Bending tests and finite element analysis of lipped channels with complex edge stiffeners and web stiffeners

In order to study the bearing capacity and stability behavior of cold-formed steel flexural members with complicated sections,a total of 12 specimens divided into 6 groups were tested,including 3 groups of pure bending tests and non-pure bending tests each.There were three types of sections considered in this investigation,including channels with complex edge stiffeners(called B1-section),Σsection with complex edge stiffeners(called B2-section),and channels with complex edge stiffeners and V-type web stiffeners(called B3-section).Local buckling,distortional buckling and interaction buckling between them were observed in tests.The experimental results indicate that the bending strengths of B2-section specimens were the largest of these three types of specimens under the same conditions.It is found that the bending strength of B2-section specimens was increased by 6.47%for pure bending state and 8.12%for non-pure bending state,compared with that of B1-section specimens.Bending strength of B3-section specimens was almost the same with that of B1-section specimens under pure bending,but a little smaller than that of B1-section under non-pure bending state.It is also shown that B2-section specimens have better plastic deformation behavior than the other two sections.In addition,a non-linear finite element model was presented and verified against tests.The finite element analysis results agree well with experimental bending strength and failure modes.

Evolutionary dynamics analysis of complex network with fusion nodes and overlap edges

Multiple complex networks, each with different properties and mutually fused, have the problems that the evolving process is time varying and non-equilibrium, network structures are layered and interlacing, and evolving characteristics are difficult to be measured. On that account, a dynamic evolving model of complex network with fusion nodes and overlap edges（CNFNOEs） is proposed. Firstly, we define some related concepts of CNFNOEs, and analyze the conversion process of fusion relationship and hierarchy relationship. According to the property difference of various nodes and edges, fusion nodes and overlap edges are subsequently split, and then the CNFNOEs is transformed to interlacing layered complex networks（ILCN）. Secondly,the node degree saturation and attraction factors are defined. On that basis, the evolution algorithm and the local world evolution model for ILCN are put forward. Moreover, four typical situations of nodes evolution are discussed, and the degree distribution law during evolution is analyzed by means of the mean field method.Numerical simulation results show that nodes unreached degree saturation follow the exponential distribution with an error of no more than 6%; nodes reached degree saturation follow the distribution of their connection capacities with an error of no more than 3%; network weaving coefficients have a positive correlation with the highest probability of new node and initial number of connected edges. The results have verified the feasibility and effectiveness of the model, which provides a new idea and method for exploring CNFNOE＇s evolving process and law. Also, the model has good application prospects in structure and dynamics research of transportation network, communication network, social contact network,etc.

Structural effects of reedbed grazing and its cessation on reed-nesting songbird densities

Reedbeds are crucial breeding habitats for vulnerable songbird species.Irrespective of their protection status,these habitats may be threatened by organic matter accumulation,progressively leading to structural homoge-nization and habitat succession towards woodland.Managers prevent excessive litter build-up with various in-terventions opening-up the reedbeds,such as grazing,which may be detrimental or suitable for some reed bird species.We assessed the effects of extensive grazing by horses and its cessation in the medium and long terms on reedbed structure,and the consequences on reed-nesting songbird densities in Estagnol Nature Reserve,a pro-tected wetland near the French Mediterranean coast.We compared reedbed structural features between grazed,newly ungrazed and old-ungrazed plots.During nine years,we censused four songbird species in spring and collected water level data in the same survey plots.Grazing reduced reedbed extent,rejuvenated the vegetation with more short green stems on a thinner litter,and produced higher structural heterogeneity and discontinuity compared to long-lasting non grazing.Newly ungrazed plot showed intermediate effects.All surveyed songbird total densities were similar among plots while species numbers and densities differed.Grazed reedbed was more attractive to Moustached Warblers(Acrocephalus melanopogon)and Great Reed Warblers(Acrocephalus arundi-naceus),likely due to the large edges and the high vegetation structural heterogeneity.However,Moustached Warblers were more negatively affected by higher water level in grazed reedbed,presumably because flooding prevents litter foraging.The newly ungrazed reedbed was not preferred by any species.All warbler species were found under low density in the old-ungrazed reedbed,where Reed Buntings(Emberiza schoeniclus)were exclu-sively found.Food availability related to thick litter layer may explain this predilection.Common Reed Warblers(Acrocephalus scirpaceus)were found everywhere in similar densities.We conclude that reedbed management by extensive horse grazing and also its long-term cessation may benefit several songbird species.Within a context of wetland degradation and disappearance,both management strategies are useful to establish and maintain suitable habitats for reed-nesting songbird communities.

'SoS Call' at the Other Edge of Chaos

The focus of this study is to understand and pave the way to build theory of System of Systems(SoS).The authors try to marshal the established thoughts and develop new insights to shed light on the topic.Although the research thrashes the proposed rudimentary concepts,yet they are important to caste clarity to lay the concrete foundation for the emerging concept of SoS.The first part of the paper discusses about the conceptual milieu of SoS.It tries to help resolve their identity crisis by proposing two edges of chaos.SoS and monolithic systems self-organize at two opposite edges.Then the research work defines SoS locus on extended system of systems methodology(E-SoSM) framework,and dissects it to decode its contradictory and aberrant behavior.Upon this understanding,the second part traces out the incapacitation of traditional military techniques for asymmetric warfare,typifying with a friendly fire incident of the current Afghan War.Seeing through this lens,conjures up that military SoS and anti SoS(enemy) fight to annihilate each other during the clashes of systems of systems in the theater of war.