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Effects of Sintering Temperature and SiC Contents on the Microstructure and Superconducting Properties of In-situ $MgB_2$ Wires (In-situ $MgB_2$ 선재의 소결온도와 SiC 함량에 따른 미세조직 및 초전도 특성 연구)

  • Hwang, Soo-Min;Park, Eui-Cheol;Park, Si-Hong;Jang, Seok-Hern;Kim, Kyu-Tae;Lim, Jun-Hyung;Joo, Jin-Ho;Kang, Won-Nam;Kim, Chan-Joong
    • Progress in Superconductivity
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    • v.9 no.1
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    • pp.68-73
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    • 2007
  • We fabricated the in-situ $MgB_2$ wires using the powder-in-tube method and investigated the effects of sintering temperature and SiC contents on the microstructure and superconducting properties. Pure $MgB_2$ wires and 5, 10, 20 wt.% SiC doped $MgB_2$ wires were sintered at $600-1000^{\circ}C$ for 30 minutes in Ar atmosphere. We found that $MgB_2$ phase was mostly formed at the sintering temperature of $700^{\circ}C$ and above, and the critical temperature ($T_c$) increased with increasing sintering temperature. For the $MgB_2$ sintered at $850^{\circ}C$, the highest critical current density ($J_c$) was obtained to be $3.7{\times}10^5\;A/cm^2$ at 5 K and 1.6 T by a magnetic properties measurement system (MPMS). The addition of SiC to the $MgB_2$ wires changed microstructure and critical properties. SEM observation showed that the $MgB_2$ core had considerable micro-cracks in undoped wire and the density of micro-cracks decreased with increasing SiC contents. The critical temperature decreased as the SiC contents increased, on the other hand, the critical current density of SiC doped $MgB_2$ wires in high magnetic field was enhanced compared to that of undoped $MgB_2$ wires.

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Synthesis of Li2MnSiO4 by Solid-state Reaction (고상반응법을 이용한 Li2MnSiO4 합성)

  • Kim, Ji-Su;Shim, Joong-Pyo;Park, Gyung-Se;Sun, Ho-Jung
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.25 no.5
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    • pp.398-402
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    • 2012
  • Synthesis of $Li_2MnSiO_4$ was attempted by the conventional solid-state reaction method, and the phase formation behavior according to the change of the calcination condition was investigated. When the mixture of the three source materials, $Li_2O$, MnO and $SiO_2$ powders, were used for calcination in air, it was difficult to develop the $Li_2MnSiO_4$ phase because the oxidation number of $Mn^{2+}$ could not be maintained. Therefore, two-step calcination was applied: $Li_2SiO_3$ was made from $Li_2O$ and $SiO_2$ at the first step, and $Li_2MnSiO_4$ was synthesized from $Li_2SiO_3$ and MnO at the second step. It was easy to make $Li_2MnSiO_3$ from $Li_2O$ and $SiO_2$. $Li_2MnSiO_4$ single phase was developed by the calcination at $900^{\circ}C$ for 24 hr in Ar atmosphere as the oxidation of $Mn^{2+}$ was prevented. However, the $Li_2MnSiO_4$ was ${\gamma}-Li_2MnSiO_4$, one of the polymorph of $Li_2MnSiO_4$, which could not be used as the cathode materials in Li-ion batteries. By applying the additional low temperature annealing at $400^{\circ}C$, the single phase ${\beta}-Li_2MnSiO_4$ powder was synthesized successfully through the phase transition from ${\gamma}$ to ${\beta}$ phase.

Pattern of the Occurrence of Tomato spotted wilt virus in Jeonnam Province (전남 지역의 토마토반점위조바이러스병 발생 양상)

  • Ko, Sug-Ju;Kang, Beom-Ryong;Choi, Duck-Soo;Kim, Do-Ik;Lee, Gwan-Seok;Kim, Chang-Seok;Choi, Hong-Soo
    • Research in Plant Disease
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    • v.19 no.4
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    • pp.273-280
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    • 2013
  • Tomato spotted wilt virus (TSWV) was occurred at 8 areas including Naju, Suncheon, Younggwang, Youngam, and Shinan in Jeonnam province and the crops of Younggwang were severely damaged by TSWV. The hot pepper (Capsicum annuum), bell pepper (Capsicum annuum v ar. angulosum) and tomato (Solanum lycopersicon) in greenhouse and hot pepper in open field were infected by TSWV. Especially, hot pepper was severely damaged by TSWV infection. The survey data indicated that 1.1-30% in the nursery field at Naju, Suncheon, and Jangheung were infected by TSWV. Plants were infected by TSWV from early June to August. However, TSWV-infected seedlings from nursery fields showed the disease symptoms from May after transplanting. In pepper greenhouses, Frankliniella occidentalis was more dominant insect vector than Frankliniella intonsa. But in open field, the population of insect vector was opposed to greenhouse. In addition, the removal of weeds was able to delay the incidence of TSWV via side-window of greenhouse in Winter. Taken together, the control of weed and insect vector nearby side-window of greenhouse is important to prevent TSWV infection of plants.

Process Optimization of ITO Film on PC Substrate Deposited by In-line Sputtering Method for a Resistive-type Touch Panel (인라인 스퍼터링에 의한 저항막 방식 터치패널용 ITO 기판 제조공정 최적화 기술)

  • Ahn, M.H.;Cho, E.S.;Kwon, S.J.
    • Journal of the Korean Vacuum Society
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    • v.18 no.6
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    • pp.440-446
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    • 2009
  • Indium tin oxide(ITO) substrate is one of the key components of the touch panel and its sputtering process is dependent on the characteristics of various touch panel, such as driving type, size of panel, and the intended use. In this study, we optimized the sputtering condition of ITO film on polycarbonate(PC) by using in-line sputtering method for the application to resistive type touch panel. We varied the $O_2$/Ar gas ratio, sputtering power, pressure and moving speed of substrate to deposit ITO films at room temperature with the base vacuum of $1{\times}10^{-6}\;torr$. The sheet resistance and its uniformity, the transmittance, the thickness of the ITO film on PC substrate are investigated and analyzed. The optimized process parameters are as follows : the sheet resistance is $500{\pm}50\;{\Omega}$/□, the uniformity of sheet resistance is lower than 10%, the transmittance is higher than 87 % at 550nm, and the thickness is about 120~250. The optimized deposition conditions by in-line sputtering method can be applied to the actual mass production for the ITO film manufacturing technology.

W 도핑된 ZnO 박막을 이용한 저항 변화 메모리 특성 연구

  • Park, So-Yeon;Song, Min-Yeong;Hong, Seok-Man;Kim, Hui-Dong;An, Ho-Myeong;Kim, Tae-Geun
    • Proceedings of the Korean Vacuum Society Conference
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    • 2013.02a
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    • pp.410-410
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    • 2013
  • Next-generation nonvolatile memory (NVM) has attracted increasing attention about emerging NVMs such as ferroelectric random access memory, phase-change random access memory, magnetic random access memory and resistance random access memory (RRAM). Previous studies have demonstrated that RRAM is promising because of its excellent properties, including simple structure, high speed and high density integration. Many research groups have reported a lot of metal oxides as resistive materials like TiO2, NiO, SrTiO3 and ZnO [1]. Among them, the ZnO-based film is one of the most promising materials for RRAM because of its good switching characteristics, reliability and high transparency [2]. However, in many studies about ZnO-based RRAMs, there was a problem to get lower current level for reducing the operating power dissipation and improving the device reliability such an endurance and an retention time of memory devices. Thus in this paper, we investigated that highly reproducible bipolar resistive switching characteristics of W doped ZnO RRAM device and it showed low resistive switching current level and large ON/OFF ratio. This may be caused by the interdiffusion of the W atoms in the ZnO film, whch serves as dopants, and leakage current would rise resulting in the lowering of current level [3]. In this work, a ZnO film and W doped ZnO film were fabricated on a Si substrate using RF magnetron sputtering from ZnO and W targets at room temperature with Ar gas ambient, and compared their current levels. Compared with the conventional ZnO-based RRAM, the W doped ZnO ReRAM device shows the reduction of reset current from ~$10^{-6}$ A to ~$10^{-9}$ A and large ON/OFF ratio of ~$10^3$ along with self-rectifying characteristic as shown in Fig. 1. In addition, we observed good endurance of $10^3$ times and retention time of $10^4$ s in the W doped ZnO ReRAM device. With this advantageous characteristics, W doped ZnO thin film device is a promising candidates for CMOS compatible and high-density RRAM devices.

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Development of HPLC Determination Method for Trace Levels of 1-, 2-Nitropyrenes and 2-Nitrofluoranthene in Airborne Particulates and Its Application to Samples Collected at Noto Peninsula

  • Hayakawa, Kazuichi;Tang, Ning;Sato, Kosuke;Izaki, Akihiko;Tatematsu, Michiya;Hama, Hirotaka;Li, Ying;Kameda, Takayuki;Toriba, Akira
    • Asian Journal of Atmospheric Environment
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    • v.5 no.3
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    • pp.146-151
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    • 2011
  • 1-Nitropyrene (1-NP), 2-NP and 2-nitrofluoranthene (2-NFR) are useful markers for studying the atmospheric behaviors of polycyclic aromatic hydrocarbons (PAHs) and nitropolycyclic aromatic hydrocarbons (NPAHs). However, present methods for measuring trace levels of these compounds are lesssensitive and laborious. Here we describe several improvements to a previously reported high-performance liquid chromatography-chemiluminescence detection system that allows it to determine trace levels of 1-, 2-NPs and 2-NFR. The proposed system was equipped with a reducer column packed with Pt/Rh instead of zinc whose life-time was limited. The combination of Cosmosil MS-II (monomeric ODS) and AR-II (polymeric ODS) columns was used instead of polymeric ODS columns as the separator column to improve the separation. An ethanol mixture with acetate buffer (pH 5.5) was used in place of an acetonitrile mixture with the same buffer to activate the reducer column. The same ethanol mixture was used as the mobile phase for the clean-up column. The switching time of the column switching valve was optimized to concentrate the amino-derivatives of above NPAHs quantitatively on the concentrator column. The concentrations of bis(2,4,6-trichlorophenly) oxalate and hydrogen peroxide in the chemiluminescence reagent solution were optimized to 0.4 mM and 30 mM, respectively, to increase the sensitivity. Under the above conditions, the detection limits (S/N=3) of 1-, 2-NPs and 2-NFR were 1 fmol (0.25 pg), 10 fmol (2.5 pg) and 4 fmol (1 pg), respectively. The proposed system was effectively used to determine trace levels of 1-, 2-NPs and 2-NFR in airborne particulates collected at Noto Peninsula. The atmospheric concentrations of 1-, 2-NPs and 2-NFR were not more than sub pg $m^{-3}$ levels. They were higher in winter (January) than in summer (July). In both seasons, the concentrations were in decreasing order, [2-NFR]>[1-NP]>[2-NP].

The Effect of Extrusion Temperature on Microstructure and Thermoelectric Properties of Rapidly Solidified P-type $P-type Bi_{0.5}Sb_{1.5}Te_3$ alloy (급속응고된 $P-type Bi_{0.5}Sb_{1.5}Te_3$ 합금 열전재료의 미세조직과 열전특성에 미치는 압출 온도의 효과)

  • 이영우;천병선;홍순직;손현택
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2001.11a
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    • pp.28-28
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    • 2001
  • $Bi_2Te_3$계 열전반도체 재료는 200 ~ 400K 정도의 저온에서 에너지 변환 효율이 가장 높은 재료로서 열전냉각 및 발전재료로 제조볍 및 특성에 관한 많은 연구가 진행되어 왔다. 전자냉각 모듈의 제조에는 P형 및 N형 $Bi_2Te_3$계 단결정이 주로 사용되고 있으나. $Bi_2Te_3$ 단결정은 C축에 수직한 벽개면을 따라 균열이 쉽게 전파하기 때문에 소자 가공사 수윤 저하가 가장 큰 문제점으로 지적되고 있다. 이에 따라 최근 열전재료의 가공방법에 따른 회수율 증가 및 열전특성 향상에 관한 열간압출, 단조와 같은 연구가 활발히 이루어지고 있다. 본 연구는 가스분사법(gas atomizer)을 이용하여 용질원자 편석의 감소, 고용도의 증가,균일고용체 형성, 결정립미세화 둥 급속응고의 장점을 이용하여 화학적으로 균질한$Bi_2Te_3$계 열전재료 분말을 제조하고, 제조된 분발을 압출가공하여 기계적성질, 소자의 가공성 및 열전 성능 지수율 향상시키는데 연구 목적이 있다. 본 설험에서는 99.9%이상의 고순도 Bi. Te. Se. Sb를 이용하여, 고주파 유도로에서 Ar 분위기로 용융하고, 가스분사법를 이용하여 균질한 $Bi_2Te_3$계 열전재료 분만을 제조하였다. 분말표면의 산화막을 제거하기 위하여 수소분위기에서 환원처리를 행하였고, 된 분말을 Al 캔 주입하여 냉간성형 한 후 진공중에서 압출온도를 변화시켜 열간압출 가공을 행하였다. 압출 온도변화에 따른 압출재의 미세조직 및 열전특성에 중요한 영향을 미치는 C면 배향에 대한 결정방위 해석, 압출재의 압축강도 등을 분석하였으며, 압출온도에 따삼 미세조직 변화와 결정방위의 변화에 따른 열전특성의 관계를 해석하였다성시켰고 이들이 산인 HNO3에서 녹았기 때문이다. 본 연구에서 개발된 새로운 에칭 용액인 90H2O2 - 10HNO3 (vol%)의 에칭 원리가 똑같이 적용 가능한 다른 종류의 초경 합금에서도 사용이 가능할 것으로 판단된다.로 판단된다.멸과정은 다음과 같다. 출발물질인 123 분말이 211과 액상으로 분해될 때 산소가스가 배출되며, 이로 인해 액상에서 구형의 기공이 생성된다. 이들 중 일부는 액상으로 채워져 소멸되나, 나머지는 그대로 남는다. 특히, 시편 중앙에 서는 수십-수백 마이크론 크기의 커다란 기공이 다수 관찰된는데, 이는 기공의 합체로 만들어진 것이다. 포정반응 열처리 시 기공 소멸로 만들어진 액상포켓들은 주변 211 입자와 반응하여 123 영역으로 변한다. 이곳은 다른 지역과 비교하여 211 밀도 가 낮기 때문에, 미반응 액상이 남거나 211 밀도가 낮은 123 영역이 된다. 액상으로 채워지지 못한 구형의 기공들 중 다수가 123 결정 내로 포획되며, 그 형상은 액상/ 기공/고상 계면에너지에 의해 결정된다.단의 경우, 파단면이 매끄럽고 파변상의 결정립도 매우 미세하였으며, 산확물 의 용집도 찾아보기 어려웠 나, 접합부 파단의 경우에는 파변의 굴곡이 비교척 심하고 연성 입계파괴의 형태를 보였£며, 결정립도 모채부 파단의 경우에 비해 조대하였다. 조대하였다. 셋째, 주상기간 중 총 에너지 유입률 지수와 $Dst_{min}$ 사이에 높은 상관관계가 확인되었다. 특히 환전류를 구성하는 주요 입자의 에너지 영역(75~l13keV)에서 가장 높은(0.80) 상관계수를 기록했다. 넷째, 회복기 중에 일어나는 입자들의 유입은 자기폭풍의 지속시간을 연장시키는 경향을 보이며 큰 자기폭풍일수록 현저했다. 주상에서 관측된 이러한 특성은 서브스톰 확장기 활동이 자기폭풍의

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Effect of Unilateral Ovariectomy on Development of Ovarian Follicle, Corpus Luteum and Serum Progesteron Level in Immature Female Rats (미성숙 암흰쥐에 있어서 편측난소척출이 난포발육, 황체 및 혈청 Progesterone 수준에 미치는 영향)

  • 정재혁;김종대;정영채;김창근
    • Korean Journal of Animal Reproduction
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    • v.9 no.2
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    • pp.97-104
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    • 1985
  • This study was conducted to investigate the effects of unilateral ovariectomy on the weight of the remaining ovary, the change of number of ovarian follicle, number of corpus luteum and serum progesterone level. Sixty Sprague-Dawley female rats, 23$\pm$2 days old, were divided into 2 groups (control and unilaterally ovariectomized goup) with 30 heads per groups. Each group was again subdivided into 6 groups according to 6 experimental periods; Day 4, 8, 12, 16, 20 and 24 after uniteral ovariectomy. Five arts at every 4 day intervals were sacrificed for the measuring of ovarian weight and for quantitative histologic examination of ovary and at the same time, blood samples were taken for the determination of serum progesterone level of radioimmunoassy. The results obtained were as follows: During the experimental periods, a significant hypertrophy occured in the remaining ovary of unilaterally ovariectomized group from day 16 after operation. The average ovarian weight of control group at day 16 was 21.0$\pm$1.7mg, which is samller than that of unilaterally ovariectomized group weighing 50.5$\pm$8.4mg(P<0.01). The ovarian weight of the unilaterally ovariectomized rats at day 20 and day 24 was 75.9$\pm$2.2 mg and 63.3$\pm$7.0 mg, which is heavier than those of control group; 29.1$\pm$2.3 and 26.3$\pm$1.7 mg(P<0.01 and P<0.01). 2. A same degree of ovarian follicle development was observed in the unilaterally ovariectomized group. Following unilateral ovariectomy and there was no change in total number of follicles larger than 130$\mu$ during the period from day 4 till day 24 after operation. 3. Although the size fo ovarian follicle did not significantly change between two groups from day 4 till day 16, the size of vesicular follicle in unilaterally ovariectomized group (406.3$\pm$26.2$\mu$) was significantly greater as compared to that of control group (323.8$\pm$19.3$\mu$)(P<0.05). 4. Corpus luteum in unilaterally ovariectomized and control group began to a, pp.ar from day 16 after operation and then the number of corpus luteum slightly increased. The number of corpus luteum in unilaterally ovariectomized group at day 24 ws remarkably increased (13.7$\pm$1.41) than that of control (5.2$\pm$2.01)(P<0.01). 5. Serum progesterone levels in unilaterally ovariectomized group were slightly higher than those of control but there were no significant difference between treatment groups.

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Analysis of Frozen-Thawed Sperm Characteristic in Alpha 1,3-Galactosyltransferase(GalT) Knock-out Cloned Miniature Pig (Alpha 1,3-Galactosyltransferase (GalT) Knock-out 복제 미니돼지 정액의 동결-융해 후 정액 성상 분석)

  • Woo, Jea-Seok;Lee, Yong-Seung;Yoo, Han-Jun;Hwang, Seong-Soo;Oh, Keon-Bong;Cheong, Hee-Tae;Yang, Boo-Keun;Park, Soo-Bong;Park, Choon-Keun
    • Reproductive and Developmental Biology
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    • v.35 no.3
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    • pp.385-390
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    • 2011
  • The purpose of this study was undertaken to evaluate of cryopreservation efficiency in ${\alpha}$ 1,3-galactosyltransferase knock-out(GalT KO) cloned miniature pig sperm. To compare ability of frozen-thawed sperm characteristics, three different pig strains (GalT KO) cloned miniature pig, PWG miniature pig and Duroc were used. The ejaculated semen from the three pig species was diluted with same volume extender and added to LEY solution for freezing. The diluted semen was placed in 0.5 ml straws, and freezing was initiated by exposing the straws to liquid nitrogen ($LN_2$) vapours for 10 min before placing them into $LN_2$ for cryopreservation. After thawing, the sperm ability were assessed for viability (SYBR-14/PI staining), abnormality (Rose Bengal staining), and acrosome status (intactness, intensity and capacitation) (chlorotetracycline, CTC staining). The viability of frozen-thawed GalT KO pig sperm had no significant difference as compared with Duroc and PWG miniature pig sperm. However, The CTC pattern of frozen-thawed GalT KO cloned miniature pig spermatozoa showed significantly lower rates in F pattern and AR pattern (p<0.05) and significantly higher rates in B pattern than Duroc and PWG miniature pig (p<0.05). The abnormality of GalT KO cloned miniature pig sperm was significantly lower as compared to Duroc and PWG miniature pig sperm (p<0.05). In conclusion, GalT KO cloned miniature pig semen can be cryopreserved successfully and used for artificial insemination reasonably.

Establishment of Freezing Conditions for Improving Cryosurvival in Miniature Pig Spermatozoa (미니돼지 정액의 동결-융해 후 생존율 향상을 위한 동결 조건 확립)

  • Lee, Yong-Seung;Yoo, Han-Jun;Cheong, Hee-Tae;Yang, Boo-Keun;Woo, Jea-Seok;Park, Choon-Keun
    • Reproductive and Developmental Biology
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    • v.35 no.3
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    • pp.329-334
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    • 2011
  • This study was conducted to establish a freezing method of miniature pig spermatozoa. The semen 더aculated from PWG M-type miniature pig was collected by gloved-hand method. The semen was diluted with same volume extender (m-Modena B). The frozen solution used frozen solution of four different (LEY, TCG, BF-5 and m-Modena+egg yolk) for find optimal frozen solution in miniature pig sperm. The diluted semen for frozen rate assay was added to LEY solution (solution I: 11% lactose+egg yolk; solution II: solution I+glycerol+OEP), and frozen depending on freezing rate by the three different freezing methods (A: until $5^{\circ}C$ for 1 hrs, holding at $-102^{\circ}C$ for 10 min; B: until $5^{\circ}C$ for 2 hrs, holding at $-102^{\circ}C$ for 10 min; C: until $5^{\circ}C$ for 3 hrs, holding at -80 and $-102^{\circ}C$ for 10 min). Semen cooled until $5^{\circ}C$ was added with glycerol 1, 3 and 5%, and take a equilibrium time for 0, 10 and 30min. Frozen-thawed sperm were evaluated for viability, acrosomal status and morphological abnormality. The results of frozen-thawed sperm ability by frozen solution, viability was higher in LEY solution compared to other three different frozen solution. AR pattern of LEY solution were lower than other three different frozen solution. The results of freezing rate, viability was higher in B method compared to other methods (p<0.05). Acrosomal statute was intacted in A and B methods than C method. The experiment for glycerol condition was showed that sperm viability was higher in extender with 1% and 3% glycerol and equilibrium time of 0 min. The acrosome damage was lower in extender with 1% glycerol and equilibrium time of 10 min than other conditions. In conclusion, the optimal conditions for cryopreservation of miniature pig spermatozoa obtained in LEY frozen solution, cooling rate of 1~2 hrs, 1~3% glycerol concentrations and glycerol equilibrium time of 0~10 min.