• Structural Engineering and Mechanics
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• v.64 no.1
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• pp.121-133
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• 2017

This paper proposes an analytical solution method for free vibration of curved functionally graded (FG) nonlocal beam supposed to different thermal loadings, by considering porosity distribution via nonlocal elasticity theory for the first time. Material properties of curved FG beam are assumed to be temperature-dependent. Thermo-mechanical properties of porous FG curved beam are supposed to vary through the thickness direction of beam and are assumed to be temperature-dependent. Since variation of pores along the thickness direction influences the mechanical and physical properties, porosity play a key role in the mechanical response of curved FG structures. The rule of power-law is modified to consider influence of porosity according to even distribution. The governing equations of curved FG porous nanobeam under temperature field are derived via the energy method based on Timoshenko beam theory. An analytical Navier solution procedure is used to achieve the natural frequencies of porous FG curved nanobeam supposed to thermal loadings with simply supported boundary condition. The results for simpler states are confirmed with known data in the literature. The effects of various parameters such as nonlocality, porosity volume fractions, type of temperature rising, gradient index, opening angle and aspect ratio of curved FG porous nanobeam on the natural frequency are successfully discussed. It is concluded that these parameters play key roles on the dynamic behavior of porous FG curved nanobeam. Presented numerical results can serve as benchmarks for future analyses of curve FG nanobeam with porosity phases.

• Proceedings of the SCSK Conference
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• 2003.09b
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• pp.464-478
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• 2003

Free radicals and reactive oxygen species (ROS) caused by UV exposure or other environmental facts play critical roles in cellular damage and aging. The extract of tinged autumnal leaves of maple tree(Acer palmatum) has proven to be a powerful antioxidant. The Acer palmatum extract is very effective on the stabilization of biological membranes( containing unsaturated fatty acid). We studied photoprotective effect of the extract against UVB-induced cytotoxicity in human keratinocytes. The extract improved cell viability comparing to control after UVB irradiation. In the determination test of pro inflammatory cytokines the extract decreased expression of interleukin 1 a and 6, which play an important role in inflammation and skin erythema caused by UV. We also studied property of varying cosmetic formulations on the percutaneous absorption of the extract. After 24 hour in vitro penetration study, the content of the extract was more highly detected in skin residue part. This result showed the extract had relatively high compatibility of skin in our emulsion system. On human skin, after appling the product containing the extract we obtained a good result of antiwrinkle effect by skin visiometer. In conclusion, the Acer palmatum extract is a photoprotective and very effective in stressed and aged skin care. And we can predict the extract mainly affects on the skin cell and tissue in our emulsion system.

• Journal of Dairy Science and Biotechnology
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• v.37 no.2
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• pp.83-93
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• 2019

Food spoilage by fungi is responsible for considerable food waste and economical losses. Among the food products, fermented dairy products are susceptible to deterioration due to the growth of fungi, which are resistant to low pH and can proliferate at low storage temperatures. For controlling fungal growth in dairy products, potassium sorbate and natamycin are the main preservatives used, and natamycin is approved by most countries for use in cheese surface treatment. However, a strong societal demand for less processed and preservative-free food has emerged. In the dairy products, lactic acid bacteria (LAB) are naturally present or used as cultures and play a key role in the fermentation process. Fermentation is a natural preservation technique that improves food safety, nutritional value, and specific organoleptic features. Production of organic acids is one of the main features of the LAB used for outcompeting organisms that cause spoilage, although other mechanisms such as antifungal peptides obtained from the cleavage of food proteins and competition for nutrients also play a role. More studies for better understanding these mechanisms are required to increase antifungal LAB available in the market.

• Toxicological Research
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• v.16 no.1
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• pp.1-8
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• 2000

Astrocytes generate free radicals including nitric oxide (NO) and reactive oxygen intermediates(ROI) which in turn play roles in the pathogenesis of degenerative diseases and sclerotic changes of the brain. This study was designed to evaluate the mechanism that free radicals contribute to the cytotoxicty of rat neonatal primary astrocytes. Treatment with NO donors alone including soldium nitroprusside(SNP), S-nitrosoglucathinoe (GSNO), and S-nitroso-n-acetylpenicillamine (SNAP) showed a little effect on the death of rat neonatal primary astrocytes, whereas SNP markedly induced the death of RAW 264.7 cells. ROI inculding H2O2 and O2 donor also slightly induced the death of rat primary astrocytes. However, 3-morpholinosydnonimine(SIN-1), a donor of peroxynitrite (ONOO), which is a reactive compound of NO with superoxide, significantly decreased the viability of rat primary astrocytes in a dose-dependent manner. Cells were retarded in outgrowth of viability of cellular processes with cell shrinkage and detachment from culture dishes. Hoechst staining demonstrated that SIN-1-induced cell death might be due to an apoptosis which was characterized by nuclear condensation and fragmentation. SIN-1-induced apoptosis was prevented by the pretreatment with superoxide dismutase (SOD) and catalase in rat primary astorocytes. Furthermore, prevention of the generation of reduced glutathione (GSH) by DL-buthionine-[S, R]-sulfoximine (BSO) aggravated the cytotoxic effects of SNP, benzene triol, and SIN-1 in rat primary astrocytes. Taken together, it is suggested that peroxynitrite may be a major effector of apoptosis and cellular antioxidant system is important for cell survival in rat prima교 astrocytes.

• Korean Journal of Environmental Agriculture
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• v.16 no.1
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• pp.14-18
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• 1997

The objective of this research was to increase phytoprotective effects by combined treatment of uniconazole and free radical scavengers such as ascorbic acid or sodium benzoate on $SO_2$ injury in P. occidentalis. The plant injury, chlorophyll content and enzyme activity of superoxide dismutase(SOD) and peroxidase(POD) affected by combined treatment were also investigated. The phytoprotective role of uniconazole was nullified by spray of Diethyldithiocarbamate(DDTC) resulting in the decrease of SOD and POD activities. Free radical scavengers, sodium benzoate and ascorbic acid, did not affect SOD and POD activity, but significantly inhibited the development of visible injury, degradation of chlorophyll, and SOD and POD activity in leaves exposed to $SO_2$. The spray of ascorbic acid decreased plant susceptibility to $SO_2$ induced by DDTC application. These results indicate that uniconazole application increase SOD activity that play a role of antioxidant in plant body, but sodium benzoate and ascorbic acid do not affect enzyme activities of SOD or POD.

• Food Science of Animal Resources
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• v.36 no.4
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• pp.558-565
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• 2016

The aim of this study was to investigate the influence of proteolytic pork hydrolysate (PPH) on yoghurt production by Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus. Fresh lean pork was cut into pieces and mixed with deionized water and dealt with protease, then the resulting PPH was added to milk to investigate the effects of PPH on yoghurt production. The fermentation time, the viable cell counts, the flavor, free amino acids compounds, and sensory evaluation of yoghurt were evaluated. These results showed that PPH significantly stimulated the growth and acidification of the both bacterial strains. When the content of PPH reached 5% (w/w), the increased acidifying rate occurred, which the fermentation time was one hour less than that of the control, a time saving of up to 20% compared with the control. The viable cell counts, the total free amino acids, and the scores of taste, flavor and overall acceptability in PPH-supplemented yoghurt were higher than the control. Furthermore, the contents of some characteristic flavor compounds including acids, alcohols, aldehydes, ketones and esters were richer than the control. We concluded that the constituents of PPH such as small peptide, vitamins, and minerals together to play the stimulatory roles and result in beneficial effect for the yoghurt starter cultures growth.

• Toxicological Research
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• v.13 no.4
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• pp.359-365
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• 1997

Many factors are known to be responsible for cerebral ischemic injury, such as excitatory neurotransmitters, increased intraneuronal calcium, or disturbance of cellular energy metabolism. Recently, oxygen free radicals, formed during ischemia/reperfusion, have been proposed as one of the main causes of ischemia/reperfusion injury. Therefore, to investigate the role of oxygen free radical during ischemia/reperfusion, in the present study the effect of endogenous oxygen free radical scavenger, superoxide dismutase / catalase(SOD / catalase) on the release of [$^3$H]-5-hydroxytryptamine([$^3$H]-5-HT) during hypoxia/reoxygenation in rat hippocampal slices was measured. The hippocampus was obtained from the rat brain and sliced 400 gm thickness with manual chopper. After 30 min's preincubation in the normal buffer, the slices were incubated for 20 min in a buffer containing [$^3$H]-5-HT(0.1 $\mu$M, 74 $\mu$Ci) for uptake, and washed. To measure the release of [$^3$H]-5-HT into the buffer, the incubation medium was drained off and refilled every ten minutes through a sequence of 14 tubes. Induction of hypoxia for 20 min (gassing it with 95% N$_2$/5% CO$_2$) was done in the 6th and 7th tube, and oxygen free radical scavenger, SOD / catalase was added 10 minutes prior to induction of hypoxia. The radioactivity in each buffer and the tissue were counted using liquid scintillation counter and the results were expressed as a percentage of the total activity. When slices were exposed to hypoxia for 20 min, [$^3$H]-5-HT release was markedly decreased and a rebound release of [$^3$H]-5-HT was observed on the post-hypoxic reoxygenation period. SOD / catalase did not changed the release of [$^3$H]-5-HT in control group, but inhibited the decrease of [$^3$H]-5-HT release in hypoxic period and rebound increase of [$^3$H]-5-HT in reoxygenation period. This result suggest that superoxide anion may play a role in the hypoxic-, and reoxygenation-induced change of [$^3$H]-5-HT release in rat hippocampal slices.

• KIPS Transactions on Software and Data Engineering
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• v.2 no.5
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• pp.347-352
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• 2013

In impulse noise filtering techniques window size play an important role. Usually, an appropriate window is determined according to the noise density. A small window may not be able to suppress noise properly whereas a large window may remove edges and fine image details. Moreover, the value of the central pixel is estimated by considering all pixels within the window. In this work, contrary to the previous approaches, we propose an iterative impulse noise removal scheme that emphasizes on noise-free pixels within a small neighborhood. The iterative process continues until all noisy pixels are replaced with the estimated pixels. In order to estimate the optimal value for a noisy pixel, a genetic programming (GP) based estimator is evolved that takes few noise-free pixels as input. The estimator is constituent of noise-free pixels, arithmetic operators and random constants. Experimental results show that theproposed scheme is capable of removing impulse noise effectively while preserving the fine image details. Especially, our approach has shown effectiveness against high impulse noise density.

• The Journal of Korean Association of Computer Education
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• v.22 no.3
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• pp.123-133
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• 2019

The purpose of this study is to establish Smart Education Environment for children's personalized learning based on the data are accumulated by Smart Device which is one of element on Smart Education. In this study, we propose the operational improvement plan for the free choice activity in the 5-year-old kindergarten and also implement the Free Choice Activity(FCA) management system for children to select and to evaluate the play plans for themselves. Children participating in this study have fun the whole time for the process of self-planning, the playing activities and the self-assessment of playing. As a result, it is confirmed that children participate actively in decision-making of interesting areas through the smart device than the traditional education environment before. A single teacher using FCA management system with smart device in this study can get useful information without difficulty of individual child's interests, learning and the statistics of children in the classroom.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.1
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• pp.290-296
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• 2019

Head-up displays for vehicles play an important role in displaying various information about the safety and convenience of driving on the windshield of the vehicle. In this study, ultra-precision machining was performed and evaluated as a method for machining a large-area aspheric free-form mirror that is applicable to augmented reality technology. Precision diamond cutting is highly accurate and suitable for the production of advanced parts with excellent surface integrity, low surface roughness, and low residual stress. By using an aspheric free-form mold, it is possible to improve the optical transfer function, reduce the distortion path, and realize a special image field curvature. To make such a mold, the diamond cutting method was used, and the result was evaluated using an aspherical shape-measuring machine. As a result, it was possible to the mold with shape accuracy (PV) below $1{\mu}m$ and surface roughness (Ra) below $0.02{\mu}m$.