含72元环的二维网状结构超分子配合物的合成与结构

用自组装方法合成具有特殊网状结构及光学、电学、磁学、离子或分子交换、催化等性能的化合物的分子工程学和超分子化学近年来成为人们研究的热点,并已取得了很大进展［１,２］．当前常用的一种三角架结构单元是刚性芳基三角架配体［３～５］,而对柔性芳基三角架配体及...     

Microfluidic platform serves as controllable fabrication of binary Mo/Ir nanodots/carbon hetero-material for efficient electrocatalytic nitrogen reduction

Electrocatalytic nitrogen reduction reaction (NRR) is regarded as a potential routine to achieve environment-friendly ammonia production, because of its abundant nitrogen resources, clean energy utilization and flexible operation. However, it is hindered by low activity and selectivity, in which condition well-designed catalysts are urgently in need. In this work, a binary Mo/Ir nanodots/carbon (Mo/Ir/C) hetero-material is efficiently constructed via microfluidic strategy, of which the nanodots are homogeneously distributed on the carbon skeleton and the average size is approximately 1 nm. Excellent performance for NRR is obtained in 1 mol L⁻¹ KOH, of which the optimized ammonia yield and faradic efficiency are 7.27 μg h⁻¹ cm⁻² and 2.31% respectively. Moreover, the optimized ammonia yield of 6.20 μg h⁻¹ cm⁻² and faradic efficiency of 10.59% are also obtained in 0.005 mol L⁻¹ H₂SO₄. This work achieves the continuous-flow synthesis and controllable adjustment of hetero-materials for favorable morphologies, which provides an innovative pathway for catalyst design and further promotes the development of ammonia production field.     

Analytical method for the attitude stability of partially liquid filled spacecraft with flexible appendage

In this paper, the attitude stability of liquid-filled spacecraft with flexible appendage is investigated. The motion of liquid sloshing is modeled as the spherical pen-dulum, and the flexible appendage is approached by a linear shearing beam. Nonlinear dynamic equations of the coupled system are derived from the Hamiltonian. The stability of the coupled system was analyzed by using the energy-Casimir method, and the nonlinear stability theorem of the coupled spacecraft system was also obtained. Through numerical computation, the correctness of the proposed theorem is verified and the boundary curves of the stable region are presented. The increase of the angular velocity and flexible attachment length will weaken the attitude stability, and the change of the filled ratio of liquid fuel tank has a different influence on the stability of the coupled spacecraft, depend-ing on the different conditions. The attitude stability analysis of the coupled spacecraft system in this context is useful for selecting appropriate parameters in the complex spacecraft design.     

Degradation of flexible thin-film solar cells due to a mechanical strain

Many variants of thin film technology are nowadays part of the photovoltaic market. The most popular are amorphous silicon, CIS (Copper Indium Selenide)/CIGS (Copper Indium Gallium Selenide)/CIGSS (Copper Indium Gallium Sulphur Selenide), and CdS/CdTe (Cadmium Sulphide/Cadmium-Telluride) cells. All mentioned types allow potentially for a flexible cell structure. Most emitter contacts are currently based on TCOs (Transparent Conductive Oxides), however, wider approach with alternative carbon nanoforms, silver nanolayers and polymer materials, called TCLs (Transparent Conductive Layers) are also in use. Authors decided to investigate influence of mechanical stresses on physical and electrical behaviour of these layers. Consequently, the aim of work is to determine the level and possible mechanisms of flexible a-Si cell parameters degradation due to a deterioration of transparent contact properties.     

Hydroelastic analysis of gravity wave interaction with submerged horizontal flexible porous plate

The present study deals with the surface gravity wave interaction with submerged horizontal flexible porous plate under the assumption of small amplitude water wave theory and structural response. The flexible porous plate is modeled using the thin plate theory and wave past porous structure is based on the generalized porous wavemaker theory. The wave characteristics due to the interaction of gravity waves with submerged flexible porous structure are studied by analyzing the complex dispersion relation using contour plots. Three different problems such as (i) wave scattering by a submerged flexible porous plate, (ii) wave trapping by submerged flexible porous plate placed at a finite distance from a rigid wall and (iii) wave reflection by a rigid wall in the presence of a submerged flexible porous plate are analyzed. The role of flexible porous plate in attenuating wave height and creating a tranquility zone is studied by analyzing the reflection, transmission and dissipation coefficients for various wave and structural parameters such as angle of incidence, depth of submergence, plate length, compression force and structural flexibility. In the case of wave trapping, the optimum distance between the porous plate and rigid wall for wave reflection is analyzed in different cases. In addition, effects of various physical parameters on free surface elevation, plate deflection, wave load on the plate and rigid wall are studied. The present approach can be extended to deal with acoustic wave interaction with flexible porous plates.     

Different crystal structures and luminescent properties of zinc and cadmium coordination polymers constructed from two flexible thioether ligands with different alkyl chains

Treatments of nitrogen-containing heterocyclic dithioether ligands, 1,2-bis(4-(pyridin-3-yl) pyrimidin-2-ylthio) ethane (L¹) and 1,3-bis (4-(pyridin-3-yl) pyrimidin-2-ylthio) propane (L²), with zinc or cadmium salts have resulted in the interesting frameworks with structural motifs from a mononuclear macrocycle or a dinuclear macrocycle to an one-dimensional structure. A small difference of the alkyl length between L¹ and L² led to conspicuous changes of the fluorescent properties of both ligands and their complexes. Mainly due to the size of metal atoms, structures of [ZnL²I₂] (1) and [CdL²I₂] (2) are varied from a mononuclear macrocycle to a 1D framework, while {[ZnL²(H₂O)₄](ClO₄)₂}₂ (3) and {[CdL²(H₂O)₄](ClO₄)₂}₂ (4) are dinuclear macrocycles in which perchlorate anions may play an important template role. As for complexes 5–8 ([ZnL¹I₂]_n (5), [CdL¹I₂]_n (6), {{[ZnL¹₂(H₂O)₄](ClO₄)₂}_0.5 · L¹_0.5 · CH₃OH} (7), {{[Cd_0.5L¹(H₂O)₂](ClO₄)}₂ · CH₃OH · L¹} (8)), the self-assemble processes were mainly directed by the organic ligand in the reactions of L¹ with metal salts. Complexes 1–4 exhibit blue fluorescence emissions, among which 1 and 2 may be suitable as candidates for blue fluorescent materials.     

Biomimetic flexible plate actuators are faster and more efficient with a passive attachment

Using three-dimensional computer simulations, we probe biomimetic free swimming of an internally actuated flexible plate in the regime near the first natural frequency. The plate is driven by an oscillating internal moment approx-imating the actuation mechanism of a piezoelectric macro fiber composite (MFC) bimorph. We show in our simulations that the addition of a passive attachment increases both swim-ming velocity and efficiency. Specifically, if the active and passive sections are of similar size, the overall performance is the best. We determine that this optimum is a result of two competing factors. If the passive section is too large, then the actuated portion is unable to generate substantial deflection to create sufficient thrust. On the other hand, a large actu-ated section leads to a bending pattern that is inefficient at generating thrust especially at higher frequencies.     

New method for oblique impact dynamics research of a flexible beam with large overall motion considering impact friction force

A flexible beam with large overall rotating motion impacting with a rigid slope is studied in this paper. The tangential friction force caused by the oblique impact is analyzed. The tangential motion of the system is divided into a stick state and a slip state. The contact constraint model and Coulomb friction model are used respectively to deal with the two states. Based on this hybrid mod-eling method, dynamic equations of the system, which include all states (before, during, and after the collision) are obtained. Simulation results of a concrete example are compared with the results obtained from two other models: a nontangential friction model and a modified Coulomb model. Differences in the results from the three models are discussed. The tangential friction force cannot be ignored when an oblique impact occurs. In addition, the results obtained from the model proposed in this paper are more consistent with real movement.     

Effect of wheelset flexibility on wheel–rail contact behavior and a specific coupling of wheel–rail contact to flexible wheelset

The fexibility of a train's wheelset can have a large effect on vehicle–track dynamic responses in the medium to high frequency range.To investigate the effects of wheelset bending and axial deformation of the wheel web,a specifi coupling of wheel–rail contact with a fexible wheelset is presented and integrated into a conventional vehicle–track dynamic system model.Both conventional and the proposed dynamic system models are used to carry out numerical analyses on the effects of wheelset bending and axial deformation of the wheel web on wheel–rail rolling contact behaviors.Excitations with various irregularities and speeds were considered.The irregularities included measured track irregularity and harmonic irregularities with two different wavelengths.The speeds ranged from 200 to400km/h.The results show that the proposed model can characterize the effects of fexible wheelset deformation on the wheel–rail rolling contact behavior very well.     

Cu(II) Compounds with Pyrimidine-Based Chelating Ligands,Bridged by a Flexible Alkyl Spacer: Synthesis,Characterisation and X-Ray Structures of Methoxide-Bridged Dinuclear-Based Species

Abstract  The synthesis and full structural characterisation is described of 3 dinuclear-based Cu(II) compounds bridged by methoxide anions, and flexible linear bis(pyrimidine)-α,ω-diaminoalkane ligands. The structures are dinuclear based in all cases, in which the bis(pyrimidine)diaminoalkane ligand chelates to 2 Cu(II) ions in the same dinuclear unit (N–C–C–C–C–C–N linker), or to two different dinuclear units (with the short N–C–C–N linker), thereby generating a polymeric chain. The magnetic exchange in the compounds is dominated by the alkoxido-bridged ligands, which generate a very strong antiferromagnetic coupling between the Cu(II) ions, resulting in diamagnetism at room temperature and below, and EPR silent behaviour. Index Abstract  Dinuclear-based Cu(II) compounds with pyrimidine-based chelating ligands flexible linear bis(pyrimidine)-α,ω-diaminoalkane ligands are described, bridged by methoxide anions. The structures are dinuclear based in all cases, with the ligand chelating to 2 Cu(II) ions in the same dinuclear unit (N–C–C–C–C–C–N linker), or to 2 different dinuclear units (with short N–C–C–N linkers). The very strong antiferromagnetic magnetic exchange in all compounds is caused by the alkoxido-bridged ligands. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.