• Geomechanics and Engineering
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• v.22 no.2
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• pp.119-132
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• 2020

In this study a new innovative three unknowns trigonometric shear deformation theory is proposed for the buckling and vibration responses of exponentially graded sandwich plates resting on elastic mediums under various boundary conditions. The key feature of this theoretical formulation is that, in addition to considering shear deformation effect, it has only three unknowns in the displacement field as in the case of the classical plate theory (CPT), contrary to five as in the first shear deformation theory (FSDT) and higher-order shear deformation theory (HSDT). Material characteristics of the sandwich plate faces are considered to vary within the thickness direction via an exponential law distribution as a function of the volume fractions of the constituents. Equations of motion are obtained by employing Hamilton's principle. Numerical results for buckling and free vibration analysis of exponentially graded sandwich plates under various boundary conditions are obtained and discussed. Verification studies confirmed that the present three -unknown shear deformation theory is comparable with higher-order shear deformation theories which contain a greater number of unknowns.

• Smart Structures and Systems
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• v.20 no.3
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• pp.369-383
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• 2017

In this work, the effects of moisture and temperature on free vibration characteristics of functionally graded (FG) nanobeams resting on elastic foundation is studied by proposing a novel simple trigonometric shear deformation theory. The main advantage of this theory is that, in addition to including the shear deformation influence, the displacement field is modeled with only 2 unknowns as the case of the classical beam theory (CBT) and which is even less than the Timoshenko beam theory (TBT). Three types of environmental condition namely uniform, linear, and sinusoidal hygrothermal loading are studied. Material properties of FG beams are assumed to vary according to a power law distribution of the volume fraction of the constituents. Equations of motion are derived from Hamilton's principle. Numerical examples are presented to show the validity and accuracy of present shear deformation theories. The effects of hygro-thermal environments, power law index, nonlocality and elastic foundation on the free vibration responses of FG beams under hygro-thermal effect are investigated.

• Journal of Korean Society for Geospatial Information Science
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• v.18 no.3
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• pp.49-56
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• 2010

The Genetic Algorithm is one of the population surface modelling tool in the field of urban and environmental research based on the gridded population data. Taking the East-Hwasung area as the case, this study first builds a gridded population data based on the GIS databases as well as municipal population survey data. The study then constructs the attribute values of the explanatory variables by way of GIS tools. The regression model constructed with the same variables is also run as a comparative purpose at the same time. It is shown that the GenAlg output predicted as much consistent and meaningful coefficient estimates for the explanatory variables as the regression model, indicating that it is a very useful interdisciplinary research tool to find optimal solutions in urban problems.

• Atmosphere
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• v.29 no.4
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• pp.429-438
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• 2019

Organic carbon (OC) and elemental carbon (EC) in PM_2.5 were measured with Sunset Laboratory Model-5 Semi-Continuous OC/EC Field Analyzer by NIOSH/TOT method at Anmyeondo Global Atmosphere Watch (GAW) Regional Station (37°32'N, 127°19'E) in July and August, 2017. The mean values of OC and EC were 3.7 ㎍ m^-3 and 0.7 ㎍ m^-3, respectively. During the study period, the concentrations of reactive gases and aerosol compositions were evidently lower than those of other seasons. It is mostly due to meteorological setting of the northeast Asia, where the influence of continental outflow is at its minimum during this season under southwesterly wind. While the diurnal variation of OC and EC were not clear, the concentrations of O₃, CO, NOx, EC, and OC were evidently enhanced under easterly wind at night from 20:00 to 8:00. However, the high concentration of EC was observed concurrently with CO and NOx under northerly wind during 20:00~24:00. It indicates the influence of thermal power plant and industrial facilities, which was recognized as a major emission source during KORUS-AQ campaign. The diurnal variations of pollutants clearly showed the influence of land-sea breeze, in which OC showed good correlation between EC and O₃ in seabreeze. It is estimated to be the recirculation of pollutants in land-sea breeze cycle. This study suggests that in general, Anmyeondo station serves well as a background monitoring station. However, the variation in meteorological condition is so dynamic that it is primary factor to determine the concentrations of secondary species as well as primary pollutants at Anmyeondo station.

• Journal of Korean Society for Atmospheric Environment
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• v.14 no.5
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• pp.479-490
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• 1998

The concentrations of ten inorganic (sodium, chloride, sulfate, ammonia, etc.) and three organic (acetate, formate, and MSA) ions associated with airborne particulate matter were measured from Cheju Island, Korea during the three field intensive campaigns conducted in (1) Sept./oct. 1997 (fall), (2) Dec. 1997 (winter), and (3) April 1998 (spring). The results of our measurements indicated that the concentration levels of most ionic species were decreasing significantly across the three experimental periods. The patterns of concentration reduction were clear as the sum of all cation and anion species changed dramatically across those periods such as 294> 144 > 65 and 193 >96>74 nequiv/m3, respectively. The changes were best explained in terms of the wind rose patterns of the study site. Since our sampling spot is located on the western-end point of Cheju Island, it is likely to reflect the effects of diverse sources such as natural, marine processes during NW and local non-maritime ones during SE winds. .Hence, the periodical changes in ionic concentrations may be accounted for by the comparable changes in wind direction. To further investigate environmental characteristics of these ionic components, correlation analysis was conducted not only between meteorological and ion data but between different ion-pairs. The results of these analyses confirm that the concentration levels of ionic species are strongly affected by wind speed and temperature and that there are certain patterns between ion species to which such effects apply. In light of the significance of the wind rose patterns in the area, we further extended these analyses into four data groups that were divided on the basis of wind direction. The results of these analyses showed that the strength of correlations between important pairs (e.g.:. between windspeed and most of major inorganic species including sodium and chloride) can be ranked on the distribution of major ions are very diverse, depending on data grouping scheme for such analysis. The results of this study thus suggest that environmental behavior of chemical components be analyzed in various respects, rather than simple standard, especially if measurements are made in complex environmental condition under which both natural and anthropogenic effects are competing each other.

• The Korean Journal of Ecology
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• v.18 no.3
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• pp.307-321
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• 1995

Division of ecoregions having respective functions was attempted through quantitative and qualitative analysis on vegetation diversity, and heterogeneity and on soil environment of the study sites. Field research was carried out in a square of 81 ㎢ around Andongpo (126°38'E, 37°30'N), Kimpo-gun, Kyonggi provice. Conventional methods applied are as follows: classical syntaxonomy by the Zurich-Montpellier School, interpolation method to determine the degree of diversity, heterogeneity and distribution pattern of vegetation, and correlation analysis between soil properties and plant communities. 41 plant communities were identified and composed of 6 forests, 4 mantle and 31 herb communities including 6 saltmarsh plant communities. In a mesh, number of plant communities was highly correlated to the number of species. The highest number of plant community and species was 25 communities·km-2·mesh-1 and 381 species· km-2·mesh-1 ,and the highest value of vegetation heterogeneity was 28.1 species· community-1·mesh-1. Their lowest numbers were 4 communities·km-2·mesh-1. and 28 species·km-2·mesh-1. and 7 species·community-1·mesh-1, respectively. Contour map on vegetation diversity and heterogeneity enabled us to establish two regions; coastal and inland vegetation. Isoline 〔150〕,〔10〕and〔10〕and〔15〕on the species diversity, the community diversity and the vegetation heterogeneity, respectively, were regarded as ecolines in the study area. Cl- content was recognized as the most important factor from correlation analysis between soil properties. Ordination of sites indicated that the study area be divided into two edaphic types: inland and coastal habitats. It was considered that the extent of desalinization in soil played a major role in determining the species composition in the reclamed area. By matching edaphic division of habitats with division of vegetation structures, designation of ecoregion was endorsed. The approach of current study was suggested as an effective tool to implement an assessment of the vegetation dynamics by the disparity of natural environment and anthropogenic interferences.

• Communications of Mathematical Education
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• v.32 no.3
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• pp.435-453
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• 2018

The results analysis of National Assessment of Educational Achievement(NAEA) can provide various implications for teaching and learning in the school field. In this study we analyzed the deviation of NAEA achievement level-based correct-answer rate and the distribution of the responses percentages for three years from 2015 to 2017 focused on multiple-choice items. First we calculated the deviation of correct-answer rate between advanced level and proficient level and between proficient level and basic level, and then we selected the items whose deviation of correct-answer rate is more than the third quartile. We explored what the content areas, behavior areas and achievement standards of each item are and what the achievement standards and characteristics of these questions are. Based on the results of the analysis, we intended to derive implications for appropriate teaching-learning methods at each achievement-level.

• Geomechanics and Engineering
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• v.19 no.5
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• pp.393-405
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• 2019

This paper evaluates the geotechnical and geo-engineering properties of the South Pars Zone (SPZ) marls in Assalouyeh, Iran. These marly beds mostly belong to the Aghajari and Mishan formations which entail the gray, cream, black, green, dark red and pink types. Marls can be observed as rock (soft rock) or soil. Marlstone outcrops show a relatively rapid change to soils in the presence of weathering. To geotechnically characterise the marls, field and laboratory experiments such as particle-size distribution, hydrometer, Atterberg limits, uniaxial compression, laboratory direct-shear, durability and carbonate content tests have been performed on soil and rock samples to investigate the physico-mechanical properties and behaviour of the SPZ marls in order to establish empirical relations between the geo-engineering features of the marls. Based on the experiments conducted on marly soils, the USCS classes of the marls is CL to CH which has a LL ranging from 32 to 57% and PL ranging from 18 to 27%. Mineralogical analyses of the samples revealed that the major clay minerals of the marls belong to the smectite or illite groups with low to moderate swelling activities. The geomechanical investigations revealed that the SPZ marls are classified as argillaceous lime, calcareous marl and marlstone (based on the carbonate content) which show variations in the geomechanical properties (i.e., with a cohesion ranging from 97 to 320 kPa and a friction angle ranging from 16 to 35 degrees). The results of the durability tests revealed that the degradation potential showed a wide variation from none to fully disintegrated. According to the results of the experiments, the studied marls have been classified as calcareous marl, marlstone and argillaceous lime due to the variations in the carbonate and clay contents. The results have shown that an increase in the carbonate content leads to a decrease in the degradation potential and an increase in the density and strength parameters such as durability and compressive strength. A comparison of the empirical relationships obtained from the regression analyses with similar studies revealed that the results obtained herein are reasonably reliable.

• Economic and Environmental Geology
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• v.16 no.1
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• pp.11-18
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• 1983

Gyeongsang Basin in the southeastern part of the Korean peninsular is characterized by many fault systems. To decipher the geotectonical evolution of the Korean peninsular and marginal basins in her adjacent areas it is prerequisite to understand the spatial distribution pattern and mutual relationships of these fault systems. Because of difficulties in finding any criterion to recognize the faults in field, their extension and mutual relationships in ages are not very clear yet. As an attempt to find geophysical criteria to recognize the fault, geoelectrical resistivity survey was carried out in this study. With the Wenner configuration four resistivity soundings and twenty seven resistivity profilings were done. The electrode distance used was up to 50m. From the results of the resistivity soundings and boring data of earlier groundwater investigations the depth of alluvial and weathered zone was established to be at most 20m in the study area. In the resistivity profiling low resistivity anomaly zones are detected on every traverse, which are interpreted as caused by fractures, fault clays and mylonites in the fault zone. The width of the fault zone amounts to 0.3-1km. By correlating and connecting the negative anomaly zones from traverse to traverse one can determine the trend of th of the faultzone and therefore that of fault itself. The recognized fault trend in this way was $N15^{\circ}-20^{\circ}E$ and this coincides with the direction of the inferred fault line from earlier geological surface mapping. With the help of this characteristical negative anomaly the existance of another $N80^{\circ}W$ trending fault was estabished. This study has shown that geoelectrical resistivity survey can be applied successfully to the problem of tracing fault line insofar as a fault zone has been developed along fault line.

• Progress in Superconductivity
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• v.7 no.1
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• pp.41-45
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• 2005

The diagnostic management of patients with chest pain remains a clinical challenge. Magnetocardiography (MCG) has been proposed as a new non-invasive method for detection of myocardial ischemia. To date, however, MCG technique is not intensively introduced for clinical use. One of the main reasons might be the absence of statistically valid and diagnostically clean criteria, which can determine the presence of certain heart disease. In this work, we suggested a new method to classify the diagnostic value of MCG for the detection of coronary artery disease (CAD) in patients with chest pain. MCG was recorded for three groups (healthy subjects and patients without and with CAD) by means of the 64 channel SQUID gradiometer system installed at a hospital. Using four parameters, which were found to be significantly different between groups, we evaluated a probability, in which parameters can be classified into each group based on the distribution function of the parameter in each group. For all parameters, sum of probabilities was compared between groups to determine the presence of CAD. Our classification method shows that the MCG can be a useful tool to predict the presence of CAD with sensitivity and specificity of higher than $80\%$ each.