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Fluorescence Lifetime and Blinking of Individual Semiconductor Nanocrystals on Graphene
Rogez, Benoix302,t,Yang, Heejun,Le Moal, Eric,Lex301,vex302,que-Fort, Sandrine,Boer-Duchemin, Elizabeth,Yao, Fei,Lee, Young-Hee,Zhang, Yang,Wegner, K. David,Hildebrandt, Niko,Mayne, Andrew,Dujar American Chemical Society 2014 The Journal of Physical Chemistry Part C Vol.118 No.32
<P>A new class of optoelectronic nanodevices consisting of 0D semiconductor nanocrystals and 2D single graphene layers is attracting much attention. In particular, such a system may be used to investigate and control the transfer of energy and charge in low-dimensional systems. To this end, the fluorescence dynamics of individual colloidal quantum dots (QDs) on graphene are investigated on both the 10<SUP>–9</SUP>–10<SUP>–8</SUP> s time scale (fluorescence lifetime) and the 10<SUP>0</SUP>–10<SUP>2</SUP> s time scale (blinking statistics) in this paper. We find that (i) a nonradiative energy transfer rate of ≈5 × 10<SUP>8</SUP> s<SUP>–1</SUP> is obtained from the reduced lifetimes of QDs on graphene as opposed to those on insulating substrates such as glass; (ii) QDs still exhibit fluorescence intermittency (“blinking”) on graphene; (iii) the cumulative distribution functions of the “off” times may be described by power-law statistics; (iv) QD coupling to graphene increases the time spent in the “on” state while the time spent in the “off” state remains relatively unchanged; and (v) the fluorescence emission spectrum of the QDs is practically unaltered by the QD–graphene coupling.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2014/jpccck.2014.118.issue-32/jp5061446/production/images/medium/jp-2014-061446_0006.gif'></P>
OPTIMIZATION RESEARCH FOR A HIGH PRESSURE COMMON RAIL DIESEL ENGINE BASED ON SIMULATION
Y. LIU,Y.-T. ZHANG,T. QIU,X. DING,Q. XIONG 한국자동차공학회 2010 International journal of automotive technology Vol.11 No.5
ABSTRACT−A TP (Temperature Phase) model is presented to carry out optimization calculation for a high-pressure common rail diesel engine. Temperature is the most important parameter in the TP model. For the lower branch (when temperature T < 850 K) of the S-shaped curve (auto-ignition phase), a 6-step ad-hoc model with adjusted rate constants of nheptane is used, referred to steady state assumption. Steady state assumption is based on the observation that, due to very fast chemical processes in combustion problems, many chemical species and reactions are in a quasi-steady state or partial equilibrium. When a species is assumed to be in the steady state, the corresponding differential equation can be replaced by an algebraic relation, which reduces the computational costs. For the middle branch (850 K ≤ T < 1100 K) of the S-shaped curve, a 4-step model is used to calculate the unstable phase. For the upper branch (T≥1100 K) of the S-shaped curve, onestep model is used because the one-step model has widely been used in descriptions of flame stability where it essentially serves as a model that produces a thin flame with strong temperature sensitivity. When zone temperature T<1500 K, only the soot precursors –PAHs (Polycyclic aromatic hydrocarbons) is created and there is no soot emission. When zone temperature T≥1500 K, PAHs and soot source terms (particle inception, surface growth, oxidation, coagulation) are calculated. The TP model is then applied in multidimensional simulations to carry out optimizing, which reduces experiment cost. The results of cylinder pressures, the corresponding heat release rates, NOx and soot with variation of injection time at constant rail pressure, variation of EGR-rate at constant rail pressure and variation of rail pressure at constant EGR-rate between simulation and experimental data are analyzed. The results indicate that the TP model can carry out optimization and CFD (computational fluid dynamics) and can be a tool to calculate for a high-pressure common rail diesel engine.
Y. C. Gao,Y. Zhang,X. T. Wang 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.66 No.6
By using the first-principles calculations, we have systematically investigated the phase stability,band gap, and electronic structures and magnetic properties of quaternary Heusler alloys FeMnScZ(Z = Al, Ga, In). We found that FeMnScZ (Z = Al, Ga, In) alloys are half-metallic ferrimagnetsat their equilibrium lattice constants and retain a high spin polarization over a quite wide rangeof lattice distortions. The half-metallic band gap in the FeMnScZ (Z = Al, Ga, In) alloys arisesfrom t1u-t2g splitting but not eu-t1u splitting. The total magnetic moments are 3 μB per unit cellfor FeMnScZ (Z = Al, Ga, In) alloys, following the Slater−Pauling rule with the total number ofvalence electrons minus 18 rather than 24. Moreover, all of these alloys have a negative formationenergy, which implies that they can be synthesized experimentally.
Zheng, W.,Shen, R. F.,Sakamoto, T.,Beardmore, A. P.,De Pasquale, M.,Wu, X. F.,Gorosabel, J.,Urata, Y.,Sugita, S.,Zhang, B.,Pozanenko, A.,Nissinen, M.,Sahu, D. K.,Im, M.,Ukwatta, T. N.,Andreev, M.,Klun IOP Publishing 2012 The Astrophysical journal Vol.751 No.2
<P>We present a comprehensive analysis of a bright, long-duration (T-90 similar to 257 s) GRB 110205A at redshift z = 2.22. The optical prompt emission was detected by Swift/UVOT, ROTSE-IIIb, and BOOTES telescopes when the gamma-ray burst (GRB) was still radiating in the gamma-ray band, with optical light curve showing correlation with gamma-ray data. Nearly 200 s of observations were obtained simultaneously from optical, X-ray, to gamma-ray (1 eV to 5 MeV), which makes it one of the exceptional cases to study the broadband spectral energy distribution during the prompt emission phase. In particular, we clearly identify, for the first time, an interesting two-break energy spectrum, roughly consistent with the standard synchrotron emission model in the fast cooling regime. Shortly after prompt emission (similar to 1100 s), a bright (R = 14.0) optical emission hump with very steep rise (alpha similar to 5.5) was observed, which we interpret as the reverse shock (RS) emission. It is the first time that the rising phase of an RS component has been closely observed. The full optical and X-ray afterglow light curves can be interpreted within the standard reverse shock (RS) + forward shock (FS) model. In general, the high-quality prompt and afterglow data allow us to apply the standard fireball model to extract valuable information, including the radiation mechanism (synchrotron), radius of prompt emission (R-GRB similar to 3 x 10(13) cm), initial Lorentz factor of the outflow (Gamma(0) similar to 250), the composition of the ejecta (mildly magnetized), the collimation angle, and the total energy budget.</P>
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>
c-Cbl-Mediated Neddylation Antagonizes Ubiquitination and Degradation of the TGF-β Type II Receptor
Zuo, W.,Huang, F.,Chiang, Y.,Li, M.,Du, J.,Ding, Y.,Zhang, T.,Lee, H.,Jeong, L.,Chen, Y.,Deng, H.,Feng, X.H.,Luo, S.,Gao, C.,Chen, Y.G. Cell Press 2013 Molecular cell Vol.49 No.3
Transforming growth factor β (TGF-β) is a potent antiproliferative factor in multiple types of cells. Deregulation of TGF-β signaling is associated with the development of many cancers, including leukemia, though the molecular mechanisms are largely unclear. Here, we show that Casitas B-lineage lymphoma (c-Cbl), a known proto-oncogene encoding an ubiquitin E3 ligase, promotes TGF-β signaling by neddylating and stabilizing the type II receptor (TβRII). Knockout of c-Cbl decreases the TβRII protein level and desensitizes hematopoietic stem or progenitor cells to TGF-β stimulation, while c-Cbl overexpression stabilizes TβRII and sensitizes leukemia cells to TGF-β. c-Cbl conjugates neural precursor cell-expressed, developmentally downregulated 8 (NEDD8), a ubiquitin-like protein, to TβRII at Lys556 and Lys567. Neddylation of TβRII promotes its endocytosis to EEA1-positive early endosomes while preventing its endocytosis to caveolin-positive compartments, therefore inhibiting TβRII ubiquitination and degradation. We have also identified a neddylation-activity-defective c-Cbl mutation from leukemia patients, implying a link between aberrant TβRII neddylation and leukemia development.
X. Y. Le,S. Yan,W. J. Zhao,B. H. Han,Y. G. Wang,J. M. Xue,H. T. Zhang 한국진공학회(ASCT) 2002 Journal of Korean Vacuum Science & Technology Vol.6 No.2
In this paper, we treated the Ni₃Al based alloy samples with intense pulsed ion beams (IPIB) at the beam parameters of 250KV acceleration voltage, 100 - 200 A/㎤ current density and 60 ㎱ pulse duration. We simulated the thermal-mechanical process near the surface of Ni₃Al based alloy with our STEIPIB codes. The surface morphology and the cross-section microstructures of samples were observed with SEM, the composition of the sample surface layer was determined by X-ray Energy Dispersive Spectrometry (XEDS) and the microstructure on the surface was observed by Transmission Electron Microscope (TEM). The results show that heating rate increases with the current density of IPIB and cooling rate reached highest value less than 150 A/㎤. The irradiation of IPIB induced the segregation of Mo and adequate beam parameter can improve anti-oxidation property of IC6 alloy. Some craters come from extraneous debris and liquid droplets, and some maybe due to the melting of the intersection region of interphase. Increasing the pulse number enlarges average size of craters and decreases number density of craters.
Watanabe, H.,Zhang, G.X.,Yoshida, K.,Walker, P.M.,Liu, J.J.,Wu, J.,Regan, P.H.,Soderstrom, P.A.,Kanaoka, H.,Korkulu, Z.,Lee, P.S.,Nishimura, S.,Yagi, A.,Ahn, D.S.,Alharbi, T.,Baba, H.,Browne, F.,Bruce North-Holland Pub. Co 2016 Physics letters. Section B Vol.760 No.-
The level structure of <SUP>172</SUP>Dy has been investigated for the first time by means of decay spectroscopy following in-flight fission of a <SUP>238</SUP>U beam. A long-lived isomeric state with T<SUB>½</SUB>=0.71(5) s and K<SUP>π</SUP>=8<SUP>-</SUP> has been identified at 1278 keV, which decays to the ground-state and γ-vibrational bands through hindered electromagnetic transitions, as well as to the daughter nucleus <SUP>172</SUP>Ho via allowed β decays. The robust nature of the K<SUP>π</SUP>=8<SUP>-</SUP> isomer and the ground-state rotational band reveals an axially-symmetric structure for this nucleus. Meanwhile, the γ-vibrational levels have been identified at unusually low excitation energy compared to the neighboring well-deformed nuclei, indicating the significance of the microscopic effect on the non-axial collectivity in this doubly mid-shell region. The underlying mechanism of enhanced γ vibration is discussed in comparison with the deformed Quasiparticle Random-Phase Approximation based on a Skyrme energy-density functional.