• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.7B
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• pp.818-826
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• 2011

This paper proposes a novel FTL (Flash Translation Layer) algorithm employing sector-level mapping technique based on locality to reduce the number of erase operations in flash memory accesses. Sector-level mapping technique shows higher performance than other mapping techniques, even if it requires a large mapping table. The proposed algorithm reduces the size of mapping table by employing dynamic table update, processes sequential writes by exploiting sequential locality and extracts hot sector in random writes. Experimental results show that the number of erase operations has been reduced by 75.4%, 65.8%, and 10.3% respectively when compared with well-known BAST, FAST and sector mapping algorithms.

• Proceedings of the Korean Information Science Society Conference
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• 2007.06c
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• pp.69-74
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• 2007

플래시 메모리는 하드디스크와 다른 물리적 특성을 가지고 있다. 대표적으로 덮어쓰기가 되지 않고 데이터를 읽고 쓰는 단위와 지우는 단위가 서로 다르다. 이러한 물리적 제약을 소프트웨어적으로 보완해주기 위해서 플래시 메모리를 사용하는 시스템에서는 대부분 Flash Translation Layer (FTL)을 사용한다. 지금까지 FTL 알고리즘의 대부분이 임의 쓰기 패턴보다 순차 쓰기 패턴에 훨씬 더 효율적으로 작용한다. 그러나 B-트리와 같은 자료구조에서는 일반적으로 순차 쓰기 패턴 보다는 임의 쓰기 패턴이 발생된다. 따라서 플래시 메모리상에서 B-트리를 관리할 경우 FTL에 비효율적인 쓰기 패턴을 생성하게 된다. 본 논문에서는 플래시 메모리상에서 B-트리와 같은 자료구조를 효율적으로 저장 관리하기 위한 새로운 방식을 제안한다. 새로운 방식은 B-트리에서 발생되는 임의 쓰기를 플래시 메모리상의 버퍼를 이용하여 FTL에 효율적인 순차 쓰기를 발생시킨다. 실험 결과, 본 논문에서 제안하는 방식은 기존의 방식보다 플래시 메모리에서 발생되는 쓰기 및 블록소거 연산 횟수를 60%이상 감소시킨다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.3
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• pp.31-38
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• 2003

In the present work, a nonlinear inverse perturbation method which has been used in the structural optimization, is adopted so as to identify the structural damages. Unlike the structural optimization, a larger number of constrained equations than the number of unknown parameters are often required detect structural damage. Therefore, nonlinear least squares method is utilized to solve the problem. Because only a limited number of sensors are available I real situation of damage detection, the determination of sensor location becomes one of the most important issues. Hence, this work concentrates on the issue of sensor placement in the framework of nonlinear inverse perturbation method, and the performances of various methodologies concerning to sensor placement are compared with each other. The comparisons show tat the successive elimination method gets good performance for sensor placement. From the several numerical studies, it is confirmed that the inverse perturbation method, combined with the successive elimination method, is very promising in structural damage detection.

• Journal of Applied Biological Chemistry
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• v.65 no.4
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• pp.453-456
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• 2022

Phragmites communis rhizome (Phragmitis rhizoma) was extracted with 70% ethanol, and then the extract was fractionated sequentially using n-hexane, chloroform, and ethyl acetate as solvents. Among the solvent fractions of Phragmitis rhizoma extract, the polyphenol content in ethyl acetate fraction was the highest. The chloroform and ethyl acetate fractions possessed a good nitrite scavenging activity. In addition, each solvent fraction showed an effective lipid peroxidation inhibitory ability at a concentration of 10 mg/mL.

• KSBB Journal
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• v.19 no.1
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• pp.67-71
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• 2004

An antioxidant activity of Rosa rugosa extract and its solvent-partitioned fractions was determined not only by measuring lipid peroxide produced when a mouse liver homogenate was exposed to the air at 37$^{\circ}C$, using thiobarbituric acid (TBA) but also by evaluating the free radical scavenging effect against DPPH radical, authentic peroxynitrite, and 3-morpholinsydnonimine (SIN-1). All its partitioned fractions including crude extract showed potent scavenging effect against DPPH radical, peroxynitrite, and lipid peroxidation. n-BuOH fraction, in particular, was found to be the most effective in DPPH radical scavenging ability as well as inhibition against lipid peroxidation. The 15% aqueous MeOH fraction also showed a strong potency which was slightly lower than n-BuOH fraction. Based on these results, we suggest that Rosa rugosa could be useful for preventing an oxidative damage.

• KSBB Journal
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• v.18 no.3
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• pp.165-169
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• 2003

The antioxidative activity of Portulaca oleracea was tested using in vitro experimental models. Antioxidative activities were determined by measuring DPPH radical scavenging activity and lipid peroxide using 2-thiobarbituric and (TBA). The crude extract was sequentially partitioned with n-hexane, 15% aq. MeOH, EtOAc, n-BuOH, $H_2O$. A remarkable antioxidative effect was observed in the EtOAc and n-BuOH fractions. The DPPH radical scavenging effect ($IC_{50}$=17.90 $\mu\textrm{g}$/ml) of the n-BuOH soluble fraction was comparable with that of the natural antioxidant, $\alpha$-tocopherol ($IC_{50}$=6.99 $\mu\textrm{g}$/ml) and the inhibition effect of lipid peroxidation in mouse liver homogenate was similar to that of the natural antioxidant, L-ascorbic acid at a concentration of 1.0 mg/ml to 5 mg/ml.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.10
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• pp.1167-1175
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• 2016

This paper proposes an efficient page-level mapping algorithm that reduces the erase count in the FTL for flash memory systems. By maintaining the weight for each write request in the request buffer, the proposed algorithm estimates the degree of temporal locality for each incoming write request. To exploit temporal locality deliberately for determination of hot request, the degree of temporal locality should be much higher than the reference point determined experimentally. While previous LRU algorithm treats a new write request to have high temporal locality, the proposed algorithm allows write requests that are estimated to have high temporal locality to access hot blocks to store hot data intensively. The pages are more frequently updated in hot blocks than warm blocks. A hot block that has most of invalid pages is always selected as victim block at Garbage Collection, which results in delayed erase operation and in reduced erase count. Experimental results show that erase count is reduced by 9.3% for real I/O workloads, when compared to the previous LRU algorithm.

• Journal of the Korean Society of Food Science and Nutrition
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• v.40 no.12
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• pp.1635-1641
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• 2011

This study was designed to investigate antioxidant activities of pomegranate endocarp extracts. Pomegranate endocarp extract contains the highest antioxidant function compared to pomegranate extracts from other parts. Pomegranate endocarp extract was fractionated with hexane, dichloromethane, ethyl acetate, butanol extract, and water, followed by evaluation for antioxidant activity. During this experiment, various antioxidant tests such as nitrite scavenging activity, reducing power, superoxide anion scavenging activity, $ABTS^+$ scavenging activity, SOD like-activity, and DPPH radical scavenging activity were conducted on the $CH_2Cl_2$, EtOAc, BuOH, $H_2O$ fractions of pomegranate endocarp extract. Results showed that the ethyl acetate fraction contained the highest DPPH radical scavenging activity among the samples. For SOD like-activity, the dichloromethane fraction had the highest antioxidant activity. For superoxide anion scavenging activity, the ethyl acetate fraction had the highest antioxidant activity. In the $ABTS^+$ scavenging activity test, the ethyl acetate fraction $IC_{50}$ was 39.26 ${\mu}g$/mL, whereas that of the butanol fraction was 40.95 ${\mu}g$/mL. In testing reduction power at 0.1 mg/mL, the O.D. of the ethyl acetate fraction was highest at 1.404 and showed higher activity than ascorbic acid at 1.332. The results of the nitrite scavenging activity test were very similar to those of the SOD like-activity test. These results suggest that pomegranate endocarp extract may have value as a natural antioxidant.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.453-458
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• 2004

This study proposes a new two-level condensation scheme for the construction of a reduced system. In the first step, the candidate area is selected for the construction of the reduced system by energy estimation in element-level. In the second step, primary degrees of freedom are selected by sequential elimination from the candidate degrees of freedom linked to the selected elements. Numerical examples demonstrate that the proposed method saves the computational cost effectively and provides a reduced system which predicts the eigenvalues accurately. Moreover, the well-constructed reduced system can present the reliable behavior of the structure under arbitrary dynamic loads comparing to that of global system. Time integration in a reduced system can save the computing time remarkably. Through a few numerical examples, the efficiency and reliability of the proposed scheme are verified.

• KSBB Journal
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• v.23 no.1
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• pp.77-82
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• 2008

We investigated several biological activities using the ethanol extract and its fractions from Pimpinella komarovii leaves to evaluate the usefulness of its extract as a functional biomaterial. The ethanol extract showed antioxidant activities, such as DPPH scavenging activity $(IC_{50}=231.8{\mu}g/m{\ell})$. superoxide scavenging activity $(IC_{50}=23.6{\mu}g/m{\ell})$, and xanthine oxidase inhibitory activity $(IC_{50}=587.8{\mu}g/m{\ell})$. Its EtOAc fraction showed the strongest antioxidant activities among several fractions. The inhibitory effect of ethanol extract on tyrosinase activity was higher than water fraction. When $50{\mu}g/m{\ell}$ of EtOAc fraction was applied, the inhibition ratio of tyrosinase activity was much higher (42%) than that of melasolv. The EtOAc fraction also showed higher inhibitory effect on melanogenesis in Melan-a cells. The n-hexane and EtOAc fractions dose-dependently inhibited the NO production in a RAW 264.7 cells. These results suggest that extract of Pimpinella komarovii could be used as functional biomaterial in developing a skin whitening agent having the antioxidant activity.