• The Journal of Korean Institute of Communications and Information Sciences
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• v.37A no.12
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• pp.1031-1037
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• 2012

We study an algorithm that can efficiently find square roots and cube roots by modifying Tonelli-Shanks algorithm, which has an application in Number Field Sieve (NFS). The Number Field Sieve, the fastest known factoring algorithm, is a powerful tool for factoring very large integer. NFS first chooses two polynomials having common root modulo N, and it consists of the following four major steps; 1. Polynomial Selection 2. Sieving 3. Matrix 4. Square Root. The last step of NFS needs the process of square root computation in Number Field, which can be computed via square root algorithm over finite field.

• Journal of Korea Multimedia Society
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• v.24 no.4
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• pp.558-568
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• 2021

The digital image to be accepted as legal evidence, it is important to verify the authentication of the digital image. This study proposes a method of authenticating digital images through three steps of comparing the file structure of digital images taken with iPhone, analyzing the encoding information as well as media logs of the iPhone storing the digital images. For the experiment, digital image samples were acquired from nine iPhones through a camera application built into the iPhone. And the characteristics of file structure and media log were compared between digital images generated on the iPhone and digital images edited through a variety of image editing tools. As a result of examining those registered during the digital image creation process, it was confirmed that differences from the original characteristics occurred in file structure and media logs when manipulating digital images on the iPhone, and digital images take with the iPhone. In this way, it shows that it can prove its forensic authentication in iPhone.

• Journal of the Korean Wood Science and Technology
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• v.50 no.5
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• pp.315-324
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• 2022

The termicidal activity and chemical components of wood vinegar from two sources of biomass, nipah fruit shells (NFS) and a mixture of shells and fiber (MSF), were evaluated against Coptotermes curvignathus. A no-choice test was carried out to evaluate their termicidal activity using filter paper samples treated with 2.5%, 5.0%, 7.5%, 10.0%, and 12.5% NFS or MSF vinegar. Both wood vinegars exhibited antitermitic activity against C. curvignathus. The results show that increased concentrations of NFS and MSF vinegar significantly increased termite mortality. In particular, the NFS vinegar caused complete mortality and the lowest filter paper mass losses at 2.18% when treated with 12.5% wood vinegar. The most abundant chemical compounds of NFS vinegar were cyclopropanecarbonyl chloride, 2,5-dichlorophenol, 2-propanone, acetic acid, propanoic acid, benzenesulfonic acid, 3,7-dimethyl-6-octenal, and trans-geraniol. Meanwhile, the main compounds in the MSF vinegar were 1,2-ethanediol, formic acid, acetic acid, ethanoic acid, 2-furancarboxaldehyde, phenol, 2-methoxy phenol, and 4-methyl phenol.

• Proceedings of the Korean Information Science Society Conference
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• 2012.06a
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• pp.1-3
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• 2012

네트워크 환경에서 가장 범용적으로 사용되는 파일시스템인 NFS는 클라이언트 수가 증가할수록 I/O 병목 현상이 심각하게 발생한다. 이를 해결하기 위해 클라이언트가 직접 데이터 서버에 연결하여 I/O 처리를 병렬화한 NFS 버전s 4.1 표준이 제정되었다. 본 논문에서는 이러한 pNFS를 지원하는 메타데이터 서버를 사용자 영역에서 손쉽게 개발할 수 있도록 FUSE를 활용하는 방안을 제안한다.

• Proceedings of the Korean Information Science Society Conference
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• 2012.06a
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• pp.221-223
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• 2012

많은 대학과 스토리지 업체에서 고성능 병렬 파일시스템 관련 연구를 활발히 진행하고 있다. 그러나 대학이나 업체에서 연구된 병렬 파일시스템 기술은 상호 호환성에 제약이 있다. 네트워크 파일시스템 관련해서 유일한 표준 기술인 NFS은 최근 pNFS 기능을 포함한 NFSv4.1로 확장되었다. pNFS은 NFS 서버를 거치지 않고 데이터를 병렬적으로 접근함으로써 고성능 입출력을 보장해 주고 있으며 기존 스토리지 기술과의 호환성을 제공하고 있다. 본 연구에서는 pNFS의 성능 평가를 위해서 pNFS을 사용하는 대용량 스토리지 시스템을 구현하고 NFSv4와 NFSv4.1간 성능을 비교한다. 성능 비교는 파일 사이즈와 동시 수행 프로세스 수 별로 수행되며 읽기 및 쓰기 연산에 대한 pNFS의 성능 향상을 확인한다.

• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.1073-1075
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• 1996

This paper presents a neuro fuzzy system(NFS) for implementing fuzzy inference system with a monotonic membership function. The modeling and control of a discrete nonlinear system using a NFS is described. The membership function parameters of a identifier and controller are adjusted by back-propagation algorithm. These identifier and controller is constructed to proposed NFS. A on-line identification and control are accomplished by this NFS. A controller is gived information of the system, that is variation of the system output according to that of the control input by a identifier. A controller makes control input in order to control discrete-time nonlinear system. A Simulation is presented to demonstrate the efficiency of a suggested method.

• Transactions on Electrical and Electronic Materials
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• v.17 no.4
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• pp.208-211
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• 2016

In this study, thermal-treatment-derived variations of the thermoelectric characteristics of ZnO nanofibers (NFs) are examined. NFs that were prepared by electrospinning were transformed into n-type ZnO NFs after they were exposed to thermal heating for 30 min at 550℃. For the ZnO NFs, the Seebeck coefficient decreased from - 132.1 μV/K to - 44.6 μV/K over the heating-time range of 30 min to 120 min, while the electrical conductivity increased from 2.07 × 10^-3 S/m to 0.18 S/m.

• The KIPS Transactions:PartC
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• v.16C no.5
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• pp.597-604
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• 2009

An SMTP(Simple Mail Transfer Protocol) server was designed for delivering and storing user's email across a network. An SMTP server can be distributed as multiple servers for large service, huge users or massive emails. An SMTP server can be constructed by multiple servers with separating file system as email storing space, and each SMTP server can usually share each file system by using the NFS(Network File system). However the NFS is originally designed for sharing each file system across a network, and contains all attributes and features of regular file system. Using this NFS for email storing space of SMTP servers, it makes overhead due to unnecessary work of regular file system. In this paper, we propose a method to do directly operation with socket for reducing work overhead caused by the NFS. For doing directly operation with socket, this paper defines information based storing space structure and a protocol for storing emails. We performed experiments using Mailstone made by Netscape. The experimental results show the performance improvement of the proposed method compared to the existing method.

• Journal of Electrochemical Science and Technology
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• v.9 no.2
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• pp.118-125
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• 2018

Herein we report on the selective synthesis and direct growth of nanostructures using an aqueous chemical growth route. Specifically, Al-doped ZnO (AZO) nanoflakes (NFs) are vertically grown on indium tin oxide (ITO) coated flexible polyethylene terephthalate (PET) sheets at low temperature and ambient environment. The morphological, optical, and electrical properties of the NFs are investigated as a function of the Al content. Furthermore, these AZO-NFs are integrated into perovskite solar devices as the electron transport layer (ETL) and the fabricated devices are tested for photovoltaic performance. It was determined that the doping of AZO-NFs significantly increases the performance metrics of the solar cells, mainly by increasing the short-circuit current of the devices. The observed enhancement is primarily attributed to the improved conductivity of the doped AZO-NF, which facilitates charge separation and reduces recombination. Further, our flexible solar cells fabricated through this low temperature process demonstrate an acceptable reproducibility and stability when exposed to a mechanical bending test.

• Journal of Korea Multimedia Society
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• v.24 no.12
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• pp.1641-1652
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• 2021

To analyze the crime scene, the role of digital evidence such as CCTV and black box is very important. Such digital evidence is often damaged due to device defects or intentional deletion. In this case, the deleted video can be restored by well-known techniques like the frame-based recovery method. Especially, the data such as the video can be generally fragmented and saved in the case of the memory used almost fully. If the fragmented video were recovered in units of images, the sequence of the recovered images may not be continuous. In this paper, we proposed a new video restoration method to match the sequence of recovered images. First, the images are recovered through a frame-based recovery technique. Then, after analyzing the time information marked on the images, the time information was extracted and recognized via optical character recognition (OCR). Finally, the recovered images are rearranged based on the time information obtained by OCR. For performance evaluation, we evaluate the recovery rate of our proposed video restoration method. As a result, it was shown that the recovery rate for the fragmented video was recovered from a minimum of about 47% to a maximum of 98%.