• International journal of advanced smart convergence
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• v.10 no.1
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• pp.142-150
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• 2021

Open-channel SSD is a new type of Solid-State Disk (SSD) that improves the garbage collection overhead and write amplification due to physical constraints of NAND flash memory by exposing the internal structure of the SSD to the host. However, the host-level Flash Translation Layer (FTL) provided for open-channel SSDs in the current Linux kernel consumes host memory excessively because it use page-level mapping table to translate logical address to physical address. Therefore, in this paper, we implemente a selective mapping table loading scheme that loads only a currently required part of the mapping table to the mapping table cache from SSD instead of entire mapping table. In addition, to increase the hit ratio of the mapping table cache, filesystem information and mapping table access history are utilized for cache replacement policy. The proposed scheme is implemented in the host-level FTL of the Linux kernel and evaluated using open-channel SSD emulator. According to the evaluation results, we can achieve 80% of I/O performance using the only 32% of memory usage compared to the previous host-level FTL.

• The Korea Journal of Herbology
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• v.29 no.6
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• pp.73-83
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• 2014

Objectives : This study was investigated the effects of the root of Polygala tenuifolia (POL) on learning and memory impairment induced by chronic cerebral hypoperfusion in rats. Methods : Chronic cerebral hypoperfusion was produced by permanent bilateral common carotid artery occlusion (pBCAO). POL was administered orally once a day (130 mg/kg of water-extract) for 28 days starting at 4 weeks after the pBCAO. The acquisition of learning and the retention of memory were tested on 9th week after the pBCAO using the Morris water maze. In addition, effects of POL on $A{\beta}$ generation and expressions of APP and BACE1 were observed in the hippocampus of rats. Results : POL significantly prolonged the swimming time spent in target quadrant and significantly reduced the swimming time spent in the quadrant far from the target. POL significantly increased the percentage of swim in the targer quadrant in the retention test, while POL was not effective on the escape latencies in the acquisition training trials. POL significantly reduced the levels of $A{\beta}_{(1-40)}$ and $A{\beta}_{(1-42)}$ in the cerebral cortex and the level of $A{\beta}_{(1-42)}$ in the hippocampus produced by chronic cerebral hypoperfusion. POL also significantly attenuated the up-regulation of APP and BACE1 expression in the hippocampus produced by chronic cerebral hypoperfusion. Conclusions : The results show that POL alleviated memory deficit and up-regulation of $A{\beta}$ and BACE1 expressions in the hippocampus. This result suggests that POL may exert ameliorating effect on memory deficit through inhibition of ${\beta}$-secretase activity and $A{\beta}$ generation.

• Korean Journal of Acupuncture
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• v.19 no.2
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• pp.63-78
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• 2002

Kupunggibodan(KU), Gamisamul-tang(GA) and Whangryunhaedok-tang(WH) are clinically the most popular prescriptions as an herbal medicine in the treatment of ischemia. In order to compare and evaluate their protective effects on the ischema-induced cognitive deficits by middle cerebral artery occlusion (MCAO), we examined its ability to improve ischemia-induced cell loss and impairements of learning and memory in the Morris water maze and eight-arm radial arm maze. Focal cerebral ischemia produced a marked cell loss, decrease in acetylcholinesterase(AchE) reactivity in the hippocampus, and learning and memory deficits in two behavioral tasks. Pretreatment with WH (100 mg/kg, p.o.) produced a substantial increase in acquisition in the Morris water maze. Pretreatment with KU increased the perfomance of the resention test in the Morris water maze. WH, KU and GA caused a significant improvement in choice accuracy in radial arm maze test. WH was superior to KU and GA in perfomance of the radial arm maze test. Consistent with behavioral data, staining with cresyl violet showed that pretreatments with WH, but not KU and GA significantly recovered the ischemia-induced cell loss in the hippcampal CA1 area. In addition, pretreatments with WH and KU recovered the ischemia-induced reduction of AchE reactivity in the hippocampal CA1 area. These results demonstrated that KU, GA and WH have protective effects against ischimea-induced learning and memory impairments and that the efficacy was the order of WH>KU>GA in tratment of ischemia induced memory deficits. The present studies provide an evidence of KU, GA and WH as putative treatment of vascular dementia. Supported by a fund from the Ministry of Health and Welfare(HMP-00-OO-04-0004), and the Brain Korea 21 Project from Korean Ministry of Education, Korea.

• Anxiety and mood
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• v.18 no.1
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• pp.32-37
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• 2022

Objective : Impaired working memory has been known to play an important role in the pathophysiology of obsessive-compulsive disorder (OCD) with growing evidence. Delayed matching-to-sample task (DMST) is a working memory task which have an advantage in analyzing several different working memory processes in one task. However, most of the studies have failed to reveal the working memory impairment with the DMST. The aim of this study was to identify whether working memory deficit in OCD can be evaluated with the DMST. Methods : The participants included 20 OCD patients and 20 healthy volunteers. Working memory was evaluated with the DMST with two different working memory loads. Accuracy of response and mean response time were measured. Results : OCD patients showed a significantly longer reaction time and lower accuracy in DMST compared to healthy controls in the task with high working memory loads. Moreover, the difference in accuracy showed interaction with the working memory load. Conclusion : The present results indicate that working memory deficit in patients with OCD can be evaluated with the DMST. The findings also suggest that previous negative behavioral results using the DMST were from low working memory load of the task.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.10 s.101
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• pp.1010-1019
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• 2005

In this paper, we used neural network technique to model memory effects of RF power amplifier which is fed by two-tone input signals. The memory effects in power amplifier were identified by observing the unsymmetrical distribution of IMD(Inter-Modulation Distortion) measurements with the change of tone spacings and power levels. Different asymmetries of IMD were also found at different center frequencies. We applied TDNN technique to model LDMOS power amplifier based on two tone IMD data, and the accuracy was very high compared to other modeling methods such as the(memoryless) adaptive modeling method.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• v.22 no.4
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• pp.302-306
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• 2011

Objectives : To investigate the cognitive functions of pediatric cancer patients and to test the hypotheses that the impairment of processing speed and working memory are more prevalent in children with medulloblastoma (MBL) compared to children with neuroblastoma (NBL). Methods : We gave the Korean version of the Wechsler Intelligent Scale for Children-III to 21 children with MBL and 24 children with NBL during outpatient follow-up after the treatment was completed. Results : Children with MBL showed below average performance across most of the sub-tests. The full scale IQ, verbal IQ, and performance IQ of children with MBL were significantly lower than those of children with NBL. There were significant differences between two groups in coding and Digit Span subtest scores. Children with MBL performed especially poorly in the coding subtest. Conclusion : These findings support previous reports of generally low IQ and the dysfunction of processing speed and working memory among children with MBL, a kind of central nervous system tumor. Further investigation is needed to determine how the deficit of processing speed and working memory affect neurocognitive development and general intelligent functions.

• Smart Structures and Systems
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• v.4 no.2
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• pp.247-259
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• 2008

The potential use of Cu-based shape memory alloys (SMA) in retrofitting historical monuments is investigated in this paper. This study is part of the ongoing work conducted in Tunisia within the framework of the FP6 European Union project (WIND-CHIME) on the use of appropriate modern seismic protective systems in the conservation of Mediterranean historical buildings in earthquake-prone areas. The present investigation consists of a finite element simulation, as a preliminary to an experimental study where a cantilever masonry wall, representing a part of a historical monument, is subjected to monotonic and quasi-static cyclic loadings around a horizontal axis at the base level. The wall was retrofitted with an array of copper SMA wires with different cross-sectional areas. A new model is proposed for heat-treated copper SMAs and is validated based on published experimental results. A series of nonlinear finite element analyses are then performed on the wall for the purpose of assessing the SMA device retrofitting capabilities. Simulation results show an improvement of the wall response for the case of monotonic and quasi-static cyclic loadings.

• Applied Microscopy
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• v.42 no.4
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• pp.207-211
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• 2012

We examined the electrical properties and microstructure of NiO produced using a sol-gel method and Ni nitrate hexahydrate ($Ni[NO_3]_2{\cdot}6H_2O$) to investigate if this NiO thin film can be used as an insulator layer for resistance random access memory (ReRAM) devices. It was found that as-prepared NiO film was polycrystalline and presented as the nonstoichiometric compound $Ni_{1+x}O$ with Ni interstitials (oxygen vacancies). Resistances-witching behavior was observed in the range of 0~2 V, and the low-resistance state and high-resistance state were clearly distinguishable (${\sim}10^3$ orders). It was also demonstrated that NiO could be patterned directly by KrF eximer laser irradiation using a shadow mask. NiO thin film fabricated by the sol-gel method does not require any photoresist or vacuum processes, and therefore has potential for application as an insulating layer in low-cost ReRAM devices.

• Journal of Power Electronics
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• v.19 no.1
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• pp.158-167
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• 2019

This research comparatively studies three kinds of flux regulation methods, namely, stored capacitor discharge pulse (SCDP), constant current source pulse (CCSP), and quantitative flux regulation pulse (QFRP), which are used for hybrid permanent magnet (PM) axial field flux-switching memory machines (HPM-AFFSMMs). Through an analysis of the operation principle and the series hybrid PM flux regulation mechanism of the objective machine, the circuit topologies and flux regulation process of these flux regulation methods are addressed in detail. On the basis of a simulation, the flux regulation characteristics of the researched machine during the magnetization and demagnetization processes are comparatively evaluated. Then, machine performance, including back EMF, direct and quadrature axis inductances, and magnetization and demagnetization characteristics, is quantitatively investigated. Results show that the QFRP enables the HPM-AFFSMM to achieve a less harmonic component of back EMF by approximately 7.28% and 7.97% at the magnetization and demagnetization states, respectively, and a more complete magnetization process than the SCDP and CCSP.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1998.06a
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• pp.57-60
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• 1998

Lean zirconate titanate (PZT) is an attractive material for the memory device applications. We have investigated Pt and{{{{ { RuO}_{2 } }}}} as a botton electrode for a device application of PZT thin film. The bottom electrodes were prepared by using an RF magnetron sputtering method. The substrate temperature influenced the resistivity of Pt and {{{{ { RuO}_{2 } }}}} a s well as the film crystal structure. XRD examination shows that a preferred(111) orientations for the substrate temperature of 30$0^{\circ}C$. From the XRD and AFM results, we recommend the substrate temperature of 30$0^{\circ}C$ for the bottom electrode growth. We investigated and anneal temperature effect because Perovskite PZT structure is recommended for the memory device applications and the structural transformation is occurred only after and elevated heat treatment. As post anneal temperature was increased from RT to $700^{\circ}C$, the resistivity of Rt and {{{{ { RuO}_{2 } }}}} w as decreased. Surface morphology was observed by AFM as a function of post anneal temperature.