• Journal of Information Processing Systems
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• v.18 no.3
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• pp.402-410
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• 2022

Digital data can be manipulated easily, so information related to the timestamp is important in establishing the reliability of the data. The time values for a certain file can be extracted following the analysis of the filesystem metadata or file internals, and the information can be utilized to organize a timeline for a digital investigation. Suppose the reversal of a timestamp is found on a mobile device during this process. In this case, a more detailed analysis is required due to the possibility of anti-forensic activity, but little previous research has investigated the handling and possible manipulation of timestamps on mobile devices. Therefore, in this study, we determine how time values for multimedia files are handled according to the operating system or filesystem on mobile devices. We also discuss five types of timestamps-file created (C), last modified (M), last accessed (A), digitalized (Di), and filename (FN) of multimedia files, and experimented with their operational features across multiple devices such as smartphones and cameras.

• Journal of Korea Multimedia Society
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• v.18 no.9
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• pp.1098-1104
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• 2015

With the widespread use of smartphones and IoT (Internet of Things), data are being generated on a large scale, and there is increased for the analysis of such data. Hence, distributed processing systems have gained much attention. Hadoop, which is a distributed processing system, saves the metadata of stored files in name nodes; in this case, the main problems are as follows: the memory becomes insufficient; load occurs because of massive small files; scheduling and file processing time increases because of the increased number of small files. In this paper, we propose a solution to address the increase in processing time because of massive small files, and thus improve the processing performance, using the Reuse JVM method provided by Hadoop. Through environment setting, the Reuse JVM method modifies the JVM produced conventionally for every task, so that multiple tasks are reused sequentially in one JVM. As a final outcome, the Reuse JVM method showed the best processing performance when used together with CombineFileInputFormat.

• The Transactions of the Korea Information Processing Society
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• v.4 no.11
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• pp.2849-2860
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• 1997

In this paper, we present efficient cache replacement policies for the software RAID file system. The performance of this policies is compared to two other policies previously proposed for conventional file systems and adapted for the software RAID file system. As in hardware RAID systems, we found small-writes to be the performance bottleneck in software RAID file systems. To tackle this small-write problem, we propose cache replacement policies. Using trace driven simulations we show that the proposed policies improve performance in the aspect of the average response time and the average system busy time.

• Journal of KIISE:Computing Practices and Letters
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• v.14 no.7
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• pp.625-635
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• 2008

Portable multimedia players have some different properties compared to general multimedia file server. Some of those properties are single user ownership, relatively low hardware performance, I/O burst by user special functions, and short software development cycles. Though suitable for processing multiple user requests at a time, the general multimedia file systems are not efficient for special user functions such as fast forwards/backwards. Soml' methods has been proposed to improve the performance and functionality, which the application programs give prediction hints to the file system. Unfortunately, they require the modification of all applications and recompilation. In this paper, we present a file system that efficiently supports user special functions in embedded multimedia systems using file block allocation, buffer-cache, and prefetch. A prefetch algorithm, SPRA (SPeed-based PRefetch Algorithm) predicts the next block using I/O patterns instead of hints from applications and it is resident in the file system, so doesn't affect application development process. From the experimental file system implementation and comparison with Linux readahead-based algorithms, the proposed system shows $4.29%{\sim}52.63%$ turnaround time and 1.01 to 3,09 times throughput in average.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.256-259
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• 2003

This paper presents the analyses of Auto CAD plot file for carving machine. The plot file is first analyzed and then sorted to properly perform a sequence of the line segments. The experimental results show that this technique can improve the carving performance, reduce the operating time, and save the tool and machine’s lifetime. In addition, this proposed technique can also be extended to apply for other coordinate machines.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2009.01a
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• pp.364-367
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• 2009

This paper presents a scheme that generates a caption file by extracting a Closed Caption stream from DTV signal. Note that Closed-Captioning service helps to bridge "digital divide" through extending broadcasting accessibility of a neglected class such as hearing-impaired person and foreigner. In Korea, DTV Closed Captioning standard was developed in June 2007, and Closed Captioning service should be supported by an enforcing law in all broadcasting services in 2008. In this paper, we describe the method of extracting a caption data from MPEG-2 Transport Stream of ATSC-based digital TV signal and generating a caption file (SAMI and SRT) using the extracted caption data and time information. Experimental results verify the feasibility of a generated caption file using a PC-based media player which is widely used in multimedia service.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.1C
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• pp.90-95
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• 2002

Though the FTP(File Transfer Protocol) has been used widely and stable, It has the structural weakness that can't support current file transmissions so that we have to wait the completion of previous file transmission when try to transmit another file. If try to transmit multiple files concurrently using this FTP, It has to forking multiple FTP servers and clients in each user's PC and ISP's host machine it would result in the waist of memory, resource of network and the high workload of system. In order to solving previous problem, in this paper I have designed the new model of FTP which based on multi-thread and created NFTP(Next-Generation FTP)protocol so that may reduce the workload of system and support current file transmission effectively. I have implemented NFTP and also applied to real service, as a result It have provided reliable service by reducing the workload of system and saved the waiting time which would happened.

• Journal of the Institute of Convergence Signal Processing
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• v.14 no.3
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• pp.181-190
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• 2013

In this paper, we designed file system in order to utilize data analysis by using correlation result from Daejeon correlator including related software development. Correlation results are consisted of visibility component (amplitude and phase) of radio source, but for data analysis of correlation result, various information such as weather, radio telescope position, observation time, radio source position, source type, and receiver noise temperature are needed. In this paper, we designed file system as a directory-structure for making use of these informations at Linux system for analyzing data and developed software to make file system. To verify the effectiveness of designed file system and developed software, file system generation experiment is conducted, and then astronomers accepted that there is no severe problem for scientific analysis using designed file system.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.27 no.6
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• pp.1271-1280
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• 2017

The android packer service using runtime execution compression technology switches to the original application using DexClassLoader. However the API interface of the DexClassLoader receives the path of the loaded DEX(Dalvik EXcutable) and the path of the compiled file. So there is a problem that the original file is exposed to the file system. Therefore, it is not safe to use the API for the packer service. In this paper, we solve this problem by changing the compile and load flow of the DexClassLoader API. Due to this changed execution flow, the complied file can be encrypted and stored in the file system or only in the memory and it can be decrypted or substituted at the time of subsequent loading to enable the original application conversion. we expected that the stability of the packer will increase beacause the proposed method does not expose the original file to the file system.

• The Transactions of the Korea Information Processing Society
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• v.3 no.3
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• pp.617-630
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• 1996

In this paper, a shared-concurrent file system (S-CFS) is designed and implemented using conventional disks as disk arrays on a Workstation Cluster which can be used as a small-scale server. Since it is implemented on UNIX operating systems, S_CFS is not only portable and flexible but also efficient in resource usage because it does not require additional I/O nodes. The result of the research shows that on small-scale systems with enough disks, the performance of the concurrent file system on transaction processing applications is bounded by the bottleneck of CPUs computing powers while the performance of the concurrent file system on massive data I/Os is bounded by the time required to copy data between buffers. The concurrent file system,which has been implemented on a Workstation Cluster with 8 disks,shows a throughput of 388 tps in case of transaction processing applications and can provide the bandwidth of 15.8 Mbytes/sec in case of massive data processing applications. Moreover,the concurrent file system has been dsigned to enhance the throughput of applications requirring high performance I/O by controlling the paralleism of the concurrent file system on user's side.