• Steel and Composite Structures
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• v.25 no.3
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• pp.315-326
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• 2017

In this work, thermoelastic dynamic behavior of functionally graded carbon nanotube reinforced composite (FG-CNTRC) cylinders subjected to mechanical pressure loads, uniform temperature environment or thermal gradient loads is investigated by a mesh-free method. The material properties and thermal stress wave propagation of the nanocomposite cylinders are derived after solving of the transient thermal equation and obtaining of the time history of temperature field of the cylinders. The nanocomposite cylinders are made of a polymer matrix and wavy single-walled carbon nanotubes (SWCNTs). The volume fraction of carbon nanotubes (CNTs) are assumed variable along the radial direction of the axisymmetric cylinder. Also, material properties of the polymer and CNT are assumed temperature-dependent and mechanical properties of the nanocomposite are estimated by a micro mechanical model in volume fraction form. In the mesh-free analysis, moving least squares shape functions are used to approximate temperature and displacement fields in the weak form of motion equation and transient thermal equation, respectively. Also, transformation method is used to impose their essential boundary conditions. Effects of waviness, volume fraction and distribution pattern of CNT, temperature of environment and direction of thermal gradient loads are investigated on the thermoelastic dynamic behavior of FG-CNTRC cylinders.

• Bulletin of the Korean Chemical Society
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• v.35 no.11
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• pp.3244-3248
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• 2014

Two ethylenediamine cobalt(II) oxalate complexes Co(ox)(en), 1 and $Co(ox)(en){\cdot}2H_2O$, 2 have been hydrothermally synthesized and characterized by single crystal X-ray diffraction, IR spectrum, TG analysis, and magnetic measurements. In 1, Co atoms are coordinated by two bis-bidentate oxalate ions in transconfiguration to form Co(ox) chains, which are further bridged by ethylenediamine molecules to produce 2D grid layers, Co(ox)(en). In 2, Co atoms are coordinated by bridging oxalate ions in cis-configuration to form Co(ox) chains, and the additional chelation of ethylenediamine to Co atoms completes 1D zigzag chain, Co(en)(ox). Two lattice water molecules stabilize the chains through hydrogen bonding. Magnetic susceptibility measurements indicate that both complexes exhibit weak antiferromagnetic coupling between cobalt(II) ions with the susceptibility maxima at 23 K for 1 and 20 K for 2, respectively. In 1 and 2, the oxalate ligands afford a much shorter and more effective pathway for the magnetic interaction between cobalt ions compared to the ethylenediamine ligands, so the magnetic behaviors of both complexes could be well described with 1D infinite magnetic chain model.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.39.3-39.3
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• 2016

About one tenth of dwarf elliptical galaxies found in the Virgo cluster have a disk component, and some of them even possess substructures such as bars, lens, and spiral arms. We use N-body simulations to study the formation of these non-axisymmetric features in disky dwarf elliptical galaxies. By mimicking VCC 856, a bulgeless dwarf galaxy with embedded faint spiral arms, we construct 11 sets of initial conditions with slight dynamical variations based on observational data. Our standard model starts slowly to form a bar at ~3 Gyr and then undergoes buckling instability that temporarily weakens the bar although the bar strength continues to grow afterward. We find 9 of our models are unstable to bar formation and undergo buckling instability. This suggests that disky dwarf elliptical galaxies are intrinsically unstable to form bars, accounting for a population of barred dwarf galaxies in the outskirts of the Virgo cluster. To understand the origin of the faint grand-design spiral arms, we additionally construct 6 sets of models that undergo tidal interactions with their neighbors. We find that faint spiral arms consistent with observations develop when tidal forcing is relatively weak although strong encounter still results in bar formation. We discuss our results in light of the dynamical evolution of dwarf elliptical galaxies including mergers.

• Structural Engineering and Mechanics
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• v.12 no.3
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• pp.249-266
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• 2001

Current seismic design provisions allow structures to deform into inelastic range during design level earthquakes since the chance to meet such event is quite rare. For this purpose, design base shear is defined in current seismic design provisions as the value of elastic seismic shear force divided by strength reduction factor, R (${\geq}1$). Strength reduction factor generally consists of four different factors, which can account for ductility capacity, overstrength, damping, and redundancy inherent in structures respectively. In this study, R factor is assumed to account for only the ductility rather than overstrength, damping, and redundancy. The R factor considering ductility is called "ductility factor" ($R_{\mu}$). This study proposes ductility factor with correction factor, C, which can account for dynamic P-${\Delta}$ effect. Correction factor, C is established as the functional form since it requires computational efforts and time for calculating this factor. From the statistical study using the results of nonlinear dynamic analysis for 40 earthquake ground motions (EQGM) it is shown that the dependence of C factor on structural period is weak, whereas C factor is strongly dependant on the change of ductility ratio and stability coefficient. To propose the functional form of C factor statistical study is carried out using 79,920 nonlinear dynamic analysis results for different combination of parameters and 40 EQGM.

• Electrical & Electronic Materials
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• v.9 no.7
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• pp.674-679
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• 1996

Using the home made Kuhn type LB (Langmuir - Blodgett) film's deposition apparatus, We measured the displacement current of monolayer film on the water surface. The obtained displacement current had each different pattern by the kind of solution while varying pressure of the monolayer. Solution of 4 - octyl - 4' - (5 - carboxyl - pentamethyleneoxy ) - azobenzene (8A5H) and stearic acid (CH$_{3}$(CH$_{2}$)$_{16}$COOH) (C18) were spreaded at the air water interface respectively, and the current induced by the dynamic behavior of molecules were pressed by barrier. Displacement current of 8A5H measured small current than C18 at same condition and it was positive direction when increasing pressure but it was negative direction when decreasing pressure. Also, Two patterns of displacement current were symmetrical form and appeared repeatedly. The C18 has unsymmetrical form of displacement current and weak current when decreasing pressure (expansion). The C18 molecules have two distinct peak values of displacement current that show that the orientations of molecules were changed largely at this points. From these results, we obtained that the 8A5H has more elasticity than the C18.8.C18.

• Conservation Science in Museum
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• v.11
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• pp.43-48
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• 2010

Excavated lacquer wares can be divided into waterlogged lacquer wares supersatuated with moisture and dry lacquer wares with little moisture. This conservation was done with dry damaged lacquer wares excavated from Daho-ri. Lacquer ware artifacts with lacquer fragments and no surface material remaining were processed using the three following methods. The three methods are reinforcing while sustaining three-dimensional form; reinforcing with earth after cleansing so that fragments are revealed due to weak lacquer fragments; and reinforcing the whole lacquer ware or parts by connecting and supporting missing parts with rayon paper, an artificial fiber paper, if the form cannot be sustained only with lacquer fragments.

• Advances in Computational Design
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• v.5 no.1
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• pp.55-89
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• 2020

For the first time, an accurate analytical solution, based on coupled three-dimensional (3D) piezoelasticity equations, is presented for free vibration analysis of the angle-ply elastic and piezoelectric flat laminated panels under arbitrary boundary conditions. The present analytical solution is applicable to composite, sandwich and hybrid panels having arbitrary angle-ply lay-up, material properties, and boundary conditions. The modified Hamiltons principle approach has been applied to derive the weak form of governing equations where stresses, displacements, electric potential, and electric displacement field variables are considered as primary variables. Thereafter, multi-term multi-field extended Kantorovich approach (MMEKM) is employed to transform the governing equation into two sets of algebraic-ordinary differential equations (ODEs), one along in-plane (x) and other along the thickness (z) direction, respectively. These ODEs are solved in closed-form manner, which ensures the same order of accuracy for all the variables (stresses, displacements, and electric variables) by satisfying the boundary and continuity equations in exact manners. A robust algorithm is developed for extracting the natural frequencies and mode shapes. The numerical results are reported for various configurations such as elastic panels, sandwich panels and piezoelectric panels under different sets of boundary conditions. The effect of ply-angle and thickness to span ratio (s) on the dynamic behavior of the panels are also investigated. The presented 3D analytical solution will be helpful in the assessment of various 1D theories and numerical methods.

• Journal of Korean Association for Spatial Structures
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• v.22 no.1
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• pp.17-24
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• 2022

Currently, the construction trend of high-rise structures is changing from a cube-shaped box to a free-form. In the case of free-form structures, it is difficult to predict the behavior of the structure because it induces torsional deformation due to inclined columns and the eccentricity of the structure by the horizontal load. For this reason, it is essential to review the stability by considering the design variables at the design stage. In this paper, the position of the weak vertical member was analyzed by analyzing the behavior of the structure according to the change in the core position of the twisted high-rise structures. In the case of the shear wall, the shear force was found to be high in the order of proximity to the center of gravity of each floor of the structure. In the case of the column, the component force was generated by the axial force of the outermost beam, so the bending moment was concentrated on the inner column with no inclination.

• Journal of Korean Society of Steel Construction
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• v.27 no.6
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• pp.513-523
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• 2015

In steel moment frames constructed of H-shapes, strong-axis moment connections should be used for maximum structural efficiency if possible. And most of cyclic seismic testing, domestic and international, has been conducted for strong-axis moment connections and cyclic test data for weak-axis connections is quite limited. However, when perpendicular moment frames meet, weak-axis moment connections are also needed at the intersecting locations. Especially, both strong- and weak-axis moment connections have been frequently used in domestic practice. In this study, cyclic seismic performance of RBS (reduced beam section) weak-axis welded moment connections was experimentally investigated. Test specimens, designed according to the procedure proposed by Gilton and Uang (2002), performed well and developed an excellent plastic rotation capacity of 0.03 rad or higher, although a simplified sizing procedure for attaching the beam web to the shear plate in the form of C-shaped fillet weld was used. The test results of this study showed that the sharp corner of C-shaped fillet weld tends to be the origin of crack propagation due to stress concentration there and needs to be trimmed for the better weld shape. Different from strong-axis moment connections, due to the presence of weld access hole, a kind of CJP butt joint is formed between the beam flange and the horizontal continuity plate in weak-axis moment connections. When weld access hole is large, this butt joint can experience cyclic local buckling and subsequent low cycle fatigue fracture as observed in this testing program. Thus the size of web access hole at the butt joint should be minimized if possible. The recommended seismic detailing such as stickout, trimming, and thicker continuity plate for construction tolerance should be followed for design and fabrication of weak-axis welded moment connections.

• Archives of Plastic Surgery
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• v.36 no.1
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• pp.66-74
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• 2009

Purpose: The importance of the deformities in alar - columellar complex has been underestimated in Asian ethnic groups for the last decades. Fortunately, with increasing familiarity of the open rhinoplasty techniques, the anatomic details of the nasal tip have been pointed up. Definitely, having an interest and demand for improving the sub - normal relationship between the alar rim and columella are indebted for such growing of knowledge about nasal tip anatomy. However, it is true that any single procedure is not settled as versatile and fully confident modality to correct the retracted notching of the alar rim. With this article, I should like to propose another useful option for treating retracted ala. Methods: The author has tried to correct alar rim retraction by means of: (1) Triangular onlay septal cartilage graft on the lower lateral cartilage with the medial end fixed to the anterior surface of the lateral crus(Alar extension graft), (2) Inserting lateral end of the alar extension graft to the vestibular skin pocket in the form of a finger - in - groove, (3) using the vestibular skin in the form of an advancement flap, and (4) using the soft shield graft to prevent possible visible step - off of the alar margin. Results: The author applied an alar extension graft to 16 patients in order to correct a retracted ala for the last 27 months (August, 2003 - October, 2005). The distances from alar rim to long axis of nostril were improved to be within 2 mm in all of the cases, and also the shape of the alar rim changed to a round form. Nostril asymmetry (6%) in one case, temporary palpable step - off (18%) in three cases, temporary visible step - off (6%) in one case, and temporary paresthesia of the tip (25%) in four cases were observed. Conclusion: The alar extension graft is simple and efficacious. It does not need donor sites other than the operative field, and its results are predictable. In particular, since it may give structural intensity to a weak lower lateral cartilage, it may be preferentially used for the correction of a retracted ala that arises from hypoplastic lower lateral cartilage. Moreover intensified lower lateral cartilage also improves the esthetic shape of lobule.