• 대한치과기공학회지
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• 제5권1호
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• pp.13-17
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• 1983

The experimental investication wax performed to study fitness of casting crowns with various investment widely used in Korea. 36 wax patterns were invested and casted according to the regular casting method. The result were as follow : 1. Casting with cristobalite investments of Shofu were seen apart, 0.04mm the tightest space in the linguo and bucco-cervical margin. And the largest deviation, 0.1mm was shown in the central groove 0.1mm was shown in the central groove area of occlusal surface(Jensen Metal) 2. Casting with cristobalite investments of kerr were seen apart, 0.04mm the tightest space in the linguo and bucco-cervical margin And the largest deviation, 0.09 was shown in the central groove area of occlusal surface(Jensen Metal) 3. Casting with Quartz investments of G-C were seen apart, 0.04mm the tightest space in the linguo-cervical margin, And the largest deviation, 0.1mm was shown in the central groove area of occlusal surface(Jensen Metal) 4. Casting with cristobalite investments of shofu were seen apart, 0.01mm the tightest space in the linguo-cervical margin, And the largest deviation, 0.03mm was shown in the central groove of occusal surface(Bo-sung A type gold alloy) 5. Casting with cristobalite investments of kerr showed the best fintness in linguo-cervical margin. And the largest deviation, 0.02mm was shown in the central groove area of occlusal surface(Bosung A type gold alloy) 6. Casting with Quartz investments of G-C were Seen apart, 0.02mm the tightest space in the linguo-cervical margin, And the largest deviation, 0.04mm was shown in the central groove area of occlusal surface(Bo-sung A type gold alloy) 7. Casting with cristobalite investments of shofu were seen apart, 0.01mm the tightest space in the linguo-cervical margin. And the largest deviation, 0.08mm was shown in the buccal cusp area of occlusal surface(Bo-sung B type gold alloy) 8. Casting with cristobalite investments of kerr shown the best fitness in linguo-cervical margin. And the largest deviation, 0.04mm was shown in the central groove atea of occlusal surface(Bosung B type gold alloy) 9. Casting with Quartz investments of G-C were seen apart, 0.03mm the tightest space in the linguo-cervical margin. And the largest deviation, 0.04mm was shown in the central groove area of occlusal surface(Bo-sung B type gold alloy) 10. Casting with cristobalite investments of kerr shown the best fitness and Bo-sung A type gold alloy showed the best fitness.

• 대한치과보철학회지
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• 제30권1호
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• pp.125-132
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• 1992

The purpose of this study was to evaluate the effect of the metal coping design on the fracture resistance of ceramometal crown. The Ni-Cr alloy(Supranium, Krupp Co., German) and Vaccm-fired porcelain powder(Vita VMK 689, Vita Co., Germany) were used in this study. The measurement of fracture resisitance of ceramometal crown was done with Instron Universial Testing Machine(Instro Co., Model no.4201). The obained results were as fellows : 1. The fracture resistance measured at the buccal cusp tip was the highest value in the group that those position of ceramometal junction was 2mm superior to the lingual finshing margin(100.25Kg) and the fracture resistance revealed on order of the group that those position was 2mm buccal to the central groove(51.64Kg). 2. The fracture resistance measured at the central groove was higher value in the group that those position was 2mm lingual to the central groove than in the group that those position was 2mm lingual to the central groove than in the group that those position was 2mm superior to lingual finishing margin(132.48Kg). 3. In all cases, the fracture resistance at the central groove was higher than that at the buccal cusp tip.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2000년도 춘계학술대회논문집
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• pp.167-170
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• 2000

Recently the sub-micron structured substrates of 0.74 ${mu}ell$ track pitch and 800 $\AA$groove depth are required for DVD-RAM and the track pitch is expected to be narrower as the need for the information storage density is getting higher. For the accurate replication of the land-groove structure in the stamper to the plastic substrates it is important to control the injection -compression molding process such that the integrity of the replication for the land-groove structure is maximized. in the present study polycarbonate substrates were fabricated by injection comression molding and the land-groove structure regarded as one of mold temperature and the compression pressure on the integrity of the replication were examined experimentally. An efficient design methodology using the response surface method (RSM) the central composite design(CCD) technique and the analysis-of-variance (ANOVA) was developed to obtain the optimum processing conditions which maximize the integrity of the replication with a limited number of experiments.

• 대한치과기공학회지
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• 제11권1호
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• pp.65-70
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• 1989

The development of the lobe pattern in the human dentition plays a part in the form and function of each individual teeth. In order to determin the morphological categories used to describe the occlusal surfaces of the maxillary and mandibular molars, the variation of the developmental grooves which separate each lobe in the molars was examined and analysed. The obtained conclusions were as follow. 1. Most of the maxillary first molars with more distinct and more developmental grooves than the other molars but in most cases of the third molar, a heart-shaped outline due to poorly developed or abscent distolingual cusp was most frequent and in this case the third molar had the 3 cusps separated by the central developmental groove and the buccal developmental groove. 2. In most cases, the mandibular first molar had the 5-cusp type that the groove patter resembles a Y, the second molar the 4-cusp type arranged in such a way that the buccal and lingual developmental grooves meet the central developmental groove at right angle on the occlusal surface and many instances of the mandibular third molars had the 5-cusp thpe with a+groove pattern which separatess the mesiolingual cusp from the distobuccal cusp and the 4-cusp type with a+groove pattern. 3. The maxillary and mandibular third molar were most variable in the developmental groove.

• 대한치과보철학회지
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• 제42권1호
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• pp.58-72
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• 2004

Statement of problem : Clinically, maxillary first premolar has a high risk of fracture. This is thought to be caused by the susceptible figure which the maxillary first premolar has In other words, sharp cusp angles of the premolar is thought to influence this situation. Purpose : This study was to know stress distribution of all-ceramic crown according to the cusp angle. Material and Method : It was manufactured a three dimensional finite element model simplified maxillary first premolar, and then analyzed stress distribution when cusp angle was each $80^{\circ}$, $90^{\circ}$, $100^{\circ}$, $110^{\circ}$ and $120^{\circ}$. Results and conclusion : 1. The von Misses stress showed that stress decreases as cusp angle increases in the central groove of the occlusal surface. 2. It showed that maximum principal stress was centered at the region of the central groove of the occlusal surface and a region which the force was inflicted. And also it appeared high on the lingual and buccal side of finish line. 3. The X axis of normal stress was focused in the central groove of the occlusal surface. The Y axis normal stress appeared high in the central groove of the occlusal surface, buccal and lingual side. 4. The Stress near the finish line showed a low value compared with stress in the region of the central groove of the occlusal surface. 5. It shows that the most dangerous angle for tooth fracture was on $80^{\circ}$ of the cusp angle and low on $120^{\circ}$ of its.

• Clinics in Shoulder and Elbow
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• 제2권2호
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• pp.151-156
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• 1999

Purpose : Average humeral head retroversion was showed significant wide range from literatures based on variable measuring technique, We performed computed tomography(CT) study in an effort to define the specific anatomy relationships and evaluate their use. Materials and Methods : Two hundreds shoulders and distal humeri CT scan with no known pathology were examined. The study population was divided to 10 groups by gender and age (from third to seventh decade). The number of each group was twenty. Retroversion of proximal humerus and glenoid were measured using the lines that were connected the central axis of humeral head, central points of the humeral epicondyles paralleling to the trochlea, paralled to the glenoid surface, midpoint between the transverse glenoid diameter and medial edge of the scapular. We also measured the bicipital groove distance from the humeral central axis and scapulothoracic angle. Results: Retroversion of proximal humerus was highly variable, ranging in this study from 13 to 58 degrees(mean 28.73) These values correlated with sex, not age, height or hand dominance. Glenoid retroversion at the inferior sections showed average 1.3 degree, did not signigicant differences. The central axis was an average of l0mm(5-15mm) posterior to the posterior margin of the bicipital groove. Scapulothoracic angle was average 43 degrees(25-53 degrees) Conclusion: Anatomical reconstruction of retroversion angle should be individualized and bicipital groove could be useful as landmark for the lateral fin of the prosthesis to be positioned an average of 10mm posteriorly.

• 대한치과기공학회지
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• 제42권3호
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• pp.220-227
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• 2020

Purpose: This study aims to investigate the cusp variation pattern of the Korean mandibular second premolar and to determine the difference in tooth diameter and surface area using a virtual three-dimensional model. Methods: Dental casts from 69 students were scanned as a virtual dental models with a three-dimensional dental model scanner. Tooth diameter, absolute and relative individual areas, total crown area, the number of lingual cusps and central groove pattern were analyzed using RapidForm 2004. The Mann-Whitney U-test and the Kruskal-Wallis test were performed to verify sexual dimorphism, the difference in tooth diameter and surface according to the cusp variation pattern (α=0.05). Results: There was no significant difference except in buccolingual diameter (p<0.05) and buccolingual diameter at the cervix (p<0.05). The relative surface area of the total clinical crown was 65.76% for the buccal half and 34.24% for the lingual half, with a ratio of 2:1. In the case of the presence of two lingual cusps, the ratio was 21.47% for the mesiolingual half and 14.12% for the distaolingual half, with a ratio of 3:2. The dominant central groove patterns of the second premolar were the H-pattern (42.0%), followed by the Y-pattern (37.7%), then the U-pattern (20.3%). The relative buccal half was largest in the U-pattern central groove and the relative lingual half was largest in the Y-pattern central groove (p<0.05). Conclusion: This study is significant in that it measured quantitative surface areas and the findings could be a meaningful reference to comprehend dental anatomy in Koreans.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문초록집
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• pp.342.1-342
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• 2002

In this work, the dynamic characteristics of an oil-lubricated, short SFD with a central feeding groove are derived based on a theoretical analysis considering the effect of a groove. The validity of the analysis is investigated experimentally using an Active Magnetic Bearing (AMB) system as an exciter. For the theoretical solution, the fluid film forces of a grooved SFD are analytically derived so that the dynamic coefficients of a SFD are expressed in terms of its design parameters. (omitted)

• 대한전자공학회논문지
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• 제27권11호
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• pp.1-8
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• 1990

4개의 Quantum well을 갖는 GRINSCH InGaAs/Inp Buried Heterostructure의 laser diode 12개로 구성되어 있는 12-laser diode array를 제작하여, 각 laser diode의 전자 흡수 영역의 인가 전압에 의하여 lasing 작용을 조절할 수 있는 가능성을 조사하였다. 12개의 V가 홈을 갖는 Si V-groove와 12개의 광섬유를 이용하여 12-laser diode array의 빛출력을 coupling하여 전자 흡수영역의 인가 전압의 변화에 따른 각 laser diode의 여러특성을 조사하였다. 마지막으로 12-laser diode array와 Si V-Groove와 광섬유를 이용하여 디지털 논리 gate들로 구성되어 있는 전자 회로 board들 간의 광대역 근거리 통신 및 B-ISDN을 위한 central office와 가입자 간의 통신을 구현하는 방법에 대하여 생각해 보았다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.381-387
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• 2002

In this work, the dynamic characteristics of an oil-lubricated, short SFD with a central feeding groove are derived based on a theoretical analysis considering the effect of a groove. The validity of the analysis is investigated experimentally using an Active Magnetic Bearing (AMB) system as an exciter. For the theoretical solution, the fluid film forces of a grooved SFD are analytically derived so that the dynamic coefficients of a SFD are expressed in terms of its design parameters. For the experimental validation of the analysis, a test rig using AMB as an exciter is proposed to identify the dynamic characteristics of a short SFD with a central groove. As an exciter, the AMB represents a mechatronic device to levitate and position the test journal without any mechanical contact, to generate relative motions of the journal inside the tested SFD and to measure the generated displacements during experiments with fairly high accuracy. Using this test rig, experiments are extensively conducted with different clearance, which is one of the most important design parameters, in order to investigate its effect on the dynamic characteristics and the performance of SFDs. Damping and inertia coefficients of the SFD that are experimentally identified are compared with the analytical results to demonstrate the effectiveness of the analysis. It is also shown that AMB is an ideal device for tests of SFDs.