• Journal of the Korean Society for Precision Engineering
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• v.17 no.11
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• pp.69-74
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• 2000

Roughness of curved surfaces finished with flexible tools depends on the tool/work contact pressure and area. In this study, non-Hertzian closely conforming elastic contact theory is employed to analyze the tool/work contact and to generate a tool path producing a constant pressure at initial contact points. Finishing experiments on curved surfaced are conducted using the tool path. For comparison, curved surface finishing is also performed along the tool path producing a constant tool/work interference depth. It is demonstrated that the tool path of constant contact pressure improves the finished surface roughness.

• Steel and Composite Structures
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• v.41 no.6
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• pp.821-829
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• 2021

Nonlinear dynamic response of a sandwich beam considering porous core and nano-composite face sheet on nonlinear viscoelastic foundation with temperature-variable material properties is investigated in this research. The Hamilton's principle and beam theory are used to drive the equations of motion. The nonlinear differential equations of sandwich beam respect to time are obtained to solve nonlinear differential equations by Homotopy perturbation method (HPM). The effects of various parameters such as linear and nonlinear damping coefficient, linear and nonlinear spring constant, shear constant of Pasternak type for elastic foundation, temperature variation, volume fraction of carbon nanotube, porosity distribution and porosity coefficient on nonlinear dynamic response of sandwich beam are presented. The results of this paper could be used to analysis of dynamic modeling for a flexible structure in many industries such as automobiles, Shipbuilding, aircrafts and spacecraft with solar easured at current time step and the velocity and displacement were estimated through linear integration.

• Advances in nano research
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• v.16 no.6
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• pp.549-564
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• 2024

This paper aims to analyze the dynamic response of thermoelectric carbon nanotube-reinforced composite (CNTRC) beams under moving harmonic load resting on Pasternak elastic foundation. The governing equations of thermoelectric CNTRC beam are obtained based on the Karama shear deformation beam theory. The beams are resting on the Pasternak foundation. Previous articles have not performed the moving load mode with the analytical method. The exact solution for the transverse and axial dynamic response is presented using the Laplace transform. A comparison of previous studies has been published, where a good agreement is observed. Finally, some examples were used to analyze, such as excitation frequency, voltage, temperature, spring constant factors, the volume fraction of Carbon nanotubes (CNTs), the velocity of a moving harmonic load, and their influence on axial and transverse dynamic and maximum deflections. The advantages of the proposed method compared to other numerical methods are zero reduction of the error percentage that exists in numerical methods.

• Journal of the Korean Magnetics Society
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• v.15 no.5
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• pp.261-264
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• 2005

The elastic constants, C', of $Th_{3}P_4$-type structure compounds, $La_{3}S_4\;and\;Ce_{3}S_4$, have been analyzed on the basis of band Jahn-Teller mechanism. The distinct difference between two compounds lies in the fact that $Ce^{3+}$ ion has a f electron which produces magnetism. It is shown that the band Jahn-Teller effect is sensitively influenced by the energy splitting of f electronic bands by a cubic crystal field in $Ce_{3}S_4$, and f electrons suppress the elastic softening effect. The energy splitting value obtained from the calculation of elastic constants is found to agree well with the experimental value obtained from the magnetic susceptibility measurement.

• Structural Engineering and Mechanics
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• v.65 no.3
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• pp.303-314
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• 2018

Shear walls are a typical member under a complex stress state and have complicated mechanical properties and failure modes. The separated-elements model Genetic Evolutionary Structural Optimization (GESO), which is a combination of an elastic-plastic stress method and an optimization method, has been introduced in the literature for designing such members. Although the separated-elements model GESO method is well recognized due to its stability, feasibility, and economy, its adequacy has not been experimentally verified. This paper seeks to validate the adequacy of the separated-elements model GESO method against experimental data and demonstrate its feasibility and advantages over the traditional elastic stress method. Two types of reinforced concrete shear wall specimens, which had the location of an opening in the middle bottom and the center region, respectively, were utilized for this study. For each type, two specimens were designed using the separated-elements model GESO method and elastic stress method, respectively. All specimens were subjected to a constant vertical load and an incremental lateral load until failure. Test results indicated that the ultimate bearing capacity, failure modes, and main crack types of the shear walls designed using the two methods were similar, but the ductility indexes including the stiffness degradation, deformability, reinforcement yielding, and crack development of the specimens designed using the separated-elements model GESO method were superior to those using the elastic stress method. Additionally, the shear walls designed using the separated-elements model GESO method, had a reinforcement layout which could closely resist the actual critical stress, and thus a reduced amount of steel bars were required for such shear walls.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.5
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• pp.232-236
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• 2010

Silicon carbide (SiC) ceramics are widely used in the application of high-temperature structural devices due to their light weight as well as superior hardness, fracture toughness, and temperature stability. In this paper, we employed classical molecular dynamics simulations using Tersoff's potential to investigate the elastic constants of the SiC crystal at high temperature. The stress-strain characteristics of the SiC crystal were calculated with the LAMMPS software and the elastic constants of the SiC crystal were analyzed. Based on the stress-strain analysis, the SiC crystal has shown the elastic deformation characteristics at the low temperature region. But the slight plastic deformation behavior was shown as applied the high strain over $1,000^{\circ}C$. Also the elastic constants of the SiC crystal were changed from about 475 GPa to 425 GPa as increased the temperature to $1,250^{\circ}C$.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.843-846
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• 2004

For the fast growing Liquid Crystal Display (LCD) TV market, it is essential to make the LCD panels to show moving images without any visual difficulties such as blurring or tailing. Owing to reduction of the cell gap and the improved Liquid Crystal (LC) mixtures with low viscosity, it is possible that our S-IPS TFT-LCDs feature a response time (R/T) as fast as 1-frame time (16ms) for a white-black operation and less than a 16rns in all gray levels without Over Driving Circuit (ODC) technology. Currently, mass production of the large size IPS panels with high speed has been successfully achieved. In order to achieve faster response time, new LC mixtures have been developed, optimizing the physical properties of rotational viscosity (${\gamma}$1) and elastic constants (Kii). Also, the LC mixtures with high elastic constant allow us to increase the cell gap. In this paper, realization of fast switching time in IPS mode with optimized '${\gamma}$1/Kii' parameter in the LC mixtures forms the core of this paper.

• The Journal of Engineering Geology
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• v.13 no.2
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• pp.227-238
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• 2003

Understanding of a creep behavior in rocks under a constant load, due to visco-elastic properties of rock, is an essential element to predict a long term ground deformation. In order to clarify the creep characteristics of the mudstone in Duho formation at Pohang basin, deposited during Tertiary, a series of laboratory tests including physical properties, unconfined compressive strength and uniaxial creep tests, was performed. The mudstone showed a higher creep potential due to 26% of clay minerals such as illite and chlorite. The unconfined compressive strength of the rock was $462{\;}kg/\textrm{cm}^2$ in average, and four creep tests were performed under constant stress of 40 to 70 % of the strength. The creep constants in the empirical and theoretical equations were deduced from the time-strain curves obtained from the tests. Among the several equations, the empirical equation proposed by Griggs and theoretical equation of Burger’s model are appreciated as the best one to express the creep behavior of the mudstone. Instantaneous elastic strain was linearly increased with stress level but strain velocity during the first creep is decreased with a similar pattern by time lapse regardless the stress level.

• Journal of the Mineralogical Society of Korea
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• v.17 no.3
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• pp.201-208
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• 2004

$CaSiO_3$-garnet phase was observed in the phase transformation sequences on a natural hedenbergite, (Ca, Fe)$ SiO_3$ between 14 and 24 GPa when quenched from $～1200^{\circ}C$. Bulk modulus K = 155 GPa, $V_{\Phi}$ = 6.58 km/sec and other elastic properties of the $CaSiO_3$-garnet were obtaiend on the basis of the systematics of structural analogs in varius garnet phases and relationship of $KV_{m}$ = constant and $V_{\Phi}$$M^{$\frac{1}{2}$}$ = constant. The quenchable garnet phase apears to be stabilized by the considerable amount of Mn and other cations, and shows a wide stability range. As one of the host minerals of Ca composition, $CaSiO_3$-garnet would be one of the important mineral phases in the mantle transition region.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.11
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• pp.1595-1602
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• 2010

A disposable drug infuser is used to provide drugs to patients who are not hospitalized; in this infuser, an elastic recovery force is exerted by a diaphragm made of a rubber-like materialsuch that a constant amount of drugs is provided to a patient. The drug infuser has to control the speed and amount of drugs to be released, as well as the overall duration for which they are to be administered. However, in a drug infuser with an elastic diaphragm, the infusion pressure depends on the amount of drug remaining within the infuser, and the amount of drug infused gradually decreases as the amount remaining in the infuser decreases. In this study, a finite element procedure involving the application of the fluid-structure interaction technique was developed and the performance of the elastic type disposable drug infuser was analyzed. The optimum design for ensuring that the infusion pressure remains constant throughout the duration of usage, including during infusion and discharge, was determined by this procedure.