• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.10
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• pp.1461-1466
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• 2014

GIS(Gas Insulated Switchgear) is important power apparatus which have strong dielectric strength, supply electric power and is a part of the power system. Most substation type is configured as GIS. Recently, because of continuous increasement of GIS demand resulted from high quality & big capacity of electric power, the necessity of the preventive & diagnosis system is being expanded gradually. GIS partial discharge occurred on the UHF band is detected effectively by the method to IEC 60270 that recommend to be able to detect the apparent minimum discharge, 5 pC. Additionally, the UHF sensor should be installed to detect PD signal if Partial discharge signal, 5 pC occur in every part of GIS. Currently PD diagnosis system applying UHF sensor for GIS with various voltage level like 154 kV, 345 kV, 765 kV have been operated. And it is necessary to measure and analyze insulation breakdown phenomenon of inside GIS exactly. In this paper, we proposed Fat-dipole patch UHF sensor that is developed and more sensitive, excellent wide-range characteristic than the exising UHF sensor. And we performed KERI (Korea Electrotechnology Research Institute) reference test, which showed the excellent result for the all tests.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.5
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• pp.9-16
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• 2019

Recent economic trends are worsening and becoming longer, and Korean shipbuilding is focused on high value added and high technology, especially for LNG carriers and large container ships. Both ship types increased in size in the 2010s but have requirements such as high strength, toughness at low temperatures and continuous weldability for preventing brittle fractures at service temperatures. In particular, as container ships become larger, the International Classification Society (IACS) has established a provision (IACS UR S33) that mandates the use of BCA (Brittle Crack Arrest) certified vessels for large container vessels contracted after 2014 to ensure safety. Therefore, studies on BCA 47Y.P are currently being undertaken, but BCA 40Y.P has not been actively studied yet. We will test BCA 40Y.P to verify why it can be applied to a large container ship and measure fatigue cracking.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.5
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• pp.488-496
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• 2023

Ship and bridge structures are a type of long box-shaped structure, and resistance to vertical bending moment is a key factor in their structural design. In particular, because box girders are repeatedly exposed to irregular wave loads for a long time, the continuous collapse behavior of structural members must be accurately predicted. In this study, plastic collapse behavior, including buckling according to load changes of the box girder receiving pure bending moments, was analyzed using a numerical analysis method. The analysis targets were selected as three box girders used in the Gordo experiment. The cause of the difference was considered by comparing the results of the structural strength experiment with those of non-linear finite element analysis. This study proposed a combination of the entire and local sagging shape to reflect the effect of the initial sagging caused by welding heat that is inevitably used to manufacture carbon steel materials. The procedures reviewed in the study and the contents of the initial sagging configuration can be used as a good guide for analyzing the final strength of similar structures in the future.

• Journal of Korean Tunnelling and Underground Space Association
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• v.26 no.1
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• pp.39-58
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• 2024

Tunnel Boring Machines (TBM) use multiple disc cutters to excavate tunnels through rock. These cutters wear out due to continuous contact and friction with the rock, leading to decreased cutting efficiency and reduced excavation performance. The rock's abrasivity significantly affects cutter wear, with highly abrasive rocks causing more wear and reducing the cutter's lifespan. The Cerchar Abrasivity Index (CAI) is a key indicator for assessing rock abrasivity, essential for predicting disc cutter life and performance. This study aims to develop a new method for effectively estimating CAI using rock strength, petrological characteristics, linear regression, and machine learning. A database including CAI, uniaxial compressive strength, Brazilian tensile strength, and equivalent quartz content was created, with additional derived variables. Variables for multiple linear regression were selected considering statistical significance and multicollinearity, while machine learning model inputs were chosen based on variable importance. Among the machine learning prediction models, the Gradient Boosting model showed the highest predictive performance. Finally, the predictive performance of the multiple linear regression analysis and the Gradient Boosting model derived in this study were compared with the CAI prediction models of previous studies to validate the results of this research.

• Journal of Power System Engineering
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• v.16 no.6
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• pp.52-58
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• 2012

Roll forming process is one of the most widely used processes in the world for forming metals such as a furniture drawer guide or an up and down slide guide. It can manufacture goods of the uniform cross section on a large scale throughout the continuous processing. In the domestic design and manufacture, roll forming process for production is taking most of the method of 2-point under rail slide. However, this method is vulnerable to the structural strength and stiffness is not suitable for high load conditions. Therefore, through systematic study of high load, low noise 3-point ball type of under rail slide its own design and manufacturing technology is the need to build. In this paper, to make center member of 3-point ball-type under rail slide for the refrigerator doors, the roll forming modeling and simulation are performed. Tensile test is performed about SCP-1 1/2H for determine the mechanical properties of materials. Modeling and simulation of roll forming is used MSC.MARC software of a dedicated analysis program used by rigid plastic finite element method. Interference between the roll and the final shape are predicted from the results of the simulation.

• Journal of Korean Society of Steel Construction
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• v.28 no.1
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• pp.35-42
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• 2016

This paper presents the structural analysis of two-span structures constructed by incremental launching method to traverse the existing facilities. The structure with a relatively short launching span can not be secure the structural stability caused by excessive deflection and overturning prior to reaching the maximum strength, because the length of the other span is different or the rear structure is not continuous. In order to estimate the stability of the construction stages of deflection and the overturning, the structural analysis was carried out. The parameters of the analysis is launching span ratio of the launching nose and the upper structure, weight ratio and so on. From the analysis result, the effects of parameters were investigated and a deflection formula of the launching nose and the condition of the overturning of structure were proposed.

• Journal of the Korea Institute of Military Science and Technology
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• v.23 no.4
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• pp.407-416
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• 2020

Recent complex battle field demands Network Centric Warfare(NCW) ability to control various parts into a cohesive unit. In path planning filed, the NCW ability increases complexity of path planning algorithm, and it has to consider a communication coverage map as well as traditional parameters such as minimum radar exposure and survivability. In this paper, pros and cons of various propagation models are summarized, and we suggest a coverage map generation method using a Longley-Rice propagation model. Previous coverage map based on line of sight has significant discontinuities that limits selection of path planning algorithms such as Dijkstra and fast marching only. If there is method to remove discontinuities in the coverage map, optimization based path planning algorithms such as trajectory optimization and Particle Swarm Optimization(PSO) can also be used. In this paper, the Longley-Rice propagation model is used to calculate continuous RF strengths, and convert the strength data using smoothed leaky BER for the coverage map. In addition, we also suggest other types of rough coverage map generation using a lookup table method with simple inputs such as terrain type and antenna heights only. The implemented communication coverage map can be used various path planning algorithms, especially in the optimization based algorithms.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.1
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• pp.27-35
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• 2021

This paper proposes a method to mitigate the Catastrophic Forgetting phenomenon in which artificial neural networks forget information on previous data. This method adjusts the Regularization strength by measuring the relationship between previous data and present data. MNIST and EMNIST data were used for performance evaluation and experimented in three scenarios. The experiment results showed a 0.1~3% improvement in the accuracy of the previous task for the same domain data and a 10~13% improvement in the accuracy of the previous task for different domain data. When continuously learning data with various domains, the accuracy of all previous tasks achieved more than 50% and the average accuracy improved by about 7%. This result shows that neural network learning can be properly performed in a CL environment in which data of different domains are successively entered by the method of this paper.

• Journal of Korean Society of Steel Construction
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• v.19 no.6
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• pp.737-749
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• 2007

Flexural design of double composite box girder over the interior pier for three-span continuous bridge was performed by the LRFD method. The maximum span length of the continuous bridge ranged from 80m to 120m and the relative ratio of the span length was assumed to be 1:1.25:1. The girder section was designed for the strength limit state and service limit state with additional design check for constructibility. Before the bottom concrete and compression flange showed a complete composite action, the buckling of lower compression flange was checked. The flexural stiffness and flexural resistance characteristics for the section and for the constituent members such as tension flange, compression flange, and web were analyzed for different thicknesses of the bottom concrete on top of the compression flange. The effect of the distribution ratio of steel between the top and bottom flanges was investigated by analyzing ductility behavior and stress distribution through the girder's depth for several different relative area ratios of steel between the top and bottom flanges. It was found that a total amount of 15% of steel can be saved by applying the double composite system compared with that of the conventional composite system.

• Composites Research
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• v.14 no.5
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• pp.1-11
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• 2001

The particulates reinforced metal matrix composites(PMMC) have a number of interesting mechanical properties. including high strength and good resistance to wear at high temperature and low thermal expansion. The equipment structure to obtain the homogeneous distribution in composites are proposed for the continuous pouring of reinforcement at the desired temperature. The particulates reinforced metal matrix composites(A357/SiCp) were fabricated by the process of the combined stirring method with the various fabrication process. The combined stirring method to niform distribution of particle is consisted of two stirring force both electro-magnetic stirring generated from induction heating and mechanical stirring with graphite stirrer. PMMC billets were fabricated with the volume fractions ranged from 0% to 20% and particle sizes ranged from 14${\mu}{\textrm}{m}$ to 25${\mu}{\textrm}{m}$. It is important to cont the size of primary $\alpha$-Al solid particles because it could become the cause of the particle pushing or capture phenomena from the fact that secondary dendrite arm spacing size depends on the cooling rate during the solidification in hypoeutectic Al-Si alloy. Therefore, the effect of primary $\alpha$-Al on the reinforcement distribution in matrix alloys has been investigated. The microstructure of PMMC fabracated with various volume fractions(0%, 10%, and 20%) and particle size were observed.