• Smart Structures and Systems
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• 제26권6호
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• pp.703-720
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• 2020

This paper investigates the safety of the wind turbine blade against excessive deformation. For this purpose, the performance of the blade in the along-wind direction is improved by longitudinal stiffener made of shape memory alloy. The rationale behind the selection of this smart material is due to its ability to offer excellent thermo-mechanical behaviour at low strain. Here, Liang-Roger model is adopted for vibration control, and the super-elastic effects are utilised for blade stiffening. Turbulent wind fields are generated at the hub height using TurbSim and the corresponding loads are evaluated using blade element momentum theory. An efficient switching algorithm is developed along with performance curves that enable the designer to select an optimal mode of heating depending upon the operational scenario. Numerical results presented in this paper clearly demonstrate the performance envelope of the proposed stiffener and its influence on the reliability of the blade.

• Biomolecules & Therapeutics
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• 제22권3호
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• pp.232-238
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• 2014

Alzheimer's disease (AD) is the most common neurodegenerative disease without known ways to cure. A key neuropathologic manifestation of the disease is extracellular deposition of beta-amyloid peptide (Ab). Specific mechanisms underlying the development of the disease have not yet been fully understood. In this study, we investigated effects of 4-O-methylhonokiol on memory dysfunction in APP/PS1 double transgenic mice. 4-O-methylhonokiol (1 mg/kg for 3 month) significantly reduced deficit in learning and memory of the transgenic mice, as determined by the Morris water maze test and step-through passive avoidance test. Our biochemical analysis suggested that 4-O-methylhonokiol ameliorated $A{\beta}$ accumulation in the cortex and hippocampus via reduction in beta-site APP-cleaving enzyme 1 expression. In addition, 4-O-methylhonokiol attenuated lipid peroxidation and elevated glutathione peroxidase activity in the double transgenic mice brains. Thus, suppressive effects of 4-O-methylhonokiol on $A{\beta}$ generation and oxidative stress in the brains of transgenic mice may be responsible for the enhancement in cognitive function. These results suggest that the natural compound has potential to intervene memory deficit and progressive neurodegeneration in AD patients.

• 전자공학회논문지S
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• 제34S권6호
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• pp.38-45
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• 1997

Skin color reappearance problem in color processing system is necessary to transform a specific color sand improve color reappearance quality as a reference color. The skin color has been situated as an important memory color not only in our lives but also in color application systems such as TV. Thus, skin color reappearance problem is more important than other color processing problem. In this paper, we propose a skin color reappearance algorithm for color enhancement in TV which use phase detector to detect the skin colors at real-time from 3.58 MHz color burst signal and color signal, comparators to discriminate the types of skin color, and micom to reprodece standard skin colors for races.

• Journal of Magnetics
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• 제14권3호
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• pp.104-107
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• 2009

The effects of the magnetic property variation on current-induced magnetization switching in magnetic tunnel junction with perpendicular magnetic anistoropy (PMA) and the soft magnetic polarization-enhancement layers (PELs) inserted between the layers with PMA and the MgO layer was studied. A micromatnetic model was used to estimate the switching time of the free layer by different applied current densities, with changing saturation magnetization ($M_s$) of the PELs, interlayer exchange coupling between PMA layers and PELs. The switching time could be significantly reduced at low current densities, by increasing $M_s$ of PELs and decreasing interlayer exchange coupling.

• The Korean Journal of Physiology and Pharmacology
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• 제8권4호
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• pp.173-179
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• 2004

Amyloid ${\beta}-peptide\;(A{\beta})$ contributes to the pathogenesis of Alzheimer's disease (AD), causing neuronal death through apoptosis. In this study, the neuroprotective role of BF-7, extracted form sericultural product, was examined against $A{\beta}-induced$ toxicity in cultured human neuronal cell SKN-SH. In order to know if the BF-7 has positive role on the cognition and memory in human, the mixture of BF-7, DHA and EPA (BDE) was examined using Rey Kim and K-WAIS test with 50 healthy high school student. We report here that BDE significantly attenuated $A{\beta}-induced$ apoptosis through the reduction of ROS accumulation, and diminished caspase-like protease activity. Moreover, the memory index and memory preservation, and attentative concentration of BDE treated group for 1 month were significantly improved, in contrast to the case of placebo control treated with DHA and EPA. This result represent that the BF-7 play significant positive role on learning memory. Taken together, our result suggested the natural product BF-7 is a good substance for the brain functionally and physiologically.

• Biomolecules & Therapeutics
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• 제21권6호
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• pp.462-469
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• 2013

Eucommia ulmoides Oliv. Bark (EUE) is commonly used for the treatment of hypertension, rheumatoid arthritis, lumbago, and ischialgia as well as to promote longevity. In this study, we tested the effects of EUE aqueous extract in graded doses to protect and enhance cognition in scopolamine-induced learning and memory impairments in mice. EUE significantly improved the impairment of short-term or working memory induced by scopolamine in the Y-maze and significantly reversed learning and memory deficits in mice as measured by the passive avoidance and Morris water maze tests. One day after the last trial session of the Morris water maze test (probe trial session), EUE dramatically increased the latency time in the target quadrant in a dose-dependent manner. Furthermore, EUE significantly inhibited acetylcholinesterase (AChE) and thiobarbituric acid reactive substance (TBARS) activities in the hippocampus and frontal cortex in a dose-dependent manner. EUE also markedly increased brain-derived neurotrophic factor (BDNF) and phosphorylation of cAMP element binding protein (CREB) in the hippocampus of scopolamine-induced mice. Based on these findings, we suggest that EUE may be useful for the treatment of cognitive deficits, and that the beneficial effects of EUE are mediated, in part, by cholinergic signaling enhancement and/or protection.

• 대한전자공학회논문지TC
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• 제49권1호
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• pp.47-52
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• 2012

전력증폭기는 기지국의 효율을 결정하는 중요한 요소이며, 효율성 제고를 위하여 GaN증폭소자를 사용한 Doherty 전력증폭기 구조에 대한 연구가 지속되고 있다. Doherty 전력증폭기의 메모리 효과는 선형성과 효율특성과 연관된 동작특성에 큰 영향을 미친다. 본 논문에서는 GaN Doherty 전력증폭기의 전열적인 비선형성 모델링과 전열적 메모리 효과가 GaN Doherty 증폭기의 왜곡형성과 보상에 대하여 연구하였다. GaN Doherty 증폭기의 전열적 메모리 특성을 모델링하기 위하여 순시적으로 소모되는 전력과 순시 접합온도의 정확한 관계식을 정립하였다. 제안된 모델의 파라미터로부터 GaN Doherty 전력증폭기의 비선형왜곡과 전열적 메모리 효과를 보상할 수 있는 전치왜곡선형화기 모델을 설계하였다. 제안된 모델의 성능평가는 37dBm GaN Doherty 전력증폭기와 ADS Tool을 사용하여 왜곡특성 성능개선정도를 검증하였다. 선형화된 GaN 전력증폭기의 2-tone 출력스펙트럼에서 약 16 dB의 왜곡개선효과를 보였다.

• 정보처리학회논문지A
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• 제13A권5호
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• pp.387-398
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• 2006

본 논문에서는 플래시 메모리 파일 시스템을 위한 새로운 페이지 할당 기법을 제안한다. 제안된 기법은 순수도를 고려하여 페이지를 할당하며, 이때 순수도는 플래시 메모리에서 유효한 페이지와 유효하지 않은 페이지가 공존하는 블록의 비율로 정의된다. 순수도는 플래시 메모리 파일 시스템의 블록 클리닝(block cleaning) 비용, 구체적으로 블록 클리닝을 수행할 때 복사해야할 페이지와 삭제해야할 블록의 양을 결정한다. 제안된 기법은 순수도를 향상시키기 위해 빈번하게 변경되는 데이터와 그렇지 않은 데이터를 구분하고, 이들을 서로 다른 블록에 할당한다 데 이터의 구분은 데이터의 속성 등의 정적 특성과 수행 시 변경 횟수 등의 동적 특성을 모두 고려한다 제안된 기법은 내장형 보드와 YAFFS 상에 구현되었으며, 성능 분석 결과 기존 YAFFS에 비해 최대 15.4초 (평균 7.8초) 블록 클리닝 시간을 단축시켰다. 또한 이용율이 증가함에 따라 제안된 기법이 더욱 좋은 성능을 제공하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.396-396
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• 2013

The resistive random access memory (ReRAM) has several advantages to apply next generation non-volatile memory device, because of fast switching time, long retentions, and large memory windows. The high mobility of monolayered graphene showed several possibilities for scale down and electrical property enhancement of memory device. In this study, the monolayered graphene grown by chemical vapor deposition was transferred to $SiO_2$ (100 nm)/Si substrate and glass by using PMMA coating method. For formation of metal-oxide nanoparticles, we used a chemical reaction between metal films and polyamic acid layer. The 50-nm thick BPDA-PDA polyamic acid layer was coated on the graphene layer. Through soft baking at $125^{\circ}C$ or 30 min, solvent in polyimide layer was removed. Then, 5-nm-thick indium layer was deposited by using thermal evaporator at room temperature. And then, the second polyimide layer was coated on the indium thin film. After remove solvent and open bottom graphene layer, the samples were annealed at $400^{\circ}C$ or 1 hr by using furnace in $N_2$ ambient. The average diameter and density of nanoparticle were depending on annealing temperature and times. During annealing process, the metal and oxygen ions combined to create $In_2O_3$ nanoparticle in the polyimide layer. The electrical properties of $In_2O_3$ nanoparticle ReRAM such as current-voltage curve, operation speed and retention discussed for applictions of transparent and flexible hybrid ReRAM device.

• 대한전자공학회논문지SD
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• 제41권10호
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• pp.85-94
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• 2004

본 논문에서는 메모리 접근 연산을 레지스터 접근 연산으로 변환함으로써 레지스터를 할당하여 내장형 소프트웨어의 성능 향상을 도모할 수 있는 위한 레지스터 할당 기법을 제안한다. 제안된 방법에서는 프로파일링(Profiling)을 통하여 메모리 트레이스(trace)를 얻는다. 그리고 각 함수의 수행 횟수에 대한 프로파일링 결과로부터 높은 동적 호출 횟수를 가지는 대상 함수를 선정하여 제안된 레지스터 할당 기법을 적용한다. 이와 같이 최적화의 대상이 되는 함수의 수를 줄임으로써 전체적인 컴파일 시간을 줄일 수 있다. 최적화대상 함수의 메모리 트레이스를 탐색하여 레지스터 접근 연산으로 변경될 경우 수행 사이클을 줄일 수 있는 메모리 접근 연산을 찾는다. 찾아진 메모리 접근 연산에 대해서는 컴파일러의 중간단계 코드를 수정하여 프로모션 레지스터(promotion register)를 할당한다. 이와 같은 과정을 거쳐 메모리 접근 연산이 프로모션 레지스터에 대한 접근 연산으로 대체되고 이로부터 성능향상을 얻을 수 있다. 제안된 레지스터 프로모션 기법을 ARM과 MCORE 프로세서용 컴파일러에 적용한 후 MediaBench와 DSPStone 벤치마크를 이용하여 cycle count를 비교함으로써 성능을 측정하였다. 그 결과 ARM과 MCORE에 대하여 평균 14%와 18%의 성능향상을 얻을 수 있었다.