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Glycine nitrate process로 합성된 La0.8Sr0.2Ga0.8Mg0.1Co0.1O3-δ 전해질의 제조 및 특성평가 (Preparation and characterization of La0.8Sr0.2Ga0.8Mg0.1Co0.1O3-δ electrolyte using glycine-nitrate process)

  • 옥경민;김경록;김태완;김동현;박희대;성열문;박홍채;윤석영
    • 한국결정성장학회지
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    • 제23권1호
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    • pp.37-43
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    • 2013
  • 이차상의 편석, 분말의 조성 및 합성방법은 $La_{0.8}Sr_{0.2}Ga_{0.8}Mg_{0.1}Co_{0.1}O_{3-{\delta}}$(LSGMC) 물질의 전도도에 영향을 미친다. 조성이 균일하고 순도가 높은 분말을 얻기 위해 GNP(Glycine nitrate process)를 이용하여 고체산화물 연료전지의 전해질재료인 $La_{0.8}Sr_{0.2}Ga_{0.8}Mg_{0.1}Co_{0.1}O_{3-{\delta}}$를 합성하였다. 자발연소반응 시, 글리신의 양에 따른 물질의 특성을 확인하기 위하여, 글리신/양이온 비를 0.5, 1, 1.5, 2, 2.5로 변화시켜 분말을 합성하였다. 합성된 분말의 단상의 perovskite상 동정 및 소결체의 미세구조 변화를 XRD와 SEM을 이용하여 분석하였다. 조성비가 1.5인 경우, 상대적으로 치밀하며, $800^{\circ}C$에서 0.131 $Scm^{-1}$의 우수한 전기전도특성을 나타냈다. 또한, $25{\sim}800^{\circ}C$ 사이의 온도에서 열팽창거동이 선형을 나타내었다.

Bias-reduced ℓ1-trend filtering

  • Donghyeon Yu;Johan Lim;Won Son
    • Communications for Statistical Applications and Methods
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    • 제30권2호
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    • pp.149-162
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    • 2023
  • The ℓ1-trend filtering method is one of the most widely used methods for extracting underlying trends from noisy observations. Contrary to the Hodrick-Prescott filtering, the ℓ1-trend filtering gives piecewise linear trends. One of the advantages of the ℓ1-trend filtering is that it can be used for identifying change points in piecewise linear trends. However, since the ℓ1-trend filtering employs total variation as a penalty term, estimated piecewise linear trends tend to be biased. In this study, we demonstrate the biasedness of the ℓ1-trend filtering in trend level estimation and propose a two-stage bias-reduction procedure. The newly suggested estimator is based on the estimated change points of the ℓ1-trend filtering. Numerical examples illustrate that the proposed method yields less biased estimates for piecewise linear trends.

수중 유기물처리를 위한 광펜톤반응의 최적조건 도출 (Identifications of Optimal Conditions for Photo-Fenton Reaction in Water Treatment)

  • 오태협;이한욱;박성직;박재우
    • 한국지하수토양환경학회지:지하수토양환경
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    • 제21권1호
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    • pp.86-93
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    • 2016
  • Fenton is the reaction using the OH· radicals generating by interaction between hydrogen peroxide and Fe2+ which can oxidize the contaminants. Fe2+ ions are oxidized to Fe3+ ions by reaction with H2O2 and formed OH· radicals. UV-Fenton process includes the additional reaction that generates the OH· radicals by photodegradation of H2O2. In methylorange (MO) decolourization experiment with UV-Fenton, optimal Fe2+: H2O2 ratio was obtained at 1 : 10. Based on the obtained condition (H2O2= 10mM, Fe2+ = 1 mM) with/without UV-fenton experiment was carried out. Removal efficiency and sludge production were measured at 30 min. The case of w/o UV irradiation and only H2O2 was hardly treated and only Fe2+ showed 65% removal owing to coagulation. When UV-Fenton process in optimal ratio (Fe2+: H2O2 = 1 : 10), UV irradiation showed better removal efficiency than of w/o UV irradiation. Also, MO decolourization was a function of the hydrogen peroxide concentration (x1), Fe2+:H2O2 ratio (x2), and numbers of UV lamp (x3) from the application of the response surface methodology. Statistical results showed the order of significance of the independent variables to be hydrogen peroxide concentration > numbers of UV l amp > Fe2+: H2O2 ratio.

무연 Ba0.99(Bi1/2Na1/2)0.01TiO3 세라믹의 PTCR 특성에 미치는 Nb2O5와 MnO2의 효과 (Effects of Nb2O5 and MnO2 on the PTCR behavior of Lead-free Ba0.99(Bi1/2Na1/2)0.01TiO3 Ceramics)

  • 박용준;남산;이영진;정영훈;백종후;김대준;이우영
    • 한국전기전자재료학회논문지
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    • 제21권7호
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    • pp.638-644
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    • 2008
  • The effects of $Nb_2O_5$ and $MnO_2$ on the positive temperature coefficient of resistivity (PTCR) behavior of lead-free $Ba_{0.99}(Bi_{1/2}Na_{1/2})_{0.01}TiO_3$ (BaBiNT) ceramics were investigated in order to fabricate a PTC thermistor available at high temperature of > $120^{\circ}C$. In particular, 0.05 mol% $Nb_2O_5$ added BaBiNT ceramic, which has significantly increased Curie temperature (Tc) of $160^{\circ}C$, showed good PTCR behavior; low resistivity at room temperature $(\rho_r)$ of $80.1{\Omega}{\cdot}cm$, a high $\rho_{max}/\rho_{min}$ ratio of $5.65{\times}10^3$ and a large resistivity temperature factor (a) of 18.5%/$^{\circ}C$. Furthermore, the improved $\rho_{max}/\rho_{min}$ of $6.48{\times}10^4$ and a of 25.4%/$^{\circ}C$ along with higher $T_c$ of $167^{\circ}C$ despite slightly increased $\rho_r$ of $569{\Omega}{\cdot}cm$, could be obtained for the BaBiNT + 0.05 mol% $Nb_2O_5$ + 0.02 wt% $MnO_2$ ceramic cooled down at a rate of $200^{\circ}C/h$.

Optimization of Monochamus alternatus media and culture period for cordycepin production in Cordyceps militaris culture using solid-state fermentation

  • Ha, Si Young;Jung, Ji Young;Yang, Jae-Kyung
    • 한국버섯학회지
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    • 제19권3호
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    • pp.126-133
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    • 2021
  • In this study, we investigated the effect of solid culture medium on the production of cordycepin in Cordyceps militaris. The regression equation was expressed as follows: Y1 = 755.3-58.6625X1+4.79432E-14X2-46.6625X3-5.66269E-14X1X2-0.025X1X3+1.62475E-14X2X3-160.6625X12+0.0125X22-206.9625X32, where, Y represents the value of cordycepin content (㎍/g), X1 corresponds to the weight of M. alternatus in solid culture medium (g/bottle), X2 to the water content of the solid culture medium (%), and X3 to the culture period (day). The solid culture medium was optimized using the response surface methodology, and the optimal medium composition was as follows: the weight of M. alternatus in solid culture medium and water content were 16.2% and 100.7% (20.14 mL water/20 g solid culture medium), respectively, with a culture period of 39 days. Under these conditions, the cordycepin content of the fruiting bodies reached 150.0 ㎍/g (actual value). The supplementation of M. alternatus in solid culture for improved cordycepin content of C. militaris seems to be a promising alternative to wild and solid cultivation.

LiNi0.8Co0.15Al0.05O2 양극활물질의 전기화학적 특성 향상을 위한 MgF2 표면처리 효과 (Effect of MgF2 Surface Modification for LiNi0.8Co0.15Al0.05O2 Cathode Material on Improving Electrochemical Characteristics)

  • 진수진;서진성;나병기
    • Korean Chemical Engineering Research
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    • 제58권1호
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    • pp.52-58
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    • 2020
  • 본 연구에서는 MgF2를 이용하여 LiNi0.8Co0.15Al0.05O2 양극활물질의 표면을 코팅하여 전기화학적 특성과 열적 안정성을 평가하였다. 코팅된 MgF2의 비율은 0.5, 1, 3 wt%로 조절하였다. 전기화학적 특성은 CV, 충·방전 프로파일, 출력특성, 수명특성을 분석하였고, 열적 안정성은 DSC 분석을 통하여 이루어졌다. 전기화학적 특성 분석 결과 0.1C에서 초기 방전 용량은 MgF2 코팅이 되었을 때 감소하였지만, 2C까지 출력을 향상 시켰을 때는 약간 향상된 방전 용량을 얻을 수 있었고, 수명특성 또한 향상되었다. 또한 DSC 분석 결과 코팅이 되었을 때 발열 온도가 증가하였고, 발열 피크의 세기 또한 감소하였다.

비화학양론적 Bi1±xFeO3±δ와 Ti가 첨가된 BiFeO3의 소결조건에 따른 결정구조와 미세구조 변화 (Crystal Structure and Microstructure Variation of Nonstoichiometric Bi1±xFeO3±δ and Ti-doped BiFeO3 Ceramics under Various Sintering Conditions)

  • 배지희;김준찬;김명호;이순일
    • 한국재료학회지
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    • 제30권2호
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    • pp.61-67
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    • 2020
  • BiFeO3 with perovskite structure is a well-known material that has both ferroelectric and antiferromagnetic properties called multiferroics. However, leaky electrical properties and difficulty of controlling stoichiometry due to Bi volatility and difficulty of obtaining high relative density due to high dependency on the ceramic process are issues for BiFeO3 applications. In this work we investigated the sintering behavior of samples with different stoichiometries and sintering conditions. To understand the optimum sintering conditions, nonstoichiometric Bi1±xFeO3±δ ceramics and Ti-doped Bi1.03Fe1-4x/3TixO3 ceramics were synthesized by a conventional solid-state route. Dense single phase BiFeO3 ceramics were successfully fabricated using a two-step sintering and quenching process. The effects of Bi volatility on microstructure were determined by Bi-excess and Ti doping. Bi-excess increased grain size, and Ti doping increased sintering temperature and decreased grain size. It should be noted that Ti-doping suppressed Bi volatility and stabilized the BiFeO3 phase.

K5.4Cu1.3Ta10O29 첨가에 따른 0.97[(K0.5Na0.5)(Nb0.97Sb0.03)O3]-0.03[(Bi0.5K0.5)TiO3] 세라믹스의 압전 및 유전 특성 (Piezoelectric and Dielectric Properties of 0.97[(K0.5Na0.5)(Nb0.97Sb0.03)O3]-0.03[(Bi0.5K0.5)TiO3] Ceramics Modified with K5.4Cu1.3Ta10O29)

  • 이갑수;류주현
    • 한국전기전자재료학회논문지
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    • 제24권9호
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    • pp.728-732
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    • 2011
  • In this study, piezoelectric and dielectric properties of Lead-free $0.97[(K_{0.5}Na_{0.5})(Nb_{0.97}Sb_{0.03})O_3]+0.03[(Bi_{0.5}K_{0.5})TiO_3]$ (abbreviated as 0.97NKNS-0.03BKT)ceramics synthesized by conventional solid-state reaction process were investigated as a function of $K_{5.4}Cu_{1.3}Ta_{10}O_{29}$ addition. The results indicated that the $K_{5.4}Cu_{1.3}Ta_{10}O_{29}$ addition significantly improved the sinterability, grain growth and piezoelctric properties of 0.97NKNS-0.03BKT ceramics. The optimum values as planar piezoelectric coupling coefficient ($k_p$= 0.355), piezoelectric constant ($d_{33}$= 207 pC/N) and mechanical quality factor ($Q_m$= 128) were obtained when 0.009KCT was added. The electromechanical coupling factor($k_p$) was slightly decreased according to the increasing temperature.

국내 대학병원에서 분리된 Metallo-β-Lactamase (MBL) 생성 Acinetobacter spp. 분리주의 높은 출현율과 유전형 특징 (High Prevalence and Genotypic Characterization of Metallo-β-Lactamase (MBL)-Producing Acinetobacter spp. Isolates Disseminated in a Korean Hospital)

  • 염종화
    • 대한임상검사과학회지
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    • 제51권4호
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    • pp.444-452
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    • 2019
  • 주요 획득성 metallo-β-lactamase (MBL) 유전자에 의해 매개되는 carbapenem 내성, 특히 Acinetobacter spp. 균종의 임상 분리주에 대한 보고가 증가하고 있다. 본 연구에서 임상에서 비 중복으로 분리된 carbapenem 비감수성 Acinetobacter spp. 191주 중 125 (65.4%)주가 imipenem 혹은 meropenem-Hodge 변법시험에 양성이었고, 49 (25.7%)주가 imipenem-EDTA+SMA double disk synergy (DDS) 시험에 양성이었다. blaVIM-2 allele와 blaIMP-2 allele 검출을 위한 중합효소연쇄반응과 염기서열분석을 시행한 결과, A. baumannii와 A. calcoaceticus에서 각각 29주와 1주가 blaVIM-2를 갖고 있었고, A. baumannii 16주와 A. calcoaceticus 2주가 blaIMP-1을 갖고 있었다. A. genomospecies 3는 blaVIM-2와 blaAIM-1을 동시에 갖고 있었다. 이들 MBL 유전자는 모두 class 1 integron에 있었다. blaVIM-2 혹은 blaIMP-6를 갖는 class 1 integron의 크기는 A. baumannii 분리주에서는 2.8 kb에서 3.2 kb이었고, A. genomospecies 3 분리주에서는 3.2 kb에서 3.5 kb이었다. blaVIM-2는 대부분 class 1 integron에 첫번째 혹은 두번째에 위치하였고, aacA4를 흔히 가지고 있었다. 다양한 내성 유전자를 가질 수 있는 MBL 생성 Acinetobacter spp.뿐 아니라 다양한 내성 유전자를 가질 수 있는 integron의 전파로 imipenem이나 meropenem과 같은 carbapenem 내성을 포함하여 다제 내성 그람음성 세균의 증가가 예상된다. 또한, 위중한 Acinetobacter spp. 감염증 치료를 위한 새로운 항균제 개발이 필요하다.

ON A THREE-DIMENSIONAL SYSTEM OF DIFFERENCE EQUATIONS WITH VARIABLE COEFFICIENTS

  • KARA, MERVE;YAZLIK, YASIN;TOUAFEK, NOURESSADAT;AKROUR, YOUSSOUF
    • Journal of applied mathematics & informatics
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    • 제39권3_4호
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    • pp.381-403
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    • 2021
  • Consider the three-dimensional system of difference equations $x_{n+1}=\frac{{\prod_{j=0}^{k}}z_n-3j}{{\prod_{j=1}^{k}}x_n-(3j-1)\;\(a_n+b_n{\prod_{j=0}^{k}}z_n-3j\)}$, $y_{n+1}=\frac{{\prod_{j=0}^{k}}x_n-3j}{{\prod_{j=1}^{k}}y_n-(3j-1)\;\(c_n+d_n{\prod_{j=0}^{k}}x_n-3j\)}$, $z_{n+1}=\frac{{\prod_{j=0}^{k}}y_n-3j}{{\prod_{j=1}^{k}}z_n-(3j-1)\;\(e_n+f_n{\prod_{j=0}^{k}}y_n-3j\)}$, n ∈ ℕ0, where k ∈ ℕ0, the sequences $(a_n)_{n{\in}{\mathbb{N}}_0$, $(b_n)_{n{\in}{\mathbb{N}}_0$, $(c_n)_{n{\in}{\mathbb{N}}_0$, $(d_n)_{n{\in}{\mathbb{N}}_0$, $(e_n)_{n{\in}{\mathbb{N}}_0$, $(f_n)_{n{\in}{\mathbb{N}}_0$ and the initial values x-3k, x-3k+1, …, x0, y-3k, y-3k+1, …, y0, z-3k, z-3k+1, …, z0 are real numbers. In this work, we give explicit formulas for the well defined solutions of the above system. Also, the forbidden set of solution of the system is found. For the constant case, a result on the existence of periodic solutions is provided and the asymptotic behavior of the solutions is investigated in detail.