• Journal of Korea Foresty Energy
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• v.25 no.2
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• pp.1-8
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• 2006

The physical, mechanical and chemical properties of old and new Korean red pine (Pinus densiflora) were analyzed. The old woods were from dismantled timbers of Bonjungsa temple. The crystallized resin in the latewood was observed by microscopic analysis. Also, reduction of specific gravity, occurrence of microscopic cleavage of tracheid was observed in the old wood. The angle of microscopic cleavage of tracheid is estimated with the same angle of micro-fibril angle of 52 layer. The bending, compression and shear strength of old world were decreased about 35-27% than those of new wood. Dynamic modulus of elasticity measured by ultrasonic nondestructive test has the tendency of reducing by the time elapse of the wood usage. Therefore, deterioration of wood could be measured by reduction of specific gravity and dynamic MOE. The static MOE and mechanical properties of old wood could be predictable by measuring dynamic MOE in the longitudinal direction. Extractives of the old wood in 1-% NaOH solution are larger quantity than new wood. Therefore the decay of the wood could be evaluated by analyzing the chemical compound, especially 1-% NaOH solution. The results of this research could be used for understanding and prediction of the changing properties with elapsing time of wood.

• Tunnel and Underground Space
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• v.19 no.5
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• pp.432-439
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• 2009

For more reliable estimation of seismic source, attenuation properties and dynamic ground property, site amplification function should be considered. Among various estimation methods, this study used the Nakamura's method (1989) for estimating site amplification characteristics. This method was originally applied to the surface waves of background noise and therefore there are some limitations in applying to general wave energy. However, recently this method has been extended and applied to the S wave energy successfully. This study applied the method to S wave and Coda wave energy, which is equivalent to the backscattered S wave energy. We used more than 60 observed ground motions from 5 earthquakes which were occurred recently, with magnitude range from 3.6 to 5.1. Each station showed characteristic site amplification property in low-, high- and resonance frequencies. Some of the stations showed as high as 4 times of site amplification in the range of specific frequencies, which may imply abnormal small scale geologic strata below the station or development of various trapped modes in the basin structure. Moreover, removal of site amplification can give us more reliable seismic source and attenuation parameters, addition to the seismic hazard estimation.

• Journal of the Korean earth science society
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• v.36 no.7
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• pp.632-642
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• 2015

Seismograms are composed of 3 characteristics, that is, seismic source, attenuation, and site amplification. Among them, site amplification characteristics should be considered significantly to estimate seismic source and attenuation characteristics with more confidence. This purpose of this study is to estimate the site amplification characteristics at each site using horizontal to vertical (H/V) spectral ratio method. This method, originally proposed by Nakamura (1989), has been applied to study the surface waves in microtremor records. It has been recently extended to the shear wave energy of strong motion and applied to the study of site amplification. This study analyzed the H/V spectral ratio of 6 ground motions respectively using observed data from 4 sites nearby in Yedang Reservoir. And then, site amplification effects at each site, from 3 kinds of seismic energies, that is, S waves, Coda waves energy, and background noise were compared each other. The results suggested that 4 sites showed its own characteristics of site amplification property in specific resonance frequency ranges (YDS: ~11 Hz, YDU: ~4 Hz, YDD: ~7 Hz). Comparison of this study to other studies using different analysis method can give us much more information about dynamic amplification of domestic sites characteristics and site classification.

• Composites Research
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• v.15 no.6
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• pp.16-23
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• 2002

In this work, the effect of anodic oxidation on surface characteristics of high strength PAN-based carbon fibers was investigated in mechanical interfacial properties of composites. The surface properties of the carbon fibers were determined by acid-base values, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and contact angles. And their mechanical interfacial properties of the composites were studied in interlaminar shear strength (ILSS) and critical stress intensity factor ($K_{IC}$). As a result, the acidity or the $O_{ls}/C_{ls}$ ratio of carbon fiber surfaces was increased, due to the development of the oxygen functional groups. Consequently, the anodic oxidation led to an increase in surface free energy of the carbon fibers, mainly due to the increase of its specific (or polar) component. The mechanical interfacial properties of the composites, including ILSS and $K_{IC}$, had been improved in the anodic oxidation on fibers. These results were explained that good wetting played an important role in improving the degree of adhesion at interfaces between fibers and epoxy resin matrix.

• Journal of the Korean GEO-environmental Society
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• v.10 no.1
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• pp.35-41
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• 2009

It is necessary to consider the site amplification for estimating SSI (soil structure interaction) and seismic source with more confidence. The horizontal to vertical (H/V) ratio technique in spectral domain is one of several techniques to estimate empirical site transfer function. The technique, originally proposed by Nakamura (1989), is applied to analyze the surface waves in the microtremor records. However, the application of this technique has been widened to the shear wave energy of strong motions for estimating site amplification. The purpose of this paper is to estimate spectral ratio using observed data at the seismic stations distributed within Southern Korean Peninsula from the Fukuoka earthquake including 11 aftershocks. The results show that each station has the its own characteristics of the specific resonance, high-band, and low-band frequency. The characteristics of the resonance frequency is more important because the quality of the seismic records are dependent on the resonance frequency. The result can be used for the study of site classification and removal of the site amplification effects from observed records can give us more reliable seismic source parameters.

• Steel and Composite Structures
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• v.48 no.1
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• pp.19-25
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• 2023

Due to high application of concrete structures in construction industry, however, the quality improvement is essential. One of the new ways for this purpose is adding the nanoparticles to the concrete. In this work, vibration analysis of concrete beams reinforced by graphene oxide (GO) nanoparticles based on mathematical model has been investigated. For the accuracy of the presented model, the experimental study is done for comparing the compressive strength. Since the nanoparticles can not be solved in water without any specific process, at the first, GO nanoparticles should be dispersed in water by using shaker, magnetic striker, ultrasonic devices and finally mechanical mixer. For modelling of the strucuture, sinusoidal shear deformation beam theory (SSDBT) is utilized. Mori-Tanak model model is utilized for obtaining the effective properties of the beam including agglomeration influences. Utilizing the energy method and Hamilton's principal, the motion equations are calculated. The frequency of the concrete beam is obtanied by analytical method. Three samples with 0.02% GO nanoparticles are built and its compressive strength is compared which shows a good accuracy with maximum 1.29% difference with mathematical model and other papers. The aim of this work from the theoretical study is investigating the effects of nanoparticles volume percentage and agglomeration, length and thickness of the beam on the frequency of the structure. The results show that the with enhancing the GO nanoparticles, the frequency is increased. For example, with enhancing the volume percent of GO nanoparticles from zero to 0.08%, the compressive strength is increased 48.91%. and 46.83%, respectively for two cases of with and without agglomeration.

• The Journal of Engineering Geology
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• v.26 no.3
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• pp.383-392
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• 2016

This study is to evaluate the physical and mechanical properties on the Ipseok-dae columnar joints of Mt. Mudeung National Park. For these purposes, physical and mechanical properties as well as discontinuity property on the Mudeungsan tuff, measurement of vibration and local meteorology around columnar joints, and ground deformation by self-weight of columnar joints were examined. For the physical and mechanical properties, average values were respectively 0.65% for porosity, 2.69 for specific gravity, 2.68 g/cm³ for density, and 2411 m/s for primary velocity, 323 MPa for uniaxial compressive strength, 81 GPa Young's modulus, and 0.25 for Poisson's ratio. For the joint shear test, average values were respectively 3.15 GPa/m for normal stiffness, 0.38 GPa/m for shear stiffness, 0.50 MPa for cohesion, and 35° for internal friction angle. The JRC standard and JRC chart was in the range of 4~6, and 1~1.5, respectively. The rebound value Q of silver schmidt hammer was 57 (≒ 90 MPa). It corresponds 20% of the uniaxial compressive strength of intact rock. The maximum vibration value around the Ipseok=dae columnar joints was in the range of 0.57 PPV (mm/s)~2.35 PPV (mm/s). The local meteorology of surface temperature, air temperature, humidity, and wind on and around columnar joints appeared to have been greatly influenced the weather on the day of measurement. For the numerical analysis of ground deformation due to its self-weight of the Ipseok-dae columnar joints, the maximum displacement of the right ground shows when the ground distance is approximately 2 m, while drastically decreased by 2~4 m, thereafter was insignificant. The maximum displacement of the middle ground shows when the ground distance is approximately 0~2 m, while drastically decreased by 3~10 m, thereafter was insignificant. The maximum displacement of the left ground shows when the ground distance is approximately 5~6 m, while drastically decreased by 6~10 m, thereafter was insignificant.

• Geotechnical Engineering
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• v.11 no.2
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• pp.139-156
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• 1995

A set of field investigations was performed to estimate accurately the predominant periods of seismic 8round motions and the attenuation characteristics of the seismic ground vibration. Predominant periods of ground motions were estimated from the measurement of the continuous microseismic vibratins of certain periods, inherent in the ground and in the buildings, utilizing the high sensitivity digital velocity seismometer consisting of 3-component geophones and a digital seismograph. Estimated predominant periods of microseismic vibraion of the ground(measured on'the ground surface) and the building (measured on the second floor) were in the range of 0.18~0.235 sec. and 0.26~0.31 sec. respectively. The subsurface structure of the site ground was surveyed by the seismic refraction method utilizing the digital seismicwave probing system. The ground structure was found to be a two-layered system : an upper top soil layer of 7m in thickness with the P-wave velocity of 662m1sec and a lower layer of silty-clayey soils with the P -wave velocity of 2210m1 sec. The attenuation characteristics of the seismic ground vibrations were determined by the amplitude decay measurement method us;ng the Seisgun, which produces strong artificial seismic energy. Measured spatial attenuation coefficients of the ground vibration in vertical(Z) longitudinal(X), transverse(Y) direction were 0.1137, 0.0025, and 0.0290 respectively. Estimated Spartial QP's (inverse of the specific dissipation constant w.r.t. shear waved of X, Y, and Z directions were in the range of 5.913~7.575, 32.371~41.452, 2.794~3.579 re spectively. This indicates that aseimic design of the structures on the site should take stronger consideration regarding the earthquake resistance characteristics of the structures against longitudinal ground motion.

• Journal of Animal Science and Technology
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• v.45 no.5
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• pp.679-688
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• 2003

The leptin receptor gene(LEPR) produces a high affinity receptor that mediates the regulation of the leptin gene. Leptin secreted from adipose tissue plays an important role in regulating feed intake and energy balance. In this study, a microsatellite marker within LEPR was selected and genotyped for the F2 population composed of 354 individuals from an intercross between Korean Native boars and Landrace sows. Totally, six alleles (255, 259, 261, 263, 265 and 267bp) and nineteen genotypes were detected in the population, of which the CE (261/265), CC (261/261) and EE (265/265) types were observed by 20.0%, 10.1% and 9.6%, respectively. Relationships between their genotypes and economic traits were analyzed. We found specific genotypes associated with economic traits such as body weight at 12 weeks of age/body fat including abdominal and trimmed fat/shear force (P〈0.001), body weight of 30 weeks of age (P〈0.01) and body weight of 3 weeks of age/back fat thickness (P〈0.05). The DD (263/263) and DF (263/267) types were associated with body weight at 3, 5, 12 and 30 weeks of age. The DF (263/267) type showed a highly significant effect on back fat thickness and body fat including abdominal and trimmed fat. The DF (263/267) type showed positive effect on shear force, whereas the BB (259/259) and DD (263/263) types negatively affected on tenderness.