• The Journal of Engineering Geology
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• v.27 no.2
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• pp.133-141
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• 2017

In this study, filter conditions by difference in grading between core material and filter material used for dam construction was applied as evaluation condition for surrounding ground conditions near excavation site in a bid to identify the risk of land subsidence resulting from the erosion of soil particles. To that end, filter conditions proposed for the test was evaluated and the risk of land subsidence depending on grain size conditions was also evaluated using the filter conditions developed by COE. Consequently, evaluation diagram that can be used to determine the risk of land subsidence using grain size conditions obtained from ground investigation data was developed, which is expected to help evaluate the possibility of land subsidence depending on changes to the stratum. To simulate the particle flow process, PFC3D program was used. It's not only intended to determine the land subsidence pattern caused by falling ground water level but also predict and evaluate the land subsidence caused by soil erosion using grain size condition which can be verified by numerical analysis approach.

• Ecology and Resilient Infrastructure
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• v.2 no.3
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• pp.191-197
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• 2015

Invasive alien species are considered to be one of the main factors that cause biodiversity loss. Establishment of management strategies through continuous monitoring and risk assessment is a key element for invasive alien species management policy. In the present study, we introduce examples of ecological risk assessment tools developed in Japan, Germany-Austria and Belgium. Invasive alien species have been designated in Japan based on the assessment of risks to ecosystems, human health and primary industry. German-Austrian Black List Information System categorized alien species into Black List, White List and Grey List according to their risks to biodiversity. In the Harmonia Information System developed in Belgium, invasiveness, adverse impacts on native species and ecosystem functions and invasion stages were assessed and alien species were categorized into Black List, Watch List and Alert List. These international risk assessment tools may be helpful to improve our national risk assessment protocol for the prioritization of invasive alien species management.

• Archives of design research
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• v.17 no.1
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• pp.373-382
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• 2004

Large sized buildings have proliferated in the modern world in order to solve problems caused by the growth of cities, and this trend has lead to diversity in style and utilization of interiors. In particular, wayfinding within the shopping mall for a customer is a common problem, so if customers do not have to face these navigational problems and could find the way more easily, then shopping mall or the store can expect much better profits. Therefore, directional sign system that can provide accurate and speedy information for customers with diversified ages, gender and knowledge is necessary. Firstly, the definition and element of all directional sign are analyzed through the existing literature survey. The elements are based on the practical elements and six categories such as type, pictogram, color, layout, form, and location were considered. Secondly, directional signs in large underground shopping mall was considered, and the speciality of the underground shopping mall was investigated, and finally top three underground shopping malls was analyzed. Thirdly, through the questionnaire, an objective appraisal of directional signs and problems was developed, and following possible improvement was suggested. This study has its own limitations since it is only applicable to the specific locations, however, directional designs will be useful in other types of buildings as well. Through the continuous studies of the users' psychology, these kinds of studies will be related to the environmental characteristics of various places.

• Applied Chemistry for Engineering
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• v.23 no.2
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• pp.176-182
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• 2012

The methane dry reforming has received the considerable attention in recent years, mainly as an attractive route to produce synthesis gas (CO, $H_2$) from green-house gases ($CH_4$, $CO_2$) for resources. However, this process has not been commercialized due to the high temperature and catalyst deactivation. In this study, Co-Ru-Zr catalysts supported on $SiO_2$ were studied for the characterization of methane dry reforming reaction and the preliminary data for process development were achieved. The crystal structure of catalysts was measured by XRD, the surface area and pore size were analyzed by BET, and the element composition of catalyst were analyzed by EDS. Conversions of methane and carbon dioxide were analyzed by GC. In addition, reaction rate constants were obtained from the reaction kinetic study and the optimum catalyst size that does not affect mass transfer from reactants was also determined. The selected pellet-type catalyst maintained activation for 720 h at $850^{\circ}C$.

• Journal of the Society of Disaster Information
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• v.17 no.4
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• pp.747-754
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• 2021

Purpose: Seismic safety evaluation of a curved bridge must be performed since the curved bridges exhibit the complex behavior rather than the straight bridges, due to geometrical characteristics. In order to conduct the probabilistic seismic assessment of the curved bridge, Seismic fragility evaluation was performed using the uncertainty of the steel material properties of a curved bridge girde, in this study. Method: The finite element (FE) model using ABAQUS platform of the curved bridge girder was constructed, and the statistical parameters of steel materials presented in previous studies were used. 100 steel material models were sampled using the Latin Hypercube Sampling method. As an input ground motion in this study, seismic fragility evaluation was performed by the normalized scale of the Gyeongju earthquake to 0.2g, 0.5g, 0.8g, 1.2g, and 1.5g. Result: As a result of the seismic fragility evaluation of the curved girder, it was found that there was no failure up to 0.03g corresponding to the limit state of allowable stress design, but the failure was started from 0.11g associated with using limit state design. Conclusion: In this study, seismic fragility evaluation was performed considering steel materials uncertainties. Further it must be considered the seismic fragility of the curved bridge using both the uncertainties of input motions and material properties.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.44 no.3
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• pp.10-21
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• 2021

Recently, the demand for atypical structures with functions and sculptural beauty is increasing in the construction industry. Existing mold-based structure production methods have many advantages, but building complex atypical structures represents limitations due to the cost and technical characteristics. Production methods using molding are suitable for mass production systems, but production cost, construction period, construction cost, and environmental pollution can occur in small quantity batch production. The recent trend in the construction industry calls for new construction methods of customized small quantity batch production methods that can produce various types of sophisticated structures. In addition to the economic effects of developing related technologies of 3D Concrete Printers (3DCP), it can enhance national image through the image of future technology, the international status of the construction civil engineering industry, self-reliance, and technology export. Until now, 3DCP technology has been carried out in producing and utilizing residential houses, structures, etc., on land or manufacturing on land and installing them underwater. The final purpose of this research project is to produce marine structures by directly printing various marine structures underwater with 3DCP equipment. Compared to current underwater structure construction techniques, constructing structures directly underwater using 3DCP equipment has the following advantages: 1) cost reduction effects: 2) reduction of construct time, 3) ease of manufacturing amorphous underwater structures, 4) disaster prevention effects. The core element technology of the 3DCP equipment is to extrude the transferred composite materials at a constant quantitative speed and control the printing flow of the materials smoothly while printing the output. In this study, the extruding module of the 3DCP equipment operates underwater while developing an extruding module that can control the printing flow of the material while extruding it at a constant quantitative speed and minimizing the external force that can occur during underwater printing. The research on the development of 3DCP equipment for printing concrete structures underwater and the preliminary experiment of printing concrete structures using high viscosity low-flow concrete composite materials is explained.

• Journal of Bio-Environment Control
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• v.30 no.3
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• pp.244-249
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• 2021

The hydroponic culture for growing 'Duke' blueberry was evaluated in a protective greenhouse provided with similar environmental conditions to the conventional blueberry cultivations. One year old 'Duke' blueberry bushes planted in 180 L containers filled with 130 L peat moss and 40 L pearlite (v/v) were selected for the experiment. A nutrient solution consisted with NO₃-N 4.6, NH₄-N 3.4, PO₄-P 3.3, K 3, Ca 4.6, and Mg 2.2 mmol^-1 was supplied to the plants, comparing non-hydroponic treatment (provided with only underground water). Hydroponic culture increased number of shoot per bush by 18% and total shoot length by 24% compared with non-hydroponic culture. Total dry weight of a bush increased in the hydroponic with vigorous root growth 1.4-fold more than the non-hydroponic. Higher concentrations of inorganic elements and organic compounds were found in the hydroponic, indicating active nutrient absorption of the bush. The hydroponic produced high yield similar to adult bush from 4 years old age, maintaining the yield until 8 years old age. The findings of this study indicated that hydroponic cultivation systems will be useful for growing blueberry crop.

• Journal of the Korean Geosynthetics Society
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• v.17 no.4
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• pp.119-128
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• 2018

Limit state design has been implemented in Korea since 2015; however, there exists no specification of lateral load determination on retaining wall due to the Korean standard traffic load on retaining wall's backfill surface. The lateral load from traffic depends on lane number, standard truck's axle loads and locations, loading distance from the inner wall. The concept of equivalent height of soil accounting for traffic loadings is typically used for design of retaining walls to quantify the traffic loads transmitted to the inner wall faces. Due to the different characteristics of the standard design trucks between Korea and US (AASHTO), the direct use of the guidelines from AASHTO LRFD leads to incorrect estimation of traffic load effects on retaining walls. This paper presents the results of evaluation of equivalent height of soil to reflect the Korean standard truck, based on the findings from analytical solutions using Bounessq's theory and numerical assessment using 2D finite element method. Consequently, it was found that the equivalent heights of soil from the Korean standard truck load were lower for lower retaining wall height.

• Journal of the Korean Geotechnical Society
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• v.35 no.4
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• pp.15-26
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• 2019

The stability of the gravity quay wall against earthquakes is evaluated on the basis of the allowable displacement of the wall. To estimate the displacement caused by external forces, empirical equations based on the Newmark sliding block method or numerical analysis are widely used. In numerical analysis, it is possible to analyze precisely a complicated site and structure, but difficult to set the appropriate parameters and environments; there are limitations in obtaining reliable results, depending on one's level of expertise. The Newmark method, with only seismic motions, is widely used because it is simpler than numerical simulations when estimating permanent displacement. However, the empirical equations do not have any parameters for the response characteristics and sliding block of the structure, and sliding blocks being assumed as rigid bodies does not consider the nonlinear behavior of the soil and interaction with the structure. Therefore, in order to evaluate the seismic stability of the gravity quay wall, a newly-developed empirical equation is needed to overcome the above-mentioned limitations. In this study, numerical simulations are performed to analyze the response characteristics of the backfill of the structure, and to propose an optimal method of calculating the active area. For this purpose, finite element analyses were performed to analyze the response characteristics, and stress-strain relationships for various seismic motions. As a result, the response characteristics, sliding block, and failure surface of the backfill vary depending on the input seismic motions.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.2
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• pp.335-344
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• 2019

Micropiles are widely used for foundation underpinning to enhance bearing capacity and reduce settlement of existing foundation. In this study, the main objective is to evaluate underpinning performance of a newly developed micropile called waveform micropile for foundation underpinning during vertical extension. Finite element method (FEM) was used to evaluate the underpinning performance of waveform micropile in terms of load-settlement response of underpinned foundation and load sharing behavior. For comparison, underpinning effects of three conventional micropiles with different lengths were also discussed in this study. Numerical results of load-settlement response for single pile demonstrated that bearing capacity and axial stiffness of waveform micropiles were higher than those of conventional micropiles because of the effect of shear keys of waveform micropiles. When additional loads 20 %, which is according to design loads of the vertical extension, were applied to the underpinned foundation, load sharing capacity of waveform micropile was 40 % higher than conventional micropile at the same size. The waveform micropile also showed better underpinning performance than the conventional micropile of length 1~1.5 times of waveform micropile.