• 공업화학
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• 제21권3호
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• pp.311-316
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• 2010

본 연구는 높은 분산 안정성을 유지하는 antimony-doped tin oxide (ATO) 분산액을 제조하기 위하여, 습식 볼밀법으로 분쇄시간에 따른 ATO의 입자크기, 입도분포, 분산성의 변화를 고찰하였다. 또한 각각의 습식 볼밀 처리된 ATO 분산액의 pH를 변화시켜 ATO 분산액의 분산 특성을 고찰하였다. 습식 볼밀 분쇄 조건에 의하여 ATO의 입자크기 및 입도 분포 변화는 레이저회절 입도분석기와 주사전자현미경을 이용하여 평가하였고, 습식 볼밀 분쇄 시간 및 pH조건에 따른 ATO 입자의 분산성은 제타전위 측정법과 다중광산란(multiple light scattering)법을 이용하여 평가하였다. 분쇄 조건 중 60 min 동안 처리된 ATO 입자 크기는 30% 이하로 작아지고, $1{\sim}35{\mu}m$에서 $0.1{\sim}5{\mu}m$로 입도분포를 갖는 균일한 입자를 얻을 수 있었다. 그러나 분쇄조건을 60 min 이상 처리한 것은 역분쇄 및 재응집 현상의 발생으로 인하여 한계 분쇄 시간이 나타나는 것을 알 수 있었다. 이러한 결과로부터 ATO 분산액은 습식 볼밀 분쇄 시간을 증가시킬수록 입자 크기가 감소하고 표면 에너지가 증가하여 입자간의 반발력이 커지게 됨을 알 수 있었고, 또한 용액의 pH를 증가시킬수록 입자의 표면 이온화도가 커짐으로 인하여 ATO 분산액의 분산성이 향상되는 것을 알 수 있었다.

• Kyungpook Mathematical Journal
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• 제49권2호
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• pp.255-263
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• 2009

For an endomorphism ${\alpha}$ of R, in [1], a module $M_R$ is called ${\alpha}$-compatible if, for any $m{\in}M$ and $a{\in}R$, ma = 0 iff $m{\alpha}(a)$ = 0, which are a generalization of ${\alpha}$-reduced modules. We study on the relationship between the quasi-Baerness and p.q.-Baer property of a module MR and those of the polynomial extensions (including formal skew power series, skew Laurent polynomials and skew Laurent series). As a consequence we obtain a generalization of [2] and some results in [9]. In particular, we show: for an ${\alpha}$-compatible module $M_R$ (1) $M_R$ is p.q.-Baer module iff $M[x;{\alpha}]_{R[x;{\alpha}]}$ is p.q.-Baer module. (2) for an automorphism ${\alpha}$ of R, $M_R$ is p.q.-Baer module iff $M[x,x^{-1};{\alpha}]_{R[x,x^{-1};{\alpha}]}$ is p.q.-Baer module.

• 한국식생활문화학회지
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• 제3권2호
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• pp.163-175
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• 1988

본 조사는 서울시, 충남 대전시, 경북 영주시, 충남 서천군에 거주하는 530명의 주부를 대상으로 1987. 11. $16{\sim}11$. 28 사이에 떡의 이용실태와 시판제품의 품질특성에 대한 주부들의 평가도를 조사했던 바 여기에서 얻어진 결과를 요약하면 다음과 같다. (1) 조사대상자의 가정에서 이용하는 떡의 종류는 총 37종 이었고 그중 인절미(67.9%), 송편(66.6%), 흰떡 (51.4%), 개피떡(43.4%) 등 일부 도병류의 이용율이 높았고 전병류, 단자류 및 일부 증병류의 이용율은 아주 낮았다. (2) 의례시 떡의 이용율은 혼례때 가장 높았고 상례때 가장 낮았으며 돐, 혼례, 회갑때는 백일, 어른과 아이의 생일, 제사, 상례때보다 떡의 이용율이 높은 경향이었다. (3) 의례시 가장 많이 이용하는 떡은 백일, 돐, 아이의 생일에는 백설기로 어른의 생일, 혼례, 제사, 회갑에는 인절미로 나타났다. (4) 어른과 아이의 생일에는 케이크의 이용율이 (36%내외) 떡보다 높은 경향이었다. (5) 절식시 떡의 이용율은 설날에 가장 높았고 그 다음이 추석으로 나타났으며 그밖의 절식은 조사대상자의 가정에서 거의 지켜지지 않고 있었다. (6) 전체조사대상주부들중 61.7%가 앞으로도 계속 가정에서 떡을 만들겠다고 응답했던 바 아직까지 대부분의 주부들은 의뢰 또는 구입하기보다는 가정에서 직접 만들고 싶어하는 경향임을 알 수 있었다. (7) 조사대상주부들이 시판제품을 구입하는 이유는 간편해서가(65.8%) 가장 많았고 또한 시판제품을 구입하지 않는 이유는 내 손으로 직접 만들고 싶어서가(44.3%) 가장 많았던 바 두가지 이유가 상반되는 경향이었다. (8) 조사대상주부들은 시판되는 떡의 품질특성중 맛과 색 등 관능적인 면은 비교적 좋게 평가하는 경향이었고 가격, 위생성, 포장 및 저장성 등을 나쁘게 평가하는 경향이었다. 시판제품의 색은 주부의 거주지에 따라 농어촌에 거주하는 주부가 도시에 거주하는 주부보다 더 좋게 평가하는 경향이었다. (p<0.05) 위생성은 주부의 학력과 거주지에 따라 주부의 학력이 높을수록, 농어촌지역보다는 도시에 거주하는 주부일수록 시판제품이 더 비위생적이라고 평가하는 경향이었고(p<0.01) 포장에 대해서는 주택형태에 따라 농가나 아파트에 거주하는 주부가 단독주택이나 연립주택에 거주하는 주부보다 더 나쁘게 평가하는 경향이었다. (p<0.05) (9) 조사대상주부들은 시판제품의 가장 개선해야 할 점으로 위생성(37.0%), 가격(23.8%), 포장(15.6%), 맛(11.1%), 저장성(10.1%) 및 색(2.4%) 등의 순으로 지적하였고 주부의 거주지에 따라 대도시에 거주할수록 위생성을, 농어촌에 거주할수록 가격을 가장 개선해야 할 점으로 보는 경향이었다. (p<0.05)

• 한국분말재료학회지
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• 제24권6호
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• pp.457-463
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• 2017

Nanosized $Gd_2O_3:Eu^{3+}$ red phosphor is prepared using a template method from metal salt impregnated into a crystalline cellulose and is dispersed using a bead mill wet process. The driving force of the surface coating between $Gd_2O_3:Eu^{3+}$ and mica is induced by the Coulomb force. The red phosphor nanosol is effectively coated on mica flakes by the electrostatic interaction between positively charged $Gd_2O_3:Eu^{3+}$ and negatively charged mica above pH 6. To prepare $Gd_2O_3:Eu^{3+}$-coated mica ($Gd_2O_3:Eu/mica$), the coating conditions are optimized, including the stirring temperature, pH, calcination temperature, and coating amount (wt%) of $Gd_2O_3:Eu^{3+}$. In spite of the low luminescence of the $Gd_2O_3:Eu/mica$, the luminescent property is recovered after calcination above $600^{\circ}C$ and is enhanced by increasing the $Gd_2O_3:Eu^{3+}$ coating amount. The $Gd_2O_3:Eu/mica$ is characterized using X-ray diffraction, field emission scanning electron microscopy, zeta potential measurements, and fluorescence spectrometer analysis.

• Korean Journal of Radiology
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• 제24권6호
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• pp.564-573
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• 2023

Objective: To investigate the feasibility of assessing the viscoelastic properties of the brain using magnetic resonance elastography (MRE) and a novel MRE transducer to determine the relationship between the viscoelastic properties and glymphatic function in neurologically normal individuals. Materials and Methods: This prospective study included 47 neurologically normal individuals aged 23-74 years (male-to-female ratio, 21:26). The MRE was acquired using a gravitational transducer based on a rotational eccentric mass as the driving system. The magnitude of the complex shear modulus |G^*| and the phase angle 𝛗 were measured in the centrum semiovale area. To evaluate glymphatic function, the Diffusion Tensor Image Analysis Along the Perivascular Space (DTI-ALPS) method was utilized and the ALPS index was calculated. Univariable and multivariable (variables with P < 0.2 from the univariable analysis) linear regression analyses were performed for |G^*| and 𝛗 and included sex, age, normalized white matter hyperintensity (WMH) volume, brain parenchymal volume, and ALPS index as covariates. Results: In the univariable analysis for |G^*|, age (P = 0.005), brain parenchymal volume (P = 0.152), normalized WMH volume (P = 0.011), and ALPS index (P = 0.005) were identified as candidates with P < 0.2. In the multivariable analysis, only the ALPS index was independently associated with |G^*|, showing a positive relationship (β = 0.300, P = 0.029). For 𝛗, normalized WMH volume (P = 0.128) and ALPS index (P = 0.015) were identified as candidates for multivariable analysis, and only the ALPS index was independently associated with 𝛗 (β = 0.057, P = 0.039). Conclusion: Brain MRE using a gravitational transducer is feasible in neurologically normal individuals over a wide age range. The significant correlation between the viscoelastic properties of the brain and glymphatic function suggests that a more organized or preserved microenvironment of the brain parenchyma is associated with a more unimpeded glymphatic fluid flow.

• 한국재료학회지
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• 제14권12호
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• pp.863-869
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• 2004

The purpose of this research is to investigate the mechanical property and ductile-brittle transition temperature of Ti-Nb-P added extra low carbon interstitial free steel having a tensile strength of 440 MPa. The mechanical property and transition temperature of hot rolled steel sheets were more influenced by the coiling temperature rather than by the small amount of alloying element. Further, at the same composition, the property of the specimen coiled at low temperature was superior to that obtained at higher coiling temperature. The fracture surface of 0.005C-0.2Si-1.43Mn steel coiled at $630^{\circ}C$ showed a ductile fracture mode at $-100^{\circ}C$, but coiling at $670^{\circ}C$ showed a transgranular brittle fracture mode at $-90^{\circ}C$. The galvannealed 0.006C-0.07Si-1.33Mn steel sheet annealed at $810^{\circ}C$ has tensile strength and elongation of 442.8 MPa and $36.6\%$, respectively. The transition temperature of galvannealed 0.006C-0.07Si-1.33Mn steel sheet was increased with a drawing ratio, and the transition temperature of the galvannealed 0.006C-0.07Si-1.33Mn steel was $-60^{\circ}C$ at a drawing ratio of 1.8

• Korea-Australia Rheology Journal
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• 제16권4호
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• pp.175-182
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• 2004

Colloidal coating solution was prepared to enhance the hydrophilic property of the film surface. Water and ethanol were used as the dispersion media and (glycidoxypropyl) trimethoxysilane (GPS) as a binder in the colloidal silica coatings. Ethylene diamine was added to the colloidal silica solution as the curing agent. The colloidal silica solution was regarded as a hard-sphere suspension model with low volume fraction of the silica particles. Rheological properties of the silica suspensions modified with GPS have been investigated as a function of pH and concentration. The acidic solution showed high viscosity change by fast hydrolysis reaction and adsorption of the organic binders on the surface of silica particles. However, the hydrolysis was slow at the basic condition and the binders combined with themselves by condensation. The viscosity change was smallest at pH 7. The viscosity increased with the curing time after adding ethylenediamine, and the increase of viscosity at low pH was higher than that at high pH. The hydrophilic properties of the coating film were investigated by the contact angle of water and film surface. The smallest contact angle was shown under the strong acidic condition of pH 2.

• 한국전기전자재료학회논문지
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• 제15권5호
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• pp.383-387
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• 2002

N-channel metal-ferroelectric-insulator-semiconductor field-effect-transistors (MFISFET's) by using $SrBi_2Ta_2O_9$/Silicon Nitride/Si (100) structure were fabricated. The fabricated devices exhibit comfortable memory windows, fast switching speeds, good fatigue resistances, and long retention times that are suitable for advanced ferroelectric memory applications. The estimated switching time and polarization ($2P_r$) of the fabricated FET measured at applied electric field of 376 kV/cm were less than 50 ns and about 1.5 uC/$\textrm{cm}^2$, respectively. The magnitude of on/off ratio indicating the stored information performance was maintained more than 3 orders until 3 days at room temperature. The $I_DV_G$ characteristics before and after being subjected to $10^11$ cycles of fatigue at a frequency of 1 MHz remained almost the same except a little distortion in off state.

• Journal of applied mathematics & informatics
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• 제32권1_2호
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• pp.137-152
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• 2014

In this paper, we prove, in the spirit of [3, 12, 20, 22, 23], the existence of infinitely many small solutions to the following quasilinear elliptic equation $-{\Delta}_{p(x)}u+{\mid}u{\mid}^{p(x)-2}u={\mid}u{\mid}^{q(x)-2}u+{\lambda}f(x,u)$ in a smooth bounded domain ${\Omega}$ of ${\mathbb{R}}^N$. We also assume that $\{q(x)=p^*(x)\}{\neq}{\emptyset}$, where $p^*(x)$ = Np(x)/(N - p(x)) is the critical Sobolev exponent for variable exponents. The proof is based on a new version of the symmetric mountainpass lemma due to Kajikiya [22], and property of these solutions are also obtained.

• 호남수학학술지
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• 제39권3호
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• pp.431-442
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• 2017

For a quadrilateral P, we consider the centroid $G_0$ of the vertices of P, the perimeter centroid $G_1$ of the edges of P and the centroid $G_2$ of the interior of P, respectively. We denote by M the intersection point of two diagonals of P. If P is a parallelogram, then we have $G_0=G_1=G_2=M$. Conversely, one of $G_0=M$ and $G_2=M$ implies that P is a parallelogram. In this paper, we show that $G_1=M$ is also a characteristic property of parallelograms.