Effect of oxygen on regulation of properties of moderately boron-doped diamond films

Regulation of oxygen on properties of moderately boron-doped diamond films is fully investigated. Results show that, with adding a small amount of oxygen (oxygen-to-carbon ratio < 5.0%), the crystal quality of diamond is improved, and a suppression effect of residual nitrogen is observed. With increasing ratio of O/C from 2.5% to 20.0%, the hole concentration is firstly increased then reduced. This change of hole concentration is also explained. Moreover, the results of Hall effect measurement with temperatures from 300 K to 825 K show that, with adding a small amount of oxygen, boron and oxygen complex structures (especially B₃O and B₄O) are formed and exhibit as shallow donor in diamond, which results in increase of donor concentration. With further increase of ratio of O/C, the inhibitory behaviors of oxygen on boron leads to decrease of acceptor concentration (the optical emission spectroscopy has shown that it is decreased with ratio of O/C more than 10.0%). This work demonstrates that oxygen-doping induced increasement of the crystalline and surface quality could be restored by the co-doping with oxygen. The technique could achieve boron-doped diamond films with both high quality and acceptable hole concentration, which is applicable to electronic level of usage.     

Yield enhancement of elliptical high harmonics driven by bicircular laser pulses

We theoretically investigate the yield enhancement of elliptical high harmonics in the interaction of molecules with bicircular laser pulses by solving the time-dependent Schrödinger equation. It is shown that by adjusting the relative intensity ratio of the two bicircular field components in specific ranges the yield of the molecular high harmonics for the plateau and cutoff regions can be respectively enhanced. To analyze this enhancement phenomenon, we calculate the weights of the electron classical trajectories. Additionally, we also study the ellipticity distribution of harmonics for different intensity ratios. We find that these enhanced harmonics are elliptically polarized, which we mainly attribute to the recombination dipole moment of the major weighted trajectories. These enhanced elliptical extreme ultraviolet and soft x-ray radiations may serve as essential tools for exploring the ultrafast dynamics in magnetic materials and chiral media.     

Pd–H and Ni–H phase diagrams using cluster variation method and Monte Carlo simulation

This work focuses on interstitial solid solutions of hydrogen in the face-centred cubic (fcc) host lattice of palladium and nickel, using a first-principles based approach. Cluster Variation Method (CVM) and Monte Carlo simulation algorithms were especially designed, allowing a coupled use of both techniques, to study hydrogen–vacancy interactions inside an fcc metallic host lattice. First-principles calculations provided the H–Vac interaction energies by structure inversion method. The phase diagrams and thermodynamic properties were computed using only theoretical inputs. The mechanisms leading to the formation of the miscibility gaps observed for both Pd–H and Ni–H systems and the hydrogen ordering on palladium interstitial lattice were reproduced without any empirical term.     

基于内聚力模型的快速荷载下CFRP-混凝土界面剪切剥离模拟

鉴于纤维增强复合材料(Fiber Reinforced Polymer, FRP)已在混凝土结构加固中普遍应用, 能有效提高结构的承载和变形能力. 为揭示动载作用下FRP-混凝土界面的剥离机理, 本文基于ABAQUS平台, 采用内聚力模型模拟CFRP-混凝土界面层, 实现了快速荷载下CFRP-混凝土界面剥离的高效模拟. 结果表明: CFRP表面应变在加载过程中由加载端向自由端方向传递, 随着加载速率的提高, 界面承载能力也随之提高; 界面峰值剪应力也存在显著的应变率效应; 模拟结果与试验结果基本吻合, 说明了新方法的有效性.     

Thermoelastic solutions for thermal distributions moving over thin slim rod under memory-dependent three-phase lag magneto-thermoelasticity

Abstract

Enlightened by the Caputo fractional derivative, the present study deals with a novel mathematical model of generalized thermoelasticity to investigate the transient phenomena due to the influence of magnetic field and moving heat source in a rod in the context of three-phase lag (TPL) theory of thermoelasticity. Both ends of the rod are fixed and heat insulated. Employing Laplace transform as a tool, the problem has been transformed into the space-domain and solved analytically. Finally, solutions in the real-time domain are obtained by applying the inverse Laplace transform. Numerical calculation for stress, displacement, and temperature within the rod is carried out and displayed graphically. The effect of moving heat source speed on temperature, stress, and temperature is studied. It is found from the distributions that the temperature, thermally induced displacement and stress of the rod are found to decrease at large source speed. For the better understanding of the effect of moving heat source on all the distributions, three animations are added.     

梁柱简化模型在自立塔塔线体系动态响应中的适用性研究

对输电塔进行合理简化可以提高塔线体系动力学仿真的效率。本文给出自立塔梁柱简化模型的计算方法，并提出利用梁柱简化模型计算方法建立自立塔塔线体系整体模型，同时采用桁梁混合模型建立精细化塔线体系整体模型，对两种模型塔线体系静力特性及振型和固有频率等动力特性进行对比分析。以脱冰工况为例，采用生死单元技术将施加在输电线节点上的集中质量单元杀死来模拟脱冰，实现对塔线体系动力学响应的有限元模拟，研究塔线体系简化模型在动态响应中的适用性。结果表明，两种模型弯曲变形误差小，低阶的振型相同，固有频率值误差小，动力特性基本相同；脱冰工况下，自立塔节点位移和塔材内力时程曲线一致，在提高计算效率的情况下，能有效保证计算精度。     

明代生命损失型地震的时空分布特征及成因分析

利用史料记录建立了明代生命损失型地震的数据库，构建生命损失型地震等级序列、10 a尺度上生命损失型地震的频次序列和县次序列，再现明代生命损失型地震的时空分布特征，探讨了生命损失型地震发生及导致人口死亡的时空差异原因。结果表明：（1）从明初到明末，生命损失型地震等级强度有逐渐扩大的趋势。（2）明代前期处于生命损失型地震发生较少的稳定时期；明代中后期处于生命损失型地震发生较多的波动时期。明代生命损失型地震发生频次存在明显的周期性变化特征。（3）生命损失型地震在明代大部分区域皆有分布。灾害重心随时间变化发生移动，由西南到中部再到华北、华东。（4）明代地震频繁的原因除地球本身因素外，太阳活动通过影响气候变化，进而间接影响地壳活动。气候寒冷与干旱和地震有较好的对应关系。明代后期生命损失型地震导致死亡人数大量增加，与明代经济发展，人口密度逐渐增长有关；不同地区生命损失型地震导致的死亡人数不同，且死亡人数与地震频发地区是否处于板块之间的活动构造带和人口分布密度有关。     

以含碘氨基酸类激素为例刍议微量非金属元素在生物体内的作用机制

选取第五周期元素碘,结合多学科的研究方法论对含碘氨基酸类激素在生物体内的合成和分解代谢进行系统性分析。通过解析碘元素本身性质及其各个氧化态之间的转化,探讨碘元素在生物体内的作用机制,揭示自然界对物质代谢的精细调控。这一教学模式探索性地融入无机化学、元素有机化学、分子生物学、生物化学、生物物理学、化学生物学等一系列学科内容,旨在让学生在领悟生命科学内在规律,从而激发其科研及学习热情,并训练学生的类比思维和思辨能力。期对培养21世纪跨学科综合型人才的培养有所助益。     

An improved depth-averaged nonhydrostatic shallow water model with quadratic pressure approximation

Phase-resolved information is necessary for many coastal wave problems, for example, for the wave conditions in the vicinity of harbor structures. Two-dimensional (2D) depth-averaging shallow water models are commonly used to obtain a phase-resolved solution near the coast. These models are in general more computationally effective compared with computational fluid dynamics software and will be even more capable if equipped with a parallelized code. In the current article, a 2D wave model solving the depth-averaged continuity equation and the Euler equations is implemented in the open-source hydrodynamic code REEF3D. The model is based on a nonhydrostatic extension and a quadratic vertical pressure profile assumption, which provides a better approximation of the frequency dispersion. It is the first model of its kind to employ high-order discretization schemes and to be fully parallelized following the domain decomposition strategy. Wave generation and absorption are achieved with a relaxation method. The simulations of nonlinear long wave propagations and transformations over nonconstant bathymetries are presented. The results are compared with benchmark wave propagation cases. A large-scale wave propagation simulation over realistic irregular topography is shown to demonstrate the model's capability of solving operational large-scale problems.     

Interfacial Synthesis of a Monolayered Fluorescent Two-Dimensional Polymer through Dynamic Imine Chemistry

A fluorescent monolayered two-dimensional polymer (2DP) containing both tetraphenylethylene (TPE) and imine linkages is synthesized at air-water interface using the Langmuir-Blodgett method. We designed TPE-based monomers with long distances between the TPE and the imine linkages to avoid the charge transfer and therefore keep the fluorescence. A monolayered 2DP provided with more than 104 μm² in domain size and around 0.8 nm thickness was obtained through a successive Schiff base reaction at air-water interface. The nanostructures and fluorescent property of 2DP films were characterized by optical microscopy, SEM, TEM, AFM and fluorescence spectrum. Most importantly, the tip-enhanced Raman spectroscopy (TERS) was utilized here to confirm the success of the polycondensation of monolayered 2DP.