• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.34 no.4
• /
• pp.1043-1052
• /
• 2014

This paper deals with in-plane free vibrations of the horseshoe circular arch. Simultaneous ordinary differential equations governing free vibration of the arch are derived with respect to the radial and tangential deformations. Particularly, differential equations are obtained under the arc length coordinate rather than the angular one in order to extend the horseshoe arch whose subtended angle is greater than ${\pi}$ radians. The differential equations are numerically solved for calculating the natural frequencies accompanying with the corresponding mode shapes. In parametric studies, effects of the rotatory inertia, slenderness ratio and circumferential arc length ratio on frequency parameters are extensively discussed.

• Journal of the Ergonomics Society of Korea
• /
• v.14 no.1
• /
• pp.59-67
• /
• 1995

Depending upon the eye and head movement, the visual field is often classified into three categories ; stationary field, eye field and head and eye field. To investigate the effect of background condition on the size of the visual field, an experiment was conducted, in which the subject was instructed to search a target with distinct orientations. In each trial, a single target was presented on the perimeter modified to cover the range of 330 .deg. around the fixation point, with the visual angle subtended 1.4 .deg. vertically and horizontally. Nontarget density, meridian, size contrast and subject showed a significant effect on the visual field at .alpha. =0.01, where density was inversely proportional to the size of the visual field, and size contrast linearly proportional to the size of the visual field. The size of the visual field on horizontal axis was larger than that on vertical axis, and that on right and upper meridian was also larger than on left and lower meridian. The shape was found to be horizontally oriented oval and statistically asymmetric with respect to horizontal and vertical axes. In addition, the regression equations to predict the visual field on the given background condition were suggested. These results were expected to be used as a design guideline when arranging displays and controls on panels such as automobile display panels, cockpits, etc.

• Nuclear Engineering and Technology
• /
• v.46 no.2
• /
• pp.217-224
• /
• 2014

The present work used the efficiency transfer method used to calculate the full energy peak efficiency (FEPE) curves of the (2"*2" & 3"*3") NaI (Tl) detectors based on the effective solid angle subtended between the source and the detector. The study covered the effect of the self attenuation coefficient of the source matrix (with a radius greater than the detector's radius) on the detector efficiency. $^{152}$ An Eu aqueous radioactive source covering the energy range from 121.78 keV up to 1408.01 keV was used. In this study an empirical formula was deduced to calculate the difference between the measured and the calculated efficiencies [without self attenuation] at low and high energy regions. A proper balance between the measured and calculated efficiencies [with self attenuation] was achieved with discrepancies less than 3%, while reaching 39% for calculating values [without self attenuation] due to working with large sources, or for low photon energies.

• Nuclear Engineering and Technology
• /
• v.21 no.2
• /
• pp.63-72
• /
• 1989

An analysis for the gamma radiation fields in the research reactor MAPLE-X10 facility has been peformed under the assumption of partial loss of reactor and service pool water to assess the safety from the view point of design. Four photon source terms considered in the analysis were calculated using the ORIGEN-S code. Gamma dose rate calculations over the reactor and service pools during the water-loss accident conditions were performed using QAD-CG code. MCNP code (Monte Carlo Neuron and Photon Transport code), also, was used to assess the scattered radiation fields away from the pools, which is appropriate for calculating the scattered photon dose rates outside of the solid angle subtended by the source and pool walls.

• Nuclear Engineering and Technology
• /
• v.49 no.1
• /
• pp.254-266
• /
• 2017

Finite-element analysis based on elastic-perfectly plastic material was conducted to examine the influence of structural deformations on collapse loads of circumferential through-wall critically cracked $90^{\circ}$ pipe bends undergoing in-plane closing bending and internal pressure. The critical crack is defined for a through-wall circumferential crack at the extrados with a subtended angle below which there is no weakening effect on collapse moment of elbows subjected to in-plane closing bending. Elliptical and semioval cross sections were postulated at the bend regions and compared. Twice-elastic-slope method was utilized to obtain the collapse loads. Structural deformations, namely, ovality and thinning, were each varied from 0% to 20% in steps of 5% and the normalized internal pressure was varied from 0.2 to 0.6. Results indicate that elliptic cross sections were suitable for pipe ratios 5 and 10, whereas for pipe ratio 20, semioval cross sections gave satisfactory solutions. The effect of ovality on collapse loads is significant, although it cancelled out at a certain value of applied internal pressure. Thinning had a negligible effect on collapse loads of bends with crack geometries considered.

• Advances in biomechanics and applications
• /
• v.1 no.2
• /
• pp.85-93
• /
• 2014

In this paper, two procedures of enumerating the axial rotation are proposed using the unit sphere of the spherical rotation coordinate system specifying 3D rotation. If the trajectory of the movement is known, the integration of the axial component of the angular velocity plus the geometric effect equal to the enclosed area subtended by the geodesic path on the surface of the unit sphere. If the postures of the initial and final positions are known, the axial rotation is determined by the angular difference from the parallel transport along the geodesic path. The path dependency of the axial rotation of the three dimensional rigid body motion is due to the geometric effect corresponding to the closed loop discontinuity. Firstly, the closed loop discontinuity is examined for the infinitesimal region. The general closed loop discontinuity can be evaluated by the summation of those discontinuities of the infinitesimal regions forming the whole loop. This general loop discontinuity is equal to the surface area enclosed by the closed loop on the surface of the unit sphere. Using this quantification of the closed loop discontinuity of the axial rotation, the geometric effect is determined in enumerating the axial rotation. As an example, the axial rotation of the arm by the Codman's movement is evaluated, which other methods of enumerating the axial rotations failed.

• Journal of Korean Foot and Ankle Society
• /
• v.12 no.1
• /
• pp.36-40
• /
• 2008

Purpose: The purpose of this study is to find out the normal results in ankle on varus stress, valgus stress, and anterior draw stress in young men in korea. This would be helpful as the basic data of measuring of ankle instability for operational indication. Materials and Methods: Varus and Valgus stress anteroposterior radiographs and Anterior drawing stress lateral radiographs of 600 normal ankles were reviewed. First, A line parallel was drawn parallel to the articular surface of the distal tibia, and another line was drawn parallel to the articular surface of the talus on anteroposterior radiographs. The interior angle that subtended by these two lines was measured. Second, the reference point is located at the posterior border of the tibia, and the shortest distance from this point to the proximal posterior articular surface of the talus is measured. Results: There were 300 males and 600 ankles. The mean age overall was 21 years (19-22 years) old. The mean length of ankle on anterior draw stress was $5.54{\pm}3.33\;mm$. The mean a interior angle of ankle on varus stress was $0^{\circ}-8.93^{\circ}$, and on valgus stress $0^{\circ}-7.78^{\circ}$. Conclusion: We can consider for operational indication at over the 8.87 mm on anterior draw stress, over the $8.93^{\circ}$ on varus stress, and over the $7.78^{\circ}$ on valgus.

• Journal of the Korean Society for Advanced Composite Structures
• /
• v.1 no.3
• /
• pp.24-34
• /
• 2010

This paper analyzed the partial differential equations of laminated composite shells of revolution by using the finite difference method. The proof that numerical results are reasonable and accurate is obtained through converge ratio analysis and commercial program LUSAS for the structural analysis. The purpose of this study is to examine closely the engineering advantages and to analyze the structural behaviors of the anisotropic shells of revolution. Thus, the relevant reinforcement and most suitable arrangement of fiber to produce the highest strength are proposed through the numerical results according to a variety of parameter study. Namely, the distribution of displacements and stress resultants are analyzed according to the change of meridian's curvature, the ratio of height-width of shell, subtended angle, fiber angle, and so on. Using these distribution, the most suitable shell may be proposed to produce the highest strength. Also, the configuration of the entire laminated composite conical shells is analysed, and a variety of the design criterion of circular conical shell are proposed and studied in engineering view points.

• Journal of Korean Society of Steel Construction
• /
• v.12 no.2 s.45
• /
• pp.187-196
• /
• 2000

In this paper, stability analysis is carried out for the out of plane behaviors under compressive loads to the direction of the generator in anisotropic cylindrical shells. It is not easy to obtain the analytic solutions about the stability analysis of anisotropic cylindrical shells consisted of composite materials. For solving this problems, this paper used the finite difference method which is one of the numerical methods. Geometrical property of cylindrical shells transforms the compressive loads into the inplane behaviors. This paper studied the change of stiffness in the direction of the circumferential and stability of shells according to change of fiber angle, curvature, subtended angle and aspect ratio. From result of this study, anisotropic cylindrical shells under compressive loads to the direction of the generator vary greatly with respect to the change of the circumferential stiffness. Therefore, it will be more safe to strengthen the circumferential stiffness of anisotropic cylindrical shells under compressive loads.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.9
• /
• pp.6325-6332
• /
• 2015

Although distortions of horizontally curved box girder are more susceptible than which of the straight girder due to curvature effect, current domestic design standards does not present spacing of intermediate diaphragms for the curved box girder. In this study, parametric studies for straight and curved box girder considering distortional warping normal stresses based on linear finite element analysis were carried out. Single span curved girders were chosen for analysis based on current domestic bridge data with 1-6 of solid intermediate diaphragms, 0-30 degree of subtended angle, 30m and 60m of span length and 2-3m of flange width and web height. The adequate spacing of diaphragms for the box girder were suggested considering subtended angles and bending and distortional warping normal stress ratios with 5%, 10%, 15% and 20%. The analysis results were also compared to a current design standard and suggested spacing of diaphragm were evaluated.