• Journal of the Earthquake Engineering Society of Korea
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• v.26 no.3
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• pp.117-125
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• 2022

In this study, centrifuge model tests were performed to evaluate the seismic response of multi-DOF structures with shallow foundations. Also, elastic time history analysis on the fixed-base model was performed and compared with the experimental results. As a result of the centrifuge model test, earthquake amplification at the fundamental vibration frequency of the soil (= 2.44 Hz) affected the third vibration mode frequency (= 2.50 Hz) of the long-period structure and the first vibration mode (= 2.27 Hz) of the short-period structure. The shallow foundation lengthened the periods of the structures by 14-20% compared to the fixed base condition. The response spectrum of acceleration measured at the shallow foundation was smaller than that of free-field motion due to the foundation damping effect. The ultimate moment capacity of the soil-foundation system limited the dynamic responses of the multi-DOF structures. Therefore, the considerations on period lengthening, foundation damping, and ultimate moment capacity of the soil-foundation system might improve the seismic design of the multi-DOF building structures.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.11a
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• pp.227-228
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• 2023

A floating floor generally consists of mortar bed separated from the structural RC slab by a continuous resilient layer. It is known that the floating floors are a type of vibration-isolation system to improve the impact sound insulation performance. However, some researchers have demonstrated that the amplification of vibration response at a specific range of frequencies results in an increase in the impact sound level. This study carried out the forced vibration tests to obtain the frequency response function (FRF) of a floating floor compared with a bare RC slab. Test results shows that the additional peak occur in vibrational spectrum of the floating floor except natural vibration modes of the bare RC slab. This is because the relatively flexible resilient material and mass of the mortar bed offer an additional degree of freedom in the structural system. Therefore, it could be efficient for reduction of floor impact vibration and noise to control the additional mode frequency and response of floating floors.

• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.6
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• pp.11-25
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• 2009

A method of instrumentally estimating the seismic intensity (MMI) based on Fourier Acceleration Spectrum, which is the so-called 'FAS MMI method' of Sokolov and Wald (2002), was considered for its applicability to Korea. In order to implement the FAS MMI method, the empirical models of mean (m) and standard deviation (${\sigma}$) for Korea were derived for MMI ${\leq}$ IV according to individual seismic intensity by using the site-consistent horizontal FAS of 580 records from 65 isoseismal maps prepared based on the reported MMI of Korea Meteorological Administration. The site-consistent FAS at a site were obtained by correcting the observed FAS for the difference of the site amplification function relative to that of the target site of Class D station (Yun and Suh, 2007) which was evaluated to be a representative site for the generic soil profile of Korea. The FAS m model for MMI ${\leq}$ IV follows the overall linear relation in log space according to seismic intensities, featuring the FAS mean model for MMI = IV similar to that of the global model of Sokolov and Wald (2002). The ${\sigma}$-values of the FAS model are found to be greater than those of the global model for MMI ${\geq}$ V, while significantly lower than those of the global model for MMI = IV.

• Korean Journal of Clinical Laboratory Science
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• v.48 no.3
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• pp.210-216
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• 2016

Recently, there has been a considerable increase in the prevalence of CTX-M type extended-spectrum ${\beta}$-lactamase (ESBL)-producing E. coli isolates worldwide, including Korea. To investigate the ESBL genes in the E. coli strains isolated from a university hospital in the Chungcheong area, a study was conducted using PCR amplification and nucleotide sequence analysis of the amplified products to detect the plasmid mediated quinolone resistance (PMQR) genes in ESBL producing E. coli isolates. The number of CTX-M-14 producing isolates was 25 (16.0%) isolates, and of them, 9 (5.8%) isolates also produced CTX-M-15. All CTX-M type ESBL producing E. coli isolates showed resistance to cefotaxime. Twelve (48%) CTX-M type ESBL producing E. coli isolates contained the PMQR genes, 8 contained qnrS1, and 8 contained aac(6')-Ib-cr. Four isolates harbored both qnrS1 and aac(6')-Ib-cr genes. In our study, we confirmed that the plasmid mediated antimicrobial resistant determinants-the ESBL and PMQR genes-were distributed in the E. coli isolates. To prevent further spreading of the resistant genes among the E. coli isolates, consistent effort is required to investigate and monitor the resistant genes.

• Molecules and Cells
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• v.19 no.1
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• pp.114-123
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• 2005

Nitropyrene, the predominant nitropolycyclic hydrocarbon found in diesel exhaust, is a mutagenic and tumorigenic environmental pollutant that requires metabolic activation via nitroreduction and ring oxidation. In order to determine the role of ring oxidation in the mutagenicity of 1-nitropyrene, its oxidative metabolites, 1-nitropyrene 4,5-oxide and 1-nitropyrene 9,10-oxide, were synthesized and their mutation spectra were determined in the coding region of hprt gene of CHO cells by a PCR amplification of reverse-transcribed hprt mRNA, followed by a DNA sequence analysis. A comparison of the two metabolites for mutation frequencies showed that 1-nitropyrene 9,10-oxide was 2-times higher than 1-nitropyrene 4,5-oxide. The mutation spectrum for 1-nitropyrene 4,5-oxide was base substitutions (33/49), one base deletions (11/49) and exon deletions (5/49). In the case of 1-nitropyrene 9,10-oxide, base substitutions (27/50), one base deletions (15/50), and exon deletions (8/50) were observed. Base substitutions were distributed randomly throughout the hprt gene. The majority of the base substitutions in mutant from 1-nitropyrene 4,5-oxide treated cells were $A{\rightarrow}G$ transition (15/33) and $G{\rightarrow}A$ transition (8/33). The predominant base substitution, $A{\rightarrow}G$ transition (11/27) and $G{\rightarrow}A$ transition (8/27), were also observed in mutant from 1-nitropyrene 9,10-oxide treated cells. The mutation at the site of adenine and guanine was consistent with the previous results, where the sites of DNA adduct formed by these compounds were predominant at the sites of purines. A comparison of the mutational patterns between 1-nitropyrene 4,5-oxide and 1-nitropyrene 9,10-oxide showed that there were no significant differences in the overall mutational spectrum. These results indicate that each oxidative metabolite exhibits an equal contribution to the mutagenicity of 1-nitropyrene, and ring oxidation of 1-nitropyrene is an important metabolic pathway to the formation of significant lethal DNA lesions.

• Journal of the Korean GEO-environmental Society
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• v.11 no.6
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• pp.5-20
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• 2010

One-dimensional equivalent linear site response analysis is widely used in practice due to its simplicity, requiring only few input parameters, and low computational cost. The main limitation of the procedure is that it is essentially a linear method, in which the time dependent change in the soil properties cannot be modeled and constant values of shear modulus and damping is used throughout the duration of the analysis. Various forms of modified equivalent linear analyses have been developed to enhance the accuracy of the equivalent linear method by incorporating the dependence of the shear strain with the loading frequency. The methods are identical in that it uses the shear strain Fourier spectrum as the backbone of the analysis, but differ in the method in which the strain Fourier spectrum is smoothed. This study used two domestically measured soil profiles to perform a series of nonlinear, equivalent linear, and modified equivalent linear site response analyses to verify the accuracy of two modified procedures. The results of the analyses indicate that the modified equivalent linear analysis can highly overestimate the amplification of the high frequency components of the ground motion. The degree of overestimation is dependent on the characteristics of the input ground motion. Use of a motion rich in high frequency contents can result in unrealistic response.

• Journal of the Korean Geotechnical Society
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• v.25 no.10
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• pp.87-97
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• 2009

The seismic site coefficients are often used with the seismic hazard maps to develop the design response spectrum at the surface. The site coefficients are most commonly developed deterministically, while the seismic hazarde maps are derived probabilistically. There is, hence, an inherent incompatibility between the two approaches. However, they are used together in the seismic design codes without a clear rational basis. To resolve the fundamental imcompatibility between the site coefficients and hazard maps, this study uses a novel probabilistic seismic hazard analysis (PSHA) technique that simulates the results of a standard PSHA at a rock outcrop, but integrates the site response analysis function to capture the site amplification effects within the PSHA platform. Another important advantage of the method is its ability to model the uncertainty, variability, and randomness of the soil properties. The new PSHA was used to develop fully probabilistic site coefficients for site classes of the seismic design code and another sets of site classes proposed in Korea. Comparisons highlight the pronounced discrepancy between the site coefficients of the seismic design code and the proposed coefficients, while another set of site coefficients show differences only at selected site classes.

• Journal of the Korean earth science society
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• v.31 no.6
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• pp.541-554
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• 2010

Fifteen min-microtremor data sets were collected at 136 sites from a coastal area of Kunsan and 117 sites from an inland area of Jeonju located in SW Korea, and were analyzed for the HVSR (Horizontal to Vertical Spectral Ratio) of the sites. The microtremor spectra of the coastal area have stronger energy in the lower frequency range from 1-6 Hz than those of the coastal area. This result can be attributed to the effect of the waves and tides in the Keum river and the Yellow sea. Twenty four hours of measurement of the microtremor indicated that the microtremor spectrum correlates with the human activities, but the microtremor HVSR peak was observed consistently at the characteristic frequency for the site. The HVSR peaks were grouped into 4 types -"single peak", "double peak", "broad peak" or "no peak"- based on their shapes. More than 90% of the data sets exhibit peak frequencies ($F_0$) which can be easily identified. The distribution of $F_0$ reveals a close relationship with the topography and local geology of the areas, exhibiting high F0s in the hillside areas and low $F_0s$ in the reclaimed land area. While the amplitudes of microtremor HVSR peak frequencies are less than 4 in the downstream of the inland area, those of the recently reclaimed land in the coastal area are extremely high (more than 10). The results of this study indicate that detailed HVSR studies are essential for the earthquake hazard reduction of reclaimed lands.

• Parasites, Hosts and Diseases
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• v.53 no.6
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• pp.737-743
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• 2015

In order to examine the prevalence of Cryptosporidium infection in wild rodents and insectivores of South Korea and to assess their potential role as a source of human cryptosporidiosis, a total of 199 wild rodents and insectivore specimens were collected from 10 regions of South Korea and screened for Cryptosporidium infection over a period of 2 years (2012-2013). A nested-PCR amplification of Cryptosporidium oocyst wall protein (COWP) gene fragment revealed an overall prevalence of 34.2% (68/199). The sequence analysis of 18S rRNA gene locus of Cryptosporidium was performed from the fecal and cecum samples that tested positive by COWP amplification PCR. As a result, we identified 4 species/genotypes; chipmunk genotype I, cervine genotype I, C. muris, and a new genotype which is closely related to the bear genotype. The new genotype isolated from 12 Apodemus agrarius and 2 Apodemus chejuensis was not previously identified as known species or genotype, and therefore, it is supposed to be a novel genotype. In addition, the host spectrum of Cryptosporidium was extended to A. agrarius and Crosidura lasiura, which had not been reported before. In this study, we found that the Korean wild rodents and insectivores were infected with various Cryptosporidium spp. with large intra-genotypic variationa, indicating that they may function as potential reservoirs transmitting zoonotic Cryptosporidium to livestock and humans.

• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.6
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• pp.27-37
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• 2009

A method of instrumentally estimating seismic intensity (MMI) based on the Fourier Acceleration Spectrum of earthquake ground-motion, the so-called 'FAS MMI method' of Sokolov and Wald (2002), was evaluated for its applicability to Korea based on the empirical models of mean (m) and standard deviation (${\sigma}$) for Korea according to individual seismic intensity for MMI ${\leq}$ IV (Yun et al., 2009). This evaluation showed that the error in estimating the seismic intensity using the FAS MMI method is ${\sigma}$ = 0.74 MMI, and was further reduced to ${\sigma}$ = 0.61 MMI if the dependency of the error on earthquake magnitude and distance is additionally corrected. It is also shown that FAS MMI based on the FAS semi-empirically evaluated from small earthquakes for damaging earthquakes in Korea with maximum MMI ${\geq}$ VI could predict the observed MMI with the maximum error of 0.63 by using the combined FAS m-${\sigma}$ models of Korea for MMI ${\leq}$ IV and global region for MMI ${\geq}$ V.