DEPLOYMENT DYNAMICS OF FLEXIBLE SOLAR ARRAYS CONSIDERING FRICTIONAL JOINT

研究了空间漂浮航天器太阳阵展开与锁定过程的刚柔耦合动力学问题. 基于Jourdain 速度变分原理和单项递推组集方法, 建立了太阳阵展开与锁定过程的刚柔耦合多体系统动力学模型,采用虚功率原理推导了铰摩擦对系统动力学方程的贡献. 在以上动力学模型中引入3-D 鬃毛摩擦模型来研究铰链的摩擦特性对太阳阵展开动力学的影响. 所建动力学模型的正确性通过与商业软件ADAMS 和NASTRAN 的联合仿真对比得到了验证,该模型能够有效地预测太阳阵的展开历程以及航天器姿态的动态行为.     

The second harmonic generation in GaAs/GaAlAs spherical quantum dots under Woods-Saxon plus attractive inversely quadratic potential

We examine the profile of second harmonic generation (SHG) for GaAs/GaAlAs spherical quantum dots (QDs) of Woods-Saxon (WS) plus attractive inversely quadratic (AIQ) potential under the joint influence of additional factors (pressure and temperature) and structural parameters (strengths and radius). The energies and wave functions in GaAs/GaAlAs spherical QDs under WS-AIQ limiting potential are calculated using the parametric Nikiforov-Uvarov (NU) method. Depending on the calculated energies and corresponding wave functions, the SHG coefficient is examined by the iterative procedure in the density matrix method for this system. Finally, the calculated results display that a strong SHG coefficient response, and red shift or blue shift energy can be acquired by adjusting parameters.     

硼烯/石墨烯异质结缺陷态电子结构的第一性原理研究

采用密度泛函理论系统研究了硼烯-石墨烯异质结中缺陷态对体系电子结构特性的影响.发现缺陷态存在于石墨烯一侧时会破坏异质结结构;但缺陷态存在于硼烯一侧时异质结结构仍然会稳定存在,并且体系电子结构随缺陷态密度改变而发生明显变化:从无缺陷态时的金属特性变为多缺陷态时的半导体特性.常温下的分子动力学模拟进一步验证了相关体系的动力学稳定性.     

碳化硅中点缺陷对热传导性能影响的分子动力学研究

碳化硅(SiC)由于性能优异,已广泛应用于核技术领域.在辐照环境下,载能入射粒子可使材料中的原子偏离晶体格点位置,进而产生过饱和的空位、间隙原子、错位原子等点缺陷,这些缺陷将改变材料的热物性能,劣化材料的服役性能.因此,本文利用平衡分子动力学方法(Green-Kubo方法)采用Tersoff型势函数研究了点缺陷对立方碳化硅(β-SiC或3C-SiC)热传导性能的影响规律.研究过程中考虑的点缺陷包括:Si间隙原子(Si_Ⅰ)、Si空位(Si_Ⅴ)、Si错位原子(Si_C)、C间隙原子(C_Ⅰ)、C空位(C_Ⅴ)和C错位原子(C_Si).研究结果表明,热导率(λ)随点缺陷浓度(c)的增加而减小.在研究的点缺陷浓度范围(点缺陷与格点的比例范围为0.2%—1.6%),额外热阻率(Δ_R-R_defect-R_perfect,R=1/λ,R_defect为含缺陷材料的热阻率,R_perfec...     

二维范德瓦尔斯异质结构的制备与物性研究

二维范德瓦尔斯材料(可简称二维材料)已发展成为备受瞩目的材料大家族,而由其衍生的二维范德瓦尔斯异质结构的集成、性能及应用是现今凝聚态物理和材料科学领域的研究热点之一.二维范德瓦尔斯异质结构为探索丰富多彩的物理效应和新奇的物理现象,以及构建新型的自旋电子学器件提供了灵活而广阔的平台.本文从二维材料的转移技术着手,介绍二维范德瓦尔斯异质结构的构筑、性能及应用.首先,依据湿法转移和干法转移的分类,详细介绍二维范德瓦尔斯异质结构的制备技术,内容包括转移技术的通用设备、常用转移方法的具体操作步骤、三维操纵二维材料的方法、异质界面清洁.随后介绍二维范德瓦尔斯异质结构的性能和应用,重点介绍二维磁性范德瓦尔斯异质结构,并列举在二维范德瓦尔斯磁隧道结和摩尔超晶格领域的应用.因此,二维材料转移技术的发展和优化将进一步助力二维范德瓦尔斯异质结构在基础科学研究和实际应用上取得突破性的成果.     

A Mid-Irfrared Rectangle Ring OPO Pumped by an Actively/Passively Q-Switched 2.09 μm Polycrystalline Laser

Journal of Russian Laser Research - We demonstrate a mid-infrared (mid-IR) ZnGeP2 (ZGP) rectangle ring optical parametric oscillator (OPO) pumped by an actively/passively Q-switched polycrystalline...     

High Tc superconductivity in layered hydrides XH15 (X = Ca,Sr, Y,La) under high pressures

The theoretical predictions and experimental synthesis of H₃S and LaH₁₀ superconductors with record high superconducting transition temperatures (T_c) have promoted the hydrogen-based superconducors to be a research hotspot in the field of solid-state physics. Here, we predict an unprecedented layered structure CaH₁₅, with high T_c of 189 K at 200 GPa using ab initio calculations. As concerns the novel structure, one layer is made of a hydrogen nonagon, the other layer consists of a Ca atom and six H₂ molecular units surrounding the Ca atom. This layered structure was also found in SrH₁₅, YH₁₅, and LaH₁₅ at high pressures, each materials exhibit high T_c especially YH₁₅ can reach above 200 K at 220 GPa. It represents the second class of layered superhydrides with high value of T_c after pentagraphene like HfH₁₀.     

Receding horizon control for multiple UAV formation flight based on modified brain storm optimization

Formation flight for unmanned aerial vehicles (UAVs) is a rather complicated global optimum problem. In the global optimum problem, the complex relationship between the controller parameters and the performance index, and the different kinds of constrains under complex combat field environment are taken into account. Brain storm optimization (BSO) is a brand-new swarm intelligence optimization algorithm inspired by a human being’s behavior of brainstorming. In this paper, in allusion to the drawbacks that the basic BSO algorithm traps into local optimum easily and has a slow convergent speed, some novel designs are proposed to enhance the performance of the optimization algorithm. The modified BSO is applied to solve the optimization problem based on the nonlinear Receding horizon control (RHC) mode of UAVs to seek the RHC control parameters for UAV formation flight. Series of comparative experimental results are presented to show the feasibility, validity, and superiority of our proposed method.     

Amphiphilic Schiff base organogels: metal-ion-mediated chiral twists and chiral recognition

New amphiphilic gelators that contained both Schiff base and L-glutamide moieties, abbreviated as o-SLG and p-SLG, were synthesized and their self-assembly in various organic solvents in the absence and presence of metal ions was investigated. Gelation test revealed that o-SLG formed a thermotropic gel in many organic solvents, whilst p-SLG did not. When metal ions, such as Cu(2+), Zn(2+), Mg(2+), Ni(2+), were added, different behaviors were observed. The addition of Cu(2+) induced p-SLG to from an organogel. In the case of o-SLG, the addition of Cu(2+) and Mg(2+) ions maintained the gelating ability of the compound, whilst Zn(2+) and Ni(2+) ions destroyed the gel. In addition, the introduction of Cu(2+) ions caused the nanofiber gel to perform a chiral twist, whilst the Mg(2+) ions enhanced the fluorescence of the gel. More interestingly, the Mg(2+)-ion-mediated organogel showed differences in the fluorescence quenching by D- and L-tartaric acid, thus showing a chiral recognition ability.     

Geissoschizine methyl ether, a corynanthean-type indole alkaloid from Uncaria rhynchophylla as a potential acetylcholinesterase inhibitor

Geissoschizine methyl ether (1), a newly discovered strong acetylcholinesterase (AChE) inhibitor, along with six weakly active alkaloids, vallesiachotamine (2), hisuteine (3), hirsutine (4), isorhynchophylline (5), cisocorynoxeine (6) and corynoxeine (7) have been isolated from Uncaria rhynchophylla. Geissoschizine methyl ether (1) inhibited 50% of AChE activity at concentrations of 3.7?±?0.3?μg?mL(-1) while the IC(50) value of physostigmine as a standard was 0.013?±?0.002?μg?mL(-1). The mode of AChE inhibition by 1 was reversible and non-competitive. In addition, molecular modelling was performed to explore the binding mode of inhibitor 1 at the active site of AChE.