• 한국자기학회:학술대회 개요집
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• 한국자기학회 2011년도 임시총회 및 하계학술연구발표회
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• pp.7-8
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• 2011

Basically, the lattice mismatch between film and substrate can make those BiFeO3(BFO) films distorted with strain structure. BFO phase can be stabilized on LaAlO3(LAO) represents the example of a multiferroic with giant axial ratio. Its crystal structure is not strictly tetragonal, but tetragonal with a slight monoclinic distortion and related to the rotation of the oxygen octahedra. In this study, we show that phases with a tetragonal-like epitaxial BFO films can indeed be ferroelectric and also can be stabilized via epitaxial growth onto LAO. Recent reports on epitaxial BFO films show that the crystal structure changes from nearly rhombohedral ("R-like") to nearly tetragonal("T-like") at strains exceeding approximately -4.5%, with the "T-like" structure being characterized by a highly enhanced c/a ratio. While both the "R-like" and the "T-like" phases are monoclinic, our detailed x-ray diffraction results reveal asymmetry change from MA and MC type, respectively. By applying additional strain or by modifying the unit cell volume of the film by substituting Ba for Bi, the monoclinic distortion in the "T-like" MC phase is reduced, i.e. the system approaches a true tetragonal symmetry. There are two different M-H loops for $Bi_{1-x}Ba_xFeO_{3-{\delta}}$(BBFO) and BFO films on SrTiO3(STO) & LAO substrates. Along with the ferroelectric characterization, these magnetic data indicate that the BFO phase stabilized on LAO represents the first example of a multiferroic with giant axial ratio. However, there is a significant difference between this phase and other predicted ferroelectrics with a giant axial ratio: its crystal structure is not strictly tetragonal, but tetragonal with a slight monoclinic distortion. Therefore, in going from bulk to highly-strained films, a phase sequence of rhombohedral(R)-to-monoclinic ["R-like" MA-to-monoclinic, "T-like" MC-to-tetragonal (T)] is observed. This sequence is otherwise seen only near morphotropic phase boundaries in lead-based solid-solution perovskites (i.e. near a compositionally induced phase instability), where it can be controlled by electric field, temperature, or composition. Our results show that this evolution can occur in a lead-free, stoichiometric material and can be induced by stress alone. Those major results are summarized as follows ; 1) Ba-doping increases the unit cell volume, 2) BBFO on LAO can be fully strained up to x=0.08 as a strain limit (Fig. 1), 3) P(E) & M(H) properties can be tuned by the variation of composition, strain, and film thickness.

• Parasites, Hosts and Diseases
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• 제59권6호
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• pp.625-634
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• 2021

Based on the field investigations in 91 investigation sites (counties) in southwest China between 2001 and 2019, the present paper reported the chigger mites on A. agrarius mice in southwest China for the first time by using a series of statistical methods. From 715 striped field mice captured in 28 of 91 investigated sites, only 255 chiggers were collected, and they were identified as 14 species, 6 genera in 3 subfamilies under 2 families. Of 715 A. agrarius mice, only 24 of them were infested with chigger mites with low overall prevalence (P_M=3.4%), overall mean abundance (M_A=0.36 mites/host) and overall mean intensity (M_I=10.63 mites/host). The species diversity and infestation of chiggers on A. agrarius were much lower than those previously reported on some other rodents in southwest China. On a certain species of rodent, A. agrarius mouse in southwest China seems to have a very low susceptibility to chigger infestations than in other geographical regions. Of 14 chigger species, there were 3 dominant species, Leptotrombidium sialkotense, L. rupestre and Schoengastiella novoconfuciana, which were of aggregated distribution among different individuals of A. agrarius hosts. L. sialkotense, one of 6 main vectors of scrub typhus in China, was the first dominant on A. agrarius. The species similarity of chigger mites on male and female hosts was low with C_SS=0.25, and this reflects the sex-bias of different genders of A. agrarius mice in harboring different chigger species.

• 자원환경지질
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• 제16권1호
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• pp.19-36
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• 1983

The study revealed that the sequence of volcanism in Ulrung island can be classified into 5 stages, and the volcanic history is summerized as follow: 1st stage: Eruption of basaltic agglomerates, tuffs and lavas, 2nd stage: Eruption of trachytic and trachyandesitic agglomerates and tuffs, 3rd stage: Eruption of trachyte lavas and their lapilli tuffs, 4th stage: Eruption of trachyte lavas and nepheline phonolites, 5th stage: Eruption of pumice, trachytic ash and lapilli, and plutonic ejecta (fragments of alkali gabbro, monzonite and alkali feldspar syenite) and a subsequent caldera formation. Finally, a small scale eruption of leucite bearing trachyandesite lava in the caldera. Several evidences show that there have been long erosional intervals between the 1st and 2nd stages and between the 4th and 5th stages. A K-Ar age for trachybasalt lava of the 1st stage was determined to be 1.8 Ma, and a $C^{14}$ age, 9300Y. (Machida, 1981) is available for these volcanic events. Therefore, it is considered that volcanic activity of the island above sea level began at least in early Pleistocene, and continued to until 9300 years ago exploding large amount of pumice, prior to pouring out of leucite bearing trachyandesite from the inner caldera. Using solidification index (SI) of Kuno, microscopic texture and mineral composition as criteria of the classification, the volcanic rocks are classified into alkali basalt, trachybasalt, trachyandesite, trachyte and phonolite. These are mostly prophyritic in texture. Main constituent minerals of alkali basalt and trachybasalt are plagioclase, olivine, Ti-augite and magnetite. Principal minerals of trachyandesite are plagioclase, anorthoclase, clinopyroxenes, kaersutite, biotite and magnetite. Trachyte and phonolite consist mainly of anorthoclase, clinopyroxene and magnetite, showing typical trachytic texture in groundmass. In solidification index, alkali basalt ranges from 39 to 27, trachybasalt 17 to 14, trachyandesite 12 to 9 and trachyte 8.15 to 0.72. A trend of compositional variation showing a typical alkali volcanic rock series is revealed on $SiO_2$-oxides and SI-oxides diagrams. In $SiO_2$-total alkali diagram, alkali lime index and An-Ab'-Or diagram, the samples fall into the fields of potassic series of the alkali volcanic rock series, whereas in A-F-M diagram show a trend toward the alkali enrichment with a curve approaching toward the iron apex. In particular, trachybasalt lavas in this island have higher total iron contents which is comparable to alkali rocks in other areas, e. g. as Gough and Tristan volcanic islands located near the Mid-Oceanic ridge in South Atlantic Ocean.

• 한국방사선학회논문지
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• 제17권7호
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• pp.1197-1205
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• 2023

본 연구에서는 영남지역 해수욕장의 모래 시료 중에 함유되어 있는 방사능 농도를 측정하였다. 해수욕장에서 채취한 모래 표본은 영남지역의 유명해수욕장 8곳을 대상으로 선정하였다. 모래 표본을 반도체검출기인 고순도게르마늄검출기(HPGe)에 넣어 다채널분석기(MCA)를 이용한 정밀 감마 방사성핵종 분석을 실시했다. 방사선핵종의 농도를 측정하기 위해 측정 시간을 8,000 초로 설정하여 스펙트럼 파일을 얻어서 감마 방사성핵종의 농도를 분석하였다. 연구결과 8곳 해변 모두 TI-208의 방사능이 가장 높았다. 결론적으로 영남지역 해수욕장 모래표본에서 검출된 방사성핵종은 자연 방사성핵종이지만 인체 내부에 영향을 미칠 수 있다. 따라서 지속적으로 조사할 필요가 있다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 추계학술대회 논문집
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• pp.5-5
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• 2009

Thin-film-transistors (TFTs) that can be prepared at low temperatures have attracted much attention because of the great potential for transparent and flexible electronics. One of the mainstreams in this field is the use of organic semiconductors such as pentacene. But device performance of the organic TFTs is still limited due to low field-effect mobility and rapid degradation after exposing to air. Alternative approach is the use of amorphous oxide semiconductors as a channel. Amorphous oxide semiconductors (AOSs) based TFTs showed the fast technological development, because AOS films can be fabricated at room temperature and exhibit the possibility in application like flexible display, electronic paper, and larges solar cells. Among the various AOSs, a-IGZO has lots of advantages because it has high channel mobility, uniform surface roughness and good transparency. [1] The high mobility is attributed to the overlap of spherical s-orbital of the heavy post-transition metal cations. This study demonstrated the effect of the variation in channel thickness from 30nm to 200nm on the TFT device performance. When the thickness was increased, turn-on voltage and subthreshold swing was decreased. The a-IGZO channels and source/drain metals were deposited with shadow mask. The a-IGZO channel layer was deposited on $SiO_2$/p-Si substrates by RF magnetron sputtering, where RF power is 150W. And working pressure is 3m Torr, at $O_2/Ar$ (2/28 sccm) atmosphere. The electrodes were formed with electron-beam evaporated Ti (30 nm) and Au (70 nm) bilayer. Finally, Al (150nm) as a gate metal was thermal-evaporated. TFT devices were heat-treated in a furnace at 250 $^{\circ}C$ and nitrogen atmosphere for 1hour. The electrical properties of the TFTs were measured using a probe-station. The TFT with channel thickness of 150nm exhibits a good subthreshold swing (SS) of 0.72 V/decade and on-off ratio of $1{\times}10^8$. The field effect mobility and threshold voltage were evaluated as 7.2 and 8 V, respectively.

• 한국세라믹학회지
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• 제49권5호
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• pp.475-483
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• 2012

High capacitance X5R MLCCs based on $BaTiO_3$ ceramic dielectric layers exhibit a single broad, asymmetric arc shape impedance and modulus response over the wide frequency range between 1 MHz to 0.01 Hz. Analysis according to the conventional brick-layer model for polycrystalline conductors employing a series connection of multiple RC parallel circuits leads to parameters associated with large errors and of little physical significance. A new parametric impedance model is shown to satisfactorily describe the experimental spectra, which is a parallel network of one resistor R representing the DC conductivity thermally activated by 1.32 eV, one ideal capacitor C exactly representing bulk capacitance, and a constant phase element (CPE) Q with complex capacitance $A(i{\omega})^{{\alpha}-1}$ with ${\alpha}$ close to 2/3 and A thermally activated by 0.45 eV or ca. 1/3 of activation energy of DC conductivity. The feature strongly indicate the CK1 model by J. R. Macdonald, where the CPE with 2/3 power-law exponent represents the polarization effects originating from mobile charge carriers. The CPE term is suggested to be directly related to the trapping of the electronic charge carriers and indirectly related to the ionic defects responsible for the insulation resistance degradation.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.193-193
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• 2012

In thin film silicon solar cells, p-i-n structure is adopted instead of p/n junction structure as in wafer-based Si solar cells. PECVD is the most widely used thin film deposition process for a-Si:H or ${\mu}c$-Si:H solar cells. Single-chamber PECVD system for a-Si:H solar cell manufacturing has the advantage of lower initial investment and maintenance cost for the equipment. However, in single-chamber PECVD system, doped and intrinsic layers are deposited in one plasma chamber, which inevitably impedes sharp dopant profiles at the interfaces due to the contamination from previous deposition process. The cross-contamination between layers is a serious drawback of single-chamber PECVD system. In this study, a new plasma process to solve the cross-contamination problem in a single-chamber PECVD system was suggested. In order to remove the deposited B inside of the plasma chamber during p-layer deposition, a high RF power was applied right after p-layer deposition with SiH4 gas off, which is then followed by i-layer, n-layer, and Ag top-electrode deposition without vacuum break. In addition to the p-i interface control, various interface control techniques such as FTO-glass pre-annealing in O2 environment to further reduce sheet resistance of FTO-glass, thin layer of TiO2 deposition to prevent H2 plasma reduction of FTO layer, and hydrogen plasma treatment prior to n-layer deposition, etc. were developed. The best initial solar cell efficiency using single-chamber PECVD system of 10.5% for test cell area of 0.2 $cm^2$ could be achieved by adopting various interface control methods.

• 한국방재학회 논문집
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• 제11권1호
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• pp.107-112
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• 2011

본 연구는 CPC 시스템 내에서 $Tio_2$ 슬러리와 UVA 광촉매 반응을 이용한 내분비계장애물질의 하나인 Bisphenol A(BPA)의 분해와 무기화에 대한 연구이다. 실험 영향인자로는 초기농도, 촉매량, UVA 램프 파워, 온도를 고려하였고, 초기농도는 5, 10, 20 mg/L, 촉매량은 0.1, 0.5, 1.0 g/L, UV 램프는 40, 80, 120 W, 온도는 10, 20, 30 로 조절하여 실험하였다. 초기농도 가 5 mg/L일 때 BPA는 반응시간 10분에서 80%이상이 분해되었고, 1시간 이후 10 mg/L에서는 97%, 20 mg/L에서는 49%가 분해되었다. $Tio_2$ 주입량이 0.1, 0.5 g/L일 때 BPA 분해는 비슷한 경향을 보였으며, 1시간 이후 약 70%가 분해되었으며, 1 g/L에서는 30분 이후에는 80%이상이 분해되었다. 이것은 촉매량이 증가할수록 오염물질과 반응하는 활성점이 증가하여, 광촉 매 반응 또한 증가하기 때문이라 판단된다. UV 램프가 120W일 때 반응시간 10분에서 BPA는 약 60% 이상 급격히 분해 되었다. 온도에 따른 분해정도를 알아보기 위해 온도를 조절하며 수행하였고, 온도에 따른 영향은 크지 않았다. 10 에서는 1시간 이후 46% 분해되었으며, 20에서 67%, 30에서는 69% 분해되었다.

• 한국미생물·생명공학회지
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• 제40권4호
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• pp.396-402
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• 2012

이 연구에서 참쑥(Artemisia dubia) 오일의 화학적 조성, 돼지 유행성 설사 바이러스(porcine epidemic diarrhea virus, PEDV)에 대한 항바이러스 활성 및 항균 활성을 평가하였다. 참쑥 오일로부터 질량 분석기가 장착된 가스 크로마토 그래피(gas chromatography-mass spectrometry, GC-MS)에 의해 58개의 화합물이 분석되어졌다. 그 오일의 주요한 성분은 각각 camphor (17.18%), germacrene-D (15.70%), trans(${\beta}-$)caryophyllene (6.79%), ${\beta}$-thujones (6.57%), 1, 8-cineole (5.94%) and camphene (5.08%) 순으로 나타났다. 참쑥 오일의 돼지 유행성 설사 바이러스에 대한 항바이러스능을 세포독성 감소 방법 [cytopathic effect (CPE) reduction method]에 의해 베로 세포(원숭이 신장세포, Vero cells)에서 평가하였다. 그 오일은 43.7 ${\mu}g/ml$의 50% 저해농도 ($IC_{50}$)와 함께 돼지 유행성 설사 바이러스 복제를 억제하였다. 또한 그 오일은 100 ${\mu}g/ml$ 이상에서 세포독성을 나타내지 않았으며, 그 치료지수(therapeutic index, TI value)는 2.3 이상이였다. 리바비린(rivabirin)은 그 오일에 비해 상대적으로 낮은 항바이러스능을 나타내었다. 다섯개 미생물(Staphyloscoccus aureus, Staphylococcus epidermidis, Streptococcus pyogenes, Propionibacterium acnes, Candida albicans)에 대한 참쑥 오일의 항균 활성은 페이퍼 디스크 방법(paer disck diffusion method)에 의해 평가하였다. 그 결과 그 오일은 5가지 미생물에 대해 8-22 mm의 투명환(clear zone)을 나타내며 항균활성을 보였다. 테스트된 미생물들 가운데 S. pyogenes가 가장 높은 활성을 나타냈으며, C. albicans가 가장 낮은 활성을 나타냈다. 이상의 결과로부터 참쑥 오일은 항균 및 돼지 유행성 설사 바이러스 유래 질병을 조절하는데 응용 가능할 것이라 사료된다.

• 대한치과보철학회지
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• 제42권3호
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• pp.307-326
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• 2004

Statement of problem. The long-term success of implants is the development of a stable direct connection between bone and implant surface, which must be structural and functional. To improve a direct implant fixation to the bone, various strategies have been developed focusing on the surface of materials. Among them, altering the surface properties can modify cellular responses such as cell adhesion, cell motility and bone deposition. Purpose. This study was to evaluate the cellular behaviors on the surface-modified titanium by morphological observation, cellular proliferation and differentiation. Material and methods. Specimens were divided into five groups, depending on their surface treatment: electropolishing(EP) anoclizing(AN), machining(MA), blasting with hydroxyapatite particle(RBM) and electrical discharge machining(EDM). Physicochemical properties and microstructures of the specimens were examined and the responses of osteoblast-like cells were investigated. The microtopography of specimens was observed by scanning electron microscopy(SEM). Surface roughness was measured by a three-dimensional roughness measuring system. The microstructure was analyzed by X-ray diffractometer(XRD) and scanning auger electron microscopy(AES). To evaluate cellular responses to modified titanium surfaces, osteoblasts isolated from neonatal rat were cultured. The cellular morphology and total protein amounts of osteoblast-like cell were taken as the marker for cellular proliferation, while the expression of alkaline phosphatase was used as the early differentiation marker for osteoblast. In addition, the type I collagen production was determined to be a reliable indicator of bone matrix synthesis. Results. 1. Each prepared specimen showed specific microtopography at SEM examination. The RBM group had a rough and irregular pattern with reticulated appearance. The EDM-treated surface had evident cracks and was heterogeneous consisting of broad sheet or plate with smooth edges and clusters of small grains, deep pores or craters. 2. Surface roughness values were, from the lowest to the highest, electropolished group, anodized group, machined group, RBM group and EDM group. 3. All groups showed amorphous structures. Especially anodized group was found to have increased surface oxide thickness and EDM group had titaniumcarbide(TiC) structure. 4. Cells on electropolished, anodized and machined surfaces developed flattened cell shape and cells on RBM appeared spherical and EDM showed both. After 14 days, the cells cultured from all groups were formed to be confluent and exhibited multilayer proliferation, often overlapped or stratified. 5. Total protein amounts were formed to be quite similar among all the group at 48 hours. At 14 days, the electropolished group and the anodized group induced more total protein amount than the RBM group(P<.05). 6. There was no significant difference among five groups for alkaline phosphatase(ALP) activity at 48 hours. The AN group showed significantly higher ALP activity than any other groups at 14 days(P<.05). 7. All the groups showed similar collagen synthesis except the EDM group. The amount of collagen on the electropolished and anodized surfaces were higher than that on the EDM surface(P<.05).