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Search Results: 1 - 10 of 104235 matches for " Qingbin Zhang "
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One-Dimensional Constitutive Model of Shape Memory Alloy with an Empirical Kinetics Equation
Lei Li,Qingbin Li,Fan Zhang
Journal of Metallurgy , 2011, DOI: 10.1155/2011/563413
Abstract: Characteristics of NiTi shape memory alloy (SMA) and its constitutive model with an empirical kinetics equation were investigated in this paper. Firstly, the transformation characters of the NiTi SMA were obtained through a differential scanning calorimetry (DSC) analysis technology, and the properties during incomplete and discontinuous transformation process and the effects of plastic deformation on the transformation were studied. The uniaxial tension, SME, and constrained recovery process of NiTi SMA were examined through an improved 10KN universal material testing machine. Experimental results indicated that the phase transformation characters and the mechanical properties could be affected by the loading process considerably, and the plastic deformation should be taken into account. To simulate the characteristics of NiTi SMA more effectively, a one-dimensional constitutive model derived from the internal variable approach with the consideration of the plastic deformation was constructed based on the DSC and the uniaxial tension experimental results, and a new simple empirical kinetics equation was presented, with the transformation temperature parameters redefined according to the DSC experiment evidence. Comparison between the numerical and experimental results indicated that this constitutive model could simulate the phase transformation characters, the uniaxial tension, SME, and the constrained recovery behavior of NiTi SMA well. 1. Introduction Since the Shape Memory Effect (SME for short) was observed in Cu-Zn alloy by Greninger and Mooradian [1], and in NiTi alloy by Buehler et al. [2], SMA (especially NiTi alloy) has been widely used as intelligent material for its particular characteristics, such as large load capacity, high recovery strain up to 8%, excellent fatigue performance, variable elastic modulus with phase transformation, and especially the two main interesting properties, SME and Pseudoelasticity (PE) due to the diffusionless martensitic transformation, as discussed elsewhere [3–7]. To simulate these specific properties, many constitutive laws have been proposed, such as the phenomenological models [8–12], micromechanics models [13, 14], 3D model for polycrystalline SMA based on microplane theory [15], and so forth. Among them, phenomenological models based on the internal variable method were the most popular used in the practical engineering. The mechanical constitutive equation was derived from the principles of thermodynamics, martensite fraction as an internal variable was used to represent the stage of the transformation,
Genome-Wide Screening for Genes Associated with Valproic Acid Sensitivity in Fission Yeast
Lili Zhang, Ning Ma, Qingbin Liu, Yan Ma
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0068738
Abstract: We have been studying the action mechanisms of valproic acid (VPA) in fission yeast Schizosaccharomyces pombe by developing a genetic screen for mutants that show hypersensitivity to VPA. In the present study, we performed a genome-wide screen of 3004 haploid deletion strains and confirmed 148 deletion strains to be VPA sensitive. Of the 148 strains, 93 strains also showed sensitivity to another aliphatic acids HDAC inhibitor, sodium butyrate (SB), and 55 strains showed sensitivity to VPA but not to SB. Interestingly, we found that both VPA and SB treatment induced a marked increase in the transcription activity of Atf1 in wild-type cells. However, in clr6-1, a mutant allele the clr6+ gene encoding class I HDAC, neither VPA- nor SB induced the activation of Atf1 transcription activity. We also found that VPA, but not SB, caused an increase in cytoplasmic Ca2+ level. We further found that the cytoplasmic Ca2+ increase was caused by Ca2+ influx from extracellular medium via Cch1-Yam8 channel complex. Altogether, our present study indicates that VPA and SB play similar but distinct roles in multiple physiological processes in fission yeast.
Efficient generation of isolated attosecond pulses with high beam-quality by two-color Bessel-Gauss beams
Zhe Wang,Weiyi Hong,Qingbin Zhang,Shaoyi Wang,Peixiang Lu
Physics , 2011, DOI: 10.1364/OL.37.000238
Abstract: The generation of isolated attosecond pulses with high efficiency and high beam quality is essential for attosec- ond spectroscopy. We numerically investigate the supercontinuum generation in a neutral rare-gas medium driven by a two-color Bessel-Gauss beam. The results show that an efficient smooth supercontinuum in the plateau is obtained after propagation, and the spatial profile of the generated attosecond pulse is Gaussian-like with the divergence angle of 0.1 degree in the far field. This bright source with high beam quality is beneficial for detecting and controlling the microscopic processes on attosecond time scale.
Laser-polarization-dependent photoelectron angular distributions from polar molecules
Xiaosong Zhu,Qingbin Zhang,Weiyi Hong,Peixiang Lu,Zhizhan Xu
Physics , 2011, DOI: 10.1364/OE.19.024198
Abstract: Photoelectron angular distributions (PADs) of oriented polar molecules in response to different polarized lasers are systematically investigated. It is found that the PADs of polar CO molecules show three distinct styles excited by linearly, elliptically and circularly polarized lasers respectively. In the case of elliptical polarization, a deep suppression is observed along the major axis and the distribution concentrates approximately along the minor axis. Additionally, it is also found that the concentrated distributions rotate clockwise as the ellipticity increases. Our investigation presents a method to manipulate the motion and angular distribution of photoelectrons by varying the polarization of the exciting pulses, and also implies the possibility to control the processes in laser-molecule interactions in future work.
Wavelength dependence of electron localization in the laser-driven dissociation of H$_2^+$
Kunlong Liu,Weiyi Hong,Qingbin Zhang,Peixiang Lu
Physics , 2011, DOI: 10.1364/OE.19.026359
Abstract: We theoretically investigate the laser wavelength dependence of asymmetric dissociation of H$_2^+$. It is found that the electron localization in molecular dissociation is significantly manipulated by varying the wavelength of the driving field. Through creating a strong nuclear vibration in the laser-molecular interaction, our simulations demonstrate that the few-cycle mid-infrared pulse can effectively localize the electron at one of the dissociating nuclei with weak ionization. Moreover, we show that the observed phase-shift of the dissociation asymmetry is attributed to the different population transfers by the remaining fields after the internuclear distances reach the one-photon coupling point.
Tomographic imaging of asymmetric molecular orbitals with a two-color multicycle laser field
Meiyan Qin,Xiaosong Zhu,Qingbin Zhang,Peixiang Lu
Physics , 2013, DOI: 10.1364/OL.37.005208
Abstract: We theoretically demonstrate a scheme for tomographic reconstruction of asymmetric molecular orbitals based on high-order harmonic generation with a two-color multicycle laser field. It is shown that by adjusting the relative phase of the two fields, the returning electrons can be forced to recollide from one direction for all the orientations of molecules. Thus the reconstruction of the asymmetric orbitals can be carried out with multicycle laser field. This releases the stringent requirement of a single-cycle pulse with a stabilized and controllable carrier-envelop phase for the tomographic imaging of asymmetric molecular orbitals.
Imprints of the molecular-orbital geometry on the high-harmonic ellipticity
Meiyan Qin,Xiaosong Zhu,Kunlong Liu,Qingbin Zhang,Peixiang Lu
Physics , 2013, DOI: 10.1364/OE.20.020181
Abstract: The influence of the orbital symmetry on the ellipticity of the high-order harmonics is investigated. It is found that the ellipticity maps have distinct shapes for the molecular orbital with different symmetry. Our analysis shows that the feature of the harmonic ellipticity map is essentially determined by the nodal structure of the nonsymmetric orbital. The results indicate that the molecular-orbital geometry is imprinted on the ellipticity of the high-order harmonics, which invites the use of ellipticity measurements as a probe of the orbital structure for polar molecules.
Revealing Correlated Electron-Nuclear Dynamics in Molecules with Energy-Resolved Population Image
Kunlong Liu,Pengfei Lan,Cheng Huang,Qingbin Zhang,Peixiang Lu
Physics , 2014, DOI: 10.1103/PhysRevA.89.053423
Abstract: We explore a new fashion, named energy-resolved population image (EPI), to represent on an equal footing the temporary electronic transition and nuclear motion during laser-molecular interaction. By using the EPI we have intuitively demonstrated the population transfer in vibrational H$_2^+$ exposed to extreme ultraviolet pulses, revealing the energy sharing rule for the correlated electron and nuclei. We further show that the EPI can be extended to uncover the origins of the distinct energy sharing mechanisms in multi-photon and tunneling regimes. The present study has clarified a long-standing issue about the dissociative ionization of H$_2^+$ and paves the way to identify instantaneous molecular dynamics in strong fields.
Anomalous isotopic effect on electron-directed reactivity by a 3-μm midinfrared pulse
Kunlong Liu,Qingbin Zhang,Pengfei Lan,Peixiang Lu
Physics , 2012, DOI: 10.1364/OE.21.005107
Abstract: We have theoretically studied the effect of nuclear mass on electron localization in dissociating H_2^+ and its isotopes subjected to a few-cycle 3-{\mu}m laser pulse. Compared to the isotopic trend in the near-infrared regime, our results reveal an inverse isotopic effect in which the degree of electron-directed reactivity is even higher for heavier isotopes. With the semi-classical analysis, we find, for the first time, the pronounced electron localization is established by the interferences through different channels of one- and, more importantly, higher-order photon coupling. Interestingly, due to the enhanced high-order above-threshold dissociation of heavier isotopes, the interference maxima gradually become in phase with growing mass and ultimately lead to the anomalous isotopic behavior of the electron localization. This indicates that the multi-photon coupling channels will play an important role in controlling the dissociation of larger molecules with midinfrared pulses.
Broadband large-ellipticity harmonic generation with polar molecule
Meiyan Qin,Xiaosong Zhu,Qingbin Zhang,Weiyi Hong,Peixiang Lu
Physics , 2011, DOI: 10.1364/OE.19.025084
Abstract: We investigate the polarization properties of high harmonic generation from polar molecules with a linearly polarized field. It is found that elliptically polarized harmonics are observed in a wide spectral range from the plateau to the cutoff. Further analyses show that the nonsymmetric structure of the highest occupied molecular orbital is the origin of ellipticity of the harmonics. The results provide a method for generation of large-ellipticity XUV pulses, which will benefit the application of HHG as a tool of detection in materials and biology science.
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