• 한국농공학회:학술대회논문집
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• 한국농공학회 2000년도 학술발표회 발표논문집
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• pp.266-271
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• 2000

This study was performed to find out how much water the cement hydration reaction need. It is real situation that it is difficult to find out the amount of chemical combined water with stoichiometric chemical reaction form. Because several variation occurred during hydration reaction it's not easy to divide water which used at cement paste mixture. In this study high temperature(105$^{\circ}C$) dry method was used to divide evaporable water and non-evaporable water. The last is combined water chemically and some free water absorbed to products of hydration physically. The test was processed with variation of water cement ratio from 10% to 45% with 5% intervals. The weight of cement paste specimens were measured after dry for 72hours at each checking time(0.5, 1, 3, 5, 10, 24, 48, 72, 168hour). In this study some conclusions such as follows were derived. Firstly, Pure combined water contents required at cement hydration result in 23.3percent of the weight of cement. Secondly, The sufficient mixing water needed to fully hydrated cement result in about 40∼45percent of weight of cement. That is, gel pores water could be about 16.7∼21.7percent of weight of cement.

• 설비공학논문집
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• 제14권9호
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• pp.725-733
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• 2002

In this study, the heat transport limitations of a two-phase closed thermosyphon were investigated. For the test, a two-phase closed thermosyphon ($L_t/: 600 mm,\;L_e:105mm,\;L_a:75mm,\;L_c:420mm,\;D_o:22.2mm,$ container: copper (inner grooved surface), working fluid: PFC ($C_6F_14$) was fabricated with a reservoir that can change the fill charge ratio. The following was imposed as the factors on the heat transport limitations of a two-phase closed thermosyphon. 1) Fill charge ratio of the working fluid. 2) Tilt angle of the longitudinal axis. From tile experimental data, some results were obtained as follows. When the fill charge ratio was relatively small ($\psi$20%), the heat transport limitation occurred about 100W by dry-out limitation. However over 40%, it shelved nearly constant value (500 W) by flooding limitation. The heat transport limitation according to the tilt angle increased smoothly until the tilt angle was $60^{\circ}$,/TEX>, after then decreased slowly.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 춘계학술대회 논문집
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• pp.421-424
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• 2007

Dry sliding wear behavior of ultra-fine grained (UFG) plain low carbon dual phase steel, of which microstructure consists of hard martensite in a ductile ferrite matrix, has been investigated. The wear characteristics of the UFG dual phase steel was compared with that of a coarse grained dual phase steel under various applied load conditions. Dry sliding wear test were carried out using a pin-on-disk type tester at various loads of 1N to 100N under a constant sliding speed condition of 0.20m/s against an AISI 52100 bearing steel ball at room temperature. The sliding distance was fixed as 1000m for all wear tests. The wear rate was calculated by dividing the weight loss, measured to the accuracy of 10-5g by the specific gravity and sliding distance. The worn surfaces and wear debris were analyzed by SEM, EDS and profilometer. Micro-vickers hardness of the cross section of worn surfaces were conducted to analyze strain hardening underneath the contact surfaces. The wear mechanism of the UFG dual phase steel was investigated with emphasis on the unstable nature of the grain boundaries of the UFG microstructure.

• 한국화재소방학회논문지
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• 제22권3호
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• pp.208-215
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• 2008

기존의 목모시멘트보드는 폐목재칩을 이용한 낮은 품질의 시멘트보드였으나, 최근 목재를 섬유형태로 가공하여 제조되는 목모보드는 미관이 수려하고, 흡음 및 단열성이 우수한 내장재로 외국에는 널리 알려진 재료이나, 국내에서는 전량 수입에 의존함에 따라 고가이며 안정적 자재확보의 문제로 인해 다양한 방면의 활용이 이루어지지 못하였다. 그러나, 2005년부터 국내생산이 가능해짐에 따라 경제성 확보 및 자재의 안정적 공급이 가능해짐에 따라 다양한 분야로의 활용이 모색되어지고 있다. 본 연구에서는 목모보드의 활용을 높이기 위하여, 목모보드의 일반특성, 난연성능을 평가하고 건식벽체로 구성하였을 경우 내화성능을 평가함으로써 그 활용성을 모색해보고자 하였다.

• ALGAE
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• 제18권2호
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• pp.129-134
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• 2003

In order to examine the effects of deep seawater (mesopelagic water in the broad sense) on the growth of macroalgae, the growth and nutrient uptake (nitrate and phosphate) of Ulva sp. (Ulvophyceae, Chlorophyta) were investigated by cultivation in deep seawater (taken from 687 m depth at Yaizu, central Japan, in August 2001), surface seawater (taken from 24 m depth), and a combination of the two. Culture experiments were carried out in a continuous water supply system and an intermittent water supply system, in which aerated 500-mL flasks with 4 discs of Ulva sp. (cut sections of ca. 2 $cm_2$) were cultured at 20$^{\circ}C$ water temperature, 100 $\mu$mol photons $m^{-2}{\cdot}s^{-1}$ light intensity, and a 14:10 light:dark cycle. Nutrient uptake by Ulva sp. was high in all seawater media in both culture systems. The frond area, dry weight, chlorophyll a content, dry weight per unit area, and chlorophyll a content per unit area of Ulva sp. at the end of the experimental period were the highest in deep seawater and the lowest in surface seawater in both culture systems. These values, except for dry weight per unit area and chlorophyll a content per unit area, for each seawater media in the intermittent water supply system were higher than those in the continuous water supply system. We conclude that not only deep seawater as the culture medium but also the seawater supply system is important for effective cultivation of macroalgae.

• 한국기계가공학회지
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• 제14권2호
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• pp.67-74
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• 2015

In this study, analysis and experiments were carried out on temperature distributions and thermal deformations in a dry vacuum pump with vertical screws for safe operation. When a vacuum pump is working, it is necessary to get rid of the heat generated by the friction of bearings and the compression of air to prevent the vacuum pump from being damaged by interference between two screws and housing through thermal deformation. Additional cooling was proposed by using oil flow through the inner channel of the rotating axis for lower temperature control of the vacuum pump. Analysis and experimental results were compared in terms of temperature distribution and thermal deformation of the vacuum pump, and two sets of results matched reasonably well. These results for a dry vacuum pump with vertical screws can be used in similar model development and can minimize errors in design and manufacture by providing reasonably accurate prediction in advance.

• Asian-Australasian Journal of Animal Sciences
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• 제20권1호
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• pp.70-74
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• 2007

An in vitro study was carried out to investigate the differences in rumen microbes and fiber degradation capacity between sheep and goats. Three local male sheep and three Inner Mongolia male cashmere goats (aged 1.5 to 2 years; weight 25.0 to 32.0 kg) were each fitted with a permanent rumen cannula used to provide rumen fluid. Cycloheximide was used to eliminate rumen anaerobic fungi. The results showed that the quantities of fungal zoospores in the culture fluid of the control group were significantly greater in the sheep than in the goats; however, bacteria and protozoa counts were significantly higher in goats than in sheep. The digestibility of straw dry matter did not differ significantly between the two species before elimination of fungi, but tended to be higher for sheep (55.4%) than for goats (53.3%). The results also indicated that bacteria counts increased significantly after elimination of anaerobic fungi; however, the digestibility of straw dry matter significantly decreased by 12.1% and 8.6% for sheep and goats respectively. This indicated that the anaerobic fungi of the rumen played an important role in degradation of fiber.

• Wind and Structures
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• 제25권5호
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• pp.475-492
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• 2017

Inclined and yawed circular cylinder is an essential element in the widespread range of structures. As one of the applications, cables on bridges were reported to have the possibility of suffering a kind of large amplitude vibration called dry galloping. In order to have a detailed understanding of the aerodynamics related to dry galloping, this study carried out a set of wind tunnel tests for the inclined and yawed circular cylinders. The aerodynamic coefficients of circular cylinders with three surface configurations, including smooth, dimpled pattern and helical fillet are tested using the force balance under a wide range of inclination and yaw angles in the wind tunnel. The Reynolds number ranges from $2{\times}10^5$ to $7{\times}10^5$ during the test. The influence of turbulence intensity on the drag and lift coefficients is corrected. The effects of inclination angle yaw angle and surface configurations on the aerodynamic coefficients are discussed. Adopting the existed the quasi-steady model, the nondimensional aerodynamic damping parameters for the cylinders with three kinds of surface configurations are evaluated. It is found that surface with helical fillet or dimpled pattern have the potential to suppress the dry galloping, while the latter one is more effective.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제49권4호
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• pp.203-209
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• 2000

This paper proposes the improvement of the etch rate of GaN using a magnetized inductively coupled $CH_4/H_2/Ar$plasma. The gradient magnetic field with the axial direction is investigated using Gauss-meter and the ion current density is measured using double Langmuir probe. The applied magnetic field changes the ion current density profile in the radial direction, resulting in producing the higher density in the outer region than in the center. GaN dry etching process is carried out based on the measurements of the ion current density. The each rate of 2000 /min is achieved with $CH_4/H_2/Ar$ chemistries at 800 W input power, 250W rf bias power, 10 mTorr pressure and 100 gauss magnetic field.

• KSBB Journal
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• 제7권2호
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• pp.144-148
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• 1992

투과성이 증가된 Z. mobilis를 K-carrageenan으로 고정화한 건조beads를 이용하여 sorbitol연속생성공정의 향상에 관한 실험을 하였다. 투과성을 증가시킨 균체를 K-carrageenan으로 고정화 하여서 연속공정을 실시한 결과 효소의 안정성이 30일 이상 지속되었다. K-carrageenan으로 고정화한 균체를 건조시 bead의 견고성과 저장성이 향상되었다. 건조 bead를 이용한 72시간의 반회분식 공정에서 효소 활성도의 감소는 8%였으며, 건조 bead에서의 Vmax값은 $39^{\circ}C$와 pH6.2에서 free cell의 거의 절반값을 나타내었다. 연속공정에서 희석속도 $0.1h^{-1}$일 때 wet bead와 건조bead에서의 sorbitol생산성은 각각 3.4, 2.88g/l-h를 나타내었다.