• Journal of Energy Engineering
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• v.17 no.3
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• pp.167-174
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• 2008

Line source model is commonly used in analyzing the data obtained from thermal response test to estimate the effective soil formation thermal conductivity. In the application of line source model some part of initial data must be ignored in order to achieve more accurate result. The period of time for this initial data is called initial ignoring time(IIT) in this paper. However there has been no definite rule in determining this initial ignoring time. Therefore line source model requires experienced analyzer to select the useful data, which is somewhat subjective. One method often suggested is the calculation of IIT with non dimensional time $\tau=5$. However, this is a very theoretical result derived from a system of perfect line source model, which is somewhat different from the real system. A new method to determine IIT is presented in this study. This method requires error estimation first and IIT can be decided from the results of error estimation. This method is applied in the analysis of field test data and shows better result than the one obtained from the method using non dimensional time mentioned above as shown in Table 2.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.129-129
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• 2020

전국적으로 약 18,000여개가 축조되어 있는 농업용 저수지는 국내농업용수 사용량 중 약 60%를 공급하는 핵심 농업기반시설로서 홍수기에 풍부한 수량을 저류한 후 관개기 혹은 갈수기에 주로 논벼 재배지역에 용수를 공급한다. 최근에는 가뭄에 의한 피해 심각성이 증가함에 따라 농업용 수확보대책 수립, 저수지 준설, 관정개발, 양수저류 등의 다양한 대응 방안을 마련하여 농업가뭄 극복을 위해 노력하고 있으나, 농업용수공급은 현장 물관리자의 경험을 토대로 공급되고 있어 공급량 관리가 정성적이고 제한적인 한계가 발생한다. 따라서, 농업용수의 효율적인 물 관리, 수원공으로부터 물공급의 합리적인 분배, 말단 수로 및 포장까지 안정적인 용수공급을 위한 물공급 및 분배 효율 분석이 필요하다. 본 연구에서는 서산지역의 신송저수지를 대상으로 2019년 5월부터 8월까지 통수일지 자료를 활용하여 농업용수 물공급 및 분배 모의, 관개효율을 분석하였다. 이를 위하여 부정류해석이 가능한 SWMM (Storm Water Management Model) 모형을 기반으로관개지구 용수공급 체계 네트워크와 들녘별로 용수공급이 가능하도록 구축하였고, 해당 지구의 실제 통수 시 수위 유량 계측을 통해 모델의 필수 변수 입력자료를 구축하였다. 전체면적 대비 수혜면적 비율과 전체 관개량 대비 해당 간선의 관개량 비율의 비교를 통해 수혜면적에 따른 관개효율을 분석하였으며, 각 수로별 공급량 대비 관개량 비율을 산정하여 수로별 관개효율을 분석하였다. 농업용수공급 효율 평가 결과는 수혜면적의 용수부족지역 파악, 시기별 용수배분의 공간적인 분포 모니터링 등 농업용수 이수대책에 활용하여 농업가뭄 상황 시 효율적인 물 배분 및 관리에 활용될 수 있을 것으로 판단된다.

• The Journal of Engineering Geology
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• v.23 no.4
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• pp.329-340
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• 2013

A geologic survey of the Bukpyeong and Pohang basins, as candidate basins for the geological storage of $CO_2$, was performed to evaluate storage capacity and security. To analyze the mechanical stability of the storage reservoir and cap rocks, we measured the porosity, seismic velocity, uniaxial strength, internal frictional angle, and Young's modulus of core samples recovered from the two basins. It is costly and sometimes impossible to conduct tests over the entire range of drill holes, and continuous logging data do not yield the mechanical parameters directly. In this study, to derive the mechanical properties of geologic formations from the geophysical logging data, we determined the empirical relations between the physical properties (seismic velocity, porosity, and dynamic modulus) and the mechanical properties (uniaxial strength, internal friction angle) of the core samples. From the comparison with our core test data, the best fits to the two basins were selected from the relations suggested in previous studies. The relations between uniaxial strength, Young's modulus, and porosity of samples from the Bukpyeong and Pohang basins are more consistent with certain rock types than with the locality of the basins. The relations between the physical and mechanical properties were used to estimate the mechanical rock properties of geologic formations from seismic logging data. We expect that the mechanical properties could also be used as input data for a modeling study to understand the mechanical instability of rock formations prior to $CO_2$ injection.

• Journal of the Korean Geotechnical Society
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• v.37 no.9
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• pp.13-24
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• 2021

Recently, attempts have been made to detect fouling patterns in the ground using Ground Penetrating Radar (GPR) during the maintenance of gravel ballast railway tracks. However, dealing with GPR signal data obtained with a large amount of noise in a site where complex ground conditions are mixed, often depends on the experience of experts, and there are many difficulties in precise analysis. Therefore, in this study, a numerical modeling technique that can quantitatively simulate the GPR signal characteristics according to the degree of fouling of the gravel ballast material was proposed using python-based open-source code gprMax and RSA (Random sequential Absorption) algorithm. To confirm the accuracy of the simulation model, model tests were manufactured and the results were compared to each other. In addition, the identification of the fouling layer in the model test and analysis by various test conditions was evaluated and the results were analyzed.

• Journal of Practical Engineering Education
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• v.14 no.2
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• pp.425-437
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• 2022

In this study, the role and function of Edutech, as well as the application and expectations in the field of future vocational competency development, were gathered to define Edutech as a comprehensive working definition. Based on this redefinition of Edutech, this study analyzes Edutech technology trends and examines the level of actual technology applied to education and vocational training based on written interviews with experts, and finds out significant implications from the point of view of vocational training. Finally we propose an Edutech-based Vocational Education and Training Model.

• Journal of Service Research and Studies
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• v.11 no.3
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• pp.43-54
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• 2021

This study focused on indoor spaces and convenience devices among vehicle interior designs suitable for the autonomous driving era, and presented an interior design model for future automobiles by applying the STEEP analysis method. The service design methodology is applied to deal with changes in display devices installed for the purpose of rearranging layouts and providing driver-centered information. Changes in types and installation locations of displays for various purposes such as connected and infotainment are expected. In particular, through this analysis, trends and experiences through indoor interior research in future self-driving cars will be studied, and subsequent studies will be used as basic data for actual development and application. Key drivers were extracted after deriving future trends linking the research project conducted in five stages to STEEP and consulting experts through FGI. Through this, it was later presented as a direction for indoor design. Through user-centered participatory design methods, emotional keyword derivation methods were used, summarized the derived drivers in five major trends in the future society, and each derived drivers were grouped to consider the relevant technology fields, and added elements to the autonomous driving level. This is an indoor ray viewed from the perspective of various social issues as well as personal tendencies in the future self-driving car industry.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.4
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• pp.262-272
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• 2020

A large number of studies on wave breaking have been carried out, and many experimental data have been documented. Moreover, on the basis of various experimental data set, many empirical or semi-empirical formulas based primarily on regression analysis have been proposed to quantitatively estimate wave breaking for engineering applications. However, wave breaking has an inherent variability, which imply that a linear statistical approach such as linear regression analysis might be inadequate. This study presents an alternative nonlinear method using an neural network, one of the machine learning methods, to estimate breaking wave height and breaking depth. The neural network is modeled using Tensorflow, a machine learning open source platform distributed by Google. The neural network is trained by randomly selecting the collected experimental data, and the trained neural network is evaluated using data not used for learning process. The results for wave breaking height and depth predicted by fully trained neural network are more accurate than those obtained by existing empirical formulas. These results show that neural network is an useful tool for the prediction of wave breaking.

• The Journal of Korean Institute for Practical Engineering Education
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• v.4 no.2
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• pp.110-115
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• 2012

IPP (Industry Professional Practice) is an educational model that combines academic study and industrial work through university-industry cooperation. Students would decide suitable career based on their IPP experience, that will lead a university graduate to improve their recruitment potential. IPP could also be a key to solve national employment problems as well as a chronic manpower supply and demand mismatch issue between university and industry. This paper discusses about an academic program operation for the IPP implementation, that includes operation plan for semester-based quarter system, a guideline for new curriculum, an academic credit allocation, evaluation guideline, a capstone design class operation, and interim measures.

• Journal of the Korean Geotechnical Society
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• v.24 no.12
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• pp.85-92
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• 2008

It is necessary to develop a rational design method for surface reinforcement of very soft ground because most current design works rely on merely crude empirical correlations. In this paper, the mechanical behavior of very soft ground that is surficially reinforced was investigated with the aid of a series of numerical analyses. Several material properties of each dredged soft ground, reinforcement and backfill sand mat have been exercised in the numerical analysis. The result of numerical analysis was compared with those of the laboratory model test. Through the matching process between the numerical and experimental result, it is possible to determine representative material properties of the dredged soft ground, reinforcements and backfill sand mat. These verified material properties permit to evaluate the effect of the stiffness of reinforcement and the thickness of sand mat on the overall deformation of the reinforced soft ground.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.2
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• pp.105-114
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• 2016

When impact load is applied to a plate structure, a common phenomenon that occurs in structures is plastic deformation accompanied by a large strain and eventually it will experience a fracture accordingly. In this study, for the rational design against accidental limit state, the plastic material constants of steel plate which is formed by line heating and by cold bending procedure have been defined through the numerical simulation for the high speed tension test. The usefulness of the material constants included in Cowper-Symonds model and Johnson-Cook model with the assumption that strain rate can be neglected when strain rate is less than the intermediate speed is verified through comparing the present numerical results with those in references. This paper ends with describing the future study.