• Journal of the Korean Geotechnical Society
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• v.37 no.4
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• pp.19-26
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• 2021

The high-level radioactive waste (HLW) produced from nuclear power plants is disposed in a rock-mass at a depth of hundreds meters below the ground level. Since HLW is very dangerous to human being, it must be disposed of safely by the engineered barrier system (EBS). The EBS consists of a disposal canister, backfill material, buffer material, and so on. When the components of EBS are installed, gaps inevitably exist not only between the rock-mass and buffer material but also between the canister and buffer material. The gap can reduce water-retarding capacity and heat release efficiency of the buffer material, so it is necessary to investigate properties of gap-filling materials and to analyze gap spacing effect. Furthermore, there has been few researches considering domestic disposal system compared to overseas researches. In this reason, this research derived the peak temperature of the bentonite buffer material considering domestic disposal system based on the numerical analysis. The gap between the canister and buffer material had a minor effect on the peak temperature of the bentonite buffer material, but there was 40% difference of the peak temperature of the bentonite buffer material because of the gap existence between the buffer material and rock mass.

• Tunnel and Underground Space
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• v.33 no.4
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• pp.228-243
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• 2023

Bentonite is widely recognized and utilized as a buffer material in high-level radioactive waste repositories, mainly due to its favorable characteristics such as swelling capability and low permeability. Bentonite buffers play an important role in ensuring the safe disposal of radioactive waste by providing a low permeability barrier and effectively preventing the migration of radionuclides into the surrounding rock. However, the long-term performance of bentonite buffers still remains a subject of ongoing research, and one of the main concerns is the erosion of the buffer induced by swelling and groundwater flow. The erosion of the bentonite buffer can significantly impact repository safety by compromising the integrity of buffer and leading to the formation of colloids that may facilitate the transport of radionuclides through groundwater, consequently elevating the risk of radionuclide migration. Therefore, it is very important to numerically quantify the erosion of bentonite buffer to evaluate the long-term performance of bentonite buffer, which is crucial for the safety assessment of high-level radioactive waste disposal. In this technical note, Two-region model is introduced, a proposed model to simulate the erosion behavior of bentonite based on a dynamic bentonite diffusion model, and quantitative evaluation is conducted for the bentonite buffer erosion with this model.

• Environmental Engineering Research
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• v.16 no.2
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• pp.61-67
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• 2011

The water quality from nonpoint source run off results from different land use types has been studied. The construction of a buffer strip is one method of nonpoint source pollutant control. The Soil and Water Assessment Tool (SWAT) model has been applied to estimate the pollutant removal through the buffer strip. When the non-business land has been changed into grass to form a buffer-strip, the change of land use effects the results of the model according to measures of the water quality. The data from a water level station within the watershed in the years 2006 and 2007 was used for calibration and validation of the model. Under the rainfall conditions in 2007, the removal rates of SS, BOD, TN, TP were 11.5%, 9.5%, 1.2%, and 4.5%, respectively. During the rainy days, the removal rates at the buffer strip were 92.3% of SS, 91.2% of BOD, 82.4% of TN, and 83.5% of TP. The pollutants from nonpoint sources were effectively removed by over 80% as they passed through the buffer strips. Rainfall resulted in soil erosion, which led to an increase in the SS concentration, therefore, the construction of buffer strips protected the streams from SS inflows. Since TN concentrations are affected by the inflows of ground water and the N concentration of the rainfall, the removal rate of TN was relatively lower than for the other pollutants.

• Journal of KIISE:Computing Practices and Letters
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• v.7 no.6
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• pp.703-714
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• 2001

In C language, a local buffer overflow in stack can destroy control information stored near the buffer. In case the buffer overflow is used maliciously to overwrite the stored return address, the system is exposed to serious security vulnerabilities. This paper analyzes the process of buffer overflow hacking and methodologies to avoid the attacks in details. And it proposes a device of static buffer overflow detection by using function summary and tracking information flow of buffer domain at assembly source code level(SASS, Static Assembly Source code Scanner) and then show the feasibility and validity of it by implementing a prototype in Pentium based Linux environment.

• Journal of the Korean Institute of Landscape Architecture
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• v.32 no.2
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• pp.25-35
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• 2004

The purpose of the study is to analyze the existing situation of the green buffer zone in the large scale industrial site and other major residential apartment areas. In this study, it is specifically intended that the planning guideline be upgraded to adopt future landuse trends and thus to suggest design criteria for management of the buffer zone. The framework of the analysis is to review the current landuse, noise reduction, ecological implications and landscape in general. Although the major function of a green buffer zone is considered to protect the residential area from various hazards of industrial, traffic, and visual environment, the situation is that most of the zones are maintained at a minimum level of services by local government. The study carried out intensively almost every type of case studied throughout the country, which implies that the management of the green buffer zone should be expanded physically enough to function for its original objectives. The study recommends that ecological management of the green buffer zone be emphasized and therefore the criteria for this purpose as well as noise issue should be developed prior to the landuse aspects. The study suggests specific guidelines for planning and design for the green buffer zone development. This study should be verified positively through the sustainable monitoring and requires nationwide and overall examination so that it may be applied to whole green spaces.

• Nuclear Engineering and Technology
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• v.55 no.11
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• pp.4120-4124
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• 2023

High-level radioactive waste produced by nuclear power plants are disposed subterraneously utilizing an engineered barrier system (EBS). A gap inevitably exists between the disposal canisters and buffer materials, which may have a negative effect on the thermal transfer and water-blocking efficiency of the system. As few previous experimental works have quantified this effect, this study aimed to create an experimental model for investigating differences in the temperature changes of bentonite buffer in the presence and absence of air gaps between it and a surrounding stainless steel cell. Three test scenarios comprised an empty cell and cells partially or completely filled with bentonite. The temperature was measured inside the buffers and on the inner surface of their surrounding cells, which were artificially heated. The time required for the entire system to reach 100℃ was approximately 40% faster with no gap between the inner cell surface and the bentonite. This suggests that rock-buffer spaces should be filled in practice to ensure the rapid dissipation of heat from the buffer materials to their surroundings. However, it can be advantageous to retain buffer-canister gaps to lower the peak buffer temperature.

• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.6
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• pp.415-423
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• 2018

This study uses a level selection algorithm with fixed sampling frequency for modular multilevel converter (MMC) systems. Theoretically, the proposed method increases the level infinitely while the sampling time remains the same. The proposed method called cluster stream buffer (CSB) consists of several clusters, wherein each cluster is composed of 32 submodules that depend on the level of the submodules in the MMC system. To increase the level of the MMC system, additional clusters are used, and the sampling time between clusters is determined from the sampling time between levels needed for utilizing the entire level from the MMC system. This method is crucial in the control of MMC-type HVDC systems because it improves scalability and precision.

• Journal of Electrical Engineering and information Science
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• v.3 no.2
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• pp.274-279
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• 1998

We investigate a Leaky Bucket(LB) scheme with a threshold in the data buffer, where leaky rate changes depending on the contents of data buffer. We use the fluid flow model for the analysis of the LB scheme with a threshold. We model the bursty input source as markov modulated fluid flow(MMFF) As performance measures we obtain loss probability and mean delay. We present some numerical results to show the effects of the level of a threshold, the rate of token generation, the size of token pool, and the size the data buffer on the performances of the LB scheme with a threshold.

• Journal of Korea Multimedia Society
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• v.13 no.3
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• pp.349-358
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• 2010

Adaptability is an important issue in video streaming over mobile environments, since the clients may request videos with great differences in their workload. In this paper, we propose the issues in limited bandwidth scheduling for efficient MPEG-4 video stream transmission over a mobile or wireless network. In the phase of admission control, the amount of bandwidth allocated to serve a video request is the mean bandwidth requirement of its requested video. The dynamic allocation of bandwidth in the phase of scheduling depends on the playback buffer levels of the clients with an objective to make it more adaptive to the playback situation of individual clients. In the proposed RTA scheduling protocol, more bandwidth may be allocated temporarily to the client whose buffer level is low. By employing the buffer level based scheduling policy, this protocol attempts to maximize the real-time performance of individual playback while minimizing the impact of transient overloading. Extensive simulation experiments have been performed to investigate the performance characteristics of the RTA protocol as comparing with BSBA protocol. This RTA protocol shows the better performance by transferring more frames than BSBA protocol.Computer simulations reveals that the standard deviation of the bit rate error of the proposed scheme is 50% less than that of the conventional method.

• Tunnel and Underground Space
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• v.24 no.4
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• pp.316-324
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• 2014

In the underground 500 m depth, the high level radioactive waste disposal system is made by boring the tunnel in the base rock and putting the high level waste disposal canister that is the surrounding form with the buffer material. According to the many statistics, it is the tendency that the earthquake increases in the Korean peninsula every year. In case that the earthquake is generated, the disposal canister in the rock mass can be broken due to the shearing force in the underground. Furthermore, a major environmental problems can be caused by the radioactive harmful substances. In this study, the earthquake-proof type buffer material was developed with the protection method safely on the earthquake. The main parameter having an effect on the earthquake-resistant performance was analyzed and the earthquake-proof type buffer material was designed. The shear analysis model was developed and the performance of the earthquake-proof type buffer material was evaluated by using ABAQUS.