• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.6 no.1
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• pp.39-44
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• 1976

The study was performed in order to avoid misunderstanding of the image production in the orthopantomograph and auther tried artificially, the object was not placed on the image layer children who was in mixed dentition was taken with 3 sheets of the film at one time. The results were obtained as following; 1. If the object was placed in front of the image layer and back of it, width of the anterior teeth was narrowed and widened. 2. If the object's midline was not placed on the median line of the equipment, the one side was narrowed and the another side was widened. 3. If the head was inclined upward and downward, the former was shown V shape and the latter was shown inverted V shape outline of the arches. 4. In mixed dentition, auther obtained in each other that the image layer was placed on the deciduous arch, on the permanent arch, in the middle of the deciduous teeth and permanent teeth at one exposure.

• Journal of Korean Dental Science
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• v.7 no.2
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• pp.66-79
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• 2014

Purpose: To analyze the amount and pattern of tooth movement and the changes in arch dimension of mandibular dentition after orthodontic treatment using a new three-dimensional (3D)-indirect superimposition method. Materials and Methods: The samples consisted of fifteen adult patients with class I bialveolar protrusion and minimal anterior crowding, treated by extraction of four first premolars with conventional sliding mechanics. After superimposition of 3D-virtual maxillary models before and after treatment using best-fit method, 3D-virtual mandibular model at each stage was placed into a common coordinate of superimposition using 3D-bite information, which resulted in 3D-indirect superimposition for mandibular dentition. The changes in mandibular dental and arch dimensional variables were measured with Rapidform 2006 (INUS Technology). Paired t-test was used for statistical analysis. Result: The anterior teeth moved backward, displaced laterally, and inclined lingually. The posterior teeth showed statistically significant contraction toward midsagittal plane. The amounts of backward movement of anterior teeth and forward movement of posterior teeth showed a ratio of 6 : 1. Although the inter-canine width increased slightly (0.8 mm, P<0.05), the inter-second premolar, inter-first molar, and inter-second molar widths decreased significantly with similar amounts (2.2 mm, P<0.05; 2.3 mm, P<0.01; 2.3 mm, P<0.001). The molar depth decreased (6.7 mm, P<0.001) but canine depth did not change. Conclusion: A new 3D-indirect superimposition of the mandibular dentitions using best-fit method and 3D-bite information can present a guideline for virtual treatment planning in terms of tooth position and arch dimension.

• Geotechnical Engineering
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• v.12 no.4
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• pp.47-60
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• 1996

Of the classical theories on lateral earth pressure, the Coulomb's and the Rankine's theories, which have been usually used in practice for design of retaining walls, assumed that the lateral earth pressure was a triangular distribution. However, the experimental results obtained by Terzaghi(1934), Tsagreli(1967), Fang & Ishibashi(1986), etc showed that lateral pressure were not triangular distribution. ' In this study, for rigid walls with inclined backfaces and inclined surfaces backfilled by $C-\phi$ soils, an analytical method of earth pressure distribution has been newly suggested by using the concept of the flat arch. The results calculated by the newly suggested equations were compared with ones by the existed theories. And'the influence factors of the earth pressures by the suggested equations were investigated. As a result, the thrusts obtained by this method agree well with those by the existing theories, except the Rankine's solution. It was showed that the height to the centre of pressure(h) depends mainly upon the inclinations of the backface and the backfilled surface, the angle of internal friction, and the adhesion between the wall and the backfilled soil, instead of 0.33H, where H is the wall height.

• Journal of the Korea Concrete Institute
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• v.18 no.3 s.93
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• pp.379-388
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• 2006

This paper presents a model for evaluating the contribution by arch action to shear resistance in shear-critical reinforced concrete beams. Based on the relationship between shear and bending moment in beams subjected to combined shear and bending, the behavior of a beam is explicitly divided into two base components of the flexural action and the tied arch action. The compatibility condition of the shear deformation that deviates from Bernoulli bending plane is formulated utilizing the smeared truss idealization with an inclined compression chord. The Modified Compression Filed Theory is employed to calculate the shear deformation of the web, and the relative axial displacements of the compression and the tension chord by the shear flow are also calculated. From this shear compatibility condition in a beam, the shear contribution by the arch action is numerically decoupled. Then the validity of the model is examined by applying the model to some selected test beams in literatures. The results may confirm the rationale of the proposed behavioral model.

• Geotechnical Engineering
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• v.9 no.1
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• pp.69-78
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• 1993

The Coulomb and Rankine theories have been usually used for design of retaining walls, in which the earth pressures have been assumed as a triangular distribution For the rigid retaining w리1 with inclined bacuace and horizontal surface backfilled by cohesionless soils, the analytical method of earth pressure distribution has been newly suggested by using the concept of the flat arch. The active thrust obtained by this method agrees well with those by the existing theories, except the Rankine solution. The analyzed results show that the height to the center of pressure depends mainly on the inclination of the back wall and the wall friction, instead of 0.33H, where H is the wall height.

• Wind and Structures
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• v.10 no.1
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• pp.83-97
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• 2007

In the last decades there have been frequent reports of oscillations of slender tension members under simultaneous action of rain and wind - characterized by large amplitudes and low frequencies. The members, e.g. cables of cable-stayed bridges, slightly inclined hangers of arch bridges or cables of guyed-masts, show a circular cross section and low damping. These rain-wind induced vibrations negatively affect the serviceability and the lifespan of the structures. The present article gives a short literature review, describes a mathematical approach for the simulation of rain-wind induced vibrations, sums up some examples to verify the calculated results and discusses measures to suppress the vibrations.

• Journal of the Korean Institute of Rural Architecture
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• v.12 no.3
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• pp.27-34
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• 2010

Unbraced vinyl house frame that is economically installed is certainly easy to collapse under the influence of excess snow load. To make it more cheaply in putting up as well as more efficiently in withstanding the applied snow load, it is essential to insert additional bracing into the existing unbraced vinyl house frame. On the other hand, there are varieties of possible bracing shapes that can be formed. However, their efficiencies are different. Therefore, it is important to identify the most effective bracing shape. In this study, 2 different kinds of bracing shapes, horizontal and inclined bracing, are used to additionally install in the ordinary single frames in order to show the effect of the bracing resisting the applied snow load and compare the bending moment, axial force, combined stress and vertical displacement of the vinyl house frame.

• Tunnel and Underground Space
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• v.22 no.3
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• pp.205-213
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• 2012

In this study, scaled model tests were performed to investigate the stability of twin tunnels constructed in anisotropic rocks with $30^{\circ}$ inclined bedding planes under the condition of lateral pressure ratio, 2. Five types of test models which had respectively different pillar widths and shapes of tunnel sections were experimented, where both crack initiating pressures and deformation behaviors around tunnels were investigated. The models with shallower pillar width showed shear failure of pillar according to the existing bedding planes and they were cracked under lower pressure than the models with thicker pillar width. In order to find the effect of tunnel sectional shape on stability, the models with four centered arch section, circular section and semi-circular arch section were experimented. As results of the comparison of the crack initiating pressures and the deformation behaviors around tunnels, the semi-circular arched tunnel model was the most unstable whereas the circular tunnel model was the most stable among them. Furthermore, the results of FLAC analysis were qualitatively coincident with the experimental results.

• Journal of the Korea Concrete Institute
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• v.18 no.6 s.96
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• pp.819-825
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• 2006

The objective of the present study is to verify the validity of a new truss model for evaluating the contribution by arch action to shear resistance in shear-critical reinforced concrete beams. The new truss model is based on the relationship between shear and bending moment in a beam subjected to combined shear and bending. The compatibility condition of the shear deformation that deviates from Bernoulli bending plane is formulated utilizing the smeared truss idealization with an inclined compression chord. The Modified Compression Filed Theory is employed to calculate the shear deformation of the web, and the relative axial displacements of the compression and the tension chord by the shear flow are also calculated. From this shear compatibility condition in a beam, the shear contribution by the arch action is numerically decoupled. Then the validity of the model is examined by applying the model to some selected test beams in literatures. On the basis of the analytical results, the contribution by the web to shear resistance can be constant and have an excellent linear correlation with the web reinforcement ratio. The present decoupling approach may provide a simple way for the assessment of the role of each parameter or mechanism that affects the ultimate shear behavior of reinforced concrete beams.

• Journal of the korean academy of Pediatric Dentistry
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• v.24 no.4
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• pp.771-775
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• 1997

Ectopic eruption is defined as abnormal eruption and results in malpositioned teeth and abnormal root resorption of adjacent teeth. Ectopic eruption, first reported by Chapman, occurs in 3% of the population and that mostly in the maxilla. Etiologic factors include narrow maxilla, large maxillary teeth, retarded calcification of the first molar, inclined eruption path of the first molar and retruded position of the maxilla. Impaction of the second molar is rare and occurs mostly in the mandible. Major causes are large teeth and insufficient arch length. Halterman has devised a method of distalizing a ectopically erupting first molar by cementing a band on the second deciduous molar with a hook soldered and a button bonded to the occlusal surface of the first permanent molar. Ectopically erupted posterior teeth should be treated early to maintain normal development of the dentition, harmony of facial growth and occlusal support, a failure to do so could result in severe malocclusion, periodontal damage and continued root resorption of the adjacent teeth. Early detection and treatment is thus vital. The author is submitting this report as he has obtained favorable results in treating a patient who came to the SNUDH Dept. of Pediatric Dentistry complaining of the first molar by using a modified Halterman appliance.