• Applied Chemistry for Engineering
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• v.23 no.4
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• pp.372-376
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• 2012

Carbon nanotubes (CNT) are considered as one of ideal nano-fillers in the field of composites with their excellent electrical, mechanical, and thermal properties. Therefore CNT composites are increasingly used in fabricating conductive materials, structural materials with high strength and low weight, and multifunctional materials. The main problem of the CNT composites is difficulty in the dispersion of CNT in the polymer matrix. In this study multi-walled carbon nanotubes (MWNT) were pretreated by the physical process utilizing a wrapping method. After the pretreatment polymer/MWNT nanocomposites were prepared by melt processing. The effect of functionalization MWNT by wrapping with styrene acrylonitrile (SAN) on the mechanical and electrical properties of acrylonitrile butadiene styrene resin (ABS)/MWNT composites was studied by comparing the properties of ABS mixed with the neat MWNT. Electrical and mechanical properties of ABS/MWNT nanocomposites were studied as a function of the functionalization and content of MWNT. The tensile strength of the ABS/MWNT nanocomposites increased, but the impact strength decreased. The polymer wrapping in ABS system has little effect on the improvement of electrical properties.

• Journal of The Korean Society of Grassland and Forage Science
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• v.27 no.2
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• pp.79-84
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• 2007

This study was carried out to investigate the effects of growing period and cultivars on physiological characteristics and photosynthetic rates of kenaf in Cheorwon, Korea, The possibility of their utilization as forage plant was also discussed. A split plot design composing 3 growing periods (53, 84 and 115 days after sowing) and 3 cultivars (Dowling, Everglade-41 and Tainung-2) was applied for this experiment. Leaf photosynthetic rate was highest 28.6 $CO_2{\mu}mol\;m^{-2}s^{-1}$ in Everglade-41 at the beginning of August when solar irradiation was most intense. In the final biomass of kenaf, Dowing wa the highest among cultivars, with 534.6g/F.W./plant and 109.6g/D.W./plant, respectively. In addition, Dowling was the best in stem thickness among cultivars evaluated. Our results exhibited that all cultivars planted in Cheorwon exhibited decreased yield production compared to a previous report experimented in Jaeju. It may result that cultivation in Jaeju utilized wider planting space and longer cultivating time. In the basis of our data, it is suggest that extending cultivation time and using wider planting space should increase yield in Cheorwon with potential utilization of kanef as a forage crop.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.106-106
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• 2018

해양환경용 선박재료는 전기화학적인 부식을 발생시키는 염소이온($Cl^-$)이 다량 포함된 부식 환경에 장기간 노출되어 있어 부식에 대해 취약하다. 따라서 우수한 내식성 및 내침식성을 가진 재료를 선정하는 것은 매우 중요하다. 알루미늄 합금은 충분한 강도와 부동태 피막 형성으로 인해 내식성이 우수하여 해양환경용 선박 재료로서 널리 이용되고 있으며, 이에 따른 부식 특성에 관한 연구도 활발히 이뤄지고 있다. 그러나 선박에서는 부식에 의한 손상뿐만 아니라 전식에 의한 부식 손상도 발생할 수 있다. 특히 선미 부분은 프로펠러의 동합금과 알루미늄 합금의 이종금속 간 전위차에 의한 전식이 발생하여 선체의 다른 부위에 비해 부식이 더 심하게 진행될 수도 있다. 또한 전식은 해안 부두에 접안된 선박의 용접 시미주전류(stray current)에 의한 부식손상이 발생할 수 있으나 이에 대한 연구는 미미한 실정이다. 따라서 본 연구는 해양환경에서의 전식을 인위적으로 모사할 수 있는 부식 정전류 시험법을 이용하여 다양한 크기의 전식 손상을 유발시켰으며, 해양환경 하에서 선박재료로 주로 사용되는 알루미늄 합금인 Al5083-H321, Al5052-O, Al6061-T6에 대한 전식 특성을 비교, 분석하였다. 실험 방법으로 작동전극은 각 재료의 시험편을 $2cm{\times}2cm$ 으로 절단하여 sand paper # 2000 번까지 연마 후 아세톤과 증류수로 세척하고 건조하였으며, 제작된 시험편은 자체 제작한 홀더를 이용하여 $1cm^2$만 노출시킨 후 정전류 가속 실험을 실시하였다. 기준전극은 은/염화은(Ag/AgCl) 전극을, 대응전극은 백금(Pt) 전극을 사용하였다. 정전류 가속 조건은 $0.001mA/cm^2$, $0.1mA/cm^2$, $1mA/cm^2$, $5mA/cm^2$, $10mA/cm^2$의 전류 밀도를 천연해수에서 30분간 인가하였다. 각 재료에 대한 전식 특성은 실험 전후의 무게 감소량으로 전식의 저항 특성을 확인하였다. 그리고 3D 현미경으로 표면 손상 경향과 깊이를 측정하였으며, 주사전자현미경 (SEM)을 통해 표면 형상을 미시적으로 관찰하였다. 부식 정전류 시험 결과 모든 시편에서 $0.01mA/cm^2$에서 미세한 국부적인 부식이 일어났으며, 전류밀도가 증가할수록 표면 전반에 부식이 진행되고 성장하였다. 그리고 모든 인가 전류밀도의 조건에서 Al6061-T6가 5000계열(Al5083-H321, Al5052-O)보다 더 우수한 내식성을 나타났다.

• Journal of Biomedical Engineering Research
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• v.24 no.5
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• pp.427-434
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• 2003

In this paper, we present a speech-based Environmental Control System(ECS) and its application. In the concrete, an ECS using the speech recognition and an portable wheelchair lift control system with the speech synthesis are developed through the simulation and the embodiment. The developed system apply to quadriplegic man and we evaluate the result of physical effect and of mental effect. Speech recognition system is constructed by real time modules using HMM model. For the clinical application of the device, we investigate the result applied to 54-years old quadriplegic man during a week through the questionnaires of Beck Depression Inventory and of Activity Pattern Indicator. Also the motor drive control system of potable wheelchair lift is implemented and the mechanical durability is tested by structural analysis. Speech recognition rate results in over 95% through the experiment. The result of the questionnaires shows higher satisfaction and lower nursing loads. In addition, the depression tendency of the subject were decreased. The potable wheelchair lift shows good fatigue life-cycle as the material supporting the upper wheelchair and shows the centroid mobility of safety. In this paper we present an example of ECS which consists of real-time speech recognition system and potable wheelchair lift. Also the experiments shows needs of the ECS for korean environments. This study will be the base of a commercial use.

• Korean Journal of Agricultural and Forest Meteorology
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• v.17 no.3
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• pp.202-206
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• 2015

'Hei' (Lycopersicon Esculentum Mill.) Black Tomato examined changes in fruit shape, fruit weight and cracking percentage with increasing temperature in high-rise tomato greenhouse during long-term cultivation in summer season. Fruit diameter is greater than fruit length from the first cluster to the ninth cluster. However, fruit length is longer than fruit diameter from the tenth cluster to the fifteenth cluster. Fruit shape index (L/D) is below 100% from the first cluster to the ninth cluster and above 100% from the tenth cluster to the fifteenth cluster. Fruit weight was decreased during temperature increasing in greenhouse. However, fruit cracking percentage was increased to temperature increasing during cultivation period. Thus, fruit shape, fruit weight and fruit cracking of 'Hei' black tomato were influenced by increasing of temperature in greenhouse during long-term cultivation.

• Korean Journal of Animal Reproduction
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• v.25 no.4
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• pp.349-357
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• 2001

This study was conducted to examine the effect of caffeine and three dietary levels of fat, i.e., 0%, 5% and 20% on mammary gland development. Mice were assigned to three groups (dietary levels 0%, 5%, 20% fat), and treated caffeine of half within the each group. Caffeine-treated mice with 0% or 20% fat levels significantly increased 4$^{th}$ mammary gland development in comparison with that of no caffeine -treated mice (P＜0.05). Caffeine-treated mice significantly increased DNA contents of 4$^{th}$ mammary gland in comparison with that of no caffeine-treated mice (P＜0.05), and DNA contents of mammary gland increased as fat levels increased within caffeine-treated or no caffeine-treated group. nteraction effect was shown between caffeine and 20% fat diet, ［(20% fat+caffeine) - (20% fat + no caffeine) vs (0% fat + caffeine) - (0% fat + no caffeine)］(P＜0.01). Conclusively, caffeine significantly increased mouse mammary gland development possibly by inhibiting phosphodiesterase activity, and dietary fat supplements increased mammary gland development as the fat content of the diet increased from 0 to 20%. The stimulatory effect of caffeine in mammary development interacted with high level of fat diet.

• Korean journal of food and cookery science
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• v.14 no.3
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• pp.232-240
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• 1998

The effect of various levels of perilla seed powder on physicochemical, microbiological, and sensory characteristics of Puchukimchi during fermentation was investigated. Puchukimchi is a kind of korean kimchi made with Leek (Allium odorum L.). In a laboratory model of Puchukimchi made with various levels (0, 1, 2, 3, 5%) of perilla seed powder fermentated at 10$^{\circ}C$ up to 45 days. As a fermentation progressed, the initial high decrease in pH has been retarded in all the treatments, of which the delaying extent was noted from Puchukimchi made with perilla seed powder. The pH dropped with accumulation of total acidity. The total vitamin C content increased sharply at the palatable period of Puchukimchi during initial fermentation and then, especially from the 8th-day, gradually decreased later following sigmoidal changing pattern. And the total vitamin C content was the highest in the Puchukimchi made with 5% perilla seed powder. The lactic acid bacteria count increased remarkably and then decreased gradually after optimum ripening period, i.e., the palatable period of Puchukimchi during fermentation. During the early stage of fermentation, sensory evaluation showed the higher scores on the overall taste of Puchukimchi made with 3, 5% on the 2nd-day, 1, 2% on the 5th-day of fermentation. However, the trend of acceptability has been reversed by the Puchukimchi made with little amount of perilla seed powder, more notably 2% at the later stage of fermentation.

• Korean Journal of Environmental Agriculture
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• v.3 no.1
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• pp.10-15
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• 1984

To get information on the behavior of phorate in vegetables under the subtropical conditions, phorate granule (10%) was applied to silt loam soil at the rate of 40㎏ a.i./ha and incorporated to 10㎝ soil depth just befere sowing. Insecticide residues in vegetables were determined with GLC and confirmed qualitatively with TLC. Phorate and its metabolites were absorbed by the radish and carrot roots and rapidly translocated into foliages. The compounds detected in vegetables were phorate, phorate sulfoxide, and phorate sulfone. Residue levels of compounds in radishes were higher in foliages than in roots and much more residues were present in leaf lamina than in midribs. The concentration of the total residues in vegetable roots was rapidly decreased with the time, while the amount of total residues in radish roots was increased with the time. Therefore, the rapid decline of residue levels in vegetables was mainly attributed to the dilution of insecticide residues by the rapid growth of these vegetables.

• Korean Journal of Food Science and Technology
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• v.34 no.2
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• pp.319-324
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• 2002

Hypocholesterolemic effects in rats of two hull-less barleys, waxy and nonwaxy-starch genotype, were evaluated by analyzing liver cholesterol and triglycerides. A group fed cellulose control and fiber-free exhibited significant liver lipid accumulation by morphologically observation. In barley fed group, however, lipid disposition in liver was effectively suppressed. The concentrations of cholesterol and triglyceride in liver were significantly reduced in rat fed 5 and 10% fiber diets containing barley flour and ${\beta}-glucan-enriched$ fraction. ${\beta}-Glucan-enriched$ barley fraction as a fiber source showed more cholesterol-lowering than barley flour with cellulose, and this effect of ${\beta}-glucan$ from two hull-less barleys was similar. Liver cholesterol and triglyceride in cellulose control group were 14.5 mg/g and 46.1 mg/g, respectively, while those of barley and ${\beta}-glucan$ fed groups were $5.1{\sim}8.2\;mg/g$ and $20.1{\sim}31.3\;mg/g$, respectively.

• Korean Journal of Food Science and Technology
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• v.35 no.5
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• pp.856-864
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• 2003

The purpose of this study was to examine the quality variations of cake and cake batter when either butter or soybean oil was added in plain sponge cake batter. Soybean oil or butter was added to the batter at ratios of 20, 40, and 60% at 20, 35, 60, and $80^{\circ}C$. The physico-chemical properties of cake batter and cake were measured to evaluate the effects of ratio and temperature of butter and soybean oil. At higher ratios of butter or soybean oil and lower temperatures, the specific gravity of the cake batter increased while the interrelations among weight, volume, and specific loaf volume decreased. L- and b- values were the same, but a-value increased remarkably with higher ratios of butter. The effect of adding butter or soybean oil on hardness was shown to be lowest at 40% and $80^{\circ}C$. Baking loss in the baking process with soybean oil decreased with increasing oil quantity and temperature. Moisture content did not change with temperature, but did decline with increasing amounts of butter or soybean oil. These results show that the optimum condition for sponge cake would be 40% soybean oil at $80^{\circ}C$.