• 소성∙가공
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• 제14권1호
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• pp.65-70
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• 2005

A phase mixture model was employed to simulate the deformation behaviour of metallic materials covering a wide grain size range from micrometer to nanometer scale. In this model a polycrystalline material is treated as a mixture of two phases: grain interior phase whose plastic deformation is governed by dislocation and diffusion mechanisms and grain boundary 'phase' whose plastic flow is controlled by a boundary diffusion mechanism. The main target of this study was the effect of grain size on stress and its strain rate sensitivity as well as on the strain hardening. Conventional Hall-Petch behaviour in coarse grained materials at high strain rates governed by the dislocation glide mechanism was shown to be replaced with inverse Hall-Petch behaviour in ultrafine grained materials at low strain rates, when both phases deform predominantly by diffusion controlled mechanisms. The model predictions are illustrated by examples from literature.

• 한국세라믹학회지
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• 제24권3호
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• pp.270-276
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• 1987

The microstructure and dielectric properties of a SrTiO3-based GBL (Grain Boundary Layer) capacitor were investigated. The 0.6 mol% Nb2O5 doped SrTiO3 was sintered for 3 hr at 1450$^{\circ}C$ in mixed gas(N2/H2) atmosphere. The Nb2O5 promoted the grain growth of the SrTiO3 ceramics was decreased with the amount of Nb2O5. The oxide mixture(PbO, Bi2O3, B2O3) were painted on the reduced specimen and fired at 1000$^{\circ}C$ to 1100$^{\circ}C$ in air. The penetrated oxide mixture into specimen were located in grain boundaries. A SrTiO3-based GBL capacitor had the apparent permittivity of about 3.0${\times}$104, the dielectric loss of 0.01-0.02, and insulating resistance of 108-109$\Omega$.cm. The capacitor had the stable temperature coefficient of capacitance and exhibited dielectric dispersion over 107 Hz. The capacitance-voltage measurements indicated that the grain boundary was composed of the continuous insulating layers.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.554-554
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• 2000

To improve mechanical properties of Cu-Al-Ni alloy by the grain refinement, Cu-Al-Ni SMA ribbons were fabricated by melt spinning apparatus. The variations of microstructure, mechanical properties and transformation characteristics with the condition of rapid solidification and annealing time-temperature were investigated in Cu-Al-Ni SMA ribbons. The ribbons fabricated by melt spinning obtained around 1.5nm in width and 50-60${\mu}{\textrm}{m}$ in thickness. With increasing wheel speed in order of 10m/s, 15m/s, 20m/s, 30m/s and 3m/s, the grain size was decreased in order of 10${\mu}{\textrm}{m}$, 6.25${\mu}{\textrm}{m}$, 5.5${\mu}{\textrm}{m}$, 3${\mu}{\textrm}{m}$ and 3${\mu}{\textrm}{m}$. $M_{s}$ and $A_{s}$ temperature were decreased with decreasing grain size. By X-ray diffraction test, ordered $\beta$$_1$ phase was observed in all the SMA ribbons and the volume friction of it was increased with increasing wheel speed. With increasing wheel speed, strain was increased from 4.2% to 5.8% and fracture mode has changed from mixture of intergranular and dimple fracture to mixture of fiber structure and dimple fracture. The grain size of ribbon heat-treated at $600^{\circ}C$ was increased with increasing time. In the heat-treated ribbons at 55$0^{\circ}C$, ${\gamma}$$_2$ phases were observed.d.d.

• 한국세라믹학회지
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• 제50권6호
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• pp.429-433
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• 2013

Silicon, carbon, and B4C powders were used as raw materials for the fabrication of porous SiC. ${\beta}$-SiC was synthesized at $1500^{\circ}C$ in an Ar atmosphere from a silicon and carbon mixture. The synthesized powders were pressed into disk shapes and then heated at $2100^{\circ}C$. ${\beta}$-SiC particles transformed to ${\alpha}$-SiC at over $1900^{\circ}C$, and rapid grain growth of ${\alpha}$-SiC subsequently occurred and a porous structure with elongated plate-type grains was formed. The mechanism of this rapid grain growth is thought to be an evaporation-condensation reaction. The mechanical properties of the fabricated porous SiC were investigated and discussed.

• 한국주조공학회지
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• 제3권3호
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• pp.167-173
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• 1983

The effect of sand grain size on the various properties of mold is not only basic but important interest which we have to deal with.And the relation among the various properties of mold (strength, permeability, flowability, compactability, hardness, deformation, toughness etc.) is very complicated and inaccurate, so we can delineate the behavior of mixture (sand+water+bentonite) with experience only. Within recent years a so-called rigid-water theory has been accepted as a means of advancing logical explanations for the research aimed at delineating sand-clay-water relationships. By changing grain size or mesh no. of grain, specimens have been subjected to green compressive strength, permeability, deformation, flowability, compactablity, toughness at room temperature. Under constant mulling energy and ratio of water/bentonite, the results obtained were as follows: 1. With decreasing grain size green compressive strength of the specimen increased. 2. With decreasing grain size permeability decreased. 3. With decreasing grain size flowability and bulk density decreased but compactability increased. 4. With decreasing grain size deformation decreased but toughness increased. 5. At 60 mesh no., the properties of specimen are conspicuously changed. The reason is that the total surface area of sand grain which affects the type of bonding between sand grains is more changed at 60 mesh number.

• 한국염색가공학회지
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• 제19권2호
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• pp.24-31
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• 2007

This paper addresses factors of line image quality on grain leather printed via inkjet printer. Lines were printed onto coated leather media, and line width, edge blurriness, and edge raggedness were evaluated for line image quality. Various factors influenced to wetting and capillary wicking were studied and found out that wicking through capillary between fibers causes significant feathering on leather surface similar with pulp capillary in copy Paper. Polyurethane and acrylic resin coating resulted good image qualify by reducing capillary wicking. The mixture of polyurethane and acrylic resin applied on grain leather satisfied with both image quality and surface hand. $AllWrite^{TM}$ ink brought best results of image quality, comparing with $VeraPrint^{TM}$ ink and $JetWrite^{TM}$ ink.

• 한국농공학회지
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• 제27권2호
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• pp.57-71
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• 1985

The characteristics of compaction and unconfined compressive strength were investigated by mixing with lime to all soils adjusted by given percentages of two kinds of clays to sand to obtain the most effective distribution of grain size and the optimum lime content for soil stabilization. In addition, unconfined compressive strength and durability tested by adding of sodium metasilicate, sodium sulfate, sodium carbonate, sodium gydroxide and magnesium oxide to lime-soil mixture mixed with 8 percent lime to adjusted soil having the mixing percentage of 60 percent of cohesive black clay and 40 percent of sand by weight to get the effect and the optimum content of chemicals. The results obtained were as follows; 1.With the addition of more lime, the optimum moisture content was increased, and the maximum dry density was decreased, whereas the more the amount of clay and the less was the maximum drt density. 2. In the soil having more fine grain size the unconfined compressive strength was larger in the earlier stage of curing period, in accordance with the longer period, the mixing percentages of sand to clay showing the maximum unconfined compressive strength, on the basis of 28-day strength, were 60% : 40% (black clay) and 40% : 60% (brown clay) respectively. 3. The reason why the soil adjusted with black clay was remarkably bigger in the unconfined compressive strength than ones adjusted with brown clay for all specimen of lime-soil mixture was the difference in the kind of clay, the amount of chemical compositions the value of pH. Black clay was mainly composed of halloysite that reacted with lime satisfactorily, whereas the main composition of brown clay was kaolinite that was less effect in the enhance of unconfined compressive strength. Also the difference of unconfined compressive strength was because black clay was larger in the amount of composition of calcium oxide and magnesium oxide in the value of pH affecting directly on the unconfined compressive strength of lime-soil mixture than brown clay. 4. In the lime-soil mixture mixed with 8 percent of lime to soil that mixing percentage of sand to black clay was 60% : 40%, on the standard of 7-day strength, the effect of chemical was arranged in the order of magnesium oxide, sodium carbonate, sodium sulfate, sodium hydroxide and sodium metasilicate. 5. The optimum amount of chemical being applicable to the maximum unconfined compressive strength of lime-chemical-soil mixture was 1 percent by weight for air dry soil in the case of adding sodium carbonated and 0.75 percent on sodium hydroxide, the unconfined compressive strength was increased continuously with increase of the amount of chemical up to 2 percent of chemical content is the lime-chemical-soil mixture added sodium metasilicate, sodium sulfate and magnesium oxide. 6. It was considered that the chemical played and accelerant role of early revelation of strength because the rate of increase of unconfined compressive strength of all of lime-chemical-soil mixtures was largest on the 7-day cured specimen. 7. The effect of test on freezing and thawing after adding suitable amount of chemical on the lime-soil mixture mixed with 8 percent of lime to soil that mixing percentage of sand to black clay was 60% : 40% was arranged in the order of magnesium oxide, sodium carbonate, sodium sulfate, sodium metasilicate and sodium hydroxide.

• 농업과학연구
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• 제14권2호
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• pp.232-247
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• 1987

충남(忠南) 지역(地域) 일반계(一般系) 장려품종인 동진(東津)벼, 대청(大晴)벼, 추청(秋晴)벼 3품종(品種)의 혼식재배(混植栽培)가 병해(病害) 및 수량(收量)에 미치는 영향(影響)을 구명(究明)하기 위하여 1987년(年)에 충남대학(忠南大學) 농과대학(農科大學) 시험포(試驗圃)에서 수행(遂行)한 시험결과(試驗結果)를 요약(要約)하면 다음과 같다. 1. 혼식(混植)에 따른 품종(品種) 및 처리간(處理間) 출수기(出穗期) 변화(變化)는 차이(差異)가 없었고 추청(秋晴)벼 보비구(普肥區)에서만 1일(日) 지연(遲延)되었다. 2. 초장(草長)의 혼식효과(混植效果)는 소비구(少肥區)에서 높았으며 혼식조합별(混植組合別)로는 동진(東津)벼와 대청(大晴)벼 혼식조합구(混植組合區)에서 5.1%로 가장 높게 나타났고 경수(莖數)에서는 보비구(普肥區)에서 혼식효과(混植效果)가 나타났으며 혼식조합별(混植組合別)로는 추청(秋晴)벼와 동진(東津)벼의 혼식조합구(混植組合區)에서 단식구(單植區) 평균치(平均値)보다 5.7%가 증가(增加)하여 혼식효과(混植效果)가 가장 높았다. 3. 간장(稈長)은 시비량(施肥量)이 많을수록 혼식효과(混植效果)도 증가(增加)하였으며 동진(東津)벼와 대청(大晴)벼 혼식조합구(混植組合區)에서 간장(稈長)이 가장 길었으며 혼식효과(混植效果)도 높았다. 반대로 수장(穗長)은 시비량(施肥量)이 많을수록 감소(減少)하였으며 혼식효과(混植效果)도 떨어졌다. 혼식조합별(混植組合別)로는 동진(東津)벼와 대청(大晴)벼 혼식조합구(混植組合區)에서 수장(穗長)이 가장 길었으며, 혼식효과(混植效果)도 현저했다. 4. 성숙기(成熟期)의 지상부(地上部) 건물중(乾物重)은 단식구(單植區)에 비해 2품종(品種) 혼식구(混植區)에서 3.5%, 3품종(品種) 혼식구(混植區)에서 8.5% 증가(增加)하였으며 비료수준별(肥料水準別)로는 보비구(普肥區)에서 혼식효과(混植效果)가 현저했다. 5. 목도열병(稻熱病)과 지경(枝莖) 도열병(稻熱病)은 혼식구(混植區)에서 각각(各各) 11.7%, 14.0% 감소(減少)하였으며, 소비구(少肥區)보다는 보비구(普肥區)에서 혼식효과(混植效果)가 현저했으며, 혼식조합별(混植組合別)로는 동진(東津)벼와 대청(大晴)벼 혼식조합구(混植組合區)에서 도열병(稻熱病) 발생(發生)이 가장 적었다. 6. $m^2$당(當) 수수(穗數)는 추청(秋晴)벼와 동진(東津)벼 혼식조합구(混植組合區)에서 혼식효과(混植效果)가 가장 높았으나 수당(穗當) 영화수(穎花數)는 추청(秋晴)벼와 동진(東津)벼 혼식조합구(混植組合區)에서 가장 낮았다. 비료수준별(肥料水準別) 혼식효과(混植效果)는 $m^2$당(當) 수수(穗數)에서 비료수준(肥料水準)이 높을수록, 수당(穗當) 영화수(穎花數)는 비료수준(肥料水準)이 낮을수록 컸다. 7. 등숙율(登熟率)은 비료수준(肥料水準)에 관계(關係)없이 전(全) 혼식조합구(混植組合區)에서 혼식효과(混植效果)가 나타났으며, 1000립중(粒重)은 소비구(少肥區)에서 혼식조합간(混植組合間)에는 추청(秋晴)벼와 동진(東津)벼 혼식조합(混植組合)과 3품종(品種) 혼식조합구(混植組合區)에서 혼식효과(混植效果)가 높았다. 8. 수량(收量)은 단식구(單植區)보다 혼식구(混植區)에서 4.6% 증수(增收)되었으며 특히 소비구(少肥區)에서 증수(增收)가 현저했다. 혼식조합별(混植組合別)로는 추청(秋晴)벼와 동진(東津)벼 혼식조합구(混植組合區)에서 6.8% 증수(增收)되어 혼식효과(混植效果)가 가장 높았다. 9. 수량(收量)은 $m^2$당(當) 수수(穗數)와 건물중(乾物重)에 고도(高度)의 유의차(有意差)가 인정(認定)되었으며 수당(穗當) 영화수(穎花數)와 등숙율(登熟率)과는 유의차(有意差)가 인정(認定)되지 않았다.

• Journal of Biosystems Engineering
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• 제14권4호
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• pp.251-261
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• 1989

The amount of grain loss incurred during harvesting operation through the chaff-outlet of combine may not be negligible. To minimize this grain loss and optimize condition of combining, it may be necessary that the amount of chaff-outlet loss dependent on varying crop condition is to be estimated as exactly as possible. This study was thus intended to develop the monitor that could indicate the amount of grain loss occurred through the chaff-outlet of combine during harvesting operation. The function of this monitor is to measure at the sounding board the impact sound of paddy kernels which could be distinguished from those of other threshing products through chaff-outlet, and from vibration or noise created by the combine engine and other moving parts. To develop such monitor, the frequency distributions of each sound generated by the impact of grain and chaff, the sound generated by the impact of the mixture of grain and chaff, and vibration or noise created by the combine engine and other moving parts were investigated experimentally. From the results of frequency analyses, the trainsducer adequate for the monitering system was selected and sounding board was constructed. The grain loss monitor thus obtained was tested by attaching the sounding board to the chaff-outlet of combine.

• 한국해양바이오학회지
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• 제2권4호
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• pp.238-244
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• 2007

Nowadays many people are concerned about being healthy, and many dairy products are taken as health supplementary foods. Among dairy products, kefir, also called as Tibet mushroom, is a yogurt fermented by kefir grain, which is a mixture of lactic acid bacteria and yeasts. Although there are many empirical evidences that kefir is very influential for human body, the exact reason is not definitively discovered. Therefore, it would be useful to understand characteristics of a kefir grain and to categorize bacteria in a kefir grain. In this paper, molecular biological apparatus such as PCR, electrophoresis, PCR purification, DNA sequencing were used to identify and classify the species of lactic acid bacteria and yeast in a kefir grain. We used PCR-based identification method using 16S rRNA primer and Internal Transcribed Spacer (ITS) primer. We identified 6 different species which were selected on different medium. In addition, observation with scanning electron microscope (SEM) enabled us to grasp an external shape of the kefir grain. Although we found a limited number of microbial species, more intensive research are needed for extensive identification of microorganism species in Korean kefir grain.