• 천문학논총
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• 제30권2호
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• pp.397-399
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• 2015

Recently, cosmic voids have been recognized as a powerful cosmological probe. A number of studies have focused on the effects of the gravitational lensing by voids on the temperature (and in some cases polarization) anisotropy of the Cosmic Microwave Background (CMB) background at relatively large to medium scales, l ~ 1000. Many of these studies attempt to explain the unusually large cold spot in CMB temperature maps and dynamical evidence of dark energy via detections of late-time integrated Sachs Wolfe (ISW) effect. Here, the effects of lensing by voids on the CMB temperature anisotropy at small scales, up to l = 3000, will be investigated. This work is carried out in the light of the benefits of adding large catalogues of cosmic voids, to be identified by future large galaxy surveys such as EUCLID and LSST, to the analysis of CMB data such as those from Planck mission. Our numerical simulation utilizes two methods, namely, the small-de ectionangle approximation and full ray-tracing analysis. Using the fitted void density profiles and radius (RV ) distribution available in the literature from N-body simulations, we simulated the secondary temperature anisotropy (lensing) of CMB photons induced by voids along a line of sight from redshift 0 to 2. Each line of sight contains approximately 1000 voids of effective radius $RV_{,eff}=35h^{-1}Mpc$ with randomly distributed radial and projected positions. Both methods are used to generate temperature maps. The two methods will be compared for their accuracy and effciency in the implementation of theoretical modeling.

• 지질공학
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• 제18권4호
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• pp.423-431
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• 2008

충적층의 구성물질 중에서 포화된 실트 또는 점토층은 다른 층들에 비해 상대적으로 낮은 전기비저항 값을 나타낸다. 따라서 자료해석에 있어서 실트 및 점토층이 전기비저항이 작고 투수성이 높은 대수층으로 오인될 수 있다. 본 연구에서는 이러한 문제를 극복하고 충적층 내 포화된 실트 또는 점토층과 모래 또는 자갈 대수층을 구분하기 위해 충적층을 구설하고 있는 물질의 전기비저항 및 유도분극 값을 함께 측정하는 실내실험을 실시하였다. 실험결과 실트 또는 점토시료가 모래시료보다 충전성이 높게 나타났으며, 또한 모래와 점토 혼합시료에서 점토함량이 증가함에 따라 전기비저항은 감소하고 충전성은 증가하다가 다시 감소하는 경향을 보였다.

• 한국재료학회지
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• 제22권7호
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• pp.342-345
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• 2012

The dielectric properties and phase transformation of poled <001>-oriented $Pb(Mg_{1/3}Nb_{2/3})O_3-x%PbTiO_3$(PMN-x%PT) single crystals with compositions of x = 20, 30, and 35 mole% are investigated for orientations both parallel and perpendicular to the [001] poling direction. An electric-field-induced monoclinic phase was observed for the initial poled PMN-30PT and PMN-35PT samples by means of high-resolution synchrotron x-ray diffraction. The monoclinic phase appears from $-25^{\circ}C$ to $100^{\circ}C$ and from $-25^{\circ}C$ to $80^{\circ}C$ for the PMN-30PT and PMN-35PT samples, respectively. The dielectric constant (${\varepsilon}$)-temperature (T) characteristics above the Curie temperature were found to be described by the equation$(1/{\varepsilon}-1/{\varepsilon}_m)^{1/n}=(T-T_m)/C$, where ${\varepsilon}_m$ is the maximum dielectric constant and $T_m$ is the temperature giving ${\varepsilon}_m$, and n and C are constants that change with the composition. The value of n was found to be 1.82 and 1.38 for 20PT and 35PT, respectively. The results of mesh scans and the temperature-dependence of the dielectric constant demonstrate that the initial monoclinic phase changes to a single domain tetragonal phase and a to paraelectric cubic phase. In the ferroelectric tetragonal phase with a single domain state, the dielectric constant measured perpendicular to the poling direction was dramatically higher than that measured in the parallel direction. A large dielectric constant implies easier polarization rotation away from the polar axis. This enhancement is believed to be related to dielectric softening close to the morphotropic phase boundary.

• 한국재료학회지
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• 제21권7호
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• pp.391-395
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• 2011

The structure and dielectric properties of poled <001>-oriented 0.7Pb($Mg_{1/3}Nb_{2/3})O_3-0.3PbTiO_3$ (PMN-0.3PT) crystals have been investigated for orientations both parallel and perpendicular to the [001] poling direction. An electric field induced monoclinic phase was observed for the initial poled sample. The phase remained stable after the field was removed. A quite different temperature dependence of dielectric constant has been observed between heating and cooling due to an irreversible phase transformation. The results of mesh scans and temperature dependence of the dielectric constant demonstrate that the initial monoclinic phase changes to a single domain tetragonal phase at 370K and to a paraelectric cubic phase at 405K upon heating. However, upon subsequent cooling from the unpoled state, the cubic phase changes to a poly domain tetragonal phase and to a rhombohedral phase. In the ferroelectric tetragonal phase with a single domain state, the dielectric constant measured perpendicular to the poling direction was dramatically higher than that of the parallel direction. A large dielectric constant implies easier polarization rotation away from the polar axis. This enhancement is believed to be related to dielectric softening close to the morphotropic phase boundary and at the phase transition temperature.

• 한국산학기술학회논문지
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• 제11권11호
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• pp.4468-4472
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• 2010

ICP-CVD 방법에 의해 제작된 SiOC 박막을 유전상수와 화학적 이동의 상관성에 대하여 조사하였다. SiOC 박막은 플라즈마 에너지에 의해서 해리작용과 재결합작용에 의해서 cross link 구조를 갖게 되는 Si-O 와 C-O 결합으로 구성된 $930{\sim}1230\;cm^{-1}$ 영역에서 혼합된 Si-O-C 주 결합으로 이루어졌다. C-O 결합은 $1270cm^{-1}$에서 보여지는 Si-$CH_3$ 결합의 말단부분인 C-H 결합이 전기음성도가 큰 산소에 의해서 끌리는 효과로부터 만들어진 결합이다. 그러나 Si-O 결합은 Si-$CH_3$ 결합이 분해되고 난뒤 2차 이온결합에 의해서 만들어진 결합이다. Si-O 결합의 증가는 주결합에서 오른쪽 결합이 증가하기 때문이며, FTIR 스펙트라에 의해서 red shift로 나타났다. 이러한 결과는 SiOC 박막이 보다 더 안정되고 강한 박막임을 의미한다. 그래서 SiOC 박막은 열처리 후 비정질도가 높고 거칠기가 감소되는 것을 확인하였다.

• 한국광학회지
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• 제13권5호
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• pp.449-454
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• 2002

$^85Rb\;D_1$ 전이선의 바닥준위 $F_g$=2에서 여기준위 $F_e$=3 전이를 이용하여 열린 원자계에서의 전자기 유도 흡수 현상을 관측하고, 전자기 유도 흡수에서의 비결맞음 펌핑 효과를 조사했다. 비결맞음 광원의 편광과 세기의 변화에 따른 전자기 유도 흡수에 대한 연구를 통해 비결맞음 광원의 편광에 따라서 자기부준위들 사이의 원자밀도 분포의 변화를 유도할 수 있고, 이러한 원자밀도 재분포 효과에 의해서 전자기 유도 흡수의 정도가 달라짐을 확인하였다

• 산업식품공학
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• 제22권4호
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• pp.353-357
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• 2018

Previous studies have suggested that rice bran oil (RBO), an edible oil from the byproducts of rice milling, has anti-inflammatory effects in inflammation inducing macrophages, known as M1 subsets. Yet the effects of RBO on the counterpart M2 subsets, the "healing" macrophages, were poorly investigated to date. In this regard, recent studies on the molecular/cellular anti-inflammatory mechanisms of dietary components have demonstrated that mitochondrial respiration contributes to macrophage functioning. Therefore, the current study examined whether RBO regulates cytokine secretion by modulating mitochondrial metabolism in wound healing M2 subsets. Palm oil (PO), enriched with medium-chain fatty acids, served as a positive control. C57BL/6 mice were fed a diet containing either corn oil (CO), PO or RBO for 4 weeks, followed by purification of bone marrow-derived macrophages (BMDM) from their tibias and femurs. Cells were further polarized to M2-BMDM, and the expression of M2 marker (CD206) on cellular surfaces were not affected by dietary intervention. In addition, the secretion of anti-inflammatory cytokine (IL-10) in the culture supernatant was not affected by dietary lipids. Oxygen consumption rate, the indicator of mitochondrial respiration in M2-BMDM was not regulated by RBO intervention and PO treatment. Taken together, this study imply that RBO did not intervene both the regulation of inflammatory responses and mitochondrial respiration in M2 macrophages.

• 한국표면공학회지
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• 제54권3호
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• pp.102-111
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• 2021

The corrosion behaviors of laser-welded super duplex stainless steel tubes with post-weld heat treatment(PWHT) conditions(950, 1000, 1050, 1100 ℃ for 5 and 30 min) were evaluated by electrochemical potentiodynamic polarization and critical pitting temperature measurements. This study showed that the critical metallurgical factors affecting the degradation of corrosion resistance of a steel tube in as-welded condition were the unbalanced phase fraction(ferrite:austenite = 94:4), Cr₂N precipitation, and phase transformation from the austenite phase to ɛ-martensite(via stress-induced phase transformation). The improvement in the corrosion resistance of the welded specimen depends greatly on the PWHT conditions. The specimens after PWHT conducted below 1000 ℃ showed inferior corrosion resistance, caused by precipitation of the sigma phase enriched with Cr and Mo. At 1100 ℃ for a longer duration in PWHT, the ferrite phase grows, and its fraction increases, leading to an unbalanced phase fraction in the microstructure. As a result, pitting can be initiated primarily at the interface between the ferrite/austenite phase, particularly in base metal.

• 한국전기전자재료학회논문지
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• 제34권5호
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• pp.386-392
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• 2021

Multiferroics exhibiting the coexistence and a possible coupling of ferromagnetic and ferroelectric order are attracting widespread interest in terms of academic interests and possible applications. However, room-temperature single-phase multiferroics with soft ferromagnetic and displacive ferroelectric properties are still rare owing to the contradiction in the origin of ferromagnetism and ferroelectricity. In this study, we demonstrated that sizable ferromagnetic properties are induced in the ferroelectric bismuth ferrite-barium titanate system simply by introducing Co ions into the A-site. It is noted that all modified compositions exhibit well-saturated magnetic hysteresis loops at room temperature. Especially, 70Bi_0.95Co_0.05FeO₃-30Ba_0.95Co_0.05TiO₃ manifests noticeable ferroelectric and ferromagnetic properties; the spontaneous polarization and the saturation magnetization are 42 µC/cm² and 3.6 emu/g, respectively. We expect that our methodology will be widely used in the development of perovskite-structured multiferroic oxides.

• 조명전기설비학회논문지
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• 제17권6호
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• pp.47-53
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• 2003

본 논문은 자기광학효과에 의한 초고압 전력설비에서의 광전류 센서의 특성에 대한 기초 연구를 하였다. 광원은 He-Ne laser(633[nm])를 사용하고, 수신부는 PIN-Photodiode를 사용하였다. Faraday 효과에 의한 편광면의 회전각은 도체에 인가된 전류에 비례하므로 광섬유를 도체 주위에 감아서 센싱부를 구성하였다. 광섬유센서를 통과한 광신호를 입력편광에 대하여 $\theta$방향으로 정렬된 검광자를 통과시켜 그 회 각을 분석하여 l00[A] 에서 1000[A] 까지의 광 CT 동작특성과 60[Hz] 교류전류측정을 하였다. 측정 결과에서는 전류에 따른 출력 신호가 선형적으로 증가함을 알 수 있었고 파이버의 권수에 따른 출력차이를 통해 파이버의 권수가 많을수록 강도가 커진다는 것을 알 수 있었다. 또한 자장과 감긴 파이버 사이의 매질에 따라 출력의 차이뿐만 아니라 선형성까지도 차이가 난다는 것을 알 수 있었다. 기준값과 광전류 센서의 출력 강도와의 오차율을 구했을 때 약 $\pm$7% 이하의 오차가 나왔고 이는 매질과 권수에 따라 그 오차율이 점점 나아질 수 있다는 것을 확인 시켜주었다.