• Journal of the Korean Geotechnical Society
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• v.39 no.2
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• pp.19-30
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• 2023

Underground structures, such as compacted sand piles applied as soft ground countermeasures, are analyzed for settlement and stability by the composite ground design method. The basic principle of the composite ground design method is the arching effect. The reinforcing effect of the pile is evaluated as the stress-distribution ratio. When applying grouting piles with elastic properties using the ground reinforcement method, the existing stress-distribution ratio was only considered when the pile was installed. This study shows that the method of applying the stress-distribution ratio applied in previous studies should be changed when the ground reinforcement pile is installed at an arbitrary location in the ground without raising it to the ground surface. When high strength jet routing is applied, the stress-distribution ratio (n) to the in-situ ground generally ranges from 30 to 50. However, if the pile is located far from the surface and the depth goes down to the boundary depth of the stress sphere, the stress-distribution effect rapidly decreases, and the stress-distribution ratio converges to 1.5.

• Steel and Composite Structures
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• v.51 no.1
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• pp.25-41
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• 2024

The measurement of pile bearing capacity is crucial for the design of pile foundations, where in-situ tests could be costly and time needed. The primary objective of this research was to investigate the potential use of fuzzy-based techniques to anticipate the maximum weight that concrete driven piles might bear. Despite the existence of several suggested designs, there is a scarcity of specialized studies on the exploration of adaptive neuro-fuzzy inference systems (ANFIS) for the estimation of pile bearing capacity. This paper presents the introduction and validation of a novel technique that integrates the fire hawk optimizer (FHO) and equilibrium optimizer (EO) with the ANFIS, referred to as ANFIS_FHO and ANFIS_EO, respectively. A comprehensive compilation of 472 static load test results for driven piles was located within the database. The recommended framework was built, validated, and tested using the training set (70%), validation set (15%), and testing set (15%) of the dataset, accordingly. Moreover, the sensitivity analysis is performed in order to determine the impact of each input on the output. The results show that ANFIS_FHO and ANFIS_EO both have amazing potential for precisely calculating pile bearing capacity. The R² values obtained for ANFIS_FHO were 0.9817, 0.9753, and 0.9823 for the training, validating, and testing phases. The findings of the examination of uncertainty showed that the ANFIS_FHO system had less uncertainty than the ANFIS_EO model. The research found that the ANFIS_FHO model provides a more satisfactory estimation of the bearing capacity of concrete driven piles when considering various performance evaluations and comparing it with existing literature.

• Korean Journal of Remote Sensing
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• v.39 no.6_1
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• pp.1255-1272
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• 2023

Satellite-based chlorophyll-a concentration, produced as a long-term time series, is crucial for global climate change research. The production of data without gaps through the merging of time-synthesized or multi-satellite data is essential. However, studies related to satellite-based chlorophyll-a concentration in the waters around the Korean Peninsula have mainly focused on evaluating seasonal characteristics or proposing algorithms suitable for research areas using a single ocean color sensor. In this study, a merging dataset of remote sensing reflectance from the geostationary sensor GOCI-II and polar-orbiting sensors (MODIS, VIIRS, OLCI) was utilized to achieve high spatial coverage of chlorophyll-a concentration in the waters around the Korean Peninsula. The spatial coverage in the results of this study increased by approximately 30% compared to polar-orbiting sensor data, effectively compensating for gaps caused by clouds. Additionally, we aimed to quantitatively assess accuracy through comparison with global chlorophyll-a composite data provided by Ocean Colour Climate Change Initiative (OC-CCI) and GlobColour, along with in-situ observation data. However, due to the limited number of in-situ observation data, we could not provide statistically significant results. Nevertheless, we observed a tendency for underestimation compared to global data. Furthermore, for the evaluation of practical applications in response to marine disasters such as red tides, we qualitatively compared our results with a case of a red tide in the East Sea in 2013. The results showed similarities to OC-CCI rather than standalone geostationary sensor results. Through this study, we plan to use the generated data for future research in artificial intelligence models for prediction and anomaly utilization. It is anticipated that the results will be beneficial for monitoring chlorophyll-a events in the coastal waters around Korea.

• The Journal of the Petrological Society of Korea
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• v.23 no.3
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• pp.197-208
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• 2014

Zircon separated from a biotite schist of the Guryong Group in Odesan area, eastern part of the Gyeonggi Massif in Korea were analysed for SHRIMP U-Pb ages. CL images display composite core-rim structures of the zircon, indicating an in-situ overgrowth of zircon through a high-grade metamorphism. The metamorphic zircon rims give a weighted mean age of $247{\pm}6Ma$. While the detrital zircon cores have zoning patterns and Th/U ratios indicative of a magmatic origin. Among 53 analyses from the cores, 46 data yield near concordant ages which are concentrated at $378{\pm}10Ma$ (n=9), $420{\pm}4Ma$ (n=6) and $1845{\pm}9Ma$ (n=18) with sporadic Neoproterozoic ($687{\pm}9Ma$) to late Archean ($2519{\pm}20Ma$) ages. The age data constraint sedimentation age of protolith of the Guryong Group, so far unknown, as late Paleozoic. The Guryong Group of this study is the first late Paleozoic strata reported from eastern Gyeonggi Massif, and its maximum depositional age (ca 378 Ma) is identical with those of the late Paleozoic strata in the southwestern Ogcheon Belt. The Triassic metamorphic age and abundant middle Paleozoic provenance (361~425 Ma) of the Guryong Group are similar with those reported from the Triassic collisional belt in central China. Thus this study indicates that the Odesan area would be an possible eastward extension of the Triassic collisional belt in central China.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3D
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• pp.499-509
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• 2006

Precast concrete deck has many advantages comparing with the in-situ concrete deck, and has been successfully applied to replacement of the deteriorated decks and to the newly constructed highway bridges in domestic region. In order to apply the precast decks into the railway bridges, however, differences of the load characteristics between the highway and the railway should be properly taken into account including the train load, longitudinal force of the continuous welded rail, acceleration or braking force, temperature change and shrinkage. Proper level of the longitudinal prestress of the tendons that can ensure integrity of the transverse joints in the deck system is of a primary importance. To this aim, the longitudinal tensile stresses induced by the design loads are derived using three-dimensional finite element analyses for the frequently adopted PSC composite girder railway bridge. The effect of the temperature change is also investigated considering the design codes and theoretical equations in an in-depth manner. The estimated proper prestress level to counteract those tensile stresses is above 2.4 MPa, which is similar to the case of the highway bridges.

• Magazine of the Korea Concrete Institute
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• v.6 no.2
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• pp.97-107
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• 1994

The objective of this study is to develop polymer-impregnated concrete(PIC), which is a newly developed composite material made by impregnating polymer impregnanls into hardened normal concrete, and to develop analytical techniques for its proper applications. Crystalline methyl methacrylate(MMA) is chosen as a monomer of polymer impregnants. The corrlpositions of polymer impregnants and producing processes are developed by analyzing the effects of penetration, polymerization, thermal safety, and strengthening characteristics. On t he basis of experimental results of this study, various strength characteristics and stress strain constitutive relations are formulated in terms of the compressive strength of normal concrete and the polymer loadings, which can be applied for analysis and design of PIC members. In order to provide a model for fracture analysis of flexural members, fracture toughness, fracture energy, critical crack width, and tension softening relations near crack tip are also formulated in terms of member depth, initial notch depth, and the flexural strength of normal concrete. The structural analysis procedure and the finite element computer program developed in the study are applicable to evaluate elastic behavior, ultimate strength, and tension softening behavior of MMA type PIC structural members subject to various loading conditions. The accuracy and effectiveness of the developed computer program is examined by comparing the anal ytical results with the experimental results. Therefore, it is concluded that the developed structural analysis procedure and the finite element computer program are applicable to analysis and design of in-situ and precast PIC structural members.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.6
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• pp.779-788
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• 2019

The compaction grouting method is one of the conventional ground improvement methods, which consolidates and compacts the surrounding ground through the injection of grout materials with low mobility. Injecting the grout into the ground can improve the soil properties, as well as form a composite of soil-grout columns. However, the conventional grout pumping is not applicable to handle multiple injection holes at the same time, which may diminish its constructability when the construction time is not enough. This paper proposes a simultaneous multiple compaction-grouting method using a new pump system developed to cover up simultaneously three injection holes at a time. Field injection tests with a single injection hole and with triangular arrangement of injection holes were conducted to evaluate the applicability of the proposed method to soft clay ground. In addition, a series of standard penetration tests (SPTs) were performed to assess the efficiency of each arrangement in improving the soft ground. It is noted from the in-situ test results that the interval distances between injection holes and the elapse time for ground stabilization are the crucial factors governing the applicability of the simultaneous multiple compaction-grouting method to improve the soft clay ground.