• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.9 s.339
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• pp.29-34
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• 2005

This paper describes a novel internal clock generator, called duty cycle-corrected analog synchronous mirror delay (DCC-ASMD). The proposed circuit is well suited for dual edge-triggered systems such as double data-rate synchronous DRAM since it can achieve clock synchronization within two clock cycles with accurate duty cycle correction. To evaluate the performance of the proposed circuit, DCC-ASMD was designed using a $0.35\mu$m CMOS process technology. Simulation results show that the proposed circuit generates an internal clock having $50\%$ duty ratio within two clock cycles from the external clock having duty ratio range of $40\;\~\;60$.

• Journal of KIISE:Databases
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• v.30 no.6
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• pp.651-665
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• 2003

To reduce cache misses emerges as the most important issue in today's situation of main memory databases, in which CPU speeds have been increasing at 60% per year, and memory speeds at 10% per year. Recent researches have demonstrated that cache-conscious index structure such as the CR-tree outperforms the R-tree variants. Its search performance can be poor than the original R-tree, however, since it uses a lossy compression scheme. In this paper, we propose alternatively a cache-conscious version of the R-tree, which we call MR-tree. The MR-tree propagates node splits upward only if one of the internal nodes on the insertion path has empty room. Thus, the internal nodes of the MR-tree are almost 100% full. In case there is no empty room on the insertion path, a newly-created leaf simply becomes a child of the split leaf. The height of the MR-tree increases according to the sequence of inserting objects. Thus, the HeightBalance algorithm is executed when unbalanced heights of child nodes are detected. Additionally, we also propose the CCMR-tree in order to build a more cache-conscious MR-tree. Our experimental and analytical study shows that the two-dimensional MR-tree performs search up to 2.4times faster than the ordinary R-tree while maintaining slightly better update performance and using similar memory space.

• Herbal Formula Science
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• v.25 no.1
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• pp.69-87
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• 2017

Objectives : Cheongnoemyeongsin-hwan (CNMSH) is a herb medicine to treat cognitive impairment. This study was investigated the effects of CNMSH on learning and memory impairment induced by cerebral hypoperfusion. Cerebral hypoperfusion was produced chronically by permanent bilateral common carotid artery occlusion (BCCAO) in rats. Methods : CNMSH was administered orally once a day (250 mg/kg) for 28 days starting at 4th week after the BCCAO. The acquisition of learning and the retention of memory were tested on 9th week after the BCCAO using the Morris water maze. In addition, effect of CNMSH on neuronal apoptosis and ${\beta}-amyloid$ accumulation in the hippocmapus was evaluated with immunohistochemistry and Western blotting. Results : 1. CNMSH and ChAL significantly shortened the escape latencies on the 2nd day of acquisition training trials. 2. ChAL significantly prolonged the swimming time spent in the target and peri-target zones and CNMSH also significantly prolonged the swimming time spent in the peri-target zone. 3. CNMSH and ChAL significantly increased the number of target heading in the retention test. 4. ChAL significantly shortened the time of the 1st target heading in the retention test, but CNMSH insignificantly shortened the time of that. 5. CNMSH and ChAL significantly increased the memory score in the retention test. 6. CNMSH and ChAL significantly attenuated the reduction of CA1 neurons, but insignificantly attenuated the reduction of CA1 thickness. 7. CNMSH and ChAL significantly attenuated the up-regulation of Bax expression in the CA1 of hippocampus. 8. CNMSH and ChAL significantly attenuated the up-regulation of cascapse-3 expression in the CA1 of hippocampus. 9. CNMSH and ChAL significantly attenuated the ${\beta}-amyloid$ accumulation in the CA1 of hippocampus. 10. CNMSH and ChAL significantly attenuated the up-regulation of APP expression in the CA1 of hippocampus. 11. CNMSH and ChAL significantly attenuated the up-regulation of BACE-1 expression in the CA1 of hippocampus. Conclusions : The results show that CNMSH attenuates neuronal apoptosis and ${\beta}-amyloid$ accumulation in the hippocampus and alleviates the impairment of learning and memory produced by chronic cerebral hypoperfusion. These results suggest that CNMSH may be a beneficial medicinal herb to treat cognitive impairment associated with neurodegenerative diseases.

• Journal of Korean Elementary Science Education
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• v.29 no.1
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• pp.93-101
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• 2010

The purpose of this study was to investigate the internal factors whether teachers execute experiments at the science classes in the elementary school. Semi-structured in-depth interviews were performed with 9 elementary school teachers who have served for more than three years. In-depth interviews were performed individually and all the interviews were recorded. Data sources were analyzed by grounded theory. The results were as follows: The internal factors that they did experiments at the science classes were science teaching faiths in experiment, self confidence in experiment, interest in science. and the internal factors that they did not experiment at the science classes were lack of science content knowledge, lack of science education knowledge, memory of failure at experiment, and so on. The investigation results imply inquiry activities should be more strengthened in elementary teacher education program and pre-service teacher curriculum. And it needs to give a materials of receiving information and guidance detailed about the experiments.

• Journal of Digital Contents Society
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• v.16 no.4
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• pp.535-543
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• 2015

Recently, NAND flash based storage devices are being used as a storage device in various fields through hiding the limitations of NAND flash memory and maximizing the advantages. In particular, those storage devices contain a software layer called Flash Translation Layer(FTL) to hide the "erase-before-write" characteristics of NAND flash memory. FTL includes the metadata for managing the data requested from host. That metadata is stored in internal memory because metadata is very frequently accessed data for processing the requests from host. Thus, if the power-loss occurs, all data in memory is lost. So metadata management scheme is necessary to store the metadata periodically and to load the metadata in the initialization step. Therefore we proposed the scheme which satisfies the core requirements for metadata management and efficient operation. And we verified the efficiency of proposed scheme by experiments.

• The Korean Journal of Physiology and Pharmacology
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• v.13 no.4
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• pp.315-319
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• 2009

Astragalus Membranaceus (AM) is a useful Korean herb that has been clinically prescribed for stress-related illness. The objective of the present study was to examine the anti-stress effects of AM on repeated stress-induced alterations of anxiety, learning and memory in rats. Restraint stress was administered for 14 days (2h/day) and AM (400mg/kg) given by oral administration, in the AM group, for the same period. Starting on the eighth day, the rats were tested for spatial memory on the Morris water maze test (MW) and for anxiety on the elevated plus maze (EPM). Changes of expression on immunohistochemistry were studied for cholineacetyl transferase (ChAT) and tyrosine hydroxylase (TH) in the brain. The results showed that the rats treated with AM had significantly reduced stress-induced deficits on learning and memory on the spatial memory tasks. In addition, the ChAT immunoreactivities were increased. In the EPM, treatment with AM increased the time spent in the open arms (p<0.001) compared to the control group. In addition, AM treatment also normalized increases of TH expression in the LC (p<0.001). In conclusion, administration of AM improved spatial learning and memory and reduced stress-induced anxiety. Thus, the present results suggest that AM is able to recover behavioral and neurochemical impairments induced by stress.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.3
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• pp.55-61
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• 2000

This paper presents an efficient hardware architecture of frame memory interface in MPEG-2 video encoder. To reduce the size of memory buffers between SDRAM and the frame memory module, the number of clocks needed for each memory access is minimized with dual bank operation and burst length change. By allocating the remaining cycles not used by SDRAM access, to the random access cycle, the internal buffer size, the data bus width, and the size of the control logic can be minimized. The proposed architecture is operated with 54MHz clock and designed with the VT $I^{тм}$ 0.5 ${\mu}{\textrm}{m}$ CMOS TLM standard cell library. It is verified by comparing the test vectors generated by the c-code model with the simulation results of the synthesized circuit. The buffer area of the proposed architecture is reduced to 40 % of the existing architecture.

• Geophysics and Geophysical Exploration
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• v.21 no.4
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• pp.213-219
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• 2018

In this study, we simulated 3D wave propagation modeling using a Xeon Phi x200 processor and compared the parallel computation performance with that using a Xeon CPU. Unlike the 1st generation Xeon Phi coprocessor codenamed Knights Corner, the 2nd generation x200 Xeon Phi processor requires no additional communication between the internal memory and the main memory since it can run an operating system directly. The Xeon Phi x200 processor can run large-scale computation independently, with the large main memory and the high-bandwidth memory. For comparison of parallel computation, we performed the modeling using the MPI (Message Passing Interface) and OpenMP (Open Multi-Processing) libraries. Numerical examples using the SEG/EAGE salt model demonstrated that we can achieve 2.69 to 3.24 times faster modeling performance using the Xeon Phi with a large number of computational cores and high-bandwidth memory compared to that using the 12-core CPU.

• Journal of Internet of Things and Convergence
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• v.9 no.3
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• pp.7-12
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• 2023

One of the most important characteristics of digital forensics is integrity. Integrity means that the data has not been tampered with. If evidence is collected during digital forensic and later tampered with, it cannot be used as evidence. With analog evidence, it's easy to see if it's been tampered with, for example, by taking a picture of it. However, the data on the storage media, or digital evidence, is invisible, so it is difficult to tell if it has been tampered with. Therefore, hash values are used to prove that the evidence data has not been tampered with during the process of collecting evidence and submitting it to the court. The hash value is collected from the stored data during the evidence collection phase. However, due to the internal behavior of NAND flash memory, the physical data shape may change over time from the acquisition phase. In this paper, we study the characteristics and techniques of flash memory that can cause the physical shape of flash memory to change even if no intentional data corruption is attempted.

• Structural Engineering and Mechanics
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• v.81 no.6
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• pp.691-703
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• 2022

To obtain the seismic response of lead-cored rubber, shape memory alloy (SMA)-rubber isolation Plate-shell Integrated Concrete Liquid-Storage Structure (PSICLSS), based on a PSICLSS in a water treatment plant, built a scale experimental model, and a shaking table test was conducted. Discussed the seismic responses of rubber isolation, SMA-rubber isolation PSICLSS. Combined with numerical model analysis, the vibration characteristics of rubber isolation PSICLSS are studied. The results showed that the acceleration, liquid sloshing height, hydrodynamic pressure of rubber and SMA-rubber isolation PSICLSS are amplified when the frequency of seismic excitation is close to the main frequency of the isolation PSICLSS. The earthquake causes a significant leakage of liquid, at the same time, the external liquid sloshing height is significantly higher than internal liquid sloshing height. Numerical analysis showed that the low-frequency acceleration excitation causes a more significant dynamic response of PSICLSS. The sinusoidal excitation with first-order sloshing frequency of internal liquid causes a more significant sloshing height of the internal liquid, but has little effect on the structural principal stresses. The sinusoidal excitation with first-order sloshing frequency of external liquid causes the most enormous structural principal stress, and a more significant external liquid sloshing height. In particular, the principal stress of PSICLSSS with long isolation period will be significantly enlarged. Therefore, the stiffness of the isolation layer should be properly adjusted in the design of rubber and SMA-rubber isolation PSICLSS.