• Journal of KIISE:Computing Practices and Letters
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• v.13 no.6
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• pp.422-426
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• 2007

Personal mobile devices equipped with non-volatile storage such as MP3 player, PMP, cellular phone, and USB memory require safety for the stored data on the devices. One of the safety requirements is secure deletion, which is removing stored data completely so that the data can not be restored illegally. In this paper, we study how to design the secure deletion on Flash memory, commonly used as storage media for mobile devices. We consider two possible secure deletion policy, named zero-overwrite and garbage-collection respectively, and analyze how each policy affects the performance of Flash memory file systems. Then, we propose an adaptive file deletion scheme that exploits the merits of the two possible policies. Specifically, the proposed scheme applies the zero-overwrite policy for small files, whereas it employs the garbage-collection policy for large files. Real implementation experiments show that the scheme is not only secure but also efficient.

• Journal of KIISE:Computing Practices and Letters
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• v.14 no.3
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• pp.251-255
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• 2008

In most file systems, if a file is deleted, only the metadata of the file is deleted or modified and the file's data is still stored on the physical media. Some users require that deleted files no longer be accessible. This requirement is more important in embedded systems that employ flash memory as a storage medium. In this paper, we propose a secure deletion method for NAND flash file system and apply the method to YAFFS. Our method uses encryption to delete files and forces all keys of a specific file to be stored in the same block. Therefore, only one erase operation is required to securely delete a file. Our simulation results show that the amortized number of block erases is smaller than the simple encryption method. Even though we apply our method only to the YAFFS, our method can be easily applied to other NAND flash file systems.

• Proceedings of the Korean Society of Computer Information Conference
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• 2016.07a
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• pp.233-234
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• 2016

본 프로젝트는 편안하고 안전하게 세상과 소통하고 관심사를 공유할 수 있는 커뮤니티 사이트이다. 게시글에 수명을 설정하여 자동으로 글이 삭제되는 기능을 통해 사용자의 보안성을 향상시키며, 기본적으로 닉네임을 사용하여 안전한 익명성을 보장한다. 즉, 자동으로 게시글이 삭제되는 커뮤니티 웹 사이트로 사용자들의 일상, 관심사, 정보 공유 등을 게시글을 통해 공유하고 소통할 수 있고, 커뮤니티 활동에 따라 마일리지를 누적하여 게시글의 기본 수명을 연장 할 수도 있다.

• Journal of Oral Medicine and Pain
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• v.30 no.3
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• pp.375-381
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• 2005

Er:YAG laser has been considered a promising alternative to dental drill and many researches indicate that adjustment to variable parameters, including water flow rate, pulse energy and pulse repetition rate, can be made to improve ablation ability and efficiency of the laser. Of these parameters, addition of water spray during irradiation has been thought to ablate dental hard tissue more rapidly and safely. The purpose of this study was to investigate tooth ablation amount by Er:YAG laser irradiation as related to varied water flow rates added and, ultimately to find the most effective water flow rate for ablation. In addition, the temperature change of pulp chamber during irradiation was also monitored on the irradiated and opposite pulpal walls, respectively. An Er:YAG laser with contact mode was employed. Extracted human molars were split into two pieces for ablation experiment. Pulse energies of 200 and 300 mJ with a pulse repetition rate of 20 Hz and 5 water flow rates (1.6, 3.0, 5.0, 7.0, and 10.0 ml/min) were applied. Each irradiation was performed for 3 seconds. According to these parameters, experimental groups were divided into 10 subgroups which consisted of 5 specimens. For temperature experiment, another 5 tooth-specimens were prepared in the manner that pulp chamber was open through access cavity preparation and two temperature-measuring probes were placed respectively on the irradiated and the opposite walls of pulp chamber. From the experiment on ablation amount related to different water flow rates, it was shown that the least water flow rate of 1.6 ml/min ablated more than any other water flow rates (p<0.000). When the irradiation for 3 seconds, combined with the pulse repetition time of 20Hz and the water flow rate of 1.6 ml/min was done to tooth specimen, the temperature rise was not noticeable both on the irradiated and the opposite pulpal walls (less than 3$^{\circ}C$) and there was no significant difference in temperature rise between the two pulse energies, 200 and 300 mJ. From the results of this study, it is suggested that tooth ablation with Er:YAG laser can be done effectively and safely at a energy between 200 and 300 mJ/pulse and a pulse repetition rate of 20 Hz when the lasing is conjugated with the water flow rate of 1.6ml/min.

• 정보화사회
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• s.111
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• pp.26-30
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• 1997

정보사회가 고도화될수록 통신정보의 불법적인 도청과 함게, 원거리 엑세스에 발생되는 개인식별 문제, 컴퓨터 정보의 무단삭제 및 변조 등의 무결성 문제가 심각한 문제로 대두되고 있다. 이런 문제를 해결하는 암호기술이 정보보호 프로토콜(Cryptographic Protocol:또는 암호 프로토콜)분야이다.

• Proceedings of the Korea Information Processing Society Conference
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• 2000.04a
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• pp.562-568
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• 2000

분산 가상 현실 시스템에서는 네트웍크상에서 분산되어 있는 다수의 사용자들에게 하나의 공통된 가상 공간 객체를 제공하고 있다 이러한 가상 공간에서 다수의 사용자들은 상호작용을 자유롭게 실시간으로 하여야 할 뿐만 아니라 객체들을 공유공간 내에서 결합하거나 추가,삭제, 검색 등을 안전하게 수행해야 한다. 본 논문은 웹상에서 다중 사용자들이 원하는 특정 이미지나 텍스트 등을 실시간으로 안전하게 처리될 수 있는 모델을 제안하고 이를 반도체 레이져 마킹 시스템에 적용시켜 보았다.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.17 no.3
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• pp.69-80
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• 2007

To protect personal information when releasing data, a general privacy-protecting technique is the removal of all the explicit identifiers, such as names and social security numbers. De-identifying data, however, provides no guarantee of anonymity because released information can be linked to publicly available information to identify them and to infer information that was not intended for release. In recent years, two emerging concepts in personal information protection are k-anonymity and $\ell$-diversity, which guarantees privacy against homogeneity and background knowledge attacks. While these solutions are signigicant in static data environment, they are insufficient in dynamic environments because of vulnerability to inference. Specially, the problem appeared in record deletion is to deconstruct the k-anonymity and $\ell$-diversity. In this paper, we present an approach to securely anonymizing a continuously changeable dataset in an efficient manner while assuring high data quality.

• Life and Agrochemicals
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• v.26 no.5 s.208
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• pp.32-36
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• 2005

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.107-107
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• 2023

자연재해대책법은 각 지방자치단체의 장이 매 5년마다 우수유출저감대책을 수립하도록 정하고 있다. 이에, 행정안전부는 2018년 '지방자치단체 우수유출저감대책 세부수립기준'을 고시하여 우수유출저감대책 수립에 필요한 세부사항을 정하고 있다. 최근에는 자연재해대책법의 개정, 제도 변화, 수립기준 고시 이후의 여건 변화 등으로 인하여 새로운 수립지침의 필요성이 대두되고 있다. 이에 본 연구에서는 우수유출저감시설 세부 수립기준의 항목을 검토하고 최근의 상황을 반영하여 우수유출저감대책의 효율적 운영을 위한 개정안을 제시하였다. 주요 개정 내용으로는 우수유출저감대책의 목표를 목표홍수량의 안전한 통수로 변경하고, 자연재해대책법 개정사항을 반영하여 유하시설을 우수유출저감대책의 범위에 포함하였다. 우수유출저감대책 수립 제도의 목적 변화를 반영하여 침투시설의 의무 배분량을 삭제하고, 목표연도 홍수량 개념을 삭제하였다. 또한, 대상 강우량을 50년 빈도 강우량, 방재성능목표강우량, 기왕최대강우량을 고려하여 설정하도록 하였다. 본 연구의 결과가 지자체의 우수유출저감대책 수립 및 효율적 운영에 도움이 되기를 기대한다.

• Journal of Digital Convergence
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• v.18 no.8
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• pp.511-518
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• 2020

The purpose of this study is to emphasize the importance of the safety and health ability to safely protect body in a risky situation in infancy, but due to the lack of a valid test tool for measuring infant safety knowledge, measure the safety and health knowledge of infants. In order to achieve the purpose of the study, opinions of education experts and early childhood education experts were collected, and suitable factors for measuring safety and health knowledge of children aged 3-5 years were extracted. The measurement questions developed based on this were surveyed on 186 children aged 3-5 years old to verify the relevance of the question composition and the reliability of the contents. In the distribution of the item response, values of 0.8 or less were deleted, and items with a correlation of r<.40 or less were also deleted, and the reliability test showed more than .70. After exploratory factor analysis, it was developed into 23 questions in 3 areas. The total score of safety and health knowledge for the final question and the degree of correlation were above .80. The tool for measuring child safety and health knowledge developed in this study was confirmed to be appropriate for item discrimination, item reliability, and content validity, and thus will be used as basic data for measuring child safety and health knowledge. After the early childhood safety and health education program is implemented, Further research should verify the effectiveness of the early childhood safety and health program.