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무가압 침투법에 의한 Al-3wt%Mg/Al2O3 복합재료의 제조 및 특성
권훈,이건배,김기욱,허성우,조수연 대한금속재료학회(대한금속학회) 1997 대한금속·재료학회지 Vol.35 No.5
Al-3wt%Mg/Al₂O_(3p) composite fabricated by pressureless infiltration method was investigated in terms of the infiltration behavior of molten metal, mechanical properties and interfacial reaction products. A direct addition of Mg powder to the bed of Al₂O₃ and Al powder mixture made the spontaneous infiltration of molten Al-3Mg alloy occur at a relatively lower temperature 700℃, compared with using the bed without Mg particulates. Tensile and yield strength and elongation tend to decrease with increasing infiltration temperature while the infiltration time had little effect on tensile properties. Both strength and ductility of the hot-rolled composite increased even in a relatively low reduction of 20% as compared to the as-fabricated composite. Also, the solution treatment greatly improved the ductility in both as-fabricated and hot -rolled conditions. MgAl₂O₄, was formed at interfaces as a reasult of interfacial reaction. In addition, AlN was formed in the matrix by in-situ reaction of molten Al alloy and nitrogen.
문경희(K.H Mun),고강훈(K.H. Koh),김은수(E.S Kim),곽동걸(D.K Kwaku),조판제(P.J. Chou),이현우(H.W. Lee) 전력전자학회 1999 전력전자학술대회 논문집 Vol.1999 No.7
For decrease the harmonic current components of the power source, a first method is insert the choke coil that used the choke Input type rectifier, the booster chopper circuit and buck chopper circuit. And the several method are studying like as the PWM (Pulse Width Modulation) converter and the active filter type witch is used the high frequency switching and the sinusoidal wave formed input current. In this type, there are many problem as a low efficiency, Increased the noise, the high leakage current and cost up by the high frequency switching For improve this problems, the partlal resonan method 1S used on the booster inducter and lossles snubber condenser. This method decreased the distortion factor has lower harmonic components than the hard switching and there is no switching loss by the ZCS(Zero Current Switching) at switch turn-on and the ZVS(Zero Voltage switching) at switch turn-off
DISCOVERY OF AN X-RAY-EMITTING CONTACT BINARY SYSTEM 2MASS J11201034−2201340
Hu, Chin-Ping,Yang, Ting-Chang,Chou, Yi,Liu, L.,Qian, S.-B.,Hui, C. Y.,Kong, Albert K. H.,Lin, L. C. C.,Tam, P. H. T.,Li, K. L.,Ngeow, Chow-Choong,Chen, W. P.,Ip, Wing-Huen American Astronomical Society 2016 The Astronomical journal Vol.151 No.6
<P>We report the detection of orbital modulation, a model solution, and the X-ray properties of a newly discovered contact binary, Two Micron All Sky Survey (2MASS) J11201034-2201340. We serendipitously found this X-ray point source outside the error ellipse when searching for possible X-ray counterparts of 7-ray millisecond pulsars among the unidentified objects detected by the Fermi Gamma-ray Space Telescope. The optical counterpart of the X-ray source (unrelated to the 7-ray source) was then identified using archival databases. The long-term Catalina Real-Time Transient Survey detected a precise signal with a period of P = 0.28876208 (56) days. A follow-up observation made by the Super Light Telescope of Lulin Observatory revealed the binary nature of the object. Utilizing archived photometric data of multi-band surveys, we construct the spectral energy distribution (SED), which is well fit by a K2V spectral template. The fitting result of the orbital profile using the Wilson Devinney code suggests that 2MASS J11201034-2201340 is a short-period A-type contact binary and the more massive component has a cool spot. The X-ray emission was first noted in observations made by Swift, and then further confirmed and characterized by an XMM-Newton observation. The X-ray spectrum can be described by a power law or thermal Bremsstrahlung. Unfortunately, we could not observe significant X-ray orbital modulation. Finally, according to the SED, this system is estimated to be 690 pc from Earth with a calculated X-ray intensity of (0.7 - 1.5) x 10(30) erg s(-1), which is in the expected range of an X-ray emitting contact binary.</P>
Li, C.W.,Yu, J.H.,Liang, Y.M.,Chou, Y.H.,Park, H.J.,Choo, K.H.,Chen, S.S. Elsevier Scientific Pub. Co 2016 Journal of hazardous materials Vol.320 No.-
The chemical precipitation of Ni ions from industrial wastewater at alkaline pH values creates waste chemical sludge (e.g., Ni(OH)<SUB>2</SUB>). We herein focused on Ni removal via chemical reduction using dithionite, by converting Ni(II) to its elemental or other valuable forms. Without the presence of a chelator (e.g., citrate), the nickel reduction efficiency increased with increasing dithionite:Ni molar ratio, reaching @?99% at ratios above 3:1. The effect of pH on Ni reduction was in agreement with the standard redox potentials (pe<SUP>0</SUP>) of dithionite, which became more negative with an increase in pH leading to greater Ni reduction efficiencies. With the formation of Ni-citrate chelates, however, the Ni reduction deteriorated. Elevated pH and temperature improved nickel reduction, due to the greater reducing power of dithionite. The optimal pH value for Ni(II) reduction was found to be @?8. Injecting Cu seed particles enhanced the rate and amount of Ni reduced. NiS and Ni<SUB>3</SUB>S<SUB>2</SUB> were identified in the crystal of the resulting solids by X-ray crystallography, and the presence of elemental Ni was explained by X-ray photoelectron spectroscopy. The chemical reduction of actual printed circuit board wastewater with the dithionite:Ni(II) molar ratio dose of 12:1 retrieved @?99% nickel after 30-min reaction at 40<SUP>o</SUP>C.
Cha, M. W,Chou, K. C,B. Pathangey,Anderson, T.J 서울市立大學校 1993 論文集 Vol.27 No.-
저압하에서 유기금속증착에피탁시(MOCVD)로 격자가 일치하는 GaInP/GaAs 양자우물(Quantum well)과 superlattice heterostructure들을 성장시켰다. 온도, 단절(interruption), 성장속도 V/III 몰비의 영향을 연구하였다. 성장온도와 단절이 양질의 양자우물을 얻는데 가장 큰 영향을 미쳤다. 저온 PL양자우물 peak는 550℃ 부근의 좁은 온도범위에서만 얻어졌고 575℃ 이상에서는 양자우물 peak는 나타나지 않았다. 530℃ 이하에서는 표면가까이에 낮은 강도의 PL peak가 관찰되었다. 낮은 온도에서 GaAs에서 GaInP로의 정상계면에서의 성장단절이 양질의 PL 양자우물 peak를 얻는데 결정적이었으며 고온에서 GaInP에서 GaAs로의 역계면에서는 기체를 바꿀때 As에 의한 P의 치환에 기인하여 양자우물이 소멸하였으며 이것은 간단한 열역학계산에 의하여 이해될수 있고 계면의 정확성(abruptness)은 성장속도와 PH₃, 세척시간과 GaAs성장시 V/III 몰비에 의존하였다. 가장 정확한 양자우물은 낮은 V/III몰비와 높은 성장속도에서 얻어졌다. Lattice-matched GaAs/GaInP quantum-wells and superlattice heterostructures have been grown by low pessure organometallic vapor phase epitaxy. The effect of growth temperature, interruption schedules. growth rate and molar V/III ratio have been studied. Growth temperature and interruption schedules are found to be most crucial in achieving high quality quantum well structures. Low temperature PL quantum well peaks could only be obtained within a narrow window near 550℃, while no quantum well peaks could be obseved for temperatures above 575℃. For temperature below 530℃, only a low intensity PL peak from quantum well closest to surface was observed. For lower growth temperatures, growth interruption at the GaAs to GaInP normal interfaces was found to be critical in obtaining high quality PL quantum well peaks. For high temperatures, GaInp to GaAs inverted interface is attributed to the lose of quantum well confinement due to the high tendency of P substituition by As during the gas switching. The interface abruptness was found also to be a function of growth rate, PH₃ purging duration and molar V/III raio during GaAs Growth. Most abrupt QWs were obtained at lower molar V/III ratio and higher growth rate.
C. S. Yang,K. F. Chien,J. Y. Lai,C. W. Luo,W. C. Chou,Y. T. Shih,J. S. Wang,S. R. Jian 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.5
Self-assembled CdTe/ZnSe Stranski-Krastanow quantum-dot (QD) structures, which have a CdSe-like precursor-layer (PCL) between CdTe quantum dots and ZnSe matrix, were grown by molecular beam epitaxy. The carrier dynamics of the structures was studied by photoluminescence (PL) and time-resolved photoluminescence (TRPL) measurements. The temperature-dependent PL spectra revealed that there is a carrier transformation from small dots to larger dots via the precursor layer. Temperature-dependent PL measurements verify the existence of the QD excited excitonic state in 5.0 mono-layer (ML) coverage. In 0.6 ML coverage, the TRPL spectra exhibited a double-exponential decay process, as the detection energy at PCL emission energy. The faster decay time is corresponded to the carrier lifetime in PCL, the slower decay time exhibits the carrier in small QD. However, in 5.0 ML coverage, a faster and slower decay time represents the carrier lifetime in QD excited state for larger QD and the carrier lifetime in QD ground state for smaller QD.
Sen, Sinol,Ingale, S.L.,Kim, J.S.,Kim, K.H.,Kim, Y.W.,Khong, Chou,Lohakare, J.D.,Kim, E.K.,Kim, H.S.,Kwon, I.K.,Chae, B.J. Asian Australasian Association of Animal Productio 2011 Animal Bioscience Vol.24 No.8
A feeding trial was conducted to investigate the effect of dietary supplementation of Bacillus subtilis LS 1-2 grown on citrus-juice waste and corn-soybean substrate on growth performance, nutrient retention, caecal microbial population and intestinal morphology in broilers. Three hundred twenty d-old Ross chicks were randomly allotted to 4 treatments on the basis of BW in a randomized complete block design. Each treatment had 4 replicates of 20 chicks in each. Experimental diets were fed in 2 phases, starter (d 0 to 21) and finisher (d 21 to 35). Dietary treatments were; negative control (NC: basal diet without any antimicrobial), positive control (PC: basal diet added with 20 mg/kg Avilamycin), basal diet added with 0.30% Bacillus subtilis LS 1-2 grown on corn-soybean substrate (P1), and basal diet added with 0.30% Bacillus subtilis LS 1-2 grown on citrus-juice waste substrate (P2). Overall BW gain, feed intake and FCR were better (p<0.05) in PC, P1 and P2 treatments as compared to NC. Moreover, overall BW gain and FCR in PC and P2 treatments were greater than P1. Retention of CP, GE (d 21, d 35) and DM (d 35) were increased (p<0.05) in treatments PC, P1 and P2 compared with NC. At d 35, caecal Clostridium and Coliform counts were lower (p<0.05) in treatments PC, P1 and P2 than NC. Moreover, Clostridium and Coliform counts in treatment PC was lower (p<0.05) than P1. Villus height and villus height to crypt depth ratio in both duodenum and ileum were increased (p<0.05) in treatments PC, P1, P2 as compared to NC. However, retention of nutrients, caecal microbial population and intestinal morphology remained comparable among treatments P1 and P2. It is concluded that Bacillus subtilis LS 1-2 inclusion at 0.30% level had beneficial effects on broilers' growth performance, nutrient retention, caecal microflora and intestinal morphology. Additionally, citrus-juice waste can be used as substrate for growth of probiotic Bacillus subtilis LS 1-2.