• Journal of KIISE:Computer Systems and Theory
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• v.31 no.5_6
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• pp.268-278
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• 2004

In this paper, we describe our experience in the design and implementation of the SMART file system to handle multimedia workload. Our work has three design objectives: (ⅰ) efficient support for sequential workload, (ⅱ) avoiding disk fragmentation, (ⅲ) logical unit based file access. To achieve these three objectives, we develop a file system where a file consists of linked list of Data Unit Group. Instead of tree like structure of the legacy Unix file system, we use single level file structure. Our file system can also access the file based upon the logical unit which can be video frame or audio samples. Data Unit Group is a group of logical data units which is allocated continuous disk blocks. At the beginning of each Data Unit Group, there exists an index array. Each index points to the beginning of logical data units, e.g. frames in the Data Unit Group. This index array enables the random access and sequencial access of semantic data units. SMART file system is elaborately tailored to effectively support multimedia workload. We perform physical experiments and compare the performance of SMART file system with EXT2 file system and SGI XFS file system. In this experiment, SMART file system exhibits superior performance under streaming workload.

• Journal of Advanced Navigation Technology
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• v.17 no.1
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• pp.39-46
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• 2013

If a file system is damaged because of the unusual system close, the system performs the consistency test using fsch and it takes long time. Especially, if it is a big file system, it will take a lot of time. The journaling file system that uses journaling technique, can reduce the restoring time because it uses meta data and it may increase the chance of restoration when restoring. The goal of this paper compared performance evaluation journaling file systems focused on the reading and writing using Iozone tool which is the kernel based benchmarking tool in linux operating system. In this paper, Ex4 which is the current basic Linux file system. is 1.28x faster than XFS file system in terms of file read performance and 1.22x faster than Ext3 file system in terms of file write performance.

• Restorative Dentistry and Endodontics
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• v.22 no.1
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• pp.388-395
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• 1997

Maintaining the original canal path during instrumentation is a challenge in narrow curved canals. This study compared the maintenance of the original canal path of curved root canals during instrumentation with two kinds of stainless steel K-files(Brassler USA & Mani Japan), K-flexofiles(Maillefer Swiss) and Ni-Ti files(Brassler USA, Savannah, GA) using circumferential filing technique to # 40 MAF on 60 extracted human molars. Buccal and mesial canals with minimal initial curvature of 20 degrees were used. The maximal initial curvature was 41.5 degrees. Sixty curved canals divided into four groups according to file type(Group 1 : Ni-Ti file, Group 2 : K-flexofile, Group 3: K-file(Brassler), Group 4 : K-file(Mani)). Radiographs of canals were obtained before and after canal shaping. And postoperative radiographs were compared with preoperative radiographs using superimposition method. Data analysis was performed using Covariance analysis and paired-comparison test. The results observed were as follow ; 1. The angle of curvature was better maintained with Ni-Ti file than with stainless steel files. (p<0.01) 2. There was no significant difference in maintaining canal curvature between K-flexofile, Brassler$^{(R)}$ K-file and Mani$^{(R)}$ K-file, although there was some differences in mean values of postoperative canal curvature. 3. Paired-comparison t test revealed significant differences within each of the three stainless steel file types when comparing the mean differences before and after instrumentation, but no significant differences were observed within Ni-Ti file group.

• The KIPS Transactions:PartA
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• v.17A no.2
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• pp.63-72
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• 2010

Recently, the need for multimedia devices, such as digital TV, and camcorder has increased. These devices provide many services on multimedia files such as playing, recording, and editing. Throughout these services, in case of storing edited large-scaled multimedia files, existing file system have several capability problems that are taking too much time and requiring disk I/O. In this paper, we propose the use of Linux Ext2 file system based 'Block-Link file (BL-file) system' in order to solve these problems. For the BL-file system, when editing and storing large-scaled files, there is no data input or output but only modification of the metadata. Additionally, by sharing data blocks between multimedia files, we can save disk spaces. Moreover, because the managing of data block sharing information is more convenient than the existing FWAE technique, we can lessen system overhead. The BL-file system is based on Ext2 file system and implemented in a Linux environment, and the usefulness of the proposed technique is validated by applying the Linux multimedia file-editing tool 'Avidemux'.

• The KIPS Transactions:PartA
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• v.12A no.6 s.96
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• pp.493-498
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• 2005

P2P service is a method that can share various information through direct connection between computer of a person who have information and a Person who have information without server in the Internet and it is getting a lot of popularity by method for free ex change of file. P2P file sharing systems have become popular as a new paradigm for information exchange. Because all users who use service in P2P file sharing system can use shared files of several users freely by equal access privilege, it is happening the 'free rider' that only download shared file of other users without share own files. Although a user share a malicious file including virus, worm or file that have title differing with actuality contents, can use file sharing service without limitation. In this paper, we propose a method that restrict access of 'free rider' that only download using reputation information that indicate reliability of user. Also, we restrict usage ons hared file of other users about users who share harmful file.

• International Journal of Advanced Culture Technology
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• v.7 no.1
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• pp.243-247
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• 2019

The most commonly used 3D modeling file formats are OBJ (Wavefront file format specification) and STL (STereoLithography). Although they have a common point of view in 3D on the screen, detailed functions are different according to purpose of development. OBJ is the most commonly used 3D file format and STL is mainly used as 3D file format for 3D printing. However, in the field of Scientific Visualization, precise analysis is required. There is a difference in accuracy depending on the type of 3D file format. OBJ and STL are not suitable for delicate surface description because they form meshes in the form of triangular polygons. And if you increase the number of triangle polygons, it will be smoother, but the file size also increases exponentially and causes excessive CPU usage. In contrast, VTK provides a variety of polygon structures, including triangular polygons as well as rectangular polygons and cube polygons. Thus, delicate surface depiction is possible. Delicate surface rendering is possible and file size is not large. This paper describes the concept and structure of VTK. We also compared the load times and file sizes between VTK, STL, and OBJ in the Chrome browser. In addition, the difference in surface rendering ability between VTK, STL, and OBJ is intuitively viewed based on the screen in which each 3D file format is implemented under the same conditions. This study is expected to be helpful for efficient 3D file format for precise implementation of Web - based Scientific Visualization.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.10
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• pp.1397-1402
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• 2021

The overlay2 file system is one of the union file systems that mounts multiple directories into one. The source directory used for this overlay2 file system mount has a characteristic that it operates independently of the write-able layer after mounting, so it is often used for container platforms for application delivery. However, the overlay2 file system has a security vulnerability that the write-able layer is also modified when file in the source directory is modified. In this study, I proposed the overlay2 file system protection technology to remove the security vulnerabilities of the overlay2 file system. As a result of empirically implementing the proposed overlay2 file system protection technology and verifying the function, the protection technology proposed in this study was verified to be effective. However, since the method proposed in this study is a passive protection method, a follow-up study is needed to automatically protect it at the operating system level.

• Journal of Platform Technology
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• v.12 no.2
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• pp.12-22
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• 2024

With the rapid increase in digital data in modern society, digital forensics plays a crucial role, and file type identification is one of its integral components. Research on the development of identification models utilizing artificial intelligence is underway to identify file types swiftly and accurately. However, existing studies do not support the identification of file types with high domestic usage rates, making them unsuitable for use within the country. Therefore, this paper proposes a more accurate file type identification model using Convolutional Neural Networks (CNN) and Gated Recurrent Units (GRU). To overcome limitations of existing methods, the proposed model demonstrates superior performance on the FFT-75 dataset, effectively identifying file types with high domestic usage rates such as HWP, ALZ, and EGG. The model's performance is validated by comparing it with three existing research models (CNN-CO, FiFTy, CNN-LSTM). Ultimately, the CNN and GRU based file type identification and classification model achieved 68.2% accuracy on 512-byte file fragments and 81.4% accuracy on 4096-byte file fragments.

• IEMEK Journal of Embedded Systems and Applications
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• v.2 no.3
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• pp.184-193
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• 2007

Flash memory adoption in the mobile devices is increasing or vanous multimedia services such as audio, videos, and games. Although the traditional research issues such as out-place update, garbage collection, and wear-leveling are important, the performance, memory usage, and fast mount issues of flash memory file system are becoming much more important than ever because flash memory capacity is rapidly increasing. In this paper, we address the problems of the existing log-based flash memory file systems analytically and propose an efficient log-based file system, which produces higher performance, less memory usage and mount time than the existing log-based file systems. Our ideas are applied to a well-known log-based flash memory file system (YAFFS2) and the performance tests are conducted by comparing our prototype with YAFFS2. The experimental results show that our prototype achieves higher performance, less system memory usage, and faster mounting than YAFFS2, which is better than JFFS2.

• Journal of Korea Society of Digital Industry and Information Management
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• v.10 no.2
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• pp.91-105
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• 2014

This paper proposes a digital forensic method by an evaluation function based on timestamp changing patterns. Operations on file or folder leave changed timestamps, which give the ways to know what operations were executed. Changes of timestamps of ten operations of a file and eight operations of a folder were examined. Analyses on the changes on the eight folder operations are newly added in this paper, which are not performed in the previous works. Based on the timestamps changes of the file and the folder, two evaluation functions are proposed. The first evaluation function checks whether timestamps are changed by file and folder operations, and the second evaluation function checks whether timestamps are originated from a source file or other attribute field. By the two output values from these evaluation functions, a digital forensic investigation on the file or the folder is performed. With some cases, i. e. file copy and folder creation operations, the proposed forensic method is tested for its usefulness.