• Journal of KIISE:Computer Systems and Theory
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• v.37 no.4
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• pp.215-225
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• 2010

The NAND flash memory based SSDs are considered to replace the existing HDDs. To maximize the I/O performance, SSD is composed of several NAND flash memories in parallel. However, to adopt the hybrid mapping scheme in SSD may cause degradation of the I/O performance. In this paper, we propose a new mapping scheme for the SSD called WADPM. WADPM loads only necessary mapping information into RAM and dynamically adjusts the size of mapping information in the RAM. So, WADPM avoids the shortcoming of page-level mapping scheme that requires too large mapping table. Performance evaluation using simulations shows that I/O performance of WADPM is 3.5 times better than the hybrid-mapping scheme and maximum size of mapping table of WADPM is about 50% in comparison with the page-level mapping scheme.

• Korean Journal of Materials Research
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• v.20 no.5
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• pp.241-245
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• 2010

One of the weak points of the Cr-doped SZO is that until now, it has only been fabricated on perovskite substrates, whereas NiO-ReRAM devices have already been deposited on Si substrates. The fabrication of RAM devices on Si substrates is important for commercialization because conventional electronics are based mainly on silicon materials. Cr-doped ReRAM will find a wide range of applications in embedded systems or conventional memory device manufacturing processes if it can be fabricated on Si substrates. For application of the commercial memory device, Cr-doped $SrZrO_3$ perovskite thin films were deposited on a $SrRuO_3$ bottom electrode/Si(100)substrate using pulsed laser deposition. XRD peaks corresponding to the (112), (004) and (132) planes of both the SZO and SRO were observed with the highest intensity along the (112) direction. The positions of the SZO grains matched those of the SRO grains. A well-controlled interface between the $SrZrO_3$:Cr perovskite and the $SrRuO_3$ bottom electrode were fabricated, so that good resistive switching behavior was observed with an on/off ratio higher than $10^2$. A pulse test showed the switching behavior of the Pt/$SrZrO_3:Cr/SrRuO^3$ device under a pulse of 10 kHz for $10^4$ cycles. The resistive switching memory devices made of the Cr-doped $SrZrO_3$ thin films deposited on Si substrates are expected to be more compatible with conventional Si-based electronics.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.21 no.1
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• pp.119-132
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• 2018

This study was conducted to suggest an assessment indices to evaluate the ecosystem services of the unique functions of wetlands as well as economic value provided by the village wetlands. The assessment indicators applied in this study were used by the RAM indices. The results of RAM assessment on the village wetlands in Cheonan city were analyzed by item and critical functions of the village wetland. They were derived by assessment indicators of ecosystem services, and the village wetland ecosystem were presented by Focus Group Interview (FGI). The 20 critical indices were selected from 52 different indices by analyzing the wetland function assessment items. 13 indicators excluding duplicate indexes by function, were selected as ecological service impact indicators. Finally, ecosystem services were evaluated by using AHP analysis to calculate the weight of each assessment indices and apply it to the 9 village wetlands. The results of this study confirmed that the functions of the village wetlands are compliant with the ecosystem services. Based on this assessment of the unique functions of wetlands, it will serve as a methodology for assessing ecosystem services. The study was also conducted on 49 wetlands in Cheonan. The detailed assessment of wetland ecosystem services based on the wetland ecosystem function proposed by this study, was further developed as a follow-up study. It suggested that the wetland areas should be compared and be used as a general standard. In addition to the assessment of the economic value of ecosystem services provided by the village wetlands, it would be useful to assess the unique features and convert them into value.

• Journal of KIISE
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• v.42 no.2
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• pp.183-189
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• 2015

Recently, computer systems have encountered difficulties in making further progress due to the technical limitations of DRAM based main memory technologies. This has motivated the development of next generation memory technologies that have high density and non-volatility. However, these new memory technologies also have their own intrinsic limitations, making it difficult for them to currently be used as main memory. In order to overcome these problems, we propose a hybrid main memory system, namely HyMN, which utilizes the merits of next generation memory technologies by combining two types of memory: Write-Affable RAM(WAM) and Read-Affable RAM(ReAM). In so doing, we analyze the appropriate WAM size for HyMN, at which we can avoid the performance degradation. Further, we show that the execution time performance of HyMN, which provides an additional benefit of durability against unexpected blackouts, is almost comparable to legacy DRAM systems under normal operations.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.47 no.5
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• pp.35-40
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• 2010

NAND flash memory has been widely used than traditional HDD in PDA and other mobile devices, embedded systems, PC because of faster access speed, low power consumption, vibration resistance and other benefits. DiskSim and other HDD simulators has been developed that for find improvements for the software or hardware. But there is a few Linux-based simulators for NAND flash memory and SSD. There is necessary for Windows-based NAND flash simulator because storage devices and PC using Windows. This paper describe for development of simulator-NFSim for FTL performance analysis in NAND flash. NFSim is used to measure performance of various FTL algorithms and FTL wear-level. NAND flash memory model and FTL algorithm developed using Windows Driver Model and class for scalability. There is no need for another tools because NFSim using graph tool for data measure of FTL performance.

• Korean Journal of Materials Research
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• v.32 no.9
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• pp.384-390
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• 2022

A spin coating process for RRAM, which is a TiN/TiO₂/FTO structure based on a PTC sol solution, was developed in this laboratory, a method which enables low-temperature and eco-friendly manufacturing. The RRAM corresponds to an OxRAM that operates through the formation and extinction of conductive filaments. Heat treatment was selected as a method of controlling oxygen vacancy (V_O), a major factor of the conductive filament. It was carried out at 100 ℃ under moisture removal conditions and at 300 ℃ and 500 ℃ for excellent phase stability. XRD analysis confirmed the anatase phase in the thin film increased as the heat treatment increased, and the Ti³⁺ and OH- groups were observed to decrease in the XPS analysis. In the I-V analysis, the device at 100 ℃ showed a low primary SET voltage of 5.1 V and a high ON/OFF ratio of 10⁴. The double-logarithmic plot of the I-V curve confirmed the device at 100 ℃ required a low operating voltage. As a result, the 100 ℃ heat treatment conditions were suitable for the low voltage driving and high ON/OFF ratio of TiN/TiO₂/FTO RRAM devices and these results suggest that the operating voltage and ON/OFF ratio required for OxRAM devices used in various fields under specific heat treatment conditions can be compromised.

• International Journal of Aeronautical and Space Sciences
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• v.17 no.3
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• pp.358-365
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• 2016

In this study, one-dimensional analysis under the assumption of an inviscid flow was conducted for the experiment initiated by the French-German Research Institute of Saint-Louis (ISL) in order to investigate the energy effect of aluminum combustion. Previous theoretical analysis based on the assumptions of isentropic compression and a constant specific heat derived by ISL claimed that the experiment was not affected by the heat of aluminum combustion. However, rigorous analysis in present investigation that considered the average properties behind the shock wave compression and temperature-dependent specific heat showed that the S225 experiment was partially affected by the aluminum combustion. The increase in heat due to aluminum combustion was estimated from the rigorous analysis.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1590-1594
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• 2007

This paper describes a case study on dynamic characteristics analysis of a 5-axis multi-tasking machine tool of ram-head typed. Natural frequency and corresponding vibration modes of the machine tool structure were obtained by using both FEM modal analysis and an experimental modal test(impulse hammer test). Both the theoretical and experiment analysis results showed good agreement with each other. Finally, some discussion and review, from the view point of resonance vibration and/or mode coupled chatter, were made based on the analysis results.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.1
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• pp.64-72
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• 1993

We propose "algorithm MA" which can detect PSF that is the functional fault in RAM. This algorithm based on the restricted PSF(or neighborhood PSF) and can detect not only conventional stuck-at and transition faults but also SNPSF, PNPSF and partially ANPSF. The time complexity of "algorithm MA" has 1536xP(P=no. of partition). We propose total BIST(built-in self test) scheme which implement this algorithm in memory chip.ithm in memory chip.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.413-414
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• 2012

Programmable Metallization Cell (PMC) memory, which utilizes electrochemical control of nanoscale quantities of metal in thin films of solid electrolyte, shows great promise as a future solid state memory. The technology utilizes the electrochemical formation and removal of metallic pathways in thin films of solid electrolyte. Key attributes are low voltage and current operation, excellent scalability, and a simple fabrication sequence. In this study, we investigated the nature of thin films formed by photo doping of Ag+ ions into chalcogenide materials for use in solid electrolyte of programmable metallization cell devices. We measured the I-V characteristics by field-effect of the device. The results imply that a Ag-rich phase separates owing to the reaction of Ag with free atoms from chalcogenide materials.