• Journal of the Computational Structural Engineering Institute of Korea
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• v.31 no.6
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• pp.339-346
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• 2018

An Industry Foundation Classes(IFC), which is a data schema developed focusing on architecture, is being expanded to civil engineering structures. However, it is difficult to create an information model based on extended IFC since the BIM software cannot provide support functions. To manage a railway track based on the extended IFC, this paper proposed a method to create an alignment-centered separated railway track model and convert it to an extended IFC-based information model. First, railway track elements have been classified into continuous and discontinuous structures. The continuous structures were created by an alignment-based software, and discontinuous structures were created as independent objects through linkage of the discretized alignment. Second, a classification system and extended IFC schema for railway track have been proposed. Finally, the semantic information was identified by using the property of classification code and user interface. The availability of the methods was verified by developing an extended IFC-based information model of the Osong railway site.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.4
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• pp.470-478
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• 2019

As the growth of the domestic defense industry is remarkable regarding technology level and export size, technology protection is necessary. Particularly, there is a need to apply anti-tamper measures to prevent critical technologies from illegally being taken out of weapon systems. However, there is no security protection strategy and system built yet in ROK. Precedent studies discussed the trend analysis and technical research for specific protective techniques, and the application of anti-tamper using limited procedures was provided. Recently, methods of how to select the technology for protection were studied based on risk management. Nonetheless, these studies cannot be associated with the acquisition process for the whole life-cycle, having difficulty with actual development and evaluation of the weapon systems. The objective of our study is to derive the system requirements of the weapon system for which anti-tamper measures have been determined to apply. Specifically, requirements items suitable for the development of anti-tamper weapon systems were derived based on ISO/IEC 19790, the CMVP standard for the development and verification of cryptographic modules. Also, its utilization in technical reviews and test & evaluations was presented. The usefulness of the research results was confirmed through inductive inference and comparative evaluation. The result can be expected to play a role in initiating extensive activities needed for technology protection of the weapon systems.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.1
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• pp.61-68
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• 2021

The application of renewable energies such as wind and solar has become an inevitable choice for many countries in order to achieve the reduction of greenhouse gases and healthy economic development. However, due to the intermittent characteristics of renewable energy, the issue with integrating a larger proportion of renewable energy into the grid becomes more prominent. A complex energy system, usually consists of two or more renewable energy sources used together to provide increased system efficiency as well as greater balance in energy supply. Compared with the power system, control and optimization of the complex energy system become more difficult in terms of modeling, operation, and planning. The main purpose of the complex energy system retrofit for samado island with microgrid system is to coordinate the operation with various distributed energy resources, energy storage systems, and power grids to ensure its reliability, while reducing the operating costs and achieving the optimal economic benefits. This paper suggests the improved complex energy system of samado island with optimal microgrid system. The results of test operation show about 12% lower SOC variation band of ESS, elimination of operation limit in PV and reduction of operation time in diesel generator.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.3
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• pp.1-12
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• 2021

Technologies for an MVDC(medium voltage direct current) distribution system are being considered as an effective alternative to overcome the interconnection delay issues of PV systems. However, the implementation of a DC distribution system might lead to economic problems because of the development of DC devices. Therefore, this paper deals with the scale of a PV plant based on its capacity and proposes hosting-capacity models for PV systems to establish a network to evaluate the feasibility of an MVDC distribution system. The proposed models can be classified as AC and DC distribution systems by the power-supply method. PV systems with hundreds of MW, dozens of MW, and a few MW can be categorized as large-scale, medium-scale, and small-scale models, respectively. This paper also performed modeling for an economic evaluation of MVDC distribution system by considering both the cost of AC and DC network construction, converter replacement, operation, etc. The profit was composed of the SMP and REC rate of a PV plant. A simulation for economic evaluation was done for the MVDC distribution system using the present worth and equal-principal costs repayment method. The results confirmed that the proposed model is a useful tool to evaluate economic issues of a DC distribution system.

• Journal of Korea Society of Industrial Information Systems
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• v.25 no.6
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• pp.33-45
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• 2020

This paper aims to look at the perspective that the latest cutting-edge technologies are predicting individual diseases in the actual medical environment in a situation where various types of wearable devices are rapidly increasing and used in the healthcare domain. Through the process of collecting, processing, and transmitting data by merging clinical data, genetic data, and life log data through a user-participating wearable device, it presents the process of connecting the learning model and the feedback model in the environment of the Deep Neural Network. In the case of the actual field that has undergone clinical trial procedures of medical IT occurring in such a high-tech medical field, the effect of a specific gene caused by metabolic syndrome on the disease is measured, and clinical information and life log data are merged to process different heterogeneous data. That is, it proves the objective suitability and certainty of the deep neural network of heterogeneous data, and through this, the performance evaluation according to the noise in the actual deep learning environment is performed. In the case of the automatic encoder, we proved that the accuracy and predicted value varying per 1,000 EPOCH are linearly changed several times with the increasing value of the variable.

• Journal of Appropriate Technology
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• v.6 no.2
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• pp.115-125
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• 2020

Housing issues such as mushrooming slums remain as chronic in most developing countries. Due to the state's restrained capacity, the housing-vulnerable's self-help approaches have been increasingly inevitable and vital for addressing the housing issues. However, there are still two challenges: securing good quality with economic efficiency, and climate change mitigation and adaptation. This study aims at doing an architectural experiment by developing and educating the production of eco-friendly interlocking stabilized soil bricks (ISSB) by employing vernacular materials and technologies for housing-vulnerable communities in Indonesia. In collaboration with a local architectural NGO, the study features a co-creation workshop in which 40 evicted households participate in the whole process. Soil analysis, mixed design, compression tests, and economic analysis are carried out. This paper illustrates that ISSB also has a high potential as an alternative to a burned brick or a cement block. The application of ISSB to self-help housing is expected to have socioeconomic and environmental effects, thereby facilitating the housing-vulnerable's self-help approaches and contributing to addressing the housing challenges in Indonesia.

• The Journal of the Acoustical Society of Korea
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• v.40 no.4
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• pp.261-269
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• 2021

Without any validation of the incompressible assumption, most of previous studies on cavitation flow and its noise have utilized numerical methods based on the incompressible Reynolds Average Navier-Stokes (RANS) equations because of advantage of its efficiency. In this study, to investigate the effects of the flow compressibility on the Tip Vortex Cavitation (TVC) flow and noise, both the incompressible and compressible simulations are performed to simulate the TVC flow, and the Ffowcs Williams and Hawkings (FW-H) integral equation is utilized to predict the TVC noise. The DARPA Suboff submarine body with an underwater propeller of a skew angle of 17 degree is targeted to account for the effects of upstream disturbance. The computation domain is set to be same as the test-section of the large cavitation tunnel in Korea Research Institute of Ships and Ocean Engineering to compare the prediction results with the measured ones. To predict the TVC accurately, the Delayed Detached Eddy Simulation (DDES) technique is used in combination with the adaptive grid techniques. The acoustic spectrum obtained using the compressible flow solver shows closer agreement with the measured one.

• Tunnel and Underground Space
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• v.32 no.6
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• pp.373-385
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• 2022

The drum cutter, which is used in the form of an attachment of a excavator, is very useful in that it can be used in connection with a excavator that can perform various tasks in the field. This study estimated the load and torque acting on the drum cutter attachment by measuring the hydraulic pressure and strain that appear during excavation on the exposed rock slope using the drum cutter installed in the excavator. Working conditions such as the operation angle between the boom and arm of the excavator were divided into eight working modes. And as a result of analyzing the variations in hydraulic pressure and action force according to the working mode, it was confirmed that the hydraulic pressure and flow rate can be driven without any problems within the range considered in the manufacturing specifications of the drum cutter. The average load and torque acting on the drum cutter were within the range of the manufacturing specifications, but the maximum load was up to four times the specification. Because sumping was not properly performed due to the high ground strength and the ground included discontinuous surfaces in some locations, no trend of load and torque was found depending on the angle between the boom and arm of the excavator. However, it is believed that this result can be used to determine the range of loads and torques that appear on the drum cutter when excavating a high-intensity rock.

• Tunnel and Underground Space
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• v.32 no.6
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• pp.568-585
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• 2022

In the present study, we proposed a numerical method for simulating thermally induced fracture slip using a grain-based distinct element model (GBDEM). As a part of DECOVALEX-2023, the thermo-mechanical loading test on a saw-cut rock fracture conducted at the Korea Institute of Civil Engineering and Building Technology was simulated. In the numerical model, the rock sample including a saw-cut fracture was represented as a group of random Voronoi polyhedra. Then, the coupled thermo-mechanical behavior of grains and their interfaces was calculated using 3DEC. The key concerns focused on the temperature evolution, thermally induced principal stress increment, and fracture normal and shear displacements under thermo-mechanical loading. The comparisons between laboratory experimental results and the numerical results revealed that the numerical model reasonably captured the heat transfer and heat loss characteristics of the rock specimen, the horizontal stress increment due to constrained displacement, and the progressive shear failure of the fracture. However, the onset of the fracture slip and the magnitudes of stress increment and fracture displacement showed discrepancies between the numerical and experimental results. We expect the numerical model to be enhanced by continuing collaboration and interaction with other research teams of DECOVALEX-2023 Task G and validated in further study.

• The Journal of the Acoustical Society of Korea
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• v.40 no.6
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• pp.555-565
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• 2021

The goal of this study is to improve flow and noise performances of existing backward-curved blade centrifugal fan system used for circulating cold air in a refrigerator freezer by optimally designing airfoil shape. The unique characteristics of the system is to drive cold airflow with two volute tongues in combination with duct system in a back side of a refrigerator without scroll housing generally used in a typical centrifugal fan system. First, flow and noise performances of existing fan system were evaluated experimentally. A P-Q curve was obtained using a fan performance tester in the flow experiment, and noise spectrum was measured in an anechoic chamber in the noise experiment. Then, flow characteristics were numerically analyzed by solving the three-dimensional unsteady Navier-Stokes equations and noise analysis was performed by solving the Ffowcs Williams and Hawkins equation with input from the flow simulation results. The validity of numerical results was confirmed by comparing them with the measured ones. Based on the verified numerical method, blade inlet and outlet angles were optimized for maximum flow rate using the two-factor central composite design of the response surface method. Finally, the flow and noise performances of a prototype manufactured with the optimum design were experimentally evaluated, which showed the improvement in flow and noise performance.