A Hybrid Level Set Optimization Design Method of Functionally Graded Cellular Structures Considering Connectivity

With the continuous advancement in topology optimization and additive manufacturing(AM)technology,the capability to fabricate functionally graded materials and intricate cellular structures with spatially varying microstructures has grown significantly.However,a critical challenge is encountered in the design of these structures–the absence of robust interface connections between adjacent microstructures,potentially resulting in diminished efficiency or macroscopic failure.A Hybrid Level Set Method(HLSM)is proposed,specifically designed to enhance connectivity among non-uniform microstructures,contributing to the design of functionally graded cellular structures.The HLSM introduces a pioneering algorithm for effectively blending heterogeneous microstructure interfaces.Initially,an interpolation algorithm is presented to construct transition microstructures seamlessly connected on both sides.Subsequently,the algorithm enables the morphing of non-uniform unit cells to seamlessly adapt to interconnected adjacent microstructures.The method,seamlessly integrated into a multi-scale topology optimization framework using the level set method,exhibits its efficacy through numerical examples,showcasing its prowess in optimizing 2D and 3D functionally graded materials(FGM)and multi-scale topology optimization.In essence,the pressing issue of interface connections in complex structure design is not only addressed but also a robust methodology is introduced,substantiated by numerical evidence,advancing optimization capabilities in the realm of functionally graded materials and cellular structures.

Structural and functional connectivity of the whole brain and subnetworks in individuals with mild traumatic brain injury:predictors of patient prognosis

Patients with mild traumatic brain injury have a diverse clinical presentation,and the underlying pathophysiology remains poorly understood.Magnetic resonance imaging is a non-invasive technique that has been widely utilized to investigate neuro biological markers after mild traumatic brain injury.This approach has emerged as a promising tool for investigating the pathogenesis of mild traumatic brain injury.G raph theory is a quantitative method of analyzing complex networks that has been widely used to study changes in brain structure and function.However,most previous mild traumatic brain injury studies using graph theory have focused on specific populations,with limited exploration of simultaneous abnormalities in structural and functional connectivity.Given that mild traumatic brain injury is the most common type of traumatic brain injury encounte red in clinical practice,further investigation of the patient characteristics and evolution of structural and functional connectivity is critical.In the present study,we explored whether abnormal structural and functional connectivity in the acute phase could serve as indicators of longitudinal changes in imaging data and cognitive function in patients with mild traumatic brain injury.In this longitudinal study,we enrolled 46 patients with mild traumatic brain injury who were assessed within 2 wee ks of injury,as well as 36 healthy controls.Resting-state functional magnetic resonance imaging and diffusion-weighted imaging data were acquired for graph theoretical network analysis.In the acute phase,patients with mild traumatic brain injury demonstrated reduced structural connectivity in the dorsal attention network.More than 3 months of followup data revealed signs of recovery in structural and functional connectivity,as well as cognitive function,in 22 out of the 46 patients.Furthermore,better cognitive function was associated with more efficient networks.Finally,our data indicated that small-worldness in the acute stage could serve as a predictor of longitudinal changes in connectivity in patients with mild traumatic brain injury.These findings highlight the importance of integrating structural and functional connectivity in unde rstanding the occurrence and evolution of mild traumatic brain injury.Additionally,exploratory analysis based on subnetworks could serve a predictive function in the prognosis of patients with mild traumatic brain injury.

Multiscale Characteristics and Connection Mechanisms of Attraction Networks:A Trajectory Data Mining Approach Leveraging Geotagged Data

Urban tourism is considered a complex system,and multiscale exploration of the organizational patterns of attraction networks has become a topical issue in urban tourism,so exploring the multiscale characteristics and connection mechanisms of attraction networks is important for understanding the linkages between attractions and even the future destination planning.This paper uses geotagging data to compare the links between attractions in Beijing,China during four different periods:the pre-Olympic period(2004–2007),the Olympic Games and subsequent‘heat period’(2008–2013),the post-Olympic period(2014–2019),and the COVID-19(Corona Virus Disease 2019)pandemic period(2020–2021).The aim is to better understand the evolution and patterns of attraction networks at different scales in Beijing and to provide insights for tourism planning in the destination.The results show that the macro,meso-,and microscales network characteristics of attraction networks have inherent logical relationships that can explain the commonalities and differences in the development process of tourism networks.The macroscale attraction network degree Matthew effect is significant in the four different periods and exhibits a morphological monocentric structure,suggesting that new entrants are more likely to be associated with attractions that already have high value.The mesoscale links attractions according to the common purpose of tourists,and the results of the community segmentation of the attraction networks in the four different periods suggest that the functional polycentric structure describes their clustering effect,and the weak links between clusters result from attractions bound by incomplete information and distance,and the functional polycentric structure with a generally more efficient network of clusters.The pattern structure at the microscale reveals the topological transformation relationship of the regional collaboration pattern,and the attraction network structure in the four different periods has a very similar importance profile structure suggesting that the attraction network has the same construction rules and evolution mechanism,which aids in understanding the attraction network pattern at both macro and micro scales.Important approaches and practical implications for planners and managers are presented.

Structure optimization of connection frames based on frequency sensitivity in macro-micro motion platforms

High-performance connection frames are of great significance for ultra-high acceleration and ultra-precision positioning in macro-micro motion platforms. This paper first takes the connection frame as a research object,builds a finite element model(FEM) of the natural frequency of the frame, and then verifies the correctness of this model. The frequency sensitivity method is then used to perturb the structural parameters of the FEM of the connection frame, and the sensitivities of the first-order natural frequency and mass of the corresponding structural parameters are obtained by calculation and analysis. The design variables are also determined. The natural frequency is used as the optimization objective, and the design parameters and mass of the connection frame are constrained. The structural parameters of the connecting frame are obtained through optimization, and the model is built and verified by experiments. The results show that the first-order natural frequency of the connecting frame is effectively improved by the frequency sensitivity method, avoids resonance between the connecting frame and the voice coil motor, and realizes the lightweight design of the connection frame. This research provides a reliable basis for the stable operation and ultra-precision positioning of ultra-high acceleration macro-motion platforms.

The dynamic response of a high-density polyethylene slow-release structure under launching overload

Based on the 60 mm artillery grenade,a slow-release structure was designed to reduce the severity of ammunitions response to accidental thermal stimulation and improve the thermal stability of ammunitions.The slow-release structure was made of high-density polyethylene(HDPE) and connected the fuse and the projectile body through internal and external threads.To study the safety of the slowrelease structure under artillery launching overload,mechanical analysis of the slow-release structure was simulated via finite element analysis(FEA).The impacts of various factors(e.g.,fuse mass,number of threads,and nominal diameter of internal threads of the slow-release structure) on the connection strength of the slow-release structure were studied.A strength-prediction model based on the fuse mass and internal thread parameters was established by fitting the maximum effective stress of the slowrelease structure.This led to good prediction results.In conclusion,this study provides references and theoretical support for the design of thermal protection structures insensitive to ammunition.

Structural Connectivity Enhanced Anisotropic 3D Network for Brain Midline Delineation

Brain midline delineation can facilitate the clinical evaluation of brain midline shift,which has a pivotal role in the diagnosis and prognosis of various brain pathology.However,there are still challenges for brain midline delineation:1)the largely deformed midline is hard to localize if mixed with severe cerebral hemorrhage;2)the predicted midlines of recent methods are not smooth and continuous which violates the structural priority.To overcome these challenges,we propose an anisotropic three dimensional(3D)network with context-aware refinement(A3D-CAR)for brain midline modeling.The proposed network fuses 3D context from different two dimensional(2D)slices through asymmetric context fusion.To exploit the elongated structure of the midline,an anisotropic block is designed to balance the difference between the adjacent pixels in the horizontal and vertical directions.For maintaining the structural priority of a brain midline,we present a novel 3D connectivity regular loss(3D CRL)to penalize the disconnectivity between nearby coordinates.Extensive experiments on the CQ dataset and one in-house dataset show that the proposed method outperforms three state-of-the-art methods on four evaluation metrics without excessive computational burden.

Formation and thermal stability of connected hard skeleton structure in ATX525 cast alloys

The formation and the thermal stability of a connected hard skeleton structure(CHSS) in the matrix of Mg-5Al-2Sn-5Ca(ATX525) alloy were investigated by using X-ray diffractometer, scanning electron microscopy, differential scanning calorimeter, creep tester and isothermal treatment method. The results indicated that the CHSS composed of Mg2(Al,Ca) and Al2 Ca intermetallics was formed into a typical eutectic structure and no obvious change occurred when the samples were isothermally treated at 250 °C for 96 h and 350 °C for 72 h, respectively. It became a chained structure when isothermally treated at 450 °C for 48 h. The dissolution and reconstruction processes, however, were observed for the CHSS when the processing temperature was up to 550 °C. The creep life at the stress-temperature condition of 50MPa/200°C for the alloy treated at 450 °C for 48 h was as high as 510 h, and the strain at creep time of 100 h was as low as 0.03%, which indicated that the present alloy has not only a good thermal stability, but also a better heat resistance.

Lightweight Technologies in Sustainable Architecture:The Importance of Connections in Disassembly

The aim of this paper is to investigate the role of lightweight structures and connections in the DfD(design for disassembly)framework.The construction sector is facing pressure to reduce its environmental impact,which has led to heightened interest in DfD as a strategy for transitioning from a linear“Cradle to Grave”economic model to a circular“Cradle to Cradle”model.At the social level,DfD’s technological and spatial flexibility provides opportunities for self-build and self-maintenance processes,which can decrease land consumption and reduce costs for both owners and tenants.In this context,lightweight structures and connections are crucial for enabling these processes.The methodology used for analysis involves breaking down three technological elements chosen from three different projects to evaluate ease of disassembly,flexibility,potential for reuse,and recyclability.As a result,this paper aims to promote the development of an abacus of existing technological solutions,to provide designers with a tool that can help them pursue DfD strategies.

Landscape structures of different rural landscape connectivity in typical plateau karst regions: Taking the Houzhai River area of Anshun City, Guizhou Province as an example

Landscape connectivity is important for energy and material flow in ecosystems as well as for the survival of species. The landscape structure influences and reflects the degree of landscape connectivity. In order to study the coupling relationship between landscape structure and connectivity and reveal the succession relationship between its structure and connectivity in the typical karst plateau area. The study analyzed the typical area of Houzhai River in Puding County, Anshun City, Guizhou Province, according to the landscape pattern index and probability landscape connectivity index. The results show:(1) The landscape structure of the study area A is mainly characterized by large patches and uniform distribution. The main land is woodland and cultivated land, and the overall landscape is low fragmentation.(2) The landscape structure of the study area B is mainly characterized by the clustering of a certain type of land cover and the uneven distribution of the patches, for example, cultivated land. Other types of patches are scatteredly distributed, and the overall landscape is highly fragmented.(3) The study area A, B in 100, 500, 1000, 2000, 3000, 5 distance thresholds of landscape connectivity were 1.55, 1.99, 2.26, 2.49, 2.58 and 0.02, 0.10, 0.15, 0.19, 0.20, respectively. The average landscape connectivity is 2. 18 and 0. 13, respectively. Study Area A has a higher degree of landscape connectivity than B. Landscape pattern indicators can represent the landscape structure and probability landscape connectivity index calculates the landscape connectivity in the study area. The results of the study can provide a basis for ecological restoration of plateau karst regions and well-oriented rural development planning.

Connecting parameters optimization on unsymmetrical twin-tower structure linked by sky-bridge

Based on a simplified 3-DOF model of twin-tower structure linked by a sky-bridge,the frequency response functions,the displacement power spectral density(PSD)functions,and the time-averaged total vibration energy were derived,by assuming the white noise as the earthquake excitation.The effects of connecting parameters,such as linking stiffness ratio and linking damping ratio,on the structural vibration responses were then studied,and the optimal connecting parameters were obtained to minimize the vibration energy of either the independent monomer tower or the integral structure.The influences of sky-bridge elevation position on the optimal connecting parameters were also discussed.Finally,the distribution characteristics of the top displacement PSD and the structural responses,excited by El Centro,Taft and artificial waves,were compared in both frequency and time domain.It is found that the connecting parameters at either end of connection interactively affect the responses of the towers.The optimal connecting parameters can greatly improve the damping connections on their seismic reduction effectiveness,but are unable to reduce the seismic responses of the towers to the best extent simultaneously.It is also indicated that the optimal connecting parameters derived from the simplified 3-DOF model are applicable for two multi-story structures linked by a sky-bridge with dampers.The seismic reduction effectiveness obtained varies from 0.3 to 1.0 with different sky-bridge mass ratio.The displacement responses of the example structures are reduced by approximately 22% with sky-bridge connections.

A Quantitative Structure Property Relationship for Prediction of Flash Point of Alkanes Using Molecular Connectivity Indices

Many structure-property/activity studies use graph theoretical indices, which are based on the topological properties of a molecule viewed as a graph. Since topological indices can be derived directly from the molecular structure without any experimental effort, they provide a simple and straightforward method for property prediction. In this work the flash point of alkanes was modeled by a set of molecular connectivity indices (χ), modified molecular connectivity indices ( mχth ) and valance molecular connectivity indices ( mχv ), with mχv calculated using the hydrogen perturbation. A stepwise Multiple Linear Regression (MLR) method was used to select the best indices. The predicted flash points are in good agreement with the experimental data, with the average absolute deviation 4.3 K.

THE MOLECULAR ALGORITHM OF CONNECTIVITY BASED ON THREE DIMENSIONAL DNA STRUCTURE

Inspired by the potential computational capability of 3-Dimensional (3D) DNA structure,this paper presents a graph structure constructed by k-armed (k = 3or 4) branched junction DNA molecules to explore the possibility of solving some intractable problems. In the proposed procedure,vertex building blocks consisting of 3,4-armed branched junction molecules are selectively used to form different graph structures. After separating these graph structures by gel electrophoresis,the connec-tivity of this graph can be determined. Furthermore,the amount of potential solutions can be reduced by a theorem of graph theory.

Analysis and Modeling of k-regular and k-connected Protection Structure in Ultra-High Capacity Optical Networks

This paper proposes k-regular and k-connected(k&k) structure against multifaults in ultra-high capacity optical networks.Theoretical results show that pre-configured k&k structure can reach the lower bound on logical redundancy.The switching time of k&k protection structure is as quickly as ringbased protection in SDH network.It is the optimal protection structure in ultra-high capacity optical networks against multi-faults.We develop the linear programming model for k&k structure and propose a construction method for k&k structure design.Simulations are conducted for spare spectrum resources effi ciency of the pre-confi gured k&k structure under multi-faults on representative COST239 and NSFnet topologies.Numerical results show that the spare spectrum resources efficiency of k&k structure can reach the lower bound on logical redundancy in static networks.And it can largely improve spare spectrum resources effi ciency compared with p-cycles based protection structure without reducing protection effi ciency under dynamic traffi cs.

Development of a new connection for precast concrete walls subjected to cyclic loading

The Industrialized Building System （IBS） was recently introduced to minimize the time and cost of project construction. Accordingly, ensuring the integration of the connection of precast components in IBS structures is an important factor that ensures stability of buildings subjected to dynamic loads from earthquakes, vehicles, and machineries. However, structural engineers still lack knowledge on the proper connection and detailed joints o fiBS structure construction. Therefore, this study proposes a special precast concrete wall-to-wall connection system for dynamic loads that resists multidirectional imposed loads and reduces vibration effects （PI2014701723）. This system is designed to connect two adjacent precast wall panels by using two steel U-shaped channels （i.e., male and female joints）. During casting, each joint is adapted for incorporation into a respective wall panel after considering the following conditions： one side of the steel channel opens into the thickness face of the panel; a U-shaped rubber is implemented between the two channels to dissipate the vibration effect; and bolts and nuts are used to create an extension between the two U-shaped male and female steel channels. The developed finite element model of the precast wall is subjected to cyclic loads to evaluate the performance of the proposed connection during an imposed dynamic load. Connection performance is then compared with conventional connections based on the energy dissipation, stress, deformation, and concrete damage in the plastic range. The proposed precast connection is capable of exceeding the energy absorption of precast walls subjected to dynamic load, thereby improving its resistance behavior in all principal directions.

Experimental study on seismic behavior of semi-rigid connection between steel beam and concrete wall

Beam-column or beam-wall connections are an important problem in high-rise buildings. In this study, based on the analysis of an example structure, an analytical model for design of the semi-rigid connections between steel beams and RC walls in high-rise hybrid buildings is proposed. Also, the mechanical characteristics of these connections subjected to low-reversed cyclic loading are investigated through comparison of experimental results from three semi-rigid connections and two rigid connections. Moreover, some latent problems for design of these connections as well as the corresponding solutions are discussed. The results from the experiments and analyses indicate that semi-rigid connections exhibit satisfactory capacity and seismic performance, and the proposed design can be used in practice.

Analysis of the Spatial Structure of Tourism Resources in Ji'an City

This paper analyzed characteristics of tourism resources in Ji'an City,and carried out quantitative analysis of local tourism resources based on agglomeration effect of resources,connectivity analysis,and accessibility analysis. The results showed that the city has poor loop of tourism network,major scenic areas(spots) have moderate network accessibility,in view of this,suggestions for the optimum development of local tourism industry were proposed.

Strengthening Steel Joint of Architectural Structure under Loading Condition

Through the comparative analysis of steel plate reinforced, ceramics reinforced and non- reinforced joints under loading condition, the feasibility of strengthening steel joint of architectural structure was studied. By using element birth and death technology simulation of the finite element software ANSYS, it is found that when the reinforced structure is 10 mm in thickness and using steel structure to reinforce the concemed areas, the equivalent stress in concerned regionals reduces by 31.1% compared with that when the structure is not reinforced. When reinforced with ceramics, the equivalent stress in concerned regionals reduces by 24.1% compared with that reinforced with steels; when the reinforced structure is 20 mm in thickness using steels to reinforce the concerned area, the equivalent stress in concerned regionals reduces by 39.4% compared with that when the structure is not reinforced. When using ceramics to reinforce the concerned areas, the eauivalent stress only decreases by 3.7% compared with that reinforced with steels.

Evaluation and optimization analysis of high-speed rail network structure in Northeast China under the background of northeast revitalization

The construction of high-speed rail(HSR)network has promoted the social-economic ties of cities,accelerated the compression of time and space,and changed the pattern of regional development.In this paper,with the adoption of the operation frequency data of HSR from 12306 website,and based on the HSR connection strength model and social network analysis model,as well as according to the HSR connection strength,HSR network density,centrality,agglomeration subgroup,and other indicators,we analyzed the characteristics of HSR network structure in Northeast China.Results show that the number of HSR cities in Northeast China is small,cities in HSR network generally exhibit weak connectivity,and the existence of HSR network marginalizes cities such as Ulanhot,Baicheng,and Songyuan,which significantly reduce the overall network connectivity of Northeast China.The overall centrality of HSR network in Northeast China is characterized by“one axis,four edges”;specifically,the one axis is located in Harbin-Dalian transportation line and the four edges are located on both sides of the main axis of Harbin-Dalian transportation line.Eight agglomeration subgroups(four double city subgroups and four multi city subgroups)have formed in Northeast China.The core status of Shenyang in HSR network is improved significantly,and“one axis and two wings”HSR network in Liaoning Province is improved significantly.With the gradual expansion of Chaoyang-Fuxin,Dandong-Benxi,and Jilin-Yanji branch networks,the“point axis”HSR network mode in Northeast China has gradually developed and matured.In the future,it is recommended to rely on eight agglomerating subgroups to encrypt HSR network structure,create secondary node central cities,and gradually build a new pattern of opening up in Northeast China.

Fatigue Strength Evaluation of Resin-Injected Bolted Connections Using Statistical Analysis

在对老旧的螺栓和铆接金属桥进行修补和加固时可以使用不同的方案。由于铆接链接技术目前并不常用,连接它需要特定的设备和熟练的工人。另一种解决方案是使用焊接。但是,老旧钢材的可焊性较差。螺栓是一种非常可行的替代解决方案,并且常用于修复旧金属桥。装配螺栓的解决方案成本高昂,另一种方法是使用树脂灌注式螺栓。带有预紧力的树脂灌注式老旧螺栓连接的受力性能已经用准静态和蠕变试验进行了研究,然而,关于这些连接节点的滑移和疲劳行为的文献很少。本文概述了几位研究者的实验项目,旨在评估单侧受剪和双侧受剪的树脂灌注式螺栓连接的疲劳行为。对有预紧力的标准螺栓和有预紧力的树脂灌注式螺栓的连接节点的实验数据进行比较分析,显示后者的疲劳强度较低。但欧洲规范3(EC3)对树脂灌注式螺栓和标准螺栓的连接节点提出的疲劳强度曲线大致相同,这应得到足够的重视。此外,本研究还展示了使用黏结螺栓连接的可行性研究。最后的研究是用高强度低合金结构钢板和用于金属黏结的丙烯酸结构黏结剂进行的。针对两个实际工程案例,使用线性化边界及Castillo和Fernández-Canteli模型对疲劳实验数据进行统计分析。最终提出疲劳设计曲线,并与欧洲和北美规范中的几个设计建议进行比较。