• Journal of Ocean Engineering and Technology
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• v.14 no.4
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• pp.79-85
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• 2000

Press-fit pin connection is the solderless interference-fit between pins and plated through holes(PTH) in the printed curcuit board(PCB). Because of not only its simple assembly and absence of problems associated with soldering, but also its good mechanical and electrical characteristics, the press-fit pin connection technology has quickly gained wide acceptance in the telecommunications and computer industries. In this paper, the contact stress characteristics of the domestic CPF pin when inserted into the friction coefficients were compared and the stress variations of the compliant part of the pin, which have an influence on the performance, were displayed with the time and arc length after complete connected. It is supposed that the results will provide useful data to improve the performance of the pin-PCB interconnection mechanism.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1996.04a
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• pp.1-8
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• 1996

Many studies showed that small imperfections can also have a considerable influence on the behaviour of structures. Especially, in Single-Layer Latticed Domes, initial imperfection occurred by human error and construction error is very important to the buckling load. The definition of imperfection is that a node of structure shifts from perfect condition. For example, in the case of truss structures, imperfections are represented by shifting the location of nodal points relative to the position in which they would be for a perfect structure. This paper uses Arc-length Method in nonlinear iteration analysis, choosing star dome, in which many studies have been accomplished, as a model. The results of analysis show that initial imperfection can reduce the buckling load of structures.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.11a
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• pp.232-237
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• 2000

Thermopiezoelastic snap-through phenomena of piezolaminated plates are numerically investigated by applying a cylindrical arc-length scheme to Newton-Raphson method. Based on the layerwise displacement theory and von-Karman strain-displacement relationships, nonlinear finite element formulations are derived for thermopiezoelastic composite plates. From the static and dynamic viewpoint, nonlinear thermopiezoelastic behavior and vibration characteristics are studied for symmetric and eccentric structural models with various piezoelectric actuation modes. Present results show the possibility to enhance the performance of thermal structures using piezoelectric actuators and report new phenomena, namely thermopiezoelastic snapping, induced by the excessive piezoelectric actuation in the active suppression of thermally buckled large deflection of piezolaminated plates.

• International Journal of Ocean System Engineering
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• v.2 no.2
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• pp.63-70
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• 2012

This paper presents a new curvature based kinematic displacement theory and a numerical method to calculate the planar displacement of structures from a geometrical viewpoint. The theory provides an opportunity to satisfy the kinematic equilibrium of a planar structure using a progressive numerical approach, in which the cross sections are assumed to remain plane, and the deflection curve was evaluated geometrically using the curvature values despite being solved using differential equations. The deflection curve is parameterized with the arc-length, and was taken as an assembly of the chains of circular arcs. Fast and accurate solutions of most complex deflections can be obtained with few inputs.

• Advances in Computational Design
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• v.4 no.4
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• pp.397-413
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• 2019

In this paper, static nonlinear analysis of gable frame is performed using OpenSees software. Both geometric and material nonlinearities are considered in analyses. To consider large displacements, co-rotational coordinate transformation is used in software. The effects of symmetric and asymmetric support conditions including clamped and simple supports are studied. On the other hand, the material nonlinearity is reflected on analyses using Giuffre-Menegotto-Pinto steel material. Note that strain hardening characteristics are also considered in this model. Moreover, I-shaped cross-section is assumed for all members. The results are provided for different geometry properties of gable frame including shallow and deep inclined roof. It should be added that buckling and post-buckling behaviors of gable frame are investigated using related equilibrium paths. A comparison study is also implemented on the responses of buckling loads obtained for different support and geometry conditions. To trace snap-through paths completely, a displacement control method entitled arc-length is utilized. Findings show the capability of proposed model in nonlinear analysis of gable frames.

• Journal of Astronomy and Space Sciences
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• v.32 no.1
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• pp.51-62
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• 2015

I investigated a method for drawing the star chart in the planisphere Cheonsang-yeolcha-bunyajido. The outline of the star chart can be constructed by considering the astronomical information given in the planisphere alone and the drawing method described in Xin-Tangshu; further the chart can be completed by using additional information on the shape and linking method of asterisms out of an inherited star chart. The circles of perpetual visibility, the equator, and the circle of perpetual invisibility are concentric, and their common center locates the Tianshu-xing, which was defined to be a pole star in the Han dynasty. The radius of the circle of perpetual visibility was modified in accordance with the latitude of Seoul, whereas the other circles were drawn for the latitude of $35^{\circ}$, which had been the reference latitude in ancient Chinese astronomy. The ecliptic was drawn as an exact circle by parallel transference of the equator circle to fix the location of the equinoxes at the positions recorded in the epitaph of the planisphere. The positions of equinoxes originated from the Han dynasty. The 365 ticks around the boundary of the circle of perpetual invisibility were possibly drawn by segmenting the circumference with an arc length instead of a chord length with the ratio of the circumference of a circle to its diameter as accurate as 3.14 presumed. The 12 equatorial sectors were drawn on the boundary of the star-chart in accordance with the beginning and ending lodge angles given in the epitaph that originated from the Han dynasty. The determinative lines for the 28 lunar lodges were drawn to intersect their determinative stars, but seven determinative stars are deviated. According to the treatises of the Tang dynasty, these anomalies were inherited from charts of the period earlier than the Tang dynasty. Thus, the star chart in Cheonsang-yeolcha-bunyajido preserves the old tradition that had existed before the present Chinese tradition reformed in approximately 700 CE. In conclusion, the star chart in Cheonsang-yeolcha-bunyajido shows the sky of the former Han dynasty with the equator modified to the latitude of Seoul.

• Steel and Composite Structures
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• v.27 no.1
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• pp.13-25
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• 2018

The main objective of this study is to develop a dual approach for geometrically nonlinear finite element analysis of plane truss structures. The geometric nonlinearity is considered using the Total Lagrangian formulation. The nonlinear solution is obtained by introducing and minimizing an objective function subjected to displacement-type constraints. The proposed method can fully trace the whole equilibrium path of geometrically nonlinear plane truss structures not only before the limit point but also after it. No stiffness matrix is used in the main approach and the solution is acquired only based on the direct classical stress-strain formulations. As a result, produced errors caused by linearization and approximation of the main equilibrium equation will be eliminated. The suggested algorithm can predict both pre- and post-buckling behavior of the steel plane truss structures as well as any arbitrary point of equilibrium path. In addition, an equilibrium path with multiple limit points and snap-back phenomenon can be followed in this approach. To demonstrate the accuracy, efficiency and robustness of the proposed procedure, numerical results of the suggested approach are compared with theoretical solution, modified arc-length method, and those of reported in the literature.

• Composites Research
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• v.14 no.4
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• pp.27-34
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• 2001

The finite element method based on the total Lagrangian description of the motion and the Hellinger-Reissner principle with independent strain is applied to investigate the nonlinear behavior and vibration characteristics for patched reinforced laminated spherical panels. The patched elements are formulated using variable thickness at arbitrary point on the reference plane. The cylindrical arc-length method is adopted to obtain a nonlinear solution. The post-buckled vibration is assumed to be small amplitude. The effect of patch in the spherical shell Panel is investigated on the nonlinear response and the fundamental vibration characteristics. The present results show that the load-carrying capability can be improved by reinforcing patch. The fundamental frequency of patched panel is lower than that of equivalent shell panel. However, the fundamental frequency of patched panel does not decrease greatly due to the increase of nonlinear geometrical stiffness under loading.

• Steel and Composite Structures
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• v.28 no.4
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• pp.427-438
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• 2018

Static stability is a decisive factor in the design of domes. Stability-related external factors, such as load and supports, are incorporated into structural vulnerability theory by the definition of a relative rate of joint well-formedness ($r_r$). Hence, the instability mechanism of domes can be revealed. To improve stability, an optimization model against instability, which takes the maximization of the lowest $r_r$ ($r_{r,min}$) as the objective and the discrete member sections as the variables, is established with constraints on the design requirements and steel consumption. Optimizations are performed on two real-life Kiewitt-6 model domes with a span of 23.4 m and rise of 11.7 m, which are initially constructed for shaking table collapse test. Well-formedness analyses and stability calculation (via arc-length method) of the models throughout the optimization history demonstrate that this proposed method can effectively enhance $r_{r,min}$ and optimize the static stability of shell-like structures. Additionally, seismic performance of the optimum models subjected to the same earthquake as in the shaking table test is checked. The supplemental simulations prove that the optimum models are superior to the original models under earthquake load as well.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.536-540
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• 2003

A new concept of adaptive focusing, using a Rotman lens, is presented in this paper. A Rotman lens is a microwave lens which is able to focus microwave power on its focal arc or generate multiple beams. By adding the array of phase shifters between a Rotman lens and antenna elements, the wavefront can be adaptively modulated to focus objects distributed in short range rather than far-field zone. From the optical point of view, the propagations of the lens have been simplified from the Fresnel diffraction integral to the Fourier transform. Using Fourier Transform, a beam propagation method has been developed to show improvement of the resolution by controlling wavefront of wave propagating from an aperture-type antenna array. The beam width(or spot size) and intensity have been calculated for a focused beam propagating from an array having $10{\lambda}$ of its size. For the beam with $20{\lambda},\;30{\lambda}$, and $50{\lambda}$ of geometrical focal length, the half-power beamwidth (spot size) is about $1.1{\lambda},\;1.3{\lambda}$, and $1.9{\lambda}$, respectively.