• 대한치과보철학회지
• /
• 제40권5호
• /
• pp.441-450
• /
• 2002

The purpose of this study was compare the fracture strength of the IPS Empress ceramic crown according to the occlusal depth (1.5mm, 2.0mm, 2.5mm) and axial inclination ($4^{\circ},\;8^{\circ},\;12^{\circ}$) of the lower second premolar. After 10 metal dies were made for each group, the IPS Empress ceramic crowns were fabricated and cemented with resin cement. The cemented crowns were mounted on the testing jig with inclination of 30 degrees and the universal testing machine was used to measure the fracture strength. The results of this study were as follows : 1. The fracture strength of the ceramic crown with 2.5mm depth and $12^{\circ}$ inclination was the highest (1284 N). Crowns of 1.5mm depth and $8^{\circ}$ inclination had the lowest strength (951 N). 2. There were no significant differences in the fracture strength by axial inclination of the same occlusal depth group. 3. Most fracture lines began at the loading area and extended through proximal surface perpendicular to the margin, irrespective of occlusal depth.

• 대한치과보철학회지
• /
• 제26권1호
• /
• pp.51-61
• /
• 1988

The recently introduced castable glass ceramics incorporate properties characteristic of natural teeth and they are regarded as an ideal material to restore lost tooth structure. The purpose of this study was to compare the marginal fit of castable ceramic crown with that of the metal-ceramic crown in the process of heat treatment. Two master dies for castable ceramic crowns and metal-ceramic crowns were fabricated from being cast with the base metal. Each master die was duplicated with addition silicone and hard stone. Ten castable ceramic crowns were made on each hard stone die and their marginal openings were measured three times first, after casting; second, after ceramming; third, after shading. The other ten metal-ceramic crowns were made on each hard stone die and their marginal openings were measured three times : first, after casting; second, after degassing; third, after porcelain veneering. Each crown was seated on its master die with the constant force delivered by loading jig. And then, marginal openings were measured on four locations by optical projector at X50 magnification. The results were as follows: 1. The mean marginal openings of castable ceramic crowns were $31.1{\pm}12.7{\mu}m$ after casting; $44.6{\pm}12.8{\mu}m$ after ceramming; $51.2{\pm}16.8{\mu}m$ after shading. 2. The mean marginal openings of the metal-ceramic crowns were $26.2{\pm}13.8{\mu}m$ after casting; $29.8{\pm}10.3{\mu}m$ after degassing; $38.0{\pm}14.5{\mu}m$ after porcelain veneering. 3. There was significant increase in the marginal opening of castable ceramic crowns after ceramming, while metal-ceramic crowns sho(wed significant increase after porcelain veneering (p<0.05). 4. Marginal fit of metal-ceramic crown was better than that of castable ceramic crown (p<0.01).

• 구강회복응용과학지
• /
• 제20권1호
• /
• pp.19-29
• /
• 2004

The purpose of this study was to compare the fracture strength of the IPS Empress ceramic crown according to the incisal reduction(2.0mm, 2.5mm, 3.0mm) and axial inclination ($4^{\circ}$, $8^{\circ}$, $12^{\circ}$) of the lower canine. After 10 metal dies were made for each group, the IPS Empress ceramic crowns were fabricated and each crown was cemented on each metal die with resin cement. The cemented crowns mounted on the testing jig were inclined 30 degrees and a universal testing machine was used to measure the fracture strength. The results of this study were as follows : 1. The fracture strength of the ceramic crown with 3.0mm depth and $12^{\circ}$ inclination was the highest(1377N). Crowns of 2.0mm depth and $4^{\circ}$ inclination had the lowest strength (731 N). 2. There were no significant differences of the fracture strength by axial inclination in same incisal reduction group. 3. The fracture mode of the crowns was similar. Most of fracture lines began at the loading area and extended through proximal surface perpendicular to the margin irrespective of incisal reduction.

• 항공우주정책ㆍ법학회지
• /
• 제6권
• /
• pp.239-266
• /
• 1994

In den 30er Jahren fing man an, sich Gedanken $\ddot{u}ber$ eine internationale Regelung der Rechtsstellung des Luftfahrtpersonals zu machen, um Konflikte zwischen den verschiedenen nationalen Gesetzgebungen hinsichtlich der Handlungen des Luftfahrtpersonals bei der Aus bung seiner Verrichtungen zu verhindern. Aber bisher gibt es keine ausreichende Erfolg. Aus dem Vorhergehenden ergibt sich, $da{\beta}$ eine internationale Regelung der Rechtsstellung des Personals der Zivilluftfahrt erw nscht $w\ddot{a}re$. In der Praxis wird dies jedoch wegen der verschiedenen Arbeitsgesetzgebungen und der anderen nationalen Bestimmungen schwer durchzuf hren sein. Weil aber das Luftfahrtpersonal, insbesondere das Flugpersonal, eine arbeits - und sozialrechtliche Sonderstellung einnimmt, $w\ddot{a}re$ es zu empfehlen, allgemeine internationale Richtlinie zu schaffen, welche in den nationalen $Gesamtarbeitsvertr\ddot{a}gen$ $n\ddot{a}her$ ausgearbeitet werden $k\hat{o}nnten$, sowohl $f\ddot{u}r$ das Kabinenpersonal als $f\ddot{u}r$ die Piloten. Ferner $d\ddot{u}rfte$ es dringend notwendig sein, die Haftpflicht des Kommandanten ausf hrlicher und einheitlicher zu regeln, weil die Intensivierung des Lufttransports und die Anzahl der Flugg ste $st\ddot{a}ndig$ zunehmen. Hinsichtlich der Befugnisse des Kommandanten im Faile von an Bord des Luftfahrzeuges begangenen strafbaren Handlungen gibt das Abkommen von Tokio einige Bestimmungen. Die zivilrechtlichen Aspekte seiner Stellung sind noch nicht festgelegt. Es $k\ddot{o}nnte$ bei internationalen Regelung eine Vorschrift aufgenommen werden, die es $erm\ddot{o}glicht$, einem anderen als dem Kommandanten aile Vollmachten zu erteilen. $Au{\beta}erdem$ $k\ddot{o}nnten$ Regelungen geschaffen werden, welche die Rolle der $\ddot{u}brigen$ Besatzung bei der $Unterst\ddot{u}zung$ des Kommandanten $n\ddot{a}her$ umschreiben. $K\hat{o}nnte$ eine internationale Regelung in diesen Punkten erzielt werden, so $w\ddot{a}re$ sowohl der Einheitlichkeit der Rechtsvorschriften als auch der Rechtssicherheit gedient.

• 대한기계학회논문집
• /
• 제14권1호
• /
• pp.1-12
• /
• 1990

본 연구에서는 자유단조용 프레서를 이용하여 돌출부가 있는 비대칭 중공형단 조 제품을 생산할 수 있도록 금형장치를 설계.제작하고, Fig.1에서 보는 바와 같이 경 사진 돌출부가 있는 비축대칭 복합단조에 UBET를 적용하여 해석하였다. 단조시편은 원주형태를 가지도록 하였다. 즉 원주형 소재가 요구되는 비축대칭 단조제품으로 변 형되는 과정에서 단조하중, 재료가 돌출부를 충만하도록 하는 유동특성, 재료가 돌출 부로 차들어가는 속도 등에 영향을 주는 인자(예:펀치 직경의 크기, 금형 상하면의 각 도)의 특성을 이론적으로 해석하고 실험으로 확인하였다.

• 식물병연구
• /
• 제16권3호
• /
• pp.320-322
• /
• 2010

2010년 2월 경기도 용인시 소엽풍란 재배농가에서 뿌리와 벌브가 심하게 마르고 식물체 전체가 말라죽는 증상이 나타났다. 마른 뿌리와 수태표면에 흰색 곰팡이 균사와 함께 뚜렷한 둥근 형태의 적갈색 균핵이 관찰되었다. 균학적 특징으로 균사는 $25{\sim}30^{\circ}C$에서 가장 활발한 생장을 보였으며, 균핵은 갈색의 둥근형태로 직경은 1~3 mm였다. 병원성 검정결과 발병이 초기부터 빠른 강한 병원성을 보였다. 균학적 특성 조사 결과 Sclerotium rolfsii에 의한 흰비단병으로 동정하였으며 본 병을 소엽풍란 흰비단병으로 명명하였다.

• 소성∙가공
• /
• 제21권3호
• /
• pp.179-185
• /
• 2012

In this paper, it is proposed to produce high precision screws with a diameter of $800{\mu}m$ and a thread pitch of $200{\mu}m$ ($M0.8{\times}P0.2$) by means of a cold thread rolling process. In this part II of the study, the focus is on the production and reliability testing of the prototype $M0.8{\times}P0.2$ micro-screw. Designs for two flat dies were developed with the aid of the literature and previous studies. Process parameters during the cold thread rolling process were established through FE simulations. The simulation results showed that the threads of the micro-screw are completely formed through the rolling process. Prototype $M0.8{\times}P0.2$ micro-screw were fabricated with a high precision thread rolling machine. In order to verify the simulation results, the deformed shape and dimensions obtained from the experiment were compared with those from the simulations. Hardness and failure torque of the fabricated micro-screw were also measured. The values obtained indicate that the CAE based process design used in this paper is very appropriate for the thread rolling of micro-sized screws.

• Restorative Dentistry and Endodontics
• /
• 제9권1호
• /
• pp.81-87
• /
• 1983

The purpose of this study was to observe and identify the phases of amalgam and to know the transformation of microstructure in the set amalgam by lapse of time. In this study, shofu spherical-D alloy was used. After trituration of amalgam alloy and mercury (Wig-L-Bug), it was filled in the stone dies. This specimens being polished and etched by usual method was observed under optical microscope using metallurgical microscope. And then X-ray diffractometer was used to analyze the phases contents and transformation of microstructure at $2{\frac{1}{2}}$ hours, 15 hours, 28 hours and 2 years after being amalgamated. The following results were obtained: 1. Shofu spherical-D alloy powder was composed of ${\gamma}$ phase, ${\epsilon}$phase and Ag-Cu eutectic phases. 2. ${\gamma}_2$ phases were appeared at $2{\theta}$ values ($32.0^{\circ}$ and $43.8^{\circ}$) in the amalgam which was analyzed at $2{\frac{1}{2}}$ hours and 15 hours after trituration with mercury. 3. In the amalgam at 28 hours, ${\gamma}_2$ phase was found at $2{\theta}$ value ($43.8^{\circ}$) at 35 hour, $r_2$ phase was appeared at $2{\theta}$ value $32.0^{\circ}$. 4. No ${\gamma}_2$ phases were observed in the 2 years old amalgam. But ${\eta}$ ($Cu_6Sn_5$) phases were found at $2{\eta}$ values $29.4^{\circ}$ and $42.4^{\circ}$.

• 한국산학기술학회논문지
• /
• 제12권3호
• /
• pp.1051-1057
• /
• 2011

최근 개발된 GMP공정의 활용으로 디지털 카메라, 광저장기기, 각종 전자기기 등의 광응용 기기에서 비구면 유리렌즈가 폭넓게 활용되고 있다. GMP공정은 복잡한 형상의 유리렌즈를 정밀하면서도 경제적으로 생산할 수 있다. 본 연구에서는 다구치 실험계획법을 이용하여 순차이송형 GMP공정에서 비구면 유리렌즈의 성형 조건을 최적화 하였다. 냉각 1단계에서의 압력과 온도, 시간을 3가지 주요 공정변수로 정하였으며, 3캐비티 금형을 이용하여 실험한 결과 순차이송형 유리렌즈 성형공정에서 냉각시간이 비구면 유리렌즈의 형상정밀도(PV)에 가장 큰 영향을 미치는 것을 알 수 있었다.

• 대한공업교육학회지
• /
• 제34권2호
• /
• pp.321-330
• /
• 2009

사출-연신 블로우(injection-stretch blowing) 성형은 양방향 분자배향을 가지는 병(bottle)과 같은 중공 제품을 성형하는데 적용되며, 양방향의 배향은 강화된 물리적 상태량, 탄산음료병과 같은 제품에 중요한 가스 불 투과성 상태량을 제공한다. 사출-연신 블로우 성형 중 분리형(two-stage) 공정은 사출 성형으로 생산된 프리폼을 적외선 히팅 기구로 재 가열하고. 재 가열된 프리폼을 블로우 금형 안에 장착한 후 고압의 공기를 분사시켜 병의 형상을 생성 및 유지하면서 완성시킨다. 그러나 블로우 성형은 연신율이 10배 이상이 되기 때문에 최종 두께 분포를 예측하는 것이 매우 어렵다. 따라서 균일한 두께를 가질 수 있는 프리폼 형상 최적화가 필요하다. 본 연구에서는 블로우 성형 연신 과정에 따라 페트 용기의 두께 변화를 알아보기 위하여 사출-연신 블로우 성형시 두께 편차에 대한 해석을 수행하였으며, 그 결과 첫째 사출-블로우 성형 로우 결과를 이용하여 프리폼 초기 설계를 최적화하였고, 연신 및 블로우 과정에서 공정 편차에용기 두께며, 그 결과 을 수치적으로 로우하여 공정 편를 최적화하였다. 둘째, 사출-블로우 성형시 연신 과정과 동시에 공기를 블로우하는 방법이 용기 두께의 편차를 최소화하였으며, PET용기 제작 기술의 안정화 및 신뢰성을 향상시킬 수 있었다.