on diagnostic medical image such as CT, MRI data. By using reconstructed 3D patient model, AR interface could express structure of patient body that is invisible outside visual field of laparoscope. Therefore, an augmented reality system improved sight information of limited laparoscope. In our augmented reality system, the laparoscopic view is located at the center of a wide-angle concave screen and reconstructed 3D patient model is displayed outside the laparoscope. By using a joystick, the laparoscopic view and the reconstructed 3D patient model view are changed concurrently. With our augmented reality system, the surgeon can see the peritoneal cavity from a wide angle of view, without having to move the laparoscope. Since the concave screen serves immersive environments, the surgeon can feel as if she is in the patient body. For these reasons, a surgeon can recognize easily depth information about inner parts of patient and position information of surgical instruments without laparoscope motion. It is possible for surgeon to manipulate surgical instruments more exact and fast. Therefore immersive augmented reality interface for minimally invasive surgery will reduce bodily, environmental load of a surgeon and increase efficiency of MIS.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2002년도 금형가공 심포지엄
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• pp.253-259
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• 2002

Micro cell structures with high aspect ratio were fabricated by injection molding method. The mold inserts had dimension $1.9cm\times8.3cm$ composed of a lot of micro posts and were fabricated by LIGA process. The size of the micro posts was $157{\mu}m\times157{\mu}m\times500{\mu}m$ and the gaps between two adjacent posts were $50{\mu}m$. Using Polymethylmethacrylate (PMMA) injection molding was performed. The key experimental variables were temperature, pressure, and time. By controlling these, good shaped mim cell structures with $50{\mu}m$ in wall thickness and $500{\mu}m$ in depth were obtained. In order to understand micro molding mechanism, shape changes of molded PMMA were studied with experimental variables. And the durability of mold insert was investigated, too. The results show that the most important factor in molding processes was the mold temperature that is closely related to the filling of the melt into the micro cavity. And the holding time before cooling showed a great effect on the quality of molded PMMA.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 춘계학술대회 논문집
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• pp.401-404
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• 2009

The purpose of this study is investigating the joint characteristics of advanced high strength steel DP780 and Al5052 alloy sheet in the clinching process. It is difficult to join the advanced high strength steel with light-weight materials like aluminum alloy, because of low formability of DP780. The defects of clinching joint such as necking of the upper sheet, cracks of the lower sheet and no interlocking were occurred by different ductility between advanced high strength steel and aluminum alloy. The clinching conditions should be optimized to interlock without any defects. In this study, the effect of process parameters of clinching process on joinability of advanced high strength steel with Al5052 alloy was investigated by using FE-analysis. From the result of FE-analysis, the clearance between clinching punch and die, die depth and the shape of die cavity mainly affected the joinability of advanced high strength steel with Al5052 alloy.

• Restorative Dentistry and Endodontics
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• 제15권1호
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• pp.67-80
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• 1990

This study was performed for elucidating the effects on surface polishing of composite resins. In this study, Silux(microfilled), Graft(hybrid), Bisfil- I (hybrid posterior) and Hi-pol(conventional) were used. Sixty specimens were made with 4 brands of composite resins and Optilux system in $2.0{\times}1.3{\times}1.0cm$ resin block which has a cavity with 0.5cm diameter and 0.5cm depth. Polishing was done with #600 sand paper and Soflex, Super-snap, Micron finishing system, or Composite polishing kit. Final polished surfaces were measured by roughness tester(Kasaka Lab. Ltd., Japan) and image analyser(Omnimet Image Analyser, Buehler, USA). The results were as follows, 1. The celluloid strip produced the smoothest surfaces. 2. Light curing microfilled composite resin, Silux, had smoother surface than any others. 3. The surfaces polished by Soflex were smoothest. 4. Aluminum oxide disk, Soflex and Super-Snap, made smoother surface than diamond bur, M.F.S., or silicon point, Composite polishing kit. 5. The roughness values of surface polished by M.F.S. composed of diamond burs, were less than those of Composite polishing kit made from silicone points.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2009년도 추계학술발표대회 논문집
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• pp.142-147
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• 2009

In order to achieve performance assessment and optimal control of a double-skin system, an accurate simulation model is required. In the previous study, a lumped simulation model of such system was developed. As a follow-up of the previous research, the first objective of this paper is to investigate how the mathematical model should be calibrated according to system configuration(cavity width, depth, height, airflow pattern, local environment, etc.). And the second objective of this study is to discuss the effect of local weather information. In conclusion, this paper describes that the model should be recalibrated according to configuration. And it is necessary to have local weather information for accurate prediction and optimal control of the system.