• 소성∙가공
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• 제8권3호
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• pp.233-233
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• 1999

To investigate the effect of tungsten addition on mechanical properties, we prepared refractory (62χ)Nb-18Si-l00Mo-l0Ti-χW (χ=0, 5, 10 and 15 mol.%) in-situ composites by the conventional arc-casting technique, and then explored the microstructure, hardness and elastic modulus at ambient temperature and tensile properties at 1670 K. The microstructure consists of relatively fine (Nb, Mo, W, Ti)/sub 5/Si₃, silicide and a Nb solid solution matrix, and the fine eutectic microstructure becomes predominant at a Si content of around 18 mol.%. The hardness of (Nb, Mo, W, Ti(/sub 5/Si₃, silicide in a W-free sample is 1680 GPa, and goes up to 1980 GPa in a W 15 mol.% sample. The hardness, however, of Nb solid solution does not exhibit a remarkable difference when the nominal W content is increased. The elastic modulus shows a similar tendency to the hardness. The optimum tensile properties of the composites investigated are achieved at W 5 mol.% sample, which exhibits a relatively good ultimate strength of 230 MPa and an excellent balance of yield strength of 215 MPa, and an elongation of 3.7%. The SEM fractography generally indicates a ductile fracture in the W-free sample, and a cleavage rupture in W-impregnated ones.

• 충청수학회지
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• 제36권1호
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• pp.1-8
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• 2023

Let C be a smooth projective curve and W a symplectic bundle over C of degree w. Let π : 𝕃𝔾(W) → C be the relative Lagrangian Grassmannian over C and S_d(W) be the space of Lagrangian subbundles of degree w -d. Then Kontsevich's space ${\bar{\mathcal{M}}}_g$(𝕃𝔾(W), β_d) of stable maps to 𝕃𝔾(W) is a compactification of S_d(W). In this article, we give an upper bound on the dimension of ${\bar{\mathcal{M}}}_g$(𝕃𝔾(W), β_d), which is an analogue of a result in [8] for the relative Lagrangian Grassmannian.

• 대한수학회보
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• 제59권1호
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• pp.213-226
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• 2022

Let R be a ring and M an R-module. Then M is said to be regular w-flat provided that the natural homomorphism I ⊗_R M → R ⊗_R M is a w-monomorphism for any regular ideal I. We distinguish regular w-flat modules from regular flat modules and w-flat modules by idealization constructions. Then we give some characterizations of total quotient rings and Prüfer v-multiplication rings (PvMRs for short) utilizing the homological properties of regular w-flat modules.

• 대한수학회보
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• 제59권5호
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• pp.1289-1304
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• 2022

In this note, we show that a strongly 𝜙-ring R is a 𝜙-PvMR if and only if any 𝜙-torsion-free R-module is 𝜙-w-flat, if and only if any GV-torsion-free divisible R-module is nonnil-absolutely w-pure, if and only if any GV-torsion-free h-divisible R-module is nonnil-absolutely w-pure, if and only if any finitely generated nonnil ideal of R is w-projective.

• 대한화장품학회지
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• 제40권3호
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• pp.227-236
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• 2014

본 연구에서는 친수성 계면활성제와 친유성 계면활성제가 조합된 다양한 HLB (Hydrophilic Lipophilic Balance) 값을 갖는 유화 시스템의 조건에서, required HLB 값이 각기 다른 오일들을 적용하여 제조한 O/W 및 W/S 에멀젼들의 특성 및 유화 안정성을 조사해 보았다. 그 결과 O/W 에멀젼은 유화제의 HLB 값이 낮을수록 점도가 높고, 유화입자는 작고 조밀한 경향을 나타내었으며, 원심분리에서도 더 안정한 경향을 나타내었다. W/S 에멀젼은 유화제의 HLB 값이 높을수록 유화입자는 작고 조밀해지는 경향을 나타내었으며, 원심분리에서도 더 안정한 경향을 나타내었다. 그러나 W/S 에멀젼은 시간이 경과할수록 모든 유화제의 HLB 조건에서 점도가 낮아지는 경향이 나타나 장기 안정도에서는 불안정한 특성을 나타내었다. 이번 연구의 결과는 O/W 에멀젼은 HLB 값이 높은 비이온 계면활성제의 적용이 적합하며 W/S 에멀젼은 HLB 값이 낮은 비이온 계면활성제의 적용이 적합하다는 기본 이론과 상반되는 결과로서 앞으로의 화장품 연구 개발 시 유용한 연구 자료가 될 것으로 사료된다.

• 한국식품영양과학회지
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• 제19권6호
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• pp.612-616
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• 1990

전상이 일어나기 직전의 W/O형 에멀젼에는 W/O형 에멀젼과 섞여 O/W/O 형 에멀젼이 생성한다는 것을 알았다. 그래서 W/O형 에멀젼 중에 분산된 O/W/O형 분산의 정도를 평가하기 위한 목적으로 시료 에멀젼(수상 :물, 유상 TGCR을 함유한 올리브유)을 원추 평판형 회전 점도계를 사용하여 전단속도 1.92-384sec$^{-1}$(온도 25$\pm$0.1$^{\circ}C$)에서 점도를 측정하고 이 값을 Mooney의 점도식에 대입하여 이론치와 실측치의 차로부터 O/W/O형 분산의 정도를 평가했다. O/W/O형 에멀젼의 생성은 전상 직전의 시료에서 높았고, 유화제인 TGCR의 농도가 낮을수록 O/W/O형 에멀젼의 생성이 증가되는 경향이 나타났다. 이러한 사실로부터 W/O형 에멀젼이 전상 직전 부근에서 이론적으로 설명할 수 없는 고점도 현상이 전상직전의 O/W/O형 에멀젼의 생성에 의해서도 일어날 가능성이 있다고 사료된다.

• 한국식품영양과학회지
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• 제24권6호
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• pp.901-905
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• 1995

기호음료 및 약용으로 사용되는 두충나무잎의 품질 평가를 위한 HPLC로서 함유된 flavonoid 화합물을 정성, 정량 분석하였다. 즉 두충나무잎의 n-BuOH 분획으로 부터 astragalin, isoquercitrin, quercetin $3-O-{\beta}-D-xylopyranosyl(1-2)-{\beta}-D-glucopyranoside$의 3종 flavonoid 성분들을 분리하였으며, 이들 화합물은 LPLC의 THF-dioxane-MeOH-HOAc-5% $H_3PO_4-H_2O$(145 : 125 : 50 : 20 : 2 : 658) 혼합용매에서 양호한 분리능을 나타내었다. MeOH 엑스와 n-BuOH 분획 중에 astragaline의 함량은 각각 0.09%(w/w), 0.46%(w/w), isoquercitrin은 0.08%(w/w), 0.48(w/w), quercetin $3-O-{\beta}-D-xylopyranosyl(1-2)-{\beta}-D-glucopyranoside$은 0.40%(w/w), 1.22%(w/w) 함유되어있다.

• 한국분말재료학회지
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• 제1권1호
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• pp.52-59
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• 1994

Since the coefficient of thermal expansion (CTE) of matrix phase is larger about 4 times than that of W particle in tungsten heavy alloy, the thermal stresses due to the CTE difference between the two phases are induced in the alloy during heating and cooling processes. In the present study, a series of W heavy alloy containing various W particle volumes of 0 to 90% is made to investigate the residual stress taking place during cooling process. The CTE and residual stress of the series of alloy are measured by dilatometer and X-ray diffractometer. The residual stress of W particle is in compressive stress irrespective of W particle vol% and tends to increase with decreasing W particle vol% while that of the matrix phase is in tensile stress. The measured residual stress of W particle is about a third of calculated thermal stress. The influence of W particle vol% on the residual stress of W heavy alloy is discussed in terms of the deformation behaviors of W particle and matrix phase.

• 한국소음진동공학회논문집
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• 제16권2호
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• pp.124-131
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• 2006

This study introduces an environmental noise evaluation procedure for wind turbines(W/T) and the evaluation result of a 750 kW wind turbine(W/T) system. Test and evaluation are performed according to the international standard IEC 61400-11 on J48 W/T which is under operation in Daekwanryung W/T test site. With the meteorological data and W/T operational data, noise data are monitored and analysed. An integrated monitoring system is constructed in the test site and is utilized for the evaluation. From the measured noise data, acoustic power level, directivity and tonality of the W/T are estimated under the wind speeds required fly the International standard. The purpose of the study is to establish an W/T noise evaluating system satisfying the international standard and to obtain noise data for home made 750 kW W/T.

• 한국분말재료학회지
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• 제11권1호
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• pp.43-49
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• 2004

The electrical and thermal conductivity of W-Cu composites were investigated as a function of the W-particle size and W-W contiguity. Powder mixtures were prepared by ball milling or mechanical alloying process, and then sintered at various temperatures. The electrical conductivity of sintered composite was increased with decreasing W grain size. Dependence of electrical conductivity on the W grain size was explained by the W-W contiguity concept. The thermal conductivity was increased with increasing the temperature up to $600^{\circ}C$ but decreased at the temperature above $600^{\circ}C$ Also, thermal conductivity value was influenced by the W particle size. Change of thermal conductivity in W-Cu composites was discussed based on the observed microstructural characteristics and theoretical considerations.