• The Journal of the Acoustical Society of Korea
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• v.37 no.5
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• pp.338-342
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• 2018

In order to solve the floor impact sound problem in the upper and lower floors, the Ministry of Land, Transport and Maritime Affairs also notifies the physical properties of the resilient material affecting the floor impact sound level. The dynamic modulus of elasticity and the loss factor before and after heating are most related to the floor impact noise, especially for the cushioning material. Therefore, in this study, the rate of change with respect to the dynamic modulus and loss factor with temperature change was examined by increasing $10^{\circ}C$ by $10^{\circ}C$ from the temperature condition of $70^{\circ}C$ specified in the standard. The dynamic modulus of elasticity and the loss modulus were measured by using the pulse excitation method for eight kinds of samples. The calculation method was calculated by the time series analysis method using the damped vibration waveform.

• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.2
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• pp.98-106
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• 2003

Nondestructive test (NDT) provides much information on concrete without damage of structural functions. Of NDT methods, elastic wave propagation methods, such as ultrasonic pulse velocity (UPV) method and impact-echo (IE) method, have been successfully used to estimate the strength, elastic modulus, and Poisson's ratio of concrete as well as to detect the internal microstructural change and defects. In this study, the concretes with water-binder ratio ranging from 0.27 to 0.50 and fly ash content of 20% were made and then their longitudinal wave velocities were measured by UPV and IE method, respectively. Test results showed that the UPV is greater than the longitudinal wave velocity measured by the If method, i.e., rod-wave velocity obtained from the same concrete cylinder. It was found that the difference between the two types of velocities decreased with increasing the ages of concrete and strength level. Moreover, for the empirical formula, the dynamic Poisson's ratio, static and dynamic moduli of elasticity, and velocity-strength relationship were determined. It was observed that the Poisson's ratio and the modulus of elasticity determined by the dynamic method are greater than those determined by the static test. Consequently, for the more accurate estimation of concrete properties using the elastic wave velocities, the characteristics of these velocities should be understood.

• 제어로봇시스템학회:학술대회논문집
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• 1992.10a
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• pp.248-253
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• 1992

In the development of a high speed and light weight manipulator, it is necessary to consider the structural elasticity of a robotic arm. The analysis of the infinite mode dynamic of robotic arm must be performed to obtain the finite mode modelling to achieve the feasible controller design of the robotic arm. The modelling procedure of the robotic arm is also illustrated. The controlled mode of the modelled dynamic can be derived by truncating the higher vibrational mode to result in the low order system for the sampling in the control signal is confined to the higher mode. And it is controlled by the pole assignment which can compensate the unmodelled dynamic effects. The unmodelled dynamic can result in the instability of the controlled system, which is known as spillover. The controller design of the low order system is simulated by the pole assignment and optimal control theory.

• Tribology and Lubricants
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• v.5 no.1
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• pp.64-68
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• 1989

The dynamic characteristics of the annular pressure seal employed in pump have been theoretically deduced with consideration of the effects of elastic deformation due to the centrifugal stress. The deformation of the shaft is governed by the linear theory of elasticity. The results derived herein considering the elastic deformation are compared with the previously published author's results in the stiffness and damping coefficients.

• Environmental and Resource Economics Review
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• v.33 no.2
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• pp.135-157
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• 2024

In this study, we analyzed the changes in copper consumption according to copper price fluctuations and identified the domestic copper price elasticity. A total of 408 time series data from January 1989 to December 2022 were analyzed using the vector autoregressive (VAR) model with net import volume, price, and production index as variables. In addition, to identify changes in the correlation between variables over time, the dynamic relationship between variables was identified using the time-varying vector autoregressive (TV-VAR) model. As a result of the analysis, it was confirmed that the negative price elasticity for copper is -0.1835. In addition, the interquartile range was -0.3130 ~ 0.0886, with no consistent trend over time, but mainly negative elasticity. This study can be used to quantify the expected impact of various policy proposals and changes related to minerals.

• Journal of the Korean Ceramic Society
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• v.45 no.7
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• pp.387-394
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• 2008

The Physical property changes of calcined clay by carburization were investigated studied. The carburization mechanism is the penetration of carbon which occurred during incomplete fuel combustion into crevice of clay structure. The experiments for elasticity and freeze-thaw resistance were conducted, and the results can be summarized as follows: Dynamic modulus of elasticity and also freeze-thaw resistance of calcined clay by carburization treatment increased more than 92% after testing 300 cycle, which was more improved than 88% of calcined clay. Therefore, it can decrease the possibility of winter-sowing, which is one the weakness of calcined clay. It is on the basis of the fact that the porosity of calcined clay by carburization treatment is about 12%, which indicates smaller pore spaces comparing with the 14% of porosity of calcined clay and those values were calculated by apparent porosity show and also supported by SEM images. Infrared emissivity of calcined clay by carburization treatment and calcined clay were respectively 0.92 and 0.9l at $80^{\circ}C$. However, those values were 0.91 and 0.88 at $200^{\circ}C$, which means infrared emissivity of calcined clay by carburization treatment shows 3.6% higher than the calcined clay. Moreover, within the wavelength range from 3 to $7\;{\mu}m$, while the calcined clay had low infrared emissivity, the calcined clay by carburization treatment had increased infrared emissivity. It is inferred that it was affected by carbon element that has high infrared absorptivity within this wavelength range.

• Magazine of the Korean Society of Agricultural Engineers
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• v.38 no.6
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• pp.83-95
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• 1996

The normal cement concrete is widely used material to build the construction recently, but it has a fault to increase the dead load on account of its unit weight is large compared with strength. So, main purpose of this study was to establish the physical and mechanical properties of lightweight concrete using expanded polystyrene bead on fine aggregate and natural gravel, expanded clay and pumice stone on coarse aggregate. The test rusults of this study are summarized as follows; 1. The water-cement ratio of concrete using pumice stone was larger than that of the concrete using natural gravel and expanded clay. 2. The unit weights of concrete using pumice stone and expanded caly were shown less than 1,000g/$m^3$. 3. The compressive strengths of all types were shown less than 60kg/$cm^2$, tensile and bending strengths were shown less than l3kg/$cm^2$ and 3lkg/$cm^2$$^2$, respectively. 4. The pulse velocity of concrete was shown similar with using natural gravel and pumice stone, and shown the lowest using pumice stone. 5. The dynamic modulus of elasticity of concrete was shown considerably smaller, and shown the lowest using pumice stone. 6. The static modulus of elasticity of concrete using expanded clay and pumice stone were shown considerably smaller, and shown 22% ~29% as compared with the dynamic modulus of elasticity. 7. The stress-strain curves of concrete were shown similar, generally. And the curves were repeated at short intervals increase and decreased irregularly.

• Journal of Korea Foresty Energy
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• v.22 no.2
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• pp.60-68
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• 2003

In forest products industry, a variety of nondestructive evaluation techniques are now being used to assess the mechanical properties of structural lumber. Ultrasonic and longitudinal vibration technique are frequently used to assess the modulus of elasticity(MOE) of lumber. The objective of this research was to evaluate the MOE and modulus of rupture(MOR) of small-diameter of Larix log(Larix kaempferi Carr.), using these techniques. In this study, 50 small-diameter logs were nondestructiveively evaluated. The dynamic modulus of elasticity(Eu) of the logs was first evaluated, using an ultrasonic method. After ultrasonic tests, the logs were measured using a longitudinal vibration technique(Ev). Static bending test was then performed on the logs to obtain the static modulus of elasticity(Es) and modulus of rupture of these logs. In general, the dynamic MOE (Ev) of logs was closely co..elated with the stati, MOE for log. Based on the results of these experiments, it can be concluded that small-diameter Larix logs can be successfully evaluated by Ultrasonic and longitudinal vibration technique. The experimental results indicated that the ultrasonic technique is effective to the log, which contains many knots. The longitudinal vibration technique is effective to the log, in which many cracks are included.

• Advances in nano research
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• v.14 no.4
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• pp.375-389
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• 2023

In this study, free vibration analysis of functionally graded (FG) porous truncated conical shell panels reinforced by graphene platelets (GPLs) has been investigated for the first time. Additionally, the effect of three different types of porosity distribution and five different types of GPLs patterns on dynamic response of the shell are also studied. Halpin-Tsai micromechanical model and Voigt's rule are used to determine Young modulus, shear modulus and Poisson's ratio with mass densities of the shell, respectively. The main novelties of present study are: applying 3D elasticity theory and the finite element method in conjunction with Rayleigh-Ritz method to give more accurate results unlike other simplified shell theories, and also presenting a general 3D solution in cylindrical coordinate system that can be used for analyses of different structures such as circular, annular and annular sector plates, cylindrical shells and panels, and conical shells and panels. A convergence study is performed to justify the correctness of the obtained solution and numerical results. The impact of porosity and GPLs patterns, the volume of voids, the weight fraction of graphene nanofillers, semi vertex and span angles of the cone, and various boundary conditions on natural frequencies of the functionally graded panel have been comprehensively studied and discussed. The results show that the most important parameter on dynamic response of FG porous truncated conical panel is the weight fraction of nanofiller and adding 1% weight fraction of nanofiller could increase 57% approximately the amounts of natural frequencies of the shell. Moreover, the porosity distribution has great effect on the value of natural frequency of structure rather than the porosity coefficient.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.5
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• pp.939-951
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• 2002

We propose a new multiscale Galerkin method based on interpolation wavelets for two-dimensional Poisson's and plane elasticity problems. The major contributions of the present work are: 1) full multiresolution numerical analysis is carried out, 2) general boundaries are handled by a fictitious domain method without using a penalty term or the Lagrange multiplier, 3) no special integration rule is necessary unlike in the (bi-)orthogonal wavelet-based methods, and 4) an efficient adaptive scheme is easy to incorporate. Several benchmark-type problems are considered to show the effectiveness and the potentials of the present approach. is 1-2m/s and impact deformation of the electrode depends on the strain rate at that velocity, the dynamic behavior of the sinter-forged Cu-Cr is a key to investigate the impact characteristics of the electrodes. The dynamic response of the material at the high strain rate is obtained from the split Hopkinson pressure bar test using disc-type specimens. Experimental results from both quasi-static and dynamic compressive tests are Interpolated to construct the Johnson-Cook model as the constitutive relation that should be applied to simulation of the dynamic behavior of the electrodes. The impact characteristics of a vacuum interrupter are investigated with computer simulations by changing the value of five parameters such as the initial velocity of a movable electrode, the added mass of a movable electrode, the wipe spring constant, initial offset of a wipe spring and the virtual fixed spring constant.