• Journal of Radiation Protection and Research
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• v.29 no.3
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• pp.205-212
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• 2004

Three-dimensional wind field and atmospheric dispersion models have been developed for estimating the concentration distributions of radioactive materials released into atmosphere. The field tracer experiment near the Kori nuclear power plant located over complex terrain was carried out for validating the atmospheric dispersion model. The wind fields were one of the most important factors for calculating the concentration. Therefore several numerical simulations using the measured wind data were performed to get more accurate concentration distributions compared with the analyzed values of the tracer gas. The calculated concentration distributions agreed well in the case of the usage of the more measured wind data in wind field model.

• Journal of Radiation Protection and Research
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• v.29 no.3
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• pp.157-163
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• 2004

Atmospheric dispersion modelling has been widely used to predict the fate and transport of radioactive or toxic materials released from nuclear facilities which is an unlikely accidental event. To improve the forecasting performance of the dispersion model, it is required that source rate and dispersion characteristics must be defined appropriately. Generally, source term of the radioactive materials is much uncertain at the early phase of an accidental event. In this study, we computed the source rate with the experimental field data monitored at the Yeoung-Kwang nuclear site and obtained the optimal source rate to minimize the errors between the measured concentrations and the computed ones by the Gaussian plume model. Computed source term showed a good result within 24% of the artificially released source rate.

• Journal of The Korean Association For Science Education
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• v.22 no.2
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• pp.378-386
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• 2002

In this study, the students' responses on the chemistry items of in the general science of College Scholastics Ability Test (CSAT) implemented for the past 3 years since 1999 were investigated. The number of items by content and inquiry process, the average percent correct by content and inquiry process, the distribution of items by the level of percent correct, and the items with high and/or low percent correct were analysed. There were the fewest items in 'environment' area, especially in 'ozon layer', no test item had been made. The most difficult content area was 'acid rain' in 'environment'. By inquiry process, the most number of items belonged to 'analyzing & interpreting data', and 'identifying problems & formulating hypothesis' was the most difficult process. No test item came under the level of 'very difficult', and many items under the 'easy' or 'very easy' level. Students were generally poor at solving test items demanding several concepts, and very good at simply requiring basic concept treated in lower grade. Educational implications are discussed.

• Journal of the Korea Society for Simulation
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• v.16 no.1
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• pp.1-9
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• 2007

The development of efficient Qualify of Service (QoS) routing algorithms in high speed networks is extremely difficult to achieve, because in order to operate, divergent services require various quality conditions. If the parameter of concern is to measure the delay on a specific link, the routing algorithm obtains the Least Delay (LD) path. Meanwhile, if the parameter is to measure the link cost, the Least Cost (LC) path is calculated. The Delay Constrained Least Cost (DCLC) path problem of the mixed issues on the LD and LC has been shown to be NP-hard. The path cost of LD path is relatively more expensive than that of the LC path, and the path delay of the LC path is relatively higher than that of the LD path in the DCLC problem. In this paper, we introduce the new factor for balancing cost and delay. The simulation result shows that our introduced factor is satisfied to solve the DCLC problem.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.12
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• pp.562-567
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• 2003

Lightning arresters are deteriorated by repetition of protective operation against overvoltages or impulse currents in environments of its use. If a deteriorated arrester is left in power lines, it can lead to an accident such as a line to ground fault even in a normal system. Therefore, it is necessary to eliminate the deteriorated arrester in advance by checking the soundness of arresters on a regular basis, and to ensure the reliability of power systems by preventing accidents. Various deterioration diagnostic techniques and devices are suggested, and most of which measure leakage current components as an indicator of arrester ageing. However, the techniques based on the magnitude of leakage current measure simply RMS or peak value of leakage current components and do not provide detailed information needed in the diagnosis. In this study, we found that the wave height distributions of the total leakage currents are remarkably changed or a new wave height are produced with the progress of arrester deterioration. To propose a new technique for the diagnosis, we designed a leakage current detection unit and an analysis program which can measure leakage current magnitudes and analyze wave height distributions. From the experimental results, we confirmed that the proposed technique by analyzing the wave height distribution can simply diagnose the mode of defects such as a partial damage and an existence of punctures in arresters as well as deterioration of arresters.

• Journal of KIISE:Software and Applications
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• v.31 no.2
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• pp.203-212
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• 2004

The watermarking is a method to achieve the copyright protection of multimedia contents. Among several media, the left documents show very peculiar properties: block/line/word patterning, clear separation between foreground and background areas. So algorithms specific to the text documents are required that meet those properties. This paper proposes a novel watermarking algorithm for the grayscale text document images. The algorithm inserts the watermark signals through the edge direction histograms. A concept of sub-image consistency is developed that the sub-images have similar shapes in terms of edge direction histograms. Using Korean, Chinese, and English document images, the concept is evaluated and proven to be valid over a wide range of document images. To insert watermark signals, the edge direction histogram is modified slightly. The experiments were performed on various document images and the algorithm was evaluated in terms of imperceptibility and robustness.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.7
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• pp.2648-2653
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• 2010

Three books of home economics were published in Korea 1907 and approved as textbooks for women's education by Korean government from 1908 to 1910 and by the Choseon Government-General from 1912 to 1914. The textbooks contained modern knowledge about housing which was focused on hygine matters and most systematic among the knowledge of that time. The original book of the three was Sinsen Gajunhak(新選家政學) by Shimoda Yutako published in Japan 1990 after her surveying western home economics knowledge. It means the modern housing knowledge educated in Korea around 1910 was affected by Western modern thinking in home economics field that gave the responsibility of housing cleanness for family members' health to housewives. So the knowledge even made the educated women to practice their learning only as wives, which was still traditional.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.10
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• pp.662-667
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• 2014

B-doped Si nanoparticles were synthesized by using inductive coupled plasma and specially designed double tube reactor, and their microstructures were investigated. 0~10 sccm of $B_2H_6$ gas was injected during the synthesis of Si nanoparticles from $SiH_4$ gas. Highly crystalline Si nanoparticles were synthesized, and their crystallinity did not change with increase of $B_2H_6$ flow rates. From SEM measurement, their particle sizes were approximately 30 nm regardless of $B_2H_6$ flow rates. From SIMS analysis, almost saturation of B in Si nanoparticles was detected only when 1 sccm of $B_2H_6$ was injected. When $B_2H_6$ flow rate exceeded 5 sccm, higher concentration of B than solubility limit was detected even if any secondary phase was not detected in XRD or HR-TEM results. Due to their high electronic conductivity, those heavily B-doped Si nanoparticles can be a potential candidate for an active material in Li-ion battery anode.

• Membrane Journal
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• v.23 no.5
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• pp.367-374
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• 2013

In the present study, Pebax-2533 plate membranes were prepared by drying precursor solutions which were obtained by dissolving Pebax-2533 polymer in 1-Propanol/n-Butanol mixed solvents. And then the $CO_2$ and $N_2$ permeation behaviors were tested by using a time-lag system. The prepared Pebax-2533 plate membranes showed a considerable $CO_2/N_2$ separation performance : the $CO_2$ permeability was 130 to 288 barr, and the $CO_2/N_2$ permselectivity was 5-8. The $CO_2$ permeation data obtained by varying feed pressure, permeation temperature, and solvent composition announced that not only the $CO_2$ sorption but also the $CO_2$ diffusion is equally important in the overall $CO_2$ permeation.

• Journal of KIISE:Computer Systems and Theory
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• v.28 no.11
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• pp.581-591
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• 2001

We consider some problems of remote file accesses of multiple clients in mobile computing environments. In this environment, user mobility affects file access latency. Mobile hosts have severe resource constraints in terms of limited size of non-volatile storage. Thus, the burden of computation and communication load raise file access latency. In this paper, we propose a scheme for reducing the file access latency through the file migration. The objective is to minimize of file accesses for all mobile hosts which delivering the file to clients as quickly as possible. We develope an on-demand scheme which determines when the file server should migrate files to another server, or when it should transfer files to mobile hosts. Using simulation, we examine the effects which parameters such as file access frequency, file size, mobility rate have on file system access latency. Through simulation results, we show that our proposed migration scheme is effective in reducing the access latency on the requested file of a mobile host with high access rate and low mobility.