Meter-Scale Thin-Walled Structure with Lattice Infill for Fuel Tank Supporting Component of Satellite:Multiscale Design and Experimental Verification

Lightweight thin-walled structures with lattice infill are widely desired in satellite for their high stiffness-to-weight ratio and superior buckling strength resulting fromthe sandwich effect.Such structures can be fabricated bymetallic additive manufacturing technique,such as selective laser melting(SLM).However,the maximum dimensions of actual structures are usually in a sub-meter scale,which results in restrictions on their appliance in aerospace and other fields.In this work,a meter-scale thin-walled structure with lattice infill is designed for the fuel tank supporting component of the satellite by integrating a self-supporting lattice into the thickness optimization of the thin-wall.The designed structure is fabricated by SLM of AlSi10Mg and cold metal transfer welding technique.Quasi-static mechanical tests and vibration tests are both conducted to verify the mechanical strength of the designed large-scale lattice thin-walled structure.The experimental results indicate that themeter-scale thin-walled structure with lattice infill could meet the dimension and lightweight requirements of most spacecrafts.

Causal associations of brain structure with bone mineral density:a large-scale genetic correlation study

In this study,we aimed to investigate the causal associations of brain structure with bone mineral density(BMD).Based on the genome-wide association study(GWAS)summary statistics of 1325 brain imaging-derived phenotypes(BIDPs)of brain structure from the UK Biobank and GWAS summary datasets of 5 BMD locations,including the total body,femoral neck,lumbar spine,forearm,and heel from the GEFOS Consortium,linkage disequilibrium score regression(LDSC)was conducted to determine the genetic correlations,and Mendelian randomization(MR)was then performed to explore the causal relationship between the BIDPs and BMD.Several sensitivity analyses were performed to verify the strength and stability of the present MR outcomes.To increase confidence in our findings,we also performed confirmatory MR between BIDPs and osteoporosis.LDSC revealed that 1.93%of BIDPs,with a false discovery rate(FDR)<0.01,were genetically correlated with BMD.Additionally,we observed that 1.31%of BIDPs exhibited a significant causal relationship with BMD(FDR<0.01)through MR.Both the LDSC and MR results demonstrated that the BIDPs“Volume of normalized brain,”“Volume of gray matter in Left Inferior Frontal Gyrus,pars opercularis,”“Volume of Estimated Total Intra Cranial”and“Volume-ratio of brain segmentation/estimated total intracranial”had strong associations with BMD.Interestingly,our results showed that more left BIDPs were causally associated with BMD,especially within and around the left frontal region.In conclusion,a part of the brain structure causally influences BMD,which may provide important perspectives for the prevention of osteoporosis and offer valuable insights for further research on the brain-bone axis.

A Footpad Structure with Reusable Energy Absorption Capability for Deep Space Exploration Lander:Design and Analysis

The footpad structure of a deep space exploration lander is a critical system that makes the initial contact with the ground,and thereby plays a crucial role in determining the stability and energy absorption characteristics during the impact process.The conventional footpad is typically designed with an aluminum honeycomb structure that dissipates energy through plastic deformation.Nevertheless,its effectiveness in providing cushioning and energy absorption becomes significantly compromised when the structure is crushed,rendering it unusable for reusable landers in the future.This study presents a methodology for designing and evaluating structural energy absorption systems incorporating recoverable strain constraints of shape memory alloys(SMA).The topological configuration of the energy absorbing structure is derived using an equivalent static load method(ESL),and three lightweight footpad designs featuring honeycomb-like Ni-Ti shape memory alloys structures and having variable stiffness skins are proposed.To verify the accuracy of the numerical modelling,a honeycomb-like structure subjected to compression load is modeled and then compared with experimental results.Moreover,the influence of the configurations and thickness distribution of the proposed structures on their energy absorption performance is comprehensively evaluated using finite element simulations.The results demonstrate that the proposed design approach effectively regulates the strain threshold to maintain the SMA within the constraint of maximum recoverable strain,resulting in a structural energy absorption capacity of 362 J/kg with a crushing force efficiency greater than 63%.

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.

Approximations by Ideal Minimal Structure with Chemical Application

The theory of rough set represents a non-statistical methodology for analyzing ambiguity and imprecise information.It can be characterized by two crisp sets,named the upper and lower approximations that are used to determine the boundary region and accurate measure of any subset.This article endeavors to achieve the best approximation and the highest accuracy degree by using the minimal structure approximation space MSAS via ideal J.The novel approach(indicated by JMSAS)modifies the approximation space to diminish the bound-ary region and enhance the measure of accuracy.The suggested method is more accurate than Pawlak’s and EL-Sharkasy techniques.Via illustrated examples,several remarkable results using these notions are obtained and some of their properties are established.Several sorts of near open(resp.closed)sets based on JMSAS are studied.Furthermore,the connections between these assorted kinds of near-open sets in JMSAS are deduced.The advantages and disadvan-tages of the proposed approach compared to previous ones are examined.An algorithm using MATLAB and a framework for decision-making problems are verified.Finally,the chemical application for the classification of amino acids(AAs)is treated to highlight the significance of applying the suggested approximation.

Narrow and Dual-Band Tunable Absorption of a Composite Structure with a Graphene Metasurface

A tunable absorber, composed of a graphene ribbon on two layers of TiO2-Au between two slabs of dielectric material all on a metal substrate, is designed and numerically investigated. The absorption of the composite structure varies with the geometrical parameters of the structure and the physical parameters of graphene at mid-infrared frequencies. The numerical simulation shows that a near-perfect absorption with single and alum bands can be achieved in a certain frequency range. We also analyze the electric and surface current distributions to study the dual-band absorber. The results show that the absorber can be tuned by the chemical potential and electron phonon relaxation time of graphene, and electromagnetically induced transparency phenomenon can be obtained. The results of this study may be beneficial in the fields of infrared communication, perfect absorbers, sensors and filters.

ICM method for topology optimization of multimaterial continuum structure with displacement constraint

A new topology optimization method is formulated for lightweight design of multimaterial structures, using the independent continuous mapping (ICM) method to minimize the weight with a prescribed nodal displacement constraint. Two types of independent topological variable are used to identify the presence of elements and select the material for each phase, to realize the interpolations of the element stiffness matrix and total weight. Furthermore, an explicit expression for the optimized formulation is derived, using approximations of the displacement and weight given by first- and second-order Taylor expansions. The optimization problem is thereby transformed into a standard quadratic programming problem that can be solved using a sequential quadratic programming approach. The feasibility and effectiveness of the proposed multimaterial topology optimization method are demonstrated by determining the best load transfer path for four numerical examples. The results reveal that the topologically optimized configuration of the multimaterial structure varies with the material properties, load conditions, and constraint. Firstly, the weight of the optimized multimaterial structure is found to be lower than that composed of a single material. Secondly, under the precondition of a displacement constraint, the weight of the topologically optimized multimaterial structure decreases as the displacement constraint value is increased. Finally, the topologically optimized multimaterial structures differ depending on the elastic modulus of the materials. Besides, the established optimization formulation is more reliable and suitable for use in practical engineering applications with structural performance parameters as constraint.

TOPOLOGY OPTIMIZATION OF TRUSS STRUCTURE WITH FUNDAMENTAL FREQUENCY AND FREQUENCY DOMAIN DYNAMIC RESPONSE CONSTRAINTS

In this paper, adaptive genetic algorithm （AGA） is applied to topology optimization of truss structure with frequency domain excitations. The optimization constraints include fundamental frequency, displacement responses under force excitations and acceleration responses under foundation acceleration excitations. The roulette wheel selection operator, adaptive crossover and mutation operators are used as genetic operators. Some heuristic strategies are put forward to direct the deletion of the extra bars and nodes on truss structures. Three examples demonstrate that the proposed method can yield the optimum structure form and the lightest weight of the given ground structure while satisfying dynamic response constraints.

Learning Bayesian network structure with immune algorithm

Finding out reasonable structures from bulky data is one of the difficulties in modeling of Bayesian network （BN）, which is also necessary in promoting the application of BN. This pa- per proposes an immune algorithm based method （BN-IA） for the learning of the BN structure with the idea of vaccination. Further- more, the methods on how to extract the effective vaccines from local optimal structure and root nodes are also described in details. Finally, the simulation studies are implemented with the helicopter convertor BN model and the car start BN model. The comparison results show that the proposed vaccines and the BN-IA can learn the BN structure effectively and efficiently.

Imaging shallow structure with active-source surface wave signal recorded by distributed acoustic sensing arrays

Distributed acoustic sensing(DAS) is one recently developed seismic acquisition technique that is based on fiber-optic sensing. DAS provides dense spatial spacing that is useful to image shallow structure with surface waves.To test the feasibility of DAS in shallow structure imaging,the PoroTomo team conducted a DAS experiment with the vibroseis truck T-Rex in Brady’s Hot Springs, Nevada, USA.The Rayleigh waves excited by the vertical mode of the vibroseis truck were analyzed with the Multichannel Analysis of Surface Waves(MASW) method. Phase velocities between5 and 20 Hz were successfully extracted for one segment of cable and were employed to build a shear-wave velocity model for the top 50 meters. The dispersion curves obtained with DAS agree well with the ones extracted from co-located geophones data and from the passive source Noise Correlation Functions(NCF). Comparing to the co-located geophone array, the higher sensor density that DAS arrays provides help reducing aliasing in dispersion analysis, and separating different surface wave modes. This study demonstrates the feasibility and advantage of DAS in imaging shallow structure with surface waves.

Hydraulic Design Method of Wave Dissipating Structure with Partially Perforated Front Wall

Based on the matching conditions of different fluid regions, the eigenfunction expansion method is used to develop a theoretical formula for wave reflection in front of the perforated structure with a partially slit front wall. The accuracy of the solution is verified by comparing the numerical results with experimental data. In addition, a new hydraulic design method is developed by derivation of the theoretical formula with respect to the porosity of the slit wall, and the results of this design method is drafted for harbour engineers to use.

Damage Detection of Composite Material Intelligent Structure with a New Photoelectric System

A kind of photoelectric system that is suitable to measuring and to testing the damage of the composite material intelligent structure was presented. It can measure the degree of damage of the composite intelligent structure and it also can tell us the damage position in the structure. This system consists of two parts ： software and hardware. Experiments of the damage detection and the analysis of the composite material structure with the photoelectric system were performed, and a series of damage detection experiments was conducted. The results prove that the performance of the system is well and the effects of the measure and test are evident. Through all the experiments, the damage detection technology and test system are approved to be real-time, effective and reliable in the damage detection of the composite intelligent structure.

Experimental study on anti-penetration mechanism of bolted composite protective structure with limited span under impact of low-velocity projectile

In order to study the influence of the bolt joint mode on low-velocity projectiles penetrating the composite protective structure,two bolt joint models which connect the composite target to the fixed frame were designed,the ballistic test of the bolted composite protective structure with limited span was carried out,and the bearing and failure characteristics of the bolted region,as well as the energy dissipation of each part of the structure,were analyzed.The results show that in the condition of lowvelocity impact,there are three failure modes for the bolted composite protective structure subjected to projectile penetration,including failure of the impact point of the composite target,failure of protective structure connecting components and failure of the holes in the bolted region of the composite target;the failure mode of bolt holes in the bolted region has a great influence on the protection performance,and the allowable value of the bearing capacity of the bolted region depends on the sum of the minimum failure load in the failure modes and the friction force;shear-out failure occurring in the bolt holes in the bolted region exerts the greatest effect on ballistic performance,which should be avoided;When simultaneous failure occurs in the bolted region and the free deformation region of the composite protective structure,the energy absorption per unit surface density of the composite protective structure reaches the maximum,which can give full play to its anti-penetration efficiency.

Study of crustal structure with S-wave data from Maqen-Jingbian profile

D crustal velocity structure and vP/vS are obtained by processing and interpretation of S-wave data from Maqen-Jingbian deep seismic sounding (DSS) profile. The result shows that there exist obvious differences in 2-D S-wave velocity structure and vP/vS ratio structure along the profile. The S-wave velocities are low and vP/vS ratio is high for the western section of the profile and Haiyuan region, while they are normal for the middle and eastern sections. The changes in lithologic characters of two major anomalous zones are discussed according to lateral variation of S-wave velocity structure and vP/vS ratio structure. It is concluded that the development and occurrence of the Haiyuan strong earthquake is not only related to tectonic activities, but also to lithologic characters of the region.

Hydrogen etching induced hierarchical meso/micro-pore structure with increased active density to boost ORR performance of Fe-N-C catalyst

Rational regulation on pore structure and active site density plays critical roles in enhancing the performance of Fe-N-C catalysts. As the microporous structure of the carbon substrate is generally regarded as the active site hosts, its hostility to electron/mass transfer could lead to the incomplete fulfillment of the catalytic activity. Besides, the formation of inactive metallic Fe particles during the conventional catalyst synthesis could also decrease the active site density and complicate the identification of real active site. Herein, we developed a facial hydrogen etching methodology to yield single site Fe-N-C catalysts featured with micro/mesoporous hierarchical structure. The hydrogen concentration in pyrolysis process was designated to effectively regulate the pore structure and active site density of the resulted catalysts.The optimized sample achieves excellent ORR catalytic performance with an ultralow H2O2 yield(1%)and superb stability over 10,000 cycles. Our finding provides new thoughts for the rational design of hierarchically porous carbon-based materials and highly promising non-precious metal ORR catalysts.

Fe-doped CoP core–shell structure with open cages as efficient electrocatalyst for oxygen evolution

Developing a facile approach based on transition metal-based Prussian blue(PB)and its analogues(PBAs)with core-shell nanostructure is a very promising choice for constructing cost-effective electrocatalysts for oxygen evolution reaction(OER).Herein,a bimetallic core-shell structure with open cages of Fe-doped CoP(Fe-CoP cage)has been synthesized using CoFe-PBA cage-4 as precursor through a facile hydrothermal method and following phosphating process.Interestingly,there is an open hole in each face center of Fe-CoP cage,which suggests the more exposure of active sites for OER.Electrochemical measurements show that Fe-CoP cage can afford a current density of 10 mA cm-2 at a low overpotential(300 mV),which is better than that of RuO2.The excellent performance can be attributed to Fe doping composition and unique open-cage core-shell structure.The synergistic effect derived from bimetallic active for OER has been discussed.And its great catalytic stability has been evaluated via 1000 cycles of CV and chronoamperometry measurement.This work provides a potential method to design multiple transitional metal-doping electrocatalysts with complex framework derived from PBAs for water splitting.

Analysis of Wave Height in Front of a Wave Absorbing Structure with Rubble Foundation

Wave absorbing structures have been widely applied in many countries. In the present paper, the wave heights in front of a vertical wave absorbing structure with rubble foundation as well as in the wave chamber of the structure are analysed using an approximative calculation method, and the dissipating effect of the structure is verified. On the basis of the results of regular waves, the relative wave heights of irregular waves in front of the wave absorbing structure as well as in the chamber have also been analysed.

Study on interface failure of shape memory alloy(SMA)reinforced smart structure with damages

Shape memory alloy （SMA） reinforced smart structure can be used to make structural shape and strength selfadapted and structural damage self-restrained. Although SMA smart structures without damages were extensively studied, researches on SMA smart structures with damages have rarely been reported thus far. In this paper, thermo-mechanical behaviors of SMA fiber reinforced smart structures with damages are analyzed through a shear lag model and the variational principle, Mathematical expressions of the meso-displacement field and the stress-strain field of a typical element with damages are obtained, and a failure criterion for interface failure between SMA fibers and matrix is established, which is applied to an example. Results presented herein may provide a theoretical foundation for further studies on integrity of SMA smart structures.

A Surface Plasmon Polariton Electro-Optic Switch Based on a Metal-Insulator-Metal Structure with a Strip Waveguide and Two Side-Coupled Cavities

We propose and numerically simulate a nanoscale electro-optic (EO) switch based on a metal-insulator-metal structure composed of a strip waveguide and two side-coupled cavities filled with an EO material of 4-dimethylamino-N-methyl-4-stilbazolium tosylate,using the finite difference time domain method.It is found that the structure can be operated as an EO switch at a wavelength of 945nm,with a modulation depth of 27dB,a half-wave voltage of 5.3 V and a switching time of about 50 ps.

Seismic Response Analysis of Structure with Cooperation of Laminated Rubber Bearing and Wind-Resistant Support

The purpose is to study the seismic reduction effect of an isolated structure,with wind-resistant bearings( WRBs) setting on its isolation layer to withstand great wind load,and the working mechanism of the WRB. In this paper,two isolation models with /without WRBs,taking an actual engineering as the background,are established in the finite element software ETABS. The one with WRBs has horizontal damping coefficient less than 0. 40 while the other between 0. 40 and 0. 53. WRBs are simulated by Plastic 1element and the collaborative work between them and isolation layer is described by a mechanical model. Time history analysis is conducted on the models to compare their responses under earthquake excitations. Results show that the one with WRBs,but less lead-rubber bearings( LRBs),has better damping effect than the other,although they both can meet wind requirements. It is also shown that under normal conditions and small earthquakes,WRBs function well and the isolation layer will not yield; under moderate earthquakes,WRBs will yield and be destroyed to stop functioning but without affecting the damping effect of the upper structure.Additionally, the total yield shear force provided by LRBs is proposed to be close to the standard value of wind load.