• 대한치과보철학회지
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• 제18권1호
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• pp.37-47
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• 1980

The purpose of this study was to investigate the stresses in different proximal margins and to measure, quantitatively, the effect of different modifications in the design of preparations on the stresses using two-dimensional photoelasticity. Photoelastic stress analysis is based on the phenomenon, exhibited by most transparent solids, of becoming birefringent, or doubly refracting, when strained. Two birefringent materials were used in this study, PSM-1 and PSM-5 in .standard sheet ($10'{\times}10'{\times}\frac{1}{4}'$ thickness), PSM-1(polyester) was used for constructing the substructure, and PSM-5(epoxy resin) was used in making the restorations to be investigated. Two birefringent materials were used in the construction of composite photoelastic model. Seven variable models were constructed. The peripheral dimensions of all model were constant and the models represent an occlusomesial section of a lower posterior molar. Model 1 represents the knife edge margin (shoulderless), Model 2 represents the chamfer, Model 3 represents a rounded shoulder(no sharp angle between the axial wall and gingival floor), Model 4 represents a flat shoulder (axial wall is a $90^{\circ}$ angle to the gingival wall), Model 5 represents $+15^{\circ}$ angulation, Model 6 has a $-15^{\circ}$ angulation, and Model 7 is the same as Model 4 except that it has a $45^{\circ}$ bevel. Improved artificial stone was used to represent dental cement in luting the composite photoelastic model. Static loading procedures(100 pounds) were used at preplanned sites. The results were as follows; 1. The stresses in the proximal portion of all tested models were compressive in nature when the proximal shoulders were loaded vertically on the same proximal marginal ridge. 2. The round and chamfered preparations were the optimum designs in proximoocclusal restorations. They showed the lowest stress concentration factor, i.e. 2.16 and 2.23, respectively. The knife edged shoulder had the highest value, K=5.39. Round type shoulder geometry experiments reduced the stress concentration factor (S.C.F.) 3. The gingival portion of proximal shoulder geometry was a critical location for stress concentration.

• Advances in aircraft and spacecraft science
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• 제11권2호
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• pp.177-194
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• 2024

The objective of this paper is to compute entire flow field over Apollo-II, Aerospace Reentry Demonstrator (ARD), Orbital Experiment (OREX) with sharp shoulder and rounded shape shoulder and Space Recovery Experiment (SRE) at different flare-cone half-angle of 20° and 35°. This paper addresses numerical solutions of the compressible three-dimensional Euler equations on hexahedral meshes for a freestream Mach 6 and at an angle of incidence 5°. Furthermore, spatial discretization is accomplished by a cell centred finite volume formulation solution and advanced in time by an explicit multi-stage Runge-Kutta method. The flow field characteristics, distribution of surface pressure coefficient and Mach number on fore-body and aft-body are presented as a function of the geometrical parameters of many reentry capsules. The surface pressure variation is numerically integrated to obtain the aerodynamic drag and compared well with impact theory. The present numerical study has observed the significant dependence of the blunt body and the aft-body geometry of the vehicle and can be used to study atmospheric conditions during re-entry trajectory. The numerical analysis reveals the significant influence of capsule geometry on the flow characteristics of the mechanism of upstream and structure of the flow near the wake region and aerodynamic drag coefficient.

• 대한물리치료과학회지
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• 제31권1호
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• pp.33-45
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• 2024

Background: This study aimed to investigate the effect of elastic band-resistive exercise using audio-visual medium on pain, proprioception, and motor function in adults with chronic neck and shoulder pain. Design: One group pretest-posttest follow-up experimental design. Method: Twenty adult women with neck and shoulder pain voluntarily participated in this study. Elastic band-resistive exercise using audio-visual medium including cervical flexion and extension, shoulder external rotation, and scapular retraction-protraction motions was conducted 5 times a week for 3 weeks. The Numerical Rating Scale, pressure threshold tool, CROM goniometer, and Image J software were used to assess subjective pain level, tenderness threshold (pain), joint position sense error (proprioception), joint range of motion, and postural alignment (motor function), respectively. Result:: The pain intensity and threshold and joint position sense error showed significant decreases after the intervention, whereas the joint range of motion angle revealed significant increases. The postural alignment including forward head posture and rounded shoulder revealed significant improvements after the intervention. Conclusions: Therefore, we suggest that elastic band-resistive exercise through audio-visual medium would be helpful in preventing and managing pain and physical dysfunction in individuals with chronic neck and shoulder pain, and then it would support the development of health management-related online education content.

• 한국의류학회지
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• 제14권3호
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• pp.183-195
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• 1990

The author has studied the effect of clothes design to mask the dorsal curvature that is one of the commonest changes in elderly women. Body measurements including the body type and the status of dorsal curvature were perfor-med on 153 women of over 60 years of age, and then a body form to fit to the mean measure-ments was made to evaluate the effects of various designs to it. With 31 pattern designs modified by changing in their slash lines and gathers using darts, the diminishing effect of the rounded back were evaluated by means of sensory test. The results of this study can be summarized as follows: I . Results from the body measurements 1) The mean body type in elderly women was that of obesity. 2) With the advancement of age, the angle to indicate the degree of dorsal curvature as well as the angle to indicate the posture are increased. II . Concerning to the clothes design to diminish the shape of dorsal curvature 1) Among the designs by the position of darts, the basic pattern (Fig. 5-1-(1)) showed the best effect to mask the shape of dorsal curvature. 2) Out of the applied designs of princess lines, that in which the slash line is pointing toward the shoulder point (Fig. 5-2-(1)) seemed to be most effective. 3) What has angled princess line (Fig. 5-3-(1)) had the most diminishing effect among the waist darts and armhole princess lines. 4) Among the V-shaped designs, the slashed at the shoulder point (Fig. 5-4-(1)) had the best effect to lessen the shape of the dorsal cuuature. 5) Wider angle yoke had better effect to the narrow angle one among the designs with straight yoke, and that with downward direction (Fig. 5-5-(1)) showed the best effect. 6) Between straight wide angle yoke and curved yoke, that of curved one with downward direction (Fig. 5-6-(1)) had better effect as far as the masking effect of dorsal curvature is concerned. 7) Gathers around the neck showed better effect to those around the shoulder, and the more amount of gathers (Fig. 5-7-(1)), there was better effect. 8) The design with midline gathers at the level of horizontal slash line of armhole (Fig. 5-8-(1)) showed better effect to that with seperated gathers. 9) In case of design with gathers at the horizontal line of armhole, it showed the better effect with less amount of gathers in midline ones, but with more amount in the side ones. 10) Considering all 7 different designs with better effect in covering the shape of dorsal curvature, it was evident that the design with gathers was far better than the design with application of slash lines.

• The Journal of Advanced Prosthodontics
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• 제10권5호
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• pp.381-387
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• 2018

PURPOSE. Cement-retained implant prostheses can lack proper retrievability during repair, and residual cement can cause peri-implantitis. The purpose of this in vitro study was to evaluate the influence of abutment height and convergence angle on the retrievability of cement-retained implant prostheses with lingual slots, known as retrievable cement-type slots (RCS). MATERIALS AND METHODS. We fabricated six types of titanium abutments (10 of each type) with two different heights (4 mm and 6 mm), three different convergence angles ($8^{\circ}$, $10^{\circ}$, and $12^{\circ}$), a sloped shoulder margin (0.6 mm depth), a rectangular shape ($6mm{\times}6.5mm$) with rounded edges, and a rectangular ledge ($2mm{\times}1mm$) for the RCS. One monolithic zirconia crown was fabricated for each abutment using a dental computer-aided design/computer-aided manufacturing system. The abutments and crowns were permanently cemented together with dual-curing resin cement, followed by 24 hours in demineralized water at room temperature. Using a custom-made device with a slot driver and torque gauge, we recorded the torque ($N{\cdot}cm$) required to remove the crowns. Statistical analysis was conducted using multiple regression analysis and Mann-Whitney U tests (${\alpha}=.05$). RESULTS. Removal torques significantly decreased as convergence angles increased. Multiple regression analysis showed no significant interaction between the abutment height and the convergence angle (Durbin-Watson ratio: 2.186). CONCLUSION. Within the limitations of this in vitro study, we suggest that the retrievability of cement-retained implant prostheses with RCS can be maintained by adjusting the abutment height and convergence angle, even when they are permanently cemented together.

• 대한치과보철학회지
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• 제34권4호
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• pp.850-868
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• 1996

The accuracy and dimensional stability of impression materials are one of the most important factors for successful prosthodontic treatment. The purpose of this study was to evaluate the accuracy of several dental elastomeric impression materials used widely and clinically : Impregum-$F^{(R)},\;Permlastic^{(R)},\;Silascon^{(R)},\;Perfect^{(R)},\;Xantopren^{(R)}$. There have been many studies to evaluate the accuracy of impression materials. But it has not been decided yet, which method was most suitable for the evaluation of the accuracy. In this study, two resin teeth, #15 & 25, were prepared with rounded shoulder margin and 90 degree cavosurface angle. For the polysulfide rubber and polyether, the custom tray was made at least 24 hours prior to impression taking. For the silicone rubber materials, putty/wash impression technique was applied in taking impressions. Marginal openings of the castings on the master dies and prepared resin teeth were measured under stereomicroscope. The results were statistically analyzed and compared between tested impression materials. The results were as follows ; 1. In the overall accuracy of impression materials, polyether was the most accurate one, followed by polysulfide, additional silicone and condensation silicone. 2. On the first model pouring, condensation silicone had the largest discrepancies and there was significant difference compared to the other impression materials. 3. Polysulfide had the least discrepancies in the first model pouring, but showed larger discrepancies in the immediate second pouring than the first pouring. 4. On the immediate second pouring, the discrepancy of polyether was shown to be the smallest, while the largest one was additional silicone. 5. Polyether and polysulfide rubber using custom impression trays showed superior accuracy to silicone rubber, putty/wash impression technique.