• Journal of Welding and Joining
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• 제34권6호
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• pp.20-27
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• 2016

This study deals with the proper conditions of the trail rolling method (TRM) for the prevention of the buckling welding distortion at the AA5083 GMA butt weldment. For it, the effect of the working conditions of TRM including the rolling depth and the rolling distance between the welding torch and the roller on the longitudinal welding shrinkage force of the weldment was evaluated by using 3 dimensional thermo-mechanical FE analyses. The longitudinal welding shrinkage force inducing the buckling welding distortion at the GMA butt weldment was mitigated with an increase in the rolling depth and the rolling distance between the welding torch and the roller. Based on the results, the proper conditions of trail rolling method were established to reduce the longitudinal welding shrinkage force of the GMA butt weldment to below the critical value corresponding to the bucking distortion.

• 한국해양공학회지
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• 제25권5호
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• pp.47-51
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• 2011

This paper analyzes the fatigue-life of welded joints using the notch stress approach. In the notch stress approach, the notch effects are usually approximated by introducing weld-bead parameters for the local detailed weld joints. The actual bead shape is complex and 3-dimensional. It may also greatly influence the fatigue strength. In this study, the welded shape was modeled using a 3D-scanner. The critical distance method was adopted in the evaluation of the fatigue effective notch stress for the weldments. Fatigue life tests were performed to verify the present method of fatigue life estimation for two types of welded plates with longitudinal attachments. The estimated results of the present methods were applied to the results of the experiment. The results of the analysis showed that the scatter of fatigue-life for the experimental data expressed in the nominal stress was significantly reduced by applying the effective fatigue stress of the present study.

• 한국전기전자재료학회논문지
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• 제15권1호
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• pp.67-74
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• 2002

A phosphor for Plasma Display Panel, BaMgAl$_{10}$ O$_{17}$ :Eu$^{2+}$, showing a blue emission band at about 450nm was prepared by a solid-state reaction using BaCO$_3$, $Al_2$O$_3$, MgO, Eu$_2$O$_3$ as starting materials wish flux AlF$_3$. The study of the behaviour of Eu in BAM phosphor was carried out by the photoluminescence spectra and the Rietveld method with X-ray and neutron powder diffraction data to refine the structural parameters such as lattice constants, the valence state of Eu, the preferential site of Mg atom and the site fraction of each atom. The phenomenon of the concentration quenching was abound 2.25~2.3wt% of Eu due to a decrease in the critical distance for energy transfer of inter-atomic Eu. Through the combined Rietveld refinement, R-factor, R$_{wp}$, was 8.11%, and the occupancy of Eu and Mg was 0.0882 and 0.526 at critical concentration. The critical distance of Eu$^{2+}$ in BAM was 18.8$\AA$ at 2.25% Eu of the concentration quenching. Furthermore, c/a ratio was decreased to 3.0wt% and no more change was observed over that concentration. The maximum entropy electron density was found that the modeling of $\beta$-alumina structure in BaMgAl$_{10}$ O$_{17}$ :Eu$^{2+}$correct coincided showing Ba, Eu, O atoms of z= 1/4 mirror plane.e.ane.e.

• Earthquakes and Structures
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• 제8권3호
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• pp.713-732
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• 2015

The application of the compressive force path method for the design of earthquake-resistant reinforced concrete structural walls with a shear span-to-depth ratio larger than 2.5 has been shown by experiment to lead to a significant reduction of the code specified transverse reinforcement within the critical lengths without compromising the code requirements for structural performance. The present work complements these findings with experimental results obtained from tests on structural walls with a shear span-to-depth ratio smaller than 2.5. The results show that the compressive force path method is capable of safeguarding the code performance requirements without the need of transverse reinforcement confining concrete within the critical lengths. Moreover, it is shown that ductility can be considerably increased by improving the strength of the two bottom edges of the walls through the use of structural steel elements extending to a small distance of the order of 100 mm from the wall base.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권2호
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• pp.742-762
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• 2015

In this study, we propose a distance metric learning approach called discriminant metric learning (DML) for face verification, which addresses a binary-class problem for classifying whether or not two input images are of the same subject. The critical issue for solving this problem is determining the method to be used for measuring the distance between two images. Among various methods, the large margin nearest neighbor (LMNN) method is a state-of-the-art algorithm. However, to compensate the LMNN's entangled data distribution due to high levels of appearance variations in unconstrained environments, DML's goal is to penalize violations of the negative pair distance relationship, i.e., the images with different labels, while being integrated with LMNN to model the distance relation between positive pairs, i.e., the images with the same label. The likelihoods of the input images, estimated using DML and LMNN metrics, are then weighted and combined for further analysis. Additionally, rather than using the k-nearest neighbor (k-NN) classification mechanism, we propose a verification mechanism that measures the correlation of the class label distribution of neighbors to reduce the false negative rate of positive pairs. From the experimental results, we see that DML can modify the relation of negative pairs in the original LMNN space and compensate for LMNN's performance on faces with large variances, such as pose and expression.

• 디지털융복합연구
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• 제18권10호
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• pp.315-323
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• 2020

본 연구의 목적은 코로나19 원격 교육에서 간호대학 신입생의 대학생활 적응에 영향을 미치는 요인을 확인하기 위해 시도되었다. 자료는 2020년 8월 31일부터 9월 4일까지 S시 소재의 간호대학 신입생 165명을 대상으로 하였다. 자료분석은 t-test, one-way ANOVA, Pearson 상관분석, 다중회귀 분석을 이용하여 분석하였다. 일반적 특성 중 대학생활 적응과 관련된 요인은 연령, 입학 당시 학력, 입학 동기, 성적이었다. 대학생활 적응은 학업적 자기효능감, 비판적 사고 성향, 문제해결능력과 유의한 양의 상관관계에 있었으며, 이들 변수는 대학생활 적응을 37.7% 설명하였다. 따라서 코로나19로 원격 교육을 받는 간호대학 신입생의 대학생활 적응을 위해 학업적 자기효능감, 비판적 사고 성향, 문제해결능력을 고려한 수업방식과 학생지도가 필요하다.

• 대한교통학회:학술대회논문집
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• 대한교통학회 1998년도 Proceedings The 4th International Transport Symposium
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• pp.141-151
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• 1998

Provision of Passing Sight Distance (PSD) is an important component in two-lane highway design and has a critical impact on capacity of highway and safety of drivers. Many models have been developed to estimate PSD reasonably. However, each of them has a number of shortcomings for reflecting the real traffic conditions. This paper introduces a revised model that reflects the characteristics of the passing maneuver. The changes in passing sight distances under different assumptions about acceleration and vehicle length, which are related to vehicle types, are presented. The results obtained by the revised model are compared with those obtained from the existing models. There is an important link between geometric design decisions which determine the available sight distance and the quality of service which the road provides. In this paper, we examine one aspect of this relationship. That is to determine whether the passing sight distance is provided by improving horizontal alignment for a specific roadway section or passing may be restricted to save the road construction cost. To do so, a simple method for estimating traffic delay in no-passing is introduced.

• Journal of Positioning, Navigation, and Timing
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• 제10권2호
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• pp.113-120
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• 2021

The Distance Measuring Equipment (DME) is a ground-based aircraft navigation system and is considered as an infrastructure that ensures resilient aircraft navigation capability during the event of a Global Navigation Satellite System (GNSS) outage. The main problem of DME as a GNSS back up is a poor positioning accuracy that often reaches over 100 m. In this paper, a novel approach of applying deep reinforcement learning to a DME pulse design is introduced to improve the DME distance measuring accuracy. This method is designed to develop multipath-resistant DME pulses that comply with current DME specifications. In the research, a Markov Decision Process (MDP) for DME pulse design is set using pulse shape requirements and a timing error. Based on the designed MDP, we created an Environment called PulseEnv, which allows the agent representing a DME pulse shape to explore continuous space using the Soft Actor Critical (SAC) reinforcement learning algorithm.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.131.4-131
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• 2001

A lot of path planning algorithms have been developed to find the collision-free path with minimum cost. But most of them require complicated computations. In this paper, a thinning method, which is one of the image processing schemes, was adopted to simplify the path planning procedure. In addition, critical points are used to find the shortest-distance path among all possible paths from the start to the goal point. Since the critical points contain the information on the neighboring paths, a new path can be quickly obtained on the map even when the start and goal points change. To investigate the validity of the proposed algorithm, various simulations have been performed for the environment where the obstacles with arbitrary shapes exist. It is shown that the optimal paths can be found with relative easiness.

• 한국터널지하공간학회 논문집
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• 제6권2호
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• pp.129-139
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• 2004

터널의 환기설계에 관련하여 종류식과 횡류식의 환기용량의 산정을 위해서 필요한 제반 가정들을 검토하였고, 종류식 설계에서의 최종 값인 임계유속 산정을 위한 몇 가지의 공식을 분석하였다. 이를 토대로 특정 공식을 개선하기 위한 방안을 실험결과를 토대로 제시하였다. 횡류식 설계에서 국제적으로 사용되고 있는 용량산정에 관한 지침은 화재공학적 의미가 전혀 없으며 관행적으로 적용되어 온 것임을 알 수 있었다. 뿐만 아니라 기존의 횡류식 환기설계에는 설계개념조차 명확하지 않음을 입증하였다. 즉 횡류식 시스템에서는 종류식에서의 "연기의 역류 방지를 위한 최소 유속의 유지"라는 개념조차 없이 환기용량이 결정되어 왔으며, 이것은 터널의 화재환기가 오염물질의 환기로부터 시작되어 정확한 화재공학적 분석이 결여되었기 때문이다. 이러한 문제를 해결하기 위한 시도로 횡류식 환기의 설계개념으로서 연기전파거리와 연기축적을 제안하였다. 축소모델 터널을 이용하여 연기전파거리에 관한 실험결과를 제시하였고, 이를 이용하여 기존의 관행대로 설계된 유럽의 터널들에 적용하였을 때 안전성에 문제가 있음을 보였다.