• Journal of Korean Association for Spatial Structures
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• v.23 no.4
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• pp.89-96
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• 2023

The seismic retrofits of existing structures have been focused on the control of structural responses which can be achieved by providing displacement capacity through inelastic ductile action at supplemental devices. Due to their hysteretic characteristics, it is expected to sustain damage through repeated inelastic behaviors including residual deformation which might increase repair costs. To solve such drawbacks of existing yielding devices, this study proposes a self-centering disc spring brace that sustains large axial deformation without structural damage while providing stable energy dissipation capacity. The hysteretic behaviors of suggested brace are first investigated based on the quasi-static cyclic test procedure. Experimental results present the effective self-centering behavior and an analytical model is then suggested in order to reasonably capture the flag-shaped hysteretic behavior of the disc spring brace.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.5
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• pp.37-43
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• 2012

The closed-loop multiple-input multiple-output (MIMO) system has been adopted by long term evolution (LTE) system. Many techniques are proposed to enhance the transmission of LTE's advanced version to meet the increasing requirement, in which differential codebook gains a lot of interest. Previous researches on designing differential codebooks focused on quasi-diagonal unitary matrix which cannot guarantee the equal gain property. The equal gain property is very important to uplink because the performance of uplink is very sensitive to the peak-to-average power ratio (PAPR). In this paper, we derive the analytical expression of average bit error rate and PAPR for differential precoding MIMO system. Using the analytical results, we investigate the performances of several differential precoding schemes considering non-linear amplifier at the transmitter. Some selected simulation results indicate that the conventional differential precoding schemes have good performances without the consideration of non-linear amplifier. While considering non-linear amplifier, the proposed differential codebook outperforms other differential precoding schemes because it maintains the equal gain per transmit antenna.

• Analytical Science and Technology
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• v.15 no.2
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• pp.97-101
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• 2002

Co(II) complexes with tridentate Schiff base-NOIPH and tetradentate Schiff base-$NOTDH_2$ and $TNBPH_4$ were synthesized. The redox process of the complexes in DMF solution containing 0.1M TBAP was investigated at glassy carbon electrode by cyclic voltammetry and differential pulse voltammetry techniques. Reduction step of [Co(II)$(NOIP)_2$] and [Co(II)$(H_2O)_2$] complexes were observed in two step as one electron process of irreversible or quasi-reversible and diffusion-controlled reaction. [$Co(II)_2$(TNBP)] complex was observed in one step as one electron process of quasi-reversible and diffusion-controlled reaction.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.1
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• pp.21-26
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• 2005

In order to simulate the powder compaction process and to assess the effects of packing randomness and particle arrangement 2-dimensional model of rod array compaction using quasi-random multiparticle array is introduced. The elastic modulus of porous ceramics is computed by the homogenization method. With 3 Al₂O₃ and 3 Al particles the compaction processes associated with the porosities are simulated by the explicit finite element method, based on the elastic modulus found by the homogenization method. The simulation results are compared with both previous analytical ones and experimental measurements. Finally, in order to find the relationship between the friction coefficient of powder particles and the relative density, the sensitivity analysis is performed.

• Advances in materials Research
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• v.5 no.4
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• pp.223-244
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• 2016

In this paper, a higher order shear and normal deformation theory is presented for functionally graded material (FGM) plates. By dividing the transverse displacement into bending, shear and thickness stretching parts, the number of unknowns and governing equations for the present theory is reduced, significantly facilitating engineering analysis. Indeed, the number of unknown functions involved in the present theory is only five, as opposed to six or even greater numbers in the case of other shear and normal deformation theories. The present theory accounts for both shear deformation and thickness stretching effects by a hyperbolic variation of ail displacements across the thickness and satisfies the stress-free boundary conditions on the upper and lower surfaces of the plate without requiring any shear correction factor. Equations of motion are derived from Hamilton's principle. Analytical solutions for the bending and free vibration analysis are obtained for simply supported plates. The obtained results are compared with three-dimensional and quasi- three-dimensional solutions and those predicted by other plate theories. It can be concluded that the present theory is not only accurate but also simple in predicting the bending and free vibration responses of functionally graded plates.

• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.6
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• pp.45-52
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• 2010

This paper presents a mathematical-physical model to predict the performance of a gas pusher used as a separation system powered by a gas generator. A quasi-steady model is used in order to aid ballistic analysis for a propellant actuated device(PAD). The empirical coefficients of heat loss and friction were determined from experiments. The analytical approach of combustion, flow and movement of a piston inside the chamber of the PAD, consisted of a gas generator and a gas pusher, was simulated by numerical method based on the grain configuration design of the gas generator. The prediction method developed can be usefully applied to the design of separation mechanism systems.

• Journal of the Earthquake Engineering Society of Korea
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• v.16 no.1
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• pp.13-25
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• 2012

The purpose of this study was to investigate the seismic behavior of hollow circular reinforced concrete bridge columns with confinement steel, and to develop improved seismic design criteria. Three hollow circular columns were tested under a constant axial load and a quasi-static, cyclically reversed horizontal load. The accuracy and objectivity of the assessment process can be enhanced by using a sophisticated nonlinear finite element analysis program. The numerical method used gives a realistic prediction of the seismic performance throughout the loading cycles for the several test specimens investigated. Based on the experimental and analytical results, design recommendations are presented to improve current practice in the design and construction of hollow circular reinforced concrete bridge columns.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.321-327
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• 2010

A simplified analytical modeling for micro-sized single metal particle combustion in air was conducted in the present study. The metal particle combustion consists of two distinct reaction regimes, ignition and quasi-steady burning, and the thermo-fluidic phenomena in each stage are formulated by virtue of the conservation and transport equations. Reliability of the model is shown by rigorous validation of the method with emphasis laid on the characterizing the commanding parameters. Effects of Initial particle size, initial oxide film thickness, convection, ambient pressure and temperature are examined and addressed with validation.

• Smart Structures and Systems
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• v.12 no.5
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• pp.483-499
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• 2013

A new piezoceramic $d_{15}$ shear-induced torsion actuation mechanism representative benchmark is proposed and its experimentations and corresponding 3D finite element (FE) simulations are conducted. For this purpose, a long and thin smart sandwich cantilever beam is dimensioned and built so that it can be used later for either validating analytical Saint Venant-type solutions or for analyzing arm or blade-based smart structures and systems applications. The sandwich beam core is formed by two adjacent rows of 8 oppositely axially polarized d15 shear piezoceramic patches, and its faces are dimensionally identical and made of the same glass fiber reinforced polymer composite material. Quasi-static and static experimentations were made using a point laser sensor and a scanning laser vibrometer, while the 3D FE simulations were conducted using the commercial software $ABAQUS^{(R)}$. The measured transverse deflection by both sensors showed strong nonlinear and hysteretic (static only) variation with the actuation voltage, which cannot be caught by the linear 3D FE simulations.

• International Journal of Advanced Culture Technology
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• v.8 no.2
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• pp.48-57
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• 2020

This study aims to examine the impact of Korean paternalistic leadership under a hierarchical structure on employee voice and also to compare the differences in leaders' behaviors-authoritarian, benevolent, and moral, and the effects on employee voice between governmental organizations and Quasi-government organizations. The sample of governmental organizations includes 195 employees under job control from at least middle-range or higher managers at local governments and local police agencies in Daegu and Busan metropolitan. The other sample also includes 189 employees reporting directly to managers with job control in public enterprises and government-funded Korean institutes in the same cities. This study employs t-test and regression analysis to test presumed hypotheses. As the results of the analysis, there is a significant difference in authoritarian leadership between governmental organizations and Quasi-government organizations, but both benevolent and moral leadership are not. Benevolent and moral leadership are positively related to employee voice, but authoritarian leadership is not. Based on the analytical results, this research suggests the theoretical implications and the limitations on the applicability of paternalistic leadership into the Korean cultural context for an expanded understanding of leadership theory and practical implications for managers in terms of improvement of employee voice.