Infall Signatures in a Prestellar Core Embedded in the High-mass 70 <i>μ</i>m Dark IRDC G331.372-00.116

Contreras, Yanett,Sanhueza, Patricio,Jackson, James M.,Guzmá,n, André,s E.,Longmore, Steven,Garay, Guido,Zhang, Qizhou,Nguyê,&#x303,n-Lu’o’, Quang,Tatematsu, Ken’ichi,Nakamura, Fumita American Astronomical Society 2018 The Astrophysical journal Vol.861 No.1

<P>Using Galactic Plane surveys, we have selected a massive (1200M circle dot), cold (14 K) 3.6-70 mu m dark IRDC, G331.372-00.116. This infrared dark cloud (IRDC) has the potential to form high-mass stars, and given the absence of current star formation signatures, it seems to represent the earliest stages of high-mass star formation. We have mapped the whole IRDC with the Atacama Large Millimeter/submillimeter Array (ALMA) at 1.1 and 1.3 mm in dust continuum and line emission. The dust continuum reveals 22 cores distributed across the IRDC. In this work, we analyze the physical properties of the most massive core, ALMA1, which has no molecular outflows detected in the CO (2-1), SiO (5-4), and H2CO (3-2) lines. This core is relatively massive (M = 17.6M circle dot), subvirialized (virial parameter alpha(vir) = M-vir/M = 0.14), and is barely affected by turbulence (transonic Mach number of 1.2). Using the HCO+ (3-2) line, we find the first detection of infall signatures in a relatively massive, prestellar core (ALMA1) with the potential to form a high-mass star. We estimate an infall speed of 1.54 km s(-1) and a high accretion rate of 1.96. x. 10(-3) M circle dot yr(-1). ALMA1 is rapidly collapsing, out of virial equilibrium, which is more consistent with competitive accretion scenarios rather than the turbulent core accretion model. On the other hand, ALMA1 has a mass similar to 6 times larger than the clumps Jeans mass, as it is in an intermediate mass regime (M-J = 2.7 < M less than or similar to 30 M circle dot), contrary to what both the competitive accretion and turbulent core accretion theories predict.</P>

XRD studies on phase formation and the crystallite structure of BaTiO3 synthesized by HBM: the effect of calcination temperature

X.M. Chen,Y. Zhang,W.W. Kong,X.B. Bian,J.P. Zhou,P. Liu 한양대학교 세라믹연구소 2010 Journal of Ceramic Processing Research Vol.11 No.4

Barium titanate (BaTiO3, or BT) powders were synthesized via a solid state reaction of BaCO3-TiO2 by combining a highenergy ball milling (HBM) technique and a calcination method. Using X-ray diffraction (XRD) methods with a Rietveld refinement, the effects of calcination temperature on the phase formation and crystallite structure of BT powders were studied. It is found that by means of HBM the synthesis temperature for obtaining BT single phase is decreased to 960 oC, which is much lower than that required by the conventional solid-state reaction process, and the crystallite structure of BT is in the (pseudo)cubic form. As the calcination temperature is increased to 980 oC, the structure of BT crystallites transforms from the (pseudo)cubic to the tetragonal form. With an increase in the calcination temperature, both the tetragonality (c/a-1) and crystallite size are increased.

Benzodithiophene and benzotrithiophene-based conjugated polymers for organic thin-film transistors application: Impact of conjugated- and acyl-side chain

Zhang, G.,Zhu, M.,Guo, J.,Ma, J.,Wang, X.,Lu, H.,Qiu, L. Elsevier Science 2014 ORGANIC ELECTRONICS Vol.15 No.10

A series of benzodithiophene (BDT) and benzotrithiophene (BTT)-based conjugated polymers (P1-P4), with/without conjugated- and acyl-side chain, have been synthesized by Stille cross-coupling reaction. Their thermal, photophysical, electrochemical properties, devices performances, and microstructure have been investigated. Conjugated-side chain can significantly raise the thermal stability and acyl-side chain can lower HOMO/LUMO energy levels. Organic thin-film transistors (OTFTs) based on conjugated polymers were fabricated and the transistor electrical characterization showed the device performance was sensitive to the conjugated- and acyl-side chain substituent of polymers. A maximum hole mobility of 1.70x10<SUP>-3</SUP>cm<SUP>2</SUP>V<SUP>-1</SUP>s<SUP>-1</SUP> was obtained for P1-based devices, which is an order of magnitude higher than those of P3 and P4-based devices. The corresponding microstructures were investigated by grazing-incidence X-ray diffraction (GIXD) to correlate with conjugated- and acyl-side chain dependent carrier mobility of P1-P4. The results showed that the conjugated- and acyl-side chain have an impact on the polymer packing models and device performances.

Interfacial fabrication and property of hydroxyapatite/polylactideresorbable bone fixation composites

S.M. Zhang,J. Liu,W. Zhou,L. Cheng,X.D. Guo 한국물리학회 2005 Current Applied Physics Vol.5 No.5

Based on surface modication of hydroxyapatite with silane derivatives, interfacial fabrications of hydroxyapatite (HAP)/poly-lactide (PLA) resorbable bone xation composites are realized. The results indicate that interfacial adhesion, swelling property, andultimate mechanical properties of the HAP/PLA composites are signicantly improved. As a result, the maximum bending strengthenhances 27.8%. Scanning electron microscopy (SEM) observation suggests that the modied HA particles are homogeneously dis-persed in the composites, their size ranges are about 215l m. The modied HA/PLA composites are of toughened rupture. Thisconclusion is consistent with bending property of the composites. Finally, a possible mechanism for the interfacial adhesion is alsodiscussed..

Effects of Brazing Temperature on Microstructure and High-Temperature Strength of Joints Using a Novel Fourth-Generation Nickel-Based Single Crystal Superalloy

Z. P. Zhang,J. D. Liu,K. Q. Qiu,Y. Y. Huang,J. G. Li,X. G. Wang,J. L. Liu,M. Wang,M. K. Zou,Y. Z. Zhou 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.2

A novel fourth-generation nickel-based single crystal superalloy was bonded by vacuum brazing at 1230 °C, 1260 °C and1290 °C for 60 min using a new type of Co-based filler alloy. The effects of the brazing temperature on the microstructureand mechanical properties of the brazed joint were investigated. The brazed joint was mainly composed of the non-isothermalsolidification zone (M3B2 type-boride, CrB boride, Ni3Bboride and MC carbide), isothermal solidification zone (γ and γ'Phase) and base metal. With the increase of brazing temperature, the volume fraction of borides and γ' phase in the centerof the joint decreased and increased, respectively. The high-temperature tensile test results show that the tensile strength ofthe joints was improved with increasing brazing temperature, and the maximum tensile strength of the joint was 766 MPaafter brazing at 1290 °C for 60 min. Fracture observation shows that the fracture modes of the joints were the same, whichbelongs to the typical quasi cleavage fracture. The element distribution in the joint was homogenized to a certain extent at1290 °C. The segregation of Si and Ru was found, but they were still dissolved in the γ solid solution. The experimentalresults help to better understand the microstructure characteristics of the novel fourth-generation nickel-based single crystalsuperalloy and provide guidance for further optimizing the process parameters of the brazed joint.

High-efficiency p–i–n organic light-emitting diodes with a novel n-doping electron transport layer

Wei Xu,M.A. Khan,Yu Bai,X.Y. Jiang,Z.L. Zhang,W.Q. Zhu 한국물리학회 2009 Current Applied Physics Vol.9 No.4

We demonstrate p–i–n organic light-emitting diodes (OLEDs) incorporating an n-doping transport layer which comprises 8-hydroxy-quinolinato lithium (Liq) doped into 4'7-diphyenyl-1,10-phenanthroline (Bphen) as ETL and a p-doping transport layer which includes tetrafluro-tetracyano-quinodimethane (F4-TCNQ) doped into 4,4',4''-tris(3-methylphenylphenylamono) triphenylamine (m-MTDATA). In order to examine the improvement in the conductivity of transport layers, hole-only and electron-only devices are fabricated. The current and power efficiency of organic light-emitting diodes have been improved significantly after introducing a novel n-doping (Bphen: 33 wt% Liq) layer as an electron transport layer (ETL) and a p-doping layer composed of m-MTDATA and F4-TCNQ as a hole transport layer (HTL). Compared with the control device (without doping), the current efficiency and power efficiency of Device C (most efficient) is enhanced by approximately 51% and 89%, respectively, while driving voltage is reduced by 29%. This improvement is attributed to the improved conductivity of the transport layers that leads to the efficient charge balance in the emission zone. We demonstrate p–i–n organic light-emitting diodes (OLEDs) incorporating an n-doping transport layer which comprises 8-hydroxy-quinolinato lithium (Liq) doped into 4'7-diphyenyl-1,10-phenanthroline (Bphen) as ETL and a p-doping transport layer which includes tetrafluro-tetracyano-quinodimethane (F4-TCNQ) doped into 4,4',4''-tris(3-methylphenylphenylamono) triphenylamine (m-MTDATA). In order to examine the improvement in the conductivity of transport layers, hole-only and electron-only devices are fabricated. The current and power efficiency of organic light-emitting diodes have been improved significantly after introducing a novel n-doping (Bphen: 33 wt% Liq) layer as an electron transport layer (ETL) and a p-doping layer composed of m-MTDATA and F4-TCNQ as a hole transport layer (HTL). Compared with the control device (without doping), the current efficiency and power efficiency of Device C (most efficient) is enhanced by approximately 51% and 89%, respectively, while driving voltage is reduced by 29%. This improvement is attributed to the improved conductivity of the transport layers that leads to the efficient charge balance in the emission zone.

Study of the dry methane reforming process using a rotating gliding arc reactor

Wu, A.,Yan, J.,Zhang, H.,Zhang, M.,Du, C.,Li, X. Pergamon Press 2014 International journal of hydrogen energy Vol.39 No.31

Dry methane reforming (DMR) via rotating gliding arc (RGA) discharge, co-driven by a magnetic field and tangential flow, was investigated in this study. Optical emission spectroscopy (OES) was used to characterize the major active species (energetic electrons, radicals, ions, atoms and excited molecules) in the DMR chemical process. The influence of the operational conditions (applied voltage and CH<SUB>4</SUB>/CO<SUB>2</SUB> ratio) on the basic spectroscopic parameters (electron excitation temperature, electron density and rotational temperature) was determined by spectroscopic methods. The rotational and electron excitation temperatures were approximately 1100-1200 K and 1.1-1.7 eV, respectively, indicating the non-thermal equilibrium characteristics of the RGA discharge. The electron density was approximately 5-20 x 10<SUP>21</SUP> m<SUP>-3</SUP> by fitting the line shape of H<SUB>α</SUB> at 656 nm. The conversions of the reactants (CH<SUB>4</SUB> and CO<SUB>2</SUB>) and the selectivities of the products (H<SUB>2</SUB>, CO and C<SUB>2</SUB> hydrocarbon) were analyzed using a gas chromatograph (GC) under different energy inputs or feed gas proportions. The structure and morphology of carbon black produced during the chemical process was characterized by high-resolution transmission electron microscopy (HRTEM) and Raman spectroscopy, indicating the properties of electrical conductivity and high absorption capacity that can be useful for potential application.

Spectral tomographic analysis of Bremsstrahlung X-rays generated in a laser-produced plasma

Rhee, Y.J.,Nam, S.M.,Peebles, J.,Sawada, H.,Wei, M.,Vaisseau, X.,Sasaki, T.,Giuffrida, L.,Hulin, S.,Vauzour, B.,Santos, J.J.,Batani, D.,McLean, H.S.,Patel, P.K.,Li, Y.T.,Yuan, D.W.,Zhang, K.,Zhong, J. Cambridge University Press 2016 Laser and particle beams Vol.34 No.4

<B>Abstract</B><P>A new approach is proposed to analyze Bremsstrahlung X-rays that are emitted from laser-produced plasmas (LPP) and are measured by a stack type spectrometer. This new method is based on a spectral tomographic reconstruction concept with the variational principle for optimization, without referring to the electron energy distribution of a plasma. This approach is applied to the analysis of some experimental data obtained at a few major laser facilities to demonstrate the applicability of the method. Slope temperatures of X-rays from LPP are determined with a two-temperature model, showing different spectral characteristics of X-rays depending on laser properties used in the experiments.</P>

Growth and Electronic Structure Studies of Metal Intercalated Transition Metal Dichalcogenides M_xNbSe₂ (M: Fe and Cu) (4 pages)

Koh, Y.,Cho, S.,Lee, J.,Yang, L.-X.,Zhang, Y.,He, C.,Chen, F.,Feng, D.-L.,Arita, M.,Shimada, K. JAPAN SOCIETY OF APPLIED PHYSICS 2013 Japanese journal of applied physics Vol.52 No.10

Magnetic Study of Heavily Mn-doped CuO Thin Films

L. Li,B. Lv,J. Z. Cai,W. Q. Zou,X. S. Wu,F. M. Zhang 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.10

Cu0.7Mn0.3O films were deposited by Plasma Enhanced Chemical Vapor Deposition and annealed in different atmospheres. The XRD diffraction results indicate that samples annealed in air and N2 both show pure CuO phases, while the film annealed in O2 has a secondary phase CuMn2O4. The content of Mn was confirmed by Energy dispersive X-ray spectroscopy. The M-T and M-H curves show that the average magnetic moment of the films prepared in O2 is larger than those prepared in air and in N2 atmosphere. Ferromagnetic segments Mn-O-Cu-O-Mn can be used to understand the ferromagnetism of CuO under heavily Mn-doping. And the magnetic moment per Mn ions calculated on the base of this chain model is consistent with the experimental result.