• Restorative Dentistry and Endodontics
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• v.15 no.1
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• pp.57-66
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• 1990

The author conducted a dental survey of college girl students and compared with that of college students 20 years and 10 years ago which based on the same criteria. The items of this survey included the prevalence of dental caries, DMFT and the kinds of restored materials. College girl students 2,294 were examined in May 1988, with the recommended criteria and method of W.H.O.. Among them, the data of 2,243 were analyzed and compared with the data of 1968 and 1978. The following results were obtained : 1. The average number of present teeth was $28.86{\pm}1.65$, which does not show much difference when compared to $29.00{\pm}1.94$ of 1968 and $28.97{\pm}1.64$ of 1978. 2. The prevalence of dental caries was 86.22%, which increased in comparison to 83.25% of 1968 and 84.92% of 1978. 3. DMF index was 19.98, which considerably increased in comparison to 14.56 of 1968 and 15.51 of 1978. 4. The number of DMFT was $5.75{\pm}5.04$ per student. Compared to $4.23{\pm}3.88$ of 1968 and $4.49{\pm}3.69$ of 1978, there is a considerable increase. I) The average number of decayed(D) teeth was $1.14{\pm}1.63$, which decreased from $1.16{\pm}1.57$ of 1968 and $2.09{\pm}2.16$ of 1978. II) The average number of missing(M) teeth was $0.23{\pm}0.73$, which also decreased from $0.69{\pm}1.11$ of 1968 and $0.32{\pm}0.79$ of 1978. III) The average number of filled(F) teeth was $4.39{\pm}4.91$, which increased from $2.38{\pm}3.33$ of 1968 and $2.09{\pm}3.17$ of 1978. 5. According to the analysis of filling material, filling baby including amalgam, gold inlay, resin, silicate cement and paladium inlay was 90.5%, which increased in comparison to 72.8% of 1968 and 83.6% of 1978. Among them, amalgam occupied 62.93%, which showed the most increase. On the other hand, crown and bridge was 6.5%, 3.0%, respectively, which showed continuous decrease from 12.1%, 15.1% of 1968 and 8.7%, 7.7% of 1978. Therefore, the prosthodontic treatment reduced due to the decrease of tooth extraction. In contrast, there is continuous increase of conservative treatment which maintaining natural tooth.

• Journal of Korean society of Dental Hygiene
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• v.6 no.4
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• pp.469-479
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• 2006

The purpose of this study is to prevent the oral disease and to improve the oral sanitation by investigating the behavior on the awareness of oral health aimed at the residents who lives in the Yeongdong-gun, Choongbuk, Korea. This study was carried out from September 26th to September 27th of 2006 and surveyed aim at 176 persons of residents of Yeongdong-gun. The results of this study can be utilized as a base data of program development on the oral health education of sectional residents and can be reached at the following conclusions. 1. The number of residents who have not experienced oral health education takes possession of 67.5% for men and 48.4% for women, the path how to learn of oral health education holds 67.7% for men and 51.6% for women(p<0.001). In case of the content of oral health education, prothodontics treatment is predominantly showed up as 60.2% for men and 44.2% for women(p<0.01). 2. The number of residents who has visited the dental clinics within 6 months holds 52.4% for men and 27.3% for women(p<0.01). With regard to the number of residents who has visited the dental clinics on the purpose of prevention(examination) of oral disease within 1 year, 'not experienced' showed up no differences as 52.4% for men and 57.6% for women. In case of the number of residents who has experienced prothodontic and conservative treatment, scaling is extremely much as 37.6% for men and 52.6% for women(p<0.05). 3. In case of brushing teeth, 2 times a day is the first rank of 52.3% on the frequency of toothbrushing and the time when brush your teeth after breakfast, lunch and dinner is 22.2%, 16.5% and 20.3% respectively. Below 2 minutes is 64.7% and over 3 minutes is 10.3% on how long do you brush your teeth. With regard to the method on how to brush teeth, `up, down & across' is the first rank of 35.2%. In case of utilization of oral hygiene utensils, the number of resident who is `not used' occupies 62.5%. 4. In the knowledge of oral health, 60.7% of residents replied that the cause of dental carious is the infection by the bacteria. The relationship between the smoking and oral health, 50.5% of them replied `Not relevant' and 33.6% of them replied `Relevant'. The average point of the correct response rate of 9 items related with the knowledge of oral health is merely showed up as 3.39 point. Therefore, it shows up that the knowledge and education related with the prevention of oral disease is much deficient.

• Journal of the korean Society of Automotive Engineers
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• v.6 no.3
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• pp.45-54
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• 1984

Bending strength of an internal gear tooth is discussed as tooth form factor taking into account the actual stress magnitude. Stress analysis was carried out by the finite element method(FEM) for the calculation of tooth form factor of an internal gear. This paper also investigated the influences of number of teeth and addendum modification coefficient of the internal gear and the influences of number of teeth, addendum modification coefficient, pressure angle, radius of rounding of tooth tip, and bottom clearance coefficient of the pinion-shaped cutter on tooth form factor of internal gear. Generalizing the resultant data, a simple formula for the tooth form factor of an internal gear was derived for the calculation of tooth bending strength of an internal gear.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1992.10a
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• pp.52-56
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• 1992

A kinematically admissible velocity field for closed-die forging of spur gear is proposed. The velocity field is divided into three regions of deformation. In the analysis, the involute curve is approximated to be straight line and the upper-bound method is used to calculate energy dissipation rate. A constant frictional factor has been assumed on the contacting surfaces. The effects of root diameter relative pressure is independent of root diameter for the same number of teeth, but increases with the number of teeth on a given root diameter. In the presence of friction, relative forging pressure increases with increasing root diameter at the start of forging, but decreases with increasing root diameter in the processing of forging.

• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.118-120
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• 1999

This paper describes a new procedure to develop a systems model of a universal motor based on finite element analysis. The purpose of this paper optimized fabrication of Universal Motor for improving its efficiency and performance and driving range. To do this, various design parameters are set such as a number of teeth and stator shape, etc. As results, the optimized model has made good improvement compared with those of the initial.

• Journal of Biosystems Engineering
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• v.17 no.2
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• pp.171-176
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• 1992

This study was intended to develop the design theory of the threshing unit of a head-feeding rice combine. It may be applied for various combining capacities with different cutting widths and forward speeds. Design factors in the theoretical development are : (1) dimensions of the threshing drum, (2) tooth approching angle, (3) distance between the adjacent teeth on their spiral setting line, (4) number of spirals, and (5) total number of teeth on the drum. A computer simulation program was developed to predict the proper dimensions for the threshing drum and tooth arrangement. A simulation for the prospective combine with varied capacities was also demonstrated. The parameters analyzed in the developed design theory were shown to be consistent with those of existing combines.

• Proceedings of the KIEE Conference
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• summer
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• pp.917-919
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• 2004

This paper deals with the stator design solution of a synchronous reluctance motor (SynRM) with various slot number by loss & torque evaluations related to the slot open, teeth width using coupled Preisach modeling & FEM. The coupled Finite Elements Analysis (FEA) & Preisach model have been used to evaluate the nonlinear solution. Comparisons are given with characteristics of a SynRM according to the stator winding, slot number, slot open, teeth width variation, respectively

• Restorative Dentistry and Endodontics
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• v.7 no.1
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• pp.53-57
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• 1981

A total of 130 extracted human maxillary second molars were used to study the configuration of the floor of the pulp chamber. The specimens were ground and the pulp chamber was examined with a magnifier and explored with sharp explorer. The study showed the shape of the pulp chamber, number of root canals, and the type of canal orifice. The results were as follows; 1. In so far as observing the shape of the pulp chamber of the teeth, 16.9% of the teeth were quadrilateral, 70.0% were triangle and 13.1% were ovoid shape. 2. 13.1% of the specimens have 4 root canal orifices. 73.9% have 3 root canal orifices, 11.5% have 2 root canal orifices and 1.5% have single orifice. 3. 13.1% of the specimens have 2 mesio-buccal canal orifices and among the teeth those have 3 canals, 20.8% show 'Y' shape, 29.1% show straight line and 23.8% show obtuse triangle shape.

• Tribology and Lubricants
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• v.28 no.1
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• pp.27-32
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• 2012

Oval gears are typical kinds of non-circular gears and are widely used in flow meters. This paper presents a tooth profile design of an oval gear according to the curvature of the pitch curve. The length of the pitch oval is divided by the number of teeth and the curvature of the divided points is obtained. The tooth profile is designed on the circle of the curvature as if it is the pitch circle of a gear. The teeth of the oval gear have the same module and pressure angle, but the pitch circle of each tooth differs in size. Thus, the teeth on the divided points of the pitch oval are different in shape. This type of oval gear will improve the meshing properties.

• Oral Biology Research
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• v.42 no.4
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• pp.216-221
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• 2018

The purpose of this study was to assess the clinical outcomes of active periodontal therapy (APT) and supportive periodontal therapy (SPT) through loss of teeth in the Korean patients with aggressive periodontitis. The number of missing and residual teeth, probing pocket depth were examined in 33 patients diagnosed with aggressive periodontitis at the baseline and who had participated in APT and SPT for 3 years or more. A 20 and 3 teeth were lost during the APT and SPT, respectively. The mean tooth loss rate of 0.13 per patient and year. There was no significant statistical difference in clinical improvement between the smoker and non-smoker groups. Within the limitation of this study, APT combined with supportive therapy could decrease the risk of tooth loss in patients suffering from aggressive periodontitis.