• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.6
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• pp.1483-1495
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• 1994

A quantitative analysis of a surface roughness for a precision machining of a sculptured surface in milling process is treated under superposition theory in this paper. The geometrical surface rouhgness is calculated as a function of feed per tooth, path interval, radii of tool and cutting edge, and radii of curvatures of workiece. Through machining experiments in a 3-axis machining center, we confirmed the adequacy of the adequacy of the analysis. While cutter mark is neglegible in ball endmilling, it is significant in flat endmilling. When feed per tooth is very small, flat endmilling gives superior finish to ball endmilling. In flat endmilling, cutting condition and cutter path should be strategically chosen to balance the cutter mark height and cusp height.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.10a
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• pp.52-57
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• 1993

In this study, the inclined endmilling process with a 3-axis machining center using inalined jigs is introduced for the purpose of reducing overall Dies/Molds machining time and improving the machining accuracies. In order to analyse the cutting mechanism of a given endmill more accurateky, the unification of the cutting mechanism model of 3-different-kind endmills is examined by using the mose radius as a parameter. By adding radial runouts as a parameter which influences on surface roughness, the superposition method which defines the effective cusp heigh superposing the cutter mark height and the conventional cusp height is modified. And 3-D surface topography predicted in this paper looks like the surface normally observed in practice. Through machining experiments, the adequacy of the superposition algorithm was confirmed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.910-913
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• 2000

In this research we investigate geometric issues involved while using a particular rapid prototyping system, called Stereolithography(SLA). SLA create prototypes layer by layer, each layer being formed by scanning a laser beam across the x, y surface of a vat of liquid monomer mix. The performance of SLA is influenced by orientation and layer thickness of designed fabrication. The number of layer and the area needed support is influenced by the orientation and layer thickness of designed fabrication. The step influence and volume error is influenced by slice thickness. We minimize the support are, the number of layer and cusp height. These variables of fabrication is minimized using genetic algorithm. The time for genetic algorithm is as little as we can accept. So we calculate support area and cusp height simply.

• Journal of Mechanical Science and Technology
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• v.18 no.5
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• pp.753-761
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• 2004

In this paper, an efficient method for generating 5-axis cutting data for a turbine blade is presented. The interference elimination of 5-axis cutting currently is very complicated, and it takes up a lot of time. The proposed method can generate an interference-free tool path, within an allowance range. Generating the cutting data just point to the cutting process and using it to obtain NC data by calculating the feed rate, allows us to maintain the proper feed rate of the 5-axis machine. This paper includes the algorithms for: (1) CL data generation by detecting an interference-free heel angle, (2) finding the optimal tool path interval considering the cusp-height, (3) finding the adaptive feed rate values for each cutter path, and (4) the inverse kinematics depending on the structure of the 5-axis machine, for generating the NC data.

• International Journal of CAD/CAM
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• v.7 no.1
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• pp.21-30
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• 2007

The inverse offset method (IOM) is widely used for generating cutter paths from the point-based surface where the surface is characterised by a set of surface points rather than parametric polynomial surface equations. In the IOM, cutter path planning is carried out by specifying the grid sizes, called the step-forward and step-interval distances respectively in the forward and transverse cutting directions. The step-forward distance causes the chordal deviation and the step-forward distance produces the cusp. The chordal deviation and cusp are also functions of local surface slopes and curvatures. As the slopes and curvatures vary over the surface, different step-forward and step-interval distances are appropriate in different areas for obtaining the machined surface accurately and efficiently. In this paper, the chordal deviation and cusp height are calculated in consideration with the surface slopes and curvatures, and their combined effect is used to estimate the machined surface error. An adaptive grid generation algorithm is proposed, which enables the IOM to generate cutter paths adaptively using different step-forward and step-interval distances in different regions rather than constant step-forward and step-interval distances for entire surface.

• The korean journal of orthodontics
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• v.17 no.1
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• pp.93-106
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• 1987

The purpose of this study was to investigate the fittness of Golden relation items was advocated by Ricketts whether or not it is applicable to the young adult Korean dentitions and also to evaluate the several new Golden relation items conducted by the author. The material was consisted of 81 dental casts (34 male, 47 female) with ideal occlusion, which never undergone orthodontic, prosthodontic procedures. Measurements were made on the arch dimensions using sliding caliper (Mitutoyo. Co) and data were computerized and analyzed. The findings of this study were as follows, 1. The Golden proportion advocated by Ricketts dose not seem to directly applicable to the Korean normal dentition, however, the modification from the Ricketts' original shows the Golden proportion as follow: A first series of progressive Golden relations was found on the Golden ratio among the lower central incisors width, the inter mesioincisal width of the upper lateral incisors, and the upper first premolars width. A second series was found on the Golden ratio among the lower lateral incisors width, lower inter canine tips width and theupper first molar distal cusp tips width. A third series was found on the Golden ratio between the inter distal aspect width of e lower canine and the mesial cusp tips width of the lower second molars or inter cusp tips width of upper second premolars. 2. In addition to Ricketts' original, 4 new Golden proportions were found in young adult Korean dentition, these are as follows; The tips of lower canine width had Golden relation with the width of the upper first premolar buccal cusp tips or the width of the lower first molar central fossae. The distal aspect of the lower first premolars had Golden relation with the buccal surface widths of the lower or upper second molars. The width of upper lateral incisors had Golden relation with the upper second molar height. The width of the lower canine tips had Golden relation with the lower second molar height.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.53.2-53.2
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• 2019

$H{\alpha}$ surges (i.e. cool/dense collimated plasma ejections) may act as a guide for a propagation of magnetohydrodynamic waves. We report a high-resolution observation of a surge observed with 1.6m Goody Solar Telescope (GST) on 2009 August 26, from 18:20~UT to 18:45UT. Characteristics of plasma motions in the surge are determined with the normalizing radial gradient filter and the Fourier motion filter. The shape of the surge is found to change from a 'C' shape to an inverse 'C' shape after a formation of a cusp, a signature of reconnection. There are apparent upflows seen above the cusp top and downflows below it. The upflows show rising and rotational motions in the right-hand direction, with the rotational speed decreasing with height. Near the cusp top, we find a transverse oscillation of the surge, with the period of ~2 min. There is no change of the oscillation phase below the cusp top, but above the top a phase change is identified, giving a vertical phase speed about 86kms-1. As the height increases, the initial amplitude of the oscillation increases, and the oscillation damping time decreases from 5.13 to 1.18min. We conclude that the oscillation is a propagating kink wave that is possibly excited by an x-point oscillation.

• The Journal of Korean Academy of Prosthodontics
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• v.33 no.4
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• pp.753-768
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• 1995

For accurate impression taking of dental patient and esthetic denture treatment of ednetulous patient, measuring between intraoral anatomic landmarks is useful.In this study the subjects selected at a random were two-jundred forty persons with a mean age 22.5(range 21-24) and were taken impression of by irreversible hydrocolloid impression material(Alginate). On the study model made by dental stone, each individual tray was made and final impresion was taken by border moilding. On final model measurings were performed with 3-dimensional measuring device and the values were analyzed by t-test The results is following : ABOUT THE MEASURED VALUES. 1. The width between maxillary right and left canine cusp tip was average 36.44mm(s.d. 2.48), man 36.67mm, woman 35.83mm(p<0.05). 2. The width between labial height of contour of maxillary right and left canine was average 40.08mm(s.d. 2.42), man 40.29mm, woman 39.52mm(p<0.05). 3. The width between mesio-lingual cusps of maxillary first molar was average 43.14mm(s.d. 3.33), man 43.56mm, woman 42.05mm(p<0.05). 4. The width between buccal alveolar ridge on axis of mesiolingual cusp of right and left maxillary first molar was average 64.89mm(s.d. 3.88), man 65.58mm, woman 62.92mm(p<0.05). 5. The width between buccal alveolar ridge on axis of mesiolingual cusp of right and left maxillary second molar was average 68.58mm(s.d. 3.91), man 69.29mm, woman 66.30mm (p<0.05). 6. The width between right and left hamular notch was average 49.80mm(s.d. 3.96), man 50.70mm, woman 48.20mm(p<0.05). 7. The length from labial heigth of contour of maxillary central incisor to center of incisive papilla was average 9.52mm(s.d. 1.18), man 9.46mm, woman 9.63mm(p>0.05). 8. The length from labial heigth of contour of maxillary central incisor to palatine fovea was average 53.27mm(s.d. 2.93), man 53.93mm, woman 52.08mm(p<0.05). 9. The center of incisive papilla ws located posterior to intercanine line at 0.40mm(s.d. 1.16), man 0.51mm, woman 0.11mm(p<0.05). 10. The height from incisal edge of maxillary central incisor to the labial vestibule was average 21.84mm(s.d. 1.38), man 22.01mm, woman 21.00mm(p<0.05). 11. The height from mesiolingual cusp of maxillary first molar to buccalvestible was average 17.45mm(s.d. 1.42), man 17.56mm, woman 17.08mm(p>0.05). 12. The height from hamular notch to standard occlusal plane was average 6.84mm(s.d. 1.06), man 6.91mm, woman 6.70mm(p>0.05). 13. The height from the deepest point of palatal vault to standard occlsalplane was average 19.95 mm(s.d. 2.03), man 20.19mm, woman 19.12mm(p<0.05). ABOUT THE ARCH FORM 1. The arch form was able to classify into four typr by the rate of the measured values. Each arch form distribution was that the 1 group had 32.46% the 2 group 2.19%, the 3 group 52.83%, the 4 group 12.72%. The sexual composition was that in 1 group man had 73.5%, woman 26.5%, in 2 group man had 40.0%, woman 60.0%, in 3 group man had 83.3%, woman 16.7%, and in 4 group man had 55.17%, woman 44.83%. 2. When canine cusp tip was marked as point O, the intersection point between labial height of contour of maxillary central incisor and intermaxillary suture as point A, height of contour of maxillary second molar buccal alveolar ridge as B point, ${\angle}$AOB was measured $133.8^{\circ}$for the 1 group, $133.0^{\circ}$for the 2 group, $132.3^{\circ}$for the 3 group, $128.9^{\circ}$for the 4 group.

• Journal of Korean Dental Science
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• v.4 no.1
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• pp.1-5
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• 2011

Purpose: Exact knowledge of the location and dimension of the pulp chamber help to maintain the pulp healthy during operative procedure and also reduces the risk of perforation of pulp chamber during root canal treatment. This in-vivo study was carried out to measure critical morphology of pulp chamber of mandibular molar using intra-oral periapical radiograph. Materials and Methods: Mandibular molar teeth of 56 patients were evaluated. The mandibular molar teeth whose pulp chamber was not violated by caries, restoration, fracture crown and those having closed apex were included in the study. The intraoral periapical radiographs were taken with paralleling angle technique using radio-opaque grid with 1 mm space. This grid was placed directly on the film. Results: In 94% of the mandibular first molars specimens the pulp chamber ceiling was at the level of the cemento-enamel junction. The measurements showing the lowest percentage variance were buccal cusp to furcation (approximately 11%) and buccal cusp to pulp chamber ceiling (approximately 15%). The distance from the cusp tip to pulp chamber ceiling height was approximately 6.0 mm, the distance from the pulpal floor to the furcation was approximately 3.0 mm, and the average height of a pulp chamber was 1.5 to 2.0 mm. Conclusion: The exact knowledge of distances of pulp chamber from various anatomical landmarks helps in proper assessment of root canals and ultimately avoids the failure of root canal treatment.

• Geomechanics and Engineering
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• v.36 no.1
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• pp.27-37
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• 2024

The roof-filling body system stability plays a key role in gob-side entry retained (GER). Taking the GER of the 1103 belt transportation roadway in Heilong Coal Mine as engineering background, stability analysis of roof-filling body system was conducted based on the cusp catastrophe theory. Theoretical results showed that the current design parameters of 1103 belt transportation roadway could ensure the roof-filling body system stable during the resistance-increasing support stage of the filling body and the stable support stage of the filling body. Moreover, a verified global numerical model in FLAC3D was established to analyze the failure characteristics including surrounding rock deformation, stress distribution, and plastic zone. Numerical simulation indicated that the width-height ratio of the filling body had a great influence on the stability of the roof-filling body system. When the width-height ratio was greater than 0.62, with the decrease of the width-height ratio, the peak stress of the filling body gradually decreased; when the width-height ratio was greater than 0.92, as the distance to the roadway increased, the roof stress increased and then decreased. The theoretical analysis and numerical simulation findings in this study provide a new research method to analyze the stability of the roof-filling body system in GER.