• Journal of the Korean Society for Nondestructive Testing
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• v.26 no.2
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• pp.69-76
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• 2006

TRISO(tri-isotropic)-coated fuel particle technology is utilized owing to its higher stability at a high temperature and Its efficient retention capability for fission products In the HTGR(high temperature gas-reeled reactor). The typical spherical TRISO fuel panicle with a diameter of about 1mm is composed of a nuclear fuel kernel and outer coating layers. The outer coating layers consist of a buffer PyC(pyrolytic carbon) layer, Inner PyC(1-PyC) layer, SiC layer, and outer PyC(O-PyC) layer Most of the Inspection Items for the TRTSO-coated fuel particle depend on destructive methods. The coating thickness of the TRISO fuel particle can be nondestructively measured by the X-ray radiography without generating radioactive wastel. In this study, the coaling thickness for the simulated TRISO-coated fuel particle with $ZrO_2$ kernel Instead of $%UO_2$ kernel was measured by using micro-focus X-ray radiography with micro-focus X-ray generator and flat panel detector The radiographic image was also enhanced by image processing technique to acquire clear boundary lines between coating layers. The coaling thickness wat effectively measured by applying the micro-focus X-ray radiography The inspection process for the TRISO-coated fuel particles will be improved by the developed micro-focus X-ray radiography and digital image processing technology.

• Tunnel and Underground Space
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• v.30 no.4
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• pp.404-416
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• 2020

An analytical procedure for calculating the failure load of a V-shaped rock notch under two-dimensional stress conditions was developed based on the slip-line plastic analysis method. The key idea utilized in the development is the fact that the α-line, one of the slip-lines, extends from the rock notch surface to the horizontal surface outside the notch when the rock around the notch is in the plastic state, and that there exists an invariant which is constant along the α-line. Since the stress boundary condition of the horizontal surface outside the rock notch is known, it is possible to calculate the normal and shear stresses acting on the rock notch surface by solving the invariant equation. The notch failure load exerted by the wedge was calculated using the calculated stress components for the notch surface. Rock notch failure analysis was performed by applying the developed analytical procedure. The analysis results show that the failure load of the rock notch increases with exponential nonlinearity as the angle of the notch and the friction of the notch surface increase. The analytical procedure developed in this study is expected to have applications to the study of fracture initiation in rocks through wedge-shaped notch formation, calculation of bearing capacity of the rock foundation, and stability analysis of rock slopes and circular tunnels.

• Geophysics and Geophysical Exploration
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• v.17 no.4
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• pp.216-230
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• 2014

Based on the interpretation of 3D seismic profiles acquired in the northwestern area of the Ulleung Basin, East Sea, the shallow sediments consist of five seismic units separated by regional reflectors. An anticline is present in the study area that documents activity of many faults. Bottom simulating reflectors are characterized by high RMS amplitude. Acoustic blanking with low RMS amplitude is distinctively recognized in the gas hydrate stability zone. Seismic attribute analysis shows that if gas hydrates are underlain by free gas, the high reflection strength and the low instantaneous frequency are displayed below the boundary between them. Whereas, if not, the reflection strength is low and instantaneous frequency is high continuously below the gas hydrate zone. Based on the spectral decomposition of the bottom simulating reflector, the high envelope at the specific high frequency range indicates the generation of the tuning effect due to the lower free gas content. Four models for the occurrence of the gas hydrate are suggested considering the slope of sedimentary layers as well as the presence of gas hydrate or free gas.

• 한국지구물리탐사학회:학술대회논문집
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• 2002.09a
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• pp.46-66
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• 2002

High-resolution multichannel seismic data were collected in the coastal area near the Gori nuclear power plant to investigate Quaternary fault pattern and timing. A 12 channel streamer, a sparker, and a portable recorder were used for data acquisition. Because the group interval of the streamer was 6.25 m and the sparker can generate acoustic waves with the frequency content of up to 500 Hz, the data show a significant improvement both in horizontal and vertical resolution. The area surveyed is covered with 30-40 m thick Holocene sediments that constitute the mud belt along the southeastern coast of Korea. The survey area is characterized by the well discriminated Pleistocene and Holocene boundary and shallow gas-charged zones. A number of Quaternary faults were found in the sediment column, that are nearly vertical and extend north-south. The Quaternary faults, arranged at a spacing of a few hundred meters, suggest that they were formed in response to compression, although some of them reveal extensional characteristics. Locally, faults disrupt Incised-channel fills that are interpreted to have formed in the early stage of transgression after the beginning of the Holocene. Seismic sections suggest that shallow gas in the mud belt sediments made its way upward through the fractured fault planes. The tectonism responsible for the opening of the East Sea has not persisted since the late Miocene, but vigorous Quaternary faulting activity in the vicinity of the southeastern Korean Peninsula indicates that tectonic stability has yet to be achieved in this region underlain by the hotter than normal mantle.

• Journal of the Korean Society for Marine Environment & Energy
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• v.17 no.2
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• pp.81-89
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• 2014

The present study aims to design an optimized hull shape of a floating pendulum-type wave energy converter(WEC). The purpose of these structure is to improve the performance and stability of the WEC by reducing its motion under operating and survival wave conditions. In this study, motion reduction structures, like restoring and dampling plates were installed on a floating pendulum WEC that has been the subject of previous studies. Restoring plates were installed to increase the restoring force and shift the natural period to a shorter period. Damping plates were installed to shift the natural period to a longer period by increasing the added mass. The effects of the structures were then analyzed under different incident wave conditions. The design parameters for the motion reduction structures were size, shape, and installed position. The wave-induced motion characteristics and performance of the floating pendulum WEC were also investigated numerically. Based on the simulation results, we are able to optimize the motion reduction structure of the WEC, thus improving its efficiency and durability.

• The KIPS Transactions:PartB
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• v.12B no.7 s.103
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• pp.811-822
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• 2005

Automated text categorization is to classify free text documents into predefined categories automatically and whose main goals is to reduce considerable manual process required to the task. The researches to improving the text categorization performance(efficiency) in recent years, focused on enhancing existing classification models and algorithms itself, but, whose range had been limited by feature based statistical methodology. In this paper, we propose RTPost system of different style from i.ny traditional method, which takes fault tolerant system approach and data mining strategy. The 2 important parts of RTPost system are reinforcement training and post-processing part. First, the main point of training method deals with the problem of defining category to be classified before selecting training sample documents. And post-processing method deals with the problem of assigning category, not performance of classification algorithms. In experiments, we applied our system to documents getting low classification accuracy which were laid on a decision boundary nearby. Through the experiments, we shows that our system has high accuracy and stability in actual conditions. It wholly did not depend on some variables which are important influence to classification power such as number of training documents, selection problem and performance of classification algorithms. In addition, we can expect self learning effect which decrease the training cost and increase the training power with employing active learning advantage.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.12
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• pp.803-808
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• 2014

$Bi_{0.5+x}(Na_{0.78}K_{0.22})_{0.5-3x}TiO_3$ ceramics with an excess $Bi^{3+}$ and a deficiency of $Na^+$ and $K^+$ were synthesized by a conventional solid state reaction method. The structure and morphology of $Bi_{0.5+x}(Na_{0.78}K_{0.22})_{0.5-3x}TiO_3$ ceramics were characterized by X-ray diffraction and field emission scanning electron microscopy. The electric polarization and mechanical strain induced by external electric field, and the temperature dependence of dielectric constant were investigated. These results demonstrated that an ergodic relaxor phase can be induced by controls of the mole ratio of $Bi^{3+}$, $Na^+$ and $K^+$. A phase boundary between non-ergodic and ergodic relaxor phases can be observed at ambient temperature. The ergodic relaxor phase can be transferred to the ferroelectric phase by application of the electric field. The stability of the induced ferroelectric phases strongly depends on the mole ratio of $Bi^{3+}$, $Na^+$ and $K^+$. The maximum strain of 0.31% was observed in $Bi_{0.51}(Na_{0.78}K_{0.22})_{0.47}TiO_3$ ceramics sintered at $1,150^{\circ}C$ for 2 h.

• Korean Security Journal
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• no.61
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• pp.59-85
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• 2019

In the reality that the boundary between the real world and the virtual world disappears with the 4th Industrial Revolution, cyber crimes that occur beyond time and space have clear limitations in fulfilling their duties only with the police force of government organizations established under the real law system. The research method of this thesis is based on the literature research and the experience of security work. The purpose of this paper is to establish a social system where collective intelligence of each social field can participate voluntarily to respond to cyber crimes occurring beyond the time and space before the law and institutionalization. In addition, the social system in which collective intelligence in each social sector can participate voluntarily was established to define crime types in cyberspace in real time and to prevent crimes defined by the people themselves and the counter-measures had been proposed in order to form social consensus. First, it is necessary to establish a collective intelligent network-type cyberpolice volunteer system. The organization consists of professors of security and security related departments at universities nationwide, retired public officials from the National Intelligence Service, the National Police Agency, and the National Emergency Management Agency, security companies and the organizations, civilian investigators, security & guard, firefighting, police, transportation, intelligence, security, national security, and research experts. Second, private sector regulation should be established newly under the Security Business Act. Third, the safety guard of the collective intelligent cyberpolice volunteer system for the stability of the people's lives should strengthen volunteer work. Fourth, research lessons and legal countermeasures against cybercrime in advanced countries should be introduced. Fifth, the Act on the Protection of Personal Information, the Act on Promotion of Information and Communication Network Utilization and Information Protection, the Act on the Utilization and Protection of Credit Information, and the Special Act on the Materials and Parts Industry should be amended. Sixth, police officers should develop cybercrime awareness skills for proactive prevention activities.

• Membrane Journal
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• v.25 no.5
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• pp.373-384
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• 2015

In the past few decades, polymeric membrane has played an important role in gas separation applications. For the separation of $CO_2$, one of greenhouse gases, high permselectivity, long-term stability and scale-up are needed. However, conventional polymeric membranes have shown a trade-off relation between permeability and selectivity while inorganic materials are highly permeable but expensive. Mixed matrix membranes (MMMs) combining the advantages of both polymeric and inorganic materials have become a possible breakthrough for the next-generation gas separation membranes. The MMMs could be either symmetric or asymmetric but the latter is more preferred to improve the permeance. Important factors influencing the MMM fabrication include homogeneous distribution of inorganic particles and good interfacial contact between inorganic filler and organic matrix. Recently, metal organic frameworks (MOFs) have received much attention as a new class of porous crystalline materials and a potential candidate for $CO_2$ separation. Zeolitic imidazolate frameworks (ZIFs), a sub-branch of MOFs, are the most widely used in MMMs due to small particle size and appropriate pore size for $CO_2$ separation. One of the major issues associated with the incorporation of porous particles in a polymeric membrane is to control the microstructure of the porous particle materials such as particle size, orientation, and boundary conditions etc. In this review, major challenges surrounding MMMs and the strategies to tackle these challenges are given in detail.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.10
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• pp.300-309
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• 2016

Curved beams are increasingly used in buildings, vehicles, ships, and aircraft, which has resulted in considerable effort towards developing an accurate method for analyzing the dynamic behavior of such structures. The stability behavior of elastic curved beams has been the subject of many investigations. Solutions to the relevant differential equations have traditionally been obtained by the standard finite difference or finite element methods. However, these techniques require a great deal of computer time for a large number of discrete nodes with conditions of complex geometry and loading. One efficient procedure for the solution of partial differential equations is the differential quadrature method (DQM). This method has been applied to many cases to overcome the difficulties of complex algorithms and high storage requirements for complex geometry and loading conditions. Out-of-plane buckling of curved beams with rotatory inertia were analyzed using DQM under uniformly distributed radial loads. Critical loads were calculated for the member with various parameter ratios, boundary conditions, and opening angles. The results were compared with exact results from other methods for available cases. The DQM used only a limited number of grid points and shows very good agreement with the exact results (less than 0.3% error). New results according to diverse variation are also suggested, which show important roles in the buckling behavior of curved beams and can be used for comparisons with other numerical solutions or experimental test data.