Rectification effect in asymmetric Kerr nonlinear medium

Based on the transfer matrix method, the recursion of an electromagnetic wave propagating in an asymmetric Kerr nonlinear medium is analytically formulated, from which the rectification effect is clearly presented. The effects on the rectification regioh of the linear part and nonlinear coefficient of permittivity are both studied, and the energy densities before and after rectification are discussed. We use a rectifying factor to describe the intensity of the rectification effect. The result shows that every transmission peak is divided into two parts when the symmetry is broken, and nonlinear asymmetry has a more significant effect on the rectification effect than the linear asymmetry. The rectification intensity and area will be enlarged when the asymmetry factor is increased in a certain range.     

On Prop erties of p-critical Points of Convex Bo dies

Properties of the p-measures of asymmetry and the corresponding affine equivariant p-critical points, defined recently by the second author, for convex bodies are discussed in this article. In particular, the continuity of p-critical points with respect to p on(1, +∞) is confirmed, and the connections between general p-critical points and the Minkowski-critical points(∞-critical points) are investigated. The behavior of p-critical points of convex bodies approximating a convex bodies is studied as well.     

A crystal plasticity finite element model for flow stress anomalies in Ni3Al single crystals

This paper presents a dislocation density-based non-Schmid constitutive model to address the anomalous thermo-mechanical behaviour of the L1₂ intermetallic single-crystal Ni₃Al. Ni₃Al is used as a strengthening precipitate (γ′ phase) in Ni-based superalloys. Addressing such anomalous behaviour by accounting for temperature-dependent flow stress and hardening evolution, as well as orientation-dependent tension–compression asymmetry, is necessary for modelling superalloys across a range of temperatures. While hardening in cube-slip systems results from statistically stored dislocations (SSDs), hardening in octahedral slip systems is due to both SSDs and cross-slip dislocations (CSDs). The constitutive model incorporates hardening evolution due to SSDs and CSDs. Experimental data for Ni₃Al-type single crystals, available in the literature, are used to calibrate material parameters. Subsequently, results of crystal plasticity FEM simulations are compared with experimental data for several orientations under constant strain rate and creep loading conditions for a wide range of temperatures. The model is able to correctly predict the response of L1₂ intermetallic single crystals including features of anomalous flow stress and non-Schmid yield behaviour.     

社会化媒体环境下不可辩解型产品伤害危机演化博弈研究

社会化媒体的普及改变了信息传播模式,使得产品伤害危机的演化发生了变化。针对社会化媒体环境下不可辩解型产品伤害危机构建演化博弈模型,并引入前景理论构建收益矩阵,对社会化媒体环境下不可辩解型产品伤害危机的演化稳定策略进行分析,通过数值仿真发现社会化媒体环境下不可辩解型产品伤害危机演化中存在:损失规避态度的变化对企业-消费者利益损失的影响存在非对称性现象;合理的政府协调补偿会引导企业和消费者进行策略调整,从而有利于危机的快速平息;外界干预对企业-消费者责任性的影响存在非对称性现象,舆论等干预会对企业行为起到责任约束作用。     

Chiral 2-(2-Diphenylphosphinophenyl)-oxazolines: Synthesis and Use in Pd-Catalyzed Asymmetric Allylic Alkylation

The synthesis of 2-(2-diphenylphosphinophenyl)-oxazolines from o-fluoroben-zonitrile and (-)-norephedrine or (+)-endo-2-hydroxy-endo-3-aminobornane is described. The Pa-catalyzed alkylation of (E)-1,3-diphenylallyl acetate with the sodium salt of dimethylmalonate using these chiral ligands occurs with an 82–87% yield and 88–93% ee.     

Chiral crystallization and the origin of chiral life on earth

The creation of chirality on Earth and the development of chiral life have been discussed in this highlight. Convincing evidence for the introduction of chirality on Earth is still fragmentary. We believe that by a combination of chiral crystallization and formation of helical polymers with preferred chiral conformational structure is the key to this question. This concept of macromolecular asymmetry has inspired ideas and resulted in possible rules for how chiral life as we know it, could have been introduced. These investigations needed the understanding of the requirements for chiral crystallization, for the stereochemistry of the initial formation of helical polymers, the measurements of optical activity of solids and their coordination with the fundamentals of chirality. Spacial modeling of the “oligo‐crystallization” of sodium chlorate led to the conception of “isotactic” linear crystallization, which involves helical propagation. It seems to require unequal sizes of the cations and anions, which, by branching propagation leads to three‐dimensional chiral crystal formation. Linear “isotactic” propagation of crystallization seems to be equivalent to stereo and conformational specific polymerization. One and a half turns of the helix seems to be required for stereo‐ and conformational specificity, that is, between the pentamer and hexamer in chloral polymerization (11/3 or nearly 4/1 helix) and between trimer and tetramer for the sodium chlorate crystal (2/1 helix). © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

NQR study of chalcogenide glasses Ge-As-Se

A three‐component Ge‐As‐Se system is studied by the nuclear quadrupole resonance (NQR) method on ⁷⁵As nuclei and by the nutation NQR spectroscopy. The NQR ⁷⁵As spectra of the glasses Ge_0.021As_0.375Se_0.604, Ge_0.043As_0.348Se_0.609 and Ge_0.068As_0.318Se_0.614reveal broad lines with two peaks assigned to the main structural unit of As₂Se₃. With increasing average coordination number (r?), the spectrum signals are shifted towards higher frequencies. At r? > 2.54, the spectrum becomes complex, which is a consequence of formation of more complex molecular structures in the glasses of high content of germanium. At fixed frequencies the asymmetry parameter η of the samples studied is determined. Copyright © 2011 John Wiley & Sons, Ltd.     

Syntheses and catalytic activities of Pd(II) dicarbene and hetero-dicarbene complexes

A series of palladium(II) complexes (1-6) bearing cis-chelating homo-dicarbene ligands with varying alkyl bridges (C1-C3) and N-heterocyclic backbones (imidazole and benzimidazole) have been synthesized by reaction of Pd(OAc)₂ with the respective diazolium bromides (A·2HBr - F·2HBr) in DMSO. A comparative catalytic study employing aryl chlorides in the Mizoroki-Heck reaction revealed the superiority of methylene- and propylene-bridged dibenzimidazolin-2-ylidenes over their imidazole-derived analogues. Based on these results, two new propylene-bridged hetero-dicarbene complexes (7 and 8) were designed containing a mixed benzimidazole/imidazole-derived NHC-donor set. Notably, both complexes outperformed their homo-dicarbene analogues, which may be due to the electronic asymmetry induced by hetero-dicarbene ligands. The molecular structures of complex 6 and 8 are also presented.     

非对称量子点中强耦合束缚磁极化子的基态寿命

采用线性组合算符和幺正变换方法,研究了非对称量子点中电子和体纵光学声子强耦合下束缚磁极化子的性质.得到了非对称量子点中强耦合束缚磁极化子的基态能量.讨论了量子点横向和纵向受限长度.磁极化子基态能量,电子-声子耦合强度和外界温度对磁极化子基态寿命的影响.由于电子-声子相互作用和外界温度的影响导致了量子体系的跃迁,即磁极化子吸收了声子的能量由摹态跃迁到激发态,造成极化子在基态的寿命发生变化.通过计算发现束缚磁极化子基态寿命随基态能量的增加而变大,随电子-声子耦合强度,量子点横向和纵向受限长度,外界温度的增加而变小.     

Nitrogen dilution effect for small angle GDH experiment in JLab Hall-A

In the GDH sum rule measurement in JLab Hall-A, to obtain the cross section of electron scattering on polarized ³He and its asymmetry in different helicity states, the dilution effect from unpolarized nitrogen mixed in the polarized ³He target were calculated at different kinematic settings.