• Proceedings of the IEEK Conference
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• 2003.11b
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• pp.15-18
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• 2003

Flash memory becomes more important for its fast access speed, low-power, shock resistance and nonvolatile storage. But its native restrictions that have limited 1ifetime, inability of update in place, different size unit of read/write and erase operations need to managed by FTL(Flash Translation Layer). FTL has to control the wear-leveling, address mapping, bad block management of flash memory. In this paper, we focuses on the fast access to address mapping table and proposed the way of faster valid page search in the flash memory using the VPLT(Valid Page Lookup Table). This method is expected to decrease the frequency of access of flash memory that have an significant effect on performance of read and block-transfer operations. For the validations, we implemented the FTL based on Windows CE platform and obtained an improved result.

• Journal of Industrial Technology
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• v.15
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• pp.51-62
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• 1995

Databases can crash due to various failures in computer systems. Recovery is a mechanism for restoring consistent data from damages caused by the by the failures and is an essential feature in database systems. This paper surveys recovery techniques for memory resident database systems. We first describe the basic architecture for memory resident database systems, and point out the main factors affecting their performance enhancement. Next, we explain the write-ahead logging(WAL), a recovery technique widely-used in most disk resident database systems, for easy understanding of basic recovery mechanisms. And then, we discuss some new concepts employed in memory resident database systems recovery. Finally, we present a representative memory resident database recovery technique, which is based on a special purpose hardware called HALO, as a case study.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.7 s.238
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• pp.1028-1034
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• 2005

In this paper, the failure analysis of an optical disk drive is carried out and the limit ranges of the misalignment f3r the higher performance are presented. Since optical disks are removable from optical disk drive, the translational and angular misalignments, which causes read/write errors, always exist. Therefore, the limit ranges of the misalignment should be investigated. For this reason, the failure analysis by the vibration analysis is studied. The influences of the misalignment are tested by the aging test. And the limit ranges of the misalignment are proposed for the reliability of optical disk drives.

• Transactions of the Society of Information Storage Systems
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• v.8 no.1
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• pp.22-26
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• 2012

Optical disk drives (ODDs) are subjected to vibrations caused by the high-speed rotation of the optical disk, and these vibrations can be excessive and reduce the read/write performance. Elastic rubber mounts with cushioning materials are often used to minimize these problems. In this paper, the source of vibrations was identified by experimental modal tests and high-speed photography. Structural modifications were made based on a lumped parameter model and a finite element model.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.9
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• pp.3539-3558
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• 2015

This paper investigates and analyzes the default block placement strategy of HDFS. HDFS is a typical representative distributed file system to stream vast amount of data effectively at high bandwidth to user applications. However, the default HDFS block placement policy assumes that all nodes in the cluster are homogeneous, and places blocks with a simple RoundRobin strategy without considering any nodes' resource characteristics, which decreases self-adaptability of the system. The primary contribution of this paper is the proposition of a network load sensitive block placement strategy. We have implemented our algorithm and justify it through extensive simulations and comparison with similar existing studies. The results indicate that our work not only performs much better in the data distribution but also improves write performance more significantly than the others.

• Journal of the Semiconductor & Display Technology
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• v.19 no.3
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• pp.112-117
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• 2020

NAND flash memory is a non-volatile memory that retains stored data even without power supply. Internal memory used as a data storage device and solid-state drive (SSD) is used in portable devices such as smartphones and digital cameras. However, NAND flash memory carries the risk of electric shock, which can cause errors during read/write operations, so use error correction codes to ensure reliability. It efficiently recovers bad block information, which is a defect in NAND flash memory. BBT (Bad Block Table) is configured to manage data to increase stability, and as a result of experimenting with the error correction code algorithm, the bit error rate per page unit of 4Mbytes memory was on average 0ppm, and 100ppm without error correction code. Through the error correction code algorithm, data stability and reliability can be improved.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.94-103
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• 2002

Accurately controlling the shape of the read/write head structure is critical in the performance of a modern hard disk drive. The sliders investigated are composed of alumina and titanium carbide (AlTiC) and act as an air bearing when passing over the disks. Controlling the curvature of the slider is of primary importance. A laser scribing system that produces curvature by Inducing residual stress into the slider can be utilized. Predicting the curvature created by a pattern of scribes is of great importance to increase the control over the sliders' shape. Using finite element analysis a force system that produces stresses similar to the laser scribing is applied. The curvatures created by the force system are calibrated to experimental measurements.

• Journal of Arbitration Studies
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• v.14 no.1
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• pp.157-184
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• 2004

Dispute plays a key role in maintaining the desirable trading performance. There are many problems such as problems of enforcement of arbitral award and the uncertainty of legal system in PRC. Therefore, the Korean trading companies with Chinese companies should be more concerned with mediation. It's because mediation are more likely to be effective than arbitration and litigation to resolve disputes with chinese companies. This article investigates some differences of mediation between ROK and PRC, and suggests the following ways to resolve dispute. First, the Korean companies should utilize the mediation in small claim but arbitration in big claim. Second, Write a contract and insert mediation clause in BCC or the standard arbitration clause in KCAB. Third, the companies should be more concerned with prevention of dispute than dispute resolution. In conclusion, to expand mediation system into an effective dispute resolution system, The Korean Dispute Resolution Center should be established.

• Proceedings of the KIEE Conference
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• 1998.07c
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• pp.1210-1212
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• 1998

The complexity of newly developed protection algorithm and higher performance requested by the user makes the software embedded in the protective relay much harder to develop and maintain. The versatility of 32bit microprocessor and the availability of cheaper memory semiconductors introduced the fertile developing background for the protective relay developers. The use of component object model(COM) in the software developing process enables the developer to write much complex code in the easy and safe way and to maintain the code easily, too. And the aid of the COM library, the distributed computing environment will be expected to appear by the use of the COM programming model in the protective relay firmware program.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.22 no.53
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• pp.89-97
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• 1999

We are concerned with the optimal design of flexible manufacturing cells in this study, thus try to suggest the detail information for each resource on the optimal conditions. Object oriented simulation technology is used to write models more easily and to execute simulation running time more rapidly, and the optimal level of relevant decision variables is probed by response surface methodology(RSM), which is well known for the optimization technology based on experiment design and regression equation. We investigate the optimal level for the number of pallets and the speed of AGVs of FMC systems, carry out the performance analysis of this system. Consequently we suggest systematic procedures for the optimization of FMCs in detail design stage.