• Journal of the Korean Vacuum Society
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• v.17 no.4
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• pp.270-277
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• 2008

Vacuum is any air or gas pressure less than a prevailing pressure in an environmental or, specifically, any pressure lower than the atmospheric pressure and is used by a wide variety of scientists and engineering - including clean environment, thermal insulation, very long mean free path, plasma, space simulation[1]. The space environment is characterized by such a severe condition as high vacuum, and very low and high temperature. Since a satellite will be exposed to such a space environment as soon as it goes into its orbit, space environmental test should be carried out to verify the performance of the satellite on the ground under the space environmental conditions. A general and widely used method to simulate the space environment is using a thermal vacuum chamber which consists of vacuum vessel and thermally controlled shroud. As indicated by name of vacuum chamber, the vacuum technology is applied to design and manufacture of the thermal vacuum chamber. This paper describe the vacuum technology which is applied to space business.

• Journal of The Korean Society of Grassland and Forage Science
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• v.24 no.1
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• pp.37-42
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• 2004

This study was conducted to select the optimum herbicide combination on agronomic characteristics, dry matter yield, nutritive values and weed control of the silage corn at Daekwanryong branch(altitude 800m a.s.1.) of National Livestock Research Institute from 2001 to 2002. The treatments consisted of control, metolachlor, thiobencarb＋linuron, pendimethalin, pendimethalin＋linuron, propisochlor, nicosulfuron, propisochlor＋nicosulfuron, and non treatment. The plant height and ear height of corn were no significant different among herbicide combination. However, the highest dry matter(DM) and ear rate of silage corn were observed with nicosulfuron treatment; 31.4% and 52.7%, respectively. Also, Dry matter yield of silage corn was the highest of 16,503kg/ha with propisochlor＋nicosulfuron(P<0.05). The control of annual weeds was the greatest of 96.4% in the plots of propisochlor＋nicosulfuron application. These results indicate that propisochlor＋nicosulfuron treatment would be the optimum combination for dry matter yield, weed control and nutritive value of silage corn in alpine area.

• Journal of The Korean Society of Grassland and Forage Science
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• v.29 no.2
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• pp.121-128
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• 2009

A field study was conducted from 2007 to 2008 at Department Rice and Winter Cereal Crop, NICS, RDA, to evaluate the effects of harvest time and cultivar on forage yield and quality. Four whole crop barley cultivars ('Youngyang', 'Wooho', 'Yuyeon' and 'Dami') were selected and harvested on five separate growth stages (heading, and intervals of 1, 2, 3 and 4 weeks after heading) in split plot design with three replications. Results from this experiment indicated significant differences due to harvest time and cultivar in dry matter yield and total digestible nutrients (TDN) yield for forage. The interaction between harvest time and cultivar was not significant. The TDN yield trends were increasing with later harvest time due to higher dry matter yield and TDN content. This experiment provides some interesting results with respects to optimum harvest time, feed value and ultimately yield for the different whole crop barley cultivars.

• Journal of the Korean Society for Railway
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• v.19 no.2
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• pp.135-144
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• 2016

It is essential to lighten the weight of switch girders in order to reduce their costs of manufacturing and make it easier to use them in construction. Lightening the weight of switch is also important to the Maglev 3-way switches system, however, the design variables should be considered very carefully if lightening is to be applied to the system, because these variables are vitally related to the levitation stability. Because Urban Maglev trains have a structure in which train bogie wraps around the guiderail, the adjustment of a girder's height is a possible way to reduce the weight. The safety of the application of this concept is ensured by repeated experiments in a test bed, however, due to a lack of space and budget limits, the design parametric study for the system model can substitute for actual application. The purpose of this paper is to study the design parameters that are concerned with levitation stability while a Maglev train is running on the Maglev 3-way system depending on the weight of the switch girders. In this study, switch girder weight is reduced by adjustment of girder height and girders are and modeled as a flexible body. The effect of the adjustment of girder height on the levitation stability can be analyzed by comparing the velocity of the train when it passes the switch girders, with the lateral gap, and the levitation gap which are obtained from the co-simulation of the Maglev train's dynamics model and flexible switching system. The results of this research will be used to design a Maglev switch.

• Korean Journal of Medicinal Crop Science
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• v.5 no.2
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• pp.147-153
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• 1997

This experiment was carried out to clarify the effect of different fertilizer on growth and yield of Fritjllaria thunbergii in Chungbuk Rural Development Administration from 1993 to 1995. Emergence date was faster about 1 to 5 days in fertilizer application than that of non-fertilizer, and emergence ratio was lower about 2.4% to 35.7% in fertilizer application than that of non-fertilizer. Plant height was longer about 2.8cm to 10.6cm in fertilizer application than that of non-fertilizer, and leaf length and width had same tendencies. Bulb height was increased about 0.1 to 0.2cm in fertilizer application than 1.9cm in non-fertilizer and bulb width was increased about 0.5 to 0.7cm in fertilizer application than 2.2cm in non-fertilizer. Total yield was increased about 27% in N-P-K fertilizer, 24% in compost, 23% in compound fertilizer for garlic and 21 % in fowl dropping manure than 572kg/10a in non-fertilizer. Yield of marketable goods was high about 79% in compost. 72% in compound fertilizer for garlic and fowl dropping manure, and 69% in organic fertilizer than 229kg/l0a in non-fertilizer. Therfore, in the cultivation of Fritillaria thunbergii the application of organic fertilizer such as compost and fowl dropping manure was considered more profitable than the application of chemical fertilizer in middle region.

• Journal of the Korea Concrete Institute
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• v.13 no.2
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• pp.107-113
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• 2001

This study was conducted preliminarily to develop the crack source location technique for plain concrete beam using acoustic emission(AE). Before the main experiment, the test of virtual An source location was achieved in plain concrete block. The sensor layout was mutually compared between triangular layout and rectangular layout. As the results of test, AE source location by triangular layout was evaluated more effective than that by rectangular layout. The specimen to apply he source location technique was man in total nine specimens (each three in 40 %, 50%, 60% of W/C ratio) which the experiment variable was the compressive strength level(W/C ratio). The bending loading method is selected by cyclic loadings to evaluate the degree of concrete damage. It is seen that Kaiser effect and Felicity effect exists through analysis of AE parameters in coming failure experiment. As a result of analyzing the felicity ratio(FR) values, it is shown that this values can be used for evaluating the degree of concerto damage. AE activity is started highly at the 70% of failure load without the compressive strength level. Thus considered by a index in constructing the system of the failure warning at application of the field structure. And the results compared the real cracking location with the source location has perceived by AE monitoring before it is appeared the primary crack by visual observation.

• Restorative Dentistry and Endodontics
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• v.34 no.2
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• pp.103-112
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• 2009

The purpose of this study was to compare the effect of curing methods of adhesive resins and resin cements in the root canal. Crown portions of 32 single-rooted mandibular premolars were removed. Routine endodontic treatment was done, and 9 mm deep post spaces were prepared within root canals. No.3 FRC Postec posts (Ivoclar-Vivadent AG, Liechtensteih) were cemented in the post spaces by self-(SC) or light-curing (LC) using two dual-cured adhesives (Adper Scotchbond multi-purpose plus and Exite DSC )and resin cements (RelyX ARC and Variolink II). They were assigned to 4 groups (n=8): R-SC, R-LC, V-SC, V-LC group. After stored in distilled water for 24 hours, each root was transversally sectioned with 1.5 mm thick and made three slices. The specimens were subjected to push-out test in a universal testing machine (EZ Test, Shimadzu Co., Japan) with a crosshead speed of 1 mm/min. The data were analyzed with repeated ANOVA and one-way ANOVA. Also the interface of post-resin cement and resin cement-canal wall of each group was observed under FE-SEM. When fiber posts were cemented into the root canal using total-etch adhesives, the bond strength and adaptation between post and root canal dentin was affected by curing method. Self-cure of adhesives and resin cements showed higher bond strength and closer adaptation than light-cure of them.

• Korean Journal of Agricultural and Forest Meteorology
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• v.13 no.3
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• pp.109-114
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• 2011

A breeding population of Quercus glauca has been established via simple direct selection. Seedlings from naturally crossed seeds of 35 selected families growing in Jeju Island were placed using stroll repeated planting into two experimental forest located at Hannam and Sanghyo in Jeju. After 3 years of planting, characteristics of growth were examined. Growth pattern of trees in Sanghyo was better than those in Hannam. The average heights of filial were 66.8 cm in Hannam and 92.5 cm in Sanghyo. Root collar diameters of filial in Hannam and Sanghyo were 9.3 mm and 12.2 mm, respectively. A great weather differences especially in precipitation and temperature were shown between two test sites. The result of difference of growth pattern between two sites could be useful in provenance adaptability test. Data within families and individuals obtained from this study was also useful for establishment of seed orchard of Q. glauca.

• Journal of the Korean Institute of Gas
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• v.12 no.2
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• pp.69-76
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• 2008

Three failure cases of CNG composite vessels were reported since after January 2005. The 1st and 2nd accidents were indebted to vessel defect and installation mistake. The 3rd was caused by gas leak at pipe connections. In this paper various aspects were studied based on information of the three failure analysis, which must be improved for better safety of the CNG bus system. Overpressure region caused by vessel explosion was theoretically predicted and also assessed by PHAST program. Explosion of 120 l vessel under 20 MPa is equivalent to 1.2 kg TNT explosion. The predicted value by PHAST was more serious than theoretical one. However, actual consequence of explosion was much less than both of the predicted consequences. Since the CNG vessel was designed by the performance based design methodology, it is difficult to verify whether the required process and tests were properly conducted or not after production. If material toughness is not enough, the vessel should be weak in brittle fracture at early in the morning of winter season since the metal temperature can be lower than the transition temperature. If autofrettage pressure is not correct, fatigue failure due to tensile stress during repeated charging is possible. One positive aspect is that fire did not ocurred after vessel failure. This may be indebted to fast diffusion of natural gas which hindered starting fire.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.229-229
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• 2007

나노결정 합금재료를 전력선 통신 커플러용 자심재료로 응용하기 위해서는 고주파 대역에서의 손실 특성이 제어되어야 한다. 즉 고속 전력선 통신을 위한 자심재료의 투자율 및 완화 주파수 등의 전자기적 특성은 30MHz까지 우수하고 안정적으로 유지되어야 하며, 높은 투자율 및 자속밀도, 공진주파수뿐만 아니라 낮은 전력손실 값을 가져야 한다. 따라서 본 연구에서는 나노결점 합금 리본 표면에 딥 코팅, 졸-겔법, 진공함침 등의 방법을 이용하여 PZT, $TiO_2$ 및 $SiO_2$ 등의 산화물 고저항층을 형성시켜 자기적 성질을 유지하면서 고주파 대역의 와전류 손실을 감소시켜 통신용 자심재료로의 응용성을 향상시키고자 하였다. PZT 슬러리의 제타전위 조절을 통해 최적의 분산조건을 얻을 수 있었고, 평균 150nm인 PZT 입자의 초미립자와 가소제, 분산제, 결합제의 첨가조건을 확립할 수 있었다. 딥-코팅은 슬러리 내 유지시간 10초, 인상속도 5mm/min로 30회 반복되었을 때 가정 우수한 특성을 나타내었으며, 고주파 대역에서의 손실 감소효과를 나타내었다. 그리고 졸-겔법에 의해 제조된 슬러리를 이용한 $TiO_2$와 $SiO_2$ 산화물 저항층 코팅을 통해 금속 알콕사이드의 혼합조건 및 저항층 형성용 슬러리의 제조조건을 확립하였고, 합금 리본표면에 균일하고 우수한 점착력을 가지는 저항층을 형성시킬 수 있었으며, 이에 따른 코어손실의 감소효과를 나타낼 수 있었다. 또한 진공 함침법을 통한 저항층 형성에서, $TiO_2$ 나노분말을 표면 저항층으로 코팅했을 때, 가장 높은 코어손실 감소효과를 나타내었다. 한편, 표면 저항층이 형성된 나노결정 합금으로 제조한 자심재료를 이용하여 전력선 통신용 비접촉식 커플러에의 적용과 시험을 통해 고주파 손실 감소효과에 의한 신호전송 특성과 전류특성을 향상시킬 수 있었다.