• Tunnel and Underground Space
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• v.31 no.5
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• pp.333-359
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• 2021

Gases such as hydrogen and radon can be generated around the canister in high-level radioactive waste disposal systems due to several reasons including the corrosion of metal materials. When the gas generation rate exceeds the gas diffusion rate in the low-permeability bentonite buffer, the gas phase will form and accumulate in the engineered barrier system. If the gas pressure exceeds the gas entry pressure, gas can migrate into the bentonite buffer, resulting in pathway dilation flow and advective flow. Because a sudden occurrence of dilation flow can cause radionuclide leakage out of the engineered barrier of the radioactive waste disposal system, it is necessary to understand the gas migration behavior in the bentonite buffer to quantitatively evaluate the long-term safety of the engineered barrier. Experimental research investigating the characteristics of gas migration in saturated bentonite and research developing numerical models capable of simulating such behaviors are being actively conducted worldwide. In this technical note, previous gas injection experiments and the numerical models proposed to verify such behaviors are introduced, and the future challenges necessary for the investigation of gas migration are summarized.

• Tunnel and Underground Space
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• v.31 no.5
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• pp.309-332
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• 2021

Natural barrier systems surrounding the geological repository for the high-level radioactive waste should guarantee the hydraulic performance for preventing or delaying the leakage of radionuclide. In the case of the behavior of a crystalline rock, the hydraulic performance tends to be decided by the existence of discontinuities, so the coupled hydro-mechanical(HM) processes on the discontinuities should be characterized. The discontinuum modelling can describe the complicated behavior of discontinuities including creation, propagation, deformation and slip, so it is appropriate to model the behavior of a crystalline rock. This paper investigated the coupled HM processes in discontinuum modelling such as UDEC, 3DEC, PFC, DDA, FRACOD and TOUGH-UDEC. Block-based discontinuum methods tend to describe the HM processes based on the fluid flow through the discontinuities, and some methods are combined with another numerical tool specialized in hydraulic analysis. Particle-based discontinuum modelling describes the overall HM processes based on the fluid flow among the particles. The discontinuum methods that are currently available have limitations: exclusive simulations for two-dimension, low hydraulic simulation efficiency, fracture-dominated fluid flow and simplified hydraulic analysis, so it could be improper to the modelling the geological repository. Based on the concepts of various discontinuum modelling compiled in this paper, the advanced numerical tools for describing the accurate coupled HM processes of the deep geological repository should be developed.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.19 no.4
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• pp.125-135
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• 2009

Logs from various security system can reveal the attack trials for accessing private data without authorization. The logs can be a kind of confidence deriving factors that a certain IP address is involved in the trial. This paper presents a rule-based expert system for derivation of privacy violation confidence using various security systems. Generally, security manager analyzes and synthesizes the log information from various security systems about a certain IP address to find the relevance with privacy violation cases. The security managers' knowledge handling various log information can be transformed into rules for automation of the log analysis and synthesis. Especially, the coverage of log analysis for personal information leakage is not too broad when we compare with the analysis of various intrusion trials. Thus, the number of rules that we should author is relatively small. In this paper, we have derived correlation among logs from IDS, Firewall and Webserver in the view point of privacy protection and implemented a rule-based expert system based on the derived correlation. Consequently, we defined a method for calculating the score which represents the relevance between IP address and privacy violation. The UI(User Interface) expert system has a capability of managing the rule set such as insertion, deletion and update.

• Environmental and Resource Economics Review
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• v.30 no.1
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• pp.129-167
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• 2021

The emission trading system is an essential policy for reducing greenhouse gas emissions and converting low-carbon society. EU ETS is a good benchmark that is ahead of Korea's emission trading system in terms of operating period and design know-how. Therefore, this study focused on the key design elements of EU ETS phase 4 such as total emission allowances issued (Cap), free allocation method, carbon leakage list, market stability reserve, and innovation supporting system. In addition, we analyzed the impact of key design elements and their changes during EU ETS Phase 1 to 4 on the design and operation of Korea emission trading system in the future. First of all, the expected impact on the design of Korea emission trading system is to increase three demands: preparing benchmark renewal plans, establishing criteria for selecting free allocation industries that reflect domestic industrial structure and characteristics and introducing two-stage evaluations for free allocation industries, and preparing specific plan to support innovation and industries using allowance auction revenues. The next three impacts on the operation of Korea emission trading system are the increased needs for objective and in-depth impact assessment of plan and amendments, provision of system stability and response opportunities by quickly confirming plan and amendments prior to the implementation, and coordination of the emission trading system governance and stakeholder participation encouragement.

• Journal of the Korean GEO-environmental Society
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• v.23 no.5
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• pp.33-39
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• 2022

For a slag-cement-bentonite (slag-CB) cut-off wall, GGBS replaces a part of the cement mixed to build a CB cut-off wall, which is used to block the flow and leakage of pollutants or groundwater; prevent seawater infiltration; and repair or reinforcement an aged embankments. Slag-CB cut-off walls are used in various applications in different fields where groundwater control is required due to its excellent characteristics. Such properties include high strength, low permeability, high durability and chemical resistance. However, despite these advantages, slag-CB cut-off walls are not extensively studied in Korea and thus are not applied in many cases. Particularly, GGBS, which replaces cement in a mixture, has different properties depending on its country of production. Consequently, it is necessary to perform various studies on slag-CB cut-off walls that use GGBS produced in Korea in order to increase its usability. This study has evaluated the bleeding rate, setting time, strength, and permeability in relation to the cement replacement rate of GGBS produced in Korea for slag-CB cut-off walls, with the aim to increase its usability. The evaluation found that slag-CB cut-off walls, made of a mixture containing GGBS produced in Korea, have a lower bleeding rate and permeability, and higher strengththan CB cut-off walls. It was also analyzed that such improved performance is more effective with a higher cement replacement rate of GGBS.

• Journal of the Microelectronics and Packaging Society
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• v.28 no.4
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• pp.85-89
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• 2021

AlGaN-based UV-C light-emitting diodes (LEDs) were applied for p-type activation by electrochemical potentiostatic activation (EPA). The p-type activation efficiency was increased by removing hydrogen atoms through EPA treatment using a neutral Mg-H complex that causes high resistance and low conductivity. A neutral Mg-H complex is decomposed into Mg^- and H⁺ depending on the key parameters of solution, voltage, and time. The improved hole carrier concentration was confirmed by secondary ion mass spectroscopy (SIMS) analysis. This mechanism eventually improved the internal quantum efficiency (IQE), the light extraction efficiency, the leakage current value in the reverse current region, and junction temperature, resulting in better UV-C LED lifetime. For systematic analysis, SIMS, Etamax IQE system, integrating sphere, and current-voltage measurement system were used, and the results were compared with the existing N₂-annealing method.

• Journal of the Korea Society of Computer and Information
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• v.27 no.12
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• pp.131-139
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• 2022

In this paper, to verify the authenticity of UxNB that assists terrestrial base stations, the solutions for SI (System Information) security presented in 3GPP TR 33.809 are analyzed from the perspective of UxNB. According to the definition of 3GPP (Third Generation Partnership Project), UxNB is a base station mounted on a UAV (Unmanned Aerial Vehicle), is carried in the air by the UAV, and is a radio access node that provides a connection to the UE (User Equipment). Such solutions for SI security can be classified into hash based, MAC (Message Authentication Codes) based, and digital signature based, and a representative solution for each category is introduced one by one. From the perspective of verifying the authenticity of UxNB for each solution, we compare and analyze the solutions in terms of provisioning information and update, security information leakage of UxNB, and additionally required amount of computation and transmission. As a result of the analysis, the solution for verifying the authenticity of the UxNB should minimize the secret information to be stored in the UxNB, be stored in a secure place, and apply encryption when it is updated over the air. In addition, due to the properties of the low computing power of UxNB and the lack of power, it is necessary to minimize the amount of computation and transmission.

• Journal of the Korean Geotechnical Society
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• v.23 no.2
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• pp.47-60
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• 2007

Conventional active surface wave measurements performed using a transient or continuous source are often limited in the maximum depth of penetration due to the difficulty of generating low-frequency energy with reasonably portable sources. This limitation may inhibit accurate seismic site response calculations because of the inability to define deeper subsurface structure. By measuring surface wave generated by passive sources including microtremors and cultural noise, it is possible to overcome this problem and develop soil stiffness profiles to much larger depth. Reliability of dispersion estimates from the passive surface wave measurements is critical to present reliable shear wave velocity profiles and can be improved by the measurements and analyses of passive surface waves based on correct understanding of systematic errors included in passive dispersion data. In this study, the systematic errors caused by poor wavenumber resolution and energy leakage into sidelobes in passive tests are mainly explored. Recommendations for reliable passive surface wave measurements and dispersion estimates are presented and illustrated at a site in San Jose, California, U.S.

• Journal of the Korean Geosynthetics Society
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• v.22 no.4
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• pp.73-82
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• 2023

In this study, the optimal method for injection of neutralizer to restraint the leakage of acid drainage in embankment structure composed of pyrite rocks is proposed. Finite Element Analysis was performed to examine the seepage effect caused by injection of neutralizer into the embankment structure. The diameter of the neutralizer injection hole was selected as 50cm, the interval space of injection ranged from 1m to 4m and the injecting pressure ranged from 100kPa to 220 kPa were applied for the numerical analysis. According to the analysis results, the saturation time of the whole embankment structure was shown to be fast at a relatively low injecting pressure in the case of injecting interval space of 1.0m and injecting pressure of 130kPa and in the case of injecting interval space of 2.0m and injecting pressure of 160kPa. When the interval space of injection for saturation of whole embankment structure is selected as 3m, various injection pressures can be applied from 130kPa to 190kPa, and the saturation time of whole embankment is similar regardless of the injection pressure. Therefore, the optimal method for injection of neutralizer considering economic efficiency was selected as injecting interval space of 3.0m and injection pressure of 130kPa.

• Progress in Medical Physics
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• v.34 no.4
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• pp.41-47
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• 2023

Purpose: This study aimed to dosimetrically compare the technique of three-dimensional conformal radiotherapy (3D CRT), which is a traditional prophylactic cranial irradiation method, and the intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) techniques used in the last few decades with the dynamic conformal arc therapy (DCAT) technique. Methods: The 3D CRT, VMAT, IMRT, and DCAT plans were prepared with 25 Gy in 10 fractions in a Monaco planning system. The target volume and the critical organ doses were compared. A comparison of the body V₂, V₅, and V₁₀ doses, monitor unit (MU), and beam on-time values was also performed. Results: In planned target volume of the brain (PTV_Brain), the highest D99 dose value (P<0.001) and the most homogeneous (P=0.049) dose distribution according to the heterogeneity index were obtained using the VMAT technique. In contrast, the lowest values were obtained using the 3D CRT technique in the body V₂, V₅, and V₁₀ doses. The MU values were the lowest when DCAT (P=0.001) was used. These values were 0.34% (P=0.256) lower with the 3D CRT technique, 66% (P=0.001) lower with IMRT, and 72% (P=0.001) lower with VMAT. The beam on-time values were the lowest with the 3D CRT planning (P<0.001), 3.8% (P=0.008) lower than DCAT, 65% (P=0.001) lower than VMAT planning, and 76% (P=0.001) lower than IMRT planning. Conclusions: Without sacrificing the homogeneous dose distribution and the critical organ doses in IMRTs, three to four times less treatment time, less low-dose volume, less leakage radiation, and less radiation scattering could be achieved when the DCAT technique is used similar to conventional methods. In short, DCAT, which is applicable in small target volumes, can also be successfully planned in large target volumes, such as the whole-brain.