• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2005.05a
• /
• pp.441-445
• /
• 2005

In the resent years, as the research and the development of micro and precision machinery become active, the interest of micro actuators using SMA(Shape Memory Alloy) has been increased. But, no detailed researches between the thermo-dynamic property in Nitinol alloy have been done yet. In this study, the thermal property of high temperature Nitinol shape memory alloy were evaluated using differential scanning calorimeter(DSC). The structure property was investigated using X-ray diffraction(XRD). A dynamic mechanical analyzer(DMA) with three point bending mode was used to study storage and loss modulus of shape memory alloy according to the thirteen frequencies in the temperature range between 30 and $200^{\circ}C$. The effects of the temperature heating/cooling rate, the frequency on the damping capacity have been systematically investigated. Such a frequency and temperature changes also influenced significantly to the damping behavior of the shape memory alloy. It was also found that Nitinol exhibited high damping capacity during phase transformation.

• Journal of KIISE
• /
• v.42 no.8
• /
• pp.972-978
• /
• 2015

Non-volatile memory (NVM) supports both byte addressability and non-volatility. These characteristics make it feasible for NVM to be employed at any layer of the memory hierarchy such as cache, memory and disk. An interesting characteristic of NVM is that, even though it supports non-volatility, its retention capability is limited. Furthermore NVM has tradeoff between its retention capability and write latency. In this paper, we propose a novel NVM-based file cache management scheme that makes use of the limited retention capability to improve the cache performance. Experimental results with real-workloads show that our scheme can reduce access latency by up to 31% (24.4% average) compared with the conventional LRU based cache management scheme.

• Journal of KIISE:Databases
• /
• v.37 no.6
• /
• pp.292-299
• /
• 2010

Recently, as flash memory is used as digital storage devices, necessity for digital forensics is growing in a flash memory area for digital evidence analysis. For this purpose, it is important to recover crashed files stored on flash memory efficiently. However, it is inefficient to apply the hard disk based file recovery techniques to flash memory, since hard disk and flash memory have different characteristics, especially flash memory being unable to in-place update. In this paper, we propose a flash-aware file recovery technique for digital forensics. First, we propose an efficient search technique to find all crashed files. This uses meta-data maintained by FTL(Flash Translation Layer) which is responsible for write operation in flash memory. Second, we advise an efficient recovery technique to recover a crashed file which uses data location information of the mapping table in FTL. Through diverse experiments, we show that our file recovery technique outperforms the hard disk based technique.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.51 no.4
• /
• pp.33-41
• /
• 2014

This paper presents an effective memory access method for a high-speed data transfer on mobile systems using a direct memory access controller that considers the characteristics of a multi-port memory controller. The direct memory access controller has an integrated channel management function to control multiple direct memory access channels. The channels are physically separated and operate independently from each other. Experimental results show that the proposed direct memory access method improves the transfer performance by up to 72% and 69% on read and write transfer cycles, respectively. The total number of transfer cycles of the proposed method is 63% less than in a commercial method under 4-channel access.

• Journal of KIISE:Computer Systems and Theory
• /
• v.36 no.6
• /
• pp.521-531
• /
• 2009

Flash memory has physical characteristics different from hard disk where two costs of a read and write operations differ each other and an overwrite on flash memory is impossible to be done. In order to solve these restrictions with software, storage systems equipped with flash memory deploy FTL(Flash Translation Layer) software. Several FTL algorithms have been suggested so far and most of them prefer sequential write pattern to random write pattern. In this paper, we provide a new technique to efficiently store and maintain the B-tree index on flash memory. The operations like inserts, deletes, updates of keys for the B-tree generate random writes rather than sequential writes on flash memory, leading to inefficiency to the B-tree maintenance. In our technique, we convert random writes generated by the B-tree into sequential writes and then store them to the write-buffer on flash memory. If the buffer is full later, some sequential writes in the buffer will be issued to FTL. Our diverse experimental results show that our technique outperforms the existing ones with respect to the I/O cost of flash memory.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.34 no.1
• /
• pp.56-64
• /
• 2006

This paper presents the development and application of a conducting shape memory polyurethane (CSMPU) actuator. While conventional shape memory polyurethanes were activated by external heat source, conducting shape memory polyurethanes introduced in 2004 are activated by electric power. Conducting shape memory polyurethane actuators were manufactured by adding carbon nano tube to conventional shape memory polyurethane. The main problem of the CSMPU developed in 2004 was bad dispersion of carbon nano tubes. In this paper, we tried to find how to solve the dispersion problem, and with a lot of elaborative works, conducting shape memory polyurethane actuators which had better electrical characteristics were developed. Then the actuation performance of the conducting shape memory polyurethane actuators was also measured and assessed. Finally, the possibility of applications were examined through the installation to Micro Air Vehicle.

• Journal of KIISE
• /
• v.42 no.2
• /
• pp.183-189
• /
• 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 agricultural medicine and community health
• /
• v.48 no.1
• /
• pp.1-12
• /
• 2023

Objective: The purpose of this study was to identify factors associated with subjective memory impairment in patients with diabetes mellitus in a metropolitan city. Methods: The subjects of this study were 351 patients with diabetes mellitus aged 50 and over from five districts of Gwangju who participated in the 2018 Community Health Survey. We analyzed general characteristics, health-related behaviors and health related conditions and subjective experience of memory impairment. To find factors associated with subjective memory impairment, the chi-square test and multiple logistic regression analysis were used. Results: Of all subjects, 31.3% was reported subjective experience of memory impairment. The odds ratios (ORs; 95% confidence interval (CI)) for subjective memory impairment according to age were statistically significant at 1.9 (0.9-4.3) in patients in 60s and 2.2 (1.1-4.7) in patients in beyond 70s compared to those in 50s. The OR (95% CI) of ex-smoker compared to the non-smoker was 0.3 (0.8-0.9). The OR (95% CI) of depressive symptom compared to no depressive symptoms was 4.9 (95% CI: 1.8-13.7). Conclusion: In this study, subjective memory impairment in patients with diabets mellitus was associated with age, smoking, and depressive symptoms. Based on the results of this study, subjective memory impairment should be detected early through periodic cognitive function evaluation for elderly patients with diabetes mellitus, and a program for healthy cognitive function should be included in diabetes management program.

• Korean Institute of Interior Design Journal
• /
• v.18 no.5
• /
• pp.12-20
• /
• 2009

Memory and schema are very similar in terms of human accumulated mental and physical experiences. However, while memory has more personal aspect, schema discussed in this paper has more collective aspect. Schema has been developed through different generations and times, and has become a specific psychological or visual element(s) that can be applied to various fields, such as all, design and architecture. This study focuses on Aldo Rossi's architectural design characteristics based on his 'Autobiographical Concept' as well as personal schema. 'Autobiographical Concept' is the crucial structure supporting Aldo Rossi's distinctive formalization and spatialization. 4 case projects were comparatively analyzed by the 5 elements included in 'Autobiographical Concept'. It was not easy to relate each element to a specific design aspect because the 5 elements are somehow theoretically and conceptually inter-connected each other. Even though it is very difficult to directly relate a conceptual element with a real spatial element, it is found that the 5 elements have some differences in the spatialization process. Thus, in the conclusion, this study attempted to show the unique characteristics of the Aldo Rossi's architectural design process based on his 'Autobiographical Concept'.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.24 no.11
• /
• pp.855-858
• /
• 2011

In this paper, in order to suppress unwanted current paths originating from adjacent cells in a passive crossbar array based on resistive random access memory (RRAM) without extrinsic switching devices, 1-diode type RRAM which consists of a 0.2% chromium-doped strontium titanate (Cr-$SrTiO_3$) film deposited on a silicon substrate, was proposed for high packing density, and intrinsic rectifying characteristics from the current versus voltage characteristics were successfully demonstrated.