Hierarchical model updating strategy of complex assembled structures with uncorrelated dynamic modes

In structural simulation and design,an accurate computational model directly determines the effectiveness of performance evaluation.To establish a high-fidelity dynamic model of a complex assembled structure,a Hierarchical Model Updating Strategy(HMUS)is developed for Finite Element(FE)model updating with regard to uncorrelated modes.The principle of HMUS is first elaborated by integrating hierarchical modeling concept,model updating technology with proper uncorrelated mode treatment,and parametric modeling.In the developed strategy,the correct correlated mode pairs amongst the uncorrelated modes are identified by an error minimization procedure.The proposed updating technique is validated by the dynamic FE model updating of a simple fixed–fixed beam.The proposed HMUS is then applied to the FE model updating of an aeroengine stator system(casings)to demonstrate its effectiveness.Our studies reveal that(A)parametric modeling technique is able to build an efficient equivalent model by simplifying complex structure in geometry while ensuring the consistency of mechanical characteristics;(B)the developed model updating technique efficiently processes the uncorrelated modes and precisely identifies correct Correlated Mode Pairs(CMPs)between FE model and experiment;(C)the proposed HMUS is accurate and efficient in the FE model updating of complex assembled structures such as aeroengine casings with large-scale model,complex geometry,high-nonlinearity and numerous parameters;(D)it is appropriate to update a complex structural FE model parameterized.The efforts of this study provide an efficient updating strategy for the dynamic model updating of complex assembled structures with experimental test data,which is promising to promote the precision and feasibility of simulation-based design optimization and performance evaluation of complex structures.

Design methods of rhombic tensegrity structures

As a special type of novel flexible structures, tensegrity holds promise for many potential applications in such fields as materials science, biomechanics, civil and aerospace engineering. Rhombic systems are an important class of tensegrity structures, in which each bar constitutes the longest diagonal of a rhombus of four strings. In this paper, we address the design methods of rhombic structures based on the idea that many tensegrity structures can be constructed by assembling one-bar elementary cells. By analyzing the properties of rhombic cells, we first develop two novel schemes, namely, direct enumeration scheme and cell-substitution scheme. In addition, a facile and efficient method is presented to integrate several rhombic systems into a larger tensegrity structure. To illustrate the applications of these methods, some novel rhombic tensegrity structures are constructed.

Response Spectrum Analysis of 7-story Assembled Frame Structure with Energy Dissipation System

Viscoelastic damper is an effective passive damping device,which can reduce the seismic response of the structure by increasing the damping and dissipating the vibration energy of structures.It has a wide application prospect in actual structural vibration control because of simple device and economical material.In view of the poor seismic behaviors of assembled frame structure connections,various energy dissipation devices are proposed to improve the seismic performance.The finite element numerical analysis method is adopted to analyze relevant energy dissipation structural parameters.The response spectrum of a 7-story assembled frame structure combined the ordinary steel support,ordinary viscoelastic damper,and viscoelastic damper with displacement amplification device is analyzed.The analysis results show that the mechanical behavior of assembled frame structure with ordinary steel supports are not significantly different from those without energy dissipation devices.The assembled frame structure with viscoelastic damper has better seismic performance and energy dissipation,especially for the viscoelastic damper with displacement amplification devices.The maximum value of inter-story displacement angle decreases by 32.24%;the maximum floor displacement decreases by 31.91%,and the base shear decreases by 13.62%compared with the assembled frame structures without energy dissipation devices.The results show that the seismic fortification ability of the structure is significantly improved,and the overall structure is more uniformly stressed.The damping structure with viscoelastic damper mainly reduces the dynamic response of the structure by increasing the damping coefficient,rather than by changing the natural vibration period of the structure.This paper provides an effective theoretical basis and reference for improving the energy dissipation system and the seismic performance of assembled frame structures.

Optimization Design of an Embedded Multi-Cell Thin-Walled Energy Absorption Structures with Local Surface Nanocrystallization

Bymeans of the local surface nanocrystallization that enables to change the material on local positions,an innovative embedded multi-cell(EMC)thin-walled energy absorption structures with local surface nanocrystallization is proposed in this paper.The local surface nanacrystallization stripes are regarded as the moving morphable components in the domain for optimal design.Results reveal that after optimizing the local surface nanocrystallization layout,the specific energy absorption(SEA)is increased by 50.78%compared with the untreated counterpart.Besides,in contrast with the optimized 4-cell structure,the SEA of the nanocrystallized embedded 9-cell structure is further enhanced by 27.68%,in contrast with the 9-cell structure,the SEA of the nanocrystallized embedded clapboard type 9-cell structure is enhanced by 3.61%.Thismethod provides a guidance for the design of newenergy absorption devices.

Analysis of Soundproof Technology of Assembled Steel Structure Houses

The problem of noise has always been highlighted in assembled steel structure houses.Therefore,it is necessary to use effective soundproof measures where steel beams intersect with the reserved line pipe openings,doors,windows,elevator shafts,and other locations.In this paper,we will investigate the areas with subpar soundproof performance in an assembled steel structure residential project and propose suitable noise control measures to address this issue.

Integrated Assembly Structure Design Within Concurrent Engineering

Taking a microwave product as an example, a system of integrated assembly structure design is presented. Getting design constraints from the upstream design section through product data management(PDM), the system generates the assembly scheme using the case? based method, then assigns the design requirements into each component of the assembly. The detail design for each component can be performed under these design constraints. In order to practise concurrent design, the system sends the final design result to the upstream section and downstream section through PDM to achieve information sharing and integration.

Ordered mesoporous Cu-ZnO-Al_2O_3 adsorbents for reactive adsorption desulfurization with enhanced sulfur saturation capacity

To enhance sulfur adsorption and reactive activity, ordered mesoporous Cu-ZnO-Al2O3 adsorbents were prepared by a novel one-pot evaporation-induced self-assembly strategy using P123 as a structure-directing agent and ethanol as the solvent for reactive adsorption desulfurization. The metal oxide precursor molecules around P123 micellized, and self-assembly simultaneously occurred during evaporation from an ethanol solution at 60 °C, leading to the formation of the p6 mm hexagonal symmetry mesoporous structure. Characterization results prove that the Cu-ZnO-Al2O3 adsorbents possess an ordered mesoporous structure with high thermal stability, large surface area（386–226 m2/g）, large pore volume（0.60–0.46 cm3/g）, and good dispersion of ZnO and Cu, which is beneficial for transforming S-compounds to ZnO. The sulfur saturation capacity of the ordered-mesoporous-structure Cu-ZnO-Al2O3 adsorbents is larger（49.4 mg/g） than that of the unordered mesoporous structure（13.5 mg/g）.

Review on multi-dimensional assembled S-scheme heterojunction photocatalysts

S-scheme heterostructure photocatalysts utilize the synergistic and superposition effects of materials,ef-fectively separating electrons and holes,maintaining strong redox capacity,and addressing issues en-countered by current photocatalytic reactions.This review explores the origins and unique benefits of S-scheme heterojunctions.Specifically,we summarized and discussed the effects of different dimensions of semiconductors constituting S-scheme heterojunctions and the similarities and differences in elec-tron transfer processes when constructing heterojunctions.Additionally,we analyzed several methods for proving the formation of S-scheme heterojunctions and the electron transfer process,both directly and indirectly.Finally,we review the applications of S-scheme heterojunctions in various fields of photo-catalysis,including photocatalytic water splitting,pollution degradation,CO_(2) reduction and other related photocatalytic applications.Our hope is that this review will provide an essential reference for the devel-opment and application of S-scheme heterojunction photocatalysis.

Ag_(2)S Quantum Dots Decorated on Porous Cubic-CdS Nanosheets-assembled Flowers for Photocatalytic CO_(2)Reduction

The production of renewable fossil fuels such as CH_(4) and CO by photocatalytic CO_(2)reduction has attracted more and more attention.However,single photocatalyst is less efficient for photocatalytic reduction of CO_(2)due to the fast recombination of photogenerated electron pairs.Herein,we successfully prepare CdS-Ag_(2)S composite by assembling the Ag_(2)S QDs cocatalyst on the surface of CdS nanosheet-assembled flower through oil-bath solvothermal method.This composite is prepared through a simple self-assembly strategy using cadmium chloride,ammonia and thiourea as precursors of the CdS nanosheet-assembled flower and silver nitrate and 3-mercaptopropionic acid as the precursors of Ag_(2)S QDs.The average diameter of Ag_(2)S QDs is apparently 6.0 nm.The light absorption edge of the composite is at around 560 nm,with the corresponding band gap at 2.14 eV.The CdS-Ag_(2)S QDs composite with 5 wt%Ag_(2)S QDs loaded achieves CO evolution rate of 16.6μmol·g^(-1)·h^(-1)without noble-metal cocatalysts.This strengthened photocatalytic performance and photocatalytic stability were attributed to the energy band broadening of Ag_(2)S QDs caused by quantum size effect and the large specific surface area due to the assembled flower.The mechanism underlying the enhanced photocatalytic CO_(2)reduction activity is further proposed.This study demonstrates that semiconductor-based quantum dots are strong candidates for excellent cocatalysts in photocatalysis.

Facile and Convenient Fabrication of Color-controlled Colloidal Magnetically Assembled Photonic Crystals

A facile, convenient and flexible method to tune the structural color of the colloidal magnetically assembled photonic crystals（CMA-PCs） was proposed. The mechanism to tune structural color could be attributed to the significant influence of the surfactant sodium dodecyl sulfate（SDS） concentration on the particle size, especially on the magnetite content of the superparamagnetic composite nanoparticles（MCNPs）. By adjusting SDS concentra- tion in miniemulsion polymerization of MCNPs, CMA-PCs with desired diffraction colors could be obtained.

Robotic compliant assembly for complex-shaped composite aircraft frame based on Gaussian process considering uncertainties

Robots are finding increasing application in aircraft composite structure assembly due to their flexibility and the growing demand of aircraft manufacturers for high production rates.The contact force of the composite frame in a robotic assembly of the aircraft composite fuselage panel can hardly be controlled due to the multi-surface variable contact stiffness caused by compliance and complex shape with multiple mating surfaces.The paper proposes a robotic assembly system for the aircraft composite fuselage frame with a compliant contact force control strategy using the Gaussian process surrogate model.First,a robotic assembly system is introduced,and the global coordinate system transformation model is built.Then,a compliant force control architecture is designed to generate the desired output force.Subsequently,a Gaussian process surrogate model with uncertainties is utilized to model the complicated relationship between the robot’s output force and the normal contact force acting on the mating surface of the composite frame.Furthermore,an optimal contact force control strategy is implemented to improve the contact quality.Finally,an experiment demonstrates that the proposed methodology can ensure that the contact force on each surface is within the limit of the engineering specification and uniformly distributed,improving the quality compared to the traditional assembly process.

Fabrication of polymeric-Laponite composite hollow microspheres via LBL assembly

Hollow structure microspheres with composite polymeric-Laponite shells were prepared by electrostatic self-assembly of Laponite on the polymeric hollow microspheres in this work.The multilayer hydrophilic core/hydrophobic shell polymer latex particles containing carboxyl groups inside were first synthesized via seeded emulsion polymerization,followed by alkali treatment,generating polymeric hollow microspheres.Then,polyethyleneimine（PEI） and Laponite were alternately electrostatic adsorbed on the prepared polymeric hollow microspheres to form polymeric-Laponite composite hollow microspheres.It was indicated that the morphology of alkali-treated microspheres could be tuned through simply altering the dosage of alkali used in the post-treatment process.Along with the increasing of the coating layers,the zeta potential of microspheres absorbed PEI or Laponite approximately tended to be constant respectively,and the thickness of Laponite layer around the hollow microspheres increased clearly,getting more uniform and homogenous.Furthermore,the corresponding polymeric-Laponite hollow microspheres showed high pressure resistance ability compared to the polymeric hollow microspheres.

Layered and three-dimensional uranyl–organic assemblies with 4,4′-oxidiphthalic acid

Hydrothermal reactions of uranyl nitrate and 4,4＇-oxidiphthalic acid（H4L） resulted in the formation of three new uranyl-organic framework materials,namely（NH4）2[（UO2）3（L）2]·5H2O（1）,（NEt4）[（UO2）3（H2O）（L）（HL）]（2） and（UO2）7（H2O）2（phen）4（L）2（HL）2（3）（NEt4 = tetraethylammonium,phen = 1,10-phenanthroline）.These three structures all comprise common uranyl pentagonal bipyramids.In 1,UO7polyhedra are linked by hexadentate ligands to form a 3D framework with 1D channels,in which are located NH4^＋ ions and water molecules.While in 2,the organic ligands adopt pentadentate and hexadentate coordination modes,ligating UO7 units to create a layered structure with channels filled by NEt4^＋ ions.For 3,uranyl square bipyramids are also accommodated together with pentagonal bipyramids,which are linked by tetradentate carboxylate ligands to produce the layered assembly.Phen molecules also coordinate to the uranyl centers to build up the structure.Luminescent studies indicate that 2 and 3 exhibit the characteristic uranyl emission.

Recent progress of sugar amino acids: Synthetic strategies and applications as glycomimetics and peptidomimetics

In order to meet the increasing demands for the development of large varieties of new molecules for discovering new drugs and materials, organic chemists are developing many novel multifunctional building blocks, which are assembled rationally to create ‘nature-like＇ and yet unnatural organic molecules with well-defined structures and useful properties. Sugar amino acids（SAAs）, the carbohydrate derivatives bearing both amino and carboxylic acid functional groups, are important ones of these multifunctional building blocks, which can be used to create novel materials with potential applications as glycomimetics and peptidomimetics. This review will focus on recent synthetic strategies of SAAs and their applications in creating large number of structurally diverse glycomimetics and peptidomimetics.

Structural modulation and assembling of metal halide perovskites for solar cells and light-emitting diodes

Metal halide perovskites possess appealing optoelectronic properties and have been widely applied for solar energy harvesting and light emitting.Although perovskite solar cells(PeSCs)and perovskite light-emitting diodes(PeLEDs)have been developed rapidly in recent years,there are still no universal rules for the selection of perovskites to achieve high-performance optoelectronic devices.In this review,the working mechanisms of PeSCs and PeLEDs are first demonstrated with the discussion on the factors which determine the device performance.We then examine the optoelectronic properties of perovskites with structures modulated from 3D,2D,1D to 0D,and analyze the corresponding structure-property relationships in terms of photo-electric and electric-photo conversion processes.Based on the unique optoelectronic properties of structurally modulated perovskites,we put forward the concept of structural assembling engineering that integrate the merits of different types of perovskites within one matrix and elaborate their excellent properties for applications of both PeSCs and PeLEDs.Finally,we discuss the potential challenges and provide our perspectives on the structural assembling engineering of perovskites for future optoelectronic applications.

Assembly mechanisms and energy transfer pathways deciphered in the cryo-EM structure of spinach photosystem Ⅱ-LHCⅡ supercomplex

Funded by the National Natural Science Foundation of China(NSFC),Ministry of Science and Technology of China,and Chinese Academy of Sciences,ajoint team of three laboratories from the Institute of Biophysics of Chinese Academy of Sciences,led by Dr.Liu Zhenfeng(柳振峰),Dr.Zhang Xinzheng(章新政)and Dr.Li Mei(李梅)respectively,solved the structure of spinach photosystem II-LHCII supercom-