• 한국안광학회지
• /
• 제7권2호
• /
• pp.181-187
• /
• 2002

수정체는 조절력의 변화에 의해서 곡률이 변화한다. 조절력은 탄성체인 수정체에 힘을 수직으로 주는 경우 정점 방향으로 길이가 늘어난다. 힘을 받는 수정체는 밀도 분포와 형태가 후면에 치우쳐있어, 후면 방향의 수평 힘 보다 전면 방향의 수평 힘이 더 크다. 그러므로 후면 방향 보다 전면 방향의 두께가 더 많아 늘어난다. 그러나 조절력이 일정 값 보다 커지기 시작하면 전면에서는 팽창률이 한계에 도달하다. 이 때 전면 방향의 수평 힘 보다 후면 방향의 수평 힘이 더 커지게 되어, 전면 방향 보다 후면 방향의 두께가 더 많아 늘어난다. 전면과 후면의 두께변화 차이는 조절력에 대해 2차 곡선(${\Delta}=B_1D+B_2D^2$)을 이룬다. 조절력에 따른 전면과 후면의 두께(${\Delta}t_a$, ${\Delta}t_p$) 차이 변화 곡선은 다음과 같이 표현된다. $${\Delta}t_a=t_a-t_{ao}=t_{max}+t_0{\exp}(-A/B)-t_{ao}$$ $${\Delta}t_p=t_p-t_{po}=t_{min}+t_0{\exp}(A/B)-t_{po}$$ 인간의 수정체에서 구한 각각의 Parameter값은 전면에서 $t_{min}=1.1.06$, $t_0=-0.33$, B=9.32, 후면에서 $t_{max}=1.97$, $t_0=0.10$ B=7.96 등을 얻었다. 조절력에 따른 수정체의 전면과 후면에서 정점 곡률 안정의 변화는 다음과 같다. $$R=R_0+R_1{\exp}(D/k)$$ 수정체에서 구한 각각의 Parameter 값은 전면에서 $R_{min}=5.55$, $R_1=6.87$, k=4.65, 후면에서 $R_{max}=-68.6$, $R_1=76.7$, k=308.5 등을 얻었다.

• 한국지진공학회:학술대회논문집
• /
• 한국지진공학회 2000년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Fall 2000
• /
• pp.407-414
• /
• 2000

The friction pendulum type seismic isolation system (FPS) has been developed to provide a simple and effective way to achieve earthquake resistance for buildings . The major advantages are: the isolation frequency can be easily achieved by designing a curvature of the surface and does not depend on the supported weight of a structure. The function of carrying vertical load is separated to the function of providing horizontal stiffness. Next the friction provides sufficient energy dissipation to protect the structure from earthquake response and resistance to the weak external disturbances such as wind load and ground vibrations due to traffic. In this paper, the friction coefficients are evaluated from number of experiments on the FPS test specimens. The relations between friction coefficient and the test waveform, velocity, and pressure are reviewed and further works are discussed.

• 한국가시화정보학회지
• /
• 제7권1호
• /
• pp.21-28
• /
• 2009

The study of swirling flow is of technical and scientific interest because it has an internal recirculation field, and its tangential velocity is related to the curvature of streamline. The fluid flow for tubes and elbow of heat exchangers has been studied largely through experiments and numerical methods, but studies about swirling flow have been insufficient. Using the particle image velocimetry(PTV) method, this study found the time averaged velocity distribution with swirl and without swirl along longitude sections and the results appear to be physically reasonable. In addition, streamwise mean velocity distribution was compares with that of other. Furthermore, other experimental investigation was performed to study the characteristics of turbulent water flow in a horizontal circular tube by using liquid crystal. 2D PIV technique is employed for velocity measurement and liquid crystal is used for heat transfer experiments in water. Temperature visualization was made quantitatively by calibrating the colour of the liquid crystal versus temperature using various approaches.

• 한국정밀공학회지
• /
• 제17권9호
• /
• pp.62-69
• /
• 2000

Uneven clearances in the left and right sides of a press die cause deformation of the punch in precision shearing process. This deformation results from the compression stress and bending moment from shearing force in vertical direction and from the side force in horizontal direction acting to the punch, In this study the behavior of punch deformation is investigated in order to clarify the deformation state of the punch by using strain gauge deformation to shearing force side force bending moment radius of curvature and shear plane of the punch. Also we presented the calculation method of deformation size for the punch.

• Steel and Composite Structures
• /
• 제17권6호
• /
• pp.951-965
• /
• 2014

Point bending is commonly used for cambering and curving steel girders to large radii. In this system, a hydraulic ram or press is used to apply concentrated loads at selected points to obtain the required vertical (cambering) or horizontal (curving) curved profile from induced permanent deformations. This paper derives closed form solutions that relate loads to permanent deformations for horizontally curving wide flange steel beams based on their post-yield response. These solutions are presented in a parametric form to identify the relationship between key variables and their impact on the accuracy of the curving operation. It is shown that point bending could yield parabolic curved profiles that are within 1% of a desired circular curve if the span length to radius of curvature ratio (L / R) is less than 1.5 and the point loads are spaced at one third the beam length. Safe limits are then established on loads, strains and curvatures to avoid damaging the steel section. This leads to optimization of the point bending operation for inducing a circular profile in wide flange steel beams of any size.

• Structural Engineering and Mechanics
• /
• 제30권4호
• /
• pp.427-444
• /
• 2008

A mathematical model for the nonlinear dynamics of a rotating beam with flexible root attached to a rotating hub with elastic foundation is developed. The model is developed based on the large planar and flexural deformation theory and the potential energy method to account for axial shortening due to bending deformation. In addition the exact nonlinear curvature is used in the system potential energy. The Lagrangian dynamics and the assumed mode method is used to derive the nonlinear coupled equations of motion hub rotation, beam tip deflection and hub horizontal and vertical displacements. The derived nonlinear model is simulated numerically and the results are presented and discussed for the effect of root flexibility, hub stiffness, torque type, torque period and excitation frequency and amplitude on the dynamic behavior of the rotating beam-hub and on its stability.

• 한국의류학회지
• /
• 제15권4호
• /
• pp.437-445
• /
• 1991

The effect of diameter of rods or fibers on contact angle was studied in a vertical rod configuration. A contact angle measuring device described in the previous paper was optimized for the measurement of small-diameter fibers. It was shown that contact angles of water and hexadecane on nylon 6 monofilsments and glass rods increased with decrease of diameter below a critical diameter, which varied from one system to another. Beyond the critical value, contact angle of the liquid on the vertical glass rod reached to an equilibrium value which is equal to the unique value of the contact angle of the liquid drop on the horizontal glass plate.

• 한국생활과학회지
• /
• 제14권2호
• /
• pp.303-312
• /
• 2005

The purpose of this research is to analyze the lower part of dress forms with different sectional rotation-angles ($e.g.\;9^{\circ},\;15^{\circ},\;30^{\circ},\;45^{\circ}$) using three-dimensional measurement system and to investigate measurement properties for dress making. The dress forms used in this experiment were size 8 and six types: four from Korea and two from Japan. The instrument and tools for three-dimensional measurement was Whole Body 3D scanner (Exyma-WBS2H). The analysis program used in this experiment was Rapid Form 2004 PP1 (INUS technology, Inc, Korea). The measurement of dress forms was done three times with different sectional rotation-angles and its data were analyzed using SPSS WIN 10.0 Package. The following results were obtained: 1. With mean and standard deviation of each measured part, it was found out that the dress forms from two countries were different in size per each part. For example, the Japanese one was relatively large in middle hip and hip, compared to the Korean one. 2. The 3D analysis of the sectional rotation-angles revealed some differences between the two dress forms in sectional length per each part. 3. With cluster analysis results, it was found that there were definite differences among measurements per each part, especially in $30^{\circ}\;and\;45^{\circ}$ sections. 4. The proportion of the dress forms showed significant differences in the curvature between center and side section of the lower parts. In addition, the shapes on the horizontal section map of the four levels (waist, middle hip, hip, and bottom) were analyzed.

• 한국의류학회지
• /
• 제26권6호
• /
• pp.901-910
• /
• 2002

This study is to classify somatotypes of the upper class boys in elementary school. The study is conducted through anthoropometric measurements and photometric measurements. The subjects are 320 boys in the age group of 10 to 11 years old. The following conclusions are drawn from this study. 1. The height items are increased along with age increase. The increases in the factors, which specify vertical sizes such as height and length, are a little larger than those of breadth, depth, and girth, which specify ; horizontal sizes. 2. The factor analysis on anthropometric measurements and photometric measurements reveals five somatic composition factors and those factors comprised 79.60% of total variance. 3. The torso shapes of the upper class boys in elementary school are classified into three categories. The first type is taller and heavier than the average elementary school upper class boys and has the highest rising shoulders. The shape of the back is about average and the chest is developed above average. The curvature of the lower back is gentle and lower abdomen protrudes the most of the three types. The second type is tall and slightly heavier than average and shoulders are raised a little. The shoulder blades protrude about average and the curvature of lower back is the most developed of all. The cheat is developed about average and the abdomen is a little protruding. The third type is the most common with the smallest height of the three and skinny with dropped shoulders. The chest is somewhat flat and the shoulder blades protrude about average.

• 대한치과교정학회지
• /
• 제47권2호
• /
• pp.87-99
• /
• 2017

Objective: The aims of this study were to measure and compare the facial dimensions of the Miss Korea pageant contestants and a selected group of women from the general population by using three-dimensional (3D) image analysis, as well as to compare various facial ratios to the golden ratio within each group. Methods: Three-dimensional images of 52 Miss Korea pageant contestants (MK group) and 41 young female adults selected from the general population (GP group) were acquired. Fifty-four variables and ratios were measured and calculated. Intergroup comparisons were performed using multivariate analysis of variance. Results: Compared to the GP group, the MK group showed greater total facial height and eye width, lesser lower-facial height, and lesser facial, lower-facial, and nasal widths. Moreover, compared to the GP group, the MK group had more protruded noses with greater nasolabial angle, greater vertical curvature of the foreheads, lesser horizontal curvature of the cheek, and lesser lower-lip-and-chin volume. Conclusions: The MK group had longer faces but smaller lower lips and chins than did the GP group. The golden ratio was not matching the current facial esthetic standards. These data might be beneficial for treatment planning of patients undergoing orthognathic and plastic surgeries.