Experimental determination and molecular dynamics simulation of specific heat for high temperature undercooled liquid

The accurate data of specific heat are of great significance in the thermodynamic analysis of phase transformation. Here, we report the experimental and calculated specific heat of liquid Ni_90.1Si_9.9 alloy by electromagnetic levitation drop calorimeter and molecular dynamics calculation, respectively. The experimental result, 39.54 J mol^?1 K^?1, is in good agreement with the calculated value of 38.03 J mol^?1 K^?1, and there exists only a little difference between them. The calculated undercooling range of 0 ～ 623 K is much wider than the experimental range of 0 ～ 218 K. The undercooled liquid structure of this alloy is analyzed according to the total and partial pair distribution functions, which show that the in-order degree of atom distribution enhances from normal liquid to undercooled liquid. The Si atoms are homogeneously dispersed among the Ni atoms, whereas the average distance among Ni atoms changes little.     

Simulation of surface effects on the intrinsic dissipation of nanooscillators

The rapid increase of surface area-volume ratio (SVR) with shrinking structure size has a great impact on surface-related intrinsic dissipation, which usually leads to low quality factors for the devices composed of nanoelectromechanical systems. In the present study, the flexural oscillations of nanocantilevers with varying thicknesses and lengths were simulated using the molecular dynamics method, in which the surface effects on the energy dissipation was evaluated when SVR was increased to extremely large values (between 0.4 and 2.0 nm^?1). And, it is also interesting to note that the prediction of the size-dependent Young's modulus by means of resonant frequency of the underdamped oscillation showed good agreement with previous findings.     

Dielectric and thermodynamic behaviour of binary mixtures of anisole with o-chlorophenol and with o-cresol

The molecular interactions in binary mixtures of anisole with o-chlorophenol and o-cresol have been studied at three different temperatures using dielectric measurements. The static permittivity and the permittivity at optical frequency have also been determined and used to obtain the Kirkwood correlation factors, the Bruggeman parameter, the excess permittivity and the excess free energy for different concentrations of two binary mixtures, namely (1) anisole + o-chlorophenol and (2) anisole + o-cresol. Using the effective Kirkwood correlation factor, parallel and anti-parallel alignments among the dipoles are identified. The corrective Kirkwood correlation factor, the excess permittivity and the Bruggeman parameter are used to explain the interaction between unlike molecules. The temperature dependences of the above parameters are also reported. The investigation shows systematic changes in the dielectric behaviour with variations in concentration and temperature.     

Deformation twins induced by multi-mode deformation in nanocrystalline copper

A multi-mode deformation model is used in a molecular dynamics simulation of nanocrystalline copper. Abundant deformation twin lamellae are developed by shearing the following compression to the elastic limit. Deformation twins (DTs) nucleate through two different mechanisms facilitated by Shockley partial slips. Interactions between DTs and Shockley partials are observed in this simulation.     

Molecular dynamics simulations of the size effect of titanium single-crystal nanopillars orientated for double prismatic slips

An inverse “smaller is stronger” trend is predicted on the basis of molecular dynamics simulations of α-titanium (Ti) single-crystal nanopillars orientated for double prismatic slips when the nanopillars are less than 7?nm wide. This trend is attributed to a significant increase in the surface energy due to the nucleation and propagation of edge dislocations on the surface of the pillars.     

最优化与满意型决策风格孰优孰劣?

最优化决策者追求决策的最优解,满意型决策者寻求决策的满意解.已有研究以理性模型和有限理性模型为基础,提出了两类决策风格的概念并且从两类决策者的决策特征和心理指标这两个角度详细对比了两类决策风格的差异.就纯粹的经济学效益、主观的心理学意义和现实的决策选择这三方面而言,“两类决策风格孰优孰劣”是一个因人而异,因决策目标而异的问题.未来研究可以在清晰界定两类决策风格概念的基础上进一步完善测量工具,从而深入探讨两类决策风格的领域特异性、与正性情绪的关系及其心理悖论的根源.     

Facile route to synthesising mesoporous SBA-15 using phosphoric acid

A facile route has been developed to synthesise mesoporous SBA-15 using mild H₃PO₄ (replacing the most commonly used strong acid HC1) as the medium and the effects of H₃PO₄ concentration and synthesis temperature on the mesostructure and morphology of the resultant materials investigated. The results demonstrate that a more ordered structure can be obtained at low H₃PO₄ concentration (1–2?M), while a higher H₃PO₄ concentration (3–4?M) results in a less ordered structure. Furthermore, the morphology of SBA-15 particles transforms from rod-like to sphere-like with increasing H₃PO₄ concentration.     

腹腔镜手术治疗子宫内膜异位症的临床价值

子宫内膜异位症是妇科常见病、多发病之一,可引起痛经、慢性盆腔痛、性交痛和不孕等症状,严重影响育龄期妇女的身心健康和生活质量,日益受到人们的关注。以人为本,微创手术是当代医学的模式之一。本文从哲学的角度出发、以辩证的观点对腹腔镜手术治疗子宫内膜异位症的临床价值进行综述。