• The Journal of Engineering Geology
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• v.18 no.4
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• pp.567-576
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• 2008

It is possible to understand rainfall infiltration characteristics by identification of wetting front in the soil. The wetting front by rainfall infiltration has close relationships among soil density, grain size distribution, and permeability coefficient in the soil. The infiltration velocity is a similar concept of permeability coefficient in the soil. In this study, infiltration velocity of rainfall was calculated by a field monitoring of volumetric water contents at the depths of 50 cm and 80 cm below the surface in the gneiss weathered soil. The calculated field infiltration velocity was compared with a permeability coefficient by a laboratory soil test using undisturbed soil samples in the study area. The permeability coefficient of the soil sample is $3.15{\times}10^{-3}cm/sec$, while the field infiltration velocity is $1.87{\times}10^{-3}cm/sec$. It is interpreted that the lower infiltration velocity is induced by complicate condition of porosity and grain size distribution of soil in the field. The rainfall intensity which influences on the volumetric water content and infiltration velocity is more than 20 mm/day resulting in expansion of wetting front in the soil.

• Journal of the Korean Institute of Landscape Architecture
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• v.48 no.5
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• pp.42-58
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• 2020

The purpose of this study is to classify types of urban flower landscape. As a result of the study, first, through literature and case review, it was found that the four elements of place element, form element, natural element, artificial element, should be included in the sentence and key expression for defining the concept of flower landscape. In contemplating these four elements, a newly reconstructed concept of flower landscape was presented. This is expected to be the basis for the flower landscape integration theory. Second, flower landscape was defined as a genre and a unit of urban landscape. In addition, in order to build a system of flower landscape as a specialized area, after considering the concept, characteristics, and functions of a large category of urban landscape, its hierarchical categories with flower landscape were newly arranged. Thus, the flower landscape as an urban landscape was suggested. Third, in order to provide rational selection materials to consumers through type classification, related theories were investigated by expanding not only to the flower field, but also to the urban planning and urban ecology fields. 41 elements for the type classification were extracted, and 4 core elements were derived through the clustering process. Based on the 4 elements as the classification criteria, through the opinion verification from the FGI with experts, 9 types of middle-classification and 30 types of small-classification were derived. As a follow-up research suggestion, if a valid type is additionally established through a monitoring in the type application process, and more specified application types are developed and organized by expanding second-level classification hierarchy to the third-level hierarchy, this will lead to great studies improving the system of the types.

• Journal of Wetlands Research
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• v.22 no.2
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• pp.161-170
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• 2020

Constructed wetlands (CWs) are widely used to solve water quality problems caused by diffuse pollution from agricultural areas; however, phytoplankton blooms in CW systems can occur due to long hydraulic retention time (HRT), high nutrient loading, and exposure to sunlight. This study was conducted to evaluate the efficiency of a CW designed to treat agricultural diffuse pollution and develop a design concept to improve the nature-based capabilities of the system. Monitoring was conducted to assess contribution of individual wetland components (i.e. water, sediments, and plants) in the treatment performance of the system. During dry days, the turbidity and particulates concentration in the CW increased by 80 to 197% and 10 to 87%, respectively, due to the excessive growth of phytoplankton. On storm events, the concentration of particulates, organics, and nutrients were reduced by 43% to 70%, 22% to 49%, and 15% to 69% due to adequate water circulation and constant flushing of pollutants in the system. Based on the results, adequate water circulation is necessary to improve the performance of the CW. Free water surface CWs are usually designed to have a constant water level; however, the climate in South Korea is characterized by distinct dry and rainy seasons, which may not be suitable for this conventional design. This study presented a concept of multifunctional design in order to solve current CW design problems and improve the flood control, water quality management, and environmental functions of the facility.

• Tunnel and Underground Space
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• v.18 no.5
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• pp.343-354
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• 2008

A new method is suggested herein to measure the virgin earth stresses by means of a borehole. This novel concept is basically a combination of borehole stress relieving and borehole fracturing techniques. The destressing of the borehole is achieved by means of inducing thermal tensile stresses at the borehole periphery by using a cryogenic fluid such as Liquid Nitrogen($LN_2$). The borehole wall eventually develops fractures when the induced thermal stresses exceed the existing compressive stresses at the borehole periphery in addition to the tensile strength of the rock. The above concept is theoretically analyzed for its potential applicability to interpret in situ stress levels from the tensile fracture stresses and the corresponding borehole wall temperatures. Coupled thermo-mechanical numerical simulations are also conducted using FLAC3D, with thermal option, to check the validity of the proposed techniques. From the preliminary theoretical and numerical analysis, the method suggested for the measurement of in situ stresses appears to be capable of accurate estimation of the virgin stresses by monitoring tensile crack formation at a borehole wall and recording the wall temperatures at the time of crack initiation.

• Journal of the Korean Chemical Society
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• v.60 no.2
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• pp.137-143
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• 2016

Effective teaching and learning is a continuous process of monitoring and re-organization of teaching method, so to benefit both students and educators. Reflective journal writing is an effective method for students to reflect on their learning experience about a new concept or subject taught and at the same time enables educators to improve on their academic skills. In the present paper, we have examined and evaluated the effectiveness of the Uncritical Inference Test (UIT) that was conducted in our basic organic chemistry course through a systematic network built based on students’ reflective writing. From the data analysis, the UIT has benefited students in three dimensions, namely cognitive, affective and group learning domains. Moreover, the UIT activity instilled an active learning environment in organic chemistry classroom and deeper learning among chemistry students as shown in the collected data. In future, this activity could be adapted as a teaching method to enhance students’ critical thinking skills and question-asking capability in other teaching courses.

• Proceedings of the IEEK Conference
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• 2004.08c
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• pp.876-879
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• 2004

The buried fiber optic cable as a distributed intrusion sensor for detecting and locating intruders along the long perimeters is proposed. Phase changes resulting from either the pressure of the intruder on the ground immediately above the buried fiber or from seismic disturbances in the vicinity are sensed by a phase-sensitive optical time-domain reflectometer. Light pulses from a Er:fiber cw laser with a narrow, <3kHz-range, spectral width and a frequency drift of < 1 MHz/min are injected into one end of the fiber, and the backscattered light from the fiber is monitored with a photodetector. Results of preliminary studies, measurement of phase changes produced by pressure and seismic disturbances in buried fiber optic cables and simulation of ${\varphi}-OTDR$ response over long fiber paths, to establish the feasibility of the concept are described. The field experiments indicate adequate phase changes, more than 1t-rad, are produced by intruders on foot and vehicle for burial depths in the 0.2 m to 1 m range in sand, clay and fine gravel soils. The simulations predict a range of 10 km with 35 m range resolution and 30 km with 90 m range resolution. This technology could in a cost-effective manner provide enhanced perimeter security.

• Korean Journal of Computational Design and Engineering
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• v.16 no.6
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• pp.414-423
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• 2011

The collaboration hub has been developed since 2004 as an online collaboration space, which supports the various collaborative works amongst small and medium enterprises using information sharing, collaboration project management, and project history management. Because of the change of manufacturing environment and rapid development of information technologies, it should be evolved from the existing version called Collaboration Hub 1.0. Recently, a lot of manufacturing enterprises know the importance of business process management(BPM) and start to introduce BPM systems. Our research group has developed the new version of Collaboration Hub 1.0 called Collaboration Hub 2.0 which contains the BPM concept, the consistent product data management, and the specialized functions overcoming the various variation of manufacturing. This study scrutinizes the meaning and role of the Collaboration Hub 2.0 and introduces an application study of it to the value chain of automobile module development consisted of a leading company and subcontractors. The case study covers the definition, execution and monitoring of collaboration process, the specialized functions overcoming the manufacturing variation and the key performance index of collaboration business.

• Structural Monitoring and Maintenance
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• v.3 no.4
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• pp.349-375
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• 2016

The tension of an arch bridge hanger is estimated using a number of experimentally identified modal frequencies. The hanger is connected through metallic plates to the bridge deck and arch. Two different categories of model classes are considered to simulate the vibrations of the hanger: an analytical model based on the Euler-Bernoulli beam theory, and a high-fidelity finite element (FE) model. A Bayesian parameter estimation and model selection method is used to discriminate between models, select the best model, and estimate the hanger tension and its uncertainty. It is demonstrated that the end plate connections and boundary conditions of the hanger due to the flexibility of the deck/arch significantly affect the estimate of the axial load and its uncertainty. A fixed-end high fidelity FE model of the hanger underestimates the hanger tension by more than 20 compared to a baseline FE model with flexible supports. Simplified beam models can give fairly accurate results, close to the ones obtained from the high fidelity FE model with flexible support conditions, provided that the concept of equivalent length is introduced and/or end rotational springs are included to simulate the flexibility of the hanger ends. The effect of the number of experimentally identified modal frequencies on the estimates of the hanger tension and its uncertainty is investigated.

• KIPS Transactions on Software and Data Engineering
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• v.4 no.9
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• pp.331-336
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• 2015

On the IoT-based sensor networks, users or sensor nodes must perform a Service Discovery (SD) procedure before access to the wanted service. Current approach uses a center-concentrated Resource Directory (RD) servers or P2P technique, but these can cause a point-of-failure or flooding of SD messages. In this paper, we proposes an improved SWoT SD approach for CoAP-based sensor networks, which integrates Social Web of Things (SWoT) concept to current CoAP-based SD approach that makes up for weak points of existing systems. This new approach can perform a function like a keyword or location-based search originated from SNS, which can enhances the usability. Finally, we implemented a real system to evaluate.

• Advances in nano research
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• v.9 no.1
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• pp.59-67
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• 2020

Filter cake formation during rotary drilling operation is an unavoidable scenario, hence there is need for constant improvement in the approaches used in monitoring the cake thickness growth in order to prevent drill-string sticking. This study proposes an improved model that predicts the growth of mud cake thickness overtime with the consideration of the addition of nanoparticles in the formulated drilling fluid system. Ferric oxide, titanium dioxide and copper oxide nanoparticles were used in varying amounts (2 g, 4 g and 6 g), and filtration data were obtained from the HPHT filtration test. The filter cakes formed were further analyzed with scanning electron microscope to obtain the morphological characteristics. The data obtained was used to validate the new filtrate loss model. This model specifically presents the concept of time variation in filter cake formation as against the previous works of constant and definite time. Regression coefficient which is a statistical measure was used to validate the new model and the predicted results were compared with the API model. The new model showed R² values of 99.9%, and the predictions from the proposed filtration model can be said to be more closely related to the experimental data than that predicted from the API model from the SSE and RMSE results.