• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.5
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• pp.1102-1110
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• 2005

In this paper, we proposed a advanced approach to resolve the trade-off problem for the threshold value determining the photo-consistency in the previous algorithms. The threshold value for the surface voxel is substituted the photo-consistency value of the inside voxel. As iterating the voxel coloring process, the threshold is approached to the optimal value for the individual surface voxel. we present an energy minimization formulation of the binary labeling problem that surface voxels classify into opacity or transparency. The energy formula consists of the data term and the smoothness term. As considering neighboring voxels in the labeling problem, the unevenness of reconstructed surface is reduced. The labeling whose energy is the global minimum can be computed using a graph cut.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.48 no.1
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• pp.33-45
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• 2011

In this paper, we present a method for extracting video objects efficiently by using the modified graph cut algorithm based on contour information. First, we extract objects at the first frame by an automatic object extraction algorithm or the user interaction. To estimate the objects' contours at the current frame, motion information of objects' contour in the previous frame is analyzed. Block-based histogram back-projection is conducted along the estimated contour point. Each color model of objects and background can be generated from back-projection images. The probabilities of links between neighboring pixels are decided by the logarithmic based distance transform map obtained from the estimated contour image. Energy of the graph is defined by predefined color models and logarithmic distance transform map. Finally, the object is extracted by minimizing the energy. Experimental results of various test images show that our algorithm works more accurately than other methods.

• Communications of the Korean Mathematical Society
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• v.25 no.4
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• pp.609-614
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• 2010

We prove that if graphs of bounded degree are roughly isometric to each other, then the spaces of bounded energy finite solutions of the Schr$\ddot{o}$dinger operator on the graphs are isomorphic to each other. This is a direct generalization of the results of Soardi [5] and of Lee [3].

• Nuclear Engineering and Technology
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• v.48 no.2
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• pp.386-403
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• 2016

The safety of nuclear power plants is analyzed by a probabilistic risk assessment, and the fault tree analysis is the most widely used method for a risk assessment with the event tree analysis. One of the well-known disadvantages of the fault tree is that drawing a fault tree for a complex system is a very cumbersome task. Thus, several graphical modeling methods have been proposed for the convenient and intuitive modeling of complex systems. In this paper, the reliability graph with general gates (RGGG) method, one of the intuitive graphical modeling methods based on Bayesian networks, is improved for the reliability analyses of dynamic systems that have various operation modes with time. A reliability matrix is proposed and it is explained how to utilize the reliability matrix in the RGGG for various cases of operation mode changes. The proposed RGGG with a reliability matrix provides a convenient and intuitive modeling of various operation modes of complex systems, and can also be utilized with dynamic nodes that analyze the failure sequences of subcomponents. The combinatorial use of a reliability matrix with dynamic nodes is illustrated through an application to a shutdown cooling system in a nuclear power plant.

• Nuclear Engineering and Technology
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• v.51 no.2
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• pp.444-452
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• 2019

To assess the availability of a nuclear power plant's dynamic systems, it is necessary to consider the impact of dynamic interactions, such as components, software, and operating processes. However, there is currently no simple, easy-to-use tool for assessing the availability of these dynamic systems. The existing method, such as Markov chains, derives an accurate solution but has difficulty in modeling the system. When using conventional fault trees, the reliability of a system with dynamic characteristics cannot be evaluated accurately because the fault trees consider reliability of a specific operating configuration of the system. The dynamic reliability graph with general gates (DRGGG) allows an intuitive modeling similar to the actual system configuration, which can reduce the human errors that can occur during modeling of the target system. However, because the current DRGGG is able to evaluate the dynamic system in terms of only reliability without repair, a new evaluation method that can calculate the availability of the dynamic system with repair is proposed through this study. The proposed method extends the DRGGG by adding the repair condition to the dynamic gates. As a result of comparing the proposed method with Markov chains regarding a simple verification model, it is confirmed that the quantified value converges to the solution.

• IEMEK Journal of Embedded Systems and Applications
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• v.10 no.5
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• pp.281-296
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• 2015

This paper describes a novel disaster evacuation system using embedded systems such as smart devices for crisis and emergency management. In indoor environments deployed with the Bluetooth Low Energy(BLE) beacons, smart devices detect their indoor positions from beacon messages and interact with Map Server(MS) and Route Server(RS) in the Internet over the LTE and/or Wi-Fi functions. The MS and RS generate an optimal path to the nearest emergency exit based on a novel graph generation method for less route computation, called the Disaster Evacuation Graph(DEG), for each smart device. The DEG also enables efficient processing of some constraints in the computation of route, such as load balancing in situation of different capacities of paths or exits. All data interfaces among three system components, the MS, RS, smart devices, have been defined for modular implementation of our disaster evacuation system. Our experimental system has been deployed and tested in our building thoroughly and gives a good evidence that the modular design of the system and a novel approach to compute emergency route based on the DEG is competitive and viable.

• Journal of the Korean Ceramic Society
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• v.53 no.5
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• pp.521-528
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• 2016

Kinetic Monte Carlo (KMC) and graph searches show that proton conduction limiting barriers and trajectories in $BaZr_{0.875}Y_{0.125}O_3$ are affected by the presence of other protons. At 1000 K, KMC limiting conduction barriers increase from 0.39 eV to 0.45 eV as the proton number is increased. The proton-proton radial distribution begins to rise at $2{\AA}$ and peaks at $4{\AA}$, which is half the distance expected, based on the proton concentration. Density functional theory (DFT) calculations find proton/proton distances of 2.60 and $2.16{\AA}$ in the lowest energy two-proton configurations. A simple average of the limiting barriers for 7-10 step periodic long range paths found via graph theory at 1100 K shows an increase in activation barrier from 0.32 eV to 0.37 eV when a proton is added. Both KMC and graph theory show that protons can affect each other's pathways and raise the overall conduction barriers.

• Journal of KIISE:Computing Practices and Letters
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• v.14 no.3
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• pp.281-285
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• 2008

Wireless sensor networks are closely related with the geometric environment in which they are deployed. We consider the probable case when a routing protocol runs on an environment with many complex obstacles like downtown surroundings. In addition, there are no unrealistic assumptions in order to increase practicality of the protocol. Our goal is to find a routing protocol for maximizing network lifetime by using only connectivity information in the complex sensor network environment. We propose a topology-based routing algorithm that accomplishes good performance in terms of network lifetime and routing complexity as measures. Our routing algorithm makes routing decision based on a weighted graph as topological abstraction of the complex network. The graph conduces to lifetime enhancement by giving alternative paths, distributing the skewed burden. An energy estimation method is used so as to maintain routing information without any additional cost. We show how our approach can be used to maximize network lifetime and by extensive simulation we prove that out approach gives good results in terms of both measures-network lifetime and routing complexity.

• Journal of the Semiconductor & Display Technology
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• v.16 no.2
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• pp.70-74
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• 2017

Given two stereo images of a scene, it is possible to recover a 3D understanding of the scene. This is the primary way that the human visual system estimates depth. This process is useful in applications like robotics, where depth sensors may be expensive but a pair of cameras is relatively cheap. In this work, we combined our interests to implement a graph cut algorithm for stereo correspondence, and performed evaluation against a baseline algorithm using normalized cross correlation across a variety of metrics. Experimental trials revealed that the proposed descriptor exhibited a significant improvement, compared to the other existing methods.

• Proceedings of the Korean Nuclear Society Conference
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• 2004.10a
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• pp.337-338
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• 2004